Phase transitions in spin-orbital coupled model for pyroxene titanium oxides

We study the competing phases and the phase transition phenomena in an effective spin-orbital coupled model derived for pyroxene titanium oxides ATiSi2O6 (A=Na, Li). Using the mean-field-type analysis and the numerical quantum transfer matrix method, we show that the model exhibits two different ordered states, the spin-dimer and orbital-ferro state and the spin-ferro and orbital-antiferro state. The transition between two phases is driven by the relative strength of the Hund's-rule coupling to the onsite Coulomb repulsion and/or by the external magnetic field. The ground-state phase diagram is determined. There is a keen competition between orbital and spin degrees of freedom in the multicritical regime, which causes large fluctuations and significantly affects finite-temperature properties in the paramagnetic phase.Comment: 4 pages, 6 figures, proceedings submitted to SPQS200

A study to assess COPD Symptom-based Management and to Optimise treatment Strategy in Japan (COSMOS-J) based on GOLD 2011

Background and objective: The Global initiative for chronic Obstructive Lung Disease(GOLD) Committee has proposed a chronic obstructive pulmonary disease (COPD) assessment framework focused on symptoms and on exacerbation risk. This study will evaluate a symptom and exacerbation risk-based treatment strategy based on GOLD in a real-world setting in Japan. Optimal management of COPD will be determined by assessing symptoms using the COPD Assessment Test (CAT) and by assessing the frequency of exacerbations. Methods: This study (ClinicalTrials.gov identifier: NCT01762800) is a 24-week, multicenter, randomized, double-blind, double-dummy, parallel-group study. It aims to recruit 400 patients with moderate-to-severe COPD. Patients will be randomized to receive treatment with either salmeterol/fluticasone propionate (SFC) 50/250μg twice daily or with tiotropium bromide 18μg once daily. Optimal management of patients will be assessed at four-weekly intervals and, if patients remain symptomatic, as measured using the CAT, or experience an exacerbation, they have the option to step up to treatment with both drugs, ie, SFC twice daily and tiotropium once daily (TRIPLE therapy). The primary endpoint of the study will be the proportion of patients who are able to remain on the randomized therapy. Results: No data are available. This paper summarizes the methodology of the study in advance of the study starting. Conclusion: The results of this study will help physicians to understand whether TRIPLE therapy is more effective than either treatment strategy alone in controlling symptoms and exacerbations in patients with moderate-to-severe COPD. It will also help physicians to understand the GOLD recommendation work in Japan

Molecular dissection of Arabidopsis RAR1 and SGT1 functions in plant immunity

Plants possess several layers of defence against pathogens. RAR1 (required for Ml-a12 conditioned resistance) and SGT1 (suppressor of G2 allele of skp1) are regulators of disease resistance conditioned by Resistance (R) proteins that recognise specific pathogen effectors. The model plant, Arabidopsis thaliana, has one copy of RAR1 (AtRAR1) and two recently duplicated copies of SGT1 (AtSGT1a and AtSGT1b). Despite their high sequence homology (78% identity at the amino acid level), AtSGT1b, but not AtSGT1a, is genetically recruited for resistance mediated by a subset of R proteins and for phytohormone signalling controlled by at least two plant SCF E3 ligases (SCF TIR1 and SCF COI1). AtRAR1, but not AtSGT1a or AtSGT1b, was also shown to contribute to plant basal defence against virulent pathogens, in which Arabidopsis EDS1 (Enhanced Disease Susceptibility 1) is an essential regulator. Recent studies revealed roles of RAR1 as co-chaperones of HSP90 to promote accumulation of pre-activated R proteins. SGT1 also shares molecular features of known cochaperones. SGT1 from plant, yeast and human interact with HSP90 and, in human and yeast, is an assembly factor in kinetocore complex formation. The precise role of SGT1 in plant defence was unclear. Recent biochemical experiments showed that SGT1 is required for Bs2 R protein folding that implies SGT1 activity in R protein complex assembly. However, recent genetic data in Arabidopsis suggested that SGT1 acts antagonistically with RAR1 in R protein accumulation, suggesting of a role of SGT1 in R protein degradation. The presence of an additional copy of SGT1 in Arabidopsis and lethality of the sgt1a/sgt1b double mutant complicates genetic interpretation using this system. This study aimed to characterize further the activities of RAR1 and SGT1 in plant immunity using various approaches. Several pieces of key data on the activities of RAR1 and SGT1 in plant immunity were generated in this study. AtRAR1, AtSGT1a and AtSGT1b proteins were expressed in all tissue tested and, although direct interaction between these proteins was not found, Hsc70 was identified as a potential interacting partner of AtRAR1. AtRAR1 regulates AtSGT1b accumulation in the nucleus. I established that both AtSGT1b and AtSGT1a are capable of functioning in R protein-mediated defence and phytohormone signalling in a dose-dependent manner. Lower levels of AtSGT1a in plant cells are likely insufficient to show a genetic effect on sgt1a mutants due to the presence of the more abundant AtSGT1b. The finding of AtSGT1a activity prompts us to reconsider the current model of RAR1/SGT1 antagonism in defence based on purely genetic data using Arabidopsis. I found that AtRAR1 and AtSGT1b contribute to basal defence. Intriguingly, the rar1 and sgt1b mutants lower EDS1 protein accumulation and change the molecular character of EDS1. The activities of AtRAR1 and AtSGT1b in basal defence may be through EDS1. EDS1 is an indispensable regulator of resistance conditioned by the TIR (Toll-Interleukin-1 Receptor) class of nucleotide-binding/leucine-rich-repeat (NB-LRR) R protein. These data therefore suggest a potential molecular link between EDS1 and TIR-NB-LRR via RAR and SGT1. My results highlight the need for further analysis to dissect mechanisms of TIR-NBLRR protein assembly and activation and their molecular connection with EDS1 and the chaperone/cochaperone machinery

