Showing papers by "University of Rochester published in 1980"
TL;DR: In this article, observed stock return data are employed to examine various methodologies which are used 111 event studies to measure security price performance, and abnormal performance is introduced into this data and misuse of any of the methodologies can result in false inferences about the presence of abnormal performance.
3,389 citations
TL;DR: The implications of the biopsychosocial model for the study and care of a patient with an acute myocardial infarction are presented and contrasted with approaches used by adherents of the more traditional biomedical model.
Abstract: How physicians approach patients and the problems they present is much influenced by the conceptual models around which their knowledge is organized. In this paper the implications of the biopsychosocial model for the study and care of a patient with an acute myocardial infarction are presented and contrasted with approaches used by adherents of the more traditional biomedical model. A medical rather than psychiatric patient was selected to emphasize the unity of medicine and to help define the place of psychiatrists in the education of physicians of the future.
2,428 citations
TL;DR: In this paper, the authors examined two alternative models of the process generating stock returns: calendar time hypothesis and trading time hypothesis, and found that returns are generated only during active trading and the expected return is the same for each day of the week.
1,980 citations
TL;DR: A coherent view, based on sound theoretical principles, of what is presently known about the representation of solids is provided by providing a simple mathematical framework for characterizing certain important aspects of representations, for example, their semantic (geometric) integrity.
Abstract: Computer-based systems for modehng the geometry of rigid solid objects are becoming increasingly important in mechanical and civil engineering, architecture, computer graphics, computer vision, and other fields that deal with spatial phenomena. At the heart of such systems are symbol structures (representations) designating "abstract solids" (subsets of Euclidean space) that model physical solids. Representations are the sources of data for procedures which compute useful properties of objects. The variety and uses of systems embodying representations of solids are growing rapidly, but so are the difficulties in assessing current designs, specifying the characteristics that future systems should exhibit, and designing systems t9 meet such specifications. This paper resolves many of these difficulties by providing a coherent view, based on sound theoretical principles, of what is presently known about the representation of solids. The paper is divided into three parts. The first introduces a simple mathematical framework for characterizing certain important aspects of representations, for example, their semantic (geometric) integrity. The second part uses the framework to describe and compare all of the major knownschemes fo~ representing solids. The third part briefly surveys extant geometric modeling systems and then applies the concepts developed in the paper to the high-level design of a multiple*representation geometric modeling system which exhibits a level of reliability and versatility supermr to that of systems currently used in industrial computer-aided design and manufacturing.
1,483 citations
TL;DR: The chapter presents the performance-contingent rewards that actually enhance intrinsic motivation when administered in a way that places emphasis on effective performance rather than on reward acquisition.
Abstract: Publisher Summary The chapter discusses the empirical exploration of intrinsic motivational processes. Intrinsically motivated behaviors, motivated by the underlying need for competence and self-determination, are investigated in a variety of ways at the physiological, psychological, and operational levels. One of the two general approaches; the incongruity theories and the competence and/or self-determination theories generally guides those focused on the psychological level. The chapter presents the performance-contingent rewards that actually enhance intrinsic motivation when administered in a way that places emphasis on effective performance rather than on reward acquisition. The research literature that explored the nature of intrinsic motivation and the effects of rewards and controls on intrinsic motivation highly support the competence and self-determination formulation of intrinsic motivation and also the propositions of cognitive evaluation theory. The results of individual studies provided the basis for greater understanding of the phenomena and greater specificity of the theory. Understanding of motivational processes is critical for explicating and predicting human behavior as well as a variety of interrelated beliefs, attitudes, and affects, the complex referred to as motivational subsystems. The chapter also describes a field study conducted in the fourth, fifth, and sixth grades of four elementary schools.
1,227 citations
TL;DR: In this paper, the authors consider the problem of a price-setting monopolistic marketmaker in a dealership market where the stochastic demand and supply are depicted by price-dependent Poisson processes.
1,070 citations
TL;DR: In this paper, the existence of periodic spontaneous collapse and revival of coherence in the dynamics of a simple quantum model were reported. And the first accurate expressions for the intermediate-time and long-time dynamical behavior of the model were given.
Abstract: This Letter reports on the existence of periodic spontaneous collapse and revival of coherence in the dynamics of a simple quantum model. Also given are the first accurate expressions for the intermediate-time and long-time dynamical behavior of the model.
