Te concentration dependent photoemission and inverse-photoemission study of FeSe1?xTex

We have characterized the electronic structure of FeSe_1−xTe_x for various x values using soft x-ray photoemission spectroscopy (SXPES), high-resolution photoemission spectroscopy (HRPES) and inverse photoemission spectroscopy (IPES). The SXPES valence band spectral shape shows that the 2 eV feature in FeSe, which was ascribed to the lower Hubbard band in previous theoretical studies, becomes less prominent with increasing x. HRPES exhibits systematic x dependence of the structure near the Fermi level (E_F): its splitting near E_F and filling of the pseudogap in FeSe. IPES shows two features, near E_F and approximately 6 eV above E_F; the former may be related to the Fe 3d states hybridized with chalcogenide p states, while the latter may consist of plane-wave-like and Se d components. In the incident electron energy dependence of IPES, the density of states near E_F for FeSe and FeTe has the Fano lineshape characteristic of resonant behavior. These compounds exhibit different resonance profiles, which may reflect the differences in their electronic structures. By combining the PES and IPES data the on-site Coulomb energy was estimated at 3.5 eV for FeSe.     

Calderon's preconditioning for periodic fast multipole method for elastodynamics in 3D

Preconditioning methods based on Calderon's formulae for the periodic fast multipole method for elastodynamics in 3D are investigated. Three different types of formulations are proposed. The first type is a preconditioning just by appropriately ordering the coefficient matrix without multiplying preconditioners. The other two types utilise preconditioners constructed using matrices needed in the main fast multipole method algorithms. We make several numerical experiments with proposed preconditioners to confirm the efficiency of these proposed methods. We also conclude that the preconditioning of the first type is faster with respect to the computational time than other preconditioning methods discussed in this article. Copyright © 2012 John Wiley & Sons, Ltd.     

In situ TEM study on changes in structure and electrical conductance of carbon nanotube-gold contact induced by local joule heating

Electrical conductance of multi-walled carbon nanotubes (MWCNTs) with closed and open tips contacting with a gold (Au) electrode was studied by in situ transmission electron microscopy. When a current density through the contact region reached a threshold value of 2.6 × 10⁸ A/cm², the MWCNT tip was embedded into the Au surface by local melting of Au, and the total resistance was reduced with the increase of the contact area. Conductance per unit area at the contact between the MWCNT and Au electrode for the open-ended MWCNT is four times larger than that for the close-ended one, which is due to the direct connection of inner walls of the open-ended MWCNT with the Au surface.     

Forgetting curve of cricket,Gryllus bimaculatus,derived by using serotonin hypothesis

It is thought that the adjustment of intraspecific aggression is an essential factor in the development of a social structure. To understand the natural laws for organizing the social structure, we focus on the fighting behavior of crickets, Gryllus bimaculatus, and investigate the neuronal mechanisms to adjust aggressiveness associated with a neuromodulatory biological amine: serotonin (5-HT).In this paper, we present a working theory of a neurophysiological mechanism based on the past biological studies on the 5-HT hypothesis, and a mathematical model of the mechanism. We analyzed this model and concluded that this neurophysiological mechanism makes the forgetting process slower. Next, we fitted our theoretical forgetting curve to an experimental curve and estimated the parameters of our model. These estimated values were in agreement with common belief in biological science.     

An overview on the cellulose based conducting composites

Biopolymer based composites have been employed in numerous applications with increasing interest not only due to renewable, eco-friendly nature, but also because of the flexibility in processing conditions and competitive cost of their end products. The conductive materials from biopolymers have been found applicable in robots, medical imaging, sensitive membranes, actuators, visual displays, electronic wiring and shielding, and components in batteries. Cellulose is one of the most abundant biopolymers in the nature, which has received special attention for development of conducting materials due to biocompatibility for protein and drug immobilization and ability to form the composites with synthetic polymers. The present review is aimed to provide concisely the current status in this field of conducting composites from cellulose, with brief discussions of associated problems and future applications.     

Total reflection X-ray spectroscopy as a rapid analytical method for uranium determination in drainage water

Uranium concentrations in drainage water are typically determined by α-spectrometry. However, due to the low specific radioactivity of uranium, the evaporation of large volumes of drainage water, followed by several hours of measurements, is required. Thus, the development of a rapid and simple detection method for uranium in drainage water would enhance the operation efficiency of radiation control workers. We herein propose a novel methodology based on total reflection X-ray fluorescence (TXRF) for the measurement of uranium in contaminated water. TXRF is a particularly desirable method for the rapid and simple evaluation of uranium in contaminated water, as chemical pretreatment of the sample solution is not necessary, measurement times are typically several seconds, and the required sample volume is low. We herein employed sample solutions containing several different concentrations of uranyl acetate with yttrium as an internal standard. The solutions were placed onto sample holders, and were dried prior to TXRF measurements. The relative intensity, otherwise defined as the net intensity ratio of the Lα peak of uranium to the Kα peak of yttrium, was directly proportional to the uranium concentration. Using this method, a TXRF detection limit for uranium in contaminated water of 0.30 µg/g was achieved.     

Tuning catalytic performances of cobalt catalysts for clean hydrogen generation via variation of the type of carbon support and catalyst post-treatment temperature

Multi-walled carbon nanotubes, three types of activated carbons, single wall carbon nanotube and reduced graphene oxides were used to synthesize nano-sized Co catalysts for H₂ preparation via NH₃ decomposition. Catalyst samples were characterized by number of techniques such as N₂ physisorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopes (XPS), Transmission electron microscopy (TEM), CO chemisorption, temperature-programmed reduction (H₂-TPR) and temperature-programmed desorption (N₂-TPD). The catalytic activities of the studied catalysts for H₂ production via NH₃ decomposition were measured in a fixed-bed micro-reactor. Co catalyst supported on multi-wall carbon nanotubes has shown the highest catalytic activity. The Co particles size was significantly affected by the variation of the post-treatment temperature. The Co particles size in the range of 4.7–64.8 nm can be effectively controlled by varying post-treatment temperature between 230 and 700 °C. The maximum TOF of NH₃ decomposition was registered on cobalt catalyst post-treated at 600 °C.     

Prevention of peroxynitrite-induced oxidation and nitration reactions by ellagic acid

Four benzoic acid derivatives and three phenylpropanoids were tested for their ability to suppress oxidation of dichlorodihydrofluorescein (DCDHF) induced by 3-morpholinosydnonimine (SIN-1, a peroxynitrite donor). Ellagic acid was found to potently inhibit this oxidation and to inhibit oxidation of DCDHF induced by peroxynitrite itself. Moreover, this compound prevented peroxynitrite-induced oxidative single strand breaks in pTZ 18U plasmid DNA and nitration of tyrosyl residues in bovine serum albumin. These results show that ellagic acid protects biomolecules against oxidative and nitrative damage induced by peroxynitrite in vitro.