Influence of fabrication errors on wölter mirror imaging performance

The resolution of the W?lter mirror, which is utilized as an objective in soft-x-ray microscopes, is limited by fabrication errors. We studied the relation between fabrication errors and imaging performance of the W?lter mirror to determine how this performance could be improved. Figure errors, which are characterized by low spatial frequency, were analyzed by ray tracing, and surface roughness, characterized by high spatial frequency, was analyzed by modified ray tracing. Modified ray tracing was based on ray tracing but took scattering into account. The results of these analyses were compared with experimental data. As a result, we obtained a simple and practical fabricating tolerance criterion that may be employed to obtain higher W?lter mirror resolution. Additionally, we discuss problems in current W?lter mirror fabrication techniques and the changes that might be made in both the design and the fabrication process to improve imaging performance.     

Strength of β-sialon/Si3N4 layered composites

The strength of layered composites consisting of -sialon and Si3N4 layers, which were prepared by hot pressing, was investigated. The strength increased as the thickness of the sialon (outer layer) decreased, and reached almost the same level of Si3N4 (inner layer) when the sialon thickness was 250–300 m. No specific fracture morphologies were recognized around the interface of sialon and Si3N4. The aluminium concentration changed sharply around the interface, while the yttrium tended to diffuse deeper than aluminium. This tendency was remarkable in the samples hot-pressed at higher temperature (1900°C). The existence of compressive residual stress in the surface sialon layer was revealed and the residual stress increased as the sialon thickness decreased down to 250–300 m. The increase of strength with the decrease of sialon thickness was discussed based on the mechanical calculations in which the residual stress was considered. This calculation approximately agreed with the results of the samples hot-pressed at lower temperature (1800°C). However, the strength of the samples hot-pressed at 1900°C was much higher than the prediction in the thin range of the sialon thickness. The deep diffusion of yttrium into the sialon layers was thought to be one of the causes of this unpredictable effect.     

Differential display with carboxy-X-rhodamine-labeled primers and the selection of differentially amplified cDNA fragments without cloning

Pregnancy block, whereby recently mated female mice abort their pregnancies when exposed to novel (strange) males, was studied in house mice (Mus domesticus) differing in t-complex genotype; t-mutations are deleterious and +/t females avoid +/t males as mates. The results of Experiment 1, in which the genotype of the female, stud male, and strange male was systematically varied, showed that pregnancy block was most frequent when the strange male was +/+. Because this effect was not enhanced among +/t females when stud males were +/t, the results cannot clearly be explained by the hypothesis that pregnancy block is a manifestation of mate choice. Moreover, the "strange male" effect in Experiment 1 is unlikely to be a female response correlated with the risk of male infanticide, as +/+ and +/t males did not differ in their infanticidal tendencies (Experiments 2 & 3). Alternative hypotheses, including a modified version of the mate choice hypothesis, are discussed.     

Pyrrolidone carboxyl peptidase from the hyperthermophilic Archaeon Pyrococcus furiosus: cloning and overexpression in Escherichia coli of the gene, and its application to protein sequence analysis

A gene for a pyrrolidone carboxyl peptidase (Pcp: EC 3.4.19.3, pyroglutamyl peptidase), which removes amino-terminal pyroglutamyl residues from peptides and proteins, has been cloned from the hyperthermophilic Archaeon Pyrococcus furiosus using its cosmid protein library, sequenced, and expressed in Escherichia coli. The DNA sequence encodes a protein containing 208 amino acid residues with methionine at the N-terminus. Analysis of the recombinant protein expressed in E. coli, including amino acid sequence analysis from the N-terminus by automated Edman degradation and ionspray mass spectrometric analysis of the peptides generated by enzymatic digestions with lysylendopeptidase and Staphylococcus aureus V8 protease, showed its primary structure to be completely identical with that deduced from its cDNA sequence. Comparison of the amino acid sequence of P. furiosus Pcp (P.f.Pcp) with those of bacterial Pcps revealed that a high degree of sequence identity (more than 40%) and conservation of the amino acid residues comprising the catalytic triad, Cys142, His166, and Glu79. On the other hand, a unique short stretch sequence (positions around 175-185) that is absent in bacterial Pcps was found in P.f.Pcp. A similar stretch has also been reported recently in the amino acid sequence of Pcp from the hyperthermophilic Archaeon Thermococcus litoralis [Littlechild et al., in abstracts of the "International Congress on Exthermophiles '98" p. 58 (1998)]. To elucidate their contribution to the hyperthermostability of these enzymes, further structural studies are required.     

