An EXAFS study of Cu/ZnO and Cu/ZnO-Al2O3 methanol synthesis catalysts

Cu K-absorption edge and EXAFS measurements on binary Cu/ZnO and ternary Cu/ ZnO-Al₂O₃ catalysts of varying compositions on reduction with hydrogen at 523 K, show the presence of Cu microclusters and a species of Cu¹⁺ dissolved in ZnO apart from metallic Cu and Cu₂O. The proportions of different phases critically depend on the heating rate especially for catalysts of higher Cu content. Accordingly, hydrogen reduction with a heating rate of 10 K/min predominantly yields the metal species (>50%), while a slower heating rate of 0.8 K/min enhances the proportion of the Cu¹⁺ species ( 60%). Reduced Cu/ZnO-Al₂O₃ catalysts show the presence of metallic Cu (upto 20%) mostly in the form of microclusters and Cu¹⁺ in ZnO as the major phase ( 60%). The addition of alumina to the Cu/ZnO catalyst seems to favour the formation of Cu¹⁺/ZnO species.     

Deformation and recrystallization textures in compressed polycrystalline silicon

Cylindrical samples of polycrystalline semiconductor-grade silicon have been compressed 30 pct at 1380°C at a rate of 0.08 s^-1. The starting material had a strong «110» fiber texture, resulting from its growth by chemical vapor deposition; the fiber axis was perpendicular to the compression axis. The compression texture is very clearly defined after only 30 pct deformation, and has a «110» axis parallel to the compression axis and a «111» axis parallel to the original «110» fiber axis (perpendicular to the compression axis). Annealing for 10 min at 1380°C causes recrystallization. The recrystallization texture has a «100» axis parallel to the compression axis, and a «110» axis parallel to the original «110» fiber axis. Compression of a recrystallized sample gives the same deformation texture as does compression of the original material.     

BiP maintains the permeability barrier of the ER membrane by sealing the lumenal end of the translocon pore before and early in translocation

Secretory proteins are cotranslationally translocated across the mammalian ER membrane through an aqueous pore in the translocon while the permeability barrier is maintained by a tight ribosome-membrane junction. The lumenal end of the pore is also blocked early in translocation. Extraction of soluble lumenal proteins from microsomes and reconstitution with purified proteins demonstrate, by fluorescence collisional quenching, that BiP seals the lumenal end of this pore. BiP also seals translocons that are assembled but are not engaged in translocation. These ribosome-free translocons have smaller pores (9-15 A diameter versus 40-60 A in functioning translocons) and are generated when ribosomes dissociate from functioning translocons with large pores. BiP therefore maintains the permeability barrier by sealing both nontranslocating and newly targeted translocons.     

Comparison between enzyme-linked immunosorbent assay and cytotoxic cross-match procedures for detecting IgG anti-donor antibodies

BACKGROUND: Disadvantages inherent to complement-dependent cytotoxicity cross-match (CDC XM) methods are the requirements for complement and viable target cells, detection of antibodies (Abs) against non-HLA antigens, and subjective scoring. Cross-Stat (SangStat Medical Corp., Menlo Park, CA), a recently developed enzyme-linked immunosorbent assay XM procedure for the detection of IgG anti-donor HLA Abs, is theoretically devoid of these flaws. METHODS: We compared results of Cross-Stat and our standard anti-human globulin (AHG)-enhanced CDC XM procedure on 524 sera from 230 transplant candidates, which were evaluated against 51 cadaveric donors. RESULTS: There was a significant correlation between AHG-CDC IgG XM and Cross-Stat results (P<0.001). For false negative sera, repeat AHG-CDC IgG XMs were still positive after platelet absorption, indicating that the Abs present were either non-HLA Abs or anti-HLA class II. Flow cytometry testing of false positive sera usually (42/62) substantiated Cross-Stat results, indicating that the discrepancy with AHG-CDC IgG XM is caused by greater sensitivity of Cross-Stat. Relative to the AHG-CDC XM, the sensitivity of Cross-Stat was 100%, the specificity was 93%, the positive predictive value was 73%, and the negative predictive value was 100%. A technical shortcoming of the Cross-Stat assay is that the frequency of indeterminate samples in the assays was 15%. Among 49 Cross-Stat negative vs. 13 Cross-Stat positive primary cadaveric renal allograft recipients (all AHG-CDC IgG-XM negative), there was no statistical difference in overall graft survival. CONCLUSION: Given the important theoretical advantages of enzyme-linked immunosorbent assay-based XM methods over the CDC XM, however, further testing of the clinical relevance of the Cross-Stat is warranted.     

Mesoscopic assembly of magnetic Pd-Ni nanocrystals into ordered arrays by using alkane thiols

Two-dimensional arrays of core-shell Pd561 Nin (n = 38, 280, 561, 800, 1500, 3000, 4500) nanocrystals have been prepared by using alkanethiols. The arrays of Pd561 Nin nanocrystals are particularly well ordered; those with high Ni coverage show a tendency to form multilayers or crystallites. Two-dimensional arrays also have been obtained of Pd561 Ni3000 nanocrystals further covered by a Pd layer with a Pd561 Ni3000 Pd1500 composition.     

Web services: e-commerce partner integration

Online retailers have used a succession of technologies to showcase their products and services on the Web. That experience gives them a greater insight into what it is that the latest technology, Web services, can offer them. This article gives a brief survey of the evolution of evolving e-commerce technologies, explaining what each offered and could not offer to retailers. It then describes how Amazon's investment in its e-commerce services (ECS) gives Amazon partners access to common online retailing functionalities. These researchers also present the partner integration framework they developed to help retailers define what services they need in an online retail system.