Showing papers by "University of South Carolina published in 2002"

Adoption of an Organizational Practice by Subsidiaries of Multinational Corporations: Institutional and Relational Effects

Abstract: We examine the adoption of an organizational practice by subsidiaries of a multinational corporation (MNC) under conditions of “institutional duality.” Drawing on institutional theory, we identify ...

Generalized estimating equations

Abstract: Correlated datasets develop when multiple observations are collected from a sampling unit (e.g., repeated measures of a bank over time, or hormone levels in a breast cancer patient over time), or from clustered data where observations are grouped based on a shared characteristic (e.g., observations on different banks grouped by zip code, or on cancer patients from a specific clinic). The generalized linear model framework for independent data is extended to model correlated data via the introduction of second-order variance components directly into the independent data model's estimating equation. This generalization of the estimating equation from the independence model is thus referred to as a Generalized Estimating Equation (GEE). This article discusses the foundation of GEEs as well as how user-specified correlation structures are accommodated in the model-building process. This article also discusses the relationship and similarity to the underlying generalized linear model framework and we point out alternative approaches to GEEs for modeling correlated data such as fixed-effects models and random-effects models. Keywords: working correlation matrix; sandwich estimate of variance; generalized linear models; subject-specific models; population-averaged models

Psychological sequelae of the September 11 terrorist attacks in New York City

Abstract: Background The scope of the terrorist attacks of September 11, 2001, was unprecedented in the United States. We assessed the prevalence and correlates of acute post-traumatic stress disorder (PTSD) and depression among residents of Manhattan five to eight weeks after the attacks. Methods We used random-digit dialing to contact a representative sample of adults living south of 110th Street in Manhattan. Participants were asked about demographic characteristics, exposure to the events of September 11, and psychological symptoms after the attacks. Results Among 1008 adults interviewed, 7.5 percent reported symptoms consistent with a diagnosis of current PTSD related to the attacks, and 9.7 percent reported symptoms consistent with current depression (with “current“ defined as occurring within the previous 30 days). Among respondents who lived south of Canal Street (i.e., near the World Trade Center), the prevalence of PTSD was 20.0 percent. Predictors of PTSD in a multivariate model were Hispanic ethnicity, ...

Responses of coastal wetlands to rising sea level

Abstract: Salt marsh ecosystems are maintained by the dominant macrophytes that regulate the elevation of their habitat within a narrow portion of the intertidal zone by accumulating organic matter and trapping inorganic sediment. The long-term stability of these ecosystems is explained by interactions among sea level, land elevation, primary production, and sediment accretion that regulate the elevation of the sediment surface toward an equilibrium with mean sea level. We show here in a salt marsh that this equilibrium is adjusted upward by increased production of the salt marsh macrophyte Spartina alterniflora and downward by an increasing rate of relative sea-level rise (RSLR). Adjustments in marsh surface elevation are slow in comparison to interannual anomalies and long-period cycles of sea level, and this lag in sediment elevation results in significant variation in annual primary productivity. We describe a theoretical model that predicts that the system will be stable against changes in relative mean sea level when surface elevation is greater than what is optimal for primary production. When surface elevation is less than optimal, the system will be unstable. The model predicts that there is an optimal rate of RSLR at which the equilibrium elevation and depth of tidal flooding will be optimal for plant growth. However, the optimal rate of RSLR also represents an upper limit because at higher rates of RSLR the plant community cannot sustain an elevation that is within its range of tol- erance. For estuaries with high sediment loading, such as those on the southeast coast of the United States, the limiting rate of RSLR was predicted to be at most 1.2 cm/yr, which is 3.5 times greater than the current, long-term rate of RSLR.

Controlling the aspect ratio of inorganic nanorods and nanowires

Abstract: Semiconductors and metals exhibit unusual optical, electronic, and magnetic properties on the nanometer scale. Chemists and materials scientists are developing methods to make non-spherical shapes of semiconductors and metals on the nanometer scale. We use a seed-mediated growth approach to make metallic nanorods and nanowires in homogeneous solution. Control of the ratio of metallic spherical seeds to metal salt in the reduction reaction contyrols the aspect ratio of the resulting rods and wires.

