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Showing papers by "University of Delaware published in 1981"


Journal ArticleDOI
TL;DR: In this paper, it is suggested that the correlation coefficieness between observed and simulated variates is not as good as observed variates, and that correlation can be improved.
Abstract: Traditional methods of evaluating geographic models by statistical comparisons between observed and simulated variates are criticized. In particular, it is suggested that the correlation coefficien...

3,761 citations


Journal ArticleDOI
15 May 1981-Science
TL;DR: Research on chitin as a marine resource is pointing to novel applications for this cellulose-like biopolymer, and new methods for preparing the bioactive alkyl glycoside of N-acetyl-D-glucosamine and microcrystalline Chitin have encouraged their use as promoters for growth of bifidobacteria and as an aid in digestion of high-lactose cheese whey by domestic animals.
Abstract: Research on chitin as a marine resource is pointing to novel applications for this cellulose-like biopolymer. Discovery of nondegrading solvent systems has permitted the spinning of filaments, for example, for use as surgical sutures. New methods for preparing the bioactive alkyl glycoside of N-acetyl-D-glucosamine (the monomer unit of chitin) and a microcrystalline chitin has encouraged their use as promoters for growth of bifidobacteria and as an aid in digestion of high-lactose cheese whey by domestic animals. Chitin-protein complexes of several crustacean species show great variability in ratios of chitin to covalently bound protein and in residual protein in the "purified" chitins.

340 citations


Journal ArticleDOI
TL;DR: It is shown that some well-known iterative methods of image reconstruction fall into the class of algorithms under consideration, and are thus covered by the convergence theory, and a novel application to truly three-dimensional image reconstruction is described.

276 citations


Journal ArticleDOI
TL;DR: In this article, the authors present a method for wave and wave forces on an offshore structure due to a directional wave spectrum, which is correct to second-order in wave height.
Abstract: Most available methods for wave force computation incorporate either the nonlinearities of the ocean surface for a single fundamental component or the random and/or directional characteristics using the superposition of linear wave components. An exception is the intuitive "hybrid" method 1 which combines elements of linear and nonlinear waves. The present paper describes and applies a method, which is correct to second order in wave height, for calculating waves and wave forces on an offshore structure due to a directional wave spectrum. Starting with a prescribed linear spectrum of directional waves, a set of random phases is generated and the second-order spectrum computered with phases defined by all contributing pairs of first-order components. With one realization of the spectrum thus complete up to the second order, the wave profile and water particle kinematics can be simulated in the time domain. The wave forces are also computed in the time domain taking full account of their nonlinear and directional properties. The resulting wave forces at any level vary in direction and magnitude. The total wave forces summed over all piling of a structure are less than those for a unidirectional train of waves with the same one-dimensional spectrum. Several examples are presented to illustrate reductions in maximum wave forces due to the directional distribution of the waves. It is found that for a single piling the maximum force decreases by a factor ranging from 1.0 to 0.61 as the directional spread increases from unidirectional to omnidirectional. For a four-pile group on a square array of 300 ft. spacing, the corresponding decrease in the factor is from 1.0 to 0.51 for a Bretschneider spectrum with a peak period of approximately 12 seconds. The results of this complete model are compared with the more intuitive and approximate hybrid method and are found to agree quite well. Force spectra are presented and discussed for the inline and transverse directions.

206 citations


Journal ArticleDOI
TL;DR: In this paper, the adsorption of Cu(II) by aluminosilicates with varying Si/Al ratios was investigated and the contribution of each mechanism to the total amount of CuGly++ adsorbed is related to the Si/A1 ratio.

202 citations


Journal ArticleDOI
TL;DR: In this paper, a model which accounts for the effect of a confining wall and the resulting voidage variations near it on the flow behavior in packed columns is proposed, which reasonably describes the pressure drop-flow rate relationship for both linear and non-Newtonian fluids.
Abstract: A model which accounts for the effect of a confining wall and the resulting voidage variations near it on the flow behavior in packed columns is proposed. The model, which is restricted to columns randomly packed with spheres of uniform size, reasonably describes the pressure drop-flow rate relationship for both linear and non-Newtonian fluids. The mass flux distribution is also studied in order to provide an insight into processes in which the flow behavior near the wall may be important.

