Mechanism of resonant x-ray magnetic scattering in NiO

We study the resonant x-ray magnetic scattering (RXMS) around the K edge of Ni in the antiferromagnet NiO, by treating the 4p states of Ni as a band and the 3d states as localized states. We propose a mechanism that the 4p states are coupled to the magnetic order through the intra-atomic Coulomb interaction between the 4p and the 3d states and through the p-d mixing to the 3d states of neighboring Ni atoms. These couplings induce the orbital moment in the 4p band, and thereby give rise to the RXMS intensity at the K edge in the dipolar process. It is found that the spin-orbit interaction in the 4p band has negligibly small contribution to the RXMS intensity. The present model reproduces well the experimental spectra. We also discuss the azimuthal angle dependence of the intensity.Comment: 10 pages (revtex) and 7 postscript figure

X-Ray Magnetic Circular Dichroism at the K edge of Mn3GaC

We theoretically investigate the origin of the x-ray magnetic circular dichroism (XMCD) spectra at the K edges of Mn and Ga in the ferromagnetic phase of Mn3GaC on the basis of an ab initio calculation. Taking account of the spin-orbit interaction in the LDA scheme, we obtain the XMCD spectra in excellent agreement with the recent experiment. We have analyzed the origin of each structure, and thus elucidated the mechanism of inducing the orbital polarization in the p symmetric states. We also discuss a simple sum rule connecting the XMCD spectra with the orbital moment in the p symmetric states.Comment: 5 pages, 5 figures, accepted for publication in Physical Review

Sitagliptin and Carotid Atherosclerosis in Type 2 Diabetes

Background Experimental studies have suggested that dipeptidyl peptidase-4 (DPP-4) inhibitors provide cardiovascular protective effects. We performed a randomized study to evaluate the effects of sitagliptin added on to the conventional therapy compared with conventional therapy alone (diet, exercise, and/or drugs, except for incretin-related agents) on the intima-media thickness (IMT) of the carotid artery, a surrogate marker for the evaluation of atherosclerotic cardiovascular disease, in people with type 2 diabetes mellitus (T2DM). Methods and Findings We used a multicenter PROBE (prospective, randomized, open label, blinded endpoint) design. Individuals aged ≥30 y with T2DM (6.2% ≤ HbA1c < 9.4%) were randomly allocated to receive either sitagliptin (25 to 100 mg/d) or conventional therapy. Carotid ultrasound was performed at participating medical centers, and all parameters were measured in a core laboratory. Of the 463 enrolled participants with T2DM, 442 were included in the primary analysis (sitagliptin group, 222; conventional therapy group, 220). Estimated mean (± standard error) common carotid artery IMT at 24 mo of follow-up in the sitagliptin and conventional therapy groups was 0.827 ± 0.007 mm and 0.837 ± 0.007 mm, respectively, with a mean difference of −0.009 mm (97.2% CI −0.028 to 0.011, p = 0.309). HbA1c level at 24 mo was significantly lower with sitagliptin than with conventional therapy (6.56% ± 0.05% versus 6.72%± 0.05%, p = 0.008; group mean difference −0.159, 95% CI −0.278 to −0.041). Episodes of serious hypoglycemia were recorded only in the conventional therapy group, and the rate of other adverse events was not different between the two groups. As it was not a placebo-controlled trial and carotid IMT was measured as a surrogate marker of atherosclerosis, there were some limitations of interpretation. Conclusions In the PROLOGUE study, there was no evidence that treatment with sitagliptin had an additional effect on the progression of carotid IMT in participants with T2DM beyond that achieved with conventional treatment

Cyanobacterial Cell Lineage Analysis of the Spatiotemporal hetR Expression Profile during Heterocyst Pattern Formation in Anabaena sp. PCC 7120

Diazotrophic heterocyst formation in the filamentous cyanobacterium, Anabaena sp. PCC 7120, is one of the simplest pattern formations known to occur in cell differentiation. Most previous studies on heterocyst patterning were based on statistical analysis using cells collected or observed at different times from a liquid culture, which would mask stochastic fluctuations affecting the process of pattern formation dynamics in a single bacterial filament. In order to analyze the spatiotemporal dynamics of heterocyst formation at the single filament level, here we developed a culture system to monitor simultaneously bacterial development, gene expression, and phycobilisome fluorescence. We also developed micro-liquid chamber arrays to analyze multiple Anabaena filaments at the same time. Cell lineage analyses demonstrated that the initial distributions of hetR::gfp and phycobilisome fluorescence signals at nitrogen step-down were not correlated with the resulting distribution of developed heterocysts. Time-lapse observations also revealed a dynamic hetR expression profile at the single-filament level, including transient upregulation accompanying cell division, which did not always lead to heterocyst development. In addition, some cells differentiated into heterocysts without cell division after nitrogen step-down, suggesting that cell division in the mother cells is not an essential requirement for heterocyst differentiation

