Displacement cascade simulation of LiAlO2 using molecular dynamics

To elucidate the radiation damage process on an atomic scale, displacement cascade simulations of LiAlO₂ were performed using molecular dynamics. Results of simulations obtained when an oxygen atom as the primary knock-on atom was displaced with the energy of 1-5 keV showed that the correlation between migration barriers of point defects and the declining rate of the maximum kinetic energy of atom in the system determined the thermal spike duration. The thermal spike of each element might finish when the maximum kinetic energy among all atoms of each element diminishes at around the point defects’ migration barrier. Defect-cluster analysis revealed that vacancies produce larger clusters than interstitials do, perhaps because the strong Coulomb interaction in ionic materials renders interstitials resistant to aggregation.     

Corrosion Behavior of Sialon Ceramics in Supercritical Water

The corrosion behavior of sialon ceramics was investigated in supercritical water at 450°C under 45 MPa for 2–50 h. α-sialon exhibited better corrosion resistance than β-sialon and α/β-sialon. Pitting corrosion with the formation of corrosion products was observed in the case of β-sialon and α/β-sialon. By contrast, the corrosion behavior of α-sialon was characterized by uniform corrosion with the formation of corrosion products. The degree of strength deterioration was strongly dependent on the corrosion morphology. The bending strength of α-sialon after corrosion for 30 h was about 90% of its initial strength, while the strength of β-sialon decreased to 65% of its original strength.     

Understanding the thyrotropin receptor function-structure relationship

The thyrotropin (TSH) receptor (TSHR) is a key protein in the control of thyroid function and a major thyroid autoantigen. Recently, molecular cloning of the receptor has been carried out and we now review the impact of this work on our understanding of the physiology and pathophysiology of the TSHR. Analysis of recombinant TSHR proteins expressed in prokaryotic and eukaryotic systems has indicated that post-translational processing is important for the formation of active receptors. Studies of TSHR glycosylation have shown that a 'mature' form of the receptor containing mainly complex-type sugar residues is principally involved in TSH and TSHR autoantibody (TRAb) binding. In addition, the processing of the TSHR peptide chain into two subunits observed with native TSHR has been confirmed using recombinant TSHR. However, despite considerable efforts in many laboratories, the binding site(s) for TSH and TRAb on the TSHR have not been well characterized as yet and lessons learned from the discovery of naturally occurring amino acid mutations of the TSHR confirm the complexity of the hormone and autoantibody binding sites. Future progress in producing large amounts of pure TSHR as well as monoclonal TRAbs, followed by crystallographic analysis of TSHR-TSH complexes and TSHR-TRAb complexes, should be helpful in providing a better insight into the relationship between TSHR structure and function.     

Device design with automatic simulation system for basic CCDcharacteristics

A simulation system has been developed to automatically analyze basic electrical characteristics of a charge-coupled device (CCD) image sensor from a process simulation result. This system shortened the simulation period to approximately 1/10 by getting rid of complicated repetitious procedures. A high-performance new cell technology has been developed successfully with improving impurity distribution in shorter development time by using this system. This technology has been realized as a CCD cell pixel with CCD charge quantity of 1.8 times, effective transfer efficiency of over 99%, no image lag for driving read-out pulse voltage in comparison with conventional technology. A 1/4-in 330 K square pixel progressive-scan CCD was fabricated with this technology. These results are described to demonstrate the effectiveness of the automatic simulation system     

Carnitine depletion during total parenteral nutrition despite oral L-carnitine supplementation

This study examined the behavioral mechanisms that support transfer of food from adults to infants in tufted capuchins (Cebus apella). Two captive groups of capuchins were presented with abundant quantities of unshelled pecans or commercial pellets. Five of 11 infant subjects could not open the nuts. A variety of tolerated interactions were initiated by infants toward adults, and food was frequently transferred. All such interactions were more frequent with nuts (a preferred food) than with pellets. Adult capuchins were equally tolerant of infant capuchins that could open nuts and those that could not. Tolerated interactions during feeding could result in acquisition of dietary information by young capuchins or to important, if intermittent, nutritional support.     

