Showing papers by "University of South Carolina published in 2013"

Ultrathin, Molecular-Sieving Graphene Oxide Membranes for Selective Hydrogen Separation

Abstract: Ultrathin, molecular-sieving membranes have great potential to realize high-flux, high-selectivity mixture separation at low energy cost. Current microporous membranes [pore size < 1 nanometer (nm)], however, are usually relatively thick. With the use of current membrane materials and techniques, it is difficult to prepare microporous membranes thinner than 20 nm without introducing extra defects. Here, we report ultrathin graphene oxide (GO) membranes, with thickness approaching 1.8 nm, prepared by a facile filtration process. These membranes showed mixture separation selectivities as high as 3400 and 900 for H2/CO2 and H2/N2 mixtures, respectively, through selective structural defects on GO.

HIV Infection and the Risk of Acute Myocardial Infarction

Abstract: Importance Whether people infected with human immunodeficiency virus (HIV) are at an increased risk of acute myocardial infarction (AMI) compared with uninfected people is not clear. Without demographically and behaviorally similar uninfected comparators and without uniformly measured clinical data on risk factors and fatal and nonfatal AMI events, any potential association between HIV status and AMI may be confounded. Objective To investigate whether HIV is associated with an increased risk of AMI after adjustment for all standard Framingham risk factors among a large cohort of HIV-positive and demographically and behaviorally similar (ie, similar prevalence of smoking, alcohol, and cocaine use) uninfected veterans in care. Design and Setting Participants in the Veterans Aging Cohort Study Virtual Cohort from April 1, 2003, through December 31, 2009. Participants After eliminating those with baseline cardiovascular disease, we analyzed data on HIV status, age, sex, race/ethnicity, hypertension, diabetes mellitus, dyslipidemia, smoking, hepatitis C infection, body mass index, renal disease, anemia, substance use, CD4 cell count, HIV-1 RNA, antiretroviral therapy, and incidence of AMI. Main Outcome Measure Acute myocardial infarction. Results We analyzed data on 82 459 participants. During a median follow-up of 5.9 years, there were 871 AMI events. Across 3 decades of age, the mean (95% CI) AMI events per 1000 person-years was consistently and significantly higher for HIV-positive compared with uninfected veterans: for those aged 40 to 49 years, 2.0 (1.6-2.4) vs 1.5 (1.3-1.7); for those aged 50 to 59 years, 3.9 (3.3-4.5) vs 2.2 (1.9-2.5); and for those aged 60 to 69 years, 5.0 (3.8-6.7) vs 3.3 (2.6-4.2) (P Conclusions and Relevance Infection with HIV is associated with a 50% increased risk of AMI beyond that explained by recognized risk factors.

Population genomic and genome-wide association studies of agroclimatic traits in sorghum

Abstract: Accelerating crop improvement in sorghum, a staple food for people in semiarid regions across the developing world, is key to ensuring global food security in the context of climate change. To facilitate gene discovery and molecular breeding in sorghum, we have characterized ∼265,000 single nucleotide polymorphisms (SNPs) in 971 worldwide accessions that have adapted to diverse agroclimatic conditions. Using this genome-wide SNP map, we have characterized population structure with respect to geographic origin and morphological type and identified patterns of ancient crop diffusion to diverse agroclimatic regions across Africa and Asia. To better understand the genomic patterns of diversification in sorghum, we quantified variation in nucleotide diversity, linkage disequilibrium, and recombination rates across the genome. Analyzing nucleotide diversity in landraces, we find evidence of selective sweeps around starch metabolism genes, whereas in landrace-derived introgression lines, we find introgressions around known height and maturity loci. To identify additional loci underlying variation in major agroclimatic traits, we performed genome-wide association studies (GWAS) on plant height components and inflorescence architecture. GWAS maps several classical loci for plant height, candidate genes for inflorescence architecture. Finally, we trace the independent spread of multiple haplotypes carrying alleles for short stature or long inflorescence branches. This genome-wide map of SNP variation in sorghum provides a basis for crop improvement through marker-assisted breeding and genomic selection.

Disaster resilience: A national imperative

Abstract: Escalating disaster losses coupled with the increasing frequency of billion-dollar disaster events, such as the recent Hurricane Sandy, highlight some of the challenges to hazards and disaster poli...