Estimating Individual Discount Rates in Denmark: A Field Experiment

Abstract: We estimate individual discount rates with respect to time streams of money using controlled laboratory experiments. These discount rates are elicited by means of field experiments involving real monetary rewards. The experiments were carried out across Denmark using a representative sample of 268 people between 19 and 75 years of age. Individual discount rates are estimated for various households differentiated by socio-demographic characteristics such as income and age. Our conclusions are that discount rates are constant over the 12-month to 3-year horizons used in these experiments, and that discount rates vary substantially with respect to several socio-demographic variables. Hence we conclude that it would be reasonable to assume constant discount rates for specific household types, but not the same rates across all households.

Does Function Follow Organizational Form? Evidence from the Lending Practices of Large and Small Banks

Abstract: Theories based on incomplete contracting suggest that small organizations may do better than large organizations in activities that require the processing of soft information. We explore this idea in the context of bank lending to small firms, an activity that is typically thought of as relying heavily on soft information. We find that large banks are less willing than small banks to lend to informationally "difficult" credits, such as firms that do not keep formal financial records. Moreover, controlling for the endogeneity of bank-firm matching, large banks lend at a greater distance, interact more impersonally with their borrowers, have shorter and less exclusive relationships, and do not alleviate credit constraints as effectively. All of this is consistent with small banks being better able to collect and act on soft information than large banks.

Growth and form of gold nanorods prepared by seed-mediated, surfactant-directed synthesis

Abstract: Gold nanorods were prepared via a seed-mediated sequential growth process involving the use of citrate-stabilised seed crystals and their subsequent growth in a series of reaction solutions containing [AuCl4]−, ascorbic acid and the cationic surfactant cetyltrimethylammonuim bromide (CTAB). Electron diffraction analysis and HRTEM images of mature nanorods showed superpositions of two specific pairs of crystallographic zones, either and or and , which were consistent with a cyclic penta-twinned crystal with five {111} twin boundaries arranged radially to the [110] direction of elongation. The nanorods have an idealised 3-D prismatic morphology with ten {111} end faces and five {100} or {110} side faces, or both. TEM studies of crystals at various stages of growth indicated that the seed crystals are initially transformed by growth and aggregation into decahedral penta-twinned crystals, 4% of which become elongated when a fresh reaction solution is added, whilst the remaining twins grow isometrically. Reiteration of this procedure increases the length of the existing nanorods, induces further transformation of isometric particles to produce a second (and third) population of shorter, wider nanorods, and increases the size of the isometric crystals. The data indicate that symmetry breaking in fcc metallic structures to produce anisotropic nanoparticles is based on an intrinsic structural mechanism (twinning) that is subsequently modulated extrinsically during growth in solution by specific adsorption of AuI–surfactant complexes on the side faces/edges of the isometric penta-twinned crystals and which is responsible for the preferential growth along the common [110] axis. We propose that the coupling of multiple twinning and habit modification is a general mechanism that applies to other experimental procedures (electrochemical, inverse micellar media) currently used to prepare metallic nanoparticles with a high aspect ratio.

The BABAR detector

Abstract: BABAR, the detector for the SLAC PEP-II asymmetric e+e- B Factory operating at the upsilon 4S resonance, was designed to allow comprehensive studies of CP-violation in B-meson decays. Charged particle tracks are measured in a multi-layer silicon vertex tracker surrounded by a cylindrical wire drift chamber. Electromagentic showers from electrons and photons are detected in an array of CsI crystals located just inside the solenoidal coil of a superconducting magnet. Muons and neutral hadrons are identified by arrays of resistive plate chambers inserted into gaps in the steel flux return of the magnet. Charged hadrons are identified by dE/dx measurements in the tracking detectors and in a ring-imaging Cherenkov detector surrounding the drift chamber. The trigger, data acquisition and data-monitoring systems, VME- and network-based, are controlled by custom-designed online software. Details of the layout and performance of the detector components and their associated electronics and software are presented.

Dynamic lithium-ion battery model for system simulation

Abstract: Presents here a complete dynamic model of a lithium ion battery that is suitable for virtual-prototyping of portable battery-powered systems. The model accounts for nonlinear equilibrium potentials, rate- and temperature-dependencies, thermal effects and response to transient power demand. The model is based on publicly available data such as the manufacturers' data sheets. The Sony US18650 is used as an example. The model output agrees both with manufacturer's data and with experimental results. The model can be easily modified to fit data from different batteries and can be extended for wide dynamic ranges of different temperatures and current rates.

