Showing papers by "University of Chicago published in 1994"
TL;DR: The revised interview has been reorganized, shortened, modified to be appropriate for children with mental ages from about 18 months into adulthood and linked to ICD-10 and DSM-IV criteria.
Abstract: Describes the Autism Diagnostic Interview-Revised (ADI-R), a revision of the Autism Diagnostic Interview, a semistructured, investigator-based interview for caregivers of children and adults for whom autism or pervasive developmental disorders is a possible diagnosis. The revised interview has been reorganized, shortened, modified to be appropriate for children with mental ages from about 18 months into adulthood and linked to ICD-10 and DSM-IV criteria. Psychometric data are presented for a sample of preschool children.
8,264 citations
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TL;DR: In this paper, the authors investigate the determinants of capital structure choice by analyzing the financing decisions of public firms in the major industrialized countries and find that factors identified by previous studies as important in determining the cross-section of the capital structure in the U.S. affect firm leverage in other countries as well.
Abstract: We investigate the determinants of capital structure choice by analyzing the financing decisions of public firms in the major industrialized countries. At an aggregate level, firm leverage is fairly similar across the G-7 countries. We find that factors identified by previous studies as important in determining the cross- section of capital structure in the U.S. affect firm leverage in other countries as well. However, a deeper examination of the U.S. and foreign evidence suggests that the theoretical underpinnings of the observed correlations are still largely unresolved.
5,935 citations
TL;DR: This article present a model of bargaining between politicians and managers that explains many stylized facts about the behavior of state firms, their commercialization, and privatization, including subsidies to public enterprises and bribes from managers to politicians.
Abstract: We present a model of bargaining between politicians and managers that explains many stylized facts about the behavior of state firms, their commercialization, and privatization. Subsidies to public enterprises and bribes from managers to politicians emerge naturally in the model. We use the model and several extensions to understand why commercialization and privatization might work, and what forces contribute to effective restructuring of public enterprises. We illustrate the model using examples from several countries.
3,143 citations
TL;DR: It is proved that the first law of black hole mechanics holds for arbitrary perturbations of a stationary black hole, and a local, geometrical prescription is proposed for the entropy, $S_{dyn}$, of a dynamical black hole.
Abstract: We consider a general, classical theory of gravity with arbitrary matter fields in n dimensions, arising from a diffeomorphism-invariant Lagrangian L. We first show that L alwasy can be written in a ``manifestly covariant'' form. We then show that the symplectic potential current (n-1)-form FTHETA and the symplectic current (n-1)-form \ensuremath{\omega} for the theory always can be globally defined in a covariant manner. Associated with any infinitesimal diffeomorphism is a Noether current (n-1)-form J and corresponding Noether charge (n-2)-form Q. We derive a general ``decomposition formula'' for Q. Using this formula for the Noether charge, we prove that the first law of black hole mechanics holds for arbitrary perturbations of a stationary black hole. (For higher derivative theories, previous arguments had established this law only for stationary perturbations.) Finally, we propose a local, geometrical prescription for the entropy ${\mathit{S}}_{\mathrm{dyn}}$ of a dynamical black hole. This prescription agrees with the Noether charge formula for stationary black holes and their perturbations, and is independent of all ambiguities associated with the choices of L, FTHETA, and Q. However, the issue of whether this dynamical entropy in general obeys a ``second law'' of black hole mechanics remains open. In an appendix, we apply some of our results to theories with a nondynamical metric and also briefly develop the theory of stress-energy pseudotensors.
2,321 citations
TL;DR: Results suggest that the MAb may obstruct the interaction of CTLA-4 with its natural ligand and block a negative signal, or directly signal T cells to down-regulate immune function.
2,086 citations
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TL;DR: In this article, the fundamental role played by factor accumulation in explaining the extraordinary postwar growth of Hong Kong, Singapore, South Korea and Taiwan is discussed, and the authors show that participation rates, educational levels and investment rates have risen rapidly in all four economies, with non-agricultural and manufacturing employment growing one and a half to two times as fast as the aggregate working population.
