Showing papers by "Texas A&M University published in 1979"

Safeguarding cryptographic keys

Abstract: Certain cryptographic keys, such as a number which makes it possible to compute the secret decoding exponent in an RSA public key cryptosystem, 1 , 5 or the system master key and certain other keys in a DES cryptosystem, 3 are so important that they present a dilemma. If too many copies are distributed one might go astray. If too few copies are made they might all be destroyed.

An Assessment of the Image of Mexico as a Vacation Destination and the Influence of Geographical Location Upon That Image

Abstract: A sample of 617 student respondents was drawn from 12 universities, in different parts of the United States. Semantic differential instruments were used to measure respondents' descriptive and importance dimensions of thei.- image of Mexico.The analysis indicated major differences between the two image dimensions. Those image attributes which respondents considered to be important when considering a vacation in Mexico were related primarily to sanitation and safety. The most positive attributes respondents reported about Mexico related to climate and low costs.Measurement of respondents' descriptive image of Mexico indicated that the farther away respondents resided from Mexico, the more favorable was their image of that country as a vacation destination. Analysis indicated that the regional differences were not significant. However, significant differences were found on 12 of the 30 individual attributes which were used to measure image.

Nonparametric Statistical Data Modeling

Abstract: This article attempts to describe an approach to statistical data analysis which is simultaneously parametric and nonparametric. Given a random sample X 1, …, X n of a random variable X, one would like (1) to test the parametric goodness-of-fit hypothesis H 0 that the true distribution function F is of the form F(x) = F0[(x − μ)/σ)], where F 0 is specified, and (2) when H 0 is not accepted, to estimate nonparametrically the true density-quantile function fQ(u) and score function J(u) = − (fQ)'(u). The article also introduces density-quantile functions, autoregressive density estimation, estimation of location and scale parameters by regression analysis of the sample quantile function, and quantile-box plots.

Effect of surface roughness on the microwave emission from soils

Abstract: The effect of surface roughness on the brightness temperature of a moist terrain was studied through the modification of Fresnel reflection coefficient and using the radiative transfer equation. The modification involves introduction of a single parameter to characterize the roughness. It is shown that this parameter depends on both the surface height variance and the horizontal scale of the roughness. Model calculations are in good quantitative agreement with the observed dependence of the brightness temperature on the moisture content in the surface layer. Data from truck mounted and airborne radiometers are presented for comparison. The results indicate that the roughness effects are greatest for wet soils where the difference between smooth and rough surfaces can be as great as 50K.

Splines as a Useful and Convenient Statistical Tool

Abstract: The framework for a unified statistical theory of spline regression assuming fixed knots using the truncated polynomial or “+” function representation is presented. In particular, a partial ordering of some spline models is introduced to clarify their relationship and to indicate the hypotheses that can be tested by using either standard multiple regression procedures or a little-used conditional test developed by Hotelling (1940). The construction of spline models with polynomial pieces of different degrees is illustrated. A numerical example from a chemical experiment is given by using the GLM procedure of the statistical software package SAS (Barr et al. 1976).

Viruses and Parasitism in Insects

Abstract: Publisher Summary This chapter focuses on viruses and parasitism in insects. In recent years, virus-like particles have been observed in the reproductive tracts of a large number of endoparasitic hymenoptera (i.e., wasps whose larvae develop inside host larvae), belonging to the families of braconidae and ichneumonidae. Some of these agents have now been characterized to the extent that one does not hesitate in referring to them as viruses, in which context they are discussed in the chapter; indeed, the most prevalent type of particle observed in braconid wasps appears to represent a highly unusual form of baculovirus. A unique feature of all parasitoid viruses, thus far discovered, is that they replicate only in the ovary (of wasps), from which they are transmitted to host larvae or eggs during oviposition. In affected species, large concentrations of virions can always be observed in either cell nuclei of the calyx, an epithelium situated between the ovarioles and oviduct, or within the lumen of calyces and oviducts. It is now apparent that the presence of virus particles in the ovaries of parasitoid wasps is not an isolatcd phenomenon. Indeed, it may represent the rule rather than the exception among certain groups of endoparasitic hymenoptera. The invariable presence of particulate calyx fluids in some parasitoid species suggests that these particles represent an integral component of the parasitoid life cycle.

