Showing papers by "Virginia Commonwealth University published in 1989"
TL;DR: In this paper, a randomized, double-blind, placebo-controlled multicenter trial was conducted to determine the efficacy of a corticosteroid in reducing the short-term mortality of patients with severe alcoholic hepatitis.
Abstract: Study objective To determine the efficacy of a corticosteroid in reducing the short-term mortality of patients with severe alcoholic hepatitis. Design Randomized, double-blind, placebo-controlled multicenter trial. Setting Four university teaching hospitals. Patients We enrolled 66 patients with alcoholic hepatitis and either spontaneous hepatic encephalopathy or a discriminant function value greater than 32, calculated using the formula: 4.6 (prothrombin time - control time) + serum bilirubin [in mumol/L]/17.1. Fifty-nine patients (89%) completed the study. Two patients withdrew from the trial. The other 64 patients were hospitalized for the duration of the trial; however, treatment was discontinued in 5 patients because of potential drug toxicity. Interventions Patients were randomly assigned to receive either methylprednisolone (32 mg) or placebo within 7 days of admission. Treatment was given for 28 days. The doses were then tapered over 2 weeks and discontinued. Measurements and main results The endpoint of the study was death. Of the 31 recipients of placebo, 11 (35%) died within 28 days of randomization compared with 2 (6%) of the 35 patients given methylprednisolone (P = 0.006). The 95% CI for the difference in mortality was 12% to 70%. In the patients with spontaneous hepatic encephalopathy at entry, 9 of 19 recipients of placebo died (47%) compared with 1 (7%) of the 14 patients given methylprednisolone (P = 0.02). The 95% CI for the difference in mortality was 14% to 66%. The Cox proportional hazards regression model showed the advantage of methylprednisolone over placebo after adjustment for other potentially important prognostic variables (P = 0.004). Conclusions Methylprednisolone therapy decreases short-term mortality in patients with severe alcoholic hepatitis manifested either by spontaneous hepatic encephalopathy or a markedly elevated discriminant function value.
456 citations
TL;DR: The overlapping coefficient as discussed by the authors is defined as a measure of the agreement between two probability distributions, and its relationship to the dissimilarity index and its propertie are described in detail.
Abstract: The overlapping coefficient is defined as a measure of the agreement between two probability distributions. Its relationship to the dissimilarity index and its propertie are described. An extensive treatment of maximum-likelihood estimation of the overlap between two normal distributions is presented as an example of estimating the overlapping coefficient from sample data.
322 citations
TL;DR: No correlation could be established between the course of ICP or PVI and the occurrence of hyperemia, nor was there a correlation between the levels of CBF and ICP at the time of the measurements.
Abstract: ✓ The literature suggests that in children with severe head injury, cerebral hyperemia is common and related to high intracranial pressure (ICP). However, there are very few data on cerebral blood flow (CBF) after severe head injury in children. This paper presents 72 measurements of cerebral blood flow (“CBF15”), using the 133Xe inhalation method, with multiple detectors over both hemispheres in 32 children aged 3 to 18 years (mean 13.6 years) with severe closed head injury (average Glasgow Coma Scale (GCS) score 5.4). In 25 of the children, these were combined with measurements of arteriojugular venous oxygen difference (AVDO2) and of cerebral metabolic rate of oxygen (CMRO2). In 30 patients, the first measurement was taken approximately 12 hours postinjury. In 18 patients, an indication of brain stiffness was obtained by withdrawal and injection of ventricular cerebrospinal fluid and calculation of the pressure-volume index (PVI) of Marmarou. The CBF and CMRO2 data were correlated with the GCS score, o...
318 citations
TL;DR: The difference in effect size between treatments was maintained both when only published studies were included and when only the studies with the strongest design were included, and the overall conclusions were unchanged.