A 1920(H)×1035(V) pixel high-definition CCD image sensor

A 1920(H)×1035(V)-pixel high-definition CCD (charge-coupled-device) image sensor compatible with an 1125-scanning-lines and 16:9 aspect-ratio television system is described. The device basically uses an interline scheme with a vertical overflow drain. To maintain 74.25-MHz ultrahigh-data-rate operation, the device adopts a dual-channel configuration for the horizontal CCD (H-CCD) register. To accomplish both vertical signal charge transfer in the vertical CCD (V-CCD) register and signal charge distribution from the V-CCD registers into the dual-channel horizontal CCD registers simultaneously within a 3.77-μs short horizontal blanking period, a one-horizontal-period signal storage memory electrode and optical black memory are introduced. Bipolar buffer transistor chips are hybridized in the same package as the device, so as to reduce parasitic capacitance at CCD output terminals and maintain a wide-bandwidth operation. The device operates successfully and 1000-TV-line limiting resolution was obtained for both vertical and horizontal directions. Total random noise was evaluated to be 41 electrons. Dynamic range reached 66 dB. Signal-to-noise ratio for a black/white (B/W) camera was 51.5 dB under F4.0 and 2000-lux illumination conditions     

Growth of Ge-Si nanowire heterostructures via chemical vapor deposition

The growth of Ge-Si and Ge-Si nanowire (NW) heterostructures was demonstrated via chemical vapor deposition. Due to the influence of interface energy, differing topographies of the heterostructures were observed. On initially grown Ge NWs, numerous Si NW branches were grown near the tip due to Au migration. However, on initially grown Si NWs, high-density Ge nanodots were observed.     

Intracellular retention and degradation of tissue-nonspecific alkaline phosphatase with a Gly317-->Asp substitution associated with lethal hypophosphatasia

One point mutation which converts glycine-317 to aspartate of tissue-nonspecific alkaline phosphatase (TNSALP) was reported to be associated with lethal hypophosphatasia (Greenberg, C. R., et al. Genomics 17, 215-217, 1993). In order to define the molecular defect of TNSALP underlying the pathogenesis of hypophosphatasia, we have examined the biosynthesis of TNSALP with a Gly317-->Asp substitution. When expressed in COS-1 cells, the mutant did not exhibit alkaline phosphatase activity at all, indicating that the replacement of glycine-317 with aspartate abolishes the catalytic activity of TNSALP. Pulse-chase experiments showed that the newly synthesized mutant failed to acquire Endo H-resistance and to reach the cell surface. Interestingly, this TNSALP mutant was found to form a disulfide-bonded high-molecular-mass aggregate and was rapidly degraded within the cell, though the mutant protein was modified by glycosylphosphatidylinositol (GPI). Lactacystin, an inhibitor of the proteasome, obstructed the degradation of the mutant protein, suggesting the involvement of proteasome as a part of quality control of TNSALP.     

Design, synthesis and evaluation of transition-state analogue inhibitors of Escherichia coli gamma-glutamylcysteine synthetase

Phosphinic acid-, sulfoximine- and sulfone-based transition-state analogues were synthesized and evaluated as inhibitors of Escherichia coli gamma-glutamylcysteine synthetase. These compounds have a carboxyl function at the beta-carbon to the tetrahedral central hetero atom so as to mimic the carboxyl group of the attacking cysteine in the transition state. The phosphinic acid- and the sulfoximine-based compounds were found to be potent ATP-dependent inactivators, both showing a slow-binding kinetics with overall affinities and second-order inactivation rates of one to two orders of magnitude greater than those of L-buthionine (SR)-sulfoximine (L-BSO). The sulfone was a simple reversible inhibitor without causing ATP-dependent enzyme inactivation, but its affinity toward the enzyme was still five times greater than that of L-BSO, indicating that the beta-carboxyl function plays a key role in the recognition of the inhibitors by the enzyme. The sulfoximine with (S)-beta-carbon to the sulfur was synthesized stereoselectively, and the two diastereomers with respect to the chiral sulfur atom were separated as a cyclic sulfoximine derivative. The sulfoximine with R-configuration around the sulfur served as an extremely powerful ATP-dependent inactivator with an overall inhibition constant of 39 nM and an inactivation rate of 6750 M-1 s-1, which correspond to 1260-fold higher affinity and almost 1400-fold greater inactivation rate as compared with L-BSO. The sulfoximine with (S)-sulfur was a simple reversible inhibitor with an inhibition potency comparable to that of the sulfone. The synthesis and inhibition profile of the N-phosphoryl sulfoximine is also described.