scispace - formally typeset
Search or ask a question

Showing papers by "Northwestern University published in 1979"


Journal ArticleDOI
TL;DR: In this article, the authors present a model for competitive entry and long run equilibrium in industry equilibria, and propose a welfare analysis of industry equilibrium, and conclude that the model is not optimal.
Abstract: I. Introduction, 395.—II. The model, 397.—III. Competitive entry and long-run equilibrium, 402.—IV. Welfare analysis of industry equilibria, 405.—V. Conclusion, 408.

1,474 citations


Journal ArticleDOI
TL;DR: In this article, the learned helplessness theory of depression was used to predict the degree of contingency between responses and outcomes relative to the objective degree of contingencies, and the predicted subjective judgments of contingency were surprisingly accurate in all four experiments.
Abstract: SUMMARY How are humans' subjective judgments of contingencies related to objective contingencies? Work in social psychology and human contingency learning predicts that the greater the frequency of desired outcomes, the greater people's judgments of contingency will be. Second, the learned helplessness theory of depression provides both a strong and a weak prediction concerning the linkage between subjective and objective contingencies. According to the strong prediction, depressed individuals should underestimate the degree of contingency between their responses and outcomes relative to the objective degree of contingency. According to the weak prediction, depressed individuals merely should judge that there is a smaller degree of contingency between their responses and outcomes than nondepressed individuals should. In addition, the present investigation deduced a new strong prediction from the helplessness theory: Nondepressed individuals should overestimate the degree of contingency between their responses and outcomes relative to the objective degree of contingency. In the experiments, depressed and nondepressed students were presented with one of a series of problems varying in the actual degree of contingency. In each problem, subjects estimated the degree of contingency between their responses (pressing or not pressing a button) and an environmental outcome (onset of a green light). Performance on a behavioral task and estimates of the conditional probability of green light onset associated with the two response alternatives provided additional measures for assessing beliefs about contingencies. Depressed students' judgments of contingency were surprisingly accurate in all four experiments. Nondepressed students, on the other hand, overestimated the degree of contingency between their responses and outcomes when noncontingent outcomes were frequent and/or desired and underestimated the degree of contingency when contingent outcomes were undesired. Thus, predictions derived from social psychology concerning the linkage between subjective and objective contingencies were confirmed for nondepressed students but not for depressed students. Further, the predictions of helplessness theory received, at best, minimal support. The learned helplessness and self-serving motivational bias hypotheses are evaluated as explanations of the results. In addition, parallels are drawn between the present results and phenomena in cognitive psychology, social psychology, and animal learning. Finally, implications for cognitive illusions in normal people, appetitive helplessness, judgment of contingency between stimuli, and learning theory are discussed.

1,302 citations



Journal ArticleDOI
TL;DR: In this paper, the authors report on program impact assessment methodology as it is developing in the United States today, and assume that social project evaluation methodology is one of the fields of science that has enough universality to make scientific sharing mutually beneficial.

737 citations


Journal ArticleDOI
TL;DR: Vygotsky's notions of speech, language and thought have recently begun to receive more attention in the west, but some of his basic distinctions are not well understood.
Abstract: Vygotsky’s notions of speech, language and thought have recently begun to receive more attention in the west, but some of his basic distinctions are not well understood. The first part of this paper d

684 citations


Journal ArticleDOI
TL;DR: A comparison of the production costs of "pure" discrimination and positive production costs shows that the former is higher than the latter and the latter is lower.
Abstract: Presents a model that examines the behavior of a monopolist selling a new product. Factors that influence time as a medium for price discrimination; Example that assumes no production costs to illustrate that discrimination is the only motive for selling to different buyers at different dates at different prices; Introduction of positive costs of production to explore an alternative motive for inter temporal price variation. (Из Ebsco)

558 citations


Journal ArticleDOI
TL;DR: In this article, the results of accurate fully relativistic Dirac-Fock studies of some electronic properties of rare-earth ions were reported, in addition to eigenvalue information including spin-orbit splittings.

