scispace - formally typeset
Search or ask a question

Showing papers by "University of Arkansas published in 1999"


Journal ArticleDOI
TL;DR: In this paper, a meta-analysis of 131 samples (N = 20,620) provided systematic evidence of nonzero, positive, true population estimates of board size-performance relationships.
Abstract: Although a host of theory-driven rationales suggest a relationship between board of directors size and firm performance, the literature provides no consensus about the direction of that relationship. A meta-analysis of 131 samples (N = 20,620) provided systematic evidence of nonzero, positive, true population estimates of board size-performance relationships.

1,714 citations


Journal ArticleDOI
TL;DR: In this paper, a 2° lat × 3° long grid of summer drought reconstructions for the continental United States estimated from a dense network of annual tree-ring chronologies is described.
Abstract: The development of a 2° lat × 3° long grid of summer drought reconstructions for the continental United States estimated from a dense network of annual tree-ring chronologies is described. The drought metric used is the Palmer Drought Severity Index (PDSI). The number of grid points is 154 and the reconstructions cover the common period 1700–1978. In producing this grid, an automated gridpoint regression method called “point-by-point regression” was developed and tested. In so doing, a near-optimal global solution was found for its implementation. The reconstructions have been thoroughly tested for validity using PDSI data not used in regression modeling. In general, most of the gridpoint estimates of drought pass the verification tests used. In addition, the spatial features of drought in the United States have been faithfully recorded in the reconstructions even though the method of reconstruction is not explicitly spatial in its design. The drought reconstructions show that the 1930s “Dust Bow...

1,113 citations


Journal ArticleDOI
TL;DR: It is shown that the estimation error remains bounded if the system satisfies the nonlinear observability rank condition and the initial estimation error as well as the disturbing noise terms are small enough.
Abstract: The authors analyze the error behavior for the discrete-time extended Kalman filter for general nonlinear systems in a stochastic framework. In particular, it is shown that the estimation error remains bounded if the system satisfies the nonlinear observability rank condition and the initial estimation error as well as the disturbing noise terms are small enough. This result is verified by numerical simulations for an example system.

867 citations


Journal ArticleDOI
TL;DR: There is a strong rekindling of academic and practitioner interest in the marketing strategy making (MSM) process and its effect on firm performance as mentioned in this paper, however, there is a dearth of research on proce...
Abstract: There is a strong rekindling of academic and practitioner interest in the marketing strategy making (MSM) process and its effect on firm performance. However, there is a dearth of research on proce...

664 citations


Journal ArticleDOI
TL;DR: The risk of stroke, myocardial infarction, and death within 30 days and 3 months of endarterectomy is lower for patients taking 81 mg or 325 mg acetylsalicylic acid daily than for those taking 650 mg or 1300 mg.

506 citations


Journal ArticleDOI
TL;DR: A number of studies have indicated that a nitrogenous signal(s), associated with N accumulation in the shoot and nodule, exists in legume plants so that N 2 fixation is inhibited early in soil drying, which opens the possibility for enhancing N 1 fixation tolerance to drought through selection and breeding.
Abstract: Symbiotic nitrogen fixation is highly sensitive to drought, which results in decreased N accumulation and yield of legume crops. The effects of drought stress on N 2 fixation usually have been perceived as a consequence of straightforward physiological responses acting on nitrogenase activity and involving exclusively one of three mechanisms: carbon shortage, oxygen limitation, or feedback regulation by nitrogen accumulation. The sensitivity of the nodule water economy to the volumetric flow rate of the phloem into the nodule offers a common framework to understand each of these mechanisms. As these processes are sensitive to volumetric phloem flow into the nodules, variations in phloem flow as a result of changes in turgor pressure in the leaves are likely to cause rapid changes in nodule activity. This could explain the special sensitivity of N 2 fixation to drying soils. It seems likely that N feedback may be especially important in explaining the response mechanism in nodules. A number of studies have indicated that a nitrogenous signal(s), associated with N accumulation in the shoot and nodule, exists in legume plants so that N 2 fixation is inhibited early in soil drying. The existence of genetic variation in N 2 fixation response to water deficits among legume cultivars opens the possibility for enhancing N 2 fixation tolerance to drought through selection and breeding.

