Showing papers by "University of Minnesota published in 1991"
TL;DR: It is found that these pseudopotentials are extremely efficient for the cases where the plane-wave expansion has a slow convergence, in particular, for systems containing first-row elements, transition metals, and rare-earth elements.
Abstract: We present a simple procedure to generate first-principles norm-conserving pseudopotentials, which are designed to be smooth and therefore save computational resources when used with a plane-wave basis. We found that these pseudopotentials are extremely efficient for the cases where the plane-wave expansion has a slow convergence, in particular, for systems containing first-row elements, transition metals, and rare-earth elements. The wide applicability of the pseudopotentials are exemplified with plane-wave calculations for copper, zinc blende, diamond, \ensuremath{\alpha}-quartz, rutile, and cerium.
13,174 citations
1,377 citations
TL;DR: Two representative molecular architectures, binary linear homopolymer mixtures and diblock copolymers, exhibiting macrophase separation and microphase segregation, respectively, are examined in some detail.
Abstract: Different polymers can be combined into a single material in many ways, which can lead to a wide range of phase behaviors that directly influence the associated physical properties and ultimate applications. Four factors control polymer-polymer phase behavior: choice of monomers, molecular architecture, composition, and molecular size. Current theories and experiments that deal with the equilibrium thermodynamics and non-equilibrium dynamics of polymer mixtures are described in terms of these experimentally accessible parameters. Two representative molecular architectures, binary linear homopolymer mixtures and diblock copolymers, exhibiting macrophase separation and microphase segregation, respectively, are examined in some detail. Although these model systems are fairly well understood, a myriad of mixing scenarios, with both existing and unrealized materials applications, remain unexplored at a fundamental level.
1,332 citations
TL;DR: This review summarizes the virtual explosion of information regarding the epidemiology, biochemistry, mechanisms of action, and genetic basis of these urovirulence factors that has occurred in the past decade and identifies areas in need of further study.
Abstract: Uropathogenic strains of Escherichia coli are characterized by the expression of distinctive bacterial properties, products, or structures referred to as virulence factors because they help the organism overcome host defenses and colonize or invade the urinary tract. Virulence factors of recognized importance in the pathogenesis of urinary tract infection (UTI) include adhesins (P fimbriae, certain other mannose-resistant adhesins, and type 1 fimbriae), the aerobactin system, hemolysin, K capsule, and resistance to serum killing. This review summarizes the virtual explosion of information regarding the epidemiology, biochemistry, mechanisms of action, and genetic basis of these urovirulence factors that has occurred in the past decade and identifies areas in need of further study. Virulence factor expression is more common among certain genetically related groups of E. coli which constitute virulent clones within the larger E. coli population. In general, the more virulence factors a strain expresses, the more severe an infection it is able to cause. Certain virulence factors specifically favor the development of pyelonephritis, others favor cystitis, and others favor asymptomatic bacteriuria. The currently defined virulence factors clearly contribute to the virulence of wild-type strains but are usually insufficient in themselves to transform an avirulent organism into a pathogen, demonstrating that other as-yet-undefined virulence properties await discovery. Virulence factor testing is a useful epidemiological and research tool but as yet has no defined clinical role. Immunological and biochemical anti-virulence factor interventions are effective in animal models of UTI and hold promise for the prevention of UTI in humans. Images
1,290 citations
TL;DR: In this article, the determinants of organizational risk taking and its impact on economic performance are critical issues in strategic management using a model that included risk, performance, performance expecta, and expectation.
Abstract: The determinants of organizational risk taking and its impact on economic performance are critical issues in strategic management. Using a model that included risk, performance, performance expecta...
1,262 citations
TL;DR: The epidemiologic literature on the relationship between vegetable and fruit consumption and human cancer at a variety of sites is reviewed systematically and it is concluded that consumption of higher levels of vegetables and fruit is associated consistently, although not universally, with a reduced risk of cancer at most sites.
Abstract: The epidemiologic literature on the relationship between vegetable and fruit consumption and human cancer at a variety of sites is reviewed systematically. A total of 13 ecologic studies, nine cohort studies, and 115 case-control studies are included. Cancer of all sites, cancers of lung, breast, colon, rectum, esophagus, larynx, oral cavity and pharynx, stomach, pancreas, prostate, bladder, ovary, endometrium, cervix, and thyroid, as well as mesothelioma and gestational trophoblastic disease, are considered. Relevant data from clinical trials, animal, and in vitro studies are included. It is concluded that consumption of higher levels of vegetables and fruit is associated consistently, although not universally, with a reduced risk of cancer at most sites. The association is most marked for epithelial cancers--particularly those of the alimentary and respiratory tracts--and, currently, is weak to nonexistent for hormone-related cancers. The association exists for a wide variety of vegetables and fruit with some suggestion that raw forms are associated most consistently with lower risk. Possible mechanisms by which vegetable and fruit intake might alter risk of cancer and possible adverse effects of vegetable and fruit consumption will be considered in Part II of this review.
