Showing papers by "University of Nevada, Reno published in 1996"

Cumulative trauma: The impact of child sexual abuse, adult sexual assault, and spouse abuse

Abstract: The present study investigated the relationship between trauma symptoms and a history of child sexual abuse, adult sexual assault, and physical abuse by a partner as an adult. While there has been some research examining the correlation between individual victimization experiences and traumatic stress, the cumulative impact of multiple victimization experiences has not been addressed. Subjects were recruited from psychological clinics and community advocacy agencies. Additionally, a nonclinical undergraduate student sample was evaluated. The results of this study indicate not only that victimization and revictimization experiences are frequent, but also that the level of trauma specific symptoms are significantly related to the number of different types of reported victimization experiences. The research and clinical implications of these findings are discussed.

Interstitial cells of Cajal mediate inhibitory neurotransmission in the stomach.

Abstract: The structural relationships between interstitial cells of Cajal (ICC), varicose nerve fibers, and smooth muscle cells in the gastrointestinal tract have led to the suggestion that ICC may be involved in or mediate enteric neurotransmission. We characterized the distribution of ICC in the murine stomach and found two distinct classes on the basis of morphology and immunoreactivity to antibodies against c-Kit receptors. ICC with multiple processes formed a network in the myenteric plexus region from corpus to pylorus. Spindle-shaped ICC were found within the circular and longitudinal muscle layers (IC-IM) throughout the stomach. The density of these cells was greatest in the proximal stomach. IC-IM ran along nerve fibers and were closely associated with nerve terminals and adjacent smooth muscle cells. IC-IM failed to develop in mice with mutations in c-kit. Therefore, we used W/W(V) mutants to test whether IC-IM mediate neural inputs in muscles of the gastric fundus. The distribution of inhibitory nerves in the stomachs of c-kit mutants was normal, but NO-dependent inhibitory neuro-regulation was greatly reduced. Smooth muscle tissues of W/W(V) mutants relaxed in response to exogenous sodium nitroprusside, but the membrane potential effects of sodium nitroprusside were attenuated. These data suggest that IC-IM play a critical serial role in NO-dependent neurotransmission: the cellular mechanism(s) responsible for transducing NO into electrical responses may be expressed in IC-IM. Loss of these cells causes loss of electrical responsiveness and greatly reduces responses to nitrergic nerve stimulation.

Proteasome-dependent endoplasmic reticulum-associated protein degradation: An unconventional route to a familiar fate

Abstract: Until recently, the degradation of aberrant and unassembled proteins retained in the endoplasmic reticulum (ER) was thought to involve unidentified ER-localized proteases. We now show that the ER-associated degradation (ERAD) of two mutant proteins that accumulate in the ER lumen is inhibited in a proteasome-defective yeast strain and when cytosol from this mutant is used in an in vitro assay. In addition, ERAD is limited in vitro in the presence of the proteasome inhibitors, 3,4-dichloroisocoumarin and lactacystin. Furthermore, we find that an ERAD substrate is exported from ER-derived microsomes, and the accumulation of exported substrate is 2-fold greater when proteasome mutant cytosol is used in place of wild-type cytosol. We conclude that lumenal ERAD substrates are exported from the yeast ER to the cytoplasm for degradation by the proteasome complex.

Assembly of ER-associated protein degradation in vitro: dependence on cytosol, calnexin, and ATP.

Abstract: To investigate the mechanisms of ER-associated protein degradation (ERAD), this process was reconstituted in vitro. Established procedures for post-translational translocation of radiolabeled prepro-alpha factor into isolated yeast microsomes were modified to inhibit glycosylation and to include a posttranslocation "chase" incubation period to monitor degradation. Glycosylation was inhibited with a glyco-acceptor peptide to compete for core carbohydrates, or by using a radio-labeled alpha factor precursor that had been genetically engineered to eliminate all three glycosylation sites. Inhibition of glycosylation led to the production of unglycosylated pro-alpha factor (p alpha F), a processed form of the alpha factor precursor shown to be a substrate of ERAD in vivo. With this system, both glycosylated and unglycosylated forms of pro-alpha factor were stable throughout a 90-min chase incubation. However, the addition of cytosol to the chase incubation reaction induced a selective and rapid degradation of p alpha F. These results directly reflect the behavior of alpha factor precursor in vivo; i.e., p alpha F is a substrate for ERAD, while glycosylated pro-alpha factor is not. Heat inactivation and trypsin treatment of cytosol, as well as addition of ATP gamma S to the chase incubations, led to a stabilization of p alpha F. ERAD was observed in sec12 microsomes, indicating that export of p alpha F via transport vesicles was not required. Furthermore, p alpha F but not glycosylated pro-alpha factor was found in the supernatant of the chase incubation reactions, suggesting a specific transport system for this ERAD substrate. Finally, the degradation of p alpha F was inhibited when microsomes from a yeast strain containing a disrupted calnexin gene were examined. Together, these results indicate that cytosolic protein factor(s), ATP hydrolysis, and calnexin are required for ER-associated protein degradation in yeast, and suggest the cytosol as the site for degradation.