417 citations


Journal ArticleDOI
TL;DR: The result of amino acid analysis showed that RBPI had a similar profile of essential amino acid requirements for 2-5-year-old children in comparison to that of casein and soy protein isolate.
Abstract: Rice bran protein isolate (RBPI) containing approximately 92.0% protein was prepared from unstabilized and defatted rice bran using phytase and xylanase. The yield of RBPI increased from 34% to 74.6% through the use of the enzymatic treatment. Nitrogen solubilities of RBPI were 53, 8, 62, 78, 82, and 80% at pHs 2.0, 4.0, 6.0, 8.0, 10.0, and 12.0, respectively. Differential scanning calorimetry showed that RBPI had denaturation temperature of 83.4 degrees C with low endotherm (0.96 J/g of protein). RBPI had similar foaming properties in comparison to egg white. But emulsifying properties of RBPI were significantly lower than those of bovine serum albumin. The result of amino acid analysis showed that RBPI had a similar profile of essential amino acid requirements for 2-5-year-old children in comparison to that of casein and soy protein isolate.

369 citations


Journal ArticleDOI
TL;DR: The proposed roles of tryptophan and lysine side chains as “anchoring” residues of transmembrane proteins are investigated, and a model in which the Trp side chain has a specific affinity for a well defined site near the lipid carbonyl region is supported.

329 citations



Journal ArticleDOI
TL;DR: In this article, four conceptual models of health are presented to summarize the current meanings for health and are a prelude to improving health status assessment in a variety of contexts.
Abstract: The meaning of health is complex and subject to change. In this article, four conceptual models of health are presented to summarize the current meanings for health. The medical model is the most widely used definition in the United States, but the World Health Organization model has gained in popularity during the past several decades. In addition, there are other newer models--the wellness model and the environmental model--that are adding new meanings to the definition of health. By understanding and combining these different meanings, the prospects for improving medical outcomes and the quality of care are enhanced. This conceptual work is a prelude to improving health status assessment in a variety of contexts.

302 citations


Journal ArticleDOI
TL;DR: Reducing phenyl Propanoid biosynthesis by silencing the expression of phenylalanine ammonialyase (PAL) reduces SAR to tobacco mosaic virus (TMV), whereas overexpression of PAL enhances SAR, demonstrating phenylpropanoid-mediated cross-talk in vivo between microbially induced and herbivore-induced pathways of systemic resistance.

Journal ArticleDOI
01 Jan 1999-Ecology
TL;DR: In this article, the authors quantified the long-term consequences of surface disturbance in an arid ecosystem on the Colorado Plateau by comparing pristine sites with those of known disturbance history.
Abstract: Anthropogenic activity is causing dramatic changes in the nitrogen (N) cycle in many ecosystems. Most research has focused on the increase in N input caused by atmospheric deposition and invasion of N-fixing species, and on their effects on resource availability and species composition. However, in contrast to many ecosystems experiencing large increases in N input, many arid ecosystems are experiencing loss of nutrients due to land-use change. An important component of many arid ecosystems on a worldwide basis is the microbiotic crust, a biological soil crust composed of lichens, cyanobacteria, mosses, and algae. Nitrogen fixation by lichens and cyanobacteria comprising the crust is the primary source of N input in many of these ecosystems. We quantified the long-term consequences of surface disturbance in an arid ecosystem on the Colorado Plateau by comparing pristine sites with those of known disturbance history. Disturbance caused an increase in the abun- dance of cyanobacteria and a decrease in lichens within the microbiotic crust. Carbon isotope composition (813C) of the crust reflects this shift in species composition; values for disturbed sites were 4.5%o higher than undisturbed sites. Nitrogen isotope composition (615N) of the microbiotic crust was 1 .5-2.2%o higher for disturbed sites, probably resulting from relatively greater gaseous N loss from the crust. Historic disturbance has caused a long-term decrease in rates of N fixation by the microbiotic crust; nitrogenase activity in pristine sites was 250% greater than sites intermittently disturbed 30 yr ago. The decrease in N input from fixation and continued gaseous N loss has caused a 25-75% decrease in soil N content. Altering relative rates of N input and loss, coupled with input of N from microbiotic crusts with relatively higher 615N, has caused an increase in soil and plant 615N at disturbed sites. This decrease in soil N caused by disturbance will likely cause changes in species com- position similar to those observed in ecosystems that have been disrupted by excess N input from atmospheric deposition.

