Showing papers by "University of Pennsylvania published in 1990"
TL;DR: In this paper, the authors argue that the ability of a firm to recognize the value of new, external information, assimilate it, and apply it to commercial ends is critical to its innovative capabilities.
Abstract: In this paper, we argue that the ability of a firm to recognize the value of new, external information, assimilate it, and apply it to commercial ends is critical to its innovative capabilities. We label this capability a firm's absorptive capacity and suggest that it is largely a function of the firm's level of prior related knowledge. The discussion focuses first on the cognitive basis for an individual's absorptive capacity including, in particular, prior related knowledge and diversity of background. We then characterize the factors that influence absorptive capacity at the organizational level, how an organization's absorptive capacity differs from that of its individual members, and the role of diversity of expertise within an organization. We argue that the development of absorptive capacity, and, in turn, innovative performance are history- or path-dependent and argue how lack of investment in an area of expertise early on may foreclose the future development of a technical capability in that area. We formulate a model of firm investment in research and development (R&D), in which R&D contributes to a firm's absorptive capacity, and test predictions relating a firm's investment in R&D to the knowledge underlying technical change within an industry. Discussion focuses on the implications of absorptive capacity for the analysis of other related innovative activities, including basic research, the adoption and diffusion of innovations, and decisions to participate in cooperative R&D ventures. **
31,623 citations
TL;DR: The authors update and extend their 1978 review of conjoint analysis, discussing several new developments and considering alternative approaches for measuring preference structures in the presence of a large number of attributes.
Abstract: The authors update and extend their 1978 review of conjoint analysis. In addition to discussing several new developments, they consider alternative approaches for measuring preference structures in...
2,541 citations
TL;DR: It is suggested that follicular stem cells reside in the bulge region, instead of the lower bulb, which provides insights into hair cycle control and the possible involvement of hair follicle stem cells in skin carcinogenesis.
2,238 citations
TL;DR: In this article, the authors propose an elaboration of the Diamond model that permits multiple, locally stable stationary states, and this multiplicity is due to increasing social returns to scale in the accumulation of human capital.
Abstract: Standard one-sector growth models often have the counterfactual implication that economies with access to similar technologies will converge to a common balanced growth path. We propose an elaboration of the Diamond model that permits multiple, locally stable stationary states. This multiplicity is due to increasing social returns to scale in the accumulation of human capital.
2,070 citations
TL;DR: Adjuvant therapy with levamisole and fluorouracil should be standard treatment for Stage C colon carcinoma, and this approach should be readily adaptable to conventional medical practice.
Abstract: Twelve hundred ninety-six patients with resected colon cancer that either was locally invasive (Stage B2) or had regional nodal involvement (Stage C) were randomly assigned to observation or to treatment for one year with levamisole combined with fluorouracil. Patients with Stage C disease could also be randomly assigned to treatment with levamisole alone. The median follow-up time at this writing is 3 years (range, 2 to 5 1/2). Among the patients with Stage C disease, therapy with levamisole plus fluorouracil reduced the risk of cancer recurrence by 41 percent (P<0.0001). The overall death rate was reduced by 33 percent (P ≈ 0.006). Treatment with levamisole alone had no detectable effect. The results in the patients with Stage B2 disease were equivocal and too preliminary to allow firm conclusions. Toxic effects of levamisole alone were infrequent, usually consisting of mild nausea with occasional dermatitis or leukopenia, and those of levamisole plus fluorouracil were essentially the same as t...
2,063 citations
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TL;DR: In this article, the authors introduce a utility function that nests three classes of utility functions: (1) time-separable utility functions, (2) "catching up with the Joneses" utility functions that depend on the consumer's level of consumption relative to the lagged cross-sectional average level, and (3) utility functions displaying habit formation.
