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981.
Strength and Toughness of Slip-Cast Fused-Silica Composites 总被引:12,自引:0,他引:12
The effects of fiber composition, size, and surface treatment on the mechanical behavior of slip-cast fused-silica composites were investigated. The ambient and 1000°C stiffness and strength, fracture toughness, G R -curve behavior, and fiber-matrix interface bond strength were determined. Quantitative fractography and scanning electron microscopy were used to ascertain the mechanisms of toughening and strengthening. Composites with weak interface bonding exhibited good strength retention and rising G R -curve behavior. The fracture resistance was improved primarily through crack deflection. 相似文献
982.
Solar radiation is a key factor determining electricity produced by photovoltaic (PV) systems. This paper presents a solar radiation database of Europe developed in the geographical information system, and three interactive web applications providing an access to it. The database includes monthly and yearly average values of the global irradiation on horizontal and inclined surfaces, as well as climatic parameters needed for an assessment of the potential PV electricity generation (Linke atmospheric turbidity, the ratio of diffuse to global irradiation, an optimum inclination angle of modules to maximize energy yield). In the first web application, a user may browse radiation maps and query irradiation incident on a PV module for different inclination angles. The second application simulates daily profiles of irradiance for a chosen month and module inclination and orientation. The third web application estimates electricity generation for a chosen PV configuration. It also calculates optimal inclination and orientation of a PV module for a given location. The database and the applications are accessible at http://re.jrc.cec.ev.int/pvgis/pv/imaps/imaps.htm. 相似文献
983.
Electricity theft: a comparative analysis 总被引:1,自引:0,他引:1
Electricity theft can be in the form of fraud (meter tampering), stealing (illegal connections), billing irregularities, and unpaid bills. Estimates of the extent of electricity theft in a sample of 102 countries for 1980 and 2000 are undertaken. The evidence shows that theft is increasing in most regions of the world. The financial impacts of theft are reduced income from the sale of electricity and the necessity to charge more to consumers. Electricity theft is closely related to governance indicators, with higher levels of theft in countries without effective accountability, political instability, low government effectiveness and high levels of corruption. Electricity theft can be reduced by applying technical solutions such as tamper-proof meters, managerial methods such as inspection and monitoring, and in some cases restructuring power systems ownership and regulation. 相似文献
984.
Namchu Kim Dean A. McHenry Sei-Joo Jang Thomas R. Shrout 《Journal of the American Ceramic Society》1990,73(4):923-928
The physical, dielectric, and optical properties of hot isostatically pressed lead magnesium niobate polycrystalline ceramics modified with 1/2 mol% La2 O3 , Pb1–3/2 x La x □ x /2 -(Mg1/3 Nb2/3 )O3 , have been investigated. Methods used to characterize the ceramics included determination of the dielectric permittivity, optical transmittance, and refractive index dispersion. The materials exhibited relaxor ferroelectric type behavior with a peak dielectric constant K > 14000 and average T c ∼−35°C. Various sintering, hot isostatic pressing, and annealing conditions were examined to produce highly dense and optically transparent materials. Through the use of hot isostatic pressing, densities more than 99.5% theoretical and transmittance greater than 50% at 633-nm wavelength were obtained. Hot isostatic pressing technique appears to be a good alternative to hot uniaxial pressing without the associated problem of PbO volatility, reactivity with the pressure vessel, and geometrical constraints. 相似文献
985.
The thermoplastic properties of ten coals of rank 301a to 902 in the NCB Classification Scheme have been investigated using a high pressure dilatometer. The results show that the swelling behaviour of a coal at high pressure cannot be accurately predicted from a single measurement under standard conditions (3°C min?1, 0.1 MPa). The data also clearly show that the large differences in dilatation observed under standard conditions for the range of coals investigated are much reduced at high pressures, e.g. > 4 MPa. The trends in dilatometry parameters in relation to rank and pressure are discussed in detail. The relative order of coals based on dilatation may change with increase in pressure and this mainly occurs in the pressure range up to 2.5 MPa. The results suggest that the characterization of coals for high pressure gasifiers should include measurements under simulated gasifier conditions rather than standard tests at atmospheric pressure. 相似文献
986.
Ariel Cohen Peishan Liu-Synder Dan Storey Thomas J. Webster 《Nanoscale research letters》2007,2(8):385-390
Bioactive coatings are in high demand to control cellular functions for numerous medical devices. The objective of this in vitro
study was to characterize for the first time fibroblast (fibrous scar tissue forming cells) adhesion and proliferation on
an important polymeric biomaterial (silicone) coated with titanium using a novel ionic plasma deposition (IPD) process. Fibroblasts
are one of the first anchorage-dependent cells to arrive at an implant surface during the wound healing process. Persistent
excessive functions of fibroblasts have been linked to detrimental fibrous tissue formation which may cause implant failure.
