Showing papers by "University of Delaware published in 1995"

The role of visual attention in saccadic eye movements.

Abstract: The relationship between saccadic eye movements and covert orienting of visual spatial attention was investigated in two experiments. In the first experiment, subjects were required to make a saccade to a specified location while also detecting a visual target presented just prior to the eye movement. Detection accuracy was highest when the location of the target coincided with the location of the saccade, suggesting that subjects use spatial attention in the programming and/or execution of saccadic eye movements. In the second experiment, subjects were explicitly directed to attend to a particular location and to make a saccade to the same location or to a different one. Superior target detection occurred at the saccade location regardless of attention instructions. This finding shows that subjects cannot move their eyes to one location and attend to a different one. The results of these experiments suggest that visuospatial attention is an important mechanism in generating voluntary saccadic eye movements.

The WIND magnetic field investigation

Abstract: The magnetic field experiment on WIND will provide data for studies of a broad range of scales of structures and fluctuation characteristics of the interplanetary magnetic field throughout the mission, and, where appropriate, relate them to the statics and dynamics of the magnetosphere. The basic instrument of the Magnetic Field Investigation (MFI) is a boom-mounted dual triaxial fluxgate magnetometer and associated electronics. The dual configuration provides redundancy and also permits accurate removal of the dipolar portion of the spacecraft magnetic field. The instrument provides (1) near real-time data at nominally one vector per 92 s as key parameter data for broad dissemination, (2) rapid data at 10.9 vectors s−1 for standard analysis, and (3) occasionally, snapshot (SS) memory data and Fast Fourier Transform data (FFT), both based on 44 vectors s−1. These measurements will be precise (0.025%), accurate, ultra-sensitive (0.008 nT/step quantization), and where the sensor noise level is <0.006 nT r.m.s. for 0–10 Hz. The digital processing unit utilizes a 12-bit microprocessor controlled analogue-to-digital converter. The instrument features a very wide dynamic range of measurement capability, from ±4 nT up to ±65 536 nT per axis in eight discrete ranges. (The upper range permits complete testing in the Earth's field.) In the FTT mode power spectral density elements are transmitted to the ground as fast as once every 23 s (high rate), and 2.7 min of SS memory time series data, triggered automatically by pre-set command, requires typically about 5.1 hours for transmission. Standard data products are expected to be the following vector field averages: 0.0227-s (detail data from SS), 0.092 s (‘detail’ in standard mode), 3 s, 1 min, and 1 hour, in both GSE and GSM coordinates, as well as the FFT spectral elements. As has been our team's tradition, high instrument reliability is obtained by the use of fully redundant systems and extremely conservative designs. We plan studies of the solar wind: (1) as a collisionless plasma laboratory, at all time scales, macro, meso and micro, but concentrating on the kinetic scale, the highest time resolution of the instrument (=0.022 s), (2) as a consequence of solar energy and mass output, (3) as an external source of plasma that can couple mass, momentum, and energy to the Earth's magnetosphere, and (4) as it is modified as a consequence of its imbedded field interacting with the moon. Since the GEOTAIL Inboard Magnetometer (GIM), which is similar to the MFI instrument, was developed by members of our team, we provide a brief discussion of GIM related science objectives, along with MFI related science goals.

A fully nonlinear Boussinesq model for surface waves. Part 1. Highly nonlinear unsteady waves

Abstract: Fully nonlinear extensions of Boussinesq equations are derived to simulate surface wave propagation in coastal regions. By using the velocity at a certain depth as a dependent variable (Nwogu 1993), the resulting equations have significantly improved linear dispersion properties in intermediate water depths when compared to standard Boussinesq approximations. Since no assumption of small nonlinearity is made, the equations can be applied to simulate strong wave interactions prior to wave breaking. A high-order numerical model based on the equations is developed and applied to the study of two canonical problems: solitary wave shoaling on slopes and undular bore propagation over a horizontal bed. Results of the Boussinesq model with and without strong nonlinearity are compared in detail to those of a boundary element solution of the fully nonlinear potential flow problem developed by Grilli et al. (1989). The fully nonlinear variant of the Boussinesq model is found to predict wave heights, phase speeds and particle kinematics more accurately than the standard approximation.