Ryanodine receptor ca2+ release channels : does diversity in form equal diversity in function ?

Abstract: Complexities in calcium signaling in eukaryotic cells require diversity in the proteins involved in generating these signals. In this review, we consider the ryanodine receptor (RyR) family of intracellular calcium release channels. This includes species, tissue, and cellular distributions of the RyRs and mechanisms of activation, deactivation, and inactivation of RyR calcium release events. In addition, as first observed in nonmammalian vertebrate skeletal muscles, it is now clear that more than one RyR isoform is frequently coexpressed within many cell types. How multiple ryanodine receptor release channels are used to generate intracellular calcium transients is unknown. Therefore, a primary focus of this review is why more than one RyR is required for this purpose, particularly in a tissue, such as vertebrate fast-twitch skeletal muscles, where a relatively simple and straightforward change in calcium would appear to be required to elicit contraction. Finally, the roles of the RyR isoforms and the calcium release events they mediate in the development of embryonic skeletal muscle are considered.

Treatment of X-Linked Severe Combined Immunodeficiency by in Utero Transplantation of Paternal Bone Marrow

Abstract: Severe combined immunodeficiency is a congenital syndrome due to various genetic abnormalities that cause susceptibility to infection, failure to thrive, lymphoid hypoplasia, very low levels of T lymphocytes, and hypogammaglobulinemia.1,2 Untreated, the disorder is usually fatal within the first year of life. We report the successful treatment of a fetus with the X-linked variant of severe combined immunodeficiency by the in utero transplantation of paternal bone marrow that was enriched with hematopoietic cell progenitors. Case Report The patient, 11 months old at this writing, is the second son of a 28-year-old woman known to carry a mutation found in . . .

Fault trace complexity, cumulative slip, and the shape of the magnitude-frequency distribution for strike-slip faults : a global survey

Abstract: SUMMARY We examine whether the shape of the magnitude-frequency distribution for strike-slip faults is described by the Gutenburg-Richter relationship (log n = a - bM) or by the characteristic earthquake model, by analysing a data set of faults from California, Mexico, Japan, New Zealand, China and Turkey. For faults within regional seismic networks, curves of the form log n yrpl= a - bM, where n yr-' is the number of events per year equal to magnitude M, are fit to the instrumental record of seismicity, and geological data are used to estimate independently the size and recurrence rate of the largest expected earthquakes that would rupture the total length of the fault. Extrapolation of instrumentally derived curves to larger magnitudes agrees with geological estimates of the recurrence rate of the largest earthquakes for only four of the 22 faults if uncertainties in curve slope are considered, and significantly underestimates the geological recurrence rates in the remaining cases. Also, if we predict the seismicity of the faults as a function of fault length and slip rate, and the predicted seismicity is distributed in accord with the Gutenburg-Richter relationship, we find the predicted recurrence rate to be greater than the observed recurrence rates of smaller earthquakes along most faults. If individual fault zones satisfy the Gutenburg-Richter relationship over the long term, our observations imply that, during the recurrence interval of the largest expected earthquakes, the recurrence of lesser-sized events is not steady but, rather, strongly clustered in time. However, if the instrumental records provide an estimate of the long-term rate of small to moderate earthquakes along the faults, our observations imply that the faults generally exhibit a magnitude-frequency distribution consistent with the characteristic earthquake model. Also, we observe that the geometrical complexity of strike-slip faults is a decreasing function of cumulative strike-slip offset. The four faults we observe to be consistent with the GutenburgRichter relationship are among those characterized by the least amount of cumulative slip and greatest fault-trace complexity. We therefore suggest that the ratio of the recurrence rate of small to large earthquakes along a fault zone may decrease as slip accumulates and the fault becomes smoother.

Meta-analyses of the association between multilocus heterozygosity and fitness.

