Advanced manufacturing technology and work design: Towards a theoretical framework

This paper introduces a theoretical framework to guide research into the psychological effects of advanced manufacturing technology (AMT) on shopfloor operators. The framework has two main aspects. First, based on the emerging literature on the job content implications of AMT, it identifies four key constructs, namely: control, cognitive demand, production responsibility and social interaction. Second, by drawing on the more established job design, stress and related literatures, it predicts how these independent variables differentially affect system performance, job-related strain and job satisfaction. The wider implications and limitations of the theoretical framework are discussed.     

Further evidence on some new measures of job control,cognitive demand and production responsibility

Current approaches to job design and job stress, and their application in the context of new manufacturing technologies and practices, call for new widely applicable measures of job properties. In response to this need, Jackson, Wall, Martin and Davids (1993) described the development of new scales of timing control, method control, monitoring demand, problem-solving demand and production responsibility. This article provides further evidence concerning these measures, based on the responses of nearly 1700 employees from five separate samples. The evidence includes: investigation through confirmatory factor analysis of the applicability of the underlying five-factor measurement model on two new samples; improvement of the problem-solving demand scale; a test of the replicability of the measurement model by formal factorial invariance tests across four samples; additional information on scale reliability and construct validity; and normative data for a wide range of shopfloor and related jobs.     

The ecology of the molluscs of Thalassia communities,Jamaica, West Indies. II. Molluscan population variability along an environmental stress gradient

Along a composite onshore-offshore gradient, 4 homogeneous areas within beds of the marine angiosperm Thalassia were studied in detail. Eleven environmental variables, and molluscan and echinoderm abundance were sampled at monthly intervals for 1 year. Environmental conditions were generally more extreme, and their variance greatest, nearshore; they decreased significantly with distance from shore. Environmental predictability and cumulative diversity (H) increased with distance from shore, whereas abundance was greatest in the higher-stress environments. Over the year, the population variance (number of species, density, and diversity) was no greater in the unpredictable, low diversity environments than in the more predictable, high-diversity environments. Bivalves collected from the low-diversity environments were markedly eurytopic forms. whereas the highest-diversity area contained predominantly stenotopic taxa. Typical suspension feeders were dominant only in the most diverse area, whereas more generalized feeders dominated the higher-stress environments. There was no correlation between bivalve diversity increased with the variety of available food. Evidence suggests that catastrophes and other long-term phenomena, and biological factors such as predation, are of great importance in determining the differences in fauna between these areas.     

Prenatal diagnosis for Tay-Sachs disease using chorionic villus sampling

Prenatal diagnosis for Tay-Sachs disease was performed on 25 patients using chorionic villus sampling (CVS). Nineteen were diagnosed as normal, and six were affected. Normal villus extracts had both hexosaminidase (hex) A and B activity, as determined by Cellogel and polyacrylamide gel electrophoresis, while extracts from affected fetuses had only hex B activity. Compared to cultured amniotic fluid cells or fibroblasts, villi contained less hex A. Hex A levels in fresh villi and cultured trophoblasts were roughly comparable.     

Placental mosaicism in a case of 46,XY, −22, +t(22;22)(p11;q11) or i(22q) diagnosed at amniocentesis

46,XY, −22,+t(22;22)(p11;q11) or i(22q) was diagnosed in 15/15 cells from two cultures from the amniotic fluid culture of a 31-year-old patient whose fetus demonstrated cystic hygroma on ultrasound. Cytogenetic studies performed on fetal skin from the abortus revealed the same karyotype as that seen on amniocentesis, but the placenta demonstrated a 46,XY,46,XY, −22,+t(22;22) or i(22q) mosaicism, with 65 per cent of the cells being 46,XY. This case provides an example of placental mosaicism for a normal male karyotype, while the fetus demonstrated non-mosaic trisomy 22.     

