Showing papers by "Clemson University published in 2006"

Quantum-sized carbon dots for bright and colorful photoluminescence.

Abstract: We report that nanoscale carbon particles (carbon dots) upon simple surface passivation are strongly photoluminescent in both solution and the solid state. The luminescence emission of the carbon dots is stable against photobleaching, and there is no blinking effect. These strongly emissive carbon dots may find applications similar to or beyond those of their widely pursued silicon counterparts.

How Important are Job Attitudes? Meta-Analytic Comparisons of Integrative Behavioral Outcomes and Time Sequences

Abstract: Drawing on the compatibility principle in attitude theory, we propose that overall job attitude (job satisfaction and organizational commitment) provides increasingly powerful prediction of more integrative behavioral criteria (focal performance, contextual performance, lateness, absence, and turnover combined). The principle was sustained by a combination of meta-analysis and structural equations showing better fit of unified versus diversified models of meta-analytic correlations between those criteria. Overall job attitude strongly predicted a higher-order behavioral construct, defined as desirable contributions made to one’s work role (r .59). Time-lagged data also supported this unified, attitude-engagement model.

Kinematics for multisection continuum robots

Abstract: We introduce a new method for synthesizing kinematic relationships for a general class of continuous backbone, or continuum , robots. The resulting kinematics enable real-time task and shape control by relating workspace (Cartesian) coordinates to actuator inputs, such as tendon lengths or pneumatic pressures, via robot shape coordinates. This novel approach, which carefully considers physical manipulator constraints, avoids artifacts of simplifying assumptions associated with previous approaches, such as the need to fit the resulting solutions to the physical robot. It is applicable to a wide class of existing continuum robots and models extension, as well as bending, of individual sections. In addition, this approach produces correct results for orientation, in contrast to some previously published approaches. Results of real-time implementations on two types of spatial multisection continuum manipulators are reported.

Application of inkjet printing to tissue engineering.

Abstract: Recent advances in organ printing technology for applications relating to medical interventions and organ replacement are described. Organ printing refers to the placement of various cell types into a soft scaffold fabricated according to a computer-aided design template using a single device. Computer aided scaffold topology design has recently gained attention as a viable option to achieve function and mass transport requirements within tissue engineering scaffolds. An exciting advance pioneered in our laboratory is that of simultaneous printing of cells and biomaterials, which allows precise placement of cells and proteins within 3-D hydrogel structures. This advance raises the possibility of spatially controlling not only the scaffold structure, but also the type of tissue that can be grown within the scaffold and the thickness of the tissue as capillaries and vessels could be constructed within the scaffolds. Here we summarize recent advances in printing cells and materials using the same device.

Variational formulation for the stationary fractional advection dispersion equation

Abstract: In this article a theoretical framework for the Galerkin finite element approximation to the steady state fractional advection dispersion equation is presented. Appropriate fractional derivative spaces are defined and shown to be equivalent to the usual fractional dimension Sobolev spaces Hs. Existence and uniqueness results are proven, and error estimates for the Galerkin approximation derived. Numerical results are included that confirm the theoretical estimates. © 2005 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2005

Emergent Properties of Reduced-Genome Escherichia coli

Abstract: With the use of synthetic biology, we reduced the Escherichia coli K-12 genome by making planned, precise deletions. The multiple-deletion series (MDS) strains, with genome reductions up to 15%, were designed by identifying nonessential genes and sequences for elimination, including recombinogenic or mobile DNA and cryptic virulence genes, while preserving good growth profiles and protein production. Genome reduction also led to unanticipated beneficial properties: high electroporation efficiency and accurate propagation of recombinant genes and plasmids that were unstable in other strains. Eradication of stress-induced transposition evidently stabilized the MDS genomes and provided some of the new properties.

Radioactive 26Al from massive stars in the Galaxy.

Abstract: Gamma-rays from radioactive 26Al (half-life approximately 7.2 x 10(5) years) provide a 'snapshot' view of continuing nucleosynthesis in the Galaxy. The Galaxy is relatively transparent to such gamma-rays, and emission has been found concentrated along its plane. This led to the conclusion that massive stars throughout the Galaxy dominate the production of 26Al. On the other hand, meteoritic data show evidence for locally produced 26Al, perhaps from spallation reactions in the protosolar disk. Furthermore, prominent gamma-ray emission from the Cygnus region suggests that a substantial fraction of Galactic 26Al could originate in localized star-forming regions. Here we report high spectral resolution measurements of 26Al emission at 1808.65 keV, which demonstrate that the 26Al source regions corotate with the Galaxy, supporting its Galaxy-wide origin. We determine a present-day equilibrium mass of 2.8 (+/- 0.8) solar masses of 26Al. We use this to determine that the frequency of core collapse (that is, type Ib/c and type II) supernovae is 1.9 (+/- 1.1) events per century.

