Showing papers by "University of Delaware published in 2000"
TL;DR: In this paper, an estimation procedure based on adding small positive quantities to the diagonal of X′X was proposed, which is a method for showing in two dimensions the effects of nonorthogonality.
Abstract: In multiple regression it is shown that parameter estimates based on minimum residual sum of squares have a high probability of being unsatisfactory, if not incorrect, if the prediction vectors are not orthogonal. Proposed is an estimation procedure based on adding small positive quantities to the diagonal of X′X. Introduced is the ridge trace, a method for showing in two dimensions the effects of nonorthogonality. It is then shown how to augment X′X to obtain biased estimates with smaller mean square error.
8,091 citations
Journal Article•
Lawrence Berkeley National Laboratory1, University of Zurich2, Stanford University3, College of William & Mary4, University of Genoa5, University of Urbino6, CERN7, Budker Institute of Nuclear Physics8, Cornell University9, Argonne National Laboratory10, ETH Zurich11, Tata Institute of Fundamental Research12, Hillsdale College13, Spanish National Research Council14, Tohoku University15, Ohio State University16, University of California, San Diego17, University of California, Berkeley18, Aix-Marseille University19, University of Minnesota20, University of Alabama21, University of Helsinki22, California Institute of Technology23, George Washington University24, University of Kansas25, RWTH Aachen University26, Boston University27, University of California, Los Angeles28, Institut des Hautes Études Scientifiques29, University of Pennsylvania30, University of Tokyo31, University of Delaware32, Fermilab33, Carnegie Mellon University34, University of California, Santa Cruz35, Lawrence Livermore National Laboratory36, University of Washington37, Karlsruhe Institute of Technology38, Heidelberg University39, Florida State University40, Carleton University41, National Science Foundation42, University of Mainz43, University of Edinburgh44, University of Chicago45, Brookhaven National Laboratory46, Kent State University47, Paul Scherrer Institute48, Max Planck Society49, Massachusetts Institute of Technology50, Nagoya University51, Harvard University52
TL;DR: In this article, a biennial review summarizes much of particle physics using data from previous editions., plus 2778 new measurements from 645 papers, including measurements of gauge bosons, leptons, quarks, mesons, and baryons.
Abstract: This biennial Review summarizes much of particle physics. Using data from previous editions., plus 2778 new measurements from 645 papers, we list, evaluate, and average measured properties of gauge bosons, leptons, quarks, mesons, and baryons. We also summarize searches for hypothetical particles such as Higgs bosons, heavy neutrinos, and supersymmetric particles. All the particle properties and search limits are listed in Summary Tables. We also give numerous tables, figures, formulae, and reviews of topics such as the Standard Model, particle detectors., probability, and statistics. Among the 108 reviews are many that are new or heavily revised including those on CKM quark-mixing matrix, V-ud & V-us, V-cb & V-ub, top quark, muon anomalous magnetic moment, extra dimensions, particle detectors, cosmic background radiation, dark matter, cosmological parameters, and big bang cosmology.
1,520 citations
TL;DR: Biological traits associated with both risk-taking and personality, particularly sensation seeking, such as the D4 dopamine receptor gene, the enzyme monoamine oxidase, and augmenting or reducing of the cortical evoked potential are discussed.
Abstract: The first part of this article describes a study of the relationships between personality and risk-taking in six areas: smoking, drinking, drugs, sex, driving, and gambling. The participants, 260 college students, were given self-report measures of risky behaviors in each of the six areas and the Zuckerman- Kuhlman five-factor personality questionnaire. Generalized risk-taking (across all six areas) was related to scales for impulsive sensation seeking, aggression, and sociability, but not to scales for neuroticism or activity. Gender differences on risk-taking were mediated by differences on impulsive sensation seeking. The second part discusses biological traits associated with both risk-taking and personality, particularly sensation seeking, such as the D4 dopamine receptor gene, the enzyme monoamine oxidase, and augmenting or reducing of the cortical evoked potential. Comparative studies show relationships between biological markers shared with other species and correlated behaviors similar to sensation seeking in humans. A biosocial model of the traits underlying risk-taking is presented. Many of life's decisions involve a balance between anticipated reward and risk. The wild rodent venturing into an open field balances the possibility of finding food against the chance of being devoured by a predator on the ground or from the sky. The married man or woman who
1,221 citations
TL;DR: In this article, a large variability is observed among the reported values that could be used to predict metal mobility and bioavailability, and a semi-mechanistic model based on the competitive adsorption of metamodel was proposed.
