Fluctuations in Tracer Amounts in a Compartmental System with a Markovian Transition Process

This communication considers a method for evaluating fluctuations in the integral type output of a linear time-invariant compartmental system with a Markovian transition process. First, we derived a mathematical formula to calculate variances and covariances of integral type. outputs, as with radioisotope data, when transition rates are known. Then, an estimate for the upper limits of variances and covariances, i.e., 1/2?initial dose, when the transition rates are not given beforehand, was introduced.     

Apatite crystal in hard tissue of conodont fossils

The present study was aimed at examining the nature of apatite crystal in the tooth apparatus of a conodont fossil using transmission electron microscopy (TEM), scanning electron microscopy (SEM), laser Raman microprobe spectrometry and electron-probe microanalysis (EPMA). The hard tissue of the condont consisted of 2 layers and the organization varied with the size of the crystal. Higher magnification showed that the crystals were observed in the lattice of (100) and the central dark lines were not present. Ca, P, and F were detected in the crystal using EPMA. Our results indicate that the apatite crystal in conodont fossils is not hydroxyapatite but fluorapatite.     

Efficient Assembly of Bridged β‐Ga2O3 Nanowires for Solar‐Blind Photodetection

An increasing number of applications using ultraviolet radiation have renewed interest in ultraviolet photodetector research. Particularly, solar‐blind photodetectors sensitive to only deep UV (<280 nm), have attracted growing attention because of their wide applicability. Among recent advances in UV detection, nanowire (NW)‐based photodetectors seem promising, however, none of the reported devices possesses the required attributes for practical solar‐blind photodetection, namely, an efficient fabrication process, a high solar light rejection ratio, a low photocurrent noise, and a fast response. Herein, the assembly of β‐Ga₂O₃ NWs into high‐performance solar‐blind photodetectors by use of an efficient bridging method is reported. The device is made in a single‐step chemical vapor deposition process and has a high 250‐to‐280‐nm rejection ratio (～2 × 10³), low photocurrent fluctuation (<3%), and a fast decay time (<<20 ms). Further, variations in the synthesis parameters of the NWs induce drastic changes in the photoresponse properties, which suggest a possibility for tuning the performance of the photodetectors. The efficient fabrication method and high performance of the bridged β‐Ga₂O₃ NW photodetectors make them highly suitable for solar‐blind photodetection.     

Characterization of plasma membrane H+-ATPase from salt-tolerant yeast Candida versatilis

Plasma membrane was isolated from the salt-tolerant yeast Candida versatilis and the ATPase in plasma membrane was characterized. The ATPase was a typical H⁺-ATPase with similar properties to the Saccharomyces cerevisiae and Zygosaccharomyces rouxii enzymes. It was reacted with antibody (IgG) raised against S. cerevisiae plasma membrane H⁺-ATPase. The ATPase activity was not changed by adding NaCl and KCl to the assay solutions, but was increased by NH, especially by ammonium sulfate. In vivo stimulation of ATPase activity was observed by the addition of NaCl into the culture medium, as observed in Z. rouxii. No in vivo activation of H⁺-ATPase by glucose metabolism was observed in C. versatilis cells and the activity was independent of the growth phase, like Z. rouxii and unlike S. cerevisiae cells.     

Experimental and numerical analysis of channel-length-dependent electrical properties in bottom-gate,bottom-contact organic thin-film transistors with Schottky contact

Channel length dependence of field-effect mobility and source/drain parasitic resistance in pentacene thin-film transistors with a bottom-gate, bottom-contact configuration was investigated. Schottky barrier effect such as nonlinear behaviors in transistor output characteristics appeared and became more prominent for shorter channel length less than 10 μm, raising some concerns for a simple utilization of conventional parameter extraction methods. Therefore the gate-voltage-dependent hole mobility and the source/drain parasitic resistance in the pentacene transistors were evaluated with the aid of device simulation accounting for Schottky contact with a thermionic field emission model. The hole mobility in the channel region shows smaller values with shorter channel length even after removing the influence of Schottky barrier, suggesting that some disordered semiconductor layers with low carrier mobility exist near the contact electrode. This experimental data analysis with the simulation enables us to discuss and understand in detail the operation mechanism of bottom-gate, bottom-contact transistors by considering properly each process of charge carrier injection, carrier flow near the contact region, and actual channel transport.