Browsing by Subject "carbon"
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Item 2nd Annual Jackson School Research Symposium(Jackson School of Geosciences, The University of Texas at Austin, 2013-02) The University of Texas at Austin; Jackson School of GeosciencesItem 3rd Annual Jackson School Research Symposium(Jackson School of Geosciences, The University of Texas at Austin, 2014-01-25) Jackson School of Geosciences; The University of Texas at AustinItem 4th Annual Jackson School Research Symposium(2015-02) Jackson School of Geosciences; The University of Texas at AustinItem 5th Annual Jackson School Research Symposium(Jackson School of Geosciences; The University of Texas at Austin, 2016-02) Jackson School of Geosciences; The University of Texas at AustinItem 6th Annual Jackson School of Geosciences Student Research Symposium, February 4, 2017(Jackson School of Geosciences; The University of Texas at Austin, 2017-02) Jackson School of Geosciences; The University of Texas at AustinItem 7th Annual Jackson School of Geosciences Student Research Symposium, February 3, 2018(Jackson School of Geosciences; The University of Texas at Austin, 2018-02-03) Jackson School of Geosciences; The University of Texas at AustinItem 8th Annual Jackson School of Geosciences Student Research Symposium, February 2, 2019(Jackson School of Geosciences; The University of Texas at Austin, 2019-02) Jackson School of Geosciences; The University of Texas at AustinItem 9th Annual Jackson School of Geosciences Student Research Symposium, February 15, 2020(Jackson School of Geosciences; The University of Texas at Austin, 2020-02) Jackson School of Geosciences; The University of Texas at AustinItem Abundances Of C, N, Sr, And Ba On The Red Giant Branch Of Omega Centauri(2010-05) Stanford, Laura M.; Da Costa, G. S.; Norris, John E.; Stanford, Laura M.Abundances relative to iron for carbon, nitrogen, strontium, and barium are presented for 33 stars on the red giant branch (RGB) of the globular cluster omega Centauri. They are based on intermediate-resolution spectroscopic data covering the blue spectral region analyzed using spectrum synthesis techniques. The data reveal the existence of a broad range in the abundances of these elements, and a comparison with similar data for main-sequence stars enables insight into the evolutionary history of the cluster. The majority of the RGB stars were found to be depleted in carbon, i.e., [C/Fe] < 0, while [N/Fe] for the same stars shows a range of similar to 1 dex, from [N/Fe] approximate to 0.7 to 1.7 dex. The strontium-to-iron abundance ratios varied from solar to mildly enhanced (0.0 <= [Sr/Fe] <= 0.8), with [Ba/Fe] generally equal to or greater than [Sr/Fe]. The carbon and nitrogen abundance ratios for the one known CH star in the sample, ROA 279, are [C/Fe] = 0.6 and [N/Fe] = 0.5 dex. Evidence for evolutionary mixing on the RGB is found from the fact that the relative carbon abundances on the main sequence are generally higher than those on the RGB. However, comparison of the RGB and main-sequence samples shows that the upper level of nitrogen enhancement is similar in both sets at [N/Fe] approximate to 2.0 dex. This is most likely the result of primordial rather than evolutionary mixing processes. One RGB star, ROA 276, was found to have Sr and Ba abundance ratios similar to the anomalous Sr-rich main-sequence star S2015448. High-resolution spectra of ROA 276 were obtained with the Magellan Telescope/mike spectrograph combination to confirm this result, revealing that ROA 276 is indeed an unusual star. For this star, calculations of the depletion effect, the potential change in surface abundance that results from the increased depth of the convective envelope as a star moves from the main sequence to the RGB, strongly suggest that the observed Sr enhancement in ROA 276 is of primordial origin, rather than originating from a surface accretion event.Item The Abundances Of Polyacetylenes Toward CRL618(2011-02) Fonfria, J. P.; Cernicharo, J.; Richter, Matthew J.; Lacy, John H.; Lacy, John H.We present a mid-infrared high spectral resolution spectrum of CRL618 in the frequency ranges 778-784 and 1227-1249 cm(-1) (8.01-8.15 and 12.75-12.85 mu m) taken with the Texas Echelon-cross-Echelle Spectrograph (TEXES) and the Infrared Telescope Facility (IRTF). We have identified more than 170 rovibrational lines