WorldWideScience

Sample records for unitary-response selection mechanism

  1. Unitary Response Regression Models

    Science.gov (United States)

    Lipovetsky, S.

    2007-01-01

    The dependent variable in a regular linear regression is a numerical variable, and in a logistic regression it is a binary or categorical variable. In these models the dependent variable has varying values. However, there are problems yielding an identity output of a constant value which can also be modelled in a linear or logistic regression with…

  2. Selected topics of fluid mechanics

    Science.gov (United States)

    Kindsvater, Carl E.

    1958-01-01

    the Euler, Froude, Reynolds, Weber, and Cauchy numbers are defined as essential tools for interpreting and using experimental data. The derivations of the energy and momentum equations are treated in detail. One-dimensional equations for steady nonuniform flow are developed, and the restrictions applicable to the equations are emphasized. Conditions of uniform and gradually varied flow are discussed, and the origin of the Chezy equation is examined in relation to both the energy and the momentum equations. The inadequacy of all uniform-flow equations as a means of describing gradually varied flow is explained. Thus, one of the definitive problems of river hydraulics is analyzed in the light of present knowledge. This report is the outgrowth of a series of short schools conducted during the spring and summer of 1953 for engineers of the Surface Water Branch, Water Resources Division, U. S. Geological Survey. The topics considered are essentially the same as the topics selected for inclusion in the schools. However, in order that they might serve better as a guide and outline for informal study, the arrangement of the writer's original lecture notes has been considerably altered. The purpose of the report, like the purpose of the schools which inspired it, is to build a simple but strong framework of the fundamentals of fluid mechanics. It is believed that this framework is capable of supporting a detailed analysis of most of the practical problems met by the engineers of the Geological Survey. It is hoped that the least accomplishment of this work will be to inspire the reader with the confidence and desire to read more of the recent and current technical literature of modern fluid mechanics.

  3. Physicochemical Mechanics of Materials (Selected Articles),

    Science.gov (United States)

    1986-03-05

    85 L4. Ln FOREIGN TECHNOLOGY DIVISION c- I DTIC _S 2LECTIE IIII 8~ ~~11 ---- - PHYSICOCHEMICAL MECHANICS OF MATERIALS - (Selected Articles) I""." .j...FTD-86-c-o01583 PHYSICOCHEMICAL MECHANICS OF MATERIALS (Selected Articles) English pages: 8 Source: Fiziko-Khimicheskaya Mekhanika Materialov, Nr. 4

  4. Realization and performance of cryogenic selection mechanisms

    Science.gov (United States)

    Aitink-Kroes, Gabby; Bettonvil, Felix; Kragt, Jan; Elswijk, Eddy; Tromp, Niels

    2014-07-01

    Within Infra-Red large wavelength bandwidth instruments the use of mechanisms for selection of observation modes, filters, dispersing elements, pinholes or slits is inevitable. The cryogenic operating environment poses several challenges to these cryogenic mechanisms; like differential thermal shrinkage, physical property change of materials, limited use of lubrication, high feature density, limited space etc. MATISSE the mid-infrared interferometric spectrograph and imager for ESO's VLT interferometer (VLTI) at Paranal in Chile coherently combines the light from 4 telescopes. Within the Cold Optics Bench (COB) of MATISSE two concepts of selection mechanisms can be distinguished based on the same design principles: linear selection mechanisms (sliders) and rotating selection mechanisms (wheels).Both sliders and wheels are used at a temperature of 38 Kelvin. The selection mechanisms have to provide high accuracy and repeatability. The sliders/wheels have integrated tracks that run on small, accurately located, spring loaded precision bearings. Special indents are used for selection of the slider/wheel position. For maximum accuracy/repeatability the guiding/selection system is separated from the actuation in this case a cryogenic actuator inside the cryostat. The paper discusses the detailed design of the mechanisms and the final realization for the MATISSE COB. Limited lifetime and performance tests determine accuracy, warm and cold and the reliability/wear during life of the instrument. The test results and further improvements to the mechanisms are discussed.

  5. Binding Mechanisms in Selective Laser Sintering and Selective Laser Melting

    NARCIS (Netherlands)

    Kruth, J.-P.; Mercelis, P.; Van Vaerenbergh, J.; Froyen, L.; Rombouts, M.

    2005-01-01

    Purpose – This paper provides an overview of the different binding mechanisms in selective laser sintering (SLS) and selective laser melting (SLM), thus improving the understanding of these processes. Design/methodology/approach – A classification of SLS/SLM processes was developed, based on the bin

  6. Selecting appropriate cases when tracing causal mechanisms

    DEFF Research Database (Denmark)

    Beach, Derek; Pedersen, Rasmus Brun

    2016-01-01

    The last decade has witnessed resurgence in the interest in studying the causal mechanisms linking causes and outcomes in the social sciences. This article explores the overlooked implications for case selection when tracing mechanisms using in-depth case studies. Our argument is that existing case...... is to unpack the causal mechanism between X and Y, enabling causal inferences to be made because empirical evidence is provided for how the mechanism actually operated in a particular case. The in-depth, within-case tracing of how mechanisms operate in particular cases produces what can be termed mechanistic...... selection guidelines are appropriate for research aimed at making cross-case claims about causal relationships, where case selection is primarily used to control for other causes. However, existing guidelines are not in alignment with case-based research that aims to trace mechanisms, where the goal...

  7. Exploring Mechanisms of Selective Directed Forgetting

    Science.gov (United States)

    Aguirre, Carmen; Gómez-Ariza, Carlos J.; Andrés, Pilar; Mazzoni, Giuliana; Bajo, Ma T.

    2017-01-01

    While some studies have shown that providing a cue to selectively forget one subset of previously learned facts may cause specific forgetting of this information, little is known about the mechanisms underlying this memory phenomenon. In three experiments, we aimed to better understand the nature of the selective directed forgetting (SDF) effect. Participants studied a List 1 consisting of 18 sentences regarding two (or three) different characters and a List 2 consisting of sentences regarding an additional character. In Experiment 1, we explored the role of rehearsal as the mechanism producing SDF by examining the effect of articulatory suppression after List 1 and during List 2 presentation. In Experiments 2 and 3, we explored the role of attentional control mechanisms by introducing a concurrent updating task after List 1 and during List 2 (Experiment 2) and by manipulating the number of characters to be selectively forgotten (1 out of 3 vs. 2 out of 3). Results from the three experiments suggest that neither rehearsal nor context change seem to be the mechanisms underlying SDF, while the pattern of results is consistent with an inhibitory account. In addition, whatever the responsible mechanism is, SDF seems to rely on the available attentional resources and the demands of the task. Our results join other findings to show that SDF is a robust phenomenon and suggest boundary conditions for the effect to be observed. PMID:28316584

  8. Quantum mechanics new approaches to selected topics

    CERN Document Server

    Lipkin, Harry J

    2007-01-01

    Acclaimed as ""excellent"" (Nature) and ""very original and refreshing"" (Physics Today), this collection of self-contained studies is geared toward advanced undergraduates and graduate students. Its broad selection of topics includes the Mössbauer effect, many-body quantum mechanics, scattering theory, Feynman diagrams, and relativistic quantum mechanics.Author Harry J. Lipkin, a well-known teacher at Israel's Weizmann Institute, takes an unusual approach by introducing many interesting physical problems and mathematical techniques at a much earlier point than in conventional texts. This meth

  9. Skewed factor models using selection mechanisms

    KAUST Repository

    Kim, Hyoung-Moon

    2015-12-21

    Traditional factor models explicitly or implicitly assume that the factors follow a multivariate normal distribution; that is, only moments up to order two are involved. However, it may happen in real data problems that the first two moments cannot explain the factors. Based on this motivation, here we devise three new skewed factor models, the skew-normal, the skew-tt, and the generalized skew-normal factor models depending on a selection mechanism on the factors. The ECME algorithms are adopted to estimate related parameters for statistical inference. Monte Carlo simulations validate our new models and we demonstrate the need for skewed factor models using the classic open/closed book exam scores dataset.

  10. Selection of software for mechanical engineering undergraduates

    Energy Technology Data Exchange (ETDEWEB)

    Cheah, C. T.; Yin, C. S.; Halim, T.; Naser, J.; Blicblau, A. S., E-mail: ablicblau@swin.edu.au [Swinburne University of Technology, Faculty of Science Engineering and Technology, PO Box 218 Hawthorn, Victoria, Australia, 3122 (Australia)

    2016-07-12

    A major problem with the undergraduate mechanical course is the limited exposure of students to software packages coupled with the long learning curve on the existing software packages. This work proposes the use of appropriate software packages for the entire mechanical engineering curriculum to ensure students get sufficient exposure real life design problems. A variety of software packages are highlighted as being suitable for undergraduate work in mechanical engineering, e.g. simultaneous non-linear equations; uncertainty analysis; 3-D modeling software with the FEA; analysis tools for the solution of problems in thermodynamics, fluid mechanics, mechanical system design, and solid mechanics.

  11. Selection of software for mechanical engineering undergraduates

    Science.gov (United States)

    Cheah, C. T.; Yin, C. S.; Halim, T.; Naser, J.; Blicblau, A. S.

    2016-07-01

    A major problem with the undergraduate mechanical course is the limited exposure of students to software packages coupled with the long learning curve on the existing software packages. This work proposes the use of appropriate software packages for the entire mechanical engineering curriculum to ensure students get sufficient exposure real life design problems. A variety of software packages are highlighted as being suitable for undergraduate work in mechanical engineering, e.g. simultaneous non-linear equations; uncertainty analysis; 3-D modeling software with the FEA; analysis tools for the solution of problems in thermodynamics, fluid mechanics, mechanical system design, and solid mechanics.

  12. Phenotypic plasticity and selection: nonexclusive mechanisms of adaptation

    OpenAIRE

    Grenier, S.; Barre, P.; Litrico, I.

    2016-01-01

    Selection and plasticity are two mechanisms that allow the adaptation of a population to a changing environment. Interaction between these nonexclusive mechanisms must be considered if we are to understand population survival. This review discusses the ways in which plasticity and selection can interact, based on a review of the literature on selection and phenotypic plasticity in the evolution of populations. The link between selection and phenotypic plasticity is analysed at the level of th...

  13. Statistical mechanics principles and selected applications

    CERN Document Server

    Hill, Terrell L

    1987-01-01

    ""Excellent … a welcome addition to the literature on the subject."" - ScienceBefore the publication of this standard, oft-cited book, there were few if any statistical-mechanics texts that incorporated reviews of both fundamental principles and recent developments in the field.In this volume, Professor Hill offers just such a dual presentation - a useful account of basic theory and of its applications, made accessible in a comprehensive format. The book opens with concise, unusually clear introductory chapters on classical statistical mechanics, quantum statistical mechanics and the relatio

  14. Mechanisms underlying selecting objects for action

    Directory of Open Access Journals (Sweden)

    Melanie eWulff

    2015-04-01

    Full Text Available We assessed the factors which affect the selection of objects for action, focusing on the role of action knowledge and its modulation by distracters. 14 neuropsychological patients and 10 healthy aged-matched controls selected pairs of objects commonly used together among distracters in two contexts: with real objects and with pictures of the same objects presented sequentially on a computer screen. Across both tasks, semantically related distracters led to slower responses and more errors than unrelated distracters and the object actively used for action was selected prior to the object that would be passively held during the action. We identified a sub-group of patients (N=6 whose accuracy was 2SD below the controls performances in the real object task. Interestingly, these impaired patients were more affected by the presence of unrelated distracters during both tasks than intact patients and healthy controls. Note the impaired had lesions to left parietal, right anterior temporal and bilateral pre-motor regions. We conclude that: (1 motor procedures guide object selection for action, (2 semantic knowledge affects action-based selection, (3 impaired action decision is associated with the inability to ignore distracting information and (4 lesions to either the dorsal or ventral visual stream can lead to deficits in making action decisions. Overall, the data indicate that impairments in everyday tasks can be evaluated using a simulated computer task. The implications for rehabilitation are discussed.

  15. Multiple mechanisms shape FM sweep rate selectivity: complementary or redundant?

    Directory of Open Access Journals (Sweden)

    Zoltan M Fuzessery

    2012-08-01

    Full Text Available Auditory neurons in the inferior colliculus (IC of the pallid bat have strong rate selective responses to downward frequency modulated (FM sweeps attributable to the spectrotemporal pattern of their echolocation call (a brief FM pulse. Several mechanisms are known to shape FM rate selectivity within the pallid bat IC. Here we explore how two mechanisms, stimulus duration and high-frequency inhibition (HFI, can interact to shape FM rate selectivity within the same neuron. Results from extracellular recordings indicated that a derived duration-rate function (based on tonal response was highly predictive of the shape of the FM rate response. Longpass duration selectivity for tones was predictive of slowpass rate selectivity for FM sweeps, both of which required long stimulus durations and remained intact following iontophoretic blockade of inhibitory input. Bandpass duration selectivity for tones, sensitive to only a narrow range of tone durations, was predictive of bandpass rate selectivity for FM sweeps. Conversion of the tone duration response from bandpass to longpass after blocking inhibition was coincident with a change in FM rate selectivity from bandpass to slowpass indicating an active inhibitory component to the formation of bandpass selectivity. Independent of the effect of duration tuning on FM rate selectivity, the presence of HFI acted as a fastpass FM rate filter by suppressing slow FM sweep rates. In cases where both mechanisms were present, both had to be eliminated, by removing inhibition, before bandpass FM rate selectivity was affected. It is unknown why the auditory system utilizes multiple mechanisms capable of shaping identical forms of FM rate selectivity though it may represent distinct but convergent modes of neural signaling directed at shaping response selectivity for important biologically relevant sounds.

  16. SEMANTIC NETWORK PRESENTATION OF MECHANICAL MOTION SCHEME AND ITS MECHANISM TYPES SELECTION METHOD

    Institute of Scientific and Technical Information of China (English)

    Ye Zhigang; Zou Huijun; Zhang Qing; Tian Yongli

    2004-01-01

    The presentation method of the mechanical motion scheme must support the whole process of conceptual design.To meet the requirement,a semantic network method is selected to represent process level,action level,mechanism level and relationships among them.Computer aided motion cycle chart exploration can be realized by the representation and revision of time coordination of mechanism actions and their effect on the design scheme.The uncertain reasoning technology based on semantic network is applied in the mechanism types selection of the needle driving mechanism of industrial sewing mechanism,and the application indicated it is correct,useful and advance.

  17. Ion-selective electrodes: historical, mechanism of response, selectivity and concept review

    Directory of Open Access Journals (Sweden)

    Fernandes Julio Cesar Bastos

    2001-01-01

    Full Text Available This paper presents a review of the concepts involved in the working mechanism of the ion-selective electrodes, searching a historical overview, moreover to describe the new advances in the area.

  18. Neural mechanisms of selective attention in the somatosensory system.

    Science.gov (United States)

    Gomez-Ramirez, Manuel; Hysaj, Kristjana; Niebur, Ernst

    2016-09-01

    Selective attention allows organisms to extract behaviorally relevant information while ignoring distracting stimuli that compete for the limited resources of their central nervous systems. Attention is highly flexible, and it can be harnessed to select information based on sensory modality, within-modality feature(s), spatial location, object identity, and/or temporal properties. In this review, we discuss the body of work devoted to understanding mechanisms of selective attention in the somatosensory system. In particular, we describe the effects of attention on tactile behavior and corresponding neural activity in somatosensory cortex. Our focus is on neural mechanisms that select tactile stimuli based on their location on the body (somatotopic-based attention) or their sensory feature (feature-based attention). We highlight parallels between selection mechanisms in touch and other sensory systems and discuss several putative neural coding schemes employed by cortical populations to signal the behavioral relevance of sensory inputs. Specifically, we contrast the advantages and disadvantages of using a gain vs. spike-spike correlation code for representing attended sensory stimuli. We favor a neural network model of tactile attention that is composed of frontal, parietal, and subcortical areas that controls somatosensory cells encoding the relevant stimulus features to enable preferential processing throughout the somatosensory hierarchy. Our review is based on data from noninvasive electrophysiological and imaging data in humans as well as single-unit recordings in nonhuman primates.

  19. Sexual selection and speciation : mechanisms in Lake Victoria cichlid fish

    NARCIS (Netherlands)

    Maan, Martine Elisabeth

    2006-01-01

    The several hundred species of cichlid fish endemic to Lake Victoria (East-Africa) are textbook examples of explosive speciation. This thesis evaluates the hypothesis that sexual selection by female mate choice has contributed to this process of divergence, by investigating the mechanisms that drive

  20. Phenotypic Plasticity and Selection: Nonexclusive Mechanisms of Adaptation.

    Science.gov (United States)

    Grenier, S; Barre, P; Litrico, I

    2016-01-01

    Selection and plasticity are two mechanisms that allow the adaptation of a population to a changing environment. Interaction between these nonexclusive mechanisms must be considered if we are to understand population survival. This review discusses the ways in which plasticity and selection can interact, based on a review of the literature on selection and phenotypic plasticity in the evolution of populations. The link between selection and phenotypic plasticity is analysed at the level of the individual. Plasticity can affect an individual's response to selection and so may modify the end result of genetic diversity evolution at population level. Genetic diversity increases the ability of populations or communities to adapt to new environmental conditions. Adaptive plasticity increases individual fitness. However this effect must be viewed from the perspective of the costs of plasticity, although these are not easy to estimate. It is becoming necessary to engage in new experimental research to demonstrate the combined effects of selection and plasticity for adaptation and their consequences on the evolution of genetic diversity.

  1. Selective laser sintering mechanism of polymer-coated molybdenum powder

    Institute of Scientific and Technical Information of China (English)

    BAI Pei-kang; WANG Wen-feng

    2007-01-01

    A type of polymer-coated molybdenum powder used in selective laser sintering technology was prepared by coating polymer on molybdenum particles and frozen grinding techniques, with the maximum particle diameter of 71 μm. The laser sintering experiments of polymer-coated molybdenum powder were conducted by using the self-developed selective laser sintering machine (HLRP-350I). The method of microscopic analysis was used to investigate the dynamic laser sintering process of polymer-coated molybdenum powder. Based on the study, the laser sintering mechanisms of polymer-coated molybdenum powder were presented. It is found that the mechanism is viscous flow when the laser sintering temperature is between 100 ℃ and 160 ℃, which can be described by a two-sphere model; and the mechanism is melting /solidification when the temperature is above 160 ℃.

  2. An entropic mechanism of generating selective ion binding in macromolecules.

    Directory of Open Access Journals (Sweden)

    Michael Thomas

    Full Text Available Several mechanisms have been proposed to explain how ion channels and transporters distinguish between similar ions, a process crucial for maintaining proper cell function. Of these, three can be broadly classed as mechanisms involving specific positional constraints on the ion coordinating ligands which arise through: a "rigid cavity", a 'strained cavity' and 'reduced ligand fluctuations'. Each operates in subtly different ways yet can produce markedly different influences on ion selectivity. Here we expand upon preliminary investigations into the reduced ligand fluctuation mechanism of ion selectivity by simulating how a series of model systems respond to a decrease in ligand thermal fluctuations while simultaneously maintaining optimal ion-ligand binding distances. Simple abstract-ligand models, as well as simple models based upon the ion binding sites in two amino acid transporters, show that limiting ligand fluctuations can create ion selectivity between Li(+, Na(+ and K(+ even when there is no strain associated with the molecular framework accommodating the different ions. Reducing the fluctuations in the position of the coordinating ligands contributes to selectivity toward the smaller of two ions as a consequence of entropic differences.

  3. The mechanism of selective molecular capture in carbon nanotube networks.

    Science.gov (United States)

    Wan, Yu; Guan, Jun; Yang, Xudong; Zheng, Quanshui; Xu, Zhiping

    2014-07-28

    Recently, air pollution issues have drawn significant attention to the development of efficient air filters, and one of the most promising materials for this purpose is nanofibers. We explore here the mechanism of selective molecular capture of volatile organic compounds in carbon nanotube networks by performing atomistic simulations. The results are discussed with respect to the two key parameters that define the performance of nanofiltration, i.e. the capture efficiency and flow resistance, which demonstrate the advantages of carbon nanotube networks with high surface-to-volume ratio and atomistically smooth surfaces. We also reveal the important roles of interfacial adhesion and diffusion that govern selective gas transport through the network.

  4. Characterization of a possible uptake mechanism of selective antibacterial peptides.

    Science.gov (United States)

    Polanco, Carlos; Samaniego, José Lino; Castañón-González, Jorge Alberto; Buhse, Thomas; Sordo, Marili Leopold

    2013-01-01

    Selective antibacterial peptides containing less than 30 amino acid residues, cationic, with amphipathic properties, have been the subject of several studies due to their active participation and beneficial effects in strengthening the immune system of all living organisms. This manuscript reports the results of a comparison between the group of selective antibacterial peptides and another group called "cell penetrating peptides". An important number of the selective antibacterial peptides are cell penetrating peptides, suggesting that their toxicity is related to their uptake mechanism. The verification of this observation also includes the adaptation of a method previously published, called Polarity index, which reproduces and confirms the action of this new set of peptides. The efficiency of this method was verified based on four different databases, yielding a high score. The verification was based exclusively on the peptides already reported in the databases which have been experimentally verified.

  5. Mechanisms of selective antitumor action of cold atmospheric plasma

    Science.gov (United States)

    Graves, David; Bauer, Georg

    2016-09-01

    Transformed (precancerous) cells are known to be subject to elimination through intercellular RONS-dependent apoptosis-inducing signaling. It is a remarkable fact that the chemical species utilized by apoptosis induction in transformed cells are essentially identical to chemical species created by cold atmospheric plasma (CAP) in aqueous solutions. The association between CAP-induced biochemistry and natural cell anti-tumor mechanisms offers the opportunity to establish a rationale for the observed successes of CAP in selectively eliminating tumor cells in vitro and in vivo. In particular, 1O2 appears to act to selectively induce apoptosis in tumor cells, and can also result in self-perpetuating, cell-to-cell apoptotic signaling. Various CAP-generated liquid phase species can react to form 1O2, thus providing a hypothetical mechanism to explain how CAP can trigger therapeutic apoptosis in tumors. The analysis of model experiments performed with defined RONS in vitro implies that CAP-derived 1O2 induces the mechanism through which CAP acts selectively against cancer cells in vitro and tumors in vivo. This hypothesis needs to be tested experimentally in order to establish its validity.

  6. A prototype of behavior selection mechanism based on emotion

    Science.gov (United States)

    Zhang, Guofeng; Li, Zushu

    2007-12-01

    In bionic methodology rather than in design methodology more familiar with, summarizing the psychological researches of emotion, we propose the biologic mechanism of emotion, emotion selection role in creature evolution and a anima framework including emotion similar to the classical control structure; and consulting Prospect Theory, build an Emotion Characteristic Functions(ECF) that computer emotion; two more emotion theories are added to them that higher emotion is preferred and middle emotion makes brain run more efficiently, emotional behavior mechanism comes into being. A simulation of proposed mechanism are designed and carried out on Alife Swarm software platform. In this simulation, a virtual grassland ecosystem is achieved where there are two kinds of artificial animals: herbivore and preyer. These artificial animals execute four types of behavior: wandering, escaping, finding food, finding sex partner in their lives. According the theories of animal ethnology, escaping from preyer is prior to other behaviors for its existence, finding food is secondly important behavior, rating is third one and wandering is last behavior. In keeping this behavior order, based on our behavior characteristic function theory, the specific functions of emotion computing are built of artificial autonomous animals. The result of simulation confirms the behavior selection mechanism.

  7. Selective social learning in infancy: looking for mechanisms.

    Science.gov (United States)

    Crivello, Cristina; Phillips, Sara; Poulin-Dubois, Diane

    2017-08-30

    Although there is mounting evidence that selective social learning begins in infancy, the psychological mechanisms underlying this ability are currently a controversial issue. The purpose of this study is to investigate whether theory of mind abilities and statistical learning skills are related to infants' selective social learning. Seventy-seven 18-month-olds were first exposed to a reliable or an unreliable speaker and then completed a word learning task, two theory of mind tasks, and a statistical learning task. If domain-general abilities are linked to selective social learning, then infants who demonstrate superior performance on the statistical learning task should perform better on the selective learning task, that is, should be less likely to learn words from an unreliable speaker. Alternatively, if domain-specific abilities are involved, then superior performance on theory of mind tasks should be related to selective learning performance. Findings revealed that, as expected, infants were more likely to learn a novel word from a reliable speaker. Importantly, infants who passed a theory of mind task assessing knowledge attribution were significantly less likely to learn a novel word from an unreliable speaker compared to infants who failed this task. No such effect was observed for the other tasks. These results suggest that infants who possess superior social-cognitive abilities are more apt to reject an unreliable speaker as informant. A video abstract of this article can be viewed at: https://youtu.be/zuuCniHYzqo. © 2017 John Wiley & Sons Ltd.

  8. Estimating seabed scattering mechanisms via Bayesian model selection.

    Science.gov (United States)

    Steininger, Gavin; Dosso, Stan E; Holland, Charles W; Dettmer, Jan

    2014-10-01

    A quantitative inversion procedure is developed and applied to determine the dominant scattering mechanism (surface roughness and/or volume scattering) from seabed scattering-strength data. The classification system is based on trans-dimensional Bayesian inversion with the deviance information criterion used to select the dominant scattering mechanism. Scattering is modeled using first-order perturbation theory as due to one of three mechanisms: Interface scattering from a rough seafloor, volume scattering from a heterogeneous sediment layer, or mixed scattering combining both interface and volume scattering. The classification system is applied to six simulated test cases where it correctly identifies the true dominant scattering mechanism as having greater support from the data in five cases; the remaining case is indecisive. The approach is also applied to measured backscatter-strength data where volume scattering is determined as the dominant scattering mechanism. Comparison of inversion results with core data indicates the method yields both a reasonable volume heterogeneity size distribution and a good estimate of the sub-bottom depths at which scatterers occur.

  9. Selection and inhibition mechanisms for human voluntary action decisions.

    Science.gov (United States)

    Zhang, Jiaxiang; Hughes, Laura E; Rowe, James B

    2012-10-15

    One can choose between action alternatives that have no apparent difference in their outcomes. Such voluntary action decisions are associated with widespread frontal-parietal activation, and a tendency to inhibit the repetition of a previous action. However, the mechanism of initiating voluntary actions and the functions of different brain regions during this process remains largely unknown. Here, we combine computational modeling and functional magnetic resonance imaging to test the selection and inhibition mechanisms that mediate trial-to-trial voluntary action decisions. We fitted an optimized accumulator model to behavioral responses in a finger-tapping task in which participants were instructed to make chosen actions or specified actions. Model parameters derived from each individual were then applied to estimate the expected accumulated metabolic activity (EAA) engaged in every single trial. The EAA was associated with blood oxygenation level-dependent responses in a decision work that was maximal in the supplementary motor area and the caudal anterior cingulate cortex, consistent with a competitive accumulation-to-threshold mechanism for action decision by these regions. Furthermore, specific inhibition of the previous action's accumulator was related to the suppression of response repetition. This action-specific inhibition correlated with the activity of the right inferior frontal gyrus, when the option to repeat existed. Our findings suggest that human voluntary action decisions are mediated by complementary processes of intentional selection and inhibition.

  10. Lectures on the mathematics of quantum mechanics II selected topics

    CERN Document Server

    Dell'Antonio, Gianfausto

    2016-01-01

    The first volume (General Theory) differs from most textbooks as it emphasizes the mathematical structure and mathematical rigor, while being adapted to the teaching the first semester of an advanced course in Quantum Mechanics (the content of the book are the lectures of courses actually delivered.). It differs also from the very few texts in Quantum Mechanics that give emphasis to the mathematical aspects because this book, being written as Lecture Notes, has the structure of lectures delivered in a course, namely introduction of the problem, outline of the relevant points, mathematical tools needed, theorems, proofs. This makes this book particularly useful for self-study and for instructors in the preparation of a second course in Quantum Mechanics (after a first basic course). With some minor additions it can be used also as a basis of a first course in Quantum Mechanics for students in mathematics curricula. The second part (Selected Topics) are lecture notes of a more advanced course aimed at giving th...

  11. Fundamental consolidation mechanisms during selective beam melting of powders

    Science.gov (United States)

    Körner, Carolin; Bauereiß, Andreas; Attar, Elham

    2013-12-01

    During powder based additive manufacturing processes, a component is realized layer upon layer by the selective melting of powder layers with a laser or an electron beam. The density of the consolidated material, the minimal spatial resolution as well as the surface roughness of the resulting components are complex functions of the material and process parameters. So far, the interplay between these parameters is only partially understood. In this paper, the successive assembling in layers is investigated with a recently described 2D-lattice Boltzmann model, which considers individual powder particles. This numerical approach makes several physical phenomena accessible, which cannot be described in a standard continuum picture, e.g. the interplay between capillary effects, wetting conditions and the local stochastic powder configuration. In addition, the model takes into account the influence of the surface topology of the previous consolidated layer on the subsequent powder layer. The influence of the beam power, beam velocity and layer thickness on the formation and quality of simple walls is investigated. The simulation results are compared with experimental findings during selective electron beam melting. The comparison shows that our model, although 2D, is able to predict the main characteristics of the experimental observations. In addition, the numerical simulation elucidates the fundamental mechanisms responsible for the phenomena that are observed during selective beam melting.

  12. Stability as a natural selection mechanism on interacting networks

    Directory of Open Access Journals (Sweden)

    Francisco A. Tamarit

    2010-02-01

    Full Text Available Biological networks of interacting agents exhibit similar topological properties for a wide range of scales, from cellular to ecological levels, suggesting the existence of a common evolutionary origin. A general evolutionary mechanism based on global stability has been proposed recently  [J I Perotti, et al., Phys. Rev. Lett. 103, 108701 (2009]. This mechanism was incorporated into a  model of a growing network of interacting agents in which each new agent's membership in the network is determined by the agent's effect on the network's global stability. In this work, we analyze different quantities that characterize the topology of the emerging networks, such as global connectivity, clustering and average nearest neighbors degree, showing that they reproduce scaling behaviors frequently observed in several biological systems. The influence of the stability selection  mechanism on the dynamics associated to the resulting network, as well as  the interplay  between some topological and functional features are also analyzed.Received: 17 July 2010; Accepted: 27 September 2010; Edited by: D. H. Zanette; Reviewed by: V. M. Eguiluz, Inst. Fisica Interdisciplinar y Sist. Complejos, Palma de Mallorca, Spain; DOI: 10.4279/PIP.020005

  13. Membrane selectivity and disordering mechanism of antimicrobial peptide protegrin-1

    Science.gov (United States)

    Ishitsuka, Yuji

    Protegrin-1 (PG-1) is a beta-sheet antimicrobial peptide (AMP), a class of peptides innate to various organisms and functions as a defense agent against harmful microorganisms by means of membrane disordering. Characteristic chemical and structural properties of AMPs allow selective interaction against invaders' cell membranes. Despite their enormous biomedical potential, progress towards developing them into therapeutic agents has been hampered by a lack of insight into their mechanism of action. AMP insertion assays using Langmuir monolayers reveal that both electrostatic properties of the lipid head group as well as the packing density of the lipid tail group play important roles in determining the membrane selectivity of AMPs. These results help elucidate how the AMP selectively targets the cell membrane of microorganisms over the cell membrane of the host. In addition, these results also explain the higher hemolytic ability of PG-1 against human red blood cells (RBCs) compared to the hemolytic ability of PG-1 against sheep and pig RBCs. Synchrotron X-ray reflectivity shows that PG-1 penetrates into the lipid layer. Grazing incidence X-ray diffraction and fluorescence microscopy indicate that the insertion of PG-1 disorders tail group packing. Membrane selectivity and insertion location information of AMPs with different primary sequence and secondary structure have been obtained by using a truncated version of PG-1: PC-17, and an alpha-helical AMP, LL-37, respectively. The similarity of the membrane disordering process across these various peptides motivated us to test the membrane disordering effect of molecules designed to mimic these peptides. Peptide-mimics based on meta-phenylene ethynylenes demonstrate similar membrane disordering effects, showing that the potency of AMPs is derived from their overall chemical and structural properties, rather than exact peptide sequence. Atomic force microscopy (AFM) was used to directly image first, the PG-1

  14. Mechanisms of selective attention and space motion sickness

    Science.gov (United States)

    Kohl, R. L.

    1987-01-01

    The neural mismatch theory of space motion sickness asserts that the central and peripheral autonomic sequelae of discordant sensory input arise from central integrative processes falling to reconcile patterns of incoming sensory information with existing memory. Stated differently, perceived novelty reaches a stress level as integrative mechanisms fail to return a sense of control to the individual in the new environment. Based on evidence summarized here, the severity of the neural mismatch may be dependent upon the relative amount of attention selectively afforded to each sensory input competing for control of behavior. Components of the limbic system may play important roles in match-mismatch operations, be therapeutically modulated by antimotion sickness drugs, and be optimally positioned to control autonomic output.

  15. The effect of selective desorption mechanisms during interstellar ice formation

    CERN Document Server

    Kalvans, Juris

    2015-01-01

    Major components of ices on interstellar grains in molecular clouds - water and carbon oxides - occur at various optical depths. This implies that selective desorption mechanisms are at work. An astrochemical model of a contracting low-mass molecular cloud core is presented. Ice was treated as consisting of the surface and three subsurface layers (sublayers). Photodesorption, reactive desorption, and indirect reactive desorption were investigated. The latter manifests itself through desorption from H+H reaction on grains. Desorption of shallow subsurface species was included. Modeling results suggest the existence of a "photon-dominated ice" during the early phases of core contraction. Subsurface ice is chemically processed by interstellar photons, which produces complex organic molecules. Desorption from the subsurface layer results in high COM gas-phase abundances at Av = 2.4...10mag. This may contribute towards an explanation for COM observations in dark cores. It was found that photodesorption mostly gove...

  16. Resistant mechanism study of benzalkonium chloride selected Salmonella Typhimurium mutants.

    Science.gov (United States)

    Guo, Wei; Cui, Shenghui; Xu, Xiao; Wang, Haoyan

    2014-02-01

    Benzalkonium chloride is one of the invaluable biocides that is extensively used in healthcare settings as well as in the food processing industry. After exposing wild-type Salmonella Typhimurium 14028s or its AcrAB inactivation mutant to gradually increasing levels of benzalkonium chloride, resistance mutants S-41, S-150, S-AB-23, S-AB-38, and S-AB-73 were selected and these mutants also showed a 2-64-fold stable minimum inhibitory concentration (MIC) increase to chloramphenicol, ciprofloxacin, nalidixic acid, and tetracycline. In S-41 and S-150, the expression of acrB was increased 2.7- and 7.6-fold, and ΔtolC or ΔacrAB mutants of S-41 and S-150 showed the same MICs to all tested antimicrobials as the equivalent Salmonella Typhimurium 14028s mutants. However, in S-AB-23, S-AB-38, and S-AB-73, the expression of acrF was increased 96-, 230-, and 267-fold, respectively, and ΔtolC or ΔacrEF mutants of S-AB-23, S-AB-38, and S-AB-73 showed the similar MICs to all tested antimicrobials as the ΔtolC mutant of Salmonella Typhimurium 14028s. Our data showed that constitutively over-expressed AcrAB working through TolC was the main resistance mechanism in ST14028s benzalkonium chloride resistance mutants. However, after AcrAB had been inactivated, benzalkonium chloride-resistant mutants could still be selected and constitutively over-expressed, AcrEF became the dominant efflux pump working through TolC and being responsible for the increasing antimicrobial resistance. These data indicated that different mechanisms existed for acrB and acrF constitutive over-expression. Since exposure to benzalkonium chloride may lead to Salmonella mutants with a decreased susceptibility to quinolones, which is currently one of the drugs of choice for the treatment of life-threatening salmonelosis, research into the pathogenesis and epidemiology of the benzalkonium chloride resistance mutants will be of increasing importance.

  17. STRATEGIES AND MECHANISMS IN NONSELECTIVE AND SELECTIVE INHIBITORY MOTOR CONTROL

    NARCIS (Netherlands)

    DEJONG, R; COLES, MGH; LOGAN, GD

    Motor inhibition was studied in 3 versions of the stop-signal paradigm, with the stop signal requiring inhibition of any response (stop-all), a fixed alternative response (stop-change), or selective inhibition of only 1 of the responses (selective-stop). The lateralized readiness potential was used

  18. Anion conductance selectivity mechanism of the CFTR chloride channel.

    Science.gov (United States)

    Linsdell, Paul

    2016-04-01

    All ion channels are able to discriminate between substrate ions to some extent, a process that involves specific interactions between permeant anions and the so-called selectivity filter within the channel pore. In the cystic fibrosis transmembrane conductance regulator (CFTR) anion-selective channel, both anion relative permeability and anion relative conductance are dependent on anion free energy of hydration--anions that are relatively easily dehydrated tend to show both high permeability and low conductance. In the present work, patch clamp recording was used to investigate the relative conductance of different anions in CFTR, and the effect of mutations within the channel pore. In constitutively-active E1371Q-CFTR channels, the anion conductance sequence was Cl(-) > NO3(-) > Br(-) > formate > SCN(-) > I(-). A mutation that disrupts anion binding in the inner vestibule of the pore (K95Q) disrupted anion conductance selectivity, such that anions with different permeabilities showed almost indistinguishable conductances. Conversely, a mutation at the putative narrowest pore region that is known to disrupt anion permeability selectivity (F337A) had minimal effects on anion relative conductance. Ion competition experiments confirmed that relatively tight binding of permeant anions resulted in relatively low conductance. These results suggest that the relative affinity of ion binding in the inner vestibule of the pore controls the relative conductance of different permeant anions in CFTR, and that the pore has two physically distinct anion selectivity filters that act in series to control anion conductance selectivity and anion permeability selectivity respectively.

  19. Halfphones: a backoff mechanism for Diphone Unit Selection Synthesis

    CSIR Research Space (South Africa)

    Louw, JA

    2006-11-01

    Full Text Available . This lack of naturalness can be attributed, at least in part, to the limited set of units from which speech ischosen, coupled with the need to prosodically modify the speech signal of each diphone. Diphone Backoff mechanisms in text-to-speech provide a means...

  20. On the mechanism of spectral selective sensitivity of photonic biosensors

    Energy Technology Data Exchange (ETDEWEB)

    Khudaverdyan, Surik [State Engineering University of Armenia, SEUA, 105 Teryan Str., 0009 Yerevan (Armenia)], E-mail: khsuren@seua.am; Dokholyan, Janna; Arustamyan, Vladimir; Khudaverdyan, Ashot [State Engineering University of Armenia, SEUA, 105 Teryan Str., 0009 Yerevan (Armenia); Clinciu, Daniel L. [Department of Information Management, National Chiao Tung University, Hsinchu, Taiwan (China)

    2009-10-21

    We report a new optical sensor exploiting the innovative operation principle developed for the selective registration of UV and visible radiations. The operation is based on the mutual influence of depletion regions in the photovoltaic structure composed by Schottky barrier and n-p junction. The important feature of this structure is that the depletion regions expand over the whole base so that they contact each other. We have shown that the position of the contact point in the base is a function of voltage applied to the structure. Also absorption spectrum for each of the depletion regions and the photoresponse of the structure are functions of the applied voltage. We have revealed that the change induced by the applied voltage in the photoresponse, {delta}I, is proportional to the change {delta}{lambda} induced in the spectrum, {delta}{lambda}{approx}{delta}I. This linear correlation between {delta}I and {delta}{lambda} is a very important spectrophotometric property required for the precise selective registration of bio signals in dynamic and static biological processes.

  1. Probing protein flexibility reveals a mechanism for selective promiscuity

    Science.gov (United States)

    Pabon, Nicolas A; Camacho, Carlos J

    2017-01-01

    Many eukaryotic regulatory proteins adopt distinct bound and unbound conformations, and use this structural flexibility to bind specifically to multiple partners. However, we lack an understanding of how an interface can select some ligands, but not others. Here, we present a molecular dynamics approach to identify and quantitatively evaluate the interactions responsible for this selective promiscuity. We apply this approach to the anticancer target PD-1 and its ligands PD-L1 and PD-L2. We discover that while unbound PD-1 exhibits a hard-to-drug hydrophilic interface, conserved specific triggers encoded in the cognate ligands activate a promiscuous binding pathway that reveals a flexible hydrophobic binding cavity. Specificity is then established by additional contacts that stabilize the PD-1 cavity into distinct bound-like modes. Collectively, our studies provide insight into the structural basis and evolution of multiple binding partners, and also suggest a biophysical approach to exploit innate binding pathways to drug seemingly undruggable targets. DOI: http://dx.doi.org/10.7554/eLife.22889.001 PMID:28432789

  2. Prize-linked savings mechanism in the portfolio selection framework

    Directory of Open Access Journals (Sweden)

    Anna Kaliciak

    2016-01-01

    Full Text Available Prize-linked savings (PLS instruments implement the lottery-like component into the structure of traditional financial products. Following existing research based on both real and experimental data, such programs appeared highly successful in raising the overall savings rates within the given environments. PLS accounts seem to be treated by decision-makers as substitutes to ordinary lotteries, but this does not hold when comparing PLS with traditional interest-bearing savings products. This paper explains such empirical observations in a framework of portfolio selection problem. For that purpose, two models have been presented and used for deriving optimal portfolios in a presence of PLS, lottery and savings products. As shown in the analysis, the standard mean-variance model does not allow for a PLS instrument to be of optimum choice, whereas in the case of behavioural portfolio model allocating all disposable income

  3. Selected hormonal and neurotransmitter mechanisms regulating feed intake in sheep.

    Science.gov (United States)

    Sartin, J L; Daniel, J A; Whitlock, B K; Wilborn, R R

    2010-11-01

    Appetite control is a major issue in normal growth and in suboptimal growth performance settings. A number of hormones, in particular leptin, activate or inhibit orexigenic or anorexigenic neurotransmitters within the arcuate nucleus of the hypothalamus, where feed intake regulation is integrated. Examples of appetite regulatory neurotransmitters are the stimulatory neurotransmitters neuropeptide Y (NPY), agouti-related protein (AgRP), orexin and melanin-concentrating hormone and the inhibitory neurotransmitter, melanocyte-stimulating hormone (MSH). Examination of messenger RNA (using in situ hybridization and real-time PCR) and proteins (using immunohistochemistry) for these neurotransmitters in ruminants has indicated that physiological regulation occurs in response to fasting for several of these critical genes and proteins, especially AgRP and NPY. Moreover, intracerebroventricular injection of each of the four stimulatory neurotransmitters can increase feed intake in sheep and may also regulate either growth hormone, luteinizing hormone, cortisol or other hormones. In contrast, both leptin and MSH are inhibitory to feed intake in ruminants. Interestingly, the natural melanocortin-4 receptor (MC4R) antagonist, AgRP, as well as NPY can prevent the inhibition of feed intake after injection of endotoxin (to model disease suppression of appetite). Thus, knowledge of the mechanisms regulating feed intake in the hypothalamus may lead to mechanisms to increase feed intake in normal growing animals and prevent the wasting effects of severe disease in animals.

  4. Single molecule insights on conformational selection and induced fit mechanism

    DEFF Research Database (Denmark)

    Hatzakis, Nikos

    2014-01-01

    Biomolecular interactions regulate a plethora of vital cellular processes, including signal transduction, metabolism, catalysis and gene regulation. Regulation is encoded in the molecular properties of the constituent proteins; distinct conformations correspond to different functional outcomes...... of unsynchronized molecules, often masking intrinsic dynamic behavior of proteins and biologically significant transient intermediates. Single molecule measurements are emerging as a powerful tool for characterizing protein function. They offer the direct observation and quantification of the activity, abundance...... and lifetime of multiple states and transient intermediates in the energy landscape, that are typically averaged out in non-synchronized ensemble measurements. Here we survey new insights from single molecule studies that advance our understanding of the molecular mechanisms underlying biomolecular recognition....

  5. Identifying the receptor subtype selectivity of retinoid X and retinoic acid receptors via quantum mechanics.

    Science.gov (United States)

    Tsuji, Motonori; Shudo, Koichi; Kagechika, Hiroyuki

    2017-03-01

    Understanding and identifying the receptor subtype selectivity of a ligand is an important issue in the field of drug discovery. Using a combination of classical molecular mechanics and quantum mechanical calculations, this report assesses the receptor subtype selectivity for the human retinoid X receptor (hRXR) and retinoic acid receptor (hRAR) ligand-binding domains (LBDs) complexed with retinoid ligands. The calculated energies show good correlation with the experimentally reported binding affinities. The technique proposed here is a promising method as it reveals the origin of the receptor subtype selectivity of selective ligands.

  6. Mechanisms and Evidence of Genital Coevolution: The Roles of Natural Selection, Mate Choice, and Sexual Conflict

    National Research Council Canada - National Science Library

    Brennan, Patricia L R; Prum, Richard O

    2015-01-01

    .... Here we review the diverse mechanisms of genital coevolution that include natural selection, female mate choice, male-male competition, and how their interactions generate sexual conflict that can...

  7. Dynamic access clustering selecting mechanism based on Markov decision process for MANET

    Institute of Scientific and Technical Information of China (English)

    WANG Dao-yuan; TIAN Hui

    2007-01-01

    Clustering is an important method in the mobile Ad-hoc network (MANET). As a result of their mobility, the cluster selection is inevitable for the mobile nodes during their roaming between the different clusters. In this study, based on the analysis of the cluster-selecting problem in the environment containing multiple clusters, which are overlaying and intercrossing, a novel dynamic selecting mechanism is proposed to resolve the dynamic selection optimization of roaming between the different clusters in MANET. This selecting mechanism is also based on the consideration of the stability of communication system, the communicating bandwidth, and the effect of cluster selecting on the communication and also in accordance with the Markov decision-making model.

  8. Architectural mechanisms for dynamic changes of behavior selection strategies in behavior-based systems.

    Science.gov (United States)

    Scheutz, Matthias; Andronache, Virgil

    2004-12-01

    Behavior selection is typically a "built-in" feature of behavior-based architectures and hence, not amenable to change. There are, however, circumstances where changing behavior selection strategies is useful and can lead to better performance. In this paper, we demonstrate that such dynamic changes of behavior selection mechanisms are beneficial in several circumstances. We first categorize existing behavior selection mechanisms along three dimensions and then discuss seven possible circumstances where dynamically switching among them can be beneficial. Using the agent architecture framework activation, priority, observer, and component (APOC), we show how instances of all (nonempty) categories can be captured and how additional architectural mechanisms can be added to allow for dynamic switching among them. In particular, we propose a generic architecture for dynamic behavior selection, which can integrate existing behavior selection mechanisms in a unified way. Based on this generic architecture, we then verify that dynamic behavior selection is beneficial in the seven cases by defining architectures for simulated and robotic agents and performing experiments with them. The quantitative and qualitative analyzes of the results obtained from extensive simulation studies and experimental runs with robots verify the utility of the proposed mechanisms.

  9. Pay-based Screening Mechanism: Personnel Selection in the View of Economics Theory

    Institute of Scientific and Technical Information of China (English)

    刘帮成; 唐宁玉

    2003-01-01

    Based on economic theories,the paper studies the personnel selection at the asymmetric job market using signaling and screening model.The authors hold the opinion that an organization can screen the candidates'signaling based on the self-selection principle by providing an apropriate compensation choice.A pay-based screening mechanism is qualified applicants and retain the excellent applicants.

  10. Amyloid beta modulated the selectivity of heme-catalyzed protein tyrosine nitration: an alternative mechanism for selective protein nitration.

    Science.gov (United States)

    Yuan, Can; Li, Hailing; Gao, Zhonghong

    2012-10-01

    Protein tyrosine nitration is a post-translational modification associated with numerous pathological conditions. The biological consequences of this modification strongly depend on the site selectivity. Unfortunately, to date there is still no reliable model for predicting the selectivity of protein tyrosine nitration. Previously, we found that amyloid beta (Aβ) changed the selectivity of enolase tyrosine nitration upon binding to heme. It seemed that there was a link between the hydrophilicity of Aβ and the site-specific tyrosine nitration. We further investigated the role of the hydrophilicity of the molecules that bind to heme in the selectivity of protein tyrosine nitration. We found that Aβ(1-16), Aβ(1-20), and Aβ(1-40), upon binding to heme and interacting with glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in a site-specific manner, differently modulated the site selectivity of heme-catalyzed GAPDH tyrosine nitration. The modulation is associated with the hydrophilicity of the Aβ peptides, which changed the surrounding environment of the heme. At the same time, the Aβ-heme complexes were found to be more effective at inactivating GAPDH than heme alone, and the selective tyrosine nitration that was catalyzed by Aβ-heme played an important role. These findings suggest an alternative mechanism for the selectivity of protein tyrosine nitration, which may lead to a better understanding of the factors that influence protein tyrosine nitration selectivity and the important roles of Aβ and heme in the pathogenesis of Alzheimer's disease, where Aβ accumulation and Aβ-dependent protein nitration play central roles.

  11. Selective laser melting of titanium alloy: investigation of mechanical properties and microstructure

    Science.gov (United States)

    Agapovichev, A. V.; Kokareva, V. V.; Smelov, V. G.; Sotov, A. V.

    2016-11-01

    This article presents the mechanical properties and microstructure of titanium alloy after selective laser melting (SLM). Titanium alloys are ideal material for selective laser melting (SLM), because they are expensive and difficult to machinery using traditional technologies. The application of SLM in the biomedical area has been slow due to the stringent performance criteria and concerns related to personification and part quality. In this article we focused on the manufacture by SLM and determination of microstructure and mechanical properties of titanium alloy (Ti Grade 2 Powder) using tensile tests and X-ray diffraction. The results reveal that the alloy exhibits a pronounced the homogeneous microstructure and high mechanical strength.

  12. Different Cortical Mechanisms for Spatial vs. Feature-Based Attentional Selection in Visual Working Memory.

    Science.gov (United States)

    Heuer, Anna; Schubö, Anna; Crawford, J D

    2016-01-01

    The limited capacity of visual working memory (VWM) necessitates attentional mechanisms that selectively update and maintain only the most task-relevant content. Psychophysical experiments have shown that the retroactive selection of memory content can be based on visual properties such as location or shape, but the neural basis for such differential selection is unknown. For example, it is not known if there are different cortical modules specialized for spatial vs. feature-based mnemonic attention, in the same way that has been demonstrated for attention to perceptual input. Here, we used transcranial magnetic stimulation (TMS) to identify areas in human parietal and occipital cortex involved in the selection of objects from memory based on cues to their location (spatial information) or their shape (featural information). We found that TMS over the supramarginal gyrus (SMG) selectively facilitated spatial selection, whereas TMS over the lateral occipital cortex (LO) selectively enhanced feature-based selection for remembered objects in the contralateral visual field. Thus, different cortical regions are responsible for spatial vs. feature-based selection of working memory representations. Since the same regions are involved in terms of attention to external events, these new findings indicate overlapping mechanisms for attentional control over perceptual input and mnemonic representations.

  13. Different Cortical Mechanisms for Spatial vs. Feature-Based Attentional Selection in Visual Working Memory

    Science.gov (United States)

    Heuer, Anna; Schubö, Anna; Crawford, J. D.

    2016-01-01

    The limited capacity of visual working memory (VWM) necessitates attentional mechanisms that selectively update and maintain only the most task-relevant content. Psychophysical experiments have shown that the retroactive selection of memory content can be based on visual properties such as location or shape, but the neural basis for such differential selection is unknown. For example, it is not known if there are different cortical modules specialized for spatial vs. feature-based mnemonic attention, in the same way that has been demonstrated for attention to perceptual input. Here, we used transcranial magnetic stimulation (TMS) to identify areas in human parietal and occipital cortex involved in the selection of objects from memory based on cues to their location (spatial information) or their shape (featural information). We found that TMS over the supramarginal gyrus (SMG) selectively facilitated spatial selection, whereas TMS over the lateral occipital cortex (LO) selectively enhanced feature-based selection for remembered objects in the contralateral visual field. Thus, different cortical regions are responsible for spatial vs. feature-based selection of working memory representations. Since the same regions are involved in terms of attention to external events, these new findings indicate overlapping mechanisms for attentional control over perceptual input and mnemonic representations. PMID:27582701

  14. Different cortical mechanisms for spatial vs. feature-based attentional selection in visual working memory

    Directory of Open Access Journals (Sweden)

    Anna Heuer

    2016-08-01

    Full Text Available The limited capacity of visual working memory necessitates attentional mechanisms that selectively update and maintain only the most task-relevant content. Psychophysical experiments have shown that the retroactive selection of memory content can be based on visual properties such as location or shape, but the neural basis for such differential selection is unknown. For example, it is not known if there are different cortical modules specialized for spatial versus feature-based mnemonic attention, in the same way that has been demonstrated for attention to perceptual input. Here, we used transcranial magnetic stimulation (TMS to identify areas in human parietal and occipital cortex involved in the selection of objects from memory based on cues to their location (spatial information or their shape (featural information. We found that TMS over the supramarginal gyrus (SMG selectively facilitated spatial selection, whereas TMS over the lateral occipital cortex selectively enhanced feature-based selection for remembered objects in the contralateral visual field. Thus, different cortical regions are responsible for spatial vs. feature-based selection of working memory representations. Since the same regions are involved in attention to external events, these new findings indicate overlapping mechanisms for attentional control over perceptual input and mnemonic representations.

  15. Mechanical Harvesting of Aquatic Plants. Report 2. Evaluation of Selected Handling Functions of Mechanical Control.

    Science.gov (United States)

    1980-06-01

    Table 3. 22. Pushing tests. The pushing tests were conducted along the 23 / SONNET "LAKE TOWING BOOM LOCATION SCALE 0.5 0.5 MILES Figure 9. Location... 73 . The preceding paragraphs present quantitative data and their implication in regard to improving the ability to accomplish selected functions in the...sufficient power to move the boat and cutter reliably through the plant infestation at a speed of at least 3 mph. 73 ... . . 0 0W. - .00 004. m 0 w0 wv m

  16. Control of ion selectivity in LeuT: two Na+ binding sites with two different mechanisms.

    Science.gov (United States)

    Noskov, Sergei Y; Roux, Benoît

    2008-03-28

    The x-ray structure of LeuT, a bacterial homologue of Na(+)/Cl(-)-dependent neurotransmitter transporters, provides a great opportunity to better understand the molecular basis of monovalent cation selectivity in ion-coupled transporters. LeuT possesses two ion binding sites, NA1 and NA2, which are highly selective for Na(+). Extensive all-atom free-energy molecular dynamics simulations of LeuT embedded in an explicit membrane are performed at different temperatures and various occupancy states of the binding sites to dissect the molecular mechanism of ion selectivity. The results show that the two binding sites display robust selectivity for Na(+) over K(+) or Li(+), the competing ions of most similar radii. Of particular interest, the mechanism primarily responsible for selectivity for each of the two binding sites appears to be different. In NA1, selectivity for Na(+) over K(+) arises predominantly from the strong electrostatic field arising from the negatively charged carboxylate group of the leucine substrate coordinating the ion directly. In NA2, which comprises only neutral ligands, selectivity for Na(+) is enforced by the local structural restraints arising from the hydrogen-bonding network and the covalent connectivity of the polypeptide chain surrounding the ion according to a "snug-fit" mechanism.

  17. Selectivity Mechanism of the Voltage-gated Proton Channel, HV1

    Science.gov (United States)

    Dudev, Todor; Musset, Boris; Morgan, Deri; Cherny, Vladimir V.; Smith, Susan M. E.; Mazmanian, Karine; Decoursey, Thomas E.; Lim, Carmay

    2015-05-01

    Voltage-gated proton channels, HV1, trigger bioluminescence in dinoflagellates, enable calcification in coccolithophores, and play multifarious roles in human health. Because the proton concentration is minuscule, exquisite selectivity for protons over other ions is critical to HV1 function. The selectivity of the open HV1 channel requires an aspartate near an arginine in the selectivity filter (SF), a narrow region that dictates proton selectivity, but the mechanism of proton selectivity is unknown. Here we use a reduced quantum model to elucidate how the Asp-Arg SF selects protons but excludes other ions. Attached to a ring scaffold, the Asp and Arg side chains formed bidentate hydrogen bonds that occlude the pore. Introducing H3O+ protonated the SF, breaking the Asp-Arg linkage and opening the conduction pathway, whereas Na+ or Cl- was trapped by the SF residue of opposite charge, leaving the linkage intact, thus preventing permeation. An Asp-Lys SF behaved like the Asp-Arg one and was experimentally verified to be proton-selective, as predicted. Hence, interacting acidic and basic residues form favorable AspH0-H2O0-Arg+ interactions with hydronium but unfavorable Asp--X-/X+-Arg+ interactions with anions/cations. This proposed mechanism may apply to other proton-selective molecules engaged in bioenergetics, homeostasis, and signaling.

  18. Analysis of Adverse Selection for Motivation Mechanism in Engineering Project Cost Management

    Directory of Open Access Journals (Sweden)

    Lin Yiyong

    2013-04-01

    Full Text Available When the principal-agent contracts for design, supervision and construction of an engineering project are signed, the agent and the principal have hidden information. By means of tendering and negotiation, etc., it selects an agent offering a lower quotation which leads to “Bad money drives out good”, that is, commonly termed adverse selection problem. This study starts from the discussion of adverse selection and introduces a motivation mechanism to motivate the agent to exert initiative strategies more efficiently so that the agent can expose its hidden information automatically. The study also analyzes the project principal-agent strategies and finally uses a calculation example to demonstrate that the motivation mechanism in this study is efficient in inducing the agent to tell the truth, which aids the principal in selecting an agent with higher operational level.

  19. Media evolution and ‘epi-technic’ digital media: Media as cultural selection mechanisms

    DEFF Research Database (Denmark)

    Olesen, Mogens

    2016-01-01

    The explosive development of new digital media technologies is often described as a media evolution but hardly ever is the concept of ‘media evolution’ taken at face value. This article takes up that challenge by combining cultural evolution theories with medium theory. The article argues...... that biological selection mechanisms can provide an inroad into a new kind of historical and structural understanding of the relation between human culture and our technologies. In specific, human history is seen as a cultural evolution in which media technologies are the selection mechanisms....

  20. Mechanisms of nociceptive transduction and transmission: a machinery for pain sensation and tools for selective analgesia.

    Science.gov (United States)

    Binshtok, Alexander M

    2011-01-01

    Many surgical and dental procedures depend on use of local anesthetics to reversibly eliminate pain. By the blockade of voltage-gated sodium channels, local anesthetics prevent the transmission of nociceptive information. However, since all local anesthetics act non-selectively on all types of axons they also cause a loss of innocuous sensation, motor paralysis and autonomic block. Thus, approaches that produce only a selective blockade of pain fibers are of great potential clinical importance. In this chapter we will review the recent findings describing mechanisms of pain transduction and transmission and introduce novel therapeutic approaches to produce pain-selective analgesia.

  1. Cation Selectivity in Biological Cation Channels Using Experimental Structural Information and Statistical Mechanical Simulation.

    Science.gov (United States)

    Finnerty, Justin John; Peyser, Alexander; Carloni, Paolo

    2015-01-01

    Cation selective channels constitute the gate for ion currents through the cell membrane. Here we present an improved statistical mechanical model based on atomistic structural information, cation hydration state and without tuned parameters that reproduces the selectivity of biological Na+ and Ca2+ ion channels. The importance of the inclusion of step-wise cation hydration in these results confirms the essential role partial dehydration plays in the bacterial Na+ channels. The model, proven reliable against experimental data, could be straightforwardly used for designing Na+ and Ca2+ selective nanopores.

  2. Contribution of Innate Cortical Mechanisms to the Maturation of Orientation Selectivity in Parvalbumin Interneurons.

    Science.gov (United States)

    Figueroa Velez, Dario X; Ellefsen, Kyle L; Hathaway, Ethan R; Carathedathu, Mathew C; Gandhi, Sunil P

    2017-01-25

    The maturation of cortical parvalbumin-positive (PV) interneurons depends on the interaction of innate and experience-dependent factors. Dark-rearing experiments suggest that visual experience determines when broad orientation selectivity emerges in visual cortical PV interneurons. Here, using neural transplantation and in vivo calcium imaging of mouse visual cortex, we investigated whether innate mechanisms contribute to the maturation of orientation selectivity in PV interneurons. First, we confirmed earlier findings showing that broad orientation selectivity emerges in PV interneurons by 2 weeks after vision onset, ∼35 d after these cells are born. Next, we assessed the functional development of transplanted PV (tPV) interneurons. Surprisingly, 25 d after transplantation (DAT) and >2 weeks after vision onset, we found that tPV interneurons have not developed broad orientation selectivity. By 35 DAT, however, broad orientation selectivity emerges in tPV interneurons. Transplantation does not alter orientation selectivity in host interneurons, suggesting that the maturation of tPV interneurons occurs independently from their endogenous counterparts. Together, these results challenge the notion that the onset of vision solely determines when PV interneurons become broadly tuned. Our results reveal that an innate cortical mechanism contributes to the emergence of broad orientation selectivity in PV interneurons.

  3. Brain mechanisms underlying the effects of aging on different aspects of selective attention

    NARCIS (Netherlands)

    Geerligs, Linda; Saliasi, Emi; Maurits, Natasha M; Renken, Remco J; Lorist, Monicque M

    2014-01-01

    The ability to suppress irrelevant information declines with age, while the ability to enhance relevant information remains largely intact. We examined mechanisms behind this dissociation in an fMRI study, using a selective attention task in which relevant and irrelevant information appeared simulta

  4. Neural Network Identification Model for Technology Selection of Fully-Mechanized Top-Coal Caving Mining

    Institute of Scientific and Technical Information of China (English)

    孟宪锐; 徐永勇; 汪进

    2001-01-01

    This paper mainly discusses the selection of the technical parameters of fully-mechanized top-coal caving mining using the neural network technique. The comparison between computing results and experiment data shows that the set-up neural network model has high accuracy and decision-making benefit.

  5. Social capital and employee well-being : Disentangling intrapersonal and interpersonal selection and influence mechanisms

    NARCIS (Netherlands)

    Agneessens, F.; Wittek, R.P.M.

    2008-01-01

    We argue that sociological explanations proposed within the social capital framework to explain individual well-being are incomplete because they do not differentiate between interpersonal influence and selection mechanisms, on the one hand, and cognitive intra-personal processes. on the other. To t

  6. Selection of checkpoints provided by the ergonomic checkpoints in agriculture tool for mechanized sugarcane harvesting

    Directory of Open Access Journals (Sweden)

    Ana Lucy Rodrigues Ferreira

    2014-11-01

    Full Text Available The changing work dynamics of sugarcane harvesting owing to increasing mechanization has submitted workers to new working conditions, including interaction with machinery and equipment, thereby changing the profile of work-related diseases and injuries. One of the ways to solve problems resulting from the impact of mechanization on working conditions is the use of instruments that allow risk identification from man-labor ratio. This study aimed at selecting checkpoints applicable to mechanized sugarcane harvesting provided by the Ergonomic Checkpoints in Agriculture tool. A literature review of the mechanical sugarcane harvesting stages was conducted and, in light of its particularities, checkpoints provided by the aforementioned tool were analyzed. As a result, there were identified thirty-four checkpoints with potential application to mechanical sugarcane harvesting.

  7. Oriented scanning is the leading mechanism underlying 5' splice site selection in mammals.

    Directory of Open Access Journals (Sweden)

    Keren Borensztajn

    2006-09-01

    Full Text Available Splice site selection is a key element of pre-mRNA splicing. Although it is known to involve specific recognition of short consensus sequences by the splicing machinery, the mechanisms by which 5' splice sites are accurately identified remain controversial and incompletely resolved. The human F7 gene contains in its seventh intron (IVS7 a 37-bp VNTR minisatellite whose first element spans the exon7-IVS7 boundary. As a consequence, the IVS7 authentic donor splice site is followed by several cryptic splice sites identical in sequence, referred to as 5' pseudo-sites, which normally remain silent. This region, therefore, provides a remarkable model to decipher the mechanism underlying 5' splice site selection in mammals. We previously suggested a model for splice site selection that, in the presence of consecutive splice consensus sequences, would stimulate exclusively the selection of the most upstream 5' splice site, rather than repressing the 3' following pseudo-sites. In the present study, we provide experimental support to this hypothesis by using a mutational approach involving a panel of 50 mutant and wild-type F7 constructs expressed in various cell types. We demonstrate that the F7 IVS7 5' pseudo-sites are functional, but do not compete with the authentic donor splice site. Moreover, we show that the selection of the 5' splice site follows a scanning-type mechanism, precluding competition with other functional 5' pseudo-sites available on immediate sequence context downstream of the activated one. In addition, 5' pseudo-sites with an increased complementarity to U1snRNA up to 91% do not compete with the identified scanning mechanism. Altogether, these findings, which unveil a cell type-independent 5'-3'-oriented scanning process for accurate recognition of the authentic 5' splice site, reconciliate apparently contradictory observations by establishing a hierarchy of competitiveness among the determinants involved in 5' splice site selection.

  8. Thermal and mechanical properties of selected 3D printed thermoplastics in the cryogenic temperature regime

    Science.gov (United States)

    Weiss, K.-P.; Bagrets, N.; Lange, C.; Goldacker, W.; Wohlgemuth, J.

    2015-12-01

    Insulating materials for use in cryogenic boundary conditions are still limited to a proved selection as Polyamid, Glasfiber reinforced resins, PEEK, Vespel etc. These materials are usually formed to parts by mechanical machining or sometimes by cast methods. Shaping complex geometries in one piece is limited. Innovative 3D printing is now an upcoming revolutionary technology to construct functional parts from a couple of thermoplastic materials as ABS, Nylon and others which possess quite good mechanical stability and allow realizing very complex shapes with very subtle details. Even a wide range of material mixtures is an option and thermal treatments can be used to finish the material structure for higher performance. The use of such materials in cryogenic environment is very attractive but so far poor experience exists. In this paper, first investigations of the thermal conductivity, expansion and mechanical strength are presented for a few selected commercial 3D material samples to evaluate their application prospects in the cryogenic temperature regime.

  9. The Establishment of a Green Supplier Selection and Guidance Mechanism with the ANP and IPA

    Directory of Open Access Journals (Sweden)

    Chih-Chao Chung

    2016-03-01

    Full Text Available This study aims to establish a green supplier selection and guidance mechanism by integrating the features of an ANP (Analytic Network Process and an IPA (Importance–Performance Analysis to achieve sustainable management for green supply chains. Using an expert survey, this study developed green supplier selection criteria. It adopted an ANP, which allows for interdependencies and feedback between the various criteria, to select competitive green suppliers. Then, it used an IPA, which can analyze the criteria’s significance and performance levels, to provide green suppliers with direction for guidance and improvements. The green supplier selection and guidance mechanism featuring an ANP and IPA is thus established and validated through case studies. The research results showed the following: (1 the green supplier selection criteria comprise a total of 11 performance evaluation criteria from the three dimensions of operation, competence, and environmental consciousness; (2 as shown by the APN evaluation results, environmental benefits, environmental regulations, finance, technological competence, and delivery time are the top five among the overall green criteria of the company; the performance of the various suppliers is thus arranged in order, and the most competitive supplier is selected; (3 an IPA is used to analyze the criteria’s significance and supplier performance levels and to provide the suppliers with suggestions on priority improvements, including implementing the requirements in the environmental regulations, establishing comprehensive financial management procedures, improving corporate technological competence, and consolidating customer service; (4 it is suggested that an ANP and IPA should be integrated in the applications, which could simplify the green supplier selection and guidance mechanisms and increase the efficiency of supplier management, thus creating a three-win situation for the clients, the company, and the

  10. In-Built Customised Mechanical Failure of 316L Components Fabricated Using Selective Laser Melting

    Directory of Open Access Journals (Sweden)

    Andrei Ilie

    2017-02-01

    Full Text Available The layer-by-layer building methodology used within the powder bed process of Selective Laser Melting facilitates control over the degree of melting achieved at every layer. This control can be used to manipulate levels of porosity within each layer, effecting resultant mechanical properties. If specifically controlled, it has the potential to enable customisation of mechanical properties or design of in-built locations of mechanical fracture through strategic void placement across a component, enabling accurate location specific predictions of mechanical failure for fail-safe applications. This investigation examined the process parameter effects on porosity formation and mechanical properties of 316L samples whilst maintaining a constant laser energy density without manipulation of sample geometry. In order to understand the effects of customisation on mechanical properties, samples were manufactured with in-built porosity of up to 3% spanning across ~1.7% of a samples’ cross-section using a specially developed set of “hybrid” processing parameters. Through strategic placement of porous sections within samples, exact fracture location could be predicted. When mechanically loaded, these customised samples exhibited only ~2% reduction in yield strength compared to samples processed using single set parameters. As expected, microscopic analysis revealed that mechanical performance was closely tied to porosity variations in samples, with little or no variation in microstructure observed through parameter variation. The results indicate that there is potential to use SLM for customising mechanical performance over the cross-section of a component.

  11. Structure and mechanical properties of austenitic 316L steel produced by selective laser melting

    Science.gov (United States)

    Kuznetsov, P. A.; Zisman, A. A.; Petrov, S. N.; Goncharov, I. S.

    2016-10-01

    The mechanical properties and the impact toughness of austenitic 316L steel produced by selective laser melting at a laser power of 175-190 W have been studied. It is shown that the selective laser melting method makes it possible to significantly increase the strength properties of the steel with some decrease in the ductility and the impact toughness as compared to those of the steel produced by a traditional technology. The laser power influences insignificantly. The methods of making notches and its orientation is found to influence the impact toughness.

  12. Integrated environmental and safety assessment of selected mechanical energy storage systems

    Science.gov (United States)

    1982-01-01

    The environmental, safety, and social impacts of two mechanical storage systems, underground pumped hydro (UPH) and compressed air energy storage (CAES) are similar to those of existing peaking power plants. These impacts, with engineering factors, form a methodology for selecting sites for these two systems. Application of this methodology to a hypothetical case indicates that, although design alternatives which mitigate adverse environmental impacts are recommended, site selection effectively limits the environmental effect of CAES or UPH plants. Public perception of CAES and UPH energy storage facilities should generally be positive, provided that those affected are informed and allowed to participate in the siting process.

  13. Catalytic conversion reactions in nanoporous systems with concentration-dependent selectivity: Statistical mechanical modeling

    Science.gov (United States)

    García, Andrés; Wang, Jing; Windus, Theresa L.; Sadow, Aaron D.; Evans, James W.

    2016-05-01

    Statistical mechanical modeling is developed to describe a catalytic conversion reaction A →Bc or Bt with concentration-dependent selectivity of the products, Bc or Bt, where reaction occurs inside catalytic particles traversed by narrow linear nanopores. The associated restricted diffusive transport, which in the extreme case is described by single-file diffusion, naturally induces strong concentration gradients. Furthermore, by comparing kinetic Monte Carlo simulation results with analytic treatments, selectivity is shown to be impacted by strong spatial correlations induced by restricted diffusivity in the presence of reaction and also by a subtle clustering of reactants, A .

  14. The influence of mechanical activation of chalcopyrite on the selective leaching of copper by sulphuric acid

    Directory of Open Access Journals (Sweden)

    Achimovičová, M.

    2006-01-01

    Full Text Available In this paper chalcopyrite, CuFeS2, has been selective leached by H2SO4 as leaching agent (170 g/dm3 in procedure of hydrometallurgical production of copper. Mechanical activation of the chalcopyrite resulted in mechanochemical surface oxidation as well as in the mineral surface and bulk disordering. Furthermore, the formation of agglomerates during grinding was also occured. Surface changes of the samples using infrared spectroscopy and scanning electron microscopy methods were investigated before and after leaching. The leaching rate, specific surface area, structural disorder as well as copper extraction increased with the mechanical activation of mineral.

  15. Selective synthesis and growth mechanism of CeVO4 nanoparticals via hydrothermal method

    Institute of Scientific and Technical Information of China (English)

    LIU Fengzhen; SHAO Xin; YIN Yibin; ZHAO Limin; SUN Qiaozhen; SHAO Zhuwei; LIU Xuehua; MENG Xianhua

    2011-01-01

    Selective-controlled structure and shape of CeVO4 nanocrystals were successfully synthesized via a hydrothermal method from electron microscopy (FESEM) and energy dispersive spectroscopy (EDS). The influence of hydrothermal temperature, precursor solution concentration on the crystal and morphology of products were further studied. The results showed that the as-synthesized products exhibited pure single-crystal CeVO4 nanoparticles with tetragonal structure. The hydrothermal temperature and precursor solution concentration had important effects on the formation of CeVO4 nanoparticles. Furthermore, the growth mechanism of CeVO4 nanoparticles was explained with Ostwald ripening mechanism.

  16. Effects of the Ordering of Natural Selection and Population Regulation Mechanisms on Wright-Fisher Models.

    Science.gov (United States)

    He, Zhangyi; Beaumont, Mark; Yu, Feng

    2017-07-05

    We explore the effect of different mechanisms of natural selection on the evolution of populations for one- and two-locus systems. We compare the effect of viability and fecundity selection in the context of the Wright-Fisher model with selection under the assumption of multiplicative fitness. We show that these two modes of natural selection correspond to different orderings of the processes of population regulation and natural selection in the Wright-Fisher model. We find that under the Wright-Fisher model these two different orderings can affect the distribution of trajectories of haplotype frequencies evolving with genetic recombination. However, the difference in the distribution of trajectories is only appreciable when the population is in significant linkage disequilibrium. We find that as linkage disequilibrium decays the trajectories for the two different models rapidly become indistinguishable. We discuss the significance of these findings in terms of biological examples of viability and fecundity selection, and speculate that the effect may be significant when factors such as gene migration maintain a degree of linkage disequilibrium. Copyright © 2017 He et al.

  17. Effects of the Ordering of Natural Selection and Population Regulation Mechanisms on Wright-Fisher Models

    Directory of Open Access Journals (Sweden)

    Zhangyi He

    2017-07-01

    Full Text Available We explore the effect of different mechanisms of natural selection on the evolution of populations for one- and two-locus systems. We compare the effect of viability and fecundity selection in the context of the Wright-Fisher model with selection under the assumption of multiplicative fitness. We show that these two modes of natural selection correspond to different orderings of the processes of population regulation and natural selection in the Wright-Fisher model. We find that under the Wright-Fisher model these two different orderings can affect the distribution of trajectories of haplotype frequencies evolving with genetic recombination. However, the difference in the distribution of trajectories is only appreciable when the population is in significant linkage disequilibrium. We find that as linkage disequilibrium decays the trajectories for the two different models rapidly become indistinguishable. We discuss the significance of these findings in terms of biological examples of viability and fecundity selection, and speculate that the effect may be significant when factors such as gene migration maintain a degree of linkage disequilibrium.

  18. Mechanism of selective separation on the surface of ionic sieve of removal of lead

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    This note describes a kind of ionic sieve with high selectivity to remove trace lead in water, in which stannic molybdopyrophosphate is used to be the substrate. The mechanism of selective separation on the surface of ionic sieve of removal of lead was explored by analyzing fourier transformation infrared spectra (FTIR), X-ray photoelectron spectrometry (XPS) and the results of selective adsorptivity experiment. The investigation suggests that in the process of synthesizing ionic sieve the olation reactions occur in solid phase by thermodynamic recrystallization and the adsorp- tion units with special selectivity to lead are formed by chemical modification. After the ion exchange for Pb2+, the oaltion reactions not only keep the microstructures of adsorption units from collapse, but also provide lead cavties with special selectivity to lead ion that are capable of having special binding "memory effect" to Pb2+ by SnO32? and P2O74 ? groups on the surface of this ionic sieve. Meanwhile, the selective separation capacity is a kind of weak chemical effect that is relative to the valence electron state of the adsorbed ion directly and tightly.

