Diffusion of Water in Bentonite

Because of the low permeability and the high sorption coefficient, compacted sodium bentonite has been proposed as an effective backfill material in the repository of high-level radioactive waste. The only possible mechanism of nuclide transport in bentonite must be the diffusion. The diffusivity has been considered to have a close relationship with the retardation factor and the self-diffusivity of water. Then, we performed the experiments to determine the self-diffusivity of water in bentonite by using tritiated water as a tracer. The obtained self-diffusivity can be written as Da= (3.4 ± 0.2) × 10-6 [cm²/s] under the condition of temperature T= 25°C and compacted density of bentonite ρ= 2.7 [g/cm³]. It was revealed quantitatively that the self-diffusivity of water in bentonite is much smaller than that of free water (2.13 × 10-5 [cm²/s] at T= 25°C). Also discussed is the analysis of experimental results on the basis of a new solution derived for the diffusion in one dimensional finite zone

Epitaxially stabilized iridium spinel oxide without cations in the tetrahedral site

Single-crystalline thin film of an iridium dioxide polymorph Ir2O4 has been fabricated by the pulsed laser deposition of LixIr2O4 precursor and the subsequent Li-deintercalation using soft chemistry. Ir2O4 crystallizes in a spinel (AB2O4) without A cations in the tetrahedral site, which is isostructural to lambda-MnO2. Ir ions form a pyrochlore sublattice, which is known to give rise to a strong geometrical frustration. This Ir spinel was found to be a narrow gap insulator, in remarkable contrast to the metallic ground state of rutile-type IrO2. We argue that an interplay of strong spin-orbit coupling and a Coulomb repulsion gives rise to an insulating ground state as in a layered perovskite Sr2IrO4.Comment: 9 pages, 3 figure

Long-term effect of cinacalcet hydrochloride on abdominal aortic calcification in patients on hemodialysis with secondary hyperparathyroidism

Background: Secondary hyperparathyroidism (SHPT) is one of the common complications in dialysis patients, and is associated with increased risk of vascular calcification. The effects of cinacalcet hydrochloride treatment on bone and mineral metabolism have been previously reported, but the benefit of cinacalcet on vascular calcification remains uncertain. The aim of this study was to evaluate the impact of cinacalcet on abdominal aortic calcification in dialysis patients. Subjects and methods: Patients were on maintenance hemodialysis with insufficiently controlled SHPT (intact parathyroid hormone [PTH] >180 pg/mL) by conventional therapies. All subjects were initially administered 25 mg cinacalcet daily, with concomitant use of calcitriol analogs. Abdominal aortic calcification was annually evaluated by calculating aortic calcification area index (ACAI) using multidetector computed tomography (MDCT), from 12 months before to 36 months after the initiation of cinacalcet therapy. Results: Twenty-three patients were analyzed in this study. The mean age was 59.0±8.7 years, 34.8% were women, and the mean dialysis duration was 163.0±76.0 months. After administration of cinacalcet, serum levels of intact PTH, phosphorus, and calcium significantly decreased, and mean Ca × P values significantly decreased from 67.4±7.9 mg2/dL2 to 52±7.7 mg2/dL2. Although the ACAI value did not decrease during the observation period, the increase in ACAI between 24 months and 36 months after cinacalcet administration was significantly suppressed. Conclusion: Long-term administration of cinacalcet was associated with reduced progression of abdominal aortic calcification, and achieving appropriate calcium and phosphorus levels may reduce the rates of cardiovascular events and mortality in patients on hemodialysis

Pressure effects on an organic radical ferromagnet: 2,5-difluorophenyl-a-nitronyl nitroxide

Raising a transition temperature (Tc) in organic radical ferromagnets is a desire for material scientists. We investigated the pressure effects on an organic radical ferromagnet 2,5-difluorophenyl-α-nitronyl nitroxide (2,5-DFPNN), which has a ferromagnetic transition at 0.45 K. The hydrostatic pressure effects were investigated through measurements of ac magnetic susceptibility (χ) up to P=1.7GPa, heat capacity (Cp) up to P=1.5GPa, and powder x-ray diffraction up to P=4.7GPa. Furthermore, ac magnetic susceptibility under nonhydrostatic pressure was also measured in the pressure region up to 10.0 GPa. As for 2,5-DFPNN, we observed the pressure-induced enhancement of Tc as dTc/dP=7.9×10−2K/GPa [Tc(P=1.5GPa)=0.57K], while other prototypes, the β phase of p-NPNN and p−Cl−C6H4−CH=N−TEMPO show the negative pressure effects. The results for the Cp and the crystal structural analysis suggest that the magnetic dimension of the short-range order developing above Tc transforms from one dimension (a axis) to two dimensions (ac plane) under high pressure. This increase of the magnetic dimension probably promotes to increase Tc. The ferromagnetic signal of χ, however, decreases with increasing pressure, and finally disappears for P>~5.0GPa. The decrease seems to originate from the decrease of the ferromagnetic interaction along the b axis. Similar instability of organic ferromagnetic long range order against pressure has been observed for the β phase of p-NPNN and p−Cl−C6H4−CH=N−TEMPO