Emotions and emotion regulation in developmental psychopathology

Abstract: The understanding of emotions possesses important implications for elucidating normal as well as abnormal development. The contributions that the emotions have made for enhancing our understanding of psychopathology have been evident throughout history. In this article, an overview of the historical links between the emotions and psychopathology is presented. Despite its rich history, much contemporary theory and research on emotions has been conducted primarily within a nonpathology perspective. In recent decades, investigators have become more interested in examining the role and development of the emotions in atypical populations. It has been argued that the modularity of the emotions system requires a developmental model of emotion regulation.

Strength of the Quadriceps Femoris Muscle and Functional Recovery after Reconstruction of the Anterior Cruciate Ligament. A Prospective, Randomized Clinical Trial of Electrical Stimulation *

Abstract: Immediately after reconstruction of the anterior cruciate ligament, 110 patients were randomly assigned to treatment with high-intensity neuromuscular electrical stimulation (thirty-one patients), high-level volitional exercise (thirty-four patients), low-intensity neuromuscular electrical stimulation (twenty-five patients), or combined high and low-intensity neuromuscular electrical stimulation (twenty patients). All treatment was performed isometrically with the knee in 65 degrees of flexion. All of the patients participated in an intensive program of closed-kinetic-chain exercise. After four weeks of treatment, the strength of the quadriceps femoris muscle and the kinematics of the knee during stance phase were measured. Quadriceps strength averaged 70 per cent or more of the strength on the uninvolved side in the two groups that were treated with high-intensity electrical stimulation (either alone or combined with low-intensity electrical stimulation), 57 per cent in the group that was treated with high-level volitional exercise, and 51 per cent in the group that was treated with low-intensity electrical stimulation. The kinematics of the knee joint were directly and significantly (p < 0.05) correlated with the strength of the quadriceps. There was a clinically and statistically significant (p < 0.05) difference in the recovery of the quadriceps and the gait parameters according to the type of operation that had been performed: the patients who had had reconstruction of the anterior cruciate ligament with use of an autologous patellar-ligament graft did poorly compared with the other patients.

Smart Interpolation of Annually Averaged Air Temperature in the United States

Abstract: Two “smart” interpolation procedures are presented and assessed with respect to their ability to estimate annual-average air temperatures at unsampled points in space from available station averages. Smart approaches examined here improve upon commonly used procedures in that they incorporate spatially high-resolution digital elevation information, an average environmental lapse rate, and/or another higher-resolution longer-term average temperature field. Two other straightforward or commonly used interpolation methods also are presented and evaluated as benchmarks to which the smart interpolators can be compared. Interpolation from a spatially high-resolution, long-term-average air temperature climatology serves as a first approximation, while “traditional” interpolation (from a single realization of annual average air temperature on a single station network) is the other benchmark. Traditional interpolation continues to be the most commonly used interpolation approach within many of the atmosph...

Transgenic canola and soybean seeds with increased lysine.

Abstract: We have increased the lysine content in the seeds of canola and soybean plants by circumventing the normal feedback regulation of two enzymes of the biosynthetic pathway, aspartokinase (AK) and dihydrodipicolinic acid synthase (DHDPS). Lysine-feedback-insensitive bacterial DHDPS and AK enzymes encoded by the Corynebacterium dapA gene and a mutant E. coli lysC gene, respectively, were linked to a chloroplast transit peptide and expressed from a seed-specific promoter in transgenic canola and soybean seeds. Expression of Corynebacterium DHDPS resulted in more than a 100-fold increase hi the accumulation of free lysine in the seeds of canola; total seed lysine content approximately doubled. Expression of Corynebacterium DHDPS plus lysine-insensitive E. coli AK in soybean transformants similarly caused several hundred-fold increases in free lysine and increased total seed lysine content by as much as 5-fold. Accumulation of α-amino adipic acid (AA) in canola and saccharopine in soybean, which are intermediates in lysine catabolism, was also observed.

