Showing papers by "University of Alabama published in 1995"

Firm Performance and Mechanisms to Control Agency Problems between Managers and Shareholders

Abstract: This paper examines the use of seven mechanisms to control agency problems between managers and shareholders. These mechanisms are: shareholdings of insiders, institutions, and large blockholders; use of outside directors; debt policy; the managerial labor market; and the market for corporate control. We present direct empirical evidence of interdependence among these mechanisms in a large sample of firms. This finding suggests that cross-sectional OLS regressions of firm performance on single mechanisms may be misleading. Indeed, we find relations between firm performance and four of the mechanisms when each is included in a separate OLS regression. These are insider shareholdings, outside directors, debt, and corporate control activity. Importantly, the effect of insider shareholdings disappears when all of the mechanisms are included in a single OLS regression, and the effects of debt and corporate control activity also disappear when estimations are made in a simultaneous systems framework. Together, these findings are consistent with optimal use of each control mechanism except outside directors.

The Comparative Advantage Theory of Competition

Abstract: A new theory of competition is evolving in the strategy literature. The authors explicate the foundations of this new theory, the “comparative advantage theory of competition,” and contrast them wi...

A Closer Look at Learning Strategies, L2 Proficiency, and Gender

Abstract: This study builds on previous research using the Strategy Inventory for Language Learning (SILL). Most previous SILL research has made comparisons across the entire survey or in terms of strategy categories and has stressed proficiency level at the expense of other variables. The present largescale (N = 374) study of language learning strategy use by students at three different course levels at the University of Puerto Rico relates strategy use to gender as well as to L2 proficiency level and includes analysis of variation in the use of individual strategies on the SILL. Like previous researchers, we found greater use of learning strategies among more successful learners and higher levels of strategy use by women than by men. Our analysis, however, revealed more complex patterns of use than have appeared in previous studies. With both proficiency level and gender, only some items showed significant variation, and significant variation by proficiency level did not invariably mean more frequent strategy use by more successful students. The strategies reported as used more often by the more successful students emphasized active, naturalistic practice and were used in combination with a variety of what we term bedrock strategies, which were used frequently or moderately frequently by learners at all levels. The study's generalizability and its implications for teachers and researchers are discussed.

Cognition Plus: Correlates Of Language Learning Success

Abstract: This article examines the relationships of a variety of individual difference variables to end-of-training proficiency ratings in speaking and reading for a large sample of adults in intensive training in a wide range of languages at the U.S. Department of State. Variables included tested cognitive aptitude, learning strategies, learning styles, personality, motivation, and anxiety. Although tested cognitive aptitude showed the strongest correlations with proficiency test results in both skills, the other variables also correlated in ways that show how rich and complex the individual learner's role in language is. Results may contribute to increasingly sophisticated student counseling and to efforts to enhance student autonomy by tailoring treatments to student characteristics. They also increase knowledge of attributes that may affect language training to the upper proficiency levels.

Natural photolysis by ultraviolet irradiance of recalcitrant dissolved organic matter to simple substrates for rapidbacterial metabolism

Abstract: Whole leachate and humic and fulvic acid fractions of dissolved organic matter (DOM) released from senescent littoral aquatic plants were exposed to varying spectra of ultraviolet radiation as well as natural UV of sunlight over different periods of time. Examination of the DOM by solid-state 13C nuclear magnetic resonance and pyrolytic gas chromatography-mass spectrometry before and after photolysis revealed only subtle changes to the bulk DOM. However, the DOM exposed to natural UV radiation showed immediate stimulation of and sustained bacterial growth. Chemical analyses by high performance liquid chromatography (HPLC) of the small organic fractions generated by photolysis of humic substances showed marked, pro- ’ gressively increasing release of numerous small fatty acids, particularly acetic, formic, citric, pyruvic, and levulinic, among others. Use of radiolabeled humic substances demonstrated that these small compounds photolyzed from the humic substances were readily metabolized by the bacteria.

Developmental change in attention-deficit hyperactivity disorder in boys: a four-year longitudinal study.

