Showing papers by "University of Nevada, Reno published in 1968"

The biological and mechanical role of soil fungi.

Abstract: The major role assigned to soil microorganisms is that of decomposition of the litter that collects on or under the soil surface. Additional roles are: synthesis of growth factors such as vitamins and auxins, fixing of atmospheric nitrogen (restricted to bacteria and blue-green algae), production of soil-aggregating substances, and several others. The relative importance of fungi and bacteria (including actinomycetes) is not accurately known as far as their dissimilatory roles are concerned, but it is generally accepted that bacteria assimilate only a minor fraction of the dissimilation products into their bodies, whereas nearly half the decomposition products are transformed by fungi into cell materials. This seems quite plausible if one observes the amount of mushrooms formed on rotting logs, whereas bacteria have very little to show for their activities. Therefore, in terms of biomass the fungi seem to be more important than bacteria in soil; but this may differ very much from one soil to the other, depending largely on the amounts of free water present. In general, fungi can grow where there is less free water. One does not get an accurate picture of the relative importance of bacteria and fungi in the soil by plating methods. When a suspension of soil is plated on nutrient agar, a large proportion of the active microorganisms, plus the sporeformers, will produce colonies. Most soil fungi do not sporulate but live as sterile hyphae that are seldom counted as colonies, partly because of their slow growth. The most commonly counted soil fungi are the fast growers with abundant conidiospore production such as Penicillium, Aspergillus, and a few others, which, by microscopic inspection of the soil, do not seem to play an important role there, but live mainly on recently dropped litter. It has been found in studying mycelium cultures that Rhizoctonia and Basidiomycetes are more common inhabitants of soil. It is usually claimed that most microorganisms in the soil live in the rhizosphere, a narrow sheath a fraction of a millimeter in width around living roots. This may be true for bacteria and actinomycetes, but it is not correct in the case of fungi. It is easier to observe fungi around and near roots, and especially if they form ectotrophic mycorrhizas because a dense mat of hyphae will be seen around the roots. But in any humus-containing soil there is a more or less dense network of hyphae anywhere in the soil away from the roots and rootlets. This is most easily observed in sandy soils. The following observations on fungi were made mainly in two environments: (1) in the Amazonian rain forest in poor to very poor soils, in both the central and western parts of the Amazon basin, and (2) in the southwestern deserts of the United States. The Brazilian forests were studied while we were participants of the Alpha Helix expedition to the Amazon in 1967, and those in Eastern Peru were visited while we were the recipients of a travel grant from the Smithsonian

Optimal Timing of Irrigation

Abstract: A methodology is derived permitting determination by dynamic programming of the optimal timing of irrigation, to produce the greatest net return inclusive of the cost of irrigation. It will be particularly useful under conditions in which seasonal supply is inadequate but reasonably predictable. Analysis is based upon the principle that the adverse effects of deficiencies (nutrition, excessive salinity, soil moisture, etc.) are geometric when existing in combination. For general use, additional data concerning the yield coefficients will be required covering each of the critical stages in the growth of the crops independently.

Hydrogeology of Desert Basinsa

Abstract: Hydrologic systems in arid lands normally include a recharge area in mountains and a discharge area in lowlands often with an intermediate area of lateral flow between recharge and discharge areas. This system is often modified by local geologic, climatic, and physiographic factors. Most water-supply, contamination and disposal problems arise from a combination of features superimposed on this system by concentration of population and agricultural activity in the discharge areas. Also most of our data on the system comes from the lowlands and little data is available from the recharge areas. In the Great Basin two general categories of ground-water flow systems are recognized: (1) local flow systems where drainage areas are usually small, flow paths are relatively short, interbasin flow is uncommon, springs have large fluctuations in discharge, water temperature is low, and concentration of Na, K, Cl, and SO4 is low, and (2) regional flow systems, where drainage areas are large, flow paths long, interbasin flow common, springs have large discharge, and the water is characteristically of higher temperature and contains higher concentrations of K, Na, Cl, and SO4. Hydrologic approaches used, in addition to conventional methods, include hydrologic budget, water-potential, and water-chemistry studies. Although detailed delineation of most flow systems in Nevada has not been accomplished, integration of hydrologic, geologic, and chemical methods allow approximate portrayal of many systems, both local and regional. Adequate methods upon which to base planning for optimum development of water resources in desert basins are now available. A conceptual model of optimal ground-water reservoir development illustrates how to determine optimum use of storage and perennial yield provided the use to which the water is to be put and the time of withdrawal are known.

