TiN粒子在焊接热循环过程中的溶解、粗化及再析出行为

采用萃取复型技术,对经受焊接热循环不同阶段的试样进行研究,分析TiN粒子在焊接热循环不同阶段的溶解、粗化及再析出行为。结果表明,在焊接热循环加热过程的低温阶段（1200℃以下）,粒子的溶解以粒子的尺寸减小为主要特征,粒子数量变化不大。在焊接热循环加热过程的高温阶段（1200-1350℃）,大量小尺寸粒子消失,粒子平均尺寸显著增大。研究发现,TiN粒子的溶解存在很大的滞后效应,在冷却过程的高温阶段（1350-1300℃）,粒子仍继续溶解,在冷却过程的低温阶段（1300℃以下）,固溶状态的Ti与N结合并沉淀到残留的TiN粒子上,使粒子粗化。在焊接热循环过程中,Ti微合金钢原始奥氏体晶粒长大主要发生在冷却阶段。     

热镀锌钢板点焊性能研究

采用正交试验方法,对热镀锌板进行了电阻点焊接头性能试验以研究其焊接性能,获得了热镀锌板最佳的点焊焊接工艺参数。     

Human MDR 1 protein overexpression delays the apoptotic cascade in Chinese hamster ovary fibroblasts

Several laboratories have reported that overexpression of the multidrug resistance (MDR) protein is associated with intracellular alkalinization, and several investigators have reported that cells induced to undergo programmed cell death (apoptosis) acidify quite significantly. Because it is difficult to fully explain the resistance to apoptosis-inducing chemotherapeutic drugs that is exhibited by MDR tumor cells solely via altered drug transport alone [Hoffman et al. (1996) J. Gen. Physiol. 108, 295-313], we have investigated whether overexpression of the hu MDR 1 protein alters progression of the apoptotic cascade. LR73 fibroblasts induced to undergo apoptosis either via treatment with the chemotherapeutic drug colchicine or by serum withdrawal exhibit cellular volume changes, intracellular acidification, nuclear condensation, and chromosomal digestion ("ladder formation"), characteristic of apoptosis, in a temporally well-defined pattern. However, multidrug resistant LR73/20E or LR73/27 hu MDR 1 transfectants recently created in our laboratory without selection on chemotherapeutic drug are significantly delayed in the onset of apoptosis as defined by the above criteria, regardless of whether apoptosis is induced by colchicine treatment or by serum withdrawal. Thus, the delay cannot simply be due to the well-known ability of MDR protein overexpression to lower chemotherapeutic drug accumulation in MDR cells. LR73/27V500 "selectants", exhibiting similar levels of MDR protein overexpression but higher multidrug resistance due to selection with the chemotherapeutic drug vincristine, exhibit a slightly longer delay in the progression of apoptosis. Normal apoptotic cascade kinetics are partially restored by pre-treatment of the MDR cells with the MDR protein inhibitor verapamil. Untransfected LR73 cells not expressing MDR protein but elevated in pHi via manipulation of CO2/HCO3- as described [Hoffman et al. (1996) J. Gen. Physiol. 108, 295-313] are inhibited in DNA ladder formation, similar to LR73/hu MDR 1 transfectants. These results uncover an additional mechanism whereby MDR protein overexpression may promote the survival of tumor cells and further support the notion that in some systems intracellular acidification may be either causal or permissive for proper progression of the apoptotic cascade.     