Nanocomposites with Polymer Grafted Nanoparticles

Abstract: A recurring challenge in the field of nanocomposites is to control the spatial distribution of nanoparticles (NPs) in a polymer matrix. This issue is of critical importance since it is now well-established that a specific NP dispersion state is necessary to optimize a desired property of polymer nanocomposites (PNCs). This Perspective focuses on one particular approach to controlling NP spatial dispersion, and hence the properties of polymer-based nanocomposites: the use of polymer-grafted NPs. Novel developments over the past decade in synthesis techniques allow us to controllably functionalize NPs with polymer chains. This has ignited considerable interest in this field, leading to significant advances in creating nanocomposites with tunable physical properties. We begin by briefly outlining the various synthetic strategies for functionalizing NPs and then discuss various methods for controllably dispersing them in a polymer matrix. The consequences of having states with controlled NP dispersion on nano...

Measurement of an excess of B̄→D(*) τ-ν̄τ decays and implications for charged Higgs bosons

Abstract: The concept for this analysis is to a large degree based on earlier BABAR work and we acknowledge the guidance provided by M. Mazur. The authors consulted with theorists A. Datta, S. Westhoff, S. Fajfer, J. Kamenik, and I. Nisandzic on the calculations of the charged Higgs contributions to the decay rates. We are grateful for the extraordinary contributions of our PEP-II colleagues in achieving the excellent luminosity and machine conditions that have made this work possible. The success of this project also relied critically on the expertise and dedication of the computing organizations that support BABAR. The collaborating institutions wish to thank SLAC for its support and the kind hospitality extended to them. This work is supported by the U.S. Department of Energy and National Science Foundation, the Natural Sciences and Engineering Research Council (Canada), the Commissariat a l'Energie Atomique and Institut National de Physique Nucleaire et de Physique des Particules (France), the Bundesministerium fur Bildung und Forschung and Deutsche Forschungsgemeinschaft (Germany), the Istituto Nazionale di Fisica Nucleare (Italy), the Foundation for Fundamental Research on Matter (Netherlands), the Research Council of Norway, the Ministry of Education and Science of the Russian Federation, Ministerio de Economia y Competitividad (Spain), and the Science and Technology Facilities Council (United Kingdom). Individuals have received support from the Marie-Curie IEF program (European Union) and the A. P. Sloan Foundation (USA).

Assembling genomes and mini-metagenomes from highly chimeric reads

Abstract: Recent advances in single-cell genomics provide an alternative to gene-centric metagenomics studies, enabling whole genome sequencing of uncultivated bacteria. However, single-cell assembly projects are challenging due to (i) the highly non-uniform read coverage, and (ii) a greatly elevated number of chimeric reads and read pairs. While recently developed single-cell assemblers have addressed the former challenge, methods for assembling highly chimeric reads remain poorly explored. We present algorithms for identifying chimeric edges and resolving complex bulges in de Bruijn graphs, which significantly improve single-cell assemblies. We further describe applications of the single-cell assembler SPAdes to a new approach for capturing and sequencing "dark matter of life" that forms small pools of randomly selected single cells (called a mini-metagenome) and further sequences all genomes from the mini-metagenome at once. We demonstrate that SPAdes enables sequencing mini-metagenomes and benchmark it against various assemblers. On single-cell bacterial datasets, SPAdes improves on the recently developed E+V-SC and IDBA-UD assemblers specifically designed for single-cell sequencing. For standard (multicell) datasets, SPAdes also improves on A5, ABySS, CLC, EULER-SR, Ray, SOAPdenovo, and Velvet.

Progress in Renewable Polymers from Natural Terpenes, Terpenoids, and Rosin

Abstract: The development of sustainable renewable polymers from natural resources has increasingly gained attention from scientists, engineers as well as the general public and government agencies. This review covers recent progress in the field of renewable bio-based monomers and polymers from natural resources: terpenes, terpenoids, and rosin, which are a class of hydrocarbon-rich biomass with abundance and low cost, holding much potential for utilization as organic feedstocks for green plastics and composites. This review details polymerization and copolymerization of terpenes such as pinene, limonene, and myrcene and their derivatives, terpenoids including carvone and menthol, and rosin-derived monomers. The future direction on the utilization of these natural resources is discussed.