Photo-ionization cross section of beryllium near threshold.

Abstract: The $^{1}P$ continuum wave functions of beryllium with energies from 0 to \ensuremath{\sim}3.5 eV above the $2s$ threshold are calculated with the inclusion of auto-ionizing lines by configuration interaction. These functions are then combined with a ten-configuration ground-state function to compute the photo-ionization cross section which is found to be dominated by auto-ionization from the $2pns$ and the $2pnd$ series. The energy region studied contains the first three $2pns$ lines, which have widths of a significant fraction of a volt, comparable to their separation; and the first two $2pnd$ lines, which are about a thousand times narrower. There are no experimental measurements of the cross section for comparison; however, the computed phase shift agrees reasonably well with recent close-coupling calculations.

Detection of gravitational waves by stellar scintillation in space.

Abstract: It is shown that gravitational waves generated by close binaries in our galaxy will lead to stellar scintillation This scintillation seems to be large enough to be detectable with sensitive photocounters in space With two observation stations separated by a sufficiently large distance in space, it should be also possible to measure the space-time correlation of the predicted scintillation effect and, hence, the propagation velocity of gravitational waves It is believed that quasars, depending on their state of gravitational collapse, can emit a large amount of gravitational radiation Under certain assumptions, one can show that the gravitational waves emitted by quasars may result in large brightness scintillation of far distant quasars The observations of quasars seem to support the theoretically-predicted brightness fluctuations and characteristic fluctuation times Finally, the question of gravitational background radiation in the universe is considered in connection with the recently discovered 4°K electromagnetic black-body radiation

Neutron Activation Procedures for Silver Analysis in Precipitation

Abstract: Laboratory techniques have been developed for concentrating and isolating silver from aqueous samples. When these concentrated samples are activated in a thermal neutron flux of 4 × 1012n cm−2 sec−1, quantitative measurements down to 10−9 gm masses of silver can be made. When 1-liter samples of water are used, the lower limit of detection of silver in the sample is about 3 × 10−12 gm cm−3 concentration. Typical Ag concentrations being observed in snow collected in the western United States range from this lower limit to 10−8 gm cm−3, the majority being between 10−9 and 10−11. The lower limit does not therefore appear to be a serious factor in silver determinations in snow collected at ground stations. The system described is a non-destructive one, the accuracy of measurement using γ-ray spectrometry being 1, 2, 10 and 80% for masses of silver 10−6, 10−7, 10−8 and 10−9 gm, respectively. By using a 24-sec half-life radioisotope for the Ag determination, the cost of activation and turn-around time o...

Creativity and verbal ability: a direct examination of their relationship

Abstract: Summary. The threshold concept of the relation between creativity and intelligence implies that measures of creativity begin to differ markedly from measures of IQ only above a certain level of intelligence. This hypothesis was tested by comparing the variance of scores on RAT at different levels of performance on ACT by 292 Nevada students. The hypothesis was not confirmed. A similar finding was got from analysis of the scores of 107 Australian boys.

On the Connection Between the Telford and Kinetic-Equation Approaches to Droplet Coalescence Theory

Abstract: The Telford statistical approach to cloud droplet growth by coalescence and the kinetic-equation approach are shown to give identical results when the Telford assumptions are used to linearize the latter. It is concluded that in this case the kinetic equation contains all relevant statistical information. A brief demonstration is given that the nonlinear kinetic equation also is statistically complete.

Career development concepts--significance and utility.

Abstract: Trustees of four appropriate professional associations determined the relative value of significant career-development concepts from a preselected list. Comparisons among the trustee groups are made, composite data are reported, suggestions for using the rank-ordered concepts in research as an external criterion are provided, and ideas for incorporating the concepts as topics for group guidance classes are given.

Neutron activation measurements of silver in precipitation from locations in western north america.

