Showing papers by "University of Kentucky published in 2006"

Using Self-Report Assessment Methods to Explore Facets of Mindfulness

Abstract: The authors examine the facet structure of mindfulness using five recently developed mindfulness questionnaires. Two large samples of undergraduate students completed mindfulness questionnaires and measures of other constructs. Psychometric properties of the mindfulness questionnaires were examined, including internal consistency and convergent and discriminant relationships with other variables. Factor analyses of the combined pool of items from the mindfulness questionnaires suggested that collectively they contain five clear, interpretable facets of mindfulness. Hierarchical confirmatory factor analyses suggested that at least four of the identified factors are components of an overall mindfulness construct and that the factor structure of mindfulness may vary with meditation experience. Mindfulness facets were shown to be differentially correlated in expected ways with several other constructs and to have incremental validity in the prediction of psychological symptoms. Findings suggest that conceptualizing mindfulness as a multifaceted construct is helpful in understanding its components and its relationships with other variables.

Scalable Recognition with a Vocabulary Tree

Abstract: A recognition scheme that scales efficiently to a large number of objects is presented. The efficiency and quality is exhibited in a live demonstration that recognizes CD-covers from a database of 40000 images of popular music CD’s. The scheme builds upon popular techniques of indexing descriptors extracted from local regions, and is robust to background clutter and occlusion. The local region descriptors are hierarchically quantized in a vocabulary tree. The vocabulary tree allows a larger and more discriminatory vocabulary to be used efficiently, which we show experimentally leads to a dramatic improvement in retrieval quality. The most significant property of the scheme is that the tree directly defines the quantization. The quantization and the indexing are therefore fully integrated, essentially being one and the same. The recognition quality is evaluated through retrieval on a database with ground truth, showing the power of the vocabulary tree approach, going as high as 1 million images.

Hydrogels in Biology and Medicine: From Molecular Principles to Bionanotechnology†

Abstract: Hydrophilic polymers are the center of research emphasis in nanotechnology because of their perceived “intelligence”. They can be used as thin films, scaffolds, or nanoparticles in a wide range of biomedical and biological applications. Here we highlight recent developments in engineering uncrosslinked and crosslinked hydrophilic polymers for these applications. Natural, biohybrid, and synthetic hydrophilic polymers and hydrogels are analyzed and their thermodynamic responses are discussed. In addition, examples of the use of hydrogels for various therapeutic applications are given. We show how such systems’ intelligent behavior can be used in sensors, microarrays, and imaging. Finally, we outline challenges for the future in integrating hydrogels into biomedical applications.

Clopidogrel and Aspirin versus Aspirin Alone for the Prevention of Atherothrombotic Events

Abstract: Background Dual antiplatelet therapy with clopidogrel plus low-dose aspirin has not been studied in a broad population of patients at high risk for atherothrombotic events. Methods We randomly assigned 15,603 patients with either clinically evident cardiovascular disease or multiple risk factors to receive clopidogrel (75 mg per day) plus low-dose aspirin (75 to 162 mg per day) or placebo plus low-dose aspirin and followed them for a median of 28 months. The primary efficacy end point was a composite of myocardial infarction, stroke, or death from cardiovascular causes. Results The rate of the primary efficacy end point was 6.8 percent with clopidogrel plus aspirin and 7.3 percent with placebo plus aspirin (relative risk, 0.93; 95 percent confidence interval, 0.83 to 1.05; P = 0.22). The respective rate of the principal secondary efficacy end point, which included hospitalizations for ischemic events, was 16.7 percent and 17.9 percent (relative risk, 0.92; 95 percent confidence interval, 0.86 to 0.995; P = 0.04), and the rate of severe bleeding was 1.7 percent and 1.3 percent (relative risk, 1.25; 95 percent confidence interval, 0.97 to 1.61 percent; P = 0.09). The rate of the primary end point among patients with multiple risk factors was 6.6 percent with clopidogrel and 5.5 percent with placebo (relative risk, 1.2; 95 percent confidence interval, 0.91 to 1.59; P = 0.20) and the rate of death from cardiovascular causes also was higher with clopidogrel (3.9 percent vs. 2.2 percent, P = 0.01). In the subgroup with clinically evident atherothrombosis, the rate was 6.9 percent with clopidogrel and 7.9 percent with placebo (relative risk, 0.88; 95 percent confidence interval, 0.77 to 0.998; P = 0.046). Conclusions In this trial, there was a suggestion of benefit with clopidogrel treatment in patients with symptomatic atherothrombosis and a suggestion of harm in patients with multiple risk factors. Overall, clopidogrel plus aspirin was not significantly more effective than aspirin alone in reducing the rate of myocardial infarction, stroke, or death from cardiovascular causes. (ClinicalTrials.gov number, NCT00050817.)

