Showing papers by "Lehigh University published in 2002"
TL;DR: Trust was increased through perceived responsive relationships in the virtual community, by a general disposition to trust, and by the belief that others confide personal information.
Abstract: This study explores several downstream effects of trust in virtual communities and the antecedents of trust in this unique type of environment. The data, applying an existing scale to measure two dimensions of trust (ability and benevolence/integrity), show that trust had a downstream effect on members' intentions to both give information and get information through the virtual community. Both these apparent dimensions of trust were increased through perceived responsive relationships in the virtual community, by a general disposition to trust, and by the belief that others confide personal information.
1,418 citations
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TL;DR: In this paper, the authors examined the factors that may be responsible for the rapidly increasing prevalence of obesity in the United States and found that these factors have the expected effects on obesity and explain a substantial amount of its trend.
Abstract: Since the late 1970s, the number of obese adults in the United States has grown by over 50 percent. This paper examines the factors that may be responsible for this rapidly increasing prevalence rate. To study the determinants of adult obesity and related outcomes, we employ micro-level data from the 1984-1999 Behavioral Risk Factor Surveillance System. These repeated cross sections are augmented with state level measures pertaining to the per capita number of fast- food restaurants, the per capita number of full-service restaurants, the price of a meal in each type of restaurant, the price of food consumed at home, the price of cigarettes, clean indoor air laws, and hours of work per week and hourly wage rates by age, gender, race, years of formal schooling completed, and marital status. Our main results are that these variables have the expected effects on obesity and explain a substantial amount of its trend. These findings control for individual-level measures of household income, years of formal schooling completed, and marital status.
1,066 citations
TL;DR: It is demonstrated that optical discrete solitons are possible in appropriately oriented biased photorefractive crystals in optically induced periodic waveguide lattices that are created via plane-wave interference and paves the way towards the observation of entirely new families of discretesolitons.
Abstract: We demonstrate that optical discrete solitons are possible in appropriately oriented biased photorefractive crystals. This can be accomplished in optically induced periodic waveguide lattices that are created via plane-wave interference. Our method paves the way towards the observation of entirely new families of discrete solitons. These include, for example, discrete solitons in two-dimensional self-focusing and defocusing lattices of different group symmetries, incoherently coupled vector discrete solitons, discrete soliton states in optical diatomic chains, as well as their associated collision properties and interactions. We also present results concerning transport anomalies of discrete solitons that depend on their initial momentum within the Brillouin zone.
551 citations
TL;DR: In this paper, a multi-method field study indicates that larger more mechanistic firms especially those in resource intense industrial sectors use knowledge transfer and research support relationships to build competencies in non-core technological areas.
533 citations
TL;DR: It is suggested that phosphorylation occurs in a localized fashion, resulting in decreased microtubule destabilizing activity near chromatin or micro Tubule polymer, and a spatial gradient of inactive Op18/stathmin associated with chromatinor microtubules could contribute significantly to mitotic spindle assembly.
427 citations
TL;DR: Continuously tunable and coherent radiation in the wide range 56-1618 mum (0.18-5.27 THz) has been achieved as a novel and promising terahertz source based on collinear phase-matched difference frequency generation in a GaSe crystal.
Abstract: Continuously tunable and coherent radiation in the wide range 56.8–1618 µm (0.18–5.27 THz) has been achieved as a novel and promising terahertz source based on collinear phase-matched difference frequency generation in a GaSe crystal. This source has the advantages of high coherence, simplicity for tuning, simple alignment, and stable output. The peak output power for the terahertz radiation reaches 69.4 W at a wavelength of 196 µm (1.53 THz), which corresponds to a photon conversion efficiency of 3.3%. A simple optimization of the design can yield a compact terahertz source.
401 citations
TL;DR: This study comprehensively evaluated driving in adults with ADHD by comparing 105 young adults with the disorder to 64 community control adults on five domains of driving ability and a battery of executive function tasks, finding that driving difficulties were not a function of comorbid oppositional defiant disorder, depression, anxiety, or frequency of alcohol or illegal drug use.