Journal ArticleDOI
TL;DR: In this paper, a sample of 683 non-indexed U.S. equity funds over the 1993-95 period, the authors found that 20% of the mutual funds were smaller than the breakeven-cost fund size and 10 percent of the largest funds overinvested in information acquisition and trading.
Abstract: Fund size (net assets under management) affects mutual fund performance. Mutual funds must attain a minimum fund size in order to achieve sufficient returns to justify their costs of acquiring and trading on information. Furthermore, there are diminishing marginal returns to information acquisition and trading, and the marginal returns become negative when the mutual fund exceeds its optimal fund size. In a sample of 683 nonindexed U.S. equity funds over the 1993–95 period, we found that 20 percent of the mutual funds were smaller than the breakeven-cost fund size and 10 percent of the largest funds overinvested in information acquisition and trading. In addition, we found that value funds and blend (value-and-growth) funds have more to gain than growth funds from these information activities.

Journal ArticleDOI
20 May 1999-Nature
TL;DR: This work compiles the ranges of thepasserine (perching) birds of the Americas to produce a map showing where species losses might occur in the long term.
Abstract: Greater numbers and higher proportions of recent species extinctions have been on islands rather than on continents. In contrast, predictions of massive future extinctions stem from the current clearing of continental, tropical forests1. For instance, since 1600, 97 out of 108 bird extinctions have been on islands2. However, 452 of the total 1,111 species currently considered to be threatened are continental3. Island flora and fauna are uniquely vulnerable to the human introduction of previously absent predators, diseases and other menaces4, whereas species on continents are not so ecologically naive. So could predictions of future continental extinctions based on island histories be exaggerated1? Most threatened species have small geographic ranges5, and the ranges of island species are inevitably smaller than those of continental species. For a given range size, how do the proportions of threatened island and continental species compare? Here we compile the ranges of thepasserine (perching) birds of the Americas. Corrected for range size, continental species are more—not less—likely to be threatened. We use this unexpected vulnerability of continental species with small ranges to produce a map showing where species losses might occur in the long term.

Journal ArticleDOI
TL;DR: In this paper, a study was conducted to determine how well amylography conducted with a Rapid Visco Analyser (RVA) serves as a predictor of cooked rice texture, alone and in combination with amylose content.
Abstract: Although amylose content is considered the most important determinant of cooked rice texture, this constituent falls short as a predictor, because cultivars with similar amylose contents may differ in textural properties. Thus, amylography is used as one of a battery of tests, in addition to measuring amylose content, to improve differentiation of cultivars. The purpose of our study was to determine how well amylography conducted with a Rapid Visco Analyser (RVA) serves as a predictor of cooked rice texture, alone and in combination, with amylose content. Textural properties of 87 samples representing short-, medium-, and long-grain rice cultivars were assessed by descriptive sensory and instrumental texture profile (TPA) analyses and related to RVA measurements. None of the cooked rice textural attributes, whether measured by descriptive analysis or TPA, were modeled by RVA with high accuracy (i.e., high r2). Sensory texture attributes cohesiveness of mass, stickiness, and initial starchy coatin...

