Showing papers by "Virginia Tech published in 1994"
TL;DR: The present review considers a number of the features that appear to be critical to the withstanding of a long-term water deficit, including the elaboration of a conspicuous extracellular glycan, synthesis of abundant UV-absorbing pigments, and maintenance of protein stability and structural integrity.
1,259 citations
1,051 citations
TL;DR: In this paper, a coupled electro-mechanical analysis of piezoelectric ceramic (PZT) actuators integrated in mechanical systems to determine the actuator power consumption and energy transfer is presented.
Abstract: This article presents a coupled electro-mechanical analysis of piezoelectric ceramic (PZT) actuators integrated in mechanical systems to determine the actuator power consumption and energy transfer in the electro-mechanical systems. For a material system with integrated PZT actua tors, the power consumed by the PZT actuators consists of two parts: the energy used to drive the system, which is dissipated in terms of heat as a result of the structural damping, and energy dissi pated by the PZT actuators themselves because of their dielectric loss and internal damping. The coupled analysis presented herein uses a simple model, a PZT actuator-driven one-degree-of- freedom spring-mass-damper system, to illustrate the methodology used to determine the actuator power consumption and energy flow in the coupled electro-mechanical systems. This method can be applied to more complicated mechanical structures or systems, such as a fluid-loaded shell for active structural acoustic control. The determination of the act...
741 citations
TL;DR: Allelic diversity was greater in wild than in cultivated barley and surveys of two generations of Composite Cross II, an experimental population of cultivated barley, showed that few of the alleles present in the 28 parents survived into generation F53, whereas some infrequent alleles reached high frequencies.
Abstract: This study was undertaken to assess the extent of genetic variation in barley simple sequence repeats (SSRs) and to study the evolutionary dynamics of SSR alleles. SSR polymorphisms were resolved by the polymerase chain reaction with four pairs of primers. In total, 71 variants were observed in a sample of 207 accessions of wild and cultivated barley. Analyses of wheat-barley addition lines and barley doubled haploids identified these variants (alleles) with four loci, each located on a different chromosome. The numbers of alleles detected at a locus corresponded to the number of nucleotide repeats in the microsatellite sequences. The numbers of alleles at two loci were 28 and 37; to our knowledge these are the largest numbers of alleles for single Mendelian loci reported in plants. Three alleles were resolved by each of the other two loci. Allelic diversity was greater in wild than in cultivated barley and surveys of two generations (F8 and F53) of Composite Cross II, an experimental population of cultivated barley, showed that few of the alleles present in the 28 parents survived into generation F53, whereas some infrequent alleles reached high frequencies. Such changes in frequency indicate that the chromosomal segments marked by the SSR alleles are under the influence of natural selection. The SSR variants allow specific DNA sequences to be followed through generations. Thus, the great resolving power of SSR assays may provide clues regarding the precise targets of natural and man-directed selection.
664 citations
TL;DR: It was found that during this course of transformation, firms exhibited distinctive strategies despite a long tradition of central planning, and these strategies were significantly related to perceived environmental uncertainty.
Abstract: This study examined the strategy-environment-performance paradigm in a centrally planned economy (People's Republic of China) in transition to a more market-driven economy. Based on a survey of top Chinese managers in the electronics industry, it was found that during this course of transformation, firms exhibited distinctive strategies despite a long tradition of central planning, and these strategies were significantly related to perceived environmental uncertainty. Specifically, managers' perceptions of increased environmental uncertainty were found to be negatively related to proactive strategies and positively related to defensive strategies. Defensive strategies were also linked to higher performance.
654 citations
TL;DR: In this article, a series of batch and mixed flow reactor experiments were performed to determine the effect of SO42−, Cl−, ionic strength, and dissolved oxygen on the rate of reaction of pyrite with ferric iron.
625 citations
TL;DR: Time delay comparison shows that the amplitudes of many significant multipath components are accurately predicted by this model, and the effective building material properties are derived for two dissimilar buildings based upon comparison of measured and predicted power delay profiles.
Abstract: The paper describes a geometrical optics based model to predict propagation within buildings for personal communication system (PCS) design. A ray tracing model for predicting propagation based on a building blueprint representation is presented for a transmitter and receiver located on the same floor inside a building. Measured and predicted propagation data are presented as power delay profiles that contain the amplitude and arrival time of individual multipath components. Measured and predicted power delay profiles are compared on a location-by-location basis to provide both a qualitative and a quantitative measure of the model accuracy. The concept of effective building material properties is developed, and the effective building material properties are derived for two dissimilar buildings based upon comparison of measured and predicted power delay profiles. Time delay comparison shows that the amplitudes of many significant multipath components are accurately predicted by this model. Path loss between a transmitter and receiver is predicted with a standard deviation of less than 5 dB over 45 locations in two different buildings. >
610 citations
TL;DR: In this paper, the authors examined the strategy-environment-performance paradigm in a centrally planned economy (People's Republic of China) in transition to a more market-driven economy and found that firms exhibited distinctive strategies despite a long tradition of central planning, and these strategies were signijcantly related to perceived environmental uncertainty.
