Metabolic cytometry. Glycosphingolipid metabolism in single cells

Glycosphingolipids are found on all vertebrate cells and constitute major cell surface determinants on all nerve cells, where they contribute to cellular diversity and function. We report a method for the analysis of glycosphingolipid metabolism in single cells. The ganglioside GM1 was tagged with the fluorescent dye tetramethylrhodamine. This labeled compound was taken up and metabolized by a culture of pituitary tumor (AtT-20) cells. After 50 h, the cells were formalin fixed. Cells were aspirated into a fused-silica capillary and lysed, and components were separated by capillary electrophoresis with a laser-induced fluorescence detector. All metabolic products that retained the fluorescent dye could be detected at the low-zeptomole level. A total of 54 AtT-20 cells were individually analyzed using this procedure. The electrophoretic profiles were remarkably reproducible, which facilitated identification of components based on the migration time of fluorescently labeled standards. Eleven components were detected, and the average peak height of these components spanned more than 2 orders of magnitude, so that trace metabolites can be detected in the presence of abundant components. The most highly abundant components generated 10% relative standard deviation in normalized abundance. The average cell took up roughly 2 amol (10(6) copies) of the labeled substrate. This method allows determination of cell-to-cell diversity and regulation of glycosphingolipid metabolism.     

Consequences of Orbital Degeneracy in Insulating and Doped Manganites

We derive a spin-orbital model for manganites which includes the complete e _g and t _2g superexchange of S=2 spins at Mn³⁺ ions and predicts that the same type of antiferromagnetic and orbital ordering is stabilized in insulating La₃Mn₂O₇ as in LaMnO₃ by a purely electronic mechanism dominated by the e _g-superexchange. At finite doping we consider a model of t–J variety which describes a metal–insulator transition due to a competition between lattice polarons and kinetic energy in the metallic ferromagnetic ground state.     

Risk management in the oil industry: can information on long-run equilibrium prices be utilized?

We analyze co-movements between the prices of crude oil and major refined products during the period 1992–1998. Specifically, we explore the existence of long-run equilibrium price relationships, and whether deviations from estimated equilibrium can be utilized for predictions of short-term price changes and for risk management. The econometric evidence strongly supports the hypothesis that crude and product prices are co-integrated. Past deviations from long-term equilibrium are significant in an error correction specification of short-term product price changes. The results represent valuable information for hedging, particularly in integrated oil companies for which price risk is related to margin variations.     

如何保证区域供热系统的寿命

本文尝试将40年的供热系统水处理经验加以总结,目的是提醒大家正确的水处理对于提高能源效率与系统寿命至关重要。     

Biodegradation, bioaccessibility, and genotoxicity of diffuse polycyclic aromatic hydrocarbon (PAH) pollution at a motorway site

Diffuse pollution of surface soil with polycyclic aromatic hydrocarbons (PAHs) is problematic in terms of the large areas and volumes of polluted soil. The levels and effects of diffuse PAH pollution at a motorway site were investigated. Surface soil was sampled with increasing distance from the asphalt pavement and tested for total amounts of PAHs, amounts of bioaccessible PAHs, total bacterial populations, PAH degrader populations, the potential for mineralization of 14C-PAHs, and mutagenicity. Elevated PAH concentrations were found in the samples taken 1-8 m from the pavement. Soil sampled at greater distances (12-24 m) contained only background levels of PAHs. The total bacterial populations (CFU and numbers of 16S rDNA genes) were similar for all soil samples, whereas the microbial degrader populations (culturable PAH degraders and numbers of PAH dioxygenase genes) were most abundant in the most polluted samples close to the pavement. Hydroxypropyl-beta-cyclodextrin extraction of soil PAHs, as a direct estimate of the bioaccessibility, indicated that only 1-5% of the PAHs were accessible to soil bacteria. This low bioaccessibility is suggested to be due to sorption to traffic soot particles. The increased PAH level close to the pavement was reflected in slightly increased mutagenic activity (1 m, 0.32 +/- 0.08 revertants g(-1) soil; background/ 24 m: 0.08 +/- 0.04), determined by the Salmonella/ microsome assay of total extractable PAHs activated by liver enzymes. The potential for lighter molecular weight PAH degradation in combination with low bioaccessibility of heavier PAHs is proposed to lead to a likely increase in concentration of heavier PAHs over time. These residues are, however, likely to be of low biological significance.     

