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Sample records for recombination shaped dynamic

  1. The Dynamics of Shape

    CERN Document Server

    Gomes, Henrique

    2011-01-01

    This thesis consists of two parts, connected by one central theme: the dynamics of the "shape of space". The first part of the thesis concerns the construction of a theory of gravity dynamically equivalent to general relativity (GR) in 3+1 form (ADM). What is special about this theory is that it does not possess foliation invariance, as does ADM. It replaces that "symmetry" by another: local conformal invariance. In so doing it more accurately reflects a theory of the "shape of space", giving us reason to call it \\emph{shape dynamics} (SD). In the first part we will try to present some of the highlights of results so far, and indicate what we can and cannot do with shape dynamics. Because this is a young, rapidly moving field, we have necessarily left out some interesting new results which are not yet in print and were developed alongside the writing of the thesis. The second part of the thesis will develop a gauge theory for "shape of space"--theories. To be more precise, if one admits that the physically re...

  2. 'Shape Dynamics': Foundations Reassessed

    CERN Document Server

    Anderson, Edward

    2015-01-01

    `Shape dynamics' is meant here in the sense of a type of conformogeometrical reformulation of GR, some of which have of late been considered as generalizations of or alternatives to GR. This note concerns in particular cases based on the notion of volume-preserving conformal transformations (VPCTs), in the sense of preserving a solitary global volume of the universe degree of freedom. The extent to which various ways of modelling VPCTs make use of group theory at all, in a congruous manner, and with minimal departure from standard Lie group theory, is considered. This points to changing conception of VPCTs from the current finite integral implementation to an infinitesimal differential implementation (or to avoiding using them at all). Some useful observations from flat-space conformal groups (well-known from CFT) concerning the existence or otherwise of VPCT groups are also provided.

  3. A Shape Dynamics Tutorial

    CERN Document Server

    Mercati, Flavio

    2014-01-01

    Shape Dynamics (SD) is a new theory of gravity that is based on fewer and more fundamental first principles than General Relativity (GR). The most important feature of SD is the replacement of GR's relativity of simultaneity with a more tractable gauge symmetry, namely invariance under spatial conformal transformations. This Tutorial contains both a quick introduction for readers curious about SD and a detailed walk-through of the historical and conceptual motivations for the theory, its logical development from first principles and an in-depth description of its present status. The Tutorial is sufficiently self-contained for an undergrad student with some basic background in General Relativity and Lagrangian/Hamiltonian mechanics. It is intended both as a reference text for students approaching the subject, and as a review article for researchers interested in the theory. This is a first version of the Tutorial, which will be periodically expanded and updated with the latest results.

  4. Robust Hitting with Dynamics Shaping

    Science.gov (United States)

    Yashima, Masahito; Yamawaki, Tasuku

    The present paper proposes the trajectory planning based on “the dynamics shaping” for a redundant robotic arm to hit a target robustly toward the desired direction, of which the concept is to shape the robot dynamics appropriately by changing its posture in order to achieve the robust motion. The positional error of the end-effector caused by unknown disturbances converges onto near the singular vector corresponding to its maximum singular value of the output controllability matrix of the robotic arm. Therefore, if we can control the direction of the singular vector by applying the dynamics shaping, we will be able to control the direction of the positional error of the end-effector caused by unknown disturbances. We propose a novel trajectory planning based on the dynamics shaping and verify numerically and experimentally that the robotic arm can robustly hit the target toward the desired direction with a simple open-loop control system even though the disturbance is applied.

  5. A ring-shaped recombination chamber for hadron therapy dosimetry.

    Science.gov (United States)

    Jakubowska, E; Zielczyński, M; Golnik, N; Gryziński, M A; Krzemiński, Ł

    2014-10-01

    An innovative recombination chamber has been designed for estimation of stray radiation doses and quality factors in hadron therapy. The chamber allows for determination of absorbed dose and recombination index of radiation quality in phantoms at small distances from simulated organs. The chamber body and electrodes are ring shaped, so the beam may be directed through the empty centre of the ring. The ionisation of the filling gas is caused by secondary or scattered radiation and can be related to the dose absorbed in the tissues close to the irradiated target volume.

  6. Shape dynamics of growing cell walls

    CERN Document Server

    Banerjee, Shiladitya; Dinner, Aaron R

    2015-01-01

    We introduce a general theoretical framework to study the shape dynamics of actively growing and remodeling surfaces. Using this framework we develop a physical model for growing bacterial cell walls and study the interplay of cell shape with the dynamics of growth and constriction. The model allows us to derive constraints on cell wall mechanical energy based on the observed dynamics of cell shape. We predict that exponential growth in cell size requires a constant amount of cell wall energy to be dissipated per unit volume. We use the model to understand and contrast growth in bacteria with different shapes such as spherical, ellipsoidal, cylindrical and toroidal morphologies. Coupling growth to cell wall constriction, we predict a discontinuous shape transformation, from partial constriction to cell division, as a function of the chemical potential driving cell-wall synthesis. Our model for cell wall energy and shape dynamics relates growth kinetics with cell geometry, and provides a unified framework to d...

  7. Recombination Dynamics in Quantum Well Semiconductor Structures

    Science.gov (United States)

    Fouquet, Julie Elizabeth

    Time-resolved and time-integrated photoluminescence as a function of excitation energy density have been observed in order to study recombination dynamics in GaAs/Al(,x)Ga(,1 -x)As quantum well structures. The study of room temperature photoluminescence from the molecular beam epitaxy (MBE) -grown multiple quantum well structure and photoluminescence peak energy as a function of tem- perature shows that room temperature recombination at excitation densities above the low 10('16) cm('-3) level is due to free carriers, not excitons. This is the first study of time-resolved photoluminescence of impurities in quantum wells; data taken at different emission wave- lengths at low temperatures shows that the impurity-related states at photon energies lower than the free exciton peaks luminesce much more slowly than the free exciton states. Results from a similar structure grown by metal -organic chemical vapor deposition (MOCVD) are explained by saturation of traps. An unusual increase in decay rate observed tens of nanoseconds after excitation is probably due to carriers falling out of the trap states. Since this is the first study of time-resolved photoluminescence of MOCVD-grown quantum well structures, this unusual behavior may be realted to the MOCVD growth process. Further investigations indi- cate that the traps are not active at low temperatures; they become active at approximately 150 K. The traps are probably associated with the (hetero)interfaces rather than the bulk Al(,x)Ga(,1-x)As material. The 34 K photoluminescence spectrum of this sample revealed a peak shifted down by approximately 36 meV from the main peak. Time-resolved and time-integrated photoluminescence results here show that this peak is not a stimulated phonon emission sideband, but rather is an due to an acceptor impurity, probably carbon. Photo- luminescence for excitation above and below the barrier bandgap shows that carriers are efficiently collected in the wells in both single and multiple

  8. The role of recombination in the emergence of a complex and dynamic HIV epidemic

    Directory of Open Access Journals (Sweden)

    Morgenstern Burkhard

    2010-03-01

    Full Text Available Abstract Background Inter-subtype recombinants dominate the HIV epidemics in three geographical regions. To better understand the role of HIV recombinants in shaping the current HIV epidemic, we here present the results of a large-scale subtyping analysis of 9435 HIV-1 sequences that involve subtypes A, B, C, G, F and the epidemiologically important recombinants derived from three continents. Results The circulating recombinant form CRF02_AG, common in West Central Africa, appears to result from recombination events that occurred early in the divergence between subtypes A and G, followed by additional recent recombination events that contribute to the breakpoint pattern defining the current recombinant lineage. This finding also corrects a recent claim that G is a recombinant and a descendant of CRF02, which was suggested to be a pure subtype. The BC and BF recombinants in China and South America, respectively, are derived from recent recombination between contemporary parental lineages. Shared breakpoints in South America BF recombinants indicate that the HIV-1 epidemics in Argentina and Brazil are not independent. Therefore, the contemporary HIV-1 epidemic has recombinant lineages of both ancient and more recent origins. Conclusions Taken together, we show that these recombinant lineages, which are highly prevalent in the current HIV epidemic, are a mixture of ancient and recent recombination. The HIV pandemic is moving towards having increasing complexity and higher prevalence of recombinant forms, sometimes existing as "families" of related forms. We find that the classification of some CRF designations need to be revised as a consequence of (1 an estimated > 5% error in the original subtype assignments deposited in the Los Alamos sequence database; (2 an increasing number of CRFs are defined while they do not readily fit into groupings for molecular epidemiology and vaccine design; and (3 a dynamic HIV epidemic context.

  9. A shape dynamical approach to holographic renormalization

    Energy Technology Data Exchange (ETDEWEB)

    Gomes, Henrique [University of California at Davis, Davis, CA (United States); Gryb, Sean [Utrecht University, Institute for Theoretical Physics, Utrecht (Netherlands); Radboud University Nijmegen, Institute for Mathematics, Astrophysics and Particle Physics, Nijmegen (Netherlands); Koslowski, Tim [University of New Brunswick, Fredericton, NB (Canada); Mercati, Flavio; Smolin, Lee [Perimeter Institute for Theoretical Physics, Waterloo, ON (Canada)

    2015-01-01

    We provide a bottom-up argument to derive some known results from holographic renormalization using the classical bulk-bulk equivalence of General Relativity and Shape Dynamics, a theory with spatial conformal (Weyl) invariance. The purpose of this paper is twofold: (1) to advertise the simple classical mechanism, trading off gauge symmetries, that underlies the bulk-bulk equivalence of General Relativity and Shape Dynamics to readers interested in dualities of the type of AdS/conformal field theory (CFT); and (2) to highlight that this mechanism can be used to explain certain results of holographic renormalization, providing an alternative to the AdS/CFT conjecture for these cases. To make contact with the usual semiclassical AdS/CFT correspondence, we provide, in addition, a heuristic argument that makes it plausible that the classical equivalence between General Relativity and Shape Dynamics turns into a duality between radial evolution in gravity and the renormalization group flow of a CFT. We believe that Shape Dynamics provides a new perspective on gravity by giving conformal structure a primary role within the theory. It is hoped that this work provides the first steps toward understanding what this new perspective may be able to teach us about holographic dualities. (orig.)

  10. Dynamics and impact of homologous recombination on the evolution of Legionella pneumophila.

    Science.gov (United States)

    David, Sophia; Sánchez-Busó, Leonor; Harris, Simon R; Marttinen, Pekka; Rusniok, Christophe; Buchrieser, Carmen; Harrison, Timothy G; Parkhill, Julian

    2017-06-01

    Legionella pneumophila is an environmental bacterium and the causative agent of Legionnaires' disease. Previous genomic studies have shown that recombination accounts for a high proportion (>96%) of diversity within several major disease-associated sequence types (STs) of L. pneumophila. This suggests that recombination represents a potentially important force shaping adaptation and virulence. Despite this, little is known about the biological effects of recombination in L. pneumophila, particularly with regards to homologous recombination (whereby genes are replaced with alternative allelic variants). Using newly available population genomic data, we have disentangled events arising from homologous and non-homologous recombination in six major disease-associated STs of L. pneumophila (subsp. pneumophila), and subsequently performed a detailed characterisation of the dynamics and impact of homologous recombination. We identified genomic "hotspots" of homologous recombination that include regions containing outer membrane proteins, the lipopolysaccharide (LPS) region and Dot/Icm effectors, which provide interesting clues to the selection pressures faced by L. pneumophila. Inference of the origin of the recombined regions showed that isolates have most frequently imported DNA from isolates belonging to their own clade, but also occasionally from other major clades of the same subspecies. This supports the hypothesis that the possibility for horizontal exchange of new adaptations between major clades of the subspecies may have been a critical factor in the recent emergence of several clinically important STs from diverse genomic backgrounds. However, acquisition of recombined regions from another subspecies, L. pneumophila subsp. fraseri, was rarely observed, suggesting the existence of a recombination barrier and/or the possibility of ongoing speciation between the two subspecies. Finally, we suggest that multi-fragment recombination may occur in L. pneumophila

  11. Charge carrier recombination dynamics in perovskite and polymer solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Paulke, Andreas; Kniepert, Juliane; Kurpiers, Jona; Wolff, Christian M.; Schön, Natalie; Brenner, Thomas J. K.; Neher, Dieter [Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24–25, 14476, Potsdam (Germany); Stranks, Samuel D. [Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU (United Kingdom); Research Laboratory of Electronics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 (United States); Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE (United Kingdom); Snaith, Henry J. [Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU (United Kingdom)

    2016-03-14

    Time-delayed collection field experiments are applied to planar organometal halide perovskite (CH{sub 3}NH{sub 3}PbI{sub 3}) based solar cells to investigate charge carrier recombination in a fully working solar cell at the nanosecond to microsecond time scale. Recombination of mobile (extractable) charges is shown to follow second-order recombination dynamics for all fluences and time scales tested. Most importantly, the bimolecular recombination coefficient is found to be time-dependent, with an initial value of ca. 10{sup −9} cm{sup 3}/s and a progressive reduction within the first tens of nanoseconds. Comparison to the prototypical organic bulk heterojunction device PTB7:PC{sub 71}BM yields important differences with regard to the mechanism and time scale of free carrier recombination.

  12. Lozenge Tilings, Glauber Dynamics and Macroscopic Shape

    Science.gov (United States)

    Laslier, Benoît; Toninelli, Fabio Lucio

    2015-09-01

    We study the Glauber dynamics on the set of tilings of a finite domain of the plane with lozenges of side 1/ L. Under the invariant measure of the process (the uniform measure over all tilings), it is well known (Cohn et al. J Am Math Soc 14:297-346, 2001) that the random height function associated to the tiling converges in probability, in the scaling limit , to a non-trivial macroscopic shape minimizing a certain surface tension functional. According to the boundary conditions, the macroscopic shape can be either analytic or contain "frozen regions" (Arctic Circle phenomenon Cohn et al. N Y J Math 4:137-165, 1998; Jockusch et al. Random domino tilings and the arctic circle theorem, arXiv:math/9801068, 1998). It is widely conjectured, on the basis of theoretical considerations (Henley J Statist Phys 89:483-507, 1997; Spohn J Stat Phys 71:1081-1132, 1993), partial mathematical results (Caputo et al. Commun Math Phys 311:157-189, 2012; Wilson Ann Appl Probab 14:274-325, 2004) and numerical simulations for similar models (Destainville Phys Rev Lett 88:030601, 2002; cf. also the bibliography in Henley (J Statist Phys 89:483-507, 1997) and Wilson (Ann Appl Probab 14:274-325, 2004), that the Glauber dynamics approaches the equilibrium macroscopic shape in a time of order L 2+ o(1). In this work we prove this conjecture, under the assumption that the macroscopic equilibrium shape contains no "frozen region".

  13. Dynamics of carrier recombination in a semiconductor laser structure

    Energy Technology Data Exchange (ETDEWEB)

    Dzhioev, R. I., E-mail: dzhioev@orient.ioffe.ru; Kavokin, K. V.; Kusrayev, Yu. G.; Poletaev, N. K. [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation)

    2015-11-15

    Carrier-recombination dynamics is studied by the method of optical orientation at room temperature in the active layer of a laser diode structure. The dependence of the degree of electron-spin orientation on the excitation density is attributed to saturation of the nonradiative-recombination channel. The time of electron capture at recombination centers is determined to be τ{sub e} = 5 × 10{sup –9} s. The temperature of nonequilibrium electrons heated by a He–Ne laser is estimated.

  14. Manipulating or superseding host recombination functions: a dilemma that shapes phage evolvability.

    Science.gov (United States)

    Bobay, Louis-Marie; Touchon, Marie; Rocha, Eduardo P C

    2013-01-01

    Phages, like many parasites, tend to have small genomes and may encode autonomous functions or manipulate those of their hosts'. Recombination functions are essential for phage replication and diversification. They are also nearly ubiquitous in bacteria. The E. coli genome encodes many copies of an octamer (Chi) motif that upon recognition by RecBCD favors repair of double strand breaks by homologous recombination. This might allow self from non-self discrimination because RecBCD degrades DNA lacking Chi. Bacteriophage Lambda, an E. coli parasite, lacks Chi motifs, but escapes degradation by inhibiting RecBCD and encoding its own autonomous recombination machinery. We found that only half of 275 lambdoid genomes encode recombinases, the remaining relying on the host's machinery. Unexpectedly, we found that some lambdoid phages contain extremely high numbers of Chi motifs concentrated between the phage origin of replication and the packaging site. This suggests a tight association between replication, packaging and RecBCD-mediated recombination in these phages. Indeed, phages lacking recombinases strongly over-represent Chi motifs. Conversely, phages encoding recombinases and inhibiting host recombination machinery select for the absence of Chi motifs. Host and phage recombinases use different mechanisms and the latter are more tolerant to sequence divergence. Accordingly, we show that phages encoding their own recombination machinery have more mosaic genomes resulting from recent recombination events and have more diverse gene repertoires, i.e. larger pan genomes. We discuss the costs and benefits of superseding or manipulating host recombination functions and how this decision shapes phage genome structure and evolvability.

  15. Manipulating or superseding host recombination functions: a dilemma that shapes phage evolvability.

    Directory of Open Access Journals (Sweden)

    Louis-Marie Bobay

    Full Text Available Phages, like many parasites, tend to have small genomes and may encode autonomous functions or manipulate those of their hosts'. Recombination functions are essential for phage replication and diversification. They are also nearly ubiquitous in bacteria. The E. coli genome encodes many copies of an octamer (Chi motif that upon recognition by RecBCD favors repair of double strand breaks by homologous recombination. This might allow self from non-self discrimination because RecBCD degrades DNA lacking Chi. Bacteriophage Lambda, an E. coli parasite, lacks Chi motifs, but escapes degradation by inhibiting RecBCD and encoding its own autonomous recombination machinery. We found that only half of 275 lambdoid genomes encode recombinases, the remaining relying on the host's machinery. Unexpectedly, we found that some lambdoid phages contain extremely high numbers of Chi motifs concentrated between the phage origin of replication and the packaging site. This suggests a tight association between replication, packaging and RecBCD-mediated recombination in these phages. Indeed, phages lacking recombinases strongly over-represent Chi motifs. Conversely, phages encoding recombinases and inhibiting host recombination machinery select for the absence of Chi motifs. Host and phage recombinases use different mechanisms and the latter are more tolerant to sequence divergence. Accordingly, we show that phages encoding their own recombination machinery have more mosaic genomes resulting from recent recombination events and have more diverse gene repertoires, i.e. larger pan genomes. We discuss the costs and benefits of superseding or manipulating host recombination functions and how this decision shapes phage genome structure and evolvability.

  16. Encoded Dynamical Recoupling with Shaped Pulses

    Science.gov (United States)

    Li, Yunfan; Lidar, Daniel A.; Pryadko, Leonid P.

    2008-03-01

    Encoded Dynamical Recoupling is a passive error correction techique which can be used to enhance the performance of a quantum error correction code (QECC) against low-frequency component of the thermal bath. The elements of the stabilizer group are used in the decoupling cycle which makes the encoded logic operations fault-tolerant. We studied the effectiveness of this techique both analytically and numerically for several three- and five-qubit codes, with decoupling sequences utilizing either Gaussian or self-refocusing pulse shapes. When logic pulses are intercalated between the decoupling cycles, the technique may be very effective in cancelling constant perturbation terms, but its performance is much weaker against a time-dependent perturbation simulated as a classical correlated noise. The decoupling accuracy can be substantially improved if logic is applied slowly and concurrently with the decoupling, so that a certain adiabaticity condition is satisfied.

  17. Shape recovery using high dynamic range images

    Institute of Scientific and Technical Information of China (English)

    Zheng Zuoyong; Ma Lizhuang; Li Zhong

    2008-01-01

    An effective method for object shape recovery using HDRIs (high dynamic range images) is proposed. The radiance values of each point on the reference sphere and target object are firstly calculated, thus the set of candidate normals of each target point are found by comparing its radiance to that of each reference sphere point. In single-image shape recovery, a smoothness operation is applied to the target normals to obtain a stable and reasonable result; while in photometric stereo, radiance vectors of reference and target objects formed due to illuminations under different light source directions are directly compared to get the most suitable target normals. Finally, the height values can be recovered from the resulting normal field. Because diffuse and specular reflection are handled in an unified framework with radiance, our approach eliminates the limitation presented in most recovery strategies, i.e., only Lambertian model can be used. The experiment results from the real and synthesized images show the performance of our approach.

  18. Proton to pion ratio at RHIC from dynamical quark recombination

    CERN Document Server

    Ayala, Alejandro; Paic, Guy; Toledo-Sanchez, Genaro

    2008-01-01

    We propose an scenario to study, from a dynamical point of view, the thermal recombination of quarks in the midsts of a relativistic heavy-ion collision. We coin the term dynamical quark recombination to refer to the process of quark-antiquark and three-quark clustering, to form mesons and baryons, respectively, as a function of energy density. Using the string-flip model we show that the probabilities to form such clusters differ. We apply these ideas to the calculation of the proton and pion spectra in a Bjorken-like scenario that incorporates the evolution of these probabilities with proper time and compute the proton to pion ratio, comparing to recent RHIC data at the highest energy. We show that for a standard choice of parameters, this ratio reaches one, though the maximum is very sensitive to the initial evolution proper time.

  19. Dynamic composition, shaping and organization of plastid nucleoids

    Directory of Open Access Journals (Sweden)

    Marta ePowikrowska

    2014-09-01

    Full Text Available In this article recent progress on the elucidation of the dynamic composition and structure of plastid nucleoids is reviewed from a structural perspective. Plastid nucleoids are compact structures of multiple copies of different forms of ptDNA, RNA, enzymes for replication and gene expression as well as DNA binding proteins. Although early electron microscopy suggested that plastid DNA is almost free of proteins, it is now well established that the DNA in nucleoids similarly as in the nuclear chromatin is associated with basic proteins playing key roles in organization of the DNA architecture and in regulation of DNA associated enzymatic activities involved in transcription, replication, and recombination. This group of DNA binding proteins has been named plastid nucleoid associated proteins (ptNAPs. Plastid nucleoids are unique with respect to their variable number, genome copy content and dynamic distribution within different types of plastids. The mechanisms underlying the shaping and reorganization of plastid nucleoids during chloroplast development and in response to environmental conditions involve posttranslational modifications of ptNAPs, similarly to those changes known for histones in the eukaryotic chromatin, as well as changes in the repertoire of ptNAPs, as known for nucleoids of bacteria. Attachment of plastid nucleoids to membranes is proposed to be important not only for regulation of DNA availability for replication and transcription, but also for the coordination of photosynthesis and plastid gene expression.

  20. Gravitational collapse of thin shells of dust in Shape Dynamics

    CERN Document Server

    Gomes, Henrique; Mercati, Flavio; Napoletano, Andrea

    2015-01-01

    Shape dynamics is a theory of gravity whose physical configuration space is composed of spatial conformal equivalence classes of 3-dimensional geometries. This physical configuration space is not a priori related to the one given by 4-dimensional space-time geometries, familiar to general relativists. Although one can largely match dynamical solutions arising in each theory, this is not always the case. One expects such differences in collapse situations that lead to the formation of black holes. In this paper we study spherical collapse of thin-shells of pressureless dust as a fully back-reacting dynamical system, in a context related to both shape dynamics and general relativity in ADM form in Constant Mean Curvature (CMC) gauge -- the particular time slicing where any correspondence between ADM and shape dynamics is manifest. To better accommodate the relational setting of shape dynamics, we also begin a study of collapse of two such shells in a compact Universe.

  1. Self-gravitating fluid solutions of Shape Dynamics

    CERN Document Server

    Guariento, Daniel C

    2016-01-01

    Shape Dynamics is a 3D conformally invariant theory of gravity which possesses a large set of solutions in common with General Relativity. When looked closely, these solutions are found to behave in surprising ways, so in order to probe the fitness of Shape Dynamics as a viable alternative to General Relativity one must find and understand increasingly more complex, less symmetrical exact solutions, on which to base perturbative studies and numerical analyses in order to compare them with data. Spherically symmetric exact solutions have been studied, but only in a static vacuum setup. In this work we construct a class of time-dependent exact solutions of Shape Dynamics from first principles, representing a central inhomogeneity in an evolving cosmological environment. By assuming only a perfect fluid source in a spherically symmetric geometry we show that this fully dynamic non-vacuum solution satisfies in all generality the Hamiltonian structure of Shape Dynamics. The simplest choice of solutions is shown to...

  2. Particle Filtering With Dynamic Shape Priors

    Science.gov (United States)

    2006-01-01

    continuous curves have been proposed, perhaps most prominently the B-spline representation used for a “snake model” as in [2]. Isard and Blake (see...shapes of the object being tracked so that LLE can be used. References 1. Blake, A., Isard , M., eds.: Active Contours. Springer (1998) 2. Terzopoulos, D

  3. Optical 3D shape measurement for dynamic process

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    3D shape dynamic measurement is essential to the study of machine vision, hydromechanics, high-speed rotation, deformation of material, stress analysis, deformation in impact, explosion process and biomedicine. in recent years. In this paper,the results of our research, including the theoretical analysis, some feasible methods and relevant verifying experiment results, are compendiously reported. At present, these results have been used in our assembling instruments for 3D shape measurement of dynamic process.

  4. Influence of nanoparticle shape on charge transport and recombination in polymer/nanocrystal solar cells.

    Science.gov (United States)

    Li, Zhe; Wang, Weiyuan; Greenham, Neil C; McNeill, Christopher R

    2014-12-21

    A key consideration for the efficient operation of hybrid solar cells based upon conjugated polymers and inorganic semiconductor nanocrystals is charge transport in the nanocrystal phase. Here we report the results of a study into the charge transport kinetics of polymer/nanocrystal solar cells based on blends poly(3-hexylthiophene) (P3HT) with either CdSe nano-dots or CdSe nano-tetrapods. Transient photocurrent measurements reveal significant differences in the charge transport kinetics of nano-dot and nano-tetrapod hybrid cells, with the charge collection of the P3HT/CdSe nano-dot device severely limited by charge trapping. In comparison the nano-tetrapod cell exhibits significantly reduced charge trapping compared to the nano-dot cell accounting for the improved fill-factor and overall device efficiency. Transient photovoltage measurements have also been employed that demonstrate slower recombination rates in the P3HT/CdSe tetrapod device compared to the P3HT/CdSe dot device. These observations directly identify nanoparticle shape as a critical factor influencing the charge transport and hence recombination in this benchmark hybrid system, confirming the hypothesis that the use of tetrapods improves device performance through an improvement in electron transport in the nanocrystal phase.

  5. Actin dynamics shape microglia effector functions.

    Science.gov (United States)

    Uhlemann, Ria; Gertz, Karen; Boehmerle, Wolfgang; Schwarz, Tobias; Nolte, Christiane; Freyer, Dorette; Kettenmann, Helmut; Endres, Matthias; Kronenberg, Golo

    2016-06-01

    Impaired actin filament dynamics have been associated with cellular senescence. Microglia, the resident immune cells of the brain, are emerging as a central pathophysiological player in neurodegeneration. Microglia activation, which ranges on a continuum between classical and alternative, may be of critical importance to brain disease. Using genetic and pharmacological manipulations, we studied the effects of alterations in actin dynamics on microglia effector functions. Disruption of actin dynamics did not affect transcription of genes involved in the LPS-triggered classical inflammatory response. By contrast, in consequence of impaired nuclear translocation of phospho-STAT6, genes involved in IL-4 induced alternative activation were strongly downregulated. Functionally, impaired actin dynamics resulted in reduced NO secretion and reduced release of TNFalpha and IL-6 from LPS-stimulated microglia and of IGF-1 from IL-4 stimulated microglia. However, pathological stabilization of the actin cytoskeleton increased LPS-induced release of IL-1beta and IL-18, which belong to an unconventional secretory pathway. Reduced NO release was associated with decreased cytoplasmic iNOS protein expression and decreased intracellular arginine uptake. Furthermore, disruption of actin dynamics resulted in reduced microglia migration, proliferation and phagocytosis. Finally, baseline and ATP-induced [Ca(2+)]int levels were significantly increased in microglia lacking gelsolin, a key actin-severing protein. Together, the dynamic state of the actin cytoskeleton profoundly and distinctly affects microglia behaviours. Disruption of actin dynamics attenuates M2 polarization by inhibiting transcription of alternative activation genes. In classical activation, the role of actin remodelling is complex, does not relate to gene transcription and shows a major divergence between cytokines following conventional and unconventional secretion.

  6. Nasal bone shape is under complex epistatic genetic control in mouse interspecific recombinant congenic strains.

    Directory of Open Access Journals (Sweden)

    Gaétan Burgio

    Full Text Available BACKGROUND: Genetic determinism of cranial morphology in the mouse is still largely unknown, despite the localization of putative QTLs and the identification of genes associated with Mendelian skull malformations. To approach the dissection of this multigenic control, we have used a set of interspecific recombinant congenic strains (IRCS produced between C57BL/6 and mice of the distant species Mus spretus (SEG/Pas. Each strain has inherited 1.3% of its genome from SEG/Pas under the form of few, small-sized, chromosomal segments. RESULTS: The shape of the nasal bone was studied using outline analysis combined with Fourier descriptors, and differential features were identified between IRCS BcG-66H and C57BL/6. An F2 cross between BcG-66H and C57BL/6 revealed that, out of the three SEG/Pas-derived chromosomal regions present in BcG-66H, two were involved. Segments on chromosomes 1 (∼32 Mb and 18 (∼13 Mb showed additive effect on nasal bone shape. The three chromosomal regions present in BcG-66H were isolated in congenic strains to study their individual effect. Epistatic interactions were assessed in bicongenic strains. CONCLUSIONS: Our results show that, besides a strong individual effect, the QTL on chromosome 1 interacts with genes on chromosomes 13 and 18. This study demonstrates that nasal bone shape is under complex genetic control but can be efficiently dissected in the mouse using appropriate genetic tools and shape descriptors.

  7. IMF shape constraints from stellar populations and dynamics from CALIFA

    CERN Document Server

    Lyubenova, M; van de Ven, G; Falcón-Barroso, J; Galbany, L; Gallazzi, A; García-Benito, R; Delgado, R González; Husemann, B; La Barbera, F; Marino, R A; Mast, D; Mendez-Abreu, J; Peletier, R F P; Sánchez-Blázquez, P; Sánchez, S F; Trager, S C; Bosch, R C E van den; Vazdekis, A; Walcher, C J; Zhu, L; Zibetti, S; Ziegler, B; Bland-Hawthorn, J

    2016-01-01

    In this letter we describe how we use stellar dynamics information to constrain the shape of the stellar IMF in a sample of 27 early-type galaxies from the CALIFA survey. We obtain dynamical and stellar mass-to-light ratios, $\\Upsilon_\\mathrm{dyn}$ and $\\Upsilon_{\\ast}$, over a homogenous aperture of 0.5~$R_{e}$. We use the constraint $\\Upsilon_\\mathrm{dyn} \\ge \\Upsilon_{\\ast}$ to test two IMF shapes within the framework of the extended MILES stellar population models. We rule out a single power law IMF shape for 75% of the galaxies in our sample. Conversely, we find that a double power law IMF shape with a varying high-mass end slope is compatible (within 1$\\sigma$) with 95% of the galaxies. We also show that dynamical and stellar IMF mismatch factors give consistent results for the systematic variation of the IMF in these galaxies.

  8. Dynamics of Shape Fluctuations of Quasi-spherical Vesicles Revisited

    DEFF Research Database (Denmark)

    Miao, L.; Lomholt, Michael Andersen; Kleis, J.

    2002-01-01

    In this paper, the dynamics of spontaneous shape fluctuations of a single, giant quasi-spherical vesicle formed from a single lipid species is revisited theoretically. A coherent physical theory for the dynamics is developed based on a number of fundamental principles and considerations, and a sy...

  9. Cell shape dynamics: from waves to migration.

    Directory of Open Access Journals (Sweden)

    Meghan K Driscoll

    Full Text Available We observe and quantify wave-like characteristics of amoeboid migration. Using the amoeba Dictyostelium discoideum, a model system for the study of chemotaxis, we demonstrate that cell shape changes in a wave-like manner. Cells have regions of high boundary curvature that propagate from the leading edge toward the back, usually along alternating sides of the cell. Curvature waves are easily seen in cells that do not adhere to a surface, such as cells that are electrostatically repelled from surfaces or cells that extend over the edge of micro-fabricated cliffs. Without surface contact, curvature waves travel from the leading edge to the back of a cell at -35 µm/min. Non-adherent myosin II null cells do not exhibit these curvature waves. At the leading edge of adherent cells, curvature waves are associated with protrusive activity. Like regions of high curvature, protrusive activity travels along the boundary in a wave-like manner. Upon contact with a surface, the protrusions stop moving relative to the surface, and the boundary shape thus reflects the history of protrusive motion. The wave-like character of protrusions provides a plausible mechanism for the zig-zagging of pseudopods and for the ability of cells both to swim in viscous fluids and to navigate complex three dimensional topography.

  10. Modeling self-occlusions in dynamic shape and appearance tracking

    KAUST Repository

    Yang, Yanchao

    2013-12-01

    We present a method to track the precise shape of a dynamic object in video. Joint dynamic shape and appearance models, in which a template of the object is propagated to match the object shape and radiance in the next frame, are advantageous over methods employing global image statistics in cases of complex object radiance and cluttered background. In cases of complex 3D object motion and relative viewpoint change, self-occlusions and disocclusions of the object are prominent, and current methods employing joint shape and appearance models are unable to accurately adapt to new shape and appearance information, leading to inaccurate shape detection. In this work, we model self-occlusions and dis-occlusions in a joint shape and appearance tracking framework. Experiments on video exhibiting occlusion/dis-occlusion, complex radiance and background show that occlusion/dis-occlusion modeling leads to superior shape accuracy compared to recent methods employing joint shape/appearance models or employing global statistics. © 2013 IEEE.

  11. NEW METHOD FOR SHAPE RECOGNITION BASED ON DYNAMIC PROGRAMMING

    Directory of Open Access Journals (Sweden)

    NOREDINNE GHERABI

    2011-02-01

    Full Text Available In this paper we present a new method for shape recognition based on dynamic programming. First, each contour of shape is represented by a set of points. After alignment and matching between two shapes, the outline of the shape is divided into parts according to N angular and M radial sectors , Each Sector contains a portion of the contour; thisportion is divided at the inflexion points into convex and concave sections, and the information about sections are extracted in order to provide a semantic content to the outline shape, then this information are coded and transformed into a string of symbols. Finally we find the best alignment of two complete strings and compute the optimal cost of similarity. The algorithm has been tested on a large set of shape databases and real images (MPEG-7, natural silhouette database.

  12. Cluster dynamics largely shapes protoplanetary disc sizes

    CERN Document Server

    Vincke, Kirsten

    2016-01-01

    It is still on open question to what degree the cluster environment influences the sizes of protoplanetary discs surrounding young stars. Particularly so for the short-lived clusters typical for the solar neighbourhood in which the stellar density and therefore the influence of the cluster environment changes considerably over the first 10 Myr. In previous studies often the effect of the gas on the cluster dynamics has been neglected, this is remedied here. Using the code NBody6++ we study the stellar dynamics in different developmental phases - embedded, expulsion, expansion - including the gas and quantify the effect of fly-bys on the disc size. We concentrate on massive clusters ($M_{\\text{cl}} \\geq 10^3 - 6 \\cdot 10^4 M_{\\text{Sun}}$), which are representative for clusters like the Orion Nebula Cluster (ONC) or NGC 6611. We find that not only the stellar density but also the duration of the embedded phase matters. The densest clusters react fastest to the gas expulsion and drop quickly in density, here 98...

  13. Dynamic 3-D visualization of vocal tract shaping during speech.

    Science.gov (United States)

    Zhu, Yinghua; Kim, Yoon-Chul; Proctor, Michael I; Narayanan, Shrikanth S; Nayak, Krishna S

    2013-05-01

    Noninvasive imaging is widely used in speech research as a means to investigate the shaping and dynamics of the vocal tract during speech production. 3-D dynamic MRI would be a major advance, as it would provide 3-D dynamic visualization of the entire vocal tract. We present a novel method for the creation of 3-D dynamic movies of vocal tract shaping based on the acquisition of 2-D dynamic data from parallel slices and temporal alignment of the image sequences using audio information. Multiple sagittal 2-D real-time movies with synchronized audio recordings are acquired for English vowel-consonant-vowel stimuli /ala/, /a.ιa/, /asa/, and /a∫a/. Audio data are aligned using mel-frequency cepstral coefficients (MFCC) extracted from windowed intervals of the speech signal. Sagittal image sequences acquired from all slices are then aligned using dynamic time warping (DTW). The aligned image sequences enable dynamic 3-D visualization by creating synthesized movies of the moving airway in the coronal planes, visualizing desired tissue surfaces and tube-shaped vocal tract airway after manual segmentation of targeted articulators and smoothing. The resulting volumes allow for dynamic 3-D visualization of salient aspects of lingual articulation, including the formation of tongue grooves and sublingual cavities, with a temporal resolution of 78 ms.

  14. Modeling Self-Occlusions/Disocclusions in Dynamic Shape and Appearance Tracking for Obtaining Precise Shape

    KAUST Repository

    Yang, Yanchao

    2013-05-01

    We present a method to determine the precise shape of a dynamic object from video. This problem is fundamental to computer vision, and has a number of applications, for example, 3D video/cinema post-production, activity recognition and augmented reality. Current tracking algorithms that determine precise shape can be roughly divided into two categories: 1) Global statistics partitioning methods, where the shape of the object is determined by discriminating global image statistics, and 2) Joint shape and appearance matching methods, where a template of the object from the previous frame is matched to the next image. The former is limited in cases of complex object appearance and cluttered background, where global statistics cannot distinguish between the object and background. The latter is able to cope with complex appearance and a cluttered background, but is limited in cases of camera viewpoint change and object articulation, which induce self-occlusions and self-disocclusions of the object of interest. The purpose of this thesis is to model self-occlusion/disocclusion phenomena in a joint shape and appearance tracking framework. We derive a non-linear dynamic model of the object shape and appearance taking into account occlusion phenomena, which is then used to infer self-occlusions/disocclusions, shape and appearance of the object in a variational optimization framework. To ensure robustness to other unmodeled phenomena that are present in real-video sequences, the Kalman filter is used for appearance updating. Experiments show that our method, which incorporates the modeling of self-occlusion/disocclusion, increases the accuracy of shape estimation in situations of viewpoint change and articulation, and out-performs current state-of-the-art methods for shape tracking.

  15. Experimental analyses of dynamical systems involving shape memory alloys

    DEFF Research Database (Denmark)

    Enemark, Søren; Savi, Marcelo A.; Santos, Ilmar F.

    2015-01-01

    The use of shape memory alloys (SMAs) in dynamical systems has an increasing importance in engineering especially due to their capacity to provide vibration reductions. In this regard, experimental tests are essential in order to show all potentialities of this kind of systems. In this work, SMA...... springs are incorporated in a dynamical system that consists of a one degree of freedom oscillator connected to a linear spring and a mass, which is also connected to the SMA spring. Two types of springs are investigated defming two distinct systems: a pseudoelastic and a shape memory system......-tension of the springs. This article shows several experimental tests that allow one to obtain a general comprehension of the dynamical behaviour of SMA systems. Results show the general thermo-mechanical behaviour of SMA dynamical systems and the obtained conclusions can be applied in distinct situations as in rotor...

  16. Dynamic protein assemblies in homologous recombination with single DNA molecules

    NARCIS (Netherlands)

    van der Heijden, A.H.

    2007-01-01

    What happens when your DNA breaks? This thesis describes experimental work on the single-molecule level focusing on the interaction between DNA and DNA-repair proteins, in particular bacterial RecA and human Rad51, involved in homologous recombination. Homologous recombination and its central event

  17. Dynamical Jumps in a Shape Memory Alloy Oscillator

    Directory of Open Access Journals (Sweden)

    H. S. Oliveira

    2014-01-01

    Full Text Available The dynamical response of systems with shape memory alloy (SMA elements presents a rich behavior due to their intrinsic nonlinear characteristic. SMA’s nonlinear response is associated with both adaptive dissipation related to hysteretic behavior and huge changes in properties caused by phase transformations. These characteristics are attracting much technological interest in several scientific and engineering fields, varying from medical to aerospace applications. An important characteristic associated with dynamical response of SMA system is the jump phenomenon. Dynamical jumps result in abrupt changes in system behavior and its analysis is essential for a proper design of SMA systems. This paper discusses the nonlinear dynamics of a one degree of freedom SMA oscillator presenting pseudoelastic behavior and dynamical jumps. Numerical simulations show different aspects of this kind of behavior, illustrating its importance for a proper understanding of nonlinear dynamics of SMA systems.

  18. Intergenerational continuity of cell shape dynamics in Caulobacter crescentus

    Science.gov (United States)

    Wright, Charles S.; Banerjee, Shiladitya; Iyer-Biswas, Srividya; Crosson, Sean; Dinner, Aaron R.; Scherer, Norbert F.

    2015-03-01

    We investigate the intergenerational shape dynamics of single Caulobacter crescentus cells using a novel combination of imaging techniques and theoretical modeling. We determine the dynamics of cell pole-to-pole lengths, cross-sectional widths, and medial curvatures from high accuracy measurements of cell contours. Moreover, these shape parameters are determined for over 250 cells across approximately 10000 total generations, which affords high statistical precision. Our data and model show that constriction is initiated early in the cell cycle and that its dynamics are controlled by the time scale of exponential longitudinal growth. Based on our extensive and detailed growth and contour data, we develop a minimal mechanical model that quantitatively accounts for the cell shape dynamics and suggests that the asymmetric location of the division plane reflects the distinct mechanical properties of the stalked and swarmer poles. Furthermore, we find that the asymmetry in the division plane location is inherited from the previous generation. We interpret these results in terms of the current molecular understanding of shape, growth, and division of C. crescentus.

  19. First Principles Modelling of Shape Memory Alloys Molecular Dynamics Simulations

    CERN Document Server

    Kastner, Oliver

    2012-01-01

    Materials sciences relate the macroscopic properties of materials to their microscopic structure and postulate the need for holistic multiscale research. The investigation of shape memory alloys is a prime example in this regard. This particular class of materials exhibits strong coupling of temperature, strain and stress, determined by solid state phase transformations of their metallic lattices. The present book presents a collection of simulation studies of this behaviour. Employing conceptually simple but comprehensive models, the fundamental material properties of shape memory alloys are qualitatively explained from first principles. Using contemporary methods of molecular dynamics simulation experiments, it is shown how microscale dynamics may produce characteristic macroscopic material properties. The work is rooted in the materials sciences of shape memory alloys and  covers  thermodynamical, micro-mechanical  and crystallographical aspects. It addresses scientists in these research fields and thei...

  20. Shaping the learning curve: epigenetic dynamics in neural plasticity

    Directory of Open Access Journals (Sweden)

    Zohar Ziv Bronfman

    2014-07-01

    Full Text Available A key characteristic of learning and neural plasticity is state-dependent acquisition dynamics reflected by the non-linear learning curve that links increase in learning with practice. Here we propose that the manner by which epigenetic states of individual cells change during learning contributes to the shape of the neural and behavioral learning curve. We base our suggestion on recent studies showing that epigenetic mechanisms such as DNA methylation, histone acetylation and RNA-mediated gene regulation are intimately involved in the establishment and maintenance of long-term neural plasticity, reflecting specific learning-histories and influencing future learning. Our model, which is the first to suggest a dynamic molecular account of the shape of the learning curve, leads to several testable predictions regarding the link between epigenetic dynamics at the promoter, gene-network and neural-network levels. This perspective opens up new avenues for therapeutic interventions in neurological pathologies.

  1. Spatial shaping with dynamic priority VDQ in RPR

    Science.gov (United States)

    Yu, Xin; Huang, Benxiong; Tu, Lai; Zhang, Jian

    2004-04-01

    Resilient Packet Ring is a new technology being standardized by IEEE 802.17 working group. This paper describes the ways to accomplish uniform traffic handling and spatial traffic handling by comparison. Since uniform shaping cannot avoid head of line blocking or decrease the jitter of bandwidth utilization on multiple chock point ringlet, this paper proposes a solution for shaping of spatial traffic handling. Virtual destination queues are introduced to the shaper to avoid HOL, and a special kind of dynamic priority is added to the scheduler to optimize bandwidth utilization. A simulation model is set up to exam the performance of VDQ aware shaper, which is the first phase to accomplish spatial shaping.

  2. Dynamic Characteristics of Electrostatically Actuated Shape Optimized Variable Geometry Microbeam

    Directory of Open Access Journals (Sweden)

    Sha Zhang

    2015-01-01

    Full Text Available We mainly analyze the dynamic characteristics of electrostatically actuated shape optimized variable geometry microbeam. A nonlinear dynamic model considering midplane stretching, electrostatic force, and electrical field fringing effects is developed. Firstly, we study the static responses of the optimized microbeams under DC polarization voltage. The generalized differential quadrature method (GDQM is used. Secondly, the dynamic responses of the shape optimized microbeams driven by DC and AC voltages are investigated using GDQM in conjunction with Levenberg-Marquardt optimization method. The results show that the more gradual change in width, the larger the resonant frequency and the maximum amplitude at resonance. Then we further discuss in detail how do the maximum width, midsection width, and curvature of the width function affect the frequency response of the microbeams. We find that the amplitude and resonant frequency of the dynamic response are not monotonically increasing as the curvature of the width function increases and there exists a critical curvature. This analysis will be helpful in the optimal design of MEMS actuators. Finally, for more consideration, different residual stress, squeeze-film damping, and fringing effect models are introduced into the governing equation of motion and we compare the corresponding dynamic response.

  3. Dynamic Simulation for Hysteresis in Shape Memory Alloy under Tension

    Institute of Scientific and Technical Information of China (English)

    WANG Ping; ZHAO Jian-Bo; TANG Shao-Qiang

    2008-01-01

    We demonstrate that the Suliciu model is capable to model the hysteresis phenomenon observed experimentally in NiTi shape memory alloy micro-tubes.This model allows a class of stationary phase interfaces.By a series of fully dynamic numerical simulations that mimic quasi-static loading and unloading,the nominal stress-strain curve exhibits a big hysteresis loop,which quantitatively agrees with the experimental results.

  4. Microscopic and Macroscopic Dynamic Interface Shapes and the Interpretation of Dynamic Contact Angles.

    Science.gov (United States)

    Ramé; Garoff

    1996-01-15

    We have studied shapes of dynamic fluid interfaces at distances contact line at capillary numbers (Ca) ranging from 10(-3) to 10(-1). Near the moving contact line where viscous deformation is important, an analysis valid to O(1) in Ca describes the shape of the fluid interface. Static capillarity should describe the interface shape far from the contact line. We have quantitatively determined the extent of the regions described by the analysis with viscous deformation and by a static shape as a function of Ca. We observe a third portion of the interface between the two regions cited above, which is not described by either the analysis with viscous deformation or a static shape. In this third region the interface shape is controlled by viscous and gravitational forces of comparable magnitude. We detect significant viscous deformation even far from the contact line at Ca approximately > 0.01. Our measured dynamic contact angle parameter extracted by fitting the analysis with viscous deformation to the shape near the moving contact line coincides with the contact angle of the static-like shape far from the contact line. We measure and explain the discrepancy between this dynamic contact angle parameter and the apparent contact angles based on meniscus or apex heights. Our observations of viscous effects at large distances from the contact line have implications for dynamic contact angle measurements in capillary tubes.

  5. Manipulating or Superseding Host Recombination Functions: A Dilemma That Shapes Phage Evolvability

    OpenAIRE

    2013-01-01

    Phages, like many parasites, tend to have small genomes and may encode autonomous functions or manipulate those of their hosts'. Recombination functions are essential for phage replication and diversification. They are also nearly ubiquitous in bacteria. The E. coli genome encodes many copies of an octamer (Chi) motif that upon recognition by RecBCD favors repair of double strand breaks by homologous recombination. This might allow self from non-self discrimination because RecBCD degrades DNA...

  6. Extreme recombination frequencies shape genome variation and evolution in the honeybee, Apis mellifera.

    Directory of Open Access Journals (Sweden)

    Andreas Wallberg

    2015-04-01

    Full Text Available Meiotic recombination is a fundamental cellular process, with important consequences for evolution and genome integrity. However, we know little about how recombination rates vary across the genomes of most species and the molecular and evolutionary determinants of this variation. The honeybee, Apis mellifera, has extremely high rates of meiotic recombination, although the evolutionary causes and consequences of this are unclear. Here we use patterns of linkage disequilibrium in whole genome resequencing data from 30 diploid honeybees to construct a fine-scale map of rates of crossing over in the genome. We find that, in contrast to vertebrate genomes, the recombination landscape is not strongly punctate. Crossover rates strongly correlate with levels of genetic variation, but not divergence, which indicates a pervasive impact of selection on the genome. Germ-line methylated genes have reduced crossover rate, which could indicate a role of methylation in suppressing recombination. Controlling for the effects of methylation, we do not infer a strong association between gene expression patterns and recombination. The site frequency spectrum is strongly skewed from neutral expectations in honeybees: rare variants are dominated by AT-biased mutations, whereas GC-biased mutations are found at higher frequencies, indicative of a major influence of GC-biased gene conversion (gBGC, which we infer to generate an allele fixation bias 5 - 50 times the genomic average estimated in humans. We uncover further evidence that this repair bias specifically affects transitions and favours fixation of CpG sites. Recombination, via gBGC, therefore appears to have profound consequences on genome evolution in honeybees and interferes with the process of natural selection. These findings have important implications for our understanding of the forces driving molecular evolution.

  7. Dynamic conductance in L-shaped graphene nanosystems

    Energy Technology Data Exchange (ETDEWEB)

    Ye, En-Jia, E-mail: yeenjia@jiangnan.edu.cn; Nie, Yanguang; Shi, Haifeng; Zhang, Chengliang [School of Science, Jiangnan University, Wuxi 214122 (China); Zhao, Xuean [Department of Physics, Zhejiang Institute of Modern Physics, Zhejiang University, Hangzhou 310027 (China)

    2015-01-07

    Dynamic conductance of nanocircuit, which demonstrates dc and ac transport properties, is regarded as vital indicator for device feature. With the help of nonequilibrium Green's function technology and Buttiker's ac transport theory, we present dynamic conductance in L-shaped graphene nanosystems (LGNSs). It is found that electronic transport is highly sensitive to the geometric feature as well as the size of LGNSs. The armchair edge lead determines whether LGNS shows ac response or not around Dirac point. The increase of width of zigzag edge lead suppresses dc conductance and induces capacitive responses at the anti-resonance states. This is due to large dwell time originated from edge state in zigzag edge lead. In the energy region far away from Dirac point, LGNS responds inductively with the transportation channel opens. Behaviors of dynamic conductance at Dirac point and anti-resonance states are discussed by interesting spacial-resolved local density of states.

  8. Meiotic recombination shapes precision of pedigree- and marker-based estimates of inbreeding.

    Science.gov (United States)

    Knief, U; Kempenaers, B; Forstmeier, W

    2017-03-01

    The proportion of an individual's genome that is identical by descent (GWIBD) can be estimated from pedigrees (inbreeding coefficient 'Pedigree F') or molecular markers ('Marker F'), but both estimators come with error. Assuming unrelated pedigree founders, Pedigree F is the expected proportion of GWIBD given a specific inbreeding constellation. Meiotic recombination introduces variation around that expectation (Mendelian noise) and related pedigree founders systematically bias Pedigree F downward. Marker F is an estimate of the actual proportion of GWIBD but it suffers from the sampling error of markers plus the error that occurs when a marker is homozygous without reflecting common ancestry (identical by state). We here show via simulation of a zebra finch and a human linkage map that three aspects of meiotic recombination (independent assortment of chromosomes, number of crossovers and their distribution along chromosomes) contribute to variation in GWIBD and thus the precision of Pedigree and Marker F. In zebra finches, where the genome contains large blocks that are rarely broken up by recombination, the Mendelian noise was large (nearly twofold larger s.d. values compared with humans) and Pedigree F thus less precise than in humans, where crossovers are distributed more uniformly along chromosomes. Effects of meiotic recombination on Marker F were reversed, such that the same number of molecular markers yielded more precise estimates of GWIBD in zebra finches than in humans. As a consequence, in species inheriting large blocks that rarely recombine, even small numbers of microsatellite markers will often be more informative about inbreeding and fitness than large pedigrees.

  9. Shape Optimization of Vehicle Radiator Using Computational Fluid Dynamics (cfd)

    Science.gov (United States)

    Maddipatla, Sridhar; Guessous, Laila

    2002-11-01

    Automotive manufacturers need to improve the efficiency and lifetime of all engine components. In the case of radiators, performance depends significantly on coolant flow homogeneity across the tubes and overall pressure drop between the inlet and outlet. Design improvements are especially needed in tube-flow uniformity to prevent premature fouling and failure of heat exchangers. Rather than relying on ad-hoc geometry changes, the current study combines Computational Fluid Dynamics with shape optimization methods to improve radiator performance. The goal is to develop an automated suite of virtual tools to assist in radiator design. Two objective functions are considered: a flow non-uniformity coefficient,Cf, and the overall pressure drop, dP*. The methodology used to automate the CFD and shape optimization procedures is discussed. In the first phase, single and multi-variable optimization methods, coupled with CFD, are applied to simplified 2-D radiator models to investigate effects of inlet and outlet positions on the above functions. The second phase concentrates on CFD simulations of a simplified 3-D radiator model. The results, which show possible improvements in both pressure and flow uniformity, validate the optimization criteria that were developed, as well as the potential of shape optimization methods with CFD to improve heat exchanger design. * Improving Radiator Design Through Shape Optimization, L. Guessous and S. Maddipatla, Paper # IMECE2002-33888, Proceedings of the 2002 ASME International Mechanical Engineering Congress and Exposition, November 2002

  10. Assembly and dynamics of the bacteriophage T4 homologous recombination machinery

    Directory of Open Access Journals (Sweden)

    Morrical Scott W

    2010-12-01

    Full Text Available Abstract Homologous recombination (HR, a process involving the physical exchange of strands between homologous or nearly homologous DNA molecules, is critical for maintaining the genetic diversity and genome stability of species. Bacteriophage T4 is one of the classic systems for studies of homologous recombination. T4 uses HR for high-frequency genetic exchanges, for homology-directed DNA repair (HDR processes including DNA double-strand break repair, and for the initiation of DNA replication (RDR. T4 recombination proteins are expressed at high levels during T4 infection in E. coli, and share strong sequence, structural, and/or functional conservation with their counterparts in cellular organisms. Biochemical studies of T4 recombination have provided key insights on DNA strand exchange mechanisms, on the structure and function of recombination proteins, and on the coordination of recombination and DNA synthesis activities during RDR and HDR. Recent years have seen the development of detailed biochemical models for the assembly and dynamics of presynaptic filaments in the T4 recombination system, for the atomic structure of T4 UvsX recombinase, and for the roles of DNA helicases in T4 recombination. The goal of this chapter is to review these recent advances and their implications for HR and HDR mechanisms in all organisms.

  11. A Dynamic Bayesian Approach to Computational Laban Shape Quality Analysis

    Directory of Open Access Journals (Sweden)

    Dilip Swaminathan

    2009-01-01

    kinesiology. LMA (especially Effort/Shape emphasizes how internal feelings and intentions govern the patterning of movement throughout the whole body. As we argue, a complex understanding of intention via LMA is necessary for human-computer interaction to become embodied in ways that resemble interaction in the physical world. We thus introduce a novel, flexible Bayesian fusion approach for identifying LMA Shape qualities from raw motion capture data in real time. The method uses a dynamic Bayesian network (DBN to fuse movement features across the body and across time and as we discuss can be readily adapted for low-cost video. It has delivered excellent performance in preliminary studies comprising improvisatory movements. Our approach has been incorporated in Response, a mixed-reality environment where users interact via natural, full-body human movement and enhance their bodily-kinesthetic awareness through immersive sound and light feedback, with applications to kinesiology training, Parkinson's patient rehabilitation, interactive dance, and many other areas.

  12. Dynamics of male meiotic recombination frequency during plant development using Fluorescent Tagged Lines in Arabidopsis thaliana.

    Science.gov (United States)

    Li, Fan; De Storme, Nico; Geelen, Danny

    2017-02-13

    Meiotic homologous recombination plays a central role in creating genetic variability, making it an essential biological process relevant to evolution and crop breeding. In this study, we used pollen-specific fluorescent tagged lines (FTLs) to measure male meiotic recombination frequency during the development of Arabidopsis thaliana. Interestingly, a subset of pollen grains consistently shows loss of fluorescence expression in tested lines. Using nine independent FTL intervals, the spatio-temporal dynamics of male recombination frequency was assessed during plant development, considering both shoot type and plant age as independent parameters. In most genomic intervals assayed, male meiotic recombination frequency is highly consistent during plant development, showing no significant change between different shoot types and during plant aging. However, in some genomic regions, such as I1a and I5a, a small but significant effect of either developmental position or plant age were observed, indicating that the meiotic CO frequency in those intervals varies during plant development. Furthermore, from an overall view of all nine genomic intervals assayed, both primary and tertiary shoots show a similar dynamics of increasing recombination frequency during development, while secondary and lateral shoots remain highly stable. Our results provide new insights in the dynamics of male meiotic recombination frequency during plant development.

  13. High dynamic range real-time 3D shape measurement.

    Science.gov (United States)

    Jiang, Chufan; Bell, Tyler; Zhang, Song

    2016-04-04

    This paper proposes a method that can measure high-contrast surfaces in real-time without changing camera exposures. We propose to use 180-degree phase-shifted (or inverted) fringe patterns to complement regular fringe patterns. If not all of the regular patterns are saturated, inverted fringe patterns are used in lieu of original saturated patterns for phase retrieval, and if all of the regular fringe patterns are saturated, both the original and inverted fringe patterns are all used for phase computation to reduce phase error. Experimental results demonstrate that three-dimensional (3D) shape measurement can be achieved in real time by adopting the proposed high dynamic range method.

  14. Exciton recombination dynamics in single ZnO tetrapods

    Energy Technology Data Exchange (ETDEWEB)

    Fernandes-Silva, Lígia C. [Departamento de Física de Materiales, Universidad Autónoma de Madrid, E-28049 Madrid (Spain); Martín, Maria D.; Meulen, Herko P. van der; Calleja, José M.; Viña, Luis [Departamento de Física de Materiales, Universidad Autónoma de Madrid, E-28049 Madrid, Spain and Instituto de Ciencia de Materiales Nicolás Cabrera, Universidad Autónoma de Madrid, E-28049 Madrid (Spain); Klopotowski, Lukasz [Polish Academy of Sciences, Institute of Physics, 02-668 Warsaw (Poland)

    2013-12-04

    We present the optical properties of individual ZnO tetrapods as a function of excitation power and temperature by time-integrated and time-resolved spectroscopy. At 10K, we identify the different excitonic transitions by both their characteristic energy and their excitation power dependence. When we increase the tetrapod temperature we observe that the emission intensity decrease and occur a red shift of the emission energies. Our time-resolved studies confirm the predominance of the radiative recombination at low temperatures (< 45 K). Increasing the temperature opens up the non-radiative channels, which are evidenced by a much faster decay time.

  15. Exciton recombination dynamics in single ZnO tetrapods

    Science.gov (United States)

    Fernandes-Silva, Lígia C.; Martín, Maria D.; van der Meulen, Herko P.; Klopotowski, Lukasz; Calleja, José M.; Viña, Luis

    2013-12-01

    We present the optical properties of individual ZnO tetrapods as a function of excitation power and temperature by time-integrated and time-resolved spectroscopy. At 10K, we identify the different excitonic transitions by both their characteristic energy and their excitation power dependence. When we increase the tetrapod temperature we observe that the emission intensity decrease and occur a red shift of the emission energies. Our time-resolved studies confirm the predominance of the radiative recombination at low temperatures (< 45 K). Increasing the temperature opens up the non-radiative channels, which are evidenced by a much faster decay time.

  16. Photocarrier dynamics near V-shaped pits in In{sub x}Ga{sub 1−x}N/GaN multiple quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Taeho; Li, Xiang-Shu; Ko, Dong-Su; Won, Jung-Yeon; Kim, Seong-Heon [Analytical Science Group, Samsung Advanced Institute of Technology, Suwon, Gyeonggi-do 443-803 (Korea, Republic of); Kim, Jaekyun; Kim, Joosung; Tak, Youngjo; Kim, Jun-Youn [GaN Device Group, Samsung Advanced Institute of Technology, Suwon, Gyeonggi-do 443-803 (Korea, Republic of); Park, Gyeong-Su [Analytical Science Group, Samsung Advanced Institute of Technology, Suwon, Gyeonggi-do 443-803 (Korea, Republic of); Lee, Eunha, E-mail: eunhayo.lee@samsung.com [Analytical Science Group, Samsung Advanced Institute of Technology, Suwon, Gyeonggi-do 443-803 (Korea, Republic of)

    2014-06-03

    Highlights: • Correlations between carrier dynamics and structural defects of InGaN MQWs exist. • PL intensity is much weaker in the V-shaped pits than in the regular c-plane. • Blue-shifted photoluminescence spectrum is not observed at the V-pits. • A kinetic model including carriers recombination and diffusion is presented. • The model estimates the nonradiative recombination time as 10 ps at the V-pits. - Abstract: Space- and time-resolved photoluminescence (PL) has been employed to investigate correlations between the carrier dynamics and structural defects known as V-shaped pits in InGaN/GaN multiple quantum wells (MQWs). The pits exhibit much lower PL intensity compared to MQWs of the normal c-plane indicating a high density of nonradiative recombination centers in the pits. However, the PL peak wavelength, which is expected to experience a blueshift at the pits due to the stronger confinement effect and reduced quantum-confined Stark effect, do not show any spatial dependence that is correlated with the defects. This is ascribed to dominant ultrafast (<10 ps) nonradiative recombination at the pits and additional diffusion into the c-plane leading to radiative recombination. By contrast, weak but clear correlations between the pits and PL decay time were observed on nanosecond timescales. This can be explained by a kinetic model that includes the nonradiative recombination and diffusion of carriers at the pits.

  17. Automatic anatomical structures location based on dynamic shape measurement

    Science.gov (United States)

    Witkowski, Marcin; Rapp, Walter; Sitnik, Robert; Kujawinska, Malgorzata; Vander Sloten, Jos; Haex, Bart; Bogaert, Nico; Heitmann, Kjell

    2005-09-01

    New image processing methods and active photonics apparatus have made possible the development of relatively inexpensive optical systems for complex shape and object measurements. We present dynamic 360° scanning method for analysis of human lower body biomechanics, with an emphasis on the analysis of the knee joint. The anatomical structure (of high medical interest) that is possible to scan and analyze, is patella. Tracking of patella position and orientation under dynamic conditions may lead to detect pathological patella movements and help in knee joint disease diagnosis. The processed data is obtained from a dynamic laser triangulation surface measurement system, able to capture slow to normal movements with a scan frequency between 15 and 30 Hz. These frequency rates are enough to capture controlled movements used e.g. for medical examination purposes. The purpose of the work presented is to develop surface analysis methods that may be used as support of diagnosis of motoric abilities of lower limbs. The paper presents algorithms used to process acquired lower limbs surface data in order to find the position and orientation of patella. The algorithms implemented include input data preparation, curvature description methods, knee region discrimination and patella assumed position/orientation calculation. Additionally, a method of 4D (3D + time) medical data visualization is proposed. Also some exemplary results are presented.

  18. Using Shape Memory Alloys: A Dynamic Data Driven Approach

    KAUST Repository

    Douglas, Craig C.

    2013-06-01

    Shape Memory Alloys (SMAs) are capable of changing their crystallographic structure due to changes of either stress or temperature. SMAs are used in a number of aerospace devices and are required in some devices in exotic environments. We are developing dynamic data driven application system (DDDAS) tools to monitor and change SMAs in real time for delivering payloads by aerospace vehicles. We must be able to turn on and off the sensors and heating units, change the stress on the SMA, monitor on-line data streams, change scales based on incoming data, and control what type of data is generated. The application must have the capability to be run and steered remotely as an unmanned feedback control loop.

  19. Collective Behavior of Hair, and Ponytail Shape and Dynamics

    Science.gov (United States)

    Ball, Robin

    I will discuss how we can build a mathematical model of the behaviour of a bundle of hair, comparing the results with experimental studies of the shape and dynamics of human ponytails. We treat the individual fibers as elastic filaments with random intrinsic curvature, in which the balance of bending elasticity, gravity, orientational disorder and inertia is recast as a differential equation for the envelope of the fibre bundle. The static elements of this work were first reported in R.E. Goldstein, P.B. Warren and R.C. Ball, Physical Review Letters 108, 078101 (2012). The compressibility of the bundle enters through an ``equation of state'' whose empirical form is shown to arise from a Confined Helix Model, in which the constraint of the surrounding hair is on a given fibre is represented as a confining cylinder. Using this model we find the ponytail shape is well fit with only one adjustable parameter, which is the degree to which the confining cylinders over fill space. The dynamics of driven vertical ponytail motion is well reproduced provided we introduce some damping, and we find the level of damping required is consistent with that arising from viscous drag of the lateral motion of the hair fibres through the interstitial air. Most of our match with experiment is achieved by approximating the fibre density of the ponytail to to be uniform across its cross-section, and to vary only length-wise. However we show that detail near the exit from a confining clamp (aka hairband) is only captured by computing the full cross-sectional variation. The work reported is joint with RE Goldstein (Cambridge UK) and PB Warren (Unilever Research).

  20. Femtosecond dynamics of fundamental reaction processes in liquids: Proton transfer, geminate recombination, isomerization and vibrational relaxation

    Energy Technology Data Exchange (ETDEWEB)

    Schwartz, Benjamin Joel [Univ. of California, Berkeley, CA (United States)

    1992-11-01

    The fast excited state intramolecular proton transfer of 3-hydroxyflavone is measured and effects of external hydrogen-bonding interactions on the proton transfer are studied. The proton transfer takes place in ~240 fsec in nonpolar environments, but becomes faster than instrumental resolution of 110 fsec in methanol solution. The dynamics following photodissociation of CH2I2 and other small molecules provide the first direct observations of geminate recombination. The recombination of many different photodissociating species occurs on a ~350 fsec time scale. Results show that recombination yields but not rates depend on the solvent environment and suggest that recombination kinetics are dominated by a single collision with surrounding solvent cage. Studies of sterically locked phenyl-substituted butadienes offer new insights into the electronic structure and isomerization behavior of conjugated polyenes. Data show no simple correlation between hinderance of specific large amplitude motions and signatures of isomerizative behavior such as viscosity dependent excited state lifetimes, implying that the isomerization does not provide a suitable for simple condensed phase reaction rate theories. The spectral dynamics of a photochromic spiropyran indicate that recombination, isomerization and vibrational relaxation all play important roles in photoreactivity of complex molecules. The interplay of these microscopic phenomena and their effect on macroscopic properties such as photochromism are discussed. All the results indicate that the initial steps of the photochromic reaction process occur extremely rapidly. Laser system and computer codes for data analysis are discussed.

  1. The size, shape, and dynamics of cellular blebs

    CERN Document Server

    Lim, Fong Yin; Mahadevan, L

    2015-01-01

    A cellular bleb grows when a portion of the cell membrane detaches from the underlying cortex under the influence of a cytoplasmic pressure. We develop a quantitative model for the growth and dynamics of these objects in a simple two-dimensional setting. In particular, we first find the minimum cytoplasmic pressure and minimum unsupported membrane length for a stationary bleb to nucleate and grow as a function of the membrane-cortex adhesion. We next show how a bleb may travel around the periphery of the cell when the cytoplasmic pressure varies in space and time in a prescribed way and find that the traveling speed is governed by the speed of the pressure change induced by local cortical contraction while the shape of the traveling bleb is governed by the speed of cortical healing. Finally, we relax the assumption that the pressure change is prescribed and couple it hydrodynamically to the cortical contraction and membrane deformation. By quantifying the phase space of bleb formation and dynamics, our framew...

  2. Dynamics of an Imperfect Microbeam Considering its Exact Shape

    KAUST Repository

    Bataineh, Ahmad M.

    2014-08-17

    We study the static and dynamic behavior of electrically actuated micromachined arches. First, we conduct experiments on micromachined polysilicon beams by driving them electrically and varying their amplitude and frequency of voltage loads. The results reveal several interesting nonlinear phenomena of jumps, hysteresis, and softening behaviors. Next, we conduct analytical and theoretical investigation to understand the experiments. First, we solve the Eigen value problem analytically. We study the effect of the initial rise on the natural frequency and mode shapes, and use a Galerkin-based procedure to derive a reduced order model, which is then used to solve both the static and dynamic responses. We use two symmetric modes in the reduced order model to have accurate and converged results. We use long time integration to solve the nonlinear ordinary differential equations, and then modify our model using effective length to match experimental results. To further improve the matching with the experimental data, we curve-fit the exact profile of the microbeam to match the experimentally measured profile and use it in the reduced-order model to generate frequency-response curves. Finally, we use another numerical technique, the shooting technique, to solve the nonlinear ordinary differential equations. By using shooting and the curve fitted function, we found that we get good agreement with the experimental data.

  3. A molecular dynamics investigation of the deformation mechanism and shape memory effect of epoxy shape memory polymers

    Science.gov (United States)

    Yang, Hua; Wang, ZhengDao; Guo, YaFang; Shi, XingHua

    2016-03-01

    Following deformation, thermally induced shape memory polymers (SMPs) have the ability to recover their original shape with a change in temperature. In this work, the thermomechanical properties and shape memory behaviors of three types of epoxy SMPs with varying curing agent contents were investigated using a molecular dynamics (MD) method. The mechanical properties under uniaxial tension at different temperatures were obtained, and the simulation results compared reasonably with experimental data. In addition, in a thermomechanical cycle, ideal shape memory effects for the three types of SMPs were revealed through the shape frozen and shape recovery responses at low and high temperatures, respectively, indicating that the recovery time is strongly influenced by the ratio of E-51 to 4,4'-Methylenedianiline.

  4. On quantitative analysis of interband recombination dynamics: Theory and application to bulk ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Lettieri, S. [Institute for Superconductors, Oxides and Innovative Materials, National Research Council (CNR-SPIN), U.O.S. Napoli, Via Cintia, I-80126 Napoli (Italy); Capello, V.; Santamaria, L. [Physics Department, University of Naples “Federico II,” Via Cintia I-80126 Napoli (Italy); Maddalena, P. [Institute for Superconductors, Oxides and Innovative Materials, National Research Council (CNR-SPIN), U.O.S. Napoli, Via Cintia, I-80126 Napoli (Italy); Physics Department, University of Naples “Federico II,” Via Cintia I-80126 Napoli (Italy)

    2013-12-09

    The issue of the quantitative analysis of time-resolved photoluminescence experiments is addressed by developing and describing two approaches for determination of unimolecular lifetime, bimolecular recombination coefficient, and equilibrium free-carrier concentration, based on a quite general second-order expression of the electron-hole recombination rate. Application to the case of band-edge emission of ZnO single crystals is reported, evidencing the signature of sub-nanosecond second-order recombination dynamics for optical transitions close to the interband excitation edge. The resulting findings are in good agreement with the model prediction and further confirm the presence, formerly evidenced in literature by non-optical methods, of near-surface conductive layers in ZnO crystals with sheet charge densities of about 3–5×10{sup 13} cm{sup −2}.

  5. Molecular Dynamics Simulations of Surface Processes: Oxygen Recombination on Silica Surfaces at High Temperature

    Science.gov (United States)

    2007-07-01

    size-scalable cluster approach with SixOy clusters of increasing size cleaved from the β- cristobalite unit cell. In this study the hybrid Hartree...values of the β- cristobalite cell and extending the Molecular Dynamics Simulations of Surface Processes: Oxygen Recombination on Silica Surfaces at... cristobalite surface is reported as a function of the distance of the N atom from the Si active atom. The dashed line shows the interaction

  6. Nonlinear photoluminescence in monolayer WS2: parabolic emission and excitation fluence-dependent recombination dynamics.

