Application of Acoustic Emission to the Study on Cathodic Polarization and SCC for High Strength Steels

The ambiguous effect of cathodic polarization onSCC of two high strength steels in 0.1 M Na_2HPO_4 and0.1 M NaNO_3 has been investigated by means of meas-uring electric resistance(R)and recording acoustic emis-sion(AE)signals simultaneously.Results showed that AEsensitivity strongly depends on K value in different solu-tions.Both anodic and cathodic polarization can acceler-ate crack growth rate at high K values,but it appears thatthere are only subtle differences in their AEcharacteristics.AE signals only reflect the macroprocessesof crack growth rather than the elementary ones and cannot be used for identification of the micro-mechanisms ofSCC.     

Methotrexate transport and resistance

Methotrexate (MTX), the antifolate drug widely used as both an anticancer chemotherapeutic drug and as an immunosuppressive agent, mimics natural folates to inhibit critical cellular biosynthetic pathways. One of the most important determinants of cellular sensitivity to MTX is the degree to which this drug is internalized by cancer cells, and one of the major pathways of folate uptake results from the activity of the reduced folate carrier (RFC). Decreased RFC activity has been associated with several models of transport-mediated MTX resistance. Recently, the rodent and human genes which encode this protein have been isolated (RFC1), and defects in the expression of RFC1 genes have been identified in transport-deficient, MTX-resistant cell lines. Therefore, these studies have demonstrated the importance of RFC1 expression in transport-mediated antifolate drug resistance. In addition, however, studies of both MTX uptake in cancer cells and of folate transport in physiologic systems indicate that there are other proteins with uptake characteristics similar to RFC, and which maybe encoded by genes other than RFC1.     

感光材料稳定剂的作用机理

本文对几种稳定剂作用机理作了研究和讨论。一些化合物的稳定作用与 (AgAu)S感 光中心的吸附有关 ,而另一些化合物的稳定作用则与 AgX晶体表面的吸附有关,第三类化合物的稳定作用是由于氧化感光材料储存期间所生成的银颗粒 (灰雾中心 )。把不同性能的稳定剂组合使用能有效地改善感光材料的稳定性。     

Methods of electrochemical study of natural metal sulfides

1　ＩＮＴＲＯＤＵＣＴＩＯＮＭｅｔａｌｓｕｌｆｉｄｅｓａｒｅｔｈｅｍａｉｎｓｏｕｒｃｅｏｆｎｏｎ ｆｅｒｒｏｕｓｍｅｔａｌｓ .Ｉｎｔｈｅｉｒｅｘｔｒａｃｔｉｏｎｆｒｏｍｏｒｅｓ ,ｔｈｅｐｒｏｃｅｓｓｏｆｍｉｎｅｒａｌｆｌｏｔａｔｉｏｎｐｌａｙｓａｍｏｓｔｉｍｐｏｒｔａｎｔｒｏｌｅ .Ｅｌｅｃ ｔｒｏｃｈｅｍｉｃａｌｍｅｔｈｏｄｓｂｅｃｏｍｅｖｅｒｙｕｓｅｆｕｌｆｏｒｓｔｕｄｙｏｆｍｅｔａｌｓｕｌｆｉｄｅｓａｎｄｔｈｅｉｒｆｌｏｔａｔｉｏｎｄｕｅａｎｅｌｅｃｔｒｏｃｈｅｍｉ ｃａｌｎａｔｕｒｅｏｆｔｈｅ…     

Titanium Aluminides: Science, Technology, Applications and Synthesis by Mechanical Alloying

The production. characteristics. and commercialization of monolithic and composite titanium aluminides are summanzed with emphasis on use in the demanding aerospace industry. The attractive elevated temperature properties combined with alow density make these materials of great interest, but inherently low "forgiveness", and environmental concerns, must be overcome before widespread use will occur One synthesis method for the production of monolithic titanium aluminides-mechanical alloying- will be discussed in detail     

Decreased melphalan accumulation in a human breast cancer cell line selected for resistance to melphalan

An in vitro model of acquired melphalan resistance was developed by serial incubation of an MCF-7 human breast cancer cell line in increasing concentrations of melphalan. The resulting derivative cell line, Me1R MCF-7, was 30-fold resistant to melphalan. Uptake studies demonstrated decreased initial melphalan accumulation in Me1R MCF-7 cells. Inverse-reciprocal plots of initial melphalan uptake revealed a 4-fold decrease in the apparent Vmax of Me1R MCF-7 compared with WT MCF-7 (516 amol cell-1 min-1 vs 2110 amol cell-1 min-1 respectively) as well as a decrease in the apparent Kt (36 microM vs 70 microM respectively). Two amino acid transporters have previously been identified as melphalan transporters: system L, which is sodium-independent and inhibited by 2-amino-bicyclo[2,2,1]heptane-2-carboxylic acid (BCH), and system ASC which is sodium dependent and unaffected by BCH. At low concentrations of melphalan (3-30 microM), 1mM BCH competition eliminated the differences between the two cell lines, thus implicating an alteration of the system L transporter in the transport defect in the resistant cells. Me1R MCF-7 cells were also evaluated for glutathione-mediated detoxification mechanisms associated with melphalan resistance. There was no difference between Me1R MCF-7 and WT MCF-7 in glutathione content, glutathione-S-transferase activity and expression of pi class glutathione S-transferase RNA. In addition, buthionine sulfoximine did not reverse melphalan resistance in Me1R MCF-7 cells. Therefore, Me1R MCF-7 cells provide an in vitro model of transport-mediated melphalan resistance in human breast cancer cells.     

Utilization of multiple polyadenylation signals in the human RHOA protooncogene

The lasting effects of a 9-day neonatal exposure to vasopressin and oxytocin were examined in the rat to discover if peptide administration results in organizational effects. When tested in young adulthood, brain growth, not body growth, appeared to be impaired. Basal and challenge tests of urine production, carried out to see the development of the hormonal antidiuretic function of vasopressin, revealed no lasting changes, and therefore did not confirm earlier findings of an induced mild polyurea. Behavioral testing of learning by making use of a one-trail step-through paradigm with a 24-h retention trial--a test that is sensitive to vasopressin--did not show impairments. Open field tests, however, showed enhanced emotionality in the vasopressin-treated females, as well as an initially increased ambulation in the males, and increased grooming in both sexes, the latter also having been reported to be induced by vasopressin administration in the septal areas. Oxytocin treatment did not produce lasting changes. Our conclusion, therefore, is that peripherally circulating vasopressin can affect the organizational development of the rat brain. It remains to be established whether this is an effect obtained through changes in the general peripheral physiology or a reflection of plasticity phenomena at the level of central vasopressin neurotransmission.     

ADVANCED HIGH GRADIENT TECHNOLOGY FOR CASTING OF SUPERALLOY TURBINE BLADES

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内燃机振动声学特性的预测

本文提出了在设计的初始阶段预测柴油机结构传递特性和声辐射的方法.在确定发动机结构广义传递函数时,利用了发动机重量和外表面面积与基本参数之间的统计关系式.激励力谱由柴油机工作过程的数学模拟和谱分析得到,发动机结构噪声的声功率谱等于结构广义传递函数和激励力谱的迭加,预测精度对于设计初始阶段是可以接受的.     

注入式半导体激光二极管的传输函数

根据电光耦合速率方程提出了注入式激光二极管的小信号——电光等效电路模型，并据此推导出激光二极管小信号传输函数，所得结果物理意义清楚，对以注入式半导体激光器为基础的光电系统和光纤系统的工程设计、分析很有意义。