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71.
72.
核磁共振谱的岩石孔喉结构分析 总被引:20,自引:1,他引:19
刘堂宴 ,王绍民 ,傅容珊 ,周明顺 ,李艳华 ,罗曼 .核磁共振谱的岩石孔喉结构分析 .石油地球物理勘探 ,2 0 0 3,38(3) :32 8~ 333岩心核磁共振 T2 谱和压汞分析数据均在一定程度上反映了岩石的孔喉结构 ,理论分析表明 ,这两组数据具有相关性。应用岩心核磁共振 T2 谱研究岩石孔喉结构 ,关键是确定 T2 与 Pc的转换系数。但以前的方法在 T2与 Pc 的转换过程中 ,需要涉及某些岩石特性参数 ,实用中有一定困难。本文直接利用岩心核磁共振 T2 谱和压汞分析数据之间的相关性 ,客观地确定 T2 与 Pc之间的转换系数 ,避免了确定岩石特性参数的困难。应用本文方法 ,对 6块岩心的多种核磁共振分析数据进行了对比分析 ,做出了 NMR (Nuclear Magnetic Resonance,简称NMR) T2 毛管力曲线和孔喉半径分布 ,并将这些结果与压汞分析的结果进行了对比。结果表明 ,岩心 NMR T2谱在实用性和评价精度上均略显优势 ;至少是在饱含油的条件下 ,岩心的 NMR T2 谱可以用于研究孔喉结构分布 ,油气的弛豫特性作为影响背景值存在 ,对于评价结果没有明显的影响 ;在全部 6块岩心中 ,T2 与 Pc 的转换系数位于 2 5 0 0~ 4 0 0 0μs· MPa之间。 相似文献
73.
Termites live in a material world: exploration of their ability to differentiate between food sources. 下载免费PDF全文
Ra Inta Joseph C S Lai Eugene W Fu Theodore A Evans 《Journal of the Royal Society Interface》2007,4(15):735-744
Drywood termites are able to assess wood size using vibratory signals, although the exact mechanism behind this assessment ability is not known. Important vibratory characteristics such as the modal frequencies of a wooden block depend on its geometry and boundary conditions; however, they are also dependent on the material characteristics of the block, such as mass, density and internal damping. We report here on choice experiments that tested the ability of the drywood termite Cryptotermes secundus to assess wooden block size using a solid wooden block paired with a composite block, the latter made of either wood and aluminium or wood and rubber. Each composite block was constructed to match mass or low-frequency vibratory modes (i.e. fundamental frequency) of the solid wooden block. The termites always chose the blocks with more wood; they moved to the solid wooden blocks usually within a day and then tunnelled further into the solid wooden block by the end of the experiment. Termites offered composite blocks of wood and rubber matched for mass were the slowest to show a preference for the solid wooden block and this preference was the least definitive of any treatment, which indicated that mass and/or damping may play a role in food assessment. This result clearly shows that the termites were not fooled by composite blocks matched for mass or frequency, which implies that they probably employ more than a single simple measure in their food assessment strategy. This implies a degree of sophistication in their ability to assess their environment hitherto unknown. The potential importance of alternative features in the vibrational signals is discussed. 相似文献
74.
75.
AB Deisseroth Z Zu D Claxton EG Hanania S Fu D Ellerson L Goldberg M Thomas K Janicek WF Anderson 《Canadian Metallurgical Quarterly》1994,83(10):3068-3076
Relapse after autologous bone marrow transplantation for chronic myelogenous leukemia (CML) can be due either to the persistence of leukemia cells in systemic tissues following preparative therapy, or due to the persistence of leukemia cells in the autologous marrow used to restore marrow function after intensive therapy. To help distinguish between these two possible causes of relapse, we used safety-modified retroviruses, which contain the bacterial resistance gene NEO, to mark autologous marrow cells that had been collected from patients early in the phase of hematopoietic recovery after in vivo chemotherapy. The cells were then subjected to ex vivo CD34 selection following collection and 30% of the bone marrow were exposed to a safety-modified virus. This marrow was infused after delivery of systemic therapy, which consisted of total body irradiation (1,020 cGy), cyclophosphamide (120 mg/kg), and VP-16 (750 mg/m2). RT PCR assays specific for the bacterial NEO mRNA, which was coded for by the virus, and the bcr-abl mRNA showed that in two evaluable CML patients transplanted with marked cells, sufficient numbers of leukemia cells remained in the infused marrow to contribute to systemic relapse. In addition, both normal and leukemic cells positive for the retroviral transgenome persisted in the systemic circulation of the patients for at least 280 days posttransplant showing that the infused marrow was responsible for the return of hematopoiesis following the preparative therapy. This observation shows that it is possible to use a replication-incompetent safety-modified retrovirus in order to introduce DNA sequences into the hematopoietic cells of patients undergoing autologous bone marrow transplantation. Moreover, this data suggested that additional fractionation procedures will be necessary to reduce the probability of relapse after bone marrow transplantation in at least the advanced stages of the disease in CML patients undergoing autologous bone marrow transplantation procedures. 相似文献
76.
