Showing papers by "University of Chicago published in 1996"

Law and Finance

Abstract: This paper examines legal rules covering protection of corporate shareholders and creditors, the origin of these rules, and the quality of their enforcement in 49 countries. The results show that common law countries generally have the best, and French civil law countries the worst, legal protections of investors, with German and Scandinavian civil law countries located in the middle. We also find that concentration of ownership of shares in the largest public companies is negatively related to investor protections, consistent with the hypothesis that small, diversified shareholders are unlikely to be important in countries that fail to protect their rights.

A Survey of Corporate Governance

Abstract: This paper surveys research on corporate governance, with special attention to the importance of legal protection of investors and of ownership concentration in corporate governance systems around the world.

Financial Dependence and Growth

Abstract: Does finance affect economic growth? A number of studies have identified a positive correlation between the level of development of a country's financial sector and the rate of growth of its per capita income. As has been noted elsewhere, the observed correlation does not necessarily imply a causal relationship. This paper examines whether financial development facilitates economic growth by scrutinizing one rationale for such a relationship; that financial development reduces the costs of external finance to firms. Specifically, we ask whether industrial sectors that are relatively more in need of external finance develop disproportionately faster in countries with more developed financial markets. We find this to be true in a large sample of countries over the 1980s. We show this result is unlikely to be driven by omitted variables, outliers, or reverse causality.

Creativity: Flow and the Psychology of Discovery and Invention

Abstract: Creativity is about capturing those moments that make life worth living. The author's objective is to offer an understanding of what leads to these moments, be it the excitement of the artist at the easel or the scientist in the lab, so that knowledge can be used to enrich people's lives. Drawing on 100 interviews with exceptional people, from biologists and physicists to politicians and business leaders, poets and artists, as well as his 30 years of research on the subject, Csikszentmihalyi uses his famous theory to explore the creative process. He discusses such ideas as why creative individuals are often seen as selfish and arrogant, and why the tortured genius is largely a myth. Most important, he clearly explains why creativity needs to be cultivated and is necessary for the future of our country, if not the world."Accessible and enjoyable reading." "--Washington Times" "Although the benefits of this study to scholars are obvious, this thought-provoking mixture of scholarly and colloquial will enlighten inquisitive general readers, too." "--Library Journal (starred review)"

Improved survival with an implanted defibrillator in patients with coronary disease at high risk for ventricular arrhythmia

Abstract: Background Unsustained ventricular tachycardia in patients with previous myocardial infarction and left ventricular dysfunction is associated with a two-year mortality rate of about 30 percent. We studied whether prophylactic therapy with an implanted cardioverter–defibrillator, as compared with conventional medical therapy, would improve survival in this high-risk group of patients. Methods Over the course of five years, 196 patients in New York Heart Association functional class I, II, or III with prior myocardial infarction; a left ventricular ejection fraction <0.35; a documented episode of asymptomatic unsustained ventricular tachycardia; and inducible, nonsuppressible ventricular tachyarrhythmia on electrophysiologic study were randomly assigned to receive an implanted defibrillator (n = 95) or conventional medical therapy (n = 101). We used a two-sided sequential design with death from any cause as the end point. Results The base-line characteristics of the two treatment groups were similar. During...

Synthesis and Characterization of Strongly Luminescing ZnS-Capped CdSe Nanocrystals

Abstract: We describe the synthesis of ZnS-capped CdSe semiconductor nanocrystals using organometallic reagents by a two-step single-flask method X-ray photoelectron spectroscopy, transmission electron microscopy and optical absorption are consistent with nanocrystals containing a core of nearly monodisperse CdSe of 27−30 A diameter with a ZnS capping 6 ± 3 A thick The ZnS capping with a higher bandgap than CdSe passivates the core crystallite removing the surface traps The nanocrystals exhibit strong and stable band-edge luminescence with a 50% quantum yield at room temperature

Cd28/b7 system of t cell costimulation

Abstract: ▪ Abstract T cells play a central role in the initiation and regulation of the immune response to antigen. Both the engagement of the TCR with MHC/Ag and a second signal are needed for the complete activation of the T cell. The CD28/B7 receptor/ligand system is one of the dominant costimulatory pathways. Interruption of this signaling pathway with CD28 antagonists not only results in the suppression of the immune response, but in some cases induces antigen-specific tolerance. However, the CD28/B7 system is increasingly complex due to the identification of multiple receptors and ligands with positive and negative signaling activities. This review summarizes the state of CD28/B7 immunobiology both in vitro and in vivo; summarizes the many experiments that have led to our current understanding of the participants in this complex receptor/ligand system; and illustrates the current models for CD28/B7-mediated T cell and B cell regulation. It is our hope and expectation that this review will provoke additional ...

