Showing papers by "University of Texas at Austin published in 1998"

Surface-enhanced Raman scattering

Abstract: We present an introduction to surface-enhanced Raman scattering (SERS) which reviews the basic experimental facts and the essential features of the mechanisms which have been proposed to account for the observations. We then review very recent fundamental developments which include: SERS from single particles and single molecules; SERS from fractal clusters and surfaces; and new insights into the chemical enhancement mechanism of SERS.

Market orientation and organizational performance: Is innovation a missing link?

Abstract: In recent years, a market-oriented corporate culture increasingly has been considered a key element of superior corporate performance. Although organizational innovativeness is believed to be a pot...

Is anybody out there?: antecedents of trust in global virtual teams

Abstract: A global virtual team is an example of a boundaryless network organization form where a temporary team is assembled on an as-needed basis for the duration of a task and staffed by members from different countries. In such teams, coordination is accomplished via trust and shared communication systems. The focus of the reported study was to explore the antecedents of trust in a global virtual-team setting. Seventyfive teams, consisting of four to six members residing in different countries, interacted and worked together for eight weeks. The two-week trust-building exercises did have a significant effect on the team members' perceptions of the other members' ability, integrity, and benevolence. In the early phases of teamwork, team trust was predicted strongest by perceptions of other team members' integrity, and weakest by perceptions of their benevolence. The effect of other members' perceived ability on trust decreased over time. The members' own propensity to trust had a significant, though unchanging, effect on trust. A qualitative analysis of six teams' electronic mail messages explored strategies that were used by the three highest trust teams, but were used infrequently or not at all by the three lowest trust teams. The strategies suggest the presence of "swift" trust. The paper advances a research model for explaining trust in global virtual teams.

Market-Based Assets and Shareholder Value: A Framework for Analysis

Abstract: The authors develop a conceptual framework of the marketing–finance interface and discuss its implications for the theory and practice of marketing. The framework proposes that marketing is concern...

Evolutionary Psychology: The New Science of the Mind

Abstract: PART ONE - FOUNDATIONS OF EVOLUTIONARY PSYCHOLOGY Chapter 1. The Scientific Movements Leading to Evolutionary Psychology Chapter 2. The New Science of Evolutionary Psychology PART TWO - PROBLEMS OF SURVIVAL Chapter 3. Combating the Hostile Forces of Nature: Human Survival Problems PART THREE - CHALLENGES OF SEX AND MATING Chapter 4. Women's Long-Term Mating Strategies Chapter 5. Men's Long-Term Mating Strategies Chapter 6. Short-Term Sexual Strategies PART FOUR - CHALLENGES OF PARENTING AND KINSHIP Chapter 7. Problems of Parenting Chapter 8. Problems of Kinship PART FIVE - PROBLEMS OF GROUP LIVING Chapter 9. Cooperative Alliances Chapter 10. Aggression and Warfare Chapter 11. Conflict between the Sexes Chapter 12. Status, Prestige, and Social Dominance PART SIX - AN INTEGRATED PSYCHOLOGICAL SCIENCE Chapter 13. Toward a Unified Evolutionary Psychology

Intensive lifestyle changes for reversal of coronary heart disease.