Electronic structure and electric-field gradients analysis in CeIn3CeIn_3

Electric field gradients (EFG's) were calculated for the $CeIn_3$ compound at both $^{115}In$ and $^{140}Ce$ sites. The calculations were performed within the density functional theory (DFT) using the augmented plane waves plus local orbital (APW+lo) method employing the so-called LDA+U scheme. The $CeIn_3$ compound were treated as nonmagnetic, ferromagnetic, and antiferromagnetic cases. Our result shows that the calculated EFG's are dominated at the $^{140}Ce$ site by the Ce-4f states. An approximately linear relation is intuited between the main component of the EFG's and total density of states (DOS) at Fermi level. The EFG's from our LDA+U calculations are in better agreement with experiment than previous EFG results, where appropriate correlations had not been taken into account among 4f-electrons. Our result indicates that correlations among 4f-electrons play an important role in this compound and must be taken into account

Thermodynamics of the anisotropic Heisenberg chain calculated by the density matrix renormalization group method

The density matrix renormalization group (DMRG) method is applied to the anisotropic Heisenberg chain at finite temperatures. The free energy of the system is obtained using the quantum transfer matrix which is iteratively enlarged in the imaginary time direction. The magnetic susceptibility and the specific heat are calculated down to T=0.01J and compared with the Bethe ansatz results. The agreement including the logarithmic correction in the magnetic susceptibility at the isotropic point is fairly good.Comment: 4 pages, 3 Postscript figures, REVTeX, to appear in J. Phys. Soc. Jpn. Vol.66 No.8 (1997

Phylogeny and ontogeny of mental time

Humans have mental time in our mind, apart from physical time that is a part of system that governs the physical world, and memory is our key cognitive ability for recognizing the passage of time. Recent studies have suggested that the memory system of several nonhuman animals may have an incidental nature, which is also a feature of episodic memory. In addition, apes, which are phylogenetically close to humans, have an ability to remember a single past event. In the case of humans, preverbal infants under the age of two are able to retain long-term memory of a single event and apply it to predict a future event. Thus, nonhuman animals and preverbal human infants both have their own specific mental time travel abilities, and there is a phylogenetic and ontogenic basis of full-fledged mental time travel that can be found in human adults

The Free Energy and the Scaling Function of the Ferromagnetic Heisenberg Chain in a Magnetic Field

A nonlinear susceptibilities (the third derivative of a magnetization $m_S$ by a magnetic field $h$ ) of the $S$=1/2 ferromagnetic Heisenberg chain and the classical Heisenberg chain are calculated at low temperatures $T.$ In both chains the nonlinear susceptibilities diverge as $T^{-6}$ and a linear susceptibilities diverge as $T^{-2}.$ The arbitrary spin $S$ Heisenberg ferromagnet $[$ ${\cal H} = \sum_{i=1}^{N} \{ - J{\bf S}_{i} {\bf S}_{i+1} - (h/S) S_{i}^{z} \}$ $(J>0),$ $]$ has a scaling relation between $m_S,$ $h$ and $T:$ $m_S(T,h) = F( S^2 Jh/T^2).$ The scaling function $F(x)$=(2$x$/3)-(44$x^{3}$/135) + O($x^{5}$) is common to all values of spin $S.$Comment: 16 pages (revtex 2.0) + 6 PS figures upon reques

One-Dimensional Confinement and Enhanced Jahn-Teller Instability in LaVO3_3

Ordering and quantum fluctuations of orbital degrees of freedom are studied theoretically for LaVO$_3$ in spin-C-type antiferromagnetic state. The effective Hamiltonian for the orbital pseudospin shows strong one-dimensional anisotropy due to the negative interference among various exchange processes. This significantly enhances the instability toward lattice distortions for the realistic estimate of the Jahn-Teller coupling by first-principle LDA+$U$ calculations, instead of favoring the orbital singlet formation. This explains well the experimental results on the anisotropic optical spectra as well as the proximity of the two transition temperatures for spin and orbital orderings.Comment: 4 pages including 4 figure

Exact dimer ground state of the two dimensional Heisenberg spin system SrCu_2(BO_3)_2

The two dimensional Heisenberg model for SrCu_2(BO_3)_2 has the exact dimer ground state which was proven by Shastry and Sutherland almost twenty years ago. The critical value of the quantum phase transition from the dimer state to the N\'{e}el ordered state is determined. Analysis of the experimental data shows that SrCu_2(BO_3)_2 has the dimer ground state but is close to the transition point, which leads to the unusual temperature dependence of the susceptibility. Almost localized nature of the triplet excitations explains the plateaus observed in the magnetization curve.Comment: 4 pages, 5 figures, to appear in PR