Half-magnetization plateau stabilized by structural distortion in the antiferromagnetic Heisenberg model on a pyrochlore lattice

Magnetization plateaus, visible as anomalies in magnetic susceptibility at low temperatures, are one of the hallmarks of frustrated magnetism. We show how an extremely robust half-magnetization plateau can arise from coupling between spin and lattice degrees of freedom in a pyrochlore antiferromagnet, and develop a detailed symmetry of analysis of the simplest possible scenario for such a plateau state. The application of this theory to the spinel oxides CdCr2O4 and HgCr2O4, where a robust half magnetization plateau has been observed, is discussed.Comment: 4 pages, 4 figure

Studies on Constructing a Scale for Word Meaning Comprehension

To construct a broad-range scale for word meaning comprehension, we have studied various methods of equating scales obtained from different version of vocabulary test administered to different groups of subjects. In this report, we propose a new equating method which uses longitudinal data. We applied the method to a set of new data of vocabulary tests which had been administered to a panel of subjects once a year during last six years. Parameter values of difficulty and discrimination of 315 items were estimated on the equated common scale

Expression levels of novel cytokine IL-32 in periodontitis and its role in the suppression of IL-8 production by human gingival fibroblasts stimulated with Porphyromonas gingivalis

Background:IL-32 was recently found to be elevated in the tissue of rheumatoid arthritis and inflammatory bowel disease. Periodontitis is a chronic inflammatory disease caused by polymicrobial infections that result in soft tissue destruction and alveolar bone loss. Although IL-32 is also thought to be associated with periodontal disease, its expression and possible role in periodontal tissue remain unclear. Therefore, this study investigated the expression patterns of IL-32 in healthy and periodontally diseased gingival tissue. The expression of IL-32 in cultured human gingival fibroblasts (HGF) as well as effects of autocrine IL-32 on IL-8 production from HGF were also examined.Methods:Periodontal tissue was collected from both healthy volunteers and periodontitis patients, and immunofluorescent staining was performed in order to determine the production of IL-32. Using real-time PCR and ELISA, mRNA expression and protein production of IL-32 in HGF, stimulated by Porphyromonas gingivalis (Pg), were also investigated.Results:Contrary to our expectation, the production of IL-32 in the periodontitis patients was significantly lower than in the healthy volunteers. According to immunofluorescent microscopy, positive staining for IL-32 was detected in prickle and basal cell layers in the epithelium as well as fibroblastic cells in connective tissue. Addition of fixed Pg in vitro was found to suppress the otherwise constitutive expression of IL-32 mRNA and protein in HGF. However, recombinant IL-32 in vitro inhibited the expression of IL-8 mRNA by HGF stimulated with Pg. Interestingly, anti-IL-32 neutralizing antibody upregulated the IL-8 mRNA expression in non-stimulated HGF, indicating that constitutive expression of IL-32 in HGF suppressed IL-8 mRNA expression in the absence of bacterial stimulation.Conclusion:These results indicate that IL-32 is constitutively produced by HGF which can be suppressed by Pg and may play a role in the downregulation of inflammatory responses, such as IL-8 production, in periodontal tissue

Selective cytotoxicity of dihydroorotate dehydrogenase inhibitors to human cancer cells under hypoxia and nutrient-deprived conditions

Human dihydroorotate dehydrogenase (HsDHODH) is a key enzyme of pyrimidine de novo biosynthesis pathway. It is located on the mitochondrial inner membrane and contributes to the respiratory chain by shuttling electrons to the ubiquinone pool. We have discovered ascofuranone (1), a natural compound produced by Acremonium sclerotigenum, and its derivatives are a potent class of HsDHODH inhibitors. We conducted a structure–activity relationship study and have identified functional groups of 1 that are essential for the inhibition of HsDHODH enzymatic activity. Furthermore, the binding mode of 1 and its derivatives to HsDHODH was demonstrated by co-crystallographic analysis and we show that these inhibitors bind at the ubiquinone binding site. In addition, the cytotoxicities of 1 and its potent derivatives 7, 8, and 9were studied using human cultured cancer cells. Interestingly, they showed selective and strong cytotoxicity to cancer cells cultured under microenvironment (hypoxia and nutrient-deprived) conditions. The selectivity ratio of 8 under this microenvironment show the most potent inhibition which was over 1000-fold higher compared to that under normal culture condition. Our studies suggest that under microenvironment conditions, cancer cells heavily depend on the pyrimidine de novo biosynthesis pathway. We also provide the first evidence that 1 and its derivatives are potential lead candidates for drug development which target the HsDHODH of cancer cells living under a tumor microenvironment

Ferromagnetism in multi--band Hubbard models: From weak to strong Coulomb repulsion

We propose a new mechanism which can lead to ferromagnetism in Hubbard models containing triangles with different on-site energies. It is based on an effective Hamiltonian that we derive in the strong coupling limit. Considering a one-dimensional realization of the model, we show that in the quarter-filled, insulating case the ground-state is actually ferromagnetic in a very large parameter range going from Tasaki's flat-band limit to the strong coupling limit of the effective Hamiltonian. This result has been obtained using a variety of analytical and numerical techniques. Finally, the same results are shown to apply away from quarter-filling, in the metallic case.Comment: 12 pages, revtex, 12 figures,needs epsf and multicol style file

