Showing papers by "University of Missouri published in 2003"

Localization from mere connectivity

Abstract: It is often useful to know the geographic positions of nodes in a communications network, but adding GPS receivers or other sophisticated sensors to every node can be expensive. We present an algorithm that uses connectivity information who is within communications range of whom to derive the locations of the nodes in the network. The method can take advantage of additional information, such as estimated distances between neighbors or known positions for certain anchor nodes, if it is available. The algorithm is based on multidimensional scaling, a data analysis technique that takes O(n3) time for a network of n nodes. Through simulation studies, we demonstrate that the algorithm is more robust to measurement error than previous proposals, especially when nodes are positioned relatively uniformly throughout the plane. Furthermore, it can achieve comparable results using many fewer anchor nodes than previous methods, and even yields relative coordinates when no anchor nodes are available.

Distinct Cysteine Residues in Keap1 Are Required for Keap1-Dependent Ubiquitination of Nrf2 and for Stabilization of Nrf2 by Chemopreventive Agents and Oxidative Stress

Abstract: A common feature of diverse chemopreventive agents is the ability to activate expression of a genetic program that protects cells from reactive chemical species that, if left unchecked, would cause mutagenic DNA damage. The bZIP transcription factor Nrf2 has emerged as a key regulator of this cancer-preventive genetic program. Nrf2 is normally sequestered in the cytoplasm by a protein known as Keap1. Chemopreventive agents allow Nrf2 to escape from Keap1-mediated repression, although the molecular mechanism(s) responsible for activation of Nrf2 is not understood. In this report, we demonstrate that Keap1 does not passively sequester Nrf2 in the cytoplasm but actively targets Nrf2 for ubiquitination and degradation by the proteosome under basal culture conditions. We have identified two critical cysteine residues in Keap1, C273 and C288, that are required for Keap1-dependent ubiquitination of Nrf2. Both sulforaphane, a chemopreventive isothiocyanate, and oxidative stress enable Nrf2 to escape Keap1-dependent degradation, leading to stabilization of Nrf2, increased nuclear localization of Nrf2, and activation of Nrf2-dependent cancer-protective genes. We have identified a third cysteine residue in Keap1, C151, that is uniquely required for inhibition of Keap1-dependent degradation of Nrf2 by sulforaphane and oxidative stress. This cysteine residue is also required for a novel posttranslational modification to Keap1 that is induced by oxidative stress. We propose that Keap1 is a component of a novel E3 ubiquitin ligase complex that is specifically targeted for inhibition by both chemopreventive agents and oxidative stress.

Nrf2 is a direct PERK substrate and effector of PERK-dependent cell survival.

Abstract: Activation of PERK following the accumulation of unfolded proteins in the endoplasmic reticulum (ER) promotes translation inhibition and cell cycle arrest. PERK function is essential for cell survival following exposure of cells to ER stress, but the mechanisms whereby PERK signaling promotes cell survival are not thoroughly understood. We have identified the Nrf2 transcription factor as a novel PERK substrate. In unstressed cells, Nrf2 is maintained in the cytoplasm via association with Keap1. PERK-dependent phosphorylation triggers dissociation of Nrf2/Keap1 complexes and inhibits reassociation of Nrf2/Keap1 complexes in vitro. Activation of PERK via agents that trigger the unfolded protein response is both necessary and sufficient for dissociation of cytoplasmic Nrf2/Keap1 and subsequent Nrf2 nuclear import. Finally, we demonstrate that cells harboring a targeted deletion of Nrf2 exhibit increased cell death relative to wild-type counterparts following exposure to ER stress. Our data demonstrate that Nrf2 is a critical effector of PERK-mediated cell survival.

Too Busy to Mind the Business? Monitoring by Directors with Multiple Board Appointments

Abstract: We examine the number of external appointments held by corporate directors. Directors who serve larger firms and sit on larger boards are more likely to attract directorships. Consistent with Fama and Jensen (1983), we find that firm performance has a positive effect on the number of appointments held by a director. We find no evidence that multiple directors shirk their responsibilities to serve on board committees. We do not find that multiple directors are associated with a greater likelihood of securities fraud litigation. We conclude that the evidence does not support calls for limits on directorships held by an individual. INSTITUTIONAL INVESTORS AND SHAREHOLDER ACTIVISTS criticize firms for appointing directors who hold directorships in multiple companies, contending that such directors are incapable of effectively monitoring the management of so many firms. Informed observers such as ChancellorWilliam Allen (1992) of the Delaware Court of Chancery argue that "effective monitoring requires a commitment of time and resources ... The demands of the position, if properly understood, are inconsistent in my opinion, with service on an impressively long list of boards (p. 457)" Corporate governance activists echo these criticisms and propose specific limits to deal with the perceived problem. The Council of Institutional Investors (1998) argues that in the absence of unusual and highly specific circumstances, directors with full-time jobs should not serve on more than two other boards. The National Association of Corporate Directors (1996) is more lenient, suggesting that directors with full-time positions should not serve on more than three or four other boards. The Business Roundtable (1997), by contrast, believes that limits on the number of directorships are ill advised. Directors themselves disagree over the issue of multiple directorships. The most commonly shared complaint among directors, according to Lipton and

