Showing papers by "University of Delaware published in 1975"

Ridge regression:some simulations

Abstract: An algorithm is given for selacting the biasing paramatar, k, in RIDGE regrassion. By means of simulaction it is shown that the algorithm has the following properties: (i) it produces an aberaged squared error for the regrassion coafficiants that is les than least squares, (ii) the distribuction of squared arrots for the regression coafficiants has a smallar variance than does that for last squares, and (iii) regradless of he signal-to-noiss retio the probability that RIDGE producas a smaller squared error than least squares is greatar than 0.50.

Wind-induced drift currents

Abstract: Systematic measurements of drift currents below and of airflows above an air-water interface have been made under various wind conditions. The current near but not immediately below the water surface is found to follow a Karman-Prandtl (logarithmic) velocity distribution. The current immediately below the water surface varies linearly with depth. The transitions of the current boundary layer to various regimes appear to lag behind, or to occur a t a higher wind velocity than, those of the airflow. The fraction of the wind stress supported by the wave drag seems to vary with the wind and wave conditions: a large fraction is obtained at low wind velocities with shorter waves and a small fraction is obtained a t high wind velocities with longer waves. At the air-water interface, the wind-induced current is found to be proportional to the friction velocity of the wind. The Stokes mass transport, related to wave characteristics, is only a small component of the surface drift in laboratory tanks. However, in terms of the fraction of the wind velocity, the mass transport increases, while the wind drift decreases, as the fetch increases. The ratio between the total surface drift and the wind velocity decreases gradually as the fetch increases and approaches a constant value of about 3·5% at very long fetches.

Two kinds of self-preserving size spectra of a cloud of particles

Abstract: The population balances describing the time dependence of the size distribution can, under some conditions, be trasformed by means of a similarity transformation into an ordinary integro-differential equation containing two instead of three variables. If there is compatibility between the transformed equation and the constraints given by the total mass conservation equation and the equation for the total number of particles, a self-preserving spectrum of the first kind can be obtaiened. There are, however, many situations such as the sintering controlled aging of supported metal catalysts, coagulation of colloidal particles in laminar shear flow, and coagulation of colloidal particles in a turbulent flow when the particles are smaller than the size of the smallest eddy for which, although a similarity transformation is possible, the transformed equation has no solution because of incompatibility with the above mentioned constraints. A second kind of self-preserving spectrum is suggested for these situations. The new variables are induced from a particular case for which an analytical result is available. A detailed presentation of the sintering controlled aging of supported metal catalysts is presented.

The Efficient Design of Adhesive Bonded Joints

Abstract: A concise method of analysis is used to study the numerous parameters influencing the stress distribution within the adhesive of a single lap joint. The formulation includes transverse shear and normal strain deformations. Both isotropic or anisotropic material systems of similar or dissimilar adherends are analysed. Results indicate that the primary Young's modulus of the adherend, the overlap length, and the adhesive's material properties are the parameters most influential in optimizing the design of a single lap joint.

Mechanics of steady spinning of a viscoelastic liquid

Abstract: The equations for steady isothermal spinning of a viscoelastic liquid are solved for a fluid model with constant modulus and a single constant relaxation time. High stress levels are predicted for elastic liquids, and the velocity approaches a linear profile in the limit of maximum drawdown. These predictions are in accordance with the observed behavior of polymeric liquids in isothermal spinning. Relaxation times computed from spinning data of Spearot and Metzner and Acierno et al. for four low density polyethylene melts are comparable to those measured rheogoniometrically, though the spinning relaxation times are 20 to 80% larger.

Drug-induced phase change in bilayer as possible mode of action of membrane expanding drugs.

