664 research outputs found
Effects of pH and Concentrations of Linoleic and Linolenic Acids on Extent and Intermediates of Ruminal Biohydrogenation in Vitro
Three experiments were conducted by in vitro incubations in ruminal fluid to investigate the effects of pH and amounts of linoleic and linolenic acids on the extent of their biohydrogenation, the proportions of conjugated linoleic acid (CLA) and trans-C18:1 as intermediates, and the ratio trans-10:trans-11 intermediates. The effects of pH and amount of linoleic acid were investigated in kinetic studies, and effects of the amount of linolenic acid were studied with 6-h incubations. With identical initial amounts of linoleic acid, its disappearance declined when the mean pH during incubation was under 6.0 compared with a mean pH over 6.5, and when the amount of linolenic acid increased from 10 to 180 mg/160-ml flask, suggesting an inhibition of the isomerization step of the biohydrogenation. Low pH decreased the ratio of trans-10:trans-11 intermediates. With initial amounts of linoleic acid increasing from 100 to 300 mg, the percentage of linoleic acid disappearance declined, but the amount that disappeared increased, without modification of the trans-10:trans-11 ratio, suggesting a maximal capacity of isomerization rather than an inhibition. Moreover, increasing initial linoleic acid resulted in high amounts of trans-C18:1 and an increase of C18:0 that was a linear function of time, suggesting a maximal capacity for the second reduction step of biohydrogenation. High amounts of initial linolenic acid did not affect the amounts of CLA, trans-C18:1, or the ratio trans-10:trans-11. Based on these experiments, a ruminal pH near neutrality with high amount of dietary linoleic acid should modulate the reactions of biohydrogenation in a way that supports CLA and trans-11C18:1 in the rumen
In Vitro Versus in Situ Ruminal Biohydrogenation of Unsaturated Fatty Acids from a Raw or Extruded Mixture of Ground Canola Seed/Canola Meal
Raw or extruded blends of ground canola seeds and canola meal were used to compare in vitro and in situ lag times and rates of disappearance due to ruminal biohydrogenation of unsaturated fatty acids. The in situ study resulted in higher lag times for biohydrogenation for polyunsaturated fatty acids and lower rates of biohydrogenation of unsaturated fatty acids than the in vitro study, so the in situ biohydrogenation of polyunsaturated fatty acids was not complete at 24 h of incubation. With both methods, rates of biohydrogenation of polyunsaturated fatty acids were higher than for cis-9C18:1. Extrusion did not affect the rate of biohydrogenation of cis-9C18:1, but resulted in higher rates of biohydrogenation of polyunsaturated fatty acids with higher proportions of trans intermediates of biohydrogenation at 4 h of incubation in vitro and at 8 h of incubation in situ. These results suggest that extrusion affects the isomerization of polyunsaturated fatty acids, rather than the hydrogenation steps. In conclusion, in vitro and in situ methods can both show differences of ruminal metabolism of unsaturated fatty acids due to processing, but the methods provide very different estimates of the rates of disappearance due to biohydrogenation
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Oil & Gas Water Use in Texas: Update to the 2011 Mining Water Use Report
In Spring 2012, we undertook an update of the hydraulic fracturing sections of the TWDB-sponsored report titled “Current and Projected Water Use in the Texas Mining and Oil and Gas Industry” that we published in June 2011 (Nicot et al., 2011). The 2011 report provided estimated county-level water use in the oil and gas industry in 2008 and projections to 2060. This 2012 update was prompted by two main events: (1) a major shift of the oil and gas industry from gas to oil production, displacing production centers across the state and impacting county-level amounts; (2) rapid development of technological advances, resulting in more common reuse and in the ability to use more brackish water. The timely update was enabled by a faster than anticipated development, translating into abundant statistical data sets from which to derive projections, and by an increased willingness of the industry to participate in providing detailed information about water use in its operations. This document follows the same methodology as the 2011 report but differs from it in two ways. Our current update clearly distinguishes between water use and water consumption. The 2011 report does not include reuse from neighboring hydraulic fracturing jobs, recycling from other industry operations or other treatment plants, and use of brackish water. Our update also presents three scenarios: high, low, and most likely water use and consumption with a focus on water consumption. This update has been reviewed by the TWDB and should supersede oil and gas industry projections from the 2011 report.Bureau of Economic Geolog
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Area of review: how large is large enough for carbon storage?