Body mass index, serum sex hormones, and breast cancer risk in postmenopausal women.

Abstract: Body mass index, serum sex hormones, and breast cancer risk in postmenopausal women. Background: Obesity is associated with increased breast cancer risk among postmenopausal women. We examined whether this association could be explained by the relationship of body mass index (BMI) with serum sex hormone concentrations. Methods: We analyzed individual data from eight prospective studies of postmenopausal women. Data on BMI and prediagnostic estradiol levels were available for 624 case subjects and 1669 control subjects; data on the other sex hormones were available for fewer subjects. The relative risks (RRs) with 95% confidence intervals (CIs) of breast cancer associated with increasing BMI were estimated by conditional logistic regression on case- control sets, matched within each study for age and recruitment date, and adjusted for parity. All statistical tests were two- sided. Results: Breast cancer risk increased with increasing BMI (P-trend = .002), and this increase in RR was substantially reduced by adjustment for serum estrogen concentrations. Adjusting for free estradiol reduced the RR for breast cancer associated with a 5 kg/m(2) increase in BMI from 1.19 (95% CI = 1.05 to 1.34) to 1.02 (95% CI = 0.89 to 1.17). The increased risk was also substantially reduced after adjusting for other estrogens (total estradiol, non-sex hormone-binding globulin- bound estradiol, estrone, and estrone sulfate), and moderately reduced after adjusting for sex hormone-binding globulin, whereas adjustment for the androgens (androstenedione, dehydroepiandrosterone, dehydroepiandrosterone sulfate, and testosterone) had little effect on the excess risk. Conclusion: The results are compatible with the hypothesis that the increase in breast cancer risk with increasing BMI among postmenopausal women is largely the result of the associated increase in estrogens, particularly bioavailable estradiol.

Friction stir processing: a novel technique for fabrication of surface composite

Abstract: A novel surface modifying technique, friction stir processing (FSP), has been developed for fabrication of surface composite. Al–SiC surface composites with different volume fractions of particles were successfully fabricated. The thickness of the surface composite layer ranged from 50 to 200 μm. The SiC particles were uniformly distributed in the aluminum matrix. The surface composites have excellent bonding with the aluminum alloy substrate. The microhardness of the surface composite reinforced with 27vol.%SiC of 0.7 μm average particle size was ∼173 HV, almost double of the 5083Al alloy substrate (85 HV). The solid-state processing and very fine microstructure that results are also desirable for high performance surface composites.

Leading us not unto temptation: momentary allurements elicit overriding goal activation.

Abstract: The present research explored the nature of automatic associations formed between short-term motives (temptations) and the overriding goals with which they interfere. Five experimental studies, encompassing several self-regulatory domains, found that temptations tend to activate such higher priority goals, whereas the latter tend to inhibit the temptations. These activation patterns occurred outside of participants' conscious awareness and did not appear to tax their mental resources. Moreover, they varied as a function of subjective goal importance and were more pronounced for successful versus unsuccessful self-regulators in a given domain. Finally, priming by temptation stimuli was found not only to influence the activation of overriding goals but also to affect goal-congruent behavioral choices.

Sensor networks: an overview

Abstract: Advances in hardware and wireless network technologies have created low-cost, low-power, multifunctional miniature sensor devices. These devices make up hundreds or thousands of ad hoc tiny sensor nodes spread across a geographical area. These sensor nodes collaborate among themselves to establish a sensing network. A sensor network can provide access to information anytime, anywhere by collecting, processing, analyzing and disseminating data. Thus, the network actively participates in creating a smart environment.