Abstract: One hundred six clinic-referred boys meeting criteria for DSM-III-R attention-deficit hyperactivity disorder (ADHD) (mean age 9.4 years) were assessed annually for 4 years using structured interviews of multiple informants. Hyperactivity—impulsivity symptoms declined with increasing age, but inattention symptoms did not. Rather, inattention declined only from the first to the second assessment and remained stable thereafter in boys of all ages. The rate of decline in hyperactivity—impulsivity symptoms was independent of the amount and type of treatment received. Boys who still met criteria for ADHD in Years 3 and 4 were significantly younger, more hyperactive—impulsive, and more likely to exhibit conduct disorder in Year 1 than boys who no longer met criteria in Years 3 and 4.

The Risk-Averse and Prudent Newsboy

Abstract: The effects of risk and risk aversion in the single-period inventory "newsboy" problem are examined. Comparative-static effects of changes in the various price and cost parameters are determined and related to the newsboy's risk aversion. The addition of a random background wealth and of an increase in the riskiness of newspaper demand are also examined. Although many of the comparative effects generally are ambiguous, some fairly simple restrictions on preferences and/or risk increases are shown to lead to qualitatively deterministic results.

Regulation of Leaf Breakdown by Fungi in Streams: Influences of Water Chemistry

Abstract: We examined the influence of stream water chemistry on relationships between fungal activity and breakdown rates of yellow poplar (Liriodendron tulipifera) leaves in eight streams that varied with respect to pH and nutrient (nitrate and phosphate) con- centrations. We also performed a reciprocal exchange experiment of leaves that had been colonized by microorganisms in two streams with contrasting water chemistries. Decom- poser activity varied greatly depending on the stream in which the leaves were placed. Variation in breakdown rates of yellow poplar leaves was over 9-fold maximum ATP concentrations associated with leaves varied as much as 8-fold, and maximum sporulation rates of fungi associated with leaves varied over 80-fold among streams. Among all streams, nitrate, phosphate, and temperature were positively correlated with one another and with decomposer biomass and activity. When hardwater streams were analyzed separately, nitrate concentration was the only variable that was significantly correlated with all measures of microbial activity and leaf breakdown. Consequently, nitrate concentration appeared to explain much of the variation we detected among streams. Responses to the reciprocal exchange experiment were rapid, with significant changes occurring within the first 5 d after the transfer. Leaves transferred from the hardwater stream containing relatively high concentrations of nitrate and phosphate to the softwater stream containing low concentra- tions of nutrients exhibited by large decreases in both ATP concentrations and sporulation rates, whereas ATP concentrations and sporulation rates increased when leaves received the reciprocal transfer. The fungi associated with decomposing leaves in streams appear to obtain a significant portion of their nutrients (e.g., nitrogen and phosphorus) from the water passing over the leaf surface. These results indicate that the chemistry of the water can be an important regulator of leaf breakdown in streams by affecting the activity of decomposer fungi.

Fibromyalgia in women. Abnormalities of regional cerebral blood flow in the thalamus and the caudate nucleus are associated with low pain threshold levels.

Abstract: Objective. To determine if regional cerebral blood flow (rCBF) in the left and right hemithalami or the left and right heads of the caudate nucleus is abnormal in women with fibromyalgia (FM). Methods. Resting-state rCBF in the hemithalami and left and right heads of the caudate nucleus of 10 untreated women with FM and 7 normal control women was measured by single-photon–emission computed tomography. Pain threshold levels at tender and control points also were assessed in both the women with FM and the controls. Results. The rCBF in the left and right hemithalami and the left and right heads of the caudate nucleus was significantly lower in women with FM than in normal controls (P = 0.01, P = 0.003, P = 0.01, and P = 0.02, respectively). Compared with controls, the women with FM also were characterized by significantly lower cortical rCBF (P = 0.001) and lower pain threshold levels at both tender points (P = 0.0001) and control points (P = 0.0001). Conclusion. The findings of low rCBF and generalized low pain thresholds support the hypothesis that abnormal pain perception in women with FM may result from a functional abnormality within the central nervous system.