“Strong objectivity”: A response to the new objectivity question

Abstract: Where the old “objectivity question” asked, “Objectivity or relativism: which side are you on?”, the new one refuses this choice, seeking instead to bypass widely recognized problems with the conceptual framework that restricts the choices to these two. It asks, “How can the notion of objectivity be updated and made useful for contemporary knowledge-seeking projects?” One response to this question is the “strong objectivity” program that draws on feminist standpoint epistemology to provide a kind of logic of discovery for maximizing our ability to block “might makes right” in the sciences. It does so by delinking the neutrality ideal from standards for maximizing objectivity, since neutrality is now widely recognized as not only not necessary, not only not helpful, but, worst of all, an obstacle to maximizing objectivity when knowledge-distorting interests and values have constituted a research project. Strong objectivity provides a method for correcting this kind of situation. However, standpoint approaches have their own limitations which are quite different from the misreadings of them upon which most critics have tended to focus. Unfortunately, historically limited epistemologies and philosophies of science are all we get to choose from at this moment in history.

Climatologically aided interpolation (cai) of terrestrial air temperature

Abstract: A new and relatively straightforward approach to interpolating and spatially averaging air temperature from weather-station observations is introduced and evaluated using yearly station averages taken from the Jones et al. archive. All available terrestrial station records over the period from 1881 through to 1988 are examined. Called climatologically aided interpolation, or CAI, our procedure makes combined use of (i) a spatially high-resolution air-temperature climatology recently compiled by Legates and Willmott, as well as (ii) spatially interpolated yearly temperature deviations (evaluated at the stations) from the climatology. Spherically based inverse-distance-weighting and triangular-decomposition interpolation algorithms are used to interpolate yearly station temperatures and temperature deviations to the nodes of a regular, spherical lattice. Interpolation errors are estimated using a cross-validation methodology. Interpolation errors associated with CAI estimates of annual-average air temperatures over the terrestrial surface are quite low. On average, CAI errors are of the order of 0.8°C, whereas interpolations made directly (and only) from the yearly station temperatures exhibit average errors between 1.3°C and 1.9°C. Although both the high-resolution climatology and the interpolated temperature-deviation fields explain non-trivial portions of the space-time variability in terrestrial air temperature, most of CAI's accuracy can be attributed to the spatial variability captured by the high-resolution (Legates and Willmott's) climatology. Our results suggest that raw air-temperature fields as well as temperature anomaly fields can be interpolated reliably.

Passive, Adaptive and Active Tuned Vibration Absorbers—A Survey

Abstract: An overview of the recent development of tuned vibration absorbers (TVAs) for vibration and noise suppression is presented. The paper summarizes some popular theory for analysis and optimal tuning of these devices, discusses various design configurations, and presents some contemporary applications of passive TVAs. Furthermore, the paper also presents a brief discussion on the recent progress of adaptive and semi-active TVAs along with their on-line tuning strategies, and active and hybrid fail-safe TVAs.

Improved algorithms for synchronizing computer network clocks

Abstract: The Network Time Protocol (NTP) is widely deployed in the Internet to synchronize computer clocks to each other and to international standards via telephone modem, radio and satellite. The protocols and algorithms have evolved over more than a decade to produce the present NTP Version 3 specification and implementations. Most of the estimated deployment of 100000 NTP servers and clients enjoy synchronization to within a few tens of milliseconds in the Internet of today. This paper describes specific improvements developed for NTP Version 3 which have resulted in increased accuracy, stability and reliability in both local-area and wide-area networks. These include engineered refinements of several algorithms used to measure time differences between a local clock and a number of peer clocks in the network, as well as to select the best subset from among an ensemble of peer clocks and combine their differences to produce a local dock accuracy better than any in the ensemble. This paper also describes engineered refinements of the algorithms used to adjust the time and frequency of the local clock, which functions as a disciplined oscillator. The refinements provide automatic adjustment of algorithm parameters in response to prevailing network conditions, in order to minimize network traffic between clients and busy servers while maintaining the best accuracy. Finally, this paper describes certain enhancements to the Unix operating system kernel software in order to realize submillisecond accuracies with fast workstations and networks. >

Scheimpflug stereocamera for particle image velocimetry in liquid flows.

