Magnetic properties of high petrologic grade L-LL chondrites: Tenham,Tuxtuac,Willard and Forrest(b)

Temperature dependence of the hysteresis parameters (saturation magnetization, Js; saturation remanent magnetization, Jr; coercivity, Hc; and initial susceptibility, Xi) were examined from room temperature to 780℃ for Tenham (L6), Tuxtuac (LL5), Willard (L6) and Forrest (b) (L6) chondrites. Their main magnetic minerals were determined from the analyses of transition temperatures (Θ_, Θ_, Θ_). The NRM characteristics of these chondrites were measured and are discussed on the basis of magnetic properties. The main magnetic minerals of the Tenham chondrite are taenite (γ-(Fe, Ni)) with 54 at % Ni and kamacite (α-(Fe, Ni)) with 7 at % Ni, and the main NRM carrier is taenite. Tenham has a stable NRM. Tuxtuac mainly contains tetrataenite and taenite (the ratio tetrataenite : taenite is 15 : 85,T. NAGATA et al., Mem. Natl Inst. Polar Res., Spec. Issue, 41,364,1986) and they both contribute to NRM. The NRM of Tuxtuac is rather unstable magnetically. The main magnetic minerals of the Willard chondrite are the same as those of Tenham, i. e. taenite with 54 at % Ni and kamacite with 7 at % Ni. The main NRM carrier is taenite. Willard has an unstable NRM. Forrest is suggested to have experienced some alteration, on the basis of the analysis of the Js-T curve, and may have acquired a secondary NRM of probable terrestrial origin

Double-Exchange Model on Triangle Chain

We study ground state properties of the double-exchange model on triangle chain in the classical limit on $t_{2g}$ spins. The ground state is determined by a competition among the kinetic energy of the $e_g$ electron, the antiferromagnetic exchange energy between the $t_{2g}$ spins, and frustration due to a geometric structure of the lattice. The phase diagrams are obtained numerically for two kinds of the models which differ only in the transfer integral being real or complex. The properties of the states are understood from the viewpoint of the spin-induced Peierls instability. The results suggest the existence of a chiral glass phase which is characterized by a local spin chirality and a continuous degeneracy.Comment: 6 pages, 4 figure

A GC polymorphism associated with serum 25-hydroxyvitamin D level is a risk factor for hip fracture in Japanese patients with rheumatoid arthritis: 10-year follow-up of the Institute of Rheumatology, Rheumatoid Arthritis cohort study

INTRODUCTION: Vitamin D deficiency has been reported to be common in patients with rheumatoid arthritis (RA) who have a higher prevalence of osteoporosis and hip fracture than healthy individuals. Genetic variants affecting serum 25-hydroxyvitamin D (25(OH)D) concentration, an indicator of vitamin D status, were recently identified by genome-wide association studies of Caucasian populations. The purpose of this study was to validate the association and to test whether the serum 25(OH)D-linked genetic variants were associated with the occurrence of hip fracture in Japanese RA patients. METHODS: DNA samples of 1,957 Japanese RA patients were obtained from the Institute of Rheumatology, Rheumatoid Arthritis (IORRA) cohort DNA collection. First, five single nucleotide polymorphisms (SNPs) that were reported to be associated with serum 25(OH)D concentration by genome-wide association studies were genotyped. The SNPs that showed a significant association with serum 25(OH)D level in the cross-sectional study were used in the longitudinal analysis of hip fracture risk. The genetic risk for hip fracture was determined by a multivariate Cox proportional hazards model in 1,957 patients with a maximum follow-up of 10 years (median, 8 years). RESULTS: Multivariate linear regression analyses showed that rs2282679 in GC (the gene encoding group-specific component (vitamin D binding protein)) locus was significantly associated with lower serum 25(OH)D concentration (P = 8.1 × 10(-5)). A Cox proportional hazards model indicated that rs2282679 in GC was significantly associated with the occurrence of hip fracture in a recessive model (hazard ratio (95% confidence interval) = 2.52 (1.05-6.05), P = 0.039). CONCLUSIONS: A two-staged analysis demonstrated that rs2282679 in GC was associated with serum 25(OH)D concentration and could be a risk factor for hip fracture in Japanese RA patients

Studies of the efficacy and safety of methotrexate at dosages over 8 mg/week using the IORRA cohort database