Factors Affecting Water Blocking and Gas Flow From Hydraulically Fractured Gas Wells

Abstract: This study presents results which were generated and analyzed over a 2-yr period. Several hundred computer runs were made during this project and an extensive amount of rock property data was reviewed to insure that these data were representative of tight gas reservoirs. The following conclusions reflect the combined information which was generated during the study. The reservoir properties, such as capillary pressure, change of capillary pressure in damaged zones, and relative permeability (in low permeability gas reservoirs) are primary factors in determining the behavior of a fractured well during cleanup. If the reservoir rock permeability is not damaged by frac fluid invasion, no serious water blockage to gas flow will occur when (1) the pressure drawdown is much greater than the capillary pressure in the formation, or (2) the capillary pressure and water mobility are large enough to rapidly imbibe the frac water into the formation. If the reservoir rock permeability is not damaged by frac fluid invasion, a complete water block to gas flow cannot occur; however, gas production can be severely curtailed if the pressure drawdown does not exceed the formation capillary pressure and the water mobility is so low that the frac water remains immobile nextmore » to the fracture face.« less

Mechanisms for charge transfer (or for the capture of any light particle) at asymptotically high impact velocities

Abstract: Within the nonrelativistic approximation the authors discuss three different mechanisms for the capture of a light particle from a bare heavy nucleus by another bare heavy nucleus which is incident with a very high relative velocity. The emphasis is on physical interpretation. For each mechanism a ''physical'' (i.e., more readily comprehensible) derivation is given of the asymptotic form of the total cross section, and a comparison is made of the relative importance of the different mechanisms in the case of electron capture from hydrogenlike ''atoms.'' The first mechanism is knock-on capture, where the two nuclei have equal masses and simply switch places. The second mechanism is radiative capture, which occurs with the emission of a photon. The third mechanism, which is perhaps the most interesting one, is double scattering, first suggested within the framework of classical mechanics by Thomas in 1927.

Herbivory and detritivory among gammaridean amphipods from a Florida seagrass community

Abstract: The gammaridean amphipods Cymadusa compta (Smith), Gammarus mucronatus Say, Melita nitida Smith and Grandidierella bonnieroides Stephensen from a seagrass community in the Indian River estuary of Florida (USA) fed variously upon large drift algae, small algae epiphytic on seagrasses and seagrass leaf debris and detritus. Consumption was measured in the laboratory using an index (CI) equivalent to mg ingested mg-1 amphipod day-1. Observations revealed that the amphipods fed by macrophagy, an attack upon large algae and seagrass debris, and by microphagy, small particle detritus feeding and scraping of plant surfaces for diatoms and other epiphytic algae. C. compta was a macrophagous feeder with a generalized diet of algae and seagrass debris, preferring epiphytic algae and drift algae at mean rates of 1.10 and 0.87 CI, respectively. Gammarus mucronatus fed upon epiphytes and seagrass debris equally at mean rates of 0.90 and 0.97 CI, respectively. The diet of M. nitida condisted primarily of epiphytes, consumed at an average rate of 1.05 CI. Grandidierella bonnieroides fed in a specialized microphagous manner, “grooming” plant surfaces for small particle detritus and diatoms at an approximate CI rate of 1.45. Assimilation of plants ingested, as reflected by carbon-14 uptake, varied similarly among the 4 amphipods. Epiphytic algae appeared to be most useful as food, providing means of 41 to 75% carbon-14 uptake as ingesta. Drift algae and seagrass debris were of less value, with means varying between 11 and 24 % of carbon-14 uptake by the amphipods. The data show a pattern of feeding which resembles resource partitioning of food both by size and kind. Other evidence, however, including population limitation by predators and an apparent overabundance of food, indicate that resource partitioning as seen may be an artifact, and one which has no co-evolutionary basis among the present species.

Source credibility, information favorability, and job offer acceptance

Abstract: The impact of the favorability of information about a job and the source of information upon applicant perception of source credibility and upon job offer acceptance was examined. Results showed th...

Restriction Maps of Five Autographa californica MNPV Variants, Trichoplusia ni MNPV, and Galleria mellonella MNPV DNAs with Endonucleases SmaI, KpnI, BamHI, SacI, XhoI, and EcoRI.

Abstract: The restriction sites of Autographa californica nuclear polyhedrosis virus (Ac M NPV) E2 DNA were mapped for the endonucleases Sma I, Kpn I, Bam HI, Sac I, Xho I, and Eco RI. The restriction maps of four other Ac M NPV variants, Trichoplusia ni (Tn M NPV), and Galleria mellonella (Gm M NPV) genomes were determined and compared to the endonuclease cleavage maps of Ac M NPV E2 DNA. The viral structural polypeptides of Ac M NPV variants S3, E2, S1, M3, and R9 were the same when analyzed by polyacrylamide gel electrophoresis. The major structural polypeptides of Gm M NPV and Tn M NPV had the same pattern in polyacrylamide gels as did Ac M NPV structural polypeptides. Gm M NPV and Tn M NPV had several minor structural protein differences as compared with Ac M NPV. Ac M NPV variants, Tn M NPV, and Gm M NPV were distinct but with very similar genomes and protein structures. Images