Journal ArticleDOI
TL;DR: The greatest benefits with cochlear implantation have occurred in patients who (1) acquired speech and language before their hearing loss, and (2) have shorter duration of deafness.
Abstract: Cochlear implants have been very successful in restoring partial hearing to profoundly deaf people. Many individuals with implants are now able to communicate and understand speech without lip-reading, and some are able to talk over the phone. Children with implants can develop spoken-language skills and attend normal schools (i.e., schools with normal-hearing children). The greatest benefits with cochlear implantation have occurred in patients who (1) acquired speech and language before their hearing loss, and (2) have shorter duration of deafness. Gradual, but steady, improvements in speech production and speech perception have also occurred in prelingually deafened adults or children.

Journal ArticleDOI
TL;DR: This study investigates a new method based on a distributed and locally autonomous decision structure using the notion of combinatorial auction, and shows that not only can this auction mechanism be used to handle complex resource scheduling problems, but there exist strong links between combinatorsial auction and Lagrangean-based decomposition.
Abstract: Most existing methods for scheduling are based on centralized or hierarchical decision making using monolithic models. In ihis study, we investigate a new method based on a distributed and locally autonomous decision structure using the notion of combinatorial auction. In combinatorial auction the bidders demand a combination of dependent objects with a single bid. We show that not only can we use this auction mechanism to handle complex resource scheduling problems, but there exist strong links between combinatorial auction and Lagrangean-based decomposition. Exploring some of these properties, we characterize combinatorial auction using auction protocols and payment functions. This study is a first step toward developing a distributed scheduling framework that maintains system-wide performance while accommodating local preferences and objectives. We provide some insights to this framework by demonstrating four different versions of the auction mechanism using job shop scheduling problems.

Journal ArticleDOI
TL;DR: In this article, the authors employ corporate takeover decisions to investigate the impact of institutional ownership on corporate performance and find that institutional ownership is significantly determined by firm size, insider ownership and the firm's presence in the S&P 500 index.

Journal ArticleDOI
TL;DR: It is concluded that sperm mobility is a primary determinant of fertility in the fowl and the hypothesis that vaginal immunoglobulins constitute an immunological barrier to sperm transport was rejected.
Abstract: Previous research demonstrated that sperm mobility is a quantitative trait of the domestic fowl. The trait is quantified by measuring the absorbance of an Accudenz solution after overlay with a sperm suspension and brief incubation at body temperature. In the present work, average and high sperm mobility phenotypes (n = 30 males per phenotype) were selected from a base population. Differences were found between sperm oxygen consumption (p < 0.0001), acylcarnitine content (p < 0.05), linear velocity (p < 0.001), and straightness (p < 0.001), a trajectory variable measured with the Hobson SpermTracker. Oxygen consumption and stearoylcarnitine content of sperm from the high-mobility phenotype were twice those observed with sperm from average males, implying a pivotal role for mitochondria. On the basis of these results, a graded relationship was predicted between fertility and sperm mobility. Males (n = 48) were chosen at random from another base population, sperm mobility was measured per male, and each ejaculate was used to inseminate 8-12 hens (8 x 10(7) viable sperm per hen). When fertility was plotted as a function of sperm mobility, data points approximated a skewed logistic function. The hypothesis that vaginal immunoglobulins constitute an immunological barrier to sperm transport was tested and rejected. Therefore, we concluded that sperm mobility is a primary determinant of fertility in the fowl.

Journal ArticleDOI
TL;DR: Soil temperature was a better indicator of internal buried carcass temperature than was ambient air temperature, and should be used to determine developmental rates of insects for determination of the postmortem interval by a forensic entomologist.
Abstract: We established a database of insect succession on buried carrion in two biogeoclimatic zones of British Columbia over a 16-month period beginning June 1995. Pig (Sus scrofa L.) carcasses were buried shortly after death in the Coastal Western Hemlock and Sub-boreal Spruce biogeoclimatic zones of British Columbia. Buried pigs exhibited a distinct pattern of succession from that which occurred on above-ground carrion. The species composition and time of colonization for particular species differed between the two zones. Therefore ideally, a database of insect succession on buried carrion should be established for each major biogeoclimatic zone. We did not observe maggot masses on any of the buried carcasses; therefore, the presence of maggot masses may indicate a delayed burial. Soil temperature was a better indicator of internal buried carcass temperature (r2 = 0.92, p < 0.0001) than was ambient air temperature (r2 = 0.60, p < 0.0001); thus soil temperature should be used to determine developmental rates of insects for determination of the postmortem interval by a forensic entomologist.