  19. The mechanisms of neurotoxicity and the selective vulnerability of nervous system sites.

    Science.gov (United States)

    Maurer, Laura L; Philbert, Martin A

    2015-01-01

    The spatial heterogeneity of the structure, function, and cellular composition of the nervous system confers extraordinary complexity and a multiplicity of mechanisms of chemical neurotoxicity. Because of its relatively high metabolic demands and functional dependence on postmitotic neurons, the nervous system is vulnerable to a variety of xenobiotics that affect essential homeostatic mechanisms that support function. Despite protection from the neuroglia and blood-brain barrier, the central nervous system is prone to attack from lipophilic toxicants and those that hijack endogenous transport, receptor, metabolic, and other biochemical systems. The inherent predilection of chemicals for highly conserved biochemical systems confers selective vulnerability of the nervous system to neurotoxicants. This chapter discusses selective vulnerability of the nervous system in the context of neuron-specific decrements (axonopathy, myelinopathy, disruption of neurotransmission), and the degree to which neuronal damage is facilitated or ameliorated by surrounding nonneural cells in both the central and peripheral nervous systems.

  20. A symmetry breaking mechanism for selecting the speed of relativistic solitons

    Energy Technology Data Exchange (ETDEWEB)

    Cadoni, Mariano [Dipartimento di Fisica, Universita di Cagliari and INFN, Sezione di Cagliari, Cittadella Universitaria, 09042 Monserrato (Italy); De Leo, Roberto [Dipartimento di Fisica, Universita di Cagliari and INFN, Sezione di Cagliari, Cittadella Universitaria, 09042 Monserrato (Italy); Gaeta, Giuseppe [Dipartimento di Matematica, Universita di Milano, via Saldini 50, 20133 Milan (Italy)

    2007-07-20

    We propose a mechanism for fixing the velocity of relativistic solitons based on the breaking of the Lorentz symmetry of the sine-Gordon (SG) model. The proposal is first elaborated for a molecular chain model as the simple pendulum limit of a double pendulums chain. It is then generalized to a full class of two-dimensional field theories of the sine-Gordon type. From a phenomenological point of view, the mechanism allows one to select the speed of a SG soliton just by tuning elastic couplings constants and kinematical parameters. From a fundamental, field-theoretical point of view we show that the characterizing features of relativistic SG solitons (existence of conserved topological charges and stability) may be still preserved even if the Lorentz symmetry is broken and a soliton of a given speed is selected.

  1. Simple arithmetic: evidence of an inhibitory mechanism to select arithmetic facts.

    Science.gov (United States)

    Megías, Patricia; Macizo, Pedro; Herrera, Amparo

    2015-09-01

    In two experiments we evaluated the coactivation of arithmetic facts and the possible inhibitory mechanism used to select the correct one. To this end, we introduced an adapted version of the negative priming paradigm in which participants received additions and they decided whether they were correct or not. When the addition was incorrect but the result was that of multiplying the operands (e.g., 2 + 4 = 8), participants took more time to respond relative to control additions with unrelated results. This finding corroborated that participants coactivated arithmetic facts of multiplications even when they were irrelevant to perform the task. Moreover, the participants were slower to respond to an addition whose result was that of multiplying the operands of the previous trial (e.g., 2 + 6 = 8). These results support the existence of an inhibitory mechanism involved in the selection of arithmetic facts.

  2. Breaking the hierarchy - a new cluster selection mechanism for hierarchical clustering methods

    Directory of Open Access Journals (Sweden)

    Zweig Katharina A

    2009-10-01

    Full Text Available Abstract Background Hierarchical clustering methods like Ward's method have been used since decades to understand biological and chemical data sets. In order to get a partition of the data set, it is necessary to choose an optimal level of the hierarchy by a so-called level selection algorithm. In 2005, a new kind of hierarchical clustering method was introduced by Palla et al. that differs in two ways from Ward's method: it can be used on data on which no full similarity matrix is defined and it can produce overlapping clusters, i.e., allow for multiple membership of items in clusters. These features are optimal for biological and chemical data sets but until now no level selection algorithm has been published for this method. Results In this article we provide a general selection scheme, the level independent clustering selection method, called LInCS. With it, clusters can be selected from any level in quadratic time with respect to the number of clusters. Since hierarchically clustered data is not necessarily associated with a similarity measure, the selection is based on a graph theoretic notion of cohesive clusters. We present results of our method on two data sets, a set of drug like molecules and set of protein-protein interaction (PPI data. In both cases the method provides a clustering with very good sensitivity and specificity values according to a given reference clustering. Moreover, we can show for the PPI data set that our graph theoretic cohesiveness measure indeed chooses biologically homogeneous clusters and disregards inhomogeneous ones in most cases. We finally discuss how the method can be generalized to other hierarchical clustering methods to allow for a level independent cluster selection. Conclusion Using our new cluster selection method together with the method by Palla et al. provides a new interesting clustering mechanism that allows to compute overlapping clusters, which is especially valuable for biological and

  3. Hybrid Micro-Electro-Mechanical Systems for Highly Reliable and Selective Characterization of Tank Waste

    Energy Technology Data Exchange (ETDEWEB)

    Panos G. Datskos; Michael J. Sepaniak; Nickolay Lavrik; Pampa Dutta; Mustafa Culha

    2005-12-28

    The main objective of this research program is to develop robust and reliable micro-electro-mechanical sensing systems, based on microcantilevers (MCs), that can operate in liquid environments with high levels of sensitivity and selectivity. The chemical responses of MCs result from analyte-induced differential stress at the cantilever surfaces. We aim to employ various surface nanostructuring strategies that enhance these stresses and hence the degree of static bending of the cantilevers. Receptor phases as self assembled monolayers (SAMs) and thin films are being synthesized and tested to provide selectivity. Selectivity is chemically enhanced by using different phases on individual MCs in arrays and by adding a spectroscopic component, surface enhanced Raman spectrometry (SERS), in hybrid approaches to sensing. Significant progress was made in tasks that were listed in the work plan for DOE EMSP project ''Hybrid Micro-Electro-Mechanical Systems for Highly Reliable and Selective Characterization of Tank Waste''. Several project areas are listed below and discussed and referenced to our literature on the topics.

  4. Hybrid Micro-Electro-Mechanical Systems for Highly Reliable and Selective Characterization of Tank Waste

    Energy Technology Data Exchange (ETDEWEB)

    Panos G. Datskos; Michael J. Sepaniak; Nickolay Lavrik; Pampa Dutta; Mustafa Culha

    2005-12-28

    The main objective of this research program is to develop robust and reliable micro-electro-mechanical sensing systems, based on microcantilevers (MCs), that can operate in liquid environments with high levels of sensitivity and selectivity. The chemical responses of MCs result from analyte-induced differential stress at the cantilever surfaces. We aim to employ various surface nanostructuring strategies that enhance these stresses and hence the degree of static bending of the cantilevers. Receptor phases as self assembled monolayers (SAMs) and thin films are being synthesized and tested to provide selectivity. Selectivity is chemically enhanced by using different phases on individual MCs in arrays and by adding a spectroscopic component, surface enhanced Raman spectrometry (SERS), in hybrid approaches to sensing. Significant progress was made in tasks that were listed in the work plan for DOE EMSP project ''Hybrid Micro-Electro-Mechanical Systems for Highly Reliable and Selective Characterization of Tank Waste''. Several project areas are listed below and discussed and referenced to our literature on the topics.

  5. Biotechnological Wood Modification with Selective White-Rot Fungi and Its Molecular Mechanisms

    Directory of Open Access Journals (Sweden)

    Cornelia Gradinger

    2007-01-01

    Full Text Available Microbial mechanisms of lignin degradation may be utilised for solid-state fermentations other than biopulping, during which the selective conversion of lignin is required. The current paper reviews current work into selective lignin conversion, with emphasis on the contributions made by our research group, which consists of researchers from five different laboratories. Three of them cooperate within Wood K plus. The recent research of this group has focussed on fermentations utilising the unique metabolism of selective white-rot fungi to modify wood surfaces during relatively short fermentation times of less than one week and on research into the molecular mechanisms causing these modifications. Lignin degradation by selective fungi (e.g. Ceriporiopsis subvermispora and species of the genus Phlebia on the wood surfaces was significant after three days. After seven days the overall lignin content of spruce wood shavings was reduced by more than 3.5 %. Lignin loss was accompanied by an increase of extractable substances. To evaluate small changes and to trace the fungal modification processes, Fourier transform infrared spectroscopic (FTIR techniques and electron paramagnetic resonance (EPR spectroscopy were applied and adapted. The spectra recorded in the near infrared region (FT-NIR turned out to be very useful for kinetic studies of the biopulping/biomodification processes and a good method to evaluate the capabilities of fungi to modify wood surfaces within this short period.

  6. The role of alpha-band brain oscillations as a sensory suppression mechanism during selective attention.

    Directory of Open Access Journals (Sweden)

    John J Foxe

    2011-07-01

    Full Text Available Evidence has amassed from both animal intracranial recordings and human electrophysiology that neural oscillatory mechanisms play a critical role in a number of cognitive functions such as learning, memory, feature binding and sensory gating. The wide availability of high-density electrical and magnetic recordings (64-256 channels over the past two decades has allowed for renewed efforts in the characterization and localization of these rhythms. A variety of cognitive effects that are associated with specific brain oscillations have been reported, which range in spectral, temporal, and spatial characteristics depending on the context. Our laboratory has focused on investigating the role of alpha-band oscillatory activity (8-14 Hz as a potential attentional suppression mechanism, and this particular oscillatory attention mechanism will be the focus of the current review. We discuss findings in the context of intersensory selective attention as well as intrasensory spatial and feature-based attention in the visual, auditory, and tactile domains. The weight of evidence suggests that alpha-band oscillations can be actively invoked within cortical regions across multiple sensory systems, particularly when these regions are involved in processing irrelevant or distracting information. That is, a central role for alpha seems to be as an attentional suppression mechanism when objects or features need to be specifically ignored or selected against.

  7. Molecular Mechanism of Selectivity among G Protein-Coupled Receptor Kinase 2 Inhibitors

    Energy Technology Data Exchange (ETDEWEB)

    Thal, David M.; Yeow, Raymond Y.; Schoenau, Christian; Huber, Jochen; Tesmer, John J.G. (Sanofi); (Michigan)

    2012-07-11

    G protein-coupled receptors (GPCRs) are key regulators of cell physiology and control processes ranging from glucose homeostasis to contractility of the heart. A major mechanism for the desensitization of activated GPCRs is their phosphorylation by GPCR kinases (GRKs). Overexpression of GRK2 is strongly linked to heart failure, and GRK2 has long been considered a pharmaceutical target for the treatment of cardiovascular disease. Several lead compounds developed by Takeda Pharmaceuticals show high selectivity for GRK2 and therapeutic potential for the treatment of heart failure. To understand how these drugs achieve their selectivity, we determined crystal structures of the bovine GRK2-G{beta}{gamma} complex in the presence of two of these inhibitors. Comparison with the apoGRK2-G{beta}{gamma} structure demonstrates that the compounds bind in the kinase active site in a manner similar to that of the AGC kinase inhibitor balanol. Both balanol and the Takeda compounds induce a slight closure of the kinase domain, the degree of which correlates with the potencies of the inhibitors. Based on our crystal structures and homology modeling, we identified five amino acids surrounding the inhibitor binding site that we hypothesized could contribute to inhibitor selectivity. However, our results indicate that these residues are not major determinants of selectivity among GRK subfamilies. Rather, selectivity is achieved by the stabilization of a unique inactive conformation of the GRK2 kinase domain.

  8. Cooperation between Trust and Routing Mechanisms for Relay Node Selection in Hybrid MANET-DTN

    Directory of Open Access Journals (Sweden)

    Jan Papaj

    2016-01-01

    Full Text Available Today’s mobile networks require integration of the different networks in order to transport data between mobile devices. The main problems of all networks occur if the communication paths are disconnected for a short time. The hybrid MANET-DTN is an evolution of the Mobile Ad Hoc Networks (MANET and Delay/Disruption Tolerant Network (DTN and it gives the possibilities of data transport between the disconnected islands of the nodes. The key problem is how to select reliable and secure nodes to transport messages between isolated islands with limited connectivity. The selection of the relay nodes is a critical factor because the data are transported via these devices in hostile environments. Two algorithms for a relay node selection based on trust are introduced. These algorithms are activated if the connections are disrupted. The selected relay nodes transport data across the disconnected environment via store-carry-forward mode. The proposed algorithms enable selecting reliable relay nodes based on collecting routing information and contact history. We introduce the network performance analyses of these algorithms. The main idea of the analyses is studying how the algorithms can affect the behaviour of the routing and forwarding mechanisms in the simulator OPNET modeler.

  9. A biological mechanism for Bayesian feature selection: Weight decay and raising the LASSO.

    Science.gov (United States)

    Connor, Patrick; Hollensen, Paul; Krigolson, Olav; Trappenberg, Thomas

    2015-07-01

    Biological systems are capable of learning that certain stimuli are valuable while ignoring the many that are not, and thus perform feature selection. In machine learning, one effective feature selection approach is the least absolute shrinkage and selection operator (LASSO) form of regularization, which is equivalent to assuming a Laplacian prior distribution on the parameters. We review how such Bayesian priors can be implemented in gradient descent as a form of weight decay, which is a biologically plausible mechanism for Bayesian feature selection. In particular, we describe a new prior that offsets or "raises" the Laplacian prior distribution. We evaluate this alongside the Gaussian and Cauchy priors in gradient descent using a generic regression task where there are few relevant and many irrelevant features. We find that raising the Laplacian leads to less prediction error because it is a better model of the underlying distribution. We also consider two biologically relevant online learning tasks, one synthetic and one modeled after the perceptual expertise task of Krigolson et al. (2009). Here, raising the Laplacian prior avoids the fast erosion of relevant parameters over the period following training because it only allows small weights to decay. This better matches the limited loss of association seen between days in the human data of the perceptual expertise task. Raising the Laplacian prior thus results in a biologically plausible form of Bayesian feature selection that is effective in biologically relevant contexts.

  10. Temperature dependency of cupular mechanics and hair cell frequency selectivity in the fish canal lateral line organ

    NARCIS (Netherlands)

    Wiersinga-Post, JEC; van Netten, SM

    2000-01-01

    The mechanical frequency selectivity of the cupula located in the supraorbital lateral line canal and the frequency selectivity of the hair cells driven by the cupula were measured simultaneously in vivo. Laser interferometry was used to measure cupular mechanics and extracellular receptor potential

  11. Directional, stabilizing, and disruptive trait selection as alternative mechanisms for plant community assembly.

    Science.gov (United States)

    Rolhauser, Andrés G; Pucheta, Eduardo

    2017-03-01

    How plant functional traits (e.g., seed mass) drive species abundance within communities remains an unsolved question. Borrowing concepts from natural selection theory, we propose that trait-abundance relationships can generally correspond to one of three modes of trait selection: directional (a rectilinear relationship, where species at one end of a trait axis are most abundant), stabilizing (an n-shaped relationship), and disruptive (a u-shaped relationship). Stabilizing selection (i.e., the functional convergence of abundant species) would result from positive density-dependent interactions (e.g., facilitation) or due to generalized trade-offs in resource acquisition/use, while disruptive selection (i.e., the divergence of abundant species) would result from negative density-dependent interactions (e.g., competition) or due to environmental heterogeneity. These selection modes can be interpreted as proxies for community-level trait-fitness functions, which establish the degree to which traits are truly "functional". We searched for selection modes in a desert annual-plant community in Argentina (which was divided into winter and summer guilds) to test the hypothesis that the relative importance of disruptive mechanisms (competition, disturbances) decreases with the increase of abiotic stress, a stabilizing agent. Average density was analyzed as a function of eight traits generally linked to resource acquisition and competitive ability (maximum plant height, leaf size, specific leaf area, specific root length), resource retention and stress tolerance (leaf dissection, leaf dry matter content, specific root volume), and regeneration (seed mass) using multiple quadratic-regression models. Trait selection was stabilizing and/or directional when the environment was harshest (winter) and disruptive and/or directional when conditions were milder (summer). Selection patterns differed between guilds for two important traits: plant height and seed mass. These results

  12. Selective LPCVD growth of graphene on patterned copper and its growth mechanism

    Science.gov (United States)

    Zhang, M.; Huang, B.-C.; Wang, Y.; Woo, J. C. S.

    2016-12-01

    Copper-catalyzed graphene low-pressure chemical-vapor deposition (LPCVD) growth has been regarded as a viable solution towards its integration to CMOS technology, and the wafer-bonding method provides a reliable alternative for transferring the selective graphene grown on a patterned metal film for IC manufacturing. In this paper, selective LPCVD graphene growth using patterned copper dots has been studied. The Raman spectra of grown films have demonstrated large dependence on the growth conditions. To explain the results, the growth mechanisms based on surface adsorption and copper-vapor-assisted growth are investigated by the comparison between the blanket copper films with/without the additional copper source. The copper vapor density is found to be critical for high-quality graphene growth. In addition, the copper-vapor-assisted growth is also evidenced by the carbon deposition on the SiO2 substrate of the patterned-copper-dot sample and chamber wall during graphene growth. This growth mechanism explains the correlation between the growth condition and Raman spectrum for films on copper dots. The study on the copper-catalyzed selective graphene growth on the hard substrate paves the way for the synthesis and integration of the 2D material in VLSI.

  13. Tribochemical interaction between nanoparticles and surfaces of selective layer during chemical mechanical polishing

    Energy Technology Data Exchange (ETDEWEB)

    Ilie, Filip, E-mail: filip@meca.omtr.pub.ro [Polytechnic University of Bucharest, Department of Machine Elements and Tribology (Romania)

    2013-11-15

    Nanoparticles have been widely used in polish slurries such as those in the chemical mechanical polishing (CMP) process. For understanding the mechanisms of CMP, an atomic force microscope (AFM) is used to characterize polished surfaces of selective layers, after a set of polishing experiments. To optimize the CMP polishing process, one needs to get information on the interaction between the nano-abrasive slurry nanoparticles and the surface of selective layer being polished. The slurry used in CMP process of the solid surfaces is slurry with large nanoparticle size colloidal silica sol nano-abrasives. Silica sol nano-abrasives with large nanoparticle are prepared and characterized by transmission electron microscopy, particles colloidal size, and Zeta potential in this paper. The movement of nanoparticles in liquid and the interaction between nanoparticles and solid surfaces coating with selective layer are very important to obtain an atomic alloy smooth surface in the CMP process. We investigate the nanoparticle adhesion and removal processes during CMP and post-CMP cleaning. The mechanical interaction between nanoparticles and the wafer surface was studied using a microcontact wear model. This model considers the nanoparticle effects between the polishing interfaces during load balancing. Experimental results on polishing and cleaning are compared with numerical analysis. This paper suggests that during post-CMP cleaning, a combined effort in chemical and mechanical interaction (tribochemical interactions) would be effective in removal of small nanoparticles during cleaning. For large nanoparticles, more mechanical forces would be more effective. CMP results show that the removal rate has been improved to 367 nm/min and root mean square (RMS) of roughness has been reduced from 4.4 to 0.80 nm. Also, the results show that the silica sol nano-abrasives about 100 nm are of higher stability (Zeta potential is −65 mV) and narrow distribution of nanoparticle

  14. FTIR spectra and mechanical strength analysis of some selected rubber derivatives.

    Science.gov (United States)

    Gunasekaran, S; Natarajan, R K; Kala, A

    2007-10-01

    Rubber materials have wide range of commercial applications such as, infant diapers, famine hygiene products, drug delivery devices and incontinency products such as rubber tubes, tyres, etc. In the present work, studies on mechanical properties of some selected rubber materials viz., natural rubber (NR), styrene butadiene rubber (SBR), nitrile butadiene rubber (NBR) and ethylene propylene diene monomer (EPDM) have been carried out in three states viz., raw, vulcanized and reinforced. To enhance the quality of rubber elastomers, an attempt is made to prepare new elastomers called polyblends. In the present study an attempt is made to blend NR with NBR and with EPDM. We here report, a novel approach for the evaluation of various physico-mechanical properties such as mechanical strength, tensile strength, elongation and hardness. The method is simple, direct and fast and involves infrared spectral measurements for the evaluation of these properties. With the applications of modern infrared spectroscopy, the mechanical strength of these rubber materials have been analyzed by calculating the internal standards among the methyl and methylene group vibrational frequencies obtained from FTIR spectroscopy. Also the tensile strength measurements carried out by universal testing machine. The results pertaining physico-mechanical properties of the rubber derivatives undertaken in the present study obtained by IR-based method are in good agreement with data resulted from the standard methods.

  15. Distractor suppression when attention fails: behavioral evidence for a flexible selective attention mechanism.

    Science.gov (United States)

    Elliott, James C; Giesbrecht, Barry

    2015-01-01

    Despite consistent evidence showing that attention is a multifaceted mechanism that can operate at multiple levels of processing depending on the structure and demands of the task, investigations of the attentional blink phenomenon have consistently shown that the impairment in reporting the second of two targets typically occurs at a late, or post-perceptual, stage of processing. This suggests that the attentional blink phenomenon may represent the operation of a unique attentional mechanism that is not as flexible as other attentional mechanisms. To test whether the attentional blink is a fixed or flexible phenomenon, we manipulated first target task demands (i.e., difficulty) and measured the influence this had on processing a subsequently presented distractor and the second target. If the attentional blink represents a mechanism that is fixed and consistently fails at a single stage of processing, then manipulations of task difficulty should not affect distractor processing. However, if the attentional blink represents a more multifaceted and flexible mechanism, then task difficulty should modulate distractor processing. The results revealed that distractor processing during the AB was attenuated under high task difficulty. In addition, unlike previous studies, we failed to find a correlation between distractor processing and the severity of the attentional blink. Using a simulation, we demonstrate that the previously reported correlations may have been spurious and due to using variables that were not independent. Overall, the present results support the conclusion that the selectivity of attention during the AB is flexible and depends on the structure and demands of the task.

  16. Game theory-based mode cooperative selection mechanism for device-to-device visible light communication

    Science.gov (United States)

    Liu, Yuxin; Huang, Zhitong; Li, Wei; Ji, Yuefeng

    2016-03-01

    Various patterns of device-to-device (D2D) communication, from Bluetooth to Wi-Fi Direct, are emerging due to the increasing requirements of information sharing between mobile terminals. This paper presents an innovative pattern named device-to-device visible light communication (D2D-VLC) to alleviate the growing traffic problem. However, the occlusion problem is a difficulty in D2D-VLC. This paper proposes a game theory-based solution in which the best-response dynamics and best-response strategies are used to realize a mode-cooperative selection mechanism. This mechanism uses system capacity as the utility function to optimize system performance and selects the optimal communication mode for each active user from three candidate modes. Moreover, the simulation and experimental results show that the mechanism can attain a significant improvement in terms of effectiveness and energy saving compared with the cases where the users communicate via only the fixed transceivers (light-emitting diode and photo diode) or via only D2D.

  17. Slide-and-exchange mechanism for rapid and selective transport through the nuclear pore complex

    Science.gov (United States)

    Raveh, Barak; Karp, Jerome M.; Sparks, Samuel; Rout, Michael P.; Sali, Andrej; Cowburn, David

    2016-01-01

    Nucleocytoplasmic transport is mediated by the interaction of transport factors (TFs) with disordered phenylalanine-glycine (FG) repeats that fill the central channel of the nuclear pore complex (NPC). However, the mechanism by which TFs rapidly diffuse through multiple FG repeats without compromising NPC selectivity is not yet fully understood. In this study, we build on our recent NMR investigations showing that FG repeats are highly dynamic, flexible, and rapidly exchanging among TF interaction sites. We use unbiased long timescale all-atom simulations on the Anton supercomputer, combined with extensive enhanced sampling simulations and NMR experiments, to characterize the thermodynamic and kinetic properties of FG repeats and their interaction with a model transport factor. Both the simulations and experimental data indicate that FG repeats are highly dynamic random coils, lack intrachain interactions, and exhibit significant entropically driven resistance to spatial confinement. We show that the FG motifs reversibly slide in and out of multiple TF interaction sites, transitioning rapidly between a strongly interacting state and a weakly interacting state, rather than undergoing a much slower transition between strongly interacting and completely noninteracting (unbound) states. In the weakly interacting state, FG motifs can be more easily displaced by other competing FG motifs, providing a simple mechanism for rapid exchange of TF/FG motif contacts during transport. This slide-and-exchange mechanism highlights the direct role of the disorder within FG repeats in nucleocytoplasmic transport, and resolves the apparent conflict between the selectivity and speed of transport. PMID:27091992

  18. A Three-Phase Multiobjective Mechanism for Selecting Retail Stores to Close

    Directory of Open Access Journals (Sweden)

    Rong-Chang Chen

    2016-01-01

    Full Text Available To operate a successful and growing business, a retail store manager has to make tough decisions about selectively closing underperforming stores. In this paper, we propose using a three-phase multiobjective mechanism to help retail industry practitioners determine which stores to close. In the first phase, a geographic information system (GIS and k-means clustering algorithm are used to divide all the stores into clusters. In the second phase, stores can be strategically selected according to the requirements of the company and the attributes of the stores. In the third phase, a neighborhood-based multiobjective genetic algorithm (NBMOGA is utilized to determine which stores to close. To examine the effectiveness of the proposed three-phase mechanism, a variety of experiments are performed, based partly on a real dataset from a stock-list company in Taiwan. Results from the experiments show that the proposed three-phase mechanism can help efficiently decide which store locations to close. In addition, the neighborhood radius has a considerable influence on the results.

  19. Nutrient availability as a mechanism for selection of antibiotic tolerant Pseudomonas aeruginosa within the CF airway.

    Directory of Open Access Journals (Sweden)

    Lucas R Hoffman

    2010-01-01

    Full Text Available Microbes are subjected to selective pressures during chronic infections of host tissues. Pseudomonas aeruginosa isolates with inactivating mutations in the transcriptional regulator LasR are frequently selected within the airways of people with cystic fibrosis (CF, and infection with these isolates has been associated with poorer lung function outcomes. The mechanisms underlying selection for lasR mutation are unknown but have been postulated to involve the abundance of specific nutrients within CF airway secretions. We characterized lasR mutant P. aeruginosa strains and isolates to identify conditions found in CF airways that select for growth of lasR mutants. Relative to wild-type P. aeruginosa, lasR mutants exhibited a dramatic metabolic shift, including decreased oxygen consumption and increased nitrate utilization, that is predicted to confer increased fitness within the nutrient conditions known to occur in CF airways. This metabolic shift exhibited by lasR mutants conferred resistance to two antibiotics used frequently in CF care, tobramycin and ciprofloxacin, even under oxygen-dependent growth conditions, yet selection for these mutants in vitro did not require preceding antibiotic exposure. The selection for loss of LasR function in vivo, and the associated adverse clinical impact, could be due to increased bacterial growth in the oxygen-poor and nitrate-rich CF airway, and from the resulting resistance to therapeutic antibiotics. The metabolic similarities among diverse chronic infection-adapted bacteria suggest a common mode of adaptation and antibiotic resistance during chronic infection that is primarily driven by bacterial metabolic shifts in response to nutrient availability within host tissues.

  20. SELECTION OF METHOD FOR REGULATION OF TRACTOR PROPULSION ASYNCHRONOUS ELECTRIC MOTOR AND CONSTRUCTION OF MECHANICAL CHARACTERISTICS

    Directory of Open Access Journals (Sweden)

    Ch. I. Zhdanovich

    2015-01-01

    Full Text Available Nowadays the work is in progress to develop wheeled and caterpillar tractors with electromechanical transmission. Range of changes in transmission gear ratio while using propulsion electric motor depends on mechanical characteristics of a tractor propulsion electric motor which is equipped with electromechanical transmission. In case when the range is rather high then it is possible to minimize number of gearings in the tractor gearing box or exclude its usage at all. Type of the applied propulsion electric motor and regulation method specify type of mechanical characteristics (characteristics family of the propulsion electric motor.The paper considers a propulsion asynchronous electric motor with frequency control. While using frequency control it is possible to regulate electric motor revolutions by mutual changes in voltage and voltage frequency. There are various laws of mutual changes in voltage and frequency (regulation laws. Selection of a regulation law influences on type of mechanical characteristics of a propulsion electric motor. Application of any law can be admissible only for some specific range of voltage frequency otherwise it is possible to exceed some parameters (for example, admissible voltage in the winding of electric motor stator. It is necessary to ensure the required moment within wide range for a tractor propulsion electric motor. In this case losses in the electric motor must be minimal. Losses in the rotor of the propulsion asynchronous electric motor are directly proportional to its sliding and its best propulsion and mechanical properties of a mobile machine will be ensured in the case when sliding is preserved at a constant value. According to these reasons selection of regulation laws has been carried out for operation of the propulsion asynchronous electric motor with nominal sliding and mechanical characteristics at nominal sliding is conventionally called a nominal characteristics.The paper analyzes the possible

  1. A repulsion mechanism explains magnesium permeation and selectivity in CorA.

    Science.gov (United States)

    Dalmas, Olivier; Sandtner, Walter; Medovoy, David; Frezza, Ludivine; Bezanilla, Francisco; Perozo, Eduardo

    2014-02-25

    Magnesium (Mg(2+)) plays a central role in biology, regulating the activity of many enzymes and stabilizing the structure of key macromolecules. In bacteria, CorA is the primary source of Mg(2+) uptake and is self-regulated by intracellular Mg(2+). Using a gating mutant at the divalent ion binding site, we were able to characterize CorA selectivity and permeation properties to both monovalent and divalent cations under perfused two-electrode voltage clamp. The present data demonstrate that under physiological conditions, CorA is a multioccupancy Mg(2+)-selective channel, fully excluding monovalent cations, and Ca(2+), whereas in absence of Mg(2+), CorA is essentially nonselective, displaying only mild preference against other divalents (Ca(2+) > Mn(2+) > Co(2+) > Mg(2+) > Ni(2)(+)). Selectivity against monovalent cations takes place via Mg(2+) binding at a high-affinity site, formed by the Gly-Met-Asn signature sequence (Gly312 and Asn314) at the extracellular side of the pore. This mechanism is reminiscent of repulsion models proposed for Ca(2+) channel selectivity despite differences in sequence and overall structure.

  2. Quantum mechanics, high energy physics and accelerators selected papers of John S Bell (with commentary)

    CERN Document Server

    Bell, John Stewart; Gottfried, Kurt; Veltman, Martinus J G

    1994-01-01

    The scientific career of John Stewart Bell was distinguished by its breadth and its quality. He made several very important contributions to scientific fields as diverse as accelerator physics, high energy physics and the foundations of quantum mechanics. This book contains a large part of J S Bell's publications, including those that are recognized as his most important achievements, as well as others that are for no good reason less well known. The selection was made by Mary Bell, Martinus Veltman and Kurt Gottfried, all of whom were involved with John Bell both personally and professionally throughout a large part of his life. An introductory chapter has been written to help place the selected papers in a historical context and to review their significance. This book comprises an impressive collection of outstanding scientific work of one of the greatest scientists of the recent past, and it will remain important and influential for a long time to come.

  3. Application of the quantum mechanical IEF/PCM-MST hydrophobic descriptors to selectivity in ligand binding.

    Science.gov (United States)

    Ginex, Tiziana; Muñoz-Muriedas, Jordi; Herrero, Enric; Gibert, Enric; Cozzini, Pietro; Luque, F Javier

    2016-06-01

    We have recently reported the development and validation of quantum mechanical (QM)-based hydrophobic descriptors derived from the parametrized IEF/PCM-MST continuum solvation model for 3D-QSAR studies within the framework of the Hydrophobic Pharmacophore (HyPhar) method. In this study we explore the applicability of these descriptors to the analysis of selectivity fields. To this end, we have examined a series of 88 compounds with inhibitory activities against thrombin, trypsin and factor Xa, and the HyPhar results have been compared with 3D-QSAR models reported in the literature. The quantitative models obtained by combining the electrostatic and non-electrostatic components of the octanol/water partition coefficient yield results that compare well with the predictive potential of standard CoMFA and CoMSIA techniques. The results also highlight the potential of HyPhar descriptors to discriminate the selectivity of the compounds against thrombin, trypsin, and factor Xa. Moreover, the graphical representation of the hydrophobic maps provides a direct linkage with the pattern of interactions found in crystallographic structures. Overall, the results support the usefulness of the QM/MST-based hydrophobic descriptors as a complementary approach for disclosing structure-activity relationships in drug design and for gaining insight into the molecular determinants of ligand selectivity. Graphical Abstract Quantum Mechanical continuum solvation calculations performed with the IEF/PCM-MST method are used to derived atomic hydrophobic descriptors, which are then used to discriminate the selectivity of ligands against thrombin, trypsin and factor Xa. The descriptors provide complementary view to standard 3D-QSAR analysis, leading to a more comprehensive understanding of ligand recognition.

  4. Ion Selectivity Mechanism in a Bacterial Pentameric Ligand-Gated Ion Channel

    Energy Technology Data Exchange (ETDEWEB)

    Fritsch, Sebastian M [ORNL; Ivanov, Ivaylo N [ORNL; Wang, Hailong [Mayo Clinic College of Medicine; Cheng, Xiaolin [ORNL

    2011-01-01

    The proton-gated ion channel from Gloeobacter violaceus (GLIC) is a prokaryotic homolog of the eukaryotic nicotinic acetylcholine receptor (nAChR) that responds to the binding of neurotransmitter acetylcholine and mediates fast signal transmission. Recent emergence of a high resolution crystal structure of GLIC captured in a potentially open state allowed detailed, atomic-level insight into ion conduction and selectivity mechanisms in these channels. Herein, we have examined the barriers to ion conduction and origins of ion selectivity in the GLIC channel by the construction of potential of mean force (PMF) profiles for sodium and chloride ions inside the transmembrane region. Our calculations reveal that the GLIC channel is open for a sodium ion to transport, but presents a ~10 kcal/mol free energy barrier for a chloride ion, which arises primarily from the unfavorable interactions with a ring of negatively charged glutamate residues (E-2 ) at the intracellular end and a ring of hydrophobic residues (I9 ) in the middle of the transmembrane domain. Our collective findings further suggest that the charge selection mechanism can, to a large extent, be attributed to the narrow intracellular end and a ring of glutamate residues in this position their strong negative electrostatics and ability to bind cations. By contrast, E19 at the extracellular entrance only plays a minor role in ion selectivity of GLIC. In addition to electrostatics, both ion hydration and protein dynamics are found to be crucial for ion conduction as well, which explains why a chloride ion experiences a much greater barrier than a sodium ion in the hydrophobic region of the pore.

  5. Abnormal Base Excision Repair at Trinucleotide Repeats Associated with Diseases: A Tissue-Selective Mechanism

    Directory of Open Access Journals (Sweden)

    Agathi-Vasiliki Goula

    2013-07-01

    Full Text Available More than fifteen genetic diseases, including Huntington’s disease, myotonic dystrophy 1, fragile X syndrome and Friedreich ataxia, are caused by the aberrant expansion of a trinucleotide repeat. The mutation is unstable and further expands in specific cells or tissues with time, which can accelerate disease progression. DNA damage and base excision repair (BER are involved in repeat instability and might contribute to the tissue selectivity of the process. In this review, we will discuss the mechanisms of trinucleotide repeat instability, focusing more specifically on the role of BER.

  6. A Mixed Mechanism of Weighted-Driven and Inner Selection in Networks

    Institute of Scientific and Technical Information of China (English)

    ZHANG Gui-Qing; WANG Lin; CHEN Tian-Lun

    2009-01-01

    For most networks, the weight of connection is changing with their attachment and inner affinity. By introducing a mixed mechanism of weighted-driven and inner selection, the model exhibits wide range power-law dis-tributions of node strength and edge weight, and the exponent can be adjusted by not only the parameter δ but also the probability q. Furthermore, we investigate the weighted average shortest distance, clustering coefficient, and the correlation of our network. In addition, the weighted assortativity coefficient which characterizes important information of weighted topological networks has been discussed, but the variation of coefficients is much smaller than the former researches.

  7. Mathematical physics of quantum mechanics. Selected and refereed lectures from QMath9

    Energy Technology Data Exchange (ETDEWEB)

    Asch, J. [Universite du Sud Toulon Var, 83 - La Garde (France). Dept. de Mathematiques; Joye, A. (eds.) [Grenoble-1 Univ., 38 (France). Inst. Fourier

    2006-07-01

    QMath9 is a meeting for young scientists to learn about the state of the art in the Mathematical Physics of Quantum Systems. This selection of outstanding articles written in pedagogical style has six sections that cover new techniques and recent results on spectral theory, statistical mechanics, Bose-Einstein condensation, random operators, magnetic Schroedinger operators and much more. For postgraduate students this book can be used as a useful introduction to the research literature. For more expert researcher this book will be a concise and modern source of reference. (orig.)

  8. Reaction Mechanism and Control of Selectivity in Catalysis by Oxides: Some Challenges and Open Questions

    Directory of Open Access Journals (Sweden)

    Siglinda Perathoner

    2001-11-01

    Full Text Available Some aspects of the reaction mechanisms in multistep selective (ammoxidation reactions over oxide surfaces are discussed evidencing some of the challenges for surface science and theory in describing these reactions, and for applied catalysis in order to have a more in deep identification of the key factors governing surface reactivity and which may be used to improve catalytic performances. In particular, the role of chemisorbed species in the modification of the surface reactivity and the presence of multiple pathways of reaction are evidenced by comparing the behavior of V-based catalysts in C3-C4 alkanes and alkene oxidation.

  9. Selection of tRNA charging quality control mechanisms that increase mistranslation of the genetic code

    DEFF Research Database (Denmark)

    Yadavalli, Srujana S; Ibba, Michael

    2013-01-01

    Mistranslation can follow two events during protein synthesis: production of non-cognate amino acid:transfer RNA (tRNA) pairs by aminoacyl-tRNA synthetases (aaRSs) and inaccurate selection of aminoacyl-tRNAs by the ribosome. Many aaRSs actively edit non-cognate amino acids, but editing mechanisms...... are not evolutionarily conserved, and their physiological significance remains unclear. To address the connection between aaRSs and mistranslation, the evolutionary divergence of tyrosine editing by phenylalanyl-tRNA synthetase (PheRS) was used as a model. Certain PheRSs are naturally error prone, most notably...... a Mycoplasma example that displayed a low level of specificity consistent with elevated mistranslation of the proteome. Mycoplasma PheRS was found to lack canonical editing activity, relying instead on discrimination against the non-cognate amino acid by kinetic proofreading. This mechanism of discrimination...

  10. Research on the mechanical behaviour of an airplane component made by selective laser melting technology

    Directory of Open Access Journals (Sweden)

    Păcurar Răzvan

    2017-01-01

    Full Text Available The main objective of the presented research consists in the redesign of an airplane component to decrease its weight, without affecting the mechanical behaviour of the component, at the end. Femap NX Nastran and ANSYS FEA programs were used for the shape optimization and for the estimation of the mechanical behaviour of a fixing clamp that was used to sustain the hydraulic pipes that are passing through an airplane fuselage, taking into consideration two types of raw materials – Ti6Al4V and AlSi12 powder from which this component could be manufactured by using the selective laser melting (SLM technology. Based on the obtained results, the airplane component was finally manufactured from titanium alloy using the SLM 250 HL equipment that is available at SLM Solutions GmbH company from Luebeck, in Germany.

  11. Hybridization of Evolutionary Mechanisms for Feature Subset Selection in Unsupervised Learning

    Science.gov (United States)

    Torres, Dolores; Ponce-de-León, Eunice; Torres, Aurora; Ochoa, Alberto; Díaz, Elva

    Feature subset selection for unsupervised learning, is a very important topic in artificial intelligence because it is the base for saving computational resources. In this implementation we use a typical testor’s methodology in order to incorporate an importance index for each variable. This paper presents the general framework and the way two hybridized meta-heuristics work in this NP-complete problem. The evolutionary mechanisms are based on the Univariate Marginal Distribution Algorithm (UMDA) and the Genetic Algorithm (GA). GA and UMDA - Estimation of Distribution Algorithm (EDA) use a very useful rapid operator implemented for finding typical testors on a very large dataset and also, both algorithms, have a local search mechanism for improving time and fitness. Experiments show that EDA is faster than GA because it has a better exploitation performance; nevertheless, GA’ solutions are more consistent.

  12. Microstructure and Mechanical Behavior of 17-4 Precipitation Hardenable Steel Processed by Selective Laser Melting

    Science.gov (United States)

    Rafi, H. Khalid; Pal, Deepankar; Patil, Nachiket; Starr, Thomas L.; Stucker, Brent E.

    2014-12-01

    The mechanical behavior and the microstructural evolution of 17-4 precipitation hardenable (PH) stainless steel processed using selective laser melting have been studied. Test coupons were produced from 17-4 PH stainless steel powder in argon and nitrogen atmospheres. Characterization studies were carried out using mechanical testing, optical microscopy, scanning electron microscopy, and x-ray diffraction. The results show that post-process heat treatment is required to obtain typically desired tensile properties. Columnar grains of smaller diameters (<2 µm) emerged within the melt pool with a mixture of martensite and retained austenite phases. It was found that the phase content of the samples is greatly influenced by the powder chemistry, processing environment, and grain diameter.

  13. Mechanical versus clinical data combination in selection and admissions decisions: a meta-analysis.

    Science.gov (United States)

    Kuncel, Nathan R; Klieger, David M; Connelly, Brian S; Ones, Deniz S

    2013-11-01

    In employee selection and academic admission decisions, holistic (clinical) data combination methods continue to be relied upon and preferred by practitioners in our field. This meta-analysis examined and compared the relative predictive power of mechanical methods versus holistic methods in predicting multiple work (advancement, supervisory ratings of performance, and training performance) and academic (grade point average) criteria. There was consistent and substantial loss of validity when data were combined holistically-even by experts who are knowledgeable about the jobs and organizations in question-across multiple criteria in work and academic settings. In predicting job performance, the difference between the validity of mechanical and holistic data combination methods translated into an improvement in prediction of more than 50%. Implications for evidence-based practice are discussed. (c) 2013 APA, all rights reserved.

  14. Mechanical response and deformation mechanisms of ferritic oxide dispersion strengthened steel structures produced by selective laser melting

    Energy Technology Data Exchange (ETDEWEB)

    Dryepondt, Sebastien N [ORNL; Boegelein, T [University of Liverpool, UK; Pandey, Amit [LGFCS; Dawson, K [University of Liverpool, UK; Tatlock, G.J. [University of Liverpool, UK

    2015-01-28

    Oxide dispersion strengthened (ODS) ferritic steels typically contain a fine dispersion of nanoscopic Y(Al, Ti) oxides, leading to an improvement in mechanical and physical properties. For a rapid prototyping technique, selective laser melting (SLM), was successfully applied to consolidate as-mechanically alloyed ODS-PM2000 (Fe 19Cr 5.5Al 0.5Ti 0.5Y2O3; all wt.%) powder to fabricate solid and thin-walled builds of different thickness. Our work is intended to act as a first study to investigate the tensile response of such configurations at room temperature, using miniaturized test specimens along and perpendicular to the growth direction. The 0.2% offset yield strength of as-grown wall builds was inferior to conventional PM2000 alloy (recrystallized), but could be significantly increased by conducting post-build heat treatments. Young s modulus and yield strength showed anisotropy and were enhanced when testing perpendicular to the build growth direction. Electron backscatter diffraction revealed a strong [001] fibre texture along the growth direction, which explains the anisotropic behaviour. In addition, studies on the morphology of the individual fracture surfaces, the grain structure of the cross-section near this region and the size distribution of ODS particles in such builds were conducted. A fine dispersion of precipitates was retained in all SLM builds, and findings suggest that a certain amount of Y is probably still in atomic solution in the as-grown condition and forms new small nanoscopic dispersoids during annealing, which lead to enhanced strengthening.

  15. Compensation strategy to reduce geometry and mechanics mismatches in porous biomaterials built with Selective Laser Melting.

    Science.gov (United States)

    Bagheri, Zahra S; Melancon, David; Liu, Lu; Johnston, R Burnett; Pasini, Damiano

    2016-05-06

    The accuracy of Additive Manufacturing processes in fabricating porous biomaterials is currently limited by their capacity to render pore morphology that precisely matches its design. In a porous biomaterial, a geometric mismatch can result in pore occlusion and strut thinning, drawbacks that can inherently compromise bone ingrowth and severely impact mechanical performance. This paper focuses on Selective Laser Melting of porous microarchitecture and proposes a compensation scheme that reduces the morphology mismatch between as-designed and as-manufactured geometry, in particular that of the pore. A spider web analog is introduced, built out of Ti-6Al-4V powder via SLM, and morphologically characterized. Results from error analysis of strut thickness are used to generate thickness compensation relations expressed as a function of the angle each strut formed with the build plane. The scheme is applied to fabricate a set of three-dimensional porous biomaterials, which are morphologically and mechanically characterized via micro Computed Tomography, mechanically tested and numerically analyzed. For strut thickness, the results show the largest mismatch (60% from the design) occurring for horizontal members, reduces to 3.1% upon application of the compensation. Similar improvement is observed also for the mechanical properties, a factor that further corroborates the merit of the design-oriented scheme here introduced.

  16. Mechanism, kinetics and selectivity of selenocyclization of 5-alkenylhydantoins: an experimental and computational study

    Directory of Open Access Journals (Sweden)

    Biljana M. Šmit

    2015-10-01

    Full Text Available The mechanism and selectivity of a bicyclic hydantoin formation by selenium-induced cyclization are investigated. The proposed mechanism involves the intermediates formed by an electrophilic addition of the selenium reagent on a double bond of the starting 5-alkenylhydantoin prior the cyclization. These intermediates are readily converted into the more stable cyclic seleniranium cations. A key step of the mechanism is an intramolecular cyclization which is realized through an anti-attack of the internal nucleophile, the amidic nitrogen, to the seleniranium cation yielding the intermediate imidazolinium cations. Their deprotonation is followed by the formation of the fused bicyclic reaction products. Important intermediates and key transition states are studied by using density functional theory (DFT methods. The pathways of the reaction are investigated in detail. There are two regioselective pathways related to 5-exo and 6-endo products. Theoretical calculations and the monitoring of the cyclization reaction using 1H NMR spectroscopy are in a good agreement with the proposed mechanism and are consistent with our experimental results. The preferred pathway for formation of 5-exo products is confirmed.

  17. Design and Lessons Learned on the Development of a Cryogenic Pupil Select Mechanism (PSM)

    Science.gov (United States)

    Mitchell, Alissa L.; Capon, Thomas L.; Hakun, Claef; Haney, Paul; Koca, Corina; Guzek, Jeffrey

    2014-01-01

    Calibration and testing of the instruments on the Integrated Science Instrument Module (ISIM) of the James Webb Space Telescope (JWST) is being performed by the use of a cryogenic, full-field, optical simulator that was constructed for this purpose. The Pupil Select Mechanism (PSM) assembly is one of several mechanisms and optical elements that compose the Optical Telescope Element SIMulator, or OSIM. The PSM allows for several optical elements to be inserted into the optical plane of OSIM, introducing a variety of aberrations, distortions, obscurations, and other calibration states into the pupil plane. The following discussion focuses on the details of the design evolution, analysis, build, and test of this mechanism along with the challenges associated with creating a sub arc-minute positioning mechanism operating in an extreme cryogenic environment. In addition, difficult challenges in the control system design will be discussed including the incorporation of closed-loop feedback control into a system that was designed to operate in an open-loop fashion.

  18. Standard Practice for Steel Bars, Selection Guide, Composition, and Mechanical Properties

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2012-01-01

    1.1 This practice is intended as a guide for the selection of steel bars according to section and to the mechanical properties desired in the part to be produced. This is not a specification for the procurement of steel. Applicable procurement specifications are listed in Section 5. 1.2 Several steel compositions intended for various sections and mechanical property requirements are presented in Tables 2 to 7. The criteria for placing a steel composition in one of the three general class designations, Classes P, Q, and R (described in Section 3) are as follows: 1.2.1 Classes P and Q should be capable of developing the mechanical properties shown in Tables 2 to 5 by liquid quenching from a suitable austenitizing temperature, and tempering at 800°F (427°C) or higher. A hardness indicated by tests made at a location shown in Fig. 1, A, B, or C, is taken as evidence that a composition is capable of meeting other equivalent mechanical properties shown in the tables. Normal good shop practices are assumed, with c...

  19. Computational insights into the selectivity mechanism of APP-IP over matrix metalloproteinases

    Science.gov (United States)

    Geng, Lingling; Gao, Jian; Cui, Wei; Tang, Yancheng; Ji, Mingjuan; Chen, Bozhen

    2012-12-01

    In this work, selectivity mechanism of APP-IP inhibitor (β-amyloid precursor protein-derived inhibitory peptide) over matrix metalloproteinases (MMPs including MMP-2, MMP-7, MMP-9 and MMP-14) was investigated by molecular modeling methods. Among MMPs, MMP-2 is the most favorable one for APP-IP interacting based on our calculations. The predicted binding affinities can give a good explanation of the activity difference of inhibitor APP-IP. In Comparison with MMP-2/APP-IP complex, the side chain of Tyr214MMP-7 makes the binding pocket so shallow that the whole side chain of Tyr3APP-IP can not be fully embraced, thus unfavorable for the N-terminal of APP-IP binding to MMP-7. The poor selectivity of APP-IP toward MMP-9 is mainly related with the decrease of interaction between the APP-IP C-terminal and MMP-9 due to the bulky side chains of Pro193 and Gln199, which is in agreement with experiment. The mutations at residues P193A and Q199G of MMP-9 alternate the binding pattern of the C-terminal of APP-IP by forming two new hydrogen bonds and hydrophobic interactions with MMP-9. The mutants favor the binding affinity of MMP-9 largely. For MMP-14/APP-IP, the large steric effect of Phe204MMP-14 and the weak contributions of the polar residues Asn231MMP-14 and Thr190MMP-14 could explain why MMP-14 is non-selective for APP-IP interacting. Here, the molecular modeling methods were successfully employed to explore the selective inhibitor of MMPs, and our work gives valuable information for future rational design of selective peptide inhibitors toward individual MMP.

  20. Single-molecule FRET unveils induced-fit mechanism for substrate selectivity in flap endonuclease 1

    Science.gov (United States)

    Rashid, Fahad; Harris, Paul D; Zaher, Manal S; Sobhy, Mohamed A; Joudeh, Luay I; Yan, Chunli; Piwonski, Hubert; Tsutakawa, Susan E; Ivanov, Ivaylo; Tainer, John A; Habuchi, Satoshi; Hamdan, Samir M

    2017-01-01

    Human flap endonuclease 1 (FEN1) and related structure-specific 5’nucleases precisely identify and incise aberrant DNA structures during replication, repair and recombination to avoid genomic instability. Yet, it is unclear how the 5’nuclease mechanisms of DNA distortion and protein ordering robustly mediate efficient and accurate substrate recognition and catalytic selectivity. Here, single-molecule sub-millisecond and millisecond analyses of FEN1 reveal a protein-DNA induced-fit mechanism that efficiently verifies substrate and suppresses off-target cleavage. FEN1 sculpts DNA with diffusion-limited kinetics to test DNA substrate. This DNA distortion mutually ‘locks’ protein and DNA conformation and enables substrate verification with extreme precision. Strikingly, FEN1 never misses cleavage of its cognate substrate while blocking probable formation of catalytically competent interactions with noncognate substrates and fostering their pre-incision dissociation. These findings establish FEN1 has practically perfect precision and that separate control of induced-fit substrate recognition sets up the catalytic selectivity of the nuclease active site for genome stability. DOI: http://dx.doi.org/10.7554/eLife.21884.001 PMID:28230529

  1. An electrostatic selection mechanism controls sequential kinase signaling downstream of the T cell receptor

    Science.gov (United States)

    Shah, Neel H; Wang, Qi; Yan, Qingrong; Karandur, Deepti; Kadlecek, Theresa A; Fallahee, Ian R; Russ, William P; Ranganathan, Rama; Weiss, Arthur; Kuriyan, John

    2016-01-01

    The sequence of events that initiates T cell signaling is dictated by the specificities and order of activation of the tyrosine kinases that signal downstream of the T cell receptor. Using a platform that combines exhaustive point-mutagenesis of peptide substrates, bacterial surface-display, cell sorting, and deep sequencing, we have defined the specificities of the first two kinases in this pathway, Lck and ZAP-70, for the T cell receptor ζ chain and the scaffold proteins LAT and SLP-76. We find that ZAP-70 selects its substrates by utilizing an electrostatic mechanism that excludes substrates with positively-charged residues and favors LAT and SLP-76 phosphosites that are surrounded by negatively-charged residues. This mechanism prevents ZAP-70 from phosphorylating its own activation loop, thereby enforcing its strict dependence on Lck for activation. The sequence features in ZAP-70, LAT, and SLP-76 that underlie electrostatic selectivity likely contribute to the specific response of T cells to foreign antigens. DOI: http://dx.doi.org/10.7554/eLife.20105.001 PMID:27700984

  2. Organic fraction of municipal solid waste from mechanical selection: biological stabilization and recovery options.

    Science.gov (United States)

    Cesaro, Alessandra; Russo, Lara; Farina, Anna; Belgiorno, Vincenzo

    2016-01-01

    Although current trends address towards prevention strategies, the organic fraction of municipal solid waste is greatly produced, especially in high-income contexts. Its recovery-oriented collection is a common practice, but a relevant portion of the biodegradable waste is not source selected. Mechanical and biological treatments (MBT) are the most common option to sort and stabilize the biodegradable matter ending in residual waste stream. Following the changes of the framework around waste management, this paper aimed at analyzing the quality of the mechanically selected organic waste produced in MBT plants, in order to discuss its recovery options. The material performance was obtained by its composition as well as by its main chemical and physical parameters; biological stability was also assessed by both aerobic and anaerobic methods. On this basis, the effectiveness of an aerobic biostabilization process was assessed at pilot scale. After 21 days of treatment, results proved that the biomass had reached an acceptable biostabilization level, with a potential Dynamic Respirometric Index (DRIP) value lower than the limit required for its use as daily or final landfill cover material. However, the final stabilization level was seen to be influenced by scaling factors and the 21 days of treatment turned to be not so adequate when applied in the existing full-scale facility.

  3. Single-molecule FRET unveils induced-fit mechanism for substrate selectivity in flap endonuclease 1

    KAUST Repository

    Rashid, Fahad

    2017-02-23

    Human flap endonuclease 1 (FEN1) and related structure-specific 5\\'nucleases precisely identify and incise aberrant DNA structures during replication, repair and recombination to avoid genomic instability. Yet, it is unclear how the 5\\'nuclease mechanisms of DNA distortion and protein ordering robustly mediate efficient and accurate substrate recognition and catalytic selectivity. Here, single-molecule sub-millisecond and millisecond analyses of FEN1 reveal a protein-DNA induced-fit mechanism that efficiently verifies substrate and suppresses off-target cleavage. FEN1 sculpts DNA with diffusion-limited kinetics to test DNA substrate. This DNA distortion mutually \\'locks\\' protein and DNA conformation and enables substrate verification with extreme precision. Strikingly, FEN1 never misses cleavage of its cognate substrate while blocking probable formation of catalytically competent interactions with noncognate substrates and fostering their pre-incision dissociation. These findings establish FEN1 has practically perfect precision and that separate control of induced-fit substrate recognition sets up the catalytic selectivity of the nuclease active site for genome stability.

  4. Transduction mechanism of carbon nanotubes in solid-contact ion-selective electrodes.

    Science.gov (United States)

    Crespo, Gastón A; Macho, Santiago; Bobacka, Johan; Rius, F Xavier

    2009-01-15

    Porous carbon materials and carbon nanotubes were recently used as solid contacts in ion-selective electrodes (ISE), and the signal transduction mechanism of these carbon-based materials is therefore of great interest. In this work the ion-to-electron transduction mechanism of carbon nanotubes is studied by using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Single-walled carbon nanotubes (SWCNT) are deposited on glassy carbon (GC) disk electrodes by repetitive spraying, resulting in SWCNT layers with thicknesses of 10, 35, and 50 mum. The impedance spectra of these GC/SWCNT electrodes in contact with aqueous electrolyte solution show a very small resistance and a large bulk capacitance that is related to a large effective double layer at the SWCNT/electrolyte interface. Interestingly, the impedance response of GC/SWCNT is very similar to that of poly(3,4-ethylenedioxythiophene) (PEDOT) film electrodes studied earlier under the same experimental conditions. The same equivalent circuit is valid for both types of materials. The reason is that both materials can be described schematically as an asymmetric capacitor where one side is formed by electronic charge (electrons/holes) in the SWCNT wall or along the conjugated polymer chain of PEDOT and the other side is formed by ions (anions/cations) in the solution (or in the ion-selective membrane when used as a solid contact in ISE).

  5. Detecting Selection on Protein Stability through Statistical Mechanical Models of Folding and Evolution

    Directory of Open Access Journals (Sweden)

    Ugo Bastolla

    2014-03-01

    Full Text Available The properties of biomolecules depend both on physics and on the evolutionary process that formed them. These two points of view produce a powerful synergism. Physics sets the stage and the constraints that molecular evolution has to obey, and evolutionary theory helps in rationalizing the physical properties of biomolecules, including protein folding thermodynamics. To complete the parallelism, protein thermodynamics is founded on the statistical mechanics in the space of protein structures, and molecular evolution can be viewed as statistical mechanics in the space of protein sequences. In this review, we will integrate both points of view, applying them to detecting selection on the stability of the folded state of proteins. We will start discussing positive design, which strengthens the stability of the folded against the unfolded state of proteins. Positive design justifies why statistical potentials for protein folding can be obtained from the frequencies of structural motifs. Stability against unfolding is easier to achieve for longer proteins. On the contrary, negative design, which consists in destabilizing frequently formed misfolded conformations, is more difficult to achieve for longer proteins. The folding rate can be enhanced by strengthening short-range native interactions, but this requirement contrasts with negative design, and evolution has to trade-off between them. Finally, selection can accelerate functional movements by favoring low frequency normal modes of the dynamics of the native state that strongly correlate with the functional conformation change.

  6. High-throughput virtual screening using quantum mechanical probes: discovery of selective kinase inhibitors.

    Science.gov (United States)

    Zhou, Ting; Caflisch, Amedeo

    2010-07-05

    A procedure based on semi-empirical quantum mechanical (QM) calculations of interaction energy is proposed for the rapid screening of compound poses generated by high-throughput docking. Small molecules (consisting of 2-10 atoms and termed "probes") are overlapped with polar groups in the binding site of the protein target. The interaction energy values between each compound pose and the probes, calculated by a semi-empirical Hamiltonian, are used as filters. The QM probe method does not require fixed partial charges and takes into account polarization and charge-transfer effects which are not captured by conventional force fields. The procedure is applied to screen approximately 100 million poses (of 2.7 million commercially available compounds) obtained by high-throughput docking in the ATP binding site of the tyrosine kinase erythropoietin-producing human hepatocellular carcinoma receptor B4 (EphB4). Three QM probes on the hinge region and one at the entrance pocket are employed to select for binding affinity, while a QM probe on the side chain of the so-called gatekeeper residue (a hypervariable residue in the kinome) is used to enforce selectivity. The poses with favorable interactions with the five QM probes are filtered further for hydrophobic matching and low ligand strain. In this way, a single-digit micromolar inhibitor of EphB4 with a relatively good selectivity profile is identified in a multimillion-compound library upon experimental tests of only 23 molecules.

  7. Mechanism study of selective heavy metal ion removal with polypyrrole-functionalized polyacrylonitrile nanofiber mats

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jianqiang; Luo, Chao [Key Laboratory of Carbon Fiber and Functional Polymers, Ministry of Education, Beijing University of Chemical Technology, Beijing 100029 (China); Qi, Genggeng [Department of Materials Science and Engineering, Cornell University, Ithaca, NY (United States); Pan, Kai, E-mail: pankai@mail.buct.edu.cn [Key Laboratory of Carbon Fiber and Functional Polymers, Ministry of Education, Beijing University of Chemical Technology, Beijing 100029 (China); Department of Materials Science and Engineering, Cornell University, Ithaca, NY (United States); Cao, Bing, E-mail: bcao@mail.buct.edu.cn [Key Laboratory of Carbon Fiber and Functional Polymers, Ministry of Education, Beijing University of Chemical Technology, Beijing 100029 (China)

    2014-10-15

    Graphical abstract: - Highlights: • PAN/PPy core/shell nanofiber used for Cr(VI) removal. • Adsorption mechanisms were investigated. • Selective adsorption performances were investigated. - Abstract: Polyacrylonitrile/polypyrrole (PAN/PPy) core/shell nanofiber mat was prepared through electrospinning followed by a simple chemical oxidation method. The polypyrrole-functionalized nanofiber mats showed selective adsorption performance for anions. The interaction between heavy metal anions and polypyrrole (especially the interaction between Cr{sub 2}O{sub 7}{sup 2−} and polypyrrole) during the adsorption process was studied. The results showed that the adsorption process included two steps: one was the anion exchange process between the Cl{sup −} and Cr(VI), and the other was the redox process for the Cr(VI) ions. The adsorption amount was related to the protonation time of the PAN/PPy nanofiber mat and increased as protonation time increased. Meanwhile, the Cr(VI) ions were reduced to Cr(III) through the reaction with amino groups of polypyrrole (from secondary amines to tertiary amines). PAN/PPy nanofiber mat showed high selectivity for Cr(VI), and the adsorption performance was nearly unaffected by other co-existing anions (Cl{sup −}, NO{sub 3}{sup −}, and SO{sub 4}{sup 2−}) except for PO{sub 4}{sup 3−} for the pH change.

  8. Mechanism of selective corrosion in electrical resistance seam welded carbon steel pipe

    Energy Technology Data Exchange (ETDEWEB)

    Lopez Fajardo, Pedro; Godinez Salcedo, Jesus; Gonzalez Velasquez, Jorge L. [Instituto Politecnico Nacional, Mexico D.F., (Mexico). Escuela Superior de Ingenieria Quimica e Industrias Extractivas. Dept. de Ingenieria Metalurgica

    2009-07-01

    In this investigation the studies of the mechanism of selective corrosion in electrical resistance welded (ERW) carbon steel pipe was started. Metallographic characterizations and evaluations for inclusions were performed. The susceptibility of ERW pipe to selective corrosion in sea water (NACE 1D182, with O{sub 2} or CO{sub 2} + H{sub 2}S) was studied by the stepped potential Potentiostatic electrochemical test method in samples of 1 cm{sup 3} (ASTM G5) internal surface of the pipe (metal base-weld). The tests were looking for means for predicting the susceptibility of ERW pipe to selective corrosion, prior to placing the pipeline in service. Manganese sulfide inclusions are observed deformed by the welding process and they are close to the weld centerline. A slight decarburization at the weld line is observed, and a distinct out bent fiber pattern remains despite the post-weld seam annealing. The microstructure of the weld region consists of primarily polygonal ferrite grains mixed with small islands of pearlite. It is possible to observe the differences of sizes of grain of the present phases in the different zones. Finally, scanning electron microscopic observation revealed that the corrosion initiates with the dissolution of MnS inclusions and with small crack between the base metal and ZAC. (author)

  9. Aging Behaviour and Mechanical Performance of 18-Ni 300 Steel Processed by Selective Laser Melting

    Directory of Open Access Journals (Sweden)

    Riccardo Casati

    2016-09-01

    Full Text Available An 18-Ni 300 grade maraging steel was processed by selective laser melting and an investigation was carried out on microstructural and mechanical behaviour as a function of aging condition. Owing to the rapid cooling rate, the as-built alloy featured a full potential for precipitate strengthening, without the need of a solution treatment prior to aging. The amount of reversed austenite found in the microstructure increased after aging and revealed to depend on aging temperature and time. Similarly to the corresponding wrought counterpart, also in the selective laser-melted 18-Ni 300 alloy, aging promoted a dramatic increase in strength with respect to the as-built condition and a drop in tensile ductility. No systematic changes were found in tensile properties as a function of measured amount of austenite. It is proposed that the submicrometric structure and the phase distribution inherited by the rapid solidification condition brought by selective laser melting are such that changes in tensile strength and ductility are mainly governed by the effects brought by the strengthening precipitates, whereas the concurrent reversion of the γ-Fe phase in different amounts seems to play a minor role.

  10. Selective estrogen receptor modulators (SERMs): Mechanisms of anticarcinogenesis and drug resistance

    Energy Technology Data Exchange (ETDEWEB)

    Lewis, Joan S. [Fox Chase Cancer Center, Alfred G. Knudson Chair of Cancer Research, 333 Cottman Avenue, Philadelphia, PA 19111 (United States); Jordan, V. Craig [Fox Chase Cancer Center, Alfred G. Knudson Chair of Cancer Research, 333 Cottman Avenue, Philadelphia, PA 19111 (United States)]. E-mail: v.craig.jordan@fccc.edu

    2005-12-11

    Despite the beneficial effects of estrogens in women's health, there is a plethora of evidence that suggest an important role for these hormones, particularly 17{beta}-estradiol (E{sub 2}), in the development and progression of breast cancer. Most estrogenic responses are mediated by estrogen receptors (ERs), either ER{alpha} or ER{beta}, which are members of the nuclear receptor superfamily of ligand-dependent transcription factors. Selective estrogen receptor modulators (SERMs) are ER ligands that in some tissues (i.e. bone and cardiovascular system) act like estrogens but block estrogen action in others. Tamoxifen is the first SERM that has been successfully tested for the prevention of breast cancer in high-risk women and is currently approved for the endocrine treatment of all stages of ER-positive breast cancer. Raloxifene, a newer SERM originally developed for osteoporosis, also appears to have preventive effect on breast cancer incidence. Numerous studies have examined the molecular mechanisms for the tissue selective action of SERMs, and collectively they indicate that different ER ligands induce distinct conformational changes in the receptor that influence its ability to interact with coregulatory proteins (i.e. coactivators and corepressors) critical for the regulation of target gene transcription. The relative expression of coactivators and corepressors, and the nature of the ER and its target gene promoter also affect SERM biocharacter. This review summarizes the therapeutic application of SERMs in medicine; particularly breast cancer, and highlights the emerging understanding of the mechanism of action of SERMs in select target tissues, and the inevitable development of resistance.

  11. Distractor suppression when attention fails: behavioral evidence for a flexible selective attention mechanism.

    Directory of Open Access Journals (Sweden)

    James C Elliott

    Full Text Available Despite consistent evidence showing that attention is a multifaceted mechanism that can operate at multiple levels of processing depending on the structure and demands of the task, investigations of the attentional blink phenomenon have consistently shown that the impairment in reporting the second of two targets typically occurs at a late, or post-perceptual, stage of processing. This suggests that the attentional blink phenomenon may represent the operation of a unique attentional mechanism that is not as flexible as other attentional mechanisms. To test whether the attentional blink is a fixed or flexible phenomenon, we manipulated first target task demands (i.e., difficulty and measured the influence this had on processing a subsequently presented distractor and the second target. If the attentional blink represents a mechanism that is fixed and consistently fails at a single stage of processing, then manipulations of task difficulty should not affect distractor processing. However, if the attentional blink represents a more multifaceted and flexible mechanism, then task difficulty should modulate distractor processing. The results revealed that distractor processing during the AB was attenuated under high task difficulty. In addition, unlike previous studies, we failed to find a correlation between distractor processing and the severity of the attentional blink. Using a simulation, we demonstrate that the previously reported correlations may have been spurious and due to using variables that were not independent. Overall, the present results support the conclusion that the selectivity of attention during the AB is flexible and depends on the structure and demands of the task.

  12. Selective serotonin reuptake inhibitors to improve outcome in acute ischemic stroke: possible mechanisms and clinical evidence.

    Science.gov (United States)

    Siepmann, Timo; Penzlin, Ana Isabel; Kepplinger, Jessica; Illigens, Ben Min-Woo; Weidner, Kerstin; Reichmann, Heinz; Barlinn, Kristian

    2015-10-01

    Several clinical studies have indicated that selective serotonin reuptake inhibitors (SSRIs) administered in patients after acute ischemic stroke can improve clinical recovery independently of depression. Due to small sample sizes and heterogeneous study designs interpretability was limited in these studies. The mechanisms of action whereby SSRI might improve recovery from acute ischemic stroke are not fully elucidated. We searched MEDLINE using the PubMed interface to identify evidence of SSRI mediated improvement of recovery from acute ischemic stroke and reviewed the literature on the potential underlying mechanisms of action. Among identified clinical studies, a well-designed randomized, double-blind, and placebo-controlled study (FLAME - fluoxetine for motor recovery after acute ischemic stroke) demonstrated improved recovery of motor function in stroke patients receiving fluoxetine. The positive effects of SSRIs on stroke recovery were further supported by a meta-analysis of 52 trials in a total of 4060 participants published by the Cochrane collaboration. Based on animal models, the mechanisms whereby SSRIs might ameliorate functional and structural ischemic-brain damage were suggested to include stimulation of neurogenesis with migration of newly generated cells toward ischemic-brain regions, anti-inflammatory neuroprotection, improved regulation of cerebral blood flow, and modulation of the adrenergic neurohormonal system. However, to date, it remains speculative if and to what degree these mechanisms convert into humans and randomized controlled trials in large populations of stroke patients comparing different SSRIs are still lacking. In addition to the need of comprehensive-clinical evidence, further elucidation of the beneficial mechanisms whereby SSRIs may improve structural and functional recovery from ischemic-brain damage is needed to form a basis for translation into clinical practice.

  13. A Security Mechanism for Cluster-Based WSN against Selective Forwarding

    Directory of Open Access Journals (Sweden)

    Hai Zhou

    2016-09-01

    Full Text Available A wireless sensor network (WSN faces a number of outsider and insider attacks, and it is difficult to detect and defend against insider attacks. In particular, an insider selective-forwarding attack, in which the attackers select some of the received packets to drop, most threatens a WSN. Compared to a distributed WSN, a cluster-based WSN will suffer more losses, even the whole network’s destruction, if the cluster head is attacked. In this paper, a scheme solving the above issues is proposed with three types of nodes, the Cluster Head (CH, the Inspector Node (IN and Member Nodes (MNs. The IN monitors the CH’s transmission to protect the cluster against a selective-forwarding attack; the CH forwards packets from MNs and other CHs, and randomly checks the IN to ascertain if it works properly; and the MNs send the gathered data packets to the CH and evaluate the behaviors of the CH and IN based on their own reputation mechanism. The novelty of our scheme is that in order to take both the safety and the lifespan of a network into consideration, the composite reputation value (CRV including forwarding rate, detecting malicious nodes, and surplus energy of the node is utilized to select CH and IN under the new suggested network arrangement, and the use of a node’s surplus energy can balance the energy consumption of a node, thereby prolonging the network lifespan. Theoretical analysis and simulation results indicate that the proposed scheme can detect the malicious node accurately and efficiently, so the false alarm rate is lowered by 25.7% compared with Watchdog and the network lifespan is prolonged by 54.84% compared with LEACH (Low Energy Adaptive Clustering Hierarchy.

  14. A Security Mechanism for Cluster-Based WSN against Selective Forwarding.

    Science.gov (United States)

    Zhou, Hai; Wu, Yuanming; Feng, Li; Liu, Daolei

    2016-09-20

    A wireless sensor network (WSN) faces a number of outsider and insider attacks, and it is difficult to detect and defend against insider attacks. In particular, an insider selective-forwarding attack, in which the attackers select some of the received packets to drop, most threatens a WSN. Compared to a distributed WSN, a cluster-based WSN will suffer more losses, even the whole network's destruction, if the cluster head is attacked. In this paper, a scheme solving the above issues is proposed with three types of nodes, the Cluster Head (CH), the Inspector Node (IN) and Member Nodes (MNs). The IN monitors the CH's transmission to protect the cluster against a selective-forwarding attack; the CH forwards packets from MNs and other CHs, and randomly checks the IN to ascertain if it works properly; and the MNs send the gathered data packets to the CH and evaluate the behaviors of the CH and IN based on their own reputation mechanism. The novelty of our scheme is that in order to take both the safety and the lifespan of a network into consideration, the composite reputation value (CRV) including forwarding rate, detecting malicious nodes, and surplus energy of the node is utilized to select CH and IN under the new suggested network arrangement, and the use of a node's surplus energy can balance the energy consumption of a node, thereby prolonging the network lifespan. Theoretical analysis and simulation results indicate that the proposed scheme can detect the malicious node accurately and efficiently, so the false alarm rate is lowered by 25.7% compared with Watchdog and the network lifespan is prolonged by 54.84% compared with LEACH (Low Energy Adaptive Clustering Hierarchy).

  15. Corticostriatal circuit mechanisms of value-based action selection: Implementation of reinforcement learning algorithms and beyond.

    Science.gov (United States)

    Morita, Kenji; Jitsev, Jenia; Morrison, Abigail

    2016-09-15

    Value-based action selection has been suggested to be realized in the corticostriatal local circuits through competition among neural populations. In this article, we review theoretical and experimental studies that have constructed and verified this notion, and provide new perspectives on how the local-circuit selection mechanisms implement reinforcement learning (RL) algorithms and computations beyond them. The striatal neurons are mostly inhibitory, and lateral inhibition among them has been classically proposed to realize "Winner-Take-All (WTA)" selection of the maximum-valued action (i.e., 'max' operation). Although this view has been challenged by the revealed weakness, sparseness, and asymmetry of lateral inhibition, which suggest more complex dynamics, WTA-like competition could still occur on short time scales. Unlike the striatal circuit, the cortical circuit contains recurrent excitation, which may enable retention or temporal integration of information and probabilistic "soft-max" selection. The striatal "max" circuit and the cortical "soft-max" circuit might co-implement an RL algorithm called Q-learning; the cortical circuit might also similarly serve for other algorithms such as SARSA. In these implementations, the cortical circuit presumably sustains activity representing the executed action, which negatively impacts dopamine neurons so that they can calculate reward-prediction-error. Regarding the suggested more complex dynamics of striatal, as well as cortical, circuits on long time scales, which could be viewed as a sequence of short WTA fragments, computational roles remain open: such a sequence might represent (1) sequential state-action-state transitions, constituting replay or simulation of the internal model, (2) a single state/action by the whole trajectory, or (3) probabilistic sampling of state/action.

  16. Effects of selected casting methods on mechanical behaviour of Al-Mg-Si alloy

    Directory of Open Access Journals (Sweden)

    Henry Kayode TALABI

    2014-11-01

    Full Text Available This study investigated the effects of selected casting methods on mechanical behaviour of Al-Mg-Si alloy. The casting methods used was spin, sand and die casting, these were done with a view to determine which of the casting methods will produce the best properties. The pure aluminium scrap, magnesium and silicon were subjected to chemical analysis using spectrometric analyzer, thereafter the charge calculation to determine the amount needed to be charged into the furnace was properly worked out and charged into the crucible furnace from which as-cast aluminium was obtained. The mechanical properties of the casting produced were assessed by hardness and impact toughness test. The optical microscopy and experimental density and porosity were also investigated. From the results it was observed that magnesium and silicon were well dispersed in aluminium matrix of the spin casting. It was observed from visual examination after machining that there were minimal defects. It was also observed that out of the three casting methods, spin casting possesses the best mechanical properties (hardness and impact toughness.

  17. L-ALLIANCE: a mechanism for adaptive action selection in heterogeneous multi-robot teams

    Energy Technology Data Exchange (ETDEWEB)

    Parker, L.E.

