Showing papers by "University of Minnesota published in 1989"

State-space solutions to standard H/sub 2/ and H/sub infinity / control problems

Abstract: Simple state-space formulas are derived for all controllers solving the following standard H/sub infinity / problem: For a given number gamma >0, find all controllers such that the H/sub infinity / norm of the closed-loop transfer function is (strictly) less than gamma . It is known that a controller exists if and only if the unique stabilizing solutions to two algebraic Riccati equations are positive definite and the spectral radius of their product is less than gamma /sup 2/. Under these conditions, a parameterization of all controllers solving the problem is given as a linear fractional transformation (LFT) on a contractive, stable, free parameter. The state dimension of the coefficient matrix for the LFT, constructed using the two Riccati solutions, equals that of the plant and has a separation structure reminiscent of classical LQG (i.e. H/sub 2/) theory. This paper is intended to be of tutorial value, so a standard H/sub 2/ solution is developed in parallel. >

Validating instruments in MIS research

Abstract: Calls for new directions in MIS research bring with them a call for renewed methodological rigor. This article offers an operating paradigm for renewal along dimensions previously unstressed. The basic contention is that confirmatory empirical findings will be strengthened when instrument validation precedes both internal and statistical conclusion validity and that, in many situations, MIS researchers need to validate their research instruments. This contention is supported by a survey of instrumentation as reported in sample IS journals over the last several years. A demonstration exercise of instrument validation follows as an illustration of some of the basic principles of validation. The validated instrument was designed to gather data on the impact of computer security administration on the incidence of computer abuse in the U.S.A.

An Instrument for Measuring the Critical Factors of Quality Management

Abstract: Much has been written about how quality should be managed in an organization. The quality literature contains many case studies of successful companies and descriptions of quality concepts and quality improvement programs. To date, however, there has been no systematic attempt to organize and synthesize the various prescriptions offered, nor have measures of organizational quality management been proposed for areas such as top management leadership, training, employee involvement, and supplier management. While many organizations collect quality data such as defect rates, error rates, rework cost, and scrap cost, these are not measures of organization-wide quality management. This paper provides a synthesis of the quality literature by identifying eight critical factors (areas) of quality management in a business unit. Operational measures of these factors are developed using data collected from 162 general managers and quality managers of 89 divisions of 20 companies. The measures can be used individually or in concert to produce a profile of organization-wide quality practices. The measures are found to be both valid and reliable. Such measures could be used by decision makers in an organization to assess the status of quality management in order to direct improvements in the quality area. Researchers can use such measures to better understand quality management practice and to build theories and models that relate the critical factors of quality management to the organization's quality environment and quality performance.

Finite-temperature field theory

Abstract: In relativistic theories particle number is not conserved (although both lepton and baryon number are). Therefore when discussing the thermodynamics of a quantum field theory one uses the grand canonical formalism: the entropy S is maximised, keeping fixed the ensemble averages E and N of energy and lepton or baryon number. To implement these constraints two Lagrange multipliers are introduced, beta =1/kT and mu the chemical potential.

The effect of price, brand name, and store name on buyers' perceptions of product quality: An integrative review.

Abstract: The authors integrate previous research that has investigated experimentally the influence of price, brand name, and/or store name on buyers’ evaluations of product quality. The meta-analysis sugge...

Using Paradox to Build Management and Organization Theories

Abstract: Most contemporary theory construction methodologies attempt to build internally consistent theories of limited scope. Relatively little attention has been paid to the opportunities offered by tensions, oppositions, and contradictions among explanations of the same phenomenon. This essay attempts to spell out a set of theory-building strategies to help researchers take advantage of theoretical tensions. Such tensions can be regarded as paradoxes of social theory, and four different modes of working with paradoxes can be distinguished: (1) accept the paradox and use it constructively; (2) clarify levels of analysis; (3) temporally separate the two levels; and (4) introduce new terms to resolve the paradox. These four modes of paradox resolution are illustrated by application to the action:.-structure paradox in organizational theory.