Global burden of COPD: systematic review and meta-analysis

Abstract: The aim of this study was to quantify the global prevalence of chronic obstructive pulmonary disease (COPD) by means of a systematic review and random effects meta-analysis. PubMed was searched for population-based prevalence estimates published during the period 1990-2004. Articles were included if they: 1) provided total population or sex-specific estimates for COPD, chronic bronchitis and/or emphysema; and 2) gave method details sufficiently clearly to establish the sampling strategy, approach to diagnosis and diagnostic criteria. Of 67 accepted articles, 62 unique entries yielded 101 overall prevalence estimates from 28 different counties. The pooled prevalence of COPD was 7.6% from 37 studies, of chronic bronchitis alone (38 studies) was 6.4% and of emphysema alone (eight studies) was 1.8%. The pooled prevalence from 26 spirometric estimates was 8.9%. The most common spirometric definitions used were those of the Global Initiative for Chronic Obstructive Lung Disease (13 estimates). There was significant heterogeneity, which was incompletely explained by subgroup analysis (e.g. age and smoking status). The prevalence of physiologically defined chronic obstructive pulmonary disease in adults aged > or =40 yrs is approximately 9-10%. There are important regional gaps, and methodological differences hinder interpretation of the available data. The efforts of the Global Initiative for Chronic Obstructive Lung Disease and similar groups should help to standardise chronic obstructive pulmonary disease prevalence measurement.

The Reactive-Proactive Aggression Questionnaire: Differential Correlates of Reactive and Proactive Aggression in Adolescent Boys.

Abstract: This study reports the development of the Reactive–Proactive Aggression Questionnaire (RPQ), and the differential correlates of these two forms of aggression. Antisocial, psychosocial and personality measures were obtained at ages 7 and 16 years in schoolboys, while the RPQ was administered to 334 of the boys at age 16 years. Confirmatory factor analysis indicated a significant fit for a two-factor proactive–reactive model that replicated from one independent subsample to another. Proactive aggression was uniquely characterized at age 7 by initiation of fights, strong-arm tactics, delinquency, poor school motivation, poor peer relationships, single-parent status, psychosocial adversity, substance-abusing parents, and hyperactivity, and at age 16 by a psychopathic personality, blunted affect, delinquency, and serious violent offending. Reactive aggression was uniquely characterized at age 16 by impulsivity, hostility, social anxiety, lack of close friends, unusual perceptual experiences, and ideas of reference. Findings confirm and extend the differential correlates of proactive–reactive aggression, and demonstrate that this brief but reliable and valid self-report instrument can be used to assess proactive and reactive aggression in child and adolescent samples.

Insights from the genome of the biotrophic fungal plant pathogen Ustilago maydis

Abstract: Ustilago maydis is a ubiquitous pathogen of maize and a well-established model organism for the study of plant-microbe interactions. This basidiomycete fungus does not use aggressive virulence strategies to kill its host. U. maydis belongs to the group of biotrophic parasites (the smuts) that depend on living tissue for proliferation and development. Here we report the genome sequence for a member of this economically important group of biotrophic fungi. The 20.5-million-base U. maydis genome assembly contains 6,902 predicted protein-encoding genes and lacks pathogenicity signatures found in the genomes of aggressive pathogenic fungi, for example a battery of cell-wall-degrading enzymes. However, we detected unexpected genomic features responsible for the pathogenicity of this organism. Specifically, we found 12 clusters of genes encoding small secreted proteins with unknown function. A significant fraction of these genes exists in small gene families. Expression analysis showed that most of the genes contained in these clusters are regulated together and induced in infected tissue. Deletion of individual clusters altered the virulence of U. maydis in five cases, ranging from a complete lack of symptoms to hypervirulence. Despite years of research into the mechanism of pathogenicity in U. maydis, no 'true' virulence factors had been previously identified. Thus, the discovery of the secreted protein gene clusters and the functional demonstration of their decisive role in the infection process illuminate previously unknown mechanisms of pathogenicity operating in biotrophic fungi. Genomic analysis is, similarly, likely to open up new avenues for the discovery of virulence determinants in other pathogens.