Abstract: Environmental risk assessment of metals depends to a great extent on modeling the fate and the mobility of metals based on soil−liquid partitioning coefficients. A large variability is observed among the reported values that could be used to predict metal mobility and bioavailability. To evaluate this, soil−liquid partitioning coefficients (Kd) for many elements but especially for the metals cadmium, copper, lead, nickel, and zinc were compiled from over 70 studies of various origins collected from the literature. The relationships between the reported values are explored relative to variations in soil solution pH, soil organic matter (SOM), and concentrations of total soil metal. The results of multiple linear regressions show that Kd values are best predicted using empirical linear regressions with pH (with R 2 values of 0.29−0.58) or with pH and either the log of SOM or the log of total metal and with resulting R 2 values of 0.42−0.76. A semi-mechanistic model based on the competitive adsorption of met...
1,066 citations
TL;DR: It is found that utilization of even simple low-molecular-weight DOM components by bacteria differed across the major phylogenetic groups and often did not correlate with the relative abundance of these bacterial groups in estuarine and coastal environments.
Abstract: We used a method that combines microautoradiography with hybridization of fluorescent rRNA-targeted oligonucleotide probes to whole cells (MICRO-FISH) to test the hypothesis that the relative contributions of various phylogenetic groups to the utilization of dissolved organic matter (DOM) depend solely on their relative abundance in the bacterial community. We found that utilization of even simple low-molecular-weight DOM components by bacteria differed across the major phylogenetic groups and often did not correlate with the relative abundance of these bacterial groups in estuarine and coastal environments. The Cytophaga-Flavobacter cluster was overrepresented in the portion of the assemblage consuming chitin, N-acetylglucosamine, and protein but was generally underrepresented in the assemblage consuming amino acids. The amino acid-consuming assemblage was usually dominated by the alpha subclass of the class Proteobacteria, although the representation of alpha-proteobacteria in the protein-consuming assemblages was about that expected from their relative abundance in the entire bacterial community. In our experiments, no phylogenetic group dominated the consumption of all DOM, suggesting that the participation of a diverse assemblage of bacteria is essential for the complete degradation of complex DOM in the oceans. These results also suggest that the role of aerobic heterotrophic bacteria in carbon cycling would be more accurately described by using three groups instead of the single bacterial compartment currently used in biogeochemical models.
1,056 citations
TL;DR: Self-reported prejudice was lower in 1998–1999 than it was in 1988–1989, and at both time periods, white participants did not discriminate against black relative to white candidates when the candidates' qualifications were clearly strong or weak, but they did discriminate when the appropriate decision was more ambiguous.
Abstract: The present study investigated differences over a 10-year period in whites' self-reported racial prejudice and their bias in se- lection decisions involving black and white candidates for employ- ment We examined the hypothesis, derived from the aversive-racism framework, that although overt expressions of prejudice may decline significantly across time, subtle manifestations of bias may persist Consistent with this hypothesis, self-reported prejudice was lower in 1998-1999 than it was in 1988-1989, and at both time periods, white participants did not discriminate against black relative to white can- didates when the candidates' qualifications were clearly strong or weak, but they did discriminate when the appropriate decision was more ambiguous Theoretical and practical implications are considered
1,022 citations
TL;DR: In this article, two different theoretical perspectives are used to develop sets of hypotheses regarding the mechanisms used to manage foreign subsidiaries of multinational corporations, and the results indicate that agency theory, although a useful foundation for studies of control within MNCs, is limited in its ability to explain fully the phenomenon of foreign subsidiary control, however, the model based on intra-firm interdependence had much greater predictive ability.