Monitoring and Understanding Trends in Extreme Storms: State of Knowledge

Abstract: The state of knowledge regarding trends and an understanding of their causes is presented for a specific subset of extreme weather and climate types. For severe convective storms (tornadoes, hailstorms, and severe thunderstorms), differences in time and space of practices of collecting reports of events make using the reporting database to detect trends extremely difficult. Overall, changes in the frequency of environments favorable for severe thunderstorms have not been statistically significant. For extreme precipitation, there is strong evidence for a nationally averaged upward trend in the frequency and intensity of events. The causes of the observed trends have not been determined with certainty, although there is evidence that increasing atmospheric water vapor may be one factor. For hurricanes and typhoons, robust detection of trends in Atlantic and western North Pacific tropical cyclone (TC) activity is significantly constrained by data heterogeneity and deficient quantification of internal variab...

Corporate Social Responsibility and Credit Ratings

Abstract: This study provides evidence on the relationship between corporate social responsibility (CSR) and firms’ credit ratings. We find that credit rating agencies tend to award relatively high ratings to firms with good social performance. This pattern is robust to controlling for key firm characteristics as well as endogeneity between CSR and credit ratings. We also find that CSR strengths and concerns influence credit ratings and that the individual components of CSR that relate to primary stakeholder management (i.e., community relations, diversity, employee relations, environmental performance, and product characteristics) matter most in explaining firms’ creditworthiness. Overall, our results suggest that CSR performance conveys important non-financial information that rating agencies are likely to use in their evaluation of firms’ creditworthiness, and that CSR investments—particularly those that extend beyond compliance behavior to reflect what is desired by society—can lead to lower financing costs resulting from higher credit ratings.

Integrated environmental modeling: A vision and roadmap for the future

Abstract: Integrated environmental modeling (IEM) is inspired by modern environmental problems, decisions, and policies and enabled by transdisciplinary science and computer capabilities that allow the environment to be considered in a holistic way. The problems are characterized by the extent of the environmental system involved, dynamic and interdependent nature of stressors and their impacts, diversity of stakeholders, and integration of social, economic, and environmental considerations. IEM provides a science-based structure to develop and organize relevant knowledge and information and apply it to explain, explore, and predict the behavior of environmental systems in response to human and natural sources of stress. During the past several years a number of workshops were held that brought IEM practitioners together to share experiences and discuss future needs and directions. In this paper we organize and present the results of these discussions. IEM is presented as a landscape containing four interdependent elements: applications, science, technology, and community. The elements are described from the perspective of their role in the landscape, current practices, and challenges that must be addressed. Workshop participants envision a global scale IEM community that leverages modern technologies to streamline the movement of science-based knowledge from its sources in research, through its organization into databases and models, to its integration and application for problem solving purposes. Achieving this vision will require that the global community of IEM stakeholders transcend social, and organizational boundaries and pursue greater levels of collaboration. Among the highest priorities for community action are the development of standards for publishing IEM data and models in forms suitable for automated discovery, access, and integration; education of the next generation of environmental stakeholders, with a focus on transdisciplinary research, development, and decision making; and providing a web-based platform for community interactions (e.g., continuous virtual workshops).

BayesHammer: Bayesian clustering for error correction in single-cell sequencing

Abstract: Error correction of sequenced reads remains a difficult task, especially in single-cell sequencing projects with extremely non-uniform coverage. While existing error correction tools designed for standard (multi-cell) sequencing data usually come up short in single-cell sequencing projects, algorithms actually used for single-cell error correction have been so far very simplistic. We introduce several novel algorithms based on Hamming graphs and Bayesian subclustering in our new error correction tool BAYES HAMMER. While BAYES HAMMER was designed for single-cell sequencing, we demonstrate that it also improves on existing error correction tools for multi-cell sequencing data while working much faster on real-life datasets. We benchmark BAYES HAMMER on both k-mer counts and actual assembly results with the SPADES genome assembler.

Dynamic managerial capabilities: Configuration and orchestration of top executives' capabilities and the firm's dominant logic: Research Notes and Commentaries

Abstract: This paper contributes to the understanding of the executive team dynamic managerial capabilities by developing theory about the interplay between the firm's dominant logic and dynamic managerial capabilities (including managerial human capital, social capital, and cognition). We underscore the criticality of the two key CEO-level functions: configuration and orchestration of senior executive team dynamic capabilities. We develop theory on how these functions create and sculpt the management team's absorptive capacity, which in turn shapes the team's adaptive capacity. We present theory about the distributed nature of efforts for organizational renewal where CEO's dynamic managerial capabilities in concerto with senior executive managerial capabilities will drive top management's ability to revitalize the firm's dominant logic and to achieve evolutionary fit. Copyright © 2012 John Wiley & Sons, Ltd.