Abstract: Thermal neutron activation methods have been applied to the determination of silver content in samples of hail, rain and snow. Hail and rain samples were collected in South Dakota in regions where AgI cloud seeding was being conducted; the snow was collected in the eastern Sierra Nevada in an area where no such seeding was being conducted. No silver was detected in the snow samples analyzed, indicating concentrations on the average less than 2.5 × 10−11 gm ml−1. Eighty percent of the hail and rain samples analyzed contained measurable quantities of silver up to 70 times the minimum detectable amount. Some of these latter samples were collected in nominally unseeded areas, and although the chemical form in which the silver entered the precipitation is unknown—thereby casting doubt on its consequence—the observations raise important questions which deserve answers, particularly as they may affect statistical evaluations of weather modification experiments.

Clayton: a new metropolitan focus in the st. louis area1

Abstract: Clayton, Missouri, has recently developed into a major retailing and office center, rivaling downtown St. Louis, long-time central business district of the metropolis. Established in 1877, Clayton grew during the early twentieth century into a high quality residential suburb. After World War II, while population increased rapidly in St. Louis County, a retailing boom occurred in the business district of Clayton. Next, many office buildings were built here. Moving into them were salesmen, professional men, and others, many of whom do business or provide services, principally in St. Louis County. As a result of these developments, Clayton ranks second to downtown St. Louis, both as a retailing center and as an office center. Though smaller, Clayton resembles the CBD in the relatively broad array of services it offers. The metropolitan role that Clayton seems to be assuming is neither that of the CBD nor of the minor office center. Rather, with the rise of Clayton, the expanding metropolis has been ...

An Empirical test of the Validity of Rokeach's Opinionation Scale

Abstract: (1968). An Empirical test of the Validity of Rokeach's Opinionation Scale. The Journal of Psychology: Vol. 69, No. 1, pp. 47-52.

Order preference in serial learning

Abstract: Thirty-six Ss arranged three sets of 15 words into easy serial orders. Approximately three weeks later they were required to learn three serial lists derived from the same sets of words. One serial list conformed to S’s own preferred order, one conformed to a preferred order developed by another S, and one was presented in a random order. Lists and presentation order of the three serial arrangements were counterbalanced. Serial learning was more rapid with easy orders, but there were only slight differences between the two preferred orders.

Inelastic molecular collisions with an orientation‐averaged interaction energy

Abstract: The importance of molecular orientations for vibrational-translational energy transfers between diatomic molecules has been investigated. An angle-dependent potential function is assumed, and it is averaged over the orientations and vibrations of colliding molecules. For I2I2 and Cl2Cl2, it is found that the calculated average vibrational transition probability for a colinear collision is over-estimated by large factors (1/γ) compared to that obtained when all possible molecular orientations are considered. At 3000K, 1/γ = 34.4 for I2I2 and 17.6 for Cl2Cl2, while it is 6.8 and 5.9 for N2N2 and O22, respectively. It is also shown that 1/γ decreases rapidly as temperature increases. At 20000K, 1/γ ≈ 3 for I2I2, Cl2Cl2, and N2N2, while it is ≈ 2.5 for O2O2. In general, when the molecules are large, and when strong attractive forces act between them, 1/γ is very large at low temperatures (<10000K). On a etudie l'importance des orientations moleculaires pour le transfert d'energie vibrationelle-translationelle entre des molecules diatomiques. On admet que le potentiel depend des angles et l'on en calcule la moyenne sur les orientations et les vibrations des molecules. Pour I2I2 et Cl2CI2 on trouve que la probabilite moyenne de transition vibrationelle pour une collision colineaire est surestimee de grands facteurs (1/γ) relatif a ce qu'on obtient en considerant toutes orientations moleculaires possibles. A 3000K, 1/γ = 34.4 pour I2I2 et 17.6 pour Cl2Cl2, tandis que pour N2N2 on trouve 6.8 et pour O2O2 5.9. On demontre aussi que 1/γ diminue rapidement quand la temperature augmente. A 20000K, 1/γ ≈ 3 pour I2I2, Cl2Cl2, et N2N2 tandis que 1/γ ≈ 2.5 pour O2O2. En general 1/γ est tres grand pour les temperatures basses (<10000K) si les molecules sont grandes et quand les forces d'interaction sont fortes et attractives. Die Bedeutung molekularer Orientierungen fur die Ubertragung von Schwingungs-und Translationsenergien zwischen zweiatomigen Molekulen wurde untersucht. Es wurde eine Winkelabhangige Potentialfunktion angenommen. Der Mittelwert uber den Orientierungen und Schwingungen der zusammenstossenden Molekule wurde dann berechnet. Fur I2I2 und Cl2Cl2 erwies sich dass die berechneten Mittelwerte der Schwingungsubergangswahrscheinlichkeiten fur einen kolinearen Stoss mit grossen Faktoren (1/γ) uberschatzt ist, im Vergleich zum Fall wenn alle moglichen molekularen Orientierungen betrachtet sind. Bei 3000K, 1/γ = 34.4 fur I2-I2 und 17.6 fur Cl2Cl2, wahrend fur N2N2 1/γ = 6.8 und fur O2O2 1/γ = 5.9. Es wurde auch gezeigt dass 1/γ sehr schnell abnimmt, wenn die Temperature wachst. Bei 20000K, 1/γ ≈ 3 fur I2I2, Cl2Cl2, und N2N2 wahrend fur O2O2, 1/γ ≈ 2.5. In allgemeinen ist 1/γ sehr gross bei tiefe Temperaturen (<10000K) wenn die Molekule gross sind und wenn starke Attraktionskrafte zwischen ihnen wirken.