    Science.gov (United States)

    Fan, Xiaopeng; Zheng, Weihao; Liu, Hongjun; Zhuang, Xiujuan; Fan, Peng; Gong, Yanfang; Li, Honglai; Wu, Xueping; Jiang, Ying; Zhu, Xiaoli; Zhang, Qinglin; Zhou, Hong; Hu, Wei; Wang, Xiao; Duan, Xiangfeng; Pan, Anlian

    2017-06-01

    Recombination dynamics during photoluminescence (PL) in two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDs) are complicated and can be easily affected by the surroundings because of their atomically thin structures. Herein, we studied the excitation power and temperature dependence of the recombination dynamics on the chemical vapor deposition-grown monolayer WS2via a combination of Raman, PL, and time-resolved PL spectroscopies. We found a red shift and parabolic intensity increase in the PL emission of the monolayer WS2 with the increasing excitation power and the decay time constants corresponding to the recombination of trions and excitons from transient PL dynamics. We attributed the abovementioned nonlinear changes in the PL peak positions and intensities to the combination of increasing carrier interaction and band structure renormalization rather than to the thermal effect from a laser. Furthermore, the excitation power-dependent Raman measurements support our conclusion. These findings and understanding will provide important information for the development of TMD-based optoelectronics and photonics.

  7. Emergence of recombinant forms in geographic regions with co-circulating HIV subtypes in the dynamic HIV-1 epidemic

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Ming [Los Alamos National Laboratory; Letiner, Thomas K [Los Alamos National Laboratory; Korber, Bette T [Los Alamos National Laboratory; Foley, Brian [Los Alamos National Laboratory

    2009-01-01

    We have reexamined the subtype designations of {approx}10,000 subtype A, B, C, G, and AG, BC, BF recombinant sequences, and compared the results of the new analysis with their published designations. Intersubtype recombinants dominate HIV epidemics in three different geographical regions. The circulating recombinant from (CRF) CRF02-AG, common in West Central Africa, appears to result from a recombination event that occurred early in the divergence between subtypes A and G, although additional more recent recombination events may have contributed to the breakpoint pattern in this recombinant lineage as well. The Chinese recombinant epidemic strains CRF07 and CRF08, in contrast, result from recent recombinations between more contemporary strains. Nevertheless, CRF07 and CRF08 contributed to many subsequent recombination events. The BF recombinant epidemics in two HIV-1 epicenters in South America are not independent and BF epidemics in South America have an unusually high fraction of unique recombinant forms (URFs) that have each been found only once and carry distinctive breakpoints. Taken together, these analyses reveal a complex and dynamic picture of the current HIV-1 epidemic, and suggest a means of grouping and tracking relationships between viruses through preservation of shared breakpints.

  8. Structure and Dynamics of Single-isoform Recombinant Neuronal Human Tubulin.

    Science.gov (United States)

    Vemu, Annapurna; Atherton, Joseph; Spector, Jeffrey O; Szyk, Agnieszka; Moores, Carolyn A; Roll-Mecak, Antonina

    2016-06-17

    Microtubules are polymers that cycle stochastically between polymerization and depolymerization, i.e. they exhibit "dynamic instability." This behavior is crucial for cell division, motility, and differentiation. Although studies in the last decade have made fundamental breakthroughs in our understanding of how cellular effectors modulate microtubule dynamics, analysis of the relationship between tubulin sequence, structure, and dynamics has been held back by a lack of dynamics measurements with and structural characterization of homogeneous isotypically pure engineered tubulin. Here, we report for the first time the cryo-EM structure and in vitro dynamics parameters of recombinant isotypically pure human tubulin. α1A/βIII is a purely neuronal tubulin isoform. The 4.2-Å structure of post-translationally unmodified human α1A/βIII microtubules shows overall similarity to that of heterogeneous brain microtubules, but it is distinguished by subtle differences at polymerization interfaces, which are hot spots for sequence divergence between tubulin isoforms. In vitro dynamics assays show that, like mosaic brain microtubules, recombinant homogeneous microtubules undergo dynamic instability, but they polymerize slower and have fewer catastrophes. Interestingly, we find that epitaxial growth of α1A/βIII microtubules from heterogeneous brain seeds is inefficient but can be fully rescued by incorporating as little as 5% of brain tubulin into the homogeneous α1A/βIII lattice. Our study establishes a system to examine the structure and dynamics of mammalian microtubules with well defined tubulin species and is a first and necessary step toward uncovering how tubulin genetic and chemical diversity is exploited to modulate intrinsic microtubule dynamics.

  9. Femtosecond Dynamics of Fundamental Reaction Processes in Liquids: Proton Transfer, Geminate Recombination, Isomerization and Vibrational Relaxation.

    Science.gov (United States)

    Schwartz, Benjamin Joel

    Femtosecond and picosecond transient absorption spectroscopy are used to probe several fundamental aspects of chemical reactivity in the condensed phase including proton transfer, germinate recombination, isomerization and vibrational relaxation. The fast excited state intramolecular proton transfer of 3-hydroxyflavone is measured for the first time, and the effects of external hydrogen-bonding interactions on the proton transfer are studied in detail. The proton transfer takes place in ~240 fsec in non-polar environments, but becomes faster than the instrumental resolution of 110 fsec in methanol solutions. A simple model is proposed to explain these results. The dynamics following photodissociation of CH _2I_2 and other small molecules provide the first direct observations of germinate recombination. The recombination of many different photodissociating species occurs on a ~350 fsec time scale. Results also show that recombination yields but not rates depend on the molecular details of the solvent environment and suggest that recombination kinetics are dominated by a single collision with the surrounding solvent cage. Studies of sterically locked phenyl-substituted butadienes offer new insights into the electronic structure and isomerization behavior of conjugated polyenes. The data show no simple correlation between the hinderance of specific large amplitude motions and signatures of isomerizative behavior such as viscosity dependent excited state lifetimes. This strongly implies that the isomerization of these systems does not provide a suitable testing ground for simple condensed phase reaction rate theories. The spectral dynamics of a photochromic spiropyran indicate that recombination, isomerization and vibrational relaxation all play important roles in the photoreactivity of complex molecules. The interplay of these microscopic phenomena and their effect on macroscopic properties such as photochromism are discussed. All the results indicate that the initial

  10. Ultrafast dynamics of charge carrier photogeneration and geminate recombination in conjugated polymer:fullerene solar cells

    Science.gov (United States)

    Müller, J. G.; Lupton, J. M.; Feldmann, J.; Lemmer, U.; Scharber, M. C.; Sariciftci, N. S.; Brabec, C. J.; Scherf, U.

    2005-11-01

    We investigate the nature of ultrafast exciton dissociation and carrier generation in acceptor-doped conjugated polymers. Using a combination of two-pulse femtosecond spectroscopy with photocurrent detection, we compare the exciton dissociation and geminate charge recombination dynamics in blends of two conjugated polymers, MeLPPP [methyl-substituted ladder-type poly( p -phenylene)] and MDMO-PPV [poly(2-methoxy,5-(3,7-dimethyloctyloxy)-1,4-phenylenevinylene], with the electron accepting fullerene derivative PCBM [1-(3-methoxycarbonyl)-propyl-1-phenyl- (6,6)C61 ]. This technique allows us to distinguish between free charge carriers and Coulombically bound polaron pairs. Our results highlight the importance of geminate pair recombination in photovoltaic devices, which limits the device performance. The comparison of different materials allows us to address the dependence of geminate recombination on the film morphology directly at the polymer:fullerene interface. We find that in the MeLPPP:PCBM blend exciton dissociation generates Coulombically bound geminate polaron pairs with a high probability for recombination, which explains the low photocurrent yield found in these samples. In contrast, in the highly efficient MDMO-PPV:PCBM blend the electron transfer leads to the formation of free carriers. The anisotropy dynamics of electronic transitions from neutral and charged states indicate that polarons in MDMO-PPV relax to delocalized states in ordered domains within 500fs . The results suggest that this relaxation enlarges the distance of carrier separation within the geminate pair, lowering its binding energy and favoring full dissociation. The difference in geminate pair recombination concurs with distinct dissociation dynamics. The electron transfer is preceded by exciton migration towards the PCBM sites. In MeLPPP:PCBM the exciton migration time decays smoothly with increasing PCBM concentration, indicating a trap-free exciton hopping. In MDMO-PPV:PCBM, however

  11. Integrating molecular dynamics simulations with chemical probing experiments using SHAPE-FIT

    Science.gov (United States)

    Kirmizialtin, Serdal; Hennelly, Scott P.; Schug, Alexander; Onuchic, Jose N.; Sanbonmatsu, Karissa Y.

    2016-01-01

    Integration and calibration of molecular dynamics simulations with experimental data remains a challenging endeavor. We have developed a novel method to integrate chemical probing experiments with molecular simulations of RNA molecules by using a native structure-based model. Selective 2’-hydroxyl acylation by primer extension (SHAPE) characterizes the mobility of each residue in the RNA. Our method, SHAPE-FIT, automatically optimizes the potential parameters of the forcefield according to measured reactivities from SHAPE. The optimized parameter set allows simulations of dynamics highly consistent with SHAPE probing experiments. Such atomistic simulations, thoroughly grounded in experiment, can open a new window on RNA structure-function relations. PMID:25726467

  12. Dynamical heavy-quark recombination and the non-photonic single electron puzzle at RHIC

    CERN Document Server

    Ayala, Alejandro; Montano, Luis Manuel; Sanchez, G Toledo

    2009-01-01

    We show that the single, non-photonic electron nuclear modification factor $R_{AA}^e$ is affected by the thermal enhancement of the heavy-baryon to heavy-meson ratio in relativistic heavy-ion collisions with respect to proton-proton collisions. We make use of the dynamical quark recombination model to compute such ratio and show that this produces a sizable suppression factor for $R_{AA}^e$ at intermediate transverse momenta. We argue that such suppression factor needs to be considered, in addition to the energy loss contribution, in calculations of $R_{AA}^e$

  13. Small shape deviations causes complex dynamics in large electric generators

    Science.gov (United States)

    Lundström, Niklas L. P.; Grafström, Anton; Aidanpää, Jan-Olov

    2014-05-01

    We prove that combinations of small eccentricity, ovality and/or triangularity in the rotor and stator can produce complex whirling motions of an unbalanced rotor in large synchronous generators. It is concluded which structures of shape deviations that are more harmful, in the sense of producing complex whirling motions, than others. For each such structure, we derive simplified equations of motions from which we conclude analytically the relation between shape deviations and mass unbalance that yield non-smooth whirling motions. Finally we discuss validity of our results in the sense of modeling of the unbalanced magnetic pull force.

  14. Fuzzy Shape Control Based on Elman Dynamic Recursion Network Prediction Model

    Institute of Scientific and Technical Information of China (English)

    JIA Chun-yu; LIU Hong-min

    2006-01-01

    In the strip rolling process, shape control system possesses the characteristics of nonlinearity, strong coupling, time delay and time variation. Based on self-adapting Elman dynamic recursion network prediction model, the fuzzy control method was used to control the shape on four-high cold mill. The simulation results showed that the system can be applied to real time on line control of the shape.

  15. Recombination dynamics of optically excited charge carriers in bulk MoS2

    Science.gov (United States)

    Völzer, Tim; Lütgens, Matthias; Fennel, Franziska; Lochbrunner, Stefan

    2017-10-01

    Transition metal dichalcogenides (TMDCs), such as MoS2, are promising candidates for optoelectronic or catalytic applications. On that account, a detailed characterization of the electronic dynamics in these materials is of pivotal importance. Here, we investigate the temporal evolution of an excited carrier population by all-optical pump-probe spectroscopy. On the sub-picosecond time scale we observe thermal relaxation of the excited carriers by electron–phonon coupling. The dynamics on the nanosecond time scale can be understood in terms of defect-assisted Auger recombination over a broad carrier density regime spanning more than one order of magnitude. Hence, our results emphasize the importance of defect states for electronic processes in TMDCs at room temperature.

  16. Determination of a dynamic feeding strategy for recombinant Pichia pastoris strains.

    Science.gov (United States)

    Spadiut, Oliver; Dietzsch, Christian; Herwig, Christoph

    2014-01-01

    The knowledge of certain strain specific parameters of recombinant P. pastoris strains is required to be able to set up a feeding regime for fed-batch cultivations. To date, these parameters are commonly determined either by time-consuming and labor-intensive continuous cultivations or by several, consecutive fed-batch cultivations. Here, we describe a fast method based on batch experiments with methanol pulses to extract certain strain characteristic parameters, which are required to set up a dynamic feeding strategy for P. pastoris strains based on specific substrate uptake rate (q(s)). We further describe in detail the course of actions which have to be taken to obtain the desired dynamics during feeding.

  17. Automated Computational Fluid Dynamics Design With Shape Optimization Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Computational fluid dynamics (CFD) is used as an analysis tool to help the designer gain greater understanding of the fluid flow phenomena involved in the...

  18. Automated Computational Fluid Dynamics Design With Shape Optimization Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Computational fluid dynamics (CFD) is used as an analysis tool to help the designer gain greater understanding of the fluid flow phenomena involved in the components...

  19. Dynamics of bow-tie shaped bursting: Forced pendulum with dynamic feedback

    Science.gov (United States)

    Hongray, Thotreithem; Balakrishnan, Janaki

    2016-12-01

    A detailed study is performed on the parameter space of the mechanical system of a driven pendulum with damping and constant torque under feedback control. We report an interesting bow-tie shaped bursting oscillatory behaviour, which is exhibited for small driving frequencies, in a certain parameter regime, which has not been reported earlier in this forced system with dynamic feedback. We show that the bursting oscillations are caused because of a transition of the quiescent state to the spiking state by a saddle-focus bifurcation, and because of another saddle-focus bifurcation, which leads to cessation of spiking, bringing the system back to the quiescent state. The resting period between two successive bursts (Trest) is estimated analytically.

  20. Tunable Optical Phenomena and Carrier Recombination Dynamics in III-V Semiconductor Nanostructures

    Science.gov (United States)

    Kumar Thota, Venkata Ramana

    Semiconductor nanostructures such as quantum dots, quantum wires and quantum wells have gained significant attention in the scientific community due to their peculiar properties, which arise from the quantum confinement of charge carriers. In such systems, confinement plays key role and governs the emission spectra. With the advancements in growth techniques, which enable the fabrication of these nanostructured devices with great precision down to the atomic scale, it is intriguing to study and observe quantum mechanical effects through light-matter interactions and new physics governed by the confinement, size, shape and alloy composition. The goal is to reduce the size of semiconductor bulk material to few nanometers, which in turn localizes the charge carriers inside these structures such that the spin associated with them is used to carry and process information within ultra-short time scales. The main focus of this dissertation is the optical studies of quantum dot molecule (QDM) systems. A system where the electrons can tunnel between the two dots leading to observable tunneling effects. The emission spectra of such system has been demonstrated to have both intradot transitions (electron-hole pair residing in the same dot) and interdot transitions (electron-hole pair participating in the recombination origin from different dots). In such a system, it is possible to apply electric field such that the wavefunction associated with the charge carriers can be tuned to an extent of delocalizing between the two dots. This forms the first project of this dissertation, which addresses the origin of the fine structure splitting in the exciton-biexciton cascade. Moreover, we also show how this fine structure can be tuned in the quantum dot molecule system with the application of electric field along the growth direction. This is demonstrated through high resolution polarization dependent photoluminescence spectroscopy on a single QDM, which was described in great detail

  1. Shape Distributions of Nonlinear Dynamical Systems for Video-Based Inference.

    Science.gov (United States)

    Venkataraman, Vinay; Turaga, Pavan

    2016-12-01

    This paper presents a shape-theoretic framework for dynamical analysis of nonlinear dynamical systems which appear frequently in several video-based inference tasks. Traditional approaches to dynamical modeling have included linear and nonlinear methods with their respective drawbacks. A novel approach we propose is the use of descriptors of the shape of the dynamical attractor as a feature representation of nature of dynamics. The proposed framework has two main advantages over traditional approaches: a) representation of the dynamical system is derived directly from the observational data, without any inherent assumptions, and b) the proposed features show stability under different time-series lengths where traditional dynamical invariants fail. We illustrate our idea using nonlinear dynamical models such as Lorenz and Rossler systems, where our feature representations (shape distribution) support our hypothesis that the local shape of the reconstructed phase space can be used as a discriminative feature. Our experimental analyses on these models also indicate that the proposed framework show stability for different time-series lengths, which is useful when the available number of samples are small/variable. The specific applications of interest in this paper are: 1) activity recognition using motion capture and RGBD sensors, 2) activity quality assessment for applications in stroke rehabilitation, and 3) dynamical scene classification. We provide experimental validation through action and gesture recognition experiments on motion capture and Kinect datasets. In all these scenarios, we show experimental evidence of the favorable properties of the proposed representation.

  2. A divide-conquer-recombine algorithmic paradigm for large spatiotemporal quantum molecular dynamics simulations

    Science.gov (United States)

    Shimojo, Fuyuki; Hattori, Shinnosuke; Kalia, Rajiv K.; Kunaseth, Manaschai; Mou, Weiwei; Nakano, Aiichiro; Nomura, Ken-ichi; Ohmura, Satoshi; Rajak, Pankaj; Shimamura, Kohei; Vashishta, Priya

    2014-05-01

    We introduce an extension of the divide-and-conquer (DC) algorithmic paradigm called divide-conquer-recombine (DCR) to perform large quantum molecular dynamics (QMD) simulations on massively parallel supercomputers, in which interatomic forces are computed quantum mechanically in the framework of density functional theory (DFT). In DCR, the DC phase constructs globally informed, overlapping local-domain solutions, which in the recombine phase are synthesized into a global solution encompassing large spatiotemporal scales. For the DC phase, we design a lean divide-and-conquer (LDC) DFT algorithm, which significantly reduces the prefactor of the O(N) computational cost for N electrons by applying a density-adaptive boundary condition at the peripheries of the DC domains. Our globally scalable and locally efficient solver is based on a hybrid real-reciprocal space approach that combines: (1) a highly scalable real-space multigrid to represent the global charge density; and (2) a numerically efficient plane-wave basis for local electronic wave functions and charge density within each domain. Hybrid space-band decomposition is used to implement the LDC-DFT algorithm on parallel computers. A benchmark test on an IBM Blue Gene/Q computer exhibits an isogranular parallel efficiency of 0.984 on 786 432 cores for a 50.3 × 106-atom SiC system. As a test of production runs, LDC-DFT-based QMD simulation involving 16 661 atoms is performed on the Blue Gene/Q to study on-demand production of hydrogen gas from water using LiAl alloy particles. As an example of the recombine phase, LDC-DFT electronic structures are used as a basis set to describe global photoexcitation dynamics with nonadiabatic QMD (NAQMD) and kinetic Monte Carlo (KMC) methods. The NAQMD simulations are based on the linear response time-dependent density functional theory to describe electronic excited states and a surface-hopping approach to describe transitions between the excited states. A series of techniques

  3. A divide-conquer-recombine algorithmic paradigm for large spatiotemporal quantum molecular dynamics simulations

    Energy Technology Data Exchange (ETDEWEB)

    Shimojo, Fuyuki; Hattori, Shinnosuke [Collaboratory for Advanced Computing and Simulations, Department of Physics and Astronomy, Department of Computer Science, and Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California 90089-0242 (United States); Department of Physics, Kumamoto University, Kumamoto 860-8555 (Japan); Kalia, Rajiv K.; Mou, Weiwei; Nakano, Aiichiro; Nomura, Ken-ichi; Rajak, Pankaj; Vashishta, Priya [Collaboratory for Advanced Computing and Simulations, Department of Physics and Astronomy, Department of Computer Science, and Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California 90089-0242 (United States); Kunaseth, Manaschai [Collaboratory for Advanced Computing and Simulations, Department of Physics and Astronomy, Department of Computer Science, and Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California 90089-0242 (United States); National Nanotechnology Center, Pathumthani 12120 (Thailand); Ohmura, Satoshi [Collaboratory for Advanced Computing and Simulations, Department of Physics and Astronomy, Department of Computer Science, and Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California 90089-0242 (United States); Department of Physics, Kumamoto University, Kumamoto 860-8555 (Japan); Department of Physics, Kyoto University, Kyoto 606-8502 (Japan); Shimamura, Kohei [Collaboratory for Advanced Computing and Simulations, Department of Physics and Astronomy, Department of Computer Science, and Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California 90089-0242 (United States); Department of Physics, Kumamoto University, Kumamoto 860-8555 (Japan); Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, Fukuoka 819-0395 (Japan)

    2014-05-14

    We introduce an extension of the divide-and-conquer (DC) algorithmic paradigm called divide-conquer-recombine (DCR) to perform large quantum molecular dynamics (QMD) simulations on massively parallel supercomputers, in which interatomic forces are computed quantum mechanically in the framework of density functional theory (DFT). In DCR, the DC phase constructs globally informed, overlapping local-domain solutions, which in the recombine phase are synthesized into a global solution encompassing large spatiotemporal scales. For the DC phase, we design a lean divide-and-conquer (LDC) DFT algorithm, which significantly reduces the prefactor of the O(N) computational cost for N electrons by applying a density-adaptive boundary condition at the peripheries of the DC domains. Our globally scalable and locally efficient solver is based on a hybrid real-reciprocal space approach that combines: (1) a highly scalable real-space multigrid to represent the global charge density; and (2) a numerically efficient plane-wave basis for local electronic wave functions and charge density within each domain. Hybrid space-band decomposition is used to implement the LDC-DFT algorithm on parallel computers. A benchmark test on an IBM Blue Gene/Q computer exhibits an isogranular parallel efficiency of 0.984 on 786 432 cores for a 50.3 × 10{sup 6}-atom SiC system. As a test of production runs, LDC-DFT-based QMD simulation involving 16 661 atoms is performed on the Blue Gene/Q to study on-demand production of hydrogen gas from water using LiAl alloy particles. As an example of the recombine phase, LDC-DFT electronic structures are used as a basis set to describe global photoexcitation dynamics with nonadiabatic QMD (NAQMD) and kinetic Monte Carlo (KMC) methods. The NAQMD simulations are based on the linear response time-dependent density functional theory to describe electronic excited states and a surface-hopping approach to describe transitions between the excited states. A series of

  4. A thermo dynamical model for the shape and size effect on melting of boron carbide nanoparticles.

    Science.gov (United States)

    Antoniammal, Paneerselvam; Arivuoli, Dakshanamoorthy

    2012-02-01

    The size and shape dependence of the melting temperature of Boron Carbide (B4C) nanoparticles has been investigated with a numerical thermo dynamical approach. The problem considered in this paper is the inward melting of nanoparticles with spherical and cylindrical geometry. The cylindrical Boron Carbide (B4C) nanoparticles, whose melting point has been reported to decrease with decreasing particle radius, become larger than spherical shaped nanoparticle. Comparative investigation of the size dependence of the melting temperature with respect to the two shapes is also been done. The melting temperature obtained in the present study is approximately a dealing function of radius, in a good agreement with prediction of thermo dynamical model.

  5. Measurement of Size-dependent Dynamic Shape Factors of Quartz Particles in Two Flow Regimes

    Energy Technology Data Exchange (ETDEWEB)

    Alexander, Jennifer M.; Bell, David M.; Imre, D.; Kleiber, Paul; Grassian, Vicki H.; Zelenyuk, Alla

    2016-08-02

    Understanding and modeling the behavior of quartz dust particles, commonly found in the atmosphere, requires knowledge of many relevant particles properties, including particle shape. This study uses a single particle mass spectrometer, a differential mobility analyzer, and an aerosol particle mass analyzer to measure quartz aerosol particles mobility, aerodynamic, and volume equivalent diameters, mass, composition, effective density, and dynamic shape factor as a function of particle size, in both the free molecular and transition flow regimes. The results clearly demonstrate that dynamic shape factors can vary significantly as a function of particle size. For the quartz samples studied here, the dynamic shape factors increase with size, indicating that larger particles are significantly more aspherical than smaller particles. In addition, dynamic shape factors measured in the free-molecular (χv) and transition (χt) flow regimes can be significantly different, and these differences vary with the size of the quartz particles. For quartz, χv of small (d < 200 nm) particles is 1.25, while χv of larger particles (d ~ 440 nm) is 1.6, with a continuously increasing trend with particle size. In contrast χt, of small particles starts at 1.1 increasing slowly to 1.34 for 550 nm diameter particles. The multidimensional particle characterization approach used here goes beyond determination of average properties for each size, to provide additional information about how the particle dynamic shape factor may vary even for particles with the same mass and volume equivalent diameter.

  6. Nonlinear dynamics of a pseudoelastic shape memory alloy system - theory and experiment

    DEFF Research Database (Denmark)

    Enemark, Søren; A Savi, M.; Santos, Ilmar

    2014-01-01

    In this work, a helical spring made from a pseudoelastic shape memory alloy was embedded in a dynamic system also composed of a mass, a linear spring and an excitation system. The mechanical behaviour of shape memory alloys is highly complex, involving hysteresis, which leads to damping...... capabilities and varying stiffness. Besides, these properties depend on the temperature and pretension conditions. Because of these capabilities, shape memory alloys are interesting in relation to engineering design of dynamic systems. A theoretical model based on a modification of the 1D Brinson model...... and forced vibrations of the system setup under different temperature conditions. The experiments give a thorough insight into dynamic systems involving pseudoelastic shape memory alloys. Comparison between experimental results and the proposed model shows that the model is able to explain and predict...

  7. Dynamic products shaping information to engage and persuade

    CERN Document Server

    Colombo, Sara

    2016-01-01

    This book explores how dynamic changes in products' sensory features can be used to convey information to the user in an effective and engaging way. The aim is to supply the reader with a clear understanding of an important emerging area of research and practice in product design, referred to as dynamic products, which is opening up new possibilities for the integration of product design with digital and smart technologies and offering an alternative to the use of digital interfaces. Dynamic products are artifacts displaying sensory characteristics – visual, tactile, auditory, or olfactory – that change in a proactive and reversible way over time, addressing one or more of the user's senses. The reader will learn why and how to communicate by means of such dynamic products. Their potential advantages and limitations are identified and design tools are proposed to support the design activity. It is hoped that the book will stimulate the design community to reflect upon the ever more compelling need to merg...

  8. Non-transcriptional regulatory processes shape transcriptional network dynamics

    OpenAIRE

    Ray, J. Christian J; Tabor, Jeffrey J.; Igoshin, Oleg A.

    2011-01-01

    Information about the extra- or intracellular environment is often captured as biochemical signals propagating through regulatory networks. These signals eventually drive phenotypic changes, typically by altering gene expression programs in the cell. Reconstruction of transcriptional regulatory networks has given a compelling picture of bacterial physiology, but transcriptional network maps alone often fail to describe phenotypes. In many cases, the dynamical performance of transcriptional re...

  9. Effects of surface reflectance on local second order shape estimation in dynamic scenes

    NARCIS (Netherlands)

    Dövencioglu, D.N.; Wijntjes, M.W.A.; Ben-Sharar, O.; Doerschner, K.

    2015-01-01

    In dynamic scenes, relative motion between the object, the observer, and/or the environment projects as dynamic visual information onto the retina (optic flow) that facilitates 3D shape perception. When the object is diffusely reflective, e.g. a matte painted surface, this optic flow is directly lin

  10. Coexistence of minicircular and a highly rearranged mtDNA molecule suggests that recombination shapes mitochondrial genome organization.

    Science.gov (United States)

    Mao, Meng; Austin, Andrew D; Johnson, Norman F; Dowton, Mark

    2014-03-01

    Recombination has been proposed as a possible mechanism to explain mitochondrial (mt) gene rearrangements, although the issue of whether mtDNA recombination occurs in animals has been controversial. In this study, we sequenced the entire mt genome of the megaspilid wasp Conostigmus sp., which possessed a highly rearranged mt genome. The sequence of the A+T-rich region contained a number of different types of repeats, similar to those reported previously in the nematode Meloidogyne javanica, in which recombination was discovered. In Conostigmus, we detected the end products of recombination: a range of minicircles. However, using isolated (cloned) fragments of the A+T-rich region, we established that some of these minicircles were found to be polymerase chain reaction (PCR) artifacts. It appears that regions with repeats are prone to PCR template switching or PCR jumping. Nevertheless, there is strong evidence that one minicircle is real, as amplification primers that straddle the putative breakpoint junction produce a single strong amplicon from genomic DNA but not from the cloned A+T-rich region. The results provide support for the direct link between recombination and mt gene rearrangement. Furthermore, we developed a model of recombination which is important for our understanding of mtDNA evolution.

  11. Dynamics of landslides on comets of irregular shape

    Science.gov (United States)

    Czechowski, Leszek

    2017-04-01

    Landslides were observed on a few comet's nuclei, e.g. [1], [2]. The mechanism of their origin is not obvious because of very low gravity. According to [2] fluidization and multiphase transport of cometary material could be an explanation. We investigate here motion of the mass on a comet of irregular shape. The mechanism responsible for the low friction is not considered here. In fact, mass motion often occurs without contact with the surface. The motion could be triggered by meteoroids impacts or by the tidal forces. Comets nuclei are believed to be built of soft materials like snow and dust. The landing of Philae on the comet 67P/Czuriumow-Gierasimienko indicates a different situation. According to [1]: "thermal probe did not fully penetrate the near-surface layers, suggesting a local resistance of the ground to penetration of >4 megapascals, equivalent to >2 megapascal uniaxial compressive strength". Here we assume that elastic properties of comet's nuclei could be similar to elastic properties of dry snow, namely Young modulus is assumed to be 1 - 100 MPa, see [3] and [4]. We consider nucleus of the shape of 67P/Churyumov-Gerasimenko with density 470 kg/m3. The impact or tidal forces result in changing of rotation of the comet. In general, the vector of angular velocity will be a subject to nutation that results in changing of centrifugal force, and consequently could be a factor triggering landslides. Note that nucleus' shape does not resemble the shape of surface of constant value of gravitational potential (i.e. 'geoid'). Our numerical models indicate the parts of the nucleus where landslides start and other parts where landslides stop. Of course, the regolith from the first type of regions would be removed to the regions of the second class. The motion of the mass is often complicated because of complicated distribution of the gravity and complicated shape of the nucleus. Acknowledgement: The research is partly supported by Polish National Science Centre

  12. Seasonal sediment dynamics shape temperate bedrock reef communities

    Science.gov (United States)

    Figurski, Jared D.; Freiwald, Jan; Lonhart, Steve I.; Storlazzi, Curt

    2016-01-01

    Mobilized seafloor sediment can impact benthic reef communities through burial, scour, and turbidity. These processes are ubiquitous in coastal oceans and, through their influence on the survival, fitness, and interactions of species, can alter the structure and function of benthic communities. In northern Monterey Bay, California, USA, as much as 30% of the seafloor is buried or exposed seasonally, making this an ideal location to test how subtidal temperate rocky reef communities vary in the presence and absence of chronic sediment-based disturbances. Designated dynamic plots were naturally inundated by sediment in summer (50 to 100% cover) and swept clean in winter, whereas designated stable plots remained free of sediment during our study. Multivariate analyses indicated significant differences in the structure of sessile and mobile communities between dynamic and stable reef habitats. For sessile species, community structure in disturbed plots was less variable in space and time than in stable plots due to the maintenance of an early successional state. In contrast, community structure of mobile species varied more in disturbed plots than in stable plots, reflecting how mobile species distribute in response to sediment dynamics. Some species were found only in these disturbed areas, suggesting that the spatial mosaic of disturbance could increase regional diversity. We discuss how the relative ability of species to tolerate disturbance at different life history stages and their ability to colonize habitat translate into community-level differences among habitats, and how this response varies between mobile and sessile communities.

  13. The resonant dynamics of arbitrarily-shaped meta-atoms

    CERN Document Server

    Powell, David A

    2014-01-01

    Meta-atoms, nano-antennas, plasmonic particles and other small scatterers are commonly modeled in terms of their modes. However these modal solutions are seldom determined explicitly, due to the conceptual and numerical difficulties in solving eigenvalue problems for open systems with strong radiative losses. Here it is shown that these modes can be directly calculated from Maxwell's equations expressed in integral form, by finding the complex frequencies which yield a homogenous solution. This gives a clear physical interpretation of the modes, and enables their conduction or polarization current distribution to be calculated numerically for particles of arbitrary shape. By combining the modal current distribution with a scalar impedance function, simple yet accurate models of scatterers can be constructed which describe their response to an arbitrary incident field over a broad bandwidth. These models generalize both equivalent-dipole and and equivalent-circuit models to finite sized structures with multipl...

  14. Recurrent circuitry dynamically shapes the activation of piriform cortex.

    Science.gov (United States)

    Franks, Kevin M; Russo, Marco J; Sosulski, Dara L; Mulligan, Abigail A; Siegelbaum, Steven A; Axel, Richard

    2011-10-06

    In the piriform cortex, individual odorants activate a unique ensemble of neurons that are distributed without discernable spatial order. Piriform neurons receive convergent excitatory inputs from random collections of olfactory bulb glomeruli. Pyramidal cells also make extensive recurrent connections with other excitatory and inhibitory neurons. We introduced channelrhodopsin into the piriform cortex to characterize these intrinsic circuits and to examine their contribution to activity driven by afferent bulbar inputs. We demonstrated that individual pyramidal cells are sparsely interconnected by thousands of excitatory synaptic connections that extend, largely undiminished, across the piriform cortex, forming a large excitatory network that can dominate the bulbar input. Pyramidal cells also activate inhibitory interneurons that mediate strong, local feedback inhibition that scales with excitation. This recurrent network can enhance or suppress bulbar input, depending on whether the input arrives before or after the cortex is activated. This circuitry may shape the ensembles of piriform cells that encode odorant identity.

  15. Recombination dynamics in aerotaxy-grown Zn-doped GaAs nanowires

    Science.gov (United States)

    Zhang, Wei; Yang, Fangfang; Messing, Maria E.; Mergenthaler, Kilian; Pistol, Mats-Erik; Deppert, Knut; Samuelson, Lars; Magnusson, Martin H.; Yartsev, Arkady

    2016-11-01

    In this paper we have investigated the dynamics of photo-generated charge carriers in a series of aerotaxy-grown GaAs nanowires (NWs) with different levels of Zn doping. Time-resolved photo-induced luminescence and transient absorption have been employed to investigate radiative (band edge transition) and non-radiative charge recombination processes, respectively. We find that the photo-luminescence (PL) lifetime of intrinsic GaAs NWs is significantly increased after growing an AlGaAs shell over them, indicating that an AlGaAs shell can effectively passivate the surface of aerotaxy-grown GaAs NWs. We observe that PL decay time as well as PL intensity decrease with increasing Zn doping, which can be attributed to thermally activated electron trapping with the trap density increased due to the Zn doping level.

  16. Electronic fine structure and recombination dynamics in single InAs quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Seguin, R.

    2008-01-28

    In the work at hand single InAs/GaAs quantum dots (QDs) are examined via cathodoluminescence spectroscopy. A thorough analysis of the spectra leads to an unambiguous assignment of the lines to the decay of specific excitonic complexes. A special aspect of the Coulomb interaction, the exchange interaction, gives rise to a fine structure in the initial and final states of an excitonic decay. This leads to a fine structure in the emission spectra that again is unique for every excitonic complex. The exchange interaction is discussed in great detail in this work.QDs of different sizes are investigated and the influence on the electronic properties is monitored. Additionally, the structure is modified ex situ by a thermal annealing process. The changes of the spectra under different annealing temperatures are traced. Finally, recombination dynamics of different excitonic complexes are examined by performing time-resolved cathodoluminescence spectroscopy. (orig.)

  17. Non-transcriptional regulatory processes shape transcriptional network dynamics.

    Science.gov (United States)

    Ray, J Christian J; Tabor, Jeffrey J; Igoshin, Oleg A

    2011-10-11

    Information about the extra- or intracellular environment is often captured as biochemical signals that propagate through regulatory networks. These signals eventually drive phenotypic changes, typically by altering gene expression programmes in the cell. Reconstruction of transcriptional regulatory networks has given a compelling picture of bacterial physiology, but transcriptional network maps alone often fail to describe phenotypes. Cellular response dynamics are ultimately determined by interactions between transcriptional and non-transcriptional networks, with dramatic implications for physiology and evolution. Here, we provide an overview of non-transcriptional interactions that can affect the performance of natural and synthetic bacterial regulatory networks.

  18. Evolutionary Dynamics and Temporal/Geographical Correlates of Recombination in the Human Enterovirus Echovirus Types 9, 11, and 30▿

    Science.gov (United States)

    McWilliam Leitch, E. C.; Cabrerizo, M.; Cardosa, J.; Harvala, H.; Ivanova, O. E.; Kroes, A. C. M.; Lukashev, A.; Muir, P.; Odoom, J.; Roivainen, M.; Susi, P.; Trallero, G.; Evans, D. J.; Simmonds, P.

    2010-01-01

    The relationship between virus evolution and recombination in species B human enteroviruses was investigated through large-scale genetic analysis of echovirus type 9 (E9) and E11 isolates (n = 85 and 116) from 16 European, African, and Asian countries between 1995 and 2008. Cluster 1 E9 isolates and genotype D5 and A E11 isolates showed evidence of frequent recombination between the VP1 and 3Dpol regions, the latter falling into 23 (E9) and 43 (E11) clades interspersed phylogenetically with 46 3Dpol clades of E30 and with those of other species B serotypes. Remarkably, only 2 of the 112 3Dpol clades were shared by more than one serotype (E11 and E30), demonstrating an extremely large and genetically heterogeneous recombination pool of species B nonstructural-region variants. The likelihood of recombination increased with geographical separation and time, and both were correlated with VP1 divergence, whose substitution rates allowed recombination half-lives of 1.3, 9.8, and 3.1 years, respectively, for E9, E11, and E30 to be calculated. These marked differences in recombination dynamics matched epidemiological patterns of periodic epidemic cycles of 2 to 3 (E9) and 5 to 6 (E30) years and the longer-term endemic pattern of E11 infections. Phylotemporal analysis using a Bayesian Markov chain Monte Carlo method, which placed recombination events within the evolutionary reconstruction of VP1, showed a close relationship with VP1 lineage expansion, with defined recombination events that correlated with their epidemiological periodicity. Whether recombination events contribute directly to changes in transmissibility that drive epidemic behavior or occur stochastically during periodic population bottlenecks is an unresolved issue vital to future understanding of enterovirus molecular epidemiology and pathogenesis. PMID:20610722

  19. Evolutionary dynamics and temporal/geographical correlates of recombination in the human enterovirus echovirus types 9, 11, and 30.

    Science.gov (United States)

    McWilliam Leitch, E C; Cabrerizo, M; Cardosa, J; Harvala, H; Ivanova, O E; Kroes, A C M; Lukashev, A; Muir, P; Odoom, J; Roivainen, M; Susi, P; Trallero, G; Evans, D J; Simmonds, P

    2010-09-01

    The relationship between virus evolution and recombination in species B human enteroviruses was investigated through large-scale genetic analysis of echovirus type 9 (E9) and E11 isolates (n = 85 and 116) from 16 European, African, and Asian countries between 1995 and 2008. Cluster 1 E9 isolates and genotype D5 and A E11 isolates showed evidence of frequent recombination between the VP1 and 3Dpol regions, the latter falling into 23 (E9) and 43 (E11) clades interspersed phylogenetically with 46 3Dpol clades of E30 and with those of other species B serotypes. Remarkably, only 2 of the 112 3Dpol clades were shared by more than one serotype (E11 and E30), demonstrating an extremely large and genetically heterogeneous recombination pool of species B nonstructural-region variants. The likelihood of recombination increased with geographical separation and time, and both were correlated with VP1 divergence, whose substitution rates allowed recombination half-lives of 1.3, 9.8, and 3.1 years, respectively, for E9, E11, and E30 to be calculated. These marked differences in recombination dynamics matched epidemiological patterns of periodic epidemic cycles of 2 to 3 (E9) and 5 to 6 (E30) years and the longer-term endemic pattern of E11 infections. Phylotemporal analysis using a Bayesian Markov chain Monte Carlo method, which placed recombination events within the evolutionary reconstruction of VP1, showed a close relationship with VP1 lineage expansion, with defined recombination events that correlated with their epidemiological periodicity. Whether recombination events contribute directly to changes in transmissibility that drive epidemic behavior or occur stochastically during periodic population bottlenecks is an unresolved issue vital to future understanding of enterovirus molecular epidemiology and pathogenesis.

  20. Photocarrier recombination dynamics in perovskite CH3NH3PbI3 for solar cell applications.

    Science.gov (United States)

    Yamada, Yasuhiro; Nakamura, Toru; Endo, Masaru; Wakamiya, Atsushi; Kanemitsu, Yoshihiko

    2014-08-20

    Using time-resolved photoluminescence and transient absorption measurements at room temperature, we report excitation-intensity-dependent photocarrier recombination processes in thin films made from the organo-metal halide perovskite semiconductor CH3NH3PbI3 for solar-cell applications. The photocarrier dynamics are well described by a simple rate equation including single-carrier trapping and electron-hole radiative recombination. This result provides clear evidence that the free-carrier model is better than the exciton model for interpreting the optical properties of CH3NH3PbI3. The observed large two-carrier recombination rate suggests the promising potential of perovskite semiconductors for optoelectronic device applications. Our findings provide the information about the dynamical behaviors of photoexcited carriers that is needed for developing high-efficiency perovskite solar cells.

  1. Charge transport and recombination dynamics in organic bulk heterojunction solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Baumann, Andreas

    2011-08-02

    The charge transport in disordered organic bulk heterojunction (BHJ) solar cells is a crucial process affecting the power conversion efficiency (PCE) of the solar cell. With the need of synthesizing new materials for improving the power conversion efficiency of those cells it is important to study not only the photophysical but also the electrical properties of the new material classes. Thereby, the experimental techniques need to be applicable to operating solar cells. In this work, the conventional methods of transient photoconductivity (also known as ''Time-of-Flight'' (TOF)), as well as the transient charge extraction technique of ''Charge Carrier Extraction by Linearly Increasing Voltage'' (CELIV) are performed on different organic blend compositions. Especially with the latter it is feasible to study the dynamics - i.e. charge transport and charge carrier recombination - in bulk heterojunction (BHJ) solar cells with active layer thicknesses of 100-200 nm. For a well performing organic BHJ solar cells the morphology is the most crucial parameter finding a trade-off between an efficient photogeneration of charge carriers and the transport of the latter to the electrodes. Besides the morphology, the nature of energetic disorder of the active material blend and its influence on the dynamics are discussed extensively in this work. Thereby, the material system of poly(3-hexylthiophene-2,5-diyl) (P3HT) and [6,6]-phenyl-C{sub 61}butyric acid methyl ester (PC{sub 61}BM) serves mainly as a reference material system. New promising donor or acceptor materials and their potential for application in organic photovoltaics are studied in view of charge dynamics and compared with the reference system. With the need for commercialization of organic solar cells the question of the impact of environmental conditions on the PCE of the solar cells raises. In this work, organic BHJ solar cells exposed to synthetic air for finite duration are

  2. A dynamic spar numerical model for passive shape change

    Science.gov (United States)

    Calogero, J. P.; Frecker, M. I.; Hasnain, Z.; Hubbard, J. E., Jr.

    2016-10-01

    A three-dimensional constraint-driven dynamic rigid-link numerical model of a flapping wing structure with compliant joints (CJs) called the dynamic spar numerical model is introduced and implemented. CJs are modeled as spherical joints with distributed mass and spring-dampers with coupled nonlinear spring and damping coefficients, which models compliant mechanisms spatially distributed in the structure while greatly reducing computation time compared to a finite element model. The constraints are established, followed by the formulation of a state model used in conjunction with a forward time integrator, an experiment to verify a rigid-link assumption and determine a flapping angle function, and finally several example runs. Modeling the CJs as coupled bi-linear springs shows the wing is able to flex more during upstroke than downstroke. Coupling the spring stiffnesses allows an angular deformation about one axis to induce an angular deformation about another axis, where the magnitude is proportional to the coupling term. Modeling both the leading edge and diagonal spars shows that the diagonal spar changes the kinematics of the leading edge spar verses only considering the leading edge spar, causing much larger axial rotations in the leading edge spar. The kinematics are very sensitive to CJ location, where moving the CJ toward the wing root causes a stronger response, and adding multiple CJs on the leading edge spar with a CJ on the diagonal spar allows the wing to deform with larger magnitude in all directions. This model lays a framework for a tool which can be used to understand flapping wing flight.

  3. Quadrupole shape dynamics in view from a theory of large amplitude collective motion

    CERN Document Server

    Matsuo, M; Sato, K; Matsuyanagi, K; Nakatsukasa, T; Yoshida, K

    2014-01-01

    Low-lying quadrupole shape dynamics is a typical manifestation of large amplitude collective motion in finite nuclei. To describe the dynamics on a microscopic foundation, we have formulated a consistent scheme in which the Bohr collective Hamiltonian for the five dimensional quadrupole shape variables is derived on the basis of the time-dependent Hartree-Fock-Bogoliubov theory. It enables us to incorporates the Thouless-Valatin effect on the shape inertial functions, which has been neglected in previous microscopic Bohr Hamiltonian approaches. Quantitative successes are illustrated for the low-lying spectra in $^{68}$Se, $^{30-34}$Mg and $^{58-64}$Cr, which display shape-coexistence, -mixing and -transitional behaviors.

  4. Microscopic derivation of the Bohr-Mottelson collective Hamiltonian and its application to quadrupole shape dynamics

    Science.gov (United States)

    Matsuyanagi, Kenichi; Matsuo, Masayuki; Nakatsukasa, Takashi; Yoshida, Kenichi; Hinohara, Nobuo; Sato, Koichi

    2016-06-01

    We discuss the nature of the low-frequency quadrupole vibrations from small-amplitude to large-amplitude regimes. We consider full five-dimensional quadrupole dynamics including three-dimensional rotations restoring the broken symmetries as well as axially symmetric and asymmetric shape fluctuations. Assuming that the time evolution of the self-consistent mean field is determined by five pairs of collective coordinates and collective momenta, we microscopically derive the collective Hamiltonian of Bohr and Mottelson, which describes low-frequency quadrupole dynamics. We show that the five-dimensional collective Schrödinger equation is capable of describing large-amplitude quadrupole shape dynamics seen as shape coexistence/mixing phenomena. We summarize the modern concepts of microscopic theory of large-amplitude collective motion, which is underlying the microscopic derivation of the Bohr-Mottelson collective Hamiltonian.

  5. Microscopic derivation of the Bohr-Mottelson collective Hamiltonian and its application to quadrupole shape dynamics

    CERN Document Server

    Matsuyanagi, Kenichi; Nakatsukasa, Takashi; Yoshida, Kenichi; Hinohara, Nobuo; Sato, Koichi

    2016-01-01

    We discuss the nature of the low-frequency quadrupole vibrations from small-amplitude to large-amplitude regimes. We consider full five-dimensional quadrupole dynamics including three-dimensional rotations restoring the broken symmetries as well as axially symmetric and asymmetric shape fluctuations. Assuming that the time-evolution of the self-consistent mean field is determined by five pairs of collective coordinates and collective momenta, we microscopically derive the collective Hamiltonian of Bohr and Mottelson, which describes low-frequency quadrupole dynamics. We show that the five-dimensional collective Schr\\"odinger equation is capable of describing large-amplitude quadrupole shape dynamics seen as shape coexistence/mixing phenomena. We summarize the modern concepts of microscopic theory of large-amplitude collective motion, which is underlying the microscopic derivation of the Bohr-Mottelson collective Hamiltonian.

  6. Dynamic shaping of dopamine signals during probabilistic Pavlovian conditioning.

    Science.gov (United States)

    Hart, Andrew S; Clark, Jeremy J; Phillips, Paul E M

    2015-01-01

    Cue- and reward-evoked phasic dopamine activity during Pavlovian and operant conditioning paradigms is well correlated with reward-prediction errors from formal reinforcement learning models, which feature teaching signals in the form of discrepancies between actual and expected reward outcomes. Additionally, in learning tasks where conditioned cues probabilistically predict rewards, dopamine neurons show sustained cue-evoked responses that are correlated with the variance of reward and are maximal to cues predicting rewards with a probability of 0.5. Therefore, it has been suggested that sustained dopamine activity after cue presentation encodes the uncertainty of impending reward delivery. In the current study we examined the acquisition and maintenance of these neural correlates using fast-scan cyclic voltammetry in rats implanted with carbon fiber electrodes in the nucleus accumbens core during probabilistic Pavlovian conditioning. The advantage of this technique is that we can sample from the same animal and recording location throughout learning with single trial resolution. We report that dopamine release in the nucleus accumbens core contains correlates of both expected value and variance. A quantitative analysis of these signals throughout learning, and during the ongoing updating process after learning in probabilistic conditions, demonstrates that these correlates are dynamically encoded during these phases. Peak CS-evoked responses are correlated with expected value and predominate during early learning while a variance-correlated sustained CS signal develops during the post-asymptotic updating phase.

  7. The effect of shockwave profile shape on dynamic brittle failure

    Directory of Open Access Journals (Sweden)

    Gray G.T.

    2012-08-01

    Full Text Available The role of shock wave loading profile is investigated for the failure processes in a brittle material. The dynamic damage response of ductile metals has been demonstrated to be critically dependent on the shockwave profile and the stress-state of the shock. Changing from a square to triangular (Taylor profile with an identical peak compressive stress has been reported to increase the “spall strength” by over a factor of two and suppress damage mechanisms. The spall strength of tungsten heavy alloy (WHA based on plate impact square-wave loading has been extensively reported in the literature. Here a triangular wave loading profile is achieved with a composite flyer plate of graded density in contrast to the square-wave loading. Counter to the strong dependence in wave profile in ductile metals, for WHA, both square and triangle wave profiles the failure is by brittle cleavage fracture with additional energy dissipation through crack branching in the more brittle tungsten particles, largely indistinguishable between wave profiles. The time for crack nucleation is negligible compared to the duration of the experiment and the crack propagation rate is limited to the sound speed as defined by the shock velocity.

  8. Shape memory alloys applied to improve rotor-bearing system dynamics - an experimental investigation

    DEFF Research Database (Denmark)

    Enemark, Søren; Santos, Ilmar; Savi, Marcelo A.

    2015-01-01

    tor-bearing systems have critical speeds and to pass through them is an ongoing challenge in the field of mechanical engineering. The incorporation of shape memory alloys in rotating systems has an increasing importance to improve system performance and to avoid potential damaging situations when...... passing through critical speeds. In this work, the feasibility of applying shape memory alloys to a rotating system is experimentally investigated. Shape memory alloys can change their stiffness with temperature variations and thus they may change system dynamics. Shape memory alloys also exhibit...... hysteretic stress-strain relations which may be utilized for damping purposes. These ideas are tested in this study on a dedicated test-rig, consisting of a rigid shaft and disc held vertically by passive magnetic bearings, where the damping is low. The bearing housings is flexibly supported by shape memory...

  9. Dynamics and shapes of ferrofluid drops under spatially uniform magnetic fields

    Science.gov (United States)

    Rowghanian, Payam; Serwane, Friedhelm; Kealhofer, David; Meinhart, Carl D.; Campas, Otger

    2016-11-01

    We study the shape and dynamics of a Newtonian ferrofluid drop immersed in a Newtonian and non-magnetic viscous fluid under the action of a uniform external magnetic field. We obtain the exact equilibrium drop shapes for arbitrary ferrofluids which describe unexplained previous experiments, characterize the extent of deviations of the exact shape from the commonly assumed ellipsoidal shape, and analyze the smoothness of highly curved tips in elongated drops. We present a comprehensive study of drop deformation for a Langevin ferrofluid. Using a computational scheme that allows fast and accurate simulations of ferrofluid drop dynamics, we show that the dynamics of drop deformation by an applied magnetic field is described up to a numerical factor by the same time scale as drop relaxation in the absence of any magnetic field. The numerical factor depends on the ratio of viscosities and the ratio of magnetic to capillary stresses, but is independent of the nature of the ferrofluid in most practical cases. Finally, we use the shape and dynamics of the magnetic drops to measure the rheology of complex fluids.

  10. Gender and weight shape brain dynamics during food viewing.

    Directory of Open Access Journals (Sweden)

    Ulrike Toepel

    Full Text Available Hemodynamic imaging results have associated both gender and body weight to variation in brain responses to food-related information. However, the spatio-temporal brain dynamics of gender-related and weight-wise modulations in food discrimination still remain to be elucidated. We analyzed visual evoked potentials (VEPs while normal-weighted men (n = 12 and women (n = 12 categorized photographs of energy-dense foods and non-food kitchen utensils. VEP analyses showed that food categorization is influenced by gender as early as 170 ms after image onset. Moreover, the female VEP pattern to food categorization co-varied with participants' body weight. Estimations of the neural generator activity over the time interval of VEP modulations (i.e. by means of a distributed linear inverse solution [LAURA] revealed alterations in prefrontal and temporo-parietal source activity as a function of image category and participants' gender. However, only neural source activity for female responses during food viewing was negatively correlated with body-mass index (BMI over the respective time interval. Women showed decreased neural source activity particularly in ventral prefrontal brain regions when viewing food, but not non-food objects, while no such associations were apparent in male responses to food and non-food viewing. Our study thus indicates that gender influences are already apparent during initial stages of food-related object categorization, with small variations in body weight modulating electrophysiological responses especially in women and in brain areas implicated in food reward valuation and intake control. These findings extend recent reports on prefrontal reward and control circuit responsiveness to food cues and the potential role of this reactivity pattern in the susceptibility to weight gain.

  11. Femtosecond dynamics of fundamental reaction processes in liquids: Proton transfer, geminate recombination, isomerization and vibrational relaxation. [Spiropyrans

    Energy Technology Data Exchange (ETDEWEB)

    Schwartz, B.J.

    1992-11-01

    The fast excited state intramolecular proton transfer of 3-hydroxyflavone is measured and effects of external hydrogen-bonding interactions on the proton transfer are studied. The proton transfer takes place in [approximately]240 fsec in nonpolar environments, but becomes faster than instrumental resolution of 110 fsec in methanol solution. The dynamics following photodissociation of CH[sub 2]I[sub 2] and other small molecules provide the first direct observations of geminate recombination. The recombination of many different photodissociating species occurs on a [approximately]350 fsec time scale. Results show that recombination yields but not rates depend on the solvent environment and suggest that recombination kinetics are dominated by a single collision with surrounding solvent cage. Studies of sterically locked phenyl-substituted butadienes offer new insights into the electronic structure and isomerization behavior of conjugated polyenes. Data show no simple correlation between hinderance of specific large amplitude motions and signatures of isomerizative behavior such as viscosity dependent excited state lifetimes, implying that the isomerization does not provide a suitable for simple condensed phase reaction rate theories. The spectral dynamics of a photochromic spiropyran indicate that recombination, isomerization and vibrational relaxation all play important roles in photoreactivity of complex molecules. The interplay of these microscopic phenomena and their effect on macroscopic properties such as photochromism are discussed. All the results indicate that the initial steps of the photochromic reaction process occur extremely rapidly. Laser system and computer codes for data analysis are discussed.

  12. Recombination Dynamics in Thin-film Photovoltaic Materials via Time-resolved Microwave Conductivity.

    Science.gov (United States)

    Guse, Joanna A; Jones, Timothy W; Danos, Andrew; McCamey, Dane R

    2017-03-06

    A method for investigating recombination dynamics of photo-induced charge carriers in thin film semiconductors, specifically in photovoltaic materials such as organo-lead halide perovskites is presented. The perovskite film thickness and absorption coefficient are initially characterized by profilometry and UV-VIS absorption spectroscopy. Calibration of both laser power and cavity sensitivity is described in detail. A protocol for performing Flash-photolysis Time Resolved Microwave Conductivity (TRMC) experiments, a non-contact method of determining the conductivity of a material, is presented. A process for identifying the real and imaginary components of the complex conductivity by performing TRMC as a function of microwave frequency is given. Charge carrier dynamics are determined under different excitation regimes (including both power and wavelength). Techniques for distinguishing between direct and trap-mediated decay processes are presented and discussed. Results are modelled and interpreted with reference to a general kinetic model of photoinduced charge carriers in a semiconductor. The techniques described are applicable to a wide range of optoelectronic materials, including organic and inorganic photovoltaic materials, nanoparticles, and conducting/semiconducting thin films.

  13. Dynamic Solvent Effect on Ultrafast Charge Recombination Kinetics in Excited Donor-Acceptor Complexes.

    Science.gov (United States)

    Mikhailova, Tatyana V; Mikhailova, Valentina A; Ivanov, Anatoly I

    2016-11-23

    Manifestation of the dynamic solvent effect (DSE) on the charge recombination (CR) kinetics of photoexcited donor-acceptor complexes in polar solvents has been investigated within the framework of the multichannel stochastic model. The model takes into account the reorganization of both the solvent and a number of intramolecular high-frequency vibration modes as well as their relaxation. The non-Markovian solvent dynamics is described in terms of two relaxation modes. The similarities and differences inherent to ultrafast charge transfer reactions occurring in the nonequilibrium and thermal regimes have been identified. The most important differences are as follows: (1) the DSE is strong in the area of weak exergonicity and is weak in the area of strong exergonicity for thermal reactions, whereas for the nonequilibrium reactions, the regions of strong and weak DSEs are reversed; (2) an increase in the electronic coupling value results in a decrease in the magnitude of DSE for nonequilibrium electron transfer and in its increase for the thermal reactions; and (3) the two-staged regime most clearly manifests if the reorganization energy of the relaxation modes noticeably exceeds the CR free-energy gap. With an increase in electronic coupling, the kinetics approaches the exponential regime because in the limit of strong electronic coupling, the reaction includes only single, nonequilibrium, stage.

  14. Microbial community dynamics in soil aggregates shape biogeochemical gas fluxes from soil profiles

    Science.gov (United States)

    Ebrahimi, Ali; Or, Dani

    2016-04-01

    Microbial communities inhabiting soil aggregates dynamically adjust their activity and composition in response to variations in hydration and other external conditions. These rapid dynamics shape signatures of biogeochemical activity and gas fluxes emitted from soil profiles. Mechanistic models of microbial processes in unsaturated aggregate pore networks revealed dynamic interplay between oxic and anoxic microsites that are jointly shaped by hydration and by aerobic and anaerobic microbial communities. The spatial extent of anoxic niches (hotspots) flicker in time (hot moments) and support significant anaerobic microbial activity even in aerated soil profiles. We employed an individual-based model for microbial community life in soil aggregate assemblies represented by 3-D angular pore networks with profiles of water, carbon, and oxygen that vary with soil depth as boundary conditions. The study integrates microbial activity within aggregates of different sizes and soil depth to obtain biogeochemical fluxes over the soil profile. The results quantify impacts of dynamic shifts in microbial community composition on CO2 and N2O production rates in soil profiles in good agreement with experimental data. Aggregate size distribution and the shape of resource profiles in a soil determine how hydration dynamics shape denitrification and carbon utilization rates. Results from the mechanistic model for microbial activity in aggregates of different sizes were used to derive parameters for analytical representation of soil biogeochemical processes across large scales of interest for hydrological and climate models.

  15. Solution dynamics by line shape analysis, resonance light scattering and femtosecond four-wave mixing

    NARCIS (Netherlands)

    Nibbering, Erik T.J.; Duppen, Koos; Wiersma, Douwe A.

    1992-01-01

    The results of line shape analysis, resonance light scattering and femtosecond four-wave mixing measurements are reported on several organic molecules in solution. It is shown that a Brownian oscillator model for line broadening provides a full description for the optical dynamics in aprotic solutio

  16. Triggering cell adhesion, migration or shape change with a dynamic surface coating.

    Science.gov (United States)

    van Dongen, Stijn F M; Maiuri, Paolo; Marie, Emmanuelle; Tribet, Christophe; Piel, Matthieu

    2013-03-25

    There's an APP for that: cell-repellent APP (azido-[polylysine-g-PEG]) is used to create substrates for spatially controlled dynamic cell adhesion. The simple addition of a functional peptide to the culture medium rapidly triggers cell adhesion. This highly accessible yet powerful technique allows diverse applications, demonstrated through tissue motility assays, patterned coculturing and triggered cell shape change.

  17. Shape-Tunable Charge Carrier Dynamics at the Interfaces between Perovskite Nanocrystals and Molecular Acceptors

    KAUST Repository

    Ahmed, Ghada H.

    2016-09-19

    Hybrid organic/inorganic perovskites have recently emerged as an important class of materials and have exhibited remarkable performance in photovoltaics. To further improve their device efficiency, an insightful understanding of the interfacial charge transfer (CT) process is required. Here, we report the first direct experimental observation of the tremendous effect that the shape of perovskite nanocrystals (NCs) has on interfacial CT in the presence of a molecular acceptor. A dramatic change in CT dynamics at the interfaces of three different NC shapes, spheres, platelets, and cubes, is recorded. Our results clearly demonstrate that the mechanism of CT is significantly affected by the NC shape. More importantly, the results demonstrate that complexation on the NC surface acts as an additional driving force not only to tune the CT dynamics but also to control the reaction mechanism at the interface. This observation opens a new venue for further developing perovskite NCs-based applications.

  18. Modulation measuring profilometry with cross grating projection and single shot for dynamic 3D shape measurement

    Science.gov (United States)

    Lu, Mingteng; Su, Xianyu; Cao, Yiping; You, Zhisheng; Zhong, Min

    2016-12-01

    In order to determine Dynamic 3-D shape with vertical measurement mode, a fast modulation measuring profilometry (MMP) with a cross grating projection and single shot is proposed. Unlike the previous methods, in our current projection system, one cross grating is projected by a special projection lens consisting of a common projection lens and a cylindrical lens. Due to the characteristics of cylindrical lens, the image of the vertical component and the horizontal component of the cross grating is separated in the image space, and the measuring range is just the space between the two image planes. Through a beam splitter, the CCD camera can coaxially capture the fringe pattern of the cross grating modulated by the testing object's shape. In one fringe pattern, by applying Fourier transform, filtering and inverse Fourier transform, the modulation corresponding to the vertical and horizontal components of the cross grating can be obtained respectively. Then the 3-D shape of the object can be reconstructed according to the mapping relationship between modulation and height, which was established by calibration process in advance. So the 3-D shape information can be recorded at the same speed of the frame rate of the CCD camera. This paper gives the principle of the proposed method and the set-up for measuring experiment and system calibration. The 3-D shape of a still object and a dynamic process of liquid vortex were measured and reconstructed in the experiments, and the results proved the method's feasibility. The advantage of the proposed method is that only one fringe pattern is needed to extract the modulation distribution and to reconstruct the 3-D shape of the object. Therefore, the proposed method can achieve high speed measurement and vertical measurement without shadow and occlusion. It can be used in the dynamic 3-D shape measurement and vibration analysis.

  19. Nonspherical dynamics and shape mode stability of ultrasound contrast agent microbubbles

    Science.gov (United States)

    Calvisi, Michael

    2016-11-01

    Ultrasound contrast agents (UCAs) are shell encapsulated microbubbles developed originally for ultrasound imaging enhancement. UCAs are more recently being exploited for therapeutic applications, such as for drug delivery, gene therapy, and tissue ablation. Ultrasound transducer pulses can induce spherical (radial) UCA oscillations, translation, and nonspherical shape oscillations, the dynamics of which are highly coupled. If driven sufficiently strongly, the ultrasound can induce breakup of UCAs, which can facilitate drug or gene delivery but should be minimized for imaging purposes to increase residence time and maximize diagnostic effect. Therefore, an understanding of the interplay between the acoustic driving and nonspherical shape mode stability of UCAs is essential for both diagnostic and therapeutic applications. In this work, we use both analytical and numerical methods to analyze shape mode stability for cases of small and large nonspherical oscillations, respectively. To analyze shape mode stability in the limit of small nonspherical perturbations, we couple a radial model of a lipid-coated microbubble with a model for bubble translation and nonspherical shape oscillation. This hybrid model is used to predict shape mode stability for ultrasound driving frequencies and pressure amplitudes of clinical interest. In addition, calculations of the stability of individual shape modes, residence time, maximum radius, and translation are provided with respect to acoustic driving parameters and compared to an unshelled bubble. The effects of shell elasticity, shell viscosity, and initial radius on stability are investigated. Furthermore, the well-established boundary element method (BEM) is used to investigate the dynamics and shape stability of large amplitude nonspherical oscillations of an ultrasonically-forced, polymer-coated microbubble near a rigid boundary. Different instability modes are identified based on the degree of jetting and proximity to the

  20. Ultrafast Dynamics of Hole Injection and Recombination in Organometal Halide Perovskite Using Nickel Oxide as p-Type Contact Electrode.

    Science.gov (United States)

    Corani, Alice; Li, Ming-Hsien; Shen, Po-Shen; Chen, Peter; Guo, Tzung-Fang; El Nahhas, Amal; Zheng, Kaibo; Yartsev, Arkady; Sundström, Villy; Ponseca, Carlito S

    2016-04-01

    There is a mounting effort to use nickel oxide (NiO) as p-type selective electrode for organometal halide perovskite-based solar cells. Recently, an overall power conversion efficiency using this hole acceptor has reached 18%. However, ultrafast spectroscopic investigations on the mechanism of charge injection as well as recombination dynamics have yet to be studied and understood. Using time-resolved terahertz spectroscopy, we show that hole transfer is complete on the subpicosecond time scale, driven by the favorable band alignment between the valence bands of perovskite and NiO nanoparticles (NiO(np)). Recombination time between holes injected into NiO(np) and mobile electrons in the perovskite material is shown to be hundreds of picoseconds to a few nanoseconds. Because of the low conductivity of NiO(np), holes are pinned at the interface, and it is electrons that determine the recombination rate. This recombination competes with charge collection and therefore must be minimized. Doping NiO to promote higher mobility of holes is desirable in order to prevent back recombination.

  1. Undrained dynamical behavior of Nanjing flake-shaped fine sand under cyclic loading

    Institute of Scientific and Technical Information of China (English)

    陈国兴; 刘雪珠; 战吉艳

    2008-01-01

    A series of dynamic behavior tests on Nanjing flake-shaped fine sand were performed by using the WFI cyclic triaxial apparatus made in England. The dynamic behaviors of Nanjing flake-shaped fine sand under different static deviator stress levels and cyclic stress ratios were studied. Through comparing the effective stress path under cyclic loading with static loading, the processes of liquefaction of saturated Nanjing flake-shaped fine sand with development of dynamic pore-water pressure, including the initial compact state, compression state and dilative state, were investigated. The variation of the shear stiffness with the number of cycles and cyclic strain was investigated by analyzing the secant shear modulus in each unload-reload loop of dynamic stress-strain relationship. And by means of the exponential function, the empirical equations of the relationship between secant shear modulus Gsec, shear modulus ratio Gsec/Gmax and cyclic strain ε were established based on series of test results. The results show that according to different combinations of static deviator stress and cyclic stress, two kinds of failure patterns with deviator stress reversal or no deviator stress reversal are observed in the samples tested in this series, including cyclic mobility and the failure of accumulation residual strain. In addition, the degradation of dynamic shear modulus is due to the development of vibration pore-water pressure and it is observed that the shear modulus reduces with the progressive number of cycles.

  2. Connectivity and dynamics of neuronal networks as defined by the shape of individual neurons

    Energy Technology Data Exchange (ETDEWEB)

    Ahnert, Sebastian E [Theory of Condensed Matter, Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE (United Kingdom); A N Travencolo, Bruno; Costa, Luciano da Fontoura [Instituto de FIsica de Sao Carlos, Universidade de Sao Paulo, Av. Trabalhador Sao Carlense 400, Caixa Postal 369, CEP 13560-970, Sao Carlos, Sao Paulo (Brazil)], E-mail: luciano@if.sc.usp.br

    2009-10-15

    Biological neuronal networks constitute a special class of dynamical systems, as they are formed by individual geometrical components, namely the neurons. In the existing literature, relatively little attention has been given to the influence of neuron shape on the overall connectivity and dynamics of the emerging networks. The current work addresses this issue by considering simplified neuronal shapes consisting of circular regions (soma/axons) with spokes (dendrites). Networks are grown by placing these patterns randomly in the two-dimensional (2D) plane and establishing connections whenever a piece of dendrite falls inside an axon. Several topological and dynamical properties of the resulting graph are measured, including the degree distribution, clustering coefficients, symmetry of connections, size of the largest connected component, as well as three hierarchical measurements of the local topology. By varying the number of processes of the individual basic patterns, we can quantify relationships between the individual neuronal shape and the topological and dynamical features of the networks. Integrate-and-fire dynamics on these networks is also investigated with respect to transient activation from a source node, indicating that long-range connections play an important role in the propagation of avalanches.

  3. Thickness and Shape Synthetical Adjustment for DC Mill Based on Dynamic Nerve-Fuzzy Control

    Institute of Scientific and Technical Information of China (English)

    JIA Chun-yu; WANG Ying-rui; ZHOU Hui-feng

    2004-01-01

    Due to the complexity of thickness and shape synthetical adjustment system and the difficulties to build a mathematical model, a thickness and shape synthetical adjustment scheme on DC mill based on dynamic nerve-fuzzy control was put forward, and a self-organizing fuzzy control model was established. The structure of the network can be optimized dynamically. In the course of studying, the network can automatically adjust its structure based on the specific questions and make its structure the optimal. The input and output of the network are fuzzy sets, and the trained network can complete the composite relation, the fuzzy inference. For decreasing the off-line training time of BP network, the fuzzy sets are encoded. The simulation results indicate that the self-organizing fuzzy control based on dynamic neural network is better than traditional decoupling PID control.

  4. Ultrafast Charge Recombination Dynamics in Ternary Electron Donor-Acceptor Complexes: (Benzene)2-Tetracyanoethylene Complexes.

    Science.gov (United States)

    Chiu, Chih-Chung; Hung, Chih-Chang; Cheng, Po-Yuan

    2016-12-08

    The charge-transfer (CT) state relaxation dynamics of the binary (1:1) and ternary (2:1) benzene/tetracyanoethylene (BZ/TCNE) complexes are reported. Steady-state and ultrafast time-resolved broadband fluorescence (TRFL) spectra of TCNE dissolved in a series of BZ/CCl4 mixed solvents are measured to elucidate the spectroscopic properties of the BZ/TCNE complexes and their CT-state relaxation dynamics. Both steady-state and TRFL spectra exhibit marked BZ concentration dependences, which can be attributed to the formation of two types of 2:1 complexes in the ground and excited states. By combining with the density functional theory (DFT) calculations, it was concluded that the BZ concentration dependence of the absorption spectra is mainly due to the formation and excitation of the sandwich-type 2:1 ternary complexes, whereas the changes in fluorescence spectra at high BZ concentrations are due to the formation of the asymmetric-type 2:1 ternary complex CT1 state. A unified mechanism involving both direct excitation and secondary formation of the 2:1 complexes CT states are proposed to account for the observations. The equilibrium charge recombination (CR) time constant of the 1:1 CT1 state is determined to be ∼150 ps in CCl4, whereas that of the 2:1 DDA-type CT1 state becomes ∼70 ps in 10% BZ/CCl4 and ∼34 ps in pure BZ. The CR rates and the CT1-S0 energy gap of these complexes in different solvents exhibit a correlation conforming to the Marcus inverted region. It is concluded that partial charge resonance occurring between the two adjacent BZs in the asymmetric-type 2:1 CT1-state reduces the CR reaction exothermicity and increases the CR rate.

  5. Dynamic Error Analysis Method for Vibration Shape Reconstruction of Smart FBG Plate Structure

    Directory of Open Access Journals (Sweden)

    Hesheng Zhang

    2016-01-01

    Full Text Available Shape reconstruction of aerospace plate structure is an important issue for safe operation of aerospace vehicles. One way to achieve such reconstruction is by constructing smart fiber Bragg grating (FBG plate structure with discrete distributed FBG sensor arrays using reconstruction algorithms in which error analysis of reconstruction algorithm is a key link. Considering that traditional error analysis methods can only deal with static data, a new dynamic data error analysis method are proposed based on LMS algorithm for shape reconstruction of smart FBG plate structure. Firstly, smart FBG structure and orthogonal curved network based reconstruction method is introduced. Then, a dynamic error analysis model is proposed for dynamic reconstruction error analysis. Thirdly, the parameter identification is done for the proposed dynamic error analysis model based on least mean square (LMS algorithm. Finally, an experimental verification platform is constructed and experimental dynamic reconstruction analysis is done. Experimental results show that the dynamic characteristics of the reconstruction performance for plate structure can be obtained accurately based on the proposed dynamic error analysis method. The proposed method can also be used for other data acquisition systems and data processing systems as a general error analysis method.

