Unemployment, job satisfaction, and employee turnover: A meta-analytic test of the Muchinsky model.

We conducted a meta-analysis to determine the relation between satisfaction–turnover correlations across studies and unemployment rates at the time those studies were conducted. On the basis of theoretical work by Muchinsky and Morrow (1980), we hypothesized that low relations would be found in studies conducted during times of high unemployment and limited employment opportunity, and high relations would be found in studies conducted during times of low unemployment and expanded opportunity. Results supported the hypothesis; correlations were found that ranged from –.18 to –.52 between unemployment rates and the magnitude of satisfaction–turnover relations across studies. A similar analysis was conducted for the relation between intention to quit and turnover. The correlations between the intention–turnover relation and unemployment were similar in magnitude to the corresponding satisfaction correlations, indicating that the behavioral-intention–turnover relation is also moderated by economic alternatives. Severe methodological problems with a similar study, which indicated the opposite results (Shikiar & Freudenberg, 1982), are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of dihydroergotoxine on lipid peroxidation in vitro

Dihydroergotoxine mesylate (DHET), an ergot alkaloid derivative, is widely used to treat senile cerebral vascular insufficiency. Aspects of this age-related phenomenon may be due to deterioration by lipid oxidation of cellular membranes. DHET stabilizes EEG alpha frequencies, increases cerebral blood flow and oxygen uptake and accumulates in lipid-rich structures of the brain. The effect of DHET was studied on iron-catalyzed peroxidation of liposomes as measured by the thiobarbituric acid assay. It was found that DHET inhibits peroxidation in vitro in a dose-dependent manner. These results suggest that DHET acts in part as a lipid antioxidant when used to treat senile cerebral vascular insufficiency.     

The effects of substitution on the eletrochemical reduction of dihydroxynaphtacenequinone in N,N-dimethylformamide

The electrochemical reduction of 6,11-dihydroxy-5,12-naphthacenequinone (DHNQ) in N,N- dimethylformamide was investigated. Under polarographic conditions, DHNQ behaves like a simple aromatic quinone with reduction occuring in two successive one-electron steps followed by protonation in the aprotic system and a single two-electron irreversible in the protic medium. The substituent inductive effects in several DHNQ derivatives were noted. The electron withdrawing groups, chloro and phenylsulfonyl, enhance the oxidation potentials, and the eletron-releasing groups, methyl and methoxy, make the reduction more difficult. The strength of the substituents follows the order: C₆H₅SO₂ ? Cl ? CH₃ ? CH₃O. A linear Hammett relationship exists in this series when the averaged value of σ_meta and σ_para are used as substitution constants.     

Dynamically mapping tasks with priorities and multiple deadlines in a heterogeneous environment

In a distributed heterogeneous computing system, the resources have different capabilities and tasks have different requirements. To maximize the performance of the system, it is essential to assign the resources to tasks (match) and order the execution of tasks on each resource (schedule) to exploit the heterogeneity of the resources and tasks. Dynamic mapping (defined as matching and scheduling) is performed when the arrival of tasks is not known a priori. In the heterogeneous environment considered in this study, tasks arrive randomly, tasks are independent (i.e., no inter-task communication), and tasks have priorities and multiple soft deadlines. The value of a task is calculated based on the priority of the task and the completion time of the task with respect to its deadlines. The goal of a dynamic mapping heuristic in this research is to maximize the value accrued of completed tasks in a given interval of time. This research proposes, evaluates, and compares eight dynamic mapping heuristics. Two static mapping schemes (all arrival information of tasks are known) are designed also for comparison. The performance of the best heuristics is 84% of a calculated upper bound for the scenarios considered.     

A Consideration of Graphite Electrodes

Graphite electrodes are one of the many material options for making contact to a molten glass bath for electric melting. Graphite has advantages and disadvantages over other materials, but laboratory testing against the specific glass confirms the success of use. The graphite grade is another important criterion for using the material as a glass melting electrode. The cost of graphite electrodes is about one-tenth that of molybdenum.     

