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Showing papers by "Stanford University published in 1993"


Journal ArticleDOI
TL;DR: This paper describes a mechanism for defining ontologies that are portable over representation systems, basing Ontolingua itself on an ontology of domain-independent, representational idioms.

12,962 citations


Journal ArticleDOI
TL;DR: In this article, a conceptual model of brand equity from the perspective of the individual consumer is presented, which is defined as the differential effect of brand knowledge on consumers' perceptions of the brand.
Abstract: The author presents a conceptual model of brand equity from the perspective of the individual consumer. Customer-based brand equity is defined as the differential effect of brand knowledge on consu...

12,021 citations


Journal ArticleDOI
TL;DR: In this article, the authors examine how recent econometric policy evaluation research on monetary policy rules can be applied in a practical policymaking environment, and the discussion centers around a hypothetical but representative policy rule much like that advocated in recent research.

8,414 citations


Journal ArticleDOI
TL;DR: In this paper, the authors review the diverse ways in which perceived selfefficacy contributes to cognitive development and functioning and find that teachers' beliefs in their personal efficacy to motivate and promote learning affect the types of learning environments they create and the level of academic progress their students achieve.
Abstract: In this article, I review the diverse ways in which perceived self-efficacy contributes to cognitive development and functioning. Perceived self-efficacy exerts its influence through four major processes. They include cognitive, motivational, affective, and selection processes. There are three different levels at which perceived self-efficacy operates as an important contributor to academic development. Students' beliefs in their efficacy to regulate their own learning and to master academic activities determine their aspirations, level of motivation, and academic accomplishments. Teachers' beliefs in their personal efficacy to motivate and promote learning affect the types of learning environments they create and the level of academic progress their students achieve. Faculties' beliefs in their collective instructional efficacy contribute significantly to their schools' level of academic achievement. Student body characteristics influence school-level achievement more strongly by altering faculties' beli...

7,013 citations


Journal ArticleDOI
TL;DR: The imperfections of learning are not so great as to require abandoning attempts to improve the learning capabilities of organizations, but that those imperfections suggest a certain conservatism in expectations.
Abstract: Organizational learning has many virtues, virtues which recent writings in strategic management have highlighted. Learning processes, however, are subject to some important limitations. As is well-known, learning has to cope with confusing experience and the complicated problem of balancing the competing goals of developing new knowledge (i.e., exploring) and exploiting current competencies in the face of dynamic tendencies to emphasize one or the other. We examine the ways organizations approach these problems through simplification and specialization and how those approaches contribute to three forms of learning myopia, the tendency to overlook distant times, distant places, and failures, and we identify some ways in which organizations sustain exploration in the face of a tendency to overinvest in exploitation. We conclude that the imperfections of learning are not so great as to require abandoning attempts to improve the learning capabilities of organizations, but that those imperfections suggest a certain conservatism in expectations.

6,071 citations


Proceedings ArticleDOI
01 Nov 1993
TL;DR: A modification to the matching pursuit algorithm of Mallat and Zhang (1992) that maintains full backward orthogonality of the residual at every step and thereby leads to improved convergence is proposed.
Abstract: We describe a recursive algorithm to compute representations of functions with respect to nonorthogonal and possibly overcomplete dictionaries of elementary building blocks e.g. affine (wavelet) frames. We propose a modification to the matching pursuit algorithm of Mallat and Zhang (1992) that maintains full backward orthogonality of the residual (error) at every step and thereby leads to improved convergence. We refer to this modified algorithm as orthogonal matching pursuit (OMP). It is shown that all additional computation required for the OMP algorithm may be performed recursively. >