Abstract: This paper documents the fundamental role played by factor accumulation in explaining the extraordinary postwar growth of Hong Kong, Singapore, South Korea and Taiwan. Participation rates, educational levels and (with the exception of Hong Kong) investment rates have risen rapidly in all four economies. In addition, there have been large intersectoral reallocations of labour, with (again, excepting Hong Kong) non-agricultural and manufacturing employment growing one and a half to two times as fast as the aggregate working population. Thus, while the growth of output per capita in these economies has averaged 6% to 7% per annum over the past two and a half decades, the growth of output per effective worker in the non- agricultural sector of these economies has been only 3% to 4% per annum. If one then allows for the doubling, tripling and even quadrupling of the investment to GDP ratio in these economies, one arrives at total factor productivity growth rates, both for the non- agricultural economy and for manufacturing in particular, which are well within the bounds of those experienced by the OECD and Latin American economies over equally long periods of time. While the growth of output and manufacturing exports in the newly industrializing economies of East Asia is virtually unprecedented, the growth of total factor productivity in these economies is not.
2,062 citations
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TL;DR: The advantages of using research designs patterned after randomized experiments and how they can be improved are described and aids in judging the validity of inferences they draw are provided.
Abstract: Using research designs patterned after randomized experiments, many recent economic studies examine outcome measures for treatment groups and comparison groups that are not randomly assigned. By using variation in explanatory variables generated by changes in state laws, government draft mechanisms, or other means, these studies obtain variation that is readily examined and is plausibly exogenous. This paper describes the advantages of these studies and suggests how they can be improved. It also provides aids in judging the validity of inferences they draw. Design complications such as multiple treatment and comparison groups and multiple pre- or post-intervention observations are advocated.
1,899 citations
TL;DR: In this paper, the authors modeled international crises as a political "war of attrition" in which state leaders choose at each moment whether to attack, back down, or escalate, and found that the side with a stronger domestic audience is always less likely to back down than the side less able to generate audience costs.
Abstract: International crises are modeled as a political “war of attrition” in which state leaders choose at each moment whether to attack, back down, or escalate. A leader who backs down suffers audience costs that increase as the public confrontation proceeds. Equilibrium analysis shows how audience costs enable leaders to learn an adversary's true preferences concerning settlement versus war and thus whether and when attack is rational. The model also generates strong comparative statics results, mainly on the question of which side is most likely to back down. Publicly observable measures of relative military capabilities and relative interests prove to have no direct effect once a crisis begins. Instead, relative audience costs matter: the side with a stronger domestic audience (e.g., a democracy) is always less likely to back down than the side less able to generate audience costs (a nondemocracy). More broadly, the analysis suggests that democracies should be able to signal their intentions to other states more credibly and clearly than authoritarian states can, perhaps ameliorating the security dilemma between democratic states.
1,829 citations
TL;DR: In this paper, a cyclic metropolis algorithm is used to construct a Markov-chain simulation tool for the analysis of stochastic volatility models in which the logarithm of conditional variance follows an autoregressive model.
Abstract: New techniques for the analysis of stochastic volatility models in which the logarithm of conditional variance follows an autoregressive model are developed. A cyclic Metropolis algorithm is used to construct a Markov-chain simulation tool. Simulations from this Markov chain coverage in distribution to draws from the posterior distribution enabling exact finite-sample inference. The exact solution to the filtering/smoothing problem of inferring about the unobserved variance states is a by-product of our Markov-chain method. In addition, multistep-ahead predictive densities can be constructed that reflect both inherent model variability and parameter uncertainty. We illustrate our method by analyzing both daily and weekly data on stock returns and exchange rates. Sampling experiments are conducted to compare the performance of Bayes estimators to method of moments and quasi-maximum likelihood estimators proposed in the literature. In both parameter estimation and filtering, the Bayes estimators outperform ...
1,711 citations
TL;DR: Intravenous cyclosporine therapy is rapidly effective for patients with severe corticosteroid-resistant ulcerative colitis.