557 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of cancer on the patient's interpersonal relationships and the ultimate impact of these relationships on patient's emotional adjustment to the disease was explored. But, the authors focused on the effect on the patients' interpersonal relationships.
Abstract: This paper focuses on the effect of cancer on the patient's interpersonal relationships, and the ultimate impact of these relationships on the patient's emotional adjustment to the disease. In a detailed theoretical analysis, both the patient's reaction to the illness and others' responses toward the patient are explored. Concerning the patient, the following issues are discussed: (1) fears and uncertainties that develop as one attempts to cope with the diagnosis; (2) the consequent need for clarification and support; and (3) the barriers to receiving validation and support from others. Others' reactions to the patient are hypothesized to be a function of a conflict between (1) their feelings about the illness, which are predominantly negative; and (2) their beliefs about appropriate behaviors to display when interacting with cancer patients (optimism and cheerfulness). This conflict results in behavioral responses that are unintentionally damaging to the patient, including physical avoidance, avoidance of open discussion of the illness, and discrepancies among behaviors. The impact of others' behavior on the patient and the patient's subsequent attempts to solve their interpersonal problems are discussed. The paper concludes with implications for intervention and research.

515 citations


Journal ArticleDOI
TL;DR: In this article, the authors presented global data for sources of atmospheric input for 20 trace metals, and the relative importance of natural and anthropogenic sources is assessed, where interference factors are calculated as (total anthropogenic emissions/total natural emissions) × 100.

487 citations


Journal ArticleDOI
TL;DR: Forward masking in single fibers is related to the period of poststimulus recovery of spontaneous activity, a component of a fiber's response pattern to the masker, and this component is tentatively identified as a period of recovery from short-term adaptation.
Abstract: 1. Responses of single fibers were obtained from the auditory nerve of chinchillas. Tone-burst stimuli consisted of a masking stimulus followed by a probe stimulus. Forward masking of a fiber's response is defined as a reduction in the magnitude of the probe-evoked response caused by the addition of the masking stimulus. 2. The recovery of probe response magnitude as a function of the time interval between masker offset and probe onset (delta T) follows an exponential time course. A relationship between the time course or magnitude of poststimulus recovery and the characteristic frequency (CF) of a fiber was not detected. 3. The iso-forward masking contour near the threshold of the masking effect across masker frequencies approximates a fiber's frequency threshold curve (FTC). In other words, forward masking tuning curves are essentially the same as frequency threshold curves. 4. The frequency dependence of forward masking is compared to that of two-tone suppression. Tonal stimuli outside the boundaries of a fiber's FTC that produce two-tone suppression are ineffective forward maskers. Certain frequency/intensity combinations within the FTC may produce both suppression and forward masking and tones within the remaining area of the FTC produce no suppression but are effective forward maskers. 5. Both the time course and the magnitude of the forward masking effect are dependent on the discharge rate evoked by the masker regardless of the masker's absolute level or spectral content. An increase in masker-evoked excitation causes an increase in time constant and a greater reduction in probe response magnitude, rd. The function relating rd to masker level parallels the firing rate/masker level function up to 40 dB above response threshold. 6. A decrease in masker duration from 100 ms leads to a decrease in both rd and the time constant of recovery. There is no significant difference between the 100 and 200 ms duration conditions. 7. Forward masking in single fibers is related to the period of poststimulus recovery of spontaneous activity, a component of a fiber's response pattern to the masker, and this component is tentatively identified as a period of recovery from short-term adaptation.

405 citations


Journal ArticleDOI
TL;DR: In this article, a physical-mathematical model for concrete exposed to sea water is developed for concrete, which describes: (1)Diffusion of oxygen, chloride ions, and pore water through the concrete cover of reinforcement; (2) ferrous hydroxide near steel surface; (3) depassivation of steel due to critical chloride ion concentration; (4) the cathodic and anodic electric potentials depending on oxygen and ferrous hyroxide concentrations according to Nernst equation; (5) the polarization of electrodes due to changes in concentration
Abstract: A physical-mathematical model is developed for concrete exposed to sea water. The model describes: (1)Diffusion of oxygen, chloride ions, and pore water through the concrete cover of reinforcement; (2)ferrous hydroxide near steel surface; (3)the depassivation of steel due to critical chloride ion concentration; (4)the cathodic and anodic electric potentials depending on oxygen and ferrous hydroxide concentrations according to Nernst equation; (5)the polarization of electrodes due to changes in concentration of oxygen and ferrous hydroxide; (6)the flow of electric current through the electrolyte in pores of concrete; (7)the mass sinks or sources of oxygen, ferrous hydroxide, and hydrated red rust electrodes, based on Faraday law; and (8)the rust production rate, based on reaction kinetics. To enable calculations, numerical values of all coefficients are indicated. The theory is completed by formulating the problem as an initial-boundary value problem.

