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911.
神经网络在CB油田储层预测和储层厚度计算中的应用 总被引:1,自引:0,他引:1
根据CB油田的特点提出了利用神经网络进行储层预测和计算地层厚度的方法。将传统的储层预测方法与人工神经网络相结合,能较好地解决CB油田的储层预测问题。利用神经网络的非线性映射特点实现了地震特征与地层厚度之间的映射,从而可以准确地求取地层厚度。用该方法设计了2口探井,实际钻井结果表明,这种方法的预测结果准确、可靠。 相似文献
912.
B Zheng D W Larkin U Albrecht Z S Sun M Sage G Eichele C C Lee A Bradley 《Nature》1999,400(6740):169-173
Circadian rhythms are driven by endogenous biological clocks that regulate many biochemical, physiological and behavioural processes in a wide range of life forms. In mammals, there is a master circadian clock in the suprachiasmatic nucleus of the anterior hypothalamus. Three putative mammalian homologues (mPer1, mPer2 and mPer3) of the Drosophila circadian clock gene period (per) have been identified. The mPer genes share a conserved PAS domain (a dimerization domain found in Per, Arnt and Sim) and show a circadian expression pattern in the suprachiasmatic nucleus. To assess the in vivo function of mPer2, we generated and characterized a deletion mutation in the PAS domain of the mouse mPer2 gene. Here we show that mice homozygous for this mutation display a shorter circadian period followed by a loss of circadian rhythmicity in constant darkness. The mutation also diminishes the oscillating expression of both mPer1 and mPer2 in the suprachiasmatic nucleus, indicating that mPer2 may regulate mPer1 in vivo. These data provide evidence that an mPer gene functions in the circadian clock, and define mPer2 as a component of the mammalian circadian oscillator. 相似文献
913.
Effects of Shoe Heel Height on Loading and Muscle Activity for Trans-Tibial Amputees During Standing
This study accesses the effects of shoe heel heights on loading, muscle activity, and plantar foot pressure of trans-tibial amputees during standing. Five male subjects with unilateral trans-tibial amputation volunteered to participate in this study. Three pairs of shoes with zero, 20 mm, and 40 mm heel heights were used. The loading line of the prosthetic side, the plantar foot pressure, and the surface electromyography (EMG) of 10 muscles were simultaneously recorded. With increasing shoe heel heights dur... 相似文献
914.
在强场中发展了时间相关的光谱理论,提出了一个有很好性质的近似,籍此长脉冲激发体系的计算将变得非常容易,讨论了强场下的连续拉曼光谱,发现产生类荧光散射的入射频率范围比弱场大。 相似文献
915.
Contributions in the domain of cancer research: Review¶Negative regulators of cyclin-dependent kinases and their roles in cancers 总被引:25,自引:0,他引:25
In the past decade, the discovery and characterization of cyclin-dependent kinases (CDKs), the engine cores of the cell cycle machinery, have advanced our understanding of the cell cycle. Both positive and negative regulators of CDKs have been characterized, accelerating the important research to unravel the mechanisms of the cell cycle disease--cancer. Cancer can originate from overexpression of positive regulators, such as cyclins, or from underexpression of negative regulators, such as CDK inhibitors (CKIs). CKIs are the focus of much cancer research because they are capable of controlling cell cycle proliferation--the Holy Grail for cancer treatment. CDKs can be inactivated by several mechanisms:, (i) by association with CKIs including p16 (INK4a), p15 (INK4b), p21 (Cip1), p27 (Kip1), and p57 (Kip2), (ii) by disassociation from their cyclin regulatory unit, (iii) by dephosphorylation of a conserved threonine residue in the T-loop, and (iv) by adding inhibitory phosphate. Here we discuss what is known about each mechanism with a hope that these insights will become useful in developing strategies to eliminate cancer in the future. 相似文献
916.
Zhongliang Shi Mingyuan Gu Junyou Liu Guoquan Liu Jae-chul Lee Di Zhang Renjie Wu 《科学通报(英文版)》2001,46(23):1948-1952
The interfacial reactions of oxidized SiC particles reinforced Al-Mg matrix composites were investigated by the field emission-scanning
electron microscopy (FE-SEM), TEM and X-ray diffraction. It was found that the nanoscale MgO forms initially due to the interfacial
reaction, then whether it reacts with molten Al continuously or not depends on the content of Mg in the matrix and its covering
densification at the surface of particles. When there is not enough Mg in the matrix for the formation of dense MgO layer,
MgO will transform into MgAl2O4 crystal owing to the continuous reaction with SiO2 and molten Al. When dense MgO layer forms at the surface of the particles due to the affluence of Mg for the initial reaction,
it will protect the inner SiC from the attack of molten Al. However, the reaction products of both MgO and MgAl2O4 are thermo-stable phases at the surface of the particles under high temperature. The results clarify the interfacial reaction
route and they are of great value to the control of the interfacial reactions and their interfacial design of the composites. 相似文献
917.
Value of video-assisted thoracoscopic surgery in the diagnosis and treatment of pulmonary tuberculoma: 53 cases analysis and review of literature
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Tuberculoma of the lung is one of manifestations in tuberculosis and usually presents as a solitary pulmonary nodule (SPN). It is difficult to differentiate tuberculoma from SPN by other benign or malignant diseases. At present, the crucial role of video-assisted thoracoscopic surgery (VATS) in diagnosis and treatment of pulmonary diseases has been well acknowledged. Here, we reported 53 patients undergoing VATS resection for tuberculomas in our series. No postoperative mortality was found and only two patients experienced prolonged air-leakage (>7 d) and two had minor wound infections that were recovered after anti-tuberculosis or antibiotic treatment. Anti-tuberculosis chemotherapy from 6 to 12 months was routinely used postoperatively. We conclude that VATS is a satisfactory tool for the diagnosis and treatment of tuberculoma and can also establish a reliable diagnosis for all patients with SPNs. 相似文献
918.