Preemptive therapy of human herpesvirus-6 encephalitis with foscarnet sodium for high-risk patients after hematopoietic SCT

金沢大学医薬保健研究域医学系Human herpesvirus-6 (HHV-6) is a major cause of limbic encephalitis with a dismal prognosis after allogeneic hematopoietic SCT (HSCT). A prospective, multicenter study was conducted to assess the safety and efficacy of preemptive therapy with foscarnet sodium (PFA) for the prevention of HHV-6 encephalitis. Plasma HHV-6 DNA was measured thrice weekly from day 7 until day 36 after umbilical cord blood transplantation (UCBT) or HSCT from HLA-haploidentical relatives. PFA, 90 mg/kg/day, was started when HHV-6 DNA exceeded 5 × 102 copies/mL. Mild and transient adverse events were associated with PFA in 7 of 8 patients. Twelve of 15 UCBT recipients became positive for HHV-6 DNAemia, defined by greater than 1 × 102 copies/mL of HHV-6 DNA in plasma. The virus exceeded 5 × 102 copies/mL in seven patients, whereas none of the five HLA-haploidentical HSCT recipients became positive. One patient developed mild limbic encephalitis just after initial PFA administration. Preemptive PFA therapy is safe, but as HHV-6 DNAemia can abruptly develop before neutrophil engraftment in UCBT recipients, prophylactic PFA administration from day 7 or earlier after UCBT may be needed. © 2011 Macmillan Publishers Limited All rights reserved

Comparison of Internal Fixations for Distal Clavicular Fractures Based on Loading Tests and Finite Element Analyses

It is difficult to apply strong and stable internal fixation to a fracture of the distal end of the clavicle because it is unstable, the distal clavicle fragment is small, and the fractured region is near the acromioclavicular joint. In this study, to identify a superior internal fixation method for unstable distal clavicular fracture, we compared three types of internal fixation (tension band wiring, scorpion, and LCP clavicle hook plate). Firstly, loading tests were performed, in which fixations were evaluated using bending stiffness and torsional stiffness as indices, followed by finite element analysis to evaluate fixability using the stress and strain as indices. The bending and torsional stiffness were significantly higher in the artificial clavicles fixed with the two types of plate than in that fixed by tension band wiring (P<0.05). No marked stress concentration on the clavicle was noted in the scorpion because the arm plate did not interfere with the acromioclavicular joint, suggesting that favorable shoulder joint function can be achieved. The stability of fixation with the LCP clavicle hook plate and the scorpion was similar, and plate fixations were stronger than fixation by tension band wiring

Airway wall structure assessed by endobronchial ultrasonography and bronchial hyperresponsiveness in patients with asthma

金沢大学医薬保健研究域医学系Background and Objective: The purpose of this study was to evaluate the relationship between the wall structure assessed by using endobronchial ultrasonography (EBUS) and bronchial hyperresponsiveness in patients with asthma. Methods: Twenty-four patients with stable asthma and 11 individuals without asthma were studied. EBUS was performed with a radial 20-MHz ultrasonic probe inserted into the intermediate bronchus undergoing flexible bronchoscopy to assess the airway wall structure. The percentage of airway wall thickness {WT%; defined as [(ideal outer diameter-ideal luminal diameter)/ideal outer diameter] × 100} was determined by EBUS. We measured bronchial hyperresponsiveness to methacholine [the provocative concentration of methacholine causing a decrease of 20% or more in forced expiratory volume in 1 s (PC20)]. Results: Percentage wall thickness measured by EBUS was significantly greater in patients with asthma than that in subjects without asthma (P < 0.01). The evaluation of the laminar structure using EBUS indicated that the thickness of the second layer in patients with asthma was greater than that in subjects without asthma (P < 0.05). PC20 was negatively correlated with the thickness of the second layer (r=0.52, P < 0.01) but was not significantly correlated with other layers in patients with asthma. Conclusions: The evaluation of the bronchial mural structure using EBUS might be advantageous for assessing the relationship between airway wall remodeling and bronchial hyperresponsiveness. © 2010 Lippincott Williams & Wilkins