Classroom Goal Structure, Student Motivation, and Academic Achievement

Abstract: Over the past 25 years, achievement goal theory has emerged as one of the most prominent theories of achievement motivation. This chapter uses an achievement goal framework to examine the influence of classroom and school environments on students' academic motivation and achievement. Considerable evidence suggests that elementary and secondary students show the most positive motivation and learning patterns when their school settings emphasize mastery, understanding, and improving skills and knowledge. Whereas school environments that are focused on demonstrating high ability and competing for grades can increase the academic performance of some students, research suggests that many young people experience diminished motivation under these conditions. The implications of achievement goal theory for examining the impact of school reform are discussed.

Dispositional Optimism and Coping: A Meta-Analytic Review:

Abstract: The relation between dispositional optimism and better adjustment to diverse stressors may be attributable to optimism's effects on coping strategies. A meta-analytic review (K = 50, N = 11,629) examined the impact of dispositional optimism on coping. Dispositional optimism was found to be positively associated with approach coping strategies aiming to eliminate, reduce, or manage stressors or emotions (r = .17), and negatively associated with avoidance coping strategies seeking to ignore, avoid, or withdraw from stressors or emotions (r = -.21). Effect sizes were larger for the distinction between approach and avoidance coping strategies than for that between problem and emotion-focused coping. Meta-analytic findings also indicate that optimists may adjust their coping strategies to meet the demands of the stressors at hand, and that the optimism-coping relationship is strongest in English-speaking samples.

Oxidative Alterations in Alzheimer's Disease

Abstract: There is increasing evidence that free radical damage to brain lipids, carbohydrates, proteins, and DNA is involved in neuron death in neurodegenerative disorders. The largest number of studies have been performed in Alzheimer's disease (AD) where there is considerable support for the oxidative stress hypothesis in the pathogenesis of neuron degeneration. In autopsied brain there is an increase in lipid peroxidation, a decline in polyunsaturated fatty acids (PUFA) and an increase in 4-hydroxynonenal (HNE), a neurotoxic aldehyde product of PUFA oxidation. Increased protein oxidation and a marked decline in oxidative-sensitive enzymes, glutamine synthetase and creatinine kinase, are found in the brain in AD. Increased DNA oxidation, especially 8-hydroxy-2′-deoxyguanosine (8-OHdG) is present in the brain in AD. Immunohistochemical studies show the presence of oxidative stress products in neurofibrillary tangles and senile plaques in AD. Markers of lipid peroxidation (HNE, isoprostanes) and DNA (8-OHdG) are increased in CSF in AD. In addition, inflammatory response markers (the complement cascade, cytokines, acute phase reactants and proteases) are present in the brain in AD. These findings, coupled with epidemiologic studies showing that anti-inflammatory agents slow the progression or delay the onset of AD, suggest that inflammation plays a role in AD. Overall these studies indicate that oxidative stress and the inflammatory cascade, working in concert, are important in the pathogenetic cascade of neurodegeneration in AD, suggesting that therapeutic efforts aimed at both of these mechanisms may be beneficial.

A 10-Year Retrospective of Research in Health Mass Media Campaigns: Where Do We Go From Here?

Abstract: Mass media campaigns have long been a tool for promoting public health. How effective are such campaigns in changing health-related attitudes and behaviors, however, and how has the literature in this area progressed over the past decade? The purpose of the current article is threefold. First, I discuss the importance of health mass media campaigns and raise the question of whether they are capable of effectively impacting public health. Second, I review the literature and discuss what we have learned about the effectiveness of campaigns over the past 10 years. Finally, I conclude with a discussion of possible avenues for the health campaign literature over the next 10 years. The overriding conclusion is the following: The literature is beginning to amass evidence that targeted, well-executed health mass media campaigns can have small-to-moderate effects not only on health knowledge, beliefs, and attitudes, but on behaviors as well, which can translate into major public health impact given the wide reach of mass media. Such impact can only be achieved, however, if principles of effective campaign design are carefully followed.

The production of social capital in US counties

Abstract: A growing belief exists that social capital contributes to economic growth of communities. In this paper, we identify inputs into the production of social capital at the level of US counties, using an array of individual and community factors that are theoretically important determinants of social capital. We use data from the Bureau of the Census, County Business Patterns, USA Counties on CD, National Center for Charitable Statistics, and the Regional Economic Information System for two time periods. Ethnic homogeneity, income inequality, attachment to place, education, age, and female labor force participation are strongly associated with levels of social capital across US counties.