Abstract: MANY small molecules modulate membrane functions. Substances such as neurotransmitters interact directly with specific protein receptor sites, whereas others such as anaesthetics, interact with membrane lipids or with hydrophobic regions of membrane. This is consistent with a correlation of their activity with their lipid solubility and lipid–water partition coefficient1. Several lipid-soluble drugs are antihaemolytic2, which correlates not only with their pharmacological activity but also with their ability to expand the lipid bilayer of a biomembrane3. Although expansion of bilayers implies a drug-induced reorganisation of lipids, the mechanism involved remains to be established. We now have evidence that the lipid-soluble drugs may induce a transition of lipid acyl chains from organised gel to randomised liquid crystalline phase. Such drug-induced changes in the lipid phase in a bilayer may affect the function of various membrane-bound proteins4.

Visual Behavior as an Aspect of Power Role Relationships

Abstract: There is an intriguing paradox inherent in the shared glance. On the one hand, there is the suggestion that willingness to engage in mutual glances is a means of establishing union with another (Simmel, 1969) — a suggestion which is supported by empirical evidence that affiliative motives (Exline, 1963) and loving relationships (Rubin, 1970) are characterized by relatively greater amounts of mutual looks than are their opposites. On the other hand, there is the suggestion, also backed with empirical evidence, that a mutual glance elicits threat displays between subhuman primates (Hinde and Rowell, 1962; Hall and Devore, 1965; Jay, 1965), that the fixed glance of one human is associated with another’s accelerated movement away (Ellsworth, Carlsmith, & Henson, 1972), and that, in specified circumstances, the one who first breaks off a mutual glance is socially subordinate (Edelman, Omark, & Freedman, 1971), while one who looks steadily at another in silence is perceived to be more dominant than one who looks briefly (Thayer, 1969).

Role of Cholesterol in Biomembranes and Related Systems

Abstract: Publisher Summary This chapter examines the molecular aspects of interaction between cholesterol and phospholipids. It reviews mainly how these subtle interlipid interactions modify the gross functions of membranes. In the solid state, cholesterol is not readily dispersed in water or electrolyte solutions that could occur naturally. Yet, because cholesterol is integrated into all cells and most body fluids in nonparticulate form, some very efficient methods of microdispersion and phase change must operate biologically. Solubilization of cholesterol can be achieved in ternary systems with lecithin as the amphiphile, in which case, a complex, stable mesophase develops at a certain critical concentration. Evidence for the interaction of cholesterol with phospholipids to modify a bilayer has come from a variety of sources. Studies on sonicated dispersions of phospholipid in water indicate that the dispersions containing cholesterol are heavier, more asymmetrical, less hydrated, and more rigid. These changes are reflected in various properties of the liposomes. The effect of cholesterol on phospholipid dispersions in benzene is not so significant. However, available evidence does suggest that cholesterol is incorporated into the phospholipid aggregates. The chapter describes the evidence concerning possible interaction of cholesterol with phospholipids in the aqueous phase from the use of physical techniques.

Toxicity of ammonia, nitrite ion, nitrate ion, and orthophosphate to Mercenaria mercenaria and Crassostrea virginica.

Abstract: The 96-h lethal tolerance limits of the hard clam Mercenaria mercenaria (Linne) and the oyster Crassostrea virginica (Gmelin) to ammonia, nitrite ion, nitrate ion, and orthophosphate were defined. Sublethal effects of the chemicals upon the rates at which the shellfish removed algal cells from suspension were also studied. In comparison with other marine and aquatic species which have been studied, hard clams and oysters are extremely tolerant.

Diatom communities from a delaware salt marsh 1,2

Abstract: SUMMARY Edaphic diatoms were collected from 5 representative habitats of Canary Creek salt marsh, Lewes, Delaware, from 24 July 1969 to 21 July 1970. Of the 104 taxa encountered, 32 had a general distribution on the marsh and 41 were endemic to one of the 5 habitats sampled. Three of the habitats supported stands of grasses: tall Spartina alterniflora Loisel., dwarf S. alterniflora, and Distichlis spicata (L.) Greene; and these habitats possessed the highest species diversity (H') and the greatest number of diatom species. The remaining 2 habitats, a bare bank and a panne, were devoid of macroscopic vegetation. The diatoms of these last 2 habitats were exposed to hypersaline conditions during warmer periods of the year and this was considered a contributing factor to the lower values observed for the aforementioned parameters of community structure. A comprehensive examination of the community structure characterizing the 5 habitats, employing statistical analyses and the distribution of species, showed each habitat to support its own unique and easily recognizable edaphic diatom community. A multiple regression analysis indicated that the differences between the 5 communities were closely related to differences in temperature and elevation between the habitats, and also a result of significant interactions between edaphic diatoms and filamentous algae.