Death, detritus, and energy flow in aquatic ecosystems

Abstract: SUMMARY 1. Pelagic trophic structure and energy fluxes are evaluated predominantly on the basis of ingestion of particulate organic matter by living organisms and the effects of consumption on the population dynamics of trophic levels. 2. Population fluxes are not representative of the material and energy fluxes of either the composite pelagic region or the lake ecosystem. Metabolism of particulate and especially dissolved organic detritus from many pelagic and non-pelagic autochthonous and from allochthonous sources dominates both material and energy fluxes. Because of the very large magnitudes and relative chemical recalcitrance of these detrital sources, the large but slow metabolism of detritus provides an inherent ecosystem stability that energetically dampens the ephemeral, volatile fluctuations of higher trophic levels. 3. The annual time period is the only meaningful interval in comparative quantitative analyses of material and energy fluxes at population, community, and ecosystem levels. 4. Non-predatory death and metabolism by prokaryotic and protistian heterotrophs dominate. Continued application of animal-orientated relationships to the integrated, process-driven couplings of the aquatic ecosystems impedes understanding of quantitative ecosystem pathways and control mechanisms.

Interactions in Undersaturated and Supersaturated Lysozyme Solutions: Static and Dynamic Light Scattering Results

Abstract: We have performed multiangle static and dynamic light scattering studies of lysozyme solutions at pH=4.7. The Rayleigh ratio R(sub g) and the collective diffusion coefficient D(sub c) were determined as function of both protein concentration c(sub p) and salt concentration c(sub s) with two different salts. At low salt concentrations, the scattering ratio K(sub c)(sub p)/R(sub theta) and diffusivity increased with protein concentration above the values for a monomeric, ideal solution. With increasing salt concentration this trend was eventually reversed. The hydrodynamic interactions of lysozyme in solution, extracted from the combination of static and dynamic scattering data, decreased significantly with increasing salt concentration. These observations reflect changes in protein interactions, in response to increased salt screening, from net repulsion to net attraction. Both salts had the same qualitative effect, but the quantitative behavior did not scale with the ionic strength of the solution. This indicates the presence of salt specific effects. At low protein concentrations, the slopes of K(sub c)(sub p)/R(sub theta) and D(sub c) vs c(sub p) were obtained. The dependence of the slopes on ionic strength was modeled using a DLVO potential for colloidal interactions of two spheres, with the net protein charge Z(sub e) and Hamaker constant A(sub H) as fitting parameters. The model reproduces the observed variations with ionic strength quite well. Independent fits to the static and dynamic data, however, led to different values of the fitting parameters. These and other shortcomings suggest that colloidal interaction models alone are insufficient to explain protein interactions in solutions.

Genistein suppresses mammary cancer in rats

Abstract: Female Sprague-Dawley CD rats were injected s.c. with 5 mg genistein, a soy phytoestrogen, or 20 microliters of the vehicle, dimethylsulfoxide (DMSO), on days 2,4 and 6 postpartum. At day 50, they were exposed to 80 micrograms dimethylbenz[a]anthracene (DMBA)/g body wt. Animals treated neonatally with genistein as compared to DMSO had increased latency and reduced incidence and multiplicity of DMBA-induced mammary adenocarcinomas. Mammary whole mount analysis showed that 50 day old female rats treated neonatally with genistein had fewer terminal end buds. Cell proliferation studies revealed that 50 day old genistein-treated rats had lower percentages and total numbers of cells in the S-phase of the cell cycle in terminal end buds, terminal ducts, lobules I and lobules II. In genistein-treated as compared to vehicle-treated female rats, vaginal openings occurred earlier, the estrus cycle was disrupted and the uterine-ovarian weights were smaller. In 50 day old genistein-treated females there were atretic antral follicles, fewer corpora lutea, and lower circulating progesterone but not estradiol-17 beta concentrations. In 21 day old rats treated neonatally with genistein, mammary glands were larger and there were more terminal end buds and terminal ducts, and more proliferative activity in all terminal ductals structures. It appears that neonatal genistein-treatment exerted its chemoprevention action by acting directly to enhance maturation of terminal ductal structures and by altering the endocrine system to reduce cell proliferation in the mammary gland.

Growth and survival of Escherichia coli O157:H7 under acidic conditions.