  6. Nuclear dynamics of RAD52 group homologous recombination proteins in response to DNA damage.

    NARCIS (Netherlands)

    J. Essers (Jeroen); A.B. Houtsmuller (Adriaan); L.R. van Veelen (Lieneke); C. Paulusma (Coen); A.L. Nigg (Alex); A. Pastink (Albert); W. Vermeulen (Wim); J.H.J. Hoeijmakers (Jan); R. Kanaar (Roland)

    2002-01-01

    textabstractRecombination between homologous DNA molecules is essential for the proper maintenance and duplication of the genome, and for the repair of exogenously induced DNA damage such as double-strand breaks. Homologous recombination requires the RAD52 group proteins, including Rad51, Rad52 and

  7. Effect of the Shape Factor on the Cold-Spraying Dynamic Characteristics of Sprayed Particles

    Science.gov (United States)

    Song, Jun; Liu, Juanfang; Chen, Qinghua; Li, Kepin

    2017-09-01

    Silicon powder was chosen to be deposited by cold spraying for the consideration of possible applications in lithium ion batteries. The influence of the silicon particle shapes other than spherical on the impact velocity and temperature for different working parameters of the gas streams have been numerically investigated by using computational fluid dynamics modeling. The results show that, for same equivalent diameter, the particle impact velocities increase to a maximum velocity when the shape factor increases to a certain value and then decreases to the impact velocity of spherical particles. In the cold-spraying process, the particle velocity profile for smaller shape factors is much closer to that of the gas stream due to the larger particle surface area. Furthermore, the particle impact velocity increment for smaller shape factors is much more remarkable with a higher main propulsion gas temperature and higher carrier gas pressure. The effect of raising the main propulsion gas pressure on the impact velocity of the particles with very smaller shape factors is negligible. The particle impact velocity and temperature can be altered by not only the change of the working parameters of the gas steams but also the change of the sizes and shapes of the sprayed particles.

  8. H-shaped supra-amphiphiles based on a dynamic covalent bond.

    Science.gov (United States)

    Wang, Guangtong; Wang, Chao; Wang, Zhiqiang; Zhang, Xi

    2012-10-16

    The imine bond, a kind of dynamic covalent bond, is used to bind two bolaform amphiphiles together with spacers, yielding H-shaped supra-amphiphiles. Micellar aggregates formed by the self-assembly of the H-shaped supra-amphiphiles are observed. When pH is tuned down from basic to slightly acidic, the benzoic imine bond can be hydrolyzed, leading to the dissociation of H-shaped supra-amphiphiles. Moreover, H-shaped supra-amphiphiles have a lower critical micelle concentration than their building blocks, which is very helpful in enhancing the stability of the benzoic imine bond being hydrolyzed by acid. The surface tension isotherms of the H-shaped supra-amphiphiles with different spacers indicate their twisty conformation at a gas-water interface. The study of H-shaped supra-amphiphiles can enrich the family of amphiphiles, and moreover, the pH-responsiveness may make them apply to controlled or targetable drug delivery in a biological environment.

  9. Growth and shape modelling of the rabbit tibia: study of the dynamics of developing skeleton.

    Science.gov (United States)

    Pazzaglia, U E; Zarattini, G; Spagnuolo, F; Superti, G; Marchese, M

    2012-06-01

    The proliferative impulse of the growth plate cartilage and related structures and its effect on the dimensions of long bones are well documented. The modulation of shape, however, is less known, and in general, it is referred to the coupled resorption/apposition process of bone modelling. A morphometric study was carried out on rabbit tibiae comparing size increments and shape changes in relation to age. Utilizing measurements made using dried bones, radiography and computerized tomography, it was possible to perform a three-dimensional analysis of shape modulation occurring during a period of growth extending from 3 months to 1 year of age. The dynamics of the shape changes related to growth were studied with a fluorescent tetracycline labelling. This enabled correlation of shape modulation with the 3-D distribution of apposition and resorption. The current thinking behind the influences and mechanical forces affecting bone architecture was discussed in the light of these findings. Several factors play a role in the structural organization of the human and upper vertebrates' skeleton, whose shape is genetically determined in the complex process usually referred as 'modelling'. This does not conflict with the existing evidence of remodelling being influenced by mechanical stimuli, but the unsolved question remains how physical forces (strains) act on the biological substrate of cartilage and bone cells.

  10. Ultrafast carrier dynamics and radiative recombination in multiferroic BiFeO3 single crystals and thin films

    Directory of Open Access Journals (Sweden)

    Taylor A. J.

    2013-03-01

    Full Text Available We report a detailed comparison of ultrafast carrier dynamics in single crystals and thin films of multiferroic BiFeO3 (BFO. Using degenerate femtosecond optical pump-probe spectroscopy, we find that the observed dynamics are qualitatively similar in both samples. After photoexcitation, electrons relax to the conduction band minimum through electron-phonon coupling, with subsequent carrier relaxation proceeding via various recombination pathways that extend to a nanosecond timescale. Subtle differences observed in our measurements indicate that BFO films have a higher band gap than single crystals. Overall, our results demonstrate that carrier relaxation in BFO is analogous to that in bulk semiconductors.

  11. The population and evolutionary dynamics of homologous gene recombination in bacterial populations.

    Directory of Open Access Journals (Sweden)

    Bruce R Levin

    2009-08-01

    Full Text Available In bacteria, recombination is a rare event, not a part of the reproductive process. Nevertheless, recombination -- broadly defined to include the acquisition of genes from external sources, i.e., horizontal gene transfer (HGT -- plays a central role as a source of variation for adaptive evolution in many species of bacteria. Much of niche expansion, resistance to antibiotics and other environmental stresses, virulence, and other characteristics that make bacteria interesting and problematic, is achieved through the expression of genes and genetic elements obtained from other populations of bacteria of the same and different species, as well as from eukaryotes and archaea. While recombination of homologous genes among members of the same species has played a central role in the development of the genetics and molecular biology of bacteria, the contribution of homologous gene recombination (HGR to bacterial evolution is not at all clear. Also, not so clear are the selective pressures responsible for the evolution and maintenance of transformation, the only bacteria-encoded form of HGR. Using a semi-stochastic simulation of mutation, recombination, and selection within bacterial populations and competition between populations, we explore (1 the contribution of HGR to the rate of adaptive evolution in these populations and (2 the conditions under which HGR will provide a bacterial population a selective advantage over non-recombining or more slowly recombining populations. The results of our simulation indicate that, under broad conditions: (1 HGR occurring at rates in the range anticipated for bacteria like Streptococcus pneumoniae, Escherichia coli, Haemophilus influenzae, and Bacillus subtilis will accelerate the rate at which a population adapts to environmental conditions; (2 once established in a population, selection for this capacity to increase rates of adaptive evolution can maintain bacteria-encoded mechanisms of recombination and prevent

  12. Efficiency Enhancement of an Envelope Tracking Power Amplifier Combining Supply Shaping and Dynamic Biasing

    DEFF Research Database (Denmark)

    Tafuri, Felice Francesco; Sira, Daniel; Jensen, Ole Kiel

    2013-01-01

    This paper presents a new method to improve the performance of envelope tracking (ET) power amplifiers (PAs). The method consists of combining the supply modulation that characterizes the envelope tracking architecture with supply shaping and dynamic biasing. The inclusion of dynamic biasing allows...... of the input envelope by means of two shaping functions jointly designed on the basis of a single-tone characterization. The presented technique is demonstrated by means of measurements on a commercial GaAs HBT power amplifier. Measured results showed a PA power added efficiency (PAE) of 51.9%, an error vector...... magnitude (EVM) of 1.2% and an adjacent channel power ratio (ACPR) of -39.4/-43.5 dBc. The presented transmitter architecture allowed an improvement of 12% PAE compared to a classical ET transmitter where the measured PA was biased in class-AB, maintaining the linearity indicators....

  13. Stimuli-Responsive Reversible Two-Level Adhesion from a Structurally Dynamic Shape-Memory Polymer.

    Science.gov (United States)

    Michal, Brian T; Spencer, Emily J; Rowan, Stuart J

    2016-05-01

    A shape-memory adhesive has been prepared that exhibits two levels of reversible adhesion. The adhesive is a semicrystalline cross-linked polymer that contains dynamic disulfide bonds. Melting of the crystalline regions via heat causes a drop in the modulus of the material facilitating wetting of the substrate as well as enhancing the surface contact area with the substrate, which result in the formation of an adhesive bond. Exposure to higher heat or UV light results in dynamic exchange of the disulfide bonds, which yields a further drop in the modulus/viscosity that improves surface wetting/contact and strengthens the adhesive bond. This improvement in adhesion is shown to apply over different substrates, contact forces, and deformation modes. Furthermore, the adhesive acts as a thermal shape-memory material and can be used to create joints that can reposition themselves upon application of heat.

  14. Dynamics of cell shape and forces on micropatterned substrates predicted by a cellular Potts model.

    Science.gov (United States)

    Albert, Philipp J; Schwarz, Ulrich S

    2014-06-03

    Micropatterned substrates are often used to standardize cell experiments and to quantitatively study the relation between cell shape and function. Moreover, they are increasingly used in combination with traction force microscopy on soft elastic substrates. To predict the dynamics and steady states of cell shape and forces without any a priori knowledge of how the cell will spread on a given micropattern, here we extend earlier formulations of the two-dimensional cellular Potts model. The third dimension is treated as an area reservoir for spreading. To account for local contour reinforcement by peripheral bundles, we augment the cellular Potts model by elements of the tension-elasticity model. We first parameterize our model and show that it accounts for momentum conservation. We then demonstrate that it is in good agreement with experimental data for shape, spreading dynamics, and traction force patterns of cells on micropatterned substrates. We finally predict shapes and forces for micropatterns that have not yet been experimentally studied. Copyright © 2014 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  15. Dynamic metabolomics differentiates between carbon and energy starvation in recombinant Saccharomyces cerevisiae fermenting xylose

    Directory of Open Access Journals (Sweden)

    Bergdahl Basti

    2012-05-01

    Full Text Available Abstract Background The concerted effects of changes in gene expression due to changes in the environment are ultimately reflected in the metabolome. Dynamics of metabolite concentrations under a certain condition can therefore give a description of the cellular state with a high degree of functional information. We used this potential to evaluate the metabolic status of two recombinant strains of Saccharomyces cerevisiae during anaerobic batch fermentation of a glucose/xylose mixture. Two isogenic strains were studied, differing only in the pathways used for xylose assimilation: the oxidoreductive pathway with xylose reductase (XR and xylitol dehydrogenase (XDH or the isomerization pathway with xylose isomerase (XI. The isogenic relationship between the two strains ascertains that the observed responses are a result of the particular xylose pathway and not due to unknown changes in regulatory systems. An increased understanding of the physiological state of these strains is important for further development of efficient pentose-utilizing strains for bioethanol production. Results Using LC-MS/MS we determined the dynamics in the concentrations of intracellular metabolites in central carbon metabolism, nine amino acids, the purine nucleotides and redox cofactors. The general response to the transition from glucose to xylose was increased concentrations of amino acids and TCA-cycle intermediates, and decreased concentrations of sugar phosphates and redox cofactors. The two strains investigated had significantly different uptake rates of xylose which led to an enhanced response in the XI-strain. Despite the difference in xylose uptake rate, the adenylate energy charge remained high and stable around 0.8 in both strains. In contrast to the adenylate pool, large changes were observed in the guanylate pool. Conclusions The low uptake of xylose by the XI-strain led to several distinguished responses: depletion of key metabolites in glycolysis and NADPH

  16. Gravitational collapse of thin shells of dust in asymptotically flat shape dynamics

    Science.gov (United States)

    Mercati, Flavio; Gomes, Henrique; Koslowski, Tim; Napoletano, Andrea

    2017-02-01

    In a recent paper, one of us studied spherically symmetric, asymptotically flat solutions of shape dynamics, finding that the spatial metric has characteristics of a wormhole—two asymptotically flat ends and a minimal-area sphere, or "throat," in between. In this paper, we investigate whether that solution can emerge as a result of gravitational collapse of matter. With this goal, we study the simplest kind of spherically symmetric matter: an infinitely-thin shell of dust. Our system can be understood as a model of a star accreting a thin layer of matter. We solve the dynamics of the shell exactly and find that, indeed, as it collapses, the shell leaves in its wake the wormhole metric. In the maximal-slicing time we use for asymptotically flat solutions, the shell only approaches the throat asymptotically and does not cross it in a finite amount of time (as measured by a clock "at infinity"). This leaves open the possibility that a more realistic cosmological solution of shape dynamics might see this crossing happening in a finite amount of time (as measured by the change of relational or shape degrees of freedom).

  17. Charge recombination kinetics and protein dynamics in wild type and carotenoid-less bacterial reaction centers: studies in trehalose glasses.

    Science.gov (United States)

    Francia, Francesco; Malferrari, Marco; Sacquin-Mora, Sophie; Venturoli, Giovanni

    2009-07-30

    The coupling between electron transfer and protein dynamics has been investigated in reaction centers (RCs) from the wild type (wt) and the carotenoid-less strain R26 of the photosynthetic bacterium Rhodobacter sphaeroides. Recombination kinetics between the primary photoreduced quinone acceptor (QA-) and photoxidized donor (P+) have been analyzed at room temperature in RCs incorporated into glassy trehalose matrices of different water/sugar ratios. As previously found in R26 RCs, also in the wt RC, upon matrix dehydration, P+QA- recombination accelerates and becomes broadly distributed, reflecting the inhibition of protein relaxation from the dark-adapted to the light-adapted conformation and the hindrance of interconversion between conformational substates. While in wet trehalose matrices (down to approximately one water per trehalose molecule) P+QA- recombination kinetics are essentially coincident in wt and R26 RCs, more extensive dehydration leads to two-times faster and more distributed kinetics in the carotenoid-containing RC, indicating a stronger inhibition of the internal protein dynamics in the wt RC. Coarse-grained Brownian dynamics simulations performed on the two RC structures reveal a markedly larger flexibility of the R26 RC, showing that a rigid core of residues, close to the quinone acceptors, is specifically softened in the absence of the carotenoid. These experimental and computational results concur to indicate that removal of the carotenoid molecule has long-range effects on protein dynamics and that the structural/dynamical coupling between the protein and the glassy matrix depends strongly upon the local mechanical properties of the protein interior. The data also suggest that the conformational change stabilizing P+QA- is localized around the QA binding pocket.

  18. Cytoskeletal dynamics and supracellular organisation of cell shape fluctuations during dorsal closure.

    Science.gov (United States)

    Blanchard, Guy B; Murugesu, Sughashini; Adams, Richard J; Martinez-Arias, Alfonso; Gorfinkiel, Nicole

    2010-08-01

    Fluctuations in the shape of amnioserosa (AS) cells during Drosophila dorsal closure (DC) provide an ideal system with which to understand contractile epithelia, both in terms of the cellular mechanisms and how tissue behaviour emerges from the activity of individual cells. Using quantitative image analysis we show that apical shape fluctuations are driven by the medial cytoskeleton, with periodic foci of contractile myosin and actin travelling across cell apices. Shape changes were mostly anisotropic and neighbouring cells were often, but transiently, organised into strings with parallel deformations. During the early stages of DC, shape fluctuations with long cycle lengths produced no net tissue contraction. Cycle lengths shortened with the onset of net tissue contraction, followed by a damping of fluctuation amplitude. Eventually, fluctuations became undetectable as AS cells contracted rapidly. These transitions were accompanied by an increase in apical myosin, both at cell-cell junctions and medially, the latter ultimately forming a coherent, but still dynamic, sheet across cells. Mutants with increased myosin activity or actin polymerisation exhibited precocious cell contraction through changes in the subcellular localisation of myosin. thick veins mutant embryos, which exhibited defects in the actin cable at the leading edge, showed similar timings of fluctuation damping to the wild type, suggesting that damping is an autonomous property of the AS. Our results suggest that cell shape fluctuations are a property of cells with low and increasing levels of apical myosin, and that medial and junctional myosin populations combine to contract AS cell apices and drive DC.

  19. Effects of chamber shape and fiber orientation on relations between fiber dynamics and chamber dynamics.

    Science.gov (United States)

    Regen, D M

    1988-01-01

    The function of a chamber depends on its hydrodynamic properties: isometric pressures it can exert in the operating range of distensions, compliances in the operating range of distensions, and wall-displacement resistances in the operating range of distensions. Wall-displacement resistance is the departure of pressure from isometric pressure relative to rate of cavity-volume change. The dependence of pressure on average stress and wall/cavity volume ratio is indifferent to chamber shape, which suggests that the volume-based compliance-elastance and resistance-viscosity equations would be only moderately shape dependent. The present study shows that this supposition is correct. If the wall is thin, these relations are shape indifferent. At higher wall/cavity volume ratio, cylindricity increases slightly the P-V-curve slope relative to elastance and either increases slightly or does not affect resistance relative to viscosity. The compliance-elastance and resistance-viscosity relations also depend only slightly on fiber orientation. Therefore, with the sphere equations, one can account accurately for normal and abnormal function of a prolate spheroid in terms of volume dimensions of the wall and apparent average fiber properties.

  20. Cross-Spectral Analysis of Earth's Geoid and Shape Reveals Dynamic Topography

    Science.gov (United States)

    Patton, R. L.; Menard, J.; Watkinson, A. J.

    2016-12-01

    Vertical deviations of the planet's surface due to large-scale dynamics should be expressed as topography measured with respect to an equipotential `level' surface, like the geoid. However, this dynamic effect must be separated from others affecting topography, such as isostatic compensation, effective rigidity, and enhancement via crustal deformation and volcanism. Conventional procedures used to isolate `dynamic topography' involve model-dependent corrections to Earth's shape, which introduce additional assumptions and uncertainties related to the density, strength, thickness, and thermal properties of crustal and mantle rock layers. Alternatively, global cross-spectral analysis of gravity and shape data offers a means of isolating the dynamic signal prior to the introduction of geophysical hypotheses. It is well-known that Earth's gravity and shape are poorly-correlated at long wavelengths. This is expressed in regional gravity disturbance maps as a low amplitude bias, the origin of which, although unknown, is reasonably associated with large-scale dynamics. This signal dominates the harmonic geoid, leading to the counter-intuitive observations that trenches and island arcs are associated with geoid highs, and that the Himalaya-Tibet plateau occupies a geoid low. Here it is shown that Earth's geoid-shape admittance exhibits a distinct change at spherical harmonic degree 13, from high-and-variable to low and nearly constant. This is coincident with a change in the gravity-topography degree correlation, from low-and-variable, to consistently above 0.57. Thus the `dynamic anomaly', defined as the 13th partial sum of the disturbance gravity field, exhibits a range of -82 to +56 mGal. Scaled by the mean surface gravity gradient of -0.3082 mGal/m, and referenced to the harmonic geoid, a long-wavelength topographic surface is found with range -121 to +170 m. Coincidentally, all earthquakes with centroids deeper than about 255 km have epicenters within or adjacent to

  1. Charge-carrier relaxation dynamics in highly ordered poly( p -phenylene vinylene): Effects of carrier bimolecular recombination and trapping

    Science.gov (United States)

    Soci, Cesare; Moses, Daniel; Xu, Qing-Hua; Heeger, Alan J.

    2005-12-01

    We have studied the charge-carrier relaxation dynamics in highly ordered poly( p -phenylene vinylene) over a broad time range using fast (t>100ps) transient photoconductivity measurements. The carrier density was also monitored (t>100fs) by means of photoinduced absorption probed at the infrared active vibrational modes. We find that promptly upon charge-carrier photogeneration, the initial polaron dynamics is governed by bimolecular recombination, while later in the subnanosecond time regime carrier trapping gives rise to an exponential decay of the photocurrent. The more sensitive transient photocurrent measurements indicate that in the low excitation regime, when the density of photocarriers is comparable to that of the trapping states (˜1016cm-3) , carrier hopping between traps along with transport via extended states determines the carrier relaxation, a mechanism that is manifested by a long-lived photocurrent “tail.” This photocurrent tail is reduced by lowering the temperature and/or by increasing the excitation density. Based on these data, we develop a comprehensive kinetic model that takes into account the bipolar charge transport, the free-carrier bimolecular recombination, the carrier trapping, and the carrier recombination involving free and trapped carriers.

  2. Dynamics of arbitrary shaped propellers driven by a rotating magnetic field

    Science.gov (United States)

    Morozov, Konstantin I.; Mirzae, Yoni; Kenneth, Oded; Leshansky, Alexander M.

    2017-04-01

    Motion in fluids at the micro(nano)metric scale is dominated by viscosity. One efficient propulsion method relies on a weak uniform rotating magnetic field that drives a chiral object. From bacterial flagella to artificial magnetic micro- or nanohelices, rotation of a corkscrew is considered as a universally efficient propulsion gait in viscous environments. However, recent experimental studies have demonstrated that geometrically achiral microscale objects or random-shaped magnetic aggregates can propel similarly to helical micromotors. Although approximate theories concerning dynamics of helical magnetic propellers are available, propulsion of achiral particles or objects with complex shapes is not understood. Here we present a general theory of rotation and propulsion of magnetized object of arbitrary shape driven by a rotating magnetic field. Intrinsic symmetries of the viscous mobility tensors yield compact classification of stable rotational states depending on the orientation of the magnetic moment with respect to principal rotation axes of the object. Propulsion velocity can be written in terms of geometry-dependent chirality matrix Ch , where both the diagonal elements (owing to orientation-dependent handedness) and off-diagonal entries (that do not necessitate handedness) contribute in a similar way. In general, the theory anticipates multiplicity of stable rotational states corresponding to two (complimentary to π ) angles the magnetization forms with the field rotation axis. Thus, two identical magnetic objects may propel with different speeds or even in opposite directions. However, for a class of simple achiral objects, there is a particular magnetization whereas the pair of symmetric rotational states gives rise to a unique chiral-like propulsion gait, closely resembling that of an ideal helical propeller. In other words, a geometrically achiral object can acquire apparent chirality due to its interaction with the external magnetic field. The

  3. Photoinduced Charge Separation Catalyzed by Manganese Oxides onto a Y-Shaped Branching Acceptor Efficiently Preventing Charge Recombination.

    Science.gov (United States)

    Yamamoto, Kentaro; Takatsuka, Kazuo

    2017-03-03

    A full-dimensional nonadiabatic electron wavepacket study is performed on Mn oxide catalytic charge separation to be created on an accepting molecular system, which is of Y-shaped structure and has a track-branching function for protons and electrons. This branching is necessary in cases in which the transferred electrons and protons are to be eventually carried to mutually different destinations without quick annihilation of the created pair (charge separation). However, as a result of the larger size of such a branched acceptor, the distance between the Mn oxide and the acceptor is so great that it is far from obvious whether an electron is successfully delivered through conical intersections. It is shown here that this can actually occur.

  4. Double-strand breaks in heterochromatin move outside of a dynamic HP1a domain to complete recombinational repair.

    Science.gov (United States)

    Chiolo, Irene; Minoda, Aki; Colmenares, Serafin U; Polyzos, Aris; Costes, Sylvain V; Karpen, Gary H

    2011-03-04

    Double-strand breaks (DSBs) in heterochromatic repetitive DNAs pose significant threats to genome integrity, but information about how such lesions are processed and repaired is sparse. We observe dramatic expansion and dynamic protrusions of the heterochromatin domain in response to ionizing radiation (IR) in Drosophila cells. We also find that heterochromatic DSBs are repaired by homologous recombination (HR) but with striking differences from euchromatin. Proteins involved in early HR events (resection) are rapidly recruited to DSBs within heterochromatin. In contrast, Rad51, which mediates strand invasion, only associates with DSBs that relocalize outside of the domain. Heterochromatin expansion and relocalization of foci require checkpoint and resection proteins. Finally, the Smc5/6 complex is enriched in heterochromatin and is required to exclude Rad51 from the domain and prevent abnormal recombination. We propose that the spatial and temporal control of DSB repair in heterochromatin safeguards genome stability by preventing aberrant exchanges between repeats.

  5. Draft dynamic student learning in design and manufacturing of complex shape parts

    Directory of Open Access Journals (Sweden)

    Ivana Kleinedlerová

    2013-04-01

    Full Text Available The contribution deals with the dynamic teaching of students through blended learning and teaching online distance teaching which can be considered nowadays to be a very effective and dynamic education of students. Content of the article is focused on the sphere of programming with CNC machines and use Cax systems for the production of a particular shape complex parts - shearing knife. The article presented also proposed effective teaching resources. The motivation for solution of this project is that dynamic education leads students to gaining experience and skills, individual identification of the issue, creativity, suggestion of problem solving variations. The achieved way of education and its confirmed and verified positive results can be applied for various target groups of students and their fields of study

  6. Geoid-Shape Cross-Spectral Method for Assessing Planetary Compensation and Dynamics

    Science.gov (United States)

    Menard, J.; Patton, R. L.; Watkinson, A. J.

    2016-12-01

    Cross-spectral methods of gravity-topography analysis are valuable tools for assessing the isostasy of surface features and dynamics of planetary bodies. Historically defined as the degree to which uncompensated topography over-predicts observed gravity, isostasy is used to infer the density, strength, thermal characteristics, and thickness of various layers. These results are necessarily model dependent, given the non-uniqueness of potential fields. The correlation of gravity and topography at most wavelengths is positive. Negative correlations, where found, admit interesting geological interpretations. Examples include the Moon's `mascons', associated with spherical harmonic degrees l = 10,20, and the Earth's plate dynamics, associated with negative correlations at l = 3,5, and a near null correlation at l = 12. The former is consistent with the large basalt-filled impact basins found on the Moon's surface. The latter is only slightly more difficult to see. Earth's gravity-topography cross-spectrum is isostatically compensated for l ≤ 416. Unfortunately, this transition lies well beyond the typical resolution of orbital mapping surveys, which is about l = 120. Given that gravity is a derivative of the potential, which emphasizes shorter wavelength components, another measure is required, based on the same data, which is sensitive to long-wavelength components. Earth's gravity disturbance field exhibits a low-amplitude long-wavelength regional bias, apparently linked to global plate dynamics. This `dynamic' signal dominates at spherical harmonic degrees l ≤ 13, as shown by the geoid-shape cross-spectrum. Thus, Earth's `isostatic anomaly', defined as the difference between the 416th and 13th partial sums of the disturbance field, offers an opportunity to infer the properties of near surface layers. Moreover, Earth's dynamic-isostatic transition occurs well within the range of orbital surveys. Consequently, we use the geoid-shape cross-spectral method to assess

  7. Dynamical passage to approximate equilibrium shapes for spinning, gravitating rubble asteroids

    Science.gov (United States)

    Sharma, Ishan; Jenkins, James T.; Burns, Joseph A.

    2009-03-01

    Many asteroids are thought to be particle aggregates held together principally by self-gravity. Here we study — for static and dynamical situations — the equilibrium shapes of spinning asteroids that are permitted for rubble piles. As in the case of spinning fluid masses, not all shapes are compatible with a granular rheology. We take the asteroid to always be an ellipsoid with an interior modeled as a rigid-plastic, cohesion-less material with a Drucker-Prager yield criterion. Using an approximate volume-averaged procedure, based on the classical method of moments, we investigate the dynamical process by which such objects may achieve equilibrium. We first collapse our dynamical approach to its statical limit to derive regions in spin-shape parameter space that allow equilibrium solutions to exist. At present, only a graphical illustration of these solutions for a prolate ellipsoid following the Drucker-Prager failure law is available [Sharma, I., Jenkins, J.T., Burns, J.A., 2005a. Bull. Am. Astron. Soc. 37, 643; Sharma, I., Jenkins, J.T., Burns, J.A., 2005b. Equilibrium shapes of ellipsoidal soil asteroids. In: García-Rojo, R., Hermann, H.J., McNamara, S. (Eds.), Proceedings of the 5th International Conference on Micromechanics of Granular Media, vol. 1. A.A. Balkema, UK; Holsapple, K.A., 2007. Icarus 187, 500-509]. Here, we obtain the equilibrium landscapes for general triaxial ellipsoids, as well as provide the requisite governing formulae. In addition, we demonstrate that it may be possible to better interpret the results of Richardson et al. [Richardson, D.C., Elankumaran, P., Sanderson, R.E., 2005. Icarus 173, 349-361] within the context of a Drucker-Prager material. The graphical result for prolate ellipsoids in the static limit is the same as those of Holsapple [Holsapple, K.A., 2007. Icarus 187, 500-509] because, when worked out, his final equations will match ours. This is because, though the formalisms to reach these expressions differ, in statics

  8. Universal shape characteristics for the mesoscopic polymer chain via dissipative particle dynamics

    Science.gov (United States)

    Kalyuzhnyi, O.; Ilnytskyi, J. M.; Holovatch, Yu; von Ferber, C.

    2016-12-01

    In this paper we study the shape characteristics of a polymer chain in a good solvent using a mesoscopic level of modelling. The dissipative particle dynamics simulations are performed in 3D space at a range of chain lengths N. The scaling laws for the end-to-end distance and gyration radius are examined first and found to hold for N≥slant 10 yielding a reasonably accurate value for the Flory exponent ν. Within the same interval of chain lengths, the asphericity, prolateness and some other shape characteristics of the chain are found to become independent of N. Their mean values are found to agree reasonably well with the respective theoretical results and lattice Monte Carlo (MC) simulations. We found the probability distribution for a wide range of shape characteristics. For the asphericity and prolateness they are quite broad, resembling in form the results of lattice MC simulations. By means of the analytic fitting of these distributions, the most probable values for the shape characteristics are found to supplement their mean values.

  9. Effect of concentration on surfactant micelle shapes--A molecular dynamics study

    Institute of Scientific and Technical Information of China (English)

    GAO Jian; GE Wei; LI Jinghai

    2005-01-01

    Many aspects of the behavior of surfactants have not been well understood due to the coupling of many different mechanisms. Computer simulation is, therefore, attractive in the sense that it can explore the effect of different mechanisms separately. In this paper, the shapes, structures and sizes of sodium dodecylbenzenesulfonate (SDBS) micelles under different concentrations in an oil/water mixture were studied via molecular dynamics (MD) simulations using a simplified atomistic model which basically maintains the hydrophile and lipophile properties of the surfactant molecules. Above the critical micellar concentration (cmc), surfactant molecules aggregate spontaneously to form a wide variety of assemblies, from spherical to rodlike, wormlike and bilayer micelles. Changes in their ratios of the principle moments of inertia (g1/g3, g2/g3) indicated the transition of micelle shapes at different concentrations. The aggregation number of micelle is found to have a power-law dependence on surfactant concentration.

  10. Dynamic recrystallization of electroformed copper liners of shaped charges in high—strain—rate plastic deformation

    Institute of Scientific and Technical Information of China (English)

    WenhuaiTian; QiSun; 等

    2002-01-01

    The microstructures in the electroformed copper liners of shaped charges after high-strain-rate plastic deformation were in vestigated by transmission microscopy(TEM).Meanwhile,the orientation distribution of the grains in the recovered slug was examined by the electron backscattering Kikuchi pattern(EBSP) technique.EBSP analysis illustrated that unlike the as-formed electroformed copper liners of shaped charges the grain orientations in the recovered slug are distributed along randomly all the directions after undergoing heavily strain deformation at high-strain rate.Optical microscopy shows a typical recrystallization structure,and TEM examination reveals dislocation cells existed in the thin foil specimen.These results indicate that dynamic recovery and recrystallization occur during this plastic deformation process,and the associated deformation temperature is considered to be higher than 0.6 times the melting point of copper.

  11. Dynamic recrystallization of electroformed copper liners of shaped charges in high-strain-rate plastic deformation

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The microstructures in the electroformed copper liners of shaped charges after high-strain-rate plastic deformation were investigated by transmission electron microscopy (TEM). Meanwhile, the orientation distribution of the grains in the recovered slug was examined by the electron backscattering Kikuchi pattern (EBSP) technique. EBSP analysis illustrated that unlike the as-formed electroformed copper linersof shaped charges the grain orientations in the recovered slug are distributed along randomly all the directions after undergoing heavily strain deformation at high-strain rate. Optical microscopy shows a typical recrystallization structure, and TEM examination reveals dislocation cells existed in the thin foil specimen. These results indicate that dynamic recovery and recrystallization occur during this plastic deformation process, and the associated deformation temperature is considered to be higher than 0.6 times the melting point of copper.

  12. Computational fluid dynamics evaluation of liquid food thermal process in a brick shaped package

    Directory of Open Access Journals (Sweden)

    Pedro Esteves Duarte Augusto

    2012-03-01

    Full Text Available Food processes must ensure safety and high-quality products for a growing demand consumer creating the need for better knowledge of its unit operations. The Computational Fluid Dynamics (CFD has been widely used for better understanding the food thermal processes, and it is one of the safest and most frequently used methods for food preservation. However, there is no single study in the literature describing thermal process of liquid foods in a brick shaped package. The present study evaluated such process and the influence of its orientation on the process lethality. It demonstrated the potential of using CFD to evaluate thermal processes of liquid foods and the importance of rheological characterization and convection in thermal processing of liquid foods. It also showed that packaging orientation does not result in different sterilization values during thermal process of the evaluated fluids in the brick shaped package.

  13. Production of Dynamic Frozen Waves: Controlling shape, location (and speed) of diffraction-resistant beams

    CERN Document Server

    Vieira, Tárcio A; Zamboni-Rached, Michel; Recami, Erasmo

    2015-01-01

    In recent times, we experimentally realized a quite efficient modeling of the shape of diffraction-resistant optical beams; thus generating for the first time the so-called Frozen Waves (FW), whose longitudinal intensity pattern can be arbitrarily chosen, within a prefixed space interval of the propagation axis. Such waves possess a host of potential applications: in medicine, biomedical optics, optical tweezers, atom guiding, remote sensing, tractor beams, optical communications or metrology, and other topics in photonic areas. In this work, we extend our theory of FWs -- which led to beams endowed with a static envelope -- through a dynamic modeling of the FWs, whose shape is now allowed to evolve in time in a predetermined way. And we experimentally create such dynamic FWs in Optics, via a computational holographic technique and a spatial light modulator. Experimental results are here presented for two cases of dynamic FWs, one of the zeroth and the other of higher order, the last one being the most intere...

  14. How the dynamics and structure of sexual contact networks shape pathogen phylogenies.

    Directory of Open Access Journals (Sweden)

    Katy Robinson

    Full Text Available The characteristics of the host contact network over which a pathogen is transmitted affect both epidemic spread and the projected effectiveness of control strategies. Given the importance of understanding these contact networks, it is unfortunate that they are very difficult to measure directly. This challenge has led to an interest in methods to infer information about host contact networks from pathogen phylogenies, because in shaping a pathogen's opportunities for reproduction, contact networks also shape pathogen evolution. Host networks influence pathogen phylogenies both directly, through governing opportunities for evolution, and indirectly by changing the prevalence and incidence. Here, we aim to separate these two effects by comparing pathogen evolution on different host networks that share similar epidemic trajectories. This approach allows use to examine the direct effects of network structure on pathogen phylogenies, largely controlling for confounding differences arising from population dynamics. We find that networks with more heterogeneous degree distributions yield pathogen phylogenies with more variable cluster numbers, smaller mean cluster sizes, shorter mean branch lengths, and somewhat higher tree imbalance than networks with relatively homogeneous degree distributions. However, in particular for dynamic networks, we find that these direct effects are relatively modest. These findings suggest that the role of the epidemic trajectory, the dynamics of the network and the inherent variability of metrics such as cluster size must each be taken into account when trying to use pathogen phylogenies to understand characteristics about the underlying host contact network.

  15. Optical feather and foil for shape and dynamic load sensing of critical flight surfaces

    Science.gov (United States)

    Black, Richard J.; Costa, Joannes M.; Faridian, Fereydoun; Moslehi, Behzad; Pakmehr, Mehrdad; Schlavin, Jon; Sotoudeh, Vahid; Zagrai, Andrei

    2014-04-01

    Future flight vehicles may comprise complex flight surfaces requiring coordinated in-situ sensing and actuation. Inspired by the complexity of the flight surfaces on the wings and tail of a bird, it is argued that increasing the number of interdependent flight surfaces from just a few, as is normal in an airplane, to many, as in the feathers of a bird, can significantly enlarge the flight envelope. To enable elements of an eco-inspired Dynamic Servo-Elastic (DSE) flight control system, IFOS is developing a multiple functionality-sensing element analogous to a feather, consisting of a very thin tube with optical fiber based strain sensors and algorithms for deducing the shape of the "feather" by measuring strain at multiple points. It is envisaged that the "feather" will act as a unit of sensing and/or actuation for establishing shape, position, static and dynamic loads on flight surfaces and in critical parts. Advanced sensing hardware and software control algorithms will enable the proposed DSE flight control concept. The hardware development involves an array of optical fiber based sensorized needle tubes for attachment to key parts for dynamic flight surface measurement. Once installed the optical fiber sensors, which can be interrogated over a wide frequency range, also allow damage detection and structural health monitoring.

  16. Characterisation and modelling of vacancy dynamics in Ni–Mn–Ga ferromagnetic shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Merida, D., E-mail: david.merida@ehu.es [Fisika Aplikatua II Saila, Euskal Herriko Unibertsitatea UPV/EHU, p.k. 644, 48080 Bilbao (Spain); Elektrizitate eta Elektronika Saila, Euskal Herriko Unibertsitatea UPV/EHU, p.k. 644, 48080 Bilbao (Spain); García, J.A. [Fisika Aplikatua II Saila, Euskal Herriko Unibertsitatea UPV/EHU, p.k. 644, 48080 Bilbao (Spain); BC Materials (Basque Centre for Materials, Application and Nanostructures), 48040 Leioa (Spain); Sánchez-Alarcos, V. [Departamento de Física, Universidad Pública de Navarra, Campus de Arrosadia, 31006 Pamplona (Spain); Pérez-Landazábal, J.I.; Recarte, V. [Departamento de Física, Universidad Pública de Navarra, Campus de Arrosadia, 31006 Pamplona (Spain); Institute for Advanced Materials (INAMAT), Universidad Pública de Navarra, Campus de Arrosadía, 31006 Pamplona (Spain); Plazaola, F. [Elektrizitate eta Elektronika Saila, Euskal Herriko Unibertsitatea UPV/EHU, p.k. 644, 48080 Bilbao (Spain)

    2015-08-05

    Highlights: • We study the dynamics of vacancies for three different Ni–Mn–Ga alloy samples. • The formation and migration energies have been obtained experimentally. • The entropic factor and the distance a vacancy has to reach a sink are measured. • We present a theoretical model to explain the dynamics of vacancies. • Results are applicable for any thermal treatment and extensible to other alloys. - Abstract: The dynamics of vacancies in Ni–Mn–Ga shape memory alloys has been studied by positron annihilation lifetime spectroscopy. The temperature evolution of the vacancy concentration for three different Ni–Mn–Ga samples, two polycrystalline and one monocrystalline, have been determined. The formation and migration energies and the entropic factors are quite similar in all cases, but vary slightly according to composition. However, the number of jumps a vacancy has to overtake to reach a sink is five times higher in the single crystal. This is an expected result, due to the role that surfaces and grain boundaries should play in balancing the vacancy concentration. In all cases, the initial vacancy concentration for the samples quenched from 1173 K lies between 1000 ppm and 2000 ppm. A phenomenological model able to explain the dynamics of vacancies has been developed in terms of the previous parameters. The model can reproduce the vacancy dynamics for any different kind of thermal history and can be easily extended to other alloys.

  17. Csm4, in collaboration with Ndj1, mediates telomere-led chromosome dynamics and recombination during yeast meiosis.

    Directory of Open Access Journals (Sweden)

    Jennifer J Wanat

    2008-09-01

    Full Text Available Chromosome movements are a general feature of mid-prophase of meiosis. In budding yeast, meiotic chromosomes exhibit dynamic movements, led by nuclear envelope (NE-associated telomeres, throughout the zygotene and pachytene stages. Zygotene motion underlies the global tendency for colocalization of NE-associated chromosome ends in a "bouquet." In this study, we identify Csm4 as a new molecular participant in these processes and show that, unlike the two previously identified components, Ndj1 and Mps3, Csm4 is not required for meiosis-specific telomere/NE association. Instead, it acts to couple telomere/NE ensembles to a force generation mechanism. Mutants lacking Csm4 and/or Ndj1 display the following closely related phenotypes: (i elevated crossover (CO frequencies and decreased CO interference without abrogation of normal pathways; (ii delayed progression of recombination, and recombination-coupled chromosome morphogenesis, with resulting delays in the MI division; and (iii nondisjunction of homologs at the MI division for some reason other than absence of (the obligatory CO(s. The recombination effects are discussed in the context of a model where the underlying defect is chromosome movement, the absence of which results in persistence of inappropriate chromosome relationships that, in turn, results in the observed mutant phenotypes.

  18. Emergent Structures in an Active Polar Fluid : dynamics of shape, scattering and merger

    CERN Document Server

    Husain, Kabir

    2016-01-01

    Spatially localised defect structures emerge spontaneously in a hydrodynamic description of an active polar fluid comprising polar 'actin' filaments and 'myosin' motor proteins that (un)bind to filaments and exert active contractile stresses. These emergent defect structures are characterized by distinct textures and can be either static or mobile - we derive effective equations of motion for these 'extended particles' and analyse their shape, kinetics, interactions and scattering. Depending on the impact parameter and propulsion speed, these active defects undergo elastic scattering or merger. Our results are relevant for the dynamics of actomyosin-dense structures at the cell cortex, reconstituted actomyosin complexes and 2D active colloidal gels.

  19. Dynamic Decoupling for Combined Shape and Gauge Control System in Wide Strip Rolling Process

    Institute of Scientific and Technical Information of China (English)

    LINGHU Ke-zhi; HE An-rui; YANG Quan; ZHAO Lin; GUO Xiao-bo

    2008-01-01

    The precision of profile and thickness is the most important target for wide strip rolling, but the coupling of profile control and thickness control is ignored in rolling schedule, which holds down the simultaneous quality improvement of profile and thickness. A cross-coupled process control model for combined shape and gauge control was developed on the basis of the fact that both controls for profile and thickness are realized by controlling the rolling gap. A dynamic deeoupling controller was then proposed to decouple the model. Both the simulation results and the online production data are valid and ensure the quality of the deeoupling controller.

  20. Nonlinear Strain Measures, Shape Functions and Beam Elements for Dynamics of Flexible Beams

    Energy Technology Data Exchange (ETDEWEB)

    Sharf, I. [University of Victoria, Department of Mechanical Engineering (Canada)

    1999-05-15

    In this paper, we examine several aspects of the development of an explicit geometrically nonlinear beam element. These are: (i) linearization of the displacement field; (ii) the effect of a commonly adopted approximation for the nonlinear Lagrangian strain; and (iii) use of different-order shape functions for discretization. The issue of rigid-body check for a nonlinear beam element is also considered. An approximate check is introduced for an element based on an (approximate) intermediate strain measure. Several numerical examples are presented to support the analysis. The paper concludes with a discussion on the use of explicit nonlinear beam elements for multibody dynamics simulation.

  1. Shape memory alloy nanostructures with coupled dynamic thermo-mechanical effects

    Science.gov (United States)

    Dhote, R. P.; Gomez, H.; Melnik, R. N. V.; Zu, J.

    2015-07-01

    Employing the Ginzburg-Landau phase-field theory, a new coupled dynamic thermo-mechanical 3D model has been proposed for modeling the cubic-to-tetragonal martensitic transformations in shape memory alloy (SMA) nanostructures. The stress-induced phase transformations and thermo-mechanical behavior of nanostructured SMAs have been investigated. The mechanical and thermal hysteresis phenomena, local non-uniform phase transformations and corresponding non-uniform temperatures and deformations' distributions are captured successfully using the developed model. The predicted microstructure evolution qualitatively matches with the experimental observations. The developed coupled dynamic model has provided a better understanding of underlying martensitic transformation mechanisms in SMAs, as well as their effect on the thermo-mechanical behavior of nanostructures.

  2. Photoresponsive Liquid Crystalline Epoxy Networks with Shape Memory Behavior and Dynamic Ester Bonds.

    Science.gov (United States)

    Li, Yuzhan; Rios, Orlando; Keum, Jong K; Chen, Jihua; Kessler, Michael R

    2016-06-22

    Functional polymers are intelligent materials that can respond to a variety of external stimuli. However, these materials have not yet found widespread real world applications because of the difficulties in fabrication and the limited number of functional building blocks that can be incorporated into a material. Here, we demonstrate a simple route to incorporate three functional building blocks (azobenzene chromophores, liquid crystals, and dynamic covalent bonds) into an epoxy-based liquid crystalline network (LCN), in which an azobenzene-based epoxy monomer is polymerized with an aliphatic dicarboxylic acid to create exchangeable ester bonds that can be thermally activated. All three functional building blocks exhibited good compatibility, and the resulting materials exhibits various photomechanical, shape memory, and self-healing properties because of the azobenzene molecules, liquid crystals, and dynamic ester bonds, respectively.

  3. A Computational Fluid Dynamics (CFD) Analysis of an Undulatory Mechanical Fin Driven by Shape Memory Alloy

    Institute of Scientific and Technical Information of China (English)

    Yong-Hua Zhang; Jian-Hui He; Jie Yang; Shi-Wu Zhang; Kin Huat Low

    2006-01-01

    Many fishes use undulatory fin to propel themselves in the underwater environment. These locomotor mechanisms have a popular interest to many researchers. In the present study, we perform a three-dimensional unsteady computation of an undulatory mechanical fin that is driven by Shape Memory Alloy (SMA). The objective of the computation is to investigate the fluid dynamics of force production associated with the undulatory mechanical fin. An unstructured,grid-based, unsteady Navier-Stokes solver with automatic adaptive remeshing is used to compute the unsteady flow around the fin through five complete cycles. The pressure distribution on fin surface is computed and integrated to provide fin forces which are decomposed into lift and thrust. The velocity field is also computed throughout the swimming cycle. Finally, a comparison is conducted to reveal the dynamics of force generation according to the kinematic parameters of the undulatory fin (amplitude, frequency and wavelength).

  4. Unhooking dynamics of U-shaped DNA molecule undergoing gel electrophoresis.

    Science.gov (United States)

    Song, L; Maestre, M F

    1991-08-01

    It has been found that DNA molecules are often hooked around obstacles in a U-shaped configuration in gel electrophoresis. To understand the dynamics of the unhooking of U-shaped DNA molecules undergoing gel electrophoresis, we have examined the length changes of the longer and shorter arms of the U-shape as a function of time. Two types of unhooking have been found. In one type, the length changes of both arms are expontential in time but with different time constants. In another type, the length changes of the shorter arm is exponential and that of the longer one is linear with time. The interpretation is that the extent of stretch of the spring-like DNA chain decreases as the length difference between the two arms increases during the unhooking processes, and that the frictions at the pivot point can be relatively large depending upon the local structure of the gel. The friction coefficient at the pivot point is estimated to be nu 0 = (2.98 +/- 1.42)x10(-5) g/sec.

  5. Thermal and shape stability of high-index-faceted rhodium nanoparticles: a molecular dynamics investigation.

    Science.gov (United States)

    Zeng, Xiang-Ming; Huang, Rao; Wen, Yu-Hua; Sun, Shi-Gang

    2015-02-28

    Nanosized noble metallic particles enclosed by high-index facets exhibit superior catalytic activity because of their high density of low-coordinated step atoms at the surface, and thus have attracted growing interest over the past decade. In this article, we employed molecular dynamics simulations to investigate the thermodynamic evolution of tetrahexahedral Rh nanoparticles respectively covered by {210}, {310}, and {830} facets during the heating process. Our results reveal that the {210} faceted nanoparticle exhibits better thermal and shape stability than the {310} and {830} faceted ones. Meanwhile, because the {830} facet consists of {210} and {310} subfacets, the stability of the {830} faceted Rh nanoparticle is dominated by the {310} subfacet, which possesses a relatively poor stability. Furthermore, the shape transformation of these nanoparticles occurs much earlier than their melting. Further analyses indicate that surface atoms with higher coordination numbers display lower surface diffusivity, and are thus more helpful for stabilizing the particle shape. This study offers an atomistic understanding of the thermodynamic behaviors of high-index-faceted Rh nanoparticles.

  6. Shape and dynamics of seepage erosion in a horizontal granular bed

    CERN Document Server

    Berhanu, Michael; Devauchelle, Olivier; Kudrolli, Arshad; Rothman, Daniel H; 10.1103/PhysRevE.86.041304

    2012-01-01

    We investigate erosion patterns observed in a horizontal granular bed resulting from seepage of water motivated by observation of beach rills and channel growth in larger scale landforms. Our experimental apparatus consists of a wide rectangular box filled with glass beads with a narrow opening in one of the side walls from which eroded grains can exit. Quantitative data on the shape of the pattern and erosion dynamics are obtained with a laser-aided topography technique. We show that the spatial distribution of the source of groundwater can significantly impact the shape of observed patterns. An elongated channel is observed to grow upstream when groundwater is injected at a boundary adjacent to a reservoir held at constant height. An amphitheater (semi-circular) shape is observed when uniform rainfall infiltrates the granular bed to maintain a water table. Bifurcations are observed as the channels grow in response to the ground water. We further find that the channels grow by discrete avalanches as the heig...

  7. Computational lfuid dynamics simulation of intracranial aneurysms - comparing size and shape

    Institute of Scientific and Technical Information of China (English)

    Zifeng Yang; Hongtao Yu; George P Huang; Ryan Schwieterman; Bryan Ludwig

    2015-01-01

    Objective:To study the hemodynamics of an anatomic internal carotid artery aneurysm derived from a patient-specific model and then manipulate into two phantom morphologies: one growing uniformly by size and the other changing shape unevenly. Methods: The computational model of the saccular, internal carotid artery, aneurysm was constructed from 3D rotational, digitally subtracted, catheter angiography images. Computational fluid dynamics simulations were performed under pulsatile cardiac flow conditions. Velocity vectors, streamlines, pressure, and wall shear stress (WSS) and its variance distributions were quantitatively visualized. Results: The maximum pressure andWSS from the time-averaged distribution on the inside saccular surface of the original case are 415.38 and 17.61 Pa. In contrast, the bi-lobed shape gives rise to higher peak values of pressure (461.00 Pa) andWSS (33.20 Pa) on the saccular dome. Conversely, the evenly enlarged aneurysm actually results in a slightly lower peak pressure (399.58 Pa) and drastically decreasedWSS (9.81 Pa). Conclusions:The current study indicates that the size of the aneurysm should not be the only determining factor for the rupture risk consideration, the irregularity of the aneurysm shape and the corresponding aberrant hemodynamics might be a more important factor to consider for risk assessment.

  8. Transient flow model and pressure dynamic features of tree-shaped fractal re- servoirs

    Institute of Scientific and Technical Information of China (English)

    TAN Xiao-hua; LI Xiao-ping

    2014-01-01

    A transient flow model of tree-shaped fractal reservoirs is built by embedding a fracture network simulated by a tree-shaped fractal network into a matrix system. The model can be solved using the Laplace conversion method. The dimensionless bottom hole pressure can be obtained using the Stehfest numerical inversion method. The bi-logarithmic type curves for the tree-shaped fractal reservoirs are thus obtained. The pressure transient responses under different fractal factors are discussed. The factors with a primary effect on the inter-porosity flow regime include the initial branch numberN, the length ratioα, and the branch angleθ. The diameter ratioβ has a significant effect on the fracture radial flow, the inter-porosity and the total system radial flow regimes. The total branch levelM of the network mainly influences the total system radial flow regime. The model presented in this paper provides a new methodology for analyzing and predicting the pressure dynamic characteristics of naturally fractured reservoirs.

  9. Shape selection in Landsat time series: a tool for monitoring forest dynamics.

    Science.gov (United States)

    Moisen, Gretchen G; Meyer, Mary C; Schroeder, Todd A; Liao, Xiyue; Schleeweis, Karen G; Freeman, Elizabeth A; Toney, Chris

    2016-10-01

    We present a new methodology for fitting nonparametric shape-restricted regression splines to time series of Landsat imagery for the purpose of modeling, mapping, and monitoring annual forest disturbance dynamics over nearly three decades. For each pixel and spectral band or index of choice in temporal Landsat data, our method delivers a smoothed rendition of the trajectory constrained to behave in an ecologically sensible manner, reflecting one of seven possible 'shapes'. It also provides parameters summarizing the patterns of each change including year of onset, duration, magnitude, and pre- and postchange rates of growth or recovery. Through a case study featuring fire, harvest, and bark beetle outbreak, we illustrate how resultant fitted values and parameters can be fed into empirical models to map disturbance causal agent and tree canopy cover changes coincident with disturbance events through time. We provide our code in the r package ShapeSelectForest on the Comprehensive R Archival Network and describe our computational approaches for running the method over large geographic areas. We also discuss how this methodology is currently being used for forest disturbance and attribute mapping across the conterminous United States.

  10. Integrated optical design for highly dynamic laser beam shaping with membrane deformable mirrors

    Science.gov (United States)

    Pütsch, Oliver; Stollenwerk, Jochen; Loosen, Peter

    2017-02-01

    The utilization of membrane deformable mirrors has raised its importance in laser materials processing since they enable the generation of highly spatial and temporal dynamic intensity distributions for a wide field of applications. To take full advantage of these devices for beam shaping, the huge amount of degrees of freedom has to be considered and optimized already within the early stage of the optical design. Since the functionality of commercial available ray-tracing software has been mainly specialized on geometric dependencies and their optimization within constraints, the complex system characteristics of deformable mirrors cannot be sufficiently taken into account yet. The main reasons are the electromechanical interdependencies of electrostatic membrane deformable mirrors, namely saturation and mechanical clamping, that result in non-linear deformation. This motivates the development of an integrative design methodology. The functionality of the ray-tracing program ZEMAX is extended with a model of an electrostatic membrane mirror. This model is based on experimentally determined influence functions. Furthermore, software routines are derived and integrated that allow for the compilation of optimization criteria for the most relevant analytically describable beam shaping problems. In this way, internal optimization routines can be applied for computing the appropriate membrane deflection of the deformable mirror as well as for the parametrization of static optical components. The experimental verification of simulated intensity distributions demonstrates that the beam shaping properties can be predicted with a high degree of reliability and precision.

  11. A model of shape memory materials with hierarchical twinning: Statics and dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Saxena, A.; Bishop, A.R. [Los Alamos National Lab., NM (United States); Shenoy, S.R. [International Center for Theoretical Physics, Trieste (Italy); Wu, Y.; Lookman, T. [Western Ontario Univ., London, Ontario (Canada). Dept. of Applied Mathematics

    1995-07-01

    We consider a model of shape memory material in which hierarchical twinning near the habit plane (austenite-martensite interface) is a new and crucial ingredient. The model includes (1) a triple-well potential ({phi} model) in local shear strain, (2) strain gradient terms up to second order in strain and fourth order in gradient, and (3) all symmetry allowed compositional fluctuation induced strain gradient terms. The last term favors hierarchy which enables communication between macroscopic (cm) and microscopic ({Angstrom}) regions essential for shape memory. Hierarchy also stabilizes between formation (critical pattern of twins). External stress or pressure (pattern) modulates the spacing of domain walls. Therefore the ``pattern`` is encoded in the modulated hierarchical variation of the depth and width of the twins. This hierarchy of length scales provides a hierarchy of time scales and thus the possibility of non-exponential decay. The four processes of the complete shape memory cycle -- write, record, erase and recall -- are explained within this model. Preliminary results based on 2D Langevin dynamics are shown for tweed and hierarchy formation.

  12. Short-term synaptic depression and stochastic vesicle dynamics reduce and shape neuronal correlations.

    Science.gov (United States)

    Rosenbaum, Robert; Rubin, Jonathan E; Doiron, Brent

    2013-01-01

    Correlated neuronal activity is an important feature in many neural codes, a neural correlate of a variety of cognitive states, as well as a signature of several disease states in the nervous system. The cellular and circuit mechanics of neural correlations is a vibrant area of research. Synapses throughout the cortex exhibit a form of short-term depression where increased presynaptic firing rates deplete neurotransmitter vesicles, which transiently reduces synaptic efficacy. The release and recovery of these vesicles are inherently stochastic, and this stochasticity introduces variability into the conductance elicited by depressing synapses. The impact of spiking and subthreshold membrane dynamics on the transfer of neuronal correlations has been studied intensively, but an investigation of the impact of short-term synaptic depression and stochastic vesicle dynamics on correlation transfer is lacking. We find that short-term synaptic depression and stochastic vesicle dynamics can substantially reduce correlations, shape the timescale over which these correlations occur, and alter the dependence of spiking correlations on firing rate. Our results show that short-term depression and stochastic vesicle dynamics need to be taken into account when modeling correlations in neuronal populations.

  13. Spatial emission distribution and carrier recombination dynamics in regularly arrayed InGaN/GaN quantum structure nanocolumns

    Science.gov (United States)

    Oto, Takao; Mizuno, Yutaro; Miyagawa, Rin; Kano, Tatsuya; Yoshida, Jun; Ema, Kazuhiro; Kishino, Katsumi

    2016-10-01

    Emission mechanisms in regularly arrayed InGaN/GaN quantum structures on GaN nanocolumns were investigated, focusing on the spatial emission distribution at the nanocolumn tops and the carrier recombination dynamics. The double-peak emission originated from the dot- and well-like InGaN areas with different In compositions was observed. From the results regarding the spatial emission distribution, we proposed a simple analytical approach to evaluating the carrier recombination dynamics using the rate equations based on the two energy states. The considerable six lifetimes can be uniquely determined from the experimental results. Carrier transfer from the high- to the low-energy state is dominant at high temperatures, producing the increased total emission efficiency of the inner low-energy area. In addition, the internal quantum efficiency should not be simply discussed using only the integrated intensity ratio between low and room temperatures because of the carrier transfer from high- to low-energy states.

  14. Dynamics and Predictive Potential of Antibodies against Insect-Derived Recombinant Leishmania infantum Proteins during Chemotherapy of Naturally Infected Dogs

    Science.gov (United States)

    Todolí, Felicitat; Galindo, Inmaculada; Gómez-Sebastián, Silvia; Pérez-Filgueira, Mariano; Escribano, José M.; Alberola, Jordi; Rodríguez-Cortés, Alhelí

    2010-01-01

    A predictive marker for the success treatment of canine leishmaniasis is required for the application of a more rational therapy protocol, which must improve the probability of cure and reduce Leishmania resistance to drugs. We investigated the dynamics and predictive value of antibodies against insect-derived recombinant L. infantum proteins rKMPII and rTRYP by using an enzyme-linked immunosorbent assay with retrospective serum samples from 36 dogs during treatment of canine leishmaniasis. In the entire group of dogs, concentrations of antibodies against rKMPII and rTRYP significantly decreased earlier than concentrations of antibodies against crude total Leishmania antigen (one versus six months), which suggested that the dynamics of antibodies against recombinant proteins may be useful for assessing clinical improvement after treatment. Interestingly, decreases in antibody concentrations against rKMPII occurred earlier in disease-free dogs than in dogs that remain clinically ill one year after beginning of treatment, which suggested that these antibodies may be useful for predicting disease-free survival one year after the beginning of therapy against canine leishmaniasis. PMID:20439957

  15. Carrier dynamics and recombination in GaN quantum discs embedded in AlGaN nanocolumns

    Energy Technology Data Exchange (ETDEWEB)

    Zamfirescu, M.; Abbarchi, M.; Gurioli, M.; Vinattieri, A. [INFM, Dept. of Physics and LENS, Universita di Firenze, Via Sansone 1, 50019 Sesto Fiorentino (Italy); Ristic, J.; Calleja, E. [Dept. Ingenieria Electronica, ETSI Telecomunicacion-ISOM, Universidad Politecnica, Ciudad Universitaria, Madrid 28040 (Spain)

    2005-02-01

    We report on the study of carrier dynamics and recombination by time resolved PL in GaN quantum discs embedded in Al{sub 0.16}Ga{sub 0.84}N nanocolumns, grown by MBE on AlN buffered Si (111) substrates. The emission band of GaN quantum discs and the Al{sub 0.16}Ga{sub 0.84}N nanocolumns are strongly overlapped and the standard analysis of PL decays is not useful to fully characterize the recombination kinetics. We make use of time resolved spectroscopy to clearly distinguish the different contributions to the PL spectra and therefore to obtain the intrinsic carrier time evolution in the quantum discs. We observe a dynamical red shift of the PL band together with a non exponential decay, very likely due to screening of the internal piezoelectric field provided by the photoinjected carriers. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Vascular dynamics of a shape memory polymer foam aneurysm treatment technique.

    Science.gov (United States)

    Ortega, Jason; Maitland, Duncan; Wilson, Tom; Tsai, William; Savaş, Omer; Saloner, David

    2007-11-01

    The vascular dynamics of a shape memory polymer foam aneurysm treatment technique are assessed through the simulated treatment of a generic basilar aneurysm using coupled fluid dynamics and heat transfer calculations. The shape memory polymer foam, which expands to fill the aneurysm when heated, is modeled at three discrete stages of the treatment procedure. To estimate an upper bound for the maximum amount of thermal damage due to foam heating, a steady velocity is specified through the basilar artery, corresponding to a minimum physiological flow velocity over a cardiac cycle. During expansion, the foam alters the flow patterns within the aneurysm by shielding the aneurysm dome from a confined jet that issues from the basilar artery. The time scales for thermal damage to the artery walls and surrounding blood flow are computed from the temperature field. The flow through the post-treatment bifurcation is comprised of two counter-rotating vortex tubes that are located beneath the aneurysm neck and extend downstream into the outlet arteries. Beneath the aneurysm neck, a marked increase in the wall shear stress is observed due to the close proximity of the counter-rotating vortex tubes to the artery wall.

  17. High hydrostatic pressure specifically affects molecular dynamics and shape of low-density lipoprotein particles

    Science.gov (United States)

    Golub, M.; Lehofer, B.; Martinez, N.; Ollivier, J.; Kohlbrecher, J.; Prassl, R.; Peters, J.

    2017-04-01

    Lipid composition of human low-density lipoprotein (LDL) and its physicochemical characteristics are relevant for proper functioning of lipid transport in the blood circulation. To explore dynamical and structural features of LDL particles with either a normal or a triglyceride-rich lipid composition we combined coherent and incoherent neutron scattering methods. The investigations were carried out under high hydrostatic pressure (HHP), which is a versatile tool to study the physicochemical behavior of biomolecules in solution at a molecular level. Within both neutron techniques we applied HHP to probe the shape and degree of freedom of the possible motions (within the time windows of 15 and 100 ps) and consequently the flexibility of LDL particles. We found that HHP does not change the types of motion in LDL, but influences the portion of motions participating. Contrary to our assumption that lipoprotein particles, like membranes, are highly sensitive to pressure we determined that LDL copes surprisingly well with high pressure conditions, although the lipid composition, particularly the triglyceride content of the particles, impacts the molecular dynamics and shape arrangement of LDL under pressure.

  18. Social Dynamics Shaping the Diffusion of Sustainable Aquaculture Innovations in the Solomon Islands

    Directory of Open Access Journals (Sweden)

    Jessica Blythe

    2017-01-01

    Full Text Available Sustainably feeding the world’s growing population represents one of our most significant challenges. Aquaculture is well positioned to make contributions towards this challenge. Yet, the translation of aquaculture production innovations into benefits for rural communities is constrained by a limited understanding of the social dynamics that influence the adoption of new agricultural practices. In this paper, we investigate the factors that shape the spread of small-scale tilapia aquaculture through rural Solomon Islands. Based on diffusion of innovation theory, we focus on three potentially influential factors: (i socio-economic characteristics of adopters; (ii the role of opinion leaders; and (iii characteristics of the innovation. We find that farmers who were wealthier, older, and had more diverse livelihoods were most likely to be adopters. Opinion leaders facilitated the adoption of tilapia aquaculture, but lacked the capacity to provide fundamental knowledge necessary to realize its potential benefits to food security. The paper argues for more explicit attention to the poorest households and makes the case for a deeper engagement with the broader social and institutional contexts that shape the adoption process. Aquaculture interventions that account for these social dynamics are critical for translating production innovations into sustainable benefits to rural communities.

  19. Ultrafast and slow charge recombination dynamics of diketopyrrolopyrrole-NiO dye sensitized solar cells.

    Science.gov (United States)

    Zhang, Lei; Favereau, Ludovic; Farré, Yoann; Mijangos, Edgar; Pellegrin, Yann; Blart, Errol; Odobel, Fabrice; Hammarström, Leif

    2016-07-21

    In a photophysical study, two diketopyrrolopyrrole (DPP)-based sensitizers functionalized with 4-thiophenecarboxylic acid as an anchoring group and a bromo (DPPBr) or dicyanovinyl (DPPCN2) group, and a dyad consisting of a DPP unit linked to a naphthalenediimide group (DPP-NDI), were investigated both in solution and grafted on mesoporous NiO films. Femtosecond transient absorption measurements indicate that ultrafast hole injection occurred predominantly on a timescale of ∼200 fs, whereas the subsequent charge recombination occurred on a surprisingly wide range of timescales, from tens of ps to tens of μs; this kinetic heterogeneity is much greater than is typically observed for dye-sensitized TiO2 or ZnO. Also, in contrast to what is typically observed for dye-sensitized TiO2, there was no significant dependence on the excitation power of the recombination kinetics, which can be explained by the hole density being comparatively higher near the valence band of NiO before excitation. The additional acceptor group in DPP-NDI provided a rapid electron shift and stabilized charge separation up to the μs timescale. This enabled efficient (∼95%) regeneration of NDI by a Co(III)(dtb)3 electrolyte (dtb = 4,4'-di-tert-butyl-2,2'-bipyridine), according to transient absorption measurements. The regeneration of DPPBr and DPPCN2 by Co(III)(dtb)3 was instead inefficient, as most recombination for these dyes occurred on the sub-ns timescale. The transient spectroscopy data thus corroborated the trend of the published photovoltaic properties of dye-sensitized solar cells (DSSCs) based on these dyes on mesoporous NiO, and show the potential of a design strategy with a secondary acceptor bound to the dye. The study identifies rapid initial recombination between the dye and NiO as the main obstacle to obtaining high efficiencies in NiO-based DSSCs; these recombination components may be overlooked when studies are conducted using only methods with ns resolution or slower.

  20. Modelling runoff dynamics from information on river network and shape of catchment area

    Science.gov (United States)

    Skaugen, T.

    2009-12-01

    In a new approach, the dynamics of discharge is derived from the distribution of distances to the nearest river reach within a natural catchment. The river network and the shape of catchment provide a unique distribution function for each catchment which can be determined from a GIS. The distribution can be considered as a detailed description of the drainage density, where the location of the river relative to the catchment is taken into account. Within a fixed time interval, water flows through the catchment a certain distance which defines a fractional area. This fraction is estimated as an area enveloping the river network, whose width, perpendicular to the river network, is determined for the time interval of interest by the flow velocity. For a constant flow velocity, the time steps define adjacent areas which , for a sufficient number of time intervals, cover the entire catchment. For different flow velocities, we have different horizontal layers and the total discharge is the sum of discharge from each of the layers for each time step. The proposed principle for modelling the dynamics of discharge is implemented in the Swedish HBV model. The new model, named 3D (distance distribution dynamics), has the same precision as the HBV model but requires fewer parameters and represents thus a step in the right direction for meeting the challenge of predictions in ungauged basins.

  1. 3D shape measurement of objects with high dynamic range of surface reflectivity.

    Science.gov (United States)

    Liu, Gui-hua; Liu, Xian-Yong; Feng, Quan-Yuan

    2011-08-10

    This paper presents a method that allows a conventional dual-camera structured light system to directly acquire the three-dimensional shape of the whole surface of an object with high dynamic range of surface reflectivity. To reduce the degradation in area-based correlation caused by specular highlights and diffused darkness, we first disregard these highly specular and dark pixels. Then, to solve this problem and further obtain unmatched area data, this binocular vision system was also used as two camera-projector monocular systems operated from different viewing angles at the same time to fill in missing data of the binocular reconstruction. This method involves producing measurable images by integrating such techniques as multiple exposures and high dynamic range imaging to ensure the capture of high-quality phase of each point. An image-segmentation technique was also introduced to distinguish which monocular system is suitable to reconstruct a certain lost point accurately. Our experiments demonstrate that these techniques extended the measurable areas on the high dynamic range of surface reflectivity such as specular objects or scenes with high contrast to the whole projector-illuminated field.

  2. Recombination dynamics in heterostructures with two planar arrays of II-VI quantum dots

    Science.gov (United States)

    Mikhailov, T. N.; Belyaev, K. G.; Toropov, A. A.; Sorokin, S. V.; Pozina, G.; Shubina, T. V.

    2016-08-01

    We present time-resolved photoluminescence studies of epitaxial heterostructures with two arrays of Cd(Zn)Se/ZnSe quantum dots (QDs), which are formed by the successive insertion of CdSe fractional monolayers of different nominal thicknesses into a ZnSe matrix. Our data are suggestive of the appearance of effective channels of the energy transfer from the insertion comprising the array with smaller QDs, emitting at higher energy, towards the array with larger QDs, emitting at lower energy. The effect of dark excitons on characteristic times of radiative recombination is discussed.

  3. The influence of morphology on charge transport/recombination dynamics in planar perovskite solar cells

    Science.gov (United States)

    Yu, Man; Wang, Yi; Wang, Hao-Yi; Han, Jun; Qin, Yujun; Zhang, Jian-Ping; Ai, Xi-Cheng

    2016-10-01

    The photovoltaic performance of planar perovskite solar cell is significantly influenced by the morphology of perovskite film. In this work, five kinds of devices with different perovskite film morphologies were prepared by varying the concentration of CH3NH3Cl in precursor solutions. We found that best morphology of perovskite film results in the excellent photovoltaic performance with an average efficiency of 15.52% and a champion efficiency of 16.38%. Transient photovoltage and photocurrent measurements are performed to elucidate the mechanism of photoelectric conversion processes, which shows that the charge recombination is effectively suppressed and the charge transport is obviously promoted by optimized morphology.

  4. Effects of recombinant human insulin-like growth factor I on glomerular dynamics in the rat.

    OpenAIRE

    Hirschberg, R; Kopple, J D; Blantz, R C; Tucker, B J

    1991-01-01

    This study was undertaken to investigate the mechanisms by which an infusion of recombinant human insulin-like growth factor I (rhIGF-I) increases GFR and renal plasma flow (RPF) in rats. Glomerular micropuncture studies were carried out in 14 nonstarved Munich Wistar rats and in 12 rats deprived of food for 60-72 h. Animals were given an intravenous injection and infusion of either rhIGF-I or vehicle. In both nonstarved and starved animals, the IGF-I injection and infusion increased the seru...

  5. Model for the dynamics of two interacting axisymmetric spherical bubbles undergoing small shape oscillations

    Science.gov (United States)

    Kurihara, Eru; Hay, Todd A.; Ilinskii, Yurii A.; Zabolotskaya, Evgenia A.; Hamilton, Mark F.

    2011-01-01

    Interaction between acoustically driven or laser-generated bubbles causes the bubble surfaces to deform. Dynamical equations describing the motion of two translating, nominally spherical bubbles undergoing small shape oscillations in a viscous liquid are derived using Lagrangian mechanics. Deformation of the bubble surfaces is taken into account by including quadrupole and octupole perturbations in the spherical-harmonic expansion of the boundary conditions on the bubbles. Quadratic terms in the quadrupole and octupole amplitudes are retained, and surface tension and shear viscosity are included in a consistent manner. A set of eight coupled second-order ordinary differential equations is obtained. Simulation results, obtained by numerical integration of the model equations, exhibit qualitative agreement with experimental observations by predicting the formation of liquid jets. Simulations also suggest that bubble-bubble interactions act to enhance surface mode instability. PMID:22088009

  6. Dynamic light scattering study of peanut agglutinin: Size, shape and urea denaturation

    Indian Academy of Sciences (India)

    Sagarika Dev; Avadhesha Surolia

    2006-12-01

    Peanut agglutinin (PNA) is a homotetrameric protein with a unique open quaternary structure. PNA shows non-two state profile in chaotrope induced denaturation. It passes through a monomeric molten globule like state before complete denaturation (Reddy et al 1999). This denaturation profile is associated with the change in hydrodynamic radius of the native protein. Though the molten globule-like state is monomeric in nature it expands in size due to partial denaturation. The size and shape of the native PNA as well as the change in hydrodynamic radius of the protein during denaturation has been studied by dynamic light scattering (DLS). The generation of two species is evident from the profile of hydrodynamic radii. This study also reveals the extent of compactness of the intermediate state.