The IPD process creates a surface-engineered nanostructure (with features usually below 100 nm) by first using a vacuum to
remove all contaminants, then guiding charged metallic ions or plasma to the surface of a medical device at ambient temperature.
Results demonstrated that compared to currently used titanium and uncoated silicone, silicone coated with titanium using IPD
significantly decreased fibroblast adhesion and proliferation. Results also showed competitively increased osteoblast (bone-forming
cells) over fibroblast adhesion on silicone coated with titanium; in contrast, osteoblast adhesion was not competitively increased
over fibroblast adhesion on uncoated silicone or titanium controls. In this manner, this study strongly suggests that IPD
should be further studied for biomaterial applications in which fibrous tissue encapsulation is undesirable (such as for orthopedic
implants, cardiovascular components, etc.). 相似文献
987.
988.
Micelle‐Enhanced Bioorthogonal Labeling of Genetically Encoded Azido Groups on the Lipid‐Embedded Surface of a GPCR 下载免费PDF全文
He Tian Prof. Thomas P. Sakmar Prof. Thomas Huber 《Chembiochem : a European journal of chemical biology》2015,16(9):1314-1322
Genetically encoded p‐azido‐phenylalanine (azF) residues in G protein‐coupled receptors (GPCRs) can be targeted with dibenzocyclooctyne‐modified (DIBO‐modified) fluorescent probes by means of strain‐promoted [3+2] azide–alkyne cycloaddition (SpAAC). Here we show that azF residues situated on the transmembrane surfaces of detergent‐solubilized receptors exhibit up to 1000‐fold rate enhancement relative to azF residues on water‐exposed surfaces. We show that the amphipathic moment of the labeling reagent, consisting of hydrophobic DIBO coupled to hydrophilic Alexa dye, results in strong partitioning of the DIBO group into the hydrocarbon core of the detergent micelle and consequently high local reactant concentrations. The observed rate constant for the micelleenhanced SpAAC is comparable with those of the fastest bioorthogonal labeling reactions known. Targeting hydrophobic regions of membrane proteins by use of micelle‐enhanced SpAAC should expand the utility of bioorthogonal labeling strategies. 相似文献
989.
Aditi Mehta Stephanie Dobersch Reinhard H. Dammann Saverio Bellusci Olga N. Ilinskaya Thomas Braun Guillermo Barreto 《International journal of molecular sciences》2015,16(3):4492-4511
The expression ratio between the analysed gene and an internal control gene is the most widely used normalization method for quantitative RT-PCR (qRT-PCR) expression analysis. The ideal reference gene for a specific experiment is the one whose expression is not affected by the different experimental conditions tested. In this study, we validate the applicability of five commonly used reference genes during different stages of mouse lung development. The stability of expression of five different reference genes (Tuba1a, Actb Gapdh, Rn18S and Hist4h4) was calculated within five experimental groups using the statistical algorithm of geNorm software. Overall, Tuba1a showed the least variability in expression among the different stages of lung development, while Hist4h4 and Rn18S showed the maximum variability in their expression. Expression analysis of two lung specific markers, surfactant protein C (SftpC) and Clara cell-specific 10 kDA protein (Scgb1a1), normalized to each of the five reference genes tested here, confirmed our results and showed that incorrect reference gene choice can lead to artefacts. Moreover, a combination of two internal controls for normalization of expression analysis during lung development will increase the accuracy and reliability of results. 相似文献
990.
Transformation of Free and Dipeptide‐Bound Glycated Amino Acids by Two Strains of Saccharomyces cerevisiae 下载免费PDF全文
Dr. Michael Hellwig Marie Börner Falco Beer Prof. Dr. Karl‐Heinz van Pée Prof. Dr. Thomas Henle 《Chembiochem : a European journal of chemical biology》2017,18(3):266-275
The yeast Saccharomyces cerevisiae transforms branched‐chain and aromatic amino acids into higher alcohols in the Ehrlich pathway. During microbiological culturing and industrial fermentations, this yeast is confronted with amino acids modified by reducing sugars in the Maillard reaction (glycation). In order to gain some preliminary insight into the physiological “handling” of glycated amino acids by yeasts, individual Maillard reaction products (MRPs: fructosyllysine, carboxymethyllysine, pyrraline, formyline, maltosine, methylglyoxal‐derived hydroimidazolone) were administered to two strains of S. cerevisiae in a rich medium. Only formyline was converted into the corresponding α‐hydroxy acid, to a small extent (10 %). Dipeptide‐bound pyrraline and maltosine were removed from the medium with concomitant emergence of several metabolites. Pyrraline was mainly converted into the corresponding Ehrlich alcohol (20–60 %) and maltosine into the corresponding α‐hydroxy acid (40–60 %). Five specific metabolites of glycated amino acids were synthesized and characterized. We show for the first time that S. cerevisiae can use glycated amino acids as a nitrogen source and transform them into new metabolites, provided that the substances can be transported across the cell membrane. 相似文献