有机酚醛聚合物凝胶深部调驱体系孔渗适应性研究

聚合物凝胶体系在地层中的渗流及封堵特性对深部调驱效果具有重要的影响。利用长填砂管驱替物模试验,研究了有机酚醛聚合物凝胶体系在不同渗透率填砂管中的注入特性、渗流行为和封堵性能,结果表明有机酚醛聚合物体系是一种注入性和流动性均较好的凝胶体系。通过对有机酚醛聚合物凝胶体系在长填砂管中的封堵特性和渗流参数结果分析,确定了有机酚醛聚合物凝胶体系组分质量浓度与3种地层渗透率的匹配关系。最后通过室内驱油物模试验,对凝胶体系与渗透率的匹配关系进行了验证。     

一种基于时钟差的双端数据同步方法

文章对已有的双端数据采样同步方法进行了对比分析并指出了其优缺点.随着自愈环网和可变路由的光纤通道在高压电网中的普遍应用,采样数字同步网络复用通道作为传输信道时有可能出现通信路由不一致的情况,为了解决收、发通道延时不一致时的数据同步问题,文章引入装置“时钟差”的概念,以传统的“乒乓对时”为主,辅助以电气量对时,可以解决由...     

Resuscitation equipment board for nurseries and delivery rooms

A resuscitation equipment board for mounting in delivery rooms and nurseries facilitates orderly and effective resuscitation of asphyxiated neonates.     

Restriction endonucleases can be used to confirm a structure of unusual DNA duplexes

Cyclic and polycyclic oligonucleotides were synthesized using chemical ligation. Two types of catenanes with one and several intertwinings were produced. The yield of these molecules depended on the ligation conditions and nucleotide sequence of the ligated oligonucleotide and its template. Structure of ligation products was investigated and confirmed using restriction endonuclease MvaI. Interaction of the synthesized molecules with restriction endonucleases SsoII, EcoRII and HindIII was also studied.     

Carotid atherosclerosis in renal transplant recipients

BACKGROUND: Cardiovascular accidents are the major cause of morbidity and mortality in renal transplant recipients. However, there is little information concerning carotid atherosclerotic wall changes in renal transplant recipients, their relationship with cardiovascular accidents and their possible association with cardiovascular risk factors in such patients. METHODS: Between April 1991 and December 1997, we prospectively assessed cardiovascular accidents in 79 renal transplant recipients who had received a transplant at our institution before January 1, 1986. Carotid morphology by B-mode ultrasonography, relevant clinical and laboratory cardiovascular risk factors, including lipid abnormalities and total homocyst(e)ine, were determined at the start of the follow-up period. Seventeen healthy subjects matched for age and sex with renal transplant recipients served as controls who volunteered for ultrasonographic examination of carotid arteries. RESULTS: Nine patients experienced cardiovascular events during the period of follow-up. Compared with healthy, age- and sex-matched control subjects (n = 17), the frequency of carotid plaques was higher in renal transplant recipients with cardiovascular events (n = 9), but not in those without such events (n = 70). The frequency of cardiovascular accidents was related to the number of carotid plaques (4, 17 and 24% for no plaque, one plaque and > 1 plaque respectively, P < 0.04). However, by multivariate analysis, serum total cholesterol [odds ratio (OR) of 1.8 for each 1.0 mM, P < 0.07) and the presence of diabetes mellitus (OR of 28.4 for presence, P < 0.01) were the only predictors of cardiovascular events in such patients, whereas the presence of carotid plaques was not. Moreover, neither serum lipoprotein (a) nor total homocyst(e)ine concentrations could be identified as risk factors. CONCLUSIONS: This prospective study shows that although a close association exists between asymptomatic carotid atherosclerosis and cardiovascular accidents in renal transplant recipients with long-term follow-up and relatively good renal function, other potentially modifiable risk factors appear to be better predictors of cardiovascular events. Consequently, the assessment of carotid atherosclerosis may not be clinically useful for the systematic identification of renal transplant recipients with an increased risk of developing cardiovascular events.     

Thin film deposition for permeability increase of gas being implanted (theoretical consideration)

A theoretical model has been developed for diffusive permeation of gas injected by ion bombardment through thin metallic targets, including membranes with thin films deposited onto the surface. The film material differs from the substrate material. Calculations for gas atom distribution in the film and substrate have been carried out, as well as gas fluxes to the source and sink sides in such a system in a quasi-stationary régime. The possibility of a permeability increase is revealed under implantation of gas ions both with low (～ keV) and higher energies (of the order of tens of keV) by deposition onto an irradiated target surface having a film of material with a lower diffusion coefficient for the gas being implanted than the substrate material itself. It has been shown that the most significant effect may be obtained under relatively high energy implantation for deposited film thicknesses markedly less than the mean ion range, and where the film permeability (diffusion coefficient and/or gas solubility) is much smaller than that of the substrate material itself. Periodic or simultaneous with implantation film renewal on the target surface has been suggested to compensate for sputtering.