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Sample records for ptba-p3ht multi-arm star-like

  1. Multiple Identifications in Multi-Armed Bandits

    CERN Document Server

    Bubeck, Sébastien; Viswanathan, Nitin

    2012-01-01

    We study the problem of identifying the top $m$ arms in a multi-armed bandit game. Our proposed solution relies on a new algorithm based on successive rejects of the seemingly bad arms, and successive accepts of the good ones. This algorithmic contribution allows to tackle other multiple identifications settings that were previously out of reach. In particular we show that this idea of successive accepts and rejects applies to the multi-bandit best arm identification problem.

  2. Multi-Armed Bandits in Metric Spaces

    CERN Document Server

    Kleinberg, Robert; Upfal, Eli

    2008-01-01

    In a multi-armed bandit problem, an online algorithm chooses from a set of strategies in a sequence of trials so as to maximize the total payoff of the chosen strategies. While the performance of bandit algorithms with a small finite strategy set is quite well understood, bandit problems with large strategy sets are still a topic of very active investigation, motivated by practical applications such as online auctions and web advertisement. The goal of such research is to identify broad and natural classes of strategy sets and payoff functions which enable the design of efficient solutions. In this work we study a very general setting for the multi-armed bandit problem in which the strategies form a metric space, and the payoff function satisfies a Lipschitz condition with respect to the metric. We refer to this problem as the "Lipschitz MAB problem". We present a complete solution for the multi-armed problem in this setting. That is, for every metric space (L,X) we define an isometry invariant which bounds f...

  3. Characterizing Truthful Multi-Armed Bandit Mechanisms

    CERN Document Server

    Babaioff, Moshe; Slivkins, Aleksandrs

    2008-01-01

    We consider a multi-round auction setting motivated by pay-per-click auctions for Internet advertising. In each round the auctioneer selects an advertiser and shows her ad, which is then either clicked or not. An advertiser derives value from clicks; the value of a click is her private information. Initially, neither the auctioneer nor the advertisers have any information about the likelihood of clicks on the advertisements. The auctioneer's goal is to design a (dominant strategies) truthful mechanism that (approximately) maximizes the social welfare. If the advertisers bid their true private values, our problem is equivalent to the "multi-armed bandit problem", and thus can be viewed as a strategic version of the latter. In particular, for both problems the quality of an algorithm can be characterized by "regret", the difference in social welfare between the algorithm and the benchmark which always selects the same "best" advertisement. We investigate how the design of multi-armed bandit algorithms is affect...

  4. The KALI multi-arm robot programming and control environment

    Science.gov (United States)

    Backes, Paul; Hayati, Samad; Hayward, Vincent; Tso, Kam

    1989-01-01

    The KALI distributed robot programming and control environment is described within the context of its use in the Jet Propulsion Laboratory (JPL) telerobot project. The purpose of KALI is to provide a flexible robot programming and control environment for coordinated multi-arm robots. Flexibility, both in hardware configuration and software, is desired so that it can be easily modified to test various concepts in robot programming and control, e.g., multi-arm control, force control, sensor integration, teleoperation, and shared control. In the programming environment, user programs written in the C programming language describe trajectories for multiple coordinated manipulators with the aid of KALI function libraries. A system of multiple coordinated manipulators is considered within the programming environment as one motion system. The user plans the trajectory of one controlled Cartesian frame associated with a motion system and describes the positions of the manipulators with respect to that frame. Smooth Cartesian trajectories are achieved through a blending of successive path segments. The manipulator and load dynamics are considered during trajectory generation so that given interface force limits are not exceeded.

  5. Octopus-inspired multi-arm robotic swimming.

    Science.gov (United States)

    Sfakiotakis, M; Kazakidi, A; Tsakiris, D P

    2015-05-13

    The outstanding locomotor and manipulation characteristics of the octopus have recently inspired the development, by our group, of multi-functional robotic swimmers, featuring both manipulation and locomotion capabilities, which could be of significant engineering interest in underwater applications. During its little-studied arm-swimming behavior, as opposed to the better known jetting via the siphon, the animal appears to generate considerable propulsive thrust and rapid acceleration, predominantly employing movements of its arms. In this work, we capture the fundamental characteristics of the corresponding complex pattern of arm motion by a sculling profile, involving a fast power stroke and a slow recovery stroke. We investigate the propulsive capabilities of a multi-arm robotic system under various swimming gaits, namely patterns of arm coordination, which achieve the generation of forward, as well as backward, propulsion and turning. A lumped-element model of the robotic swimmer, which considers arm compliance and the interaction with the aquatic environment, was used to study the characteristics of these gaits, the effect of various kinematic parameters on propulsion, and the generation of complex trajectories. This investigation focuses on relatively high-stiffness arms. Experiments employing a compliant-body robotic prototype swimmer with eight compliant arms, all made of polyurethane, inside a water tank, successfully demonstrated this novel mode of underwater propulsion. Speeds of up to 0.26 body lengths per second (approximately 100 mm s(-1)), and propulsive forces of up to 3.5 N were achieved, with a non-dimensional cost of transport of 1.42 with all eight arms and of 0.9 with only two active arms. The experiments confirmed the computational results and verified the multi-arm maneuverability and simultaneous object grasping capability of such systems.

  6. Contextual Multi-armed Bandits under Feature Uncertainty

    Energy Technology Data Exchange (ETDEWEB)

    Yun, Seyoung [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Nam, Jun Hyun [Korea Advanced Inst. Science and Technology (KAIST), Daejeon (Korea, Republic of); Mo, Sangwoo [Korea Advanced Inst. Science and Technology (KAIST), Daejeon (Korea, Republic of); Shin, Jinwoo [Korea Advanced Inst. Science and Technology (KAIST), Daejeon (Korea, Republic of)

    2017-03-03

    We study contextual multi-armed bandit problems under linear realizability on rewards and uncertainty (or noise) on features. For the case of identical noise on features across actions, we propose an algorithm, coined NLinRel, having O(T⁷/₈(log(dT)+K√d)) regret bound for T rounds, K actions, and d-dimensional feature vectors. Next, for the case of non-identical noise, we observe that popular linear hypotheses including NLinRel are impossible to achieve such sub-linear regret. Instead, under assumption of Gaussian feature vectors, we prove that a greedy algorithm has O(T²/₃√log d)regret bound with respect to the optimal linear hypothesis. Utilizing our theoretical understanding on the Gaussian case, we also design a practical variant of NLinRel, coined Universal-NLinRel, for arbitrary feature distributions. It first runs NLinRel for finding the ‘true’ coefficient vector using feature uncertainties and then adjust it to minimize its regret using the statistical feature information. We justify the performance of Universal-NLinRel on both synthetic and real-world datasets.

  7. Photovoltaic Devices from Multi-Armed CdS Nanorods and Conjugated Polyme, Composites

    Institute of Scientific and Technical Information of China (English)

    LIU Yan-Shan; WANG Li; QIN Dong-Huan; CAO Yong

    2006-01-01

    We demonstrate the preparation of composite photovoltaic devices by using the blends of multi-armed CdS nanorods with conjugated polymer, poly[2-methoxy-5-(2'-ethylhexyloxy)-l,4-phenylenevinylene] (MEH-PPV). Multi-armed CdS nanorods are prepared by thermolysing single precursor cadmium ethylxanthate [Cd(exan)2] in pure hexadecylamine solution under ambient conditions. The photoluminescence of MEH-PPV can be ef fectively quenched in the composites at high CdS nanocrystal (nc-CdS)/MEH-PPV ratios. Post-treatment of the multi-armed CdS nanorods by refluxing in pyridine significantly increases the performance of the composite photovoltaic devices. Power conversion efficiency is obtained to be 0.17% under AM 1.5 illumination for this composite device.

  8. Regret Analysis of Stochastic and Nonstochastic Multi-armed Bandit Problems

    CERN Document Server

    Bubeck, Sébastien

    2012-01-01

    Multi-armed bandit problems are the most basic examples of sequential decision problems with an exploration-exploitation trade-off. This is the balance between staying with the option that gave highest payoffs in the past and exploring new options that might give higher payoffs in the future. Although the study of bandit problems dates back to the Thirties, exploration-exploitation trade-offs arise in several modern applications, such as ad placement, website optimization, and packet routing. Mathematically, a multi-armed bandit is defined by the payoff process associated with each option. In this survey, we focus on two extreme cases in which the analysis of regret is particularly simple and elegant: i.i.d. payoffs and adversarial payoffs. Besides the basic setting of finitely many actions, we also analyze some of the most important variants and extensions, such as the contextual bandit model.

  9. Structural properties of star-like dendrimers in solution

    Energy Technology Data Exchange (ETDEWEB)

    Rathgeber, S. [Forschungszentrum Juelich GmbH, IFF Weiche Materie, 52425 Juelich (Germany); Gast, A.P. [Stanford University, Stanford, CA 94305-5025 (United States); Hedrick, J.L. [IBM Almaden Research Center, San Jose, CA 95120-6099 (United States)

    2002-07-01

    We measured the form factor of star-like poly-{epsilon}-caprolactone dendrimers under good solvent conditions with small-angle neutron scattering (SANS). The parameters varied in the experiment were the dendrimer generation g=1,2,3 and the number of segments between the branching units n=5,10,15,20. The results are discussed in the frame work of the Beaucage model from which we cannot only derive the radius of gyration R{sub g} of the dendrimers but also their fractal dimensions. Decreasing the number of spacer units between the branching points results in a strong stretching of the dendrons. The fractal dimension increases monotonically with increasing generation and spacer number between the limit expected for a low-functionality star P{approx}5/3 (loose, polymeric structure) and that expected for a high-functionality star P{approx}3 (compact shape). (orig.)

  10. Structural properties of star-like dendrimers in solution

    Science.gov (United States)

    Rathgeber, S.; Gast, A. P.; Hedrick, J. L.

    We measured the form factor of star-like poly-ɛ-caprolactone dendrimers under good solvent conditions with small-angle neutron scattering (SANS). The parameters varied in the experiment were the dendrimer generation g=1,2,3 and the number of segments between the branching units n=5,10,15,20. The results are discussed in the frame work of the Beaucage model from which we cannot only derive the radius of gyration Rg of the dendrimers but also their fractal dimensions. Decreasing the number of spacer units between the branching points results in a strong stretching of the dendrons. The fractal dimension increases monotonically with increasing generation and spacer number between the limit expected for a low-functionality star P 5/3 (loose, polymeric structure) and that expected for a high-functionality star P 3 (compact shape).

  11. Enhanced ionic conductivity of intrinsic solid polymer electrolytes using multi-armed oligo(ethylene oxide) plasticizers

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Joung-In; Kim, Dong Wook; Lee, Changjin; Kang, Yongku [Advanced Materials Division, Korea Research Institute of Chemical Technology, P.O. Box 107 Yuseong, 305-600 Daejeon (Korea)

    2010-09-15

    In this work, we report on star-shaped plasticizers with the various chain lengths of multi-armed oligo(ethylene oxide) in order to prevent the plasticizers from crystallizing and eventually to enhance the ionic conductivity at low temperature. The multi-armed plasticizers are compared with the linear ones in terms of the ionic conductivity of the polymer electrolytes using them. The ionic conductivity of the polymer electrolytes using the linear plasticizer abruptly decreases below 0 C, while the temperature dependence of the ionic conductivity of the polymer electrolytes based on the multi-armed plasticizers shows a typical Vogel-Tamman-Fuelcher (VTF) relationship in the temperature range from -30 to 100 C. Such enhanced ionic conductivity at low temperature is because the multi-armed plasticizers are not crystallizing due to the branches or the multi-arms structure. The multi-armed plasticizers are found to be electrochemically stable up to 5.2 V by cyclic voltammetry analysis, which means that they are electrochemically stable enough for the application in the lithium ion batteries. (author)

  12. Star-like superalkali cations featuring planar pentacoordinate carbon.

    Science.gov (United States)

    Guo, Jin-Chang; Tian, Wen-Juan; Wang, Ying-Jin; Zhao, Xue-Feng; Wu, Yan-Bo; Zhai, Hua-Jin; Li, Si-Dian

    2016-06-28

    Superalkali cations, known to possess low vertical electron affinities (VEAs), high vertical detachment energies, and large highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy gaps, are intriguing chemical species. Thermodynamically, such species need to be the global minima in order to serve as the promising targets for experimental realization. In this work, we propose the strategies of polyhalogenation and polyalkalination for designing the superalkali cations. By applying these strategies, the local-minimum planar pentacoordinate carbon (ppC) cluster CBe5 can be modified to form a series of star-like superalkali ppC or quasi-ppC CBe5X5 (+) (X = F, Cl, Br, Li, Na, K) cations containing a CBe5 moiety. Polyhalogenation and polyalkalination on the CBe5 unit may help eliminate the high reactivity of bare CBe5 molecule by covering the reactive Be atoms with noble halogen anions and alkali cations. Computational exploration of the potential energy surfaces reveals that the star-like ppC or quasi-ppC CBe5X5 (+) (X = F, Cl, Br, Li, Na, K) clusters are the true global minima of the systems. The predicted VEAs for CBe5X5 (+) range from 3.01 to 3.71 eV for X = F, Cl, Br and 2.12-2.51 eV for X = Li, Na, K, being below the lower bound of the atomic ionization potential of 3.89 eV in the periodic table. Large HOMO-LUMO energy gaps are also revealed for the species: 10.76-11.07 eV for X = F, Cl, Br and 4.99-6.91 eV for X = Li, Na, K. These designer clusters represent the first series of superalkali cations with a ppC center. Bonding analyses show five Be-X-Be three-center two-electron (3c-2e) σ bonds for the peripheral bonding, whereas the central C atom is associated with one 6c-2e π bond and three 6c-2e σ bonds, rendering (π and σ) double aromaticity. Born-Oppenheimer molecular dynamics simulations indicate that the CBe5 motif is robust in the clusters. As planar hypercoordination carbon species are often thermodynamically

  13. Broadband and stable acoustic vortex emitter with multi-arm coiling slits

    KAUST Repository

    Jiang, Xue

    2016-05-16

    We present the analytical design and experimental realization of a scheme based on multi-arm coiling slits to generate the stable acoustic vortices in a broadband. The proposed structure is able to spiral the acoustic wave spatially and generate the twisted acoustic vortices with invariant topological charge for a long propagation distance. Compared with conventional methods which require the electronic control of a bulky loudspeaker, this scheme provides an effective and compact solution to generate acoustic vortices with controllable topological charge in the broadband, which offers more initiatives in the demanding applications.

  14. lil' UCB : An Optimal Exploration Algorithm for Multi-Armed Bandits

    OpenAIRE

    Jamieson, Kevin; Malloy, Matthew; Nowak, Robert; Bubeck, Sébastien

    2013-01-01

    The paper proposes a novel upper confidence bound (UCB) procedure for identifying the arm with the largest mean in a multi-armed bandit game in the fixed confidence setting using a small number of total samples. The procedure cannot be improved in the sense that the number of samples required to identify the best arm is within a constant factor of a lower bound based on the law of the iterated logarithm (LIL). Inspired by the LIL, we construct our confidence bounds to explicitly account for t...

  15. Analysis of Thompson Sampling for the multi-armed bandit problem

    CERN Document Server

    Agrawal, Shipra

    2011-01-01

    The multi-armed bandit problem is a popular model for studying exploration/exploitation trade-off in sequential decision problems. Many algorithms are now available for this well-studied problem. One of the earliest algorithms, given by W. R. Thompson, dates back to 1933. This algorithm, referred to as Thompson Sampling, is a natural Bayesian algorithm. The basic idea is to choose an arm to play according to its probability of being the best arm. Thompson Sampling algorithm has experimentally been shown to be close to optimal. In addition, it is efficient to implement and exhibits several desirable properties such as small regret for delayed feedback. However, theoretical understanding of this algorithm was quite limited. In this paper, for the first time, we show that Thompson Sampling algorithm achieves logarithmic expected regret for the Bernoulli multi-armed bandit problem. More precisely, for the two-armed Bernoulli bandit problem, the expected regret in time $T$ is $O(\\frac{\\ln T}{\\Delta} + \\frac{1}{\\De...

  16. Recommendations on multiple testing adjustment in multi-arm trials with a shared control group.

    Science.gov (United States)

    Howard, Dena R; Brown, Julia M; Todd, Susan; Gregory, Walter M

    2016-09-19

    Multi-arm clinical trials assessing multiple experimental treatments against a shared control group can offer efficiency advantages over independent trials through assessing an increased number of hypotheses. Published opinion is divided on the requirement for multiple testing adjustment to control the family-wise type-I error rate (FWER). The probability of a false positive error in multi-arm trials compared to equivalent independent trials is affected by the correlation between comparisons due to sharing control data. We demonstrate that this correlation in fact leads to a reduction in the FWER, therefore FWER adjustment is not recommended solely due to sharing control data. In contrast, the correlation increases the probability of multiple false positive outcomes across the hypotheses, although standard FWER adjustment methods do not control for this. A stringent critical value adjustment is proposed to maintain equivalent evidence of superiority in two correlated comparisons to that obtained within independent trials. FWER adjustment is only required if there is an increased chance of making a single claim of effectiveness by testing multiple hypotheses, not due to sharing control data. For competing experimental therapies, the correlation between comparisons can be advantageous as it eliminates bias due to the experimental therapies being compared to different control populations.

  17. Two Multi-armed Neutral Receptors for α, ω-Dicarboxylate Anions

    Institute of Scientific and Technical Information of China (English)

    WU, Jin-Long; HE, Yong-Bing; WEI, Lan-Hua; LIU, Shun-Ying; XU, Kuo-Xi; MENG, Ling-Zhi

    2006-01-01

    Two new multi-armed neutral receptors 1 and 2 containing thiourea and amide groups were synthesized by simple steps in good yields. Receptors 1 and 2 have a better selectivity and higher association constants for malonate anion than other anions examined by the present work. In particular, distinct color changes were observed upon addition of dicarboxylate anions to the solution of 1 in DMSO. The UV-Vis and fluorescence spectra data indicate that a 1: 2 stoichiometry complex was formed between compound 1 or 2 and dicarboxylate anions of shorter carbon chain, and a 1: 1 stoichiometry complex was formed between compound 1 or 2 and dicarboxylate anions of longer carbon chain through hydrogen bonding interactions.

  18. Analysis of Multi-Arm Caliper Data for the U.S. Strategic Petroleum Reserve

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, Barry L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-03-01

    The U.S. Strategic Petroleum Reserve (SPR) has an increasing reliance on mul t i - arm caliper surveys to assess the integrity of casing for cavern access wells and to determine priorities for casing remediation. Multi - arm caliper (MAC) surveys provide a view of well casing deformation by reporting radial measurements of the inner cas ing wall as the tool is drawn through the casing. Over the last several years the SPR has collected a large number of modern MAC surveys. In total, these surveys account for over 100 million individual measurements. The surveys were collected using diff ering survey vendors and survey hardware. This has resulted in a collection of disparate data sets which confound attempts to make well - to - well or time - dependent evaluations. In addition, the vendor supplied MAC interpretations often involve variables wh ich are not well defined or which may not be applicable to casings for cavern access wells. These factors reduce the usability of these detailed data sets. In order to address this issue and provide an independent analysis of multi - arm caliper survey data, Sandia National Labs has developed processing techniques and analysis variables which allow for the comparison of MAC survey data regardless of the source of the survey data. These techniques use the raw radial arm information and newly developed analysis variables to assess the casing status and provide a means for well - to - well and time - dependent analyses. Well - to - well and t ime - dependent investigation of the MAC survey data provide s information to prioritize well remediation activities and identify wells with integrity issues. This paper presents the challenges in using disparate MAC survey data, techniques developed to address these challenges and some o f the insights gained from these new techniques.

  19. Analysis of Multi-Arm Caliper Data for the U.S. Strategic Petroleum Reserve

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, Barry L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-03-01

    The U.S. Strategic Petroleum Reserve (SPR) has an increasing reliance on mul t i - arm caliper surveys to assess the integrity of casing for cavern access wells and to determine priorities for casing remediation. Multi - arm caliper (MAC) surveys provide a view of well casing deformation by reporting radial measurements of the inner cas ing wall as the tool is drawn through the casing. Over the last several years the SPR has collected a large number of modern MAC surveys. In total, these surveys account for over 100 million individual measurements. The surveys were collected using diff ering survey vendors and survey hardware. This has resulted in a collection of disparate data sets which confound attempts to make well - to - well or time - dependent evaluations. In addition, the vendor supplied MAC interpretations often involve variables wh ich are not well defined or which may not be applicable to casings for cavern access wells. These factors reduce the usability of these detailed data sets. In order to address this issue and provide an independent analysis of multi - arm caliper survey data, Sandia National Labs has developed processing techniques and analysis variables which allow for the comparison of MAC survey data regardless of the source of the survey data. These techniques use the raw radial arm information and newly developed analysis variables to assess the casing status and provide a means for well - to - well and time - dependent analyses. Well - to - well and t ime - dependent investigation of the MAC survey data provide s information to prioritize well remediation activities and identify wells with integrity issues. This paper presents the challenges in using disparate MAC survey data, techniques developed to address these challenges and some o f the insights gained from these new techniques.

  20. Single-crystal star-like zinc oxide: synthesis, characterization and growth mechanism

    Institute of Scientific and Technical Information of China (English)

    WANG Qingxiao; YOU Liping; Zhang Xinzheng; WANG Rongming; LV Yuzhen; GUO Lin

    2006-01-01

    A novel star-like single-crystal ZnO structure was synthesized by a simple solvothermal method.The as-prepared products were characterized by XRD, SEM and TEM.The star-like ZnO, which shows sixfold symmetry, was constructed by six uniform arms distributing symmetrically around the [0001] zone axis.It is also found that the arms are not perpendicular to the [0001] zone axis and each arm is grown at a certain angle with the [0001] direction.CBED pattern and corresponding simulation demonstrate that the convex part of the star-like ZnO is O-terminated (000-1) plane and the concave part is Zn-terminated (0001) plane.H2S plays a crucial role in the synthesis process.The anisotropic growth habit along [0001] and [000-1] results in the formation of star-like structure.

  1. Deterministic Sequencing of Exploration and Exploitation for Multi-Armed Bandit Problems

    CERN Document Server

    Liu, Keqin

    2011-01-01

    In the Multi-Armed Bandit (MAB) problem, there are a given set of arms with unknown reward distributions. At each time, a player selects one arm to play, aiming to maximize the total expected reward over a horizon of length T. The essence of the problem is the tradeoff between exploration and exploitation: playing a less explored arm to learn its reward statistics for future benefit or playing the arm with the largest sample mean at the current time. An approach based on a Deterministic Sequencing of Exploration and Exploitation (DSEE) is developed for constructing sequential arm selection policies. Under this approach, the key issue is the cardinality of the exploration sequence, which balances the accuracy and the cost of learning and defines a lower bound on the regret. It is show that when the moment-generating functions of the arm reward distributions are properly bounded, the optimal logarithmic order of the regret can be achieved by DSEE. The condition on the reward distributions can be gradually relax...

  2. Learning in A Changing World: Non-Bayesian Restless Multi-Armed Bandit

    CERN Document Server

    Liu, Haoyang; Zhao, Qing

    2010-01-01

    We consider the restless multi-armed bandit (RMAB) problem with unknown dynamics. In this problem, at each time, a player chooses K out of N (N > K) arms to play. The state of each arm determines the reward when the arm is played and transits according to Markovian rules no matter the arm is engaged or passive. The Markovian dynamics of the arms are unknown to the player. The objective is to maximize the long-term reward by designing an optimal arm selection policy. The performance of a policy is measured by regret, defined as the reward loss with respect to the case where the player knows which K arms are the most rewarding and always plays these K best arms. We construct a policy, referred to as Restless Upper Confidence Bound (RUCB), that achieves a regret with logarithmic order of time when an arbitrary nontrivial bound on certain system parameters is known. When no knowledge about the system is available, we extend the RUCB policy to achieve a regret arbitrarily close to the logarithmic order. In both ca...

  3. Mesomorphic properties of multi-arm liquid crystals containing glucose and sorbitol as cores

    Science.gov (United States)

    Tian, Mei; Zhang, Bao-Yan; Cong, Yue-Hua; Zhang, Na; Yao, Dan-Shu

    2009-04-01

    Six thermotropic cholesteric multi-arm liquid crystals (MALCs) were synthesized with glucose and sorbitol as chiral cores. b0, b1 and b2 were introduced into hydroxy groups of the chiral cores as the mesogenic units in the arm scaffold. The roles played by the chiral cores and the terminal chain length of the mesogenic units to the mesomorphic behavior of the MALCs were studied. b0, b1 and b2 displayed nematic phase. c0, c1, c2, d0, d1 and d2 exhibited cholesteric phases and wide mesogenic regions. The results indicated that the chiral cores played an important effect on inducing the cholesteric phase and an obvious effect on the melting temperature, clear point and mesophase region of the MALCs. The corresponding melting temperature and the clear point of d0, d1 and d2, were lower than those of the c0, c1 and c2. The mesophase regions of the formers were narrower than those of the latters. The terminal chain length of the mesogenic units played an important effect on mesogenic region, too. The mesogenic region increased as the terminal chain length increasing for the MALCs containing the same chiral core.

  4. Complex wireframe DNA origami nanostructures with multi-arm junction vertices.

    Science.gov (United States)

    Zhang, Fei; Jiang, Shuoxing; Wu, Siyu; Li, Yulin; Mao, Chengde; Liu, Yan; Yan, Hao

    2015-09-01

    Structural DNA nanotechnology and the DNA origami technique, in particular, have provided a range of spatially addressable two- and three-dimensional nanostructures. These structures are, however, typically formed of tightly packed parallel helices. The development of wireframe structures should allow the creation of novel designs with unique functionalities, but engineering complex wireframe architectures with arbitrarily designed connections between selected vertices in three-dimensional space remains a challenge. Here, we report a design strategy for fabricating finite-size wireframe DNA nanostructures with high complexity and programmability. In our approach, the vertices are represented by n × 4 multi-arm junctions (n = 2-10) with controlled angles, and the lines are represented by antiparallel DNA crossover tiles of variable lengths. Scaffold strands are used to integrate the vertices and lines into fully assembled structures displaying intricate architectures. To demonstrate the versatility of the technique, a series of two-dimensional designs including quasi-crystalline patterns and curvilinear arrays or variable curvatures, and three-dimensional designs including a complex snub cube and a reconfigurable Archimedean solid were constructed.

  5. Interactive Restless Multi-armed Bandit Game and Swarm Intelligence Effect

    CERN Document Server

    Yoshida, Shunsuke; Mori, Shintaro

    2015-01-01

    We obtain the conditions for the emergence of the swarm intelligence effect in an interactive game of restless multi-armed bandit (rMAB). A player competes with multiple agents. Each bandit has a payoff that changes with a probability $p_{c}$ per round. The agents and player choose one of three options: (1) Exploit (a good bandit), (2) Innovate (asocial learning for a good bandit among $n_{I}$ randomly chosen bandits), and (3) Observe (social learning for a good bandit). Each agent has two parameters $(c,p_{obs})$ to specify the decision: (i) $c$, the threshold value for Exploit, and (ii) $p_{obs}$, the probability for Observe in learning. The parameters $(c,p_{obs})$ are uniformly distributed. We determine the optimal strategies for the player using complete knowledge about the rMAB. We show whether or not social or asocial learning is more optimal in the $(p_{c},n_{I})$ space and define the swarm intelligence effect. We conduct a laboratory experiment (67 subjects) and observe the swarm intelligence effect ...

  6. Local heterogeneities in cardiac systems suppress turbulence by generating multi-armed rotors

    Science.gov (United States)

    Zhang, Zhihui; Steinbock, Oliver

    2016-05-01

    Ventricular fibrillation is an extremely dangerous cardiac arrhythmia that is linked to rotating waves of electric activity and chaotically moving vortex lines. These filaments can pin to insulating, cylindrical heterogeneities which swiftly become the new rotation backbone of the local wave field. For thin cylinders, the stabilized rotation is sufficiently fast to repel the free segments of the turbulent filament tangle and annihilate them at the system boundaries. The resulting global wave pattern is periodic and highly ordered. Our cardiac simulations show that also thicker cylinders can establish analogous forms of tachycardia. This process occurs through the spontaneous formation of pinned multi-armed vortices. The observed number of wave arms N depends on the cylinder radius and is associated to stability windows that for N = 2, 3 partially overlap. For N = 1, 2, we find a small gap in which the turbulence is removed but the pinned rotor shows complex temporal dynamics. The relevance of our findings to human cardiology are discussed in the context of vortex pinning to more complex-shaped anatomical features and remodeled myocardium.

  7. Multi-arm spiral electron vortices in multiphoton ionization by circularly polarized pulses

    Science.gov (United States)

    Ngoko Djiokap, Jean Marcel; Meremianin, Alexei V.; Manakov, Nikolai L.; Hu, Suxing; Madsen, Lars B.; Starace, Anthony F.

    2016-05-01

    Single ionization of helium by single-color two-photon absorption or two-color one-photon/two-photon absorption from two time-delayed circularly-polarized ultraviolet pulses are shown to produce ionized-electron momentum distributions in the polarization plane having respectively even-arm (zero- and four-start) or odd-arm (one- and three-start) spiral vortex structures. Results are obtained by both ab initio numerical solution of the six-dimensional two-electron time-dependent Schrödinger equation and by perturbation theory. The multi-arm patterns are sensitive to the carrier frequencies, handedness, time-delay, and relative phase of the two pulses, allowing control of electron angular distributions. Even-arm spiral vortices have been observed in optics. Thus, our even-arm spiral electron vortices are a dramatic example of wave-particle duality. Moreover, our odd-arm electron matter-wave vortices are consistent with recent findings in strong-field physics. Research supported in part by DOE, BES, Chem. Sciences, Geosciences, and Bio-sciences Div., Grant No. DE-FG02-96ER14646.

  8. Dynamic Balance Control of Multi-arm Free-Floating Space Robots

    Directory of Open Access Journals (Sweden)

    Bin Liang

    2008-11-01

    Full Text Available This paper investigates the problem of the dynamic balance control of multi-arm free-floating space robot during capturing an active object in close proximity. The position and orientation of space base will be affected during the operation of space manipulator because of the dynamics coupling between the manipulator and space base. This dynamics coupling is unique characteristics of space robot system. Such a disturbance will produce a serious impact between the manipulator hand and the object. To ensure reliable and precise operation, we propose to develop a space robot system consisting of two arms, with one arm (mission arm for accomplishing the capture mission, and the other one (balance arm compensating for the disturbance of the base. We present the coordinated control concept for balance of the attitude of the base using the balance arm. The mission arm can move along the given trajectory to approach and capture the target with no considering the disturbance from the coupling of the base. We establish a relationship between the motion of two arm that can realize the zeros reaction to the base. The simulation studies verified the validity and efficiency of the proposed control method.

  9. Synthesis and Characterization of Star-like Liquid Crystals Centered by Silicon

    Institute of Scientific and Technical Information of China (English)

    Jian Qiang LIU; Qi Zhen ZHANG; Jing Zhi ZHANG

    2004-01-01

    The synthesis and characterization of two new star-like liquid crystals are reported.They are made of a silicon core and four alkoxyazobenzene monomers in the periphery. Their phase behaviors and the structures are determined by infrared absorption spectroscopy (IR),nuclear magnetic resonance spectroscopy (NMR), elemental analysis (EA), polarizing optical microscope (POM) and differential scanning calorimetry (DSC).

  10. Comprehensive theory for star-like polymer micelles: combining classical nucleation and polymer brush theory

    NARCIS (Netherlands)

    Sprakel, J.H.B.; Leermakers, F.A.M.; Cohen Stuart, M.A.; Besseling, N.A.M.

    2008-01-01

    A comprehensive theory is proposed that combines classical nucleation and polymer brush theory to describe star-like polymer micelles. With a minimum of adjustable parameters, the model predicts properties such as critical micelle concentrations and micellar size distributions. The validity of the p

  11. Trigeminal star-like platinum complexes induce cancer cell senescence through quadruplex-mediated telomere dysfunction.

    Science.gov (United States)

    Zheng, Xiao-Hui; Mu, Ge; Zhong, Yi-Fang; Zhang, Tian-Peng; Cao, Qian; Ji, Liang-Nian; Zhao, Yong; Mao, Zong-Wan

    2016-12-01

    Two trigeminal star-like platinum complexes were synthesized to induce the formation of human telomere G-quadruplex (hTel G4) with extremely high selectivity and affinity. The induced hTel G4 activates strong telomeric DNA damage response (TDDR), resulting in telomere dysfunction and cell senescence.

  12. TOWARDS A SIMPLIFIED APPROACH TO THE MODELLING OF THE STAR-LIKE MOLECULE FLUIDS

    Directory of Open Access Journals (Sweden)

    Yu.Duda

    2002-01-01

    Full Text Available A theoretical approach to considering a wide spectrum of equilibrium properties of fluids formed from the four-branched molecules (e.g. four-arm star polysterene samples, four-arm block copolymers, etc. is presented and discussed. The proposed approach is within the framework of an associative version of integral equation theory and is based on an analytical solution of the four-site associative hard-sphere model. Results and discussion are explained by the comparison against Monte Carlo computer simulation data generated for a freely-joined tangent hard-sphere model of a star-like molecule fluid. It is shown that the proposed theory works well for the star-like molecule fluids in homogeneous phase where it predicts the structure for molecules with relatively long arms and at high densities. The obtained results qualitatively reproduce the most important experimental features of the solvation force induced between two macrosurfaces due to the presence of star-like aggregates.

  13. Precisely Size-Tunable Monodisperse Hairy Plasmonic Nanoparticles via Amphiphilic Star-Like Block Copolymers.

    Science.gov (United States)

    Chen, Yihuang; Yoon, Young Jun; Pang, Xinchang; He, Yanjie; Jung, Jaehan; Feng, Chaowei; Zhang, Guangzhao; Lin, Zhiqun

    2016-12-01

    In situ precision synthesis of monodisperse hairy plasmonic nanoparticles with tailored dimensions and compositions by capitalizing on amphiphilic star-like diblock copolymers as nanoreactors are reported. Such hairy plasmonic nanoparticles comprise uniform noble metal nanoparticles intimately and perpetually capped by hydrophobic polymer chains (i.e., "hairs") with even length. Interestingly, amphiphilic star-like diblock copolymer nanoreactors retain the spherical shape under reaction conditions, and the diameter of the resulting plasmonic nanoparticles and the thickness of polymer chains situated on the surface of the nanoparticle can be readily and precisely tailored. These hairy nanoparticles can be regarded as hard/soft core/shell nanoparticles. Notably, the polymer "hairs" are directly and permanently tethered to the noble metal nanoparticle surface, thereby preventing the aggregation of nanoparticles and rendering their dissolution in nonpolar solvents and the homogeneous distribution in polymer matrices with long-term stability. This amphiphilic star-like block copolymer nanoreactor-based strategy is viable and robust and conceptually enables the design and synthesis of a rich variety of hairy functional nanoparticles with new horizons for fundamental research on self-assembly and technological applications in plasmonics, catalysis, energy conversion and storage, bioimaging, and biosensors.

  14. Rich Variety of Three-Dimensional Nanostructures Enabled by Geometrically Constraining Star-like Block Copolymers.

    Science.gov (United States)

    Wang, Chao; Xu, Yuci; Li, Weihua; Lin, Zhiqun

    2016-08-01

    The influence of star-like architecture on phase behavior of star-like block copolymer under cylindrical confinement differs largely from the bulk (i.e., nonconfinement). A set of intriguing self-assembled morphologies and the corresponding phase diagrams of star-like (AB)f diblock copolymers with different numbers of arms f (i.e., f = 3, 9, 15, and 21) in four scenarios (ϕA = 0.3 and V0 > 0; ϕA = 0.3 and V0 0; and ϕA = 0.7 and V0 0 represent that the pore wall of cylindrical confinement prefers the inner A block (i.e., A-preferential) and B block (i.e., B-preferential), respectively) were for the first time scrutinized by employing the pseudospectral method of self-consistent mean-field theory. Surprisingly, a new nanoscopic phase, that is, perforated-lamellae-on-cylinder (denoted PC), was observed in star-like (AB)3 diblock copolymer at ϕA = 0.3 and V0 > 0. With a further increase in f, a single lamellae (denoted L1) was found to possess a larger phase region. Under the confinement of A-preferential wall (i.e., V0 0, where an inverted cylinder was formed in bulk, the PC phase became stable, and its free energy decreased as f increased, suggesting the propensity to form PC phase under this condition. Moreover, in stark contrast to the phase transition of C1 → L1 → PC (C1, a single cylindrical microdmain) at ϕA = 0.3 and V0 > 0, when subjected to the A-preferential wall (ϕA = 0.7), a different phase transition sequence (i.e., C1 → PC → L1) was identified due to the formation of a double-layer structure. On the basis of our calculations, the influence of star-like architecture on (AB)f diblock copolymer under the imposed cylindrical confinement, particularly the shift of the phase boundaries as a function of f, was thoroughly understood. These self-assembled nanostructures may hold the promise for applications as lithographic templates for nanowires, photonic crystals, and nanotechnology.

  15. Comprehensive theory for star-like polymer micelles; combining classical nucleation and polymer brush theory.

    Science.gov (United States)

    Sprakel, Joris; Leermakers, Frans A M; Cohen Stuart, Martien A; Besseling, Nicolaas A M

    2008-09-14

    A comprehensive theory is proposed that combines classical nucleation and polymer brush theory to describe star-like polymer micelles. With a minimum of adjustable parameters, the model predicts properties such as critical micelle concentrations and micellar size distributions. The validity of the present theory is evidenced in direct comparison to experiments; this revealed that the proportionality constant in the Daoud-Cotton model is of the order of unity and that the star-limit is valid down to relatively short corona chains. Furthermore, we show that the predicted saddle points in the free energy correspond to those solutions that are accessible with self-consistent field methods for self-assembly.

  16. A new family of star-like icosahedral structures for small cobalt clusters

    Energy Technology Data Exchange (ETDEWEB)

    Aguilera-Granja, F. [Instituto de Física, Universidad Autónoma de San Luis Potosí, 7800 San Luis Potosí (Mexico); Vega, Andrés [Departamento de Física Teórica, Atómica, y Óptica, Universidad de Valladolid, 47011 Valladolid (Spain); Balbás, Luis Carlos, E-mail: balbas@fta.uva.es [Departamento de Física Teórica, Atómica, y Óptica, Universidad de Valladolid, 47011 Valladolid (Spain)

    2013-03-29

    Highlights: ► First principles calculation of cobalt clusters structures under different approaches. ► Unexpected icosahedral growth pattern of cobalt clusters with 20–25 atoms. ► Effects of magnetism in the stabilization of cobalt clusters with 13–26 atoms. ► Comparison of Ionization potential and electron affinity with experiments supports the new cluster structures. ► Non-crystalline structure of cobalt clusters isomers are compared to crystalline one. - Abstract: Using a fully unconstrained version of the density-functional method with the generalized gradient approximation to exchange and correlation, we investigate the electronic structure and related properties of free-standing Co{sub 13-26} atomic clusters with star-like geometries belonging to an unexpected icosahedral growth pattern. Our results for the binding energies, ionization potentials and electron affinities, provide compelling evidence of the preference for this new family of star-like structures of Co{sub N} clusters in the range N = 20–25 instead of the planar hcp- or fcc-based structures proposed so far as the ground state.

  17. High-dose rifampicin, moxifloxacin, and SQ109 for treating tuberculosis: a multi-arm, multi-stage randomised controlled trial

    NARCIS (Netherlands)

    Boeree, M.J.; Heinrich, N.; Aarnoutse, R.; Diacon, A.H.; Dawson, R.; Rehal, S.; Kibiki, G.S.; Churchyard, G.; Sanne, I.; Ntinginya, N.E.; Minja, L.T.; Hunt, R.D.; Charalambous, S.; Hanekom, M.; Semvua, H.H.; Mpagama, S.G.; Manyama, C.; Mtafya, B.; Reither, K.; Wallis, R.S.; Venter, A.; Narunsky, K.; Mekota, A.; Henne, S.; Colbers, A.; Balen, G.P. van; Gillespie, S.H.; Phillips, P.P.; Hoelscher, M.

    2017-01-01

    BACKGROUND: Tuberculosis is the world's leading infectious disease killer. We aimed to identify shorter, safer drug regimens for the treatment of tuberculosis. METHODS: We did a randomised controlled, open-label trial with a multi-arm, multi-stage design. The trial was done in seven sites in South A

  18. Synthesis and Characterization of Stimuli-Responsive Star-Like Polypept(o)ides: Introducing Biodegradable PeptoStars.

    Science.gov (United States)

    Holm, Regina; Weber, Benjamin; Heller, Philipp; Klinker, Kristina; Westmeier, Dana; Docter, Dominic; Stauber, Roland H; Barz, Matthias

    2017-02-15

    Star-like polymers are one of the smallest systems in the class of core crosslinked polymeric nanoparticles. This article reports on a versatile, straightforward synthesis of three-arm star-like polypept(o)ide (polysarcosine-block-polylysine) polymers, which are designed to be either stable or degradable at elevated levels of glutathione. Polypept(o)ides are a recently introduced class of polymers combining the stealth-like properties of the polypeptoid polysarcosine with the functionality of polypeptides, thus enabling the synthesis of materials completely based on endogenous amino acids. The star-like homo and block copolymers are synthesized by living nucleophilic ring opening polymerization of the corresponding N-carboxyanhydrides (NCAs) yielding polymeric stars with precise control over the degree of polymerization (Xn = 25, 50, 100), Poisson-like molecular weight distributions, and low dispersities (Đ = 1.06-1.15). Star-like polypept(o)ides display a hydrodynamic radius of 5 nm (μ2 < 0.05) as determined by dynamic light scattering (DLS). While star-like polysarcosines and polypept(o)ides based on disulfide containing initiators are stable in solution, degradation occurs at 100 × 10(-3) m glutathione concentration. The disulfide cleavage yields the respective polymeric arms, which possess Poisson-like molecular weight distributions and low dispersities (Đ = 1.05-1.12). Initial cellular uptake and toxicity studies reveal that PeptoStars are well tolerated by HeLa, HEK 293, and DC 2.4 cells.

  19. Antimicrobial properties of CuO nanorods and multi-armed nanoparticles against B. anthracis vegetative cells and endospores

    Directory of Open Access Journals (Sweden)

    Pratibha Pandey

    2014-06-01

    Full Text Available Two different kinds of CuO nanoparticles (NPs namely CuO nanorods (PS2 and multi-armed nanoparticles (P5 were synthesized by wet and electrochemical routes, respectively. Their structure, morphology, size and compositions were characterized by SEM, EDX and XRD. The NPs demonstrated strong bactericidal potential against Bacillus anthracis cells and endospores. PS2 killed 92.17% of 4.5 × 104 CFU/mL B. anthracis cells within 1 h at a dose of 1 mg/mL. Whereas P5 showed a higher efficacy by killing 99.92% of 7 × 105 CFU/mL B. anthracis cells within 30 min at a dose of 0.5 mg/mL and 99.6% of 1.25 × 104 CFU/mL B. anthracis cells within 5 min at a dose of 2 mg/mL. More than 99% of spores were killed within 8 h with 2 mg/mL PS2 in LB media.

  20. On Optimality of Greedy Policy for a Class of Standard Reward Function of Restless Multi-armed Bandit Problem

    CERN Document Server

    Liu, Quan; Chen, Lin

    2011-01-01

    In this paper,we consider the restless bandit problem, which is one of the most well-studied generalizations of the celebrated stochastic multi-armed bandit problem in decision theory. However, it is known be PSPACE-Hard to approximate to any non-trivial factor. Thus the optimality is very difficult to obtain due to its high complexity. A natural method is to obtain the greedy policy considering its stability and simplicity. However, the greedy policy will result in the optimality loss for its intrinsic myopic behavior generally. In this paper, by analyzing one class of so-called standard reward function, we establish the closed-form condition about the discounted factor \\beta such that the optimality of the greedy policy is guaranteed under the discounted expected reward criterion, especially, the condition \\beta = 1 indicating the optimality of the greedy policy under the average accumulative reward criterion. Thus, the standard form of reward function can easily be used to judge the optimality of the greed...

  1. Rational geometrical engineering of palladium sulfide multi-arm nanostructures as a superior bi-functional electrocatalyst.

    Science.gov (United States)

    Nandan, R; Nanda, K K

    2017-08-31

    Geometrical tunability offers sharp edges and an open-armed structure accompanied with a high electrochemical active surface area to ensure the efficient and effective utilization of materials by exposing the electrochemical active sites for facile accessibility of reactant species. Herein, we report a one-step, single-pot, surfactant-free, electroless, and economic route to synthesize palladium sulfide nanostructures with different geometries at mild temperatures and their catalytic properties towards the oxygen reduction reaction (ORR) and methanol electro-oxidation (MOR). For ORR, the positive on-set, half wave potentials, smaller Tafel slope, high electrochemical active surface area, large roughness factor, and better cyclic stability of the proposed nanostructures as compared to those of the commercial state-of-the-art Pt-C/PdS catalysts suggest their superiority in an alkaline medium. In addition, high mass activity (Jf ∼ 715 mA mg(-1)), in comparison with that of the commercial state-of-the-art Pt-C/PdS catalysts (Jf ∼ 138/41 mA mg(-1), respectively), and high Jf/Jb (1.52) along with the superior operational stability of the multi-arm palladium sulfide nanostructures towards MOR advocates the bi-functional behavior of the catalyst and its potential as a promising Pt-free anode/cathode electrocatalyst in fuel cells.

  2. A Spatially Resolved X-ray Image of a Star Like the Sun.

    Science.gov (United States)

    Schmitt, J H; Kürster, M

    1993-10-08

    Observations made with the x-ray satellite ROSAT (Roentgen Satellite) have produced the first spatially resolved x-ray image of a corona around a star like our sun. The star is the secondary in the eclipsing binary system alpha Coronae Borealis (CrB), which consists of one star of spectral type A0V and one of type G5V. The x-ray light curve of alpha CrB shows a total x-ray eclipse during secondary optical minimum, with the G star behind the A star. The totality of the eclipse demonstrates that the A-type component in alpha CrB is x-ray dark and that the x-ray flux arises exclusively from the later-type companion. The x-ray eclipse ingress and egress are highly asymmetric compared with the optical eclipse, indicating a highly asymmetric x-ray intensity distribution on the surface of the G star. From a detailed modeling of the ingress and egress of the x-ray light curve, an eclipse map of the G star was constructed by a method based on an optimization by simulated annealing.

  3. Peculiar spectral statistics of ensembles of trees and star-like graphs

    Science.gov (United States)

    Kovaleva, V.; Maximov, Yu; Nechaev, S.; Valba, O.

    2017-07-01

    In this paper we investigate the eigenvalue statistics of exponentially weighted ensembles of full binary trees and p-branching star graphs. We show that spectral densities of corresponding adjacency matrices demonstrate peculiar ultrametric structure inherent to sparse systems. In particular, the tails of the distribution for binary trees share the ‘Lifshitz singularity’ emerging in the one-dimensional localization, while the spectral statistics of p-branching star-like graphs is less universal, being strongly dependent on p. The hierarchical structure of spectra of adjacency matrices is interpreted as sets of resonance frequencies, that emerge in ensembles of fully branched tree-like systems, known as dendrimers. However, the relaxational spectrum is not determined by the cluster topology, but has rather the number-theoretic origin, reflecting the peculiarities of the rare-event statistics typical for one-dimensional systems with a quenched structural disorder. The similarity of spectral densities of an individual dendrimer and of an ensemble of linear chains with exponential distribution in lengths, demonstrates that dendrimers could be served as simple disorder-less toy models of one-dimensional systems with quenched disorder.

  4. First Star-Like Oligophenylene Molecules Containing a Dinuclear Organometallic Core

    OpenAIRE

    Chérioux, Frédéric; Therrien, Bruno; Süss-Fink, Georg

    2006-01-01

    The cationic complexes Ru2[(p-MeC6H4iPr)2(p-SC6H4Br)3]+ and Rh2 [(C5Me5)2(p-SC6H4Br)3]+ are available in quantitative yields from the reaction of p-HSC6H4Br with [Ru(p-MeC6H4iPr)Cl2]2 and [Rh(C5Me5)Cl2]2 respectively. These complexes are found to undergo triple Suzuki coupling with oligophenylene boronic acids to give [Ru2 (p-MeC6H4iPr)2{p-S-(C6H4)n-C6H5}3]+ and [Rh2(C5Me5)2{p-S-(C6H4)n-C6H5}3]+ respectively. The star-like trisbromo complexes are potential precursors for the insertion of dinu...

  5. Electrochemical synthesis of multi-armed CuO nanoparticles and their remarkable bactericidal potential against waterborne bacteria

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, Pratibha, E-mail: rkpratibha@yahoo.com; Merwyn, S.; Agarwal, G. S.; Tripathi, B. K.; Pant, S. C. [Defence Research and Development Establishment (India)

    2012-01-15

    Copper (II) oxide multi-armed nanoparticles composed of 500-1000 nm long radiating nanospicules with 100-200 nm width near the base and 50-100 nm width at the tapered ends and {approx}25 nm thickness were synthesized by electrochemical deposition in the presence of an oxidant followed by calcination at 150 Degree-Sign C. The nanoparticles were characterized using SEM/EDX for morphology and composition, Raman spectroscopy for compound identification, and broth culture method for antibacterial efficacy. The CuO nanoparticles have shown remarkable bactericidal efficacy against Gram-positive and -negative waterborne disease causing bacteria like Escherichia coli, Salmonella typhi, staphylococcus aureus and Bacillus subtilis. E. coli has been chosen as representative species for waterborne disease causing bacteria. In antibacterial tests 500 {mu}g/mL nano CuO killed 3 Multiplication-Sign 10{sup 8} CFU/mL E. coli bacteria within 4 h of exposure. Moreover, 8.3 Multiplication-Sign 10{sup 6} CFU/mL E. coli were killed by 100 and 10 {mu}g/mL nano CuO within 15 min and 4 h of exposure, respectively. Antibacterial activity of nano CuO has been found many-fold compared with commercial bulk CuO. The fate of nanoparticles after antibacterial test has also been studied. The synthesized CuO nanoparticles are expected to have potential antibacterial applications in water purification and in paints and coatings used on frequently touched surfaces and fabrics in hospital settings.

  6. 多臂星形聚乙二醇的合成%Preparation of multi-arm star polyethylene glycol

    Institute of Scientific and Technical Information of China (English)

    张海连; 郭晖; 向清祥

    2012-01-01

    Two carboxyl groups were introduced at the chain end of esterification product derived from the reaction between PEG and succinic anhydride and then, the product reacted with thionyl chloride to prepare CIOC -PEG -COCI. Furthermore, the resultant intermediate reacted with polyols, such as glycerol, pentaerythritol or D-sorbitol, to make three-, four-, or six-arm PEGs, respectively. The ultimate products were characterized by Fourier transform infrared spectroscopy (FTIR) and hydrogen nuclear magnetic resonance (1H-NMR). The number average molecular mass of three-, four-, or six-arm PEGs was 3 794, 4 738, and 6 432, respectively, as measured with the end group titration method. The results indicate that the aforementioned synthesis route is a feasible method to prepare multi-arm star PEG with carboxyl end group.%聚乙二酵(PEG)经与丁二酸酐发生酯化后,在两末端引入羧基,再与氯化亚砜反应得到聚乙二醇二酰氯,此产物再分别与丙三醇、季戊四醇或D-山梨醇等多元醇反应,可分别得到三臂、四臂和六臂星形PEG.用傅里叶变换红外光谱和核磁共振氢谱等对各产物进行了表征,端基分析法得到三臂、四臂和六臂PEG的数均分子量平均值分别为3794,4738,6432,表明采用上述合成路线可成功得到末端为羧基的多臂星形PEG.

  7. Methods for meta-analysis of pharmacodynamic dose-response data with application to multi-arm studies of alogliptin.

    Science.gov (United States)

    Langford, Oliver; Aronson, Jeffrey K; van Valkenhoef, Gert; Stevens, Richard J

    2016-03-17

    Standard methods for meta-analysis of dose-response data in epidemiology assume a model with a single scalar parameter, such as log-linear relationships between exposure and outcome; such models are implicitly unbounded. In contrast, in pharmacology, multi-parameter models, such as the widely used Emax model, are used to describe relationships that are bounded above and below. We propose methods for estimating the parameters of a dose-response model by meta-analysis of summary data from the results of randomized controlled trials of a drug, in which each trial uses multiple doses of the drug of interest (possibly including dose 0 or placebo). We assume that, for each randomized arm of each trial, the mean and standard error of a continuous response measure and the corresponding allocated dose are available. We consider weighted least squares fitting of the model to the mean and dose pairs from all arms of all studies, and a two-stage procedure in which scalar inverse-variance meta-analysis is performed at each dose, and the dose-response model is fitted to the results by weighted least squares. We then compare these with two further methods inspired by network meta-analysis that fit the model to the contrasts between doses. We illustrate the methods by estimating the parameters of the Emax model to a collection of multi-arm, multiple-dose, randomized controlled trials of alogliptin, a drug for the management of diabetes mellitus, and further examine the properties of the four methods with sensitivity analyses and a simulation study. We find that all four methods produce broadly comparable point estimates for the parameters of most interest, but a single-stage method based on contrasts between doses produces the most appropriate confidence intervals. Although simpler methods may have pragmatic advantages, such as the use of standard software for scalar meta-analysis, more sophisticated methods are nevertheless preferable for their advantages in estimation.

  8. PGMA-Based Star-Like Polycations with Plentiful Hydroxyl Groups Act as Highly Efficient miRNA Delivery Nanovectors for Effective Applications in Heart Diseases.

    Science.gov (United States)

    Li, Rui-Quan; Wu, Yina; Zhi, Ying; Yang, Xinchao; Li, Yulin; Xua, Fu-Jian; Du, Jie

    2016-09-01

    Poly(glycidyl methacrylate)-based star-like polycations with rich hydrophilic hydroxyl groups can efficiently transfer miRNA into primary cardiac fibroblasts for effective applications in cardiac diseases, such as inhibition of cardiac fibrosis and hypertrophy.

  9. A novel protein characterization based on Pseudo Amino Acids composition and Star-like graph topological indices.

    Science.gov (United States)

    He, Pingan; Tao, Hong; Ma, Tingting; Dai, Qi; Yao, Yuhua

    2017-02-17

    In the work, a new description of proteins based on five topological indices of star-like graph representation and the occurrence frequency of 20 amino acids was proposed to compare the similarities of proteins. A phylogenetic tree of eight ND6 proteins was constructed to demonstrate the effectiveness and rationality of our approach. Analogously, we applied this method to RNA polymerase proteins of some subtypes of influenza virus to infer their phylogenetic relationship. The results showed that the phylogenetic relationship among RNA polymerase of influenza virus is closely related to distributions of species virus host and geographical distribution.

  10. Phosphatized rare star-like mouth disc of Punctatus and its functional morphology from the earliest Cambrian of the South Shaanxi China

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The Meishucun stage is the prelude in decipher-ing the Cambrian Explosion. In this prominent stage, rapid radioactive evolution and body-plan innovation have taken place and different associations of organism have been shaped. In this paper we report several 3D-preserved rare star-like fossils with finely preserved soft tissues which were recovered from the Kuanchuanpu Member of the Dengying Formation in South Shaanxi, China in 2003. By studying on functional morphology and analogy with mouthpart of Punctatus, there are evidences that this star-like organism approaches the coelenterates in systematic classification and the centre of star-like organism is its mouth. The appearance of coelenterates marks the real beginning of metazoan evolution. Therefore, it has the prominent position in the origin and evolutionary history of organisms. Perhaps the star-like organism represents the early types of coelenterate with original tentacles. These new materials provide new evidence for the origin, evolution and the functional evolution of the metazoan during the early stage of the Cambrian Explosion.

  11. HBP Builder: A Tool to Generate Hyperbranched Polymers and Hyperbranched Multi-Arm Copolymers for Coarse-grained and Fully Atomistic Molecular Simulations

    Science.gov (United States)

    Yu, Chunyang; Ma, Li; Li, Shanlong; Tan, Haina; Zhou, Yongfeng; Yan, Deyue

    2016-05-01

    Computer simulation has been becoming a versatile tool that can investigate detailed information from the microscopic scale to the mesoscopic scale. However, the crucial first step of molecular simulation is model building, particularly for hyperbranched polymers (HBPs) and hyperbranched multi-arm copolymers (HBMCs) with complex and various topological structures. Unlike well-defined polymers, not only the molar weight of HBPs/HBMCs with polydispersity, but the HBPs/HBMCs with the same degree of polymerization (DP) and degree of branching (DB) also have many possible topological structures, thus making difficulties for user to build model in molecular simulation. In order to build a bridge between model building and molecular simulation of HBPs and HBMCs, we developed HBP Builder, a C language open source HBPs/HBMCs building toolkit. HBP Builder implements an automated protocol to build various coarse-grained and fully atomistic structures of HBPs/HBMCs according to user’s specific requirements. Meanwhile, coarse-grained and fully atomistic output structures can be directly employed in popular simulation packages, including HOOMD, Tinker and Gromacs. Moreover, HBP Builder has an easy-to-use graphical user interface and the modular architecture, making it easy to extend and reuse it as a part of other program.

  12. Ultrasound irradiation based in-situ synthesis of star-like Tragacanth gum/zinc oxide nanoparticles on cotton fabric.

    Science.gov (United States)

    Ghayempour, Soraya; Montazer, Majid

    2017-01-01

    Application of natural biopolymers for green and safe synthesis of zinc oxide nanoparticles on the textiles is a novel and interesting approach. The present study offers the use of natural biopolymer, Tragacanth gum, as the reducing, stabilizing and binding agent for in-situ synthesis of zinc oxide nanoparticles on the cotton fabric. Ultrasonic irradiation leads to clean and easy synthesis of zinc oxide nanoparticles in short-time at low-temperature. FESEM/EDX, XRD, FT-IR spectroscopy, DSC, photocatalytic activities and antimicrobial assay are used to characterize Tragacanth gum/zinc oxide nanoparticles coated cotton fabric. The analysis confirmed synthesis of star-like zinc oxide nanoparticles with hexagonal wurtzite structure on the cotton fabric with the average particle size of 62nm. The finished cotton fabric showed a good photocatalytic activity on degradation of methylene blue and 100% antimicrobial properties with inhibition zone of 3.3±0.1, 3.1±0.1 and 3.0±0.1mm against Staphylococcus aureus, Escherichia coli and Candida albicans.

  13. Formation of nanophases in epoxy thermosets containing amphiphilic block copolymers with linear and star-like topologies.

    Science.gov (United States)

    Wang, Lei; Zhang, Chongyin; Cong, Houluo; Li, Lei; Zheng, Sixun; Li, Xiuhong; Wang, Jie

    2013-07-11

    In this work, we investigated the effect of topological structures of block copolymers on the formation of the nanophase in epoxy thermosets containing amphiphilic block copolymers. Two block copolymers composed of poly(ε-caprolactone) (PCL) and poly(2,2,2-trifluoroethyl acrylate) (PTFEA) blocks were synthesized to possess linear and star-shaped topologies. The star-shaped block copolymer composed a polyhedral oligomeric silsesquioxane (POSS) core and eight poly(ε-caprolactone)-block-poly(2,2,2-trifluoroethyl acrylate) (PCL-b-PTFEA) diblock copolymer arms. Both block copolymers were synthesized via the combination of ring-opening polymerization and reversible addition-fragmentation chain transfer/macromolecular design via the interchange of xanthate (RAFT/MADIX) process; they were controlled to have identical compositions of copolymerization and lengths of blocks. Upon incorporating both block copolymers into epoxy thermosets, the spherical PTFEA nanophases were formed in all the cases. However, the sizes of PTFEA nanophases from the star-like block copolymer were significantly lower than those from the linear diblock copolymer. The difference in the nanostructures gave rise to the different glass transition behavior of the nanostructured thermosets. The dependence of PTFEA nanophases on the topologies of block copolymers is interpreted in terms of the conformation of the miscible subchain (viz. PCL) at the surface of PTFEA microdomains and the restriction of POSS cages on the demixing of the thermoset-philic block (viz. PCL).

  14. 基于多臂赌博机模型的信道选择%Channel Selection Based on Multi-armed Bandit

    Institute of Scientific and Technical Information of China (English)

    朱江; 陈红翠; 熊加毫

    2015-01-01

    In the opportunistic spectrum access( OSA) system,in order to solve the problem of channel se-lection without the priori channel statistic information,a novel channel selection strategy is proposed which applies improved upper confidence bound(UCB) based on multi-armed bandit(MAB). Through adding the revenue variance into the confidence factor of UCB index,the proposed strategy can effectively adjust the exploration process of unknown channel environment and reduce the cost of exploration. It is theoreti-cally proved that the proposed strategy has a faster convergent speed and its learning regret curve with time slot is approximately logarithmic and can bring a slower growing rate. The simulation results show that, compared with UCB index algorithm and greedy algorithm,the proposed strategy can adaptively select the channel with better availability,effectively reduce the learning regret and accelerate the convergent speed, thus improving the system throughput.%在择机频谱接入系统中,为解决未知信道环境先验知识下的信道选择问题,提出了一种基于多臂赌博机( MAB )模型的改进 UCB ( Upper Confidence Bound ) 索引选择策略. 该策略是通过在UCB索引的置信因子中引入收益方差值来调整对未知信道环境的探索过程,以降低探索成本. 结合理论证明了本策略有较快的收敛速度,还证明了本策略下的学习后悔值曲线与时隙呈近似对数关系而较缓慢增长. 仿真结果表明,与原UCB策略以及贪心算法相比,所提策略更能自适应地选择可用性较好的信道,有效降低学习后悔值并加快其收敛速度,从而提高了系统吞吐量.

  15. Nano-photo active cellulosic fabric through in situ phytosynthesis of star-like Ag/ZnO nanocomposites: Investigation and optimization of attributes associated with photocatalytic activity.

    Science.gov (United States)

    Aladpoosh, Razieh; Montazer, Majid

    2016-05-05

    In this study, nano-photo active cellulosic fabric was prepared through in situ phytosynthesis of star-like Ag/ZnO nanocomposites using the ashes of Seidlitzia rosmarinus plants so-called Keliab. This is provided alkali media as a vital condition for synthesis of nanocomposites, further increasing the reduce-ability of cellulosic chains by activation of hydroxyl groups. The intermolecular dehydrolysis of intermediates ions under thermal and alkaline conditions leads to formation of Ag/ZnO heterostructure. Various analytical techniques were employed to confirm Ag/ZnO nanocomposites on the cotton fabric. The surface morphology, crystal phase and chemical structure of the treated fabrics were characterized by field emission and scanning electron microscopy (FE-SEM and SEM), X-ray diffraction (XRD), and energy dispersive X-ray spectroscopy (EDX). Moreover, influence of precursors: silver nitrate, zinc acetate and Keliab solution on attributes associated with photocatalytic activities including self-cleaning, whiteness and wettability was investigated via central composite design (CCD). The treated cotton samples exhibited self-cleaning activities through methylene blue degradation under day-light exposure along with improved wettability and whiteness. The prepared sample in optimized conditions showed good antibacterial activities against Staphylococcus aureus and Escherichia coli with enhanced fabric tensile strength.

  16. Formation of Star-Like and Core-Shell AuAg Nanoparticles during Two- and Three-Step Preparation in Batch and in Microfluidic Systems

    Directory of Open Access Journals (Sweden)

    J. Michael Köhler

    2007-01-01

    Full Text Available Regular dendrit-like metal nanoparticles and core-shell nanoparticles were formed by the reduction of mixtures of tetrachloroaurate and silver nitrate solutions with ascorbic acid at room temperature in two- and three-step procedures. The formation of these particles was found in batch experiments as well as in micro flow-through processes using static micromixers. The characteristic diameters of 4-branched star particles were in the range between 60 and 100 nm. The typical particles consist of four metal cores which are embedded in a common shell. Additionally, particles with five and more metallic cores were formed, to some extent, and aggregates of the 4-branched particles also were formed. Larger aggregates and network-like structures of connected star particles were formed after sedimentation. The properties of the formed particles are dependent on the educt concentrations as well as on the order of mixing steps and on the time interval between them. Obviously, the relation of nucleation and particle growth in relation to the concentrations of metal ions determines the composition and the properties of formed nanoparticles. So, star-like particles are observed in case of nucleation of Au in absence of silver ions but with silver deposition after short nucleation time. Spherical core shell particles are formed in case of silver salt addition after complete reduction of tetrachloroaurate in flow-through experiments with sufficient residence time between both mixing steps. Polymer layers are always found in the form of a second outer shell even if the polymer solutions are added in an early stage of particle formation.

  17. Research of multi-arm caliper logging tool imaging based on VC++%基于VC++的多臂井径测井成像软件研究

    Institute of Scientific and Technical Information of China (English)

    朱晓娇; 高嵩; 陈超波; 何宁

    2011-01-01

    In order to meet the demand of test results of the oil well casing during logging in the engineering and production, the article introduces how to draw the curve of the casing diameter and gray-scale image real time, by the object-oriented, database and digital image processing techniques through the multi-arm caliper logging tool casing test data. Experimental results show that curve and image of the casing displayed provide more intuitive, clear information on down hole casing. It lay a good foundation to the interpretation and evaluation of oil and it can improve the efficiency of oil well casing detection.%在工程和生产测井中,为满足油井套管检测资料清晰和直观的需求。详细阐述了如何借助数据库、数字图像处理及面向对象等软件技术,将多臂井径测井仪检测到的套管数据,以曲线及灰度图像方式实时绘制在PC屏幕上。实验结果表明,曲线及图像显示的内容清晰、直观地反映了井下套管情况,给油井的解释和评价打下了良好基础,提高了油井套管检测的效率。

  18. Flexible trial design in practice - stopping arms for lack-of-benefit and adding research arms mid-trial in STAMPEDE: a multi-arm multi-stage randomized controlled trial.

    Science.gov (United States)

    Sydes, Matthew R; Parmar, Mahesh K B; Mason, Malcolm D; Clarke, Noel W; Amos, Claire; Anderson, John; de Bono, Johann; Dearnaley, David P; Dwyer, John; Green, Charlene; Jovic, Gordana; Ritchie, Alastair W S; Russell, J Martin; Sanders, Karen; Thalmann, George; James, Nicholas D

    2012-09-15

    Systemic Therapy for Advanced or Metastatic Prostate cancer: Evaluation of Drug Efficacy (STAMPEDE) is a randomized controlled trial that follows a novel multi-arm, multi-stage (MAMS) design. We describe methodological and practical issues arising with (1) stopping recruitment to research arms following a pre-planned intermediate analysis and (2) adding a new research arm during the trial. STAMPEDE recruits men who have locally advanced or metastatic prostate cancer who are starting standard long-term hormone therapy. Originally there were five research and one control arms, each undergoing a pilot stage (focus: safety, feasibility), three intermediate 'activity' stages (focus: failure-free survival), and a final 'efficacy' stage (focus: overall survival). Lack-of-sufficient-activity guidelines support the pairwise interim comparisons of each research arm against the control arm; these pre-defined activity cut-off becomes increasingly stringent over the stages. Accrual of further patients continues to the control arm and to those research arms showing activity and an acceptable safety profile. The design facilitates adding new research arms should sufficiently interesting agents emerge. These new arms are compared only to contemporaneously recruited control arm patients using the same intermediate guidelines in a time-delayed manner. The addition of new research arms is subject to adequate recruitment rates to support the overall trial aims. (1) Stopping Existing Therapy: After the second intermediate activity analysis, recruitment was discontinued to two research arms for lack-of-sufficient activity. Detailed preparations meant that changes were implemented swiftly at 100 international centers and recruitment continued seamlessly into Activity Stage III with 3 remaining research arms and the control arm. Further regulatory and ethical approvals were not required because this was already included in the initial trial design.(2) Adding New Therapy: An application to

  19. Flexible trial design in practice - stopping arms for lack-of-benefit and adding research arms mid-trial in STAMPEDE: a multi-arm multi-stage randomized controlled trial

    Directory of Open Access Journals (Sweden)

    Sydes Matthew R

    2012-09-01

    Full Text Available Abstract Background Systemic Therapy for Advanced or Metastatic Prostate cancer: Evaluation of Drug Efficacy (STAMPEDE is a randomized controlled trial that follows a novel multi-arm, multi-stage (MAMS design. We describe methodological and practical issues arising with (1 stopping recruitment to research arms following a pre-planned intermediate analysis and (2 adding a new research arm during the trial. Methods STAMPEDE recruits men who have locally advanced or metastatic prostate cancer who are starting standard long-term hormone therapy. Originally there were five research and one control arms, each undergoing a pilot stage (focus: safety, feasibility, three intermediate ‘activity’ stages (focus: failure-free survival, and a final ‘efficacy’ stage (focus: overall survival. Lack-of-sufficient-activity guidelines support the pairwise interim comparisons of each research arm against the control arm; these pre-defined activity cut-off becomes increasingly stringent over the stages. Accrual of further patients continues to the control arm and to those research arms showing activity and an acceptable safety profile. The design facilitates adding new research arms should sufficiently interesting agents emerge. These new arms are compared only to contemporaneously recruited control arm patients using the same intermediate guidelines in a time-delayed manner. The addition of new research arms is subject to adequate recruitment rates to support the overall trial aims. Results (1 Stopping Existing Therapy: After the second intermediate activity analysis, recruitment was discontinued to two research arms for lack-of-sufficient activity. Detailed preparations meant that changes were implemented swiftly at 100 international centers and recruitment continued seamlessly into Activity Stage III with 3 remaining research arms and the control arm. Further regulatory and ethical approvals were not required because this was already included in the

  20. Testing many treatments within a single protocol over 10 years at MRC Clinical Trials Unit at UCL: Multi-arm, multi-stage platform, umbrella and basket protocols.

    Science.gov (United States)

    Parmar, Mahesh Kb; Cafferty, Fay H; Sydes, Matthew R; Choodari-Oskooei, Babak; Langley, Ruth E; Brown, Louise; Phillips, Patrick Pj; Spears, Melissa R; Rowley, Sam; Kaplan, Richard; James, Nicholas D; Maughan, Timothy; Paton, Nicholas; Royston, Patrick J

    2017-08-01

    There is real need to change how we do some of our clinical trials, as currently the testing and development process is too slow, too costly and too failure-prone - often we find that a new treatment is no better than the current standard. Much of the focus on the development and testing pathway has been in improving the design of phase I and II trials. In this paper we present examples of new methods for improving the design of phase III trials (and the necessary lead up to them) as they are the most time-consuming and expensive part of the pathway. Key to all these methods is the aim to test many treatments and/or pose many therapeutic questions within one protocol. The four principles underlying these solutions are: evaluate many primary hypotheses/treatments within the same protocol if there is a pilot/feasibility/phase II part of the process, aim to have a seamless run through to the phase III part of the process whenever possible and appropriate, conduct an adaptive trial, with the adaptations being major ones such as adding or dropping arms in situations where we are considering subgroups of a specific disease, often biomarker-defined, aim to include questions testing new treatments in all (or most) subgroups, using an adaptive approach. We present some examples of the application of these principles to particular areas, and show how they have led us to develop and launch multi-arm, multi-stage platform, umbrella and basket protocols: STAMPEDE, TRUNCATE-TB, FOCUS-4 and Add-Aspirin. There are clear challenges when embarking on such protocols. They include the need: to garner large scale collaboration bringing large parts of the research community together; to obtain significant and long-term funding; to obtain long term commitment from the key research leaders; to ensure that responsibilities (and also acclaim) are shared as widely as possible; and to have operational structures and systems which allow the implementation of such long-term adaptive protocols

  1. The past and future evolution of a star like Betelgeuse

    CERN Document Server

    Meynet, Georges; Ekstrom, Sylvia; Georgy, Cyril; Groh, Jose; Maeder, Andre

    2013-01-01

    We discuss the physics and the evolution of a typical massive star passing through an evolutionary stage similar to that of Betelgeuse. After a brief introduction recalling various observed parameters of Betelgeuse, we discuss the Pre-Main-Sequence phase (PMS), the Main-Sequence (MS) phase, the physics governing the duration of the first crossing of the HR diagram, the red supergiant stage (RSG), the post-red supergiant phases and the final fate of solar metallicity stars with masses between 9 and 25 M$_\\odot$. We examine the impact of different initial rotation and of various prescriptions for the mass loss rates during the red supergiant phase. We show that, whatever the initial rotation rate (chosen between 0 and 0.7$\\times\\upsilon_{\\rm crit}$, $\\upsilon_{\\rm crit}$ being the surface equatorial velocity producing a centrifugal acceleration balancing exactly the gravity) and the mass loss rates during the RSG stage (varied between a standard value and 25 times that value), a 15 M$_\\odot$ star always ends it...

  2. On Integral Means of Star-Like Functions

    Indian Academy of Sciences (India)

    Larisa Gromova; Alexander Vasil'ev

    2002-11-01

    We study univalent holomorphic functions in the unit disk $U = \\{z:|z| < 1\\}$ of the form $f(z) = z + _{n=2}^∞ a_n z^n$ that satisfy the condition Re $zf'(z)/f(z) > $ with $ \\in [0, 1)$ in . Some integral means of such functions are estimated.

  3. Study of Multi-Armed Bandits for Energy Conservation in Cognitive Radio Sensor Networks

    Directory of Open Access Journals (Sweden)

    Juan Zhang

    2015-04-01

    Full Text Available Technological advances have led to the emergence of wireless sensor nodes in wireless networks. Sensor nodes are usually battery powered and hence have strict energy constraints. As a result, energy conservation is very important in the wireless sensor network protocol design and the limited power resources are the biggest challenge in wireless network channels. Link adaptation techniques improve the link quality by adjusting medium access control (MAC parameters such as frame size, data rate, and sleep time, thereby improving energy efficiency. In this paper we present an adaptive packet size strategy for energy efficient wireless sensor networks. The main goal is to reduce power consumption and extend the whole network life. In order to achieve this goal, the paper introduces the concept of a bounded MAB to find the optimal packet size to transfer by formulating different packet sizes for different arms under the channel condition. At the same time, in achieve fast convergence, we consider the bandwidth evaluation according to ACK. The experiment shows that the packet size is adaptive when the channel quality changes and our algorithm can obtain the optimal packet size. We observe that the MAB packet size adaptation scheme achieves the best energy efficiency across the whole simulation duration in comparison with the fixed frame size scheme, the random packet size and the extended Kalman filter (EKF.

  4. Optimal Path Planning for Multi-Arm, Multi-Link Robotic Manipulators

    Science.gov (United States)

    2008-12-01

    Hamiltonian yields: ( , , , , ) TH t H μ λ x u μ h (3) 8 Similarly, an end-point Lagrangian is given by TE E  ν e (4) where N eν . The...the control and state vectors 18 defined in Equation set (1515). Equation (17) defines the Lagrangian of the Hamiltonian , H...K. Millsaps Chairman, Department of Mechanical and Astronautical Engineering iv THIS PAGE INTENTIONALLY LEFT BLANK v ABSTRACT This

  5. Towards image guided robotic surgery: multi-arm tracking through hybrid localization

    Energy Technology Data Exchange (ETDEWEB)

    Kwartowitz, David Morgan [Vanderbilt University, Department of Biomedical Engineering, Nashville, TN (United States); Mayo Clinic, Biomedical Imaging Resource, Rochester, MN (United States); Miga, Michael I. [Vanderbilt University, Department of Biomedical Engineering, Nashville, TN (United States); Herrell, S.D. [Vanderbilt University, Department of Urology, Nashville, TN (United States); Galloway, Robert L. [Vanderbilt University, Department of Biomedical Engineering, Nashville, TN (United States); Vanderbilt University, Department of Surgery, Nashville, TN (United States); Vanderbilt University, Department of Neurological Surgery, Nashville, TN (United States)

    2009-05-15

    Use of the robotic assisted surgery has been increasing in recent years, due both the continuous increase in the number of applications and the clinical benefits that surgical robots can provide. Currently robotic assisted surgery relies on endoscopic video for navigation, providing only surface visualization, thus limiting subsurface vision. To be able to visualize and identify subsurface information, techniques in image-guidance can be used. As part of designing an image guidance system, all arms of the robot need to be co-localized in a common coordinate system. In order to track multiple arms in a common coordinate space, intrinsic and extrinsic tracking methods can be used. First, the intrinsic tracking of the daVinci, specifically of the setup joints is analyzed. Because of the inadequacy of the setup joints for co-localization a hybrid tracking method is designed and implemented to mitigate the inaccuracy of the setup joints. Different both optical and magnetic tracking methods are examined for setup joint localization. The hybrid localization method improved the localization accuracy of the setup joints. The inter-arm accuracy in hybrid localization was improved to 3.02 mm. This inter-arm error value was shown to be further reduced when the arms are co-registered, thus reducing common error. (orig.)

  6. Digital system for automatic control of multi-arm neutron spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Patwardhan, P.K.; Srivastava, H.M.L.; Chawla, H.K.

    1975-01-01

    A flexible system for automatic and Simultaneous control of a Multiarm Neutron Spectrometer has been designed, developed and installed at CIRUS Reactor at Trombay. It controls digitally up to a maximum of nine angular/linear position variable to an accuracy of 0.01/sup 0/. Each variable is associated with one slow speed fractional horsepower bidirectional induction motor. The system receives control data pertaining to the positions of these variable from a preprogrammed paper tape and generates the necessary movement of the motors to set the variable to the desired values. The system employs IC Technology, is computer compatible and has varied applications.