Proceedings ArticleDOI
01 Dec 1999
TL;DR: Computer simulation can be used to help identify process inefficiencies and to evaluate the effects of staffing, layout, resource, and patient flow changes on system performance without disturbing the actual system.
Abstract: Efficient allocation and utilization of staff resources is an important issue facing emergency department (ED) administrators. Increased pressure from competition, health care reform, reimbursement difficulties, and rising health care costs are primarily responsible for the high level of interest in this, and other ED operating efficiency issues. The paper discusses the use of computer simulation to test alternative ED attending physician staffing schedules and to analyze the corresponding impacts on patient throughput and resource utilization. The simulation model can also be used to help identify process inefficiencies and to evaluate the effects of staffing, layout, resource, and patient flow changes on system performance without disturbing the actual system. The development of this model was based on the Emergency Department at the University of Virginia Medical Center in Charlottesville, Virginia.

Journal ArticleDOI
TL;DR: In this article, a review of polishing and planarization techniques for polycrystalline chemically vapor-deposited (CVD) diamond films and substrates is presented.

Journal ArticleDOI
TL;DR: The labial glands of Helicoverpa zea produced a glucose oxidase (GOX), which was present in the saliva and midgut lumen and appears to have similar kinetic and physical attributes to other insect GOXs.
Abstract: Labial glands of Helicoverpa zea produced a glucose oxidase (GOX), which was present in the saliva and midgut lumen. We purified GOX 23-fold by isoelectric focusing of labial gland homogenates and investigated physical and kinetic properties of the enzyme. D-glucose and 6-deoxy-D-glucose were the optimal substrates of 22 carbohydrates tested with GOX. The enzyme was not inhibited by several inhibitors of fungal GOX but was sensitive to HgCl(2). Labial gland GOX activities varied daily during larval development with highest activities found when larvae were actively feeding. Based on pH optimum, pI, molecular weight estimate and K(m(glucose)), the insect enzyme is not derived from fungal GOXs but appears to have similar kinetic and physical attributes to other insect GOXs. Some possible functions are discussed, including antimicrobial properties, manipulating midgut O(2) levels, altering host plant defense responses, and metabolizing carbohydrates. Arch. Copyright 1999 Wiley-Liss, Inc.

Journal ArticleDOI
TL;DR: Field trials conducted at commercial broiler farms in conjunction with the Environmental Protection Agency showed that alum additions to poultry litter lowered litter pH, particularly during the first 3 to 4 wk of each growout, which resulted in less NH3 volatilization and lower atmospheric NH3.