197 citations


Journal ArticleDOI
TL;DR: The results suggest that the interference between simultaneous visual discriminations depends critically on their separation in visual space.
Abstract: To what extent does successful search for a target letter in a visual display depend on the allocation of attention to the target’s spatial position? To investigate this question, we required subjects to discriminate the orientation of a briefly flashed U-shaped form while searching for a target letter. Performance operating characteristics (POCs) were derived by varying the relative amounts of attention subjects were to devote to each task. Extensive tradeoffs in performance were observed when the orientation form and target letter occurred in nonadjacent display positions. In contrast, the tradeoff was much more restricted when the two targets occurred in adjacent positions. These results suggest that the interference between simultaneous visual discriminations depends critically on their separation in visual space. Both visual search and form discrimination require a common limited-capacity visual resource.

196 citations


Book ChapterDOI
TL;DR: Folding of proteins to native-like structure has been demonstrated with fragments of 8-galactosidase, lysozyme, serum albumin, penicillinase, and tryptophan synthetase.
Abstract: Publisher Summary Folding of proteins to native-like structure has been demonstrated with fragments of 8-galactosidase, lysozyme, serum albumin, penicillinase, and tryptophan synthetase. The capability of protein fragments for independent formation of structure has substantial experimental basis. Protein folding occurs “by parts”—that is, in a modular fashion. The structural feature of chain continuity within a compact domain is realized in the fragments of only two of the systems in which independent folding has been shown. These two are lysozyme and thermolysin. Most of the proteins on which fragment folding studies have been carried out are extracellular. Many secreted proteins are synthesized with 20 or so additional amino acid residues at the N-terminus of the peptide chain. Secretion can impose additional constraints on protein folding. Different parts of protein molecules can form native-like structure independently. Some protein fragments show the ability to form native-like structures in vivo . So, protein folding “by parts” is a process that goes on in real life as well as in vitro . The chapter also outlines the experimental findings, protein by protein, roughly in chronological order, and explains the significance of these findings.

194 citations


Journal ArticleDOI
TL;DR: In this article, the problem of two kinds of ellipsoidal inhomogeneities embedded in an elastic body is formulated with an application to a hybrid (three-phase) composite.

194 citations


Journal ArticleDOI
TL;DR: In this paper, a relative sea-level curve for Delaware, obtained from radiocarbon dates on basal peats, rises smoothly from 25 m below present sea level 10,000 years B.P.

158 citations


Journal ArticleDOI
TL;DR: A general framework for regularization and approximation methods for ill-posed problems is developed in this paper, where three levels in the resolution processes are distinguished and emphasized: philosophy of resolution, regularization-approximation schema, and regularization algorithms.
Abstract: A general framework for regularization and approximation methods for ill-posed problems is developed. Three levels in the resolution processes are distinguished and emphasized: philosophy of resolution, regularization-approximation schema, and regularization algorithms. Dilemmas and methodologies of resolution of ill-posed problems and their numerical implementations are examined in this framework with particular reference to the problem of finding numerically minimum weighted-norm least-squares solutions of first kind integral equations (and more generally of linear operator equations with nonclosed range). A common problem in all these methods is delineated: each method reduces the problem of resolution to a "nonstandard" minimization problem involving an unknown critical "parameter" whose "optimal" value is crucial to the numerical realization and amenability of the method. The "nonstandardness" results from the fact that one does not have explicitly, or a priori, the function to be minimized; it has to built up using additional information, convergence rate estimates, and robustness conditions, etc. Several results are developed that complement recent advances in numerical analysis and regularization of inverse and ill-posed (identification and pattern synthesis) problems. An emphasis is placed on the role of constraints, function space methods, the role of generalized inverses, and reproducing kernels in the regularization and stable computational resolution of these problems. The results will be applied specifically to problems of antenna synthesis and identification. However the thrust of the paper is devoted to the interdisciplinary character of operator-theoretic and numerical methods for ill-posed problems.



