39,342 research outputs found
Stiff polymer in monomer ensemble
We make use of the previously developed formalism for a monomer ensemble and
include angular dependence of the segments of the polymer chains thus
described. In particular we show how to deal with stiffness when the polymer
chain is confined to certain regions. We investigate the stiffness from the
perspectives of a differential equation, integral equations, or recursive
relations for both continuum and lattice models. Exact analytical solutions are
presented for two cases, whereas numerical results are shown for a third case.Comment: 10 pages, including 6 figure
Separability problem for multipartite states of rank at most four
One of the most important problems in quantum information is the separability
problem, which asks whether a given quantum state is separable. We investigate
multipartite states of rank at most four which are PPT (i.e., all their partial
transposes are positive semidefinite). We show that any PPT state of rank two
or three is separable and has length at most four. For separable states of rank
four, we show that they have length at most six. It is six only for some
qubit-qutrit or multiqubit states. It turns out that any PPT entangled state of
rank four is necessarily supported on a 3x3 or a 2x2x2 subsystem. We obtain a
very simple criterion for the separability problem of the PPT states of rank at
most four: such a state is entangled if and only if its range contains no
product vectors. This criterion can be easily applied since a four-dimensional
subspace in the 3x3 or 2x2x2 system contains a product vector if and only if
its Pluecker coordinates satisfy a homogeneous polynomial equation (the Chow
form of the corresponding Segre variety). We have computed an explicit
determinantal expression for the Chow form in the former case, while such
expression was already known in the latter case.Comment: 19 page
Global Newtonian limit for the Relativistic Boltzmann Equation near Vacuum
We study the Cauchy Problem for the relativistic Boltzmann equation with near
Vacuum initial data. Unique global in time "mild" solutions are obtained
uniformly in the speed of light parameter . We furthermore prove that
solutions to the relativistic Boltzmann equation converge to solutions of the
Newtonian Boltzmann equation in the limit as on arbitrary time
intervals , with convergence rate for any . This may be the first proof of unique global in time validity of the
Newtonian limit for a Kinetic equation.Comment: 35 page
Pre- and Post-Adaptation Effects of Buffers in High-Concentrate Lamb Diets
A gradual increase in grain cover a period of 2 to 4 weeks is commonly required before ruminant animals become adapted to high-concentrate diets. Various dietary materials including sodium bicarbonate, sodium betonite, limestone and forage have been indicated as potential adis in the prevention of acidosis during adaptation. Benefits from feeding of these materials following adaptation have been less pronounced or lacking. Objectives of studies reported herein were (1) to investigate the effects of buffers and limited quantitites of alfalfa hay on physiological and rumen fermentation changs occuring in lambs during the early phase of adaptation to high-concentrate diets and (2) to study ruminal and systemic parameters and nutrient utilization as influenced by buffers in the diets of lambs previously adapted to the high-concentrate diet
Response process and test-retest reliability of the Context Assessment for Community Health tool in Vietnam
Background: The recently developed Context Assessment for Community Health (COACH) tool aims to measure aspects of the local healthcare context perceived to influence knowledge translation in low- and middle-income countries. The tool measures eight dimensions (organizational resources , community engagement, monitoring services for action, sources of knowledge, commitment to work, work culture, leadership, and informal payment) through 49 items. Objective: The study aimed to explore the understanding and stability of the COACH tool among health providers in Vietnam. Designs: To investigate the response process, think-aloud interviews were undertaken with five community health workers, six nurses and midwives, and five physicians. Identified problems were classified according to Conrad and Blair's taxonomy and grouped according to an estimation of the magnitude of the problem's effect on the response data. Further, the stability of the tool was examined using a test–retest survey among 77 respondents. The reliability was analyzed for items (intraclass correlation coefficient (ICC) and percent agreement) and dimensions (ICC and Bland–Altman plots). Results: In general, the think-aloud interviews revealed that the COACH tool was perceived as clear, well organized, and easy to answer. Most items were understood as intended. However, seven prominent problems in the items were identified and the content of three dimensions was perceived to be of a sensitive nature. In the test–retest survey, two-thirds of the items and seven of eight dimensions were found to have an ICC agreement ranging from moderate to substantial (0.5–0.7), demonstrating that the instrument has an acceptable level of stability. Conclusions: This study provides evidence that the Vietnamese translation of the COACH tool is generally perceived to be clear and easy to understand and has acceptable stability. There is, however, a need to rephrase and add generic examples to clarify some items and to further review items with low ICC.Duong M. Duc, Anna Bergström, Leif Eriksson, Katarina Selling, Bui Thi Thu Ha and Lars Walli