On the Distribution and Role of Oxygen in the Geochemistry of the Earth's Crust

Abstract: Literature relating to geochemistry of oxygen for the period of 1955 to 1966 is reviewed and recent progress in geochemical research in this field is discussed. The importance of oxygen as the major constituent of the Earth's siliceous crust and mantle is re-emphasized. Recent studies on the effect of the fugacity of this element in magmas and the isotopic fractionation of O 16 and O 18 in igneous rocks show that the path of fractional differentiation of a magma is greatly affected by varying influence of this element. Silica-rich residual melts of the calc-alkaline series type, common in orogenic belts, may result when relatively high oxygen fugacity causes magnetite to crystallize early with the ferromagnesian minerals. Iron-rich residual melts, of the Skaergaard type in Greenland, may form at lower oxygen activities through crystallization of Mg, Fe-olivine, which causes a relative increase of iron toward the residual end. Oxygen as the main anion or electron acceptor in the early stages of magmatic differentiation may be the cause of the enrichment of the light major elements in the Earth's crust. The concentration of odd-numbered major elements Al, Na and K is so explained. All the light major elements have a high affinity for oxygen. Isotope fractionation studies of oxygen-18 and -16 have greatly contributed to our ability to study and interpret the complex history of magmas and metamorphic rocks. It has been found that minerals group in relation to their tendency to retain and thus concentrate the heavy isotope O 18 . This tendency increases with the growing complexity of the silicate framework. Measured equilibria of oxygen isotopes vary according to the conditions during the formation of a rock, thus enabling the geochemist to indicate the processes through which the rock has been passing during its formation. In the study of granites, for example, the wide scatter of data measured may speak of a metamorphic origin, whereas equilibria corresponding to igneous rocks may indicate igneous derivation or a thorough homogenization due to remelting of a sediment. Paleotemperature studies become possible when we know the equilibria of O 18 /O 16 at certain temperatures. Oxygen fugacities in metamorphic processes and the formation of magnetite and hematite are of major importance when we try to explain the genesis of the Precambrian iron deposits. Due to a possible buffer-effect of Fe 2 O 3 present in these systems and sometimes due to the presence of C and S, no simple picture can be obtained, but a satisfactory explanation of the formation of iron oxides from siderite-bearing muds without the necessity of introducing oxygen is indicated. In the formation of planets through the accretion of solar nebula dust particles the relative abundance of oxygen and hydrogen may even influence the final structure of the planet and the spherical distribution of major elements, especially iron. This because the oxidation-reduction equilibria in metal-oxide-silicate mixtures are very sensitive over a relatively narrow temperature range of about 100° to 850°C. Reporting and calculation of rock analyses in cationic percentages is strongly recommended. This has become practically feasible due to the recent developments in fast-neutron activation analysis for oxygen in rocks, minerals and meteorites. This is due to methods of accurate oxygen analysis developed in the past 5 years. Studies of oxygen- and other elemental-gradients in rocks formed at different pressures are proposed.