A mixed-Weibull regression model for the analysis of automotive warranty data

This paper presents a case study regarding the reliability analysis of some automotive components based on field failure warranty data. The components exhibit two different failure modes, namely early and wearout failures, and are mounted on different vehicles, which differ among themselves for car model and engine type, thus involving different operating conditions. Hence, the failure time of each component is a random variable with a bimodal pdf which also depends upon a vector of covariates that indexes the specific operating condition. Then, a mixed-Weibull distribution, where the pdf of each subpopulation (namely the ‘weak’ and ‘strong’ subpopulation) depends on the covariates through the scale parameter, is used to analyze the component lifetime. A Fortran algorithm for the maximum likelihood estimation of model parameters has been implemented and a stepwise procedure, in its backwards version, has been used to test the significance of covariates and to construct the regression model. The presence of a weak subpopulation has been verified and the fraction of weak units in the population has also been estimated. Finally, the adequacy of the proposed model to fit the observed data has been assessed.     

Assessment of cell damage in high-pressure-shift frozen broccoli: comparison with market samples

Pressure-shift freezing (PSF) is one of the most promising methods for obtaining high-quality frozen products. The aim of this work was to analyse the differences between broccoli that was frozen using two different PSF processes. In one of the processes, all the freezing was done inside the high-pressure vessel tempered at −20.5 °C. In the other process, the sample was taken out of the vessel after expansion, and freezing was completed using liquid N₂. Colour, texture, electrical conductivity, microstructure and drip losses after centrifugation were analysed and a sensory test was performed. The results were compared with those for conventionally frozen broccoli purchased at the market. PSF broccoli presented less cell damage, lower drip losses and better texture than the market samples. The two different PSF processes assayed produced no significant differences in the final quality of the samples.     

Prolonged fasting in humans results in diminished plasma choline concentrations but does not cause liver dysfunction

The potential antiatherogenic actions of the angiotensin II receptor antagonist, losartan were investigated in apolipoprotein (apo) E deficient mice, an animal model with severe hypercholesterolemia and extensive atherosclerosis. In these animals accelerated atherosclerosis is associated with increased lipid peroxidation which may play a crucial role in the build up of the atherosclerotic lesions. Administration of losartan (25mg/kg/d) to the apo E deficient mice for a 3-month period increased the plasma renin activity 3.5-fold compared to the placebo group. Losartan increased the resistance of LDL to CuSO4-induced oxidative modification as shown by a significant reduction in the LDL content of malondialdehyde by 55% compared to placebo, as well as by the prolongation of the lag time required for LDL oxidation, from 60 min in the placebo-treated mice to more than 140 min in the losartan-treated mice. Losartan reduced significantly the mean atherosclerotic lesion area by 80% compared to the placebo group. We conclude that losartan inhibits LDL lipid peroxidation in the apo E deficient mice and this effect may have an important role in the attenuation of the accelerated atherosclerosis.     

A single gene of chloroplast origin codes for mitochondrial and chloroplastic methionyl-tRNA synthetase in Arabidopsis thaliana

One-fifth of the tRNAs used in plant mitochondrial translation is coded for by chloroplast-derived tRNA genes. To understand how aminoacyl-tRNA synthetases have adapted to the presence of these tRNAs in mitochondria, we have cloned an Arabidopsis thaliana cDNA coding for a methionyl-tRNA synthetase. This enzyme was chosen because chloroplast-like elongator tRNAMet genes have been described in several plant species, including A. thaliana. We demonstrate here that the isolated cDNA codes for both the chloroplastic and the mitochondrial methionyl-tRNA synthetase (MetRS). The protein is transported into isolated chloroplasts and mitochondria and is processed to its mature form in both organelles. Transient expression assays using the green fluorescent protein demonstrated that the N-terminal region of the MetRS is sufficient to address the protein to both chloroplasts and mitochondria. Moreover, characterization of MetRS activities from mitochondria and chloroplasts of pea showed that only one MetRS activity exists in each organelle and that both are indistinguishable by their behavior on ion exchange and hydrophobic chromatographies. The high degree of sequence similarity between A. thaliana and Synechocystis MetRS strongly suggests that the A. thaliana MetRS gene described here is of chloroplast origin.     

Employment interview on trial: Linking interview structure with litigation outcomes.

