Showing papers by "University of Delaware published in 1984"
TL;DR: The Chesapeake Bay anoxia appears to have had significant ecological effects on many marine species, including several of economic importance.
Abstract: Anoxia occurs annually in deeper waters of the central portion of the Chesapeake Bay and presently extends from Baltimore to the mouth of the Potomac estuary. This condition, which encompasses some 5 billion cubic meters of water and lasts from May to September, is the result of increased stratification of the water column in early spring, with consequent curtailment of reoxygenation of the bottom waters across the halocline, and benthic decay of organic detritus accumulated from plankton blooms of the previous summer and fall. The Chesapeake Bay anoxia appears to have had significant ecological effects on many marine species, including several of economic importance.
654 citations
TL;DR: A model is suggested that relates mood, behavioral activity, sociability, and clinical states to activity of the central catecholamine neurotransmitters and to neuroregulators and other transmitters that act in opposite ways on behavior or stabilize activity in the arousal systems.
Abstract: A comparative method of studying the biological bases of personality compares human trait dimensions with likely animal models in terms of genetic determination and common biological correlates. The approach is applied to the trait of sensation seeking, which is defined on the human level by a questionnaire, reports of experience, and observations of behavior, and on the animal level by general activity, behavior in novel situations, and certain types of naturalistic behavior in animal colonies. Moderately high genetic determination has been found for human sensation seeking, and marked strain differences in rodents have been found in open-field behavior that may be related to basic differences in brain neurochemistry. Agonistic and sociable behaviors in both animals and humans and the trait measure of sensation seeking in humans have been related to certain common biological correlates such as gonadal hormones, monoamine oxidase (MAO), and augmenting of the cortical evoked potential.The monoamine systems in the rodent brain are involved in general activity, exploratory behavior, emotionality, socialization, dominance, sexual and consummately behaviors, and intracranial self-stimulation. Preliminary studies have related norepinephrine and enzymes involved in its production and degradation to human sensation seeking. A model is suggested that relates mood, behavioral activity, sociability, and clinical states to activity of the central catecholamine neurotransmitters and to neuroregulators and other transmitters that act in opposite ways on behavior or stabilize activity in the arousal systems. Stimulation and behavioral activity act on the catecholamine systems in a brain–behavior feedback loop. At optimal levels of catecholamine systems activity (CSA) mood is positive and activity and sociability are adaptive. At very low or very high levels of CSA mood is dysphoric, activity is restricted or stereotyped, and the organism is unsocial or aggressively antisocial. Novelty, in the absence of threat, may be rewarding through activation of noradrenergic neurons.
624 citations
TL;DR: In this article, a parabolic model for calculating the combined refraction/diffraction of monochromatic linear waves is developed, including a term which allows for the dissipation of wave energy.
Abstract: A parabolic model for calculating the combined refraction/diffraction of monochromatic linear waves is developed, including a term which allows for the dissipation of wave energy. The coefficient of the dissipation term is related to a number of dissipative models. Wave calculations are performed for a localized area of dissipation, based on a friction model for a spatial distribution of rigid vertical cylinders. The region of localized dissipation creates a shadow region of low wave energy, which may have important implications for the response of neighboring shore lines.
484 citations
TL;DR: In this article, it was shown that the undertow is driven by the local difference between radiation stress and the set-up pressure gradient which only balance each other in average over the depth.
457 citations
01 Jan 1984
TL;DR: Following the lead of Haggett and Chorley (1967), Rayner (1974), Terjung (1976), Strahler (1980) and many others, physical geography has adopted a “model-based paradigm” and, as a result, the development and application of a wide variety of models is now commonplace within virtually every sub-field from geomorphology to bioclimatology.
