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Biomedical subjects

T Scharf

Publications and source records attributed to T Scharf.

11 recordsLinked to original sources
PubMed2002

Piezoelectricity of a ferroelectric liquid crystal with a glass transition.

Pressure-electric (hydrostatic piezoelectric) measurements are reported on bookshelf textures of a ferroelectric smectic-C (Sm C*) liquid crystal with a glass transition. The continuous variation of a partially fluid state to the solid glass enables one to trace how the piezoelectric effect depends on the consistency of the material. It was observed that in the Sm C* samples with poled glass the piezoelectric constants are comparable to conventional piezoelectric crystals and poled piezoelectric polymers. This implies their application possibilities. The magnitude of the piezoelectric constant in the glassy state depends very much on the poling conditions. The studies indicate that there are two counteracting effects, which cancel each other out in the Sm C* phase near the glass transition. Our analysis indicates that the pressure-induced director tilt change has a dominating effect both in the fluid and the glassy Sm C* states.

Journal Article↗
PubMed2001

Covariation between workplace physical and psychosocial stressors: evidence and implications for occupational health research and prevention.

There is increasing interest in distinguishing the effects of physical and psychosocial workplace stressors on the aetiology of work-related musculoskeletal disorders (MSD). Modest associations have been found between psychosocial stressors and MSD, such as intensive load, monotonous work and low job control. Interpretation of these results has been limited by likely covariation between physical and psychosocial stressors. This investigation examined exposure covariation among blue- and white-collar workers employed in a mass production manufacturing environment (N = 410). Physical stressors were assessed from questionnaire and accelerometry. Psychosocial stressors were assessed from questionnaire. Pearson and Spearman correlation coefficients were computed. An exploratory factor analysis procedure identified possible common factors linking specific physical and psychosocial stressors. Moderate to high correlations between some physical and psychosocial stressors showed evidence of covariation both across and within groups. Covariation was strongest among blue-collar production and low-status office workers. Factor analysis results showed considerable shared variance between some physical and psychosocial stressors, such as repetition and job control, suggesting that these disparate stressors manifest from common work organization factors that govern the structure of work. While recognizing the conceptual differences between physical and psychosocial stressors, these results call attention to the strong empirical relationships that can exist between some stressors in the workplace setting. To guard against ambiguous study findings that can occur when exposures are mixed, it is critical that future epidemiologic studies include information about the degree of association between task-level stressors. Future research on work organization determinants of task-level stressors, and their coincident occurrence in jobs with greater specialization, may provide promising new insights into the nature of risk for MSD and effective prevention strategies.

Adult↗
PubMed1997

Informal support for older people in post-unification East Germany: stability and change.

German unification led to a substantial out-migration of younger east Germans to the West. This paper discusses possible impacts of this out-migration upon the social support networks of older people in the east German city of Leipzig. Using Wenger's network typology, information was sought about the social support networks of 54 people aged 65+ for 1989 and 1993. The intention was to identify the extent to which support networks were resistant to change and, where changes occurred, whether such changes could directly be attributed to unification. The study's findings indicate only a modest impact of unification upon older people's social support networks in Leipzig. The overwhelming majority of support networks remained the same over the period of analysis, suggesting that informal support for older people is more robust and resistant to social change than might be anticipated.

Journal Article↗
PubMed1996

Intervention research in agriculture: examples from the swine confinement and respiratory health project.

The "Measurement and Analysis in Agricultural Interventions" workshop session of the "Intervention Research in Occupational Health and Safety: Science, Skills, Strategies" conference considered a variety of approaches to safety and health interventions in agriculture. The "Respiratory Health in Swine Confinement Project" in Iowa, an educational intervention to improve respiratory health and safety in swine confinement workers, was presented as a case study for the discussion. Results from the project were used to illustrate the advantages and disadvantages of a variety of research techniques in interventions and program evaluation, including specific issues related to measurement and analysis. The discussion reflects comments from workshop participants along with summary observations reported to conference attendees. Themes of the session include the complementary nature of quantitative and qualitative techniques, and the importance of developing interventions that are community based.

Air Pollution, Indoor↗
PubMed1996

Linking stress and injury in the farming environment: a secondary analysis of qualitative data.