Climate Change and Latitudinal Patterns of Intertidal Thermal Stress

Abstract: The interaction of climate and the timing of low tides along the West Coast of the United States creates a complex mosaic of thermal environments, in which northern sites can be more thermally stressful than southern sites. Thus, climate change may not lead to a poleward shift in the distribution of intertidal organisms, as has been proposed, but instead will likely cause localized extinctions at a series of "hot spots." Patterns of exposure to extreme climatic conditions are temporally variable, and tidal predictions suggest that in the next 3 to 5 years "hot spots" are likely to appear at several northern sites.

Social Support Protects against the Negative Effects of Partner Violence on Mental Health

Abstract: Objectives: Social support for abused women may reduce the impact of abuse on mental health, yet few studies have addressed this issue. We wish to determine associations between intimate partner violence (IPV) and mental health outcomes and to assess the protective role of abuse disclosure and support on mental health among abused women. Methods: A cross-sectional survey was conducted of 1152 women, ages 18-65, recruited from family practice clinics from 1997 through 1999. They were screened for IPV during a brief in-clinic interview, and physical and mental health status was assessed in a follow-up interview. Results: IPV, defined as sexual, physical, or psychological abuse, was associated with poor perceived mental and physical health, substance abuse, symptoms of posttraumatic stress disorder (PTSD), current depression, anxiety, and suicide ideation/actions. Among women experiencing IPV and controlling for IPV frequency, higher social support scores were associated with a significantly reduced risk of ...

Utility of pedometers for assessing physical activity: convergent validity.

Abstract: Valid assessment of physical activity is important to researchers and practitioners interested in surveillance, screening, programme evaluation and intervention. The validity of an assessment instrument is commonly considered its most important attribute. Convergent validity is the extent to which an instrument’s output is associated with that of other instruments intended to measure the same exposure of interest. A systematic review of the literature produced 25 articles directly relevant to the question of convergent validity of pedometers against accelerometers, observation, and self-reported measures of physical activity. Reported correlations were pooled and a median r-value was computed. Pedometers correlate strongly (median r = 0.86) with different accelerometers (specifically uniaxial accelerometers) depending on the specific instruments used, monitoring frame and conditions implemented, and the manner in which the outputs are expressed. Pedometers also correlate strongly (median r = 0.82) with time in observed activity. Time in observed inactivity correlated negatively with pedometer outputs (median r = -0.44). The relationship with observed steps taken depended upon monitoring conditions and speed of walking. The highest agreement was apparent during ambulatory activity (running, walking) or during sitting (when both observation and pedometers would register few steps taken). There was consistent evidence of reduced accuracy during slow walking. Pedometers correlate moderately with different measures of energy expenditure (median r = 0.68). The relationship between pedometer outputs and energy expenditure is complicated by the use of many different direct and indirect measures of energy expenditure and population samples. Concordance with self-reported physical activity (median r = 0.33) varied depending upon the self-report instrument used, individuals assessed, and how pedometer outputs are expressed (e.g. steps, distance travelled, energy expenditure). Pedometer output has an inverse relationship with reported time spent sitting (r = -0.38). The accumulated evidence herein provides ample support that the simple and inexpensive pedometer is a valid option for assessing physical activity in research and practice.

The Economic Effects of Technological Progress: Evidence from the Banking Industry

Abstract: This paper examines technological progress and its effects in the banking industry. Banks are intensive users of both IT and financial technologies, and have a wealth of data available that may be helpful for the general understanding of the effects of technological change. The research suggests improvements in costs and lending capacity due to improvements in “back-office” technologies, as well as consumer benefits from improved “front-office” technologies. The research also suggests significant overall productivity increases in terms of improved quality and variety of banking services. In addition, the research indicates that technological progress likely helped facilitate consolidation of the industry. This paper examines the available evidence on technological progress and its effects in the banking industry. Innovations in information processing, telecommunications, and related technologies—known collectively as “information technology” or “IT”—are often credited with helping fuel strong growth in the U.S. economy, although questions remain about the relative importance of IT versus other factors. The extensive research on the banking industry may help in the general understanding about the effects of technological change. The category of Depository and Nondepository Financial Institutions—of which banking is an integral part—is the most IT-intensive industry in the U.S. as measured by the ratio of computer equipment and software to value added (Triplett and Bosworth 2002, Table 2).