Abstract: Past studies find that attention deficit hyperactivity disorder (ADHD) creates a higher risk for adverse driving outcomes. This study comprehensively evaluated driving in adults with ADHD by comparing 105 young adults with the disorder (age 17-28) to 64 community control (CC) adults on five domains of driving ability and a battery of executive function tasks. The ADHD group self-reported significantly more traffic citations, particularly for speeding, vehicular crashes, and license suspensions than the CC group, with most of these differences corroborated in the official DMV records. Cognitively, the ADHD group was less attentive and made more errors during a visual reaction task under rule-reversed conditions than the CC group. The ADHD group also obtained lower sceres on a test of driving rules and decision-making but not on a simple driving simulator. Both self- and other-ratings showed the CC group employed safer routine driving habits than the ADHD group. Relationships between the cognitive and driving measures and the adverse outcomes were limited or absent, calling into question their use in screening ADHD adults for driving risks. Several executive functions also were significantly yet modestly related to accident frequency and total traffic violations after controlling for severity of ADHD. These results are consistent with earlier studies showing significant driving problems are associated with ADHD. This study found that these driving difficulties were not a function of comorbid oppositional defiant disorder, depression, anxiety, or frequency of alcohol or illegal drug use. Findings to date argue for the development of interventions to reduce driving risks among adults with ADHD.
381 citations
TL;DR: In this paper, the use of in situ Raman spectroscopy to study the molecular structures of supported metal oxide catalysts under different environments is reviewed and the effect of moisture at elevated temperatures is also discussed with regard to its implications for catalytic phenomena.
Abstract: The use of in situ Raman spectroscopy to study the molecular structures of supported metal oxide catalysts under different environments is reviewed. The molecular structures under ambient (hydrated) and dehydrated conditions are presented. The effect of moisture at elevated temperatures is also presented and discussed with regard to its implications for catalytic phenomena. The molecular structural transformations during C2–C4 lower alkane (LPG) oxidation, methane oxidation, methanol oxidation and selective catalytic reduction of NO with NH3 reaction conditions are presented. In situ spectroscopy during catalytic reaction with simultaneous activity/selectivity measurement (‘operando’ spectroscopy) is emphasized owing to its contribution to the fundamental understanding of catalytic performance. The reducibility of the different surface metal oxide species, the relevance of surface coverage (surface monomeric vs polymeric species) and the specific oxide support are discussed when LPG, methane, methanol or hydrogen is the reducing agent. In situ Raman spectroscopy provides molecular-level information about the surface metal oxide species: structures, stability and transformations under different environments. In many cases, the use of complementary spectroscopic techniques results in a more complete understanding of the molecular structure–activity/selectivity relationships for supported metal oxide catalysts. Copyright © 2002 John Wiley & Sons, Ltd.
327 citations
TL;DR: The authors suggest that people make such predictions by imagining the event without temporal context and then considering how this reaction might change were the event displaced in time (temporal correction), and that this initial prediction is then corrected with information about the time at which the event will actually occur.
308 citations
TL;DR: The results suggest that linguistic and non-linguistic performance are dissociable, but language-specific regularities made available in the experimental context may mediate the speaker's performance in specific tasks.
301 citations
TL;DR: Eight experiments supported the hypotheses that reflexive testosterone release by male mice during sexual encounters reduces male anxiety and that this anxiolysis is mediated by the conversion of testosterone to neurosteroids that interact with GABA(A) receptors.
TL;DR: In this paper, a liquid drop (1−2 μL) is placed on a surface possessing a continuous gradient of wettability, it moves toward the more wettable part of the gradient with typical speeds of 1−2 mm/s.
Abstract: When a liquid drop (1−2 μL) is placed on a surface possessing a continuous gradient of wettability, it moves toward the more wettable part of the gradient with typical speeds of 1−2 mm/s. This low speed arises because the driving force due to surface tension is reduced by contact angle hysteresis. The hysteresis force acting on a drop on a gradient surface is, however, spatially asymmetricits magnitude against the gradient being larger than that along the gradient. If a periodic force is applied to a drop resting on such a gradient surface, the force against the gradient is rectified whereas it is enhanced along the gradient. This half-wave rectification of periodic force causes 1−2 μL size drops to move with enhanced speeds of 5−10 mm/s.