Abstract: A novel stereocamera has been developed based on the angular-displacement method, wherein the two camera axes are oriented in a nonorthogonal manner toward the object plane. The stereocamera satisfies the Scheimpflug condition such that the image plane, the object plane, and the lens plane are nominally colinear. A unique feature of the stereocamera is the introduction of a liquid prism between the object plane and the recording lens, which significantly reduces the radial distortions that arise when imaging through a thick liquid layer. The design of the camera and its computer optimization with geometric modeling are described. Results indicate that the use of a liquid prism reduces the amount of radial distortion by an order of magnitude. The results have been shown to agree very well with experiments.

Enhanced magnetization of nanoscale colloidal cobalt particles.

Abstract: We have used a microemulsion technique to synthesize metallic cobalt particles in the size range 18 to 44 \AA{} diameter. The particles are spherical, not aggregated due to their surfactant coating, and free of oxide. Magnetic properties such as total moment per particle, blocking temperature, and hysteresis all show reasonable size dependencies. The effects of small size are seen in: (1) the anisotropy constant increased markedly as particle size decreased, and (2) the total magnetic moment per atom in the Co particles was enhanced with decreasing particle size by as much as 30% over the bulk value. Magnetization versus applied field curves indicate the particles are heterogeneous with two magnetic phases, possibly a core-shell structure. The core phase has a large total moment and the shell phase is superparamagnetic with an effective moment of 7.5\ifmmode\pm\else\textpm\fi{}1${\mathrm{\ensuremath{\mu}}}_{\mathit{B}}$ for all sizes. We propose that the shell phase is responsible for the enhanced anisotropy and magnetization.

Police Involvement in Domestic Violence: The Interactive Effects of Victim Injury, Offender's History of Violence, and Race

Abstract: While there is a proliferation of research devoted to ascertaining the efficacy of arrest and other formal sanctions in deterring domestic violence, little research has focused on factors related to the pivotal point at which this formal sanctioning process begins, namely, in a victim's decision to report her victimization to police. This paper is an attempt to rectify this omission by examining those factors most important in predicting the police-reporting behavior of 1535 female victims of intimate-perpetrated violence (e.g., by husbands and boyfriends) taken from the National Crime Victimization Survey during 1987-1992. In addition to predicting the reporting decision of these victims, models predicting various police responses to a victim's report were also examined, including police response times, police actions at the scene, and the probability of an arrest being made. A combination of contextual and demographic characteristics affected the probability that incidents would be placed into the realm of formal sanctioning. Black victims, victims who sustained injury as the result of their victimization, and victims who reported that the offender had not victimized them before were more likely to report their victimization to police. These same factors were also significant predictors of arrest. Police were more likely to make an arrest in incidents in which victims had sustained injuries, when the offender did not have a history of violence, and in incidents which involved Black offenders victimizing Black victims. Implications for the "Battered Women Syndrome" and suggestions for future research are discussed.

Gendering Orientalism: Race, Femininity and Representation

Abstract: In contrast to most cultural histories of imperialism, which analyse Orientalist images of rather than by women, Gendering Orientalism focuses on the contributions of women themselves Drawing on the little-known work of Henriette Browne, other `lost' women Orientlist artists and the literary works of George Eliot, Reina Lewis challenges masculinist assumptions relating to the stability and homogeneity of the Orientalist gaze Gendering Orientalism argues that women did not have a straightforward access to an implicitly male position of western superiority, Their relationship to the shifting terms of race, nation and gender produced positions from which women writers and artists could articulate alternative representations of racial difference It is this different, and often less degrading, gaze on the Orientalized `Other' that is analysed in this book By revealing the extent of women's involvement in the popular field of visual Orientalism and highlighting the presence of Orientalist themes in the work of Browne, Eliot and Charlotte Bronte, Reina Lewis uncovers women's roles in imperial culture and discourse