Serum cholesterol levels and six-year mortality from stroke in 350,977 men screened for the multiple risk factor intervention trial

Abstract: We examined the relation between the serum total cholesterol level and the risk of death from stroke during six years of follow-up in 350,977 men, 35 to 57 years of age, who had no history of heart attack and were not currently being treated for diabetes mellitus. The diagnosis of stroke and the type of stroke were obtained from death certificates. Using proportional-hazards regression to control for age, cigarette smoking, diastolic blood pressure, and race or ethnic group, we found that the six-year risk of death from intracranial hemorrhage (International Classification of Diseases, ninth edition [ICD-9], categories 431 and 432) was three times higher in men with serum cholesterol levels under 4.14 mmol per liter (160 mg per deciliter) than in those with higher cholesterol levels (P = 0.05 by omnibus test across five cholesterol levels). On the other hand, a positive association was observed between the serum cholesterol level and death from nonhemorrhagic stroke (P = 0.007). The inverse association of the serum cholesterol level with the risk of death from intracranial hemorrhage was confined to men with diastolic blood pressure greater than or equal to 90 mm Hg, in whom death from intracranial hemorrhage is relatively common. We conclude that there is an inverse relation between the serum cholesterol level and the risk of death from hemorrhagic stroke in middle-aged American men, but that its public health impact is overwhelmed by the positive association of higher serum cholesterol levels with death from nonhemorrhagic stroke and total cardiovascular disease (ICD-9 categories 390 through 459).

Familial clustering of diabetic kidney disease. Evidence for genetic susceptibility to diabetic nephropathy

Abstract: Diabetic nephropathy develops in less than half of all patients with diabetes. To study heredity as a possible risk factor for diabetic kidney disease, we examined the concordance rates for diabetic nephropathy in two sets of families in which both probands and siblings had diabetes mellitus. In one set, the probands (n = 11) had no evidence of diabetic nephropathy, with normal creatinine clearance and a urinary albumin excretion rate below 45 mg per day. In the other set, the probands (n = 26) had undergone kidney transplantation because of diabetic nephropathy. Evidence of nephropathy was found in 2 of the 12 diabetic siblings of the probands without nephropathy (17 percent). Of the 29 diabetic siblings of probands with diabetic nephropathy, 24 (83 percent) had evidence of nephropathy (P less than 0.001), including 12 with end-stage renal disease. No significant differences were noted between the sibling groups with respect to the duration of diabetes, blood pressure, glycemic control, or glycosylated hemoglobin levels. Logistic regression analysis found nephropathy in the proband to be the only factor significantly predictive of the renal status of the diabetic sibling. We conclude that diabetic nephropathy occurs in familial clusters. This is consistent with the hypothesis that heredity helps to determine susceptibility to diabetic nephropathy. However, this study cannot rule out the possible influences of environmental factors shared by siblings.

Organization-Based Self-Esteem: Construct Definition, Measurement, And Validation

Abstract: The article introduces the construct “organization-based self-esteem” and its measurement. We developed a partial nomological network resulting in a set of hypotheses that guided efforts to validat...

Computability in analysis and physics

Abstract: This book represents the first treatment of computable analysis at the graduate level within the tradition of classical mathematical reasoning. Among the topics dealt with are: classical analysis, Hilbert and Banach spaces, bounded and unbounded linear operators, eigenvalues, eigenvectors, and equations of mathematical physics. The book is self-contained, and yet sufficiently detailed to provide an introduction to research in this area.

Neurobehavioral aspects of affective disorders.

Abstract: A PSYCHOLOGICAL PERS PECTIVE ON THE NEUROBIOLOGY OF AFFECTIVE DISORDERS . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . 457 DOPAMINE FUNCTIONING, BEHAVIORAL FACILITATION, AND B I POLAR AFFECTIVE DISORDERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . 458 The Behavioral Facilitation System . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 458 Neurobiology of the Behavioral Facilitation System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 462 Implications for Bipolar Affective Disorders . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . 471 BRAIN IMAGING AND THE MAJOR AFFECTIVE DISORDERS. . . . . . . . . . . . . . . . . . . . . . . 476 Overview of Imaging Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 477 CT Scan Studies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 481 PET and MRI Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . 484 Conclusion . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 486 FINAL REMARKS . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . 487

The Empire of Chance: How Probability Changed Science and Everyday Life

Abstract: The Empire of Chance tells how quantitative ideas of chance transformed the natural and social sciences, as well as daily life over the last three centuries. A continuous narrative connects the earliest application of probability and statistics in gambling and insurance to the most recent forays into law, medicine, polling and baseball. Separate chapters explore the theoretical and methodological impact in biology, physics and psychology. Themes recur - determinism, inference, causality, free will, evidence, the shifting meaning of probability - but in dramatically different disciplinary and historical contexts. In contrast to the literature on the mathematical development of probability and statistics, this book centres on how these technical innovations remade our conceptions of nature, mind and society. Written by an interdisciplinary team of historians and philosophers, this readable, lucid account keeps technical material to an absolute minimum. It is aimed not only at specialists in the history and philosophy of science, but also at the general reader and scholars in other disciplines.

