Lanczos exact diagonalization study of field-induced phase transition for Ising and Heisenberg antiferromagnets

Using an exact diagonalization treatment of Ising and Heisenberg model Hamiltonians, we study field-induced phase transition for two-dimensional antiferromagnets. For the system of Ising antiferromagnet the predicted field-induced phase transition is of first order, while for the system of Heisenberg antiferromagnet it is the second-order transition. We find from the exact diagonalization calculations that the second-order phase transition (metamagnetism) occurs through a spin-flop process as an intermediate step.Comment: 4 pages, 4 figure

A pulse of meteoric subsurface fluid discharging into the Chukchi Sea during the Early Holocene Thermal Maximum (EHTM)

This work was supported bythe Korea Ministry of Science and ICT (GP2020-038), by the Korea Ministry of Oceans and Fisheries (NP2011-040 and 1525011795), and by the Korea Polar Research Institute (Grants No. PE20350). W.-L.H. acknowledges the supports from the ArcticSGD, a project supported by the Norway Grants and the EEA Grants (2019/34/H/ST10/00645). Additional funds were contributed by the AWI Research Program PACES-II Workpackage 3.1 and 3.2.The response of Arctic Ocean biogeochemistry to subsurface flow driven by permafrost thaw is poorly understood. We present dissolved chloride and water isotopic data from the Chukchi Sea Shelf sediments that reveal the presence of a meteoric subsurface flow enriched in cations with a radiogenic Sr fingerprint. This subsurface fluid is also enriched in dissolved inorganic carbon and methane that bear isotopic compositions indicative of a carbon reservoir modified by reactions in a closed system. Such fluid characteristics are in stark contrast with those from other sites in the Chukchi Sea where the pore water composition shows no sign of meteoric input, but reflect typical biogeochemical reactions associated with early diagenetic sequences in marine sediment. The most likely source of the observed subsurface flow at the Chukchi Sea Shelf is from the degradation of permafrost that had extended to the shelf region during the Last Glacial Maximum. Our data suggest that the permafrost-driven subsurface flow most likely took place during the 2-3 oC warming in the Early Holocene Thermal Maximum (EHTM). This time scale is supported by numerical simulation of pore fluid profiles, which indicate that a minimum of several thousand years must have passed since the cessation of the subsurface methane-bearing fluid flow.Publisher PDFPeer reviewe

Ohmic Contacts to N-Face p-GaN Using Ni/Au for the Fabrication of Polarization Inverted Light-Emitting Diodes

The electrical properties of Ni-based ohmic contacts to N-face p-type GaN were investigated. The specific contact resistance of N-face p-GaN exhibits a linear decrease from 1.01 cm 2 to 9 05 × 10 −3 cm 2 for the as-deposited and the annealed Ni/Au contacts, respectively, with increasing annealing temperature. However, the specific contact resistance could be decreased down to 1 03× 10 −4 cm 2 by means of surface treatment using an alcohol-based (NH 4 2 S solution. The depth profile data measured from the intensity of O1s peak in the X-ray photoemission spectra showed that the alcohol-based (NH 4 2 S treatment was effective in removing the surface oxide layer of GaN

DJ-1 Null Dopaminergic Neuronal Cells Exhibit Defects in Mitochondrial Function and Structure: Involvement of Mitochondrial Complex I Assembly

DJ-1 is a Parkinson's disease-associated gene whose protein product has a protective role in cellular homeostasis by removing cytosolic reactive oxygen species and maintaining mitochondrial function. However, it is not clear how DJ-1 regulates mitochondrial function and why mitochondrial dysfunction is induced by DJ-1 deficiency. In a previous study we showed that DJ-1 null dopaminergic neuronal cells exhibit defective mitochondrial respiratory chain complex I activity. In the present article we investigated the role of DJ-1 in complex I formation by using blue native-polyacrylamide gel electrophoresis and 2-dimensional gel analysis to assess native complex status. On the basis of these experiments, we concluded that DJ-1 null cells have a defect in the assembly of complex I. Concomitant with abnormal complex I formation, DJ-1 null cells show defective supercomplex formation. It is known that aberrant formation of the supercomplex impairs the flow of electrons through the channels between respiratory chain complexes, resulting in mitochondrial dysfunction. We took two approaches to study these mitochondrial defects. The first approach assessed the structural defect by using both confocal microscopy with MitoTracker staining and electron microscopy. The second approach assessed the functional defect by measuring ATP production, O2 consumption, and mitochondrial membrane potential. Finally, we showed that the assembly defect as well as the structural and functional abnormalities in DJ-1 null cells could be reversed by adenovirus-mediated overexpression of DJ-1, demonstrating the specificity of DJ-1 on these mitochondrial properties. These mitochondrial defects induced by DJ-1mutation may be a pathological mechanism for the degeneration of dopaminergic neurons in Parkinson's disease