The authors linked interview structure and litigation outcomes conceptually and empirically. Using legal and psychological literatures, they established a conceptual link based on reduced opportunities for differential treatment through standardization, reduced potential for bias through increased objectivity, and increased job relatedness. Analyzing decisions regarding 84 disparate treatment claims and 46 disparate-impact claims in federal court cases, they established an empirical link between interview structure and how judges explained their verdicts. The 17 aspects of interview structure were scored in these cases. They collapsed into 3 composites: objective-job related, standardized administration, and multiple interviewers. Most items and composites were significantly related to favorable verdicts for defendants in both types of claims. The objective-job related composite was most highly related, followed by standardized administration. It is concluded that structure enhances interview reliability and validity, and it is also linked to litigation outcomes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Le fluage du béton en fonction de la température

Résumé Le texte présenté résume les résultats d'essais de fluage du béton en fonction de la température en prenant comme exemple l'un des matériaux étudiés, le béton d'agrégats de quartzite. Une tentative d'analyse est faite en prenant comme support de raisonnement la variation de l'énergie d'activation et l'équation d'Arrhénius; les conclusions semblent encourageantes lorsqu'on examine les résultats obtenus sur des bétons privés de leur eau libre.

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Summary The text presented summarizes the results of creep tests on concrete in terms of temperature, taking one of the materials studied, concrete with quartzite aggregates, as an example. An attempt at analysis is made, taking the variation of activation energy and the Arrhenius equation as the basis of approach. The conclusions seem encouraging when the results obtained with concretes deprived of free water are examined.

     

Reading skill: Some adult comparisons.

Three groups of college readers were compared on several information-processing and language comprehension tasks that tap the cognitive components of reading. The groups were skilled readers with high verbal and nonverbal abilities, low-skilled readers with a disparity between verbal and nonverbal abilities, and low-skilled readers who were low in both verbal and nonverbal ability. Results confirm the importance of word processing and general language comprehension in distinguishing skilled from less skilled readers. Results also support the view that reading ability is best described as a continuous function and provide evidence of the reemergence of lower level processing skills in adults as a function of text difficulty. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age, executive functions, and visuospatial functioning in healthy older adults.

Visuospatial test performance declines with age, whereas verbal test performance remains fairly constant. This pattern has been attributed to an age-related decline in either right-hemisphere functioning or executive functions (EFs), which may be associated with prefrontal cortical decline. Timed and untimed EF tests, and visuospatial tests requiring substantial integrative skill (I-VS) or little or no integrative skill (non-I-VS) were administered to young-old (aged 74 yrs and younger) and old-old (aged 75 yrs and older) healthy volunteers. Groups differed on I-VS tests and on many EF tests but not on non-I-VS tests. I-VS tests correlated highly with tests of EFs, but non-I-VS tests did not. These results are interpreted as supporting the proposal that an age-related decline in EF underlies the decline in visuospatial test performance observed with advancing age. Other issues regarding the relationship between age and EF are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hole boil-off and the magnetoresitance of the semimagnetic semiconductor Hg1−x MnxTe1−y Sey

Galvanomagnetic effects were investigated in gapless and narrow-gap semiconductors of the form Hg_1−x Mn_xTe_1−y Se_y with x=0.03–0.11, y=0.01–0.10 (−150<ɛ _g <190)meV and acceptor concentration 5.4×10¹⁶<N _A <4.3×10¹⁸ cm⁻³. In magnetic fields H=5–50 kOe and at T=1.3–4.2 K, the observed hole concentration p=1/eR was found to increase by a substantial factor (of up to 500). This was accompanied by a fall in the longitudinal (ρ _zz ) and transverse (ρ _xx ) magnetoresistivities. The hole “boil-off” is assumed to be a consequence of the existence at H=0 of a bound magnetic polaron and the delocalization of carriers when these states are destroyed by the external magnetic field. The anomalous ratio of longitudinal-to-transverse resistivities (ρ _zz >ρ _xx ), observed at liquid-helium temperatures and in magnetic fields H>10 kOe, is explained in terms of the properties of the energy spectrum of the valence band of semimagnetic semiconductors in quantizing magnetic fields. Fiz. Tekh. Poluprovodn. 31, 1198–1205 (October 1997)