The complete genome sequence of the Arabidopsis and tomato pathogen Pseudomonas syringae pv. tomato DC3000

Abstract: We report the complete genome sequence of the model bacterial pathogen Pseudomonas syringae pathovar tomato DC3000 (DC3000), which is pathogenic on tomato and Arabidopsis thaliana. The DC3000 genome (6.5 megabases) contains a circular chromosome and two plasmids, which collectively encode 5,763 ORFs. We identified 298 established and putative virulence genes, including several clusters of genes encoding 31 confirmed and 19 predicted type III secretion system effector proteins. Many of the virulence genes were members of paralogous families and also were proximal to mobile elements, which collectively comprise 7% of the DC3000 genome. The bacterium possesses a large repertoire of transporters for the acquisition of nutrients, particularly sugars, as well as genes implicated in attachment to plant surfaces. Over 12% of the genes are dedicated to regulation, which may reflect the need for rapid adaptation to the diverse environments encountered during epiphytic growth and pathogenesis. Comparative analyses confirmed a high degree of similarity with two sequenced pseudomonads, Pseudomonas putida and Pseudomonas aeruginosa, yet revealed 1,159 genes unique to DC3000, of which 811 lack a known function.

The Roles of Auxin Response Factor Domains in Auxin-Responsive Transcription

Abstract: Auxin response factors (ARFs) are transcription factors that bind to TGTCTC auxin response elements in promoters of early auxin response genes. ARFs have a conserved N-terminal DNA binding domain (DBD) and in most cases a conserved C-terminal dimerization domain (CTD). The ARF CTD is related in amino acid sequence to motifs III and IV found in Aux/IAA proteins. Just C terminal to the DBD, ARFs contain a nonconserved region referred to as the middle region (MR), which has been proposed to function as a transcriptional repression or activation domain. Results with transfected protoplasts reported here show that ARFs with Q-rich MRs function as activators, whereas most, if not all other ARFs, function as repressors. ARF DBDs alone are sufficient to recruit ARFs to their DNA target sites, and auxin does not influence this recruitment. ARF MRs alone function as activation or repression domains when targeted to reporter genes via a yeast Gal4 DBD, and auxin does not influence the potency of activation or repression. ARF CTDs, along with a Q-rich MR, are required for an auxin response whether the MRs plus CTDs are recruited to a promoter by an ARF DBD or by a Gal4 DBD. The auxin response is mediated by the recruitment of Aux/IAA proteins to promoters that contain a DNA binding protein with a Q-rich MR and an attached CTD.

Biological Criteria for Buffer Zones around Wetlands and Riparian Habitats for Amphibians and Reptiles

Abstract: Terrestrial habitats surrounding wetlands are critical to the management of natural resources. Al- though the protection of water resources from human activities such as agriculture, silviculture, and urban development is obvious, it is also apparent that terrestrial areas surrounding wetlands are core habitats for many semiaquatic species that depend on mesic ecotones to complete their life cycle. For purposes of conser- vation and management, it is important to define core habitats used by local breeding populations surround- ing wetlands. Our objective was to provide an estimate of the biologically relevant size of core habitats sur- rounding wetlands for amphibians and reptiles. We summarize data from the literature on the use of terrestrial habitats by amphibians and reptiles associated with wetlands (19 frog and 13 salamander species representing 1363 individuals; 5 snake and 28 turtle species representing more than 2245 individuals). Core terrestrial habitat ranged from 159 to 290 m for amphibians and from 127 to 289 m for reptiles from the edge of the aquatic site. Data from these studies also indicated the importance of terrestrial habitats for feed- ing, overwintering, and nesting, and, thus, the biological interdependence between aquatic and terrestrial habitats that is essential for the persistence of populations. The minimum and maximum values for core hab- itats, depending on the level of protection needed, can be used to set biologically meaningful buffers for wet- land and riparian habitats. These results indicate that large areas of terrestrial habitat surrounding wetlands are critical for maintaining biodiversity.

The Effects of Firm‐Wide and Office‐Level Industry Expertise on Audit Pricing

Abstract: This study examines the role of auditor industry expertise in the pricing of Big 5 audits in Australia. We test if the audit market prices an auditor's firm‐wide industry expertise, or alternatively if the audit market only prices office‐level expertise in those specific cities where the auditor is the industry leader. We document that there is an average premium of 24 percent associated with industry expertise when the auditor is both the city‐specific industry leader and one of the top two firms nationally in the industry. However, the top two firms nationally do not earn a premium in cities where they are not city leaders. We further document that national leadership rankings are, in fact, driven by the specific offices where accounting firms are city leaders. Thus, the overall evidence supports that the market perception and pricing of industry expertise in Australia is primarily based on office‐level industry leadership in city‐specific audit markets.

