1,281 research outputs found
Entanglement and particle correlations of Fermi gases in harmonic traps
We investigate quantum correlations in the ground state of noninteracting
Fermi gases of N particles trapped by an external space-dependent harmonic
potential, in any dimension. For this purpose, we compute one-particle
correlations, particle fluctuations and bipartite entanglement entropies of
extended space regions, and study their large-N scaling behaviors. The
half-space von Neumann entanglement entropy is computed for any dimension,
obtaining S_HS = c_l N^(d-1)/d ln N, analogously to homogenous systems, with
c_l=1/6, 1/(6\sqrt{2}), 1/(6\sqrt{6}) in one, two and three dimensions
respectively. We show that the asymptotic large-N relation S_A\approx \pi^2
V_A/3, between the von Neumann entanglement entropy S_A and particle variance
V_A of an extended space region A, holds for any subsystem A and in any
dimension, analogously to homogeneous noninteracting Fermi gases.Comment: 15 pages, 22 fig
Modelling diffusional transport in the interphase cell nucleus
In this paper a lattice model for diffusional transport of particles in the
interphase cell nucleus is proposed. Dense networks of chromatin fibers are
created by three different methods: randomly distributed, non-interconnected
obstacles, a random walk chain model, and a self avoiding random walk chain
model with persistence length. By comparing a discrete and a continuous version
of the random walk chain model, we demonstrate that lattice discretization does
not alter particle diffusion. The influence of the 3D geometry of the fiber
network on the particle diffusion is investigated in detail, while varying
occupation volume, chain length, persistence length and walker size. It is
shown that adjacency of the monomers, the excluded volume effect incorporated
in the self avoiding random walk model, and, to a lesser extent, the
persistence length, affect particle diffusion. It is demonstrated how the
introduction of the effective chain occupancy, which is a convolution of the
geometric chain volume with the walker size, eliminates the conformational
effects of the network on the diffusion, i.e., when plotting the diffusion
coefficient as a function of the effective chain volume, the data fall onto a
master curve.Comment: 9 pages, 8 figure
Some Physical Consequences of Abrupt Changes in the Multipole Moments of a Gravitating Body
The Barrab\`es-Israel theory of light-like shells in General Relativity is
used to show explicitly that in general a light-like shell is accompanied by an
impulsive gravitational wave. The gravitational wave is identified by its
Petrov Type N contribution to a Dirac delta-function term in the Weyl conformal
curvature tensor (with the delta-function singular on the null hypersurface
history of the wave and shell). An example is described in which an
asymptotically flat static vacuum Weyl space-time experiences a sudden change
across a null hypersurface in the multipole moments of its isolated axially
symmetric source. A light-like shell and an impulsive gravitational wave are
identified, both having the null hypersurface as history. The stress-energy in
the shell is dominated (at large distance from the source) by the jump in the
monopole moment (the mass) of the source with the jump in the quadrupole moment
mainly responsible for the stress being anisotropic. The gravitational wave
owes its existence principally to the jump in the quadrupole moment of the
source confirming what would be expected.Comment: 26 pages, tex, no figures, to appear in Phys.Rev.
Confronting the Challenge of Whale Detection from Large Vessels
As a result of a moratorium on commercial whaling, most populations of large whales are increasing across the globe. However, concurrent growth in shipping means that lethal ship-whale collisions constitute a significant threat to whale conservation efforts. This study investigates the ability of ship operators to detect and avoid whales by quantifying the predictability of whale surfacing behaviors, which are the cues used to determine whale presence. Whale avoidance is challenging because whales spend most of their time underwater and thus unavailable to be detected (the âavailability processâ), but must be detected at sufficiently large distances (the âdetection processâ) to enact an effective avoidance maneuver. We quantified one of the main characteristics of whale behavior that governs detectability â time breaking the surface â to create a novel model of whale surfacing patterns around ships while accounting for the detection process. We then estimated the frequency with which cues go undetected (i.e. whales break the surface but ship operators are unaware of them), as well as the frequency with which whales are present but unavailable for detection (i.e. below the surface of the water). This work will enable the prediction of close ship-whale encounters given different combinations of detected and/or missed cues at varying ship speeds. It will support ship operatorsâ avoidance efforts by quantifying the availability and detection processes in a way that facilitates the development of whale avoidance protocols
TNF and ILâ6 mediate MIPâ1α expression in bleomycinâinduced lung injury