  7. Development of a Multi-Arm Mobile Robot for Nuclear Decommissioning Tasks

    Directory of Open Access Journals (Sweden)

    Mohamed J. Bakari

    2007-12-01

    Full Text Available This paper concerns the design of a two-arm mobile delivery platform for application within nuclear decommissioning tasks. The adoption of the human arm as a model of manoeuvrability, scale and dexterity is the starting point for operation of two seven-function arms within the context of nuclear decommissioning tasks, the selection of hardware and its integration, and the development of suitable control methods. The forward and inverse kinematics for the manipulators are derived and the proposed software architecture identified to control the movements of the arm joints and the performance of selected decommissioning tasks. We discuss the adoption of a BROKK demolition machine as a mobile platform and the integration with its hydraulic system to operate the two seven-function manipulators separately. The paper examines the modelling and development of a real-time control method using Proportional-Integral-Derivative (PID and Proportional-Integral-Plus (PIP control algorithms in the host computer with National Instruments functions and tools to control the manipulators and obtain feedback through wireless communication. Finally we consider the application of a third party device, such as a personal mobile phone, and its interface with LabVIEW software in order to operate the robot arms remotely.

  8. Study of multi-armed bandits for energy conservation in cognitive radio sensor networks.

    Science.gov (United States)

    Zhang, Juan; Jiang, Hong; Huang, Zhenhua; Chen, Chunmei; Jiang, Hesong

    2015-04-21

    Technological advances have led to the emergence of wireless sensor nodes in wireless networks. Sensor nodes are usually battery powered and hence have strict energy constraints. As a result, energy conservation is very important in the wireless sensor network protocol design and the limited power resources are the biggest challenge in wireless network channels. Link adaptation techniques improve the link quality by adjusting medium access control (MAC) parameters such as frame size, data rate, and sleep time, thereby improving energy efficiency. In this paper we present an adaptive packet size strategy for energy efficient wireless sensor networks. The main goal is to reduce power consumption and extend the whole network life. In order to achieve this goal, the paper introduces the concept of a bounded MAB to find the optimal packet size to transfer by formulating different packet sizes for different arms under the channel condition. At the same time, in achieve fast convergence, we consider the bandwidth evaluation according to ACK. The experiment shows that the packet size is adaptive when the channel quality changes and our algorithm can obtain the optimal packet size. We observe that the MAB packet size adaptation scheme achieves the best energy efficiency across the whole simulation duration in comparison with the fixed frame size scheme, the random packet size and the extended Kalman filter (EKF).

  9. Development of a Multi-Arm Mobile Robot for Nuclear Decommissioning Tasks

    Directory of Open Access Journals (Sweden)

    Mohamed J. Bakari

    2008-11-01

    Full Text Available This paper concerns the design of a two-arm mobile delivery platform for application within nuclear decommissioning tasks. The adoption of the human arm as a model of manoeuvrability, scale and dexterity is the starting point for operation of two seven-function arms within the context of nuclear decommissioning tasks, the selection of hardware and its integration, and the development of suitable control methods. The forward and inverse kinematics for the manipulators are derived and the proposed software architecture identified to control the movements of the arm joints and the performance of selected decommissioning tasks. We discuss the adoption of a BROKK demolition machine as a mobile platform and the integration with its hydraulic system to operate the two seven-function manipulators separately. The paper examines the modelling and development of a real-time control method using Proportional-Integral-Derivative (PID and Proportional-Integral-Plus (PIP control algorithms in the host computer with National Instruments functions and tools to control the manipulators and obtain feedback through wireless communication. Finally we consider the application of a third party device, such as a personal mobile phone, and its interface with LabVIEW software in order to operate the robot arms remotely.

  10. Form graphics construction of a double-plate framework that has an iso-rhomboidal star-like shape ФОРМОГРАФИЧЕСКОЕ ПОСТРОЕНИЕ ДВУХПЛАСТИНЧАТОГО КАРКАСА ИЗОРОМБОИДНОЙ ЗВЕЗДЧАТОЙ ФОРМЫ

    Directory of Open Access Journals (Sweden)

    Filin Yuriy Nikolaevich

    2013-01-01

    Full Text Available The author has generated an original solution of simulated surfaces of a doubleplate framework for the new iso-rhomboidal star-like shape that has 16 faces.The aforesaid solution was successfully applied in the construction of projectivegraphical images and in the design of basic models of plate frameworks generated in the form of two inter-crossing tetrahedrons.The bi-coloured solution has proven the original nature of the drawing thanks to the faces of both tetrahedrons. The computer simulation of images of new iso-rhomboidal star-like items contemplates a reliable transfer of separate dimensions of their faces and typical stripes of their lattices.Similarly, a bi-coloured plate framework for the new iso-rhomboidal star-like item may be produced. A 3D plate framework was successfully produced using the aforesaid drawings, inclusive of axonometric and graphic images of typical faces.Two types of plate modules were used in the design of the new iso-rhomboidal starlike shape. The new unique graphical solution implemented in the bi-coloured double-plate framework, produced using the module assembly method, has a practical importance for the purposes of design of landscape architecture products and major structural design projects.Изложено формографическое построение модели двухпластинчатого каркаса для новой 16-гранной изоромбоидной звездчатой формы, полученной на базе звездчатого изоромбоидного суперкомпакта, в свою очередь конструктивно образуемого парой частным образом пересекающихся правильных компонентных тетраэдров.

  11. Ultrafast Photophysics of Star-Like Molecules with Benzene and Triazine Core

    Institute of Scientific and Technical Information of China (English)

    FENG Wen-Ke; KONG sheng; XIAO Li-Xin; MENG Kang; WANG Shu-Feng; GONG Qi-Huang

    2009-01-01

    Static and transient spectroscopic characters of newly synthesized start-like molecules,1,3,5-tri(10-butyl-3-propenyl-10H-phenothiazine)-benzene(TP3B)and 2,4,6-tri(10-butyl-3-propenyl-10H-phenothiazine)-[1,3,5]triazine(TP3T),are studied using static,picosecond fluorescence and femtosecond transient absorption spectroscopy.The results show that when the benzene group is in the center,a large conjugation system is formed,while a fast electron transfer process happens when the center group is triazine.

  12. Structure analysis of adsorbed star-like polymers with GISAS and SFM

    CERN Document Server

    Wolkenhauer, M; Wunnicke, O; Stamm, M; Roovers, J; Krosigk, G V; Cubitt, R

    2002-01-01

    The lateral structures of dried adsorbed binary mixtures of star polymers were investigated. Blends of protonated and deuterated polybutadiene stars were prepared from cyclohexane solutions and adsorbed onto silicon substrates. The number of arms and the molecular weight of the arms was varied. With grazing incidence small angle scattering techniques (GISAS) and scanning force microscopy (SFM), different dominant in-plane length scales were determined. The morphology of these structures is dominated by blob-like structures created from single stars or agglomerates of star polymers. (orig.)

  13. Amine-functionalized, multi-arm star polymers: A novel platform for removing glyphosate from aqueous media.

    Science.gov (United States)

    Samuel, Lianna; Wang, Ran; Dubois, Geraud; Allen, Robert; Wojtecki, Rudy; La, Young-Hye

    2017-02-01

    We describe a novel method for efficiently removing glyphosate from aqueous media via adsorption onto highly functionalized star-shaped polymeric particles. These particles have a polystyrene core with more than 35 attached methacrylate polymer arms, each containing a plurality of pendant amines (poly(dimethylamino ethyl methacrylate): PDMAEMA) that are partially protonated in water. Kinetic studies demonstrate that these star-polymers successfully remove up to 93% of glyphosate present in aqueous solution (feed concentration: 5 ppm), within 10 min contact time, outperforming activated carbon, which removed 33% after 20 min. On these star-polymers, glyphosate adsorption closely follows the Langmuir model indicating monolayer coverage at most. Ionic interaction between the protonated amines and glyphosate's dissociated carboxylic and phosphoric acid groups lead to effective glyphosate capture even at feed concentrations below 1 ppm. Surface charge of these star polymers and dissociation of glyphosate are both influenced by pH, thus glyphosate removal efficiency increases from 63% to 93% when pH increases from 4.2 to 7.7. NMR studies conducted with butylamine as a proxy for these polymeric particles confirm that the amine group binds with both glyphosate's carboxylic and phosphoric acid groups when its concentrations are in a 2:1 or higher molar ratio with glyphosate. Copyright © 2016 Elsevier Ltd. All rights reserved.

  14. Drug-loaded pseudo-block copolymer micelles with a multi-armed star polymer as the micellar exterior

    Science.gov (United States)

    Xie, Chen; Zhang, Peng; Zhang, Zhengkui; Yang, Chenchen; Zhang, Jialiang; Wu, Wei; Jiang, Xiqun

    2015-07-01

    Supramolecular constructed pseudo block copolymer micelles based on β-cyclodextrin terminated 4 and 7 armed star poly(N-vinylpyrrolidone) and adamantane terminated linear poly(ε-caprolactone) were prepared. The size, morphology, stability and protein adsorption were experimentally examined. The micelles with 7 armed PVP chains as the micellar exterior showed the lowest amount of protein adsorption and the best stability in media. When cabazitaxel, a new taxane, was loaded into the micelles, 14.4% drug loading content and 85% encapsulation efficacy were achieved. In vitro cytotoxicity studies demonstrated that the cabazitaxel-loaded micelles show significant cytotoxicity against drug-resistant A2780/T cell lines. Biodistribution studies showed that the micelles can almost double the content of cargo in tumor sites compared with the free cargo. In vivo antitumor activity examinations indicated that cabazitaxel-loaded micelles show superior antitumor activity over free paclitaxel and free cabazitaxel.Supramolecular constructed pseudo block copolymer micelles based on β-cyclodextrin terminated 4 and 7 armed star poly(N-vinylpyrrolidone) and adamantane terminated linear poly(ε-caprolactone) were prepared. The size, morphology, stability and protein adsorption were experimentally examined. The micelles with 7 armed PVP chains as the micellar exterior showed the lowest amount of protein adsorption and the best stability in media. When cabazitaxel, a new taxane, was loaded into the micelles, 14.4% drug loading content and 85% encapsulation efficacy were achieved. In vitro cytotoxicity studies demonstrated that the cabazitaxel-loaded micelles show significant cytotoxicity against drug-resistant A2780/T cell lines. Biodistribution studies showed that the micelles can almost double the content of cargo in tumor sites compared with the free cargo. In vivo antitumor activity examinations indicated that cabazitaxel-loaded micelles show superior antitumor activity over free paclitaxel and free cabazitaxel. Electronic supplementary information (ESI) available: Synthetic procedures, tables and figures for the synthesized polymers. See DOI: 10.1039/c5nr02861b

  15. Methods for meta-analysis of pharmacodynamic dose-response data with application to multi-arm studies of alogliptin

    NARCIS (Netherlands)

    Langford, Oliver; Aronson, Jeffrey K; van Valkenhoef, Gert; Stevens, Richard J

    2016-01-01

    Standard methods for meta-analysis of dose-response data in epidemiology assume a model with a single scalar parameter, such as log-linear relationships between exposure and outcome; such models are implicitly unbounded. In contrast, in pharmacology, multi-parameter models, such as the widely used E

  16. Multi-arm multilateral haptics-based immersive tele-robotic system (HITS) for improvised explosive device disposal

    Science.gov (United States)

    Erickson, David; Lacheray, Hervé; Lai, Gilbert; Haddadi, Amir

    2014-06-01

    This paper presents the latest advancements of the Haptics-based Immersive Tele-robotic System (HITS) project, a next generation Improvised Explosive Device (IED) disposal (IEDD) robotic interface containing an immersive telepresence environment for a remotely-controlled three-articulated-robotic-arm system. While the haptic feedback enhances the operator's perception of the remote environment, a third teleoperated dexterous arm, equipped with multiple vision sensors and cameras, provides stereo vision with proper visual cues, and a 3D photo-realistic model of the potential IED. This decentralized system combines various capabilities including stable and scaled motion, singularity avoidance, cross-coupled hybrid control, active collision detection and avoidance, compliance control and constrained motion to provide a safe and intuitive control environment for the operators. Experimental results and validation of the current system are presented through various essential IEDD tasks. This project demonstrates that a two-armed anthropomorphic Explosive Ordnance Disposal (EOD) robot interface can achieve complex neutralization techniques against realistic IEDs without the operator approaching at any time.

  17. Seeing Stars Like Never Before: A Multi-Year Interferometric Imaging Study of Red Supergiants in the H-Band.

    Science.gov (United States)

    Norris, Ryan P.; Baron, Fabien

    2017-01-01

    As some of the largest stars, red supergiants (RSG) are ideal candidates for interferometric imaging. 3D radiative hydrodynamic (RHD) models suggest that RSG have large convection cells with lifetimes on the order of 1000s of days. Many imaging projects have hinted at the existence of these features but, until recently, we have lacked the angular resolution to directly compare models to observations. In this presentation, we discuss early results from a multi-year survey of red supergiants using the Michigan InfraRed Combinber (MIRC) on the Center for High Angular Resolution Astronomy (CHARA Array), which has a maximum baseline of 330 m. We will present H-band images of RSG spanning several years developed using a new machine learning based image reconstruction tool for interferometric data. We will also present fundamental parameters for the targets, and discuss the implications of these results on 1D model atmospheres and 3D RHD models of RSG.

  18. Fostering emotional, social, physical and educational wellbeing in rural India: the methods of a multi-arm randomized controlled trial of Girls First.

    Science.gov (United States)

    Leventhal, Katherine Sachs; DeMaria, Lisa M; Gillham, Jane; Andrew, Gracy; Peabody, John W; Leventhal, Steve

    2015-10-26

    There are 600 million girls in low and middle income countries (LMICs), many of whom are at great risk for poor health and education. There is thus great need for programs that can effectively improve wellbeing for these girls. Although many interventions have been developed to address these issues, most focus on health and education without integrating attention to social and emotional factors. This omission is unfortunate, as nascent evidence indicates that these factors are closely related to health and education. This paper describes the methods of a 4-arm randomized controlled trial among 3,560 adolescent girls in rural Bihar, India that tested whether adding an intervention targeting social-emotional issues (based on a "resilience framework") to an adolescent health intervention would improve emotional, social, physical, and educational wellbeing to a greater extent than its components and a control group. Study arms were: (1) Girls First, a combination of the Girls First Resilience Curriculum (RC) and the Girls First Health Curriculum (HC); (2) Girls First Resilience Curriculum (RC) alone; (3) Girls First Health Curriculum (HC) alone; and (4) a school-as-usual control group (SC). Seventy-six schools were randomized (19 per condition) and 74 local women with a tenth grade education were trained and monitored to facilitate the program. Quantitative data were collected from 3,560 girls over 4 assessment points with very low rates of participant attrition. Qualitative assessments were conducted with a subset of 99 girls and 27 facilitators. In this article, we discuss guiding principles that facilitated trial implementation, including integrating diverse local and non-local sources of knowledge, focusing on flexibility of planning and implementation, prioritizing systematic measurement selection, and striking a balance between scientific rigor and real-world feasibility. Clinicaltrials.gov NCT02429661 . Registered 24 April 2015.

  19. 中9-31井多臂井径和井温噪声资料综合解析%Interpretation Analysis Based on Multi-arm Caliper and Temperature & Noise Logging Data in Zhong 9-31 Well

    Institute of Scientific and Technical Information of China (English)

    王海莹; 王莱雪; 王娇莉

    2015-01-01

    Based on the temperature&noise logging data of Zhong 9-31 well, and combined with the MIT logging data of the same well in the same year, this paper disproved the original hypothesis, and drew the correct conclusion. The comprehensive interpretation of logging data can improve the accuracy of the interpretation results.%文章在中9-31井井温噪声测井资料分析基础上,结合同年同一管柱结构下的四十臂井径测井资料,对井温噪声测井资料中的矛盾点进行推论和证实,最后推翻最初假设,得出正确解释结论,实现测井资料综合解释,确保测井解释成果的准确性。

  20. 星状C60(CH3)x(PAN)x共聚物的光致发光研究%Photoluminescence Study of Star-like C60(CH3)x(PAN)x Copolymer

    Institute of Scientific and Technical Information of China (English)

    马国宏; 钱士雄; 陈彧; 蔡瑞芳; 赵太平; 叶学敏

    2000-01-01

    利用物理喷束淀积(PJD)技术制备C60(CH3)x(PAN)x共聚物的薄膜.这种共聚物中,C60分子位于星状结构的中心,聚丙烯腈(PAN)主链修饰在C60分子的周围.吸收及荧光光谱表明:C60分子与聚丙烯腈(PAN)有明显的相互作用,而且这种相互作用与PAN的链长有关.C60分子与PAN间存在一定的激发传递过程,从而导致PAN荧光的部分猝灭.

  1. 载阿霉素星型多臂PLGA-PEG嵌段共聚物纳米胶束的构建%Study on doxoru bicin-loaded star-shaped multi-arm PLGA-PEG-NH2 nanomicelles

    Institute of Scientific and Technical Information of China (English)

    陈旼旼; 赵顺新; 金旭; 宋存先; 张政朴; 马桂蕾

    2012-01-01

    Objective To develop doxorubicine-loaded nanomicelles based on a type of novel starshaped 4-arm PLGA-PEG-NH2 amphiphilic block copolymers.Methods 4s-(PLGA-PEG-NH2) synthesized by 4s-PLGA and (H2N-PEG-NH2) according to N,N'-dicyclohexylcarbodiimide(DCC) condensation reaction was demonstrated by 1H NMR spectroscopy and gel permeation chromatography(GPC); DOX-loaded 4s-(PLGA-PEG-NH2) nanomicelles were self-assembled by doxorubicin(DOX) and 4s-(PLGA-PEG-NH2) via emulsion-solvent evaporation method and characterized in terms of morphology,particle size and size distribution,drug loading,encapsulation efficacy,cell uptake and cytotoxicity studies.Results 4s-(PLGA-PEG-NH2) were capable of selfassembling into "core-shell" nanomicelles structure and encapsulating DOX into their hydrophobic cores.The mean size of DOX-loaded 4s-(PLGA-PEG-NH2) was nanometer size; drug loading and encapsulation efficacy were around 7.5% and 75.2%,respectively.Mean surface charge of the micelles was around -17.6 mV.In vitro cell uptake and cytotoxicity studies indicated that comparing to the DOX-loaded linear-(PLGA-PEG-PLGA)nanomicelles,DOX-loaded 4s-(PLGA-PEG-NH2) nanomicelles showed better performance in uptaking by HeLa cells and higher cytotoxicity to cancer cells.Conclusion 4s-(PLGA-PEG-NH2) amphiphilic block copolymers can be successfully used in encapsulating DOX,self-assembling "core-shell" nanomicelles in aqueous solvent.Therefore,4s-(PLGA-PEG-NH2) copolymers can be considered as a promising drug carrier in effectively carrying hydrophobic drug,improving the efficacy while reducing the side effect.%目的 利用星型多臂端氨基聚乙丙交酯/聚乙二醇[4s-( PLGA-PEG-NH2)]两亲性嵌段共聚物作为载体材料,构建抗肿瘤药物阿霉素纳米胶束载药体系.方法 合成聚合物4s-( PLGA-PEG-NH2),通过核磁共振氢谱(1H NMR)和凝胶渗透色谱(GPC)对其组成、结构及相对分子质量进行表征;采用溶剂挥发法制备阿霉素(DOX)聚合物纳米胶束,并通过透射电子显微镜(TEM)、粒径分析仪及荧光分析法对载药纳米胶束进行表征;对阿霉素载药纳米胶束在HeLa细胞中的摄取及细胞毒性进行了初步评价.结果 1H NMR与GPC测定结果表明:合成的共聚物符合设计的4s-( PLGA-PEG-NH2)结构;能成功物理包埋DOX药物分子在水溶液中自组装成核-壳结构的纳米胶束,载药量约为7.5%,包埋率约为75.2%,Zeta电位为-17.6 mV;体外细胞实验显示:载阿霉素星型4臂聚合物纳米胶束[DOX-loaded 4s-(PLGA-PEG-NH2)micelles]比载阿霉素线性聚合物纳米胶束[DOX-loaded linear-( PLGA-PEG-PLGA)micelles]可更有效地被HeLa细胞摄取,并对HeLa细胞的毒性更强.结论 4s-( PLGA-PEG-NH2)阿霉素载药纳米胶束可有效提高HeLa细胞的摄取率以及对HeLa细胞的杀伤率,提示其可作为一类新型的抗肿瘤药物递送载体.

  2. pH-sensitive micelles self-assembled from multi-arm star triblock co-polymers poly(ε-caprolactone)-b-poly(2-(diethylamino)ethyl methacrylate)-b-poly(poly(ethylene glycol) methyl ether methacrylate) for controlled anticancer drug delivery.

    Science.gov (United States)

    Yang, You Qiang; Zhao, Bin; Li, Zhen Dong; Lin, Wen Jing; Zhang, Can Yang; Guo, Xin Dong; Wang, Ju Fang; Zhang, Li Juan

    2013-08-01

    A series of amphiphilic 4- and 6-armed star triblock co-polymers poly(ε-caprolactone)-b-poly(2-(diethylamino)ethyl methacrylate)-b-poly(poly(ethylene glycol) methyl ether methacrylate) (4/6AS-PCL-b-PDEAEMA-b-PPEGMA) were developed by a combination of ring opening polymerization and continuous activators regenerated by electron transfer atom transfer radical polymerization. The critical micelle concentration values of the star co-polymers in aqueous solution were extremely low (2.2-4.0mgl(-1)), depending on the architecture of the co-polymers. The self-assembled blank and doxorubicin (DOX)-loaded three layer micelles were spherical in shape with an average size of 60-220nm determined by scanning electron microscopy and dynamic light scattering. The in vitro release behavior of DOX from the three layer micelles exhibited pH-dependent properties. The DOX release rate was significantly accelerated by decreasing the pH from 7.4 to 5.0, due to swelling of the micelles at lower pH values caused by the protonation of tertiary amine groups in DEAEMA in the middle layer of the micelles. The in vitro cytotoxicity of DOX-loaded micelles to HepG2 cells suggested that the 4/6AS-PCL-b-PDEAEMA-b-PPEGMA micelles could provide equivalent or even enhanced anticancer activity and bioavailability of DOX and thus a lower dosage is sufficient for the same therapeutic efficacy. The results demonstrate that the pH-sensitive multilayer micelles could have great potential application in delivering hydrophobic anticancer drugs for improved cancer therapy.

  3. Prospects for bandit solutions in sensor management

    OpenAIRE

    Pavlidis, N.; Adams, N.M.; Nicholson, M.; Hand, D J

    2010-01-01

    Sensor management in information-rich and dynamic environments can be posed as a sequential action selection problem with side information. To study such problems we employ the dynamic multi-armed bandit with covariates framework. In this generalization of the multi-armed bandit, the expected rewards are time-varying linear functions of the covariate vector. The learning goal is to associate the covariate with the optimal action at each instance, essentially learning to partition the covariat...

  4. On Finding the Largest Mean Among Many

    OpenAIRE

    Jamieson, Kevin; Malloy, Matthew; Nowak, Robert; Bubeck, Sebastien

    2013-01-01

    Sampling from distributions to find the one with the largest mean arises in a broad range of applications, and it can be mathematically modeled as a multi-armed bandit problem in which each distribution is associated with an arm. This paper studies the sample complexity of identifying the best arm (largest mean) in a multi-armed bandit problem. Motivated by large-scale applications, we are especially interested in identifying situations where the total number of samples that are necessary and...

  5. New Linear and Star-Shaped Thermogelling Poly([R]-3-hydroxybutyrate) Copolymers.

    Science.gov (United States)

    Barouti, Ghislaine; Liow, Sing Shy; Dou, Qingqing; Ye, Hongye; Orione, Clément; Guillaume, Sophie M; Loh, Xian Jun

    2016-07-18

    The synthesis of multi-arm poly([R]-3-hydroxybutyrate) (PHB)-based triblock copolymers (poly([R]-3-hydroxybutyrate)-b-poly(N-isopropylacrylamide)-b-[[poly(methyl ether methacrylate)-g-poly(ethylene glycol)]-co-[poly(methacrylate)-g-poly(propylene glycol)

  6. Pack Light on the Move: Exploitation and Exploration in a Dynamic Environment

    DEFF Research Database (Denmark)

    LiCalzi, Marco; Marchiori, Davide

    2014-01-01

    This paper revisits a recent study by Posen and Levinthal (Manag Sci 58:587–601, 2012) on the exploration/exploitation tradeoff for a multi-armed bandit problem, where the reward probabilities undergo random shocks. We show that their analysis suffers two shortcomings: it assumes that learning is...

  7. Lung-MAP Launches: First Precision Medicine Trial From National Clinical Trials Network

    Science.gov (United States)

    A unique public-private collaboration today announced the initiation of the Lung Cancer Master Protocol (Lung-MAP) trial, a multi-drug, multi-arm, biomarker-driven clinical trial for patients with advanced squamous cell lung cancer. Squamous cell carcinom

  8. Manipulability measure of dual-arm space robot and its application to design an optimal configuration

    Science.gov (United States)

    Zhang, Bo; Liang, Bin; Wang, Xueqian; Li, Gang; Chen, Zhang; Zhu, Xiaojun

    2016-11-01

    Coupling effect exists among different arms and the base in a multi-arm space robot. The manipulability measure of one arm can be affected by the base and the other arms, which has important effects on the configuration optimization, the singularity avoidance and the compliant control. The manipulability measure for a multi-arm space robot is more complex than that of a single-arm space robot. At present, the manipulability measure of a multi-arm space robot has not been studied. In the paper, a new concept of manipulability measure is applied to analyze the manipulability measure for a dual-arm space robot, especially for the manipulability measure of the mission arm subjecting to the influence from coupling effect of auxiliary arm and the base. Based on the manipulability measure of mission arm, a performance index is introduced and used to design and choose an optimization configuration for a dual-arm space robot. Finally, a plane dual-arm space robot is simulated, which is illustrated the influence of joint angles and the base attitude on mission arm's manipulability measure. Simulation results show that the proposed manipulability measure is useful for a multi-arm space robot and optimal configuration can be extended and applied to the coordinated soft rendezvous and docking and the target capture in the field of on-orbit servicing.

  9. A Note on Information-Directed Sampling and Thompson Sampling

    OpenAIRE

    Zhou, Li

    2015-01-01

    This note introduce three Bayesian style Multi-armed bandit algorithms: Information-directed sampling, Thompson Sampling and Generalized Thompson Sampling. The goal is to give an intuitive explanation for these three algorithms and their regret bounds, and provide some derivations that are omitted in the original papers.

  10. Radiogenomics Monitoring in Breast Cancer Identifies Metabolism and Immune Checkpoints as Early Actionable Mechanisms of Resistance to Anti-angiogenic Treatment

    Directory of Open Access Journals (Sweden)

    Shaveta Mehta

    2016-08-01

    These findings support that anti-angiogenesis trials should incorporate initial enrichment of patients with high Ktrans, and a range of targeted therapeutic options to meet potential early resistance pathways. Multi-arm adaptive trials are ongoing using molecular markers for targeted agents, but our results suggest this needs to be further modified by much earlier adaptation when using drugs affecting the tumor microenvironment.

  11. Stars rich in heavy metals tend to harbor planets

    CERN Multimedia

    2003-01-01

    "A comparison of 754 nearby stars like our Sun - some with planets and some without - shows definitively that the more iron and other metals there are in a star, the greater the chance it has a companion planet" (1 page).

  12. Dynamic Probing for Intrusion Detection under Resource Constraints

    Science.gov (United States)

    2013-06-01

    performance measure of regret, defined as the performance loss compared to that of a genie who knows the entire attack processes a priori and probes...performance as that of the omniscient genie . Index Terms—Intrusion detection, dynamic probing, non- stochastic multi-armed bandit, regret. I...dynamic probing strategy under the performance measure of regret, de ned as the performance loss compared to that of a genie who knows the entire attack

  13. Graphical Models for Bandit Problems

    CERN Document Server

    Amin, Kareem; Syed, Umar

    2012-01-01

    We introduce a rich class of graphical models for multi-armed bandit problems that permit both the state or context space and the action space to be very large, yet succinctly specify the payoffs for any context-action pair. Our main result is an algorithm for such models whose regret is bounded by the number of parameters and whose running time depends only on the treewidth of the graph substructure induced by the action space.

  14. Can Subjects be Guided to Optimal Decisions The Use of a Real-Time Training Intervention Model

    Science.gov (United States)

    2016-06-01

    GROUP CODE # Optimal Decision Making Demonstration # Military Wargaming, Convoy Route Selection # # Multi Arm Bandit (n=4) # In support of...root.bind(“ə>,” callback) app.mainloop() root.destroy() B. FEEDBACK GROUP CODE # Optimal Decision Making Demonstration 76 # Military... DECISIONS ? THE USE OF A REAL-TIME TRAINING INTERVENTION MODEL 5. FUNDING NUMBERS 6. AUTHOR(S) Travis D. Carlson 7. PERFORMING ORGANIZATION NAME(S) AND

  15. Autonomous Adaptive Acoustic Relay Positioning

    Science.gov (United States)

    2013-09-01

    equipment construction and repair tasks [51]. Commercial ROVs range from large, versatile work-class vehicles like Soil Machine Dynamics (SMD) QUANTUM and...range-only formation control using teams of heterogeneous vehicles with wifi and acoustic communications. Shankar and Chitre formulated the multi-armed...acoustic communication and sensing by marine robots. IEEE Journal of Oceanographic Engineering, 38:522–533, 2013. [43] S. Shankar and Chitre. Tuning

  16. Adaptive designs for sequential experiments

    Institute of Scientific and Technical Information of China (English)

    林正炎; 张立新

    2003-01-01

    Various adaptive designs have been proposed and applied to clinical trials, bioassay, psychophysics, etc.Adaptive designs are also useful in high cost engineering trials.More and more people have been paying attention to these design methods. This paper introduces several broad families of designs, such as the play-the-winner rule, randomized play-the-winner rule and its generalization to the multi-arm case, doubly biased coin adaptive design, Markov chain model.

  17. Alginate-Poly(ethylene glycol) Hybrid Microspheres for Primary Cell Microencapsulation

    OpenAIRE

    Redouan Mahou; Meier, Raphael P H; Bühler, Léo H.; Christine Wandrey

    2014-01-01

    The progress of medical therapies, which rely on the transplantation of microencapsulated living cells, depends on the quality of the encapsulating material. Such material has to be biocompatible, and the microencapsulation process must be simple and not harm the cells. Alginate-poly(ethylene glycol) hybrid microspheres (alg-PEG-M) were produced by combining ionotropic gelation of sodium alginate (Na-alg) using calcium ions with covalent crosslinking of vinyl sulfone-terminated multi-arm poly...

  18. Self-construction of complex forms in a simple chemical system

    Science.gov (United States)

    Maselko, Jerzy; Geldenhuys, Adeline; Miller, John; Atwood, David

    2003-05-01

    We observed spontaneous formation of very complex structures, measurable on the centimeter and millimeter scales, in a simple dual-component inorganic chemical system. The diffusion, convection, and chemical reactions self-organize in space and time and produce domes, multi-arms, or more complex structures with different spatial organization depending on the concentration of reagents in the aqueous environment into which the 'seed' is immersed.

  19. Proceedings of the 1986 IEEE international conference on robotics and automation

    Energy Technology Data Exchange (ETDEWEB)

    1986-01-01

    This book presents the papers given at a conference on robots. Topics considered at the conference included manipulator simulations and solutions, robot dynamics and control, control mechanization, multi-arm control and planning, computer vision, planning and scheduling for automated electronics manufacturing, machining simulation, programming, adaptive manipulator control, manipulator dynamics, advanced control techniques, robot control organization, advanced sensing techniques, advanced robot control concepts and mechanizations, machine vision techniques, and multiple view and motion in computer vision.

  20. Decision maker based on atomic switches

    OpenAIRE

    Song-Ju Kim; Tohru Tsuruoka; Tsuyoshi Hasegawa; Masashi Aono; Kazuya Terabe; Masakazu Aono

    2016-01-01

    We propose a simple model for an atomic switch-based decision maker (ASDM), and show that, as long as its total number of metal atoms is conserved when coupled with suitable operations, an atomic switch system provides a sophisticated ``decision-making'' capability that is known to be one of the most important intellectual abilities in human beings. We considered a popular decision-making problem studied in the context of reinforcement learning, the multi-armed bandit problem (MAB); the probl...

  1. Final Performance Report on Grant FA9550-07-1-0366 (Simulation-Based and Sampling Method for Global Optimization)

    Science.gov (United States)

    2010-01-25

    IEEE Transactions on Automatic Control , 52, 1349- 1355, 2007. • H.S. Chang, J. Hu, M.C. Fu, and S.I. Marcus, Adaptive Adversarial Multi...Armed Bandit Approach to Two-Person Zero-Sum Markov Games, IEEE Transactions on Automatic Control , forthcoming, 2010. • M. Chen, J.Q. Hu, and M.C. Fu...Perturbation Analysis of a Dynamic Priority Call Center, IEEE Transactions on Automatic Control , forthcoming, 2010. 15 • C.H.

  2. Apolipoprotein E genotyping by multiplex amplification refractory mutation system PCR with optimized conditions%优化的多重扩增阻滞突变系统-PCR对载脂蛋白E基因的简易分型

    Institute of Scientific and Technical Information of China (English)

    刘静; 刘建伟; 叶玲

    2011-01-01

    Objective To set up a simple method for apolipoprotein E (ApoE) genotyping by modifying the conditions of multiplex amplification refractory mutation system PCR (multi-ARMS-PCR). Methods Based on the principle of multi-ARMS-PCR and considering the faults existed in some published papers, new primers were designed to improve PCR conditions. DNA genome of peripheral white blood cells was used as the template. Four allele-specific oligonucleotide upstream primers, one common downstream primer and a pair of internal positive control primers were constructed. Multi-ARMS-PCR were performed with combination of different primers in 2 reaction tubes synchronously. Amplified multiplex products were electrophoresed on agarose gels containing ethidium bromide. Six ApoE genotypes were distinguished by the band sizes. Results Using the new primers,amplification efficiency and specificity were significantly increased and the misclassification was diminished due to removing the interference of non-specific bands. Conclusion The optimized multi-ARMS-PCR is an easy, time-saving, efficient and economical method for determination of ApoE genotypes applied in a minimally equipped laboratory.%目的 通过改进和优化多重扩增阻滞突变系统-PCR(multi-ARMS-PCR)条件,建立载脂蛋白E(ApoE)基因的简易分型方法.方法 基于multi-ARMS-PCR的原理和特点,针对文献报道方法中存在的缺陷和错误,重新设计或改进引物.以外周血白细胞基因组DNA为模板,应用4个等位基因特异性寡核酸上游引物、1个通用下游引物和一对内参引物,分A,B两个管同步进行多重PCR反应.PCR扩增产物经过琼脂糖凝胶电泳分离-EB染色,根据电泳带型的差异,实现对ApoE 6种基因型的判定.结果 新引物显著提高了扩增效率和反应特异性,排除了非特异条带的干扰,减少了ApoE基因分型的错判.结论 采用优化后的multi-ARMS-PCR方法对ApoE基因型进行鉴定,具有操作简便、时间短

  3. Dynamics of inequalities in geometric function theory

    Directory of Open Access Journals (Sweden)

    Reich Simeon

    2001-01-01

    Full Text Available A domain in the complex plane which is star-like with respect to a boundary point can be approximated by domains which are star-like with respect to interior points. This approximation process can be viewed dynamically as an evolution of the null points of the underlying holomorphic functions from the interior of the open unit disk towards a boundary point. We trace these dynamics analytically in terms of the Alexander–Nevanlinna and Robertson inequalities by using the framework of complex dynamical systems and hyperbolic monotonicity.

  4. Rollout Sampling Approximate Policy Iteration

    CERN Document Server

    Dimitrakakis, Christos

    2008-01-01

    Several researchers have recently investigated the connection between reinforcement learning and classification. We are motivated by proposals of approximate policy iteration schemes without value functions which focus on policy representation using classifiers and address policy learning as a supervised learning problem. This paper proposes variants of an improved policy iteration scheme which addresses the core sampling problem in evaluating a policy through simulation as a multi-armed bandit machine. The resulting algorithm offers comparable performance to the previous algorithm achieved, however, with significantly less computational effort. An order of magnitude improvement is demonstrated experimentally in two standard reinforcement learning domains: inverted pendulum and mountain-car.

  5. SYNTHESES AND OPTOELECTRONIC PROPERTIES OF A HEXA-ARMED FLUORENE-BENZENE COPOLYMER BASED ON 2,4,6,8,10,12-HEXABENZYL 2,4,6,8,10,12-HEXAAZAISOWURTZITANECAGED-CORE

    Institute of Scientific and Technical Information of China (English)

    Qian-jin Zhao; Wen-hui Wu; Qiao-li Niu; Jun-biao Peng; Yiu-wing Mai

    2009-01-01

    A novel kind of hexa-armed fluorene-benzene copolymer based on a hexaazaisowurtzitane core was synthesized through Suzuki coupling polycondensation.The introduction of this bulky caged-core could not only enhance the photoluminescence quantum efficiency,but also improve the electroluminescence properties,especially suppress the common green-color emission of polyfluorenes(PFs)material during device operation.These features can be attributed to the successful suppression of PF's chain aggregation which profits from the introduction of the bulky hexaazaisowurtzitane core and the design of multi-armed architecture.

  6. Thompson Sampling: An Optimal Finite Time Analysis

    CERN Document Server

    Kaufmann, Emilie; Munos, Rémi

    2012-01-01

    The question of the optimality of Thompson Sampling for solving the stochastic multi-armed bandit problem had been open since 1933. In this paper we answer it positively for the case of Bernoulli rewards by providing the first finite-time analysis that matches the asymptotic rate given in the Lai and Robbins lower bound for the cumulative regret. The proof is accompanied by a numerical comparison with other optimal policies, experiments that have been lacking in the literature until now for the Bernoulli case.

  7. Reviewing the observational evidence against long-lived spiral arms in galaxies

    CERN Document Server

    Martinez-Garcia, Eric E

    2013-01-01

    We review Foyle et al. (2011) previous results, by applying a Fourier intensity phases method to a nine object sample of galaxies. It was found that two of the objects (NGC 628 and NGC 5194), with strong two-arm patterns, present positive evidence for long-lived spirals. Only one of the objects (NGC 3627) shows the contrary evidence. As determined by an analysis of resolved mass maps, the rest of the objects can not be included in the analysis because they belong to flocculent and multi-arm type of spiral arms, which are not described by density wave theory.

  8. Adaptive designs for sequential experiments

    Institute of Scientific and Technical Information of China (English)

    林正炎; 张立新

    2003-01-01

    Various adaptive designe have been proposed and applied to clinical trials,bioassay,psycho-physics,etc.Adaptive designs are also useful in high cost engineering trials.More and More people have been paying attention to these desing methods.This paper introduces several broad families of designs,such as the play-the-winner rele,randomized play-the-winner rule and its generalization to the multi-arm case,doubly bi-ased coin adaptive design,Markov chain model.

  9. A modest proposal for dropping poor arms in clinical trials.

    Science.gov (United States)

    Proschan, Michael A; Dodd, Lori E

    2014-08-30

    This paper presents a simple procedure for clinical trials comparing several arms with control. Demand for streamlining the evaluation of new treatments has led to phase III clinical trials with more arms than would have been used in the past. In such a setting, it is reasonable that some arms may not perform as well as an active control. We introduce a simple procedure that takes advantage of negative results in some comparisons to lessen the required strength of evidence for other comparisons. We evaluate properties analytically and use them to support claims made about multi-arm multi-stage designs.

  10. Channel selection based on trust and multiarmed bandit in multiuser, multichannel cognitive radio networks.

    Science.gov (United States)

    Zeng, Fanzi; Shen, Xinwang

    2014-01-01

    This paper proposes a channel selection scheme for the multiuser, multichannel cognitive radio networks. This scheme formulates the channel selection as the multiarmed bandit problem, where cognitive radio users are compared to the players and channels to the arms. By simulation negotiation we can achieve the potential reward on each channel after it is selected for transmission; then the channel with the maximum accumulated rewards is formally chosen. To further improve the performance, the trust model is proposed and combined with multi-armed bandit to address the channel selection problem. Simulation results validate the proposed scheme.

  11. Channel Selection Based on Trust and Multiarmed Bandit in Multiuser, Multichannel Cognitive Radio Networks

    Directory of Open Access Journals (Sweden)

    Fanzi Zeng

    2014-01-01

    Full Text Available This paper proposes a channel selection scheme for the multiuser, multichannel cognitive radio networks. This scheme formulates the channel selection as the multiarmed bandit problem, where cognitive radio users are compared to the players and channels to the arms. By simulation negotiation we can achieve the potential reward on each channel after it is selected for transmission; then the channel with the maximum accumulated rewards is formally chosen. To further improve the performance, the trust model is proposed and combined with multi-armed bandit to address the channel selection problem. Simulation results validate the proposed scheme.

  12. Structure and Optimality of Myopic Policy in Opportunistic Access with Noisy Observations

    CERN Document Server

    Zhao, Qing

    2008-01-01

    A restless multi-armed bandit problem that arises in multichannel opportunistic communications is considered, where channels are modeled as independent and identical Gilbert-Elliot channels and channel state observations are subject to errors. A simple structure of the myopic policy is established under a certain condition on the false alarm probability of the channel state detector. It is shown that myopic actions can be obtained with a simple counting procedure without knowing the underlying Markovian model. The optimality of the myopic policy is proved for the case of two channels and conjectured based on simulations for the general case.

  13. X-ray emission from open star clusters with Spectrum-Rontgen-Gamma

    DEFF Research Database (Denmark)

    Singh, K.P.; Ojha, D.K.; Schnopper, H.W.;

    1998-01-01

    throughput of SPECTRUM-Rontgen-Gamma will help detect main sequence stars like Sun in middle-aged and old clusters. We will study the relationships between various parameters - age, rotation, abundance, UBV colors, X-ray luminosity, coronal temperature etc. X-ray spectra of younger and brighter populations...

  14. Interaction of a hydophobic weak polyelectrolyte star with an apolar surface

    NARCIS (Netherlands)

    Rudd, O.V.; Leermakers, F.A.M.; Birshtein, T.M.

    2014-01-01

    We consider star-like polymers with weak, that is, pH-dependent, hydrophobic polyelectrolyte arms. For low ionic strength conditions, a microphase-segregated quasimicellar structure is found, for which the star features a compact apolar core and a charged and swollen corona. This state is jump-like

  15. Reel Plastic Magic; A History of Films and Filmmaking in America.

    Science.gov (United States)

    Kardish, Laurence

    This topical history of American films begins with an explanation of how movies work and describes the earlier American films from the nickelodeons through D.W. Griffith. The development of the studios and the major American films of the 1920's through the 1950's is treated largely in terms of important stars, like Mary Pickford, Charlie Chaplin,…

  16. The properties of ten O-type stars in the low-metallicity galaxies IC 1613, WLM, and NGC 3109

    NARCIS (Netherlands)

    Tramper, F.; Sana, H.; de Koter, A.; Kaper, L.; Ramírez-Agudelo, O.H.

    2014-01-01

    Context. Massive stars likely played an important role in the reionization of the Universe, and the formation of the first black holes. They are potential progenitors of long-duration gamma-ray bursts, seen up to redshifts of about ten. Massive stars in low-metallicity environments in the local Univ

  17. Exploiting the energy source of the stars

    DEFF Research Database (Denmark)

    Rasmussen, Jesper; Jensen, Thomas; Jessen, Martin

    With increasing energy demands and a limited supply of fossil fuels, the need for efficient, clean, and sustainable energy sources grows ever more pressing. Nuclear fusion – the process from which stars like the Sun derive their energy – holds the potential to help address this challenge. To mimic...

  18. Physics and chemistry of gas in planetary nebulae

    NARCIS (Netherlands)

    Bernard Salas, Jeronimo

    2003-01-01

    Stars are born, live and die similarly to any human being in the Universe. This thesis deals with the final stages of evolution (life) experíenced by stars like our Sun prior to their death, the so-called Planetary Nebula phase. In 5 billion years our Sun also will experience this phase and will bec

  19. On a certain subclass of meromorphic univalent functions with fixed second positive coefficients

    Directory of Open Access Journals (Sweden)

    Firas Ghanim

    2010-03-01

    Full Text Available In the present paper, we consider the subclass of meromorphic univalent functions Sp*[k,α,β,c] with fixed second positive coefficient. The object of the present paper is to show coefficient estimates, onvex liner combinations, some distortion theorems, and redii of star likeness and convexity for f(z in the class Sp*[k,α,β,c].

  20. Distribuciones de masas de estrellas PG; DO y DB: posibles conexiones evolutivas

    Science.gov (United States)

    Panei, J. A.; Althaus, L. G.; Miller Bertolami, M. M.; García-Berro, E.; Córsico, A. H.; Romero, A. D.; Kepler, S. O.; Rohrmann, R. D.

    A 20 % of white dwarf stars has hydrogen deficient atmospheres, known like no-DA white dwarfs. The results of this work allow for the first time to study a possible evolutionary connection between different low mass and hydrogen deficient post-AGB stars, like DO white dwarfs, PG 1159, O(He), DB and RCrB, among others. FULL TEXT IN SPANISH

  1. Shape and phase control of CdS nanocrystals using cationic surfactant in noninjection synthesis

    Directory of Open Access Journals (Sweden)

    Zou Yu

    2011-01-01

    Full Text Available Abstract Monodispersed CdS nanocrystals with controllable shape and phase have been successfully synthesized in this study by adding cationic surfactant in noninjection synthesis system. With the increase of the amount of cetyltrimethylammonium chloride (CTAC added, the shape of the CdS nanocrystals changed from spherical to multi-armed, and the phase changed from zinc-blende to wurtzite. It was found that halide ion Cl- plays a key role in the transformation, and other halide ions such as Br- can also induce similar transformation. We proposed that the strong binding between Cd2+ and halide ions reduced the reactivity of the precursors, decreased the nuclei formed in the nucleation stage, and led to the high concentration of precursor in the growth stage, resulting in the increase of size and phase transformation of CdS nanocrystals. In addition, it was found that the multi-armed CdS nanocrystals lost quantum confinement effect because of the increase of the size with the increase of the concentration of CTAC.

  2. Computational design of chemically propelled catalytic nanorotors.

    Science.gov (United States)

    Chen, Yanping; Shi, Yunfeng

    2013-08-14

    We designed catalytic nanorotors and investigated the rotational motion and energy conversion efficiency using reactive molecular dynamics in two dimensions. First, a two-arm nanorotor was constructed by decorating a slender beam with catalysts asymmetrically on its two long edges, while fixing the beam center as the rotational axis. Autonomous rotation was observed for the two-arm nanorotor immersing in a fuel environment. Here fuel molecules undergo exothermic combination reaction facilitated by the catalysts. It was found that the angular velocity increases with the catalyst coverage parabolically, while the rotary nanomotor efficiency stays roughly constant. These observations are consistent with a single-collision-momentum-transfer-based propulsion model. Furthermore, multi-arm nanorotors (up to eight arms) were constructed by carving radially distributed arms followed by decorating catalysts. For multi-arm nanorotors, both the angular velocity and the efficiency decrease as the number of arms increases. These behaviors contradict the aforementioned model, which are likely due to the deceleration from secondary collisions between products and the nanorotor arms. Our simulation results show that the optimal design for a nanorotor that maximizes its angular velocity and the motor efficiency is a two-arm nanorotor with nearly full coverage of catalysts.

  3. Sharp Dichotomies for Regret Minimization in Metric Spaces

    CERN Document Server

    Kleinberg, Robert

    2009-01-01

    The Lipschitz multi-armed bandit (MAB) problem generalizes the classical multi-armed bandit problem by assuming one is given side information consisting of a priori upper bounds on the difference in expected payoff between certain pairs of strategies. Classical results of (Lai and Robbins 1985) and (Auer et al. 2002) imply a logarithmic regret bound for the Lipschitz MAB problem on finite metric spaces. Recent results on continuum-armed bandit problems and their generalizations imply lower bounds of $\\sqrt{t}$, or stronger, for many infinite metric spaces such as the unit interval. Is this dichotomy universal? We prove that the answer is yes: for every metric space, the optimal regret of a Lipschitz MAB algorithm is either bounded above by any $f\\in \\omega(\\log t)$, or bounded below by any $g\\in o(\\sqrt{t})$. Perhaps surprisingly, this dichotomy does not coincide with the distinction between finite and infinite metric spaces; instead it depends on whether the completion of the metric space is compact and coun...

  4. Method and apparatus for adaptive force and position control of manipulators

    Science.gov (United States)

    Seraji, Homayoun (Inventor)

    1995-01-01

    The described and improved multi-arm invention of this application presents three strategies for adaptive control of cooperative multi-arm robots which coordinate control over a common load. In the position-position control strategy, the adaptive controllers ensure that the end-effector positions of both arms track desired trajectories in Cartesian space despite unknown time-varying interaction forces exerted through a load. In the position-hybrid control strategy, the adaptive controller of one arm controls end-effector motions in the free directions and applied forces in the constraint directions; while the adaptive controller of the other arm ensures that the end-effector tracks desired position trajectories. In the hybrid-hybrid control strategy, the adaptive controllers ensure that both end-effectors track reference position trajectories while simultaneously applying desired forces on the load. In all three control strategies, the cross-coupling effects between the arms are treated as disturbances which are compensated for by the adaptive controllers while following desired commands in a common frame of reference. The adaptive controllers do not require the complex mathematical model of the arm dynamics or any knowledge of the arm dynamic parameters or the load parameters such as mass and stiffness. Circuits in the adaptive feedback and feedforward controllers are varied by novel adaptation laws.

  5. Robustness, Death of Spiral Wave in the Network of Neurons under Partial Ion Channel Block

    Institute of Scientific and Technical Information of China (English)

    MA Jun; HUANG Long; WANG Chun-Ni; PU Zhong-Sheng

    2013-01-01

    The development of spiral wave in a two-dimensional square array due to partial ion channel block (Potassium,Sodium) is investigated,the dynamics of the node is described by Hodgkin-Huxley neuron and these neurons are coupled with nearest neig(h)bor connection.The parameter ratio xNa (and xK),which defines the ratio of working ion channel number of sodium (potassium) to the total ion channel number of sodium (and potassium),is used to measure the shift conductance induced by channel block.The distribution of statistical variable R in the two-parameter phase space (parameter ratio vs.poisoning area) is extensively calculated to mark the parameter region for transition of spiral wave induced by partial ion channel block,the area with smaller factors of synchronization R is associated the parameter region that spiral wave keeps alive and robust to the channel poisoning.Spiral wave keeps alive when the poisoned area (potassium or sodium) and degree of intoxication are small,distinct transition (death,several spiral waves coexist or multi-arm spiral wave emergence) occurs under moderate ratio xNa (and xK) when the size of blocked area exceeds certain thresholds.Breakup of spiral wave occurs and multi-arm of spiral waves are observed when the channel noise is considered.

  6. Efficient Online Learning for Opportunistic Spectrum Access

    CERN Document Server

    Dai, Wenhan; Krishnamachari, Bhaskar

    2011-01-01

    The problem of opportunistic spectrum access in cognitive radio networks has been recently formulated as a non-Bayesian restless multi-armed bandit problem. In this problem, there are N arms (corresponding to channels) and one player (corresponding to a secondary user). The state of each arm evolves as a finite-state Markov chain with unknown parameters. At each time slot, the player can select K < N arms to play and receives state-dependent rewards (corresponding to the throughput obtained given the activity of primary users). The objective is to maximize the expected total rewards (i.e., total throughput) obtained over multiple plays. The performance of an algorithm for such a multi-armed bandit problem is measured in terms of regret, defined as the difference in expected reward compared to a model-aware genie who always plays the best K arms. In this paper, we propose a new continuous exploration and exploitation (CEE) algorithm for this problem. When no information is available about the dynamics of th...

  7. Channel Exploration and Exploitation with Imperfect Spectrum Sensing in Cognitive Radio Networks

    CERN Document Server

    Zhang, Zhou; Tan, Peng; Slevinsky, Jim

    2012-01-01

    In this paper, the problem of opportunistic channel sensing and access in cognitive radio networks when the sensing is imperfect and a secondary user has limited traffic to send at a time is investigated. Primary users' statistical information is assumed to be unknown, and therefore, a secondary user needs to learn the information online during channel sensing and access process, which means learning loss, also referred to as regret, is inevitable. In this research, the case when all potential channels can be sensed simultaneously is investigated first. The channel access process is modeled as a multi-armed bandit problem with side observation. And channel access rules are derived and theoretically proved to have asymptotically finite regret. Then the case when the secondary user can sense only a limited number of channels at a time is investigated. The channel sensing and access process is modeled as a bi-level multi-armed bandit problem. It is shown that any adaptive rule has at least logarithmic regret. Th...

  8. The pressure distribution in thermally bistable turbulent flows

    OpenAIRE

    2005-01-01

    We present a systematic numerical study of the effect of turbulent velocity fluctuations on the thermal pressure distribution in thermally bistable flows. The simulations employ a random turbulent driving generated in Fourier space rather than star-like heating. The turbulent fluctuations are characterized by their rms Mach number M and the energy injection wavenumber, k_for. Our results are consistent with the picture that as either of these parameters is increased, the local ratio of turbul...

  9. Statistical mechanics of confined quantum particles

    CERN Document Server

    Bannur, V M; Bannur, Vishnu M.

    2006-01-01

    We develop statistical mechanics and thermodynamics of Bose and Fermi systems in relativistic harmonic oscillator (RHO) confining potential, which may be applicable in quark gluon plasma (QGP), astrophysics, Bose-Einstein condensation (BEC), condensed matter physics etc. Detailed study of QGP system is carried out and compared with lattice results. Further, as an application, our equation of state (EoS) of QGP is used to study compact stars like quark star.

  10. Statistical Mechanics of Confined Quantum Particles

    Science.gov (United States)

    Bannur, Vishnu M.; Udayanandan, K. M.

    We develop statistical mechanics and thermodynamics of Bose and Fermi systems in relativistic harmonic oscillator (RHO) confining potential, which is applicable in quark gluon plasma (QGP), astrophysics, Bose-Einstein condensation (BEC) etc. Detailed study of QGP system is carried out and compared with lattice results. Furthermore, as an application, our equation of state (EoS) of QGP is used to study compact stars like quark star.

  11. Self-Assembled Monolayers: Star-Shaped Crystallographic Cracking of Localized Nanoporous Defects (Adv. Mater. 33/2015).

    Science.gov (United States)

    Renner, Frank Uwe; Ankah, Genesis Ngwa; Bashir, Asif; Ma, Duancheng; Biedermann, P Ulrich; Shrestha, Buddha Ratna; Nellessen, Monika; Khorashadizadeh, Anahita; Losada-Pérez, Patricia; Duarte, Maria Jazmin; Raabe, Dierk; Valtiner, Markus

    2015-09-02

    On page 4877, F. U. Renner, A. Bashir, M. Valtiner, and co-workers describe a star-like dealloying corrosion morphology that appears during the localized attack of smooth well-prepared Cu-Au surfaces. The surfaces are initially protected by thiol or selenol inhibitior films. Localized dealloying of Cu-Au produces nanoporous gold under stress and crystallographic cracks - thereby opening a new approach combining surface science with nanoscale mechanical testing.

  12. A Circumstellar Disk Observed around a Massive Star

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    @@ Although the formation process of low-mass stars like our Sun has been well understood, the birth of high-mass stars with more than eight solar masses still remains a mystery. A recent study by CAS astronomers and their collaborators from Japan and UK offered direct observational evidence for demystifying the puzzle. The work was published in the Sept. 1 issue of Nature.

  13. Dynamic control of gold nanoparticle morphology in a microchannel flow reactor by glucose reduction in aqueous sodium hydroxide solution.

    Science.gov (United States)

    Ishizaka, Takayuki; Ishigaki, Atsushi; Kawanami, Hajime; Suzuki, Akira; Suzuki, Toshishige M

    2012-02-01

    Continuous flow synthesis of gold nanoparticles was demonstrated using a microchannel reactor with glucose reduction in aqueous alkaline medium. Particle size, morphology, and visual/optical properties of the dispersion liquid were controlled dynamically by tuning of the rate of NaOH addition. Characteristic star-like nanoparticles formed spontaneously as a quasi-stable state, but they changed the morphology to round shape and showed spectral change over time.

  14. Biofluorescent Worlds: Biological fluorescence as a temporal biosignature for flare star worlds

    OpenAIRE

    O'Malley-James, Jack T.; Kaltenegger, Lisa

    2016-01-01

    Habitability for planets orbiting active stars has been questioned. Especially, planets in the Habitable Zone (HZ) of M-stars, like our closest star Proxima Centauri, experience temporal high-ultraviolet (UV) radiation. The high fraction of M-stars (75%) within the solar neighborhood, the high occurrence rate of rocky planets around M-stars, and the favorable contrast ratio between the star and a potentially habitable rocky planet, makes such planets interesting targets for upcoming observati...

  15. Resilin-like polypeptide-poly(ethylene gylcol) hybrid hydrogels for mechanically-demanding tissue engineering applications

    Science.gov (United States)

    McGann, Christopher Leland

    Technological progress in the life sciences and engineering has combined with important insights in the fields of biology and material science to make possible the development of biological substitutes which aim to restore function to damaged tissue. Numerous biomimetic hydrogels have been developed with the purpose of harnessing the regenerative capacity of cells and tissue through the rational deployment of biological signals. Aided by recombinant DNA technology and protein engineering methods, a new class of hydrogel precursor, the biosynthetic protein polymer, has demonstrated great promise towards the development of highly functional tissue engineering materials. In particular, protein polymers based upon resilin, a natural protein elastomer, have demonstrated outstanding mechanical properties that would have great value in soft tissue applications. This dissertation introduces hybrid hydrogels composed of recombinant resilin-like polypeptides (RLPs) cross-linked with multi-arm PEG macromers. Two different chemical strategies were employed to form RLP-PEG hydrogels: one utilized a Michael-type addition reaction between the thiols of cysteine residues present within the RLP and vinyl sulfone moieties functionalized on a multi-arm PEG macromer; the second system cross-links a norbornene-functionalized RLP with a thiol-functionalized multi-arm PEG macromer via a photoinitiated thiol-ene step polymerization. Oscillatory rheology and tensile testing confirmed the formation of elastic, resilient hydrogels in the RLP-PEG system cross-linked via Michael-type addition. These hydrogels supported the encapsulation and culture of both human aortic adventitial fibroblasts and human mesenchymal stem cells. Additionally, these RLP-PEG hydrogels exhibited phase separation behavior during cross-linking that led to the formation of a heterogeneous microstructure. Degradation could be triggered through incubation with matrix metalloproteinase. Photocross-linking was conferred to

  16. Properties of Neutron Star Critical Collapses

    Science.gov (United States)

    Wan, Mew-Bing

    2010-01-01

    Critical phenomena in gravitational collapse opened a new mathematical vista into the theory of general relativity and may ultimately entail fundamental physical implication in observations. However, at present, the dynamics of critical phenomena in gravitational collapse scenarios are still largely unknown. My thesis seeks to understand the properties of the threshold in the solution space of the Einstein field equations between the black hole and neutron star phases, understand the properties of the neutron star critical solution and clarify the implication of these results on realistic astrophysical scenarios. We develop a new set of neutron star-like initial data to establish the universality of the neutron star critical solution and analyze the structure of neutron star and neutron star-like critical collapses via the study of the phase spaces. We also study the different time scales involved in the neutron star critical solution and analyze the properties of the critical index via comparisons between neutron star and neutron star-like initial data. Finally, we explore the boundary of the attraction basin of the neutron star critical solution and its transition to a known set of non-critical fixed points.

  17. Cool Stars May Have Different Prebiotic Chemical Mix

    Science.gov (United States)

    2009-01-01

    NASA's Spitzer Space Telescope detected a prebiotic, or potentially life-forming, molecule called hydrogen cyanide (HCN) in the planet-forming disks around yellow stars like our sun, but not in the disks around cooler, reddish stars. The observations are plotted in this graph, called a spectrum, in which light from the gas in the disks around the stars has been split up into its basic components, or wavelengths. Data from stars like our sun are yellow, and data from cool stars are orange. Light wavelengths are shown on the X-axis, and the relative brightness of disk emission is shown on the Y-axis. The signature of a baseline molecule, called acetylene (C2H2), was seen for both types of stars, but hydrogen cyanide was seen only around stars like our sun. Hydrogen cyanide is an organic, nitrogen-containing molecule. Five hydrogen cyanide molecules can link up to form adenine, one of the four chemical bases of DNA.

  18. Contextual Bandits with Similarity Information

    CERN Document Server

    Slivkins, Aleksandrs

    2009-01-01

    In a multi-armed bandit (MAB) problem, an online algorithm makes a sequence of choices. In each round it chooses from a time-invariant set of alternatives and receives the payoff associated with this alternative. While the case of small strategy sets is by now well-understood, a lot of recent work has focused on MAB problems with exponentially or infinitely large strategy sets, where one needs to assume extra structure in order to make the problem tractable. In particular, recent literature considered information on similarity between arms. We consider similarity information in the setting of "contextual bandits", a natural extension of the basic MAB problem where before each round an algorithm is given the "context" -- a hint about the payoffs in this round. Contextual bandits are directly motivated by placing advertisements on webpages, one of the crucial problems in sponsored search. A particularly simple way to represent similarity information in the contextual bandit setting is via a "similarity distance...

  19. Single-photon decision maker

    CERN Document Server

    Naruse, Makoto; Drezet, Aurelien; Huant, Serge; Aono, Masashi; Hori, Hirokazu; Kim, Song-Ju

    2015-01-01

    Decision making is critical in our daily lives and for society in general and is finding evermore practical applications in information and communication technologies. Herein, we demonstrate experimentally that single photons can be used to make decisions in uncertain, dynamically changing environments. Using a nitrogen-vacancy in a nanodiamond as a single-photon source, we demonstrate the decision-making capability by solving the multi-armed bandit problem. This capability is directly and immediately associated with single-photon detection in the proposed architecture, leading to adequate and adaptive autonomous decision making. This study makes it possible to create systems that benefit from the quantum nature of light to perform practical and vital intelligent functions.

  20. Self-assembly of two-dimensional binary quasicrystals: a possible route to a DNA quasicrystal

    Science.gov (United States)

    Reinhardt, Aleks; Schreck, John S.; Romano, Flavio; Doye, Jonathan P. K.

    2017-01-01

    We use Monte Carlo simulations and free-energy techniques to show that binary solutions of penta- and hexavalent two-dimensional patchy particles can form thermodynamically stable quasicrystals even at very narrow patch widths, provided their patch interactions are chosen in an appropriate way. Such patchy particles can be thought of as a coarse-grained representation of DNA multi-arm ‘star’ motifs, which can be chosen to bond with one another very specifically by tuning the DNA sequences of the protruding arms. We explore several possible design strategies and conclude that DNA star tiles that are designed to interact with one another in a specific but not overly constrained way could potentially be used to construct soft quasicrystals in experiment. We verify that such star tiles can form stable dodecagonal motifs using oxDNA, a realistic coarse-grained model of DNA.

  1. UCB Algorithm for Exponential Distributions

    CERN Document Server

    Jouini, Wassim

    2012-01-01

    We introduce in this paper a new algorithm for Multi-Armed Bandit (MAB) problems. A machine learning paradigm popular within Cognitive Network related topics (e.g., Spectrum Sensing and Allocation). We focus on the case where the rewards are exponentially distributed, which is common when dealing with Rayleigh fading channels. This strategy, named Multiplicative Upper Confidence Bound (MUCB), associates a utility index to every available arm, and then selects the arm with the highest index. For every arm, the associated index is equal to the product of a multiplicative factor by the sample mean of the rewards collected by this arm. We show that the MUCB policy has a low complexity and is order optimal.

  2. Category theoretic analysis of single-photon decision maker

    CERN Document Server

    Kim, Makoto Naruse Song-Ju; Berthel, Martin; Drezet, Aurélien; Huant, Serge; Hori, Hirokazu

    2016-01-01

    Decision making is a vital function in the era of artificial intelligence; however, its physical realizations and their theoretical fundamentals are not yet known. In our former study [Sci. Rep. 5, 513253 (2015)], we demonstrated that single photons can be used to make decisions in uncertain, dynamically changing environments. The multi-armed bandit problem was successfully solved using the dual probabilistic and particle attributes of single photons. Herein, we present the category theoretic foundation of the single-photon-based decision making, including quantitative analysis that agrees well with the experimental results. The category theoretic model unveils complex interdependencies of the entities of the subject matter in the most simplified manner, including a dynamically changing environment. In particular, the octahedral structure in triangulated categories provides a clear understanding of the underlying mechanisms of the single-photon decision maker. This is the first demonstration of a category the...

  3. Cognitive Medium Access: Exploration, Exploitation and Competition

    CERN Document Server

    Lai, Lifeng; Jiang, Hai; Poor, H Vincent

    2007-01-01

    This paper establishes the equivalence between cognitive medium access and the competitive multi-armed bandit problem. First, the scenario in which a single cognitive user wishes to opportunistically exploit the availability of empty frequency bands in the spectrum with multiple bands is considered. In this scenario, the availability probability of each channel is unknown to the cognitive user a priori. Hence efficient medium access strategies must strike a balance between exploring the availability of other free channels and exploiting the opportunities identified thus far. By adopting a Bayesian approach for this classical bandit problem, the optimal medium access strategy is derived and its underlying recursive structure is illustrated via examples. To avoid the prohibitive computational complexity of the optimal strategy, a low complexity asymptotically optimal strategy is developed. The proposed strategy does not require any prior statistical knowledge about the traffic pattern on the different channels....

  4. Three-port mode-(de)interleaver in silicon waveguide

    Science.gov (United States)

    Chen, Weiwei; Wang, Pengjun; Yang, Jianyi

    2016-06-01

    We propose a three-port silicon mode-(de)interleaver (TSMIL) using an asymmetric multi-arm Y-junction to flexibly address optical modes and efficiently increase the ports with less cascaded stages in mode-division multiplexing transmission. The design criteria developed for multi-port mode-(de)interleaving is presented. The qualitative functionality of the device is mainly determined by the widths of the arms. The example of a six-mode TSMIL is designed and analyzed in detail. Numerical simulations show that a low excess loss (<1 dB) and a low mode crosstalk (<-17 dB) over a 60 nm wavelength range can be obtained.

  5. A Restless Bandit Formulation of Multi-channel Opportunistic Access: Indexablity and Index Policy

    CERN Document Server

    Liu, Keqin

    2008-01-01

    We focus on an opportunistic communication system consisting of multiple independent channels with time-varying states. With limited sensing, a user can only sense and access a subset of channels and accrue rewards determined by the states of the sensed channels. We formulate the problem of optimal sequential channel selection as a restless multi-armed bandit process, for which a powerful index policy--Whittle's index policy--can be implemented based on the indexability of the system. Exploiting the underlying structure of the multi-channel opportunistic access problem, we establish the indexability and obtain Whittle's index in closed-form for both discounted reward and average reward criteria. These results lead to the direct implementation of Whittle's index policy with remarkably low complexity. Furthermore, we develop a simple approach to evaluate the optimal performance under a relaxed constraint on sensing actions, which provides an upper bound of the optimal performance of the original restless multi-...

  6. Self-assembly of two-dimensional binary quasicrystals: A possible route to a DNA quasicrystal

    CERN Document Server

    Reinhardt, Aleks; Romano, Flavio; Doye, Jonathan P K

    2016-01-01

    We use Monte Carlo simulations and free-energy techniques to show that binary solutions of penta- and hexavalent two-dimensional patchy particles can form thermodynamically stable quasicrystals even at very narrow patch widths, provided their patch interactions are chosen in an appropriate way. Such patchy particles can be thought of as a coarse-grained representation of DNA multi-arm `star' motifs, which can be chosen to bond with one another very specifically by tuning the DNA sequences of the protruding arms. We explore several possible design strategies and conclude that DNA star tiles that are designed to interact with one another in a specific but not overly constrained way could potentially be used to construct soft quasicrystals in experiment. We verify that such star tiles can form stable dodecagonal motifs using oxDNA, a realistic coarse-grained model of DNA.

  7. Infomax strategies for an optimal balance between exploration and exploitation

    CERN Document Server

    Reddy, Gautam; Vergassola, Massimo

    2016-01-01

    Proper balance between exploitation and exploration is what makes good decisions, which achieve high rewards like payoff or evolutionary fitness. The Infomax principle postulates that maximization of information directs the function of diverse systems, from living systems to artificial neural networks. While specific applications are successful, the validity of information as a proxy for reward remains unclear. Here, we consider the multi-armed bandit decision problem, which features arms (slot-machines) of unknown probabilities of success and a player trying to maximize cumulative payoff by choosing the sequence of arms to play. We show that an Infomax strategy (Info-p) which optimally gathers information on the highest mean reward among the arms saturates known optimal bounds and compares favorably to existing policies. The highest mean reward considered by Info-p is not the quantity actually needed for the choice of the arm to play, yet it allows for optimal tradeoffs between exploration and exploitation.

  8. Radial migration and its effects on the thin and thick disks

    CERN Document Server

    Vera-Ciro, Carlos; Navarro, Julio; Abadi, Mario

    2014-01-01

    We study the radial migration of stars driven by recurring multi-arm spiral features in an exponential disk embedded in a dark matter halo. The spiral perturbations redistribute angular momentum within the disk and lead to substantial radial displacements of individual stars, in a manner that largely preserves the circularity of their orbits and that results, after 5 Gyr (~40 full rotations at the disk scalelength), in little radial heating and no appreciable changes to the vertical or radial structure of the disk. Our results suggest that the radial displacements are driven by Sellwood & Binney's corotation scattering process and clarify a number of issues related to the spatial distribution and kinematics of migrators. In particular, we find that migrators are a heavily biased subset of stars with preferentially low vertical velocity dispersions. This "provenance bias" for migrators is not surprising in hindsight, for stars with small vertical excursions spend more time near the disk plane and thus resp...

  9. Decision making based on optical excitation transfer via near-field interactions between quantum dots

    CERN Document Server

    Naruse, Makoto; Aono, Masashi; Ohtsu, Motoichi; Sonnefraud, Yannick; Drezet, Aurélien; Huant, Serge; Kim, Song-Ju

    2014-01-01

    Optical near-field interactions between nanostructured matter, such as quantum dots, result in unidirectional optical excitation transfer when energy dissipation is induced. This results in versatile spatiotemporal dynamics of the optical excitation, which can be controlled by engineering the dissipation processes and exploited to realize intelligent capabilities such as solution searching and decision making. Here we experimentally demonstrate the ability to solve a decision making problem on the basis of optical excitation transfer via near-field interactions by using colloidal quantum dots of different sizes, formed on a geometry-controlled substrate. We characterize the energy transfer behavior due to multiple control light patterns and experimentally demonstrate the ability to solve the multi-armed bandit problem. Our work makes a decisive step towards the practical design of nanophotonic systems capable of efficient decision making, one of the most important intellectual attributes of the human brain.

  10. Self-perpetuating Spiral Arms in Disk Galaxies

    Science.gov (United States)

    D'Onghia, Elena; Vogelsberger, Mark; Hernquist, Lars

    2013-03-01

    The causes of spiral structure in galaxies remain uncertain. Leaving aside the grand bisymmetric spirals with their own well-known complications, here we consider the possibility that multi-armed spiral features originate from density inhomogeneities orbiting within disks. Using high-resolution N-body simulations, we follow the motions of stars under the influence of gravity, and show that mass concentrations with properties similar to those of giant molecular clouds can induce the development of spiral arms through a process termed swing amplification. However, unlike in earlier work, we demonstrate that the eventual response of the disk can be highly non-linear, significantly modifying the formation and longevity of the resulting patterns. Contrary to expectations, ragged spiral structures can thus survive at least in a statistical sense long after the original perturbing influence has been removed.

  11. Acoustic Array Development for Wind Turbine Noise Characterization

    Energy Technology Data Exchange (ETDEWEB)

    Buck, S.; Roadman, J.; Moriarty, P.; Palo, S.

    2013-11-01

    This report discusses the design and use of a multi-arm, logarithmic spiral acoustic array by the National Renewable Energy Laboratory (NREL) for measurement and characterization of wind turbine-generated noise. The array was developed in collaboration with a team from the University of Colorado Boulder. This design process is a continuation of the elliptical array design work done by Simley. A description of the array system design process is presented, including array shape design, mechanical design, design of electronics and the data acquisition system, and development of post-processing software. System testing and calibration methods are detailed. Results from the initial data acquisition campaign are offered and discussed. Issues faced during this initial deployment of the array are presented and potential remedies discussed.

  12. Optimality of Myopic Sensing in Multi-Channel Opportunistic Access

    CERN Document Server

    Ahmad, Sahand H A; Javidi, Tara; Zhao, Qing; Krishnamachari, Bhaskar

    2008-01-01

    We consider opportunistic communications over multiple channels where the state ("good" or "bad") of each channel evolves as independent and identically distributed Markov processes. A user, with limited sensing and access capability, chooses one channel to sense and subsequently access (based on the sensed channel state) in each time slot. A reward is obtained when the user senses and accesses a "good" channel. The objective is to design the optimal channel selection policy that maximizes the expected reward accrued over time. This problem can be generally cast as a Partially Observable Markov Decision Process (POMDP) or a restless multi-armed bandit process, to which optimal solutions are often intractable. We show in this paper that the myopic policy, with a simple and robust structure, achieves optimality under certain conditions. This result finds applications in opportunistic communications in fading environment, cognitive radio networks for spectrum overlay, and resource-constrained jamming and anti-ja...

  13. From Bandits to Experts: On the Value of Side-Observations

    CERN Document Server

    Mannor, Shie

    2011-01-01

    We consider an adversarial online learning setting where a decision maker can choose an action in every stage of the game. In addition to observing the reward of the chosen action, the decision maker gets side observations on the reward he would have obtained had he chosen some of the other actions. The observation structure is encoded as a graph, where node $i$ is linked to node $j$ if sampling $i$ provides information on the reward of $j$. This setting naturally interpolates between the well-known "experts" setting, where the decision maker can view all rewards, and the multi-armed bandits setting, where the decision maker can only view the reward of the chosen action. We develop practical algorithms with provable regret guarantees, as well as partially-matching lower bounds. The regret depends on non-trivial graph theoretic properties of the information feedback structure, and reveals an interesting trade-off between regret optimality and computational efficiency.

  14. Hedging Strategies for Bayesian Optimization

    CERN Document Server

    Brochu, Eric; de Freitas, Nando

    2010-01-01

    Bayesian optimization with Gaussian processes has become an increasingly popular tool in the machine learning community. It is efficient and can be used when very little is known about the objective function, making it popular in expensive black-box optimization scenarios. It is able to do this by sampling the objective using an acquisition function which incorporates the model's estimate of the objective and the uncertainty at any given point. However, there are several different parameterized acquisition functions in the literature, and it is often unclear which one to use. Instead of using a single acquisition function, we adopt a portfolio of acquisition functions governed by an online multi-armed bandit strategy. We describe the method, which we call GP-Hedge, and show that this method almost always outperforms the best individual acquisition function.

  15. Trajectory generation of space telerobots

    Science.gov (United States)

    Lumia, R.; Wavering, A. J.

    1989-01-01

    The purpose is to review a variety of trajectory generation techniques which may be applied to space telerobots and to identify problems which need to be addressed in future telerobot motion control systems. As a starting point for the development of motion generation systems for space telerobots, the operation and limitations of traditional path-oriented trajectory generation approaches are discussed. This discussion leads to a description of more advanced techniques which have been demonstrated in research laboratories, and their potential applicability to space telerobots. Examples of this work include systems that incorporate sensory-interactive motion capability and optimal motion planning. Additional considerations which need to be addressed for motion control of a space telerobot are described, such as redundancy resolution and the description and generation of constrained and multi-armed cooperative motions. A task decomposition module for a hierarchical telerobot control system which will serve as a testbed for trajectory generation approaches which address these issues is also discussed briefly.

  16. Collaboration and Coordination in Secondary Networks for Opportunistic Spectrum Access

    CERN Document Server

    Jouini, Wassim; Bononi, Luciano; Moy, Christophe

    2012-01-01

    In this paper, we address the general case of a coordinated secondary network willing to exploit communication opportunities left vacant by a licensed primary network. Since secondary users (SU) usually have no prior knowledge on the environment, they need to learn the availability of each channel through sensing techniques, which however can be prone to detection errors. We argue that cooperation among secondary users can enable efficient learning and coordination mechanisms in order to maximize the spectrum exploitation by SUs, while minimizing the impact on the primary network. To this goal, we provide three novel contributions in this paper. First, we formulate the spectrum selection in secondary networks as an instance of the Multi-Armed Bandit (MAB) problem, and we extend the analysis to the collaboration learning case, in which each SU learns the spectrum occupation, and shares this information with other SUs. We show that collaboration among SUs can mitigate the impact of sensing errors on system perf...

  17. Self-Perpetuating Spiral Arms in Disk Galaxies

    CERN Document Server

    D'Onghia, Elena; Hernquist, Lars

    2012-01-01

    The precise nature of spiral structure in galaxies remains uncertain. Recent studies suggest that spiral arms result from interactions between disks and satellite galaxies. Instead, leaving aside the grand bisymmetric spirals, here we consider the possibility that the multi-armed spiral features originate from density inhomogeneities orbiting within disks. Using high-resolution N-body simulations, we follow the motions of stars under the influence of gravity, and show that mass concentrations with properties similar to those of giant molecular clouds can induce the development of spiral arms through a process termed swing amplification. However, unlike in earlier work, we demonstrate that the eventual response of the disk can be highly non-linear, significantly modifying the formation and longevity of the resulting patterns. Contrary to expectations, ragged spiral structures can survive at least in a statistical sense long after the original perturbing influence has been removed. Our findings thus motivate a ...

