Analysis of the effect of structural materials in a wall-less tissue-equivalent proportional counter irradiated by 290 MeV u(-1) carbon beam

Effects of structural materials in a wall-less tissue-equivalent proportional counter were evaluated based on the calculation of energy deposits by EGS5 and the measurement of lineal energy distributions using 290 MeV u(-1) carbon beams. It is found that the correction of measured data based on simulation is necessary for understanding the energy deposition spectra in the homogeneous condition in tissues.     

Sorption characteristics of fluoride on to magnesium oxide-rich phases calcined at different temperatures

The effect of calcination temperature during production of magnesium oxide-rich phases from MgCO(3) on the sorption of F(-) ions in the aqueous phase has been investigated. Magnesium oxide-rich phases were formed by calcination at over 873 K for 1h. Higher calcination temperatures produced more crystalline MgO with smaller specific surface area and provided larger values of the total basicity per unit surface area. The higher calcination temperatures lead to slower F(-) removal rate, and lower equilibrium F(-) concentrations, when the equilibrium F(-) concentrations are less than 1 mmol dm(-3). Larger total basicity per unit surface area made the reactivity with F(-) ions in aqueous phase more feasible, resulting in a greater degree of F(-) sorption. For equilibrium F(-) concentrations more than 1 mmol dm(-3), lower calcination temperatures favored the co-precipitation of F(-) with Mg(OH)(2), probably leading to the formation of Mg(OH)(2-x)F(x), and the achievement of larger sorption density. This is the first paper which describes the relationship between the solid base characteristics obtained by CO(2)-TPD for MgO with different calcination temperatures as a function of the reactivity of F(-) sorption in the aqueous phase.     

Method of component assay of alpha-glucosyltransferase-treated stevia (enzymatically modified stevia) products using enzymatic hydrolysis

We have developed an analytical method for components of alpha-glucosyltransferase-treated stevia, a food additive product. Suitable conditions to separate additional sugar from alpha-glucosyltransferase-treated stevia by using glucoamylase were found (55 degrees C for 3 hr with 250 U of glucoamylase in 10 mL of reaction solution). By solid-phase extraction using a C18 cartridge column, polysaccharides were excluded from the sample, and the glycosides and sugar obtained after hydrolysis with glucoamylase were separated on another C18 cartridge column. The glycosides and sugar contents were determined by HPLC. By this method, additional sugar was detected in all of three product samples tested and the sugar was glucose. The contents of glucose and total glycosides (minus unreacted glycoside) were 25-42% and 35.7-52.5%, respectively. In alpha-glucosyltransferase-treated stevia, the sum of total glycosides and glucose amounted to 77.5-80.4% of the total and their recoveries from samples from which polysaccharide had been excluded by C18 cartridge column processing were over 85%. The contents of alpha-glucosyltransferase-treated stevia obtained by multiplying the sugar content by the coefficient (0.9) for hydrolysis and converting on dry weight basis were all over 80.0% and met the standard set by the Japan Food Additives Association.     

Preparation of silk protein sericin as mitogenic factor for better mammalian cell culture

We previously reported that sericin small (sericin-S), with a molecular weight that ranges from 5 to 100 kDa, is a cell culture supplement used to accelerate cell proliferation. In this study, a novel preparation method for sericin and several applications of sericin were examined. Sericin large, prepared under nonhydrolyzing conditions and ranging from 50 to 200 kDa, also accelerated cell proliferation, but its effects were inferior to those of sericin-S. Additional sericin preparations with various molecular weights that were differentially hydrolyzed were also tested but none of them was significantly superior to sericin-S, and neither were several recombinant sericin peptides. Sericin-S successfully accelerated the proliferation of hybridoma cells in various serum-free media, implying the mitogenic effect of sericin is independent from media. We also demonstrated that sericin-S successfully induced the proliferation of CTLL-2, an established T lymphocyte cell line, under IL-2 starvation conditions. These results indicate that sericin, particularly sericin-S, improves serum-free mammalian cell culture.     

