Browsing by Subject "Nuclear magnetic resonance"
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Item A nuclear magnetic resonance study of cis and trans-2-butenes(1966-08) Victor, Bob Lawrence; Hecht, Harry G.; Draper, Arthur L.; Wilde, Richard E.Not AvailableItem Item Beta-gamma correlation with resonance fluorescence(Texas Tech University, 1966-08) Liu, YiNot availableItem Complexations of dichlorobis(triphenylphosphine)cobalt(II) with crown ethers(Texas Tech University, 1977-08) Siripaisarnpipat, SutatipNot availableItem Development of variable temperature NMR force microscopy : proton spin relaxation measurements in ammonium sulfate(2012-08) Manzanera Esteve, Isaac Vicente, 1977-; Markert, John T.; de Lozanne, Alejandro; Li, Xiaoqin; Yao, Zhen; Goodenough, JohnNuclear magnetic resonance force microscopy (NMRFM) of a micron size sample of ammonium sulfate was performed by measuring the cantilever deflection produced by coupling the magnetic force to a mechanical cantilever at its resonance frequency. Spin-lattice and spin-spin relaxation measurements were obtained with our newly developed NMRFM probe. A system with more advanced positioning, acquisition and analysis has been fabricated. A new device in which a semi-automatic system performs nanoposition control, spin manipulation, dynamical measurements, and data analysis has been demonstrated to be successful. The new system has proven to be an improvement with respect to other versions of NMRFM probes, thanks to its versatility for pulse sequence designs, faster data acquisition, and automatic analysis of the information. This thesis presents an explanation of the theoretical details of nuclear magnetic resonance force microscopy, and experiments are described in which dynamical measurements of proton spin interactions are obtained. Finally, relaxation time e ffects of the observed force signal are considered in detail. A novel spin manipulation technique which is being implemented for future measurements is described in detail, and magnet con figurations for larger magnetic field gradients and consequently larger signal-to-noise ratio, are also described.Item Force detected nuclear magnetic resonance on (NH₄)₂SO₄ and MgB₂(2009-12) Chia, Han-Jong; Markert, John T.; de Lozanne, Alex; Shih, Chih-Kang; Yao, Zhen; Shi, LiNuclear magnetic resonance force microscopy (NMRFM) is a technique that combines aspects of scanning probe microscopy (SPM) and nuclear magnetic resonance (NMR) to obtain 3 dimensional nanoscale spatial resolution and perform spectroscopy. We describe the components of a helium-3 NMRFM probe and studies of ammonium sulfate ((NH₄)₂SO₄) and magnesium diboride (MgB₂). For our room temperature (NH₄)₂SO₄ studies we were able to perform a 1-D scan and perform nutation and spin echo experiments. In our 77 K MgB₂ we demonstrate a 1-D scan of a 30 micron powder sample. In addition, we describe magnetic measurements of the possible dilute semiconductors Mn[subscript x]Sc[subscript 1-x]N and Fe₀.₁Sc₀.₉N.Item Force detection of nuclear magnetic resonance using double-torsional micro-oscillators(2001-08) Chabot, Michelle Diane; Markert, John T.Item NMR relaxation in synthetic porous media(Texas Tech University, 1999-05) Xu, XinweiDue to their central importance in interpreting NMR logs, the NMR relaxation mechanisms in rocks are being thoroughly investigated by the industry. The bulk fluid response and the surface relaxivity are currently better characterized than is the diffusional relaxation. This latter T2 relaxation mechanism is due to the diffusion of the molecules across the strong internal field gradients generated by the susceptibility contrast between rock and pore fluid when the rock is placed in a magnetic field. The CPMG T2 measurement sequence is unable to refocus the spins effectively, since they see a time-varying internal field. This contributes an additional signal loss mechanism that is not present in a simple Ti measurement. To better characterize this diffusional loss mechanism, the T2 relaxation in synthetic mono-disperse porous media were measured in the lab at room temperature as a function of pore size at 2 MHz. Since the samples were oil-wet, decane was used as the pore fluid. The results are compared to higher field data (85 MHz) and to the relaxation of brine in Berea sandstone at low field. The author observed diffusional relaxation for these samples. As expected, the mono-disperse samples could be characterized by a single exponential decay constant. For small values of the refocusing time T (the inter-echo CPMG pulse spacing or interpulse spacing time), the T2 rate was proportional to t. For large values of x, the T2 relaxation was independent of the refocusing time x. Over the entire x regime, this T2 loss mechanism had a very well-characterized simple inverse dependence on pore radius.Item Nuclear magnetic resonance relaxation measurements in shales(Texas Tech University, 2000-05) Martínez, Gabriela AlejandraShales are important constituents of petroleum systems, and it is necessary to study their petrophysical properties as both reservoir components and as seals. Nuclear magnetic resonance (NMR) has proven to be a good technique for measuring the reservoir engineering properties of rocks. This paper presents measurements