Piezoelectric Wafer Embedded Active Sensors for Aging Aircraft Structural Health Monitoring

Abstract: Piezoelectric wafer active sensors may be applied on aging aircraft structures to monitor the onset and progress of structural damage such as fatigue cracks and corrosion. The state of the art in piezoelectric-wafer active sensors structural health monitoring and damage detection is reviewed. Methods based on (a) elastic wave propagation and (b) the Electro–Mechanical (E/M) impedance technique are cited and briefly discussed. For health monitoring of aging aircraft structures, two main detection strategies are considered: the E/M impedance method for near field damage detection, and wave propagation methods for far-field damage detection. These methods are developed and verified on simple-geometry specimens and on realistic aging aircraft panels with seeded cracks and corrosion. The experimental methods, signal processing, and damage detection algorithms are tuned to the specific method used for structural interrogation. In the E/M impedance method approach, the high-frequency spectrum, representative of the structural resonances, is recorded. Then, overallstatistics damage metrics can be used to compare the impedance signatures and correlate the change in these signatures with the damage progression and intensity. In our experiments, the (1 � R 2 ) 3 damage metric was found to best fit the results in the 300–450 kHz band. In the wave propagation approach, the pulse-echo and acousto-ultrasonic methods can be utilized to identify the additional reflections generated from crack damage and the changes in transmission phase and velocity associated with corrosion damage. The paper ends with a conceptual design of a structural health monitoring system and suggestions for aging aircraft installation utilizing active-sensor arrays, data concentrators, wireless transmission, and a health monitoring and processing unit.

Super ENSO and Global Climate Oscillations at Millennial Time Scales

Abstract: The late Pleistocene history of seawater temperature and salinity variability in the western tropical Pacific warm pool is reconstructed from oxygen isotope (delta18O) and magnesium/calcium composition of planktonic foraminifera. Differentiating the calcite delta18O record into components of temperature and local water delta18O reveals a dominant salinity signal that varied in accord with Dansgaard/Oeschger cycles over Greenland. Salinities were higher at times of high-latitude cooling and were lower during interstadials. The pattern and magnitude of the salinity variations imply shifts in the tropical Pacific ocean/atmosphere system analogous to modern El Nino-Southern Oscillation (ENSO). El Nino conditions correlate with stadials at high latitudes, whereas La Nina conditions correlate with interstadials. Millennial-scale shifts in atmospheric convection away from the western tropical Pacific may explain many paleo-observations, including lower atmospheric CO2, N2O, and CH4 during stadials and patterns of extratropical ocean variability that have tropical source functions that are negatively correlated with El Nino.

Sources of variance in daily physical activity levels as measured by an accelerometer.

Abstract: MATTHEWS, C. E., B. E. AINSWORTH, R. W. THOMPSON, and D. R. BASSETT, JR. Sources of variance in daily physical activity levels as measured by an accelerometer. Med. Sci. Sports Exerc., Vol. 34, No. 8, pp. 1376–1381, 2002.PurposeTo examine sources of variance in objective measures of physical

Solution-Phase Synthesis of Sub-10 nm Au−Ag Alloy Nanoparticles

Abstract: Gold−silver alloy nanoparticles were synthesized via reduction of varying mole fractions of HAuCl4 and AgNO3 by sodium borohydride in the presence of sodium citrate as a capping agent, in water. Solution concentrations were adjusted to avoid the precipitation of AgCl during the course of the reaction. The plasmon absorption band of Ag−Au nanoparticles shifts linearly to the red with increasing Au content. Due to the direct dependence of the metal salt ratio to the shift of the absorbance peak and the lack of an apparent core−shell structure in transmission electron microscope images, it is concluded that the nanoparticles are alloys, rather than core−shell composites.