TL;DR: Five studies merged the priming methodology with the bystander apathy literature and demonstrate how merely priming a social context at Time 1 leads to less helping behavior on a subsequent, completely unrelated task at Time 2.
Abstract: Five studies merged the priming methodology with the bystander apathy literature and demonstrate how merely priming a social context at Time 1 leads to less helping behavior on a subsequent, completely unrelated task at Time 2. In Study 1, participants who imagined being with a group at Time 1 pledged significantly fewer dollars on a charity-giving measure at Time 2 than did those who imagined being alone with one other person. Studies 2-5 build converging evidence with hypothetical and real helping behavior measures and demonstrate that participants who imagine the presence of others show facilitation to words associated with unaccountable on a lexical decision task. Implications for social group research and the priming methodology are discussed.
TL;DR: Recently, a new orthorhombic phase has been discovered in the ferroelectric system as discussed by the authors, which is in contrast to the monoclinic (M}_{C}$-type symmetry recently identified at low temperatures in the PZT system over a triangle-shaped region of the phase diagram.
Abstract: Recently, a new orthorhombic phase has been discovered in the ferroelectric system $(1\ensuremath{-}x)\mathrm{Pb}({\mathrm{Zn}}_{1/3}{\mathrm{Nb}}_{2/3}){\mathrm{O}}_{3}\ensuremath{-}x{\mathrm{PbTiO}}_{3}$ $(\mathrm{PZN}\ensuremath{-}x\mathrm{PT})$ for $x=9%,$ and for $x=8%$ after the application of an electric field. In the present work, synchrotron x-ray measurements have been extended to higher concentrations $10%l~xl~15%.$ The orthorhombic phase was observed for $x=10%,$ but, surprisingly, for $xg~11%$ only a tetragonal phase was found down to 20 K. The orthorhombic phase thus exists only in a narrow concentration range with near-vertical phase boundaries on both sides. This orthorhombic symmetry ${(M}_{C}$ type) is in contrast to the monoclinic ${M}_{A}$-type symmetry recently identified at low temperatures in the $\mathrm{Pb}({\mathrm{Zr}}_{1\ensuremath{-}x}{\mathrm{Ti}}_{x}){\mathrm{O}}_{3}$ (PZT) system over a triangle-shaped region of the phase diagram in the range $x=0.46--0.52.$ To further characterize this relaxor-type system, neutron inelastic scattering measurements have also been performed on a crystal of $\mathrm{PZN}\ensuremath{-}x\mathrm{PT}$ with $x=15%.$ The anomalous soft-phonon behavior (``waterfall'' effect) previously observed for $x=0%$ and 8% is clearly observed for the 15% crystal, which indicates that the presence of polar nanoregions extends to large values of x.
TL;DR: In this paper, a cognitive-affective-conative baseline model is proposed and tested for measuring perceived service quality in a company-related and employee-related setting. But the model is not suitable for the task of service evaluation.
Abstract: The authors first propose and test a cognitive-affective-conative baseline model: Perceived service quality (both tangible company-related and employee-related factors) is modeled antecedent to sat...
TL;DR: In this article, a post-tensioned wide flange beam-to-column connection for steel moment resisting frames subjected to seismic loading conditions is presented, which includes top and seat angles bolted to the beam and column.
Abstract: Nine large-scale subassembly tests were conducted to investigate the behavior of an innovative posttensioned wide flange beam-to-column connection for steel moment resisting frames subjected to seismic loading conditions. The connection includes top and seat angles bolted to the beam and column. Strands are placed along the length of the beam, passing through the column and posttensioned to provide a precompression of the beam against the column. The parameters investigated in the study include the angle thickness, angle gage length, beam flange reinforcing plates, connection shim plates, and posttensioning force. The test results demonstrate that posttensioned connections provide excellent elastic stiffness, strength, and ductility under cyclic loading, with energy dissipation occurring primarily in the angles. The connection initial elastic stiffness is comparable to that of a fully restrained welded connection. In addition, the connection has essentially no residual deformation following several cycles...
TL;DR: A stochastic model of microtubule (MT) assembly dynamics that estimates tubulin–tubulin bond energies, mechanical energy stored in the lattice dimers, and the size of the tubulin-GTP cap at MT tips is developed and generates MT dynamic instability with rates and transition frequencies similar to those measured experimentally.