Antecedents and outcomes of strategic IS alignment: an empirical investigation

Abstract: Prior research argues that alignment between business and information systems (IS) strategies enhances organizational performance. However, factors affecting alignment have received relatively little empirical attention. Moreover, IS strategic alignment is assumed to facilitate the performance of all organizations, regardless of type or business strategy. By using two studies of business firms and academic institutions, this paper: 1) develops and tests a model relating alignment, its antecedents, and its consequences and 2) examines differences in these relationships across organizational types and strategies. Findings indicate that alignment depends on shared domain knowledge and prior IS success, and also support the expected positive impact of alignment on organizational performance. Differences across Prospector, Analyzer, and Defender business strategies are examined. A key research contribution is the empirical demonstration that the importance of alignment, as well as the mechanisms used to attain alignment, vary by business strategy and industry. In past alignment studies, controlling for industry has not been uncommon. The findings suggest that future research studies should also control for business strategy. The article also empirically demonstrates that past implementation success influences alignment. In addition, it highlights the influence of a process variable, strategic planning, on the development of shared knowledge and, consequently, on alignment. This paper examines strategic issues related to the management of technology. Data from multiple surveys are used to test the extent to which strategic planning, shared business-IS knowledge, prior IS success, and other variables consistently enhance IS alignment. The study also provides empirical support for the popular argument that IS alignment improves organizational performance. It extends the current literature by examining the extent to which these findings hold across firm strategies and industries. The authors argue that not all firms are equally well served by allocating scarce resources to improve IS alignment.

Visual representations in science education: The influence of prior knowledge and cognitive load theory on instructional design principles

Abstract: Visual representations are essential for communicating ideas in the science classroom; however, the design of such representations is not always beneficial for learners. This paper presents instructional design considerations providing empirical evidence and integrating theoretical concepts related to cognitive load. Learners have a limited working memory, and instructional representations should be designed with the goal of reducing unnecessary cognitive load. However, cognitive architecture alone is not the only factor to be considered; individual differences, especially prior knowledge, are critical in determining what impact a visual representation will have on learners' cognitive structures and processes. Prior knowledge can determine the ease with which learners can perceive and interpret visual representations in working memory. Although a long tradition of research has compared experts and novices, more research is necessary to fully explore the expert–novice continuum and maximize the potential of visual representations. © 2006 Wiley Periodicals, Inc. Sci Ed90:1073–1091, 2006

Religion and Public Opinion about Same‐Sex Marriage*

Abstract: Objective. The goal of this article is to analyze the relationship between religion, measured in terms of religious affiliation and religiosity, and public opinion about same-sex marriage, civil unions, and a federal constitutional amendment that would prohibit gay marriage. Methods. We use logistic regression with calculated standardized coefficients to analyze data from a nationally representative survey of 1,610 respondents conducted in March–April 2004. Results. Religious variables perform better than demographic measures in models of attitudes about same-sex unions. Non-Protestants are much more likely to support same-sex unions than are Protestants, and individuals with conservative attitudes toward morality and secularism and (to a lesser extent) those who participate actively in religious life are more likely to oppose such unions. On the whole, religious variables play a weaker role in predicting support for a constitutional amendment to prevent gay marriage than they do in predicting attitudes toward same-sex unions. Conclusions. Religious variables play powerful roles in structuring attitudes about same-sex unions. Moreover, homosexuality appears to be a major component of the “moral values” discourse that is currently so popular in American politics.

Denial-of-service attack-detection techniques

Abstract: Denial-of-service (DoS) detection techniques - such as activity profiling, change-point detection, and wavelet-based signal analysis - face the considerable challenge of discriminating network-based flooding attacks from sudden increases in legitimate activity or flash events. This survey of techniques and testing results provides insight into our ability to successfully identify DoS flooding attacks. Although each detector shows promise in limited testing, none completely solve the detection problem. Combining various approaches with experienced network operators most likely produce the best results.

Field trials and testing of the OctArm continuum manipulator

Abstract: This paper describes the results of field trials and associated testing of the OctArm series of multi-section continuous backbone "continuum" robots. This novel series of manipulators has recently (Spring 2005) undergone a series of trials including open-air and in-water field tests. Outcomes of the trials, in which the manipulators demonstrated the ability for adaptive and novel manipulation in challenging environments, are described. Implications for the deployment of continuum robots in a variety of applications are discussed

Preparation and encapsulation of highly fluorescent conjugated polymer nanoparticles.

Abstract: A facile method has been developed to prepare aqueous dispersions of encapsulated conjugated polymer nanoparticles exhibiting high fluorescence brightness. Salient features of the nanoparticles include their small diameter and spherical morphology. Encapsulation of the nanoparticles with a silica shell reduces the rate of photooxidation and allows facile attachment of functional groups for subsequent bioconjugation and nanoparticle assembly. Functionalization of the nanoparticle with amine groups followed by the addition of Au nanoparticles resulted in the formation of nanoparticle assemblies, as evidenced by the efficient quenching of the conjugated polymer fluorescence by the Au nanoparticles.