1,044 citations
TL;DR: The marine diatom Thalassiosira jluvintilis was grown in a continuous culture system at 20°C on a 12:12 L:D cycle over a series of nutrient- and light-limited dilution rates and Bannister’s theoretical model describing nutrient-saturated growth gave an excellent fit to the light- limited data.
Abstract: The marine diatom Thalassiosira jluvintilis was grown in a continuous culture system at 20°C on a 12:12 L:D cycle over a series of nutrient- and light-limited dilution rates. Bannister’s theoretical model describing nutrient-saturated growth gave an excellent fit to the light-limited data. A simple extension of the model allows description of nutrient-limited growth as well. Dark carbon loss rates were in the range lo-20% of daytime production rates at dilution rates >0.25*d-‘. The relationship hctwcen Chl n:C ratios and dilution rate was linear under nutrient limitation and independent of the type of limiting nutrient. Productivity indices under nutrient limitation were found to be a hyperbolic function of dilution rate. N:C ratios were linearly correlated with dihltion rate llnder both light and nutrient limitation, but with the regressions having opposite signs.
497 citations
TL;DR: In this paper, a rigorous theory of dispersion in both granular and sintered spatially-periodic porous media is presented, utilizing concepts originating from Brownian motion theory.
Abstract: A rigorous theory of dispersion in both granular and sintered spatially-periodic porous media is presented, utilizing concepts originating from Brownian motion theory. A precise prescription is derived for calculating both the Darcy-scale interstitial velocity vector $\overline{v}^{\ast}$ and dispersivity dyadic $\overline{D}^{\ast}$ of a tracer particle. These are expressed in terms of the local fluid velocity vector field v at each point within the interstices of a unit cell of the spatially periodic array and, for the dispersivity, the molecular diffusivity D of the tracer particle through the fluid. Though the theory is complete, numerical results are not yet available owing to the complex structure of the local interstitial velocity field v. However, as an illustrative exercise, the theory is shown to correctly reduce in an appropriate limiting case to the well-known Taylor-Aris results for dispersion in circular capillaries.
430 citations
TL;DR: A survey of electrophoretic variation in 20 enzymes from 109 clones of Escherichia coli from natural populations yielded an estimate of mean genetic diversity approximately twice that reported in an earlier study and four to five times larger than estimates fro most eukaryotic species.
Abstract: A survey of electrophoretic variation in 20 enzymes from 109 clones of escherichia coli from natural populations yielded an estimate of mean genetic diversity approximately twice that reported in an earlier study and four to five times larger than estimates fro most eukaryotic species. Despite this extensive variability, the number of distinctive genotypes apparently is rather limited. Identical clones were obtained from unassociated hosts, and a clone that is electrophoretically indistinguishable from the laboratory strain Escherichia coli K-12 was isolated from a human infant. The results suggest that rates of genetic recombination in natural populations of Escherichia coli are low. These findings have implications for our understanding of the genetic structure of Escherichia coli populations and the factors determining the amount of neutral gene variability in this bacterial species.
422 citations
TL;DR: The results suggest that neurophysin-containing cells of the paraventricular nucleus are relatively segregated into neurohypophysial- projecting and brainstem/ spinal cord-projecting groups and that release of hormone from the neurohypophysis does not necessarily imply a coincidental release of hormones into other extrahypothalamic sites.
TL;DR: Data provide strong support for the role of vitamin E as the major cellular antioxidant, especially in the highly oxygenated tissues of heart and lung, and demonstrate the utility of the microsomal system in characterizing tissue differences in susceptibility to peroxidative membrane decomposition.
Abstract: Rates of in vitro lipid peroxidation of microsomes and homogenates were found to vary widely among different tissues and species. In rats and rabbits, lung microsomes peroxidized at a 25- to 50-fold lower rate than liver, kidney, testes and brain microsomes. Heart microsomes peroxidized at a rate slightly greater than, but most similar to, lung microsomes. Comparison of tissue homogenates also revealed the unique resistance of lung and heart to lipid peroxidation. The ratio of vitamin E to peroxidizable polyunsaturated fatty acids in lung and heart microsomes was several-fold higher than in microsomes from the other tissues studied, which accounted for the relative resistance of lung and heart to lipid peroxidation. Liposomes of extracted rat lung microsomal lipid were also resistant to peroxidation and the amount of vitamin E contained in the lung lipid extract was sufficient to confer the same degree of resistance when incorported into an equivalent amount of rat liver lipid. Higher rates of peroxidation in mouse lung microsomes relative to rabbit, rat and human lung microsomes were similarly correlated with a lower ratio of vitamin E to peroxidizable fatty acids in mouse lung microsomes. These data provide strong support for the role of vitamin E as the major cellular antioxidant, especially in the highly oxygenated tissues of heart and lung, and demonstrate the utility of the microsomal system in characterizing tissue differences in susceptibility to peroxidative membrane decomposition.
