Another way of looking at bonding on bimetallic surfaces: the role of spin polarization of surface metal d states

The nature of electronic and chemical properties of an unstrained Pt monolayer on a 3d transition metal substrate, M (M = Cr, Mn, Fe), is studied using spin-polarized density functional theory calculations. High spin polarization of Pt d states is noted, verifying the magnetization induced on Pt, which is observed to be responsible for redirecting the analysis of bond formation on a metal surface towards a different perspective. While the shift in the Pt d band center (the average energy of the Pt d band, commonly used to predict the reactivity of surfaces) does give the expected trend in adsorbate (oxygen) chemisorption energy across the bimetallic surfaces in this work, our results show that for spin-polarized Pt d states, the variation in strength of adsorption with respect to the Fermi level density of states is more predictive of Pt chemisorption properties. Hence, this study introduces a scheme for analyzing trends in reactivity of bimetallic surfaces where adsorption energies are used as reactivity parameters and where spin polarization effects cannot be neglected.

Cross-sectional study on respiratory effect of toner-exposed work in manufacturing plants, Japan: pulmonary function, blood cells, and biochemical markers

The aim of the study is to examine the relationship between toner-exposed work and health indices related to respiratory disorders and to confirm the baseline of a cohort study to clarify the effect of toner exposure in manufacturing plants. Subjects were 1614 male workers (809 toner-exposed workers and 805 referents) who were engaged in toner manufacturing plants in Japan (Fuji Xerox Co., Ltd). The age of subjects was from 19 to 59 years, and the average age was 40.2 years(median 40 years, SD 7.67). We conducted a pulmonary function test (PEFR, VC, FVC, FEV(1.0)%, V25/Ht) and a blood cell test (RBC, Hb, Hct, Plt, WBC, cell contents of WBC) and measured biochemical indices in blood (ALT, AST, gamma-GTP, CRP, IgE) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) in urine. Student t-test and logistic regression analysis were applied to compare between the toner-exposed workers and the referents and to analyze the relationship among indices of effects and independent factors. There was no significant difference between the two groups in blood cell count and biochemical indices. Inflammation- and allergy-related markers such as 8OHdG and IgE also showed no significant difference between toner-exposed workers and the referents. The influence of smoking on pulmonary function indices was observed, but there was no relationship between the pulmonary function and toner-exposed work. In this article, we report a preliminary cross-sectional analysis in the subjects of a cohort study. No difference in pulmonary function indices was observed between the toner-exposed workers and the referents, and there was no consistent relationship between the exposure status and examined indices; however, the prevalence of subjective respiratory symptoms was higher in the exposed workers as presented in another report. Further analysis is important in the ongoing cohort study to clarify the effect of toner exposure on respiratory systems.

High-uptake graphene hydrogenation: a computational perspective

We review the physical mechanisms that lead toward the conversion of graphene into its fully hydrogenated counterpart, which is a material that possesses properties closer to those of diamond than graphene. These are discussed from a theoretical perspective, i.e., from calculations based on density functional theory. We first discuss stability trends in small clusters of adsorbed hydrogen, as well as surface structure and concurrent reactivity changes for graphene one-face and two-face hydrogenation. Effects of adsorbed hydrogen on graphene electronic states, which are essential to adsorbed hydrogen structure discrimination, are also discussed.

Proton transport through aqueous Nafion membrane

We introduce a new model for proton transport through a single proton-conducting channel of an aqueous Nafion membrane based on a mechanism in which protons move under electrostatic effect provided by the sulfonate (SO3-)groups of the Nafion side chains, the spin effect of active components, the hydrogen bonding effect with water molecules, and the screening effect of water media. This model can describe the proton transport within various levels of humidification ranging from the low humidity to the high humidity as a function of operating temperature. At low humidity, this model approaches to the so-called surface mechanism, while at high humidity, it approaches the well-known Grotthuss one. Proton motion is considered as the transfer from cluster to cluster under a potential energy. A proton-proton interaction is comprised in the calculation. Using Green function method, we obtained the proton current as a function of the Nafion membrane temperature. We found that the lower the temperature, the higher the proton current transfer through the Nafion membrane in low temperatures compared to the critical point 10K, which separates magnetic regime from non-magnetic regime. The increasing of proton current at very low temperatures is attributed to the spin effect. As the membrane temperature is higher than 40 ( degrees ) C , the decreasing of proton current is attributed to the loss of water uptake and the polymer contraction. The results of this study are qualitatively in good agreement with experiments. The expression for the critical temperature is also presented as a function of structural and tunable parameters, and interpreted by experimental data.

Hydrogen peroxide adsorption on Fe-filled single-walled carbon nanotubes: a theoretical study

We investigated the adsorption of hydrogen peroxide molecules on Fe-filled single-walled carbon nanotubes (SWNTs) based on density functional theory (DFT) calculations. The adsorption possibilities for the hydrogen peroxide molecule were tested by finding the minimum energy as a function of distance of the molecule from the Fe-filled SWNT. Stable structures were obtained by optimizing the hydrogen peroxide (H(2)O(2)) as it was adsorbed on to the Fe-filled SWNT. This study may serve as an initial investigation into the possibility of Fe-filled single-walled carbon nanotubes (SWNTs) as catalyst material for the proton exchange membrane fuel cell (PEMFC).

