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991.
Deuterated scintillators (NE230) can provide, without time-of-flight, usable neutron energy spectra for neutrons E n⩾1 MeV. The authors have assembled and calibrated several of these detectors and used them in experiments searching for d+d fusion-neutron emission (En, 2.5 MeV) in Pd+D 2O electrolysis and Ti+D2 adsorption at LN temperatures. The detectors yielded direct fusion-neutron spectra and set limits in the Pd+D and Ti+D experiments of <7×10-24 fusion n/s/dd pair and <3×10-24 fusion n/s/dd pair respectively. In addition, these detectors have been used for in-beam accelerator experiments requiring coincidence between fast neutrons and scattered ions  相似文献   
992.
An averaging circuit model is developed for the class E resonant DC-DC converter regulated at a fixed switching frequency. The regulation is achieved by use of an auxiliary switch. The model is obtained based on the circuit analysis using the Fourier series expansion. Steady-state and small-signal dynamic analysis is presented, which reveals that the DC output is well controlled by the control angle of the auxiliary switch and that there exists a right-half-plane zero in the control-to-output transfer function. The analysis results are verified by the experiments  相似文献   
993.
In this work 23 month old rats were fed for 200 days with different protein diets (NT-diet: 19% protein, 72% of animal origin and LP-diet: 8.8% protein exclusively of vegetable origin). Some metabolic parameters and lifespan (on the base of a 50% death-rate) were determined. The relations of the liver free amino acids glycine + alanine and tyrosine + phenylalanine + branched chain amino acids and the ratio of phenylalanine/tyrosine were determined to be higher in the LP-group. Phenylalanine in liver and urea concentrations in liver and serum were lower in the LP-group. Furthermore the dopamine or serotonin levels were significantly lower in lateral and medial or lateral regions of the hypothalamus respectively in LP-diet fed rats. The norepinephrine content was not modified by the diets. The median lifespan of 23 month old rats was higher by 24% following LP-treatment. These results suggest that the protein component (amino acids) of different diets may modify metabolic parameters and lifespan of animals by mechanisms in which the central regulation may be involved.  相似文献   
994.
A method has been developed for the analysis of cimaterol and clenbuterol residues in liver, with detection limits of 0.25 micrograms/kg and 0.5 micrograms/kg, respectively. The recovery varied from 55% to 60%. After extraction, a clean-up procedure with Baker-spe C-18 columns was performed. The two chemical compounds of interest were eluted with methanol. Cimaterol and clenbuterol were quantitatively determined by high-performance liquid chromatography (HPLC) using an RP-Select B (5 microns) column and a post-column reaction procedure. The positive results were confirmed by high-performance thin-layer chromatography (HPTLC) as this technique reaches the same level of sensitivity as the HPLC method.  相似文献   
995.
The first observation is reported of ultrafast all-optical switching in an integrated asymmetric Mach-Zehnder interferometer, using the nonresonant nonlinearity in Ga/sub 0.82/Al/sub 0.18/As below half the bandgap. A relative switching fraction of more than 80% has been achieved using 330 fs pulses at around 1.55 mu m from a coupled-cavity mode-locked colour centre laser.<>  相似文献   
996.
Performance on computer-simulated, everyday memory tasks was found to deteriorate with age in 434 Belgian (aged 14–88 yrs) and 434 American Ss matched on gender and age. This age-related memory decline was reasonably consistent across samples. Difficulties in cross-cultural research and the advantages of ecologically valid measurement instruments are discussed. Instruments included a grocery list selective reminding test, the Wechsler Memory Scale, the Benton Visual Retention Test, and the Wechsler Adult Intelligence Scale (WAIS). (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
997.
Acrosomal integrity of bovine spermatozoa was evaluated using naphthol yellow S-erythrosine B stain with bright-field microscopy, .2% glutaraldehyde fixation with Nomarski optics, and live wet smears with Nomarski optics to compare the evaluation techniques. Four ejaculates per two Holstein bulls were enriched through a Percoll gradient, capacitated with heparin, and acrosome-reacted with lysophosphatidylcholine to prepare spermatozoa for in vitro fertilization. Spermatozoa samples were taken after each preparatory step, and percentage of intact acrosomes was evaluated with the stain, .2% glutaraldehyde, and live wet smear. Acrosomal integrity decreased with each preparatory step across all techniques. The decrease in integrity from heparin to lysophosphatidylcholine indicated that all methods detected the acrosome reaction. Technique means across preparation steps showed no differences. Correlations between microscopy techniques were high. The live wet smear used no fixation methods. Both the naphthol yellow S-erythrosine B stain and the .2% glutaraldehyde techniques employed fixation steps that may have introduced artifacts that could influence the data. The live wet smear evaluated by Nomarski optics allowed a comparable evaluation of the acrosome-reacted bovine spermatozoa. Comparing brightfield with differential interference contrast microscopy for detecting the acrosome reaction in bovine spermatozoa showed that both methods were equally accurate.  相似文献   
998.
Mining Institute, Moscow. Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 2, pp. 26–29, March–April, 1991.  相似文献   
999.
A novel wiggler design for use in free-electron lasers (FELs) is proposed, consisting of a staggered array of magnetic poles situated inside the bore of a solenoid. The resultant field pattern consists of a periodic transverse magnetic field on axis, as well as a longitudinal guide field. Such a wiggler has several advantages: the longitudinal field acts to confine the electrons near the FEL axis, high fields can be attained at short wiggler periods, the field strength is easily varied, and fabrication and testing of the wiggler are relatively easy. It is planned to use this wiggler design in a far infrared FEL to be built at Stanford University  相似文献   
1000.
On the capacity of a cellular CDMA system   总被引:37,自引:0,他引:37  
It is shown that, particularly for terrestrial cellular telephony, the interference-suppression feature of CDMA (code division multiple access) can result in a many-fold increase in capacity over analog and even over competing digital techniques. A single-cell system, such as a hubbed satellite network, is addressed, and the basic expression for capacity is developed. The corresponding expressions for a multiple-cell system are derived. and the distribution on the number of users supportable per cell is determined. It is concluded that properly augmented and power-controlled multiple-cell CDMA promises a quantum increase in current cellular capacity  相似文献   
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