TL;DR: Acute knee injuries with hemarthrosis, rather than being a contraindication to arthroscopy, are in fact one of the best indications for use of this procedure.
Abstract: One hundred thirteen consecutive athletes, who had sustained significant acute trauma to the knee with immediate disability and the early onset of hemarthrosis but who did not have demonstrable clinical laxity, were examined under anesthesia and had arthroscopy within 3 weeks of injury (the majority within 10 days) Lesions of surgical significance were found in 102 of the 113 cases (90%) Anterior cruciate ligament tears were present in 81 (72%), of which two-thirds also had associ ated meniscus lesions Major meniscus tears with no associated cruciate lesions were found in 17 cases (15%), osteochondral fractures in 7 cases (6%), posterior cruciate ligament tears in 3 cases (3%), and no internal derangement in 5 cases (4%) Acute knee injuries with hemarthrosis, rather than being a contraindication to arthroscopy, are in fact one of the best indications for use of this procedure
TL;DR: The authors study the occurrence of excess morbidity and mortality among subsets of the adult population of a large prepaid group practice during two epidemics of type A influenza to provide a basis for increasing the precision of clinical and public decision-making regarding the prevention of serious consequences of epidemic influenza.
Abstract: The authors studied the occurrence of excess morbidity and mortality among subsets of the adult population (persons over 14 years of age) of a large prepaid group practice during two epidemics of type A influenza (1968-1969 and 1972-1973). The experience from 1970-1971, a nonepidemic years, was used as a reference for estimating excesses. Ambulatory visits for influenza and influenza-related acute respiratory disease increased by 5-7 visits per 100 persons (30-50% excess) and pneumonia and influenza (P&I) hospitalization rates increased by 79-86 per 100,000 (140-150% excess) over the rates in the nonepidemic period. There were 11-13 excess deaths per 100,000 population, most of which involved persons over 65 years of age. Excess rates of ambulatory visits were similar for all adult age groups. Excess rates of persons hospitalized with P&I ranged from 23-25 per 100,000 among non-high risk persons aged 15-44 years to 150-172 per 100,000 among persons over age 65 years without underlying "high risk" conditions and 476-636 per 100,000 persons over 65 with underlying "high risk" conditions. These data provide a basis for increasing the precision of clinical and public decision-making regarding the prevention of serious consequences of epidemic influenza.
Journal Article•
TL;DR: The data revealed that healing following the four different regenerative procedures resulted in the reformation of an epithelial lining (long junctional epithelium) along the treated root surfaces, with no new connective tissue attachment.
Abstract: The present study was undertaken to determine the effect of four periodontal regenerative procedures on the connective tissue attachment level. The procedures tested were: 1) the modified Widman flap procedure, 2) the modified Widman flap procedure combined with transplantation of previously frozen autogenous red marrow and cancellous bone, 3) the modified Widman flap procedure in combination with implantation of beta tricalcium phosphate, and 4) periodic root planing and soft tissue curettage. Eight adult Rhesus monkeys, divided into four equal groups, were used. Periodontal pockets were produced around contralateral teeth in a standardized manner. In each group of animals, the pockets on one side of the jaws were subjected to one of the above-mentioned surgical treatments, while the contralateral pockets remained as unoperated controls. Three weeks before surgery, a carefully designed plaque control program was instituted and continued until the animals were sacrificed 12 months after surgery. In histologic sections, linear measurements along the root surfaces were made from the cemento-enamel junction (CEJ) to the most apical cells of the junctional epithelium (JE). These measurements from operated and unoperated sites were then compared. The data revealed that healing following the four different regenerative procedures resulted in the reformation of an epithelial lining (long junctional epithelium) along the treated root surfaces, with no new connective tissue attachment.