Simulation models with correct statistical properties for Rayleigh fading channels

Abstract: In this paper, new sum-of-sinusoids statistical simulation models are proposed for Rayleigh fading channels. These new models employ random path gain, random initial phase, and conditional random Doppler frequency for all individual sinusoids. It is shown that the autocorrelations and cross correlations of the quadrature components, and the autocorrelation of the complex envelope of the new simulators match the desired ones exactly, even if the number of sinusoids is as small as a single-digit integer. Moreover, the probability density functions of the envelope and phase, the level crossing rate, the average fade duration, and the autocorrelation of the squared fading envelope which contains fourth-order statistics of the new simulators, asymptotically approach the correct ones as the number of sinusoids approaches infinity, while good convergence is achieved even when the number of sinusoids is as small as eight. The new simulators can be directly used to generate multiple uncorrelated fading waveforms for frequency selective fading channels, multiple-input multiple-output channels, and diversity combining scenarios. Statistical properties of one of the new simulators are evaluated by numerical results, finding good agreements.

Firm reputation and applicant pool characteristics

Abstract: Scholars have suggested that a firm's reputation can provide it with a competitive advantage by attracting more, and possibly higher-caliber, applicants. No research has actually investigated this relationship, however, in large part because researchers have not assessed applicant pool characteristics but instead have measured applicants' intentions. Therefore, we conducted two studies to investigate whether organizational reputation influenced the number and the quality of applicants actually seeking positions with firms. Company reputation was operationalized using two different published reputation measures, and applicant quality data were obtained from career services offices at business schools at two universities. Results from both studies supported the previously untested belief that firms with better reputations attract more applicants. Furthermore, some evidence suggested that firms with better reputations could select higher-quality applicants. Copyright © 2003 John Wiley & Sons, Ltd.

The Value of Organizational Reputation in the Recruitment Context: A Brand-Equity Perspective

Abstract: We extend the recruitment literature by examining how and why firms’ reputations affect job seekers, and by expanding the outcome variables that can be used to judge recruitment success. Results from 339 individuals suggested that job seekers’ reputation perceptions affected job pursuit because (a) individuals use reputation as a signal about job attributes, and (b) reputation affects the pride that individuals expect from organizational membership. Moreover, individuals were willing to pay a premium in the form of lower wages to join firms with positive reputations, and individuals’ familiarity with organizations affected the amount of information they could recall about a recruitment job posting after 1 week. Finally, the results suggested that reputation advertising did not affect job seekers’ reputation perceptions, suggesting that past research on fictitious companies may not generalize to actual organizations.

Metasynthesis: The State of the Art—So Far

Abstract: To make qualitative results more accessible to clinicians, researchers, and policy makers, individuals are urged to synthesize findings from related studies. Since 1994, several types of metasynthesis have been conducted, resulting in theory building, theory explication, and substantive descriptions of phenomena. A variety of methodologies have been used to complete these projects, as no firm metasynthesis guidelines exist. As such, the purpose of this article is to discuss recently completed works and draw inferences regarding key methodological elements and research study integrity. The author also offers suggestions for future investigations.

The value of knowledge and the pursuit of understanding

Abstract: Epistemology has for a long time focused on the concept of knowledge and tried to answer questions such as whether knowledge is possible and how much of it there is. Often missing from this inquiry, however, is a discussion on the value of knowledge. In The Value of Knowledge and the Pursuit of Understanding Jonathan Kvanvig argues that epistemology properly conceived cannot ignore the question of the value of knowledge. He also questions one of the most fundamental assumptions in epistemology, namely that knowledge is always more valuable than the value of its subparts. Taking Platos' Meno as a starting point of his discussion, Kvanvig tackles the different arguments about the value of knowledge and comes to the conclusion that knowledge is less valuable than generally assumed. Clearly written and well argued, this 2003 book will appeal to students and professionals in epistemology.

Institutional Ownership Differences and International Diversification: The Effects of Boards of Directors and Technological Opportunity

Abstract: We examined the roles of institutional investors, boards of directors, and technological opportunity in relation to international diversification. Our research contributes to both agency and foreign direct investment theories. In data on 197 large U.S. firms, we found significant relationships between institutional ownership and international diversification. International diversification was favored by (1) professional investment funds along with outside board members and (2) pension funds along with inside board members. Also, pension funds' long-term orientation facilitated internationalization in industries with high technological opportunities. The results suggest that different institutional owners have different stakes in firms' international strategies, and the effects of boards of directors and technological opportunity accentuate these differences.

