Showing papers by "Duquesne University published in 2000"

The role of microbes in accretion, lamination and early lithification of modern marine stromatolites

Abstract: For three billion years, before the Cambrian diversification of life, laminated carbonate build-ups called stromatolites were widespread in shallow marine seas. These ancient structures are generally thought to be microbial in origin and potentially preserve evidence of the Earth's earliest biosphere. Despite their evolutionary significance, little is known about stromatolite formation, especially the relative roles of microbial and environmental factors in stromatolite accretion. Here we show that growth of modern marine stromatolites represents a dynamic balance between sedimentation and intermittent lithification of cyanobacterial mats. Periods of rapid sediment accretion, during which stromatolite surfaces are dominated by pioneer communities of gliding filamentous cyanobacteria, alternate with hiatal intervals. These discontinuities in sedimentation are characterized by development of surface films of exopolymer and subsequent heterotrophic bacterial decomposition, forming thin crusts of microcrystalline carbonate. During prolonged hiatal periods, climax communities develop, which include endolithic coccoid cyanobacteria. These coccoids modify the sediment, forming thicker lithified laminae. Preservation of lithified layers at depth creates millimetre-scale lamination. This simple model of modern marine stromatolite growth may be applicable to ancient stromatolites.

Cybersex users, abusers, and compulsives: New findings and implications

Abstract: Literature regarding sexual use of the Internet has primarily focused on anecdotal data of clinical cases. This study empirically examines the characteristics and usage patterns of individuals who use the Internet for sexual purposes. The Kalichman Sexual Compulsivity Scale was the primary tool used to divide the sample (n = 9,265) into four groups: nonsexually compulsive (n = 7,738), moderately sexually compulsive (n = 1,007), sexually compulsive (n = 424), and cybersex compulsive (n = 96); 17% of the entire sample scored in the problematic range for sexual compulsivity. Data analysis of the four groups indicated statistically significant differences on descriptive characteristics such as gender, sexual orientation, relationship status, and occupation. In addition, patterns of use differed across groups including the primary method of pursuing sexual materials, primary location of accessing sexual material, and the extent to which cybersex has interfered with a respondent's life. This study is o...

A compound poisson process for relaxing the molecular clock.

Abstract: The molecular clock hypothesis remains an important conceptual and analytical tool in evolutionary biology despite the repeated observation that the clock hypothesis does not perfectly explain observed DNA sequence variation. We introduce a parametric model that relaxes the molecular clock by allowing rates to vary across lineages according to a compound Poisson process. Events of substitution rate change are placed onto a phylogenetic tree according to a Poisson process. When an event of substitution rate change occurs, the current rate of substitution is modified by a gamma-distributed random variable. Parameters of the model can be estimated using Bayesian inference. We use Markov chain Monte Carlo integration to evaluate the posterior probability distribution because the posterior probability involves high dimensional integrals and summations. Specifically, we use the Metropolis-Hastings-Green algorithm with 11 different move types to evaluate the posterior distribution. We demonstrate the method by analyzing a complete mtDNA sequence data set from 23 mammals. The model presented here has several potential advantages over other models that have been proposed to relax the clock because it is parametric and does not assume that rates change only at speciation events. This model should prove useful for estimating divergence times when substitution rates vary across lineages.

Spacetime perspective of Schwarzschild lensing

Abstract: (November 29, 1999)We propose a definition of an exact lens equation without reference to a background spacetime,and construct the exact lens equation explicitly in the case of Schwarzschild spacetime For theSchwarzschild case, we give exact expressions for the angular-diameter distance to the sources aswell as for the magnification factor and time of arrival of the images We compare the exactlens equation with the standard lens equation, derived under the thin-lens-weak-field assumption(where the light rays are geodesics of the background with sharp bending in the lens plane, andthe gravitational field is weak), and verify the fact that the standard weak-field thin-lens equationis inadequate at small impact parameter We show that the second-order correction to the weak-field thin-lens equation is inaccurate as well Finally, we compare the exact lens equation with therecently proposed strong-field thin-lens equation, obtained under the assumption of straight pathsbut without the small angle approximation, ie, with allowed large bending angles We show thatthe strong-field thin-lens equation is remarkably accurate, even for lightrays that take several turnsaround the lens before reaching the observerI INTRODUCTION

A study of the genetic and environmental etiology of stuttering in a selected twin sample.