A test for independence based on the correlation dimension

Abstract: This paper presents a test of independence that can be applied to the estimated residuals of any time series model that can be transformed into a model driven by independent and identically distributed errors. The first order asymptotic distribution of the test statistic is independent of estimation error provided that the parameters of the model under test can be estimated -consistently. Because of this, our method can be used as a model selection tool and as a specification test. Widely used software1 written by Dechert and LeBaron can be used to implement the test. Also, this software is fast enough that the null distribution of our test statistic can be estimated with bootstrap methods. Our method can be viewed as a nonlinear analog of the Box-Pierce Q statistic used in ARIMA analysis.

Structure of Staphylococcal α-Hemolysin, a Heptameric Transmembrane Pore

Abstract: The structure of the Staphylococcus aureus α-hemolysin pore has been determined to 1.9 A resolution. Contained within the mushroom-shaped homo-oligomeric heptamer is a solvent-filled channel, 100 A in length, that runs along the sevenfold axis and ranges from 14 A to 46 A in diameter. The lytic, transmembrane domain comprises the lower half of a 14-strand antiparallel β barrel, to which each protomer contributes two β strands, each 65 A long. The interior of the β barrel is primarily hydrophilic, and the exterior has a hydrophobic belt 28 A wide. The structure proves the heptameric subunit stoichiometry of the α-hemolysin oligomer, shows that a glycine-rich and solvent-exposed region of a water-soluble protein can self-assemble to form a transmembrane pore of defined structure, and provides insight into the principles of membrane interaction and transport activity of β barrel pore-forming toxins.

Granular solids, liquids, and gases

Abstract: Granular materials are ubiquitous in the world around us. They have properties that are different from those commonly associated with either solids, liquids, or gases. In this review the authors select some of the special properties of granular materials and describe recent research developments.[S0034-6861(96)00204-8]

Trust in Large Organizations

Abstract: Several authors suggest that trust is an important determinant of cooperation between strangers in a society, and therefore of performance of social institutions. We argue that trust should be particularly important for the performance of large organizations. In a cross-section of countries, evidence on government performance, participation in civic and professional societies, importance of large firms, and the performance of social institutions more generally supports this hypothesis. Moreover, trust is lower in countries with dominant hierarchical religions, which may have deterred networks of cooperation trust hold up remarkably well on a cross-section of countries.

Supercooled Liquids and Glasses

Abstract: Selected aspects of recent progress in the study of supercooled liquids and glasses are presented in this review. As an introduction for nonspecialists, several basic features of the dynamics and thermodynamics of supercooled liquids and glasses are described. Among these are nonexponential relaxation functions, non-Arrhenius temperature dependences, and the Kauzmann temperature. Various theoretical models which attempt to explain these basic features are presented next. These models are conveniently categorized according to the temperature regimes deemed important by their authors. The major portion of this review is given to a summary of current experimental and computational research. The utility of mode coupling theory is addressed. Evidence is discussed for new relaxation mechanisms and new time and length scales in supercooled liquids. Relaxations in the glassy state and significance of the “boson peak” are also addressed.