Ore-forming event and geodynamic setting of molybdenum deposit at Wenquan in Gansu Province, Western Qinling 总被引:4,自引:0,他引:4
LEE Ben 《科学通报(英文版)》2009,54(13):2309-2324
The Wenquan molybdenum deposit is associated with a Triassic granite in this area. The Wenquan granite is enriched in LILE and LREE, poor in HFSE, and has significantly higher contents of alkali (K2O+Na2O) and Sr, Ba than those of the island arc volcanic rocks. These geochemical characteristics are similar to post-collisional granites in high K calc-alkaline series. Studies of major elements, trace elements, REEs and chronology of the Wenquan pluton show that, in the geodynamic transition stage of continent-continent convergence to extension, the partial melting of the enriched lithospheric mantle generated the basaltic magma and triggered the partial melting of the thickened lower crust which produceded the acidic magma, and the Wenquan pluton was formed by mixing of the two magmas. Molybdenite Re-Os isotopic dating gave Os model ages of 212.7±2.6 Ma to 215.1±2.6 Ma with a weighted mean of 214.1±1.1 Ma, and an Re-Os isochron age of 214.4±7.1 Ma. These ages are close to K-Ar ages (223 to 226 Ma) and a SHRIMP zircon U-Pb age (223±7 Ma) for the Wenquan granite within the error range, but relatively younger. This implies that the Mo mineralization occurred in a late stage of the magmatic intrusion, and the metallogenesis took place in the transition stage from syn-collision to post-collision in the tectonic setting of the Qinling Orogenic Belt (QOB) after continental collision between the North China Block (NCB) and the South China Block (SCB). This process is also corresponding to the geological events of metamorphism and deformation in South Qinling, closure of the Mian-Lue oceanic basin, and exhumation of the Dabie-Sulu ultrahigh-pressure metamorphic rocks. The large-scale continent-continent collision between NCB and SCB in the middle Triassic triggered significant crustal thickening and exhumation of subducted slab. In the late Triassic, the tectonic setting was transformed to the transition stage from collision to extension. Materials from the asthenospheric mantle would ascend into the root of the lower crust, which could induce partial melting of the lower crust and generate Mo-enriched granitic magma. The ore-forming elements enriched in the fluid derived from the condensation and fraction of the magma resulted in the Mo mineralization. The Mo deposits in the QOB are mainly formed in two episodes, namely 220± Ma and 140± Ma. The two episodes of metallogenesis were developed in the tectonic transition settings from compression to extension, but they were in the different stages of the tectonic evolution. The occurrence of the Wenquan Mo-bearing pluton indicates that the Triassic tectonic-magmatic belt of Western Qinling is another favorable region for Mo mineralization in the QOB. Therefore, it is significant to pay more attention to evaluation of the ore-forming potentiality in the Triassic granites in Western Qinling. 相似文献
919.
聚合物纳米复合材料因其分散相的高度精细化和纳米尺寸效应而具有与传统复合材料明显不同的力学性能和功能性能。其中,层状硅酸盐聚合物纳米复合材料又以分散相的高形状系数比而具有更为突出或特异的性能,如高刚性、高强度、高阻隔、高阻燃性等。因此聚合物纳米复合材料自问世以来便受到各国学者和工业界广泛关注。在轮胎气密层橡胶中,可以充分利用纳米层状硅酸盐材料的高阻隔性,从而起到提高气密性的作用。更进一步的应用研究表明,可以通过使用纳米层状硅酸盐填充橡胶作为气密层,在不损失气密性的情况下,减少气密层厚度,从而降低轮胎重量,实现原价节俭和滚动阻力降低的双重效果。 相似文献
920.
The redox state of arc mantle using Zn/Fe systematics 总被引:5,自引:0,他引:5
Many arc lavas are more oxidized than mid-ocean-ridge basalts and subduction introduces oxidized components into the mantle. As a consequence, the sub-arc mantle wedge is widely believed to be oxidized. The Fe oxidation state of sub-arc mantle is, however, difficult to determine directly, and debate persists as to whether this oxidation is intrinsic to the mantle source. Here we show that Zn/Fe(T) (where Fe(T) = Fe(2+)?+?Fe(3+)) is redox-sensitive and retains a memory of the valence state of Fe in primary arc basalts and their mantle sources. During melting of mantle peridotite, Fe(2+) and Zn behave similarly, but because Fe(3+) is more incompatible than Fe(2+), melts generated in oxidized environments have low Zn/Fe(T). Primitive arc magmas have identical Zn/Fe(T) to mid-ocean-ridge basalts, suggesting that primary mantle melts in arcs and ridges have similar Fe oxidation states. The constancy of Zn/Fe(T) during early differentiation involving olivine requires that Fe(3+)/Fe(T) remains low in the magma. Only after progressive fractionation does Fe(3+)/Fe(T) increase and stabilize magnetite as a fractionating phase. These results suggest that subduction of oxidized crustal material may not significantly alter the redox state of the mantle wedge. Thus, the higher oxidation states of arc lavas must be in part a consequence of shallow-level differentiation processes, though such processes remain poorly understood. 相似文献