Abstract: This paper introduces a utility function that nests three classes of utility functions: (1) time-separable utility functions; (2) "catching up with the Joneses" utility functions that depend on the consumer's level of consumption relative to the lagged cross-sectional average level of consumption; and (3) utility functions that display habit formation. Closed-form solutions for equilibrium asset prices are derived under the assumption that consumption growth is i.i.d. The equity premia under catching up with the Joneses and under habit formation are, for some parameter values, as large as the historically observed equity premium in the United States.
1,773 citations
TL;DR: Criteria for the diagnosis of Guillain‐Barré syndrome are reaffirmed and Electrodiagnostic criteria are expanded and specific detail added.
Abstract: Criteria for the diagnosis of Guillain-Barre syndrome are reaffirmed. Electrodiagnostic criteria are expanded and specific detail added.
1,767 citations
TL;DR: The field of finite-dimensional variational inequality and complementarity problems has seen a rapid development in its theory of existence, uniqueness and sensitivity of solution(s), in the theory of algorithms, and in the application of these techniques to transportation planning, regional science, socio-economic analysis, energy modeling, and game theory as mentioned in this paper.
Abstract: Over the past decade, the field of finite-dimensional variational inequality and complementarity problems has seen a rapid development in its theory of existence, uniqueness and sensitivity of solution(s), in the theory of algorithms, and in the application of these techniques to transportation planning, regional science, socio-economic analysis, energy modeling, and game theory. This paper provides a state-of-the-art review of these developments as well as a summary of some open research topics in this growing field.
1,647 citations
TL;DR: In this article, the authors show that despite negative autocorrelation in individual stock returns, weekly portfolio returns are strongly positively auto-correlated and are the result of important cross-autocorrelations.
Abstract: If returns on some stocks systematically lead or lag those of others, a portfolio strategy that sells "winners" and buys "losers" can produce positive expected returns, even if no stock's returns are negatively autocorrelated as virtually all models of overreaction imply. Using a particular contrarian strategy, the authors show that, despite negative autocorrelation in individual stock returns, weekly portfolio returns are strongly positively autocorrelated and are the result of important cross-autocorrelations. The authors find that the returns of large stocks lead those of smaller stocks, and present evidence against overreaction as the only source of contrarian profits. Article published by Oxford University Press on behalf of the Society for Financial Studies in its journal, The Review of Financial Studies.
1,351 citations
TL;DR: Alterations in the response of dark-grown seedlings to ethylene (the "triple response") were used to isolate a collection of ethylene-related mutants in Arabidopsis thaliana and should prove to be useful tools for dissecting the mode of Ethylene action in plants.
Abstract: Alterations in the response of dark-grown seedlings to ethylene (the "triple response") were used to isolate a collection of ethylene-related mutants in Arabidopsis thaliana. Mutants displaying a constitutive response (eto1) were found to produce at least 40 times more ethylene than the wild type. The morphological defects in etiolated eto1-1 seedlings reverted to wild type under conditions in which ethylene biosynthesis or ethylene action were inhibited. Mutants that failed to display the apical hook in the absence of ethylene (his1) exhibited reduced ethylene production. In the presence of exogenous ethylene, hypocotyl and root of etiolated his1-1 seedlings were inhibited in elongation but no apical hook was observed. Mutants that were insensitive to ethylene (ein1 and ein2) produced increased amounts of ethylene, displayed hormone insensitivity in both hypocotyl and root responses, and showed an apical hook. Each of the "triple response" mutants has an effect on the shape of the seedling and on the production of the hormone. These mutants should prove to be useful tools for dissecting the mode of ethylene action in plants.
1,284 citations
TL;DR: It is concluded that genetic influences on body-mass index are substantial, whereas the childhood environment has little or no influence.