    1995-11-01

    In practical applications of robotics, it is usually quite difficult, if not impossible, for the system designer to fully predict the environmental states in which the robots will operate. The complexity of the problem is further increased when dealing with teams of robots which themselves may be incompletely known and characterized in advance. It is thus highly desirable for robot teams to be able to adapt their performance during the mission due to changes in the environment, or to changes in other robot team members. In previous work, we introduced a behavior-based mechanism called the ALLIANCE architecture -- that facilitates the fault tolerant cooperative control of multi-robot teams. However, this previous work did not address the issue of how to dynamically update the control parameters during a mission to adapt to ongoing changes in the environment or in the robot team, and to ensure the efficiency of the collective team actions. In this paper, we address this issue by proposing the L-ALLIANCE mechanism, which defines an automated method whereby robots can use knowledge learned from previous experience to continually improve their collective action selection when working on missions composed of loosely coupled, discrete subtasks. This ability to dynamically update robotic control parameters provides a number of distinct advantages: it alleviates the need for human tuning of control parameters, it facilitates the use of custom-designed multi-robot teams for any given application, it improves the efficiency of the mission performance, and It allows robots to continually adapt their performance over time due to changes in the robot team and/or the environment. We describe the L-ALLIANCE mechanism, present the results of various alternative update strategies we investigated, present the formal model of the L-ALLIANCE mechanism, and present the results of a simple proof of concept implementation on a small team of heterogeneous mobile robots.

  18. Mechanical characterization of selected adhesives and bulk materials at liquid nitrogen and room temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Fitzpatrick, C.M.; Stoddart, W.C.T.

    1977-01-01

    This paper presents the results of a series of mechanical tests on selected adhesives and bulk materials. The materials tested are of general interest to designers of magnets for cryogenic service and include several epoxies, a varnish, a B-stage glass cloth, insulation papers, and commercially available fiber-reinforced composites. These tests were performed at room temperature (293 K) and at liquid nitrogen temperature (77 K). The tests include both simple tension tests and lap shear tests with various adherends. The parameters critical to tensile or bond strength were varied as part of the test program. The procedures used to manufacture and test these specimens and the results of the tests are reported in this paper.

  19. Selection of an Appropriate Mechanized Mining Technical Process for Thin Coal Seam Mining

    Directory of Open Access Journals (Sweden)

    Chen Wang

    2015-01-01

    Full Text Available Mechanized mining technical process (MMTP related to the control method of the shearer is a vital process in thin coal seam mining operations. An appropriate MMTP is closely related to safety, productivity, labour intensity, and efficiency. Hence, the evaluation of alternative MMTP is an important part of the mining design. Several parameters should be considered in MMTP evaluation, so the evaluation is complex and must be compliant with a set of criteria. In this paper, two multiple criteria decision-making (MCDM methods, Analytic Hierarchy Process (AHP and Preference Ranking Organization Method for Enrichment Evaluation (PROMETHEE, were adopted for this evaluation. Then, the most appropriate MMTP for a thin coal seam working face was selected in China.

  20. A service brokering and recommendation mechanism for better selecting cloud services.

    Directory of Open Access Journals (Sweden)

    Zhipeng Gui

    Full Text Available Cloud computing is becoming the new generation computing infrastructure, and many cloud vendors provide different types of cloud services. How to choose the best cloud services for specific applications is very challenging. Addressing this challenge requires balancing multiple factors, such as business demands, technologies, policies and preferences in addition to the computing requirements. This paper recommends a mechanism for selecting the best public cloud service at the levels of Infrastructure as a Service (IaaS and Platform as a Service (PaaS. A systematic framework and associated workflow include cloud service filtration, solution generation, evaluation, and selection of public cloud services. Specifically, we propose the following: a hierarchical information model for integrating heterogeneous cloud information from different providers and a corresponding cloud information collecting mechanism; a cloud service classification model for categorizing and filtering cloud services and an application requirement schema for providing rules for creating application-specific configuration solutions; and a preference-aware solution evaluation mode for evaluating and recommending solutions according to the preferences of application providers. To test the proposed framework and methodologies, a cloud service advisory tool prototype was developed after which relevant experiments were conducted. The results show that the proposed system collects/updates/records the cloud information from multiple mainstream public cloud services in real-time, generates feasible cloud configuration solutions according to user specifications and acceptable cost predication, assesses solutions from multiple aspects (e.g., computing capability, potential cost and Service Level Agreement, SLA and offers rational recommendations based on user preferences and practical cloud provisioning; and visually presents and compares solutions through an interactive web Graphical

  1. Synergistic chemoprotective mechanisms of dietary phytoestrogens in a select combination against prostate cancer.

    Science.gov (United States)

    Kumar, Rajeev; Verma, Vikas; Jain, Ashish; Jain, Rajeev K; Maikhuri, Jagdamba P; Gupta, Gopal

    2011-08-01

    Combination of dietary phytoestrogens with diverse molecular mechanisms may enhance their anticancer efficacy at physiological concentrations, as evidenced in epidemiological studies. A select combination of three dietary phytoestrogens containing 8.33 μM each of genistein (G), quercetin (Q) and biochanin A (B) was found to be more potent in inhibiting the growth of androgen-responsive prostate cancer cells (LNCaP) as well as DU-145 and PC-3 prostate cancer cells in vitro than either 25 μM of G, B or Q or 12.5+12.5 μM of G+Q, Q+B or G+B. Subsequent mechanistic studies in PC-3 cells indicated that the action of phytoestrogens was mediated both through estrogen receptor (ER)-dependent and ER-independent pathways as potent estrogen antagonist ICI-182780 (ICI, 5 μM) could not completely mask the synergistic anticancer effects, which were sustained appreciably in presence of ICI. G+Q+B combination was significantly more effective than individual compounds or their double combinations in increasing ER-β, bax (mRNA expression); phospho-JNK, bax (protein levels); and in decreasing bcl-2, cyclin E, c-myc (mRNA expression); phospho-AKT, phospho-ERK, bcl-2, proliferating cell nuclear antigen (protein levels) in PC-3 cells. Phytoestrogens also synergistically stimulated caspase-3 activity. Our findings suggest that selectively combining anticancer phytoestrogens could significantly increase the efficacy of individual components resulting in improved efficacy at physiologically achievable concentrations. The combination mechanism of multiple anticancer phytochemicals may be indicative of the potential of some vegetarian diet components to elicit chemopreventive effects against prostate cancer at their physiologically achievable concentrations, in vivo.

  2. A Service Brokering and Recommendation Mechanism for Better Selecting Cloud Services

    Science.gov (United States)

    Gui, Zhipeng; Yang, Chaowei; Xia, Jizhe; Huang, Qunying; Liu, Kai; Li, Zhenlong; Yu, Manzhu; Sun, Min; Zhou, Nanyin; Jin, Baoxuan

    2014-01-01

    Cloud computing is becoming the new generation computing infrastructure, and many cloud vendors provide different types of cloud services. How to choose the best cloud services for specific applications is very challenging. Addressing this challenge requires balancing multiple factors, such as business demands, technologies, policies and preferences in addition to the computing requirements. This paper recommends a mechanism for selecting the best public cloud service at the levels of Infrastructure as a Service (IaaS) and Platform as a Service (PaaS). A systematic framework and associated workflow include cloud service filtration, solution generation, evaluation, and selection of public cloud services. Specifically, we propose the following: a hierarchical information model for integrating heterogeneous cloud information from different providers and a corresponding cloud information collecting mechanism; a cloud service classification model for categorizing and filtering cloud services and an application requirement schema for providing rules for creating application-specific configuration solutions; and a preference-aware solution evaluation mode for evaluating and recommending solutions according to the preferences of application providers. To test the proposed framework and methodologies, a cloud service advisory tool prototype was developed after which relevant experiments were conducted. The results show that the proposed system collects/updates/records the cloud information from multiple mainstream public cloud services in real-time, generates feasible cloud configuration solutions according to user specifications and acceptable cost predication, assesses solutions from multiple aspects (e.g., computing capability, potential cost and Service Level Agreement, SLA) and offers rational recommendations based on user preferences and practical cloud provisioning; and visually presents and compares solutions through an interactive web Graphical User Interface (GUI

  3. A service brokering and recommendation mechanism for better selecting cloud services.

    Science.gov (United States)

    Gui, Zhipeng; Yang, Chaowei; Xia, Jizhe; Huang, Qunying; Liu, Kai; Li, Zhenlong; Yu, Manzhu; Sun, Min; Zhou, Nanyin; Jin, Baoxuan

    2014-01-01

    Cloud computing is becoming the new generation computing infrastructure, and many cloud vendors provide different types of cloud services. How to choose the best cloud services for specific applications is very challenging. Addressing this challenge requires balancing multiple factors, such as business demands, technologies, policies and preferences in addition to the computing requirements. This paper recommends a mechanism for selecting the best public cloud service at the levels of Infrastructure as a Service (IaaS) and Platform as a Service (PaaS). A systematic framework and associated workflow include cloud service filtration, solution generation, evaluation, and selection of public cloud services. Specifically, we propose the following: a hierarchical information model for integrating heterogeneous cloud information from different providers and a corresponding cloud information collecting mechanism; a cloud service classification model for categorizing and filtering cloud services and an application requirement schema for providing rules for creating application-specific configuration solutions; and a preference-aware solution evaluation mode for evaluating and recommending solutions according to the preferences of application providers. To test the proposed framework and methodologies, a cloud service advisory tool prototype was developed after which relevant experiments were conducted. The results show that the proposed system collects/updates/records the cloud information from multiple mainstream public cloud services in real-time, generates feasible cloud configuration solutions according to user specifications and acceptable cost predication, assesses solutions from multiple aspects (e.g., computing capability, potential cost and Service Level Agreement, SLA) and offers rational recommendations based on user preferences and practical cloud provisioning; and visually presents and compares solutions through an interactive web Graphical User Interface (GUI).

  4. Test selection and optimization for PHM based on failure evolution mechanism model

    Institute of Scientific and Technical Information of China (English)

    Jing Qiu; Xiaodong Tan; Guanjun Liu; Kehong LÜ

    2013-01-01

    The test selection and optimization (TSO) can improve the abilities of fault diagnosis, prognosis and health-state evalua-tion for prognostics and health management (PHM) systems. Tra-ditional y, TSO mainly focuses on fault detection and isolation, but they cannot provide an effective guide for the design for testa-bility (DFT) to improve the PHM performance level. To solve the problem, a model of TSO for PHM systems is proposed. Firstly, through integrating the characteristics of fault severity and propa-gation time, and analyzing the test timing and sensitivity, a testabi-lity model based on failure evolution mechanism model (FEMM) for PHM systems is built up. This model describes the fault evolution-test dependency using the fault-symptom parameter matrix and symptom parameter-test matrix. Secondly, a novel method of in-herent testability analysis for PHM systems is developed based on the above information. Having completed the analysis, a TSO model, whose objective is to maximize fault trackability and mini-mize the test cost, is proposed through inherent testability analysis results, and an adaptive simulated annealing genetic algorithm (ASAGA) is introduced to solve the TSO problem. Final y, a case of a centrifugal pump system is used to verify the feasibility and effectiveness of the proposed models and methods. The results show that the proposed technology is important for PHM systems to select and optimize the test set in order to improve their perfor-mance level.

  5. Selected mechanical properties of aluminum composite materials reinforced with SiC particles

    Directory of Open Access Journals (Sweden)

    A. Kurzawa

    2008-07-01

    Full Text Available This work presents the results of research concerning influence of ceramic particles’ content of silicon carbide on selected mechanical properties of type AW-AlCu4Mg2Mn - SiC composite materials. Composites produced of SiC particles with pressure infiltration method of porous preform and subject to hot plastic forming in the form of open die forging were investigated. The experimental samples contained from 5% up to 45% of reinforcing SiC particles of 8÷10μm diameter. Studies of strength properties demonstrated that the best results, in case of tensile strength as well as offset yield strength, might be obtained while applying reinforcement in the amount of 20-25% vol. of SiC. Application of higher than 25% vol. contents of reinforcing particles leads to gradual strength loss. The investigated composites were characterized by very high functional properties, such as hardness and abrasive wear resistance, whose values increase strongly with the increase of reinforcement amount. The presented results of the experiments shall allow for a more precise component selection of composite materials at the stage of planning and design of their properties.

  6. Corticothalamic Synaptic Noise as a Mechanism for Selective Attention in Thalamic Neurons

    Directory of Open Access Journals (Sweden)

    Sébastien eBéhuret

    2015-12-01

    Full Text Available A reason why the thalamus is more than a passive gateway for sensory signals is that two-third of the synapses of thalamocortical neurons are directly or indirectly related to the activity of corticothalamic axons. While the responses of thalamocortical neurons evoked by sensory stimuli are well characterized, with ON- and OFF-center receptive field structures, the prevalence of synaptic noise resulting from neocortical feedback in intracellularly recorded thalamocortical neurons in vivo has attracted little attention. However, in vitro and modeling experiments point to its critical role for the integration of sensory signals. Here we combine our recent findings in a unified framework suggesting the hypothesis that corticothalamic synaptic activity is adapted to modulate the transfer efficiency of thalamocortical neurons during selective attention at three different levels: First, on ionic channels by interacting with intrinsic membrane properties, second at the neuron level by impacting on the input-output gain, and third even more effectively at the cell assembly level by boosting the information transfer of sensory features encoded in thalamic subnetworks. This top-down population control is achieved by tuning the correlations in subthreshold membrane potential fluctuations and is adapted to modulate the transfer of sensory features encoded by assemblies of thalamocortical relay neurons. We thus propose that cortically-controlled (de-correlation of subthreshold noise is an efficient and swift dynamic mechanism for selective attention in the thalamus.

  7. Corticothalamic Synaptic Noise as a Mechanism for Selective Attention in Thalamic Neurons.

    Science.gov (United States)

    Béhuret, Sébastien; Deleuze, Charlotte; Bal, Thierry

    2015-01-01

    A reason why the thalamus is more than a passive gateway for sensory signals is that two-third of the synapses of thalamocortical neurons are directly or indirectly related to the activity of corticothalamic axons. While the responses of thalamocortical neurons evoked by sensory stimuli are well characterized, with ON- and OFF-center receptive field structures, the prevalence of synaptic noise resulting from neocortical feedback in intracellularly recorded thalamocortical neurons in vivo has attracted little attention. However, in vitro and modeling experiments point to its critical role for the integration of sensory signals. Here we combine our recent findings in a unified framework suggesting the hypothesis that corticothalamic synaptic activity is adapted to modulate the transfer efficiency of thalamocortical neurons during selective attention at three different levels: First, on ionic channels by interacting with intrinsic membrane properties, second at the neuron level by impacting on the input-output gain, and third even more effectively at the cell assembly level by boosting the information transfer of sensory features encoded in thalamic subnetworks. This top-down population control is achieved by tuning the correlations in subthreshold membrane potential fluctuations and is adapted to modulate the transfer of sensory features encoded by assemblies of thalamocortical relay neurons. We thus propose that cortically-controlled (de-)correlation of subthreshold noise is an efficient and swift dynamic mechanism for selective attention in the thalamus.

  8. Aiptasia sp. larvae as a model to reveal mechanisms of symbiont selection in cnidarians

    KAUST Repository

    Wolfowicz, Iliona

    2016-09-01

    Symbiosis, defined as the persistent association between two distinct species, is an evolutionary and ecologically critical phenomenon facilitating survival of both partners in diverse habitats. The biodiversity of coral reef ecosystems depends on a functional symbiosis with photosynthetic dinoflagellates of the highly diverse genus Symbiodinium, which reside in coral host cells and continuously support their nutrition. The mechanisms underlying symbiont selection to establish a stable endosymbiosis in non-symbiotic juvenile corals are unclear. Here we show for the first time that symbiont selection patterns for larvae of two Acropora coral species and the model anemone Aiptasia are similar under controlled conditions. We find that Aiptasia larvae distinguish between compatible and incompatible symbionts during uptake into the gastric cavity and phagocytosis. Using RNA-Seq, we identify a set of candidate genes potentially involved in symbiosis establishment. Together, our data complement existing molecular resources to mechanistically dissect symbiont phagocytosis in cnidarians under controlled conditions, thereby strengthening the role of Aiptasia larvae as a powerful model for cnidarian endosymbiosis establishment.

  9. The selective tRNA aminoacylation mechanism based on a single G•U pair.

    Science.gov (United States)

    Naganuma, Masahiro; Sekine, Shun-ichi; Chong, Yeeting Esther; Guo, Min; Yang, Xiang-Lei; Gamper, Howard; Hou, Ya-Ming; Schimmel, Paul; Yokoyama, Shigeyuki

    2014-06-26

    Ligation of tRNAs with their cognate amino acids, by aminoacyl-tRNA synthetases, establishes the genetic code. Throughout evolution, tRNA(Ala) selection by alanyl-tRNA synthetase (AlaRS) has depended predominantly on a single wobble base pair in the acceptor stem, G3•U70, mainly on the kcat level. Here we report the crystal structures of an archaeal AlaRS in complex with tRNA(Ala) with G3•U70 and its A3•U70 variant. AlaRS interacts with both the minor- and the major-groove sides of G3•U70, widening the major groove. The geometry difference between G3•U70 and A3•U70 is transmitted along the acceptor stem to the 3'-CCA region. Thus, the 3'-CCA region of tRNA(Ala) with G3•U70 is oriented to the reactive route that reaches the active site, whereas that of the A3•U70 variant is folded back into the non-reactive route. This novel mechanism enables the single wobble pair to dominantly determine the specificity of tRNA selection, by an approximate 100-fold difference in kcat.

  10. Selective deficit of spatial short-term memory: Role of storage and rehearsal mechanisms.

    Science.gov (United States)

    Bonnì, Sonia; Perri, Roberta; Fadda, Lucia; Tomaiuolo, Francesco; Koch, Giacomo; Caltagirone, Carlo; Carlesimo, Giovanni Augusto

    2014-10-01

    We report the neuropsychological and MRI investigation of a patient (GP) who developed a selective impairment of spatial short-term memory (STM) following damage to the dorso-mesial areas of the right frontal lobe. We assessed in this patient spatial STM with an experimental procedure that evaluated immediate and 5-20 s delayed recall of verbal, visual and spatial stimuli. The patient scored significantly worse than normal controls on tests that required delayed recall of spatial data. This could not be ascribed to a deficit of spatial episodic long-term memory because amnesic patients performed normally on these tests. Conversely, the patient scored in the normal range on tests of immediate recall of verbal, visual and spatial data and tests of delayed recall of verbal and visual data. Comparison with a previously described patient who had a selective deficit in immediate spatial recall and an ischemic lesion that affected frontal and parietal dorso-mesial areas in the right hemisphere (Carlesimo GA, Perri R, Turriziani P, Tomaiuolo F, Caltagirone C. Remembering what but not where: independence of spatial and visual working memory in the human brain. Cortex. 2001 Sep; 37(4):519-34) suggests that the right parietal areas are involved in the short-term storage of spatial information and that the dorso-mesial regions of the right frontal underlie mechanisms for the delayed maintenance of the same data.

  11. Corticothalamic Synaptic Noise as a Mechanism for Selective Attention in Thalamic Neurons

    Science.gov (United States)

    Béhuret, Sébastien; Deleuze, Charlotte; Bal, Thierry

    2015-01-01

    A reason why the thalamus is more than a passive gateway for sensory signals is that two-third of the synapses of thalamocortical neurons are directly or indirectly related to the activity of corticothalamic axons. While the responses of thalamocortical neurons evoked by sensory stimuli are well characterized, with ON- and OFF-center receptive field structures, the prevalence of synaptic noise resulting from neocortical feedback in intracellularly recorded thalamocortical neurons in vivo has attracted little attention. However, in vitro and modeling experiments point to its critical role for the integration of sensory signals. Here we combine our recent findings in a unified framework suggesting the hypothesis that corticothalamic synaptic activity is adapted to modulate the transfer efficiency of thalamocortical neurons during selective attention at three different levels: First, on ionic channels by interacting with intrinsic membrane properties, second at the neuron level by impacting on the input-output gain, and third even more effectively at the cell assembly level by boosting the information transfer of sensory features encoded in thalamic subnetworks. This top-down population control is achieved by tuning the correlations in subthreshold membrane potential fluctuations and is adapted to modulate the transfer of sensory features encoded by assemblies of thalamocortical relay neurons. We thus propose that cortically-controlled (de-)correlation of subthreshold noise is an efficient and swift dynamic mechanism for selective attention in the thalamus. PMID:26733818

  12. [Myoanabolic steroids and selective androgen receptor modulators: mechanism of action and perspectives].

    Science.gov (United States)

    Tóth, Miklós

    2009-11-01

    Interest in anabolic steroids has been renewed in the last decade with the discovery of tissue-selective androgen receptor modulators exhibiting high myotropic and small androgenic activity. An explanation put forward by us in 1982 for the mechanism of the preferential myotropic effect of nandrolone (19-nortestosterone) exploits the fundamental difference between the 5alpha-reductase concentrations in skeletal muscle and androgenic target tissue. In androgenic tissue, testosterone is converted to the more potent 5alpha-dihydrotestosterone whereas nandrolone is converted to a less potent derivative. As 5alpha-reduction is negligible in skeletal muscle, this explains why nandrolone shows a greater myotropic to androgenic ratio when compared with testosterone. Anabolic steroids that do not undergo 5alpha-reduction exert myotropic-androgenic dissociation because their effect in androgenic tissues is not amplified by 5alpha-reduction. Tissue selectivity by receptor modulators may be achieved by inducing specific conformational changes of the androgen receptor that affect its interaction with transcriptional coregulators. Anabolic activity is mediated by the stimulation of ribosomal RNA synthesis therefore regulation of this synthesis by anabolic steroids would deserve detailed studies.

  13. Mechanisms of selective head cooling for resuscitating damaged neurons during post-ischemic reperfusion

    Institute of Scientific and Technical Information of China (English)

    段满林; 李德馨; 徐建国

    2002-01-01

    Objective To evaluate the efficacy and the mechanism of application of selective head cooling on neuronal morphological damage during postischemic reperfusion in a rabbit model. Methods 168 New Zealand rabbits were randomized into three groups. Group Ⅰ [n=24, (38±0.5)℃, non-ischemic control]; Group Ⅱ [n=72, (38±0.5)℃, normothermic reperfusion]; Group Ⅲ [n=72, (28±0.5)℃, selective head cooling, initiated at the beginning of reperfusion). Animals in three subgroups (n=24, each) of Group Ⅱ and Group Ⅲ had reperfused lasting for 30, 180 and 360 min respectively. Using computerized image analysis technique on morphological changes of nucleus, the degree of neuronal damage in 12 regions were differentiated into type A (normal), type B (mild damaged), type C (severely damaged) and type D (necrotic). Fourteen biochemical parameters in brain tissues were measured. Results As compared with Group Ⅰ, the counts of type A neuron decreased progressively, and those of type B, C and D increased significantly in Group Ⅱ during reperfusion (P<0.01). In Group Ⅱ, vasoactive intestinal peptide, b-endorphine, prostacyclin, T3 and Na+, K+-ATPase were correlated with the changes of type A; b-endorphine and thromboxane with type B; glucose and vasopressin with type C; Na+, K+-ATPase, glutamic acid, T3 and vasoactive intestinal peptide with type D (P<0.05). As compared with Group Ⅱ, the counts of type A increased, and those of type C and D significantly decreased in Group Ⅲ (P<0.01). In Group Ⅲ, Ca2+, Mg2+-ATPase were correlated with the changes of type A, C and D (P<0.01). Conclusion Selective head cooling for sex hours during postischemic reperfusion does improve neuronal morphological outcomes in terms of morphological changes.

  14. Mechanism of the tissue-specific action of the selective androgen receptor modulator S-101479.

    Science.gov (United States)

    Furuya, Kazuyuki; Yamamoto, Noriko; Ohyabu, Yuki; Morikyu, Teruyuki; Ishige, Hirohide; Albers, Michael; Endo, Yasuhisa

    2013-01-01

    Selective androgen receptor modulators (SARMs) comprise a new class of molecules that induce anabolic effects with fewer side effects than those of other anabolic agents. We previously reported that the novel SARM S-101479 had a tissue-selective bone anabolic effect with diminished side effects in female animals. However, the mechanism of its tissue selectivity is not well known. In this report, we show that S-101479 increased alkaline phosphatase activity and androgen receptor (AR) transcriptional activity in osteoblastic cell lines in the same manner as the natural androgen ligand dihydrotestosterone (DHT); conversely, stimulation of AR dimerization was very low compared with that of DHT (34.4%). S-101479 increased bone mineral content in ovariectomized rats without promoting endometrial proliferation. Yeast two-hybrid interaction assays revealed that DHT promoted recruitment of numerous cofactors to AR such as TIF2, SRC1, β-catenin, NCoA3, gelsolin and PROX1 in a dose-dependent manner. SARMs induced recruitment of fewer cofactors than DHT; in particular, S-101479 failed to induce recruitment of canonical p160 coactivators such as SRC1, TIF2 and notably NCoA3 but only stimulated binding of AR to gelsolin and PROX1. The results suggest that a full capability of the AR to dimerize and to effectively and unselectively recruit all canonical cofactors is not a prerequisite for transcriptional activity in osteoblastic cells and resulting anabolic effects in bone tissues. Instead, few relevant cofactors might be sufficient to promote AR activity in these tissues.

  15. Evolutionary Psychology: How Psychological Mechanisms Shaped by Natural Selection for Ancestral Environments Produce Current Behaviours

    Institute of Scientific and Technical Information of China (English)

    Charles Crawford

    2009-01-01

    The central purpose of this paper is to explain how Darwin's theory of evolution by natural selection can be used in understanding current human behaviour. First, Darwin's logic is briefly described. Development is an important issue when applying evolutionary theory to human behaviour. The notion of innate developmental orga-nization of psychological mechanisms is introduced. The possible social and political outcomes produced when differ-ent levels of innate developmental organization are paired with different beliefs about it are considered. The notion of psychological mechanisms as evolved adaptations is considered in some detail. Then I discuss different ways evo-htionists think about how genes are involved in the development of adaptations. The paper concludes with a frame-work for considering how ancestral adaptations function in current environments and outlines some ways of studying them. In China and many other parts of the world people desire a more harmonious society. Ⅰ hope that this paper will be of some small help in achieving this great task.

  16. Influence of Annealing on Mechanical Properties of Al-20Si Processed by Selective Laser Melting

    Directory of Open Access Journals (Sweden)

    Pan Ma

    2014-01-01

    Full Text Available The microstructure and mechanical properties of Al-20Si produced by selective laser melting (SLM are investigated for different heat treatment conditions. As a result of the high cooling rate during processing, the as-built SLM material displays a microstructure consisting of a supersaturated Al(Si solid solution along with heavily refined eutectic Si and Si particles. The Si particles become coarser, and the eutectic Si gradually changes its morphology from fibrous to plate-like shape with increasing annealing temperature. The microstructural variations occurring during heat treatment significantly affect the mechanical behavior of the samples. The yield and ultimate strengths decrease from 374 and 506 MPa for the as-built SLM material to 162 and 252 MPa for the sample annealed at 673 K, whereas the ductility increases from 1.6 to 8.7%. This offers the possibility to tune microstructure and corresponding properties of the Al-20Si SLM parts to meet specific requirements.

  17. SMFs-supported Pd nanocatalysts in selective acetylene hydrogenation:Pore structure-dependent deactivation mechanism

    Institute of Scientific and Technical Information of China (English)

    Elaheh; Esmaeili; Ali; Morad; Rashidi; Yadollah; Mortazavi; Abbas; Ali; Khodadadi; Mehdi; Rashidzadeh

    2013-01-01

    In the present study,CNFs,ZnO and Al2O3 were deposited on the SMFs panels to investigate the deactivation mechanism of Pd-based catalysts in selective acetylene hydrogenation reaction.The examined supports were characterized by SEM,NH3-TPD and N2adsorption-desorption isotherms to indicate their intrinsic characteristics.Furthermore,in order to understand the mechanism of deactivation,the resulted green oil was characterized using FTIR and SIM DIS.FTIR results confirmed the presence of more unsaturated constituents and then,more branched hydrocarbons formed upon the reaction over alumina-supported catalyst in comparison with the ones supported on CNFs and ZnO,which in turn,could block the pores mouths.Besides the limited hydrogen transfer,N2 adsorption-desorption isotherms results supported that the lowest pore diameters of Al2O3/SMFs close to the surface led to fast deactivation,compared with the other catalysts,especially at higher temperatures.

  18. Selection mechanisms underlying high impact biomedical research--a qualitative analysis and causal model.

    Directory of Open Access Journals (Sweden)

    Hilary Zelko

    selection mechanism provides insights that can be translated into research coaching programs as well as research policy models to optimize the introduction of high impact research at a broad scale among institutional and governmental agencies.

  19. Spectroelectrochemical and computational studies on the mechanism of hypoxia selectivity of copper radiopharmaceuticals.

    Science.gov (United States)

    Holland, Jason P; Barnard, Peter J; Collison, David; Dilworth, Jonathan R; Edge, Ruth; Green, Jennifer C; McInnes, Eric J L

    2008-01-01

    Detailed chemical, spectroelectrochemical and computational studies have been used to investigate the mechanism of hypoxia selectivity of a range of copper radiopharmaceuticals. A revised mechanism involving a delicate balance between cellular uptake, intracellular reduction, reoxidation, protonation and ligand dissociation is proposed. This mechanism accounts for observed differences in the reported cellular uptake and washout of related copper bis(thiosemicarbazonato) complexes. Three copper and zinc complexes have been characterised by X-ray crystallography and the redox chemistry of a series of copper complexes has been investigated by using electronic absorption and EPR spectroelectrochemistry. Time-dependent density functional theory (TD-DFT) calculations have also been used to probe the electronic structures of intermediate species and assign the electronic absorption spectra. DFT calculations also show that one-electron oxidation is ligand-based, leading to the formation of cationic triplet species. In the absence of protons, metal-centred one-electron reduction gives the reduced anionic copper(I) species, [CuIATSM](-), and for the first time it is shown that molecular oxygen can reoxidise this anion to give the neutral, lipophilic parent complexes, which can wash out of cells. The electrochemistry is pH dependent and in the presence of stronger acids both chemical and electrochemical reduction leads to quantitative and rapid dissociation of copper(I) ions from the mono- or diprotonated complexes, [CuIATSMH] and [Cu(I)ATSMH2]+. In addition, a range of protonated intermediate species have been identified at lower acid concentrations. The one-electron reduction potential, rate of reoxidation of the copper(I) anionic species and ease of protonation are dependent on the structure of the ligand, which also governs their observed behaviour in vivo.

  20. Microstructural Evolution and Mechanical Property Development of Selective Laser Melted Copper Alloys

    Science.gov (United States)

    Ventura, Anthony Patrick

    Selective Laser Melting (SLM) is an additive manufacturing technology that utilizes a high-power laser to melt metal powder and form a part layer-by-layer. Over the last 25 years, the technology has progressed from prototyping polymer parts to full scale production of metal component. SLM offers several advantages over traditional manufacturing techniques; however, the current alloy systems that are researched and utilized for SLM do not address applications requiring high electrical and thermal conductivity. This work presents a characterization of the microstructural evolution and mechanical property development of two copper alloys fabricated via SLM and post-process heat treated to address this gap in knowledge. Tensile testing, conductivity measurement, and detailed microstructural characterization was carried out on samples in the as-printed and heat treated conditions. A single phase solid solution strengthened binary alloy, Cu-4.3Sn, was the first alloy studied. Components were selectively laser melted from pre-alloyed Cu-4.3Sn powder and heat treated at 873 K (600 °C) and 1173 K (900 °C) for 1 hour. As-printed samples were around 97 percent dense with a yield strength of 274 MPa, an electrical conductivity of 24.1 %IACS, and an elongation of 5.6%. Heat treatment resulted in lower yield strength with significant increases in ductility due to recrystallization and a decrease in dislocation density. Tensile sample geometry and surface finish also showed a significant effect on measured yield strength but a negligible change in measured ductility. Microstructural characterization indicated that grains primarily grow epitaxially with a sub-micron cellular solidification sub-structure. Nanometer scale tin dioxide particles identified via XRD were found throughout the structure in the tin-rich intercellular regions. The second alloy studied was a high-performance precipitation hardening Cu-Ni-Si alloy, C70250. Pre-alloyed powder was selectively laser melted to

  1. Elucidation of Mechanisms and Selectivities of Metal-Catalyzed Reactions using Quantum Chemical Methodology.

    Science.gov (United States)

    Santoro, Stefano; Kalek, Marcin; Huang, Genping; Himo, Fahmi

    2016-05-17

    solving complex problems and proposing new detailed reaction mechanisms that rationalize the experimental findings. For each of the considered reactions, a consistent mechanism is presented, the experimentally observed selectivities are reproduced, and their sources are identified. Reproducing selectivities requires high accuracy in computing relative transition state energies. As demonstrated by the results summarized in this Account, this accuracy is possible with the use of the presented methodology, benefiting of course from a large extent of cancellation of systematic errors. It is argued that as the employed models become larger, the number of rotamers and isomers that have to be considered for every stationary point increases and a careful assessment of their energies is therefore necessary in order to ensure that the lowest energy conformation is located. This issue constitutes a bottleneck of the investigation in some cases and is particularly important when analyzing selectivities, since small energy differences need to be reproduced.

  2. Investigation into the Effect of Concentration of Benzotriazole on the Selective Layer Surface in the Chemical Mechanical Planarization Process

    Science.gov (United States)

    Ilie, Filip; Laurian, Tiberiu

    2015-12-01

    During selective layer chemical mechanical planarization (CMP), the surface layer is selectively oxidized and removed. Material removal rate in selective layer CMP depends on the depth of removal, pH of the solution, slurry chemistry, potential, percentage of oxidizer, and the applied load. Benzotriazole (BTA) has been used as a corrosion inhibitor in the CMP process. The role of BTA is to prevent corrosion of a pattern via a chemical reaction that forms a Cu-BTA passive film on the selective-layer surface. This paper focuses on the concentration effect of BTA in the slurry of a selective layer CMP process by measuring the friction force during CMP and the modification of the selective layer films immersed in slurries containing various concentrations of BTA. Additionally; the friction characteristics with the concentration of BTA in the selective layer CMP slurry. The effect of BTA concentration was verified using an empirical model based on the friction energy ( E f).

  3. Explanation of the mechanism of carcinogenesis and syntheses of anticancer agents with high selectivity

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    In 1979, the mechanism of chemical carcinogenesis, a challenging and difficult scientific problem pending for a number of years, was explained by Dai Qianhuan. The mechanism named di-region theory predicted that a carcinogen always metabolizes to form a special bi-functional alkylating agent. This agent induces cross-linkages between the complementary base pairs in DNA and switches on initial mutageneses in genomes including point and frameshift mutations. This, in turn, induces further deep mutageneses including the production of various chimeric chromosomes, deletions and other aberrations found in genomes. In the end this initiates carcinogenesis of the whole cell through the reverse transcription mechanism after a lengthy incubation period. Recently, this laboratory has verified that physical carcinogenesis, including the oncogenesis induced by radiation and asbestos as well as the carcinogenesis induced by endogenous factors such as estrogen or diethylstilbestrol switch on carcinogenesis by inducing the formation of cross-linkages between the complementary base pairs in DNA. Di-region theory has now been supported by many experimental observations such as mutational spectra of various carcinogens. The potential for carcinogenesis, teratogenesis, sterility and mutagenesis lumped together as genetic toxicity appears to originate almost uniformly from the cross-linking between complementary bases, i.e. malignant cross-linking, which is in accordance with di-region theory. Other forms of cross-linking between non-complementary bases, benign cross-linkings, show bi-functional alkylation anticancer activity but lack genetic toxicity. The predictable design and synthesis of a high selectivity anticancer agent with high efficacy and low genetic toxicity, a goal long pursued in cancer chemotherapy, have been realized for the first time in this laboratory by inhibiting malignant and heightening benign cross-linking using the principles of di-region theory. A series of

  4. A Flexible Mechanism of Rule Selection Enables Rapid Feature-Based Reinforcement Learning.

    Science.gov (United States)

    Balcarras, Matthew; Womelsdorf, Thilo

    2016-01-01

    Learning in a new environment is influenced by prior learning and experience. Correctly applying a rule that maps a context to stimuli, actions, and outcomes enables faster learning and better outcomes compared to relying on strategies for learning that are ignorant of task structure. However, it is often difficult to know when and how to apply learned rules in new contexts. In our study we explored how subjects employ different strategies for learning the relationship between stimulus features and positive outcomes in a probabilistic task context. We test the hypothesis that task naive subjects will show enhanced learning of feature specific reward associations by switching to the use of an abstract rule that associates stimuli by feature type and restricts selections to that dimension. To test this hypothesis we designed a decision making task where subjects receive probabilistic feedback following choices between pairs of stimuli. In the task, trials are grouped in two contexts by blocks, where in one type of block there is no unique relationship between a specific feature dimension (stimulus shape or color) and positive outcomes, and following an un-cued transition, alternating blocks have outcomes that are linked to either stimulus shape or color. Two-thirds of subjects (n = 22/32) exhibited behavior that was best fit by a hierarchical feature-rule model. Supporting the prediction of the model mechanism these subjects showed significantly enhanced performance in feature-reward blocks, and rapidly switched their choice strategy to using abstract feature rules when reward contingencies changed. Choice behavior of other subjects (n = 10/32) was fit by a range of alternative reinforcement learning models representing strategies that do not benefit from applying previously learned rules. In summary, these results show that untrained subjects are capable of flexibly shifting between behavioral rules by leveraging simple model-free reinforcement learning and context

  5. A flexible mechanism of rule selection enables rapid feature-based reinforcement learning

    Directory of Open Access Journals (Sweden)

    Matthew eBalcarras

    2016-03-01

    Full Text Available Learning in a new environment is influenced by prior learning and experience. Correctly applying a rule that maps a context to stimuli, actions, and outcomes enables faster learning and better outcomes compared to relying on strategies for learning that are ignorant of task structure. However, it is often difficult to know when and how to apply learned rules in new contexts. In our study we explored how subjects employ different strategies for learning the relationship between stimulus features and positive outcomes in a probabilistic task context. We test the hypothesis that task naive subjects will show enhanced learning of feature specific reward associations by switching to the use of an abstract rule that associates stimuli by feature type and restricts selections to that dimension. To test this hypothesis we designed a decision making task where subjects receive probabilistic feedback following choices between pairs of stimuli. In the task, trials are grouped in two contexts by blocks, where in one type of block there is no unique relationship between a specific feature dimension (stimulus shape or colour and positive outcomes, and following an un-cued transition, alternating blocks have outcomes that are linked to either stimulus shape or colour. Two-thirds of subjects (n=22/32 exhibited behaviour that was best fit by a hierarchical feature-rule model. Supporting the prediction of the model mechanism these subjects showed significantly enhanced performance in feature-reward blocks, and rapidly switched their choice strategy to using abstract feature rules when reward contingencies changed. Choice behaviour of other subjects (n=10/32 was fit by a range of alternative reinforcement learning models representing strategies that do not benefit from applying previously learned rules. In summary, these results show that untrained subjects are capable of flexibly shifting between behavioural rules by leveraging simple model-free reinforcement

  6. Mechanisms for selective toxicity of fipronil insecticide and its sulfone metabolite and desulfinyl photoproduct.

    Science.gov (United States)

    Hainzl, D; Cole, L M; Casida, J E

    1998-12-01

    Fipronil, an N-phenylpyrazole with a trifluoromethylsulfinyl substituent, initiated the second generation of insecticides acting at the gamma-aminobutyric acid (GABA) receptor to block the chloride channel. The first generation includes the polychlorocycloalkanes alpha-endosulfan and lindane. In this study, we examine the mechanisms for selective toxicity of the sulfoxide fipronil and its sulfone metabolite and desulfinyl photoproduct relative to their target site interactions in vitro and ex vivo and the importance in fipronil action of biooxidation to the sulfone. Differences in GABA receptor sensitivity, assayed by displacement of 4'-ethynyl-4-n-[2, 3-3H2]propylbicycloorthobenzoate ([3H]EBOB) from the noncompetitive blocker site, appear to be a major factor in fipronil being much more toxic to the insects (housefly and fruit fly) than to the vertebrates (humans, dogs, mice, chickens, quail, and salmon) examined; in insects, the IC50s range from 3 to 12 nM for fipronil and its sulfone and desulfinyl derivatives, while in vertebrates, the IC50 average values are 1103, 175, and 129 nM for fipronil, fipronil sulfone, and desulfinyl fipronil, respectively. The insect relative to the vertebrate specificity decreases in the following order: fipronil > lindane > desulfinyl fipronil > fipronil sulfone > alpha-endosulfan. Ex vivo inhibition of [3H]EBOB binding in mouse brain is similar for fipronil and its sulfone and desulfinyl derivatives at the LD50 dose, but surprisingly, at higher doses fipronil can be lethal without detectably blocking the [3H]EBOB site. The P450 inhibitor piperonyl butoxide, acting in houseflies, increases the metabolic stability and effectiveness of fipronil and the sulfone but not those of the desulfinyl compound, and in mice it completely blocks the sulfoxide to sulfone conversion without altering the poisoning. Thus, the selective toxicity of fipronil and fipronil-derived residues is due in part to the higher potency of the parent compound at

  7. Selected Remarks about Computer Processing in Terms of Flow Control and Statistical Mechanics

    Directory of Open Access Journals (Sweden)

    Dominik Strzałka

    2016-03-01

    Full Text Available Despite the fact that much has been said about processing in computer science, it seems that there is still much to do. A classical approach assumes that the computations done by computers are a kind of mathematical operation (calculations of functions values and have no special relations to energy transformation and flow. However, there is a possibility to get a new view on selected topics, and as a special case, the sorting problem is presented; we know many different sorting algorithms, including those that have complexity equal to O(n lg(n , which means that this problem is algorithmically closed, but it is also possible to focus on the problem of sorting in terms of flow control, entropy and statistical mechanics. This is done in relation to the existing definitions of sorting, connections between sorting and ordering and some important aspects of computer processing understood as a flow that are not taken into account in many theoretical considerations in computer science. The proposed new view is an attempt to change the paradigm in the description of algorithms’ performance by computational complexity and processing, taking into account the existing references between the idea of Turing machines and their physical implementations. This proposal can be expressed as a physics of computer processing; a reference point to further analysis of algorithmic and interactive processing in computer systems.

  8. Selected physico-mechanical characteristics of cryogenic and ambient ground turmeric

    Science.gov (United States)

    Barnwal, Pradyuman; Mohite, Ashish M.; Singh, Krishna K.; Kumar, Pankaj

    2014-03-01

    In this communication, selected physicomechanical characteristics of ground turmeric (cv. Prabha) were investigated for cryogenic and ambient grinding conditions of turmeric at different moisture contents (4, 6, 8 and 10% w.b.). A cryogenic grinder (Model: 100 UPZ, Hosokawa Alpine, Germany) and a micro pulverizer (hammer mill) were used for cryogenic and ambient grinding, respectively. The ground turmeric was graded in three grades viz. Gr-I, Gr-II and Gr-III with a sieve shaker using BSS Nos. 40, 85 and pan, respectively. Tap densities for cryogenic and ambient ground turmeric decreased from 678.7 (Gr-I) to 546.7 kgm-3 (Gr-III) and from 642.3 (Gr-I) to 468.6 kgm-3 (Gr-III), respectively, with the moisture increase. The angle of repose for cryogenic and ambient ground turmeric increased linearly from 26.85 (Gr-I) to 34.0° (Gr-III) and from 23.10 (Gr-I) to 28.06° (Gr-III), respectively with the increase in moisture content. The static coefficient of friction was the highest on plywood surface followed by mild steel sheet and galvanized iron sheet. The cryoground samples were found better in colour. Thermal conductivity of cryo-ground samples was higher than that of ambient ground samples. These physico-mechanical characteristics of cryogenic and ambient ground turmeric will be helpful for packaging, handling, and storage.

  9. Selectivity mechanism of Anoplophora glabripennis on four different species of maples

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Anoplophora glabripennis (Motsch.) is a wood-boring beetle that is native to China. For a long time, it caused great losses in the economy and ecology of northwest China. Attractants are often used to control insects. The volatiles emitted from the host plant play an important role for insects in finding their target. To explore the mechanism of selec-tivity to different host plants, the response of Anoplophora glabripennis to four different host plants was investigated, which included Acer negundo L., Acer mono Maxim., Acer truncatum Bunge. and Acer platanoides L., and the com-pounds in the profiles of volatiles were identified from these species. The olfactory responses ofAnoplophora glabripennis to the odors of different plants showed preference for certain host plants: Acer negundo, Acer mono and Acer truncatum. The attraction ofAcer negundo and Acer mono was signifi-cantly different (pAcer mono Maxim.>Acer truncatum Bunge.>Acer platanoides L.. 1-penten-3-ol, ocimene and trans-Germanylacetone were repellent to Anoplophora glabripennis. 1-penten-3-ol and trans-gerranylacetone were identified in Acer platanoides, and Ocimene was the most attractive to Anoplophora glabripennis among these species. The extent of feeding damage caused by Anoplophora glabripennis differed among four species. The sequences was Acer negundo > Acer mono > Acer truncatum > Acer platanoides. The epidermal hairs of the four host plants revealed that the extent of damage was related to the physical characteristics of the host plants.

  10. An Expert System for Supporting the Design and Selection of Mechanical Equipment for Recreational Crafts

    Directory of Open Access Journals (Sweden)

    T. Gonciarz

    2014-06-01

    Full Text Available Expert Systems can be defined as computer programs, whose main task is to simulate a human expert, usually in a narrow field of expertise. Expert Systems have experienced tremendous growth and popularity since their commercial introduction in the early 1970’s. Today, Expert Systems are used in business, science, engineering, manufacturing and other engineering applications such as planning, scheduling, diagnosing equipment failures and are used in almost every stage of the manufacturing process and also in medicine and many other fields. Expert Systems belong to the field of artificial intelligence. An intelligent computer program that uses knowledge and inference procedures to solve problems that are difficult enough to require significant human expertise for the solution. The purpose of this paper is to present an Expert System which assists with the design of yachts and supports the selection of mechanical equipment for yachts and includes knowledge in the field of yachting engineering. Using the presented Expert System reduces the time during the design and production preparation process.

  11. Selection principles and pattern formation in fluid mechanics and nonlinear shell theory

    Science.gov (United States)

    Sather, Duane P.

    1987-01-01

    Research accomplishments are summarized and publications generated under the contract are listed. The general purpose of the research was to investigate various symmetry breaking problems in fluid mechanics by the use of structure parameters and selection principles. Although all of the nonlinear problems studied involved systems of partial differential equations, many of these problems led to the study of a single nonlinear operator equation of the form F(w, lambda, gamma) = 0, (w is an element of H), (lambda is an element of R1), (gamma is an element of R1). Instead of varying only the load parameter lambda, as is often done in the study of such equations, one of the main ideas used was to vary the structure parameter gamma in such a way that stable solutions were obtained. In this way one determines detailed stability results by making use of the structure of the model equations and the known physical parameters of the problem. The approach was carried out successfully for Benard-type convection problems, Taylor-like problems for short cylinders, rotating Couette-Poiseuille channel flows, and plane Couette flows. The main focus of the research was on wave theory of vortex breakdown in a tube. A number of preliminary results for inviscid axisymmetric flows were obtained.

  12. The mechanism of selective catalytic reduction of NOx on Cu-SSZ-13 - a computational study.

    Science.gov (United States)

    Crandell, Douglas W; Zhu, Haiyang; Yang, Xiaofan; Hochmuth, John; Baik, Mu-Hyun

    2017-01-03

    The copper-exchanged aluminosilicate zeolite SSZ-13 is a leading catalyst for the selective catalytic reduction of NO. Density functional theory calculations are used to construct a complete catalytic cycle of this process paying special attention to the coordination geometries and redox states of copper. N2 can be produced in the reduction half-cycle via a nitrosamine intermediate generated from the reaction of the additive reductant NH3 with a NO(+) intermediate stabilized by the zeolite lattice. The decomposition of this nitrosamine species can be assisted by incipient Brønsted acid sites generated during catalysis. Our calculations also suggest that the reoxidation of Cu(i) to Cu(ii) requires the addition of both NO and O2. The production of a second equivalent of N2 during the oxidation half-cycle proceeds through a peroxynitrite intermediate to form a Cu-nitrite intermediate, which may react with an acid, either HNO2 or NH4(+) to close the catalytic cycle. Models of copper neutralized by an external hydroxide ligand are also examined. These calculations form a key basis for understanding the mechanism of NO reduction in Cu-SSZ-13 in order to develop strategies for rationally optimizing the performance in future experiments.

  13. Computational study of the mechanical behavior of steel produced by selective laser melting

    Science.gov (United States)

    Zinovieva, O.; Zinoviev, A.; Ploshikhin, V.; Romanova, V.; Balokhonov, R.

    2016-11-01

    A two-dimensional numerical analysis of the evolution of grain structure observed during selective laser melting and of the mesomechanical behavior of additive manufactured specimens is performed. Cellular automata finite-difference model is developed to simulate the evolution of grain structure. A heat equation is solved with the use of the classical finite-difference scheme. The cellular automata model for the simulation of microstructural development is based on the approach put forward by Rappaz and Gandin. The Goldak double ellipsoid heat source model is adopted to describe the heat input during laser additive manufacturing process. An elastoplastic constitutive model including isotropic strain hardening is used to describe the mechanical response of additive manufactured specimens. A dynamic boundary-value problem in a plane strain formulation is solved numerically with the use of a Wilkins-type finite-difference scheme. The mesoscopic stress-strain state of additive manufactured specimens subjected to the uniaxial tension is analyzed. The focus is on the role of the inhomogeneous material microstructure in the evolution of the stress-strain state. A combined effect of grain structure and boundary conditions is investigated.

  14. Microstructure and mechanical properties of stainless steel/calcium silicate composites manufactured by selective laser melting.

    Science.gov (United States)

    Zheng, Zeng; Wang, Lianfeng; Jia, Min; Cheng, Lingyu; Yan, Biao

    2017-02-01

    Selective laser melting (SLM) is raised as one kind of additive manufacturing (AM) which is based on the discrete-stacking concept. This technique can fabricate advanced composites with desirable properties directly from 3D CAD data. In this research, 316L stainless steel (316L SS) and different fractions of calcium silicate (CaSiO3) composites (weight fractions of calcium silicate are 0%, 5%,10% and 15%, respectively) were prepared by SLM technique with a purpose to develop biomedical metallic materials. The relative density, tensile, microhardness and elastic modulus of the composites were tested, their microstructures and fracture morphologies were observed using optical microscope (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was found that the addition of CaSiO3 particles influenced the microstructure and mechanical properties of specimens significantly. The CaSiO3 precipitates from the overlap of adjacent tracks and became the origin of the defects. The tensile strength of specimens range 320-722MPa. The microhardness and elastic modulus are around 250HV and 215GPa respectively. These composites were ductile materials and the fracture mode of the composites was mixed mode of ductile and brittle fracture. The 316L SS/CaSiO3 composites can be a potential biomedical metallic materials in the medical field.

  15. Interest rate transmission mechanism of monetary policy in the selected EMU candidate countries

    Directory of Open Access Journals (Sweden)

    Mirdala Rajmund

    2009-01-01

    Full Text Available The stable macroeconomic environment, as one of the primary objectives of the Visegrad countries in the 1990s, was partially supported by the exchange rate policy. Fixed exchange rate systems within gradually widen bands (Czech Republic, Slovak Republic and crawling peg system (Hungary, Poland were replaced by the managed floating in the Czech Republic (May 1997, Poland (April 2000, Slovak Republic (October 1998 and fixed exchange rate to euro in Hungary (January 2000 with broad band (October 2001. Higher macroeconomic and banking sector stability allowed countries from the Visegrad group to implement the monetary policy strategy based on the interest rate transmission mechanism. Continuous harmonization of the monetary policy framework (with the monetary policy of the ECB and the increasing sensitivity of the economy agents to the interest rates changes allowed the central banks from the Visegrad countries to implement monetary policy strategy based on the key interest rates determination. In the paper we analyze the impact of the central banks' monetary policy in the Visegrad countries on the selected macroeconomic variables in the period 1999-2008 implementing SVAR (structural vector autoregression approach. We expect that higher sensitivity of domestic variables to interest rates shocks can be interpreted as a convergence of monetary policies in candidate countries towards the ECB's monetary policy.

  16. Mechanism of Selective Desulphurization in Iron Ore Sintering Process by Adding Urea

    Science.gov (United States)

    Long, Hongming; Wu, Xuejian; Chun, Tiejun; Li, Jiaxin; Wang, Ping; Meng, Qingmin; Di, Zhanxia; Zhang, Xiangyang

    2017-02-01

    Iron ore sintering is an important part during the ironmaking process, and a large amount of SO2 is also generated. Our previous research shows that it is an effective way to reduce SO2 content of flue gas by adding urea to a special sintering material zone position. In this paper, the mechanism of selective desulphurization by adding urea during the iron ore sintering was carried out. The results show that 88.14 % desulphurization rate was obtained with the addition of 0.05 % urea particles at 100 mm height from the feed bottom. During the sintering process, when drying zone reached the added position of urea, large amounts of NH3 were generated by urea decomposition, and then reacted with SO2 to produce (NH4)2SO4 in the wetting zone. With the accumulated desulphurization reactions during the sintering, the low SO2 emission in the flue gas was achieved. Moreover, the addition of urea in the bottom zone avoided the ammonia present in the sintering ore and promoted the urea utilization efficiency.

  17. A covalent PIN1 inhibitor selectively targets cancer cells by a dual mechanism of action

    Science.gov (United States)

    Campaner, Elena; Rustighi, Alessandra; Zannini, Alessandro; Cristiani, Alberto; Piazza, Silvano; Ciani, Yari; Kalid, Ori; Golan, Gali; Baloglu, Erkan; Shacham, Sharon; Valsasina, Barbara; Cucchi, Ulisse; Pippione, Agnese Chiara; Lolli, Marco Lucio; Giabbai, Barbara; Storici, Paola; Carloni, Paolo; Rossetti, Giulia; Benvenuti, Federica; Bello, Ezia; D'Incalci, Maurizio; Cappuzzello, Elisa; Rosato, Antonio; Del Sal, Giannino

    2017-06-01

    The prolyl isomerase PIN1, a critical modifier of multiple signalling pathways, is overexpressed in the majority of cancers and its activity strongly contributes to tumour initiation and progression. Inactivation of PIN1 function conversely curbs tumour growth and cancer stem cell expansion, restores chemosensitivity and blocks metastatic spread, thus providing the rationale for a therapeutic strategy based on PIN1 inhibition. Notwithstanding, potent PIN1 inhibitors are still missing from the arsenal of anti-cancer drugs. By a mechanism-based screening, we have identified a novel covalent PIN1 inhibitor, KPT-6566, able to selectively inhibit PIN1 and target it for degradation. We demonstrate that KPT-6566 covalently binds to the catalytic site of PIN1. This interaction results in the release of a quinone-mimicking drug that generates reactive oxygen species and DNA damage, inducing cell death specifically in cancer cells. Accordingly, KPT-6566 treatment impairs PIN1-dependent cancer phenotypes in vitro and growth of lung metastasis in vivo.

  18. Comparison of the Mechanical Behaviour of Selected Oilseeds under Compression Loading

    Directory of Open Access Journals (Sweden)

    David HERAK

    2012-11-01

    Full Text Available The present study provides information about the comparison of mechanical behaviour of selected oil bearing crops namely rapeseeds (Brassica napus L., sunflower seeds (Helianthus annus L. and jatropha seeds (Jatropha curcas L. under compression loading. In this research, the compression device ZDM 50 with a chart recorder and a pressing vessel with diameter 100 mm were used to determine the relationship between the magnitude of the pressing force and deformation characteristics of the oilseed crops pressed at initial height 80 mm. From the compression test, the amounts of true deformation, maximal deformation energy and compressive force of the pressed samples were calculated and also mathematical equations describing the limit deformation, maximal deformation ratio, energy ratio and oil point deformation ratio were determined. The oil point position on the deformation curve, that is, the first leakage of oil from the pressing vessel of the various oilseeds was determined and compared. Based on the measured amounts rapeseeds achieved the highest values followed by jatropha seed and then sunflower seed. The amount of deformation energy required for the seed deformation gives the indication the amount of energy needed for obtaining the oil from the seed. It was found that the measured amounts as well as the oil point position on the force-deformation curve of the pressed samples showed varying results due to the seeds physical and inherent characteristics.

  19. Molecular mechanisms in the selective basal activation of pyrabactin receptor 1: Comparative analysis of mutants.

    Science.gov (United States)

    Dorosh, Lyudmyla; Rajagopalan, Nandhakishore; Loewen, Michele C; Stepanova, Maria

    2014-01-01

    Pyrabactin receptors (PYR) play a central role in abscisic acid (ABA) signal transduction; they are ABA receptors that inhibit type 2C protein phosphatases (PP2C). Molecular aspects contributing to increased basal activity of PYR against PP2C are studied by molecular dynamics (MD) simulations. An extensive series of MD simulations of the apo-form of mutagenized PYR1 as a homodimer and in complex with homology to ABA-insensitive 1 (HAB1) phosphatase are reported. In order to investigate the detailed molecular mechanisms mediating PYR1 activity, the MD data was analyzed by essential collective dynamics (ECD), a novel approach that allows the identification, with atomic resolution, of persistent dynamic correlations based on relatively short MD trajectories. Employing the ECD method, the effects of select mutations on the structure and dynamics of the PYR1 complexes were investigated and considered in the context of experimentally determined constitutive activities against HAB1. Approaches to rationally design constitutively active PYR1 constructs to increase PP2C inhibition are discussed.

  20. Molecular mechanisms in the selective basal activation of pyrabactin receptor 1: Comparative analysis of mutants

    Directory of Open Access Journals (Sweden)

    Lyudmyla Dorosh

    2014-01-01

    Full Text Available Pyrabactin receptors (PYR play a central role in abscisic acid (ABA signal transduction; they are ABA receptors that inhibit type 2C protein phosphatases (PP2C. Molecular aspects contributing to increased basal activity of PYR against PP2C are studied by molecular dynamics (MD simulations. An extensive series of MD simulations of the apo-form of mutagenized PYR1 as a homodimer and in complex with homology to ABA-insensitive 1 (HAB1 phosphatase are reported. In order to investigate the detailed molecular mechanisms mediating PYR1 activity, the MD data was analyzed by essential collective dynamics (ECD, a novel approach that allows the identification, with atomic resolution, of persistent dynamic correlations based on relatively short MD trajectories. Employing the ECD method, the effects of select mutations on the structure and dynamics of the PYR1 complexes were investigated and considered in the context of experimentally determined constitutive activities against HAB1. Approaches to rationally design constitutively active PYR1 constructs to increase PP2C inhibition are discussed.

  1. Selective Guide to Literature on Mechanical Engineering. Engineering Literature Guides, Number 2.

    Science.gov (United States)

    Franklin, Hugh Lockwood, Comp.

    Mechanical engineering has become highly interdisciplinary. It would not be possible to single out particular reference sources that are uniquely applicable to mechanical engineering. For the purpose of this guide, mechanical engineering deals with the generation, transmission and utilization of heat and mechanical power and with the production of…

  2. Spontaneous mutation frequency and molecular mechanisms of Shigella flexneri fluoroquinolone resistance under antibiotic selective stress.

    Science.gov (United States)

    Pu, Xiao-Ying; Zhang, Qijing; Pan, Jing-Cao; Shen, Zhangqi; Zhang, Wei

    2013-02-01

    The incidence of fluoroquinolone-resistant Shigella strains has risen rapidly, presumably in response to ciprofloxacin antibiotic stress. Understanding the molecular mechanisms underlying this resistance phenotype is critical to developing novel and effective therapeutic strategies. In this study, the frequency of ciprofloxacin-induced mutation was measured in antibiotic resistance genes (gyrA, gyrB, parC, parE, marOR, and marA) of Shigella flexneri. The S. flexneri 2a strain 301 was cultured on Luria-Bertani agar plates containing one of seven different ciprofloxacin concentrations (range: 0.03125-2 μg mL(-1)). Resistant colonies were selected for gene-targeted sequencing analysis; the identified point mutations were subsequently confirmed by insertion into antibiotic cassette plasmids and growth under ciprofloxacin stress. The results demonstrated that the seven different ciprofloxacin concentrations produced dose-dependent frequencies of spontaneous mutations: 10(-8) (0.03125 and 0.0625 μg mL(-1)), 10(-9) (0.125 μg mL(-1)), and resistant colonies (minimum inhibitory concentrations (MICs) of 0.125 μg mL(-1), n = 5 and 0.25 μg mL(-1), n = 5) revealed that all colonies had mutations in the gyrA gene at either codon 83 (Ser83 → Leu) or 87 (Asp87 → Tyr or → Gly), both of which were confirmed at MIC of 0.125 μg mL(-1). None of the spontaneous mutation colonies exhibited gyrB, parC, parE, marOR, or marA mutations. In conclusion, S. flexneri is normomutable under ciprofloxacin antibiotic stress and fluoroquinolone resistance by spontaneous mutation occurs at a low rate. Codon mutations gyrA 83 and/or gyrA 87 cause a 4-fold increase in the ciprofloxacin MIC, and may represent the natural mechanism of fluoroquinolone resistance.

  3. Molecular and hereditary mechanisms of sensorineural hearing loss with focus on selected endocrinopathies.

    Science.gov (United States)

    Masindova, I; Varga, L; Stanik, J; Valentinova, L; Profant, M; Klimes, I; Gasperikova, D

    2012-07-01

    Hearing loss is one of the most widespread sensory disorders. The incidence of deafness in general population is 1:1000 newborns. About one half of the cases of the congenital sensorineural hearing loss (SNHL) is inherited. Recessive mutations in the gap junction beta 2 (GJB2) gene are the most common genetic causes of the nonsyndromic SNHL. The GJB2 encodes a protein connexin 26 which forms a subunit of gap junction essential for the correct function of the inner ear. The syndromic SNHL is associated with a wide range of other symptoms, which encompass also dysfunctions of endocrine organs. The Pendred syndrome associated with the hearing impairment is characterized by a prelingual, bilateral sever to profound SNHL, goiter, and iodine organification defect. It is an autosomal recessive disorder, which develops due to mutations in pendrin, an anion channel encoded by SLC26A4 gene. Another important type of syndromic hearing loss is the Maternally Inherited Diabetes and Deafness syndrome, which is caused by several mitochondrial DNA mutations. These mutations are clinically manifested by a hearing impairment with development of the diabetes in the adult age. Hearing impairment occurs during puberty when sensation of high frequency tones is affected following with further progress to profound bilateral sensorineural hearing impairment in the whole frequency range. This review deals with the molecular mechanisms of common genetic causes of the hereditary SNHL along with the selected endocrinopathies emphasizing that the DNA analyses along with the functional studies significantly contribute to the early SNHL diagnosis followed by personalized therapy and genetic counseling.

  4. Design of an Action Selection Mechanism for Cooperative Soccer Robots Based on Fuzzy Decision Making Algorithm

    Directory of Open Access Journals (Sweden)

    S. Alireza Mohades Kasaei

    2010-04-01

    Full Text Available Robocup is an international competition for multi agent research and related subject like: Artificial intelligence, Image processing, machine learning, robot path planning, control, and
    obstacle avoidance. In a soccer robot game, the environment is highly competitive and dynamic. In order to work in the dynamically changing environment, the decision-making system of a soccer robot system should have the features of flexibility and real-time adaptation. In this paper we will
    focus on the Middle Size Soccer Robot league (MSL and new hierarchical hybrid fuzzy methods for decision making and action selection of a robot in Middle Size Soccer Robot league (MSL are presented. First, the behaviors of an agent are introduced, implemented and classified in two layers,
    the Low_Level_Behaviors and the High_Level_Behaviors. In the second layer, a two phase mechanism for decision making is introduced. In phase one, some useful methods are implemented which check the robot’s situation for performing required behaviors. In the next phase, the team strategy, team formation, robot’s role and the robot’s positioning system are introduced. A fuzzy logical approach is employed to recognize the team strategy and further more to tell the player the
    best position to move. We believe that a Dynamic role engine is necessary for a successful team. Dynamic role engine and formation control during offensive or defensive play, help us to prevent collision avoidance among own players when attacking the ball and obstacle avoidance of the opponents. At last, we comprised our implemented algorithm in the Robocup 2007 and 2008 and results showed the efficiency of the introduced methodology. The results are satisfactory which has already been successfully implemented in ADRO RoboCup team. This project is still in progress and some new interesting methods are described in the current report.

  5. Corrosion inhibition mechanisms of aluminum alloy 2024-T3 by selected non-chromate inhibitors

    Science.gov (United States)

    Lopez-Garrity, Omar A.

    The pursuit to find a chromate-alternative has led to the development of several chromate-free aerospace primers and coating systems that offer good protection. However, fundamental understanding of the functionality of the chromate-free pigments that are embedded within these coating systems is lacking. The objective of this study was to understand the fundamental mechanism of corrosion inhibition of aluminum alloy 2024-T3 by molybdate (MoO 42-), silicate (SiO32-), and praseodymium (Pr3+) with the goal of developing the kind of understanding that was accomplished for chromate. Furthermore, since most inhibiting conversion coatings and pigments act by releasing soluble species into the local environment, it was of interest to understand the mechanism of inhibition in aqueous 0.1 M NaCl solution. The mechanism of inhibition of AA2024-T3 by the select non-chromate inhibitors was investigated using various electrochemical, microscopic and spectroscopic techniques. Naturally aerated polarization curves showed that molybdate provided mixed inhibition in near-neutral pH and at a threshold concentration of 0.1 M. The largest effect was a 250 mV increase in the breakdown potential associated with pitting and a 350 mV decrease in the open-circuit potential (OCP). In addition, electrochemical impedance indicated that the corrosion inhibition mechanism is oxygen-dependent owing to the protection afforded by Mo(VI) species. It was proposed that the corrosion inhibition of AA2024-T3 by molybdate may occur following a two-step process whereby molybdate is rapidly reduced to MoO.(OH)2 over the intermetallic particles and is subsequently oxidized to intermediate molybdenum oxides (e.g. Mo4O11) in the presence of oxygen which is reduced. This in turn may lead to a local acidification, promoting the condensation and polymerization of molybdate species in solution to form polymolybdate species (Mo7O24 6- and Mo8O264-). Furthermore, S-phase particle dissolution is decreased

  6. Selection of insensitive acetylcholinesterase as a resistance mechanism in Aedes aegypti (Diptera: Culicidae) from Santiago de Cuba.

    Science.gov (United States)

    Bisset, Juan; Rodríguez, María M; Fernández, Ditter

    2006-11-01

    A sample of Aedes aegypti (L.) (Diptera: Culicidae) from Santiago de Cuba, Cuba, with a high level of propoxur resistance compared with the reference susceptible Rockefeller strain (12.60 x at the 50% lethal concentration [LC50] and 18.08 at the 90% lethal concentration [LC90]), with a 4.3% frequency of insensitive acetylcholinesterase (AChE) frequency, was subjected to propoxur selection for 13 successive generations to increase the frequency of this resistance mechanism in Ae. aegypti. High resistance to propoxur was developed during this selection (41.73-fold), and the frequency of insensitive AChE mechanism was increased 13.25-fold. Other mechanisms (overproduced esterases, glutathione transferases, or monooxygenases) were not detected in the propoxur-selected strain. The selection of an insensitive AChE resistance mechanism in Ae. aegypti has important implications and will be a valuable resource for genetic studies and molecular characterization of the ace gene mutation(s) associated with insecticide resistance in Ae. aegypti.

  7. Automated Determination of the Power Required and Selection of Electric Motors for Forging Fly-Press Mechanisms

    Directory of Open Access Journals (Sweden)

    K. Karakoulidis

    2015-06-01

    Full Text Available The current work deals with appropriate selection of electric motors for forging fly-press machines. To solve the equation of motion of the electric drive of these mechanisms characterized by impact (pulsating load and presence of flywheel, numerical methods (calculus have been used.

  8. The Mechanisms and Quantification of the Selective Permeability in Transport Across Biological Barriers : the Example of Kyotorphin

    NARCIS (Netherlands)

    Serrano, Isa D.; Freire, Joao M.; Carvalho, Miguel V.; Neves, Mafalda; Melo, Manuel N.; Castanho, Miguel A. R. B.

    2014-01-01

    This paper addresses the mechanisms behind selective endothelial permeability and their regulations. The singular properties of each of the seven blood-tissues barriers. Then, it further revisits the physical, quantitative meaning of permeability, and the way it should be measured based on sound phy

  9. A multicriteria decision making approach based on fuzzy theory and credibility mechanism for logistics center location selection.

    Science.gov (United States)

    Wang, Bowen; Xiong, Haitao; Jiang, Chengrui

    2014-01-01

    As a hot topic in supply chain management, fuzzy method has been widely used in logistics center location selection to improve the reliability and suitability of the logistics center location selection with respect to the impacts of both qualitative and quantitative factors. However, it does not consider the consistency and the historical assessments accuracy of experts in predecisions. So this paper proposes a multicriteria decision making model based on credibility of decision makers by introducing priority of consistency and historical assessments accuracy mechanism into fuzzy multicriteria decision making approach. In this way, only decision makers who pass the credibility check are qualified to perform the further assessment. Finally, a practical example is analyzed to illustrate how to use the model. The result shows that the fuzzy multicriteria decision making model based on credibility mechanism can improve the reliability and suitability of site selection for the logistics center.

  10. Genomic Comparison of Indigenous African and Northern European Chickens Reveals Putative Mechanisms of Stress Tolerance Related to Environmental Selection Pressure.

    Science.gov (United States)

    Fleming, Damarius S; Weigend, Steffen; Simianer, Henner; Weigend, Annett; Rothschild, Max; Schmidt, Carl; Ashwell, Chris; Persia, Mike; Reecy, James; Lamont, Susan J

    2017-05-05

    Global climate change is increasing the magnitude of environmental stressors, such as temperature, pathogens, and drought, that limit the survivability and sustainability of livestock production. Poultry production and its expansion is dependent upon robust animals that are able to cope with stressors in multiple environments. Understanding the genetic strategies that indigenous, noncommercial breeds have evolved to survive in their environment could help to elucidate molecular mechanisms underlying biological traits of environmental adaptation. We examined poultry from diverse breeds and climates of Africa and Northern Europe for selection signatures that have allowed them to adapt to their indigenous environments. Selection signatures were studied using a combination of population genomic methods that employed FST , integrated haplotype score (iHS), and runs of homozygosity (ROH) procedures. All the analyses indicated differences in environment as a driver of selective pressure in both groups of populations. The analyses revealed unique differences in the genomic regions under selection pressure from the environment for each population. The African chickens showed stronger selection toward stress signaling and angiogenesis, while the Northern European chickens showed more selection pressure toward processes related to energy homeostasis. The results suggest that chromosomes 2 and 27 are the most diverged between populations and the most selected upon within the African (chromosome 27) and Northern European (chromosome 2) birds. Examination of the divergent populations has provided new insight into genes under possible selection related to tolerance of a population's indigenous environment that may be baselines for examining the genomic contribution to tolerance adaptions. Copyright © 2017 Fleming et al.

  11. 5-HTTLPR polymorphism is linked to neural mechanisms of selective attention in preschoolers from lower socioeconomic status backgrounds

    Directory of Open Access Journals (Sweden)

    Elif Isbell

    2016-12-01

    Full Text Available While a growing body of research has identified experiential factors associated with differences in selective attention, relatively little is known about the contribution of genetic factors to the skill of sustained selective attention, especially in early childhood. Here, we assessed the association between the serotonin transporter linked polymorphic region (5-HTTLPR genotypes and the neural mechanisms of selective attention in young children from lower socioeconomic status (SES backgrounds. Event-related potentials (ERPs were recorded during a dichotic listening task from 121 children (76 females, aged 40–67 months, who were also genotyped for the short and long allele of 5-HTTLPR. The effect of selective attention was measured as the difference in ERP mean amplitudes elicited by identical probe stimuli embedded in stories when they were attended versus unattended. Compared to children homozygous for the long allele, children who carried at least one copy of the short allele showed larger effects of selective attention on neural processing. These findings link the short allele of the 5-HTTLPR to enhanced neural mechanisms of selective attention and lay the groundwork for future studies of gene-by-environment interactions in the context of key cognitive skills.

  12. 5-HTTLPR polymorphism is linked to neural mechanisms of selective attention in preschoolers from lower socioeconomic status backgrounds.

    Science.gov (United States)

    Isbell, Elif; Stevens, Courtney; Hampton Wray, Amanda; Bell, Theodore; Neville, Helen J

    2016-12-01

    While a growing body of research has identified experiential factors associated with differences in selective attention, relatively little is known about the contribution of genetic factors to the skill of sustained selective attention, especially in early childhood. Here, we assessed the association between the serotonin transporter linked polymorphic region (5-HTTLPR) genotypes and the neural mechanisms of selective attention in young children from lower socioeconomic status (SES) backgrounds. Event-related potentials (ERPs) were recorded during a dichotic listening task from 121 children (76 females, aged 40-67 months), who were also genotyped for the short and long allele of 5-HTTLPR. The effect of selective attention was measured as the difference in ERP mean amplitudes elicited by identical probe stimuli embedded in stories when they were attended versus unattended. Compared to children homozygous for the long allele, children who carried at least one copy of the short allele showed larger effects of selective attention on neural processing. These findings link the short allele of the 5-HTTLPR to enhanced neural mechanisms of selective attention and lay the groundwork for future studies of gene-by-environment interactions in the context of key cognitive skills.

  13. Palladium-catalyzed meta-selective C-H bond activation with a nitrile-containing template: computational study on mechanism and origins of selectivity.

    Science.gov (United States)

    Yang, Yun-Fang; Cheng, Gui-Juan; Liu, Peng; Leow, Dasheng; Sun, Tian-Yu; Chen, Ping; Zhang, Xinhao; Yu, Jin-Quan; Wu, Yun-Dong; Houk, K N

    2014-01-08

    Density functional theory investigations have elucidated the mechanism and origins of meta-regioselectivity of Pd(II)-catalyzed C-H olefinations of toluene derivatives that employ a nitrile-containing template. The reaction proceeds through four major steps: C-H activation, alkene insertion, β-hydride elimination, and reductive elimination. The C-H activation step, which proceeds via a concerted metalation-deprotonation (CMD) pathway, is found to be the rate- and regioselectivity-determining step. For the crucial C-H activation, four possible active catalytic species-monomeric Pd(OAc)2, dimeric Pd2(OAc)4, heterodimeric PdAg(OAc)3, and trimeric Pd3(OAc)6-have been investigated. The computations indicated that the C-H activation with the nitrile-containing template occurs via a Pd-Ag heterodimeric transition state. The nitrile directing group coordinates with Ag while the Pd is placed adjacent to the meta-C-H bond in the transition state, leading to the observed high meta-selectivity. The Pd2(OAc)4 dimeric mechanism also leads to the meta-C-H activation product but with higher activation energies than the Pd-Ag heterodimeric mechanism. The Pd monomeric and trimeric mechanisms require much higher activation free energies and are predicted to give ortho products. Structural and distortion energy analysis of the transition states revealed significant effects of distortions of the template on mechanism and regioselectivity, which provided hints for further developments of new templates.

  14. Three-dimensional motion aftereffects reveal distinct direction-selective mechanisms for binocular processing of motion through depth

    Science.gov (United States)

    Czuba, Thaddeus B.; Rokers, Bas; Guillet, Kyle; Huk, Alexander C.; Cormack, Lawrence K.

