Report of Investigations No. 135 Oligocene Volcanism and Multiple Caldera Formation in the Chinati Mountains, Presidio County, Texas

UT Librarie

Regulation of nitrogen uptake and assimilation: Effects of nitrogen source, root-zone pH, and aerial CO2 concentration on growth and productivity of soybeans

An important feature of controlled-environment crop production systems such as those to be used for life support of crews during space exploration is the efficient utilization of nitrogen supplies. Making decisions about the best sources of these supplies requires research into the relationship between nitrogen source and the physiological processes which regulate vegetative and reproductive plant growth. Work done in four areas within this research objective is reported: (1) experiments on the effects of root-zone pH on preferential utilization of NO3(-) versus NH4(+) nitrogen; (2) investigation of processes at the whole-plant level that regulate nitrogen uptake; (3) studies of the effects of atmospheric CO2 and NO3(-) supply on the growth of soybeans; and (4) examination of the role of NO3(-) uptake in enhancement of root respiration

Observations of the diffuse UV radiation field

Spectra are presented for the diffuse UV radiation field between 1250 to 3100 A from eight different regions of the sky, which were obtained with the Johns Hopkins UVX experiment. UVX flew aboard the Space Shuttle Columbia (STS-61C) in January 1986 as part of the Get-Away Special project. The experiment consisted of two 1/4 m Ebert-Fastie spectrometers, covering the spectral range 1250 to 1700 A at 17 A resolution and 1600 to 3100 A at 27 A resolution, respectively, with a field of view of 4 x .25 deg, sufficiently small to pick out regions of the sky with no stars in the line of sight. Values were found for the diffuse cosmic background ranging in intensity from 300 to 900 photons/sq cm/sec/sr/A. The cosmic background is spectrally flat from 1250 to 3100 A, within the uncertainties of each spectrometer. The zodiacal light begins to play a significant role in the diffuse radiation field above 2000 A, and its brightness was determined relative to the solar emission. Observed brightnesses of the zodiacal light in the UV remain almost constant with ecliptic latitude, unlike the declining visible brightnesses, possibly indicating that those (smaller) grains responsible for the UV scattering have a much more uniform distribution with distance from the ecliptic plane than do those grains responsible for the visible scattering

Nitrogen uptake and utilization by intact plants

The results of experiments support the proposed conceptual model that relates nitrogen uptake activity by plants as a balanced interdependence between the carbon-supplying function of the shoot and the nitrogen-supplying function of the roots. The data are being used to modify a dynamic simulation of plant growth, which presently describes carbon flows through the plant, to describe nitrogen uptake and assimilation within the plant system. Although several models have been proposed to predict nitrogen uptake and partitioning, they emphasize root characteristics affecting nutrient uptake and relay on empirical methods to describe the relationship between nitrogen and carbon flows within the plant. Researchers, on the other hand, propose to continue to attempt a mechanistic solution in which the effects of environment on nitrogen (as well as carbon) assimilation are incorporated through their direct effects on photosynthesis, respiration, and aging processes

Surface Encapsulation for Low-Loss Silicon Photonics

Encapsulation layers are explored for passivating the surfaces of silicon to reduce optical absorption in the 1500-nm wavelength band. Surface-sensitive test structures consisting of microdisk resonators are fabricated for this purpose. Based on previous work in silicon photovoltaics, coatings of SiNx and SiO2 are applied under varying deposition and annealing conditions. A short dry thermal oxidation followed by a long high-temperature N2 anneal is found to be most effective at long-term encapsulation and reduction of interface absorption. Minimization of the optical loss is attributed to simultaneous reduction in sub-bandgap silicon surface states and hydrogen in the capping material.Comment: 4 pages, 3 figure

ELSA: An Integrated, Semi-Automated Nebular Abundance Package

We present ELSA, a new modular software package, written in C, to analyze and manage spectroscopic data from emission-line objects. In addition to calculating plasma diagnostics and abundances from nebular emission lines, the software provides a number of convenient features including the ability to ingest logs produced by IRAF's splot task, to semi-automatically merge spectra in different wavelength ranges, and to automatically generate various data tables in machine-readable or LaTeX format. ELSA features a highly sophisticated interstellar reddening correction scheme that takes into account temperature and density effects as well as He II contamination of the hydrogen Balmer lines. Abundance calculations are performed using a 5-level atom approximation with recent atomic data, based on R. Henry's ABUN program. Improvements planned in the near future include use of a three-region ionization model, similar to IRAF's nebular package, error propagation, and the addition of ultraviolet and infrared line analysis capability. Detailed documentation for all aspects of ELSA are available at http://www.williams.edu/Astronomy/research/PN .Comment: 2 pages, contributed paper, IAU Symp. 234, Planetary Nebulae in Our Galaxy and Beyon