Hierarchical Modular Optimization of Convolutional Networks Achieves Representations Similar to Macaque IT and Human Ventral Stream
Humans recognize visually-presented objects rapidly and accurately. To understand this ability, we seek to construct models of the ventral stream, the series of cortical areas thought to subserve object recognition. One tool to assess the quality of a model of the ventral stream is the Representational Dissimilarity Matrix (RDM), which uses a set of visual stimuli and measures the distances produced in either the brain (i.e. fMRI voxel responses, neural firing rates) or in models (fea-ures). Previous work has shown that all known models of the ventral stream fail to capture the RDM pattern observed in either IT cortex, the highest ventral area, or in the human ventral stream. In this work, we construct models of the ventral stream using a novel optimization procedure for category-level object recognition problems, and produce RDMs resembling both macaque IT and human ventral stream. The model, while novel in the optimization procedure, further develops a long-standing functional hypothesis that the ventral visual stream is a hierarchically arranged series of processing stages optimized for visual object recognition
Deep Neural Networks Rival the Representation of Primate IT Cortex for Core Visual Object Recognition
The primate visual system achieves remarkable visual object recognition
performance even in brief presentations and under changes to object exemplar,
geometric transformations, and background variation (a.k.a. core visual object
recognition). This remarkable performance is mediated by the representation
formed in inferior temporal (IT) cortex. In parallel, recent advances in
machine learning have led to ever higher performing models of object
recognition using artificial deep neural networks (DNNs). It remains unclear,
however, whether the representational performance of DNNs rivals that of the
brain. To accurately produce such a comparison, a major difficulty has been a
unifying metric that accounts for experimental limitations such as the amount
of noise, the number of neural recording sites, and the number trials, and
computational limitations such as the complexity of the decoding classifier and
the number of classifier training examples. In this work we perform a direct
comparison that corrects for these experimental limitations and computational
considerations. As part of our methodology, we propose an extension of "kernel
analysis" that measures the generalization accuracy as a function of
representational complexity. Our evaluations show that, unlike previous
bio-inspired models, the latest DNNs rival the representational performance of
IT cortex on this visual object recognition task. Furthermore, we show that
models that perform well on measures of representational performance also
perform well on measures of representational similarity to IT and on measures
of predicting individual IT multi-unit responses. Whether these DNNs rely on
computational mechanisms similar to the primate visual system is yet to be
determined, but, unlike all previous bio-inspired models, that possibility
cannot be ruled out merely on representational performance grounds.Comment: 35 pages, 12 figures, extends and expands upon arXiv:1301.353
A Study on Knowledge Sharing in Vietnamese Organizations
Knowledge sharing is very much a sign for the atmosphere of social interactions in the organizations, it depends on the quality of the conversation, formally or informally. In other words, for more effective knowledge sharing, communication competence is required in order to have appropriate conversation. During the past decades, most theories of communication competence have been developed on the basis of “western” conceptualization. This empirical research is conducted in order to study the organizational communication competence in a non-western country, Vietnam, and the effect of such competence to the employees’ knowledge sharing behavior respectively. Base on the data collected from 11 organizations, the effects of three culture dimensions, namely individualism, power distance, and uncertainty avoidance to the communication competence were statistically analyzed; then, stemming from the certain level of communication competence, the behavior of organizational members towards knowledge sharing was explaine
Rodrigues Formula for the Nonsymmetric Multivariable Laguerre Polynomial
Extending a method developed by Takamura and Takano, we present the Rodrigues
formula for the nonsymmetric multivariable Laguerre polynomials which form the
orthogonal basis for the -type Calogero model with distinguishable
particles. Our construction makes it possible for the first time to
algebraically generate all the nonsymmetric multivariable Laguerre polynomials
with different parities for each variable.Comment: 6 pages, LaTe
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