Chitosan Film Mechanical and Permeation Properties as Affected by Acid, Plasticizer, and Storage

Abstract: The effects of acid (acetic, formic, lactic, propionic) concentrations, plasticizer concentrations, and storage time (up to 9 wk) on mechanical properties, water vapor permeability, and oxygen permeability of solution-cast chitosan films were determined. Measured water vapor permeability coefficients ranged from 5.35 to 13.20 x 10 -1 g/m.day.atm. Oxygen permeated coefficients ranged from 0.08 to 31.67 x 10 -3 cc O 2 / m.day.atm. Neither property was affected by storage time. Tensile strength (6.85-31.88 Mpa) also was not time dependent, but elongation (14-70%) decreased with storage time. Lactic acid solutions produced the lowest oxygen permeability values, formic acid the highest. Films formed with 7.5% lactic acid solutions had uniquely high values for elongation at break.

Place bonding for recreation places : Conceptual and empirical development

Abstract: Place bonding is a common phenomenon in many recreation areas, where people develop an affective and cognitive based attachment to special resource settings. Conceptually, place bonding is fairly well understood; empirically it is less so. In this study, a five dimensional orientation to place bonding of trout anglers for a wild and scenic stream was conceptually and empirically developed. The dimensions of place familiarity, belongingness, identity, dependence, and rootedness were examined by having respondents (n = 203) rate a 26‐item scale of recreation place bonding. Exploratory and confirmatory factor analyses produced a five‐dimension solution to place bonding. The five‐dimensional model was examined for convergent validity and predictive validity, with the latter predicting 75% of variance in an overall measure of place bonding. Research and management implications are discussed for recreation resource place bonding.

Current Management in a Hybrid Fuel Cell Power System: A Model-Predictive Control Approach

Abstract: The problem of oxygen starvation in fuel cells coupled with air compressor saturation limits, is addressed in this paper. We propose using a hybrid configuration, in which a bank of ultracapacitors supplements the polymer electrolyte membrane fuel cell during fast current transients. Our objective is to avoid fuel cell oxygen starvation, prevent air compressor surge and choke, and simultaneously match an arbitrary level of current demand. We formulate the distribution of current demand between the fuel cell and the bank of ultracapacitors in a model predictive control framework, which can handle multiple constraints of the hybrid system. Simulation results show that reactant deficit during sudden increase in stack current is reduced from 50% in stand-alone architecture to less than 1% in the hybrid configuration. In addition, the explicit constraint handling capability of the current management scheme prevents compressor surge and choke and maintains the state-of-charge of the ultracapacitor within feasible bounds

Erosion and Deposition in Turbomachinery

Abstract: This paper presents a review of erosion and deposition research in turbomachines and the associated degradation in engine performance caused by particulate matter ingestion Parameters affecting surface material losses as a result of erosion and development of experimental and analytical approaches to predict flowpath erosion and deposition are discussed Tests results that quantify the effects of temperature, impact particle composition, impact velocity and angle, and surface material composition are reviewed along with particle restitution data (ratios of rebound to impact velocities and angles) Development and application of models using these data to calculate surface erosion in turbomachinery are described These models predict particle trajectories in turbomachinery passages to determine impact rates, impact velocities, impact angles and uses the experimentally-obtained erosion data to calculate material losses Literature on the effects of erosion on turbomachine performance and life is surveyed Mechanisms of particle delivery and attachment upon arrival at turbomachine flowpath surfaces are also discussed along with experiential models that have been developed to predict surface deposit buildup Delivery to turbine surfaces can occur as a result of inertial flight, as for erosion, but also through transport mechanisms involving turbulence, Brownian diffusion, and thermophoresis The particle size range, where each of these mechanisms is dominant for delivery to surfaces, is described The history and experience of developing models that use these mechanisms to quantify particle delivery rates to turbine flow path surfaces is discussed, along with the use of sticking fraction data to determine the amount of material retained on the surfaces after delivery and the resulting deposit buildup rates Finally, factors that control whether extreme rates of deposition can occur in turbomachinery are described

Nanoassembly of a Fractal Polymer: A Molecular "Sierpinski Hexagonal Gasket"

Abstract: Mathematics and art converge in the fractal forms that also abound in nature. We used molecular self-assembly to create a synthetic, nanometer-scale, Sierpinski hexagonal gasket. This nondendritic, perfectly self-similar fractal macromolecule is composed of bis-terpyridine building blocks that are bound together by coordination to 36 Ru and 6 Fe ions to form a nearly planar array of increasingly larger hexagons around a hollow center.