  7. Automated three-dimensional single cell phenotyping of spindle dynamics, cell shape, and volume

    CERN Document Server

    Plumb, Kemp; Pelletier, Vincent; Kilfoil, Maria L

    2015-01-01

    We present feature finding and tracking algorithms in 3D in living cells, and demonstrate their utility to measure metrics important in cell biological processes. We developed a computational imaging hybrid approach that combines automated three-dimensional tracking of point-like features with surface determination from which cell (or nuclear) volume, shape, and planes of interest can be extracted. After validation, we applied the technique to real space context-rich dynamics of the mitotic spindle, and cell volume and its relationship to spindle length, in dividing living cells. These methods are additionally useful for automated segregation of pre-anaphase and anaphase spindle populations in budding yeast. We found that genetic deletion of the yeast kinesin-5 mitotic motor cin8 leads to large mother and daughter cells that were indistinguishable based on size, and that in those cells the spindle length becomes uncorrelated with cell size. The technique can be used to visualize and quantify tracked feature c...

  8. Shape optimization of an autonomous underwater vehicle with a ducted propeller using computational fluid dynamics analysis

    Directory of Open Access Journals (Sweden)

    Tae-Hwan Joung

    2012-03-01

    Full Text Available Autonomous Underwater Vehicles (AUVs provide a useful means of collecting detailed oceano-graphic information. The hull resistance of an AUV is an important factor in determining the power requirements and range of the vehicle. This paper describes a procedure using Computational Fluid Dynamics (CFD for determining the hull resistance of an AUV under development, for a given propeller rotation speed and within a given range of AUV velocities. The CFD analysis results reveal the distribution of the hydrodynamic values (velocity, pressure, etc. around the AUV hull and its ducted propeller. The paper then proceeds to present a methodology for optimizing the AUV profile in order to reduce the total resistance. This paper demonstrates that shape optimization of conceptual designs is possible using the commercial CFD package contained in Ansys™. The optimum design to minimize the drag force of the AUV was identified for a given object function and a set of constrained design parameters.

  9. Phonatory Strategies of Male Vocalists in Singing Diatonic Scales With Various Dynamic Shapings.

    Science.gov (United States)

    Vurma, Allan

    2017-03-01

    This work aimed to investigate glottal adduction in the case of the singing of diatonic D major ascending scales with different dynamic shapings on vowel [a:] by 10 classically trained male singers. The parameters obtained by inverse filtering-closed quotient (CQ), normalized amplitude quotient (NAQ), and the level difference between the first two partials of the glottal flow waveform spectrum (H1-H2)-all indicated statistically significant systematic changes when singers sang (1) with habitual dynamics without intentional dynamic changes; (2) with sempre crescendo from piano to forte; and (3) with sempre diminuendo from forte to piano. Adduction on average was lower if the tone with the same pitch was sung piano compared with when it was sung forte. The piano tones with the limit of one and the same dynamic task were sung with lower adduction on average compared with one octave higher or lower tones sung forte, although here the agreement between different parameters was poorer and the individual variability was greater. There was only a moderate negative correlation between CQ and NAQ (r = -0.41) but a strong negative correlation between CQ and H1-H2 (r = -0.8). CQ showed a moderate positive correlation with sound level but no significant correlation with pitch. NAQ showed a strong and significant positive correlation with pitch but not with sound level (except when it was calculated only at constant pitch). Some of the most experienced singers used quite high glottal adduction levels, questioning the concept of whether flow phonation is always the favorite classical style. Copyright © 2017 The Voice Foundation. Published by Elsevier Inc. All rights reserved.

  10. Probing nuclear dynamics in jet production with a global event shape

    CERN Document Server

    Kang, Zhong-Bo; Mantry, Sonny; Qiu, Jian-Wei

    2013-01-01

    We study single jet production in electron-nucleus collisions e^- + N_A -> J + X, using the 1-jettiness (\\tau_1) global event shape. It inclusively quantifies the pattern of radiation in the final state, gives enhanced sensitivity to soft radiation at wide angles from the nuclear beam and final-state jet, and facilitates the resummation of large Sudakov logarithms associated with the veto on additional jets. Through their effect on the observed pattern of radiation, 1-jettiness can be a useful probe of nuclear PDFs and power corrections from dynamical effects in the nuclear medium. This formalism allows for the standard jet shape analysis while simultaneously providing sensitivity to soft radiation at wide angles from the jet. We use a factorization framework for cross-sections differential in $\\tau_1$ and the transverse momentum (P_{J_T}) and rapidity (y) of the jet, in the region \\tau_1<< P_{J_T}. The restriction $\\tau_1 << P_{J_T}$ allows only soft radiation between the nuclear beam and jet dir...

  11. Effects of adhesion dynamics and substrate compliance on the shape and motility of crawling cells.

    Directory of Open Access Journals (Sweden)

    Falko Ziebert

    Full Text Available Computational modeling of eukaryotic cells moving on substrates is an extraordinarily complex task: many physical processes, such as actin polymerization, action of motors, formation of adhesive contacts concomitant with both substrate deformation and recruitment of actin etc., as well as regulatory pathways are intertwined. Moreover, highly nontrivial cell responses emerge when the substrate becomes deformable and/or heterogeneous. Here we extended a computational model for motile cell fragments, based on an earlier developed phase field approach, to account for explicit dynamics of adhesion site formation, as well as for substrate compliance via an effective elastic spring. Our model displays steady motion vs. stick-slip transitions with concomitant shape oscillations as a function of the actin protrusion rate, the substrate stiffness, and the rates of adhesion. Implementing a step in the substrate's elastic modulus, as well as periodic patterned surfaces exemplified by alternating stripes of high and low adhesiveness, we were able to reproduce the correct motility modes and shape phenomenology found experimentally. We also predict the following nontrivial behavior: the direction of motion of cells can switch from parallel to perpendicular to the stripes as a function of both the adhesion strength and the width ratio of adhesive to non-adhesive stripes.

  12. Computational Fluid Dynamics Prediction of a Modified Savonius Wind Turbine with Novel Blade Shapes

    Directory of Open Access Journals (Sweden)

    Wenlong Tian

    2015-07-01

    Full Text Available The Savonius wind turbine is a type of vertical axis wind turbine (VAWTs that is simply composed of two or three arc-type blades which can generate power even under poor wind conditions. A modified Savonius wind turbine with novel blade shapes is introduced with the aim of increasing the power coefficient of the turbine. The effect of blade fullness, which is a main shape parameter of the blade, on the power production of a two-bladed Savonius wind turbine is investigated using transient computational fluid dynamics (CFD. Simulations are based on the Reynolds Averaged Navier-Stokes (RANS equations with a renormalization group turbulent model. This numerical method is validated with existing experimental data and then utilized to quantify the performance of design variants. Results quantify the relationship between blade fullness and turbine performance with a blade fullness of 1 resulting in the highest coefficient of power, 0.2573. This power coefficient is 10.98% higher than a conventional Savonius turbine.

  13. Characterization of Shape Memory Polymer Estane by Means of Dynamic Mechanical Thermal Analysis Technique

    Directory of Open Access Journals (Sweden)

    Rasa Kazakevičiūtė-Makovska

    2014-01-01

    Full Text Available Commercially available shape memory polymer (SMP Estane (designation: ETE75DT3 NAT022 is investigated by means of dynamic mechanical thermal analysis (DMTA technique in torsion mode using the Modular Compact Rheometer MCR-301 (Anton Paar GmbH. Amplitude sweep tests have been run below and above the glass transition temperature to establish the linear viscoelastic range (LVR in glassy and rubbery phase of this SMP for the correct physical interpretation of DMTA data. Temperature sweep tests were performed at various frequencies to study the influence of this parameter on values of the storage and loss moduli and the storage and loss compliances as well as the viscosities. These tests have been carried out in heating mode with different rates and at different strain amplitudes. The short- and long-term behavior of SMP Estane have been studied by frequency sweep tests performed at different temperatures and data have been transformed into time-domain properties by applying time-temperature superposition principles. All these DMTA data provide the experimental basis for the study of relaxation processes, property-structure relationships, and the shape memory effect in this little-known SMP.

  14. Experimental investigation of granule size and shape dynamics in twin-screw granulation.

    Science.gov (United States)

    Kumar, Ashish; Vercruysse, Jurgen; Bellandi, Giacomo; Gernaey, Krist V; Vervaet, Chris; Remon, Jean Paul; De Beer, Thomas; Nopens, Ingmar

    2014-11-20

    A twin-screw granulator (TSG), a promising equipment for continuous high shear wet granulation (HSWG), achieves the desired level of mixing by a combination of the appropriate screw configuration and a suitable set of process settings (e.g. feed rate, screw speed, etc.), thus producing a certain granule size and shape distribution (GSSD). However, the primary sizing and shaping mechanism behind the resulting distribution is not well understood due to the opacity of the multiphase system in the granulator. This study experimentally characterised the GSSD dynamics along the TSG barrel length in order to understand the function of individual screw modules and process settings, as well as their interaction. Particle size analysis of granules collected at the outlet of the TSG suggested significant interaction between the process and screw configuration parameters influencing the heterogeneity in the GSSD. By characterising the samples collected along the screw length, a variable influence of the screw modules at different process conditions was observed. At low liquid-to-solid ratio (L/S), the first kneading module seemed to play a significant role in mixing, whereas the second kneading module was found to be more involved in reshaping the granules. At high L/S and high throughput, aggregation mainly took place in the second kneading module changing the GSSD. The results obtained from this study will be further used for the calibration and validation of a mechanistic model and, hence, support future development of a more detailed understanding of the HSWG process in a TSG.

  15. Enhanced high dynamic range 3D shape measurement based on generalized phase-shifting algorithm

    Science.gov (United States)

    Wang, Minmin; Du, Guangliang; Zhou, Canlin; Zhang, Chaorui; Si, Shuchun; Li, Hui; Lei, Zhenkun; Li, YanJie

    2017-02-01

    Measuring objects with large reflectivity variations across their surface is one of the open challenges in phase measurement profilometry (PMP). Saturated or dark pixels in the deformed fringe patterns captured by the camera will lead to phase fluctuations and errors. Jiang et al. proposed a high dynamic range real-time three-dimensional (3D) shape measurement method (Jiang et al., 2016) [17] that does not require changing camera exposures. Three inverted phase-shifted fringe patterns are used to complement three regular phase-shifted fringe patterns for phase retrieval whenever any of the regular fringe patterns are saturated. Nonetheless, Jiang's method has some drawbacks: (1) the phases of saturated pixels are estimated by different formulas on a case by case basis; in other words, the method lacks a universal formula; (2) it cannot be extended to the four-step phase-shifting algorithm, because inverted fringe patterns are the repetition of regular fringe patterns; (3) for every pixel in the fringe patterns, only three unsaturated intensity values can be chosen for phase demodulation, leaving the other unsaturated ones idle. We propose a method to enhance high dynamic range 3D shape measurement based on a generalized phase-shifting algorithm, which combines the complementary techniques of inverted and regular fringe patterns with a generalized phase-shifting algorithm. Firstly, two sets of complementary phase-shifted fringe patterns, namely the regular and the inverted fringe patterns, are projected and collected. Then, all unsaturated intensity values at the same camera pixel from two sets of fringe patterns are selected and employed to retrieve the phase using a generalized phase-shifting algorithm. Finally, simulations and experiments are conducted to prove the validity of the proposed method. The results are analyzed and compared with those of Jiang's method, demonstrating that our method not only expands the scope of Jiang's method, but also improves

  16. From Agglomerates of Spheres to Irregularly Shaped Particles: Determination of Dynamic Shape Factors from Measurements of Mobility and Vacuum Aerodynamic Diameters

    Energy Technology Data Exchange (ETDEWEB)

    Zelenyuk, Alla; Cai, Yong; Imre, Dan G.

    2006-03-01

    With the advert of aerosol instrumentation it has become possible to simultaneously measure individual particle mobility and vacuum aerodynamic diameters. For spherical particles these two diameters yield individual particle density. In contrast, assigning a physical meaning to the mobility or aerodynamic diameter of aspherical particles is not straightforward. This paper presents an experimental exploration of the effect of particle shape on the relationship between mobility and vacuum aerodynamic diameters. We make measurements on systems of three types: 1) Agglomerates of spheres, for which the density and the volume are known; 2) Ammonium sulfate, sodium chloride, succinic acid and lauric acid irregularly shaped particles of known density; and 3) Internally mixed particles, containing organics and ammonium sulfate, of unknown density and shape. For agglomerates of spheres we observed alignment effects in the DMA and report the first measurements of the dynamic shape factors (DSFs) in free molecular regime. We present here the first experimental determination of the DSF of ammonium sulfate particles. We find for ammonium sulfate particles a DSF that increases from 1.03 to 1.07 as particle mobility diameter increases from 160 nm to 500 nm. Three types of NaC1 particles were generated and characterized: nearly spherical particles with DSF of ~1.02; cubic with DSF that increases from 1.065 to 1.17 as particle mobility diameter increases from 200 nm to 900 nm; and compact agglomerates with DSF 1.3-1.4. Organic particles were found very nearly spherical. The data suggest that particles composed of binary mixtures of ammonium sulfate and succinic acid have lower dynamic shape factors than pure ammonium sulfate particles. However, for internally mixed ammonium sulfate and lauric acid particles we cannot distinguish between nearly spherical particles with low density and particles with DSF of 1.17.

  17. Hydrophobic distal pocket affects NO-heme geminate recombination dynamics in dehaloperoxidase and H64V myoglobin.

    Science.gov (United States)

    Franzen, Stefan; Jasaitis, Audrius; Belyea, Jennifer; Brewer, Scott H; Casey, Robin; MacFarlane, Alexander W; Stanley, Robert J; Vos, Marten H; Martin, Jean-Louis

    2006-07-27

    The recombination dynamics of NO with dehaloperoxidase (DHP) from Amphitrite ornata following photolysis were measured by femtosecond time-resolved absorption spectroscopy. Singular value decomposition (SVD) analysis reveals two important basis spectra. The first SVD basis spectrum reports on the population of photolyzed NO molecules and has the appearance of the equilibrium difference spectrum between the deoxy and NO forms of DHP. The first basis time course has two kinetic components with time constants of tau(11) approximately 9 ps and tau(12) approximately 50 ps that correspond to geminate recombination. The fast geminate process tau(11) arises from a contact pair with the heme iron in a bound state with S = 3/2 spin. The slow geminate process tau(12) corresponds to the recombination from a more remote docking site >3 A from the heme iron with the greater barrier corresponding to a S = 5/2 spin state. The second SVD basis spectrum represents a time-dependent Soret band shift indicative of heme photophysical processes and protein relaxation with time constants of tau(21) approximately 3 ps and tau(22) approximately 17 ps, respectively. A comparison between the more rapid rate constant of the slow geminate phase in DHP-NO and horse heart myoglobin (HHMbNO) or sperm whale myoglobin (SWMbNO) suggests that protein interactions with photolyzed NO are weaker in DHP than in the wild-type MbNOs, consistent with the hydrophobic distal pocket of DHP. The slower protein relaxation rate tau(22) in DHP-NO relative to HHMbNO implies less effective trapping in the docking site of the distal pocket and is consistent with a greater yield for the fast geminate process. The trends observed for DHP-NO also hold for the H64V mutant of SWMb (H64V MbNO), consistent with a more hydrophobic distal pocket for that protein as well. We examine the influence of solution viscosity on NO recombination by varying the glycerol content in the range from 0% to 90% (v/v). The dominant effect of

  18. Mediator facilitates transcriptional activation and dynamic long-range contacts at the IgH locus during class switch recombination

    Science.gov (United States)

    Thomas-Claudepierre, Anne-Sophie; Robert, Isabelle; Rocha, Pedro P.; Raviram, Ramya; Schiavo, Ebe; Heyer, Vincent; Bonneau, Richard; Luo, Vincent M.; Reddy, Janardan K.; Borggrefe, Tilman; Skok, Jane A.

    2016-01-01

    Immunoglobulin (Ig) class switch recombination (CSR) is initiated by the transcription-coupled recruitment of activation-induced cytidine deaminase (AID) to Ig switch regions (S regions). During CSR, the IgH locus undergoes dynamic three-dimensional structural changes in which promoters, enhancers, and S regions are brought to close proximity. Nevertheless, little is known about the underlying mechanisms. In this study, we show that Med1 and Med12, two subunits of the mediator complex implicated in transcription initiation and long-range enhancer/promoter loop formation, are dynamically recruited to the IgH locus enhancers and the acceptor regions during CSR and that their knockdown in CH12 cells results in impaired CSR. Furthermore, we show that conditional inactivation of Med1 in B cells results in defective CSR and reduced acceptor S region transcription. Finally, we show that in B cells undergoing CSR, the dynamic long-range contacts between the IgH enhancers and the acceptor regions correlate with Med1 and Med12 binding and that they happen at a reduced frequency in Med1-deficient B cells. Our results implicate the mediator complex in the mechanism of CSR and are consistent with a model in which mediator facilitates the long-range contacts between S regions and the IgH locus enhancers during CSR and their transcriptional activation. PMID:26903242

  19. Mediator facilitates transcriptional activation and dynamic long-range contacts at the IgH locus during class switch recombination.

    Science.gov (United States)

    Thomas-Claudepierre, Anne-Sophie; Robert, Isabelle; Rocha, Pedro P; Raviram, Ramya; Schiavo, Ebe; Heyer, Vincent; Bonneau, Richard; Luo, Vincent M; Reddy, Janardan K; Borggrefe, Tilman; Skok, Jane A; Reina-San-Martin, Bernardo

    2016-03-07

    Immunoglobulin (Ig) class switch recombination (CSR) is initiated by the transcription-coupled recruitment of activation-induced cytidine deaminase (AID) to Ig switch regions (S regions). During CSR, the IgH locus undergoes dynamic three-dimensional structural changes in which promoters, enhancers, and S regions are brought to close proximity. Nevertheless, little is known about the underlying mechanisms. In this study, we show that Med1 and Med12, two subunits of the mediator complex implicated in transcription initiation and long-range enhancer/promoter loop formation, are dynamically recruited to the IgH locus enhancers and the acceptor regions during CSR and that their knockdown in CH12 cells results in impaired CSR. Furthermore, we show that conditional inactivation of Med1 in B cells results in defective CSR and reduced acceptor S region transcription. Finally, we show that in B cells undergoing CSR, the dynamic long-range contacts between the IgH enhancers and the acceptor regions correlate with Med1 and Med12 binding and that they happen at a reduced frequency in Med1-deficient B cells. Our results implicate the mediator complex in the mechanism of CSR and are consistent with a model in which mediator facilitates the long-range contacts between S regions and the IgH locus enhancers during CSR and their transcriptional activation.

  20. Dynamics of asteroid family halos constrained by spin/shape models

    Science.gov (United States)

    Broz, Miroslav

    2016-10-01

    A number of asteroid families cannot be identified solely on the basis of the Hierarchical Clustering Method (HCM), because they have additional 'former' members in the surroundings which constitute a so called halo (e.g. Broz & Morbidelli 2013). They are usually mixed up with the background population which has to be taken into account too.Luckily, new photometric observations allow to derive new spin/shape models, which serve as independent constraints for dynamical models. For example, a recent census of the Eos family shows 43 core and 27 halo asteroids (including background) with known spin orientations.To this point, we present a complex spin-orbital model which includes full N-body dynamics and consequently accounts for all mean-motion, secular, or three-body gravitational resonances, the Yarkovsky drift, YORP effect, collisional reorientations and also spin-orbital interactions. These are especially important for the Koronis family. In this project, we make use of data from the DAMIT database and ProjectSoft Blue Eye 600 observatory.

  1. Shape and Dynamics of Adhesive Cells: Mechanical Response of Open Systems

    Science.gov (United States)

    Yang, Yuehua; Jiang, Hongyuan

    2017-05-01

    Cell adhesion is an essential biological process. However, previous theoretical and experimental studies ignore a key variable, the changes of cellular volume and pressure, during the dynamic adhesion process. Here, we treat cells as open systems and propose a theoretical framework to investigate how the exchange of water and ions with the environment affects the shape and dynamics of cells adhered between two adhesive surfaces. We show that adherent cells can be either stable (convex or concave) or unstable (spontaneous rupture or collapse) depending on the adhesion energy density, the cell size, the separation of two adhesive surfaces, and the stiffness of the flexible surface. Strikingly, we find that the unstable states vanish when cellular volume and pressure are constant. We further show that the detachments of convex and concave cells are very different. The mechanical response of adherent cells is mainly determined by the competition between the loading rate and the regulation of the cellular volume and pressure. Finally, we show that as an open system the detachment of adherent cells is also significantly influenced by the loading history. Thus, our findings reveal a major difference between living cells and nonliving materials.

  2. Hoxb1b controls oriented cell division, cell shape and microtubule dynamics in neural tube morphogenesis.

    Science.gov (United States)

    Zigman, Mihaela; Laumann-Lipp, Nico; Titus, Tom; Postlethwait, John; Moens, Cecilia B

    2014-02-01

    Hox genes are classically ascribed to function in patterning the anterior-posterior axis of bilaterian animals; however, their role in directing molecular mechanisms underlying morphogenesis at the cellular level remains largely unstudied. We unveil a non-classical role for the zebrafish hoxb1b gene, which shares ancestral functions with mammalian Hoxa1, in controlling progenitor cell shape and oriented cell division during zebrafish anterior hindbrain neural tube morphogenesis. This is likely distinct from its role in cell fate acquisition and segment boundary formation. We show that, without affecting major components of apico-basal or planar cell polarity, Hoxb1b regulates mitotic spindle rotation during the oriented neural keel symmetric mitoses that are required for normal neural tube lumen formation in the zebrafish. This function correlates with a non-cell-autonomous requirement for Hoxb1b in regulating microtubule plus-end dynamics in progenitor cells in interphase. We propose that Hox genes can influence global tissue morphogenesis by control of microtubule dynamics in individual cells in vivo.

  3. Dynamical Behavior of a Pseudoelastic Vibration Absorber Using Shape Memory Alloys

    Directory of Open Access Journals (Sweden)

    Hugo De S. Oliveira

    2017-01-01

    Full Text Available The tuned vibration absorber (TVA provides vibration reduction of a primary system subjected to external excitation. The idea is to increase the number of system degrees of freedom connecting a secondary system to the primary system. This procedure promotes vibration reduction at its design forcing frequency but two new resonance peaks appear introducing critical behaviors that must be avoided. The use of shape memory alloys (SMAs can improve the performance of the classical TVA establishing an adaptive TVA (ATVA. This paper deals with the nonlinear dynamics of a passive pseudoelastic tuned vibration absorber with an SMA element. In this regard, a single degree of freedom elastic oscillator is used to represent the primary system, while an extra oscillator with an SMA element represents the secondary system. Temperature dependent behavior of the system allows one to change the system response avoiding undesirable responses. Nevertheless, hysteretic behavior introduces complex characteristics to the system dynamics. The influence of the hysteretic behavior due to stress-induced phase transformation is investigated. The ATVA performance is evaluated by analyzing primary system maximum vibration amplitudes for different forcing amplitudes and frequencies. Numerical simulations establish comparisons of the ATVA results with those obtained from the classical TVA. A parametric study is developed showing the best performance conditions and this information can be useful for design purposes.

  4. Fortune favours the brave: Movement responses shape demographic dynamics in strongly competing populations.

    Science.gov (United States)

    Potts, Jonathan R; Petrovskii, Sergei V

    2017-05-07

    Animal movement is a key mechanism for shaping population dynamics. The effect of interactions between competing animals on a population's survival has been studied for many decades. However, interactions also affect an animal's subsequent movement decisions. Despite this, the indirect effect of these decisions on animal survival is much less well-understood. Here, we incorporate movement responses to foreign animals into a model of two competing populations, where inter-specific competition is greater than intra-specific competition. When movement is diffusive, the travelling wave moves from the stronger population to the weaker. However, by incorporating behaviourally induced directed movement towards the stronger population, the weaker one can slow the travelling wave down, even reversing its direction. Hence movement responses can switch the predictions of traditional mechanistic models. Furthermore, when environmental heterogeneity is combined with aggressive movement strategies, it is possible for spatially segregated co-existence to emerge. In this situation, the spatial patterns of the competing populations have the unusual feature that they are slightly out-of-phase with the environmental patterns. Finally, incorporating dynamic movement responses can also enable stable co-existence in a homogeneous environment, giving a new mechanism for spatially segregated co-existence. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. A sliding-mode approach to the simultaneous shape and attitude control of flexible space structures with uncertain dynamics

    Science.gov (United States)

    Dodds, S. J.; Senior, M.

    1993-09-01

    A new sliding-mode approach is applied to the simultaneous shape and attitude control of large space structures, such as an antenna reflector whose shape is to be accurately preserved. Arrangements of collocated sensors and continuous actuators are catered for. The control system is able to maintain a specified closed-loop transient performance over a wide range of dynamics parameters. This property enables the system to continue to operate satisfactorily after the occurrence of sensor and actuator failures, thereby greatly enhancing the system reliability. It also enables the control system to be designed without the need to derive a detailed dynamics model.

  6. Dynamics of photoexcited carrier relaxation and recombination in CdTe/CdS thin films

    Energy Technology Data Exchange (ETDEWEB)

    Levi, D.H.; Fluegel, B.D.; Ahrenkiel, R.K. [National Renewable Energy Lab., Golden, CO (United States)] [and others

    1996-05-01

    Efficiency-limiting defects in photovoltaic devices are readily probed by time-resolved spectroscopy. This paper presents the first direct optical measurements of the relaxation and recombination pathways of photoexcited carriers in the CdS window layer of CdTe/CdS polycrystalline thin films. Femtosecond time-resolved pump/probe measurements indicate the possible existence of a two-phase CdS/CdSTe layer, rather than a continuously graded alloy layer at the CdTe/CdS interface. Complementary time-resolved photoluminescence (PL) measurements show that the photoexcited carriers are rapidly captured by deep-level defects. The temporal and density-dependent properties of the photoluminescence prove that the large Stokes shift of the PL relative to the band edge is due to strong phonon coupling to deep-level defects in CdS. The authors suggest that modifications in the CdS processing may enhance carrier collection efficiency in the blue spectral region.

  7. Probing nuclear dynamics in jet production with a global event shape

    Science.gov (United States)

    Kang, Zhong-Bo; Liu, Xiaohui; Mantry, Sonny; Qiu, Jian-Wei

    2013-10-01

    We study single jet production in electron-nucleus collisions e-+NA→J+X, using the 1-jettiness (τ1) global event shape. It inclusively quantifies the pattern of radiation in the final state, gives enhanced sensitivity to soft radiation at wide angles from the nuclear beam and final-state jet, and facilitates the resummation of large Sudakov logarithms associated with the veto on additional jets. Through their effect on the observed pattern of radiation, 1-jettiness can be a useful probe of nuclear parton distribution functions and power corrections from dynamical effects in the nuclear medium. This formalism allows for the standard jet shape analysis while simultaneously providing sensitivity to soft radiation at wide angles from the jet. We use a factorization framework for cross-sections differential in τ1 and the transverse momentum (PJT) and rapidity (y) of the jet, in the region τ1≪PJT. The restriction τ1≪PJT allows only soft radiation between the nuclear beam and jet directions, thereby acting as a veto on additional jets. This region is also insensitive to the details of the jet algorithm, allowing for better theoretical control over resummation, while providing enhanced sensitivity to nuclear medium effects. We give numerical results at leading twist, with resummation at the next-to-next-to-leading logarithmic level of accuracy, for a variety of nuclear targets. Such studies would be ideal for the electron-ion collider and the LHeC proposals for a future electron-ion collider, where a range of nuclear targets are planned.

  8. Cerebellar inhibitory output shapes the temporal dynamics of its somatosensory inferior olivary input.

    Science.gov (United States)

    Hogri, Roni; Segalis, Eyal; Mintz, Matti

    2014-08-01

    The cerebellum is necessary and sufficient for the acquisition and execution of adaptively timed conditioned motor responses following repeated paired presentations of a conditioned stimulus and an unconditioned stimulus. The underlying plasticity depends on the convergence of conditioned and unconditioned stimuli signals relayed to the cerebellum by the pontine nucleus and the inferior olive (IO), respectively. Adaptive timing of conditioned responses relies on the correctly predicted onset of the unconditioned stimulus, usually a noxious somatosensory stimulus. We addressed two questions: First, does the IO relay information regarding the duration of somatosensory stimuli to the cerebellum? Multiple-unit recordings from the IO of anesthetized rats that received periorbital airpuffs of various durations revealed that sustained somatosensory stimuli are invariably transformed into phasic IO outputs. The phasic response was followed by a post-peak depression in IO activity as compared to baseline, providing the cerebellum with a highly synchronous signal, time-locked to the stimulus' onset. Second, we sought to examine the involvement of olivocerebellar interactions in this signal transformation. Cerebello-olivary inhibition was interrupted using temporary pharmacological inactivation of cerebellar output nuclei, resulting in more sustained (i.e., less synchronous) IO responses to sustained somatosensory stimuli, in which the post-peak depression was substituted with elevated activity as compared to baseline. We discuss the possible roles of olivocerebellar negative-feedback loops and baseline cerebello-olivary inhibition levels in shaping the temporal dynamics of the IO's response to somatosensory stimuli and the consequences of this shaping for cerebellar plasticity and its ability to adapt to varying contexts.

  9. Dynamic behaviour of dagger-shaped cantilevers for atomic force microscopy

    Science.gov (United States)

    Shen, Kangzhi; Hurley, Donna C.; Turner, Joseph A.

    2004-11-01

    Experimental techniques based on the atomic force microscope (AFM) have been developed for characterizing mechanical properties at the nanoscale and applied to a variety of materials and structures. Atomic force acoustic microscopy (AFAM) is one such technique that uses spectral information of the AFM cantilever as it vibrates in contact with a sample. In this paper, the dynamic behaviour of AFM cantilevers that have a dagger shape is investigated using a power-series method. Dagger-shaped cantilevers have plan-view geometry consisting of a rectangular section at the clamped end and a triangular section at the tip. Their geometry precludes modelling using closed-form expressions. The convergence of the series is demonstrated and the convergence radius is shown to be related to the given geometry. The accuracy and efficiency of the method are investigated by comparison with finite element results for several different cases. AFAM experiments are modelled by including a linear spring at the tip that represents the contact stiffness. The technique developed is shown to be very effective for inversion of experimental frequency information into contact stiffness results for AFAM. In addition, the sensitivities of the frequencies to the contact stiffness are discussed in terms of the various geometric parameters of the problem including the slope, the ratio of the rectangular to triangular lengths and the tip location. Calculations of contact stiffness from experimental data using this model are shown to be very good in comparison with other models. It is anticipated that this approach may be useful for other cantilever geometries as well, such that AFAM accuracy may be improved.

  10. Charge Recombination, Transport Dynamics, and Interfacial Effects in Organic Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Heeger, Alan [Univ. of California, Santa Barbara, CA (United States); Bazan, Guillermo [Univ. of California, Santa Barbara, CA (United States); Nguyen, Thuc-Quyen [Univ. of California, Santa Barbara, CA (United States); Wudl, Fred [Univ. of California, Santa Barbara, CA (United States)

    2015-02-12

    The need for renewable sources of energy is well known. Conversion of sunlight to electricity using solar cells is one of the most important opportunities for creating renewable energy sources. The research carried out under DE-FG02-08ER46535 focused on the science and technology of “Plastic” solar cells comprised of organic (i.e. carbon based) semiconductors. The Bulk Heterojunction concept involves a phase separated blend of two organic semiconductors each with dimensions in the nano-meter length scale --- one a material that functions as a donor for electrons and the other a material that functions as an acceptor for electrons. The nano-scale inter-penetrating network concept for “Plastic” solar cells was created at UC Santa Barbara. A simple measure of the impact of this concept can be obtained from a Google search which gives 244,000 “hits” for the Bulk Heterojunction solar cell. Research funded through this program focused on four major areas: 1. Interfacial effects in organic photovoltaics, 2. Charge transfer and photogeneration of mobile charge carriers in organic photovoltaics, 3. Transport and recombination of the photogenerated charge carriers in organic photovoltaics, 4. Synthesis of novel organic semiconducting polymers and semiconducting small molecules, including conjugated polyelectrolytes. Following the discovery of ultrafast charge transfer at UC Santa Barbara in 1992, the nano-organic (Bulk Heterojunction) concept was formulated. The need for a morphology comprising two interpenetrating bicontinuous networks was clear: one network to carry the photogenerated electrons (negative charge) to the cathode and one network to carry the photo-generated holes (positive charge) to the anode. This remarkable self-assembled network morphology has now been established using Transmission electron Microscopy (TEM) either in the Phase Contrast mode or via TEM-Tomography. The steps involved in delivering power from a solar cell to an external circuit

  11. Charge Recombination, Transport Dynamics, and Interfacial Effects in Organic Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Heeger, Alan; Bazan, Guillermo; Nguyen, Thuc-Quyen; Wudl, Fred

    2015-02-27

    The need for renewable sources of energy is well known. Conversion of sunlight to electricity using solar cells is one of the most important opportunities for creating renewable energy sources. The research carried out under DE-FG02-08ER46535 focused on the science and technology of “Plastic” solar cells comprised of organic (i.e. carbon based) semiconductors. The Bulk Heterojunction concept involves a phase separated blend of two organic semiconductors each with dimensions in the nano-meter length scale --- one a material that functions as a donor for electrons and the other a material that functions as an acceptor for electrons. The nano-scale inter-penetrating network concept for “Plastic” solar cells was created at UC Santa Barbara. A simple measure of the impact of this concept can be obtained from a Google search which gives 244,000 “hits” for the Bulk Heterojunction solar cell. Research funded through this program focused on four major areas: 1. Interfacial effects in organic photovoltaics, 2. Charge transfer and photogeneration of mobile charge carriers in organic photovoltaics, 3. Transport and recombination of the photogenerated charge carriers in organic photovoltaics, 4. Synthesis of novel organic semiconducting polymers and semiconducting small molecules, including conjugated polyelectrolytes. Following the discovery of ultrafast charge transfer at UC Santa Barbara in 1992, the nano-organic (Bulk Heterojunction) concept was formulated. The need for a morphology comprising two interpenetrating bicontinuous networks was clear: one network to carry the photogenerated electrons (negative charge) to the cathode and one network to carry the photo-generated holes (positive charge) to the anode. This remarkable self-assembled network morphology has now been established using Transmission electron Microscopy (TEM) either in the Phase Contrast mode or via TEM-Tomography. The steps involved in delivering power from a solar cell to an external circuit

  12. Flexible Wire-Shaped Supercapacitors in Parallel Double Helix Configuration with Stable Electrochemical Properties under Static/Dynamic Bending.

    Science.gov (United States)

    Guo, Kai; Ma, Ying; Li, Huiqiao; Zhai, Tianyou

    2016-02-24

    Wire-shaped flexible supercapacitors (SCs) have aroused much attention due to their small size, light weight, high flexibility, and deformability. However, the previously reported wire-shaped SCs usually involve complex assembly processes, encounter potential structural instabilities, and the influence of dynamic bending on the electrochemical stability of wire-shaped SCs is also not clear. Here, a parallel double helix wire-shaped supercapacitor (PDWS) protocol has been developed with two symmetric titanium@MnO2 fiber electrodes winded on a flexible nylon fiber by a simple and reliable process. The PDWSs show an operate voltage of 0.8 V, a high capacitance of 15.6 mF cm(-2) and an energy density of 1.4 µWh cm(-2) . Due to rational structure design, the PDWSs demonstrate excellent mechanical and electrochemical stability under both static and dynamic deformations. Over 3500 bending cycles, 88.0% of the initial capacitance can still be retained. In terms of dynamic bending, it is found that the cyclic voltammetry curves show periodically fluctuations simultaneously with the bending frequency and the intensity of fluctuation increases with higher bending frequency, while the dynamic capacitance is almost not affected. With extraordinary mechanical flexibility and excellent electrochemical stability, the high performance PDWS is considered to be a promising power source for wearable electronics. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Confined martensitic phase transformation kinetics and lattice dynamics in Ni–Co–Fe–Ga shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Cong, Daoyong; Rule, Kirrily Clair; Li, Wen-Hsien; Lee, Chi-Hung; Zhang, Qinghua; Wang, Haoliang; Hao, Yulin; Wang, Yandong; Huang, E-Wen (UST - China); (NCU-Taiwan); (Beijing Inst. Tech.); (Chinese Aca. Sci.); (ANSTO); (NCTU)

    2016-09-02

    Here we describe insights into the phase transformation kinetics and lattice dynamics associated with the newly discovered confined martensitic transformation, which are of great significance to the in-depth understanding of the phase transformation behavior responsible for the rich new physical phenomena in shape memory alloys and could shed light on the design of novel multifunctional properties through tuning the confined martensitic transformation.

  14. DMPD: Shaping of monocyte and macrophage function by adenosine receptors. [Dynamic Macrophage Pathway CSML Database

    Lifescience Database Archive (English)

    Full Text Available 17056121 Shaping of monocyte and macrophage function by adenosine receptors. Hasko ...tml) (.csml) Show Shaping of monocyte and macrophage function by adenosine receptors. PubmedID 17056121 Titl...e Shaping of monocyte and macrophage function by adenosine receptors. Authors Has

  15. Incremental dynamic analysis of concrete moment resisting frames reinforced with shape memory composite bars

    Science.gov (United States)

    Zafar, Adeel; Andrawes, Bassem

    2012-02-01

    Fiber reinforced polymer (FRP) reinforcing bars have been used in concrete structures as an alternative to conventional steel reinforcement, in order to overcome corrosion problems. However, due to the linear behavior of the commonly used reinforcing fibers, they are not considered in structures which require ductility and damping characteristics. The use of superelastic shape memory alloy (SMA) fibers with their nonlinear elastic behavior as reinforcement in the composite could potentially provide a solution for this problem. Small diameter SMA wires are coupled with polymer matrix to produce SMA-FRP composite, which is sought in this research as reinforcing bars. SMA-FRP bars are sought in this study to enhance the seismic performance of reinforced concrete (RC) moment resisting frames (MRFs) in terms of reducing their residual inter-story drifts while still maintaining the elastic characteristics associated with conventional FRP. Three story one bay and six story two bay RC MRF prototype structures are designed with steel, SMA-FRP and glass-FRP reinforcement. The incremental dynamic analysis technique is used to investigate the behaviors of the two frames with the three different reinforcement types under a suite of ground motion records. It is found that the frames with SMA-FRP composite reinforcement exhibit higher performance levels including lower residual inter-story drifts, high energy dissipation and thus lower damage, which are important for structures in highly seismic zones.

  16. Water mass dynamics shape Ross Sea protist communities in mesopelagic and bathypelagic layers

    Science.gov (United States)

    Zoccarato, Luca; Pallavicini, Alberto; Cerino, Federica; Fonda Umani, Serena; Celussi, Mauro

    2016-12-01

    Deep-sea environments host the largest pool of microbes and represent the last largely unexplored and poorly known ecosystems on Earth. The Ross Sea is characterized by unique oceanographic dynamics and harbors several water masses deeply involved in cooling and ventilation of deep oceans. In this study the V9 region of the 18S rDNA was targeted and sequenced with the Ion Torrent high-throughput sequencing technology to unveil differences in protist communities (>2 μm) correlated with biogeochemical properties of the water masses. The analyzed samples were significantly different in terms of environmental parameters and community composition outlining significant structuring effects of temperature and salinity. Overall, Alveolata (especially Dinophyta), Stramenopiles and Excavata groups dominated mesopelagic and bathypelagic layers, and protist communities were shaped according to the biogeochemistry of the water masses (advection effect and mixing events). Newly-formed High Salinity Shelf Water (HSSW) was characterized by high relative abundance of phototrophic organisms that bloom at the surface during the austral summer. Oxygen-depleted Circumpolar Deep Water (CDW) showed higher abundance of Excavata, common bacterivores in deep water masses. At the shelf-break, Antarctic Bottom Water (AABW), formed by the entrainment of shelf waters in CDW, maintained the eukaryotic genetic signature typical of both parental water masses.

  17. A reagent-based dynamic trigger for cell adhesion, shape change, or cocultures.

    Science.gov (United States)

    van Dongen, Stijn F M; Maiuri, Paolo; Piel, Matthieu

    2014-01-01

    The described protocol is a simple and easily implemented method for making dynamic micropatterns for cell culture. It is based on the use of a surface coating material (azido-PLL-g-PEG (APP)) that initially repels cells, but which can be made strongly adherent by addition of a small functional peptide (BCN-RGD) to the cell culture medium. The method can be applied to trigger the adhesion, migration, or shape change of single cells or of populations of cells, and it can be used to create patterned cocultures. The entire process can be subdivided into three main parts. The first part describes the creation of patterned APP substrates. The second part describes cell seeding and "click" triggering of cell adhesion; the final part describes variations that allow the overlay of multiple patterns or the creation of patterned cocultures. The APP coating of substrates and the triggering of adhesion only involves treating the surface with aqueous stock solutions, allowing any biology lab to adopt this technique.

  18. Solute Dynamics and Imaging in the Tear Film on an Eye-shaped Domain

    Science.gov (United States)

    Braun, R. J.; Li, Longfei; Henshaw, William; Driscoll, Tobin; King-Smith, P. E.

    2015-11-01

    The concentration of ions in the tear film (osmolarity) is a key variable in understanding dry eye symptoms and disease, yet its global distribution is not available; direct measurements are restricted to a region near the temporal canthus. It has been suggested that imaging methods that use solutes such as fluorescein can be used as a proxy for estimating the osmolarity. The concentration of fluorescein is not measured directly either but the intensity as a function of concentration and thickness of the film is well established. We derived a mathematical model that couples multiple solutes and fluid dynamics within the tear film on a 2D eye-shaped domain. The model includes the physical effects of evaporation, surface tension, viscosity, ocular surface wettability, osmolarity, osmosis, fluorescence and tear fluid supply and drainage. We solved the governing system of coupled nonlinear PDEs using the Overture computational framework developed at LLNL, together with a hybrid time stepping scheme (using variable step BDF and RKC). Results of our numerical simulations provide new insight about the osmolarity distribution and its connection with images obtained in vivo over the whole ocular surface and in local regions of tear thinning due to evaporation and other effects. This work was supported in part by NSF grants 1022706 and 1412085, and NIH grant 1R01EY021794.

  19. Dynamic Shape Reconstruction of Three-Dimensional Frame Structures Using the Inverse Finite Element Method

    Science.gov (United States)

    Gherlone, Marco; Cerracchio, Priscilla; Mattone, Massimiliano; Di Sciuva, Marco; Tessler, Alexander

    2011-01-01

    A robust and efficient computational method for reconstructing the three-dimensional displacement field of truss, beam, and frame structures, using measured surface-strain data, is presented. Known as shape sensing , this inverse problem has important implications for real-time actuation and control of smart structures, and for monitoring of structural integrity. The present formulation, based on the inverse Finite Element Method (iFEM), uses a least-squares variational principle involving strain measures of Timoshenko theory for stretching, torsion, bending, and transverse shear. Two inverse-frame finite elements are derived using interdependent interpolations whose interior degrees-of-freedom are condensed out at the element level. In addition, relationships between the order of kinematic-element interpolations and the number of required strain gauges are established. As an example problem, a thin-walled, circular cross-section cantilevered beam subjected to harmonic excitations in the presence of structural damping is modeled using iFEM; where, to simulate strain-gauge values and to provide reference displacements, a high-fidelity MSC/NASTRAN shell finite element model is used. Examples of low and high-frequency dynamic motion are analyzed and the solution accuracy examined with respect to various levels of discretization and the number of strain gauges.

  20. Shaping the Globular Cluster Mass Function by Stellar-Dynamical Evaporation

    CERN Document Server

    McLaughlin, Dean E

    2007-01-01

    Dynamical-evolution models of old globular cluster mass functions (GCMFs), in which the depletion of an initial power-law distribution at low masses is caused predominantly by evaporation driven by internal two-body relaxation, can explain the turnover mass scale M_{TO} and the generic shape of the GCMF at M < M_{TO}. We point out that such models inherently predict that the GCMF should depend on the cluster half-mass density, rho_h, and we show that the Galactic GCMF exhibits precisely the expected variations: M_{TO} increases systematically with rho_h, while the width of the distribution decreases. The quantitative details are consistent with a cluster mass-loss rate, -dM/dt = mu_{ev} ~ rho_h^{1/2} with rho_h approximately constant in time, which we adopt as the simplest description of evaporation. The normalization of mu_{ev} is within a factor of two of standard theoretical expectations. We show that the known, weak dependence of the Milky Way GCMF on Galactocentric position r_{gc} results from its bas...

  1. Enhanced high dynamic range 3D shape measurement based on generalized phase-shifting algorithm

    CERN Document Server

    Wang, Minmin; Zhou, Canlin; Zhang, Chaorui; Si, Shuchun; Li, Hui; Lei, Zhenkun; Li, YanJie

    2016-01-01

    It is a challenge for Phase Measurement Profilometry (PMP) to measure objects with a large range of reflectivity variation across the surface. Saturated or dark pixels in the deformed fringe patterns captured by the camera will lead to phase fluctuations and errors. Jiang et al. proposed a high dynamic range real-time 3D shape measurement method without changing camera exposures. Three inverted phase-shifted fringe patterns are used to complement three regular phase-shifted fringe patterns for phase retrieval when any of the regular fringe patterns are saturated. But Jiang's method still has some drawbacks: (1) The phases in saturated pixels are respectively estimated by different formulas for different cases. It is shortage of an universal formula; (2) it cannot be extended to four-step phase-shifting algorithm because inverted fringe patterns are the repetition of regular fringe patterns; (3) only three unsaturated intensity values at every pixel of fringe patterns are chosen for phase demodulation, lying i...

  2. Adaptive digital fringe projection technique for high dynamic range three-dimensional shape measurement.

    Science.gov (United States)

    Lin, Hui; Gao, Jian; Mei, Qing; He, Yunbo; Liu, Junxiu; Wang, Xingjin

    2016-04-04

    It is a challenge for any optical method to measure objects with a large range of reflectivity variation across the surface. Image saturation results in incorrect intensities in captured fringe pattern images, leading to phase and measurement errors. This paper presents a new adaptive digital fringe projection technique which avoids image saturation and has a high signal to noise ratio (SNR) in the three-dimensional (3-D) shape measurement of objects that has a large range of reflectivity variation across the surface. Compared to previous high dynamic range 3-D scan methods using many exposures and fringe pattern projections, which consumes a lot of time, the proposed technique uses only two preliminary steps of fringe pattern projection and image capture to generate the adapted fringe patterns, by adaptively adjusting the pixel-wise intensity of the projected fringe patterns based on the saturated pixels in the captured images of the surface being measured. For the bright regions due to high surface reflectivity and high illumination by the ambient light and surfaces interreflections, the projected intensity is reduced just to be low enough to avoid image saturation. Simultaneously, the maximum intensity of 255 is used for those dark regions with low surface reflectivity to maintain high SNR. Our experiments demonstrate that the proposed technique can achieve higher 3-D measurement accuracy across a surface with a large range of reflectivity variation.

  3. Dynamic Motion and Rearranged Molecular Shape of Heme in Myoglobin: Structural and Functional Consequences

    Directory of Open Access Journals (Sweden)

    Saburo Neya

    2013-03-01

    Full Text Available Myoglobin, a simple oxygen binding protein, was reconstituted with various types of synthetic hemes to manipulate the heme-globin interactions. From the paramagnetic NMR analysis, small heme was found to rotate rapidly about the iron-histidine bond upon. This is a novel and typical example for the fluctuation of protein. The dynamic NMR analysis indicated that the 360° rotational rate of a small heme was 1,400 s−1 at room temperature. The X-ray analyses revealed that the tertiary structure of globin containing the smallest heme was closely similar to that of native protein despite extensive destruction of the specific heme-globin interactions. The functional analyses of O2 binding showed that the loose heme-globin contacts do not significantly affect the oxygen binding. On the other hand, the rearrangement of tetrapyrrole array and the non-planar deformation in porphyrin ring significantly affect the functional properties of myoglobin. These results, taken together, indicate that the essential factors to regulate the myoglobin function are hidden under the molecular shape of prosthetic group rather than in the nonbonded heme-globin contacts.

  4. Improved non-dimensional dynamic influence function method for vibration analysis of arbitrarily shaped plates with clamped edges

    Directory of Open Access Journals (Sweden)

    Sang-Wook Kang

    2016-03-01

    Full Text Available A new formulation for the non-dimensional dynamic influence function method, which was developed by the authors, is proposed to efficiently extract eigenvalues and mode shapes of clamped plates with arbitrary shapes. Compared with the finite element and boundary element methods, the non-dimensional dynamic influence function method yields highly accurate solutions in eigenvalue analysis problems of plates and membranes including acoustic cavities. However, the non-dimensional dynamic influence function method requires the uneconomic procedure of calculating the singularity of a system matrix in the frequency range of interest for extracting eigenvalues because it produces a non-algebraic eigenvalue problem. This article describes a new approach that reduces the problem of free vibrations of clamped plates to an algebraic eigenvalue problem, the solution of which is straightforward. The validity and efficiency of the proposed method are illustrated through several numerical examples.

  5. Roll System and Stock's Multi-parameter Coupling Dynamic Modeling Based on the Shape Control of Steel Strip

    Science.gov (United States)

    Zhang, Yang; Peng, Yan; Sun, Jianliang; Zang, Yong

    2017-05-01

    The existence of rolling deformation area in the rolling mill system is the main characteristic which distinguishes the other machinery. In order to analyze the dynamic property of roll system's flexural deformation, it is necessary to consider the transverse periodic movement of stock in the rolling deformation area which is caused by the flexural deformation movement of roll system simultaneously. Therefore, the displacement field of roll system and flow of metal in the deformation area is described by kinematic analysis in the dynamic system. Through introducing the lateral displacement function of metal in the deformation area, the dynamic variation of per unit width rolling force can be determined at the same time. Then the coupling law caused by the co-effect of rigid movement and flexural deformation of the system structural elements is determined. Furthermore, a multi-parameter coupling dynamic model of the roll system and stock is established by the principle of virtual work. More explicitly, the coupled motion modal analysis was made for the roll system. Meanwhile, the analytical solutions for the flexural deformation movement's mode shape functions of rolls are discussed. In addition, the dynamic characteristic of the lateral flow of metal in the rolling deformation area has been analyzed at the same time. The establishment of dynamic lateral displacement function of metal in the deformation area makes the foundation for analyzing the coupling law between roll system and rolling deformation area, and provides a theoretical basis for the realization of the dynamic shape control of steel strip.

  6. Roll System and Stock's Multi-parameter Coupling Dynamic Modeling Based on the Shape Control of Steel Strip

    Science.gov (United States)

    Zhang, Yang; Peng, Yan; Sun, Jianliang; Zang, Yong

    2017-03-01

    The existence of rolling deformation area in the rolling mill system is the main characteristic which distinguishes the other machinery. In order to analyze the dynamic property of roll system's flexural deformation, it is necessary to consider the transverse periodic movement of stock in the rolling deformation area which is caused by the flexural deformation movement of roll system simultaneously. Therefore, the displacement field of roll system and flow of metal in the deformation area is described by kinematic analysis in the dynamic system. Through introducing the lateral displacement function of metal in the deformation area, the dynamic variation of per unit width rolling force can be determined at the same time. Then the coupling law caused by the co-effect of rigid movement and flexural deformation of the system structural elements is determined. Furthermore, a multi-parameter coupling dynamic model of the roll system and stock is established by the principle of virtual work. More explicitly, the coupled motion modal analysis was made for the roll system. Meanwhile, the analytical solutions for the flexural deformation movement's mode shape functions of rolls are discussed. In addition, the dynamic characteristic of the lateral flow of metal in the rolling deformation area has been analyzed at the same time. The establishment of dynamic lateral displacement function of metal in the deformation area makes the foundation for analyzing the coupling law between roll system and rolling deformation area, and provides a theoretical basis for the realization of the dynamic shape control of steel strip.

  7. Impact of Reabsorption on the Emission Spectra and Recombination Dynamics of Hybrid Perovskite Single Crystals.

    Science.gov (United States)

    Diab, Hiba; Arnold, Christophe; Lédée, Ferdinand; Trippé-Allard, Gaëlle; Delport, Géraud; Vilar, Christèle; Bretenaker, Fabien; Barjon, Julien; Lauret, Jean-Sébastien; Deleporte, Emmanuelle; Garrot, Damien

    2017-07-06

    Understanding the surface properties of organic-inorganic lead-based perovskites is of high importance to improve the device's performance. Here, we have investigated the differences between surface and bulk optical properties of CH3NH3PbBr3 single crystals. Depth-resolved cathodoluminescence was used to probe the near-surface region on a depth of a few microns. In addition, we have studied the transmitted luminescence through thicknesses between 50 and 600 μm. In both experiments, the expected spectral shift due to the reabsorption effect has been precisely calculated. We demonstrate that reabsorption explains the important variations reported for the emission energy of single crystals. Single crystals are partially transparent to their own luminescence, and radiative transport is the dominant mechanism for propagation of the excitation in thick crystals. The transmitted luminescence dynamics are characterized by a long rise time and a lengthening of their decay due to photon recycling and light trapping.

  8. Avalanche dynamics of structural phase transitions in shape memory alloys by acoustic emission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ludwig, Benno

    2009-09-24

    In this work the avalanche dynamics of five shape memory samples has been analyzed by acoustic emission spectroscopy. The acoustic emission spectroscopy is particularly suitable for this analysis as it couples with high sensitivity to small structural changes caused by nucleation processes, interface movements, or variant rearrangements [91]. Owing to its high time resolution it provides a statistical approach to describe the jerky and intermittent character of the avalanche dynamics [20]. Rate-dependent cooling and heating runs have been conducted in order to study time-dependent aspects of the transition dynamics of the single crystals Ni{sub 63}Al{sub 37}, Au{sub 50.5}Cd{sub 49.5}, and Fe{sub 68.8}Pd{sup single}{sub 31.2}, and the polycrystalline sample Fe{sub 68.8}Pd{sup poly}{sub 31.2}. Moreover, a ferromagnetic Ni{sub 52}Mn{sub 23}Ga{sub 25} single crystal has been studied by temperature cycles under an applied magnetic field and additionally by magnetic-field cycles at a constant temperature in the martensitic phase. All samples analyzed in this work show power law behavior in the acoustic emission features amplitude, energy, and duration, which indicates scale-free behavior. The access to these power law spectra allows an investigation of energy barriers separating the metastable states, which give rise to avalanche transition dynamics. By performing rate-dependent experiments the importance of thermal fluctuations and the impact of martensite respectively twin stabilization processes have been examined. In the case of the Ni{sub 52}Mn{sub 23}Ga{sub 25} sample, the magnetic-field-induced variant rearrangement at slow field cycles leads to stronger signals than the rearrangement at quick cycles. This behavior can be explained by twin stabilization processes, which are accompanied by a reduction of the twin boundary mobility. For Ni{sub 63}Al{sub 37}, the combination of relevant thermal fluctuations, different involved time scales, and a high degree of

  9. Avalanche dynamics of structural phase transitions in shape memory alloys by acoustic emission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ludwig, Benno

    2009-09-24

    In this work the avalanche dynamics of five shape memory samples has been analyzed by acoustic emission spectroscopy. The acoustic emission spectroscopy is particularly suitable for this analysis as it couples with high sensitivity to small structural changes caused by nucleation processes, interface movements, or variant rearrangements [91]. Owing to its high time resolution it provides a statistical approach to describe the jerky and intermittent character of the avalanche dynamics [20]. Rate-dependent cooling and heating runs have been conducted in order to study time-dependent aspects of the transition dynamics of the single crystals Ni{sub 63}Al{sub 37}, Au{sub 50.5}Cd{sub 49.5}, and Fe{sub 68.8}Pd{sup single}{sub 31.2}, and the polycrystalline sample Fe{sub 68.8}Pd{sup poly}{sub 31.2}. Moreover, a ferromagnetic Ni{sub 52}Mn{sub 23}Ga{sub 25} single crystal has been studied by temperature cycles under an applied magnetic field and additionally by magnetic-field cycles at a constant temperature in the martensitic phase. All samples analyzed in this work show power law behavior in the acoustic emission features amplitude, energy, and duration, which indicates scale-free behavior. The access to these power law spectra allows an investigation of energy barriers separating the metastable states, which give rise to avalanche transition dynamics. By performing rate-dependent experiments the importance of thermal fluctuations and the impact of martensite respectively twin stabilization processes have been examined. In the case of the Ni{sub 52}Mn{sub 23}Ga{sub 25} sample, the magnetic-field-induced variant rearrangement at slow field cycles leads to stronger signals than the rearrangement at quick cycles. This behavior can be explained by twin stabilization processes, which are accompanied by a reduction of the twin boundary mobility. For Ni{sub 63}Al{sub 37}, the combination of relevant thermal fluctuations, different involved time scales, and a high degree of

  10. Shape memory alloys applied to improve rotor-bearing system dynamics - an experimental investigation

    OpenAIRE

    2015-01-01

    tor-bearing systems have critical speeds and to pass through them is an ongoing challenge in the field of mechanical engineering. The incorporation of shape memory alloys in rotating systems has an increasing importance to improve system performance and to avoid potential damaging situations when passing through critical speeds. In this work, the feasibility of applying shape memory alloys to a rotating system is experimentally investigated. Shape memory alloys can change their stiffness with...

  11. Spatial vision in insects is facilitated by shaping the dynamics of visual input through behavioural action

    Directory of Open Access Journals (Sweden)

    Martin eEgelhaaf

    2012-12-01

    Full Text Available Insects such as flies or bees, with their miniature brains, are able to control highly aerobatic flight manoeuvres and to solve spatial vision tasks, such as avoiding collisions with obstacles, landing on objects or even localizing a previously learnt inconspicuous goal on the basis of environmental cues. With regard to solving such spatial tasks, these insects still outperform man-made autonomous flying systems. To accomplish their extraordinary performance, flies and bees have been shown by their characteristic behavioural actions to actively shape the dynamics of the image flow on their eyes (optic flow. The neural processing of information about the spatial layout of the environment is greatly facilitated by segregating the rotational from the translational optic flow component through a saccadic flight and gaze strategy. This active vision strategy thus enables the nervous system to solve apparently complex spatial vision tasks in a particularly efficient and parsimonious way. The key idea of this review is that biological agents, such as flies or bees, acquire at least part of their strength as autonomous systems through active interactions with their environment and not by simply processing passively gained information about the world. These agent-environment interactions lead to adaptive behaviour in surroundings of a wide range of complexity. Animals with even tiny brains, such as insects, are capable of performing extraordinarily well in their behavioural contexts by making optimal use of the closed action–perception loop. Model simulations and robotic implementations show that the smart biological mechanisms of motion computation and visually-guided flight control might be helpful to find technical solutions, for example, when designing micro air vehicles carrying a miniaturized, low-weight on-board processor.

  12. Spatial vision in insects is facilitated by shaping the dynamics of visual input through behavioral action.

    Science.gov (United States)

    Egelhaaf, Martin; Boeddeker, Norbert; Kern, Roland; Kurtz, Rafael; Lindemann, Jens P

    2012-01-01

    Insects such as flies or bees, with their miniature brains, are able to control highly aerobatic flight maneuvres and to solve spatial vision tasks, such as avoiding collisions with obstacles, landing on objects, or even localizing a previously learnt inconspicuous goal on the basis of environmental cues. With regard to solving such spatial tasks, these insects still outperform man-made autonomous flying systems. To accomplish their extraordinary performance, flies and bees have been shown by their characteristic behavioral actions to actively shape the dynamics of the image flow on their eyes ("optic flow"). The neural processing of information about the spatial layout of the environment is greatly facilitated by segregating the rotational from the translational optic flow component through a saccadic flight and gaze strategy. This active vision strategy thus enables the nervous system to solve apparently complex spatial vision tasks in a particularly efficient and parsimonious way. The key idea of this review is that biological agents, such as flies or bees, acquire at least part of their strength as autonomous systems through active interactions with their environment and not by simply processing passively gained information about the world. These agent-environment interactions lead to adaptive behavior in surroundings of a wide range of complexity. Animals with even tiny brains, such as insects, are capable of performing extraordinarily well in their behavioral contexts by making optimal use of the closed action-perception loop. Model simulations and robotic implementations show that the smart biological mechanisms of motion computation and visually-guided flight control might be helpful to find technical solutions, for example, when designing micro air vehicles carrying a miniaturized, low-weight on-board processor.

  13. Static and dynamic responses of a microcantilever with a T-shaped tip mass to an electrostatic actuation

    Institute of Scientific and Technical Information of China (English)

    B Firouzi; M Zamanian; S A A Hosseini

    2016-01-01

    In this study, nonlinear static and dynamic responses of a microcantilever with a T-shaped tip mass excited by electrostatic actuations are investigated. The elec-trostatic force is generated by applying an electric voltage between the horizontal part of T-shaped tip mass and an opposite electrode plate. The cantilever microbeam is mod-eled as an Euler–Bernoulli beam. The T-shaped tip mass is assumed to be a rigid body and the nonlinear effect of electrostatic force is considered. An equation of motion and its associated boundary conditions are derived by the aid of combining the Hamilton principle and Newton’s method. An exact solution is obtained for static deflection and mode shape of vibration around the static position. The differen-tial equation of nonlinear vibration around the static position is discretized using the Galerkin method. The system mode shapes are used as its related comparison functions. The dis-cretized equations are solved by the perturbation theory in the neighborhood of primary and subharmonic resonances. In addition, effects of mass inertia, mass moment of iner-tia as well as rotation of the T-shaped mass, which were ignored in previous works, are considered in the analysis. It is shown that by increasing the length of the horizontal part of the T-shaped mass, the amount of static deflection increases, natural frequency decreases and nonlinear shift of the res-onance frequency increases. It is concluded that attaching an electrode plate with a T-shaped configuration to the end of the cantilever microbeam results in a configuration with larger pull-in voltage and smaller nonlinear shift of the reso-nance frequency compared to the configuration in which the electrode plate is directly attached to it.

  14. Static and dynamic responses of a microcantilever with a T-shaped tip mass to an electrostatic actuation

    Science.gov (United States)

    Firouzi, B.; Zamanian, M.; Hosseini, S. A. A.

    2016-12-01

    In this study, nonlinear static and dynamic responses of a microcantilever with a T-shaped tip mass excited by electrostatic actuations are investigated. The electrostatic force is generated by applying an electric voltage between the horizontal part of T-shaped tip mass and an opposite electrode plate. The cantilever microbeam is modeled as an Euler-Bernoulli beam. The T-shaped tip mass is assumed to be a rigid body and the nonlinear effect of electrostatic force is considered. An equation of motion and its associated boundary conditions are derived by the aid of combining the Hamilton principle and Newton's method. An exact solution is obtained for static deflection and mode shape of vibration around the static position. The differential equation of nonlinear vibration around the static position is discretized using the Galerkin method. The system mode shapes are used as its related comparison functions. The discretized equations are solved by the perturbation theory in the neighborhood of primary and subharmonic resonances. In addition, effects of mass inertia, mass moment of inertia as well as rotation of the T-shaped mass, which were ignored in previous works, are considered in the analysis. It is shown that by increasing the length of the horizontal part of the T-shaped mass, the amount of static deflection increases, natural frequency decreases and nonlinear shift of the resonance frequency increases. It is concluded that attaching an electrode plate with a T-shaped configuration to the end of the cantilever microbeam results in a configuration with larger pull-in voltage and smaller nonlinear shift of the resonance frequency compared to the configuration in which the electrode plate is directly attached to it.

  15. Polarization-independent etching of fused silica based on electrons dynamics control by shaped femtosecond pulse trains for microchannel fabrication.

    Science.gov (United States)

    Yan, X; Jiang, L; Li, X; Zhang, K; Xia, B; Liu, P; Qu, L; Lu, Y

    2014-09-01

    We propose an approach to realize polarization-independent etching of fused silica by using temporally shaped femtosecond pulse trains to control the localized transient electrons dynamics. Instead of nanograting formation using traditional unshaped pulses, for the pulse delay of pulse trains larger than 1 ps, coherent field-vector-related coupling is not possible and field orientation is lost. The exponential growth of the periodic structures is interrupted. In this case, disordered and interconnected nanostructures are formed, which is probably the main reason of etching independence on the laser polarization. As an application example, square-wave-shaped and arc-shaped microchannels are fabricated by using pulse trains to demonstrate the advantage of the proposed method in fabricating high-aspect-ratio and three-dimensional microchannels.

  16. Full-density, net-shape powder consolidation using dynamic magnetic pulse pressures

    Science.gov (United States)

    Chelluri, Bhanu; Barber, John P.

    1999-07-01

    The full-density consolidation of powders into net-shape parts yields high green strength, low shrinkage, short sinter times, superior mechanical properties, and low manufacturing costs. The conventional lowcost, single-press, single-sinter process typically densifies powders at less than 65 percent green density. This article describes the Magnepress™ process, a powder-processing technique wherein pulsed magnetic pressures consolidate powders into full-density parts without admixed lubricants or binders. The Magnepress technique is especially suitable for producing net-shape products with radial symmetry (e.g., rods, cylindrical parts with internal features, tubular shapes, and high aspect-ratio specimens).

  17. Results from a survey of the dynamics shaping Uranus' Mab/μ-ring system

    Science.gov (United States)

    Kumar, Kartik; de Pater, Imke; Showalter, Mark R.

    2014-11-01

    Based on Hubble Space Telescope (HST) data, Showalter and Lissauer (2006) reported the discovery of two faint rings beyond Uranus’ main rings: the ν- and μ- rings. They constitute Uranus' outer ring system and are located beyond the ɛ-ring but interior to the large classical moons. After co-adding a series of HST images, Showalter and Lissauer (2006) obtained radial profiles for both new rings. They discovered that the peak radial intensity of the μ-ring aligns closely with the orbit of Mab. Along with numerous other observations, this points to the fact that the Mab/μ-ring system is highly coupled.The discovery of the μ-ring has led to open questions about dust dynamics beyond Uranus' main rings. Like Saturn's E-ring, observations reveal that the μ-ring is blue, indicative of a pre-dominance of sub-micron-sized particles (de Pater et al., 2006). The E-ring results from plumes on Enceladus' south pole, however the origin of the μ-ring remains a mystery. The latter is likely fed by ejecta from micro-meteorite impacts with Mab, much like Jupiter's faint rings are regenerated by companion (small) moons (Burns et al., 1999). The μ-ring's steep size-distribution suggests that there is an unknown mechanism at play that hides or removes large dust particles. We present results from an investigation into the forces shaping the μ-ring. To simulate the motion of dust in the Mab/μ-ring system, we developed a numerical toolbox (Dustsim; Kumar et al., 2015) that uses Tudat (Kumar et al., 2012). We performed integrations using Dustsim that included the effects of Uranus' gravity field, titled magnetic moment, solar radiation pressure, and collisions with a putative suite of large μ-ring bodies, hypothesized as the cause of Mab's anomalous orbital motion (Kumar et al., 2014). Following on from previous studies (e.g., Sfair and Giuliatti Winter, 2009; Sfair and Giuliatti Winter, 2012), we present a survey of the expected lifetime of μ-ring dust, as a function of

  18. Nonlinear dynamics and bifurcation characteristics of shape memory alloy thin films subjected to in-plane stochastic excitation

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Zhi-Wen [Department of Mechanics, Tianjin University, 92 Weijin Road, Nankai District, Tianjin 300072 (China); Tianjin Key Laboratory of Nonlinear Dynamics and Chaos Control 92 Weijin Road, Nankai District, Tianjin 300072 (China); Zhang, Qing-Xin [Department of Mechanics, Tianjin University, 92 Weijin Road, Nankai District, Tianjin 300072 (China); Xu, Jia, E-mail: xujia_ld@163.com [Department of Mechanics, Tianjin University, 92 Weijin Road, Nankai District, Tianjin 300072 (China)

    2014-11-03

    A kind of shape memory alloy (SMA) hysteretic nonlinear model was developed, and the nonlinear dynamics and bifurcation characteristics of the SMA thin film subjected to in-plane stochastic excitation were investigated. Van der Pol difference item was introduced to describe the hysteretic phenomena of the SMA strain–stress curves, and the nonlinear dynamic model of the SMA thin film subjected to in-plane stochastic excitation was developed. The conditions of global stochastic stability of the system were determined in singular boundary theory, and the probability density function of the system response was obtained. Finally, the conditions of stochastic Hopf bifurcation were analyzed. The results of theoretical analysis and numerical simulation indicate that self-excited vibration is induced by the hysteretic nonlinear characteristics of SMA, and stochastic Hopf bifurcation appears when the bifurcation parameter was changed; there are two limit cycles in the stationary probability density of the dynamic response of the system in some cases, which means that there are two vibration amplitudes whose probabilities are both very high, and jumping phenomena between the two vibration amplitudes appear with the change in conditions. The results obtained in this current paper are helpful for the application of the SMA thin film in stochastic vibration fields. - Highlights: • Hysteretic nonlinear model of shape memory alloy was developed. • Van der Pol item was introduced to interpret hysteretic strain–stress curves. • Nonlinear dynamic characteristics of the shape memory alloy film were analyzed. • Jumping phenomena were observed in the change of the parameters.

  19. Integrated Aerodynamic/Structural/Dynamic Analyses of Aircraft with Large Shape Changes

    Science.gov (United States)

    Samareh, Jamshid A.; Chwalowski, Pawel; Horta, Lucas G.; Piatak, David J.; McGowan, Anna-Maria R.

    2007-01-01

    The conceptual and preliminary design processes for aircraft with large shape changes are generally difficult and time-consuming, and the processes are often customized for a specific shape change concept to streamline the vehicle design effort. Accordingly, several existing reports show excellent results of assessing a particular shape change concept or perturbations of a concept. The goal of the current effort was to develop a multidisciplinary analysis tool and process that would enable an aircraft designer to assess several very different morphing concepts early in the design phase and yet obtain second-order performance results so that design decisions can be made with better confidence. The approach uses an efficient parametric model formulation that allows automatic model generation for systems undergoing radical shape changes as a function of aerodynamic parameters, geometry parameters, and shape change parameters. In contrast to other more self-contained approaches, the approach utilizes off-the-shelf analysis modules to reduce development time and to make it accessible to many users. Because the analysis is loosely coupled, discipline modules like a multibody code can be easily swapped for other modules with similar capabilities. One of the advantages of this loosely coupled system is the ability to use the medium-to high-fidelity tools early in the design stages when the information can significantly influence and improve overall vehicle design. Data transfer among the analysis modules are based on an accurate and automated general purpose data transfer tool. In general, setup time for the integrated system presented in this paper is 2-4 days for simple shape change concepts and 1-2 weeks for more mechanically complicated concepts. Some of the key elements briefly described in the paper include parametric model development, aerodynamic database generation, multibody analysis, and the required software modules as well as examples for a telescoping wing, a

  20. Computational Fluid Dynamics Prediction of a Modified Savonius Wind Turbine with Novel Blade Shapes

    OpenAIRE

    2015-01-01

    The Savonius wind turbine is a type of vertical axis wind turbine (VAWTs) that is simply composed of two or three arc-type blades which can generate power even under poor wind conditions. A modified Savonius wind turbine with novel blade shapes is introduced with the aim of increasing the power coefficient of the turbine. The effect of blade fullness, which is a main shape parameter of the blade, on the power production of a two-bladed Savonius wind turbine is investigated using transient com...

  1. Analysis of ion dynamics and peak shapes for delayed extraction time-of-flight mass spectrometers

    Science.gov (United States)

    Collado, V. M.; Ponciano, C. R.; Fernandez-Lima, F. A.; da Silveira, E. F.

    2004-06-01

    The dependence of time-of-flight (TOF) peak shapes on time-dependent extraction electric fields is studied theoretically. Conditions for time focusing are analyzed both analytically and numerically for double-acceleration-region TOF spectrometers. Expressions for the spectrometer mass resolution and for the critical delay time are deduced. Effects due to a leakage field in the first acceleration region are shown to be relevant under certain conditions. TOF peak shape simulations for the delayed extraction method are performed for emitted ions presenting a Maxwellian initial energy distribution. Calculations are compared to experimental results of Cs+ emission due to CsI laser ablation.

  2. FtsZ rings and helices: physical mechanisms for the dynamic alignment of biopolymers in rod-shaped bacteria

    Science.gov (United States)

    Fischer-Friedrich, Elisabeth; Friedrich, Benjamin M.; Gov, Nir S.