4,607 citations


Journal Article
TL;DR: The international index and the age-adjusted international index should be used in the design of future therapeutic trials in patients with aggressive non-Hodgkin's lymphoma and in the selection of appropriate therapeutic approaches for individual patients.
Abstract: BACKGROUND Although many patients with intermediate-grade or high-grade (aggressive) non-Hodgkin's lymphoma are cured by combination chemotherapy, the remainder are not cured and ultimately die of their disease. The Ann Arbor classification, used to determine the stage of this disease, does not consistently distinguish between patients with different long-term prognoses. This project was undertaken to develop a model for predicting outcome in patients with aggressive non-Hodgkin's lymphoma on the basis of the patients' clinical characteristics before treatment. METHODS Adults with aggressive non-Hodgkin's lymphoma from 16 institutions and cooperative groups in the United States, Europe, and Canada who were treated between 1982 and 1987 with combination-chemotherapy regimens containing doxorubicin were evaluated for clinical features predictive of overall survival and relapse-free survival. Features that remained independently significant in step-down regression analyses of survival were incorporated into models that identified groups of patients of all ages and groups of patients no more than 60 years old with different risks of death. RESULTS In 2031 patients of all ages, our model, based on age, tumor stage, serum lactate dehydrogenase concentration, performance status, and number of extranodal disease sites, identified four risk groups with predicted five-year survival rates of 73 percent, 51 percent, 43 percent, and 26 percent. In 1274 patients 60 or younger, an age-adjusted model based on tumor stage, lactate dehydrogenase level, and performance status identified four risk groups with predicted five-year survival rates of 83 percent, 69 percent, 46 percent, and 32 percent. In both models, the increased risk of death was due to both a lower rate of complete responses and a higher rate of relapse from complete response. These two indexes, called the international index and the age-adjusted international index, were significantly more accurate than the Ann Arbor classification in predicting long-term survival. CONCLUSIONS The international index and the age-adjusted international index should be used in the design of future therapeutic trials in patients with aggressive non-Hodgkin's lymphoma and in the selection of appropriate therapeutic approaches for individual patients.

4,310 citations


Journal ArticleDOI
TL;DR: In this article, a coding scheme for classifying physical activity by rate of energy expenditure, i.e., by intensity, was presented for classification of physical activity using five digits that classify activity by purpose (i.e. sports, occupation, sel
Abstract: A coding scheme is presented for classifying physical activity by rate of energy expenditure, i.e., by intensity. Energy cost was established by a review of published and unpublished data. This coding scheme employs five digits that classify activity by purpose (i.e., sports, occupation, sel

3,679 citations


Journal ArticleDOI
TL;DR: In this article, the authors examined partial least squares and principal components regression from a statistical perspective and compared them with other statistical methods intended for those situations, such as variable subset selection and ridge regression.
Abstract: Chemometrics is a field of chemistry that studies the application of statistical methods to chemical data analysis. In addition to borrowing many techniques from the statistics and engineering literatures, chemometrics itself has given rise to several new data-analytical methods. This article examines two methods commonly used in chemometrics for predictive modeling—partial least squares and principal components regression—from a statistical perspective. The goal is to try to understand their apparent successes and in what situations they can be expected to work well and to compare them with other statistical methods intended for those situations. These methods include ordinary least squares, variable subset selection, and ridge regression.

2,309 citations


Posted Content
TL;DR: The authors found that agglomeration more than offsets congestion effects in denser areas, which explains more than 50% of the observed state productivity differences, given the large differences in density.
Abstract: Two different models - one based on local geographical externalities and the other on the variety of only locally available intermediate services - are shown to give rise to a simple, estimable relation between employment density and productivity. Using data on gross state output for the U.S., we find that agglomeration more than offsets congestion effects in denser areas. While our estimate of the elasticity of productivity with respect to density is small, it explains more than 50% of the observed state productivity differences, given the large differences in density.