Abstract: In this study, two different theoretical perspectives are used to develop sets of hypotheses regarding the mechanisms used to manage foreign subsidiaries of multinational corporations. First, agency theory serves as the basis for a model that predicts the use of monitoring mechanisms and incentive compensation. Then, it is argued that these mechanisms are insufficient for managing subsidiaries characterized by high levels of intra-firm international interdependence, the management of which is critical to many of today's complex global firms. A second set of hypotheses is argued, linking international interdependence to several social control mechanisms. Primary and secondary data from U.S. based multinational corporations were used to test both sets of hypotheses. The results indicate that agency theory, although a useful foundation for studies of control within MNCs, is limited in its ability to explain fully the phenomenon of foreign subsidiary control, however, the model based on intra-firm interdependence had much greater predictive ability. Copyright © 2000 John Wiley & Sons, Ltd.
782 citations
University of Washington1, University of Bristol2, Ohio State University3, University of Delaware4, University of North Carolina at Chapel Hill5, Centre national de la recherche scientifique6, Technische Universität München7, RWTH Aachen University8, University of Hamburg9, University of Oldenburg10
TL;DR: The origins, reactions and fates of molecularly-uncharacterized organic matter are relatively obscure, in large part because the rich vein of geochemical information that typically derives from detailed structural and stereochemical analysis is yet to be tapped.
706 citations
TL;DR: A new mathematical model was developed for the filtrate flux which accounts for initial foulingDue to pore blockage and subsequent fouling due to the growth of a protein cake or deposit over these initially blocked regions, eliminating the need to use different mathematical formulations to describe these two phenomena.
674 citations
TL;DR: In this article, an extended Boussinesq model for surf zone hydrodynamics in two horizontal dimensions is implemented and verified using an eddy viscosity term.
Abstract: In this paper, we focus on the implementation and verification of an extended Boussinesq model for surf zone hydrodynamics in two horizontal dimensions The time-domain numerical model is based on the fully nonlinear Boussinesq equations As described in Part I of this two-part paper, the energy dissipation due to wave breaking is modeled by introducing an eddy viscosity term into the momentum equations, with the viscosity strongly localized on the front face of the breaking waves Wave runup on the beach is simulated using a permeable-seabed technique We apply the model to simulate two laboratory experiments in large wave basins They are wave transformation and breaking over a submerged circular shoal and solitary wave runup on a conical island Satisfactory agreement is found between the numerical results and the laboratory measurements
659 citations
TL;DR: The principle of stereoscopic PIV, the different stereoscopic configurations that have been used, the relative error in the out-of-plane to the in-plane measurement, and the relative merits of calibration-based methods for reconstructing the three-dimensional displacement vector in comparison to geometric reconstruction are discussed.
Abstract: Stereoscopic particle image velocimetry (PIV) employs two cameras to record simultaneous but distinct off-axis views of the same region of interest (illuminated plane within a flow seeded with tracer particles). Sufficient information is contained in the two views to extract the out-of-plane motion of particles, and also to eliminate perspective error which can contaminate the in-plane measurement. This review discusses the principle of stereoscopic PIV, the different stereoscopic configurations that have been used, the relative error in the out-of-plane to the in-plane measurement, and the relative merits of calibration-based methods for reconstructing the three-dimensional displacement vector in comparison to geometric reconstruction. It appears that the current trend amongst practitioners of stereoscopic PIV is to use digital cameras to record the two views in the angular displacement configuration while incorporating the Scheimpflug condition. The use of calibration methods has also gained prominence over geometric reconstruction.
