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Abstract : The recent development of metallic alloy systems which can be processed with an amorphous structure over large dimensions, specifically to form metallic glasses at low cooling rates (tilde 10 K/s), has permitted novel measurements of important mechanical properties. These include, fatigue crack growth and fracture toughness behavior, representing the conditions governing the subcritical and critical propagation of cracks. In the present study, bulk plates of a Zr41.2 Ti13.8 Cu12.5 Ni10 Be22.5 alloy, machined into 7 mm thick, 33 mm wide compact tension specimens and fatigue precracked following standard procedures, revealed fracture toughness in the fully amorphous structure of KIc tilde 55 MPa(square root m), i.e., comparable with that of a high strength steel or aluminum alloy. However, annealing to induce partial and full crystallization was found to result in a drastic reduction in fracture toughness to 1 MPa(square root m), i.e., comparable with silica glass. Under cyclic loading, whereas crack propagation behavior of the bulk amorphous metal was similar to that observed in traditional steel and aluminum alloys, the stress-life (S-N) properties of were markedly different. As in more traditional crystalline metallic alloys, the crack propagation mechanism in the metallic glass was associated with alternating blunting and resharpening of the crack tip as evidenced by striations on fatigue fracture surfaces. Alternatively, during S-N tests flaws apparently initiated quite easily due to the lack of microstructural barriers which would normally provide local crack arrest points, thereby giving rise to poor S-N properties.
The corrosion and cell viability behaviors of nanostructured, nickel-free stainless steel implants were studied and compared with AISI 316L. The electrochemical studies were conducted by potentiodynamic polarization and electrochemical impedance spectroscopic measurements in a simulated body fluid. Cytocompatibility was also evaluated by the adhesion behavior of adult human stem cells on the surface of the samples. According to the results, the electrochemical behavior is affected by a compromise among the specimen's structural characteristics, comprising composition, density, and grain size. The cell viability is interpreted by considering the results of the electrochemical impedance spectroscopic experiments.
Organizations increasingly need to collaborate by performing a computation on their combined dataset, while keeping their data hidden from each other. Certain kinds of collaboration, such as collaborative data analytics and AI, require a level of performance beyond what current cryptographic techniques for distributed trust can provide. This is because the organizations run software in different trust domains, which can require them to communicate over WANs or the public Internet. In this paper, we explore how to instead run such applications using fast datacenter-type LANs. We show that, by carefully redesigning distributed trust frameworks for LANs, we can achieve up to order-of-magnitude better performance than naïvely using a LAN. Then, we develop deployment models for Distributed But Proximate Trust (DBPT) that allow parties to use a LAN while remaining physically and logically distinct. These developments make secure collaborative data analytics and AI significantly more practical and set new research directions for developing systems and cryptographic theory for high-performance distributed trust.
Abstract Grand canonical ensemble Monte Carlo (GCMC) simulatios of methane in the zeolite silicalite have been used to predict adsorption isotherms over a wide range of occupancies at several temperatures. The zeolite has been modeled using a detailed atomistic description, as have the methane molecules. Lennard-Jones parameters for the atomic interactions have been taken from the literature. Adsorption isotherms and heats of sorption have been predicted in good agreement with experiment. Structural features of the intracrystalline fluid have also been studied. In a complementary study, the test particle insertion method has been used to generate isotherms from molecular dynamics simulations. The results are in excellent agreement with those from GCMC.
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Abstract We have characterized two new cytotoxic, monoclonal IgM antibodies specific for the murine T lymphocyte differentiation antigens Lyt-2.2 and Lyt-3.1. Initially, we determined the fractions of thymocytes and lymph node T cells that react with the antibodies; then we studied their effect on a functional subpopulation of T cells, namely cytotoxic T lymphocytes (CTL) specific for major and minor histocompatibility antigens. The antibodies lyse 45% of lymph node T cells and 90% of thymocytes of C57BL/6 series mice, in agreement with the original findings of Cantor and Boyse. However, in BALB/c series mice, only about 30% of lymph node T cells are sensitive to the antibodies. This difference probably reflects a genetic difference between C57BL/6 and BALB/ c mice that affects the relative proportions of T cell subsets. Thymocytes from an Lyt-3.1 congenic strain of BALB/ c were fractionated into peanut lectin agglutinable and nonagglutinable populations and tested with anti-Lyt-3.1 monoclonal antibodies. Twenty percent of peanut lectin nonagglutinable thymocytes, 70% of peanut lectin agglutinable thymocytes, and 70% of unseparated thymocytes were sensitive to monoclonal anti-Lyt-3.1 antibodies. Therefore, the immature peanut lectin agglutinable fraction of thymocytes contains Lyt-3 negative cells. Both hybridoma antibodies eliminate >95% of anti-H-2 and anti-minor H specific CTL activity generated in 5-day mixed lymphocyte cultures (MLC). Furthermore, pretreatment of spleen cells with the monoclonal antibodies and complement almost completely eliminated the generation of CTL, but left most of the T cells that proliferate in MLC. However, a small fraction (<5%) of CTL activity from primary MLC was resistant to elimination by monoclonal anti-Lyt-3.1 antibodies. By pre-treating spleen cells with monoclonal anti-Lyt-3.1 and complement and stimulating the surviving cells in MLC a number of times, we isolated a stable subpopulation of CTL that were completely resistant to any concentration of anti-Lyt-3.1 monoclonal antibodies, but were sensitive to anti-Thy-1.2 monoclonal antibodies. The specificity of this minor subpopulation of CTL, in terms of H-2 restriction and target antigen specificity, did not seem to be different from that of the bulk of CTL. Furthermore, the CTL resistant to lysis by monoclonal anti-Lyt-3.1 antibodies were sensitive to lysis by high concentrations of conventional anti-Lyt-3.1 serum. On this basis, we postulated that lysis by the monoclonal anti-Lyt-3.1 antibodies is very sensitive to determinant density, and that the resistant fraction of CTL have a sub-threshold density of the determinant. To investigate the effect of lowering the determinant density, we compared the lytic behavior of monoclonal and conventional antibodies on target cells homozygous or heterozygous at the Lyt-3 locus. Unlike the case with conventional serum, the titer of the monoclonal anti-Lyt-3.1 ascites dropped drastically on heterozygous target cells. Thus, it seems likely that the CTL resistant to monoclonal anti-Lyt-3.1 antibodies are a stable subpopulation with low Lyt-3.1 density.
A symmetrical alpha,omega-substituted sexithiophene derivative containing thermally removable branched ester solubilizing groups has been prepared. These oligomers can be solution cast into thin films and then thermolyzed to remove the solubilizing group, leaving short pendant alkene groups on the oligomer. Device testing of thin film transistors shows an increase in hole mobility from 1 x 10-5 cm2/(V s) with on/off ratios of approximately 100 before thermolysis to 5 x 10-2 cm2/(V s) with on/off ratios >105 after thermolysis. This method offers an attractive route to easily processed and highly performing thiophene oligomers.