    2013-01-01

    Motion aftereffects are historically considered evidence for neuronal populations tuned to specific directions of motion. Despite a wealth of motion aftereffect studies investigating 2D (frontoparallel) motion mechanisms, there is a remarkable dearth of psychophysical evidence for neuronal populations selective for the direction of motion through depth (i.e., tuned to 3D motion). We compared the effects of prolonged viewing of unidirectional motion under dichoptic and monocular conditions and found large 3D motion aftereffects that could not be explained by simple inheritance of 2D monocular aftereffects. These results (1) demonstrate the existence of neurons tuned to 3D motion as distinct from monocular 2D mechanisms, (2) show that distinct 3D direction selectivity arises from both interocular velocity differences and changing disparities over time, and (3) provide a straightforward psychophysical tool for further probing 3D motion mechanisms. PMID:21945967

  15. Selected studies on the thermal and mechanical responses of amorphous glassy polymers at different length scales

    Science.gov (United States)

    Crawford, Emmett Dudley

    This thesis describes investigations into the mechanical and thermal characteristics of amorphous polymeric materials by structural changes on the molecular and the microscopic scale. On the molecular scale, the structure of a cross-linked polymeric material is controlled by changes in the molecular weight between cross-links, cross-link functionality, and chain stiffness. With control of the network structure, an expansive range of mechanical and thermal characteristics is possible. These properties range from intrinsic properties, such as the glass transition temperature, to performance properties, such as impact behavior. Relationships between the network structure and measured properties are established by the use of a variety of theories from rubber elasticity to free volume. Relationships are also established between the various measured properties through solid and fracture mechanics. The introduction of soft rubbery particles on the microscopic scale into a glassy polymeric matrix is commonly employed to create a tougher material. Despite the prevalent use, the mechanisms and sequence of mechanisms of toughening are poorly understood. The mechanisms and sequence of mechanisms are elucidated in this investigation through the use of unique mechanical tests and materials with favorable properties. The unique mechanical tests in this investigation include tensile dilatometry and a multi-axial stress state test. The multi-axial stress state test, which allows independent control of the dilational and deviatoric stresses of a material between uniaxial compression and equal biaxial tension, consists of a uniaxially loaded and pressurized thin walled hollow cylinder. The materials include liquid rubber modified epoxies, voided epoxies, and core-shell rubber modified polyvinylchloride. The voided epoxy material separates the matrix contributions from those of the rubbery phase, while the core-shell rubber modified polyvinylchloride provides optical verification of

  16. cis-Dihydroxylation and Epoxidation of Alkenes by Manganese Catalysts - Selectivity, Reactivity and Mechanism

    NARCIS (Netherlands)

    Boer, Johannes Wietse de

    2008-01-01

    Oxidation reactions are among the most elementary of organic transformations and are essential in biology, chemical industry and (synthetic organic) chemistry. Selective oxidation of hydrocarbons, such as cis-dihydroxylation and epoxidation of alkenes, introduces functional groups and yields useful

  17. Music training relates to the development of neural mechanisms of selective auditory attention.

    Science.gov (United States)

    Strait, Dana L; Slater, Jessica; O'Connell, Samantha; Kraus, Nina

    2015-04-01

    Selective attention decreases trial-to-trial variability in cortical auditory-evoked activity. This effect increases over the course of maturation, potentially reflecting the gradual development of selective attention and inhibitory control. Work in adults indicates that music training may alter the development of this neural response characteristic, especially over brain regions associated with executive control: in adult musicians, attention decreases variability in auditory-evoked responses recorded over prefrontal cortex to a greater extent than in nonmusicians. We aimed to determine whether this musician-associated effect emerges during childhood, when selective attention and inhibitory control are under development. We compared cortical auditory-evoked variability to attended and ignored speech streams in musicians and nonmusicians across three age groups: preschoolers, school-aged children and young adults. Results reveal that childhood music training is associated with reduced auditory-evoked response variability recorded over prefrontal cortex during selective auditory attention in school-aged child and adult musicians. Preschoolers, on the other hand, demonstrate no impact of selective attention on cortical response variability and no musician distinctions. This finding is consistent with the gradual emergence of attention during this period and may suggest no pre-existing differences in this attention-related cortical metric between children who undergo music training and those who do not.

  18. Selective recovery of Pd(II) from extremely acidic solution using ion-imprinted chitosan fiber: Adsorption performance and mechanisms.

    Science.gov (United States)

    Lin, Shuo; Wei, Wei; Wu, Xiaohui; Zhou, Tao; Mao, Juan; Yun, Yeoung-Sang

    2015-12-15

    A novel, selective and acid-resisting chitosan fiber adsorbent was prepared by the ion-imprinting technique using Pd(II) and epichlorohydrin as the template and two-step crosslinking agent, respectively. The resulting ion-imprinted chitosan fibers (IIF) were used to selectively adsorb Pd(II) under extremely acidic synthetic metal solutions. The adsorption and selectivity performances of IIF including kinetics, isotherms, pH effects, and regeneration were investigated. Pd(II) rapidly adsorbed on the IIF within 100 min, achieving the adsorption equilibrium. The isotherm results showed that the maximum Pd(II) uptake on the IIF was maintained as 324.6-326.4 mg g(-1) in solutions containing single and multiple metals, whereas the Pd(II) uptake on non-imprinted fibers (NIF) decreased from 313.7 to 235.3 mg g(-1) in solution containing multiple metals. Higher selectivity coefficients values were obtained from the adsorption on the IIF, indicating a better Pd(II) selectivity. The amine group, supposedly the predominant adsorption site for Pd(II), was confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The pH value played a significant role on the mechanism of the selective adsorption in the extremely acidic conditions. Furthermore, the stabilized performance for three cycles of sorption/desorption shows a potential for further large-scale applications. Copyright © 2015 Elsevier B.V. All rights reserved.

  19. Computational Experiment Study on Selection Mechanism of Project Delivery Method Based on Complex Factors

    Directory of Open Access Journals (Sweden)

    Xiang Ding

    2014-01-01

    Full Text Available Project delivery planning is a key stage used by the project owner (or project investor for organizing design, construction, and other operations in a construction project. The main task in this stage is to select an appropriate project delivery method. In order to analyze different factors affecting the PDM selection, this paper establishes a multiagent model mainly to show how project complexity, governance strength, and market environment affect the project owner’s decision on PDM. Experiment results show that project owner usually choose Design-Build method when the project is very complex within a certain range. Besides, this paper points out that Design-Build method will be the prior choice when the potential contractors develop quickly. This paper provides the owners with methods and suggestions in terms of showing how the factors affect PDM selection, and it may improve the project performance.

  20. Selected aspects of security mechanisms for cloud computing – current solutions and development perspectives

    OpenAIRE

    Aneta Poniszewska-Maranda

    2014-01-01

    The security aspects of cloud computing, especially the security of data, become more and more important. It is necessary to find and develop the new mechanisms to secure the cloud. The problem presented in the paper concerns the mechanisms for security of cloud computing with special attention paid to aspects of access control in clouds - the state of the art and the perspectives for the future.

  1. Distractor Suppression When Attention Fails: Behavioral Evidence for a Flexible Selective Attention Mechanism

    OpenAIRE

    James C. Elliott; Barry Giesbrecht

    2015-01-01

    Despite consistent evidence showing that attention is a multifaceted mechanism that can operate at multiple levels of processing depending on the structure and demands of the task, investigations of the attentional blink phenomenon have consistently shown that the impairment in reporting the second of two targets typically occurs at a late, or post-perceptual, stage of processing. This suggests that the attentional blink phenomenon may represent the operation of a unique attentional mechanism...

  2. Patterns of Selection of Human Movements IV: Energy Efficiency, Mechanical Advantage, and Asynchronous Arm-Cranking

    OpenAIRE

    Hagler, Stuart

    2017-01-01

    Human movements are physical processes combining the classical mechanics of the human body moving in space and the biomechanics of the muscles generating the forces acting on the body under sophisticated sensory-motor control. The characterization of the performance of human movements is a problem with important applications in clinical and sports research. One way to characterize movement performance is through measures of energy efficiency that relate the mechanical energy of the body and m...

  3. Patterns of Selection of Human Movements III: Energy Efficiency, Mechanical Advantage, and Walking Gait

    OpenAIRE

    Hagler, Stuart

    2016-01-01

    Human movements are physical processes combining the classical mechanics of the human body moving in space and the biomechanics of the muscles generating the forces acting on the body under sophisticated sensory-motor control. One way to characterize movement performance is through measures of energy efficiency that relate the mechanical energy of the body and metabolic energy expended by the muscles. We expect the practical utility of such measures to be greater when human subjects execute m...

  4. Distinct effects on diversifying selection by two mechanisms of immunity against Streptococcus pneumoniae.

    Directory of Open Access Journals (Sweden)

    Yuan Li

    Full Text Available Antigenic variation to evade host immunity has long been assumed to be a driving force of diversifying selection in pathogens. Colonization by Streptococcus pneumoniae, which is central to the organism's transmission and therefore evolution, is limited by two arms of the immune system: antibody- and T cell- mediated immunity. In particular, the effector activity of CD4(+ T(H17 cell mediated immunity has been shown to act in trans, clearing co-colonizing pneumococci that do not bear the relevant antigen. It is thus unclear whether T(H17 cell immunity allows benefit of antigenic variation and contributes to diversifying selection. Here we show that antigen-specific CD4(+ T(H17 cell immunity almost equally reduces colonization by both an antigen-positive strain and a co-colonized, antigen-negative strain in a mouse model of pneumococcal carriage, thus potentially minimizing the advantage of escape from this type of immunity. Using a proteomic screening approach, we identified a list of candidate human CD4(+ T(H17 cell antigens. Using this list and a previously published list of pneumococcal Antibody antigens, we bioinformatically assessed the signals of diversifying selection among the identified antigens compared to non-antigens. We found that Antibody antigen genes were significantly more likely to be under diversifying selection than the T(H17 cell antigen genes, which were indistinguishable from non-antigens. Within the Antibody antigens, epitopes recognized by human antibodies showed stronger evidence of diversifying selection. Taken together, the data suggest that T(H17 cell-mediated immunity, one form of T cell immunity that is important to limit carriage of antigen-positive pneumococcus, favors little diversifying selection in the targeted antigen. The results could provide new insight into pneumococcal vaccine design.

  5. XPS study on the selective wet etching mechanism of GeSbTe phase change thin films with tetramethylammonium hydroxide

    Science.gov (United States)

    Deng, Changmeng; Geng, Yongyou; Wu, Yiqun

    Phase change lithography has pretty potential applications for high density optical data storage mastering and micro/nano structure patterning because it is not restricted by optical diffraction limitation and at relatively low cost. GeSbTe, as an initially investigated material for phase change lithography, its mechanism of selective etching in inorganic or organic alkaline aqueous solutions, such as NaOH and tetramethylammonium hydroxide (TMAH), is still unknown. In this paper, XPS measurement is used to study the selective wet etching mechanism of GeSbTe phase change thin films with TMAH solution, and the results show that oxidization played an important role in the etching process. Ge, Sb and Te are oxidized into GeO2, Sb2O5 and TeO2, respectively, and then as the corresponding salts dissolved into the etchant solution. Ge-X (X is Ge, Sb or Te) bonds are first broken in the etching, then Sb-X bonds, and finally Te-Te bonds. To confirm the effect of oxidization in the etching, H2O2 as an oxidant is added into the TMAH solution, and the etching rates are increased greatly for both amorphous and crystalline states. The selective etching mechanism of Ge2Sb2Te5 phase change films is discussed by the difference of bonds breakage between the amorphous and crystalline states.

  6. Removal of hazardous organics from water using metal-organic frameworks (MOFs): plausible mechanisms for selective adsorptions.

    Science.gov (United States)

    Hasan, Zubair; Jhung, Sung Hwa

    2015-01-01

    Provision of clean water is one of the most important issues worldwide because of continuing economic development and the steady increase in the global population. However, clean water resources are decreasing everyday, because of contamination with various pollutants including organic chemicals. Pharmaceutical and personal care products, herbicides/pesticides, dyes, phenolics, and aromatics (from sources such as spilled oil) are typical organics that should be removed from water. Because of their huge porosities, designable pore structures, and facile modification, metal-organic frameworks (MOFs) are used in various adsorption, separation, storage, and delivery applications. In this review, the adsorptive purifications of contaminated water with MOFs are discussed, in order to understand possible applications of MOFs in clean water provision. More importantly, plausible adsorption or interaction mechanisms and selective adsorptions are summarized. The mechanisms of interactions such as electrostatic interaction, acid-base interaction, hydrogen bonding, π-π stacking/interaction, and hydrophobic interaction are discussed for the selective adsorption of organics over MOFs. The adsorption mechanisms will be very helpful not only for understanding adsorptions but also for applications of adsorptions in selective removal, storage, delivery and so on.

  7. Selective recovery of Pd(II) from extremely acidic solution using ion-imprinted chitosan fiber: Adsorption performance and mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Shuo [School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Wei, Wei [School of Chemical Engineering, Chonbuk National University, Jeonbuk 561-756 (Korea, Republic of); Wu, Xiaohui; Zhou, Tao [School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Mao, Juan, E-mail: monicamao45@hust.edu.cn [School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Yun, Yeoung-Sang, E-mail: ysyun@jbnu.ac.kr [School of Chemical Engineering, Chonbuk National University, Jeonbuk 561-756 (Korea, Republic of)

    2015-12-15

    Highlights: • An acid-resisting chitosan fiber was prepared by ion-imprinting technique. • Pd(II) and ECH were as template and two-step crosslinking agent, respectively. • IIF showed a good adsorption and selectivity performance on Pd(II) solutions. • Selectivity was due to the electrostatic attraction between −NH{sub 3}{sup +} and [PdCl{sub 4}]{sup 2−}. • Stable sorption/desorption performance shows a potential in further application. - Abstract: A novel, selective and acid-resisting chitosan fiber adsorbent was prepared by the ion-imprinting technique using Pd(II) and epichlorohydrin as the template and two-step crosslinking agent, respectively. The resulting ion-imprinted chitosan fibers (IIF) were used to selectively adsorb Pd(II) under extremely acidic synthetic metal solutions. The adsorption and selectivity performances of IIF including kinetics, isotherms, pH effects, and regeneration were investigated. Pd(II) rapidly adsorbed on the IIF within 100 min, achieving the adsorption equilibrium. The isotherm results showed that the maximum Pd(II) uptake on the IIF was maintained as 324.6–326.4 mg g{sup −1} in solutions containing single and multiple metals, whereas the Pd(II) uptake on non-imprinted fibers (NIF) decreased from 313.7 to 235.3 mg g{sup −1} in solution containing multiple metals. Higher selectivity coefficients values were obtained from the adsorption on the IIF, indicating a better Pd(II) selectivity. The amine group, supposedly the predominant adsorption site for Pd(II), was confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The pH value played a significant role on the mechanism of the selective adsorption in the extremely acidic conditions. Furthermore, the stabilized performance for three cycles of sorption/desorption shows a potential for further large-scale applications.

  8. Altering the interfacial activation mechanism of a lipase by solid-phase selective chemical modification.

    Science.gov (United States)

    López-Gallego, Fernando; Abian, Olga; Guisán, Jose Manuel

    2012-09-04

    This study presents a combined protein immobilization, directed mutagenesis, and site-selective chemical modification approach, which was used to create a hyperactivated semisynthetic variant of BTL2. Various alkane chains were tethered at three different positions in order to mimic the lipase interfacial activation exogenously triggered by detergents. Optimum results were obtained when a dodecane chain was introduced at position 320 by solid-phase site-selective chemical modification. The resulting semisynthetic variant showed a 2.5-fold higher activity than the wild-type nonmodified variant in aqueous conditions. Remarkably, this is the maximum hyperactivation ever observed for BTL2 in the presence of detergents such as Triton X-100. We present evidence to suggest that the endogenous dodecane chain hyperactivates the enzyme in a similar fashion as an exogenous detergent molecule. In this way, we also observe a faster irreversible enzyme inhibition and an altered detergent sensitivity profile promoted by the site-selective chemical modification. These findings are also supported by fluorescence studies, which reveal that the structural conformation changes of the semisynthetic variant are different to those of the wild type, an effect that is more pronounced in the presence of detergent. Finally, the optimal immobilized semisynthetic variant was successfully applied to the selective synthesis of oxiran-2-yl butyrate. Significantly, this biocatalyst is 12-fold more efficient than the immobilized wild-type enzyme, producing the S-enantiomer with higher enantiospecificity (ee = 92%).

  9. Neural systems for sign language production: mechanisms supporting lexical selection, phonological encoding, and articulation.

    Science.gov (United States)

    San José-Robertson, Lucila; Corina, David P; Ackerman, Debra; Guillemin, Andre; Braun, Allen R

    2004-11-01

    Overt production of ASL signs was evaluated using H(2)(15)O PET to differentiate brain systems that support sign language production at the lexical-selection and phonological-articulatory levels. Subjects were 16 right-handed, congenitally deaf native ASL signers (10 women, six men; age 20 to 29 years). Scans were performed while subjects (1) passively viewed ASL nouns, (2) repeated nouns, (3) generated verbs in response to these nouns, (4) passively viewed videotaped segments depicting transitive actions, and (5) generated a verb to describe these actions. Conjunctions between the two verb-generation tasks revealed left-lateralized activation of perisylvian, frontal, and subcortical regions commonly observed in spoken language generation tasks and implicated in processes of semantic feature binding and lexical selection. Analysis of noun repetition minus viewing condition revealed activation of distinct systems supporting phonological encoding and articulation, including bilateral activation of sensorimotor areas and association cortices in the temporal, parietal, and occipital lobes. In addition, lexical-selection and articulatory processes were associated with activation of different corticostriatal-thalamocortical circuits: articulation with activation of the motor, and lexical-selection with activation of the prefrontal circuits, respectively. The results collectively provide insight into dissociable neural systems underlying these psycholinguistic functions. In addition, activation of regions that are typically associated with the auditory system during sign production suggests that these regions may support modality-independent linguistic processes, or may indicate cross-modal plasticity within the deaf brain.

  10. Darwinian and neo-Darwinian selection mechanisms in bacteria: Effects on antibiotic resistance

    Science.gov (United States)

    Darwin’s concept of survival of the fittest is as critical when applied to bacteria as it is to animals. Bacteria live in a highly competitive environment that is similar to the macrobiological world with its selective pressures. Neo-Darwinism views genes as selfish and as the ultimate unit of nat...

  11. Structural analysis of the catalytic mechanism and stereo selectivity in Streptomyces coelicolor alditol oxidase

    NARCIS (Netherlands)

    Forneris, Federico; Heuts, Dominic P. H. M.; Delvecchio, Manuela; Rovida, Stefano; Fraaije, Marco W.; Mattevi, Andrea

    2008-01-01

    Alditol oxidase (AldO) from Streptomyces coelicolor A3(2) is a soluble monomeric flavin-dependent oxidase that performs selective oxidation of the terminal primary hydroxyl group of several alditols. Here, we report the crystal structure of the recombinant enzyme in its native state and in complex w

  12. ss-siRNAs allele selectively inhibit ataxin-3 expression: multiple mechanisms for an alternative gene silencing strategy.

    Science.gov (United States)

    Liu, Jing; Yu, Dongbo; Aiba, Yuichiro; Pendergraff, Hannah; Swayze, Eric E; Lima, Walt F; Hu, Jiaxin; Prakash, Thazha P; Corey, David R

    2013-11-01

    Single-stranded silencing RNAs (ss-siRNAs) provide an alternative approach to gene silencing. ss-siRNAs combine the simplicity and favorable biodistribution of antisense oligonucleotides with robust silencing through RNA interference (RNAi). Previous studies reported potent and allele-selective inhibition of human huntingtin expression by ss-siRNAs that target the expanded CAG repeats within the mutant allele. Mutant ataxin-3, the genetic cause of Machado-Joseph Disease, also contains an expanded CAG repeat. We demonstrate here that ss-siRNAs are allele-selective inhibitors of ataxin-3 expression and then redesign ss-siRNAs to optimize their selectivity. We find that both RNAi-related and non-RNAi-related mechanisms affect gene expression by either blocking translation or affecting alternative splicing. These results have four broad implications: (i) ss-siRNAs will not always behave similarly to analogous RNA duplexes; (ii) the sequences surrounding CAG repeats affect allele-selectivity of anti-CAG oligonucleotides; (iii) ss-siRNAs can function through multiple mechanisms and; and (iv) it is possible to use chemical modification to optimize ss-siRNA properties and improve their potential for drug discovery.

  13. Selective hydrogenolysis of glycerol to propylene glycol on Cu-ZnO composite catalysts: structural requirements and reaction mechanism.

    Science.gov (United States)

    Wang, Shuai; Zhang, Yichi; Liu, Haichao

    2010-05-03

    Cu-ZnO catalysts were prepared by homogeneous coprecipitation with varying Cu/Zn atomic ratios (0.4-2:1). The catalysts were examined in selective hydrogenolysis of glycerol to propylene glycol. Although propylene glycol selectivities remained essentially constant (over 93%) on the different Cu-ZnO catalysts, the turnover frequencies changed markedly with the Cu/Zn ratio, and reached the greatest value at the ratio of 1:1. Such activity dependence on the Cu/Zn ratio was in parallel with the change in the interaction between Cu and ZnO and in the Cu microstrain, as a consequence of the effects on the crystalline phases of hydroxycarbonate precursors for the Cu-ZnO catalysts, reflecting the structural requirements for glycerol hydrogenolysis. The hydrogenolysis mechanism was also examined and apparently involves kinetically relevant glycerol dehydrogenation to glyceraldehyde on Cu-ZnO and subsequent glyceraldehyde dehydration and hydrogenation to propylene glycol. The mechanism is consistent with the observed superior activities of the more strained Cu particles, and the higher propylene glycol selectivities obtained at higher glycerol and hydrogen concentrations. These findings provide a rationale for the design of more effective Cu-based catalysts in selective hydrogenolysis of glycerol and other biomass-derived polyols, for example, by synthesis of highly strained Cu particles strongly interacting with ZnO or other oxide supports.

  14. ERP time course of perceptual and post-perceptual mechanisms of spatial selection.

    Science.gov (United States)

    Shedden, J M; Nordgaard, C L

    2001-03-01

    Event-related potentials (ERPs) were recorded from volunteers performing a task requiring simple judgements about the spatial location of a single target that could appear with equal probability to the left or right of fixation. A robust finding in the ERP literature is a dichotomy between attentional selection for spatial and non-spatial features. Visual spatial selection is manifest as a modulation of early components (P1, N1) that reveal exogenous processes, while non-spatial selection is revealed by the presence of longer latency endogenous components (N2). We present an analysis of several conditions that require different degrees of visual analysis to confirm the location of the single target, and show that spatial selection can be manifest at early (N1) or later (N2) stages. Observers identified the location of targets that were more salient (2D line drawings with abrupt onset) or less salient (2D line drawings without abrupt onset or 3D objects embedded in random-dot stereograms). We examined differences in amplitude, latency, and topography of early ERP components (P1, N1, P2, N2), and compared responses measured over the left and right hemispheres in response to left and right targets. The results support the hypothesis that the processes involved in spatial selection can be manifest at early or late stages, dependent on the quality of the incoming data. Moreover, the iterative process by which the percept is established benefits from a change in the visual input that is specific to the target.

  15. 不确定性行为选择情绪机制%Emotion Mechanism of Uncertain Behavior Selection

    Institute of Scientific and Technical Information of China (English)

    张国锋; 李祖枢

    2011-01-01

    Through thorough analysis of the emotion-related theories in psychology and microeconomics, the attributes of emotion were clarified whose essence is energy, function is driving behavior, sort reflects the sort of survival resources,and the emotional essence of motivation, (inner) drive and utility(subjective value) was discovered.According to the common law abided by these kinds of sense,and consulting Prospect Theory,emotion schema function was built up to obtain the principle of functional relationship between emotion and living resource Based on these work, adopting optimistic selection principle, emotion-driven behavior selection mechanism was established.In order to validate the mechanism,emotion-driven competitive, cooperative behavior selection mechanism and fight behavior selection mechanism were constructed and simulations of them on platform Swarm were achieved.The simulation results confirm the proposed mechanism.Thus, the theory base of autonomous behavior selection achievement under uncertain conditions is provided.%通过对心理学、微观经济学有关情绪理论的深入剖析,阐明了情绪所具有的能量本质属性、行为驱动的功能作用属性、资源获取的内容属性,实现了对动机、(内)驱力、效用(主观价值)等概念的情绪本质的揭示.根据这4种感觉所遵守的共同函数规律,借鉴前景理论,建立情绪图式函数,获得了情绪与资源之间的函数关系原理.以上述结果为基础,采用情绪理性原则,建立了情绪驱动的行为选择机制.为验证该机制,建立了情绪驱动的竞争型、合作型行为选择机制和战斗行为选择机制,并在仿真平台Swarm上完成了仿真实验.实验结果证明,该机制是合理和有效的,为解决不确定环境条件的自主选择行为问题奠定了一定的理论基础.

  16. Energy transfer mechanisms in photobiological reactions. Final report, 1 April 1960--31 March 1979. [Photodynamic processes in selected biomolecules

    Energy Technology Data Exchange (ETDEWEB)

    Spikes, J.D.

    1979-03-31

    This project was concerned primarily with studies of the mechanisms of the sensitized photooxidation of selected biomolecules using a variety of phtosensitizers. Such reactions are often termed photodynamic processes. In particular we have carried out steady-state kinetic studies, flash photolysis and spectral studies, and product formation studies of the sensitized photooxidation of the five susceptible amino acids (cycteine, histidine, methonine, tryptophan, and tyrosine) and their derivatives, as well as purines and pyrimidines. A number of studies were also carried out on the mechanisms of the photodynamic inactivation of enzymes (trypsin, ribonuclease, lysozyme). Mechanism of photosensitization were studied using a variety of sensitizers including flavins, porphyrins, and a number of synthetic dyes (substituted fluoresceins, acridines, thyazines).

  17. Discovery of Selective Small Molecule ROMK Inhibitors as Potential New Mechanism Diuretics

    Science.gov (United States)

    2012-01-01

    The renal outer medullary potassium channel (ROMK or Kir1.1) is a putative drug target for a novel class of diuretics that could be used for the treatment of hypertension and edematous states such as heart failure. An internal high-throughput screening campaign identified 1,4-bis(4-nitrophenethyl)piperazine (5) as a potent ROMK inhibitor. It is worth noting that this compound was identified as a minor impurity in a screening hit that was responsible for all of the initially observed ROMK activity. Structure–activity studies resulted in analogues with improved rat pharmacokinetic properties and selectivity over the hERG channel, providing tool compounds that can be used for in vivo pharmacological assessment. The featured ROMK inhibitors were also selective against other members of the inward rectifier family of potassium channels. PMID:24900480

  18. Correlated responses to clonal selection in populations of Daphnia pulicaria: mechanisms of genetic correlation and the creative power of sex.

    Science.gov (United States)

    Dudycha, Jeffry L; Snoke-Smith, Margaret; Alía, Ricardo

    2013-02-01

    Genetic correlations among traits alter evolutionary trajectories due to indirect selection. Pleiotropy, chance linkage, and selection can all lead to genetic correlations, but have different consequences for phenotypic evolution. We sought to assess the mechanisms contributing to correlations with size at maturity in the cyclic parthenogen Daphnia pulicaria. We selected on size in each of four populations that differ in the frequency of sex, and evaluated correlated responses in a life table. Size at advanced adulthood, reproductive output, and adult growth rate clearly showed greater responses in high-sex populations, with a similar pattern in neonate size and r. This pattern is expected only when trait correlations are favored by selection and the frequency of sex favors the creation and demographic expansion of highly fit clones. Juvenile growth and age at maturity did not diverge consistently. The inter-clutch interval appeared to respond more strongly in low-sex populations, but this was not statistically significant. Our data support the hypothesis that correlated selection is the strongest driver of genetic correlations, and suggest that in organisms with both sexual and asexual reproduction, adaptation can be enhanced by recombination.

  19. Intensity of production organisation versus level of mechanization in selected farms in the Lublin region

    Directory of Open Access Journals (Sweden)

    Edmund Lorencowicz

    2009-01-01

    Full Text Available 167 farms were analysed in period 1992-2001. The relations between intensity of production organisation and factors characterising the level of mechanization were established. It was proved that the changes of intensiveness were positively correlated with machines value and energetic outfitting of farms.

  20. Some selected research item of the micro mechanics department at MESA

    NARCIS (Netherlands)

    Elwenspoek, Michael Curt

    1994-01-01

    New developments within the micro mechanics department at MESA are presented. The developments are: (1) a description will be provided of dry etch processes-reactive ion etching, RIE-of silicon in a mixture of SF6, 02, and CHF3. (2) The design, fabrication and performance of new electrostatic

  1. Colour variation in cichlid fish : Developmental mechanisms, selective pressures and evolutionary consequences

    NARCIS (Netherlands)

    Maan, Martine E.; Sefc, Kristina M.

    2013-01-01

    Cichlid fishes constitute one of the most species-rich families of vertebrates. In addition to complex social behaviour and morphological versatility, they are characterised by extensive diversity in colouration, both within and between species. Here, we review the cellular and molecular mechanisms

  2. Method for predicting selective uprooting by mechanical weeders from plant anchorage forces

    NARCIS (Netherlands)

    Kurstjens, D.A.G.; Kropff, M.J.; Perdok, U.D.

    2004-01-01

    Reliable mechanical weed control requires knowledge of the achievable levels of weed control and crop damage when using certain implements in specific conditions. Quantitative methods that use weed, crop, soil, and cultivator characteristics to predict weed control and crop damage need to be develop

  3. Colour variation in cichlid fish : Developmental mechanisms, selective pressures and evolutionary consequences

    NARCIS (Netherlands)

    Maan, Martine E.; Sefc, Kristina M.

    2013-01-01

    Cichlid fishes constitute one of the most species-rich families of vertebrates. In addition to complex social behaviour and morphological versatility, they are characterised by extensive diversity in colouration, both within and between species. Here, we review the cellular and molecular mechanisms

  4. Health-selection mechanisms in the pathway towards a disability pension.

    Science.gov (United States)

    Reinholdt, Sofia; Upmark, Marianne; Alexanderson, Kristina

    2010-01-01

    Studies emphasizing the disability pension (DP) process are rare. To identify similarities and differences in work and health between persons who, prior to DP changed jobs due to health-reasons (health-selectors) to other disability pensioners. a retrospective cohort study was performed on a random sample of all individuals in three counties of Sweden who, in 1998, were under the age of 65 and had been granted DP. A questionnaire was administered in 2000 (n=917, response rate 52%). The responses and register data on sickness absence in 1990-1998 and DP diagnoses were analysed. The health-selection group had lower self-perceived health; more partial sick-leave days during the eight years preceding DP, and DP diagnoses were more often musculoskeletal and psychiatric disorders, than the other disability pensioners. The groups did not differ regarding occupational affiliation before the last job. For subjects in the health-selection group, the job change did more often not involve a change of employer, and more had switched to jobs entailing less physical strain, particularly customer service work. Work history did not differ between the groups regarding the average level of physical work demands during the work career, however, disparities were found in the distribution of demands. The findings pinpoint the importance of studying disability pensioning as a process over time in order to identify and elucidate how exposure and selection interact and contribute to early exclusion from the labour market.

  5. Controllable synthesis of VSB-5 microspheres and microrods: growth mechanism and selective hydrogenation catalysis.

    Science.gov (United States)

    Liu, Shu-Juan; Cheng, Hai-Yang; Zhao, Feng-Yu; Gong, Jun-Yan; Yu, Shu-Hong

    2008-01-01

    Nanoporous VSB-5 nickel phosphate molecular sieves with relatively well controllable sizes and morphology of microspheres assembled from nanorods were synthesized at 140 degrees C over a short time in the presence of hexamethylenetetramine (HMT) by a facile hydrothermal method. The pH value, reaction time, and ratio of HMT to NaHPO2.H2O crucially influence the morphology and quality of the final products. By adjusting the pH value of the initial reaction solution, the morphology changes from disperse rods to microspheres assembled from rods and finally to a large quantity of fibers, and the diameters of the VSB-5 rods can be varied. The catalytic activity of VSB-5 in selective hydrogenation of several unsaturated organic compounds was tested. Nickel(II) in VSB-5 can selectively catalyze hydrogenation of C=C in trans-cinnamaldehyde and 3-methylcrotonaldehyde. In addition, since nitrobenzene (NB) and 2-chloronitrobenzene could be reduced to aniline (AN) and 2-chloroaniline with high selectivity, VSB-5 could have potential applications in synthesizing dyes, agrochemicals, and pharmaceuticals.

  6. Doublet III limiter performance and implications for mechanical design and material selection for future limiters

    Energy Technology Data Exchange (ETDEWEB)

    Sabado, M.M.; Marcus, F.B.; Trester, P.W.; Wesley, J.C.

    1979-10-01

    The plasma limiter system for Doublet III is described. Initially, high-Z materials, Ta-10W for the primary limiter and Mo for the backup limiters, were selected as the most attractive metallic candidates from the standpoint of thermal and structural properties. For the purpose of evaluating the effect of material Z on plasma performance, the nonmagnetic, Ni-base alloy Inconel X-750 was selected for a medium-Z limiter material. Graphite, a low-Z material, will likely be the next limiter material for evaluation. Design and material selection criteria for the different Z ranges are presented. The performance of the high-Z limiters in Doublet III is reviewed for an operation period that included approximately 5000 plasma shots. Changes in surface appearance and metallurgical changes are characterized. Discussion is presented on how and to what extent the high-Z elements affected the performance of the plasma based on theory and measurements in Doublet III. The fabrication processes for the Inconel X-750 limiters are summarized, and, last, observations on early performance of the Inconel limiters are described. (MOW)

  7. Insight into the labeling mechanism of acceleration selective arterial spin labeling

    DEFF Research Database (Denmark)

    Schmid, Sophie; Petersen, Esben T; Van Osch, Matthias J P

    2016-01-01

    OBJECTIVES: Acceleration selective arterial spin labeling (AccASL) is a spatially non-selective labeling technique, used in traditional ASL methods, which labels spins based on their flow acceleration rather than spatial localization. The exact origin of the AccASL signal within the vasculature...... of the control and label conditions in both the acceleration and velocity selective module. The cut-off acceleration (0.59 m/s(2)) or velocity (2 cm/s) was kept constant in one module, while it was varied over a large range in the other module. With the right subtractions this resulted in AccASL, VS......-ASL, combined AccASL and VS-ASL signal, and signal from one module with crushing from the other. RESULTS: The label created with AccASL has an overlap of approximately 50% in the vascular region with VS-ASL, but also originates from smaller vessels closer to the capillaries. CONCLUSION: AccASL is able to label...

  8. Comparative study of mechanical properties of 316L stainless steel between traditional production methods and selective laser melting

    Science.gov (United States)

    Lackey, Alton Dale

    Additive manufacturing, also known as 3D printing, is a technology which has recently seen expanding use, as well as expansion of the materials and methods able to be used. This thesis looks at the comparison of mechanical properties of 316L stainless steel manufactured by both traditional methods and selective laser melting found by tensile testing. The traditional method used here involved cold rolled 316L steel being machined to the desired part geometry. Selective laser melting used additive manufacturing to produce the parts from powdered 316L stainless steel, doing so in two different build orientations, flat and on edge with regards to the build plate. Solid test specimens, as well as specimens containing a circular stress concentration in the center of the parts, were manufactured and tensile tested. The tensile tests of the specimens were used to find the mechanical properties of the material; including yield strength, ultimate tensile strength (UTS), and Young's modulus of elasticity; where statistical analyses were performed to determine if the different manufacturing processes caused significant differences in the mechanical properties of the material. These analysis consisting of f-tests, to test for variance, and t-test, testing for significant difference of means. Through this study it was found that there were statistically significant differences existing between the mechanical properties of selective laser melting, and its orientations, and cold roll forming of production of parts. Even with a statistical difference, it was found that the results were reasonably close between flat oriented SLM parts and purchased parts. So it can be concluded that, with regards to strength, SLM methods produce parts similar to traditional production methods.

  9. Models for selecting GMA Welding Parameters for Improving Mechanical Properties of Weld Joints

    Science.gov (United States)

    Srinivasa Rao, P.; Ramachandran, Pragash; Jebaraj, S.

    2016-02-01

    During the process of Gas Metal Arc (GMAW) welding, the weld joints mechanical properties are influenced by the welding parameters such as welding current and arc voltage. These parameters directly will influence the quality of the weld in terms of mechanical properties. Even small variation in any of the cited parameters may have an important effect on depth of penetration and on joint strength. In this study, S45C Constructional Steel is taken as the base metal to be tested using the parameters wire feed rate, voltage and type of shielding gas. Physical properties considered in the present study are tensile strength and hardness. The testing of weld specimen is carried out as per ASTM Standards. Mathematical models to predict the tensile strength and depth of penetration of weld joint have been developed by regression analysis using the experimental results.

  10. [Effects of SERMs on bone health. Mechanisms of bone mass control by selective estrogen receptor modulator].

    Science.gov (United States)

    Imai, Yuuki; Kato, Shigeaki

    2010-03-01

    The bone mass, which is controlled by the balances between bone formation and bone resorption can be reduced by estrogen deficiency in post-menopausal osteoporosis. Reduced bone mass can be recovered by hormone replacement therapy (HRT) , however, HRT has various side effects. Although SERMs can rescue the bone mass with less side effect compared to HRT, the precise mechanisms of this effect is still elusive. From the results of the analyses for osteoclast specific estrogen receptor (ER) alphaknockout mice and the genome wide approach of ERalphabinding site, estrogen and SERMs can, at least in part, protect the bone mass by inducing the expression of Fas ligand and controling the life span of osteoclasts. More precise molecular mechanisms of the effect of SERM, especially in tissue/cell type specificity, may help to investigate new SERM, which is more specific and effective to treat post-menopausal osteoporosis.

  11. Logical Framework,Path Selection and Mechanism Design for Cultivation of New Type Professional Farmers

    Institute of Scientific and Technical Information of China (English)

    Guangying; LIU; Jianfeng; ZHANG; Yingliang; ZHANG; Qinghua; HUANG

    2013-01-01

    New type professional farmers are farmers who possess certain resources and capitals,have certain extent of spirit of entrepreneurship,and are fully capable of obtaining and allocating resources related to agricultural production and management,and engaged in agricultural production and management for obtaining average profit.Cultivation of new type professional farmers should be promoted in the process and at the background of"coordinated development of industrialization,informationization,urbanization and agricultural modernization".It should establish a proper cultivation subject system consisting of government,enterprises,rural communities and nonprofit organizations.Relying on multiple motive forces,efforts should be concentrated on cultivating those farmers with enterprising,highly innovative and learning ability,to guide traditional farmers to change into learning,enterprising and innovative ones.In addition,cultivation of new type professional farmers must rely on farmer education and training,modern agricultural development,increase in agricultural comparative advantage,innovation of rural management system and mechanism,multiple types of agricultural operation on a fairly large scale,as well as construction and regulation of new rural communities.Finally,it is recommended to provide system guarantee from long-term input mechanism of new type professional farmer education and training,incentive and restrictive mechanism of new type professional farmer cultivation,and construction of favorable environment for agricultural entrepreneurship.

  12. Replicative Homeostasis: A fundamental mechanism mediating selective viral replication and escape mutation

    Directory of Open Access Journals (Sweden)

    Sallie Richard

    2005-02-01

    Full Text Available Abstract Hepatitis C (HCV, hepatitis B (HBV, the human immunodeficiency viruses (HIV, and other viruses that replicate via RNA intermediaries, cause an enormous burden of disease and premature death worldwide. These viruses circulate within infected hosts as vast populations of closely related, but genetically diverse, molecules known as "quasispecies". The mechanism(s by which this extreme genetic and antigenic diversity is stably maintained are unclear, but are fundamental to understanding viral persistence and pathobiology. The persistence of HCV, an RNA virus, is especially problematic and HCV stability, maintained despite rapid genomic mutation, is highly paradoxical. This paper presents the hypothesis, and evidence, that viruses capable of persistent infection autoregulate replication and the likely mechanism mediating autoregulation – Replicative Homeostasis – is described. Replicative homeostasis causes formation of stable, but highly reactive, equilibria that drive quasispecies expansion and generates escape mutation. Replicative homeostasis explains both viral kinetics and the enigma of RNA quasispecies stability and provides a rational, mechanistic basis for all observed viral behaviours and host responses. More importantly, this paradigm has specific therapeutic implication and defines, precisely, new approaches to antiviral therapy. Replicative homeostasis may also modulate cellular gene expression.

  13. Dual selection mechanisms drive efficient single-gene reverse genetics for rotavirus

    OpenAIRE

    Trask, Shane D.; Taraporewala, Zenobia F.; Boehme, Karl W.; Dermody, Terence S.; Patton, John T.

    2010-01-01

    Current methods for engineering the segmented double-stranded RNA genome of rotavirus (RV) are limited by inefficient recovery of the recombinant virus. In an effort to expand the utility of RV reverse genetics, we developed a method to recover recombinant viruses in which independent selection strategies are used to engineer single-gene replacements. We coupled a mutant SA11 RV encoding a temperature-sensitive (ts) defect in the NSP2 protein with RNAi-mediated degradation of NSP2 mRNAs to is...

  14. Feeding, prey selection and prey encounter mechanisms in the heterotrophic dinoflagellate Noctiluca scintillans

    DEFF Research Database (Denmark)

    Kiørboe, Thomas; Titelman, J.

    1998-01-01

    by modeling N.scintillans both as a spherical and as a cylindrical collector. The latter model assumes that prey particles are collected on the string of mucus that may form at the tip of the tentacle. Feeding, growth and prey selection experiments all demonstrated that diatoms are cleared at substantially...... and that the high ascent velocity accounts for encounters with prey. However, the flow field around the cell-mucus complex is too complicated to be described accurately by simple geometric models. Fluid shear (0.7-1.8 s(-1)) had a negative impact on feeding rates, which were much less than predicted by models...

  15. In Pursuit of Teacher Quality in Diversity: A Study of the Selection Mechanisms of New Secondary Teacher Education Programmes in Taiwan

    Science.gov (United States)

    Wang, Hsiou-Huai; Fwu, Bih-Jen

    2007-01-01

    As the definition of teacher quality changes with time, the selection mechanism of students into teacher education programmes may also change accordingly. In Taiwan, before the 1994 teacher education reform, selection of pre-service students was based solely on academic achievement. Afterwards, the selection was delegated to individual teacher…

  16. A Round Robin study for Selective Laser Sintering of polyamide 12: Microstructural origin of the mechanical properties

    Science.gov (United States)

    Stichel, Thomas; Frick, Thomas; Laumer, Tobias; Tenner, Felix; Hausotte, Tino; Merklein, Marion; Schmidt, Michael

    2017-03-01

    The mechanical and microstructural investigation of polymer parts (polyamide 12) fabricated by Selective Laser Sintering as part of a Round Robin initiative is presented. The paper focuses on the microstructural analysis of the Round Robin samples and their evaluation regarding their effect on mechanical properties with respect to each other. Therefore optical microscopy on microtomed samples, X-ray computed tomography and Differential Scanning Calorimetry is used to determine the morphology of residual particle cores and of internal pores. The mechanical tensile testing revealed a high variability of the ductility of the samples among the used machines and a distinctive anisotropic mechanical response. Especially the quite brittle characteristic along the building direction has shown to be still a crucial challenge for the process. However, one machine delivered samples with outstanding ductility with total elongation values of about 21% along the building direction and of about 32% planar to the layer. This result was back traced to a distinctive pore and residual particle morphology which is characterized by low pore concentration, the absence of coplanar pore or residual particle arrangements and the highest degree of particle melting measured. Furthermore, the analysis depicts that both features, pores and residual particles, contribute to the mechanical properties significantly and that they are not necessarily linked since they can vary independently in a certain range depending on the machine configuration.

  17. Angiogenic Signalling Pathways Altered in Gliomas: Selection Mechanisms for More Aggressive Neoplastic Subpopulations with Invasive Phenotype

    Directory of Open Access Journals (Sweden)

    Susana Bulnes

    2012-01-01

    Full Text Available The angiogenesis process is a key event for glioma survival, malignancy and growth. The start of angiogenesis is mediated by a cascade of intratumoural events: alteration of the microvasculature network; a hypoxic microenvironment; adaptation of neoplastic cells and synthesis of pro-angiogenic factors. Due to a chaotic blood flow, a consequence of an aberrant microvasculature, tissue hypoxia phenomena are induced. Hypoxia inducible factor 1 is a major regulator in glioma invasiveness and angiogenesis. Clones of neoplastic cells with stem cell characteristics are selected by HIF-1. These cells, called “glioma stem cells” induce the synthesis of vascular endothelial growth factor. This factor is a pivotal mediator of angiogenesis. To elucidate the role of these angiogenic mediators during glioma growth, we have used a rat endogenous glioma model. Gliomas induced by prenatal ENU administration allowed us to study angiogenic events from early to advanced tumour stages. Events such as microvascular aberrations, hypoxia, GSC selection and VEGF synthesis may be studied in depth. Our data showed that for the treatment of gliomas, developing anti-angiogenic therapies could be aimed at GSCs, HIF-1 or VEGF. The ENU-glioma model can be considered to be a useful option to check novel designs of these treatment strategies.

  18. Quantum Mechanics and First-Principles Molecular Dynamics Selection of Polymer Sensing Materials

    Science.gov (United States)

    Blanco, Mario; Shevade, Abhijit V.; Ryan, Margaret A.

    We present two first-principles methods, density functional theory (DFT) and a molecular dynamics (MD) computer simulation protocol, as computational means for the selection of polymer sensing materials. The DFT methods can yield binding energies of polymer moieties to specific vapor bound compounds, quantities that were found useful in materials selection for sensing of organic and inorganic compounds for designing sensors for the electronic nose (ENose) that flew on the International Space Station (ISS) in 2008-2009. Similarly, we present an MD protocol that offers high consistency in the estimation of Hildebrand and Hansen solubility parameters (HSP) for vapor bound compounds and amorphous polymers. HSP are useful for fitting measured polymer sensor responses with physically rooted analytical models. We apply the method to the JPL electronic nose (ENose), an array of sensors with conducting leads connected through thin film polymers loaded with carbon black. Detection relies on a change in electric resistivity of the polymer film as function of the amount of swelling caused by the presence of the analyte chemical compound. The amount of swelling depends upon the chemical composition of the polymer and the analyte molecule. The pattern is unique and it unambiguously identifies the compound. Experimentally determined changes in relative resistivity of fifteen polymer sensor materials upon exposure to ten vapors were modeled with the first-principles HSP model.

  19. Angiogenic Signalling Pathways Altered in Gliomas: Selection Mechanisms for More Aggressive Neoplastic Subpopulations with Invasive Phenotype

    Science.gov (United States)

    Bulnes, Susana; Bengoetxea, Harkaitz; Ortuzar, Naiara; Argandoña, Enrike G.; Garcia-Blanco, Álvaro; Rico-Barrio, Irantzu; Lafuente, José V.

    2012-01-01

    The angiogenesis process is a key event for glioma survival, malignancy and growth. The start of angiogenesis is mediated by a cascade of intratumoural events: alteration of the microvasculature network; a hypoxic microenvironment; adaptation of neoplastic cells and synthesis of pro-angiogenic factors. Due to a chaotic blood flow, a consequence of an aberrant microvasculature, tissue hypoxia phenomena are induced. Hypoxia inducible factor 1 is a major regulator in glioma invasiveness and angiogenesis. Clones of neoplastic cells with stem cell characteristics are selected by HIF-1. These cells, called “glioma stem cells” induce the synthesis of vascular endothelial growth factor. This factor is a pivotal mediator of angiogenesis. To elucidate the role of these angiogenic mediators during glioma growth, we have used a rat endogenous glioma model. Gliomas induced by prenatal ENU administration allowed us to study angiogenic events from early to advanced tumour stages. Events such as microvascular aberrations, hypoxia, GSC selection and VEGF synthesis may be studied in depth. Our data showed that for the treatment of gliomas, developing anti-angiogenic therapies could be aimed at GSCs, HIF-1 or VEGF. The ENU-glioma model can be considered to be a useful option to check novel designs of these treatment strategies. PMID:22852079

  20. Site-selective sulfurization of bromide-capped palladium nanocubes by polysulfide and the underlying mechanism

    Science.gov (United States)

    Lu, Ping; Lu, Ning; Wang, Jinguo; Kim, Moon J.; Xia, Younan

    2014-01-01

    This article describes site-selective sulfurization of Pd nanocubes capped by a monolayer of chemisorbed Br- ions. High-resolution transmission electron microscopy and high-angle annular dark-field scanning TEM observations showed that PdS was not formed until a certain quantity of polysulfide ({{S}}_{x}^{2-}) ions had been introduced (300 μl, or 18.8 ppm in the final reaction solution). Spot energy dispersive x-ray spectroscopy and x-ray photoelectron spectroscopy analyses confirmed that the surface-chemisorbed Br- ions were completely substituted by {{S}}_{x}^{2-} ions before the initiation of the sulfurization reaction. In the presence of sufficient {{S}}_{x}^{2-} ions (>300 μl or >18.8 ppm), PdS phase was selectively developed from the highly active corners, which then moved to the edges and finally towards the center until the entire nanocube was converted into PdS. The resultant PdS was found to be amorphous by electron microscopy and powder x-ray diffraction measurements. The amorphous structure of PdS facilitated the penetration and diffusion of {{S}}_{x}^{2-} species and thus acceleration of the reaction kinetics. As a result, the sulfurization of 13 nm Pd nanocubes was completed within a few minutes after the addition of adequate Na2Sx, leading to a much more severe poisoning effect, compared with other noble metals such as Ag, by sulfur.

  1. Ubiquitin dynamics in complexes reveal molecular recognition mechanisms beyond induced fit and conformational selection.

    Directory of Open Access Journals (Sweden)

    Jan H Peters

    Full Text Available Protein-protein interactions play an important role in all biological processes. However, the principles underlying these interactions are only beginning to be understood. Ubiquitin is a small signalling protein that is covalently attached to different proteins to mark them for degradation, regulate transport and other functions. As such, it interacts with and is recognised by a multitude of other proteins. We have conducted molecular dynamics simulations of ubiquitin in complex with 11 different binding partners on a microsecond timescale and compared them with ensembles of unbound ubiquitin to investigate the principles of their interaction and determine the influence of complex formation on the dynamic properties of this protein. Along the main mode of fluctuation of ubiquitin, binding in most cases reduces the conformational space available to ubiquitin to a subspace of that covered by unbound ubiquitin. This behaviour can be well explained using the model of conformational selection. For lower amplitude collective modes, a spectrum of zero to almost complete coverage of bound by unbound ensembles was observed. The significant differences between bound and unbound structures are exclusively situated at the binding interface. Overall, the findings correspond neither to a complete conformational selection nor induced fit scenario. Instead, we introduce a model of conformational restriction, extension and shift, which describes the full range of observed effects.

  2. Mechanisms of in vivo binding site selection of the hematopoietic master transcription factor PU.1.

    Science.gov (United States)

    Pham, Thu-Hang; Minderjahn, Julia; Schmidl, Christian; Hoffmeister, Helen; Schmidhofer, Sandra; Chen, Wei; Längst, Gernot; Benner, Christopher; Rehli, Michael

    2013-07-01

    The transcription factor PU.1 is crucial for the development of many hematopoietic lineages and its binding patterns significantly change during differentiation processes. However, the 'rules' for binding or not-binding of potential binding sites are only partially understood. To unveil basic characteristics of PU.1 binding site selection in different cell types, we studied the binding properties of PU.1 during human macrophage differentiation. Using in vivo and in vitro binding assays, as well as computational prediction, we show that PU.1 selects its binding sites primarily based on sequence affinity, which results in the frequent autonomous binding of high affinity sites in DNase I inaccessible regions (25-45% of all occupied sites). Increasing PU.1 concentrations and the availability of cooperative transcription factor interactions during lineage differentiation both decrease affinity thresholds for in vivo binding and fine-tune cell type-specific PU.1 binding, which seems to be largely independent of DNA methylation. Occupied sites were predominantly detected in active chromatin domains, which are characterized by higher densities of PU.1 recognition sites and neighboring motifs for cooperative transcription factors. Our study supports a model of PU.1 binding control that involves motif-binding affinity, PU.1 concentration, cooperativeness with neighboring transcription factor sites and chromatin domain accessibility, which likely applies to all PU.1 expressing cells.

  3. Potentiometric response and mechanism of anionic recognition of heterocalixarene-based ion selective electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Shishkanova, T.V. [Department of Analytical Chemistry, Institute of Chemical Technology, Technicka 5, 166 28 Prague 6 (Czech Republic)]. E-mail: tatiana.shishkanova@vscht.cz; Sykora, D. [Department of Analytical Chemistry, Institute of Chemical Technology, Technicka 5, 166 28 Prague 6 (Czech Republic); Sessler, J.L. [Department of Chemistry and Biochemistry, Institute for Cellular and Molecular Biology, University of Texas, Austin, TX 78712-0615 (United States); Kral, V. [Department of Analytical Chemistry, Institute of Chemical Technology, Technicka 5, 166 28 Prague 6 (Czech Republic)

    2007-03-28

    The ion selective electrode (ISE)-based potentiometric approach is shown to be an effective means of characterizing the anion recognition sites in the molecular receptor calix[2]pyridino[2]pyrrole (CPP). In particular, potentiometric pH-measurements involving the use of experimental PVC-membranes based on CPP revealed the existence of both mono- and diprotonated forms of the receptor under readily accessible conditions. Based on these analyses, apparent surface protonation constants for this heterocalixarene were found to lie between 8.5-8.9 (pK {sub B1}) and 3.3-3.8 (pK {sub B2}). CPP was found to interact with targeted anionic analytes based on both coulombic and hydrogen bond interactions, as inferred from varying the kinds of ionic sites present within the membrane phase. Potentiometric selectivity studies revealed that CPP preferred 'Y-shaped' anions (e.g. acetate, lactate, benzoate) over spherical anions (e.g. fluoride and chloride), fluoride over chloride within the set of spherical anions, and the ortho-isomer over the corresponding meta- and para-isomers in the case of hydroxybenzoate (salicylate and congeners). In the context of this study, the advantages of potentiometric determinations of acetylsalicylic acid using optimized PVC-membranes based on CPP relative to more conventional PVC-membrane ISEs based on traditional anion exchanger were also demonstrated.

  4. Comparison of high-intensity sound and mechanical vibration for cleaning porous titanium cylinders fabricated using selective laser melting.

    Science.gov (United States)

    Seiffert, Gary; Hopkins, Carl; Sutcliffe, Chris

    2017-01-01

    Orthopedic components, such as the acetabular cup in total hip joint replacement, can be fabricated using porous metals, such as titanium, and a number of processes, such as selective laser melting. The issue of how to effectively remove loose powder from the pores (residual powder) of such components has not been addressed in the literature. In this work, we investigated the feasibility of two processes, acoustic cleaning using high-intensity sound inside acoustic horns and mechanical vibration, to remove residual titanium powder from selective laser melting-fabricated cylinders. With acoustic cleaning, the amount of residual powder removed was not influenced by either the fundamental frequency of the horn used (75 vs. 230 Hz) or, for a given horn, the number of soundings (between 1 and 20). With mechanical vibration, the amount of residual powder removed was not influenced by the application time (10 vs. 20 s). Acoustic cleaning was found to be more reliable and effective in removal of residual powder than cleaning with mechanical vibration. It is concluded that acoustic cleaning using high-intensity sound has significant potential for use in the final preparation stages of porous metal orthopedic components. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 117-123, 2017.

  5. Mechanics and molecular filtration performance of graphyne nanoweb membranes for selective water purification

    Science.gov (United States)

    Lin, Shangchao; Buehler, Markus J.

    2013-11-01

    Two-dimensional carbon materials such as the 2D nanoweb-like graphyne membrane are promising as molecular sieves for energy and environmental applications. Based on the application of water purification - the removal of contaminants from wastewater and seawater - here we use molecular dynamics (MD) simulations to investigate the interplay between mechanical forces, filtration mechanisms, and overall performance for graphyne membranes with different pore sizes. We carry out biaxial tensile tests and verify the superior mechanical robustness and tolerance of graphyne membranes against possible deformations from the membrane installation process. A possible ultimate stress in excess of 15 GPa and an ultimate strain of 1.2-2.7% are determined. We also demonstrate their excellent filtration performance with barrier-free water permeation and perfect rejection of the representative contaminants considered here, including divalent heavy metal salts (copper sulfate), hydrophobic organic chemicals (benzene and carbon tetrachloride), and inorganic monovalent salts (sodium chloride). We find that graphtriyne, with an effective pore diameter of 3.8 Å, exhibits an optimal purification performance, because the contaminant rejection rate is more sensitive to pore size than water permeability. In addition, we find that the hydrophobic graphyne membranes exhibit higher rejection rates for hydrophilic contaminants compared to the hydrophobic ones. This size exclusion effect is a result of the larger hydrated radii of hydrophilic species due to stronger interactions between them and water molecules. Finally, we find that the maximum deformation of graphtriyne at the ultimate strain before material failure has only a minor impact on its filtration performance. One of the advantages of using graphyne for water purification is that no chemical functionalization or defects need to be introduced, which maintains the structural integrity of the membrane, and possibly, the long-term device

  6. Biochemical mechanism of Caffeic Acid Phenylethyl Ester (CAPE) selective toxicity towards melanoma cell lines

    OpenAIRE

    Kudugunti, Shashi K.; Vad, Nikhil M.; Whiteside, Amanda J.; Naik, Bhakti U.; Yusuf, Mohd. A.; Srivenugopal, Kalkunte S.; Moridani, Majid Y.

    2010-01-01

    In the current work, we investigated the in-vitro biochemical mechanism of caffeic acid phenylethyl ester (CAPE) toxicity and eight hydroxycinnamic/caffeic acid derivatives in-vitro, using tyrosinase enzyme as a molecular target in human SK-MEL-28 melanoma cells. Enzymatic reaction models using tyrosinase/O2 and HRP/H2O2 were used to delineate the role of one- and two-electron oxidation. Ascorbic acid (AA), NADH and GSH depletion were used as markers of quinone formation and oxidative stress ...

  7. Understanding the Photoluminescence Mechanism of Nitrogen-Doped Carbon Dots by Selective Interaction with Copper Ions.

    Science.gov (United States)

    Ganiga, Manjunatha; Cyriac, Jobin

    2016-08-04

    Doped fluorescent carbon dots (CDs) have drawn widespread attention because of their diverse applications and attractive properties. The present report focusses on the origin of photoluminescence in nitrogen-doped CDs (NCDs), which is unraveled by the interaction with Cu(2+) ions. Detailed spectroscopic and microscopic studies reveal that the broad steady-state photoluminescence emission of the NCDs originates from the direct recombination of excitons (high energy) and the involvement of defect states (low energy). In addition, highly selective detection of Cu(2+) is achieved, with a detection limit of 10 μm and a dynamic range of 10 μm-0.4 mm. The feasibility of the present sensor for the detection of Cu(2+) in real water samples is also presented. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Selective modulation of cellular voltage dependent calcium channels by hyperbaric pressure - a suggested HPNS partial mechanism

    Directory of Open Access Journals (Sweden)

    Ben eAviner

    2014-05-01

    Full Text Available Professional deep sea divers experience motor and cognitive impairment, known as High Pressure Neurological Syndrome (HPNS, when exposed to pressures of 100 msw (1.1MPa and above, considered to be the result of synaptic transmission alteration. Previous studies have indicated modulation of presynaptic Ca2+ currents at high pressure. We directly measured for the first time pressure effects on the currents of voltage dependent Ca2+ channels (VDCCs expressed in Xenopus oocytes. Pressure selectivity augmented the current in CaV1.2 and depressed it in CaV3.2 channels. Pressure application also affected the channels' kinetics, such as ƮRise, ƮDecay. Pressure modulation of VDCCs seems to play an important role in generation of HPNS signs and symptoms.

  9. A dedicated neural mechanism for vowel selection: a case of relative vowel deficit sparing the number lexicon.

    Science.gov (United States)

    Semenza, Carlo; Bencini, Giulia M L; Bertella, Laura; Mori, Ileana; Pignatti, Riccardo; Ceriani, Francesca; Cherrick, Danielle; Caldognetto, Emanuela Magno

    2007-01-28

    We report the case of an Italian speaker (GBC), with classical Wernicke's aphasia following a vascular lesion in the posterior middle temporal region. GBC exhibited a selective deficit in spoken language production affecting vowels more than consonants. In reading from a newspaper, GBC substituted vowels for other vowels from the Italian inventory at a rate of 7/1 compared to consonants. No effects of frequency or grammatical class were found. Vowel errors could also not be accounted for by morphological or known phonological processes. Production of number words, in contrast, was free from phonological errors. While GBC has intact representations of Italian vowels and consonants, his data argue for a separate selection mechanism for vowels that is dissociable from that used for consonants. This case provides neuropsychological evidence for models of word production that distinguish between the abstract phonological properties of a word (e.g., sequencing of phonemic slots, or "CV skeleton") and a separate representation for the specific sounds (melody).

  10. Structural, Biochemical, and Computational Studies Reveal the Mechanism of Selective Aldehyde Dehydrogenase 1A1 Inhibition by Cytotoxic Duocarmycin Analogues.

    Science.gov (United States)

    Koch, Maximilian F; Harteis, Sabrina; Blank, Iris D; Pestel, Galina; Tietze, Lutz F; Ochsenfeld, Christian; Schneider, Sabine; Sieber, Stephan A

    2015-11-09

    Analogues of the natural product duocarmycin bearing an indole moiety were shown to bind aldehyde dehydrogenase 1A1 (ALDH1A1) in addition to DNA, while derivatives without the indole solely addressed the ALDH1A1 protein. The molecular mechanism of selective ALDH1A1 inhibition by duocarmycin analogues was unraveled through cocrystallization, mutational studies, and molecular dynamics simulations. The structure of the complex shows the compound embedded in a hydrophobic pocket, where it is stabilized by several crucial π-stacking and van der Waals interactions. This binding mode positions the cyclopropyl electrophile for nucleophilic attack by the noncatalytic residue Cys302, thereby resulting in covalent attachment, steric occlusion of the active site, and inhibition of catalysis. The selectivity of duocarmycin analogues for ALDH1A1 is unique, since only minor alterations in the sequence of closely related protein isoforms restrict compound accessibility. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Molecular Mechanism for Inhibition of G Protein-Coupled Receptor Kinase 2 by a Selective RNA Aptamer

    Energy Technology Data Exchange (ETDEWEB)

    Tesmer, Valerie M.; Lennarz, Sabine; Mayer, Günter; Tesmer, John J.G. (Bonn); (Michigan)

    2012-08-31

    Cardiovascular homeostasis is maintained in part by the rapid desensitization of activated heptahelical receptors that have been phosphorylated by G protein-coupled receptor kinase 2 (GRK2). However, during chronic heart failure GRK2 is upregulated and believed to contribute to disease progression. We have determined crystallographic structures of GRK2 bound to an RNA aptamer that potently and selectively inhibits kinase activity. Key to the mechanism of inhibition is the positioning of an adenine nucleotide into the ATP-binding pocket and interactions with the basic {alpha}F-{alpha}G loop region of the GRK2 kinase domain. Constraints imposed on the RNA by the terminal stem of the aptamer also play a role. These results highlight how a high-affinity aptamer can be used to selectively trap a novel conformational state of a protein kinase.

  12. Effect of selected microadditives on the mechanical properties of aluminium alloys

    Directory of Open Access Journals (Sweden)

    Rzadkosz S.

    2007-01-01

    Full Text Available The effect of iron impurities on microstructure and mechanical properties of cast Al-Cu and Al-Zn-Mg alloys was discussed. The role of iron in the process of solutioning and ageing of these alloys was described. Basing on the results of investigations, a comparative analysis was made to disclose the effect of low content (microadditives of the elements, like Mn, Ti, Zr, B, Cr, Ni, Zn, Sn, Cd, In, Mg, Sb, and Ag on the primary structure of castings, mainly on the morphology of iron-bonding intermetallic phases. The studies also allowed for an effect of these elements on dispersion hardening of the examined alloys, reflected in an improvement of the principal mechanical properties (Rm, A5, HV, and on the kinetics of ageing. Tin, cadmium and indium, added in an amount of 0,1 – 0,15 %, were reported to have the strong-est effect on the process of dispersion hardening. Beneficial effect on the morphology of iron phases have manganese, chromium and nickel.

  13. Selecting novel material of vegetable pea for mechanical harvesting and canning

    Directory of Open Access Journals (Sweden)

    Kaigorodova Irina M.

    2016-01-01

    Full Text Available Breeding of novel pea cultivars is of significant interest in scope of increasing food shortages. The cultivars of new generation have to be highly technological and appropriate for mechanical treatment in all stages of planting. To provide higher outcome of plant products, pea is to be harvested for prolonged seasonal period, i.e. bred for conveyor usage. In this paper we presented the results of preliminary investigation of pea germplasm collection and studies on inheritance of flowering time in a series of crosses. We evaluated all hybrid progeny for duration of vegetation, lodging resistance and seed mass. Seven maturity groups were emphasized with most of obtained lines exhibiting an average duration of vegetation period measured as number of sterile nodes (11-15 for average fraction. As a result of this survey, the prospective genotypes for breeding new forms resistant to lodging and suitable for mechanical harvest were isolated. We propose a scheme of conveyor usage of new forms for sustainable delivery of stock for conversion industry. The obtained material is recommended for further improvement as the initial material for breeding.

  14. Devitrification kinetics and phase selection mechanisms in Cu-Zr metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Kalay, Ilkay [Iowa State Univ., Ames, IA (United States)

    2010-01-01

    Metallic glasses have been a promising class of materials since their discovery in the 1960s. Indeed, remarkable chemical, mechanical and physical properties have attracted considerable attention, and several excellent reviews are available. Moreover, the special group of glass forming alloys known as the bulk metallic glasses (BMG) become amorphous solids even at relatively low cooling rates, allowing them to be cast in large cross sections, opening the scope of potential applications to include bulk forms and net shape structural applications. Recent studies have been reported for new bulk metallic glasses produced with lower cooling rates, from 0.1 to several hundred K/s. Some of the application products of BMGs include sporting goods, high performance springs and medical devices. Several rapid solidification techniques, including melt-spinning, atomization and surface melting have been developed to produce amorphous alloys. The aim of all these methods is to solidify the liquid phase rapidly enough to suppress the nucleation and growth of crystalline phases. Furthermore, the production of amorphous/crystalline composite (ACC) materials by partial crystallization of amorphous precursor has recently given rise to materials that provide better mechanical and magnetic properties than the monolithic amorphous or crystalline alloys. In addition, these advances illustrate the broad untapped potential of using the glassy state as an intermediate stage in the processing of new materials and nanostructures. These advances underlie the necessity of investigations on prediction and control of phase stability and microstructural dynamics during both solidification and devitrification processes. This research presented in this dissertation is mainly focused on Cu-Zr and Cu-Zr-Al alloy systems. The Cu-Zr binary system has high glass forming ability in a wide compositional range (35-70 at.% Cu). Thereby, Cu-Zr based alloys have attracted much attention according to fundamental

  15. Selected biometric and mechanical properties of the common reed Phragmites australis and the reed sweet grass Glyceria maxima rhizomes

    Directory of Open Access Journals (Sweden)

    Kowalik Weronika

    2016-12-01

    Full Text Available The results on the selected biometric and mechanical properties of common reed Phragmites australis and reed sweet grass Glyceria maxima were presented. The experiments were conducted with the help of the universal testing machine Instron 5966. The underground biomasses, diameters, tensile forces, displacements and tensile strengths for summer and winter rhizomes of both species were assessed and compared. The final results indicate that rhizomes of common reed had higher values of the studied parameters of biometric and stretching than sweet reed grass rhizomes. Therefore, there are more opportunities to use them to protect the coastline.

  16. Statistical Mechanics Ideas and Techniques Applied to Selected Problems in Ecology

    Directory of Open Access Journals (Sweden)

    Hugo Fort

    2013-11-01

    Full Text Available Ecosystem dynamics provides an interesting arena for the application of a plethora concepts and techniques from statistical mechanics. Here I review three examples corresponding each one to an important problem in ecology. First, I start with an analytical derivation of clumpy patterns for species relative abundances (SRA empirically observed in several ecological communities involving a high number n of species, a phenomenon which have puzzled ecologists for decades. An interesting point is that this derivation uses results obtained from a statistical mechanics model for ferromagnets. Second, going beyond the mean field approximation, I study the spatial version of a popular ecological model involving just one species representing vegetation. The goal is to address the phenomena of catastrophic shifts—gradual cumulative variations in some control parameter that suddenly lead to an abrupt change in the system—illustrating it by means of the process of desertification of arid lands. The focus is on the aggregation processes and the effects of diffusion that combined lead to the formation of non trivial spatial vegetation patterns. It is shown that different quantities—like the variance, the two-point correlation function and the patchiness—may serve as early warnings for the desertification of arid lands. Remarkably, in the onset of a desertification transition the distribution of vegetation patches exhibits scale invariance typical of many physical systems in the vicinity a phase transition. I comment on similarities of and differences between these catastrophic shifts and paradigmatic thermodynamic phase transitions like the liquid-vapor change of state for a fluid. Third, I analyze the case of many species interacting in space. I choose tropical forests, which are mega-diverse ecosystems that exhibit remarkable dynamics. Therefore these ecosystems represent a research paradigm both for studies of complex systems dynamics as well as to

  17. Hydrolases Part I: Enzyme Mechanism, Selectivity and Control in the Synthesis of Well-Defined Polymers

    Science.gov (United States)

    Veld, Martijn A. J.; Palmans, Anja R. A.

    Lipases are highly activity in the polymerization of a range of monomers. Both ring-opening polymerization of cyclic esters and polycondensation reactions of AA-BB and AB monomers have been investigated in great detail. This paper reviews the increased understanding in enzymatic strategies for the production of well-defined polymers. Major advantages of enzymatic catalysts are the relatively mild reaction conditions, and the often-observed excellent regio-, chemo-, and enantioselectivity that allow for the direct preparation of functional materials. However, as a result of the monomer activation mechanism, polymers of low polydispersity and low quantitative degree of endgroup functionality are difficult to attain. A wide variety of (co)polymers have been synthesized and explored in a variety of applications using lipase catalysts.

  18. Insights into the selective binding and toxic mechanism of microcystin to catalase

    Science.gov (United States)

    Hu, Yuandong; Da, Liangjun

    2014-03-01

    Microcystin is a sort of cyclic nonribosomal peptides produced by cyanobacteria. It is cyanotoxin, which can be very toxic for plants and animals including humans. The present study evaluated the interaction of microcystin and catalase, under physiological conditions by means of fluorescence, three-dimensional (3D) fluorescence, circular dichroism (CD), Fourier Transform infrared (FT-IR) spectroscopy, and enzymatic reactionkinetic techniques. The fluorescence data showed that microcystin could bind to catalase to form a complex. The binding process was a spontaneous molecular interaction procedure, in which electrostatic interactions played a major role. Energy transfer and fluorescence studies proved the existence of a static binding process. Additionally, as shown by the three-dimensional fluorescence, CD and FT-IR results, microcystin could lead to conformational and microenvironmental changes of the protein, which may affect the physiological functions of catalase. The work provides important insights into the toxicity mechanism of microcystin in vivo.

  19. Peroxisome homeostasis: Mechanisms of division and selective degradation of peroxisomes in mammals.

    Science.gov (United States)

    Honsho, Masanori; Yamashita, Shun-ichi; Fujiki, Yukio

    2016-05-01

    Peroxisome number and quality are maintained by its biogenesis and turnover and are important for the homeostasis of peroxisomes. Peroxisomes are increased in number by division with dynamic morphological changes including elongation, constriction, and fission. In the course of peroxisomal division, peroxisomal morphogenesis is orchestrated by Pex11β, dynamin-like protein 1 (DLP1), and mitochondrial fission factor (Mff). Conversely, peroxisome number is reduced by its degradation. Peroxisomes are mainly degraded by pexophagy, a type of autophagy specific for peroxisomes. Upon pexophagy, an adaptor protein translocates on peroxisomal membrane and connects peroxisomes to autophagic machineries. Molecular mechanisms of pexophagy are well studied in yeast systems where several specific adaptor proteins are identified. Pexophagy in mammals also proceeds in a manner dependent on adaptor proteins. In this review, we address the recent progress in studies on peroxisome morphogenesis and pexophagy.

  20. Mapping the Indicators. An Analysis of Sustainable Development Requirements of Selected Market Mechanisms and Multilateral Institutions

    DEFF Research Database (Denmark)

    Arens, Christof; Mersmann, Florian; Beuermann, Christiane

    produce additional outcomes on other environmental, social or economic aspects of sustainable development. The Clean Development Mechanism (CDM) was created precisely to cover these two aspects: firstly, to achieve cost-effective mitigation of greenhouse gases and secondly, to assist developing countries...... is a complex multilayer process covering environmental as well as social and economic aspects that can be affected both positively and negatively, there is a variety of possibilities of how to assess the impact an intervention may have. The high number of approaches analysed by this study reflects this......Investors are paying more and more attention to the co-benefits of climate finance. Financing activities aimed at emission mitigation must not only result in the reduction of greenhouse gas emissions, the enhancement of mitigation, adaptive capacity and adaptation strategies, but should also...

  1. Noninvasive ultrasonic monitoring of the mechanical properties of selected muscles and connected tendons

    Science.gov (United States)

    Zakir Hossain, M.; Grill, W.

    2012-04-01

    The force-length relation is one of the most important mechanical properties of skeletal muscular tissue. Due to the rather limited availability of non-invasive methods suitable to quantify the in-vivo biomechanical properties of activated human muscles and connected tendons, the quantification of the bio-mechanical properties is difficult. The measurement principle applied here is based on the detection of the dynamics of the muscle under observation by an ultrasonic caliper and monitoring of the externally present forces by a synchronously operated ultrasonic force sensor. The developed monitoring scheme is exemplified for gradual increasing voluntary isometric contraction (MVIC) of the gastrocnemius muscle up to maximum contraction, with the force sensor restricting the flexion of the joint. The temporal resolution for the monitoring is 0.01 s, relating to a monitoring rate of 100 Hz and is achieved with a spatial resolution concerning the observed lateral extension of the muscle of 0.01 mm. The employed low power, economic and non-intrusive detection scheme and respective instrumentation have the demonstrated potential to quantify the in-vivo hysteretic behavior of the observed force-length relation for MVIC of the human gastrocnemius muscle for the first time. The purpose of this study was to determine in-vivo the force-length relations for the human gastrocnemius and biceps muscles noninvasively by suitable experimental techniques with high temporal and spatial resolution concerning monitoring of the biomechanical relevant parameters involved in the dynamics of activated muscle. The data is collected and analyzed to derive quantitative information on force-length relations, essential for the analysis of muscle performance and interpretation by musculoskeletal models. The involved technologies are demonstrated and the respective results are presented and discussed.

  2. Microstructure and mechanical behavior of porous Ti-6Al-4V parts obtained by selective laser melting.

    Science.gov (United States)

    Sallica-Leva, E; Jardini, A L; Fogagnolo, J B

    2013-10-01

    Rapid prototyping allows titanium porous parts with mechanical properties close to that of bone tissue to be obtained. In this article, porous parts of the Ti-6Al-4V alloy with three levels of porosity were obtained by selective laser melting with two different energy inputs. Thermal treatments were performed to determine the influence of the microstructure on the mechanical properties. The porous parts were characterized by both optical and scanning electron microscopy. The effective modulus, yield and ultimate compressive strength were determined by compressive tests. The martensitic α' microstructure was observed in all of the as-processed parts. The struts resulting from the processing conditions investigated were thinner than those defined by CAD models, and consequently, larger pores and a higher experimental porosity were achieved. The use of the high-energy input parameters produced parts with higher oxygen and nitrogen content, their struts that were even thinner and contained a homogeneous porosity distribution. Greater mechanical properties for a given relative density were obtained using the high-energy input parameters. The as-quenched martensitic parts showed yield and ultimate compressive strengths similar to the as-processed parts, and these were greater than those observed for the fully annealed samples that had the lamellar microstructure of the equilibrium α+β phases. The effective modulus was not significantly influenced by the thermal treatments. A comparison between these results and those of porous parts with similar geometry obtained by selective electron beam melting shows that the use of a laser allows parts with higher mechanical properties for a given relative density to be obtained.

