Fundamental study on the NOx direct decomposition catalysts

We are developing direct decomposition catalysts to decompose the NO_x involved in high temperature exhaust gases to N₂ and O₂ without any reductants such as urea and plan to bring this technology into practice in the 21st century. We expect to create very simple deNO_x systems using direct decomposition catalysts applicable to a wide range of fields (co-generation, boilers, automobiles and so on) after overcoming the technical difficulties. Perovskite catalyst and zeolite catalyst are the most promising materials for direct decomposition catalysts. This study focuses on seeking and designing novel NO_x direct decomposition catalysts having high activities through theoretical studies using computational chemistry and experimental studies using surface-science techniques.     

Apoptosis induction by the binding of the carboxyl terminus of human immunodeficiency virus type 1 gp160 to calmodulin

The role of calmodulin (CaM) in apoptosis induced by gp160 of human immunodeficiency virus type 1 was investigated with cells undergoing single-cell killing. These cells were found to express, under the control of an inducible promoter, wild-type gp160 or mutant gp160 devoid of various lengths of the carboxyl terminus. Immunoprecipitation accompanied by immunoblotting revealed binding of CaM to wild-type gp160 but not to mutant gp160 bearing a carboxyl terminus with a deletion spanning more than five amino acid residues. A significant coenzyme activity was detected in the CaM bound to gp160 even in the presence of a Ca2+ chelater, EGTA. The cells forming this gp160-CaM complex exhibited an elevated intracellular Ca2+ level followed by DNA fragmentation, which is a hallmark of apoptosis, and finally cell killing, while the cells not forming this complex did not show any significant elevation in Ca2+ level or DNA fragmentation. These results thus indicated that CaM plays a key role in gp160-induced apoptosis.     

A cutaneous agranular CD2- CD4+ CD56+ "lymphoma": report of two cases and review of the literature

One of the universal characteristics of the long bones and spines of middle-age and older mammals is a loss in bone mass (osteopenia). In humans, if this bone loss is severe enough, it results in osteoporosis, a skeletal disorder characterized by a markedly increased incidence of fractures with sequelae that may include pain, loss of mobility, and in the event of hip fracture, even death within a relatively few months of injury. An important contributing factor to the development of osteoporosis appears to be a diminution in the number and activity of osteoblasts responsible for synthesizing new bone matrix. The findings in the present and other similar studies suggest that this reduction in osteoblast number and activity is due to an age-related diminution in the size and osteogenic potential of the bone marrow osteoblast progenitor cell (OPC or CFU-f) compartment. We previously postulated that these regressive changes in the OPC/CFU-f compartment occurred in old animals because of a reduction in the amount and/or activity of TGF-beta1, an autocrine growth factor important in the promotion of OPC/CFU-f proliferation and differentiation. In support of this hypothesis, we now report that (1) the osteogenic capacity of the bone marrow of 24-month-old BALB/c mice, as assessed in vivo, is markedly reduced relative to that of 3-4-month-old animals, (2) that the matrix of the long bones of old mice contains significantly less TGF-beta than that of young mice, (3) that OPC's/CFU-f's isolated from old mice produce less TGF-beta in vitro than those recovered from young mice, and (4) that OPC's/CFU-f's from old mice express significantly more TGF-beta receptor (Types I, II, and III) than those of young animals and that such cells are more responsive in vitro to exogenous recombinant TGF-beta1. We also find that colony number and proliferative activity of OPC's/CFU-f's of young mice and old mice, respectively, are significantly reduced when incubated in the presence of neutralizing TGF-beta1 antibody. Collectively, these data are consistent with the hypothesis that in old male mice the reduction in the synthesis and, perhaps, availability from the bone matrix of TGF-beta1 contributes to a diminution in the size and development potential of the bone marrow osteoprogenitor pool.     