The maximum dosage of methotrexate (MTX) for treatment of rheumatoid arthritis (RA) formally approved in Japan is 8 mg/week. We intended to examine the efficacy and safety of MTX at dosages over 8 mg/week in Japanese rheumatoid arthritis patients using the large Institute of Rheumatology, Rheumatoid Arthritis (IORRA) cohort database. Among 9,122 patients registered in the IORRA database from the October 2000 survey to the October 2007 survey, 5,201 patients who had been treated with MTX were selected. We attempted to overcome the drawbacks innate to nonrandomized studies by using longitudinal analyses and multifactorial logistic regression analyses. Cross-sectional analysis of data obtained from the October 2007 survey indicated that dosages of MTX higher than 8 mg/week were used in 27.5% of patients treated with MTX. Longitudinal analyses based on data from three consecutive phases showed that final Disease Activity Score-28 (DAS28) values were significantly lower [n = 260, mean difference 0.563, 95% confidence interval (CI) 0.438–0.688, P < 2.2 × 10−22, two-sided paired t test] than initial values when MTX was increased from 8 mg/week or lower to over 8 mg/week. In addition, longitudinal analyses based on data from two consecutive phases indicated decreases in DAS28 values of 0.26 ± 1.04 (n = 690, P = 6.78 × 10−11, two-sided paired t test) when MTX dosages were increased from 8 mg/week or lower to over 8 mg/week, compared with decreases of 0.07 ± 0.89 (n = 2,125, P = 0.000307) when the dosage was maintained at 8 mg/week. The decreases in DAS28 values were significantly larger in the former than the latter (P = 2.27 × 10−6, two-sided unpaired t test). Concerning safety of MTX at dosages over 8 mg/week, we performed logistic regression analysis in which the objective variable was the existence or nonexistence of self-reported side-effects and the explanatory variable was the MTX dosage in the former phase, with adjustments made for age, sex, body mass index (BMI), steroid administration, folic acid administration, concomitant pulmonary diseases, and renal dysfunction. The results indicated that MTX dosages over 8 mg/week did not have any association with either severe or severe + moderate side-effects. These data regarding both efficacy and safety of MTX at dosages over 8 mg/week in Japanese RA patients would provide the basis for use of the drug at dosages currently not formally approved by the Japanese government

Cantor Spectra for Double Exchange Model

We numerically study energy spectra and localization properties of the double exchange model at irrational filling factor. To obtain variational ground state, we use a mumerical technique in momentum space by ``embedded'' boundary condition which has no finite size effect a priori. Although the Hamiltonian has translation invariance, the ground state spontaneously exhibits a self-similarity. Scaling and multi-fractal analysis for the wave functions are performed and the scaling indices $\alpha$'s are obtained. The energy spectrum is found to be a singular continuous, so-called the Cantor set with zero Lebesque measure.Comment: 4 pages, 4 figures, revtex, corrected some typos, accepted for publication in PR

Genome-Wide Association Study and Gene Expression Analysis Identifies CD84 as a Predictor of Response to Etanercept Therapy in Rheumatoid Arthritis

Anti-tumor necrosis factor alpha (anti-TNF) biologic therapy is a widely used treatment for rheumatoid arthritis (RA). It is unknown why some RA patients fail to respond adequately to anti-TNF therapy, which limits the development of clinical biomarkers to predict response or new drugs to target refractory cases. To understand the biological basis of response to anti-TNF therapy, we conducted a genome-wide association study (GWAS) meta-analysis of more than 2 million common variants in 2,706 RA patients from 13 different collections. Patients were treated with one of three anti-TNF medications: etanercept (n = 733), infliximab (n = 894), or adalimumab (n = 1,071). We identified a SNP (rs6427528) at the 1q23 locus that was associated with change in disease activity score (ΔDAS) in the etanercept subset of patients (P = 8×10-8), but not in the infliximab or adalimumab subsets (P>0.05). The SNP is predicted to disrupt transcription factor binding site motifs in the 3′ UTR of an immune-related gene, CD84, and the allele associated with better response to etanercept was associated with higher CD84 gene expression in peripheral blood mononuclear cells (P = 1×10-11 in 228 non-RA patients and P = 0.004 in 132 RA patients). Consistent with the genetic findings, higher CD84 gene expression correlated with lower cross-sectional DAS (P = 0.02, n = 210) and showed a non-significant trend for better ΔDAS in a subset of RA patients with gene expression data (n = 31, etanercept-treated). A small, multi-ethnic replication showed a non-significant trend towards an association among etanercept-treated RA patients of Portuguese ancestry (n = 139, P = 0.4), but no association among patients of Japanese ancestry (n = 151, P = 0.8). Our study demonstrates that an allele associated with response to etanercept therapy is also associated with CD84 gene expression, and further that CD84 expression correlates with disease activity. These findings support a model in which CD84 genotypes and/or expression may serve as a useful biomarker for response to etanercept treatment in RA patients of European ancestry. © 2013 Cui et al