Provocation of bradycardia and hypotension by isoproterenol and upright posture in patients with unexplained syncope.

Abstract: Neurally mediated hypotension and bradycardia are believed to be common causes of syncope. We used the "upright-tilt test" (duration, less than or equal to 10 minutes) with or without an infusion of exogenous catecholamine (isoproterenol [1 to 5 micrograms per minute], given intravenously) to elicit bradycardia, hypotension, or both in 24 patients with recurrent syncope and in 18 control subjects. A conventional electrophysiologic test performed before the tilt test was positive in 9 of the 24 patients, revealing arrhythmias that may have caused recurrent syncope, but was negative and thus nondiagnostic in 15 patients. The tilt test alone (i.e., without isoproterenol) induced symptomatic bradycardia or hypotension in 1 of the 9 patients with positive electrophysiologic tests (11 percent), 4 of the 15 patients with negative electrophysiologic tests (27 percent), and none of the controls. When the isoproterenol infusion was administered during the tilt test, 9 of the 11 patients with negative electrophysiologic and tilt tests had syncope, marked slowing of the heart rate, and hypotension. In contrast, isoproterenol was associated with tachycardia and only a slight decline in arterial pressure in the 8 remaining patients with positive electrophysiologic tests and the 18 control subjects, and syncope developed in only 1 of the 8 patients with positive electrophysiologic tests and negative tilt tests (13 percent) and 2 of the 18 control subjects (11 percent). We conclude that an isoproterenol infusion administered in conjunction with the upright-tilt test may be useful for identifying susceptibility to neurally mediated recurrent syncope.

Job Satisfaction: Environmental and Genetic Components

Abstract: Monozygotic twins reared apart from an early age were used to test the hypothesis that there is a significant genetic component to job satisfaction. Thirty-four monozygotic twin pairs who had been reared apart completed the Minnesota Job Satisfaction Questionnaire as part of a comprehensive work-history assessment. Three subscales were formed from the job satisfaction items to reflect intrinsic, extrinsic, and general satisfaction with the current (or major) job. Intraclass correlations were computed to estimate the proportion of observed variability resulting from genetic factors for all job satisfaction items and for the three subscales. Resulting values indicated that approximately 30% of the observed variance in general job satisfaction was due to genetic factors. Additional analysis indicated that these results obtained even when job characteristics such as complexity, motor skill requirements, and the physical demands were held constant via partialing methods. Finally, the data indicated significant heritabilities for several of these job characteristics, which is consistent with the hypothesis of a genetic disposition to seek and remain in similar environments (jobs). Implications of these findings for theories of job satisfaction, selection, and job enrichment are discussed.

Onset of superconductivity in the two-dimensional limit.

Abstract: The onset of superconductivity in homogeneous ultrathin films is found to occur when their normal-state sheet resistance falls below a value close to h/4${e}^{2}$, the quantum resistance for pairs. The data further suggest that in the T\ensuremath{\rightarrow}0 limit such films are either superconducting or insulating. The existence of a threshold in systems which are not granular implies that its explanation involves more general arguments than those which follow from the modeling of films by Josephson-coupled arrays.

Sensorimotor representations for pointing to targets in three-dimensional space

Abstract: 1. The accuracy with which subjects pointed to targets in extrapersonal space was assessed under a variety of experimental conditions. 2. When subjects pointed in the dark to remembered target locations, they made substantial errors. Errors in distance, measured from the shoulder to the target, were sometimes as much as 15 cm. Errors in direction, also measured from the shoulder, were smaller. 3. An analysis of the information transmitted by the location of the subject's finger about the location of the target showed that the information about the target's distance was consistently lower than the information about its direction. 4. The errors in distance persisted when subjects had their arm in view and pointed in the light to remembered target locations. 5. The errors were much smaller when subjects used a pointer to point to the target or when they were asked to reproduce the position of their finger after it had been passively moved to the target. 6. From these findings we conclude that subjects have a reasonably accurate visual representation of target location and are able to effectively use kinesthetically derived information about target location. We therefore suggest that errors in pointing result from errors in the sensorimotor transformation from the visual representation of the target location to the kinematic representation of the arm movement.