Abstract: Context.— The Lifestyle Heart Trial demonstrated that intensive lifestyle changes may lead to regression of coronary atherosclerosis after 1 year. Objectives.— To determine the feasibility of patients to sustain intensive lifestyle changes for a total of 5 years and the effects of these lifestyle changes (without lipid-lowering drugs) on coronary heart disease. Design.— Randomized controlled trial conducted from 1986 to 1992 using a randomized invitational design. Patients.— Forty-eight patients with moderate to severe coronary heart disease were randomized to an intensive lifestyle change group or to a usual-care control group, and 35 completed the 5-year follow-up quantitative coronary arteriography. Setting.— Two tertiary care university medical centers. Intervention.— Intensive lifestyle changes (10% fat whole foods vegetarian diet, aerobic exercise, stress management training, smoking cessation, group psychosocial support) for 5 years. Main Outcome Measures.— Adherence to intensive lifestyle changes, changes in coronary artery percent diameter stenosis, and cardiac events. Results.— Experimental group patients (20 [71%] of 28 patients completed 5-year follow-up) made and maintained comprehensive lifestyle changes for 5 years, whereas control group patients (15 [75%] of 20 patients completed 5-year follow-up) made more moderate changes. In the experimental group, the average percent diameter stenosis at baseline decreased 1.75 absolute percentage points after 1 year (a 4.5% relative improvement) and by 3.1 absolute percentage points after 5 years (a 7.9% relative improvement). In contrast, the average percent diameter stenosis in the control group increased by 2.3 percentage points after 1 year (a 5.4% relative worsening) and by 11.8 percentage points after 5 years (a 27.7% relative worsening) (P = .001 between groups. Twenty-five cardiac events occurred in 28 experimental group patients vs 45 events in 20 control group patients during the 5-year follow-up (risk ratio for any event for the control group, 2.47 [95% confidence interval, 1.48-4.20]). Conclusions.— More regression of coronary atherosclerosis occurred after 5 years than after 1 year in the experimental group. In contrast, in the control group, coronary atherosclerosis continued to progress and more than twice as many cardiac events occurred.

The Religion-Health Connection: Evidence, Theory, and Future Directions

Abstract: The volume and quality of research on what we term the religion-health connection have increased markedly in recent years. This interest in the complex relationships between religion and mental and physical health is being fueled by energetic and innovative research programs in several fields, including sociology, psychology, health behavior and health education, psychiatry, gerontology, and social epidemiology. This article has three main objectives: (1) to briefly review the medical and epidemiologic research on religious factors and both physical health and mental health; (2) to identify the most promising explanatory mechanisms for religious effects on health, giving particular attention to the relationships between religious factors and the central constructs of the life stress paradigm, which guides most current social and behavioral research on health outcomes; and (3) to critique previous work on religion and health, pointing out limitations and promising new research directions.

A homologue of Drosophila aurora kinase is oncogenic and amplified in human colorectal cancers

Abstract: Genetic and biochemical studies in lower eukaryotes have identified several proteins that ensure accurate segregation of chromosomes. These include the Drosophila aurora and yeast Ipl1 kinases that are required for centrosome maturation and chromosome segregation. We have identified two human homologues of these genes, termed aurora1 and aurora2, that encode cell-cycle-regulated serine/threonine kinases. Here we demonstrate that the aurora2 gene maps to chromosome 20q13, a region amplified in a variety of human cancers, including a significant number of colorectal malignancies. We propose that aurora2 may be a target of this amplicon since its DNA is amplified and its RNA overexpressed, in more than 50% of primary colorectal cancers. Furthermore, overexpression of aurora2 transforms rodent fibroblasts. These observations implicate aurora2 as a potential oncogene in many colon, breast and other solid tumors, and identify centrosome-associated proteins as novel targets for cancer therapy.

A new Voronoi-based surface reconstruction algorithm

Abstract: Author(s): Amenta, Nina; Bern, Marshall; Kamvysselis, Manolis | Abstract: We describe our experience with a new algorithm for the reconstruction of surfaces from unorganized sample points in IR3. The algorthim is the first for this problem with provable guarantees. Given a ''good sample'' from a smooth surface, the output is guaranteed to be topologically correct and convergent to the original surface as the sampling sensity increases. The definition of a good sample is itself interesting: the required sampling density varies locally, rigorously capturing the intuitive notion that featureless areas can be reconstructed from fewer samples. The output mesh interpolates, rather than approximates, the input points. Our algorithm is based on the three-dimensional Voronoi diagram. Given a good program for thsi fundamental subroutine, the algorithm is quite easy to implement.

Secure group communications using key graphs

Abstract: Many emerging applications (e.g., teleconference, real-time information services, pay per view, distributed interactive simulation, and collaborative work) are based upon a group communications model, i.e., they require packet delivery from one or more authorized senders to a very large number of authorized receivers. As a result, securing group communications (i.e., providing confidentiality, integrity, and authenticity of messages delivered between group members) will become a critical networking issue.In this paper, we present a novel solution to the scalability problem of group/multicast key management. We formalize the notion of a secure group as a triple (U,K,R) where U denotes a set of users, K a set of keys held by the users, and R a user-key relation. We then introduce key graphs to specify secure groups. For a special class of key graphs, we present three strategies for securely distributing rekey messages after a join/leave, and specify protocols for joining and leaving a secure group. The rekeying strategies and join/leave protocols are implemented in a prototype group key server we have built. We present measurement results from experiments and discuss performance comparisons. We show that our group key management service, using any of the three rekeying strategies, is scalable to large groups with frequent joins and leaves. In particular, the average measured processing time per join/leave increases linearly with the logarithm of group size.