熔盐电解精炼提纯金属硅(英文)

对熔盐电解质中硅的沉积过程进行电化学研究。在 973~223K,在硅氯化物熔盐中采用电解精炼提纯金属硅。结果表明,液态硅铜合金阳极有利于 CaCl2-NaCl-CaO-Si 熔盐体系的电解精炼。ICP-AES 分析结果显示,通过电解精炼可有效去除原料中大量的钛、铝、铁等金属杂质,硅中的硼和磷含量分别由 36×106和 25×106降低至 4.6×10 6和 2.8×10 6,电解能耗约为 9.3 kW·h/kg。     

In situ TEM creation and electrical characterization of nanowire devices

We demonstrate the observation and measurement of simple nanoscale devices over their complete lifecycle from creation to failure within a transmission electron microscope. Devices were formed by growing Si nanowires, using the vapor-liquid-solid method, to form bridges between Si cantilevers. We characterize the formation of the contact between the nanowire and the cantilever, showing that the nature of the connection depends on the flow of heat and electrical current during and after the moment of contact. We measure the electrical properties and high current failure characteristics of the resulting bridge devices in situ and relate these to the structure. We also describe processes to modify the contact and the nanowire surface after device formation. The technique we describe allows the direct analysis of the processes taking place during device formation and use, correlating specific nanoscale structural and electrical parameters on an individual device basis.     

Thin films of two functional oxides patterned laterally by soft lithography

Thin films of two laterally patterned functional oxides of uniform thickness were obtained in a two-step soft-lithographic micromolding process. CoFe(2)O(4)/ZnO and CoFe(2)O(4)/BaTiO(3) dual-phase patterns were fabricated. The films showed good replication of the pattern that was defined in the first patterning step. X-ray diffraction showed that the films consisted of two distinct phases, and magnetic force microscopy showed that the compounds were laterally separated, the separation pattern being the same as that of the initial soft-lithographic process. The films exhibited slight height variations near the edges of the phases, which were introduced in the first deposition step and were not fully compensated in the second deposition step. The films are sufficiently smooth to allow fabrication of multilayer structures.     

PH-dependent self-assembly of the short Surfactant-like peptide KA6

Self-assembly of amphiphilic peptides designed during the last ten years by different research groups lead to a large variety of 3D-structures that already found applications in e.g., for stabilization of large protein complexes, cell culturing systems etc. We present synthesis and characterization of a novel amphiphilic peptide KA6 that exhibits clear charge separation controllable by the pH of the environment. The self-assembly in this system is largely governed by electrostatic interaction, thus a change in pH will not only lead to a change in critical micellar concentration (CMC) of the peptide but also to the changes in micellar structure as revealed by atomic force microscopy (AFM) and circular dichroism (CD) study. At basic pH the micellar structure inverts exposing the opposite end of the peptide chain to the solution. This interesting phenomenon could provide basis for novel pH sensitive materials including drug delivery and controlled release systems.     

Stacks of functional oxide thin films patterned by micromolding

Stacks of up to five relief patterned functional oxide thin films were obtained by a low-cost and low-tech soft-lithographic patterning technique. Micromolding was used to pattern a film of a metal-organic precursor solution for Y-stabilized ZrO(2) (YSZO). Subsequent drying and pyrolysis yielded a line-patterned YSZO film. The process was repeated up to four times with a precursor solution for BaTiO(3) on top of the YSZO film, resulting in stacks of YSZO and BaTiO(3) lines with well-defined edges. This approach presents a step forward on the way to a versatile additive micropatterning technique with which simple multi-material device structures can be fabricated in a reliable, fast, and cost-effective manner.