Parental correlates of children's peer relations: An empirical test of a tripartite model.

In recognition of the multiple pathways through which family and peer systems are linked, this short-term longitudinal study tested a tripartite model of family-peer relationships. One hundred fifty-nine fourth-grade children (82 boys, 77 girls) and their parents participated in a study of the links between parent behaviors and children's peer relations both concurrently and 1 year later. A multimethod approach--including observations of parent?child interactions, parent report, child report, and teacher and peer ratings--was used to evaluate a tripartite model of family-peer relations. Results indicate that parent?child interaction, parent advice giving, and parental provision of opportunities by both mothers and fathers predict children's social competence and, in turn, social acceptance 1 year later. Suggestions for future research and practical implications are noted, and limitations of the study are acknowledged. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cyclic loading of railway ballast under triaxial conditions and in a railway test facility

A recently developed large-scale triaxial test apparatus for railway ballast testing comprises a double-cell arrangement for measuring volume change by differential pressure. Monotonic and cyclic tests were performed on limestone ballast samples. Axial and volumetric strains and breakage were determined from both types of test. Resilient modulus and Poisson’s ratio were obtained only from the cyclic tests. The permanent axial strain and breakage results from the cyclic tests are compared with the simulated traffic loading in the railway test facility (RTF) which comprises three sleepers embedded in ballast over a subgrade. The traffic loading in the RTF was applied by hydraulic actuators with built-in displacement transducers. A column of painted ballast was placed under a rail seat of the middle sleeper to ease sample collection for sieve analysis at the end of the test. The stress condition in the RTF is predicted by a simple calculation based on findings of previous literature. It was found that the results from the cyclic triaxial test with conditions similar to the predicted conditions in the RTF were comparable to those results from the RTF tests.     

Effect of pre-exposure on crack initiation life of a directionally solidified Ni-base superalloy

Blades and vanes are just two of several industrial gas turbine (IGT) components often subjected to long periods of elevated temperature before, during, and after high stress operating conditions. In these systems, cyclic loading is induced by repeated start-ups, firings, and shut-down ramps. Combinations of complex thermal and mechanical service conditions in the presence of aggressive reactants facilitate crack initiation via oxide spike formation. In the current study, the effect of pre-exposure on the oxide spiking damage mechanism and crack initiation life is characterized for a representative directionally solidified (DS) Ni-base superalloy, e.g. DS GTD-111. Comparisons of unexposed and pre-exposed samples reveal that 100 h of either creep pre-strain and/or thermal pre-exposure strongly influences the dominant damage mechanism that leads to crack initiation under subsequent fatigue cycling. A mechanistic model for crack initiation is modified to capture the influence of pre-exposure on life.     

Role of sigma B factor in the alkaline tolerance response of Listeria monocytogenes 10403S and cross-protection against subsequent ethanol and osmotic stress

Many of the considerable abilities of Listeria monocytogenes to persist and grow in a wide range of adverse environmental conditions are thought to be at least partly under the control of the alternative sigma factor (sigmaB), encoded by the sigB gene. However, little is known about the role of this master regulon in the impressive ability of Listeria to persist and grow under conditions of alkaline pH. In this study, Northern blot analysis of parent Listeria mRNA revealed that alkali adaptation (pH 9.5 for 1 h) significantly increased the expression of sigB-derived mRNA. The study included a comparison of the relative survival of mid-exponential populations of adapted and nonadapted parent type (sigmaB expressing) and mutant (not sigmaB expressing, deltasigB) Listeria strains during subsequent alkaline (pH 12.0), osmotic (25% NaCl, wt/vol), or ethanol (16.5%) stress. Alkali-adapted parent strains were more resistant to pH 12.0 than were adapted deltasigB type strains, but both alkali-adapted parent and deltasigB strains were more resistant to pH 12.0 than were nonadapted strains. Alkali-adapted parent strains were more resistant to osmotic stress than were adapted deltasigB type strains. No significant differences in viability were observed between alkali-adapted parent and deltasigB strains after ethanol stress, suggesting that cross-protection against osmotic stress is mediated by sigmaB whereas cross-protection against ethanol is sigmaB independent. Overall, alkali-induced cross-protection against osmotic and ethanol challenges may have serious implications for food safety and human health because such stress conditions are routinely used as part of food preservation and surface cleaning processes.     

Fate of Escherichia coli O157:H7 during silage fermentation

The survival characteristics of Escherichia coli O157:H7 in silage derived from contaminated grass were investigated. The survival of other enteric bacteria was also investigated to determine if E. coli O157:H7 demonstrates enhanced acid tolerance in comparison. Samples of chopped grass were treated as follows: (i) no additive (control); (ii) inoculation with E. coli O157:H7 to a final concentration of log10 4.0 CFU g(-1); (iii) addition of an 85% solution of formic acid at 3.0 ml kg(-1) grass; and (iv) addition of both E. coli O157:H7 and formic acid, at the above concentrations. Treated 6-kg grass samples were packed into laboratory silos, sealed, and stored at 15 degrees C for up to 180 days. Individual replicate silos were removed from storage periodically and subjected to microbiological and chemical analyses. Chemical analyses of the silage samples indicated that lactic acid-dominant fermentations, with a rapid drop in pH, occurred. Numbers of enteric bacteria decreased from log10 7.0 to 8.0 CFU g(-1) to undetectable levels within 19 days' storage. E. coli O157:H7 did not survive the silage fermentation process, with numbers declining from approximately log10 4.0 CFU g(-1) to undetectable levels within 19 days of ensiling. The pattern of decline in numbers of E. coli O157:H7 was the same as that for the enteric bacteria, indicating that under the conditions tested, the acid tolerance of E. coli O157:H7 was not significantly different from the acid tolerance of other enteric bacteria. This study found that E. coli O157:H7 did not survive a good silage fermentation process, indicating that properly ensiled grass that is correctly stored is unlikely to be a vector for the transmission of the pathogen among cattle.     