TL;DR: In this article, the authors describe four middle school African American girls' engagement with science and find that they expressed a fondness for science in school or had science-related hobbies outside of school, and their stories provide a better understanding of the variety of ways girls choose to engage in science and how this engagement is shaped by their views of what kind of girl they are.
Abstract: A view of science as a culturally-mediated way of thinking and knowing suggests that learning can be defined as engagement with scientific practices. How students engage in school science is influenced by whether and how students view themselves and whether or not they are the kind of person who engages in science. It is therefore crucial to understand students' identities and how they do or do not overlap with school science identities. In this paper, we describe four middle school African American girls' engagement with science. They were selected in the 7th grade because they expressed a fondness for science in school or because they had science-related hobbies outside of school. The data were collected from the following sources: interviews of students, their parents and their teachers; observations in science classes; journal writing; and focus groups. These girls' stories provide us with a better understanding of the variety of ways girls choose to engage in science and how this engagement is shaped by their views of what kind of girl they are. © 2000 John Wiley & Sons, Inc. J Res Sci Teach 37: 441–458, 2000.
TL;DR: The formation of nanostructured materials by using colloidal crystals as templates is a relatively new but rapidly growing area of materials science as mentioned in this paper, which holds promise for use as photonic crystals, advanced catalysts, and in a variety of other applications.
Abstract: The formation of nanostructured materials by using colloidal crystals as templates is a relatively new but rapidly growing area of materials science. Colloid crystalline templates are three-dimensional close-packed crystals of submicrometer spheres, whose long-ranged ordered structure is replicated in a solid matrix, to yield materials with ordered pores. These materials hold promise for use as photonic crystals, advanced catalysts, and in a variety of other applications. Here we review the wide range of materials that have been made following the original synthesis of structured porous silica. This method has been recently modified to produce porous metals.
TL;DR: Microstructured particles were synthesized by growing colloidal crystals in aqueous droplets suspended on fluorinated oil to allow control of particle size and shape from spheres through ellipsoids to toroids by varying the droplet composition.
Abstract: Microstructured particles were synthesized by growing colloidal crystals in aqueous droplets suspended on fluorinated oil. The droplets template highly ordered and smooth particle assemblies, which diffract light and have remarkable structural stability. The method allows control of particle size and shape from spheres through ellipsoids to toroids by varying the droplet composition. Cocrystallization in colloidal mixtures yields anisotropic particles of organic and inorganic materials that can, for example, be oriented and turned over by magnetic fields. The results open the way to controllable formation of a wide variety of microstructures.
TL;DR: In this article, the authors hypothesized that moral awareness is influenced by issue-related factors (magnitude of consequences of the moral issue and issue framing in moral terms) and social contextrelated factors(competitive context and perceived social consensus that the issue isethically problematic).
Abstract: Individuals' awarenessof moral issues is an important first step in the ethicaldecision-making process. Relying on research in social cognition andbusiness ethics, we hypothesized that moral awareness is influenced byissue-related factors (magnitude of consequences of the moral issueand issue framing in moral terms) and social contextrelated factors(competitive context and perceived social consensus that the issue isethically problematic). The hypotheses were tested in a fieldexperiment involving 291competitive intelligence practitioners.Results generally supported the hypotheses. Qualitative analysisyielded additional insights into the content of respondents' moralawareness.
TL;DR: The data show that the Cytophaga-Flavobacter group can be a numerically dominant component of coastal marine bacterioplankton communities.