Epidemiology and costs of chronic obstructive pulmonary disease.

Abstract: SERIES “THE GLOBAL BURDEN OF CHRONIC OBSTRUCTIVE PULMONARY DISEASE” Edited by K.F. Rabe and J.B. Soriano Number 1 in this Series Chronic obstructive pulmonary disease (COPD) is a leading but under-recognised cause of morbidity and mortality worldwide 1. The prevalence of COPD in the general population is estimated to be ∼1% across all ages rising steeply to >10% amongst those aged ≥40 yrs. The prevalence climbs appreciably higher with age. The 30-yr projections for the global increase in COPD from 1990–2020 are startling. COPD is projected to move from the sixth to the third most common cause of death worldwide, whilst rising from fourth to third in terms of morbidity within the same time-frame 2. The cofactors responsible for this remarkable increase are the continued use of tobacco, coupled with the changing demographics of the world, such that many more people, especially those in developing countries, are living into the COPD age range. COPD is under-diagnosed not only in its early stages, but even when lung function is severely impaired. This is perhaps surprising, since simple and inexpensive spirometers that are suitable in clinical practice are now available, and lung function is a powerful predictor of all-cause mortality, regardless of smoking status. No other disease that is responsible for comparable morbidity, mortality and cost is neglected by healthcare providers as much as COPD. It may well be that the true burden of the disease is not fully appreciated, and the message that COPD is both preventable and treatable has yet to be fully understood by most healthcare providers. The hope is that highlighting these facts will help to raise the profile of COPD and begin to change long-held attitudes. Up to 2001, only 32 prevalence surveys of COPD had been reported 3. This is remarkable given the hundreds …

Identifiability at the boundary for first-order terms

Abstract: Let Ω be a domain in R n whose boundary is C 1 if n≥3 or C 1,β if n=2. We consider a magnetic Schrodinger operator L W , q in Ω and show how to recover the boundary values of the tangential component of the vector potential W from the Dirichlet to Neumann map for L W , q . We also consider a steady state heat equation with convection term Δ+2W·∇ and recover the boundary values of the convection term W from the Dirichlet to Neumann map. Our method is constructive and gives a stability result at the boundary.

Corneal avascularity is due to soluble VEGF receptor-1

Abstract: Corneal avascularity-the absence of blood vessels in the cornea-is required for optical clarity and optimal vision, and has led to the cornea being widely used for validating pro- and anti-angiogenic therapeutic strategies for many disorders. But the molecular underpinnings of the avascular phenotype have until now remained obscure and are all the more remarkable given the presence in the cornea of vascular endothelial growth factor (VEGF)-A, a potent stimulator of angiogenesis, and the proximity of the cornea to vascularized tissues. Here we show that the cornea expresses soluble VEGF receptor-1 (sVEGFR-1; also known as sflt-1) and that suppression of this endogenous VEGF-A trap by neutralizing antibodies, RNA interference or Cre-lox-mediated gene disruption abolishes corneal avascularity in mice. The spontaneously vascularized corneas of corn1 and Pax6+/- mice and Pax6+/- patients with aniridia are deficient in sflt-1, and recombinant sflt-1 administration restores corneal avascularity in corn1 and Pax6+/- mice. Manatees, the only known creatures uniformly to have vascularized corneas, do not express sflt-1, whereas the avascular corneas of dugongs, also members of the order Sirenia, elephants, the closest extant terrestrial phylogenetic relatives of manatees, and other marine mammals (dolphins and whales) contain sflt-1, indicating that it has a crucial, evolutionarily conserved role. The recognition that sflt-1 is essential for preserving the avascular ambit of the cornea can rationally guide its use as a platform for angiogenic modulators, supports its use in treating neovascular diseases, and might provide insight into the immunological privilege of the cornea.