Abstract: Hand and computer searches located studies on the effects of relaxation techniques on trait anxiety. Effect sizes for the different treatments (e.g., Progressive Relaxation, EMG Biofeedback, various forms of meditation, etc.) were calculated. Most of the treatments produced similar effect sizes except that Transcendental Meditation had significantly larger effect size (p <.005), and meditation that involved concentration had significantly smaller effect. Correlations with effect size were calculated for many variables, e.g., population, age, sex, experimental design, duration and hours of treatment, pretest anxiety, demand characteristics, experimenter attitude, type of publication, attrition, etc. Only a few variables (mainly population, duration, hours, and attrition) significantly influenced effect size. Controlling for possible confounding variables did not alter the overall conclusions. The difference in effect size between treatments was maintained both when only published studies were included and when only the studies with the strongest design were included. Possible explanations for the findings are examined.
306 citations
TL;DR: It is concluded that even mild mechanical injury can potentiate selective ischemic hippocampal neuronal necrosis in the absence of overt axonal injury, and this potentiation also occurs in conjunction with more generalized electrophysiological disturbances such as EEG evidence of postischemic neuronal hyperactivity suggesting that mild concussion may also decrease the threshold for post-ischemics neuronal excitation.
263 citations
TL;DR: Whether laser-Doppler (LD) flowmetry can be utilized to assess changes in cerebral cortical blood flow and to determine whether changes in blood perfusion measured by LD flowmetry correlate with simultaneously measured changes in flow measured by H2 clearance in cats or with changes in pial arteriolar diameter measured with a microscope in rabbits equipped with a closed cranial window.
Abstract: The objective of this study was to determine whether changes in blood perfusion measured by laser-Doppler (LD) flowmetry correlate with simultaneously measured changes in pial arteriolar diameter after local application of vasoactive agents on the brain surface. A closed cranial window was implanted in anesthetized rabbits. A 0.84-mm-diam LD probe was inserted through one window port and fixed at a distance of 1-2 mm from the cortical surface. The probe detects changes in perfusion within a tissue volume of approximately 1 mm3. The diameter of pial arterioles in the area adjacent to the LD probe was simultaneously measured with a microscope and image-splitting device. Topical application of bradykinin (80 nM to 8 microM), which stimulates the formation of dilator prostaglandins and O2 radicals, induced a dose-dependent arteriolar dilation and increase in LD flow. Topical application of 33 microM 2-chloroadenosine, a stable analogue of adenosine, induced the same degree of pial arteriolar dilation as 8 microM bradykinin but produced a much larger increase in LD flow, probably due to its greater tissue penetration and stability. At 5 min after bradykinin washout the arterioles had nearly returned to their control diameter, whereas LD flow was still increased. Similarly, there was a discrepancy between LD flow and diameter changes after washout of 2-chloroadenosine. We conclude that LD flowmetry is a useful technique for continuous assessment of cortical blood flow in response to topically applied agents.(ABSTRACT TRUNCATED AT 250 WORDS)
236 citations
TL;DR: In the young sample (average age 35 years), there is no evidence that individuals genetically predisposed to heavy drinking are any less likely to be married than the rest of the population, and statistical analyses show that marital status is an important modifier of genetic effects on drinking habits.
Abstract: Information about drinking practices has been obtained by questionnaire from 1,984 monozygotic and dizygotic adult female twin pairs from the Australian twin register, including 1,690 pairs where both twins have used alcohol. Statistical analyses of these data show that marital status is an important modifier of genetic effects on drinking habits. In young twins, aged 30 years or less, genetic differences between individuals account for only 31% of the variance in alcohol consumption of married respondents, but for 60% of the variance of unmarried respondents. In twin pairs, aged 31 years or more, genetic differences account for 46-59% of the variance in married twins, but for 76% of the variance in unmarried twins. In our young sample (average age 35 years) there is no evidence that individuals genetically predisposed to heavy drinking are any less likely to be married than the rest of the population. Some alternative explanations of these findings are also rejected.
209 citations
TL;DR: Autoregulation was statistically significantly more often impaired when CBF was either below normal -2 standard deviations (SD) (reduced flow) or above normal +2 SD (absolute hyperemia), and the consequences of these findings in the management of ICP problems with blood pressure control are discussed.