Abstract: Background There has been no new effective drug therapy for patients with severe ulcerative colitis since corticosteroids were introduced almost 40 years ago. In an uncontrolled study, 80 percent of 32 patients with active ulcerative colitis refractory to corticosteroid therapy had a response to cyclosporine therapy. Methods We conducted a randomized, double-blind, controlled trial in which cyclosporine (4 mg per kilogram of body weight per day) or placebo was administered by continuous intravenous infusion to 20 patients with severe ulcerative colitis whose condition had not improved after at least seven days of intravenous corticosteroid therapy. A response to therapy was defined as an improvement in a numerical symptom score (0 indicated no symptoms, and 21 severe symptoms) leading to discharge from the hospital and treatment with oral medications. Failure to respond to therapy resulted in colectomy, but some patients in the placebo group who had no response and no urgent need for surgery were subseque...
1,589 citations
TL;DR: Features of the organization of repetitive sequences in eukaryotic genomes, and their distribution in natural populations, reflect the evolutionary forces acting on selfish DNA.
Abstract: Repetitive DNA sequences form a large portion of the genomes of eukaryotes. The 'selfish DNA' hypothesis proposes that they are maintained by their ability to replicate within the genome. The behaviour of repetitive sequences can result in mutations that cause genetic diseases, and confer significant fitness losses on the organism. Features of the organization of repetitive sequences in eukaryotic genomes, and their distribution in natural populations, reflect the evolutionary forces acting on selfish DNA.
TL;DR: The developmental programs of lymphoid and myeloid lineages require a common genetic function likely acting at the level of a multipotential progenitor, and mice carrying a mutation in the PU.1 locus were generated by gene targeting.
Abstract: The transcription factor PU.1 is a hematopoietic-specific member of the ets family. Mice carrying a mutation in the PU.1 locus were generated by gene targeting. Homozygous mutant embryos died at a late gestational stage. Mutant embryos produced normal numbers of megakaryocytes and erythroid progenitors, but some showed an impairment of erythroblast maturation. An invariant consequence of the mutation was a multilineage defect in the generation of progenitors for B and T lymphocytes, monocytes, and granulocytes. Thus, the developmental programs of lymphoid and myeloid lineages require a common genetic function likely acting at the level of a multipotential progenitor.
TL;DR: The recent discovery that CD28 and B7 are each members of larger gene families suggests that the regulation of co-stimulation is more complex than previously imagined.
TL;DR: In this article, the authors proposed an iterated cumulative sum of squares (ICSS) algorithm to detect variance changes in a sequence of independent observations, and compared the results of the ICSS algorithm to those obtained by a Bayesian approach or by likelihood ratio tests.
Abstract: This article studies the problem of multiple change points in the variance of a sequence of independent observations. We propose a procedure to detect variance changes based on an iterated cumulative sums of squares (ICSS) algorithm. We study the properties of the centered cumulative sum of squares function and give an intuitive basis for the ICSS algorithm. For series of moderate size (i.e., 200 observations and beyond), the ICSS algorithm offers results comparable to those obtained by a Bayesian approach or by likelihood ratio tests, without the heavy computational burden required by these approaches. Simulation results comparing the ICSS algorithm to other approaches are presented.
TL;DR: The three-dimensional structure of prostaglandin H2 synthase-1, an integral membrane protein, has been determined at 3.5 Å resolution by X-ray crystallography and suggests that the enzyme integrates into only one leaflet of the lipid bilayer and is thus a monotopic membrane protein.
Abstract: The three-dimensional structure of prostaglandin H2 synthase-1, an integral membrane protein, has been determined at 3.5 A resolution by X-ray crystallography. This bifunctional enzyme comprises three independent folding units: an epidermal growth factor domain, a membrane-binding motif and an enzymatic domain. Two adjacent but spatially distinct active sites were found for its haem-dependent peroxidase and cyclooxygenase activities. The cyclooxygenase active site is created by a long, hydrophobic channel that is the site of non-steroidal anti-inflammatory drug binding. The conformation of the membrane-binding motif strongly suggests that the enzyme integrates into only one leaflet of the lipid bilayer and is thus a monotopic membrane protein.