Two Suns in The Sky: Stellar Multiplicity in Exoplanet Systems

We present results of a reconnaissance for stellar companions to all 131 radial-velocity-detected candidate extrasolar planetary systems known as of July 1, 2005. CPM companions were investigated using the multi-epoch DSS images, and confirmed by matching the trigonometric parallax distances of the primaries to companion distances estimated photometrically. We also attempt to confirm or refute companions listed in the Washington Double Star Catalog, the Catalogs of Nearby Stars, in Hipparcos results, and in Duquennoy & Mayor (1991). Our findings indicate that a lower limit of 30 (23%) of the 131 exoplanet systems have stellar companions. We report new stellar companions to HD 38529 and HD 188015, and a new candidate companion to HD 169830. We confirm many previously reported stellar companions, including six stars in five systems that are recognized for the first time as companions to exoplanet hosts. We have found evidence that 20 entries in the Washington Double Star Catalog are not gravitationally bound companions. At least three, and possibly five, of the exoplanet systems reside in triple star systems. Three exoplanet systems have potentially close-in stellar companions ~ 20 AU away from the primary. Finally, two of the exoplanet systems contain white dwarf companions. This comprehensive assessment of exoplanet systems indicates that solar systems are found in a variety of stellar multiplicity environments - singles, binaries, and triples; and that planets survive the post-main-sequence evolution of companion stars.Comment: 52 pages, 7 figures, Accepted for publication in Ap

Observation et étude expérimentale de mycobactéries atypiques en aquariums d'eau douce et d'eau de mer