Journal ArticleDOI
TL;DR: Feeding patterns during four 24-h periods, sampled at 3-h intervals, were investigated for the mummichog Fundulus heteroclitus, an important link in energy transfers between the marsh surface and subtidal systems, enhancing its own energy supplies by consuming marsh surface prey whenever available.
Abstract: Feeding patterns during four 24-h periods, sampled at 3-h intervals, were investigated for the mummichog Fundulus heteroclitus, in a Delaware, USA tidal marsh. Two factors potentially influencing feeding patterns, time of day and tide height, were examined. On 2 of the sampling periods a low tide occurred in the morning, while on the other 2 sampling periods a high tide occurred in the morning. Results are reported as g-dry wt. of food per g-dry wt. of fish. F. heteroclitus is primarily a daytime feeder that most actively feeds at high tide, regardless of whether or not the high tide inundates marsh surface areas. When tide height was sufficient to inundate the marsh surface, fish invaded these areas and consumed prey characteristic of the marsh surface. F. heteroclitus is an important link in energy transfers between the marsh surface and subtidal systems, enhancing its own energy supplies by consuming marsh surface prey whenever available.

Journal ArticleDOI
TL;DR: Comparable series of chitins were derived from blue, red, stone, and horseshoe crabs by representative mild acid and EDTA decalcification followed by alkali deproteinization, finding a family of closely-related products with variable solubility, molecular weight, optical rotation, and acetyl values.
Abstract: 1. 1. Comparable series of chitins were derived from blue, red, stone, and horseshoe crabs by representative mild acid and EDTA decalcification followed by alkali deproteinization. 2. 2. These chitins were found to comprise a family of closely-related products with variable solubility, molecular weight, optical rotation, and acetyl values, which are a function of both the species from which they originated and their method of preparation. 3. 3. Substantial differences in the chitins were observed even from a single species, depending upon the details of their isolation.

Journal ArticleDOI
TL;DR: In this paper, the authors developed an analysis for predicting the stress distribution in unidirectional discontinuous fiber composites, where the basic approach is based upon the shear-lag analysis, the load transfer at fiber ends is taken into consideration.
Abstract: This paper develops an analysis for predicting the stress distribution in unidirectional discontinuous fiber composites. Although the basic ap proach is based upon the shear-lag analysis, the load transfer at fiber ends is taken into consideration. This consideration becomes important if the bonding between the fiber and matrix at the fiber end is perfect such as the cases often observed in metal matrix composites, as well as during the early stage of loading of polymeric matrix composites. The present analysis in cludes the ordinary shear-lag analysis as a special case.

Journal ArticleDOI
TL;DR: In this article, a variety of reliability models with a small number of components may be studied in terms of finite-state Markov processes, assuming that the time-to-failure and repair time distributions are of phase type.
Abstract: Assuming that the time-to-failure and repair time distributions areof phase type, a variety of reliability models with a small number of components may be studied in terms of finite-state Markov processes. Although the state spaces of these processes are typically large, their infinitesimal generators are highly structured. By utilizing the formalism of PH-distributions, it is possible to construct efficient algorithms to evaluate a large number of quantities of interest. Some new properties of PH-distributions are also established.

Journal ArticleDOI
TL;DR: In this paper, various models that have been proposed to predict the properties of particulate filled systems are reviewed and compared with experimental data, and theoretical combining rules are presented to predict Young's modulus, Poisson's ratio shear modulus and bulk modulus.
Abstract: Various models that have been proposed to predict the properties of particulate filled systems are reviewed and compared with experimental data. At filler volume fractions less than ∼0.2-∼0.3, these models give essentially equivalent predictions that are within the scatter of experimental measurements. At higher volume fraction of inclusions, significantly different results are obtained from the various models. These predictions either overestimate or underestimate observed properties. New, theoretical combining rules are presented to predict the Young's modulus, Poisson's ratio shear modulus, bulk modulus, and coefficient of thermal expansion in terms of the properties of the matrix and inclusion and the volume fraction concentration of the inclusion. The predictions of these combining rules are in good agreement with experimental data that cover the feasible concentration range of inclusions for a variety of composite materials, ranging from particulate filled thermosetting resins to thermoplastic foams.

Journal ArticleDOI
TL;DR: In this paper, it was shown that the maximum number of superweakly interacting, light (< 1 MeV) particles is between ∼1 and ∼20, depending on the strength of their interaction.