Abstract: Meta-analyses of published correlation coefficients between multilocus heterozygosity (MLH) and two fitness surrogates, growth rate and fluctuating asymmetry, suggested that the strength of these correlations are generally weak. A variety of plants and animals was included in the meta-analyses. A statistically homogeneous group of MLH-growth rate correlation coefficients that included both plants and animals yielded a common correlation of rz = 0.133. A common correlation of rz = -0.170 was estimated for correlations between MLH and fluctuating asymmetry in three species of salmonid fishes. These results suggest that selection, including overdominance, has at most a weak effect at allozyme loci and cast some doubt on the widely held notion that heterozygosity and individual fitness are strongly correlated.

Should the behavioral sciences become more pragmatic? The case for functional contextualism in research on human behavior

Abstract: Although societal need for behavioral science research is enormous, current research practices seem to be inefficient vehicles for producing knowledge that guides practical action. Many of our most popular theories provide little direct guidance for application. They focus on the development of models of the relationships among organismic events such as attitudes, self-efficacy expectations, and behavior, but pay little or no attention to the contextual influences on behavior. Such research is in keeping with a long-standing mechanistic tradition in psychology. We propose a version of contextualism as an alternative paradigm for the behavioral sciences. According to this paradigm, theories and research are evaluated in terms of their contribution to the prediction and influence of behavior. Basic research organized to pursue this goal has a direct bearing on how behavioral phenomena can be changed for practical purposes. Conversely, applied research contributes to basic understanding of the determinants of psychological phenomena.

Augmenting travel cost models with contingent behavior data

Abstract: This paper proposes contingent behavior survey questions as a valuable supplement to observed data in travel cost models of non-market demand for recreational resources. A set of observed and contingent behavior results for each survey respondent allows the researcher to control for individual heterogeneity by taking advantage of panel data methods when exploring the nature of respondent demands. The contingent scenarios also provide opportunities to (a) test for differences between observed and contingent preferences and/or (b) assess likely demands under conditionsbeyond the domain of observed variation in costs or resource attributes. Most importantly, contingent scenarios allow the researcher to imposeexogenously varying travel costs. Exogenous imposition of travel costs together with panel methods reduces the omitted variables bias that plagues observed-data travel cost models of recreational demand. Using a convenience sample of data for illustrative purposes, we show how to estimate the demand for recreational angling by combining observed and contingent behavior data. We begin with simple naive pooled Poisson models and progress to more theoretically appropriate fixed effects panel Poisson specifications.

Competition and facilitation : Contrasting effects of Artemisia tridentata on desert vs. montane pines

Abstract: Circumstantial evidence suggests that Artemisia tridentata may out-compete Pinus ponderosa and P. jefferyi for water at ecotones between shrub steppe and montane forest vegetation in the Great Basin. Other studies indicate that within the shrub steppe Artemisia may act as a nurse plant for a third species of pine, P. monophylla. We used field experiments to study these contrasting effects of Artemisia on P. ponderosa and P. monophylla within the context of the distributional patterns in western Nevada of all three species on andesite, and on sites where hydrothermal activity has altered the andesite. At intermediate elevations in the Great Basin Artemisia and P. monophylla are restricted to unaltered desert soils, whereas P. ponderosa is restricted to acidic, nutrient-poor altered andesite. Although mature P. monophylla were virtually absent in our study plots on altered andesite, first- and second-year seedlings were common. On adjacent unaltered andesite, all size classes of P. monophylla occurred, and P. monophylla seedlings were associated with Artemisia shrubs. Pinus ponderosa and P. jefferyi adults and seedlings were rare on unaltered andesite, but a wide range of size classes was found on altered andesite. In experiments, all P. ponderosa seedlings on unaltered andesite were consumed by predators regardless of positive or negative spatial association with shrubs. Of the P. monophylla seedlings that germinated on unaltered andesite, all that were under shrubs survived, but only 6% of those that germinated in the intershrub spaces survived. On the open altered andesite the mortality of P. monophylla seedlings due to abiotic stress was high, with a final survival of only 3%, whereas 28% of P. ponderosa seedlings survived the first growing season on altered andesite. On unaltered andesite, survival and conductance of P. ponderosa saplings was enhanced by shrub removal, but P. monophylla survival was significantly higher under shrubs than in shrub-removal plots or in intershrub spaces. In Artemisia- removal experiments, we found that Artemisia competed with P. ponderosa seedlings and saplings for water. Removal of Artemisia decreased water use efficiency (WUE) of P. monophylla seedlings. The absence of Artemisia may restrict Pinus monophylla from out- crops of altered andesite in the Great Basin, but provide refuges for P. ponderosa.

