Showing papers by "Clemson University published in 1999"

Ferroelectric ceramics : History and technology

Abstract: Ferroelectric ceramics were born in the early 1940s with the discovery of the phenomenon of ferroelectricity as the source of the unusually high dielectric constant in ceramic barium titanate capacitors. Since that time, they have been the heart and soul of several multibillion dollar industries, ranging from high-dielectric-constant capacitors to later developments in piezoelectric transducers, positive temperature coefficient devices, and electrooptic light valves. Materials based on two compositional systems, barium titanate and lead zirconate titanate, have dominated the field throughout their history. The more recent developments in the field of ferroelectric ceramics, such as medical ultrasonic composites, high-displacement piezoelectric actuators (Moonies, RAINBOWS), photostrictors, and thin and thick films for piezoelectric and integrated-circuit applications have served to keep the industry young amidst its growing maturity. Various ceramic formulations, their form (bulk, films), fabrication, function (properties), and future are described in relation to their ferroelectric nature and specific areas of application.

Generality of leaf trait relationships: a test across six biomes

Abstract: Convergence in interspecific leaf trait relationships across diverse taxonomic groups and biomes would have important evolutionary and ecological implications. Such convergence has been hypothesized to result from trade-offs that limit the combination of plant traits for any species. Here we address this issue by testing for biome differences in the slope and intercept of interspecific relationships among leaf traits: longevity, net pho- tosynthetic capacity (Amax), leaf diffusive conductance (Gs), specific leaf area (SLA), and nitrogen (N) status, for more than 100 species in six distinct biomes of the Americas. The six biomes were: alpine tundra-subalpine forest ecotone, cold temperate forest-prairie ecotone, montane cool temperate forest, desert shrubland, subtropical forest, and tropical rain forest. Despite large differences in climate and evolutionary history, in all biomes mass-based leaf N (Nmass), SLA, Gs, and Amax were positively related to one another and decreased with increasing leaf life span. The relationships between pairs of leaf traits exhibited similar slopes among biomes, suggesting a predictable set of scaling relationships among key leaf morphological, chemical, and metabolic traits that are replicated globally among terrestrial ecosystems regardless of biome or vegetation type. However, the intercept (i.e., the overall elevation of regression lines) of relationships between pairs of leaf traits usually differed among biomes. With increasing aridity across sites, species had greater Amax for a given level of Gs and lower SLA for any given leaf life span. Using principal components analysis, most variation among species was explained by an axis related to mass-based leaf traits (Amax, N, and SLA) while a second axis reflected climate, Gs, and other area-based leaf traits.

SKUTTERUDITES : A phonon-glass-electron crystal approach to advanced thermoelectric energy conversion applications

Abstract: ▪ Abstract Recently there has been a resurgence of research efforts related to the investigation of new and novel materials for small-scale thermoelectric refrigeration and power generation applications. These materials need to couple and optimize a variety of properties in order to exhibit the necessary figure of merit, i.e. the numerical expression that is commonly used to compare one potential thermoelectric material with another. The figure of merit is related to the coefficient of performance or efficiency of a particular device made from a material. The best thermoelectric material should possess thermal properties similar to that of a glass and electrical properties similar to that of a perfect single-crystal material, i.e. a poor thermal conductor and a good electrical conductor. Skutterudites are materials that appear to have the potential to fulfill such criteria. These materials exhibit many types of interesting properties. For example, skutterudites are members of a family of compounds we call...

Holey and Unholey Semiconductors

Abstract: Thermoelectric materials, which have applications in refrigeration and power generation, are experiencing a surge in research activity. Many different materials are investigated with the goal of maximizing electrical conductivity while minimizing thermal conductivity, which is required for good thermoelectric performance. Only recently was a 30-year deadlock in thermoelectric performance overcome. Predictions for the new materials suggest that important further improvements are on the horizon, with promising applications in the computer and other high-tech industries.

Test‐data generation using genetic algorithms

Abstract: This paper presents a technique that uses a genetic algorithm for automatic test-data generation. A genetic algorithm is a heuristic that mimics the evolution of natural species in searching for the optimal solution to a problem. In the test-data generation application, the solution sought by the genetic algorithm is test data that causes execution of a given statement, branch, path, or definition–use pair in the program under test. The test-data-generation technique was implemented in a tool called TGen, in which parallel processing was used to improve the performance of the search. To experiment with TGen, a random test-data generator called Random was also implemented. Both Tgen and Random were used to experiment with the generation of test-data for statement and branch coverage of six programs. Copyright © 1999 John Wiley & Sons, Ltd.