Controlled Polymerization of Next-Generation Renewable Monomers and Beyond

Abstract: Natural molecular biomass plays an important role in the field of renewable polymers, as they can be directly used or derivatized as monomers for controlled polymerization, in a way similar to many petroleum-derived monomers. We deliver this perspective primarily based on a monomer approach. Biomass-derived monomers are separated into four major categories according to their natural resource origins: (1) oxygen-rich monomers including carboxylic acids (lactic acid, succinic acid, itaconic acid, and levulinic acid) and furan; (2) hydrocarbon-rich monomers including vegetable oils, fatty acids, terpenes, terpenoids and resin acids; (3) hydrocarbon monomers (bio-olefins); and (4) non-hydrocarbon monomers (carbon dioxide). A variety of emerging synthetic tools (controlled polymerization and click chemistry) are particularly summarized. An overview on future opportunities and challenges, which are critical to promote biorefinery in the production of renewable chemicals and polymers, is given.

The intriguing metabolically healthy but obese phenotype: cardiovascular prognosis and role of fitness

Abstract: Current knowledge on the prognosis of metabolically healthy but obese phenotype is limited due to the exclusive use of the body mass index to define obesity and the lack of information on cardiorespiratory fitness. We aimed to test the following hypotheses: (i) metabolically healthy but obese individuals have a higher fitness level than their meta- bolically abnormal and obese peers; (ii) after accounting for fitness, metabolically healthy but obese phenotype is a benign condition, in terms of cardiovascular disease and mortality. Methods and results Fitness was assessed by a maximal exercise test on a treadmill and body fat per cent (BF%) by hydrostatic weighing or skinfolds (obesity ¼ BF% ≥25 or ≥30%, men or women, respectively) in 43 265 adults (24.3% women). Metabolically healthy was considered if meeting 0 or 1 of the criteria for metabolic syndrome. Metabolically healthy but obese participants (46% of the obese subsample) had a better fitness than metabolically abnormal obese participants (P , 0.001). When adjusting for fitness and other confounders, metabolically healthy but obese individuals had lower risk (30-50%, estimated by hazard ratios) of all-cause mortality, non-fatal and fatal cardiovascular disease, and cancer mortality than their metabolically unhealthy obese peers; while no significant differences were observed between metabolically healthy but obese and metabolically healthy normal-fat participants. Conclusions (i) Higher fitness should be considered a characteristic of metabolically healthy but obese phenotype. (ii) Once fitness is accounted for, the metabolically healthy but obese phenotype is a benign condition, with a better prognosis for mortality and morbidity than metabolically abnormal obese individuals.

Assessing the reliability and validity of a shorter walk test compared with the 10-Meter Walk Test for measurements of gait speed in healthy, older adults.

Abstract: Background and purpose Walking speed is associated with several health-related outcomes. Research examining how differences in test walking distance affect walking speed reliability and validity is limited. The primary purpose of this study was to examine the reliability and concurrent validity of gait speed measurements obtained from a 4-Meter Walk Test compared with the commonly used 10-Meter Walk Test. A second objective was to similarly examine 2 different timing methods: stopwatch and automatic timers. Methods Forty-three healthy, older adults (mean age = 84.3 ± 6.9 years) performed 3 consecutive walking trials on the 4- and 10-Meter Walk Tests at their self-selected walking speed. Results Gait speed measurements for both tests were shown to have excellent test-retest reliability (ICC values of 0.96-0.98), with similar results for stopwatch and automatic timer assessments (ICC values of 0.99-1.00). Standard error of the measurement (SEM) values were small (0.004-0.008 m/s) across measurement methods. While the ICC value for gait speed measurements between the 2 walk tests was 0.93, the Bland-Altman analysis revealed a discrepancy of ±0.15 to ±0.17 m/s between measurement methods. Discussion Both 4- and 10-m gait speed assessments had excellent test-retest reliability with similar SEM and minimal detectable change values. There was little difference in SEM values between the 2 timing methods. While the mean difference in gait speed between the 4- and 10-Meter Walk Tests was small, the range of the measurement differences was large enough to potentially mask meaningful changes in gait speed over time if both methods were used interchangeably. Conclusions While the reliability of both walking tests is excellent, the 4-Meter Walk Test does not exhibit a high enough degree of concurrent validity with the 10-Meter Walk Test to be used interchangeably for gait speed assessments in healthy, older adults. We therefore recommend using the 10-Meter Walk Test to obtain the most valid clinical assessment of walking speed when using it as a 1-time indicator of health status.

