Stress-corrosion cracking of reactor feed pump wear rings

Stress-corrosion cracking (SCC) is observed in machine components when an optimal combination of stress levels and environmental conditions is present in susceptible material. An interesting case history of intergranular SCC failure is presented in this paper. This failure occurred in wear rings that were shrink-fitted on the impellers of a multistage horizontal feed pump during the project procurement phase. After manufacture and assembly, two pumps were performance-tested in the supplier's test loop for a combined total of approximately 600 h. The test duration lasted for approximately three months. During this duration, the two pump internals were not absolutely dry and were exposed to an indoor environment in the supplier's test plant. After the completion of the tests, the pump internals were inspected, cleaned, dried, and packaged before air freighting to the reactor site. The pumps were in storage at the site for approximately two months. When the pumps were opened for inspection, two wear rings on each of the pumps were cracked. This paper summarizes the results of the studies to evaluate the root cause of the wear ring failures and the corrective actions implemented to avoid similar failures.     

Grouping in Short-Term Memory: Do Oscillators Code the Positions of Items?

According to several current models of short-term memory, items are retained in order by associating them with positional codes. The models differ as to whether temporal oscillators provide those codes. The authors examined errors in recall of sequences comprising 2 groups of 4 consonants. A critical manipulation was the precise timing of items within the groups, whereby temporal position (time from group onset) and ordinal position (number of items from group onset) were partially unconfounded. Errors that involve items migrating across groups should preserve within-group temporal position according to oscillator models, but should preserve within-group ordinal position according to nonoscillator models. Results from the intergroup errors strongly favored preservation of ordinal rather than temporal position. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Six Regularities of Source Recognition.

In recent work, researchers have shown that source-recognition memory can be incorporated in an extended signal detection model that covers both it and item-recognition memory (A. Hilford, M. Glanzer, K. Kim, & L. T. DeCarlo, 2002). In 5 experiments, using learning variables that have an established effect on item recognition, the authors tested further implications of that extended model. The results establish 6 source-recognition regularities that support the model. An important regularity in that set is the linkage of source and item recognition: Any learning variable that increases item recognition increases source recognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evidence that protein kinase Cepsilon mediates phorbol ester inhibition of calphostin C- and tumor necrosis factor-alpha-induced apoptosis in U937 histiocytic lymphoma cells

Protein kinase C (PKC) activators, such as the tumor-promoting phorbol esters, have been reported to protect several cell lines from apoptosis induced by a variety of agents. Recent evidence suggests that PKCepsilon is involved in protection of cardiac myocytes from hypoxia-induced cell death (Gray, M. O., Karliner, J. S., and Mochly-Rosen, D. (1997) J. Biol. Chem. 272, 30945-30951). We investigated the protective effects of the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) on U937 histiocytic lymphoma cells induced to undergo apoptosis by tumor necrosis factor-alpha (TNF-alpha) or by the specific PKC inhibitor calphostin C. U937 cells were transiently permeabilized with a peptide (epsilonV1-2) derived from the V1 region of PKCepsilon that has been reported to specifically block translocation of PKCepsilon. The epsilonV1-2 peptide blocked the inhibitory effect of TPA on both TNF-alpha- and calphostin C-induced apoptosis. A scrambled version of epsilonV1-2 and a peptide reported to inhibit PKCbeta translocation (betaC2-4) had no effect on the ability of TPA to inhibit apoptosis. These results suggest that PKCepsilon is required for the protective effect of TPA in TNF-alpha- and calphostin C-induced apoptosis. Furthermore, calphostin C reduced membrane-associated PKCepsilon activity and immunoreactivity, suggesting that PKCepsilon may play an important role in leukemic cell survival.     