Abstract: We developed a stochastic model of microtubule (MT) assembly dynamics that estimates tubulin–tubulin bond energies, mechanical energy stored in the lattice dimers, and the size of the tubulin-GTP cap at MT tips. First, a simple assembly/disassembly state model was used to screen possible combinations of lateral bond energy (ΔGLat) and longitudinal bond energy (ΔGLong) plus the free energy of immobilizing a dimer in the MT lattice (ΔGS) for rates of MT growth and shortening measured experimentally. This analysis predicts ΔGLat in the range of −3.2 to −5.7 kBT and ΔGLong plus ΔGS in the range of −6.8 to −9.4 kBT. Based on these estimates, the energy of conformational stress for a single tubulin-GDP dimer in the lattice is 2.1–2.5 kBT. Second, we studied how tubulin-GTP cap size fluctuates with different hydrolysis rules and show that a mechanism of directly coupling subunit addition to hydrolysis fails to support MT growth, whereas a finite hydrolysis rate allows growth. By adding rules to mimic the mechanical constraints present at the MT tip, the model generates tubulin-GTP caps similar in size to experimental estimates. Finally, by combining assembly/disassembly and cap dynamics, we generate MT dynamic instability with rates and transition frequencies similar to those measured experimentally. Our model serves as a platform to examine GTP-cap dynamics and allows predictions of how MT-associated proteins and other effectors alter the energetics of MT assembly.
TL;DR: In this article, the behavior of CFT beam-columns made from high-strength materials was investigated experimentally and the effects of the width-to-thickness ratio, yield stress of the steel tube and axial load level on the stiffness, strength and ductility of high strength CFT beams were studied.
TL;DR: A review of theoretical and empirical models of educational outcomes to identify student attitudes and behaviors that researchers have hypothesized to influence academic achie... as mentioned in this paper includes a review of academic outcomes and student attitudes.
Abstract: This article includes a review of theoretical and empirical models of educational outcomes to identify student attitudes and behaviors that researchers have hypothesized to influence academic achie...
TL;DR: In this article, the authors extended the research on schema-based strategy instruction by investigating its effects on the mathematical problem solving of 4 middle school students with learning disabilities who were low-performing in mathematics.
Abstract: This exploratory study extends the research on schema-based strategy instruction by investigating its effects on the mathematical problem solving of 4 middle school students with learning disabilities who were low-performing in mathematics. A multiple-probe-across-participants design included baseline, treatment, generalization, and maintenance. During treatment, students received schema strategy training in problem schemata (conceptual understanding) and problem solution (procedural understanding). Results indicated that the schema-based strategy was effective in substantially increasing the number of correctly solved multiplication and division word problems for all 4 participants. Maintenance of strategy effects was evident for 10, 51/2, and 21/2 weeks following the termination of instruction for Sara, Tony, and Percy, respectively. In addition, the effects of instruction generalized to novel word problems for all 4 participants.
TL;DR: The central plank of the account is a theory of autonomous systems that are composed of webs of interdependent processes whose collective activity is self-generating, that possess a process organization that performs work to guide energy into the processes of the system itself.
Abstract: The central plank of our account is a theory of autonomous (or "self governed") systems that are composed of webs of interdependent processes whose collective activity is self-generating. In other words, au tonomous systems possess a process organization that, in interaction with the environment, performs work to guide energy into the processes of the system itself. A paradigm autonomous system is a living cell, which trans forms energy and materials from the environment through metabolic pathways into the forms of chemical energy and organic molecules required by the processes that sustain the cell. Examples of the processes by which cells help generate the conditions under which they survive include enzymatic catalysis, membrane regulation of energy and material flows in and out of the cell, and chemotaxic amoebic motion to find a food
TL;DR: The authors found that when goals were accessible, attention was drawn toward goal-relevant items, even when these items were to be ignored and when responses occurred too fast for conscious control, despite the fact that these goals were not chronically held, but manipulated in the lab.
TL;DR: The concept of academic enablers was introduced by DiPerna et al. as discussed by the authors, who defined academic competence as a multidimensional construct consisting of the skills, attitudes, and behaviors of students that contribute to success in the classroom.