Abstract: To assess the relative importance of genetic and environmental effects on the body-mass index (weight in kilograms divided by the square of the height in meters), we studied samples of identical and fraternal twins, reared apart or reared together. The samples consisted of 93 pairs of identical twins reared apart, 154 pairs of identical twins reared together, 218 pairs of fraternal twins reared apart, and 208 pairs of fraternal twins reared together. The intrapair correlation coefficients of the values for body-mass index of identical twins reared apart were 0.70 for men and 0.66 for women. These are the most direct estimates of the relative importance of genetic influences (heritability) on the body-mass index, and they were only slightly lower than those for twins reared together in this and earlier studies. Similar estimates were derived from maximum-likelihood model-fitting analyses--0.74 for men and 0.69 for women. Nonadditive genetic variance made a significant contribution to the estimates of heritability, particularly among men. Of the potential environmental influences, only those unique to the individual and not those shared by family members were important, contributing about 30 percent of the variance. Sharing the same childhood environment did not contribute to the similarity of the body-mass index of twins later in life. We conclude that genetic influences on body-mass index are substantial, whereas the childhood environment has little or no influence. These findings corroborate and extend the results of earlier studies of twins and adoptees.
TL;DR: The course is focused on historical texts, most of them philosophical as discussed by the authors, and context for understanding the texts and the course of democratic development will be provided in lecture and discussions, and by some background readings (Dunn).
Abstract: The course is focused on historical texts, most of them philosophical. Context for understanding the texts and the course of democratic development will be provided in lecture and discussions, and by some background readings (Dunn). We begin with the remarkable Athenian democracy, and its frequent enemy the Spartan oligarchy. In Athens legislation was passed directly by an assembly of all citizens, and executive officials were selected by lot rather than by competitive election. Athenian oligarchs such as Plato more admired Sparta, and their disdain for the democracy became the judgment of the ages, until well after the modern democratic revolutions. Marsilius of Padua in the early Middle Ages argued for popular sovereignty. The Italian citystates of the Middle Ages did without kings, and looked back to Rome and Greece for republican models. During the English Civil War republicans debated whether the few or the many should be full citizens of the regime. The English, French, and American revolutions struggled with justifying and establishing a representative democracy suitable for a large state, and relied on election rather than lot to select officials. The English established a constitutional monarchy, admired in Europe, and adapted by the Americans in their republican constitution. The American Revolution helped inspire the French, and the French inspired republican and democratic revolution throughout Europe during the 19 century.
TL;DR: The authors found that women lead men in rejecting linguistic changes as they are recognized by the speech community, a differentiation that is maximal for the second highest status group, and that sexual differentiation is independent of social class at the beginning of a change, but that interaction develops gradually as social awareness of the change increases.
Abstract: Two general principles of sexual differentiation emerge from previous sociolinguistic studies: that men use a higher frequency of nonstandard forms than women in stable situations, and that women are generally the innovators in linguistic change. It is not clear whether these two tendencies can be unified, or how differences between the sexes can account for the observed patterns of linguistic change. The extensive interaction between sex and other social factors raises the issue as to whether the curvilinear social class pattern associated with linguistic change is the product of a rejection of female-dominated changes by lower-class males. Multivariate analysis of data from the Philadelphia Project on Linguistic Change and Variation indicates that sexual differentiation is independent of social class at the beginning of a change, but that interaction develops gradually as social awareness of the change increases. It is proposed that sexual differentiation of language is generated by two distinct processes: (1) for all social classes, the asymmetric context of language learning leads to an initial acceleration of female-dominated changes and retardation of male-dominated changes; (2) women lead men in the rejection of linguistic changes as they are recognized by the speech community, a differentiation that is maximal for the second highest status group.
TL;DR: In this paper, the authors show that the effects of data snooping can be substantial, and two empirical examples demonstrate that the effect of this type of data-snooping on the performance of financial asset pricing models is substantial.
Abstract: Tests of financial asset pricing models may yield misleading inferences when properties of the data are used to construct the test statistics. In particular, such tests are often based on returns to portfolios of common stock, where portfolios are constructed by sorting on some empirically motivated characteristic of the securities such as market value of equity. Analytical calculations, Monte Carlo simulations, and two empirical examples show that the effects of this type of data snooping can be substantial. Article published by Oxford University Press on behalf of the Society for Financial Studies in its journal, The Review of Financial Studies.
