Showing papers by "University of Delaware published in 1985"
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TL;DR: The aim of this chapter is to examine structural and functional roles of turns in peptides and proteins.
Abstract: Publisher Summary Turns are a fundamental class of polypeptide structure and are defined as sites where the peptide chain reverses its overall direction. In the past 20 years, the peptide field has witnessed major development, stimulated by the discovery of a host of bioactive peptides. Turn structures have been proposed and implicated in the bioactivity of several of these naturally occurring peptides. In addition, many structural details of turns have been derived from conformational studies of model peptides. During this same period, more than 100 complete protein structures have been elucidated in single-crystal X-ray studies. These examples document the rich diversity of structural patterns in the chain folds of native proteins. Turns are intrinsically polar structures with backbone groups that pack together closely and side chains that project outward. Such an array of atoms may constitute a site for molecular recognition, and indeed, the literature abounds with suggestions that turns serve as loci for receptor binding, antibody recognition, and post-translational modification. In peptides, turns are the conformations of choice for simultaneously optimizing both backbone–chain compactness (intramolecular nonbonded contacts) and side-chain clustering (to facilitate intermolecular recognition). Presence of turns in bioactive conformations may in fact also reflect the lack of alternative conformational possibilities. The aim of this chapter is to examine structural and functional roles of turns in peptides and proteins.
1,580 citations
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TL;DR: In this article, the spatial and seasonal variations of the continental fields of snow-cover, soil moisture and evapotranspiration are presented and interpreted using a modified version of the method of Thornthwaite.
Abstract: Calculations of the spatial and seasonal variations of the continental fields of snow-cover, soil moisture and evapotranspiration are presented and interpreted. The calculations were made with a water budget analysis that is based on observed average monthly precipitation and an estimate of potential evapotranspiration derived from observed average monthly surface temperature, using a modified version of the method of Thornthwaite. Monthly average water budget analyses were made for 13,332 stations over the globe and, then spatially interpolated to a regular grid at 1° by 1° latitude-longitude intervals. From the monthly fields on a 4° by 5° subset of the 1° by 1° grid, the annual mean and standard deviation as well as the first and second annual harmonics were extracted and are displayed on global maps. Of the three fields, soil moisture has the largest space-time variation; snow-cover the smallest variation; and evapotranspiration an intermediate level of variation.
488 citations
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01 Jan 1985398 citations
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TL;DR: In this article, the authors consider constraints on the masses and lifetimes of weakly interacting massive particles (WIMPs) based on the assumption that the observed large-scale structure of the universe is allowed to develop, leading to much more restrictive bounds on the properties of WIMPs than those which follow from considerations of the age and density of the entire universe alone.
371 citations
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01 Jan 1985TL;DR: In this paper, the authors developed algorithms for contouring on spherical surfaces and in Cartesian two-space to investigate errors on small-scale climate maps caused by the common practice of interpolating from irregularly-spaced data points to regular-lattice nodes.
Abstract: From Shepard's (1968) local-search method, algorithms are developed for contouring on spherical surfaces and in Cartesian two-space. These algorithms are used to investigate errors on small-scale climate maps caused by the common practice of interpolating—from irregularly-spaced data points to regular-lattice nodes—and contouring in Cartesian two-space. Using mean annual air temperatures drawn from 100 irregularly-spaced weather stations, the annual air-temperature field over the western half of the northern hemisphere is estimated both on the sphere (assumed to be correct) and in Cartesian two-space. When these fields are mapped and compared, error magnitudes as large as 5° to 10° C appear in the air-temperature field approximated in Cartesian two-space.
370 citations
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TL;DR: In this article, the effective thermal conductivity of a misoriented short fiber composite was examined based on the equivalent inclusion method for steady-state heat conduction in composite which was recently proposed.
Abstract: This paper examines the effective thermal conductivity of a misoriented short fiber composite The analysis is based on the equivalent inclusion method for steady‐state heat conduction in composite which we have recently proposed The present approach is unique in that it takes into account the interaction among fibers at different orientations Closed form solutions are given for the thermal conductivity of a misoriented short fiber composite Then, numerical results are presented to demonstrate the effects of volume fraction, fiber aspect ratio, and distribution function of fiber orientation on the thermal conductivity
358 citations
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TL;DR: Evidence of selection bias in the subgroup of women who remarry is found, suggesting that currently unmarried women might not improve their economic status through remarriage as much as women who have remarried.
Abstract: We use longitudinal data from the Panel Study of Income Dynamics to assess the economic consequences of divorce and separation for the women and men involved. In contrast to previous studies focusing exclusively on those who remain unmarried, our approach integrates the probability of remarriage into the analysis and produces a much less dramatic picture of change in economic status than analyses not incorporating remarriage. However, we also find evidence of selection bias in the subgroup of women who remarry, suggesting that currently unmarried women might not improve their economic status through remarriage as much as women who have remarried.