Abstract: Following the lead of Haggett and Chorley (1967), Rayner (1974), Terjung (1976), Strahler (1980) and many others, physical geography has adopted a “model-based paradigm” and, as a result, the development and application of a wide variety of models is now commonplace within virtually every sub-field from geomorphology to bioclimatology. Within climatology, many models have a predominately deductive genesis while other models are collages of statistical and empirical reasoning and, in a few cases, “best-fit” functions are extracted from data with seemingly little regard for the safeguards of a deductive stance. Still other models combine the mathematics of probability theory with empirically derived probabilities to create stochastic simulation models, e.g., Markov or Monte Carlo models. These categories of models are, by no means, mutually exclusive (or exhaustive for that matter) and a number of recent models may be considered combinatorial in that they incorporate two or more of the above-mentioned strategies into a single model.
448 citations
TL;DR: Socially responsible consumption is an important prerequisite to successful voluntary conservation programs as mentioned in this paper, and a review of past research describing the socially responsible consumer and consumer behavior can be found in this article.
Abstract: Socially responsible consumption is an important prerequisite to successful voluntary conservation programs. This article reviews past research describing the socially responsible consumer and prov...
403 citations
TL;DR: In this paper, a mathematical analysis of bubble growth in an expanding foam is presented based on a cell model whereby the foam is divided into spherical microscopic unit cells of equal and constant mass, each consisting of a liquid envelope or shell and a concentric spherical gas bubble.
Abstract: A mathematical analysis of bubble growth in an expanding foam is presented. The analysis is based on a cell model whereby the foam is divided into spherical microscopic unit cells of equal and constant mass, each consisting of a liquid envelope (or shell) and a concentric spherical gas bubble. Expansion occurs by diffusion of a dissolved gas from the supersaturated envelope into the bubble. This cell model is capable of describing important qualitative features of a real system of numerous bubbles growing in close proximity to one another, and is intended as the building block of a global analysis of macroscopic foam expansion. The coupled algebraic and differential equations governing the growth of a cell are derived and solved numerically. Five dimensionless parameters are identified for the case of constant temperature and pressure outside the cell, and their effects are demonstrated through computer simulations of the system. Of these parameters, surface tension and initial radius prove to be of relatively little importance in the practical cases considered. The other parameters are the thermodynamic driving force, the cell mass (inversely proportional to the number density of bubbles), and the ratio of characteristic times for mass and momentum transport.
329 citations
TL;DR: In this paper, a theoretical model for wave heights and set-up in a surf zone is developed for wave flux, radiation stress and energy dissipation by simple approximations which include the effect of the surface roller in the breaker and actual shape of the waves.
327 citations
TL;DR: In this paper, the authors studied various transport processes including dispersion, convection, Brownian motion, chemotaxis and tumbling of bacteria, and the differences between bacteria and viruses in their transport mechanisms, decay and growth kinetics have also been investigated.
254 citations
TL;DR: In this paper, preliminary screening tests comparing the total Hg(II) removal capacity of 11 different brands of commercial activated carbon indicated that a very high percent (99-100%) total hg removal was attained by all types of activated carbon especially at pH 4-5.
215 citations
TL;DR: In this article, the helium isoelectronic sequence for values of the nuclear charge $Z$ ranging from 1 to 10 was computed using 230-term wave functions, and the results illustrate the importance of using basis functions which have the same analytic structure as the exact wave function being approximated.
Abstract: We have performed variational calculations on the helium isoelectronic sequence for values of the nuclear charge $Z$ ranging from 1 to 10. The basis used is a modification of that employed by Frankowski and Pekeris in 1966, whose calculation has not been superseded before now. Using 230-term wave functions, we obtain for $Z=2$ through 10 variational energies accurate to better than a few parts in ${10}^{13}$. Our results illustrate the importance of using basis functions which have the same analytic structure as the exact wave function being approximated.
TL;DR: In this paper, the double loop (DL) test is used to detect susceptibility to intergranular attack associated with precipitation of chromium carbides at grain boundaries, where the surface is first polarized anodically through the active region before the reactivation scan in the opposite direction is conducted.
