Showing papers by "Texas A&M University published in 1981"

Thermodynamic parameters in the Earth as determined from seismic profiles

Abstract: Summary. A Debye model using two cut-off frequencies corresponding to compressional and shear velocities is used to calculate mineral entropies. This model permits entropy and heat capacity in the Earth to be calculated from seismic profiles, and iteration yields temperature profiles along an isentrope. With an adiabatic temperature profile it is possible to obtain Griineisen’s parameter and thermal expansion as a function of depth. Only in the lower mantle is the calculated Griineisen’s parameter along an isentrope approximately proportional to volume.

Maximization theory in behavioral psychology

Abstract: Maximization theory, which is borrowed from economics, provides techniques for predicing the behavior of animals - including humans. A theoretical behavioral space is constructed in which each point represents a given combination of various behavioral alternatives. With two alternatives - behavior A and behavior B - each point within the space represents a certain amount of time spent performing behavior A and a certain amount of time spent performing behavior B. A particular environmental situation can be described as a constraint on available points (a circumscribed area) within the space. Maximization theory assumes that animals always choose the available point with the highest numerical value. The task of maximization theory is to assign to points in the behavioral space values that remain constant across various environmental situations; as those situations change, the point actually chosen is always the one with the highest assigned value.Maximization theory is an alternative to reinforcement theory as a description of steady-state behavior. Situations to which reinforcement theory has been directly applied (such as reinforcement of rats pressing levers and pigeons pecking keys in Skinner boxes) and situations to which reinforcement theory has occasionally been extended (such as human economic behavior and human self-control) can be described by maximization theory. This approach views behavior as a quantitative outcome of the interaction of the putative instrumental response, the reinforcer, and the other activities available in the situation. It provides new insight into these situations and, because it takes context into account, has greater predictive power than reinforcement theory.

Energy-loss effect in inner-shell Coulomb ionization by heavy charged particles

Abstract: The influence of the energy loss of slow projectiles during inelastic collisions on the inner-shell ionization cross sections is treated analytically. The result agrees with available experimental cross sections for $K$-shell ionization by protons. Residual trends in the data may gauge the quality of wave functions employed in calculations of Coulomb ionization cross sections.

Applied Welfare Economics and Public Policy

Abstract: Applied welfare economics and public policy , Applied welfare economics and public policy , کتابخانه دیجیتالی دانشگاه علوم پزشکی و خدمات درمانی شهید بهشتی

Optimal Control of Reactive Power flow for Improvements in Voltage Profiles and for Real Power Loss Minimization

Abstract: A mathematical formulation of the optimal reactive power control (optimal VAR control) problem and results from tests of the algorithm are presented in this paper. The model minimizes the real power losses in the system. The constraints include the reactive power limits of the generators, limits on the load bus voltages, and the operating limits of the control variables, i.e., the transformer tap positions, generator terminal voltages and switchable reactive power sources. Real power economic dispatch is accomplished by standard techniques.

Global Transport of Organic Pollutants: Ambient Concentrations in the Remote Marine Atmosphere

Abstract: Concentrations of organic pollutants in the air and in precipitation have been measured at Enewetak Atoll in the North Pacific Ocean These data from a site removed from industrial and human activity indicate the present concentrations of synthetic organic pollutants in the atmosphere and establish the long-range atmospheric transport of organic pollutants to remote marine areas Hexachlorobenzene and hexachlorocyclohexane isomers are present in the remote marine atmosphere Polychlorobiphenyls, total DDT, dieldrin, chlordane, and two phthalate ester plasticizers were also found in the samples The concentrations of pollutants in the atmosphere remote from continental sources are good measures of the minimum concentrations of air pollutants on Earth

Virus in a parasitoid wasp: suppression of the cellular immune response in the parasitoid's host.

Abstract: A virus that replicates in the ovary of a parasitoid wasp is injected into the parasitoid's host during oviposition. Successful development of th parasitoid egg within the host depends on the presence of th virus, which acts to suppress the host's immune response (encapsulation) toward the egg. This is an example of obligatory mutualism between a virus and a eukaryotic organism.

Scattering of electromagnetic waves from random media with strong permittivity fluctuations

Abstract: By taking into account the singularity of the dyadic Green's function in the renormalization method, a theory is derived for vector electromagnetic wave propagation in a random medium with large permittivity fluctuations and with anisotropic correlation function. The strong fluctuation theory is then applied to a discrete scatterer problem in which the permittivity can assume only two values. The results are found to be consistent with those derived from discrete scatterer theory for all values of dielectric constants of the scatterers.