TL;DR: In this paper, a prospective study of 1,958 outpatients found that hopelessness, as measured by the Beck Hopelessness Scale, was significantly related to eventual suicide, and a scale cutoff score of 9 or above identified 16 (94.2%) of the 17 patients who eventually committed suicide.
Abstract: A prospective study of 1,958 outpatients found that hopelessness, as measured by the Beck Hopelessness Scale, was significantly related to eventual suicide. A scale cutoff score of 9 or above identified 16 (94.2%) of the 17 patients who eventually committed suicide, thus replicating a previous study with hospitalized patients. The high-risk group identified by this cutoff score was 11 times more likely to commit suicide than the rest of the outpatients. The Beck Hopelessness Scale thus may be used as a sensitive indicator of suicide potential.
TL;DR: By combining the least complicated and expedient methods of sample handling with the sensitivity and specificity of the GSH assay by enzymatic recycling and the small volumes and software capabilities of microtiter plate technology, this work devised a rapid, sensitive, and easy assay for GSH and GSSG in biological samples.
Journal Article•
TL;DR: The distribution of integrin adhesion receptors was examined in benign and malignant lesions of human melanocytes and in tissue sections from benign to increasingly malignant melanocytic lesions using a panel of monoclonal antibodies against specific integrin subunits to examine the presence of this integrin.
Abstract: Since tumor progression is dependent on the ability of malignant cells to interact with the extracellular matrix, molecules on the cell surface which mediate cell-substratum interactions are likely to be important regulators of tumor invasion and metastasis The purpose of this study was to examine the distribution of one such group of cell adhesion receptors, the integrins, in benign and malignant lesions of human melanocytes The distribution of integrin adhesion receptors was defined on cells in culture derived from normal and malignant melanocytes and in tissue sections from benign to increasingly malignant melanocytic lesions using a panel of monoclonal antibodies against specific integrin subunits Cells in culture expressed a large variety of integrins, including all of the previously characterized members of the beta 1 subfamily plus the alpha v/beta 3 vitronectin receptor The expression of integrins was similar in cells cultured from either benign or malignant lesions In contrast, consistent differences were noted in integrin expression by cells within tissues containing metastatic and vertical growth phase melanomas when compared to radial growth phase melanoma cells and cells within nevi Most notably, the expression of the beta 3 subunit was restricted exclusively to cells within vertical growth phase and metastatic melanomas The presence of this integrin may be important in the development of tumor invasiveness and could be useful as a marker of melanoma cells entering the more aggressive phase of the malignant process
TL;DR: In this article, the authors argue that neither interpretive nor process-product classroom research has foregrounded the teacher's role in the generation of knowledge about teaching, and that what is missing from the knowledge base for teaching is the voices of the teachers themselves, the questions teachers ask, the ways teachers use writing and intentional talk in their work lives.
Abstract: Neither interpretive nor process-product classroom research has foregrounded the teacher's role in the generation of knowledge about teaching. What is missing from the knowledge base for teaching, therefore, are the voices of the teachers themselves, the questions teachers ask, the ways teachers use writing and intentional talk in their work lives, and the interpretive frames teachers use to understand and improve their own classroom practices. Limiting the official knowledge base for teaching to what academics have chosen to study and write about has contributed to a number of problems, including discontinuity between what is taught in universities and what is taught in classrooms, teachers' ambivalence about the claims of academic research, and a general lack of information about classroom life from a truly emic perspective. This article proposes that teacher research has the potential to provide this perspective; however, several critical issues divide teacher research from research on teaching and mak...
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TL;DR: In this paper, the authors analyze the acquisition of resources through social transactions by independent entrepreneurs and corporate entrepreneurs, with a focus primarily on the corporate entrepreneurs and identify cooptation as the mechanism by which resources can be obtained.