  18. Ring Opening Metathesis Polymerization of Cyclopentene Using a Ruthenium Catalyst Confined by a Branched Polymer Architecture

    KAUST Repository

    Mugemana, Clement

    2016-03-22

    Multi-arm polystyrene stars functionalized with Grubbs-type catalysts in their cores were synthesized and used for the ring-opening metathesis polymerization (ROMP) of cyclopentene. The spatial confinement of the catalytic sites and the nanoscale phase separation between polystyrene and the growing polypentenamer chains lead to a dramatic inhibition of the ROMP termination and chain transfer steps. Consequently, cyclopentene polymerizations proceeded fast and with a high degree of conversion even in air. The Grubbs second generation catalyst was oxidatively inactivated under the same conditions. In contrast to conventional small-molecule catalysts, the ultimate degree of conversion of cyclopentene monomer and the polydispersity of the product polypentenamer are not affected by the temperature. This indicates that spatial confinement of the catalyst resulted in a significant change in the activation parameters for the alkene metathesis ring-opening.

  19. Making friends on the fly advances in ad hoc teamwork

    CERN Document Server

    Barrett, Samuel

    2015-01-01

    This book is devoted to the encounter and interaction of agents such as robots with other agents and describes how they cooperate with their previously unknown teammates, forming an Ad Hoc team. It presents a new algorithm, PLASTIC, that allows agents to quickly adapt to new teammates by reusing knowledge learned from previous teammates.  PLASTIC is instantiated in both a model-based approach, PLASTIC-Model, and a policy-based approach, PLASTIC-Policy.  In addition to reusing knowledge learned from previous teammates, PLASTIC also allows users to provide expert-knowledge and can use transfer learning (such as the new TwoStageTransfer algorithm) to quickly create models of new teammates when it has some information about its new teammates. The effectiveness of the algorithm is demonstrated on three domains, ranging from multi-armed bandits to simulated robot soccer games.

  20. Hierarchical construction of PbS architectures based on the adsorption and sustained release of H{sub 2}S by TBAB

    Energy Technology Data Exchange (ETDEWEB)

    Li Guowei [College of Material Science and Engineering, Jiangsu University, Zhenjiang, Jiangsu 212013 (China); Li Changsheng, E-mail: changshengli@ujs.edu.cn [College of Material Science and Engineering, Jiangsu University, Zhenjiang, Jiangsu 212013 (China); Yang Xiaofei [College of Material Science and Engineering, Jiangsu University, Zhenjiang, Jiangsu 212013 (China); Ng Dikon, H.L. [Department of Physics, Chinese University of Hong Kong, Shatin (Hong Kong); Tang Hua [College of Material Science and Engineering, Jiangsu University, Zhenjiang, Jiangsu 212013 (China)

    2011-10-03

    Graphical abstract: PbS uniform hierarchical microstars were grown on a large scale by a simple hydrothermal method with the help of a new surfactant: tetrabutyl ammonium bromide (C{sub 16}H{sub 36}BrN). A possible new formation mechanism of hierarchical hollow PbS structures based on the adsorption and sustained release of S{sup 2+} by TBAB is presented. Highlights: {yields} Multi-arm PbS hierarchical structures were successfully synthesized by a simple hydrothermal method at low temperature: 90 deg. C. {yields} A new surfactant: tetrabutyl ammonium bromide (TBAB) was used in the process, a possible new formation mechanism of hierarchical hollow PbS structures based on the adsorption and sustained release of S{sup 2+} by TBAB is presented. - Abstract: Multi-arm PbS architectures were successfully synthesized in high yield by a facile hydrothermal process at 90 deg. C for 48 h, employing lead nitrate (Pb(NO{sub 3}){sub 2}) and thioacetamide (TAA) as precursors. A new surfactant: tetrabutyl ammonium bromide (TBAB), was used in this process. The as-prepared PbS products are characterized by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and Fourier transform infrared (FT-IR) spectroscopy. The results showed that the concentration of TBAB, as well as the molar ratio of Pb(NO{sub 3}){sub 2} to TAA are crucial factors on the morphologies and sizes of the hierarchical PbS microcrystals. A reasonable possible new formation mechanism of hierarchical PbS structures based on the adsorption and sustained release of H{sub 2}S by TBAB has been presented.

  1. On the Effect of Particle Shape on Toxicity of CdS Nanomaterials Using Luminous Bacteria%发光细菌法检测不同形状CdS纳米材料毒性

    Institute of Scientific and Technical Information of China (English)

    隆异娟; 高梅; 梁立平; 郑鹄志

    2013-01-01

    采用发光细菌法考察了纳米材料的形状对其毒性的影响.通过对硫化镉(CdS)量子点、米粒状的硫化镉棒以及多臂硫化镉棒毒性的评价,发现多臂硫化镉棒在三者中尺寸最大,毒性最大;而粒径最小的硫化镉量子点毒性最小.实验证实,这3种硫化镉纳米粒子均可进入细菌,产生不同的毒性.紫外照射和维生素C实验证明了这几种硫化镉纳米材料的毒性差异与其形状有关,其原因在于不同形状的纳米粒子对细胞膜具有不同的刺伤能力.%The effect of particle shape on the toxicity of nanomaterials was investigated using luminous bacteria as a microbial sensor.CdS quantum dots (QDs),rice-like CdS nanorods and multi-armed nanorods were modified with dihydrolipoic acid (DHLA) and their toxicity was assayed,separately.Of the three CdS nanomaterials studied,multi-armed rods had the biggest size and the maximal toxicity,and QDs had the smallest size and the lowest toxicity.TEM confirmed that three kinds of CdS nanomaterials can all penetrate into bacterial cells.UV illumination and vitamin C exposure experiments showed that the mechanism of toxicity of quantum dots was different from that of nanorods.The shape-dependent toxicity of CdS nanomaterials can be attributed to their different capacity for impaling cell membranes.

  2. Design of fishnet metamaterials with broadband negative refractive index in the visible spectrum.

    Science.gov (United States)

    Zhou, Shiwei; Townsend, Scott; Xie, Yi Min; Huang, Xiaodong; Shen, Jianhu; Li, Qing

    2014-04-15

    We propose a technique capable of designing fishnet metamaterials that have a negative refractive index (NRI) over a broad range in the visible and infrared. The technique relies on optimizing the shape and scale of the fishnet apertures as well as the depth of different layers of the composite. A metamaterial is obtained that exhibits an unbroken 552 nm bandwidth of NRI, covering the entire red and infrared regions. Moreover, two fishnet structures perforated with star-like holes are found to render refractive index negative in the yellow and green spectra.

  3. Population genetic structure and historical demography of Oratosquilla oratoria revealed by mitochondrial DNA sequences.

    Science.gov (United States)

    Zhang, D; Ding, Ge; Ge, B; Zhang, H; Tang, B

    2012-12-01

    Genetic diversity, population genetic structure and molecular phylogeographic pattern of mantis shrimp Oratosquilla oratoria in Bohai Sea and South China Sea were analyzed by mitochondrial DNA sequences. Nucleotide and haplotype diversities were 0.00409-0.00669 and 0.894-0.953 respectively. Neighbor-Joining phylogenetic tree clustered two distinct lineages. Both phylogenetic tree and median-joining network showed the consistent genetic structure corresponding to geographical distribution. Mismatch distributions, negative neutral test and "star-like" network supported a sudden population expansion event. And the time was estimated about 44000 and 50000 years ago.

  4. Gold nanostars as thermoplasmonic nanoparticles for optical heating.

    Science.gov (United States)

    Rodríguez-Oliveros, R; Sánchez-Gil, José A

    2012-01-02

    Gold nanostars are theoretically studied as efficient thermal heaters at their corresponding localized surface-plasmon resonances (LSPRs). Numerical calculations are performed through the 3D Green's Theorem method to obtain the absorption and scattering cross sections for Au nanoparticles with star-like shape of varying symmetry and tip number. Their unique thermoplasmonic properties, with regard to their (red-shifted) LSPR wavelentgh, (∼ 30-fold increase) steady-state temperature, and scattering/absorption cross section ratios, make them specially suitable for optical heating and in turn for cancer thermal therapy.

  5. Morphology evolution of gold nanoparticles as function of time, temperature, and Au(III)/sodium ascorbate molar ratio

    Science.gov (United States)

    Priolisi, Ornella; Fabrizi, Alberto; Deon, Giovanna; Bonollo, Franco; Cattini, Stefano

    2016-01-01

    In this work the morphology evolution of Au nanoparticles (AuNPs), obtained by direct reduction, was studied as a function of time, temperature, and Au(III)/sodium ascorbate molar ratio. The NPs morphology was examined by transmission electron microscope with image analysis, while time evolution was investigated by visible and near-infrared absorption spectroscopy and dynamic light scattering. It is found that initially formed star-like NPs transform in more spheroidal particles and the evolution appears more rapid by increasing the temperature while a large amount of reducing agent prevents the remodeling of AuNPs. An explication of morphology evolution is proposed.

  6. Morphology evolution of gold nanoparticles as function of time, temperature, and Au(III)/sodium ascorbate molar ratio

    Energy Technology Data Exchange (ETDEWEB)

    Priolisi, Ornella, E-mail: ornella.priolisi@depretto.gov.it [ITIS “De Pretto” (Italy); Fabrizi, Alberto, E-mail: fabrizi@gest.unipd.it [University of Padova, Department of Management and Engineering (Italy); Deon, Giovanna, E-mail: giovanna.deon@depretto-vi.it [ITIS “De Pretto” (Italy); Bonollo, Franco, E-mail: bonollo@gest.unipd.it [University of Padova, Department of Management and Engineering (Italy); Cattini, Stefano, E-mail: stefano.cattini@unimore.it [University of Modena and Reggio Emilia, Department of Engineering Enzo Ferrari (Italy)

    2016-01-15

    In this work the morphology evolution of Au nanoparticles (AuNPs), obtained by direct reduction, was studied as a function of time, temperature, and Au(III)/sodium ascorbate molar ratio. The NPs morphology was examined by transmission electron microscope with image analysis, while time evolution was investigated by visible and near-infrared absorption spectroscopy and dynamic light scattering. It is found that initially formed star-like NPs transform in more spheroidal particles and the evolution appears more rapid by increasing the temperature while a large amount of reducing agent prevents the remodeling of AuNPs. An explication of morphology evolution is proposed.

  7. THE PARAMETRIC REPRESENTATION FOR SPIRAL-LIKE MAPPINGS OF TYPE α ON BOUNDED BALANCED PSEUDOCONVEX DOMAINS

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Let Ω be a bounded balanced pseudoconvex domain in Cn that admits a plurisubhamonic defining function of class C2. The authors prove that if f is a spiral-like mapping of type α on Ω, then f can be expressed as a limiting form concerning a Schwarz mapping. Moreover, the characteristics for star-like mappings and spiral-like mappings of type α are obtained. As a direct application, the growth theorem for spiral-like mappings of type α is set up.

  8. The joy of discovery great encounters along the way

    CERN Document Server

    Thirring, Walter

    2011-01-01

    Walter Thirring is the last offspring of an Austrian family of scientists. In this moving narrative, he describes how he survived the Nazi occupation and became instrumental in reconstructing European science. Thirring is one of the last living physicists who worked on the greatest discoveries and with the greatest scientists of the 20th century. He recollects encounters with the old masters like Einstein, Schrodinger, Heisenberg, Pauli and others as well as his collaborations with the present stars like Murray Gell-Mann and Elliott Lieb. The book presents the challenges faced when one of the

  9. Hydrothermal growth of ZnO nanoflowers and their photocatalyst application

    Indian Academy of Sciences (India)

    Jincheng Fan; Tengfei Li; Hang Heng

    2016-02-01

    ZnO nanoflowers were prepared by the hydrothermal method and studied by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy and photoluminescence. ZnO nanoflowers with star-like morphology were of pure wurtzite phase. The edges of the petals were composed of assemblies of smaller nanocrystallites. Green and orange emissions in photoluminescence were attributed to O vacancies and O interstitials, respectively. Furthermore, ZnO nanoflowers demonstrated the effective photocatalytic activities, and O vacancies and O interstitials were considered to be the active sites of the ZnO photocatalyst.

  10. Design and Development of Novel Hierarchically Ordered Block Copolymer-Magnetoelectric Particle Nanocomposites

    Science.gov (United States)

    2012-06-08

    dendrimers have been used as templates to prepare zerovalent metal NPs encapsulated within the dendrimer. 17 However, the synthesis of dendrimers... encapsulation of its precursors (e.g., FeCl2·4H2O:FeCl3·6H2O:ammonium hydroxide = 1:1:1 by mole for Fe3O4) within the innermost P4VP regime, followed...radical polymerization (ATRP), in which β- cyclodextrin (β-CD)-based star-like 21-Br--CD with 21 initiating sites was used as macroinitiator 16

  11. The X-Ray Environment During the Epoch of Terrestrial Planet Formation: Chandra Observations of h Persei

    CERN Document Server

    Currie, Thayne; Spitzbart, Brad; Irwin, Jonathan; Wolk, Scott J; Hernandez, Jesus; Kenyon, Scott J; Pasachoff, Jay

    2008-01-01

    We describe Chandra/ACIS-I observations of the massive ~ 13--14 Myr-old cluster, h Persei, part of the famous Double Cluster (h and chi Persei) in Perseus. Combining the list of Chandra-detected sources with new optical/IR photometry and optical spectroscopy reveals ~ 165 X-ray bright stars with V 1.5 Msun) fall out of X-ray saturation by ~ 10--15 Myr. Changes in stellar structure for > 1.5 Msun stars likely play an important role in this decline of X-ray emission.

  12. Gelatin-assisted hydrothermal synthesis of single crystalline zinc oxide nanostars and their photocatalytic properties.

    Science.gov (United States)

    Fang, Ke-Ming; Wang, Zhen-Zhen; Zhang, Ming; Wang, Ai-Jun; Meng, Zi-Yan; Feng, Jiu-Ju

    2013-07-15

    Biotemplate-assisted approach is simple and friendly to the environment. With the assistance of gelatin as a soft biotemplate and a structure-directing agent, star-like zinc oxide (ZnO) nanostructures have been prepared by assembly of well-defined nanorods under hydrothermal conditions. Their morphology and structures were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The growth mechanism of the ZnO nanostars is also investigated. The as-prepared ZnO nanostars display high photocatalytic activity toward the degradation of methyl orange (MO) under ultraviolet (UV) irradiation.

  13. Cytochrome b sequence data suggest rapid speciation within the Paramecium aurelia species complex.

    Science.gov (United States)

    Barth, Dana; Przyboś, Ewa; Fokin, Sergei I; Schlegel, Martin; Berendonk, Thomas U

    2008-11-01

    We investigated mitochondrial Cytochrome b sequences from all 15 members of the enigmatic Paramecium aurelia species complex (Ciliophora). The analysis revealed high genetic distances between the different P. aurelia species (6.1-19.8%) and a largely unresolved, star-like phylogenetic tree. This result strongly supports a rapid radiation in the evolutionary history of this species complex and it correlates well with the hypothesis that the extant species diversity may have originated from the neutral consequences of a whole genome duplication in the common ancestor of P. aurelia.

  14. Homes for extraterrestrial life: extrasolar planets.

    Science.gov (United States)

    Latham, D W

    2001-12-01

    Astronomers are now discovering giant planets orbiting other stars like the sun by the dozens. But none of these appears to be a small rocky planet like the earth, and thus these planets are unlikely to be capable of supporting life as we know it. The recent discovery of a system of three planets is especially significant because it supports the speculation that planetary systems, as opposed to single orbiting planets, may be common. Our ability to detect extrasolar planets will continue to improve, and space missions now in development should be able to detect earth-like planets.

  15. News and Views: Stellar baby boom in the young universe; School pupils observe and publish CV data; Neutron star with C atmosphere; Meeting on magma; Process for exoplanets; Floods off the charts

    Science.gov (United States)

    2009-12-01

    RESEARCH NOTES Gravitational lensing has allowed researchers to examine in detail one of the most distant known galaxies. They found a surprisingly high rate of star formation, with up to 50 stars like the Sun forming per year at the peak of the boom in starbirth. Time on a remote-control telescope has led to German secondary school students not only collecting useful data, but also being part of the team publishing the results in a professional journal. The neutron star at the heart of the Cassiopeia A supernova remnant has a thin carbon atmosphere, masking the X-ray emission that was expected, but not detected.

  16. News and Views: Very short GRBs may be Hawking radiation source; CubeSat for the UK: UKube1 seeks payloads; Galactic centre? It's just up there… There could be a lot of Earths out there

    Science.gov (United States)

    2010-12-01

    A particular group of gamma-ray bursts, those of very short duration, have characteristics that suggest they may be the signature of an evaporating primordial black hole - the Hawking radiation proposed by Stephen Hawking in 1974. The UK Space Agency is seeking small innovative payloads for the pilot UK CubeSat, UKube1. Planet-hunters have examined the distribution of exoplanets around stars like the Sun in our galaxy, and concluded that they can expect to find planets the size of Earth around a quarter of them - 46 billion or thereabouts.

  17. Density functional for ternary non-additive hard sphere mixtures.

    Science.gov (United States)

    Schmidt, Matthias

    2011-10-19

    Based on fundamental measure theory, a Helmholtz free energy density functional for three-component mixtures of hard spheres with general, non-additive interaction distances is constructed. The functional constitutes a generalization of the previously given theory for binary non-additive mixtures. The diagrammatic structure of the spatial integrals in both functionals is of star-like (or tree-like) topology. The ternary diagrams possess a higher degree of complexity than the binary diagrams. Results for partial pair correlation functions, obtained via the Ornstein-Zernike route from the second functional derivatives of the excess free energy functional, agree well with Monte Carlo simulation data. © 2011 IOP Publishing Ltd

  18. Ghost Images in Schmidt CCD Photometry

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The wide field of the Schmidt telescope implies a greater chance of the field containing bright objects, and the presence of a corrector lens produces a certain type of ghost images. We summarize and confirm the features of such ghost images in Schmidt CCD photometry. The ghost images could be star-like under special observational conditions. The zenith distance of the telescope, among other factors, is found to correlate with different patterns of the ghost images. Some relevant issues are discussed and possible applications of our results are suggested.

  19. Criteria for spectral classification of cool stars in the near-IR GAIA wavelength region

    CERN Document Server

    Boschi, F; Sordo, R; Marrese, P M

    2002-01-01

    The far-red portion of the spectrum offers bright prospects for an accurate classification of cool stars, like the giant components of symbiotic stars. The 8480--8740 Ang region, free from telluric absorptions and where the GAIA Cornerstone mission by ESA will record spectra for 3x10^8 stars, is investigated on the base of available observed and synthetic spectral atlases. We have identified and calibrated diagnostic line ratios useful to derive the effective temperature (spectral type) and gravity (luminosity class) for cool stars observed at spectral resolutions 10,000 <= lambda/delta-lambda <= 20,000, bracketing that eventually chosen for GAIA. A few are presented here.

  20. Kepler: NASA's First Mission Capable of Finding Earth-Size Planets

    Science.gov (United States)

    Borucki, William J.

    2009-01-01

    Kepler, a NASA Discovery mission, is a spaceborne telescope designed to search a nearby region of our galaxy for Earth-size planets orbiting in the habitable zone of stars like our sun. The habitable zone is that region around a start where the temperature permits water to be liquid on the surface of a planet. Liquid water is considered essential forth existence of life. Mission Phases: Six mission phases have been defined to describe the different periods of activity during Kepler's mission. These are: launch; commissioning; early science operations, science operations: and decommissioning

  1. Singularly perturbed hyperbolic problems on metric graphs: asymptotics of solutions

    Directory of Open Access Journals (Sweden)

    Golovaty Yuriy

    2017-04-01

    Full Text Available We are interested in the evolution phenomena on star-like networks composed of several branches which vary considerably in physical properties. The initial boundary value problem for singularly perturbed hyperbolic differential equation on a metric graph is studied. The hyperbolic equation becomes degenerate on a part of the graph as a small parameter goes to zero. In addition, the rates of degeneration may differ in different edges of the graph. Using the boundary layer method the complete asymptotic expansions of solutions are constructed and justified.

  2. Evolutionary Processes in Multiple Systems

    Energy Technology Data Exchange (ETDEWEB)

    Eggleton, P P; Kisseleva-Eggleton, L

    2006-02-14

    There are several ways in which triple stars can evolve in somewhat unusual ways. They discuss two situations where Case A Roche-lobe overflow, followed by a merger, can produce anomalous wide binaries such as {gamma} Per; and Kozai cycles in triples with non-parallel orbits, which can produce merged rapidly-rotating stars like AB Dor, and which can also lead to the delayed ejection of one component of a multiple, as may have been observed in T Tau in 1998.

  3. Clustering siRNA conjugates for MMP-responsive therapeutics in chronic wounds of diabetic animals

    Science.gov (United States)

    Kim, Hye Sung; Son, Young Ju; Yoo, Hyuk Sang

    2016-07-01

    The MMP-responsive breakdown of siRNA clusters was translated to site-specific gene transfection and enhanced wound healing in diabetic ulcers. MMP-2 siRNA was chemically tethered to the end of multi-armed PEG via MMP-cleavable linkers (4PEG-siRNA) and subsequently clustered into submicron particles complexed with LPEI. 4PEG-siRNA was more tightly complexed with LPEI and the associated cluster showed higher resistance against RNase attack, in comparison to naked siRNA. Because the size of the clusters increased depending on the increase in charge ratio of LPEI to siRNA, cellular uptake of the 4PEG-siRNA/LPEI cluster was significantly attenuated due to the huge size of the cluster. However, upon MMP treatment, the cluster dissociated into smaller particles and was efficiently endocytosed by cells. An in vivo fluorescence resonance energy transfer (FRET) study also revealed that the clusters were effectively dissociated in MMP-rich environments of dorsal wounds in diabetic animals. In addition, diabetic ulcers treated with the clusters showed a faster wound closure rate and the recovered tissue expressed a larger amount of cytokeratin along with a lower expression level of MMP-2 compared to the other groups.The MMP-responsive breakdown of siRNA clusters was translated to site-specific gene transfection and enhanced wound healing in diabetic ulcers. MMP-2 siRNA was chemically tethered to the end of multi-armed PEG via MMP-cleavable linkers (4PEG-siRNA) and subsequently clustered into submicron particles complexed with LPEI. 4PEG-siRNA was more tightly complexed with LPEI and the associated cluster showed higher resistance against RNase attack, in comparison to naked siRNA. Because the size of the clusters increased depending on the increase in charge ratio of LPEI to siRNA, cellular uptake of the 4PEG-siRNA/LPEI cluster was significantly attenuated due to the huge size of the cluster. However, upon MMP treatment, the cluster dissociated into smaller particles and was

  4. Designs for clinical trials with time-to-event outcomes based on stopping guidelines for lack of benefit

    Directory of Open Access Journals (Sweden)

    Choodari-Oskooei Babak

    2011-03-01

    Full Text Available Abstract background The pace of novel medical treatments and approaches to therapy has accelerated in recent years. Unfortunately, many potential therapeutic advances do not fulfil their promise when subjected to randomized controlled trials. It is therefore highly desirable to speed up the process of evaluating new treatment options, particularly in phase II and phase III trials. To help realize such an aim, in 2003, Royston and colleagues proposed a class of multi-arm, two-stage trial designs intended to eliminate poorly performing contenders at a first stage (point in time. Only treatments showing a predefined degree of advantage against a control treatment were allowed through to a second stage. Arms that survived the first-stage comparison on an intermediate outcome measure entered a second stage of patient accrual, culminating in comparisons against control on the definitive outcome measure. The intermediate outcome is typically on the causal pathway to the definitive outcome (i.e. the features that cause an intermediate event also tend to cause a definitive event, an example in cancer being progression-free and overall survival. Although the 2003 paper alluded to multi-arm trials, most of the essential design features concerned only two-arm trials. Here, we extend the two-arm designs to allow an arbitrary number of stages, thereby increasing flexibility by building in several 'looks' at the accumulating data. Such trials can terminate at any of the intermediate stages or the final stage. Methods We describe the trial design and the mathematics required to obtain the timing of the 'looks' and the overall significance level and power of the design. We support our results by extensive simulation studies. As an example, we discuss the design of the STAMPEDE trial in prostate cancer. Results The mathematical results on significance level and power are confirmed by the computer simulations. Our approach compares favourably with methodology

  5. Application of High Temperature Caliper-gamma-CCL Logging Tools to Jidong Oilfield%高温井径伽马磁定位组合测井仪在冀东油田的应用

    Institute of Scientific and Technical Information of China (English)

    刘大鹏

    2016-01-01

    The multi-arm caliper imaging logging tool is used to evaluate the casing damage, detect the quality of the perforation and the cas-ing. Since the two-time lifting and lowering of the tool can increase the intensity of labor, a type of gamma-CCL tool is designed to be com-bined with multi-arm caliper instrument. Hence one-time lowering of the tool could complete the extraction of well diameter, gamma and CCL signal. After the completion of the instrument, field experiments are carried out in Daqing oil field. It has been proved that the instru-ment can work stably and reliably under 150 /80MPa. The production taskes of 10 wells in Jidong oilfield show the new instrument can ac-curately measure the casing corrosion and deformation degree. It can provide detailed and reliable basis for monitoring casing conditions and prolonging the service life of the oil wells.%多臂井径成像测井仪是用来评价套损、检测射孔质量和检测套管状况的仪器。两次起下仪器增加劳动强度,设计一种伽马磁定位仪器,组合多臂井径仪器,一次下井完成井径、伽马和磁定位信号的录取。仪器研制完成后,在大庆油田进行了现场试验,仪器能在150℃/80 MPa下稳定、可靠地工作。在冀东油田完成10口井的生产任务,能准确地测量套管腐蚀变形程度。该仪器能为监测套管的状况,延长油水井的使用寿命,提供详实可靠的资料。

  6. The coolest 'stars' are free-floating planets

    CERN Document Server

    Joergens, V; Liu, Y; Bayo, A; Wolf, S

    2014-01-01

    We show that the coolest known object that is probably formed in a star-like mode is a free-floating planet. We discovered recently that the free-floating planetary mass object OTS,44 (M9.5, ~12 Jupiter masses, age ~2 Myr) has significant accretion and a substantial disk. This demonstrates that the processes that characterize the canonical star-like mode of formation apply to isolated objects down to a few Jupiter masses. We detected in VLT/SINFONI spectra that OTS44 has strong, broad, and variable Paschen beta emission. This is the first evidence for active accretion of a free-floating planet. The object allows us to study accretion and disk physics at the extreme and can be seen as free-floating analog of accreting planets that orbit stars. Our analysis of OTS44 shows that the mass-accretion rate decreases continuously from stars of several solar masses down to free-floating planets. We determined, furthermore, the disk mass (10 Earth masses) and further disk properties of OTS44 through modeling its SED inc...

  7. Dermoscopy of Pigmented Actinic Keratosis of the Face: A Study of 232 Cases.

    Science.gov (United States)

    Kelati, A; Baybay, H; Moscarella, E; Argenziano, G; Gallouj, S; Mernissi, F Z

    2017-07-11

    The diagnosis of pigmented actinic keratosis (PAK) is often challenging because of overlapping features with lentigo maligna. To investigate dermoscopic patterns of PAK according to their different evolutionary stages, and to correlate the pattern with clinical characteristics of the patients. Descriptive and analytical study of 232 PAK. Dermoscopic patterns were divided into two categories: the follicule surroundings' abnormalities (FSA) and follicular keratosis' abnormalities (FKA). FSA and FKA dermoscopic patterns were related to male gender, except for star-like appearance, double white clods and dermoscopic horn (p≤0.04). Rhomboidal, annular granular pattern, gray halo, white circle and double clods were dermoscopic pattern significantly related to xeroderma pigmentosum's type of skin. Based on the evolutionary stages of PAK, the jelly sign was significantly related to thin patches of PAK. Central crusts and scales were related to thick plaques and the star-like appearance to hypertrophic PAK. The presence of 2 or more dermoscopic signs in both FSA and FKA was noticed in 99.1% of lesions. The dermoscopic diagnosis of PAK vary according to the evolutionary stages of the disease, this will increase the diagnosis accuracy, with therapeutic implications. Copyright © 2017 AEDV. Publicado por Elsevier España, S.L.U. All rights reserved.

  8. Research on the evolution of stock correlation based on maximal spanning trees

    Science.gov (United States)

    Yang, Chunxia; Zhu, Xueshuai; Li, Qian; Chen, Yanhua; Deng, Qiangqiang

    2014-12-01

    In this study, we choose the daily closing price of 268 constituent stocks of the S&P 500 index, 221 stocks of London Stock Exchange, 148 constituent stocks of the Shanghai Composite index and 152 constituent stocks of the Hang Seng index as the research objects and select the sample of all the stock markets from 2 January, 2003, to 16 September, 2013. For each stock market, first, using a moving window to scan through every stock return series and mutual information to measure the statistical interdependence between stock returns, we construct a corresponding weighted network in every given window. Then we study the evolution of stock correlation by analyzing the average mutual information, mutual information distribution and topology structure’s variation of the maximal spanning tree extracting from every weighted network. All the obtained results indicate that for all the stock markets, both the average mutual information and the standard deviation of mutual information distribution first gradually increase and they reach a peak during the full-outbreak periods, and finally, they decrease again. In addition, the topology structure of the maximal spanning tree also changes from compact star-like to loose chain-like first and then turns to compact star-like once more. All the facts tell us that the crisis does change the stock correlation and the stock correlation is from weak to strong first, and then becomes weak again.

  9. Ferrimagnetism and spin excitation in a Ni–Mn partially inverted spinel prepared using a modified polymeric precursor method

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira, Rafael A. [Programa de Pos-Graduação em Ciência e Tecnologia de Materiais (POSMAT), Universidade Estadual Paulista, Faculdade de Ciências, Caixa Postal 473, 17033-360 Bauru, São Paulo (Brazil); Institut des Sciences Chimiques de Rennes – UMR 6226, Université de Rennes 1, F-35042 Rennes (France); Tedesco, Julio C.G.; Birk, Jonas O. [The Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen (Denmark); Kalceff, Walter, E-mail: wkalceff@uts.edu.au [School of Physics and Advanced Materials, University of Technology Sydney (UTS), P.O. Box 123, Broadway, NSW 2007 (Australia); Yokaichiya, Fabiano [Laboratório Nacional de Luz Síncrotron (LNLS), Caixa Postal 6192, CEP 13083-970 Campinas, São Paulo (Brazil); Comissao Nacional de Energia Nuclear (CNEN), Instituto de Pesquisas Energeticas e Nucleares (IPEN), Reactor Multiproposito Brasileiro - RMB, Avenida Lineo Prestes 2242, Bloco A, Cidade Universitaria Armando Salles de Oliveira, Sao Paulo (Brazil); Rasmussen, Nina [The Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen (Denmark); Peña, Octavio [Institut des Sciences Chimiques de Rennes – UMR 6226, Université de Rennes 1, F-35042 Rennes (France); Henry, Paul F. [European Spallation Source ESS AB, Box 176, 22100 Lund (Sweden); Simeoni, Giovanna G. [Heinz Maier-Leibnitz Zentrum (MLZ) and Physics Department, Technische Universität München, Lichtenbergstr. 1, 85748 Garching (Germany); Bordallo, Heloisa N. [The Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen (Denmark); European Spallation Source ESS AB, Box 176, 22100 Lund (Sweden); and others

    2014-07-01

    We demonstrate that a Ni–Mn oxide partially inverted spinel (Ni{sub 1−ν}Mn{sub ν})[Ni{sub ν}Mn{sub 2−ν}]O{sub 4} having inversion degree ν ≈ 0.8 and produced by a modified polymeric precursor method exhibits behaviour previously reported only in monophased samples. The structure of the specimen was determined using Rietveld analysis of X-ray and neutron powder diffraction data, showing that at room temperature the material crystallizes in the Fd3{sup ¯}m space group with a lattice constant a = 8.392 Å. Combining magnetization measurements with neutron powder diffraction, we show that the magnetic structure of this spinel is associated with the interplay between the ferromagnetic and antiferromagnetic lattices which coexist due to the cations' presence on both tetrahedral and octahedral sites. Our analysis of the neutron diffraction data confirms the postulated magnetic structure involving a star-like moment arrangement, arising from competition for the B (octahedral) spinel sites by the Ni and Mn cations. Finally, we show that strong magnetic fluctuations are observed in the inelastic neutron scattering data. - Highlights: • Ni–Mn oxide partially-inverted spinel made by modified polymeric precursor method. • Magnetic measurements showed a ferrimagnetic and a parasitic magnetic transition. • NPD revealed a magnetic structure consistent with a star-like moment arrangement. • INS measurements indicated four distinct temperature-dependent magnetic regimes.

  10. Bioprinting Cellularized Constructs Using a Tissue-specific Hydrogel Bioink.

    Science.gov (United States)

    Skardal, Aleksander; Devarasetty, Mahesh; Kang, Hyun-Wook; Seol, Young-Joon; Forsythe, Steven D; Bishop, Colin; Shupe, Thomas; Soker, Shay; Atala, Anthony

    2016-04-21

    Bioprinting has emerged as a versatile biofabrication approach for creating tissue engineered organ constructs. These constructs have potential use as organ replacements for implantation in patients, and also, when created on a smaller size scale as model "organoids" that can be used in in vitro systems for drug and toxicology screening. Despite development of a wide variety of bioprinting devices, application of bioprinting technology can be limited by the availability of materials that both expedite bioprinting procedures and support cell viability and function by providing tissue-specific cues. Here we describe a versatile hyaluronic acid (HA) and gelatin-based hydrogel system comprised of a multi-crosslinker, 2-stage crosslinking protocol, which can provide tissue specific biochemical signals and mimic the mechanical properties of in vivo tissues. Biochemical factors are provided by incorporating tissue-derived extracellular matrix materials, which include potent growth factors. Tissue mechanical properties are controlled combinations of PEG-based crosslinkers with varying molecular weights, geometries (linear or multi-arm), and functional groups to yield extrudable bioinks and final construct shear stiffness values over a wide range (100 Pa to 20 kPa). Using these parameters, hydrogel bioinks were used to bioprint primary liver spheroids in a liver-specific bioink to create in vitro liver constructs with high cell viability and measurable functional albumin and urea output. This methodology provides a general framework that can be adapted for future customization of hydrogels for biofabrication of a wide range of tissue construct types.

  11. Infomax Strategies for an Optimal Balance Between Exploration and Exploitation

    Science.gov (United States)

    Reddy, Gautam; Celani, Antonio; Vergassola, Massimo

    2016-06-01

    Proper balance between exploitation and exploration is what makes good decisions that achieve high reward, like payoff or evolutionary fitness. The Infomax principle postulates that maximization of information directs the function of diverse systems, from living systems to artificial neural networks. While specific applications turn out to be successful, the validity of information as a proxy for reward remains unclear. Here, we consider the multi-armed bandit decision problem, which features arms (slot-machines) of unknown probabilities of success and a player trying to maximize cumulative payoff by choosing the sequence of arms to play. We show that an Infomax strategy (Info-p) which optimally gathers information on the highest probability of success among the arms, saturates known optimal bounds and compares favorably to existing policies. Conversely, gathering information on the identity of the best arm in the bandit leads to a strategy that is vastly suboptimal in terms of payoff. The nature of the quantity selected for Infomax acquisition is then crucial for effective tradeoffs between exploration and exploitation.

  12. A novel star-shaped poly(carboxylic acid) for resin-modified glass-ionomer restoratives.

    Science.gov (United States)

    Weng, Y; Howard, L; Xie, D

    2014-07-01

    We have developed a novel glass-ionomer cement (GIC) system composed of photo-curable star-shaped poly(acrylic acid-co-itaconic acid)s. These polyacids were synthesized via a chain-transfer radical polymerization using a newly synthesized multi-arm chain-transfer agent. The star-shaped polyacids showed significantly lower viscosities in water as compared to the linear polyacids. Due to the lower viscosities, the molecular weight (MW) of the polyacids can be significantly increased for enhancing the mechanical strengths while keeping the ease of mixing and handling. The effects of MW, GM-tethering ratio, P/L ratio, and aging on the compressive properties of the experimental cements were significant. The light-cured experimental cements showed significantly improved mechanical strengths i.e. 49% in yield strength, 41% in modulus, 25% in CS, 20% in DTS, and 36% in FS, higher than commercial Fuji II LC. After aging in water for 1 month, the compressive strength of the novel light-cured experimental cement reached 343 MPa, which was 34% and 42% higher than Fuji II and Fuji II LC, respectively. This one-month aged experimental cement was also 23% higher than itself after one day aging, indicating that aging in water can significantly enhance salt-bridge formation for this novel star-shaped polyacid-comprised GIC.

  13. The collision-free trajectory planning for the space robot to capture a target based on the wavelet interpolation algorithm

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In the research of path planning for manipulators with many DOF, generally there is a problem in most traditional methods, which is that their computational cost (time and memory space) increases exponentially as DOF or resolution of the discrete configuration space increases. So this paper presents the collision-free trajectory planning for the space robot to capture a target based on the wavelet interpolation algorithm. We made wavelet sample on the desired trajectory of the manipulator' s end-effector to do trajectory planning by use of the proposed wavelet interpolation formula, and then derived joint vectors from the trajectory information of the endeffector based on the fixed-attitude-restrained generalized Jacobian matrix of multi-arm coordinated motion, so as to control the manipulator to capture a static body along the desired collision-free trajectory. The method overcomes the shortcomings of the typical methods, and the desired trajectory of the end-effector can be any kind of complex nonlinear curve. The algorithm is simple and highly effective and the real trajectory is close to the desired trajectory. In simulation, the planar dual-arm three DOF space robot is used to demonstrate the proposed method, and it shows that the algorithm is feasible.

  14. Coumarin-containing-star-shaped 4-arm-polyethylene glycol: targeted fluorescent organic nanoparticles for dual treatment of photodynamic therapy and chemotherapy.

    Science.gov (United States)

    Gangopadhyay, Moumita; Singh, Tanya; Behara, Krishna Kalyani; Karwa, S; Ghosh, S K; Singh, N D Pradeep

    2015-07-01

    Single component fluorescent organic polymeric nanoparticles (NPs) have been synthesized based on a star shaped 4-arm PEG containing coumarin chromophore for the concomitant employment of photodynamic therapy (PDT) and chemotherapy synergistically to wipe out tumour cells with a high efficiency. Polymeric NPs are emerging as the most promising nanoparticulates in the area of drug delivery systems due to their ability to overcome the disadvantages like premature and imprecise control over the drug release, lack of loading capacity etc. Among polymeric NPs, star shaped branched polymers have attracted great attention mainly due to their multiple functionalization properties. Hence, herein we have made use of a multi-arm PEG, functionalized with a targeting unit biotin and a coumarin fluorophore for site-specific and image guided synergic treatment of cancer cells. The anticancer drug chlorambucil is released by the coumarin chromophore in a photocontrolled manner. In addition to that, coumarin also generated singlet oxygen upon irradiation with UV/vis light (≥365 nm) with a moderate quantum yield of ∼0.37. In vitro application of thus prepared organic polymeric nanoparticles (PEG-Bio-Cou-Cbl) in the HeLa cell line shows a reduction of cell viability by up to ∼5% in the case of a combined treatment of PDT and chemotherapy whereas analogous organic polymeric NPs without the chemotherapeutic drug (PEG-Bio-Cou) result in ∼49% cell viability by means of PDT process only.

  15. An Injectable PEG-BSA-Coumarin-GOx Hydrogel for Fluorescence Turn-on Glucose Detection.

    Science.gov (United States)

    Srinivasan, Gayathri; Chen, Jun; Parisi, Joseph; Brückner, Christian; Yao, Xudong; Lei, Yu

    2015-11-01

    Diabetes mellitus is a chronic metabolic disorder, requiring vigilant monitoring of blood glucose levels. In this study, an injectable fluorescent enzymatic hydrogel was designed for rapid glucose detection. The leakage-free glucose-responsive hydrogel was constructed by the covalent linkage of a multi-arm poly-(ethylene glycol) (PEG), bovine serum albumin (BSA), glucose oxidase (GOx), and 4-(aminomethyl)-6,7-dimethoxycoumarin (Coumarin-NH2). The GOx serves as glucose-recognition element and the pH-sensitive Coumarin-NH2 as a fluorescence turn-on reporter. The material properties of the fluorescent hydrogel were systematically characterized which show high elasticity with good mechanical strength. Upon the addition of glucose, the as-developed fluorescent hydrogel shows a fast response time, good sensitivity, and good reproducibility at physiological pH and ambient temperature. The glucose-sensing mechanism is based on the oxidation of the glucose by GOx that generates protons to change the local pH. Consequently, protonation of the covalently immobilized and pH-sensitive Coumarin-NH2 turns on the fluorescence of the coumarin. The fluorescence hydrogel developed holds great promise as an injectable, implantable glucose-sensing biomaterials for in vivo continuous glucose monitoring.

  16. Dust Penetrated Arm Classes: Insights from rising and falling rotation curves

    CERN Document Server

    Seigar, M S; Puerari, I; Chorney, N E; James, P A

    2005-01-01

    In the last decade, near-infrared imaging has highlighted the decoupling of gaseous and old stellar disks: the morphologies of optical (Population I) tracers compared to the old stellar disk morphology, can be radically different. Galaxies which appear multi-armed and even flocculent in the optical may show significant Grand-Design spirals in the near-infrared. Furthermore, the optically determined Hubble classification scheme does not provide a sound way of classifying dust-penetrated stellar disks: spiral arm pitch angles (when measured in the near-infrared) do not correlate with Hubble type. The dust--penetrated classification scheme of Block & Puerari provides an alternative classification based on near-infrared morphology, and which is thus more closely linked to the dominant stellar mass component. Here we present near--infrared K band images of 14 galaxies, on which we have performed a Fourier analysis of the spiral structure in order to determine their near-infrared pitch angles and dust--penetrat...

  17. Instability of counter-rotating stellar disks

    Science.gov (United States)

    Hohlfeld, R. G.; Lovelace, R. V. E.

    2015-09-01

    We use an N-body simulation, constructed using GADGET-2, to investigate an accretion flow onto an astrophysical disk that is in the opposite sense to the disk's rotation. In order to separate dynamics intrinsic to the counter-rotating flow from the impact of the flow onto the disk, we consider an initial condition in which the counter-rotating flow is in an annular region immediately exterior the main portion of the astrophysical disk. Such counter-rotating flows are seen in systems such as NGC 4826 (known as the "Evil Eye Galaxy"). Interaction between the rotating and counter-rotating components is due to two-stream instability in the boundary region. A multi-armed spiral density wave is excited in the astrophysical disk and a density distribution with high azimuthal mode number is excited in the counter-rotating flow. Density fluctuations in the counter-rotating flow aggregate into larger clumps and some of the material in the counter-rotating flow is scattered to large radii. Accretion flow processes such as this are increasingly seen to be of importance in the evolution of multi-component galactic disks.

  18. Wide brick tunnel randomization - an unequal allocation procedure that limits the imbalance in treatment totals.

    Science.gov (United States)

    Kuznetsova, Olga M; Tymofyeyev, Yevgen

    2014-04-30

    In open-label studies, partial predictability of permuted block randomization provides potential for selection bias. To lessen the selection bias in two-arm studies with equal allocation, a number of allocation procedures that limit the imbalance in treatment totals at a pre-specified level but do not require the exact balance at the ends of the blocks were developed. In studies with unequal allocation, however, the task of designing a randomization procedure that sets a pre-specified limit on imbalance in group totals is not resolved. Existing allocation procedures either do not preserve the allocation ratio at every allocation or do not include all allocation sequences that comply with the pre-specified imbalance threshold. Kuznetsova and Tymofyeyev described the brick tunnel randomization for studies with unequal allocation that preserves the allocation ratio at every step and, in the two-arm case, includes all sequences that satisfy the smallest possible imbalance threshold. This article introduces wide brick tunnel randomization for studies with unequal allocation that allows all allocation sequences with imbalance not exceeding any pre-specified threshold while preserving the allocation ratio at every step. In open-label studies, allowing a larger imbalance in treatment totals lowers selection bias because of the predictability of treatment assignments. The applications of the technique in two-arm and multi-arm open-label studies with unequal allocation are described.

  19. Online Learning Algorithms for Stochastic Water-Filling

    CERN Document Server

    Gai, Yi

    2011-01-01

    Water-filling is the term for the classic solution to the problem of allocating constrained power to a set of parallel channels to maximize the total data-rate. It is used widely in practice, for example, for power allocation to sub-carriers in multi-user OFDM systems such as WiMax. The classic water-filling algorithm is deterministic and requires perfect knowledge of the channel gain to noise ratios. In this paper we consider how to do power allocation over stochastically time-varying (i.i.d.) channels with unknown gain to noise ratio distributions. We adopt an online learning framework based on stochastic multi-armed bandits. We consider two variations of the problem, one in which the goal is to find a power allocation to maximize $\\sum\\limits_i \\mathbb{E}[\\log(1 + SNR_i)]$, and another in which the goal is to find a power allocation to maximize $\\sum\\limits_i \\log(1 + \\mathbb{E}[SNR_i])$. For the first problem, we propose a \\emph{cognitive water-filling} algorithm that we call CWF1. We show that CWF1 obtai...

  20. Organocatalysis by hydrogen-bonding: a new approach to controlled/living polymerization of α-amino acid N-carboxyanhydrides

    KAUST Repository

    Zhao, Wei

    2015-01-01

    A new method, based on hydrogen-bonding organocatalysis, was developed to achieve living ring-opening polymerization of N-carboxyanhydride of α-amino acids using aminoalcohols as initiators in the presence of N,N′-bis[3,5-bis(trifluoromethyl)phenyl]thiourea (TU-S). The thiourea provides, through hydrogen bonding, simultaneous activation of NCA monomers/reversible deactivation of polymer chain-ends/silencing of the tertiary amine and thus allows the polymerization to proceed in a highly controllable mode. For example, by using N,N-dimethyl ethanolamine (DMEA), as an initiator in the presence of TU-S, a series of well-defined linear polypeptides with differently designed Mns (3.01 × 104-18.10 × 104) and low PDI values (1.02-1.05) were successfully synthesized. This general strategy was also extended to the synthesis of well-defined di- and multi-armed polypeptides by using di-, tri-, or tetra-aminoalcohol initiators (methyldiethanolamine (MDEA), triethanolamine (TEA) or N,N,N′,N′-tetrakis(2-hydroxyethyl)ethylenediamine (THEED)) in the presence of TU-S. © The Royal Society of Chemistry 2015.

  1. Alginate-Poly(ethylene glycol Hybrid Microspheres for Primary Cell Microencapsulation

    Directory of Open Access Journals (Sweden)

    Redouan Mahou

    2014-01-01

    Full Text Available The progress of medical therapies, which rely on the transplantation of microencapsulated living cells, depends on the quality of the encapsulating material. Such material has to be biocompatible, and the microencapsulation process must be simple and not harm the cells. Alginate-poly(ethylene glycol hybrid microspheres (alg-PEG-M were produced by combining ionotropic gelation of sodium alginate (Na-alg using calcium ions with covalent crosslinking of vinyl sulfone-terminated multi-arm poly(ethylene glycol (PEG-VS. In a one-step microsphere formation process, fast ionotropic gelation yields spherical calcium alginate gel beads, which serve as a matrix for simultaneously but slowly occurring covalent cross-linking of the PEG-VS molecules. The feasibility of cell microencapsulation was studied using primary human foreskin fibroblasts (EDX cells as a model. The use of cell culture media as polymer solvent, gelation bath, and storage medium did not negatively affect the alg-PEG-M properties. Microencapsulated EDX cells maintained their viability and proliferated. This study demonstrates the feasibility of primary cell microencapsulation within the novel microsphere type alg-PEG-M, serves as reference for future therapy development, and confirms the suitability of EDX cells as control model.

  2. Spatio-temporal modification of collagen scaffolds mediated by triple helical propensity.

    Science.gov (United States)

    Wang, Allen Y; Foss, Catherine A; Leong, Shirley; Mo, Xiao; Pomper, Martin G; Yu, Seungju M

    2008-07-01

    Functionalized collagen that incorporates exogenous compounds may offer new and improved biomaterials applications, especially in drug-delivery, multifunctional implants, and tissue engineering. To that end, we developed a specific and reversible collagen modification technique utilizing associative chain interactions between synthetic collagen mimetic peptide (CMP) [(ProHypGly) chi; Hyp = hydroxyproline] and type I collagen. Here we show temperature-dependent collagen binding and subsequent release of a series of CMPs with varying chain lengths indicating a triple helical propensity driven binding mechanism. The binding took place when melted, single-strand CMPs were allowed to fold while in contact with reconstituted type I collagens. The binding affinity is highly specific to collagen as labeled CMP bound to nanometer scale periodic positions on type I collagen fibers and could be used to selectively image collagens in ex vivo human liver tissue. When heated to physiological temperature, bound CMPs discharged from the collagen at a sustained rate that correlated with CMP's triple helical propensity, suggesting that sustainability is mediated by dynamic collagen-CMP interactions. We also report on the spatially defined modification of collagen film with linear and multi-arm poly(ethylene glycol)-CMP conjugates; at 37 degrees C, these PEG-CMP conjugates exhibited temporary cell repelling activity lasting up to 9 days. These results demonstrate new opportunities for targeting pathologic collagens for diagnostic or therapeutic applications and for fabricating multifunctional collagen coatings and scaffolds that can temporally and spatially control the behavior of cells associated with the collagen matrices.

  3. Finding the most biased coin with fewest flips

    CERN Document Server

    Chandrasekaran, Karthekeyan

    2012-01-01

    We study the problem of learning the most biased coin among a set of coins by tossing the coins adaptively. The goal is to minimize the number of tosses to identify a coin i* such that prob{coin i* is most biased} is at least 1-\\delta\\ for any given \\delta>0. Under a particular probabilistic model, we give an optimal algorithm, i.e., an algorithm that minimizes the expected number of tosses, to learn a most biased coin. The problem is equivalent to finding the best arm in the multi-armed bandit problem using adaptive strategies. Dar et al. (2002) and Mannor and Tsitsiklis (2004) show upper and lower bounds matching up to constant factors on the number of coin tosses for several underlying settings of the bias probabilities. For a class of such settings we bridge the constant factor gap by giving an optimal adaptive strategy -- a strategy that performs the best possible action under any given history of outcomes. For any given history, tossing the coin chosen by our strategy minimizes the expected number of to...

  4. Alginate-Poly(ethylene glycol) Hybrid Microspheres for Primary Cell Microencapsulation.

    Science.gov (United States)

    Mahou, Redouan; Meier, Raphael P H; Bühler, Léo H; Wandrey, Christine

    2014-01-09

    The progress of medical therapies, which rely on the transplantation of microencapsulated living cells, depends on the quality of the encapsulating material. Such material has to be biocompatible, and the microencapsulation process must be simple and not harm the cells. Alginate-poly(ethylene glycol) hybrid microspheres (alg-PEG-M) were produced by combining ionotropic gelation of sodium alginate (Na-alg) using calcium ions with covalent crosslinking of vinyl sulfone-terminated multi-arm poly(ethylene glycol) (PEG-VS). In a one-step microsphere formation process, fast ionotropic gelation yields spherical calcium alginate gel beads, which serve as a matrix for simultaneously but slowly occurring covalent cross-linking of the PEG-VS molecules. The feasibility of cell microencapsulation was studied using primary human foreskin fibroblasts (EDX cells) as a model. The use of cell culture media as polymer solvent, gelation bath, and storage medium did not negatively affect the alg-PEG-M properties. Microencapsulated EDX cells maintained their viability and proliferated. This study demonstrates the feasibility of primary cell microencapsulation within the novel microsphere type alg-PEG-M, serves as reference for future therapy development, and confirms the suitability of EDX cells as control model.

  5. Online Least Squares Estimation with Self-Normalized Processes: An Application to Bandit Problems

    CERN Document Server

    Abbasi-Yadkori, Yasin; Szepesvari, Csaba

    2011-01-01

    The analysis of online least squares estimation is at the heart of many stochastic sequential decision making problems. We employ tools from the self-normalized processes to provide a simple and self-contained proof of a tail bound of a vector-valued martingale. We use the bound to construct a new tighter confidence sets for the least squares estimate. We apply the confidence sets to several online decision problems, such as the multi-armed and the linearly parametrized bandit problems. The confidence sets are potentially applicable to other problems such as sleeping bandits, generalized linear bandits, and other linear control problems. We improve the regret bound of the Upper Confidence Bound (UCB) algorithm of Auer et al. (2002) and show that its regret is with high-probability a problem dependent constant. In the case of linear bandits (Dani et al., 2008), we improve the problem dependent bound in the dimension and number of time steps. Furthermore, as opposed to the previous result, we prove that our bou...

  6. Cosmic Bandits: Exploration versus Exploitation in CMB B-Mode Experiments

    CERN Document Server

    Kovetz, Ely D

    2016-01-01

    A preferred method to detect the curl-component, or B-mode, signature of inflationary gravitational waves (IGWs) in the cosmic microwave background (CMB) polarization, in the absence of foregrounds and lensing, is a prolonged integration over a single patch of sky of a few square degrees. In practice, however, foregrounds abound and the sensitivity to B modes can be improved considerably by finding the region of sky cleanest of foregrounds. The best strategy to detect B modes thus involves a tradeoff between exploration (to find lower-foreground patches) and exploitation (through prolonged integration). This problem is akin to the multi-armed bandit (MAB) problem in probability theory, wherein a bandit faces a series of slot machines with unknown winning odds and must develop a strategy to maximize his/her winnings with some finite number of pulls. While the optimal MAB strategy remains to be determined, a number of algorithms have been developed in an effort to maximize the winnings. Here, we formulate the s...

  7. Automated generation of node-splitting models for assessment of inconsistency in network meta-analysis.

    Science.gov (United States)

    van Valkenhoef, Gert; Dias, Sofia; Ades, A E; Welton, Nicky J

    2016-03-01

    Network meta-analysis enables the simultaneous synthesis of a network of clinical trials comparing any number of treatments. Potential inconsistencies between estimates of relative treatment effects are an important concern, and several methods to detect inconsistency have been proposed. This paper is concerned with the node-splitting approach, which is particularly attractive because of its straightforward interpretation, contrasting estimates from both direct and indirect evidence. However, node-splitting analyses are labour-intensive because each comparison of interest requires a separate model. It would be advantageous if node-splitting models could be estimated automatically for all comparisons of interest. We present an unambiguous decision rule to choose which comparisons to split, and prove that it selects only comparisons in potentially inconsistent loops in the network, and that all potentially inconsistent loops in the network are investigated. Moreover, the decision rule circumvents problems with the parameterisation of multi-arm trials, ensuring that model generation is trivial in all cases. Thus, our methods eliminate most of the manual work involved in using the node-splitting approach, enabling the analyst to focus on interpreting the results.

  8. The ASAS Criteria for Axial Spondyloarthritis: Strengths, Weaknesses, and Proposals for a Way Forward.

    Science.gov (United States)

    van der Linden, Sjef; Akkoc, Nurullah; Brown, Matthew A; Robinson, Philip C; Khan, Muhammad A

    2015-09-01

    Classification criteria should facilitate selection of similar patients for clinical and epidemiologic studies, therapeutic trials, and research on etiopathogenesis to enable comparison of results across studies from different centers. We critically appraise the validity and performance of the Assessment of SpondyloArthritis international Society (ASAS) classification criteria for axial spondyloarthritis (axSpA). It is still debatable whether all patients fulfilling these criteria should be considered as having true axSpA. Patients with radiographically evident disease by the ASAS criteria are not necessarily identical with ankylosing spondylitis (AS) as classified by the modified New York criteria. The complex multi-arm selection design of the ASAS criteria induces considerable heterogeneity among patients so classified, and applying them in settings with a low prevalence of axial spondyloarthritis (SpA) greatly increases the proportion of subjects falsely classified as suffering from axial SpA. One of the unmet needs in non-radiographic form of axial SpA is to have reliable markers that can identify individuals at risk for progression to AS and thereby facilitate early intervention trials designed to prevent such progression. We suggest needed improvements of the ASAS criteria for axSpA, as all criteria sets should be regarded as dynamic concepts open to modifications or updates as our knowledge advances.

  9. ASAS classification criteria for axial spondyloarthritis: time to modify.

    Science.gov (United States)

    Akkoc, Nurullah; Khan, Muhammad A

    2016-06-01

    The relationship between ankylosing spondylitis and the recently proposed entity called axial spondyloarthritis with its radiographic and non-radiographic forms that have been defined by the Assessment of Spondyloarthritis International Society (ASAS) criteria for axial spondyloarthritis (axSpA), is currently being debated. The Food and Drug Agency (FDA) had criticized the ASAS criteria and the studies which used these criteria to enroll patients in a clinical trial of certolizumab and adalimumab for the treatment of non-radiographic axial spondyloarthritis. The primary aim of classification criteria is to create homogenous patient populations for basic and clinical research. But the multi-arm construct of the ASAS criteria is a potential source of heterogeneity reducing their utility. Criteria sets should be regarded as dynamic concepts open to modifications or updates as our knowledge advances. We provide evidence to conclude that it is time to modify the ASAS Criteria for axSpA, and we propose some of the steps that can be taken to start moving forward in improving the validity of these criteria.

  10. The effect of radial migration on galactic disks

    Energy Technology Data Exchange (ETDEWEB)

    Vera-Ciro, Carlos; D' Onghia, Elena [Department of Astronomy, University of Wisconsin, 2535 Sterling Hall, 475 North Charter Street, Madison, WI 53076 (United States); Navarro, Julio [Department of Physics and Astronomy, University of Victoria, Victoria, BC, V8P 5C2 (Canada); Abadi, Mario, E-mail: ciro@astro.wisc.edu [Observatorio Astronómico, Universidad Nacional de Córdoba, Córdoba X5000BGR (Argentina)

    2014-10-20

    We study the radial migration of stars driven by recurring multi-arm spiral features in an exponential disk embedded in a dark matter halo. The spiral perturbations redistribute angular momentum within the disk and lead to substantial radial displacements of individual stars, in a manner that largely preserves the circularity of their orbits and that results, after 5 Gyr (∼40 full rotations at the disk scale length), in little radial heating and no appreciable changes to the vertical or radial structure of the disk. Our results clarify a number of issues related to the spatial distribution and kinematics of migrators. In particular, we find that migrators are a heavily biased subset of stars with preferentially low vertical velocity dispersions. This 'provenance bias' for migrators is not surprising in hindsight, for stars with small vertical excursions spend more time near the disk plane, and thus respond more readily to non-axisymmetric perturbations. We also find that the vertical velocity dispersion of outward migrators always decreases, whereas the opposite holds for inward migrators. To first order, newly arrived migrators simply replace stars that have migrated off to other radii, thus inheriting the vertical bias of the latter. Extreme migrators might therefore be recognized, if present, by the unexpectedly small amplitude of their vertical excursions. Our results show that migration, understood as changes in angular momentum that preserve circularity, can strongly affect the thin disk, but cast doubts on models that envision the Galactic thick disk as a relic of radial migration.

  11. A π-π conjugation-containing soft and conductive injectable polymer hydrogel highly efficiently rebuilds cardiac function after myocardial infarction.

    Science.gov (United States)

    Bao, Rui; Tan, Baoyu; Liang, Shuang; Zhang, Ning; Wang, Wei; Liu, Wenguang

    2017-04-01

    Previous studies suggested that a stiffer hydrogel system exhibited a better performance to promote heart function after myocardial infarction (MI). However, the nature of myocardium, a tissue that alternately contracts and relaxes with electrical impulses, leads us to hypothesize that a soft and conductive hydrogel may be in favor of mechanical and electrical signals transmission to enhance heart function after MI. In this work, π-π conjugation interaction was first employed to produce a soft injectable hydrogel with conductive property. Melamine with π-π conjugation ring was used as a core to synthesize a multi-armed crosslinker PEGDA700-Melamine (PEG-MEL), which could crosslink with thiol-modified hyaluronic acid (HA-SH) to form an injectable hydrogel rapidly. By incorporating graphene oxide (GO), the injectable PEG-MEL/HA-SH/GO hydrogel exhibited a soft (G' = 25 Pa) and anti-fatigue mechanical property and conductive property (G = 2.84 × 10(-4) S/cm). The hydrogel encapsulating adipose tissue-derived stromal cells (ADSCs) was injected into MI area of rats. The significant increase in α-Smooth Muscle Actin (α-SMA) and Connexin 43 (Cx43) expression confirmed that the gel efficiently promoted the transmission of mechanical and electrical signals. Meanwhile, a significant improvement of heart functions, such as distinct increase of ejection fraction (EF), smaller infarction size, less fibrosis area, and higher vessel density, was achieved.

  12. Biodegradable DNA-enabled poly(ethylene glycol) hydrogels prepared by copper-free click chemistry.

    Science.gov (United States)

    Barker, Karolyn; Rastogi, Shiva K; Dominguez, Jose; Cantu, Travis; Brittain, William; Irvin, Jennifer; Betancourt, Tania

    2016-01-01

    Significant research has focused on investigating the potential of hydrogels in various applications and, in particular, in medicine. Specifically, hydrogels that are biodegradable lend promise to many therapeutic and biosensing applications. Endonucleases are critical for mechanisms of DNA repair. However, they are also known to be overexpressed in cancer and to be present in wounds with bacterial contamination. In this work, we set out to demonstrate the preparation of DNA-enabled hydrogels that could be degraded by nucleases. Specifically, hydrogels were prepared through the reaction of dibenzocyclooctyne-functionalized multi-arm poly(ethylene glycol) with azide-functionalized single-stranded DNA in aqueous solutions via copper-free click chemistry. Through the use of this method, biodegradable hydrogels were formed at room temperature in buffered saline solutions that mimic physiological conditions, avoiding possible harmful effects associated with other polymerization techniques that can be detrimental to cells or other bioactive molecules. The degradation of these DNA-cross-linked hydrogels upon exposure to the model endonucleases Benzonase(®) and DNase I was studied. In addition, the ability of the hydrogels to act as depots for encapsulation and nuclease-controlled release of a model protein was demonstrated. This model has the potential to be tailored and expanded upon for use in a variety of applications where mild hydrogel preparation techniques and controlled material degradation are necessary including in drug delivery and wound healing systems.

  13. Phase transition of social learning collectives and "Echo chamber"

    CERN Document Server

    Mori, Shintaro; Hisakado, Masato

    2016-01-01

    An "Echo chamber" is the state of social learning agents whose performances are deteriorated by excessive observation of others. We understand this to be the collective behavior of agents in a restless multi-armed bandit. The bandit has $M$ good levers and bad levers. A good lever changes to a bad one randomly with probability $q_{C}$ and a new good lever appears. $N$ agents exploit ones' lever if they know that it is a good one. Otherwise, they search for a good one by (i) random search (success probability $q_{I}$) and (ii) observe a good lever that is known by other agents (success probability $q_{O}$) with probability $1-p$ and $p$, respectively. The distribution of agents in good levers obeys the Yule distribution with power law exponent $1+\\gamma$ in the limit $N,M\\to \\infty$ and $\\gamma=1+\\frac{(1-p)q_{I}}{pq_{O}}$. The expected value of the number of the agents with a good lever $N_{1}$ increases with $p$. The system shows a phase transition at $p_{c}=\\frac{q_{I}}{q_{I}+q_{o}}$. For $pp_{c})$, the var...

  14. A New Mechanism of Dynamic Spectrum Access Based on Restless Bandit Allocation Indices

    Directory of Open Access Journals (Sweden)

    Zhu Jiang

    2015-10-01

    Full Text Available Based on the theory of Restless Multi-Armed Bandit model, a novel mechanism of dynamic spectrum access was proposed for the problem that how to coordinate multi-user access multi-channel which were idle. Firstly, take care of the sensing error must be exist in the practical network, the Whittle index policy which can deal with sensing error effectively was derived, in this policy, the users achieved one belief value for every channel based on the historical experience accumulation and chose the channels, which was need to sense and access, by considering the reward of immediate and future based on the belief values. Secondly, this paper used the multi-bid auction algorithm to deal with the collision among secondary users when they select the channels to improve the spectrum utilization. The simulation results demonstrate that, in the same environment, the cognitive users with the proposed mechanism have higher throughtput than the mechanism without dealing with sensing error or without multi-bid.

  15. Decision maker based on atomic switches

    Directory of Open Access Journals (Sweden)

    Song-Ju Kim

    2016-02-01

    Full Text Available We propose a simple model for an atomic switch-based decision maker (ASDM, and show that, as long as its total number of metal atoms is conserved when coupled with suitable operations, an atomic switch system provides a sophisticated ``decision-making'' capability that is known to be one of the most important intellectual abilities in human beings. We considered a popular decision-making problem studied in the context of reinforcement learning, the multi-armed bandit problem (MAB; the problem of finding, as accurately and quickly as possible, the most profitable option from a set of options that gives stochastic rewards. These decisions are made as dictated by each volume of precipitated metal atoms, which is moved in a manner similar to the fluctuations of a rigid body in a tug-of-war game. The ``tug-of-war (TOW dynamics'' of the ASDM exhibits higher efficiency than conventional reinforcement-learning algorithms. We show analytical calculations that validate the statistical reasons for the ASDM to produce such high performance, despite its simplicity. Efficient MAB solvers are useful for many practical applications, because MAB abstracts a variety of decision-making problems in real-world situations where an efficient trial-and-error is required. The proposed scheme will open up a new direction in physics-based analog-computing paradigms, which will include such things as ``intelligent nanodevices'' based on self-judgment.

  16. Characterizing DNA Star-Tile-Based Nanostructures Using a Coarse-Grained Model.

    Science.gov (United States)

    Schreck, John S; Romano, Flavio; Zimmer, Matthew H; Louis, Ard A; Doye, Jonathan P K

    2016-04-26

    We use oxDNA, a coarse-grained model of DNA at the nucleotide level, to simulate large nanoprisms that are composed of multi-arm star tiles, in which the size of bulge loops that have been incorporated into the tile design is used to control the flexibility of the tiles. The oxDNA model predicts equilibrium structures for several different nanoprism designs that are in excellent agreement with the experimental structures as measured by cryoTEM. In particular we reproduce the chiral twisting of the top and bottom faces of the nanoprisms, as the bulge sizes in these structures are varied due to the greater flexibility of larger bulges. We are also able to follow how the properties of the star tiles evolve as the prisms are assembled. Individual star tiles are very flexible, but their structures become increasingly well-defined and rigid as they are incorporated into larger assemblies. oxDNA also finds that the experimentally observed prisms are more stable than their inverted counterparts, but interestingly this preference for the arms of the tiles to bend in a given direction only emerges after they are part of larger assemblies. These results show the potential for oxDNA to provide detailed structural insight as well as to predict the properties of DNA nanostructures and hence to aid rational design in DNA nanotechnology.

  17. A New Cosmological Model: Black Hole Universe

    Directory of Open Access Journals (Sweden)

    Zhang T. X.

    2009-07-01

    Full Text Available A new cosmological model called black hole universe is proposed. According to this model, the universe originated from a hot star-like black hole with several solar masses, and gradually grew up through a supermassive black hole with billion solar masses to the present state with hundred billion-trillion solar masses by accreting ambient mate- rials and merging with other black holes. The entire space is structured with infinite layers hierarchically. The innermost three layers are the universe that we are living, the outside called mother universe, and the inside star-like and supermassive black holes called child universes. The outermost layer is infinite in radius and limits to zero for both the mass density and absolute temperature. The relationships among all layers or universes can be connected by the universe family tree. Mathematically, the entire space can be represented as a set of all universes. A black hole universe is a subset of the en- tire space or a subspace. The child universes are null sets or empty spaces. All layers or universes are governed by the same physics - the Einstein general theory of relativity with the Robertson-walker metric of spacetime - and tend to expand outward physically. The evolution of the space structure is iterative. When one universe expands out, a new similar universe grows up from its inside. The entire life of a universe begins from the birth as a hot star-like or supermassive black hole, passes through the growth and cools down, and expands to the death with infinite large and zero mass density and absolute temperature. The black hole universe model is consistent with the Mach principle, the observations of the universe, and the Einstein general theory of relativity. Its various aspects can be understood with the well-developed physics without any difficulty. The dark energy is not required for the universe to accelerate its expansion. The inflation is not necessary because the black hole universe

  18. The Black Hole Universe Model

    Science.gov (United States)

    Zhang, Tianxi

    2014-06-01

    The black hole universe model is a multiverse model of cosmology recently developed by the speaker. According to this new model, our universe is a fully grown extremely supermassive black hole, which originated from a hot star-like black hole with several solar masses, and gradually grew up from a supermassive black hole with million to billion solar masses to the present state with trillion-trillion solar masses by accreting ambient matter or merging with other black holes. The entire space is structured with infinite layers or universes hierarchically. The innermost three layers include the universe that we live, the inside star-like and supermassive black holes called child universes, and the outside space called mother universe. The outermost layer is infinite in mass, radius, and entropy without an edge and limits to zero for both the matter density and absolute temperature. All layers are governed by the same physics and tend to expand physically in one direction (outward or the direction of increasing entropy). The expansion of a black hole universe decreases its density and temperature but does not alter the laws of physics. The black hole universe evolves iteratively and endlessly without a beginning. When one universe expands out, a new similar one is formed from inside star-like and supermassive black holes. In each of iterations, elements are resynthesized, matter is reconfigurated, and the universe is renewed rather than a simple repeat. The black hole universe is consistent with the Mach principle, observations, and Einsteinian general relativity. It has only one postulate but is able to explain all phenomena occurred in the universe with well-developed physics. The black hole universe does not need dark energy for acceleration and an inflation epoch for flatness, and thus has a devastating impact on the big bang model. In this talk, I will present how this new cosmological model explains the various aspects of the universe, including the origin

  19. Magnetic field amplification in hypermassive neutron stars via the magnetorotational instability

    CERN Document Server

    Siegel, Daniel M

    2014-01-01

    Mergers of binary neutron stars likely lead to the formation of a hypermassive neutron star (HMNS), which is metastable and eventually collapses to a black hole. This merger scenario is thought to explain the phenomenology of short gamma-ray bursts (SGRBs). The very high energies observed in SGRBs have been suggested to stem from neutrino-antineutrino annihilation and/or from very strong magnetic fields created during or after the merger by mechanisms like the magnetorotational instability (MRI). Here, we report on results that show for the first time the development of the MRI in HMNSs in three-dimensional, fully general-relativistic magnetohydrodynamic simulations. This instability amplifies magnetic fields exponentially and could be a vital ingredient in solving the SGRB puzzle.

  20. On the Habitability of Our Universe

    CERN Document Server

    Loeb, Abraham

    2016-01-01

    Is life most likely to emerge at the present cosmic time near a star like the Sun? We consider the habitability of the Universe throughout cosmic history, and conservatively restrict our attention to the context of "life as we know it" and the standard cosmological model, LCDM. The habitable cosmic epoch started shortly after the first stars formed, about 30 Myr after the Big Bang, and will end about 10 Tyr from now, when all stars will die. We review the formation history of habitable planets and find that unless habitability around low mass stars is suppressed, life is most likely to exist near 0.1 solar mass stars ten trillion years from now. Spectroscopic searches for biosignatures in the atmospheres of transiting Earth-mass planets around low mass stars will determine whether present-day life is indeed premature or typical from a cosmic perspective.

  1. Y chromosomes of 40% Chinese descend from three Neolithic super-grandfathers.

    Science.gov (United States)

    Yan, Shi; Wang, Chuan-Chao; Zheng, Hong-Xiang; Wang, Wei; Qin, Zhen-Dong; Wei, Lan-Hai; Wang, Yi; Pan, Xue-Dong; Fu, Wen-Qing; He, Yun-Gang; Xiong, Li-Jun; Jin, Wen-Fei; Li, Shi-Lin; An, Yu; Li, Hui; Jin, Li

    2014-01-01

    Demographic change of human populations is one of the central questions for delving into the past of human beings. To identify major population expansions related to male lineages, we sequenced 78 East Asian Y chromosomes at 3.9 Mbp of the non-recombining region, discovered >4,000 new SNPs, and identified many new clades. The relative divergence dates can be estimated much more precisely using a molecular clock. We found that all the Paleolithic divergences were binary; however, three strong star-like Neolithic expansions at ∼6 kya (thousand years ago) (assuming a constant substitution rate of 1×10(-9)/bp/year) indicates that ∼40% of modern Chinese are patrilineal descendants of only three super-grandfathers at that time. This observation suggests that the main patrilineal expansion in China occurred in the Neolithic Era and might be related to the development of agriculture.

  2. Molecular CsF 5 and CsF 2 +

    KAUST Repository

    Rogachev, Andrey Yu.

    2015-06-03

    D5h star-like CsF5, formally isoelectronic with known XeF5− ion, is computed to be a local minimum on the potential energy surface of CsF5, surrounded by reasonably large activation energies for its exothermic decomposition to CsF+2 F2, or to CsF3 (three isomeric forms)+F2, or for rearrangement to a significantly more stable isomer, a classical Cs+ complex of F5−. Similarly the CsF2+ ion is computed to be metastable in two isomeric forms. In the more symmetrical structures of these molecules there is definite involvement in bonding of the formally core 5p levels of Cs.

  3. Revealing the structure of the world airline network

    CERN Document Server

    Verma, Trivik; Herrmann, Hans J

    2014-01-01

    Resilience of most critical infrastructures against failure of elements that appear insignificant is usually taken for granted. The World Airline Network (WAN) is an infrastructure that reduces the geographical gap between societies, both small and large, and brings forth economic gains. With the extensive use of a publicly maintained data set that contains information about airports and alternative connections between these airports, we empirically reveal that the WAN is a redundant and resilient network for long distance air travel, but otherwise breaks down completely due to removal of short and apparently insignificant connections. These short range connections with moderate number of passengers and alternate flights are the connections that keep remote parts of the world accessible. It is surprising, insofar as there exists a highly resilient and strongly connected core consisting of a small fraction of airports (around 2.3%) together with an extremely fragile star-like periphery. Yet, in spite of their ...

  4. Impact of Nanoparticles on Nematic Ordering in Square Wells

    Directory of Open Access Journals (Sweden)

    M. Slavinec

    2015-01-01

    Full Text Available Nematic liquid crystalline structures within square wells are studied numerically using both Lebwohl-Lasher lattice semimicroscopic and the Landau-de Gennes mesoscopic approach. At lateral boundary wall strong planar anchoring is enforced. The cell thickness h along the z Cartesian coordinate is assumed to be smaller than the characteristic square well size R. Using semimicroscopic modelling we restrict to effectively two-dimensional systems which we study in terms of the tensor nematic order parameter. We consider impact of appropriate nanoparticles (NPs on nematic configuration for cases where R becomes comparable to the biaxial order parameter correlation length. In this case a star-like order reconstruction biaxial profile could be formed in absence of NPs. We demonstrate existence of a rich variety of different nematic structures, including topological defects, which are enabled by presence of appropriate NPs.

  5. Doppler- and recoil-free laser excitation of Rydberg states via three-photon transitions

    CERN Document Server

    Ryabtsev, I I; Tretyakov, D B; Entin, V M; Yakshina, E A

    2011-01-01

    Three-photon laser excitation of Rydberg states by three different laser beams can be arranged in a star-like geometry that simultaneously eliminates the recoil effect and Doppler broadening. Our analytical and numerical calculations for a particular laser excitation scheme 5S_{1/2}->5P_{3/2}->6S_{1/2}->nP in Rb atoms have shown that compared to the one- and two-photon laser excitation this approach provides much narrower line width and longer coherence time for both cold atom samples and hot vapors, if the intermediate one-photon resonances of the three-photon transition are detuned by more than respective single-photon Doppler widths. This method can be used to improve fidelity of Rydberg quantum gates and precision of spectroscopic measurements in Rydberg atoms.

  6. A Large Hubble Space Telescope Survey of Low-Mass Exoplanets

    Science.gov (United States)

    Benneke, Björn; Crossfield, Ian; Knutson, Heather; Lothringer, Joshua; McCullough, Peter R.; Dragomir, Diana; Morley, Caroline; Kempton, Eliza

    2016-10-01

    The discovery of short-period planets with masses and radii between Earth and Neptune was one of the biggest surprises in the brief history of exoplanet science. From the Kepler mission, we know that these "super-Earths" or "sub-Neptunes" orbit at least 40% of stars, likely representing the most common outcome of planet formation. Despite this ubiquity, we know little about their typical compositions and formation histories. In this talk, we will shed new light on these worlds by presenting the multiple the main results from our 124-orbit HST transit spectroscopy survey to probe the chemical compositions of low-mass exoplanets. We will report on multiple molecular detections. Our unprecedented HST survey provides the first comprehensive look at this intriguing new class of planets by covering seven planets ranging from 1 Neptune mass and temperatures close to 2000K to a 1 Earth-mass planet near the habitable zone of its host star.

  7. Relative Likelihood for Life as a Function of Cosmic Time

    CERN Document Server

    Loeb, Abraham; Sloan, David

    2016-01-01

    Is life most likely to emerge at the present cosmic time near a star like the Sun? We address this question by calculating the relative formation probability per unit time of habitable Earth-like planets within a fixed comoving volume of the Universe, dP(t)/dt, starting from the first stars and continuing to the distant cosmic future. We conservatively restrict our attention to the context of "life as we know it" and the standard cosmological model, LCDM. We find that unless habitability around low mass stars is suppressed, life is most likely to exist near 0.1 solar-mass stars ten trillion years from now. Spectroscopic searches for biosignatures in the atmospheres of transiting Earth-mass planets around low mass stars will determine whether present-day life is indeed premature or typical from a cosmic perspective.