1,056 citations
TL;DR: Electroporation has found applications in introduction of plasmids or foreign DNA into living cells for gene transfections, fusion of cells to prepare heterokaryons, hybridoma, hybrid embryos, and constructing animal model by fusing human cells with animal tissues.
1,053 citations
TL;DR: Results of a laboratory experiment in which response times and verbal protocols were used to examine processes related to the evaluation of brand extensions showed that subjects’ attitudes toward brand extensions were correlated highly with their ratings of brand extension typicality.
Abstract: The authors explore the implications of considering a brand as representing a category consisting of its products. They report results of a laboratory experiment in which response times and verbal ...
890 citations
McGill University1, Massachusetts Institute of Technology2, University of Minnesota3, Oregon Health & Science University4, French Institute of Health and Medical Research5, Necker-Enfants Malades Hospital6, University of Washington7, Stony Brook University8, Children's Memorial Hospital9, Harvard University10
TL;DR: Analysis of coding exons of the Wilms' tumor suppressor gene (WT1) for germline mutations provides evidence of a direct role for WT1 in Denys-Drash syndrome and thus urogenital system development.
876 citations
TL;DR: Although the mechanisms of the decreased endothelium-dependent responses in heart failure are not known, this impaired local vasodilation may contribute to characteristic of heart failure.
Abstract: BACKGROUNDEndothelial cells produce a number of substances, collectively termed endothelium-derived relaxing factor (EDRF), that promote local relaxation of vascular smooth muscle. Although studies have demonstrated defects in endothelium-dependent vasodilation in animal models of hypertension, atherosclerosis, and heart failure, there are only limited data from human subjects because of the difficulty in obtaining fresh vascular segments.METHODS AND RESULTSTo address the hypothesis that endothelium-dependent vasodilation is attenuated in patients with heart failure, we measured forearm blood flow responses to the intra-arterial administration of methacholine, a known stimulus of EDRF release through muscarinic receptors. In 14 normal subjects, a dosage range of methacholine increased forearm blood flow by 5.26 +/- 0.63, 10.50 +/- 0.63, and 13.22 +/- 0.86 ml/min/100 ml forearm volume (FAV); these responses were 1.98 +/- 0.46, 5.48 +/- 0.79, and 8.50 +/- 1.53 ml/min/100 ml FAV in 14 patients with heart fai...
791 citations
TL;DR: It was concluded that consumption of higher levels of vegetables and fruit is associated consistently, although not universally, with a reduced risk of cancer at most sites, and particularly with epithelial cancers of the alimentary and respiratory tracts.
Abstract: The epidemiologic literature on the relationship between vegetable and fruit consumption and human cancer at a variety of sites was reviewed systematically in Part I.1 It was concluded that consumption of higher levels of vegetables and fruit is associated consistently, although not universally, with a reduced risk of cancer at most sites, and particularly with epithelial cancers of the alimentary and respiratory tracts. Possible mechanisms by which vegetable and fruit intake might alter risk of cancer are addressed here. A large number of potentially anticarcinogenic agents are found in these food sources, including carotenoids, vitamins C and E, selenium, dietary fiber, dithiolthiones, glucosinolates and indoles, isothiocyanates, flavonoids, phenols, protease inhibitors, plant sterols, allium compounds, and limonene. These agents have both complementary and overlapping mechanisms of action, including the induction of detoxification enzymes, inhibition of nitrosamine formation, provision of substrate for formation of antineoplastic agents, dilution and binding of carcinogens in the digestive tract, alteration of hormone metabolism, antioxidant effects, and others. It appears extremely unlikely that any one substance is responsible for all the associations seen. Possible adverse effects of vegetable and fruit consumption are also examined. One way to consider the relationships reviewed here is to hypothesize that humans are adapted to a high intake of plant foods that supply substances crucial to the maintenance of the organism, but only some of which are currently called ‘essential nutrients.’ Cancer may be the result of reducing the level of intake of foods that are metabolically necessary—it may be a disease of maladaptation.