Abstract: Measurement of the amount of electric charge (coulombs) generated during electrochemical reactivation from a potential in the passive range to the corrosion potential has been used to detect susceptibility to intergranular attack associated with precipitation of chromium carbides at grain boundaries. The surfaces to be tested must be given a diamond paste polish to 1 μm. To simplify such measurements, a technique has recently been proposed for which a 140 μm or 100 grit (SiC) finish has been specified. For this test, called the double loop (DL) test, the surface is first polarized anodically through the active region before the reactivation scan in the opposite direction is conducted. In this test, the degree of sensitization is measured by determining the ratio of the maximum current generated by the reactivation scan to that of the anodic scan, Ir:Ia. The characteristics of the DL method have been investigated. It is independent of the surface finish as well as the presence of random pitting; i...
TL;DR: In this paper, it is pointed out that this apparent conflict could be resolved if the mass density of the universe today were dominated by relativistic particles produced by the recent decay of massive, relic particle species, or by a relic cosmological constant.
Abstract: Theoretical prejudices argue strongly for a flat universe; however, observations do not support this view. It is pointed out that this apparent conflict could be resolved if the mass density of the universe today were dominated by (1) relativistic particles produced by the recent decay of massive, relic particle species, or by (2) a relic cosmological constant. Scenario (1) has several advantages in the context of galaxy formation, but must confront the problem of a young universe.
TL;DR: In this article, a general mechanistic scheme involving both interfacial electrostatic and chemical interactions is proposed for cytochrome c electrode reactions, and it is concluded that electron transfer between an electrode surface and the exposed heme edge of properly oriented cyto-chrome c molecules involves maximum distances of ca. 0.6-0.9 nm.
Patent•
13 Nov 1984TL;DR: In this paper, a periodic radiation transmissive diffraction grating incorporating radiation reflecting elements in spaced array, preselected, in demultiplexing service, is employed to separate into individual entities an optical signal input constituting a multiplicity of coherent radiation signals.
Abstract: A wavelength division method and system employing a radiation transmissive planar waveguide provided with collimating and focusing lenses and with a periodic radiation transmissive diffraction grating incorporating radiation reflecting elements in spaced array, preselected, in demultiplexing service, to separate into individual entities an optical signal input constituting a multiplicity of coherent radiation signals of different characteristic wavelengths transmitted simultaneously via the waveguide and, in multiplexing service, to consolidate a multiplicity of coherent radiation signals individually introduced to the grating via the waveguide along angular courses substantially coincident with the angular courses taken by individual radiation signals of corresponding wavelengths exiting the grating during demultiplexing service, and means directing the signals to dedicated receptors.
TL;DR: In this paper, the authors proposed a predictive model for peptides and proteins as samples, using reversed-phase high-performance liquid chromatography, assuming that isocratic and gradient retention are interrelated for peptide molecules.
TL;DR: In this paper, two simple methods for determining the parameters of the Weibull distribution function are developed based upon the analysis of the tensile curves of fibre bundles, which greatly simplified the fibre testing process.
Abstract: The strength of fibres used as reinforcement materials for advanced composites is often assumed to follow the two-parameter Weibull distribution function. However, the experimental process widely used for obtaining the two parameters is tedious and prone to error. In this paper, two simple methods for determining the parameters of the Weibull distribution function are developed based upon the analysis of the tensile curves of fibre bundles. The first method focuses on the relation between the shape of a fibre bundle tensile curve and the survivability of fibres; the second method makes use of the relation between the maximum load point of a fibre bundle tensile curve and the shape parameter of the Weibull distribution of fibre strength. These two methods, in particular the second one, have greatly simplified the fibre testing process. Experimental results on Thornel-300 carbon fibres further demonstrate the validity of these techniques.
TL;DR: In this paper, the failure characteristics of [0/90/0] and [90/ 0/90] cross-ply laminates based on statistical strength analysis were analyzed.
Abstract: This paper treats the failure characteristics of [0/90/0] and [90/0/90] cross-ply laminates based upon the statistical strength analysis. The stress redistributions at the failure of the 90 ° ply are analyzed using a shear-lag model, taking the thermal residual stresses and Poisson effect into consideration. The formulae for determining first cracking, subsequent multiple cracking and ultimate fracture are derived. The present analysis is compared with the existing experimental results for graphite/epoxy cross-ply laminates, and reasonable agreements have been obtained.