Phosphorylation of ATPase subunits of the 26S proteasome

OBJECTIVE: To evaluate the impact of the 1993 French National Policy which made it mandatory to offer screening for the presence of human immunodeficiency virus (HIV) to all pregnant women who planned to give birth, although women remained free to refuse the test. DESIGN: Successive surveys in April 1992 and May 1994 in south-eastern France. Logistic regressions were performed to identify factors which affected access to HIV testing for women who gave birth and those who terminated their pregnancy, and for each year of study. MAIN OUTCOME MEASURES: Attitudes and access to HIV testing among pregnant women, irrespective of pregnancy outcome. SETTING: All obstetrics and gynaecology departments and abortion clinics in the region. POPULATION: 3497 women in 1992 (2775 who were delivered and 722 who chose termination) and 3407 in 1994 (2701 who were delivered and 766 who chose termination). The response rates were 82% and 88%, respectively. RESULTS: In 1994 of women who were delivered, 73% had an HIV test, compared with 63% in 1992 (P < 0.001); however of women who terminated their pregnancy, only 28% had an HIV test, compared with 24.5% in 1992 (P not significant), although they were more at risk for HIV infection. Socioeconomic differences affecting access to testing were reduced between 1992 and 1994, but only among women who gave birth. CONCLUSION: Introduction of a policy which makes it mandatory to offer HIV screening to all women who intended to have their baby improved access to screening but did not improve the rate of preventative counselling. A mandatory requirement to offer HIV screening should be extended to women who request termination of pregnancy.     

Antioxidant defenses influence HIV-1 replication and associated cytopathic effects

HIV-infected cells often exhibit reduced levels of antioxidant enzymes and thiols. To investigate the role of cellular antioxidant defenses in the progression of an acutely spreading HIV-1 infection, human Sup-T1 T cells were engineered to overexpress the selenium-dependent glutathione peroxidase, GSHPx-1. This enzyme represents a major cellular defense mechanism against toxicity associated with reactive oxygen species (ROS). T cells engineered to produce elevated GSHPx-1 activity displayed accelerated viral replication and associated cytopathic effects compared to control cells. Conversely, the inhibition of the synthesis of glutathione with buthione sulfoximine (BSO) resulted in the attenuation of viral replication in Sup-T1 cells. Similarly, exposure of human peripheral blood lymphocytes (PBLs) to low, nontoxic levels of BSO resulted in an approximately 80% decline in HIV-1 replication as indicated by Western blot analysis of viral proteins.     

Guidelines and care pathways for genetic diseases: the Scottish collaborative project on tuberous sclerosis

In Scotland a national audit project has been undertaken to devise evidence-based guidelines for the clinical management of patients with tuberous sclerosis (TS), a dominantly inherited multisystem disorder. In order to facilitate the audit and use of these guidelines a 'Care Pathway' was devised to form the patient records. We describe the process of guideline development for TS and our TS Care Pathway.     

Evaluating inheritance depth on the maintainability of object-oriented software

This empirical research was undertaken as part of a multi-method programme of research to investigate unsupported claims made of object-oriented technology. A series of subject-based laboratory experiments, including an internal replication, tested the effect of inheritance depth on the maintainability of object-oriented software. Subjects were timed performing identical maintenance tasks on object-oriented software with a hierarchy of three levels of inheritance depth and equivalent object-based software with no inheritance. This was then replicated with more experienced subjects. In a second experiment of similar design, subjects were timed performing identical maintenance tasks on object-oriented software with a hierarchy of five levels of inheritance depth and the equivalent object-based software.The collected data showed that subjects maintaining object-oriented software with three levels of inheritance depth performed the maintenance tasks significantly quicker than those maintaining equivalent object-based software with no inheritance. In contrast, subjects maintaining the object-oriented software with five levels of inheritance depth took longer, on average, than the subjects maintaining the equivalent object-based software (although statistical significance was not obtained). Subjects' source code solutions and debriefing questionnaires provided some evidence suggesting subjects began to experience difficulties with the deeper inheritance hierarchy.It is not at all obvious that object-oriented software is going to be more maintainable in the long run. These findings are sufficiently important that attempts to verify the results should be made by independent researchers.     

A homotopy algorithm for approximating geometric distributions by integrable systems

In the geometric theory of nonlinear control systems, the notion of a distribution and the dual notion of codistribution play a central role. Many results in nonlinear control theory require certain distributions to be integrable. Distributions (and codistributions) are not generically integrable and, moreover, the integrability property is not likely to persist under small perturbations of the system. Therefore, it is natural to consider the problem of approximating a given codistribution by an integrable codistribution, and to determine to what extent such an approximation may be used for obtaining approximate solutions to various problems in control theory. In this note, we concentrate on the mathematical problem of approximating a given codistribution by an integrable codistribution. We present an algorithm for approximating an m-dimensional non-integrable codistribution by an integrable one using a homotopy approach. The method yields an approximating codistribution that agrees with the original codistribution on an m-dimensional submanifold E₀ of ⁿ.