arising from C2H2, HCN, C4H2, and C6H2. We have found no unmistakable trace of C8H2. The line profiles display a complex structure suggesting the presence of polyacetylenes in several components of the circumstellar envelope (CSE). We derive total column densities of 2.5x10(17), 3.1x10(17), 2.1x10(17), 9.3x10(16) cm(-2), and less than or similar to 5x10(16) cm(-2) for HCN, C2H2, C4H2, C6H2, and C8H2, respectively. The observations indicate that both the rotational and vibrational temperatures in the innermost CSE depend on the molecule, varying from 100 to 350 K for the rotational temperatures and 100 to 500 K for the vibrational temperatures. Our results support a chemistry in the innermost CSE based on radical-neutral reactions triggered by the intense UV radiation field.Item Biogeochemical Cycling of Carbon, Nitrogen, and Phosphorus in Saltwater Marshes of Lavaca Bay, Texas(University of Texas at Austin, 1975-01-24) Armstrong, N.E.; Hinson, M.O. Jr.; Collins, J.H.; Fruh, E.G.Item Chemical Abundances In Field Red Giants From High-Resolution H-Band Spectra Using The APOGEE Spectral Linelist(2013-03) Smith, Verne V.; Cunha, Katia; Shetrone, Matthew D.; Meszaros, Szabolcs; Prieto, Carlos Allende; Bizyaev, Dmitry; Perez, Ana Garcia; Majewski, Steven R.; Schiavon, Ricardo; Holtzman, Jon; Johnson, John A.; Shetrone, Matthew D.High-resolution H-band spectra of five bright field K, M, and MS giants, obtained from the archives of the Kitt Peak National Observatory Fourier transform spectrometer, are analyzed to determine chemical abundances of 16 elements. The abundances were derived via spectrum synthesis using the detailed linelist prepared for the Sloan Digital Sky Survey III Apache Point Galactic Evolution Experiment (APOGEE), which is a high-resolution near-infrared spectroscopic survey to derive detailed chemical abundance distributions and precise radial velocities for 100,000 red giants sampling all Galactic stellar populations. The red giant sample studied here was chosen to probe which chemical elements can be derived reliably from the H-band APOGEE spectral region. These red giants consist of two K-giants (a Boo and mu Leo), two M-giants (beta And and delta Oph), and one thermally pulsing asymptotic giant branch (TP-AGB) star of spectral type MS (HD 199799). Measured chemical abundances include the cosmochemically important isotopes C-12, C-13, N-14, and O-16, along with Mg, Al, Si, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu. The K and M giants exhibit the abundance signature of the first dredge-up of CN-cycle material, while the TP-AGB star shows clear evidence of the addition of C-12 synthesized during He-4-burning thermal pulses and subsequent third dredge-up. A comparison of the abundances derived here with published values for these stars reveals consistent results to similar to 0.1 dex. The APOGEE spectral region and linelist is thus well suited for probing both Galactic chemical evolution, as well as internal nucleosynthesis and mixing in populations of red giants via high-resolution spectroscopy.Item The CN Isotopic Ratios In Comets(2009-08) Manfroid, J.; Jehin, E.; Hutsemekers, D.; Cochran, A.; Zucconi, J. M.; Arpigny, C.; Schulz, R.; Stuwe, J. A.; Ilyin, I.; Cochran, A.Our aim is to determine the isotopic ratios (12)C/(13)C and (14)N/(15)N in a variety of comets and link these measurements to the formation and evolution of the solar system. The (12)C/(13)C and (14)N/(15)N isotopic ratios are measured for the CN radical by means of high-resolution optical spectra of the R branch of the B-X (0, 0) violet band. 23 comets from different dynamical classes have been observed, sometimes at various heliocentric and nucleocentric distances, in order to estimate possible variations of the isotopic ratios in parent molecules. The (12)C/(13)C and (14)N/(15)N isotopic ratios in CN are remarkably constant (average values of, respectively, 91.0 +/- 3.6 and 147.8 +/- 5.7) within our measurement errors, for all comets whatever their origin or heliocentric distance. While the carbon isotopic ratio does agree with the terrestrial value (89), the nitrogen ratio is a factor of two lower than the terrestrial value (272), indicating a fractionation in the early solar system, or in the protosolar nebula, common to all the comets of our sample. This points towards a common origin of the comets independently of their