Library

Notes: This paper evaluates the accuracy of estimates of pension wealth based on self-reports by comparing them to estimates based on provider data. Using data from the Health and Retirement Study, we found that few workers are well informed about their future pension benefits. Self-reports were often incomplete and typically varied widely from those based on information from providers. In defined benefit (DB) plans, discrepancies were greatest for workers who had limited education, earned low wages, and did not expect to retire soon. Differences in median pension wealth were smaller at the aggregate level than the individual level, because individual differences tended to offset each other when aggregated. Provider data appear better than self-reports for DB plans, but not for defined contribution (DC) plans. Where both are available, the best method of computing pension wealth may be to estimate DB wealth from provider data and to estimate DC wealth from self-reports.

Notes: 1. Comparative studies of distinct, but not ecologically isolated, systems such as lakes and streams may improve our understanding of the importance of ecological linkages in aquatic ecosystems.2. In this study we compared the macroinvertebrate benthos of stony habitats in Swedish lakes and streams. Community composition was used to evaluate zoogeographic patterns and functional feeding guilds were used to identify mechanisms potentially affecting such patterns.3. Stream communities were generally more diverse and species-rich and had a higher proportion of grazers, shredders and passive-filter feeders than lakes. Lake communities had a higher proportion of predators and collector-gatherers. Of the 10 most common taxa, only Leptophlebia mayflies, clams (Sphaeriidae) and the isopod Asellus aquaticus were recorded in both lakes and streams.4. Among-site variance in macroinvertebrate communities accounted for by regional-scale variables was low (6.4% for lakes and 10.1% for streams), compared with that by local-scale variables (21% for lakes and 37.6% for streams). For lakes, the among-site variance in macroinvertebrate communities was best explained by habitat-scale characteristics followed by ecosystem, riparian, catchment, geographic position and ecoregion. For streams, the variance in macroinvertebrate communities was best explained by ecosystem characteristics followed by habitat, catchment, riparian, ecoregion and geographic position.5. Conspicuous differences in spatial pattern were revealed between lakes and streams. For lakes, the most unequivocal differences in community composition and function occurred at the transition zone between the mixed forests in the south and the boreal coniferous forests in the north. Surprisingly, streams did not respond as strongly to profound landscape-level differences in climate and vegetation cover.6. The spatial differences noted between macroinvertebrate communities of lakes and streams may be because of differences in retention of detrital matter. Our findings imply that detrital inputs are qualitatively similar, but that the retention and processing of coarse particulate organic matter was presumably higher in lake littoral regions than in stream riffle habitats.7. Although our findings support the conjecture that species distribution is determined fundamentally by conditions prevailing at the local-scale, regional factors such as land use/type and the role of history were important and seemingly act as strong determinants of large-scale patterns in biodiversity.

Notes: Abstract An outbreak of bovine spongiform encephalopathy (BSE) arose in the United Kingdom as a result of prions entering and being recycled through the ruminant food chain. Humans have since developed a variant form of Creutzfeldt-Jakob disease (vCJD), also mostly in the United Kingdom, that occurs in younger individuals and causes prominent psychiatric and/or behavioral manifestations early in disease. Laboratory studies now provide strong evidence that the causative agent of BSE in cattle and vCJD in humans share a common origin. Because of a lack of information regarding the incubation period of vCJD and the number of people who may have been exposed, the future scope of this disease remains unknown. Control of the current and any future outbreaks in cattle requires strict measures to prevent contamination of the animal food chain with prions of any species. Prevention of human exposure mandates the avoidance of neural tissue in all human foods.