In situ induction of dendritic cell–based T cell tolerance in humanized mice and nonhuman primates

Administration of an ICAM-1–specific antibody arrests dendritic cells in a semi-immature state and facilitates antigen-specific T cell tolerance to islet allografts in humanized mice and Rhesus monkeys

Variation in the ICAM1-ICAM4-ICAM5 locus is associated with systemic lupus erythematosus susceptibility in multiple ancestries

Objective: Systemic lupus erythematosus (SLE; OMIM 152700) is a chronic autoimmune disease for which the aetiology includes genetic and environmental factors. ITGAM, integrin ?M(complement component 3 receptor 3 subunit) encoding a ligand for intracellular adhesion molecule (ICAM) proteins, is an established SLE susceptibility locus. This study aimed to evaluate the independent and joint effects of genetic variations in the genes that encode ITGAM and ICAM. Methods: The authors examined several markers in the ICAM1-ICAM4-ICAM5 locus on chromosome 19p13 and the single ITGAM polymorphism (rs1143679) using a large-scale case-control study of 17 481 unrelated participants from four ancestry populations. The singlemarker association and gene-gene interaction were analysed for each ancestry, and a meta-analysis across the four ancestries was performed. Results: The A-allele of ICAM1-ICAM4-ICAM5 rs3093030, associated with elevated plasma levels of soluble ICAM1, and the A-allele of ITGAM rs1143679 showed the strongest association with increased SLE susceptibility in each of the ancestry populations and the trans-ancestry meta-analysis (ORmeta=1.16, 95% CI 1.11 to 1.22; p=4.88 × 10-10 and ORmeta=1.67, 95% CI 1.55 to 1.79; p=3.32 × 10-46, respectively). The effect of the ICAM single-nucleotide polymorphisms (SNPs) was independent of the effect of the ITGAM SNP rs1143679, and carriers of both ICAM rs3093030-AA and ITGAM rs1143679-AA had an OR of 4.08 compared with those with no risk allele in either SNP (95% CI 2.09 to 7.98; p=3.91 × 10-5). Conclusion: These findings are the first to suggest that an ICAM-integrin-mediated pathway contributes to susceptibility to SLE

GABAergic inhibition is weakened or converted into excitation in the oxytocin and vasopressin neurons of the lactating rat

BACKGROUND: Increased secretion of oxytocin and arginine vasopressin (AVP) from hypothalamic magnocellular neurosecretory cells (MNCs) is a key physiological response to lactation. In the current study, we sought to test the hypothesis that the GABA(A) receptor-mediated inhibition of MNCs is altered in lactating rats. RESULTS: Gramicidin-perforated recordings in the rat supraoptic nucleus (SON) slices revealed that the reversal potential of GABA(A) receptor-mediated response (E(GABA)) of MNCs was significantly depolarized in the lactating rats as compared to virgin animals. The depolarizing E(GABA) shift was much larger in rats in third, than first, lactation such that GABA exerted an excitatory, instead of inhibitory, effect in most of the MNCs of these multiparous rats. Immunohistochemical analyses confirmed that GABAergic excitation was found in both AVP and oxytocin neurons within the MNC population. Pharmacological experiments indicated that the up-regulation of the Cl(−) importer Na(+)-K(+)-2Cl(−) cotransporter isotype 1 and the down-regulation of the Cl(−) extruder K(+)-Cl(−) cotransporter isotype 2 were responsible for the depolarizing shift of E(GABA) and the resultant emergence of GABAergic excitation in the MNCs of the multiparous rats. CONCLUSION: We conclude that, in primiparous rats, the GABAergic inhibition of MNCs is weakened during the period of lactation while, in multiparous females, GABA becomes excitatory in a majority of the cells. This reproductive experience-dependent alteration of GABAergic transmission may help to increase the secretion of oxytocin and AVP during the period of lactation