The Texas Gulf Coast is an attractive target for carbon storage. Stacked sand-shale layers provide large potential storage volumes and defense-in-depth leakage protection. However, multiple perforations resulting from intensive hydrocarbon exploration and production have weakened seal integrity in many favorable locations. If the ultimate goal of carbon storage is to isolate large volumes of CO2 for hundreds to thousands of years, plume migration will encounter inadequately completed wells miles away from the injection zone. Moreover, the detrimental impact of CO2 on cement could undermine the structural integrity of all contacted wells, although pressure effects subside quickly after injection. Even wells abandoned to current standards cannot be guaranteed leak-free in the long term. We describe spatial statistics extracted from the Texas RRC Well Bore database as applied to carbon storage.
Although the Area of Review (AOR) has been traditionally defined by a fixed radius with the strong regulatory requirement that the injectate stays within the injection layer, buoyancy is a major characteristic of CO2 that introduces a third dimension into the Area of Review process. Using simple geological mapping to characterize structural traps, we determine the likely pathway and the contacted volume of a migrating plume. The latter can be as large as a fault compartment with dimensions of 20 km × 20 km. However, the contacted volume is ultimately a function of the total injected volume, and the specifics of each project should dictate the dimensions of the zone of endangering influence (ZEI).
An option, viable for the Texas Gulf Coast, to reduce geologic uncertainty, to decrease the impact of wells, and to limit the amount of information to be collected, is to inject CO2 below the maximum penetration of most wells.Bureau of Economic Geolog
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Ground Water Surface Water Interactions in Texas
Groundwater-surface water interactions need to be evaluated to optimize water management in Texas. This study provides an overview of the impacts of groundwater-surface water (gw-sw) interactions on water quality and water quantity using available data. A literature review was conducted to assess the status of knowledge of gw-sw interactions. A total of 300 references were compiled. References were subdivided into those related to water quantity issues, water quality including point and nonpoint sources of contamination, and methods such as seepage and temperature approaches and modeling analyses. Additional topics covered by the reference list include impacts of climate variability and land use/land cover changes on gw-sw interactions and ecological issues. A compilation of data and information sources for assessing gw-sw interactions in Texas is also provided. This section includes web links to online report catalogs and databases and a listing of offline reports and catalogs provided by state and federal agencies.Bureau of Economic Geolog
Oidium neolycopersici: Intra-specific variability inferred from AFLP analysis and relationship with closely related powdery mildew fungi infecting various plant species
Previous works indicated a considerable variation in the pathogenicity, virulence, and host range of Oidium neolycopersici isolates causing tomato powdery mildew epidemics in many parts of the world. In this study, rDNA internal transcribed spacer (ITS) sequences, and amplified fragment length polymorphism (AFLP) patterns were analyzed in 17 O. neolycopersici samples collected in Europe, North America, and Japan, including those which overcame some of the tomato major resistance genes. The ITS sequences were identical in all 10 samples tested and were also identical to ITS sequences of eight previously studied O. neolycopersici specimens. The AFLP analysis revealed a high genetic diversity in O. neolycopersici and indicated that all 17 samples represented different genotypes. This might suggest the existence of either a yet unrevealed sexual reproduction or other genetic mechanisms that maintain a high genetic variability in O. neolycopersici. No clear correlation was found between the virulence and the AFLP patterns of the O. neolycopersici isolates studied. The relationship between O. neolycopersici and powdery mildew anamorphs infecting Aquilegia vulgaris, Chelidonium majus, Passiflora caerulea, and Sedum alboroseum was also investigated. These anamorphs are morphologically indistinguishable from and phylogenetically closely related to O. neolycopersici. The cross-inoculation tests and the analyses of ITS sequences