Dopamine transporter immunoreactivity in rat brain

Abstract: The dopamine transporter (DAT) is a primary site for the action of cocaine in inducing euphoria. Its action is necessary for the selectivities of dopaminergic neurotoxins that provide the best current experimental models of Parkinson's disease. In the present report, rat dopamine transporter-like immunoreactivity (iDAT) was assessed by immunohistochemistry using newly developed polyclonal antisera raised against conjugated peptides corresponding to sequences found in the dopamine transporter's carboxy- and amino-termini. Dense iDAT was observed in patterns consistent with neural processes and terminals in the striatum, nucleus accumbens, olfactory tubercle, nigrostriatal bundle, and lateral habenula. Perikarya in the substantia nigra pars compacta were immunostained with moderate intensity using one of two immunohistochemical methods, while scattered ventral tegmental area perikarya were stained with somewhat less intensity. Immunoreactive neuronal processes with axonal and dendritic morphologies were stained in the substantia nigra and the paranigral and parabrachialis pigmentosus nuclei of the ventral tegmental area, while sparser processes were noted more medially in the ventral tegmental area. Neuronal processes were found in several laminae in the cingulate cortex, with notable fiber densities in the superficial aspects of lamina I and laminae II/III. The intensities of immunoreactivities in striatum and cerebral cortex were dramatically attenuated ipsilateral to nigrostriatal bundle 6-hydroxydopamine lesions. Specificity of immunostaining was supported by agreement of the results using sera directed against two distinct DAT segments, studies with preimmune and preadsorbed sera and studies of the extracted protein. These antisera identify and reveal details of the distribution of DAT immunoreactivity in rat brain and display variations in levels of DAT expression of likely functional significance.

Patterns of sheltering and housing in US disasters

Abstract: The terms “sheltering” and “housing” are used in a variety of unclear and inconsistent ways in the disaster literature. Proposes a differentiation among emergency sheltering, temporary sheltering, temporary housing and permanent housing. Indicates how they are paid differential attention in American disaster planning and gives specific observations about the four patterns, noting especially how they differ from one another. Suggests there will be a future increase in problems in all the patterns, and that it is not yet fully established to what extent these patterns are applicable in all types of societies.

Studying Consideration Effects in Empirical Choice Models Using Scanner Panel Data

Abstract: The authors develop a dynamic consideration set formation model, complementary to the static model developed by Roberts and Lattin (1991). The model does not require direct consumer reports of cons...

Flow mechanism of glaciers on soft beds.

Abstract: Subhourly measurements of bed deformation, bed shear strength, subglacial water pressure, and surface speed at Storglaciaren, a glacier in northern Sweden, showed that the shear-strain rates of the bed decrease during periods of high water pressure and surface speed. High water pressures appear to be accompanied by a reduction in the coupling of ice with the bed that is sufficient to reduce or eliminate shearing. The instability of large ice masses may result from similar decoupling rather than from pervasive bed deformation, as has been commonly thought.

Linear and nonlinear modes in nonrelativistic electron-positron plasmas

Abstract: A comprehensive two-fluid model is developed for collective modes in a nonrelativistic electron-positron plasma. Longitudinal and transverse electrostatic and electromagnetic modes, both in the presence and absence of a magnetic field, are studied. Wave properties are discussed in terms of dispersion relations, wave normal surfaces, and cylindrical mirror analyzer clemmow-Mullaly-Allis diagrams. The results are extended to include the two-stream instability and ion acoustic solitary waves. For the two-stream instability, a similar result is found as in the electron-ion plasma. For ion acoustic solitary waves, only subsonic solutions are found to exist. Furthermore, their width is proportional to their amplitude, unlike the electron-ion plasma case, where the speed is proportional to the amplitude.