Notes: A natural gradient tracer test using perdeuterated MTBE was conducted in an anaerobic aquifer to determine the relative importance of dispersion and degradation in reducing MTBE concentrations in ground water. Preliminary ground water chemistry and hydraulic conductivity data were used to place the tracer within an existing dissolved MTBE plume at Port Hueneme, California. Following one year of transport, the tracer plume was characterized in detail.Longitudinal dispersion was identified as the dominant mechanism for lowering the perdeuterated MTBE concentrations. The method of moments was used to determine the longitudinal and lateral dispersion coefficients (0.85 m2/day and 0.08 m2/day, respectively). A mass-balance analysis, carried out after one year of transport, accounted for 110% of the injected mass and indicated that no significant mass loss occurred. The plume structure created by zones of higher and lower hydraulic conductivity at the site was complex, consisting of several localized areas of high tracer concentration in a lower concentration plume. This is important because the aquifer has generally been characterized as exhibiting fairly minor heterogeneity. In addition, the tracer plume followed a curved flowpath that deviated from the more macroscopic direction of ground water flow inferred from local ground water elevation measurements and the behavior of the existing plume. Understanding the mass balance, plume structure, curvature of the tracer plume, and consequently natural attenuation behavior required the detailed sampling approach employed in this study. These data imply that a detailed understanding of site hydrogeology and an extensive sampling network may be critical for the correct interpretation of monitored natural attenuation of MTBE.

Notes: Use of the Internet continues to grow at an explosive rate. While entertainment, education and communication serve as important applications of the Internet, e-commerce continues to emerge as an increasingly significant business phenomenon. However, little empirical research exists to ide.pngy factors that influence the extent to which individuals use the Internet and e-commerce. With the aid of survey research and a neural network, this study analyzes a wide range of variables in an attempt to ide.pngy accurate predictors of this usage. The results of the analysis ide.pngy gender, overall computer usage, job-related use, and home access as important characteristics that should influence use of the Internet and e-commerce.

Notes: SUMMARY:  Recent studies in both humans and experimental animals have led to renewed interest in uric acid and its association with hypertension, cardiovascular events and renal disease progression. This has also refuelled a longstanding debate regarding the precise role of this ubiquitous breakdown product of purine metabolism in these disease processes. Various lines of evidence suggest that uric acid may have a direct role in the pathogenesis of hypertension and vascular disease. Regardless of this possibility, it is apparent that serum uric acid levels serve as a powerful ‘biomarker’ or independent predictor of prognosis and outcome in certain renal, cardiovascular and cerebrovascular diseases. Whether these outcomes can be improved by specifically treating asymptomatic hyperuricaemia remains inadequately resolved at this stage. Data from various animal studies suggests that lowering uric acid levels may be of benefit, but the crucial human studies are still lacking. This review will examine some of the recent evidence supporting a causal and contributory role for uric acid in cardiovascular and renal disease. How clarification of the role of uric acid may guide future treatment strategies will also be discussed.

Notes: Cell proliferation, matrix accumulation and cell infiltration are characteristic features of progressive glomerulosclerosis and tubulointerstitial fibrosis. Platelet-derived growth factor (PDGF), a cytokine which has proliferative, prosclerotic and chemokine properties, has been shown to be upregulated in the rat remnant kidney model. Inhibition of the renin–angiotensin system by angiotensin-converting enzyme (ACE) inhibitors has a beneficial effect on renal function and morphology, but the effect of ACE inhibition on PDGF gene expression and PDGF-mediated cellular proliferation in subtotal nephrectomy has not been studied in detail. Twelve rats were subtotally nephrectomized (STNx) and received either the ACE inhibitor perindopril or a placebo for 12 weeks. Five sham-operated rats served as controls. Subtotal nephrectomy was associated with hypertension, proteinuria, elevated plasma creatinine and increased kidney weight. After 12 weeks, PDGF B-chain mRNA was significantly upregulated in the glomeruli and tubulointerstitium of subtotally nephrectomized rats. ACE inhibition attenuated PDGF mRNA expression in association with a reduction in tubular and glomerular proliferation, as assessed by staining for proliferating cell nuclear antigen. In the context of the known in vitro and in vivo effects of PDGF, it is postulated that the renoprotective action of ACE inhibitors may be partially related to PDGF-mediated antiproliferative mechanisms.