2,028 research outputs found
The Metric of Yang-Mills Orbit Space on the Lattice
We find coordinates, the metric tensor, the inverse metric tensor and the
Laplace-Beltrami operator for the orbit space of Hamiltonian SU(2) gauge theory
on a finite, rectangular lattice. This is done using a complete axial gauge
fixing. The Gribov problem can be completely solved, with no remaining gauge
ambiguities.Comment: Title is changed in journal. Now 19 pages, still one figure, AMSTe
A laser spectrometer and wavemeter for pulsed lasers
The design, construction, calibration, and evaluation of a pulsed laser wavemeter and spectral analyzer are described. This instrument, called the Laserscope for its oscilloscope-like display of laser spectral structure, was delivered to NASA Langley Research Center as a prototype of a laboratory instrument. The key component is a multibeam Fizeau wedge interferometer, providing high (0.2 pm) spectral resolution and a linear dispersion of spectral information, ideally suited to linear array photodiode detectors. Even operating alone, with the classic order-number ambiguity of interferometers unresolved, this optical element will provide a fast, real-time display of the spectral structure of a laser output. If precise wavelength information is also desired then additional stages must be provided to obtain a wavelength measurement within the order-number uncertainty, i.e., within the free spectral range of the Fizeau wedge interferometer. A Snyder (single-beam Fizeau) wedge is included to provide this initial wavelength measurement. Difficulties in achieving the required wide-spectrum calibration limit the usefulness of this function
MHC Class II Expression Restricted to CD8α+ and CD11b+ Dendritic Cells Is Sufficient for Control of Leishmania major
Control of the intracellular protozoan, Leishmania major, requires major histocompatibility complex class II (MHC II)âdependent antigen presentation and CD4+ T cell T helper cell 1 (Th1) differentiation. MHC IIâpositive macrophages are a primary target of infection and a crucial effector cell controlling parasite growth, yet their function as antigen-presenting cells remains controversial. Similarly, infected Langerhans cells (LCs) can prime interferon (IFN)Îłâproducing Th1 CD4+ T cells, but whether they are required for Th1 responses is unknown. We explored the antigen-presenting cell requirement during primary L. major infection using a mouse model in which MHC II, I-AÎČb, expression is restricted to CD11b+ and CD8α+ dendritic cells (DCs). Importantly, B cells, macrophages, and LCs are all MHC IIânegative in these mice. We demonstrate that antigen presentation by these DC subsets is sufficient to control a subcutaneous L. major infection. CD4+ T cells undergo complete Th1 differentiation with parasite-specific secretion of IFNÎł. Macrophages produce inducible nitric oxide synthase, accumulate at infected sites, and control parasite numbers in the absence of MHC II expression. Therefore, CD11b+ and CD8α+ DCs are not only key initiators of the primary response but also provide all the necessary cognate interactions for CD4+ T cell Th1 effectors to control this protozoan infection
HIT: a Human-Inspired Trust model
This paper presents a new approach to assign trust levels in ad hoc networks. Our system is inspired by the human concept of trust.
The trust level considers the recommendation of trustworthy neighbors and their own experience. For the recommendation computation, we take into account not only the trust level, but also its accuracy and the relationship maturity. We also propose the Recommendation Exchange Protocol (REP), which minimizes the number of exchanged messages.
The results show the efficacy of the system and the influence of main parameters.8th IFIP/IEEE International conference on Mobile and Wireless CommunicationRed de Universidades con Carreras en InformĂĄtica (RedUNCI
Density-functional theory of inhomogeneous electron systems in thin quantum wires
Motivated by current interest in strongly correlated quasi-one-dimensional
(1D) Luttinger liquids subject to axial confinement, we present a novel
density-functional study of few-electron systems confined by power-low external
potentials inside a short portion of a thin quantum wire. The theory employs
the 1D homogeneous Coulomb liquid as the reference system for a Kohn-Sham
treatment and transfers the Luttinger ground-state correlations to the
inhomogeneous electron system by means of a suitable local-density
approximation (LDA) to the exchange-correlation energy functional. We show that
such 1D-adapted LDA is appropriate for fluid-like states at weak coupling, but
fails to account for the transition to a ``Wigner molecules'' regime of
electron localization as observed in thin quantum wires at very strong
coupling. A detailed analyzes is given for the two-electron problem under axial
harmonic confinement.Comment: 8 pages, 7 figures, submitte
Exchange-correlation vector potentials and vorticity-dependent exchange-correlation energy densities in two-dimensional systems
We present a new approach how to calculate the scalar exchange-correlation
potentials and the vector exchange-correlation potentials from current-carrying
ground states of two-dimensional quantum dots. From these exchange-correlation
potentials we derive exchange-correlation energy densities and examine their
vorticity (or current) dependence. Compared with parameterizations of
current-induced effects in literature we find an increased significance of
corrections due to paramagnetic current densities.Comment: 5 figures, submitted to PR
A simply connected surface of general type with p_g=0 and K^2=2
In this paper we construct a simply connected, minimal, complex surface of
general type with p_g=0 and K^2=2 using a rational blow-down surgery and
Q-Gorenstein smoothing theory.Comment: 19 pages, 6 figures. To appear in Inventiones Mathematica
The Effect of Content Retelling on Vocabulary Uptake from a TED Talk
This study investigates the potential benefits for incidental vocabulary acquisition of implementing a particular sequence of input-output-input activities. More specifically, EFL learners (n = 32) were asked to watch a TED Talks video, orally sum up its content in English, and then watch the video once more. A comparison group (n = 32) also watched the TED Talks video twice but were not required to sum it up in between. Immediate and delayed post-tests showed significantly better word-meaning recall in the former condition. An analysis of the oral summaries showed that it was especially words which learners attempted to use that stood a good chance of being recalled later. These findings are interpreted with reference to Swainâs (e.g., 1995) Output Hypothesis, Laufer and Hulstijnâs (2001) Involvement Load Hypothesis, and Nation and Webbâs (2011) Technique Feature Analysis. What makes the text-based output task in this experiment fundamentally different from many previous studies which have investigated the merits of text-based output activities is that it was at no point stipulated for the participants that they should use particular words from the input text. The study also illustrates the potential of TED Talks as a source of authentic audio-visual input in EFL classrooms
Information transmission in oscillatory neural activity
Periodic neural activity not locked to the stimulus or to motor responses is
usually ignored. Here, we present new tools for modeling and quantifying the
information transmission based on periodic neural activity that occurs with
quasi-random phase relative to the stimulus. We propose a model to reproduce
characteristic features of oscillatory spike trains, such as histograms of
inter-spike intervals and phase locking of spikes to an oscillatory influence.
The proposed model is based on an inhomogeneous Gamma process governed by a
density function that is a product of the usual stimulus-dependent rate and a
quasi-periodic function. Further, we present an analysis method generalizing
the direct method (Rieke et al, 1999; Brenner et al, 2000) to assess the
information content in such data. We demonstrate these tools on recordings from
relay cells in the lateral geniculate nucleus of the cat.Comment: 18 pages, 8 figures, to appear in Biological Cybernetic
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