Drusen complement components C3a and C5a promote choroidal neovascularization

Abstract: Age-related macular degeneration (AMD) is the leading cause of irreversible blindness in industrialized nations, affecting 30-50 million people worldwide. The earliest clinical hallmark of AMD is the presence of drusen, extracellular deposits that accumulate beneath the retinal pigmented epithelium. Although drusen nearly always precede and increase the risk of choroidal neovascularization (CNV), the late vision-threatening stage of AMD, it is unknown whether drusen contribute to the development of CNV. Both in patients with AMD and in a recently described mouse model of AMD, early subretinal pigmented epithelium deposition of complement components C3 and C5 occurs, suggesting a contributing role for these inflammatory proteins in the development of AMD. Here we provide evidence that bioactive fragments of these complement components (C3a and C5a) are present in drusen of patients with AMD, and that C3a and C5a induce VEGF expression in vitro and in vivo. Further, we demonstrate that C3a and C5a are generated early in the course of laser-induced CNV, an accelerated model of neovascular AMD driven by VEGF and recruitment of leukocytes into the choroid. We also show that genetic ablation of receptors for C3a or C5a reduces VEGF expression, leukocyte recruitment, and CNV formation after laser injury, and that antibody-mediated neutralization of C3a or C5a or pharmacological blockade of their receptors also reduces CNV. Collectively, these findings establish a mechanistic basis for the clinical observation that drusen predispose to CNV, revealing a role for immunological phenomena in angiogenesis and providing therapeutic targets for AMD.

Exploring the Social Ledger: Negative Relationships and Negative Asymmetry in Social Networks in Organizations

Abstract: We explore the role of negative relationships in the context of social networks in work organizations. Whereas network researchers have emphasized the benefits and opportunities derived from positive interpersonal relationships, we examine the social liabilities that can result from negative relationships in order to flesh out the entire “social ledger.” Deriving our argument from theory and research on negative asymmetry, we propose that these negative relationships may have greater power than positive relationships to explain workplace outcomes

Outcomes of patients with differentiated thyroid carcinoma following initial therapy.

Abstract: This analysis was performed to determine the effect of initial therapy on the outcomes of thyroid cancer patients. The study setting was a prospectively followed multi-institutional registry. Patients were stratified as low risk (stages I and II) or high risk (stages III and IV). Treatments employed included near-total thyroidectomy, administration of radioactive iodine, and thyroid hormone suppression therapy. Outcome measures were overall survival, disease-specific survival, and disease-free survival. Near-total thyroidectomy, radioactive iodine, and aggressive thyroid hormone suppression therapy were each independently associated with longer overall survival in high-risk patients. Near-total thyroidectomy followed by radioactive iodine therapy, and moderate thyroid hormone suppression therapy, both predicted improved overall survival in stage II patients. No treatment modality, including lack of radioactive iodine, was associated with altered survival in stage I patients. Based on our overall survival data, we confirm that near-total thyroidectomy is indicated in high-risk patients. We also conclude that radioactive iodine therapy is beneficial for stage II, III, and IV patients. Importantly, we show for the first time that superior outcomes are associated with aggressive thyroid hormone suppression therapy in high-risk patients, but are achieved with modest suppression in stage II patients. We were unable to show any impact, positive or negative, of specific therapies in stage I patients.

Characteristics of Adolescents Who Report Very High Life Satisfaction

Abstract: This study investigated the characteristics of adolescents who report high levels of life global satisfaction. A total of 485 adolescents completed the Students’ Life Satisfaction Scale (SLSS) (Huebner, E. S. (1991). Sch. Psychol. Int. 12: 231–240.) along with self-report measures of intrapersonal, interpersonal, and school-related functioning. Based on their SLSS scores, students were divided into three groups: “low” (bottom 20% of the distribution), “average” (middle 50%), and “high” (upper 20%). Youth in the high satisfaction group reported significantly higher adaptive functioning on all dependent variables than youth in the low satisfaction group. Relative to students with average life satisfaction, students with high life satisfaction reported superior scores on a measure of social stress, a measure of attitudes toward teachers, and on all measures of intrapersonal functioning. Also, no adolescents in the high life satisfaction group demonstrated clinical levels of psychological symptoms, whereas 7% of the average group and 42% of the low satisfaction group reported clinical levels of symptoms. Taken together, the findings suggested that high life satisfaction is associated with some mental health benefits that are not found among youth reporting comparatively lower satisfaction levels.

Procedural injustice, victim precipitation, and abusive supervision

Abstract: We used data collected from a field survey of 334 supervisor‐subordinate dyads to test a model of the antecedents of abusive supervision. Path analytic tests of moderated mediation provided support for our prediction that supervisors’ depression mediates the relationship between supervisors’ procedural justice and subordinates’ perceptions of their supervisors’ abusiveness and that the mediation framework is stronger when subordinates are higher in negative affectivity. We discuss the study’s implications for theory, research, and practice.