birthplaces, and a relationship between HCN and CN.Item Effect of Powdered Activated Carbon on the Biodegradation of Benzene(University of Texas at Austin, 1980-12) Allen, D.A.; Gloyna, E.F.Item Effect of the Print Bed Temperature on Void Distribution within the Microstructure of Short Carbon Fiber Reinforced/ABS Manufactured via Large Area Additive Manufacturing(University of Texas at Austin, 2023) Sayah, Neshat; Smith, Douglas E.Short carbon fiber-reinforced polymer composite structures produced using Large Area Additive Manufacturing (LAAM) have garnered significant attention due to the design flexibility, energy savings, and materials selection associated with this process. However, the physical and mechanical properties of the additively manufactured composite parts often fall below expectations due to void formation between printed beads and within the microstructure of individual beads. This study aims to investigate the effect of bed temperature on the microstructure within the beads of two-layer Short Carbon Fiber reinforced Acrylonitrile Butadiene Styrene (SCF/ABS) beads manufactured via the LAAM system. This study employs high-resolution 3D micro-computed tomography (µCT) to evaluate the void shape and distribution within the microstructure of composite parts printed at various bed temperatures. The results of this study demonstrate substantial variation in the void volume fraction among four bead sets deposited at different print bed temperatures. Moreover, within each part, a noticeable discrepancy in void volume fraction is observed between the top and bottom bead of the two-bead test samples. Preliminary results indicate that increasing the bed temperature from 25°C to 75°C reduces void volume fraction within the microstructure of the composite parts. However, an opposite trend emerges when the bed temperature is further increased to 100°C, increasing void volume fraction, which needs further investigation to understand. This study also evaluated the void shapes through the calculation of their sphericity. The preliminary results reveal that as the bed temperature increases from 25°C to 75°C, the voids exhibit higher sphericity within the printed parts as the interconnected voids decrease.Item Estimation of CO₂ emissions from petroleum refineries based on the total operable capacity for carbon capture applications(2021) Madugula, Adhish Chandra Saketh; Sachde, Darshan; Hovorka, Susan D.; Meckel, Tim A.; Benson, Tracy J.Carbon capture and storage processes are sought to play a major role in reducing carbon emissions from large point sources. Petroleum refineries, in particular, produce several streams that are CO2-rich, including fluidized catalytic cracking, steam methane reforming, and natural gas combustion processes that generate heat for re- finery operations. Of these, stationary combustion processes account for nearly two-thirds of all CO2 generated within a refinery. In this work, a regression analysis was performed to correlate the size and power requirements for the combined capture, compression, and dehydration process dependent upon a refinery’s operating capacity. Refinery capacity and CO2 generation data from 128 U.S. refineries were normalized, and a linear regression model was developed. A capture, compression, and dehydration process model was developed using Aspen HYSYS for delivery of CO2 (10–15 wt. % in steam) to pipeline specifications (500 ppm H2O, 15.2 MPa). Predicted CO2 emissions were 0.1 to 7.7 % of actual emissions, depending on whether a refinery had a low, medium, or high carbon emission/capacity ratio.Item Exchange of Carbon, Nitrogen and Phosphorus in Lavaca Bay, Texas Marshes: Volume II. The Role of Plants in Nutrient Exchange in the Lavaca Bay Brackish Marsh System(University of Texas at Austin, 1975-08-31) Dawson, A.J.; Armstrong, N.E.Item Final Report: Exchange Rates for Carbon, Nitrogen, and Phosphorus in Nueces and San Antonio Bay Marshes(University of Texas at Austin, 1977-08-31) Armstrong, N.E.; Gordon, V.N.Item Final Report: Exchange Rates for Carbon, Nitrogen, and Phosphorus in the Colorado River Delta Marshes(University of Texas at Austin, 1977-08-31) Armstrong, N.E.; Gordon, V.N.Item Final Report: Exchange Rates for Carbon, Nitrogen, and Phosphorus in the Trinity River Delta Marshes(University of Texas at Austin, 1977-08-31) Armstrong, N.E.; Harris, S.E.; Gordon, V.N.