Abstract: Analyzes the acquisition of resources through social transactions by independent entrepreneurs and corporate entrepreneurs, with a focus primarily on the corporate entrepreneurs. These social transactions include previous working relationships, voluntary connections, and community ties for independent entrepreneurs. Corporate entrepreneurs steal personnel time, appropriate materials, and conceal development activities. The importance of these social transactions in securing key resources for little to no cost is demonstrated through two examples: a Cuban American in the United States and a Swedish venture manager in a European mini-conglomerate. Two types of venture managers are discussed – the administrative venture manager and the social transactions-oriented manager. Cooptation is identified as the mechanism by which resources can be obtained. Two types of cooptation, legitimacy and underutilized goods, are presented. It is proposed that the social transactions-oriented managers are more likely to co-opt legitimacy (primiarly through association or endorsement) than are the administrative venture managers. Begging, borrowing, scavenging, and amplifying are the four strategies used for taking advantage of underutilized activities. This cooptation process involves the exploitation of social assets. These social assets are built by sharing information, solving and receiving help with problems, giving and receiving favors, and creating opportunities for people to demonstrate their skills and competence. Reasons why it is difficult for corporate entrepreneurs to take advantage of network resources are provided. The propositions presented in this analysis can provide the basis for future research. (SRD)
Veterans Health Administration1, University of Miami2, University of Florida3, Brown University4, University of California, Los Angeles5, Mount Sinai St. Luke's and Mount Sinai Roosevelt6, Harvard University7, University of Pennsylvania8, University of Louisville9, Cornell University10, University of Arizona11, Columbia University12, Abbott Laboratories13, Merck & Co.14
TL;DR: Hepatitis B e antigen and hepatitis B viral DNA disappeared from serum significantly more often in the patients given prednisone plus interferon or 5 million units of interferons alone than in the untreated controls.
Abstract: Background and Methods. Chronic hepatitis B is a common and often progressive liver disorder for which there is no accepted therapy. To assess the efficacy of treatment with interferon, we randomly assigned patients with chronic hepatitis B to one of the following regimens: prednisone for 6 weeks followed by 5 million units of recombinant interferon alfa-2b daily for 16 weeks; placebo followed by 5 million units of interferon daily for 16 weeks; placebo followed by 1 million units of interferon daily for 16 weeks; or observation with no treatment. Results. Hepatitis B e antigen and hepatitis B viral DNA disappeared from serum significantly more often in the patients given prednisone plus interferon (16 of 44 patients, or 36 percent) or 5 million units of interferon alone (15 of 41; 37 percent) than in the untreated controls (3 of 43; 7 percent; P<0.001); the difference between those given 1 million units of interferon (7 of 41; 17 percent) and the controls was not significant. The strongest indep...
TL;DR: This article showed that an increase in the quality of private information received by a manager results in more disclosure on his part, and also discussed how this result influences a manager's choice over levels of quality.
TL;DR: For example, this paper found that a risk group for death from a disease has no effect on reluctance to vaccinate a child when the vaccination itself can cause death, even when this is much less likely than death from the disease prevented.
Abstract: Subjects are reluctant to vaccinate a (hypothetical) child when the vaccination itself can cause death, even when this is much less likely than death from the disease prevented. This effect is even greater when there is a ‘risk group’ for death (with its overall probability held constant), even though the test for membership in the risk group is unavailable. This effect cannot be explained in terms of a tendency to assume that the child is in the risk group. A risk group for death from the disease has no effect on reluctance to vaccinate. The reluctance is an example of omission bias (Spranca, Minsk & Baron, in press), an overgeneralization of a distinction between commissions and omissions to a case in which it is irrelevant. Likewise, it would ordinarily be prudent to find out whether a child is in a risk group before acting, but in this case it is impossible, so knowledge of the existence of the risk group is irrelevant. The risk-group effect is consistent with Frisch & Baron's (1988) interpretation of ambiguity.
TL;DR: Metallothionein-directed expression of TGF alpha in transgenic mice induced a spectrum of changes in the growth and differentiation of certain adult tissues and displays characteristics of both a potent epithelial cell mitogen and an oncogenic protein in vivo.