  8. Changes of hierarchical network in local and world stock market

    Science.gov (United States)

    Patwary, Enayet Ullah; Lee, Jong Youl; Nobi, Ashadun; Kim, Doo Hwan; Lee, Jae Woo

    2017-10-01

    We consider the cross-correlation coefficients of the daily returns in the local and global stock markets. We generate the minimal spanning tree (MST) using the correlation matrix. We observe that the MSTs change their structure from chain-like networks to star-like networks during periods of market uncertainty. We quantify the measure of the hierarchical network utilizing the value of the hierarchy measured by the hierarchical path. The hierarchy and betweenness centrality characterize the state of the market regarding the impact of crises. During crises, the non-financial company is established as the central node of the MST. However, before the crisis and during stable periods, the financial company is occupying the central node of the MST in the Korean and the U.S. stock markets. The changes in the network structure and the central node are good indicators of an upcoming crisis.

  9. Beyond the Main Sequence: Testing the accuracy of stellar masses predicted by the PARSEC evolutionary tracks

    CERN Document Server

    Ghezzi, Luan

    2015-01-01

    Characterizing the physical properties of exoplanets, and understanding their formation and orbital evolution requires precise and accurate knowledge of the physical properties of their host stars. Accurately measuring stellar mass is particularly important because the masses of host stars likely influence planet occurrence and the architectures of planetary systems observed today. Single main-sequence stars typically have masses estimated from evolutionary tracks, which generally provide accurate results due to their extensive empirical calibration. However, the validity of this method for subgiants and giants has been called into question, with suggestions that the evolutionary models could contain systematic errors that would cause mass estimates of these evolved stars to be overestimated. We investigate these concerns using a sample of 59 benchmark evolved stars with model-independent masses (from binary systems or asteroseismology) obtained from the extant literature. We find very good agreement between ...

  10. Djehuty, a Code for Modeling Stars in Three Dimensions

    CERN Document Server

    Bazán, G; Dossa, D D; Eggleton, P P; Taylor, A; Castor, J I; Murray, S; Cook, K H; Eltgroth, P G; Cavallo, R M; Turcotte, S; Keller, S C; Pudliner, B S

    2003-01-01

    Current practice in stellar evolution is to employ one-dimensional calculations that quantitatively apply only to a minority of the observed stars (single non-rotating stars, or well detached binaries). Even in these systems, astrophysicists are dependent on approximations to handle complex three-dimensional processes like convection. Understanding the structure of binary stars, like those that lead to the Type Ia supernovae used to measure the expansion of the universe, are grossly non-spherical and await a 3D treatment. To approach very large problems like multi-dimensional modeling of stars, the Lawrence Livermore National Laboratory has invested in massively parallel computers and invested even more in developing the algorithms to utilize them on complex physics problems. We have leveraged skills from across the lab to develop a 3D stellar evolution code, Djehuty (after the Egyptian god for writing and calculation) that operates efficiently on platforms with thousands of nodes, with the best available phy...

  11. Stochastic Vehicle Routing with Recourse

    CERN Document Server

    Goertz, Inge Li; Saket, Rishi

    2012-01-01

    We study the classic Vehicle Routing Problem in the setting of stochastic optimization with recourse. StochVRP is a two-stage optimization problem, where demand is satisfied using two routes: fixed and recourse. The fixed route is computed using only a demand distribution. Then after observing the demand instantiations, a recourse route is computed -- but costs here become more expensive by a factor lambda. We present an O(log^2 n log(n lambda))-approximation algorithm for this stochastic routing problem, under arbitrary distributions. The main idea in this result is relating StochVRP to a special case of submodular orienteering, called knapsack rank-function orienteering. We also give a better approximation ratio for knapsack rank-function orienteering than what follows from prior work. Finally, we provide a Unique Games Conjecture based omega(1) hardness of approximation for StochVRP, even on star-like metrics on which our algorithm achieves a logarithmic approximation.

  12. Spatial and Temporal Variations of Light Curves in Gravitationally Lensed Sources

    CERN Document Server

    Minakov, A A

    2004-01-01

    Effects of macro-and microlensing on the spatial and temporal characteristics of images of remote sources, observed through the inner regions of lensing galaxies are discussed. A particular attention was given to the case, when microlenses, - stars, star-like or planetary bodies, - are situated near the critical curves of macrolenses, - galaxies, stellar clusters, etc. The investigation is of interest for the gravitational lens (GL) systems, where the lensed images are observed close to the critical curve of a macrolens. Annular, arched or confluent images should be regarded as an indication to such a proximity. Numerical simulation allowed to determine the structure of critical curves and caustics, formed by macro and microlenses, and to evaluate possible distortions, caused by microlenses for various locations with respect to the critical curve of a regular lens. The difference of our results from those obtained earlier with the standard (linearized) approach to describe the regular gravitational lens was s...

  13. Beating the confusion limit: the necessity of high angular resolution for probing the physics of Sagittarius A* and its environment: opportunities for LINC-NIRVANA (LBT), GRAVITY (VLTI) and and METIS (E-ELT)

    Science.gov (United States)

    Eckart, A.; Sabha, N.; Witzel, G.; Straubmeier, C.; Shahzamanian, B.; Valencia-S., M.; García-Marín, Macarena; Horrobin, M.; Moser, L.; Zuther, J.; Fischer, S.; Rauch, C.; Rost, S.; Iserlohe, C.; Yazici, S.; Smajic, S.; Wiest, M.; Araujo-Hauck, C.; Wank, I.

    2012-07-01

    The super-massive 4 million solar mass black hole (SMBH) SgrA* shows variable emission from the millimeter to the X-ray domain. A detailed analysis of the infrared light curves allows us to address the accretion phenomenon in a statistical way. The analysis shows that the near-infrared flux density excursions are dominated by a single state power law, with the low states of SgrA* are limited by confusion through the unresolved stellar background. We show that for 8-10m class telescopes blending effects along the line of sight will result in artificial compact star-like objects of 0.5-1 mJy that last for about 3-4 years. We discuss how the imaging capabilities of GRAVITY at the VLTI, LINC-NIRVANA at the LBT and METIS at the E-ELT will contribute to the investigation of the low variability states of SgrA*.

  14. Molecular CsF{sub 5} and CsF{sub 2}{sup +}

    Energy Technology Data Exchange (ETDEWEB)

    Rogachev, Andrey Yu. [Illinois Institute of Technology, IL (United States). Dept. of Biological and Chemical Sciences; Miao, Mao-sheng [California State Univ., Northridge, CA (United States). Dept. of Chemistry and Biochemistry; Beijing Computational Science Research Center (China); Merino, Gabriel [Centro de Investigacion y de Estudios Avanzados, Unidad Merida (Mexico). Dept. de Fisica Aplicada; Hoffmann, Roald [Cornell Univ., Ithaca, NY (United States). Dept. of Chemistry and Chemical Biology

    2015-07-06

    D{sub 5h} star-like CsF{sub 5}, formally isoelectronic with known XeF{sub 5}{sup -} ion, is computed to be a local minimum on the potential energy surface of CsF{sub 5}, surrounded by reasonably large activation energies for its exothermic decomposition to CsF + 2F{sub 2}, or to CsF{sub 3} (three isomeric forms) + F{sub 2}, or for rearrangement to a significantly more stable isomer, a classical Cs{sup +} complex of F{sub 5}{sup -}. Similarly the CsF{sub 2}{sup +} ion is computed to be metastable in two isomeric forms. In the more symmetrical structures of these molecules there is definite involvement in bonding of the formally core 5p levels of Cs.

  15. Sdssj103913.70+533029.7: a super star cluster in the outskirts of a galaxy merger

    Energy Technology Data Exchange (ETDEWEB)

    Knapp, Gillian R.; Tremonti, Christy A.; Rockosi, Constance M.; Schlegel, David J.; Yanny, Brian; Beers, Timothy C.; Allende Prieto, Carlos; Wilhelm, Ron; Lupton, Robert; Gunn, James E.; Niederste-Ostholt, Martin; Schneider, Donald P.; Covey, Kevin; Seth, Anil; Ivezic, Zeljko; Eisenstein, Daniel J.; Helmboldt, Joe; Finkbeiner, Douglas P.; Padmanabhan, Nikhil; Kleinman, Scot J.; Long, Dan; /Princeton U. /Arizona U., Astron. Dept. - Steward Observ. /Lick Observ. /LBL, Berkeley /Fermilab /Michigan State U. /Texas U.,

    2005-11-01

    We describe the serendipitous discovery in the spectroscopic data of the Sloan Digital Sky Survey of a star-like object, SDSSJ103913.70+533029.7, at a heliocentric radial velocity of +1012 km s{sup -1}. Its proximity in position and velocity to the spiral galaxy NGC 3310 suggests an association with the galaxy. At this distance, SDSSJ103913.70+533029.7 has the luminosity of a super star cluster and a projected distance of 17 kpc from NGC 3310. Its spectroscopic and photometric properties imply a mass of > 10{sup 6} M{sub {circle_dot}} and an age close to that of the tidal shells seen around NGC 3310, suggesting that it formed in the event which formed the shells.

  16. Evolution of correlated multiplexity through stability maximization

    CERN Document Server

    Dwivedi, Sanjiv K

    2016-01-01

    Investigating relation between various structural patterns found in real-world networks and stability of underlying systems is crucial to understand importance and evolutionary origin of such patterns. We evolve multiplex networks, comprising of anti-symmetric couplings in one layer, depicting predator-prey relation, and symmetric couplings in the other, depicting mutualistic (or competitive) relation, based on stability maximization through the largest eigenvalue. We find that the correlated multiplexity emerges as evolution progresses. The evolved values of the correlated multiplexity exhibit a dependence on the inter-link coupling strength. Furthermore, the inter-layer coupling strength governs the evolution of disassortativity property in the individual layers. We provide analytical understanding to these findings by considering star like networks in both the layers. The model and tools used here are useful for understanding the principles governing the stability as well as importance of such patterns in ...

  17. Shape matters: tuning plasmonic resonances into single nanoparticles and their arrays (Conference Presentation)

    Science.gov (United States)

    Cordova Castro, R. Margoth; Krasavin, Alexey V.; Dickson, Wayne; Mendez Mendez, Eugenio R.; Zayats, Anatoly V.

    2016-09-01

    We present a numerical study of the interaction of light with isolated nanoparticles of various symmetry shapes described by the Gielis superformula as well as nanoparticle arrays composed from them. Using the discrete dipole approximation and finite element numerical methods the effects of particle shape symmetry on the spectral properties of gold and silver nanoparticles were investigated. Starting from the spherical and cylindrical geometries and progressing to star-like polygonal shapes, we demonstrate that the variation of the symmetry can significantly enhance the strength of the dipolar resonance and shift the resonance to the red spectral range by hundreds of nanometres. Thus, is possible to tune the optical properties of the nanostructures all across the visible spectral range only by changing their shapes. Finally, we investigate the collective resonances of arrays of interacting nanoparticles of different shapes, elucidating the role of the particle symmetry in the collective response.

  18. Astrophysical and biological constraints on radiopanspermia.

    Science.gov (United States)

    Secker, J; Wesson, P S; Lepock, J R

    1996-08-01

    We have carried out a series of calculations involving bacteria and viruses embedded in dust grains, which are ejected from our solar system by radiation pressure and travel through space to other star systems. Under many conditions this type of panspermia is impractical, primarily because the ultraviolet (UV) radiation of the present Sun inactivates the micro-organisms. However, if the organisms are shielded by an absorbing material like carbon and if ejection takes place in the red-giant phase of a one solar mass star like our Sun, there is a significant probability that the micro-organisms can reach another star system alive (i.e. with only sub-lethal damage from UV and ionizing radiation). In addition to panspermia with viable micro-organisms, it is possible to seed the Galaxy with inactivated ones whose DNA and RNA fragments may provide the initial information necessary to start biological evolution in favourable environments.

  19. Modeling motion of a small black hole through a star or a planet

    Science.gov (United States)

    Turova, Victoria; Panin, Alexander

    2012-10-01

    In some scenarios of Big Bang the fluctuations of density in early universe result in the formation of various sized primordial black holes. The black holes of mass range 10^10 -10^22 kg are suitable candidates for a dark matter (or at least for a part of it). Such black holes could from time to time pass via Solar system or Sun or even Earth. What would a trajectory of a small black hole passing through Sun or through Earth look like? Would a black hole slow down and stuck consuming matter and causing cataclysmic collapse of Earth or Sun, or would it just pass? What other effects would take place? We model computationally a motion of a small black hole moving with various initial velocities (10- 1000 km/sec) through a planet-like and a star-like body of various density distributions. The results of this modeling are presented.

  20. Dippers and Dusty Disks Edges: A Unified Model

    CERN Document Server

    Bodman, Eva H L; Ansdell, Megan; Hippke, Michael; Boyajian, Tabetha S; Mamajek, Eric E; Blackman, Eric G; Rizzuto, Aaron; Kastner, Joel H

    2016-01-01

    A search for dips in observed stellar flux in the Upper Scorpius and $\\rho$ Ophiuchus star formation regions with the Kepler mission by Ansdell et al. primarily identified young, low mass stars (dippers) with low accretion rates and hosting moderately evolved dusty circumstellar disks. These young stars likely exhibit rotating star spots that cause quasi-periodic photometric variations. However, a separate period associated with the dips is not evident in spectrograms constructed from the light curves. The material causing the dips in most of these light curves must be approximately corotating with the star. We find that disk temperatures computed at the disk corotation radius are cool enough that dust should not sublimate. Dippers are preferentially associated with young, low mass stars as they have low enough luminosities to allow dust to survive within a few stellar radii. Crude estimates for stellar magnetic field strengths and accretion rates are consistent with magnetospheric truncation near the corotat...

  1. Magnetospherically driven optical and radio aurorae at the end of the stellar main sequence

    CERN Document Server

    Hallinan, G; Cotter, G; Bourke, S; Harding, L K; Pineda, J S; Butler, R P; Golden, A; Basri, G; Doyle, J G; Kao, M M; Berdyugina, S V; Kuznetsov, A; Rupen, M P; Antonova, A

    2015-01-01

    Aurorae are detected from all the magnetized planets in our Solar System, including Earth. They are powered by magnetospheric current systems that lead to the precipitation of energetic electrons into the high-latitude regions of the upper atmosphere. In the case of the gas-giant planets, these aurorae include highly polarized radio emission at kilohertz and megahertz frequencies produced by the precipitating electrons, as well as continuum and line emission in the infrared, optical, ultraviolet and X-ray parts of the spectrum, associated with the collisional excitation and heating of the hydrogen-dominated atmosphere. Here we report simultaneous radio and optical spectroscopic observations of an object at the end of the stellar main sequence, located right at the boundary between stars and brown dwarfs, from which we have detected radio and optical auroral emissions both powered by magnetospheric currents. Whereas the magnetic activity of stars like our Sun is powered by processes that occur in their lower a...

  2. Impulse-Induced Optimum Signal Amplification in Scale-Free Networks

    CERN Document Server

    Martínez, Pedro J

    2015-01-01

    Optimizing information transmission across a network is an essential task for controlling and manipulating generic information-processing systems. Here, we show how topological amplification effects in scale-free networks of signaling devices are optimally enhanced when the $\\it{impulse}$ transmitted by periodic external signals (time integral over two consecutive zeros) is maximum. This is demonstrated theoretically by means of a star-like network of overdamped bistable systems subjected to $\\it{generic}$ zero-mean periodic signals, and confirmed numerically by simulations of scale-free networks of such systems. Our results show that the enhancer effect of increasing values of the signal's impulse is due to a correlative increase of the energy transmitted by the periodic signals, while it is found to be resonant-like with respect to the topology-induced amplification mechanism.

  3. Galaxies in the Early Universe

    DEFF Research Database (Denmark)

    Krogager, Jens-Kristian

    analyses are biased towards the brightest galaxies at all times (as these are easier to observe and identify). A complementary method relies on the absorption imprint from neutral gas in galaxies, the so-called damped Ly absorbers (DLAs) seen towards distant bright objects. This thesis seeks to understand...... how the absorption selected galaxies relate to the emission selected galaxies by identifying the faint glow from the absorbing galaxies at redshift z 2. In Chapters 2 and 3, the emission properties of DLAs are studied in detail using state-of-the-art instrumentation. The specific DLA studied......), there might exist a bias against dusty foreground absorbers due to the reddening causing the background quasars to appear star-like in their optical colours. In Chapters 4 and 5, these hypothesized dusty absorbers are sought for through a combination of optical and near-infrared colour criteria. While a large...

  4. NESTOR Deep Sea Neutrino Telescope. Deployment and results

    Science.gov (United States)

    Aggouras, G.; Anassontzis, E. G.; Ball, A. E.; Bourlis, G.; Chinowsky, W.; Fahrun, E.; Grammatikakis, G.; Green, C.; Grieder, P.; Katrivanos, P.; Koske, P.; Leisos, A.; Markopoulos, E.; Minkowsky, P.; Nygren, D.; Papageorgiou, K.; Przybylski, G.; Resvanis, L. K.; Siotis, I.; Sopher, J.; Staveris-Polikalas, A.; Tsagli, V.; Tsirigotis, A.; Tzamarias, S.; Zhukov, V. A.; Nestor Collaboration

    2006-01-01

    One module of NESTOR, the Mediterranean deep-sea neutrino telescope, was deployed at a depth of 4000m, 14km off the Sapienza Island, off the South West coast of Greece. The deployment site provides excellent environmental characteristics. The deployed NESTOR module is constructed as a hexagonal star like latticed titanium star with 12 Optical Modules and an one-meter diameter titanium sphere which houses the electronics. Power and data were transferred through a 30km electro-optical cable to the shore laboratory. In this report we describe briefly the detector and the detector electronics and discuss the first physics data acquired and give the zenith angular distribution of the reconstructed muons.

  5. NESTOR Deep Sea Neutrino Telescope

    Science.gov (United States)

    NESTOR Collaboration; Aggouras, G.; Anassontzis, E. G.; Ball, A. E.; Bourlis, G.; Chinowsky, W.; Fahrun, E.; Grammatikakis, G.; Green, C.; Grieder, P.; Katrivanos, P.; Koske, P.; Leisos, A.; Markopoulos, E.; Minkowsky, P.; Nygren, D.; Papageorgiou, K.; Przybylski, G.; Resvanis, L. K.; Siotis, I.; Sopher, J.; Staveris-Polikalas, A.; Tsagli, V.; Tsirigotis, A.; Tzamarias, S.; Zhukov, V. A.

    2006-01-01

    One module of NESTOR, the Mediterranean deep-sea neutrino telescope, was deployed at a depth of 4000m, 14km off the Sapienza Island, off the South West coast of Greece. The deployment site provides excellent environmental characteristics. The deployed NESTOR module is constructed as a hexagonal star like latticed titanium star with 12 Optical Modules and an one-meter diameter titanium sphere which houses the electronics. Power and data were transferred through a 30km electro-optical cable to the shore laboratory. In this report we describe briefly the detector and the detector electronics and discuss the first physics data acquired and give the zenith angular distribution of the reconstructed muons.

  6. Photovoltaic Power Generation in the Stellar Environments

    CERN Document Server

    Girish, T E

    2010-01-01

    In this paper we have studied the problem of photovoltaic power generation near selected stars in the solar neighborhood. The nature of the optical radiation from a star will depend on its luminosity,HR classification and spectral characteristics. The solar celloperation in the habitable zones of the stars is similar to AM1.0 operation near earth.Thecurrent space solar cell technology can be adopted for power generation near G,K and Mtype stars. Silicon solar cells with good near IR response are particularly suitable in theenvironments of M type stars which are most abundant in the universe. . Photovoltaicpower generation near binary stars like Sirius and Alpha Centauri is also discussed.

  7. Signatures of Dark Star Remnants in the Galactic Halo

    CERN Document Server

    Sandick, Pearl; Freese, Katherine; Spolyar, Douglas

    2010-01-01

    The very first stars likely formed from metal-free, molecular hydrogen-cooled gas at the centers of dark matter minihalos. Prior to nuclear fusion, these stars may have been supported by dark matter heating from annihilations in the star, in which case they could have grown to be quite massive before collapsing to black holes. Many remnant black holes and their surrounding dark matter density spikes may be part of our Milky Way halo today. Here we explore the gamma-ray signatures of dark matter annihilations in the dark matter spikes surrounding these black holes for a range of star formation scenarios, black hole masses, and dark matter annihilation modes. Data from the Fermi Gamma-Ray Space Telescope are used to constrain models of dark matter annihilation and the formation of the first stars.

  8. Drastic disorded-induced reduction of signal amplification in scale-free networks

    CERN Document Server

    Chacón, Ricardo

    2014-01-01

    Understanding information transmission across a network is a fundamental task for controlling and manipulating both biological and man-made information processing systems. Here, we show how topological resonant-like amplification effects in scale-free networks of signaling devices are drastically reduced when phase disorder in the external signals is considered. This is demonstrated theoretically by means of a star-like network of overdamped bistable systems, and confirmed numerically by simulations of scale-free networks of such systems. The taming effect of the phase disorder is found to be sensitive to the amplification's strength, while the topology-induced amplification mechanism is robust against this kind of quenched disorder in the sense that it does not significantly change the values of the coupling strength where amplification is maximum in its absence.

  9. Localized attack on clustering networks

    CERN Document Server

    Dong, Gaogao; Du, Ruijin; Shao, Shuai; Stanley, H Eugene; Shlomo, Havlin

    2016-01-01

    Clustering network is one of which complex network attracting plenty of scholars to discuss and study the structures and cascading process. We primarily analyzed the effect of clustering coefficient to other various of the single clustering network under localized attack. These network models including double clustering network and star-like NON with clustering and random regular (RR) NON of ER networks with clustering are made up of at least two networks among which exist interdependent relation among whose degree of dependence is measured by coupling strength. We show both analytically and numerically, how the coupling strength and clustering coefficient effect the percolation threshold, size of giant component, critical coupling point where the behavior of phase transition changes from second order to first order with the increase of coupling strength between the networks. Last, we study the two types of clustering network: one type is same with double clustering network in which each subnetwork satisfies ...

  10. Cold Dark Clouds: The Initial Conditions for Star Formation

    CERN Document Server

    Bergin, Edwin A

    2007-01-01

    Cold dark clouds are nearby members of the densest and coldest phase in the galactic interstellar medium, and represent the most accessible sites where stars like our Sun are currently being born. In this review we discuss recent progress in their study, including the newly discovered infrared dark clouds that are likely precursors to stellar clusters. At large scales, dark clouds present filamentary mass distributions with motions dominated by supersonic turbulence. At small, sub-parsec scales, a population of subsonic starless cores provides a unique glimpse of the conditions prior to stellar birth. Recent studies of starless cores reveal a combination of simple physical properties together with a complex chemical structure dominated by the freeze-out of molecules onto cold dust grains. Elucidating this combined structure is both an observational and theoretical challenge whose solution will bring us closer to understanding how molecular gas condenses to form stars.

  11. Revealing the Cytotoxicity of Residues of Phosphazene Catalysts Used for Synthesis of Poly(ethylene oxide)

    KAUST Repository

    Xia, Yening

    2017-08-24

    We herein report a case study on the toxicity of residual catalyst in metal-free polymer. Eight-arm star-like poly(ethylene oxide)s were successfully synthesized via phosphazene-catalyzed ring-opening polymerization of ethylene oxide using sucrose as an octahydroxy initiator. The products were subjected to MTT assay using human cancer cell lines (MDA-MB-231 and A2780). Comparison between the crude and purified products clearly revealed that the residual phosphazenium salts were considerably cytotoxic regardless of the anionic species, and that the cytotoxicity of more bulky t-BuP4 salt was higher than that of t-BuP2 salt. Such results have therefore put forward the necessity for removal of the catalyst residues from PEO-based polymers synthesized through phosphazene catalysis for bio-related applications, and for the development of less or non-toxic organocatalysts for such polymers.

  12. VizieR Online Data Catalog: UV-excess quasar candidates (Moreau+, 1995)

    Science.gov (United States)

    Moreau, O.; Reboul, H.

    1995-01-01

    We have developed a procedure (so called PAPA) for measurement of magnitudes (about 0.1mag accurate) and positions (with accuracy better than 0.5arcsec) of all the objects present on photographic plates digitised with the MAMA machine. This homogeneous procedure was applied to four Schmidt plates - in U, B and twice V - covering the Palomar-Sky-Survey field PS +30deg 13h00m, a 40-square-degree zone at the North Galactic Pole. A general-interest exhaustive tricolour catalogue of 19542 star-like objects down to V=20.0 has been produced and we selected 1681 quasar candidates on the basis of ultraviolet excess and, when possible, absence of any measurable proper motion. The astrometric and photometric catalogue of the candidates is given in electronic form. (4 data files).

  13. The use of a central beam stop for contrast enhancement in TEM imaging

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Chao [Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ, Delft (Netherlands); College of Computer, National University of Defense Technology, Changsha (China); Xu, Qiang, E-mail: q.xu@tudelft.nl [Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ, Delft (Netherlands); Peters, Peter J. [Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ, Delft (Netherlands); Antoni van Leeuwenhoek Hospital NKI AVL, Netherlands Cancer Institute, Division Cell Biology 2, NL-1066 CX Amsterdam (Netherlands); Zandbergen, Henny [Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ, Delft (Netherlands)

    2013-11-15

    Dark field TEM imaging using a stop of the central beam (DF-000) is reported. It is shown that a strong enhancement in the contrast can be obtained for graphene as example of weak phase object and endocytic multivescilar body as example of an unstained biological sample. No charging or significant contamination of the central beam stop is observed. For graphene, a resolution beyond 1 Å{sup −1} was easily obtained. DF-000 imaging can be considered as a good and easy to use alternative of a phase plate. - Highlights: • Center stop DF imaging is a good method to improve contrast for weak phase object • Charging problem is avoided by using a Mercedes-star-like center stop • C{sub s} correction and CMOS camera improve the center stop DF imaging quality.

  14. Y chromosomes of 40% Chinese descend from three Neolithic super-grandfathers.

    Directory of Open Access Journals (Sweden)

    Shi Yan

    Full Text Available Demographic change of human populations is one of the central questions for delving into the past of human beings. To identify major population expansions related to male lineages, we sequenced 78 East Asian Y chromosomes at 3.9 Mbp of the non-recombining region, discovered >4,000 new SNPs, and identified many new clades. The relative divergence dates can be estimated much more precisely using a molecular clock. We found that all the Paleolithic divergences were binary; however, three strong star-like Neolithic expansions at ∼6 kya (thousand years ago (assuming a constant substitution rate of 1×10(-9/bp/year indicates that ∼40% of modern Chinese are patrilineal descendants of only three super-grandfathers at that time. This observation suggests that the main patrilineal expansion in China occurred in the Neolithic Era and might be related to the development of agriculture.

  15. Dynamical Convergence Trajectory in Networks

    Institute of Scientific and Technical Information of China (English)

    TAN Ning; ZHANG Yun-Jun; OUYANG Qi; GENG Zhi

    2005-01-01

    @@ It is well known that topology and dynamics are two major aspects to determine the function of a network. We study one of the dynamic properties of a network: trajectory convergence, i.e. how a system converges to its steady state. Using numerical and analytical methods, we show that in a logical-like dynamical model, the occurrence of convergent trajectory in a network depends mainly on the type of the fixed point and the ratio between activation and inhibition links. We analytically proof that this property is induced by the competition between two types of state transition structures in phase space: tree-like transition structure and star-like transition structure. We show that the biological networks, such as the cell cycle network in budding yeast, prefers the tree-like transition structures and suggest that this type of convergence trajectories may be universal.

  16. Featured Image: A Search for Stellar Bow Shock Nebulae

    Science.gov (United States)

    Kohler, Susanna

    2017-02-01

    These dynamic infrared images (click for the full view!) reveal what are known as bow shock nebulae nebulae that form at the interface between the interstellar medium and the stellar wind from a high-speed star zipping through the galaxy (the arrows show the direction of motion of the star). When the relative speed between the two is supersonic, an arc-shaped bow shock forms ahead of the star, like the six prototypical ones pictured here. A team of scientists led by Henry Kobulnicky (University of Wyoming) has recently searched through survey data from the Spitzer Space Telescope and the Wide Field Infrared Explorer (WISE) to build a catalog of more than 700 such bow-shock nebula candidates, the vast majority of which are new discoveries. To find out more about their sample, check out the paper below!CitationHenry A. Kobulnicky et al 2016 ApJS 227 18. doi:10.3847/0067-0049/227/2/18

  17. Discovery of New Type of Exoplanets Made of Liquid Metallic Hydrogen

    Science.gov (United States)

    Flor Torres, L. M.; Coziol, R.; Schröeder, K.-P.; Caretta, C. A.

    2017-07-01

    The study of exoplanets does not only consist in finding them, but also in establishing and understanding their physical characteristics. One of the most important results so far is that many exoplanets might possess internal structures than differ significantly from what is observable in the solar system, like, for example, Hot Jupiters and Super-Earths. In our study, we have created a new diagnostic diagram, the BGP diagram that allows to separate exoplanets according to their possible physical structures. We have also introduced a different physical boundary that allows us to identified a new type of massive exoplanets that are Self-Gravitating (SG). By comparing their mass-radius relation (MRR) with those of other exoplanets, and with low-mass stars like Brown Dwarf, we have discovered that the SG exoplanets may have a structure that is different from any other exoplanet observed so far. Comparison with structure model suggests the SG exoplanets would be formed of liquid metallic hydrogen.

  18. Stochastic vehicle routing with recourse

    DEFF Research Database (Denmark)

    Gørtz, Inge Li; Nagarajan, Viswanath; Saket, Rishi

    2012-01-01

    We study the classic Vehicle Routing Problem in the setting of stochastic optimization with recourse. StochVRP is a two-stage problem, where demand is satisfied using two routes: fixed and recourse. The fixed route is computed using only a demand distribution. Then after observing the demand...... instantiations, a recourse route is computed - but costs here become more expensive by a factor λ. We present an O(log2n ·log(nλ))-approximation algorithm for this stochastic routing problem, under arbitrary distributions. The main idea in this result is relating StochVRP to a special case of submodular...... orienteering, called knapsack rank-function orienteering. We also give a better approximation ratio for knapsack rank-function orienteering than what follows from prior work. Finally, we provide a Unique Games Conjecture based ω(1) hardness of approximation for StochVRP, even on star-like metrics on which our...

  19. 2003年金球奖得主名单%Golden Globes 2003:Complete List of Winners

    Institute of Scientific and Technical Information of China (English)

    魏凯

    2003-01-01

    @@ No one can say the Hollywood Foreign Press doesn' t know how to mix things up, and we' re not just talking about the martinis (马提尼酒) the stars were sipping (吸吮) at tonight's Golden Globe Awards. With a list of winners that includes a classic Broadway show (that would be Chicago) and stars like Martin Scorsese, Jack Nicholson, Richard Gere, Meryl Streep and Donald Sutherland, the evening at times seemed like a who's who of Hollywood. But younger shows and stars had their moments, too; The Shield, Curb Your Enthusiasm, Renee Zellweger, Uma Thurman and Michael Chiklis will all be celebrating well-deserved wins tonight. The complete list of winners follows.

  20. Revealing the Cytotoxicity of Residues of Phosphazene Catalysts Used for the Synthesis of Poly(ethylene oxide).

    Science.gov (United States)

    Xia, Yening; Shen, Jizhou; Alamri, Haleema; Hadjichristidis, Nikos; Zhao, Junpeng; Wang, Yucai; Zhang, Guangzhao

    2017-09-01

    We herein report a case study on the toxicity of residual catalyst in metal-free polymer. Eight-arm star-like poly(ethylene oxide)s were successfully synthesized via phosphazene-catalyzed ring-opening polymerization of ethylene oxide using sucrose as an octahydroxy initiator. The products were subjected to MTT assay using human cancer cell lines (MDA-MB-231 and A2780). Comparison between the crude and purified products clearly revealed that the residual phosphazenium salts were considerably cytotoxic, regardless of the anionic species, and that the cytotoxicity of more bulky t-BuP4 salt was higher than that of t-BuP2 salt. Such results have therefore put forward the necessity for removal of the catalyst residues from PEO-based polymers synthesized through phosphazene catalysis for biorelated applications and for the development of less or nontoxic organocatalysts for such polymers.

  1. Coated platelets function in platelet-dependent fibrin formation via integrin αIIbβ3 and transglutaminase factor XIII.

    Science.gov (United States)

    Mattheij, Nadine J A; Swieringa, Frauke; Mastenbroek, Tom G; Berny-Lang, Michelle A; May, Frauke; Baaten, Constance C F M J; van der Meijden, Paola E J; Henskens, Yvonne M C; Beckers, Erik A M; Suylen, Dennis P L; Nolte, Marc W; Hackeng, Tilman M; McCarty, Owen J T; Heemskerk, Johan W M; Cosemans, Judith M E M

    2016-04-01

    Coated platelets, formed by collagen and thrombin activation, have been characterized in different ways: i) by the formation of a protein coat of α-granular proteins; ii) by exposure of procoagulant phosphatidylserine; or iii) by high fibrinogen binding. Yet, their functional role has remained unclear. Here we used a novel transglutaminase probe, Rhod-A14, to identify a subpopulation of platelets with a cross-linked protein coat, and compared this with other platelet subpopulations using a panel of functional assays. Platelet stimulation with convulxin/thrombin resulted in initial integrin α(IIb)β3 activation, the appearance of a platelet population with high fibrinogen binding, (independently of active integrins, but dependent on the presence of thrombin) followed by phosphatidylserine exposure and binding of coagulation factors Va and Xa. A subpopulation of phosphatidylserine-exposing platelets bound Rhod-A14 both in suspension and in thrombi generated on a collagen surface. In suspension, high fibrinogen and Rhod-A14 binding were antagonized by combined inhibition of transglutaminase activity and integrin α(IIb)β3 Markedly, in thrombi from mice deficient in transglutaminase factor XIII, platelet-driven fibrin formation and Rhod-A14 binding were abolished by blockage of integrin α(IIb)β3. Vice versa, star-like fibrin formation from platelets of a patient with deficiency in α(IIb)β3(Glanzmann thrombasthenia) was abolished upon blockage of transglutaminase activity. We conclude that coated platelets, with initial α(IIb)β3 activation and high fibrinogen binding, form a subpopulation of phosphatidylserine-exposing platelets, and function in platelet-dependent star-like fibrin fiber formation via transglutaminase factor XIII and integrin α(IIb)β3.

  2. Cyclodextrin-Based Topological Macromolecules%含环糊精链节的拓扑高分子

    Institute of Scientific and Technical Information of China (English)

    白阳; 范晓东; 穆承广; 杨臻; 王丹; 张海涛

    2013-01-01

    星形、超支化、树枝状、刷状等具有支化拓扑结构的高分子通常具有不同于直链结构高分子的优异性能.将有客体包合功能的环糊精与其结合构筑环糊精拓扑高分子体系,有望在分子识别、基因传输、药控释放等领域得到应用.本文根据高分子拓扑形态的不同,从星形、超支化、树枝状以及其他拓扑形态环糊精聚合物的合成及自组装构筑等方面进行了总结和评述,并在此基础上展望了基于环糊精的拓扑高分子的研究方向和发展趋势.%Branched topological macromoleeules, such as star-like, hyperbranched, dendritic and brush-like macromoleeules, have many unique properties compared with their linear counterparts. Thus in recent years, when a combination of cyclodextrin (CD) possessing molecule cavities with topological structures is obtained, some important applications in various fields, such as molecular recognition, gene delivery and drug delivery system are endowed. In this article, the investigations and applications on the construction and self-assembly of cyclodextrin-based topological polymers are summarized according to the different topologies. The main content includes four aspects as following: ( a ) star-like cyclodextrin polymers, ( b ) hyperbranched cyclodextrin polymers, ( c ) dendritic cyclodextrin polymers, (d) cyclodextrin polymers with other topologies. In addition, new research trends are also expected based on the progress of this kind of polymer.

  3. A model analysis of mechanisms for radial microtubular patterns at root hair initiation sites

    Directory of Open Access Journals (Sweden)

    Pawel Krupinski

    2016-10-01

    Full Text Available Plant cells have two main modes of growth generating anisotropic structures. Diffuse growth where whole cell walls extend in specific directions, guided by anisotropically positioned cellulose fibers, and tip growth, with inhomogeneous addition of new cell wall material at the tip of the structure. Cells are known to regulate these processes via molecular signals and the cytoskeleton. Mechanical stress has been proposed to provide an input to the positioning of the cellulose fibers via cortical microtubules in diffuse growth. In particular, a stress feedback model predicts a circumferential pattern of fibers surrounding apical tissues and growing primordia, guided by the anisotropic curvature in such tissues. In contrast, during the initiation of tip growing root hairs, a star-like radial pattern has recently been observed. Here, we use detailed finite element models to analyze how a change in mechanical properties at the root hair initiation site can lead to star-like stress patterns in order to understand whether a stress-based feedback model can also explain the microtubule patterns seen during root hair initiation. We show that two independent mechanisms, individually or combined, can be sufficient to generate radial patterns. In the first, new material is added locally at the position of the root hair. In the second, increased tension in the initiation area provides a mechanism. Finally, we describe how a molecular model of Rho-of-plant (ROP GTPases activation driven by auxin can position a patch of activated ROP protein basally along a 2D root epidermal cell plasma membrane, paving the way for models where mechanical and molecular mechanisms cooperate in the initial placement and outgrowth of root hairs.

  4. Adaptive Randomization of Neratinib in Early Breast Cancer

    Science.gov (United States)

    Park, John W.; Liu, Minetta C.; Yee, Douglas; Yau, Christina; van 't Veer, Laura J.; Symmans, W. Fraser; Paoloni, Melissa; Perlmutter, Jane; Hylton, Nola M.; Hogarth, Michael; DeMichele, Angela; Buxton, Meredith B.; Chien, A. Jo; Wallace, Anne M.; Boughey, Judy C.; Haddad, Tufia C.; Chui, Stephen Y.; Kemmer, Kathleen A.; Kaplan, Henry G.; Liu, Minetta C.; Isaacs, Claudine; Nanda, Rita; Tripathy, Debasish; Albain, Kathy S.; Edmiston, Kirsten K.; Elias, Anthony D.; Northfelt, Donald W.; Pusztai, Lajos; Moulder, Stacy L.; Lang, Julie E.; Viscusi, Rebecca K.; Euhus, David M.; Haley, Barbara B.; Khan, Qamar J.; Wood, William C.; Melisko, Michelle; Schwab, Richard; Lyandres, Julia; Davis, Sarah E.; Hirst, Gillian L.; Sanil, Ashish; Esserman, Laura J.; Berry, Donald A.

    2017-01-01

    Background I-SPY2, a standing, multicenter, adaptive phase 2 neoadjuvant trial ongoing in high-risk clinical stage II/III breast cancer, is designed to evaluate multiple, novel experimental agents added to standard chemotherapy for their ability to improve the rate of pathologic complete response (pCR). Experimental therapies are compared against a common control arm. We report efficacy for the tyrosine kinase inhibitor neratinib. Methods Eligible women had ≥2.5 cm stage II/III breast cancer, categorized into 8 biomarker subtypes based on HER2, hormone-receptor status (HR), and MammaPrint. Neratinib was evaluated for 10 signatures (prospectively defined subtype combinations), with primary endpoint pCR. MR volume changes inform likelihood of pCR for each patient prior to surgery. Adaptive assignment to experimental arms within disease subtype was based on current Bayesian probabilities of superiority over control. Accrual to experimental arm stop at any time for futility or graduation within a particular signature based on Bayesian predictive probability of success in a confirmatory trial. The maximum sample size in any experimental arm is 120 patients, Results With 115 patients and 78 concurrently randomized controls, neratinib graduated in the HER2+/HR− signature, with mean pCR rate 56% (95% PI: 37 to 73%) vs 33% for controls (11 to 54%). Final predictive probability of success, updated when all pathology data were available, was 79%. Conclusion Adaptive, multi-armed trials can efficiently identify responding tumor subtypes. Neratinib added to standard therapy is highly likely to improve pCR rates in HER2+/HR2212; breast cancer. Confirmation in I-SPY 3, a phase 3 neoadjuvant registration trial, is planned. PMID:27406346

  5. Linking sexual and reproductive health and HIV interventions: a systematic review

    Directory of Open Access Journals (Sweden)

    Kennedy Caitlin E

    2010-07-01

    Full Text Available Abstract Background The international community agrees that the Millennium Development Goals will not be achieved without ensuring universal access to both sexual and reproductive health (SRH services and HIV/AIDS prevention, treatment, care and support. Recently, there has been increasing awareness and discussion of the possible benefits of linkages between SRH and HIV programmes at the policy, systems and service delivery levels. However, the evidence for the efficacy of these linkages has not been systematically assessed. Methods We conducted a systematic review of the evidence for interventions linking SRH and HIV. Structured methods were employed for searching, screening and data extraction. Studies from 1990 to 2007 reporting pre-post or multi-arm evaluation data from SRH-HIV linkage interventions were included. Study design rigour was scored on a nine-point scale. Unpublished programme reports were gathered as "promising practices". Results Of more than 50,000 citations identified, 185 studies were included in the review and 35 were analyzed. These studies had heterogeneous interventions, populations, objectives, study designs, rigour and measured outcomes. SRH-HIV linkage interventions were generally considered beneficial and feasible. The majority of studies showed improvements in all outcomes measured. While there were some mixed results, there were very few negative findings. Generally, positive effects were shown for key outcomes, including HIV incidence, sexually transmitted infection incidence, condom use, contraceptive use, uptake of HIV testing and quality of services. Promising practices (n = 23 tended to evaluate more recent and more comprehensive programmes. Factors promoting effective linkages included stakeholder involvement, capacity building, positive staff attitudes, non-stigmatizing services, and engagement of key populations. Conclusions Existing evidence provides support for linkages, although significant gaps in the

  6. Characteristics of networks of interventions: a description of a database of 186 published networks.

    Science.gov (United States)

    Nikolakopoulou, Adriani; Chaimani, Anna; Veroniki, Areti Angeliki; Vasiliadis, Haris S; Schmid, Christopher H; Salanti, Georgia

    2014-01-01

    Systematic reviews that employ network meta-analysis are undertaken and published with increasing frequency while related statistical methodology is evolving. Future statistical developments and evaluation of the existing methodologies could be motivated by the characteristics of the networks of interventions published so far in order to tackle real rather than theoretical problems. Based on the recently formed network meta-analysis literature we aim to provide an insight into the characteristics of networks in healthcare research. We searched PubMed until end of 2012 for meta-analyses that used any form of indirect comparison. We collected data from networks that compared at least four treatments regarding their structural characteristics as well as characteristics of their analysis. We then conducted a descriptive analysis of the various network characteristics. We included 186 networks of which 35 (19%) were star-shaped (treatments were compared to a common comparator but not between themselves). The median number of studies per network was 21 and the median number of treatments compared was 6. The majority (85%) of the non-star shaped networks included at least one multi-arm study. Synthesis of data was primarily done via network meta-analysis fitted within a Bayesian framework (113 (61%) networks). We were unable to identify the exact method used to perform indirect comparison in a sizeable number of networks (18 (9%)). In 32% of the networks the investigators employed appropriate statistical methods to evaluate the consistency assumption; this percentage is larger among recently published articles. Our descriptive analysis provides useful information about the characteristics of networks of interventions published the last 16 years and the methods for their analysis. Although the validity of network meta-analysis results highly depends on some basic assumptions, most authors did not report and evaluate them adequately. Reviewers and editors need to be aware

  7. INDEXABILITY AND OPTIMAL INDEX POLICIES FOR A CLASS OF REINITIALISING RESTLESS BANDITS

    Science.gov (United States)

    Villar, Sofía S.

    2016-01-01

    Motivated by a class of Partially Observable Markov Decision Processes with application in surveillance systems in which a set of imperfectly observed state processes is to be inferred from a subset of available observations through a Bayesian approach, we formulate and analyze a special family of multi-armed restless bandit problems. We consider the problem of finding an optimal policy for observing the processes that maximizes the total expected net rewards over an infinite time horizon subject to the resource availability. From the Lagrangian relaxation of the original problem, an index policy can be derived, as long as the existence of the Whittle index is ensured. We demonstrate that such a class of reinitializing bandits in which the projects’ state deteriorates while active and resets to its initial state when passive until its completion possesses the structural property of indexability and we further show how to compute the index in closed form. In general, the Whittle index rule for restless bandit problems does not achieve optimality. However, we show that the proposed Whittle index rule is optimal for the problem under study in the case of stochastically heterogenous arms under the expected total criterion, and it is further recovered by a simple tractable rule referred to as the 1-limited Round Robin rule. Moreover, we illustrate the significant suboptimality of other widely used heuristic: the Myopic index rule, by computing in closed form its suboptimality gap. We present numerical studies which illustrate for the more general instances the performance advantages of the Whittle index rule over other simple heuristics. PMID:27212781

  8. Cognitively inspired reinforcement learning architecture and its application to giant-swing motion control.

    Science.gov (United States)

    Uragami, Daisuke; Takahashi, Tatsuji; Matsuo, Yoshiki

    2014-02-01

    Many algorithms and methods in artificial intelligence or machine learning were inspired by human cognition. As a mechanism to handle the exploration-exploitation dilemma in reinforcement learning, the loosely symmetric (LS) value function that models causal intuition of humans was proposed (Shinohara et al., 2007). While LS shows the highest correlation with causal induction by humans, it has been reported that it effectively works in multi-armed bandit problems that form the simplest class of tasks representing the dilemma. However, the scope of application of LS was limited to the reinforcement learning problems that have K actions with only one state (K-armed bandit problems). This study proposes LS-Q learning architecture that can deal with general reinforcement learning tasks with multiple states and delayed reward. We tested the learning performance of the new architecture in giant-swing robot motion learning, where uncertainty and unknown-ness of the environment is huge. In the test, the help of ready-made internal models or functional approximation of the state space were not given. The simulations showed that while the ordinary Q-learning agent does not reach giant-swing motion because of stagnant loops (local optima with low rewards), LS-Q escapes such loops and acquires giant-swing. It is confirmed that the smaller number of states is, in other words, the more coarse-grained the division of states and the more incomplete the state observation is, the better LS-Q performs in comparison with Q-learning. We also showed that the high performance of LS-Q depends comparatively little on parameter tuning and learning time. This suggests that the proposed method inspired by human cognition works adaptively in real environments.

  9. Neural Cell Chip Based Electrochemical Detection of Nanotoxicity

    Directory of Open Access Journals (Sweden)

    Md. Abdul Kafi

    2015-07-01

    Full Text Available Development of a rapid, sensitive and cost-effective method for toxicity assessment of commonly used nanoparticles is urgently needed for the sustainable development of nanotechnology. A neural cell with high sensitivity and conductivity has become a potential candidate for a cell chip to investigate toxicity of environmental influences. A neural cell immobilized on a conductive surface has become a potential tool for the assessment of nanotoxicity based on electrochemical methods. The effective electrochemical monitoring largely depends on the adequate attachment of a neural cell on the chip surfaces. Recently, establishment of integrin receptor specific ligand molecules arginine-glycine-aspartic acid (RGD or its several modifications RGD-Multi Armed Peptide terminated with cysteine (RGD-MAP-C, C(RGD4 ensure farm attachment of neural cell on the electrode surfaces either in their two dimensional (dot or three dimensional (rod or pillar like nano-scale arrangement. A three dimensional RGD modified electrode surface has been proven to be more suitable for cell adhesion, proliferation, differentiation as well as electrochemical measurement. This review discusses fabrication as well as electrochemical measurements of neural cell chip with particular emphasis on their use for nanotoxicity assessments sequentially since inception to date. Successful monitoring of quantum dot (QD, graphene oxide (GO and cosmetic compound toxicity using the newly developed neural cell chip were discussed here as a case study. This review recommended that a neural cell chip established on a nanostructured ligand modified conductive surface can be a potential tool for the toxicity assessments of newly developed nanomaterials prior to their use on biology or biomedical technologies.

  10. Human collective intelligence under dual exploration-exploitation dilemmas.

    Directory of Open Access Journals (Sweden)

    Wataru Toyokawa

    Full Text Available The exploration-exploitation dilemma is a recurrent adaptive problem for humans as well as non-human animals. Given a fixed time/energy budget, every individual faces a fundamental trade-off between exploring for better resources and exploiting known resources to optimize overall performance under uncertainty. Colonies of eusocial insects are known to solve this dilemma successfully via evolved coordination mechanisms that function at the collective level. For humans and other non-eusocial species, however, this dilemma operates within individuals as well as between individuals, because group members may be motivated to take excessive advantage of others' exploratory findings through social learning. Thus, even though social learning can reduce collective exploration costs, the emergence of disproportionate "information scroungers" may severely undermine its potential benefits. We investigated experimentally whether social learning opportunities might improve the performance of human participants working on a "multi-armed bandit" problem in groups, where they could learn about each other's past choice behaviors. Results showed that, even though information scroungers emerged frequently in groups, social learning opportunities reduced total group exploration time while increasing harvesting from better options, and consequentially improved collective performance. Surprisingly, enriching social information by allowing participants to observe others' evaluations of chosen options (e.g., Amazon's 5-star rating system in addition to choice-frequency information had a detrimental impact on performance compared to the simpler situation with only the choice-frequency information. These results indicate that humans groups can handle the fundamental "dual exploration-exploitation dilemmas" successfully, and that social learning about simple choice-frequencies can help produce collective intelligence.

  11. Summary and Recommendations from the National Cancer Institute's Clinical Trials Planning Meeting on Novel Therapeutics for Non-Muscle Invasive Bladder Cancer.

    Science.gov (United States)

    Lerner, Seth P; Bajorin, Dean F; Dinney, Colin P; Efstathiou, Jason A; Groshen, Susan; Hahn, Noah M; Hansel, Donna; Kwiatkowski, David; O'Donnell, Michael; Rosenberg, Jonathan; Svatek, Robert; Abrams, Jeffrey S; Al-Ahmadie, Hikmat; Apolo, Andrea B; Bellmunt, Joaquim; Callahan, Margaret; Cha, Eugene K; Drake, Charles; Jarow, Jonathan; Kamat, Ashish; Kim, William; Knowles, Margaret; Mann, Bhupinder; Marchionni, Luigi; McConkey, David; McShane, Lisa; Ramirez, Nilsa; Sharabi, Andrew; Sharpe, Arlene H; Solit, David; Tangen, Catherine M; Amiri, Abdul Tawab; Van Allen, Eliezer; West, Pamela J; Witjes, J A; Quale, Diane Zipursky

    2016-04-27

    The NCI Bladder Cancer Task Force convened a Clinical Trials Planning Meeting (CTPM) Workshop focused on Novel Therapeutics for Non-Muscle Invasive Bladder Cancer (NMIBC). Meeting attendees included a broad and multi-disciplinary group of clinical and research stakeholders and included leaders from NCI, FDA, National Clinical Trials Network (NCTN), advocacy and the pharmaceutical and biotech industry. The meeting goals and objectives were to: 1) create a collaborative environment in which the greater bladder research community can pursue future optimally designed novel clinical trials focused on the theme of molecular targeted and immune-based therapies in NMIBC; 2) frame the clinical and translational questions that are of highest priority; and 3) develop two clinical trial designs focusing on immunotherapy and molecular targeted therapy. Despite successful development and implementation of large Phase II and Phase III trials in bladder and upper urinary tract cancers, there are no active and accruing trials in the NMIBC space within the NCTN. Disappointingly, there has been only one new FDA approved drug (Valrubicin) in any bladder cancer disease state since 1998. Although genomic-based data for bladder cancer are increasingly available, translating these discoveries into practice changing treatment is still to come. Recently, major efforts in defining the genomic characteristics of NMIBC have been achieved. Aligned with these data is the growing number of targeted therapy agents approved and/or in development in other organ site cancers and the multiple similarities of bladder cancer with molecular subtypes in these other cancers. Additionally, although bladder cancer is one of the more immunogenic tumors, some tumors have the ability to attenuate or eliminate host immune responses. Two trial concepts emerged from the meeting including a window of opportunity trial (Phase 0) testing an FGFR3 inhibitor and a second multi-arm multi-stage trial testing combinations

  12. Myocardial matrix-polyethylene glycol hybrid hydrogels for tissue engineering

    Science.gov (United States)

    Grover, Gregory N.; Rao, Nikhil; Christman, Karen L.

    2014-01-01

    Similar to other protein-based hydrogels, extracellular matrix (ECM) based hydrogels, derived from decellularized tissues, have a narrow range of mechanical properties and are rapidly degraded. These hydrogels contain natural cellular adhesion sites, form nanofibrous networks similar to native ECM, and are biodegradable. In this study, we expand the properties of these types of materials by incorporating poly(ethylene glycol) (PEG) into the ECM network. We use decellularized myocardial matrix as an example of a tissue specific ECM derived hydrogel. Myocardial matrix-PEG hybrids were synthesized by two different methods, cross-linking the proteins with an amine-reactive PEG-star and photo-induced radical polymerization of two different multi-armed PEG-acrylates. We show that both methods allow for conjugation of PEG to the myocardial matrix by gel electrophoresis and infrared spectroscopy. Scanning electron microscopy demonstrated that the hybrid materials still contain a nanofibrous network similar to unmodified myocardial matrix and that the fiber diameter is changed by the method of PEG incorporation and PEG molecular weight. PEG conjugation also decreased the rate of enzymatic degradation in vitro, and increased material stiffness. Hybrids synthesized with amine-reactive PEG had gelation rates of 30 min, similar to the unmodified myocardial matrix, and incorporation of PEG did not prevent cell adhesion and migration through the hydrogels, thus offering the possibility to have an injectable ECM hydrogel that degrades more slowly in vivo. The photo-polymerized radical systems gelled in 4 min upon irradiation, allowing 3D encapsulation and culture of cells, unlike the soft unmodified myocardial matrix. This work demonstrates that PEG incorporation into ECM-based hydrogels can expand material properties, thereby opening up new possibilities for in vitro and in vivo applications.

  13. Rationale and design of ASTEROID 2, a randomized, placebo- and active comparator-controlled study to assess the efficacy and safety of vilaprisan in patients with uterine fibroids.

    Science.gov (United States)

    Seitz, Christian; Bumbuliene, Žana; Costa, Ana Rosa; Heikinheimo, Oskari; Heweker, Andrea; Hudeček, Robert; Jacquemyn, Yves; Melis, Gian Benedetto; Parashar, Pooja; Rechberger, Tomasz; Sánchez, Antonio Cano; van Aken, Bart; Zatik, János; Gemzell-Danielsson, Kristina

    2017-04-01

    Uterine fibroids (UFs) may be treated with progesterone receptor modulators (PRMs), which have been shown to reduce heavy menstrual bleeding and the size of UFs. To date, one PRM (ulipristal acetate) has received regulatory approval for the treatment of UFs; therapy comprises intermittent treatment courses of up to 3months each, followed by a break to allow two menstruations to occur. We report the design of ASTEROID (Assess Safety and efficacy of vilaprisan in patients with uTERine fibrOIDs) 2, a phase 2 study examining the efficacy and safety of a novel PRM, vilaprisan, in women with UFs. In this randomized multi-arm study, vilaprisan (2mg daily) will be administered in different regimens: continuous treatment for 12 or 24weeks, or two 12-week treatment periods separated by a break to allow one menstruation to occur. Efficacy and safety will be compared with that of ulipristal acetate (5mg daily) and placebo. Patients randomized to receive placebo for 12weeks will also be given active treatment for 12weeks. The primary measure of efficacy will be amenorrhoea rate; secondary measures include time to normalized menstrual bleeding and percentage change in UF volume. Endometrial changes will be monitored throughout the study. The placebo- and active comparator-controlled trial ASTEROID 2 is the first study to evaluate systematically the efficacy and safety of different treatment regimens of PRMs in women with UFs. The findings of this study will direct the planning of future clinical trials of vilaprisan. Copyright © 2017 Bayer AG. Published by Elsevier Inc. All rights reserved.

  14. Comparative study among glutamine, acetyl-L-carnitine, vitamin-E and methylcobalamine for treatment of paclitaxel-induced peripheral neuropathy

    Directory of Open Access Journals (Sweden)

    Santu Mondal

    2014-01-01

    Full Text Available Context: One of the major toxicity of paclitaxel is peripheral neuropathy. Sensory components are affected more than motor and autonomic dysfunction. Aims: Acetyl-L-carnitine (ALC, methylcobalamine, vitamin E and glutamine have been used in various trials against placebos. With head on trials among these four drugs missing, this randomized study was conducted to compare the efficacy in relieving symptoms of paclitaxel induced peripheral neuropathy. Settings and Design : This single institutional, prospective, multi-arm, randomized study was conducted as per Helsinki protocol and with local ethical committee clearances. Materials and Methods: Patients of carcinomas of lung, breast and ovary recruited, would receive paclitaxel 175 mg/m 2 intravenous as 1 st or 2 nd line drug. They underwent randomization to any of four treatment arms: Arm A (vitamin E 400 mg OD day 1 of the cycle to 1 month after completion of clinical trial [CT]; Arm B (ALC 250 mg OD from day 1 to day 7 in each cycle of CT; Arm C (glutamine 10 mg TDS from day 2 to day 5 in each cycle and Arm D (methylcobalamine 500 μg TDS from day 1 of the first cycle to 1 month after completion of CT. All drugs were started at the onset of symptoms. CTCAE v 4.02 was used for assessments. Statistical Analysis Used : Changes in scores for sensory, motor and pain symptoms over the study period were compared using repeated measures of General Linear Model of SPSS version 17. Results : 22, 24, 21 and 23 patients were eligible for analysis in four arms. Vitamin E was producing comparable relief as methylcobalamine of peripheral neuropathy. Both vitamin E and methylcobalamine was superior to glutamine and ALC in relieving sensory, motor and pain symptoms. Glutamine and ALC had comparable effects. Conclusions: All four drugs were effective in the alleviation of symptoms with vitamin E and methylcobalaine more effective than glutamine and ALC in control of symptoms of paclitaxel induced peripheral

  15. Nonaxisymmetric instabilities in self-gravitating disks III. Angular momentum transport

    Science.gov (United States)

    Hadley, Kathryn Z.; Dumas, William; Imamura, James N.; Keever, Erik; Tumblin, Rebecka

    2015-09-01

    We follow the development of nonaxisymmetric instabilities of self-gravitating disks from the linear regime to the nonlinear regime. Particular attention is paid to comparison of nonlinear simulation results with previous linear and quasi-linear modeling results to study the mass and angular momentum transport driven by nonaxisymmetric disk instabilities. Systems with star-to-disk mass ratios of and 5 and inner-to-outer disk radius ratios of to 0.66 are investigated. In disks where self-gravity is important, systems with small and large , Jeans-like J modes are dominant and the gravitational stress drives angular momentum transport. In disks where self-gravity is weak, systems with large and large , shear-driven P modes dominate and the Reynolds stress drives angular momentum transport. In disks where self-gravity is intermediate in strength between disks where P modes dominate and disks where J modes dominate, I modes control the evolution of the system and the Reynolds and gravitational stresses both play important roles in the angular momentum transport. In all cases, redistribution of angular momentum takes place on the characteristic disk timescale defined as the orbital period at the location of maximum density in the disk midplane. The disk susceptible to one-armed modes behaves differently than disks dominated by multi-armed spirals. Coupling between the star and the disk driven by one-armed modes leads to angular momentum transfer between the star and disk even when instability is in the linear regime. All modes drive spreading of the disk material and eventually accretion onto the star. The disks dominated by an I mode and one-armed mode do not lead to prompt fission or fragmentation. The J mode dominated disk fragments after instability develops.

  16. Kefir drink leads to a similar weight loss, compared with milk, in a dairy-rich non-energy-restricted diet in overweight or obese premenopausal women: a randomized controlled trial.

    Science.gov (United States)

    Fathi, Yasamin; Faghih, Shiva; Zibaeenezhad, Mohammad Javad; Tabatabaei, Sayed Hamid Reza

    2016-02-01

    Controversy exists regarding whether increasing dairy intake without energy restriction would lead to weight loss. We aimed to compare the potential weight-reducing effects of kefir drink (a probiotic dairy product) and milk in a dairy-rich non-energy-restricted diet in overweight or obese premenopausal women. One hundred and forty-four subjects were assessed for eligibility in this single-center, multi-arm, parallel-group, randomized controlled trial. Of these, seventy-five eligible women aged 25-45 years were randomly assigned to three groups, labeled as control, milk, and kefir, to receive an outpatient dietary regimen for 8 weeks. Subjects in the control group received a diet providing a maintenance level of energy intake, containing 2 servings/day of low-fat dairy products, while those in the milk and kefir groups received a weight maintenance diet, containing 2 additional servings/day (a total of 4 servings/day) of dairy products from low-fat milk or commercial kefir drink, respectively. Anthropometric outcomes including weight, body mass index (BMI), and waist circumference (WC) were measured every 2 weeks. Fifty-eight subjects completed the study. Using analysis of covariance models in the intention-to-treat population (n = 75), we found that at 8 weeks, subjects in the kefir and milk groups had significantly greater reductions in weight, BMI, and WC compared to those in the control group (all p kefir and milk groups. Kefir drink leads to a similar weight loss, compared with milk, in a dairy-rich non-energy-restricted diet in overweight or obese premenopausal women. However, further studies are warranted.

  17. Summary and Recommendations from the National Cancer Institute’s Clinical Trials Planning Meeting on Novel Therapeutics for Non-Muscle Invasive Bladder Cancer

    Science.gov (United States)

    Lerner, Seth P.; Bajorin, Dean F.; Dinney, Colin P.; Efstathiou, Jason A.; Groshen, Susan; Hahn, Noah M.; Hansel, Donna; Kwiatkowski, David; O’Donnell, Michael; Rosenberg, Jonathan; Svatek, Robert; Abrams, Jeffrey S.; Al-Ahmadie, Hikmat; Apolo, Andrea B.; Bellmunt, Joaquim; Callahan, Margaret; Cha, Eugene K.; Drake, Charles; Jarow, Jonathan; Kamat, Ashish; Kim, William; Knowles, Margaret; Mann, Bhupinder; Marchionni, Luigi; McConkey, David; McShane, Lisa; Ramirez, Nilsa; Sharabi, Andrew; Sharpe, Arlene H.; Solit, David; Tangen, Catherine M.; Amiri, Abdul Tawab; Van Allen, Eliezer; West, Pamela J.; Witjes, J. A.; Quale, Diane Zipursky

    2016-01-01

    The NCI Bladder Cancer Task Force convened a Clinical Trials Planning Meeting (CTPM) Workshop focused on Novel Therapeutics for Non-Muscle Invasive Bladder Cancer (NMIBC). Meeting attendees included a broad and multi-disciplinary group of clinical and research stakeholders and included leaders from NCI, FDA, National Clinical Trials Network (NCTN), advocacy and the pharmaceutical and biotech industry. The meeting goals and objectives were to: 1) create a collaborative environment in which the greater bladder research community can pursue future optimally designed novel clinical trials focused on the theme of molecular targeted and immune-based therapies in NMIBC; 2) frame the clinical and translational questions that are of highest priority; and 3) develop two clinical trial designs focusing on immunotherapy and molecular targeted therapy. Despite successful development and implementation of large Phase II and Phase III trials in bladder and upper urinary tract cancers, there are no active and accruing trials in the NMIBC space within the NCTN. Disappointingly, there has been only one new FDA approved drug (Valrubicin) in any bladder cancer disease state since 1998. Although genomic-based data for bladder cancer are increasingly available, translating these discoveries into practice changing treatment is still to come. Recently, major efforts in defining the genomic characteristics of NMIBC have been achieved. Aligned with these data is the growing number of targeted therapy agents approved and/or in development in other organ site cancers and the multiple similarities of bladder cancer with molecular subtypes in these other cancers. Additionally, although bladder cancer is one of the more immunogenic tumors, some tumors have the ability to attenuate or eliminate host immune responses. Two trial concepts emerged from the meeting including a window of opportunity trial (Phase 0) testing an FGFR3 inhibitor and a second multi-arm multi-stage trial testing combinations

  18. A mixed treatment comparison to compare the efficacy and safety of botulinum toxin treatments for cervical dystonia.

    Science.gov (United States)

    Han, Yi; Stevens, Andrea L; Dashtipour, Khashayar; Hauser, Robert A; Mari, Zoltan

    2016-04-01

    A systematic pair-wise comparison of all available botulinum toxin serotype A and B treatments for cervical dystonia (CD) was conducted, as direct head-to-head clinical trial comparisons are lacking. Five botulinum toxin products: Dysport(®) (abobotulinumtoxinA), Botox(®) (onabotulinumtoxinA), Xeomin(®) (incobotulinumtoxinA), Prosigne(®) (Chinese botulinum toxin serotype A) and Myobloc(®) (rimabotulinumtoxinB) have demonstrated efficacy for managing CD. A pair-wise efficacy and safety comparison was performed for all toxins based on literature-reported clinical outcomes. Multi-armed randomized controlled trials (RCTs) were identified for inclusion using a systematic literature review, and assessed for comparability based on patient population and efficacy outcome measures. The Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) was selected as the efficacy outcome measurement for assessment. A mixed treatment comparison (MTC) was conducted using a Bayesian hierarchical model allowing indirect comparison of the interventions. Due to the limitation of available clinical data, this study only investigated the main effect of toxin treatments without explicitly considering potential confounding factors such as gender and formulation differences. There was reasonable agreement between the number of unconstrained data points, residual deviance and pair-wise results. This research suggests that all botulinum toxin serotype A and serotype B treatments were effective compared to placebo in treating CD, with the exception of Prosigne. Based on this MTC analysis, there is no significant efficacy difference between Dysport, Botox, Xeomin and Myobloc at week four post injection. Of the adverse events measured, neither dysphagia nor injection site pain was significantly greater in the treatment or placebo groups.

  19. Peptide-functionalized starPEG/heparin Hydrogels Direct Mitogenicity, Cell Morphology and Cartilage Matrix Distribution in vitro and in vivo.

    Science.gov (United States)

    Hesse, Eliane; Freudenberg, Uwe; Niemietz, Thomas; Greth, Carina; Weisser, Melanie; Hagmann, Sébastien; Binner, Marcus; Werner, Carsten; Richter, Wiltrud

    2017-01-13

    Cell-based tissue engineering is a promising approach for treating cartilage lesions, but available strategies still provide a distinct composition of the extracellular matrix and an inferior mechanical property compared to native cartilage. To achieve fully functional tissue replacement more rationally designed biomaterials may be needed, introducing bioactive molecules which modulate cell behavior and guide tissue regeneration. This study aimed at exploring the impact of cell instructive, adhesion (GCWGGRGDSP called RGD) and collagen-binding (CKLER/CWYRGRL) peptides, incorporated in a tunable, matrixmetalloprotease (MMP)-responsive multi-arm poly(ethylene glycol) (starPEG)/heparin hydrogel on cartilage regeneration parameters in vitro and in vivo. MMP-responsive-starPEG-conjugates with cysteine termini and heparin-maleimide, optionally pre-functionalized with RGD, CKLER, CWYRGRL or control peptides, were cross-linked by Michael type addition to embed and grow mesenchymal stromal cells (MSC) or chondrocytes. While starPEG/heparin-hydrogel strongly supported chondrogenesis of MSC according to COL2A1, BGN and ACAN induction, MMP-degradability enhanced cell viability and proliferation. RGD-modification of the gels promoted cell spreading with intense cell network formation without negative effects on chondrogenesis. However, CKLER and CWYRGRL were unable to enhance the collagen content of constructs. RGD-modification allowed more even collagen type II distribution by chondrocytes throughout the MMP-responsive constructs especially in vivo. Collectively, peptide-instruction via heparin-enriched MMP-degradable starPEG allowed adjustment of self-renewal, cell morphology and cartilage matrix distribution in order to guide MSC and chondrocyte-based cartilage regeneration towards an improved outcome.

  20. A six-month crossover chemoprevention clinical trial of tea in smokers and non-smokers: methodological issues in a feasibility study

    Directory of Open Access Journals (Sweden)

    Dash Chiranjeev

    2012-07-01

    Full Text Available Abstract Background Chemoprevention crossover trials of tea can be more efficient than parallel designs but the attrition and compliance rates with such trials are unknown. Methods Attrition (dropouts and compliance with treatment were assessed in a 25-week randomized, placebo controlled, crossover, feasibility clinical trial of four tea treatments to investigate the effect of tea on oral cancer biomarkers. Each treatment lasted 4 weeks with 2 weeks of washout in between. Participants were 32 smokers and 33 non-smokers without any evidence of premalignant oral lesions. The interventions consisted of packets of green tea, black tea, caffeinated water, or placebo. Participants were assigned to each treatment for four weeks, and were instructed to drink five packets per day while on the treatment. Dropout from the trial and compliance (consumption of ≥ 85% of the prescribed treatment packets are the main outcome measures reported. Results There was a high rate of dropout (51% from the study, and the rates were significantly higher among smokers (64% than non-smokers (36%. Among participants who completed the study the rate of compliance was 72%. The highest rates of dropouts occurred between the first and second treatment visits in both smokers (38% dropout and non-smokers (18% dropout. Throughout the study smokers were more likely to dropout than non-smokers. Black tea treatment was associated with the highest rates of dropout among smokers (37%, but was associated with the lowest rate of dropout among non-smokers (4%. Conclusions In a study conducted to test the feasibility of a four-treatment crossover tea trial, a high rate of dropout among smokers and non-smokers was observed. Multi-arm crossover tea trials might pose a higher burden on participants and research is needed to improve adherence and treatment compliance in such trials. Trial registration number ISRCTN70410203

  1. Synthesis of β-cyclodextrin-Based Star Block Copolymers with Thermo-Responsive Behavior

    Directory of Open Access Journals (Sweden)

    Agnes Wycisk

    2015-05-01

    Full Text Available Star polymers are one example of three-dimensional macromolecules containing several arms with similar molecular weight connected to a central core. Due to their compact structure and their enhanced segment density in comparison to linear polymers of the same molecular weight, they have attracted significant attention during recent years. The preparation of block-arm star copolymers with a permanently hydrophilic block and an “environmentally” sensitive block, which can change its nature from hydrophilic to hydrophobic, leads to nanometer-sized responsive materials with unique properties. These polymers are able to undergo a conformational change or phase transition as a reply to an external stimulus resulting in the formation of core–shell nanoparticles, which further tend to aggregate. Star-shaped copolymers with different cores were synthesized via atom transfer radical polymerization (ATRP. The core-first method chosen as synthetic strategy allows good control over the polymer architecture. First of all the multifunctional initiators were prepared by esterification reaction of the hydroxyl groups with 2-chloropropionyl chloride. Using β-cyclodextrin as core molecules, which possess a well-defined number of functional groups up to 21, allows defining the number of arms per star polymer. In order to prepare stimuli-responsive multi-arm copolymers, containing a stimuli-responsive (poly(N-isopropylacrylamide (PNIPAAm and a non-responsive block (poly(N,N-dimethylacrylamide (PDMAAm, consecutive ATRP was carried out. The polymers were characterized intensively using NMR spectroscopy and size exclusion chromatography (SEC, whereas the temperature-depending aggregation behavior in aqueous solution was determined via turbidimetry and differential scanning calorimetry (DSC.

  2. A Planet Found by Pulsations

    Science.gov (United States)

    Kohler, Susanna

    2016-10-01

    Searching for planets around very hot stars is much more challenging than looking around cool stars. For this reason, the recent discovery of a planet around a main-sequence A star is an important find both because of its unique position near the stars habitable zone, and because of the way in which the planet was discovered.Challenges in VariabilityIn the past three decades, weve discovered thousands of exoplanets yet most of them have been found around cool stars (like M dwarfs) or moderate stars (like G stars like our Sun). Very few of the planets that weve found orbit hot stars; in fact, weve only discovered ~20 planets orbiting the very hot, main-sequence A stars.The instability strip, indicated on an H-R diagram. Stellar classification types are listed across the bottom of the diagram. Many main-sequence A stars reside in the instability strip. [Rursus]Why is this? We dont expect that main-sequence A stars host fewer planets than cooler stars. Instead, its primarily because the two main techniques that we use to find planets namely, transits and radial velocity cant be used as effectively on the main-sequence A stars that are most likely to host planets, because the luminosities of these stars are often variable.These stars can lie on whats known as the classical instability strip in the Herzsprung-Russell diagram. Such variable stars pulsate due to changes in the ionization state of atoms deep in their interiors, which causes the stars to puff up and then collapse back inward. For variable main-sequence A stars, the periods for these pulsations can be several to several tens of times per day.These very pulsations that make transits and radial-velocity measurements so difficult, however, can potentially be used to detect planets in a different way. Led by Simon Murphy (University of Sydney, Australia and Aarhus University, Denmark), a team of scientists has recently detected the first planet ever to be discovered around a main-sequence A star from the timing

  3. Block copolymer/ferroelectric nanoparticle nanocomposites

    Science.gov (United States)

    Pang, Xinchang; He, Yanjie; Jiang, Beibei; Iocozzia, James; Zhao, Lei; Guo, Hanzheng; Liu, Jin; Akinc, Mufit; Bowler, Nicola; Tan, Xiaoli; Lin, Zhiqun

    2013-08-01

    Nanocomposites composed of diblock copolymer/ferroelectric nanoparticles were formed by selectively constraining ferroelectric nanoparticles (NPs) within diblock copolymer nanodomains via judicious surface modification of ferroelectric NPs. Ferroelectric barium titanate (BaTiO3) NPs with different sizes that are permanently capped with polystyrene chains (i.e., PS-functionalized BaTiO3NPs) were first synthesized by exploiting amphiphilic unimolecular star-like poly(acrylic acid)-block-polystyrene (PAA-b-PS) diblock copolymers as nanoreactors. Subsequently, PS-functionalized BaTiO3 NPs were preferentially sequestered within PS nanocylinders in the linear cylinder-forming polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer upon mixing the BaTiO3 NPs with PS-b-PMMA. The use of PS-b-PMMA diblock copolymers, rather than traditional homopolymers, offers the opportunity for controlling the spatial organization of PS-functionalized BaTiO3 NPs in the PS-b-PMMA/BaTiO3 NP nanocomposites. Selective solvent vapor annealing was utilized to control the nanodomain orientation in the nanocomposites. Vertically oriented PS nanocylinders containing PS-functionalized BaTiO3 NPs were yielded after exposing the PS-b-PMMA/BaTiO3 NP nanocomposite thin film to acetone vapor, which is a selective solvent for PMMA block. The dielectric properties of nanocomposites in the microwave frequency range were investigated. The molecular weight of PS-b-PMMA and the size of BaTiO3 NPs were found to exert an apparent influence on the dielectric properties of the resulting nanocomposites.Nanocomposites composed of diblock copolymer/ferroelectric nanoparticles were formed by selectively constraining ferroelectric nanoparticles (NPs) within diblock copolymer nanodomains via judicious surface modification of ferroelectric NPs. Ferroelectric barium titanate (BaTiO3) NPs with different sizes that are permanently capped with polystyrene chains (i.e., PS-functionalized BaTiO3NPs) were

  4. Nanomolar detection of glucose using SERS substrates fabricated with albumin coated gold nanoparticles

    Science.gov (United States)

    Perez-Mayen, Leonardo; Oliva, Jorge; Salas, P.; de La Rosa, Elder

    2016-06-01

    This work presents the design of substrates for Surface Enhanced Raman Scattering (SERS) using star-like gold nanoparticles synthesized by a wet chemical method. The SERS substrates were used for glucose detection for concentrations as low as 10-7 M, which represents an enhancement factor (EF) of 109, as a result of the hot spot formed by the spike termination and appropriate distribution of the gold nanoparticles. An improvement of two orders of magnitude was obtained by coating the gold nanoparticles with albumin with the configuration: glass/Au nanoparticles/albumin. In this case the lowest detection was at a concentration of 10-9 M for an EF of 1011. The albumin molecule allowed us to enhance the Raman signal because of the formation of peptide bonds (COOH-NH2) generated due to the interaction of glucose with albumin, and the appropriate separation distance between the glucose molecules and gold nanoparticles. The presence of such peptide conjugates was confirmed by FTIR spectra. Thus, our results suggest that our SERS substrates can be useful for the detection of very low concentrations of glucose, which is important for the diagnosis of diabetes in the field of medicine.This work presents the design of substrates for Surface Enhanced Raman Scattering (SERS) using star-like gold nanoparticles synthesized by a wet chemical method. The SERS substrates were used for glucose detection for concentrations as low as 10-7 M, which represents an enhancement factor (EF) of 109, as a result of the hot spot formed by the spike termination and appropriate distribution of the gold nanoparticles. An improvement of two orders of magnitude was obtained by coating the gold nanoparticles with albumin with the configuration: glass/Au nanoparticles/albumin. In this case the lowest detection was at a concentration of 10-9 M for an EF of 1011. The albumin molecule allowed us to enhance the Raman signal because of the formation of peptide bonds (COOH-NH2) generated due to the

  5. A Slice of Orion

    Science.gov (United States)

    2006-01-01

    [figure removed for brevity, see original site] Extended Orion Nebula Cloud This image composite shows a part of the Orion constellation surveyed by NASA's Spitzer Space Telescope. The shape of the main image was designed by astronomers to roughly follow the shape of Orion cloud A, an enormous star-making factory containing about 1,800 young stars. This giant cloud includes the famous Orion nebula (bright circular area in 'blade' part of hockey stick-shaped box at the bottom), which is visible to the naked eye on a clear, dark night as a fuzzy star in the hunter constellation's sword. The region that makes up the shaft part of the hockey stick box stretches 70 light-years beyond the Orion nebula. This particular area does not contain massive young stars like those of the Orion nebula, but is filled with 800 stars about the same mass as the sun. These sun-like stars don't live in big 'cities,' or clusters, of stars like the one in the Orion nebula; instead, they can be found in small clusters (right inset), or in relative isolation (middle insert). In the right inset, developing stars are illuminating the dusty cloud, creating small wisps that appear greenish. The stars also power speedy jets of gas (also green), which glow as the jets ram into the cloudy material. Since infrared light can penetrate through dust, we see not only stars within the cloud, but thousands of stars many light-years behind it, which just happen to be in the picture like unwanted bystanders. Astronomers carefully separate the young stars in the Orion cloud complex from the bystanders by looking for their telltale infrared glow. The infrared image shows light captured by Spitzer's infrared array camera. Light with wavelengths of 8 and 5.8 microns (red and orange) comes mainly from dust that has been heated by starlight. Light of 4.5 microns (green) shows hot gas and dust; and light of 3.6 microns (blue) is from starlight.