Explaining the Variation in Elasticity Estimates of Gasoline Demand in the United States: A Meta-Analysis

Abstract: systematically affect price and income elasticity estimates in studies of gasoline demand in the United States . Elasticity estimates from previous studies are used as the dependent variable with data characteristics, model structure , and estimation technique as the independent variables. Included among the explanatory variables are functional form, lag structure, time span, and national setting (U.S. versus the U.S. pooled with other countries). Inclusion of vehicle ownership in gasoline demand studies is found to result in lower estimates of income elasticity, data sets which pool U.S. and foreign data result in larger (absolute) estimates of both price and income elasticity, and the small difference between static and dynamic models suggests that lagged responses to price or income changes are relatively short. This study also found that elasticity estimates appear relatively robust across estimation techniques.

Potential atmospheric impact of the Toba Mega‐Eruption ∼71,000 years ago

Abstract: An {approx}6 year-long period of volcanic sulfate recorded in the GISP2 ice core about 71,000 {+-} 5000 years ago may provide detailed information on the atmospheric and climate impact in the Toba mega-eruption. Deposition of these aerosols occur beginning of an {approx}1000-year long stadial event, but not immediately before the longer glacial period beginning {approx}67,500 years ago. Total stratospheric loading estimates over this {approx}6 year period range from 2200 to 4400 Mt of H{sub 2}SO{sub 4} aerosols. The range in values is given to compensate for uncertainties in aerosol transport. Magnitude and longevity of the atmospheric loading may have led directly to enhanced cooling during the initial two centuries of this {approx}1000-year cooling event. 25 refs., 2 fig., 1 tab.

Regulation of ion channels in smooth muscles by calcium.

Abstract: Intracellular Ca2+ concentration ([Ca2+]i) plays a central role in regulating tone and contractility of smooth muscle cells. In contrast to the “classic” model of electromechanical coupling where m...

Resurgence of derived stimulus relations.

Abstract: Resurgence has been shown in human and nonhuman operant behavior, but not in derived relational responses. The present study examined this issue. Twenty-three undergraduates were trained to make conditional discriminations in a three-choice matching-to-sample paradigm. The training resulted in three equivalence classes, each consisting of four arbitrarily configured visual stimuli. The same 12 stimuli were then reorganized, and the conditional discrimination training was repeated such that three new classes were possible. In a subsequent test of derived relations, most subjects showed response patterns that were consistent with the altered conditional discriminations. Subjects were then exposed to conditional discrimination trials under extinction. Most subjects continued to respond consistently with the most recently reinforced conditional discrimination trials. During the next phase, subjects were exposed to symmetry and equivalence trials. Responses consistent with the most recent training produced feedback saying that the responses were incorrect, whereas other responses produced no feedback. Most subjects showed a resurgence of responding that was consistent with their earlier training. Finally, subjects were exposed to conditional discrimination trials carried out in extinction. Most subjects continued to show a resurgence of responding that was consistent with their early training.

Is coordination of leaf and root growth mediated by abscisic acid? Opinion

Abstract: Leaf growth is more inhibited than root growth when the soil is nitrogen-deficient, dry, saline, compacted, or of restricted volume. Similar differential responses in leaf and root growth occur when ABA is applied to plants in well-watered and well-fertilised conditions, and opposite responses are often found in ABA-deficient mutants. ABA levels increase in plants in dry or saline soils, suggesting a regulating role in leaf and root growth in soils of low water potential. In nitrogen-deficient or compacted soils, or soils of restricted volume, ABA only sometimes increases, and in these situations its accumulation may be of secondary importance. Use of ABA-deficient mutants has so far indicated that ABA influences leaf and root growth in unstressed plants, and plants in dry soils, but not in soils that are compacted, of restricted volume, or are nitrogen-deficient. For ABA to determine the relationship between the rate of leaf growth and the rate of root growth, there must be long-distance transport of either ABA itself or a compound that controls ABA synthesis in the growing cells of leaves and roots. ABA invariably increases in xylem sap as the soil becomes dry or saline, and sometimes when it becomes nitrogen-deficient or compacted, however the ABA is of too low a concentration to affect leaf growth. There may be a compound in xylem sap that controls the synthesis of ABA in the leaf, but no such compound has been identified. ABA accumulates in phloem sap of plants in dry or saline soil, but its function in controlling root or leaf growth is unknown. We conclude that ABA affects the ratio of root growth to leaf growth via its independent effects on root and leaf growth, and may regulate the ratio of root to leaf growth via feedforward signals in xylem or phloem, but there is no satisfactory explanation of its mechanism of control.