TL;DR: A trained hawk was flown over flocks of granivorous yellow-eyed juncos to compare time budgets in the presence and absence of a predator, and it was found that time budgets changed after the predator was introduced and also that flock size increased in the absence of the predator.
Abstract: Although there are several possible advantages of flocking1–3, many authors suggest that birds forage in groups to reduce the risk of predation (see citations in ref. 4). One version of the ‘many eyes’ hypothesis proposes that flocking allows individuals to spend less time scanning for predators and more time feeding5,6. However, flocking may also cause individuals to lose time and energy in fighting one another. The way a bird divides its time among these activities, its time budget, may depend on variables governing foraging requirements and the chance of predation7. As one such variable is the frequency of attacks by predators8, we flew a trained hawk over flocks of granivorous yellow-eyed juncos (Junco phaeonotus) to compare time budgets in the presence and absence of a predator. We found that time budgets changed after the predator was introduced and also that flock size increased in the presence of the predator.
TL;DR: An account of indirect forms of speech acts to request and inform based on the hypothesis that language users can recognize actions being performed by others, infer goals being sought, and cooperate in their achievement is proposed.
Abstract: We propose an account of indirect forms of speech acts to request and inform based on the hypothesis that language users can recognize actions being performed by others, infer goals being sought, and cooperate in their achievement. This cooperative behaviour is independently motivated and may or may not be intended by speakers. If the hearer believes it is intended, he or she can recognize the speech act as indirect; otherwise it is interpreted directly. Heuristics are suggested to decide among the interpretations.
TL;DR: It is suggested that survival of RSV in the environment of infected infant secretions is sufficient to allow transfer of infectious virus to the hands of hospital personnel, and self-inoculation by contact with contaminated infantsecretions may be a potential mode of nosocomial transmission.
Abstract: To test whether nosocomial spread of respiratory syncytial virus (RSV) could occur through contact with environmental surfaces contaminated by RSV-infected nasal secretions, survival in the environment of RSV isolated from media, pooled adult secretions, and secretions from hospitalized infants was examined. RSV in freshly obtained infant secretions was recovered from countertops for up to 6 hr, from rubber gloves for up to 1 1/2 hr, from cloth gowns and paper tissue for 30--45 min, and from skin for up to 20 min. RSV in media and pooled secretions survived for slightly longer periods. Further experiments demonstrated that infectious virus could be transferred to hands touching these contaminated surfaces and could be recovered from these hands for up to 25 min. These studies suggest that survival of RSV in the environment of infected infant secretions is sufficient to allow transfer of infectious virus to the hands of hospital personnel. Thus, self-inoculation by contact with contaminated infant secretions may be a potential mode of nosocomial transmission of RSV.
TL;DR: The simplified results of several theoretical derivations are presented and employed in illustrative calculations and plots to ascertain the importance of nonlinear effects in applications involving plane waves, spherically diverging waves, and spheric converging waves.
Abstract: Some fundamentals of nonlinear acoustics are reviewed to facilitate their consideration in biomedical ultrasound. The phenomena described include acoustic nonlinearity, finite amplitude distortion, shock formation, harmonic components, nonlinearly induced absorption, saturation, and the influence of these effects on ultrasonic beams. The simplified results of several theoretical derivations are presented and employed in illustrative calculations and plots. These maybe used to ascertain the importance of nonlinear effects in applications involving plane waves, spherically diverging waves, and spherically converging (focused) waves. A discussion of relevant experiments is given, along with some comments on possible consequences in diagnostic, surgical, and theraputic applications.
TL;DR: The widespread distribution of SRIF is consistent with radioimmunoassay data and suggests a diverse physiological role for somatostatin, and widespread accumulations of fibers were observed throughout the telencephalon.
TL;DR: In a group of patients with unexplained nausea, epigastric bloating, and vomiting, abnormal antral myoelectric activities were found by a peroral electrode, in contrast to a regular pacesetter potential in control subjects.
TL;DR: The subject of gradient-index optics dates from the 1850s but only in the last 10 years has it been possible to design lenses, manufacture materials, measure the properties, and fabricate finished lens elements.
Abstract: The subject of gradient-index optics dates from the 1850s. However, only in the last 10 years has it been possible to design lenses, manufacture materials, measure the properties, and fabricate finished lens elements. The current status of gradient-index optics is reviewed.
