Showing papers by "University of Delaware published in 1999"
TL;DR: An operational meaning to ” controlled” and ”uncontrolled” is given and a method of analysis through which hypotheses about controlled and uncontrolled degrees of freedom can be tested is described, finding that, for the task of sit-to-stand, the position of the center of mass in the sagittal plane was controlled.
Abstract: The degrees of freedom problem is often posed by asking which of the many possible degrees of freedom does the nervous system control? By implication, other degrees of freedom are not controlled. We give an operational meaning to "controlled" and "uncontrolled" and describe a method of analysis through which hypotheses about controlled and uncontrolled degrees of freedom can be tested. In this conception, control refers to stabilization, so that lack of control implies reduced stability. The method was used to analyze an experiment on the sit-to-stand transition. By testing different hypotheses about the controlled variables, we systematically approximated the structure of control in joint space. We found that, for the task of sit-to-stand, the position of the center of mass in the sagittal plane was controlled. The horizontal head position and the position of the hand were controlled less stably, while vertical head position appears to be no more controlled than joint motions.
1,333 citations
TL;DR: In this paper, the fundamentals of electromagnetic theory, dielectric response, and applications of microwave heating to materials processing, especially fiber composites, are reviewed in this article, and a knowledge of electromagnetic theories and dielectrics is essential to optimize the processing of materials through microwave heating.
Abstract: In microwave processing, energy is supplied by an electromagnetic field directly to the material. This results in rapid heating throughout the material thickness with reduced thermal gradients. Volumetric heating can also reduce processing times and save energy. The microwave field and the dielectric response of a material govern its ability to heat with microwave energy. A knowledge of electromagnetic theory and dielectric response is essential to optimize the processing of materials through microwave heating. The fundamentals of electromagnetic theory, dielectric response, and applications of microwave heating to materials processing, especially fiber composites, are reviewed in this article.
1,296 citations
TL;DR: In this paper, the authors focused on a particular type of socially responsible processes and outcomes in organizationally integrated ways or in easily decoupled fashion and proposed a set of guidelines for socially responsible process and outcomes.
Abstract: Corporations can respond to expectations for socially responsible processes and outcomes in organizationally integrated ways or in easily decoupled fashion. This study focused on a particular type ...
857 citations
TL;DR: A new method of digital Steganography, entitled spread spectrum image steganography (SSIS), which hides and recovers a message of substantial length within digital imagery while maintaining the original image size and dynamic range.
Abstract: We present a new method of digital steganography, entitled spread spectrum image steganography (SSIS). Steganography, which means "covered writing" in Greek, is the science of communicating in a hidden manner. Following a discussion of steganographic communication theory and review of existing techniques, the new method, SSIS, is introduced. This system hides and recovers a message of substantial length within digital imagery while maintaining the original image size and dynamic range. The hidden message can be recovered using appropriate keys without any knowledge of the original image. Image restoration, error-control coding, and techniques similar to spread spectrum are described, and the performance of the system is illustrated. A message embedded by this method can be in the form of text, imagery, or any other digital signal. Applications for such a data-hiding scheme include in-band captioning, covert communication, image tamperproofing, authentication, embedded control, and revision tracking.
742 citations
TL;DR: A considerable body of observational data has accumulated that indicates very different behavior for various trace metals in sulfidic sediments as mentioned in this paper, but also reflect differences in ligand exchange reaction kinetics, and redox reaction pathways.
723 citations
TL;DR: Oxygen-18 isotope labeling showed that water is the source of the oxygen atoms in the molecular oxygen evolved, and so this system is a functional model for photosynthetic water oxidation.
Abstract: The formation of molecular oxygen from water in photosynthesis is catalyzed by photosystem II at an active site containing four manganese ions that are arranged in di-mu-oxo dimanganese units (where mu is a bridging mode). The complex [H2O(terpy)Mn(O)2Mn(terpy)OH2](NO3)3 (terpy is 2,2':6', 2"-terpyridine), which was synthesized and structurally characterized, contains a di-mu-oxo manganese dimer and catalyzes the conversion of sodium hypochlorite to molecular oxygen. Oxygen-18 isotope labeling showed that water is the source of the oxygen atoms in the molecular oxygen evolved, and so this system is a functional model for photosynthetic water oxidation.