Abstract: We determined the compositions of bacterioplankton communities in surface waters of coastal California using clone libraries of 16S rRNA genes and fluorescence in situ hybridization (FISH) in order to compare the community structures inferred from these two culture-independent approaches. The compositions of two clone libraries were quite similar to those of clone libraries of marine bacterioplankton examined by previous studies. Clones from γ-proteobacteria comprised ca. 28% of the libraries, while approximately 55% of the clones came from α-proteobacteria, which dominated the clone libraries. The Cytophaga-Flavobacter group and three others each comprised 10% or fewer of the clone libraries. The community composition determined by FISH differed substantially from the composition implied by the clone libraries. The Cytophaga-Flavobacter group dominated 8 of the 11 communities assayed by FISH, including the two communities assayed using clone libraries. On average only 10% of DAPI (4′,6′-diamidino-2-phenylindole)-stained bacteria were detected by FISH with a probe for α-proteobacteria, but 30% of DAPI-stained bacteria appeared to be in the Cytophaga-Flavobacter group as determined by FISH. α-Proteobacteria were greatly overrepresented in clone libraries compared to their relative abundance determined by FISH, while the Cytophaga-Flavobacter group was underrepresented in clone libraries. Our data show that the Cytophaga-Flavobacter group can be a numerically dominant component of coastal marine bacterioplankton communities.
TL;DR: The Circumpolar Active Layer Monitoring (CALM) program, designed to observe the response of the active layer and near surface permafrost to climate change, currently incorporates more than 100 sites involving 15 investigating countries in both hemispheres.
Abstract: The Circumpolar Active Layer Monitoring (CALM) program, designed to observe the response of the active layer and near‐surface permafrost to climate change, currently incorporates more than 100 sites involving 15 investigating countries in both hemispheres. In general, the active layer responds consistently to forcing by air temperature on an interannual basis. The relatively few long‐term data sets available from northern high‐latitude sites demonstrate substantial interannual and interdecadal fluctuations. Increased thaw penetration, thaw subsidence, and development of thermokarst are observed at some sites, indicating degradation of warmer permafrost. During the mid‐ to late‐1990s, sites in Alaska and northwestern Canada experienced maximum thaw depth in 1998 and a minimum in 2000; these values are consistent with the warmest and coolest summers. The CALM network is part of the World Meteorological Organization's (WMO) Global Terrestrial Network for Permafrost (GTN‐P). GTN‐P observations consis...
TL;DR: The data suggest that, of the measures tested, the most reliable and valid method of clinically assessing arch height across 10% and 90% of weight bearing was dividing the dorsum height at 50% of foot length by truncated foot length.
Abstract: Background and Purpose. Abnormality in the structure of the medial longitudinal arch of the foot is commonly thought to be a predisposing factor to injury. The purpose of this investigation was to compare the reliability and validity of several measurements used to characterize various aspects of the foot, including the medial longitudinal arch. Subjects. One hundred two feet (both feet of 51 subjects) were measured to establish a reference database. From this group, a subset of 20 feet (both feet of 10 subjects) was used to determine intertester and intratester reliability. Radiographs of a further subset of 10 feet (right feet of 10 subjects) were used to determine validity. Methods. Five foot measurements were taken in 2 stance conditions: 10% of weight bearing and 90% of weight bearing. Results. Intraclass correlation coefficients (ICCs) for intertester and intratester measurements were between .480 and .995. The most reliable method of characterizing arch type in 10% of weight bearing between testers was dividing navicular height by foot length in 10% of weight bearing. However, this measure yielded highly unreliable measurements in 90% of weight bearing. The most valid measurements were navicular height divided by truncated foot length, navicular height divided by foot length in 10% of weight bearing, and navicular height divided by foot length in 90% of weight bearing. Dorsum height at 50% of foot length divided by truncated foot length showed relatively high intertester reliability (ICC=.811 in 10% of weight bearing, ICC=.848 in 90% of weight bearing) and validity (ICC=.844 in 10% of weight bearing, ICC=.851 in 90% of weight bearing). Conclusion and Discussion. These data suggest that, of the measures tested, the most reliable and valid method of clinically assessing arch height across 10% and 90% of weight bearing was dividing the dorsum height at 50% of foot length by truncated foot length.
TL;DR: The authors found that the presence of a takeover defense in IPO firms is negatively related to acquisition likelihood, yet has no impact on takeover premiums for those firms that are acquired, suggesting that shareholders' marginal costs of takeover defenses exceed the benefits.