Chapter 3 – Chemical Composition and Reactivity

Abstract: Oceans are the largest reservoirs of reactive organic carbon on the Earth. Most (97%) of the organic carbon in seawater resides in the operationally defined dissolved phase. The separation of the particulate and dissolved phases is most commonly accomplished by the passage of water samples through filters with pore sizes in the range 0.2–1.0 μm. During the past decade, it has become increasingly common to avoid the filtration of open ocean water samples for the separation of the particulate and dissolved phases. Filtration is often omitted because particulate organic carbon (POC) is a small fraction of the total organic carbon and the extra handling and processing of water samples during filtration aboard ship can lead to contamination. Concentrations of organic carbon, nitrogen, and phosphorus in unfiltered water samples are referred to as total organic concentrations (TOC, TON, and TOP respectively). Relatively small volumes (milliliters) of seawater are analyzed for these measurements and larger particles are not represented in these samples. Thus, the term “total” is somewhat of a misnomer for these analyses. In this chapter the data gathered on the concentrations and chemical composition of marine DOM includes some samples that were not filtered prior to the analysis. These samples come from the open ocean and the contribution of particulate organic matter (POM) to the reported data is considered to be minimal. In some cases, data for both filtered and unfiltered samples were available and the differences among these samples were often within the error of the measurement.

Systematic errors in digital image correlation due to undermatched subset shape functions

Abstract: Digital image correlation techniques are commonly used to measure specimen displacements by finding correspondences between an image of the specimen in an undeformed or reference configuration and a second image under load. To establish correspondences between the two images, numerical techniques are used to locate an initially square image subset in a reference image within an image taken under load. During this process, shape functions of varying order can be applied to the initially square subset. Zero order shape functions permit the subset to translate rigidly, while first-order shape functions represent an affine transform of the subset that permits a combination of translation, rotation, shear and normal strains. In this article, the systematic errors that arise from the use of undermatched shape function, i.e., shape functions of lower order than the actual displacement field, are analyzed. It is shown that, under certain conditions, the shape functions used can be approximated by a Savitzky-Golay low-pass filter applied to the displacement functions, permitting a convenient error analysis. Furthermore, this analysis is not limited to the displacements, but naturally extends to the higher-order terms included in the shape functions. This permits a direct analysis of the systematic strain errors associated with an undermatched shape function. Detailed numerical studies are presented for the case of a second-order displacement field and first- and second-order shape functions. Finally, the relation of this work to previously published studies is discussed.

Power and life extension of battery-ultracapacitor hybrids

Abstract: The performance of a battery-ultracapacitor hybrid power source under pulsed load conditions is analytically described using simplified models. We show that peak power can be greatly enhanced, internal losses can be considerably reduced, and that discharge life of the battery is extended. Greatest benefits are seen when the load pulse rate is higher than the system eigenfrequency and when the pulse duty is small. Actual benefits are substantial; adding a 23 F ultracapacitor bank (3 /spl times/ 7 PC10 ultracapacitors) in parallel with a typical Li-ion battery of 7.2 V and 1.35 A hr capacity can boost the peak power capacity by 5 times and reduce the power loss by 74%, while minimally impacting system volume and weight, for pulsed loads of 5 A, 1 Hz repetition rate, and 10% duty.

Brands Matter: An Empirical Demonstration of the Creation of Shareholder Value Through Brands

Abstract: Past research has shown a correlation between measures of brand equity and stock price. However, these results are not sufficient to conclude that branding creates shareholder value. Using time-honored models from the discipline of finance, this paper specifies, and subsequently tests, the necessary and sufficient conditions to determine whether brand strength leads to the creation of shareholder value. The results presented extend previous research by showing that strong brands not only deliver greater returns to stockholders versus a relevant market benchmark, they do so with less risk. A reframing of brand research within the framework of risk management is recommended, toward a goal of greater organizational interdependence and accountability for the marketing function as a whole.