Effects of Dietary Protein and Energy on Growth, Feed Conversion Efficiency and Body Composition of Tilapia aurea

Abstract: The optimum dietary protein to energy (P:E) ratio for rapid and efficient gain of juvenile Tilapia aurea was shown to fall with increasing size of fish. The optimum concentration of protein and energy also fell with growth. A diet providing roughly 56% protein at 4,600 kcal/kg digestible energy (gross energy adjusted for indigestible fiber) with a P:E ratio of 123 mg potential/kcal produced highest gains of fry (2.5 g). Larger fish (7.5 g) grew most rapidly when fed a 34% protein, 3,200 kcal/kg diet with a P:E ratio of 108. Apparent feed conversion (grams of feed offered/grams of fish weight gain) was superior on diets having lower P:E ratios and was best on the 34% protein, 3,200 kcal/kg diet. Linear regression analysis indicated highly significant differences in average fish weight, condition [10(5) x weight (g)/total length (mm)3], and feed conversion efficiency attributable to changes in either protein or energy concentration. Significant interaction between protein and energy was also demonstrated. Condition and level of carcass fat were high on all diets which produced good growth rates and were inversely related to P:E ratio. Moisture and ash were inversely related to carcass fat. No trend was established for carcass protein.

The Marital Satisfaction Scale: Development of a Measure for Intervention Research.

Abstract: This study reviews the development of the Marital Satisfaction Scale (MSS). The MSS was designed to assess one's level of satisfaction toward his or her own marriage. Marital satisfaction was defined as an attitude of greater or lesser favorability toward one's own marital relationship. Measurement of the perception of one's marriage by means of an attitude scale was the focus of the effort. Design objectives for developing the measure were to generate a new set of items, to utilize a single-item style with an easy scoring system, to guard against contamination by marital conventionalization and social desirability, and to provide items which could reflect attitudinal change likely to occur as a result of marital intervention. Research results indicate that the instrument has very high internal consistency, sufficient test-retest reliability and validity, and a low degree of contamination with social desirability.

Primary production and standing crop of phytoplankton along the ice-edge in the Weddell Sea

Abstract: Chlorophyll a, phaepoigments, primary production, nannoplankton, inorganic nutrients, and physical measurements were made in the upper water column at 17 stations occupied in the Weddell Sea in February and March 1977. The most conspicuous feature is the marked contrast between the low standing crop and primary productivity of the northern and central regions, compared with the much more productive shelf waters at the head of the Weddell Sea. Chlorophyll a in the euphotic zone was 4.36 ± 1.75 mg m−2 for the former regions and 31.6 ± 9.5 mg m−2 for the southern stations. Production in the water columns of the southern stations (0.41 ± 0.23 g C m−2 day−1) was approximately four times that at the northern-central ones (0.104 ± 0.092 g C m−2 day−1). Based on plant carbon: chlorophyll a ratio of 30 ± 10 estimated in the present study, an average specific growth rate (μ) of 0.71 was calculated. The nutrient concentrations showed an inverse distribution compared with those of chlorophyll a and primary production; higher nutrient concentrations were recorded at the northern stations than at the southern waters. Phosphate: nitrate: silicate ratios in the water column suggested the importance of nitrate for phytoplankton production. A significant relationship (P < 0.001) between chlorophyll a concentration and day-zooplankton biomass and a significantly higher ratio (P < 0.06) of night-to-day catch of zooplankton in the northern-central regions than in the southern region were found. This suggests that zooplankton do not need to migrate vertically in the southern regions due to abundance of food supply, whereas in the northern-central regions zooplankton must migrate upwards during the night to consume available food produced through the photosynthetic process. The study demonstrates that water column stability, grazing, and proximity to land masses are the most significant factors controlling phytoplankton production in the Weddell Sea.

Climate: A Reconceptualization and Proposed Model

Abstract: Climate is presented as a perceptual attribute on an organizational, group, and individual level. The climate construct is defined and key issues concerning climate, which have been identified by past research, are addressed. These issues are level of analysis, measurement, validity, redundancy and usefulness. A model which represents the traditional conceptualization of climate is given. This model is later revised by integrating aspects from the discussion of the key issues. The paper concludes with recommendations for future climate research.

Communtiy Structure and Nutrient Content of Canopy Arthropods in Clearcut and Uncut Forest Ecosystems

Abstract: This paper describes differences in canopy arthropod community structure, major cation content, and calculated nutrient consumption between clearcut and undisturbed hardwood forest watersheds at Coweeta Hydrologic Laboratory, North Carolina, USA, during the first two growing seasons following cutting. Although canopy arthropod biomass was about 0.08% of foliage biomass on both watersheds, aphid mass increased 23-fold and ant mass increased 6-fold per unit foliage mass following cutting. These groups in general had lower nutrient concentrations than did chewing herbivores and predators. Arthropod K concentrations were 33% lower on the clearcut; Na, K, and Mg concentrations were 20 to 50% higher in 1978 than in 1977. Arthropod Mg and Ca concentrations, but not Na and K, were reduced significantly more by the greater effect of drought on the clearcut watershed. Consumption estimates based in part on consumption rates reported by others indicated increased nutrient translocation from foilage via arthropods following cutting. These data indicated that canopy arthropod responses to changes in nutrient availability following disturbance could have increased nutrient cycling rates and contributed to nutrient retention by the recovering ecosystem.