  3. Selective laser melting additive manufactured Inconel 718 superalloy parts: High-temperature oxidation property and its mechanisms

    Science.gov (United States)

    Jia, Qingbo; Gu, Dongdong

    2014-10-01

    This work presented a comprehensive study of high-temperature oxidation behaviors and mechanisms of Selective laser melting (SLM) processed Inconel 718 superalloy parts using different methods including isothermal oxidation testing, X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. The experimental results revealed that the oxidation process of the tested parts processed at a lower volumetric laser energy density experienced the severe spallation. On reasonably increasing the applied volumetric laser energy density, the oxidation kinetics of the as-produced parts obeyed a parabolic law, exhibiting the significantly improved oxidation resistance performance. The constitutional phases within the oxidation film were identified and the corresponding formation mechanisms were elucidated in detail according to the thermodynamic principles. The cross-sectional morphologies of oxidized Inconel 718 parts indicated that the oxidation microstructure mainly consisted of an external oxidation layer and an internal oxidation zone. The oxidation process was controlled by the outward diffusion of oxide forming elements and inward penetration of oxygen, by which the interaction mechanisms between the microstructures and internal oxidation zones were clarified. On the basis of the experimental results and theoretical analyses, the physical oxidation mechanisms were accordingly established to illustrate the oxidation behaviors of SLM-processed Inconel 718 parts at elevated operative temperatures.

  4. Mechanism of quizalofop-ethyl selectivity in monocotyledonous and dicotyledonous species

    Energy Technology Data Exchange (ETDEWEB)

    Ruizzo, M.A.

    1986-01-01

    Cucumber (Cucumis sativus L.) susceptibility to quizalofop-ethyl herbicide was investigated under field and greenhouse conditions. Yield of cucumber cultivars was significantly reduced under field conditions with a single or repeat application of the ethyl ester of quizalofop at 0.14 or 0.28 kg ai/ha. Under greenhouse conditions, quialofop-ethyl significantly suppressed cucumber plant fresh weight with or without the presence of an adjuvant. Enhancement of herbicide activity was directly related to concentration of adjuvant. Microliter droplet application of quizalofop-ethyl at a 10/sup -3/ M concentration, inhibited the relative growth (RGR) and net assimilation rate (NAR) of the treated cucumber leaf 45% and 52%, respectively. Expression of herbicidal injury was localized on the treated leaf with no visible symptoms observed on adjacent leaves. Radiolabeled /sup 14/C-quizalofop-ethyl was applied to leaves of cucumber and corn (Zea mays L.) to compare translocation patterns between two susceptible plant species and relate this information to the observed selectivity of the herbicide. Cucumber autoradiographs showed minimal translocation of /sup 14/C-quizalofop-ethyl 192 hours after treatment. In contrast, corn autoradiographs showed both apoplastic and symplastic transport of quizalofop-ethyl 3 and 24 hours after treatment. Quantification of /sup 14/C in cucumber revealed 96% of absorbed /sup 14/C was confined to the treated leaf after 192h of exposure.

  5. Scale-dependent mechanisms of habitat selection for a migratory passerine: an experimental approach

    Science.gov (United States)

    Donovan, Therese M.; Cornell, Kerri L.

    2010-01-01

    Habitat selection theory predicts that individuals choose breeding habitats that maximize fitness returns on the basis of indirect environmental cues at multiple spatial scales. We performed a 3-year field experiment to evaluate five alternative hypotheses regarding whether individuals choose breeding territories in heterogeneous landscapes on the basis of (1) shrub cover within a site, (2) forest land-cover pattern surrounding a site, (3) conspecific song cues during prebreeding settlement periods, (4) a combination of these factors, and (5) interactions among these factors. We tested hypotheses with playbacks of conspecific song across a gradient of landscape pattern and shrub density and evaluated changes in territory occupancy patterns in a forest-nesting passerine, the Black-throated Blue Warbler (Dendroica caerulescens). Our results support the hypothesis that vegetation structure plays a primary role during presettlement periods in determining occupancy patterns in this species. Further, both occupancy rates and territory turnover were affected by an interaction between local shrub density and amount of forest in the surrounding landscape, but not by interactions between habitat cues and social cues. Although previous studies of this species in unfragmented landscapes found that social postbreeding song cues played a key role in determining territory settlement, our prebreeding playbacks were not associated with territory occupancy or turnover. Our results suggest that in heterogeneous landscapes during spring settlement, vegetation structure may be a more reliable signal of reproductive performance than the physical location of other individuals.

  6. The RARgamma selective agonist CD437 inhibits gastric cell growth through the mechanism of apoptosis.

    Science.gov (United States)

    Jiang, S Y; Lin, D Y; Shyu, R Y; Reichert, U; Yeh, M Y

    1999-04-01

    Retinoids are differentiation-inducing agents that exhibit multiple functions. Their activities are mediated through interaction with nuclear retinoic acid receptors (RAR) and retinoid X receptors (RXR). We have investigated the activities of synthetic retinoids on the growth of five gastric cancer cell lines. The effects of agonists selective for RARalpha, RARbeta and RARgamma (AM580, CD2019 and CD437, respectively) on cell growth were determined, in comparison to all-trans retinoic acid, by measuring total cellular DNA. AM580 and CD2019 had little or no effect on the growth of all five cell lines. In contrast, the RARgamma agonist CD437 inhibited cell growth up to 90-99% in both retinoic acid sensitive and resistant gastric cancer cells at a concentration of 1 microM. The growth suppression caused by CD437 was accompanied by the induction of apoptosis as judged by morphological criteria and DNA ladder formation. However, the extent of CD437-induced growth suppression was not correlated with RARgamma mRNA levels, which indicates that CD437 induces apoptosis in gastric cancer cells via an RARgamma independent pathway.

  7. Synaptic mechanisms underlying interaural level difference selectivity in rat auditory cortex

    Science.gov (United States)

    Kyweriga, Michael; Stewart, Whitney; Cahill, Carolyn

    2014-01-01

    The interaural level difference (ILD) is a sound localization cue that is extensively processed in the auditory brain stem and midbrain and is also represented in the auditory cortex. Here, we asked whether neurons in the auditory cortex passively inherit their ILD tuning from subcortical sources or whether their spiking preferences were actively shaped by local inhibition. If inherited, the ILD selectivity of spiking output should match that of excitatory synaptic input. If shaped by local inhibition, by contrast, excitation should be more broadly tuned than spiking output with inhibition suppressing spiking for nonpreferred stimuli. To distinguish between these two processing strategies, we compared spiking responses with excitation and inhibition in the same neurons across a range of ILDs and average binaural sound levels. We found that cells preferring contralateral ILDs (often called EI cells) followed the inheritance strategy. In contrast, cells that were unresponsive to monaural sounds but responded predominantly to near-zero ILDs (PB cells) instead showed evidence of the local processing strategy. These PB cells received excitatory inputs that were similar to those received by the EI cells. However, contralateral monaural sounds and ILDs >0 dB elicited strong inhibition, quenching the spiking output. These results suggest that in the rat auditory cortex, EI cells do not utilize inhibition to shape ILD sensitivity, whereas PB cells do. We conclude that an auditory cortical circuit computes sensitivity for near-zero ILDs. PMID:25185807

  8. Effects of working memory demand on neural mechanisms of motor response selection and control.

    Science.gov (United States)

    Barber, Anita D; Caffo, Brian S; Pekar, James J; Mostofsky, Stewart H

    2013-08-01

    Inhibitory control commonly recruits a number of frontal regions: pre-supplementary motor area (pre-SMA), frontal eye fields (FEFs), and right-lateralized posterior inferior frontal gyrus (IFG), dorsal anterior insula (DAI), dorsolateral prefrontal cortex (DLPFC), and inferior frontal junction (IFJ). These regions may directly implement inhibitory motor control or may be more generally involved in executive control functions. Two go/no-go tasks were used to distinguish regions specifically recruited for inhibition from those that additionally show increased activity with working memory demand. The pre-SMA and IFG were recruited for inhibition in both tasks and did not have greater activation for working memory demand on no-go trials, consistent with a role in inhibitory control. Activation in pre-SMA also responded to response selection demand and was increased with working memory on go trials specifically. The bilateral FEF and right DAI were commonly active for no-go trials. The FEF was also recruited to a greater degree with working memory demand on go trials and may bias top-down information when stimulus-response mappings change. The DAI, additionally responded to increased working memory demand on both go and no-go trials and may be involved in accessing sustained task information, alerting, or autonomic changes when cognitive demands increase. DLPFC activation was consistent with a role in working memory retrieval on both go and no-go trials. The inferior frontal junction, on the other hand, had greater activation with working memory specifically for no-go trials and may detect salient stimuli when the task requires frequent updating of working memory representations.

  9. Measuring the spatial frequency selectivity of second-order texture mechanisms.

    Science.gov (United States)

    Sutter, A; Sperling, G; Chubb, C

    1995-04-01

    Recent investigations of texture and motion perception suggest two early filtering stages: an initial stage of selective linear filtering followed by rectification and a second stage of linear filtering. Here we demonstrate that there are differently scaled second-stage filters, and we measure their contrast modulation sensitivity as a function of spatial frequency. Our stimuli are Gabor modulations of a suprathreshold, bandlimited, isotropic carrier noise. The subjects' task is to discriminate between two possible orientations of the Gabor. Carrier noises are filtered into four octave-wide bands, centered at m = 2, 4, 8, and 16 c/deg. The Gabor test signals are w = 0.5, 1, 2, 4 and 8 c/deg. The threshold modulation of the test signal is measured for all 20 combinations of m and w. For each carrier frequency m, the Gabor test frequency w to which subjects are maximally sensitive appears to be approximately 3-4 octaves below m. The consistent m x w interaction suggests that each second-stage spatial filter may be differentially tuned to a particular first-stage spatial frequency. The most sensitive combination is a second-stage filter of 1 c/deg with first-stage inputs of 8-16 c/deg. We conclude that second-order texture perception appears to utilize multiple channels tuned to spatial frequency and orientation, with channels tuned to low modulation frequencies appearing to be best served by carrier frequencies 8 to 16 times higher than the modulations they are tuned to detect.

  10. Structural insight into mechanism and diverse substrate selection strategy of L-ribulokinase

    Energy Technology Data Exchange (ETDEWEB)

    Agarwal R.; Swaminathan S.; Burley, S. K.

    2012-01-01

    The araBAD operon encodes three different enzymes required for catabolism of L-arabinose, which is one of the most abundant monosaccharides in nature. L-ribulokinase, encoded by the araB gene, catalyzes conversion of L-ribulose to L-ribulose-5-phosphate, the second step in the catabolic pathway. Unlike other kinases, ribulokinase exhibits diversity in substrate selectivity and catalyzes phosphorylation of all four 2-ketopentose sugars with comparable k{sub cat} values. To understand ribulokinase recognition and phosphorylation of a diverse set of substrates, we have determined the X-ray structure of ribulokinase from Bacillus halodurans bound to L-ribulose and investigated its substrate and ATP co-factor binding properties. The polypeptide chain is folded into two domains, one small and the other large, with a deep cleft in between. By analogy with related sugar kinases, we identified {sup 447}{und GG}LPQ{und K}{sup 452} as the ATP-binding motif within the smaller domain. L-ribulose binds in the cleft between the two domains via hydrogen bonds with the side chains of highly conserved Trp126, Lys208, Asp274, and Glu329 and the main chain nitrogen of Ala96. The interaction of L-ribulokinase with L-ribulose reveals versatile structural features that help explain recognition of various 2-ketopentose substrates and competitive inhibition by L-erythrulose. Comparison of our structure to that of the structures of other sugar kinases revealed conformational variations that suggest domain-domain closure movements are responsible for establishing the observed active site environment.

  11. Models of self-peptide sampling by developing T cells identify candidate mechanisms of thymic selection.

    Directory of Open Access Journals (Sweden)

    Iren Bains

    Full Text Available Conventional and regulatory T cells develop in the thymus where they are exposed to samples of self-peptide MHC (pMHC ligands. This probabilistic process selects for cells within a range of responsiveness that allows the detection of foreign antigen without excessive responses to self. Regulatory T cells are thought to lie at the higher end of the spectrum of acceptable self-reactivity and play a crucial role in the control of autoimmunity and tolerance to innocuous antigens. While many studies have elucidated key elements influencing lineage commitment, we still lack a full understanding of how thymocytes integrate signals obtained by sampling self-peptides to make fate decisions. To address this problem, we apply stochastic models of signal integration by T cells to data from a study quantifying the development of the two lineages using controllable levels of agonist peptide in the thymus. We find two models are able to explain the observations; one in which T cells continually re-assess fate decisions on the basis of multiple summed proximal signals from TCR-pMHC interactions; and another in which TCR sensitivity is modulated over time, such that contact with the same pMHC ligand may lead to divergent outcomes at different stages of development. Neither model requires that T(conv and T(reg are differentially susceptible to deletion or that the two lineages need qualitatively different signals for development, as have been proposed. We find additional support for the variable-sensitivity model, which is able to explain apparently paradoxical observations regarding the effect of partial and strong agonists on T(conv and T(reg development.

  12. Experimental and Analytical Analysis of Mechanical Response and Deformation Mode Selection in Balsa Wood

    Science.gov (United States)

    Vural, Murat; Ravichandran, Guruswami

    This study investigates the influence of relative density and strain rate on the compressive response of balsa wood as a sandwich core material commonly used in naval structures. Compressive strength, plateau stress and densification strain of balsa wood along the grain direction is investigated over its entire density spectrum ranging from 55 to 380kg/m3 at both quasi-static (10-3 s-3) and dynamic (103 s-3) strain rates using a modified Kolsky (split Hopkinson) bar. Scanning electron microscopy is used on recovered specimens subjected to controlled loading histories to identify the failure mode selection as a function of density and strain rate. The results indicate that compressive strength of balsa wood increases with relative density though the rate of increase is significantly larger at high strain rates. The failure of low-density specimens is governed by elastic and/or plastic buckling, while kink band formation and end-cap collapse dominate in higher density balsa specimens. Based on the experimental results and observations, several analytical models are proposed to predict the quasi-static compressive strength of balsa wood under uniaxial loading conditions. Results also show that the initial failure stress is very sensitive to the rate of loading, and the degree of dynamic strength enhancement is different for buckling and kink band modes. Kinematics of deformation of the observed failure modes and associated micro-inertial effects are modeled to explain this different behavior. Specific energy dissipation capacity of balsa wood was computed and is found to be comparable with those of fiber-reinforced polymer composites.

  13. Mechanisms of anorexia-cachexia syndrome and rational for treatment with selective ghrelin receptor agonist.

    Science.gov (United States)

    Esposito, Angela; Criscitiello, Carmen; Gelao, Lucia; Pravettoni, Gabriella; Locatelli, Marzia; Minchella, Ida; Di Leo, Maria; Liuzzi, Rita; Milani, Alessandra; Massaro, Mariangela; Curigliano, Giuseppe

    2015-11-01

    Cancer cachexia is a multi-organ, multifactorial and often irreversible syndrome affecting many patients with cancer. Cancer cachexia is invariably associated with weight loss, mainly from loss of skeletal muscle and body fat, conditioning a reduced quality of life due to asthenia, anorexia, anaemia and fatigue. Treatment options for treating cancer cachexia are limited. The approach is multimodal and may include: treatment of secondary gastrointestinal symptoms, nutritional treatments, drug, and non-drug treatments. Nutritional counselling and physical training may be beneficial in delaying or preventing the development of anorexia-cachexia. However, these interventions are limited in their effect, and no definitive pharmacological treatment is available to address the relevant components of the syndrome. Anamorelin is a first-in-class, orally active ghrelin receptor agonist that binds and stimulates the growth hormone secretagogue receptor centrally, thereby mimicking the appetite-enhancing and anabolic effects of ghrelin. It represents a new class of drug and an additional treatment option for this patient group, whose therapeutic options are currently limited. In this review we examine the mechanisms of anamorelin by which it contrasts catabolic states, its role in regulation of metabolism and energy homeostasis, the data of recent trials in the setting of cancer cachexia and its safety profile.

  14. Selective Separation of Fe-Concentrates in EAF Slags Using Mechanical Dissimilarity of Solid Phases

    Science.gov (United States)

    Jung, Sung Suk; Jung, Keeyoung; Sohn, Il

    2017-02-01

    We sought to develop an optimized particle size-dependent separation method to lower the Fe content of pulverized glass-ceramic electric arc furnace (EAF) slag for its improved reclamation as construction materials by considering the structures and the mechanical behavior of the discrete solid phases. After an isothermal crystallization process to enhance the spinel growth, the Vickers hardness and fracture toughness were measured on the spinel and amorphous phases separately from the solidified slag using indentation methods. The characteristic differences in the hardness of the phases were magnified when this glass-ceramic composite was isothermally crystallized. The hardness of the spinel was observed to be lower in slags with higher FetO/Al2O3 mass ratios due to the triclinic unit cell expansion of the spinel, whereas the hardness of the amorphous phase decreased with increasing isothermal period because of the structural transformation into a silicate-dominant network. Fracture toughness could be calculated based on the hardness and crack length, where the Young's modulus was determined using nanoindentation. The amorphous phase with a lower Fe content and lower fracture toughness resulted in finer powder distribution after pulverization, allowing better separation of the primary crystalline spinel containing higher Fe content from the Fe-deficient amorphous phase according to the particle size.

  15. Freestanding bacterial cellulose-graphene oxide composite membranes with high mechanical strength for selective ion permeation

    Science.gov (United States)

    Fang, Qile; Zhou, Xufeng; Deng, Wei; Zheng, Zhi; Liu, Zhaoping

    2016-09-01

    Graphene oxide (GO) based membranes have been widely applied in molecular separation based on the size exclusion effect of the nanochannels formed by stacked GO sheets. However, it’s still a challenge to prepare a freestanding GO-based membrane with high mechanical strength and structural stability which is prerequisite for separation application in aqueous solution. Here, a freestanding composite membrane based on bacterial cellulose (BC) and GO is designed and prepared. BC network provides a porous skeleton to spread GO sheets and uniformly incorporates into the GO layers, which endows the BC + GO composite membrane with well water-stability, excellent tensile strength, as well as improved toughness, guaranteeing its separation applicability in water environment. The resulting BC + GO membrane exhibits obviously discrepant permeation properties for different inorganic/organic ions with different size, and in particular, it can quickly separate ions in nano-scale from angstrom-scale. Therefore, this novel composite membrane is considered to be a promising candidate in the applications of water purification, food industry, biomedicine, and pharmaceutical and fuel separation.

  16. ERK1-Based Pathway as a New Selective Mechanism To Modulate CCR5 with Natural Antibodies.

    Science.gov (United States)

    Venuti, Assunta; Pastori, Claudia; Siracusano, Gabriel; Riva, Agostino; Sciortino, Maria Teresa; Lopalco, Lucia

    2015-10-01

    Natural human Abs, recognizing an epitope within the first extramembrane loop of CCR5 (the main HIV coreceptor), induce a long-lasting internalization (48 h) of the protein, whereas all known CCR5 modulating molecules show a short-term kinetics (60-90 min). Despite extensive studies on the regulation of CCR5 signaling cascades, which are the effect of concomitant CCR5 internalization by exogenous stimuli such as Abs, downstream signaling continues to be poorly understood. In this article, we report a hitherto unrecognized mechanism of CCR5 modulation mediated by G protein-dependent ERK1 activity. We further demonstrate that ERK1 is localized mainly in the cytoplasmic compartment and that it interacts directly with the CCR5 protein, thus provoking possible CCR5 degradation with a subsequent de novo synthesis, and that re-expression of CCR5 on the cell membrane required several days. In contrast, the RANTES treatment induces a recovery of the receptor on the cell membrane in short-term kinetics without the involvement of de novo protein synthesis. The said new pathway could be relevant not only to better understand the molecular basis of all pathologic conditions in which CCR5 is involved but also to generate new tools to block viral infections, such as the use of recombinant Abs.

  17. Freestanding bacterial cellulose-graphene oxide composite membranes with high mechanical strength for selective ion permeation

    Science.gov (United States)

    Fang, Qile; Zhou, Xufeng; Deng, Wei; Zheng, Zhi; Liu, Zhaoping

    2016-01-01

    Graphene oxide (GO) based membranes have been widely applied in molecular separation based on the size exclusion effect of the nanochannels formed by stacked GO sheets. However, it’s still a challenge to prepare a freestanding GO-based membrane with high mechanical strength and structural stability which is prerequisite for separation application in aqueous solution. Here, a freestanding composite membrane based on bacterial cellulose (BC) and GO is designed and prepared. BC network provides a porous skeleton to spread GO sheets and uniformly incorporates into the GO layers, which endows the BC + GO composite membrane with well water-stability, excellent tensile strength, as well as improved toughness, guaranteeing its separation applicability in water environment. The resulting BC + GO membrane exhibits obviously discrepant permeation properties for different inorganic/organic ions with different size, and in particular, it can quickly separate ions in nano-scale from angstrom-scale. Therefore, this novel composite membrane is considered to be a promising candidate in the applications of water purification, food industry, biomedicine, and pharmaceutical and fuel separation. PMID:27615451

  18. Neural mechanisms of intermodal sustained selective attention with concurrently presented auditory and visual stimuli

    Directory of Open Access Journals (Sweden)

    Katja Saupe

    2009-11-01

    Full Text Available We investigated intermodal attention effects on the auditory steady-state response (ASSR and the steady-state visual evoked potential (SSVEP. For this purpose, 40 Hz amplitude modulated tones and a stream of flickering (7.5 Hz random letters were presented concurrently. By means of an auditory or visual target detection task, participants’ attention was directed to the respective modality for several seconds. Attention to the auditory stream led to a significant enhancement of the ASSR compared to when the visual stream was attended. This attentional modulation was located mainly in the right superior temporal gyrus. Vice versa, attention to the visual stream especially increased the second harmonic response of the SSVEP. This modulation was focused in the inferior occipital and lateral occipitotemporal gyrus of both hemispheres. To the best of our knowledge, this is the first demonstration of amplitude modulation of the ASSR and the SSVEP by intermodal sustained attention. Our results open a new avenue of research to understand the basic neural mechanisms of intermodal attention in the human brain.

  19. In and out of control: brain mechanisms linking fluency of action selection to self-agency in patients with schizophrenia.

    Science.gov (United States)

    Voss, Martin; Chambon, Valérian; Wenke, Dorit; Kühn, Simone; Haggard, Patrick

    2017-08-01

    Sense of agency refers to the feeling of control over one's actions, and their consequences. It involves both predictive processes linked to action control, and retrospective 'sense-making' causal inferences. Schizophrenia has been associated with impaired predictive processing, but the underlying mechanisms that impair patients' sense of agency remain unclear. We introduce a new 'prospective' aspect of agency and show that subliminally priming an action not only influences response times, but also influences reported sense of agency over subsequent action outcomes. This effect of priming was associated with altered connectivity between frontal areas and the angular gyrus. The effects on response times and on frontal action selection mechanisms were similar in patients with schizophrenia and in healthy volunteers. However, patients showed no effects of priming on sense of agency, no priming-related activation of angular gyrus, and no priming-related changes in fronto-parietal connectivity. We suggest angular gyrus activation reflects the experiences of agency, or non-agency, in part by processing action selection signals generated in the frontal lobes. The altered action awareness that characterizes schizophrenia may be due to impaired communication between these areas. © The Author (2017). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  20. The influence of printing parameters on selected mechanical properties of FDM/FFF 3D-printed parts

    Science.gov (United States)

    Ćwikła, G.; Grabowik, C.; Kalinowski, K.; Paprocka, I.; Ociepka, P.

    2017-08-01

    Rapid Prototyping technologies, especially 3D printing are becoming increasingly popular due to their usability and the constant decrease in price of printing equipment and materials. The article focuses on the study of selected mechanical strength properties of 3D-printed elements, which are not very important if the element is only a model for further manufacturing techniques, but which are important when 3D-printed elements will be a part of a functioning device, e.g. a part of unique scientific equipment. The research was carried out on a set of standardised samples, printed with low-cost standard materials (ABS), using a cheap 3D printer. The influence of parameters (such as the type of infill pattern, infill density, shell thickness, printing temperature, the type of material) on selected mechanical properties of the samples, were tested. The obtained results allows making conscious decisions on the printing of elements to be durable enough, either on a non-professional printer, or when to ordered by a professional manufacturer.

  1. MECHANISMS OF MICROBE-HOST-INTERACTION IN CROHN'S DISEASE: DYSBIOSIS VS. PATHOBIONT SELECTION

    Directory of Open Access Journals (Sweden)

    Ludovica F. Buttó

    2015-11-01

    Full Text Available Crohn’s disease (CD is a systemic chronic inflammatory condition mainly characterized by discontinuous transmural pathology of the gastrointestinal tract and frequent extra-intestinal manifestations with intermittent episodes of remission and relapse. Genome-wide association studies identified a number of risk loci that, catalyzed by environmental triggers, result in the loss of tolerance towards commensal bacteria based on dysregulated innate effector functions and anti-microbial defense, leading to exacerbated adaptive immune responses responsible for chronic immune-mediated tissue damage. In this review, we discuss the interrelated role of changes in the intestinal microbiota, epithelial barrier integrity and immune cell functions on the pathogenesis of CD, describing the current approaches available to investigate the molecular mechanisms underlying the disease. Substantial effort has been dedicated to define disease-associated changes in the intestinal microbiota (dysbiosis and to link pathobionts to the aetiology of IBD. A cogent definition of dysbiosis is lacking, as well as an agreement of whether pathobionts or complex shifts in the microbiota trigger inflammation in the host. Among the rarely available animal models, SAMP/Yit and TNFdeltaARE mice are the best known displaying a transmural CD-like phenotype. New hypothesis-driven mouse models e.g. epithelial-specific Caspase8-/-, ATG16L1-/- and XBP-1-/- mice validate pathway-focused function of specific CD-associated risk genes highlighting the role of Paneth cells in antimicrobial defense. To study the causal role of bacteria in initiating inflammation in the host, the use of germfree mouse models is indispensable. Unraveling the interactions of genes, immune cells and microbes constitute a criterion for the development of safe, reliable and effective treatment options for CD.

  2. Innovation of a Regulatory Mechanism Modulating Semi-determinate Stem Growth through Artificial Selection in Soybean.

    Directory of Open Access Journals (Sweden)

    Yunfeng Liu

    2016-01-01

    Full Text Available It has been demonstrated that Terminal Flowering 1 (TFL1 in Arabidopsis and its functional orthologs in other plants specify indeterminate stem growth through their specific expression that represses floral identity genes in shoot apical meristems (SAMs, and that the loss-of-function mutations at these functional counterparts result in the transition of SAMs from the vegetative to reproductive state that is essential for initiation of terminal flowering and thus formation of determinate stems. However, little is known regarding how semi-determinate stems, which produce terminal racemes similar to those observed in determinate plants, are specified in any flowering plants. Here we show that semi-determinacy in soybean is modulated by transcriptional repression of Dt1, the functional ortholog of TFL1, in SAMs. Such repression is fulfilled by recently enabled spatiotemporal expression of Dt2, an ancestral form of the APETALA1/FRUITFULL orthologs, which encodes a MADS-box factor directly binding to the regulatory sequence of Dt1. In addition, Dt2 triggers co-expression of the putative SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (GmSOC1 in SAMs, where GmSOC1 interacts with Dt2, and also directly binds to the Dt1 regulatory sequence. Heterologous expression of Dt2 and Dt1 in determinate (tfl1 Arabidopsis mutants enables creation of semi-determinacy, but the same forms of the two genes in the tfl1 and soc1 background produce indeterminate stems, suggesting that Dt2 and SOC1 both are essential for transcriptional repression of Dt1. Nevertheless, the expression of Dt2 is unable to repress TFL1 in Arabidopsis, further demonstrating the evolutionary novelty of the regulatory mechanism underlying stem growth in soybean.

  3. Mechanisms involved in the selective transfer of long chain polyunsaturted fatty acids to the fetus

    Directory of Open Access Journals (Sweden)

    Alfonso eGil-Sánchez

    2011-09-01

    Full Text Available The concentration of long chain polyunsaturated fatty acid (LCPUFA in the fetal brain increases dramatically from the third trimester until 18 months of life. Several studies have shown an association between the percentage of maternal plasma docosahexaenoic acid (DHA during gestation and development of the cognitive functions in the neonate. Since only very low levels of LCPUFA are synthesized in the fetus and placenta, their primary source for the fetus is that of maternal origin. Both in vitro and human in vivo studies using labelled fatty acids have shown the preferential transfer of LCPUFA from the placenta to the fetus compared with other fatty acids, although the mechanisms involved are still uncertain. The placenta takes up circulating maternal non-esterified fatty acids (NEFA and fatty acids released mainly by maternal lipoprotein lipase and endothelial lipase. These NEFA may enter the cell by passive diffusion or by means of membrane carrier proteins. Once in the cytosol, NEFA bind to cytosolic fatty acid-binding proteins for transfer to the fetal circulation or can be oxidized within the trophoblasts and even re-esterified and stored in lipid droplets (LD. Although trophoblast cells are not specialized in lipid storage, LCPUFA may up-regulate peroxisome proliferator activated receptor-γ (PPARγ and hence the gene expression of fatty acid transport carriers, fatty acid acyl-CoA synthetases and adipophilin or other enzymes related with lipolysis, modifying their rate of placental transfer and metabolization. The placental transfer of LCPUFA during pregnancy seems to be a key factor in the neurological development of the fetus. Increased knowledge on the factors that modify placental transfer of fatty acids would contribute to our understanding of this complex process.

  4. Investigating gas sensing mechanism of graphene oxide (GO) thin films through cross-selectivity to various gases

    Science.gov (United States)

    Kumar, Shani; Dhingra, Vishal; Garg, Amit; Chowdhuri, Arijit

    2016-05-01

    Worldwide researchers are actively engaged in utilizing Graphene and its related materials in gas sensing applications. A high surface-to-volume ratio that offers scope of optimization leading to enhanced sensing performance besides lower sensor operating temperatures are some advantages that graphene based sensors possess over conventional semiconducting metal oxide (SMO) sensors. Conventional SMO based gas sensors are known to suffer from problems of cross-selectivity where selectivity is understood to be a gas sensor's ability to preferentially detect one particular gas without responding to or experiencing interference from other gases present in the ambient. In the current study gas sensing mechanism of Graphene oxide (GO) thin films is investigated by repeatedly exposing the sensing configuration to various gases and its cross-selectivity response to the same is examined. In the investigation typical gas sensing response characteristics of the sensor configuration are studied in both oxidizing as well as reducing environments. The gas sensing data is acquired by means of Keithley 6487 picoammeter which is interfaced with a customized Gas Sensing Test Rig (GSTR) that provides a controlled ambient to the sensors for measurement of reproducible characteristics. GSTR further provided the option of varying the operating temperature and gas concentration for the different sensor configurations under study. XRD studies indicate formation of GO with typical crystallite size of 4.2 nm. UV-Vis investigations reveal a typical band-gap of 4.42 (eV) which is in conformity with those reported in the available literature.1,2

  5. Removal mechanisms and plant species selection by bioaccumulative factors in surface flow constructed wetlands (CWs): In the case of triclosan.

    Science.gov (United States)

    Zhao, Congcong; Xie, HuiJun; Xu, Jingtao; Zhang, Jian; Liang, Shuang; Hao, Jingcheng; Ngo, Huu Hao; Guo, Wenshan; Xu, Xiaoli; Wang, Qian; Wang, Jingmin

    2016-03-15

    Plants can bioaccumulate triclosan and bond with microbes and sediments in constructed wetlands (CWs) as well. However, little is known regarding the species-specific removal mechanism of CWs components and the selection of suitable wetland plant species for triclosan disposal. In this work, the use of bioaccumulation factors (BAFs) and biota to sediment accumulation factors (BSAFs) for choosing the best triclosan removal plant species was studied in laboratory-scale CWs. By the end of the experiment, over 80% of triclosan was removed and a specie-effect distribution was revealed in CWs with emergent, submerged and floating plants. By mass balance calculation, negative correlation between triclosan concentration in plants and degradation process was observed. The significant correlations between Log BSAFs values and triclosan concentration in plants or degradation contribution made it possible and reasonable in wetland plants selection. Introductions on plant species were provided considering the target removal process or regulation method. This work provided new information on plant species selection in CWs for triclosan removal or its emergency remediation by using bioaccumulative factors. Copyright © 2015 Elsevier B.V. All rights reserved.

  6. Simple and rapid mercury ion selective electrode based on 1-undecanethiol assembled Au substrate and its recognition mechanism.

    Science.gov (United States)

    Li, Xian-Qing; Liang, Hai-Qing; Cao, Zhong; Xiao, Qing; Xiao, Zhong-Liang; Song, Liu-Bin; Chen, Dan; Wang, Fu-Liang

    2017-03-01

    A simple and rapid mercury ion selective electrode based on 1-undecanethiol (1-UDT) assembled Au substrate (Au/1-UDT) has been well constructed. 1-UDT was for the purpose of generating self-assembled monolayer on gold surface to recognize Hg(2+) in aqueous solution, which had a working concentration range of 1.0×10(-8)-1.0×10(-4)molL(-1), with a Nernst response slope of 28.83±0.4mV/-pC, a detection limit of 4.5×10(-9)molL(-1), and a good selectivity over the other tested cations. Also, the Au/1-UDT possessed good reproducibility, stability, and short response time. The recovery obtained for the determination of mercury ion in practical tremella samples was in the range of 99.8-103.4%. Combined electrochemical analysis and X-ray photoelectron spectroscopy (XPS) with quantum chemical computation, the probable recognition mechanism of the electrode for selective recognition of Hg(2+) has been investigated. The covalent bond formed between mercury and sulfur is stronger than the one between gold and sulfur and thus prevents the adsorption of 1-UDT molecules on the gold surface. The quantum chemical computation with density functional theory further demonstrates that the strong interaction between the mercury atom and the sulfur atom on the gold surface leads to the gold sulfur bond ruptured and the gold mercury metallophilic interaction.

  7. Neural mechanisms of selective exposure: an EEG study on the processing of decision-consistent and inconsistent information.

    Science.gov (United States)

    Fischer, Peter; Reinweber, Matthias; Vogrincic, Claudia; Schäfer, Axel; Schienle, Anne; Volberg, Gregor

    2013-01-01

    Decision makers tend to prefer decision-consistent information and/or neglect decision-inconsistent information (selective exposure). In the present EEG study the neural mechanisms of the classic selective exposure effect were examined by investigating oscillatory brain responses to consistent vs. inconsistent information. Twenty participants made an economic decision and subsequently were exposed to 45 consistent and 45 inconsistent images concerning their decision. EEG was recorded from 31 electrodes and differences between oscillatory brain responses towards consistent and inconsistent information were examined. The main result was an increase of induced theta power (5-8Hz, 0-0.7s) in the consistent compared to the inconsistent condition at right temporo-parietal electrodes, as well as a corresponding increase of evoked theta power at frontal electrodes. Since theta oscillations are often observed during memory formation, we conclude that decision-consistent information triggers memory formation, whereas decision-inconsistent information seems not to do so. This finding supports the classic motivational perspective of Leon Festinger on the selective exposure effect.

  8. Selective defects of visual tracking in progressive supranuclear palsy (PSP): implications for mechanisms of motion vision.

    Science.gov (United States)

    Joshi, Anand C; Riley, David E; Mustari, Michael J; Cohen, Mark L; Leigh, R John

    2010-04-07

    Smooth ocular tracking of a moving visual stimulus comprises a range of responses that encompass the ocular following response (OFR), a pre-attentive, short-latency mechanism, and smooth pursuit, which directs the retinal fovea at the moving stimulus. In order to determine how interdependent these two forms of ocular tracking are, we studied vertical OFR in progressive supranuclear palsy (PSP), a parkinsonian disorder in which vertical smooth pursuit is known to be impaired. We measured eye movements of 9 patients with PSP and 12 healthy control subjects. Subjects viewed vertically moving sine-wave gratings that had a temporal frequency of 16.7 Hz, contrast of 32%, and spatial frequencies of 0.17, 0.27 or 0.44 cycles/degree. We measured OFR amplitude as change in eye position in the 70-150 ms, open-loop interval following stimulus onset. Vertical smooth pursuit was studied as subjects attempted to track a 0.27 cycles/degree grating moving sinusoidally through several cycles at frequencies between 0.1 and 2.5 Hz. We found that OFR amplitude, and its dependence on spatial frequency, was similar in PSP patients (group mean 0.10 degree) and control subjects (0.11 degree), but the latency to onset of OFR was greater for PSP patients (group mean 99 ms) than control subjects (90 ms). When OFR amplitude was re-measured, taking into account the increased latency in PSP patients, there was still no difference from control subjects. We confirmed that smooth pursuit was consistently impaired in PSP; group mean tracking gain at 0.7 Hz was 0.29 for PSP patients and 0.63 for controls. Neither PSP patients nor control subjects showed any correlation between OFR amplitude and smooth-pursuit gain. We propose that OFR is spared because it is generated by low-level motion processing that is dependent on posterior cerebral cortex, which is less affected in PSP. Conversely, smooth pursuit depends more on projections from frontal cortex to the pontine nuclei, both of which are involved

  9. Modularity beyond Perception: Evidence from the PRP Paradigm

    Science.gov (United States)

    Magen, Hagit; Cohen, Asher

    2010-01-01

    The Dimension Action (DA) model asserts that the visual system is modular, and that each task involves multiple-response mechanisms rather than a unitary-response selection mechanism. The model has been supported by evidence from single-task interference paradigms. We use the psychological refractory period paradigm and show that dual-task…

  10. Mechanism of N2O formation during the low-temperature selective catalytic reduction of NO with NH3 over Mn-Fe spinel.

    Science.gov (United States)

    Yang, Shijian; Xiong, Shangchao; Liao, Yong; Xiao, Xin; Qi, Feihong; Peng, Yue; Fu, Yuwu; Shan, Wenpo; Li, Junhua

    2014-09-02

    The mechanism of N2O formation during the low-temperature selective catalytic reduction reaction (SCR) over Mn-Fe spinel was studied. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and transient reaction studies demonstrated that the Eley-Rideal mechanism (i.e., the reaction of adsorbed NH3 species with gaseous NO) and the Langmuir-Hinshelwood mechanism (i.e., the reaction of adsorbed NH3 species with adsorbed NOx species) both contributed to N2O formation. However, N2O selectivity of NO reduction over Mn-Fe spinel through the Langmuir-Hinshelwood mechanism was much less than that through the Eley-Rideal mechanism. The ratio of NO reduction over Mn-Fe spinel through the Langmuir-Hinshelwood mechanism remarkably increased; therefore, N2O selectivity of NO reduction over Mn-Fe spinel decreased with the decrease of the gas hourly space velocity (GHSV). As the gaseous NH3 concentration increased, N2O selectivity of NO reduction over Mn-Fe spinel increased because of the promotion of NO reduction through the Eley-Rideal mechanism. Meanwhile, N2O selectivity of NO reduction over Mn-Fe spinel decreased with the increase of the gaseous NO concentration because the formation of NH on Mn-Fe spinel was restrained. Therefore, N2O selectivity of NO reduction over Mn-Fe spinel was related to the GHSV and concentrations of reactants.

  11. A new mechanism shapes the naïve CD8(+) T cell repertoire: the selection for full diversity.

    Science.gov (United States)

    Gonçalves, Pedro; Ferrarini, Marco; Molina-Paris, Carmen; Lythe, Grant; Vasseur, Florence; Lim, Annik; Rocha, Benedita; Azogui, Orly

    2017-05-01

    During thymic T cell differentiation, TCR repertoires are shaped by negative, positive and agonist selection. In the thymus and in the periphery, repertoires are also shaped by strong inter-clonal and intra-clonal competition to survive death by neglect. Understanding the impact of these events on the T cell repertoire requires direct evaluation of TCR expression in peripheral naïve T cells. Several studies have evaluated TCR diversity, with contradictory results. Some of these studies had intrinsic technical limitations since they used material obtained from T cell pools, preventing the direct evaluation of clonal sizes. Indeed with these approaches, identical TCRs may correspond to different cells expressing the same receptor, or to several amplicons from the same T cell. We here overcame this limitation by evaluating TCRB expression in individual naïve CD8(+) T cells. Of the 2269 Tcrb sequences we obtained from 13 mice, 99% were unique. Mathematical analysis of the data showed that the average number of naïve peripheral CD8(+) T cells expressing the same TCRB is 1.1 cell. Since TCRA co-expression studies could only increase repertoire diversity, these results reveal that the number of naïve T cells with unique TCRs approaches the number of naïve cells. Since thymocytes undergo multiple rounds of divisions after TCRB rearrangement and 3-5% of thymocytes survive thymic selection events the number of cells expressing the same TCRB was expected to be much higher. Thus, these results suggest a new repertoire selection mechanism, which strongly selects for full TCRB diversity.

  12. Oxygen Ion Conduction in Oxide Materials: Selected Examples and Basic Mechanisms

    Directory of Open Access Journals (Sweden)

    Traqueia, L. S. M.

    2006-06-01

    Full Text Available Oxygen ion conductors with most symmetrical structures such as fluorite- and perovskite-related phases, rely on the mobility of oxygen vacancies. High-performance electrolytes, namely with the apatite type structure, recently developed, show dominant interstitial transport. In order to assess basic composition-conductivity relationships in a fluorite-derived C-type cubic structure with high tolerance to different types of oxygen defects, a series of Y2O3-based materials were studied by impedance spectroscopy in air in the range 700-1000oC. Yttria doped with CaO exhibits reasonably high ionic conduction via the vacancy mechanism. Samples doped with ZrO2 and HfO2 possess oxygen interstitials as dominant defects, but show poor ionic conductivity when compared to Ca-doped materials. These tendencies, known for other fluorite-related phases such as pyrochlores, are opposite to those observed for apatite- and K2NiF4-type structures. Comparison of ionic conductivity levels in various oxide materials suggests that fast interstitial migration may be expected for complex multicomponent materials where the ion transport occurs in lattice fragments with high bond ionicity. Furthermore, conduction-affecting stereological parameters, to a great extent, depend on the relaxation of covalent fragments.

    Los conductores iónicos de oxígeno con estructuras más simétricas como fluorita y perovsquita dependen de la movilidad de las vacantes de oxígeno. Se han desarrollado recientemente electrolitos con elevadas prestaciones, los llamados de estructura tipo apatito, que muestran transporte intersticial dominante. Con el objeto de establecer las relaciones básicas entre composición y conductividad en una estructura cúbica tipo-C derivada de la fluorita con alta tolerancia a diferentes defectos de oxígeno, se han estudiado materiales basados en Y2O3 por espectroscopía de impedancia en el rango de temperaturas entre 700 y 1000ºC. La ytria dopada con Ca

  13. The incidence of pressure ulcer in patients on mechanical ventilation andeffects of selected risk factors on pressure ulcer development.

    Science.gov (United States)

    Karayurt, Özgül; Akyol, Özay; Kılıçaslan, Necmiye; Akgün, Nuray; Sargın, Ümran; Kondakçı, Melike; Ekinci, Hanım; Sarı, Neslihan

    2016-11-17

    This study aimed to determine the incidence of pressure ulcers in patients on mechanical ventilation and selected risk factors likely to play a role in pressure ulcer development. The study included 110 patients recruited from an anesthesia critical care unit of a university hospital. Data were collected with a demographic and clinical characteristics form. The form was composed of questions about demographic characteristics and clinical features including diagnosis, duration of mechanical ventilation, general well-being, oxygenation, perfusion, and skin condition. The incidence of pressure ulcer was 15.5%. Duration of mechanical ventilation was longer and the body mass index was higher in patients developing pressure ulcers than in those without pressure ulcers. Additionally, 90.11% of patients with pressure ulcers had edema and 82.35% of patients with pressure ulcers received vasopressin. The patients with pressure ulcers had higher PH levels, lower PaO2 levels, higher PCO2 levels, lower SaO2 levels, and higher urine output. It can be recommended that nurses and other health professionals should be aware of factors playing a role in pressure ulcer development and should be able to conduct appropriate interventions to prevent pressure ulcers.

  14. Microstructures and mechanical properties of Co-29Cr-6Mo alloy fabricated by selective laser melting process for dental applications.

    Science.gov (United States)

    Takaichi, Atsushi; Suyalatu; Nakamoto, Takayuki; Joko, Natsuka; Nomura, Naoyuki; Tsutsumi, Yusuke; Migita, Satoshi; Doi, Hisashi; Kurosu, Shingo; Chiba, Akihiko; Wakabayashi, Noriyuki; Igarashi, Yoshimasa; Hanawa, Takao

    2013-05-01

    The selective laser melting (SLM) process was applied to a Co-29Cr-6Mo alloy, and its microstructure, mechanical properties, and metal elution were investigated to determine whether the fabrication process is suitable for dental applications. The microstructure was evaluated using scanning electron microscopy with energy-dispersed X-ray spectroscopy (SEM-EDS), X-ray diffractometry (XRD), and electron back-scattered diffraction pattern analysis. The mechanical properties were evaluated using a tensile test. Dense builds were obtained when the input energy of the laser scan was higher than 400 J mm⁻³, whereas porous builds were formed when the input energy was lower than 150 J mm⁻³. The microstructure obtained was unique with fine cellular dendrites in the elongated grains parallel to the building direction. The γ phase was dominant in the build and its preferential orientation was confirmed along the building direction, which was clearly observed for the builds fabricated at lower input energy. Although the mechanical anisotropy was confirmed in the SLM builds due to the unique microstructure, the yield strength, UTS, and elongation were higher than those of the as-cast alloy and satisfied the type 5 criteria in ISO22764. Metal elution from the SLM build was smaller than that of the as-cast alloy, and thus, the SLM process for the Co-29Cr-6Mo alloy is a promising candidate for fabricating dental devices.

  15. Structural and mechanical evaluations of a topology optimized titanium interbody fusion cage fabricated by selective laser melting process.

    Science.gov (United States)

    Lin, Chia-Ying; Wirtz, Tobias; LaMarca, Frank; Hollister, Scott J

    2007-11-01

    A topology optimized lumbar interbody fusion cage was made of Ti-Al6-V4 alloy by the rapid prototyping process of selective laser melting (SLM) to reproduce designed microstructure features. Radiographic characterizations and the mechanical properties were investigated to determine how the structural characteristics of the fabricated cage were reproduced from design characteristics using micro-computed tomography scanning. The mechanical modulus of the designed cage was also measured to compare with tantalum, a widely used porous metal. The designed microstructures can be clearly seen in the micrographs of the micro-CT and scanning electron microscopy examinations, showing the SLM process can reproduce intricate microscopic features from the original designs. No imaging artifacts from micro-CT were found. The average compressive modulus of the tested caged was 2.97+/-0.90 GPa, which is comparable with the reported porous tantalum modulus of 3 GPa and falls between that of cortical bone (15 GPa) and trabecular bone (0.1-0.5 GPa). The new porous Ti-6Al-4V optimal-structure cage fabricated by SLM process gave consistent mechanical properties without artifactual distortion in the imaging modalities and thus it can be a promising alternative as a porous implant for spine fusion.

  16. Microstructures and Mechanical Properties of Ti6Al4V Parts Fabricated by Selective Laser Melting and Electron Beam Melting

    Science.gov (United States)

    Rafi, H. K.; Karthik, N. V.; Gong, Haijun; Starr, Thomas L.; Stucker, Brent E.

    2013-12-01

    This work compares two metal additive manufacturing processes, selective laser melting (SLM) and electron beam melting (EBM), based on microstructural and mechanical property evaluation of Ti6Al4V parts produced by these two processes. Tensile and fatigue bars conforming to ASTM standards were fabricated using Ti6Al4V ELI grade material. Microstructural evolution was studied using optical and scanning electron microscopy. Tensile and fatigue tests were carried out to understand mechanical properties and to correlate them with the corresponding microstructure. The results show differences in microstructural evolution between SLM and EBM processed Ti6Al4V and their influence on mechanical properties. The microstructure of SLM processed parts were composed of an α' martensitic phase, whereas the EBM processed parts contain primarily α and a small amount of β phase. Consequently, there are differences in tensile and fatigue properties between SLM- and EBM-produced Ti6Al4V parts. The differences are related to the cooling rates experienced as a consequence of the processing conditions associated with SLM and EBM processes.

  17. Positive Selection of Deleterious Alleles through Interaction with a Sex-Ratio Suppressor Gene in African Buffalo: A Plausible New Mechanism for a High Frequency Anomaly

    NARCIS (Netherlands)

    Hooft, van W.F.; Greyling, B.J.; Getz, W.M.; Helden, P.D.; Zwaan, B.J.; Bastos, A.D.S.

    2015-01-01

    Although generally rare, deleterious alleles can become common through genetic drift, hitchhiking or reductions in selective constraints. Here we present a possible new mechanism that explains the attainment of high frequencies of deleterious alleles in the African buffalo (Syncerus caffer)

  18. DMPD: Mechanisms of selection mediated by interleukin-7, the preBCR, and hemokinin-1during B-cell development. [Dynamic Macrophage Pathway CSML Database

    Lifescience Database Archive (English)

    Full Text Available 14962188 Mechanisms of selection mediated by interleukin-7, the preBCR, and hemokinin-1during B-cell develop...ng) (.svg) (.html) (.csml) Show Mechanisms of selection mediated by interleukin-7, the preBCR, and hemokinin-1during B-cell develop...ated by interleukin-7, the preBCR, and hemokinin-1during B-cell development. Authors Milne CD, Fleming HE, Z

  19. The fragile Y hypothesis: Y chromosome aneuploidy as a selective pressure in sex chromosome and meiotic mechanism evolution.

    Science.gov (United States)

    Blackmon, Heath; Demuth, Jeffery P

    2015-09-01

    Loss of the Y-chromosome is a common feature of species with chromosomal sex determination. However, our understanding of why some lineages frequently lose Y-chromosomes while others do not is limited. The fragile Y hypothesis proposes that in species with chiasmatic meiosis the rate of Y-chromosome aneuploidy and the size of the recombining region have a negative correlation. The fragile Y hypothesis provides a number of novel insights not possible under traditional models. Specifically, increased rates of Y aneuploidy may impose positive selection for (i) gene movement off the Y; (ii) translocations and fusions which expand the recombining region; and (iii) alternative meiotic segregation mechanisms (achiasmatic or asynaptic). These insights as well as existing evidence for the frequency of Y-chromosome aneuploidy raise doubt about the prospects for long-term retention of the human Y-chromosome despite recent evidence for stable gene content in older non-recombining regions.

  20. The chemistry of simple alkene molecules on Si(100)c(4 × 2): The mechanism of cycloaddition and their selectivities

    Science.gov (United States)

    Akagi, Kazuto; Yoshinobu, Jun

    2016-10-01

    The chemistry of simple alkene molecules on the Si(100) surface is reviewed with the newly-produced visual presentation by theoretical calculations. The early pioneering studies by the Kyoto Group and Pittsburgh group reported the di-σ bond formation and the precursor-mediated chemisorption for acetylene and ethylene on Si(100), respectively. Thereafter, these studies have been stimulating various studies of organic molecules on Si surfaces. Our recent studies have observed the precursor states for alkene chemisorption and elucidated the microscopic mechanisms of the di-σ bond formation (cycloaddition) with the help of theoretical calculations; the site-, stereo- and regio-selective chemisorption of simple alkene molecules on Si(100)c(4 × 2) has been established.

  1. The Influence of Selective Laser Melting Parameters on Density and Mechanical Properties of AlSi10Mg

    Directory of Open Access Journals (Sweden)

    Raus A. A.

    2016-01-01

    Full Text Available Selective Laser Melting (SLM is one of the most effective powder bed technique in the additive Manufacturing (AM which able to fabricate functional metal parts directly from 3D Computer Aided Design (CAD file data. In this paper, the influence of SLM parameters, such as laser power, scanning speed and hatching distance on the density of AlSi10Mg samples are investigated using one factor at a time (OFAT. Furthermore, the optimum results are used to fabricate samples for hardness, tensile strength, and impact toughness test. It is revealed that AlSi10Mg parts fabricated by SLM achieving the best density of 99.13% at the value of 350 watts laser power, 1650 mm/s scanning speed and hatching distance 0.13mm, whereby resulted comparable and even better mechanical properties to those of conventionally HDPC A360F and HDPC A360T6 alloys although without any comprehensive post processing methods.

  2. The analysis of the mechanical properties of F75 Co-Cr alloy for use in selective laser melting (SLM manufacturing of removable partial dentures (RPD

    Directory of Open Access Journals (Sweden)

    D. Jevremovic

    2012-04-01

    Full Text Available The presented work discusses the applicability of the selective laser melting technique (SLM in manufacture of removable partial denture (RPD frameworks with the emphasis on material properties. The paper presents initial results of a conducted test of the mechanical properties of the F75 Co-Cr dental alloy used with selective laser melting.

  3. Detection of Thermal Sublethal Injury in Escherichia coli via the Selective Medium Plating Technique: Mechanisms and Improvements

    Science.gov (United States)

    Espina, Laura; García-Gonzalo, Diego; Pagán, Rafael

    2016-01-01

    In food preservation, the synergistic combination of different technologies aims to maximize the total lethality of the process and minimize the intensity of each hurdle. This is especially the case when at least one of the treatments can cause sublethal (reparable) injury in a great proportion of the population, so that sublethally injured cells can end up being entirely inactivated by the other hurdle(s). The selective medium plating technique (SMPT) is extensively used to enumerate bacterial sublethal injury after inimical treatments, being sodium chloride added to the recovery medium to detect damaged bacterial envelopes. However, little work has been done to explain the reasons for the inability of sublethally injured cells to outgrow in selective agar media, whereas they are able to grow in non-selective agar. In the present paper, the performance of SMPT on Escherichia coli cells after heat treatments is explored by applying different selective agents in the recovery media, using mutants lacking factors involved in osmoregulation, and also by examining the integrity of the cytoplasmic membrane. In view of the results, the possibility of a specific toxic effect of Na+ as the main mechanism under SMPT was discarded, since the same level of sublethal injury was detected using KCl instead of NaCl. The synthesis of the osmoprotectant trehalose determined the maximum osmotolerance of intact cells to the selective agents, but was not crucial in the quantification of sublethal injury. Moreover, for the first time, the extent of sublethal injury detected via SMPT was directly correlated with the physical loss of integrity of the cell membrane in 99.999% of the initial population. This was achieved through statistical analysis of flow cytometry data using propidium iodide-exclusion technique when that dye was added before thermal treatments. The present work confirms the adequacy of SMPT as a tool for detecting the occurrence and quantity of sublethally injured cells

  4. Methanol and 2-methyl-1-propanol (isobutanol) coupling to ethers and dehydration over Nafion H: Selectivity, kinetics, and mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Nunan, J.G.; Klier, K.; Herman, R.G. (Lehigh Univ., Bethlehem, PA (United States))

    1993-02-01

    The dehydration of a mixture of methanol and isobutanol has been studied over the sulfonic acid Nafion H catalyst. Dehydration products consisted of dimethyl ether (DME), di-isobutyl ether (DIBE), methyl-isobutyl ether (MIBE), butenes, octenes, and traces of methyl-tertiarybutyl ether (MTBE). At low temperatures and high alcohol pressures (P [ge] 150 kPa), the dehydration product slate was dominated by ether formation with selectivity within the ethers significantly in favor of the mixed ether, MIBE. The rates of ether and butene formation as a function of alcohol pressure could be described by Langmuir-Hinshelwood kinetics in which competitive adsorption of the two alcohols on the surface -SO[sub 3]H sites was the dominant feature. The kinetics of isobutanol dehydration to isobutene were consistent with a dual-site mechanism involving the cooperative action of a free surface -SO[sub 3]H site and an adjacent adsorbed alcohol molecule. Dehydration to ethers was consistent with the reaction of two adsorbed alcohols, also by a dual-site mechanism. As a consequence, dehydration to symmetric ethers showed saturation-type kinetics as a function of alcohol pressure, while the rate of isobutene formation went through a distinct maximum. Due to the competitive adsorption of methanol and isobutanol, the mixed ether MIBE was formed at a maximum rate with an optimum ratio of partial pressures of the two alcohols. The high selectivity to MIBE was explained by stronger adsorption of isobutanol on the catalyst surface as compared to methanol. The absence of MTBE and the predominance of products such as MIBE and 2,5-dimethylhexene suggests that dehydration to give free carbenium ions that subsequently rearrange to the more stable tertiary intermediate was not occurring. It was proposed that the alcohols react with the -SO[sub 3]H groups to give oxonium ions or esters. These intermediates couple to give the product ethers or octenes. 24 refs., 13 figs., 1 tab.

  5. Design of RC frames for pre-selected collapse mechanism and target displacement using energy–balance

    Indian Academy of Sciences (India)

    Onur Merter; Taner Ucar

    2014-06-01

    In earthquake-prone countries, structures may be exposed to several seismic loads in any stage of building’s life. It is expected that the structures designed by engineers will show ductile behaviour under the effect of vertical and lateral loads and remain stable without making a sudden collapse. In consequence of nonlinear behaviour, plastic hinges are expected to form in structural members which are under the effect of external loads. Earthquake input energy is dissipated in plastic hinges, so, structures behave ductile. In this study, total energy of RC frames is calculated and the energy–based base shear force is determined by equating the total internal energy to the work done by external lateral design forces for pre-selected target displacement and collapse mechanism. Sections of RC frames are controlled if they can resist the calculated design lateral loads or not. If the capacity of the sections cannot withstand the external design loads, the design is rearranged and new sections are chosen. Beam and column sections that can resist the design loads securely are accepted as final sections of the energy–based design methodology. Pre-selected target displacement for desired performance level is checked using the results of nonlinear analyses. The results of the presented design methodology in this study are compatible with the results of nonlinear analyses.

  6. Effective adsorption of Cr(VI) on mesoporous Fe-functionalized Akadama clay: Optimization, selectivity, and mechanism

    Science.gov (United States)

    Ji, Min; Su, Xiao; Zhao, Yingxin; Qi, Wenfang; Wang, Yue; Chen, Guanyi; Zhang, Zhenya

    2015-07-01

    A Japanese volcanic soil, Akadama clay, was functionalized with metal salts (FeCl3, AlCl3, CaCl2, MgCl2, MnCl2) and tested for Cr(VI) removal from aqueous solution. FeCl3 was selected as the most efficient activation agent. To quantitatively investigate the independent or interactive contribution of influencing factors (solution pH, contact time, adsorbent dose, and initial concentration) to Cr(VI) adsorption onto Fe-functionalized AC (FFAC), factorial experimental design was applied. Results showed initial concentration contributed most to adsorption capacity of Cr(VI) (53.17%), followed by adsorbent dosage (45.15%), contact time (1.12%) and the interaction between adsorbent dosage and contact time (0.37%). The adsorption showed little dependence on solution pH from 2 to 8. Adsorption selectivity of Cr(VI) was evaluated through analyzing distribution coefficient, electrical double layer theory, as well as the valence and Pauling's ionic radii of co-existing anions (Cl-, SO42-, and PO43-). EDX and XPS analyses demonstrated the adsorption mechanism of Cr(VI) onto FFAC included electrostatic attraction, ligant exchange, and redox reaction. Improved treatment for tannery wastewater shows a potential application of FFAC as a cost-effective adsorbent for Cr(VI) removal.

  7. A Change in the Ion Selectivity of Ligand-Gated Ion Channels Provides a Mechanism to Switch Behavior.

    Directory of Open Access Journals (Sweden)

    Jennifer K Pirri

    Full Text Available Behavioral output of neural networks depends on a delicate balance between excitatory and inhibitory synaptic connections. However, it is not known whether network formation and stability is constrained by the sign of synaptic connections between neurons within the network. Here we show that switching the sign of a synapse within a neural circuit can reverse the behavioral output. The inhibitory tyramine-gated chloride channel, LGC-55, induces head relaxation and inhibits forward locomotion during the Caenorhabditis elegans escape response. We switched the ion selectivity of an inhibitory LGC-55 anion channel to an excitatory LGC-55 cation channel. The engineered cation channel is properly trafficked in the native neural circuit and results in behavioral responses that are opposite to those produced by activation of the LGC-55 anion channel. Our findings indicate that switches in ion selectivity of ligand-gated ion channels (LGICs do not affect network connectivity or stability and may provide an evolutionary and a synthetic mechanism to change behavior.

  8. Mechanism of selective VEGF-A binding by neuropilin-1 reveals a basis for specific ligand inhibition.

    Directory of Open Access Journals (Sweden)

    Matthew W Parker

    Full Text Available Neuropilin (Nrp receptors function as essential cell surface receptors for the Vascular Endothelial Growth Factor (VEGF family of proangiogenic cytokines and the semaphorin 3 (Sema3 family of axon guidance molecules. There are two Nrp homologues, Nrp1 and Nrp2, which bind to both overlapping and distinct members of the VEGF and Sema3 family of molecules. Nrp1 specifically binds the VEGF-A(164/5 isoform, which is essential for developmental angiogenesis. We demonstrate that VEGF-A specific binding is governed by Nrp1 residues in the b1 coagulation factor domain surrounding the invariant Nrp C-terminal arginine binding pocket. Further, we show that Sema3F does not display the Nrp-specific binding to the b1 domain seen with VEGF-A. Engineered soluble Nrp receptor fragments that selectively sequester ligands from the active signaling complex are an attractive modality for selectively blocking the angiogenic and chemorepulsive functions of Nrp ligands. Utilizing the information on Nrp ligand binding specificity, we demonstrate Nrp constructs that specifically sequester Sema3 in the presence of VEGF-A. This establishes that unique mechanisms are used by Nrp receptors to mediate specific ligand binding and that these differences can be exploited to engineer soluble Nrp receptors with specificity for Sema3.

  9. Mechanical Properties and Microstructures of As Printed and Heat Treated Samples of Selective Laser Melted IN625 Alloy Powder

    Directory of Open Access Journals (Sweden)

    Srinivasan Raghavan

    2015-01-01

    Full Text Available The current study focusses in evaluating the mechanical properties (yield strength, ultimate tensile strength and elongation % and microstructures of as printed and heat treated tensile samples produced by Selective Laser Melting (SLM which is an Additive Manufacturing (AM technique. The as printed IN625 alloy exhibited good mechanical properties as compared to cast and wrought alloy, owing to fast cooling rates that give very fine dendritic/cellular structures during the SLM process. Standard solutionizing and precipitation hardening treatment was given to the SLM as printed samples. The as printed sample’s ductility increased from 30% elongation to 47% elongation with small drop in tensile strength from 878MPa to 836MPa. The increase of ductility after heat treatment was evident in the change of fracture morphology from long straight striations with dimple shape ductile like features in the as printed sample to mainly dimple shaped ductile-like fracture surface in the heat treated sample as observed in the FESEM.

  10. Effects of support acidity on the reaction mechanisms of selective catalytic reduction of NO by CH4 in excess oxygen

    Institute of Scientific and Technical Information of China (English)

    Shicheng XU; Junhua LI; Dong YANG; Jiming HAO

    2009-01-01

    The reaction mechanisms of selective catalytic reduction (SCR) of nitric oxide (NO) by methane (CH4)over solid superacid-based catalysts were proposed and testified by DRIFTS studies on transient reaction as well as by kinetic models. Catalysts derived from different supports would lead to different reaction pathways, and the acidity of solid superacid played an important role in determining the reaction mechanisms and the catalytic activities. Higher ratios of Bronsted acid sites to Lewis acid sites would lead to stronger oxidation of methane and then could facilitate the step of methane activation. Strong Bronsted acid sites would not necessarily lead to better catalytic performance, however, since the active surface NOy species and the corresponding reaction routes were determined by the overall acidity strength of the support.The reaction routes where NO2 moiety was engaged as an important intermediate involved moderate oxidation of methane, the rate of which could determine the overall activity. The reaction involving NO moiety was likely to be determined by the step of reduction of NO. Therefore, to enhance the SCR activity of solid superacid catalysts,reactions between appropriate couples of active NOy species and activated hydrocarbon intermediates should be realized by modification of the support acidity.

  11. Mosaic segmental uniparental isodisomy and progressive clonal selection: a common mechanism of late onset β-thalassemia major

    Science.gov (United States)

    Harteveld, Cornelis L.; Refaldi, Chiara; Giambona, Antonino; Ruivenkamp, Claudia A. L.; Hoffer, Mariëtte J. V.; Pijpe, Jeroen; De Knijff, Peter; Borgna-Pignatti, Caterina; Maggio, Aurelio; Cappellini, Maria D.; Giordano, Piero C.

    2013-01-01

    Genomic DNA of 3 patients, born as healthy carriers and developing a late-onset severe transfusion-dependent beta-thalassemia major was studied by high-density genome wide SNP array analysis. A mosaic loss of heterozygosity for almost the entire 11p was found, not attributable to deletions but involving mosaicism for segmental paternal isodisomy of 11p. Mitotic recombination leading to mosaic segmental uniparental isodisomy on chromosome 11p in multiple tissues has been described as a molecular disease mechanism for a subset of sporadic Beckwith-Wiedemann syndrome cases. A similar mechanism also seems to be involved in causing late-onset disease in carriers of recessive mutations in other genes located in 11p, such as late-onset beta-thalassemia major and sickle cell disease. We suggest that the loss of maternally imprinted IGF-2 and H19 genes may account for the selective advantage of hematopoietic cells containing this segmental paternal isodisomy of 11p carrying the β-thalassemia mutation. PMID:22983591

  12. Mechanics

    CERN Document Server

    Hartog, J P Den

    1961-01-01

    First published over 40 years ago, this work has achieved the status of a classic among introductory texts on mechanics. Den Hartog is known for his lively, discursive and often witty presentations of all the fundamental material of both statics and dynamics (and considerable more advanced material) in new, original ways that provide students with insights into mechanical relationships that other books do not always succeed in conveying. On the other hand, the work is so replete with engineering applications and actual design problems that it is as valuable as a reference to the practicing e

  13. Dissociative Ionization Mechanism and Appearance Energies in Adipic Acid Revealed by Imaging Photoelectron Photoion Coincidence, Selective Deuteration, and Calculations.

    Science.gov (United States)

    Heringa, Maarten F; Slowik, Jay G; Prévôt, André S H; Baltensperger, Urs; Hemberger, Patrick; Bodi, Andras

    2016-05-26

    Adipic acid, a model compound for oxygenated organic aerosol, has been studied at the VUV beamline of the Swiss Light Source. Internal energy selected cations were prepared by threshold photoionization using vacuum ultraviolet synchrotron radiation and imaging photoelectron photoion coincidence spectroscopy (iPEPICO). The threshold photoelectron spectrum yields a vertical ionization energy (IE) of 10.5 eV, significantly above the calculated adiabatic IE of 8.6 eV. The cationic minimum is accessible after vertical ionization by H-transfer from one of the γ-carbons to a carbonyl oxygen and is sufficiently energetic to decay by water loss at the ionization onset. The slope of the breakdown curves, quantum chemical calculations, and selective deuteration of the carboxylic hydrogens establish the dissociative photoionization mechanism. After ionization, one γ-methylene hydrogen and the two carboxylic hydrogens are randomized prior to H2O loss. On the basis of the deuteration degree in the H2O + CO-loss product at higher energies, a direct water-loss channel without complete randomization also exists. The breakdown diagram and center of gravity of the H2O + CO-loss peak were modeled to obtain 0 K appearance energies of 10.77, 10.32, and 11.53 eV for H2O + CO loss, CH2COOH loss, and H2O + CH2COOH loss from adipic acid. These agree well with the CBS-QB3 calculated values of 10.68, 10.45, and 11.57 eV, respectively, which shows that threshold photoionization can yield energetics data as long as the dissociation is statistical, even when the parent ion cannot be observed. The results can be used as a starting point for a deeper understanding of the ionization and low-energy fragmentation of organic aerosol components.

  14. The mechanism of selecting priority options and sequence of solutions to ensure the safety of towing caravan navigation

    Directory of Open Access Journals (Sweden)

    Brazhnyy A. I.

    2016-12-01

    Full Text Available The paper considers navigational safety movement of the towed object and tugboat. Some methods of alternatives choice of decision-maker persons (DMP to manage the safety of towing a caravan have been presented. Examples of navigation safety conditions, their operational relationship, critical and emergency character with respect to the predetermined position of the band have been given; the sequence of forming actions of the algorithm based on an assessment of possible losses for the sustainability of the towing operation has been proposed. The aim is to research and develop a sequence of logical conclusions for forming some mechanism to take corrective action when navigating the composition of the output of the towing caravan of navigation stable security situation for its return to the original settings of sustainable movement. To assess the risks of navigation functions the risk analysis method has been used, with further selection of management synthesized for towing process, taking into account the possible reaction of the "human element". For estimations well-known in the probability theory and mathematical statistics methods have been used. An iterative mathematical model of the tow caravan considering the posterior distribution of parameters caravan phase coordinates for the given cases has been built. The possibility of resource losses when choosing the optimal alternative has been investigated. It has been established that while selecting and adopting a single decision under risk, including alternatives to the losses, one can always find such an alternative which is able to ensure the management of the caravan navigational safety decreasing the probability of large losses. When operating the navigation state of towing caravan one should choose the optimal alternative that minimizes the possibility of the maximum cost, and then based on it to choose (with incomplete awareness of decision-makers optimal sequence of controls which in turn

  15. Two additive mechanisms impair the differentiation of 'substrate-selective' p38 inhibitors from classical p38 inhibitors in vitro

    Directory of Open Access Journals (Sweden)

    Seidl Kelly M

    2010-03-01

    Full Text Available Abstract Background The success of anti-TNF biologics for the treatment of rheumatoid arthritis has highlighted the importance of understanding the intracellular pathways that regulate TNF production in the quest for an orally-available small molecule inhibitor. p38 is known to strongly regulate TNF production via MK2. The failure of several p38 inhibitors in the clinic suggests the importance of other downstream pathways in normal cell function. Recent work has described a 'substrate-selective' p38 inhibitor that is able to preferentially block the activity of p38 against one substrate (MK2 versus another (ATF2. Using a combined experimental and computational approach, we have examined this mechanism in greater detail for two p38 substrates, MK2 and ATF2. Results We found that in a dual (MK2 and ATF2 substrate assay, MK2-p38 interaction reduced the activity of p38 against ATF2. We further constructed a detailed kinetic mechanistic model of p38 phosphorylation in the presence of multiple substrates and successfully predicted the performance of classical and so-called 'substrate-selective' p38 inhibitors in the dual substrate assay. Importantly, it was found that excess MK2 results in a stoichiometric effect in which the formation of p38-MK2-inhibitor complex prevents the phosphorylation of ATF2, despite the preference of the compound for the p38-MK2 complex over the p38-ATF2 complex. MK2 and p38 protein expression levels were quantified in U937, Thp-1 and PBMCs and found that [MK2] > [p38]. Conclusion Our integrated mechanistic modeling and experimental validation provides an example of how systems biology approaches can be applied to drug discovery and provide a basis for decision-making with limited chemical matter. We find that, given our current understanding, it is unlikely that 'substrate-selective' inhibitors of p38 will work as originally intended when placed in the context of more complex cellular environments, largely due to a

  16. The Combination of Direct and Confined Laser Ablation Mechanisms for the Selective Structuring of Thin Silicon Nitride Layers

    Science.gov (United States)

    Rapp, Stephan; Heinrich, Gerrit; Domke, Matthias; Huber, Heinz P.

    In the production process of microelectronic devices and high efficiency solar cells, local openings in thin dielectric layers are required. Instead of photolithographic, laser based processing enables to open these dielectric layers locally in a low-cost mass production step. In this work, thin silicon nitride layers deposited on planar silicon wafers are processed by single infrared Gaussian shaped 660 fs laser pulses. The transparent silicon nitride layer, becoming absorptive at fluences higher than 0.3 J/cm2, is selectively removed by confined ablation at fluences below that value. At pulse peak fluences exceeding 1.0 J/cm2 a "SiNx island"is created by direct ablation in the spot center. In this article, theselective SiNx ablation by a combination of confined and direct laser ablation at the medium pulse peak fluence of 0.5 J/cm2 is investigated. To clarify the influence of the nonlinear absorption in the pulse center, the ablation behavior is investigated by time- and space-resolved pump-probe microscopy experiments. The results showphase changes in the silicon and in the silicon nitride in the first picoseconds after excitation, the ablation onset at around 10 ps and the subsequent mechanical materialmotion after a few nanoseconds. The actual silicon nitride layer removal starts after around 10 ns, whereas confined ablation processes are the driving mechanisms even in the nonlinearly absorbing spot center. A comparison of the energetic ablation efficiency of the SiNx layer system to further dielectric thin films shows no detrimental influence of the nonlinear absorbance.

  17. A selection fit mechanism in BMP receptor IA as a possible source for BMP ligand-receptor promiscuity.

    Directory of Open Access Journals (Sweden)

    Stefan Harth

    Full Text Available BACKGROUND: Members of the TGF-β superfamily are characterized by a highly promiscuous ligand-receptor interaction as is readily apparent from the numeral discrepancy of only seven type I and five type II receptors available for more than 40 ligands. Structural and functional studies have been used to address the question of how specific signals can be deduced from a limited number of receptor combinations and to unravel the molecular mechanisms underlying the protein-protein recognition that allow such limited specificity. PRINCIPAL FINDINGS: In this study we have investigated how an antigen binding antibody fragment (Fab raised against the extracellular domain of the BMP receptor type IA (BMPR-IA recognizes the receptor's BMP-2 binding epitope and thereby neutralizes BMP-2 receptor activation. The crystal structure of the complex of the BMPR-IA ectodomain bound to the Fab AbD1556 revealed that the contact surface of BMPR-IA overlaps extensively with the contact surface for BMP-2 interaction. Although the structural epitopes of BMPR-IA to both binding partners coincides, the structures of BMPR-IA in the two complexes differ significantly. In contrast to the structural differences, alanine-scanning mutagenesis of BMPR-IA showed that the functional determinants for binding to the antibody and BMP-2 are almost identical. CONCLUSIONS: Comparing the structures of BMPR-IA bound to BMP-2 or bound to the Fab AbD1556 with the structure of unbound BMPR-IA shows that binding of BMPR-IA to its interaction partners follows a selection fit mechanism, possibly indicating that the ligand promiscuity of BMPR-IA is inherently encoded by structural adaptability. The functional and structural analysis of the BMPR-IA binding antibody AbD1556 mimicking the BMP-2 binding epitope may thus pave the way for the design of low-molecular weight synthetic receptor binders/inhibitors.

  18. In vitro spectrum of pexiganan activity when tested against pathogens from diabetic foot infections and with selected resistance mechanisms.