and AFLP patterns jointly indicated that the powdery mildew anamorphs collected from the above mentioned plant species all represent distinct, but closely related species according to the phylogenetic species recognition. All these species were pathogenic only to their original host plant species, except O. neolycopersici which infected S. alboroseum, tobacco, petunia, and Arabidopsis thaliana, in addition to tomato, in cross-inoculation tests. This is the first genome-wide study that investigates the relationships among powdery mildews that are closely related based on ITS sequences and morphology. The results indicate that morphologically indistinguishable powdery mildews that differed in only one to five single nucleotide positions in their ITS region are to be considered as different taxa with distinct host ranges
In situ ruminal biohydrogenation of fatty acids from extruded soybeans: effects of dietary adaptation and of mixing with lecithin or wheat straw
Kinetics and intermediates of biohydrogenation of fatty acids were investigated in situ using extruded soybeans, a blend of extruded soybeans and lecithin (99:1), or a blend of extruded soybeans plus wheat straw (66:34). Two dry dairy cows received successively a diet with added palmitic acid and a diet with added extruded soybeans, and assays were completed after a 3-week adaptation to each diet. Adaptation of the cows to dietary polyunsaturated fatty acids suppressed the lag time before the beginning of biohydrogenation. Adaptation of cows, and mixing straw with soybeans, increased the rate of biohydrogenation of C18:2 and C18:3, resulting in less C18:2 and C18:3, and more trans C18:1 and C18:0 in the in situ bags. Lecithin did not affect the kinetics of biohydrogenation or the profile of fatty acids in the in situ bags. Differences in the rate of biohydrogenation, and profile of residual fatty acids in the bags were observed between the two cows. Even with a mixture of soybeans and straw in cows receiving dietary polyunsaturated fatty acids, biohydrogenation was slower and resulted in higher proportions of trans-C18:1 than expected from results of literature in vivo. Resultsshow that the biohydrogenation in situ is slow, highly dependent on experimental conditions, and that the use of several cows, adapted to the test fat source before the assay is initiated, is necessary in order to obtain a reliable estimate of kinetics parameters
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Understanding and Managing Environmental Roadblocks to Shale Gas Development: An Analysis of Shallow Gas, NORM, and Trace Metals
The main objective of the project was to document occurrences of shallow gas in fresh-water aquifers in Texas either dissolved or free phase and identify controlling processes. A secondary somewhat independent objective was to contribute to the understanding of the nature and variability of flowback and produced water associated with hydraulic fracturing in the context of rock-water interactions.
We undertook a large sampling campaign of aquifers in the footprint of major Texas plays (900+ water samples): Barnett in north-central Texas (555 unique locations), Eagle Ford in South Texas (118 unique locations), Haynesville in East Texas (70 unique locations), and in the Delaware Basin of West Texas (40 unique locations). Most of the wells (2/3) are relatively shallow residential wells sampled at or as close as possible to the wellhead but many wells are irrigation, municipal, or rig-supply wells. All samples were analyzed for major ions, dissolved gases, and, when CH4 > 0.1 mg/L, for methane and light alkanes carbon isotopes and trace elements. The vast majority of wells show some measurable methane and ~100 wells show methane > 0.1 mg/L. A total of ~20 wells have methane concentrations > 10 mg/L, these high concentrations were observed in all plays and present at least a thermogenic component. Some wells, generally with a < 10 mg/L concentration, show a clear microbial origin for methane. A number of samples show mixing between the two origins but also more complex behavior such as methane degradation. Samples with thermogenic methane are generally spatially organized in clusters. Overall the source of the dissolved methane is likely natural sourced from shallow natural gas accumulations in the Barnett Shale, lignite beds associated with a fault in the Haynesville shale, and lignite and degradation of oil and deep organic matter associated with a fractured zone in the Eagle Ford Shale. The Delaware Basin samples show no dissolved methane other than associated to a recent blowout.