    2012-02-01

    In many bacterial species, the protein FtsZ forms a cytoskeletal ring that marks the future division site and scaffolds the division machinery. In rod-shaped bacteria, most frequently membrane-attached FtsZ rings or ring fragments are reported and occasionally helices. By contrast, axial FtsZ clusters have never been reported. In this paper, we investigate theoretically how dynamic FtsZ aggregates align in rod-shaped bacteria. We study systematically different physical mechanisms that affect the alignment of FtsZ polymers using a computational model that relies on autocatalytic aggregation of FtsZ filaments at the membrane. Our study identifies a general tool kit of physical and geometrical mechanisms by which rod-shaped cells align biopolymer aggregates. Our analysis compares the relative impact of each mechanism on the circumferential alignment of FtsZ as observed in rod-shaped bacteria. We determine spontaneous curvature of FtsZ polymers and axial confinement of FtsZ on the membrane as the strongest factors. Including Min oscillations in our model, we find that these stabilize axial and helical clusters on short time scales, but promote the formation of an FtsZ ring at the cell middle at longer times. This effect could provide an explanation to the long standing puzzle of transiently observed oscillating FtsZ helices in Escherichia coli cells prior to cell division.

  3. Recombination dynamics as a key determinant of open circuit voltage in organic bulk heterojunction solar cells: a comparison of four different donor polymers

    Energy Technology Data Exchange (ETDEWEB)

    Maurano, Andrea; Hamilton, Rick; Shuttle, Chris G.; O' Regan, Brian; Zhang, Weimin; McCulloch, Iain; Durrant, James R. [Departments of Chemistry, Imperial College London, South Kensington SW7 2AZ (United Kingdom); Ballantyne, Amy M.; Nelson, Jenny [Departments of Physics, Imperial College London, South Kensington SW7 2AZ (United Kingdom); Azimi, Hamed [Konarka Austria, Altenbergerstrasse 69, A-4040 Linz (Austria); Christian Doppler Laboratory for Surface Optics, Johannes Kepler University, Linz (Austria); Morana, Mauro; Brabec, Christoph J. [Konarka Austria, Altenbergerstrasse 69, A-4040 Linz (Austria)

    2010-11-24

    Transient photovoltage and charge extraction analyses are employed to analyzes charge carrier densities and bimolecular recombination dynamics in organic polymer: fullerene solar cells under open circuit operating conditions, employing four different donor polymers. An equation is derived which allows us to calculate the device V{sub OC} from these kinetic measurements. This equation allows us to calculate voltage output of devices within {+-} 25 meV of directly measured values. This analysis thus allows us to relate device open circuit voltage directly to the kinetics of bimolecular recombination, and thereby the influence of nanomorphology upon device voltage output. (Copyright copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. Geographic coupling of juvenile and adult habitat shapes spatial population dynamics of a coral reef fish

    NARCIS (Netherlands)

    Huijbers, C.M.; Nagelekerken, I.; Debrot, A.O.; Jongejans, E.

    2013-01-01

    Marine spatial population dynamics are often addressed with a focus on larval dispersal, without taking into account movement behavior of individuals in later life stages. Processes occurring during demersal life stages may also drive spatial population dynamics if habitat quality is perceived diffe

  5. Interaction of short-term depression and firing dynamics in shaping single neuron encoding

    Directory of Open Access Journals (Sweden)

    Ashutosh eMohan

    2013-04-01

    Full Text Available We investigated how the two properties short-term synaptic depression of afferent input and postsynaptic firing dynamics combine to determine the operating mode of a neuron. While several computational roles have been ascribed to either, their interaction has not been studied. We considered two types of short-term synaptic dynamics (release-dependent and release-independent depression and two classes of firing dynamics (regular firing and firing with spike-frequency adaptation. The input-output transformation of the four possible combinations of pre- and postsynaptic dynamics was characterized. Adapting neurons receiving input from release-dependent synapses functioned largely as coincidence detectors. The other three configurations showed properties consistent with integrators, each with distinct features. These results suggest that the operating mode of a neuron is determined by both the pre- and postsynaptic dynamics and that studying them together is necessary to understand emergent properties and their implications for neuronal coding.

  6. Advance Vector Control on Based Energy Shaping for control in Wide Speed Range and Quicker Dynamic Response

    Directory of Open Access Journals (Sweden)

    Mohammad Bagher Banae Sharifian

    2013-01-01

    Full Text Available Based on the vector of the permanent magnet synchronous motor (PMSM and in order to obtain the system operation of wide variable speed range,quicker dynamic response, the maximum torque per ampere (MTPA control is often applied for the constant torque region, the flux-weakening control is used in the constant power region, moreover, the classical two closed-loop PI controller are often used. Recently, the energy-shaping nonlinear controller is increasingly used to control the nonlinear induction motor or PMSM, therefore, the comparison between both PMSM systems is devoted to research in this paper, one adopts the PI current controller, the other adopts the energy-shaping current controller. Both PMSM control systems are modeled based on the MATLAB/SIMULINK,and the system performances are tested and some conclusions are given.

  7. Early development of dynamic shape perception under slit-viewing conditions.

    Science.gov (United States)

    Imura, Tomoko; Shirai, Nobu

    2014-01-01

    The developmental processes underpinning global shape and global motion perception in infancy have been relatively well described. However, the development of the ability to integrate both global motion and global shape information has remained unclear. In this study we employed a slit-viewing task to investigate the ability to integrate spatiotemporal information among infants ranging in age from 3 to 12 months. In experiment 1 each infant was familiarised with a moving object that was only partly visible through a slit. One of the two objects in the test trial was a novel object, and the other object had appeared previously in familiarisation trials. The findings suggested that infants aged 5 months and over looked longer at the novel drawings compared with the more familiar objects in the test trials. This implies that the infants recognised the whole shape of the object under the slit-viewing condition. In experiment 2 each infant was presented with partial images in a random order. In this case the infants were unable to distinguish the whole shape of the object. The findings suggest that infants did not rely on the local cues provided in experiment .

  8. Fundamental challenges in electrowetting: from equilibrium shapes to contact angle saturation and drop dynamics

    NARCIS (Netherlands)

    Mugele, Frieder

    2009-01-01

    Electrowetting is a versatile tool for manipulating typically submillimetre-sized drops in various microfluidic applications. In recent years the microscopic understanding of the electrowetting effect has substantially improved leading to a detailed description of the drop shape and the (singular) d

  9. Efficiency Enhancement of an Envelope Tracking Power Amplifier Combining Supply Shaping and Dynamic Biasing

    DEFF Research Database (Denmark)

    Tafuri, Felice Francesco; Sira, Daniel; Jensen, Ole Kiel

    2013-01-01

    of the input envelope by means of two shaping functions jointly designed on the basis of a single-tone characterization. The presented technique is demonstrated by means of measurements on a commercial GaAs HBT power amplifier. Measured results showed a PA power added efficiency (PAE) of 51.9%, an error vector...

  10. Wake dynamics behind a seal-vibrissa-shaped cylinder: a comparative study by time-resolved particle velocimetry measurements

    Science.gov (United States)

    Wang, Shaofei; Liu, Yingzheng

    2016-03-01

    The wake dynamics behind a seal-vibrissa-shaped cylinder, which are closely related to the seal's extraordinary ability to faithfully track the hydrodynamic trails of its upstream prey, were extensively studied by using time-resolved particle image velocity. Four cylindrical configurations that shared the same hydrodynamic diameter (i.e., a circular cylinder, an elliptical cylinder, a wavy cylinder, and a vibrissa-shaped cylinder) were chosen for the comparative study at the Reynolds number 1.8 × 103. The instantaneous flow fields behind the cylinders were measured along their vertical and horizontal planes. The distinct global differences between the wakes were determined from the streamline patterns, the reverse-flow intermittences, and both the streamwise and longitudinal velocity fluctuation intensities. Compared to the other three systems tested, the vibrissa-shaped cylinder system was characterized by a considerably reduced recirculation zone in the nodal plane, the existence of a very stably reversed flow, and substantial reductions in the streamwise and longitudinal velocity fluctuation intensities. Further cross-correlation of the fluctuating longitudinal velocities showed that the unsteady events behind the vibrissa-shaped cylinder were poorly organized by sequence and considerably constrained in their spatial extent. Finally, a dynamic mode decomposition (DMD) was performed on the instantaneously varying wake flows. In the wavy cylinder system, a single dominant DMD mode at St = 0.2 (corresponding to Karman vortex street) was detected in both the saddle and nodal planes. Although the dominant DMD modes at St = 0.23 and 0.3 were determined in the saddle and nodal planes of the vibrissa-shaped cylinder system, respectively, the spatial pattern of these two DMD modes showed resolved vortical structures that were highly distorted and constrained to an extremely limited space. These DMD modes had much less energy than those in the other three systems. The

  11. Design and dynamic simulation for the transmission mechanism of drum-shaped gear with ring-involute teeth

    Institute of Scientific and Technical Information of China (English)

    LI Qing-kai; LI Xiao-fang; ZHAO Yong-qiang

    2007-01-01

    The new mechanism of drum-shaped gear with ring-involute teeth is presented to implement dimensional transmission for the stairlift. The structure of the gear and rack in this actuating mechanism is designed,and then its inherent radius of turn and modulus selection have been studied. In order to make the mechanism move steadily, the drive guide is proposed. After using the dynamics simulation software ADAMS to analyze the 3D model, this kind of mechanism is confirmed to be able to implement dimensional track. The useful method and basis would be provided for the optimization design of the mechanism.

  12. Shape optimization of plate with static and dynamic constraints via virtual laminated element

    Institute of Scientific and Technical Information of China (English)

    李芳; 徐兴; 凌道盛

    2003-01-01

    The virtual laminated element method (VLEM) can resolve structural shape optimization problems with a new method. According to the characteristics of VLEM , only some characterized layer thickness values need be defined as design variables instead of boundary node coordinates or some other parameters determining the system boundary. One of the important features of this method is that it is not necessary to regenerate the FE(finite element) grid during the optimization process so as to avoid optimization failures resulting from some distortion grid elements. The thickness distribution in thin plate optimization problems in other studies before is of stepped shape. However, in this paper, a continuous thickness distribution can be obtained after optimization using VLEM, and is more reasonable. Furthermore, an approximate reanalysis method named ″behavior model technique″ can be used to reduce the amount of structural reanalysis. Some typical examples are offered to prove the effectiveness and practicality of the proposed method.

  13. Shape optimization of plate with static and dynamic constraints via virtual laminated element.

    Science.gov (United States)

    Li, Fang; Xu, Xing; Ling, Dao-Sheng

    2003-01-01

    The virtual laminated element method (VLEM) can resolve structural shape optimization problems with a new method. According to the characteristics of VLEM, only some characterised layer thickness values need be defined as design variables instead of boundary node coordinates or some other parameters determining the system boundary. One of the important features of this method is that it is not necessary to regenerate the FE(finite element) grid during the optimization process so as to avoid optimization failures resulting from some distortion grid elements. The thickness distribution in thin plate optimization problems in other studies before is of stepped shape. However, in this paper, a continuous thickness distribution can be obtained after optimization using VLEM, and is more reasonable. Furthermore, an approximate reanalysis method named "behavior model technique" can be used to reduce the amount of structural reanalysis. Some typical examples are offered to prove the effectiveness and practicality of the proposed method.

  14. Dynamic parabolic pulse generation using temporal shaping of wavelength to time mapped pulses.

    Science.gov (United States)

    Nguyen, Dat; Piracha, Mohammad Umar; Mandridis, Dimitrios; Delfyett, Peter J

    2011-06-20

    Self-phase modulation in fiber amplifiers can significantly degrade the quality of compressed pulses in chirped pulse amplification systems. Parabolic pulses with linear frequency chirp are suitable for suppressing nonlinearities, and to achieve high peak power pulses after compression. In this paper, we present an active time domain technique to generate parabolic pulses for chirped pulse amplification applications. Pulses from a mode-locked laser are temporally stretched and launched into an amplitude modulator, where the drive voltage is designed using the spectral shape of the input pulse and the transfer function of the modulator, resulting in the generation of parabolic pulses. Experimental results of pulse shaping with a pulse train from a mode-locked laser are presented, with a residual error of less than 5%. Moreover, an extinction ratio of 27 dB is achieved, which is ideal for chirped pulse amplification applications.

  15. A fast large dynamic range shaping amplifier for particle detector front-end

    Energy Technology Data Exchange (ETDEWEB)

    Rivetti, Angelo [INFN-Sezione di Turin (Italy)]. E-mail: rivetti@to.infn.it; Delaurenti, Paolo [Dipartimento di Fisica Sperimentale-Universita di Turin (Italy)

    2007-03-01

    The paper describes a fast shaping amplifier with rail-to-rail output swing. The circuit is based on a CMOS operational amplifier with a class AB output stage. A baseline holder, incorporating a closed-loop unity gain buffer with slew rate limitation, performs the AC coupling with the preamplifier and guarantees a baseline shift smaller than 3 mV for unipolar output pulses of 3 V and 10 MHz rate.

  16. Shape characteristics of the foot arch: dynamics in the pregnancy period.

    Science.gov (United States)

    Jelen, Karel; Tetkova, Zuzana; Halounova, Lena; Pavelka, Karel; Koudelka, Tomas; Ruzicka, Pavel

    2005-12-01

    The aim is data detection and finding some load consequences generated by various mechanical or physiological changes in the interaction of the end segment of the body--the foot--and the environment. Shape instability of the foot caused by e.g. loading of the foot by long-term frequency loads--walking, by extreme loads--sport, by hormonal changes--pregnancy, by aging, by pathologies, etc. The footprint surface was numerically described in 3D by means of stereo-photo-gram-metrical method--DMR digital relief model. Density of discrete points--250-400 per one print. Detailed DMR was constructed by means of triangular web including contour picture with the use of Atlas program. The specified generated web is characterized by triangles with a cca 1 mm side in the number of up to 4,500 elements per one footprint model. The results enable us to deduce shape characteristics of DMR--the shape of the interactive boundary of the foot--the rest surface, to solve foot arch straining, to solve issues of discomfort and distribution of the pressure at the boundary of the foot--the rest surface, the shoe, etc. The gained findings can be interpreted in the field of prevention, therapy, orthopedics, podology, and enable us to come up with recommendations for the orthopedic practice and industrial use in the footwear production, etc. THE MAIN FINDINGS: The difference between volume reductions of the space under the foot arch characterizes the level of "fall" of the arch. This criterion is independent of the foot size, and is in 3D. Shape characteristics of footprints in pregnant women and in the period after childbirth were calculated on the basis of the defined criterion. The results of the group of four women tested in three periods suggest that there is no clear tendency towards the foot arch falling/increasing of the foot arch "fall" during the pregnancy period.

  17. Conservation of recombination hotspots in yeast

    OpenAIRE

    Tsai, Isheng J.; Burt, Austin; Koufopanou, Vassiliki

    2010-01-01

    Meiotic recombination does not occur randomly along a chromosome, but instead tends to be concentrated in small regions, known as “recombination hotspots.” Recombination hotspots are thought to be short-lived in evolutionary time due to their self-destructive nature, as gene conversion favors recombination-suppressing alleles over recombination-promoting alleles during double-strand repair. Consistent with this expectation, hotspots in humans are highly dynamic, with little correspondence in ...

  18. Effect of the shape of mouth pressure variation on dynamic oscillation threshold of a clarinet model

    CERN Document Server

    Bergeot, Baptiste; Vergez, Christophe

    2014-01-01

    Simple models of clarinet instruments based on iterated maps have been used in the past to successfully estimate the threshold of oscillation of this instrument as a function of a constant blowing pressure. However, when the blowing pressure gradually increases through time, the oscillations appear at a much higher value, called dynamic oscillation threshold, than what is predicted in the static case. This is known as bifurcation delay, a phenomenon studied in [1,2] for a clarinet model. In particular the dynamic oscillation threshold is predicted analytically when the blowing pressure is linearly increased. However, the mouth pressure cannot grow indefinitely. During a note attack, after an increasing phase, the musician stabilizes the mouth pressure. In the present work, the analytical prediction of the dynamic oscillation threshold is extended to a situations in which the mouth pressure approaches a steady state pressure according to an exponential time profile. The predictions still show a good agreement ...

  19. Dynamics of dark-bright solitons in cigar-shaped Bose-Einstein condensates

    Energy Technology Data Exchange (ETDEWEB)

    Middelkamp, S. [Zentrum fuer Optische Quantentechnologien, Universitaet Hamburg, 22761 Hamburg (Germany); Chang, J.J.; Hamner, C. [Washington State University, Department of Physics and Astronomy, Pullman, WA 99164 (United States); Carretero-Gonzalez, R. [Nonlinear Physics Group, Escuela Tecnica Superior de Ingenieria Informatica, Departamento de Fisica Aplicada I, Universidad de Sevilla, Avda. Reina Mercedes s/n, 41012 Sevilla (Spain); Kevrekidis, P.G., E-mail: kevrekid@gmail.co [Department of Mathematics and Statistics, University of Massachusetts, Amherst, MA 01003-4515 (United States); Achilleos, V.; Frantzeskakis, D.J. [Department of Physics, University of Athens, Panepistimiopolis, Zografos, Athens 157 84 (Greece); Schmelcher, P. [Zentrum fuer Optische Quantentechnologien, Universitaet Hamburg, 22761 Hamburg (Germany); Engels, P. [Washington State University, Department of Physics and Astronomy, Pullman, WA 99164 (United States)

    2011-01-17

    We explore the stability and dynamics of dark-bright (DB) solitons in two-component elongated Bose-Einstein condensates by developing effective one-dimensional vector equations and solving the three-dimensional Gross-Pitaevskii equations. A strong dependence of the oscillation frequency and of the stability of the DB soliton on the atom number of its components is found; importantly, the wave may become dynamically unstable even in the 1D regime. As the atom number in the dark-soliton-supporting component is further increased, spontaneous symmetry breaking leads to oscillatory dynamics in the transverse degrees of freedom. Moreover, the interactions of two DB solitons are investigated with an emphasis on the importance of their relative phases. Experimental results showcasing multiple DB soliton oscillations and a DB-DB collision in a Bose-Einstein condensate consisting of two hyperfine states of {sup 87}Rb confined in an elongated optical dipole trap are presented.

  20. Age-specific infectious period shapes dynamics of pneumonia in bighorn sheep.

    Science.gov (United States)

    Plowright, Raina K; Manlove, Kezia R; Besser, Thomas E; Páez, David J; Andrews, Kimberly R; Matthews, Patrick E; Waits, Lisette P; Hudson, Peter J; Cassirer, E Frances

    2017-09-04

    Superspreading, the phenomenon where a small proportion of individuals contribute disproportionately to new infections, has profound effects on disease dynamics. Superspreading can arise through variation in contacts, infectiousness or infectious periods. The latter has received little attention, yet it drives the dynamics of many diseases of critical public health, livestock health and conservation concern. Here, we present rare evidence of variation in infectious periods underlying a superspreading phenomenon in a free-ranging wildlife system. We detected persistent infections of Mycoplasma ovipneumoniae, the primary causative agent of pneumonia in bighorn sheep (Ovis canadensis), in a small number of older individuals that were homozygous at an immunologically relevant genetic locus. Interactions among age-structure, genetic composition and infectious periods may drive feedbacks in disease dynamics that determine the magnitude of population response to infection. Accordingly, variation in initial conditions may explain divergent population responses to infection that range from recovery to catastrophic decline and extirpation. © 2017 John Wiley & Sons Ltd/CNRS.

  1. The role of ice dynamics in shaping vegetation in flowing waters.

    Science.gov (United States)

    Lind, Lovisa; Nilsson, Christer; Polvi, Lina E; Weber, Christine

    2014-11-01

    Ice dynamics is an important factor affecting vegetation in high-altitude and high-latitude streams and rivers. During the last few decades, knowledge about ice in streams and rivers has increased significantly and a respectable body of literature is now available. Here we review the literature on how ice dynamics influence riparian and aquatic vegetation. Traditionally, plant ecologists have focused their studies on the summer period, largely ignoring the fact that processes during winter also impact vegetation dynamics. For example, the freeze-up period in early winter may result in extensive formation of underwater ice that can restructure the channel, obstruct flow, and cause flooding and thus formation of more ice. In midwinter, slow-flowing reaches develop a surface-ice cover that accumulates snow, protecting habitats under the ice from formation of underwater ice but also reducing underwater light, thus suppressing photosynthesis. Towards the end of winter, ice breaks up and moves downstream. During this transport, ice floes can jam up and cause floods and major erosion. The magnitudes of the floods and their erosive power mainly depend on the size of the watercourse, also resulting in different degrees of disturbance to the vegetation. Vegetation responds both physically and physiologically to ice dynamics. Physical action involves the erosive force of moving ice and damage caused by ground frost, whereas physiological effects - mostly cell damage - happen as a result of plants freezing into the ice. On a community level, large magnitudes of ice dynamics seem to favour species richness, but can be detrimental for individual plants. Human impacts, such as flow regulation, channelisation, agriculturalisation and water pollution have modified ice dynamics; further changes are expected as a result of current and predicted future climate change. Human impacts and climate change can both favour and disfavour riverine vegetation dynamics. Restoration of streams

  2. The static and dynamic behavior of MEMS arch resonators near veering and the impact of initial shapes

    KAUST Repository

    Hajjaj, Amal Z.

    2017-07-19

    We investigate experimentally and analytically the effect of initial shapes, arc and cosine wave, on the static and dynamic behavior of microelectromechanical systems (MEMS) arch resonators. We show that by carefully choosing the geometrical parameters and the initial shape of the arch, the veering phenomenon (avoided-crossing) among the first two symmetric modes can be strongly activated. To demonstrate this, we study electrothermally tuned and electrostatically driven initially curved MEMS resonators. Upon changing the electrothermal voltage, we demonstrate high frequency tunability of arc resonators compared to the cosine-configuration resonators for the first and third resonance frequencies. For arc beams, we show that the first resonance frequency increases up to twice its fundamental value and the third resonance frequency decreases until getting very close to the first resonance frequency triggering the veering phenomenon. Around the veering regime, we study experimentally and analytically the dynamic behavior of the arc beam for different electrostatic loads. The analytical study is based on a reduced order model of a nonlinear Euler–Bernoulli shallow arch beam model. The veering phenomenon is also confirmed through a finite-element multi-physics and nonlinear model.

  3. Vibrational branching ratios and shape resonant photoionization dynamics in N2O

    Science.gov (United States)

    Braunstein, M.; McKoy, V.

    1989-02-01

    Accurate photoelectron continuum orbitals are used to study vibrational branching ratios and photoelectron asymmetry parameters for alternative vibrational modes in the photoionization of N2O (7sigma exp -1). The strong non-Franck-Dondon vibrational ion distributions for the symmetric and antisymmetric stretching modes at low photoelectron energies observed in the dispersed ionic fluorescence measurements of Poliakoff et al. (1986) are confirmed. It is shown that these features arise from a sigma shape resonance which is associated with the molecular framework as a whole and not with either of its fragments, N-N or N-O.

  4. Shape effects on dynamics of inertia-free spheroids in wall turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Challabotla, Niranjan Reddy; Zhao, Lihao; Andersson, Helge I. [Department of Energy and Process Engineering, Norwegian University of Science and Technology (NTNU), 7491 Trondheim (Norway)

    2015-06-15

    The rotational motion of inertia-free spheroids has been studied in a numerically simulated turbulent channel flow. Although inertia-free spheroids were translated as tracers with the flow, neither the disk-like nor the rod-like particles adapted to the fluid rotation. The flattest disks preferentially aligned their symmetry axes normal to the wall, whereas the longest rods were parallel with the wall. The shape-dependence of the particle orientations carried over to the particle rotation such that the mean spin was reduced with increasing departure from sphericity. The streamwise spin fluctuations were enhanced due to asphericity, but substantially more for prolate than for oblate spheroids.

  5. Role of the interfacial area for structure and dynamics in polymer nanocomposites: molecular dynamics simulations of polystyrene with silica nanoparticles of different shapes

    Science.gov (United States)

    Liu, Shengyuan; Böhm, Michael C.; Müller-Plathe, Florian

    2016-10-01

    Polystyrene nanocomposites containing a fraction of silica nanoparticles of different geometries (sphere, cube and regular tetrahedron) have been investigated by coarse-grained molecular dynamics simulations. Structural and dynamic properties of the polymer chains in the presence of the nanoparticles have been analyzed as a function of the nanoparticle mass fraction and geometrical shape. It has been found that the dimension of the polymer chains in the interphase expands due to the polymer-nanoparticle interaction. Their global dimension (averaged over the whole sample), however, shrinks when increasing the total surface area of the nanoparticles. The conformational changes of polymer chains in the interphase are monitored by a chain orientation parameter. The profiles of the chain dimension and orientation as a function of their distance from the nanoparticle center of mass show that the interphase thickness is roughly equal to the radius of gyration of the polymer chains. Moreover, the dynamic behavior of the polymer chains in nanocomposites is analyzed by the center of mass diffusion coefficient, the relaxation time of the chain end-to-end vector and the characteristic escape time of the polymer chains from the interphase. Compared with neat polymers, both the global and local chain dynamics in nanocomposites are hindered with an increasing nanoparticle mass fraction and with an increasing surface area. The local chain dynamics in the interphase is stronger affected by the surface area of the nanoparticles than the global one. Specifically, the global diffusion coefficient of polymer chains is almost linearly reduced with the total surface area of the nanoparticles, whereas the global relaxation time of the chain end-to-end vector increases almost linearly with it. The interphase relaxation time of the polymer chains increases superlinearly with the surface area of an individual nanoparticle. Additionally, the characteristic escape time of polymer chains from

  6. Dissipative particle dynamics simulation of the phase behavior of T-shaped ternary amphiphiles possessing rodlike mesogens.

    Science.gov (United States)

    Liu, Xiaohan; Yang, Keda; Guo, Hongxia

    2013-08-01

    We employed dissipative particle dynamics simulations to explore the phase behavior of T-shaped ternary amphiphiles composed of rodlike cores connected by two incompatible end chains and side grafted segments. By fine-tuning the number of terminal and lateral beads, three phase diagrams for the model systems with different terminal chain lengths are constructed in terms of temperature and lateral chain length, which have some common features and mostly compare favorably with experimental studies with the exception a couple of new phases. It is worthwhile to highlight that the mixed cylindrical phase and the perforated layer phase, as the experimentally observed mesophases exclusive for facial amphiphilies, are found in simulations for the first time. Also, a novel gyroid structure is observed in series of T-shaped ternary amphiphiles for the first time. Furthermore, by evaluating the effective volume fraction of lateral chains, the phase sequence spanning from conventional smectic layer phase via perforated layer structures and polygonal cylindrical arrays to novel lamellar mesophase is established, which is not just qualitatively consistent with the related experimental findings but even the stability windows of some mesophases quantitatively correspond well to experimental results. The success of reproducing the in-plane ordering of rods in the lamellar phase as well as the generic phase diagram of such T-shaped ternary amphiphiles in great detail implies that our genetic model qualitatively captures many of the characteristics of the phase behavior of real T-shaped molecules and could serve as a satisfactory basis for further exploration of self-organization in other related soft matter systems.

  7. Rotor-bearing system integrated with shape memory alloy springs for ensuring adaptable dynamics and damping enhancement-Theory and experiment

    DEFF Research Database (Denmark)

    Enemark, Søren; Santos, Ilmar F.

    2016-01-01

    Helical pseudoelastic shape memory alloy (SMA) springs are integrated into a dynamic system consisting of a rigid rotor supported by passive magnetic bearings. The aim is to determine the utility of SMAs for vibration attenuation via their mechanical hysteresis, and for adaptation of the dynamic ...

  8. Wdr1-mediated cell shape dynamics and cortical tension are essential for epidermal planar cell polarity.

    Science.gov (United States)

    Luxenburg, Chen; Heller, Evan; Pasolli, H Amalia; Chai, Sophia; Nikolova, Maria; Stokes, Nicole; Fuchs, Elaine

    2015-05-01

    During mouse development, core planar cell polarity (PCP) proteins become polarized in the epidermal plane to guide angling/morphogenesis of hair follicles. How PCP is established is poorly understood. Here, we identify a key role for Wdr1 (also known as Aip1), an F-actin-binding protein that enhances cofilin/destrin-mediated F-actin disassembly. We show that cofilin and destrin function redundantly in developing epidermis, but their combined depletion perturbs cell adhesion, cytokinesis, apicobasal polarity and PCP. Although Wdr1 depletion accentuates single-loss-of-cofilin/destrin phenotypes, alone it resembles core PCP mutations. Seeking a mechanism, we find that Wdr1 and cofilin/destrin-mediated actomyosin remodelling are essential for generating or maintaining cortical tension within the developing epidermal sheet and driving the cell shape and planar orientation changes that accompany establishment of PCP in mammalian epidermis. Our findings suggest intriguing evolutionary parallels but mechanistic modifications to the distal wing hinge-mediated mechanical forces that drive cell shape change and orient PCP in the Drosophila wing disc.

  9. Shape optimization of plate with static and dynamic constralnts via virtual laminated element

    Institute of Scientific and Technical Information of China (English)

    李芳; 徐兴; 凌道盛

    2003-01-01

    The virtual laminated element method(VLEM) can resolve structural shape optimization problems with a new method.According to the characteristics of VLEM,only some characterized layer thickness values need be defined as design variables instead of boundary node coordinates or some other parameters determining the system boundary.One of the important features of this method is that it is not necessary to regenerate the FE(finite element)grid during the optimization process so as to avoid optimization failures resulting from some distortion grid elements.The thickness distribution in thin plate optimization problems in other studies before is of stepped shape.However,in this paper,a continuous thickness distribution can be obtained after optimi-zation using VLEM,and is more reasonable.Furthermore,an approximate reanalysis method named "behavior model technique" can be used to reduce the amount of structural reanalysis.Sone typical examples are offered to prove the effectiveness and practicality of the proposed method.

  10. Dynamic mechanical analyze of superelastic CuMnAl shape memory alloy

    Science.gov (United States)

    (Dragoș Ursanu, A. I.; Stanciu, S.; Pricop, B.; Săndulache, F.; Cimpoeșu, N.

    2016-08-01

    A new shape memory alloy was obtain from high purity Cu, Mn and Al elements using a induce furnace. The intelligent material present negative transformation temperatures and an austenite like state at room temperature. The austenite state of CuMnAl shape memory alloy present superelasticity property. Five kilograms ingot was obtain of Cu10Mn10Al alloy. From the base material (melted state) were cut samples with 6 mm thickness using a mechanical saw. After an homogenization heat treatment the samples were hot rolled through four passes with a reduction coefficient of 20%. Experimental lamellas were obtained with 1.5 mm thickness and 90x10 mm length and width. After the hot rolled treatment the materials were heat treated at 800°C for 20 minutes and chilled in water. Four samples, one just laminated and three heat treated by aging, were analyzed with a Netzsch DMA equipment to establish the elastic modulus and the internal friction values of the materials. Metallic materials microstructure was analyzed using a scanning electron microscope Vega Tescan LMH II type. After the aging heat treatment a decrease of internal friction is observed on the entire analyze range which is assigned to formation of Al-based precipitates that block the internal movement of the alloy characteristic phases.

  11. Assessment of the TMI-2 axial power-shaping-rod dynamic test results

    Energy Technology Data Exchange (ETDEWEB)

    Garner, R W; Owen, D E; Martin, M R

    1983-04-01

    The Three Mile Island-Unit 2 (TMI-2) nuclear power reactor contains 61 control rod assemblies and 8 axial power shaping rod assemblies (APSRs). All control rod and APSR drive leadscrews must be uncoupled and removed prior to vessel head removal. Leadscrew removal is facilitated by having the rod assemblies inserted to a down hard-stop position. Following the TMI-2 accident, the eight axial power shaping rods were in a partially withdrawn position (approx. 25% of their full travel). Therefore, a test was performed to attempt to insert the APSRs to the fully inserted, or at least a hard-stop position. In addition, accelerometers were mounted on the drive mechanisms of all the APSRs in an attempt to obtain acoustical signals that would provide some information about the physical condition of the APSRs and of the damaged TMI-2 reactor core. This report describes the TMI-2 APSR Insertion Test performance and results, and presents an evaluation of correlations between APSR insertion information and other available information on the condition of the TMI-2 reactor.

  12. Cytoskeletal actin dynamics shape a ramifying actin network underpinning immunological synapse formation

    DEFF Research Database (Denmark)

    Fritzsche, Marco; Fernandes, Ricardo A.; Chang, Veronica T.

    2017-01-01

    . This network shows all the characteristics of an inward-growing transportation network and its dynamics correlating with T cell receptor rearrangements. This actin reorganization is accompanied by an increase in the nanoscale actin meshwork size and the dynamic adjustment of the turnover times and filament...... lengths of two differently sized filamentous actin populations, wherein forminmediated long actin filaments support a very flat and stiff contact at the immunological synapse interface. The initiation of immunological synapse formation, as highlighted by calcium release, requires markedly little contact...... with activating surfaces and no cytoskeletal rearrangements. Our work suggests that incipient signaling in T cells initiates global cytoskeletal rearrangements across the whole cell, including a stiffening process for possibly mechanically supporting contact formation at the immunological synapse interface...

  13. DYNAMIC RESPONSE OF SHAPE MEMORY ALLOY SYSTEM AND ITS VIBRATION CONTROL

    Institute of Scientific and Technical Information of China (English)

    Wei Zhi; Sun Dongchang; Tan Runhua

    2000-01-01

    A hysteric model is represented to describe the dependence of restoring force on deformation of pseudoelastic SMA.The dynamic response of the system is investigated by means of mathematical models.The result shows that this kind of vibration absorbing system can suppress vibration with large amplitude effectively.Furthermore,the vibration absorbing system can work in optimum state by adjusting temperature and using piezoelectric sensors and actuators.

  14. Tuning optical absorption and photoexcited recombination dynamics in La1-xSrxFeO3-δ through A-site substitution and oxygen vacancies

    Science.gov (United States)

    Smolin, Sergey; Scafetta, Mark; Choquette, Amber; Sfeir, Matthew; Baxter, Jason; May, Steven

    We study optical absorption and recombination dynamics in La1-xSrxFeO3-δ thin films, uncovering the effects of tuning nominal Fe valence via A-site substitution and oxygen stoichiometry. Variable angle spectroscopic ellipsometry was used to measure static optical properties, revealing a linear increase in absorption coefficient at 1.25 eV and a red-shifting of the optical absorption edge with increasing Sr fraction. The absorption spectra can be similarly tuned through the introduction of oxygen vacancies, indicating the critical role that nominal Fe valence plays in optical absorption. Dynamic optoelectronic properties were studied with ultrafast transient reflectance spectroscopy, revealing similar nanosecond photoexcited carrier lifetimes for oxygen deficient and stoichiometric films with the same nominal Fe valence. These results demonstrate that while the static optical absorption is strongly dependent on Fe valence tuned through cation or anion stoichiometry, oxygen vacancies do not appear to play a significantly detrimental role in the recombination kinetics. Nsf: ECCS-1201957, MRI DMR-0922929, MRI DMR-1040166. This research used resources of the Center for Functional Nanomaterials, which is a U.S. DOE Office of Science Facility, at Brookhaven National Laboratory under Contract No. DE-SC0012704.

  15. How do copper contamination pulses shape the regime shifts of phytoplankton-zooplankton dynamics?

    Science.gov (United States)

    Camara, B. I.; Yamapi, R.; Mokrani, H.

    2017-07-01

    The presence of pollutants in waters, particularly from heavy metals, is of grave concern worldwide due to its cytotoxicity to organisms. Fish and aquatic organisms are very sensitive to the increasing Cu concentrations in water. Therefore, Cu toxicity partly depends on water quality. To address the effects of impulsive copper contamination of the phytoplankton-zooplankton population dynamics, we've built a model that focuses on the interaction between algae and Daphnia with deterministic and stochastic impulse copper. In fact the Results have shown three types of outcomes depending on copper concentration. In low (4.4 μgL-1) copper concentration, deterministic and stochastic pulses may promote the persistence of Daphnia and algae populations unlike the absence of pulses. Whereas, in high (28 μgL-1) concentration, it accelerates deficiency and toxicity processes, leads to the extinction of all populations and in intermediate concentrations. Deterministic and stochastic pulses may transform population dynamics in complex oscillations. Numerical results show that the system that has been considered has more complex dynamics including bifurcation, period-doubling oscillations and chaos. Depending on minimum copper concentration in the environment, the bifurcation diagram has highlighted the resilience or the regime shifts of the system in occurrence of pulse contamination.

  16. How active perception and attractor dynamics shape perceptual categorization: a computational model.

    Science.gov (United States)

    Catenacci Volpi, Nicola; Quinton, Jean Charles; Pezzulo, Giovanni

    2014-12-01

    We propose a computational model of perceptual categorization that fuses elements of grounded and sensorimotor theories of cognition with dynamic models of decision-making. We assume that category information consists in anticipated patterns of agent-environment interactions that can be elicited through overt or covert (simulated) eye movements, object manipulation, etc. This information is firstly encoded when category information is acquired, and then re-enacted during perceptual categorization. The perceptual categorization consists in a dynamic competition between attractors that encode the sensorimotor patterns typical of each category; action prediction success counts as "evidence" for a given category and contributes to falling into the corresponding attractor. The evidence accumulation process is guided by an active perception loop, and the active exploration of objects (e.g., visual exploration) aims at eliciting expected sensorimotor patterns that count as evidence for the object category. We present a computational model incorporating these elements and describing action prediction, active perception, and attractor dynamics as key elements of perceptual categorizations. We test the model in three simulated perceptual categorization tasks, and we discuss its relevance for grounded and sensorimotor theories of cognition.

  17. Host immunity shapes the impact of climate changes on the dynamics of parasite infections.

    Science.gov (United States)

    Mignatti, Andrea; Boag, Brian; Cattadori, Isabella M

    2016-03-15

    Global climate change is predicted to alter the distribution and dynamics of soil-transmitted helminth infections, and yet host immunity can also influence the impact of warming on host-parasite interactions and mitigate the long-term effects. We used time-series data from two helminth species of a natural herbivore and investigated the contribution of climate change and immunity on the long-term and seasonal dynamics of infection. We provide evidence that climate warming increases the availability of infective stages of both helminth species and the proportional increase in the intensity of infection for the helminth not regulated by immunity. In contrast, there is no significant long-term positive trend in the intensity for the immune-controlled helminth, as immunity reduces the net outcome of climate on parasite dynamics. Even so, hosts experienced higher infections of this helminth at an earlier age during critical months in the warmer years. Immunity can alleviate the expected long-term effect of climate on parasite infections but can also shift the seasonal peak of infection toward the younger individuals.

  18. Influence of Shape Anisotropy on Magnetization Dynamics Driven by Spin Hall Effect

    Directory of Open Access Journals (Sweden)

    X. G. Li

    2016-01-01

    Full Text Available As the lateral dimension of spin Hall effect based magnetic random-access memory (SHE-RAM devices is scaled down, shape anisotropy has varied influence on both the magnetic field and the current-driven switching characteristics. In this paper, we study such influences on elliptic film nanomagnets and theoretically investigate the switching characteristics for SHE-RAM element with in-plane magnetization. The analytical expressions for critical current density are presented and the results are compared with those obtained from macrospin and micromagnetic simulation. It is found that the key performance indicators for in-plane SHE-RAM, including thermal stability and spin torque efficiency, are highly geometry dependent and can be effectively improved by geometric design.

  19. Understanding the dynamics of the inductive plasma formation and its application to create doublet shaped plasma in the TCV tokamak

    Science.gov (United States)

    Sinha, Joyeeta; Coda, Stefano; Duval, Basil Paul; Galperti, Cristian; Moret, Jean-Marc; Reimerdes, Holger

    2016-10-01

    The dynamics of the plasma formation in TCV are revisited with the goal of improving reliability and developing new scenarios such as the creation of doublet configurations. A database for the plasma formation scenarios in TCV reveals that 15% of the attempts to form a plasma fail during the burn-through phase. Plasma formation dynamics are greatly affected by the difference between programmed and obtained plasma current ramp rates that can lead to oscillations in IP when the IP feedback control is activated. This mismatch in IP also propagates into the radial position control. Failed burn-throughs occur when the Ohmic heating power is insufficient either since IP rises too slow or due to a combined effect of the IP feedback oscillations and a regularly occurring MHD instability. Several strategies to improve the present plasma formation scenario have been implemented. Based on the improved understanding of the plasma formation dynamics, a strategy has been developed to create and control a doublet configuration by merging of two droplet-shaped plasma requiring simultaneous breakdown at two locations.

  20. a Mathematical Model for Analyzing the Influence of Shape Deviations and Mounting Errors on Gear Dynamic Behaviour

    Science.gov (United States)

    Velex, P.; Maatar, M.

    1996-04-01

    A comprehensive mathematical model is introduced for analyzing the influence of shape deviations and mounting errors on gear dynamics. Contact conditions for both rigid and deformable solids are used for characterizing the gear set excitation sources. The deformed state is modeled by a lumped parameter non-linear system with six degrees-of-freedom on pinion and gear. Each potential contact line on the base plane is discretized in independent elementary cells of constant stiffness and an original procedure is proposed for simultaneously solving the normal contact problem between active flanks and the equations of motion. Comparisons with several results from the literature prove the versatility of the model as static and dynamic load distributions, transmission errors and mesh stiffnesses can be evaluated from a unified approach. Finally, the interest of the methodology is illustrated by some practical problems in gear dynamics: i.e., the influence of some geometrical errors and the role of linear profile modifications on spur and helical gears.

  1. Recombination instability

    DEFF Research Database (Denmark)

    D'Angelo, N.

    1967-01-01

    A recombination instability is considered which may arise in a plasma if the temperature dependence of the volume recombination coefficient, alpha, is sufficiently strong. Two cases are analyzed: (a) a steady-state plasma produced in a neutral gas by X-rays or high energy electrons; and (b) an af...

  2. Analysis of Static and Dynamic Behavior of T-shape Beam Reinforced by External Prestressing Tendon

    Directory of Open Access Journals (Sweden)

    Dinghai Li

    2013-01-01

    Full Text Available External prestressing has become a primary method for strengthening existing concrete beam and has been increasingly used in the construction of newly erected ones, particularly railroad bridges in recent years. In order to evaluate the effect of this method, the static and dynamic behavior of a T-frame beam reinforced by external prestressed strengthened concrete beam was analyzed by 3D finite element method, and the field test study was also made. The study was carried out to further investigate the simply supported reinforced prestressed concrete beam strengthened by external prestressing through theory analysis and experiment.

  3. Computational modeling of seizure dynamics using coupled neuronal networks: factors shaping epileptiform activity.

    Directory of Open Access Journals (Sweden)

    Sebastien Naze

    2015-05-01

    Full Text Available Epileptic seizure dynamics span multiple scales in space and time. Understanding seizure mechanisms requires identifying the relations between seizure components within and across these scales, together with the analysis of their dynamical repertoire. Mathematical models have been developed to reproduce seizure dynamics across scales ranging from the single neuron to the neural population. In this study, we develop a network model of spiking neurons and systematically investigate the conditions, under which the network displays the emergent dynamic behaviors known from the Epileptor, which is a well-investigated abstract model of epileptic neural activity. This approach allows us to study the biophysical parameters and variables leading to epileptiform discharges at cellular and network levels. Our network model is composed of two neuronal populations, characterized by fast excitatory bursting neurons and regular spiking inhibitory neurons, embedded in a common extracellular environment represented by a slow variable. By systematically analyzing the parameter landscape offered by the simulation framework, we reproduce typical sequences of neural activity observed during status epilepticus. We find that exogenous fluctuations from extracellular environment and electro-tonic couplings play a major role in the progression of the seizure, which supports previous studies and further validates our model. We also investigate the influence of chemical synaptic coupling in the generation of spontaneous seizure-like events. Our results argue towards a temporal shift of typical spike waves with fast discharges as synaptic strengths are varied. We demonstrate that spike waves, including interictal spikes, are generated primarily by inhibitory neurons, whereas fast discharges during the wave part are due to excitatory neurons. Simulated traces are compared with in vivo experimental data from rodents at different stages of the disorder. We draw the conclusion

  4. The Influence of Stoichiometry and Flame-Holder Shape on Flame Dynamics and Acoustics (Preprint)

    Science.gov (United States)

    2012-04-01

    2915- 2923. Ingard , U., and Singhal, V., 1973, “Upstream and Downstream Sound Radiation into a Moving Flow,” Journal of the Acoustical Society of...America 45(4), 1343-1346. Ingard , U., and Singhal, V., 1973, “Emissions of Higher-Order Acoustic Modes into a Moving Fluid in a Duct,” Journal of the...Dynamics of Bluff Body Stabilized Premixed Reacting Flows,” AIAA Paper 2003-0835. Morse P., and Ingard , U., 1968, Theoretical Acoustics, McGraw Hill, NY

  5. Deformation behavior of metallic glass composites reinforced with shape memory nanowires studied via molecular dynamics simulations

    Science.gov (United States)

    Şopu, D.; Stoica, M.; Eckert, J.

    2015-05-01

    Molecular dynamics simulations indicate that the deformation behavior and mechanism of Cu64Zr36 composite structures reinforced with B2 CuZr nanowires are strongly influenced by the martensitic phase transformation and distribution of these crystalline precipitates. When nanowires are distributed in the glassy matrix along the deformation direction, a two-steps stress-induced martensitic phase transformation is observed. Since the martensitic transformation is driven by the elastic energy release, the strain localization behavior in the glassy matrix is strongly affected. Therefore, the composite materials reinforced with a crystalline phase, which shows stress-induced martensitic transformation, represent a route for controlling the properties of glassy materials.

  6. Boundaries of the Peruvian Oxygen Minimum Zone shaped by coherent mesoscale dynamics

    CERN Document Server

    Bettencourt, João H; García, Emilio Hernández; Montes, Ivonne; Sudre, Joël; Dewitte, Boris; Paulmier, Aurélien; Garçon, Véronique

    2015-01-01

    Dissolved oxygen in sea water is a major factor affecting marine habitats and biogeochemical cycles. Oceanic zones with oxygen deficits represent significant portions of the area and volume of the oceans and are thought to be expanding. The Peruvian oxygen minimum zone is one of the most pronounced and lies in a region of strong mesoscale activity in the form of vortices and frontal regions, whose effect in the dynamics of the oxygen minimum zone is largely unknown. Here, we study this issue from a modeling approach and a Lagrangian point of view, using a coupled physical-biogeochemical simulation of the Peruvian oxygen minimum zone and finite-size Lyapunov exponent fields to understand the link between mesoscale dynamics and oxygen variations. Our results show that, at depths between 380 and 600 meters, mesoscale structures have a relevant dual role. First, their mean positions and paths delimit and maintain the oxygen minimum zone boundaries. Second, their high frequency fluctuations entrain oxygen across t...

  7. Simulations of long-term community dynamics in coral reefs--how perturbations shape trajectories.

    Directory of Open Access Journals (Sweden)

    Andreas Kubicek

    Full Text Available Tropical coral reefs feature extraordinary biodiversity and high productivity rates in oligotrophic waters. Due to increasing frequencies of perturbations--anthropogenic and natural--many reefs are under threat. Such perturbations often have devastating effects on these unique ecosystems and especially if they occur simultaneously and amplify each other's impact, they might trigger a phase shift and create irreversible conditions.We developed a generic, spatially explicit, individual-based model in which competition drives the dynamics of a virtual benthic reef community--comprised of scleractinian corals and algae--under different environmental settings. Higher system properties, like population dynamics or community composition arise through self-organization as emergent properties. The model was parameterized for a typical coral reef site at Zanzibar, Tanzania and features coral bleaching and physical disturbance regimes as major sources of perturbations. Our results show that various types and modes (intensities and frequencies of perturbations create diverse outcomes and that the switch from high diversity to single species dominance can be evoked by small changes in a key parameter. Here we extend the understanding of coral reef resilience and the identification of key processes, drivers and respective thresholds, responsible for changes in local situations. One future goal is to provide a tool which may aid decision making processes in management of coral reefs.

  8. Microtopographic refuges shape consumer-producer dynamics by mediating consumer functional diversity.

    Science.gov (United States)

    Brandl, Simon J; Bellwood, David R

    2016-09-01

    Consumer-producer dynamics are critical for ecosystem functioning. In marine environments, primary production is often subject to strong consumer control, and on coral reefs, the grazing pressure exerted by herbivorous fishes has been identified as a major determinant of benthic community structure. Using experimental surfaces, we demonstrate that on coral reefs, microtopographic refuges decrease the overall grazing pressure by more than one order of magnitude. Furthermore, by functionally characterizing consumer communities, we show that refuges also restrict grazer communities to only one functional group, algal croppers, which selectively remove the apical parts of algae. In contrast, detritivorous fishes, which intensively graze flat and exposed microhabitats and can remove both particulate matter and entire stands of algal filaments, are almost entirely excluded. This preclusion of an entire ecosystem process (the removal of particulates) results in two distinct coexisting benthic regimes: communities within refuges are diverse and characterized by numerous algal types and juvenile scleractinian corals, while communities outside refuges support only low-diversity assemblages dominated by simple, unbranched filamentous turf algal mats. Although limited to the scale of a few centimeters, microtopographic refuges can, therefore, mediate the biotic control of community development by affecting both overall grazing rates and the functional diversity of consumer communities. We suggest that the coexistence of two distinct benthic regimes at a small spatial scale may be an important factor for ecosystem functioning and highlight the need to consider the ecological complexity of consumer-producer dynamics when assessing the status of coral reef ecosystems.

  9. An Introduction to a Porous Shape Memory Alloy Dynamic Data Driven Application System

    KAUST Repository

    Douglas, Craig C.

    2012-06-02

    Shape Memory Alloys are capable of changing their crystallographic structure due to changes of temperature and/or stress. Our research focuses on three points: (1) Iterative Homogenization of Porous SMAs: Development of a Multiscale Model of porous SMAs utilizing iterative homogenization and based on existing knowledge of constitutive modeling of polycrystalline SMAs. (2) DDDAS: Develop tools to turn on and off the sensors and heating unit(s), to monitor on-line data streams, to change scales based on incoming data, and to control what type of data is generated. The application must have the capability to be run and steered remotely. (3) Modeling and applications of porous SMA: Vibration isolation devices with SMA and porous SMA components for aerospace applications will be analyzed and tested. Numerical tools for modeling porous SMAs with a second viscous phase will be developed.The outcome will be a robust, three-dimensional, multiscale model of porous SMA that can be used in complicated, real-life structural analysis of SMA components using a DDDAS framework.

  10. Lattice dynamics of ferromagnetic shape memory alloys from inelastic neutron scattering

    Energy Technology Data Exchange (ETDEWEB)

    Mehaddene, Tarik [Physik-Department E13, Technische Universitaet Muenchen, Garching (Germany); Neuhaus, Juergen [Forschungsneutronenquelle Heinz Maier-Leibnitz, Garching (Germany); Petry, Winfried [Physik-Department E13, Technische Universitaet Muenchen, Garching (Germany); Forschungsneutronenquelle Heinz Maier-Leibnitz, Garching (Germany); Hradil, Klaudia [Forschungsneutronenquelle Heinz Maier-Leibnitz, Garching (Germany); Institut fuer Physikalische Chemie, Georg-August-Universitaet, Goettingen (Germany); Bourges, Philippe [Laboratoire Leon Brillouin (LLB), CEA Saclay, Gif sur Yvette (France)

    2008-07-01

    The tendency of shape memory alloys to undergo a martensitic transItion shows up in the anomalous phonon softening of particular phonon modes in their austenitic phase. We report on phonon measurements in both austenitic and martensitic phases of Ni-based alloys. We show that, contrary to NiMnSn, the anomalous softening of the TA{sub 2}[110] phonons in NiMnGa is strongly enhanced below the Curie temperature. The measurements revealed that low restoring forces against the shearing of the (111) atomic planes along develop upon cooling. The vibrational spectra measured in two different martensitic phases of NiMnGa, namely the tetragonal 5M and the orthorhombic 7M structures, revealed fundamental differences. A dispersive low-energy excitation develops from the elastic modulation peaks in the 5M structure and come into interaction with TA{sub 2}[110] phonon branch in the q-range 0.25-0.3 r.l.u where the latter shows a wiggle in the dispersion. No wiggle is seen in the TA{sub 2}[110] branch of the 7M structure. It shows a normal sinus-like dispersion curve.

  11. Hybridized wavefront shaping for high-speed, high-efficiency focusing through dynamic diffusive media

    Science.gov (United States)

    Hemphill, Ashton S.; Tay, Jian Wei; Wang, Lihong V.

    2016-12-01

    One of the prime limiting factors of optical imaging in biological applications is the diffusion of light by tissue, which prevents focusing at depths greater than the optical diffusion limit (typically ˜1 mm). To overcome this challenge, wavefront shaping techniques that use a spatial light modulator (SLM) to correct the phase of the incident wavefront have recently been developed. These techniques are able to focus light through scattering media beyond the optical diffusion limit. However, the low speeds of typically used liquid crystal SLMs limit the focusing speed. Here, we present a method using a digital micromirror device (DMD) and an electro-optic modulator (EOM) to measure the scattering-induced aberrations, and using a liquid crystal SLM to apply the correction to the illuminating wavefront. By combining phase modulation from an EOM with the DMD's ability to provide selective illumination, we exploit the DMD's higher refresh rate for phase measurement. We achieved focusing through scattering media in less than 8 ms, which is sufficiently short for certain in vivo applications, as it is comparable to the speckle correlation time of living tissue.

  12. Static torque and drag characteristics of an S-shaped Savonius rotor and prediction of dynamic characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Sadrul Islam, A.K.M.; Quamrul Islam, M.; Razzaque, M.M. [Bangladesh University (Bangladesh). Dept. of Mechanical Engineering; Ashref, R

    1995-12-31

    Drag and torque coefficients of a stationary S-shaped rotor have been investigated by measuring the pressure distribution on the blade surfaces for various rotor angles. The experiments have been carried out at a Reynolds number of 1.1 x 10{sup 5} in a uniform flow jet produced by an open circuit wind tunnel. The measurements indicate that the drag force, and hence the torque, varies with rotor angle. The maximum net static torque occurs at 45{sup o} of rotor angle and it becomes negative in the range of 135{sup o} to 165{sup o} of rotor angle. A quasi-steady approach has been applied for the prediction of the dynamic performance of the rotor using the static drag and torque coefficients. This method results in a fair agreement with the measured power coefficient. (Author)

  13. Dynamic 3D shape of the plantar surface of the foot using coded structured light: a technical report

    KAUST Repository

    Thabet, Ali Kassem

    2014-01-23

    Background The foot provides a crucial contribution to the balance and stability of the musculoskeletal system, and accurate foot measurements are important in applications such as designing custom insoles/footwear. With better understanding of the dynamic behavior of the foot, dynamic foot reconstruction techniques are surfacing as useful ways to properly measure the shape of the foot. This paper presents a novel design and implementation of a structured-light prototype system providing dense three dimensional (3D) measurements of the foot in motion. The input to the system is a video sequence of a foot during a single step; the output is a 3D reconstruction of the plantar surface of the foot for each frame of the input. Methods Engineering and clinical tests were carried out to test the accuracy and repeatability of the system. Accuracy experiments involved imaging a planar surface from different orientations and elevations and measuring the fitting errors of the data to a plane. Repeatability experiments were done using reconstructions from 27 different subjects, where for each one both right and left feet were reconstructed in static and dynamic conditions over two different days. Results The static accuracy of the system was found to be 0.3 mm with planar test objects. In tests with real feet, the system proved repeatable, with reconstruction differences between trials one week apart averaging 2.4 mm (static case) and 2.8 mm (dynamic case). Conclusion The results obtained in the experiments show positive accuracy and repeatability results when compared to current literature. The design also shows to be superior to the systems available in the literature in several factors. Further studies need to be done to quantify the reliability of the system in clinical environments.

  14. Joint estimation of shape and deformation for the detection of lesions in dynamic contrast-enhanced breast MRI

    Science.gov (United States)

    Hong, Byung-Woo

    2013-11-01

    We propose a mathematical framework for simultaneously delineating the boundary of object and estimating its temporal motion in the application of lesion detection in a dynamic contrast-enhanced (DCE) breast MRI sequence where both the appearance and the shape of region of interest is assumed to change in time. A unified energy functional for a joint segmentation and registration is proposed based on the assumption that the statistical properties of dynamic intensity curves within a region of interest are homogeneous. Our algorithm is designed to provide the morphological properties of the enhanced region and its dynamic intensity profiles, called kinetic signatures, in the analysis of DCE imagery since these features are considered as significant cues in understanding images. The proposed energy comprises a combination of a segmentation energy and a registration energy. The segmentation energy is developed based on a convex formulation being insensitive to the initialization. The registration energy is designed to compensate motion artifacts that are usually involved in the temporal imaging procedure. The major objective of this work is to provide a mathematical framework for a joint segmentation and registration on a dynamic sequence of images, and we demonstrate the mutual benefit of the estimation of temporal deformations for the registration step and the localization of regions of interest for the segmentation step. The effectiveness of the developed algorithm has been demonstrated on a number of clinical DCE breast MRI data in the application of breast lesion detection and the results show its potential to improve the accuracy and the efficiency in the diagnosis of breast cancer.

  15. Intersegmental dynamics shape joint coordination during catching in typically developing children but not in children with developmental coordination disorder.

    Science.gov (United States)

    Asmussen, Michael J; Przysucha, Eryk P; Dounskaia, Natalia

    2014-04-01

    Factors shaping joint coordination during multijoint movements were studied using a one-handed ball-catching task. Typically developing (TD) boys between 9 and 12 yr of age, at which catching becomes consistently successful, and boys with developmental coordination disorder (DCD) of the same age participated in the study. The arm was initially stretched down. Catching was performed by flexing the shoulder and elbow and extending the wrist in the parasagittal plane. Catching success rate was substantially lower in children with DCD. Amplitudes and directions of joint motions were similar in both groups. Group differences were found in shoulder and elbow coordination patterns. TD children performed the movement predominantly by actively accelerating into flexion, one joint at a time-first the elbow and then the shoulder-and allowing passive interaction torque (IT) to accelerate the other joint into extension. Children with DCD tended to accelerate both joints into flexion simultaneously, suppressing IT. The results suggest that the TD joint coordination was shaped by the tendency to minimize active control of IT despite the complexity of the emergent joint kinematics. The inefficient control of IT in children with DCD points to deficiency of the internal model of intersegmental dynamics. Together, the findings advocate that joint coordination throughout a multijoint movement is a by-product of the control strategy that benefits from movement dynamics by actively accelerating a single joint and using IT for rotation of the other joint. Reduction of control-dependent noise is discussed as a possible advantage of this control strategy.

  16. An exploration of the political economy dynamics shaping health worker incentives in three districts in Sierra Leone.

    Science.gov (United States)

    Bertone, Maria Paola; Witter, Sophie

    2015-09-01

    The need for evidence-based practice calls for research focussing not only on the effectiveness of interventions and their translation into policies, but also on implementation processes and the factors influencing them, in particular for complex health system policies. In this paper, we use the lens of one of the health system's 'building blocks', human resources for health (HRH), to examine the implementation of official policies on HRH incentives and the emergence of informal practices in three districts of Sierra Leone. Our mixed-methods research draws mostly from 18 key informant interviews at district level. Data are organised using a political economy framework which focuses on the dynamic interactions between structure (context, historical legacies, institutions) and agency (actors, agendas, power relations) to show how these elements affect the HRH incentive practices in each district. It appears that the official policies are re-shaped both by implementation challenges and by informal practices emerging at local level as the result of the district-level dynamics and negotiations between District Health Management Teams (DHMTs) and nongovernmental organisations (NGOs). Emerging informal practices take the form of selective supervision, salary supplementations and per diems paid to health workers, and aim to ensure a better fit between the actors' agendas and the incentive package. Importantly, the negotiations which shape such practices are characterised by a substantial asymmetry of power between DHMTs and NGOs. In conclusion, our findings reveal the influence of NGOs on the HRH incentive package and highlight the need to empower DHMTs to limit the discrepancy between policies defined at central level and practices in the districts, and to reduce inequalities in health worker remuneration across districts. For Sierra Leone, these findings are now more relevant than ever as new players enter the stage at district level, as part of the Ebola response and

  17. Messenger RNA Fluctuations and Regulatory RNAs Shape the Dynamics of Negative Feedback Loop

    CERN Document Server

    Martínez, María Rodríguez; Tlusty, Tsvi; Pilpel, Yitzhak; Furman, Itay; 10.1103/PhysRevE.81.031924

    2010-01-01

    Single cell experiments of simple regulatory networks can markedly differ from cell population experiments. Such differences arise from stochastic events in individual cells that are averaged out in cell populations. For instance, while individual cells may show sustained oscillations in the concentrations of some proteins, such oscillations may appear damped in the population average. In this paper we investigate the role of RNA stochastic fluctuations as a leading force to produce a sustained excitatory behavior at the single cell level. Opposed to some previous models, we build a fully stochastic model of a negative feedback loop that explicitly takes into account the RNA stochastic dynamics. We find that messenger RNA random fluctuations can be amplified during translation and produce sustained pulses of protein expression. Motivated by the recent appreciation of the importance of non--coding regulatory RNAs in post--transcription regulation, we also consider the possibility that a regulatory RNA transcri...

  18. Interaction patterns and individual dynamics shape the way we move in synchrony

    CERN Document Server

    Alderisio, Francesco; Salesse, Robin N; Bardy, Benoit G; di Bernardo, Mario

    2016-01-01

    The emergence of movement coordination in human ensembles has been seldom studied in the existing literature, in contrast to situations involving dual interaction. Here we investigate group synchronisation in a human ensemble where participants are asked to generate and coordinate an oscillatory hand motion. We separately test two groups of seven participants. We observe that the coordination level of the ensemble depends on the specific way each individual moves when isolated from the others, and on the pattern of the visual coupling among group members (who looks at whom). Despite the complexity of social interactions among individuals, we find that a network of heterogeneous Kuramoto oscillators captures and explains the group dynamics. Our findings can be relevant to any activity requiring the coordination of several people, as in music, sport or at work, and can be extended to account for other forms of interaction such as sound and feel.

  19. How structure shapes dynamics: knowledge development in Wikipedia--a network multilevel modeling approach.

    Directory of Open Access Journals (Sweden)

    Iassen Halatchliyski

    Full Text Available Using a longitudinal network analysis approach, we investigate the structural development of the knowledge base of Wikipedia in order to explain the appearance of new knowledge. The data consists of the articles in two adjacent knowledge domains: psychology and education. We analyze the development of networks of knowledge consisting of interlinked articles at seven snapshots from 2006 to 2012 with an interval of one year between them. Longitudinal data on the topological position of each article in the networks is used to model the appearance of new knowledge over time. Thus, the structural dimension of knowledge is related to its dynamics. Using multilevel modeling as well as eigenvector and betweenness measures, we explain the significance of pivotal articles that are either central within one of the knowledge domains or boundary-crossing between the two domains at a given point in time for the future development of new knowledge in the knowledge base.

  20. Subwavelength ripples adjustment based on electron dynamics control by using shaped ultrafast laser pulse trains.

    Science.gov (United States)

    Jiang, Lan; Shi, Xuesong; Li, Xin; Yuan, Yanping; Wang, Cong; Lu, Yongfeng

    2012-09-10

    This study reveals that the periods, ablation areas and orientations of periodic surface structures (ripples) in fused silica can be adjusted by using designed femtosecond (fs) laser pulse trains to control transient localized electron dynamics and corresponding material properties. By increasing the pulse delays from 0 to 100 fs, the ripple periods are changed from ~550 nm to ~255 nm and the orientation is rotated by 90°. The nearwavelength/subwavelength ripple periods are close to the fundamental/second-harmonic wavelengths in fused silica respectively. The subsequent subpulse of the train significantly impacts free electron distributions generated by the previous subpulse(s), which might influence the formation mechanism of ripples and the surface morphology.

  1. Beyond face value: does involuntary emotional anticipation shape the perception of dynamic facial expressions?

    Directory of Open Access Journals (Sweden)

    Letizia Palumbo

    Full Text Available Emotional facial expressions are immediate indicators of the affective dispositions of others. Recently it has been shown that early stages of social perception can already be influenced by (implicit attributions made by the observer about the agent's mental state and intentions. In the current study possible mechanisms underpinning distortions in the perception of dynamic, ecologically-valid, facial expressions were explored. In four experiments we examined to what extent basic perceptual processes such as contrast/context effects, adaptation and representational momentum underpinned the perceptual distortions, and to what extent 'emotional anticipation', i.e. the involuntary anticipation of the other's emotional state of mind on the basis of the immediate perceptual history, might have played a role. Neutral facial expressions displayed at the end of short video-clips, in which an initial facial expression of joy or anger gradually morphed into a neutral expression, were misjudged as being slightly angry or slightly happy, respectively (Experiment 1. This response bias disappeared when the actor's identity changed in the final neutral expression (Experiment 2. Videos depicting neutral-to-joy-to-neutral and neutral-to-anger-to-neutral sequences again produced biases but in opposite direction (Experiment 3. The bias survived insertion of a 400 ms blank (Experiment 4. These results suggested that the perceptual distortions were not caused by any of the low-level perceptual mechanisms (adaptation, representational momentum and contrast effects. We speculate that especially when presented with dynamic, facial expressions, perceptual distortions occur that reflect 'emotional anticipation' (a low-level mindreading mechanism, which overrules low-level visual mechanisms. Underpinning neural mechanisms are discussed in relation to the current debate on action and emotion understanding.

  2. Beyond face value: does involuntary emotional anticipation shape the perception of dynamic facial expressions?

    Science.gov (United States)

    Palumbo, Letizia; Jellema, Tjeerd

    2013-01-01

    Emotional facial expressions are immediate indicators of the affective dispositions of others. Recently it has been shown that early stages of social perception can already be influenced by (implicit) attributions made by the observer about the agent's mental state and intentions. In the current study possible mechanisms underpinning distortions in the perception of dynamic, ecologically-valid, facial expressions were explored. In four experiments we examined to what extent basic perceptual processes such as contrast/context effects, adaptation and representational momentum underpinned the perceptual distortions, and to what extent 'emotional anticipation', i.e. the involuntary anticipation of the other's emotional state of mind on the basis of the immediate perceptual history, might have played a role. Neutral facial expressions displayed at the end of short video-clips, in which an initial facial expression of joy or anger gradually morphed into a neutral expression, were misjudged as being slightly angry or slightly happy, respectively (Experiment 1). This response bias disappeared when the actor's identity changed in the final neutral expression (Experiment 2). Videos depicting neutral-to-joy-to-neutral and neutral-to-anger-to-neutral sequences again produced biases but in opposite direction (Experiment 3). The bias survived insertion of a 400 ms blank (Experiment 4). These results suggested that the perceptual distortions were not caused by any of the low-level perceptual mechanisms (adaptation, representational momentum and contrast effects). We speculate that especially when presented with dynamic, facial expressions, perceptual distortions occur that reflect 'emotional anticipation' (a low-level mindreading mechanism), which overrules low-level visual mechanisms. Underpinning neural mechanisms are discussed in relation to the current debate on action and emotion understanding.

  3. Messenger RNA fluctuations and regulatory RNAs shape the dynamics of a negative feedback loop

    Science.gov (United States)

    Rodríguez Martínez, María; Soriano, Jordi; Tlusty, Tsvi; Pilpel, Yitzhak; Furman, Itay

    2010-03-01

    Single-cell experiments of simple regulatory networks can markedly differ from cell population experiments. Such differences arise from stochastic events in individual cells that are averaged out in cell populations. For instance, while individual cells may show sustained oscillations in the concentrations of some proteins, such oscillations may appear damped in the population average. In this paper we investigate the role of RNA stochastic fluctuations as a leading force to produce a sustained excitatory behavior at the single-cell level. As opposed to some previous models, we build a fully stochastic model of a negative feedback loop that explicitly takes into account the RNA stochastic dynamics. We find that messenger RNA random fluctuations can be amplified during translation and produce sustained pulses of protein expression. Motivated by the recent appreciation of the importance of noncoding regulatory RNAs in post-transcription regulation, we also consider the possibility that a regulatory RNA transcript could bind to the messenger RNA and repress translation. Our findings show that the regulatory transcript helps reducing gene expression variability both at the single-cell level and at the cell population level.

  4. Dynamical density functional theory for arbitrary-shape colloidal fluids including inertia and hydrodynamic interactions

    Science.gov (United States)

    Duran-Olivencia, Miguel A.; Goddard, Ben; Kalliadasis, Serafim

    2015-11-01

    Over the last few decades the classical density-functional theory (DFT) and its dynamic extensions (DDFTs) have become a remarkably powerful tool in the study of colloidal fluids. Recently there has been extensive research to generalise all previous DDFTs finally yielding a general DDFT equation (for spherical particles) which takes into account both inertia and hydrodynamic interactions (HI) which strongly influence non-equilibrium properties. The present work will be devoted to a further generalisation of such a framework to systems of anisotropic particles. To this end, the kinetic equation for the Brownian particle distribution function is derived starting from the Liouville equation and making use of Zwanzig's projection-operator techniques. By averaging over all but one particle, a DDFT equation is finally obtained with some similarities to that for spherical colloids. However, there is now an inevitable translational-rotational coupling which affects the diffusivity of asymmetric particles. Lastly, in the overdamped (high friction) limit the theory is notably simplified leading to a DDFT equation which agrees with previous derivations. We acknowledge financial support from European Research Council via Advanced Grant No. 247031.

  5. Symmetry Breaking in Space-Time Hierarchies Shapes Brain Dynamics and Behavior.

    Science.gov (United States)

    Pillai, Ajay S; Jirsa, Viktor K

    2017-06-07

    In order to maintain brain function, neural activity needs to be tightly coordinated within the brain network. How this coordination is achieved and related to behavior is largely unknown. It has been previously argued that the study of the link between brain and behavior is impossible without a guiding vision. Here we propose behavioral-level concepts and mechanisms embodied as structured flows on manifold (SFM) that provide a formal description of behavior as a low-dimensional process emerging from a network's dynamics dependent on the symmetry and invariance properties of the network connectivity. Specifically, we demonstrate that the symmetry breaking of network connectivity constitutes a timescale hierarchy resulting in the emergence of an attractive functional subspace. We show that behavior emerges when appropriate conditions imposed upon the couplings are satisfied, justifying the conductance-based nature of synaptic couplings. Our concepts propose design principles for networks predicting how behavior and task rules are represented in real neural circuits and open new avenues for the analyses of neural data. Copyright © 2017 Elsevier Inc. All rights reserved.

  6. Time dynamics of the Bacillus cereus exoproteome are shaped by cellular oxidation.

    Science.gov (United States)

    Madeira, Jean-Paul; Alpha-Bazin, Béatrice; Armengaud, Jean; Duport, Catherine

    2015-01-01

    At low density, Bacillus cereus cells release a large variety of proteins into the extracellular medium when cultivated in pH-regulated, glucose-containing minimal medium, either in the presence or absence of oxygen. The majority of these exoproteins are putative virulence factors, including toxin-related proteins. Here, B. cereus exoproteome time courses were monitored by nanoLC-MS/MS under low-oxidoreduction potential (ORP) anaerobiosis, high-ORP anaerobiosis, and aerobiosis, with a specific focus on oxidative-induced post-translational modifications of methionine residues. Principal component analysis (PCA) of the exoproteome dynamics indicated that toxin-related proteins were the most representative of the exoproteome changes, both in terms of protein abundance and their methionine sulfoxide (Met(O)) content. PCA also revealed an interesting interconnection between toxin-, metabolism-, and oxidative stress-related proteins, suggesting that the abundance level of toxin-related proteins, and their Met(O) content in the B. cereus exoproteome, reflected the cellular oxidation under both aerobiosis and anaerobiosis.

  7. Time dynamics of the Bacillus cereus exoproteome are shaped by cellular oxidation

    Directory of Open Access Journals (Sweden)

    Jean-Paul eMadeira

    2015-04-01

    Full Text Available At low density, Bacillus cereus cells release a large variety of proteins into the extracellular medium when cultivated in pH-regulated, glucose-containing minimal medium, either in the presence or absence of oxygen. The majority of these exoproteins are putative virulence factors, including toxin-related proteins. Here, B. cereus exoproteome time courses were monitored by nanoLC-MS/MS under low-oxidoreduction potential (ORP anaerobiosis, high-ORP anaerobiosis, and aerobiosis, with a specific focus on oxidative-induced post-translational modifications of methionine residues. Principal component analysis (PCA of the exoproteome dynamics indicated that toxin-related proteins were the most representative of the exoproteome changes, both in terms of protein abundance and their methionine sulfoxide (Met(O content. PCA also revealed an interesting interconnection between toxin-, metabolism-, and oxidative stress–related proteins, suggesting that the abundance level of toxin-related proteins, and their Met(O content in the B. cereus exoproteome, reflected the cellular oxidation under both aerobiosis and anaerobiosis.