2,294 citations


Journal ArticleDOI
TL;DR: Starting moderately vigorous sports activity, quitting cigarette smoking, maintaining normal blood pressure, and avoiding obesity were separately associated with lower rates of death from all causes and from coronary heart disease among middle-aged and older men.
Abstract: Background Recent trends toward increasing physical exercise, stopping cigarette smoking, and avoiding obesity may increase longevity. We analyzed changes in the lifestyles of Harvard College alumni and the associations of these changes with mortality. Methods Men who were 45 to 84 years of age in 1977 and who had reported no life-threatening disease on questionnaires completed in 1962 or 1966 and again in 1977 were classified according to changes in lifestyle characteristics between the first and second questionnaires. We analyzed changes in their level of physical activity, cigarette smoking, blood pressure, and body weight, and the relation of these factors to mortality between 1977 and 1985. Results Of the 10,269 men, 476 died during this period (which totaled 90,650 man-years of observation). Beginning moderately vigorous sports activity (at an intensity of 4.5 or more metabolic equivalents) was associated with a 23 percent lower risk of death (95 percent confidence interval, 4 to 42 percent; P = 0.0...

Journal ArticleDOI
05 Nov 1993-Cell
TL;DR: It is reported that in the absence of SNAP and NSF, these three SNAREs form a stable complex that can also bind synaptotagmin, suggesting that synapttagmin operates as a "clamp" to prevent fusion from proceeding in the absent of a signal.

Journal ArticleDOI
Yoav Shoham1
TL;DR: The concept of agent-oriented programming is presented, the concept of mental state and its formal underpinning are discussed, a class of agent interpreters are defined, and a specific interpreter that has been implemented is described.


Journal ArticleDOI
TL;DR: The findings raise the possibility that unsuspected estrogenic activity in the form of BPA may have an impact on experiments employing media autoclaved in polycarbonate flasks, and it remains to be determined whether BPA derived from consumer products manufactured from poly carbonate could significantly contribute to the pool of estrogenic substances in the environment.
Abstract: In studies to determine whether Saccharomyces cerevisiae produced estrogens, the organism was grown in culture media prepared using distilled water autoclaved in polycarbonate flasks. The yeast-conditioned media showed the presence of a substance that competed with [3H]estradiol for binding to estrogen receptors (ER) from rat uterus. However, it soon became clear that the estrogenic substance in the conditioned media was not a product of the yeast grown in culture, but was leached out of the polycarbonate flasks during the autoclaving procedure. [3H]Estradiol displacement activity was monitored by ER RRA, and the active substance was purified from autoclaved medium using a series of HPLC steps. The final purified product was identified as bisphenol-A (BPA) by nuclear magnetic resonance spectroscopy and mass spectrometry. BPA could also be identified in distilled water autoclaved in polycarbonate flasks without the requirement of either the organism or the constituents of the culture medium. Authentic BPA was active in competitive RRAs, demonstrating an affinity approximately 1:2000 that of estradiol for ER. In functional assays, BPA (10-25 nM) induced progesterone receptors in cultured human mammary cancer cells (MCF-7) at a potency of approximately 1:5000 compared to that of estradiol. The BPA effect on PR induction was blocked by tamoxifen. In addition, BPA (25 nM) increased the rate of proliferation of MCF-7 cells assessed by [3H]thymidine incorporation. Thus, BPA exhibited estrogenic activity by both RRA and two functional bioresponse assays. Finally, MCF-7 cells grown in media prepared with water autoclaved in polycarbonate exhibited higher progesterone receptor levels than cells.grown in media prepared with water autoclaved in glass, suggesting an estrogenic effect of the water autoclaved in polycarbonate. Our findings raise the possibility that unsuspected estrogenic activity in the form of BPA may have an impact on experiments employing media autoclaved in polycarbonate flasks. It remains to be determined whether BPA derived from consumer products manufactured from polycarbonate could significantly contribute to the pool of estrogenic substances in the environment.

Journal ArticleDOI
TL;DR: The role of reasons in decision making is considered as it relates to uncertainty, conflict, context effects, and normative decision rules.