Abstract: Although previous miniseries (e.g., see Carnine, 1994; Skinner & Berninger, 1997) and numerous individual articles (e.g., Daly, Witt, Martens, & Dool, 1997; Powell-Smith, Shinn, Stoner, & Good, 2000) have appeared in School Psychology Review exploring empirical and practical issues regarding academic skills, a focused discussion of academic enablers (or nonacademic skills that contribute to academic success) has yet to occur within the field of school psychology. As such, we have assembled a panel of distinguished researchers to share their perspectives regarding conceptual, empirical, and practical issues related to the construct of academic enablers. In the following paragraphs, we describe how the construct of academic enablers has been defined to date as well as provide a context for how academic enablers relate to academic skills and academic achievement. In addition, we explain the rationale for developing this miniseries and the objectives the included articles collectively address. This introduction c oncludes with an overview of each of the articles included in this special issue. Definition of Academic Enablers and Related Constructs The idea of academic enablers evolved from the work of researchers (e.g., Gresham & Elliott, 1990; Malecki, 1998; Wentzel, 1993; Wigfield & Karpathian, 1991) who explored the relationship between students' nonacademic behaviors (e.g., social skills, motivation) and their academic achievement. Based on this earlier research, we hypothesized that a student's academic success--or competence--in the classroom required more than academic skill proficiency. Specifically, we defined academic competence as a multidimensional construct consisting of the skills, attitudes, and behaviors of students that contribute to success in the classroom. The results of our research (DiPema & Elliott, 1999,2000) exploring this construct have indicated that the skills, attitudes, and behaviors contributing to academic competence fall into one of two domains: academic skills or academic enablers. Academic skills are the basic and complex skills that are the primary focus of academic instruction in elementary and secondary schools. In contrast, academic enablers are attitudes and behaviors that allow a student to participate in, and ultimately benefit from, academic instruction in the classroom. Through a variety of means (e.g., review of research literature, discussions with educators, empirical research), we have identified specific domains of academic skill and academic enablers that contribute to academic competence. Specifically, the academic skill domains include language-based skills (reading and writing), mathematics, and critical thinking (DiPerna & Elliott, 2000). The academic enablers include interpersonal skills, motivation, study skills, and engagement (DiPerna & Elliott, 1999, 2000). Figure 1 displays the academic enablers and skills that contribute to the construct of academic competence. Rationale for the Miniseries The rationale for this miniseries is based on the recognition that the current knowledge base regarding academic enablers has--at a minimum--three significant limitations. The first such limitation is that the current definition of academic enablers may be too narrow. That is, to date, academic enablers have been defined as the nonacademic skills, attitudes, and behaviors of students that contribute to academic success in the classroom. From Carroll's Model of School Learning (1963) to Walberg's Theory of Educational Productivity (1981), there is substantial empirical evidence that a variety of environmental factors influence learning. As such, some might suggest (see Christenson and Anderson, 2002) that the construct of academic enablers should be expanded to encompass key student and environmental factors that promote the development of academic skills. …
TL;DR: It is shown that the optimum signaling, for largest ergodic capacity with antenna selection, is generally different from that which is optimum without antenna selection for some range of signal-to-noise ratios.
Abstract: Wireless communication systems with transmit and receive antenna arrays are studied when antenna selection is used. A case with very limited feedback of information from the receiver to the transmitter is considered, where the only information fed back is the selected subset of transmit antennas to be employed. It is shown that the optimum signaling, for largest ergodic capacity with antenna selection, is generally different from that which is optimum without antenna selection for some range of signal-to-noise ratios.
TL;DR: In this paper, the results of experiments of the methanol decomposition reaction catalyzed by a commercial Cu/ZnO/Al2O3 in the absence and presence of water were presented.