Nothing Is Quite So Practical as a Good Theory

Abstract: A central mission of scholars and educators in professional schools of management, health, education, and social work is to conduct research that contributes knowledge to a scientific discipline, on the one hand, and to apply that knowledge to the practice of management as a profession, on the other (Simon, 1967). To do this well, we need to design our research so that it provides an intimate understanding of the practical problems facing the profession. Equally important, we need to appreciate and strengthen our skills in developing good theory so that research conducted about these problems will advance the knowledge that is relevant to both the discipline and the profession. Lewin's (1945) statement that "nothing is so practical as a good theory" captures a theme that is as important today as it was in Lewin's time. Good theory is practical precisely because it advances knowledge in a scientific discipline, guides research toward crucial questions, and enlightens the profession of management. This spec...

Foreign Affairs and Issue Voting: Do Presidential Candidates “Waltz Before a Blind Audience?”.

Abstract: VWhile candidates regularly spend much time and effort campaigning on foreign and defense policies, the thrust of prevailing scholarly opinion is that voters possess little information and weak attitudes on these issues, which therefore have negligible impact on their voting behavior. We resolve this anomaly by arguing that public attitudes on foreign and defense policies are available and cognitively accessible, that the public has perceived clear differences between the candidates on these issues in recent elections, and that these issues have affected the public's vote choices. Data indicate that these conclusions are appropriate for foreign affairs issues and domestic issues.

Validity and Reliability of Short Physical Activity History: Cardia and the Minnesota Heart Health Program

Abstract: Validity and reliability of a short physical activity history were assessed in two studies. Validity was studied in 2766 women and 2303 men, participants in CARDIA, a biracial study. Ages ranged from 18 to 30 years. The activities performed in the past 12 months by ≥ 50 per cent of participants were

A randomized, placebo-controlled trial of oral acyclovir for the prevention of cytomegalovirus disease in recipients of renal allografts

Abstract: Cytomegalovirus is a major viral pathogen in patients who undergo renal transplantation, and cytomegalovirus disease is difficult to treat. We therefore conducted a randomized, placebo-controlled, double-blind trial of acyclovir for the prevention of cytomegalovirus disease in recipients of renal allografts from cadavers. Acyclovir was given orally in doses of 800 to 3200 mg per day, according to the patients' estimated level of renal function. Patients took the first dose of either acyclovir or placebo six hours before transplantation and continued to take the assigned medication for 12 weeks. Of 118 patients enrolled in the study, 104 completed at least 30 days on the study medication and were included in our analysis of the results. During the first year after transplantation, 4 of 53 patients (7.5 percent) in the acyclovir group had symptomatic cytomegalovirus disease, as compared with 15 of 51 (29 percent) in the placebo group (P = 0.002). There was a single case of cytomegalovirus pneumonia in the acyclovir group, as compared with nine in the placebo group. The greatest prophylactic benefit of acyclovir was observed among seronegative patients who had received a kidney from a seropositive donor; only one of six such patients in the acyclovir group had cytomegalovirus disease, as compared with all seven in the placebo group. Acyclovir decreased the incidence of documented cytomegalovirus infection (with or without symptomatic disease) to 36 percent from 61 percent among the patients who received the placebo (P = 0.011). Among the patients who received acyclovir, the rates of recovery of virus from the blood and urine were significantly reduced, but the rate of viral shedding from the pharynx was not significantly different from that in the placebo group. There were no differences between the groups in the frequency of adverse events or in the rate of survival of either grafts or patients. We conclude that the oral administration of acyclovir, beginning before the transplantation of a renal allograft from a cadaver, reduces the rate of cytomegalovirus infection and disease without affecting the survival rate of either grafts or patients.

Mesangial Expansion as a Central Mechanism for Loss of Kidney Function in Diabetic Patients

Abstract: Diabetic nephropathy leading to kidney failure is a major complication of both type I (insulin-dependent) and type II (non-insulin-dependent) diabetes mellitus, and glomerular structural lesions (especially expansion of the mesangium) may constitute the principal cause of decline in kidney function experienced by a significant fraction of diabetic patients. Although the biochemical bases of these mesangial abnormalities remain unknown, an understanding of the natural history of diabetic nephropathy from a combined structural and functional approach can lead to greater pathophysiological insight. Work in animals has supported the concept that the metabolic disturbances of diabetes mellitus cause diabetic nephropathy, with structural and functional lesions prevented or reversed with improved or normalized glycemic control. Additional research must address this fundamental issue in humans, especially the response of advancing mesangial lesions to improved glycemic control. Factors not directly related to the metabolic perturbations of diabetes may serve to accelerate or diminish the pathophysiological processes of diabetic nephropathy. The elucidation and management of these factors, when coupled with improved glycemic control, may moderate the development or progression of diabetic kidney lesions in humans.