Journal ArticleDOI
TL;DR: More research is needed into the etiologic roles of menstrual cycle characteristics, especially research examining the probability of prolonged exposure to both estrogens and progesterone concurrently.
Abstract: PIP: Early age at menarche, late age at menopause, and late age at first full-term pregnancy are linked to a modest increase in the risk of developing breast cancer. Some evidence suggests that the earlier the full-term pregnancy, the earlier the period of decreased susceptibility of breast tissue changes begins. Nulliparity is related to an increased risk for breast cancer diagnosed after 40 years old. Multiple full-term pregnancies decrease the risk of breast cancers diagnosed after 40 years regardless of the age at first birth. On the other hand, they may increase the risk for breast cancers diagnosed before 40 years old. Surgical removal of the ovaries protects against breast cancer. Breast feeding apparently protects against breast cancer in China, but a protective effect has not been established in the US. Other than shorter intervals between menstrual periods, which tend to increase the risk, research has not yet made clear the etiologic roles of menstrual cycle characteristics. Other unclear etiologic roles include increased intervals between births, spontaneous and induced abortion, infertility, multiple births at last pregnancy, and hypertension during pregnancy. Researchers tend to accept a mechanism to explain the epidemiologic characteristics of menstrual activity and the increased risk of breast cancer, but no mechanisms have emerged for the other likely risk factors. Greater exposure to estrogen and progesterone simultaneously are linked to early age at menarche, late age at menopause, and shorter menstrual cycle length. So far, data show that long-term combined estrogen/progestin hormone replacement therapy and long-term use of oral contraceptives increase the risk of breast cancer. Moderately increased risks linked to longterm estrogen replacement therapy and obesity in postmenopausal women indicate that estrogen alone influences breast cancer risk. Since much of the research on breast cancer risk factors are inconclusive, more research is needed, especially research examining the probability of prolonged exposure to both estrogens and progesterone concurrently.

Journal ArticleDOI
16 Jul 1993-Cell
TL;DR: In this paper, the authors demonstrate that the lymphocyte integrin alpha 4 beta 7, also implicated in homing to Peyer's patches and the intestinal lamina propria, is a receptor for MAdCAM-1.


Journal ArticleDOI
TL;DR: To avoid model-dependent extrapolation from irrelevant regions of ROC space, this work proposes defining a priori a value of FPR so large that the test simply would not be used at that FPR, and avalue of TPR so low that theTestWould not be use at that TPR.
Abstract: We consider how to combine several independent studies of the same diagnostic test, where each study reports an estimated false positive rate (FPR) and an estimated true positive rate (TPR). We propose constructing a summary receiver operating characteristic (ROC) curve by the following steps. (i) Convert each FPR to its logistic transform U and each TPR to its logistic transform V after increasing each observed frequency by adding 1/2. (ii) For each study calculate D = V - U, which is the log odds ratio of TPR and FPR, and S = V + U, an implied function of test threshold; then plot each study's point (Si, Di). (iii) Fit a robust-resistant regression line to these points (or an equally weighted least-squares regression line), with V - U as the dependent variable. (iv) Back-transform the line to ROC space. To avoid model-dependent extrapolation from irrelevant regions of ROC space we propose defining a priori a value of FPR so large that the test simply would not be used at that FPR, and a value of TPR so low that the test would not be used at that TPR. Then (a) only data points lying in the thus defined north-west rectangle of the unit square are used in the data analysis, and (b) the estimated summary ROC is depicted only within that subregion of the unit square. We illustrate the methods using simulated and real data sets, and we point to ways of comparing different tests and of taking into account the effects of covariates.