644 citations
TL;DR: In this paper, the authors used control theory to delineate an ethics program's scope and examine the characteristics of the program's execution. But they focused on the control theory-based approach.
Abstract: Our study asked why corporations introduce formal programs to manage ethics and why those programs display varying characteristics. We used control theory to delineate an ethics program's scope and...
600 citations
TL;DR: The results suggest that rhizobacteria able to produce ACC deaminase and, to a lesser extent, β-1,3-glucanase or siderophores or those able to solubilize P in vitro may increase early soybean growth in nonsterile soil.
Abstract: Although many studies have been conducted to identify the specific traits by which plant growth-promoting rhizobacteria (PGPR) promote plant growth, usually they were limited to studying just one or two of these traits. We selected 116 isolates from bulk soil and the rhizosphere of soybean [Glycine max (L.) Merr.] and examined them for a wide array of traits that might increase early soybean growth in nonsterile soil (PGPR traits). A subsample of 23 isolates, all but one of which tested positive for one or more of these PGPR traits, was further screened for traits associated with biocontrol, (brady)rhizobial inhibition, and rhizosphere competence. Six of eight isolates positive for 1-aminocyclopropane-1-carboxylate (ACC, a precursor of ethylene) deaminase production, four of seven isolates positive for siderophore production, three of four isolates positive for β-1,3-glucanase production, and two of five isolates positive for P solubilization increased at least one aspect of early soybean growth. One isolate. which did not share any of the PGPR traits tested in vitro except antagonism to Sclerotium rolfsii and Sclerotinia sclerotiorum, also promoted soybean growth. One of the 23 isolates changed bradyrhizo-promoted soybean growth. One of the 23 isolates changed bradyrhizobial nodule occupancy. Although the presence of a PGPR trait in vitro does not guarantee that a particular isolate is a PGPR, the results suggest that rhizobacteria able to produce ACC deaminase and, to a lesser extent, β-1,3-glucanase or siderophores or those able to solubilize P in vitro may increase early soybean growth in nonsterile soil.
566 citations
TL;DR: A model-based-predictive control algorithm is developed to maintain normoglycemia in the Type I diabetic patient using a closed-loop insulin infusion pump and outperforms an internal model controller from literature under noise-free conditions.
Abstract: A model-based-predictive control algorithm is developed to maintain normoglycemia in the Type I diabetic patient using a closed-loop insulin infusion pump. Utilizing compartmental modeling techniques, a fundamental model of the diabetic patient is constructed. The resulting nineteenth-order nonlinear pharmacokinetic-pharmacodynamic representation is used in controller synthesis. Linear identification of an input-output model from noisy patient data is performed by filtering the impulse-response coefficients via projection onto the Laguerre basis. A linear model predictive controller is developed using the identified step response model. Controller performance for unmeasured disturbance rejection (50 g oral glucose tolerance test) is examined. Glucose setpoint tracking performance is improved by designing a second controller which substitutes a more detailed internal model including state-estimation and a Kalman filter for the input-output representation The state-estimating controller maintains glucose within 15 mg/dl of the setpoint in the presence of measurement noise. Under noise-free conditions, the model based predictive controller using state estimation outperforms an internal model controller from literature (49.4% reduction in undershoot and 45.7% reduction in settling time). These results demonstrate the potential use of predictive algorithms for blood glucose control in an insulin infusion pump.
528 citations
TL;DR: Competition between prokaryotes and eukaryotes for organically-bound iron may depend on the chemical nature of available iron complexes, with consequences for ecological niche separation, plankton community size-structure and carbon export in low-iron waters.