The Role of Seals and Certifications of Approval in Consumer Decision‐Making.

Abstract: One important source of product-related information available to consumers is seals and certifications of approval. Yet little is known about the role played by these symbols in the decision-making process. This study examines the level of recognition, the perceived credibility, the perceived meaning and the use of nine seals or certifications of approval among adult female consumers. The results would appear to have significant implications for consumer protection and education.

On the Ballistic Impact of Textile Body Armor

Abstract: A mathematical model is developed and methods of analysis are formulated for determining the structural response of textile fabric flat panels subjected to ballistic impact by a dense projectile. A stepwise procedure in time is formulated which is suitable for either desk calculator use or for a digital computer in calculating strains, projectile position, forces, and decelerations as functions of time. Analytical results are compared with experimental data for impact of a .22 caliber fragment simulator impacting 1 ply and 12 ply nylon cloth as well as Kevlar (PRD)-49-IV cloth from 1–24 plies.

Hierarchical stages in the processing of visual information

Abstract: Previous research had indicated that when subjects are instructed to report one of a number of visually displayed items, both the number and spacing of the presented material affect report accuracy and latency. The present experiment sought to determine the nature and temporal course of the interference provided by nonattended visual material. Subjects reaction times were measured for deciding which of two targets occupied the indicated position in one or eight element displays. Placing replicas of the target in nonindicated display positions was equivalent to presenting the target alone. Members of the opposite response set produced maximum interference, while encodable and unencodable noise elements not belonging to a response set produced an intermediate decrement. For all display types, presenting the indicator prior to display onset decreased reaction time. Dividing each of the display elements into two parts and presenting the parts asynchronously provided evidence that subjects were indifferent to the presence of complete forms for the first 50 msec. These results were interpreted as supporting the existence of a hiararchical sequence of stages consisting of a preattentive stage which segregates the input into objects and an attentive stage which is likened to a spatial scanner responsible for synthesizing the crude preattentive features into recognized forms. The concurrent operation of these stages provides for the redirection of attention when changes in the input are detected.

Hexavalent Chromium in the Ground Water in Paradise Valley, Arizona

Abstract: Hexavalent chromium (Cr+6) of natural origin has been found in the ground water in Paradise Valley, Maricopa County, Arizona. The concentrations exceed 0.05 milligrams per liter, the U.S. Public Health Service's upper limit for Cr+6. Paradise Valley is a northwest-trending, down-faulted basin of about 225 square miles that is located in the semi-arid Basin and Range physiographic province. The accumulation of fine-grained sediments (in part gypsiferous) near the center of the basin indicates that the material was deposited in a playa-type sedimentary environment. The Cr+6 is present in the ground water in a 75-square mile area and forms an elongate northwest-trending pattern in the southern part of the basin. The largest Cr+6 concentrations are located in the approximate center of this pattern and decrease toward the margins. The Cr +6 distribution in the ground water corresponds to the location of the fine-grained part of the alluvial deposits; the highest Cr +6 concentrations are associated with the finest-grained sediments. Evidence indicates that the Cr+6 is fairly evenly distributed vertically in the ground water, at least throughout the finer-grained part of the aquifer system. Thermodynamic calculations and Eh and pH measurements of the ground water indicate that the water containing Cr +6 is oxidizing and alkaline enough to account for the observed concentrations. An alkaline environment, largely a result of primary silicate hydrolysis in the fine-grained sediments, allows chemical oxidation of the trivalent chromium to the soluble Cr+6