Preservation of EDTA-expanded grid-mounted chromosomes and nuclei for electron microscopy using a specially designed freeze-dryer

We describe methods for freezing and drying EDTA-expanded, fixed metaphase chromosomes and nuclei, attached to grids as whole-mounts, for transmission electron microscopy. These methods use a special apparatus that is simple to construct. While separate freezers and dryers are commercially available, one for freezing blocks of tissue by slamming them against a cold metal surface, and the other for vacuum drying the frozen tissue, our apparatus is designed for gentler, cryogenic liquid plunge freezing and drying, sequentially, in the same apparatus, thus avoiding any compression or damage to the sepcimen. Use of a cryoprotectant is not essential; however, good results are obtained more often when 20% ethanol is used. Freezing is accomplished by rapid propulsion of the grid, with specimens attached, into slushy N₂ (-210°C) within the drying chamber; drying is automatic, by either sublimation under vacuum or by solvent substitution using absolute ethanol followed by acetone, which, in turn, is removed with a critical-point dryer. The apparatus offers a means of drying chromosomes and nuclei in an expanded state, and avoids the shrinkage of these structures that occurs during stepwise passage through increasing concentrations of ethanol or acetone.     

Watershed sulfur biogeochemistry: shift from atmospheric deposition dominance to climatic regulation

North American atmospheric S emissions peaked in the early 1970s followed by a dramatic decrease that resulted in marked declines in sulfate (SO?2?)) concentrations in precipitation and many surface waters. These changes in S biogeochemistry have important implications with respect to the mobilization of toxic (Al(n?), H?) and nutrient (Ca2?, Mg2?, K?) cations and the acidification of watersheds. We used the continuous long-term record for watersheds 1, 3, 5, and 6 (37-44 years from 1965 through 2008) of SO?2? concentrations and fluxes at Hubbard Brook Experimental Forest in New Hampshire (U.S.) for evaluating S budgets. Analysis revealed that the annual discrepancies in the watershed S budgets (SO?2? flux in drainage waters minus total atmospheric S deposition) have become significantly (p < 0.001) more negative, indicating the increasing importance of the release of S from internal sources with time. Watershed wetness, as a function of log?? annual water flux, was highly significant (p < 0.001) and explained 57% (n = 157) of the annual variation for the combined results from watersheds 1, 3, 5, and 6. The biogeochemical control of annual SO?2? export in streamwater of forested watersheds has shifted from atmospheric S deposition to climatic factors by affecting soil moisture.     

Processes affecting oxygen isotope ratios of atmospheric and ecosystem sulfate in two contrasting forest catchments in Central Europe

Sulfate aerosols are harmful as respirable particles. They also play a role as cloud condensation nuclei and have radiative effects on global climate. A combination of delta18O-SO4 data with catchment sulfur mass balances was used to constrain processes affecting S cycling in the atmosphere and spruce forests of the Czech Republic. Extremely high S fluxes via spruce throughfall and runoff were measured at Jezeri (49 and 80 kg S ha(-1) yr(-1), respectively). The second catchment, Na Lizu, was 10 times less polluted. In both catchments, delta18O-SO4 decreased in the following order: open-area precipitation > throughfall > runoff. The delta18O-SO4 values of throughfall exhibited a seasonal pattern at both sites, with maxima in summer and minima in winter. This seasonal pattern paralleled delta18O-H2O values, which were offset by -18 per thousand. Sulfate in throughfall was predominantly formed by heterogeneous (aqueous) oxidation of SO2. Wet-deposited sulfate in an open area did not show systematic delta18O-SO4 trends, suggesting formation by homogeneous (gaseous) oxidation and/or transport from large distances. The percentage of incoming S that is organically cycled in soil was similar under the high and the low pollution. High-temperature 18O-rich sulfate was not detected, which contrasts with North American industrial sites.