Journal ArticleDOI
TL;DR: To study FHB resistance in barley, quantitative trait locus (QTL) mapping was used to determine the number, genome location, and effects of QTLs associated with Type-I and -II resistance and the concentration of DON in the grain.
Abstract: Fusarium head blight (FHB), an important disease of barley in many areas of the world, causes losses in grain yield and quality. Deoxynivalenol (DON) mycotoxin residues, produced by the primary pathogen Fusarium graminearum, pose potential health risks. Barley producers may not be able to profitably market FHB-infected barley, even though it has a low DON level. Three types of FHB resistance have been described in wheat: Type I (penetration), Type II (spread), and Type III (mycotoxin degradation). We describe putative measures of these three types of resistance in barley. In wheat, the three resistance mechanisms show quantitative inheritance. Accordingly, to study FHB resistance in barley, we used quantitative trait locus (QTL) mapping to determine the number, genome location, and effects of QTLs associated with Type-I and -II resistance and the concentration of DON in the grain. We also mapped QTLs for plant height, heading date, and morphological attributes of the inflorescence (seeds per inflorescence, inflorescence density, and lateral floret size). QTL analyses were based on a mapping population of F1-derived doubled-haploid (DH) lines from the cross of the two-rowed genotypes Gobernadora and CMB643, a linkage map constructed with RFLP marker loci, and field evaluations of the three types of FHB resistance performed in China, Mexico, and two environments in North Dakota, USA. Resistance QTLs were detected in six of the seven linkage groups. Alternate favorable alleles were found at the same loci when different inoculation techniques were used to measure Type-I resistance. The largest-effect resistance QTL (for Type-II resistance) was mapped in the centromeric region of chromosome 2. All but two of the resistance QTLs coincided with QTLs determining morphological attributes of the inflorescence and/or plant height. Additional experiments are needed to determine if these coincident QTLs are due to linkage or pleiotropy and to more clearly define the biological basis of the FHB resistance QTLs. Plant architecture should be considered in FHB resistance breeding efforts, particularly those directed at resistance QTL introgression and/or pyramiding.

Journal ArticleDOI
TL;DR: This work uses an optimal control approach to design a robust hovering control of vertical/short takeoff and landing (V/STOL) aircraft that is nonlinear state feedback whose robustness is demonstrated by numerical simulations.
Abstract: We study robust hovering control of vertical/short takeoff and landing (V/STOL) aircraft. For hovering control, we can model a V/STOL aircraft as a planar vertical takeoff and landing (PVTOL) aircraft. We use an optimal control approach to design a robust hovering control. The resulting control is a nonlinear state feedback whose robustness is demonstrated by numerical simulations.

Journal ArticleDOI
TL;DR: This comprehensive review examines and critiques recent advances achieved through GIS in regional and within-site databases, locational analysis and modeling, regional simulation, studies of landscape perception through intervisibility analysis, and models of spatial allocation, territoriality, and site access.
Abstract: Geographical information systems (GIS) are tools for handling and processing spatially referenced information that have permeated all facets of archaeology, frequently revolutionizing research by allowing easy access to vast amounts of information, new ways of data visualization that promote insight through pattern recognition, and unique methodologies that allow entirely new approaches to the study of the past. This comprehensive review examines and critiques recent advances achieved through GIS in regional and within-site databases, locational analysis and modeling, regional simulation, studies of landscape perception through intervisibility analysis, and models of spatial allocation, territoriality, and site access. The future prospects of GIS are enormous with the growth of the Internet, the resultant linking of databases, expected enhancements in satellite remote sensing, and the increasing pervasiveness of global positioning systems for spatial data capture.

Journal ArticleDOI
TL;DR: In this article, Dendrochronological analyses indicate that Pterocarpus angolensis produces anatomically distinctive annual growth rings in the indigenous forests of western Zimbabwe.

Journal ArticleDOI
TL;DR: In this paper, the authors report the preparation, crystallization, and solid-state characterization of a spiro-biphenalenyl radical and show that it is monomeric in the solid state.
Abstract: We report the preparation, crystallization, and solid-state characterization of a spiro-biphenalenyl radical. The crystal structure shows that the radical is monomeric in the solid state and withou...

Journal ArticleDOI
TL;DR: A structural equations confirmatory factor analysis (LISREL 8.03) as discussed by the authors suggests that these operationalizations do not constitute a single construct of board independence and instead strongly indicate three separate constructs.
Abstract: Over two dozen operationalizations of board composition can be identified from the empirical literature. A structural equations confirmatory factor analysis (LISREL 8.03) suggests that these operationalizations do not constitute a single construct of board independence. Instead, analyses strongly indicate three separate constructs. Common operationalizations of board composition, then, are neither tenable surrogates for one another nor are they interchangeable. Implications for empirical aggregation of studies, theory/measurement convergence, and the current corporate governance public policy debate are discussed.