  6. Quasar Formation and Energy Emission in Black Hole Universe

    Directory of Open Access Journals (Sweden)

    Zhang T. X.

    2012-07-01

    Full Text Available Formation and energy emission of quasars are investigated in accord with the black hole universe, a new cosmological model recently developed by Zhang. According to this new cosmological model, the universe originated from a star-like black hole and grew through a supermassive black hole to the present universe by accreting ambient matter and merging with other black holes. The origin, structure, evolution, expansion, and cosmic microwave background radiation of the black hole universe have been fully ex- plained in Paper I and II. This study as Paper III explains how a quasar forms, ignites and releases energy as an amount of that emitted by dozens of galaxies. A main sequence star, after its fuel supply runs out, will, in terms of its mass, form a dwarf, a neutron star, or a black hole. A normal galaxy, after its most stars have run out of their fuels and formed dwarfs, neutron stars, and black holes, will eventually shrink its size and collapse towards the center by gravity to form a supermassive black hole with billions of solar masses. This collapse leads to that extremely hot stellar black holes merge each other and further into the massive black hole at the center and meantime release a huge amount of radiation energy that can be as great as that of a quasar. Therefore, when the stellar black holes of a galaxy collapse and merge into a supermassive black hole, the galaxy is activated and a quasar is born. In the black hole universe, the observed dis- tant quasars powered by supermassive black holes can be understood as donuts from the mother universe. They were actually formed in the mother universe and then swallowed into our universe. The nearby galaxies are still very young and thus quiet at the present time. They will be activated and further evolve into quasars after billions of years. At that time, they will enter the universe formed by the currently observed distant quasars as similar to the distant quasars entered our universe

  7. Suppression of hepatic stellate cell activation by microRNA-29b

    Energy Technology Data Exchange (ETDEWEB)

    Sekiya, Yumiko; Ogawa, Tomohiro [Department of Hepatology, Graduate School of Medicine, Osaka City University, Osaka (Japan); Liver Research Center, Graduate School of Medicine, Osaka City University, Osaka (Japan); Yoshizato, Katsutoshi [Department of Hepatology, Graduate School of Medicine, Osaka City University, Osaka (Japan); Liver Research Center, Graduate School of Medicine, Osaka City University, Osaka (Japan); PhoenixBio Co. Ltd., Hiroshima (Japan); Ikeda, Kazuo [Department of Anatomy and Cell Biology, Graduate School of Medical Sciences, Nagoya City University, Aichi (Japan); Kawada, Norifumi, E-mail: kawadanori@med.osaka-cu.ac.jp [Department of Hepatology, Graduate School of Medicine, Osaka City University, Osaka (Japan); Liver Research Center, Graduate School of Medicine, Osaka City University, Osaka (Japan)

    2011-08-19

    Highlights: {yields} Expression of miR-29b was found to be down-regulated during the activation of hepatic stellate cells in primary culture. {yields} Transfection of a miR-29b precursor markedly attenuated the expression of Col1a1 and Col1a2 mRNAs. {yields} It blunted the increased expression of {alpha}-SMA, DDR2, FN1, ITGB1, and PDGFR-b mRNAs essential for stellate cell activation. {yields} miR-29b overexpression led stellate cells to remain in a quiescent state, as evidenced by their star-like morphology. {yields} miR-29b overexpression suppressed the expression of c-fos mRNA. -- Abstract: MicroRNAs (miRNAs) participate in the regulation of cellular functions including proliferation, apoptosis, and migration. It has been previously shown that the miR-29 family is involved in regulating type I collagen expression by interacting with the 3'UTR of its mRNA. Here, we investigated the roles of miR-29b in the activation of mouse primary-cultured hepatic stellate cells (HSCs), a principal collagen-producing cell in the liver. Expression of miR-29b was found to be down-regulated during HSC activation in primary culture. Transfection of a miR-29b precursor markedly attenuated the expression of Col1a1 and Col1a2 mRNAs and additionally blunted the increased expression of {alpha}-SMA, DDR2, FN1, ITGB1, and PDGFR-{beta}, which are key genes involved in the activation of HSCs. Further, overexpression of miR-29b led HSCs to remain in a quiescent state, as evidenced by their quiescent star-like cell morphology. Although phosphorylation of FAK, ERK, and Akt, and the mRNA expression of c-jun was unaffected, miR-29b overexpression suppressed the expression of c-fos mRNA. These results suggested that miR-29b is involved in the activation of HSCs and could be a candidate molecule for suppressing their activation and consequent liver fibrosis.

  8. Mirrors Containing Biomimetic Shape-Control Actuators

    Science.gov (United States)

    Bar-Cohen, Yoseph; Mouroulis, Pantazis; Bao, Xiaoqi; Sherrit, Stewart

    2003-01-01

    Curved mirrors of a proposed type would comprise lightweight sheets or films containing integral, biologically inspired actuators for controlling their surface figures. These mirrors could be useful in such applications as collection of solar energy, focusing of radio beams, and (provided sufficient precision could be achieved) imaging. These mirrors were originally intended for use in outer space, but it should also be possible to develop terrestrial versions. Several prior NASA Tech Briefs articles have described a variety of approaches to the design of curved, lightweight mirrors containing integral shape-control actuators. The primary distinction between the present approach and the prior approaches lies in the actuator design concept, which involves shapes and movements reminiscent of those of a variety of small, multi-armed animals. The shape and movement of an actuator of this type can also be characterized as reminiscent of that of an umbrella. This concept can be further characterized as a derivative of that of multifinger grippers, the fingers of which are bimorph bending actuators (see Figure 1). The fingers of such actuators can be strips containing any of a variety of materials that have been investigated for use as actuators, including such electroactive polymers as ionomeric polymer/metal composites (IPMCs), ferroelectric polymers, and grafted elastomers. A mirror according to this proposal would be made from a sheet of one of the actuator composites mentioned above. The design would involve many variables, including the pre-curvature and stiffness of the mirror sheet, the required precision of figure control, the required range of variation in focal length (see Figure 2), the required precision of figure control for imaging or non-imaging use, the bending and twisting moments needed to effect the required deformations, and voltage-tomoment coefficients of the actuators, and the voltages accordingly required for actuation. A typical design would call

  9. A systematic review of income generation interventions, including microfinance and vocational skills training, for HIV prevention.

    Science.gov (United States)

    Kennedy, Caitlin E; Fonner, Virginia A; O'Reilly, Kevin R; Sweat, Michael D

    2014-01-01

    Income generation interventions, such as microfinance or vocational skills training, address structural factors associated with HIV risk. However, the effectiveness of these interventions on HIV-related outcomes in low- and middle-income countries has not been synthesized. The authors conducted a systematic review by searching electronic databases from 1990 to 2012, examining secondary references, and hand-searching key journals. Peer-reviewed studies were included in the analysis if they evaluated income generation interventions in low- or middle-income countries and provided pre-post or multi-arm measures on behavioral, psychological, social, care, or biological outcomes related to HIV prevention. Standardized forms were used to abstract study data in duplicate and study rigor was assessed. Of the 5218 unique citations identified, 12 studies met criteria for inclusion. Studies were geographically diverse, with six conducted in sub-Saharan Africa, three in South or Southeast Asia, and three in Latin America and the Caribbean. Target populations included adult women (N = 6), female sex workers/bar workers (N = 3), and youth/orphans (N = 3). All studies targeted females except two among youth/orphans. Study rigor was moderate, with two group-randomized trials and two individual-randomized trials. All interventions except three included some form of microfinance. Only a minority of studies found significant intervention effects on condom use, number of sexual partners, or other HIV-related behavioral outcomes; most studies showed no significant change, although some may have had inadequate statistical power. One trial showed a 55% reduction in intimate partner violence (adjusted risk ratio 0.45, 95% confidence interval 0.23-0.91). No studies measured incidence/prevalence of HIV or sexually transmitted infections among intervention recipients. The evidence that income generation interventions influence HIV-related behaviors and outcomes is inconclusive. However, these

  10. Two prophylactic medication approaches in addition to a pain control regimen for early medical abortion misoprostol: study protocol for a randomized, controlled trial.

    Science.gov (United States)

    Dragoman, Monica V; Grossman, Daniel; Kapp, Nathalie; Huong, Nguyen My; Habib, Ndema; Dung, Duong Lan; Tamang, Anand

    2016-10-12

    study completion. Although pain is one of the most common side effects encountered with medical abortion, little is known about optimal pain management for this process. This multi-arm trial design offers an efficient approach to evaluating two prophylactic pain management regimens compared to use of pain medication as needed. ACTRN12613000017729 (Prospectively registered 8/1/2013).

  11. Bioactive hydrogels made from step-growth derived PEG-peptide macromers.

    Science.gov (United States)

    Miller, Jordan S; Shen, Colette J; Legant, Wesley R; Baranski, Jan D; Blakely, Brandon L; Chen, Christopher S

    2010-05-01

    Synthetic hydrogels based on poly(ethylene glycol) (PEG) have been used as biomaterials for cell biology and tissue engineering investigations. Bioactive PEG-based gels have largely relied on heterobifunctional or multi-arm PEG precursors that can be difficult to synthesize and characterize or expensive to obtain. Here, we report an alternative strategy, which instead uses inexpensive and readily available PEG precursors to simplify reactant sourcing. This new approach provides a robust system in which to probe cellular interactions with the microenvironment. We used the step-growth polymerization of PEG diacrylate (PEGDA, 3400Da) with bis-cysteine matrix metalloproteinase (MMP)-sensitive peptides via Michael-type addition to form biodegradable photoactive macromers of the form acrylate-PEG-(peptide-PEG)(m)-acrylate. The molecular weight (MW) of these macromers is controlled by the stoichiometry of the reaction, with a high proportion of resultant macromer species greater than 500kDa. In addition, the polydispersity of these materials was nearly identical for three different MMP-sensitive peptide sequences subjected to the same reaction conditions. When photopolymerized into hydrogels, these high MW materials exhibit increased swelling and sensitivity to collagenase-mediated degradation as compared to previously published PEG hydrogel systems. Cell-adhesive acrylate-PEG-CGRGDS was synthesized similarly and its immobilization and stability in solid hydrogels was characterized with a modified Lowry assay. To illustrate the functional utility of this approach in a biological setting, we applied this system to develop materials that promote angiogenesis in an ex vivo aortic arch explant assay. We demonstrate the formation and invasion of new sprouts mediated by endothelial cells into the hydrogels from embedded embryonic chick aortic arches. Furthermore, we show that this capillary sprouting and three-dimensional migration of endothelial cells can be tuned by

  12. A cluster-randomized, controlled trial of nutritional supplementation and promotion of responsive parenting in Madagascar: the MAHAY study design and rationale.

    Science.gov (United States)

    Fernald, Lia C H; Galasso, Emanuela; Qamruddin, Jumana; Ranaivoson, Christian; Ratsifandrihamanana, Lisy; Stewart, Christine P; Weber, Ann M

    2016-06-03

    Over half of the world's children suffer from poor nutrition, and as a consequence they experience delays in physical and mental health, and cognitive development. There is little data evaluating the effects of delivery of lipid-based, nutrition supplementation on growth and development during pregnancy and early childhood within the context of a scaled-up program. Furthermore, there is limited evidence on effects of scaled-up, home-visiting programs that focus on the promotion of child development within the context of an existing, national nutrition program. The MAHAY ("smart" in Malagasy) study uses a multi-arm randomized-controlled trial (RCT) to test the effects and cost-effectiveness of combined interventions to address chronic malnutrition and poor child development. The arms of the trial are: (T0) existing program with monthly growth monitoring and nutritional/hygiene education; (T1) is T0 + home visits for intensive nutrition counseling within a behavior change framework; (T2) is T1 + lipid-based supplementation (LNS) for children 6-18 months old; (T3) is T2 + LNS supplementation of pregnant/lactating women; and (T4) is T1 + intensive home visiting program to support child development. There are anticipated to be n = 25 communities in each arm (n = 1250 pregnant women, n = 1250 children 0-6 months old, and n = 1250 children 6-18 months old). Primary outcomes include growth (length/height-for-age z-scores) and child development (mental, motor and social development). Secondary outcomes include care-giver reported child morbidity, household food security and diet diversity, micro-nutrient status, maternal knowledge of child care and feeding practices, and home stimulation practices. We will estimate unadjusted and adjusted intention-to-treat effects. Study protocols have been reviewed and approved by the Malagasy Ethics Committee at the Ministry of Health in Madagascar and by the institutional review board at the University of

  13. Testing the activitystat hypothesis: a randomised controlled trial protocol

    Directory of Open Access Journals (Sweden)

    Gomersall Sjaan

    2012-10-01

    Full Text Available Abstract Background The activitystat hypothesis proposes that when physical activity or energy expenditure is increased or decreased in one domain, there will be a compensatory change in another domain to maintain an overall, stable level of physical activity or energy expenditure. To date, there has been no experimental study primarily designed to test the activitystat hypothesis in adults. The aim of this trial is to determine the effect of two different imposed exercise loads on total daily energy expenditure and physical activity levels. Methods This study will be a randomised, multi-arm, parallel controlled trial. Insufficiently active adults (as determined by the Active Australia survey aged 18–60 years old will be recruited for this study (n=146. Participants must also satisfy the Sports Medicine Australia Pre-Exercise Screening System and must weigh less than 150 kg. Participants will be randomly assigned to one of three groups using a computer-generated allocation sequence. Participants in the Moderate exercise group will receive an additional 150 minutes of moderate to vigorous physical activity per week for six weeks, and those in the Extensive exercise group will receive an additional 300 minutes of moderate to vigorous physical activity per week for six weeks. Exercise targets will be accumulated through both group and individual exercise sessions monitored by heart rate telemetry. Control participants will not be given any instructions regarding lifestyle. The primary outcome measures are activity energy expenditure (doubly labeled water and physical activity (accelerometry. Secondary measures will include resting metabolic rate via indirect calorimetry, use of time, maximal oxygen consumption and several anthropometric and physiological measures. Outcome measures will be conducted at baseline (zero weeks, mid- and end-intervention (three and six weeks with three (12 weeks and six month (24 week follow-up. All assessors will be

  14. Apolipoprotein E gene polymorphisms are associated with primary hyperuricemia in a Chinese population.

    Directory of Open Access Journals (Sweden)

    Jie Wu

    Full Text Available OBJECTIVE: Primary hyperuricemia, an excess of uric acid in the blood, is a major public health problem. In addition to the morbidity that is attributable to gout, hyperuricemia is also associated with metabolic syndrome, hypertension, and cardiovascular disease. This study aims to assess the genetic associations between Apolipoprotein E (APOE polymorphisms and hyperuricemia in a Chinese population. METHODS: A total of 770 subjects (356 hyperuricemic cases and 414 normouricemic controls were recruited from the Ningxia Hui Autonomous Region, China. A physical examination was performed and fasting blood was collected for biochemical tests, including determination of the levels of serum lipid, creatinine, and uric acid. Multi-ARMS PCR was applied to determine the APOE genotypes, followed by an investigation of the distribution of APOE genotypes and alleles frequencies in the controls and cases. RESULTS: The frequencies of the APOE-ε2ε3 genotype (17.70% vs. 10.39%, P = 0.003 and the APOE-ε2 allele (10.53% vs. 5.80%, P = 0.001 were significantly higher in the hyperuricemic group than in the normouricemic group. Furthermore, male cases were more likely to have the APOE-ε2ε3 genotype and APOE-ε2 allele, compared with male controls. In both Han and Hui subjects, cases were more likely to have the APOE-ε2ε3 genotype and the APOE-ε2 allele compared with controls. Furthermore, multivariate logistic regression showed that carriers of the APOE-ε2ε3 genotype (P = 0.001, OR = 2.194 and the ε2 allele (P = 0.001, OR = 2.099 were significantly more likely to experience hyperuricemia than carriers of the ε3/ε3 genotype and the ε3 allele after adjustment for sex, body mass index (BMI, diastolic blood pressure (DBP, triglyceride (TG, low density lipoprotein cholesterol (LDL-C, creatinine (Cr and fasting blood glucose (FBG. CONCLUSIONS: The APOE-ε2ε3 genotype and the APOE-ε2 allele are associated with serum uric acid levels

  15. Encoding physico-chemical cues in synthetic hydrogels by triple helix assembly of collagen mimetic peptides

    Science.gov (United States)

    Stahl, Patrick

    The ECM is a complex natural system evolved to promote proliferation and differentiation of cells during tissue development. In order to create synthetic biomaterials for studying cell-scaffold interactions and ultimately for engineering tissues, scientists strive to recapitulate many characteristics of ECM by developing hydrogels that contain mechanical cues and biochemical signals such as adhesion moieties and cell growth factors. While synthetic hydrogels bypass limitations of naturally-derived materials (e.g. transfer of pathogens), nature provides inspiration to enhance the functionality of synthetic hydrogels through biomimetic approaches. The collagen triple helix is the basis for the supramolecular structure of collagen in the ECM, and its adaptation in collagen mimetic peptides (CMPs) has provided hybridization mechanisms that can be employed in the formation and functionalization of synthetic hydrogels. The aim of this dissertation is to develop novel poly(ethylene glycol) (PEG)-based hydrogels that employ CMP triple helix assembly as a non-covalent yet target-specific tool to encode physical and chemical cues into the hydrogel with spatial control. We demonstrate that multi-arm PEG functionalized with CMPs form hydrogels supported by physical crosslinks mediated by CMP triple helix. Particle tracking microrheology shows that these physical crosslinks are sensitive to temperature as well as addition of exogenous CMPs that can disrupt crosslinks by competing for triple helix formation. This physical crosslink disruption enables the modulation of bulk hydrogel elasticity and the introduction of local stiffness gradients in PEG-CMP hydrogels. We also present photopolymerized PEG diacrylate (PEGDA) hydrogels displaying CMPs that can be further conjugated to CMPs with bioactive moieties via triple helix hybridization. Encoding these hydrogels with cell-adhesive CMPs induces cell spreading and proliferation. We further demonstrate generation of gradients and

  16. Industry sponsorship bias in research findings: a network meta-analysis of LDL cholesterol reduction in randomised trials of statins

    Science.gov (United States)

    Dias, Sofia; Ades, A E

    2014-01-01

    Objective To explore the risk of industry sponsorship bias in a systematically identified set of placebo controlled and active comparator trials of statins. Design Systematic review and network meta-analysis. Eligibility Open label and double blind randomised controlled trials comparing one statin with another at any dose or with control (placebo, diet, or usual care) for adults with, or at risk of developing, cardiovascular disease. Only trials that lasted longer than four weeks with more than 50 participants per trial arm were included. Two investigators assessed study eligibility. Data sources Bibliographic databases and reference lists of relevant articles published between 1 January 1985 and 10 March 2013. Data extraction One investigator extracted data and another confirmed accuracy. Main outcome measure Mean absolute change from baseline concentration of low density lipoprotein (LDL) cholesterol. Data synthesis Study level outcomes from randomised trials were combined using random effects network meta-analyses. Results We included 183 randomised controlled trials of statins, 103 of which were two-armed or multi-armed active comparator trials. When all of the existing randomised evidence was synthesised in network meta-analyses, there were clear differences in the LDL cholesterol lowering effects of individual statins at different doses. In general, higher doses resulted in higher reductions in baseline LDL cholesterol levels. Of a total of 146 industry sponsored trials, 64 were placebo controlled (43.8%). The corresponding number for the non-industry sponsored trials was 16 (43.2%). Of the 35 unique comparisons available in 37 non-industry sponsored trials, 31 were also available in industry sponsored trials. There were no systematic differences in magnitude between the LDL cholesterol lowering effects of individual statins observed in industry sponsored versus non-industry sponsored trials. In industry sponsored trials, the mean change from baseline LDL

  17. 新医改背景下医院管理人才措施研究%The Context of the New Health Reform Measures Hospital Management Per-sonnel

    Institute of Scientific and Technical Information of China (English)

    薛宇坤

    2015-01-01

    医院在新医改背景下不断改革,使得医院人才管理显著至关重要。当前我国医院人才管理过程中尚存在一些不足,问题也较多,一定程度上影响医院的发展。因此,要在新医改背景下提升竞争力和医疗水平,医院相关部门要不断完善医院的人力资源管理,促进人尽其才。该文将以新医改背景下医院人才管理为起点,分析我国医院人才过程中存在的问题并提出有效地解决措施,保证医院可持续发展。%In recent years, with the rapid development of medical technology, the social transformation of China is also in full swing, in order to adapt to the needs of the community, the hospital has also been reforms in the new health reform background, making the hospital a significant talent management is crucial. However, the current process of hospital personnel management, there are still some shortcomings, the problem is multi-arm machine, these problems have affected the development of a large an-gle of the hospital. Therefore, in order to enhance the competitiveness of the hospital and medical standards in the new context of health care reform, hospital-related departments to continue to improve the hospital's human resources management, and promote the best use. Under the new health care reform in this article will be hospital personnel management background as a starting point to analyze the process of hospital personnel problems and propose effective solutions to ensure the hospital to make the best talent, the best use, to ensure the sustainable development of the hospital.

  18. RAYLEIGH SCATTERING IN THE ATMOSPHERE OF THE WARM EXO-NEPTUNE GJ 3470B

    Energy Technology Data Exchange (ETDEWEB)

    Dragomir, Diana [Las Cumbres Observatory Global Telescope Network, 6740 Cortona Drive Suite 102, Goleta, CA 93117 (United States); Benneke, Björn [Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 (United States); Pearson, Kyle A. [Department of Physics and Astronomy, Northern Arizona University, Flagstaff, AZ 86001 (United States); Crossfield, Ian J. M.; Barman, Travis [Department of Planetary Sciences, Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721 (United States); Eastman, Jason [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Biddle, Lauren I., E-mail: diana@oddjob.uchicago.edu [Gemini Observatory, Northern Operations Center, 670 N. Aohoku Place, Hilo, HI 96720 (United States)

    2015-12-01

    GJ 3470b is a warm Neptune-size planet transiting an M dwarf star. Like the handful of other small exoplanets for which transmission spectroscopy has been obtained, GJ 3470b exhibits a flat spectrum in the near- and mid-infrared. Recently, a tentative detection of Rayleigh scattering in its atmosphere has been reported. This signal manifests itself as an observed increase of the planetary radius as a function of decreasing wavelength in the visible. We set out to verify this detection and observed several transits of this planet with the LCOGT network and the Kuiper telescope in four different bands (Sloan g, Sloan i, Harris B, and Harris V). Our analysis reveals a strong Rayleigh scattering slope, thus confirming previous results. This makes GJ 3470b the smallest known exoplanet with a detection of Rayleigh scattering. We find that the most plausible scenario is a hydrogen/helium-dominated atmosphere covered by clouds which obscure absorption features in the infrared and hazes which give rise to scattering in the visible. Our results demonstrate the feasibility of exoplanet atmospheric characterization from the ground, even with meter-class telescopes.

  19. Biantennary oligoglycines and glyco-oligoglycines self-associating in aqueous medium

    Directory of Open Access Journals (Sweden)

    Svetlana V. Tsygankova

    2014-06-01

    Full Text Available Oligoglycines designed in a star-like fashion, so-called tri- and tetraantennary molecules, were found to form highly ordered supramers in aqueous medium. The formation of these supramers occurred either spontaneously or due to the assistance of a mica surface. The driving force of the supramer formation is hydrogen bonding, the polypeptide chain conformation is related to the folding of helical polyglycine II (PG II. Tri- and tetraantennary molecules are capable of association if the antenna length reach 7 glycine (Gly residues. Properties of similar biantennary molecules have not been investigated yet, and we compared their self-aggregating potency with similar tri- and tetraantennary analogs. Here, we synthesized oligoglycines of the general formula R-Glyn-Х-Glyn-R (X = -HN-(СН2m-NH-, m = 2, 4, 10; n = 1–7 without pendant ligands (R = H and with two pendant sialoligands (R = sialic acid or sialooligosaccharide. Biantennary oligoglycines formed PG II aggregates, their properties, however, differ from those of the corresponding tri- and tetraantennary oligoglycines. In particular, the tendency to aggregate starts from Gly4 motifs instead of Gly7. The antiviral activity of end-glycosylated peptides was studied, and all capable of assembling glycopeptides demonstrated an antiviral potency which was up to 50 times higher than the activity of peptide-free glycans.

  20. Life and death of the stars

    CERN Document Server

    Srinivasan, Ganesan

    2014-01-01

    This volume is devoted to one of the fascinating things about stars: how they evolve as they age. This evolution is different for stars of different masses. How stars end their lives when their supply of energy is exhausted also depends on their masses. Interestingly, astronomers conjectured about the ultimate fate of the stars even before the details of their evolution became clear. Part I of this book gives an account of the remarkable predictions made during the 1920s and 1930s concerning the ultimate fate of stars. Since much of this development hinged on quantum physics that emerged during this time, a detailed introduction to the relevant physics is included in the book. Part II is a summary of the life history of stars. This discussion is divided into three parts: low-mass stars, like our Sun, intermediate-mass stars, and massive stars. Many of the concepts of contemporary astrophysics were built on the foundation erected by Subrahmanyan Chandrasekhar in the 1930s. This book, written during his birth c...

  1. Planet Hunters X: Searching for Nearby Neighbors of 75 Planet and Eclipsing Binary Candidates from the K2 Kepler extended mission

    CERN Document Server

    Schmitt, Joseph R; Wang, Ji; Fischer, Debra A; Kristiansen, Martti H; LaCourse, Daryll M; Gagliano, Robert; Tan, Arvin Joseff V; Schwengeler, Hans Martin; Omohundro, Mark R; Venner, Alexander; Terentev, Ivan; Schmitt, Allan R; Jacobs, Thomas L; Winarski, Troy; Sejpka, Johann; Jek, Kian J; Boyajian, Tabetha S; Brewer, John M; Ishikawa, Sascha T; Lintott, Chris; Lynn, Stuart; Schawinski, Kevin; Weiksnar, Alex

    2016-01-01

    We present high resolution observations of a sample of 75 K2 targets from Campaigns 1-3 using speckle interferometry on the Southern Astrophysical Research (SOAR) telescope and adaptive optics (AO) imaging at the Keck II telescope. The median SOAR $I$-band and Keck $K_s$-band detection limits at 1'' were $\\Delta m_{I}=4.4$ mag and $\\Delta m_{K_s}=6.1$ mag, respectively. This sample includes 37 stars likely to host planets, 32 targets likely to be EBs, and 6 other targets previously labeled as likely planetary false positives. We find nine likely physically bound companion stars within 3'' of three candidate transiting exoplanet host stars and six likely eclipsing binaries (EB). Six of the nine detected companions are new discoveries, one of them associated with a planet candidate (EPIC 206061524). Among the EB candidates, companions were only found near the shortest period ones ($P<3$ days), which is in line with previous results showing high multiplicity near short-period binary stars. This high resolutio...

  2. Stimuli-responsive HBPS-g-PDMAEMA and its application as nanocarrier in loading hydrophobic molecules

    Science.gov (United States)

    Chen, Yongsheng; Zain-Ul-Abdin; Sun, Ruoli; Jing, Guanghui; Tong, Rongbai; Deng, Zheng

    2016-01-01

    Summary The topic of stimuli-responsive nanocarriers for loading guest molecules is dynamic. It has been widely studied in applications including drug controlled release, smart sensing, catalysis, and modeling. In this paper, a graft copolymer (hyperbranched polystyrene)-g-poly[2-(dimethylamino)ethyl methacrylate] (HBPS-g-PDMAEMA) was synthesized and characterized by 1H NMR and GPC. It was observed that the star-like HBPS-g-PDMAEMA formed aggregates in aqueous solution. The influence of polymer concentration, ionic strength and pH value on the aggregates in aqueous solution was investigated by using UV–vis spectroscopy and DLS analysis. The results showed that size of aggregates was affected by a corresponding stimulus. In addition, the loading ability of HBPS-g-PDMAEMA aggregates was investigated by using pyrene or Nile red as the model guest molecules by using UV–vis and fluorescence spectroscopy. The results showed that HBPS-g-PDMAEMA aggregates were capable to encapsulate small hydrophobic molecules. These newly prepared HBPS-g-PDMAEMA nanocarriers might be used in, e.g., medicine or catalysis. PMID:27340484

  3. Univalence and Starlikeness of Nonlinear Integral Transform of Certain Class of Analytic Functions

    Indian Academy of Sciences (India)

    M Obradović; S Ponnusamy; P Vasundhra

    2009-11-01

    Let $\\mathcal{U}(, )$ denote the class of all normalized analytic functions in the unit disk $|z| < 1$ satisfying the condition \\begin{equation*}\\frac{f(z)}{z}≠ 0\\quad\\text{and}\\quad\\left|f'(z)\\left(\\frac{z}{f(z)}\\right)^{ +1}-1\\right| < ,\\quad |z| < 1.\\end{equation*} For $f\\in\\mathcal{U}(, )$ with ≤ 1 and $0≠_1≤ 1$, and for a positive real-valued integrable function defined on [0,1] satisfying the normalized condition $\\int^1_0\\varphi(t)dt=1$, we consider the transform $G_\\varphi f(z)$ defined by \\begin{equation*}G_\\varphi f(z)=z\\left[\\int^1_0\\varphi(t)\\left(\\frac{zt}{f(tz)}\\right)^ dt\\right]^{-1/ 1},\\quad z\\in.\\end{equation*} In this paper, we find conditions on the range of parameters and so that the transform $G_\\varphi f$ is univalent or star-like. In addition, for a given univalent function of certain form, we provide a method of obtaining functions in the class $\\mathcal{U}(, )$.

  4. Soap, A Free-code Tool To Study The Impact Of Stellar Activity

    Science.gov (United States)

    Boisse, Isabelle; Bonfils, X.; Santos, N.

    2011-09-01

    Dark spots and bright plages are present on the surface of all stars, even low-active stars (like the Sun in its low-active phase). Their appearance and disappearance on the stellar photosphere, combined with the stellar rotation, may lead to errors and uncertainties in the characterization of planets both in radial velocimetry and photometry. SOAP is a tool offered to the community (Boisse, Bonfils and Santos, in prep.) that enables to simulate spots and plages on rotating stars and computes their impact on RV and photometric measurements. This talk will discuss the challenges related to the knowledge of stellar activity for the next decade: detect telluric planets in the habitable zone of their stars (from G to M dwarfs), understand the activity in the low-mass end of M dwarf (on which will focus future projects like Elektra, SPIRou or CARMENES), limitation to the sum of different transit observations in order to characterize the atmospheric components (from the ground or with Spitzer, JWST), planets around young stars,... and how this can be simulated with SOAP in order to search for indices and corrections. IB and NCS would like to thank the support by the European Research Council/European Community under the FP7 through a Starting Grant, as well from Fundacao para a Ciencia e a Tecnologia (FCT), Portugal.

  5. Flexible Reconfiguration of Existing Urban Water Infrastructure Systems.

    Science.gov (United States)

    Perelman, Lina Sela; Allen, Michael; Preis, Ami; Iqbal, Mudasser; Whittle, Andrew J

    2015-11-17

    This paper presents a practical methodology for the flexible reconfiguration of existing water distribution infrastructure, which is adaptive to the water utility constraints and facilitates in operational management for pressure and water loss control. The network topology is reconfigured into a star-like topology, where the center node is a connected subset of transmission mains, that provides connection to water sources, and the nodes are the subsystems that are connected to the sources through the center node. In the proposed approach, the system is first decomposed into the main and subsystems based on graph theory methods and then the network reconfiguration problem is approximated as a single-objective linear programming problem, which is efficiently solved using a standard solver. The performance and resiliency of the original and reconfigured systems are evaluated through direct and surrogate measures. The methodology is demonstrated using two large-scale water distribution systems, showing the flexibility of the proposed approach. The results highlight the benefits and disadvantages of network decentralization.

  6. [Research progress on microbial properties of nitrite-dependent anaerobic methane-oxidising bacteria].

    Science.gov (United States)

    Shen, Li-dong

    2015-03-01

    Nitrite-dependent anaerobic methane oxidation (N-DAMO) is a recently discovered process that constitutes a unique association between the two major global elements essential for life, carbon and nitrogen. This process is one of the most important discoveries in the fields of environmental science and microbiology. The discovery of N-DAMO process supplements biogeochemical cycles of carbon and nitrogen in nature, extends microbial diversity and urges development of novel simultaneous carbon and nitrogen removal process. The N-DAMO process is mediated by the bacterium " Candidatus Methylomirabilis oxyfera" (M. oxyfera), which belongs to the candidate phylum NC10. Currently, a series of breakthroughs have been made in the research of M. oxyfera. The properties of M. oxyfera morphology, chemical composition, enrichment culture, physiology and biochemistry, and ecology have been revealed. Most importantly, the special ultrastructure (star-like) of the cell shape and unique chemical composition (10MeC(16,1Δ7)) of M. oxyfera have been revealed. In addition, a new intra-aerobic metabolism (the fourth biological pathway to produce oxygen) was discovered in M. oxyfera. It was observed that M. oxyfera bypassed the denitrification intermediate nitrous oxide by the conversion of two nitric oxide molecules to dinitrogen gas and oxygen, which was then used to oxidise methane. The present review summarises various aspects of microbiological properties of M. oxyfera.

  7. RAFT Synthesis and Self-Assembly of Free-Base Porphyrin Cored Star Polymers

    Directory of Open Access Journals (Sweden)

    Lin Wu

    2011-01-01

    Full Text Available Reversible addition fragmentation chain transfer (RAFT synthesis and self-assembly of free-base porphyrin cored star polymers are reported. The polymerization, in the presence of a free-base porphyrin cored chain transfer agent (CTA-FBP, produced porphyrin star polymers with controlled molecular weights and narrow polydispersities for a number of monomers including N, N-dimethylacrylamide (DMA and styrene (St. Well-defined amphiphilic star block copolymers, P-(PS-PDMA4 and P-(PDMA-PS4 (P: porphyrin, were also prepared and used for self-assembly studies. In methanol, a selective solvent for PDMA, spherical micelles were observed for both block copolymers as characterized by TEM. UV-vis studies suggested star-like micelles were formed from P-(PS-PDMA4, while P-(PDMA-PS4 aggregated into flower-like micelles. Spectrophotometric titrations indicated that the optical response of these two micelles to external ions was a function of micellar structures. These structure-related properties will be used for micelle studies and functional material development in the future.

  8. How neutrons and neutrinos translate into crotchets and quavers

    CERN Multimedia

    Joannah Caborn Wengler

    2012-01-01

    What unites The Strokes, Gilbert and Sullivan, Brian Eno and Alpine Kat? All of them have in some way been musically connected with CERN. German composer of electronic music, Bernd Kistenmacher, is the latest in the long list of musicians to have been inspired by CERN.   There seems to be a natural affinity between music and science. How else can it be that CERN has inspired so many different musicians to be creative? From amateurs composing in their bedrooms to professional musicians, from rock stars like Incubus to classical composers like Philip Glass, CERN’s huge-scale science and technology researching the tiniest of particles have again and again stirred artists into creative action. Electromusician Bernd Kistenmacher from Berlin, Germany is no exception. In his case, his interest in CERN goes back to a wider philosophical question: “Where do we come from?” Having composed two albums looking at the origins of the Universe in astronomy and in the depths of ...

  9. Herschel detects oxygen in the beta Pictoris debris disk

    CERN Document Server

    Brandeker, A; Olofsson, G; Vandenbussche, B; Acke, B; Barlow, M J; Blommaert, J A D L; Cohen, M; Dent, W R F; Dominik, C; Di Francesco, J; Fridlund, M; Gear, W K; Glauser, A M; Greaves, J S; Harvey, P M; Heras, A M; Hogerheijde, M R; Holland, W S; Huygen, R; Ivison, R J; Leeks, S J; Lim, T L; Liseau, R; Matthews, B C; Pantin, E; Pilbratt, G L; Royer, P; Sibthorpe, B; Waelkens, C; Walker, H J

    2016-01-01

    The young star beta Pictoris is well known for its dusty debris disk, produced through the grinding down by collisions of planetesimals, kilometre-sized bodies in orbit around the star. In addition to dust, small amounts of gas are also known to orbit the star, likely the result from vaporisation of violently colliding dust grains. The disk is seen edge on and from previous absorption spectroscopy we know that the gas is very rich in carbon relative to other elements. The oxygen content has been more difficult to assess, however, with early estimates finding very little oxygen in the gas at a C/O ratio 20x higher than the cosmic value. A C/O ratio that high is difficult to explain and would have far-reaching consequences for planet formation. Here we report on observations by the far-infrared space telescope Herschel, using PACS, of emission lines from ionised carbon and neutral oxygen. The detected emission from C+ is consistent with that previously reported being observed by the HIFI instrument on Herschel,...

  10. Detecting Asymmetric Dark Matter in the Sun with Neutrinos

    CERN Document Server

    Murase, Kohta

    2016-01-01

    Dark Matter (DM) may have a relic density that is in part determined by a particle/antiparticle asymmetry, much like baryons. If this is the case, it can accumulate in stars like the Sun to sizable number densities and annihilate to Standard Model (SM) particles including neutrinos. We show that the combination of neutrino telescope and direct detection data can be used in conjunction to determine or constrain the DM asymmetry from data. Depending on the DM mass, the current neutrino data from Super-K and IceCube give powerful constraints on asymmetric DM unless its fractional asymmetry is $\\lesssim 10^{-2}$. Future neutrino telescopes and detectors like Hyper-K and KM3NeT can search for the resulting signal of high-energy neutrinos from the center of the Sun. The observation of such a flux yields information on both the DM-nucleus cross section but also on the relative abundances of DM and anti-DM.

  11. Observations, Modeling and Theory of Debris Disks

    CERN Document Server

    Matthews, Brenda C; Wyatt, Mark C; Bryden, Geoff; Eiroa, Carlos

    2014-01-01

    Main sequence stars, like the Sun, are often found to be orbited by circumstellar material that can be categorized into two groups, planets and debris. The latter is made up of asteroids and comets, as well as the dust and gas derived from them, which makes debris disks observable in thermal emission or scattered light. These disks may persist over Gyrs through steady-state evolution and/or may also experience sporadic stirring and major collisional breakups, rendering them atypically bright for brief periods of time. Most interestingly, they provide direct evidence that the physical processes (whatever they may be) that act to build large oligarchs from micron-sized dust grains in protoplanetary disks have been successful in a given system, at least to the extent of building up a significant planetesimal population comparable to that seen in the Solar System's asteroid and Kuiper belts. Such systems are prime candidates to host even larger planetary bodies as well. The recent growth in interest in debris dis...

  12. Revealing the structure of the world airline network.

    Science.gov (United States)

    Verma, T; Araújo, N A M; Herrmann, H J

    2014-07-09

    Resilience of most critical infrastructures against failure of elements that appear insignificant is usually taken for granted. The World Airline Network (WAN) is an infrastructure that reduces the geographical gap between societies, both small and large, and brings forth economic gains. With the extensive use of a publicly maintained data set that contains information about airports and alternative connections between these airports, we empirically reveal that the WAN is a redundant and resilient network for long distance air travel, but otherwise breaks down completely due to removal of short and apparently insignificant connections. These short range connections with moderate number of passengers and alternate flights are the connections that keep remote parts of the world accessible. It is surprising, insofar as there exists a highly resilient and strongly connected core consisting of a small fraction of airports (around 2.3%) together with an extremely fragile star-like periphery. Yet, in spite of their relevance, more than 90% of the world airports are still interconnected upon removal of this core. With standard and unconventional removal measures we compare both empirical and topological perceptions for the fragmentation of the world. We identify how the WAN is organized into different classes of clusters based on the physical proximity of airports and analyze the consequence of this fragmentation.

  13. Two Small Planets Transiting HD 3167

    CERN Document Server

    Vanderburg, Andrew; Duev, Dmitry A; Jensen-Clem, Rebecca; Latham, David W; Mayo, Andrew W; Baranec, Christoph; Berlind, Perry; Kulkarni, Shrinivas; Law, Nicholas M; Nieberding, Megan N; Riddle, Reed; Salama, Maissa

    2016-01-01

    We report the discovery of two super-Earth-sized planets transiting the bright (V = 8.94, K = 7.07) nearby late G-dwarf HD 3167, using data collected by the K2 mission. The inner planet, HD 3167 b, has a radius of 1.6 R_e and an ultra-short orbital period of only 0.96 days. The outer planet, HD 3167 c, has a radius of 2.9 R_e and orbits its host star every 29.85 days. At a distance of just 45.8 +/- 2.2 pc, HD 3167 is one of the closest and brightest stars hosting multiple transiting planets, making HD 3167 b and c well suited for follow-up observations. The star is chromospherically inactive and slowly rotating, ideal for radial velocity observations to measure the planets' masses. The outer planet is large enough that it likely has a thick gaseous envelope which could be studied via transmission spectroscopy. Planets transiting bright, nearby stars like HD 3167 are valuable objects to study leading up to the launch of the James Webb Space Telescope.

  14. Temperate Earth-sized planets transiting a nearby ultracool dwarf star

    CERN Document Server

    Gillon, Michael; Lederer, Susan M; Delrez, Laetitia; de Wit, Julien; Burdanov, Artem; Van Grootel, Valerie; Burgasser, Adam J; Triaud, Amaury H M J; Opitom, Cyrielle; Demory, Brice-Olivier; Sahu, Devendra K; Gagliuffi, Daniella Bardalez; Magain, Pierre; Queloz, Didier

    2016-01-01

    Star-like objects with effective temperatures of less than 2,700 kelvin are referred to as ultracool dwarfs. This heterogeneous group includes stars of extremely low mass as well as brown dwarfs (substellar objects not massive enough to sustain hydrogen fusion), and represents about 15 per cent of the population of astronomical objects near the Sun. Core-accretion theory predicts that, given the small masses of these ultracool dwarfs, and the small sizes of their protoplanetary disk, there should be a large but hitherto undetected population of terrestrial planets orbiting them - ranging from metal-rich Mercury-sized planets to more hospitable volatile-rich Earth-sized planets. Here we report observations of three short-period Earth-sized planets transiting an ultracool dwarf star only 12 parsecs away. The inner two planets receive four times and two times the irradiation of Earth, respectively, placing them close to the inner edge of the habitable zone of the star. Our data suggest that 11 orbits remain poss...

  15. Towards A Complete Census of the Solar-Type Binaries in the Young Open Cluster M37

    Science.gov (United States)

    Geller, Aaron M.; Meibom, Soren; Barnes, Sydney A.; Mathieu, Robert D.

    2012-08-01

    Binary stars govern the dynamical evolution of star clusters and determine the formation rates and mechanisms for exotic stars like blue stragglers and X-ray sources. Understanding the near-primordial (after removal of the natal gas) binary population of star clusters is of primary importance for dynamical models of star clusters, which have the potential to revolutionize our understanding of star cluster evolution. Yet the binary frequencies and distributions of binary orbital parameters (period, eccentricity, etc.) for young coeval stellar populations are poorly known, due to a lack of necessary observations. Time-series radial-velocity surveys are essential for identifying and characterizing binary populations. Using WIYN/Hydra data, we have already identified a nearly complete sample of 329 solar-type (1.5 open cluster M37. Of these stars, 82 show significant radial-velocity variability, indicative of a binary companion. Kinematic orbital solutions are crucial to define the initial binary conditions critical for dynamical star cluster models, and to understand how binaries affects stellar rotational evolution. As we have already identified the binaries in M37, we have a unique opportunity to add significantly to our knowledge of young binaries with minimal additional telescope time. We propose to initiate a WIYN/Hydra multi-epoch radial-velocity survey of the 82 velocity variables in M37.

  16. The Solar-Type Hard-Binary Frequency and Distributions of Orbital Parameters in the Open Cluster M37

    Science.gov (United States)

    Geller, Aaron M.; Meibom, Soren; Barnes, Sydney A.; Mathieu, Robert D.

    2014-02-01

    Binary stars, and particularly the short-period ``hard'' binaries, govern the dynamical evolution of star clusters and determine the formation rates and mechanisms for exotic stars like blue stragglers and X-ray sources. Understanding the near-primordial hard-binary population of star clusters is of primary importance for dynamical models of star clusters, which have the potential to greatly advance our understanding of star cluster evolution. Yet the binary frequencies and distributions of binary orbital parameters (period, eccentricity, etc.) for young coeval stellar populations are poorly known, due to a lack of necessary observations. The young (~540 Myr) open cluster M37 hosts a rich binary population that can be used to empirically define these initial conditions. Importantly, this cluster has been the target of a comprehensive WIYN/Hydra radial-velocity (RV) survey, from which we have already identified a nearly complete sample of 329 solar-type (1.5 data with a multi-epoch RV survey using WIYN/Hydra to derive kinematic orbital solutions for these 82 binaries in M37. This project was granted time in 2013B and scheduled for later this year. We anticipate that about half of the detected binaries in M37 will acquire enough RV measurements (>=10) in 2013B to begin searching for orbital solutions. With this proposal and perhaps one additional semester we should achieve >=10 RV measurements for the remaining binaries.

  17. Dynamics of Vapor Layer Under a Leidenfrost Drop

    CERN Document Server

    Caswell, Thomas A

    2014-01-01

    In the Leidenfrost effect a small drop of fluid is levitated above a sufficiently hot surface, on a persistent vapor layer generated by evaporation from the drop. The vapor layer thermally insulates the drop from the surface leading to extraordinarily long drop lifetimes. The top-view shape of the levitated drops can exhibit persistent star-like vibrations. I extend recent work [Burton et al. PRL 2012] to study the bottom surface of the drop using interference-imaging. In this work I use a high-speed camera and automated image analysis to image, locate and classify the interference fringes. From the interference fringes I reconstruct the shape and height profile of the rim where the drop is closest to the surface. I measure the drop-size dependence of the planar vibrational mode frequencies, which agree well with previous work. I observe a distinct breathing mode in the average radius of the drop, the frequency of which scales differently with drop size than the other modes. This breathing mode can be tightly...

  18. Temperate Earth-sized planets transiting a nearby ultracool dwarf star.

    Science.gov (United States)

    Gillon, Michaël; Jehin, Emmanuël; Lederer, Susan M; Delrez, Laetitia; de Wit, Julien; Burdanov, Artem; Van Grootel, Valérie; Burgasser, Adam J; Triaud, Amaury H M J; Opitom, Cyrielle; Demory, Brice-Olivier; Sahu, Devendra K; Bardalez Gagliuffi, Daniella; Magain, Pierre; Queloz, Didier

    2016-05-12

    Star-like objects with effective temperatures of less than 2,700 kelvin are referred to as 'ultracool dwarfs'. This heterogeneous group includes stars of extremely low mass as well as brown dwarfs (substellar objects not massive enough to sustain hydrogen fusion), and represents about 15 per cent of the population of astronomical objects near the Sun. Core-accretion theory predicts that, given the small masses of these ultracool dwarfs, and the small sizes of their protoplanetary disks, there should be a large but hitherto undetected population of terrestrial planets orbiting them--ranging from metal-rich Mercury-sized planets to more hospitable volatile-rich Earth-sized planets. Here we report observations of three short-period Earth-sized planets transiting an ultracool dwarf star only 12 parsecs away. The inner two planets receive four times and two times the irradiation of Earth, respectively, placing them close to the inner edge of the habitable zone of the star. Our data suggest that 11 orbits remain possible for the third planet, the most likely resulting in irradiation significantly less than that received by Earth. The infrared brightness of the host star, combined with its Jupiter-like size, offers the possibility of thoroughly characterizing the components of this nearby planetary system.

  19. Weighted Radial Variation for Node Feature Classification

    CERN Document Server

    Andris, C

    2011-01-01

    Connections created from a node-edge matrix have been traditionally difficult to visualize and analyze because of the number of flows to be rendered in a limited feature or cartographic space. Because analyzing connectivity patterns is useful for understanding the complex dynamics of human and information flow that connect non-adjacent space, techniques that allow for visual data mining or static representations of system dynamics are a growing field of research. Here, we create a Weighted Radial Variation (WRV) technique to classify a set of nodes based on the configuration of their radially-emanating vector flows. Each entity's vector is syncopated in terms of cardinality, direction, length, and flow magnitude. The WRV process unravels each star-like entity's individual flow vectors on a 0-360{\\deg} spectrum, to form a unique signal whose distribution depends on the flow presence at each step around the entity, and is further characterized by flow distance and magnitude. The signals are processed with an un...

  20. Qualities and Inequalities in Online Social Networks through the Lens of the Generalized Friendship Paradox.

    Science.gov (United States)

    Momeni, Naghmeh; Rabbat, Michael

    2016-01-01

    The friendship paradox is the phenomenon that in social networks, people on average have fewer friends than their friends do. The generalized friendship paradox is an extension to attributes other than the number of friends. The friendship paradox and its generalized version have gathered recent attention due to the information they provide about network structure and local inequalities. In this paper, we propose several measures of nodal qualities which capture different aspects of their activities and influence in online social networks. Using these measures we analyse the prevalence of the generalized friendship paradox over Twitter and we report high levels of prevalence (up to over 90% of nodes). We contend that this prevalence of the friendship paradox and its generalized version arise because of the hierarchical nature of the connections in the network. This hierarchy is nested as opposed to being star-like. We conclude that these paradoxes are collective phenomena not created merely by a minority of well-connected or high-attribute nodes. Moreover, our results show that a large fraction of individuals can experience the generalized friendship paradox even in the absence of a significant correlation between degrees and attributes.

  1. NICMOS Snapshot Survey of Damped Lyman Alpha Quasars

    CERN Document Server

    Colbert, J W; Colbert, James W.; Malkan, Matthew A.

    2001-01-01

    We image 19 quasars with 22 damped Lyman alpha (DLA) systems using the F160W filter and the Near-Infrared Camera and Multiobject Spectrograph aboard the Hubble Space Telescope, in both direct and coronagraphic modes. We reach 5 sigma detection limits of ~H=22 in the majority of our images. We compare our observations to the observed Lyman-break population of high-redshift galaxies, as well as Bruzual & Charlot evolutionary models of present-day galaxies redshifted to the distances of the absorption systems. We predict H magnitudes for our DLAs, assuming they are producing stars like an L* Lyman-break galaxy (LBG) at their redshift. Comparing these predictions to our sensitivity, we find that we should be able to detect a galaxy around 0.5-1.0 L* (LBG) for most of our observations. We find only one new possible candidate, that near LBQS0010-0012. This scarcity of candidates leads us to the conclusion that most DLA systems are not drawn from a normal LBG luminosity function nor a local galaxy luminosity fun...

  2. M-dwarf binaries as tracers of star and brown dwarf formation

    CERN Document Server

    Marks, Michael; Kroupa, Pavel; Leigh, Nathan; Thies, Ingo

    2015-01-01

    The separation distribution for M-dwarf binaries in the ASTRALUX survey is narrower and peaking at smaller separations than the distribution for solar-type binaries. This is often interpreted to mean that M-dwarfs constitute a continuous transition from brown dwarfs (BDs) to stars. Here a prediction for the M-dwarf separation distribution is presented, using a dynamical population synthesis (DPS) model in which "star-like" binaries with late-type primaries ($\\lesssim1.5 M_{\\rm sun}$) follow universal initial distribution functions and are dynamically processed in their birth embedded clusters. A separate "BD-like" population has both its own distribution functions for binaries and initial mass function (IMF), which overlaps in mass with the IMF for stars. Combining these two formation modes results in a peak on top of a wider separation distribution for late M-dwarfs consistent with the late ASTRALUX sample. The DPS separation distribution for early M-dwarfs shows no such peak and is in agreement with the M-d...

  3. Isochoric Heating of Reduced Mass Targets

    Energy Technology Data Exchange (ETDEWEB)

    Akli, Kramer [The Ohio State Univ., Columbus, OH (United States)

    2015-11-13

    This report summarizes the experimental results of a study aimed at achieving star-like plasmas in the laboratory by isochrically heating solid-density targets with intense lasers. Of special interest is the investigation of spatial/temporal temperature and density gradients and their dependence on the target geometry and mass. The investigation was carried out in two phases. In the first phase, solid targets with variable transverse and longitudinal dimensions were investigated. We found that electron beam recirculation is enhanced for reduced mass targets. As a result, the temperature gradients are minimized for these targets yielding more uniform temperature hot plasmas. In the second phase, reduced mass targets were irradiated with intense ultra-short laser pulses. Bright monochromatic x-rays and broadband Extreme ultraviolet radiation (EUV or XUV) emissions were achieved by optimizing the electrostatic sheath fields surrounding the target. The study also revealed that this laser-driven source of radiation has a small source size, short duration, and high photon fluxes suitable for point projection radiography and for probing matter under extreme environments.

  4. Low dose rectal inoculation of rhesus macaques by SIV SME660 or SIV MAC251 recapitulates human mucosal infection by HIV-1

    Energy Technology Data Exchange (ETDEWEB)

    Koraber, Bette [Los Alamos National Laboratory; Perelson, Alan [Los Alamos National Laboratory; Hraber, Peter [Los Alamos National Laboratory; Giorgi, E [Los Alamos National Laboratory; Bhattacharya, T [Los Alamos National Laboratory

    2009-01-01

    Recently, we developed a novel approach to the identification of transmitted or early founder HIV -1 genomes in acutely infected humans based on single genome amplification and sequencing. Here we tested this approach in 18 acutely infected Indian rhesus macaques to determine the molecular features of SIV transmission. Animals were inoculated intrarectally (IR) or intravenously (IV) with stocks of SIVmac251 or SIVsmE660 that exhibited sequence diversity typical of early-chronic HIV -1 infection. 987 full-length SIV env sequences (median of 48 per animal) were determined from plasma virion RNA one to five weeks after infection. IR inoculation was followed by productive infection by one or few viruses (median 1; range 1-5) that diversified randomly with near star-like phylogeny and a Poisson distribution of mutations. Consensus viral sequences from ramp-up and peak viremia were identical to viruses found in the inocula or differed from them by only one or few nuc1eotides, providing direct evidence that early plasma viral sequences coalesce to transmitted/founder virus( es). IV infection was approximately 10,000-fold more efficient than IR infection, and viruses transmitted by either route represented the full genetic spectra of the inocula. These findings identify key similarities in mucosal transmission and early diversification between SIV and HIV -1.

  5. Large proper motion of the Thorne-\\.Zytkow object candidate HV 2112 reveals its likely nature as foreground Galactic S-star

    CERN Document Server

    Maccarone, Thomas J

    2016-01-01

    Using the Southern Proper Motion (SPM) catalog, we show that the candidate Thorne-\\.Zytkow object HV~2112 has a proper motion implying a space velocity of about 3000\\kms if the object is located at the distance of the Small Magellanic Cloud. The proper motion is statistically different from that of the SMC at approximately $4\\sigma$ in SPM, although the result can drop to about $3\\sigma$ significance by including the UCAC4 data and considering systematic uncertainties in addition to the statistical ones. Assuming the measurement is robust, this proper motion is sufficient to exclude its proposed membership of the Small Magellanic Cloud and to argue instead that it is likely to be a foreground star in the Milky Way halo. The smaller distance and therefore lower brightness argue against its proposed nature as a Thorne-\\.Zytkow object (the hypothesized star-like object formed when a normal star and a neutron star merge) or a super-Asymptotic Giant Branch (AGB) star. Instead we propose a binary scenario where thi...

  6. Stars, Galaxies and Quasars

    Directory of Open Access Journals (Sweden)

    Patrick Das Gupta

    2009-05-01

    Full Text Available This article provides a brief introduction to the basics of stars, galaxies and Quasi-stellar objects (QSOs. In stars, the central pressure and temperature must be high in order to halt the stellar gravitational collapse. High temperature leads to thermonuclear fusion in the stellar core, releasing thereby enormous amount of nuclear energy, making the star shine brilliantly. On the other hand, the QSOs are very bright nuclei lying in the centres of some galaxies. Many of these active galactic nuclei, which appear star-like when observed through a telescope and  whose power output are more than 1011 times that of the Sun, exhibit rapid time variability in their X-ray emissions.  Rapid variability along with the existence of a maximum speed limit, c, provide a strong argument in favour of a compact central engine model for QSOs in which a thick disc of hot gas going around a supermassive blackhole is what makes a QSO appear like a bright point source. Hence, unlike stars, QSOs are powered by gravitational potential energy.

  7. A BLUE POINT SOURCE AT THE LOCATION OF SUPERNOVA 2011DH

    Energy Technology Data Exchange (ETDEWEB)

    Folatelli, Gastón; Bersten, Melina C.; Nomoto, Ken' ichi; Quimby, Robert M. [Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo, Kashiwa, Chiba 277-8583 (Japan); Benvenuto, Omar G. [Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque S/N, B1900FWA La Plata (Argentina); Van Dyk, Schuyler D. [Spitzer Science Center/Caltech, Mailcode 220-6, Pasadena, CA 91125 (United States); Kuncarayakti, Hanindyo; Hamuy, Mario [Millennium Institute of Astrophysics (MAS), Casilla 36-D, Santiago (Chile); Maeda, Keiichi [Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502 (Japan); Nozawa, Takaya, E-mail: gaston.folatelli@ipmu.jp [National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan)

    2014-10-01

    We present Hubble Space Telescope (HST) observations of the field of the Type IIb supernova (SN) 2011dh in M51 performed at ≈1161 rest-frame days after explosion using the Wide Field Camera 3 and near-UV filters F225W and F336W. A star-like object is detected in both bands and the photometry indicates it has negative (F225W – F336W) color. The observed object is compatible with the companion of the now-vanished yellow supergiant progenitor predicted in interacting binary models. We consider it unlikely that the SN is undergoing strong interaction and thus estimate that it makes a small contribution to the observed flux. The possibilities of having detected an unresolved light echo or an unrelated object are briefly discussed and judged unlikely. Adopting a possible range of extinction by dust, we constrain parameters of the proposed binary system. In particular, the efficiency of mass accretion onto the binary companion must be below 50%, if no significant extinction is produced by newly formed dust. Further multiband observations are required in order to confirm the identification of the object as the companion star. If confirmed, the companion star would already be dominant in the UV-optical regime, so it would readily provide a unique opportunity to perform a detailed study of its properties.

  8. Optimal information transmission in organizations: search and congestion

    Energy Technology Data Exchange (ETDEWEB)

    Arenas, A.; Cabrales, A.; Danon, L.; Diaz-Guilera, A.; Guimera, R.; Vega-Redondo, F.

    2008-01-01

    We propose a stylized model of a problem-solving organization whose internal communication structure is given by a fixed network. Problems arrive randomly anywhere in this network and must find their way to their respective specialized solvers by relying on local information alone. The organization handles multiple problems simultaneously. For this reason, the process may be subject to congestion. We provide a characterization of the threshold of collapse of the network and of the stock of floating problems (or average delay) that prevails below that threshold. We build upon this characterization to address a design problem: the determination of what kind of network architecture optimizes performance for any given problem arrival rate. We conclude that, for low arrival rates, the optimal network is very polarized (i.e. star-like or centralized), whereas it is largely homogeneous (or decentralized) for high arrival rates. These observations are in line with a common transformation experienced by information-intensive organizations as their work flow has risen in recent years.

  9. External conference: Geneva University

    CERN Multimedia

    2007-01-01

    ECOLE DE PHYSIQUE Département de physique nucléaire et corspusculaire 24, Quai Ernest-Ansermet 1211 GENEVE 4 - Tél : 022 379 62 73 - Fax: 022 379 69 92 Monday 11 June 2007 COLLOQUE DE LA SECTION DE PHYSIQUE at 17:00 - Stückelberg Auditorium The CERN Axion Solar Telescope (CAST). Motivation, concept, results and potential implications Prof. Konstantin ZIOUTAS / University of Patras/Greece & CERN and CAST-spokesperson Axion is one of the leading dark matter particle candidates. The last few years axion searches are in the spotlight. The physics motivation will be presented. Particles like the axions should be produced also in Stars like our Sun. In magnetic fields axions can coherently oscillate to photons and vice versa (Primakoff effect). CAST searches for solar axions pointing a recycled LHC magnet towards the Sun, and, it provides new results since 2002. Its working principle might well be already at work in outer space, asking for an alternative, though exotic, point of view for certain myst...

  10. Einstein–Maxwell Field Equation in Isotropic Coordinates: An Application to Modeling Superdense Star

    Indian Academy of Sciences (India)

    Neeraj Pant; Mohammad Ahmad; N. Pradhan

    2016-03-01

    We present a charged analogue of Pant et al. (2010, Astrophys.Space Sci., 330, 353) solution of the general relativistic field equations in isotropic coordinates by using simple form of electric intensity $E$ that involve charge parameter $K$. Our solution is well behaved in all respects for all values of $X$ lying in the range 0 < $X \\leq 0.11$, $K$ lyingin the range 4 < $K \\leq 6.2$ and Schwarzschild compactness parameter $u$ lying in the range 0 < $u \\leq 0.247$. Since our solution is well behaved for wide ranges of the parameters, we can model many different types of ultra-cold compact stars like quark stars and neutron stars. We have shown that corresponding to $X = 0.077$ and $K = 6.13$ for which $u = 0.2051$ and by assuming surface density $ρb = 4.6888 × 10^14 {\\rm g cm}^(−3)$ the mass and radius are found to be 1.509 $M_\\odot$, 10.906 km respectively which match with the observed values of mass 1.51 $M_\\odot$ and radius 10.90 km of the quark star XTE J1739-217. The well behaved class of relativistic stellar models obtained in this work might have astrophysical significance in the study of more realistic internal structures of compact stars.

  11. Impact of photometric variability on age and mass determination in young stellar objects: the case of the Orion Nebula Cluster

    Science.gov (United States)

    Messina, Sergio; Parihar, Padmakar; Distefano, Elisa

    2017-03-01

    Very young stars, like the Orion Nebula Cluster (ONC) members analysed in the present study, exhibit photometric variability with a wide range of amplitudes. Such a prominent variability reflects in the inferred values of stellar colours and luminosities and, in turn, in the inferred stellar ages and masses. In this study, we measure the amplitudes of the photometric variability in V, R and I optical bands of a sample of 346 ONC members. We use these measurements to investigate how this variability affects the inferred masses and ages and whether it alone can account for the age spread among ONC members reported by earlier studies. We make use of colour-magnitude and Hertzprung-Russell (HR) diagrams. We find that members that show periodic and smooth photometric rotational modulation have masses and ages that are unaffected by variability when theoretical isochrones and evolutionary mass tracks are used in either colour-magnitude or HR diagrams. On the other hand, members with periodic but very scattered photometric rotational modulation and non-periodic members have masses and ages that are significantly affected. Moreover, using HR diagrams, we find that the observed I-band photometric variability can take account of only a fraction (˜50 per cent) of the inferred age spread, whereas the V-band photometric variability is large enough to mask any age spread.

  12. Genetic relationships among some subspecies of the Peregrine Falcon (Falco peregrinus L.), inferred from mitochondrial DNA control-region sequences

    Science.gov (United States)

    White, Clayton M.; Sonsthagen, Sarah A.; Sage, George K.; Anderson, Clifford; Talbot, Sandra L.

    2013-01-01

    The ability to successfully colonize and persist in diverse environments likely requires broad morphological and behavioral plasticity and adaptability, and this may partly explain why the Peregrine Falcon (Falco peregrinus) exhibits a large range of morphological characteristics across their global distribution. Regional and local differences within Peregrine Falcons were sufficiently variable that ∼75 subspecies have been described; many were subsumed, and currently 19 are generally recognized. We used sequence information from the control region of the mitochondrial genome to test for concordance between genetic structure and representatives of 12 current subspecies and from two areas where subspecies distributions overlap. Haplotypes were broadly shared among subspecies, and all geographic locales shared a widely distributed common haplotype (FalconCR2). Haplotypes were distributed in a star-like phylogeny, consistent with rapid expansion of a recently derived species, with observed genetic patterns congruent with incomplete lineage sorting and/or differential rates of evolution on morphology and neutral genetic characters. Hierarchical analyses of molecular variance did not uncover genetic partitioning at the continental level, despite strong population-level structure (FST = 0.228). Similar analyses found weak partitioning, albeit significant, among subspecies (FCT = 0.138). All reconstructions placed the hierofalcons' (Gyrfalcon [F. rusticolus] and Saker Falcon [F. cherrug]) haplotypes in a well-supported clade either basal or unresolved with respect to the Peregrine Falcon. In addition, haplotypes representing Taita Falcon (F. fasciinucha) were placed within the Peregrine Falcon clade.

  13. Inferring the population structure and demographic history of the tick, Amblyomma americanum Linnaeus.

    Science.gov (United States)

    Mixson, Tonya R; Lydy, Shari L; Dasch, Gregory A; Real, Leslie A

    2006-06-01

    A hierarchial population genetic study was conducted on 703 individual Amblyomma americanum from nine populations in Georgia, U.S.A. Populations were sampled from the Coastal Plain, midland Piedmont region, and the upper Piedmont region. Twenty-nine distinct haplotypes were found. A minimum spanning tree was constructed that indicated these haplotypes comprised two lineages, the root of which was distinctly star-like. The majority of the variation found was among ticks within each population, indicating high amounts of gene flow and little genetic differentiation between the three regions. An overall F(ST) value of 0.006 supported the lack of genetic structuring between collection sites in Georgia. Mantel regression analysis revealed no isolation by distance. Signatures of population expansion were detected in the shapes of the mismatch distribution and tests of neutrality. The absence of genetic differentiation combined with the rejection of the null model of isolation by distance may indicate recent range expansion in Georgia or insufficient time to reach an equilibrium where genetic drift may have affected allele frequencies. Alternatively, the high degree of panmixia found within A. americanum in Georgia may be due to bird-mediated dispersal of ticks increasing the genetic similarity between geographically separated populations.

  14. An extreme paucity of second population AGB stars in the normal globular cluster M4

    CERN Document Server

    MacLean, B T; De Silva, G M; Lattanzio, J; DOrazi, V; Simpson, J D; Momany, Y

    2016-01-01

    Galactic Globular clusters (GCs) are now known to harbour multiple stellar populations, which are chemically distinct in many light element abundances. It is becoming increasingly clear that asymptotic giant branch (AGB) stars in GCs show different abundance distributions in light elements compared to those in the red giant branch (RGB) and other phases, skewing toward more primordial, field-star-like abundances, which we refer to as subpopulation one (SP1). As part of a larger program targeting giants in GCs, we obtained high-resolution spectra for a sample of 106 RGB and 15 AGB stars in Messier 4 (NGC 6121) using the 2dF+HERMES facility on the Anglo-Australian Telescope. In this Letter we report an extreme paucity of AGB stars with [Na/O] > -0.17 in M4, which contrasts with the RGB that has abundances up to [Na/O] =0.55. The AGB abundance distribution is consistent with all AGB stars being from SP1. This result appears to imply that all subpopulation two stars (SP2; Na-rich, O-poor) avoid the AGB phase. Thi...

  15. Chloroplast DNA variation and phylogeography of Ligularia tongolensis (Asteraceae), a species endemic to the Hengduan Mountains region of China

    Institute of Scientific and Technical Information of China (English)

    Jin-Feng WANG; Yue-Zhi PAN; Xun GONG; Yu-Chung CHIANG; Chiaki KURODA

    2011-01-01

    In this research, we aimed to study the genetic variation and phylogeographic pattern of Ligularia tongolensis, a perennial herb endemic to the Hengduan Mountains region of China. We sequenced two chloroplast DNA (cpDNA) intergenic spacers (trnQ-5'rps 16, trnL-rpl32) in 140 individuals from 14 populations of three groups (Jinshajiang vs. Yalongjiang vs. Wumeng) within this species range. High levels of haplotype diversity (Hd= 0.814)and total genetic diversity (Ht = 0.862) were detected at the species level, based on a total of 12 haplotypes identified.Low levels of intrapopulation diversity (Hs = 0.349), high levels of genetic divergence (Gst = 0.595, Nst = 0.614,Fst = 0.597), and the absence of isolation by distance tests were also found in L. tongolensis. Furthermore, H2 and H5, the dominant haplotypes that located at internal nodes and deviated from extinct ancestral haplotype in the network, were found to be shared between Jinshajiang and Yalongjiang groups. These results indicate that past fragmentation may be the important factor responsible for the present phylogeographical pattern of L. tongolensis.Meanwhile, the locations occupied by each group might have served as independent refugia for L. tongolensis during the Quaternary glaciation. Unimodal mismatch distribution and star-like genealogies indicated this species underwent past demographic expansion events, with expansion ages of 274 ka BP.

  16. Actin cytoskeleton remodeling governs aquaporin-4 localization in astrocytes.

    Science.gov (United States)

    Nicchia, Grazia Paola; Rossi, Andrea; Mola, Maria Grazia; Procino, Giuseppe; Frigeri, Antonio; Svelto, Maria

    2008-12-01

    Aquaporin-4 (AQP4) is constitutively concentrated in the plasma membrane of the perivascular glial processes, and its expression is altered in certain pathological conditions associated with brain edema or altered glial migration. When astrocytes are grown in culture, they lose their characteristic star-like shape and AQP4 continuous plasma membrane localization observed in vivo. In this study, we differentiated primary astrocyte cultures with cAMP and lovastatin, both able to induce glial stellation through a reorganization of F-actin cytoskeleton, and obtained AQP4 selectively localized on the cell plasma membrane associated with an increase in the plasma membrane water transport level, but only cAMP induced an increase in AQP4 total protein expression. Phosphorylation experiments indicated that AQP4 in astrocytes is neither phosphorylated nor a substrate of PKA. Depolymerization of F-actin cytoskeleton performed by cytochalasin-D suggested that F-actin cytoskeleton plays a primary role for AQP4 plasma membrane localization and during cell adhesion. Finally, AQP4 knockdown does not compromise the ability of astrocytes to stellate in the presence of cAMP, indicating that astrocyte stellation is independent of AQP4. Copyright 2008 Wiley-Liss, Inc.

  17. The LBTI Hunt for Observable Signatures of Terrestrial Systems (HOSTS) Survey: a Key NASA Science Program on the Road to Exoplanet Imaging Missions (SPIE Proceedings 2)

    Science.gov (United States)

    Danchi, William C.; Bailey, V.; Defrere, D.; Haniff, C.; Hinz, P.; Kennedy, G.; Mennesson, B.; Millan-Gabet, R.; Rieke, G.; Roberge, Aki; Serabyn, E.; Skemer, A.; Stapelfeldt, K.; Weinberger, A.; Wyatt, M.

    2014-01-01

    Telescope Interferometer (LBTI) will survey nearby stars for faint exozodiacal dust (exozodi). This warm circumstellar dust, analogous to the interplanetary dust found in the vicinity of the Earth in our own system, is produced in comet breakups and asteroid collisions. Emission and or scattered light from the exozodi will be the major source of astrophysical noise for a future space telescope aimed at direct imaging and spectroscopy of terrestrial planets (exo- Earths) around nearby stars. About 20 of nearby field stars have cold dust coming from planetesimals at large distances from the stars (Eiroa et al. 2013, AA, 555, A11; Siercho et al. 2014, ApJ, 785, 33). Much less is known about exozodi; current detection limits for individual stars are at best 500 times our solar system's level (aka. 500 zodi). LBTI-HOSTS will be the first survey capable of measuring exozodi at the 10 zodi level (3). Detections of warm dust will also reveal new information about planetary system architectures and evolution. We will describe the motivation for the survey and progress on target selection, not only the actual stars likely to be observed by such a mission but also those whose observation will enable sensible extrapolations for stars that will not be observed with LBTI. We briefly describe the detection of the debris disk around Crv, which is the first scientific result from the LBTI coming from the commissioning of the instrument in December 2013, shortly after the first time the fringes were stabilized.

  18. Molecular identification of Echinococcus granulosus on the Tibetan Plateau using mitochondrial DNA markers.

    Science.gov (United States)

    Hu, D; Song, X; Wang, N; Zhong, X; Wang, J; Liu, T; Jiang, Z; Dawa, T; Gu, X; Peng, X; Yang, G

    2015-10-30

    Cystic echinococcosis (CE) is an important worldwide zoonotic disease that causes large economic losses and human suffering. Echinococcus granulosus, the causative agent of CE, exhibits different genotypes in different locations. In order to identify its genotypes and analyze its genetic structure on the Tibetan Plateau, we collected 72 hydatid cysts from different intermediate hosts and amplified and sequenced their mitochondrial cytochrome c oxidase subunit 2 (cox2) genes. Seventy isolates were identified as the E. granulosus G1 genotype, while two isolates belonged to the G6 genotype. There were 18 haplotypes among the 70 E. granulosus isolates, which exhibited a star-like network pattern and shared a common haplotype (H1). There was little difference between geographical sub-populations. Our results suggest that a recent E. granulosus population expansion occurred on the Tibetan Plateau, suggesting that E. granulosus was introduced into China. This study increases the basic molecular data needed for the molecular diagnosis, epidemiology, prevention, and control of Echinococcus diseases.

  19. Genetic variability of Echinococcus granulosus based on the mitochondrial 16S ribosomal RNA gene.

    Science.gov (United States)

    Wang, Ning; Wang, Jiahai; Hu, Dandan; Zhong, Xiuqin; Jiang, Zhongrong; Yang, Aiguo; Deng, Shijin; Guo, Li; Tsering, Dawa; Wang, Shuxian; Gu, Xiaobin; Peng, Xuerong; Yang, Guangyou

    2015-06-01

    Echinococcus granulosus is the etiological agent of cystic echinococcosis, a major zoonotic disease of both humans and animals. In this study, we assessed genetic variability and genetic structure of E. granulosus in the Tibet plateau, using the complete mitochondrial 16 S ribosomal RNA gene for the first time. We collected and sequenced 62 isolates of E. granulosus from 3 populations in the Tibet plateau. A BLAST analysis indicated that 61 isolates belonged to E. granulosus sensu stricto (genotypes G1-G3), while one isolate belonged to E. canadensis (genotype G6). We detected 16 haplotypes with a haplotype network revealing a star-like expansion, with the most common haplotype occupying the center of the network. Haplotype diversity and nucleotide diversity were low, while negative values were observed for Tajima's D and Fu's Fs. AMOVA results and Fst values revealed that the three geographic populations were not genetically differentiated. Our results suggest that a population bottleneck or population expansion has occurred in the past, and that this explains the low genetic variability of E. granulosus in the Tibet Plateau.

  20. Genetic variability of Echinococcus granulosus from the Tibetan plateau inferred by mitochondrial DNA sequences.

    Science.gov (United States)

    Yan, Ning; Nie, Hua-Ming; Jiang, Zhong-Rong; Yang, Ai-Guo; Deng, Shi-Jin; Guo, Li; Yu, Hua; Yan, Yu-Bao; Tsering, Dawa; Kong, Wei-Shu; Wang, Ning; Wang, Jia-Hai; Xie, Yue; Fu, Yan; Yang, De-Ying; Wang, Shu-Xian; Gu, Xiao-Bin; Peng, Xue-Rong; Yang, Guang-You

    2013-09-01

    To analyse genetic variability and population structure, 84 isolates of Echinococcus granulosus (Cestoda: Taeniidae) collected from various host species at different sites of the Tibetan plateau in China were sequenced for the whole mitochondrial nad1 (894 bp) and atp6 (513 bp) genes. The vast majority were classified as G1 genotype (n=82), and two samples from human patients in Sichuan province were identified as G3 genotype. Based on the concatenated sequences of nad1+atp6, 28 different haplotypes (NA1-NA28) were identified. A parsimonious network of the concatenated sequence haplotypes showed star-like features in the overall population, with NA1 as the major haplotype in the population networks. By AMOVA it was shown that variation of E. granulosus within the overall population was the main pattern of the total genetic variability. Neutrality indexes of the concatenated sequence (nad1+atp6) were computed by Tajima's D and Fu's Fs tests and showed high negative values for E. granulosus, indicating significant deviations from neutrality. FST and Nm values suggested that the populations were not genetically differentiated.

  1. Monophyly of Opisthorchis viverrini populations in the lower Mekong Basin, using mitochondrial DNA nad1 gene as the marker.

    Science.gov (United States)

    Thaenkham, Urusa; Nuamtanong, Supaporn; Sa-nguankiat, Surapol; Yoonuan, Tippayarat; Touch, Sarun; Manivong, Khemphavanh; Vonghachack, Youthanavanh; Sato, Megumi; Waikagul, Jitra

    2010-06-01

    The liver fluke, Opisthorchis viverrini, causes serious public-health problems in the Lower Mekong Basin. This study aimed to clarify whether O. viverrini populations may be genetically divided into sub-specific taxa. We collected 6 populations of O. viverrini from different places in Cambodia, Lao PDR, and Thailand, along both sides of the Mekong River, and analyzed the population structure of these using the mitochondrial nad1 gene as a marker. The results of the DNA polymorphism measurements, by theta-w (thetaw) and -pi (thetapi) values, neutrality tests, and mismatch distribution, suggested that the population of O. viverrini has expanded under the influence of purifying selection and selective sweep. The analysis of molecular variance (AMOVA) test revealed no significant genetic differences among the O. viverrini populations on opposite sides of the Mekong River. O. viverrini haplotypes occurred in multiple populations, and no distinct geographical clade. The star-like haplotype network confirmed a demographic expansion of the O. viverrini population. Overall, the genetic data from these populations suggested that the postulated existence of an O. viverrini species complex should be rejected. The bio-geographical diversity of O. viverrini populations should be explored further, using other appropriate markers and a wider range of samples from geographically different areas.