Commercial bank mutual fund activities: Implications for bank risk and profitability

Abstract: This paper examines the risk structure of bank holding companies and the effect of mutual fund activities on bank risk and profitability over the period 1987–1994. Findings from structural change tests indicate a significant decline in bank risk occurred near the mid-point of the study. Results from a confirmatory factor analytic model employed to examine the impact of mutual fund activities on banks suggest that mutual fund activities moderated bank industry systematic risk during the sample period. Mutual fund activities also increased the profitability of banks. These results suggest that mutual funds represent a productive avenue of expansion for bank holding companies.

Activation of the complement system by pathogenic fungi.

Abstract: Fungi have been studied as prototype activators of the complement cascade since the early 1900s. More recently, attention has focused on the role of the complement system in the pathogenesis of fungal infections. The interactions of Cryptococcus neoformans and Candida albicans with the complement system are the most widely characterized; however, all pathogenic fungi examined to date have the ability to initiate the complement cascade. The molecular mechanisms for initiation and regulation of the complement cascade differ from one fungus to another, most likely reflecting differences in the structure of the outer layers of the cell wall. The molecular bases for such differences remain to be identified. Studies of mycoses in experimental animals with induced or congenital deficiencies in the complement system demonstrate that complement is an important innate system for control of fungal infection. Contributions to host resistance include opsonization and generation of inflammatory mediators. Inflammation induced by chemotactic products of the complement system may contribute to the pathogenesis of some fungal infections.

Human colour perception and its adaptation

Abstract: Information about colour is initially extracted by the visual system in terms of the activity within a small number of receptor types with different spectral sensitivities, and then recoded within channels that respond to different combinations of the receptor signals. Many insights have been gained about these post-receptoral transformations, yet their number and nature remain poorly defined. This review examines how the signals coding colour are organized within the human visual system, and how these signals are affected by the processes of adaptation. Sensitivity is controlled by two distinct classes of adaptation that adjust to different aspects of the stimulus; retinal mechanisms of light adaptation adjust for changes in the average colour across scenes, while cortical mechanisms of contrast adaptation adjust for changes in the distribution of colours. Together these exert a profound and pervasive influence on our colour perception.

Using Statistical Probability to Increase Confidence of Inferring Species Extinction

Abstract: One of the many daunting problems in conservation biology is determining when a species has gone extinct (Diamond 1987). A superficial evaluation of the problem might lead one to believe that this is a simple task-one either finds a species extant, or it is extinct. But species sometimes are not seen for many years and then are resighted (Atkinson et al. 1991). In the same vein, the literature regularly reports the discovery of new species, even within well-known taxa such as birds (Dinesen et al. 1994), demonstrating the difficulty of detecting species during surveys. The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) and the World Conservation Union have arbitrarily set 50 years with no sightings as the cut-off for species extinction, even if no one has looked for the species (World Conservation Union 1982). Clearly, a more useful alternative for inferring extinction is needed. Extant species mnight not be seen during a survey because they are behaviorally or morphologically cryptic, because the area is difficult to survey, or because the species is unconmmon (Bibby et al. 1992). If species extinction is to be followed by habitat conversion (e.g., the habitat was previously protected only under laws such as the U.S. Endangered Species Act), increased certainty in inferring species extinction is critical. Solow (1993) presented two statistical methods for inferring species extinction based on repeated sampling of an area. His method assumes a Poisson distribution of species sightings prior to suspected extinction and uses either statistical inference or Bayesian methods to determine whether a recent lack of sightings is likely associated with extinction. I present a different method for assessing certainty of extinction using statistical probability. This method is based on statistical power (Cohen 1988) and addresses the question of how many visits without sighting a target species are required to be statistically confident of its absence.

Relative apparent synapomorphy analysis (RASA). I: The statistical measurement of phylogenetic signal.

Abstract: We have developed a new approach to the measurement of phylogenetic signal in character state matrices called relative apparent synapomorphy analysis (RASA). RASA provides a deterministic, statistical measure of natural cladistic hierarchy (phylogenetic signal) in character state matrices. The method works by determining whether a measure of the rate of increase of cladistic similarity among pairs of taxa as a function of phenetic similarity is greater than a null equiprobable rate of increase. Our investigation of the utility and limitations of RASA using simulated and bacteriophage T7 data sets indicates that the method has numerous advantages over existing measures of signal. A first advantage is computational efficiency. A second advantage is that RASA employs known methods of statistical inference, providing measurable sensitivity and power. The performance of RASA is examined under various conditions of branching evolution as the number of characters, character states per character, and mutations per branch length are varied. RASA appears to provide an unbiased and reliable measure of phylogenetic signal, and the general approach promises to be useful in the development of new techniques that should increase the rigor and reliability of phylogenetic estimates.