TL;DR: Evidence for a pivotal role of glucokinase as glucose sensor of the pancreatic β-cells is reviewed, and certain forms of diabetes mellitus might be due to glucokin enzyme deficiencies in pancreaticβ-cells, hepatocytes, or both.
Abstract: This article reviews evidence for a pivotal role of glucokinase as glucose sensor of the pancreatic beta-cells. Glucokinase explains the capacity, hexose specificity, affinities, sigmoidicity, and anomeric preference of pancreatic islet glycolysis, and because stimulation of glucose metabolism is a prerequisite of glucose stimulation of insulin release, glucokinase also explains many characteristics of this beta-cell function. Glucokinase of the beta-cell is induced or activated by glucose in contrast to liver glucokinase, which is regulated by insulin. Tissue-specific regulation corresponds with observations that liver and pancreatic beta-cell glucokinase are structurally distinct. Glucokinase could play a glucose-sensor role in hepatocytes as well, and certain forms of diabetes mellitus might be due to glucokinase deficiencies in pancreatic beta-cells, hepatocytes, or both.
TL;DR: It is concluded that the lessened clinical, electrocardiographic, hemodynamic, and metabolic evidence of myocardial ischemia during the second of two periods of coronary artery occlusion during percutaneous transluminal coronary angioplasty supports the concept of adaptation to myocardia (ischemic preconditioning).
Abstract: The clinical, electrocardiographic, and coronary hemodynamic responses to sequential 90-second occlusions of the left anterior descending coronary artery in 12 patients undergoing elective percutaneous transluminal coronary angioplasty were examined. Transmyocardial lactate metabolism was examined in an additional group of seven patients with clinical and hemodynamic features similar to the first group. We noted that in comparison with the initial balloon occlusion the second occlusion was characterized by less subjective anginal discomfort, less ST segment shift (0.44 +/- 0.13 versus 0.21 +/- 0.07 mV, p = 0.01), and lower mean pulmonary artery pressure (25 +/- 1.0 versus 20 +/- 1.7 mm Hg, p = 0.005). In addition, for the same heart rate-blood pressure product, cardiac vein flow during the second inflation was significantly lower than that recorded during the first inflation (96 +/- 1.4 versus 83 +/- 2.4 ml/min, p = 0.005). Finally, there was significantly less myocardial lactate production during the second inflation (lactate extraction ratio: first inflation, -0.11 +/- 0.03; second inflation, -0.03 +/- 0.02; p = 0.04). We conclude that the lessened clinical, electrocardiographic, hemodynamic, and metabolic evidence of myocardial ischemia during the second of two periods of coronary artery occlusion during percutaneous transluminal coronary angioplasty supports the concept of adaptation to myocardial ischemia (ischemic preconditioning).
TL;DR: In this paper, a method for recovery of compact volumetric models for shape representation of single-part objects in computer vision is introduced, where the model recovery is formulated as a least-squares minimization of a cost function for all range points belonging to a single part.
Abstract: A method for recovery of compact volumetric models for shape representation of single-part objects in computer vision is introduced. The models are superquadrics with parametric deformations (bending, tapering, and cavity deformation). The input for the model recovery is three-dimensional range points. Model recovery is formulated as a least-squares minimization of a cost function for all range points belonging to a single part. During an iterative gradient descent minimization process, all model parameters are adjusted simultaneously, recovery position, orientation, size, and shape of the model, such that most of the given range points lie close to the model's surface. A specific solution among several acceptable solutions, where are all minima in the parameter space, can be reached by constraining the search to a part of the parameter space. The many shallow local minima in the parameter space are avoided as a solution by using a stochastic technique during minimization. Results using real range data show that the recovered models are stable and that the recovery procedure is fast. >
TL;DR: In this paper, the energy levels of A = 11 and 12 nuclei with emphasis on material leading to information about the structure of the A =11 and 12 systems were analyzed.