Journal ArticleDOI
TL;DR: The degree of technical certainty or consensus is clearly affected by the fundamental nature of the subject of study, but consensus is also produced by social practices that differentiate fields that are more or less paradigmatically developed.
Abstract: The level of paradigm development—technical certainty and consensus—characterizing a field of study has numerous consequences for the social organization and operation of that field. These consequences, ranging from the ability to obtain resources to the ease of working collaboratively on research, have an impact on the subsequent development of the field (i.e., through a positive feedback loop). Although the degree of technical certainty or consensus is clearly affected by the fundamental nature of the subject of study, consensus is also produced by social practices that differentiate fields that are more or less paradigmatically developed. The study of organizations is arguably paradigmatically not well developed, in part because of values that emphasize representativeness, inclusiveness, and theoretical and methodological diversity. Although these values are attractive ideals, there are consequences for the field's ability to make scientific progress, which almost requires some level of consensus, as w...

Journal ArticleDOI
TL;DR: Three postulates asserting the validity of conventional quantum theory, semiclassical general relativity, and the statistical basis for thermodynamics are introduced as a foundation for the study of black-hole evolution are explained.
Abstract: Three postulates asserting the validity of conventional quantum theory, semiclassical general relativity, and the statistical basis for thermodynamics are introduced as a foundation for the study of black-hole evolution. We explain how these postulates may be implemented in a "stretched horizon" or membrane description of the black hole, appropriate to a distant observer. The technical analysis is illustrated in the simplified context of (1+1)-dimensional dilaton gravity. Our postulates imply that the dissipative properties of the stretched horizon arise from a course graining of microphysical degrees of freedom that the horizon must possess. A principle of black-hole complementarity is advocated. The overall viewpiont is similar to that poineered by 't Hooft but the detailed implementation is different.

Journal ArticleDOI
TL;DR: Regression analyses suggested that the more ruminative responses subjects engaged in, the longer their periods of depressed mood, even after taking into account the initial severity of the mood.
Abstract: We examined the relationship between ruminative and distracting styles of responding to depressed mood and the duration of mood. Seventy-nine subjects kept accounts of their moods and responses to their moods for 30 consecutive days. The majority of subjects (83%) showed consistent styles of responding to depressed mood. Regression analyses suggested that the more ruminative responses subjects engaged in, the longer their periods of depressed mood, even after taking into account the initial severity of the mood. In addition, women were more likely than men to have a ruminative response style and on some measures to have more severe and long-lasting periods of depression.

Journal ArticleDOI
TL;DR: The statistical distribution for the sum of the scores of multiple high-scoring segments is described and its application to the identification of possible transmembrane segments and the evaluation of sequence similarity is illustrated.
Abstract: Score-based measures of molecular-sequence features provide versatile aids for the study of proteins and DNA They are used by many sequence data base search programs, as well as for identifying distinctive properties of single sequences For any such measure, it is important to know what can be expected to occur purely by chance The statistical distribution of high-scoring segments has been described elsewhere However, molecular sequences will frequently yield several high-scoring segments for which some combined assessment is in order This paper describes the statistical distribution for the sum of the scores of multiple high-scoring segments and illustrates its application to the identification of possible transmembrane segments and the evaluation of sequence similarity

Journal ArticleDOI
TL;DR: In patients with idiopathic dilated cardiomyopathy, treatment with metoprolol prevented clinical deterioration, improved symptoms and cardiac function, and was well tolerated.

Journal ArticleDOI
TL;DR: In this article, the As and Fe K-edges were collected from samples of two-line ferrihydrite with adsorbed (ADS) and coprecipitated (CPT) arsenate prepared over a range of conditions and arsenate surface coverages.

Journal ArticleDOI
TL;DR: Viral nucleoprotein complexes isolated from arrested cells contain full‐length viral DNA and can integrate this viral DNA in vitro, showing that the block to integration in arrested cells is not due to a lack of mature integration machinery.
Abstract: In synchronized rat or mouse cells infected with Moloney murine leukemia virus (MLV), integration of viral DNA and production of viral proteins occur only after the cells traverse mitosis. Integration is blocked when cells are prevented from progressing through mitosis. Viral nucleoprotein complexes isolated from arrested cells contain full-length viral DNA and can integrate this viral DNA in vitro, showing that the block to integration in arrested cells is not due to a lack of mature integration machinery. When infected cells traverse mitosis, there is a sharp increase in nuclear accumulation of viral DNA. The dependence of integration on mitosis may therefore be due to a requirement for mitosis and nuclear envelope breakdown for entry of the viral integration complex into the nucleus.