  2. High genetic connectivity among estuarine populations of the riverbream Acanthopagrus vagus along the southern African coast

    Science.gov (United States)

    Oosthuizen, Carel J.; Cowley, Paul D.; Kyle, Scotty R.; Bloomer, Paulette

    2016-12-01

    Physical and/or physiological constraints are assumed to isolate fish populations confined to or dependent on estuarine habitats. Strong isolation by distance is thus expected to affect connectivity. Such structuring has important implications for sustainable utilisation and replenishment of estuarine stocks that are heavily exploited. Here we present a preliminary investigation of the phylogenetic relationships of the riverbream (Acanthopagrus species) along the southern African coast and the geographic genetic structure of what appears to be a locally endemic species or lineage. Mitochondrial DNA (mtDNA) cytochrome b sequences support the notion that the species occurring along the southern African coast is A. vagus and not A. berda as previously thought. Yet, the taxonomy of this widespread Indo-West Pacific species or species-complex requires more in-depth investigation. No genetic differentiation was detected among estuarine populations of A. vagus based on the analyses of mtDNA ND2 gene sequences and 10 polymorphic nuclear microsatellite markers. The star-like genealogy and statistical analyses are consistent with a recent population expansion event. Spatial analyses of microsatellite genotypes fail to reject the null hypothesis of panmixia, indicative of a recent population expansion or ongoing gene flow between different estuaries. The northern localities were identified as containing most of the observed variation. This study not only provides insight into the phylogenetic relationship of A. vagus relative to other Acanthopagrus species but also sheds light on the demographic history and contemporary gene flow of the species.

  3. Relation between Brown Dwarfs and Exoplanets

    CERN Document Server

    Torres, Lauren Melissa Flor; Schröeder, Klauss-Peter; Caretta, César A; Jack, Dennis

    2016-01-01

    One of the most debated subjects in Astronomy since the discovery of exoplanets is how can we distinguish the most massive of such objects from very-low mass stars like Brown Dwarfs (BDs)? We have been looking for evidences of a difference in physical characteristics that could be related to different formation processes. Using a new diagnostic diagram that compares the baryonic gravitational potential (BGP) with the distances from their host stars, we have classified a sample of 355 well-studied exoplanets according to their possible structures. We have then compared the exoplanets to a sample of 87 confirmed BDs, identifying a range in BGP that could be common to both objects. By analyzing the mass-radius relations (MRR) of the exoplanets and BDs in those different BGP ranges, we were able to distinguish different characteristic behaviors. By comparing with models in the literature, our results suggest that BDs and massive exoplanets might have similar structures dominated by liquid metallic hydrogen (LMH).

  4. Magnetospherically driven optical and radio aurorae at the end of the stellar main sequence.

    Science.gov (United States)

    Hallinan, G; Littlefair, S P; Cotter, G; Bourke, S; Harding, L K; Pineda, J S; Butler, R P; Golden, A; Basri, G; Doyle, J G; Kao, M M; Berdyugina, S V; Kuznetsov, A; Rupen, M P; Antonova, A

    2015-07-30

    Aurorae are detected from all the magnetized planets in our Solar System, including Earth. They are powered by magnetospheric current systems that lead to the precipitation of energetic electrons into the high-latitude regions of the upper atmosphere. In the case of the gas-giant planets, these aurorae include highly polarized radio emission at kilohertz and megahertz frequencies produced by the precipitating electrons, as well as continuum and line emission in the infrared, optical, ultraviolet and X-ray parts of the spectrum, associated with the collisional excitation and heating of the hydrogen-dominated atmosphere. Here we report simultaneous radio and optical spectroscopic observations of an object at the end of the stellar main sequence, located right at the boundary between stars and brown dwarfs, from which we have detected radio and optical auroral emissions both powered by magnetospheric currents. Whereas the magnetic activity of stars like our Sun is powered by processes that occur in their lower atmospheres, these aurorae are powered by processes originating much further out in the magnetosphere of the dwarf star that couple energy into the lower atmosphere. The dissipated power is at least four orders of magnitude larger than what is produced in the Jovian magnetosphere, revealing aurorae to be a potentially ubiquitous signature of large-scale magnetospheres that can scale to luminosities far greater than those observed in our Solar System. These magnetospheric current systems may also play a part in powering some of the weather phenomena reported on brown dwarfs.

  5. The make-up of stars

    Energy Technology Data Exchange (ETDEWEB)

    Asplund, Martin [Research School of Astronomy and Astrophysics, Australian National University, Cotter Road, Weston, ACT 2611 (Australia)

    2014-11-20

    The chemical composition of stars contain vital clues not only about the stars themselves but also about the conditions prevailing before their births. As such, stellar spectroscopy plays a key role in contemporary astrophysics and cosmology by probing cosmic, galactic, stellar and planetary evolution. In this review I will describe the theoretical foundations of quantitative stellar spectroscopy: stellar atmosphere models and spectral line formation. I will focus mainly on more recent advances in the field, in particular the advent of realistic time-dependent, 3D, (magneto-)hydrodynamical simulations of stellar surface convection and atmospheres and non-LTE radiative transfer relevant for stars like the Sun. I will also discuss some particular applications of this type of modelling which have resulted in some exciting break-throughs in our understanding and with wider implications: the solar chemical composition, the chemical signatures of planet formation imprinted in stellar abundances, the cosmological Li problem(s) and where the first stars may be residing today.

  6. Magnetars

    CERN Document Server

    Cea, P

    2005-01-01

    P-stars are compact stars made of up and down quarks in beta-equilibrium with electrons in a chromomagnetic condensate. P-stars are able to account for compact stars like RXJ 1856.5-3754 and RXJ 0720.4-3125, stars with radius comparable with canonical neutron stars, as well as super massive compact objects like SgrA*. We discuss p-stars endowed with super strong dipolar magnetic field which, following consolidated tradition in literature, are referred to as magnetars. We show that soft gamma-ray repeaters and anomalous X-ray pulsars can be understood within our theory. We find a well defined criterion to distinguish rotation powered pulsars from magnetic powered pulsars. We show that glitches, that in our magnetars are triggered by magnetic dissipative effects in the inner core, explain both the quiescent emission and bursts in soft gamma-ray repeaters and anomalous X-ray pulsars. We are able to account for the braking glitch from SGR 1900+14 and the normal glitch from AXP 1E 2259+586 following a giant burst....

  7. Biofluorescent Worlds: Biological fluorescence as a temporal biosignature for flare star worlds

    CERN Document Server

    O'Malley-James, Jack T

    2016-01-01

    Habitability for planets orbiting active stars has been questioned. Especially, planets in the Habitable Zone (HZ) of M-stars, like our closest star Proxima Centauri, experience temporal high-ultraviolet (UV) radiation. The high fraction of M-stars (75%) within the solar neighborhood, the high occurrence rate of rocky planets around M-stars, and the favorable contrast ratio between the star and a potentially habitable rocky planet, makes such planets interesting targets for upcoming observations. During M-star flares, the UV flux on a HZ planet can increase by up to two orders of magnitude. High UV radiation is harmful to life and can cause cell and DNA damage. Common UV protection methods (e.g. living underground, or underwater) would make a biosphere harder to detect. However, photoprotective biofluorescence, "up-shifting" UV to longer, safer wavelengths (a proposed UV protection mechanism for some corals), would increase the detectability of biota and even uncover normally hidden biospheres during a flare....

  8. Bringing VY Canis Majoris Down to Size: An Improved Determination of Its Effective Tempeature

    CERN Document Server

    Massey, P; Plez, B; Levesque, Emily M.; Massey, Philip; Plez, Bertrand

    2006-01-01

    The star VY CMa is a late-type M supergiant with many peculiarities, mostly related to the intense circumstellar environment due to the star's high mass-loss rate. Claims have been made that would suggest this star is considerably more luminous (L = 5 x 10^5 Lo) and larger (R=2800 Ro) than other Galactic red supergiants (RSGs). Indeed, such a location in the H-R diagram would be well in the "Hayashi forbidden zone" where stars cannot be in hydrostatic equilibrium. These extraordinary properties, however, rest upon an assumed effective temperature of 2800-3000 K, far cooler than recent work have shown RSGs to be. To obtain a better estimate, we fit newly obtained spectrophotometry in the optical and NIR with the same MARCS models used for our recent determination of the physical properties of other RSGs; we also use $V-K$ and $V-J$ from the literature to derive an effective temperatures. We find that the star likely has a temperature of 3650 K, a luminosity L = 6 x 10^4 Lo, and a radius of 600Ro. These values ...

  9. Genetic analysis of oriental fruit fly, Bactrocera dorsalis (Diptera: Tephritidae) populations based on mitochondrial cox1 and nad1 gene sequences from India and other Asian countries.

    Science.gov (United States)

    Choudhary, Jaipal S; Naaz, Naiyar; Prabhakar, Chandra S; Lemtur, Moanaro

    2016-10-01

    The study examined the genetic diversity and demographic history of Bactrocera dorsalis, a destructive and polyphagous insect pest of fruit crops in diverse geographic regions of India. 19 widely dispersed populations of the fly from India and other Asian countries were analysed using partial sequences of mitochondrial cytochrome oxidase I (cox1) and NADH dehydrogenase 1 (nad1) genes to investigate genetic diversity, genetic structure, and demographic history in the region. Genetic diversity indices [number of haplotypes (H), haloptype diversity (Hd), nucleotide diversity (π) and average number of nucleotide difference (k)] of populations revealed that B. dorsalis maintains fairly high level of genetic diversity without isolation by distance among the geographic regions. Demographic analysis showed significant (negative) Tajimas' D and Fu's F S with non significant sum of squared deviations (SSD) values, which indicate the possibility of recent sudden expansion of species and is further supported through distinctively star-like distribution structure of haplotypes among populations. Thus, the results indicate that both ongoing and historical factors have played important role in determining the genetic structure and diversity of the species in India. Consequently, sterile insect technique (SIT) could be a possible management strategy of species in the regions.

  10. The formation and assembly of a typical star-forming galaxy at z~3

    CERN Document Server

    Stark, Daniel P; Ellis, Richard S; Dye, Simon; Smail, Ian R; Richard, Johan

    2008-01-01

    Recent studies of galaxies ~2-3 Gyr after the Big Bang have revealed large, turbulent rotating systems. The existence of well-ordered rotation in galaxies during this peak epoch of cosmic star formation may suggest that gas accretion through cold streams is likely to be the dominant mode by which most star-forming galaxies at high redshift since major mergers can completely disrupt the observed velocity fields. However poor spatial resolution and sensitivity have hampered this interpretation, limiting the study to the largest and most luminous galaxies, which may have fundamentally different modes of assembly than more typical star forming galaxies. Here we report observations of a typical star forming galaxy at z=3.07 with a linear resolution of ~100 parsec. This spatial sampling is made possible by the combination of gravitational lensing and laser guide star adaptive optics. We find a well-ordered compact source in which molecular gas is being converted efficiently into stars, likely assembling a spheroida...

  11. Characterization of calcium oxalates generated as biominerals in cacti.

    Science.gov (United States)

    Monje, Paula V; Baran, Enrique J

    2002-02-01

    The chemical composition and morphology of solid material isolated from various Cactaceae species have been analyzed. All of the tested specimens deposited high-purity calcium oxalate crystals in their succulent modified stems. These deposits occurred most frequently as round-shaped druses that sometimes coexist with abundant crystal sand in the tissue. The biominerals were identified either as CaC(2)O(4).2H(2)O (weddellite) or as CaC(2)O(4).H(2)O (whewellite). Seven different species from the Opuntioideae subfamily showed the presence of whewellite, and an equal number of species from the Cereoideae subfamily showed the deposition of weddellite. The chemical nature of these deposits was assessed by infrared spectroscopy. The crystal morphology of the crystals was visualized by both conventional light and scanning electron microscopy. Weddellite druses were made up of tetragonal crystallites, whereas those from whewellite were most often recognized by their acute points and general star-like shape. These studies clearly demonstrated that members from the main traditional subfamilies of the Cactaceae family could synthesize different chemical forms of calcium oxalate, suggesting a definite but different genetic control. The direct relationship established between a given Cactaceae species and a definite calcium oxalate biomineral seems to be a useful tool for plant identification and chemotaxonomy.

  12. Characterization of Calcium Oxalates Generated as Biominerals in Cacti1

    Science.gov (United States)

    Monje, Paula V.; Baran, Enrique J.

    2002-01-01

    The chemical composition and morphology of solid material isolated from various Cactaceae species have been analyzed. All of the tested specimens deposited high-purity calcium oxalate crystals in their succulent modified stems. These deposits occurred most frequently as round-shaped druses that sometimes coexist with abundant crystal sand in the tissue. The biominerals were identified either as CaC2O4.2H2O (weddellite) or as CaC2O4.H2O (whewellite). Seven different species from the Opuntioideae subfamily showed the presence of whewellite, and an equal number of species from the Cereoideae subfamily showed the deposition of weddellite. The chemical nature of these deposits was assessed by infrared spectroscopy. The crystal morphology of the crystals was visualized by both conventional light and scanning electron microscopy. Weddellite druses were made up of tetragonal crystallites, whereas those from whewellite were most often recognized by their acute points and general star-like shape. These studies clearly demonstrated that members from the main traditional subfamilies of the Cactaceae family could synthesize different chemical forms of calcium oxalate, suggesting a definite but different genetic control. The direct relationship established between a given Cactaceae species and a definite calcium oxalate biomineral seems to be a useful tool for plant identification and chemotaxonomy. PMID:11842173

  13. Lithium Abundance Of The Solar-Type Superflare Stars

    Science.gov (United States)

    Honda, Satoshi; Notsu, Yuta; Maehara, Hiroyuki; Notsu, Shota; Shibayama, Takuya; Nogami, Daisaku; Shibata, Kazunari

    2016-07-01

    We performed the high dispersion spectroscopy of solar-type superflare stars by Subaru/HDS, and estimate the stellar parameters and lithium abundance of the stars to compare with the Sun. Our spectroscopic analysis of superflare stars show more than half of targets have no evidence of binary system and the stellar parameters are in the range of solar-type stars (Notsu et al. 2015a&b). We also investigate the correlations of Lithium abundance with stellar atmospheric parameters, rotational velocity, and superflare activities to understand the nature of superflare stars and the possibility of the nucleosynthesis of lithium by superflares. The derived lithium abundance in superflare stars do not show the correlation with stellar parameters. As compared with the lithium abundance in Hyades cluster which is younger than the sun, it is suggested that half of observed stars are young. However, there are some objects which show the low lithium and slowly rotate from the estimated v sin(i) and period of brightness variation. These results indicate that the superflare stars are not only young stars but also old stars like our sun. In our observations, we could not find the any evidence of lithium productions by superflare.

  14. Golgi Analysis of Neuron Morphology in the Presumptive Somatosensory Cortex and Visual Cortex of the Florida Manatee (Trichechus manatus latirostris).

    Science.gov (United States)

    Reyes, Laura D; Harland, Tessa; Reep, Roger L; Sherwood, Chet C; Jacobs, Bob

    2016-01-01

    The current study investigates neuron morphology in presumptive primary somatosensory (S1) and primary visual (V1) cortices of the Florida manatee (Trichechus manatus latirostris) as revealed by Golgi impregnation. Sirenians, including manatees, have an aquatic lifestyle, a large body size, and a relatively large lissencephalic brain. The present study examines neuron morphology in 3 cortical areas: in S1, dorsolateral cortex area 1 (DL1) and cluster cortex area 2 (CL2) and in V1, dorsolateral cortex area 4 (DL4). Neurons exhibited a variety of morphological types, with pyramidal neurons being the most common. The large variety of neuron types present in the manatee cortex was comparable to that seen in other eutherian mammals, except for rodents and primates, where pyramid-shaped neurons predominate. A comparison between pyramidal neurons in S1 and V1 indicated relatively greater dendritic branching in S1. Across all 3 areas, the dendritic arborization pattern of pyramidal neurons was also similar to that observed previously in the afrotherian rock hyrax, cetartiodactyls, opossums, and echidnas but did not resemble the widely bifurcated dendrites seen in the large-brained African elephant. Despite adaptations for an aquatic environment, manatees did not share specific neuron types such as tritufted and star-like neurons that have been found in cetaceans. Manatees exhibit an evolutionarily primitive pattern of cortical neuron morphology shared with most other mammals and do not appear to have neuronal specializations for an aquatic niche.

  15. A New Milky Way Satellite Discovered In The Subaru/Hyper Suprime-Cam Survey

    CERN Document Server

    Homma, Daisuke; Okamoto, Sakurako; Komiyama, Yutaka; Tanaka, Masayuki; Tanaka, Mikito; Ishigaki, Miho N; Akiyama, Masayuki; Arimoto, Nobuo; Garmilla, Jose A; Lupton, Robert H; Strauss, Michael A; Furusawa, Hisanori; Miyazaki, Satoshi; Murayama, Hitoshi; Nishizawa, Atsushi J; Takada, Masahiro; Usuda, Tomonori; Wang, Shiang-Yu

    2016-01-01

    We report the discovery of a new ultra-faint dwarf satellite companion of the Milky Way based on the early survey data from the Hyper Suprime-Cam Subaru Strategic Program. This new satellite, Virgo I, which is located in the constellation of Virgo, has been identified as a statistically significant (5.5 sigma) spatial overdensity of star-like objects with a well-defined main sequence and red giant branch in their color-magnitude diagram. The significance of this overdensity increases to 10.8 sigma when the relevant isochrone filter is adopted for the search. Based on the distribution of the stars around the likely main sequence turn-off at r ~ 24 mag, the distance to Virgo I is estimated as 87 kpc, and its most likely absolute magnitude calculated from a Monte Carlo analysis is M_V = -0.8 +/- 0.9 mag. This stellar system has an extended spatial distribution with a half-light radius of 38 +12/-11 pc, which clearly distinguishes it from a globular cluster with comparable luminosity. Thus, Virgo I is one of the ...

  16. Formation of Carbon-enhanced Metal-poor Stars in the Presence of Far-ultraviolet Radiation

    Science.gov (United States)

    Bovino, S.; Grassi, T.; Schleicher, D. R. G.; Latif, M. A.

    2014-08-01

    Recent discoveries of carbon-enhanced metal-poor stars like SMSS J031300.36-670839.3 provide increasing observational insights into the formation conditions of the first second-generation stars in the universe, reflecting the chemical conditions after the first supernova explosion. Here, we present the first cosmological simulations with a detailed chemical network including primordial species as well as C, C+, O, O+, Si, Si+, and Si2 + following the formation of carbon-enhanced metal-poor stars. The presence of background UV flux delays the collapse from z = 21 to z = 15 and cool the gas down to the cosmic microwave background temperature for a metallicity of Z/Z ⊙ = 10-3. This can potentially lead to the formation of lower-mass stars. Overall, we find that the metals have a stronger effect on the collapse than the radiation, yielding a comparable thermal structure for large variations in the radiative background. We further find that radiative backgrounds are not able to delay the collapse for Z/Z ⊙ = 10-2 or a carbon abundance as in SMSS J031300.36-670839.3.

  17. FORMATION OF CARBON-ENHANCED METAL-POOR STARS IN THE PRESENCE OF FAR-ULTRAVIOLET RADIATION

    Energy Technology Data Exchange (ETDEWEB)

    Bovino, S.; Schleicher, D. R. G.; Latif, M. A. [Institut für Astrophysik Georg-August-Universität, Friedrich-Hund Platz 1, 37077 Göttingen (Germany); Grassi, T., E-mail: sbovino@astro.physik.uni-goettingen.de [Centre for Star and Planet Formation, Natural History Museum of Denmark, Øster Voldgade 5-7, 1350 Copenhagen (Denmark)

    2014-08-01

    Recent discoveries of carbon-enhanced metal-poor stars like SMSS J031300.36–670839.3 provide increasing observational insights into the formation conditions of the first second-generation stars in the universe, reflecting the chemical conditions after the first supernova explosion. Here, we present the first cosmological simulations with a detailed chemical network including primordial species as well as C, C{sup +}, O, O{sup +}, Si, Si{sup +}, and Si{sup 2+} following the formation of carbon-enhanced metal-poor stars. The presence of background UV flux delays the collapse from z = 21 to z = 15 and cool the gas down to the cosmic microwave background temperature for a metallicity of Z/Z {sub ☉} = 10{sup –3}. This can potentially lead to the formation of lower-mass stars. Overall, we find that the metals have a stronger effect on the collapse than the radiation, yielding a comparable thermal structure for large variations in the radiative background. We further find that radiative backgrounds are not able to delay the collapse for Z/Z {sub ☉} = 10{sup –2} or a carbon abundance as in SMSS J031300.36–670839.3.

  18. The EUVE point of view of AD Leo

    CERN Document Server

    Sanz-Forcada, J

    2002-01-01

    All the Extreme Ultraviolet Explorer (EUVE) observations of AD Leo, totalling 1.1 Ms of exposure time, have been employed to analyze the corona of this single M dwarf. The light curves show a well defined quiescent stage, and a distribution of amplitude of variability following a power law with a ~-2.4 index. The flaring behavior exhibits much similarity with other M active stars like FK Aqr or YY Gem, and flares behave differently from late type active giants and subgiants. The Emission Measure Distribution (EMD) of the summed spectrum, as well as that of quiescent and flaring stages, were obtained using a line-based method. The average EMD is dominated by material at log T(K)~6.9, with a second peak around log T(K)~6.3, and a large increase in the amount of material with log T(K)>~7.1 during flares, material almost absent during quiescence. The results are interpreted as the combination of three families of loops with maximum temperatures at log T(K)~6.3, ~6.9 and somewhere beyond log T(K)>~7.1. A value of ...

  19. Speciation and phylogeography in the cosmopolitan marine moon jelly, Aurelia sp.

    Science.gov (United States)

    Schroth, Werner; Jarms, Gerhard; Streit, Bruno; Schierwater, Bernd

    2002-01-01

    The cosmopolitan moon jelly Aurelia is characterized by high degrees of morphological and ecological plasticity, and subsequently by an unclear taxonomic status. The latter has been revised repeatedly over the last century, dividing the genus Aurelia in as many as 12 or as little as two species. We used molecular data and phenotypic traits to unravel speciation processes and phylogeographic patterns in Aurelia. Mitochondrial and nuclear DNA data (16S and ITS-1/5.8S rDNA) from 66 world-wide sampled specimens reveal star-like tree topologies, unambiguously differentiating 7 (mtDNA) and 8 (ncDNA) genetic entities with sequence divergences ranging from 7.8 to 14% (mtDNA) and 5 to 32% (ncDNA), respectively. Phylogenetic patterns strongly suggest historic speciation events and the reconstruction of at least 7 different species within Aurelia. Both genetic divergences and life history traits showed associations to environmental factors, suggesting ecological differentiation forced by divergent selection. Hybridization and introgression between Aurelia lineages likely occurred due to secondary contacts, which, however, did not disrupt the unambiguousness of genetic separation. Our findings recommend Aurelia as a model system for using the combined power of organismic, ecological, and molecular data to unravel speciation processes in cosmopolitan marine organisms.

  20. The properties of ten O-type stars in the low-metallicity galaxies IC 1613, WLM and NGC 3109

    CERN Document Server

    Tramper, F; de Koter, A; Kaper, L; Ramirez-Agudelo, O H

    2014-01-01

    Massive stars likely played an important role in the reionization of the Universe, and the formation of the first black holes. Massive stars in low-metallicity environments in the local Universe are reminiscent of their high redshift counterparts. In a previous paper, we reported on indications that the stellar winds of low-metallicity O stars may be stronger than predicted, which would challenge the current paradigm of massive star evolution. In this paper, we aim to extend our initial sample of six O stars in low-metallicity environments by four. We aim to derive their stellar and wind parameters, and compare these to radiation-driven wind theory and stellar evolution models. We have obtained intermediate-resolution VLT/X-Shooter spectra of our sample of stars. We derive the stellar parameters by fitting synthetic fastwind line profiles to the VLT/X-Shooter spectra using a genetic fitting algoritm. We compare our parameters to evolutionary tracks and obtain evolutionary masses and ages. We also investigate ...

  1. Morphological effects of single-layer graphene oxide in the formation of covalently bonded polypyrrole composites using intermediate diisocyanate chemistry

    Science.gov (United States)

    Whitby, Raymond L. D.; Korobeinyk, Alina; Mikhalovsky, Sergey V.; Fukuda, Takahiro; Maekawa, Toru

    2011-10-01

    Single-layer graphene oxide (SLGO) possesses carboxylic and hydroxyl groups suitable for reactions with aliphatic or aromatic diisocyanate molecules. TEM analysis reveals that aliphatic diisocyanate molecules caused SLGO to scroll into star-like formations, whereas aromatic diisocyanate molecules retained SGLO in a flat-sheet morphology. TGA confirms the stabilisation of the formed urea and urethane groups on SLGO, but the onset of sheet pyrolysis occurs at a lower temperature due to isocyanate reactions with anhydride and epoxide groups embedded in the sheet. Pendant isocyanate groups act as bridging units to facilitate the attachment of pyrrole molecules, which are then used as anchor sites for the covalent polymerisation of pyrrole to polypyrrole (PPy). The use of FeCl3 as the polymerisation catalyst generated both covalent and free PPy, but also iron hydroxide nanoparticles were observed decorating the SLGO surface. When using ammonium persulfate as a catalyst and dodecylbenzenesulfonate as a dopant, free PPy could be removed under treatment with solvents to leave a purely covalent system. Discrete regions of SLGO were observed decorated with nanoparticles of PPy along the edge or across the surface of individual sheets. It was found that the flexibility of the SLGO sheet and the type of diisocyanate used directly affected the electrical resistance of the final composite.

  2. Could AX J1841.0$-$0536 Be an Anti-Magnetar?

    CERN Document Server

    Li, X -D

    2011-01-01

    Recent observations show that supergiant fast X-ray transients (SFXTs) spend most of their lifetime at an intermediate level luminosity $\\sim 10^{33}-10^{34}$ ergs$^{-1}$, and, when a blackbody model for the spectra is adopted, the resulting radii of the emission region are always only a few hundred meters, supporting the idea that during the intermediate state SFXTs are accreting matter from the companion star. From these observational phenomena we derive possible constraints on the magnetic field strengths of the neutron stars in four SFXTs with known spin periods. While IGR J11215$-$5952, IGR J16465$-$4507, and IGR J18483$-$0311 may have magnetic fields (up to a few $10^{11}-10^{12}$ G) similar to those of normal X-ray pulsars, the magnetic field of AX J1841.0$-$0536 is considerably low ($\\la 10^{10}$ G). The high-mass companion stars in SFXTs implies that the neutron stars are relatively young objects, with age less than $\\sim 10^7$ yr. Analysis of the spin evolution shows that neutron stars like AX J1841...

  3. SMA and CARMA observations of young brown dwarfs in ρ Ophiuchi and Taurus

    Directory of Open Access Journals (Sweden)

    Lee C.-F.

    2011-07-01

    Full Text Available Molecular outflows provide vital information about the earliest stages in the birth of stars, studying the molecular outflow properties is therefore crucial for understanding how stars form. Brown dwarfs with masses between that of stars and planets are not massive enough to maintain stable hydrogen-burning fusion reactions during most of their lifetime. Their origins are subject to much debate in recent literature because their masses are far below the typical mass where core collapse is expected to occur. Based on Submillimeter Array (SMA and Combined Array for Research in Millimeter-wave Astronomy (CARMA observations, we present the first detections of bipolar molecular outflows from young brown dwarfs in ρ Ophiuchi and Taurus. Our results demonstrate that the bipolar molecular outflow operates down to brown dwarf masses, occurring in brown dwarfs as a scaled-down version of the universal process seen in young low-mass stars. This demonstrates that brown dwarfs and low-mass stars likely share the same formation mechanism.

  4. Phylogeography of Mabuya maculilabris (Reptilia) from São Tomé Island (Gulf of Guinea) inferred from mtDNA sequences.

    Science.gov (United States)

    Jesus, José; Harris, D James; Brehm, António

    2005-11-01

    The pattern of genetic variation of the lizard Mabuya maculilabris from São Tomé Island (Gulf of Guinea) was investigated using a combination of three mitochondrial DNA gene fragments. Forty-eight haplotypes were recovered among 66 individuals covering the whole island. The genealogy inferred from the most parsimonious network of haplotypes allows us to detect two main and long branches departing from the putative group of oldest haplotypes. The tips of these branches exhibit star-like phylogenies, which may indicate of recently expanded populations, most probably from a small number of founders. A nested clade analysis suggests a complex pattern of past events that gave rise to the extant geographical pattern found in the haplotype distribution: past and allopatric fragmentation, range expansion, restricted gene flow and long-distance dispersal. These results are consistent with the complex geological history of the island where important volcanic activity with extensive lava flows has occurred during several periods. Mismatch-distribution analysis and AMOVA also support these conclusions. Substantial genetic structuring among these lizards was detected as well as high levels of differentiation between the southern edge populations (particularly those from the Rolas Islet) and the remaining ones. However, variation is low relative to the geological age of the island. Our results indicate that patterns of variation observed in reptiles in other oceanic islands are not indicative of those observed in the islands of the Gulf of Guinea.

  5. Revealing the structure of the world airline network

    Science.gov (United States)

    Verma, T.; Araújo, N. A. M.; Herrmann, H. J.

    2014-07-01

    Resilience of most critical infrastructures against failure of elements that appear insignificant is usually taken for granted. The World Airline Network (WAN) is an infrastructure that reduces the geographical gap between societies, both small and large, and brings forth economic gains. With the extensive use of a publicly maintained data set that contains information about airports and alternative connections between these airports, we empirically reveal that the WAN is a redundant and resilient network for long distance air travel, but otherwise breaks down completely due to removal of short and apparently insignificant connections. These short range connections with moderate number of passengers and alternate flights are the connections that keep remote parts of the world accessible. It is surprising, insofar as there exists a highly resilient and strongly connected core consisting of a small fraction of airports (around 2.3%) together with an extremely fragile star-like periphery. Yet, in spite of their relevance, more than 90% of the world airports are still interconnected upon removal of this core. With standard and unconventional removal measures we compare both empirical and topological perceptions for the fragmentation of the world. We identify how the WAN is organized into different classes of clusters based on the physical proximity of airports and analyze the consequence of this fragmentation.

  6. MtDNA and nuclear data reveal patterns of low genetic differentiation for the isopods Stenosoma lancifer and Stenosoma acuminatum, with low dispersal ability along the northeast Atlantic coast

    Directory of Open Access Journals (Sweden)

    Raquel Xavier

    2011-11-01

    Full Text Available Evidence for a general lack of genetic differentiation of intertidal invertebrate assemblages in the North Atlantic, based on mtDNA sequence variation, has been interpreted as resulting from recent colonization following the Last Glacial Maximum. In the present study, the phylogeographic patterns of one nuclear and one mtDNA gene fragments of two isopods, Stenosoma lancifer (Miers, 1881 and Stenosoma acuminatum Leach, 1814, from the northeast Atlantic were investigated. These organisms have direct development, which makes them poor dispersers, and are therefore expected to maintain signatures of past historical events in their genomes. Lack of genetic structure, significant deviations from neutrality and star-like haplotype networks have been observed for both mtDNA and nuclear markers of S. lancifer, as well as for the mtDNA of S. acuminatum. No sequence variation was observed for the nuclear gene fragment of S. acuminatum. These results suggest a scenario of recent colonization and demographic expansion and/or high population connectivity driven by ocean currents and sporadic long-distance dispersal through rafting.

  7. Astrophysical and Biological Constraints on Radiopanspermia

    CERN Document Server

    Secker, J; Lepock, J R; Secker, Jeff; Wesson, Paul S.; Lepock, James R.

    1996-01-01

    We have carried out a series of calculations involving bacteria and viruses embedded in dust grains, which are ejected from our solar system by radiation pressure, and travel through space to other star systems. Under many conditions, this kind of panspermia is impractical, primarily because the ultraviolet (UV) radiation of the present Sun inactivates the micro-organisms. However, if the organisms are shielded by an absorbing material like carbon, and if ejection takes place in the late-Sun (red-giant) phase of a one-solar-mass star like our Sun, there is a significant probability that these micro-organisms can reach another star system alive (i.e., with only sub-lethal damage from UV and ionizing radiation). In addition to panspermia with viable micro-organisms, we note that it is possible to seed the Galaxy with inactivated ones, whose DNA and RNA fragments may provide the initial information necessary to start biological evolution in favorable environments.

  8. SOME STRANGE FINDINGS: NON - INTERPRETABLE PATTERNS IN MODIFIED HODGE TEST

    Directory of Open Access Journals (Sweden)

    Jayashree

    2013-10-01

    Full Text Available ABSTRACT: Many clinically relevant species of Gram - negative bacilli are often resistant to β - lactam antibiotics even to c arbapenems. According to CLS I guideline 2013, Carbapenemase producers are screened by zone size <21mm to Meropenem or Etrapenem and phenotypically confirmed by Modified Hodge test. The test of Hodge et al was modified by substituting Escherichia coli for penicillin - susceptible Staphy lococcus aureus ATCC 25923, and 10 - μg Imipenem disk for a 10 - U Penicillin disk. While looking for the Carbapenemase producing strains, some astonishing, unexplainable facts were revealed in this study. Meropenem - resistant test strains were screened (zone d iameter in Modified Kirby - Bauer technique<21mm & for phenotypic confirmation of Carbapenemase production, modified Hodge test was performed. Thereafter the test strains were examined for production of Metallo β Lactamase using Imipenem (10μg disk and com bination of Imipenem and EDTA, followed by test for Bacteriocin production. Two Acinetobacter and one Pseudomonas aeruginosa strains were found to produce a Star like outward distortion. They did not produce Metallo β lactamase. Moreover, screening test fo r bacteriocin production was also found to be negative. The strains resistant to Carbapenem antibiotics but nonproducers of metallo β lactamase and/or Bacteriocins, have left behind a head twister for us

  9. Large-scale mitochondrial COI gene sequence variability reflects the complex colonization history of the invasive soft-shell clam, Mya arenaria (L.) (Bivalvia)

    Science.gov (United States)

    Lasota, Rafal; Pierscieniak, Karolina; Garcia, Pascale; Simon-Bouhet, Benoit; Wolowicz, Maciej

    2016-11-01

    The aim of the study was to determine genetic diversity in the soft-shell clam Mya arenaria on a wide geographical scale using mtDNA COI gene sequences. Low levels of genetic diversity was found, which can most likely be explained by a bottleneck effect during Pleistocene glaciations and/or selection. The geographical genetic structuring of the studied populations was also very low. The star-like phylogeny of the haplotypes indicates a relatively recent, rapid population expansion following the glaciation period and repeated expansion following the founder effect(s) after the initial introduction of the soft-shell clam to Europe. North American populations are characterized by the largest number of haplotypes, including rare ones, as expected for native populations. Because of the founder effect connected with initial and repeated expansion events, European populations have significantly lower numbers of haplotypes in comparison with those of North America. We also observed subtle differentiations among populations from the North and Baltic seas. The recently founded soft-shell clam population in the Black Sea exhibited the highest genetic similarity to Baltic populations, which confirmed the hypothesis that M. arenaria was introduced to the Gulf of Odessa from the Baltic Sea. The most enigmatic results were obtained for populations from the White Sea, which were characterized by high genetic affinity with American populations.

  10. Gamow shell model description of radiative capture reactions $^6$Li$(p,\\gamma)$$^7$Be and $^6$Li$(n,\\gamma)$$^7$Li

    CERN Document Server

    Dong, G X; Fossez, K; Płoszajczak, M; Jaganathen, Y; Betan, R M Id

    2016-01-01

    According to standard stellar evolution, lithium abundance is believed to be a useful indicator of the stellar age. However, many evolved stars like red giants show huge fluctuations around expected theoretical abundances that are not yet fully understood. The better knowledge of nuclear reactions that contribute to the creation and destruction of lithium can help to solve this puzzle. In this work we apply the Gamow shell model (GSM) formulated in the coupled-channel representation (GSM-CC) to investigate the mirror radiative capture reactions $^6$Li$(p,\\gamma)$$^7$Be and $^6$Li$(n,\\gamma)$$^7$Li. The cross-sections are calculated using a translationally invariant Hamiltonian with the finite-range interaction which is adjusted to reproduce spectra, binding energies and one-nucleon separation energies in $^{6-7}$Li, $^7$Be. All relevant $E1$, $M1$, and $E2$ transitions from the initial continuum states to the final bound states $J={3/2}_1^-$ and $J={1/2}^-$ of $^7$Li and $^7$Be are included. We demonstrate th...

  11. KELT-2Ab: A Hot Jupiter Transiting the Bright (V=8.77) Primary Star of a Binary System

    CERN Document Server

    Beatty, Thomas G; Siverd, Robert J; Eastman, Jason D; Bieryla, Allyson; Latham, David W; Buchhave, Lars A; Jensen, Eric L N; Manner, Mark; Stassun, Keivan G; Gaudi, B Scott; Berlind, Perry; Calkins, Michael L; Collins, Karen; DePoy, Darren L; Esquerdo, Gilbert A; Fulton, Benjamin J; Fűrész, Gábor; Geary, John C; Gould, Andrew; Hebb, Leslie; Kielkopf, John F; Marshall, Jennifer L; Pogge, Richard; Stanek, K Z; Stefanik, Robert P; Street, Rachel; Szentgyorgyi, Andrew H; Trueblood, Mark; Trueblood, Patricia; Stutz, Amelia M

    2012-01-01

    We report the discovery of KELT-2Ab, a hot Jupiter transiting the bright (V=8.77) primary star of the HD 42176 binary system. The host is a slightly evolved late F-star likely in the very short-lived "blue-hook" stage of evolution, with $\\teff=6151\\pm50{\\rm K}$, $\\log{g_*}=4.030_{-0.028}^{+0.013}$ and $\\feh=-0.018\\pm0.069$. The inferred stellar mass is $M_*=1.308_{-0.025}^{+0.028}$\\msun\\ and the star has a relatively large radius of $R_*=1.828_{-0.034}^{+0.070}$\\rsun. The planet is a typical hot Jupiter with period $4.113791\\pm0.00001$ days and a mass of $M_P=1.522\\pm0.078$\\mj\\ and radius of $R_P=1.286_{-0.047}^{+0.065}$\\rj. This is mildly inflated as compared to models of irradiated giant planets at the $\\sim$4 Gyr age of the system. KELT-2A is the third brightest star with a transiting planet identified by ground-based transit surveys, and the ninth brightest star overall with a transiting planet. KELT-2Ab's mass and radius are unique among the subset of planets with $V<9$ host stars, and therefore incre...

  12. Network-topology-adaptive quantum conference protocols

    Institute of Scientific and Technical Information of China (English)

    Zhang Sheng; Wang Jian; Tang Chao-Jing; Zhang Quan

    2011-01-01

    As an important application of the quantum network communication,quantum multiparty conference has made multiparty secret communication possible.Previous quantum multiparty conference schemes based on quantum data encryption are insensitive to network topology.However,the topology of the quantum network significantly affects the communication efficiency,e.g.,parallel transmission in a channel with limited bandwidth.We have proposed two distinctive protocols,which work in two basic network topologies with efficiency higher than the existing ones.We first present a protocol which works in the reticulate network using Greeberger-Horne-Zeilinger states and entanglement swapping.Another protocol,based on quantum multicasting with quantum data compression,which can improve the efficiency of the network,works in the star-like network.The security of our protocols is guaranteed by quantum key distribution and one-time-pad encryption.In general,the two protocols can be applied to any quantum network where the topology can be equivalently transformed to one of the two structures we propose in our protocols.

  13. YSOVAR: Mid-Infrared Variability in NGC 1333

    CERN Document Server

    Rebull, L M; Cody, A M; Guenther, H M; Hillenbrand, L A; Poppenhaeger, K; Wolk, S J; Hora, J; Hernandez, J; Bayo, A; Covey, K; Forbrich, J; Gutermuth, R; Morales-Calderon, M; Plavchan, P; Song, I; Bouy, H; Terebey, S; Cuillandre, J C; Allen, L

    2015-01-01

    As part of the Young Stellar Object VARiability (YSOVAR) program, we monitored NGC 1333 for ~35 days at 3.6 and 4.5 um using the Spitzer Space Telescope. We report here on the mid-infrared variability of the point sources in the ~10x~20arcmin area centered on 03:29:06, +31:19:30 (J2000). Out of 701 light curves in either channel, we find 78 variables over the YSOVAR campaign. About half of the members are variable. The variable fraction for the most embedded SEDs (Class I, flat) is higher than that for less embedded SEDs (Class II), which is in turn higher than the star-like SEDs (Class III). A few objects have amplitudes (10-90th percentile brightness) in [3.6] or [4.5]>0.2 mag; a more typical amplitude is 0.1-0.15 mag. The largest color change is >0.2 mag. There are 24 periodic objects, with 40% of them being flat SED class. This may mean that the periodic signal is primarily from the disk, not the photosphere, in those cases. We find 9 variables likely to be 'dippers', where texture in the disk occults the...

  14. Bare Quark Stars or Naked Neutron Stars: The Case of RX J1856.5-3754

    CERN Document Server

    Turolla, R; Drake, J J; Turolla, Roberto; Zane, Silvia; Drake, Jeremy J.

    2004-01-01

    In a cool neutron star (T 10^13 G), a phase transition may occur in the outermost layers. As a consequence the neutron star becomes `bare', i.e. no gaseous atmosphere sits on the top of the crust. The surface of cooling, bare neutron stars not necessary gives off blackbody radiation because of the strong suppression in the emissivity at energies below the electron plasma frequency \\omega_p. Since \\omega_p~1 keV under the conditions typical of the dense electron gas in the condensate, the emission from a T~100 eV bare neutron star will be substantially depressed with respect to that of a perfect Planckian radiator at most energies. Here we present a detailed analysis of the emission properties of a bare neutron star. In particular, we derive the surface emissivity for a Fe composition in a range of magnetic fields and temperatures representative of cooling isolated neutron stars, like RX J1856.5-3754. We find that the emitted spectrum is strongly dependent on the electron conductivity in the solid surface lay...

  15. Massive star formation by accretion I. Disc accretion

    CERN Document Server

    Haemmerlé, Lionel; Meynet, Georges; Maeder, André; Charbonnel, Corinne

    2016-01-01

    Massive stars likely form by accretion and the evolutionary track of an accreting forming star corresponds to what is called the birthline in the HR diagram. The shape of this birthline is quite sensitive to the evolution of the entropy in the accreting star. We first study the reasons why some birthlines published in past years present different behaviours for a given accretion rate. We then revisit the question of the accretion rate, which allows us to understand the distribution of the observed pre-main-sequence (pre-MS) stars in the Hertzsprung-Russell (HR) diagram. Finally, we identify the conditions needed to obtain a large inflation of the star along its pre-MS evolution that may push the birthline towards the Hayashi line in the upper part of the HR diagram. We present new pre-MS models including accretion at various rates and for different initial structures of the accreting core. From the observed upper envelope of pre-MS stars in the HR diagram, we deduce the accretion law that best matches the acc...

  16. Morphological evolution of primary TiC carbide in laser clad TiC reinforced FeAl intermetallic composite coating

    Institute of Scientific and Technical Information of China (English)

    陈瑶; 王华明

    2003-01-01

    The novel rapidly solidified TiC/FeAl composite coatings were fabricated by laser cladding on the substrate of 1Cr18Ni9Ti stainless steel, particular emphasis has been placed on the growth morphologies of TiC carbide and its growth mechanism under a constant solidification conditions. Results show that the growth morphology of TiC carbide strongly depends upon the nucleation process and mass transportation process of TiC forming elements in laser melt pool. With increasing amount of titanium and carbon in melt pool, the growth morphology of TiC carbide changes from block-like to star-like and well-developed dendrite. As the amount of titanium and carbon increases further, TiC carbide particles are found to be irregular polyhedral block. Although the growth morphologies of TiC are various,their advancing fronts are all faceted, illustrating that TiC carbide grows by the mechanism of lateral ledge growth.

  17. Deeply Embedded Protostellar Population in the Central Molecular Zone Suggested by H$_2$O Masers and Dense Cores

    CERN Document Server

    Lu, Xing; Kauffmann, Jens; Pillai, Thushara; Longmore, Steven N; Kruijssen, J M Diederik; Battersby, Cara

    2016-01-01

    The Central Molecular Zone (CMZ), usually referring to the inner 500 pc of the Galaxy, contains a dozen of massive ($\\sim10^5$ $M_\\odot$) molecular clouds. Are these clouds going to actively form stars like Sgr B2? How are they affected by the extreme physical conditions in the CMZ, such as strong turbulence? Here we present a first step towards answering these questions. Using high-sensitivity, high angular resolution radio and (sub)millimeter observations, we studied deeply embedded star formation in six massive clouds in the CMZ, including the 20 and 50 km s$^{-1}$ clouds, Sgr B1 off (as known as dust ridge clouds e/f), Sgr C, Sgr D, and G0.253-0.016. The VLA water maser observations suggest a population of deeply embedded protostellar candidates, many of which are new detections. The SMA 1.3 mm continuum observations reveal peaks in dust emission associated with the masers, suggesting the existence of dense cores. While our findings confirm that clouds such as G0.253-0.016 lack internal compact substructu...

  18. V838 Mon and M31-RV: The Stellar Populations Angle

    CERN Document Server

    Siegel, M H; Siegel, Michael H.; Bond, Howard E.

    2006-01-01

    Insight into the origin of unusual events like the eruption of V838 Mon can be obtained from studies of the stellar populations from which they arise. V838 Mon lies in an intriguing region of the Galaxy, toward the warped outer edge of the disk, with significant contributions from the Galactic thick disk and the recently discovered Monoceros tidal stream. The initial distance measures placed V838 Mon in a jumbled region of the Galaxy but the recent shorter distances make it highly likely that V838 Mon was a thin disk star -- likely in a spiral arm -- consistent with the recent detection of a young cluster in the vicinity. We compare V838 Mon to M31-RV, a red variable that erupted in the bulge of M31 in 1988 and had a peak luminosity and spectral evolution very similar to V838 Mon. Archival HST images show no nebulosity or unusual stars at M31-RV's projected location. Moreover, the only stellar population in the field is a canonic old bulge population. This indicates that whatever the origin of the red novae, ...

  19. The sedimentary structure of linear sand dunes

    Science.gov (United States)

    Bristow; Bailey; Lancaster

    2000-07-06

    Linear sand dunes--dunes that extend parallel to each other rather than in star-like or crescentic forms--are the most abundant type of desert sand dune. But because their development and their internal structure are poorly understood, they are rarely recognized in the rock record. Models of linear dune development have not been able to take into account the sub-surface structure of existing dunes, but have relied instead either on the extrapolation of short-term measurements of winds and sediment transport or on observations of near-surface internal sedimentary structures. From such studies, it has not been clear if linear dunes can migrate laterally. Here we present images produced by ground penetrating radar showing the three-dimensional sedimentary structure of a linear dune in the Namib sand sea, where some of the world's largest linear dunes are situated. These profiles show clear evidence for lateral migration in a linear dune. Moreover, the migration of a sinuous crest-line along the dune produces divergent sets of cross-stratification, which can become stacked as the dune height increases, and large linear dunes can support superimposed dunes that produce stacked sets of trough cross-stratification. These clear structural signatures of linear dunes should facilitate their recognition in geological records.

  20. Giant aeolian dune size determined by the average depth of the atmospheric boundary layer

    Science.gov (United States)

    Claudin, P.; Fourrière, A.; Andreotti, B.; Murray, A. B.

    2009-12-01

    Depending on the wind regime, sand dunes exhibit linear, crescent-shaped or star-like forms resulting from the interaction between dune morphology and sand transport. Small-scale dunes form by destabilization of the sand bed with a wavelength (a few tens of metres) determined by the sand transport saturation length. The mechanisms controlling the formation of giant dunes, and in particular accounting for their typical time and length scales, have remained unknown. Using a combination of field measurements and aerodynamic calculations, we show here that the growth of aeolian giant dunes, ascribed to the nonlinear interaction between small-scale superimposed dunes, is limited by the confinement of the flow within the atmospheric boundary layer. Aeolian giant dunes and river dunes form by similar processes, with the thermal inversion layer that caps the convective boundary layer in the atmosphere acting analogously to the water surface in rivers. In both cases, the bed topography excites surface waves on the interface that in turn modify the near-bed flow velocity. This mechanism is a stabilizing process that prevents the scale of the pattern from coarsening beyond the resonant condition. Our results can explain the mean spacing of aeolian giant dunes ranging from 300 m in coastal terrestrial deserts to 3.5 km. We propose that our findings could serve as a starting point for the modelling of long-term evolution of desert landscapes under specific wind regimes.

  1. The Stellar Imager (SI) Vision Mission

    CERN Document Server

    Carpenter, K G; Karovska, M; SI Vision Mission Team; Carpenter, Kenneth G.; Schrijver, Carolus J.; Karovska, Margarita; Team, SI Vision Mission

    2006-01-01

    The Stellar Imager (SI) is a UV-Optical, Space-Based Interferometer designed to enable 0.1 milli-arcsecond (mas) spectral imaging of stellar surfaces and of the Universe in general and asteroseismic imaging of stellar interiors. SI is identified as a "Flagship and Landmark Discovery Mission" in the 2005 Sun Solar System Connection (SSSC) Roadmap and as a candidate for a "Pathways to Life Observatory" in the Exploration of the Universe Division (EUD) Roadmap (May, 2005). SI will revolutionize our view of many dynamic astrophysical processes: its resolution will transform point sources into extended sources, and snapshots into evolving views. SI's science focuses on the role of magnetism in the Universe, particularly on magnetic activity on the surfaces of stars like the Sun. SI's prime goal is to enable long-term forecasting of solar activity and the space weather that it drives. SI will also revolutionize our understanding of the formation of planetary systems, of the habitability and climatology of distant p...

  2. Rayleigh Scattering in the Atmosphere of the Warm Exo-Neptune GJ 3470b

    CERN Document Server

    Dragomir, Diana; Pearson, Kyle A; Crossfield, Ian J M; Eastman, Jason; Barman, Travis; Biddle, Lauren I

    2015-01-01

    GJ 3470b is a warm Neptune-size planet transiting a M dwarf star. Like the handful of other small exoplanets for which transmission spectroscopy has been obtained, GJ 3470b exhibits a flat spectrum in the near- and mid-infrared. Recently, a tentative detection of Rayleigh scattering in its atmosphere has been reported. This signal manifests itself as an observed increase of the planetary radius as a function of decreasing wavelength in the visible. We set out to verify this detection and observed several transits of this planet with the LCOGT network and the Kuiper telescope in four different bands (Sloan g', Sloan i', Harris B and Harris V). Our analysis reveals a strong Rayleigh scattering slope, thus confirming previous results. This makes GJ 3470b the smallest known exoplanet with a detection of Rayleigh scattering. We find that the most plausible scenario is a hydrogen/helium-dominated atmosphere covered by clouds which obscure absorption features in the infrared and hazes which give rise to scattering i...

  3. Fourteen Thousand Solar Systems and Growing: Results From the Starchitect Online Game at One Year

    Science.gov (United States)

    Harold, J. B.

    2015-12-01

    Starchitect (www.starchitect.net) is an online, end-to-end stellar and planetary evolution game designed to teach players about a variety of astronomy and planetary topics. Supported by NASA and NSF, and developed at the National Center for Interactive Learning at the Space Science Institute, the game uses the "sporadic play" model of games such as Farmville, where players might only take actions a few times a day, but continue playing for months. This framework is a natural fit for teaching about the evolution of stars and planets. Starchitect's systems evolve at a million years a minute, so that while massive stars will supernova almost immediately, lower mass stars like our sun will live for weeks of game time, possibly evolving life before passing through a red giant stage and ending their lives as white dwarfs. The game has now been live for over a year, playable both on Facebook and externally, and over 14,000 solar systems have been created by over 11,000 players. Since the game itself is heavily instrumented we now have access to a wealth of data that can be used to examine how people are playing the game and what tasks they are successfully engaging with. Through an embedded quiz game we are even in the position to assess the prior knowledge of our audience and execute pre/post assessments tied to game play. This paper will briefly describe the game and its educational strategies, then summarize some of our current results.

  4. Habitability of super-Earth planets around other suns: models including Red Giant Branch evolution.

    Science.gov (United States)

    von Bloh, W; Cuntz, M; Schröder, K-P; Bounama, C; Franck, S

    2009-01-01

    The unexpected diversity of exoplanets includes a growing number of super-Earth planets, i.e., exoplanets with masses of up to several Earth masses and a similar chemical and mineralogical composition as Earth. We present a thermal evolution model for a 10 Earth-mass planet orbiting a star like the Sun. Our model is based on the integrated system approach, which describes the photosynthetic biomass production and takes into account a variety of climatological, biogeochemical, and geodynamical processes. This allows us to identify a so-called photosynthesis-sustaining habitable zone (pHZ), as determined by the limits of biological productivity on the planetary surface. Our model considers solar evolution during the main-sequence stage and along the Red Giant Branch as described by the most recent solar model. We obtain a large set of solutions consistent with the principal possibility of life. The highest likelihood of habitability is found for "water worlds." Only mass-rich water worlds are able to realize pHZ-type habitability beyond the stellar main sequence on the Red Giant Branch.

  5. MASH-II: More Planetary Nebulae from the AAO/UKST H\\alpha Survey

    CERN Document Server

    Miszalski, B; Acker, A; Birkby, J L; Frew, D J; Kovacevic, A

    2007-01-01

    We present a supplement to the Macquarie/AAO/Strasbourg H$\\alpha$ planetary nebulae (PNe) catalogue (MASH), which we denote MASH-II. The supplement consists of over 300 true, likely and possible new Galactic PNe found after re-examination of the entire AAO/UKST H$\\alpha$ survey of the southern Galactic Plane in digital form. We have spectroscopically confirmed over 240 of these new candidates as bona-fide PNe and we include other high quality candidates awaiting spectroscopic confirmation as possible PNe. These latest discoveries largely comprise two distinct groups: small, star-like or moderately resolved PNe at one end and mostly large, extremely low surface brightness PNe at the other. Neither group were easy to discover from simple visual scrutiny of the original survey exposures as for MASH but were relatively straightforward to uncover from the digital images via application of semi-automated discovery techniques. We suspect the few PNe still hidden in the H$\\alpha$ survey will lie outside our search cr...

  6. High orientation of long chain branched poly (lactic acid) with enhanced blood compatibility and bionic structure.

    Science.gov (United States)

    Li, Zhengqiu; Ye, Lin; Zhao, Xiaowen; Coates, Phil; Caton-Rose, Fin; Martyn, Michasel

    2016-05-01

    Highly oriented poly (lactic acid) (PLA) with bionic microgrooves was fabricated through solid hot drawing technology for further improving the mechanical properties and blood biocompatibility of PLA. In order to enhance the melt strength and thus obtain high orientation degree, long chain branched PLA was prepared at first through a two-step ring-opening reaction during processing. Linear viscoelasticity combined with branch-on-branch model was used to predict probable compositions and chain topologies of the products, and it was found that the molecular weight of PLA increased and topological structures with star like chain with three arms and tree-like chain with two generations formed during reactive processing, and consequently draw ratio as high as1200% can be achieved during the subsequent hot stretching. With the increase of draw ratio, the tensile strength and orientation degree of PLA increased dramatically. Long chain branching and orientation could significantly enhance the blood compatibility of PLA by prolonging clotting time and decreasing platelet activation. Microgrooves can be observed on the surface of the oriented PLA which were similar to the intimal layer of blood vessel, and such bionic structure resulted from the formation of the oriented shish kebab-like crystals along the draw direction.

  7. ALMA and Herschel Observations of the Prototype Dusty and Polluted White Dwarf G29-38

    CERN Document Server

    Farihi, J; Greaves, J S; Bonsor, A; Sibthorpe, B; Panić, O

    2014-01-01

    ALMA Cycle 0 and Herschel PACS observations are reported for the prototype, nearest, and brightest example of a dusty and polluted white dwarf, G29-38. These long wavelength programs attempted to detect an outlying, parent population of bodies at 1-100 AU, from which originates the disrupted planetesimal debris that is observed within 0.01 AU and which exhibits L_IR/L = 0.039. No associated emission sources were detected in any of the data down to L_IR/L ~ 1e-4, generally ruling out cold dust masses greater than 1e24 - 1e25 g for reasonable grain sizes and properties in orbital regions corresponding to evolved versions of both asteroid and Kuiper belt analogs. Overall, these null detections are consistent with models of long-term collisional evolution in planetesimal disks, and the source regions for the disrupted parent bodies at stars like G29-38 may only be salient in exceptional circumstances, such as a recent instability. A larger sample of polluted white dwarfs, targeted with the full ALMA array, has th...

  8. Formation of carbon-enhanced metal-poor stars in the presence of far ultraviolet radiation

    CERN Document Server

    Bovino, S; Schleicher, D R G; Latif, M A

    2014-01-01

    Recent discoveries of carbon-enhanced metal-poor stars like SMSS J031300.36-670839.3 provide increasing observational insights into the formation conditions of the first second-generation stars in the Universe, reflecting the chemical conditions after the first supernova explosion. Here, we present the first cosmological simulations with a detailed chemical network including primordial species as well as C, C$^+$, O, O$^+$, Si, Si$^+$, and Si$^{2+}$ following the formation of carbon-enhanced metal poor stars. The presence of background UV flux delays the collapse from $z=21$ to $z=15$ and cool the gas down to the CMB temperature for a metallicity of Z/Z$_\\odot$=10$^{-3}$. This can potentially lead to the formation of lower mass stars. Overall, we find that the metals have a stronger effect on the collapse than the radiation, yielding a comparable thermal structure for large variations in the radiative background. We further find that radiative backgrounds are not able to delay the collapse for Z/Z$_\\odot$=10$...

  9. APPLICATIONS OF "CLICK" CHEMISTRY IN SYNTHESIS OF TOPOLOGICAL POLYMERS%点击化学在拓扑结构聚合物合成中的应用

    Institute of Scientific and Technical Information of China (English)

    胡健; 何金林; 张明祖; 倪沛红

    2013-01-01

    首先对点击化学进行简述,介绍了点击化学的概况、特征及主要反应类型;随后,重点介绍点击化学在拓扑结构聚合物(包括线形、刷形、星形、环状及树枝状大分子等)合成中的应用,并对这一领域的研究进展进行综述;最后,提出目前点击化学存在的一些问题,并对其发展前景进行展望.%"Click" chemistry,proposed by Sharpless in 2001, has become a powerful and versatile synthetic tool because of some unique advantages, such as mild and simple reaction conditions, high efficiency and selectivity, and exceptional tolerance towards a wide range of functional groups and reaction conditions. In this review,the development of "click" chemistry ( e. g. , its history, characteristics and classifications) is firstly introduced. Subsequently,this paper focuses on the applications of "click" chemistry in the synthesis of a variety of topological polymers, including linear, brush-shaped, star-like, cyclic polymers, and dendrimers. Finally,the limitations and prospects of "click" chemistry are also discussed.

  10. The Minimum Mass for Opacity-Limited Fragmentation in Turbulent Cloud Cores

    CERN Document Server

    Whitworth, A P

    2004-01-01

    We present a new analysis of the minimum mass for star formation, based on opacity-limited fragmentation. Our analysis differs from the standard one, which considers hierarchical fragmentation of a 3-D medium, and yields $M_{_{\\rm MIN}} \\sim 0.007 {\\rm to} 0.010 M_\\odot$ for Population I star formation. Instead we analyse the more realistic situation in which there is one-shot fragmentation of a shock-compressed layer, of the sort which arises in turbulent star-forming clouds. In this situation, $M_{_{\\rm MIN}}$ can be smaller than $0.003 M_\\odot$. Our analysis is more stringent than the standard one in that (a) it requires fragments to have condensation timescales shorter than all competing mass scales, and (b) it takes into acount that a fragment grows by accretion whilst it is condensing out, and has to radiate away the energy dissipated in the associated accretion shock. It also accords with the recent detection, in young star clusters, of free-floating star-like objects having masses as low as $0.003 {\\r...

  11. Quaternary structure of the yeast Arc1p-aminoacyl-tRNA synthetase complex in solution and its compaction upon binding of tRNAs

    Science.gov (United States)

    Koehler, Christine; Round, Adam; Simader, Hannes; Suck, Dietrich; Svergun, Dmitri

    2013-01-01

    In the yeast Saccharomyces cerevisiae, the aminoacyl-tRNA synthetases (aaRS) GluRS and MetRS form a complex with the auxiliary protein cofactor Arc1p. The latter binds the N-terminal domains of both synthetases increasing their affinity for the transfer-RNA (tRNA) substrates tRNAMet and tRNAGlu. Until now, structural information was available only on the enzymatic domains of the individual aaRSs but not on their complexes with associated cofactors. We have analysed the yeast Arc1p-complexes in solution by small-angle X-ray scattering (SAXS). The ternary complex of MetRS and GluRS with Arc1p, displays a peculiar extended star-like shape, implying possible flexibility of the complex. We reconstituted in vitro a pentameric complex and demonstrated by electrophoretic mobility shift assay that the complex is active and contains tRNAMet and tRNAGlu, in addition to the three protein partners. SAXS reveals that binding of the tRNAs leads to a dramatic compaction of the pentameric complex compared to the ternary one. A hybrid low-resolution model of the pentameric complex is constructed rationalizing the compaction effect by the interactions of negatively charged tRNA backbones with the positively charged tRNA-binding domains of the synthetases. PMID:23161686

  12. Effect of Al–5Ti–C Master Alloy on the Microstructure and Mechanical Properties of Hypereutectic Al–20%Si Alloy

    Directory of Open Access Journals (Sweden)

    Wanwu Ding

    2014-02-01

    Full Text Available Al–5Ti–C master alloy was prepared and used to modify hypereutectic Al–20%Si alloy. The microstructure evolution and mechanical properties of hypereutectic Al–20%Si alloy with Al–5Ti–C master alloy additions (0, 0.4, 0.6, 1.0, 1.6 and 2.0 wt% were investigated. The results show that, Al–5Ti–C master alloy (0.6 wt%, 10 min can significantly refine both eutectic and primary Si of hypereutectic Al–20%Si alloy. The morphology of the primary Si crystals was significantly refined from a coarse polygonal and star-like shape to a fine polyhedral shape and the grain size of the primary Si was refined from roughly 90–120 μm to 20–50 μm. The eutectic Si phases were modified from a coarse platelet-like/needle-like structure to a fine fibrous structure with discrete particles. The Al–5Ti–C master alloy (0.6 wt%, 30 min still has a good refinement effect. The ultimate tensile strength (UTS, elongation (El and Brinell hardness (HB of Al–20%Si alloy modified by the Al–5Ti–C master alloy (0.6 wt%, 10 min increased by roughly 65%, 70% and 51%, respectively, due to decreasing the size and changing the morphology on the primary and eutectic Si crystals. The change in mechanical properties corresponds to evolution of the microstructure.

  13. Stellar Populations of BCGs, Close Companions and Intracluster Light in Abell 85, Abell 2457 and IIZw108

    CERN Document Server

    Edwards, Louise O V; Trierweiler, Isabella L; Abraham, Tara; Beizer, Victoria G

    2016-01-01

    We present the first results from an integral field (IFU) spectroscopic survey of a 75kpc region around three Brightest Cluster Galaxies (BCGs), combining over 100 IFU fibres to study the intracluster light (ICL). We fit population synthesis models to estimate age and metallicity. For Abell 85 and Abell 2457, the ICL is best-fit with a fraction of old, metal-rich stars like in the BCG, but requires 30-50% young and metal-poor stars, a component not found in the BCGs. This is consistent with the ICL having been formed by a combination of interactions with less massive, younger, more metal-poor cluster members in addition to stars that form the BCG. We find that the three galaxies are in different stages of evolution and may be the result of different formation mechanisms. The BCG in Abell 85 is near a relatively young, metal-poor galaxy, but the dynamical friction timescale is long and the two are unlikely to be undergoing a merger. The outer regions of Abell 2457 show a higher relative fraction of metal-poor ...

  14. Future prospects for the detection and characterization of extrasolar planets

    Directory of Open Access Journals (Sweden)

    Lunine J.I.

    2010-12-01

    Full Text Available Several distinctly different techniques have detected almost 500 planets orbiting around main-sequence stars, 45 multiple planet systems, and a number of extrasolar planets have been the subject of direct study. Hundreds of other “candidate” planets detected by the Kepler spacecraft await confirmation of their existence. Planets are thus common phenomena around stars, and the prospects seem good in the next few years for establishing statistics on the occurrence of Earth-sized planets. Extension of the most successful technique of Doppler spectroscopy in sensitivity to detect Earth-mass planets around Sun-like stars will be limited by the noise generated by the stellar photospheres themselves. The James Webb Space Telescope will have the capability to measure atmospheric abundances of certain gases and of liquid water on extrasolar planets, including “superEarths” within a factor of two of the radius of the Earth. The ultimate goal of measuring the atmospheric composition of an Earth-sized planet orbiting at 1 AU around a star like the Sun remains a daunting challenge that is perhaps twenty years in the future.

  15. The population structure of Acinetobacter baumannii: expanding multiresistant clones from an ancestral susceptible genetic pool.

    Directory of Open Access Journals (Sweden)

    Laure Diancourt

    Full Text Available Outbreaks of hospital infections caused by multidrug resistant Acinetobacter baumannii strains are of increasing concern worldwide. Although it has been reported that particular outbreak strains are geographically widespread, little is known about the diversity and phylogenetic relatedness of A. baumannii clonal groups. Sequencing of internal portions of seven housekeeping genes (total 2,976 nt was performed in 154 A. baumannii strains covering the breadth of known diversity and including representatives of previously recognized international clones, and in 19 representatives of other Acinetobacter species. Restricted amounts of diversity and a star-like phylogeny reveal that A. baumannii is a genetically compact species that suffered a severe bottleneck in the recent past, possibly linked to a restricted ecological niche. A. baumannii is neatly demarcated from its closest relative (genomic species 13TU and other Acinetobacter species. Multilocus sequence typing analysis demonstrated that the previously recognized international clones I to III correspond to three clonal complexes, each made of a central, predominant genotype and few single locus variants, a hallmark of recent clonal expansion. Whereas antimicrobial resistance was almost universal among isolates of these and a novel international clone (ST15, isolates of the other genotypes were mostly susceptible. This dichotomy indicates that antimicrobial resistance is a major selective advantage that drives the ongoing rapid clonal expansion of these highly problematic agents of nosocomial infections.

  16. On the structural and electronic properties of hexanuclear vanadium oxide clusters V6On-/0 (n = 12-15): Is V6O12 cluster planar or cage-like?

    Science.gov (United States)

    Wang, Ling-Fei; Xie, Lu; Fang, Hong-Ling; Li, Yun-Fei; Zhang, Xiao-Bin; Wang, Bin; Zhang, Yong-Fan; Huang, Xin

    2014-10-01

    Density functional theory (DFT) calculations are carried out to investigate the structural and electronic properties of a series of hexanuclear vanadium oxide clusters V6On-/0 (n = 12-15). Generalized Koopmans' theorem is applied to predict the vertical detachment energies (VDEs) and simulate the photoelectron spectra (PES) for V6On- (n = 12-15) clusters. Extensive DFT calculations are performed in search of the lowest-energy structures for both the anions and neutrals. All of these clusters appear to prefer the polyhedral cage structures, in contrast to the planar star-like structures observed in prior model surface studies for the V6O12 cluster. Molecular orbitals are performed to analyze the chemical bonding in the hexanuclear vanadium oxide clusters and provide insights into the sequential oxidation of V6On- (n = 12-15) clusters. The V6On- (n = 12-15) clusters possess well-defined V5+ and V3+ sites, and may serve as molecular models for surface defects. Electron spin density analyses show that the unpaired electrons in V6On- (n = 12-14) clusters are primarily localized on the V3+ sites rather than on the V5+ sites. The difference gas phase versus model surface structures of V6O12 hints the critical roles of cluster-substrate interactions in stabilizing the planar V6O12 cluster on model surfaces.

  17. On the structural and electronic properties of hexanuclear vanadium oxide clusters V6On(-/0) (n=12-15): is V6O12 cluster planar or cage-like?

    Science.gov (United States)

    Wang, Ling-Fei; Xie, Lu; Fang, Hong-Ling; Li, Yun-Fei; Zhang, Xiao-Bin; Wang, Bin; Zhang, Yong-Fan; Huang, Xin

    2014-10-15

    Density functional theory (DFT) calculations are carried out to investigate the structural and electronic properties of a series of hexanuclear vanadium oxide clusters V6On(-/0) (n=12-15). Generalized Koopmans' theorem is applied to predict the vertical detachment energies (VDEs) and simulate the photoelectron spectra (PES) for V6On(-) (n=12-15) clusters. Extensive DFT calculations are performed in search of the lowest-energy structures for both the anions and neutrals. All of these clusters appear to prefer the polyhedral cage structures, in contrast to the planar star-like structures observed in prior model surface studies for the V6O12 cluster. Molecular orbitals are performed to analyze the chemical bonding in the hexanuclear vanadium oxide clusters and provide insights into the sequential oxidation of V6On(-) (n=12-15) clusters. The V6On(-) (n=12-15) clusters possess well-defined V(5+) and V(3+) sites, and may serve as molecular models for surface defects. Electron spin density analyses show that the unpaired electrons in V6On(-) (n=12-14) clusters are primarily localized on the V(3+) sites rather than on the V(5+) sites. The difference gas phase versus model surface structures of V6O12 hints the critical roles of cluster-substrate interactions in stabilizing the planar V6O12 cluster on model surfaces. Copyright © 2014 Elsevier B.V. All rights reserved.

  18. Simulation of facet dendrite growth with strong interfacial energy anisotropy by phase field method

    Institute of Scientific and Technical Information of China (English)

    袁训锋; 刘宝盈; 李春; 周春生; 丁雨田

    2015-01-01

    Numerical simulations based on a new regularized phase-field model were presented, to simulate the solidification of hexagonal close-packed materials with strong interfacial energy anisotropies. Results show that the crystal grows into facet dendrites, displaying six-fold symmetry. The size of initial crystals has an effect on the branching-off of the principal branch tip along the direction, which is eliminated by setting the b/a (a and b are the semi-major and semi-minor sizes in the initial elliptical crystals, respectively) value to be less than or equal to 1. With an increase in the undercooling value, the equilibrium morphology of the crystal changes from a star-like shape to facet dendrites without side branches. The steady-state tip velocity increases exponentially when the dimensionless undercooling is below the critical value. With a further increase in the undercooling value, the equilibrium morphology of the crystal grows into a developed side-branch structure, and the steady-state tip velocity of the facet dendrites increases linearly. The facet dendrite growth has controlled diffusion and kinetics.

  19. Triggered star formation in a molecular shell created by a SNR?

    CERN Document Server

    Cichowolski, Silvina; Gamen, Roberto; Arnal, E Marcelo; Suad, Laura A; Ortega, Martin E

    2013-01-01

    We present a study of a new molecular shell, G126.1-0.8-14, using available multiwavelegth Galactic plane surveys and optical Gemini observations. A well defined shell-like structure is observed in the CO(1--0) line emission at (l,b) = (126.1, -0.8), in the velocity range --10.5 to --15.5 km/s. The HI, emission shows a region of low emissivity inside G126.1-0.8-14, while radio continuum observations reveal faint non-thermal emission possibly related to this shell. Optical spectra obtained with Gemini South show the existence of B-type stars likely to be associated with G126.1-0.8-14. An estimate of the stellar wind energy injected by these stars show that they alone can not be able to create such a structure. On the other hand, one supernova explosion would provide enough energy to generate the shell. Using the MSX, IRAS, and WISE Point Source Catalogues we have found about 30 young stellar objects candidates, whose birth could have been triggered by the expansion of G126.1-0.8-14. In this context, Sh2-187 co...

  20. Synthesis, characterization and photoluminescence of tin oxide nanoribbons and nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Duraia, El-Shazly M.A., E-mail: duraia_physics@yahoo.co [Suez Canal University, Faculty of Science, Physics Department, Ismailia (Egypt); Al-Farabi Kazakh National University, Almaty (Kazakhstan); Institute of Physics and Technology, 11 Ibragimov Street, 050032 Almaty (Kazakhstan); Mansorov, Z.A. [Al-Farabi Kazakh National University, Almaty (Kazakhstan); Tokmolden, S. [Institute of Physics and Technology, 11 Ibragimov Street, 050032 Almaty (Kazakhstan)

    2009-11-15

    In this work we report the successful formation of tin oxide nanowires and tin oxide nanoribbons with high yield and by using simple cheap method. We also report the formation of curved nanoribbon, wedge-like tin oxide nanowires and star-like nanowires. The growth mechanism of these structures has been studied. Scanning electron microscope was used in the analysis and the EDX analysis showed that our samples is purely Sn and O with ratio 1:2. X-ray analysis was also used in the characterization of the tin oxide nanowire and showed the high crystallinity of our nanowires. The mechanism of the growth of our1D nanostructures is closely related to the vapor-liquid-solid (VLS) process. The photoluminescence PL measurements for the tin oxide nanowires indicated that there are three stable emission peaks centered at wavelengths 630, 565 and 395 nm. The nature of the transition may be attributed to nanocrystals inside the nanobelts or to Sn or O vacancies occurring during the growth which can induce trapped states in the band gap.

  1. Polypeptoids: A perfect match for molecular definition and macromolecular engineering?

    KAUST Repository

    Luxenhofer, Robert

    2013-04-19

    Precision synthesis of polymers has been a hot topic in recent years. While this is notoriously difficult to address for polymers with a CC backbone, Merrifield has discovered a way many decades ago for polypeptides. Using a similar approach, N-substituted polypeptides, so-called polypeptoids have been synthesized and studied for about 20 years. In contrast, the living ring-opening polymerization (ROP) of N-substituted N-carboxyanhydrides was among the first living polymerizations to be discovered. More recently, a surge in new synthetic approaches led to the efficient synthesis of cyclic or linear multiblock copolypeptoids. Thus, polypeptoids can be synthesized either by solid phase synthesis to yield complex and exactly defined oligo- and small polymers or by ROP of appropriately N-substituted N-carboxyanhydrides (NNCA) to give linear, cyclic, or star-like polymers. Together with an excellent biocompatibility, this polymer family may have a bright future ahead as biomaterials. © 2013 Wiley Periodicals, Inc.

  2. A Blue Point Source at the Location of Supernova 2011dh

    CERN Document Server

    Folatelli, Gastón; Benvenuto, Omar G; Van Dyk, Schuyler D; Kuncarayakti, Hanindyo; Maeda, Keiichi; Nozawa, Takaya; Nomoto, Ken'ichi; Hamuy, Mario; Quimby, Robert M

    2014-01-01

    We present Hubble Space Telescope (HST) observations of the field of the Type IIb supernova (SN) 2011dh in M51 performed at ~1161 rest-frame days after explosion using the Wide Field Camera 3 and near-UV filters F225W and F336W. A star-like object is detected in both bands and the photometry indicates it has negative (F225W - F336W) color. The observed object is compatible with the companion of the now-vanished yellow supergiant progenitor predicted in interacting binary models. We consider it unlikely that the SN is undergoing strong interaction and thus estimate that it makes a small contribution to the observed flux. The possibilties of having detected an unresolved light echo or an unrelated object are briefly discussed and judged unlikely. Adopting a possible range of extinction by dust, we constrain parameters of the proposed binary system. In particular, the efficiency of mass accretion onto the binary companion must be below 50%, if no significant extinction is produced by newly formed dust. Further m...

  3. A blue point source at the location of supernova 2011dh

    Science.gov (United States)

    Bersten, Melina; Folatelli, Gaston; Benvenuto, Omar G.; Nomoto, Ken'ichi; Van Dyk, Schuyler D.; Kuncarayakti, Hanindyo; Maeda, Keiichi; Nozawa, Takaya; Quimby, Robert

    2014-09-01

    We conducted Hubble Space Telescope observations of the field of the Type IIb supernova (SN) 2011dh in M51 about 1161 rest-frame days after explosion using the Wide Field Camera 3 and near-UV filters F225W and F336W. A star-like object is detected in both bands and the photometry indicates it has negative (F225W - F336W) color. The photometric properties of the object are compatible with those predicted for the companion of the yellow supergiant progenitor in the interacting binary models previously presented by us (Bersten et al. 2012, ApJ, 757, 31; Benvenuto et al. 2013, ApJ, 762, 74). We also study the possibility that the observed flux is due to the SN ejecta itself in case of strong circumstellar-medium interaction, or to an unresolved light echo. Using different estimates of the dust extinction, including newly formed dust in the SN ejecta, we are able to provide parameters of the proposed binary system. Further multiband observations are required in order to confirm the identification of the object as the companion star, and to fully characterize the binary system. If confirmed, this is the first direct detection of a binary companion of a core-collapse SN progenitor.