  8. New types of experimental data shape the use of enzyme kinetics for dynamic network modeling.

    Science.gov (United States)

    Tummler, Katja; Lubitz, Timo; Schelker, Max; Klipp, Edda

    2014-01-01

    Since the publication of Leonor Michaelis and Maude Menten's paper on the reaction kinetics of the enzyme invertase in 1913, molecular biology has evolved tremendously. New measurement techniques allow in vivo characterization of the whole genome, proteome or transcriptome of cells, whereas the classical enzyme essay only allows determination of the two Michaelis-Menten parameters V and K(m). Nevertheless, Michaelis-Menten kinetics are still commonly used, not only in the in vitro context of enzyme characterization but also as a rate law for enzymatic reactions in larger biochemical reaction networks. In this review, we give an overview of the historical development of kinetic rate laws originating from Michaelis-Menten kinetics over the past 100 years. Furthermore, we briefly summarize the experimental techniques used for the characterization of enzymes, and discuss web resources that systematically store kinetic parameters and related information. Finally, describe the novel opportunities that arise from using these data in dynamic mathematical modeling. In this framework, traditional in vitro approaches may be combined with modern genome-scale measurements to foster thorough understanding of the underlying complex mechanisms.

  9. Cell biology of mitotic recombination

    DEFF Research Database (Denmark)

    Lisby, Michael; Rothstein, Rodney

    2015-01-01

    Homologous recombination provides high-fidelity DNA repair throughout all domains of life. Live cell fluorescence microscopy offers the opportunity to image individual recombination events in real time providing insight into the in vivo biochemistry of the involved proteins and DNA molecules...... of this review include the stoichiometry and dynamics of recombination complexes in vivo, the choreography of assembly and disassembly of recombination proteins at sites of DNA damage, the mobilization of damaged DNA during homology search, and the functional compartmentalization of the nucleus with respect...... as well as the cellular organization of the process of homologous recombination. Herein we review the cell biological aspects of mitotic homologous recombination with a focus on Saccharomyces cerevisiae and mammalian cells, but will also draw on findings from other experimental systems. Key topics...

  10. Cavitation dynamics of laser ablation of bulk and wire-shaped metals in water during nanoparticles production.

    Science.gov (United States)

    De Giacomo, A; Dell'Aglio, M; Santagata, A; Gaudiuso, R; De Pascale, O; Wagener, P; Messina, G C; Compagnini, G; Barcikowski, S

    2013-03-07

    Although the first nanoseconds to microseconds rule the resulting process yield of laser ablation in liquid, a comprehensive view involving combination of time-resolved measurement techniques is still lacking. In this paper, fundamental aspects of laser ablation of metals in water during the production of nanoparticles are discussed. Three fast diagnostic methods have been applied simultaneously. These are Optical Emission Spectroscopy for the plasma characterization, fast shadowgraph for plasma and cavitation bubble dynamics and laser scattering for the mechanisms of delivery of the produced materials in the liquid. Moreover, in order to validate the discussion, the effect on cavitation dynamics of the ablation of bulk and wire-shaped targets has been investigated together with the relative nanoparticles production yield. Unusual arrow-bow ejection phenomena between the cavitation bubble and the wire result in suppressed material back-deposition, causing efficient ejection of ablated matter into the liquid. The presented nanosecond and microsecond-resolved analysis allows estimating the timescale and role of the basic mechanisms involved in laser ablation in liquids as well as the thermodynamic characteristics of the processes.

  11. Renormalization of weak noises of arbitrary shape for one-dimensional critical dynamical systems Announcement of results and numerical explorations

    CERN Document Server

    Diaz-Espinosa, O

    2006-01-01

    We study the effect of noise on one--dimensional critical dynamical systems (that is, maps with a renormalization theory). We consider in detail two examples of such dynamical systems: unimodal maps of the interval at the accumulation of period--doubling and smooth homeomorphisms of the circle with a critical point and with golden mean rotation number. We show that, if we scale the space and the time, several properties of the noise (the cumulants or Wick--ordered moments) satisfy some scaling relations. A consequence of the scaling relations is that a version of the central limit theorem holds. Irrespective of the shape of the initial noise, if the bare noise is weak enough, the effective noise becomes close to Gaussian in several senses that we can make precise. We notice that the conclusions are false for maps with positive Lyapunov exponents. The method of analysis is close in spirit to the study of scaling limits in renormalization theory. We also perform several numerical experiments that confirm the ri...

  12. Study of Geometric Porosity on Static Stability and Drag Using Computational Fluid Dynamics for Rigid Parachute Shapes

    Science.gov (United States)

    Greathouse, James S.; Schwing, Alan M.

    2015-01-01

    This paper explores use of computational fluid dynamics to study the e?ect of geometric porosity on static stability and drag for NASA's Multi-Purpose Crew Vehicle main parachute. Both of these aerodynamic characteristics are of interest to in parachute design, and computational methods promise designers the ability to perform detailed parametric studies and other design iterations with a level of control previously unobtainable using ground or flight testing. The approach presented here uses a canopy structural analysis code to define the inflated parachute shapes on which structured computational grids are generated. These grids are used by the computational fluid dynamics code OVERFLOW and are modeled as rigid, impermeable bodies for this analysis. Comparisons to Apollo drop test data is shown as preliminary validation of the technique. Results include several parametric sweeps through design variables in order to better understand the trade between static stability and drag. Finally, designs that maximize static stability with a minimal loss in drag are suggested for further study in subscale ground and flight testing.

  13. Recombination monitor

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, S. Y. [Brookhaven National Lab. (BNL), Upton, NY (United States); Blaskiewicz, M. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2017-02-03

    This is a brief report on LEReC recombination monitor design considerations. The recombination produced Au78+ ion rate is reviewed. Based on this two designs are discussed. One is to use the large dispersion lattice. It is shown that even with the large separation of the Au78+ beam from the Au79+ beam, the continued monitoring of the recombination is not possible. Accumulation of Au78+ ions is needed, plus collimation of the Au79+ beam. In another design, it is shown that the recombination monitor can be built based on the proposed scheme with the nominal lattice. From machine operation point of view, this design is preferable. Finally, possible studies and the alternative strategies with the basic goal of the monitor are discussed.

  14. When Algorithms Shape Collective Action: Social Media and the Dynamics of Cloud Protesting

    Directory of Open Access Journals (Sweden)

    Stefania Milan

    2015-12-01

    Full Text Available How does the algorithmically mediated environment of social media restructure social action? This article combines social movement studies and science and technology studies to explore the role of social media in the organization, unfolding, and diffusion of contemporary protests. In particular, it examines how activists leverage the technical properties of social media to develop a joint narrative and a collective identity. To this end, it offers the notion of cloud protesting as a theoretical approach and framework for empirical analysis. Cloud protesting indicates a specific type of mobilization that is grounded on, modeled around, and enabled by social media platforms and mobile devices and the virtual universes they identify. The notion emphasizes both the productive mediation of social and mobile media and the importance of activists’ sense-making activities. It also acknowledges that social media set in motion a process that is sociotechnical in nature rather than merely sociological or communicative, and thus can be understood only by intersecting the material and the symbolic dimensions of contemporary digitally mediated collective action. The article shows how the specific materiality of social media intervenes in the actors’ meaning work by fostering four mechanisms—namely performance, interpellation, temporality, and reproducibility—which concur to create a “politics of visibility” that alters traditional identity dynamics. In addition, it exposes the connection between organizational patterns and the role of individuals, explaining how the politics of visibility is the result of a process that originates and ends within the individual—which ultimately creates individuals-in-the-group rather than groups.

  15. Geography and host species shape the evolutionary dynamics of U genogroup infectious hematopoietic necrosis virus

    Science.gov (United States)

    Black, Allison; Breyta, Rachel; Bedford, Trevor; Kurath, Gael

    2016-01-01

    Infectious hematopoietic necrosis virus (IHNV) is a negative-sense RNA virus that infects wild and cultured salmonids throughout the Pacific Coastal United States and Canada, from California to Alaska. Although infection of adult fish is usually asymptomatic, juvenile infections can result in high mortality events that impact salmon hatchery programs and commercial aquaculture. We used epidemiological case data and genetic sequence data from a 303 nt portion of the viral glycoprotein gene to study the evolutionary dynamics of U genogroup IHNV in the Pacific Northwestern United States from 1971 to 2013. We identified 114 unique genotypes among 1,219 U genogroup IHNV isolates representing 619 virus detection events. We found evidence for two previously unidentified, broad subgroups within the U genogroup, which we designated ‘UC’ and ‘UP’. Epidemiologic records indicated that UP viruses were detected more frequently in sockeye salmon (Oncorhynchus nerka) and in coastal waters of Washington and Oregon, whereas UC viruses were detected primarily in Chinook salmon (Oncorhynchus tshawytscha) and steelhead trout (Oncorhynchus mykiss) in the Columbia River Basin, which is a large, complex watershed extending throughout much of interior Washington, Oregon, and Idaho. These findings were supported by phylogenetic analysis and by FST. Ancestral state reconstruction indicated that early UC viruses in the Columbia River Basin initially infected sockeye salmon but then emerged via host shifts into Chinook salmon and steelhead trout sometime during the 1980s. We postulate that the development of these subgroups within U genogroup was driven by selection pressure for viral adaptation to Chinook salmon and steelhead trout within the Columbia River Basin.

  16. Computational fluid dynamics (CFD) simulations of aerosol in a U-shaped steam generator tube

    Science.gov (United States)

    Longmire, Pamela

    To quantify primary side aerosol retention, an Eulerian/Lagrangian approach was used to investigate aerosol transport in a compressible, turbulent, adiabatic, internal, wall-bounded flow. The ARTIST experimental project (Phase I) served as the physical model replicated for numerical simulation. Realizable k-epsilon and standard k-o turbulence models were selected from the computational fluid dynamics (CFD) code, FLUENT, to provide the Eulerian description of the gaseous phase. Flow field simulation results exhibited: (a) onset of weak secondary flow accelerated at bend entrance towards the inner wall; (b) flow separation zone development on the convex wall that persisted from the point of onset; (c) centrifugal force concentrated high velocity flow in the direction of the concave wall; (d) formation of vortices throughout the flow domain resulted from rotational (Dean-type) flow; (e) weakened secondary flow assisted the formation of twin vortices in the outflow cross section; and (f) perturbations induced by the bend influenced flow recovery several pipe diameters upstream of the bend. These observations were consistent with those of previous investigators. The Lagrangian discrete random walk model, with and without turbulent dispersion, simulated the dispersed phase behavior, incorrectly. Accurate deposition predictions in wall-bounded flow require modification of the Eddy Impaction Model (EIM). Thus, to circumvent shortcomings of the EIM, the Lagrangian time scale was changed to a wall function and the root-mean-square (RMS) fluctuating velocities were modified to account for the strong anisotropic nature of flow in the immediate vicinity of the wall (boundary layer). Subsequent computed trajectories suggest a precision that ranges from 0.1% to 0.7%, statistical sampling error. The aerodynamic mass median diameter (AMMD) at the inlet (5.5 mum) was consistent with the ARTIST experimental findings. The geometric standard deviation (GSD) varied depending on the

  17. The relative weight of shape and non-rigid motion cues in object perception: a model of the parameters underlying dynamic object discrimination.

    Science.gov (United States)

    Vuong, Quoc C; Friedman, Alinda; Read, Jenny C A

    2012-03-16

    Shape and motion are two dominant cues for object recognition, but it can be difficult to investigate their relative quantitative contribution to the recognition process. In the present study, we combined shape and non-rigid motion morphing to investigate the relative contributions of both types of cues to the discrimination of dynamic objects. In Experiment 1, we validated a novel parameter-based motion morphing technique using a single-part three-dimensional object. We then combined shape morphing with the novel motion morphing technique to pairs of multipart objects to create a joint shape and motion similarity space. In Experiment 2, participants were shown pairs of morphed objects from this space and responded "same" on the basis of motion-only, shape-only, or both cues. Both cue types influenced judgments: When responding to only one cue, the other cue could be ignored, although shape cues were more difficult to ignore. When responding on the basis of both cues, there was an overall bias to weight shape cues more than motion cues. Overall, our results suggest that shape influences discrimination more than motion even when both cue types have been made quantitatively equivalent in terms of their individual discriminability.

  18. A third measure-metastable state in the dynamics of spontaneous shape change in healthy human's white cells.

    Directory of Open Access Journals (Sweden)

    Karen A Selz

    2011-04-01

    Full Text Available Human polymorphonuclear leucocytes, PMN, are highly motile cells with average 12-15 µm diameters and prominent, loboid nuclei. They are produced in the bone marrow, are essential for host defense, and are the most populous of white blood cell types. PMN also participate in acute and chronic inflammatory processes, in the regulation of the immune response, in angiogenesis, and interact with tumors. To accommodate these varied functions, their behavior is adaptive, but still definable in terms of a set of behavioral states. PMN morphodynamics have generally involved a non-equilibrium stationary, spheroid Idling state that transitions to an activated, ellipsoid translocating state in response to chemical signals. These two behavioral shape-states, spheroid and ellipsoid, are generally recognized as making up the vocabulary of a healthy PMN. A third, "random" state has occasionally been reported as associated with disease states. I have observed this third, Treadmilling state, in PMN from healthy subjects, the cells demonstrating metastable dynamical behaviors known to anticipate phase transitions in mathematical, physical, and biological systems. For this study, human PMN were microscopically imaged and analyzed as single living cells. I used a microscope with a novel high aperture, cardioid annular condenser with better than 100 nanometer resolution of simultaneous, mixed dark field and intrinsic fluorescent images to record shape changes in 189 living PMNs. Relative radial roundness, R(t, served as a computable order parameter. Comparison of R(t series of 10 cells in the Idling and 10 in the Treadmilling state reveals the robustness of the "random" appearing Treadmilling state, and the emergence of behaviors observed in the neighborhood of global state transitions, including increased correlation length and variance (divergence, sudden jumps, mixed phases, bimodality, power spectral scaling and temporal slowing. Wavelet transformation of an R

  19. Eye rotation induced dynamics of a Newtonian fluid within the vitreous cavity: the effect of the chamber shape

    Energy Technology Data Exchange (ETDEWEB)

    Stocchino, Alessandro [Department of Environmental Engineering, University of Genoa (Italy); Repetto, Rodolfo [Department of Engineering of Structures, Water and Soil, University of L' Aquila (Italy); Cafferata, Chiara [Department of Environmental Engineering, University of Genoa (Italy)

    2007-04-07

    The dynamics of the vitreous body induced by eye rotations is studied experimentally. In particular, we consider the case in which the vitreous cavity is filled by a Newtonian fluid, either because the vitreous is liquefied or because it has been replaced, after vitrectomy, by a viscous fluid. We employ a rigid Perspex container which models, in a magnified scale, the vitreous cavity of the human eye. The shape of the cavity closely resembles that of the real vitreous chamber; in particular, the anterior part of the container is concave in order to model the presence of the eye lens. The container is filled with glycerol and is mounted on the shaft of a computer-controlled motor which rotates according to a periodic time law. PIV (particle image velocimetry) measurements are taken on the equatorial plane orthogonal to the axis of rotation. The experimental measurements show that the velocity field is strongly influenced by the deformed geometry of the domain. In particular, the formation of a vortex in the vicinity of the lens, which migrates in time towards the core of the domain, is invariably observed. The vortex path is tracked in time by means of a vortex identification technique and it is found that it is significantly influenced by the Womersley number of the flow. Particle trajectories are computed from the PIV measurements. Particles initially located at different positions on the equatorial horizontal plane (perpendicular to the axis of rotation) tend to concentrate in narrow regions adjacent to the lens, thus suggesting the existence, in such regions, of a vertical fluid ejection. Such a strong flow three-dimensionality, which is essentially induced by the irregular shape of the domain, may play a significant role in the mixing processes taking place inside the eye globe. The tangential stresses acting on the rigid boundary of the domain are also computed from the experimental measurements showing that regions subject to particularly intense stresses

  20. Phase-only shaped laser pulses in optimal control theory: Application to indirect photofragmentation dynamics in the weak-field limit

    DEFF Research Database (Denmark)

    Shu, Chuan-Cun; Henriksen, Niels E.

    2012-01-01

    We implement phase-only shaped laser pulses within quantum optimal control theory for laser-molecule interaction. This approach is applied to the indirect photofragmentation dynamics of NaI in the weak-field limit. It is shown that optimized phase-modulated pulses with a fixed frequency...

  1. Sequential and simultaneous statistical optimization by dynamic design of experiment for peptide overexpression in recombinant Escherichia coli.

    Science.gov (United States)

    Lee, Kwang-Min; Rhee, Chang-Hoon; Kang, Choong-Kyung; Kim, Jung-Hoe

    2006-10-01

    The production of recombinant anti-HIV peptide, T-20, in Escherichia coli was optimized by statistical experimental designs (successive designs with multifactors) such as 2(4-1) fractional factorial, 2(3) full factorial, and 2(2) rotational central composite design in order. The effects of media compositions (glucose, NPK sources, MgSO4, and trace elements), induction level, induction timing (optical density at induction process), and induction duration (culture time after induction) on T-20 production were studied by using a statistical response surface method. A series of iterative experimental designs was employed to determine optimal fermentation conditions (media and process factors). Optimal ranges characterized by %T-20 (proportion of peptide to the total cell protein) were observed, narrowed down, and further investigated to determine the optimal combination of culture conditions, which was as follows: 9, 6, 10, and 1 mL of glucose, NPK sources, MgSO4, and trace elements, respectively, in a total of 100 mL of medium inducted at an OD of 0.55-0.75 with 0.7 mM isopropyl-beta-D-thiogalactopyranoside in an induction duration of 4 h. Under these conditions, up to 14% of T-20 was obtained. This statistical optimization allowed the production of T-20 to be increased more than twofold (from 6 to 14%) within a shorter induction duration (from 6 to 4 h) at the shake-flask scale.

  2. Tunable configurational anisotropy in collective magnetization dynamics of Ni{sub 80}Fe{sub 20} nanodot arrays with varying dot shapes

    Energy Technology Data Exchange (ETDEWEB)

    Mahato, B. K.; Choudhury, S.; Mandal, R.; Barman, S.; Barman, A., E-mail: abarman@bose.res.in [Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700 098 (India); Otani, Y. [CEMS-RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan)

    2015-06-07

    We present broadband ferromagnetic resonance measurements of tunable spin wave anisotropy in arrays of nanodots with different dot shapes. Magnetization dynamics of the circular dot array shows two modes, while square, diamond, and triangular dot arrays show three, three, and four modes, respectively. Various distinct rotational symmetries in the configurational anisotropy of the nanodot arrays are observed with the variation of dot shape. The observed spin wave modes are reproduced by micromagnetic simulations and the calculated mode profiles show different collective modes determined by internal and stray magnetic fields. Effects of dot shapes are observed in combination with the effects of lattice symmetry and the shape of the boundary of the array. The collective behaviour is observed to be weakest in the diamond shaped dots and strongest in circular shaped dots. This is further confirmed by the stray field calculation. The large variation of spin wave mode frequencies and their configurational anisotropies with dot shapes are important for selection of suitable basis structures for future magnonic crystals.

  3. Bimolecular recombination in organic photovoltaics.

    Science.gov (United States)

    Lakhwani, Girish; Rao, Akshay; Friend, Richard H

    2014-01-01

    The recombination of electrons and holes is a major loss mechanism in photovoltaic devices that controls their performance. We review scientific literature on bimolecular recombination (BR) in bulk heterojunction organic photovoltaic devices to bring forward existing ideas on the origin and nature of BR and highlight both experimental and theoretical work done to quantify its extent. For these systems, Langevin theory fails to explain BR, and recombination dynamics turns out to be dependent on mobility, temperature, electric field, charge carrier concentration, and trapped charges. Relationships among the photocurrent, open-circuit voltage, fill factor, and morphology are discussed. Finally, we highlight the recent emergence of a molecular-level picture of recombination, taking into account the spin and delocalization of charges. Together with the macroscopic picture of recombination, these new insights allow for a comprehensive understanding of BR and provide design principles for future materials and devices.

  4. XRCC3 ATPase activity is required for normal XRCC3-Rad51C complex dynamics and homologous recombination

    Energy Technology Data Exchange (ETDEWEB)

    Yamada, N; Hinz, J; Kopf, V L; Segalle, K; Thompson, L

    2004-02-25

    Homologous recombinational repair is a major DNA repair pathway that preserves chromosomal integrity by removing double-strand breaks, crosslinks, and other DNA damage. In eukaryotic cells, the Rad51 paralogs (XRCC2, XRCC3, Rad51B, Rad51C, and Rad51D) are involved in this process, although their exact functions are largely undetermined. All five paralogs contain ATPase motifs, and XRCC3 appears to exist in a single complex with Rad51C. To begin to examine the function of this Rad51C-XRCC3 complex, we generated mammalian expression vectors that produce human wild-type XRCC3 or mutant XRCC3 with either a non-conservative mutation (K113A) or a conservative mutation (K113R) in the GKT Walker A box of the ATPase motif. The three vectors were independently transfected into Xrcc3-deficient irs1SF CHO cells. Wild-type XRCC3 complemented irs1SF cells, albeit to varying degrees, while ATPase mutants had no complementing activity, even when the mutant protein was expressed at comparable levels to that in wild-type-complemented clones. Because of the mutants' dysfunction, we propose that ATP binding and hydrolyzing activities of XRCC3 are essential. We tested in vitro complex formation by wild-type and mutant XRCC3 with His6-tagged Rad51C upon coexpression in bacteria, nickel affinity purification, and western blotting. Wild-type and K113A mutant XRCC3 formed stable complexes with Rad51C and co-purified with Rad51C, while the K113R mutant did not and was predominantly insoluble. Addition of 5 mM ATP, but not ADP, also abolished complex formation by the wild-type proteins. These results suggest that XRCC3 is likely to regulate the dissociation and formation of Rad51C-XRCC3 complex through ATP binding and hydrolysis, with both processes being essential for the complex's ability to participate in HRR.

  5. Excision dynamics of Vibrio pathogenicity island-2 from Vibrio cholerae: role of a recombination directionality factor VefA

    Directory of Open Access Journals (Sweden)

    Napolitano Michael G

    2010-11-01

    Full Text Available Abstract Background Vibrio Pathogenicity Island-2 (VPI-2 is a 57 kb region present in choleragenic V. cholerae isolates that is required for growth on sialic acid as a sole carbon source. V. cholerae non-O1/O139 pathogenic strains also contain VPI-2, which in addition to sialic acid catabolism genes also encodes a type 3 secretion system in these strains. VPI-2 integrates into chromosome 1 at a tRNA-serine site and encodes an integrase intV2 (VC1758 that belongs to the tyrosine recombinase family. IntV2 is required for VPI-2 excision from chromosome 1, which occurs at very low levels, and formation of a non-replicative circular intermediate. Results We determined the conditions and the factors that affect excision of VPI-2 in V. cholerae N16961. We demonstrate that excision from chromosome 1 is induced at low temperature and after sublethal UV-light irradiation treatment. In addition, after UV-light irradiation compared to untreated cells, cells showed increased expression of three genes, intV2 (VC1758, and two putative recombination directionality factors (RDFs, vefA (VC1785 and vefB (VC1809 encoded within VPI-2. We demonstrate that along with IntV2, the RDF VefA is essential for excision. We constructed a knockout mutant of vefA in V. cholerae N16961, and found that no excision of VPI-2 occurred, indicating that a functional vefA gene is required for excision. Deletion of the second RDF encoded by vefB did not result in a loss of excision. Among Vibrio species in the genome database, we identified 27 putative RDFs within regions that also encoded IntV2 homologues. Within each species the RDFs and their cognate IntV2 proteins were associated with different island regions suggesting that this pairing is widespread. Conclusions We demonstrate that excision of VPI-2 is induced under some environmental stress conditions and we show for the first time that an RDF encoded within a pathogenicity island in V. cholerae is required for excision of the

  6. Interplay of structural instability and lattice dynamics in Ni{sub 2}MnAl shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Mehaddene, T.

    2007-02-12

    The work presented here is devoted to investigate the interplay of lattice dynamics and structural instability in Ni{sub 2}MnAl shape memory alloys. Inelastic neutron scattering is used to get more insight on the dynamic precursors of structural instability in Ni{sub 2}MnAl. Differential Scanning Calorimetry was used to characterise the martensitic transition in Ni{sub 2}MnAl alloys. Effects of composition and heat treatments have been investigated. The measured martensitic transition temperature in Ni-Mn-Al alloys depends linearly on the valence electron concentration. Two single crystals with different compositions have been succesfully grown using the Czochralski technique. Acoustic and optical phonon modes have been measured at room temperature in the high symmetry directions of the cubic B2 phase. The force constants have been fitted to the measured data using the Born-von Karman model. The character of the phonon softening measured in Ni{sub 2}MnAl corresponds to the pattern of atomic displacements of the modulations 2M, 10M, 12M and 14M observed in bulk and thin-films of Ni{sub 2}MnAl. The effect of the composition on the lattice instability has been investigated by measuring normal modes of vibration in two different crystals, Ni{sub 51}Mn{sub 18}Al{sub 31} and Ni{sub 53}Mn{sub 22}Al{sub 25}, with e/a ratios of 7.29 and 7.59 respectively. The stabilisation of a single L2{sub 1} phase in Ni{sub 2}MnAl by annealing a Ni{sub 51}Mn{sub 18}Al{sub 31} single crystal at 673 K during 45 days has been attempted. Despite of the long-time annealing, a single L2{sub 1} phase could not be stabilised because of either a slow diffusion kinetics or the establishment of an equilibrium between the L2{sub 1} and the B2 phases. Phonon measurements of the TA{sub 2}[{xi}{xi}0] branch in the annealed sample revealed a substantial effect. The wiggle, associated with the anomalous softening, is still present but the degree of softening is smaller below 673 K and changes

  7. MRI Dynamically Evaluates the Therapeutic Effect of Recombinant Human MANF on Ischemia/Reperfusion Injury in Rats

    Directory of Open Access Journals (Sweden)

    Xian-Yun Wang

    2016-09-01

    Full Text Available As an endoplasmic reticulum (ER stress-inducible protein, mesencephalic astrocyte-derived neurotrophic factor (MANF has been proven to protect dopaminergic neurons and nondopaminergic cells. Our previous studies had shown that MANF protected against ischemia/reperfusion injury. Here, we developed a magnetic resonance imaging (MRI technology to dynamically evaluate the therapeutic effects of MANF on ischemia/reperfusion injury. We established a rat focal ischemic model by using middle cerebral artery occlusion (MCAO. MRI was performed to investigate the dynamics of lesion formation. MANF protein was injected into the right lateral ventricle at 3 h after reperfusion following MCAO for 90 min, when the obvious lesion firstly appeared according to MRI investigation. T2-weighted imaging for evaluating the therapeutic effects of MANF protein was performed in ischemia/reperfusion injury rats on Days 1, 2, 3, 5, and 7 post-reperfusion combined with histology methods. The results indicated that the administration of MANF protein at the early stage after ischemia/reperfusion injury decreased the mortality, improved the neurological function, reduced the cerebral infarct volume, and alleviated the brain tissue injury. The findings collected from MRI are consistent with the morphological and pathological changes, which suggest that MRI is a useful technology for evaluating the therapeutic effects of drugs.

  8. Roles of Municipal Councils in Poland and in the Czech Republic: Factors Shaping the Roles and the Dynamic of Change

    Directory of Open Access Journals (Sweden)

    Katarzyna Radzik-Maruszak

    2016-03-01

    Full Text Available Abstract: Research Question (RQ: After many years of not being in vogue, the issue of representative democracy at the local level has yet again caught the scholars’ attention. The interest is related both to falling turnout in local elections, disappointment in party politics as well as to the impact of the new trends such as the strengthening of the executive power or citizens’ more direct involvement in the decision-making process. Quite often the afore-mentioned trends force local councils to redefine their roles. Purpose: The main objective of the article is to investigate the factors that shape the roles of municipal councils in two CEE countries, Poland and the Czech Republic, and to track the possible dynamic of their change. Method: The analysis conducted in the paper is grounded mainly in institutional theory. The study is based on available statistic data, examination of legal regulations, documents and information included in the corpus of selected articles and books. Results: The outcome of the analysis conducted indicates that in both countries the basic roles of councils – representative, decision - making and administrative one – are being diminished. Nevertheless, the existing institutional framework as well as reforms implemented in recent years provide potential for the development of new roles, such as the facilitator of the governing process or a network coordinator. Organization: The paper may contribute to better organisation of local administration at the municipal level. Society: The study has an impact on the understanding of representative democracy in local self-governments. Originality: The paper elaborates on representative democracy at the municipal level in Poland and the Czech Republic, countries where the discussion over this issue is still much less visible than in Western Europe. Limitations / further research: The paper should be mainly perceived as a kind of theoretical introduction to further

  9. Excitation correlation photoluminescence in the presence of Shockley-Read-Hall recombination

    Energy Technology Data Exchange (ETDEWEB)

    Borgwardt, M., E-mail: mario.borgwardt@helmholtz-berlin.de [Joint Laboratory for Ultrafast Dynamics in Solutions and at Interfaces (JULiq), Institute of Methods for Material Development, Helmholtz-Zentrum Berlin, Albert-Einstein-Strasse 15, D-12489 Berlin (Germany); Sippel, P.; Eichberger, R. [Institute of Solar Fuels, Helmholtz-Zentrum Berlin, Albert-Einstein-Strasse 15, Berlin D-12489 (Germany); Semtsiv, M. P.; Masselink, W. T. [Department of Physics, Humboldt-Universität of Berlin, Newtonstrasse 15, D-12489 Berlin (Germany); Schwarzburg, K., E-mail: schwarzburg@helmholtz-berlin.de [Institute Nano-architectures for Energy Conversion, Helmholtz-Zentrum Berlin, Albert-Einstein-Strasse 15, D-12489 Berlin (Germany)

    2015-06-07

    Excitation correlation photoluminescence (ECPL) measurements are often analyzed in the approximation of a cross correlation of charge carrier populations generated by the two delayed pulses. In semiconductors, this approach is valid for a linear non-radiative recombination path, but not for a non-linear recombination rate as in the general Shockley-Read-Hall recombination scenario. Here, the evolution of the ECPL signal was studied for deep trap recombination following Shockley-Read-Hall statistics. Analytic solutions can be obtained for a fast minority trapping regime and steady state recombination. For the steady state case, our results show that the quadratic radiative term plays only a minor role, and that the shape of the measured signal is mostly determined by the non-linearity of the recombination itself. We find that measurements with unbalanced intense pump and probe pulses can directly provide information about the dominant non-radiative recombination mechanism. The signal traces follow the charge carrier concentrations, despite the complex origins of the signal, thus showing that ECPL can be applied to study charge carrier dynamics in semiconductors without requiring elaborate calculations. The model is compared with measurements on a reference sample with alternating layers of InGaAs/InAlAs that were additionally cross-checked with time resolved optical pump terahertz probe measurements and found to be in excellent agreement.

  10. Recombination dynamics of type-II excitons in (Ga,In)As/GaAs/Ga(As,Sb) heterostructures

    Science.gov (United States)

    Gies, S.; Holz, B.; Fuchs, C.; Stolz, W.; Heimbrodt, W.

    2017-01-01

    (Ga,In)As/GaAs/Ga(As,Sb) multi-quantum well heterostructures have been investigated using continuous wave and time-resolved photoluminescence spectroscopy at various temperatures. A complex interplay was observed between the excitonic type-II transitions with electrons in the (Ga,In)As well and holes in the Ga(As,Sb) well and the type-I excitons in the (Ga,In)As and Ga(As,Sb) wells. The type-II luminescence exhibits a strongly non-exponential temporal behavior below a critical temperature of T c = 70 K. The transients were analyzed in the framework of a rate-equation model. It was found that the exciton relaxation and hopping in the localized states of the disordered ternary Ga(As,Sb) are the decisive processes to describe the dynamics of the type-II excitons correctly.

  11. Recombination dynamics of a localized exciton bound at basal stacking faults within the m-plane ZnO film

    Energy Technology Data Exchange (ETDEWEB)

    Yang, S.; Liu, W.-R. [Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan (China); Hsu, H. C., E-mail: hsuhc@mail.ncku.edu.tw, E-mail: wfhsieh@mail.nctu.edu.tw [Department of Photonics and Advanced Optoelectronic Technology Center, National Cheng Kung University, 701 Tainan, Taiwan (China); Lin, B. H.; Hsu, C.-H. [Scientific Research Division, National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan (China); Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan (China); Kuo, C. C.; Hsieh, W. F., E-mail: hsuhc@mail.ncku.edu.tw, E-mail: wfhsieh@mail.nctu.edu.tw [Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan (China); Eriksson, M. O.; Holtz, P. O. [Department of Physics, Chemistry and Biology (IFM), Linköping University, Linköping (Sweden)

    2014-07-07

    We investigated the carrier dynamics near basal stacking faults (BSFs) in m-plane ZnO epitaxial film. The behaviors of the type-II quantum wells related to the BSFs are verified through time-resolved and time-integrated photoluminescence. The decay time of the emission of BSFs is observed to have a higher power law value and longer decay time than the emission of the donor-bound excitons. The spectral-dependent decay times reveal a phenomenon of carriers migrating among band tail states, which are related to the spatial distribution of the type-II quantum wells formed by the BSFs. A high density of excited carriers leads to a band bending effect, which in turn causes a blue-shift of the emission peak of BSFs with a broadened distribution of band tail states.

  12. Spectral shapes of Ar-broadened HCl lines in the fundamental band by classical molecular dynamics simulations and comparison with experiments

    Energy Technology Data Exchange (ETDEWEB)

    Tran, H., E-mail: ha.tran@lisa.u-pec.fr [Laboratoire Interuniversitaire des Systèmes Atmosphériques, UMR CNRS 7583, Université Paris Est Créteil, Université Paris Diderot, Institut Pierre-Simon Laplace, 94010 Créteil Cedex (France); Domenech, J.-L. [Instituto de Estructura de la Materia, Consejo Superior de Investigaciones Cientificas, (IEM-CSIC), Serrano 123, 28006 Madrid (Spain)

    2014-08-14

    Spectral shapes of isolated lines of HCl perturbed by Ar are investigated for the first time using classical molecular dynamics simulations (CMDS). Using reliable intermolecular potentials taken from the literature, these CMDS provide the time evolution of the auto-correlation function of the dipole moment, whose Fourier-Laplace transform leads to the absorption spectrum. In order to test these calculations, room temperature spectra of various lines in the fundamental band of HCl diluted in Ar are measured, in a large pressure range, with a difference-frequency laser spectrometer. Comparisons between measured and calculated spectra show that the CMDS are able to predict the large Dicke narrowing effect on the shape of HCl lines and to satisfactorily reproduce the shapes of HCl spectra at different pressures and for various rotational quantum numbers.

  13. Uncovering the microscopic mechanism of strand exchange during RecA mediated homologous recombination using all-atom molecular dynamics simulations

    Science.gov (United States)

    Shankla, Manish; Yoo, Jejoong; Aksimentiev, Aleksei

    2012-02-01

    Homologous recombination (HR) is a key step during the repair process of double-stranded DNA (dsDNA) breakage. RecA is a protein that mediates HR in bacteria. RecA monomers polymerize on a single-stranded DNA (ssDNA) separated from the broken dsDNA to form a helical filament, thus allowing strand exchange to occur. Recent crystal structures depict each RecA monomer in contact with three contiguous nucleotides called DNA triplets. Surprisingly, the conformation of each triplet is similar to that of a triplet in B-form DNA. However, in the filament the neighboring triplets are separated by loops of the RecA proteins. Single molecule experiments demonstrated that strand exchange propagation occurs in 3 base-pair increments. However, the temporal resolution of the experiments was insufficient to determine the exact molecular mechanism of the triplet propagation. Using all-atom molecular dynamics simulations, we investigated the effect of both the RecA protein and the conformation of the bound ssDNA fragment on the stability of the duplex DNA intermediate formed during the strand-exchange process. Specifically, we report simulations of force-induced unzipping of duplex DNA in the presence and absence of the RecA filament that explored the effect of the triplet ladder conformation.

  14. 利用CPDH和动态规划算法的形状检索%Shape retrieval based on CPDH and dynamic programming algorithm

    Institute of Scientific and Technical Information of China (English)

    束鑫; 吴小俊; 潘磊

    2011-01-01

    用形状轮廓上点的坐标位置相对于形状重心位置的分布关系描述形状,提出一种极坐标下形状轮廓点分布直方图描述符(contour points distribution histogram),该描述符不仅符合人眼的视觉直观感受、计算简单,而且其本质上具有缩放和平移不变性.用动态规划算法(dynamic programming algorithm)来度量轮廓点分布直方图之间的距离,部分解决了轮廓点分布直方图对于旋转不变性的要求.在多个形状图像数据库中的实验结果表明,该方法在单目标封闭轮廓的形状图像检索中取得了良好效果.%Using the distribution relations between the coordinates of the points on shape contour and the centroid of the shape to describe a shape, a novel shape descriptor CPDH (contour points distribution histogram) is proposed under polar coordinate.This descriptor not only satisfies the human' s visual perception and easy to be calculated, but also it essentially has the properties of invariant to scaling and translation.We also suggest using the Dynamic Programming Algorithm to measure the distance between CPDHs, and that the DP algorithm can partly solve the need of the CPDH' s invariant to rotation.With a great deal of experiments in several shape databases, it is shown that this algorithm, used in image retrieval of shape with a single closed contour, can get favorable results.

  15. Phase-only shaped laser pulses in optimal control theory: application to indirect photofragmentation dynamics in the weak-field limit.

    Science.gov (United States)

    Shu, Chuan-Cun; Henriksen, Niels E

    2012-01-28

    We implement phase-only shaped laser pulses within quantum optimal control theory for laser-molecule interaction. This approach is applied to the indirect photofragmentation dynamics of NaI in the weak-field limit. It is shown that optimized phase-modulated pulses with a fixed frequency distribution can substantially modify transient dissociation probabilities as well as the momentum distribution associated with the relative motion of Na and I.

  16. Modality-specific spectral dynamics in response to visual and tactile sequential shape information processing tasks: An MEG study using multivariate pattern classification analysis.

    Science.gov (United States)

    Gohel, Bakul; Lee, Peter; Jeong, Yong

    2016-08-01

    Brain regions that respond to more than one sensory modality are characterized as multisensory regions. Studies on the processing of shape or object information have revealed recruitment of the lateral occipital cortex, posterior parietal cortex, and other regions regardless of input sensory modalities. However, it remains unknown whether such regions show similar (modality-invariant) or different (modality-specific) neural oscillatory dynamics, as recorded using magnetoencephalography (MEG), in response to identical shape information processing tasks delivered to different sensory modalities. Modality-invariant or modality-specific neural oscillatory dynamics indirectly suggest modality-independent or modality-dependent participation of particular brain regions, respectively. Therefore, this study investigated the modality-specificity of neural oscillatory dynamics in the form of spectral power modulation patterns in response to visual and tactile sequential shape-processing tasks that are well-matched in terms of speed and content between the sensory modalities. Task-related changes in spectral power modulation and differences in spectral power modulation between sensory modalities were investigated at source-space (voxel) level, using a multivariate pattern classification (MVPC) approach. Additionally, whole analyses were extended from the voxel level to the independent-component level to take account of signal leakage effects caused by inverse solution. The modality-specific spectral dynamics in multisensory and higher-order brain regions, such as the lateral occipital cortex, posterior parietal cortex, inferior temporal cortex, and other brain regions, showed task-related modulation in response to both sensory modalities. This suggests modality-dependency of such brain regions on the input sensory modality for sequential shape-information processing.

  17. 自旋极化度对GaAs量子阱中吸收饱和效应与载流子复合动力学的影响研究%Effects of spin p olarization on absorption saturation and recombination dynamics of carriers in (001) GaAs quantum wells

    Institute of Scientific and Technical Information of China (English)

    方少寅; 陆海铭; 赖天树

    2015-01-01

    In this paper, the ultrafast dynamics of spin relaxation and recombination of photoexcited carriers has been studied in (001) GaAs quantum wells using a time-resolved pump-probe absorption spectroscopy under a nearly resonant excitation of heavy-hole excitons. It is found that the spin polarization of carriers influences both absorption saturation of linear polarized light and recombination dynamics of carriers. Pump fluence dependence of the ultrafast dynamics of spin relaxation and recombination of carriers is further studied, which shows that the effect of spin polarization on linearly polarized absorption saturation is reduced with lowering pump fluence. Spin-polarization-dependent absorption saturation effect can be ignored only as the pump fluence is weak. However, spin-polarization dependence of recombination dynamics is presented in turn at low pump fluence. Our analysis shows that such dependence originates from the spinpolarization dependence of the density of excitons formed in the excited carriers because recombination time constants of excitons and free carriers are very different so that the ratio of exciton density to free carrier density can influence the recombination dynamics. The spin-polarization dependence of ultrafast recombination dynamics of photoexcited carriers implies that the recombination time constant in the calculation of spin relaxation time from spin relaxation dynamics should be the recombination time of spin-polarized carriers, rather than the recombination lifetime of non-spin-polarized carriers as done currently. Exciton density is estimated based on 2D mass action law, which agrees very well with our experimental results. The good agreement between theoretical calculation and experimental results reveals that the effect of Coulomb screening on the formation of excitons may be ignored for a lower excited carrier density.

  18. Shape-based motion correction in dynamic contrast-enhanced MRI for quantitative assessment of renal function.

    Science.gov (United States)

    Liu, Wenyang; Sung, Kyunghyun; Ruan, Dan

    2014-12-01

    To incorporate a newly developed shape-based motion estimation scheme into magnetic resonance urography (MRU) and verify its efficacy in facilitating quantitative functional analysis. The authors propose a motion compensation scheme in MRU that consists of three sequential modules: MRU image acquisition, motion compensation, and quantitative functional analysis. They designed two sets of complementary experiments to evaluate the performance of the proposed method. In the first experiment, dynamic contrast enhanced (DCE) MR images were acquired from three sedated subjects, from which clinically valid estimates were derived and served as the "ground truth." Physiologically sound motion was then simulated to synthesize image sequences influenced by respiratory motion. Quantitative assessment and comparison were performed on functional estimates of Patlak number, glomerular filtration rate, and Patlak differential renal function without and with motion compensation against the ground truth. In the second experiment, the authors acquired a temporal series of noncontrast MR images under free breathing from a healthy adult subject. The performance of the proposed method on compensating real motion was evaluated by comparing the standard deviation of the obtained temporal intensity curves before and after motion compensation. On DCE-MR images with simulated motion, the generated relative enhancement curves exhibited large perturbations and the Patlak numbers of the left and right kidney were significantly underestimated up to 35% and 34%, respectively, compared with the ground truth. After motion compensation, the relative enhancement curves exhibited much less perturbations and Patlak estimation errors reduced within 3% and 4% for the left and right kidneys, respectively. On clinical free-breathing MR images, the temporal intensity curves exhibited significantly reduced variations after motion compensation, with standard deviation decreased from 30.3 and 38.2 to 8.3 and

  19. Shape effects on the cluster spreading process of spin-crossover compounds analyzed within an elastic model with Eden and Kawasaki dynamics

    Science.gov (United States)

    Enachescu, Cristian; Nishino, Masamichi; Miyashita, Seiji; Boukheddaden, Kamel; Varret, François; Rikvold, Per Arne

    2015-03-01

    In this paper we study the growth properties of domains of low-spin molecules in a high-spin background in open-boundary elliptically shaped spin-crossover systems within the framework of a mechanoelastic model. The molecules are situated on a triangular lattice and are linked by springs, through which they interact. Elliptical shapes are chosen in order to allow an in-depth analysis of cluster shapes as a function of the local curvature at their starting point and the length of the interface between the two phases. In contrast to the case of rectangular and hexagonal shapes, where the clusters always start from corners, we find that for ellipses clusters nucleate from vertices, covertices, or any other site. We apply and compare two kinds of dynamics, Eden-like and Kawasaki, in order to determine the stable shape of the clusters and the most probable starting points. We show that the wetting angle for small clusters is somewhat higher than π /2 and approaches this value only for large clusters. The stability of clusters is analyzed by comparing the Gibbs free energy to the elastic energy in the system and is discussed as a function of the cluster size, curvature of the starting place, and temperature.

  20. Atomic excitation and recombination in external fields

    Energy Technology Data Exchange (ETDEWEB)

    Nayfeh, M.H.; Clark, C.W.

    1985-01-01

    This volume offers a timely look at Rydberg states of atoms in external fields and dielectronic recombination. Each topic provides authoritative coverage, presents a fresh account of a flourishing field of current atomic physics and introduces new opportunities for discovery and development. Topics considered include electron-atom scattering in external fields; observations of regular and irregular motion as exemplified by the quadratic zeeman effect and other systems; Rydberg atoms in external fields and the Coulomb geometry; crossed-field effects in the absorption spectrum of lithium in a magnetic field; precise studies of static electric field ionization; widths and shapes of stark resonances in sodium above the saddle point; studies of electric field effects and barium autoionizing resonances; autoionization and dielectronic recombination in plasma electric microfields; dielectronic recombination measurements on multicharged ions; merged beam studies of dielectronic recombination; Rydberg atoms and dielectronic recombination in astrophysics; and observations on dielectronic recombination.

  1. Pulsed laser ablation of wire-shaped target in a thin water jet: effects of plasma features and bubble dynamics on the PLAL process

    Science.gov (United States)

    Dell'Aglio, Marcella; De Giacomo, Alessandro; Kohsakowski, Sebastian; Barcikowski, Stephan; Wagener, Philipp; Santagata, Antonio

    2017-05-01

    In this paper, emission spectroscopy and fast imaging surveys during pulsed laser ablation in liquid (PLAL) for nanoparticles (NPs) production have been used, in order to provide further details about the process involved and the potentialities offered by a wire-shaped sample ablated in a flowing water jet. This kind of set-up has been explored because the laser ablation efficiency in water increases when a thin water layer and a wire-shaped target are used. In order to understand the physical processes causing the increasing ablation efficiency, both the laser-induced plasma and bubble dynamics generated in a flowing liquid jet have been analysed. The plasma parameters and the bubble behaviour in such a system have been compared with those observed in conventional PLAL experiments, where either a bulk or a wire-shaped target is immersed in bulk water. From the data presented here it is evidenced that the plasma and shockwave induced during the breakdown process can play a direct role in the ablation efficiency variation observed. With regard to the cavitation bubbles evolving near a free surface (the interface between water and air) it should be noted that these have to be treated with caution as a consequence of the strong influence played in these circumstances by the boundary of the water jet during its expansion dynamics. The effects due to the size of the liquid layer, the presence of the water/air interface, the liquid characteristics, the target shape, the plasma evolution and the bubble dynamics together with their outcomes on the NPs’ production, are presented and discussed.

  2. Dynamics of aggregate size and shape properties under sequenced flocculation in a turbulent Taylor-Couette reactor.

    Science.gov (United States)

    Guérin, Léa; Coufort-Saudejaud, Carole; Liné, Alain; Frances, Christine

    2017-04-01

    This paper concerns experimental investigation of the sequenced flocculation of latex particles in a Taylor-Couette reactor. The aim of this work was to investigate the evolution of both the size and the shape of aggregates under sequenced hydrodynamics. A number of studies have focused on the evolution of the aggregate size or size distribution during steps of growth-breakage-regrowth, but aggregates generally experience steps of breakage-regrowth on repeated occasions in real operating conditions (passages near the impeller or during the transfer processes, for example). The experiments conducted in this work consisted thus of an alternation of six steps with alternately low and high shear rates under turbulent conditions. The particle size distributions were monitored throughout the sequencing, and the circularity and convexity (shape parameters) distributions were measured, enabling a more precise description of the entire floc population, rather than a fractal dimension. While the aggregate size distribution was clearly controlled by hydrodynamics, the shape distributions continuously evolved during the sequencing. The main new finding of our work notes the independence between the aggregate shape and hydrodynamics. Indeed, after multiples steps of breakage-regrowth, regardless of the aggregate size distribution and hydrodynamics, the aggregate shape seemed to reach a unique steady-state morphological distribution.

  3. Dynamic Evolution of an X-shaped Structure above a Trans-equatorial Quadrupole Solar Active Region Group

    CERN Document Server

    Sun, J Q; Guo, Y; Ding, M D; Li, Y

    2014-01-01

    In the solar corona, magnetic reconnection usually takes place at the singular configuration of magnetic field, in particular near a magnetic null owing to its high susceptibility to perturbations. In this Letter, we report a rare X-shaped structure, encompassing a magnetic null, above a trans-equatorial quadrupole active region group that is well observed by the Atmospheric Imaging Assembly (AIA). The observations show that this X-shaped structure is visible in all AIA EUV passbands and stably exists for days. However, possibly induced by flare activities at the northern part of the quadrupole active region group, the X-shaped structure starts to destabilize and meanwhile a jet erupted near its center at 15:05 UT on 2013 October 7. Through the non-linear force-free field modeling, we identify a magnetic null, which is above the quadrupole polarities and well corresponds to the X-shaped structure. After the jet eruption, the temperature and emission measure of the plasma near the X-shaped structure rise from ...

  4. Electron beam induced and microemulsion templated synthesis of CdSe quantum dots: tunable broadband emission and charge carrier recombination dynamics

    Science.gov (United States)

    Guleria, Apurav; Singh, Ajay K.; Rath, Madhab C.; Adhikari, Soumyakanti

    2015-04-01

    CdSe quantum dots (QDs) were synthesized by a rapid and one step templated approach inside the water pool of AOT (sodium bis(2-ethylhexyl) sulfosuccinate) based water-in-oil microemulsions (MEs) via electron beam (EB) irradiation technique with high dose rate, which favours high nucleation rate. The interplay of different experimental parameters such as precursor concentration, absorbed dose and {{W}0} values (aqueous phase to surfactant molar ratio) of MEs were found to have interesting consequences on the morphology, photoluminescence (PL), surface composition and carrier recombination dynamics of as-grown QDs. For instance, highly stable ultrasmall (∼1.7 nm) bluish-white light emitting QDs were obtained with quantum efficiency (η) of ∼9%. Furthermore, QDs were found to exhibit tunable broadband light emission extending from 450 to 750 nm (maximum FWHM ∼180 nm). This could be realized from the CIE (Commission Internationale d’Eclairage) chromaticity co-ordinates, which varied across the blue region to the orange region thereby, conferring their potential application in white light emitting diodes. Additionally, the average PL lifetime ≤ft( ≤ft \\right) values could be varied from 18 ns to as high as 74 ns, which reflect the role of surface states in terms of their density and distribution. Another interesting revelation was the self-assembling of the initially formed QDs into nanorods with high aspect ratios ranging from 7 to 20, in correspondence with the {{W}0} values. Besides, the fundamental roles of the chemical nature of water pool and the interfacial fluidity of AOT MEs in influencing the photophysical properties of QDs were investigated by carrying out a similar study in CTAB (cetyltrimethylammonium bromide; cationic surfactant) based MEs. Surprisingly, very profound and contrasting results were observed wherein ≤ft and η of the QDs in case of CTAB MEs were found to be at least three times lower as compared to that in AOT MEs.

  5. Recombination dynamics of a human Y-chromosomal palindrome: rapid GC-biased gene conversion, multi-kilobase conversion tracts, and rare inversions.

    Directory of Open Access Journals (Sweden)

    Pille Hallast

    Full Text Available The male-specific region of the human Y chromosome (MSY includes eight large inverted repeats (palindromes in which arm-to-arm similarity exceeds 99.9%, due to gene conversion activity. Here, we studied one of these palindromes, P6, in order to illuminate the dynamics of the gene conversion process. We genotyped ten paralogous sequence variants (PSVs within the arms of P6 in 378 Y chromosomes whose evolutionary relationships within the SNP-defined Y phylogeny are known. This allowed the identification of 146 historical gene conversion events involving individual PSVs, occurring at a rate of 2.9-8.4×10(-4 events per generation. A consideration of the nature of nucleotide change and the ancestral state of each PSV showed that the conversion process was significantly biased towards the fixation of G or C nucleotides (GC-biased, and also towards the ancestral state. Determination of haplotypes by long-PCR allowed likely co-conversion of PSVs to be identified, and suggested that conversion tract lengths are large, with a mean of 2068 bp, and a maximum in excess of 9 kb. Despite the frequent formation of recombination intermediates implied by the rapid observed gene conversion activity, resolution via crossover is rare: only three inversions within P6 were detected in the sample. An analysis of chimpanzee and gorilla P6 orthologs showed that the ancestral state bias has existed in all three species, and comparison of human and chimpanzee sequences with the gorilla outgroup confirmed that GC bias of the conversion process has apparently been active in both the human and chimpanzee lineages.

  6. The impact of particle shape on the angle of internal friction and the implications for sediment dynamics at a steep, mixed sand-gravel beach

    Science.gov (United States)

    Stark, N.; Hay, A. E.; Cheel, R.; Lake, C. B.

    2014-08-01

    The impact of particle shape on the angle of internal friction, and the resulting impact on beach sediment dynamics, is still poorly understood. In areas characterized by sediments of specific shape, particularly non-rounded particles, this can lead to large departures from the expected sediment dynamics. The steep slope (1 : 10) of the mixed sand-gravel beach at Advocate Harbour is stable in large-scale morphology over decades, despite a high tidal range of 10 m or more, and intense shore-break action during storms. The Advocate sand (d plate-like shape (Corey Shape Index, CSI ≈ 0.2-0.6). High angles of internal friction of this material were determined using direct shear, ranging from φ ≈ 41 to 49°, while the round to angular gravel was characterized as φ = 33°. The addition of 25% of the elliptic plate-like sand-sized material to the gravel led to an immediate increase in friction angle to φ = 38°. Furthermore, re-organization of the particles occurred during shearing, characterized by a short phase of settling and compaction, followed by a pronounced strong dilatory behavior and an accompanying strong increase of resistance to shear and, thus, shear stress. Long-term shearing (24 h) using a ring shear apparatus led to destruction of the particles without re-compaction. Finally, submerged particle mobilization was simulated using a tilted tray submerged in a water-filled tank. Despite a smooth tray surface, particle motion was not initiated until reaching tray tilt angles of 31° and more, being ≥7° steeper than for motion initiation of the gravel mixtures. In conclusion, geotechnical laboratory experiments quantified the important impact of the elliptic, plate-like shape of Advocate Beach sand on the angles of internal friction of both pure sand and sand-gravel mixtures. The resulting effect on initiation of particle motion was confirmed in tilting tray experiments. This makes it a vivid example of how particle shape can contribute to the

  7. Antagonistic bacterial interactions help shape host-symbiont dynamics within the fungus-growing ant-microbe mutualism

    DEFF Research Database (Denmark)

    Poulsen, Michael; Erhardt, Daniel P; Molinaro, Daniel J;

    2007-01-01

    Conflict within mutually beneficial associations is predicted to destabilize relationships, and theoretical and empirical work exploring this has provided significant insight into the dynamics of cooperative interactions. Within mutualistic associations, the expression and regulation of conflict...

  8. How Dynamic Consumer Response, Competitor Response, Company Support, and Company Inertia Shape Long-Term Marketing Effectiveness

    OpenAIRE

    Koen Pauwels

    2004-01-01

    Long-term marketing effectiveness is a high-priority research topic for managers, and emerges from the complex interplay among dynamic reactions of several market players. This paper introduces restricted policy simulations to distinguish four dynamic forces: consumer response, competitor response, company inertia, and company support. A rich marketing dataset allows the analysis of price, display, feature, advertising, and product-line extensions. The first finding is that consumer response ...

  9. How Anatomy Shapes Dynamics: A Semi-Analytical Study of the Brain at Rest by a Simple Spin Model

    Directory of Open Access Journals (Sweden)

    Gustavo eDeco

    2012-09-01

    Full Text Available Resting state networks show a surprisingly coherent and robust spatiotemporal organization. Previous theoretical studies demonstrated that these patterns can be understood as emergent on the basis of the underlying neuroanatomical connectivity skeleton. Integrating the biologically realistic DTI/DSI based neuroanatomical connectivity into a brain model of Ising spin dynamics, we found the presence of latent ghost multi-stable attractors, which can be studied analytically. The multistable attractor landscape defines a functionally meaningful dynamic repertoire of the brain network that is inherently present in the neuroanatomical connectivity. We demonstrate that the more entropy of attractors exists, the richer is the dynamical repertoire and consequently the brain network displays more capabilities of computation. We hypothesize therefore that human brain connectivity developed a scale free type of architecture in order to be able to store a large number of different and flexibly accessible brain functions

  10. The shapes of nuclei

    CERN Document Server

    Bertsch, G F

    2016-01-01

    Gerry Brown initiated some early studies on the coexistence of different nuclear shapes. The subject has continued to be of interest and is crucial for understanding nuclear fission. We now have a very good picture of the potential energy surface with respect to shape degrees of freedom in heavy nuclei, but the dynamics remain problematic. In contrast, the early studies on light nuclei were quite successful in describing the mixing between shapes. Perhaps a new approach in the spirit of the old calculations could better elucidate the character of the fission dynamics and explain phenomena that current theory does not model well.

  11. Effect of Aspect Ratio and Boundary Conditions in Modeling Shape Memory Alloy Nanostructures with 3D Coupled Dynamic Phase-Field Theories

    Directory of Open Access Journals (Sweden)

    R. Dhote

    2016-01-01

    Full Text Available The behavior of shape memory alloy (SMA nanostructures is influenced by strain rate and temperature evolution during dynamic loading. The coupling between temperature, strain, and strain rate is essential to capture inherent thermomechanical behavior in SMAs. In this paper, we propose a new 3D phase-field model that accounts for two-way coupling between mechanical and thermal physics. We use the strain-based Ginzburg-Landau potential for cubic-to-tetragonal phase transformations. The variational formulation of the developed model is implemented in the isogeometric analysis framework to overcome numerical challenges. We have observed a complete disappearance of the out-of-plane martensitic variant in a very high aspect ratio SMA domain as well as the presence of three variants in equal portions in a low aspect ratio SMA domain. The dependence of different boundary conditions on the microstructure morphology has been examined energetically. The tensile tests on rectangular prism nanowires, using the displacement based loading, demonstrate the shape memory effect and pseudoelastic behavior. We have also observed that higher strain rates, as well as the lower aspect ratio domains, resulting in high yield stress and phase transformations occur at higher stress during dynamic axial loading.

  12. [Enzymatic regulatory processes in gene recombination].

    Science.gov (United States)

    Kovarskiĭ, V A; Profir, A V

    1988-01-01

    Recombination bistability in the system of genetic regulation in pro- and eucaryots is analysed on the basis of sigmoid kinetics of regulatory enzymes. It is shown that under an increase of either exogenic factors (temperature) or endogenic factors (concentration of molecules, which activate the enzymes) of crucial values, bistability solutions for recombination frequencies are possible. Histeresic character of the dependence of this value on the external parameters is pointed out. The role of fluctuation processes in distortion of the memory effects is discussed. On the basis of monostable solutions molecular account for the empiric Plau law is given for U-shaped dependence of recombination frequency on temperature.

  13. Antagonistic bacterial interactions help shape host-symbiont dynamics within the fungus-growing ant-microbe mutualism

    OpenAIRE

    Michael Poulsen; Erhardt, Daniel P.; Daniel J Molinaro; Ting-Li Lin; Currie, Cameron R

    2007-01-01

    Conflict within mutually beneficial associations is predicted to destabilize relationships, and theoretical and empirical work exploring this has provided significant insight into the dynamics of cooperative interactions. Within mutualistic associations, the expression and regulation of conflict is likely more complex than in intraspecific cooperative relationship, because of the potential presence of: i) multiple genotypes of microbial species associated with individual hosts, ii) multiple s...

  14. Recombinant Technology and Probiotics

    Directory of Open Access Journals (Sweden)

    Icy D’Silva

    2011-09-01

    Full Text Available Recombinant technology has led the way to monumental advances in the development of useful molecules, including the development of safe probiotics. The development of novel approaches using recombinant technology and probiotics that allow accurate targeting of therapeutics to the mucosa is an interesting area of research. The creation and use of recombinant probiotics expressing recombinantovalbumin, recombinant ovalbumin mutants and yet-to-be-designed recombinant hypo/non-allergenic molecules offer the opportunity to further investigate their effects for food, nutrition, environment andhealth. This review highlights advances in native probiotics and recombinant probiotics expressing native and recombinant molecules for food, nutrition, environment and health.

  15. Line shapes and time dynamics of the Förster resonances between two Rydberg atoms in a time-varying electric field

    KAUST Repository

    Yakshina, E. A.

    2016-10-21

    The observation of the Stark-tuned Förster resonances between Rydberg atoms excited by narrowband cw laser radiation requires usage of a Stark-switching technique in order to excite the atoms first in a fixed electric field and then to induce the interactions in a varied electric field, which is scanned across the Förster resonance. In our experiments with a few cold Rb Rydberg atoms, we have found that the transients at the edges of the electric pulses strongly affect the line shapes of the Förster resonances, since the population transfer at the resonances occurs on a time scale of ∼100 ns, which is comparable with the duration of the transients. For example, a short-term ringing at a certain frequency causes additional radio-frequency-assisted Förster resonances, while nonsharp edges lead to asymmetry. The intentional application of the radio-frequency field induces transitions between collective states, whose line shape depends on the interaction strengths and time. Spatial averaging over the atom positions in a single interaction volume yields a cusped line shape of the Förster resonance. We present a detailed experimental and theoretical analysis of the line shape and time dynamics of the Stark-tuned Förster resonances Rb(nP3/2)+Rb(nP3/2)→Rb(nS1/2)+Rb([n+1]S1/2) for two Rb Rydberg atoms interacting in a time-varying electric field.

  16. [Homologous recombination among bacterial genomes: the measurement and identification].

    Science.gov (United States)

    Xianwei, Yang; Ruifu, Yang; Yujun, Cui

    2016-02-01

    Homologous recombination is one of important sources in shaping the bacterial population diversity, which disrupts the clonal relationship among different lineages through horizontal transferring of DNA-segments. As consequence of blurring the vertical inheritance signals, the homologous recombination raises difficulties in phylogenetic analysis and reconstruction of population structure. Here we discuss the impacts of homologous recombination in inferring phylogenetic relationship among bacterial isolates, and summarize the tools and models separately used in recombination measurement and identification. We also highlight the merits and drawbacks of various approaches, aiming to assist in the practical application for the analysis of homologous recombination in bacterial evolution research.

  17. Recombinant Technology and Probiotics

    OpenAIRE

    Icy D’Silva

    2011-01-01

    Recombinant technology has led the way to monumental advances in the development of useful molecules, including the development of safe probiotics. The development of novel approaches using recombinant technology and probiotics that allow accurate targeting of therapeutics to the mucosa is an interesting area of research. The creation and use of recombinant probiotics expressing recombinantovalbumin, recombinant ovalbumin mutants and yet-to-be-designed recombinant hypo/non-allergenic molecule...

  18. Dynamic observation of splenocyte apoptosis in mice immunized with recombinant vaccine Bifidobacterium bifidum pGEX-Sj14-3-3 of Schistosoma japonicum

    Institute of Scientific and Technical Information of China (English)

    张宁

    2013-01-01

    Objective To investigate the effects of recombinant vaccine Bifidobacterium bifidum(Bb) pGEX-Sj14-3-3 on splenocyte apoptosis in BALB/c mice. Methods Ninety-six BALB/c mice were randomly divided into two groups according to their body mass: per os group(PO) and

  19. How does shape affect predator- prey interactions in fish? Implications for marine food web structure and dynamics

    OpenAIRE

    Cachera, Marie; Villanueva, Ching-maria; Ernande, Bruno; Baheux, Mickael; Rouquette, Manuel; Chambord, Sophie; Lefebvre, Sebastien

    2011-01-01

    Each species pertains to a given functional niche, depending on its relationships with others species and its interactions with the abiotic environment. Understanding inter-specific interactions is critical to know and predict ecosystems' structure, functioning and dynamics, but also their response to anthropogenic impacts. Predator-prey relationship is one of the main biotic interactions as it both determines the survival of the prey and the predator and is the keystone of food webs. Unra...

  20. Dynamical scaling, domain-growth kinetics, and domain-wall shapes of quenched two-dimensional anisotropic XY models

    DEFF Research Database (Denmark)

    Mouritsen, Ole G.; Praestgaard, Eigil

    1988-01-01

    temperature, the domain-growth kinetics is found to be independent of the value of this parameter over several decades of its range. This suggests that a universal principle is operative. The domain-wall shape is analyzed and shown to be well represented by a hyperbolic tangent function. The growth process......The domain-growth kinetics in two different anisotropic two-dimensional XY-spin models is studied by computer simulation. The models have uniaxial and cubic anisotropy which leads to ground-state orderings which are twofold and fourfold degenerate, respectively. The models are quenched from...... infinite to zero temperature as well as to nonzero temperatures below the ordering transition. The continuous nature of the spin variables causes the domain walls to be ‘‘soft’’ and characterized by a finite thickness. The steady-state thickness of the walls can be varied by a model parameter, P. At zero...

  1. Dynamic cortical activity during the perception of three-dimensional object shape from two-dimensional random-dot motion.

    Science.gov (United States)

    Iwaki, Sunao; Bonmassar, Giorgio; Belliveau, John W

    2013-09-01

    Recent neuroimaging studies implicate that both the dorsal and ventral visual pathways, as well as the middle temporal (MT) areas which are critical for the perception of visual motion, are involved in the perception of three-dimensional (3D) structure from two-dimensional (2D) motion (3D-SFM). However, the neural dynamics underlying the reconstruction of a 3D object from 2D optic flow is not known. Here we combined magnetoencephalography (MEG) and functional MRI (fMRI) measurements to investigate the spatiotemporal brain dynamics during 3D-SFM. We manipulated parametrically the coherence of randomly moving groups of dots to create different levels of 3D perception and to study the associated changes in brain activity. At different latencies, the posterior infero-temporal (pIT), the parieto-occipital (PO), and the intraparietal (IP) regions showed increased neural activity during highly coherent motion conditions in which subjects perceived a robust 3D object. Causality analysis between these regions indicated significant causal influence from IP to pIT and from pIT to PO only in conditions where subjects perceived a robust 3D object. Current results suggest that the perception of a 3D object from 2D motion includes integration of global motion and 3D mental image processing, as well as object recognition that are accomplished by interactions between the dorsal and ventral visual pathways.

  2. Dynamic feedback circuits function as a switch for shaping a maturation-inducing steroid pulse in Drosophila

    Science.gov (United States)

    Moeller, Morten E.; Danielsen, E. Thomas; Herder, Rachel; O’Connor, Michael B.; Rewitz, Kim F.

    2013-01-01

    Steroid hormones trigger the onset of sexual maturation in animals by initiating genetic response programs that are determined by steroid pulse frequency, amplitude and duration. Although steroid pulses coordinate growth and timing of maturation during development, the mechanisms generating these pulses are not known. Here we show that the ecdysone steroid pulse that drives the juvenile-adult transition in Drosophila is determined by feedback circuits in the prothoracic gland (PG), the major steroid-producing tissue of insect larvae. These circuits coordinate the activation and repression of hormone synthesis, the two key parameters determining pulse shape (amplitude and duration). We show that ecdysone has a positive-feedback effect on the PG, rapidly amplifying its own synthesis to trigger pupariation as the onset of maturation. During the prepupal stage, a negative-feedback signal ensures the decline in ecdysone levels required to produce a temporal steroid pulse that drives developmental progression to adulthood. The feedback circuits rely on a developmental switch in the expression of Broad isoforms that transcriptionally activate or silence components in the ecdysone biosynthetic pathway. Remarkably, our study shows that the same well-defined genetic program that stimulates a systemic downstream response to ecdysone is also utilized upstream to set the duration and amplitude of the ecdysone pulse. Activation of this switch-like mechanism ensures a rapid, self-limiting PG response that functions in producing steroid oscillations that can guide the decision to terminate growth and promote maturation. PMID:24173800

  3. Investigating correlated few-electron dynamics and QED contributions by means of dielectronic recombination into highly-charged Fe, Kr, Xe, Ba, W, and Hg ions

    Energy Technology Data Exchange (ETDEWEB)

    Harman, Z.; Maeckel, V.; Martinez Gonzalez, A.J.; Crespo Lopez-Urrutia, J.R.; Jentschura, U.D.; Keitel, C.H.; Postavaru, O.; Tawara, H.; Ullrich, J. [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, 69117 Heidelberg (Germany); Artemyev, A.N.; Tupitsyn, I.I. [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, 69117 Heidelberg (Germany); St. Petersburg State University, Oulianovskaya 1, 198504 St. Petersburg (Russian Federation)

    2007-07-01

    The photorecombination of highly charged He- to B-like ions has been explored in the atomic number range Z=26 to 80 with the Heidelberg electron beam ion trap. The energies of state-selected dielectronic recombination (DR) resonances were determined over the KLL region. At the present level of experimental accuracy, it becomes possible to make a detailed comparison to vario us theoretical approaches and methods, all of which include relativistic and quantum electrodynamic (QED) effects. Theoretical resonance energies for KLL DR are calculated by various means. The comparison of theoretical values with the experimental energies shows a good overall agreement. Few discrepancies are found in specific recombination resonances for initially Li- and Be-like heavy ions.

  4. The tooth, the whole tooth and nothing but the tooth: tooth shape and ontogenetic shift dynamics in the white shark Carcharodon carcharias.

    Science.gov (United States)

    French, G C A; Stürup, M; Rizzuto, S; van Wyk, J H; Edwards, D; Dolan, R W; Wintner, S P; Towner, A V; Hughes, W O H

    2017-10-01

    Results from this study of the white shark Carcharodon carcharias include measurements obtained using a novel photographic method that reveal significant differences between the sexes in the relationship between tooth cuspidity and shark total length, and a novel ontogenetic change in male tooth shape. Males exhibit broader upper first teeth and increased distal inclination of upper third teeth with increasing length, while females do not present a consistent morphological change. Substantial individual variation, with implications for pace of life syndrome, was present in males and tooth polymorphism was suggested in females. Sexual differences and individual variation may play major roles in ontogenetic changes in tooth morphology in C. carcharias, with potential implications for their foraging biology. Such individual and sexual differences should be included in studies of ontogenetic shift dynamics in other species and systems. © 2017 The Fisheries Society of the British Isles.

  5. Fusion: a tale of recombination in an asexual fungus: The role of nuclear dynamics and hyphal fusion in horizontal chromosome transfer in Fusarium oxysporum

    OpenAIRE

    Shahi, S.

    2016-01-01

    Recent studies have shown that not only meiotic recombination is responsible for the fast evolution of fungal pathogens. In the asexual fungus F. oxysporum (Fo) the "fast" evolving part of the genome is organized into small chromosomes and one such chromosome houses all effector genes and is referred to as the "pathogenicity" chromosome. This pathogenicity chromosome can be horizontally transferred to a non-pathogenic strain, conferring pathogenicity. Here we use Fo as a model organism to add...

  6. Collision Induced Velocity Changes from Molecular Dynamic Simulations. Application to the Spectral Shape of the Q(1) Raman Lines of H{_2}/H{_2}

    Science.gov (United States)

    Tran, H.; Hartmann, J. M.

    2011-06-01

    Collision induced velocity changes for pure H{_2} have been computed from classical dynamic simulations. The results have been compared with the Keilson-Storer model from four different points of view. The first involves various autocorrelation functions associated with the velocity. The second and third give more detailed information, and are time evolutions of some conditional probabilities for changes of the velocity modulus and orientation and the collision kernels themselves. The fourth considers the evolutions, with density, of the half widths of the Q(1) lines of the isotropic Raman (1-0) fundamental band and of the (2-0) overtone quadrupole band. These spectroscopic data enable an indirect test of the models since velocity changes translate into line-shape modifications through the speed dependence of collisional parameters and the Dicke narrowing of the Doppler contribution to the profile. The results indicate that, while the KS approach gives a poor description of detailed velocity-to-velocty changes, it leads to accurate results for the correlation functions and spectral shapes, quantities related to large averages over the velocity. It is also shown that the use of collision kernels directly derived from MDS lead to an almost perfect prediction of all considered quantities (correlation functions, conditional probabilities, and spectral shapes). Finally, the results stress the need for very accurate calculations of line-broadening and -shifting coefficients from the intermolecular potential to obviate the need for experimental data and permit fully meaningful tests of the models. H. Tran, J.M. Hartmann J. Chem. Phys. 130, 094301, 2009.