Journal ArticleDOI
16 Oct 1981-Science
TL;DR: The use of intact bacterial cells or tissue slices of plant and animal origin as immobilized biocatalysts has extended the possible range of potentiometric bioselective membrane electrodes beyond that of conventional enzyme electrodes.
Abstract: The use of intact bacterial cells or tissue slices of plant and animal origin as immobilized biocatalysts has extended the possible range of potentiometric bioselective membrane electrodes beyond that of conventional enzyme electrodes. The use of such materials as biocatalysts offers advantages in situations where isolated enzymes are not available or where multistep reaction paths are required. The resulting bioselective electrodes also offer exceptional ease of preparation, time stability, and low cost.

Journal ArticleDOI
TL;DR: Stressing lobsters by replacing 40–80% of their hemolymph volume with physiological saline or by placing lobsters in 50% seawater for 8 hr did not induce hemocyanin biosynthesis, and in vitro incorporation of [14C]aspartic acid into proteins by tissue extracts, followed by hemOCyanin immunoprecipitation, indicated the hepatopancreas is the site of hemcyanin synthesis.
Abstract: 1. 1. The synthesis of hemocyanin in the American lobster, Homarus americanus, has been investigated. 2. 2. In vitro incorporation of [14C]aspartic acid into proteins by tissue extracts, followed by hemocyanin immunoprecipitation, indicated the hepatopancreas is the site of hemocyanin synthesis. 3. 3. Experiments to induce hemocyanin biosynthesis by maintaining lobsters under hypoxic conditions ( p O 2 30–50 mm Hg) for 2—3 days produced an increase in the hemocyanin biosynthetic rate. 4. 4. Stressing lobsters by replacing 40–80% of their hemolymph volume with physiological saline or by placing lobsters in 50% seawater for 8 hr did not induce hemocyanin biosynthesis.

Journal ArticleDOI
TL;DR: In this article, the authors present an introduction to the study of surfaces and chemically adsorbed species with nuclear magnetic resonance (NMR) spectroscopy, based on dipole-dipole couplings, chemical shift anisotropy, Knight shifts, and quadrupolar splitting.

Journal ArticleDOI
TL;DR: It is hypothesized that a respiratory stress response is linked to chorionase release during normal hatching.
Abstract: The development and physiology of the hatching mechanism were examined in Fundulus heteroclitus. Histological examination of the hatching glands revealed that they first became differentiated on or about day 5 of development. By day 7 the glands took on a granular appearance which was correlated with the first appearance of chorionase. From day 7 to day 10, growth of the glands and their increase in chorionase content were exponential. Cell size and chorionase activity peaked on day 10 and thereafter remained constant until hatching. The effects of several drugs were tested for their effects on hatching. Epinephrine and low concentrations of MS-222, in conjunction with low oxygen concentration, were found to advance the median hatching date of eggs (HD50). Turbocurarine, high concentrations of MS-222, and atropine inhibited hatching completely, as did transection of the hind brain. On the basis of these experiments we have hypothesized that a respiratory stress response is linked to chorionase release during normal hatching.


Book
01 Jan 1981
TL;DR: First-order optimality conditions for convex programming are developed using a feasible directions approach and prove useful also in studying the stability of perturbed convex programs.
Abstract: First-order optimality conditions for convex programming are developed using a feasible directions approach. Numerical implementations and applications are discussed. The concepts of constancy directions and minimal index set of binding constraints, central to our theory, prove useful also in studying the stability of perturbed convex programs.

Journal ArticleDOI
TL;DR: In this paper, a potentiometric membrane electrode with selective response to L-glutamate over the 2 × 10 -4 -1.3 × 10 −2 M concentration range is constructed by immobilizing slices of yellow squash tissue at a CO 2 gas sensor.

Journal ArticleDOI
TL;DR: In this paper, a differential flow heat-capacity calorimeter for operation at temperatures to 600 K and pressures to 20 MPa has been constructed, with an accuracy of 0.01 per cent in a 10 min experiment.

Patent
26 May 1981
TL;DR: In this article, a water wave-powered piston pump is proposed for reverse osmosis desalination of seawater. But this pump is not suitable for use in the water wave desalinization process.
Abstract: This invention provides efficient and cost effective water wave-powered piston pumps Utility of such pumps is demonstrated in the reverse osmosis desalination of seawater