Novel Mouse Xenograft Models Reveal a Critical Role of CD4+ T Cells in the Proliferation of EBV-Infected T and NK Cells

Epstein-Barr virus (EBV), a ubiquitous B-lymphotropic herpesvirus, ectopically infects T or NK cells to cause severe diseases of unknown pathogenesis, including chronic active EBV infection (CAEBV) and EBV-associated hemophagocytic lymphohistiocytosis (EBV-HLH). We developed xenograft models of CAEBV and EBV-HLH by transplanting patients' PBMC to immunodeficient mice of the NOD/Shi-scid/IL-2Rγnull strain. In these models, EBV-infected T, NK, or B cells proliferated systemically and reproduced histological characteristics of the two diseases. Analysis of the TCR repertoire expression revealed that identical predominant EBV-infected T-cell clones proliferated in patients and corresponding mice transplanted with their PBMC. Expression of the EBV nuclear antigen 1 (EBNA1), the latent membrane protein 1 (LMP1), and LMP2, but not EBNA2, in the engrafted cells is consistent with the latency II program of EBV gene expression known in CAEBV. High levels of human cytokines, including IL-8, IFN-γ, and RANTES, were detected in the peripheral blood of the model mice, mirroring hypercytokinemia characteristic to both CAEBV and EBV-HLH. Transplantation of individual immunophenotypic subsets isolated from patients' PBMC as well as that of various combinations of these subsets revealed a critical role of CD4+ T cells in the engraftment of EBV-infected T and NK cells. In accordance with this finding, in vivo depletion of CD4+ T cells by the administration of the OKT4 antibody following transplantation of PBMC prevented the engraftment of EBV-infected T and NK cells. This is the first report of animal models of CAEBV and EBV-HLH that are expected to be useful tools in the development of novel therapeutic strategies for the treatment of the diseases

Raman spectral analysis of microbial pigment compositions in vegetative cells and heterocysts of multicellular cyanobacterium

The one-dimensional multicellular cyanobacterium, Anabaena sp. PCC 7120, exhibits a simple topology consisting of two types of cells under the nitrogen-depleted conditions. Although the differentiated (heterocyst) and undifferentiated cells (vegetative cells) were distinguished by their cellular shapes, we found that their internal states, that is, microbial pigment compositions, were distinguished by using a Raman microscope. Almost of Raman bands of the cellular components were assigned to vibrations of the pigments; chlorophyll a, β-carotene, phycocyanin, and allophycocyanin. We found that the Raman spectral measurement can detect the decomposition of both phycocyanin and allophycocyanin, which are components of the light-harvesting phycobilisome complex in the photosystem II. We observed that the Raman bands of phycocyanin and allophycocyanin exhibited more remarkable decrease in the heterocysts when compared to those of chlorophyll a and β-carotene. This result indicated the prior decomposition of phycobilisome in the heterocysts. We show that the Raman measurement is useful to detect the change of pigment composition in the cell differentiation

Development of electrostatic-induced charge detector for multiturn time-of-flight mass spectrometer

We developed an autocorrelation function to resolve the overtaking problem in a multiturn time-of-flight mass spectrometer (TOF-MS). The function analyzes the characteristic period for one lap of each ion packet and derives a mass spectrum from a signal pulse train composed of multiturn ion packets. To detect the ion pulse train, a new nondestructive ion detector was developed and installed in the multiturn orbit of MULTUM-S II. This detector is composed of an electrostatically induced charge detector, a preamplifier, and a digitizer. The electrostatic noises are smaller than the single-ion signals owing to the accumulation of the multiturn TOF spectrum. The conventional ion detector of TOF-MS is operated after collecting the signal pulse train. The multiturn TOF spectrum was convolved with an autocorrelation function to derive the mass spectrum. The convolved mass spectrum performed a mass resolving power (MRP) of 28,200 at m/z 69 and mass accuracy of 28 ppm for the perfluorotributylamine (PFTBA) gas sample