Abstract: Many firms deploy takeover defenses at the time of their IPOs, although at significantly lower rates than for seasoned corporations. We find that IPO managers deploy takeover defenses particularly when their compensation is high, shareholdings are small, and the oversight from non-managerial shareholders is weak. We also find that the presence of a takeover defense in IPO firms is negatively related to acquisition likelihood, yet has no impact on takeover premiums for those firms that are acquired. Together, these results suggest that shareholders' marginal costs of takeover defenses exceed the benefits.
TL;DR: Quaternary ammonium functionalized poly(propyleneimine) dendrimers were synthesized and their antibacterial properties were evaluated using a bioluminescence method, finding that the antimicrobial properties of these novel biocides with bromide anions are more potent than those with chloride anions.
TL;DR: The results suggest that Ser32 in the GDSWG consensus sequence provides the catalytic nucleophile for the hydrolase activity of aiPLA2, while Cys47 in the PVCTTE consensus sequence is at the active site for peroxidase activity.
TL;DR: In this paper, a causal relationship between the hydrogen-bonding ability of the liquid and the colloidal microstructure observed was investigated in a range of polar organic media and it was shown that the silica forms stable low-viscosity sols exhibiting shear thickening behavior in a host of liquids, including ethylene glycol and its oligomers and short-chain alcohols, such as n-propanol.
Abstract: Dispersions of hydrophilic fumed silica are investigated in a range of polar organic media. The silica forms stable, low-viscosity sols exhibiting shear thickening behavior in a host of liquids, including ethylene glycol and its oligomers and short-chain alcohols, such as n-propanol. In contrast, the silica flocculates into colloidal gels in other liquids, such as glycols with methyl end-caps and longer-chain alcohols. We suggest that there is a causal relationship between the hydrogen-bonding ability of the liquid and the colloidal microstructure observed. In strongly hydrogen-bonding liquids, a solvation layer is envisioned to form on the silica surface through hydrogen bonding between liquid molecules and surface silanol groups (Si−OH). This gives rise to short-range, non-DLVO repulsions (“solvation forces”) which stabilize the silica particles. In contrast, in the case of liquids with limited hydrogen-bonding ability, silanols on adjacent silica particles are envisioned to interact directly by hydroge...
TL;DR: Investigating the cytokine responses to entry by the broad host range serotypes S. typhimurium and S. enteritidis in poultry found a strong inflammatory response that may limit the spread of Salmonella largely to the gut, whilst S. gallinarum does not induce an inflammatory response and may not be limited by the immune system, leading to the severe systemic disease fowl typhoid.
Abstract: Salmonella enterica is a facultative intracellular pathogen that is capable of causing disease in a range of hosts. Although human salmonellosis is frequently associated with consumption of contaminated poultry and eggs, and the serotypes Salmonella gallinarum and Salmonella pullorum are important world-wide pathogens of poultry, little is understood of the mechanisms of pathogenesis of Salmonella in the chicken. Type III secretion systems play a key role in host cell invasiveness and trigger the production of pro-inflammatory cytokines during invasion of mammalian hosts. This results in a polymorphonuclear cell influx that contributes to the resulting enteritis. In this study, a chicken primary cell culture model was used to investigate the cytokine responses to entry by the broad host range serotypes S. enteritidis and S. typhimurium, and the host specific serotype S. gallinarum, which rarely causes disease outside its main host, the chicken. The cytokines interleukin (IL)-1β, IL-2, IL-6 and interferon (IFN)-γ were measured by quantitative RT-PCR, and production of IL-6 and IFN-γ was also determined through bioassays. All serotypes were invasive and had little effect on the production of IFN-γ compared with non-infected cells; S. enteritidis invasion caused a slight down-regulation of IL-2 production. For IL-1β production, infection with S. typhimurium had little effect, whilst infection with S. gallinarum or S. enteritidis caused a reduction in IL-1β mRNA levels. Invasion of S. typhimurium and S. enteritidis caused an eight- to tenfold increase in production of the pro-inflammatory cytokine IL-6, whilst invasion by S. gallinarum caused no increase. These findings correlate with the pathogenesis of Salmonella in poultry. S. typhimurium and S. enteritidis invasion produces a strong inflammatory response, that may limit the spread of Salmonella largely to the gut, whilst S. gallinarum does not induce an inflammatory response and may not be limited by the immune system, leading to the severe systemic disease fowl typhoid.