Formation Rates of Black Hole Accretion Disk Gamma-Ray Bursts

Abstract: The cosmological origin of at least an appreciable fraction of classical gamma-ray bursts (GRBs) is now supported by redshift measurements for a half-dozen faint host galaxies. Still, the nature of the central engine (or engines) that provide the burst energy remains unclear. While many models have been proposed, those currently favored are all based upon the formation of and/or rapid accretion into stellar-mass black holes. Here we discuss a variety of such scenarios and estimate the probability of each. Population synthesis calculations are carried out using a Monte Carlo approach in which the many uncertain parameters intrinsic to such calculations are varied. We estimate the event rate for each class of model as well as the propagation distances for those having significant delay between formation and burst production, i.e., double neutron star (DNS) mergers and black hole-neutron star (BH/NS) mergers. One conclusion is a 1-2 order of magnitude decrease in the rate of DNS and BH/NS mergers compared to that previously calculated using invalid assumptions about common envelope evolution. Other major uncertainties in the event rates and propagation distances include the history of star formation in the universe, the masses of the galaxies in which merging compact objects are born, and the radii of the hydrogen-stripped cores of massive stars. For reasonable assumptions regarding each, we calculate a daily event rate in the universe for (1) merging neutron stars: ~100 day-1; (2) neutron star-black hole mergers: ~450 day-1; (3) collapsars: ~104 day-1; (4) helium star black hole mergers: ~1000 day-1; and (5) white dwarf-black hole mergers: ~20 day-1. The range of uncertainty in these numbers, however, is very large, typically 2-3 orders of magnitude. These rates must additionally be multiplied by any relevant beaming factor (fΩ < 1) and sampling fraction (if the entire universal set of models is not being observed). Depending upon the mass of the host galaxy, one-half of the DNS mergers will happen within 60 kpc (for a galaxy with a mass comparable to that of the Milky Way) to 5 Mpc (for a galaxy with negligible mass) from the Galactic center. The same numbers characterize BH/NS mergers. Because of the delay time, neutron star and black hole mergers will happen at a redshift 0.5-0.8 times that of the other classes of models. Information is still lacking regarding the hosts of short, hard bursts, but we suggest that they are due to DNS and BH/NS mergers and thus will ultimately be determined to lie outside of galaxies and at a closer mean distance than long complex bursts (which we attribute to collapsars). In the absence of a galactic site, the distance to these bursts may be difficult to determine.

Missing Data in Multiple Item Scales: A Monte Carlo Analysis of Missing Data Techniques:

Abstract: Researchers in many fields use multiple item scales to measure important variables such as attitudes and personality traits, but find that some respondents failed to complete certain items. Past missing data research focuses on missing entire instruments, and is of limited help because there are few variables to help impute missing scores and the variables are often not highly related to each other. Multiple item scales offer the unique opportunity to impute missing values from other correlated items designed to measure the same construct. A Monte Carlo analysis was conducted to compare several missing data techniques. The techniques included listwise deletion, regression imputation, hot-deck imputation, and two forms of mean substitution. Results suggest that regression imputation and substituting the mean response of a person to other items on a scale are very promising approaches. Furthermore, the imputation techniques often outperformed listwise deletion.

Trust Expectations, Information Sharing, Climate of Trust, and Negotiation Effectiveness and Efficiency:

Abstract: Trust expectations, information quantity shared, the climate of trust, and negotiated outcomes were investigated. Initial trust expectation was manipulated, and participants provided data about the quantity of information shared, the climate of trust, and the outcomes of the negotiations. The 324 participants were practicing managers who conducted a negotiating role play with win-win potential. Information sharing followed from initial trust expectations, and information sharing did not fully mediate the relationship between expectations and climate of trust. Negotiating effectiveness was associated with the quantity of information shared but not with trust. Procedural inefficiency (time to discover the solution) decreased as information quantity increased, but procedural inefficiency was not related to trust. One measure of outcome inefficiency (complexity of the agreement) decreased as trust increased, but another measure of outcome inefficiency (monetary cost of the agreement) was not related to trust....

