Some effects of matrix and interface properties on the fatigue of short fiber-reinforced thermoplastics

The fatigue behavior of injection-molded tensile bars of short-fiber-reinforced theromplastics is described and related to the fatigue behavior of the matrices and the strength of the fiber/matrix interface. A brittle matrix system based on polyphenylene sulfide is shown to behave in a similar manner to long-fiber composites. Glass-fiber reinforcement in this matrix gives fatigue sensitivity that correlaes with that of unimpregnated glass fiber strands, while carbon-fiber rein-forcement gives better fatigue resistance. A well-bonded, due-tile matrix system based on nylon 6,6 gives matrix-controlled fatigue sensitivity. Fatigue data for glass- and carbon-fiber-reinfoced nylon 6,6 superimpose on the matrix fatigue data when normalized by the ultimate tensile strength. Another ductile matrix, polyetherther ketone, is very fatigue-resistant, but its composite progressively loses its reinforcing effect in fatigue, apparently due to interface failure. A transitional matrix, polysulfone, shifts from ductile to fatigue-crack-dominated failure as the cyclic stress is reduced. Its composites show an analogous failure mode shift, and the high cycle-fatigue response is correlated with fatigue-crack-growth data.     

Psychosocial factors associated with the initiation of cocaine use among marijuana users.

A short-term prospective design was used to investigate factors associated with the initiation of cocaine use during a 1-year period among a population sample of 942 marijuana users. In addition to demographic items, variables pertaining to various psychosocial characteristics including psychiatric symptoms, personality attributes, social support, and peer pressure were examined. Using cocaine nonusers as a comparison group, male gender, risk-taking tendencies, and socializing with friends on streets or in cars were identified as significant predictors of initiation. Implications for primary prevention programs include redirecting early sensation-seeking tendencies in children and adolescents toward more positive behaviors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Urate crystal-induced chemotactic factor: isolation and partial characterization

A factor with chemotactic properties for neutrophils and mononuclear cells was extracted from the lysosomal fraction of both human and rabbit neutrophils that had been allowed to phagocytose monosodium urate crystals. The chemotactic factor was found to be a glycoprotein with a mol wt of 8,400 daltons. The factor is heat labile and has chemotactic activity for human as well as rabbit cells. Preincubation of the cells with the urate induced chemotactic factor or with complement activated plasma prevents the cell from migrating chemotactically when challenged with either factor in the chemotactic chamber. The chemotactic factor induces release of lysosomal enzymes for cytochalasin B treated human neutrophils.     

Applicability of linear elastic fracture mechanics to rigid PVC pipe materials

Linear elastic fracture mechanics (LEFM) has limitations for analyzing the fracture behavior of rigid polyvinyl chloride pipe materials. Fracture behavior shifts from notch-insensitive, yield-stress-controlled to brittle, LEFM-controlled as temperature decreases and displacement rate increases. Even under the most brittle conditions, the fracture toughness is sufficient to resist most anticipated flaws such as scratches.     

The dimensions of change in therapeutic community treatment instrument.

In this article, the authors describe the refinement and preliminary evaluation of the Dimensions of Change in Therapeutic Community Treatment Instrument (DCI), a measure of treatment process. In Study 1, a 99-item DCI, administered to a cross-sectional sample of substance abuse clients (N = 990), was shortened to 54 items on the basis of results from confirmatory factor analyses and item response theory invariance tests. In Study 2, confirmatory factor analyses of the 54-item DCI, completed by a longitudinal cohort of 993 clients, established and validated an 8-factor solution across 2 subpopulations (adults and adolescents) and 2 time points (treatment entry and 30-days postentry). The results of the 2 studies are encouraging and support use of the 54-item DCI as a tool to measure treatment process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Brainstem 3H-nicotine receptor binding in the sudden infant death syndrome