Glueball spectrum and matrix elements on anisotropic lattices

Abstract: The glueball-to-vacuum matrix elements of local gluonic operators in scalar, tensor, and pseudoscalar channels are investigated numerically on several anisotropic lattices with the spatial lattice spacing ranging from 0.1-0.2 fm. These matrix elements are needed to predict the glueball branching ratios in J/{psi} radiative decays which will help identify the glueball states in experiments. Two types of improved local gluonic operators are constructed for a self-consistent check and the finite-volume effects are studied. We find that lattice spacing dependence of our results is very weak and the continuum limits are reliably extrapolated, as a result of improvement of the lattice gauge action and local operators. We also give updated glueball masses with various quantum numbers.

The AGN-obscuring Torus: The End of the ``Doughnut'' Paradigm?

Abstract: Unified schemes of active galactic nuclei (AGNs) require an obscuring dusty torus around the central engine. The compact sizes (only a few parsecs) determined in recent high-resolution observations require that the obscuring matter be clumpy and located inside the region where the black hole gravity dominates over the galactic bulge. This location is in line with the scenario depicting the torus as the region of the clumpy wind coming off the accretion disk in which the clouds are dusty and optically thick. We study here the outflow scenario within the framework of hydromagnetic disk winds, incorporating the cloud properties determined from detailed modeling of the IR emission from clumpy tori. We find that torus clouds were likely detected in recent water maser observations of NGC 3079. In the wind scenario, the AGN main dynamic channel for release of accreted mass seems to be switching at low luminosities from torus outflow to radio jets. The torus disappears when the bolometric luminosity decreases below ~1042 ergs s-1 because the accretion onto the central black hole can no longer sustain the required cloud outflow rate. This disappearance seems to have been observed in both LINERs and radio galaxies. With further luminosity decrease, suppression of cloud outflow spreads radially inward from the disk's dusty, molecular region into its atomic, ionized zone, resulting in the disappearance of the broad emission-line region at lower luminosities yet to be determined.

A Multilevel Model of Group Social Capital

Abstract: We introduce the concept of group social capital—the set of resources made available to a group through members' social relationships within the social structure of the group and in the broader formal and informal structure of the organization. We argue that greater group social capital resources lead to greater group effectiveness and that there are many different conduits through which group social capital resources flow. We present a multilevel, multidimensional model arguing that an optimal balance of all these conduits maximizes group social capital resources and group effectiveness.

Advancing candidate link generation for requirements tracing: the study of methods

Abstract: This paper addresses the issues related to improving the overall quality of the dynamic candidate link generation for the requirements tracing process for verification and validation and independent verification and validation analysts. The contribution of the paper is four-fold: we define goals for a tracing tool based on analyst responsibilities in the tracing process, we introduce several new measures for validating that the goals have been satisfied, we implement analyst feedback in the tracing process, and we present a prototype tool that we built, RETRO (REquirements TRacing On-target), to address these goals. We also present the results of a study used to assess RETRO's support of goals and goal elements that can be measured objectively.

Infectious Prions in the Saliva and Blood of Deer with Chronic Wasting Disease

Abstract: A critical concern in the transmission of prion diseases, including chronic wasting disease (CWD) of cervids, is the potential presence of prions in body fluids. To address this issue directly, we exposed cohorts of CWD-naive deer to saliva, blood, or urine and feces from CWD-positive deer. We found infectious prions capable of transmitting CWD in saliva (by the oral route) and in blood (by transfusion). The results help to explain the facile transmission of CWD among cervids and prompt caution concerning contact with body fluids in prion infections.

The Social Network Ties of Group Leaders: Implications for Group Performance and Leader Reputation

Abstract: This paper uses data from the sales division of a financial services firm to investigate how a leader's centrality in external and internal social networks is related to the objective performance of the leader's group, and to the leader's personal reputation for leadership among subordinates, peers, and supervisors. External social network ties were based on the friendship ties among all 88 of the division's sales group leaders and the 10 high-ranking supervisors to whom they reported. Internal social network ties consisted of 28 separate networks, each representing the set of friendship relations among all members of a given sales group. Objective group performance data came directly from company records. Data on each group leader's personal reputation for leadership was based on the perceptions of three different constituencies: subordinates, peers, and supervisors. Results revealed that leaders' centrality in external and internal friendship networks was related both to objective measures of group performance and to their reputation for leadership among different organizational constituencies.