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P M Reid A E Wilkinson K C Leung M N Jones 《Computer applications in the biosciences》1989,5(2):133-135
Analytical ultracentrifugation is commonly used for the determination of molecular weights (sedimentation equilibrium) and sedimentation coefficients (sedimentation rate) of biological macromolecules in solution. A Turbo Pascal program for the analysis of sedimentation equilibrium centrifugation data produced by absorbance optical systems is described. The user may enter data from a scan of absorbance versus distance from the centre of rotation, via a graphics tablet (or ASCII file). This is subsequently manipulated to yield an apparent weight average molecular weight for the given sample. Plots of ln (absorbance) versus (radius2) may also be produced. The method described uses readily available computational equipment requiring only a graphics tablet in addition to an IBM PC compatible computer. This technique and the software developed have been used to investigate the molecular weight range of two International Humic Substances Society (IHSS) reference samples from the Suwannee River. 相似文献
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An outline of the characteristics of PEEK and the versatility of its compositional forms (micro and macro composites) are given to illustrate its wide potential for success in engineering applications. Although it is necessary to have particular tabulations of mechanical properties for engineering design, these are seldom available and consequently it is argued that an understanding of stiffness, toughness and strength properties are required to fully exploit available manufacturer's data and thus develop the full potential of PEEK and its composites. Stiffness characteristics are considered in terms of a modulus function which is dependent on time under load and temperature. In its composite forms, whether reinforced with short or continuous fibres, stiffness anistropy can be both considerable and complex, but some empirical ground-rules are apparent. For continuous fibre composites even in the form of complex lay-ups, it is also possible to attempt some stiffness prediction from certain pseudo-elastic constants. Toughness of PEEK and its composites is described in terms of both comparative and intrinsic properties. Instrumented falling weight impact data, particularly as a function of temperature enable some insight into ductile-brittle transitions for the unreinforced material, but crack initiation and crack propagation processes for the various fibre reinforced forms. Intrinsic toughness is described in terms of linear elastic fracture mechanics theory. Strength properties are described for static and dynamic loading configurations. In particular, PEEK and its composites are evaluated for increasing test severities for strength characteristics; stress concentration, loading form and test temperature are considered. 相似文献
76.
The noise generated by a ball mill during a batch grinding operation is investigated and the results show that, for a given ore, the noise levels may vary with time of grind, ore charge weight and mill speed. The role of the ore in absorbing noise energy is suggested as a possible control variable for the grinding process and as an indicator of product size distribution. The relationship between ore types and mill noise is also examined and, under conditions of wet grinding, it is demonstrated that mill noise analysis can indicate ore type and may have a possible use as a grindability-type parameter. 相似文献
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Burkholderia pseudomallei is the causative agent of melioidosis, a disease increasingly recognized as an important cause of morbidity and mortality in many regions of the world. B. pseudomallei is a facultative intracellular pathogen capable of invading eukaryotic cells. We used Tn5-OT182 mutagenesis to generate mutants deficient in the ability to invade a human type II pneumocyte cell line (A549 cells). One of these mutants, AJ1D8, exhibited approximately 10% of the ability of the parental strain, 1026b, to invade A549 cells. There was no difference in the abilities of 1026b and AJ1D8 to resist killing by RAW macrophages or the human defensin HNP-1. The nucleotide sequence flanking the Tn5-OT182 integration in AJ1D8 was determined, and two open reading frames were identified. The predicted proteins shared considerable homology with two-component regulatory systems involved in the regulation of heavy-metal resistance in other organisms. AJ1D8 was 16-fold more sensitive to Cd2+ and twofold more sensitive to Zn2+ than was 1026b but was not sensitive to any of the other heavy metals examined. The B. pseudomallei two-component regulatory system, termed irlRS, complemented the invasion-deficient and heavy-metal-sensitive phenotype of AJ1D8 in trans. There was no significant difference between the virulence of AJ1D8 and that of 1026b in infant diabetic rats and Syrian hamsters, suggesting that the irlRS locus is probably not a virulence determinant in these animal models of acute B. pseudomallei infection. 相似文献
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Pre-clerking of all patients undergoing elective general surgical operations was introduced at our hospital in an attempt to reduce an unacceptably high operation cancellation rate. A prospective audit has been performed on the effect of this policy on the cancellation rate. Before the introduction of pre-clerking there was a marked seasonal variation in the number of patients who failed to attend for surgery, which could be explained by absence on holiday. This seasonal variation disappeared after the start of pre-clerking clinics, but there has been no reduction in the number of cancellations for medical reasons. 相似文献
79.
The cytoskeletal components of hamster oocytes, zygotes, and spontaneously activated parthogenotes were examined after immunocytochemical labeling. Microtubules were found only in the anastral, tangentially arranged second meiotic spindle of unfertilized oocytes. Taxol treatment of unfertilized oocytes greatly augmented astral microtubules in both the metaphase II spindle and the cortex. Disruption of the meiotic spindle microtubules with nocodazole resulted in cortical chromosomal scattering. During hamster sperm incorporation and pronuclear formation, no sperm aster was detected in association with the male DNA. Instead, a large overlapping array of microtubules assembled in the cortex. By mitosis, this interphase array disassembled and an anastral metaphase spindle formed. Microtubule and chromatin configurations were also imaged in hamster oocytes injected with human sperm. Astral microtubules were absent from the sperm centrosome. The implications of these results are discussed in relation to the hamster oocyte penetration assay, a test commonly used by in vitro fertilization clinics to demonstrate the fertilizing ability of human sperm. We conclude that since hamsters and humans follow different methods of centrosome inheritance, maternal and paternal, respectively, the hamster may be an inappropriate model for exploring microtubule and centrosomal defects in humans or for assaying postinsemination forms of human male fertility defects. 相似文献
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