Previously, macrophage inflammatory proteinâ1α (MIPâ1α), a member of the CâC chemokine family, has been implicated in bleomycinâinduced pulmonary fibrosis, a model of the human disease idiopathic pulmonary fibrosis. Neutralization of MIPâ1α protein with antiâMIPâ1α antibodies significantly attenuated both mononuclear phagocyte recruitment and pulmonary fibrosis in bleomycinâchallenged CBA/J mice. However, the specific stimuli for MIPâ1α expression in the bleomycinâinduced lesion have not been characterized. In this report, two mediators of the inflammatory response to bleomycin, tumor necrosis factor (TNF) and interleukinâ6 (ILâ6), were evaluated as putative stimuli for MIPâ1α expression after bleomycin challenge in CBA/J mice. Elevated levels of bioactive TNF and ILâ6 were detected in bronchoalveolar lavage (BAL) fluid and lung homogenates from bleomycinâtreated CBA/J mice at time points postâbleomycin challenge, which precede MIPâ1α protein expression. Treatment of bleomycinâchallenged mice with soluble TNF receptor (sTNFr) or antiâILâ6 antibodies significantly decreased MIPâ1α protein expression in the lungs. Furthermore, normal alveolar macrophages secreted elevated levels of MIPâ1α protein in response to treatment with TNF plus ILâ6 or bleomycin plus ILâ6, but not TNF, bleomycin, or ILâ6 alone. Finally, leukocytes recovered from the BAL fluid of bleomycinâchallenged mice secreted higher levels of MIPâ1α protein, compared to controls, when treated with TNF alone. Based on the data presented here, we propose that TNF and ILâ6 are part of a cytokine network that modulates MIPâ1α protein expression in the profibrotic inflammatory lesion during the response to intratracheal bleomycin challenge. J. Leukoc. Biol. 64: 528â536; 1998.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141711/1/jlb0528.pd
KlĂŒver-Bucy syndrome associated with a recessive variant in HGSNAT in two siblings with Mucopolysaccharidosis type IIIC (Sanfilippo C)
Kluver-Bucy syndrome (KBS) comprises a set of neurobehavioral symptoms with psychic blindness, hypersexuality, disinhibition, hyperorality, and hypermetamorphosis that were originally observed after bilateral lobectomy in Rhesus monkeys. We investigated two siblings with KBS from a consanguineous family by whole-exome sequencing and autozygosity mapping. We detected a homozygous variant in the heparan-alpha-glucosaminidase-N-acetyltransferase gene (HGSNAT; c.518G>A, p.(G173D), NCBI ClinVar RCV000239404.1), which segregated with the phenotype. Disease-causing variants in this gene are known to be associated with autosomal recessive Mucopolysaccharidosis type IIIC (MPSIIIC, Sanfilippo C). This lysosomal storage disease is due to deficiency of the acetyl-CoA:alpha-glucosaminidase-N-acetyltransferase, which was shown to be reduced in patient fibroblasts. Our report extends the phenotype associated with MPSIIIC. Besides MPSIIIA and MPSIIIB, due to variants in SGSH and NAGLU, this is the third subtype of Sanfilippo disease to be associated with KBS. MPSIII should be included in the differential diagnosis of young patients with KBS
The role of ILĂą 5 in bleomycinĂą induced pulmonary fibrosis
Eosinophils are known to express cytokines capable of promoting fibrosis. InterleukinĂą 5 (ILĂą 5) is important in regulating eosinophilopoiesis, eosinophil recruitment and activation. Lung ILĂą 5 expression is elevated in pulmonary fibrosis, wherein the eosinophil is a primary source of fibrogenic cytokines. To determine the role of ILĂą 5 in pulmonary fibrosis, the effects of antiĂą ILĂą 5 antibody were investigated in a model of bleomycinĂą induced pulmonary fibrosis. Fibrosis was induced in mice by endotracheal bleomycin treatment. Animals were also treated with either antiĂą ILĂą 5 antibody or control IgG. Lungs were then analyzed for fibrosis, eosinophil influx, chemotactic activity, and cytokine expression. The results show that a primary chemotactic activity at the height of eosinophil recruitment is ILĂą 5. Furthermore, antiĂą ILĂą 5 antibody caused significant reduction in lung eosinophilia, cytokine expression, and fibrosis. These findings taken together suggest an important role for ILĂą 5 in pulmonary fibrosis via its ability to regulate eosinophilic inflammation, and thus eosinophilĂą dependent fibrogenic cytokine production. J. Leukoc. Biol. 64: 657Ăą 666; 1998.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141191/1/jlb0657.pd
Stem cell factor and IgE-stimulated murine mast cells produce chemokines (CCL2, CCL17, CCL22) and express chemokine receptors
Objective and design: In the present study we investigated the effect of SCF and/or IgE on histamine, TNF- α and chemokines released from bone marrow-derived mast cells (BMMC) as well as chemokine receptor expression.¶ Material and methods: BMMC were derived from femoral bone marrow of CBA/J mice. The purity of BMMC was >98%percnt; after 3 weeks. BMMC (2.5 à 10 6 cells/well) were incubated in the presence or absence of either SCF, IgE plus DNP or a combination of SCF and IgE for 6 and 18 h. Cell-free supernatants were recovered to measure CC chemokines, TNF- α and histamine release utilizing ELISA assays. CC chemokine family receptors were detected by RT-PCR analysis, and confirmed using functional chemotactic assays.¶ Results: Histamine levels were comparable between SCF and IgE stimulated cells, whereas TNF- α production was significantly greater after IgE compared to SCF stimulation. SCF and/or IgE-stimulated BMMC released CC chemokines, CCL22 (MDC), CCL17 (TARC) and CCL2 (MCP-1). Increased mRNA expression of CCR1, CCR2, CCR3, and CCR5 was detected in SCF and IgE-stimulated BMMCs. Functional chemotactic assays confirmed the expression data.¶ Conclusion: SCF and IgE can up-regulate the expression of chemokines and chemokine receptors on mast cells. Thus, SCF may play a significant role in their activation and inflammation during allergic responses.¶Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41824/1/11-50-3-168_10500168.pd
Increased responsiveness of murine eosinophils to MIPĂą 1ĂÂČ (CCL4) and TCAĂą 3 (CCL1) is mediated by their specific receptors, CCR5 and CCR8
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141970/1/jlb1019.pd
Birth and death processes and quantum spin chains
This papers underscores the intimate connection between the quantum walks
generated by certain spin chain Hamiltonians and classical birth and death
processes. It is observed that transition amplitudes between single excitation
states of the spin chains have an expression in terms of orthogonal polynomials
which is analogous to the Karlin-McGregor representation formula of the
transition probability functions for classes of birth and death processes. As
an application, we present a characterization of spin systems for which the
probability to return to the point of origin at some time is 1 or almost 1.Comment: 14 page
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