Abstract: Stuttering is a developmental disorder of speech production that usually emerges in childhood. In this study, a large population-based twin sample from the Australian Twin Registry (1567 pairs and 634 singles aged 17‐29 years) was screened to identify twin pairs in which one or both members reported themselves to be affected by stuttering. Telephone interview-based diagnoses were obtained for 457 of these individuals (self-reported affected cases, cotwins, and controls) to determine whether the self-report was correct. To correct for ascertainment bias we carried out a bivariate analysis of the final diagnosis in the selected sample with the screening item in the full sample, using the categorical raw data option of Mx 1.47c. After correcting for ascertainment bias, approximately 70% (95% confidence interval: 39‐86%) of the variance in liability to stuttering was found to be attributable to additive genetic effects, with the remainder due to nonshared environmental effects.

Genomic imprinting in plants: observations and evolutionary implications.

Abstract: The epigenetic phenomenon of genomic imprinting occurs among both plants and animals. In species where imprinting is observed, there are parent-of-origin effects on the expression of imprinted genes in offspring. This review focuses on imprinting in plants with examples from maize, where gene imprinting was first described, and Arabidopsis. Our current understanding of imprinting in plants is presented in the context of cytosine methylation and imprinting in mammals, where developmentally essential genes are imprinted. Important considerations include the structure and organization of imprinted genes and the role of regional, differential methylation. Imprinting in plants may be related to other epigenetic phenomena including paramutation and transgene silencing. Finally, we discuss the role of gene structure and evolutionary implications of imprinting in plants.

Physical therapy for migraine-related vestibulopathy and vestibular dysfunction with history of migraine.

Abstract: Objectives/Hypothesis: To assess the efficacy of physical therapy for patients with a diagnosis of migraine-related vestibulopathy (MRV) or vestibular dysfunction with a history of migraine headache. Study Design: Retrospective case series Methods: Thirty-nine patients were identified through a retrospective chart review, 14 with a diagnosis of MRV and 25 with migraine headache. The patients were treated with a custom-designed physical therapy exercise program for a mean of 4.9 visits over a mean duration of 4 months. Patients completed the Dizziness Handicap Inventory (DHI), the Activities-Specific Balance Confidence Scale (ABC), and the Dynamic Gait Index (DGI), reported the number of falls they had experienced in the past 4 weeks, and rated the severity of their dizziness on an analogue scale of 0 to 100 at initial evaluation and at discharge. Results: Significant differences were seen before and after therapy in each of the outcome measures used. The average decrease in DHI score was 12 points (P < .01). ABC scores increased an average of 14 points (P < .01). Subjects increased their DGI scores an average of 4 points (P < .01). The number of patients reporting more than one fall decreased by 78% at discharge. (P < .05). Baseline symptoms of dizziness decreased an average of 11 points (P < .05). Conclusions: Patients with MRV and migraine headache demonstrated improvement in physical performance measures and self

Understanding Middle Students' Beliefs About Knowledge and Learning Using a Multidimensional Paradigm

Abstract: Recent theory (Schommer, 1990) suggests that personal epistemology is multidimensional The multidimensional epistemology structure with middle school students was tested in this study Over 1,200 students in Grades 7 and 8 completed an epistemological belief questionnaire Prior theory, developed with college students, suggested 4 epistemological belief factors: Ability to Learn, Structure of Knowledge, Speed of Learning, and Stability of Knowledge Confirmatory factor analysis applied to a random half of the sample indicated that a 3-factor model was a good fit to the data That model was replicated with the second half of the data Follow-up regression analyses indicated that the more students believed in gradual learning and incremental ability to learn, the higher GPA they earned