Tuberous Sclerosis Complex Consensus Conference: Revised Clinical Diagnostic Criteria

Abstract: At the recent tuberous sclerosis complex consensus conference, the clinical diagnostic criteria for tuberous sclerosis complex were simplified and revised to reflect both new clinical information about tuberous sclerosis complex and an improved understanding of the disorder derived from molecular genetic studies. Based on this new information, some clinical signs once regarded as pathognomonic for tuberous sclerosis complex are now known to be less specific. No single sign is present in all affected patients, and there is no proof that any single clinical or radiographic sign is absolutely specific for tuberous sclerosis complex. Accordingly, the clinical and radiographic features of tuberous sclerosis complex have now been divided into major and minor categories based on the apparent degree of specificity for tuberous sclerosis complex of each feature. A definitive diagnosis of tuberous sclerosis complex now requires two or more distinct types of lesions, rather than multiple lesions of the same type in the same organ system. Although diagnosis on purely clinical grounds can continue to be difficult in a few patients, there should be little doubt about the diagnosis for those individuals who fulfill these strict criteria. Couples with more than one child with tuberous sclerosis complex, no extended family history, and no clinical features of tuberous sclerosis complex are more likely to have germline mosaicism for tuberous sclerosis than nonexpression of the mutation. Germline mosaicism, while fortunately rare, will not be suspected from either diagnostic criteria or molecular testing until a couple has multiple affected children. Genetic counseling for families with one affected child should include a small (1% to 2%) possibility of recurrence, even for parents who have no evidence of tuberous sclerosis complex after a thorough diagnostic evaluation.

Incorporation of adhesion peptides into nonadhesive hydrogels useful for tissue resurfacing

Abstract: Photopolymerized crosslinked networks of poly(ethylene glycol; PEG) diacrylate (MW 8000) were derivitized throughout their bulk with Arg-Gly-Asp (RGD)-containing peptide sequences. Incorporation was achieved by functionalizing the amine terminus of the peptide with an acrylate moiety, thereby enabling the adhesion peptide to copolymerize rapidly with the PEG diacrylate upon photoinitiation. PEG diacrylate hydrogels derivitized with RGD peptide at surface concentrations ranging from 0.001 to 1 pmol/cm2 were studied in vitro for their ability to promote spreading of human foreskin fibroblasts over 24 h. Hydrogels not derivitized with peptides were poor substrates for adhesion, permitting spreading of only 5% of the seeded cells. When immobilized with no spacer arm, both RGD and RDG (inactive control) supported spreading of approximately 50% and approximately 15% of cells at 1 and 0.1 pmol/cm2 surface concentrations respectively; lower concentrations did not promote spreading. When a MW 3400 PEG spacer arm was incorporated between the hydrogel and the peptide linkage, incorporation of 1 pmol/cm2 RGD promoted 70% spreading whereas RDG at the same concentration did not promote spreading. In addition, when cells were seeded in serum-free medium, only RGD peptides incorporated with a spacer arm were able to promote spreading. Thus peptide incorporated into PEG 8000 diacrylate hydrogels without a spacer arm nonspecifically mediated cell spreading whereas incorporation via a MW 3400 PEG spacer arm was required to permit cell spreading to be specifically mediated.

A Population-Based Study of Seizures after Traumatic Brain Injuries

Abstract: Background The risk of seizures is increased after traumatic brain injury, but the extent and duration of the increase in risk are unknown. The purpose of this study was to identify the characteristics of brain injuries that are associated with the development of seizures. Methods We identified 4541 children and adults with traumatic brain injury (characterized by loss of consciousness, post-traumatic amnesia, or skull fracture) in Olmsted County, Minnesota, during the period from 1935 through 1984. Injuries were classified as mild (loss of consciousness or amnesia lasting less than 30 minutes), moderate (loss of consciousness for 30 minutes to 24 hours or a skull fracture), or severe (loss of consciousness or amnesia for more than 24 hours, subdural hematoma, or brain contusion). We compared the incidence of new unprovoked seizures in this cohort with population rates, using standardized incidence ratios and Cox proportional-hazards analysis. Results The overall standardized incidence ratio was 3.1 (95 p...