The Length of the Cervix and the Risk of Spontaneous Premature Delivery

Abstract: Background The role of the cervix in the pathogenesis of premature delivery is controversial. In a prospective, multicenter study of pregnant women, we used vaginal ultrasonography to measure the length of the cervix; we also documented the incidence of spontaneous delivery before 35 weeks' gestation. Methods At 10 university-affiliated prenatal clinics, we performed vaginal ultrasonography at approximately 24 and 28 weeks of gestation in women with singleton pregnancies. We then assessed the relation between the length of the cervix and the risk of spontaneous preterm delivery. Results We examined 2915 women at approximately 24 weeks of gestation and 2531 of these women again at approximately 28 weeks. Spontaneous preterm delivery (at less than 35 weeks) occurred in 126 of the women (4.3 percent) examined at 24 weeks. The length of the cervix was normally distributed at 24 and 28 weeks (mean [+/- SD], 35.2 +/- 8.3 mm and 33.7 +/- 8.5 mm, respectively). The relative risk of preterm delivery increased as the length of the cervix decreased. When women with shorter cervixes at 24 weeks were compared with women with values above the 75th percentile, the relative risks of preterm delivery among the women with shorter cervixes were as follows: 1.98 for cervical lengths at or below the 75th percentile (40 mm), 2.35 for lengths at or below the 50th percentile (35 mm), 3.79 for lengths at or below the 25th percentile (30 mm), 6.19 for lengths at or below the 10th percentile (26 mm), 9.49 for lengths at or below the 5th percentile (22 mm), and 13.99 for lengths at or below the 1st percentile (13 mm) (P Conclusions The risk of spontaneous preterm delivery is increased in women who are found to have a short cervix by vaginal ultrasonography during pregnancy.

The Effect of School Resources on Student Achievement

Abstract: A universe of education production function studies was assembled in order to utilize meta-analytic methods to assess the direction and magnitude of the relations between a variety of school inputs and student achievement. The 60 primary research studies aggregated data at the level of school districts or smaller units and either controlled for socioeconomic characteristics or were longitudinal in design. The analysis found that a broad range of resources were positively related to student outcomes, with effect sizes large enough to suggest that moderate increases in spending may be associated with significant increases in achievement. The discussion relates the findings of this study with trends in student achievement from the National Assessment of Educational Progress and changes in social capital over the last two decades.

The NIMH Diagnostic Interview Schedule for Children Version 2.3 (DISC-2.3): Description, Acceptability, Prevalence Rates, and Performance in the MECA Study

Abstract: Objective To describe the NIMH Diagnostic Interview Schedule for Children (DISC) Version 2.3 and to provide data on its performance characteristics in the Methods for the Epidemiology of Child and Adolescent Mental Disorders (MECA) Study. Method Data were collected on the DISC-2.3 at four sites on 1,285 randomly selected children, aged 9 through 17 years, and their parents. Two hundred forty-seven of these child–parent pairs were reassessed on the DISC-2.3 by a clinician interviewer, 1 to 3 weeks later. Results Administration time was approximately 1 hour and the interview was acceptable to more than 90% of subjects. The reliability of questions to parents assessing impairment and age of onset was generally good to acceptable for most diagnoses but was less satisfactory for the child interview. Using information from parent and child, the prevalence for any diagnosis ranged from 50.6 If no impairment criteria were required to 5.4 if a Global Assessment Scale score of 50 or less was necessary. The prevalence of anxiety disorders and enuresis was markedly reduced by requiring attributable impairment. Conclusions The DISC-2 is a reliable and economical tool for assessing child psychopathology. Reliability of the DISC-P-2.3 is superior to that of the child DISC for most diagnoses but is least good for anxiety disorders. The 2.3 version of the instrument provides a significant improvement over earlier versions.

X-ray and NMR structure of human Bcl-xL, an inhibitor of programmed cell death.

Abstract: THE Bcl-2 family of proteins regulate programmed cell death by an unknown mechanism. Here we describe the crystal and solution structures of a Bcl-2 family member, Bcl-xL (ref. 2). The structures consist of two central, primarily hydrophobic alpha-helices, which are surrounded by amphipathic helices. A 60-residue loop connecting helices alpha1 and alpha2 was found to be flexible and non-essential for anti-apoptotic activity. The three functionally important Bcl-2 homology regions (BH1, BH2 and BH3) are in close spatial proximity and form an elongated hydrophobic cleft that may represent the binding site for other Bcl-2 family members. The arrangement of the alpha-helices in Bcl-xL is reminiscent of the membrane translocation domain of bacterial toxins, in particular diphtheria toxin and the colicins. The structural similarity may provide a clue to the mechanism of action of the Bcl-2 family of proteins.

Crime and Social Interactions

Abstract: The high variance of crime rates across time and space is one of the oldest puzzles in the social sciences; this variance appears too high to be explained by changes in the exogenous costs and benefits of crime. We present a model where social interactions create enough covariance across individuals to explain the high cross-city variance of crime rates. This model provides an index of social interactions which suggests that the amount of social interactions is highest in petty crimes, moderate in more serious crimes, and almost negligible in murder and rape.