Formation Rates of Black Hole Accretion Disk Gamma-Ray Bursts

Abstract: While many models have been proposed for GRBs, those currently favored are all based upon the formation of and/or rapid accretion into stellar mass black holes. We present population synthesis calculations of these models using a Monte Carlo approach in which the many uncertain parameters intrinsic to such calculations are varied. We estimate the event rate for each class of model as well as the propagation distance for those having significant delay between formation and burst production, i.e., double neutron star (DNS) mergers and black hole-neutron star (BH/NS) mergers. For reasonable assumptions regarding the many uncertainties in population synthesis, we calculate a daily event rate in the universe for i) merging neutron stars: ~100/day; ii) neutron-star black hole mergers: ~450/day; iii) collapsars: ~10,000/day; iv) helium star black hole mergers: ~1000/day; and v) white dwarf black hole mergers: ~20/day. The range of uncertainty in these numbers however, is very large, typically two to three orders of magnitude. These rates must additionally be multiplied by any relevant beaming factor and sampling fraction (if the entire universal set of models is not being observed). Depending upon the mass of the host galaxy, half of the DNS and BH/NS mergers will happen within 60kpc (for a Milky-Way massed galaxy) to 5Mpc (for a galaxy with negligible mass) from the galactic center. Because of the delay time, neutron star and black hole mergers will happen at a redshift 0.5 to 0.8 times that of the other classes of models. Information is still lacking regarding the hosts of short hard bursts, but we suggest that they are due to DNS and BH/NS mergers and thus will ultimately be determined to lie outside of galaxies and at a closer mean distance than long complex bursts (which we attribute to collapsars).

Face Perception During Early Infancy

Abstract: Previous studies of face perception during early infancy are difficult to interpret because of discrepant results and procedural differences. We used a standardized method based on the Teller acuity card procedure to test newborns, 6-week-olds, and 12-week-olds with three pairs of face and nonface stimuli modified from previous studies. Newborns' preferences were influenced both by the visibility of the stimuli and by their resemblance to a human face. There appears to be a mechanism, likely subcortical, predisposing newborns to look toward faces. Changes in preferences at 6 and 12 weeks of age suggest increasing cortical influence over infants' preferences for faces.

The Mla (Powdery Mildew) Resistance Cluster Is Associated With Three NBS-LRR Gene Families and Suppressed Recombination Within a 240-kb DNA Interval on Chromosome 5S (1HS) of Barley

Abstract: Powdery mildew of barley, caused by Erysiphe graminis f. sp. hordei, is a model system for investigating the mechanism of gene-for-gene interaction between large-genome cereals and obligate-fungal pathogens. A large number of loci that confer resistance to this disease are located on the short arm of chromosome 5(1H). The Mla resistance-gene cluster is positioned near the telomeric end of this chromosome arm. AFLP-, RAPD-, and RFLP-derived markers were used to saturate the Mla region in a high-resolution recombinant population segregating for the (Mla6 + Mla14) and (Mla13 + Ml-Ru3) resistance specificities. These tightly linked genetic markers were used to identify and develop a physical contig of YAC and BAC clones spanning the Mla cluster. Three distinct NBS-LRR resistance-gene homologue (RGH) families were revealed via computational analysis of low-pass and BAC-end sequence data derived from Mla-spanning clones. Genetic and physical mapping delimited the Mla-associated, NBS-LRR gene families to a 240-kb interval. Recombination within the RGH families was at least 10-fold less frequent than between markers directly adjacent to the Mla cluster.

Role of Granular Activated Carbon Surface Chemistry on the Adsorption of Organic Compounds. 1. Priority Pollutants

Abstract: Uptake of two synthetic organic contaminants (SOCs), trichloroethylene and trichlorobenzene, by one coal-based and one wood-based granular activated carbon (GAC), modified using liquid-phase oxidation (HNO3) and heat treatment in an inert atmosphere (N2), and by several different as-received GACs was compared. Carbons were characterized by elemental analysis, surface area and pore size distribution, water vapor adsorption, acid−base adsorption characteristics measured using the Boehm technique, and a mass titration/pH equilibration method to determine the pHpzc. The results of isotherm experiments with the surface-treated coal- and wood-based carbons indicated that carbon surface acidity played an important role on the adsorption of hydrophobic SOCs. It was found that increasing surface acidity increased the polarity of the surface and reduced adsorption of hydrophobic SOCs by GAC. However, no significant trend was evident for as-received carbons; their behavior differed significantly from surface-treated...