Evolving enzyme technology for pharmaceutical applications: case studies

The case studies focus on two types of enzyme applications for pharmaceutical development. Demethylmacrocin O-methyltransferase, macrocin O-methyltransferase (both putatively rate-limiting) and tylosin reductase were purified from Streptomyces fradiae, characterized and the genes manipulated for increasing tylosin biosynthesis in S. fradiae. The rate-limiting enzyme, deacetoxycephalosporin C (DAOC) synthase/hydroxylase (expandase/ hydroxylase), was purified from Cephalosporium acremonium, its gene over-expressed, and cephalosporin C biosynthesis improved in C. acremonium. Also, heterologous expression of penicillin N epimerase and DAOC synthase (expandase) genes of Streptomyces clavuligerus in Penicillium chrysogenum permitted DAOC production in the fungal strain. Second, serine hydroxymethyltransferase of Escherichia coli and phthalyl amidase of Xanthobacter agilis were employed in chemo-enzymatic synthesis of carbacephem. Similarly, echinocandin B deacylase of Actinoplanes utahensis was used in the second-type synthesis of the ECB antifungal agent.     

Secobarbital in humans discriminating triazolam under two-response and novel-response procedures

The percentage of long-term survivors after intensive chemotherapy and the outcome of MDS patients who achieve partial remission (PR) with intensive chemotherapy (IC) are not known. Between 1981 and 1996 we treated 99 patients with de novo MDS who had high-risk MDS or progression to AML, with IC. 41 (41%) achieved CR, 16 (16%) achieved partial remission (PR), 26 (26%) had failure, and 16 (16%) died in aplasia. Eight of the patients who achieved CR were autografted, three were allografted and the remaining cases received moderate consolidation chemotherapy. After IC, the 16 PR patients fulfilled the criteria for RA in 15 cases and CMML in one case. Median PR duration was 17 months, and three PR were > 3 years (39, 50+, 82+ months). Median actuarial survival of patients who achieved PR and CR was 18 months and 20 months from the onset of IC, respectively (difference not significant). Of the 71 patients treated before 1993, with sufficient follow-up, 10 (14%) had survived > 4 years (long-term survivors). Four of them were alive in first CR after 49+ to 110+ months and probably cured, two were alive in PR after 50+ and 82+ months and four had died after 49-78 months. Long-term survivors were characterized by a significantly higher incidence of RAEB-T at diagnosis, and with normal or favourable cytogenetic findings. In patients with RAEB-T at diagnosis included before 1993, 8/23 (35%) cases who had no unfavourable karyotype had survived > 4 years. Our findings suggest that MDS patients who achieve PR with IC, and not only those who achieve CR, can benefit from this type of treatment. The percentage of long-term survivors remains low, however, and is almost restricted to patients with RAEB-T at diagnosis and no unfavourable karyotype.     

Chemotherapy in stage IV (metastatic) non-small-cell lung cancer. Provincial Lung Disease Site Group

After sciatic transection a strong decrease in immunoreactivity occurred, starting at 2 days. After 6, 10, 14, and 20 days survival only 5% of the sciatic motoneurons were strongly labeled for GluR2/3 against 80% in the control situation. From Day 20, GluR2/3 labeling started to increase again, reaching near normal levels at Day 80 after sciatic transection. In contrast, after sciatic crush, the decrease in GluR2/3 labeling in motoneurons was less pronounced and returned to normal in 30 days. In all animals, the GluR1 and GluR4 labeling of motoneurons remained unchanged after sciatic transection or crush. It is concluded that sciatic nerve injury leads to a strong, time-dependent decrease in the expression of GluR2 and 3 subunits in the corresponding motoneurons. As a consequence, AMPA receptors with a different subunit composition may be assembled, leading to a change in the functional properties of these receptors. Moreover, if they lack the GluR2 subunit, they may become calcium permeable.     

Processes of memory loss, recovery, and distortion

The author proposes that many forms of memory distortion, including the progressive changes in recollection of a learning experience often observed over successive tests, are due to the same processes that yield veridical recollection in some circumstances and memory loss and recovery in others. In a framework for interpreting all of these aspects of memory, the author assumes that the objects and events of a learning experience are encoded in parallel in traces of their perceptual attributes, which are basic to recognition, and in traces of reactions made to the events during or following learning, which are basic to recall. Random perturbation of remembered attribute values in both types of traces over retention intervals is a pervasive cause of both loss and distortions of memory.