Abstract: This study examined the strategy-environment-performance paradigm in a centrally plannedeconomy (People's Republic of China) in transition to a more market-driven economy. Based on a survey of top Chinese managers in the electronics industry, it was found that during this course of transformation, firms exhibited distinctive strategies despite a long tradition of central planning, and these strategies were signijcantly related to perceived environmental uncertainty. Specifically, managers perceptions of increased environmental uncertainty were found to be negatively related to proactive strategies and positively related to defensive strategies. Defensive strategies were also linked to higher performance.
593 citations
TL;DR: Boynton et al. as mentioned in this paper presented an evaluation of tourists' experiences in rural Northern West Virginia and reported that tourism and traditional people: Forging Equitable Strategies. In Proceedings of the Travel and Tourism Educators Annual Conference, pp. 90-102.
583 citations
TL;DR: This paper examined the effect of the number and sex composition of a boy or girl's siblings on that child's educational attainment, and found that women's educational choices have been systematically affected by the Sex composition of her siblings, and men's choices have not.
Abstract: This paper documents the impact of siblings on the education of men and women born in the United States between 1920 and 1965. We examine the effect of the number and sex composition of a boy or girl's siblings on that child's educational attainment. We find that throughout the century women's educational choices have been systematically affected by the sex composition of her siblings, and that men's choices have not. Women raised only with brothers have received on average significantly more education than women raised with any sisters, controlling for household size. Since sibling sex composition affects women's educational attainment and plausibly may be unrelated to other determinants of earnings, it may provide a useful instrument for education in earnings functions for women. Our results suggest that standard estimates significantly underestimate the return to schooling for women.
536 citations
TL;DR: A cohort difference in 12-month MDE is found, with older women much more likely than older men to have recurrent episodes, and this sex difference in recurrence plays an important part in the elevated 12- month prevalence of depression among women compared to men in the 45-54 age range.
TL;DR: In this paper, a recent leadership theory, thought self-leadership, is proposed to assist employees in influencing or leading themselves towards experiencing more spirituality in their organizational life, which can assist employees to gain greater spirituality and purpose in their work.
Abstract: Offers a number of insights into the nature of spirituality in organizations and how employees can gain greater spirituality and purpose in their work. Specifically, proposes that a recent leadership theory, thought self‐leadership, can assist employees in influencing or leading themselves towards experiencing more spirituality in their organizational life.
TL;DR: In this paper, the authors examine the information content of dividend change announcements and find that announcement period excess returns are positively related to the magnitude of the standardized dividend change and to the dividend yield, but unrelated to Tobin's Q.
Abstract: We examine the cash flow signaling, overinvestment, and dividend clientele explanations for the information content of dividend change announcements. After simultaneously con? trolling for the standardized dividend change, dividend yield, and Tobin's Q, we find that announcement period excess returns are positively related to the magnitude ofthe standard? ized dividend change and to the dividend yield, but unrelated to Tobin's Q. We provide further evidence on the cash flow signaling and overinvestment hypotheses by examin? ing revisions in analysts' earnings forecasts and changes in capital expenditures following dividend change announcements. We find that analysts significantly revise their earnings forecasts following dividend changes and that Q < 1 firms actually increase their capital expenditures following dividend increases and decrease them following dividend decreases. Overall, our findings support the cash flow signaling and dividend clientele hypotheses for stock price reactions to dividend change announcements, but provide little support for the overinvestment hypothesis.
TL;DR: Current software VV&T techniques and current simulation model VV &T techniques are surveyed and how they can all be applied throughout the life cycle of a simulation study are described.
Abstract: Life cycle validation, verification, and testing (VV&T) is extremely important for the success of a simulation study. This paper surveys current software VV&T techniques and current simulation model VV&T techniques and describes how they can all be applied throughout the life cycle of a simulation study. The processes and credibility assessment stages of the life cycle are described and the applicability of the VV&T techniques for each stage is stated. A glossary is provided to explicitly define important terms and VV&T techniques.
TL;DR: In an institution the hot water system may be persistently colonised with a particular strain of M avium, and HIV-infected patients exposed to these water sources can develop disseminated MAvium infection.
