Showing papers by "Purdue University published in 2002"

PHYTOCHELATINS AND METALLOTHIONEINS: Roles in Heavy Metal Detoxification and Homeostasis

Abstract: ▪ Abstract Among the heavy metal-binding ligands in plant cells the phytochelatins (PCs) and metallothioneins (MTs) are the best characterized. PCs and MTs are different classes of cysteine-rich, heavy metal-binding protein molecules. PCs are enzymatically synthesized peptides, whereas MTs are gene-encoded polypeptides. Recently, genes encoding the enzyme PC synthase have been identified in plants and other species while the completion of the Arabidopsis genome sequence has allowed the identification of the entire suite of MT genes in a higher plant. Recent advances in understanding the regulation of PC biosynthesis and MT gene expression and the possible roles of PCs and MTs in heavy metal detoxification and homeostasis are reviewed.

ORGANIZATIONAL BEHAVIOR: Affect in the Workplace

Abstract: The study of affect in the workplace began and peaked in the 1930s, with the decades that followed up to the 1990s not being particularly fertile. Whereas job satisfaction generally continues to be loosely but not carefully thought of and measured as an affective state, critical work in the 1990s has raised serious questions about the affective status of job satisfaction in terms of its causes as well as its definition and measurement. Recent research has focused on the production of moods and emotions at work, with an emphasis, at least conceptually, on stressful events, leaders, work groups, physical settings, and rewards/punishment. Other recent research has addressed the consequences of workers' feelings, in particular, a variety of performance outcomes (e.g., helping behaviors and creativity). Even though recent interest in affect in the workplace has been intense, many theoretical and methodological opportunities and challenges remain.

Vision for mobile robot navigation: a survey

Abstract: Surveys the developments of the last 20 years in the area of vision for mobile robot navigation. Two major components of the paper deal with indoor navigation and outdoor navigation. For each component, we have further subdivided our treatment of the subject on the basis of structured and unstructured environments. For indoor robots in structured environments, we have dealt separately with the cases of geometrical and topological models of space. For unstructured environments, we have discussed the cases of navigation using optical flows, using methods from the appearance-based paradigm, and by recognition of specific objects in the environment.

High-κ dielectrics for advanced carbon- nanotube transistors and logic gates

Abstract: The integration of materials having a high dielectric constant (high-kappa) into carbon-nanotube transistors promises to push the performance limit for molecular electronics. Here, high-kappa (approximately 25) zirconium oxide thin-films (approximately 8 nm) are formed on top of individual single-walled carbon nanotubes by atomic-layer deposition and used as gate dielectrics for nanotube field-effect transistors. The p-type transistors exhibit subthreshold swings of S approximately 70 mV per decade, approaching the room-temperature theoretical limit for field-effect transistors. Key transistor performance parameters, transconductance and carrier mobility reach 6,000 S x m(-1) (12 microS per tube) and 3,000 cm2 x V(-1) x s(-1) respectively. N-type field-effect transistors obtained by annealing the devices in hydrogen exhibit S approximately 90 mV per decade. High voltage gains of up to 60 are obtained for complementary nanotube-based inverters. The atomic-layer deposition process affords gate insulators with high capacitance while being chemically benign to nanotubes, a key to the integration of advanced dielectrics into molecular electronics.

Hyperspectral image data analysis

Abstract: The fundamental basis for space-based remote sensing is that information is potentially available from the electromagnetic energy field arising from the Earth's surface and, in particular, from the spatial, spectral, and temporal variations in that field. Rather than focusing on the spatial variations, which imagery perhaps best conveys, why not move on to look at how the spectral variations might be used. The idea was to enlarge the size of a pixel until it includes an area that is characteristic from a spectral response standpoint for the surface cover to be discriminated. The article includes an example of an image space representation, using three bands to simulate a color IR photograph of an airborne hyperspectral data set over the Washington, DC, mall.

Tools for privacy preserving distributed data mining

Abstract: Privacy preserving mining of distributed data has numerous applications. Each application poses different constraints: What is meant by privacy, what are the desired results, how is the data distributed, what are the constraints on collaboration and cooperative computing, etc. We suggest that the solution to this is a toolkit of components that can be combined for specific privacy-preserving data mining applications. This paper presents some components of such a toolkit, and shows how they can be used to solve several privacy-preserving data mining problems.