355 citations
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311 citations
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TL;DR: A review of the literature on fiber-reinforced metal-matrix composites can be found in this paper, where fabrication methods, mechanical properties, secondary working techniques and interfaces are discussed.
260 citations
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TL;DR: In this paper, a computational procedure is developed for predicting the time-dependent, two-dimensional beach and dune erosion during severe storms due to elevated water levels and waves, and the model employs the equation of sediment continuity and a dynamic equation governing the cross-shore sediment transport due to a disequilibrium of wave energy dissipation levels.
238 citations
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TL;DR: In this paper, the stress field in a coated continuous fiber composite subjected to thermo- mechanical loadings is calculated by use of four concentric circular cylinders model and the target material is Ni- or SiC-...
Abstract: The stress field in a coated continuous fiber composite subjected to thermo- mechanical loadings is calculated by use of four concentric circular cylinders model. The target material is Ni- or SiC-...
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TL;DR: Two dimensions of information sharing are identified, some constraints that are used or have been suggested as useful are discussed, and constraints are described in terms of what entities a given program component can access and how it can use them.
Abstract: The use and sharing of information by program components can be constrained in a variet y of ways . The constraints supported by various programming languages . and the relationships between those constraints, deserve investigation . Most commonly, constraints are stated i n terms of what entities a given program component can access and how it can use them, an d that is the issue we investigate in this note . (A more difficult issue, which we defer, concern s the components that can access a given entity and how they can use it .) For now, we identif y two dimensions of information sharing, discuss some constraints that are used or have bee n suggested as useful, and describe those constraints in terms of our dimensions .
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TL;DR: In this article, the nonlinear dynamics of the magnetohydrodynamic sheet pinch have been investigated as an unforced initial value problem for large scale Reynolds numbers up to 1000, and it has been shown that electric field fluctuations near the X point produce irregularities in the vector potential, sometimes taking the form of magnetic bubbles, which allow rapid change of field topology.
Abstract: The nonlinear dynamics of the magnetohydrodynamic sheet pinch have been investigated as an unforced initial value problem for large scale Reynolds numbers up to 1000. Reconnection is triggered by adding to the sheet pinch a small but finite level of broadband random perturbations. Effects of turbulence in the solutions include the production of reconnected magnetic islands at rates that are insensitive to resistivity at early times. This is explained by noting that electric field fluctuations near the X point produce irregularities in the vector potential, sometimes taking the form of ‘‘magnetic bubbles,’’ which allow rapid change of field topology.
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TL;DR: A survey of 487 adult, MBA, and undergraduate business students on the business philosophies of Machiavellianism, Darwinism, Objectivism, Relativism, and Universalism showed that prospective managers tend to be less ethical than practicing ones.
Abstract: While the media and public opinion polls suggest that the state of business ethics is declining, surveys of corporate managers on the subject are less than conclusive. This study presents results of a survey of 487 adult, MBA, and undergraduate business students on the business philosophies of Machiavellianism, Darwinism, Objectivism, Relativism, and Universalism. The findings were consistent with earlier research which showed prospective managers to be less ethical than practicing ones and that women and those reporting a strong religious conviction tend to be more ethical. Explanations and several recommendations for improving the situation are offered.
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TL;DR: In this paper, the pre-Holocene surface is an erosional trellis-dendritic drainage system of tributaries to the ancestral Delaware River, cut during a time of lower Pleistocene sea level and increased flow, enhanced by glacial meltwater.
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TL;DR: In this paper, the authors found that chlorophyll concentrations in the Delaware estuary were regulated both spatially and temporally by light availability and seasonal periodicity correlated with solar irradiance.
Abstract: Phytoplankton chlorophyll concentrations in the Delaware estuary range over two orders of magnitude and display several maxima over the seasonal cycle. These maxima were found to be regulated both spatially and temporally by light availability. Both the spring chlorophyll maximum, which reaches 50–60 μg chlorophyll l−1 during a Skeletonema costatum dominated bloom, and transient fall blooms (15–20 μg l−1) are focused in mid-estuary. These blooms are regulated spatially by settling out of suspended sediment below the turbidity maximum and both spatially and temporally by physical factors (e.g. river flow) that cause vertical stratification in mid-estuary. In freshwater regions, chlorophyll concentrations display seasonal periodicity correlated with solar irradiance; summer chlorophyll concentrations average 30 μg l−1. These freshwater and mid-estuarine biomass maxima may be correctly predicted using a steady-state light-limitation model. In contrast, summer chlorophyll concentrations in the lower estuary remain below 10 μg l−1 and are not correctly modeled, despite minimum turbidity, and non-nutrient limiting conditions. These chlorophyll concentrations appear to be regulated by a combination of light availability and grazing.