Audit Committee Financial Expertise, Competing Corporate Governance Mechanisms, and Earnings Management

Abstract: A prime objective of the Sarbanes-Oxley Act and recent changes to stock exchange listing standards is to improve the quality of financial reporting. We examine the associations between audit committee financial expertise and alternate corporate governance mechanisms and earnings management. We find that both accounting and certain types of non-accounting financial expertise reduce earnings management for firms with weak alternate corporate governance mechanisms, but that independent audit committee members with financial expertise are most effective in mitigating earnings management. Importantly we find that alternate corporate governance mechanisms are an effective substitute for audit committee financial expertise in constraining earnings management. Finally, we find either no association or a positive association between financial expertise and real earnings management. Our results suggest that alternate governance approaches are equally effective in improving the quality of financial reporting, and that firms should have the flexibility to design the particular set of governance mechanisms that best fit their unique situations.

Effect of water on sulfuric acid catalyzed esterification

Abstract: This paper reports on an investigation into the impact of water on liquid-phase sulfuric acid catalyzed esterification of acetic acid with methanol at 60 °C. In order to diminish the effect of water on the catalysis as a result of the reverse reaction, initial reaction kinetics were measured using a low concentration of sulfuric acid (1 × 10 −3 M) and different initial water concentrations. It was found that the catalytic activity of sulfuric acid was strongly inhibited by water. The catalysts lost up to 90% activity as the amount of water present increased. The order of water effect on reaction rate was determined to be −0.83. The deactivating effect of water also manifested itself by changes in the activation energy and the pre-exponential kinetic factor. The decreased activity of the catalytic protons is suggested to be caused by preferential solvation of them by water over methanol. A proposed model successfully predicts esterification rate as reaction progresses. The results indicate that, as esterification progresses and byproduct water is produced, deactivation of the sulfuric acid catalyst occurs. Autocatalysis, however, was found to be hardly impacted by the presence of water, probably due to compensation effects of water on the catalytic activity of acetic acid, a weak acid.

Promoting Ethical Behavior and Organizational Citizenship Behaviors: The Influence of Corporate Ethical Values

Abstract: [enter Abstract Body]In the present study, a model of antecedents and outcomes of ethical behavior in work organizations was developed and tested. Antecedents included are corporate ethical values, organizational justice, and organizational commitment. The outcome of organizational citizenship behaviors was also examined. Data were gathered from 489 members of a regional chapter of the National Association of Purchasing Managers (NAPM). Structural equation modeling was used to test the model. Results indicated the data fit the model well. Implications for managers and directions for future research are discussed.

Phylogenetic analyses of Vitis (Vitaceae) based on complete chloroplast genome sequences: effects of taxon sampling and phylogenetic methods on resolving relationships among rosids.

Abstract: The Vitaceae (grape) is an economically important family of angiosperms whose phylogenetic placement is currently unresolved. Recent phylogenetic analyses based on one to several genes have suggested several alternative placements of this family, including sister to Caryophyllales, asterids, Saxifragales, Dilleniaceae or to rest of rosids, though support for these different results has been weak. There has been a recent interest in using complete chloroplast genome sequences for resolving phylogenetic relationships among angiosperms. These studies have clarified relationships among several major lineages but they have also emphasized the importance of taxon sampling and the effects of different phylogenetic methods for obtaining accurate phylogenies. We sequenced the complete chloroplast genome of Vitis vinifera and used these data to assess relationships among 27 angiosperms, including nine taxa of rosids. The Vitis vinifera chloroplast genome is 160,928 bp in length, including a pair of inverted repeats of 26,358 bp that are separated by small and large single copy regions of 19,065 bp and 89,147 bp, respectively. The gene content and order of Vitis is identical to many other unrearranged angiosperm chloroplast genomes, including tobacco. Phylogenetic analyses using maximum parsimony and maximum likelihood were performed on DNA sequences of 61 protein-coding genes for two datasets with 28 or 29 taxa, including eight or nine taxa from four of the seven currently recognized major clades of rosids. Parsimony and likelihood phylogenies of both data sets provide strong support for the placement of Vitaceae as sister to the remaining rosids. However, the position of the Myrtales and support for the monophyly of the eurosid I clade differs between the two data sets and the two methods of analysis. In parsimony analyses, the inclusion of Gossypium is necessary to obtain trees that support the monophyly of the eurosid I clade. However, maximum likelihood analyses place Cucumis as sister to the Myrtales and therefore do not support the monophyly of the eurosid I clade. Phylogenies based on DNA sequences from complete chloroplast genome sequences provide strong support for the position of the Vitaceae as the earliest diverging lineage of rosids. Our phylogenetic analyses support recent assertions that inadequate taxon sampling and incorrect model specification for concatenated multi-gene data sets can mislead phylogenetic inferences when using whole chloroplast genomes for phylogeny reconstruction.