Abstract: Autoregulation of cerebral blood flow ("CBF15") was tested in a series of 26 pediatric patients (mean age 13.2 years) with severe head injury (average Glasgow Coma Scale (GCS) score 5.5) in the acute stage. A baseline 133Xe CBF measurement was performed and then repeated, after blood pressure was increased by 29% with intravenous phenylephrine or decreased by 26% with intravenous trimethaphan camsylate. Correlations were made between CBF and clinical condition, outcome, time after injury, intracranial pressure (ICP), and pressure-volume index (PVI) changes, and the site of injury (hemispheres, diencephalon, or brain stem). The site of injury was determined with multimodality evoked potential measurements. Autoregulation was intact in 22 (59%) of 37 measurements. There was no correlation with GCS score, outcome, time after injury, site of injury, or way of testing (decreasing or increasing blood pressure). Autoregulation was statistically significantly more often impaired when CBF was either below normal -2 standard deviations (SD) (reduced flow) or above normal +2 SD (absolute hyperemia). In cases with intact autoregulation, mean ICP decreased from 17.5 to 15.0 mm Hg with higher blood pressure and increased from 19.0 to 21.3 mm Hg with lower blood pressure. When PVI was measured during the blood pressure manipulations, it was found to change in a direction opposite to the ICP change. The consequences of these findings in the management of ICP problems with blood pressure control are discussed.
204 citations
TL;DR: It is concluded that dietary erucic acid therapy is effective in lowering plasma C26:0 to normal in ALD patients, and may prevent further demyelination in some mildly affected boys.
Abstract: We investigated the biochemical and clinical efficacy of dietary erucic acid (C22:1) therapy for X-linked adrenoleukodystrophy (ALD). In a double-blind crossover study of patients who were on chronic oleic acid (C18:1) therapy, addition of erucic acid to the diet led to a further reduction in plasma hexacosanoic acid (C26:0) concentration. We treated 12 newly diagnosed ALD patients with a diet enriched with erucic acid and oleic acid for 2 to 19 months. Mean plasma C26:0 concentration decreased to normal by 4 weeks, and the C26:0 composition of plasma sphingomyelin and phosphatidylcholine became normal by 4 months on therapy. Fatty acid analysis of postmortem tissues from 1 boy treated for 10 months suggested that dietary erucic acid entered the heart, liver, adrenal gland, and brain. Eight patients remained on treatment long enough (mean, 12 +/- 3 months) to evaluate their clinical response; 6 of these patients with moderate to advanced disease deteriorated neurologically or showed progression of white matter disease on brain magnetic resonance imaging whereas 2 mildly affected patients remained clinically stable after 10 and 19 months. No adverse effects of the diet occurred. We conclude that dietary erucic acid therapy is effective in lowering plasma C26:0 to normal in ALD patients, and may prevent further demyelination in some mildly affected boys.
180 citations
TL;DR: The theory of efficient rent-seeking predicts that the number of rent-seekers, their risk posture, their ability to enter and exit the rentseeking process, and the manner in which the probability of receiving a rent is determined will affect the amount of rent that is dissipated as discussed by the authors.
Abstract: The debate about the measurement of the amount of rent dissipated in rent-seeking activities is unable to be answered by observations from the naturally occurring environment. Current theoretical investigations have indicated that a number of factors will affect the amount of rent that can be assumed to be dissipated by rent-seeking. The theory of efficient rent-seeking predicts that the number of rent-seekers, their risk posture, their ability to enter and exit the rent-seeking process, and the manner in which the probability of receiving a rent is determined will affect the amount of rent that is dissipated.
159 citations
TL;DR: Of all the coenzymes, tetrahydrofolate exhibits the most structural diversity, and studies now show that the polyglutamate chain of the coenzyme affects the transport properties of theCoenzyme, alters the kinetic properties of many enzymes in one-carbon metabolism, and results in channeling of thecoenzyme between several enzymes.
Journal Article•
TL;DR: Theories of religious development are reviewed in the initial section of the article as mentioned in this paper, and the implications of theory and research on religious involvement in therapy are investigated, and number of important questions for assessment, treatment, and research are identified.
Abstract: The thesis of this article is that psychologists can benefit in assessment and counseling of clients and in research by understanding the religious development of many of their religious clients throughout the life span. Theories of religious development are reviewed in the initial section of the article. Generally, the early life of the religious person is well described by using a variety of stage theories; however, at adolescence and beyond, prediction is enhanced by using life-event or transition theory perspectives. In the second section, research is reviewed on a variety of issues involving religion over the life span. In the final section, the implications of theory and research on religious involvement in therapy are investigated, and number of important questions for assessment, treatment, and research are identified
01 Jan 1989
TL;DR: Gangliosides are sialic acid-containing glycosphingolipids found primarily in the plasma membrane of virtually all vertebrate tissues and are particularly abundant in the nervous system.