  7. Research on the Dynamic Recombining Algorithm About the Multiple Missiles Cooperative Attacking Net Combat System%多弹协同攻击网络化作战系统动态重组算法研究

    Institute of Scientific and Technical Information of China (English)

    王君; 朱永文; 崔颢; 梁文波

    2011-01-01

    The combat thinking is put forward,which is to set up multiple missiles cooperative attacking net combat system based on the dynamic founded net with many remote range air-to-air missiles.And the dynamic founding net system's topology relation finding algorithm is realized by using the searching method in chart theory and defining the application layer data message,which is also used to study the dynamic founding net system's recombining algorithm and to convert the topology relation to the nothing orientation chart Abstractively.By research on dynamic recombining problem with chart theory tools,some reference is provided for new type of air-to-air missiles' cooperative attacking net combat system when the system member node is destroyed in battle field or something wrong is with the communication system.%提出了利用多枚远程空空导弹在空中动态组网,构建多弹协同攻击的网络化作战系统的作战思想.利用图论中的搜索方法、定义应用层数据报文实现动态组网系统的拓扑关系发现算法,并利用拓扑关系发现算法研究了动态组网系统的动态重组算法,将动态组网系统拓扑关系抽象成图论中的无向图,利用图论工具来研究系统成员节点战损与通信故障情况下动态重组问题,为新一代空空导弹协同攻击网络化作战系统的研究提供一定的参考.

  8. Cascading electron and hole transfer dynamics in a CdS/CdTe core-shell sensitized with bromo-pyrogallol red (Br-PGR): slow charge recombination in type II regime.

    Science.gov (United States)

    Maity, Partha; Debnath, Tushar; Chopra, Uday; Ghosh, Hirendra Nath

    2015-02-14

    Ultrafast cascading hole and electron transfer dynamics have been demonstrated in a CdS/CdTe type II core-shell sensitized with Br-PGR using transient absorption spectroscopy and the charge recombination dynamics have been compared with those of CdS/Br-PGR composite materials. Steady state optical absorption studies suggest that Br-PGR forms strong charge transfer (CT) complexes with both the CdS QD and CdS/CdTe core-shell. Hole transfer from the photo-excited QD and QD core-shell to Br-PGR was confirmed by both steady state and time-resolved emission spectroscopy. Charge separation was also confirmed by detecting electrons in the conduction band of the QD and the cation radical of Br-PGR as measured from femtosecond transient absorption spectroscopy. Charge separation in the CdS/Br-PGR composite materials was found to take place in three different pathways, by transferring the photo-excited hole of CdS to Br-PGR, electron injection from the photo-excited Br-PGR to the CdS QD, and direct electron transfer from the HOMO of Br-PGR to the conduction band of the CdS QD. However, in the CdS/CdTe/Br-PGR system hole transfer from the photo-excited CdS to Br-PGR and electron injection from the photo-excited Br-PGR to CdS take place after cascading through the CdTe shell QD. Charge separation also takes place via direct electron transfer from the Br-PGR HOMO to the conduction band of CdS/CdTe. Charge recombination (CR) dynamics between the electron in the conduction band of the CdS QD and the Br-PGR cation radical were determined by monitoring the bleach recovery kinetics. The CR dynamics were found to be much slower in the CdS/CdTe/Br-PGR system than in the CdS/Br-PGR system. The formation of the strong CT complex and the separation of charges cascading through the CdTe shell help to slow down charge recombination in the type II regime.

  9. Landscape of atomic nuclear shapes

    CERN Document Server

    Moon, Chang-Bum

    2016-01-01

    We exhibit a wide variety of the nuclear shape phases over the nuclear chart along with a shell model scheme. Various nuclear shapes are demonstrated within the framework of proton-neutron spin-orbital interactions; ferro-deformed, sub-ferro-deformed, and spherical shapes. The spherical shape is classified into the three magic-number categories in view of a large shell gap mechanism; double-magic nuclei I, double magic nuclei II, and double magic nuclei III. We discuss nuclear shape coexistence in the space Z = 76 to 84 as providing a new way to understanding the dynamical shape phases.

  10. Therapeutic Recombinant Monoclonal Antibodies

    Science.gov (United States)

    Bakhtiar, Ray

    2012-01-01

    During the last two decades, the rapid growth of biotechnology-derived techniques has led to a myriad of therapeutic recombinant monoclonal antibodies with significant clinical benefits. Recombinant monoclonal antibodies can be obtained from a number of natural sources such as animal cell cultures using recombinant DNA engineering. In contrast to…

  11. Therapeutic Recombinant Monoclonal Antibodies

    Science.gov (United States)

    Bakhtiar, Ray

    2012-01-01

    During the last two decades, the rapid growth of biotechnology-derived techniques has led to a myriad of therapeutic recombinant monoclonal antibodies with significant clinical benefits. Recombinant monoclonal antibodies can be obtained from a number of natural sources such as animal cell cultures using recombinant DNA engineering. In contrast to…

  12. The structural dynamics of α-tropomyosin on F-actin shape the overlap complex between adjacent tropomyosin molecules

    Science.gov (United States)

    Lehman, William; Li, Xiaochuan (Edward); Orzechowski, Marek; Fischer, Stefan

    2013-01-01

    Coiled-coil tropomyosin, localized on actin filaments in virtually all eukaryotic cells, serves as a gatekeeper regulating access of the motor protein myosin and other actin-binding proteins onto the thin filament surface. Tropomyosin's modular pseudo-repeating pattern of approximately 39 amino acid residues is designed to allow binding of the coiled-coil to successive actin subunits along thin filaments. Even though different tropomyosin isoforms contain varying numbers of repeat modules, the pseudo-repeat length, in all cases, matches that of a single actin subunit. Thus, the seven pseudo-repeats of 42 nm long muscle tropomyosin bind to seven successive actin subunits along thin filaments, while simultaneously bending into a super-helical conformation that is preshaped to the actin filament helix. In order to form a continuous cable on thin filaments that is free of gaps, adjacent tropomyosin molecules polymerize head-to-tail by means of a short (∼9 residue) overlap. Several laboratories have engineered peptides to mimic the N- and C-terminal tropomyosin association and to characterize the overlap structure. All overlapping domains examined show a compact N-terminal coiled-coil inserting into a partially opened C-terminal partner, where the opposing coiled-coils at the overlap junction face each other at up to ∼90° twist angles. Here, Molecular Dynamics (MD) simulations were carried out to determine constraints on the formation of the tropomyosin overlap complex and to assess the amount of twisting exhibited by full-length tropomyosin when bound to actin. With the exception of the last 20 to 40 C- and N-terminal residues, we find that the average tropomyosin structure closely resembles a “canonical” model proposed in the classic work of McLachlan and Stewart, displaying perfectly symmetrical supercoil geometry matching the F-actin helix with an integral number of coiled-coil turns, a coiled-coil helical pitch of 137 Å, a superhelical pitch of 770

  13. Single-crossover recombination and ancestral recombination trees.

    Science.gov (United States)

    Baake, Ellen; von Wangenheim, Ute

    2014-05-01

    We consider the Wright-Fisher model for a population of [Formula: see text] individuals, each identified with a sequence of a finite number of sites, and single-crossover recombination between them. We trace back the ancestry of single individuals from the present population. In the [Formula: see text] limit without rescaling of parameters or time, this ancestral process is described by a random tree, whose branching events correspond to the splitting of the sequence due to recombination. With the help of a decomposition of the trees into subtrees, we calculate the probabilities of the topologies of the ancestral trees. At the same time, these probabilities lead to a semi-explicit solution of the deterministic single-crossover equation. The latter is a discrete-time dynamical system that emerges from the Wright-Fisher model via a law of large numbers and has been waiting for a solution for many decades.

  14. Influence of velocity effects on the shape of N2 (and air) broadened H2O lines revisited with classical molecular dynamics simulations

    Science.gov (United States)

    Ngo, N. H.; Tran, H.; Gamache, R. R.; Bermejo, D.; Domenech, J.-L.

    2012-08-01

    The modeling of the shape of H2O lines perturbed by N2 (and air) using the Keilson-Storer (KS) kernel for collision-induced velocity changes is revisited with classical molecular dynamics simulations (CMDS). The latter have been performed for a large number of molecules starting from intermolecular-potential surfaces. Contrary to the assumption made in a previous study [H. Tran, D. Bermejo, J.-L. Domenech, P. Joubert, R. R. Gamache, and J.-M. Hartmann, J. Quant. Spectrosc. Radiat. Transf. 108, 126 (2007)], 10.1016/j.jqsrt.2007.03.009, the results of these CMDS show that the velocity-orientation and -modulus changes statistically occur at the same time scale. This validates the use of a single memory parameter in the Keilson-Storer kernel to describe both the velocity-orientation and -modulus changes. The CMDS results also show that velocity- and rotational state-changing collisions are statistically partially correlated. A partially correlated speed-dependent Keilson-Storer model has thus been used to describe the line-shape. For this, the velocity changes KS kernel parameters have been directly determined from CMDS, while the speed-dependent broadening and shifting coefficients have been calculated with a semi-classical approach. Comparisons between calculated spectra and measurements of several lines of H2O broadened by N2 (and air) in the ν3 and 2ν1 + ν2 + ν3 bands for a wide range of pressure show very satisfactory agreement. The evolution of non-Voigt effects from Doppler to collisional regimes is also presented and discussed.

  15. Shaped Crystal Growth

    Science.gov (United States)

    Tatartchenko, Vitali A.

    Crystals of specified shape and size (shaped crystals) with controlled crystal growth (SCG) defect and impurity structure have to be grown for the successful development of modern engineering. Since the 1950s many hundreds of papers and patents concerned with shaped growth have been published. In this chapter, we do not try to enumerate the successful applications of shaped growth to different materials but rather to carry out a fundamental physical and mathematical analysis of shaping as well as the peculiarities of shaped crystal structures. Four main techniques, based on which the lateral surface can be shaped without contact with the container walls, are analyzed: the Czochralski technique (CZT), the Verneuil technique (VT), the floating zone technique (FZT), and technique of pulling from shaper (TPS). Modifications of these techniques are analyzed as well. In all these techniques the shape of the melt meniscus is controlled by surface tension forces, i.e., capillary forces, and here they are classified as capillary shaping techniques (CST). We look for conditions under which the crystal growth process in each CST is dynamically stable. Only in this case are all perturbations attenuated and a crystal of constant cross section shaping technique (CST) grown without any special regulation. The dynamic stability theory of the crystal growth process for all CST is developed on the basis of Lyapunov's dynamic stability theory. Lyapunov's equations for the crystal growth processes follow from fundamental laws. The results of the theory allow the choice of stable regimes for crystal growth by all CST as well as special designs of shapers in TPS. SCG experiments by CZT, VT, and FZT are discussed but the main consideration is given to TPS. Shapers not only allow crystal of very complicated cross section to be grown but provide a special distribution of impurities. A history of TPS is provided later in the chapter, because it can only be described after explanation of the

  16. Antagonistic experimental coevolution with a parasite increases host recombination frequency

    Directory of Open Access Journals (Sweden)

    Kerstes Niels AG

    2012-02-01

    Full Text Available Abstract Background One of the big remaining challenges in evolutionary biology is to understand the evolution and maintenance of meiotic recombination. As recombination breaks down successful genotypes, it should be selected for only under very limited conditions. Yet, recombination is very common and phylogenetically widespread. The Red Queen Hypothesis is one of the most prominent hypotheses for the adaptive value of recombination and sexual reproduction. The Red Queen Hypothesis predicts an advantage of recombination for hosts that are coevolving with their parasites. We tested predictions of the hypothesis with experimental coevolution using the red flour beetle, Tribolium castaneum, and its microsporidian parasite, Nosema whitei. Results By measuring recombination directly in the individuals under selection, we found that recombination in the host population was increased after 11 generations of coevolution. Detailed insights into genotypic and phenotypic changes occurring during the coevolution experiment furthermore helped us to reconstruct the coevolutionary dynamics that were associated with this increase in recombination frequency. As coevolved lines maintained higher genetic diversity than control lines, and because there was no evidence for heterozygote advantage or for a plastic response of recombination to infection, the observed increase in recombination most likely represented an adaptive host response under Red Queen dynamics. Conclusions This study provides direct, experimental evidence for an increase in recombination frequency under host-parasite coevolution in an obligatory outcrossing species. Combined with earlier results, the Red Queen process is the most likely explanation for this observation.

  17. Schapiro Shapes

    Science.gov (United States)

    O'Connell, Emily

    2009-01-01

    This article describes a lesson on Schapiro Shapes. Schapiro Shapes is based on the art of Miriam Schapiro, who created a number of works of figures in action. Using the basic concepts of this project, students learn to create their own figures and styles. (Contains 1 online resource.)

  18. The recombinational anatomy of a mouse chromosome.

    Directory of Open Access Journals (Sweden)

    Kenneth Paigen

    2008-07-01

    Full Text Available Among mammals, genetic recombination occurs at highly delimited sites known as recombination hotspots. They are typically 1-2 kb long and vary as much as a 1,000-fold or more in recombination activity. Although much is known about the molecular details of the recombination process itself, the factors determining the location and relative activity of hotspots are poorly understood. To further our understanding, we have collected and mapped the locations of 5,472 crossover events along mouse Chromosome 1 arising in 6,028 meioses of male and female reciprocal F1 hybrids of C57BL/6J and CAST/EiJ mice. Crossovers were mapped to a minimum resolution of 225 kb, and those in the telomere-proximal 24.7 Mb were further mapped to resolve individual hotspots. Recombination rates were evolutionarily conserved on a regional scale, but not at the local level. There was a clear negative-exponential relationship between the relative activity and abundance of hotspot activity classes, such that a small number of the most active hotspots account for the majority of recombination. Females had 1.2x higher overall recombination than males did, although the sex ratio showed considerable regional variation. Locally, entirely sex-specific hotspots were rare. The initiation of recombination at the most active hotspot was regulated independently on the two parental chromatids, and analysis of reciprocal crosses indicated that parental imprinting has subtle effects on recombination rates. It appears that the regulation of mammalian recombination is a complex, dynamic process involving multiple factors reflecting species, sex, individual variation within species, and the properties of individual hotspots.

  19. Molecular dynamics simulations of the effect of shape and size of SiO2 nanoparticle dopants on insulation paper cellulose

    Science.gov (United States)

    Tang, Chao; Zhang, Song; Li, Xu; Zhou, Qu

    2016-12-01

    The effect of silica nanoparticle (Nano-SiO2) dopants on insulation paper cellulose, and the interaction between them, was investigated using molecular dynamics simulations. The mechanical properties, interactions, and cellulose-Nano-SiO2 compatibility of composite models of cellulose doped with Nano-SiO2 were studied. An increase in Nano-SiO2 size leads to a decrease in the mechanical properties, and a decrease in the anti-deformation ability of the composite model. The binding energies and bond energies per surface area of the composite models indicate that the bonding interaction between spherical Nano-SiO2 and cellulose is the strongest among the four different Nano-SiO2 shapes that are investigated. The solubilities of the four composite models decrease with increasing Nano-SiO2 size, and the difference between the solubility of pure cellulose and those of the composite models increases with increasing Nano-SiO2 size. Good doping effects with the highest cellulose-Nano-SiO2 compatibility are achieved for the cellulose model doped with spherical Nano-SiO2 of 10 Å in diameter. These findings provide a method for modifying the mechanical properties of cellulose by doping, perhaps for improving insulation dielectrics.

  20. Molecular dynamics simulations of the effect of shape and size of SiO2 nanoparticle dopants on insulation paper cellulose

    Directory of Open Access Journals (Sweden)

    Chao Tang

    2016-12-01

    Full Text Available The effect of silica nanoparticle (Nano-SiO2 dopants on insulation paper cellulose, and the interaction between them, was investigated using molecular dynamics simulations. The mechanical properties, interactions, and cellulose-Nano-SiO2 compatibility of composite models of cellulose doped with Nano-SiO2 were studied. An increase in Nano-SiO2 size leads to a decrease in the mechanical properties, and a decrease in the anti-deformation ability of the composite model. The binding energies and bond energies per surface area of the composite models indicate that the bonding interaction between spherical Nano-SiO2 and cellulose is the strongest among the four different Nano-SiO2 shapes that are investigated. The solubilities of the four composite models decrease with increasing Nano-SiO2 size, and the difference between the solubility of pure cellulose and those of the composite models increases with increasing Nano-SiO2 size. Good doping effects with the highest cellulose-Nano-SiO2 compatibility are achieved for the cellulose model doped with spherical Nano-SiO2 of 10 Å in diameter. These findings provide a method for modifying the mechanical properties of cellulose by doping, perhaps for improving insulation dielectrics.

  1. Sprawl Dynamics in Rural–Urban Territories Highly Suited for Wine Production. Mapping Urban Growth and Changing Territorial Shapes in North-East Italy

    Directory of Open Access Journals (Sweden)

    Luca Simone Rizzo

    2017-01-01

    Full Text Available In Italy, large-scale changes in the structure of land use can be observed. These are caused primarily by socio-economic pressures, generally determining the conversion of agricultural land into artificial surfaces. Our aim was to investigate if and how sprawl dynamics influence viticultural landscapes (that is, if they result in scattered, intermediate, or compact urban developments. We focused on selected territories in North-East Italy, where vine-growing provides almost uninterrupted land cover, as case study areas. Using GIS-based techniques, we documented the processes of land use, analyzing the resulting changes of urban-rural forms and in territorial shapes. Results at the Provincial level showed decreasing dispersed artificial surfaces and increasing clustered urban developments. This trend is also detected in areas under vine, but in general is more modest. Our research indicates that typical agricultural productions can determine resistance to the alienation of land, maintaining a sufficient consistency for areas to develop in a more varied and articulated (for example touristic manner.

  2. A frequency shaping neural recorder with 3 pF input capacitance and 11 plus 4.5 bits dynamic range.

    Science.gov (United States)

    Xu, Jian; Wu, Tong; Liu, Wentai; Yang, Zhi

    2014-08-01

    This paper presents a frequency-shaping (FS) neural recording architecture and its implementation in a 0.13 μ m CMOS process. Compared with its conventional counterpart, the proposed architecture inherently rejects electrode offset, increases input impedance 5-10 fold, compresses neural data dynamic range (DR) by 4.5-bit, simultaneously records local field potentials (LFPs) and extracellular spikes, and is more suitable for long-term recording experiments. Measured at a 40 kHz sampling clock and ± 0.6 V supply, the recorder consumes 50 μW/ch, of which 22 μW per FS amplifier, 24 μ W per buffer, 4 μ W per 11-bit successive approximation register analog-to-digital converter (SAR ADC). The input-referred noise for LFPs and extracellular spikes are 13 μ Vrms and 7 μVrms, respectively, which are sufficient to achieve high-fidelity full-spectrum neural data. In addition, the designed recorder has a 3 pF input capacitance and allows " 11+4.5"-bit neural data DR without system saturation, where the extra 4.5-bit owes to the FS technique. Its figure-of-merit (FOM) based on data DR reaches 36.0 fJ/conversion-step.

  3. Influence of aqueous electrolytes on the wetting behavior of hydrophobic solid polymers-low-rate dynamic liquid/fluid contact angle measurements using axisymmetric drop shape analysis.

    Science.gov (United States)

    Welzel, Petra B; Rauwolf, Cordula; Yudin, Olexandr; Grundke, Karina

    2002-07-01

    The interaction of inorganic ions with low-energy hydrophobic surfaces was examined using model systems of solid polymers without ionizable functional surface groups in aqueous electrolyte solutions. Low-rate dynamic contact angle measurements with captive bubbles in conjunction with axisymmetric drop shape analysis (ADSA) were performed to study the influence of electrolyte ions (in the aqueous test solutions) on the wettability of the polymers. When various types of ions were used, no significant change in advancing and receding contact angles was observed. The contact angle hysteresis was small. The zeta potential of the model polymers in aqueous electrolyte solutions was determined from streaming potential measurements. The variation of the zeta potential at different pH levels indicates preferential adsorption of hydroxyl ions at this interface. However, the presence of electrolytes at the interface between water and the different model polymers did not influence the macroscopic contact angle. The results may suggest the absence of any specific interaction between the ions and the solid polymer, as this should result in changes of hydrophobicity. Similar to the air/water interface, the composition and the potential of the polymer/water interface are obviously determined predominantly by the aqueous phase with only slight influence from the solid phase.

  4. 针对可变形履带机器人的动态变形方法研究%A dynamic shape-shifting method for a transformable tracked robot

    Institute of Scientific and Technical Information of China (English)

    李楠; 马书根; 李斌; 王明辉; 王越超

    2012-01-01

    针对可变形履带机器人在常规变形过程中履带与地面产生的摩擦力会阻碍甚至终止变形过程的问题,提出了一种新颖的动态变形方法.在动态变形过程中,该方法可使运动模块的履带单元辅助运动以配合变形模块的转动,从而将阻碍变形的部分摩擦力转化为推进变形的动力.针对动态变形的动力学仿真分析表明,采用该动态变形方法,可以有效地减小机器人在变形过程中的阻力矩和能量损耗.同时,针对变形过程的能量损耗、阻力矩以及变形空间这些性能指标,采用多目标优化方法使机器人在动态变形过程中得到最佳的综合性能.该方法动态变形的有效性通过可变形履带机器人平台的实验得到了验证.%The problem in a conventional shape-shifting process for a transformable tracked robot that the friction force between the tracks and the ground may embarrass or even stop the process of the shape-shifting, can be avoided by using the novel dynamic shape-shifting method proposed in the paper. When using the method, the tracks rotate during dynamic shape-shifting to assist the motion of the module which is in charge of the transformation, so part of the friction force can be converted into the propulsion force for the transformation by the assisting motion of the tracks. The dynamic analysis of dynamic shape-shifting shows that the dynamic shape-shifting can reduce the resistance torque and the power loss efficiently in the transformation. The multi-objective optimization method can be used to get the optimal comprehensive performance. The experiments of the dynamic shape-shifting on the transformable tracked robot Amoeba-II verified the effectiveness of this method.

  5. Computational fluid dynamics analysis of a twisted airfoil shaped two-bladed H-Darrieus rotor made from fibreglass reinforced plastic (FRP

    Directory of Open Access Journals (Sweden)

    Rajat Gupta, Sukanta Roy, Agnimitra Biswas

    2010-11-01

    Full Text Available H-Darrieus rotor is a lift type device having two to three blades designed as airfoils. The blades are attached vertically to the central shaft through support arms. The support to vertical axis helps the rotor maintain its shape. In this paper, Computational Fluid Dynamics (CFD analysis of an airfoil shaped two-bladed H-Darrieus rotor using Fluent 6.2 software was performed. Based on the CFD results, a comparative study between experimental and computational works was carried out. The H-Darrieus rotor was 20cm in height, 5cm in chord and twisted with an angle of 30° at the trailing end. The blade material of rotor was Fiberglass Reinforced Plastic (FRP. The experiments were earlier conducted in a subsonic wind tunnel for various height-to-diameter (H/D ratios. A two dimensional computational modeling was done with the help of Gambit tool using unstructured grid. Realistic boundary conditions were provided for the model to have synchronization with the experimental conditions. Two dimensional steady-state segregated solver with absolute velocity formulation and cell based grid was considered, and a standard k-epsilon viscous model with standard wall functions was chosen. A first order upwind discretization scheme was adopted for pressure velocity coupling of the flow. The inlet velocities and rotor rotational speeds were taken from the experimental results. From the computational analysis, power coefficient (Cp and torque coefficient (Ct values at ten different H/D ratios namely 0.85, 1.0, 1.10, 1.33, 1.54, 1.72, 1.80, 1.92, 2.10 and 2.20 were calculated in order to predict the performances of the twisted H-rotor. The variations of Cp and Ct with tip speed ratios were analyzed and compared with the experimental results. The standard deviations of computational Cp and Ct from experimental Cp and Ct were obtained. From the computational analysis, the highest values of Cp and Ct were obtained at H/D ratios of 1.0 and 1.54 respectively. The

  6. Microsecond ramp compression of a metallic liner driven by a 5 MA current on the SPHINX machine using a dynamic load current multiplier pulse shaping

    Science.gov (United States)

    d'Almeida, T.; Lassalle, F.; Morell, A.; Grunenwald, J.; Zucchini, F.; Loyen, A.; Maysonnave, T.; Chuvatin, A. S.

    2013-09-01

    SPHINX is a 6 MA, 1-μs Linear Transformer Driver (LTD) operated by the CEA Gramat (France) and primarily used for imploding Z-pinch loads for radiation effects studies. Among the options that are currently being evaluated to improve the generator performances are an upgrade to a 20 MA, 1-μs LTD machine and various power amplification schemes, including a compact Dynamic Load Current Multiplier (DLCM). A method for performing magnetic ramp compression experiments, without modifying the generator operation scheme, was developed using the DLCM to shape the initial current pulse in order to obtain the desired load current profile. In this paper, we discuss the overall configuration that was selected for these experiments, including the choice of a coaxial cylindrical geometry for the load and its return current electrode. We present both 3-D Magneto-hydrodynamic and 1D Lagrangian hydrodynamic simulations which helped guide the design of the experimental configuration. Initial results obtained over a set of experiments on an aluminium cylindrical liner, ramp-compressed to a peak pressure of 23 GPa, are presented and analyzed. Details of the electrical and laser Doppler interferometer setups used to monitor and diagnose the ramp compression experiments are provided. In particular, the configuration used to field both homodyne and heterodyne velocimetry diagnostics in the reduced access available within the liner's interior is described. Current profiles measured at various critical locations across the system, particularly the load current, enabled a comprehensive tracking of the current circulation and demonstrate adequate pulse shaping by the DLCM. The liner inner free surface velocity measurements obtained from the heterodyne velocimeter agree with the hydrocode results obtained using the measured load current as the input. An extensive hydrodynamic analysis is carried out to examine information such as pressure and particle velocity history profiles or magnetic

  7. Three-dimensional experimental investigation of the shape and dynamics of a rising bubble in stagnant water with particle tracking velocimetry

    Science.gov (United States)

    Ortiz-Villafuerte, Javier

    The Particle Tracking Velocimetry technique has been used for a three-dimensional, transient, experimental study of a single bubble dynamics in a restricted medium. The three-dimensional velocity field was reconstructed via stereoscopic matching of two-dimensional images. A hybrid tracking technique has been used to determine the flow around a bubble. The development of the Shadow Particle Image Velocimetry allowed studying the bubble shape and rotation. An accurate estimate of the bubble dimensions, orientation, trajectory, and velocity and acceleration of a bubble rising in water, was obtained. The flow around and within the wake of the bubble was determined from ensemble averaging instantaneous velocity fields. The ensemble average operation was performed by considering a conditional sampling technique. The conditional ensemble averaging was performed for specified bubble trajectories. It was found that bubbles rising close to the wall generate more turbulence, and the disturbances induced in the liquid reach further downstream, when compared to bubbles rising along the pipe core. The bubble Reynolds number was in the range from 350 to 700. Regarding the bubble motion, it was found that the inclusion of the disturbed flow field in the bubble motion equation generates a scattering of the data for the drag and lift coefficients. The wall influence on these coefficients was introduced through the velocities and accelerations of the liquid and the bubble. The results indicate that the presence of the seed particles in the liquid have an influence on the bubble velocity and bubble shape. The instantaneous drag coefficient did not delineate a trend with respect to the rotation parameter; however, it shows a behavior similar to the standard drag curve as function of the Reynolds number. The average drag coefficient values are 0.90 and 0.98 for the bubble trajectories along the pipe core and close to the pipe wall, respectively. No trend for the instantaneous lift

  8. Microsecond ramp compression of a metallic liner driven by a 5 MA current on the SPHINX machine using a dynamic load current multiplier pulse shaping

    Energy Technology Data Exchange (ETDEWEB)

    D' Almeida, T.; Lassalle, F.; Morell, A.; Grunenwald, J.; Zucchini, F.; Loyen, A. [CEA, DAM, GRAMAT, F-46500 Gramat (France); Maysonnave, T. [International Technologies for High Pulsed Power, F-46500 Thégra (France); Chuvatin, A. S. [Laboratoire de Physique des Plasmas, Ecole Polytechnique, F-91128 Palaiseau (France)

    2013-09-15

    SPHINX is a 6 MA, 1-μs Linear Transformer Driver (LTD) operated by the CEA Gramat (France) and primarily used for imploding Z-pinch loads for radiation effects studies. Among the options that are currently being evaluated to improve the generator performances are an upgrade to a 20 MA, 1-μs LTD machine and various power amplification schemes, including a compact Dynamic Load Current Multiplier (DLCM). A method for performing magnetic ramp compression experiments, without modifying the generator operation scheme, was developed using the DLCM to shape the initial current pulse in order to obtain the desired load current profile. In this paper, we discuss the overall configuration that was selected for these experiments, including the choice of a coaxial cylindrical geometry for the load and its return current electrode. We present both 3-D Magneto-hydrodynamic and 1D Lagrangian hydrodynamic simulations which helped guide the design of the experimental configuration. Initial results obtained over a set of experiments on an aluminium cylindrical liner, ramp-compressed to a peak pressure of 23 GPa, are presented and analyzed. Details of the electrical and laser Doppler interferometer setups used to monitor and diagnose the ramp compression experiments are provided. In particular, the configuration used to field both homodyne and heterodyne velocimetry diagnostics in the reduced access available within the liner's interior is described. Current profiles measured at various critical locations across the system, particularly the load current, enabled a comprehensive tracking of the current circulation and demonstrate adequate pulse shaping by the DLCM. The liner inner free surface velocity measurements obtained from the heterodyne velocimeter agree with the hydrocode results obtained using the measured load current as the input. An extensive hydrodynamic analysis is carried out to examine information such as pressure and particle velocity history profiles or

  9. Local carrier recombination and associated dynamics in m-plane InGaN/GaN quantum wells probed by picosecond cathodoluminescence

    Science.gov (United States)

    Zhu, Tongtong; Gachet, David; Tang, Fengzai; Fu, Wai Yuen; Oehler, Fabrice; Kappers, Menno J.; Dawson, Phil; Humphreys, Colin J.; Oliver, Rachel A.

    2016-12-01

    We report on spatially resolved and time-resolved cathodoluminescence (CL) studies of the recombination mechanisms of InGaN/GaN quantum wells (QWs) grown by metal-organic vapour phase epitaxy on bulk m-plane Ammono GaN substrates. As a result of the 2° miscut of the GaN substrate, the sample surface exhibits step bunches, where semi-polar QWs with a higher indium concentration than the planar m-plane QWs form during the QW growth. Spatially resolved time-integrated CL maps under both continuous and pulsed excitation show a broad emission band originating from the m-plane QWs and a distinct low energy emission originating from the semi-polar QWs at the step bunches. High resolution time-resolved CL maps reveal that when the m-QWs are excited well away from the step bunches the emission from the m-plane QWs decays with a time constant of 350 ps, whereas the emission originating semi-polar QWs decays with a longer time constant of 489 ps. The time constant of the decay from the semi-polar QWs is longer due to the separation of the carrier wavefunctions caused by the electric field across the semi-polar QWs.

  10. Temporal shape manipulation of adiabatons

    CERN Document Server

    Arkhipkin, V G

    2005-01-01

    We describe how to control the temporal shape of adiabaton using peculiarities of propagation dynamics under coherent population trapping. Temporal compression is demonstrated as a special case of pulse shaping. The general case of unequal oscillator strengths of two optical transitions in atom is considered.

  11. Novel Recombinant Sapovirus

    Science.gov (United States)

    Katayama, Kazuhiko; Miyoshi, Tatsuya; Uchino, Kiyoko; Oka, Tomoichiro; Tanaka, Tomoyuki; Takeda, Naokazu

    2004-01-01

    We determined the complete genome sequences of two sapovirus strains isolated in Thailand and Japan. One of these strains represented a novel, naturally occurring recombinant sapovirus. Evidence suggested the recombination site was at the polymerase-capsid junction within open reading frame one. PMID:15504283

  12. From Recombination Dynamics to Device Performance: Quantifying the Efficiency of Exciton Dissociation, Charge Separation, and Extraction in Bulk Heterojunction Solar Cells with Fluorine-Substituted Polymer Donors

    KAUST Repository

    Gorenflot, Julien

    2017-09-28

    An original set of experimental and modeling tools is used to quantify the yield of each of the physical processes leading to photocurrent generation in organic bulk heterojunction solar cells, enabling evaluation of materials and processing condition beyond the trivial comparison of device performances. Transient absorption spectroscopy, “the” technique to monitor all intermediate states over the entire relevant timescale, is combined with time-delayed collection field experiments, transfer matrix simulations, spectral deconvolution, and parametrization of the charge carrier recombination by a two-pool model, allowing quantification of densities of excitons and charges and extrapolation of their kinetics to device-relevant conditions. Photon absorption, charge transfer, charge separation, and charge extraction are all quantified for two recently developed wide-bandgap donor polymers: poly(4,8-bis((2-ethylhexyl)oxy)benzo[1,2-b:4,5-b′]dithiophene-3,4-difluorothiophene) (PBDT[2F]T) and its nonfluorinated counterpart poly(4,8-bis((2-ethylhexyl)oxy)benzo[1,2-b:4,5-b′]dithiophene-3,4-thiophene) (PBDT[2H]T) combined with PC71BM in bulk heterojunctions. The product of these yields is shown to agree well with the devices\\' external quantum efficiency. This methodology elucidates in the specific case studied here the origin of improved photocurrents obtained when using PBDT[2F]T instead of PBDT[2H]T as well as upon using solvent additives. Furthermore, a higher charge transfer (CT)-state energy is shown to lead to significantly lower energy losses (resulting in higher VOC) during charge generation compared to P3HT:PCBM.

  13. Dynamics of cervical langerhans cell counts in the course of HPV-positive CIN treatment with the use of human recombinant interferon gamma.

    Science.gov (United States)

    Sikorski, M; Bieda, T; Bobek, M; Zrubek, H

    2005-01-01

    Langerhans cells play a pivotal role as professional antigens presenting cells in cervical epithelium, thus changes in their density or/and function may profoundly influence the proper activation of the afferent arm of immune response in cases of HPV-related intraepithelial lesions. Assessment of intraepithelial Langerhans cell count changes in CIN I/CIN II after human recombinant interferon gamma (IFNgamma) application and correlation with clinical outcome. The present study is a part of prospective trial on IFNgamma application in the treatment of CIN I/CINII associated with high-risk HPV infection. Seventeen subjects underwent uniform IFNgamma treatment (four intracervical injections in a two-day interval for a total dose of 6,000,000 IU). Langerhans cells were stained within cervical punch biopsy specimens with the use of polyclonal anti-S-100 antibody according to the three-step indirect peroxidase protocol, and their mean count calculated for the following groups: before IFNgamma treatment launching, immediately after completion of the treatment, and after two months of follow-up. The analysis revealed a rapid and significant increase in Lagerhans' cell count immediately after treatment completion (21.17/mm2 and 25.94/mm2, respectively, at p = 0.019) which further increased in the group of complete response (in 9 subjects; 32.22/mm2). After transient elevation of the Langerhans' cell count it returned to a level even lower than initially in the non-responder group (4 subjects; 20.25/mm2). Our data strongly support the observation from static studies suggesting that regression of HPV-related cervical lesions is associated with increased density of epithelial Langerhans cells.

  14. DSMC Modeling of Flows with Recombination Reactions

    Science.gov (United States)

    2017-06-23

    rarefied gas dynamics community has seen the development of efficient algorithms for modern computer architectures16–19 which dramatically expand the area of...that participate in recombination. ACKNOWLEDGMENTS The work was supported by the Air Force Office of Sci - entific Research (Program Officer Dr. Ivett...flow,” Prog. Aerosp. Sci . 72, 66–79 (2015). 14R. D. Levine,Molecular Reaction Dynamics (Cambridge University Press, Cambridge, 2005). 15A. Alexeenko and

  15. Recombinant methods and materials

    Energy Technology Data Exchange (ETDEWEB)

    Roizman, B.; Post, L.E.

    1988-09-06

    This patent describes a method for stably effecting the insertion or deletion of a selected DNA sequence at a specific site in a viral genome. The method consists of: (1) isolating from the genome a linear DNA fragment comprising both (a) the specific site determined for insertion or deletion of selected DNA sequence and (b) flanking DNA sequences normally preceding and following the site; (2) preparing first and second altered genome fragments from the fragment isolated in step (1). (a) the first altered fragment comprising the fragment comprising a thymidine kinase gene in a position intermediate the ends of the fragment, and (b) the second altered fragment comprising the fragment having the selected DNA sequence inserted therein or deleted therefrom; (3) contacting the genome with the first altered fragment under conditions permitting recombination at sites of DNA sequence homology, selecting for a recombinant genome comprising the thymidine kinase gene, and isolating the recombinant genome; and (4) contacting the recombinant genome isolated in step (3) with the second altered fragment under conditions permitting recombination at sites of DNA sequence homology, selecting for a recombinant genome lacking the thymidine kinase gene, and isolating the recombinant genome product.

  16. Rheumatoid synovial inflammation: pixel-by-pixel dynamic contrast-enhanced MR imaging time-intensity curve shape analysis--a feasibility study

    NARCIS (Netherlands)

    C. van der Leij; M.G.H. van de Sande; C. Lavini; P.P. Tak; M. Maas

    2009-01-01

    PURPOSE: To analyze the distribution of different shapes of time-intensity curves (TICs) in synovial tissue of patients with rheumatoid arthritis (RA) and to compare relative numbers of TIC shapes between patients with RA and healthy control subjects. MATERIALS AND METHODS: This prospective study wa

  17. Teenagers’ Shape

    Institute of Scientific and Technical Information of China (English)

    亚玲

    2007-01-01

    <正>Teenagers have been of a new shape these days. They are about 20 pounds heavier than teenagers were 60 years ago. They are about four inches taller, too. These facts come from J. M. Tanner, a professor in England.

  18. Dissociative recombination in aeronomy

    Science.gov (United States)

    Fox, J. L.

    1989-01-01

    The importance of dissociative recombination in planetary aeronomy is summarized, and two examples are discussed. The first is the role of dissociative recombination of N2(+) in the escape of nitrogen from Mars. A previous model is updated to reflect new experimental data on the electronic states of N produced in this process. Second, the intensity of the atomic oxygen green line on the nightside of Venus is modeled. Use is made of theoretical rate coefficients for production of O (1S) in dissociative recombination from different vibrational levels of O2(+).

  19. Trends in local newspaper reporting of London cyclist fatalities 1992-2012: the role of the media in shaping the systems dynamics of cycling

    Science.gov (United States)

    Macmillan, Alex; Roberts, Alex; Woodcock, James; Aldred, Rachel; Goodman, Anna

    2016-01-01

    Background Successfully increasing cycling across a broad range of the population would confer important health benefits, but many potential cyclists are deterred by fears about traffic danger. Media coverage of road traffic crashes may reinforce this perception. As part of a wider effort to model the system dynamics of urban cycling, in this paper we examined how media coverage of cyclist fatalities in London changed across a period when the prevalence of cycling doubled. We compared this with changes in the coverage of motorcyclist fatalities as a control group. Methods Police records of traffic crashes (STATS19) were used to identify all cyclist and motorcyclist fatalities in London between 1992 and 2012. We searched electronic archives of London's largest local newspaper to identify relevant articles (January 1992–April 2014), and sought to identify which police-reported fatalities received any media coverage. We repeated this in three smaller English cities. Results Across the period when cycling trips doubled in London, the proportion of fatalities covered in the local media increased from 6% in 1992–1994 to 75% in 2010–2012. By contrast, the coverage of motorcyclist fatalities remained low (4% in 1992–1994 versus 5% in 2010–2012; p = 0.007 for interaction between mode and time period). Comparisons with other English cities suggested that the changes observed in London might not occur in smaller cities with lower absolute numbers of crashes, as in these settings fatalities are almost always covered regardless of mode share (79–100% coverage for both cyclist and motorcyclist fatalities). Conclusion In large cities, an increase in the popularity (and therefore ‘newsworthiness’) of cycling may increase the propensity of the media to cover cyclist fatalities. This has the potential to give the public the impression that cycling has become more dangerous, and thereby initiate a negative feedback loop that dampens down further increases in cycling

  20. Dissociation and recombination of D{sub 2} on Cu(111): Ab initio molecular dynamics calculations and improved analysis of desorption experiments

    Energy Technology Data Exchange (ETDEWEB)

    Nattino, Francesco, E-mail: f.nattino@chem.leidenuniv.nl; Genova, Alessandro; Guijt, Marieke; Kroes, Geert-Jan [Leiden Institute of Chemistry, Leiden University, Gorlaeus Laboratories, P.O. Box 9502, 2300 RA Leiden (Netherlands); Muzas, Alberto S.; Díaz, Cristina [Departamento de Química Módulo 13, Universitad Autónoma de Madrid, 28049 Madrid (Spain); Auerbach, Daniel J. [Leiden Institute of Chemistry, Leiden University, Gorlaeus Laboratories, P.O. Box 9502, 2300 RA Leiden (Netherlands); Max Planck Institute for Biophysical Chemistry, Göttingen (Germany)

    2014-09-28

    Obtaining quantitative agreement between theory and experiment for dissociative adsorption of hydrogen on and associative desorption of hydrogen from Cu(111) remains challenging. Particularly troubling is the fact that theory gives values for the high energy limit to the dissociative adsorption probability that is as much as two times larger than experiment. In the present work we approach this discrepancy in three ways. First, we carry out a new analysis of the raw experimental data for D{sub 2} associatively desorbing from Cu(111). We also perform new ab initio molecular dynamics (AIMD) calculations that include effects of surface atom motion. Finally, we simulate time-of-flight (TOF) spectra from the theoretical reaction probability curves and we directly compare them to the raw experimental data. The results show that the use of more flexible functional forms for fitting the raw TOF spectra gives fits that are in slightly better agreement with the raw data and in considerably better agreement with theory, even though the theoretical reaction probabilities still achieve higher values at high energies. The mean absolute error (MAE) for the energy E{sub 0} at which the reaction probability equals half the experimental saturation value is now lower than 1 kcal/mol, the limit that defines chemical accuracy, while a MAE of 1.5 kcal/mol was previously obtained. The new AIMD results are only slightly different from the previous static surface results and in slightly better agreement with experiment.

  1. Surface InP/In0.48Ga0.52P quantum dots: Carrier recombination dynamics and their interaction with fluorescent dyes

    Science.gov (United States)

    Hestroffer, Karine; Braun, Robert; Ugur, Asli; Tomm, Jens W.; Hackbarth, Steffen; Röder, Beate; Hatami, Fariba

    2013-10-01

    We describe the properties and carrier dynamics of surface InP quantum dots (QDs) on In0.48Ga0.52P, lattice-matched to GaAs (100). The structures were grown using gas-source molecular beam epitaxy. The average height and lateral size of the dots are in the range of 2-6 and 30-50 nm, respectively. The photoluminescence of the surface dots peaks between 750 and 830 nm, depending on the growth conditions, and is red-shifted compared to the emission of the capped QDs grown under similar conditions. The integrated photoluminescence intensity is comparable to that of the capped QDs. The decay time of both surface and capped QDs is around 1 ns at 15 K. The strong luminescence of surface QDs is explained by the effect of acting vacuum/air as an effective barrier and saturated surface states. Enhancement of the QDs luminescence is observed for the samples coated with a fluorescent dye.

  2. Novel intragenotype recombination in sapovirus.

    Science.gov (United States)

    Phan, Tung Gia; Yan, Hainian; Khamrin, Pattara; Quang, Trinh Duy; Dey, Shuvra Kanti; Yagyu, Fumihiro; Okitsu, Shoko; Müller, Werner E G; Ushijima, Hiroshi

    2006-01-01

    Based on the genetic analysis, a novel, naturally occurring recombination between two distinct sapovirus subtypes (subtype a and subtype b) within genogroup I genotype 1 was identified. Breakpoint analysis of recombinant sapovirus showed that the recombination site was at the polymerase-capsid junction. This is the first report of the existence of acute gastroenteritis caused by intragenotype recombinant sapovirus. The results also provided evidence that the natural recombination occurs not only in sapovirus genogroup II but also in sapovirus genogroup I.

  3. Recombination accelerates adaptation on a large-scale empirical fitness landscape in HIV-1.

    Science.gov (United States)

    Moradigaravand, Danesh; Kouyos, Roger; Hinkley, Trevor; Haddad, Mojgan; Petropoulos, Christos J; Engelstädter, Jan; Bonhoeffer, Sebastian

    2014-06-01

    Recombination has the potential to facilitate adaptation. In spite of the substantial body of theory on the impact of recombination on the evolutionary dynamics of adapting populations, empirical evidence to test these theories is still scarce. We examined the effect of recombination on adaptation on a large-scale empirical fitness landscape in HIV-1 based on in vitro fitness measurements. Our results indicate that recombination substantially increases the rate of adaptation under a wide range of parameter values for population size, mutation rate and recombination rate. The accelerating effect of recombination is stronger for intermediate mutation rates but increases in a monotonic way with the recombination rates and population sizes that we examined. We also found that both fitness effects of individual mutations and epistatic fitness interactions cause recombination to accelerate adaptation. The estimated epistasis in the adapting populations is significantly negative. Our results highlight the importance of recombination in the evolution of HIV-I.

  4. Optimal shapes for self-propelled swimmers

    Science.gov (United States)

    Koumoutsakos, Petros; van Rees, Wim; Gazzola, Mattia

    2011-11-01

    We optimize swimming shapes of three-dimensional self-propelled swimmers by combining the CMA- Evolution Strategy with a remeshed vortex method. We analyze the robustness of optimal shapes and discuss the near wake vortex dynamics for optimal speed and efficiency at Re=550. We also report preliminary results of optimal shapes and arrangements for multiple coordinated swimmers.

  5. Regulation of Meiotic Recombination

    Energy Technology Data Exchange (ETDEWEB)

    Gregory p. Copenhaver

    2011-11-09

    Meiotic recombination results in the heritable rearrangement of DNA, primarily through reciprocal exchange between homologous chromosome or gene conversion. In plants these events are critical for ensuring proper chromosome segregation, facilitating DNA repair and providing a basis for genetic diversity. Understanding this fundamental biological mechanism will directly facilitate trait mapping, conventional plant breeding, and development of genetic engineering techniques that will help support the responsible production and conversion of renewable resources for fuels, chemicals, and the conservation of energy (1-3). Substantial progress has been made in understanding the basal recombination machinery, much of which is conserved in organisms as diverse as yeast, plants and mammals (4, 5). Significantly less is known about the factors that regulate how often and where that basal machinery acts on higher eukaryotic chromosomes. One important mechanism for regulating the frequency and distribution of meiotic recombination is crossover interference - or the ability of one recombination event to influence nearby events. The MUS81 gene is thought to play an important role in regulating the influence of interference on crossing over. The immediate goals of this project are to use reverse genetics to identify mutants in two putative MUS81 homologs in the model plant Arabidopsis thaliana, characterize those mutants and initiate a novel forward genetic screen for additional regulators of meiotic recombination. The long-term goal of the project is to understand how meiotic recombination is regulated in higher eukaryotes with an emphasis on the molecular basis of crossover interference. The ability to monitor recombination in all four meiotic products (tetrad analysis) has been a powerful tool in the arsenal of yeast geneticists. Previously, the qrt mutant of Arabidopsis, which causes the four pollen products of male meiosis to remain attached, was developed as a facile system

  6. Dynamic experiment, modeling and compensation of bar-shaped strain gauge balance for wind tunnel%杆式风洞应变天平动态实验、建模与补偿

    Institute of Scientific and Technical Information of China (English)

    徐科军; 杨双龙; 张进; 赵长辉; 张平

    2009-01-01

    Bar-shaped strain gauge balance is a kind of six-dimension force/moment sensor used to measure force and moment applied to an aircraft model in wind tunnel. But the overshoot of its dynamic response is large and the adjusting time is long, i.e. its dynamic performance is so poor that it cannot meet dynamic test requirements. Therefore a dynamic calibration setup is designed for the bar-shaped strain gauge balance, and dynamic calibration experiments are conducted in this paper. The dynamic mathematic models are built up according to the experimental data, and the dynamic performance indexes are presented. In order to speed up the dynamic response of the strain gauge balance, a real-time dynamic correction system is developed with DSP to achieve dynamic compensation for the six output signals of the strain gauge balance. The effectiveness of the models built and the compensation system developed in this paper are verified by experimental results.%杆式应变天平是一种6维力传感器,在风洞实验中测量飞行器模型所受的各个方向的力和力矩.但是,其动态响应的超调量大,调节时间长,即动态性能差,无法满足动态测试的要求.为此,设计了应变天平动态标定装置,进行动态标定实验;基于实验数据建立应变天平的动态数学模型,给出性能指标;研制基于DSP的动态校正系统,实现对应变天平6路输出信号的动态补偿,以加快应变天平的动态响应.所建的模型和所研制的系统得到实验结果的验证.

  7. Intergenogroup Recombination in Sapoviruses

    Science.gov (United States)

    Hansman, Grant S.; Takeda, Naokazu; Oka, Tomoichiro; Oseto, Mitsukai; Hedlund, Kjell-Olof

    2005-01-01

    Sapovirus, a member of the family Caliciviridae, is an etiologic agent of gastroenteritis in humans and pigs. Analyses of the complete genome sequences led us to identify the first sapovirus intergenogroup recombinant strain. Phylogenetic analysis of the nonstructural region (i.e., genome start to capsid start) grouped this strain into genogroup II, whereas the structural region (i.e., capsid start to genome end) grouped this strain into genogroup IV. We found that a recombination event occurred at the polymerase and capsid junction. This is the first report of intergenogroup recombination for any calicivirus and highlights a possible route of zoonoses because sapovirus strains that infect pig species belong to genogroup III. PMID:16485479

  8. Recombination experiments at CRYRING

    Energy Technology Data Exchange (ETDEWEB)

    Spies, W.; Glans, P.; Zong, W.; Gao, H.; Andler, G.; Justiniano, E.; Saito, M.; Schuch, R

    1998-11-15

    Recent advances in studies of electron-ion recombination processes at low relative energies with the electron cooler of the heavy-ion storage ring CRYRING are shown. Through the use of an adiabatically expanded electron beam, collisions down to 10{sup -4}eV relative energies were measured with highly charged ions stored in the ring at around 15 MeV/amu energies. Examples of recombination measurements for bare ions of D{sup +}, He{sup 2+}, N{sup 7+}, Ne{sup 10+} and Si{sup 14+} are presented. Further on, results of an experiment measuring laser-induced recombination (LIR) into n=3 states of deuterium with polarized laser light are shown.

  9. Recombinant Helicobacter pylori catalase

    Institute of Scientific and Technical Information of China (English)

    Yang Bai; Ya-Li Zhang; Jian-Feng Jin; Ji-De Wang; Zhao-Shan Zhang

    2003-01-01

    AIM: To construct a recombinant strain which highly expresses catalase of Helicobacter pylori(H.pylori) and assay the activity of H. pylori catalase.METHODS: The catalase DNA was amplified from H. pylori chromosomal DNA with PCR techniques and inserted into the prokaryotie expression vector pET-22b (+), and then was transformed into the BL21 (DE3) E. coli strain which expressed catalase recombinant protein. The activity of H.pylori catalase was assayed by the Beers & Sizers.RESULTS: DNA sequence analysis showed that the sequence of catalase DNA was the same as GenBank's research. The catalase recombinant protein amounted to 24.4 % of the total bacterial protein after induced with IPTG for 3 hours at 37 ℃ and the activity of H. pylori catalase was high in the BL21 (DE3) E. coli strain.CONCLUSION: A clone expressing high activity H. pylori catalase is obtained, laying a good foundation for further studies.

  10. Recombinant protein blends: silk beyond natural design.

    Science.gov (United States)

    Dinjaski, Nina; Kaplan, David L

    2016-06-01

    Recombinant DNA technology and new material concepts are shaping future directions in biomaterial science for the design and production of the next-generation biomaterial platforms. Aside from conventionally used synthetic polymers, numerous natural biopolymers (e.g., silk, elastin, collagen, gelatin, alginate, cellulose, keratin, chitin, polyhydroxyalkanoates) have been investigated for properties and manipulation via bioengineering. Genetic engineering provides a path to increase structural and functional complexity of these biopolymers, and thereby expand the catalog of available biomaterials beyond that which exists in nature. In addition, the integration of experimental approaches with computational modeling to analyze sequence-structure-function relationships is starting to have an impact in the field by establishing predictive frameworks for determining material properties. Herein, we review advances in recombinant DNA-mediated protein production and functionalization approaches, with a focus on hybrids or combinations of proteins; recombinant protein blends or 'recombinamers'. We highlight the potential biomedical applications of fibrous protein recombinamers, such as Silk-Elastin Like Polypeptides (SELPs) and Silk-Bacterial Collagens (SBCs). We also discuss the possibility for the rationale design of fibrous proteins to build smart, stimuli-responsive biomaterials for diverse applications. We underline current limitations with production systems for these proteins and discuss the main trends in systems/synthetic biology that may improve recombinant fibrous protein design and production.

  11. 3-D simulation of transient flow patterns in a corridor-shaped air-cushion surge chamber based on computational fluid dynamics

    Institute of Scientific and Technical Information of China (English)

    XIA Lin-sheng; CHENG Yong-guang; ZHOU Da-qing

    2013-01-01

    The 3-D characteristics of the water-air flow patterns in a corridor-shaped air-cushion surge chamber during hydraulic transients need to be considered in the shape optimization.To verify the reliability of the water-air two-phase model,namely,the volume of fluid model,the process of charging water into a closed air chamber is successfully simulated.Using the model,the 3-D flow characteristics under the load rejection and acceptance conditions within the air-cushion surge chamber of a specific hydropower station are studied.The flee surface waves,the flow patterns,and the pressure changes during the surge wave process are analyzed in detail.The longitudinal flow of water in the long corridor-shaped surge chamber is similar to the open channel flow with respect to the wave propagation,reflection and superposition characteristics.The lumped parameters of the 3-D numerical simulation agree with the results of a 1-D calculation of hydraulic transients in the whole water conveying system,which validates the 3-D method.The 3-D flow structures obtained can be applied to the shape optimization of the chamber.

  12. Haptic categorical perception of shape.

    Science.gov (United States)

    Gaißert, Nina; Waterkamp, Steffen; Fleming, Roland W; Bülthoff, Isabelle

    2012-01-01

    Categorization and categorical perception have been extensively studied, mainly in vision and audition. In the haptic domain, our ability to categorize objects has also been demonstrated in earlier studies. Here we show for the first time that categorical perception also occurs in haptic shape perception. We generated a continuum of complex shapes by morphing between two volumetric objects. Using similarity ratings and multidimensional scaling we ensured that participants could haptically discriminate all objects equally. Next, we performed classification and discrimination tasks. After a short training with the two shape categories, both tasks revealed categorical perception effects. Training leads to between-category expansion resulting in higher discriminability of physical differences between pairs of stimuli straddling the category boundary. Thus, even brief training can alter haptic representations of shape. This suggests that the weights attached to various haptic shape features can be changed dynamically in response to top-down information about class membership.

  13. Stress analysis between“X”-shaped spine dynamic fixation and traditional pedicle screw fixation%“X”形弹性脊柱内固定与传统椎弓根内固定的应力分析

    Institute of Scientific and Technical Information of China (English)

    王宇; 梅继文; 穆尚强; 高峰; 黄锐

    2015-01-01

    背景:目前国内外许多学者研发了多种动态弹性脊柱内固定器,经过生物力学研究、动物实验及临床应用发现,尚无一种脊柱弹性内固定器得到临床上的普遍认可。  目的:比较自制“X”形弹性内固定器与传统椎弓根螺钉内固定的应力差异。  方法:根据成人脊柱影像学资料,分别建立“X”形弹性脊柱内固定器与传统椎弓根螺钉内固定系统三维有限元模型,比较两组模型在垂直压缩、屈、伸、侧屈、扭转时的力学差异。  结果与结论:两模型在垂直压缩状态应下的应力均小于屈、伸、侧屈及扭转状态下的应力;在垂直压缩、前屈、后伸、侧弯及旋转时,“X”形弹性脊柱内固定器的应力更多集中在“X”形连接棒上,而传统椎弓根螺钉内固定的应力更多集中在螺钉近棒段,且“X”形弹性脊柱内固定器螺钉所受应力明显小于传统椎弓根螺钉内固定(P<0.001)。表明“X”形弹性内固定器较传统椎弓根螺钉内固定系统更能分担螺钉应力,减少螺钉术后应力集中情况。%BACKGROUND:Many scholars have developed a variety of dynamic elastic spine fixator. After biomechanical research, animal experiments and clinical application found that no one elastic spine fixator was general y recognized clinical y. OBJECTIVE:To compare the stress difference between“X”-shaped spine dynamic fixation and traditional pedicle screw fixation. METHODS:Three-dimensional finite element models of“X”-shaped spine dynamic fixation and traditional pedicle screw fixation were established according to adult spine imaging data. Mechanical differences in vertical compression, flexion, extension, lateral bending and rotation were compared between the two groups. RESULTS AND CONCLUSION:The stress at vertical compression was lower than that at flexion, extension, lateral bending and rotation in both groups. The stress at“X”-shaped

  14. Recombineering linear BACs.

    Science.gov (United States)

    Chen, Qingwen; Narayanan, Kumaran

    2015-01-01

    Recombineering is a powerful genetic engineering technique based on homologous recombination that can be used to accurately modify DNA independent of its sequence or size. One novel application of recombineering is the assembly of linear BACs in E. coli that can replicate autonomously as linear plasmids. A circular BAC is inserted with a short telomeric sequence from phage N15, which is subsequently cut and rejoined by the phage protelomerase enzyme to generate a linear BAC with terminal hairpin telomeres. Telomere-capped linear BACs are protected against exonuclease attack both in vitro and in vivo in E. coli cells and can replicate stably. Here we describe step-by-step protocols to linearize any BAC clone by recombineering, including inserting and screening for presence of the N15 telomeric sequence, linearizing BACs in vivo in E. coli, extracting linear BACs, and verifying the presence of hairpin telomere structures. Linear BACs may be useful for functional expression of genomic loci in cells, maintenance of linear viral genomes in their natural conformation, and for constructing innovative artificial chromosome structures for applications in mammalian and plant cells.

  15. Recombinant DNA for Teachers.

    Science.gov (United States)

    Duvall, James G., III

    1992-01-01

    A science teacher describes his experience at a workshop to learn to teach the Cold Spring Harbor DNA Science Laboratory Protocols. These protocols lead students through processes for taking E. coli cells and transforming them into a new antibiotic resistant strain. The workshop featured discussions of the role of DNA recombinant technology in…

  16. Recombinant renewable polyclonal antibodies.

    Science.gov (United States)

    Ferrara, Fortunato; D'Angelo, Sara; Gaiotto, Tiziano; Naranjo, Leslie; Tian, Hongzhao; Gräslund, Susanne; Dobrovetsky, Elena; Hraber, Peter; Lund-Johansen, Fridtjof; Saragozza, Silvia; Sblattero, Daniele; Kiss, Csaba; Bradbury, Andrew R M

    2015-01-01

    Only a small fraction of the antibodies in a traditional polyclonal antibody mixture recognize the target of interest, frequently resulting in undesirable polyreactivity. Here, we show that high-quality recombinant polyclonals, in which hundreds of different antibodies are all directed toward a target of interest, can be easily generated in vitro by combining phage and yeast display. We show that, unlike traditional polyclonals, which are limited resources, recombinant polyclonal antibodies can be amplified over one hundred million-fold without losing representation or functionality. Our protocol was tested on 9 different targets to demonstrate how the strategy allows the selective amplification of antibodies directed toward desirable target specific epitopes, such as those found in one protein but not a closely related one, and the elimination of antibodies recognizing common epitopes, without significant loss of diversity. These recombinant renewable polyclonal antibodies are usable in different assays, and can be generated in high throughput. This approach could potentially be used to develop highly specific recombinant renewable antibodies against all human gene products.

  17. Coarse-graining MARTINI model for molecular-dynamics simulations of the wetting properties of graphitic surfaces with non-ionic, long-chain and T-shaped surfactants

    CERN Document Server

    Sergi, Danilo; Ortona, Alberto

    2012-01-01

    We report on a molecular dynamics investigation of the wetting properties of graphitic surfaces by various solutions at concentrations 1-8 wt% of commercially available non-ionic surfactants with long hydrophilic chains, linear or T-shaped. These are surfactants of length up to 160 [\\AA]. It turns out that molecular dynamics simulations of such systems ask for a number of solvent particles that can be reached without seriously compromising computational efficiency only by employing a coarse-grained model. The MARTINI force field with polarizable water offers a framework particularly suited for our problem. In general, its advantages over other coarse-grained models are the possibility to explore faster long time scales and the wider range of applicability. Although the accuracy is sometimes put under question, the results for the wetting properties by pure water are in good agreement with those for the corresponding atomistic systems and theoretical predictions. On the other hand, the bulk properties of vario...

  18. A phylogenetic survey of recombination frequency in plant RNA viruses.

    Science.gov (United States)

    Chare, E R; Holmes, E C

    2006-05-01

    The severe economic consequences of emerging plant viruses highlights the importance of studies of plant virus evolution. One question of particular relevance is the extent to which the genomes of plant viruses are shaped by recombination. To this end we conducted a phylogenetic survey of recombination frequency in a wide range of positive-sense RNA plant viruses, utilizing 975 capsid gene sequences and 157 complete genome sequences. In total, 12 of the 36 RNA virus species analyzed showed evidence for recombination, comprising 17% of the capsid gene sequence alignments and 44% of the genome sequence alignments. Given the conservative nature of our analysis, we propose that recombination is a relatively common process in some plant RNA viruses, most notably the potyviruses.

  19. Linear shaped charge

    Energy Technology Data Exchange (ETDEWEB)

    Peterson, David; Stofleth, Jerome H.; Saul, Venner W.

    2017-07-11

    Linear shaped charges are described herein. In a general embodiment, the linear shaped charge has an explosive with an elongated arrowhead-shaped profile. The linear shaped charge also has and an elongated v-shaped liner that is inset into a recess of the explosive. Another linear shaped charge includes an explosive that is shaped as a star-shaped prism. Liners are inset into crevices of the explosive, where the explosive acts as a tamper.

  20. Dynamics of localized and patterned structures in the Lugiato-Lefever equation determine the stability and shape of optical frequency combs

    Science.gov (United States)

    Parra-Rivas, P.; Gomila, D.; Matías, M. A.; Coen, S.; Gelens, L.

    2014-04-01

    It has been recently uncovered that coherent structures in microresonators such as cavity solitons and patterns are intimately related to Kerr frequency combs. In this work, we present a general analysis of the regions of existence and stability of cavity solitons and patterns in the Lugiato-Lefever equation, a mean-field model that finds applications in many different nonlinear optical cavities. We demonstrate that the rich dynamics and coexistence of multiple solutions in the Lugiato-Lefever equation are of key importance to understanding frequency comb generation. A detailed map of how and where to target stable Kerr frequency combs in the parameter space defined by the frequency detuning and the pump power is provided. Moreover, the work presented also includes the organization of various dynamical regimes in terms of bifurcation points of higher codimension in regions of parameter space that were previously unexplored in the Lugiato-Lefever equation. We discuss different dynamical instabilities such as oscillations and chaotic regimes.

  1. Dynamics of localized and patterned structures in the Lugiato-Lefever equation determine the stability and shape of optical frequency combs

    CERN Document Server

    Parra-Rivas, P; Matias, M A; Coen, S; Gelens, L

    2014-01-01

    It has been recently uncovered that coherent structures in microresonators such as cavity solitons and patterns are intimately related to Kerr frequency combs. In this work, we present a general analysis of the regions of existence and stability of cavity solitons and patterns in the Lugiato-Lefever equation, a mean-field model that finds applications in many different nonlinear optical cavities. We demonstrate that the rich dynamics and coexistence of multiple solutions in the Lugiato-Lefever equation are of key importance to understanding frequency comb generation. A detailed map of how and where to target stable Kerr frequency combs in the parameter space defined by the frequency detuning and the pump power is provided. Moreover, the work presented also includes the organization of various dynamical regimes in terms of bifurcation points of higher co-dimension in regions of parameter space that were previously unexplored in the Lugiato-Lefever equation. We discuss different dynamical instabilities such as ...

  2. SUMO Wrestles with Recombination

    Directory of Open Access Journals (Sweden)

    Lumír Krejčí

    2012-07-01

    Full Text Available DNA double-strand breaks (DSBs comprise one of the most toxic DNA lesions, as the failure to repair a single DSB has detrimental consequences on the cell. Homologous recombination (HR constitutes an error-free repair pathway for the repair of DSBs. On the other hand, when uncontrolled, HR can lead to genome rearrangements and needs to be tightly regulated. In recent years, several proteins involved in different steps of HR have been shown to undergo modification by small ubiquitin-like modifier (SUMO peptide and it has been suggested that deficient sumoylation impairs the progression of HR. This review addresses specific effects of sumoylation on the properties of various HR proteins and describes its importance for the homeostasis of DNA repetitive sequences. The article further illustrates the role of sumoylation in meiotic recombination and the interplay between SUMO and other post-translational modifications.

  3. Molecular dynamics simulations on the effect of size and shape on the interactions between negative Au18(SR)14, Au102(SR)44 and Au144(SR)60 nanoparticles in physiological saline.

    Science.gov (United States)

    Villareal, Oscar D; Rodriguez, Roberto A; Yu, Lili; Wambo, Thierry O

    2016-08-20

    Molecular dynamics simulations employing all-atom force fields have become a reliable way to study binding interactions quantitatively for a wide range of systems. In this work, we employ two recently developed methods for the calculation of dissociation constants KD between gold nanoparticles (AuNPs) of different sizes in a near-physiological environment through the potential of mean force (PMF) formalism: the method of geometrical restraints developed by Woo et al. and formalized by Gumbart et al. and the method of hybrid Steered Molecular Dynamics (hSMD). Obtaining identical results (within the margin of error) from both approaches on the negatively charged Au18(SR)14 NP, functionalized by the negatively charged 4-mercapto-benzoate (pMBA) ligand, we draw parallels between their energetic and entropic interactions. By applying the hSMD method on Au102(SR)44 and Au144(SR)60, both of them near-spherical in shape and functionalized by pMBA, we study the effects of size and shape on the binding interactions. Au18 binds weakly with KD = 13mM as a result of two opposing effects: its large surface curvature hindering the formation of salt bridges, and its large ligand density on preferential orientations favoring their formation. On the other hand, Au102 binds more strongly with KD = 30μM and Au144 binds the strongest with KD = 3.2nM.

  4. A dynamic Monte Carlo study of anomalous current voltage behaviour in organic solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Feron, K., E-mail: Krishna.Feron@csiro.au; Fell, C. J. [Centre for Organic Electronics, University of Newcastle, Callaghan, NSW 2308 (Australia); CSIRO Energy Flagship, Newcastle, NSW 2300 (Australia); Zhou, X.; Belcher, W. J.; Dastoor, P. C. [Centre for Organic Electronics, University of Newcastle, Callaghan, NSW 2308 (Australia)

    2014-12-07

    We present a dynamic Monte Carlo (DMC) study of s-shaped current-voltage (I-V) behaviour in organic solar cells. This anomalous behaviour causes a substantial decrease in fill factor and thus power conversion efficiency. We show that this s-shaped behaviour is induced by charge traps that are located at the electrode interface rather than in the bulk of the active layer, and that the anomaly becomes more pronounced with increasing trap depth or density. Furthermore, the s-shape anomaly is correlated with interface recombination, but not bulk recombination, thus highlighting the importance of controlling the electrode interface. While thermal annealing is known to remove the s-shape anomaly, the reason has been not clear, since these treatments induce multiple simultaneous changes to the organic solar cell structure. The DMC modelling indicates that it is the removal of aluminium clusters at the electrode, which act as charge traps, that removes the anomalous I-V behaviour. Finally, this work shows that the s-shape becomes less pronounced with increasing electron-hole recombination rate; suggesting that efficient organic photovoltaic material systems are more susceptible to these electrode interface effects.

  5. Recombinant Human Enterovirus 71

    OpenAIRE

    2004-01-01

    Two human enterovirus 71 (HEV71) isolates were identified from hand, foot and mouth disease patients with genome sequences that had high similarity to HEV71 (>93%) at 5´ UTR, P1, and P2 and coxsackievirus A16 (CV-A16, >85%) at P3 and 3´UTR. Intertypic recombination is likely to have occurred between HEV71 and CV-A16 or an as-yet to be described CV-A16-like virus.

  6. Tunable spin wave dynamics in two-dimensional Ni{sub 80}Fe{sub 20} nanodot lattices by varying dot shape

    Energy Technology Data Exchange (ETDEWEB)

    Mahato, Bipul Kumar; Rana, Bivas; Kumar, Dheeraj; Barman, Saswati; Barman, Anjan, E-mail: abarman@bose.res.in [Thematic Unit of Excellence on Nanodevice Technology, Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata 700098 (India); Sugimoto, Satoshi [Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan); Otani, YoshiChika [Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581 (Japan); CEMS-RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan)

    2014-07-07

    We demonstrate tunable spin wave spectrum in two-dimensional Ni{sub 80}Fe{sub 20} nanodot lattices by varying dot shape. A single collective mode in elliptical dot lattices transforms into three distinct modes for the half-elliptical, rectangular, and diamond dot lattices, albeit with different peak frequencies and intensities. A drastic change is observed for the triangular dots, where eight modes covering a broad band are observed. Using micromagnetic simulations, we characterized the modes as different localized, extended, and quantized modes, whose frequencies and spatial profiles are determined by a combination of internal field profiles within the nanodots and the stray magnetic field within the lattice.

  7. Dynamics

    CERN Document Server

    Goodman, Lawrence E

    2001-01-01

    Beginning text presents complete theoretical treatment of mechanical model systems and deals with technological applications. Topics include introduction to calculus of vectors, particle motion, dynamics of particle systems and plane rigid bodies, technical applications in plane motions, theory of mechanical vibrations, and more. Exercises and answers appear in each chapter.

  8. Recombinant human milk proteins.

    Science.gov (United States)

    Lönnerdal, Bo

    2006-01-01

    Human milk provides proteins that benefit newborn infants. They not only provide amino acids, but also facilitate the absorption of nutrients, stimulate growth and development of the intestine, modulate immune function, and aid in the digestion of other nutrients. Breastfed infants have a lower prevalence of infections than formula-fed infants. Since many women in industrialized countries choose not to breastfeed, and an increasing proportion of women in developing countries are advised not to breastfeed because of the risk of HIV transmission, incorporation of recombinant human milk proteins into infant foods is likely to be beneficial. We are expressing human milk proteins known to have anti-infective activity in rice. Since rice is a normal constituent of the diet of infants and children, limited purification of the proteins is required. Lactoferrin has antimicrobial and iron-binding activities. Lysozyme is an enzyme that is bactericidal and also acts synergistically with lactoferrin. These recombinant proteins have biological activities identical to their native counterparts. They are equally resistant to heat processing, which is necessary for food applications, and to acid and proteolytic enzymes which are needed to maintain their biological activity in the gastrointestinal tract of infants. These recombinant human milk proteins may be incorporated into infant formulas, baby foods and complementary foods, and used with the goal to reduce infectious diseases.

  9. Evolution of recombination in eutherian mammals: insights into mechanisms that affect recombination rates and crossover interference.

    Science.gov (United States)

    Segura, Joana; Ferretti, Luca; Ramos-Onsins, Sebastián; Capilla, Laia; Farré, Marta; Reis, Fernanda; Oliver-Bonet, Maria; Fernández-Bellón, Hugo; Garcia, Francisca; Garcia-Caldés, Montserrat; Robinson, Terence J; Ruiz-Herrera, Aurora

    2013-11-22

    Recombination allows faithful chromosomal segregation during meiosis and contributes to the production of new heritable allelic variants that are essential for the maintenance of genetic diversity. Therefore, an appreciation of how this variation is created and maintained is of critical importance to our understanding of biodiversity and evolutionary change. Here, we analysed the recombination features from species representing the major eutherian taxonomic groups Afrotheria, Rodentia, Primates and Carnivora to better understand the dynamics of mammalian recombination. Our results suggest a phylogenetic component in recombination rates (RRs), which appears to be directional, strongly punctuated and subject to selection. Species that diversified earlier in the evolutionary tree have lower RRs than those from more derived phylogenetic branches. Furthermore, chromosome-specific recombination maps in distantly related taxa show that crossover interference is especially weak in the species with highest RRs detected thus far, the tiger. This is the first example of a mammalian species exhibiting such low levels of crossover interference, highlighting the uniqueness of this species and its relevance for the study of the mechanisms controlling crossover formation, distribution and resolution.