Journal ArticleDOI
TL;DR: In this article, the authors derived the variational principle governing the displacement distribution on a unit sphere about point 0 of the crack front edge at the surface of an elastic body, using spherical coordinates r, θ, φ and assuming all three displacements to be of the form r λ p p F ( θ, λ ) where p = distance from the singularity line (crack front edge or notch edge) and p = given constant.

Journal ArticleDOI
TL;DR: In this paper, the authors present conditions générales d'utilisation (http://www.numdam.org/conditions), i.e., Toute copie ou impression de ce fichier doit contenir la présente mention de copyright.
Abstract: © Publications mathématiques de l’I.H.É.S., 1979, tous droits réservés. L’accès aux archives de la revue « Publications mathématiques de l’I.H.É.S. » (http:// www.ihes.fr/IHES/Publications/Publications.html) implique l’accord avec les conditions générales d’utilisation (http://www.numdam.org/conditions). Toute utilisation commerciale ou impression systématique est constitutive d’une infraction pénale. Toute copie ou impression de ce fichier doit contenir la présente mention de copyright.

Journal ArticleDOI
TL;DR: Hierachical cluster analysis is shown to be an effective method for forming scales from sets of items by testing the psychometric adequacy of each potential scale by using a new measure of internal consistency reliability, coefficient beta.
Abstract: Hierachical cluster analysis is shown to be an effective method for forming scales from sets of items. The number of scales to form from a particular item pool is found by testing the psychometric adequacy of each potential scale. Higher-order scales are formed when they are more adequate than their component sub-scales. It is suggested that a scale's adequacy should be assessed by a new measure of internal consistency reliability, coefficient beta, which is defined as the worst split-half reliability of the test. Comparisons with other procedures show that hierarchical clustering algorithms using this psychometrically based decisions rule can be more useful for scale construction using large item pools than are conventional factor analytic techniques.

Journal ArticleDOI
TL;DR: In this article, the basic set of global intraplate stress orientation data is plotted and tabulated, and several large-scale patterns can be seen, such as the E-W to NE-SW trend for the maximum compressive stress.
Abstract: In the present paper, the basic set of global intraplate stress orientation data is plotted and tabulated. Although the global intraplate stress field is complicated, several large-scale patterns can be seen. Much of stable North America is characterized by an E-W to NE-SW trend for the maximum compressive stress. South American lithosphere beneath the Andes, and perhaps farther east in the stable interior, has horizontal compressive stresses trending E-W to NW-SE. Western Europe north of the Alps is characterized by a NW-SE trending maximum horizontal compression, while Asia has the maximum horizontal compressive stress trending more nearly N-S, especially near the Himalayan front.

Journal ArticleDOI
TL;DR: In this paper, a correlation is suggested for available experimental measurements of the advancing dynamic contact angle measured through the liquid phase during the displacement of a liquid-gas interface through a glass capillary tube.

Journal ArticleDOI
TL;DR: The data have led us to conclude that the 5 day cycle is due to a prolonged progesterone secretion during the metestrous and diestrous stages of the cycle.
Abstract: The present study was undertaken to characterize hormonal and morphological events in 4 day and 5 day rat cycles, in order to test 3 different theories concerning the etiological factors altering follicular phase length in mammals. Three rats were killed at each 2 h interval throughout each cycle type. In addition to organ weight measurements, serum levels of estradiol, progesterone, 20ohydroxypreg-4-en-3-one, LH, FSH and prolactin were assessedin terminal samples. The beginning of uterine intraluminal fluid accumulation coincided with the decline in progesterone levels seen during diestrus, rather than with the rise in estrogen and was delayed 12 h in the 5 day cycle from the time of last estrus. The retention of this fluid during the evening of proestrus was 6 h longer in the 4 day cycling rat. Ovulation occurred earlier in the 5 day cycling rats than in those with a 4 day cycle. No significant differences in the gonadotropins or 2oo-hydroxypreg-4-en-3-one were seen when comparing the 2 types of cycles. Estradiol rose during the night of diestrus I (the same time in the cycle) and was identical in both cycle types. Progesterone was not released on proestrus prior to the LH surge in either type of cycle. However, we did find that progesterone values were higher for a longer period of time throughout diestrus I in 5 day cycles. These data have led us to conclude that the 5 day cycle is due to a prolonged progesterone secretion during the metestrous and diestrous stages of the cycle.