Abstract: Dissolved-iron availability plays a critical role in controlling phytoplankton growth in the oceans1,2 The dissolved iron is overwhelmingly (∼99%) bound to organic ligands with a very high affinity for iron3,4,5, but the origin, chemical identity and biological availability of this organically complexed Fe is largely unknown6 The release into sea water of complexes that strongly chelate iron could result from the inducible iron-uptake systems of prokaryotes (siderophore complexes)7,8,9 or by processes such as zooplankton-mediated degradation and release of intracellular material (porphyrin complexes) Here we compare the uptake of siderophore- and porphyrin-complexed 55Fe by phytoplankton, using both cultured organisms and natural assemblages Eukaryotic phytoplankton efficiently assimilate porphyrin-complexed iron, but this iron source is relatively unavailable to prokaryotic picoplankton (cyanobacteria) In contrast, iron bound to a variety of siderophores is relatively more available to cyanobacteria than to eukaryotes, suggesting that the two plankton groups exhibit fundamentally different iron-uptake strategies Prokaryotes utilize iron complexed to either endogenous7,8,9 or exogenous siderophores9, whereas eukaryotes may rely on a ferrireductase system10,11 that preferentially accesses iron chelated by tetradentate porphyrins, rather than by hexadentate siderophores Competition between prokaryotes and eukaryotes for organically-bound iron may therefore depend on the chemical nature of available iron complexes, with consequences for ecological niche separation, plankton community size-structure and carbon export in low-iron waters
485 citations
TL;DR: It was determined that in situ spectra of both schwertmannite and adsorbed sulfate are quite similar, suggesting that a continuum of outer- and inner-sphere sulfate occurs in both cases.
TL;DR: The Mars Global Surveyor spacecraft obtained vector magnetic field measurements above the surface of Mars and groups of quasi-parallel linear features of alternating magnetic polarity were found, reminiscent of similar magnetic features associated with sea floor spreading and crustal genesis on Earth but with a much larger spatial scale.
Abstract: The Mars Global Surveyor spacecraft, in a highly elliptical polar orbit, obtained vector magnetic field measurements above the surface of Mars (altitudes >100 kilometers). Crustal magnetization, mainly confined to the most ancient, heavily cratered martian highlands, is frequently organized in east-west-trending linear features, the longest extending over 2000 kilometers. Crustal remanent magnetization exceeds that of terrestrial crust by more than an order of magnitude. Groups of quasi-parallel linear features of alternating magnetic polarity were found. They are reminiscent of similar magnetic features associated with sea floor spreading and crustal genesis on Earth but with a much larger spatial scale. They may be a relic of an era of plate tectonics on Mars.
TL;DR: In this paper, the dramatic developments that occurred in nanophase hard magnetic materials over the last two decades are reviewed, and much emphasis is devoted to nanocomposite films consisting of nanoparticles of a high anisotropy material embedded in a non-magnetic matrix.
TL;DR: In this article, the authors reported the direct observation of coherent acoustic phonon propagation in crystalline gallium arsenide using a nonthermal, ultrafast-laser-driven plasma, a high-brightness, laboratory-scale source of subpicosecond X-ray pulses.
Abstract: Fundamental processes on the molecular level, such as vibrations and rotations in single molecules, liquids or crystal lattices and the breaking and formation of chemical bonds, occur on timescales of femtoseconds to picoseconds. The electronic changes associated with such processes can be monitored in a time-resolved manner by ultrafast optical spectroscopic techniques1, but the accompanying structural rearrangements have proved more difficult to observe. Time-resolved X-ray diffraction has the potential to probe fast, atomic-scale motions2,3,4,5. This is made possible by the generation of ultrashort X-ray pulses6,7,8,9,10, and several X-ray studies of fast dynamics have been reported6,7,8,11,12,13,14,15. Here we report the direct observation of coherent acoustic phonon propagation in crystalline gallium arsenide using a non-thermal, ultrafast-laser-driven plasma — a high-brightness, laboratory-scale source of subpicosecond X-ray pulses16,17,18,19. We are able to follow a 100-ps coherent acoustic pulse, generated through optical excitation of the crystal surface, as it propagates through the X-ray penetration depth. The time-resolved diffraction data are in excellent agreement with theoretical predictions for coherent phonon excitation20 in solids, demonstrating that it is possible to obtain quantitative information on atomic motions in bulk media during picosecond-scale lattice dynamics.
TL;DR: In situ assembly of colloidal particles onto micropatterned electrodes holds promise for creating disposable on-chip arrays of highly sensitive miniature sensors for specific proteins, DNA fragments, or other biomolecules.