A bayesian framework for the analysis of cospeciation

Abstract: Information on the history of cospeciation and host switching for a group of host and parasite species is contained in the DNA sequences sampled from each. Here, we develop a Bayesian framework for the analysis of cospeciation. We suggest a simple model of host switching by a parasite on a host phylogeny in which host switching events are assumed to occur at a constant rate over the entire evolutionary history of associated hosts and parasites. The posterior probability density of the parameters of the model of host switching are evaluated numerically using Markov chain Monte Carlo. In particular, the method generates the probability density of the number of host switches and of the host switching rate. Moreover, the method provides information on the probability that an event of host switching is associated with a particular pair of branches. A Bayesian approach has several advantages over other methods for the analysis of cospeciation. In particular, it does not assume that the host or parasite phylogenies are known without error; many alternative phylogenies are sampled in proportion to their probability of being correct.

Structure of Microbial Mats and Biofilms

Abstract: The application of new technologies, such as confocal scanning laser microscopy and molecular probes, to the study of biofilms and microbial mats has dramatically changed our view of these systems. In particular, the old idea that biofilms are simply microbes suspended in a homogeneous and diffusion limited matrix has been shattered by the realization that this matrix is actually very hydrated and honeycombed with channels. The microbial species which form the microcolonies have been shown to express genes which are not expressed when the organisms are free-swimming. Thus, many models of microbial dynamics based on planktonic studies (e.g., growth, gene exchange, biocide resistance) do not necessarily apply to biofilms. Recent studies of microbial mats have also uncovered some startling phenomenon. For instance, active sulfate reduction has been measured in the oxic zone. The impact of diurnal fluctuations in the environment cannot be underestimated, as species have been shown to migrate within the mat and use totally different metabolic pathways in response to light and oxygen. This review will highlight some of the insights into the biological structure of biofilms and microbial mats, and how the structure is affected by the physical and chemical environment, species composition, and species interactions. The chapter begins with a comparison of microbial mats and biofilms and ends with some suggestions for future studies.

Violence in Schools Rage Against a Broken World

Abstract: Violence in schools is a grave issue that is often analyzed in terms of individuals' tendencies toward destructive behavior. While this path of analysis is important, in this article, the author contextualizes violence within a cultural milieu that alienates students from their fundamental yearning for significance. It is argued that violence is a failed epiphany, that is, a heightened moment of awareness emerging out of the everyday flow of experience that seeks to overcome alienation. Violence fails because it cannot create a world of sustainable meaning. The nature of productive epiphanies and the worlds of sustainable meaning that they evoke are discussed in terms of their implication for education and overcoming violence in schools.

Measuring the impact of a business ethics course and community service experience on students' values and opinions

Abstract: Until now, there has been little research assessingthe impact and extent of business ethics education andservice learning upon students’ values and opinions. This paper studies the influence of these variables byanalyzing 129 junior-level students’ ethical valuesand opinions before and after these experiences. Through the use of the Students’ Values and OpinionsSurvey (SVOS) as a measurement gauge, we foundsignificant support for our hypotheses that a businessethics course and a community service experiencepositively affect students’ values and opinions. Thus, we found desirable improvement in the ethicalvalues and opinions of students after they wereexposed to service learning and business ethicseducation. In addition, we explored the impact ofservice learning by gender and prior communityservice. We did not find a significant difference inthe effect of service learning for men or women, butdid find that prior community service increased thepositive impact for students completing theircommunity service requirement in this study.

Design, synthesis, and X-ray crystal structure of a potent dual inhibitor of thymidylate synthase and dihydrofolate reductase as an antitumor agent.

