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861.
Heterochromatin effects on the frequency and duration of LCR-mediated gene transcription 总被引:3,自引:0,他引:3
E Milot J Strouboulis T Trimborn M Wijgerde E de Boer A Langeveld K Tan-Un W Vergeer N Yannoutsos F Grosveld P Fraser 《Canadian Metallurgical Quarterly》1996,87(1):105-114
Organ transplantation is associated with an early bone loss that subsequently increases the risk of osteopenia and bone fractures. It is not known whether bone loss continues in long-term survivors, but persistent bone demineralization could further jeopardize an already diminished bone mass. To better define long-term bone status of kidney transplant recipients (KTR), we conducted cross-sectional and longitudinal evaluations of bone mineral density (BMD) in 70 KTR with a mean posttransplantation time of 8.1 years. BMD was determined by dual-energy X-ray absorptiometry and was repeated in 55 of the patients after a mean follow-up period of 22 +/- 5 months. Lumbar and femoral osteopenia, defined as a BMD lower than 2 standard deviations from mean value of sex- and age-matched controls, was present in 28.6% and 10.5% of patients, respectively. There was a significant negative correlation between cumulative prednisone dose and adjusted lumbar as well as femoral BMD (R = 0.45, P < 0.001 and R = 0.29, P < 0.05, respectively). Five patients had a vertebral BMD below a fracture threshold of 0.777 g/cm2. Vertebral fractures (VF) were found in four men and were associated with higher prednisone dosage (P < 0.05), larger cumulative prednisone dose (P < 0.05), and significantly lower BMD values. According to World Health Organization recent criteria for women, prevalences of lumbar and femoral osteopenia and lumbar and femoral osteoporosis in female patients reach 75%, 65%, 33%, and 10%, respectively. The longitudinal part of the study showed a persistent pathological lumbar demineralization process. Over the study period, BMD, expressed as a percentage of that of controls, decreased from 89 +/- 14% to 86 +/- 14% (P < 0.001). Annual change of bone mass was -1.7 +/- 2.8% per year. Accelerated vertebral bone loss (defined as a decrease of BMD, expressed as a percentage of that of controls, of more than 1% per year) was present in 56% of patients and was associated with higher prednisone dosage (P < 0.01). In conclusion, although VF are relatively infrequent in long-term survivors of renal transplantation, osteopenia is a frequent finding, and a substantial proportion of women present lumbar osteoporosis. An ongoing demineralization process of the spine is also demonstrated and probably contributes to long-term spinal osteoporosis incidence. Prednisone dosage remains the most constantly isolated risk factor. 相似文献
862.
L. D. Pilipchatin V. V. Peschanskaya V. D. Troyan G. A. Belokrys N. G. Aleinikov 《Refractories and Industrial Ceramics》1996,37(8):281-284
Basic parameters of a resource-saving technology for manufacturing unfired articles for bottom steel casting that was developed under laboratory conditions are presented. Industrial tests of an experimental batch of unfired bottom tubes produced by the suggested technology have shown high performance properties for them and applicability of them for bottom casting of steel.Translated from Ogneupory i Tekhnicheskaya Keramika, No. 8, pp. 27–29, August, 1996. 相似文献
863.
L. V. Uzberg A. A. Malyutin G. V. Efimova A. F. Edneral N. N. Teplyakov 《Refractories and Industrial Ceramics》1996,37(11):396-398
Results of a laboratory study of the properties of corundum concrete with metallic fibers of five compositions are presented. It is shown that some of the fibers affect favorably the strength and heat resistance of the concrete. Industrial tests of parts made of the suggested reinforced concrete have proved these conclusions.Translated from Ogneupory i Tekhnicheskaya Keramika, No. 11, pp. 22–24, November, 1996. 相似文献
864.