Continuum slip foundations of elasto-viscoplasticity

Summary A continuum slip theory for dislocation glide is employed to derive macroscopic, phenomenological models for incompressible viscoplasticity. The microstructural origins of kinematic/isotropic hardening and rate-dependence are examined within the framework of the continuum slip theory of Rice and the single slip scale invariance theory of Aifantis for dislocation glide. In the process, the limitations on primitive assumptions for existing forms of state variable viscoplasticity become apparent. A form for rate-dependent evolution of backstress is derived which supports recent phenomenological approaches. Extensions to finite strain and compressible viscoplasticity are discussed.     

Measures of bone mineral content in mature dairy cows

The objectives of this investigation were to assess the relationship between chemical measures and imaging estimates (radiographic photometry and dual-energy x-ray absorptiometry) of bone mineral content in dairy cows and to evaluate the effects of parity, stage of lactation, and site of measurement (fused third and fourth metacarpal bone vs. caudal vertebrae 14 and 15) on bone mineral content. In a preliminary study, the caudal vertebrae were excised from 33 cows following slaughter. Samples were analyzed by radiographic photometry and then analyzed for mineral content chemically. In a second experiment, the caudal vertebrae and right front metacarpal (sample pairs) were excised from 107 Holstein cull cows following slaughter. Parity and days in milk (DIM) of the donor animals were obtained for 43 pairs of samples. Samples were grouped by parity (1, 2, 3, and >or=4) stage of lactation (Stage 1: <90 DIM, Stage 2: 90 to 150 DIM, Stage 3: 151 to 250 DIM, and Stage 4: >250 DIM). Samples were analyzed by radiographic photometry and dual-energy x-ray absorptiometry and then analyzed for mineral content chemically. In both experiments, the relationship between mineral content estimated via the imaging techniques and mineral content measured chemically was poor, likely because of the relative maturity of animals in the sample set and lack of variation in mineral content. Ash content was higher in the metacarpal than in the caudal vertebrae, as were concentrations of Mg (expressed as a proportion of bone ash). No effects of stage of lactation were observed on bone mineral in the caudal vertebrae, but in the metacarpal, P content (proportion of total mineral) was highest in second lactation cows. Total bone mineral content (ash) was not affected by parity in the metacarpal or caudal vertebra, but Ca and P content of the metacarpal increased with parity. Noninvasive imaging techniques are not sufficiently sensitive to detect changes in mineral content or composition of mature cows, and only modest changes in bone mineral were observed with stage of lactation and parity.     

Doctors and patients don't agree: cross sectional study of patients' and doctors' perceptions and assessments of disability in multiple sclerosis

OBJECTIVES: To compare the judgments of clinicians on which domains of health in the short form questionnaire (SF-36) would be most important to patients with multiple sclerosis with the opinions of patients themselves; to compare assessment of physical disability in multiple sclerosis by a clinician using Kurtzke's expanded disability status scale and a non-clinically qualified assistant using the Office of Population Census and Surveys' (OPCS) disability scale with self assessment of disability and other domains of health related quality of life by patients using the SF-36 and the EuroQol questionnaire; and to compare the scores of patients for each domain of the SF-36 with control data matched for age and sex. DESIGN: Cross sectional study. SETTING: Clinical department of neurology, Edinburgh. SUBJECTS: 42 consecutive patients with multiple sclerosis attending a neurology outpatient clinic for review or a neurology ward for rehabilitation. MAIN OUTCOME MEASURES: Scores on the SF-36; EuroQol; Kurtzke's expanded disability status scale; the OPCS disability scale. RESULTS: Patients and clinicians disagreed on which domains of health status were most important (chi 2 = 21, df = 7, P = 0.003). Patients' assessment of their physical disability using the physical functioning domain of the SF-36 was highly correlated with the clinicians' assessment (r = -0.87, P < 0.001) and the non-clinical assessment (r = -0.90, P < 0.001). However, none of the measures of physical disability correlated with overall health related quality of life measured with EuroQol, Quality of life correlated with vitality, general health, and mental health in the SF-36, each of which patients rated as more important than clinicians and for each of which patients scored lower than the controls. CONCLUSIONS: Patients with multiple sclerosis and possibly those with other chronic diseases are less concerned than their clinicians about physical disability in their illness. Clinical trials in multiple sclerosis should assess the effect of treatment on the other elements of health status that patients consider important, which are also affected by the disease process, are more closely related to overall health related quality of life, and may well be adversely affected by side effects of treatment.