406 research outputs found
Level statistics of XXZ spin chains with a random magnetic field
The level-spacing distribution of a spin 1/2 XXZ chain is numerically studied
under random magnetic field. We show explicitly how the level statistics
depends on the lattice size L, the anisotropy parameter , and the mean
amplitude of the random magnetic field h. In the energy spectrum, quantum
integrability competes with nonintegrability derived from the randomness, where
the XXZ interaction is modified by the parameter . When ,
the level-spacing distribution mostly shows Wigner-like behavior, while when
=0, Poisson-like behavior appears although the system is nonintegrable
due to randomness. Poisson-like behavior also appears for in the
large h limit. Furthermore, the level-spacing distribution depends on the
lattice size L, particularly when the random field is weak.Comment: 4 pages, 3 figures, to be published in Phys. Rev.
Impaired trophoblast invasion and increased numbers of immune cells at day 18 of pregnancy in the mesometrial triangle of type 1 diabetic rats
AbstractIntroductionType 1 diabetes (T1D) is associated with adverse pregnancy outcome, usually attributed to hyperglycemia. Recently, we showed that pregnancy outcome in normoglycemic T1D rats was characterized by decreased fetal and placental weight, suggesting impaired placental development. In the present study, we tested the hypothesis that trophoblast invasion and spiral artery (SA) remodeling is impaired in T1D rats ant that this is associated with aberrant local presence of NK cells and macrophages in the mesometrial triangle (MT).MethodsPlacentae with MT from pregnant biobreeding diabetes-prone (BBDP; T1D model) rats, control biobreeding diabetes-resistant (BBDR) and Wistar-rats were dissected at day 18 of gestation and stained for trophoblast invasion, SA remodeling, uNK cells and macrophages.ResultsInterstitial trophoblast invasion and SA remodeling was impaired in BBDP-rats vs. control rats, coinciding with increased presence of NK cells and an increased iNOS+/CD206+ ratio of macrophages.DiscussionDecreased fetal and placental weight in BBDP-rats was associated with diminished interstitial trophoblast invasion and less optimal SA remodeling, increased numbers of NK cells and increased iNOS+/CD206+ macrophage ratio in the MT of BBDP-rats.ConclusionsThe impaired trophoblast invasion and SA remodeling may be due to an aberrant local immune-response and may result in damage to the fetal placenta and insufficient supply of nutrients towards the fetus with eventually decreased fetal weight as a consequence
Unexpected non-Wigner behavior in level-spacing distributions of next-nearest-neighbor coupled XXZ spin chains
The level-spacing distributions of XXZ spin chains with next-nearest-neighbor
couplings are studied under periodic boundary conditions. We confirm that
integrable XXZ spin chains mostly have the Poisson distribution as expected. On
the contrary, the level-spacing distributions of next-nearest-neighbor coupled
XXZ chains are given by non-Wigner distributions. It is against the
expectations, since the models are nonintegrable.Comment: 4 pages, 4 figures, to be published in Physical Review
Human Milk Oligosaccharides Differently Modulate Goblet Cells Under Homeostatic, Proinflammatory Conditions and ER Stress
SCOPE: Human milk oligosaccharides (hMOs) have beneficial effects on intestinal barrier function, but the mechanisms of action are not well-understood. Here we study the effects of hMOs on goblet cells, which indicate that some hMOs may enhance mucus barrier function through direct modulation of goblet cell function. METHODS AND RESULTS: The modulatory effects of 2'-FL, 3-FL, LNT2, and GOS on the expression of goblet cell secretory related genes MUC2, TFF3, RETNLB, and the Golgi-sulfotransferase genes CHST5, and GAL3ST2 of LS174T were determined by real-time quantitative RT-PCR. 3-FL, LNT2, and GOS modulated LS174T gene expression profiles in a dose and time-dependent manner. In addition, the up-regulation of MUC2 was confirmed by immunofluorescence staining. Effects of 2'-FL, 3-FL, LNT2, and GOS on gene transcription of LS174T were also assessed during exposure to TNF-α, IL-13, or tunicamycin. During TNF-α challenge, 3-FL and LNT2 enhanced MUC2 and TFF3 gene expression. After IL-13 exposure, 2'-FL, 3-FL, and LNT2 all showed up-regulating effects on MUC2, 3-FL and LNT2 also enhanced TFF3 expression. LNT2 significantly reversed Tm-induced down-regulating of TFF3, RETNLB, and CHST5. CONCLUSION: Our findings indicate that hMOs may enhance mucus barrier function through direct modulation of intestinal goblet cells. Effects were structural and stressor-dependent way. This article is protected by copyright. All rights reserved
Neonatal Exposure to Thymotropic Gross Murine Leukemia Virus Induces Virus-Specific Immunologic Nonresponsiveness