Although extremely high anthropogenic nutrient inputs in the freshwater region of the Delaware River provide non-limiting nutrient concentrations throughout the estuary, regulation of phytoplankton growth by light-limitation restricts chlorophyll concentrations below the nuisance levels found in many eutrophic systems.
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TL;DR: In this paper, a general-purpose pyrolysis cell described is capable of attaining rapid heating rates (8-200K s−1) at various gas pressures (0.048-1000 psi, 0.33 KPa-6.8 MPa) and is an attempt to simulate, insofar as possible, combustor conditions.
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TL;DR: In this paper, the authors present the papers given at a conference on free convection in porous materials, including heat transfer, nonlinear temperature profiles and magnetic fields, boundary conditions, concentrated heat sources in stratified porous media, free convective flow in a cavity, heat flux, laminar mixed convection flow, and the onset of convection.
Abstract: This book presents the papers given at a conference on free convection in porous materials. Topics considered at the conference included heat transfer, nonlinear temperature profiles and magnetic fields, boundary conditions, concentrated heat sources in stratified porous media, free convective flow in a cavity, heat flux, laminar mixed convection flow, and the onset of convection in a porous medium with internal heat generation and downward flow.
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TL;DR: In this paper, a 3D mathematical approach to slope stability is presented, which is based on limiting equilibrium and variational analysis, and the analysis yields a non-linear first order partial differential equation, relating the slip surface and its first partial derivatives.
Abstract: A 3-D mathematical approach to slope stability, which is based on limiting equilibrium and variational analysis, is presented. In the initial formulation there are three unknown functions: the slip surface, the normal stress and the shear stress direction over this surface. The minimum factor of safety is sought through variational extremization. The analysis indicates that the factor of safety is independent of the normal stress distribution over the critical slip surface. It also indicates that the direction of the elementary shear force over the slip surface depends on the slip surface function, but not on the normal stress function. The analysis yields a non-linear first order partial differential equation, relating the slip surface and its first partial derivatives. By limiting the analysis to symmetrical problems an ordinary differential equation, governing the slip surface path on the plane of symmetry, is derived. This equation enables the development of a numerical procedure to determine the minimal factor of safety of symmetrical 3-D slopes. Two possible failure modes are determined for homogeneous slopes. One mode consists of finite 3-D sliding body and the second represents cylindrical failure. Numerical analyses for some simple cases, of homogencous slopes are presented.
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TL;DR: In this article, a general relationship is presented to predict the effective transport properties of composite materials in terms of the properties and concentration of the components and the internal microstructure of the composite materials.
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TL;DR: In this paper, a comprehensive review on the chemistry and mineralogy of nonexchangeable potassium is presented, including forms of soil K, the effect of mineralogy on release of non-changeable K, methods of determining nonexchangeability K, and the kinetics of non−exchangeable? release are fully discussed.
Abstract: A comprehensive review on the chemistry and mineralogy of nonexchangeable potassium is presented. Forms of soil K, the effect of mineralogy on release of nonexchangeable K, methods of determining nonexchangeable K, and the kinetics of non‐exchangeable ? release are fully discussed.
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TL;DR: Several hundred halophytes from salt marshes and salt deserts of the world have been evaluated in the laboratory at various degrees of intensity, and a few have been selected for development as crops.
Abstract: Several hundred halophytes from salt marshes and salt deserts of the world have been evaluated in our laboratory at various degrees of intensity, and a few have been selected for development as crops. The development of the cultivars and the basic biology of the plants is being studied in Delaware in the United States. Agronomic testing, feeding trials, and development of the best agronomic practices are taking place in the saline desert at the American University in Cairo research station in Sadat City. Our present efforts focus primarily on three forages, one grain, and one vegetable. Sporobolus virginicus cultivars for both hay and pasture are being tested. A Distichlis spicata cultivar for hay has been identified, and Spartina patens is being evaluated as a hay as well. Although we do not yet have the data for a full year’s growth in Egypt, forage yields of these various cultivars, when harvested as hay crops, range to 6.9 or more tons per acre, depending on the salinity and other environmental conditions, and the crude protein content as indicated by the nitrogen content ranges from 6 to 10%. Cultivars having the most useful agronomic qualities have been identified and are being increased in quantity. The grain crop Kosteletzkya virginica is a perennial, producing a seed which resembles millet; its whole seeds contain approximately 25% protein and 15% oil. The yields of one of our better cultivars are about 1460 kg/ha (1300 lb/acre) when grown under 25‰ salinity. The vegetable Atriplex triangularis (similar to spinach) has been under mass selection for four years; a cultivar has been identified and seed is now being increased for this species.
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TL;DR: In this paper, a formulation of the generalized van der Waals partition function derived earlier is used, together with insights obtained from computer simulation, to develop two new equations of state for the square-well fluid.