Abstract: The effect of pH reduction with acetic (pH 52), citric (pH 40), lactic (pH 47), malic (pH 40), mandelic (pH 50), or tartaric (pH 41) acid on growth and survival of Escherichia coli O157:H7 in tryptic soy broth with 06% yeast extract held at 25, 10, or 4 degrees C for 56 days was determined Triplicate flasks were prepared for each acid treatment at each temperature At 25 degrees C, populations increased 2 to 4 log10 CFU/ml in all treatments except that with mandelic acid, whereas no growth occurred at 10 or 4 degrees C in any treatments except the control However, at all sampling times, higher (P or = 40) for up to 56 days, but survival is affected by type of acidulant and temperature

Team-Member Exchange Under Team and Traditional Management: A Naturally Occurring Quasi-Experiment

Abstract: The quality of exchange relationships between work teams and their members was assessed for 103 manufacturing workers. Higher levels of team-member exchange quality, as well as of cohesiveness, sat...

Characterization of a messenger RNA polynucleotide vaccine vector

Abstract: We have constructed mRNA transcripts encoding luciferase and human carcinoembryonic antigen (CEA) which are capped, polyadenylated, and stabilized by human β-globin 5′ and 3′ untranslated regions. The mRNA construct encoding human CEA directed CEA expression in mouse fibroblasts in vitro following liposome-mediated transfection. The luciferase encoding mRNA transcripts mediated luciferase expression in vivo following i.m. injection. Based on the demonstration of protein expression in vitro and in vivo , the feasibility of using such a vector as a tumor vaccine was examined. In this pilot study, seven mice received 50 µg mRNA transcripts encoding CEA twice weekly for 5 weeks by i.m. injection followed by challenge with syngeneic, CEA-expressing tumor cells. This dose and schedule “primed” an immune response to CEA. Five of seven mRNA-immunized mice demonstrated anti-CEA antibody 3 weeks after tumor challenge whereas control mice had no evidence of antibody response. This strategy might be particularly useful to induce an immune response to a proto-oncogene product or growth factor which poses a risk of inducing malignant transformation consequent to prolonged protein expression.

Simultaneous Determination of the Rates of the TCA Cycle, Glucose Utilization, α-Ketoglutarate/Glutamate Exchange, and Glutamine Synthesis in Human Brain by NMR

Abstract: 13C isotopic tracer data previously obtained by 13C nuclear magnetic resonance in the human brain in vivo were analyzed using a mathematical model to determine metabolic rates in a region of the human neocortex. The tricarboxylic acid (TCA) cycle rate was 0.73 ± 0.19 μmol min-1 g-1 (mean ± SD; n = 4). The standard deviation reflects primarily intersubject variation, since individual uncertainties were low. The rate of α- ketoglutarate/glutamate exchange was 57 ± 26 μmol min-1 g-1 (n = 3), which is much greater than the TCA cycle rate; the high rate indicates that α-ketoglutarate and glutamate are in rapid exchange and can be treated as a single combined kinetic pool. The rate of synthesis of glutamine from glutamate was 0.47 μmol min-1 g-1 (n = 4), with 95% confidence limits of 0.139 and 3.094 μmol min-1 g-1; individual uncertainties were biased heavily toward high synthesis rates. From the TCA cycle rate the brain oxygen consumption was estimated to be 2.14 ± 0.48 μmol min-1 g-1 (5.07 ± 1.14 ml 100 g-1 min-1; n = 4), and the rate of brain glucose consumption was calculated to be 0.37 ± 0.08 μmol min-1 g-1 (n = 4). The sensitivity of the model to the assumptions made was evaluated, and the calculated values were found to be unchanged as long as the assumptions remained near reported physiological values.

Four-year longitudinal study of conduct disorder in boys: patterns and predictors of persistence.