TL;DR: This paper proposes a technique which first converts the problem into a nonlinear, polynomial mixed-integer zero-one problem by multiplying the constraints with some suitable d-degree polynometric factors involving the n binary variables, and subsequently linearizes the resulting problem through appropriate variable transformations.
TL;DR: The nifS gene product is a pyridoxal phosphate binding enzyme that catalyzes the desulfurization of L-cysteine to yield L-alanine and sulfur in Azotobacter vinelandii and it is suggested that NIFS participates in the biosynthesis of the nitrogenase metalloclusters by providing the inorganic sulfur required for Fe-S core formation.
Abstract: The nifS gene product (NIFS) is a pyridoxal phosphate binding enzyme that catalyzes the desulfurization of L-cysteine to yield L-alanine and sulfur In Azotobacter vinelandii this activity is required for the full activation of the nitrogenase component proteins Because the nitrogenase component proteins, Fe protein and MoFe protein, both contain metalloclusters which are required for their respective activities, it is suggested that NIFS participates in the biosynthesis of the nitrogenase metalloclusters by providing the inorganic sulfur required for Fe-S core formation [Zheng, L, White, R H, Cash, V L Jack, R F, & Dean, D R (1993) Proc Natl Acad Sci USA 90, 2754-2758] In the present study the mechanism for the desulfurization of L-cysteine catalyzed by NIFS was determined in the following ways First, the substrate analogs, L-allylglycine and vinylglycine, were shown to irreversibly inactivate NIFS by formation of a gamma-methylcystathionyl or cystathionyl residue, respectively, through nucleophilic attack by an active site cysteinyl residue on the corresponding analog-pyridoxal phosphate adduct Second, this reactive cysteinyl residue, which is required for L-cysteine desulfurization activity, was identified as Cys325 by the specific alkylation of that residue and by site-directed mutagenesis experiments Third, the formation of an enzyme-bound cysteinyl persulfide was identified as an intermediate in the NIFS-catalyzed reaction Fourth, evidence was obtained for an enamine intermediate in the formation of L-alanine(ABSTRACT TRUNCATED AT 250 WORDS)
TL;DR: In this article, the authors focus on the most important aspects of Dewey's philosophy, including his social behaviorist theory of meaning, his naturalistic metaphysics, philosophy of nature, social constructivism, and transactional realism, and conclude by trying to show how all of these themes converge into the defense of democracy as not only the best form of government but also the best way for the community of educators to conduct and consume educational research.
Abstract: In a recent exchange, Cleo H. Cherryholmes (1992)opposed Rortyan pragmatism to the “scientific realism'” of Ernest R. House (1991, 1992). In my article, I hope to find a middle ground between Cherryholmes and House that might be more attractive to many in the field of education. My article emphasizes some of the most important aspects of Dewey's philosophy, including his social behaviorist theory of meaning, his naturalistic metaphysics, philosophy of nature, social constructivism, and transactional realism. For some reason, most educational theorists, researchers, and practitioners have almost entirely ignored these crucial Deweyan themes, often with disastrous consequences. I will conclude by trying to show how all of these themes converge into Dewey's defense of democracy as not only the best form of government but also the best way for the community of educators to conduct and consume educational research.
TL;DR: A strategy for developing a pig-to-primate xenogeneic transplantation model to test whether the expression of a human complement inhibitor in transgenic pigs could render Xenogeneic organs resistant to hyperacute rejection is demonstrated.
Abstract: The serious shortage of human organs available for transplantation has engendered a heightened interest in the use of animal organs (xenografts) for transplantation. However, the major barrier to successful discordant xenogeneic organ transplantation is the phenomenon of hyperacute rejection. Hyperacute rejection results from the deposition of high-titer preformed antibodies that activate serum complement on the luminal surface of the vascular endothelium, leading to vessel occlusion and graft failure within minutes to hours. Although endogenous membrane-associated complement inhibitors normally protect endothelial cells from autologous complement, they are species restricted and thus confer limited resistance to activated xenogeneic complement. To address the pathogenesis of hyperacute rejection in xenotransplantation, transgenic mice and a transgenic pig were engineered to express the human terminal complement inhibitor hCD59. High-level cell surface expression of hCD59 was achieved in a variety of murine and porcine cell types, most importantly on both large vessel and capillary endothelium. hCD59-expressing porcine cells were significantly resistant to challenge with high-titer anti-porcine antibody and human complement. These experiments demonstrate a strategy for developing a pig-to-primate xenogeneic transplantation model to test whether the expression of a human complement inhibitor in transgenic pigs could render xenogeneic organs resistant to hyperacute rejection.