Centers for Disease Control and Prevention1, Johns Hopkins University2, University of Rochester3, Georgetown University4, University of Minnesota5, University of Pennsylvania6, Harvard University7, University of California, Los Angeles8, National Institutes of Health9, University of Pittsburgh10, Northwestern University11, University of California, San Diego12, World Health Organization13, University College London14, Columbia University15, Max Planck Society16
TL;DR: These definitions have been developed in conjunction with the International Classification of Diseases-10 (ICD-10, unpublished draft of the World Health Organization) and the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV, unpublishedDraft of the American Psychiatric Association) and are not identical.
Abstract: Infection with human immunodeficiency virus-type 1 (HIV-1) has been associated with avariety of neurologic disorders thought to be caused, directly or indirectly, by HIV-1.1-6 Although these disorders have been described clinically, there is no consensus terminology or criteria for diagnosis. To develop consensus nomenclature and case definitions for HIV-1-associated neurologic conditions for research purposes, the American Academy of Neurology AIDS Task Force convened a working group of neurologists, neuropsychologists, psychiatrists, and sociologists that included representatives of the American Neurological Association, the World Federation of Neurology, the International Neuropsychological Society, the National Academy of Neuropsychology, the American Psychological Association, the American Psychiatric Association, the World Health Organization, and the Centers for Disease Control (CDC). These definitions have been developed in conjunction with the International Classification of Diseases-10 (ICD-10, unpublished draft of the World Health Organization) and the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV, unpublished draft of the American Psychiatric Association). Although consistent with the ICD-10, the definitions are not identical. HIV-2 may cause similar disorders, but the neurologic manifestations of HIV-2 are unknown and are not addressed in this article.
TL;DR: It appears that internal effectiveness issues have made a strong comeback after being virtually ignored in 1986 and the rising importance of technology infrastructure issues is revealed as the field enters the 1990s.
Abstract: This three-round delphis urvey of senior IS executives is the third ain a series designed to determine the most critical issues in IS management. Analysis focuses on respondents' assessments of specific issues as well as emerging trends. Key findings include: (1) continued concern for traditional issues such as strategic planning and organizational alignment; (2) only six of the top issues from 1986 remained in the top 10; (3) one new issue, technology infrastructure, made the top 10: (4) three issues from previous studies rejoined the top 10-IS human resources, software development, and telecommunication systems; and (5) data-related issues now occupy the top two slots. This research reveals two important trends as the field enters the 1990s. First is the rising importance of technology infrastructure issues. Technology infrastructure issues now occupy three of the top 10 slots including the highest position. Second, it appears that internal effectiveness issues have made a strong comeback after being virtually ignored in 1986. IS human resources, software development, and the applications portfolio-issues that make up the core of the IS function-all increased in importance.
TL;DR: In this article, stabilized finite element formulations for incompressible flow computations are discussed, which involve two main sources of potential numerical instabilities associated with the Galerkin formulation of a problem.
Abstract: Publisher Summary This chapter discusses stabilized finite element formulations for incompressible flow computations. Finite element computation of incompressible flows involve two main sources of potential numerical instabilities associated with the Galerkin formulation of a problem. The stabilization techniques that are reviewed more extensively than others are the Galerkin/ least-squares (GLS), streamline-upwind/ Petrov–Galerkin (SUPG), and pressure-stabilizing/Petrov–Galerkin (PSPG) formulations. The SUPG stabilization for incompressible flows is achieved by adding to the Galerkin formulation a series of terms, each in the form of an integral over a different element. These integrals involve the product of the residual of the momentum equation and the advective operator acting on the test function. The natural boundary conditions are the conditions on the stress components, and these are the conditions assumed to be imposed at the remaining part of the boundary. The interpolation functions used for velocity and pressure are piecewise bilinear in space and piecewise linear in time. These computations involve no global coefficient matrices, and therefore need substantially less computer memory and time compared to noniterative solution of the fully discrete equations. It is suggested that for two-liquid flows, the solution and variational function spaces for pressure should include the functions that are discontinuous across the interface.
TL;DR: For systems containing a large number of atoms the computational load can be reduced if the pseudopotential operator is of a suitable form, such that it can be efficiently calculated in the position representation.
Abstract: We present an investigation of the computational requirements for the pseudopotential plane-wave method as a function of the number of atoms per unit cell. For systems containing a large number of atoms the computational load can be reduced if the pseudopotential operator is of a suitable form, such that it can be efficiently calculated in the position representation. The pseudopotentials examined here include local pseudopotentials, position-dependent electron-mass pseudopotentials, and separable nonlocal pseudopotentials.
01 Jan 1991
TL;DR: It is shown how the accuracy and convergence of integrals based on the Gibbs sample may be constructed, and how an estimate of the probability of the constraint set under the unrestricted distribution may be produced.