Abstract: Gangliosides are sialic acid-containing glycosphingolipids (GSLs) found primarily in the plasma membrane of virtually all vertebrate tissues and are particularly abundant in the nervous system. They constitute part of the glycocalyx network surrounding the cell surface and are crucial in determining the properties and functions of cells. Structurally, they contain a hydrophobic ceramide chain to which a hydrophilic oligosaccharide is glycosidically linked. Some representative brain gangliosides are shown in Figure 1.
TL;DR: Evidence demonstrating that activated B cells and plasma cells are directly involved in the pathogenic mechanisms leading to destruction of the periodontal support is still circumstantial, and further research is needed to determine how the B cell/plasma cell may participate in tissue injury in periodontitis, andHow the B-cell response to PBA factors is regulated.
Abstract: The evidence that periodontitis-associated bacteria contain potent PBA factors is very strong. Clearly, antibodies directed against non-oral antigens are produced in the inflamed periodontal lesion, and PBA appears to contribute to that production. It is also clear that B cells and plasma cells are the major cell types in the periodontal lesion. Furthermore, alterations in the regulation of B-cell responses to PBA factors are associated with severe periodontal disease. However, evidence demonstrating that activated B cells and plasma cells are directly involved in the pathogenic mechanisms leading to destruction of the periodontal support is still circumstantial. Polyclonal B-cell activation and potential pathways by which PBA-stimulated cells could be involved in periodontal destruction remain largely hypothetical. It appears that IL-1 is an important osteoclast-activating agent, and that LPS, which is a potent PBA factor in many systems, can elicit IL-1 production by B cells as well as by the monocyte/macrophage lineage. Recent data indicating that IL-1 is produced by numerous malignant B-cell lines lend support for the idea that B-cell IL-1 could be important in bone resorption. It is also likely that polyclonal activation may lead to production of autoantibody such as anti-type I and anti-type III collagens, and the destruction of self tissues through ADCC reactions, immune complex formation, and complement activation. Further research is needed to determine how the B cell/plasma cell may participate in tissue injury in periodontitis, and how the B-cell response to PBA factors is regulated.
TL;DR: It is argued that stress management and coping studies in the health care setting have not been sufficiently theoretically grounded and researchers have not adequately taken into account the nature of the stressor in terms of the degree to which it poses emotion-focused versus problem-focused coping demands for the individual.
Abstract: I argue that stress management and coping studies in the health care setting have not been sufficiently theoretically grounded. In particular, in formulating and evaluating intervention strategies, researchers have not adequately taken into account the nature of the stressor under study in terms of the degree to which it poses emotion-focused versus problem-focused coping demands for the individual. This theme is explored in examination of research in five essential areas: (a) effectiveness of problem- versus emotion-focused coping strategies, (b) effectiveness of interventions, (c) the role of individual difference variables, (d) timing of interventions, and (e) evaluation of treatment impact.
TL;DR: The trans-activator vir is required for expression of all virulence-associated genes in Bordetella pertussis and the nature of the global regulation of these factors by vir and environmental signals was examined by Northern blot analysis and with beta-galactosidase transcriptional fusions in five vir-regulated genes.