    Science.gov (United States)

    Flamm, Robert K; Rhomberg, Paul R; Simpson, Katie M; Farrell, David J; Sader, Helio S; Jones, Ronald N

    2015-03-01

    Pexiganan, a 22-amino-acid synthetic cationic peptide, is currently in phase 3 clinical trials as a topical antimicrobial agent for the treatment of mild infections associated with diabetic foot ulcers. Bacterial isolates from the 2013 SENTRY Antimicrobial Surveillance Program designated as pathogens from diabetic foot infections (DFI) and Gram-negative and -positive pathogens from various infection types that harbored selected resistance mechanisms/phenotypes were tested against pexiganan in reference cation-adjusted Mueller-Hinton broth. The MIC50 and MIC90 against all organisms tested from DFI were 16 and 32 μg/ml, respectively. Escherichia coli, Klebsiella pneumoniae, Citrobacter koseri, Enterobacter cloacae, Acinetobacter species, and Pseudomonas aeruginosa MIC values ranged from 8 to 16 μg/ml. Pexiganan MIC values among Staphylococcus aureus (methicillin-resistant S. aureus [MRSA] and methicillin-susceptible S. aureus [MSSA]), beta-hemolytic streptococci, and Enterococcus faecium ranged from 8 to 32 μg/ml. Pexiganan activity was not adversely affected for members of the family Enterobacteriaceae or P. aeruginosa that produced β-lactamases or resistance mechanisms to other commonly used antimicrobial agents. Decreased susceptibility to vancomycin did not affect pexiganan activity against S. aureus or E. faecium. Enterococcus faecalis appears to be intrinsically less susceptible to pexiganan (MIC, 32 to 256 μg/ml). The "all organism" MIC90 of 32 μg/ml for pexiganan in this study was >250-fold below the pexiganan concentration in the cream/delivery vehicle being developed for topical use. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

  19. Workers select mates for queens: a possible mechanism of gene flow restriction between supercolonies of the invasive Argentine ant

    Science.gov (United States)

    Sunamura, Eiriki; Hoshizaki, Sugihiko; Sakamoto, Hironori; Fujii, Takeshi; Nishisue, Koji; Suzuki, Shun; Terayama, Mamoru; Ishikawa, Yukio; Tatsuki, Sadahiro

    2011-05-01

    Some invasive ants form large networks of mutually non-aggressive nests, i.e., supercolonies. The Argentine ant Linepithema humile forms much larger supercolonies in introduced ranges than in its native range. In both cases, it has been shown that little gene flow occurs between supercolonies of this species, though the mechanism of gene flow restriction is unknown. In this species, queens do not undertake nuptial flight, and males have to travel to foreign nests and cope with workers before gaining access to alien queens. In this study, we hypothesized that male Argentine ants receive interference from workers of alien supercolonies. To test this hypothesis, we conducted behavioral and chemical experiments using ants from two supercolonies in Japan. Workers attacked males from alien supercolonies but not those from their own supercolonies. The level of aggression against alien males was similar to that against alien workers. The frequency of severe aggression against alien males increased as the number of recipient workers increased. Cuticular hydrocarbon profiles, which serve as cues for nestmate recognition, of workers and males from the same supercolony were very similar. Workers are likely to distinguish alien males from males of their own supercolony using the profiles. It is predicted that males are subject to considerable aggression from workers when they intrude into the nests of alien supercolonies. This may be a mechanism underlying the restricted gene flow between supercolonies of Argentine ants. The Argentine ant may possess a distinctive reproductive system, where workers participate in selecting mates for their queens. We argue that the aggression of workers against alien males is a novel form of reproductive interference.

  20. The Lande-Kirkpatrick mechanism is the null model of evolution by intersexual selection: implications for meaning, honesty, and design in intersexual signals.

    Science.gov (United States)

    Prum, Richard O

    2010-11-01

    The Fisher-inspired, arbitrary intersexual selection models of Lande (1981) and Kirkpatrick (1982), including both stable and unstable equilibrium conditions, provide the appropriate null model for the evolution of traits and preferences by intersexual selection. Like the Hardy–Weinberg equilibrium, the Lande–Kirkpatrick (LK) mechanism arises as an intrinsic consequence of genetic variation in trait and preference in the absence of other evolutionary forces. The LK mechanism is equivalent to other intersexual selection mechanisms in the absence of additional selection on preference and with additional trait-viability and preference-viability correlations equal to zero. The LK null model predicts the evolution of arbitrary display traits that are neither honest nor dishonest, indicate nothing other than mating availability, and lack any meaning or design other than their potential to correspond to mating preferences. The current standard for demonstrating an arbitrary trait is impossible to meet because it requires proof of the null hypothesis. The LK null model makes distinct predictions about the evolvability of traits and preferences. Examples of recent intersexual selection research document the confirmationist pitfalls of lacking a null model. Incorporation of the LK null into intersexual selection will contribute to serious examination of the extent to which natural selection on preferences shapes signals.

  1. Ultrafast pump-probe microscopy reveals the mechanism of selective fs laser structuring of transparent thin films for maskless micropatterning

    Science.gov (United States)

    Rapp, Stephan; Rosenberger, Janosch; Domke, Matthias; Heise, Gerhard; Huber, Heinz P.; Schmidt, Michael

    2014-01-01

    Maskless patterning of biocompatible Ta2O5/Pt/glass sensor chips can be realized by ultra-short laser pulse ablation. At a fluence of 0.2 J/cm2, the thin Ta2O5 film is selectively lifted-off by indirectly-induced ablation at laser wavelenghts where the Ta2O5 is transparent and the Pt absorbing. This enables precise and very fast structuring. Here, 660 fs laser pulses at a center wavelength of 1053 nm are applied. The driving physical effects of this ablation mechanism are revealed by pump-probe microscopy. This technique allows the observation of the whole ablation process ranging temporally from femtoseconds to microseconds. An ultrafast heat-expansion in the absorbing Pt, initiating a shock-wave to the Ta2O5 within the first 10 ps, bulges the Ta2O5 film after some nanoseconds. Bulging velocities of 750 m/s are determined corresponding to an extreme acceleration of about 1010 g. Exceeding the stress limit in the Ta2O5 causes film disintegration after 50 ns. A model, describing essential reaction steps, is developed. This model is also applicable to other industrial important layer systems, where thin transparent films have to be removed.

  2. Temporary Mechanical Circulatory Support in Cardiac Critical Care: A State of the Art Review and Algorithm for Device Selection.

    Science.gov (United States)

    Nagpal, A Dave; Singal, Rohit K; Arora, Rakesh C; Lamarche, Yoan

    2017-01-01

    With more than 60 years of continuous development and improvement, a variety of temporary mechanical circulatory support (MCS) devices and implantation strategies exist, each with unique advantages and disadvantages. A thorough understanding of each available device is essential for optimizing patient outcomes in a fiscally responsible manner. In this state of the art review we examine the entire range of commonly available peripheral and centrally cannulated temporary MCS devices, including intra-aortic balloon pumps, the Impella (Abiomed, Danvers, MA) family of microaxial pumps, the TandemHeart (CardiacAssist Inc, Pittsburg, PA) pump and percutaneous cannulas, centrally cannulated centrifugal pumps such as the CentriMag (Thoratec Corp, Pleasanton, CA/St Jude Medical, St Paul, MN/Abbott Laboratories, Abbott Park, IL) and Rotaflow (Maquet Holding BV & Co KG, Rastatt Germany), and extracorporeal membrane oxygenation. Several factors need detailed consideration when contemplating MCS in any given patient, mandating a balanced, algorithmic approach for these sick patients. In this review we describe our approach to MCS, and emphasize the need for multidisciplinary input to consider patient-related, logistical, and institutional factors. Evidence is summarized and referenced where available, but because of the lack of high-quality evidence, current best practice is described. Future directions for investigation are discussed, which will better define patient and device selection, and optimize MCS-specific patient care protocols. Copyright © 2016 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved.

  3. On the Selective Laser Melting (SLM of the AlSi10Mg Alloy: Process, Microstructure, and Mechanical Properties

    Directory of Open Access Journals (Sweden)

    Francesco Trevisan

    2017-01-01

    Full Text Available The aim of this review is to analyze and to summarize the state of the art of the processing of aluminum alloys, and in particular of the AlSi10Mg alloy, obtained by means of the Additive Manufacturing (AM technique known as Selective Laser Melting (SLM. This process is gaining interest worldwide, thanks to the possibility of obtaining a freeform fabrication coupled with high mechanical properties related to a very fine microstructure. However, SLM is very complex, from a physical point of view, due to the interaction between a concentrated laser source and metallic powders, and to the extremely rapid melting and the subsequent fast solidification. The effects of the main process variables on the properties of the final parts are analyzed in this review: from the starting powder properties, such as shape and powder size distribution, to the main process parameters, such as laser power and speed, layer thickness, and scanning strategy. Furthermore, a detailed overview on the microstructure of the AlSi10Mg material, with the related tensile and fatigue properties of the final SLM parts, in some cases after different heat treatments, is presented.

  4. Mechanical Properties of Ti-6Al-4V Octahedral Porous Material Unit Formed by Selective Laser Melting

    Directory of Open Access Journals (Sweden)

    Jianfeng Sun

    2012-01-01

    Full Text Available The Ti-6Al-4V octahedral porous material unit is designed to calculate its load. In this paper, ANSYS is adopted for the load simulation of the unit. And a simplified model of dimensional theoretical calculation is established, by which the analytical equation of the fracture load is obtained and the calculation of the load of Ti-6Al-4V is completed. Moreover, selective laser melting is adopted in processing the Ti-6Al-4V porous material unit. The experimental value of fracture load of this material is obtained through compression experiment. The results show that the simulation curves approximate the variation tendency of the elastic deformation of the compression curves; the curves of theoretical calculation approximate the general variation tendency; and the experimental value of fracture load is very close to the theoretical value. Therefore, the theoretical prediction accuracy of fracture load is high, which lays the foundation for the mechanical properties of the octahedral porous material.

  5. High-removal selectivity through interaction between polyacrylamide and SiO2 film in poly isolation chemical mechanical planarization.

    Science.gov (United States)

    Kim, Ye-Hwan; Lee, Kee-June; Park, Jea-Gun; Paik, Ungyu

    2009-06-01

    The interaction between polyacrylamide (PAM) and SiO2 film was investigated in order to elucidate the removal polycrystalline silicon (poly Si) to SiO2 selectivity in poly isolation chemical mechanical planarization (CMP). The hydrophilic characteristics of poly Si and SiO2 were analyzed by the X-ray photoelectron spectroscopy (XPS) and contact angle measurement. The surface of SiO2 is more hydrophilic than that of poly Si due to the siloxane (triple bond Si-O-Si triple bond) bonding. The adsorption behavior of PAM on poly Si and SiO2 film was determined by adsorption isotherms and force measurements using atomic force microscopy (AFM). Interaction between siloxane bonding of SiO2 film and the amine group along the backbone of PAM results in the adsorption of PAM on SiO2 film. Consequently, the passivation layer of PAM on the SiO2 film prevented abrasives from approaching the surface of SiO2 film, which led to suppression of the removal rate of SiO2 film from 82 to 12 A/min in poly isolation CMP process.

  6. Application of Silicon Selective Epitaxial Growth and Chemo-Mechanical Polishing to Bipolar and Soi Mosfet Devices.

    Science.gov (United States)

    Nguyen, Cuong Tan

    1994-01-01

    Polished Epitaxy, or the combination of silicon Selective Epitaxial Growth and Chemo-Mechanical Polishing, provides new flexibility in process and device design, including optimized isolation, planar active-area definition, low-capacitance contacts, and SOI thin films. In this work, Polished Epitaxy has been developed with particular effort on overcoming junction leakage problems widely reported in devices fabricated in similar processes. It was found that in addition to careful surface preparation and defect control in the selective epitaxy process, issues such as sidewall orientation, junction passivation, crystal annealing, and surface damage removal were equally important and needed to be addressed. Coupled with the proper processing steps, Polished Epitaxy was able to deliver material of comparable quality to bulk silicon, suitable for device applications. By growing epitaxy laterally over an oxide step followed by polishing, a pedestal structure was created in which a thin film of single-crystal silicon was formed over oxide. Serving as the extrinsic base contact to a T-Pedestal bipolar transistor device, this pedestal helped minimize the parasitic extrinsic-base-collector overlap capacitance. The cut-off frequency (f_ {T}) in a device with a 1.0-mu m wide emitter stripe was found to improve from 17GHz to 22GHz when the contact overlap was reduced from a more conventional, larger size of 1.0 mu m to 0.2 mum. It is expected that the high-frequency performance of this structure can still be improved further in an optimized process with reduced emitter and collector resistances. The same pedestal structure was applied to a Pedestal -SOI (Silicon-On-Insulator) MOSFET device concept. At one extreme, a conventional bulk MOSFET structure is obtained when the pedestal is not utilized; quasi-SOI occurs when the drain and part of the channel overlap with the pedestal over buried oxide; at the other extreme, complete-SOI behavior results when source, channel, and drain

  7. A systematic approach to pair secretory cargo receptors with their cargo suggests a mechanism for cargo selection by Erv14.

    Science.gov (United States)

    Herzig, Yonatan; Sharpe, Hayley J; Elbaz, Yael; Munro, Sean; Schuldiner, Maya

    2012-01-01

    The endoplasmic reticulum (ER) is the site of synthesis of secreted and membrane proteins. To exit the ER, proteins are packaged into COPII vesicles through direct interaction with the COPII coat or aided by specific cargo receptors. Despite the fundamental role of such cargo receptors in protein traffic, only a few have been identified; their cargo spectrum is unknown and the signals they recognize remain poorly understood. We present here an approach we term "PAIRS" (pairing analysis of cargo receptors), which combines systematic genetic manipulations of yeast with automated microscopy screening, to map the spectrum of cargo for a known receptor or to uncover a novel receptor for a particular cargo. Using PAIRS we followed the fate of ∼150 cargos on the background of mutations in nine putative cargo receptors and identified novel cargo for most of these receptors. Deletion of the Erv14 cargo receptor affected the widest range of cargo. Erv14 substrates have a wide array of functions and structures; however, they are all membrane-spanning proteins of the late secretory pathway or plasma membrane. Proteins residing in these organelles have longer transmembrane domains (TMDs). Detailed examination of one cargo supported the hypothesis that Erv14 dependency reflects the length rather than the sequence of the TMD. The PAIRS approach allowed us to uncover new cargo for known cargo receptors and to obtain an unbiased look at specificity in cargo selection. Obtaining the spectrum of cargo for a cargo receptor allows a novel perspective on its mode of action. The rules that appear to guide Erv14 substrate recognition suggest that sorting of membrane proteins at multiple points in the secretory pathway could depend on the physical properties of TMDs. Such a mechanism would allow diverse proteins to utilize a few receptors without the constraints of evolving location-specific sorting motifs.

  8. Mechanical behavior of porous commercially pure Ti and Ti–TiB composite materials manufactured by selective laser melting

    Energy Technology Data Exchange (ETDEWEB)

    Attar, H. [School of Engineering, Edith Cowan University, 270 Joondalup Drive, Joondalup, Perth, WA 6027 (Australia); IFW Dresden, Institute for Complex Materials, P.O. Box 270116, D-01171 Dresden (Germany); Löber, L.; Funk, A.; Calin, M. [IFW Dresden, Institute for Complex Materials, P.O. Box 270116, D-01171 Dresden (Germany); Zhang, L.C., E-mail: l.zhang@ecu.edu.au [School of Engineering, Edith Cowan University, 270 Joondalup Drive, Joondalup, Perth, WA 6027 (Australia); Prashanth, K.G.; Scudino, S. [IFW Dresden, Institute for Complex Materials, P.O. Box 270116, D-01171 Dresden (Germany); Zhang, Y.S. [Northwest Institute for Nonferrous Metal Research, Xi’an 710016 (China); Eckert, J. [IFW Dresden, Institute for Complex Materials, P.O. Box 270116, D-01171 Dresden (Germany); TU Dresden, Institute of Materials Science, D-01062 Dresden (Germany)

    2015-02-11

    Commercially pure titanium (CP-Ti) and Ti–TiB composite parts with three different porosity levels (i.e. 10%, 17% and 37%) were produced by selective laser melting (SLM). Scanning electron microscopy (SEM) investigations show that martensitic (α′) microstructure exists in SLM-processed CP-Ti parts, whilst SLM-processed Ti–TiB composites present needle-shape TiB particles distributed in α-Ti matrix. Mechanical properties of these porous samples decrease with porosity level increasing. The yield strength and elastic modulus of porous CP-Ti parts range 113–350 MPa and 13–68 GPa respectively, which are much lower than those for porous Ti–TiB counterparts (234–767 MPa and 25–84 GPa respectively) mainly due to the strengthening effect induced by TiB particles in Ti–TiB samples. Compression stress–strain curves of 37% porous CP-Ti parts show a typical three-stage behavior of ductile porous metals. Also, the elastic moduli of both 37% porous CP-Ti and Ti–TiB samples are similar to that of human bone. SEM investigations of the porous CP-Ti samples after compression testing show that no crack presents until 50% compressive strain and most of deformation is absorbed by porous areas. In contrast, μ-CT investigations indicate that all porous Ti–TiB samples fail at early stages of compression testing due to cracks resulting from insufficient ductility of struts of porous areas, because they are not able to accommodate high strains of the deformation at high strengths.

  9. Mechanics

    CERN Document Server

    Chester, W

    1979-01-01

    When I began to write this book, I originally had in mind the needs of university students in their first year. May aim was to keep the mathematics simple. No advanced techniques are used and there are no complicated applications. The emphasis is on an understanding of the basic ideas and problems which require expertise but do not contribute to this understanding are not discussed. How­ ever, the presentation is more sophisticated than might be considered appropri­ ate for someone with no previous knowledge of the subject so that, although it is developed from the beginning, some previous acquaintance with the elements of the subject would be an advantage. In addition, some familiarity with element­ ary calculus is assumed but not with the elementary theory of differential equations, although knowledge of the latter would again be an advantage. It is my opinion that mechanics is best introduced through the motion of a particle, with rigid body problems left until the subject is more fully developed. Howev...

  10. Chemical-Mechanical Impact of Nanoparticles and pH Effect of the Slurry on the CMP of the Selective Layer Surfaces

    Directory of Open Access Journals (Sweden)

    Filip Ilie

    2017-05-01

    Full Text Available This paper provides a tribochemical study of the selective layer surface by chemical mechanical planarization (CMP. CMP is used to remove excess material obtained in the process of selective transfer. The paper aims at a better understanding of the planarization (polishing and micromachining. The planarization becomes effective if the material removal rate (MRR is optimal and the surface defects are minimal. The pH of the slurry plays a very important role in removing the selective layer by CMP, and hydrogen peroxide (H2O2 is the most common oxidizer used in CMP slurry. The purpose of this paper is the analysis of the pH effect on the etching rate (ER and on the behavior of selective layer polishing by a constant concentration of H2O2 and the influence of nanoparticles size and concentration on selective layer surface CMP. The nanoparticle size used is 250 nm. The MRR results through CMP and ER have been shown to be influenced by the presence of oxides on the selective layer surface and have been found to vary with the slurry pH at constant H2O2 concentrations. The CMP slurry plays an important role in the CMP process performance and should be monitored for optimum results and minimal surface defects. The paper analyzes the impact of chemical-mechanical, inter-nanoparticle, and pad-nanoparticle-substrate interactions on CMP performance, taking into account the state of friction at the interface, by measuring the friction force. Selective layer CMP optimization studies were required to control the chemical and mechanical interactions at the interface between the slurry and the selective layer, the slurry chemistry, the properties, and the stability of the suspended abrasive nanoparticles.

  11. Positive Selection of Deleterious Alleles through Interaction with a Sex-Ratio Suppressor Gene in African Buffalo: A Plausible New Mechanism for a High Frequency Anomaly

    NARCIS (Netherlands)

    Hooft, van W.F.; Greyling, B.J.; Getz, W.M.; Helden, P.D.; Zwaan, B.J.; Bastos, A.D.S.

    2015-01-01

    Although generally rare, deleterious alleles can become common through genetic drift, hitchhiking or reductions in selective constraints. Here we present a possible new mechanism that explains the attainment of high frequencies of deleterious alleles in the African buffalo (Syncerus caffer) populati

  12. Positive Selection of Deleterious Alleles through Interaction with a Sex-Ratio Suppressor Gene in African Buffalo: A Plausible New Mechanism for a High Frequency Anomaly

    NARCIS (Netherlands)

    Hooft, van W.F.; Greyling, B.J.; Getz, W.M.; Helden, van P.D.; Zwaan, B.J.; Bastos, A.D.S.

    2014-01-01

    Although generally rare, deleterious alleles can become common through genetic drift, hitchhiking or reductions in selective constraints. Here we present a possible new mechanism that explains the attainment of high frequencies of deleterious alleles in the African buffalo (Syncerus caffer) populati

  13. Consequences of least tern (Sternula antillarum) microhabitat nest-site selection on natural and mechanically constructed sandbars in the Missouri River

    Science.gov (United States)

    Stucker, Jennifer H.; Buhl, Deborah A.; Sherfy, Mark H.

    2013-01-01

    Nest-habitat selection in colonial species has rarely been assessed at multiple spatial scales to evaluate its fitness consequences. Management for the federally endangered U.S. Interior population of Least Terns (Sternula antillarum) has focused on maintenance of breeding habitats, including mechanical construction of sandbars from dredged material. Least Terns are attracted to large areas of unvegetated substrate, yet small-scale habitat features are thought to trigger selection for nesting. We evaluated nest-scale habitat selection to determine (1) whether selection differs between constructed and natural sandbars and (2) the subsequent consequences of habitat selection on nest success. During 2006–2008, we examined 869 Least Tern nest sites on constructed and natural sandbars in the Missouri River for evidence of microhabitat selection at the nest in relation to habitat within the surrounding 3-m area. Least Tern nest sites had coarser and larger substrate materials at the nest, more debris, and less vegetation than the surrounding area. Nests in constructed habitats had a greater percentage of coarse substrates and less vegetation or debris than nests in naturally created habitats. Apparent nest success was 1.8× greater on constructed than on natural sandbars. Nest success was best predicted by models with two spatial scales of predictors, including substrates (nest) and vegetation and debris (nest or surrounding area). Our results indicate that Least Terns select nest microhabitat characteristics that are associated with wind- and water-scoured habitats, and that nest success increases when these habitats are selected.

  14. On closing the gap between philosophical concepts and their usage in scientific practice: A lesson from the debate about natural selection as mechanism.

    Science.gov (United States)

    Matthews, Lucas J

    2016-02-01

    In addition to theorizing about the role and value of mechanisms in scientific explanation or the causal structure of the world, there is a fundamental task of getting straight what a 'mechanism' is in the first place. Broadly, this paper is about the challenge of application: the challenge of aligning one's philosophical account of a scientific concept with the manner in which that concept is actually used in scientific practice. This paper considers a case study of the challenge of application as it pertains to the concept of a mechanism: the debate about whether natural selection is a mechanism. By making clear what is and is not at stake in this debate, this paper considers various strategies for dealing with the challenge of application and makes a case for definitional pluralism about mechanism concepts.

  15. A combined experimental and computational study of the catalytic dehydration of glycerol on microporous zeolites: an investigation of the reaction mechanism and acrolein selectivity.

    Science.gov (United States)

    Lin, Xufeng; Lv, Yanhong; Qu, Yuanyuan; Zhang, Guodong; Xi, Yanyan; Phillips, David L; Liu, Chenguang

    2013-12-14

    The catalytic activity and the acrolein selectivity for liquid phase glycerol dehydration on β zeolites (HNa-β-k) were found to be dependent on the reaction temperature as well as on the amount of acid sites on the zeolites. An increase in the reaction temperature favors the acrolein selectivity. The acrolein selectivity increases with the Na(+)/H(+) ratio and the glycerol conversion decreases with it so that a maximum acrolein yield is obtained when a certain amount of acidic sites are replaced by non-active Na(+) sites. The computational results indicate that 3-hydoxylpropanal (HPA) is an important intermediate that determines the final product selectivity. The relative rates of the different reaction pathways for HAP can be affected by the amount of water molecules involved in its homogeneous reaction. Based on the reaction mechanism proposed, it was hypothesized that smaller pores reduce activity but increase selectivity to acrolein, and results of the H-MFI zeolite were consistent with this hypothesis. Our work provides important insight into the overall landscape of the reaction mechanism and can be used to help design reaction systems that have good acrolein selectivity for the liquid phase glycerol dehydration reactions.

  16. Evidence-based selection of training compounds for use in the mechanism-based integrated prediction of drug-induced liver injury in man.

    Science.gov (United States)

    Dragovic, Sanja; Vermeulen, Nico P E; Gerets, Helga H; Hewitt, Philip G; Ingelman-Sundberg, Magnus; Park, B Kevin; Juhila, Satu; Snoeys, Jan; Weaver, Richard J

    2016-12-01

    The current test systems employed by pharmaceutical industry are poorly predictive for drug-induced liver injury (DILI). The 'MIP-DILI' project addresses this situation by the development of innovative preclinical test systems which are both mechanism-based and of physiological, pharmacological and pathological relevance to DILI in humans. An iterative, tiered approach with respect to test compounds, test systems, bioanalysis and systems analysis is adopted to evaluate existing models and develop new models that can provide validated test systems with respect to the prediction of specific forms of DILI and further elucidation of mechanisms. An essential component of this effort is the choice of compound training set that will be used to inform refinement and/or development of new model systems that allow prediction based on knowledge of mechanisms, in a tiered fashion. In this review, we focus on the selection of MIP-DILI training compounds for mechanism-based evaluation of non-clinical prediction of DILI. The selected compounds address both hepatocellular and cholestatic DILI patterns in man, covering a broad range of pharmacologies and chemistries, and taking into account available data on potential DILI mechanisms (e.g. mitochondrial injury, reactive metabolites, biliary transport inhibition, and immune responses). Known mechanisms by which these compounds are believed to cause liver injury have been described, where many if not all drugs in this review appear to exhibit multiple toxicological mechanisms. Thus, the training compounds selection offered a valuable tool to profile DILI mechanisms and to interrogate existing and novel in vitro systems for the prediction of human DILI.

  17. Oxidative Heck Reaction as a Tool for Para-selective Olefination of Aniline: A DFT Supported Mechanism.

    Science.gov (United States)

    Moghaddam, Firouz Matloubi; Pourkaveh, Raheleh; Karimi, Ashkan

    2017-09-13

    This study describes the first para-selective palladium-catalyzed alkenylation of tertiary amines. This regioselective C-H activation was conducted without any chelation moieties. A series of olefins were reacted under mild reaction conditions at 60 °C, and the corresponding products were obtained in good yields with high selectivity.

  18. Selective reduction mechanism of zinc ferrite%铁酸锌选择性还原的反应机理

    Institute of Scientific and Technical Information of China (English)

    侯栋科; 彭兵; 柴立元; 彭宁; 闫缓

    2014-01-01

    通过TG、物相分析、XPS、XRD、SEM-EDS等手段研究铁酸锌选择性还原反应机理,考察铁酸锌质量损失和分解特征、物相转变过程和产物层形貌变化以及Zn 2+与Fe2+的离子迁移行为。结果表明:反应表现为失氧过程,还原产生的Fe2+使铁酸锌分解产生ZnO,ZnO含量与Fe2+含量线性相关。Fe2+向铁酸锌内部迁移替代Zn2+, Zn2+则向外部迁移并富集于表面,促使ZnO在表面形成。铁酸锌逐步向磁铁矿转变,Fe2+的嵌入和锌的迁出使铁酸锌晶胞参数先增大后减小,还原产物为ZnO和含锌的磁铁矿。颗粒产物层中的还原产物相互夹杂,并包裹着未反应的铁酸锌。%The selective reduction mechanism of zinc ferrite was studied by TG, phase analysis, XPS, XRD and SEM-EDS. The mass loss, decomposition features of zinc ferrite, ionic migration behavior of Zn 2+ and Fe2+ ions, phase transformation process and morphological change of product layer were investigated. The results show that reaction is oxygen loss process. The reduced Fe2+ made ZnO separated from zinc ferrite, the content of ZnO has a significant linear correlation with the content of Fe2+. Fe2+ migrates into the inner zinc ferrite to substitute Zn2+, while Zn2+ moves out and enriches on the surface, promoting the formation of ZnO. Zinc ferrite transforms to magnetite, the lattice parameter of zinc ferrite increases and then decreases due to the intercalation of Fe2+ and the emigration of Zn2+. The reduction products are zinc oxide and zinc-containing magnetite. The reduction products coexist with each other in the product layer and unreacted zinc ferrite is covered with the product layer.

  19. Mechanical damage of red blood cells by rotary blood pumps: selective destruction of aged red blood cells and subhemolytic trauma.

    Science.gov (United States)

    Sakota, Daisuke; Sakamoto, Ryuki; Sobajima, Hideo; Yokoyama, Naoyuki; Waguri, Satoshi; Ohuchi, Katsuhiro; Takatani, Setsuo

    2008-10-01

    In this study, mean cell volume (MCV), mean cell hemoglobin concentration (MCHC), and mean cell hemoglobin (MCH) were measured to quantify RBC damage by rotary blood pumps. Six-hour hemolysis tests were conducted with a Bio-pump BPX-80, a Sarns 15200 roller pump, and a prototype mag-lev centrifugal pump (MedTech Heart) using fresh porcine blood circulated at 5 L/min against a 100 mm Hg head pressure. The temperature of the test and noncirculated control blood was maintained at 37 degrees C. The normalized index of hemolysis (NIH) of each pump was determined by measuring the plasma-free hemoglobin level. The MCV was measured with a Coulter counter, and MCHC was derived from total hemoglobin and hematocrit. MCH was derived from MCV and MCHC. A multivariance statistical analysis (ANOVA) revealed statistically significant differences (n = 15, P < 0.05) in MCV, MCHC, and MCH between the blood sheared by the rotary blood pumps and the nonsheared control blood. Normalized to the control blood, the Bio-pump BPX-80 showed an MCV of 1.04 +/- 0.03, an MCHC of 0.95 +/- 0.04, and an MCH of 0.98 +/- 0.02; the mag-lev MedTech Heart had an MCV of 1.02 +/- 0.02, an MCHC of 0.97 +/- 0.02, and an MCH of 0.99 +/- 0.01; and the roller pump exhibited an MCV of 1.03 +/- 0.03, an MCHC of 0.96 +/- 0.03, and an MCH of 0.99 +/- 0.01. Per 0.01 increase in NIH, the BPX-80 showed a normalized MCV change of +10.1% and a normalized MCHC change of -14.0%; the MedTech Heart demonstrated a +6.9% MCV and -9.5% MCHC change; and the roller pump had a +0.5% MCV and -0.6% MCHC change. Due to shear in the pump circuits, the RBC increased while the MCHC decreased. The likely mechanism is that older RBCs with smaller size and higher hemoglobin concentration were destroyed fast by the shear, leaving younger RBCs with larger size and lower hemoglobin concentration. Subhemolytic trauma caused the intracellular hemoglobin to decrease due to gradual hemoglobin leakage through the micropores formed in the thinned

  20. Acute ischemic stroke with tandem/terminal ICA occlusion - CT perfusion based case selection for mechanical recanalization

    Directory of Open Access Journals (Sweden)

    Rajsrinivas Parthasarathy

    2015-01-01

    Conclusion: The cerebral blood volume (CBV core estimation reliably predicted the final infarct volume. The key reasons for the significantly better outcomes seen in our cohort were the stringent perfusion imaging-based patient selection and the rapid reperfusion.

  1. Mechanisms and Influencing Factors of Selective Water Shutoff Agents%选择性堵水剂的作用机理及应用影响因素

    Institute of Scientific and Technical Information of China (English)

    杨艳; 王业飞; 张鹏; 王国瑞

    2012-01-01

    综述了目前应用较普遍的4种选择性堵水剂(聚合物类堵水剂、体膨型堵水剂、稠油类堵水剂、泡沫),总结出选择性堵水剂的4种作用机理,即吸附、捕集和物理堵塞机理、膨胀收缩机理、不稳定机理和油水通道分流机理。介绍了选择性堵水剂在现场应用中的影响因素(岩石润湿性、地层水矿化度)。为油田施工时堵水剂的选择以及方案的设计提供理论依据。图2表1参49%The selective water shutoff agents had been applied widely in many oil fields. Four common selective water shutoff agents, such as polymer, swelling grain, viscous crude and foam were reviewed. And four kinds of mechanisms for water shutoff were summarized, such as adsorption-entrapment-physical plugging mechanism, swelling/shrinking mechanism, destabilization mechanism and oil-water segregated pathways mechanism. Meanwhile, the influencing factors of selective water shutoff agents for oilfield application were introduced, such as rock wettability and formation water salinity. This review would provide theoretical supports for the selection of agents and the design of projects in oilfield.

  2. Cu(II)-vitamin D interaction leads to free radical-mediated cellular DNA damage: a novel putative mechanism for its selective cytotoxic action against malignant cells.

    Science.gov (United States)

    Rizvi, Asim; Chibber, Sandesh; Naseem, Imrana

    2015-03-01

    Vitamin D (vit D) is a known anticancer molecule, and cancer cells are reported to have elevated levels of Cu(II) ions. In this study, we show that interaction of vit D and Cu(II) leads to the formation of hydroxyl free radicals, superoxide anion and hydrogen peroxide, which causes severe oxidative stress, selectively in malignant cells. We show that the production of these reactive oxygen species causes cellular DNA fragmentation which may cause cell death. A novel putative chemical mechanism explaining how vit D causes cell death by DNA damage, selectively in malignant cells, is proposed.

  3. Selective action of an atypical neuroleptic on the mechanisms related to the development of cocaine addiction: a pre-clinical behavioural study

    OpenAIRE

    Marinho, Eduardo Ary Villela; Oliveira-Lima, Alexandre Justo de [UNIFESP; Wuo-Silva, Raphael; Santos, Renan [UNIFESP; Baldaia, Marilia Araujo [UNIFESP; Hollais, André Willian [UNIFESP; Longo, Beatriz Monteiro; Berro, Laís Fernanda; Frussa-Filho, Roberto

    2014-01-01

    An increased function in the mesolimbic dopaminergic system has been extensively associated with the rewarding effects of both natural stimuli and drugs of abuse. Thus, dopamine receptor blockers, such as neuroleptic drugs, can be proposed as candidates for potential therapeutic approaches to treat drug dependence. Notwithstanding, this therapeutic potential of neuroleptics critically depends on a selective action on the specific mechanisms related to the development of addiction. We compared...

  4. Selection of candidate genes involved in the defense mechanisms of Phytophthora infestans against fungicides by EST analysis

    Science.gov (United States)

    Preliminary research using a functional genomics approach was conducted to gain insights on how P. infestans responds to fungicides and the possible implications of these responses on its ability to adapt to such selection pressure. Two isolates with subtle differences in mefenoxam resistance were e...

  5. Selective action of an atypical neuroleptic on the mechanisms related to the development of cocaine addiction: a pre-clinical behavioural study.

    Science.gov (United States)

    Marinho, Eduardo A V; Oliveira-Lima, Alexandre J; Wuo-Silva, Raphael; Santos, Renan; Baldaia, Marilia A; Hollais, André W; Longo, Beatriz M; Berro, Laís F; Frussa-Filho, Roberto

    2014-04-01

    An increased function in the mesolimbic dopaminergic system has been extensively associated with the rewarding effects of both natural stimuli and drugs of abuse. Thus, dopamine receptor blockers, such as neuroleptic drugs, can be proposed as candidates for potential therapeutic approaches to treat drug dependence. Notwithstanding, this therapeutic potential of neuroleptics critically depends on a selective action on the specific mechanisms related to the development of addiction. We compared the effects of different doses of haloperidol, ziprasidone and aripiprazole (first-, second- and third-generation neuroleptics, respectively) on spontaneous locomotor activity of mice in a novel environment, hyperlocomotion induced by acute cocaine administration and cocaine-induced locomotor sensitization by a two-injection protocol. Whereas high doses of haloperidol abolished the three behavioural paradigms without selectivity, low doses of ziprasidone selectively abolished the development of the behavioural sensitization phenomenon. Finally, low doses of aripiprazole inhibited acute cocaine-induced hyperlocomotion and behavioural sensitization without modifying spontaneous locomotor activity. Thus, aripiprazole at lower doses was the most selective antipsychotic drug concerning the inhibition of the development of behavioural sensitization to cocaine. Because locomotor sensitization in rodents has been proposed to share plastic mechanisms with drug addiction in humans, our data provide relevant suggestions to the clinical practice.

  6. The bitter barricading of prostaglandin biosynthesis pathway: understanding the molecular mechanism of selective cyclooxygenase-2 inhibition by amarogentin, a secoiridoid glycoside from Swertia chirayita.

    Directory of Open Access Journals (Sweden)

    Shantanu Shukla

    Full Text Available Swertia chirayita, a medicinal herb inhabiting the challenging terrains and high altitudes of the Himalayas, is a rich source of essential phytochemical isolates. Amarogentin, a bitter secoiridoid glycoside from S. chirayita, shows varied activity in several patho-physiological conditions, predominantly in leishmaniasis and carcinogenesis. Experimental analysis has revealed that amarogentin downregulates the cyclooxygenase-2 (COX-2 activity and helps to curtail skin carcinogenesis in mouse models; however, there exists no account on selective inhibition of the inducible cyclooxygenase (COX isoform by amarogentin. Hence the computer-aided drug discovery methods were used to unravel the COX-2 inhibitory mechanism of amarogentin and to check its selectivity for the inducible isoform over the constitutive one. The generated theoretical models of both isoforms were subjected to molecular docking analysis with amarogentin and twenty-one other Food and Drug Authority (FDA approved lead molecules. The post-docking binding energy profile of amarogentin was comparable to the binding energy profiles of the FDA approved selective COX-2 inhibitors. Subsequent molecular dynamics simulation analysis delineated the difference in the stability of both complexes, with amarogentin-COX-2 complex being more stable after 40ns simulation. The total binding free energy calculated by MMGBSA for the amarogentin-COX-2 complex was -52.35 KCal/mol against a binding free energy of -8.57 KCal/mol for amarogentin-COX-1 complex, suggesting a possible selective inhibition of the COX-2 protein by the natural inhibitor. Amarogentin achieves this potential selectivity by small, yet significant, structural differences inherent to the binding cavities of the two isoforms. Hypothetically, it might block the entry of the natural substrates in the hydrophobic binding channel of the COX-2, inhibiting the cyclooxygenation step. To sum up briefly, this work highlights the mechanism of the

  7. Markov State Models Reveal a Two-Step Mechanism of miRNA Loading into the Human Argonaute Protein: Selective Binding followed by Structural Re-arrangement

    KAUST Repository

    Jiang, Hanlun

    2015-07-16

    Argonaute (Ago) proteins and microRNAs (miRNAs) are central components in RNA interference, which is a key cellular mechanism for sequence-specific gene silencing. Despite intensive studies, molecular mechanisms of how Ago recognizes miRNA remain largely elusive. In this study, we propose a two-step mechanism for this molecular recognition: selective binding followed by structural re-arrangement. Our model is based on the results of a combination of Markov State Models (MSMs), large-scale protein-RNA docking, and molecular dynamics (MD) simulations. Using MSMs, we identify an open state of apo human Ago-2 in fast equilibrium with partially open and closed states. Conformations in this open state are distinguished by their largely exposed binding grooves that can geometrically accommodate miRNA as indicated in our protein-RNA docking studies. miRNA may then selectively bind to these open conformations. Upon the initial binding, the complex may perform further structural re-arrangement as shown in our MD simulations and eventually reach the stable binary complex structure. Our results provide novel insights in Ago-miRNA recognition mechanisms and our methodology holds great potential to be widely applied in the studies of other important molecular recognition systems.

  8. Exploring the structure and function of Thermotoga maritima CorA reveals the mechanism of gating and ion selectivity in Co2+/Mg2+ transport.

    Science.gov (United States)

    Nordin, Nurhuda; Guskov, Albert; Phua, Terri; Sahaf, Newsha; Xia, Yu; Lu, Siyan; Eshaghi, Hojjat; Eshaghi, Said

    2013-05-01

    The CorA family of divalent cation transporters utilizes Mg2+ and Co2+ as primary substrates. The molecular mechanism of its function, including ion selectivity and gating, has not been fully characterized. Recently we reported a new structure of a CorA homologue from Methanocaldococcus jannaschii, which provided novel structural details that offered the conception of a unique gating mechanism involving conversion of an open hydrophilic gate into a closed hydrophobic one. In the present study we report functional evidence for this novel gating mechanism in the Thermotoga maritima CorA together with an improved crystal structure of this CorA to 2.7 Å (1 Å=0.1 nm) resolution. The latter reveals the organization of the selectivity filter to be similar to that of M. jannaschii CorA and also the previously unknown organization of the second signature motif of the CorA family. The proposed gating is achieved by a helical rotation upon the binding of a metal ion substrate to the regulatory binding sites. Additionally, our data suggest that the preference of this CorA for Co2+ over Mg2+ is controlled by the presence of threonine side chains in the channel. Finally, the roles of the intracellular metal-binding sites have been assigned to increased thermostability and regulation of the gating. These mechanisms most likely apply to the entire CorA family as they are regulated by the highly conserved amino acids.

  9. A systematic SNP selection approach to identify mechanisms underlying disease aetiology: linking height to post-menopausal breast and colorectal cancer risk

    Science.gov (United States)

    Elands, Rachel J. J.; Simons, Colinda C. J. M.; Riemenschneider, Mona; Isaacs, Aaron; Schouten, Leo J.; Verhage, Bas A.; Van Steen, Kristel; Godschalk, Roger W. L.; van den Brandt, Piet A.; Stoll, Monika; Weijenberg, Matty P.

    2017-01-01

    Data from GWAS suggest that SNPs associated with complex diseases or traits tend to co-segregate in regions of low recombination, harbouring functionally linked gene clusters. This phenomenon allows for selecting a limited number of SNPs from GWAS repositories for large-scale studies investigating shared mechanisms between diseases. For example, we were interested in shared mechanisms between adult-attained height and post-menopausal breast cancer (BC) and colorectal cancer (CRC) risk, because height is a risk factor for these cancers, though likely not a causal factor. Using SNPs from public GWAS repositories at p-values cancer site-specific pathways. This systematic approach identified a limited number of clustered SNPs, which pinpoint potential shared mechanisms linking together the complex phenotypes height, post-menopausal BC and CRC. PMID:28117334

  10. The study of the laser parameters and environment variables effect on mechanical properties of high compact parts elaborated by selective laser melting 316L powder

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Baicheng, E-mail: baicheng.zhang@utbm.fr; Dembinski, Lucas; Coddet, Christian

    2013-11-01

    In this work, a systematic analysis of the main parameters for the selective laser melting (SLM) of a commercial stainless steel 316L powder was conducted to improve the mechanical properties and dimensional accuracy of the fabricated parts. First, the effects of the processing parameters, such as the laser beam scanning velocity, laser power, substrate condition and thickness of the powder layer, on the formation of single tracks for achieving a continuous melting and densification of the material were analysed. Then, the influence of the environmental conditions (gas nature) and of the preheating temperature on the density and dimensional accuracy of the parts was considered. The microstructural features of the SLM SS 316L parts were carefully observed to elucidate the melting-solidification mechanism and the thermal history, which are the basis of the manufacturing process. Finally, the mechanical properties of the corresponding material were also determined.

  11. Studies on the mechanism, selectivity, and synthetic utility of lactone reduction using SmI(2) and H(2)O.

    Science.gov (United States)

    Parmar, Dixit; Duffy, Lorna A; Sadasivam, Dhandapani V; Matsubara, Hiroshi; Bradley, Paul A; Flowers, Robert A; Procter, David J

    2009-10-28

    Although simple aliphatic esters and lactones have long been thought to lie outside the reducing range of SmI(2), activation of the lanthanide reagent by H(2)O allows some of these substrates to be manipulated in an unprecedented fashion. For example, the SmI(2)-H(2)O reducing system shows complete selectivity for the reduction of 6-membered lactones over other classes of lactones and esters. The kinetics of reduction has been studied using stopped-flow spectrophotometry. Experimental and computational studies suggest that the origin of the selectivity lies in the initial electron-transfer to the lactone carbonyl. The radical intermediates formed during lactone reduction with SmI(2)-H(2)O can be exploited in cyclizations to give cyclic ketone (or ketal) products with high diastereoselectivity. The cyclizations constitute the first examples of ester-alkene radical cyclizations in which the ester carbonyl acts as an acyl radical equivalent.

  12. Enhanced selective removal of Cu(II) from aqueous solution by novel polyethylenimine-functionalized ion imprinted hydrogel: Behaviors and mechanisms.

    Science.gov (United States)

    Wang, Jingjing; Li, Zhengkui

    2015-12-30

    A novel polyethylenimine-functionalized ion-imprinted hydrogel (Cu(II)-p(PEI/HEA)) was newly synthesized by (60)Co-γ-induced polymerization for the selective removal of Cu(II) from aqueous solution. The adsorption performances including the adsorption capacity and selectivity of the novel hydrogel were much better than those of similar adsorbents reported. The hydrogel was characterized via scanning electron microscope, transmission electron microscopy, Fourier transform infrared spectra, thermal gravimetric analysis and X-ray photoelectron spectroscopy to determine the structure and mechanisms. The adsorption process was pH and temperature sensitive, better fitted to pseudo-second-order equation, and was Langmuir monolayer adsorption. The maximum adsorption capacity for Cu(II) was 40.00 mg/g. The selectivity coefficients of ion-imprinted hydrogel for Cu(II)/Pb(II), Cu(II)/Cd(II) and Cu(II)/Ni(II) were 55.09, 107.47 and 63.12, respectively, which were 3.93, 4.25 and 3.53 times greater than those of non-imprinted hydrogel, respectively. Moreover, the adsorption capacity of Cu(II)-p(PEI/HEA) could still keep more than 85% after four adsorption-desorption cycles. Because of such enhanced selective removal performance and excellent regeneration property, Cu(II)-p(PEI/HEA) is a promising adsorbent for the selective removal of copper ions from wastewater.

  13. Selectively Tuning a Buckled Si/SiO2 Membrane MEMS through Joule Heating Actuation and Mechanical Restriction

    Science.gov (United States)

    2014-03-01

    actuation speed ............................................................. 102 Reliable Force Testing...device used to store mechanical energy. From an early age children are introduced to the concept of a spring through walking their Slinky® down the... stairs . With applications ranging from early projectile weapon systems, most notably the bow and arrow, to vibration isolation in vehicles and

  14. Children and adults minimise activated muscle volume by selecting gait parameters that balance gross mechanical power and work demands.

    Science.gov (United States)

    Hubel, Tatjana Y; Usherwood, James R

    2015-09-01

    Terrestrial locomotion on legs is energetically expensive. Compared with cycling, or with locomotion in swimming or flying animals, walking and running are highly uneconomical. Legged gaits that minimise mechanical work have previously been identified and broadly match walking and running at appropriate speeds. Furthermore, the 'cost of muscle force' approaches are effective in relating locomotion kinetics to metabolic cost. However, few accounts have been made for why animals deviate from either work-minimising or muscle-force-minimising strategies. Also, there is no current mechanistic account for the scaling of locomotion kinetics with animal size and speed. Here, we report measurements of ground reaction forces in walking children and adult humans, and their stance durations during running. We find that many aspects of gait kinetics and kinematics scale with speed and size in a manner that is consistent with minimising muscle activation required for the more demanding between mechanical work and power: spreading the duration of muscle action reduces activation requirements for power, at the cost of greater work demands. Mechanical work is relatively more demanding for larger bipeds--adult humans--accounting for their symmetrical M-shaped vertical force traces in walking, and relatively brief stance durations in running compared with smaller bipeds--children. The gaits of small children, and the greater deviation of their mechanics from work-minimising strategies, may be understood as appropriate for their scale, not merely as immature, incompletely developed and energetically sub-optimal versions of adult gaits.

  15. Selective adsorption of Pb(II) from aqueous solution using porous biosilica extracted from marine diatom biomass: Properties and mechanism

    Science.gov (United States)

    Qi, Yarong; Wang, Jingfeng; Wang, Xin; Cheng, Jay Jiayang; Wen, Zhiyou

    2017-02-01

    Biosilica with a surface area of 143 m2 g-1 derived from marine diatoms was prepared using an easy two-step method involving washing with dilute acid and baking. The extracted biosilica was used to remove divalent lead ions, i.e., Pb(II), from aqueous solution. The effects on Pb(II) adsorption of initial pH, shaking speed, and adsorbent loading were investigated. The adsorption of Pb(II) in the presence of other ions was also investigated. The biosilica showed a high adsorption capacity with high selectivity for Pb(II). The experimental maximum adsorption capacity was 108.2-120.4 mg g-1 at an adsorbent loading of 1 g L-1. The adsorption process was best described by the Langmuir model. The adsorbent selectively adsorbed Pb(II) from binary ion systems in the presence of Cu(II), Cd(II), Ni(II), and Ag(I). The results of this study show that biosilica extracted from fresh marine diatoms is a more efficient and selective adsorbent for Pb(II) than other inorganic adsorbents.

  16. Blast from the Past: Reassessing Forgotten Translation Inhibitors, Antibiotic Selectivity, and Resistance Mechanisms to Aid Drug Development.

    Science.gov (United States)

    Arenz, Stefan; Wilson, Daniel N

    2016-01-07

    Protein synthesis is a major target within the bacterial cell for antibiotics. Investigations into ribosome-targeting antibiotics have provided much needed functional and structural insight into their mechanism of action. However, the increasing prevalence of multi-drug-resistant bacteria has limited the utility of our current arsenal of clinically relevant antibiotics, highlighting the need for the development of new classes. Recent structural studies have characterized a number of antibiotics discovered decades ago that have unique chemical scaffolds and/or utilize novel modes of action to interact with the ribosome and inhibit translation. Additionally, structures of eukaryotic cytoplasmic and mitochondrial ribosomes have provided further structural insight into the basis for specificity and toxicity of antibiotics. Together with our increased understanding of bacterial resistance mechanisms, revisiting our treasure trove of "forgotten" antibiotics could pave the way for the next generation of antimicrobial agents.

  17. The influence of selected elements upon mechanical properties of ductile iron EN-GJS-500-7

    Directory of Open Access Journals (Sweden)

    M. S. Soiński

    2008-10-01

    Full Text Available On the basis of chemical composition and mechanical properties analyses of EN-GJS-500-7 spheroidal graphite cast iron (as per PN-EN1563 standard, an attempt to determine the relations between the changes in the contents of elements included in alloy (such as: C, Si, Mn, P, S, Cr, Ni, Mo, Cu, Mg, and its tensile strength (Rm, proof stress (Rp0,2, elongation (A5 and hardness (HB, has been made. Cast iron subjected to the tests came from 291 heats, conducted in one of the domestic foundries. Cast iron was melted in medium-frequency induction furnace, spheroidized with bell method and modified with “in-stream” method.It results from conducted calculations that in a number of cases even small changes of the elements contents lead to statistically significant increases or decreases in examined mechanical properties of cast iron.

  18. A sensing mechanism for the detection of carbon nanotubes using selective photoluminescent probes based on ionic complexes with organic dyes

    Institute of Scientific and Technical Information of China (English)

    Petro Lutsyk; Raz Arif; Jan Hruby; Anatolii Bukivskyi; Olexander Vinijchuk; Mykola Shandura; Viktor Yakubovskyi

    2016-01-01

    The multifunctional properties of carbon nanotubes (CNTs) make them a powerful platform for unprecedented innovations in a variety of practical applications.As a result of the surging growth of nanotechnology,nanotubes present a potential problem as an environmental pollutant,and as such,an efficient method for their rapid detection must be established.Here,we propose a novel type of ionic sensor complex for detecting CNTs-an organic dye that responds sensitively and selectively to CNTs with a photoluminescent signal.The complexes are formed through Coulomb attractions between dye molecules with uncompensated charges and CNTs covered with an ionic surfactant in water.We demonstrate that the photoluminescent excitation of the dye can be transferred to the nanotubes,resulting in selective and strong amplification (up to a factor of 6) of the light emission from the excitonic levels of CNTs in the near-infrared spectral range,as experimentally observed via excitation-emission photoluminescence (PL) mapping.The chirality of the nanotubes and the type of ionic surfactant used to disperse the nanotubes both strongly affect the amplification;thus,the complexation provides sensing selectivity towards specific CNTs.Additionally,neither similar uncharged dyes nor CNTs covered with neutral surfactant form such complexes.As model organic molecules,we use a family of pelymethine dyes with an easily tailorable molecular structure and,consequently,tunable absorbance and PL characteristics.This provides us with a versatile tool for the controllable photonic and electronic engineering of an efficient probe for CNT detection.

  19. Manufacture and mechanical characterisation of high voltage insulation for superconducting busbars - (Part 1) Materials selection and development

    Science.gov (United States)

    Clayton, N.; Crouchen, M.; Devred, A.; Evans, D.; Gung, C.-Y.; Lathwell, I.

    2017-04-01

    It is planned that the high voltage electrical insulation on the ITER feeder busbars will consist of interleaved layers of epoxy resin pre-impregnated glass tapes ('pre-preg') and polyimide. In addition to its electrical insulation function, the busbar insulation must have adequate mechanical properties to sustain the loads imposed on it during ITER magnet operation. This paper reports an investigation into suitable materials to manufacture the high voltage insulation for the ITER superconducting busbars and pipework. An R&D programme was undertaken in order to identify suitable pre-preg and polyimide materials from a range of suppliers. Pre-preg materials were obtained from 3 suppliers and used with Kapton HN, to make mouldings using the desired insulation architecture. Two main processing routes for pre-pregs have been investigated, namely vacuum bag processing (out of autoclave processing) and processing using a material with a high coefficient of thermal expansion (silicone rubber), to apply the compaction pressure on the insulation. Insulation should have adequate mechanical properties to cope with the stresses induced by the operating environment and a low void content necessary in a high voltage application. The quality of the mouldings was assessed by mechanical testing at 77 K and by the measurement of the void content.

  20. Effect of material, process parameters, and simulated body fluids on mechanical properties of 13-93 bioactive glass porous constructs made by selective laser sintering.

    Science.gov (United States)

    Kolan, Krishna C R; Leu, Ming C; Hilmas, Gregory E; Velez, Mariano

    2012-09-01

    The effect of particle size distribution, binder content, processing parameters, and sintering schedule on the microstructure and mechanical properties of porous constructs was investigated. The porous constructs were produced by indirect selective laser sintering (SLS) of 13-93 bioactive glass using stearic acid as a polymeric binder. The binder content and d(50) particle size in the feedstock powders were simultaneously reduced from 22 to 12 wt% and from 20 to 11 μm, respectively, to identify the minimum binder content required for the SLS fabrication. An average particle size of ∼16 μm with a binder content of 15 wt% significantly reduced post-processing time and improved mechanical properties. Increasing the laser power and scan speed at the energy density of 1 cal/cm² maintained the feature sharpness of the parts during the fabrication of green parts and could almost double the mechanical properties of the sintered parts. Changes in the heating rates, ranging from 0.1 to 2 °C/min, during the post-processing of the fabricated "green" scaffolds showed that the heating rate significantly affects the densification and mechanical properties of the sintered scaffolds. The compressive strength of the scaffolds manufactured with the optimized parameters varied from 41 MPa, for a scaffold with a porosity of ∼50%, to 157 MPa, for a dense part. The bioactive scaffolds soaked in simulated body fluids for durations up to 6 weeks were used to evaluate the change in mechanical properties in vitro.

  1. Implications of sterically constrained n-butane oxidation reactions on the reaction mechanism and selectivity to 1-butanol

    Science.gov (United States)

    Dix, Sean T.; Gómez-Gualdrón, Diego A.; Getman, Rachel B.

    2016-11-01

    Density functional theory (DFT) is used to analyze the reaction network in n-butane oxidation to 1-butanol over a Ag/Pd alloy catalyst under steric constraints, and the implications on the ability to produce 1-butanol selectively using MOF-encapsulated catalysts are discussed. MOFs are porous crystalline solids comprised of metal nodes linked by organic molecules. Recently, they have been successfully grown around metal nanoparticle catalysts. The resulting porous networks have been shown to promote regioselective chemistry, i.e., hydrogenation of trans-1,3-hexadiene to 3-hexene, presumably by forcing the linear alkene to stand "upright" on the catalyst surface and allowing only the terminal C-H bonds to be activated. In this work, we extend this concept to alkane oxidation. Our goal is to determine if a MOF-encapsulated catalyst could be used to selectively produce 1-butanol. Reaction energies and activation barriers are presented for more than 40 reactions in the pathway for n-butane oxidation. We find that C-H bond activation proceeds through an oxygen-assisted pathway and that butanal and 1-butanol are some of the possible products.

  2. Ligand-controlled reactivity, selectivity, and mechanism of cationic ruthenium-catalyzed hydrosilylations of alkynes, ketones, and nitriles: a theoretical study.

    Science.gov (United States)

    Yang, Yun-Fang; Chung, Lung Wa; Zhang, Xinhao; Houk, K N; Wu, Yun-Dong

    2014-09-19

    Density functional theory calculations with the M06 functional have been performed on the reactivity, selectivity, and mechanism of hydrosilylations of alkynes, ketones, and nitriles catalyzed by cationic ruthenium complexes [CpRu(L)(MeCN)2](+), with L = P(i)Pr3 or MeCN. The hydrosilylation of alkynes with L = P(i)Pr3 involves an initial silyl migration mechanism to generate the anti-Markovnikov product, in contrast to the Markovnikov product obtained with L = MeCN. The bulky phosphine ligand directs the silyl group to migrate to Cβ of the alkyne. This explains the anti-Markovnikov selectivity of the catalyst with L = P(i)Pr3. By contrast, the silane additions to either ketone or nitrile proceed through an ionic SN2-Si outer-sphere mechanism, in which the substrate attacks the Si center. The P(i)Pr3 ligand facilitates the activation of the Si-H bond to furnish a η(2)-silane complex, whereas a η(1)-silane complex is formed for the MeCN ligand. This property of the phosphine ligand enables the catalytic hydrosilylation of ketones and nitriles in addition to that of alkynes.

  3. Micro-CT-based improvement of geometrical and mechanical controllability of selective laser melted Ti6Al4V porous structures

    Energy Technology Data Exchange (ETDEWEB)

    Van Bael, S., E-mail: Simon.Vanbael@mech.kuleuven.be [Department of Mechanical Engineering, Division of Production Engineering, Machine Design and Automation, Katholieke Universiteit Leuven, Celestijnenlaan 300B, B-3001 Leuven (Belgium); Department of Mechanical Engineering, Division of Biomechanics and Engineering Design, Katholieke Universiteit Leuven, Celestijnenlaan 300C, B-3001 Leuven (Belgium); Prometheus, Division of Skeletal Tissue Engineering, Katholieke Universiteit Leuven, O and N 1, Minderbroedersstraat 8A, B-3000 Leuven (Belgium); Kerckhofs, G., E-mail: Greet.Kerckhofs@mtm.kuleuven.be [Department of Metallurgy and Materials Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 44, B-3001 Leuven (Belgium); Prometheus, Division of Skeletal Tissue Engineering, Katholieke Universiteit Leuven, O and N 1, Minderbroedersstraat 8A, B-3000 Leuven (Belgium); Moesen, M., E-mail: Maarten.Moesen@mtm.kuleuven.be [Department of Metallurgy and Materials Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 44, B-3001 Leuven (Belgium); Prometheus, Division of Skeletal Tissue Engineering, Katholieke Universiteit Leuven, O and N 1, Minderbroedersstraat 8A, B-3000 Leuven (Belgium); Pyka, G., E-mail: Gregory.Pyka@mtm.kuleuven.be [Department of Metallurgy and Materials Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 44, B-3001 Leuven (Belgium); Prometheus, Division of Skeletal Tissue Engineering, Katholieke Universiteit Leuven, O and N 1, Minderbroedersstraat 8A, B-3000 Leuven (Belgium); Schrooten, J., E-mail: Jan.Schrooten@mtm.kuleuven.be [Department of Metallurgy and Materials Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 44, B-3001 Leuven (Belgium); Prometheus, Division of Skeletal Tissue Engineering, Katholieke Universiteit Leuven, O and N 1, Minderbroedersstraat 8A, B-3000 Leuven (Belgium); and others

    2011-09-15

    Highlights: {yields} Selective laser melting as a production tool for porous Ti6Al4V structures. {yields} Significant mismatch between designed and as-produced properties. {yields} Decreasing mismatch using a micro-CT-based protocol. {yields} Mismatch of pore size decreased from 45% to 5%. {yields} Increased morphological controllability increases mechanical controllability. - Abstract: Despite the fact that additive manufacturing (AM) techniques allow to manufacture complex porous parts with a controlled architecture, differences can occur between designed and as-produced morphological properties. Therefore this study aimed at optimizing the robustness and controllability of the production of porous Ti6Al4V structures using selective laser melting (SLM) by reducing the mismatch between designed and as-produced morphological and mechanical properties in two runs. In the first run, porous Ti6Al4V structures with different pore sizes were designed, manufactured by SLM, analyzed by microfocus X-ray computed tomography (micro-CT) image analysis and compared to the original design. The comparison was based on the following morphological parameters: pore size, strut thickness, porosity, surface area and structure volume. Integration of the mismatch between designed and measured properties into a second run enabled a decrease of the mismatch. For example, for the average pore size the mismatch decreased from 45% to 5%. The demonstrated protocol is furthermore applicable to other 3D structures, properties and production techniques, powder metallurgy, titanium alloys, porous materials, mechanical characterization, tomography.

  4. Mutant-prevention concentration and mechanism of resistance in clinical isolates and enrofloxacin/marbofloxacin-selected mutants of Escherichia coli of canine origin.

    Science.gov (United States)

    Gebru, Elias; Choi, Myung-Jin; Lee, Seung-Jin; Damte, Dereje; Park, Seung Chun

    2011-10-01

    The antibacterial activity and selection of resistant bacteria, along with mechanisms of fluoroquinolone resistance, were investigated by integrating the static [MIC or mutant-prevention concentration (MPC)] and in vitro dynamic model approaches using Escherichia coli isolates from diseased dogs. Using the dynamic models, selected E. coli strains and enrofloxacin and marbofloxacin at a range of simulated area under concentration-time curve over a 24 h interval (AUC(24 h))/MIC ratios were investigated. Our results indicated increasing losses in susceptibility of E. coli upon continuous exposure to enrofloxacin and marbofloxacin in vitro. This effect was transferable to other fluoroquinolones, as well as to structurally unrelated drugs. Our results also confirmed an AUC(24 h)/MIC (AUC(24 h)/MPC)-dependent antibacterial activity and selection of resistant E. coli mutants, in which maximum losses in fluoroquinolone susceptibility occurred at simulated AUC(24 h)/MIC ratios of 40-60. AUC(24 h)/MPC ratios of 39 (enrofloxacin) and 32 (marbofloxacin) were considered protective against the selection of resistant mutants of E. coli. Integrating our MIC and MPC data with published pharmacokinetic information in dogs revealed a better effect of the conventional dosing regimen of marbofloxacin than that of enrofloxacin in restricting the selection of resistant mutants of E. coli. Target mutations, especially at codon 83 (serine to leucine) of gyrA, and overexpression of efflux pumps contributed to resistance development in both clinically resistant and in vitro-selected mutants of E. coli. We also report here a previously undescribed mutation at codon 116 of parC in two laboratory-derived resistant mutants of E. coli. Additional studies would determine the exact role of this mutation in fluoroquinolone susceptibility, as well as establish the importance of our findings in the clinical setting.

  5. Selective oxidation of alcohols with alkali metal bromides as bromide catalysts: experimental study of the reaction mechanism.

    Science.gov (United States)

    Moriyama, Katsuhiko; Takemura, Misato; Togo, Hideo

    2014-07-03

    A bromide-catalyzed oxidation of alcohols was developed which proceeded in the presence of an alkali metal bromide and an oxidant under mild conditions. The reaction involved an organic-molecule-free oxidation using KBr and Oxone and a Brønsted acid assisted oxidation using KBr and aqueous H2O2 solution to provide a broad range of carbonyl compounds in high yields. Moreover, the bromide-catalyzed oxidation of primary alcohols enabled the divergent synthesis of carboxylic acids and aldehydes under both reaction conditions in the presence of TEMPO. A possible catalytic mechanism was suggested on the basis of various mechanistic studies.

  6. Chemical order and selection of the mechanism for strain relaxation in epitaxial FePd(Pt) thin layers

    Science.gov (United States)

    Halley, D.; Marty, A.; Bayle-Guillemaud, P.; Gilles, B.; Attane, J. P.; Samson, Y.

    2004-11-01

    We observed that the relaxation mechanism of the epitaxial strain is dramatically dependent on the chemical ordering within the L10 structure in FePd(Pt) thin films. In disordered or weakly ordered layers, the relaxation takes place though perfect (1)/(2)[101] dislocations, whereas well-ordered films relax through the partial 1/6[112] Shockley dislocations, piled-up within microtwins, with a huge impact on both the morphology and the magnetic properties of the film. We show that the antiphase boundary energy is the key factor preventing the propagation of perfect dislocations in ordered alloys.

  7. Parallel selection of chemotherapy-resistant cell lines to illuminate mechanisms of drug resistance in human tumors

    DEFF Research Database (Denmark)

    Krzystanek, Marcin; Eklund, Aron Charles; Birkbak, Nicolai Juul

    2011-01-01

    Treatment of cancer often involves the use of chemotherapeutic agents that preferentially target tumor cells. The idea behind personalized medicine is to characterize differences between individual cancer cases that will and to direct the therapy to those most likely to respond. This will require....... Our findings are validated on already existing gene expression profiles of patient cohorts treated with the drugs in question, and the most promising ones will be chosen for functional validation by RNAi knock down. Successful validation will improve understanding of drug resistance mechanisms......, suggest future drug targets, and enable more efficacious treatment of cancer patients....

  8. SnCl2/Cu-Mediated Carbonyl Allylation Reaction in Water:Scope,Selectivity and Mechanism

    Institute of Scientific and Technical Information of China (English)

    TAN,Xiang-Hui(谭翔晖); HOU,Yong-Quan(侯永泉); LIU,Lei(刘磊); GUO,Qing-Xiang(郭庆祥)

    2004-01-01

    Copper was found to be able to promote the SnC12-mediated carbonyl allylation reactions in water,giving the corresponding homoallylic alcohol products in very high yields.Detailed studies showed that the reaction could be applied to a variety of carbonyl compounds including those with hydroxyl,amino and nitro groups.It was also found that this reaction showed good regioselectivities for some substrates.Furthermore,carefully controled experiments and in situ NMR measurements provided important insights into the mechanism of the newly developed reaction.

  9. Rational Design of an Ultrasensitive and Highly Selective Chemodosimeter by a Dual Quenching Mechanism for Cysteine Based on a Facile Michael-Transcyclization Cascade Reaction.

    Science.gov (United States)

    Li, Xiangmin; Zheng, Yongjun; Tong, Hongjuan; Qian, Rui; Zhou, Lin; Liu, Guixia; Tang, Yun; Li, Hao; Lou, Kaiyan; Wang, Wei

    2016-06-27

    Differentiation of biologically important thiols, such as cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) is still a challenging task. Herein, we present a novel fluorescent chemodosimeter capable of selectively detecting Cys over other biothiols including Hcy and GSH and other amino acids by a facile thiol-Michael addition/transcyclization rearrangement cascade click process. The unique transcyclization step is critical for the selectivity as a result of the kinetically favorable formation of a six-membered ring with the Cys Michael adduct. Moreover, the probe adopts a distinctive dual quenching mechanism-photoinduced electron transfer (PET) and photoinduced intramolecular charge transfer (ICT) to deliver a drastic turn-on fluorescence response only at the Cys-selective transcylization step. The judicious selection of strong electron-withdrawing naphthalimide fluorophore with maleimide group enhances the electrophilicity and thus reactivity for the cascade process leading to fast detection and ultrasensitivity with a detection limit of 2.0 nm (S/N=3). The probe has demonstrated its practical utility potential in Cys imaging in live cells.

  10. Novel Design of Heptad Amphiphiles To Enhance Cell Selectivity, Salt Resistance, Antibiofilm Properties and Their Membrane-Disruptive Mechanism.

    Science.gov (United States)

    Dou, Xiujing; Zhu, Xin; Wang, Jiajun; Dong, Na; Shan, Anshan

    2017-03-23

    Coiled-coil, a basic folding pattern of native proteins, was previously demonstrated to be associated with the specific spatial recognition, association, and dissociation of proteins and can be used to perfect engineering peptide model. Thus, in this study, a series of amphiphiles composed of heptads repeats with coiled-coil structures was constructed, and the designed peptides exhibited a broad spectrum of antimicrobial activities. Circular dichroism and biological assays showed that the heptad repeats and length of the linker between the heptads largely influenced the amphiphile's helical propensity and cell selectivity. The engineered amphiphiles were also found to efficiently reduce sessile P. aeruginosa biofilm biomass, neutralize endotoxins, inhibit the inflammatory response, and remain active under physiological salt concentrations. In summary, these findings are helpful for short AMP design with a highly therapeutic index to treat bacteria-induced infection.

  11. Selectivity loss of Pt/CeO{sub 2} PROX catalysts at low CO concentrations: mechanism and active site study.

    Energy Technology Data Exchange (ETDEWEB)

    Polster, C. S.; Zhang, R.; Cyb, M. T.; Miller, J. T.; Baertsch, C. D. (Chemical Sciences and Engineering Division); (Purdue Univ.)

    2010-07-01

    CO and H{sub 2} oxidation were studied over a series of Pt/CeO{sub 2} catalysts with differing Pt loadings and dispersions. Kinetic rate analysis confirms the presence of dual Langmuir-Hinshelwood (L-H) and Mars and van Krevelen (M-vK) pathways and is used to explain the loss in CO oxidation selectivity at low CO concentrations. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) shows the strong CO coverage dependence on both CO and O{sub 2} concentrations and explains the transition from L-H to M-vK reaction character. Redox site measurements are performed on Pt/CeO{sub 2} catalysts by anaerobic titrations under conditions where the M-vK pathway dominates the reaction rate. Similar redox site densities per interfacial Pt atom suggest that interfacial Pt-O-Ce sites are responsible for M-vK redox activity.

  12. Selective femtosecond laser structuring of dielectric thin films with different band gaps: a time-resolved study of ablation mechanisms

    Science.gov (United States)

    Rapp, Stephan; Schmidt, Michael; Huber, Heinz P.

    2016-12-01

    Ultrashort pulse lasers have been increasingly gaining importance for the selective structuring of dielectric thin films in industrial applications. In a variety of works the ablation of thin SiO2 and SiNx films from Si substrates has been investigated with near infrared laser wavelengths with photon energies of about 1.2 eV where both dielectrics are transparent (E_{{gap,SiO2}}≈ 8 eV; E_{{gap,SiN}x}≈ 2.5 eV). In these works it was found that few 100 nm thick SiO2 films are selectively ablated with a "lift-off" initiated by confined laser ablation whereas the SiN_{{x}} films are ablated by a combination of confined and direct laser ablation. In the work at hand, ultrafast pump-probe imaging was applied to compare the laser ablation dynamics of the two thin film systems directly with the uncoated Si substrate—on the same setup and under identical parameters. On the SiO2 sample, results show the pulse absorption in the Si substrate, leading to the confined ablation of the SiO2 layer by the expansion of the substrate. On the SiN_{{x}} sample, direct absorption in the layer is observed leading to its removal by evaporation. The pump-probe measurements combined with reflectivity corrected threshold fluence investigations suggest that melting of the Si substrate is sufficient to initiate the lift-off of an overlaying transparent film—evaporation of the substrate seems not to be necessary.

  13. A polypeptide-DNA hybrid with selective linking capability applied to single molecule nano-mechanical measurements using optical tweezers.

    Science.gov (United States)

    Moayed, Fatemeh; Mashaghi, Alireza; Tans, Sander J

    2013-01-01

    Many applications in biosensing, biomaterial engineering and single molecule biophysics require multiple non-covalent linkages between DNA, protein molecules, and surfaces that are specific yet strong. Here, we present a novel method to join proteins and dsDNA molecule at their ends, in an efficient, rapid and specific manner, based on the recently developed linkage between the protein StrepTactin (STN) and the peptide StrepTag II (ST). We introduce a two-step approach, in which we first construct a hybrid between DNA and a tandem of two STs peptides (tST). In a second step, this hybrid is linked to polystyrene bead surfaces and Maltose Binding Protein (MBP) using STN. Furthermore, we show the STN-tST linkage is more stable against forces applied by optical tweezers than the commonly used biotin-Streptavidin (STV) linkage. It can be used in conjunction with Neutravidin (NTV)-biotin linkages to form DNA tethers that can sustain applied forces above 65 pN for tens of minutes in a quarter of the cases. The method is general and can be applied to construct other surface-DNA and protein-DNA hybrids. The reversibility, high mechanical stability and specificity provided by this linking procedure make it highly suitable for single molecule mechanical studies, as well as biosensing and lab on chip applications.

  14. A polypeptide-DNA hybrid with selective linking capability applied to single molecule nano-mechanical measurements using optical tweezers.

    Directory of Open Access Journals (Sweden)

    Fatemeh Moayed

    Full Text Available Many applications in biosensing, biomaterial engineering and single molecule biophysics require multiple non-covalent linkages between DNA, protein molecules, and surfaces that are specific yet strong. Here, we present a novel method to join proteins and dsDNA molecule at their ends, in an efficient, rapid and specific manner, based on the recently developed linkage between the protein StrepTactin (STN and the peptide StrepTag II (ST. We introduce a two-step approach, in which we first construct a hybrid between DNA and a tandem of two STs peptides (tST. In a second step, this hybrid is linked to polystyrene bead surfaces and Maltose Binding Protein (MBP using STN. Furthermore, we show the STN-tST linkage is more stable against forces applied by optical tweezers than the commonly used biotin-Streptavidin (STV linkage. It can be used in conjunction with Neutravidin (NTV-biotin linkages to form DNA tethers that can sustain applied forces above 65 pN for tens of minutes in a quarter of the cases. The method is general and can be applied to construct other surface-DNA and protein-DNA hybrids. The reversibility, high mechanical stability and specificity provided by this linking procedure make it highly suitable for single molecule mechanical studies, as well as biosensing and lab on chip applications.

  15. A Polypeptide-DNA Hybrid with Selective Linking Capability Applied to Single Molecule Nano-Mechanical Measurements Using Optical Tweezers

    Science.gov (United States)

    Tans, Sander J.

    2013-01-01

    Many applications in biosensing, biomaterial engineering and single molecule biophysics require multiple non-covalent linkages between DNA, protein molecules, and surfaces that are specific yet strong. Here, we present a novel method to join proteins and dsDNA molecule at their ends, in an efficient, rapid and specific manner, based on the recently developed linkage between the protein StrepTactin (STN) and the peptide StrepTag II (ST). We introduce a two-step approach, in which we first construct a hybrid between DNA and a tandem of two STs peptides (tST). In a second step, this hybrid is linked to polystyrene bead surfaces and Maltose Binding Protein (MBP) using STN. Furthermore, we show the STN-tST linkage is more stable against forces applied by optical tweezers than the commonly used biotin-Streptavidin (STV) linkage. It can be used in conjunction with Neutravidin (NTV)-biotin linkages to form DNA tethers that can sustain applied forces above 65 pN for tens of minutes in a quarter of the cases. The method is general and can be applied to construct other surface-DNA and protein-DNA hybrids. The reversibility, high mechanical stability and specificity provided by this linking procedure make it highly suitable for single molecule mechanical studies, as well as biosensing and lab on chip applications. PMID:23336001

  16. Thiamethoxam resistance selected in the western flower thrips Frankliniella occidentalis (Thysanoptera: Thripidae): cross-resistance patterns, possible biochemical mechanisms and fitness costs analysis.

