What is the significance of nitrogen-vacancy centers in the doping into diamond?

In order to advance quantum computer after successful synthesis of a qubit (quantum-bit) using a NV (nitrogen-vacancy) center in diamond crystal, the innovation of a NOT processor is strongly demanded. A candidate of it can be one NV center associated with an additional N atom, which is called a NV–N center. Making use of a classical molecular dynamics simulation of N ion implantation into pure diamond with an energy of 200 eV, we have examined the crystallographic structure of “NV–N” centers. However, at low temperature of 30 K, most implanted N atoms became interstitials, thus it was difficult to identify even NV centers.     

Mouse Gastric Epithelial Cells Resist CagA Delivery by the Helicobacter pylori Type IV Secretion System

The initial step in bacterial infection is adherence of the bacterium to the target cell surface. Helicobacter pylori exploits the interaction of bacterial adhesin protein HopQ with human epithelial CEACAMs (CEACAM1, 5, and 6) to stably adhere to gastric epithelial cells, which is necessary for delivery of the H. pylori CagA oncoprotein into the epithelial cells via a type IV secretion system. In contrast to human CEACAMs, however, HopQ does not interact with Ceacam1 (mouse CEACAM1) in vitro or in CHO cells ectopically expressing Ceacam1. Since the mouse genome lacks Ceacam5 and Ceacam6, no significant HopQ–Ceacam interaction may occur in mouse gastric epithelial cells. Here, we found that the mouse stomach has a much lower expression level of Ceacam1 than the expression level of CEACAM1 in the human stomach. Consistently, mouse gastric epithelial cells resist CagA delivery by cagA-positive H. pylori, and the delivery is restored by ectopic expression of human CEACAM1 or CEACAM5 in mouse gastric epithelial cells. Thus, despite the fact that mice are routinely used for H. pylori infection studies, a low expression level of Ceacam1 in the mouse stomach together with the loss or greatly reduced interaction of HopQ with Ceacams make the mouse an inappropriate model for studying the role of H. pylori-delivered CagA in gastric pathogenesis, including the development of gastric cancer.     

Bulk heterojunction organic solar cells utilizing 1,4,8,11,15,18,22,25-octahexylphthalocyanine

Bulk heterojunction solar cells utilizing soluble phthalocyanine derivative, 1,4,8,11,15,18,22,25-octahexylphthalocyanine (C6PcH₂) have been investigated. The active layer was fabricated by spin-coating the mixed solution of C6PcH₂ and 1-(3-methoxy-carbonyl)-propyl-1-1-phenyl-(6,6)C61 (PCBM). The photovoltaic properties of the solar cell with bulk heterojunction of C6PcH₂ and PCBM demonstrated the strong dependence of active layer thickness, and the optimized active layer thickness was clarified to be 120 nm. By inserting MoO₃ hole transport buffer layer between the positive electrode and active layer, the FF and energy conversion efficiency were improved to be 0.50 and 3.2%, respectively. The tandem organic thin-film solar cell has also been studied by utilizing active layer materials of C6PcH₂ and poly(3-hexylthiophene) and the interlayer of LiF/Al/MoO₃ structure, and a high V_oc of 1.27 V has been achieved.     

Effect of Non-Equilibrium Condensation of Moist Air on Flow Field in Ludwieg Tube

The time-dependent behavior of non-equilibrium condensation of moist air through a Ludwieg tube with a diaphragm downstream is investigated by using a computational fluid dynamics work. The two-dimensional, compressible, Navier-Stokes equations, fully coupled with the condensate droplet growth equations, are numerically solved by a third-order MUSCL type TVD finite-difference scheme with a second-order fractional time step. Baldwin-Lomax turbulence model is employed to close the governing equations. The present computations represent the experimental flows well. The results obtained show that for an initial relative humidity over 40 %, the periodic excursions of the condensation shock occurs in the Ludwieg tube, and the frequency increases with the initial relative humidity. It is also found that total pressure loss due to non-equilibrium condensation in the Ludwieg tube should not be ignored even for a very low initial relative humidity. Furthermore, the variations of condensation properties are also di     

用SPring-8同步辐射研究流体水银的结构变化和金属-非金属转变

随着从液态到气态的连续体积膨胀，在临界点附近，典型的液态金属水银经历了金属-非金属（M-NM）。在Spring-8的BL04B1高温高压实验站，利用同步辐射白光，采用能量色散X射线衍射（EDXD）方法，我们研究了流体水银从液体到稠密气态的宽广密度范围中的结构变化。实验方面，我们成功地开发出一个新的高压容器，它具有7个出射窗口用于收集散射X射线，测量的温度和压力上限分别是1700℃和2000bar，适合于在高温和高压下对流体物质进行能量色散X射线衍射测量。结果表明，流体水银的结构因子S(k)的精确性和可靠性有了很大的提高，并获得了流体水银的配位数和配位距离与密度变化之间的准确关系。我们发现，除了存在由配位数减少所导致的非均匀膨胀阶段之外，在水银的金属-非金属转变时还存在一新的均匀膨胀现象，即配位距离随密度减少呈线性增长阶段。基于这些新的结果，我们提出了流体水银的膨胀模型，并讨论了流体水银的金属-非金属转变与结构的关系。     