Crosslinking by advanced glycation end products increases the stiffness of the collagen network in human articular cartilage: A possible mechanism through which age is a risk factor for osteoarthritis

Abstract: Objective. Age is an important risk factor for osteoarthritis (OA). During aging, nonenzymatic glycation results in the accumulation of advanced glycation end products (AGEs) in cartilage collagen. We studied the effect of AGE crosslinking on the stiffness of the collagen network in human articular cartilage. Methods. To increase AGE levels, human adult articular cartilage was incubated with threose. The stiffness of the collagen network was measured as the instantaneous deformation (ID) of the cartilage and as the change in tensile stress in the collagen network as a function of hydration (osmotic stress technique). AGE levels in the collagen network were determined as: Ne-(carboxy[m]ethyl)lysine, pentosidine, amino acid modification (loss of arginine and [hydroxy-]lysine), AGE fluorescence (360/460 nm), and digestibility by bacterial collagenase. Results. Incubation of cartilage with threose resulted in a dose-dependent increase in AGEs and a concomitant decrease in ID (r = -0.81, P < 0.001; up to a 40% decrease at 200 mM threose), i.e., increased stiffness, which was confirmed by results from the osmotic stress technique. The decreased ID strongly correlated with AGE levels (e.g., AGE fluorescence r = -0.81, P < 0.0001). Coincubation with arginine or lysine (glycation inhibitors) attenuated the threose-induced decrease in ID (P < 0.05). Conclusion. Increasing cartilage AGE crosslinking by in vitro incubation with threose resulted in increased stiffness of the collagen network. Increased stiffness by AGE crosslinking may contribute to the age-related failure of the collagen network in human articular cartilage to resist damage. Thus, the age-related accumulation of AGE crosslinks presents a putative molecular mechanism whereby age is a predisposing factor for the development of OA.

Compliance with physical activity guidelines : prevalence in a population of children and youth

Abstract: PURPOSE To use objective monitoring of physical activity to determine the percentages of children and youth in a population that met physical activity guidelines. METHODS A total of 375 students in grades 1–12 wore an accelerometer (CSA 7164) for seven consecutive days. Bouts of continuous activity and accumulation of minutes spent in physical activity at various intensities were calculated to determine how many students met three physical activity guidelines. RESULTS Over 90% of students met Healthy People 2010, Objective 22.6 and nearly 70% met the United Kingdom Expert Consensus Group guideline, both of which recommend daily accumulation of moderate physical activity. Less than 3% met Healthy People 2010, Objective 22.7, which calls for bouts of continuous vigorous physical activity. For the United Kingdom Expert Consensus Group guideline, compliance decreased markedly with age, but gender differences were not statistically significant. CONCLUSIONS Prevalence estimates for compliance with national physical activity guidelines varied markedly for the three guidelines examined. Objective monitoring of physical activity in youth appears to be feasible and may provide more accurate prevalence rates than self-report measures.

Stable isotope compositions of biological apatite

Abstract: The stable isotope compositions of biogenic materials record a combination of environmental parameters and biological processes. In general, the environment provides a range of isotopic compositional inputs, and an animal processes those signals through dietary preference, physiology, behavior, etc. Geochemists then use isotope signals preserved in biogenic materials to infer either what the biologic filter was (i.e., a species-specific biologic process), or the environment in which the animal lived (e.g., see review of Koch 1998). Although stable isotopes of hydrogen, carbon, nitrogen, oxygen, and strontium in modern-day animals have provided fruitful information on environment or biology, preservation of hydrogen and nitrogen is poor for most fossil materials, especially those older than a few million years. Consequently, nearly all stable isotope studies focus on the best preserved tissues, which are biological apatites (or bioapatites)— bone, dentin, enamel, scales, etc.—and on the most diagenetically resistant isotopes–oxygen, carbon, and occasionally strontium, which occur as principal or substitutional components in bioapatite. Because of the inherent synergy between biology and environment, the scientific scope of stable isotope research on bioapatites is quite broad. In addition to studies of terrestrial paleoclimate and dietary preference, stable isotopes in bioapatite have helped elucidate such diverse issues as dinosaur thermoregulation (Barrick and Showers 1994, 1995; Barrick et al. 1996, 1998; Fricke and Rogers 2000), the global rise of C4 plants (Cerling et al. 1993, 1997), pinniped migration (Burton and Koch 1999), cetacean osmoregulation (Thewissen et al. 1996, Roe et al. 1998), herding practices (Bocherens et al. 2001), topographic uplift (Dettman et al. 2001, Kohn et al. 2003), the demise of Norse colonies in Greenland (Fricke et al. 1995, Arneborg et al. 1999), Miocene “rhinoceros” ecology (MacFadden 1998), and mastodon migration (Hoppe et al., 1999)! In this chapter, we first describe …