    Science.gov (United States)

    Gao, Cong-Fen; Ma, Shao-Zhi; Shan, Cai-Hui; Wu, Shun-Fan

    2014-09-01

    The western flower thrips (WFT) Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), an important pest of various crops in the world, has invaded China since 2003. To understand the risks and to determine possible mechanisms of resistance to thiamethoxam in WFT, a resistant strain was selected under the laboratory conditions. Cross-resistance and the possible biochemical resistance mechanisms were investigated in this study. A 15.1-fold thiamethoxam-resistant WFT strain (TH-R) was established after selection for 55 generations. Compared with the susceptible strain (TH-S), the selected TH-R strain showed extremely high level cross-resistance to imidaclothiz (392.1-fold) and low level cross-resistance to dinotefuran (5.7-fold), acetamiprid (2.9-fold) and emamectin benzoate (2.1-fold), respectively. No cross-resistance to other fourteen insecticides was detected. Synergism tests showed that piperonyl butoxide (PBO) and triphenyl phosphate (TPP) produced a high synergism of thiamethoxam effects in the TH-R strain (2.6- and 2.6-fold respectively). However, diethyl maleate (DEM) did not act synergistically with thiamethoxam. Biochemical assays showed that mixed function oxidase (MFO) activities and carboxylesterase (CarE) activity of the TH-R strain were 2.8- and 1.5-fold higher than that of the TH-S strain, respectively. When compared with the TH-S strain, the TH-R strain had a relative fitness of 0.64. The results show that WFT develops resistance to thiamethoxam after continuous application and thiamethoxam resistance had considerable fitness costs in the WFT. It appears that enhanced metabolism mediated by cytochrome P450 monooxygenases and CarE was a major mechanism for thiamethoxam resistance in the WFT. The use of cross-resistance insecticides, including imidaclothiz and dinotefuran, should be avoided for sustainable resistance management.

  17. In situ FT-IR studies on the mechanism of selective catalytic reduction of NOx by propene over SnO2/Al2O3 catalyst.

    Science.gov (United States)

    Liu, Zhiming; Woo, Seong Ihl; Lee, Won Su

    2006-12-28

    The mechanism of the selective catalytic reduction (SCR) of NOx by propene over SnO2/Al2O3 catalyst in the presence of oxygen has been investigated using in situ Fourier transform infrared (FT-IR) spectroscopy. In situ IR measurements indicate that acetate and formate, which are the derivatives of the partial oxidation of propene, play a crucial role in the formation of NCO by reacting with the reactive monodentate nitrate species. The resulting NCO species subsequently reacts with NOx to form N2. The presence of oxygen substantially contributes to the partial oxidation of propene and thus shows a promoting effect for the NOx reduction.

  18. A Class of Multiresponsive Colorimetric and Fluorescent pH Probes via Three Different Reaction Mechanisms of Salen Complexes: A Selective and Accurate pH Measurement.

    Science.gov (United States)

    Cheng, Jinghui; Gou, Fei; Zhang, Xiaohong; Shen, Guangyu; Zhou, Xiangge; Xiang, Haifeng

    2016-09-19

    We report a class of multiresponsive colorimetric and fluorescent pH probes based on three different reaction mechanisms including cation exchange, protonation, and hydrolysis reaction of K(I), Ca(II), Zn(II), Cu(II), Al(III), and Pd(II) Salen complexes. Compared with traditional pure organic pH probes, these complex-based pH probes exhibited a much better selectivity due to the shielding function of the filled-in metal ion in the complex. Their pH sensing performances were affected by the ligand structure and the central metal ion. This work is the first report of "off-on-on'-off" colorimetric and fluorescent pH probes that possess three different reaction mechanisms and should inspire the design of multiple-responsive probes for important analytes in biological systems.

  19. Mechanical and shape memory properties of porous Ni50.1Ti49.9 alloys manufactured by selective laser melting.

    Science.gov (United States)

    Taheri Andani, Mohsen; Saedi, Soheil; Turabi, Ali Sadi; Karamooz, M R; Haberland, Christoph; Karaca, Haluk Ersin; Elahinia, Mohammad

    2017-01-31

    Near equiatomic NiTi shape memory alloys were fabricated in dense and designed porous forms by Selective Laser Melting (SLM) and their mechanical and shape memory properties were systematically characterized. Particularly, the effects of pore morphology on their mechanical responses were investigated. Dense and porous NiTi alloys exhibited good shape memory effect with a recoverable strain of about 5% and functional stability after eight cycles of compression. The stiffness and residual plastic strain of porous NiTi were found to depend highly on the pore shape and the level of porosity. Since porous NiTi structures have lower elastic modulus and density than dense NiTi with still good shape memory properties, they are promising materials for lightweight structures, energy absorbers, and biomedical implants.

  20. Corporate Governance in Banks and its Impact on Risk and Performance: Review of Literature on the Selected Governance Mechanisms

    Directory of Open Access Journals (Sweden)

    Himaj Shkendije

    2014-09-01

    Full Text Available Corporate governance is viewed as an important, essential, and most significant factor for well-functioning of firms. Recent academic work and policy analyses have given insight into the governance problems in banks exposed to the financial crisis and suggest possible solutions. This paper begins by explaining the importance of corporate governance and its impact on risk taking and bank performance based on the theoretical background relevant to the corporate governance of banks. I combine the literature that looks at three areas of governance: ownership structure; board structure; and risk management, with the literature on risk-taking and performance effects in order to better assess the weight of the impact that these governance mechanisms have on both performance and risk. The paper concludes by highlighting the areas where further research is needed.

  1. An overview of three promising mechanical, optical, and biochemical engineering approaches to improve selective photothermolysis of refractory port wine stains.

    Science.gov (United States)

    Aguilar, Guillermo; Choi, Bernard; Broekgaarden, Mans; Yang, Owen; Yang, Bruce; Ghasri, Pedram; Chen, Jennifer K; Bezemer, Rick; Nelson, J Stuart; van Drooge, Anne Margreet; Wolkerstorfer, Albert; Kelly, Kristen M; Heger, Michal

    2012-02-01

    During the last three decades, several laser systems, ancillary technologies, and treatment modalities have been developed for the treatment of port wine stains (PWSs). However, approximately half of the PWS patient population responds suboptimally to laser treatment. Consequently, novel treatment modalities and therapeutic techniques/strategies are required to improve PWS treatment efficacy. This overview therefore focuses on three distinct experimental approaches for the optimization of PWS laser treatment. The approaches are addressed from the perspective of mechanical engineering (the use of local hypobaric pressure to induce vasodilation in the laser-irradiated dermal microcirculation), optical engineering (laser-speckle imaging of post-treatment flow in laser-treated PWS skin), and biochemical engineering (light- and heat-activatable liposomal drug delivery systems to enhance the extent of post-irradiation vascular occlusion).

  2. World Congress on Computational Mechanics, 2nd, Universitaet Stuttgart, Federal Republic of Germany, Aug. 27-31, 1990, Selected Papers

    Science.gov (United States)

    Argyris, John; Doltsinis, Ioannis St.; Oden, J. T.

    The present conference on computer methods in applied mechanics and engineering encompasses methods for describing fluids, structures, dynamics, applied physics, and computing and numerical methods. Specific issues addressed include h-p adaptive finite-element methods in computational fluid dynamics, simulations of hypersonic viscous flows about the H-II orbiting plane, chemically reacting hypersonic viscous flows, a numerical model for buckling and growth of delaminations in composite laminates, and CAD-integrated structural topology and design optimization. Also addressed are defect-mediated turbulence, geometrical concepts of nonlinear dynamics, vertical solidification of dendritic binary alloys, the parallelization of CFD codes, the integration of solid modeling and finite-element generation, studies of parallel processing for coupled-field problems, and an information system for the numerical simulation of 3D Euler flows around aircraft.

  3. Parallel selection of chemotherapy-resistant cell lines to illuminate mechanisms of drug resistance in human tumors

    DEFF Research Database (Denmark)

    Krzystanek, Marcin; Eklund, Aron Charles; Birkbak, Nicolai Juul

    2011-01-01

    the identification of reliable predictive biomarkers for each drug. Currently, we are developing a framework for systematic biomarker discovery by using a combination of gene expression and CGH arrays to keep track of consistent changes that take place during resistance acquisition in cell lines towards two anti......-cancer drugs: doxorubicin and paclitaxel. By monitoring changes at two different levels (DNA and RNA) of the genome and developing multiple cell lines developing resistance against the same drug under identical conditions, we were able to separate relevant changes from spurious ones and thus reducing the noise....... Our findings are validated on already existing gene expression profiles of patient cohorts treated with the drugs in question, and the most promising ones will be chosen for functional validation by RNAi knock down. Successful validation will improve understanding of drug resistance mechanisms...

  4. Innovative Financial Instruments and mechanisms for financing forest restoration and mitigating climate change: select cases from India

    Directory of Open Access Journals (Sweden)

    Teki Surayya

    2012-06-01

    Full Text Available Climate Change (CC is universal concern. One of the causes for CC is degradation offorest. World over every minute 22 hectares forest is degraded. Reckonings suggests thatUS$ 11880, funds must be invested every minute to restore the forest.In India Atmospheric pollution has severed in 90’s because of increasedautomobiles and electronic goods. Green car congress reported level of NO2concentration in Delhi ranged 70 - 102 microgram per cm, in 2005. It is argued that theconsumers are capable of meeting part of cost of CC mitigation. Recent survey (Teki,2008 in National Capital Region revealed that 40% of sample preferred to compensatethrough tax on petroleum products, 22 % in investing in forestry bonds, 57% favouredcompulsory investment in bonds. Awareness rate about climate change was 92%, and 88%favoured both technology transitions and economic sanctions for mitigating CC. Evolvinginnovative financing instruments and mechanisms to finance forest restoration andmitigating CC is important.Timber was considered important contribution of forests, as 2% GDP comes toexchequer. NTFPs now considered equally important for forest restoration as 25 – 55% offorest living people survival comes from NTFPs. Forests have innovative financialinstruments like Eco-tourism, to finance forest restoration. Self reliance apart from thegovernment funding and the private funding. Mobilisation of savings, bank finance,creating/strengthening global carbon fund effectively and financing the substitute sectorsare important for restoration of ecological integration and productivity and economic valueof deforested or degraded land. Objectives of paper are: a to assess level and impact offorest degradation and forest restoration in India, b to translate carbon pollution level intomitigating CC, b awareness level of CC in NCR c measure willingness of consumers tocompensate for CC, and d evolve innovative financial instruments and mechanisms tofinance sustainable forest

  5. Multiple insecticide resistance mechanisms involving metabolic changes and insensitive target sites selected in anopheline vectors of malaria in Sri Lanka

    Directory of Open Access Journals (Sweden)

    Karunaratne SHP Parakrama

    2008-08-01

    Full Text Available Abstract Background The current status of insecticide resistance and the underlying resistance mechanisms were studied in the major vector of malaria, Anopheles culicifacies, and the secondary vector, Anopheles subpictus in five districts (Anuradhapura, Kurunegala, Moneragala, Puttalam and Trincomalee of Sri Lanka. Eight other anophelines, Anopheles annularis, Anopheles barbirostris, Anopheles jamesii, Anopheles nigerrimus, Anopheles peditaeniatus, Anopheles tessellatus, Anopheles vagus and Anopheles varuna from Anuradhapura district were also tested. Methods Adult females were exposed to the WHO discriminating dosages of DDT, malathion, fenitrothion, propoxur, λ-cyhalothrin, cyfluthrin, cypermethrin, deltamethrin, permethrin and etofenprox. The presence of metabolic resistance by esterase, glutathione S-transferase (GST and monooxygenase-based mechanisms, and the sensitivity of the acetylcholinesterase target site were assessed using synergists, and biochemical, and metabolic techniques. Results All the anopheline species had high DDT resistance. All An. culicifacies and An. subpictus populations were resistant to malathion, except An. culicifacies from Kurunegala, where there was no malathion carboxylesterase activity. Kurunegala and Puttalam populations of An. culicifacies were susceptible to fenitrothion. All the An. culicifacies populations were susceptible to carbamates. Both species were susceptible to the discriminating dosages of cypermethrin and cyfluthrin, but had different levels of resistance to other pyrethroids. Of the 8 other anophelines, only An. nigerrimus and An. peditaeniatus were resistant to all the insecticides tested, probably due to their high exposure to the insecticides used in agriculture. An. vagus showed some resistance to permethrin. Esterases, GSTs and monooxygenases were elevated in both An. culicifacies and An. subpictus. AChE was most sensitive to insecticides in Kurunegala and Trincomalee An. culicifacies

  6. Cis and trans regulatory mechanisms control AP2-mediated B cell receptor endocytosis via select tyrosine-based motifs.

    Directory of Open Access Journals (Sweden)

    Kathleen Busman-Sahay

    Full Text Available Following antigen recognition, B cell receptor (BCR-mediated endocytosis is the first step of antigen processing and presentation to CD4+ T cells, a crucial component of the initiation and control of the humoral immune response. Despite this, the molecular mechanism of BCR internalization is poorly understood. Recently, studies of activated B cell-like diffuse large B cell lymphoma (ABC DLBCL have shown that mutations within the BCR subunit CD79b leads to increased BCR surface expression, suggesting that CD79b may control BCR internalization. Adaptor protein 2 (AP2 is the major mediator of receptor endocytosis via clathrin-coated pits. The BCR contains five putative AP2-binding YxxØ motifs, including four that are present within two immunoreceptor tyrosine-based activation motifs (ITAMs. Using a combination of in vitro and in situ approaches, we establish that the sole mediator of AP2-dependent BCR internalization is the membrane proximal ITAM YxxØ motif in CD79b, which is a major target of mutation in ABC DLBCL. In addition, we establish that BCR internalization can be regulated at a minimum of two different levels: regulation of YxxØ AP2 binding in cis by downstream ITAM-embedded DCSM and QTAT regulatory elements and regulation in trans by the partner cytoplasmic domain of the CD79 heterodimer. Beyond establishing the basic rules governing BCR internalization, these results illustrate an underappreciated role for ITAM residues in controlling clathrin-dependent endocytosis and highlight the complex mechanisms that control the activity of AP2 binding motifs in this receptor system.

  7. Pathway and Surface Mechanism Studies of 1,3-butadiene Selective Oxidation Over Vanadium-Molybdenum-Oxygen Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Schroeder, William David [Iowa State Univ., Ames, IA (United States)

    2001-01-01

    The partial oxidation of 1,3-butadiene has been investigated over VMoO catalysts synthesized by sol-gel techniques. Surface areas were 9-14 m2/g, and compositions were within the solid solution regime, i.e. below 15.0 mol % MoO3/(MoO3 + V2O5). Laser Raman Spectroscopy and XRD data indicated that solid solutions were formed, and pre- and post-reaction XPS data indicated that catalyst surfaces contained some V+4 and were further reduced in 1,3-butadiene oxidation. A reaction pathway for 1,3-butadiene partial oxidation to maleic anhydride was shown to involve intermediates such as 3,4-epoxy-1-butene, crotonaldehyde, furan, and 2-butene-1,4-dial. The addition of water to the reaction stream substantially increased catalyst activity and improved selectivity to crotonaldehyde and furan at specific reaction temperatures. At higher water addition concentrations, furan selectivity increased from 12% to over 25%. The catalytic effects of water addition were related to competitive adsorption with various V2O5-based surface sites, including the vanadyl V=O, corner sharing V-O-V and edge sharing V-O oxygen. Higher levels of water addition were proposed to impose acidic character by dissociative adsorption. In addition, a novel combinatorial synthesis technique for VMoO was used to investigate the phase transitions of V2O5, solid solutions of Mo in V2O5, V9Mo6O40, and other reduced VMoO compounds, characterized by laser Raman spectroscopy. The natural composition gradient imposed by the sputter deposition apparatus was used to create VMoO arrays containing 225 samples ranging from 7.0-42 mol% MoO3/(V2O5 + MoO3), determined by EDS analysis.

  8. Evaluating the effect of increasing ceramic content on the mechanical properties, material microstructure and degradation of selective laser sintered polycaprolactone/β-tricalcium phosphate materials.

    Science.gov (United States)

    Doyle, Heather; Lohfeld, Stefan; McHugh, Peter

    2015-08-01

    Orthopaedic scaffold materials were fabricated from polycaprolactone (PCL) and composite PCL-β-tricalcium phosphate (PCL/β-TCP) powders using selective laser sintering (SLS). Incorporating β-TCP particles is desirable to promote osteogenesis. The effects of increasing β-TCP content on the material's mechanical properties and microstructure were evaluated. The wt% of β-TCP and PCL particle sizes were found to influence material microstructure and mechanical properties, with increasing ceramic content causing a small but significant increase in stiffness but significant reductions in strength. Degradation of materials was achieved using accelerated ageing methods. The influence of β-TCP content on degradation at 7 weeks was evaluated through changes in mechanical properties and microstructure, and the ceramic particles were found to reduce elastic modulus and increase strength. The results of this study highlight the influence of ceramic content on mechanical properties and degradation behaviour of PCL/β-TCP SLS materials, and indicate that these changes must be considered in the design of scaffolds for critical-sized defects.

  9. Processing of Polysulfone to Free Flowing Powder by Mechanical Milling and Spray Drying Techniques for Use in Selective Laser Sintering

    Directory of Open Access Journals (Sweden)

    Nicolas Mys

    2016-04-01

    Full Text Available Polysulfone (PSU has been processed into powder form by ball milling, rotor milling, and spray drying technique in an attempt to produce new materials for Selective Laser Sintering purposes. Both rotor milling and spray drying were adept to make spherical particles that can be used for this aim. Processing PSU pellets by rotor milling in a three-step process resulted in particles of 51.8 μm mean diameter, whereas spray drying could only manage a mean diameter of 26.1 μm. The resulting powders were characterized using Differential Scanning Calorimetry (DSC, Gel Permeation Chromatography (GPC and X-ray Diffraction measurements (XRD. DSC measurements revealed an influence of all processing techniques on the thermal behavior of the material. Glass transitions remained unaffected by spray drying and rotor milling, yet a clear shift was observed for ball milling, along with a large endothermic peak in the high temperature region. This was ascribed to the imparting of an orientation into the polymer chains due to the processing method and was confirmed by XRD measurements. Of all processed powder samples, the ball milled sample was unable to dissolve for GPC measurements, suggesting degradation by chain scission and subsequent crosslinking. Spray drying and rotor milling did not cause significant degradation.

  10. Mechanical Properties and Microstructural Characterization of Cu-4.3 Pct Sn Fabricated by Selective Laser Melting

    Science.gov (United States)

    Ventura, Anthony P.; Wade, C. Austin; Pawlikowski, Gregory; Bayes, Martin; Watanabe, Masashi; Misiolek, Wojciech Z.

    2017-01-01

    Components were fabricated via selective laser melting (SLM) of prealloyed Cu-4.3 pct Sn powder and heat treated at 873 K and 1173 K (600 °C and 900 °C) for 1 hour. Tensile testing, conductivity measurement, and detailed microstructural characterization were carried out on samples in the as-printed and heat-treated conditions. Optimization of build parameters resulted in samples with around 97 pct density with a yield strength of 274 MPa, an electrical conductivity of 24.1 pct IACS, and an elongation of 5.6 pct. Heat treatment resulted in lower yield strength with significant increases in ductility due to recrystallization and a decrease in dislocation density. Tensile sample geometry and surface finish also showed a significant effect on measured yield strength but a negligible change in measured ductility. Microstructural characterization indicated that grains primarily grow epitaxially with a submicron cellular solidification substructure. Nanometer scale tin dioxide particles identified via X-ray diffraction were found throughout the structure in the tin-rich intercellular regions.

  11. Investigation of the mechanical properties and porosity relationships in selective laser-sintered polyhedral for functionally graded scaffolds.

    Science.gov (United States)

    Sudarmadji, N; Tan, J Y; Leong, K F; Chua, C K; Loh, Y T

    2011-02-01

    An important requirement for a bone tissue engineering scaffold is a stiffness gradient that mimics that of native bone. Such scaffolds can be achieved by controlling their structure and porosity and are termed functionally graded scaffolds (FGS). Currently, the main challenges in FGS fabrication include the iterative and tedious design process as well as a heavy reliance on the user's CAD/CAM skills. This work aims to bring automated FGS production a step closer by providing a database that correlates scaffold porosity values and the corresponding compressive stiffness and integrating it into the design process. To achieve this goal, scaffolds with different structural configurations were designed using CASTS (Computer Aided System for Tissue Scaffolds), an in-house developed library system consisting of 13 different polyhedral units that can be assembled into scaffold structures. Polycaprolactone (PCL) was chosen as the scaffold material, while selective laser sintering, a powder-based rapid prototyping or additive manufacturing system was employed to fabricate the scaffolds. Mathematical relations correlating scaffold porosity and compressive stiffness readings were formulated and compiled. In addition, cytotoxicity assessment was conducted to evaluate the toxicity of the fabricated PCL scaffolds. Lastly, a brief demonstration of how the formulated relations are used in the FGS design process is presented.

  12. 人工生命行为选择情绪机制研究进展%Research Progress on Emotional Behavior Selection Mechanism of Artificial Life

    Institute of Scientific and Technical Information of China (English)

    张国锋; 李祖枢

    2012-01-01

    基于智能的行为选择机制(BSM)存在两个缺陷:不确定性环境下,不能实现自主行为选择,在相同环境条件下,缺乏行为反应的多样性.受情绪机制应用于情感计算与强化学习研究的启发,将其应用于行为选择机制研究,以解决上述问题,从而,提出三类情绪行为选择机制:情绪影响机制、情绪驱动机制、情绪涌现机制.但这些机制存在:未能将其所需涉及的基本因素进行涵盖,有系统性缺陷;各种选择机制体系结构和情绪计算模型彼此各异,没有继承性;基于设计思想,缺乏相关学科关于情绪行为理论的支撑.另外,研究方法上,也存在各行为机制之间、智能机制和情绪机制之间缺乏系统性分析和比较的问题.提出,要揭示情绪行为选择机制,应从认真挖掘动物行为学、心理学、经济学等领域有关情绪研究结果之间的内在一致性入手.同时,比较方法的使用,将是加速这一过程的有效手段.%There are two defects on intelligence-based Behavior selection mechanism (BSM): under uncertainty conditions, behavior selection can't be achieved autonomously; under same conditions, behavioral response is absence of diversity. Being inspirited by research achievements in emotion mechanism application for emotion calculation and reinforcement learning, emotion mechanism is applied to research on BSM to settle the above problems. Therefore, the three kinds of emotional BSM( EBSM) are suggested :emotion-affected mechanism, emotion-driven mechanism,emotion-emerged mechanism. However, these mechanisms have three problems: a systematic drawback exists that the necessary elements, which BSM should have had, have not involved in; The EBSM architectures and their emotion models are different from each other, there is no inheritane; They are design-based, there are not the corresponding academic supports for them on emotion behavior mechanism. In addition, there exists a problem on the

  13. High Specific Selectivity and Membrane-Active Mechanism of Synthetic Cationic Hybrid Antimicrobial Peptides Based on the Peptide FV7.

    Science.gov (United States)

    Tan, Tingting; Wu, Di; Li, Weizhong; Zheng, Xin; Li, Weifen; Shan, Anshan

    2017-02-06

    Hybrid peptides integrating different functional domains of peptides have many advantages, such as remarkable antimicrobial activity, lower hemolysis and ideal cell selectivity, compared with natural antimicrobial peptides. FV7 (FRIRVRV-NH₂), a consensus amphiphilic sequence was identified as being analogous to host defense peptides. In this study, we designed a series of hybrid peptides FV7-LL-37 (17-29) (FV-LL), FV7-magainin 2 (9-21) (FV-MA) and FV7-cecropin A (1-8) (FV-CE) by combining the FV7 sequence with the small functional sequences LL-37 (17-29) (LL), magainin 2 (9-21) (MA) and cecropin A (1-8) (CE) which all come from well-described natural peptides. The results demonstrated that the synthetic hybrid peptides, in particular FV-LL, had potent antibacterial activities over a wide range of Gram-negative and Gram-positive bacteria with lower hemolytic activity than other peptides. Furthermore, fluorescent spectroscopy indicated that the hybrid peptide FV-LL exhibited marked membrane destruction by inducing outer and inner bacterial membrane permeabilization, while scanning electron microscopy (SEM) and transmission electron microscopy (TEM) demonstrated that FV-LL damaged membrane integrity by disrupting the bacterial membrane. Inhibiting biofilm formation assays also showed that FV-LL had similar anti-biofilm activity compared with the functional peptide sequence FV7. Synthetic cationic hybrid peptides based on FV7 could provide new models for combining different functional domains and demonstrate effective avenues to screen for novel antimicrobial agents.

  14. β-agonists selectively modulate proinflammatory gene expression in skeletal muscle cells via non-canonical nuclear crosstalk mechanisms.

    Directory of Open Access Journals (Sweden)

    Krzysztof Kolmus

    Full Text Available The proinflammatory cytokine Tumour Necrosis Factor (TNF-α is implicated in a variety of skeletal muscle pathologies. Here, we have investigated how in vitro cotreatment of skeletal muscle C2C12 cells with β-agonists modulates the TNF-α-induced inflammatory program. We observed that C2C12 myotubes express functional TNF receptor 1 (TNF-R1 and β2-adrenoreceptors (β2-ARs. TNF-α activated the canonical Nuclear Factor-κB (NF-κB pathway and Mitogen-Activated Protein Kinases (MAPKs, culminating in potent induction of NF-κB-dependent proinflammatory genes. Cotreatment with the β-agonist isoproterenol potentiated the expression of inflammatory mediators, including Interleukin-6 (IL-6 and several chemokines. The enhanced production of chemotactic factors upon TNF-α/isoproterenol cotreatment was also suggested by the results from migrational analysis. Whereas we could not explain our observations by cytoplasmic crosstalk, we found that TNF-R1-and β2-AR-induced signalling cascades cooperate in the nucleus. Using the IL-6 promoter as a model, we demonstrated that TNF-α/isoproterenol cotreatment provoked phosphorylation of histone H3 at serine 10, concomitant with enhanced promoter accessibility and recruitment of the NF-κB p65 subunit, cAMP-response element-binding protein (CREB, CREB-binding protein (CBP and RNA polymerase II. In summary, we show that β-agonists potentiate TNF-α action, via nuclear crosstalk, that promotes chromatin relaxation at selected gene promoters. Our data warrant further study into the mode of action of β-agonists and urge for caution in their use as therapeutic agents for muscular disorders.

  15. High Specific Selectivity and Membrane-Active Mechanism of Synthetic Cationic Hybrid Antimicrobial Peptides Based on the Peptide FV7

    Science.gov (United States)

    Tan, Tingting; Wu, Di; Li, Weizhong; Zheng, Xin; Li, Weifen; Shan, Anshan

    2017-01-01

    Hybrid peptides integrating different functional domains of peptides have many advantages, such as remarkable antimicrobial activity, lower hemolysis and ideal cell selectivity, compared with natural antimicrobial peptides. FV7 (FRIRVRV-NH2), a consensus amphiphilic sequence was identified as being analogous to host defense peptides. In this study, we designed a series of hybrid peptides FV7-LL-37 (17–29) (FV-LL), FV7-magainin 2 (9–21) (FV-MA) and FV7-cecropin A (1–8) (FV-CE) by combining the FV7 sequence with the small functional sequences LL-37 (17–29) (LL), magainin 2 (9–21) (MA) and cecropin A (1–8) (CE) which all come from well-described natural peptides. The results demonstrated that the synthetic hybrid peptides, in particular FV-LL, had potent antibacterial activities over a wide range of Gram-negative and Gram-positive bacteria with lower hemolytic activity than other peptides. Furthermore, fluorescent spectroscopy indicated that the hybrid peptide FV-LL exhibited marked membrane destruction by inducing outer and inner bacterial membrane permeabilization, while scanning electron microscopy (SEM) and transmission electron microscopy (TEM) demonstrated that FV-LL damaged membrane integrity by disrupting the bacterial membrane. Inhibiting biofilm formation assays also showed that FV-LL had similar anti-biofilm activity compared with the functional peptide sequence FV7. Synthetic cationic hybrid peptides based on FV7 could provide new models for combining different functional domains and demonstrate effective avenues to screen for novel antimicrobial agents. PMID:28178190

  16. Basic principles and mechanisms of selective oil agglomeration. Fossil energy interim report, October 1, 1983--September 30, 1992

    Energy Technology Data Exchange (ETDEWEB)

    Wheelock, T.D.

    1992-12-31

    Numerous agglomeration tests were conducted with several types of low-ash coal and graphite, high grade mineral pyrite, and other materials. Relatively pure hydrocarbons, including heptane and hexadecane, were used as agglomerants. Access of air to the system was controlled. Particle recovery by agglomeration was observed to depend on a number of system parameters. Among the most important parameters are the hydrophobicity of the particles and the oil dosage, so that the, recovery of solids per unit of oil administered is proportional to the hydrophobicity. The pH and ionic strength of the aqueous suspension affect particle recovery in different ways depending on the surface properties of the particles. On the other hand, the presence of air in the system generally improves particle recovery. The greatest effect of air was observed in a closely related study which showed that air had to be present to produce good agglomerates from a moderately hydrophobic coal in a mixer producing a lower shear rate. The rate of agglomeration was found to be much greater for a strongly hydrophobic coal than for a moderately hydrophobic coal, and the rate was observed to be proportional to the oil dosage. Also the rate was enhanced by the presence of air in the, system. For hydrophobic coals, the rate increased with increasing ionic strength of the aqueous medium, but it was not affected greatly by pH over a wide range. The separation of coal and pyrite particles by selective agglomeration was found to depend on the relative hydrophobicity of the materials, the oil dosage, and the properties of the aqueous medium.

  17. Relative importance of various regeneration mechanisms in different restoration stages of Quercus variabilis forest after selective logging

    Directory of Open Access Journals (Sweden)

    Yaoqin Xue

    2014-08-01

    Full Text Available Aim of study: Quercus variabilis (Chinese cork oak reproduces asexually and sexually. This study aimed to determine the status and growth of asexual and sexual recruits of Q. variabilis in different forest recovery stages.Area of study: Three selective logged stands and one unlogged stand in Q. variabilis forest, Shaanxi Province, China.Material and Methods: Origin, number, basal diameter, height and size structure of Q. variabilis shoots (height ≤200 cm were investigated in the plots of 5, 10, and 20-years post-logging stands and unlogged stand. Effects of recovery stage on the density and growth of the three original recruits (stump sprouts, stem base sprouts and true seedlings were analysis by One-way ANOVA.Main results: Sprouts dominated logged stands, whereas true seedlings dominated unlogged stand, stem base sprouts only existed in 20-years post-logging and unlogged stands. Stump sprout density and sprout number per stump both declined with extended post-logging time. True seedlings density increased from 7 to 20 shoots/100 m2 as the postlogging time extended, and peaked in unlogged stand (94 shoots/100 m2. An ongoing size structure was observed in true seedlings in all stands. Stump sprouts were taller and greater than true seedlings.Research highlights: Stump sprouts contributed more to Q. variabilis forest recovery in the early stage after disturbance. The contribution of true seedlings was limited in the same stage, but they were beneficial for population long-term development. Stem base sprouts were most likely to be a survival strategy rather than a reproductive strategy.Key words: asexual reproduction; true seedling; post-logging time; Chinese cork oak.

  18. Mechanical properties examined by nanoindentation for selected phases relevant to the development of monolithic uranium-molybdenum metallic fuels

    Science.gov (United States)

    Newell, Ryan; Park, Youngjoo; Mehta, Abhishek; Keiser, Dennis; Sohn, Yongho

    2017-04-01

    Nanomechanical properties, specifically the reduced modulus and hardness of several intermetallic and solid solution phases are reported to assist the development of the U-10 wt% Mo (U-10Mo) monolithic fuel system for research and test reactors. Findings from this study and reported values of mechanical properties provide data critical for understanding and predicting the structural behavior of the fuel system during fabrication and irradiation. The phases examined are products of interdiffusion and reaction between (1) the AA6061 cladding and the Zr diffusion barrier, namely (Al,Si)3Zr and Al3Zr, (2) the U-10Mo fuel and the Zr diffusion barrier, namely UZr2, Mo2Zr, and α-U, and (3) the U (or U-10Mo) and Mo, namely a mixture gradient of α- and γ-phases. The UC inclusions observed within the fuel alloy were also examined. Only phases present in thick or continuous microstructure on cross-sectioned fuel plates and diffusion couples were investigated for reduced modulus and hardness. Concentration-dependence of room-temperature reduced modulus in U solid solution with 0-10 wt% Mo was semi-quantitatively modeled based on mixture of α- and γ-phases and solid solutioning within the γ-phase.

  19. Comparison of experimental approaches to study selective properties of thick phase-amplitude holograms recorded in materials with diffusion-based formation mechanisms

    Science.gov (United States)

    Borisov, Vladimir; Klepinina, Mariia; Veniaminov, Andrey; Angervaks, Aleksandr; Shcheulin, Aleksandr; Ryskin, Aleksandr

    2016-04-01

    Volume holographic gratings, both transmission and reflection-type, may be employed as one-dimensional pho- tonic crystals. More complex two- and three-dimensional holographic photonic-crystalline structures can be recorded using several properly organized beams. As compared to colloidal photonic crystals, their holographic counterparts let minimize distortions caused by multiple inner boundaries of the media. Unfortunately, it's still hard to analyze spectral response of holographic structures. This work presents the results of thick holographic gratings analysis based on spectral-angular selectivity contours approximation. The gratings were recorded in an additively colored fluorite crystal and a glassy polymer doped with phenanthrenequinone (PQ-PMMA). The two materials known as promising candidates for 3D diffraction optics including photonic crystals, employ diffusion-based mechanisms of grating formation. The surfaces of spectral-angular selectivity were obtained in a single scan using a white-light LED, rotable table and a matrix spectrometer. The data expressed as 3D plots make apparent visual estimation of the grating phase/amplitude nature, noninearity of recording, etc., and provide sufficient information for numerical analysis. The grating recorded in the crystal was found to be a mixed phase-amplitude one, with different contributions of refractive index and absorbance modulation at different wavelengths, and demonstrated three diffraction orders corresponding to its three spatial harmonics originating from intrinsically nonlinear diffusion-drift recording mechanism. Contrastingly, the grating in the polymeric medium appeared purely phase and linearly recorded.

  20. A new kinetic model based on the remote control mechanism to fit experimental data in the selective oxidation of propene into acrolein on biphasic catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Abdeldayem, H.M.; Ruiz, P.; Delmon, B. [Unite de Catalyse et Chimie des Materiaux Divises, Universite Catholique de Louvain, Louvain-La-Neuve (Belgium); Thyrion, F.C. [Unite des Procedes Faculte des Sciences Appliquees, Universite Catholique de Louvain, Louvain-La-Neuve (Belgium)

    1998-12-31

    A new kinetic model for a more accurate and detailed fitting of the experimental data is proposed. The model is based on the remote control mechanism (RCM). The RCM assumes that some oxides (called `donors`) are able to activate molecular oxygen transforming it to very active mobile species (spillover oxygen (O{sub OS})). O{sub OS} migrates onto the surface of the other oxide (called `acceptor`) where it creates and/or regenerates the active sites during the reaction. The model contains tow terms, one considering the creation of selective sites and the other the catalytic reaction at each site. The model has been tested in the selective oxidation of propene into acrolein (T=380, 400, 420 C; oxygen and propene partial pressures between 38 and 152 Torr). Catalysts were prepared as pure MoO{sub 3} (acceptor) and their mechanical mixtures with {alpha}-Sb{sub 2}O{sub 4} (donor) in different proportions. The presence of {alpha}-Sb{sub 2}O{sub 4} changes the reaction order, the activation energy of the reaction and the number of active sites of MoO{sub 3} produced by oxygen spillover. These changes are consistent with a modification in the degree of irrigation of the surface by oxygen spillover. The fitting of the model to experimental results shows that the number of sites created by O{sub SO} increases with the amount of {alpha}-Sb{sub 2}O{sub 4}. (orig.)

  1. Novel polyazamacrocyclic receptor decorated core-shell superparamagnetic microspheres for selective binding and magnetic enrichment of palladium: synthesis, adsorptive behavior and coordination mechanism.

    Science.gov (United States)

    Wu, Fengcheng; Ye, Gang; Yi, Rong; Sun, Taoxiang; Xu, Chao; Chen, Jing

    2016-06-21

    The development of economical and green technologies for the effective recovery of palladium has attracted worldwide attention in recent years. Magnetic separation involving the use of functional magnetic nanoparticles (MNPs) with superparamagnetic characteristics holds great promise in this respect. This study presents a novel class of core-shell structured superparamagnetic microspheres decorated with polyazamacrocyclic receptors, which show a highly-selective binding to Pd(ii) in HNO3 media. The superparamagnetic microspheres possess a high saturation magnetization (53.8 emu g(-1)) and high adsorption capacity (qmax≈ 105.3 μmol g(-1)), affording efficient enrichment and fast separation (within 13 seconds) of palladium under an applied magnetic field. Adsorptive behavior was fully investigated combined with the corresponding theoretical analysis by using kinetic equations and Langmuir/Freundlich isotherm models. Moreover, the coordination mechanism of the polyazamacrocyclic receptors to Pd(ii) was carefully examined based on high resolution X-ray photoelectron spectroscopy (XPS) and FT-IR spectrophotometry. A suggested mechanism involving the synergistic effect of the cyclic amines and carboxyl arms of the polyazamacrocyclic receptors was proposed to describe the coordination manner, while explaining the selectivity to Pd(ii) in HNO3 solutions. From a practical perspective, the Pd(ii)-enriched microspheres could be readily regenerated for cycle use. We conclude that this kind of polyazamacrocyclic receptor decorated superparamagnetic microsphere is of potential use for the effective recovery of Pd(ii) as well as other precious metals.

  2. Selected papers from the 23rd MicroMechanics and Microsystems Europe Workshop (MME 2012) (Ilmenau, Germany, September 9-12, 2012)

    Science.gov (United States)

    Hoffmann, Martin

    2013-07-01

    In September 2012, the 23rd MicroMechanics Europe Workshop (MME) took place in Ilmenau, Germany. With about 120 participants from 20 countries and 76 accepted presentations, the workshop series turned out to be a successful platform for young scientists to present their work to our scientific community. Traditionally, the interaction is an important aspect of this workshop: while short presentations introduce the posters, an extended poster session allows intensive discussion which is quite useful to the participants. The discussion very often extends into the breaks and the evening events. It is also encouraging for them that the best presentations are selected and invited to submit a full paper to this journal. Thanks to the support of IOP Publishing, this next logical step to present work to the scientific world is made possible. In this issue, you can find the best papers that have been selected by a committee during the workshop taking the written workshop contribution, the poster and the presentation into account. Again, all areas of micromechanics from new technology developments up to systems integration were presented at the workshop at different levels of completion. The selected papers present those results which are almost complete. Nevertheless, it is nice to see that in some cases topics grow over the years from 'nice ideas' to realized system concepts. And although this is the 23rd workshop, it is clear that micromechanics is a topic that is not running short of new ideas. First, I would like to thank the authors of the selected papers for each of their individual excellent contributions. My gratitude also goes to my fellow members in the programme committee (Per Ohlckers, Martin Hill and Sami Franssila) for their cooperation in the selection of invited speakers and submitted papers, as well as the anonymous Journal of Micromechanics and Microengineering (JMM) reviewers for their careful selection of the final papers presented here. Last, but not

  3. The complex I subunit NDUFA10 selectively rescues Drosophila pink1 mutants through a mechanism independent of mitophagy.

    Directory of Open Access Journals (Sweden)

    Joe H Pogson

    2014-11-01

    Full Text Available Mutations in PINK1, a mitochondrially targeted serine/threonine kinase, cause autosomal recessive Parkinson's disease (PD. Substantial evidence indicates that PINK1 acts with another PD gene, parkin, to regulate mitochondrial morphology and mitophagy. However, loss of PINK1 also causes complex I (CI deficiency, and has recently been suggested to regulate CI through phosphorylation of NDUFA10/ND42 subunit. To further explore the mechanisms by which PINK1 and Parkin influence mitochondrial integrity, we conducted a screen in Drosophila cells for genes that either phenocopy or suppress mitochondrial hyperfusion caused by pink1 RNAi. Among the genes recovered from this screen was ND42. In Drosophila pink1 mutants, transgenic overexpression of ND42 or its co-chaperone sicily was sufficient to restore CI activity and partially rescue several phenotypes including flight and climbing deficits and mitochondrial disruption in flight muscles. Here, the restoration of CI activity and partial rescue of locomotion does not appear to have a specific requirement for phosphorylation of ND42 at Ser-250. In contrast to pink1 mutants, overexpression of ND42 or sicily failed to rescue any Drosophila parkin mutant phenotypes. We also find that knockdown of the human homologue, NDUFA10, only minimally affecting CCCP-induced mitophagy, and overexpression of NDUFA10 fails to restore Parkin mitochondrial-translocation upon PINK1 loss. These results indicate that the in vivo rescue is due to restoring CI activity rather than promoting mitophagy. Our findings support the emerging view that PINK1 plays a role in regulating CI activity separate from its role with Parkin in mitophagy.

  4. CRITERIA FOR SELECTION OF ALLOYING COMPONENTS AND BASE COMPOSITIONS FOR MANUFACTURING OF MECHANICALLY ALLOYED DISPERSION-STRENGTHENED MATERIALS ON THE BASIS OF METALS

    Directory of Open Access Journals (Sweden)

    F. G. Lovshenko

    2016-01-01

    Full Text Available The paper presents results of the investigations pertaining to creation of scientifically substantiated criteria for selection of alloying components and base compositions for manufacturing of mechanically alloyed dispersion-strengthened metallic materials. An analysis of dispersion strengthening mechanisms and regularities in mechanically activated phase and structural transformations serve as a reliable basis for solution of the assigned mission. Foer efficient strengthening at low and high temperatures as well materials must have fragmented and polygonized structure with maximum developed surface of grain and sub-grain boundaries which are stabilized by nano-sized inclusions of strengthening phases. Experimental investigations have shown that an optimum complex of mechanical properties is obtained in the case when nano-sized strengthening phase is equal to 3–5 % (volume. The phases applied for dispersion strengthening must have high value of shear modulus that determines their hardness and strength. Critical compressive stress should not cause deformation and destruction of disperse particles. Furthermore, they must have high stability in contact with a matrix. The substances applied as alloying components for realization of the developed technology on obtaining dispersion-strengthening materials must firstly meet the following requirements: they must be cheap, accessible and ecologically safety; they must interact with the basis or inter se at temperatures which are lower of material melting temperature; one of the phases which is formed in the process of the technology realization must have rather high thermodynamic stability and high value of the shear modulus; other formed phases must improve or, at the least, not reduce physical and mechanical properties of the materials. 

  5. Micromechanical finite-element modeling and experimental characterization of the compressive mechanical properties of polycaprolactone-hydroxyapatite composite scaffolds prepared by selective laser sintering for bone tissue engineering.

    Science.gov (United States)

    Eshraghi, Shaun; Das, Suman

    2012-08-01

    Bioresorbable scaffolds with mechanical properties suitable for bone tissue engineering were fabricated from polycaprolactone (PCL) and hydroxyapatite (HA) by selective laser sintering (SLS) and modeled by finite-element analysis (FEA). Both solid gage parts and scaffolds having 1-D, 2-D and 3-D orthogonal, periodic porous architectures were made with 0, 10, 20 and 30 vol.% HA. PCL:HA scaffolds manufactured by SLS had nearly full density (99%) in the designed solid regions and had excellent geometric and dimensional control. Through optimization of the SLS process, the compressive moduli for our solid gage parts and scaffolds are the highest reported in the literature for additive manufacturing. The compressive moduli of solid gage parts were 299.3, 311.2, 415.5 and 498.3 MPa for PCL:HA loading at 100:0, 90:10, 80:20 and 70:30, respectively. The compressive effective stiffness tended to increase as the loading of HA was increased and the designed porosity was lowered. In the case of the most 3-D porous scaffold, the compressive modulus more than doubled from 14.9 to 36.2 MPa when changing the material from 100:0 to 70:30 PCL:HA. A micromechanical FEA model was developed to investigate the reinforcement effect of HA loading on the compressive modulus of the bulk material. Using a first-principles based approach, the random distribution of HA particles in a solidified PCL matrix was modeled for any HA loading to predict the bulk mechanical properties of the composites. The bulk mechanical properties were also used for FEA of the scaffold geometries. The results of the FEA were found to be in good agreement with experimental mechanical testing. The development of patient- and site-specific composite tissue-engineering constructs with tailored properties can be seen as a direct extension of this work on computational design, a priori modeling of mechanical properties and direct digital manufacturing.

  6. Positive selection of deleterious alleles through interaction with a sex-ratio suppressor gene in African Buffalo: a plausible new mechanism for a high frequency anomaly.

    Science.gov (United States)

    van Hooft, Pim; Greyling, Ben J; Getz, Wayne M; van Helden, Paul D; Zwaan, Bas J; Bastos, Armanda D S

    2014-01-01

    Although generally rare, deleterious alleles can become common through genetic drift, hitchhiking or reductions in selective constraints. Here we present a possible new mechanism that explains the attainment of high frequencies of deleterious alleles in the African buffalo (Syncerus caffer) population of Kruger National Park, through positive selection of these alleles that is ultimately driven by a sex-ratio suppressor. We have previously shown that one in four Kruger buffalo has a Y-chromosome profile that, despite being associated with low body condition, appears to impart a relative reproductive advantage, and which is stably maintained through a sex-ratio suppressor. Apparently, this sex-ratio suppressor prevents fertility reduction that generally accompanies sex-ratio distortion. We hypothesize that this body-condition-associated reproductive advantage increases the fitness of alleles that negatively affect male body condition, causing genome-wide positive selection of these alleles. To investigate this we genotyped 459 buffalo using 17 autosomal microsatellites. By correlating heterozygosity with body condition (heterozygosity-fitness correlations), we found that most microsatellites were associated with one of two gene types: one with elevated frequencies of deleterious alleles that have a negative effect on body condition, irrespective of sex; the other with elevated frequencies of sexually antagonistic alleles that are negative for male body condition but positive for female body condition. Positive selection and a direct association with a Y-chromosomal sex-ratio suppressor are indicated, respectively, by allele clines and by relatively high numbers of homozygous deleterious alleles among sex-ratio suppressor carriers. This study, which employs novel statistical techniques to analyse heterozygosity-fitness correlations, is the first to demonstrate the abundance of sexually-antagonistic genes in a natural mammal population. It also has important

  7. Positive Selection of Deleterious Alleles through Interaction with a Sex-Ratio Suppressor Gene in African Buffalo: A Plausible New Mechanism for a High Frequency Anomaly

    Science.gov (United States)

    van Hooft, Pim; Greyling, Ben J.; Getz, Wayne M.; van Helden, Paul D.; Zwaan, Bas J.; Bastos, Armanda D. S.

    2014-01-01

    Although generally rare, deleterious alleles can become common through genetic drift, hitchhiking or reductions in selective constraints. Here we present a possible new mechanism that explains the attainment of high frequencies of deleterious alleles in the African buffalo (Syncerus caffer) population of Kruger National Park, through positive selection of these alleles that is ultimately driven by a sex-ratio suppressor. We have previously shown that one in four Kruger buffalo has a Y-chromosome profile that, despite being associated with low body condition, appears to impart a relative reproductive advantage, and which is stably maintained through a sex-ratio suppressor. Apparently, this sex-ratio suppressor prevents fertility reduction that generally accompanies sex-ratio distortion. We hypothesize that this body-condition-associated reproductive advantage increases the fitness of alleles that negatively affect male body condition, causing genome-wide positive selection of these alleles. To investigate this we genotyped 459 buffalo using 17 autosomal microsatellites. By correlating heterozygosity with body condition (heterozygosity-fitness correlations), we found that most microsatellites were associated with one of two gene types: one with elevated frequencies of deleterious alleles that have a negative effect on body condition, irrespective of sex; the other with elevated frequencies of sexually antagonistic alleles that are negative for male body condition but positive for female body condition. Positive selection and a direct association with a Y-chromosomal sex-ratio suppressor are indicated, respectively, by allele clines and by relatively high numbers of homozygous deleterious alleles among sex-ratio suppressor carriers. This study, which employs novel statistical techniques to analyse heterozygosity-fitness correlations, is the first to demonstrate the abundance of sexually-antagonistic genes in a natural mammal population. It also has important

  8. Positive selection of deleterious alleles through interaction with a sex-ratio suppressor gene in African Buffalo: a plausible new mechanism for a high frequency anomaly.

    Directory of Open Access Journals (Sweden)

    Pim van Hooft

    Full Text Available Although generally rare, deleterious alleles can become common through genetic drift, hitchhiking or reductions in selective constraints. Here we present a possible new mechanism that explains the attainment of high frequencies of deleterious alleles in the African buffalo (Syncerus caffer population of Kruger National Park, through positive selection of these alleles that is ultimately driven by a sex-ratio suppressor. We have previously shown that one in four Kruger buffalo has a Y-chromosome profile that, despite being associated with low body condition, appears to impart a relative reproductive advantage, and which is stably maintained through a sex-ratio suppressor. Apparently, this sex-ratio suppressor prevents fertility reduction that generally accompanies sex-ratio distortion. We hypothesize that this body-condition-associated reproductive advantage increases the fitness of alleles that negatively affect male body condition, causing genome-wide positive selection of these alleles. To investigate this we genotyped 459 buffalo using 17 autosomal microsatellites. By correlating heterozygosity with body condition (heterozygosity-fitness correlations, we found that most microsatellites were associated with one of two gene types: one with elevated frequencies of deleterious alleles that have a negative effect on body condition, irrespective of sex; the other with elevated frequencies of sexually antagonistic alleles that are negative for male body condition but positive for female body condition. Positive selection and a direct association with a Y-chromosomal sex-ratio suppressor are indicated, respectively, by allele clines and by relatively high numbers of homozygous deleterious alleles among sex-ratio suppressor carriers. This study, which employs novel statistical techniques to analyse heterozygosity-fitness correlations, is the first to demonstrate the abundance of sexually-antagonistic genes in a natural mammal population. It also has

  9. Investigation on the microstructure, mechanical property and corrosion behavior of the selective laser melted CoCrW alloy for dental application.

    Science.gov (United States)

    Lu, Yanjin; Wu, Songquan; Gan, Yiliang; Li, Junlei; Zhao, Chaoqian; Zhuo, Dongxian; Lin, Jinxin

    2015-04-01

    In this study, an experimental investigation on fabricating Ni-free CoCrW alloys by selective laser melting (SLM) for dental application was conducted in terms of microstructure, hardness, mechanical property, electrochemical behavior, and metal release; and line and island scanning strategy were applied to determine whether these strategies are able to obtain expected CoCrW parts. The XRD revealed that the γ-phase and ε-phase coexisted in the as-SLM CoCrW alloys; The OM and SEM images showed that the microstructure of CoCrW alloys appeared square-like pattern with the fine cellular dendrites at the borders; tensile test suggested that the difference of mechanical properties of line- and island-formed specimens was very small; whilst the outcomes from the electrochemical and metal release tests indicated that the island-formed alloys showed slightly better corrosion resistance than line-formed ones in PBS and Hanks solutions. Considering that the mechanical properties and corrosion resistance of line-formed and island-formed specimens meet the standards of ISO 22674:2006 and EN ISO 10271, CoCrW dental alloys can be successfully fabricated by line and island scanning strategies in the SLM process.

  10. In Vitro Antibacterial Mechanism of Action of Crude Garlic (Allium sativum) Clove Extract on Selected Probiotic Bifidobacterium Species as Revealed by SEM, TEM, and SDS-PAGE Analysis.

    Science.gov (United States)

    Booyens, J; Labuschagne, M C; Thantsha, M S

    2014-06-01

    There has been much research on the effects of garlic (Allium sativum) on numerous pathogens, but very few, if any, studies on its effect on beneficial, probiotic bifidobacteria. We have recently shown that garlic exhibits antibacterial activity against bifidobacteria. The mechanism by which garlic kills bifidobacteria is yet to be elucidated. This study sought to determine the mechanism of action of garlic clove extract on selected Bifidobacterium species using scanning and transmission electron microscopy and SDS-PAGE analysis. SEM micrographs revealed unusual morphological changes such as cell elongation, cocci-shaped cells with cross-walls, and distorted cells with bulbous ends. With TEM, observed changes included among others, condensation of cytoplasmic material, disintegration of membranes, and loss of structural integrity. SDS-PAGE analysis did not reveal any differences in whole-cell protein profiles of untreated and garlic clove extract-treated cells. The current study is the first to reveal the mechanism of action of garlic clove extract on probiotic Bifidobacterium species. The results indicate that garlic affects these beneficial bacteria in a manner similar to that exhibited in pathogens. These results therefore further highlight that caution should be taken especially when using raw garlic and probiotic bifidobacteria simultaneously as viability of these bacteria could be reduced by allicin released upon crushing of garlic cloves, thereby limiting the health benefits that the consumer anticipate to gain from probiotics.

  11. The dissection profile and mechanism of tissue-selective dissection of the piezo actuator-driven pulsed water jet as a surgical instrument: laboratory investigation using Swine liver.

    Science.gov (United States)

    Yamada, Masato; Nakano, Toru; Sato, Chiaki; Nakagawa, Atsuhiro; Fujishima, Fumiyoshi; Kawagishi, Naoki; Nakanishi, Chikashi; Sakurai, Tadashi; Miyata, Go; Tominaga, Teiji; Ohuchi, Noriaki

    2014-01-01

    The water jet technique dissects tissue while sparing cord-like structures such as blood vessels. The mechanism of such tissue-selective dissection has been unknown. The novel piezo actuator-driven pulsed water jet (ADPJ) system can achieve dissection with remarkably reduced water consumption compared to the conventional water jet; however, the system's characteristics and dissection capabilities on any organ have not been clarified. The purposes of this study were to characterize the physical properties of the novel ADPJ system, evaluate the dissection ability in swine organs, and reveal the mechanism of tissue-selective dissection. The pulsed water jet system comprised a pump chamber driven by a piezo actuator, a stainless steel tube, and a nozzle. The peak pressure of the pulsed water jet was measured through a sensing hole using a pressure sensor. The pulsed water jet technique was applied on swine liver in order to dissect tissue on a moving table using one-way linear ejection at a constant speed. The dissection depth was measured with light microscopy and evaluated histologically. The physical properties of swine liver were evaluated by breaking strength tests using tabletop universal testing instruments. The liver parenchyma was also cut with three currently available surgical devices to compare the histological findings. The peak pressure of the pulsed water jet positively correlated with the input voltage (R(2) = 0.9982, p dissection depth. The dissection depth negatively correlated with the breaking strength of the liver parenchyma (R(2) = 0.6694, p dissected, preserving the hepatic veins and Glisson's sheaths in contrast to what is commonly observed with electrocautery or ultrasonic instruments. The dissection depth of liver tissue is well controlled by input voltage and is influenced by the moving velocity and the physical properties of the organ. We showed that the device can be used to assure liver resection with tissue selectivity due to tissue

  12. Selective Cathepsin S Inhibition with MIV-247 Attenuates Mechanical Allodynia and Enhances the Antiallodynic Effects of Gabapentin and Pregabalin in a Mouse Model of Neuropathic Pain.

    Science.gov (United States)

    Hewitt, Ellen; Pitcher, Thomas; Rizoska, Biljana; Tunblad, Karin; Henderson, Ian; Sahlberg, Britt-Louise; Grabowska, Urszula; Classon, Björn; Edenius, Charlotte; Malcangio, Marzia; Lindström, Erik

    2016-09-01

    Cathepsin S inhibitors attenuate mechanical allodynia in preclinical neuropathic pain models. The current study evaluated the effects when combining the selective cathepsin S inhibitor MIV-247 with gabapentin or pregabalin in a mouse model of neuropathic pain. Mice were rendered neuropathic by partial sciatic nerve ligation. MIV-247, gabapentin, or pregabalin were administered alone or in combination via oral gavage. Mechanical allodynia was assessed using von Frey hairs. Neurobehavioral side effects were evaluated by assessing beam walking. MIV-247, gabapentin, and pregabalin concentrations in various tissues were measured. Oral administration of MIV-247 (100-200 µmol/kg) dose-dependently attenuated mechanical allodynia by up to approximately 50% reversal when given as a single dose or when given twice daily for 5 days. No behavioral deficits were observed at any dose of MIV-247 tested. Gabapentin (58-350 µmol/kg) and pregabalin (63-377 µmol/kg) also inhibited mechanical allodynia with virtually complete reversal at the highest doses tested. The minimum effective dose of MIV-247 (100 µmol/kg) in combination with the minimum effective dose of pregabalin (75 µmol/kg) or gabapentin (146 µmol/kg) resulted in enhanced antiallodynic efficacy without augmenting side effects. A subeffective dose of MIV-247 (50 µmol/kg) in combination with a subeffective dose of pregabalin (38 µmol/kg) or gabapentin (73 µmol/kg) also resulted in substantial efficacy. Plasma levels of MIV-247, gabapentin, and pregabalin were similar when given in combination as to when given alone. Cathepsin S inhibition with MIV-247 exerts significant antiallodynic efficacy alone, and also enhances the effect of gabapentin and pregabalin without increasing side effects or inducing pharmacokinetic interactions.

  13. The effect of the solute on the structure, selected mechanical properties, and biocompatibility of Ti-Zr system alloys for dental applications.

    Science.gov (United States)

    Correa, D R N; Vicente, F B; Donato, T A G; Arana-Chavez, V E; Buzalaf, M A R; Grandini, C R

    2014-01-01

    New titanium alloys have been developed with the aim of utilizing materials with better properties for application as biomaterials, and Ti-Zr system alloys are among the more promising of these. In this paper, the influence of zirconium concentrations on the structure, microstructure, and selected mechanical properties of Ti-Zr alloys is analyzed. After melting and swaging, the samples were characterized through chemical analysis, density measurements, X-ray diffraction, optical microscopy, Vickers microhardness, and elasticity modulus. In-vitro cytotoxicity tests were performed on cultured osteogenic cells. The results showed the formation essentially of the α' phase (with hcp structure) and microhardness values greater than cp-Ti. The elasticity modulus of the alloys was sensitive to the zirconium concentrations while remaining within the range of values of conventional titanium alloys. The alloys presented no cytotoxic effects on osteoblastic cells in the studied conditions. © 2013.

  14. Thermal capacitator design rationale. Part 1: Thermal and mechanical property data for selected materials potentially useful in thermal capacitor design and construction

    Science.gov (United States)

    Bailey, J. A.; Liao, C. K.

    1975-01-01

    The thermal properties of paraffin hydrocarbons and hydrocarbon mixtures which may be used as the phase change material (PCM) in thermal capacitors are discussed. The paraffin hydrocarbons selected for consideration are those in the range from C11H24 (n-Undecane) to C20H42 (n-Eicosane). A limited amount of data is included concerning other properties of paraffin hydrocarbons and the thermal and mechanical properties of several aluminum alloys which may find application as constructional materials. Data concerning the melting temperature, transition temperature, latent heat of fusion, heat of transition, specific heat, and thermal conductivity of pure and commercial grades of paraffin hydrocarbons are given. An index of companies capable of producing paraffin hydrocarbons and information concerning the availability of various grades (purity levels) is provided.

  15. Selective attention mechanisms applied in attention deficit hyperactivity disorder / Mecanismos de atenção selectiva na perturbação de hiperactividade com déficit de atenção

    OpenAIRE

    Ramalho,Joaquim M. F.; M. Mar García-Señorán; Salvador G. González

    2009-01-01

    The attention deficit is the major factor of Attention Deficit Hyperactivity Disorder (ADHD). This paper aims to demonstrate difficulties in selective attention of subjects with ADHD as compared to subjects without ADHD, attempting to verify which mechanisms of selective attention are more affected in subjects with ADHD. For this purpose, we evaluated selective attention in subjects with and without ADHD (152 without and 31 with ADHD), in a population of 183 subjects. The general results show...

  16. RAIRS2 a new expert system for diagnosing tuberculosis with real-world tournament selection mechanism inside artificial immune recognition system.

    Science.gov (United States)

    Saybani, Mahmoud Reza; Shamshirband, Shahaboddin; Golzari, Shahram; Wah, Teh Ying; Saeed, Aghabozorgi; Mat Kiah, Miss Laiha; Balas, Valentina Emilia

    2016-03-01

    Tuberculosis is a major global health problem that has been ranked as the second leading cause of death from an infectious disease worldwide, after the human immunodeficiency virus. Diagnosis based on cultured specimens is the reference standard; however, results take weeks to obtain. Slow and insensitive diagnostic methods hampered the global control of tuberculosis, and scientists are looking for early detection strategies, which remain the foundation of tuberculosis control. Consequently, there is a need to develop an expert system that helps medical professionals to accurately diagnose the disease. The objective of this study is to diagnose tuberculosis using a machine learning method. Artificial immune recognition system (AIRS) has been used successfully for diagnosing various diseases. However, little effort has been undertaken to improve its classification accuracy. In order to increase the classification accuracy, this study introduces a new hybrid system that incorporates real tournament selection mechanism into the AIRS. This mechanism is used to control the population size of the model and to overcome the existing selection pressure. Patient epacris reports obtained from the Pasteur laboratory in northern Iran were used as the benchmark data set. The sample consisted of 175 records, from which 114 (65 %) were positive for TB, and the remaining 61 (35 %) were negative. The classification performance was measured through tenfold cross-validation, root-mean-square error, sensitivity, and specificity. With an accuracy of 100 %, RMSE of 0, sensitivity of 100 %, and specificity of 100 %, the proposed method was able to successfully classify tuberculosis cases. In addition, the proposed method is comparable with top classifiers used in this research.

  17. Thiamethoxam Resistance in the House Fly, Musca domestica L.: Current Status, Resistance Selection, Cross-Resistance Potential and Possible Biochemical Mechanisms.

    Directory of Open Access Journals (Sweden)

    Hafiz Azhar Ali Khan

    Full Text Available The house fly, Musca domestica L., is an important ectoparasite with the ability to develop resistance to insecticides used for their control. Thiamethoxam, a neonicotinoid, is a relatively new insecticide and effectively used against house flies with a few reports of resistance around the globe. To understand the status of resistance to thiamethoxam, eight adult house fly strains were evaluated under laboratory conditions. In addition, to assess the risks of resistance development, cross-resistance potential and possible biochemical mechanisms, a field strain of house flies was selected with thiamethoxam in the laboratory. The results revealed that the field strains showed varying level of resistance to thiamethoxam with resistance ratios (RR at LC50 ranged from 7.66-20.13 folds. Continuous selection of the field strain (Thia-SEL for five generations increased the RR from initial 7.66 fold to 33.59 fold. However, resistance declined significantly when the Thia-SEL strain reared for the next five generations without exposure to thiamethoxam. Compared to the laboratory susceptible reference strain (Lab-susceptible, the Thia-SEL strain showed cross-resistance to imidacloprid. Synergism tests revealed that S,S,S-tributylphosphorotrithioate (DEF and piperonyl butoxide (PBO produced synergism of thiamethoxam effects in the Thia-SEL strain (2.94 and 5.00 fold, respectively. In addition, biochemical analyses revealed that the activities of carboxylesterase (CarE and mixed function oxidase (MFO in the Thia-SEL strain were significantly higher than the Lab-susceptible strain. It seems that metabolic detoxification by CarE and MFO was a major mechanism for thiamethoxam resistance in the Thia-SEL strain of house flies. The results could be helpful in the future to develop an improved control strategy against house flies.

  18. Thiamethoxam Resistance in the House Fly, Musca domestica L.: Current Status, Resistance Selection, Cross-Resistance Potential and Possible Biochemical Mechanisms.

    Science.gov (United States)

    Khan, Hafiz Azhar Ali; Akram, Waseem; Iqbal, Javaid; Naeem-Ullah, Unsar

    2015-01-01

    The house fly, Musca domestica L., is an important ectoparasite with the ability to develop resistance to insecticides used for their control. Thiamethoxam, a neonicotinoid, is a relatively new insecticide and effectively used against house flies with a few reports of resistance around the globe. To understand the status of resistance to thiamethoxam, eight adult house fly strains were evaluated under laboratory conditions. In addition, to assess the risks of resistance development, cross-resistance potential and possible biochemical mechanisms, a field strain of house flies was selected with thiamethoxam in the laboratory. The results revealed that the field strains showed varying level of resistance to thiamethoxam with resistance ratios (RR) at LC50 ranged from 7.66-20.13 folds. Continuous selection of the field strain (Thia-SEL) for five generations increased the RR from initial 7.66 fold to 33.59 fold. However, resistance declined significantly when the Thia-SEL strain reared for the next five generations without exposure to thiamethoxam. Compared to the laboratory susceptible reference strain (Lab-susceptible), the Thia-SEL strain showed cross-resistance to imidacloprid. Synergism tests revealed that S,S,S-tributylphosphorotrithioate (DEF) and piperonyl butoxide (PBO) produced synergism of thiamethoxam effects in the Thia-SEL strain (2.94 and 5.00 fold, respectively). In addition, biochemical analyses revealed that the activities of carboxylesterase (CarE) and mixed function oxidase (MFO) in the Thia-SEL strain were significantly higher than the Lab-susceptible strain. It seems that metabolic detoxification by CarE and MFO was a major mechanism for thiamethoxam resistance in the Thia-SEL strain of house flies. The results could be helpful in the future to develop an improved control strategy against house flies.

  19. Antiarrhythmic ionic mechanism of Guanfu base A--Selective inhibition of late sodium current in isolated ventricular myocytes from guinea pigs.

    Science.gov (United States)

    Jin, Si-Si; Guo, Qiao; Xu, Jing; Yu, Peng; Liu, Jing-Han; Tang, Yi-Qun

    2015-05-01

    The present study was designed to determine the effects of Guanfu base A (GFA) on the late sodium current (INa.L), transient sodium current (INa.T), HERG current (IHERG), and Kv1.5 current (IKv1.5). The values of INa.L, INa.T, IHERG and IKv1.5 were recorded using the whole-cell patch clamp technique. Compared with other channels, GFA showed selective blocking activity in late sodium channel. It inhibited INa.L in a concentration-dependent manner with an IC50 of (1.57 ± 0.14) μmol · L(-1), which was significantly lower than its IC50 values of (21.17 ± 4.51) μmol · L(-1) for the INa.T. The inhibitory effect of GFA on INa,L was not affected by 200 μmol · L(-1) H2O2. It inhibited IHERG with an IC50 of (273 ± 34) μmol · L(-1) and has slight blocking effect on IKv1.5, decreasing IKv1.5 by only 20.6% at 200 μmol · L(-1). In summary, GFA inhibited INa.L selectively and remained similar inhibition in presence of reactive oxygen species. These findings may suggest a novel molecular mechanism for the potential clinical application of GFA in the treatment of cardiovascular disorders.

  20. The mechanism of ammonium bisulfate formation and decomposition over V/WTi catalysts for NH3-selective catalytic reduction at various temperatures.

    Science.gov (United States)

    Li, Chenxu; Shen, Meiqing; Yu, Tie; Wang, Jianqiang; Wang, Jun; Zhai, Yanping

    2017-06-14

    In this study, the mechanism of ammonium bisulfate (ABS) formation and decomposition over V/WTi for the NH3-selective catalytic reduction (SCR) at various temperatures was deeply investigated. Bridged bidentate, chelating bidentate, and tridentate sulfates bound to TiO2 were formed as dominant intermediates at 200, 250, and 300 °C, respectively. These sulfates reacted with affinitive ammonium species to form ammonium (bi)sulfate species and also covered the active sites and embedded the VOSO4 intermediates, which resulted in an inferior intrinsic NH3-SCR conversion rate at 200 °C and 250 °C. At 300 °C, trace amounts of ABS on TiO2 presented no influence on the NH3-SCR performance. The electrons deviating towards sulfates through the bond between ABS and metal oxides (WO3 and TiO2) weakened the stability of ABS and lowered its decomposition temperature, whereas the vanadia species played the opposite role due to the sulfur species existing in an electron saturation state with the formation of the VOSO4 intermediate. The presence of NO + O2 could break the bonds inside ABS and it could react with the ammonium species originating from ABS, which pulls NH3 out of the ABS formation equilibrium and accelerates its decomposition and competitively inhibits its formation. Correspondingly, the faster NH3-SCR conversion rate and higher N2 selectivity improve the ABS poisoning resistance of the V/WTi catalyst at low temperatures.

  1. Generation process of FeS and its inhibition mechanism on iron mineral reduction in selective direct reduction of laterite nickel ore

    Institute of Scientific and Technical Information of China (English)

    Zhi-guo Liu; Ti-chang Sun; Xiao-ping Wang; En-xia Gao

    2015-01-01

    Numerous studies have demonstrated that Na2SO4 can significantly inhibit the reduction of iron oxide in the selective reduction process of laterite nickel ore. FeS generated in the process plays an important role in selective reduction, but the generation process of FeS and its inhibition mechanism on iron reduction are not clear. To figure this out, X-ray diffraction and scanning electron microscopy analyses were conducted to study the roasted ore. The results show that when Na2SO4 is added in the roasting, the FeO content in the roasted ore in-creases accompanied by the emergence of FeS phase. Further analysis indicates that Na2S formed by the reaction of Na2SO4 with CO reacts with SiO2 at the FeO surface to generate FeS and Na2Si2O5. As a result, a thin film forms on the surface of FeO, hindering the contact be-tween reducing gas and FeO. Therefore, the reduction of iron is depressed, and the FeO content in the roasted ore increases.

  2. T Cell-Independent Mechanisms Associated with Neutrophil Extracellular Trap Formation and Selective Autophagy in IL-17A-Mediated Epidermal Hyperplasia.

    Science.gov (United States)

    Suzuki, Erika; Maverakis, Emanual; Sarin, Ritu; Bouchareychas, Laura; Kuchroo, Vijay K; Nestle, Frank O; Adamopoulos, Iannis E

    2016-12-01

    IL-17A has been strongly associated with epidermal hyperplasia in many cutaneous disorders. However, because IL-17A is mainly produced by αβ and γδT cells in response to IL-23, the role of T cells and IL-23 has overshadowed any IL-17A-independent actions. In this article, we report that IL-17A gene transfer induces epidermal hyperplasia in Il23r(-/-)Rag1(-/-)- and Tcrδ-deficient mice, which can be prevented by neutrophil depletion. Moreover, adoptive transfer of CD11b(+)Gr-1(hi) cells, after IL-17A gene transfer, was sufficient to phenocopy the disease. We further show that the IL-17A-induced pathology was prevented in transgenic mice with impaired neutrophil extracellular trap formation and/or neutrophils with conditional deletion of the master regulator of selective autophagy, Wdfy3. Our data demonstrate a novel T cell-independent mechanism that is associated with neutrophil extracellular trap formation and selective autophagy in IL-17A-mediated epidermal hyperplasia. Copyright © 2016 by The American Association of Immunologists, Inc.

  3. Mechanism of promoter selection by RNA polymerase II: mammalian transcription factors alpha and beta gamma promote entry of polymerase into the preinitiation complex.

    Science.gov (United States)

    Conaway, R C; Garrett, K P; Hanley, J P; Conaway, J W

    1991-07-15

    Productive binding of RNA polymerase II at the core region of TATA box-containing promoters is controlled by the action of the TATA factor and four additional transcription factors, designated alpha, beta gamma, delta, and epsilon, which have each been purified to near homogeneity from rat liver. This process is accomplished in three distinguishable stages. In the first stage (initial complex formation), the core promoter is packaged with the TATA factor into a binary complex that serves as the recognition site for RNA polymerase II. Here we show that, in the second stage (site selection), transcription factors alpha and beta gamma act in combination to promote selective binding of RNA polymerase II to the initial complex. Several lines of evidence argue that alpha and beta gamma function at this stage by a mechanism related to that utilized by bacterial sigma factors. In the third stage, transcription factors delta and epsilon promote assembly of the functional preinitiation complex. Our evidence supports the model that delta and epsilon enter the preinitiation complex and direct formation of stable protein-DNA contacts that anchor the transcription apparatus to the core promoter at sequences near the cap site.

  4. Ribociclib (LEE011): Mechanism of Action and Clinical Impact of This Selective Cyclin-Dependent Kinase 4/6 Inhibitor in Various Solid Tumors.

    Science.gov (United States)

    Tripathy, Debu; Bardia, Aditya; Sellers, William R

    2017-07-01

    The cyclin D-cyclin-dependent kinase (CDK) 4/6-p16-retinoblastoma (Rb) pathway is commonly disrupted in cancer, leading to abnormal cell proliferation. Therapeutics targeting this pathway have demonstrated antitumor effects in preclinical and clinical studies. Ribociclib is a selective, orally bioavailable inhibitor of CDK4 and CDK6, which received FDA approval in March 2017 and is set to enter the treatment landscape alongside other CDK4/6 inhibitors, including palbociclib and abemaciclib. Here, we describe the mechanism of action of ribociclib and review preclinical and clinical data from phase I, II, and III trials of ribociclib across different tumor types, within the context of other selective CDK4/6 inhibitors. The pharmacokinetics, pharmacodynamics, safety, tolerability, and clinical responses with ribociclib as a single agent or in combination with other therapies are discussed, and an overview of the broad portfolio of ongoing clinical trials with ribociclib across a wide range of indications is presented. On the basis of the available data, ribociclib has a manageable tolerability profile and therapeutic potential for a variety of cancer types. Its high selectivity makes it an important partner drug for other targeted therapies, and it has been shown to enhance the clinical activity of existing anticancer therapies and delay the development of treatment resistance, without markedly increasing toxicity. Ongoing trials of doublet and triplet targeted therapies containing ribociclib seek to identify optimal CDK4/6-based targeted combination regimens for various tumor types and advance the field of precision therapeutics in oncology. Clin Cancer Res; 23(13); 3251-62. ©2017 AACR. ©2017 American Association for Cancer Research.

  5. Selective adsorption mechanisms of antilipidemic and non-steroidal anti-inflammatory drug residues on functionalized silica-based porous materials in a mixed solute.

    Science.gov (United States)

    Suriyanon, Nakorn; Permrungruang, Jutima; Kaosaiphun, Jidanan; Wongrueng, Aunnop; Ngamcharussrivichai, Chawalit; Punyapalakul, Patiparn

    2015-10-01

    The selective adsorption mechanisms of naproxen (NAP), acetaminophen (ACT), and clofibric acid (CFA) on silica-based porous materials were examined by single and mixed-batch adsorption. Effects of the types and densities of surface functional groups on adsorption capacities were determined, including the role of hydrophobic and hydrophilic dissolved organic matters (DOMs). Hexagonal mesoporous silica (HMS), superparamagnetic HMS (HMS-SP) and SBA-15 were functionalized and applied as adsorbents. Compared with powdered activated carbon (PAC), amine-functionalized HMS had a better adsorption capacity for CFA, but PAC possessed a higher adsorption capacity for the other pharmaceuticals than HMS and its two derivatives. In contrast to PAC, the adsorption capacity of the mesoporous silicas varied with the solution pH, being highest at pH 5. Electrostatic interactions and hydrogen bonding were found to be the main mechanisms. Increase in grafted amine group density on silica surfaces can enhance the CFA adsorption capacity. Further, hydrophilic DOM can decrease CFA adsorption capacities on amino-grafted adsorbents by adsorption site competition, while hydrophobic DOM can interfere with CFA adsorption by the interaction between hydrophobic DOM and CFA. Finally, in a competitive adsorption study, the adsorption capacity of hydrophilic adsorbents for acidic pharmaceuticals varied with their pKa values. Copyright © 2015 Elsevier Ltd. All rights reserved.

  6. Selective reduction in the expression of UGTs and SULTs, a novel mechanism by which piperine enhances the bioavailability of curcumin in rat.