Vagus nerve stimulation therapy for partial-onset seizures A randomized active-control trial

Abstract: Objective: The purpose of this multicenter, add-on, double-blind, randomized, active-control study was to compare the efficacy and safety of presumably therapeutic (high) vagus nerve stimulation with less (low) stimulation. Background: Chronic intermittent left vagus nerve stimulation has been shown in animal models and in preliminary clinical trials to suppress the occurrence of seizures. Methods: Patients had at least six partial-onset seizures over 30 days involving complex partial or secondarily generalized seizures. Concurrent antiepileptic drugs were unaltered. After a 3-month baseline, patients were surgically implanted with stimulating leads coiled around the left vagus nerve and connected to an infraclavicular subcutaneous programmable pacemaker-like generator. After randomization, device initiation, and a 2-week ramp-up period, patients were assessed for seizure counts and safety over 3 months. The primary efficacy variable was the percentage change in total seizure frequency compared with baseline. Results: Patients receiving high stimulation (94 patients, ages 13 to 54 years) had an average 28% reduction in total seizure frequency compared with a 15% reduction in the low stimulation group (102 patients, ages 15 to 60 year; p = 0.04). The high-stimulation group also had greater improvements on global evaluation scores, as rated by a blinded interviewer and the patient. High stimulation was associated with more voice alteration and dyspnea. No changes in physiologic indicators of gastric, cardiac, or pulmonary functions occurred. Conclusions: Vagus nerve stimulation is an effective and safe adjunctive treatment for patients with refractory partial-onset seizures. It represents the advent of a new, nonpharmacologic treatment for epilepsy.

Hamiltonian description of the ideal fluid

Abstract: The Hamiltonian viewpoint of fluid mechanical systems with few and infinite number of degrees of freedom is described. Rudimentary concepts of finite-degree-of-freedom Hamiltonian dynamics are reviewed, in the context of the passive advection of a scalar or tracer field by a fluid. The notions of integrability, invariant-tori, chaos, overlap criteria, and invariant-tori breakup are described in this context. Preparatory to the introduction of field theories, systems with an infinite number of degrees of freedom, elements of functional calculus and action principles of mechanics are reviewed. The action principle for the ideal compressible fluid is described in terms of Lagrangian or material variables. Hamiltonian systems in terms of noncanonical variables are presented, including several examples of Eulerian or inviscid fluid dynamics. Lie group theory sufficient for the treatment of reduction is reviewed. The reduction from Lagrangian to Eulerian variables is treated along with Clebsch variable decompositions. Stability in the canonical and noncanonical Hamiltonian contexts is described. Sufficient conditions for stability, such as Rayleigh-like criteria, are seen to be only sufficient in the general case because of the existence of negative-energy modes, which are possessed by interesting fluid equilibria. Linearly stable equilibria with negative energy modes are argued to be unstable whenmore » nonlinearity or dissipation is added. The energy-Casimir method is discussed and a variant of it that depends upon the notion of dynamical accessibility is described. The energy content of a perturbation about a general fluid equilibrium is calculated using three methods. {copyright} {ital 1998} {ital The American Physical Society}« less

On Theories Explaining the Success of the Gravity Equation

Abstract: Examining the accuracy of the monopolistic competition theory's predictions for import volumes, we assess whether this theory accounts for the empirical success of the gravity equation Since certain factor-endowment based theories have the same prediction for import volumes, we employ resampling techniques to address this model identification problem We use extraneous information on the allocation of factor endowments in a given sample to identify which model is driving trade flows We find that the accuracy of the monopolistic competition theory's prediction improves in samples where the factor endowment allocations generate a higher share of differentiated goods trade By an analogous criterion, the Heckscher-Ohlin models make a much less accurate prediction We conclude that the monopolistic competition theory is more likely to account for the gravity equation's success, especially in explaining trade among industrial nations

