First-principles calculations of lattice dynamics in CdTiO3 and CaTiO3: Phase stability and ferroelectricity

First-principles calculations of various phases of CdTiO3 carried out with the aim of obtaining insights into the mechanism of the ferroelectric phase transition and the structure of the low-temperature ferroelectric phase are reported. The results indicate that the preferred symmetry of the low-temperature phase is Pna2_1, rather than P21ma, corresponding to a small relative shift of the Ti and O ions in the paraelectric Pnma phase with the polarization axis parallel to the long axis. Calculated phonon dispersion curves show a distinct soft mode at the Γ point of the Pnma phase, which vanishes in the Pna2_1 phase, confirming that the transition to the ferroelectric phase is of the soft-mode displacive type. Calculations of perovskite CaTiO3, which also has an orthorhombic Pnma structure at room temperature but, unlike CdTiO3, does not exhibit a ferroelectric phase transition down to 4.2 K, were also carried out to help characterize the factors controlling ferroelectric phase transitions in perovskite titanates

Calibration of Setting of Mach Probes by Observing GAM Oscillations

The influence of relative displacement of Mach probe (which is placed near the top of magnetic surface) on the interference of signals is discussed. An error can arise in measured value of poloidal electric field. The Mach number perturbation at the GAM frequency has an interference from the density perturbation. The interference from the density perturbation can propagate to all of Mach number measurement. By observing the signals associated with GAM oscillations, the error in setting the probe arrays can be detected. This result can be applied to correct the positioning of probes

Determination of trace elements in natural water samples by air-segmented flow-injection/ICP-MS after preconcentration with a chitosan-based chelating resin

本法では,各種天然水中の極微量金属成分を同時定量する目的で空気分節試料導入/ICP-MSシステムを用いて,微少量試料(数十μl)を前処理せずにネブライザーに送り込み,多数の金属成分の定量が可能であった。共存主成分による質量干渉を受ける一部遷移金属や直接試料導入では感度の足りない元素については,イミノ二酢酸型キトサンキレート樹脂充填カラムによる分離·濃縮操作の併用によって更に信頼性の高いデータが得られることが分かった。前処理においては,体積1mlのミニカラムを用いて50mlの溶液試料から50倍濃縮を行い,試料·試薬·廃液すべてを少量化することができた。本ICP-MSシステムでは試料導入量は80μlで十分であり,1mlでも数回繰り返し測定が可能で,しかも多元素同時分析ができた。確立した分析法を用いて河川水や市販のミネラルウォーターに応用し,希土類を含め45種の微量元素の定量が可能となった。Ultratrace elements in natural water samples were determined simultaneously by air-segmented flow-injection/inductively coupled plasma-mass spectrometry(SFI/ICP-MS).A small volume of the sample solutions(80μl) was introduced into a nebulizer by an air-segmented flow-injection(SFI) system, and a maximum of fifteen elements were measured during each run.A chitosan-based chelating resin containing functional groups of iminodiacetate was used to separate and enrich analyte metal ions.A 50-fold preconcentration using 50ml of sample solutions was achieved by the proposed method, where 1ml of 0.1M nitric acid was added to residues after drying the chelating column effluent.At pH6, several heavy metals(Fe, Ni, Co, Cu, Zn, Ag, Cd, Pb and U) and rare earth elements(REEs) were quantitatively retained on the chelating resin column, whereas alkali and alkaline earth metals were eluted from the column by rinsing with 5ml of a 0.2M ammonium acetate solution.Metals adsorbed on the chelating resin column were recovered by elution with 10ml of 1M nitric acid.The proposed method was applied to the determination of trace elements in several natural water samples, such as river water and mineral drinking water

Thymic Alterations in GM2 Gangliosidoses Model Mice

BACKGROUND: Sandhoff disease is a lysosomal storage disorder characterized by the absence of β-hexosaminidase and storage of GM2 ganglioside and related glycolipids. We have previously found that the progressive neurologic disease induced in Hexb(-/-) mice, an animal model for Sandhoff disease, is associated with the production of pathogenic anti-glycolipid autoantibodies. METHODOLOGY/PRINCIPAL FINDINGS: In our current study, we report on the alterations in the thymus during the development of mild to severe progressive neurologic disease. The thymus from Hexb(-/-) mice of greater than 15 weeks of age showed a marked decrease in the percentage of immature CD4(+)/CD8(+) T cells and a significantly increased number of CD4(+)/CD8(-) T cells. During involution, the levels of both apoptotic thymic cells and IgG deposits to T cells were found to have increased, whilst swollen macrophages were prominently observed, particularly in the cortex. We employed cDNA microarray analysis to monitor gene expression during the involution process and found that genes associated with the immune responses were upregulated, particularly those expressed in macrophages. CXCL13 was one of these upregulated genes and is expressed specifically in the thymus. B1 cells were also found to have increased in the thy mus. It is significant that these alterations in the thymus were reduced in FcRγ additionally disrupted Hexb(-/-) mice. CONCLUSIONS/SIGNIFICANCE: These results suggest that the FcRγ chain may render the usually poorly immunogenic thymus into an organ prone to autoimmune responses, including the chemotaxis of B1 cells toward CXCL13

An Assessment of Limit Cycle Oscillation Dynamics Prior to L-H Transition

In this article, experimental observations of limit cycle oscillations (LCO) that precede L-to-H transition are discussed. Issues are: (1) the existence of zonal flows, (2) spatio-temporal evolutions of turbulence intensity, and (3) periodic generations/decays of mean radial electric field and density. The role of Reynolds stress to accelerate the LCO flow is also addressed. The propagation of changes of the density gradient and turbulence amplitude into the core is commented. Varieties in experimental reports on these issues are explained, and possible origins of different interpretations are discussed. Problem definitions for the future research for resolution are presented

Change in Edge Fluctuations Synchronized with Heat Pulse in the JFT-2M Tokamak

The change in edge fluctuations synchronized with a heat pulse during Sawtooth oscillation has been investigated inthe JFT-2M tokamak using a reciprocating Langmuir probe. Data window of a heat pulse is segmented into a number oftime frames, and time traces of auto-power spectra at each frame are calculated. Conditional averaging over a number ofheat pulse events in a single discharge is performed in order to reduce the variance of the fluctuation spectra. At eachheat pulse event, a reduction in the geodesic acoustic mode fluctuation power and an increase in the turbulencefluctuation power are observed. The change in the fluctuation powers suggests that the edge heat pulse during Sawtoothinstability could affect the edge turbulence structure