Abstract: A novel N-?2-amino-4-methyl[(pyrrolo[2, 3-d]pyrimidin-5-yl)ethyl]benzoyl?-L-glutamic acid (3a) was designed and synthesized as a potent dual inhibitor of thymidylate synthase (TS) and dihydrofolate reductase (DHFR) and as an antitumor agent. Compound 3b, the N7-benzylated analogue of 3a, was also synthesized as an antitumor agent. The synthesis of 3a was accomplished via a 12-step sequence which involved the synthesis of 2-amino-4-methylpyrrolo[2,3-d]pyrimidine (10) in 5 steps from 2-acetylbutyrolactone. Protection of the 2-amino group of 10 and regioselective iodination at the 5-position followed by palladium-catalyzed coupling afforded intermediate 14 which was converted to 3a by reduction and saponification. Similar synthetic methodology was used for 3b. X-ray crystal structure of the ternary complex of 3a, DHFR, and NADPH showed that the pyrrolo[2, 3-d]pyrimidine ring binds in a "2,4-diamino mode" in which the pyrrole nitrogen mimics the 4-amino moiety of 2,4-diaminopyrimidines. This is the first example of a classical pyrrolo[2,3-d]pyrimidine antifolate shown to have this alternate mode of binding to DHFR. Compounds 3a and 3b were more inhibitory than LY231514 against TS from Lactobacillus casei and Escherichia coli. Analogue 3a was also more inhibitory against DHFR from human, Toxoplasma gondii, and Pneumocystis carinii. Evaluation of 3a against methotrexate (MTX)-resistant cell lines with defined mechanisms indicated that cross-resistance of 3a was much lower than that of MTX. Metabolite protection studies and folylpoly-gamma-glutamate synthetase studies suggest that the antitumor activity of 3a against the growth of tumor cells in culture is a result of dual inhibition of TS and DHFR. Compound 3a inhibited the growth of CCRF-CEM and FaDu cells in culture at ED(50) values of 12.5 and 7.0 nM, respectively, and was more active against FaDu cells than MTX. In contrast, compound 3b was inactive against both cell lines. Compound 3a was evaluated in the National Cancer Institute in vitro preclinical antitumor screening program and afforded IG(50) values in the nanomolar range against a number of tumor cell lines.

Molecular recognition and binding of thermal hysteresis proteins to ice.

Abstract: Molecular recognition and binding are two very important processes in virtually all biological and chemical processes. An extremely interesting system involving recognition and binding is that of thermal hysteresis proteins at the ice-water interface. These proteins are of great scientific interest because of their antifreeze activity. Certain fish, insects and plants living in cold weather regions are known to generate these proteins for survival. A detailed molecular understanding of how these proteins work could assist in developing synthetic analogs for use in industry. Although the shapes of these proteins vary from completely alpha-helical to globular, they perform the same function. It is the shapes of these proteins that control their recognition and binding to a specific face of ice. Thermal hysteresis proteins modify the morphology of the ice crystal, thereby depressing the freezing point. Currently there are three hypotheses proposed with respect to the antifreeze activity of thermal hysteresis proteins. From structure-function experiments, ice etching experiments, X-ray structures and computer modeling at the ice-vacuum interface, the first recognition and binding hypothesis was proposed and stated that a lattice match of the ice oxygens with hydrogen-bonding groups on the proteins was important. Additional mutagenesis experiments and computer simulations have lead to the second hypothesis, which asserted that the hydrophobic portion of the amphiphilic helix of the type I thermal hysteresis proteins accumulates at the ice-water interface. A third hypothesis, also based on mutagenesis experiments and computer simulations, suggests that the thermal hysteresis proteins accumulate in the ice-water interface and actually influence the specific ice plane to which the thermal hysteresis protein ultimately binds. The first two hypotheses emphasize the aspect of the protein 'binding or accumulating' to specific faces of ice, while the third suggests that the protein assists in the development of the binding site. Our modeling and analysis supports the third hypothesis, however, the first two cannot be completely ruled out at this time. The objective of this paper is to review the computational and experimental efforts during the past 20 years to elucidate the recognition and binding of thermal hysteresis proteins at the ice-vacuum and ice-water interface.