Abstract: John GewekeDepartment of EconomicsUniversity of MinnesotaMinneapolis, MN 55455First draft: April, 1991Phone: (612)625-7563 Fax: (612)624-0209E-mail: geweke@atlas.socsci.umn.eduAbstractThe construction and implementation of a Gibbs sampler for efficient simulation from thetruncated multivariate normal and Student-t distributions is described. It is shown how theaccuracy and convergence of integrals based on the Gibbs sample may be constructed, andhow an estimate of the probability of the constraint set under the unrestricted distributionmay be produced.Keywords: Bayesian inference; Gibbs sampler; Monte Carlo; multiple integration;truncated normalThis paper was prepared for a presentation at the meeting Computing Science and Statistics:the Twenty-Third Symposium on the Interface, Seattle, April 22-24, 1991. Researchassistance from Zhenyu Wang and financial support from National Science FoundationGrant SES-8908365 are gratefully acknowledged. The software for the examples may berequested by electronic mail, and will be returned by that medium.
TL;DR: In this paper, the authors explore the macroeconomic implications of including household production in an otherwise standard real business cycle model and find that introducing home production significantly improves the quantitative performance of the standard model along several dimensions.
Abstract: This paper explores some macroeconomic implications of including household production in an otherwise standard real business cycle model. We calibrate the model on the basis of macroeconomic evidence and long-run considerations, simulate it, and examine its statistical properties. We find that introducing home production significantly improves the quantitative performance of the standard model along several dimensions. It also implies a very different interpretation of the nature of aggregate fluctuations.
TL;DR: In an effort to define the origin of low back pain and sciatica, 193 patients were carefully studied using progressive local anesthesia and the results are discussed.
TL;DR: Conditions are given which guarantee that the stability, robustness, and performance properties of the fixed operating point designs carry over to the global gain scheduled design, such as the scheduling variable should “vary slowly.”
TL;DR: In this paper, an eight-stage cascade impactor with cut sizes ranging from 0.056 to 18 μm at a flow rate of 30 L/min was developed, calibrated, and tested in field programs.
Abstract: An eight-stage cascade impactor, with cut-sizes ranging from 0.056 to 18 μm at a flow rate of 30 L/min, has been developed, calibrated, and tested in field programs. This impactor, called a microorifice uniform deposit impactor, has several features not normally found in cascade impactors. Ultrafine particles as small as 0.056 μm are collected while keeping the pressure drop moderate by utilizing multiple nozzles (up to 2000) as small as 52 μm in diameter. At each stage the collected particles are deposited uniformly over the entire impaction plate by rotating the impaction plate relative to the nozzles and by the correct radial placement of the nozzles. The particle cutoff characteristics (collection efficiency curves) of each stage and interstage losses were determined by means of monodisperse aerosols. The cutoff characteristics were found to be sharp and similar for all stages. This is Publication No. 758 from the Particle Technology Laboratory.
TL;DR: It appears that the size distribution of condensed particles is determined kinetically rather than thermodynamically, and that slow condensation kinetics may be required to overcome the high activation energy of highly distorted DNA bends or kinks at the turning points of rods.
Abstract: DNA is generally found within viruses and cells in a tightly packaged state, typically occupying only 10(-4)-10(-6) of the volume of the uncondensed DNA wormlike coil. Condensation can be induced in vitro at low salt by the naturally occurring polyamines spermidine3+ and spermine4+, by hexammine cobalt(III), and even by Mg2+ in methanol-water mixtures. These condensates generally have an orderly, toroidal, or rodlike shape and size similar to that of DNA gently lysed from phage heads. It is also striking that the condensate size distribution is independent of DNA molecular length from 400 to 40,000 base pairs (bp), but that shorter DNA molecules (e.g., 150-bp mononucleosomal DNA) cannot condense in this fashion. We have constructed a successive association equilibrium theory to attempt to explain these results, using an equation devised by Tanford for micelle formation. Most of the obvious attractive and repulsive free energy contributions (mixing, bending, hydration, and other nearest-neighbor interactions) are linear in the amount of DNA incorporated, but the net attractive delta G0 grows nonlinearly because of the increasing average number of nearest neighbors of each duplex as the particle grows. In order that the size distribution have a maximum, a quadratic repulsive free energy is also required, arising from the electrostatic self-energy of the incompletely neutralized particles. The net attractive free energy per base pair interaction is tiny, on the order of 10(-3) kT. Despite the apparent generally correct order of magnitude of the various free energy terms, the calculated size distribution is smaller and narrower than observed experimentally. It appears that the size distribution of condensed particles is determined kinetically rather than thermodynamically. Very short DNA molecules cannot nucleate stable aggregates because they cannot develop adequate overlap, either internally or intermolecularly. A substantial fraction of rodlike condensates is observed in aqueous solutions only with a rather inefficient condensing agent, permethylated spermidine. This suggests that slow condensation kinetics may be required to overcome the high activation energy of highly distorted DNA bends or kinks at the turning points of rods. Evidence is reviewed that condensation may be associated with localized helix structure distortion provoked by condensing agents.