Super dense carotenoid spectra resolved in single cone oil droplets

Abstract: CONE visual receptors in reptiles and birds contain brilliant yellow, orange or red oil droplets, 3–6 µm in diameter, through which light must pass before reaching the visual pigment. The possible role of these brightly coloured organelles in colour vision has been disputed1–6. Their colours are thought to be caused by various carotenoids whose characteristically peaked absorption spectra in organic solvent extracts of whole retinas were first reported by Wald and Zussman7. In spite of this, subsequent workers have failed to identify the dramatic carotenoid spectra8 in individual oil droplets by direct methods of microspectrophotometry9–13. Instead, structureless cutoff absorbance curves reminiscent of commercial colour filters have been found to truncate at about one absorbance unit without any evidence of carotenoid spectral fine structure (Fig. 1).

Factors affecting the accumulation and removal of mercury from tissues of the American oyster Crassostrea virginica

Abstract: Adult oysters, Crassostrea virginica (Gmelin) were held in seawater containing 10 or 100 ppb mercury in the form of mercuric acetate for 45 days. Mercury concentration in tissues was determined by analysis of individually homogenized oyster meats using wet digestion and flameless absorption spectrophotometry. After 45 days, average mercury tissue concentration was 91,600 and 12,100 ppb in the 100 and 10 ppb mercury groups, respectively. A slight decline in mercury residues in the 100 ppb group during the accumulation period was attributed to spawning. Clearance of mercury from tissues was studied in a constant temperature regime (25°C±2Co) for 25 days and in a declining temperature regime (25° to 5°C) for 80 days by exposing treated adults to estuarine water with no mercury added. The biological half-life of mercuric acetate was 16.8 and 9.3 days in the 25°C temperature regime, and 35.4 and 19.9 days in the declining temperature regime, for the 10 and 100 ppb groups, respectively. Smaller oysters (0 to 7 g) consistently accumulated more mercury per gram wet weight than larger oysters (7 to 20 g) in populations exposed to 10 and 100 ppb mercury.

Female Delinquency: An Application of Self and Opportunity Theories

Abstract: Since most theories of delinquency explicitly or implicitly deal with males, most of the research bearing upon these theories has concerned males with very little attention given to females. The intent of this paper is to apply to females two delinquency theories which have been found empirically useful in explaining male delinquency: self and opportunity theories. The data show that delinquency and self-concept are related for black females but unrelated for white females. Weak empirical support is found for the contention that repeated delinquency among females is not buttressed by subcultural support. It is found that both black and white female delinquents regard their opportunities less positively than do their non-delinquent counterparts, and that perceptions of opportunity are lowest among public policy offenders. It is suggested that the sexual behavior implied by public policy offenses may represent an attempt to fulfill the marital goal or, conversely, a rejection of it.

Catalysis for Motor Vehicle Emissions

Abstract: Publisher Summary Catalytic reactors have worked to the benefit of the chemical and petroleum industries for many decades, under the watchful eyes of plant engineers and batteries of monitor and control instruments. The automotive catalytic converter will be the first mass produced catalytic reactor placed directly in the hands of the public, who can provide little more than benign neglect. Air pollution is principally a problem in urban and heavily industrialized areas, where the flow of clean air from surrounding areas is insufficient to disperse the accumulation. Nature produces much more pollutants than all man-made sources, but natural emissions are widely dispersed and do not contribute heavily to urban pollution problems. The catalyst companies were encouraged to resume their research activities in automotive catalysis as further tightening of automotive emissions standards became imminent, and it appeared that mere engine modifications might be inadequate to meet the new standards. Critics of catalytic converters have complained about their cost and the adverse effect on the fuel economy and about the need to remove lead from gasoline.

Fall and winter movements and activity level of the mummichog, Fundulus heteroclitus, in a tidal creek

Abstract: Fall and winter movements and activity levels of Fundulus heteroclitus, the mummichog, were monitored in a Delaware tidal creek from September, 1973 to January, 1974. Fish either moved upstream into less saline waters or remained on station. As photoperiod decreased, activity levels at high salinity stations (17–29 o/oo) decreased, while activity levels at low salinity stations (1–21 o/oo) remained relatively high.