A Follow-up Study on the Developmental Change of Word Meaning Comprehension

The purpose of this paper is to report the results of statistical analysis which was performed to investigate the developmental change of the comprehension of word meaning. After the first test had been administered to the pupils of the first grade at the three public elementary schools on 1977, the follow-up tests were succesively administered every year to the same group of subjects until 1985. The latent trait model was applied in order to estimate the ability of each subject in terms of an ability parameter. The statistical structure of the distribution of these ability parameters were analyzed with regard to grade, age, sex, and other variables. Furthermore, logistic curves were fitted in order to describe individual differences of the developmental changes

Spectral function of the 1D Hubbard model in the U→+∞U\to +\infty limit

We show that the one-particle spectral functions of the one-dimensional Hubbard model diverge at the Fermi energy like $|\omega-\varepsilon_F|^{-3/8}$ in the $U\to +\infty$ limit. The Luttinger liquid behaviour $|\omega-\varepsilon_F|^\alpha$, where $\alpha \to 1/8$ as $U\to +\infty$, should be limited to $|\omega-\varepsilon_F| \sim t^2/U$ (for $U$ large but finite), which shrinks to a single point, $\omega=\varepsilon_F$,in that limit. The consequences for the observation of the Luttinger liquid behaviour in photoemission and inverse photoemission experiments are discussed.Comment: 4 pages, RevTeX, 2 figures on reques

Preparation and evaluation of 186/188Re-labeled antibody (A7) for radioimmunotherapy with rhenium(I) tricarbonyl core as a chelate site

Objective: Rhenium is one of the most valuable elements for internal radiotherapy because 186Re and 188Re have favorable physical characteristics. However, there are problems when proteins such as antibodies are used as carriers of 186/188Re. Labeling methods that use bifunctional chelating agents such as MAG3 require the conjugation of the 186/188Re complex to protein after radiolabeling with the bifunctional chelating agent. These processes are complicated. Therefore, we planned the preparation by a simple method and evaluation of a stable 186/188Re-labeled antibody. For this purpose, we selected 186/188Re(I) tricarbonyl complex as a chelating site. In this study, A7 (an IgG1 murine monoclonal antibody) was used as a model protein. 186/188Re-labeled A7 was prepared by directly reacting a 186/188Re(I) tricarbonyl precursor, [186/188Re(CO)3(H2O)3]+, with A7. We then compared the biodistribution of 186/188Re-labeled A7 in tumor-bearing mice with 125I-labeled A7. Methods: For labeling A7, [186/188Re(CO)3(H2O)3]+ was prepared according to a published procedure. 186/188Re-labeled A7 (186/188Re-(CO)3-A7) was prepared by reacting [186/188Re(CO)3(H2O)3]+ with A7 at 43°C for 2 h. Biodistribution experiments were performed by the intravenous administration of 186/188Re-(CO)3-A7 solution into tumor-bearing mice. Results: 186Re-(CO)3-A7 and 188Re-(CO)3-A7 were prepared with radiochemical yields of 23 and 28%, respectively. After purification with a PD-10 column, 186/188Re-(CO)3-A7 showed a radiochemical purity of over 95%. In biodistribution experiments, 13.1 and 13.2% of the injected dose/g of 186Re-(CO)3-A7 and 188Re-(CO)3-A7, respectively, accumulated in the tumor at 24-h postinjection, and the tumor-to-blood ratios were over 2.0 at the same time point. Meanwhile, uptake of 125I-A7 in the tumor was almost the same as that of 186/188Re-(CO)3-A7 at 24-h postinjection. Blood clearances of 186/188Re-(CO)3-A7 were faster than those of 125I-A7. Conclusion: 186/188Re-labeled A7 showed high uptakes in the tumor. However, further modification of the labeling method would be necessary to improve radiochemical yields and their biodistribution. © 2009 The Japanese Society of Nuclear Medicine

The Efficiency of Preliminary Measurement by Means of a Short Form of the Stratified Adaptive Test in Measuring Verbal Ability

The semi-adaptive testing procedure, which consists of a program test for preliminary measurement and a conventional group test for accurate measurement, is proposed. The program test is a short form of the stratified adaptive test with eight pages, each of which contains seven items of diverse difficulty. Each subject is to be tested individually, at first, by the program test and then, to be given an edition of conventional test chosen among nine editions from the easier to the more difficult one. The obtained scores of the program test are used in deciding the appropriate level of difficulty for each edition. Sixty pupils from the first graders to the sixth graders are tested by this semi-adaptive testing procedure, and the efficiency of the procedure is analyzed in terms of various aspects. It is demonstrated that this four or five minutes program test works very well as a prelimiary measurement. This testing procedure is found to be fairly efficient to measure the abilities of subjects which distribute in a broad range