TL;DR: In this paper, the authors present experimental measurements of the ultrafast solvation dynamics of a coumarin salt in water, and combine them with computer simulations to demonstrate that a solvent response on a timescale faster than 50 fs can dominate aqueous solvation dynamic.
Abstract: THE timescale of the response of solvent molecules to electronic rearrangement of solute molecules has a critical influence on the rates of chemical reactions in liquids1–10. In particular, if the solvent cannot adapt quickly enough to this rearrangement as the reactants pass through the transition state, the evolving products may recross the free-energy barrier, reducing the reaction rate. Computer simulations have shown11–18 that the response of a solvent to a change in solute charge distribution is strongly bimodal: there is an initial ultrafast response owing to inertial (mainly libra-tional) motions of the solvent molecules, followed by a slow component owing to diffusive motions. Water seems to be by far the 'fastest' solvent studied so far: simulations predict that well over half of the solvation response for atomic solutes is inertial, happening on a timescale of about 20 femtoseconds12,13. The presence of this ultrafast component implies that solvent friction plays an important role in many aqueous charge-transfer processes9,10,19–21. Experimental verification of this prediction has been lacking, however, in part because of the difficulty of obtaining sufficient time resolution. Here we present experimental measurements of the ultrafast solvation dynamics of a coumarin salt in water. When considered in conjunction with computer simulations, our results demonstrate that a solvent response on a timescale faster than 50 fs can dominate aqueous solvation dynamics.
TL;DR: This article introduces an alternative procedure that involves imputing the missing data sequentially and computing appropriate importance sampling weights, and in many applications this new procedure works very well without the need for iterations.
Abstract: For missing data problems, Tanner and Wong have described a data augmentation procedure that approximates the actual posterior distribution of the parameter vector by a mixture of complete data posteriors. Their method of constructing the complete data sets is closely related to the Gibbs sampler. Both required iterations, and, similar to the EM algorithm, convergence can be slow. We introduce in this article an alternative procedure that involves imputing the missing data sequentially and computing appropriate importance sampling weights. In many applications this new procedure works very well without the need for iterations. Sensitivity analysis, influence analysis, and updating with new data can be performed cheaply. Bayesian prediction and model selection can also be incorporated. Examples taken from a wide range of applications are used for illustration.
TL;DR: The necessarily curvilinear relationship between the finite range of recorded FIM raw scores and the conceptually infinite range of additive disability measures is resolved through Rasch analysis.
TL;DR: Estimating the genome size of extinct woody angiosperms with the use of fossil guard cell size as a proxy for cellular DNA content suggested that seven to nine is the primitive haploid chromosome number of angios perms and that most angiosPerms (approximately 70 percent) have polyploidy in their history.
Abstract: Three published estimates of the frequency of polyploidy in angiosperms (30 to 35 percent, 47 percent, and 70 to 80 percent) were tested by estimating the genome size of extinct woody angiosperms with the use of fossil guard cell size as a proxy for cellular DNA content. The inferred chromosome numbers of these extinct species suggest that seven to nine is the primitive haploid chromosome number of angiosperms and that most angiosperms (approximately 70 percent) have polyploidy in their history.
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TL;DR: In this article, the authors used disaggregated data on bank balance sheets to provide a test of the lending view of monetary policy transmission and showed that the loan and security portfolios of large and small banks respond differentially to a contraction in monetary policy.
Abstract: This paper uses disaggregated data on bank balance sheets to provide a test of the lending view of monetary policy transmission. We argue that if the lending view is correct, one should expect the loan and security portfolios of large and small banks to respond differentially to a contraction in monetary policy. We first develop this point with a theoretical model; we then test to see if the model's predictions are borne out in the data.