Life‐course transitions and desistance from crime*

Abstract: Sampson and Laub (1993) provided a major contribution to the study of criminal careers by linking criminal behavior to life-course transitions, such as marriage, employment, and entry into the military. To interpret their findings, these investigators relied exclusively on control theory. In a sharp departure from that position, this study offers evidence that life-course transitions affect criminal behavior by altering relations with delinquent peers. Focusing on marriage, the analysis shows that the transition to marriage is followed by a dramatic decline in time spent with piends as well as reduced exposure to delinquent peers, and that these factors largely explain the association between marital status and delinquent behavior. The findings suggest that changing patterns of peer relations over the life course are essential for understanding criminal life-course trajectories. In one of the most influential studies of crime in recent years, Sampson and Laub (1993) embarked on a formidable task: to explain variation in criminal behavior-onset, maintenance, and desistance-over the life course. Arguing that criminologists had narrowly fixated on the teenage years, Sampson and Laub sought to bring "both childhood and adulthood back into the criminological picture of age and crime" (19939). To that end, they adopted the conceptual tools of the life-course perspective (Elder, 1985) and the etiological principles of control theory (Durkheim, 1897; Hirschi, 1969). Strong ties to age-linked institutions of social control-family, school, and peers in childhood and adolescence; higher education, marriage/parenthood, work and community in adulthood-inhibit deviant behavior, they argued, and changing ties to these institutions over the life course produce distinctly different criminal trajectories marked by turning points (a change in the life course) from conventional to criminal behavior or vice versa. To test their thesis, Sampson and Laub revived data from the Gluecks' well-known longitudinal study of delinquents, data that were initially collected in 1939 and that had lain dormant since the 1950s. The Glueck data, as the authors rightly observed, were notable not only for their longitudinal character, but also for the rich variety of variables and sources

The frame/content theory of evolution of speech production.

Abstract: The species-specific organizational property of speech is a continual mouth open-close alternation, the two phases of which are subject to continual articulatory modulation. The cycle constitutes the syllable, and the open and closed phases are segments - vow- els and consonants, respectively. The fact that segmental serial ordering errors in normal adults obey syllable structure constraints sug- gests that syllabic "frames" and segmental "content" elements are separately controlled in the speech production process. The frames may derive from cycles of mandibular oscillation present in humans from babbling onset, which are responsible for the open-close al- ternation. These communication-related frames perhaps first evolved when the ingestion-related cyclicities of mandibular oscillation (as- sociated with mastication (chewing) sucking and licking) took on communicative significance as lipsmacks, tonguesmacks, and teeth chat- ters - displays that are prominent in many nonhuman primates. The new role of Broca's area and its surround in human vocal communication may have derived from its evolutionary history as the main cortical center for the control of ingestive processes. The frame and content components of speech may have subsequently evolved separate realizations within two general purpose primate mo- tor control systems: (1) a motivation-related medial "intrinsic" system, including anterior cingulate cortex and the supplementary motor area, for self-generated behavior, formerly responsible for ancestral vocalization control and now also responsible for frames, and (2) a lateral "extrinsic" system, including Broca's area and surround, and Wernicke's area, specialized for response to external input (and there- fore the emergent vocal learning capacity) and more responsible for content.

Bayesian CART Model Search

Abstract: In this article we put forward a Bayesian approach for finding classification and regression tree (CART) models. The two basic components of this approach consist of prior specification and stochastic search. The basic idea is to have the prior induce a posterior distribution that will guide the stochastic search toward more promising CART models. As the search proceeds, such models can then be selected with a variety of criteria, such as posterior probability, marginal likelihood, residual sum of squares or misclassification rates. Examples are used to illustrate the potential superiority of this approach over alternative methods.