Identification of a Novel Group of Bacteria in Sludge from a Deteriorated Biological Phosphorus Removal Reactor

Abstract: The microbial diversity of a deteriorated biological phosphorus removal reactor was investigated by methods not requiring direct cultivation. The reactor was fed with media containing acetate and high levels of phosphate (P/C weight ratio, 8:100) but failed to completely remove phosphate in the effluent and showed very limited biological phosphorus removal activity. Denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S ribosomal DNA was used to investigate the bacterial diversity. Up to 11 DGGE bands representing at least 11 different sequence types were observed; DNA from the 6 most dominant of these bands was further isolated and sequenced. Comparative phylogenetic analysis of the partial 16S rRNA sequences suggested that one sequence type was affiliated with the alpha subclass of the Proteobacteria, one was associated with the Legionella group of the gamma subclass of the Proteobacteria, and the remaining four formed a novel group of the gamma subclass of the Proteobacteria with no close relationship to any previously described species. The novel group represented approximately 75% of the PCR-amplified DNA, based on the DGGE band intensities. Two oligonucleotide rRNA probes for this novel group were designed and used in a whole-cell hybridization analysis to investigate the abundance of this novel group in situ. The bacteria were coccoid and 3 to 4 microm in diameter and represented approximately 35% of the total population, suggesting a relatively close agreement with the results obtained by the PCR-based DGGE method. Further, based on electron microscopy and standard staining microscopic analysis, this novel group was able to accumulate granule inclusions, possibly consisting of polyhydroxyalkanoate, inside the cells.

Derivation and implications of a meta‐analytic matrix incorporating cognitive ability, alternative predictors, and job performance

Abstract: A variety of recent articles in the personnel selection literature have used analyses of meta-analytically derived matrices to draw general conclusions for the field. The purpose of this article is to construct a matrix that incorporates as complete information as possible on the relationships among cognitive ability measures, three sets of alternative predictors, and job performance, We build upon a starting matrix used by Schmitt, Rodgers, Chan, Sheppard, and Jennings (1997). Mean differences, by race, for each of the measures and the potential for adverse impact of predictor composites are also considered. We demonstrate that the use of alternative predictors alone to predict job performance (in the absence of cognitive ability) lowers the potential for adverse impact. However, in contrast to recent claims, adverse impact continues to occur at many commonly used selection ratios. Future researchers are encouraged to use our matrix and to expand upon it as new primary research becomes available. We also report and reaffirm many methodological lessons along the way, including the many judgment calls that appear in an effort of this magnitude and a reminder that the field could benefit from even greater conceptual care regarding what is labeled an “alternative predictor.” Directions for future meta-analyses and for future primary research activities are also derived.

Strong Optical Limiting of Silver-Containing Nanocrystalline Particles in Stable Suspensions

Abstract: Metal and metal sulfide nanoparticles are prepared using a method that is based on the rapid expansion of supercritical fluid solution (RESS) into a liquid solution and characterized using transmission electron microscopy and X-ray diffraction methods. The nanoparticles form solution-like stable suspensions in the presence of a stabilization agent such as poly(N-vinyl-2-pyrrolidone) (PVP) polymer. The stable suspensions allow systematic nonlinear optical measurements. The nanocrystalline silver metal and silver sulfide particles in PVP polymer-stabilized ethanol suspensions of high linear transmittance exhibit excellent optical limiting properties, with the optical limiting responses toward nanosecond laser pulses at 532 nm being much stronger than those of benchmark materials [60]fullerene and chloroaluminum phthalocyanine in solution. A comparison of the results with those of stable suspensions of other nanoparticles including cadmium sulfide, lead sulfide, and nickel suggests that the optical limiting ...

Detecting Multiple Species of Phytophthora in Container Mixes from Ornamental Crop Nurseries.

Abstract: A baiting bioassay was developed to detect species of Phytophthora, ie, those typically associated with ornamental crops, in container mixes that are used routinely in producing container-grown landscape plants Both fresh and air-dried subsamples of container mixes were baited to improve detection of species that persist as dormant propagules Leaf disks of Camellia japonica detected Phytophthora spp most frequently and consistently, but intact needles of shore juniper also were effective baits and less likely to become contaminated Phytophthora spp were detected at baiting durations of 24, 48, and 72 h; both detection and contamination were greatest at 72 h To minimize problems from contamination and maximize detection, camellia leaf disks and shore juniper needles were used simultaneously; half of the baits were removed at 24 h and the other half were removed at 72 h Baiting at temperatures of 15, 20, and 25°C did not have a dramatic effect on detection; however, Phytophthora spp occasionally were detected more frequently at 20 and 25°C than at 15°C Both camellia leaf disks and shore juniper needles were colonized readily by zoospores of P cinnamomi, P nicotianae (= P parasitica), P cryptogea, and P citricola but were not colonized as readily by zoospores of P cactorum Disks from leaves of C sasanqua and six cultivars of C japonica were effective as baits; however, some differences among camellia types occurred P cinnamomi, P nicotianae, P citricola, P citrophthora, P cryptogea, and P cactorum have been detected in naturally infested container mixes using this baiting bioassay