TL;DR: In this article, the effects of humic acid adsorption, concentration polarization, and aggregate deposition on the rate and extent of fouling were investigated using a broad range of molecular weight cutoffs.
Abstract: Recent studies have shown that natural organic matter (e.g., humic and fulvic acids) is a major foulant during ultrafiltration of surface water. The objective of this study was to develop a more complete understanding of the mechanisms governing humic acid fouling, including the effects of humic acid adsorption, concentration polarization, and aggregate deposition on the rate and extent of fouling. Data were obtained with Aldrich and Suwannee River humic acids using ultrafiltration membranes with a broad range of molecular weight cutoffs. Fouled membranes were also examined using streaming potential and contact angle measurements. The extent of flux decline was greatest for the largest molecular weight cutoff membranes due to the greater relative hydraulic resistance of the humic acid deposit formed on the surface of these membranes. This humic acid deposit reduced the apparent zeta potential and increased the membrane contact angle. Simple static adsorption and concentration polarization caused relatively little flux decline. Humic acid aggregates had a significant effect on fouling only for the larger molecular weight cutoff membranes. The rate and extent of humic acid fouling increased at low pH, high ionic strength, and in the presence of calcium due to changes in intermolecular electrostatic interactions. These results provide important insights into the mechanisms of humic acid fouling during ultrafiltration.
TL;DR: A wide range of advanced materials have recently been synthesized by replicating the structure of colloidal crystals into durable solid matrices as discussed by the authors, such materials have promise as photonic crystals, catalysts and membranes, and in a variety of other applications.
Abstract: Close-packed colloidal crystals are promising precursors for novel materials, but only after appropriate methods are developed to fix their structure. A wide range of advanced materials has recently been synthesized by replicating the structure of colloidal crystals into durable solid matrices. Such materials with structured pores have promise as photonic crystals, catalysts, and membranes, and in a variety of other applications. This paper reviews the methods used in the formation of these materials and likely future trends in the field.
TL;DR: In this paper, a new Monte Carlo program for photohadronic interactions of relativistic nucleons with an ambient photon radiation field is presented, which can also be used for radiation and background studies at high energy colliders such as LEP2 and HERA, as well as for simulations of photon induced air showers.
TL;DR: This presentation surveys some of the highlights of inverse scattering theory as it has developed over the last 15 years, with emphasis on uniqueness theorems and reconstruction algorithms for time harmonic acoustic waves.
Abstract: We survey some of the highlights of inverse scattering theory as it has developed over the last 15 years, with emphasis on uniqueness theorems and reconstruction algorithms for time harmonic acoustic waves. Included in our presentation are numerical experiments using real data and numerical examples of the use of inverse scattering methods to detect buried objects.
TL;DR: The results indicate that coper subjects move in a manner nearly identical to uninjured persons, andKinetic data suggest that copers stabilize their knees with greater contributions from the ankle extensor muscles, and Muscle activity data demonstrate that there is no reduction in quadriceps femoris activity in theCoper subjects.