Gong S.S. Burnham M.E. Theodore N.D. Schroder D.K. 《Electron Devices, IEEE Transactions on》1993,40(7):1251-1257
Electrical time-to-breakdown (TTB) measurements have shown the charge to breakdown Q bd of gate oxide capacitors fabricated on n-type well (n-well) substrates always to be higher than that of capacitors on p-type well (p-well) substrates on the same wafer when both are biased into accumulation under normal test conditions. Here the authors correlate the higher n-well Q bd to smooth capacitor oxide/substrate interfaces and minimized grain boundary cusps at the poly-Si gate/oxide interfaces, confirming that Fowler-Nordheim tunneling is the dominant current conduction mechanisms through the oxide. They correlate higher Q bd to higher barrier height for a given substrate type and observe that the slope of the barrier height versus temperature plot is lower for both p-well and n-well cases with electrons tunneling from the silicon substrate. This is attributed to surface roughness at the poly-Si gate/SiO2 interface. A poly-Si gate deposition and annealing process with clean, smooth oxide/substrate interfaces will improve the p-well breakdown characteristics and allow higher Q bd to be achieved 相似文献
865.
The paper describes the physical and chemical mechanisms governing the tribochemical reduction of metals and non-metals from their oxides. The reduction was started by a tribochemical activation of initial constituents in a vibrating mill used as a reactor. Powders of oxides of copper, iron, molybdenum, tungsten, vanadium, titanium and boron and also such chemically pure metals as magnesium, aluminium and titanium were used as reaction constituents. The triboactivation energy contribution needed to start the explosive mechanism reduction is found to increase as the heat of reaction decreases and the heat of formation of the associated product rises. Introducing oxygen into the reactor during the tribochemical activation of powders of oxides together with magnesium causes the intense oxidation of magnesium and stimulates the reduction process. To increase the yield of tungsten monocarbide from tungsten concentrate, the reduction process should be implemented in an atmosphere of hydrogen or hydrocarbons. 相似文献
866.
The standard enzymatic assay for quantification of D-sorbitol in plasma was adapted to the automatic analyzer Cobas Mira S. In the assay, NAD (reagent) in the presence of sorbitoldehydrogenase (SDH; start reagent) converts D-sorbitol to fructose with formation of NADH, which was detected automatically as the difference between the first and last readings at 340 nm. The sample blank values for each specimen were subtracted to exclude both endogenous D-sorbitol and sugars, which also react as substrates for SDH. The method is simple, rapid (40 samples/h), precise down to endogenous concentrations (coefficient of variation < 5%; limit of determination: 0.38 mg/L) and linear up to 100 mg/L. Samples with higher D-sorbitol concentrations were estimated after dilution. The method was used to measure disposition curves of sorbitol in volunteers after a single intravenous dose of 0.8 g sorbitol. 相似文献
867.
É. P. Volchkov N. A. Dvornikov L. N. Perepechko 《Combustion, Explosion, and Shock Waves》1996,32(4):390-394
Three methods of modeling a chemical reaction in the combustion of ethanol injected into the boundary layer through a porous plate are compared. In calculations of the average velocity and temperature and also heat-transfer coefficients, simple models of combustion are shown to be close in accuracy to a model that takes into complete account the kinetics of all reactions occurring during combustion. Simple models fail to determine the composition of reaction products, and it is necessary to take into account the formation rate of each substance entrained in combustion.Translated from Fizika Goreniya i Vzryva, Vol. 32, No. 4, pp. 37–42, July–August, 1996. 相似文献
868.
PURPOSE: Little has been written regarding the ultrasound imaging features that might allow prediction of fetal viability in abdominal pregnancies. Toward this goal, we present our experience with a series of 11 abdominal pregnancies. MATERIALS AND METHODS: From 1981 to 1993, 11 patients presented to Universidad Catolica, Santiago, and Universidad de Austral, Valdivia, Chile, with third trimester abdominal pregnancies. Five had complete ultrasound examinations, and these five patients were managed expectantly. The other six women presented as acute abdominal emergencies and underwent emergent surgery. RESULTS: Four of five fetuses that survived had a complete placental attachment to the uterus, and one surviving neonate had a partial attachment of the placenta to the uterus. Three fetuses died prior to delivery, and all three had a complete mesenteric placental attachment. Two died in the early neonatal period. One had a complete uterine placental attachment, and the other had a partial attachment. CONCLUSIONS: The survival rate of abdominal pregnancies may be better than is generally believed. Placental attachment to the uterus appears to be a factor related to fetal survival and maternal morbidity. More cases are necessary to determine the feasibility of managing women with abdominal pregnancies expectantly. 相似文献
869.
870.