Is it better to add taxa or characters to a difficult phylogenetic problem

Abstract: The effects on phylogenetic accuracy of adding characters and/or taxa were explored using data generated by computer simulation. The conditions of this study were constrained but allowed for systematic investigation of certain parameters. The starting point for the study was a four-taxon tree in the ``Felsenstein zone,'' representing a dif® cult phylogenetic problem with an extreme situation of long branch attraction. Taxa were added sequentially to this tree in a manner speci® cally designed to break up the long branches, and for each tree data matrices of different sizes were simulated. Phylogenetic trees were reconstructed from these data using the criteria of parsimony and maximum likelihood. Phylogenetic accuracy was measured in three ways: (1) proportion of trees that are completely correct, (2) proportion of correctly reconstructed branches in all trees, and (3) proportion of trees in which the original four-taxon statement is correctly reconstructed. Accuracy improved dramatically with the addition of taxa and much more slowly with the addition of characters. If taxa can be added to break up long branches, it is much more preferable to add taxa than characters. (Long branch attraction; parsimony; phylogenetic recon- struction; simulation; taxon sampling.)

The Origins of Telicity

Abstract: The distinction between telic and atelic predicates has been described in terms of the algebraic properties of their meaning since the early days of model-theoretic semantics. This perspective was inspired by Aristotle’s discussion of types of actions that do or do not take time to be completed which was taken up and turned into a linguistic discussion of action-denoting predicates by Vendler (1957). The algebraic notion that seemed to be most conducive to express the Aristotelian distinction appeared to be the mereological notion of a part, applied to the time at which these predicates hold: atelic predicates, like push a cart, have the subinterval property, that is, whenever they are true at a time interval, then they are true at any part of that interval; this does not hold for telic predicates, like eat an apple, cf. Bennett & Partee (1972), Taylor (1977), and Dowty (1979)2. Bach (1986) integrated these insights into a semantics based on events.

Comparison of an Anticoagulation Clinic With Usual Medical Care: Anticoagulation Control, Patient Outcomes, and Health Care Costs

Abstract: Background The outcomes of an inception cohort of patients seen at an anticoagulation clinic (AC) were published previously. The temporary closure of this clinic allowed the evaluation of 2 more inception cohorts: usual medical care and an AC. Objective To compare newly anticoagulated patients who were treated with usual medical care with those treated at an AC for patient characteristics, anticoagulation control, bleeding and thromboembolic events, and differences in costs for hospitalizations and emergency department visits. Results Rates are expressed as percentage per patient-year. Patients treated at an AC who received lower-range anticoagulation had fewer international normalized ratios greater than 5.0 (7.0% vs 14.7%), spent more time in range (40.0% vs 37.0%), and spent less time at an international normalized ratio greater than 5 (3.5% vs 9.8%). Patients treated at an AC who received higher-range anticoagulation had more international normalized ratios within range (50.4% vs 35.0%), had fewer international normalized ratios less than 2.0 (13.0% vs 23.8%), and spent more time within range (64.0% vs 51.0%). The AC group had lower rates (expressed as percentage per patient-year) of significant bleeding (8.1% vs 35.0%), major to fatal bleeding (1.6% vs 3.9%), and thromboembolic events (3.3% vs 11.8%); the AC group also demonstrated a trend toward a lower mortality rate (0% vs 2.9%;P=.09). Significantly lower annual rates of warfarin sodium–related hospitalizations (5% vs 19%) and emergency department visits (6% vs 22%) reduced annual health care costs by $132086 per 100 patients. Additionally, a lower rate of warfarin-unrelated emergency department visits (46.8% vs 168.0%) produced an additional annual savings in health care costs of $29972 per 100 patients. Conclusions A clinical pharmacist–run AC improved anticoagulation control, reduced bleeding and thromboembolic event rates, and saved $162058 per 100 patients annually in reduced hospitalizations and emergency department visits.

Mail Versus Mall: a Strategic Analysis of Competition Between Direct Marketers and Conventional Retailers