L'eau des aquariums est source de Mycobactéries atypiques qui peuvent être pathogènes pour l'homme et les poissons.Une étude a été réalisée à l'aquarium du Musée de Zoologie de Nancy. La recherche de Mycobactéries a été effectuée dans 40 aquariums équipés de lampes germicides à UV : 11 bassins étaient alimentés en eau douce et 29 en eau de mer. Deux aquariums non équipés de système de désinfection ont également été analysés, les propriétaires de ces derniers ayant présenté un granulome cutané à M. marinum. L'action des UV sur M. marinum en suspension dans l'eau a été testée expérimentalement dans des bassins d'eau douce peuplés de Cichlidés.Pour chaque aquarium, un échantillon de 250 ml a été prélevé. Les cultures après décontamination au lauryl sulfate de soude ont été réalisées sur milieu de Loewenstein.Les résultats indiquent que, quel que soit l'aquarium, la présence de mycobactéries est constante. L'isolement des mycobactéries peut être gêné par la présence d'une flore bactérienne ou fongique importante (≥ 103 U.F.C./ml).Les espèces les plus fréquemment isolées sont M. gordonae et M. fortuitum ; M. kansasii et M. marinum ont rarement été isolées (6140 aquariums). Différents facteurs peuvent intervenir sur la sélection des espèces. La salinité de l'eau limite le développement de certaines espèces, alors qu'elle permet la croissance de M. fortuitum. Dans notre étude, la température de l'eau n'a pas été un facteur sélectif. L'utilisation de lampes UV limite le nombre de Mycobactéries. Dans les bassins expérimentaux, les radiations UV se sont révélées très actives sur M. marinum en présence ou en l'absence de poissons. A l'inverse de M. gordonae, M. fortuitum est rarement isolée en présence d'UV. Un nombre important de poissons par aquarium augmente la flore bactérienne et mycobactérienne.La prévention des infections à Mycobactéries atypiques chez l'homme comme chez les poissons devrait pouvoir être assurée par des mesures d'hygiène élémentaire.Water is a natural habitat of mycobacteria. In aquaria 3 species of atypical mycobacteria are frequently present : M. marinera, M. kansasitand M. fortuitum. They are potential pathogen for fishes and men. Tuberculosis has been recognized as the cause of mortality in marine and fresh water fishes. Clinical signs of fish tuberculosis are variable : ascites, skin ulcerations, skeletal deformities. The human infection is cutaneous granuloma occuring after in jury in aquaria.In the aquaria, of which two patients with cutaneous lesions due to M. marinum were analysed, UV lamps were not used. Many factors have an influence on the number of mycobacterial organisms in aquaria waters : number of fishes per tank, decontamination system, salinity, temperature.To determine the consequence of each factor, a study has been conducted at the “Aquarium du Musée de Zoologie de Nancy”. Research of mycobacteria was carried out in the water of 40 tanks : 11 were supplied with fresh water and 29 with salt water. Each tank was equipped with germicide UV (λ : 253,7 nm) : the intensity was 15 watts for aquaria smaller than 1 000 liters and 36 watts for aquaria larger than 5 000 liters. The effectiveness of UV radiation against M. marinum was tested in 3 experimental fresh water tanks of 280 liters. The first part of the experiment was tested without fish. Tank n° 1 was a control, lamp was switched on during the complete study, M. marinum was not added. In tank n° 2 (with UV) and n° 3 (without UV), 2 ml of M. marinum (of suspension 107 CF/ml) was added. Samples of water were analysed every two weeks. After six weeks tanks n° 2 and n° 3, were prepared for the next study : UV lamps were switched on in n° 2 and switched off in n° 3 both of which were contaminated by M. marinum. After 4 weeks 27 fishes, Cichlids, were introduced in the three aquaria. The day after, M. marinum was added to tanks n° 2 and n° 3. Every week water analysis was done, as well as an identification and quantification of all species of mycobacteria.From each tank 250 ml of water were collected. The water was passed through a 0,2 mµ membrane. The filters were introduced in distilled water and decontaminated by lauryl sulfate. The culture of mycobacteria was grown with Loewenstein medium at 30 and 37 °C. Each colony type was identified by cultural and biochemical characteristics.This study shows the richness in aquaria of mycobacteria; whatever the tanks, mycobacteria presence was constant. In non-treated home aquaria, the presence of mycobacteria was very important, 4 to 6 species per tank, (but in this case M. marinum was not found). In aquaria with UV lamps, the number of species per tank was lower (1 to 3).The growth of mycobacleria could be prevented when the samples were contaminated by fungi and bacteria. However, inability to recover mycobacteria from water occurred only when a massive over-growth by non-mycobacterial contaminant was present (103 CFU/ml). This was the case of non-treated tanks, belonging to patients who developed a chronic granuloma on their hands, M. marinum was not isolated in these aquaria. The evaluation of slowly growing mycobacteria could be altered by the important development of fast growing mycobacteria on the same culture tube. Among isolated species, M. fortuitum and M. gordonae saprophytic strains were frequent; M. kansasii and M. marinum involved in human cutaneous granuloma were unusual, as were the non-pigmented strains of groupe III of Runyon ; M. avium was not isolated.During this study, we observed a relationship between the mycobacteria presence and the cleanness of tank and the fishes population. A great number of fishes per tank was a factor which increased the bacterial and mycobacterial contamination. During this experiment fishes didn't present tubercular-lesions but when a dead fish was examinated, the culture from post-modem samples revealed the presence of M. marinum. The microbiological examination of skip and viscera was negative.The comparison of results in non-treated home tanks and UV treated tanks of the Museum indicates the role of water treatment by UV lamps on the number of isolated mycobacteria.The germicide UV camps are frequently used for the decontamination of tanks. The efficiency is good for bacteria, but unknown for mycobacteria. This study shows that UV radiation decreased the mycobacterial contamination. The species of mycobacteria differ in their sensitivity to UV radiation. In experimental tanks, the results showed the great susceptibility of M. marinum to UV lamps such they were used in aquaria. Presence of fish dues not change the results. If the addition of M. marinum and the lighting of lamps were simultaneous, M. marinum was not isolated in water. If the contamination by M. marinum preceded the lighting of UV lamps, must of bacteria was eliminated in one week and the totality in 4 weeks. For the other species, we observed that the mycobacterial sensitivity to UV light decreases in the following order : quickly growing mycobacteria, photochromogen and scotochromogen strains. During our experimental study, M. gordonae was isolated more frequently when UV lamps were switched on. The results obtained in the 40 tanks with UV lamps allowed the evaluation of the influence of salinity and temperature of water on mycobacterial survival and the selection of species. We did not observed a difference in the concentration of mycobacteria in two types of aquaria, fresh water and salt water. Na Cl is known as an inhibitor of the mycobacterial growth. The sensitivity of strains differs. The salinity of water appears to be a selection factor. M. forfuitum was isolated more frequently in salt water.M. marinum was isolated only in salt water and M. kansasii in fresh water. These results are surprising, as these strains have about the same metabolism. The temperature of water can also be a selection factor for mycobacteria, but in our study the temperature was similar in each aquarium (25°-26°). In this study, we did not observe thermophile strains such as M. avium.Aquarists must be informed of the aquarium contamination by atypical mycobacteria and their role in the evolution of skin lesions after injury of hands and arms. The use of germicide UV lamps improves the bacteriological quality of water