M Hafezparast CG Cole GP Kaur RS Athwal PA Jeggo 《Canadian Metallurgical Quarterly》1994,20(6):541-548
A hamster-human hybrid containing only the q arm of chromosome 2 has been used to construct a panel of hybrids bearing reduced regions of chromosome 2 using the technique of irradiation fusion gene transfer. The human chromosome 2 carried the Ecogpt gene and all hybrids were selected using this marker. The integrated Ecogpt gene was localized to the region 2q33-34, resulting in the selective retention of this region in the hybrids. These data were combined with another previously constructed panel of hybrids containing regions of 2q, which were enriched for the region 2q36-37. The combined hybrid panel is useful for the mapping of new markers to defined regions of chromosome 2 and for the cloning of genes located on 2q by a positional strategy. 相似文献
77.
CG Willett 《Canadian Metallurgical Quarterly》1996,8(4):329-333
For the past 10 to 15 years, radiation therapy and chemotherapy have played an increasingly important role in the treatment of various gastrointestinal malignancies, most prominently in anal and rectal cancer. Critical issues in the care of patients with anal and rectal cancer include not only local control and survival but organ preservation as well. For patients with carcinoma of the anal canal, external-beam irradiation with 5-fluorouracil and chemotherapy with mitomycin C have replaced surgery as primary therapy. Current studies are optimizing this therapy. In contrast, the management of distal rectal cancer is in evolution. Although the abdominoperineal resection has been long regarded as the definitive treatment of distal rectal cancer, it is associated with substantial morbidity (loss of anorectal function with a permanent colostomy and a high incidence of sexual and genitourinary dysfunction). As an alternative, treatment programs utilizing sphincter-preserving procedures with radiation therapy and chemotherapy are under active investigation. In selected patients, these strategies appear promising, and there have been reports of satisfactory local control and survival, as well as preservation of sphincter integrity. 相似文献
78.
研究了经溶液共混制备的聚对苯二甲酸乙二醇酯/聚碳酸酯(PET/PC)共混物的辐射效应。结果表明:PET/PC共混物在辐照过程中未发生酯交换反应和交联反应,但有降解反应发生。在研究的剂量范围内,辐照对PET/PC共混物中PET和PC的晶体形态影响不明显。 相似文献
79.
以YAG为添加剂的气压烧结氮化硅 总被引:2,自引:1,他引:1
本文以添加YAG的反应烧结氮化硅(RBSN)为前驱体,采用气氛加压烧结的工艺,在0.5~9.0MPa氮气压力范围,研究了不同氮压对烧结体的密度、相组成、强度和显微结构的影响及其相互间的关系。研究表明,通过改变氮气压力能有效地调控材料的显微结构,材料的性能又受控于显微结构的变化。 相似文献
80.
CG Enke 《Canadian Metallurgical Quarterly》1997,69(23):4885-4893
In electrospray ionization (ESI), droplets with a surface excess charge are created. The rate of production of surface excess charge is a constant and is equal to the rate of ion production. The ions appearing in the mass spectrum are postulated to be those that formed the surface excess charge at the time of droplet formation (or their collision products). An equilibrium model based on competition among the ions in the solution for the limited number of excess charge sites has been developed. This model accurately predicts the response curves of singly-charged ionic analytes as a function of the concentration of electrolyte and other analytes and provides an explanation for the selective effectiveness of ESI. At low concentrations of total analyte (micromolar and less), the response curves are linear, indifferent to the presence of other low concentration analytes, and suppressed by electrolyte concentrations in excess of the minimum required. At higher analyte concentrations, the response becomes independent of analyte concentration but highly affected by the presence of other analytes. 相似文献