Abstract: This paper presents the results of experiments of the methanol decomposition reaction catalyzed by a commercial Cu/ZnO/Al2O3 in the absence and presence of water. Methanol decomposition of 100% in the absence of water was obtained at 290 °C and a space velocity of 2 cm3/h g cat. At these conditions, the hydrogen yield was 1.9–2.0. Water addition to the feed increased the yield of hydrogen and reduced the formation of: dimethyl ether; methyl formate and methane. The variation of the catalyst’s activity and selectivity with time, temperature and feed composition was consistent with previous studies of methanol–steam reforming and water–gas shift reaction, however, this appears to be the first study over the same catalyst of methanol decomposition and methanol–steam reforming. XPS analysis of used catalyst samples and time on-stream data showed that the Cu2+ oxidation state of copper favors methanol decomposition, and we propose that the deactivation of the catalyst is mainly caused by the change in the oxidation state of copper.
TL;DR: In this paper, the number of active surface sites and their nature, redox or acidic, for bulk metal oxide catalysts using isopropanol as a chemical probe molecule was determined.
Abstract: The objective of the present study was to determine the number of active surface sites and their nature, redox or acidic, for bulk metal oxide catalysts using isopropanol as a chemical probe molecule. Isopropanol oxidation activity on the following metal oxides was investigated: MgO, CaO, SrO, BaO, Y 2 O 3 , La 2 O 3 , CeO 2 , TiO 2 , ZrO 2 , HfO 2 , V 2 O 5 , Nb 2 O 5 , Ta 2 O 5 , Cr 2 O 3 , MoO 3 , WO 3 , Mn 2 O 3 , Fe 2 O 3 , Co 3 O 4 , Rh 2 O 3 , NiO, PdO, PtO, CuO, Ag 2 O, Au 2 O 3 , ZnO, Al 2 O 3 , Ga 2 O 3 , In 2 O 3 , SiO 2 , SnO 2 and Bi 2 O 3 . On average, the number of active surface sites for isopropanol dissociative adsorption on these catalysts was ∼2–4 μmol/m 2 . The number of active surface sites enabled quantification of the turnover frequency (TOF) for these catalysts. The TOF values for the various pure metal oxides were normalized at 200 °C. The TOFs of catalysts showing redox activity vary by six-orders of magnitude (10 2 to 10 −4 s −1 ). For catalyst showing acidic activity, the TOFs varied by over eight-orders of magnitude (10 1 to 10 −7 s −1 ). The reaction products from isopropanol oxidation at low conversions reflected the nature of the active surface sites, redox or acidic, on these catalysts. Redox surface sites yield acetone and acidic surface sites yield propylene. Small amounts of isopropyl ether formation are sometimes also observed via bimolecular recombination of surface isopropoxide species on acidic surface sites. All catalysts with the exception of Fe 2 O 3 and TiO 2 , exhibited extremely high selectivity to either redox or acidic products. Except for the sharp decrease in TOFs towards redox products with increasing bulk M–O heats of formation at low −Δ H f , no correlations were found between the TOFs and bulk metal oxide properties (TPR–H 2 and −Δ H f ). However, an inverse relation was found between the TOFs (redox) and the surface isopropoxide intermediate decomposition temperature at low decomposition temperatures. At moderate and high decomposition temperatures, the TOFs (redox) were almost independent of the surface isopropoxide decomposition temperature. The selectivity of the metal oxide catalysts was found to be independent of the TOFs.
TL;DR: In this article, the flexural force-deformation behavior of high strength square concrete-filled steel tube (CFT) beam-columns was experimentally investigated, and the parameters in the study included the width-to-threshold (W2T) and the length of the beam.
Abstract: The flexural force-deformation behavior of high strength square concrete-filled steel tube (CFT) beam-columns was experimentally investigated. The parameters in the study included the width-to-thic...
TL;DR: In this paper, a robust constrained output feedback MPC algorithm that can stabilize plants with both polytopic uncertainty and norm-bound uncertainty is presented. But the design procedure involves off-line design of robust constrained state-feedback MPC law and a state estimator using linear matrix inequalities.
TL;DR: It is shown that the mutual information of a single, isolated, multiple transmit and receive antenna array link is maximized by transmitting the maximum number of independent data streams for a flat Rayleigh fading channel with independent fading coefficients for each path.
Abstract: It is shown that the mutual information of a single, isolated, multiple transmit and receive antenna array link is maximized by transmitting the maximum number of independent data streams for a flat Rayleigh fading channel with independent fading coefficients for each path. However, if such links mutually interfere, in some cases the overall system mutual information can be increased by transmitting fewer streams.