Journal ArticleDOI
TL;DR: In most articles appearing in the organizational behavior journals, little reference is made to the extensive research performed in the marketing field addressing interactions in distribution channels as mentioned in this paper, which will improve theories of interorganizational relations.
Abstract: In most articles appearing in the organizational behavior journals, little reference is made to the extensive research performed in the marketing field addressing interactions in distribution channels. This article attempts to bring to the fields of sociology and organizational behavior relevant materials from marketing that will improve theories of interorganizational relations.

Journal ArticleDOI
TL;DR: Marketing is a topic of growing interest to nonprofit organization managers as their organizations confront new, complex marketplace problems as mentioned in this paper, and these institution heads are taking their first, tentat...
Abstract: Marketing is a topic of growing interest to nonprofit organization managers as their organizations confront new, complex marketplace problems. These institution heads are taking their first, tentat...

Journal ArticleDOI
TL;DR: In this paper, a conceptual and a methodological framework for examining organizational buying behavior from a multiperson level of analysis is presented, focusing on those organizational members who buy products from multiple vendors.
Abstract: This research presents both a conceptual and a methodological framework for examining organizational buying behavior from a multiperson level of analysis. Focusing on those organizational members w...

Journal ArticleDOI
TL;DR: In this article, the extended Huygens-Fresnel principle is used to formulate general expressions of the mutual intensity function for a finite optical source with partial spatial coherence propagating in the weakly turbulent atmosphere.
Abstract: The extended Huygens-Fresnel principle is used to formulate general expressions of the mutual intensity function for a finite optical source with partial spatial coherence propagating in the weakly turbulent atmosphere. Formulations are developed for both the focused and collimated Gaussian beam. Generalized criterion for the effective far-field range is defined in terms of the source aperture, optical wave number, source coherence, and characteristic length associated with the atmospheric turbulence. Beam spread and lateral coherence length in the near and far field are investigated for a combination of parameter variations and the physical implications discussed. Finally, analytic results are calculated and plotted to illustrate the functional behavior of relevant physical parameters.

Journal ArticleDOI
TL;DR: In this article, three objective methods for the propagation of a crack band of a blunt front are proposed based on the rate of energy release by the crack band and the angle of the crack front.
Abstract: A propagating smeared crack band of blunt front is much simpler to model by finite elements than a sharp interelement crack, especially when the propagation direction is unknown. For concrete or rock, a smeared crack band is also more realistic. A strength criterion is generally used for the propagation, but this is not objective because of a strong spurious dependence of results on the chosen element size, Three objective methods, which avoid the use of singularity elements, are proposed. Method A is based on the rate of energy release by the blunt crack band. In method B, the usual strength criterion is used but an adjustment of the strength value according to the element size is proposed. In method C, the propagation direction and crack advance are determined by fitting the Mode I asymptotic series to nodal displacements around the crack front, using an optimization subroutine. Special merits of each method are analyzed and solutions of example problems are compared with exact ones.

Journal ArticleDOI
TL;DR: In this paper, a composite, two-dimensional, linear elastic wedge for singular stresses at its vertex is examined and a full range of wedge boundary and matching conditions is considered, using separation of variables on the Airy stress function.
Abstract: This paper examines the composite, two-dimensional, linear elastic wedge for singular stresses at its vertex. A full range of wedge boundary and matching conditions is considered. Using separation of variables on the Airy stress function, the usual determinant conditions for singularities of the formO(r -λ) asr → 0 are established and further conditions are derived for singularities of the formO(r -λ lnr) asr → 0. The order of the determinant involved in these conditions depends upon the number of materials comprising the wedge. Two systematic methods of expanding the determinant for theN-material wedge are presented.

Journal ArticleDOI
TL;DR: In this article, the electrical conductivity of cuprous chloride containing a dispersion of fine alumina particles was studied as a function of volume fraction (0.212) and particle size ( 0.3 and 0.06 μm initial particle size).
Abstract: The electrical conductivity of cuprous chloride containing a dispersion of fine alumina particles was studied as a function of volume fraction (0–0.212) and particle size (0.3 and 0.06 μm initial particle size). At low temperatures the ionic conductivity may be increased by as much as two orders of magnitude. The enhanced conductivity, Δσ, was proportional to the surface area of the added alumina. Both these data and the earlier data of Liang (1) were fitted to a relation, where is the radius of the alumina dispersoids and the volume fraction.