Privacy preserving association rule mining in vertically partitioned data

Abstract: Privacy considerations often constrain data mining projects. This paper addresses the problem of association rule mining where transactions are distributed across sources. Each site holds some attributes of each transaction, and the sites wish to collaborate to identify globally valid association rules. However, the sites must not reveal individual transaction data. We present a two-party algorithm for efficiently discovering frequent itemsets with minimum support levels, without either site revealing individual transaction values.

Recognizing imprecisely localized, partially occluded, and expression variant faces from a single sample per class

Abstract: The classical way of attempting to solve the face (or object) recognition problem is by using large and representative data sets. In many applications, though, only one sample per class is available to the system. In this contribution, we describe a probabilistic approach that is able to compensate for imprecisely localized, partially occluded, and expression-variant faces even when only one single training sample per class is available to the system. To solve the localization problem, we find the subspace (within the feature space, e.g., eigenspace) that represents this error for each of the training images. To resolve the occlusion problem, each face is divided into k local regions which are analyzed in isolation. In contrast with other approaches where a simple voting space is used, we present a probabilistic method that analyzes how "good" a local match is. To make the recognition system less sensitive to the differences between the facial expression displayed on the training and the testing images, we weight the results obtained on each local area on the basis of how much of this local area is affected by the expression displayed on the current test image.

IARC Monographs on the evaluation of carcinogenic risks to humans: Some traditional herbal medicines, some mycotoxins, naphthalene and styrene

Abstract: Members Ahti Anttila, Finnish Cancer Registry, Institute for Statistical and Epidemiological Cancer Research, Liisankatu 21 B, 00170 Helsinki, Finland Ramesh V. Bhat, National Institute of Nutrition, Indian Council of Medical Research, Jamai-Osmania PO, Hyderabad-500 007 AP, India James A. Bond, Chemico-Biological Interactions, Toxcon, 5505 Frenchmans Creek, Durham, NC 27713, USA Susan J. Borghoff, CIIT Centers for Health Research, 6 Davis Drive, Box 12137, Research Triangle Park, NC 27709-2127, USA F. Xavier Bosch, Epidemiology Unit and Cancer Registry, Catalan Institute of Oncology, Av. Gran via s/n, Km. 2.7, 08907 L’Hospitalet del Llobregat, Spain Gary P. Carlson, School of Health Sciences, 1338 Civil Engineering Building, Purdue University, West Lafayette, IN 47907-1338, USA Marcel Castegnaro, Les Collanges, 07240 Saint-Jean-Chambre, France George Cruzan, ToxWorks, 1153 Roadstown Road, Bridgeton, NJ 08302-6640, USA Wentzel C.A. Gelderblom, Programme on Mycotoxins and Experimental Carcinogenesis, Medical Research Council (MRC), PO Box 19070, Tygerberg, South Africa 7505 Ulla Hass, Institute of Food Safety and Toxicology, Morkhoj Bygade 19, 2860 Soborg, Denmark Sara H. Henry, 5100 Paint Branch Parkway, College Park, MD 20740-3835, USA Ronald A. Herbert, Laboratory of Experimental Pathology, National Institute of Environmental Health Sciences, PO Box 12233, Mail Drop B3-08, Research Triangle Park, NC 27709-2233, USA Marc Jackson, Integrated Laboratory Systems, Inc., PO Box 13501, Research Triangle Park, NC 27709, USA IARC WORKING GROUP ON THE EVALUATION OF CARCINOGENIC RISKS TO HUMANS: SOME TRADITIONAL HERBAL MEDICINES, SOME MYCOTOXINS, NAPHTHALENE AND STYRENE

Mapping and analysis of quantitative trait loci in experimental populations

Abstract: Simple statistical methods for the study of quantitative trait loci (QTL), such as analysis of variance, have given way to methods that involve several markers and high-resolution genetic maps. As a result, the mapping community has been provided with statistical and computational tools that have much greater power than ever before for studying and locating multiple and interacting QTL. Apart from their immediate practical applications, the lessons learnt from this evolution of QTL methodology might also be generally relevant to other types of functional genomics approach that are aimed at the dissection of complex phenotypes, such as microarray assessment of gene expression.