TL;DR: The cross-sectional and prospective regression findings suggest that received social support, as measured by the ISSB, does not have a direct or stress-buffering effect on psychological disorder, and the data suggest that the ISEL is a promising measure of this construct.
Abstract: This study investigated the relationship between negative life events and psychological disorder and the roles of positive life events and received and perceived social support in moderating this relationship. A prospective design was used and statistical analyses were based on a hierarchical regression model. College undergraduates served as subjects. Negative events were significantly related to psychological disorder at each of two measurement periods. This relationship was found even when initial disorder was statistically controlled. The cross-sectional analyses, but not the prospective analyses, provided some support for the stress-buffering (interaction) effects of positive events. There was no support for the stress-buffering effects of received social support, but the cross-sectional and prospective regression analyses provided strong support for the stress-buffering effects of perceived social support.
TL;DR: Results of a three-year survey of the occurrence of Callinectes sapidus larvae in the mouth of Delaware Bay indicated that stage I zoea larvae were most abundant insurface water as compared to mid-depths and near bottom, suggesting a tidally related, vertical migration.
Abstract: Results of a three-year survey of the occurrence of Callinectes sapidus larvae in the mouth of Delaware Bay indicated that stage I zoea larvae were most abundant insurface water as compared to mid-depths and near bottom. The major peak in abundance of stage I zoea larvae occurred in early August with a secondary peak in early September. Peaks in abundance of megalopae occurred five weeks after the respective peaks in zoeal abundance. Zoea stages II–VIII were not collected in the bay mouth. Results of sampling every 3 h over consecutive tidal cycles showed that stage I zoea larvae were most common in the water column on ebbing tidal currents. Megalopae were most common in the water column on flooding tidal currents, suggesting a tidally related, vertical migration. It was concluded that stage I zoea larvae are flushed from the estuary and undergo development on the continental shelf. Megalopae are then transported back to inshore waters by a combination of winds and currents and invade the estuary by means of migration into the water column on flooding tidal currents and migration to the bottom on ebbing tidal currents.
TL;DR: Results from the Essex estuary-coastal system of northern Massachusetts show grazing and production at rates that indicate a daily turnover of the standing crop of bacteria, with highest values in mid-estuarine waters.
Abstract: Grazing on planktonic bacteria by microzooplankton was estimated by separating bacteria from the larger plankton with 1μm pore Nuclepore filtration and measuring changes in bacteria in filtered and unfiltered samples over 24 hours. In the absence of grazers, bacteria increased linearly. The regression coefficient of linear increase was used to estimatein situ bacterial production. When grazers were present, the changes in bacteria concentration usually took the form of a linear decline, and grazing was estimated by subtracting the regression coefficient of the unfiltered sample from that of the 1μm filtrate. Results from the Essex estuary-coastal system of northern Massachusetts show grazing and production at rates that indicate a daily turnover of the standing crop of bacteria, with highest values in mid-estuarine waters. Experiments on the size distribution of grazing showed that microzooplankton from 1-3μm were responsible for most of the observed decrease in bacteria. It was suggested that the basic pattern of linear increase of the bacteria in the absence of grazing reflects density-dependent limitation by substrate present at the outset of the incubation and is indicative of a population that has been maintained around the mid-point of the logistic growth curve by grazing.
TL;DR: This article examined the changes in memory for conversation over time and found that participants recall less content and reported more descriptive statements, made more inferences, and were less accurate than when they had recalled immediately.
Abstract: Participants took part in a two-stage investigation examining the changes in memory for conversation over time. The impact of memory expectancy and mode of recall were also examined. Participants could recall only about 10% of their conversations immediately after the conversations. One month later this figure had dropped to 4%. Examination of recall protocols revealed that after a one month delay, participants recalled less content and reported more descriptive statements, made more inferences, and were less accurate than when they had recalled immediately. In addition, expectancies about memory and mode used to report recollections affected the amount and type of information reported. Finally, participants recalled more of their partner's contributions to the conversations than their own contributions.