TL;DR: In this article, the determinants of outside appointments to the boards of large non-financial Japanese corporations were investigated and they concluded that banks and corporate shareholders play an important monitoring and disciplinary role in Japan.
TL;DR: In this paper, the authors studied the large premium attributed to voting shares on the Milan Stock Exchange and found that the premium varies according to the ownership structare and the concentration of the voting rights, and can be rationalized in the presence of enormous private benefits of control.
Abstract: I study the large premium (82 percent) attributed to voting shares on the Milan Stock Exchange The premium varies according to the ownership structare and the concentration of the voting rights, and it can be rationalized in the presence of enormous private benefits of control A case study seems to indicate that in Italy private benefits of control can easily be worth more than 60 percent of the value of nonvoting equity A tentative explanation for these findings is provided Traditional finance theory disregards the value of voting rights in pricing common stock In most cases this omission does not seem harmful Many studies of differential voting stocks in different countries have indicated that voting rights are generally worth between 10 percent and 20 percent of the value of common stock’ The Italian evidence I present differs sharply from this view In Italy voting shares that have inferior dividend rights trade at an average premium
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TL;DR: In this article, the authors provide a framework for understanding the cross-section and time series approaches which have been used to test the convergence hypothesis and provide two definitions of convergence which capture the implications of the neoclassical growth model for the relationship between current and future cross-country output differences.
Abstract: This paper provides a framework for understanding the cross- section and time series approaches which have been used to test the convergence hypothesis First, we present two definitions of convergence which capture the implications of the neoclassical growth model for the relationship between current and future cross-country output differences Second, we identify how the cross-section and time series approaches relate to these definitions Cross-section tests are shown to be associated with a weaker notion of convergence than time series tests Third, we show how these alternative approaches make different assumptions on whether the data are well characterized by a limiting distribution As a result, the choice of an appropriate testing framework is shown to depend on both the specific null and alternative hypotheses under consideration as well as on the initial conditions characterizing the data being studied
TL;DR: In this article, the authors analyze twenty years of personnel data from one firm and find that career movements suggest that the employee's rate of learning and the firm's learning about ability are important.
Abstract: We analyze twenty years of personnel data from one firm. The hierarchical structure is quite simple and stable. Career movements suggest that the employee's rate of learning and the firm's learning about ability are important. There are promotion "fast tracks." Exit rates vary little with tenure or salary. The firm has personnel policies like those described in the internal labor markets literature, although several theoretical preconditions for ILMs, such as ports of entry and exit, are lacking. Job levels are important to compensation, but there is also substantial individual variation in pay within levels. Our companion paper (in this issue) explores the wage policy of this firm.
TL;DR: In this paper, a reanalysis of data from these earlier reviews, using more sophisticated synthesis methods, is presented, which shows systematic positive relations between resource inputs and school outcomes, and analyses of the magnitude of these relations suggest that the median relation is large enough to be of practical importance.
Abstract: Research on educational production functions attempts to model the relation between resource inputs and school outcomes such as educational achievement. Over the last decade a series of influential reviews of this literature have suggested that there is no systematic relation between resource inputs and school outcomes when controlling for student characteristics such as socioeconomic status. The inference procedure used in these reviews, vote counting, is known to be problematic. This study is a reanalysis of data from these earlier reviews, using more sophisticated synthesis methods. It shows systematic positive relations between resource inputs and school outcomes. Moreover, analyses of the magnitude of these relations suggest that the median relation (regression coefficient) is large enough to be of practical importance.While this reanalysis suggests that previous data do not support the conclusions that Hanushek and others derived from it, limitations of their data set warrant caution in using it for...
TL;DR: The results support the decision to subdivide the heterogeneous category of DSM-III-R attention deficit hyperactivity disorder into three subtypes and the resulting DSM-IV definition appears to be somewhat less biased toward the symptom pattern typical of elementary school boys.