Abstract: Consumers now purchase several offerings from direct sellers, including catalog and Internet marketers. These direct channels exist in parallel with the conventional retail stores. The availability of multiple channels has significant implications for the performance of consumer markets. The literature in marketing and economics has, however, been dominated by a focus on the conventional retail sector. This paper is an effort toward modeling competition in the multiple-channel environment from a strategic viewpoint. At the outset, a parsimonious model that accommodates the following consumer and market characteristics is introduced. First, the relative attractiveness of retail shopping varies across consumers. Second, the fit with the direct channel varies across product categories. Third, the strength of existing retail presence in local markets moderates competition. Fourth, in contrast with the fixed location of the retail store that anchors its localized market power, the location of the direct marketer is irrelevant to the competitive outcome. The model is first applied in a setting where consumers have complete knowledge of product availability and prices in all channels. In the resulting equilibrium, the direct marketer acts as a competitive wedge between retail stores. The direct presence is so strong that each retailer competes against the remotely located direct marketer, rather than against neighboring retailers. This outcome has implications for the marketing mix of retailers, which has traditionally been tuned to attract consumers choosing between retail stores. In the context of market entry, conditions under which a direct channel can access a local market in retail entry equilibrium are derived. Our analysis suggests that the traditional focus on retail entry equilibria may not yield informative or relevant findings when direct channels are a strong presence. Next, the role of information in multiple-channel markets is modeled. This issue is particularly relevant in the context of direct marketing where the seller can typically control the level of information in the marketplace, sometimes on a customer-by-customer basis e.g., by deciding on the mailing list for a catalog campaign. When a certain fraction of consumers does not receive information from the direct marketer, the retailers compete with each other for that fraction of the market. The retailer's marketing mix has to be tuned, in this case, to jointly address direct and neighboring retail competition. The level of information disseminated by the direct marketer is shown to have strategic implications, and the use of market coverage as a lever to control competition is described. Even with zero information costs, providing information to all consumers may not be optimal under some circumstances. In particular, when the product is not well adapted to the direct channel, the level of market information about the direct option should ideally be lowered. The only way to compete with retailers on a larger scale with a poorly adapted product is by lowering direct prices, which lowers profits. Lowering market information levels and allowing retailers to compete more with each other facilitates a higher equilibrium retail price. In turn, this allows a higher direct price to be charged and improves overall direct profit. On the other hand, when the product is well adapted, increasing direct market presence and engaging in greater competition with the retail sector yields higher returns. The finding that high market coverage may depress profits raises some issues for further exploration. First, implementing the optimal coverage is straightforward when the seller controls the information mechanism, as in the case of catalog marketing. The Internet, in contrast, is an efficient mechanism to transmit information, but does not provide the sellers with such control over the level of market information. A key reason is that the initiative to gather information on the Internet lies largely with consumers. The design and implementation of mechanisms to control aggregate information levels in electronic markets can, therefore, be an important theme for research and managerial interest. Second, direct marketers have traditionally relied on the statistical analysis of customer records to decide on contact policies. The analysis in this paper reveals that these policies can have significant strategic implications as well. Research that integrates the statistical and strategic aspects could make a valuable contribution. The paper concludes with a discussion of issues for future research in multiple-channel markets, including avenues to model competition in settings with multiple direct marketers.

The Conditional CAPM and the Cross-Section of Expected Returns

Abstract: Most empirical studies of the static CAPM assume that betas remain constant over time and that the return on the value-weighted portfolio of all stocks is a proxy for the return on aggregate wealth. The general consensus is that the static CAPM is unable to explain satisfactorily the cross-section of average returns on stocks. We assume that the CAPM holds in a conditional sense, i.e., betas and the market risk premium vary over time. We include the return on human capital when measuring the return on aggregate wealth. Our specification performs well in explaining the cross-section of average returns.

Extended use of glatiramer acetate (Copaxone) is well tolerated and maintains its clinical effect on multiple sclerosis relapse rate and degree of disability

Abstract: When 251 relapsing-remitting patients with multiple sclerosis were randomized to receive daily subcutaneous injections of glatiramer acetate, previously called copolymer 1 (Copaxone; n = 125) or placebo (n = 126) for 24 months, there were no laboratory abnormalities associated with glatiramer acetate treatment and it was well tolerated with few side effects. Patients receiving glatiramer acetate had significantly fewer relapses and were more likely to be neurologically improved, whereas those receiving placebo were more likely to worsen. This study was extended for 1 to 11 months (mean of 5.2 months for the glatiramer acetate group and 5.9 months for the placebo group). The blinding and study conditions used during the core 24-month study were unchanged throughout the extension. The results of this extension study confirm the excellent tolerance and safety profile of glatiramer acetate for injection. The clinical benefit of glatiramer acetate for both the relapse rate and for neurologic disability was sustained at the end of the extension trial.