Abstract: We show how to create arrays of biosensors by in situ assembly of colloidal particles onto micropatterned electrodes. Latex microspheres from suspension are collected via dielectrophoresis in the micrometer-sized gaps between planar electrodes. The assembled particulate patches are fixed by changing the colloidal interactions to induce coagulation. Immuno-active sites on the latex surfaces bind the target molecules. A direct electric conductivity readout is accomplished after secondary tagging with colloidal gold and its enhancement by silver nucleation. The method holds promise for creating disposable on-chip arrays of highly sensitive miniature sensors for specific proteins, DNA fragments, or other biomolecules.
TL;DR: In this article, a new class of metallic materials with long-range nano-scale ordering and hierarchical porosity was synthesized by using colloidal crystals as templates, and they were used to fabricate structures from inorganic oxides, polymers, diamond and glassy carbon.
Abstract: Colloidal crystals are ordered arrays of particles in the nanometre-to-micrometre size range. Useful microstructured materials can be created by replicating colloidal crystals in a durable matrix that preserves their key feature of long-range periodic structure1. For example, colloidal crystals have been used to fabricate structures from inorganic oxides1,2,3,4,5, polymers6,7, diamond and glassy carbon8, and semiconductor quantum dots9, and some structures have photonic properties4,8,9 or are patterned on different hierarchical length scales5. By using colloidal crystals as templates, we have synthesized a new class of metallic materials with long-range nano-scale ordering and hierarchical porosity.
TL;DR: The interaction of the solar wind with the local interstellar medium (LISM) is attracting renewed interest, thanks to the possibility that the Voyager spacecraft may, in the not too distant future, cross the heliospheric termination shock as mentioned in this paper.
Abstract: The interaction of the solar wind with the local interstellar medium (LISM) is attracting renewed interest, thanks to the possibility that the Voyager spacecraft may, in the not too distant future, cross the heliospheric termination shock. This has spurred the development of increasingly sophisticated models which attempt to describe various aspects of the physics underlying the interaction of the solar wind and the LISM. A comprehensive review of the subject is presented here.
TL;DR: In this article, the clinical performance characteristics of seven optical-based and one electromagnetic-based biomechanical measurement system were evaluated in a 3 m long volume, and the results indicated that five of the seven optical systems produced less than 2.0 mm RMS errors when measuring fully visible moving markers, and typically less that 1.0mm RMS error when measuring the stationary marker.
Book•
01 Feb 1999TL;DR: Zuckerman et al. as mentioned in this paper proposed a bio-social model to understand why people are vulnerable to the different variants of psychopathology, which is the focus of their new book "Vulnerability to psychopathology: A Biosocial Model Marvin Zuckerman".
Abstract: Vulnerability to Psychopathology: A Biosocial Model Marvin Zuckerman. Washington, DC: American Psychological Association. 1999, 535 pp., (hardcover). A great deal has been learned about psychopathology, but still many questions remain. One of the most important questions remaining to be answered is why people are vulnerable to the different variants of psychopathology ? Zuckerman has made this broad question the focus of his new book. It is a book that is remarkable by its scholarship. It provides a compendium of information on the history of mental disorders, and research findings on their course, diagnosis and prevalence, comorbidity, demographic features, genetic and biological characteristics, and social factors, and is punctuated by a strong biological orientation. Zuckerman indicates that his new book was written as a "logical sequel" to his previous book on the Psychobiology of Personality (Zuckerman, 1991). His book, which is divided into eight chapters, provides a review of the wealth of findings on psychopathology. The first cluster of chapters of the book deals with general considerations including diathesis-stress models (chapter 1), and diagnosis (chapter 2); the second cluster, and main body of the book (chapters 3 to 7), describes theory and research on a selected number of specific disorders, and the final concluding chapter is concerned with the prognosis of the future science of psychopathology. In the first chapter we learn that diathesis-stress theories are not monolithic but exhibit great variety. His model extends Paul Meehl's orientation to schizoprhenia to other disorders, and thus focuses on a biological diathesis and social stress (e.g., parenting) that increases risk of disorders. Zuckerman's book largely restricts the term diathesis to genetic and biological factors. As it happens, then, he questions the basis for the notion of cognitive vulnerability. His grounds for this are that the concept of a cognitive predisposition to psychopathology is not empirically