The first step in injury prevention is to understand the injury problem. This includes examining the nature of the problem from the perspective of the target community. This article uses qualitative methods to explain the nature of the injury problem and identifies prevention strategies through a three-step process: identify a causal model, validate the model, and identify strategies using the causal model. A causal model linking safety performance and safety demand, health decision making, and occupational stress was derived by secondary analysis of farm family focus group data (step 1) and validated by other farm family focus groups (step 2). Prevention strategies identified from the causal model (step 3) include decreasing the number of roles performed exclusively by one individual, developing an easy-to-use planning tool that assists farmers in anticipating and reducing future work demands, and developing an education module that incorporates injury costs into safety decision making.

Accidents, Occupational↗
PubMed1985

Monoclonal antibodies against human platelet membrane glycoproteins IIb-IIIa. II. Different effects on platelet function.

Preincubation of human platelets with two pairs of immunologically identical monoclonal antibodies (mab) directed against epitopes on the membrane glycoprotein IIb-IIIa complex - two of them (Gi3 and Gi5) precipitating glycoproteins IIb-IIIa, and two (Gi4 and Gi6) recognizing glycoprotein IIIa - induced slightly different inhibitory effects on platelet function. Gi3 and Gi5 blocked platelet aggregation and 14C-serotonin release from platelets induced by ADP, collagen, thrombin, arachidonic acid, ionophore A 23187, platelet activating factor and ristocetin (in the presence of divalent ions). Ristocetin-induced platelet agglutination (in the presence of EDTA) was not inhibited by these mab. Gi4 had no effect on platelet aggregation and release. Gi6 had the same effect on platelet function as Gi3 and Gi5, but only when incubated with Zw(a) (PlAl)-positive platelets with the exception that collagen-induced aggregation was not affected. We conclude that the similar, though not identical, effects on platelet function induced by mab against different epitopes on the glycoprotein complex IIb-IIIa indicate an "unspecific" interference with platelet membrane function possibly due to steric hindrance by mab of the fibrinogen receptor or by inhibition of conformational changes in the GP IIb-IIIa complex necessary for exposure of the fibrinogen binding site.

Antibodies, Monoclonal↗
PubMed1985

Visual perception dominance of fallers among community-dwelling older adults.

The authors postulated that older adult fallers show a greater tendency than older adult nonfallers to rely more on visual information sources in maintaining upright posture than on kinesthetic and vestibular cues. This paper presents descriptive statistics on 199 older adults living independently in the community. Their visual perception of the vertical and horizontal was analyzed with respect to age, sex, health status, and severity of injury as a result of a fall. The finding of significant impairments for fallers in visual perceptual abilities confirmed a trend previously established by one of the authors (Tobis). When the visual field entailed only misleading or ambiguous cues in the form of a tilted frame, fallers again showed a larger error than nonfallers in establishing the vertical and horizontal. The authors feel that this relatively greater dependence on visual sources may develop in response to impairment of feedback on posture and gait from the kinesthetic and vestibular systems as a result of age and chronic health problems. Errors in visual perception of the vertical and horizontal intercorrelated with age, sex, and a large number of medical problems. However, visual variables were more important in predicting faller status than physical characteristics.

Accidents↗
PubMed1978

Length heteromorphisms of fluorescent (f) and non-fluorescent (nf) segments of human Y chromosome: classification, frequencies, and incidence in normal Caucasians.

Sixty normal male Caucasians were selected to study the length of the Y chromosome. QFQ banding was performed. Chromosomes 19 and 20 (F) and Y were measured directly from the film. Y/F, f/F, and nf/F indices (f = fluorescent; nf = non-fluorescent segment) were determined. The length of the Y chromosome was classified into 5 groups; very small, small, average, large, and very large with Y/F indices of less than 0.8, 0.81--0.94, 0.95--1.09, 1.1--1.23, and greater than 1.23, respectively. The frequencies of Y/F indices for these groups were 0 (0%), 9 (15.0%), 40 (66.7%), 8 (13.3%), and 3 (5.0%), respectively. The most frequent class was 0.95--1.09 and was defined as the 'average' Y/F index for the human Y chromosome. The variation in the total length of the Y chromosome was accounted for by variations in the length of the non-fluorescent as well as the fluorescent segments. No relation between f and nf segments was observed. The mean Y/F, f/F, and nf/F indices were 1.022, 0.441, and 0.574, respectively.

Adult↗