  4. Elucidating dominant pathways of the nano-particle self-assembly process.

    Science.gov (United States)

    Zeng, Xiangze; Li, Bin; Qiao, Qin; Zhu, Lizhe; Lu, Zhong-Yuan; Huang, Xuhui

    2016-09-14

    Self-assembly processes play a key role in the fabrication of functional nano-structures with widespread application in drug delivery and micro-reactors. In addition to the thermodynamics, the kinetics of the self-assembled nano-structures also play an important role in determining the formed structures. However, as the self-assembly process is often highly heterogeneous, systematic elucidation of the dominant kinetic pathways of self-assembly is challenging. Here, based on mass flow, we developed a new method for the construction of kinetic network models and applied it to identify the dominant kinetic pathways for the self-assembly of star-like block copolymers. We found that the dominant pathways are controlled by two competing kinetic parameters: the encounter time Te, characterizing the frequency of collision and the transition time Tt for the aggregate morphology change from rod to sphere. Interestingly, two distinct self-assembly mechanisms, diffusion of an individual copolymer into the aggregate core and membrane closure, both appear at different stages (with different values of Tt) of a single self-assembly process. In particular, the diffusion mechanism dominates the middle-sized semi-vesicle formation stage (with large Tt), while the membrane closure mechanism dominates the large-sized vesicle formation stage (with small Tt). Through the rational design of the hydrophibicity of the copolymer, we successfully tuned the transition time Tt and altered the dominant self-assembly pathways.

  5. A Laboratory Demonstration of the Capability to Image an Earth-like Extrasolar Planet

    Science.gov (United States)

    Trauger, John T.; Wesley, A. Traub

    2007-01-01

    The detection and characterization of an Earth-like planet orbiting a nearby star requires a telescope with an extraordinarily large contrast at small angular separations. At visible wavelengths, an Earth-like planet would be 1 times 10-10 times fainter than the star at angular separations of typically 0.1 arcsecond or less. There are several proposed space telescope systems that could, in principle, achieve this. Here we report a laboratory experiment that reaches these limits. We have suppressed the diffracted and scattered light near a star-like source to a level of 6 times 10-10 times the peak intensity in individual coronagraph images. In a series of such images, together with simple image processing, we have effectively reduced this to a residual noise level of about 0.1 times 10-10. This demonstrates that a coronagraphic telescope in space could detect and spectroscopically characterize nearby exoplanetary systems, with the sensitivity to image an 'Earth-twin' orbiting a nearby star.

  6. Astrometric Evidence for a Population of Dislodged AGNs

    Science.gov (United States)

    Makarov, Valeri V.; Frouard, Julien; Berghea, Ciprian T.; Rest, Armin; Chambers, Kenneth C.; Kaiser, Nicholas; Kudritzki, Rolf-Peter; Magnier, Eugene A.

    2017-02-01

    We investigate a sample of 2293 ICRF2 extragalactic radio-loud sources with accurate positions determined by VLBI, mostly active galactic nuclei (AGNs) and quasars, which are cross-matched with optical sources in the first Gaia release (Gaia DR1). The distribution of offsets between the VLBI sources and their optical counterparts is strongly non-Gaussian, with powerful wings extending beyond 1 arcsec. Limiting our analysis to only high-confidence difference detections, we find (and publish) a list of 188 objects with normalized variances above 12 and offsets below 1 arcsec. Pan-STARRS stacked and monochromatic images resolve some of these sources, indicating the presence of double sources, confusion sources, or pronounced extended structures. Some 89 high-quality objects, however, do not show any perturbations and appear to be star-like single sources, yet they are displaced by multiples of the expected error from the radio-loud AGN. We conclude that a fraction of luminous AGNs (more than 4%) can be physically dislodged from the optical centers of their parent galaxies.

  7. Effect of Rare Earth Metals, Sr, and Ti Addition on the Microstructural Characterization of A413.1 Alloy

    Directory of Open Access Journals (Sweden)

    M. G. Mahmoud

    2017-01-01

    Full Text Available The present work was performed on A413.1 alloy containing 0.2–1.5 wt% rare earth metals (lanthanum or cerium, 0.05–0.15% Ti, and 0–0.02 wt% Sr. These elements were either added individually or combined. Thermal analysis, image analysis, and electron probe microanalysis were the main techniques employed in the present study. The results show that the use of the depression in the eutectic temperature as a function of alloy modification cannot be applied in the case when the alloy is treated with rare earth metals. Increasing the concentration of RE increases the solidification zone especially in Sr-modified alloys leading to poor feeding ability. This observation is more prominent in the case of Ce addition. Depending upon the amount of added Ti, two RE based intermetallics can be formed: (i a white phase, mainly platelet-like (approximately 2.5 μm thick, that is rich in RE, Si, Cu, and Al and (ii a second phase made up of mainly grey sludge particles (star-like branching in different directions. The grey phase is rich in Ti with some RE (almost 20% of that in the white phase with traces of Si and Cu. There is a strong interaction between RE and Sr leading to a reduction in the efficiency of Sr as a eutectic Si modifier causing particle demodification.

  8. Structural properties and optical characterization of flower-like Mg doped NiO

    Directory of Open Access Journals (Sweden)

    Ghazaleh Allaedini

    2015-07-01

    Full Text Available In this study, un-doped and Mg doped NiO nanoparticles have been synthesized through a simple sol-gel method. To investigate the effect of Mg-doping on the structure of NiO, the obtained nanoparticles were characterized using scanning electron microscopy (SEM. Flower/star like morphology was clearly observed in the SEM micrographs. The BET (Brunauer-Emmett-Teller nitrogen absorption isotherm exhibits high specific surface area (∼37 m2 /g for the Mg doped NiO nanoparticles. X-Ray diffraction (XRD of the prepared Mg-NiO nanoparticles showed a face-centered cubic (f.c.c structure, and the average particle size was estimated to be 32 nm using Scherrer’s formula. Energy Dispersive X-Ray (EDX confirms that the NiO particles are successfully doped with Mg. Photoluminescence (PL and UV-Vis optical absorption characteristics of the prepared nanoparticles have also been investigated in this study. The PL emission response showed a blue shift when NiO was doped with Mg, which is indicative of interstitial oxygen. The UV-Vis results demonstrate a band gap increase as NiO nanoparticles are doped with Mg.

  9. Observational studies of pre-stellar cores and infrared dark clouds

    CERN Document Server

    Caselli, Paola

    2011-01-01

    Stars like our Sun and planets like our Earth form in dense regions within interstellar molecular clouds, called pre-stellar cores (PSCs). PSCs provide the initial conditions in the process of star and planet formation. In the past 15 years, detailed observations of (low-mass) PSCs in nearby molecular cloud complexes have allowed us to find that they are cold (T < 10 K) and quiescent (molecular line widths are close to thermal), with a chemistry profoundly affected by molecular freeze-out onto dust grains. In these conditions, deuterated molecules flourish, becoming the best tools to unveil the PSC physical and chemical structure. Despite their apparent simplicity, PSCs still offer puzzles to solve and they are far from being completely understood. For example, what is happening to the gas and dust in their nuclei (the future stellar cradles) is still a mystery that awaits for ALMA. Other important questions are: how do different environments and external conditions affect the PSC physical/chemical structu...

  10. A Description of Multiscale Modeling for the Head-Disk Interface Focusing on Bottom-Level Lubricant and Carbon Overcoat Models

    Directory of Open Access Journals (Sweden)

    Myung S. Jhon

    2013-01-01

    Full Text Available The challenges in designing future head disk interface (HDI demand efficient theoretical modeling tools with flexibility in investigating various combinations of perfluoropolyether (PFPE and carbon overcoat (COC materials. For broad range of time and length scales, we developed multiscale/multiphysical modeling approach, which can bring paradigm-shifting improvements in advanced HDI design. In this paper, we introduce our multiscale modeling methodology with an effective strategic framework for the HDI system. Our multiscale methodology in this paper adopts a bottom to top approach beginning with the high-resolution modeling, which describes the intramolecular/intermolecular PFPE-COC degrees of freedom governing the functional oligomeric molecular conformations on the carbon surfaces. By introducing methodology for integrating atomistic/molecular/mesoscale levels via coarse-graining procedures, we investigated static and dynamic properties of PFPE-COC combinations with various molecular architectures. By bridging the atomistic and molecular scales, we are able to systematically incorporate first-principle physics into molecular models, thereby demonstrating a pathway for designing materials based on molecular architecture. We also discussed future materials (e.g., graphene for COC, star-like PFPEs and systems (e.g., heat-assisted magnetic recording (HAMR with higher scale modeling methodology, which enables the incorporation of molecular/mesoscale information into the continuum scale models.

  11. The Milky Way Project: A Citizen Science Catalog of Infrared Bow Shock Nebulae

    Science.gov (United States)

    Dixon, Don; Jayasinghe, Tharindu; Povich, Matthew S.

    2017-01-01

    We present preliminary results from the first citizen-science search for infrared stellar-wind bow shock candidates. This search uses the Milky Way project, hosted by the Zooniverse, an online platform with over 1 million volunteer citizen scientists. Milky Way Project volunteers examine 77,000 randomly-distributed Spitzer image cutouts at varying zoom levels. Volunteers mark the infrared arc of potential bow shock candidates as well as the star likely driving the nebula. We produce lists of candidates from bow shocks flagged by multiple volunteers, which after merging and final visual review form the basis for our catalog. Comparing our new catalog to a recently-published catalog of 709 infrared bow shock candidates identified by a small team of (primarily undergraduate) researchers will allow us to assess the effectiveness of citizen science for this type of search and should yield a more complete catalog. Planned studies using these large catalogs will improve constraints on the mass-loss rates for the massive stars that create these bow shock nebulae. Mass-loss rates are highly uncertain but are a critical component of evolutionary models for massive stars. This work is supported by the National Science Foundation under grants CAREER-1454334, AST-1411851 (RUI) and AST-1412845.

  12. The neocortex of cetartiodactyls: I. A comparative Golgi analysis of neuronal morphology in the bottlenose dolphin (Tursiops truncatus), the minke whale (Balaenoptera acutorostrata), and the humpback whale (Megaptera novaeangliae).

    Science.gov (United States)

    Butti, Camilla; Janeway, Caroline M; Townshend, Courtney; Wicinski, Bridget A; Reidenberg, Joy S; Ridgway, Sam H; Sherwood, Chet C; Hof, Patrick R; Jacobs, Bob

    2015-11-01

    The present study documents the morphology of neurons in several regions of the neocortex from the bottlenose dolphin (Tursiops truncatus), the North Atlantic minke whale (Balaenoptera acutorostrata), and the humpback whale (Megaptera novaeangliae). Golgi-stained neurons (n = 210) were analyzed in the frontal and temporal neocortex as well as in the primary visual and primary motor areas. Qualitatively, all three species exhibited a diversity of neuronal morphologies, with spiny neurons including typical pyramidal types, similar to those observed in primates and rodents, as well as other spiny neuron types that had more variable morphology and/or orientation. Five neuron types, with a vertical apical dendrite, approximated the general pyramidal neuron morphology (i.e., typical pyramidal, extraverted, magnopyramidal, multiapical, and bitufted neurons), with a predominance of typical and extraverted pyramidal neurons. In what may represent a cetacean morphological apomorphy, both typical pyramidal and magnopyramidal neurons frequently exhibited a tri-tufted variant. In the humpback whale, there were also large, star-like neurons with no discernable apical dendrite. Aspiny bipolar and multipolar interneurons were morphologically consistent with those reported previously in other mammals. Quantitative analyses showed that neuronal size and dendritic extent increased in association with body size and brain mass (bottlenose dolphin neocortex of cetaceans as compared to other mammals and that neuronal dendritic extent covaries with brain and body size.

  13. Monodisperse Dual-Functional Upconversion Nanoparticles Enabled Near-Infrared Organolead Halide Perovskite Solar Cells.

    Science.gov (United States)

    He, Ming; Pang, Xinchang; Liu, Xueqin; Jiang, Beibei; He, Yanjie; Snaith, Henry; Lin, Zhiqun

    2016-03-18

    Extending the spectral absorption of organolead halide perovskite solar cells from visible into near-infrared (NIR) range renders the minimization of non-absorption loss of solar photons with improved energy alignment. Herein, we report on, for the first time, a viable strategy of capitalizing on judiciously synthesized monodisperse NaYF4 :Yb/Er upconversion nanoparticles (UCNPs) as the mesoporous electrode for CH3 NH3 PbI3 perovskite solar cells and more importantly confer perovskite solar cells to be operative under NIR light. Uniform NaYF4 :Yb/Er UCNPs are first crafted by employing rationally designed double hydrophilic star-like poly(acrylic acid)-block-poly(ethylene oxide) (PAA-b-PEO) diblock copolymer as nanoreactor, imparting the solubility of UCNPs and the tunability of film porosity during the manufacturing process. The subsequent incorporation of NaYF4 :Yb/Er UCNPs as the mesoporous electrode led to a high efficiency of 17.8 %, which was further increased to 18.1 % upon NIR irradiation. The in situ integration of upconversion materials as functional components of perovskite solar cells offers the expanded flexibility for engineering the device architecture and broadening the solar spectral use.

  14. Not as the crow flies: a historical explanation for circuitous migration in Swainson's thrush (Catharus ustulatus).

    Science.gov (United States)

    Ruegg, Kristen C; Smith, Thomas B

    2002-07-07

    Many migratory songbirds follow circuitous migratory routes instead of taking the shortest path between overwintering and breeding areas. Here, we study the migration patterns in Swainson's thrush (Catharus ustulatus), a neartic-neotropical migrant songbird, using molecular genetic approaches. This species is presently separated into genetically distinct coastal and continental populations that diverged during the Late Pleistocene (as indicated by molecular dating), yet appear to have retained ancestral patterns of migration. Low nucleotide diversity, a star-like haplotype phylogeny and unimodal mismatch distributions all support the hypothesis that both the coastal and the continental populations have undergone recent demographic expansions. Nearctic-neotropical banding and genetic data show nearly complete segregation of migratory routes and of overwintering locations: coastal populations migrate along the Pacific Coast to overwintering sites in Central America and Mexico, whereas continental populations migrate along an eastern route to overwintering sites in Panama and South America. Nearctic-neotropical banding data also show that continental birds north, northwest and east of this migratory divide fly thousands of miles east before turning south. We conclude that circuitous migration in the Swainson's thrush is an artefact of a Late Pleistocene range expansion.

  15. Fluid spatial dynamics of West Nile virus in the USA: Rapid spread in a permissive host environment

    Science.gov (United States)

    Di Giallonardo , Francesca; Geoghegan, Jemma L.; Docherty, Douglas E.; McLean, Robert G.; Zody, Michael C.; Qu, James; Yang, Xiao; Birren, Bruce W.; Malboeuf, Christine M.; Newman, R.; Ip, Hon S.; Holmes, Edward C.

    2016-01-01

    The introduction of West Nile virus (WNV) into North America in 1999 is a classical example of viral emergence in a new environment, with its subsequent dispersion across the continent having a major impact on local bird populations. Despite the importance of this epizootic, the pattern, dynamics and determinants of WNV spread in its natural hosts remain uncertain. In particular, it is unclear whether the virus encountered major barriers to transmission, or spread in an unconstrained manner, and if specific viral lineages were favored over others indicative of intrinsic differences in fitness. To address these key questions in WNV evolution and ecology we sequenced the complete genomes of approximately 300 avian isolates sampled across the USA between 2001-2012. Phylogenetic analysis revealed a relatively ‘star-like' tree structure, indicative of explosive viral spread in US, although with some replacement of viral genotypes through time. These data are striking in that viral sequences exhibit relatively limited clustering according to geographic region, particularly for those viruses sampled from birds, and no strong phylogenetic association with well sampled avian species. The genome sequence data analysed here also contain relatively little evidence for adaptive evolution, particularly on structural proteins, suggesting that most viral lineages are of similar fitness, and that WNV is well adapted to the ecology of mosquito vectors and diverse avian hosts in the USA. In sum, the molecular evolution of WNV in North America depicts a largely unfettered expansion within a permissive host and geographic population with little evidence of major adaptive barriers.

  16. A new class of solutions of anisotropic charged distributions on pseudo-spheroidal spacetime

    CERN Document Server

    Ratanpal, B S; Pandya, D M

    2015-01-01

    In the present article a new class of exact solutions of Einstein's field equations for charged anisotropic distribution is obtained on the background of pseudo-spheroidal spacetime characterized by the metric potential $g_{rr}=\\frac{1+K\\frac{r^{2}}{R^{2}}}{1+\\frac{r^{2}}{R^{2}}}$, where $K$ and $R$ are geometric parameters of the spacetime. The radial pressure $p_{r}$ and electric field intensity $E$ are taken in the form $8\\pi p_{r}=\\frac{K-1}{R^{2}}\\frac{\\left(1-\\frac{r^{2}}{R^{2}} \\right)}{\\left(1+K\\frac{r^{2}}{R^{2}} \\right)^{2}}$ and $E^{2}=\\frac{\\alpha(K-1)\\frac{r^{2}}{R^{2}}}{R^{2}\\left(1+K\\frac{r^{2}}{R^{2}} \\right)^{2}}$. The bounds of geometric parameter $K$ and the parameter $\\alpha$ appearing in the expression of $E^{2}$ are obtained by imposing the requirements for a physically acceptable model. It is found that the model is in good agreement with the observational data of number of compact stars like 4U 1820-30, PSR J1903+327, 4U 1608-52, Vela X-1, PSR J1614-2230, Cen X-3 given by Gangopadhyay ...

  17. Modelling the nucleosynthetic properties of carbon-enhanced metal-poor RR Lyrae stars

    CERN Document Server

    Stancliffe, Richard J; Lau, Herbert H B; Beers, Timothy C

    2013-01-01

    Certain carbon-enhanced metal-poor stars likely obtained their composition via pollution from some of the earliest generations of asymptotic giant branch stars and as such provide important clues to early Universe nucleosynthesis. Recently, Kinman et al. discovered that the highly carbon- and barium-enriched metal-poor star SDSS J1707+58 is in fact an RR Lyrae pulsator. This gives us an object in a definite evolutionary state where the effects of dilution of material during the Main Sequence are minimised owing to the object having passed through first dredge-up. We perform detailed stellar modelling of putative progenitor systems in which we accreted material from asymptotic giant branch stars in the mass range 1-2 solar masses. We investigate how the surface abundances are affected by the inclusion of mechanisms like thermohaline mixing and gravitational settling. While we are able to find a reasonable fit to the carbon and sodium abundances of SDSS J1707+58, suggesting accretion of around 0.1 solar masses ...

  18. A new class of solutions of compact stars with charged distributions on pseudo-spheroidal spacetime

    CERN Document Server

    Thomas, V O

    2015-01-01

    In this paper a new class of exact solutions of Einstein's field equations for compact stars with charged distributions is obtained on the basis of pseudo-spheroidal spacetime characterized by the metric potential $g_{rr}=\\frac{1+K\\frac{r^{2}}{R^{2}}}{1+\\frac{r^{2}}{R^{2}}}$, where $K$ and $R$ are geometric parameters of the spacetime. The expressions for radial pressure ($ p_r $) and electric field intensity ($ E $) are chosen in such a way that the model falls in the category of physically acceptable one. The bounds of geometric parameter $K$ and the physical parameters $ p_0 $ and $\\alpha$ are obtained by imposing the physical requirements and regularity conditions. The present model is in good agreement with the observational data of various compact stars like 4U 1820-30, PSR J1903+327, 4U 1608-52, Vela X-1, SMC X-4, Cen X-3 given by Gangopadhyay {\\em{et al.}} [Gangopadhyay T., Ray S., Li X-D., Dey J. and Dey M., {\\it Mon. Not. R. Astron. Soc.} {\\bf431} (2013) 3216]. When $ \\alpha = 0, $ the model reduces...

  19. A New Milky Way Satellite Discovered in the Subaru/Hyper Suprime-Cam Survey

    Science.gov (United States)

    Homma, Daisuke; Chiba, Masashi; Okamoto, Sakurako; Komiyama, Yutaka; Tanaka, Masayuki; Tanaka, Mikito; Ishigaki, Miho N.; Akiyama, Masayuki; Arimoto, Nobuo; Garmilla, José A.; Lupton, Robert H.; Strauss, Michael A.; Furusawa, Hisanori; Miyazaki, Satoshi; Murayama, Hitoshi; Nishizawa, Atsushi J.; Takada, Masahiro; Usuda, Tomonori; Wang, Shiang-Yu

    2016-11-01

    We report the discovery of a new ultra-faint dwarf satellite companion of the Milky Way (MW) based on the early survey data from the Hyper Suprime-Cam Subaru Strategic Program. This new satellite, Virgo I, which is located in the constellation of Virgo, has been identified as a statistically significant (5.5σ) spatial overdensity of star-like objects with a well-defined main sequence and red giant branch in the color-magnitude diagram. The significance of this overdensity increases to 10.8σ when the relevant isochrone filter is adopted for the search. Based on the distribution of the stars around the likely main-sequence turnoff at r ˜ 24 mag, the distance to Virgo I is estimated as 87 kpc, and its most likely absolute magnitude calculated from a Monte Carlo analysis is M V = -0.8 ± 0.9 mag. This stellar system has an extended spatial distribution with a half-light radius of {38}-11+12 pc, which clearly distinguishes it from a globular cluster with comparable luminosity. Thus, Virgo I is one of the faintest dwarf satellites known and is located beyond the reach of the Sloan Digital Sky Survey. This demonstrates the power of this survey program to identify very faint dwarf satellites. This discovery of Virgo I is based only on about 100 square degrees of data, thus a large number of faint dwarf satellites are likely to exist in the outer halo of the MW.

  20. Himalia, a Small Moon of Jupiter

    Science.gov (United States)

    2001-01-01

    NASA's Cassini spacecraft captured images of Himalia, the brightest of Jupiter's outer moons, on Dec. 19, 2000, from a distance of 4.4 million kilometers (2.7 million miles).This near-infrared image, with a resolution of about 27 kilometers (17 miles) per pixel, indicates that the side of Himalia facing the spacecraft is roughly 160 kilometers (100 miles) in the up-down direction. Himalia probably has a non-spherical shape. Scientists believe it is a body captured into orbit around Jupiter, most likely an irregularly shaped asteroid.In the main frame, an arrow indicates Himalia. North is up. The inset shows the little moon magnified by a factor of 10, plus a graphic indicating Himalia's size and the direction of lighting (with sunlight coming from the left). Cassini's pictures of Himalia were taken during a brief period when Cassini's attitude was stabilized by thrusters instead of by a steadier reaction-wheel system. No spacecraft or telescope had previously shown any of Jupiter's outer moons as more than a star-like single dot.Cassini is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini mission for NASA's Office of Space Science, Washington, D.C.

  1. Effect of ultrasonic treatment on formation of iron-containing intermetallic compounds in Al-Si alloys

    Directory of Open Access Journals (Sweden)

    Yu-bo Zhang

    2016-09-01

    Full Text Available Iron is generally regarded as an unavoidable impurity in Al-Si casting alloys. The acicular Al3Fe and β-Al5FeSi (or Al9Si2Fe2 are common iron-containing intermetallic compounds (IMCs in conventional structure which have a detrimental impact on the mechanical properties. In this paper, ultrasonic field (USF was applied to modify acicular iron phases in Al-12%Si-2%Fe and Al-2%Fe alloys. The results show that the USF applied to Al-Fe alloys caused the morphological transformation of both primary and eutectic Al3Fe from acicular to blocky and granular without changes in their composition. In the case of Al-Si-Fe alloys, ultrasonic treatment led to both morphological and compositional conversion of the ternary iron IMCs. When the USF was applied, the acicular β-Al9Si2Fe2 was substituted by star-like α-Al12Si2Fe3. The modification rate of both binary and ternary iron IMCs relates to the USF treatment duration. The undercooling induced by the ultrasonic vibration contributes to the nucleation of intermetallics and can explain the transformation effect.

  2. Encantamento do rosto. Poses e retratos de cinema

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    Ana Carolina de Moura Delfim Maciel

    2010-01-01

    Full Text Available The purpose of this article is to describe a set of photographs of Eliane Lage (1928-, a movie actress featured in Caiçara, Ângela, Sinhá Moça and Ravina - the first three produced by Companhia Cinematográfica Vera Cruz (1950-1954, and the fourth by Cinematográfica Brasil Filmes. Companhia Cinematográfica Vera Cruz aspired to be one of the largest film producers in Brazil and, accordingly, its Advertising Department set out to establish Eliane Lage as a great movie star, like those in the world's dominant movie industries. This paper brings to light some photographs which, coupled with information published in the press, were intended to tell the public at large who Eliane Lage was by exploring extensively certain aspects of her "biography", such as her privileged background, her denial of stardom, her detachment, her passion for her husband, and her love of nature. The picture selection includes: a photo essay by the architect Gregori Warcharchik; studio marketing photographs; snapshots taken by photographers at the time; and pictures that are part of the actress's personal collection.

  3. The formation and assembly of a typical star-forming galaxy at redshift z approximately 3.

    Science.gov (United States)

    Stark, Daniel P; Swinbank, A Mark; Ellis, Richard S; Dye, Simon; Smail, Ian R; Richard, Johan

    2008-10-09

    Recent studies of galaxies approximately 2-3 Gyr after the Big Bang have revealed large, rotating disks, similar to those of galaxies today. The existence of well-ordered rotation in galaxies during this peak epoch of cosmic star formation indicates that gas accretion is likely to be the dominant mode by which galaxies grow, because major mergers of galaxies would completely disrupt the observed velocity fields. But poor spatial resolution and sensitivity have hampered this interpretation; such studies have been limited to the largest and most luminous galaxies, which may have fundamentally different modes of assembly from those of more typical galaxies (which are thought to grow into the spheroidal components at the centres of galaxies similar to the Milky Way). Here we report observations of a typical star-forming galaxy at z = 3.07, with a linear resolution of approximately 100 parsecs. We find a well-ordered compact source in which molecular gas is being converted efficiently into stars, likely to be assembling a spheroidal bulge similar to those seen in spiral galaxies at the present day. The presence of undisrupted rotation may indicate that galaxies such as the Milky Way gain much of their mass by accretion rather than major mergers.

  4. Polyglycidol, Its Derivatives, and Polyglycidol-Containing Copolymers—Synthesis and Medical Applications

    Directory of Open Access Journals (Sweden)

    Mateusz Gosecki

    2016-06-01

    Full Text Available Polyglycidol (or polyglycerol is a biocompatible polymer with a main chain structure similar to that of poly(ethylene oxide but with a –CH2OH reactive side group in every structural unit. The hydroxyl groups in polyglycidol not only increase the hydrophilicity of this polymer but also allow for its modification, leading to polymers with carboxyl, amine, and vinyl groups, as well as to polymers with bonded aliphatic chains, sugar moieties, and covalently immobilized bioactive compounds in particular proteins. The paper describes the current state of knowledge on the synthesis of polyglycidols with various topology (linear, branched, and star-like and with various molar masses. We provide information on polyglycidol-rich surfaces with protein-repelling properties. We also describe methods for the synthesis of polyglycidol-containing copolymers and the preparation of nano- and microparticles that could be derived from these copolymers. The paper summarizes recent advances in the application of polyglycidol and polyglycidol-containing polymers as drug carriers, reagents for diagnostic systems, and elements of biosensors.

  5. Value of High-frequency Color Doppler Ultrasound in Diagnosis of Inguinal Hernia in Senile Men%高频彩色多普勒超声在诊断老年性腹股沟疝中的价值

    Institute of Scientific and Technical Information of China (English)

    王福明; 衷爱华; 郭金强

    2011-01-01

    ,inguinal hernia was represented by cluster of visible objects or mesh-like bright echoes. With the color Doppler ultrasound scan, the contents of hernial sac of reducible hernia mostly contained red and blue stripes or echo spots of blood flow. For the irreducible hernia and incarcerated hernia,the contents of hernial sac contained less echoes of blood flow and showed bar-or star-like blood flow signals. For the strangulated hernia, the contents of hernial sac contained either no blood flow signals or very few star-like blood flow echoes. Conclusion High-frequency color Doppler ultrasound is an innovative and non-invasive method for diagnosing inguinalhernia in senile men.

  6. Neptune as a Mirror for the Sun

    Science.gov (United States)

    Kohler, Susanna

    2017-01-01

    How would the Kepler mission see a star like the Sun? We now know the answer to this question due to a creative approach: a new study has used the Kepler K2 mission to detect signals from the Sun reflected off of the surface of Neptune.Asteroseismology uses different oscillation modes of a star to probe its internal structure and properties. [Tosaka]Information in OscillationsKeplers most glamorous work is in discovering new planets around other stars. To successfully do this, however, the spacecraft is also quietly doing a lot of very useful work in the background, characterizing the many stars in our vicinity that planets might be found around.One of the ways Kepler gets information about these stars is from oscillations of the stars intensities. In asteroseismology, we look at oscillatory modes that are caused by convection-driven pressure changes on the inside of the star. All stars with near-surface convection oscillate like this including the Sun and by measuring the oscillations in intensity of these stars, we can make inferences about the stars properties.A Planetary MirrorWe do this by first understanding our Suns oscillations especially well (made easier by the fact that its nearby!). Then we use asteroseimic scaling relations determined empirically that relate characteristics like mass and radius of other stars to those of the Sun, based on the relation between the stars oscillation properties to the Suns.The trouble is, those oscillation properties are difficult to measure, and different instruments often measure different values. For this reason, wed like to measure the Suns oscillations with the same instrument we use to measure other stars oscillations: Kepler.Top panel: Kepler K2 49-day light curve of Neptune. Bottom panel: power density spectrum as a function of frequency (grey). Neptunes rotation frequencies and harmonics appear toward the left side (blue); the excess power due to the solar modes is visible toward the bottom right. The green curve

  7. The Terrible Twos: What Might Happen If Our Sun Had A Twi

    Science.gov (United States)

    2001-11-01

    How would our Sun behave differently if it had a closely orbiting twin? While astronomers don't know the exact answer, NASA's Chandra X-ray Observatory has observed an intriguing star system that is beginning to provide important clues. Scientists from the Smithsonian Astrophysical Observatory (SAO) used Chandra to study two stars in an incredibly tight binary system. These stars, part of the system known as 44i Bootis, orbit around so quickly that that they pass in front of one another every three hours. "The universe has gift-wrapped a wonderful laboratory for us to study stars like our Sun," said Nancy Brickhouse of SAO who led the research team. "We can use this strange alignment of these two stars whipping around each other to learn more about magnetic fields and outer atmospheres in stars like our Sun." For decades, scientists have known that the Sun at the center of our Solar System creates complex magnetic fields as it spins on its axis roughly once every month. These magnetic fields confine giant arches of hot, ionized gas that erupt from the solar surface. Occasionally, these eruptions flare out in the direction of Earth and affects satellites and power grids. Astronomers have long predicted that rapidly spinning solar-like stars could produce magnetic field patterns very different from those of our Sun. Unfortunately, any star outside of our Solar System-including 44i Bootis-is too far away for even the biggest telescopes to resolve magnetic loops on the surfaces. However, the SAO team took advantage of the fact that 44i Bootis is an eclipsing binary, where two stars circle around each other. The two stars are aligned so that Chandra can capture the ebb and flow of radiation as the stars pass in front of one another. By using the Doppler effect-the same process that causes the wavelength of an ambulance's siren to shift up and down as the ambulance approaches and recedes-astronomers were able to pinpoint the location of the source of most of the X

  8. Introduction

    Science.gov (United States)

    Luhmann, J. G.; Tatrallyay, M.

    Venus and Mars, our neighboring planets, have a long history in the human consciousness. Venus, in particular, was notable because of its brightness compared to other star-like objects in the sky. The first observations of Venus on record may be those enscribed by Babylonians on the famous "Venus tablet" in the British museum, which has been dated to ˜1700 BC. Venus has generally been associated with the female gender, except in ancient India. The name comes from the Roman goddess of love and beauty (analogous to the Babylonian Ishtar and the Greek Aphrodite). Venus was first thought by the Greeks to be two objects—a morning star "Phosphorus" and an evening star "Hesperus". Phythagoras, in 6 BC, is credited with being first to recognize they were the same object. Venus has since figured prominently in the history of physics and astronomy. The Greek Aristarchus first suggested (in ˜310-250 BC) that the planets move around the sun, but the idea lost favor to a theory of Ptolemy, which placed Earth at the center of the solar system. In the 9th-15th centuries, Arab astronomers studied Venus, and in the "new world," the Mayas used it in the organization of their calendar. In 1543, Copernicus finally published his own version of Aristarchus' vision of a heliocentric solar system, but it was probably not until Galileo, in ˜1610, telescopically observed that Venus had phases like the moon, that heliocentric theory was widely accepted (despite delays associated with the prevailing religious dogma). He announced that momentous discovery in a coded message to his contemporary Kepler (a usual practice of the time), which translated to "the mother of the loves imitates the phases of Cynthia".

  9. Go West: A One Way Stepping-Stone Dispersion Model for the Cavefish Lucifuga dentata in Western Cuba.

    Science.gov (United States)

    Hernández, Damir; Casane, Didier; Chevalier-Monteagudo, Pedro; Bernatchez, Louis; García-Machado, Erik

    2016-01-01

    Consistent with the limited dispersal capacity of most troglobitic animals, almost all Lucifuga cavefish species have very narrow geographic distribution in Cuba. However, one species, L. dentata, has a wide but disjointed distribution over 300 km in the west of the island. In order to estimate the relative role of vicariance and dispersal in the unexpected L. dentata distribution, we obtained partial sequences of the mitochondrial DNA (mtDNA) cytochrome b (cytb) gene and control region (CR), and then applied Approximate Bayesian Computation (ABC), based on the identification of five genetic and geographic congruent groups of populations. The process that best explains the distribution of genetic diversity in this species is sequential range expansion from east Matanzas to the western Pinar del Río provinces, followed by isolation of groups of populations. We found relative high haplotype diversity and low nucleotide diversity in all but the Havana group, which has high values for both diversity parameters, suggesting that this group has been demographically stable over time. For two groups of populations (Cayuco and Bolondrón), the mismatch distribution analyses suggests past demographic expansion. In the case of the Cayuco region, the star like relationships of haplotypes in the network suggests a recent founding event, congruent with other evidence indicating that this is the most recently colonized region. Over all, the results suggest that a combination of habitat availability, temporal interconnections, and possibly the biological properties of this species, may have enabled its dispersal and range expansion compared to other species of the genus, which are more geographically restricted.

  10. Natural selection and population genetic structure of domain-I of Plasmodium falciparum apical membrane antigen-1 in India.

    Science.gov (United States)

    Basu, Madhumita; Maji, Ardhendu Kumar; Mitra, Mitashree; Sengupta, Sanghamitra

    2013-08-01

    Development of a vaccine against Plasmodium falciparum infection is an urgent priority particularly because of widespread resistance to most traditionally used drugs. Multiple evidences point to apical membrane antigen-1(AMA-1) as a prime vaccine candidate directed against P. falciparum asexual blood-stages. To gain understanding of the genetic and demographic forces shaping the parasite sequence diversity in Kolkata, a part of Pfama-1 gene covering domain-I was sequenced from 100 blood samples of malaria patients. Statistical and phylogenetic analyses of the sequences were performed using DnaSP and MEGA. Very high haplotype diversity was detected both at nucleotide (0.998±0.002) and amino-acid (0.996±0.001) levels. An abundance of low frequency polymorphisms (Tajima's D=-1.190, Fu & Li's D(∗) and F(∗)=-3.068 and -2.722), unimodal mismatch distribution and a star-like median-joining network of ama-1 haplotypes indicated a recent population expansion among Kolkata parasites. The high minimum number of recombination events (Rm=26) and a significantly high dN/dS of 3.705 (PIgNAR. Alterations in the desolvation and global energies of PfAMA-1-PfRON2 interaction complexes at the hotspot contact residues were observed together with redistribution of surface electrostatic potentials at the variant alleles with respect to referent Pf3D7 sequence. Finally, a comparison of P. falciparum subpopulations in five Indian regional isolates retrieved from GenBank revealed a significant level of genetic differentiation (FST=0.084-0.129) with respect to Kolkata sequences. Collectively, our results indicated a very high allelic and haplotype diversity, a high recombination rate and a signature of natural selection favoring accumulation of non-synonymous substitutions that facilitated PfAMA-1-PfRON2 interaction and hence parasite growth in Kolkata clinical isolates.

  11. Teaching solar astronomy on march 21 th in a multicultural village during IYA 2009 Mexico

    Science.gov (United States)

    Zueck, S.; Lara, A.

    2009-12-01

    We describe activities and resources at a popularization of science event that was organized in a multicultural mystical small village and the response of the audience that attended it. On March 21 Th. 2009 (spring equinox) we conducted a social experiment of science outreach. Scientists, educators and graduate students interacted with general public at a village named Tepoztlan, State of Morelos, Mexico, that is a former farmers town in process of urbanization, which depends to an extended degree of thousands of tourists which frequents the place, most of all during the equinox day. A team of scientists and their graduate students that belong to the solar physics program of Instituto de Geofísica (UNAM)organized a solar observation, setting at the garden of an old Hispanic dominican convent (XVI century), 10 telescopes with solar filters to show on real time to the general audience, our principal star : The Sun. We also prepared a free separate resource guide to help answer questions about basic information about our star like his structure, sun spots,age,diameter,evolution etc and two researchers offer conferences to the local elementary school children. The main audience came from the local people like bakers, open market workers or home makers that after finish his labor day went to the Museum to observe the Sun trough the telescopes or to attend the conferences with their children. They have several questions about scientific and pseudo-scientific topics related not just to the solar equinox, but about the earth's magnetic field, planets etc. We also discuss our experiences communicating science face to face to an audience that came to a town that is famous for his widely mystical legends related to solar energy or vibration that humans can use to get luck or health especially on this date.

  12. Release of ATP from marginal cells in the cochlea of neonatal rats can be induced by changes in extracellular and intracellular ion concentrations.

    Directory of Open Access Journals (Sweden)

    Yating Peng

    Full Text Available BACKGROUND: Adenosine triphosphate (ATP plays an important role in the cochlea. However, the source of ATP and the mechanism by which it is released remain unclear. This study investigates the presence and release mechanism of ATP in vitro cultured marginal cells isolated from the stria vascularis of the cochlea in neonatal rats. METHODS: Sprague-Dawley rats aged 1-3 days old were used for isolation, in vitro culture, and purification of marginal cells. Cultured marginal cells were verified by flow cytometry. Vesicles containing ATP in these cells were identified by fluorescence staining. The bioluminescence assay was used for determination of ATP concentration in the extracellular fluid released by marginal cells. Assays for ATP concentration were performed when the ATP metabolism of cells was influenced, and ionic concentrations in intracellular and extracellular fluid were found to change. RESULTS: Evaluation of cultured marginal cells with flow cytometry revealed the percentage of fluorescently-labeled cells as 92.9% and 81.9%, for cytokeratin and vimentin, respectively. Quinacrine staining under fluorescence microscopy revealed numerous green, star-like spots in the cytoplasm of these cells. The release of ATP from marginal cells was influenced by changes in the concentration of intracellular and extracellular ions, namely extracellular K(+ and intra- and extracellular Ca(2+. Furthermore, changes in the concentration of intracellular Ca(2+ induced by the inhibition of the phospholipase signaling pathway also influence the release of ATP from marginal cells. CONCLUSION: We confirmed the presence and release of ATP from marginal cells of the stria vascularis. This is the first study to demonstrate that the release of ATP from such cells is associated with the state of the calcium pump, K(+ channel, and activity of enzymes related to the phosphoinositide signaling pathway, such as adenylate cyclase, phospholipase C, and phospholipase A(2.

  13. The Colorful Demise of a Sun-like Star

    Science.gov (United States)

    2007-01-01

    This image, taken by NASA's Hubble Space Telescope, shows the colorful 'last hurrah' of a star like our Sun. The star is ending its life by casting off its outer layers of gas, which formed a cocoon around the star's remaining core. Ultraviolet light from the dying star makes the material glow. The burned-out star, called a white dwarf, is the white dot in the center. Our Sun will eventually burn out and shroud itself with stellar debris, but not for another 5 billion years. Our Milky Way Galaxy is littered with these stellar relics, called planetary nebulae. The objects have nothing to do with planets. Eighteenth- and nineteenth-century astronomers named them planetary nebulae because through small telescopes they resembled the disks of the distant planets Uranus and Neptune. The planetary nebula in this image is called NGC 2440. The white dwarf at the center of NGC 2440 is one of the hottest known, with a surface temperature of nearly 400,000 degrees Fahrenheit (200,000 degrees Celsius). The nebula's chaotic structure suggests that the star shed its mass episodically. During each outburst, the star expelled material in a different direction. This can be seen in the two bow tie-shaped lobes. The nebula also is rich in clouds of dust, some of which form long, dark streaks pointing away from the star. NGC 2440 lies about 4,000 light-years from Earth in the direction of the constellation Puppis. The image was taken Feb. 6, 2007 with Hubble's Wide Field Planetary Camera 2. The colors correspond to material expelled by the star. Blue corresponds to helium; blue-green to oxygen; and red to nitrogen and hydrogen.

  14. Regulation of actin cytoskeleton architecture by Eps8 and Abi1

    Directory of Open Access Journals (Sweden)

    Miller Jeffrey R

    2005-10-01

    Full Text Available Abstract Background The actin cytoskeleton participates in many fundamental processes including the regulation of cell shape, motility, and adhesion. The remodeling of the actin cytoskeleton is dependent on actin binding proteins, which organize actin filaments into specific structures that allow them to perform various specialized functions. The Eps8 family of proteins is implicated in the regulation of actin cytoskeleton remodeling during cell migration, yet the precise mechanism by which Eps8 regulates actin organization and remodeling remains elusive. Results Here, we show that Eps8 promotes the assembly of actin rich filopodia-like structures and actin cables in cultured mammalian cells and Xenopus embryos, respectively. The morphology of actin structures induced by Eps8 was modulated by interactions with Abi1, which stimulated formation of actin cables in cultured cells and star-like structures in Xenopus. The actin stars observed in Xenopus animal cap cells assembled at the apical surface of epithelial cells in a Rac-independent manner and their formation was accompanied by recruitment of N-WASP, suggesting that the Eps8/Abi1 complex is capable of regulating the localization and/or activity of actin nucleators. We also found that Eps8 recruits Dishevelled to the plasma membrane and actin filaments suggesting that Eps8 might participate in non-canonical Wnt/Polarity signaling. Consistent with this idea, mis-expression of Eps8 in dorsal regions of Xenopus embryos resulted in gastrulation defects. Conclusion Together, these results suggest that Eps8 plays multiple roles in modulating actin filament organization, possibly through its interaction with distinct sets of actin regulatory complexes. Furthermore, the finding that Eps8 interacts with Dsh and induced gastrulation defects provides evidence that Eps8 might participate in non-canonical Wnt signaling to control cell movements during vertebrate development.

  15. Comparative phylogeography of two marine species of crustacean: Recent divergence and expansion due to environmental changes.

    Science.gov (United States)

    Zhang, Daizhen; Ding, Ge; Ge, Baoming; Zhang, Huabin; Tang, Boping; Yang, Guang

    2014-10-15

    Environmental changes, such as changes in the coastal topography due to Eurasian plate movements, climate oscillation during the Pleistocene, and alteration of ocean currents, have complicated the geographical structure of marine species and deepened their divergence between populations. As two widely distributed species of crustacean (Oratosquilla oratoria and Eriocheir japonica), weak differences were expected due to their high dispersal potential of planktonic larvae with ocean currents. However, results showed a significant genetic divergence between north of China and south of China in the study. In addition, the estimated north-south divergence time (27-30.5 Myr) of mantis shrimp was near the time of the Himalayan movement, and the China-Japan clade divergence time (10.5-11.9 Myr) of mitten crabs was also coincident with the time of the opening of the Sea of Japan. Thus, we hypothesized that environmental changes in the coastal topography contributed to the marine species divergence. Furthermore, based on phylogenetic analysis, network analysis and haplotype distribution, we surmised that mitten crabs originated from a population with the oldest haplotype (H6) and then divided into the north and south populations due to the recent Eurasian plate movements and ocean currents. And lineage of Japan originated from the north population for the opening of the Sea of Japan. While O. oratoria was guessed to originate from two separate populations in the China Sea. The results of "star-like" network, negative values in neutral test, and Tajima's D statistics of two marine species supported a recent rapid population expansion event after the Pleistocene glaciations. Copyright © 2014 Elsevier B.V. All rights reserved.

  16. Color-magnitude Diagrams of the Star-forming Galaxies Ho IX, Cam B, NGC 2976, and UGC 1281

    Science.gov (United States)

    Georgiev, T. B.; Bomans, D. J.

    We report results on a study of nearby late type galaxies performed with the 2m RC telescope of the Rozhen NAO with with 1×1 K CCD camera. The scale and the frame size are 0.32''/pix and 5.4'×5.4', respectively. At typical seeing of 1'' the data reach routinely a limiting magnitude of ˜4 mag. With these parameters many nearby galaxies, including the members of the IC 342 and M81 groups can be resolved into star-like and diffuse objects. This allows the determination of several fundamental properties of the galaxies, based on surface photometry and study of the brightest resolved objects. The most crucial parameter is the distance to the galaxy. It can be estimated to a standard error of 20 % using the brightest red and blue stars. Selection of these stars is greatly improved by analysis of the image shapes, which allows to detect diffuse objects, like cluster candidates and background galaxies. Further improvement gives the analysis of color-magnitude (CMD) and color-color diagrams. The CMDs also allow to estimate the age of the most recent star formation event and may hint at the metallicity. The CMDs of the low surface brightness irregular galaxies Ho IX and Cam B are very similar. Especially Cam B seems to be an extreme case of a low-mass star-forming dwarf galaxy. The CMD of NGC 2976 is very similar to this of the star burst galaxy M82 (Georgiev T., 2000, Compt. Rend. Acad. Bulg. Sci. 53/2, 5-8). The edge-on galaxy UGC 1281 is of intermediate star-forming activity, but the CMD is quite sparse.

  17. Limit Cycles Can Reduce the Width of the Habitable Zone

    Science.gov (United States)

    Haqq-Misra, Jacob; Kopparapu, Ravi Kumar; Batalha, Natasha E.; Harman, Chester E.; Kasting, James F.

    2016-08-01

    The liquid water habitable zone (HZ) describes the orbital distance at which a terrestrial planet can maintain above-freezing conditions through regulation by the carbonate-silicate cycle. Recent calculations have suggested that planets in the outer regions of the HZ cannot maintain stable, warm climates, but rather should oscillate between long, globally glaciated states and shorter periods of climatic warmth. Such conditions, similar to “Snowball Earth” episodes experienced on Earth, would be inimical to the development of complex land life, including intelligent life. Here, we build on previous studies with an updated energy balance climate model to calculate this “limit cycle” region of the HZ where such cycling would occur. We argue that an abiotic Earth would have a greater CO2 partial pressure than today because plants and other biota help to enhance the storage of CO2 in soil. When we tune our abiotic model accordingly, we find that limit cycles can occur but that previous calculations have overestimated their importance. For G stars like the Sun, limit cycles occur only for planets with CO2 outgassing rates less than that on modern Earth. For K- and M-star planets, limit cycles should not occur; however, M-star planets may be inhospitable to life for other reasons. Planets orbiting late G-type and early K-type stars retain the greatest potential for maintaining warm, stable conditions. Our results suggest that host star type, planetary volcanic activity, and seafloor weathering are all important factors in determining whether planets will be prone to limit cycling.

  18. Genetic Structure of Water Chestnut Beetle: Providing Evidence for Origin of Water Chestnut

    Science.gov (United States)

    Qin, Jing; Lu, Ming-Xing; Du, Yu-Zhou

    2016-01-01

    Water chestnut beetle (Galerucella birmanica Jacoby) is a pest of the water chestnut (Trapa natans L.). To analyze the phylogeny and biogeography of the beetle and provide evidence for the origin of T. natans in China, we conducted this by using three mitochondrial genes (COI, COII and Cytb) and nuclear ITS2 ribosomal DNA of G. birmanica. As for mtDNA genes, the beetle could be subdivided into three groups: northeastern China (NEC), central-northern-southern China (CC-NC-SC) and southwestern China (SWC) based on SAMOVA, phylogenetic analyses and haplotype networks. But for ITS2, no obvious lineages were obtained but individuals which were from NEC region clustered into one clade, which might be due to sequence conservation of ITS2. Significant genetic variation was observed among the three groups with infrequent gene flow between groups, which may have been restricted due to natural barriers and events in the Late Pleistocene. Based on our analyses of genetic variation in the CC-NC-SC geographical region, the star-like haplotype networks, approximate Bayesian computation, niche modelling and phylogeographic variation of the beetle, we concluded that the beetle population has been lasting in the lower, central reaches of the Yangtze River Basin with its host plant, water chestnut, which is consistent with archaeological records. Moreover, we speculate that the CC-NC-SC population of G. birmanica may have undergone a period of expansion coincident with domestication of the water chestnut approximately 113,900–126,500 years ago. PMID:27459279

  19. Radial Velocity Monitoring of Kepler Heartbeat Stars

    Science.gov (United States)

    Shporer, Avi; Fuller, Jim; Isaacson, Howard; Hambleton, Kelly; Thompson, Susan E.; Prša, Andrej; Kurtz, Donald W.; Howard, Andrew W.; O'Leary, Ryan M.

    2016-09-01

    Heartbeat stars (HB stars) are a class of eccentric binary stars with close periastron passages. The characteristic photometric HB signal evident in their light curves is produced by a combination of tidal distortion, heating, and Doppler boosting near orbital periastron. Many HB stars continue to oscillate after periastron and along the entire orbit, indicative of the tidal excitation of oscillation modes within one or both stars. These systems are among the most eccentric binaries known, and they constitute astrophysical laboratories for the study of tidal effects. We have undertaken a radial velocity (RV) monitoring campaign of Kepler HB stars in order to measure their orbits. We present our first results here, including a sample of 22 Kepler HB systems, where for 19 of them we obtained the Keplerian orbit and for 3 other systems we did not detect a statistically significant RV variability. Results presented here are based on 218 spectra obtained with the Keck/HIRES spectrograph during the 2015 Kepler observing season, and they have allowed us to obtain the largest sample of HB stars with orbits measured using a single instrument, which roughly doubles the number of HB stars with an RV measured orbit. The 19 systems measured here have orbital periods from 7 to 90 days and eccentricities from 0.2 to 0.9. We show that HB stars draw the upper envelope of the eccentricity-period distribution. Therefore, HB stars likely represent a population of stars currently undergoing high eccentricity migration via tidal orbital circularization, and they will allow for new tests of high eccentricity migration theories. The data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation.

  20. A spectroscopic orbit for the late-type Be star β CMi

    Science.gov (United States)

    Dulaney, Nick; Richardson, Noel; Gerhartz, Cody; Bjorkman, Jon Eric; Bjorkman, Karen S.; Carciofi, Alex C.; Wang, Luqian; Morrison, Nancy D.; Klement, Robert; Ritter Observing Team

    2017-01-01

    The late-type Be star beta CMi is remarkably stable compared to other Be stars that have been studied. This has led to a realistic model of the outflowing Be disk by Klement et al. (2015) These results showed that the disk is likely truncated at a finite radius from the star, which is easily accomplished by a binary companion in orbit. We report on an analysis of the Ritter Observatory spectroscopic archive of beta CMi in hopes of discovering evidence of the elusive companion. We detect orbital motion caused by a companion from small shifts in the H-alpha emission line. We then compared the small changes in the violet-to-red peak height changes (V/R) with the orbital motion. While some V/R variability seems to be present in the H-alpha profile, there is only weak evidence that it follows the orbital motion, as suggested by recent Be binary models by Panoglou et al. (2016). We also analyze several epochs of near-infrared moderate resolution spectra from the InfraRed Telescope Facility with the SpeX spectrograph. Near-infrared spectra show variations of the Pa-beta and Br-gamma lines, suggesting structure could be present in the inner parts of the Be disk. These results suggest that beta CMi is similar to several other Be stars, and is a product of binary evolution where Roche lobe overflow has spun up the current Be star, likely leaving a hot subdwarf or white dwarf in orbit around the star. Unfortunately, no sign of this star is found in the very limited archive of International Ultraviolet Explorer spectra, so future UV studies of the system are necessary.We are grateful for support of the NSF REU program at the University of Toledo through NSF grant 1262810 and addtional support from the NSF under grant AST-1412135.

  1. Pattern of genetic differentiation of an incipient speciation process: The case of the high Andean killifish Orestias

    Science.gov (United States)

    Guerrero-Jiménez, Claudia Jimena; Peña, Fabiola; Morales, Pamela; Méndez, Marco; Sallaberry, Michel; Vila, Irma; Poulin, Elie

    2017-01-01

    During the Pleistocene and Holocene, the southwest Andean Altiplano (17°-22°S) was affected by repeated fluctuations in water levels, high volcanic activity and major tectonic movements. In the early Holocene the humid Tauca phase shifted to the arid conditions that have lasted until the present, producing endorheic rivers, lakes, lagoons and wetlands. The endemic fish Orestias (Cyprinodontidae) represents a good model to observe the genetic differentiation that characterizes an incipient speciation process in allopatry since the morphospecies described inhabit a restricted geographic area, with present habitat fragmentation. The genetic diversity and population structure of four endemic morphospecies of Orestias (Cyprinodontidae) found in the Lauca National Park (LNP) analyzed with mitochondrial markers (Control Region) and eight microsatellites, revealed the existence of genetic groups that matches the fragmentation of these systems. High values of genetic and phylogeographic differentiation indices were observed between Chungará Lake and Piacota lagoon. The group composed of the Lauca River, Copapujo and Chuviri wetlands sampling sites showed a clear signal of expansion, with a star-like haplotype network. Levels of genetic differentiation were lower than in Chungará and Piacota, suggesting that these localities would have differentiated after the bottlenecks linked to the collapse of Parinacota volcano. The Parinacota sample showed a population signal that differed from the other localities revealing greater genetic diversity and a disperse network, presenting haplotypes shared with other LNP localities. A mixing pattern of the different genetic groups was evident using the microsatellite markers. The chronology of the vicariance events in LNP may indicate that the partition process of the Orestias populations was gradual. Considering this, and in view of the genetic results, we may conclude that the morphospecies from LNP are populations in ongoing

  2. The Type IIb Supernova 2013df and its Cool Supergiant Progenitor

    Science.gov (United States)

    VanDyk, Schuyler D.; Zeng, Weikang; Fox, Ori D.; Cenko, S. Bradley; Clubb, Kelsey I.; Filippenko, Alexei; Foley, Ryan J.; Miller, Adam A.; Smith, Nathan; Kelly, Patrick L.; Lee, William H.; Ben-Ami, Sagi; Gal-Yam, Avishay

    2014-01-01

    We have obtained early-time photometry and spectroscopy of supernova (SN) 2013df in NGC 4414. The SN is clearly of Type II b, with notable similarities to SN 1993J. From its luminosity at secondary maximum light, it appears that less Ni-56 (is approximately less than 0.06M) was synthesized in the SN 2013df explosion than was the case for the SNe II b 1993J, 2008ax, and 2011dh. Based on a comparison of the light curves, the SN 2013df progenitor must have been more extended in radius prior to explosion than the progenitor of SN 1993J. The total extinction for SN 2013dfis estimated to be A(sub V) = 0.30 mag. The metallicity at the SN location is likely to be solar. We have conducted Hubble Space Telescope(HST) Target of Opportunity observations of the SN with the Wide Field Camera 3, and from a precise comparison of these new observations to archival HST observations of the host galaxy obtained 14 yr prior to explosion, we have identified the progenitor of SN 2013df to be a yellow supergiant, somewhat hotter than a red supergiant progenitor for a normal Type II-Plateau SN. From its observed spectral energy distribution, assuming that the light is dominated by one star, the progenitor had effective temperature T(sub eff) = 4250+/-100 K and a bolometric luminosity L(sub bol) =10(exp 4.94+/-0.06) Solar Luminosity. This leads to an effective radius Reff = 545+/-65 Solar Radius. The star likely had an initial mass in the range of 13-17Solar Mass; however, if it was a member of an interacting binary system, detailed modeling of the system is required to estimate this mass more accurately. The progenitor star of SN 2013df appears to have been relatively similar to the progenitor of SN 1993J.

  3. Identification and validation of a logistic regression model for predicting serious injuries associated with motor vehicle crashes.

    Science.gov (United States)

    Kononen, Douglas W; Flannagan, Carol A C; Wang, Stewart C

    2011-01-01

    A multivariate logistic regression model, based upon National Automotive Sampling System Crashworthiness Data System (NASS-CDS) data for calendar years 1999-2008, was developed to predict the probability that a crash-involved vehicle will contain one or more occupants with serious or incapacitating injuries. These vehicles were defined as containing at least one occupant coded with an Injury Severity Score (ISS) of greater than or equal to 15, in planar, non-rollover crash events involving Model Year 2000 and newer cars, light trucks, and vans. The target injury outcome measure was developed by the Centers for Disease Control and Prevention (CDC)-led National Expert Panel on Field Triage in their recent revision of the Field Triage Decision Scheme (American College of Surgeons, 2006). The parameters to be used for crash injury prediction were subsequently specified by the National Expert Panel. Model input parameters included: crash direction (front, left, right, and rear), change in velocity (delta-V), multiple vs. single impacts, belt use, presence of at least one older occupant (≥ 55 years old), presence of at least one female in the vehicle, and vehicle type (car, pickup truck, van, and sport utility). The model was developed using predictor variables that may be readily available, post-crash, from OnStar-like telematics systems. Model sensitivity and specificity were 40% and 98%, respectively, using a probability cutpoint of 0.20. The area under the receiver operator characteristic (ROC) curve for the final model was 0.84. Delta-V (mph), seat belt use and crash direction were the most important predictors of serious injury. Due to the complexity of factors associated with rollover-related injuries, a separate screening algorithm is needed to model injuries associated with this crash mode. Copyright © 2010 Elsevier Ltd. All rights reserved.

  4. The type IIb supernova 2013df and its cool supergiant progenitor

    Energy Technology Data Exchange (ETDEWEB)

    Van Dyk, Schuyler D. [Spitzer Science Center/Caltech, Mail Code 220-6, Pasadena, CA 91125 (United States); Zheng, WeiKang; Fox, Ori D.; Clubb, Kelsey I.; Filippenko, Alexei V.; Kelly, Patrick L. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Cenko, S. Bradley [Astrophysics Science Division, NASA Goddard Space Flight Center, Mail Code 661, Greenbelt, MD 20771 (United States); Foley, Ryan J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Miller, Adam A. [Jet Propulsion Laboratory, MS 169-506, Pasadena, CA 91109 (United States); Smith, Nathan [Steward Observatory, University of Arizona, Tucson, AZ 85720 (United States); Lee, William H. [Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 70-264, Cd. Universitaria, México DF 04510 (Mexico); Ben-Ami, Sagi; Gal-Yam, Avishay, E-mail: vandyk@ipac.caltech.edu [Benoziyo Center for Astrophysics, The Weizmann Institute of Science, Rehovot 76100 (Israel)

    2014-02-01

    We have obtained early-time photometry and spectroscopy of supernova (SN) 2013df in NGC 4414. The SN is clearly of Type IIb, with notable similarities to SN 1993J. From its luminosity at secondary maximum light, it appears that less {sup 56}Ni (≲ 0.06 M {sub ☉}) was synthesized in the SN 2013df explosion than was the case for the SNe IIb 1993J, 2008ax, and 2011dh. Based on a comparison of the light curves, the SN 2013df progenitor must have been more extended in radius prior to explosion than the progenitor of SN 1993J. The total extinction for SN 2013df is estimated to be A{sub V} = 0.30 mag. The metallicity at the SN location is likely to be solar. We have conducted Hubble Space Telescope (HST) Target of Opportunity observations of the SN with the Wide Field Camera 3, and from a precise comparison of these new observations to archival HST observations of the host galaxy obtained 14 yr prior to explosion, we have identified the progenitor of SN 2013df to be a yellow supergiant, somewhat hotter than a red supergiant progenitor for a normal Type II-Plateau SN. From its observed spectral energy distribution, assuming that the light is dominated by one star, the progenitor had effective temperature T {sub eff} = 4250 ± 100 K and a bolometric luminosity L {sub bol} = 10{sup 4.94±0.06} L {sub ☉}. This leads to an effective radius R {sub eff} = 545 ± 65 R {sub ☉}. The star likely had an initial mass in the range of 13-17 M {sub ☉}; however, if it was a member of an interacting binary system, detailed modeling of the system is required to estimate this mass more accurately. The progenitor star of SN 2013df appears to have been relatively similar to the progenitor of SN 1993J.

  5. Urban Futures - Innovation Engines or Slums? A Stellar Evolution Model of Urban Growth

    Science.gov (United States)

    Shutters, S. T.; Timmes, F.; Desouza, K.

    2015-12-01

    Why, as cities grow in size and density, do some "ignite" into global engines of innovation and prosperity while others grow into dense slums? This is our overarching question as we explore a novel framework for thinking about the evolution of cities and, more specifically, the divergent trajectories they may take. We develop a speculative framework by examining the analogies between the evolution of cities and the evolution of stars. Like cities, stellar gas clouds can grow in mass, eventually reaching temperature and density thresholds at which they ignite the hydrogen fuel in their cores to become full-fledged stars. But not all gas and dust clouds share this fate. Some never achieve the critical conditions and do not unleash the energy we witness emanating from our own star. Some stars, after exhaustion of their initial fuel, evolve to incredible density but lack the temperature to ignite the next fuel needed to maintain the critical interactions that release so much energy. Instead they fade away to an object of intense density, but without the vibrant emission of light and energy associated with non-degenerate stars. The fate of cities, too, depends on the density of interactions - not of gas molecules, but of people. This elevated rate of face-to-face interactions in an urban core is critical for the transition to an innovative and creative economy. Yet, density is not enough, as evidenced both by many megacities in the developing world and degenerate stars. What is this missing element that, along with density, ignites a city and turns it into an innovation engine? With these analogies in mind, we explore whether they are useful for framing future research on cities, what questions they may help pose, and, more broadly, how physical, social, and natural scientists can all contribute to an interdisciplinary endeavor to understand cities more deeply.

  6. Concordance between phylogeographical and biogeographical patterns in the Brazilian Cerrado: diversification of the endemic tree Dalbergia miscolobium (Fabaceae).

    Science.gov (United States)

    Novaes, Renan Milagres Lage; Ribeiro, Renata Acácio; Lemos-Filho, José Pires; Lovato, Maria Bernadete

    2013-01-01

    Few studies have addressed the phylogeography of species of the Cerrado, the largest savanna biome of South America. Here we aimed to investigate the phylogeographical structure of Dalbergia miscolobium, a widespread tree from the Cerrado, and to verify its concordance with plant phylogeographical and biogeographical patterns so far described. A total of 287 individuals from 32 populations were analyzed by sequencing the trnL intron of the chloroplast DNA and the internal transcribed spacer of the nuclear ribosomal DNA. Analysis of population structure and tests of population expansion were performed and the time of divergence of haplotypes was estimated. Twelve and 27 haplotypes were identified in the cpDNA and nrDNA data, respectively. The star-like network configuration and the mismatch distributions indicated a recent spatial and demographic expansion of the species. Consistent with previous tree phylogeographical studies of Cerrado trees, the cpDNA also suggested a recent expansion towards the southern Cerrado. The diversity of D. miscolobium was widespread but high levels of genetic diversity were found in the Central Eastern and in the southern portion of Central Western Cerrado. The combined analysis of cpDNA and nrDNA supported a phylogeographic structure into seven groups. The phylogeographical pattern showed many concordances with biogeographical and phylogeographical studies in the Cerrado, mainly with the Cerrado phytogeographic provinces superimposed to our sampling area. The data reinforced the uniqueness of Northeastern and Southeastern Cerrados and the differentiation between Eastern and Western Central Cerrados. The recent diversification of the species (estimated between the Pliocene and the Pleistocene) and the 'genealogical concordances' suggest that a shared and persistent pattern of species diversification might have been present in the Cerrado over time. This is the first time that an extensive 'genealogical concordance' between

  7. Binaries discovered by the SPY project . V. GD 687 - a massive double degenerate binary progenitor that will merge within a Hubble time

    Science.gov (United States)

    Geier, S.; Heber, U.; Kupfer, T.; Napiwotzki, R.

    2010-06-01

    Aims: The ESO SN Ia Progenitor Survey (SPY) aims at finding merging double degenerate binaries as candidates for supernova type Ia (SN Ia) explosions. A white dwarf merger has also been suggested to explain the formation of rare types of stars like R CrB, extreme helium or He sdO stars. Here we present the hot subdwarf B binary GD 687, which will merge in less than a Hubble time. Methods: The orbital parameters of the close binary have been determined from time resolved spectroscopy. Since GD 687 is a single-lined binary, the spectra contain only information about the subdwarf primary and its orbit. From high resolution spectra the projected rotational velocity was derived. Assuming orbital synchronisation, the inclination of the system and the mass of the unseen companion were constrained. Results: The derived inclination is i = 39.3+6.2-5.6 °. The mass M2 = 0.71-0.21+0.22 M_⊙ indicates that the companion must be a white dwarf, most likely of C/O composition. This is only the fourth case that an sdB companion has been proven to be a white dwarf unambiguously. Its mass is somewhat larger than the average white dwarf mass, but may be as high as 0.93 M_⊙ in which case the total mass of the system comes close to the Chandrasekhar limit. Conclusions: GD 687 will evolve into a double degenerate system and merge to form a rare supermassive white dwarf with a mass in excess of solar. A death in a sub-Chandrasekhar supernova is also conceivable. Based on observations at the Paranal Observatory of the European Southern Observatory for programme No. 165.H-0588(A). Based on observations at the La Silla Observatory of the European Southern Observatory for programmes No. 072.D-0510(B), 079.D-0288(A), 080.D-0685(A) and 084.D-0348(A).

  8. Analyzing Crisis in Global Financial Indices

    Science.gov (United States)

    Kumar, Sunil; Deo, Nivedita

    We apply the Random Matrix Theory and complex network techniques to 20 global financial indices and study the correlation and network properties before and during the financial crisis of 2008 respectively. We find that the largest eigenvalue deviate significantly from the upper bound which shows a strong correlation between financial indices. By using a sliding window of 25 days we find that largest eigenvalue represent the collective information about the correlation between global financial indices and its trend indicate the market conditions. It is confirmed that eigenvectors corresponding to second largest eigenvalue gives useful information about the sector formation in the global financial indices. We find that these clusters are formed on the basis of the geographical location. The correlation network is constructed using threshold method for different values of threshold θ in the range 0 to 0.9, at θ=0.2 the network is fully connected. At θ=0.6, the Americas, Europe and Asia/Pacific form different clusters before the crisis but during the crisis Americas and Europe are strongly linked. If we further increase the threshold to 0.9 we find that European countries France, Germany and UK consistently constitute the most tightly linked markets before and during the crisis. We find that the structure of Minimum Spanning Tree before the crisis is more star like whereas during the crisis it changes to be more chain like. Using the multifractal analysis, we find that Hurst exponents of financial indices increases during the period of crisis as compared to the period before the crisis. The empirical results verify the validity of measures, and this has led to a better understanding of complex financial markets.

  9. Neutron Stars in X-ray Binaries and their Environments

    Science.gov (United States)

    Paul, Biswajit

    2017-09-01

    Neutron stars in X-ray binary systems are fascinating objects that display a wide range of timing and spectral phenomena in the X-rays. Not only parameters of the neutron stars, like magnetic field strength and spin period evolve in their active binary phase, the neutron stars also affect the binary systems and their immediate surroundings in many ways. Here we discuss some aspects of the interactions of the neutron stars with their environments that are revelaed from their X-ray emission. We discuss some recent developments involving the process of accretion onto high magnetic field neutron stars: accretion stream structure and formation, shape of pulse profile and its changes with accretion torque. Various recent studies of reprocessing of X-rays in the accretion disk surface, vertical structures of the accretion disk and wind of companion star are also discussed here. The X-ray pulsars among the binary neutron stars provide excellent handle to make accurate measurement of the orbital parameters and thus also evolution of the binray orbits that take place over time scale of a fraction of a million years to tens of millions of years. The orbital period evolution of X-ray binaries have shown them to be rather complex systems. Orbital evolution of X-ray binaries can also be carried out from timing of the X-ray eclipses and there have been some surprising results in that direction, including orbital period glitches in two X-ray binaries and possible detection of the most massive circum-binary planet around a Low Mass X-ray Binary.

  10. Emergence of gynodioecy in wild beet (Beta vulgaris ssp. maritima L.): a genealogical approach using chloroplastic nucleotide sequences

    Science.gov (United States)

    Fénart, Stéphane; Touzet, Pascal; Arnaud, Jean-François; Cuguen, Joël

    2006-01-01

    Gynodioecy is a breeding system where both hermaphroditic and female individuals coexist within plant populations. This dimorphism is the result of a genomic interaction between maternally inherited cytoplasmic male sterility (CMS) genes and bi-parentally inherited nuclear male fertility restorers. As opposed to other gynodioecious species, where every cytoplasm seems to be associated with male sterility, wild beet Beta vulgaris ssp. maritima exhibits a minority of sterilizing cytoplasms among numerous non-sterilizing ones. Many studies on population genetics have explored the molecular diversity of different CMS cytoplasms, but questions remain concerning their evolutionary dynamics. In this paper we report one of the first investigations on phylogenetic relationships between CMS and non-CMS lineages. We investigated the phylogenetic relationships between 35 individuals exhibiting different mitochondrial haplotypes. Relying on the high linkage disequilibrium between chloroplastic and mitochondrial genomes, we chose to analyse the nucleotide sequence diversity of three chloroplastic fragments (trnK intron, trnD–trnT and trnL–trnF intergenic spacers). Nucleotide diversity appeared to be low, suggesting a recent bottleneck during the evolutionary history of B. vulgaris ssp. maritima. Statistical parsimony analyses revealed a star-like genealogy and showed that sterilizing haplotypes all belong to different lineages derived from an ancestral non-sterilizing cytoplasm. These results suggest a rapid evolution of male sterility in this taxon. The emergence of gynodioecy in wild beet is confronted with theoretical expectations, describing either gynodioecy dynamics as the maintenance of CMS factors through balancing selection or as a constant turnover of new CMSs. PMID:16777728

  11. Impact of baseline geometry in processing of regional networks on resulting coordinates and ZTD time series

    Science.gov (United States)

    Stepniak, Katarzyna; Bock, Olivier; Wielgosz, Pawel

    2017-04-01

    The goal of this work is to determine the most accurate and homogeneous processing strategy to reprocess ground-based GNSS data from national networks for precise positioning and climate monitoring applications. We investigate the influence of the network geometry design strategy on the estimated coordinates of permanent stations and Zenith Total Delay (ZTD) time series. Three variants of processing were carried out and analyzed: 1) pre-defined network which usually contains baseline skeletons of reference stations and baselines to secondary stations forming a star-like structures with the main nodes connected to the reference skeleton; 2) the standard "obs-max" strategy available in Bernese GNSS Software; 3) a newly developed baselines design strategy optimized for ZTD estimation. The study shows that the network design has a strong impact especially on the quality and continuity of ZTD estimates. In case of sub-daily gaps in the measurements at reference stations, small clusters of stations can be disconnected from the main network in the first network strategy. This has little impact on coordinates, but offsets of a few centimeters in ZTD estimates and spikes in their formal errors can appear at all stations of the disconnected cluster. It is also responsible for significant discontinuities in the estimated ZTD series. Using the new developed network design strategy the reprocessed ZTD time series as well as time series of station positions are much more continuous and homogeneous in comparison to the standard approaches. Moreover, a post-processing screening procedure applied for ZTD and coordinates was applied to remove remaining outliers in time series. As a final screening and validation step, GNSS ZTD estimates were compared to ERA-Interim. The agreement between GNSS and ERA-Interim results with the new baseline design strategy and screening show a significant improvement.

  12. Progressive Loss of Retinal Ganglion Cells and Axons in Nonoptic Neuritis Eyes in Multiple Sclerosis: A Longitudinal Optical Coherence Tomography Study.

    Science.gov (United States)

    Graham, Elizabeth C; You, Yuyi; Yiannikas, Con; Garrick, Raymond; Parratt, John; Barnett, Michael H; Klistorner, Alexander

    2016-04-01

    To examine the rate of retinal ganglion cell (RGC) layer and retinal nerve fiber layer (RNFL) changes in nonoptic neuritis (NON) eyes of relapsing remitting multiple sclerosis (RRMS) patients, and to find a specific imaging parameter useful for identifying disease progression. Forty-five consecutive RRMS patients and 20 age- and sex-matched healthy subjects were enrolled. All patients were followed up for 3 years with annual optical coherence tomography (OCT) scans, which included a peripapillary ring scan protocol for RNFL analysis and a macular radial star-like scan to obtain RGC/inner plexiform layer (IPL) thickness measures. Healthy controls were scanned twice, 3 years apart. Retinal ganglion cell/inner plexiform layer and temporal RNFL (tRNFL) demonstrated highly significant thinning (P < 0.01), but all nasal segments and global RNFL (gRNFL) were not significantly different from normal controls. While receiver operating characteristics (ROC) analysis showed no advantage of RGC/IPL over tRNFL in cross-sectional detection of thinning, cut-off point based of fifth percentile in healthy controls demonstrated higher rate of abnormality for RGC/IPL. There was a significant progressive loss of RGC/IPL and tRNFL during the follow-up period. The largest thickness reduction was observed in tRNFL. ROC analysis demonstrated that tRNFL provided better sensitivity/specificity for detecting change over time than RGC/IPL (area under the curve [AUC] 0.78 vs. 0.52), which was confirmed by higher detection rate when 95th percentile of progression in healthy controls was used as a cut-off. This study confirmed significant thinning of RGC/IPL and tRNFL in NON eyes of RRMS patients. Progressive losses were more apparent on tRNFL, while RGC/IPL showed less change over the follow-up period.

  13. Chaotic Star Birth

    Science.gov (United States)

    2005-01-01

    [figure removed for brevity, see original site] [figure removed for brevity, see original site] Click on the image for Poster VersionClick on the image for IRAS 4B Inset Located 1,000 light years from Earth in the constellation Perseus, a reflection nebula called NGC 1333 epitomizes the beautiful chaos of a dense group of stars being born. Most of the visible light from the young stars in this region is obscured by the dense, dusty cloud in which they formed. With NASA's Spitzer Space Telescope, scientists can detect the infrared light from these objects. This allows a look through the dust to gain a more detailed understanding of how stars like our sun begin their lives. The young stars in NGC 1333 do not form a single cluster, but are split between two sub-groups. One group is to the north near the nebula shown as red in the image. The other group is south, where the features shown in yellow and green abound in the densest part of the natal gas cloud. With the sharp infrared eyes of Spitzer, scientists can detect and characterize the warm and dusty disks of material that surround forming stars. By looking for differences in the disk properties between the two subgroups, they hope to find hints of the star and planet formation history of this region. The knotty yellow-green features located in the lower portion of the image are glowing shock fronts where jets of material, spewed from extremely young embryonic stars, are plowing into the cold, dense gas nearby. The sheer number of separate jets that appear in this region is unprecedented. This leads scientists to believe that by stirring up the cold gas, the jets may contribute to the eventual dispersal of the gas cloud, preventing more stars from forming in NGC 1333. In contrast, the upper portion of the image is dominated by the infrared light from warm dust, shown as red.

  14. Hamlet's Transformation.

    Science.gov (United States)

    Usher, P. D.

    1997-12-01

    William Shakespeare's Hamlet has much evidence to suggest that the Bard was aware of the cosmological models of his time, specifically the geocentric bounded Ptolemaic and Tychonic models, and the infinite Diggesian. Moreover, Shakespeare describes how the Ptolemaic model is to be transformed to the Diggesian. Hamlet's "transformation" is the reason that Claudius, who personifies the Ptolemaic model, summons Rosencrantz and Guildenstern, who personify the Tychonic. Pantometria, written by Leonard Digges and his son Thomas in 1571, contains the first technical use of the word "transformation." At age thirty, Thomas Digges went on to propose his Perfit Description, as alluded to in Act Five where Hamlet's age is given as thirty. In Act Five as well, the words "bore" and "arms" refer to Thomas' vocation as muster-master and his scientific interest in ballistics. England's leading astronomer was also the father of the poet whose encomium introduced the First Folio of 1623. His oldest child Dudley became a member of the Virginia Company and facilitated the writing of The Tempest. Taken as a whole, such manifold connections to Thomas Digges support Hotson's contention that Shakespeare knew the Digges family. Rosencrantz and Guildenstern in Hamlet bear Danish names because they personify the Danish model, while the king's name is latinized like that of Claudius Ptolemaeus. The reason Shakespeare anglicized "Amleth" to "Hamlet" was because he saw a parallel between Book Three of Saxo Grammaticus and the eventual triumph of the Diggesian model. But Shakespeare eschewed Book Four, creating this particular ending from an infinity of other possibilities because it "suited his purpose," viz. to celebrate the concept of a boundless universe of stars like the Sun.

  15. Initial Assessment of the Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research (4STAR-Based Aerosol Retrieval: Sensitivity Study

    Directory of Open Access Journals (Sweden)

    Alexander Sinyuk

    2012-10-01

    Full Text Available The Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research (4STAR being developed for airborne measurements will offer retrievals of aerosol microphysical and optical properties from multi-angular and multi-spectral measurements of sky radiance and direct-beam sun transmittance. In this study, we assess the expected accuracy of the 4STAR-based aerosol retrieval and its sensitivity to major sources of anticipated perturbations in the 4STAR measurements. The major anticipated perturbations are (1 an apparent enhancement of sky radiance at small scattering angles associated with the necessarily compact design of the 4STAR and (2 an offset (i.e., uncertainty of sky radiance calibration independent of scattering angle. The assessment is performed through application of the operational AERONET aerosol retrieval and constructed synthetic 4STAR-like data. Particular attention is given to the impact of these perturbations on the broadband fluxes and the direct aerosol radiative forcing. The results from this study suggest that limitations in the accuracy of 4STAR-retrieved particle size distributions and scattering phase functions have diminished impact on the accuracy of retrieved bulk microphysical parameters, permitting quite accurate retrievals of properties including the effective radius (up to 10%, or 0.03, and the radiatively important optical properties, such as the asymmetry factor (up to 4%, or ±0.02 and single-scattering albedo (up to 6%, or ±0.04. Also, the obtained results indicate that the uncertainties in the retrieved aerosol optical properties are quite small in the context of the calculated fluxes and direct aerosol radiative forcing (up to 15%, or 3 W∙m−2.