The Proper Scope of Government: Theory and an Application to Prisons

Abstract: When should a government provide a service inhouse and when should it contract out provision? We develop a model in which the provider can invest in improving the quality of service or reducing cost. If contracts are incomplete, the private provider has a stronger incentive to engage in both quality improvement and cost reduction than a government employee. However, the private contractor's incentive to engage in cost reduction is typically too strong because he ignores the adverse effect on non-contractible quality. The model is applied to understanding the costs and benefits of prison privatization.

A Theory of Privatisation

Abstract: Public enterprises around the world have proved to be highly inefficient, primarily because they pursue strategies, such as excess employment, that satisfy the political objectives of politicians who control them. Privatization of public enterprises can raise the cost to politicians of influencing them, since subsidies to private firms necessary to force them to remain inefficient are politically harder to sustain than wasted profits of the state firms. In this way, privatization leads to efficient restructuring of firms. Moreover, privatization is more effective when combined with a tight monetary policy and when the new owners of firms are profit maximizing investors, rather than their employees or even managers. Copyright 1996 by Royal Economic Society.

Young Tableaux: With Applications to Representation Theory and Geometry

Abstract: Part I. Calculus Of Tableux: 1. Bumping and sliding 2. Words: the plactic monoid 3. Increasing sequences: proofs of the claims 4. The Robinson-Schensted-Knuth Correspondence 5. The Littlewood-Richardson rule 6. Symmetric polynomials Part II. Representation Theory: 7. Representations of the symmetric group 8. Representations of the general linear group Part III. Geometry: 9. Flag varieties 10. Schubert varieties and polynomials Appendix A Appendix B.

Koszul Duality Patterns in Representation Theory

Abstract: The aim of this paper is to work out a concrete example as well as to provide the general pattern of applications of Koszul duality to repre- sentation theory. The paper consists of three parts relatively independent of each other. The first part gives a reasonably selfcontained introduction to Koszul rings and Koszul duality. Koszul rings are certain Z-graded rings with particularly nice homological properties which involve a kind of duality. Thus, to a Koszul ring one associates naturally the dual Koszul ring. The second part is devoted to an application to representation theory of semisimple Lie algebras. We show License or copyright restrictions may apply to redistribution; see http://www.ams.org/journal-terms-of-use KOSZUL DUALITY PATTERNS 527 that the block of the Bernstein-Gelfand-Gelfand category O that corresponds to any fixed central character is governed by the Koszul ring. Moreover, the dual of that ring governs a certain subcategory of the category O again. This generalizes the selfduality theorem conjectured by Beilinson and Ginsburg in 1986 and proved by Soergel in 1990. In the third part we study certain cate- gories of mixed perverse sheaves on a variety stratified by affine linear spaces. We provide a general criterion for such a category to be governed by a Koszul ring. In the flag variety case this reduces to the setup of part two. In the more general case of affine flag manifolds and affine Grassmannians the criterion should yield interesting results about representations of quantum groups and affine Lie algebras. Department of Mathematics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 E-mail address: sasha@math.mit.edu Department of Mathematics, The University of Chicago, Chicago, Illinois 60637 E-mail address: ginzburg@math.uchicago.edu Max-Planck-Institut fur Mathematik, Gottfried-Claren-Strase 26, D-53 Bonn 3, Germany Current address: Mathematisches Institut, Universitat Freiburg, Albertstrase 23b, D-79104 Freiburg, Germany E-mail address: soergel@sun1.mathematik.uni-freiburg.de License or copyright restrictions may apply to redistribution; see http://www.ams.org/journal-terms-of-use

Trade Credit: Theories and Evidence

Abstract: In addition to borrowing from financial institutions, firms may be financed by their suppliers. Although there are many theories explaining why non-financial firms lend money, there are few comprehensive empirical tests of these theories. This paper attempts to fill the gap. We focus on a sample of small firms whose access to capital markets may be limited. We find evidence that firms use trade credit relatively more when credit from financial institutions is not available. Thus while short term trade credit may be routinely used to minimize transactions costs, medium term borrowing against trade credit is a form of financing of last resort. Suppliers lend to firms no one else lends to because they may have a comparative advantage in getting information about buyers cheaply, they have a better ability to liquidate goods, and they have a greater implicit equity stake in the firm's long term survival. We find some evidence consistent with the use of trade credit as a means of price discrimination. Finally, we find that firms with better access to credit from financial institutions offer more trade credit. This suggests that firms may intermediate between institutional creditors and other firms who have limited access to financial institutions.