Cytogenetic results from the U.S. collaborative study on CVS

Cytogenetic data are presented for 11 473 chorionic villus sampling (CVS) procedures from nine centres in the U.S. NICHD collaborative study. A successful cytogenetic diagnosis was obtained in 99.7 per cent of cases, with data obtained from the direct method only (26 per cent), culture method only (42 per cent), or a combination of both (32 per cent). A total of 1.1 per cent of patients had a second CVS or amniocentesis procedure for reasons related to the cytogenetic diagnostic procedure, including laboratory failures (27 cases), maternal cell contamination (4 cases), or mosaic or ambiguous cytogenetic results (98 cases). There were no diagnostic errors involving trisomies for chromosomes 21, 18, and 13. For sex chromosome aneuploidies, one patient terminated her pregnancy on the basis of non-mosaic 47,XXX in the direct method prior to the availability of results from cultured cells. Subsequent analysis of the CVS cultures and fetal tissues showed only normal female cells. Other false-positive predictions involving non-mosaic aneuploidies (n = 13) were observed in the direct or culture method, but these cases involved rare aneuploidies: four cases of tetraploidy, two cases of trisomy 7, and one case each of trisomies 3, 8, 11, 15, 16,20, and 22. This indicates that rare aneuploidies observed in the direct or culture method should be subjected to follow-up by amniocentesis. Two cases of unbalanced structural abnormalities detected in the direct method were not confirmed in cultured CVS or amniotic fluid. In addition, one structural rearrangement was misinterpreted as unbalanced from the direct method, leading to pregnancy termination prior to results from cultured cells showing a balanced, inherited translocation. False-negative results (n = 8) were observed only in the direct method, including one non-mosaic fetal abnormality (trisomy 18) detected by the culture method and seven cases of fetal mosaicism (all detected by the culture method). Mosaicism was observed in 0.8 per cent of all cases, while pseudomosaicism (including single trisomic cells) was observed in 1.6 per cent of cases. Mosaicism was observed with equal frequency in the direct and culture methods, but was confirmed as fetal mosaicism more often in cases from the culture method (24 per cent) than in cases from the direct method (10 per cent). The overall rate of maternal cell contamination was 1.8 per cent for the culture method, but there was only one case of incorrect sex prediction due to complete maternal cell contamination which resulted in the birth of a normal male. The rate of maternal cell contamination was significantly higher in samples obtained by the transcervical sampling method (2. 16 per cent) than in samples obtained by the transabdominal method (0.79 per cent). From these data, it is clear that the culture method has a higher degree of diagnostic accuracy than the direct method, which should not be used as the sole diagnostic technique. The direct method can be a useful adjunct to the culture method, in which maternal cell contamination can lead to incorrect sex prediction and potentially to false-negative diagnostic results.     

Kinetics for a membrane reactor reducing perchlorate.

The major objectives of this work were to operate and construct an autohydrogenotrophic reactor and estimate perchlorate degradation kinetics. The results show that autohydrogenotrophic bacteria were cultured in the reactor and capable of removing 3.6 mg/d of perchlorate in the presence of excess hydrogen (99% removal). The reactor was successful in treating the average influent perchlorate concentration of 532 microg/L to the level of 3 microg/L. A first-order relationship was obtained between the concentration of active biomass in the reactor and the hydraulic retention time for the given amount of substrate. During the kinetic loading study, perchlorate removal ranged from 100 to 50%. The kinetic rate of perchlorate degradation observed in this study was 1.62 hr(-1). The significant degradation of perchlorate in these samples indicates the ubiquity of perchlorate-reducing organisms. Additionally, nitrate was simultaneously removed during water treatment (greater than 90% removal). Because of the excess levels of hydrogen, simultaneous removal of nitrate was not believed to significantly affect perchlorate removal. The area of concern was the lack of complete control over biological treatment. The growth of sulfate-reducing organisms in the reactor negatively affected perchlorate removal efficiency. There were no significant effects observed on the dissolved organic carbon and total suspended solids concentration of the effluent, suggesting that the treatment did not produce a large amount of biomass washout.     

Causes of couspecific nest parasitism in the northern masked weaver

Summary Conspecific nest parasitism is a common reproductive strategy in the northern masked weaver (Ploceus taeniopterus). Parasites appear to be females with nests of their own who lay an additional egg in another female's nest as a way to enhance their reproductive success. Brood size in the northern masked weaver is practically constrained to three: starvation in four-chick broods is very common. The constraint on brood size is probably imposed by the extreme hatching asynchrony characteristic of this species: the last egg in a four-egg clutch hatches 72 h after the first egg, and when a chick starves, it is almost always the youngest chick. Late-hatching chicks also grow more slowly than do early-hatching chicks. If a female were to lay a fourth egg in her own nest, there is little chance that it would succeed. However; if she places it in another female's nest before that host lays her third egg, then it may have a greater chance of success.     

A universal method for quantifying and comparing the residual variability of element concentrations in biological tissues using 25 elements in the mussel Mytilus edulis as a model

Heavy metal concentrations (especially Cu, Cd and Zn) have been measured in oceanic hyperiid amphipods (Themisto gaudichaudii and T. compressa) and euphausiids (Meganyctiphanes norvegica and Euphausia superba), collected in the Antarctic and Atlantic Oceans. In some cases, metal concentrations displayed size-dependencies which were allowed for in interspecific or intersite comparisons, which often showed intraspecific geographical differences not attributable to anthropogenic effects. Cadmium concentrations in Themisto species are high in comparison with those of other oceanic crustaceans and may represent significant sources of cadmium in the diets of particular seabrids.