Translocations and the Preservation of Allelic Diversity

Abstract: Translocation is a tool commonly used for the conservation of threatened and endangered fish species. Despite extensive use, the biological implications of translocation remain poorly understood. Of particular interest is the effect of translocation on genetic variability. Maintenance of genetic variability in these “refuge” populations is assumed to be important for both short- and long-term success. We examined allozyme variability at 16 loci for western mosquitofish (Gambusia affinis) populations with known histories of introduction. Refuge populations had significantly lower levels of heterozygosity. Refuge populations also had considerably lower levels of allelic diversity than parental populations. All losses were of relatively rare alleles (frequency less than 0.1 in parental population). These losses were probably due to an undocumented bottleneck early in the introduction history. These results were surprising because the initial transplant involved 900 fish and because mosquitofish have numerous reproductive traits that should minimize the effects of bottlenecks on genetic diversity. A literature review revealed that genetic variability is often reduced in refuge populations and that such reductions typically involve the loss of alleles. We suggest that translocated populations be examined periodically for losses of genetic variability. Una herramienta conservacionista utilizada comunmente es la translocacion de especies de peces amenazadas yen peligro. A pesar de su uso extensivo, las implicaciones biologicas de las translocaciones han sido poco entendidas. El efecto de la translocacion sobre la variabilidad genetica es de particular interes. Se asume que el mantenimeinto de la variabilidad genetica en estas poblaciones “refugio” es importante para su exito a corto y largo plazo. Examinamos la variabilidad de alozimas.en 16 loci en poblaciones de Gambusia affinis con introduccion conocidas. Las poblaciones refugio tuvieron niveles de heterocigosidad significativamente menores. Las poblaciones refugio tambien presentaron niveles de diversidad alelica considerablemente menores alas de las poblaciones parentales. Todas las perdidas fueron de alelos relativamente raros (frecuencia menor a 0.1 en poblacion parental). Estas perdidas probablemente se debieron a un cuello de botella no documentado en el historial de introduccion. Estos resultados fueron sorprendentes porque el transplante inicial involucro 900 peces y porque la especie tiene numerosas caracteristicas reproductivas que debieran minimizar los cuellos de botella sobre la diversidad genetica. Una revision de literatura revelo que la variabilidad genetica en poblaciones refugio a menudo es reducida, y que tales reducciones tipicamente involucran la perdida de alelos. Sugerimos que las poblaciones translocadas sean examinadas periodicamente para detectar perdidas de variabilidad genetica.

Influence of a cooperative early field experience on preservice elementary teachers' science self‐efficacy

Abstract: The influence of a cooperative early field experience on preservice elementary teachers' science self-efficacy was investigated in this study. The sample was comprised of 120 preservice elementary education students enrolled in an elementary science methods course at a large midwestern university. Cooperative learning groups were formed within each of five laboratory sections of the methods course. Each cooperative group witnessed several modeled science lessons employing cooperative techniques prior to planning and teaching a cooperative elementary science lesson in a local public school. Two randomly selected elementary science methods laboratory sections were tested directly before and three other sections immediately after the performance of a cooperative teaching field experience. Testing involved obtaining scores from subjects' response to the Science Teaching Efficacy Beliefs Inventory, form B (STEBI-B). The STEBI-B measures science teaching self-efficacy beliefs. A random sample of personal interviews were also given by the researcher to a selected subsample of study participants at the end of the semester. The significant ANOVA findings reported for the data collection subgroup (time of teaching) main effect (F = 8.63, p < 0.01), lack of significant correlations between the alternative predictor variables, and the STEBI-B scores provides evidence to support an inference that early cooperative field experience had a positive influence on the subjects' science teaching self-efficacy. © 1996 John Wiley & Sons, Inc.

Third-Party Logistics Service Providers: Purchasers’ Perceptions

Abstract: A recent survey of manufacturers provides insight into their relationships with providers of international logistics services. The research examines the purchasers’ perceptions regarding the service providers’ capabilities. Further, differences between high-performance logistics providers and those perceived as providing lower levels of performance are identified and discussed.