Journal ArticleDOI
TL;DR: In this article, a generalization of the bulk linearized augmented plane-wave (LAPW) method is proposed for treating the electronic structure of thin films, which is based on a generalized version of the LAPW method and combines the advantages of energy-independent muffin-tin Hamiltonian methods.
Abstract: We present a new method for treating the electronic structure of thin films which is based on a generalization of the bulk linearized augmented-plane-wave (LAPW) method. This method avoids using the slab-superlattice geometry and combines the advantages of energy-independent muffin-tin Hamiltonian methods [fast root evaluation and rapid convergence for $d$-band metals as well as for nearly-free-electron (NFE) crystals] with the simple matrix element determination of the original augmented plane-wave (APW) method. As in the bulk LAPW method, the asymptote problem of the APW method is avoided, and the basis functions are everywhere continuous and differentiable. In addition, the film LAPW method retains such desirable features of the APW method as the ability to treat general potentials with no shape approximations, the ease with which relativistic effects can be included, and the fact that the basis size does not increase substantially for heavier elements. As a first application and test of the method, non-self-consistent calculations are performed in the local-density approximation for exchange and correlation and with the one-electron potential constructed from a superposition of atomic charge densities. A semirelativistic formulation is employed in which the Dirac equation is solved in the limit of zero spin-orbit coupling inside the muffin-tin spheres. Results are reported for up to five atomic layer thin films (slabs) of the transition metals Fe, Co, Ni, and Cu and a nine-layer film of the NFE metal Al. The results are in generally good agreement with other theoretical calculations. Some trends in the transition-metal band structures are discussed. A surface-state surface-resonance band for Al(001) is found to completely account for and clarify behavior observed in very recent photoemission measurements.

Journal ArticleDOI
TL;DR: In this paper, the authors proposed to reduce the multicollinearity among the independent variables in a regression model by centering these variables around minimizing constants before forming the multiplicative function.
Abstract: When the multicollinearity among the independent variables in a regression model is due to the high correlations of a multiplicative function with its constituent variables, the multicollinearity can be greatly reduced by centering these variables around minimizing constants before forming the multiplicative function. The values of these constants that minimize the multicollinearity are derived, and the conditions are identified under which centering the variables about their means will reduce the multicollinearity. Among the advantages of this procedure are that the mean square error remains at its minimum, that the coefficients for other variables in the model are unaffected by it, and that the OLS estimates for the original model can be calculated from those for the modified model. Thus, even when estimates of the original model are desired, the procedure can be used to reduce numerical error.

Journal ArticleDOI
TL;DR: In this paper, a simplified calculation of corrosion rates and times to corrosion cracking of concrete cover is presented, based on the theoretical physical model developed in a companion paper, which is applied to calculate the effective resistance of the corrosion cell and treating oxygen and chloride ion transport through concrete cover as quisi-stationary and one-dimensional.
Abstract: The theoretical physical model developed in a companion paper, is applied to a simplified calculation of corrosion rates and times to corrosion cracking of concrete cover. Setting up approximate estimates of effective resistance of the corrosion cell, and treating oxygen and chloride ion transport through concrete cover as quisi-stationary and one-dimensional, the corrosion problem is reduced to ordinary differential equations in time. For determining the extents of cathodic and anodic areas and the thickness of the rusting layer, a new principle stating that the actual corrosion current is maximum is postulated. Various steady-state corrosion processes are then analyzed, and after developing approximate formulas for the time of steel depassivation due to chloride ions and for cover cracking due to volume expansion of rust, a number of illustrative numerical examples are given. Diffusivities for chloride ions and oxygen are shown to be usually the controlling factors.


Journal ArticleDOI
21 Dec 1979-Science
TL;DR: Injections of rabbit antiserum to rat lymphocytes reversed hyperglycemia in 36 percent of spontaneously diabetic rats and prevented diabetes in susceptible nondiabetic controls, strengthening the hypothesis that cell-mediated autoimmunity plays a role in the pathogenesis of diabetes in this animal model.
Abstract: Injections of rabbit antiserum to rat lymphocytes reversed hyperglycemia in 36 percent of spontaneously diabetic rats (Bio Breeding/Worcester) and prevented diabetes in susceptible nondiabetic controls. These findings strengthen the hypothesis that cell-mediated autoimmunity plays a role in the pathogenesis of diabetes in this animal model that mimics many morpholigic and physiologic characteristics of human insulin-dependent diabetes mellitus.

Journal ArticleDOI
TL;DR: Three techniques for enhancing computational efficiency are presented: explicit- Implicit partitions, explicit-explicit partitions with different time steps, and implicit-implicit partitions.