Abstract: Single-leg hops are used clinically to assess knee function in patients following anterior cruciate ligament (ACL) rupture and reconstruction. Researchers study ACL-deficient individuals in order to identify movement strategies in the absence of a major knee stabilizer, thereby providing information to clinicians regarding treatment options. Single-leg hops represent an activity which places higher demands on the knee than walking or jogging. Hops are thought by some to represent demands that are more comparable to those found during high level sports. Therefore hopping might provide more information about knee stability during dynamic activities than less strenuous activities. This paper reflects one component of a larger study involving comparisons of joint motions and muscle activity patterns in uninjured individuals (n=10) and two groups of athletes who had complete ACL ruptures; one group had substantial knee instability (noncopers, n=10), and the other had no signs of knee instability (copers, n=11). In this paper we report the findings from the single-leg hop activity. The results indicate that coper subjects move in a manner nearly identical to uninjured persons. Kinetic data suggest that copers stabilize their knees with greater contributions from the ankle extensor muscles. Muscle activity data demonstrate that there is no reduction in quadriceps femoris activity in the coper subjects. In the group of ten subjects with knee instability (noncopers) who participated in the overall study involving walking, jogging, hopping, and a step activity only four were willing to hop. Work in our laboratory has established that when high level athletes rupture their ACL, the majority of them cannot return to high level sports. The small number of noncopers in this study who were willing to hop supports our previous findings. Those noncopers who did hop displayed reduced knee range of motion and external knee flexion moments, a movement strategy remarkably similar to that found during other activities. Neither the copers nor the noncopers showed evidence that quadriceps activation was diminished.
TL;DR: In this paper, a robust H∞ controller was developed to deliver insulin via a mechanical pump in Type I diabetic patients, and the controller was evaluated in terms of its ability to track a normoglycemic set point (81.1 mg/dL) in response to a 50 g meal disturbance.
Abstract: A robust H∞ controller was developed to deliver insulin via a mechanical pump in Type I diabetic patients. A fundamental nonlinear diabetic patient model was linearized and then reduced to a third-order linear form for controller synthesis. Uncertainty in the nonlinear model was characterized by up to ± 40% variation in eight physiological parameters. A sensitivity analysis identified the three-parameter set having the most significant effect on glucose and insulin dynamics over the frequency range of interest ω = [0.002, 0.2] (rad/min). This uncertainty was represented in the frequency domain and incorporated in the controller design. Controller performance was assessed in terms of its ability to track a normoglycemic set point (81.1 mg/dL) in response to a 50 g meal disturbance. In the nominal continuous-time case, the controller maintained glucose concentrations within ± 3.3 mg/dL of set point. A controller tuned to accommodate uncertainty yielded a maximum deviation of 17.6 mg/dL for the worst-case parameter variation.
TL;DR: In this paper, the collision rate of monodisperse solid particles in a turbulent gas is governed by a wide range of scales of motion in the flow and the accumulation effect is most noticeable when the particle inertial response time τp is of the order of the flow integral timescale.
Abstract: The collision rate of monodisperse solid particles in a turbulent gas is governed by a wide range of scales of motion in the flow. Recent studies have shown that large-scale energetic eddies are the dominant factor contributing to the relative velocity between two colliding particles (the turbulent transport effect), whereas small-scale dissipative eddies can enhance the collision rate significantly by inducing local non-uniform particle distribution (the accumulation effect). The turbulent transport effect is most noticeable when the particle inertial response time τp is of the order of the flow integral timescale and the accumulation effect is most pronounced when τp is comparable to the flow Kolmogorov time.We study these two contributions separately through direct numerical simulations. The two effects are quantified carefully with a numerical procedure that is independent of the computation of average collision rate. This facilitates the study of not only the statistical description of the collision kernel, but also the relative contributions and modelling of the two physical effects. Simulations at several flow Reynolds numbers were performed to suggest a model for the accumulation effect. The data show that the accumulation effect scales linearly with flow Taylor microscale Reynolds number Rλ, while the theory for fully developed turbulence indicates that the maximum level of the turbulent transport effect scales with R1/2λ. Finally, an integrated model has been developed to predict the collision rate at arbitrary flow Reynolds numbers and particle inertia.