Myths, Presumptions, and Facts about Obesity

Abstract: Background Many beliefs about obesity persist in the absence of supporting scientific evidence (presumptions); some persist despite contradicting evidence (myths). The promulgation of unsupported beliefs may yield poorly informed policy decisions, inaccurate clinical and public health recommendations, and an unproductive allocation of research resources and may divert attention away from useful, evidence-based information. Methods Using Internet searches of popular media and scientific literature, we identified, reviewed, and classified obesity-related myths and presumptions. We also examined facts that are well supported by evidence, with an emphasis on those that have practical implications for public health, policy, or clinical recommendations. Results We identified seven obesity-related myths concerning the effects of small sustained increases in energy intake or expenditure, establishment of realistic goals for weight loss, rapid weight loss, weight-loss readiness, physical-education classes, breast-...

Role of cytokines as a double-edged sword in sepsis.

Abstract: BACKGROUND Sepsis is a deadly immunological disorder and its pathophysiology is still poorly understood. We aimed to determine if specific pro-inflammatory and anti-inflammatory cytokines can be used as diagnostic and therapeutic targets for sepsis. MATERIALS AND METHODS Recent publications in the MEDLINE database were searched for articles regarding the clinical significance of inflammatory cytokines in sepsis. RESULTS In response to pathogen infection, pro-inflammatory cytokines [interleukin-6 (IL-6), IL-8, IL-18 and tumor necrosis factor-α (TNF-α)] and anti-inflammatory cytokine (IL-10) increased in patients with sepsis. Importantly, a decrease in IL-6 was associated with a better prognosis and overproduction of IL-10 was found to be the main predictor of severity and fatal outcome. CONCLUSION Both pro-inflammatory and anti-inflammatory cytokines constitute a double-edged sword in sepsis; on one hand they are critical to eliminate the infection while on the other, excessive production can cause tissue and organ damage. Increase in cytokines such as IL-6, Il-8, IL-10, IL-18 and TNF-α may have implications in diagnosis and treatment of sepsis.

Validity of U.S. Nutritional Surveillance: National Health and Nutrition Examination Survey Caloric Energy Intake Data, 1971–2010

Abstract: Importance Methodological limitations compromise the validity of U.S. nutritional surveillance data and the empirical foundation for formulating dietary guidelines and public health policies. Objectives Evaluate the validity of the National Health and Nutrition Examination Survey (NHANES) caloric intake data throughout its history, and examine trends in the validity of caloric intake estimates as the NHANES dietary measurement protocols evolved. Design Validity of data from 28,993 men and 34,369 women, aged 20 to 74 years from NHANES I (1971–1974) through NHANES 2009–2010 was assessed by: calculating physiologically credible energy intake values as the ratio of reported energy intake (rEI) to estimated basal metabolic rate (BMR), and subtracting estimated total energy expenditure (TEE) from NHANES rEI to create ‘disparity values’. Main Outcome Measures 1) Physiologically credible values expressed as the ratio rEI/BMR and 2) disparity values (rEI–TEE). Results The historical rEI/BMR values for men and women were 1.31 and 1.19, (95% CI: 1.30–1.32 and 1.18–1.20), respectively. The historical disparity values for men and women were −281 and −365 kilocalorie-per-day, (95% CI: −299, −264 and −378, −351), respectively. These results are indicative of significant under-reporting. The greatest mean disparity values were −716 kcal/day and −856 kcal/day for obese (i.e., ≥30 kg/m2) men and women, respectively. Conclusions Across the 39-year history of the NHANES, EI data on the majority of respondents (67.3% of women and 58.7% of men) were not physiologically plausible. Improvements in measurement protocols after NHANES II led to small decreases in underreporting, artifactual increases in rEI, but only trivial increases in validity in subsequent surveys. The confluence of these results and other methodological limitations suggest that the ability to estimate population trends in caloric intake and generate empirically supported public policy relevant to diet-health relationships from U.S. nutritional surveillance is extremely limited.