Power in a Theory of the Firm

Abstract: Transactions take place in the firm rather than in the market because the firm offers agents" who make specific investments power. Past literature emphasizes the allocation of ownership as the" primary mechanism by which the firm does this. Within the contractibility assumptions of this" literature, we identify a potentially superior mechanism, the regulation of access to critical resources. " Access can be better than ownership because: i) the power agents get from access is more contingent" on them making the right investment; ii) ownership has adverse effects on the incentive to specialize. " The theory explains the importance of internal organization and third party ownership. "

Trade Credit: Theories and Evidence

Abstract: In addition to borrowing from financial institutions, firms may be financed by their suppliers. Although there are many theories explaining why non-financial firms lend money, there are few comprehensive empirical tests of these theories. This paper attempts to fill the gap. We focus on a sample of small firms whose access to capital markets may be limited. We find evidence that firms use trade credit relatively more when credit from financial institutions is not available. Thus while short term trade credit may be routinely used to minimize transactions costs, medium term borrowing against trade credit is a form of financing of last resort. Suppliers lend to firms no one else lends to because they may have a comparative advantage in getting information about buyers cheaply, they have a better ability to liquidate goods, and they have a greater implicit equity stake in the firm's long term survival. We find some evidence consistent with the use of trade credit as a means of price discrimination. Finally, we find that firms with better access to credit from financial institutions offer more trade credit. This suggests that firms may intermediate between institutional creditors and other firms who have limited access to financial institutions.

Electronic structure and properties of solids

Abstract: Some of the challenges facing scientists in the area of the electronic structure and properties of solids are reviewed. At a time when computational advances have made possible high-quality calculations, not even conceivable 10 years ago, the article stresses the importance of going beyond the raw output of the calculation and understanding where the result originates. The areas selected for study include the Fermi surface and charge density waves, the stability of solids and the structures of solids under pressure, metal−insulator transitions, the method of moments, superconductivity, and the use of a relatively new technique for the study of chemical bonding, the electron localization function (ELF).

A bilinear estimate with applications to the KdV equation

Abstract: u(x, 0) = u0(x), where u0 ∈ H(R). Our principal aim here is to lower the best index s for which one has local well posedness in H(R), i.e. existence, uniqueness, persistence and continuous dependence on the data, for a finite time interval, whose size depends on ‖u0‖Hs . Equation in (1.1) was derived by Korteweg and de Vries [21] as a model for long wave propagating in a channel. A large amount of work has been devoted to the existence problem for the IVP (1.1). For instance, (see [9], [10]), the inverse scattering method applies to this problem, and, under appropriate decay assumptions on the data, several existence results have been established, see [5],[6],[14],[28],[33]. Another approach, inherited from hyperbolic problems, relies on the energy estimates, and, in particular shows that (1.1) is locally well posed in H(R) for s > 3/2, (see [2],[3],[12],[29],[30],[31]). Using these results and conservation laws, global (in time) well posedness in H(R), s ≥ 2 was established, (see [3],[12],[30]). Also, global in time weak solutions in the energy space H(R) were constructed in [34]. In [13] and [22] a “local smoothing” effect for solutions of (1.1) was discovered. This, combined with the conservation laws, was used in [13] and [22] to construct global in time weak solutions with data in H(R), and even in L(R). In [16], we introduced oscillatory integral techniques, to establish local well posedness of (1.1) in H(R), s > 3/4, and hence, global (in time) well posedness in H(R), s ≥ 1. (In [16] we showed how to obtain the above mentioned result by Picard iteration in an appropriate function space.) In [4] J. Bourgain introduced new function spaces, adapted to the linear operator ∂t+∂ 3 x, for which there are good “bilinear” estimates for the nonlinear term ∂x(u /2). Using these spaces, Bourgain was able to establish local well posedness of (1.1) in H(R) = L(R), and hence, by a conservation