Abstract: The trans-activator vir is required for expression of all virulence-associated genes in Bordetella pertussis The nature of the global regulation of these factors by vir and environmental signals was examined by Northern blot analysis and with beta-galactosidase transcriptional fusions in five vir-regulated genes Northern blots suggested that vir regulates at the level of transcription since Vir- organisms did not exhibit detectable mRNA from vir-regulated loci Environmental signals such as high levels of salts, nicotinic acid, and 6-chloronicotinic acid or growth at low temperatures were examined Of all of the cations and anions examined, only SO4 ions eliminated transcription of vir-regulated genes and reduced transcription of vir itself, suggesting that global regulation is obtained by modifying expression of the essential component, vir Organisms grown on 6-chloronicotinic acid or quinaldic acid did not have detectable transcription from vir-regulated loci Modulation by nicotinic acid, on the other hand, was strain dependent, acting at the level of transcription in strain 18-323 but not in Tohama I derivatives Growth at lower temperatures reduced, but did not eliminate, transcription from vir-regulated loci At 28 degrees C the ratio of pertussis toxin mRNA to recA mRNA (a non-vir-regulated factor) was equivalent to that at 37 degrees C, suggesting that transcription at low temperatures is reduced in a proportional manner and need not involve vir
TL;DR: The results of this study indicate that the addition of silane coated glass fiber to BIS-GMA resin increased the elastic modulus, tensile and compressive strengths compared with non-treated fibers.
Abstract: The use of short glass fibers as a filler for dental restorations or cement resins have not been examined extensively. The mechanical properties and untreated glass fibers (5 microns dia x 25 microns) in Bis-phenol A glycidyl methacrylate (BIS-GMA) diluted with triethylene-glycol dimethacrylate (TEGDMA) resin were investigated for possible use as a restorative dental composite or bone cement. Compression, uniaxial tension and fracture toughness tests were conducted for each filler composite mixtures of 40, 50, 60 and 70%. Set time and maximum temperature of polymerization were determined. The results show that the elastic modulus, tensile strength and compressive strength are dependent on the percent of filler content. Elastic modulus and compressive yield (0.2%) strength of silane treated glass fibers filled composite increased from 2.26 to 4.59 GPa and 43.3 to 66.6 MPa, respectively, wtih increasing the filler content while the tensile strength decreased from 26.7 to 18.6 MPa. The elastic modulus of the untreated composite was less than that of the silane treated fiber composite. The tensile strength and compressive strengths were 20 to 50% lower than those of silane treated composites. The fracture toughness of the silane treated glass fiber additions were not significantly different from the untreated additions. The highest fracture toughness was obtained at 50% filler content with 1.65 MPa m.5. Set time increased from 3.5 to 7.7 minutes with increased filler content and peak temperature dropped from 68.3 to 34 degrees C. The results of this study indicate that the addition of silane coated glass fiber to BIS-GMA resin increased the elastic modulus, tensile and compressive strengths compared with non-treated fibers. The addition of either treated or non-treated fibers increased the set time of the material and decreased the maximum temperature.
01 Jan 1989
TL;DR: The literature prior to 1916 has been reviewed exhaustively by Walker (1916) in his systematic account of the effects of radiant energy upon the eye as discussed by the authors, and it has been shown that the visible portion of the solar spectrum was responsible for solar retinitis and/or eclipse blindness.
Abstract: The literature prior to 1916 has been reviewed exhaustively by Walker (1916) in his systematic account of the effects of radiant energy upon the eye Birch-Hirschfeld (1912) had postulated that the visible portion of the solar spectrum was responsible for solar retinitis and/or eclipse blindness and that the effects of sunlight on the retina were abiotic in nature However, his opinions were contested by Verhoeff and Bell (1916), who produced what they considered incontrovertible evidence that solar retinitis and/or eclipse blindness resulted from thermal effects on the retina
TL;DR: The vertical distribution of invertebrates (>0.053 mm) was studied in a sandy-bottomed, first-order stream on the Coastal Plain of Virginia, U.S.A. as discussed by the authors.
Abstract: SUMMARY. 1 The vertical distribution of invertebrates (>0.053 mm) was studied in a sandy-bottomed, first-order stream on the Coastal Plain of Virginia, U.S.A. Invertebrate species composition, abundance and bio-mass were determined monthly over one year at sediment depth intervals of 0–1, 1–5, 5–15,15–30 and 30–40 cm.
2. The subsurface community was numerically dominated by species of Chironomidae, Nematoda and Crustacea, while much of the biomass was due to early instars of several species of Trichoptera.
3. Invertebrate density and biomass decreased significantly with depth in the substrate (ANOVA; P<0.05). Annual mean density decreased from 1,346,844 individuals m−3 at the surface to 13,578 individuals m−3 at 15–30 cm. Annual mean biomass decreased from 66.30 g m−3 at the surface to 0.44 g m−3 at 15–30 cm.