Climatological Characteristics of Rapidly Intensifying Typhoons

Abstract: The occurrence of rapid deepening of tropical cyclones(≥42 mb in 24 h) in the western North Pacific is examined to determine the statistics of these events and to identify features peculiar to their onset Seventy-nine cases of rapid growth during the period 1956-76 were selected to study climatological characteristics These data show that the majority (75%) of the deep central pressures(≤920 mb) in the region are attained through the rapid deepening process The bulk (67%) of these pressure reductions occur over a time interval of 18 h or less with the first 6 h most likely to account for the steepest fall The statistics reveal that development of a tropical cyclone to typhoon intensity over warm waters (temperature ≥28°C to a depth of 30 m) is a necessary (but not sufficient) prerequisite for rapid deepening An eye dimension near 40 km also is a frequently observed feature at the onset of rapid deepening The time of onset occurs most frequently at night Investigation of typhoon track direc

Sesame protein: A review and prospectus

Abstract: Sesame is one of the earliest condiments and crops grown for edible oil. Sesame is consumed directly as sweetmeat, a “peanut butter-like” product, a candy ingredient, bread condiments, and snack foods. The world production of sesame is about 2,000,000 metric tons. China and India are the largest producers but internally consume their production. Sudan is the largest exporter of seed. Sesame contains 50% oil, which is highly resistant to oxidation, and 25% protein, which has a unique balance of amino acids. Dehulling of sesame for human consumption is important since the hull contains 2–3% oxalic acid, which chelates calcium and has a bitter flavor. Dehulled, defatted meal contains 60% protein, is bland, and contains limited qualities of flatulence-causing sugars and high quantities of phytic acid. Aqueous processing yields isolated protein containing 72% protein and recovers 56% of the seed protein. Sesame protein is very stable to heat and contains large quantities of methionine. Sesame meal has a PER of about 1.35. Sesame is low in lysine and requires supplementation or can be blended with soy protein to give PERs nearly equivalent to casein. Sesame protein is composed of nearly 80% α-globulin and 20% β-globulin. Limited attempts have been made to characterize these 2 fractions. Sesame protein has low solubility that limits food applications in its native form. Sesame protein performs better than other oilseeds in baking applications. Production of sesame is limited to countries where labor is plentiful and inexpensive until indehiscent varieties and/or improved mechanical harvesting techniques are developed. However, intense breeding and engineering research programs are in progress.

Remarks on positive frequency and Hamiltonians in expanding universes.

Abstract: We examine critically the persistent belief that the physical interpretation of a quantum field theory in curved space-time is to be found by introducing a notion of particles at each time in terms of the exact eigenstates of some energylike operator at that time. It seems that all straightforward implementations of this principle suffer from either ambiguity or failure to produce finite particle densities and renormalizable energy-momentum tensors. Calculations are done for a cosmological model of Bianchi type I, containing a scalar fieldφ whose equation includes the term ξRφ. Diagonalization of thetotal energy suggests a certain particle definition, which, however, yields a finite particle creation rate only when ξ=1/6 and the universe is isotropic. Diagonalization of acanonical Hamiltonian is a prescription loose enough to be made consistent with almost any ansatz (including one that does yield physically acceptable expectation values), hence of no theoretical value. An apparently successful naive approach to the isotropic case (for any ξ) is explained as an unconscious first approximation to an adiabatic analysis of the notion of positive frequency.

A Study of the Attitudes of Impacted Groups Within a Host Community Toward Prolonged Stay Tourist Visitors

Abstract: One group which has generally been neglected in research on resort communities has been the host population. This study attempted to determine the impact of winter visitors on Corpus Christi as perceived by residents and particular interest groups in the city. The data revealed a generally positive attitude, suggesting that the major publics in the community are supportive of the state and city tourist agencies in promoting winter tourism.

Acclimation to Ammonia by Tilapia aurea

Abstract: An automatic flow-through dosing apparatus was used to determine the effect on Tilapia aurea of acute and chronic exposure to un-ionized ammonia. For fish not exposed to ammonia prior to acute testing, the 48-hour median lethal concentration (LC50) was 2.40 mg/liter un-ionized ammonia. After fish were exposed to sublethal concentrations of un-ionized ammonia (0.43–0.53 mg/liter) for 35 days, concentrations as high as 3.4 mg/liter caused no mortalities within 48 hours. Histopathological changes occurred in the gills of fish given both nonlethal and acute doses of ammonia. Capillary congestion, hemorrhaging, and telangiectasis were common symptoms of gill abnormalities.