    Science.gov (United States)

    Zeng, Xiaohui; Cai, Dake; Zeng, Qiaohuang; Chen, Zhao; Zhong, Guoping; Zhuo, Juncheng; Gan, Haining; Huang, Xuejun; Zhao, Ziming; Yao, Nan; Huang, Dane; Zhang, Chengzhe; Sun, Dongmei; Chen, Yuxing

    2017-01-01

    Curcumin (CUR) is known to exert numerous health-promoting effects in pharmacological studies, but its low bioavailability hinders the development of curcumin as a feasible therapeutic agent. Piperine (PIP) has been reported to enhance the bioavailability of curcumin, but the underlying mechanism remains poorly understood. In an attempt to find the mechanism by which piperine enhances the bioavailability of curcumin, the dosage ratio (CUR: PIP) and pre-treatment with piperine were hypothesized as key factors for improving the bioavailability in this combination. Therefore, combining curcumin with piperine at various dose ratios (1:1 to 100:1) and pre-dosing with piperine (0.5-8 h prior to curcumin) were designed to investigate their contributions to the pharmacokinetic parameters of curcumin in rats and their effects on the expression of UGT and SULT isoforms. It was shown that the Cmax and AUC0-t of curcumin were slightly increased by 1.29 and 1.67 fold at a ratio of 20:1, while curcumin exposure was enhanced significantly in all the piperine pre-treated rats (0.5-8 h), peaking at 6 h (a 6.09-fold and 5.97-fold increase in Cmax and AUC0-t , p bioavailability of curcumin through the reversible and selective inhibition of UGTs and SULTs. Copyright © 2016 John Wiley & Sons, Ltd.

  7. Study on the mechanism of NH3-selective catalytic reduction over CuCexZr1-x/TiO2

    Science.gov (United States)

    Chen, Xujuan; Sun, Xiaoliang; Gong, Cairong; Lv, Gang; Song, Chonglin

    2016-06-01

    Copper-cerium-zirconium catalysts loaded on TiO2 prepared by a wet impregnation method were investigated for NH3-selective catalytic reduction (SCR) of NOx. The reaction mechanism was proposed on the basis of results from in situ diffuse reflectance infrared transform spectroscopy (DRIFT). When NH3 is introduced, ammonia bonded to Lewis acid sites is more stable over CuCe0.25Zr0.75/TiO2 at high temperature, while Brønsted acid sites are more important than Lewis acid sites at low temperature. For the NH3+NO+O2 co-adsorption, NH3 species occupy most of activity sites on CuCe0.25Zr0.75/TiO2 catalyst, and mainly exist in the forms of NH4 + (at low temperature) and NH3 coordinated (at high temperature), playing a crucial role in the NH3-SCR process. Two different reaction routes, the L-H mechanism at low temperature ( 200°C), are presented for the SCR reaction over CuCe0.25Zr0.75/TiO2 catalyst.

  8. Micromechanical finite element modeling and experimental characterization of the compressive mechanical properties of polycaprolactone:hydroxyapatite composite scaffolds prepared by selective laser sintering for bone tissue engineering

    Science.gov (United States)

    Eshraghi, Shaun; Das, Suman

    2012-01-01

    Bioresorbable scaffolds with mechanical properties suitable for bone tissue engineering were fabricated from polycaprolactone (PCL) and hydroxyapatite (HA) by selective laser sintering (SLS) and modeled by finite element analysis (FEA). Both solid gage parts and scaffolds having 1-D, 2-D and 3-D orthogonal, periodic porous architectures were made with 0, 10, 20 and 30% HA by volume. PCL:HA scaffolds manufactured by SLS had nearly full density (99%) in the designed solid regions and had excellent geometric and dimensional control. Through optimization of the SLS process, the compressive moduli for our solid gage parts and scaffolds are the highest reported in the literature for additive manufacturing. The compressive moduli of solid gage parts were 299.3, 311.2, 415.5 and 498.3 MPa for PCL:HA loading at 100:0, 90:10, 80:20 and 70:30 respectively. The compressive effective stiffness tended to increase as the loading of HA was increased and the designed porosity was lowered. In the case of the most 3-D porous scaffold, the compressive modulus more than doubled from 14.9 MPa to 36.2 MPa when changing the material from 100:0 to 70:30 PCL:HA. A micromechanical finite element analysis (FEA) model was developed to investigate the reinforcement effect of HA loading on the compressive modulus of the bulk material. Using a first-principles based approach, the random distribution of HA particles in a solidified PCL matrix was modeled for any loading of HA to predict the bulk mechanical properties of the composites. The bulk mechanical properties were also used for FEA of the scaffold geometries. Results of the FEA were found to be in good agreement with experimental mechanical testing. The development of patient and site-specific composite tissue engineering constructs with tailored properties can be seen as a direct extension of this work on computational design, a priori modeling of mechanical properties and direct digital manufacturing. PMID:22522129

  9. Assessment of an Impact of Mechanical Regulation on Selected Morphometric and Productive Parameters of Invasive Species Solidago Canadensis Population in Agricultural Land

    Directory of Open Access Journals (Sweden)

    Končeková Lýdia

    2015-12-01

    Full Text Available Repeated mowing is considered as one of the effective control methods against species of the genus Solidago. This paper evaluates the impact of the repeated mowing on selected morphometric and productive characteristics of the invasive neophyte Solidago canadensis in the district of Rimavská Sobota in Central Slovakia. Permanent research plots (PRPs were established within anthropogenic habitat on an abandoned land that was divided into two variants. In the first variant, the mechanical regulation - mowing was applied. The second variant was without the regulation. The mechanical regulation of the populations was carried out in June and August during the growing season 2011. The results showed that the mechanical regulation did not have a clear impact on the population density. The decreasing trend of the number of shoots within the mowed variant was found only in one research plot (PRP3. The other plots showed an increase in the number of individuals by 2.7 and 32.7% between the mowings. Statistically highly significant differences in terms of the mowing impact on the height of the individuals were found in all PRPs. The difference in the weight of dry aboveground biomass between the mowings was 221.87 g, which represents 36.41%. Double the difference (48.8% was recorded in the dry weight of the underground biomass in the regulated stand compared with the unregulated stand (165.1 and 322.5 g/m2, respectively. Although there was a short-term success achieved by the application of the two mowings during the growing period, the pursued objective was not reached.

  10. Obesity resistant mechanisms in the Lean polygenic mouse model as indicated by liver transcriptome and expression of selected genes in skeletal muscle

    Directory of Open Access Journals (Sweden)

    Fievet Catherine

    2011-02-01

    Full Text Available Abstract Background Divergently selected Lean and Fat mouse lines represent unique models for a polygenic form of resistance and susceptibility to obesity development. Previous research on these lines focused mainly on obesity-susceptible factors in the Fat line. This study aimed to examine the molecular basis of obesity-resistant mechanisms in the Lean line by analyzing various fat depots and organs, the liver transcriptome of selected metabolic pathways, plasma and lipid homeostasis and expression of selected skeletal muscle genes. Results Expression profiling using our custom Steroltalk v2 microarray demonstrated that Lean mice exhibit a higher hepatic expression of cholesterol biosynthesis genes compared to the Fat line, although this was not reflected in elevation of total plasma or liver cholesterol. However, FPLC analysis showed that protective HDL cholesterol was elevated in Lean mice. A significant difference between the strains was also found in bile acid metabolism. Lean mice had a higher expression of Cyp8b1, a regulatory enzyme of bile acid synthesis, and the Abcb11 bile acid transporter gene responsible for export of acids to the bile. Additionally, a higher content of blood circulating bile acids was observed in Lean mice. Elevated HDL and upregulation of some bile acids synthesis and transport genes suggests enhanced reverse cholesterol transport in the Lean line - the flux of cholesterol out of the body is higher which is compensated by upregulation of endogenous cholesterol biosynthesis. Increased skeletal muscle Il6 and Dio2 mRNA levels as well as increased activity of muscle succinic acid dehydrogenase (SDH in the Lean mice demonstrates for the first time that changes in muscle energy metabolism play important role in the Lean line phenotype determination and corroborate our previous findings of increased physical activity and thermogenesis in this line. Finally, differential expression of Abcb11 and Dio2 identifies novel

  11. Obesity resistant mechanisms in the Lean polygenic mouse model as indicated by liver transcriptome and expression of selected genes in skeletal muscle

    Science.gov (United States)

    2011-01-01

    Background Divergently selected Lean and Fat mouse lines represent unique models for a polygenic form of resistance and susceptibility to obesity development. Previous research on these lines focused mainly on obesity-susceptible factors in the Fat line. This study aimed to examine the molecular basis of obesity-resistant mechanisms in the Lean line by analyzing various fat depots and organs, the liver transcriptome of selected metabolic pathways, plasma and lipid homeostasis and expression of selected skeletal muscle genes. Results Expression profiling using our custom Steroltalk v2 microarray demonstrated that Lean mice exhibit a higher hepatic expression of cholesterol biosynthesis genes compared to the Fat line, although this was not reflected in elevation of total plasma or liver cholesterol. However, FPLC analysis showed that protective HDL cholesterol was elevated in Lean mice. A significant difference between the strains was also found in bile acid metabolism. Lean mice had a higher expression of Cyp8b1, a regulatory enzyme of bile acid synthesis, and the Abcb11 bile acid transporter gene responsible for export of acids to the bile. Additionally, a higher content of blood circulating bile acids was observed in Lean mice. Elevated HDL and upregulation of some bile acids synthesis and transport genes suggests enhanced reverse cholesterol transport in the Lean line - the flux of cholesterol out of the body is higher which is compensated by upregulation of endogenous cholesterol biosynthesis. Increased skeletal muscle Il6 and Dio2 mRNA levels as well as increased activity of muscle succinic acid dehydrogenase (SDH) in the Lean mice demonstrates for the first time that changes in muscle energy metabolism play important role in the Lean line phenotype determination and corroborate our previous findings of increased physical activity and thermogenesis in this line. Finally, differential expression of Abcb11 and Dio2 identifies novel strong positional candidate

  12. Selective attention mechanisms applied in attention deficit hyperactivity disorder / Mecanismos de atenção selectiva na perturbação de hiperactividade com déficit de atenção

    Directory of Open Access Journals (Sweden)

    Joaquim M. F. Ramalho

    2009-01-01

    Full Text Available The attention deficit is the major factor of Attention Deficit Hyperactivity Disorder (ADHD. This paper aims to demonstrate difficulties in selective attention of subjects with ADHD as compared to subjects without ADHD, attempting to verify which mechanisms of selective attention are more affected in subjects with ADHD. For this purpose, we evaluated selective attention in subjects with and without ADHD (152 without and 31 with ADHD, in a population of 183 subjects. The general results show that the subjects with ADHD present lower selective attention skills than the subjects without ADHD, specifically as far as rightness, errors, concentration and processed elements are concerned.

  13. A p53-independent apoptotic mechanism of adenoviral mutant E1A was involved in its selective antitumor activity for human cancer

    Science.gov (United States)

    Fang, Lin; Cheng, Qian; Zhao, Jingjing; Ge, Yan; Zhu, Qi; Zhao, Min; Zhang, Jie; Zhang, Qi; Li, Liantao; Liu, Junjie; Zheng, Junnian

    2016-01-01

    The conserved regions (CR) of adenoviral E1A had been shown to be necessary for disruption of pRb-E2F transcription factor complexes and induction of the S phase. Here we constructed a mutant adenoviral E1A with Rb-binding ability absent (E1A 30-60aa and 120-127aa deletion, mE1A) and investigated its antitumor capacities in vitro and in vivo. The mE1A suppressed the viability of tumor cells as efficiently as the wild type E1A, and there was no cytotoxic effect on normal cells. Although the mE1A arrested tumor cell cycle with the same manner as E1A, the former played a different role on cell cycle regulation compared with E1A in normal cells, which might contribute to its selective antitumor activity. E1A and mE1A had accumulated inactive p53, decreased the expression of mdm2, Cdkn1a (also named p21), increased p21's nuclear distribution and induced tumor cell apoptosis in a p53-indenpent manner. Further, E1A or mE1A significantly suppressed tumor growth in subcutaneous hepatocellular carcinoma xenograft models. Especially, tumor-bearing mice treated with mE1A had higher survival rate than those treated with E1A. Our data demonstrated that mutant adenoviral E1A significantly induced tumor cell apoptosis in a p53-indenpednt manner and had selective tumor suppressing ability. The observations of adenoviral E1A mutant had provided a novel mechanism for E1A's complex activities during infection. PMID:27340782

  14. Activation of B-H, Si-H, and C-F bonds with Tp'Rh(PMe3) complexes: kinetics, mechanism, and selectivity.

    Science.gov (United States)

    Procacci, Barbara; Jiao, Yunzhe; Evans, Meagan E; Jones, William D; Perutz, Robin N; Whitwood, Adrian C

    2015-01-28

    The photochemical reactions of Tp'Rh(PMe3)H2 (1) and thermal reactions of Tp'Rh(PMe3)(CH3)H (1a, Tp' = tris(3,5-dimethylpyrazolyl)borate) with substrates containing B-H, Si-H, C-F, and C-H bonds are reported. Complexes 1 and 1a are known activators of C-H bonds, including those of alkanes. Kinetic studies of reactions with HBpin and PhSiH3 show that photodissociation of H2 from 1 occurs prior to substrate attack, whereas thermal reaction of 1a proceeds by bimolecular reaction with the substrate. Complete intramolecular selectivity for B-H over C-H activation of HBpin (pin = pinacolate) leading to Tp'Rh(PMe3)(Bpin)H is observed. Similarly, the reaction with Et2SiH2 shows a strong preference for Si-H over C-H activation, generating Tp'Rh(PMe3)(SiEt2H)H. The Rh(Bpin)H and Rh(SiEt2H)H products were stable to heating in benzene in accord with DFT calculations that showed that reaction with benzene is endoergic. The intramolecular competition with PhSiH3 yields a ∼1:4 mixture of Tp'Rh(PMe3)(C6H4SiH3)H and Tp'Rh(PMe3)(SiPhH2)H, respectively. Reaction with pentafluoropyridine generates Tp'Rh(PMe3)(C5NF4)F, while reaction with 2,3,5,6-tetrafluoropyridine yields a mixture of C-H and C-F activated products. Hexafluorobenzene proves unreactive. Crystal structures are reported for B-H, Si-H, and C-F activated products, but in the latter case a bifluoride complex Tp'Rh(PMe3)(C5NF4)(FHF) was crystallized. Intermolecular competition reactions were studied by photoreaction of 1 in C6F6 with benzene and another substrate (HBpin, PhSiH3, or pentafluoropyridine) employing in situ laser photolysis in the NMR probe, resulting in a wide-ranging map of kinetic selectivities. The mechanisms of intramolecular and intermolecular selection are analyzed.

  15. Mechanical design

    CERN Document Server

    Risitano, Antonino

    2011-01-01

    METHODOLOGICAL STATEMENT OF ENGINEERING DESIGNApproaches to product design and developmentMechanical design and environmental requirementsPROPERTIES OF ENGINEERING MATERIALSMaterials for mechanical designCharacterization of metalsStress conditionsFatigue of materialsOptimum material selection in mechanical designDESIGN OF MECHANICAL COMPONENTS AND SYSTEMSFailure theoriesHertz theoryLubrificationShafts and bearingsSplines and keysSpringsFlexible machine elementsSpur gearsPress and shrink fitsPressure tubesCouplingsClutchesBrakes

  16. The effect of the solute on the structure, selected mechanical properties, and biocompatibility of Ti–Zr system alloys for dental applications

    Energy Technology Data Exchange (ETDEWEB)

    Correa, D.R.N.; Vicente, F.B. [UNESP — Univ. Estadual Paulista, Laboratório de Anelasticidade e Biomateriais, 17.033-360, Bauru, SP (Brazil); Donato, T.A.G.; Arana-Chavez, V.E. [USP — Universidade de São Paulo, Faculdade de Odontologia, Departamento de Biologia Oral e Biomateriais, 05.508-900, São Paulo, SP (Brazil); Buzalaf, M.A.R. [USP — Universidade de São Paulo, Faculdade de Odontologia de Bauru, Departamento de Ciências Biológicas, 17.012-901, Bauru, SP (Brazil); Grandini, C.R., E-mail: betog@fc.unesp.br [UNESP — Univ. Estadual Paulista, Laboratório de Anelasticidade e Biomateriais, 17.033-360, Bauru, SP (Brazil)

    2014-01-01

    New titanium alloys have been developed with the aim of utilizing materials with better properties for application as biomaterials, and Ti–Zr system alloys are among the more promising of these. In this paper, the influence of zirconium concentrations on the structure, microstructure, and selected mechanical properties of Ti–Zr alloys is analyzed. After melting and swaging, the samples were characterized through chemical analysis, density measurements, X-ray diffraction, optical microscopy, Vickers microhardness, and elasticity modulus. In-vitro cytotoxicity tests were performed on cultured osteogenic cells. The results showed the formation essentially of the α′ phase (with hcp structure) and microhardness values greater than cp-Ti. The elasticity modulus of the alloys was sensitive to the zirconium concentrations while remaining within the range of values of conventional titanium alloys. The alloys presented no cytotoxic effects on osteoblastic cells in the studied conditions. - Highlights: • Ti–Zr alloys for biomedical applications were developed. • Only α′ phase was observed. • Influence of zirconium concentrations on the properties of Ti–Zr alloys was analyzed. • No cytotoxic effects were observed.

  17. The Influence of As-Built Surface Conditions on Mechanical Properties of Ti-6Al-4V Additively Manufactured by Selective Electron Beam Melting

    Science.gov (United States)

    Sun, Y. Y.; Gulizia, S.; Oh, C. H.; Fraser, D.; Leary, M.; Yang, Y. F.; Qian, M.

    2016-03-01

    Achieving a high surface finish is a major challenge for most current metal additive manufacturing processes. We report the first quantitative study of the influence of as-built surface conditions on the tensile properties of Ti-6Al-4V produced by selective electron beam melting (SEBM) in order to better understand the SEBM process. Tensile ductility was doubled along with noticeable improvements in tensile strengths after surface modification of the SEBM-fabricated Ti-6Al-4V by chemical etching. The fracture surfaces of tensile specimens with different surface conditions were characterised and correlated with the tensile properties obtained. The removal of a 650- μm-thick surface layer by chemical etching was shown to be necessary to eliminate the detrimental influence of surface defects on mechanical properties. The experimental results and analyses underline the necessity to modify the surfaces of SEBM-fabricated components for structural applications, particularly for those components which contain complex internal concave and convex surfaces and channels.

  18. Relationship between the microstructure and mechanical properties of an equiatomic AlCoCrFeNi high-entropy alloy fabricated by selective electron beam melting

    Energy Technology Data Exchange (ETDEWEB)

    Shiratori, Hiroshi [Department of Materials Processing, Graduate School of Engineering, Tohoku University, 6-6-02, Aoba-yama, Aoba-ku, Sendai 980-8579 (Japan); Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Fujieda, Tadashi [Center for Technology Innovation − Materials, Research & Development Group, Hitachi, Ltd., Hitachi 319-1292 (Japan); Yamanaka, Kenta, E-mail: k_yamanaka@imr.tohoku.ac.jp [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Koizumi, Yuichiro [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Kuwabara, Kosuke; Kato, Takahiko [Center for Technology Innovation − Materials, Research & Development Group, Hitachi, Ltd., Hitachi 319-1292 (Japan); Chiba, Akihiko [Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)

    2016-02-22

    Because of their superior properties, high-entropy alloys (HEAs) are considered promising novel structural materials that can substitute conventional alloys. From the viewpoint of future applications, it is important to explore methods for producing complex shaped products with HEAs. In this study, selective electron beam melting (SEBM) was employed for fabricating equiatomic AlCoCrFeNi HEA specimens, and their microstructures and mechanical properties were evaluated by comparing them with those of a conventionally cast specimen. Both cast and SEBM specimens dominantly consisted of a nano-lamellar mixture of disordered body-centered-cubic (BCC) and B2 (ordered BCC) phases. The face-centered cubic (FCC) phase was also precipitated at the grain boundaries of the B2/BCC mixture phases on the SEBM specimens. The fraction of the FCC phase at the bottom part of the SEBM specimen was higher than that at the top part. The preheating procedure—a process unique to SEBM—is responsible for the precipitation of the FCC phase, because of the long-term exposure at sufficiently high temperatures. As a result, the hardness of the SEBM specimens gradually decreased as we approached the bottom part of the specimens due to the increased fraction of the FCC phase, which had lower hardness than the B2/BCC phases. Further, the SEBM specimen exhibited much higher plastic deformability than the cast specimen, without significant loss of strength.

  19. Study into a possible mechanism responsible for the antidepressant-like activity of the selective 5-HT6 receptor antagonist SB-399885 in rats.

    Science.gov (United States)

    Wesołowska, Anna

    2007-01-01

    The mechanism of the antidepressant-like activity of the selective 5-hydroxytryptamine(6) (5-HT(6) receptor antagonist N-[3,5-dichloro-2-(methoxy)phenyl]-4-(methoxy)-3-(1-piperazinyl)benzenesulfonamide (SB-399885) was studied in the forced swim test in rats. SB-399885 administered intraperitoneally at a single dose of 10 mg/kg potently shortened the immobility time in rats. That potential antidepressant-like effect of SB-399885 was not modified in animals with a lesion of the 5-HT system produced by p-chloroamphetamine (p-CA, 2 x 10 mg/kg). The anti-immobility effect of SB-399885 was blocked by the dopamine D(1)- and D(2)-like receptor antagonists SCH 23390 (0.063 mg/kg) and sulpiride (10 mg/kg), respectively, as well as by the alpha(2)-adrenoceptor antagonist idazoxan (4 mg/kg), but it was not changed by the alpha(1)-adrenoceptor antagonist prazosin (1 mg/kg). Neither sulpiride (10 mg/kg) or idazoxan (4 mg/kg) nor SCH-23390 (0.063 mg/kg) administered jointly with SB-399885 (10 mg/kg) noticeably changed the exploratory locomotor activity of rats evaluated by the open field test. The results described in the present paper indicate that the anti-immobility activity of SB-399885 is not connected with 5-HT innervation, and that D(1)- and D(2)-like receptors and alpha(2)-adrenoceptors are involved in this action.

  20. Application of Selected Reaction Monitoring Mass Spectrometry to Field Grown Crop Plants To Allow Dissection of the Molecular Mechanisms of Abiotic Stress Tolerance.

    Directory of Open Access Journals (Sweden)

    Richard P. Jacoby

    2013-02-01

    Full Text Available One major constraint upon the application of molecular crop breeding approaches is the small number of genes linked to agronomically desirable traits through defined biochemical mechanisms. Proteomic investigations of crop plants under abiotic stress treatments have identified many proteins that differ in control versus stress comparisons, however this broad profiling of cell physiology is poorly suited to ranking the effects and identifying the specific proteins that are causative in agronomically relevant traits. Here we will reason that insights into a protein’s function, its biochemical process and links to stress tolerance are more likely to arise through approaches that evaluate these differential abundances of proteins and include varietal comparisons, precise discrimination of protein isoforms, enrichment of functionally related proteins and integration of proteomic datasets with physiological measurements of both lab and field grown plants. We will briefly explain how applying the emerging proteomic technology of multiplexed selective reaction monitoring mass spectrometry with its accuracy and throughput can facilitate and enhance these approaches and provide a clear means to rank the growing cohort of stress responsive proteins. We will also highlight the benefit of integrating proteomic analyses with cultivar-specific genetic databases and physiological assessments of cultivar performance in relevant field environments for revealing deeper insights into molecular crop improvement.

  1. Selective catalytic reduction (SCR) of NO by urea loaded on activated carbon fibre (ACF) and CeO2/ACF at 30 degrees C: the SCR mechanism.

    Science.gov (United States)

    Zeng, Zheng; Lu, Pei; Li, Caiting; Zeng, Guangming; Jiang, Xiao; Zhai, Yunbo; Fan, Xiaopeng

    2012-06-01

    Selective catalytic reduction (SCR) of NO by urea loaded on rayon-based activated carbon fibre (ACF) and CeO2/ACF (CA) was studied at ambient temperature (30 degrees C) to establish a basic scheme for its reduction. Nitric oxide was found to be reduced to N2 with urea deposited on the ACF and CA. When oxygen was present, the greater the amount of loaded urea (20-60%), the greater the NO(x) conversions, which were between 72.03% and 77.30%, whereas the NO(x) conversions were about 50% when oxygen was absent. Moreover, when the urea was loaded on CA, a catalyst containing 40% urea/ACF loaded with 10% CeO2 (UCA4) could yield a NO(x) conversion of about 80% for 24.5 h. Based on the experimental results, the catalytic mechanisms of SCR with and without oxygen are discussed. The enhancing effect of oxygen resulted from the oxidation of NO to NO2, and urea was the main reducing agent in the SCR of loaded catalysts. ACF-C was the catalytic centre in the SCR of NO of ACF, while CeO2 of urea-loaded CA was the catalytic centre.

  2. Role of the key mutation in the selective binding of avian and human influenza hemagglutinin to sialosides revealed by quantum-mechanical calculations.

    Science.gov (United States)

    Sawada, Toshihiko; Fedorov, Dmitri G; Kitaura, Kazuo

    2010-12-01

    The selective binding between avian and human influenza A viral hemagglutinins (HA) subtype H3 and Neu5Acα2-3 and α2-6Gal (avian α2-3, human α2-6) is qualitatively rationalized by the fragment molecular orbital (FMO) method. We suggest a general model of analyzing protein-ligand interactions based on the electrostatic, polarization, dispersion, and desolvation components obtained from quantum-mechanical calculations at the MP2/6-31G(d) level with the polarizable continuum model of solvation. The favorable avian H3 (A/duck/Ukraine/1963)-avian α2-3 binding arises from the hydrophilic interaction between Gal-4 OH and side-chain NH(2)CO on Gln226, which is supported by the intermolecular hydrogen-bond network to the 1-COO group on Neu5Ac moiety. A substitution of Gln226Leu in the avian H3 HA1 domain increases the binding affinity to human α2-6 due to the Leu226···human α2-6 dispersion with a small entropic penalty during the complex formation. The remarkable human H3 (A/Aichi/2/1968)-human α2-6 binding is not governed by the Ser228-OH···OH-9 Neu5Ac hydrogen bond. These fragment-based chemical aspects can help design monovalent inhibitors of the influenza viral HA-sialoside binding and the simulation studies on the viral HAs-human α2-6 binding.

  3. Effects of laser processing parameters on thermal behavior and melting/solidification mechanism during selective laser melting of TiC/Inconel 718 composites

    Science.gov (United States)

    Shi, Qimin; Gu, Dongdong; Xia, Mujian; Cao, Sainan; Rong, Ting

    2016-10-01

    A three-dimensional finite element model is proposed to study the effects of laser power and scan speed on the thermal behavior and melting/solidification mechanism during selective laser melting (SLM) of TiC/Inconel 718 powder system. The cooling time during powder delivery is taken into account to simulate the actual production process well. It shows obviously the existence of heat accumulation effect in SLM process and, the tailored set of cooling time of 10 ms during powder delivery alleviates that effectively. The maximum temperature gradient in the molten pool slightly increases from 1.30×104 °C/mm to 2.60×104 °C/mm as the laser power is increased from 75 W to 150 W. However, it is negligibly sensitive to the variation of scan speed. There is a positive corresponding relationship between the maximum rate of temperature change and processing parameters. A low laser power (75 W) or a high scan speed (300 mm/s) is more energy efficient in Z-direction of the molten pool, giving rise to a deep-narrow cross section of the pool. Whereas, a high laser power (150 W) or a low scan speed (50 mm/s) causes a shallow-wide cross section of the molten pool, meaning it is more energy efficient in the Y-direction of the melt. The combination of a laser power of 125 W and a scan speed of 100 mm/s contributes to achieve a sound metallurgical bonding between the neighbor layers and tracks, due to the proper molten pool size (width: 109.3 μm; length: 120.7 μm; depth: 67.8 μm). The SLM experiments on TiC/Inconel 718 powder system are performed to verify the reliability and accuracy of the physical model and, simulation results are proved to be correct.

  4. Area-Selective Lift-Off Mechanism Based on Dual-Triggered Interfacial Adhesion Switching: Highly Facile Fabrication of Flexible Nano-Mesh Electrode.

    Science.gov (United States)

    Yu, Seunghee; Han, Hyeuk Jin; Kim, Jong Min; Yim, Soonmin; Sim, Dong Min; Lim, Hunhee; Lee, Jung Hye; Park, Woon Ik; Park, Jae Hong; Kim, Kwang Ho; Jung, Yeon Sik

    2017-02-28

    With the recent emergence of flexible and wearable optoelectronic devices, the achievement of sufficient bendability and stretchability of transparent and conducting electrodes (TCEs) has become an important requirement. Although metal-mesh-based structures have been investigated for TCEs because of their excellent performances, the fabrication of mesh or grid structures with a sub-micron line width is still complex due to the requirements of laborious lithography and pattern transfer steps. Here, we introduce an extremely facile fabrication technique for metal patterns embedded in a flexible substrate based on sub-micron replication and an area-selective delamination (ASD) patterning. The high-yield, area-specific lift-off process is based on the principle of solvent-assisted delamination of deposited metal thin films and a mechanical triggering effect by soft wiping or ultrasonication. Our fabrication process is highly simple, convenient, and cost-effective in that it does not require any lithography/etching steps or sophisticated facilities. Moreover, their outstanding optical and electrical properties (e.g. sheet resistances of 0.43 Ω sq(-1) at 94% transmittance), which are markedly superior to those of other flexible TCEs, are demonstrated. Furthermore, there is no significant change of resistance during over 1,000 repeated bending cycles with a bending radius of 5 mm and for immersing in various solvents such as salt water and organic solvents. Finally, we demonstrate high-performance transparent heaters and flexible touch panels using the fabricated nanomesh electrode, confirming the long-range electrical conduction and reliability of the electrode.

  5. Effects of flunixin and florfenicol combined with vitamins E and/or C on selected immune mechanisms in cattle under conditions of adaptive stress

    Directory of Open Access Journals (Sweden)

    Urban-Chmiel Renata

    2015-06-01

    Full Text Available The aim of the study was to evaluate the effect of flunixin and florfenicol administered in combination with vitamin E or C on selected leukocyte immune mechanisms and on the inflammatory process during the first few weeks in the feedlot. Fifty calves divided into 5 groups (n = 10 received florfenicol and flunixin with vitamin E or C. Blood was collected on the 1st, 3rd, 7th, 14th, 21st, and 28th d of the experiment. Intracellular metabolism (NBT, apoptosis, chemotaxis, susceptibility to M. haemolytica leukotoxin, and expression of β2-integrins were determined in leukocytes. The symptoms of respiratory tract infection were observed in 40% of calves in control group, while in the other groups the morbidity rate ranged from 10% to 20%. Leukocytes showed decreased NBT, and the mean values for apoptosis ranged from 14% to 24%. The lowest percentage of apoptotic cells was observed in the calves that received florfenicol with flunixin and vitamins E and C. The chemotactic activity confirmed the significant inhibitory effect of the preparations on migration of the cells. A significant decrease (P ≤ 0.05 in the susceptibility of leukocytes to leukotoxin was noted in the group that received florfenicol and flunixin with vitamin E. Expression of β2-integrin receptors was the lowest in calves receiving florfenicol with flunixin and vitamin E or C. The application of an antibiotic and a non-steroidal anti-inflammatory drug with antioxidants protected the leukocytes involved in defence against M. haemolytica virulence factors and effectively limited oxidative stress in the calves.

  6. 我国政府组织人才选拔和管理机制的发展演变研究%The Development of Talent Selection and Management Mechanism in China

    Institute of Scientific and Technical Information of China (English)

    白海琦; 郄艳丽

    2012-01-01

    我国是世界文明古国之一,在很早以前就建立了政府组织,有着悠久的政府人才选拔历史。从史记上记载的夏代开始,一直到今天,我国政府组织的人才选拔机制从未间断,始终处于探索和发展之中。以历史为脉络,梳理了在不同时期我国政府组织人才选拔机制的制度和特点,能为今天我国政府人才选拔机制的改进和完善提供借鉴。%China is one of the ancient civilization countries in the world,the government organizations had existed long time ago.China has a long history about talent selection in government organizations.From Xia dynasty on historical records to now,talent selection mechanism of the government organizations in China has being constructed,explorated and developed.Based on the historical practices of talent selection in China,this paper summarizes the system and characteristics of talent selection mechanism in different periods of Chinese history.The author hopes that this paper can provide reference for improving talent selection mechanism of the government organizations in China.

  7. A DFT study on PBu3-catalyzed intramolecular cyclizations of N-allylic substituted α-amino nitriles for the formation of functionalized pyrrolidines: mechanisms, selectivities, and the role of catalysts.

    Science.gov (United States)

    Zheng, Linjie; Tang, Mingsheng; Wang, Yang; Guo, Xiaokang; Wei, Donghui; Qiao, Yan

    2016-03-21

    The mechanisms and chemo- and stereo-selectivities of PBu3-catalyzed intramolecular cyclizations of N-allylic substituted α-amino nitriles leading to functionalized pyrrolidines (5-endo-trig cyclization, Mechanism A) and their competing reaction leading to another kind of pyrrolidine (5-exo-trig cyclization, Mechanism B) have been investigated using density functional theory (DFT). Multiple possible reaction pathways associated with four different isomers (RR, SR, RS, and SS) for Mechanism A, and two isomers (R and S) for Mechanism B have been studied. The calculated results indicate that the Gibbs free energy barriers of Mechanism A are remarkably lower than those of Mechanism B, and the reaction pathway leading to the RS-configured product has the lowest Gibbs free energy barrier, which is in agreement with the experiments. A C-H···π interaction has been identified to be responsible for the favorability of RS isomers by non-covalent interaction (NCI) analysis. Moreover, global reaction indexes (GRIs) and NBO analyses confirm that PBu3 acts as a Lewis base to strengthen the nucleophilicity of the reaction active site. The mechanistic insights gained in the present study should be valuable for the rational design of effective organocatalysts for this kind of reaction with high chemo- and stereo-selectivities.

  8. Molecular mechanisms mediating the neuroprotective role of the selective estrogen receptor modulator, bazedoxifene, in acute ischemic stroke: A comparative study with 17β-estradiol.

    Science.gov (United States)

    Jover-Mengual, Teresa; Castelló-Ruiz, María; Burguete, María C; Jorques, María; López-Morales, Mikahela A; Aliena-Valero, Alicia; Jurado-Rodríguez, Andrés; Pérez, Salvador; Centeno, José M; Miranda, Francisco J; Alborch, Enrique; Torregrosa, Germán; Salom, Juan B

    2017-07-01

    As the knowledge on the estrogenic system in the brain grows, the possibilities to modulate it in order to afford further neuroprotection in brain damaging disorders so do it. We have previously demonstrated the ability of the selective estrogen receptor modulator, bazedoxifene (BZA), to reduce experimental ischemic brain damage. The present study has been designed to gain insight into the molecular mechanisms involved in such a neuroprotective action by investigating: 1) stroke-induced apoptotic cell death; 2) expression of estrogen receptors (ER) ERα, ERβ and the G-protein coupled estrogen receptor (GPER); and 3) modulation of MAPK/ERK1/2 and PI3K/Akt signaling pathways. For comparison, a parallel study was done with 17β-estradiol (E2)-treated animals. Male Wistar rats subject to transient right middle cerebral artery occlusion (tMCAO, intraluminal thread technique, 60min), were distributed in vehicle-, BZA- (20.7±2.1ng/mL in plasma) and E2- (45.6±7.8pg/mL in plasma) treated groups. At 24h from the onset of tMCAO, RT-PCR, Western blot and histochemical analysis were performed on brain tissue samples. Ischemia-reperfusion per se increased apoptosis as assessed by both caspase-3 activity and TUNEL-positive cell counts, which were reversed by both BZA and E2. ERα and ERβ expression, but not that of GPER, was reduced by the ischemic insult. BZA and E2 had different effects: while BZA increased both ERα and ERβ expression, E2 increased ERα expression but did not change that of ERβ. Both MAPK/ERK1/2 and PI3K/Akt pathways were stimulated under ischemic conditions. While BZA strongly reduced the increased p-ERK1/2 levels, E2 did not. Neither BZA nor E2 modified ischemia-induced increase in p-Akt levels. These results show that modulation of ERα and ERβ expression, as well as of the ERK1/2 signaling pathway accounts, at least in part, for the inhibitory effect of BZA on the stroke-induced apoptotic cell death. This lends mechanistic support to the

  9. Addressing catch mechanisms in gillnets improves modeling of selectivity and estimates of mortality rates: a case study using survey data on an endangered stock of Arctic char

    DEFF Research Database (Denmark)

    Jonsson, T.; Setzer, M.; Pope, John George;

    2013-01-01

    Estimation of fish stock size distributions from survey data requires knowledge about gear selectivity. However, selectivity models rest on assumptions that seldom are analyzed. Departures from these can lead to misinterpretations and biased management recommendations. Here, we use survey data...... on great Arctic char (Salvelinus umbla) to analyze how correcting for entanglement of fish and nonisometric growth might improve estimates of selectivity curves, and subsequently estimates of size distribution and age-specific mortality. Initial selectivity curves, using the entire data set, were wide...... and asymmetric, with poor model fits. Removing potentially nonmeshed fish had the greatest positive effect on model fit, resulting in much narrower and less asymmetric selection curves, while attempting to take nonisometric growth into account, by using girth rather than length, improved model fit...

  10. Effects of Divergent Selection Body Weight and the Quail Laying Eggs on some Physical and Mechanical Properties of Japanese Quail Eggs

    Directory of Open Access Journals (Sweden)

    mousareza baghani

    2016-08-01

    Full Text Available Introduction Breeding quail and quail egg industrial production because of the high nutritional value of these products has been developing these years. Considering the high demand and economical production, further development in the future is predicted. In order to design and effective utilization of the equipment for transportation, separation, packaging and storage, the physical and mechanical properties of quail eggs are needed. It is of great importance to study the factors which are influencing these properties. Strength of the shell is an important factor in determination of quail egg quality. Quail egg shell strength depends on several variables including specific gravity, egg weight and volume, shell thickness, weight and percentage of shell, hardness, breaking force, breaking energy, egg surface, farming conditions, type and species of birds, nutrition and geometric characteristics of eggs. Materials and Methods In this paper, initially in three phases, at 15 weeks, 19 weeks and 23 weeks, shell strength changes and physical properties of quail eggs on 90 quails during their first period of laying eggs were studied. Measured properties were included dimensions, weight, volume, specific gravity, shell thickness, weight and percentage of shell, breaking force, breaking energy, egg surface and some other properties. In the second part the effects of divergent selection for the bird’s body weight at four weeks of age on the quail eggs of fifth generation were studied. Measured properties were included dimensions, weight, volume, breaking force, breaking energy and some factors for direct and indirect measurement of strength of quail eggs. For direct measurement of the strength of eggshell of quail, two methods were employed: The first method was quasi-static compression test between two parallel plates of the universal testing machine and the second method was measuring specific gravity. In the first method, eggs were compressed between

  11. Proposal of an Amide-Directed Carbocupration Mechanism for Copper-Catalyzed meta-Selective C-H Arylation of Acetanilides by Diaryliodonium Salts

    Institute of Scientific and Technical Information of China (English)

    Song-lin Zhang; Yu-qiang Ding

    2011-01-01

    We examined the puzzling mechanism for Cu-catalyzed meta-C-H arylation reaction of anilides by diaryliodonium salts through systematic theoretical analysis.The previously proposed anti-oxy-cupration mechanism featuring anti- 1,2- or anti- 1,4-addition of cuprate and oxygen to the phenyl ring generating a meta-cuprated intermediate was excluded due to the large activation barriers.Alternatively,a new amide-directed carbocupration mechanism was proposed which involves a critical rate- and regio-determining step of amide-directed addition of the Cu(III)-aryl bond across the phenyl C2=C3 double bond to form an orthocuprated,meta-arylated intermediate.This mechanism is kinetically the most favored among several possible mechanisms such as ortho- or para-cupration/migration mechanism,direct meta C-H bond cleavage mediated by Cu(III) or Cu(I),and Cu(III)-catalyzed ortho-directed C-H bond activation mechanism.Furthermore,the predicted regioselectivity based on this mechanism has been shown to favor the meta-arylation that is consistent with the experimental observations.

  12. Oscillatory Mechanisms of Stimulus Processing and Selection in the Visual and Auditory Systems: State-of-the-Art, Speculations and Suggestions

    Directory of Open Access Journals (Sweden)

    Benedikt Zoefel

    2017-05-01

    Full Text Available All sensory systems need to continuously prioritize and select incoming stimuli in order to avoid overflow or interference, and provide a structure to the brain's input. However, the characteristics of this input differ across sensory systems; therefore, and as a direct consequence, each sensory system might have developed specialized strategies to cope with the continuous stream of incoming information. Neural oscillations are intimately connected with this selection process, as they can be used by the brain to rhythmically amplify or attenuate input and therefore represent an optimal tool for stimulus selection. In this paper, we focus on oscillatory processes for stimulus selection in the visual and auditory systems. We point out both commonalities and differences between the two systems and develop several hypotheses, inspired by recently published findings: (1 The rhythmic component in its input is crucial for the auditory, but not for the visual system. The alignment between oscillatory phase and rhythmic input (phase entrainment is therefore an integral part of stimulus selection in the auditory system whereas the visual system merely adjusts its phase to upcoming events, without the need for any rhythmic component. (2 When input is unpredictable, the visual system can maintain its oscillatory sampling, whereas the auditory system switches to a different, potentially internally oriented, “mode” of processing that might be characterized by alpha oscillations. (3 Visual alpha can be divided into a faster occipital alpha (10 Hz and a slower frontal alpha (7 Hz that critically depends on attention.

  13. Differential helical orientations among related G protein-coupled receptors provide a novel mechanism for selectivity. Studies with salvinorin A and the kappa-opioid receptor.

    Science.gov (United States)

    Vortherms, Timothy A; Mosier, Philip D; Westkaemper, Richard B; Roth, Bryan L

    2007-02-02

    Salvinorin A, the active component of the hallucinogenic sage Salvia divinorum, is an apparently selective and highly potent kappa-opioid receptor (KOR) agonist. Salvinorin A is unique among ligands for peptidergic G protein-coupled receptors in being nonnitrogenous and lipid-like in character. To examine the molecular basis for the subtype-selective binding of salvinorin A, we utilized an integrated approach using chimeric opioid receptors, site-directed mutagenesis, the substituted cysteine accessibility method, and molecular modeling and dynamics studies. We discovered that helix 2 is required for salvinorin A binding to KOR and that two residues (Val-108(2.53) and Val-118(2.63)) confer subtype selectivity. Intriguingly, molecular modeling studies predicted that these loci exhibit an indirect effect on salvinorin A binding, presumably through rotation of helix 2. Significantly, and in agreement with our in silico predictions, substituted cysteine accessibility method analysis of helix 2 comparing KOR and the delta-opioid receptor, which has negligible affinity for salvinorin A, revealed that residues known to be important for salvinorin A binding exhibit a differential pattern of water accessibility. These findings imply that differences in the helical orientation of helix 2 are critical for the selectivity of salvinorin A binding to KOR and provide a structurally novel basis for ligand selectivity.

  14. Application of statistical analysis method in selection of rock mechanics parameters%统计分析法在岩体力学参数取值分析中的应用

    Institute of Scientific and Technical Information of China (English)

    张玉灯; 郭维详

    2015-01-01

    An introduction was made on the excluding outliers principle,testing parameter standard value calcula⁃tion,shear test data linear regression of statistical analysis method. The authors demonstrate the application of sta⁃tistical analysis method in mechanics parameter selection with real engineering mechanical parameters from the geo⁃logical mechanics parameter database as data source. The results of statistical analysis of limestone mechanics pa⁃rameters demonstrate that the distribution characteristics of mechanical parameters mostly conform to normal curve. The result of statistical analysis based on the mechanical parameters database can be important reference basis for the selection of mechanics parameters.%介绍了统计分析方法中的异常值剔除原则、试验参数标准值的计算、抗剪试验数据的一元线性回归分析方法。以地质力学参数数据库中的实际工程力学参数为数据源演示了统计分析方法在力学参数分析中的应用。通过对灰岩的力学参数的统计分析,结果表明:大多力学参数的分布特点符合正态分布。运用力学参数数据库进行参数统计分析的结果为地质人员进行力学参数取值提供了重要的参考依据。

  15. 基于小世界网络的知识交流对象选择研究%The partner selection mechanism in knowledge communication on small - world network

    Institute of Scientific and Technical Information of China (English)

    林敏; 李南; 季旭

    2012-01-01

    By analyzing the behavior of knowledge communication in organizations, sufficiency index and equity index are proposed to measure the effectiveness of knowledge communication and explore the effect of partner selection mechanism. The process of knowledge communication on small - world network is simulated. Results show that the mechanism for selecting neighbors who have higher knowledge level could promote knowledge communication, on the other hand, the mechanism for selecting neighbors who have more work experiences results in a clustering effect and impedes knowledge communication in organizations.%本文在分析组织知识交流行为的基础上,提出了衡量知识交流效果的交流充分度指标和交流公平度指标。并探讨了知识交流对象选择机制对知识交流效果的影响。对小世界网络上的知识交流过程进行了模拟,并分析了结果。通过比较研究发现,就高选择机制是促进组织知识交流的积极因素,而工龄选择机制下会出现扎堆现象,妨碍组织的知识交流。

  16. The deactivation mechanism of Cl on Ce/TiO2 catalyst for selective catalytic reduction of NO with NH3

    Science.gov (United States)

    Yang, Ning-zhi; Guo, Rui-tang; Pan, Wei-guo; Chen, Qi-lin; Wang, Qing-shan; Lu, Chen-zi; Wang, Shu-xian

    2016-08-01

    The poisoning mechanism of Cl on Ce/TiO2 catalyst was investigated based on temperature programmed desorption (TPD) and the in situ diffuse reflectance infrared transform spectroscopy (DRIFT) studies. The results of NH3-TPD and NO-TPD indicated that the addition of Cl on Ce/TiO2 catalyst would inhibit the adsorption of NH3 species and NOx species on it. As can be seen from the results of in situ DRIFT study, the NH3-SCR reaction over Ce/TiO2 and Ce/TiO2-Cl were all followed both the Eley-Rideal mechanism and the Langmuir-Hinshelwood mechanism. And the decreased adsorption ability of NH3 species and NOx species on the surface of Ce/TiO2-Cl should be mainly responsible for its low SCR activity.

  17. Three Theoretical Problems in the Scientification of Personnel Selection and Appointment Mechanisms%选人用人机制科学化的三个理论问题

    Institute of Scientific and Technical Information of China (English)

    马恩

    2012-01-01

    Based on the analysis of major measures for the reform of personnel system for cadres in recent years, this paper proposes three deep-rooted theoretical problems that must be resolved currently to promote the scientification of personnel selection and appointment mechanisms: first the political attributes of the ranks of our civil servants as a ruling group must be recognized, diverse criteria and methods for personnel selection should be established from the perspective to embody the political representation function of the ranks of civil servants; sec- ondly the trap of nominator diversification must be disengaged from the perspective of scientific allocation the au- thority of cadre appointment ; thirdly the functions of the masses in cadre selection and appointment must be scien- tifically positioned, and the forms and limitations of democracy in cadre selection and appointment must be clari- fied.%本文在对近年来干部人事制度改革主要措施分析的基础上,提出当前推进选人用人机制科学化,必须解决三个方面的深层次理论问题:一是要认清我国公务员队伍作为执政群体的政治属性,从体现公务员队伍政治代表功能的角度,确立多样化的选人标准和选拔方式;二是要从科学配置干部任用权的角度,从提名权主体多元化的误区中摆脱出来;三是要对群众在干部选拔任用中的作用有科学定位,厘清干部选拔任用中民主的形式和限度。

  18. Towards a selective adsorbent for arsenate and selenite in the presence of phosphate: Assessment of adsorption efficiency, mechanism, and binary separation factors of the chitosan-copper complex.

    Science.gov (United States)

    Yamani, Jamila S; Lounsbury, Amanda W; Zimmerman, Julie B

    2016-01-01

    The potential for a chitosan-copper polymer complex to select for the target contaminants in the presence of their respective competitive ions was evaluated by synthesizing chitosan-copper beads (CCB) for the treatment of (arsenate:phosphate), (selenite:phosphate), and (selenate:sulfate). Based on work by Rhazi et al., copper (II) binds to the amine moiety on the chitosan backbone as a monodentate complex (Type I) and as a bidentate complex crosslinking two polymer chains (Type II), depending on pH and copper loading. In general, the Type I complex exists alone; however, beyond threshold conditions of pH 5.5 during synthesis and a copper loading of 0.25 mol Cu(II)/mol chitosan monomer, the Type I and Type II complexes coexist. Subsequent chelation of this chitosan-copper ligand to oxyanions results in enhanced and selective adsorption of the target contaminants in complex matrices with high background ion concentrations. With differing affinities for arsenate, selenite, and phosphate, the Type I complex favors phosphate chelation while the Type II complex favors arsenate chelation due to electrostatic considerations and selenite chelation due to steric effects. No trend was exhibited for the selenate:sulfate system possibly due to the high Ksp of the corresponding copper salts. Binary separation factors, α12, were calculated for the arsenate-phosphate and selenite-phosphate systems, supporting the mechanistic hypothesis. While, further research is needed to develop a synthesis method for the independent formation of the Type II complexes to select for target contaminants in complex matrices, this work can provide initial steps in the development of a selective adsorbent.

  19. The deactivation mechanism of Pb on the Ce/TiO2 catalyst for the selective catalytic reduction of NOx with NH3: TPD and DRIFT studies.

    Science.gov (United States)

    Wang, Shu-Xian; Guo, Rui-Tang; Pan, Wei-Guo; Li, Ming-Yuan; Sun, Peng; Liu, Shu-Ming; Liu, Shuai-Wei; Sun, Xiao; Liu, Jian

    2017-02-15

    It was well recognized that Pb had a poisoning effect on a SCR catalyst. In this study, the deactivation mechanism of Pb on the Ce/TiO2 catalyst was investigated based on the characterization results of TPD and in situ DRIFT studies. It was found that the addition of Pb on the Ce/TiO2 catalyst not only inhibited the adsorption and activation of NH3 species, but also led to the decrease of the activity of adsorbed NH3 species in the SCR reaction. The adsorption of NOx species and the oxidation of NO by O2 over the Ce/TiO2 catalyst were also suppressed by the addition of Pb, while the reactivity of adsorbed NO2 species did not decrease. Moreover, the results revealed that the NH3-SCR reaction over the Ce/TiO2 catalyst followed both the E-R and L-H mechanisms, while the NH3-SCR reaction over Ce/TiO2-Pb was mainly controlled by the L-H mechanism. The contributions of the L-H mechanism to the SCR reactions over Ce/TiO2 and Ce/TiO2-Pb decreased with increasing reaction temperature. The deactivation of Ce/TiO2-Pb was mainly attributed to the suppressed NH3 adsorption and activation, accompanied by the inhibited NO oxidation and the decrease of Brønsted acid sites.

  20. Differences in the Neural Mechanisms of Selective Attention in Children from Different Socioeconomic Backgrounds: An Event-Related Brain Potential Study

    Science.gov (United States)

    Stevens, Courtney; Lauinger, Brittni; Neville, Helen

    2009-01-01

    Previous research indicates that children from lower socioeconomic backgrounds show deficits in aspects of attention, including a reduced ability to filter irrelevant information and to suppress prepotent responses. However, less is known about the neural mechanisms of group differences in attention, which could reveal the stages of processing at…

  1. Observations and Measurements of Wing Parameters of the Selected Beetle Species and the Design of a Mechanism Structure Implementing a Complex Wing Movement

    Directory of Open Access Journals (Sweden)

    Geisler T.

    2016-12-01

    Full Text Available Beetle wings perform a flapping movement, consisting of the rotation relative to the two axes. This paper presents the results of observations and measurements of wings operating parameters in different planes of some beetle species. High speed photos and videos were used. The concept of the mechanism performing a complex wing movement was proposed and developed.

  2. Selection of a biocontrol agent based on a potential mechanism of action: degradation of nicotinic acid, a growth factor essential for Erwinia amylovora.

    Science.gov (United States)

    Paternoster, Thomas; Défago, Geneviève; Duffy, Brion; Gessler, Cesare; Pertot, Ilaria

    2010-12-01

    This work describes a medium-based screening method for selecting microbial biocontrol agents against Erwinia amylovora based on the degradation of a specific growth factor. Erwinia amylovora, the causal agent of the devastating fire blight disease, requires nicotinic acid or nicotinamide as an essential growth factor. Potential biocontrol agents are either selected for antimicrobial production in plate or directly on immature pears or apple blossoms. In this work, we have attempted to streamline the selection of a new potential biocontrol agent with a lower risk of non-target effects by isolation based on the ability to degrade nicotinic acid in vitro, using therefore few plant materials. A total of 735 bacteria and 1237 yeast were isolated from apple blossoms and pre-screened for nicotinic acid-degradation. Pseudomonas rhizosphaerae strain JAN was able to degrade both nicotinic acid and nicotinamide. Mutants deficient in this ability were constructed. JAN, but not the mutants, controlled E. amylovora on pear slices. On detached apple blossoms, JAN colonized apple hypanthia and strongly suppressed E. amylovora growth. Under greenhouse conditions, JAN was more effective in controlling blossom blight than P. fluorescens A506, a commercial biocontrol agent of fire blight unable to degrade nicotinic acid and nicotinamide.

  3. Motion Analysis of Gear Selection Mechanism Based on Virtual Prototyping and ANN%基于虚拟样机和人工神经网络的选挡机构运动分析

    Institute of Scientific and Technical Information of China (English)

    张宝; 李健

    2014-01-01

    为得到汽车选挡机构工作过程中某些变量之间具体的函数关系,在 ADAMS 软件中建立选挡机构的运动模型并进行运动仿真分析。分别将操作杆上 X 方向和 Y 方向的作用力作为输入变量,将拉索 X 方向位移和摇杆转动角度作为输出变量。然后在 MATLAB 软件中利用人工神经网络对输入和输出变量进行多次训练。得到的函数关系图与已知参数点的线性拟合度高,为选挡机构的数值分析打下基础。%To get specific functional relationship between certain variables during operation of gear election mechanism in cars, the model of gear selection mechanism was created and analyzed in the ADAMS software. The forces in X and Y direc-tions of the joystick were selected as the input variables, and the lasso displacement in X direction and rotation angle of the joystick were selected as the output variables. Then the input variables and output variables were trained in MATLAB software by ANN. The function diagram that was obtained afterward was highly fit to the linearity of the known parameters, and thus could lay the foundation for the numerical analysis of gear selection mechanism.

  4. Attention is a process of selection, perception is a process of representation, and phenomenal experience is the result of perception being modulated by a dedicated consciousness mechanism

    Directory of Open Access Journals (Sweden)

    Talis eBachmann

    2011-12-01

    Full Text Available Equivalence of attention and consciousness is disputed and necessity of attentional effects for conscious experience has become questioned. However, the conceptual landscape and interpretations of empirical evidence as related to this issue have remained controversial. Here I present some conceptual distinctions and research strategies potentially useful for moving forward. Specifically, we should differentiate between processes and the results of the processes, move the emphasis from studying the effects of attention on the modality-specific and feature-specific perception to studying attentional effects on panmodal universal attributes of whatever conscious experience there is, and acknowledge that there is a specialized autonomous mechanism for leading to conscious experience of the preconsciously represented contents apart from the mechanisms of perception, attention, memory and cognitive control.

  5. Tartaglia’s science of weights and mechanics in the sixteenth century selections from quesiti et inventioni diverse books VII–VIII

    CERN Document Server

    Pisano, Raffaele

    2016-01-01

    This book presents a historical and scientific analysis as historical epistemology of the science of weights and mechanics in the sixteenth century, particularly as developed by Tartaglia in his Quesiti et inventioni diverse, Book VII and Book VIII (1546; 1554). In the early 16th century mechanics was concerned mainly with what is now called statics and was referred to as the Scientia de ponderibus, generally pursued by two very different approaches. The first was usually referred to as Aristotelian, where the equilibrium of bodies was set as a balance of opposite tendencies to motion. The second, usually referred to as Archimedean, identified statics with centrobarica, the theory of centres of gravity based on symmetry considerations. In between the two traditions the Italian scholar Niccolò Fontana, better known as Tartaglia (1500?–1557), wrote the treatise Quesiti et inventioni diverse (1546). This volume consists of three main parts. In the first, a historical excursus regarding Tartaglia’s lifetime,...

  6. DRIFT studies on promotion mechanism of H3PW12O40 in selective catalytic reduction of NO with NH3.

    Science.gov (United States)

    Weng, Xiaole; Dai, Xiaoxia; Zeng, Qingshan; Liu, Yue; Wu, Zhongbiao

    2016-01-01

    Heteropoly acids (HPAs) have been effectively utilized in selective catalytic reduction (SCR) of NO to improve the NH3 absorption capacity and alkaline/alkali metal resistance for SCR catalysts. However, despite the promise on super-acidities, their other properties that would work on SCR process are still lack of exploration. In this study, a 12-tungstaphosphoric acid (H3PW12O40, HPW) was selected to modify a well-reported CeO2 catalyst. The resulted CeO2/HPW catalyst was subsequently utilized for SCR of NO with excess NH3, which revealed a significantly promoted performance in SCR reaction. DRIFT analyses showed that the unique NO2 absorption capacity of HPW could prevent the NO2 being further oxidized into nitrate species and the abundant Brønsted acid sites could effectively retain the NH3, avoiding them being over-oxidized at evaluated temperatures. The presence of NO2 was demonstrated able to induce a so called "fast SCR" reaction over the CeO2/HPW catalyst, which effectively facilitated the SCR reaction. Furthermore, we have also constructed a CeO2@HPW catalyst, which showed an enhanced SO2 poisoning resistance in SCR reaction.

  7. Periodic, Quasi-Periodic and Chaotic Motions in Celestial Mechanics: Theory and Applications Selected papers from the Fourth Meeting on Celestial Mechanics, CELMEC IV San Martino al Cimino (Italy), 11–16 September 2005

    CERN Document Server

    Celletti, A

    2006-01-01

    The book provides the most recent advances of Celestial Mechanics, as provided by high-level scientists working in this field. It covers theoretical investigations as well as applications to concrete problems. Outstanding review papers are included in the book and they introduce the reader to leading subjects, like the variational approaches to find periodic orbits, the stability theory of the N-body problem, the spin-orbit resonances and chaotic dynamics, the space debris polluting the circumterrestrial space.

  8. Mechanism-Based Modeling of Hydrogen Environment Assisted Cracking (HEAC) in High Strength Alloys for Marine Applications: Prediction of Monel K-500 HEAC for Select Environmental and Mechanical Conditions

    Science.gov (United States)

    2012-10-15

    activation energies (-40 kJ/mol). Moreover, possible trapping sites will differ for precipitation hardened fee Ni-based alloys compared to ferrous ...FINAL REPORT Mechanism-Based Modeling of Hydrogen Environment Assisted Cracking (HEAC) in High Strength Alloys for Marine Applications: Prediction...the microscopic scale to enable threshold and crack growth rate predictions in Ni-based alloys which differ substantially from high strength steels

  9. Synergistic effect of selectively distributed AlN/MWCNT hybrid fillers on the morphological, mechanical and thermal properties of polycarbonate/maleated poly[styrene-b-(ethylene-co-butylene)- b-styrene] triblock copolymer (SEBS-g-MA) composites

    Science.gov (United States)

    Xiao, Chao; Leng, Xinyu; Wang, Hui; Su, Zheng; Zhang, Xian; Chen, Lin; Zheng, Kang; Tian, Xingyou

    2017-02-01

    A quaternary nanocomposite polycarbonate (PC)- multi-walled carbon nanotubes (MWCNT)/SEBS-g-MA (SM)-AlN is prepared by controlling the selective distribution of nano-fillers via melt-blending. Through a two-step mixing method, surface modified AlN is selectively dispersed in the island-like SM phase; meanwhile, MWCNT acting as bridges are mainly located in the continuous phase of PC. This ‘island-bridge’ morphology is confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The selective localization results agree well with the theoretical predictions. Dynamic mechanical analysis (DMA) indicates that the addition of hybrid fillers improved the storage modulus selectively. Thermogravimetric analysis (TGA) shows that the thermal stability of the PC/SM blends increased significantly; the degradation kinetic has also been changed due to the synergistic effects of the fillers. This novel ‘island-bridge’ network contributes a higher thermal conductivity at low filler content as the effective thermal conductivity reached 0.72 W m‑1 K‑1, which is three times higher than that of 70PC/30SM. The experimental observations coincide well with the optimizing model results.

  10. Heart healthy=prostate healthy: SELECT, the symbolic end of preventing prostate cancer via heart unhealthy and over anti-oxidation mechanisms?

    Institute of Scientific and Technical Information of China (English)

    Mark A Moyad

    2012-01-01

    The Selenium and Vitamin E Cancer Prevention Trial (SELECT) randomized over 35 000 men into four groups:high-dose vitamin E (400 IU day-1),high-dose selenium (200 mcg day-1),combination of vitamin E and selenium,or placebo.1 The brief time period to reach full recruitment was unprecedented;thus,it seemed that participants and health-care professionals were equally eager to test the hypothesis that high-dose antioxidant supplementation could prevent prostate cancer.However,the trial was terminated early,after a median of 5.5 years due to a lack of efficacy,although at the time a non-significant (P=0.06) increased risk of prostate cancer in the vitamin E arm,and type 2 diabetes in the selenium group (P=0.16)were observed.

  11. Activity and mechanism of action of HDVD, a novel pyrimidine nucleoside derivative with high levels of selectivity and potency against gammaherpesviruses.

    Science.gov (United States)

    Coen, N; Singh, U; Vuyyuru, V; Van den Oord, J J; Balzarini, J; Duraffour, S; Snoeck, R; Cheng, Y C; Chu, C K; Andrei, G

    2013-04-01

    A novel nucleoside analogue, 1-[(2S,4S-2-(hydroxymethyl)-1,3-dioxolan-4-yl]5-vinylpyrimidine-2,4(1H,3H)-dione, or HDVD, was evaluated against a wide variety of herpesviruses and was found to be a highly selective inhibitor of replication of the gammaherpesviruses Kaposi's sarcoma-associated herpesvirus (KSHV) and Epstein-Barr virus (EBV). HDVD had also a pronounced inhibitory activity against murine herpesvirus 68 (MHV-68) and herpes simplex virus 1 (HSV-1). In contrast, replication of herpesvirus saimiri (HVS), HSV-2, and varicella-zoster virus (VZV) was weakly inhibited by the compound, and no antiviral activity was determined against human cytomegalovirus (HCMV) and rhesus rhadinovirus (RRV). The HDVD-resistant virus phenotype contained point mutations in the viral thymidine kinase (TK) of HSV-1, MHV-68, and HVS isolates. These mutations conferred cross-resistance to other TK-dependent drugs, with the exception of an MHV-68 mutant (E358D) that exhibited resistance only to HDVD. HSV-1 and HVS TK-mutants isolated under selective pressure with bromovinyldeoxyuridine (BVDU) also showed reduced sensitivity to HDVD. Oral treatment with HDVD and BVDU was assessed in an intranasal model of MHV-68 infection in BALB/c mice. In contrast to BVDU treatment, HDVD-treated animals showed a reduction in viral DNA loads and diminished viral gene expression during acute viral replication in the lungs in comparison to levels in untreated controls. The valyl ester prodrug of HDVD (USS-02-71-44) suppressed the latent infection in the spleen to a greater extent than HDVD. In the present study, HDVD emerged as a highly potent antiviral with a unique spectrum of activity against herpesviruses, in particular, gammaherpesviruses, and may be of interest in the treatment of virus-associated diseases.

  12. Revealing mechanisms of selective, concentration-dependent potentials of 4-hydroxy-2-nonenal to induce apoptosis in cancer cells through inactivation of membrane-associated catalase.

    Science.gov (United States)

    Bauer, Georg; Zarkovic, Neven

    2015-04-01

    Tumor cells generate extracellular superoxide anions and are protected against superoxide anion-mediated intercellular apoptosis-inducing signaling by the expression of membrane-associated catalase. 4-Hydroxy-2-nonenal (4-HNE), a versatile second messenger generated during lipid peroxidation, has been shown to induce apoptosis selectively in malignant cells. The findings described in this paper reveal the strong, concentration-dependent potential of 4-HNE to specifically inactivate extracellular catalase of tumor cells both indirectly and directly and to consequently trigger apoptosis in malignant cells through superoxide anion-mediated intercellular apoptosis-inducing signaling. Namely, 4-HNE caused apoptosis selectively in NOX1-expressing tumor cells through inactivation of their membrane-associated catalase, thus reactivating subsequent intercellular signaling through the NO/peroxynitrite and HOCl pathways, followed by the mitochondrial pathway of apoptosis. Concentrations of 4-HNE of 1.2 µM and higher directly inactivated membrane-associated catalase of tumor cells, whereas at lower concentrations, 4-HNE triggered a complex amplificatory pathway based on initial singlet oxygen formation through H2O2 and peroxynitrite interaction. Singlet-oxygen-dependent activation of the FAS receptor and caspase-8 increased superoxide anion generation by NOX1 and amplification of singlet oxygen generation, which allowed singlet-oxygen-dependent inactivation of catalase. 4-HNE and singlet oxygen cooperate in complex autoamplificatory loops during this process. The finding of these novel anticancer pathways may be useful for understanding the role of 4-HNE in the control of malignant cells and for the optimization of ROS-dependent therapeutic approaches including antioxidant treatments.

  13. Selection of Fully Mechanized Working Face Support and Roof Management%综采工作面支架选择与顶板管理

    Institute of Scientific and Technical Information of China (English)

    王海波

    2014-01-01

    为了保证综采工作面的安全生产,根据煤层赋存和顶板岩性,分析了支架合理工作阻力确定方法,通过计算选择了采面液压支架,并对顶板日常管理和采面端头支护提出了合理安排。8814工作面综采实践表明:支架运行状况良好,顶板管理措施得当,保证了工作面安全回采。%In order to ensure the safety of fully mechanized working face production,according to the occurrence of coal seam and roof lithology,bracket,and a method for determining the reasonable working resistance are analyzed by calculating chose mining hydraulic support,and the roof of daily management and mining face end support reasonable arrangement are put forward.8814 fully mechanized face practice shows that support running in good condition,roof management measures reasonable,it guarantees the safety mining working face.

  14. The Analysis on The Selection And Orgnization of Professional Skill Competition in the Mechanical majors%浅析机械类专业技能竞赛的选择与组织

    Institute of Scientific and Technical Information of China (English)

    弓锵; 钮王杰; 刘艳芳

    2011-01-01

    专业技能竞赛是应用型本科人才核心能力的外在表现之一。在应用型本科人才培养模式下,机械类专业技能竞赛的选择要与本科人才培养方案相适应,以培养方案中需强化的内容作为竞赛项目的选择依据。竞赛的组织依托技能训练模块,这样一方面前者可以为后者提供方向和标准,另一方面后者也为前者提供所需的人员选拔和培训支持,也对运城学院机械类专业技能竞赛的选择和组织方式进行了分析。%The Professional skills competition is one of the external manifestations for the core competence of application -oriented talents. In the cultivation mode of applicationoriented undergraduate talents, the selection of the mechanical professional skill competition project must adapts to the undergraduate training scheme. It require to take the contents needed to be strengthened in the training scheme as the selection basis of competition project. The organization of professional skill competition should relys on the skill training module. The former provides the direction and standard for the latter. On the other hand the latter also gives the support of personnel selection and training for the former. The article also analyzed the selection and organization of mechanical skill competition in Yuncheng University.

  15. Reactivity, Selectivity, and Reaction Mechanisms of Aminoguanidine, Hydralazine, Pyridoxamine, and Carnosine as Sequestering Agents of Reactive Carbonyl Species: A Comparative Study.

    Science.gov (United States)

    Colzani, Mara; De Maddis, Danilo; Casali, Gaia; Carini, Marina; Vistoli, Giulio; Aldini, Giancarlo

    2016-08-19

    Reactive carbonyl species (RCS) are endogenous or exogenous byproducts involved in the pathogenic mechanisms of different oxidative-based disorders. Detoxification of RCS by carbonyl quenchers is a promising therapeutic strategy. Among the most studied quenchers are aminoguanidine, hydralazine, pyridoxamine, and carnosine; their quenching activity towards four RCS (4-hydroxy-trans-2-nonenal, methylglyoxal, glyoxal, and malondialdehyde) was herein analyzed and compared. Their ability to prevent protein carbonylation was evaluated in vitro by using an innovative method based on high-resolution mass spectrometry (HRMS). The reactivity of the compounds was RCS dependent: carnosine efficiently quenched 4-hydroxy-trans-2-nonenal, pyridoxamine was particularly active towards malondialdehyde, aminoguanidine was active towards methylglyoxal and glyoxal, and hydralazine efficiently quenched all RCS. Reaction products were generated in vitro and were characterized by HRMS. Molecular modeling studies revealed that the reactivity was controlled by specific stereoelectronic parameters that could be used for the rational design of improved carbonyl quenchers.

  16. Relatively Selective Production of the Simplest Criegee Intermediate in a CH4/O2 Electric Discharge: Kinetic Analysis of a Plausible Mechanism.

    Science.gov (United States)

    Nguyen, Thanh Lam; McCarthy, Michael C; Stanton, John F

    2015-07-16

    High -accuracy coupled cluster methods in combination with microcanonical semiclassical transition state theory are used to investigate a plausible formation mechanism of the simplest Criegee intermediate in a CH4/O2 discharge experiment. Our results suggest that the Criegee intermediate is produced in a three-step process: (i) production of methyl radical by cleavage of a C-H bond of CH4; (ii) association of methyl radical with molecular oxygen to form a vibrationally excited methyl peroxy, which is in a rapid microequilibrium with the reactants; and finally, (iii) H-abstraction of CH3OO by O2, which results in the formation of cool CH2OO, which has insufficient internal energy to rearrange to dioxirane.

  17. A new method to select appropriate countermeasures against heat-island effects according to the regional characteristics of heat balance mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Sasaki, Kiyoshi [Institute of Technology, SHIMIZU Corporation, 3-4-17 Etchujima, Koto-ku, Tokyo 135-8530 (Japan); Mochida, Akashi; Yoshino, Hiroshi [Graduate School of Engineering, Tohoku University, Aoba 6-6-11-1202, Aramaki, Aoba-ku, Sendai 980-8579 (Japan); Watanabe, Hironori [Department of Architecture, Tohoku Institute of Technology, 35-1 Kasumi-cho, Yagiyama, Taihaku-ku, Sendai 982-8577 (Japan); Yoshida, Tomohiro [Tokyo Electric Power Company, 1-1-11 Babadori, Utsunomiya, Tochigi 320-0026 (Japan)

    2008-10-15

    This study aims at clarifying the regional heat balance characteristics in an urban space of a city. CFD analyses of mesoscale climates of Tokyo, Sendai and Haramachi were carried out. The influence of regional characteristics on urban climates was examined, based on the results of CFD analyses, by considering the heat balance mechanism in the central part of each city. It was confirmed that the factors greatly contributing to air temperature increasing and decreasing in each city was different. Furthermore, the spatial distribution of heat budget inside Sendai city was drawn, as 'Heat Balance Map'. The map illustrated the areas where influence of sea breeze was significant in contrast with heat generated from ground surfaces and anthropogenic heat release in this city. (author)

  18. Are the different patterns of stress-induced (Takotsubo) cardiomyopathy explained by regional mechanical overload and demand: supply mismatch in selected ventricular regions?

    Science.gov (United States)

    Redfors, Bjorn; Shao, Yangzhen; Ali, Anwar; Omerovic, Elmir

    2013-11-01

    Takotsubo cardiomyopathy (TCM) or stress-induced cardiomyopathy is an increasingly recognized syndrome characterized by severe regional left ventricular dysfunction in the absence of an explanatory coronary lesion. TCM may lead to lethal complications but is completely reversible if the patient survives the acute phase. The pathogenesis of TCM and the mechanism behind this remarkable recovery are unknown. Plasma levels of catecholamine are elevated in many TCM patients and exogenously administered catecholamine induces TCM-like cardiac dysfunction in both humans and rats. A catecholamine excess increases myocardial metabolic demand by increasing the force of contraction as well as the heart rate, and also alters cardiac depolarization patterns. We propose that an altered spatiotemporal pattern of cardiac contraction and excessive force of contraction may lead to a redistribution of wall stresses in the left ventricle. This redistribution of wall stress causes regional mechanical overload of regions where wall tension becomes disproportionately great and renders these cardiomyocytes "metabolically insufficient". In other words, these cardiomyocytes experience a demand: supply mismatch on the basis of excessive metabolic demand. In order to prevent the death of these cardiomyocytes and to prevent excessive wall tension from developing in neighboring regions, a protective metabolic shutdown occurs in the affected cardiomyocytes. This metabolic shutdown, i.e., acute down regulation of non-vital cellular functions, serves to protect the affected regions from necrosis and explains the apparently complete recovery observed in TCM. We propose that this phenomenon may share important characteristics with phenomena such as ischemic conditioning, stunning and hibernation. In this manuscript, we discuss our hypothesis in the context of available knowledge and discuss important experiments that would help to corroborate or refute the hypothesis. Copyright © 2013 Elsevier Ltd

  19. A review of the fundamental studies of the copper activation mechanisms for selective flotation of the sulfide minerals, sphalerite and pyrite.

    Science.gov (United States)

    Chandra, A P; Gerson, A R

    2009-01-30

    A review of the considerable, but often contradictory, literature examining the specific surface reactions associated with copper adsorption onto the common metal sulfide minerals sphalerite, (Zn,Fe)S, and pyrite (FeS(2)), and the effect of the co-location of the two minerals is presented. Copper "activation", involving the surface adsorption of copper species from solution onto mineral surfaces to activate the surface for hydrophobic collector attachment, is an important step in the flotation and separation of minerals in an ore. Due to the complexity of metal sulfide mineral containing systems this activation process and the emergence of activation products on the mineral surfaces are not fully understood for most sulfide minerals even after decades of research. Factors such as copper concentration, activation time, pH, surface charge, extent of pre-oxidation, water and surface contaminants, pulp potential and galvanic interactions are important factors affecting copper activation of sphalerite and pyrite. A high pH, the correct reagent concentration and activation time and a short time delay between reagent additions is favourable for separation of sphalerite from pyrite. Sufficient oxidation potential is also needed (through O(2) conditioning) to maintain effective galvanic interactions between sphalerite and pyrite. This ensures pyrite is sufficiently depressed while sphalerite floats. Good water quality with low concentrations of contaminant ions, such as Pb(2+)and Fe(2+), is also needed to limit inadvertent activation and flotation of pyrite into zinc concentrates. Selectivity can further be increased and reagent use minimised by opting for inert grinding and by carefully choosing selective pyrite depressants such as sulfoxy or cyanide reagents. Studies that approximate plant conditions are essential for the development of better separation techniques and methodologies. Improved experimental approaches and surface sensitive techniques with high spatial

  20. Examination of 12-lipoxygenase (12-LOX) as a therapeutic target in non-small cell lung cancer (NSCLC): Mechanisms controlling survival and induction of apoptosis following selective inhibition

    LENUS (Irish Health Repository)

    Cathcart, Mary Clare

    2011-06-01

    Background: Platelet-type 12-LOX is an arachidonic acid metabolising enzyme resulting in the formation of 12(S)-HETE, which stimulates tumour cell adhesion, invasion and metastasis. This study aimed to examine the expression profile and role of this enzyme in NSCLC, and determine if it is a potential target for intervention. Methods: A panel of retrospective resected lung tumours was stained for 12-LOX expression by IHC. Levels of the 12-LOX metabolite, 12(S)-HETE, were examined i