TL;DR: A portion of resilient behavior is the evaluative awareness of a difficult reality combined with a commitment to struggle, to conquer the obstacle, and to achieve one's goals despite the negative circumstances to which one has been exposed, which were and remain evocative of sadness.
Abstract: Functional adequacy (the maintenance of competent functioning despite an interfering emotionality) is a benchmark of resilient behavior under stress. While resilient adults can be identified as adults who once experienced a great deal of despair as children, I am not prepared to mark off the construct of resilience because such people may carry with them a realistic baggage of sadness and unhappiness. The very nature of despair that is present for children of the ghetto, the status of minority children in today's America, all have a reality that can neither be ignored or denied. Perhaps a portion of resilient behavior is the evaluative awareness of a difficult reality combined with a commitment to struggle, to conquer the obstacle, and to achieve one's goals despite the negative circumstances to which one has been exposed, which were and remain evocative of sadness.
TL;DR: Research suggesting that refugees are an at-risk population, making them especially suitable for public health interventions, is summarized, given its importance to prevention in refugee mental health.
Abstract: Primary prevention in refugee mental health requires information from clinical, health, and cross-cultural psychology. Primary prevention's roots are in public health, which is distinguished by a communitywide perspective for addressing mental health concerns. This article summarizes research suggesting that refugees are an at-risk population, making them especially suitable for public health interventions. Research on stress and acculturation is highlighted, given its importance to prevention in refugee mental health. The opportunities for primary prevention programs and policies at 3 levels (i.e., local community, national, and international) are illustrated with case examples from both the United States and Canada. Prevention at the international level is highlighted by a World Health Organization Mental Health Mission to camps on the Thai-Cambodian border.
TL;DR: In this article, a model is developed that explicates one process through which employee ownership operates, leading to a set of social-psychological and behavioral effects, where the formal ownership system is operationalized such that it leads to psychological ownership, a bonding or integration of the employee owner with the organization occurs.
Abstract: A model is developed that explicates one process through which employee ownership operates, leading to a set of social-psychological and behavioral effects. Where the formal ownership system is operationalized such that it leads to psychological ownership, a bonding or integration of the employee-owner with the organization occurs. It is through these processes that employee ownership exercises an influence upon group and individual outcomes. A set of antecedent and moderating variables to the operation of the formal ownership system is identified.
TL;DR: The findings suggest that poor mental development in stunted children is at least partly attributable to undernutrition.
Journal Article•
TL;DR: Like anti-CD28 mAb, autologous human APC appeared to stimulate a cyclosporine A-resistant pathway of T cell activation and suggest that the two signals required for IL-2 production by CD4+ T cells can be transduced by the TCR and CD28.
Abstract: CD4+ T cells require two signals to produce maximal amounts of IL-2, ie, TCR occupancy and an unidentified APC-derived costimulus Here we show that this costimulatory signal can be delivered by the T cell molecule CD28 An agonistic anti-CD28 mAb, but not IL-1 and/or IL-6, stimulated T cell proliferation by tetanus toxoid-specific T cells cultured with Ag-pulsed, costimulation-deficient APC Furthermore, the ability of B cell tumor lines to provide costimulatory signals to purified T cells correlated well with expression of the CD28 ligand B7/BB-1 Finally, like anti-CD28 mAb, autologous human APC appeared to stimulate a cyclosporine A-resistant pathway of T cell activation Together, these results suggest that the two signals required for IL-2 production by CD4+ T cells can be transduced by the TCR and CD28
TL;DR: In this paper, a developmental approach to the nature and functions of mother-child and father-child relationships is considered in connection with research findings from studies of middle-childhood and adolescent subjects and their parents.
TL;DR: In this paper, a stylized view of individual consumer choice decision-making is presented for the study of many marketing decisions, and the authors discuss whether consideration sets really exist and, if so, the factors that affect their composition, structure, and role in decision making.
Abstract: This paper affords a stylized view of individual consumer choice decision-making appropriate to the study of many marketing decisions. It summarizes issues relating to consideration set effects on consumer judgment and choice. It discusses whether consideration sets really exist and, if so, the factors that affect their composition, structure, and role in decision-making. It examines some new developments in the measurement and modeling of consideration set effects on decision-making. The paper concludes with suggestions for needed research.