  16. High-Resolution Spectroscopy of the Planetary Host HD 13189: Highly-Evolved and Metal-Poor

    Science.gov (United States)

    Kim, J. H.; Tinker, M. C., Jr.; Schuler, S. C.; King, J. R.; Hatzes, A. P.; Guenther, E. W.

    2005-12-01

    The preferred target for precise radial velocity (RV) exoplanetary surveys are aged main sequence (MS) late-F, G, and K dwarfs because 1) these stars are bright enough to obtain high S/N, high resolution spectra; 2) they have an ample number of spectral lines that can be used in the RV analyses; 3) their rotation rates and activity levels are low and thus facilitate the detection of planetary companions; and 4) finding planets orbiting stars like the Sun has a significant impact on Humanity. However, limiting exoplanet search programs to a small subset of the Galactic stellar population prohibits a full understanding of the formation, morphologies, and evolution of planetary systems. The Tautenburg Observatory Planet Search (TOPS) program is conducting a precise RV survey of evolved G and K giants in response of the paucity of known planetary hosts outside the solar-type dwarf regime and have recently announced the discovery of a giant planet orbiting the K2 II giant HD 13189; here, we present the results of our abundance analysis of HD 13189. We derive an Fe abundance of [Fe/H] = -0.58 ± 0.04, making HD 13189 one of the most metal-poor planetary hosts yet discovered. A census of metallicities of giant stars with planets reveals a metallicity distribution that is different than the well-known super-solar distribution of planet harboring MS dwarfs. Possible explanations for the difference are presented. Support for undergraduate students J.H. Kim and M.C. Tinker, Jr. is graciously provided by the NSF's Research Experience for Undergraduates (REU) program, award REU 0353849 to Clemson University. Support has also been provided by NSF grant AST 0239518 to J.R. King and a generous grant from the Charles Curry Foundation to Clemson University.

  17. High-resolution phylogenetics and phylogeography of human immunodeficiency virus type 1 subtype C epidemic in South America.

    Science.gov (United States)

    Véras, Nazle Mendonca Collaço; Gray, Rebecca R; Brígido, Luis Fernando de Macedo; Rodrigues, Rosângela; Salemi, Marco

    2011-07-01

    Human immunodeficiency virus type 1 subtype C (HIV-1C) represents 30-65% of HIV infections in southern Brazil, and isolated cases of HIV-1C infection have also been reported in Argentina, Uruguay, Paraguay and Venezuela. Phylogenetic studies have suggested that the Brazilian subtype C epidemic was initiated by the introduction of closely related strains. Nevertheless, because of sampling limitations, the point of entry and the timing of subtype C introduction into Brazil, as well as the origin of the founder lineage, remain controversial. The present study investigated the origin, spread and phylogeography of HIV-1C in South America. Phylogenetic analysis showed a well-supported monophyletic clade including all available strains from Brazil, Uruguay and Argentina. Only one lineage from Venezuela was unrelated to the epidemic involving the other three countries. Molecular clock and likelihood mapping analysis showed that HIV-1C introduction in Brazil dated back to the period 1960-1970, much earlier than previously thought, and was followed by a nearly simultaneous star-like outburst of viral lineages, indicating a subsequent rapid spread. Phylogeographic patterns suggested Paraná or Rio Grande do Sul as the possible entrance points of subtype C and an asymmetrical gene flow from Paraná to Sao Paulo, Santa Catarina and Rio Grande do Sul, as well as from Rio Grande do Sul to Sao Paulo fostered by the strong inter-connectivity between population centres in southern Brazil. The study illustrates how coupling phylogeography inference with geographical information system data is critical to understand the origin and dissemination of viral pathogens and potentially predict their future spread.

  18. The Clouds are breaking: tracing the Magellanic system with Gaia DR1 Mira variables

    Science.gov (United States)

    Deason, Alis J.; Belokurov, Vasily; Erkal, Denis; Koposov, Sergey E.; Mackey, Dougal

    2017-05-01

    We exploit the first data release from the Gaia mission to identify candidate Mira variables in the outskirts of the Magellanic Clouds. The repeated observations of sources during the initial phase of the Gaia mission is used to identify stars that show signs of variability. This variability information, combined with infrared photometry from Two Micron All Sky Survey and Wide-field Infrared Survey Explorer, allows us to select a clean sample of giants in the periphery of the Large Magellanic Cloud (LMC). We find evidence for Miras surrounding the LMC out to ˜20 deg in all directions, apart from the North-West quadrant. Our sample does not generally follow the gas distribution of the Magellanic system; Miras are notably absent in the gaseous bridge between the LMC and Small Magellanic Cloud (SMC), but they are likely related to the stellar RR Lyrae bridge reported by Belokurov et al. (2016). The stellar stream discovered by Mackey et al. (2016) to the North of the LMC is almost perfectly delineated by our Mira variables, and likely extends further East towards the Galactic plane. The presence of an intermediate-age population in this stream advocates an LMC disc origin. We also find a significant excess of Miras to the East of the LMC; these more diffusely distributed stars are likely stripped SMC stars due to interactions with the LMC. Miras are also identified in regions of the sky away from the Clouds; we locate stars likely associated with known massive substructures, and also find potential associations with stripped SMC debris above the Galactic plane.

  19. Detecting the Companions and Ellipsoidal Variations of RS CVn Primaries. II. o Draconis, a Candidate for Recent Low-mass Companion Ingestion

    Science.gov (United States)

    Roettenbacher, Rachael M.; Monnier, John D.; Fekel, Francis C.; Henry, Gregory W.; Korhonen, Heidi; Latham, David W.; Muterspaugh, Matthew W.; Williamson, Michael H.; Baron, Fabien; ten Brummelaar, Theo A.; Che, Xiao; Harmon, Robert O.; Schaefer, Gail H.; Scott, Nicholas J.; Sturmann, Judit; Sturmann, Laszlo; Turner, Nils H.

    2015-08-01

    To measure the stellar and orbital properties of the metal-poor RS CVn binary o Draconis (o Dra), we directly detect the companion using interferometric observations obtained with the Michigan InfraRed Combiner at Georgia State University's Center for High Angular Resolution Astronomy (CHARA) Array. The H-band flux ratio between the primary and secondary stars is the highest confirmed flux ratio (370 ± 40) observed with long-baseline optical interferometry. These detections are combined with radial velocity data of both the primary and secondary stars, including new data obtained with the Tillinghast Reflector Echelle Spectrograph on the Tillinghast Reflector at the Fred Lawrence Whipple Observatory and the 2 m Tennessee State University Automated Spectroscopic Telescope at Fairborn Observatory. We determine an orbit from which we find model-independent masses and ages of the components ({M}A=1.35+/- 0.05 {M}⊙ , {M}B=0.99+/- 0.02 {M}⊙ , system age = 3.0\\mp 0.5 Gyr). An average of a 23-year light curve of o Dra from the Tennessee State University Automated Photometric Telescope folded over the orbital period newly reveals eclipses and the quasi-sinusoidal signature of ellipsoidal variations. The modeled light curve for our system's stellar and orbital parameters confirm these ellipsoidal variations due to the primary star partially filling its Roche lobe potential, suggesting most of the photometric variations are not due to stellar activity (starspots). Measuring gravity darkening from the average light curve gives a best-fit of β =0.07+/- 0.03, a value consistent with conventional theory for convective envelope stars. The primary star also exhibits an anomalously short rotation period, which, when taken with other system parameters, suggests the star likely engulfed a low-mass companion that had recently spun-up the star.

  20. OT1_hmaness_1: Planets, Debris Disks, and the Lambda Bootis Stars

    Science.gov (United States)

    Maness, H.

    2010-07-01

    We propose to explore the link between lambda Bootis stars, debris disks, and planetesimal formation and evolution. The lambda Boo stars are a rare type of peculiar A star (2%), which are Population 1 and metal poor. Planet bearing systems and debris disk stars appear unusually well represented in the lambda Boo class: for example, beta Pic, Vega, and HR 8799 are all lambda Boo candidates. A small sample of 14 lambda Boo stars observed by Spitzer suggests an occurrence of infrared excess approaching 100%. Only two lambda Boo stars are included in the DEBRIS/DUNES Herschel key program debris disk surveys. We will use PACS/Herschel to make sensitive, high-resolution maps of 27 new lambda Boo stars. Like DEBRIS/DUNES, we will reach the stellar photosphere for all targets, enabling a measurement of the true rate of excess infrared emission among lambda Boo stars compared to normal A stars. The depletion pattern of heavy elements in the atmospheres of lambda Boo stars suggests they may have accreted gas from which dust grains have condensed and been removed: this gas may be circumstellar gas that has formed planetesimals or dusty interstellar gas. While the circumstellar disk scenario predicts sizes of a few hundred AU, the cloud accretion scenario predicts 1000-2000 AU bow structures oriented in the direction of the relative motion of the cloud and star. With target distances of stars outside of the low density Local Bubble: if interstellar medium interactions dominate the lambda Boo phenomenon then systematic variations in excess strength and morphology may occur with distance.

  1. Radiative transfer with scattering for domain-decomposed 3D MHD simulations of cool stellar atmospheres. Numerical methods and application to the quiet, non-magnetic, surface of a solar-type star

    Science.gov (United States)

    Hayek, W.; Asplund, M.; Carlsson, M.; Trampedach, R.; Collet, R.; Gudiksen, B. V.; Hansteen, V. H.; Leenaarts, J.

    2010-07-01

    Aims: We present the implementation of a radiative transfer solver with coherent scattering in the new BIFROST code for radiative magneto-hydrodynamical (MHD) simulations of stellar surface convection. The code is fully parallelized using MPI domain decomposition, which allows for large grid sizes and improved resolution of hydrodynamical structures. We apply the code to simulate the surface granulation in a solar-type star, ignoring magnetic fields, and investigate the importance of coherent scattering for the atmospheric structure. Methods: A scattering term is added to the radiative transfer equation, requiring an iterative computation of the radiation field. We use a short-characteristics-based Gauss-Seidel acceleration scheme to compute radiative flux divergences for the energy equation. The effects of coherent scattering are tested by comparing the temperature stratification of three 3D time-dependent hydrodynamical atmosphere models of a solar-type star: without scattering, with continuum scattering only, and with both continuum and line scattering. Results: We show that continuum scattering does not have a significant impact on the photospheric temperature structure for a star like the Sun. Including scattering in line-blanketing, however, leads to a decrease of temperatures by about 350 K below log10 τ5000 ⪉ -4. The effect is opposite to that of 1D hydrostatic models in radiative equilibrium, where scattering reduces the cooling effect of strong LTE lines in the higher layers of the photosphere. Coherent line scattering also changes the temperature distribution in the high atmosphere, where we observe stronger fluctuations compared to a treatment of lines as true absorbers.

  2. A new investigation of the possible X-ray counterparts of the magnetar candidate AX J1845-0258

    Science.gov (United States)

    Pintore, Fabio; Mereghetti, Sandro

    2016-07-01

    AX J1845-0258 is a transient X-ray pulsar, with spin period of 6.97 s, discovered with the ASCA satellite in 1993. Its soft spectrum and the possible association with a supernova remnant suggest that AX J1845-0258 might be a magnetar, but this has not been confirmed yet. A possible counterpart one order of magnitude fainter, AX J184453-025640, has been found in later X-ray observations, but no pulsations have been detected. In addition, some other X-ray sources are compatible with the pulsar location, which is in a crowded region of the Galactic plane. We have carried out a new investigation of all the X-ray sources in the ASCA error region of AX J1845-0258, using archival data obtained with Chandra in 2007 and 2010, and with XMM-Newton in 2010. We set an upper limit of 6 per cent on the pulsed fraction of AX J184453-025640 and confirmed its rather hard spectrum (power-law photon index of 1.2 ± 0.3). In addition to the other two fainter sources already reported in the literature, we found other X-ray sources positionally consistent with AX J1845-0258. Although many of them are possibly foreground stars likely unrelated to the pulsar, at least another new source, CXOU J184457.5-025823, could be a plausible counterpart of AX J1845-0258. It has a flux of 6 × 10-14 erg cm-2 s-1 and a spectrum well fitted by a power law with photon index ˜1.3 and NH ˜ 1022 cm-2.

  3. Epidermal sensory organs of moles, shrew moles, and desmans: a study of the family talpidae with comments on the function and evolution of Eimer's organ.

    Science.gov (United States)

    Catania, K C

    2000-09-01

    The epidermal sensory organs of members of the family Talpidae (moles, shrew-moles, and desmans) were investigated and compared to determine the range of sensory specializations and better understand how they evolved. Small domed mechanosensory organs called 'Eimer's organs' were present on the rhinarium of nearly all species of talpids, but not among the sister group of shrews (Soricidae) or other insectivore families. This suggests that the common ancestor to the talpids possessed Eimer's organs. Two species of moles from the driest habitats did not exhibit Eimer's organs - suggesting that their sensory organs degenerated in response to harsh, abrasive soil conditions. The semi-aquatic desmans uniquely possessed tiny sensory hairs interspersed with their Eimer's organs; these may act to sense water currents. Some species exhibited a subdivided, star-like, rhinarium - resembling an early embryonic stage of the star-nosed mole and providing clues to the evolution of the star. A single genera (Uropsilus) that branched off early in the evolution of the talpids had Eimer's organ-like structures but lacked some typical components. These findings fill a major gap in our knowledge of talpid sensory biology and suggest (1) how Eimer's organs evolved, (2) how the unusual appendages of the star-nosed mole evolved, (3) that the evolution of Eimer's organ is convergent with the mechanosensory push-rod of monotremes. The results also demonstrate the features that distinguish Eimer's organ from similar configurations of sensory receptors in other mammalian skin surfaces. Finally, a mechanism for Eimer's organ function in detecting object and prey specific surface features is proposed.

  4. Araucaria Project: Pulsating stars in binary systems and as distance indicators

    Science.gov (United States)

    Pilecki, Bogumił; Gieren, Wolfgang; Pietrzyński, Grzegorz; Smolec, Radosław

    2017-09-01

    Pulsating stars, like Cepheids or RR Lyrae stars, are ones of the most important distance indicators. They are also key objects for testing the predictions of stellar evolution and stellar pulsation theory. In the Araucaria Project we have studied these objects since 2002, measuring distances to the galaxies in the Local Group and beyond. In 2010 we have for the first time confirmed spectroscopically the existence of a classical Cepheid in an eclipsing binary system. This has opened an opportunity to study in great details and with high accuracy (better than 1%) the physical parameters of these very important objects. First dynamical mass determination (Mcep = 4.16 ± 0.03 M⊙) let us solve the long-standing mass discrepancy problem. Since then we have measured masses for 6 classical Cepheids in binary systems and determined projection factors for three of them. One of the analyzed systems was confirmed to consist of two first-overtone Cepheids. Type II Cepheids are recently becoming more important as distance indicators and astrophysics laboratory, although our knowledge of these stars is quite limited. Their evolutionary status is also not well understood and observational constraints are needed to confirm the current theories. We are presenting here our first results of the spectroscopic analysis of 4 of these systems. The masses of type II Cepheids seem consistent with the expected 0.5 - 0.6 M⊙. We also present first results of the fully modeled pulsator originally classified as peculiar W Vir star. The mass of this star is 1.51 ± 0.09 M⊙ and the p-factor 1.3 ± 0.03. It was eventually found not to belong to any typical Cepheid group.

  5. Histones bundle F-actin filaments and affect actin structure.

    Science.gov (United States)

    Blotnick, Edna; Sol, Asaf; Muhlrad, Andras

    2017-01-01

    Histones are small polycationic proteins complexed with DNA located in the cell nucleus. Upon apoptosis they are secreted from the cells and react with extracellular polyanionic compounds. Actin which is a polyanionic protein, is also secreted from necrotic cells and interacts with histones. We showed that both histone mixture (histone type III) and the recombinant H2A histone bundles F-actin, increases the viscosity of the F-actin containing solution and polymerizes G-actin. The histone-actin bundles are relatively insensitive to increase of ionic strength, unlike other polycation, histatin, lysozyme, spermine and LL-37 induced F-actin bundles. The histone-actin bundles dissociate completely only in the presence of 300-400 mM NaCl. DNA, which competes with F-actin for histones, disassembles histone induced actin bundles. DNase1, which depolymerizes F- to G-actin, actively unbundles the H2A histone induced but slightly affects the histone mixture induced actin bundles. Cofilin decreases the amount of F-actin sedimented by low speed centrifugation, increases light scattering and viscosity of F-actin-histone mixture containing solutions and forms star like superstructures by copolymerizing G-actin with H2A histone. The results indicate that histones are tightly attached to F-actin by strong electrostatic and hydrophobic forces. Since both histones and F-actin are present in the sputum of patients with cystic fibrosis, therefore, the formation of the stable histone-actin bundles can contribute to the pathology of this disease by increasing the viscosity of the sputum. The actin-histone interaction in the nucleus might affect gene expression.

  6. Rock paintings in Fern Cave, Lava Beds National Monument, California: Not the 1054 A.D. (Crab Nebula) Supernova

    Energy Technology Data Exchange (ETDEWEB)

    Armitage, R.A.; Hyman, M.; Rowe, M. W. [Texas A and M Univ., College Station, TX (United States). Dept. of Chemistry; Southon, J. [Lawrence Livermore National Lab., CA (United States). Center for Accelerator Mass Spectrometry; Barat, C. [Lava Beds National Monument, Tule Lake, CA (United States)

    1997-12-31

    On July 4, 1054 A.D. a supernova brighter than Venus appeared in the sky, remaining visible for approximately 23 days and 650 nights. It was chronicled in five independent historic accounts, four in China and one in Japan. For at least 40 years investigators have attributed certain distinctive rock paintings and carvings in the western United States as recordings of the 1054 A.D. supernova. More than twenty such depictions (circle or star-like symbols and a crescent) have been located. Two panels of rock paintings in Lava Beds National Monument, California, one at Fern Cave and one at Symbol Bridge, were listed as recording the 1054 A.D. supernova. The only direct means of assessing the likelihood that a `supernova` representation records the 1054 A.D. event is to date the rock painting or carving. At Texas A and M University, was developed a plasma-chemical extraction technique that permits to analyze the {sup 14}C in rock paintings, whether the pigments used were charcoal or inorganic Fe- and Mn- oxides and hydroxides with organic binder/vehicles. This paper presents direct {sup 14}C age estimates on a rock painting suggested to represent the 1054 A.D. supernova. Charcoal pigment samples were collected from three figures in proximity at Fern Cave: a crescent pointing downward and two nearby circles, one above and one below the crescent. The AMS {sup 14}C analysis on each sample using this technique show that these images do not represent the 1054 A.D. supernova. Paper no. 59; Extended abstract. 1 tab.

  7. Dynamics of Nuclear Regions of Galaxies

    Science.gov (United States)

    Miller, Richard H.

    1996-01-01

    Current research carried out with the help of the ASEE-NASA Summer Faculty Program, at NASA-Ames, is concentrated on the dynamics of nuclear regions of galaxies. From a dynamical point of view a galaxy is a collection of around 10(sup 11) stars like our Sun, each of which moves in the summed gravitational field of all the remaining stars. Thus galaxy dynamics becomes a self-consistent n-body problem with forces given by Newtonian gravitation. Strong nonlinearity in the gravitational force and the inherent nonlinearity of self-consistent problems both argue for a numerical approach. The technique of numerical experiments consis of constructing an environment in the computer that is as close as possible to the physical conditions in a real galaxy and then carrying out experiments much like laboratory experiments in physics or engineering, in this environment. Computationally, an experiment is an initial value problem, and a good deal of thought and effort goes into the design of the starting conditions that serve as initial values. Experiments are run at Ames because all the 'equipment' is in place-the programs, the necessary computational power, and good facilities for post-run analysis. Our goal for this research program is to study the nuclear regions in detail and this means replacing most of the galaxy by a suitable boundary condition to allow the full capability of numerical experiments to be brought to bear on a small region perhaps 1/1000 of the linear dimensions of an entire galaxy. This is an extremely delicate numerical problem, one in which some small feature overlook, can easily lead to a collapse or blow-up of the entire system. All particles attract each other in gravitational problems, and the 1/r(sup 2) force is: (1) nonlinear; (2) strong at short range; (3) long-range, and (4) unscreened at any distance.

  8. Does sleep deprivation alter functional EEG networks in children with focal epilepsy?

    Directory of Open Access Journals (Sweden)

    Eric evan Diessen

    2014-04-01

    Full Text Available Electroencephalography (EEG recordings after sleep deprivation increase the diagnostic yield in patients suspected of epilepsy if the routine EEG remains inconclusive. Sleep deprivation is associated with increased interictal EEG abnormalities in patients with epilepsy, but the exact mechanism is unknown. In this feasibility study, we used a network analytical approach to provide novel insights into this clinical observation. The aim was to characterize the effect of sleep deprivation on interictal functional network organization using a unique dataset of paired routine and sleep deprivation recordings in patients and controls. We included twenty-one children referred to the first seizure clinic of our center with suspected new onset focal epilepsy in whom a routine interictal and a sleep deprivation EEG (SD-EEG were performed. Seventeen children, in whom the diagnosis of epilepsy was excluded, served as controls. For both time points weighted functional networks were constructed based on interictal artifact free time-series. Routine and sleep deprivation networks were characterized at different frequency bands using minimum spanning tree (MST measures (leaf number and diameter and classical measures of integration (path length and segregation (clustering coefficient. A significant interaction was found for leaf number and diameter between patients and controls after sleep deprivation: patients showed a shift towards a more path-like MST network whereas controls showed a shift towards a more star-like MST network. This shift in network organization after sleep deprivation in patients is in accordance with previous studies showing a more regular network organization in the ictal state and might relate to the increased epileptiform abnormalities found in patients after sleep deprivation. Larger studies are needed to verify these results. Finally, MST measures were more sensitive in detecting network changes as compared to the classical measures of

  9. Stellar populations of BCGs, close companions and intracluster light in Abell 85, Abell 2457 and IIZw108

    Science.gov (United States)

    Edwards, L. O. V.; Alpert, H. S.; Trierweiler, I. L.; Abraham, T.; Beizer, V. G.

    2016-09-01

    We present the first results from an integral field unit (IFU) spectroscopic survey of a ˜75 kpc region around three brightest cluster galaxies (BCGs), combining over 100 IFU fibres to study the intracluster light (ICL). We fit population synthesis models to estimate age and metallicity. For Abell 85 and Abell 2457, the ICL is best-fit with a fraction of old, metal-rich stars like in the BCG, but requires 30-50 per cent young and metal-poor stars, a component not found in the BCGs. This is consistent with the ICL having been formed by a combination of interactions with less massive, younger, more metal-poor cluster members in addition to stars that form the BCG. We find that the three galaxies are in different stages of evolution and may be the result of different formation mechanisms. The BCG in Abell 85 is near a relatively young, metal-poor galaxy, but the dynamical friction time-scale is long and the two are unlikely to be undergoing a merger. The outer regions of Abell 2457 show a higher relative fraction of metal-poor stars, and we find one companion, with a higher fraction of young, metal-poor stars than the BCG, which is likely to merge within a gigayear. Several luminous red galaxies are found at the centre of the cluster IIZw108, with short merger time-scales, suggesting that the system is about to embark on a series of major mergers to build up a dominant BCG. The young, metal-poor component found in the ICL is not found in the merging galaxies.

  10. Mitochondrial DNA variation in space and time in the northeastern Pacific gastropod, Littorina keenae.

    Science.gov (United States)

    Lee, Hyuk Je; Boulding, Elizabeth G

    2007-08-01

    The present population structure of a species reflects the influence of population history as well as contemporary processes. To examine the relative importance of these factors in shaping the current population structure of Littorina keenae, we sequenced 762 base pairs of the mitochondrial ND6 and cytochrome b genes in 584 snails from 13 sites along the northeastern Pacific coast. Haplotype network analysis revealed a 'star-like' genealogy indicative of a recent population expansion. Nested clade and mismatch analyses also supported the hypothesis of sudden population expansion following a population bottleneck during the Last Glacial Maximum. Analysis of molecular variance and pairwise Phi(ST) showed no significant spatial population differentiation from Mexico to Oregon - not even across the recognized biogeographic boundary at Point Conception. This is probably due to high contemporary gene flow during the free-swimming larval stage of this snail. Surprisingly, we found a highly significant temporal population differentiation between a San Pedro sample from 1996 and one from 2005, which gave an estimate of effective population size (N(e)) of only 135. Nearly statistically significant changes in the frequency of a particular haplotype in three other populations over 2-3 years further support Hedgecock's 'sweepstakes' hypothesis. When by chance nearly all of the progeny from an aggregation of highly fecund sisters that possess a rare haplotype successfully recruit to become the next generation, the rare haplotype can become temporarily common across the entire species' range. This modification of the sweepstakes hypothesis can explain why the temporal variation that we observed was much greater than the spatial variation.

  11. Measuring the opacity of stellar interior matter in terrestrial laboratories

    Science.gov (United States)

    Bailey, James

    2015-11-01

    How does energy propagate from the core to the surface of the Sun, where it emerges to warm the Earth? Nearly a century ago Eddington recognized that the attenuation of radiation by stellar matter controls the internal structure of stars like the sun. Opacities for high energy density (HED) matter are challenging to calculate because accurate and complete descriptions of the energy levels, populations, and plasma effects such as continuum lowering and line broadening are needed for partially ionized atoms. This requires approximations, in part because billions of bound-bound and bound-free electronic transitions can contribute to the opacity. Opacity calculations, however, have never been benchmarked against laboratory measurements at stellar interior conditions. Laboratory opacity measurements were limited in the past by the challenges of creating and diagnosing sufficiently large and uniform samples at the extreme conditions found inside stars. In research conducted over more than 10 years, we developed an experimental platform on the Z facility and measured wavelength-resolved iron opacity at electron temperatures Te = 156-195 eV and densities ne = 0.7-4.0 x 1022 cm-3 - conditions very similar to the radiation/convection boundary zone within the Sun. The wavelength-dependent opacity in the 975-1775 eV photon energy range is 30-400% higher than models predict. This raises questions about how well we understand the behavior of atoms in HED plasma. These measurements may also help resolve decade-old discrepancies between solar model predictions and helioseismic observations. This talk will provide an overview of the measurements, investigations of possible errors, and ongoing experiments aimed at testing hypotheses to resolve the model-data discrepancy. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under contract DE-AC04-94AL85000.

  12. Unknown Aspects of Self-Assembly of PbS Microscale Superstructures

    Science.gov (United States)

    Querejeta-Fernández, Ana; Hernández-Garrido, Juan C.; Yang, Hengxi; Zhou, Yunlong; Varela, Aurea; Parras, Marina; Calvino-Gámez, José J.; González-Calbet, Jose M.; Green, Peter F.; Kotov, Nicholas A.

    2012-01-01

    A lot of interesting and sophisticated examples of nanoparticle (NP) self-assembly (SA) are known. From both fundamental and technological standpoints this field requires advancements in three principle directions: a) understanding the mechanism and driving forces of three-dimensional (3D) SA with both nano- and micro-levels of organization; b) understanding of disassembly/deconstruction processes; and c) finding synthetic methods of assembly into continuous superstructures without insulating barriers. From this perspective, we investigated the formation of well-known star-like PbS superstructures and found a number of previously unknown or overlooked aspects that can advance the knowledge of NP self-assembly in these three directions. The primary one is that the formation of large seemingly monocrystalline PbS superstructures with multiple levels of octahedral symmetry can be explained only by SA of small octahedral NPs. We found five distinct periods in the formation PbS hyperbranched stars: 1) nucleation of early PbS NPs with an average diameter of 31 nm; 2) assembly into 100–500 nm octahedral mesocrystals; 3) assembly into 1000–2500 nm hyperbranched stars; 4) assembly and ionic recrystallization into six-arm rods accompanied by disappearance of fine nanoscale structure; 5) deconstruction into rods and cubooctahedral NPs. The switches in assembly patterns between the periods occur due to variable dominance of pattern–determining forces that include vander Waals and electrostatic (charge-charge, dipole-dipole, and polarization) interactions. The superstructure deconstruction is triggered by chemical changes in the deep eutectic solvent (DES) used as the media. PbS superstructures can be excellent models for fundamental studies of nanoscale organization and SA manufacturing of (opto)electronics and energy harvesting devices which require organization of PbS components at multiple scales. PMID:22515512

  13. A High-resolution Multiband Survey of Westerlund 2 with the Hubble Space Telescope. III. The Present-day Stellar Mass Function

    Science.gov (United States)

    Zeidler, Peter; Nota, Antonella; Grebel, Eva K.; Sabbi, Elena; Pasquali, Anna; Tosi, Monica; Christian, Carol

    2017-03-01

    We present a detailed analysis of the spatial distribution of the stellar population and the present-day mass function (PDMF) of the Westerlund 2 (Wd2) region using the data from our high-resolution multiband survey with the Hubble Space Telescope. We used state-of-the-art artificial star tests to determine spatially resolved completeness maps for each of the broadband filters. We reach a level of completeness of 50% down to F555W=24.8 mag (0.7 {M}ȯ ) and F814W=23.3 mag (0.2 {M}ȯ ) in the optical and F125W=20.2 mag and F160W=19.4 mag (both 0.12 {M}ȯ ) in the infrared throughout the field of view. We had previously reported that the core of Wd2 consists of two clumps: namely the main cluster and the northern clump. From the spatial distribution of the completeness-corrected population, we find that their stellar surface densities are 1114 {stars} {{pc}}-2 and 555 {stars} {{pc}}-2, respectively, down to F814W=21.8 mag. We find that the PDMF of Wd2 has a slope of {{Γ }}=-1.46+/- 0.06, which translates to a total stellar cluster mass of (3.6+/- 0.3)\\cdot {10}4 {M}ȯ . The spatial analysis of the PDMF reveals that the cluster population is mass-segregated and most likely primordial. In addition, we report the detection of a stellar population of spatially uniformly distributed low-mass (< 0.15 {M}ȯ ) stars, extending into the gas ridges of the surrounding gas and dust cloud, as well as a confined region of reddened stars, likely caused by a foreground CO cloud. We find hints that a cloud–cloud collision might be the origin of the formation of Wd2.

  14. Hip joint centre position estimation using a dual unscented Kalman filter for computer-assisted orthopaedic surgery.

    Science.gov (United States)

    Beretta, Elisa; De Momi, Elena; Camomilla, Valentina; Cereatti, Andrea; Cappozzo, Aurelio; Ferrigno, Giancarlo

    2014-09-01

    In computer-assisted knee surgery, the accuracy of the localization of the femur centre of rotation relative to the hip-bone (hip joint centre) is affected by the unavoidable and untracked pelvic movements because only the femoral pose is acquired during passive pivoting manoeuvres. We present a dual unscented Kalman filter algorithm that allows the estimation of the hip joint centre also using as input the position of a pelvic reference point that can be acquired with a skin marker placed on the hip, without increasing the invasiveness of the surgical procedure. A comparative assessment of the algorithm was carried out using data provided by in vitro experiments mimicking in vivo surgical conditions. Soft tissue artefacts were simulated and superimposed onto the position of a pelvic landmark. Femoral pivoting made of a sequence of star-like quasi-planar movements followed by a circumduction was performed. The dual unscented Kalman filter method proved to be less sensitive to pelvic displacements, which were shown to be larger during the manoeuvres in which the femur was more adducted. Comparable accuracy between all the analysed methods resulted for hip joint centre displacements smaller than 1 mm (error: 2.2 ± [0.2; 0.3] mm, median ± [inter-quartile range 25%; inter-quartile range 75%]) and between 1 and 6 mm (error: 4.8 ± [0.5; 0.8] mm) during planar movements. When the hip joint centre displacement exceeded 6 mm, the dual unscented Kalman filter proved to be more accurate than the other methods by 30% during multi-planar movements (error: 5.2 ± [1.2; 1] mm).

  15. High Energy Density Plasmas (HEDP) for studies of basic nuclear science relevant to Stellar and Big Bang Nucleosynthesis

    Science.gov (United States)

    Frenje, Johan

    2014-06-01

    Thermonuclear reaction rates and nuclear processes have been explored traditionally by means of conventional accelerator experiments, which are difficult to execute at conditions relevant to stellar nucleosynthesis. Thus, nuclear reactions at stellar energies are often studied through extrapolations from higher-energy data or in low-background underground experiments. Even when measurements are possible using accelerators at relevant energies, thermonuclear reaction rates in stars are inherently different from those in accelerator experiments. The fusing nuclei are surrounded by bound electrons in accelerator experiments, whereas electrons occupy mainly continuum states in a stellar environment. Nuclear astrophysics research will therefore benefit from an enlarged toolkit for studies of nuclear reactions. In this presentation, we report on the first use of High Energy Density Plasmas for studies of nuclear reactions relevant to basic nuclear science, stellar and Big Bang nucleosynthesis. These experiments were carried out at the OMEGA laser facility at University of Rochester and the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory, in which spherical capsules were irradiated with powerful lasers to compress and heat the fuel to high enough temperatures and densities for nuclear reactions to occur. Four experiments will be highlighted in this presentation. In the first experiment, the differential cross section for the elastic neutron-triton (n-T) scattering at 14.1 MeV was measured with significantly higher accuracy than achieved in accelerator experiments. In the second experiment, the T(t,2n)4He reaction, a mirror reaction to the 3He(3He,2p)4He reaction that plays an important role in the proton-proton chain that transforms hydrogen into ordinary 4He in stars like our Sun, was studied at energies in the range 15-40 keV. In the third experiment, the 3He+3He solar fusion reaction was studied directly, and in the fourth experiment, we

  16. HD 106906 b: A PLANETARY-MASS COMPANION OUTSIDE A MASSIVE DEBRIS DISK

    Energy Technology Data Exchange (ETDEWEB)

    Bailey, Vanessa; Reiter, Megan; Morzinski, Katie; Males, Jared; Su, Kate Y. L.; Hinz, Philip M.; Stark, Daniel; Close, Laird M.; Follette, Katherine B.; Rodigas, Timothy [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Meshkat, Tiffany; Kenworthy, Matthew [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands); Mamajek, Eric [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627-0171 (United States); Briguglio, Runa; Puglisi, Alfio; Xompero, Marco [Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, I-50125 Firenze (Italy); Weinberger, Alycia J., E-mail: vbailey@as.arizona.edu [Carnegie Institution of Washington, Department of Terrestrial Magnetism, 5241 Broad Branch Road NW, Washington, DC 20015 (United States)

    2014-01-01

    We report the discovery of a planetary-mass companion, HD 106906 b, with the new Magellan Adaptive Optics (MagAO) + Clio2 system. The companion is detected with Clio2 in three bands: J, K{sub S} , and L', and lies at a projected separation of 7.''1 (650 AU). It is confirmed to be comoving with its 13 ± 2 Myr F5 host using Hubble Space Telescope Advanced Camera for Surveys astrometry over a time baseline of 8.3 yr. DUSTY and COND evolutionary models predict that the companion's luminosity corresponds to a mass of 11 ± 2 M {sub Jup}, making it one of the most widely separated planetary-mass companions known. We classify its Magellan/Folded-Port InfraRed Echellette J/H/K spectrum as L2.5 ± 1; the triangular H-band morphology suggests an intermediate surface gravity. HD 106906 A, a pre-main-sequence Lower Centaurus Crux member, was initially targeted because it hosts a massive debris disk detected via infrared excess emission in unresolved Spitzer imaging and spectroscopy. The disk emission is best fit by a single component at 95 K, corresponding to an inner edge of 15-20 AU and an outer edge of up to 120 AU. If the companion is on an eccentric (e > 0.65) orbit, it could be interacting with the outer edge of the disk. Close-in, planet-like formation followed by scattering to the current location would likely disrupt the disk and is disfavored. Furthermore, we find no additional companions, though we could detect similar-mass objects at projected separations >35 AU. In situ formation in a binary-star-like process is more probable, although the companion-to-primary mass ratio, at <1%, is unusually small.

  17. The Full-sky Astrometric Mapping Explorer - An optical, astrometric survey mission

    Science.gov (United States)

    Horner, S. D.; Germain, M. E.; Greene, T. P.; Harris, F. H.; Harris, H. C.; Johnson, M. S.; Johnston, K. J.; Monet, D. G.; Murison, M. A.; Phillips, J. D.; Reasenberg, R. D.; Seidelmann, P. K.; Urban, S. E.; Vassar, R. H.

    1999-12-01

    The Full-sky Astrometric Mapping Explorer (FAME) is a NASA MIDEX mission scheduled for launch in 2004. It will perform an all sky, astrometric survey with unprecedented accuracy. FAME will determine the positions, parallaxes, proper motions, and photometry of 40,000,000 stars with visual band magnitudes 5 DSS colors. FAME will enable a wide range of scientific investigations using its large, rich database of information on stellar properties. It will: * Calibrate the zero point of the extragalactic distance scale to 1% * Determine absolute luminosities of a wide range of spectral types * Detect a meaningful statistical sample of companion stars, brown dwarfs, and giant planets * Enable studies of the kinematics of our galaxy, including the effect of dark matter in the disk * Characterize stellar variability of a large sample of stars at the 0.1% level * Define a rigid optical reference frame for future scientific endeavors FAME is evolved from design concepts from the Hipparcos mission, using current CCD technology to observe more and fainter stars. Like Hipparcos, FAME has a compound mirror consisting of two flats angled relative to each other. The compound mirror feeds the two fields of view separated by the ``basic angle'' into a common telescope. The two fields of view are used to control the growth of stochastic errors in determining the relative separations of stars. FAME is a joint development effort of the U.S. Naval Observatory, the Naval Research Laboratory, Lockheed Martin Missiles and Space Advanced Technology Center, and the Smithsonian Astrophysical Observatory. Funding for FAME is provided by the NASA Office of Space Science through the Explorer program managed by Goddard Space Flight Center. Additional funding has been provided by the U.S. Navy. http://www.usno.navy.mil/fame

  18. Is traumatic axonal injury (AI) associated with an early microglial activation? Application of a double-labeling technique for simultaneous detection of microglia and AI.

    Science.gov (United States)

    Oehmichen, M; Theuerkauf, I; Meissner, C

    1999-05-01

    The aim of the present study was to determine whether axonal injury (AI) induces a microglial reaction within 15 days after brain trauma. In 40 selected cases of confirmed AI, the topographical relation of AI and microglial reaction was assessed using an immunohistochemical double-labeling technique for simultaneous demonstration of AI using beta-amyloid precursor protein (beta-APP) antibody and of microglia using CD68 antibody. Although traumatic injury was usually followed by a moderate early diffuse rise in the number of CD68-reactive cells in the white matter, increases in macrophages in areas of AI accumulation were only sporadic and did not occur until after 4 days. At survival intervals of 5-15 days a moderate microglial reaction in regions of beta-APP-positive injured axons was detected, at maximum, in half of the case material. During this interval AI-associated satellitosis-like clusters or stars described by other authors after a survival time of more than 7 weeks were an isolated phenomenon. The prolonged microglial reaction as well as the reduction of beta-APP-positive AI during longer survival periods supports the hypothesis that AI is not primarily chemotactically attractive and that the damage to a portion of beta-APPstained axons may be partly reversible. Most cases clearly require a prolonged interval of more than 15 days before initiation of the final scavenger reaction. For forensic purposes the increase in the number of microglial cells within the region of AI accumulation after a survival time of more than 5 days and the multiple and distinct demonstration of star-like microglial reactions within the white matter after survival times exceeding 7 weeks may provide valuable postmortem information on the timing of a traumatic event.

  19. Learning Resources on Ultraviolet Astronomy: The Shuttle-Borne Spacelab/Astro Missions

    Science.gov (United States)

    Waller, W. H.; Stecher, T. P.

    1994-12-01

    Beyond the blue, beyond the violet, and into the ultraviolet part of the electromagnetic spectrum, the radiant universe appears strangely altered. At these shorter wavelengths and higher photon energies, the hottest stars shine brightly, while the cooler more common stars like the Sun virtually disappear from view. Clusters and associations of young stars are dominated by just a few massive ultraviolet-bright stars, while ancient globular clusters are reduced to their hottest, most rapidly evolving members. Spiral galaxies that look like graceful pinwheels in visible-light images are transformed into knotty webs --- each knot containing thousands of young hot stars. And the space between the stars, clusters, and galaxies appears profoundly black --- up to 100 times darker than the nighttime sky as seen at visible wavelengths. Until the last decade, our view of the ultraviolet universe was impeded by the stratospheric ozone layer that protects life on Earth from the Sun's harmful UV radiation. Subsequent balloon, sounding rocket, and satellite flights have yielded fascinating glimpses of the ultraviolet universe. In 1990, the Space Shuttle Columbia flew the Spacelab/Astro-1 mission. Astro is the first and only true astronomical observatory to operate onboard the Space Shuttle. It consists of 3 ultraviolet telescopes which are attached to a single pointing system in the Shuttle bay. During the Astro-1 mission, these instruments obtained UV images and spectra of hundreds of astronomical objects. Learning resources relating to this mission include a new slide set and booklet, ``Beyond the Blue: Greatest Hits of the Ultraviolet Imaging Telescope,'' which is being distributed by the ASP through its mail-order catalogue. There is also a teacher's guide with activities, ``Astro-1: Seeing in a New Light'' which is available from the NASA Teacher Resource Laboratories. Sources of information on the upcoming flight of Spacelab/Astro-2 aboard the Endeavour (currently scheduled

  20. Genetic variability of Echinococcus granulosus complex in various geographical populations of Iran inferred by mitochondrial DNA sequences.

    Science.gov (United States)

    Spotin, Adel; Mahami-Oskouei, Mahmoud; Harandi, Majid Fasihi; Baratchian, Mehdi; Bordbar, Ali; Ahmadpour, Ehsan; Ebrahimi, Sahar

    2017-01-01

    To investigate the genetic variability and population structure of Echinococcus granulosus complex, 79 isolates were sequenced from different host species covering human, dog, camel, goat, sheep and cattle as of various geographical sub-populations of Iran (Northwestern, Northern, and Southeastern). In addition, 36 sequences of other geographical populations (Western, Southeastern and Central Iran), were directly retrieved from GenBank database for the mitochondrial cytochrome c oxidase subunit 1 (cox1) gene. The confirmed isolates were grouped as G1 genotype (n=92), G6 genotype (n=14), G3 genotype (n=8) and G2 genotype (n=1). 50 unique haplotypes were identified based on the analyzed sequences of cox1. A parsimonious network of the sequence haplotypes displayed star-like features in the overall population containing IR23 (22: 19.1%) as the most common haplotype. According to the analysis of molecular variance (AMOVA) test, the high value of haplotype diversity of E. granulosus complex was shown the total genetic variability within populations while nucleotide diversity was low in all populations. Neutrality indices of the cox1 (Tajima's D and Fu's Fs tests) were shown negative values in Western-Northwestern, Northern and Southeastern populations which indicating significant divergence from neutrality and positive but not significant in Central isolates. A pairwise fixation index (Fst) as a degree of gene flow was generally low value for all populations (0.00647-0.15198). The statistically Fst values indicate that Echinococcus sensu stricto (genotype G1-G3) populations are not genetically well differentiated in various geographical regions of Iran. To appraise the hypothetical evolutionary scenario, further study is needed to analyze concatenated mitogenomes and as well a panel of single locus nuclear markers should be considered in wider areas of Iran and neighboring countries.

  1. Pattern of genetic differentiation of an incipient speciation process: The case of the high Andean killifish Orestias.

    Science.gov (United States)

    Guerrero-Jiménez, Claudia Jimena; Peña, Fabiola; Morales, Pamela; Méndez, Marco; Sallaberry, Michel; Vila, Irma; Poulin, Elie

    2017-01-01

    During the Pleistocene and Holocene, the southwest Andean Altiplano (17°-22°S) was affected by repeated fluctuations in water levels, high volcanic activity and major tectonic movements. In the early Holocene the humid Tauca phase shifted to the arid conditions that have lasted until the present, producing endorheic rivers, lakes, lagoons and wetlands. The endemic fish Orestias (Cyprinodontidae) represents a good model to observe the genetic differentiation that characterizes an incipient speciation process in allopatry since the morphospecies described inhabit a restricted geographic area, with present habitat fragmentation. The genetic diversity and population structure of four endemic morphospecies of Orestias (Cyprinodontidae) found in the Lauca National Park (LNP) analyzed with mitochondrial markers (Control Region) and eight microsatellites, revealed the existence of genetic groups that matches the fragmentation of these systems. High values of genetic and phylogeographic differentiation indices were observed between Chungará Lake and Piacota lagoon. The group composed of the Lauca River, Copapujo and Chuviri wetlands sampling sites showed a clear signal of expansion, with a star-like haplotype network. Levels of genetic differentiation were lower than in Chungará and Piacota, suggesting that these localities would have differentiated after the bottlenecks linked to the collapse of Parinacota volcano. The Parinacota sample showed a population signal that differed from the other localities revealing greater genetic diversity and a disperse network, presenting haplotypes shared with other LNP localities. A mixing pattern of the different genetic groups was evident using the microsatellite markers. The chronology of the vicariance events in LNP may indicate that the partition process of the Orestias populations was gradual. Considering this, and in view of the genetic results, we may conclude that the morphospecies from LNP are populations in ongoing

  2. Rich club organization of macaque cerebral cortex and its role in network communication.

    Directory of Open Access Journals (Sweden)

    Logan Harriger

    Full Text Available Graph-theoretical analysis of brain connectivity data has revealed significant features of brain network organization across a range of species. Consistently, large-scale anatomical networks exhibit highly nonrandom attributes including an efficient small world modular architecture, with distinct network communities that are interlinked by hub regions. The functional importance of hubs motivates a closer examination of their mutual interconnections, specifically to examine the hypothesis that hub regions are more densely linked than expected based on their degree alone, i.e. forming a central rich club. Extending recent findings of rich club topology in the cat and human brain, this report presents evidence for the existence of rich club organization in the cerebral cortex of a non-human primate, the macaque monkey, based on a connectivity data set representing a collation of numerous tract tracing studies. Rich club regions comprise portions of prefrontal, parietal, temporal and insular cortex and are widely distributed across network communities. An analysis of network motifs reveals that rich club regions tend to form star-like configurations, indicative of their central embedding within sets of nodes. In addition, rich club nodes and edges participate in a large number of short paths across the network, and thus contribute disproportionately to global communication. As rich club regions tend to attract and disperse communication paths, many of the paths follow a characteristic pattern of first increasing and then decreasing node degree. Finally, the existence of non-reciprocal projections imposes a net directional flow of paths into and out of the rich club, with some regions preferentially attracting and others dispersing signals. Overall, the demonstration of rich club organization in a non-human primate contributes to our understanding of the network principles underlying neural connectivity in the mammalian brain, and further supports

  3. Rotten Egg Nebula

    Science.gov (United States)

    1999-01-01

    Violent gas collisions that produced supersonic shock fronts in a dying star are seen in a new, detailed image from NASA's Hubble Space Telescope. The picture, taken by Hubble's Wide Field and Planetary Camera 2, is online at http://www.jpl.nasa.gov/images/wfpc . The camera was designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Stars like our Sun will eventually die and expel most of their material outward into shells of gas and dust. These shells eventually form some of the most beautiful objects in the universe, called planetary nebulae. 'This new image gives us a rare view of the early death throes of stars like our Sun. For the first time, we can see phenomena leading to the formation of planetary nebulae. Until now, this had only been predicted by theory, but had never been seen directly,' said Dr. Raghvendra Sahai, research scientist and member of the science team at JPL for the Wide Field and Planetary Camera 2. The object is sometimes called the Rotten Egg Nebula, because it contains a lot of sulphur, which would produce an awful odor if one could smell in space. The object is also known as the Calabash Nebula or by the technical name OH231.8+4.2. The densest parts of the nebula are composed of material ejected recently by the central star and accelerated in opposite directions. This material, shown as yellow in the image, is zooming away at speeds up to one and a half million kilometers per hour (one million miles per hour). Most of the star's original mass is now contained in these bipolar gas structures. A team of Spanish and American astronomers used NASA's Hubble Space Telescope to study how the gas stream rams into the surrounding material, shown in blue. They believe that such interactions dominate the formation process in planetary nebulae. Due to the high speed of the gas, shock-fronts are formed on impact and heat the surrounding gas. Although computer calculations have predicted the existence and structure of such shocks for

  4. Rotten Egg Nebula

    Science.gov (United States)

    1999-01-01

    Violent gas collisions that produced supersonic shock fronts in a dying star are seen in a new, detailed image from NASA's Hubble Space Telescope. The picture, taken by Hubble's Wide Field and Planetary Camera 2, is online at http://www.jpl.nasa.gov/images/wfpc . The camera was designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Stars like our Sun will eventually die and expel most of their material outward into shells of gas and dust. These shells eventually form some of the most beautiful objects in the universe, called planetary nebulae. 'This new image gives us a rare view of the early death throes of stars like our Sun. For the first time, we can see phenomena leading to the formation of planetary nebulae. Until now, this had only been predicted by theory, but had never been seen directly,' said Dr. Raghvendra Sahai, research scientist and member of the science team at JPL for the Wide Field and Planetary Camera 2. The object is sometimes called the Rotten Egg Nebula, because it contains a lot of sulphur, which would produce an awful odor if one could smell in space. The object is also known as the Calabash Nebula or by the technical name OH231.8+4.2. The densest parts of the nebula are composed of material ejected recently by the central star and accelerated in opposite directions. This material, shown as yellow in the image, is zooming away at speeds up to one and a half million kilometers per hour (one million miles per hour). Most of the star's original mass is now contained in these bipolar gas structures. A team of Spanish and American astronomers used NASA's Hubble Space Telescope to study how the gas stream rams into the surrounding material, shown in blue. They believe that such interactions dominate the formation process in planetary nebulae. Due to the high speed of the gas, shock-fronts are formed on impact and heat the surrounding gas. Although computer calculations have predicted the existence and structure of such shocks for

  5. Inflation Fossils in Cosmic Structure

    Science.gov (United States)

    Kamionkowski, Marc

    these models. In a somewhat different vein, we propose to study adaptive strategies for cosmological measurements. Considerable resources are being invested in the ongoing search for B modes in the CMB polarization. This search can be performed on a small patch of sky, but it is optimized by finding the patch of sky that is cleanest of foregrounds. We propose to develop adaptive survey strategies, using lessons learned from the analogous multi-armed bandit problem in probability theory, to optimize B mode searches. Preliminary estimates suggest that such a strategy can improve the sensitivity to primordial gravitational waves by factors of at least 2--3, and possibly much more. We then plan to study the possibility to apply similar strategies to the search for 21-cm fluctuations from the epoch of reionization (EoR) and also to identify an optimal field for a possible JWST deep field survey. Finally, CO intensity mapping has recently been identified as a new and promising probe of the EoR. However, CO intensity mapping may also be used to study large-scale structure at intermediate redshifts (z~1-6) that are important for inflation, dark-energy, and galaxy formation. We propose to calculate angular power spectra of the CO intensity at these redshifts and estimate sensitivities to signals and forecast parameter estimation for various experimental configurations. This work will be essential to guide the development of experiments to seek this signal. In summary, the proposed research will open new avenues to probe the beginning of time with the CMB and LSS, optimize several ongoing measurements, and lay the theoretical groundwork to open a new experimental avenue toward LSS. The proposed research is well aligned with the goals of NASA's Physics of the Cosmos Program. It will provide theoretical support to several current and in-the-pipeline NASA missions and help guide the development of new missions.

  6. Insights into high mass star formation from methanol maser observations

    Science.gov (United States)

    Farmer, Hontas Freeman

    2013-06-01

    We present high angular resolution data on Class I and Class II methanol masers, together with other tracers of star formation like H2O masers, ultracompact (UC) ionized hydrogen (H II) regions, and 4.5 um infrared sources, taken from the literature. The aim is to study what these data tell us about the process of high mass star formation; in particular, whether disk-outflow systems are compatible with the morphology exhibited by Class I and Class II methanol masers. Stars form in the dense cores inside molecular clouds, and while the process of the formation of stars like our Sun is reasonably well understood, details of the formation of stars with masses eight times that of our Sun or greater, the so-called high mass stars, remain a mystery. Being compact and bright sources, masers provide an excellent way to observe high mass star forming regions. In particular, Class II methanol masers are found exclusively in high mass star forming regions. Based on the positions of the Class I and II methanol and H2O masers, UCHII regions and 4.5 um infrared sources, and the center velocities (vLSR) of the Class I methanol and H2O masers, compared to the vLSR of the Class II methanol masers, we propose three disk-outflow models that may be traced by methanol masers. In all three models, we have located the Class II methanol maser near the protostar, and the Class I methanol maser in the outflow, as is known from observations during the last twenty years. In our first model, the H2O masers trace the linear extent of the outflow. In our second model, the H2O masers are located in a circumstellar disk. In our third model, the H2O masers are located in one or more outflows near the terminating shock where the outflow impacts the ambient interstellar medium. Together, these models reiterate the utility of coordinated high angular resolution observations of high mass star forming regions in maser lines and associated star formation tracers.

  7. Starchitect: Building Worlds and Learning Astronomy on Facebook and Beyond

    Science.gov (United States)

    Harold, J. B.; Hines, D. C.

    2014-12-01

    Our team at the National Center for Interactive Learning at the Space Science Institute has developed Starchitect, an end-to-end stellar and planetary evolution game available both on Facebook and externally. Supported by NSF and NASA, the game uses the "sporadic play" model of games such as Farmville, where players might only take actions a few times a day, but continue playing for months. This framework is an excellent fit for teaching about the evolution of stars and planets. Players select regions of the galaxy to build their systems, and watch as they evolve in scaled real time (a million years to the minute). Massive stars will supernova within minutes, while lower mass stars like our sun will live for weeks, possibly evolving life before passing through a red giant stage and ending their lives as white dwarfs. Starchitect provides a wide variety of opportunities for communicating astronomy concepts, targeting known misconceptions, and encouraging players to dig deeper through external sites. The game directly addresses stellar lifecycles, habitable zones, and the roles of giant worlds in creating habitable solar systems as part of its core design. Meanwhile minigames can focus on additional concepts. For instance, the game's solar system visualization engine allows players to "fake" planetary scales to create more attractive images of their systems (which can then be posted to their Facebook wall), but this ability must be unlocked through completion of a minigame that looks at the relative scales of planets, moons, and solar system distances. Starchitect also incorporates current science through links to external content, science "Factlets", all-sky maps generated by missions, and more. Finally, the game is heavily instrumented to allow us to analyze the resulting gameplay in conjunction with Facebook's demographic data. This presentation will focus on the release, evaluation, and ongoing refinement of the game as well as its overall goals, which include

  8. Effects of finiteness on the thermo-fluid-dynamics of natural convection above horizontal plates

    Science.gov (United States)

    Guha, Abhijit; Sengupta, Sayantan

    2016-06-01

    A rigorous and systematic computational and theoretical study, the first of its kind, for the laminar natural convective flow above rectangular horizontal surfaces of various aspect ratios ϕ (from 1 to ∞) is presented. Two-dimensional computational fluid dynamic (CFD) simulations (for ϕ → ∞) and three-dimensional CFD simulations (for 1 ≤ ϕ cases, with the complex three-dimensional solutions revealed here. The present computational study establishes the region of a high-aspect-ratio planform over which the results of the similarity theory are approximately valid, the extent of this region depending on the Grashof number. There is, however, a region near the edge of the plate and another region near the centre of the plate (where a plume forms) in which the similarity theory results do not apply. The sizes of these non-compliance zones decrease as the Grashof number is increased. The present study also shows that the similarity velocity profile is not strictly obtained at any location over the plate because of the entrainment effect of the central plume. The 3-D CFD simulations of the present paper are coordinated to clearly reveal the separate and combined effects of three important aspects of finiteness: the presence of leading edges, the presence of planform centre, and the presence of physical corners in the planform. It is realised that the finiteness due to the presence of physical corners in the planform arises only for a finite value of ϕ in the case of 3-D CFD simulations (and not in 2-D CFD simulations or similarity theory). The presence of physical corners is related here to several significant aspects of the solution - the conversion of in-plane velocity to out-of-plane velocity near the diagonals, the star-like non-uniform distribution of surface heat flux on heated planforms, the three-dimensionality of the temperature field, and the complex spatial structure of the velocity iso-surfaces. A generic theoretical correlation for the Nusselt

  9. Turbulent Compressible Convection with Rotation. 2; Mean Flows and Differential Rotation

    Science.gov (United States)

    Brummell, Nicholas H.; Hurlburt, Neal E.; Toomre, Juri

    1998-01-01

    The effects of rotation on turbulent, compressible convection within stellar envelopes are studied through three-dimensional numerical simulations conducted within a local f-plane model. This work seeks to understand the types of differential rotation that can be established in convective envelopes of stars like the Sun, for which recent helioseismic observations suggest an angular velocity profile with depth and latitude at variance with many theoretical predictions. This paper analyzes the mechanisms that are responsible for the mean (horizontally averaged) zonal and meridional flows that are produced by convection influenced by Coriolis forces. The compressible convection is considered for a range of Rayleigh, Taylor, and Prandtl (and thus Rossby) numbers encompassing both laminar and turbulent flow conditions under weak and strong rotational constraints. When the nonlinearities are moderate, the effects of rotation on the resulting laminar cellular convection leads to distinctive tilts of the cell boundaries away from the vertical. These yield correlations between vertical and horizontal motions that generate Reynolds stresses that can drive mean flows, interpretable as differential rotation and meridional circulations. Under more vigorous forcing, the resulting turbulent convection involves complicated and contorted fluid particle trajectories, with few clear correlations between vertical and horizontal motions, punctuated by an evolving and intricate downflow network that can extend over much of the depth of the layer. Within such networks are some coherent structures of vortical downflow that tend to align with the rotation axis. These yield a novel turbulent alignment mechanism, distinct from the laminar tilting of cellular boundaries, that can provide the principal correlated motions and thus Reynolds stresses and subsequently mean flows. The emergence of such coherent structures that can persist amidst more random motions is a characteristic of turbulence

  10. Molecular and evolutionary bases of within-patient genotypic and phenotypic diversity in Escherichia coli extraintestinal infections.

    Directory of Open Access Journals (Sweden)

    Maxime Levert

    Full Text Available Although polymicrobial infections, caused by combinations of viruses, bacteria, fungi and parasites, are being recognised with increasing frequency, little is known about the occurrence of within-species diversity in bacterial infections and the molecular and evolutionary bases of this diversity. We used multiple approaches to study the genomic and phenotypic diversity among 226 Escherichia coli isolates from deep and closed visceral infections occurring in 19 patients. We observed genomic variability among isolates from the same site within 11 patients. This diversity was of two types, as patients were infected either by several distinct E. coli clones (4 patients or by members of a single clone that exhibit micro-heterogeneity (11 patients; both types of diversity were present in 4 patients. A surprisingly wide continuum of antibiotic resistance, outer membrane permeability, growth rate, stress resistance, red dry and rough morphotype characteristics and virulence properties were present within the isolates of single clones in 8 of the 11 patients showing genomic micro-heterogeneity. Many of the observed phenotypic differences within clones affected the trade-off between self-preservation and nutritional competence (SPANC. We showed in 3 patients that this phenotypic variability was associated with distinct levels of RpoS in co-existing isolates. Genome mutational analysis and global proteomic comparisons in isolates from a patient revealed a star-like relationship of changes amongst clonally diverging isolates. A mathematical model demonstrated that multiple genotypes with distinct RpoS levels can co-exist as a result of the SPANC trade-off. In the cases involving infection by a single clone, we present several lines of evidence to suggest diversification during the infectious process rather than an infection by multiple isolates exhibiting a micro-heterogeneity. Our results suggest that bacteria are subject to trade-offs during an infectious

  11. Principal stages in evolution of precambrian organic world: Communication 2. The late proterozoic

    Science.gov (United States)

    Sergeev, V. N.; Semikhatov, M. A.; Fedonkin, M. A.; Vorob'eva, N. G.

    2010-12-01

    A new suggested model outlining the evolution of the organic world from the mid-Early Proterozoic (˜2.0 Ga) to the Early Cambrian is based on data characterizing the relevant chert-embedded and compression-preserved organic-walled microbiotas, impressions of soft-bodied multicellular organisms, and biomarkers. Critical analysis of overall paleontological data resulted in the distinguishing of seven successive assemblages of Proterozoic micro- and macrofossils. Being of global geographic range, the assemblages correspond to the major stages in evolution of the organic world and typify global units which are termed the Labradorian (˜2.0-1.65 Ga), Anabarian (1.65-1.2 Ga), Turukhanian (1.2-1.03 Ga), Uchuromayan (1.03-0.85 Ga), Yuzhnouralian (0.85-0.635 Ga), Amadeusian (0.635-0.56 Ga), and Belomorian (0.56-0.535 Ga). Characteristic of the Labradorian unit are microfossil assemblages of the Gunflint type including remains of morphologically bizarre prokaryotic microorganisms: star-like Eoastrion, umbrella-shaped Kakabekia, dumbbell-shaped Xenothrix, and some others. Fine-grained siliciclastic deposits of the same age yield the oldest remains of millimeter-sized eukaryotes: spherical to ribbon-like Chuaria and Tawuia. Microfossils prevailing in shallow-water carbonate facies of the Anabarian unit are akinetes of nostocalean cyanophyceae Archaeoellipsoides and entophysalidacean cyanobacteria Eoentophysalis, whereas acanthomorphic acritarchs Tappania and Shuiyousphaeridium dominate the assemblages of open-shelf facies, where they are associated with the first-found rare macroscopic multicellular fossils Horodyskia. The distinguishing feature of the next Turukhanian unit is the first occurrence of filamentous red alga Bangiomorpha and the stalked cyanobacterium Polybessurus. The Uchuromayan unit is characterized by the appearance and worldwide radiation of structurally complicated eukaryotic microorganisms, primarily of acanthomorphic acritarchs Trachyhystrichosphaera and

  12. Spatial distribution of charged particles along the ion-optical axis in electron cyclotron resonance ion sources. Experimental results

    Energy Technology Data Exchange (ETDEWEB)

    Panitzsch, Lauri

    2013-02-08

    The experimental determination of the spatial distribution of charged particles along the ion-optical axis in electron cyclotron resonance ion sources (ECRIS) defines the focus of this thesis. The spatial distributions of different ion species were obtained in the object plane of the bending magnet ({approx}45 cm downstream from the plasma electrode) and in the plane of the plasma electrode itself, both in high spatial resolution. The results show that each of the different ion species forms a bloated, triangular structure in the aperture of the plasma electrode. The geometry and the orientation of these structures are defined by the superposition of the radial and axial magnetic fields. The radial extent of each structure is defined by the charge of the ion. Higher charge states occupy smaller, more concentrated structures. The total current density increases towards the center of the plasma electrode. The circular and star-like structures that can be observed in the beam profiles of strongly focused, extracted ion beams are each dominated by ions of a single charge state. In addition, the spatially resolved current density distribution of charged particles in the plasma chamber that impinge on the plasma electrode was determined, differentiating between ions and electrons. The experimental results of this work show that the electrons of the plasma are strongly connected to the magnetic field lines in the source and thus spatially well confined in a triangular-like structure. The intensity of the electrons increases towards the center of the plasma electrode and the plasma chamber, as well. These electrons are surrounded by a spatially far less confined and less intense ion population. All the findings mentioned above were already predicted in parts by simulations of different groups. However, the results presented within this thesis represent the first (and by now only) direct experimental verification of those predictions and are qualitatively transferable to

  13. Preliminary data on Trachurus picturatus (Bowdich 1825 phylogeography inferred from mitochondrial DNA sequence data

    Directory of Open Access Journals (Sweden)

    Cláudia Filipa Moreira

    2015-11-01

    Full Text Available The populations of marine pelagic fishes, in particular the migratory ones as the Trachurus picturatus (Bowdich 1825, may be erroneously considered an homogenous population unit because they show broad geographic distributions, large population sizes and high migratory movements. The blue jack mackerel, T. picturatus is widely distributed in the NE Atlantic and also found in the Mediterranean and Black Seas. It is an economically important resource in the Macaronesian islands of Azores, Madeira and Canaries, but despite its fishery value and ecological importance, fluctuations in the landings are difficult to explain since studies regarding the population dynamics, stocks structure, fish movements and habitat connectivity are inexistent. Moreover, genetic methods that can act as a complementary tool for stock identification and population dynamics have never been applied to this species. The blue jack mackerel was sampled by artisanal fleets in the Islands of Azores, Madeira and Canaries, and at the Portuguese mainland - Matosinhos, Peniche and Portimão -during the spring-summer of 2013. A tissue sample was taken from each individual and stored in 96% ethanol for molecular analysis. Total DNA was successfully extracted, followed by a Polymerase Chain Reaction amplification of part of the cytochrome b gene (Cyt b. Amplifications and sequencing of the Cyt b gene were carried out using published primers used for the Carangidae family (Cárdenas et al. 2005. Sequences from Greece and Turkey, available on GenBank, were added to our sequences and all analysed together. In total 46 sequences were analysed, including the closely related outgroup (Trachurus Trachurus. Preliminary results show that there are sequences in the GenBank that are incorrectly assigned to this species. In addition, within the samples collected one was proven to be T. Trachurus. Preliminary phylogeographic analyses revealed a very shallow phylogenetic tree and a star-like

  14. Mitochondrial echoes of first settlement and genetic continuity in El Salvador.

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    Antonio Salas

    Full Text Available BACKGROUND: From Paleo-Indian times to recent historical episodes, the Mesoamerican isthmus played an important role in the distribution and patterns of variability all around the double American continent. However, the amount of genetic information currently available on Central American continental populations is very scarce. In order to shed light on the role of Mesoamerica in the peopling of the New World, the present study focuses on the analysis of the mtDNA variation in a population sample from El Salvador. METHODOLOGY/PRINCIPAL FINDINGS: We have carried out DNA sequencing of the entire control region of the mitochondrial DNA (mtDNA genome in 90 individuals from El Salvador. We have also compiled more than 3,985 control region profiles from the public domain and the literature in order to carry out inter-population comparisons. The results reveal a predominant Native American component in this region: by far, the most prevalent mtDNA haplogroup in this country (at approximately 90% is A2, in contrast with other North, Meso- and South American populations. Haplogroup A2 shows a star-like phylogeny and is very diverse with a substantial proportion of mtDNAs (45%; sequence range 16090-16365 still unobserved in other American populations. Two different Bayesian approaches used to estimate admixture proportions in El Salvador shows that the majority of the mtDNAs observed come from North America. A preliminary founder analysis indicates that the settlement of El Salvador occurred about 13,400+/-5,200 Y.B.P.. The founder age of A2 in El Salvador is close to the overall age of A2 in America, which suggests that the colonization of this region occurred within a few thousand years of the initial expansion into the Americas. CONCLUSIONS/SIGNIFICANCE: As a whole, the results are compatible with the hypothesis that today's A2 variability in El Salvador represents to a large extent the indigenous component of the region. Concordant with this

  15. Surface, electrical and mechanical modifications of PMMA after implantation with laser produced iron plasma ions

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, Qazi Salman; Bashir, Shazia, E-mail: shaziabashir@gcu.edu.pk; Jalil, Sohail Abdul; Shabbir, Muhammad Kaif; Mahmood, Khaliq; Akram, Mahreen; Khalid, Ayesha; Yaseen, Nazish; Arshad, Atiqa

    2016-07-01

    Laser Produced Plasma (LPP) was employed as an ion source for the modifications in surface, electrical and mechanical properties of poly methyl (methacrylate) PMMA. For this purpose Nd:YAG laser (532 nm, 6 ns, 10 Hz) at a fluence of 12.7 J/cm{sup 2} was employed to generate Fe plasma. The fluence and energy measurements of laser produced Fe plasma ions were carried out by employing Thomson Parabola Technique in the presence of magnetic field strength of 0.5 T, using CR-39 as Solid State Nuclear Track Detector (SSNTD). It has been observed that ion fluence ejecting from ablated plasma was maximum at an angle of 5° with respect to the normal to the Fe target surface. PMMA substrates were irradiated with Fe ions of constant energy of 0.85 MeV at various ion fluences ranging from 3.8 × 10{sup 6} ions/cm{sup 2} to 1.8 × 10{sup 8} ions/cm{sup 2} controlled by varying laser pulses from 3000 to 7000. Optical microscope and Scanning Electron Microscope (SEM) were utilized for the analysis of surface features of irradiated PMMA. Results depicted the formation of chain scission, crosslinking, dendrites and star like structures. To explore the electrical behavior, four probe method was employed. The electrical conductivity of ion irradiated PMMA was increased with increasing ion fluence. The surface hardness was measured by shore D hardness tester and results showed the monotonous increment in surface hardness with increasing ion fluence. The increasing trend of surface hardness and electrical conductivity with increasing Fe ion fluence has been well correlated with the surface morphology of ion implanted PMMA. The temperature rise of PMMA surface due to Fe ion irradiation is evaluated analytically and comes out to be in the range of 1.72 × 10{sup 4} to 1.82 × 10{sup 4} K. The values of total Linear Energy Transfer (LET) or stopping power of 0.8 MeV Fe ions in PMMA is 61.8 eV/Å and their range is 1.34 μm evaluated by SRIM simulation.

  16. Gene migration for re-emerging amebiasis in Iran's northwest-Iraq borders: a microevolutionary scale for reflecting epidemiological drift of Entamoeba histolytica metapopulations.

    Science.gov (United States)

    Mohammadzadeh, Asad; Spotin, Adel; Mahami-Oskouei, Mahmoud; Haghighi, Ali; Zebardast, Nozhat; Kohansal, Kobra

    2017-01-01

    In the microevolutionary scales of Entamoeba isolates, the gene migration shows how Entamoeba spp. has epidemiologically drifted among border countries. Five hundred fecal samples were taken from patients suffering gastrointestinal disorders, abdominal pain, and diarrhea at Saggez, northwest Iran located within the border Iraq country. Following parasitological techniques, DNA samples were extracted and amplified by polymerase chain reaction (PCR) of 18S rRNA region to identify Entamoeba infections. To distinguish the Entamoeba spp., a multiplex PCR was conducted. Amplicons were sequenced to reconfirm their heterogeneity traits and phylogenetic analysis. Additionally, Entamoeba histolytica sequences of Iraq were retrieved from GenBank database. The suspected isolates were diagnosed as E. histolytica (2.2 %), Entamoeba moshkovskii (1 %), and Entamoeba dispar (0.4 %). Mixed Entamoeba infections did not detect among isolates. A parsimonious network of the sequence haplotypes displayed star-like features in the overall isolates containing E.h1, E.d2, and E.m3 as the most common haplotypes. According to analysis of molecular variance (AMOVA) test, high partial value of haplotype diversity (0.700 to 0.800) of E. histolytica was shown the total genetic variability within populations while nucleotide diversity was low among Iranian and Iraqi metapopulations. Neutrality indices of the 18S rRNA were shown negative values in E. histolytica populations which indicating significant deviations from neutrality. A pairwise fixation index (F-statistics [Fst]) as a degree of gene flow had a low value for all populations (0.001) while the number of migrants was 2.48. The statistically Fst value indicates that E. histolytica isolates are not genetically differentiated among shared isolates of Iran and Iraq. Occurrence of E.h1 between two regional populations indicates that there is dawn of Entamoeba flow due to transfer of alleles from one population to another population through

  17. Massive star formation by accretion. I. Disc accretion

    Science.gov (United States)

    Haemmerlé, L.; Eggenberger, P.; Meynet, G.; Maeder, A.; Charbonnel, C.

    2016-01-01

    Context. Massive stars likely form by accretion and the evolutionary track of an accreting forming star corresponds to what is called the birthline in the Hertzsprung-Russell (HR) diagram. The shape of this birthline is quite sensitive to the evolution of the entropy in the accreting star. Aims: We first study the reasons why some birthlines published in past years present different behaviours for a given accretion rate. We then revisit the question of the accretion rate, which allows us to understand the distribution of the observed pre-main-sequence (pre-MS) stars in the HR diagram. Finally, we identify the conditions needed to obtain a large inflation of the star along its pre-MS evolution that may push the birthline towards the Hayashi line in the upper part of the HR diagram. Methods: We present new pre-MS models including accretion at various rates and for different initial structures of the accreting core. We compare them with previously published equivalent models. From the observed upper envelope of pre-MS stars in the HR diagram, we deduce the accretion law that best matches the accretion history of most of the intermediate-mass stars. Results: In the numerical computation of the time derivative of the entropy, some treatment leads to an artificial loss of entropy and thus reduces the inflation that the accreting star undergoes along the birthline. In the case of cold disc accretion, the existence of a significant swelling during the accretion phase, which leads to radii ≳ 100 R⊙ and brings the star back to the red part of the HR diagram, depends sensitively on the initial conditions. For an accretion rate of 10-3M⊙ yr-1, only models starting from a core with a significant radiative region evolve back to the red part of the HR diagram. We also obtain that, in order to reproduce the observed upper envelope of pre-MS stars in the HR diagram with an accretion law deduced from the observed mass outflows in ultra-compact HII regions, the fraction of the

  18. Hierarchies of Models: Toward Understanding Planetary Nebulae

    Science.gov (United States)

    Knuth, Kevin H.; Hajian, Arsen R.; Clancy, Daniel (Technical Monitor)

    2003-01-01

    Stars like our sun (initial masses between 0.8 to 8 solar masses) end their lives as swollen red giants surrounded by cool extended atmospheres. The nuclear reactions in their cores create carbon, nitrogen and oxygen, which are transported by convection to the outer envelope of the stellar atmosphere. As the star finally collapses to become a white dwarf, this envelope is expelled from the star to form a planetary nebula (PN) rich in organic molecules. The physics, dynamics, and chemistry of these nebulae are poorly understood and have implications not only for our understanding of the stellar life cycle but also for organic astrochemistry and the creation of prebiotic molecules in interstellar space. We are working toward generating three-dimensional models of planetary nebulae (PNe), which include the size, orientation, shape, expansion rate and mass distribution of the nebula. Such a reconstruction of a PN is a challenging problem for several reasons. First, the data consist of images obtained over time from the Hubble Space Telescope (HST) and spectra obtained from Kitt Peak National Observatory (KPNO) and Cerro Tololo Inter-American Observatory (CTIO). These images are of course taken from a single viewpoint in space, which amounts to a very challenging tomographic reconstruction. Second, the fact that we have two disparate and orthogonal data types requires that we utilize a method that allows these data to be used together to obtain a solution. To address these first two challenges we employ Bayesian model estimation using a parameterized physical model that incorporates much prior information about the known physics of the PN. In our previous works we have found that the forward problem of the comprehensive model is extremely time consuming. To address this challenge, we explore the use of a set of hierarchical models, which allow us to estimate increasingly more detailed sets of model parameters. These hierarchical models of increasing complexity are akin

  19. Evolution and biogeography of an emerging quasispecies: diversity patterns of the fish Viral Hemorrhagic Septicemia virus (VHSv).

    Science.gov (United States)

    Pierce, Lindsey R; Stepien, Carol A

    2012-05-01

    -designated IVc in marine/estuarine North Atlantic waters (five haplotypes). Two separate substrains independently appeared in the Northwestern Pacific region (Asia) in 1996, with Ib originating from the west and IVa from the east. Our results depict an evolutionary history of relatively rapid population diversifications in star-like patterns, following a quasispecies model. This study provides a baseline for future tracking of VHSv spread and interpreting its evolutionary diversification pathways.

  20. The properties of ten O-type stars in the low-metallicity galaxies IC 1613, WLM, and NGC 3109

    Science.gov (United States)

    Tramper, F.; Sana, H.; de Koter, A.; Kaper, L.; Ramírez-Agudelo, O. H.

    2014-12-01

    Context. Massive stars likely played an important role in the reionization of the Universe, and the formation of the first black holes. They are potential progenitors of long-duration gamma-ray bursts, seen up to redshifts of about ten. Massive stars in low-metallicity environments in the local Universe are reminiscent of their high redshift counterparts, emphasizing the importance of the study of their properties and evolution. In a previous paper, we reported on indications that the stellar winds of low-metallicity O stars may be stronger than predicted, which would challenge the current paradigm of massive star evolution. Aims: In this paper, we aim to extend our initial sample of six O stars in low-metallicity environments by four. The total sample of ten stars consists of the optically brightest sources in IC 1613, WLM, and NGC 3109. We aim to derive their stellar and wind parameters, and compare these to radiation-driven wind theory and stellar evolution models. Methods: We have obtained intermediate-resolution VLT/X-shooter spectra of our sample of stars. We derive the stellar parameters by fitting synthetic fastwindline profiles to the VLT/X-shooter spectra using a genetic fitting algoritm. We compare our parameters to evolutionary tracks and obtain evolutionary masses and ages. We also investigate the effective temperature versus spectral type calibration for SMC and lower metallicities. Finally, we reassess the wind momentum versus luminosity diagram. Results: The derived parameters of our target stars indicate stellar masses that reach values of up to 50 M⊙. The wind strengths of our stars are, on average, stronger than predicted from radiation-driven wind theory and reminiscent of stars with an LMC metallicity. We discuss indications that the iron content of the host galaxies is higher than originally thought and is instead SMC-like. We find that the discrepancy with theory is reduced, but remains significant for this higher metallicity. This may