Relationships between elements of the Stokes matrix.

Abstract: Although there are sixteen elements of the Stokes matrix, they are constructed from basically four amplitudes and three phase differences. This of course implies that there exist nine independent relationships connecting the elements. These relationships are equalities for scattering by a single particle in a fixed orientation and in a fixed direction. When Stokes matrices from an ensemble of particles differing in size, orientation, morphology, or optical properties are added incoherently, only six equalities become one-way inequalities. These relations will prove to be very useful for providing consistency checks on experimental measurements of all sixteen elements.

Management of Forage Fishes in Impoundments of the Southern United States

Abstract: Forage-fish management in southern ponds began in the early 1940s, and in reservoirs in the 1950s. Need for management arises from situations of both too many and too few prey for existing predators. The principal forage fishes stocked have been shads and silversides in reservoirs, sunfishes in ponds. Recent advances have been made in predator-prey assessment methodologies, with respect to both the need for and the effects of management, but these techniques have not yet been applied widely. Management of forage fishes has included direct control of forage populations with toxicants, drawdown of water levels to increase forage availability, supplemental stocking and diversification of predators, and predator harvest regulations. Forage-fish management has progressed from forage control to forage utilization and predator management, which makes efficient use of excess forage. Forage and predator species have been introduced with little evaluation of ecological relationships. Additional research mu...

Biochemistry of Bacterial Bioluminescence

Abstract: Publisher Summary The luminous bacteria have been isolated from marine environments all over the world, both from seawater and from the light organs of certain fish and squid, and from nonmarine habitats as well. The recent taxonomic studies have placed the luminous bacteria in several major groups: marine forms in the genera Photobacterium, Beneckea and Alteromonas , and nonmarine forms in the genera Vibrio and Xenorhabdus . Among the marine luminous bacteria, Photobacterium species occur as symbionts within specialized light organs of higher organisms; Beneckea species have not been found associated with light organs, but members of both genera occur as gut symbionts. The ecology of the luminous bacteria and its relationship to the control of synthesis and expression of the luminescent system has recently been reviewed in some detail. This chapter discusses the present understanding of the reaction catalyzed by bacterial luciferase and the enzyme

Nutrient digestibility and performance of pigs fed sorghums varying in tannin concentration.

Abstract: Four sorghums, ranging widely in tannin content, and yellow corn were evaluated in two 5 x 5 Latin square digestion trials and a growth trial. All grains were grown in the same field under similar conditions. The sorgums and their tannin contents (milligrams of catechin/100 mg of dry matter, as determined by a modified vanillin-HCl method) were: Ga615, 3.40; NK300, 3.17; TAM680, .83, and G766-W, .88. Diets were supplemented with casein to provide .70 and .60% lysine in digestion trials 1 and 2, respectively. In trial 1, conducted with noncannulated, 25-kg pigs, digestibilities of dry matter, gross energy and N averaged for the low tannin sorghums (TAM680 and G766-W) were higher (P greater than .01) than the corresponding digestibilities averaged for the high tannin sorghums (Ga615 and NK300). N balance data indicated that utilization of absorbed N was not reduced in pigs fed the high tannin sorghums. Corn and the low tannin sorghums had similar digestibilities. In trial 2, conducted with 50-kg pigs fitted with T-cannulas at the terminal ileum, digestibilities of dry matter, gross energy, N and all amino acids again averaged higher (P greater than .01) for the low tannin sorghums than for the high tannin sorghums, whether measured at the end of the small intestine or over the total digestive tract. The one exception was methionine digestibilities at the terminal ileum, which did not differ between the high and low tannin sorghums. Among the amino acids, digestibilities of glycine, proline and histidine appeared to be the most depressed in the high tannin sorghums, as compared to the low tannin sorghums. Digestibilities of most nutrients were higher for NK300 than Ga615, suggesting a difference in type of tannin, or other compound, between grains. Corn and the low tannin sorghums, averaged together, had similar digestibilities for most nutrients. In the growth trial, 10 pigs, individually fed form 20 to 94 kg, received grain-soybean meal diets based on each grain except NK300. Gains were not affected by diet, but feed consumption was 9% higher (P greater than.05) and feed efficiency 10% (P greater than .01) poorer for pigs fed Ga615 than for those fed low tannin sorghums. Performance was similar (P greater than .10) for animals fed the low tannin sorghums and those fed corn.

New Design Correlations for Piles in Sand

Abstract: A critical review of the literature clearly shows that existing theories which are used to determine the bearing capacity of piles driven in sand are not satisfactory Careful examination of the results of experimental studies indicates that existing theories fail to consider all significant parameters Field load test data are used to determine which of the pile geometry and soil property parameters are significant Special attention is given to the problem of residual stresses Bearing capacity factors are calculated from measured unit point and side resistances The bearing capacity factors are correlated with relative depth (depth of penetration to diameter ratio) and friction angle or relative density of sand New design correlations are developed for use in predicting the bearing capacity of axially loaded piles in sand