We also performed autoclave experiments in controlled conditions exposing shale core fragments to various fluids, examining reacted and unreacted rocks and documenting chemical composition of the evolving fluid through time. The experiments demonstrated that shales undergo typical geochemical processes during hydraulic fracturing such as carbonate and feldspar dissolution as well as ion exchange resulting in an increase in dissolved solids. Observations suggest that rock permeability is increased two to three-fold and that porosity is increased by 50%.
Baseline sampling as it is currently practiced is not sufficient to resolve ambiguity of the source of the dissolved methane even if of thermogenic origin because it still could be natural. Additional analyses such as noble gases and isotopes are needed to better constrain origin of the methane.Bureau of Economic Geolog
Monitoring Stray Natural Gas in Groundwater With Dissolved Nitrogen. An Example From Parker County, Texas
Concern that hydraulic fracturing and natural gas production contaminates groundwater requires techniques to attribute and estimate methane flux. Although dissolved alkane and noble gas chemistry may distinguish thermogenic and microbial methane, low solubility and concentration of methane in atmosphereâ equilibrated groundwater precludes the use of methane to differentiate locations affected by high and low flux of stray methane. We present a method to estimate stray gas infiltration into groundwater using dissolved nitrogen. Due to the high concentration of nitrogen in atmosphericâ recharged groundwater and low concentration in natural gas, dissolved nitrogen in groundwater is much less sensitive to change than dissolved methane and may differentiate groundwater affected high and low flux of stray natural gas. We report alkane and nitrogen chemistry from shallow groundwater wells and eight natural gas production wells in the Barnett Shale footprint to attribute methane and estimate mixing ratios of thermogenic natural gas to groundwater. Most groundwater wells have trace to nondetect concentrations of methane. A cluster of groundwater wells have greater than 10Â mg/L dissolved methane concentrations with alkane chemistries similar to natural gas from the Barnett Shale and/or shallower Strawn Group suggesting that localized migration of natural gas occurred. Twoâ component mixing models constructed with dissolved nitrogen concentrations and isotope values identify three wells that were likely affected by a large influx of natural gas with gas:water mixing ratios approaching 1:5. Most groundwater wells, even those with greater than 10â mg/L methane, have dissolved nitrogen chemistry typical of atmosphereâ equilibrated groundwater suggesting natural gas:water mixing ratios smaller than 1:20.Plain Language SummaryHydraulic fracturing, horizontal drilling, and associated natural gas production have dramatically changed the energy landscape across America over the past 10Â years. Along with this renaissance in the energy sector has come public concern that hydraulic fracturing may contaminate groundwater. In this study we measure the chemistry of dissolved gas from shallow groundwater wells located above the Barnett Shale natural gas play, a tight gas reservoir located west of the Dallasâ Fort Worth Metroplex. We compare groundwater chemistry results to natural gas chemistry results from nearby production wells. Most groundwater wells have trace to nondetectible concentrations of methane, consistent with no measurable infiltration of natural gas into shallow groundwater. A cluster of groundwater wells have greater than 10Â mg/L dissolved methane concentrations with alkane chemistries similar to natural gas. Using dissolved nitrogen and alkane concentrations and their stable isotope ratios in combination with chemical mixing models, we conclude that natural gas transported from the shallower Strawn Group affected these groundwater wells rather than natural gas from the deeper Barnett Shale, which is the target of hydraulic fracturing in this area. These results suggest that hydraulic fracturing has not affected shallow groundwater drinking sources in this area.Key PointsDissolved nitrogen in groundwater provides a means to differentiate highâ and lowâ flux infiltration of stray gasNitrogen concentrations and isotope values may attribute natural gas sourcesPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146362/1/wrcr23523.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/146362/2/wrcr23523_am.pd
Mutation of epigenetic regulators TET2 and MLL3 in patients with HTLV-I-induced acute adult T-cell leukemia
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