In vivo transposon mutagenesis of the methanogenic archaeon Methanosarcina acetivorans C2A using a modified version of the insect mariner-family transposable element Himar1

Abstract: We present here a method for in vivo transposon mutagenesis of a methanogenic archaeon, Methanosarcina acetivorans C2A, which because of its independence from host-specific factors may have broad application among many microorganisms. Because there are no known Methanosarcina transposons we modified the mariner transposable element Himar1, originally found in the insect Hematobia irritans, to allow its use in this organism. This element was chosen because, like other mariner elements, its transposition is independent of host factors, requiring only its cognate transposase. Modified mini-Himar1 elements were constructed that carry selectable markers that are functional in Methanosarcina species and that express the Himar1 transposase from known Methanosarcina promoters. These mini-mariner elements transpose at high frequency in M. acetivorans to random sites in the genome. The presence of an Escherichia coli selectable marker and plasmid origin of replication within the mini-mariner elements allows facile cloning of these transposon insertions to identify the mutated gene. In preliminary experiments, we have isolated numerous mini-mariner-induced M. acetivorans mutants, including ones with insertions that confer resistance to toxic analogs and in genes that encode proteins involved in heat shock, nitrogen fixation, and cell-wall structures.

The contribution of market intelligence to tactical and strategic business decisions

Abstract: One of the drivers of both strategy and success in the marketplace is the role of market intelligence. Samples a broad cross section of firms regarding their level of MI activity; MI data sources and MI accountability. Regarding MI activity and its value to consumer/competitive intelligence, two‐thirds of the companies indicated a dramatic increase in level of activity and nearly three‐fifths (54 per cent) said the impact of MI contributes heavily to tactical and strategic decision making. One third said activity was level, while none indicated a reduction. 44 per cent indicated MI contributed somewhat to decision making and only 2 per cent felt MI contributed little to strategy and success in the marketplace. Regarding MI data sources, customers, manufacturing, and R&D are the central source. Regarding MI accountability, about half held marketing accountable for MI.

Organizational learning: a critical component to new product development

Abstract: Investigates the functional relationship between organizational learning and the new product development process. The two major learning styles studied included Duetero and Non‐Duetero. After surveying key employees involved in new product development from 212 diversified businesses, the results showed that businesses employing Duetero learning were more: knowledgeable about the factors that drive successful and failed products; inclined to establish business goals and employ balanced measures when benchmarking new product performance. All of which suggests that organizational learning does impact new product performance, and should be considered a critical component to the NPD process.

Melatonin induction of filamentous structures in non-neuronal cells that is dependent on expression of the human mt1 melatonin receptor.

Abstract: Melatonin has gained recent popularity as a treatment for insomnia and other sleep disorders; however, its cellular effects are unknown. We report the effects of melatonin on the cellular morphology of Chinese hamster ovary (CHO) cells transformed to express the human melatonin receptors, mt1 and MT2. Our results show that melatonin exerts a strong influence on cellular shape and cytoskeletal organization in a receptor-dependent and possibly subtype-selective manner. The cell shape change that we see after a 5-h treatment of these non-neuronal cells with a pharmacological concentration of melatonin consists of the formation of long filamentous outgrowths that are reminiscent of the neurite processes produced by differentiating nerve cells. This morphological change occurs exclusively in cells expressing the mt1 receptor. We find that the microtubule and microfilament organization within these outgrowths is similar to that of neurites. Microtubules are required for the shape change to occur as Colcemid added in combination with melatonin completely blocks outgrowth formation. We demonstrate that the number of cells showing the altered cell shape is dependent on melatonin concentration, constant exposure to melatonin and that outgrowth frequencies increase when protein kinase A (PKA) is inhibited. Concomitant melatonin-dependent increases in MEK 1/2 and ERK 1/2 phosphorylation are noted in mt1-CHO cells only. The production of filamentous outgrowths is dependent on the translation of new protein but not the transcription of new mRNA. Outgrowth number is not controlled by centrosomes but is instead controlled by the polymerization state of the actin cytoskeleton. The results of this work show that the organization of the cytoskeleton is affected by processes specifically mediated or regulated by the mt1 receptor and may represent a novel alternative mechanism for the stimulation of process formation.