Along‐Strike Variation in the Aleutian Island Arc: Genesis of High Mg# Andesite and Implications for Continental Crust

Abstract: Based on a compilation of whole rock geochemistry for approximately 1100 lava samples and 200 plutonic rock samples from the Aleutian island arc, we characterize along-strike variation, including data for the western part of the arc which has recently become available. We concentrate on the observation that western Aleutian, high Mg# andesite compositions bracket the composition of the continental crust. Isotope data show that this is not due to recycling of terrigenous sediments. Thus, the western Aleutians can provide insight into genesis of juvenile continental crust. The composition of primitive magmas (molar Mg# > 0.6) varies systematically along the strike of the arc. Concentrations of SiO 2 , Na 2 O and perhaps K 2 O increase from east to west, while MgO, FeO, CaO decrease. Thus, primitive magmas in the central and eastern Aleutians (east of 174°W) are mainly basalts, while those in the western Aleutians are mainly andesites. Along-strike variation in Aleutian magma compositions may be related to a westward decrease in sediment input, and/or to the westward decrease in down-dip subduction velocity. 206 Pb/ 204 Pb, 207 Pb/ 204 Pb, 208 Pb /204 Pb and 87 Sr/ 86 Sr all decrease from east to west, whereas 143 Nd/ 144 Nd increases from east to west. These data, together with analyses of sediment from DSDP Site 183, indicate that the proportion of recycled sediment in Aleutian magmas decreases from east to west. Some proposed trace element signatures of sediment recycling in arc magmas do not vary systematically along the strike of the Aleutians, and do not correlate with radiogenic isotope variations. Thus, for example, Th/Nb and fractionation-corrected K concentration in Aleutian lavas are not related to the flux of subducting sediment. Th/La is strongly correlated with Ba/La, rendering it doubtful that Ba/La is a proxy for an aqueous fluid component derived from subducted basalt. Ce/Pb > 4 is common in Aleutian lavas west of 174°W, in lavas with MORB-like Pb, Sr and Nd isotope ratios, and is also found behind the main arc trend in the central Aleutians. Thus, Ce/Pb in Aleutian lavas with MORB-like isotope ratios is not always low, and may be affected by a component derived from partial melting of subducted basalt in eclogite facies. Enriched, primitive andesites, with high Sr/Y, steep REE patterns, and low Yb and Y, are an important lava type in the Aleutians west of 174°W. High Sr/Y and Dy/Yb, indicative of abundant garnet in the source of melting, are correlated with major element systematics. Lavas with a garnet signature have high SiO 2 , Na 2 O and K 2 O.

Ghost Talk: Mitigating EMI Signal Injection Attacks against Analog Sensors

Abstract: Electromagnetic interference (EMI) affects circuits by inducing voltages on conductors. Analog sensing of signals on the order of a few millivolts is particularly sensitive to interference. This work (1) measures the susceptibility of analog sensor systems to signal injection attacks by intentional, low-power emission of chosen electromagnetic waveforms, and (2) proposes defense mechanisms to reduce the risks. Our experiments use specially crafted EMI at varying power and distance to measure susceptibility of sensors in implantable medical devices and consumer electronics. Results show that at distances of 1-2m, consumer electronic devices containing microphones are vulnerable to the injection of bogus audio signals. Our measurements show that in free air, intentional EMI under 10 W can inhibit pacing and induce defibrillation shocks at distances up to 1-2m on implantable cardiac electronic devices. However, with the sensing leads and medical devices immersed in a saline bath to better approximate the human body, the same experiment decreases to about 5 cm. Our defenses range from prevention with simple analog shielding to detection with a signal contamination metric based on the root mean square of waveform amplitudes. Our contribution to securing cardiac devices includes a novel defense mechanism that probes for forged pacing pulses inconsistent with the refractory period of cardiac tissue.

Managers with and without Style: Evidence Using Exogenous Variation

Abstract: In a large panel of Compustat firms, we find that firm policy changes after exogenous CEO departures do not display abnormally high levels of variability, casting doubt on the presence of idiosyncratic-style effects in policy choices. After endogenous CEO departures, we do detect abnormally large policy changes. These changes are larger when the firm is likely to draw from a deeper pool of replacement CEO candidates, suggesting the presence of causal-style effects that are anticipated by the board. Our evidence suggests that managerial styles are not transferred across employers and that standard F-tests are inappropriate for identifying style effects. The Author 2013. Published by Oxford University Press on behalf of The Society for Financial Studies. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com., Oxford University Press.

Games and Simulations and Their Relationships to Learning

Abstract: Educational games and simulations are experiential exercises that transport learners to another world. There they apply their knowledge, skills, and strategies in the execution of their assigned roles. For example, children may search for vocabulary cues to capture a wicked wizard (game), or engineers may diagnose the problems in a malfunctioning steam plant (simulation).