Abstract: OBJECTIVE Optimal diagnostic thresholds were determined for DSM-IV attention deficit hyperactivity disorder, and the psychometric properties were compared to alternative definitions. METHOD Structured diagnostic interviews of multiple informants for 380 clinic-referred youths aged 4-17 years were conducted. In addition, standardized clinicians' validation diagnoses of attention deficit disorder were obtained to assess agreement with clinical judgment. Measures of impairment were obtained to assess the accuracy of identifying youth with an impairing condition. RESULTS Three subtypes of attention deficit hyperactivity disorder (predominantly inattentive, predominantly hyperactive-impulsive, and combined types) were distinguished on the basis of the degree of deviance on separate dimensions of inattention and hyperactivity-impulsivity. These three subtypes were found to differ in terms of types of impairment, age, and sex ratio, but not ethnicity. In terms of case identification of attention deficit hyperactivity disorder, DSM-IV was found to be very similar to DSM-III-R, except that DSM-IV identified more impaired girls and preschool children. CONCLUSIONS These results support the decision to subdivide the heterogeneous category of DSM-III-R attention deficit hyperactivity disorder into three subtypes. The resulting DSM-IV definition appears to be somewhat less biased toward the symptom pattern typical of elementary school boys.
TL;DR: Hspl04 functions in a manner not previously described for other heat-shock proteins: it mediates the resolubilization of heat-inactivated luciferase from insoluble aggregates.
Abstract: The heat-inducible members of the Hsp100 (or Clp) family of proteins share a common function in helping organisms to survive extreme stress, but the basic mechanism through which these proteins function is not understood. Hsp104 protects cells against a variety of stresses, under many physiological conditions, and its function has been evolutionarily conserved, at least from Saccharomyces cerevisiae to Arabidopsis thaliana. Homology with the Escherichia coli ClpA protein suggests that Hsp104 may provide stress tolerance by helping to rid the cell of heat-denatured proteins through proteolysis. But genetic analysis indicates that Hsp104 may function like Hsp70 as a molecular chaperone. Here we investigate the role of Hsp104 in vivo using a temperature-sensitive Vibrio harveyi luciferase-fusion protein as a test substrate. We find that Hsp104 does not protect luciferase from thermal denaturation, nor does it promote proteolysis of luciferase. Rather, Hsp104 functions in a manner not previously described for other heat-shock proteins: it mediates the resolubilization of heat-inactivated luciferase from insoluble aggregates.
TL;DR: The strategy of initial conservative management and delayed hormone therapy is a reasonable choice for some men with grade 1 or 2 clinically localized prostate cancer, particularly for those who have an average life expectancy of 10 years or less.
Abstract: Background The selection of treatment for patients with localized prostate cancer requires reliable information about the outcome of conservative management. Previous studies of this question are generally considered unreliable because they were uncontrolled and nonrandomized. Methods We performed a pooled analysis of 828 case records from six nonrandomized studies, published since 1985, of men treated conservatively (with observation and delayed hormone therapy but no radical surgery or irradiation) for clinically localized prostate cancer. A Cox regression analysis was performed to determine which factors influenced survival among patients who did not die of causes other than prostate cancer (disease-specific survival). Kaplan-Meier curves for overall and metastasis-free survival among such patients were compared with use of the log-rank method and the Mantel-Haenszel test. Results Factors that had a significant effect on disease-specific survival were grade 3 tumors (risk ratio, 10.04), residence in Is...
TL;DR: In this article, the authors argue that rational bank managers with short horizons will set credit policies that influence and are influenced by other banks and demand side conditions, leading to a theory of low frequency business cycles driven by bank credit policies.
Abstract: In a rational profit-maximizing world, banks should msdntain a credit policy of lending if and only if borrowers have positive net present value projects. Why then are changes in credit policy seemingly correlated with changes in the condition of those demanding credit? This paper argues that rational bank managers with short horizons will set credit policies that influence and are influenced by other banks and demand side conditions. This leads to a theory of low frequency business cycles driven by bank credit policies. Evidence from the banking crisis in New England in the early 1990s is consistent with the assumptions and predictions of the theory.