IL-7 specifies B cell fate at the common lymphoid progenitor to pre-proB transition stage by maintaining early B cell factor expression

IL-7 plays a critical role in B cell fate decision by regulating early B cell factor (EBF) expression. However, it was not clear when IL-7 stimulation is necessary in hemato-/lymphopoiesis in adult mice. Here we show that pre-proB cells derived from IL-7-/- mice have lost B cell potential, despite up-regulation of EBF expression following IL-7 stimulation. Pre-proB cells from wild-type mice can give rise to proB cells in the absence of IL-7. In this case, EBF up-regulation during the transition from the pre-proB to proB stages occurs normally. In contrast, EBF expression by IL-7-/- pre-proB cells after IL-7 stimulation is approximately 20 times lower than wild-type pre-proB cells. In addition, only multipotent progenitors with higher levels of ectopic EBF can give rise to proB cells in the absence of IL-7. Therefore, the primary function of IL-7 before the pre-proB stage in B cell development is to maintain the EBF expression level above a certain threshold, which is necessary for pre-proB cells to further transit to the proB stage.

Domain walls in the (Ga,Mn)as diluted magnetic semiconductor

We report experimental and theoretical studies of magnetic domain walls in an in-plane magnetized (Ga,Mn)As dilute moment ferromagnetic semiconductor. Our high-resolution electron holography technique provides direct images of domain wall magnetization profiles. The experiments are interpreted based on microscopic calculations of the micromagnetic parameters and Landau-Lifshitz-Gilbert simulations. We find that the competition of uniaxial and biaxial magnetocrystalline anisotropies in the film is directly reflected in orientation dependent wall widths, ranging from approximately 40 to 120 nm. The domain walls are of the Néel type and evolve from near-90 degrees walls at low temperatures to large angle [11[over ]0]-oriented walls and small angle [110]-oriented walls at higher temperatures.

Changes of Urinary 8-Hydroxydeoxyguanosine Levels during a Two-Day Ultramarathon Race Period in Japanese Non-Professional Runners

Using the urinary 8-hydroxydeoxyguanosine (8-OHdG) concentration, effects of participation in a two-day ultramarathon race period on oxidative DNA damage were investigated in Japanese nonprofessional runners. Before the first day (baseline), after the first day (mid-race) of 40-km running, and after the second day (post-race) of 90 km running, biomaterials were successfully sampled from 95 participants (males, 79; females, 16) who completed the full race. We analyzed urine for 8-OHdG and blood for aspartate aminotransferase (AST), creatine phosphokinase (CPK) and myoglobin, and evaluated fluctuation in the values at three sampling time points. Adjusted baseline urinary 8-OHdG levels (microg/g creatinine) (mean +/- standard deviation) showed no significant differences between males and females, at 2.85 +/- 1.17 and 3.04 +/- 1.56, respectively. In males, mid-race urinary 8-OHdG levels rose to 3.29 +/- 1.15 (p < 0.01), but then returned to 2.73 +/- 1.16 at the post-race time point (p < 0.01). In females, a similar increase to 3.32 +/- 1.47 and subsequent decline to 2.80 +/- 1.47 were noted. In contrast, AST, CPK and myoglobin were increased at both mid- and post-time points and particularly the latter, independent of the sex. Extreme prolonged exercise in a two-day ultramarathon race period causes oxidative DNA damage but antioxidant repair systems are apparently induced to protect against oxidative DNA stress with physical exercise.

Pancreatic calcium waves and secretion

Pancreatic acinar cells display stereotypic Ca2+ waves resulting from Ca2+ release from internal stores during stimulation. The Ca2+ waves are initiated at the luminal pole, and, at high agonist concentrations, spread towards the basal pole. Two key mechanisms behind the generation of Ca2+ waves have been identified. First, the Ca2+ waves are composite, mediated by three distinct Ca2+ release mechanisms with a polarized distribution: high-sensitivity inositol 1,4,5-trisphosphate (InsP3) receptors at a small trigger zone (T zone) in the secretory granule area, Ca(2+)-induced Ca2+ release channels in the granular area and low-sensitivity InsP3 receptors in the basal area. Second, InsP3 can readily diffuse in the cytosol, whereas rises in cytosolic Ca2+ concentration ([Ca2+]i) can be confined through strong buffering and sequestration of Ca2+. InsP3 is thus used as a long-range messenger to transmit agonist signals to the T zone, and [Ca2+]i rises at the T zone are used as a local switch. These mechanisms enable preferential activation of the T zone, irrespective of localization of stimuli and agonist receptors. The secretion of enzymes and fluid is a direct consequence of [Ca2+]i rises at the T zone. The Ca2+ waves and oscillations probably boost the T zone functions.

A comparative study of the interaction of platinum with group 4A (germanium, tin and lead) porphyrins

Because of its vast number of applications and high price many studies have been made on how to reduce the amount of platinum in catalysts. One method includes dispersing platinum nanoparticles in porous support materials. But electrically conductive carbon-based support materials-needed for fuel cell electrodes-permit nanoparticles to migrate and form larger clusters, leading to reduced catalytic activity over time. To find a solution to this problem, we modelled the interaction of group 4A metal porphyrins (germanium (II) porphyrin (GePor), tin (II) porphyrin (SnPor) and lead (II) porphyrin (PbPor)) with platinum (Pt) using density functional theory. We showed that platinum can bond strongly on both germanium porphyrin and tin porphyrin. More importantly, valence Pt d-orbital characteristics dominate their HOMO and HOMO-1. Our study indicates that dispersing Pt as individual atoms on a SnPor and GePor surface is a good way to minimize platinum load in carbon-based reduction catalysts for reactions involving mainly the HOMO and HOMO-1 of Pt, of which the oxygen reduction reaction in fuel cells is an example.

Applying computational nanomaterials design to the reactive ion etching of NiO thin films-a preliminary investigation

We have developed and proposed a model for reactive ion etching (RIE) process design of nickel oxide thin films using a computational materials design based on ab initio calculations. On etching NiO, we found that it was necessary to have hydrogen-based reactive gases in the initial state in order to enhance RIE (e.g. NH(3), CH(4)). We strongly suggest the use of CH(4) or any H-based gas source other than CHF(3) to enhance RIE process.