Suppression of skeletal muscle lipoprotein lipase activity during physical inactivity: a molecular reason to maintain daily low-intensity activity

Abstract: We have examined the regulation of lipoprotein lipase (LPL) activity in skeletal muscle during physical inactivity in comparison to low-intensity contractile activity of ambulatory controls. From studies acutely preventing ambulatory activity of one or both the hindlimbs in rats, it was shown that ≈90–95 % of the heparin-releasable (HR) LPL activity normally present in rat muscle with ambulatory activity is lost, and thus dependent on local contractile activity. Similarly, ≈95 % of the differences in LPL activity between muscles of different fibre types was dependent on ambulatory activity. The robustness of the finding that physical inactivity significantly decreases muscle LPL activity was evident from confirmatory studies with different models of inactivity, in many rats and mice, both sexes, three muscle types and during both acute and chronic (11 days) treatment. Inactivity caused a local reduction of plasma [3H]triglyceride uptake into muscle and a decrease in high density lipoprotein cholesterol concentration. LPL mRNA was not differentially expressed between ambulatory controls and either the acutely or chronically inactive groups. Instead, the process involved a rapid loss of the HR-LPL protein mass (the portion of LPL largely associated with the vascular endothelium) by an actinomycin D-sensitive signalling mechanism (i.e. transcriptionally dependent process). Significant decreases of intracellular LPL protein content lagged behind the loss of HR-LPL protein. Treadmill walking raised LPL activity ≈8-fold (P < 0.01) within 4 h after inactivity. The striking sensitivity of muscle LPL to inactivity and low-intensity contractile activity may provide one piece of the puzzle for why inactivity is a risk factor for metabolic diseases and why even non-vigorous activity provides marked protection against disorders involving poor lipid metabolism.

In Search of the Molecular Basis of Heterosis

Abstract: Heterosis, or hybrid vigor, refers to the phenomenon that progeny of diverse inbred varieties exhibit greater biomass, speed of development, and fertility than the better of the two parents ([Figure 1][1]). This phenomenon has been exploited extensively in crop production and has been a powerful

Personality and the predisposition to engage in risky or problem behaviors during adolescence.

Abstract: Longitudinal data from a representative sample of 1,978 Black and White adolescents were used to examine the role of personality in multiple risk or problem behaviors. Results indicate that covariation among diverse behaviors (educational underachievement, delinquent behavior, substance use, sexual behavior) can be adequately modeled by a single higher order factor, and that impulsivity and avoidance coping serve as generalized risk factors for involvement in these behaviors. Whereas none of the personality variables examined explained change in problem behaviors once established, avoidance coping prospectively predicted involvement among a subgroup of adolescents with little or no prior involvement. Results suggest that dysfunctional styles of regulating emotions and emotionally driven behaviors are core features of risky or problem behaviors during adolescence.

Outcomes of early language delay: I. Predicting persistent and transient language difficulties at 3 and 4 years.

Abstract: Parent-based assessments of vocabulary, grammar, nonverbal ability, and use of language to refer to past and future (displaced reference) were obtained for 8,386 twin children at 2 years of age. Ch...

Gender and e-commerce: an exploratory study

Abstract: The authors consider the role of gender as it relates to e-commerce and offer a conceptual framework that attempts to explain why women are less satisfied than men with the online shopping experience. Perceived emotional benefits are discussed as a primary reason women lack support for e-commerce activity. Additional concepts in our model include trust (i.e., skepticism) and practicality (i.e., convenience). Our survey findings revealed that these three concepts—emotion, trust, and convenience—predicted women9s dissatisfaction (and men9s satisfaction) with online shopping, as well as men and women9s actual shopping behavior. The authors offer ideas to help e-marketers form stronger emotional bonds with female shoppers.

Measuring Anxiety in Athletics: The Revised Competitive State Anxiety Inventory–2

Abstract: The purpose of this study was to use confirmatory factor analysis (CFA) to revise the factor structure of the CSAI-2 using one data set, and then to use CFA to validate the revised structure using a second data set. The first data set (calibration sample) consisted of 503 college-age intramural athletes, and the second (validation sample) consisted of 331 intercollegiate (Division I) and interscholastic athletes. The results of the initial CFA on the calibration sample resulted in a poor fit to the data. Using the Lagrange Multiplier Test (Gamma) as a guide, CSAI-2 items that loaded on more than one factor were sequentially deleted. The resulting 17-item revised CSAI-2 was then subjected to a CFA using the validation data sample. The results of this CFA revealed a good fit of the data to the model (CFI = .95, NNFI = .94, RMSEA = .054). It is suggested that the CSAI-2R instead of the CSAI-2 be used by researchers and practitioners for measuring competitive state anxiety in athletes.