TL;DR: Lunar-synchronized spawning has been reported in four orders of fish as mentioned in this paper, including coral-reef fishes of the Perciformes, and it has been hypothesized that the spawning cyclicity in these fishes synchronizes reproduction with moonlight or current conditions that enhance parental care or predator avoidance.
Abstract: Lunar-synchronized spawning has been reported in four orders of fish. Salmoniform, atheriniform, and tetraodontiform species spawn intertidally on spring tides, leaving their eggs exposed to air between tidal inundations. This spawning mechanism may be essential to survival of species that are residents of areas such as tide marshes where dissolved-oxygen concentrations in the water column can be near zero. Spawning cycles of both lunar and semilunar periods have been reported in coral-reef fishes of the Perciformes. Reproduction by these fishes does not include aerial incubation of eggs. It has been hypothesized that the spawning cyclicity in these fishes synchronizes reproduction with moonlight or current conditions that enhance parental care or predator avoidance. The intertidal spawners that have been studied display cyclic changes in gonad maturity consistent with a semilunar periodicity in recruitment of oocytes into final maturation. Oocytes in the early stages of vitellogenesis are presen...
TL;DR: Caracteristiques de la microstructure des polymeres semi-cristallins as discussed by the authors, role des different parametres (proprietes des chaines and histoire thermique).
Abstract: Caracteristiques de la microstructure des polymeres semi-cristallins. Role des differents parametres (proprietes des chaines et histoire thermique). Relations empiriques sur les relations entre la microstructure et la rupture. Generalisations de ces relations. Cartes de la rupture (144 references)
TL;DR: In this article, the Brinkman-Forchheimer-extended Darcy model is used as the momentum equation and the effect of porosity variation is taken into consideration.
TL;DR: Several domains were identified in which siblings as well as parents of sick children were more susceptible to adjustment problems, though 'risk' seemed to relate more closely to illness-specific variables than the presence or absence of illness.
Abstract: Summary Focusing on the adjustment of the siblings of three groups of male children; with pervasive developmental disability, diabetes and no known chronic illness, the present study failed to support the view that siblings of ill children are uniformly at greater risk for psychosocial impairment. However, several domains were identified in which siblings as well as parents of ill children were more susceptible to adjustment problems, though ‘risk’ seemed to relate more closely to illness-specific variables than the presence or absence of illness. Several sex differences were found suggesting that same-sexed siblings may be more vulnerable to maladjustment than opposite-sexed pairs. The results are discussed in terms of their implications for investigation and intervention for families with an ill member.
TL;DR: In this article, it was shown that a large proportion of the metallic substances discharged into water bodies is ultimately incorporated into sediments, a complex mixture with three main components: clays, organic matter, and oxides of iron and manganese.
Abstract: The behavior of heavy metals in a natural aqueous system is attracting researchers because of environmental issues. Man's activities have increased the quantity and distribution of heavy metals in the atmosphere, on the land, and in rivers, lakes, and seas. The extent of this widespread contamination has caused concern about its possible effects on plants, animals and human beings. One of the first steps in any systematic study of the aquatic chemistry of a potential contaminant is an elucidation of the principal modes of transport and sinks for the contaminant. It appears that a large proportion of the metallic substances discharged into water bodies is ultimately incorporated into sediments. (Warren, L. J.,112 and others). The sediment is a complex mixture with three main components: clays, organic matter, and oxides of iron and manganese. While the role of clays and biota in affecting the transport of heavy metals is commonly recognized, the significance of Fe and Mn among the factors that are involved...
TL;DR: In this paper, the concentration of trace metals Cd, Cu, Fe, Mn, Ni, Pb, V and Zn has been measured in atmospheric precipitation events at the middle Atlantic coast (Lewes, DE) and on the western Atlantic island of Bermuda.
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TL;DR: A simple extension of the SU(5) Higgs system is presented and shown to yield a satisfactory inflationary scenario in this article, where a simple inflationary model is used to solve the problem.
Abstract: A simple extension of the SU(5) Higgs system is presented and shown to yield a satisfactory inflationary scenario.