Alterations in [3H]L-N(G)-nitroarginine binding in brain after transient global or transient focal ischemia in gerbils and rats

Adverse physiological effects can often interfere with the use of nitric oxide (NO) as a therapeutic agent, especially when it is systemically generated from prodrugs. NO which is generated and delivered site-specifically by transdermal donors may be useful in the treatment of parasitic, bacterial or viral skin infections without causing systemic side effects. Three diazeniumdiolates (formerly "NONOate"), including two water soluble compounds, (Z)-1-[N-2-aminoethyl)-N-(2-ammonioethyl)amino]-diazen-1- ium-1,2-diolate (DETA-NO) and (Z)-1-[N-(3-aminopropyl)-N-(3-ammoniopropyl)amino] diazen-1-ium-1,2-diolate (DPTA-NO), and one insoluble compound, DPTA-NO grafted to dextran microspheres (DPTA-NO-g-dextran) were used to transdermally deliver NO to rats. Dextran microspheres were obtained by simultaneously grafting DPTA-NO to dextran and cross-linking dextran with CNBr in an oil-water emulsion. Suspended in hydrogel, DETA-NO, DPTA-NO, and DPTA-NO-g-dextran were applied three times to depilated rats at 4 day intervals. Results show that metabolic urinary nitrate levels increase with time (24-48 h), reach a maximum, and return to baseline by the fourth day. DPTA-NO applications produced an average maximum nitrate level of 94.2 mumol/day +/- 34.2 mumol S.D. compared to the average maximum nitrate level of 39.8 mumol/day +/- 8.6 mumol S.D. obtained from treatment with DETA-NO. These results suggest that DPTA-NO delivered NO more efficiently than DETA-NO. When DPTA-NO-g-dextran microspheres were used as the NO donor, results comparable to DPTA-NO were observed with an average maximum nitrate level of 14.9 mumol/day +/- 3.0 mumol S.D. These and other conclusive data indicate that, via these diazeniumdiolates, NO can be delivered effectively through rat skin.     

Kerr electro-optic field measurement and charge dynamics intransformer-oil/solid composite insulation systems

We measured the electric field in transformer oil/solid composite insulation system under dc voltage application using a Kerr electro-optic measurement system. When a pressboard was inserted at the center between two parallel-plane electrodes, the electric field at the mid-point between the pressboard and the cathode decreased with time. On the other hand, the electric field at the mid-point between the pressboard and the anode increased initially with time, reached a maximum value and then fell down. We measured also the electric field before and after polarity reversal of the dc voltage. The results revealed that the electric field after polarity reversal reached a magnitude 2.7× as much as the average dc applied field. We interpreted the above results on the time transition of the electric field in terms of a charge dynamic model, considering the difference in charge accumulation speed on the pressboard between positive and negative charges. This model was verified to be applicable to the time transition of the electric field in oil/solid composite system and BTA added oil/solid composite system as well     

深井潜水泵用马达的振动特性

本文将通常为圆形的定子截面形状改为三圆弧形,对深井潛水泵用马达的振动特性进行了理论解析和实验研宄。结果表明,正确选择截面形状参数,可有效地提高马达的稳定界限。从而指出了改善深井潛水泵用马达稳定性的一种途径。本文所得结果也可供实际设计深井潛水泵用马达对参考。     

Multi-objective reliability optimization for dissimilar-unit cold-standby systems using a genetic algorithm

A genetic algorithm approach is used to solve a multi-objective discrete reliability optimization problem in a k dissimilar-unit non-repairable cold-standby redundant system. Each unit is composed of a number of independent components with generalized Erlang distributions arranged in a series–parallel configuration. There are multiple component choices with different distribution parameters available for being replaced with each component of the system. The objective of the reliability optimization problem is to select the best components, from the set of available components, to be placed in the standby system in order to minimize the initial purchase cost of the system, maximize the system MTTF (mean time to failure), minimize the system VTTF (variance of time to failure) and also maximize the system reliability at the mission time. Finally, we apply a genetic algorithm with double strings using continuous relaxation based on reference solution updating (GADSCRRSU) to solve this multi-objective problem, using goal attainment formulation. The results are also compared against the results of a discrete-time approximation technique to show the efficiency of the proposed GA approach.