Journal ArticleDOI
TL;DR: In this paper, the structure of the intense-vorticity regions is studied in numerically simulated homogeneous, isotropic, equilibrium turbulent flow fields at four different Reynolds numbers, in the range Re, = 35-170.
Abstract: The structure of the intense-vorticity regions is studied in numerically simulated homogeneous, isotropic, equilibrium turbulent flow fields at four different Reynolds numbers, in the range Re, = 35-170. In accordance with previous investigators this vorticity is found to be organized in coherent, cylindrical or ribbon-like, vortices (‘worms’). A statistical study suggests that they are simply especially intense features of the background, O(o’), vorticity. Their radii scale with the Kolmogorov microscale and their lengths with the integral scale of the flow. An interesting observation is that the Reynolds number y/v, based on the circulation of the intense vortices, increases monotonically with ReA, raising the question of the stability of the structures in the limit of Re, --z co. Conversely, the average rate of stretching of these vortices increases only slowly with their peak vorticity, suggesting that self-stretching is not important in their evolution. One- and two-dimensional statistics of vorticity and strain are presented; they are non-Gaussian and the behaviour of their tails depends strongly on the Reynolds number. There is no evidence of convergence to a limiting distribution in this range of Re,, even though the energy spectra and the energy dissipation rate show good asymptotic properties in the higher-Reynolds-number cases. Evidence is presented to show that worms are natural features of the flow and that they do not depend on the particular forcing scheme.

Journal ArticleDOI
TL;DR: This article found that ruminative responses to depressed mood exacerbate and prolong depressed mood, whereas distracting response shorten depressed mood and did not affect the moods of non-depressed subjects.
Abstract: Mildly-to-moderately depressed and nondepressed subjects were randomly assigned to spend 8 minutes focusing their attention on their current feeling states and personal characteristics (rumination condition) or on descriptions of geographic locations and objects (distraction condition). Depressed subjects in the rumination condition became significantly more depressed, whereas depressed subjects in the distraction condition became significantly less depressed. Rumination and distraction did not affect the moods of nondepressed subjects. These results support the hypothesis that ruminative responses to depressed mood exacerbate and prolong depressed mood. whereas distracting response shorten depressed mood.

Journal ArticleDOI
TL;DR: This essay was prompted by the Editor’s invitation to illustrate the excitement and adventure inherent in scientific work while reflecting on my own preoccupation, as an evolutionary biologist, with biological clocks.
Abstract: This essay was prompted by the Editor’s invitation to illustrate the excitement and adventure inherent in scientific work while reflecting on my own preoccupation, as an evolutionary biologist, with biological clocks. In considering the challenge, the first adventure that came to mind occurred one evening 30 years ago when a drunken graduate student, frustrated by an unwanted experimental result, attempted to throw me out of a second story window in Princeton. He didn’t succeed. That seemed a good Indiana Jones start, but nothing as exciting occurred in later years, and all the adventures I can recount are less spectacular--the excitement of experiment and the hazardous fate of observation and ideas in the pursuit of understanding. While circadian periodicities have been the immediate object of my research for 40 years, that “view of life,” which Darwin so eloquently summarized in the last paragraph of “The Origin of Species,” has so dominated and guided my approach that it gets substantial attention in these reflections and hopefully ties together much of what I have to say about biological clocks. This Darwinian approach to behavioral and physiological interests traces to the accidental way I became a biologist. At 15 I kicked a soccer ball through a very large window in the Town Hall where I lived in the north of England. The only foreseeable source of the 13 shillings needed to replace it was a prize offered to local Boy Scouts for the best wild flower collection. In winning that prize, I got more money than was needed for the window and was seduced into a lasting love affair with plant