Role of Granular Activated Carbon Surface Chemistry on the Adsorption of Organic Compounds. 2. Natural Organic Matter

Abstract: The role of granular activated carbon (GAC) surface chemistry on the adsorption of four model dissolved organic material (DOM) isolates and four surface water natural organic material (NOM) samples was investigated by using (1) ten carbons prepared by modifying the surfaces of a coal-based and a wood-based carbon and (2) seven different as-received GACs. Because changes in the pore structure resulting from surface treatment were small, while changes in the surface chemistry were significant, the impact on the DOM and NOM uptake by surface-treated carbons was systematically linked to the changes in the carbon surface chemistry alone. For the surface-treated coal-based carbons, there was (1) no significant capacity difference between acid-washed and heat-treated carbon samples, (2) oxidation of the carbon surface significantly decreased the uptake, and (3) the capacity was partially restored by subsequent heat treatment of the oxidized surfaces. A decreasing uptake with increasing surface acidity was eviden...

Manufacturing-based relatedness, synergy, and coordination

Abstract: This paper explores the basic question of whether manufacturing-based relatedness between business units within a multibusiness firm serves as a basis for a competitive advantage at the business unit level. We developed a system for describing manufacturing relatedness that combines the study of value chain activities with 4-digit SIC codes, then we assessed presence of manufacturing synergies. We found no evidence that, on average, organizations involved in manufacturing-related businesses are reaping financial benefits from shared resources in manufacturing. However, some firms, through explicit commitment to coordination, do realize performance benefits from such involvement. Copyright © 1999 John Wiley & Sons, Ltd.

Apoptosis of Cardiac Myocytes in Gsα Transgenic Mice

Abstract: -The stimulatory GTP-binding protein Gsalpha transmits signals from catecholamine receptors to activate adenylyl cyclase and thereby initiate a cascade leading to cardiac chronotropy and inotropy. Transgenic mice overexpressing the Gs alpha subunit (Gsalpha) selectively in their hearts exhibit increased cardiac contractility in response to beta-adrenergic receptor stimulation. However, with aging, these mice develop a cardiomyopathy. This study sought morphological and biochemical evidence that overexpression of Gsalpha is associated with increased myocyte apoptosis in the older animals and to determine whether such overexpression can promote apoptosis of isolated neonatal cardiac myocytes exposed to beta-adrenergic receptor agonists. In the hearts of 15- to 18-month-old Gsalpha transgenic mice, histochemistry and electron microscopy illustrated the existence of numerous myocytes with abnormal nuclei embedded in collagen-rich connective tissue. Terminal deoxyribonucleotide transferase-mediated dUTP nick-end labeling (TUNEL, for in situ labeling of DNA breaks) demonstrated that approximately 0.6% of myocyte nuclei contained fragmented DNA. Agarose gel electrophoresis provided further biochemical evidence of apoptosis by showing internucleosomal DNA fragmentation. Cultured cardiac myocytes from newborn Gsalpha transgenic mice showed increased TUNEL staining and internucleosomal DNA fragmentation compared with wild-type controls when treated with the beta-agonist isoproterenol. Thus, enhanced activation of beta-adrenergic signaling by overexpression of Gsalpha in the hearts of transgenic mice induces apoptosis of cardiac myocytes. This represents a potential mechanism that may contribute to the development of cardiomyopathy in this model.

World Development Report, 1997: The State in a Changing World

Abstract: (1999). World Development Report, 1997: The State in a Changing World. Journal of Economic Issues: Vol. 33, No. 1, pp. 204-208.

Genetic mapping of resistance to Bacillus thuringiensis toxins in diamondback moth using biphasic linkage analysis

Abstract: Transgenic plants producing environmentally benign Bacillus thuringiensis (Bt) toxins are deployed increasingly for insect control, but their efficacy will be short-lived if pests adapt quickly. The diamondback moth (Plutella xylostella), a worldwide pest of vegetables, is the first insect to evolve resistance to Bt toxins in open-field populations. A recessive autosomal gene confers resistance to at least four Bt toxins and enables survival without adverse effects on transgenic plants. Allelic variants of this gene confer resistance in strains from Hawaii, Pennsylvania, and the Philippines. Here we exploited the biphasic nature of Lepidopteran genetic linkage to map this gene in diamondback moth with 207 amplified fragment length polymorphisms as DNA markers. We also cloned and sequenced an amplified fragment length polymorphism marker for the chromosome containing the Bt resistance gene. The results provide a powerful tool for facilitating progress in understanding, monitoring, and managing resistance to Bt.