well supported, and that it could simply be a "typical expression of a biological disposition" (p. 7), or other "interpersonal" and "developmental" factors (p. 197). For example, he suggests that research has not adequately demonstrated that cognitive factors predict subsequent levels of depression or other disorders, and are not simply state-manifestations of the disorders. These views are challenged by recent research of the Temple-Wisconsin depression project (e.g., Alloy, Abramson, Hogan et al., 2000). Although Zuckerman's book clearly reflects a monumental undertaking of scholarship, its review of the rapidly advancing cognitive literature on psychopathology is dated. Readers who are interested in a cognitively oriented approach to vulnerability to psychopathology will thus need to look for other references (e.g., Alloy & Riskind, in press). Along with his restriction of the concept of vulnerability to biological diathesis, Zuckerman's book pays little attention to methodological issues, and particularly to issues important for cognitively oriented researchers. Readers who are interested in such issues will have to turn to other sources, such as the excellent chapter by Alloy, Abramson, Raniere, & Dyller, (1999). …
TL;DR: The complex and somewhat bewildering phenomenon of why people sometimes decide not to evacuate from a dangerous situation is influenced by a combination of individual characteristics and three basic social psychological processes: risk perception, social influence, and access to resources as mentioned in this paper.
Abstract: The complex and somewhat bewildering phenomenon of why people sometimes decide not to evacuate from a dangerous situation is influenced by a combination of individual characteristics and 3 basic social psychological processes: (a) risk perception, (b) social influence, and (c) access to resources. This study used a combined sample of 777 adults interviewed after Hurricanes Hugo and Andrew. Although numerous variables significantly predicted evacuation, much variance in this behavior still remained unexplained. Different population subgroups gave different reasons for not evacuating (e.g., severeness of storm, territoriality). A multifaceted and tailored approach to both individuals and communities is needed; a simple warning is often not enough.
TL;DR: In this article, a series of telephone surveys was conducted; housing was requested from the same landlord during a short time period using standard and nonstandard dialects, and the results demonstrate that landlords discriminate against prospective tenants on the basis of the sound of their voice during telephone conversations.
Abstract: The ability to discern the use of a nonstandard dialect is often enough information to also determine the speaker’s ethnicity, and speakers may consequently suffer discrimination based on their speech. This article, detailing four experiments, shows that housing discrimination based solely on telephone conversations occurs, dialect identification is possible using the word hello, and phonetic correlates of dialect can be discovered. In one experiment, a series of telephone surveys was conducted; housing was requested from the same landlord during a short time period using standard and nonstandard dialects. The results demonstrate that landlords discriminate against prospective tenants on the basis of the sound of their voice during telephone conversations. Another experiment was conducted with untrained participants to confirm this ability; listeners identified the dialects significantly better than chance. Phonetic analysis reveals that phonetic variables potentially distinguish the dialects.
TL;DR: In this paper, the effects of humic acid adsorption, concentration polarization, and aggregate deposition on the rate and extent of fouling were investigated using ultrafiltration membranes with a broad range of molecular weight cutoffs.
TL;DR: This paper investigated the framing effects of television news coverage of an anarchist protest and found that status quo support had significant effects on viewers, leading them to be more critical of, and less likely to identify with, the protesters; less critical of the police; and more likely to support the protesters' expressive rights.
Abstract: We investigated framing effects of television news coverage of an anarchist protest. Three treatment stories differed in their level of status quo support. Status quo support had significant effects on viewers, leading them to be more critical of, and less likely to identify with, the protesters; less critical of the police; and less likely to support the protesters' expressive rights. Status quo support also produced lower estimates of the protest's effectiveness, public support, and perceptions of newsworthiness. The results substantiate concerns about status quo support by showing that it can influence audience perceptions.
TL;DR: In this article, a nonlinear cascade drives fluctuations toward short wavelengths which are transverse to the mean field, thereby heating at rates insensitive to restrictive Alfven timescales, and a phenomenology is presented, providing estimates of achievable heating efficiency that are most favorable.