Numerical analysis of bulk diffusion length in thin-film c-Si solar cells

We propose a novel technique of determining relationship between effective and bulk diffusion length of single-crystalline Si (c-Si) thin-film solar cells using two-dimensional device simulator. In addition, bulk diffusion length was obtained using the result of the simulation. Effective diffusion length was measured by LBIC method in order to presume bulk diffusion length of c-Si thin film. We obtained 6.7 μm for effective diffusion length of c-Si thin-film solar cell whose thickness was about 7 μm. We compared the result of measurement and simulation, bulk diffusion length of c-Si thin film prepared by CVD method was estimated more than 30 μm and recombination velocity was presumed <10⁴ cm/s for front surface and 10³ cm/s for rear surface of the cell.     

Direct observation of X-ray induced atomic motion using scanning tunneling microscope combined with synchrotron radiation

X-ray induced atomic motion on a Ge(111)-c(2 x 8) clean surface at room temperature was directly observed with atomic resolution using a synchrotron radiation (SR)-based scanning tunneling microscope (STM) system under ultra high vacuum condition. The atomic motion was visualized as a tracking image by developing a method to merge the STM images before and after X-ray irradiation. Using the tracking image, the atomic mobility was found to be strongly affected by defects on the surface, but was not dependent on the incident X-ray energy, although it was clearly dependent on the photon density. The atomic motion can be attributed to surface diffusion, which might not be due to core-excitation accompanied with electronic transition, but a thermal effect by X-ray irradiation. The crystal surface structure was possible to break even at a lower photon density than the conventionally known barrier. These results can alert X-ray studies in the near future about sample damage during measurements, while suggesting the possibility of new applications. Also the obtained results show a new availability of the in-situ SR-STM system.     

Acoustic Resonance of Superfluid 3He in Parallel Plates

We performed an acoustic resonance experiment of superfluid ³He confined in a stack of parallel plates, and found the fourth sound resonance. From its velocity, the superfluid density fraction was calculated. No size effect was found because the gap between parallel plates were much larger than the superfluid coherence length. The energy loss of the resonance was also measured. We found that the hydrodynamic theory qualitatively described its temperature dependence, but it could not describe the gap width dependence. Possible explanations is discussed in the text. More over, we found the unidentified resonance that cannot be explained by conventional sound modes.     

Comparative study of annealing and oxidation effects in a-SiC:H and a-SiC thin films deposited by radio-frequency magnetron sputtering

Thermal annealing and oxidation effects in hydrogenated (a-SiC:H) and nonhydrogenated (a-SiC) amorphous silicon-carbon alloy films deposited by radio-frequency magnetron sputtering have been studied. The a-SiC:H and a-SiC films were thermally treated in dry Ar, wet Ar, and dry O₂ atmospheres at temperatures up to 1150 °C. The principal effects of thermal annealing in an inert atmosphere on a-SiC:H films were found to be redistribution of hydrogen bonds and formation of amorphous graphitic carbon clusters. Strong oxidation of a-SiC:H was observed after thermal treatment in oxygen at 700 °C while annealing in wet argon caused partial oxidation. Oxidation of the carbon clusters in porous a-SiC:H structures is suggested to be responsible for the higher oxidation efficiency of a-SiC:H in oxygen. In contrast, the structure of a-SiC films remained almost unchanged after annealing in dry argon up to 1000 °C. No oxidation of a-SiC was detected until 1000 °C. Water vapor was found to be more effective at oxidizing a-SiC at 1000 °C than dry oxygen, which is similar to the oxidation behavior of crystalline SiC. The high thermal and oxidation stabilities of a-SiC layers were attributed to the dense and nanovoid-free amorphous SiC network.     

Thin-film field-effect transistors of copper phthalocyanine on a rubbed polyethersulfone

We fabricated copper phthalocyanine (CuPc) thin-film field-effect transistors (FETs) on a rubbed flexible polyethersulfone (PES) substrate. Rubbing the PES film induced a unidirectional orientation of CuPc crystallites, which were oriented perpendicular to the rubbing direction. Favorable conditions for fabricating a CuPc FET were determined after fabricating CuPc FETs of two different types and evaluating their output performance. Well-aligned CuPc crystallites along the direction connecting source and drain electrodes can play an important role in improving the output performance of the fabricated FETs.