TL;DR: An experiment was carried out using trained observer-raters to evaluate the levels of drowsiness of drivers, the drivers' faces were recorded on videotape, and results indicate that observer rating are reliable and consistent.
TL;DR: In this article, the authors attribute this situation both to an underappreciation of the utility of algal indicators among non-phycologists and to a lack of standardized methods for monitoring with algae.
Abstract: Despite an increased awareness by governments and the general public of the need for protecting all types of aquatic habitats, human impacts continue to impair the services that these ecosystems provide. Increased monitoring activities that locus on all major biological compartments are needed to quantify the present condition of Earth's aquatic resources and to evaluate the effectiveness of regulations designed to rehabilitate damaged ecosystems. Algae are an ecologically important group in most aquatic ecosystems but are often ignored as indicators of aquatic ecosystem change. We attribute this situation both to an underappreciation of the utility of algal indicators among non-phycologists and to a lack of standardized methods for monitoring with algae.
TL;DR: The majority of the simple sequence repeat (SSR) alleles that were present in high or intermediate frequencies in landraces ultimately survived into modern elite cultivars and hybrids and may be particularly useful for germplasm assessment and evolutionary studies of crop plants.
Abstract: Genetic polymorphisms of ten microsatellite DNA loci were examined among 238 accessions of landraces and cultivars that represent a significant portion of the distribution range for both indica and japonica groups of cultivated rice. In all, 93 alleles were identified with these ten markers. The number of alleles varied from a low of 3 or 4 at each of four loci, to an intermediate value of 9-14 at five loci, and to an extraordinarily high 25 at one locus. The numbers of alleles per locus are much larger than those detected using other types of markers. The number of alleles detected at a locus is significantly correlated with the number of simple sequence repeats in the targeted microsatellite DNA. Indica rice has about 14% more alleles than japonica rice, and such allele number differences are more pronounced in landraces than in cultivars. The indica-japonica differentiation component accounted for about 10% of the diversity in the total sample, and twice as much differentiation was detected in cultivars as in landraces. About two-thirds as many alleles were observed in cultivars as in landraces; another two-thirds of the alleles in the cultivar group were found in modern elite cultivars or parents of hybrid rice. The majority of the simple sequence repeat (SSR) alleles that were present in high or intermediate frequencies in landraces ultimately survived into modern elite cultivars and hybrids. The greater resolving power and the efficient production of massive amounts of SSR data may be particularly useful for germplasm assessment and evolutionary studies of crop plants.
TL;DR: The results presented in this paper provide insight into the statistical distributions of measured path loss by showing the validity of a double regression model with a break point at a distance that has first Fresnel zone clearance for line-of-sight topographies.
Abstract: This paper presents results of wide-band path loss and delay spread measurements for five representative microcellular environments in the San Francisco Bay area at 1900 MHz. Measurements were made with a wide-band channel sounder using a 100-ns probing pulse. Base station antenna heights of 3.7 m, 8.5 m, and 13.3 m were tested with a mobile receiver antenna height of 1.7 m to emulate a typical microcellular scenario. The results presented in this paper provide insight into the statistical distributions of measured path loss by showing the validity of a double regression model with a break point at a distance that has first Fresnel zone clearance for line-of-sight topographies. The variation of delay spread as a function of path loss is also investigated, and a simple exponential overbound model is developed. The path loss and delay spread models are then applied to communication system design allowing outage probabilities, based on path loss or delay spread, to be estimated for a given microcell size. >
TL;DR: Quantitative measurement of ruminally degradable subfractions and estimation of their degradation rates by electrophoretic and densitometric scanning are useful in understanding ruminal degradability of corn proteins.
TL;DR: In this article, the reduction in antinutritional and toxic components in plant foods during fermentation is discussed, such as phytates, tannins, cyanogenic glycosides, oxalates, saponins, lectins and inhibitors of enzymes such as alpha-amylase, trypsin, and chymotrypsin.
TL;DR: The products of the heterogeneous oxidation of Mn(II)aq at hematite, goethite, and albite surfaces were studied, using Scanning Force Microscopy (SFM), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Micro Scopy (SEM), Auger Electron Spectrogram Spectrogram (AES), and X-Ray Diffraction (XRD).
TL;DR: This paper found that the choice of majority ownership is related to owner-specific rather than firm-specific characteristics, which implies that either these firms substitute other organizational constraints on managerial behavior or that majority control is efficient for some firms.
TL;DR: The present paper suggests several changes to the basic genetic algorithm developed previously, and demonstrates reduced computational cost and increased reliability of the algorithm due to these changes.