Abstract: A prospective study of conduct disorder (CD) was conducted using 4 annual structured diagnostic interviews of 171 clinic-referred boys, their parents, and their teachers. Only about half of the 65 boys who met criteria for CD in Year 1 met criteria again during the next year, but 88% met criteria for CD again at least once during the next 3 years. For most boys with CD, the number of symptoms fluctuated above and below the diagnostic threshold from year to year but remained relatively high. Lower socioeconomic status, parental antisocial personality disorder (APD), and attention-deficit hyperactivity disorder were significant correlates of CD in Year 1, but the interaction of parental APD and the boy's verbal intelligence predicted the persistence of CD symptoms over time (i.e., only boys without a parent with APD and with above-average verbal intelligence clearly improved). Conduct disorder (CD) is a pattern of maladaptive behavior of children that is characterized by a variety of antisocial behaviors, including physical aggression, deception, and violation of the property rights of others (Lahey, Loeber, Frick, Quay, & Grimm, 1992). It is generally considered to be a serious childhood disorder that is the primary precursor to chronic antisocial behavior during adulthood (Kazdin, 1987a; Robins, Tipp, & Pryzbeck, 1991). Because it is difficult to reduce the frequency of antisocial behavior in children with CD through psychosocial treatment (Kazdin, 1987b), CD is conceptualized as a disorder that is usually chronic (Kazdin, 1987a). Evidence from longitudinal studies is consistent with the view that antisocial behavior in childhood is persistent over time; however, these same data raise a question about the degree of persistence of the disorder. For example, studies of official court records have shown that 50%-70% of youths who are arrested for delinquent acts during childhood or adolescence are arrested in adulthood (Loeber, 1982, 1990, 1991;McCord, 1979;

Individual, Organizational/Work and Environmental Influences on Expatriate Turnover Tendencies: An Empirical Study

Abstract: Foreign postings for executives are costly undertakings for multinational corporations, especially when they fail. Yet little research has been done on the causes of expatriate turnover. This 155-expatriate survey assesses individual, organizational/work and environmental influences on both internal and external turnover tendencies. It was found that job autonomy and material life satisfaction were key predictors for both internal and external turnover tendencies. Only for organizational turnover did job autonomy supersede material life satisfaction as the lead predictor of turnover tendencies. American expatriates attach much importance to maintaining living standards in postings to foreign locations.

Zidovudine resistance and HIV-1 disease progression during antiretroviral therapy

Abstract: Objective To evaluate the association between resistance of human immunodeficiency virus type 1 (HIV-1) to zidovudine and clinical progression. Design Retrospective analysis of specimens from patients in the AIDS Clinical Trials Group (ACTG) protocol 116B/117, a randomized comparison of didanosine with continued zidovudine therapy in patients with advanced HIV-1 disease who had received 16 weeks or more of previous zidovudine therapy. Setting Participating ACTG virology laboratories. Patients 187 patients with baseline HIV-1 isolates. Measurements Zidovudine susceptibility testing and assays for syncytium-inducing phenotype were done on baseline HIV-1 isolates. Relative hazards for clinical progression or death associated with baseline clinical, virologic, and immunologic factors were determined from Cox proportional hazards regression models. Results Compared with other patients, 15% (26 of 170) with isolates showing high-level zidovudine resistance (50% inhibitory zidovudine concentration > or = 1.0 microM) had 1.74 times the risk for progressing to a new AIDS-defining event or death (95% CI, 1.00 to 3.03) and 2.78 times the risk for death (CI, 1.21 to 6.39) in analyses that controlled for baseline CD4+ T-lymphocyte count, syncytium-inducing HIV-1 phenotype, disease stage, and randomized treatment assignment. The clinical benefit of didanosine was not limited to patients with highly zidovudine-resistant baseline HIV-1 isolates. Conclusions High-level resistance of HIV-1 to zidovudine predicted more rapid clinical progression and death when adjusted for other factors. However, patients with advanced HIV-1 disease may benefit from a change in monotherapy from zidovudine to didanosine whether high-level HIV-1 resistance to zidovudine is present or absent, and laboratory assessment of zidovudine resistance is not necessary for deciding when to switch monotherapy from zidovudine to didanosine.

Protein-rejecting ability of surface-bound dextran in end-on and side-on configurations: comparison to PEG.

