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 $\Delta$, 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 $\Delta$. When $\Delta \ne 0$, the level-spacing distribution mostly shows Wigner-like behavior, while when $\Delta$=0, Poisson-like behavior appears although the system is nonintegrable due to randomness. Poisson-like behavior also appears for $\Delta \ne 0$ 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 $L \times L$ 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 $\Sigma^2$, and the spectral rigidity $\Delta_3$, 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