Tribochemical Reactions of Ionic Liquids Under Vacuum Conditions

Ionic liquids are expected to function as novel lubricants owing to their attractive characteristics such as high thermal stability and low vapor pressure. In order for ionic liquids to be used as lubricants, knowledge of their corrosion and lubricating properties must be obtained. However, the reaction mechanism and decomposition of ionic liquids have not yet been sufficiently clarified. In this study, we elucidate the tribological properties and tribochemical reaction mechanism by analyzing outgassing generated by the decomposition or reaction of ionic liquids [EMIM][DCN], [EMIM][TCB], and [BMPL][TCB] on a sliding surface. From our results, [BMPL][TCB] showed the lowest friction coefficient and [EMIM][DCN] had a lower friction coefficient than [EMIM][TCB]. In all cases, outgassing from the ionic liquid was confirmed, and main outgassing products were derived from the cation. [BMPL][TCB] had the largest amount of outgassing. Time-of-flight secondary ion mass spectroscopy analysis showed that tribochemical reactions involving the anion occurred. From sliding tests and experimental analyses, it is revealed that the [DCN] anion showed superior lubricating properties to the [TCB] anion.     

Estimating a change point in the long memory parameter

We propose an estimator of change point in the long memory parameter d of an ARFIMA(p, d, q) process using the sup Wald test. We derive the consistency and the rate of convergence of the estimator for the time of change. The convergence rate of our change point estimator depends on the magnitude of a shift. Furthermore, we obtain the limiting distribution of our change point estimator without depending on the distribution of the process. Therefore, we can construct confidence intervals for the change point. Simulations show the validity of the asymptotic theory of our estimator if the sample size is large enough. We apply our change point estimator to the yearly Nile river minimum water level.     

The influence of DLC coating on the mechanical and frictional properties of unpeened and peened Cu-based bimetal under dry sliding conditions

In this study, the influence of a combination of high-frequency ultrasonic peening (HFUP) technique and diamond-like carbon (DLC) coating on the mechanical and frictional properties of Cu-based alloy sintered on steel by a powder metallurgy (P/M) technique was investigated. The frictional behavior of the Cu-based alloy specimens was assessed using a Schwingung Reibung Verschleiss (SRV) pin-on-disk tribometer sliding against a Cr-plated bearing steel pin under dry sliding conditions. The purpose of this study is to develop a thin wear resistant layer for Cu-based alloy and to extend its application in the automotive industry. Results showed that the over-coated DLC coating deposited onto a peened Cu-based alloy specimen had higher mechanical and lower frictional properties compared to that of the over-coated DLC coating deposited onto an unpeened Cu-based alloy specimen, which may be ascribed to the undulated microstructure caused by HFUP technique resulting in good adhesion. It was revealed that the deposited DLC coating was beneficial for improving the mechanical and frictional properties of Cu-based alloy. Hence, it is expected that the results of this investigation can be applied to improve the frictional behavior of an internal combustion engine (ICE) components which are made of bimetals (sintered Cu-based alloy on a steel back).     

Enhanced bioactivity of polyvinylidene chloride films using argon ion bombardment for guided bone regeneration

Polyvinylidene chloride (PVDC) is a long chain carbon synthetic polymer. The objective of this study was to improve the bioactivity of PVDC films through surface modification using argon (Ar) ion bombardment to create Ar-modified PVDC films (Ar-PVDC) to address the clinical problems of guided bone regeneration (GBR), which is technique-sensitive, and low bone regenerative ability. First, the effects of Ar ion bombardment, a low temperature plasma etching technique widely used in industry, on PVDC film wettability, surface chemistry, and morphology were confirmed. Next, fibroblast-like and osteoblast-like cell attachment and proliferation on Ar-PVDC were assessed. As a preclinical in vivo study, Ar-PVDC was used to cover a critical-sized bone defect on rat calvaria and osteoconductivity was evaluated by micro-computed tomography analysis and histological examinations. We found that the contact angle of PVDC film decreased by 50° because of the production of –OH groups on the PVDC film surface, though surface morphological was unchanged at 30 min after Ar ion bombardment. We demonstrated that cell attachment increased by about 40 % and proliferation by more than 140 % because of increased wettability, and 2.4 times greater bone regeneration was observed at week 3 with Ar-PVDC compared with untreated PVDC films. These results suggest that Ar ion bombardment modification of PVDC surfaces improves osteoconductivity, indicating its potential to increase bone deposition during GBR.