4. Dissolved oxygen decreased markedly from the surface to the 5 cm depth in the substrate, anaerobic conditions often occurring below 10 cm. Density and biomass both showed a significant positive relationship with dissolved oxygen concentration (Linear regression; P<0.05).
5. Physical forces were important in structuring the subsurface invertebrate community. Besides low dissolved oxygen concentration, sediment scouring resulting from storm discharge dramatically reduced density and biomass
TL;DR: In this article, the effects of the local environment on the electronic structure and magnetic moments of Fe, Co, and Ni have been studied by confining these atoms to assume various structural forms such as chains, surfaces, layers, and crystals.
Abstract: The effects of the local environment on the electronic structure and magnetic moments of Fe, Co, and Ni have been studied by confining these atoms to assume various structural forms such as chains, surfaces, layers, and crystals. The coordination number of the atoms can thus be changed over a wide range. The local environment of the magnetic atom has also been altered by introducing defects such as impurities, vacancies, and vacancy complexes. A simple method based upon the real space was devised that enables us to calculate the electronic structure of perfect as well as imperfect systems with speed and accuracy. The method is based upon a cross between the molecular-cluster and the tight-binding theories and contains no adjustable parameters. The effect on the magnetic moments due to vacancies, vacancy clusters, and surface relaxations in Fe are studied to illustrate the versatility of the method. The results in chains, slabs, and bulk are compared with earlier theoretical results, as well as available experimental data. The excellent agreement achieved in these comparisons provides room for optimism that our theory can be useful in studying complex systems otherwise inaccessible to modern-day theories.
TL;DR: The evidence suggests that by altering the bioavailability of the above-listed neuroregulators, nicotine serves as a pharmacological "coping response", providing immediate though temporary improvement in affect or performance in response to environmental demands.
TL;DR: Evidence is presented to support the idea that the specific sequence and conformation (secondary structural features) of the processing recognition site within the precursor protein likely contribute in large part to the basis for limited endoproteolysis.
TL;DR: Mutants of Bordetella pertussis deficient in virulence-associated factors were identified by using the transposon Tn5 lac which generates promoter fusions for beta-galactosidase and revealed seven of the eight unidentified mutations mapped to different restriction fragments, which suggests that they could be deficient in as many as seven different genes.
Abstract: Mutants of Bordetella pertussis deficient in virulence-associated factors were identified by using the transposon Tn5 lac. Tn5 lac is a derivative of Tn5 which generates promoter fusions for beta-galactosidase. Tn5 lac insertions in the vir-regulated genes of B. pertussis were identified by selecting for kanamycin-resistant mutants that expressed beta-galactosidase when the vir-regulated genes were expressed but not when the vir-regulated genes were turned off. Fourteen different mutations in vir-regulated genes were identified. Two mutants were deficient in the production of the filamentous hemagglutinin, two mutants were deficient in the production of adenylate cyclase toxin and hemolysin, and one mutant was deficient in the production of dermonecrotic toxin. One insertion mapped adjacent to the pertussis toxin gene, but the mutant produced pertussis toxin. The phenotypes of the remaining eight mutants were not determined, but the mutants did not appear to be deficient in the production of the 69,000-dalton outer membrane protein (agglutinogen 3) or the capsule. Screening for mutations in either of the fimbrial genes proved to be problematic since the parental strain was found to switch from a fimbriated to a nonfimbriated state at a high frequency, which was suggestive of the metastable expression of pili in other bacteria. We used Southern blot analysis with a 30-mer specific for the fimbrial sequences. No bands with the predicted increase in size due to the 12 kilobases from Tn5 lac were observed, which suggests that none of these genes were mutated. Southern blot analysis also revealed that seven of the eight unidentified mutations mapped to different restriction fragments, which suggests that they could be deficient in as many as seven different genes.
TL;DR: Results indicate that all groups of individuals, regardless of their primary disability, benefited significantly from supported employment participation and that the individual placement model generated employment outcomes superior to those resulting from group employment options, particularly work crews.