TL;DR: Gap junction channels will be recognized as one of the most useful and exciting model systems to be exploited in studying the general properties of membranous channels in the years to come.
Abstract: Publisher Summary Gap junction channels are often regarded by membranologists as an unusual means of membrane permeability, having little in common with other membranous channels. Although gap junction channels establish hydrophilic paths between two cells' interiors and are a permissive type of channel, as they are bidirectionally and indiscriminately permeable to charged and neutral molecules, they have many structural and functional similarities with other membranous channels. Not only can they be easily localized in intact cells and studied by ultrastructural methods, such as thin sections, lanthanum infiltration, freeze-fracture, and negative staining, they can also be isolated in quite pure fractions and characterized chemically. Because of their crystalline configuration in isolated fractions, they can be studied by laser, X-ray, and electron diffraction techniques. Their permeability properties and the mechanisms of permeability modulation can be studied electrophysiologically, morphologically, and by tracer-transfer methods. Thus, in the years to come, gap junction channels will be recognized as one of the most useful and exciting model systems to be exploited in studying the general properties of membranous channels.
TL;DR: In this paper, the authors reexamine the anomalous evidence concerning the efficiency of the listed options exchanges and focus on the structure of trading costs in that market, and note several costs which generally have been ignored, the largest of which is the bid-ask spread.
TL;DR: The results support the general clinical impression of a recent increase in the incidence of anorexia nervosa and suggest that the disorder occurs more often in the higher socioeconomic levels.
Abstract: The Monroe County Psychiatric Case Register and hospital records were used to investigate the incidence of anorexia nervosa in Monroe County, New York, during the periods 1960-1969 and 1979-1976 to determine whether the number of newly diagnosed cases has increased over time. The results support the general clinical impression of a recent increase in the incidence of anorexia nervosa. This pattern of overall change was accounted for by the sharp increase in the number of females with the disorder, particularly those aged 15-24. The data also suggest that the disorder occurs more often in the higher socioeconomic levels.
TL;DR: In this paper, a longitudinal analysis of hair samples can provide a simple and accurate method of monitoring continuing exposure and an estimation of peak blood levels months to years after exposure, while the total mercury concentration and inorganic/organic ratio remained constant with time.
Abstract: Samples of blood and head hair were analyzed for organic and inorganic mercury from a population which consumed large amounts of fish contaminated with methylmercury. Mercury levels in newly formed hair were found to reflect those in blood with the concentration in hair being approximately 300 times that in blood. Organic and inorganic mercury levels were linearly related in both hair and blood samples, with a mean inorganic/organic ration of 0.05 in blood and 0.21 in hair, but individual differences were found to exist. In addition, the total mercury concentration and inorganic/organic ratio in hair remained constant with time. Thus, longitudinal analysis of hair samples can provide a simple and accurate method of monitoring continuing exposure and an estimation of peak blood levels months to years after exposure.
TL;DR: Primary sequence variants of the inner histones, presumably indicative of nucleosome heterogeneity, exist in a lower eucaryote, in an amitotic nucleus, and within the nucleus of a clonally propagated organism.
TL;DR: Real time two dimensional echocardiography is useful in differentiating pseudoaneurysm from true aneurysm of the left ventricle, and this finding produced a characteristic beak-like configuration in the studies of two patients.
Abstract: Real time two dimensional echocardiographic findings in four patients with a pathologically proved left ventricular pseudoaneurysm were compared with those in seven patients with a similarly proved true aneurysm of the left ventricle. Pseudoaneurysms produced a bounded echo-free space with a narrow neck that communicated with the left ventricular cavity. The maximal internal width of this neck (O max ) was much smaller than the maximal parallel internal diameter (D max ) of the aneurysmal sac, and the ratio O max /D max never exceeded 0.5. In all cases the pseudoaneurysm could be seen extending behind the intact portion of the involved left ventricular wall, and this finding produced a characteristic beak-like configuration in the studies of two patients. In contrast, true aneurysm resulted in local bulging and dilatation of the left ventricular wall so that the maximal internal width of the mouth (O max ) was nearly equal to, or actually represented, the maximal internal diameter (D max ) of the aneurysm so that the ratio O max /D max ranged from 0.9 to 1.0. Our preliminary study indicates that real time two dimensional echocardiography is useful in differentiating pseudoaneurysm from true aneurysm of the left ventricle.