Abstract: There is much interest in attaching polyethylene glycol (PEG) and other hydrophilic, neutral polymers to surfaces to reduce the extent of protein and cell adsorption. Interestingly, these same surface-bound polymers are effective in masking surface charge and reducing electrokinetic effects such as particle electrophoretic mobility, streaming potential, and electroosmosis. It is apparent that similar molecular properties are responsible for both protein and cell rejection and reduction of electrokinetic effects. In this work we compared the fibrinogen-rejecting ability and the effect on electrophoretic mobility of three polymer coatings bound to polystyrene. The three polymers were side-bound dextran, end-bound dextran, and end-bound PEG. The results of these measurements were used to elucidate the importance of polymer packing density and polymer layer thickness on protein adsorption and reduction of electrokinetic effects. Protein adsorption appears not to be sensitive to polymer layer thickness or the presence of dilute polymer tails in a surface coating, while electrokinetic effects are. Protein adsorption is, however, very sensitive to the availability of exposed surface. Finally, the unique effectiveness of PEG is apparent in this research as in previous studies. © 1995 John Wiley & Sons, Inc.

A mouse model for beta 0-thalassemia

Abstract: We have used a "plug and socket" targeting technique to generate a mouse model of beta 0-thalassemia in which both the b1 and b2 adult globin genes have been deleted. Mice homozygous for this deletion (Hbbth-3/Hbbth-3) die perinatally, similar to the most severe form of Cooley anemia in humans. Mice heterozygous for the deletion appear normal, but their hematologic indices show characteristics typical of severe thalassemia, including dramatically decreased hematocrit, hemoglobin, red blood cell counts, mean corpuscular volume, mean corpuscular hemoglobin, and mean corpuscular hemoglobin concentration, as well as dramatically increased reticulocyte counts, serum bilirubin concentrations, and red cell distribution widths. Tissue and organ damage typical of beta-thalassemia, such as bone deformities and splenic enlargement due to increased hematopoiesis, are also seen in the heterozygous animals, as is spontaneous iron overload in the spleen, liver, and kidneys. The mice homozygous for the b1 and b2 deletions should be of great value in developing therapies for the treatment of thalassemias in utero. The heterozygous animals will be useful for studying the pathophysiology of thalassemias and have the potential of generating a model of sickle cell anemia when mated with appropriate transgenic animals.

Organizational Analysis in North America and Europe: A Comparison of Co-citation Networks:

Abstract: Over the last decade, the field of organization studies has been characterized by a proliferation of divergent perspectives. Using bibliometric techniques, this paper examines the extent to which this state of differentiation may be associ ated with regional differences in scholarly orientation, specifically, between North America and Europe. The study is based on citation and co-citation analyses of articles published by North American authors in Administrative Science Quarterly and by European authors in Organization Studies in the three-year period from 1990 to 1992. Results do show that there is divergence in the perspectives that are currently dominant in Europe and North America, and, to some degree between Britain and elsewhere in Europe. The discussion section elaborates on the nature of the differences in orientation and speculates on factors that may have fostered and helped to maintain this diver gence.

A Diverse and Endangered Aquatic Ecosystem of the Southeast United States

Abstract: We document the biodiversity and conservation status of an extraordinarily diverse and endangered ecosystem in the United States that has failed to attract the same attention as tropical ecosystems—the rivers and streams of Alabama and adjoining states. Relative to North America as a whole, Alabama is a highlight of aquatic diversity supporting 38% of native fresh water fishes, 43% of native freshwater gill-breathing snails, 60% of native mussels, and 52% of native freshwater turtles. Of these, 41%, 77%, 34%, and 22% of the fishes, snails, mussels, and turtles, respectively, are endemic to Alabama and an adjacent state. Like many tropical systems of developing nations, this fauna is in an imperiled state, with 10%, 65%, 69%, and 43% of Alabama’s fishes, gill-breathing snails, mussels, and turtles, respectively, considered either extinct, endangered, threatened, or of special concern. Unlike tropical systems, however, little effort has been made to protect the taxa and their habitats. Only 40% of fishes, 1% of gill-breathing snails, 32% of mussels, and 20% of freshwater turtles are formally listed as either threatened or endangered via the U.S. Endangered Species Act of 1973; no critical habitat has been protected. Clearly, the biodiversity crisis in not limited to tropical systems of developing nations. Although the Endangered Species Act of 1973 helps to ensure a future of sustainable diversity, efforts must be made to hasten recognition, protection, and recovery of critical habitat, particularly for hotspots such as the aquatic systems of Alabama.