Neonatal exposure to Gross murine leukemia virus results in a profound inhibition of the virus-specific T and B cell responses of adult animals. Animals exposed to virus as neonates exhibit a marked depression in virus-specific T cell function as measured by the virtual absence of in vivo delayed type hypersensitivity responses and in vitro proliferative responses to virally infected stimulator cells. Further, serum obtained from neonatally treated mice failed to either immunoprecipitate viral proteins or neutralize virus in an in vitro plaque assay, suggesting the concurrent induction of a state of B cell hyporesponsiveness. The specificity of this effect at the levels of both T and B cells was demonstrated by the ability of neonatally treated mice to respond normally after adult challenge with either irrelevant reovirus or influenza virus. The replication of Gross virus within both stromal and lymphocytic compartments of the neonatal thymus suggests that thymic education plays a key role in the induction of immunologic nonresponsiveness to viruses
Проблема правової культури в історії філософсько-педагогічної думки
(uk) Стаття присвячена проблемі правової культури в історії філософсько-педагогічної думки
Interaction-induced chaos in a two-electron quantum-dot system
A quasi-one-dimensional quantum dot containing two interacting electrons is
analyzed in search of signatures of chaos. The two-electron energy spectrum is
obtained by diagonalization of the Hamiltonian including the exact Coulomb
interaction. We find that the level-spacing fluctuations follow closely a
Wigner-Dyson distribution, which indicates the emergence of quantum signatures
of chaos due to the Coulomb interaction in an otherwise non-chaotic system. In
general, the Poincar\'e maps of a classical analog of this quantum mechanical
problem can exhibit a mixed classical dynamics. However, for the range of
energies involved in the present system, the dynamics is strongly chaotic,
aside from small regular regions. The system we study models a realistic
semiconductor nanostructure, with electronic parameters typical of gallium
arsenide.Comment: 4 pages, 3ps figure
Crossover from Poisson to Wigner-Dyson Level Statistics in Spin Chains with Integrability Breaking
We study numerically the evolution of energy-level statistics as an
integrability-breaking term is added to the XXZ Hamiltonian. For finite-length
chains, physical properties exhibit a cross-over from behavior resulting from
the Poisson level statistics characteristic of integrable models to behavior
corresponding to the Wigner-Dyson statistics characteristic of the
random-matrix theory used to describe chaotic systems. Different measures of
the level statistics are observed to follow different crossover patterns. The
range of numerically accessible system sizes is too small to establish with
certainty the scaling with system size, but the evidence suggests that in a
thermodynamically large system an infinitesimal integrability breaking would
lead to Wigner-Dyson behavior.Comment: 8 pages, 8 figures, Revtex
Energy level statistics for models of coupled single-mode Bose--Einstein condensates
We study the distribution of energy level spacings in two models describing
coupled single-mode Bose-Einstein condensates. Both models have a fixed number
of degrees of freedom, which is small compared to the number of interaction
parameters, and is independent of the dimensionality of the Hilbert space. We
find that the distribution follows a universal Poisson form independent of the
choice of coupling parameters, which is indicative of the integrability of both
models. These results complement those for integrable lattice models where the
number of degrees of freedom increases with increasing dimensionality of the
Hilbert space. Finally, we also show that for one model the inclusion of an
additional interaction which breaks the integrability leads to a non-Poisson
distribution.Comment: 5 pages, 4 figures, revte
Energy level statistics of the two-dimensional Hubbard model at low filling
The energy level statistics of the Hubbard model for square
lattices (L=3,4,5,6) at low filling (four electrons) is studied numerically for
a wide range of the coupling strength. All known symmetries of the model
(space, spin and pseudospin symmetry) have been taken into account explicitly
from the beginning of the calculation by projecting into symmetry invariant
subspaces. The details of this group theoretical treatment are presented with
special attention to the nongeneric case of L=4, where a particular complicated
space group appears. For all the lattices studied, a significant amount of
levels within each symmetry invariant subspaces remains degenerated, but except
for L=4 the ground state is nondegenerate. We explain the remaining
degeneracies, which occur only for very specific interaction independent
states, and we disregard these states in the statistical spectral analysis. The
intricate structure of the Hubbard spectra necessitates a careful unfolding
procedure, which is thoroughly discussed. Finally, we present our results for
the level spacing distribution, the number variance , and the
spectral rigidity , which essentially all are close to the
corresponding statistics for random matrices of the Gaussian ensemble
independent of the lattice size and the coupling strength. Even very small
coupling strengths approaching the integrable zero coupling limit lead to the
Gaussian ensemble statistics stressing the nonperturbative nature of the
Hubbard model.Comment: 31 pages (1 Revtex file and 10 postscript figures
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