Who Is Selling the Ivory Tower? Sources of Growth in University Licensing

Abstract: Historically, commercial use of university research has been viewed in terms of spillovers. Recently, there has been a dramatic increase in technology transfer through licensing as universities attempt to appropriate the returns from faculty research. This change has prompted concerns regarding the source of this growth-specifically, whether it suggests a change in the nature of university research. We develop an intermediate input model to examine the extent to which the growth in licensing is due to the productivity of observable inputs or driven by a change in the propensity of faculty and administrators to engage in commercializing university research. We model licensing as a three-stage process, each involving multiple inputs. Nonparametric programming techniques are applied to survey data from 64 universities to calculate total factor productivity (TFP) growth in each stage. To examine the sources of TFP growth, the productivity analysis is augmented by survey evidence from businesses who license-in university inventions. Results suggest that increased licensing is due primarily to an increased willingness of faculty and administrators to license and increased business reliance on external R&D rather than a shift in faculty research.

The “Pull” of Tourism Destinations: A Means-End Investigation

Abstract: Means-end theory provides a practical framework for examining the relationships between the pull attributes of a destination (i.e., “the means”) and the higher level motivational forces important to the individual traveler (“the ends”). To the extent that these higher level forces correspond to the push factors that influenced one’s decision to travel in the first place, the means-end perspective provides a useful alternative approach for examining the relationship between push and pull factors in motivating and guiding travel behavior. This article examines the potential of using the means-end approach to examine push-pull relationships, demonstrates the use of the approach in an empirical study of spring break destination choice, and discusses key implications for future research and application.

Multiobjective optimization using dynamic neighborhood particle swarm optimization

Abstract: This paper presents a particle swarm optimization (PSO) algorithm for multiobjective optimization problems. PSO is modified by using a dynamic neighborhood strategy, new particle memory updating, and one-dimension optimization to deal with multiple objectives. Several benchmark cases were tested and showed that PSO could efficiently find multiple Pareto optimal solutions.

Applying extinction research and theory to cue-exposure addiction treatments

Abstract: Aims To evaluate the efficacy of cue-exposure addiction treatment and review modern animal learning research to generate recommendations for substantially enhancing the effectiveness of this treatment. Design Meta-analysis of cue-exposure addiction treatment outcome studies (N = 9), review of animal extinction research and theory, and evaluation of whether major principles from this literature are addressed adequately in cue-exposure treatments. Findings The meta-analytical review showed that there is no consistent evidence for the efficacy of cue-exposure treatment as currently implemented. Moreover, procedures derived from the animal learning literature that should maximize the potential of extinction training are rarely used in cue-exposure treatments. Conclusions Given what is known from animal extinction theory and research about extinguishing learned behavior, it is not surprising that cue-exposure treatments so often fail. This paper reviews current animal research regarding the most salient threats to the development and maintenance of extinction, and suggests several major procedures for increasing the efficacy of cue-exposure addiction treatment.

Tensile mechanical properties of three-dimensional type I collagen extracellular matrices with varied microstructure.

Abstract: The importance and priority of specific micro-structural and mechanical design parameters must be established to effectively engineer scaffolds (biomaterials) that mimic the extracellular matrix (ECM) environment of cells and have clinical applications as tissue substitutes. In this study, three-dimensional (3-D) matrices were prepared from type I collagen, the predominant compositional and structural component of connective tissue ECMs, and structural-mechanical relationships were studied. Polymerization conditions, including collagen concentration (0.3-3 mg/mL) and pH (6-9), were varied to obtain matrices of collagen fibrils with different microstructures. Confocal reflection microscopy was used to assess specific micro-structural features (e.g., diameter and length) and organization of component fibrils in 3-D. Microstructural analyses revealed that changes in collagen concentration affected fibril density while maintaining a relatively constant fibril diameter. On the other hand, both fibril length and diameter were affected by the pH of the polymerization reaction. Mechanically, all matrices exhibited a similar stress-strain curve with identifiable "toe," "linear," and "failure" regions. However the linear modulus and failure stress increased with collagen concentration and were correlated with an increase in fibril density. Additionally, both the linear modulus and failure stress showed an increase with pH, which was related to an increasedfibril length and a decreasedfibril diameter. The tensile mechanical properties of the collagen matrices also showed strain rate dependence. Such fundamental information regarding the 3-D microstructural-mechanical properties of the ECM and its component molecules are important to our overall understanding of cell-ECM interactions (e.g., mechanotransduction) and the development of novel strategies for tissue repair and replacement.