Maternal cigarette smoking during pregnancy has been shown to be a major risk factor for the sudden infant death syndrome (SIDS). We hypothesized that SIDS is associated with altered 3H-nicotine binding to nicotinic receptors in brainstem nuclei related to cardiorespiratory control and/or arousal. We analyzed 3H-nicotine binding in 14 regions in SIDS and control brainstems using quantitative tissue receptor autoradiography. Three groups were analyzed: SIDS (n = 42), acute controls (n = 15), and a chronic group with oxygenation disorders (n = 18). The arcuate nucleus, postulated to be important in cardiorespiratory control and abnormal in at least some SIDS victims, contained binding below the assay detection limits in all (SIDS and control) cases. We found no significant differences among the 3 groups in mean 3H-nicotine binding in the 14 brainstem sites analyzed. When a subset of the cases were stratified by the history of the presence or absence of maternal cigarette smoking during pregnancy, however, we found that there was no expected increase (upregulation) of nicotinic receptor binding in SIDS cases exposed to cigarette smoke in utero in 3 nuclei related to arousal or cardiorespiratory control. This finding raises the possibility that altered development of nicotinic receptors in brainstem cardiorespiratory and/or arousal circuits put at least some infants, i.e. those exposed to cigarette smoke in utero, at risk for SIDS, and underscores the need for further research into brainstem nicotinic receptors in SIDS in which detailed correlations with smoking history can be made.     

Bone scintigraphy in the detection of chronic recurrent multifocal osteomyelitis

In this study, we describe the importance of the whole-body bone scan in diagnosing the multifocality of chronic recurrent multifocal osteomyelitis (CRMO) and in distinguishing it from unifocal acute hematogenous osteomyelitis. MATERIALS: The medical records and two-phase, whole-body bone scans of 14 patients (mean age 10.5 yr) with the diagnosis of CRMO, were retrospectively reviewed. The diagnosis of CRMO was based on bone biopsy in 9 patients and clinical course/laboratory findings in 5. Bone scans were evaluated for geographic and anatomic locations of their lesions. Correlative radiographs of areas of abnormal uptake were performed to assess the radiographic appearance of the lesions. RESULTS: The presentation of the disease was localized to one painful, tender and swollen periarticular site 86% of the time. The number of lesions detected by bone scan varied from 1-18 (mean 6). Most lesions were metaphyseal, proximal or distal tibial lesions. Purely sclerotic or mixed (sclerosis and lysis) lesions were found on radiographs. Bilateral lesions were seen in 64% of patients. Biopsies were negative for organisms in all patients and exhibited subacute or chronic histologic changes in most instances. Complications of chronic hyperemia included marked overgrowth (5), diffuse demineralization (1), angular deformity (1) and length discrepancy (1). CONCLUSION: The identification of the multifocal configuration of the disease process by two-phase (soft-tissue and delayed) whole-body bone scintigraphy results in appropriate diagnosis and therapy of CRMO. Additional sites for possible bone biopsy become apparent for exclusion of other diagnoses. Supportive (nonsteroidal, anti-inflammatory medication) instead of antimicrobial therapy can be initiated with significant cost savings.     

Modelling quality variations in commercial Ontario pork production

This study explores the interactions of sensory and nutritional environment with genotype occurring in current commercial pork production in Ontario, Canada, which may interact to result in poor quality meat. The study focussed on identifying factors and signalling mechanisms that contribute to poor meat quality, in order to develop strategies to reduce the incidence of unacceptable product quality. In the first phase of the work reported here, animal behaviour and muscle metabolism studies were related to meat colour, tenderness and water-holding capacity measurements from commercially-produced pigs killed in a commercial packing plant. A partial least squares analysis was used to determine the most important of the principal production variables, peri-mortem biochemical measures and post-mortem carcass condition variables studied, in terms of their influence on water-holding, toughness and colour (L*-value). Variations between producer and kill day at the slaughterhouse were very strong contributors to variability in these three meat quality parameters, followed by pH variations. A second phase of the study is currently underway to characterize patterns of gene expression related to extremes of end-product quality and to reduce quality variations by nutritional and behavioural management strategies.     

Fracture of adhesive joints

This paper presents some of the important results obtained from a series of studies on cohesive fracture in adhesively bonded joints. Due to the complex nature of the adhesive joint fracture, an accurate and efficient numerical method particularly suitable for the present problem has been developed, based on a hybrid-stress finite element formulation. Fracture characteristics in adhesively bonded joints are described in terms of local crack-tip deformation and stress fields in the polymeric adhesive layer. Effects of material properties, joint geometry, and bond-line thickness on the crack behavior are studied for classical lap-shear and currently used double-cantilever-beam joints. Of particular interest are the crack-tip stress intensities in the adhesive layer; their values are obtained for several cases of practical importance.