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TL;DR: Wild-type and pseudorevertant signal peptides of the lamB gene product of Escherichia coli interact with lipid systems whereas a nonfunctional deletion mutant signal peptide does not and conformationally related amphiphilicity and consequent membrane affinity of signal sequences are important for function in vivo.
Abstract: Wild-type and pseudorevertant signal peptides of the lamB gene product of Escherichia coli interact with lipid systems whereas a nonfunctional deletion mutant signal peptide does not. This conclusion is based on interaction of synthetic signal peptides with a lipid monolayer-water surface, conformational changes induced by presence of lipid vesicles in an aqueous solution of signal peptide, and capacities of the peptides to promote vesicle aggregation. Analysis of the signal sequences and previous conformational studies suggest that these lipid interaction properties may be attributable to the tendency of the functional signal peptides to adopt alpha-helical conformations. Although the possibility of direct interaction between the signal peptide and membrane lipids during protein secretion is controversial, the results suggest that conformationally related amphiphilicity and consequent membrane affinity of signal sequences are important for function in vivo.
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TL;DR: The paired-comparison novelty technique was used to assess the 5-month-old infant's ability to discriminate between the facial expressions of anger, fear, and sadness as discussed by the authors.
Abstract: The paired-comparison novelty technique was used to assess the 5-month-old infant's ability to discriminate between the facial expressions of anger, fear, and sadness. The 72 infants met the criterion for discrimination except when anger was the novel stimulus. It was hypothesized that for some infants novelty was a less potent determinant of looking than was another aspect of the stimulus ex pression, such as its social-signal value or relative aversiveness. A second experiment was designed to test this notion. Sixty-eight infants failed to meet the criterion of discrimination between joy, anger, and interest, though infants had done so in previous studies. Results of the two experiments suggest that some 5-month-olds can discriminate between anger, sadness, and fear expressions, but that the paired-comparison novelty technique may underestimate the infant's ability to detect differences among stimuli of different social- or emotion-signal value.
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01 Nov 1985TL;DR: In this article, conditions on the common distribution such that the sum of appropriately normalized and centred upper kn extreme values based on the first n random variables converges in distribution to a normal random variable were determined.
Abstract: Given a sequence of non-negative independent and identically distributed random variables, we determine conditions on the common distribution such that the sum of appropriately normalized and centred upper kn extreme values based on the first n random variables converges in distribution to a normal random variable, where kn → ∞ and kn/ n → 0 as n → ∞. The probabilistic problem is motivated by recent statistical work on the estimation of the exponent of a regularly varying distribution function. Our main tool is a new Brownian bridge approximation to the uniform empirical and quantile processes in weighted supremum norms.
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TL;DR: In this paper, the authors measured the heats of fusion of new multicomponent eutectics and intermetallic phases using commercial calorimeters, a differential thermal analyzer, and a differential scanning calorimeter.
Abstract: Eutectic compositions and congruently melting intermetallic compounds in binary and multicomponent systems among common elements such as Al, Ca, Cu, Mg, P, Si, and Zn may be useful for high temperature heat storage. In this work, heats of fusion of new multicomponent eutectics and intermetallic phases are reported, some of which are competitive with molten salts in heat storage density at high temperatures. The method used to determine unknown eutectic compositions combined results of differential thermal analysis, metallography, and microprobe analysis. The method allows determination of eutectic compositions in no more than three steps. The heats of fusion of the alloys were measured using commercial calorimeters, a differential thermal analyzer, and a differential scanning calorimeter.
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TL;DR: In this article, the elastic moduli of fabric composites are con ducted in order to evaluate the theoretical predictions developed by the authors in their previous work, and the experimental results coincide very well with the theory for 8 harness satin carbon/epoxy systems.
Abstract: Some experiments for measuring the elastic moduli of fabric composites are con ducted in order to evaluate the theoretical predictions developed by the authors in their previous work. Experimental results coincide very well with the theory for 8 harness satin carbon/epoxy systems. There exists some discrepancy between theories for con strained and unconstrained local warping in the case of plain weave composites. Ex perimental results are bounded by these two theories. The dependency of elastic moduli on laminate ply number is discovered in plain weave composites. The ratio of ply thickness to thread width is also a very important parameter, which strongly affects the elastic moduli of plain weave composites. The in-plane shear modulus of fabric composites is mainly influenced by fiber volume fraction, which varies linearly with ng. Off-axis properties of fabric composites are measured and compared with theories. The experimental results essentially confirm the validity of the author's theoretical predict...
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TL;DR: Sandler et al. as discussed by the authors provided a new derivation of the generalized van der Waals partition function for pure fluids and mixtures, and showed how this partition function can be used as a basis for understanding equations of state, their mixing rules, and excess free energy (activity coefficient) models.