Abstract: Although recent federal legislation has led to a proliferation of supported employment programs throughout the country, little information is available that documents the success of these programs. In the present study, we examined the effect of different consumer characteristics and alternative supported employment service delivery models on key employment outcomes including hourly wage, hours worked per week, increase in earnings after supported employment participation, and level of integration on the job. The employment outcomes of a sample of 1,550 individuals receiving supported employment services through 96 local programs in eight states were analyzed to determine the effects of the key independent variables of primary disability and type of employment model. Results indicate that all groups of individuals, regardless of their primary disability, benefited significantly from supported employment participation. Further, data indicate that the individual placement model generated employment outcomes superior to those resulting from group employment options, particularly work crews. Implications of the results for future program development activities are discussed.
TL;DR: In this paper, the authors examined the effect of three different product structures on the performance of selected priority dispatching rules in a six-machine assembly job shop and found that significant relationships exist between the structure of the product bill of materials and the prioritization rule, and that specific rules are indeed better suited to certain product structures.
Abstract: SUMMARY Single-stage job-shop scheduling has received a great deal of attention in the published literature. Significantly less research has been done in the area of assembly job shops. With the onslaught of MRP implementations designed to plan and control assembly job shops, practitioners have been confronted head-on with the need to improve dispatching procedures. This paper examines the effect of three different product structures on the performance of selected priority dispatching rules in a six-machine assembly job shop. Results indicate that significant relationships exist between the structure of the product bill of materials and the priority dispatching rule, and that specific rules are indeed better suited to certain product structures.
TL;DR: The authors have identified a difficulty in the implementation of N-version programming, called the consistent comparison problem, which arises for applications in which decisions are based on the results of comparing finite-precision numbers.
Abstract: The authors have identified a difficulty in the implementation of N-version programming. The problem, called the consistent comparison problem, arises for applications in which decisions are based on the results of comparing finite-precision numbers. It is shown that when versions make comparisons involving the results of finite-precision calculations, it is impossible to guarantee the consistency of their results. It is therefore possible that correct versions may arrive at completely different outputs for an application that does not apparently have multiple correct solutions. If this problem is not dealt with explicitly, an N-version system may be unable to reach consensus even when none of its component versions falls. >
TL;DR: It is suggested that FTF activity contributes to the pathogenicity of S. mutans V403, possibly by generating extracellular fructans which serve as storage compounds.
Abstract: The Streptococcus mutans extracellular fructosyltransferase (FTF) enzyme may play a role in the formation of dental caries by synthesizing a fructan polymer that serves as an extracellular storage polysaccharide. We sought to determine if an FTF-deficient strain of S. mutans was less virulent than wild-type cells in a rat animal model system. Cloned ftf gene sequences from S. mutans GS5 were used to generate a defective copy of the ftf gene by inserting into the ftf coding region a DNA fragment which encoded erythromycin resistance. The plasmid which carried the defective ftf construct was introduced into S. mutans V403 by using genetic transformation. This defective construct replaced, by allelic exchange, the wild-type copy of the ftf gene carried on the V403 chromosome. FTF activity assays indicated that the recombinant strain, V1741, was deficient in fructan synthesis. However, extracellular protein preparations from this strain displayed an increased ability to generate glucose polymers (glucans) compared with V403 preparations. Levels of adherence to glass and rat tooth surfaces by strain V1741 were similar to those of the V403 strain. Both strains caused moderate decay on rat tooth surfaces; however, the FTF-deficient strain was less pathogenic compared with the wild-type strain. These results suggest that FTF activity contributes to the pathogenicity of S. mutans V403, possibly by generating extracellular fructans which serve as storage compounds.
TL;DR: Choi et al. as mentioned in this paper proposed and investigated the approach in trials for comparing the means of two normal populations, and the results indicate that the predictive probability can be a useful conservative measure in monitoring trials.
Abstract: At a given point in a clinical trial, investigators may ask the question: "What is the likelihood of a significant result if the trial were continued?" One possible answer to this question is to examine a predictive probability of the significant difference with further patient accrual. [See, for example, Choi, Smith, and Becker (1985, Controlled Clinical Trials 6, 280-288).] This paper proposes and investigates the approach in trials for comparing the means of two normal populations. Two methods for calculating the predictive probability are examined. The results indicate that the predictive probability can be a useful conservative measure in monitoring trials.