Numerical analysis of short-circuit safe operating area forp-channel and n-channel IGBTs

The mechanisms of destructive failure of an insulated gate bipolar transistor (IGBT) at short-circuit state are discussed. Results from two-dimensional numerical simulation of p-channel and n-channel IGBTs are presented. It is found that there are two types of destructive failure mechanisms: a secondary breakdown and a latchup. Which type is dominant in p-channel and n-channel IGBTs depends on an absolute value of forward voltage |V_CE|. At moderately low |V _CE|, the p-channel IGBT is destroyed by secondary breakdown, and the n-channel IGBT, by latchup. This is due to the difference of a type of flowing carrier crossing a base-collector junction of wide base transistor and ionization rates of electrons and holes     

InxGa1−xAs ohmic contacts to n-type GaAs with a tungsten nitride barrier

Significant reduction of the contact resistance of In_0.7Ga_0.3As/Ni/W contacts (which were previously developed by sputtering in our laboratory) was achieved by depositing a W₂N barrier layer between the Ni layer and W layer. The In_0.7Ga_0.3 As/Ni/W₂N/W contact prepared by the radio-frequency sputtering technique showed the lowest contact resistance of 0.2 Ωmm after annealing at 550°C for 10 s. This contact also provided a smooth surface, good reproducibility, and excellent thermal stability at 400°C. The polycrystalline W₂N layer was found to suppress the In diffusion to the contact surface, leading to improvement of the surface morphology and an increase in the total area of the In_xGa−As between metal and the GaAs substrate. These improvements are believed to reduce the contact resistance.     

Potential of predominant activated sludge bacteria as recipients in conjugative plasmid transfer

We investigated the possibility of conjugative plasmid transfer to the predominant bacteria in activated sludge and the factors influencing the transfer frequency in the activated sludge process. We performed conjugative transfers of a self-transmissible, broad-host-range plasmid RP4 from Escherichia coli C600 to activated sludge bacteria by broth mating. Most of the activated sludge bacteria tested could acquire plasmid RP4, although the transfer frequencies varied from 8.8 x 10(-7) to 1.3 x 10(-2) transconjugants per recipient. The transfer frequencies in several strains were similar to, or higher than, that in intraspecific transfer to E. coli HB101. Matings under various environmental conditions showed that factors relevant to physiological activity, such as temperature and nutrient conditions, seemed to affect the transfer frequency. In addition, conjugative transfer was detected even in filtered raw and treated wastewaters. Thus, the predominant activated sludge bacteria seem to have sufficient potential as recipients in conjugative plasmid transfer under the conditions likely to occur in the activated sludge process. Transfer frequency was reduced by agitation in the presence of suspended solid. This may suggest that conjugative plasmid transfer is physically inhibited in aeration tanks.     

Role of Heavy Meromyosin in Heat‐Induced Gelation in Low Ionic Strength Solution Containing l‐Histidine

The gelation of myosin has a very important role in meat products. We have already shown that myosin in low ionic strength solution containing l ‐histidine forms a transparent gel after heating. To clarify the mechanism of this unique gelation, we investigated the changes in the nature of myosin subfragments during heating in solutions with low and high ionic strengths with and without l ‐histidine. The hydrophobicity of myosin and heavy meromyosin (HMM) in low ionic strength solution containing l ‐histidine was lower than in high ionic strength solution. The SH contents of myosin and HMM in low ionic strength solution containing l ‐histidine did not change during the heating process, whereas in high ionic strength solution they decreased slightly. The heat‐induced globular masses of HMM in low ionic strength solution containing l ‐histidine were smaller than those in high ionic strength solution. These findings suggested that the polymerization of HMM molecules by heating was suppressed in low ionic strength solution containing l ‐histidine, resulting in formation of the unique gel.     

Production of recombinant SERA proteins of Plasmodium falciparum in Escherichia coli by using synthetic genes

We expressed two regions of the serine repeat antigen (SERA) protein of Plasmodium falciparum in Escherichia coli by synthesizing the genes with a changed codon usage. One of the synthetic gene sequences encodes amino acid residues 17-382 (SE47') and the other encodes amino acid residues 586-802 (SE50A). The products produced by the synthetic gene sequences in E. coli accounted for 15-30% of the total bacterial protein. Antisera against both the purified gene products prepared in rats inhibited malaria parasite growth in vitro. The anti-SE47' serum was significantly more inhibitory than the anti-SE50A serum. The described methods provide a large scale preparation of recombinant antigens for improving and producing malaria vaccine.