Abstract: A candidate mechanism for the heating of the solar corona in open field line regions is described. The interaction of Alfven waves, generated in the photosphere or chromosphere, with their reflections and the subsequent driving of quasi-two-dimensional MHD turbulence is considered. A nonlinear cascade drives fluctuations toward short wavelengths which are transverse to the mean field, thereby heating at rates insensitive to restrictive Alfven timescales. A phenomenology is presented, providing estimates of achievable heating efficiency that are most favorable.
TL;DR: The influence of acid−base interactions on the gas-phase dissociation of a series of protonated peptides was investigated and it was observed that the number of ionizing protons relative to the numberof basic residues in peptides containing acidic residues is a contributing factor in the fragmentation behavior.
Abstract: The influence of acid−base interactions on the gas-phase dissociation of a series of protonated peptides was investigated Peptides containing both acidic residues [aspartic (D), glutamic (E), and cysteic acid (C*)] and basic residues [arginine (R)] were dissociated by different activation methods that allow different time frames for dissociation The synthetic peptides investigated differ systematically in the number and position of arginine residue(s) and include RLDIFSDFR, RLEIFSEFR, RLDIFSDF, LDIFSDFR, LEIFSEFR, LDIFSDF, RLCIFSCFR, RLAIFSCFR, RLCIFSAFR, RLC*IFSC*FR, RLAIFSC*FR, and RLC*IFSAFR (where C* denotes cysteic acid) It was observed that the number of ionizing protons relative to the number of basic residues in peptides containing acidic residues is a contributing factor in the fragmentation behavior Nonselective cleavages along the peptide backbone occur when the number of ionizing protons exceeds the number of arginine residues, while dominant cleavages adjacent to the acidic residues predo
TL;DR: In this article, it was shown that Pd complexes with sterically hindered alkylphosphines accelerate reductive elimination of diaryl ethers and protected phenols from unactivated aryl halides.
Abstract: The reductive elimination of ethers from transition metal complexes is a rare elementary reaction that is limited to special cases. The importance of aryl ether substructures has created a synthetic challenge to prepare the aryl-oxygen linkage in a general fashion under mild conditions. Pd-catalyzed C-O coupling could be a solution to this synthetic problem, but the reductive elimination of acyclic ethers that is the crucial step for this catalytic process has been limited to palladium complexes with aromatic systems that are highly activated and undergo direct, uncatalyzed nucleophilic aromatic substitution chemistry. Thus, it is unactivated aryl halides that are crucial substrates to include in transition metal-catalyzed C-O coupling chemistry, and they report that Pd complexes with sterically hindered alkylphosphines (1) undergo thermal reductive elimination to form the C-O bond in diaryl ethers from complexes with unactivated metal-bound aryl groups and (2) catalyze the formation of diaryl ethers and protected phenols from unactivated aryl halides. These findings demonstrate the concept that sterically hindered alkylphosphines accelerate reductive elimination.
TL;DR: In this article, the authors make a distinction between within-session and between-session chasing, and examine the determinants of withinsession chasing in a reasonably valid laboratory analogue, where male college students who gambled (N=248) were given US$10 and an opportunity to gamble.
TL;DR: Using polyfurfuryl alcohol as the nanoporous carbon precursor and a pyrolysis temperature of 723 kelvin, a membrane was prepared with the following permeances, measured in moles per square meter per Pascal per second, to create a thin film of polymer on a tubular, macroporous, stainless steel support.
Abstract: Ultrasonic deposition creates a thin film of polymer on a tubular, macroporous, stainless steel support Using polyfurfuryl alcohol as the nanoporous carbon precursor and a pyrolysis temperature of 723 kelvin, a membrane was prepared with the following permeances, measured in moles per square meter per Pascal per second: nitrogen, 18 × 10−12; oxygen, 56 × 10−11; helium, 33 × 10−10; and hydrogen, 61 × 10−10 The ideal separation factors as compared to that for nitrogen are 30:1, 178:1, and 331:1 for oxygen, helium, and hydrogen, respectively
TL;DR: In this paper, the formation of nitrate and sulfate on coarse particles and its relationship with meteorological conditions and relative abundance of sea-salt and soil particles were studied using a MOUDI cascade impactor.