Mutagenesis of Neisseria meningitidis by In Vitro Transposition of Himar1 mariner

Abstract: Now that the meningococcal genome sequence has been completed, the lack of a suitable method for saturation mutagenesis remains a major obstacle to the unraveling of the pathogenic propensity ofNeisseria meningitidis. Here, we demonstrate that in vitroHimar1 mariner transposition on chromosomal or PCR-amplified meningococcal DNA, which is subsequently reintroduced into N. meningitidis by natural transformation, is an extremely efficient mutagenesis method. Southern blot analysis, sequencing the Himar1 insertion point in numerous transposition mutants, and a limited screening of the mutant libraries for clones impaired in maltose catabolism confirmed thatHimar1 transposed randomly in N. meningitidis. Taken together, these data demonstrate that Himar1 in vitro transposition can lead to the exhaustive mutagenesis of N. meningitidis, allowing for the first time a genomic-scale mutational analysis of this important human pathogen.

The study of life boredom

Abstract: This article extends the study of a phenomenological investigation (Bargdill, R. W., 2000) in which six participants wrote protocols and gave interviews describing the experience of being bored with their lives. This study found that the participants gradually became bored after they had compromised their life-projects for less desired projects. The participants felt emotionally ambivalent because they were thematically angry with others involved in their compromises while being pre-reflectively angry with themselves. The participants non-thematically adopted passive and avoidant stances toward their lives that allowed their boredom to spread to more aspects of their lives. The participants' boredom led them to identity issues because they no longer were actively working toward projects. They felt empty and apathetic because they felt every action led to boredom, and thus action was futile. Preliminary distinctions between the experience of life boredom and depression are considered.

Collaborative, individualized assessment.

Abstract: Collaborative, individualized assessment is an approach to psychological assessment in which the assessor and the client work together to develop productive understandings. Collaboration is a means of individualizing the assessment-its process, resulting suggestions, and written accounts. In this approach, life events are regarded as primary data. Test scores, categories, and related research are used as bridges into a particular life and as tools for then exploring that life. This article, an invited Master Lecture presented at the 1999 Society for Personality Assessment (SPA) meeting, presents examples of contextualizing, intervening, describing in life-world terms, and writing individualized reports with suggestions. Historical struggles to promote individualized assessment and current openness to its practices, especially within SPA, are mentioned. A hermeneutic approach to impression formation is described.

Effect of light on the magnetic properties of cobalt ferrite nanoparticles

Abstract: We report variations in the coercivity of CoFe/sub 2/O/sub 4/ nanoparticles as a function of particle size, temperature and light intensity. For 30 nm particles, this change in was 2300 Oe at 10 K, 120 Oe at 170 K, for a light intensity of under 2 milliwatts. The remanent magnetization was nearly unchanged by illumination. A simple model of optical absorption followed by electron transfer between Co/sup 2+/ and Fe/sup 3+/ ions is proposed.

Correction of species transformations in the analysis of Cr(VI) in solid environmental samples using speciated isotope dilution mass spectrometry

Abstract: Speciation of Cr(VI) in solid environmental samples is challenging because of the transformations between Cr(VI) and Cr(III). EPA method 3060A completely extracts Cr(VI) in a hot alkaline solution and preserves the solublized Cr(VI). This procedure, however, can oxidize Cr(III) in some chemical forms. On the other hand, the reverse transformation may occur during neutralization and acidification following the extraction step. We developed a method that is capable of monitoring and correcting for such bidirectional species transformations to determine Cr(VI) in solid samples. In this method, we spike a sample with a 53Cr(VI) spike (enriched in 53Cr) and a isoCr(III) spike (enriched in 50Cr). The large quantity of isoCr(III) in an easily oxidizable form competes with sample Cr(III) in the oxidization, reducing the method-induced oxidation of sample Cr(III). This method also corrects for the reduction of Cr(VI). The theory is presented and is evaluated experimentally. The analysis of chromite ore processing ...