  10. Line shapes and time dynamics of the F\\"orster resonances between two Rydberg atoms in a time-varying electric field

    CERN Document Server

    Yakshina, E A; Beterov, I I; Entin, V M; Andreeva, C; Cinins, A; Markovski, A; Iftikhar, Z; Ekers, A; Ryabtsev, I I

    2016-01-01

    The observation of the Stark-tuned F\\"orster resonances between Rydberg atoms excited by narrowband cw laser radiation requires usage of a Stark-switching technique in order to excite the atoms first in a fixed electric field and then to induce the interactions in a varied electric field, which is scanned across the F\\"orster resonance. In our experiments with a few cold Rb Rydberg atoms we have found that the transients at the edges of the electric pulses strongly affect the line shapes of the F\\"orster resonances, since the resonances occur mainly on a time scale of ~100 ns, which is comparable with the duration of the transients. For example, a short-term ringing at a certain frequency causes additional radio-frequency-assisted F\\"orster resonances, while non-sharp edges lead to asymmetry. The intentional application of the radio-frequency field induces transitions between collective states, whose line shape depends on the interaction strengths and time. Spatial averaging over the atom positions in a singl...

  11. Numerical investigation of effective mechanical properties of metal-ceramic composites with reinforcing inclusions of different shapes under intensive dynamic impacts

    Science.gov (United States)

    Karakulov, Valerii V.; Smolin, Igor Yu.; Skripnyak, Vladimir A.

    2016-11-01

    In the present paper, the results of numerical simulation of high-rate deformation of stochastic metal-ceramic composite materials Al-50% B4C, Al-50% SiC, and Al-50% Al2O3 at the mesoscopic scale level under loading by a plane shock wave are presented. Deformation of the mesoscopic volume of a composite, whose structure consists of the aluminum matrix and randomly distributed reinforcing ceramic inclusions, is numerically simulated. The results of the numerical simulation are used for the investigation of special features of the mechanical behavior at the mesoscopic scale level under shock-wave loading and for the numerical evaluation of effective elastic and strength properties of metal-ceramic composites with reinforcing ceramic inclusions of different shapes. Values of effective sound velocities, elastic moduli and elastic limits of investigated materials are obtained, and the character of the dependence of the effective elastic and strength properties on the structure parameters of composites is determined. The simulation results show that values of effective mechanical characteristics weakly depend on the shape of reinforcing inclusions and mainly are defined by their volume concentration.

  12. The Contribution of Genetic Recombination to CRISPR Array Evolution.

    Science.gov (United States)

    Kupczok, Anne; Landan, Giddy; Dagan, Tal

    2015-06-16

    CRISPR (clustered regularly interspaced short palindromic repeats) is a microbial immune system against foreign DNA. Recognition sequences (spacers) encoded within the CRISPR array mediate the immune reaction in a sequence-specific manner. The known mechanisms for the evolution of CRISPR arrays include spacer acquisition from foreign DNA elements at the time of invasion and array erosion through spacer deletion. Here, we consider the contribution of genetic recombination between homologous CRISPR arrays to the evolution of spacer repertoire. Acquisition of spacers from exogenic arrays via recombination may confer the recipient with immunity against unencountered antagonists. For this purpose, we develop a novel method for the detection of recombination in CRISPR arrays by modeling the spacer order in arrays from multiple strains from the same species. Because the evolutionary signal of spacer recombination may be similar to that of pervasive spacer deletions or independent spacer acquisition, our method entails a robustness analysis of the recombination inference by a statistical comparison to resampled and perturbed data sets. We analyze CRISPR data sets from four bacterial species: two Gammaproteobacteria species harboring CRISPR type I and two Streptococcus species harboring CRISPR type II loci. We find that CRISPR array evolution in Escherichia coli and Streptococcus agalactiae can be explained solely by vertical inheritance and differential spacer deletion. In Pseudomonas aeruginosa, we find an excess of single spacers potentially incorporated into the CRISPR locus during independent acquisition events. In Streptococcus thermophilus, evidence for spacer acquisition by recombination is present in 5 out of 70 strains. Genetic recombination has been proposed to accelerate adaptation by combining beneficial mutations that arose in independent lineages. However, for most species under study, we find that CRISPR evolution is shaped mainly by spacer acquisition and

  13. Dynamical analysis of the complex radio structure in 3C 293: clues on a rapid jet realignment in X-shaped radio galaxies

    Science.gov (United States)

    Machalski, J.; Jamrozy, M.; Stawarz, Ł.; Weżgowiec, M.

    2016-10-01

    Context. Radio galaxies classified as X-shaped/winged, are characterised by two pairs of extended and misaligned lobes, which suggest a rapid realignment of the jet axis, for which a potential cause (including binary supermassive black holes, a black hole merger, or a Lense-Thirring precession) is still under debate. Aims: Here we analyse the complex radio structure of 3C 293 winged source hosted by the post-merger galaxy UGC 8782, which uniquely displays a significant asymmetry between the sizes (and therefore the ages) of the two pairs of lobes, indicating that an episode of jet realignment took place only very recently. This allows us to tightly constrain the corresponding timescales, and therefore to discriminate between different models proposed for the formation of X-shaped radio galaxies in general. Methods: Based on all the available and carefully re-analysed radio data for 3C 293, we have performed a detailed spectral modelling for the older and younger lobes in the system, using the existing evolutionary DYNAGE algorithm. In this way we derived the lobes' ages and jet energetics, which we then compared to the accretion power in the source. Results: We found that the 200 kpc-scale outer lobes of 3C 293 are 60 Myr old and, until very recently, have been supplied with fresh electrons and magnetic field by the jets, i.e., jet activity related to the formation of the outer lobes ceased within the last Myr. Meanwhile, the inner 4 kpc-scale lobes, tilted by 40° with respect to the outer ones, are only about 0.3 Myr old. Interestingly, the best model fits also return identical values of the jet power supplying the outer and the inner structures. This power, moreover, is of the order of the maximum kinetic luminosity of a Blandford-Znajek jet for a given black hole mass and accretion rate, but only in the case of relatively low values of a black hole spin, a 0.2. Conclusions: The derived jet energetics and timescales, along with the presence of two optical nuclei

  14. Dynamics of localized and patterned structures in the Lugiato-Lefever equation determine the stability and shape of optical frequency combs

    OpenAIRE

    Parra-Rivas, P.; Gomila, Damià; Matías, Manuel A.; Coen, Stéphane; Gelens, Lendert

    2014-01-01

    It has been recently uncovered that coherent structures in microresonators such as cavity solitons and patterns are intimately related to Kerr frequency combs. In this work, we present a general analysis of the regions of existence and stability of cavity solitons and patterns in the Lugiato-Lefever equation, a mean-field model that finds applications in many different nonlinear optical cavities. We demonstrate that the rich dynamics and coexistence of multiple solutions in the Lugiato-Lefeve...

  15. Bacterial Recombineering: Genome Engineering via Phage-Based Homologous Recombination.

    Science.gov (United States)

    Pines, Gur; Freed, Emily F; Winkler, James D; Gill, Ryan T

    2015-11-20

    The ability to specifically modify bacterial genomes in a precise and efficient manner is highly desired in various fields, ranging from molecular genetics to metabolic engineering and synthetic biology. Much has changed from the initial realization that phage-derived genes may be employed for such tasks to today, where recombineering enables complex genetic edits within a genome or a population. Here, we review the major developments leading to recombineering becoming the method of choice for in situ bacterial genome editing while highlighting the various applications of recombineering in pushing the boundaries of synthetic biology. We also present the current understanding of the mechanism of recombineering. Finally, we discuss in detail issues surrounding recombineering efficiency and future directions for recombineering-based genome editing.

  16. Oxygen Atom Recombination in Carbon Dioxide Atmospheres

    Science.gov (United States)

    Jamieson, Corey; Garcia, R. M.; Pejakovic, D. A.; Kalogerakis, K. S.

    2009-09-01

    Understanding processes involving atomic oxygen is crucial for the study and modeling of composition, energy transfer, airglow, and transport dynamics in planetary atmospheres. Significant gaps and uncertainties exist in our understanding of the above processes, and often the relevant input from laboratory measurements is missing or outdated. We are conducting experiments to measure the rate coefficients for O + O + CO2 and O + O2 + CO2 recombination and investigate the O2 excited states produced following O-atom recombination. These laboratory measurements are key input for a quantitative understanding and reliable modeling of the atmospheres of the CO2 planets and their airglow. An ArF excimer laser with 193-nm pulsed output radiation is employed to partially photodissociate carbon dioxide. In an ambient-pressure (760 Torr) background of CO2, the O atoms produced recombine in a time scale of a few milliseconds. Detection of laser-induced fluorescence at 845 nm following two-photon excitation near 226 nm monitors the decay of the oxygen atom population. From the temporal evolution of the signal we can extract the rate coefficients for recombination of O + O and O + O2 in the presence of CO2. We also use fluorescence and resonance-enhanced multi-photon ionization techniques to detect the products of the O-atom recombination and subsequent relaxation in CO2. This work is supported by the US National Science Foundation's (NSF) Planetary Astronomy Program. Rosanne Garcia's participation was funded by the NSF Research Experiences for Undergraduates (REU) Program.

  17. Shaping Robust System through Evolution

    CERN Document Server

    Kaneko, Kunihiko

    2008-01-01

    Biological functions are generated as a result of developmental dynamics that form phenotypes governed by genotypes. The dynamical system for development is shaped through genetic evolution following natural selection based on the fitness of the phenotype. Here we study how this dynamical system is robust to noise during development and to genetic change by mutation. We adopt a simplified transcription regulation network model to govern gene expression, which gives a fitness function. Through simulations of the network that undergoes mutation and selection, we show that a certain level of noise in gene expression is required for the network to acquire both types of robustness. The results reveal how the noise that cells encounter during development shapes any network's robustness, not only to noise but also to mutations. We also establish a relationship between developmental and mutational robustness through phenotypic variances caused by genetic variation and epigenetic noise. A universal relationship betwee...

  18. Scrambling Eggs: Meiotic Drive and the Evolution of Female Recombination Rates

    Science.gov (United States)

    Brandvain, Yaniv; Coop, Graham

    2012-01-01

    Theories to explain the prevalence of sex and recombination have long been a central theme of evolutionary biology. Yet despite decades of attention dedicated to the evolution of sex and recombination, the widespread pattern of sex differences in the recombination rate is not well understood and has received relatively little theoretical attention. Here, we argue that female meiotic drivers—alleles that increase in frequency by exploiting the asymmetric cell division of oogenesis—present a potent selective pressure favoring the modification of the female recombination rate. Because recombination plays a central role in shaping patterns of variation within and among dyads, modifiers of the female recombination rate can function as potent suppressors or enhancers of female meiotic drive. We show that when female recombination modifiers are unlinked to female drivers, recombination modifiers that suppress harmful female drive can spread. By contrast, a recombination modifier tightly linked to a driver can increase in frequency by enhancing female drive. Our results predict that rapidly evolving female recombination rates, particularly around centromeres, should be a common outcome of meiotic drive. We discuss how selection to modify the efficacy of meiotic drive may contribute to commonly observed patterns of sex differences in recombination. PMID:22143919

  19. Dynamic Shape Based on Superformula in Three-dimensional Websites and Its Visual Experience%三维网站动态形状及其视觉体验——基于Superformula公式的研究

    Institute of Scientific and Technical Information of China (English)

    陈童; 张轩颖

    2011-01-01

    相对于传统二维形式的网站,三维网站提供了更高仿真度的立体影像和更高自由度的交互方式,为用户提供了全新的视觉和交互体验。但同时也要求三维网站中的三维形状要具有比较高的拟真度、传输速度和生成速度。采用基于Superformula公式的建模方法,具有单一公式生成非对称三维动态形状的能力,可以满足受众对于在互联网上浏览三维网站的速度及图像质量的要求,非常适合生成三维网站中的三维形状。基于Superformula公式生成的三维动态形状,将给受众带来前所未有的积极视觉体验。%Compared with the traditional 2D form of websites,the 3D websites can provide the higher degree of simulation of stereo images and greater freedom of the interaction,and provide the users with a brand-new visual experience and interactive experience.And the 3D shapes in the 3D websites ask for high simulation of stereo images,speed of transport and production rate at the same time.The modeling method based on Super-formula can create 3D non-symmetrical dynamic shape only with a single formula,and these shapes can meet the audience for the browsing speed and image quality.These 3D models are very suitable for constructing three-dimensional website.The dynamic 3D shapes created by Super-formula can bring the audience unprecedented positive visual experiences.

  20. Molecular mechanisms of recombination restriction in the envelope gene of the human immunodeficiency virus.

    Directory of Open Access Journals (Sweden)

    Etienne Simon-Loriere

    2009-05-01

    Full Text Available The ability of pathogens to escape the host's immune response is crucial for the establishment of persistent infections and can influence virulence. Recombination has been observed to contribute to this process by generating novel genetic variants. Although distinctive recombination patterns have been described in many viral pathogens, little is known about the influence of biases in the recombination process itself relative to selective forces acting on newly formed recombinants. Understanding these influences is important for determining how recombination contributes to pathogen genome and proteome evolution. Most previous research on recombination-driven protein evolution has focused on relatively simple proteins, usually in the context of directed evolution experiments. Here, we study recombination in the envelope gene of HIV-1 between primary isolates belonging to subtypes that recombine naturally in the HIV/AIDS pandemic. By characterizing the early steps in the generation of recombinants, we provide novel insights into the evolutionary forces that shape recombination patterns within viral populations. Specifically, we show that the combined effects of mechanistic processes that determine the locations of recombination breakpoints across the HIV-1 envelope gene, and purifying selection acting against dysfunctional recombinants, can explain almost the entire distribution of breakpoints found within this gene in nature. These constraints account for the surprising paucity of recombination breakpoints found in infected individuals within this highly variable gene. Thus, the apparent randomness of HIV evolution via recombination may in fact be relatively more predictable than anticipated. In addition, the dominance of purifying selection in localized areas of the HIV genome defines regions where functional constraints on recombinants appear particularly strong, pointing to vulnerable aspects of HIV biology.

  1. Molecular mechanisms of recombination restriction in the envelope gene of the human immunodeficiency virus.

    Science.gov (United States)

    Simon-Loriere, Etienne; Galetto, Roman; Hamoudi, Meriem; Archer, John; Lefeuvre, Pierre; Martin, Darren P; Robertson, David L; Negroni, Matteo

    2009-05-01

    The ability of pathogens to escape the host's immune response is crucial for the establishment of persistent infections and can influence virulence. Recombination has been observed to contribute to this process by generating novel genetic variants. Although distinctive recombination patterns have been described in many viral pathogens, little is known about the influence of biases in the recombination process itself relative to selective forces acting on newly formed recombinants. Understanding these influences is important for determining how recombination contributes to pathogen genome and proteome evolution. Most previous research on recombination-driven protein evolution has focused on relatively simple proteins, usually in the context of directed evolution experiments. Here, we study recombination in the envelope gene of HIV-1 between primary isolates belonging to subtypes that recombine naturally in the HIV/AIDS pandemic. By characterizing the early steps in the generation of recombinants, we provide novel insights into the evolutionary forces that shape recombination patterns within viral populations. Specifically, we show that the combined effects of mechanistic processes that determine the locations of recombination breakpoints across the HIV-1 envelope gene, and purifying selection acting against dysfunctional recombinants, can explain almost the entire distribution of breakpoints found within this gene in nature. These constraints account for the surprising paucity of recombination breakpoints found in infected individuals within this highly variable gene. Thus, the apparent randomness of HIV evolution via recombination may in fact be relatively more predictable than anticipated. In addition, the dominance of purifying selection in localized areas of the HIV genome defines regions where functional constraints on recombinants appear particularly strong, pointing to vulnerable aspects of HIV biology.

  2. Molecular Mechanisms of Recombination Restriction in the Envelope Gene of the Human Immunodeficiency Virus

    Science.gov (United States)

    Simon-Loriere, Etienne; Galetto, Roman; Hamoudi, Meriem; Archer, John; Lefeuvre, Pierre; Martin, Darren P.; Robertson, David L.; Negroni, Matteo

    2009-01-01

    The ability of pathogens to escape the host's immune response is crucial for the establishment of persistent infections and can influence virulence. Recombination has been observed to contribute to this process by generating novel genetic variants. Although distinctive recombination patterns have been described in many viral pathogens, little is known about the influence of biases in the recombination process itself relative to selective forces acting on newly formed recombinants. Understanding these influences is important for determining how recombination contributes to pathogen genome and proteome evolution. Most previous research on recombination-driven protein evolution has focused on relatively simple proteins, usually in the context of directed evolution experiments. Here, we study recombination in the envelope gene of HIV-1 between primary isolates belonging to subtypes that recombine naturally in the HIV/AIDS pandemic. By characterizing the early steps in the generation of recombinants, we provide novel insights into the evolutionary forces that shape recombination patterns within viral populations. Specifically, we show that the combined effects of mechanistic processes that determine the locations of recombination breakpoints across the HIV-1 envelope gene, and purifying selection acting against dysfunctional recombinants, can explain almost the entire distribution of breakpoints found within this gene in nature. These constraints account for the surprising paucity of recombination breakpoints found in infected individuals within this highly variable gene. Thus, the apparent randomness of HIV evolution via recombination may in fact be relatively more predictable than anticipated. In addition, the dominance of purifying selection in localized areas of the HIV genome defines regions where functional constraints on recombinants appear particularly strong, pointing to vulnerable aspects of HIV biology. PMID:19424420

  3. Recombinant Collagenlike Proteins

    Science.gov (United States)

    Fertala, Andzej

    2007-01-01

    A group of collagenlike recombinant proteins containing high densities of biologically active sites has been invented. The method used to express these proteins is similar to a method of expressing recombinant procollagens and collagens described in U. S. Patent 5,593,859, "Synthesis of human procollagens and collagens in recombinant DNA systems." Customized collagenous proteins are needed for biomedical applications. In particular, fibrillar collagens are attractive for production of matrices needed for tissue engineering and drug delivery. Prior to this invention, there was no way of producing customized collagenous proteins for these and other applications. Heretofore, collagenous proteins have been produced by use of such biological systems as yeasts, bacteria, and transgenic animals and plants. These products are normal collagens that can also be extracted from such sources as tendons, bones, and hides. These products cannot be made to consist only of biologically active, specific amino acid sequences that may be needed for specific applications. Prior to this invention, it had been established that fibrillar collagens consist of domains that are responsible for such processes as interaction with cells, binding of growth factors, and interaction with a number of structural proteins present in the extracellular matrix. A normal collagen consists of a sequence of domains that can be represented by a corresponding sequence of labels, e.g., D1D2D3D4. A collagenlike protein of the present invention contains regions of collagen II that contain multiples of a single domain (e.g., D1D1D1D1 or D4D4D4D4) chosen for its specific biological activity. By virtue of the multiplicity of the chosen domain, the density of sites having that specific biological activity is greater than it is in a normal collagen. A collagenlike protein according to this invention can thus be made to have properties that are necessary for tissue engineering.

  4. Dielectronic recombination theory

    Energy Technology Data Exchange (ETDEWEB)

    LaGattuta, K.J.

    1991-12-31

    A theory now in wide use for the calculation of dielectronic recombination cross sections ({sigma}{sup DR}) and rate coefficients ({alpha}{sup DR}) was one introduced originally by Feshbach for nuclear physics applications, and then later adapted for atomic scattering problems by Hahn. In the following, we briefly review this theory in a very general form, which allows one to account for the effects of overlapping and interacting resonances, as well as continuum-continuum coupling. An extension of our notation will then also allow for the inclusion of the effects of direct radiative recombination, along with a treatment of the interference between radiative and dielectronic recombination. Other approaches to the calculation of {sigma}{sup DR} have been described by Fano and by Seaton. We will not consider those theories here. Calculations of {alpha}{sup DR} have progressed considerably over the last 25 years, since the early work of Burgess. Advances in the reliability of theoretical predictions have also been promoted recently b a variety of direct laboratory measurements of {sigma}{sup DR}. While the measurements of {sigma}{sup DR} for {delta}n {ne} 0 excitations have tended to agree very well with calculations, the case of {delta}n = 0 has been much problematic. However, by invoking a mechanism originally proposed by Jacobs, which takes into account the effect of stray electric fields on high Rydberg states (HRS) participating in the DR process, new calculations have improved the agreement between theory and experiment for these cases. Nevertheless, certain discrepancies still remain.

  5. Did the universe recombine

    Energy Technology Data Exchange (ETDEWEB)

    Bartlett, J.G.; Stebbins, A. (California, University, Berkeley (USA) Toronto, University (Canada))

    1991-04-01

    The Zel'dovich-Sunyaev model-independent arguments for the existence of a neutral hydrogen phase is reviewed in light of new limits on the Compton y parameter from COBE. It is concluded that with baryon densities compatible with standard cosmological nucleosynthesis, the universe could have remained fully ionized throughout its history without producing a detectable spectral distortion. It is argued that it is unlikely that spectral observations of the cosmic microwave background will ever require the universe to have recombined for flat cosmologies. 22 refs.

  6. RAG and HMGB1 create a large bend in the 23RSS in the V(D)J recombination synaptic complexes.

    Science.gov (United States)

    Ciubotaru, Mihai; Trexler, Adam J; Spiridon, Laurentiu N; Surleac, Marius D; Rhoades, Elizabeth; Petrescu, Andrei J; Schatz, David G

    2013-02-01

    During V(D)J recombination, recombination activating gene proteins RAG1 and RAG2 generate DNA double strand breaks within a paired complex (PC) containing two complementary recombination signal sequences (RSSs), the 12RSS and 23RSS, which differ in the length of the spacer separating heptamer and nonamer elements. Despite the central role of the PC in V(D)J recombination, little is understood about its structure. Here, we use fluorescence resonance energy transfer to investigate the architecture of the 23RSS in the PC. Energy transfer was detected in 23RSS substrates in which the donor and acceptor fluorophores flanked the entire RSS, and was optimal under conditions that yield a cleavage-competent PC. The data are most easily explained by a dramatic bend in the 23RSS that reduces the distance between these flanking regions from >160 Å in the linear substrate to <80 Å in the PC. Analysis of multiple fluorescent substrates together with molecular dynamics modeling yielded a model in which the 23RSS adopts a U shape in the PC, with the spacer located centrally within the bend. We propose that this large bend facilitates simultaneous recognition of the heptamer and nonamer, is critical for proper positioning of the active site and contributes to the 12/23 rule.

  7. Novel recombinant sapovirus in Bangladesh.

    Science.gov (United States)

    Dey, Shuvra Kanti; Mizuguchi, Masashi; Okitsu, Shoko; Ushijima, Hiroshi

    2011-01-01

    Recombination of RNA viruses plays an important part in molecular epidemiological study, virus evolution, vaccine design, and viral control programs. Sapovirus, a member of the family Caliciviridae, is one of the major causative agents of viral gastroenteritis affecting all age groups. Sapovirus capsid and polymerase regions were amplified by PCR using specific primers. PCR products were sequenced directly and sequence analysis was performed using CLUSTAL X, SimPlot, and MEGA 4 software package. Based on the genetic analysis, a novel, naturally occurring recombinant sapovirus strain was identified in Bangladesh. Breakpoint analysis of the recombinant sapovirus showed that the recombination site was at the open reading frame ORF1/ORF2 overlap. We described the genetic characterization of a novel, naturally occurring recombinant sapovirus and provided the first evidence of recombination in sapovirus in Bangladesh.

  8. Crowd dynamics evacuations: The roles of shape optimization and real-time computational models. Comment on "Human behaviours in evacuation crowd dynamics: From modelling to "big data" toward crisis management" by Nicola Bellomo et al.

    Science.gov (United States)

    Delle Monache, Maria Laura

    2016-09-01

    This paper focuses on mathematical models for crowd dynamics in real life situations for support to decision making in critical situations. It deals with the modeling and the computations in the light of improving safety and pedestrians behavior.

  9. The Thermal Sunyaev-Zeldovich Effect of Primordial Recombination Radiation

    CERN Document Server

    Kholupenko, E E; Ivanchik, A V; Varshalovich, D A

    2014-01-01

    It is well known that recombination radiation of primordial hydrogen-helium plasma leads to the distortions of the planckian spectrum shape of the cosmic microwave background radiation (CMB). We discuss the thermal Sunayev-Zeldovich (SZ) effect with taking into account primordial recombination radiation (PRR). Since in the thermal SZ effect the redistribution of the photons depends on the derivatives of the spectrum, the value of relative correction to SZ effect due to PRR significantly higher than relative corrections due to PRR in the initial spectrum. Calculations of corrections to the thermal SZ effect due to PRR show that depending on the cluster parameters: 1) in the range of frequencies $\

  10. Development of shape memory polyurethane fiber with complete shape recoverability

    Science.gov (United States)

    Zhu, Yong; Hu, Jinlian; Yeung, Lap-Yan; Liu, Yan; Ji, Fenglong; Yeung, Kwok-wing

    2006-10-01

    To illustrate the shape memory properties of shape memory polyurethane (SMPU) fiber and the difference of thermal/mechanical properties between SMPU fiber and other various man-made fibers, series of shape memory polyurethane having various hard segment content were synthesized with the pre-polymerization method and spun with the wet spinning process. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and mechanical testing were conducted to study the particular thermal/mechanical properties of shape memory polyurethane fiber in comparison with other man-made fibers such as nylon6, polyester, Lycra and XLA. In addition, in the preparation of shape memory polyurethane fiber, the effect of thermal setting temperature was systematically investigated by mechanical properties testing, DMA and cyclic tensile testing, suggesting that the thermal setting temperature has a huge influence on the mechanical properties and shape memory property due to the elimination of internal stress. Thermal setting with a higher temperature will give rise to a lower tensile modulus and tenacity and a higher elongation ratio at break. Through employing the optimal thermal setting treatment, the complete heating responsive recovery in SMPU fiber can be achieved because of the counteracting effect of the irreversible strain and thermal shrinkage.

  11. RNA structures, genomic organization and selection of recombinant HIV.

    Science.gov (United States)

    Simon-Loriere, Etienne; Rossolillo, Paola; Negroni, Matteo

    2011-01-01

    Recombination is an evolutionary mechanism intrinsic to the evolution of many RNA viruses. In retroviruses and notably in the case of HIV, recombination is so frequent that it can be considered as part of its mode of replication. This process not only plays a central role in shaping HIV genetic diversity worldwide, but has also been involved in immune escape and development of resistance to antiviral treatments. Recombination does not create new mutations in the existing genetic repertoire of the virus, but creates new combinations of pre-existing polymorphisms. The simultaneous insertion of multiple substitutions in a single replication cycle leaves little room for the progressive coevolution of regions of proteins, RNA or, more in general, genomes, to accommodate these drastic sequence changes. Therefore, recombination, while allowing the virus to rapidly explore larger sequence space than the slow accumulation of point mutations, also runs the risk of generating non functional viruses. Recombination is the consequence of a switch in the template used during reverse transcription and is promoted by the presence of structured regions in the genomic RNA template. In this review, we discuss new observations suggesting that the distribution of RNA structures along the HIV genome may enhance recombination rates in regions where the resultant progeny is less likely to be impaired, and could therefore maximize the evolutionary value of this source of genetic diversity.

  12. 杆式应变天平变负载动态建模和分段动态补偿%Dynamic modeling and staged compensation of bar-shaped strain gauge balance with changing load

    Institute of Scientific and Technical Information of China (English)

    周全; 徐科军; 杨双龙

    2012-01-01

    杆式应变天平安装在飞行器模型中,用于测量飞行器模型在风洞实验中所受的空气动力和力矩.模型相当于天平的负载.为了研究负载对天平动态特性的影响,通过改变天平上的配重砝码质量,进行不同负载下的天平动态标定实验.采用OE模型描述在不同负载下,天平各通道的数学模型.根据模型得到动态特征参数.通过曲线拟合,表示天平特征参数与负载质量之间的变化规律.为了保证在不同负载下,天平均具有较好的动态响应性能,提出依据负载变化的分段动态补偿的思路,实现对不同负载实验数据的动态补偿,取得较好效果.%In the wind tunnel experiment, bar-shaped strain gauge balance installed in aircraft model is used to measure the aerodynamic forces and moments applied to the aircraft model. The aircraft model can be regarded as the load of the balance. In order to research the effect of load on the dynamic characteristic of the balance, the dynamic calibration experiments are conducted with different loads that are realized by changing weights. The system identification method based on output error model is adopted to describe the dynamic mathematical models for various channels of the balance with different loads. Their dynamic characteristic parameters are obtained according to the models. The curve fitting method is used to present the varying pattern between the characteristic parameters of the balance and the mass of loads. A kind of staged dynamic compensation solution is proposed to ensure good dynamic response performance under different loads. It implements the dynamic compensation for experimental data of different loads, and achieves good results.

  13. Expression of recombinant antibodies.

    Science.gov (United States)

    Frenzel, André; Hust, Michael; Schirrmann, Thomas

    2013-01-01

    Recombinant antibodies are highly specific detection probes in research, diagnostics, and have emerged over the last two decades as the fastest growing class of therapeutic proteins. Antibody generation has been dramatically accelerated by in vitro selection systems, particularly phage display. An increasing variety of recombinant production systems have been developed, ranging from Gram-negative and positive bacteria, yeasts and filamentous fungi, insect cell lines, mammalian cells to transgenic plants and animals. Currently, almost all therapeutic antibodies are still produced in mammalian cell lines in order to reduce the risk of immunogenicity due to altered, non-human glycosylation patterns. However, recent developments of glycosylation-engineered yeast, insect cell lines, and transgenic plants are promising to obtain antibodies with "human-like" post-translational modifications. Furthermore, smaller antibody fragments including bispecific antibodies without any glycosylation are successfully produced in bacteria and have advanced to clinical testing. The first therapeutic antibody products from a non-mammalian source can be expected in coming next years. In this review, we focus on current antibody production systems including their usability for different applications.

  14. Dissociative recombination of HCl+

    Science.gov (United States)

    Larson, Åsa; Fonseca dos Santos, Samantha; E. Orel, Ann

    2017-08-01

    The dissociative recombination of HCl+, including both the direct and indirect mechanisms, is studied. For the direct process, the relevant electronic states are calculated ab initio by combining electron scattering calculations to obtain resonance positions and autoionization widths with multi-reference configuration interaction calculations of the ion and Rydberg states. The cross section for the direct dissociation along electronic resonant states is computed by solution of the time-dependent Schrödinger equation. For the indirect process, an upper bound value for the cross section is obtained using a vibrational frame transformation of the elements of the scattering matrix at energies just above the ionization threshold. Vibrational excitations of the ionic core from the ground vibrational state, v = 0 , to the first three excited vibrational states, v = 1 , v = 2 , and v = 3 , are considered. Autoionization is neglected and the effect of the spin-orbit splitting of the ionic potential energy upon the indirect dissociative recombination cross section is considered. The calculated cross sections are compared to measurements.

  15. Dynamical analysis of the complex radio structure in 3C 293: Clues on a rapid jet realignment in X-shaped radio galaxies

    CERN Document Server

    Machalski, J; Stawarz, L; Wezgowiec, M

    2016-01-01

    Radio galaxies classified as X-shaped/winged, are characterised by two pairs of extended and misaligned lobes, which suggest a rapid realignment of the jet axis, for which a potential cause is still under debate. Here we analyse the complex radio structure of 3C 293 winged source hosted by the post-merger galaxy, which uniquely displays a significant asymmetry between the sizes of the two pairs of lobes, indicating that an episode of jet realignment took place only very recently. Based on all the available radio data for 3C 293, we have performed a detailed spectral modelling for the older and younger lobes in the system. In this way we derived the lobes' ages and jet energetics, which we then compared to the accretion power in the source. We found that the 200 kpc-scale outer lobes of 3C 293 are ~60 Myr old and that jet activity related to the formation of the outer lobes ceased within the last Myr. Meanwhile, the inner 4 kpc-scale lobes, tilted by ~40 deg with respect to the outer ones, are only about ~0.3 ...

  16. The relationship of recombination rate, genome structure, and patterns of molecular evolution across angiosperms.

    Science.gov (United States)

    Tiley, George P; Burleigh, J Gordon; Burleigh, Gordon

    2015-09-16

    population size, they suggest that global recombination rates may play an important role in shaping the macroevolutionary patterns of gene and genome evolution in plants. Interspecific recombination rate variation is tightly correlated with genome size as well as variation in overall LTR retrotransposon abundances. Recombination may shape gene-to-gene variation in dN/dS between species, which might impact the overall gene duplication and loss rates.

  17. Shape and strength of dynamical couplings between vibrational levels of the H2 +, HD+ and D2 + molecular ions in collision with He as a buffer gas

    Science.gov (United States)

    Iskandarov, Ibrokhim; Gianturco, Francesco Antonio; Vera, Mario Hernandez; Wester, Roland; da Silva, Humberto; Dulieu, Olivier

    2017-06-01

    We present a detailed computational analysis for the interaction between the vibrating/rotating molecular ions H2 +, HD+, D2 + colliding with He atoms employed as buffer gas within ion trap experiments. The production and preparation of these molecular ions from their neutrals usually generate rovibrationally excited species which will therefore require internal energy cooling down to their ground vibrational levels for further experimental handling. In this work we describe the calculation of the full 3D interaction potentials and of the ionic vibrational levels needed to obtain the vibrational coupling potential matrix elements which are needed in the multichannel treatment of the rovibrationally inelastic collision dynamics. The general features of such coupling potential terms are discussed for their employment within a quantum dynamical modeling of the relaxation processes, as well as in connection with their dependence on the initial and final vibrational levels which are directly coupled by the present potentials. As a preliminary test of the potential effects on scattering observables, we perform calculations between H2 + and He atoms at the energies of an ion-trap by using either the rigid rotor (RR) approximation or the more accurate vibrationally averaged (VA) description for the v = 0 state of the target. Both schemes are described in detail in the present paper and the differences found in the scattering results are also analysed and discussed. We further present and briefly discuss some examples of state-to-state rovibrationally inelastic cross sections, involving the two lowest vibrational levels of the H2 + molecular target ion, as obtained from our time-independent multichannel quantum scattering code.

  18. Effects of IGF-binding protein 5 in dysregulating the shape of human hair.

    Science.gov (United States)

    Sriwiriyanont, Penkanok; Hachiya, Akira; Pickens, William L; Moriwaki, Shigeru; Kitahara, Takashi; Visscher, Marty O; Kitzmiller, William J; Bello, Alexander; Takema, Yoshinori; Kobinger, Gary P

    2011-02-01

    The hair follicle has a unique dynamic property to cyclically regenerate throughout life. Despite significant progress in hair structure and hair shape determination using animal models, the mechanisms controlling the architecture and the shape of the human hair remain largely unexplored. In this study, comparison of the genetic expression of several human genes, especially those involved in growth, development, and differentiation, between Caucasian curly hair and naturally straight hair was performed. Thereafter, analyses using human recombinant and lentiviral vector technologies were conducted to further dissect and elucidate a molecular mechanism that regulates hair growth and development, particularly in controlling the shape of the hair shaft. Overexpression of IGF-binding protein 5 (IGFBP-5) in the human hair xenografts obtained from straight- and curly-haired individuals was found to result in the decreased expression of several extracellular matrix proteins and disassembly of adhesional junctions, resulting in twisted hair shafts as well as an unusual deposition of hair cuticle that may be derived from the disturbance of normal proliferation and differentiation. This study provides evidence that IGFBP-5 has an effect on human hair shape, and that lentiviral transduction regimen can be used for functional analysis of genes involved in human hair morphogenesis.

  19. Asymmetric recombination and electron spin relaxation in the semiclassical theory of radical pair reactions

    CERN Document Server

    Lewis, Alan M; Hore, P J

    2014-01-01

    We describe how the semiclassical theory of radical pair recombination reactions recently introduced by two of us [D. E. Manolopoulos and P. J. Hore, J. Chem. Phys. 139, 124106 (2013)] can be generalised to allow for different singlet and triplet recombination rates. This is a non-trivial generalisation because when the recombination rates are different the recombination process is dynamically coupled to the coherent electron spin dynamics of the radical pair. Furthermore, because the recombination operator is a two-electron operator, it is no longer sufficient simply to consider the two electrons as classical vectors: one has to consider the complete set of 16 two-electron spin operators as independent classical variables. The resulting semiclassical theory is first validated by comparison with exact quantum mechanical results for a model radical pair containing 12 nuclear spins. It is then used to shed light on the spin dynamics of a carotenoid-porphyrin-fullerene (CPF) triad containing considerably more nu...

  20. Probabilistic contour extraction based on shape prior model

    Institute of Scientific and Technical Information of China (English)

    FAN Xin; LIANG De-qun

    2005-01-01

    Statistical shape prior model is employed to construct the dynamics in probabilistic contour estimation.By applying principal component analysis,plausible shape samples are efficiently generated to predict contour samples.Based on the shape-dependent dynamics and probabilistic image model,a particle filter is used to estimate the contour with a specific shape.Compared with the deterministic approach with shape information,the proposed method is simple yet more effective in extracting contours from images with shape variations and occlusion.

  1. 基于形状外观关联映射的动态脸部纹理生成%Dynamic Facial Texture Generation Based on Shape-Appearance Dependence Mapping Strategy

    Institute of Scientific and Technical Information of China (English)

    杜杨洲; 林学訚

    2004-01-01

    The subtle details on an expressional face,such as creases and furrows,are very important visual cues,but they are difficult to model and synthesize as they vary dynamically from one frame to another while people speak and make expression.A novel strategy,which is different from the traditional texture mapping methods,is proposed for generating such a kind of dynamic facial textures according to the motion of facial feature points.Based on the observation that shape and appearance on face images are highly correlated,a mapping is designed to transfer one image to the other.The mapping is called SADM(shape-appearance dependence mapping).The experimental results show that the synthesized faces with SADM are very close to the real ones.The proposed SADM strategy can be integrated into a wire-frame based head model to generate the realistic animation effects,or applied to a model-based video coding to produce more efficient bit-rates.%脸部表情的变化细节(例如皱纹)是很重要的视觉线索,但是它们难以建模与合成.这是由于人们说话和作表情时,脸部纹理也在动态地改变.与传统的纹理映射方法不同,提出一种根据脸部特征点运动来生成脸部动态纹理的新方法.基于形状和外观在表情脸部图像上高度相关这个观察,设计建立了从形状到外观的映射关系.这个映射被称作"形状外观的关联映射(shape-appearance dependence mapping,简称SADM)".实验结果表明用,SADM合成出的人脸与真实的人脸十分近似.提出的SADM方法可以集成到基于线框模型的人头模型中产生真实的动画效果,也可以应用于基于模型的视频编码来进一步节省传输带宽.

  2. Shape-memory polymers

    Directory of Open Access Journals (Sweden)

    Marc Behl

    2007-04-01

    Full Text Available Shape-memory polymers are an emerging class of active polymers that have dual-shape capability. They can change their shape in a predefined way from shape A to shape B when exposed to an appropriate stimulus. While shape B is given by the initial processing step, shape A is determined by applying a process called programming. We review fundamental aspects of the molecular design of suitable polymer architectures, tailored programming and recovery processes, and the quantification of the shape-memory effect. Shape-memory research was initially founded on the thermally induced dual-shape effect. This concept has been extended to other stimuli by either indirect thermal actuation or direct actuation by addressing stimuli-sensitive groups on the molecular level. Finally, polymers are introduced that can be multifunctional. Besides their dual-shape capability, these active materials are biofunctional or biodegradable. Potential applications for such materials as active medical devices are highlighted.

  3. RECOMBINANT HORSERADISH PEROXIDASE FOR ANALYTICAL APPLICATIONS

    OpenAIRE

    2013-01-01

    The article deals with prospects of using recombinant horseradish peroxidase in analytical biochemistry and biotechnology. Problems of recombinant horseradish peroxidase cloning in different expression systems, possible approaches to their solution, advantages of recombinant recombinant horseradish peroxidase and recombinant horseradish peroxidase-fusion proteins for immunoassays are considered. Possibility for development of mediatorless bienzyme biosensor for peroxide and metabolites, yield...

  4. Recurrent partial mortality events in winter shape the dynamics of the zooxanthellate coral Oculina patagonica at high latitude in the Mediterranean

    Science.gov (United States)

    Serrano, Eduard; Ribes, Marta; Coma, Rafel

    2017-03-01

    Global warming has many biological effects on corals and plays a central role in the regression of tropical coral reefs; therefore, there is an urgent need to understand how some coral species have adapted to environmental conditions at higher latitudes. We examined the effects of temperature and light on the growth of the zooxanthellate coral Oculina patagonica (Scleractinia, Oculinidae) at the northern limit of its distribution in the eastern Iberian Peninsula (western Mediterranean) by transplanting colonies onto plates and excluding them from space competition over a 4-yr period. Each year, most of the colonies ( 70%) exhibited denuded skeletons with isolated polyps persisting on approximately half of the coral surface area. These recurrent episodes of partial coral mortality occurred in winter, and their severity appeared to be related to colony exposure to cold but not to light. Although O. patagonica exhibited high resistance to stress, coral linear extension did not resume until the coenosarc regenerated. The resumption of linear extension was related to the dissociation of the polyps from the coenosarc and the outstanding regenerative capacity of this species (10.3 mm2 d-1). These biological characteristics allow the species to survive at high latitudes. However, the recurrent and severe pattern of denuded skeletons greatly affects the dynamics of the species and may constrain population growth at high latitudes in the Mediterranean.

  5. Replication and recombination factors contributing to recombination-dependent bypass of DNA lesions by template switch.

    Directory of Open Access Journals (Sweden)

    Fabio Vanoli

    2010-11-01

    Full Text Available Damage tolerance mechanisms mediating damage-bypass and gap-filling are crucial for genome integrity. A major damage tolerance pathway involves recombination and is referred to as template switch. Template switch intermediates were visualized by 2D gel electrophoresis in the proximity of replication forks as X-shaped structures involving sister chromatid junctions. The homologous recombination factor Rad51 is required for the formation/stabilization of these intermediates, but its mode of action remains to be investigated. By using a combination of genetic and physical approaches, we show that the homologous recombination factors Rad55 and Rad57, but not Rad59, are required for the formation of template switch intermediates. The replication-proficient but recombination-defective rfa1-t11 mutant is normal in triggering a checkpoint response following DNA damage but is impaired in X-structure formation. The Exo1 nuclease also has stimulatory roles in this process. The checkpoint kinase, Rad53, is required for X-molecule formation and phosphorylates Rad55 robustly in response to DNA damage. Although Rad55 phosphorylation is thought to activate recombinational repair under conditions of genotoxic stress, we find that Rad55 phosphomutants do not affect the efficiency of X-molecule formation. We also examined the DNA polymerase implicated in the DNA synthesis step of template switch. Deficiencies in translesion synthesis polymerases do not affect X-molecule formation, whereas DNA polymerase δ, required also for bulk DNA synthesis, plays an important role. Our data indicate that a subset of homologous recombination factors, together with DNA polymerase δ, promote the formation of template switch intermediates that are then preferentially dissolved by the action of the Sgs1 helicase in association with the Top3 topoisomerase rather than resolved by Holliday Junction nucleases. Our results allow us to propose the choreography through which different

  6. Shape-Shifting Droplet Networks

    Science.gov (United States)

    Zhang, T.; Wan, Duanduan; Schwarz, J. M.; Bowick, M. J.

    2016-03-01

    We consider a three-dimensional network of aqueous droplets joined by single lipid bilayers to form a cohesive, tissuelike material. The droplets in these networks can be programed to have distinct osmolarities so that osmotic gradients generate internal stresses via local fluid flows to cause the network to change shape. We discover, using molecular dynamics simulations, a reversible folding-unfolding process by adding an osmotic interaction with the surrounding environment which necessarily evolves dynamically as the shape of the network changes. This discovery is the next important step towards osmotic robotics in this system. We also explore analytically and numerically how the networks become faceted via buckling and how quasi-one-dimensional networks become three dimensional.

  7. Biomechanic comparision between the "U" shape lumbar dynamic fixation system and traditional fixation system%腰椎弹性内固定与刚性内固定的应力对比研究

    Institute of Scientific and Technical Information of China (English)

    于博; 靳安民; 方国芳; 闵少雄; 刘成龙; 田京; 敖俊

    2009-01-01

    目的:通过有限元的方法评价自行研制的腰椎"U"型弹性内固定器的力学特性,并与传统的刚性内固定器进行比较.方法:选择一名成年患者腰椎标本,以L4~5节段为研究对象,采用64排螺旋CT对其进行层厚1.0 mm的连续水平扫描,将所得图像进行轮廓提取和阈值分割后,借助三维重建软件Mimics11.1、Simpleware和有限元软件Abaqus 6.51软件,建立L4~5节段三维非线性有限元模型.同时根据椎弓根螺钉、连接棒的几何尺寸,力学参数,分别建立两种不同内固定器的有限元模型.然后分别施加压缩、前屈、后伸、侧屈及旋转等各种生理载荷,观察各模型不同载荷下螺钉、连接棒的应力分布.结果:两种内固定器的椎弓根螺钉前、中部的应力差异无统计学意义(P>0.05);刚性固定的椎弓根螺钉与棒连接处是应立集中的部位,该部位的应力远大于弹性固定器,而弹性内固定应力集中的部位均匀的分布于整个U型连接棒上,两模型固定节段螺钉及棒的最大有效应力均出现于前屈时.结论:在加载相同的纵向载荷条件下,刚性内固定器应力主要集中在螺钉与棒交界处,容易易发生螺钉断裂,U型弹性内固定器的应力均匀分布在U型连接棒上,可以减少断钉的现象发生.%Objective: To compare biomechanical features between the new "U" shape lumbar dynamic fixation system and traditional rigid fixation system. Methods: Finite element analysis of the two fixation systems were performed on the basis of a three-dimensional model reconstructed from the images of CT scanning of an adult cadaveric lumbar with the interval of 1 mm. The stress and displacement of every nodule and element in the course of deformation of the internal fixation were tested and analyzed. Results: In the same shearing load of 500 N,The force of the dynamic fixation system concentrated on the "U" shape elastic zone,however,the force of the rigid

  8. Reinforced Airfoil Shaped Body

    DEFF Research Database (Denmark)

    2011-01-01

    The present invention relates to an airfoil shaped body with a leading edge and a trailing edge extending along the longitudinal extension of the body and defining a profile chord, the airfoil shaped body comprising an airfoil shaped facing that forms the outer surface of the airfoil shaped body...

  9. Discriminative Shape Alignment

    DEFF Research Database (Denmark)

    Loog, M.; de Bruijne, M.

    2009-01-01

    The alignment of shape data to a common mean before its subsequent processing is an ubiquitous step within the area shape analysis. Current approaches to shape analysis or, as more specifically considered in this work, shape classification perform the alignment in a fully unsupervised way......, not taking into account that eventually the shapes are to be assigned to two or more different classes. This work introduces a discriminative variation to well-known Procrustes alignment and demonstrates its benefit over this classical method in shape classification tasks. The focus is on two......-dimensional shapes from a two-class recognition problem....

  10. Shape memory polymers

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, Thomas S.; Bearinger, Jane P.

    2017-08-29

    New shape memory polymer compositions, methods for synthesizing new shape memory polymers, and apparatus comprising an actuator and a shape memory polymer wherein the shape memory polymer comprises at least a portion of the actuator. A shape memory polymer comprising a polymer composition which physically forms a network structure wherein the polymer composition has shape-memory behavior and can be formed into a permanent primary shape, re-formed into a stable secondary shape, and controllably actuated to recover the permanent primary shape. Polymers have optimal aliphatic network structures due to minimization of dangling chains by using monomers that are symmetrical and that have matching amine and hydroxl groups providing polymers and polymer foams with clarity, tight (narrow temperature range) single transitions, and high shape recovery and recovery force that are especially useful for implanting in the human body.

  11. Shape memory polymers

    Science.gov (United States)

    Wilson, Thomas S.; Bearinger, Jane P.

    2015-06-09

    New shape memory polymer compositions, methods for synthesizing new shape memory polymers, and apparatus comprising an actuator and a shape memory polymer wherein the shape memory polymer comprises at least a portion of the actuator. A shape memory polymer comprising a polymer composition which physically forms a network structure wherein the polymer composition has shape-memory behavior and can be formed into a permanent primary shape, re-formed into a stable secondary shape, and controllably actuated to recover the permanent primary shape. Polymers have optimal aliphatic network structures due to minimization of dangling chains by using monomers that are symmetrical and that have matching amine and hydroxyl groups providing polymers and polymer foams with clarity, tight (narrow temperature range) single transitions, and high shape recovery and recovery force that are especially useful for implanting in the human body.

  12. Analysis of interchromosomal mitotic recombination.

    Science.gov (United States)

    McGill, C B; Shafer, B K; Higgins, D R; Strathern, J N

    1990-07-01

    A novel synthetic locus is described that provides a simple assay system for characterizing mitotic recombinants. The locus consists of the TRP1 and HIS3 genes inserted into chromosome III of S. cerevisiae between the CRY1 and MAT loci. Defined trp1 and his3 alleles have been generated that allow the selection of interchromosomal recombinants in this interval. Trp+ or His+ recombinants can be divided into several classes based on coupling of the other alleles in the interval. The tight linkage of the CRY1 and MAT loci, combined with the drug resistance and cell type phenotypes that they respectively control, facilitates the classification of the recombinants without resorting to tetrad dissection. We present the distribution of spontaneous recombinants among the classes defined by this analysis. The data suggest that the recombination intermediate can have regions of symmetric strand exchange and that co-conversion tracts can extend over 1-3 kb. Continuous conversion tracts are favored over discontinuous tracts. The distribution among the classes defined by this analysis is altered in recombinants induced by UV irradiation.

  13. Recombinant human DNase in children with airway malacia and lower respiratory tract infection.

    NARCIS (Netherlands)

    Boogaard, R.; Jongste, J.C. de; Vaessen-Verberne, A.A.; Hop, W.C.J.; Merkus, P.J.F.M.

    2009-01-01

    BACKGROUND: Children with airway malacia often have protracted courses of airway infections, because dynamic airway collapse during coughing results in impaired mucociliary clearance. The aim of this study was to determine the effect of the mucolytic drug recombinant human deoxyribonuclease

  14. Testing for recombinant erythropoietin.

    Science.gov (United States)

    Delanghe, Joris R; Bollen, Mathieu; Beullens, Monique

    2008-03-01

    Erythropoietin (Epo) is a glycoprotein hormone that promotes the production of red blood cells. Recombinant human Epo (rhEpo) is illicitly used to improve performance in endurance sports. Doping in sports is discouraged by the screening of athletes for rhEpo. Both direct tests (indicating the presence of exogeneous Epo isoforms) and indirect tests (indicating hematological changes induced by exogenous Epo administration) can be used for Epo detection. At present, the test adopted by the World Anti Doping Agency is based on a combination of isoelectric focusing and double immunoblotting, and distinguishes between endogenous and rhEpo. However, the adopted monoclonal anti-Epo antibodies are not monospecific. Therefore, the test can occasionally lead to the false-positive detection of rhEpo (epoetin-beta) in post-exercise, protein-rich urine, or in case of contamination of the sample with microorganisms. An improved preanalytical care may counteract a lot of these problems. Adaptation of the criteria may be helpful to further refine direct Epo testing. Indirect tests have the disadvantage that they require blood instead of urine samples, but they can be applied to detect a broader range of performance improving techniques which are illicitly used in sports.

  15. The Richness and Beauty of the Physics of Cosmological Recombination

    Science.gov (United States)

    Sunyaev, Rashid

    2009-01-01

    In our Universe the initial temperature of radiation was very high and hydrogen and helium were completely ionized. At redshifts z 1400 the temperature dropped to 3800 K and, according to the Saha equation, the recombination of hydrogen should occur. In reality this process is strongly delayed and some frozen amount of electrons should be present till the reionization of the Universe at z 10. Process of recombination defines the position and the width of the last scattering surface which is crucial for the formation of the observed angular fluctuations of cosmic microwave background radiation (CMB), acoustic peaks and barionic oscillations in the distribution of galaxies and clusters of galaxies in space. The recombination of hydrogen occurs under conditions of very low density and in the presence of black body radiation. As a result, usually insignificant atomic processes begin to play a role. They influence the shape of acoustic peaks at a level which will be detectable by the Planck Surveyor spacecraft and we should take them into account when estimating the key parameters of the Universe from CMB data. The recombination of hydrogen and helium leads to the appearance of recombinational lines in centimeter and decimeter spectral bands. Observations of these lines will make it possible to check the predictions of the big bang recombination theory and will open a possibility to measure directly the density of barions, the CMB monopole temperature and specific entropy of the Universe. Observations of helium recombination lines originated at redshifts 6000 and 2500 will open a way to measure the prestellar abundance of helium in the Universe.

  16. Genetic diversity of MHC class I loci in six non-model frogs is shaped by positive selection and gene duplication

    Science.gov (United States)

    Kiemnec-Tyburczy, K M; Richmond, J Q; Savage, A E; Lips, K R; Zamudio, K R

    2012-01-01

    Comparative studies of major histocompatibility complex (MHC) genes across vertebrate species can reveal the evolutionary processes that shape the structure and function of immune regulatory proteins. In this study, we characterized MHC class I sequences from six frog species representing three anuran families (Hylidae, Centrolenidae and Ranidae). Using cDNA from our focal species, we amplified a total of 79 unique sequences spanning exons 2–4 that encode the extracellular domains of the functional alpha chain protein. We compared intra- and interspecific nucleotide and amino-acid divergence, tested for recombination, and identified codon sites under selection by estimating the rate of non-synonymous to synonymous substitutions with multiple codon-based maximum likelihood methods. We determined that positive (diversifying) selection was acting on specific amino-acid sites located within the domains that bind pathogen-derived peptides. We also found significant signals of recombination across the physical distance of the genes. Finally, we determined that all the six species expressed two or three putative classical class I loci, in contrast to the single locus condition of Xenopus laevis. Our results suggest that MHC evolution in anurans is a dynamic process and that variation in numbers of loci and genetic diversity can exist among taxa. Thus, the accumulation of genetic data for more species will be useful in further characterizing the relative importance of processes such as selection, recombination and gene duplication in shaping MHC loci among amphibian lineages. PMID:22549517

  17. Controlled release from recombinant polymers.

    Science.gov (United States)

    Price, Robert; Poursaid, Azadeh; Ghandehari, Hamidreza

    2014-09-28

    Recombinant polymers provide a high degree of molecular definition for correlating structure with function in controlled release. The wide array of amino acids available as building blocks for these materials lend many advantages including biorecognition, biodegradability, potential biocompatibility, and control over mechanical properties among other attributes. Genetic engineering and DNA manipulation techniques enable the optimization of structure for precise control over spatial and temporal release. Unlike the majority of chemical synthetic strategies used, recombinant DNA technology has allowed for the production of monodisperse polymers with specifically defined sequences. Several classes of recombinant polymers have been used for controlled drug delivery. These include, but are not limited to, elastin-like, silk-like, and silk-elastinlike proteins, as well as emerging cationic polymers for gene delivery. In this article, progress and prospects of recombinant polymers used in controlled release will be reviewed.

  18. Cell encoding recombinant human erythropoietin

    Energy Technology Data Exchange (ETDEWEB)

    Beck, A.K.; Withy, R.M.; Zabrecky, J.R.; Masiello, N.C.

    1990-09-04

    This patent describes a C127 cell transformed with a recombinant DNA vector. It comprises: a DNA sequence encoding human erythropoietin, the transformed cell being capable of producing N-linked and O-linked glycosylated human erythropoietin.

  19. Influenza Vaccine, Inactivated or Recombinant

    Science.gov (United States)

    ... die from flu, and many more are hospitalized.Flu vaccine can:keep you from getting flu, make flu ... inactivated or recombinant influenza vaccine?A dose of flu vaccine is recommended every flu season. Children 6 months ...

  20. Three Decades of Recombinant DNA.

    Science.gov (United States)

    Palmer, Jackie

    1985-01-01

    Discusses highlights in the development of genetic engineering, examining techniques with recombinant DNA, legal and ethical issues, GenBank (a national database of nucleic acid sequences), and other topics. (JN)

  1. Perovskite photovoltaics: Slow recombination unveiled

    Science.gov (United States)

    Moser, Jacques-E.

    2017-01-01

    One of the most salient features of hybrid lead halide perovskites is the extended lifetime of their photogenerated charge carriers. This property has now been shown experimentally to originate from a slow, thermally activated recombination process.

  2. Inhomogeneous recombinations during cosmic reionization

    OpenAIRE

    Sobacchi, Emanuele; Mesinger, Andrei

    2014-01-01

    By depleting the ionizing photon budget available to expand cosmic HII regions, recombining systems (or Lyman limit systems) can have a large impact during (and following) cosmic reionization. Unfortunately, directly resolving such structures in large-scale reionization simulations is computationally impractical. Instead, here we implement a sub-grid prescription for tracking inhomogeneous recombinations in the intergalactic medium. Building on previous work parameterizing photo-heating feedb...

  3. Plasmid recombination in Haemophilus influenzae

    Energy Technology Data Exchange (ETDEWEB)

    McCarthy, D.

    1982-01-01

    DNA recombination in exponential phase and competent Haemophilus influenzae was measured by an electron microscopic assay that relies on the conversion of plasmid RSF0885 monomers into multimeric forms. Dimer circles were present at a frequency of 2% in plasmid preparations from competent Rd (wild-type) cells; multimers were present at a frequency of 0.2% in preparations from exponential phase cells. Thus, plasmid recombination was stimulated in competent cells. Multimer formation occurred efficiently in cells of the transformation defective mutant rec2, implying that the rec2 gene product is not required for plasmid recombination. However, the absence of multimer plasmids in preparations from competent cells of the transformation defective mutant rec1 suggests that the rec1 gene product is required. Digestion of purified plasmids with restriction endonuclease PvuII, which makes a single cut in the monomer, revealed the presence of recombination intermediates composed of two linear plasmids joined to form two pairs of arms resembling the Greek letter chi. Length measurements of these arms taken from a population of recombination intermediates gave evidence that the plasmids were joined at sites of homology. The distributions of individual DNA strands, at the intersections of the four arms, could be resolved in some recombination intermediates and were of two types. The first type of junction appeared as a single-stranded arm appended to each corner. The second type of junction consisted of a single strand of DNA linking the two linear plasmids at a site of homology. The single-stranded linker was frequently situated at the edge of a short gap on one of the plasmids in the pair. The fine structures of the recombinational joints have been interpreted in terms of previously proposed models of recombination.

  4. Heterogeneity in recombinant protein production

    DEFF Research Database (Denmark)

    Schalén, Martin; Johanson, Ted; Lundin, Luisa;

    2012-01-01

    contribute to make a population in a fermenter heterogeneous, resulting in cell-to-cell variation in physiological parameters of the microbial culture. Our study aims at investigating how population heterogeneity and recombinant protein production is affected by environmental gradients in bioreactors...... are simulated in small bioreactors and the population heterogeneity can be visualised by analysing single cells with flow cytometry. This can give new insights to cell physiology and recombinant protein production at the industrial scale....

  5. Recombinant protein expression in Nicotiana.

    Science.gov (United States)

    Matoba, Nobuyuki; Davis, Keith R; Palmer, Kenneth E

    2011-01-01

    Recombinant protein pharmaceuticals are now widely used in treatment of chronic diseases, and several recombinant protein subunit vaccines are approved for human and veterinary use. With growing demand for complex protein pharmaceuticals, such as monoclonal antibodies, manufacturing capacity is becoming limited. There is increasing need for safe, scalable, and economical alternatives to mammalian cell culture-based manufacturing systems, which require substantial capital investment for new manufacturing facilities. Since a seminal paper reporting immunoglobulin expression in transgenic plants was published in 1989, there have been many technological advances in plant expression systems to the present time where production of proteins in leaf tissues of nonfood crops such as Nicotiana species is considered a viable alternative. In particular, transient expression systems derived from recombinant plant viral vectors offer opportunities for rapid expression screening, construct optimization, and expression scale-up. Extraction of recombinant proteins from Nicotiana leaf tissues can be achieved by collection of secreted protein fractions, or from a total protein extract after grinding the leaves with buffer. After separation from solids, the major purification challenge is contamination with elements of the photosynthetic complex, which can be solved by application of a variety of facile and proven strategies. In conclusion, the technologies required for safe, efficient, scalable manufacture of recombinant proteins in Nicotiana leaf tissues have matured to the point where several products have already been tested in phase I clinical trials and will soon be followed by a rich pipeline of recombinant vaccines, microbicides, and therapeutic proteins.

  6. Self-erecting shapes

    Energy Technology Data Exchange (ETDEWEB)

    Reading, Matthew W.

    2017-07-04

    Technologies for making self-erecting structures are described herein. An exemplary self-erecting structure comprises a plurality of shape-memory members that connect two or more hub components. When forces are applied to the self-erecting structure, the shape-memory members can deform, and when the forces are removed the shape-memory members can return to their original pre-deformation shape, allowing the self-erecting structure to return to its own original shape under its own power. A shape of the self-erecting structure depends on a spatial orientation of the hub components, and a relative orientation of the shape-memory members, which in turn depends on an orientation of joining of the shape-memory members with the hub components.

  7. Shaped Recess Flow Control

    Science.gov (United States)

    Shyam, Vikram (Inventor); Poinsatte, Philip (Inventor); Thurman, Douglas (Inventor)

    2017-01-01

    One or more embodiments of techniques or systems for shaped recess flow control are provided herein. A shaped recess or cavity can be formed on a surface associated with fluid flow. The shaped recess can be configured to create or induce fluid effects, temperature effects, or shedding effects that interact with a free stream or other structures. The shaped recess can be formed at an angle to a free stream flow and may be substantially "V" shaped. The shaped recess can be coupled with a cooling channel, for example. The shaped recess can be upstream or downstream from a cooling channel and aligned in a variety of manners. Due to the fluid effects, shedding effects, and temperature effects created by a shaped recess, lift-off or separation of cooling jets of cooling channels can be mitigated, thereby enhancing film cooling effectiveness.

  8. Transforming shape in design

    DEFF Research Database (Denmark)

    Prats, Miquel; Lim, Sungwoo; Jowers, Iestyn

    2009-01-01

    This paper is concerned with how design shapes are generated and explored by means of sketching. It presents research into the way designers transform shapes from one state to another using sketch representations. An experimental investigation of the sketching processes of designers is presented....... phenomenon of ‘subshape' and suggests that a computational mechanism for detecting sub-shapes in design sketches might augment explorative sketching by providing important opportunities for manipulating and generating shape in design....

  9. What do I want to be with my PhD? The roles of personal values and structural dynamics in shaping the career interests of recent biomedical science PhD graduates.

    Science.gov (United States)

    Gibbs, Kenneth D; Griffin, Kimberly A

    2013-01-01

    Interest in faculty careers decreases as graduate training progresses; however, the process underlying career-interest formation remains poorly defined. To better understand this process and whether/how it differs across social identity (i.e., race/ethnicity, gender), we conducted focus groups with 38 biomedical scientists who received PhDs between 2006 and 2011, including 23 women and 18 individuals from underrepresented minority (URM) backgrounds. Objective performance and quality of advisor relationships were not significantly different between scientists with high versus low interest in faculty careers. Career interests were fluid and formed in environments that generally lacked structured career development. Vicarious learning shaped similar outcome expectations about academic careers for all scientists; however, women and URMs recounted additional, distinct experiences and expectations. Scientists pursuing faculty careers described personal values, which differed by social identity, as their primary driver. For scientists with low interest in faculty careers, a combination of values, shared across social identity, and structural dynamics of the biomedical workforce (e.g., job market, grant funding, postdoc pay, etc.) played determinative roles. These findings illuminate the complexity of career choice and suggest attracting the best, most diverse academic workforce requires institutional leaders and policy makers go beyond developing individual skill, attending to individuals' values and promoting institutional and systemic reforms.

  10. 螺旋 CT动态增强扫描在肺门肿瘤立体适形放射治疗中的价值%The value of spiral CT dynamically enhanced scanning in steric shape-fitting radiotherapy of hilar tumors

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Objective To judge hilar tumors and their involvement range and improve the ability for the 3D plan of steric shape- fitting radiotherapy of pulmonary cancer dicide target area.Method Spiral CT dynamically enhanced scanning was used to localize the target area and distinguish pilar tumors,atelactasis,pilar blood vessels and enlarged lymphoid tissues,and define locus and involvement area.Result Local contour showed by spiral CT enhanced dynamically scanning was superior to that by common CT.Conclusion Spiral CT dynamically enhanced scanning is an ideal simulation for 3D conformal radiotherapy.

  11. RECOMBINANT HORSERADISH PEROXIDASE FOR ANALYTICAL APPLICATIONS

    Directory of Open Access Journals (Sweden)

    А.M. Egorov

    2012-08-01

    Full Text Available The article deals with prospects of using recombinant horseradish peroxidase in analytical biochemistry and biotechnology. Problems of recombinant horseradish peroxidase cloning in different expression systems, possible approaches to their solution, advantages of recombinant recombinant horseradish peroxidase and recombinant horseradish peroxidase-fusion proteins for immunoassays are considered. Possibility for development of mediatorless bienzyme biosensor for peroxide and metabolites, yielding hydrogen peroxide during their transformations, based on co-adsorption of recombinant horseradish peroxidase and the appropriate oxidase was demonstrated. The possibility to produce a fully active recombinant conjugate of recombinant horseradish peroxidase with human heart-type fatty acid binding protein, which may be used in competitive immunoassay for clinical diagnosis of acute myocardial infarction, and recombinant conjugates (N- and C-terminus of recombinant horseradish peroxidase with Fab-fragments of the antibody against atrazine, which may be applied for atrazine pesticides detection, are demonstra ted for the first time.

  12. Radiative instabilities in plasmas: impurity motion and recombination effects

    Energy Technology Data Exchange (ETDEWEB)

    Morozov, D.K.; Herrera, J.J.E. [Instituto de Ciencias y Artes, Chiapas (Mexico). Escuela de Biologia

    1995-03-01

    Radiative instabilities in an impurity-seeded plasma are investigated when the plasma is supposed to be highly but partially ionized. Since in such plasmas radiative losses strongly depend on neutral and impurity densities, their dynamics are taken into account. As a result, a new radiative-recombination instability is found and described. We show that the influence of the ionization-recombination balance on plasma stability is sufficient for plasma densities above 10{sup 14} cm{sup -3}. The effects of a finite impurity Larmor radius are not small and play a stabilizing role as well as the thermal forces. On the other hand, compressibility of the magnetic field leads to plasma destabilization. We note that this radiative-recombination instability accumulates impurities in a cold zone while cleaning other regions. (Author).

  13. Charge recombination in CuPc/PTCDA thin films.

    Science.gov (United States)

    Heutz, S; Nogueira, A F; Durrant, J R; Jones, T S

    2005-06-16

    The recombination kinetics of photogenerated charge carriers in perylene-3, 4, 9, 10-tetracarboxylic dianhydride (PTCDA) and copper phthalocyanine (CuPc) thin films grown by organic molecular beam deposition have been studied using transient absorption spectroscopy. Optical excitation is observed to generate long-lived polaron states, which exhibit power law recombination dynamics on time scales from microseconds to milliseconds. Studies as a function of excitation density and temperature, and comparison between heterostructures and PTCDA single layers, all indicate that this power law behavior results from trapping of PTCDA- polarons in localized states, with an estimated trap state density of approximately 6 x 10(17) polarons cm(-3). This recombination behavior is found to be remarkably similar to that previously observed for polymer/fullerene blends, suggesting that it may be generic to a range of semiconducting materials.

  14. Historical perspectives pertaining to the NIH Recombinant DNA Advisory Committee.

    Science.gov (United States)

    Wivel, Nelson A

    2014-01-01

    Science is host to a constantly emerging series of new paradigms, and it is this characteristic that makes science both interesting and dynamic. As a part of this continuum, it became possible to create recombinant DNA molecules. Immediately it was recognized that there was a potential for serious adverse events associated with this new technology. Following two scientific conferences at Asilomar, California, the National Institutes of Health moved quickly to create the Recombinant DNA Advisory Committee (RAC). For approximately 38 years the RAC has served as an open forum for review of various recombinant DNA experiments, and for the last 23 years it has played a pivotal role in the oversight of human gene therapy. The RAC's existence obviated the need for more restrictive governmental legislation and has supported the development of genetic interventions that are leading to actual human therapies.

  15. Alpha Shapes and Proteins

    DEFF Research Database (Denmark)

    Winter, Pawel; Sterner, Henrik; Sterner, Peter

    2009-01-01

    We provide a unified description of (weighted) alpha shapes, beta shapes and the corresponding simplicialcomplexes. We discuss their applicability to various protein-related problems. We also discuss filtrations of alpha shapes and touch upon related persistence issues.We claim that the full...... potential of alpha-shapes and related geometrical constructs in protein-related problems yet remains to be realized and verified. We suggest parallel algorithms for (weighted) alpha shapes, and we argue that future use of filtrations and kinetic variants for larger proteins will need such implementation....

  16. Shape-changing interfaces:

    DEFF Research Database (Denmark)

    Rasmussen, Majken Kirkegård; Pedersen, Esben Warming; Petersen, Marianne Graves;

    2015-01-01

    these shortcomings. We identify eight types of shape that are transformed in various ways to serve both functional and hedonic design purposes. Interaction with shape-changing interfaces is simple and rarely merges input and output. Three questions are discussed based on the review: (a) which design purposes may......Shape change is increasingly used in physical user interfaces, both as input and output. Yet, the progress made and the key research questions for shape-changing interfaces are rarely analyzed systematically. We review a sample of existing work on shape-changing interfaces to address...

  17. Local Solid Shape

    Directory of Open Access Journals (Sweden)

    Jan Koenderink

    2015-10-01

    Full Text Available Local solid shape applies to the surface curvature of small surface patches—essentially regions of approximately constant curvatures—of volumetric objects that are smooth volumetric regions in Euclidean 3-space. This should be distinguished from local shape in pictorial space. The difference is categorical. Although local solid shape has naturally been explored in haptics, results in vision are not forthcoming. We describe a simple experiment in which observers judge shape quality and magnitude of cinematographic presentations. Without prior training, observers readily use continuous shape index and Casorati curvature scales with reasonable resolution.

  18. Interactive Shape Design

    CERN Document Server

    Cani, Marie-Paule; Wyvill, Geoff

    2008-01-01

    Providing an intuitive modeling system, which would enable us to communicate about any free-form shape we have in mind at least as quickly as with real-world tools, is one of the main challenges of digital shape design. The user should ideally be able to create, deform, and progressively add details to a shape, without being aware of the underlying mathematical representation nor being tied by any constraint on the geometrical or topological nature of the model. This book presents the field of interactive shape design from this perspective. Since interactively creating a shape builds on the hu

  19. The nature of protein domain evolution: shaping the interaction network.

    Science.gov (United States)

    Bagowski, Christoph P; Bruins, Wouter; Te Velthuis, Aartjan J W

    2010-08-01

    The proteomes that make up the collection of proteins in contemporary organisms evolved through recombination and duplication of a limited set of domains. These protein domains are essentially the main components of globular proteins and are the most principal level at which protein function and protein interactions can be understood. An important aspect of domain evolution is their atomic structure and biochemical function, which are both specified by the information in the amino acid sequence. Changes in this information may bring about new folds, functions and protein architectures. With the present and still increasing wealth of sequences and annotation data brought about by genomics, new evolutionary relationships are constantly being revealed, unknown structures modeled and phylogenies inferred. Such investigations not only help predict the function of newly discovered proteins, but also assist in mapping unforeseen pathways of evolution and reveal crucial, co-evolving inter- and intra-molecular interactions. In turn this will help us describe how protein domains shaped cellular interaction networks and the dynamics with which they are regulated in the cell. Additionally, these studies can be used for the design of new and optimized protein domains for therapy. In this review, we aim to describe the basic concepts of protein domain evolution and illustrate recent developments in molecular evolution that have provided valuable new insights in the field of comparative genomics and protein interaction networks.