Friendship Quality and Social Development

Abstract: A high-quality friendship is characterized by high levels of prosocial behavior, intimacy, and other positive features, and low levels of conflicts, rivalry, and other negative features. Friendship quality has been assumed to have direct effects on many aspects of children's social development, including their self-esteem and social adjustment. Recent research suggests, however, that friendship quality affects primarily children's success in the social world of peers. Friendship quality could also have indirect effects, by magnifying or diminishing the influence of friends on each other's attitudes and behaviors. Having high-quality friendships may lessen children's tendencies to imitate the behavior of shy and withdrawn friends, but little evidence supports the hypothesis that high-quality friendships magnify friends’ influence.

GTAP-E: An Energy-Environmental Version of the GTAP Model

Abstract: Energy is an important commodity in many economic activities. Its usage affects the environment via CO2 emissions and the Greenhouse Effect. Modeling the energy-economy-environment-trade linkages is an important objective in applied economic policy analysis. Previously, however, the modeling of these linkages in GTAP has been incomplete. This is because energy substitution, a key factor in this chain of linkages, is absent from the standard model specification. This technical paper remedies this deficiency by incorporating energy substitution into the standard GTAP model. It begins by first reviewing some of the existing approaches to this problem in contemporary CGE models. It then suggests an approach for GTAP which incorporates some of these desirable features of energy substitution. The approach is implemented as an extended version of the GTAP model called GTAP-E, which includes the standard GTAP model as a special case. In addition, GTAP-E incorporates carbon emissions from the combustion of fossil fuels and this revised version of GTAP-E provides for a mechanism to trade these emissions internationally. The resulting behavior of agents in the model is analyzed using general equilibrium demand elasticities which summarize the combined effect of the new model specification. Implications for policy analysis are demonstrated via a simple simulation experiment in which global carbon emissions are reduced via a carbon tax. Results show that incorporating energy substitution into GTAP is essential for conducting analysis of this problem. The policy relevance of GTAP-E in the context of the existing debate about climate change is illustrated by some simulations of the implementation of the Kyoto Protocol. It is hoped that the proposed model will be used by individuals in the GTAP network who may not be themselves energy modelers, but who require a better representation of the energy-economy linkages than is currently offered in the standard GTAP model.

Simple Cu(I) complexes with unprecedented excited-state lifetimes.

Abstract: This report describes new, readily accessible copper(I) complexes that can exhibit unusually long-lived, high quantum yield emissions in fluid solution. The complexes are of the form [Cu(NN)(POP)]+ where NN denotes 1,10-phenanthroline (phen), 2,9-dimethyl-1,10-phenanthroline (dmp) or 2,9-di-n-butyl-1,10-phenanthroline (dbp) and POP denotes bis[2-(diphenylphosphino)phenyl] ether. Modes of characterization include X-ray crystallography and cyclic voltammetry. The complexes each have a pseudotetrahedral coordination geometry and a Cu(II)/Cu(I) potential upward of +1.2 V vs Ag/AgCl. In room-temperature dichloromethane solution, charge-transfer excited states of the dmp and dbp derivatives exhibit respective emission quantum yields of 0.15 and 0.16 and corresponding excited-state lifetimes of 14.3 and 16.1 μs, respectively. Despite the fact that coordinating solvents usually quench charge-transfer emission from copper systems, the photoexcited dmp (dbp) complex retains a lifetime of 2.4 μs (5.4 μs) in methanol.