of NMR relaxation in shales. It estabhshes that shale petrophysical information is accessible using standard NMR lab techniques employed in the oil industry. Even for shale seals, porosity and pseudo-capillary pressure curves can be derived from NMR relaxation data. This opens the question as to whether NMR logging can be used to ascertain seal quality for oil and gas storage reservoirs and for CO2 disposal reservoirs. About fifi;een sets of samples were analyzed in this research. The samples were mainly black shales composed of clays, quartz, with minor proportions of feldspars and calcite. Two different saturation techniques were employed to restitute the fluid content of the shales. Since the saturation driven by pressure difference fragmented some of the samples, a controlled saturation in a humidity chamber was performed to ensure the integrity of the shales. NMR measurements were performed in a low field spectrometer primarily on the shales characterizing seals. Multiexponential T2 and Ti relaxation rates were determined from CPMG and inversion recovery experiments, respectively. Mean log T2 values of the untreated samples were approximately 0.4 milhseconds. The T2 relaxation times increased afl;er the shales were saturated but remained below 2 milhseconds. Porosity for each sample was derived from the T2 magnetization and calibrated against a standard. Since NMR detects total porosity, the porosity was generally larger than that determined from laboratory flow-saturation techniques. The T2 relaxation rate distributions were normalized using the total magnetization calibration and integrated from the larger times to yield pseudo-capillary pressure curves. The data displayed a power law relationship with respect to the capillary pressure obtained by mercury injection.Item Pore network variation identified through NMR analysis : Eagle Ford Group, South Texas, USA(2015-05) Shultz, James Marion; Tinker, Scott W. (Scott Wheeler); Hammes, Ursula; Smye, Katie; Fisher, WilliamMudrock porosity is associated with both organic and inorganic matter, and hydrocarbons are found in both. The upper Eagle Ford Group is dominated by inorganic porosity, while the lower Eagle Ford Group is considered to have more organic-hosted porosity related to its high organic content. The differences in organic and inorganic pore types play a large role in the effectiveness of pore networks. This study investigates Eagle Ford Group mudrock pores through the use of nuclear magnetic resonance (NMR) in order to more accurately describe porosity. Laboratory-based NMR has been used to measure the fluid content and pore volume of mudrocks affordably and nondestructively. Although NMR is versatile, it has limitations, in that pore-throats and pores must be fluid filled in order to be detected. However, calibration to Mercury Injection Capillary Pressure (MICP) measurements yields interpretable and valuable results. Using a total of 28 core samples from three wells in Karnes and Maverick Counties, South Texas, this study examines how pore networks differ vertically within the succession. The lithology and facies vary vertically within each well and laterally between wells. The facies groups defined with visual core examination were then modeled with wireline logs. While the facies groups show significant overlap in petrophysical character measured by NMR, scanning electron microscopy (SEM), total organic carbon (TOC), x-ray fluorescence (XRF), and x-ray diffraction (XRD), the samples taken from the same facies group nonetheless have similar MICP intrusion corrected porosities. When samples are compared without regard to facies groups, both MICP and TOC strongly correlate with NMR. While NMR detects differences in the pore network including the relative amount of porosity associated with clay sized particles between the upper and lower Eagle Ford; and SEM shows that much of the upper Eagle Ford organic porosity appears to be associated with migrated organic matter. Vertically segregating the Eagle Ford by facies groups that can be modeled by wireline log, while difficult, with further sampling, may prove useful to play-wide mapping.Item Untargeted metabolomics analysis of Rheumatoid arthritis patient sera before and after rituximab treatment(2015-08) Sweeney, Shannon Renee; Tiziani, Stefano; Guma, MonicaBackground: Rheumatoid arthritis (RA) is an autoimmune disease with no known cure that affects approximately 1.3 million Americans. RA patients suffer from chronic pain and inflammation and are faced with probable disability, reduced life expectancy, and increased risk of several other diseases. In the last decade, biological therapies have revolutionized RA treatment. Although administration of a tumor necrosis factor (TNF) neutralizing agent is the first-line biological therapy, many RA patients show only partial or no clinical response to treatment. Subsequently, anti-B cell, anti-T cell, or anti-IL6 therapies can be evaluated. Streamlining of treatment protocols is necessary to improve patient outcomes. Methods: Serum was collected from 23 active, seropositive RA patients on concomitant methotrexate, at baseline and six months after treatment with rituximab. Based on the American College of Rheumatology improvement criteria, at a level of 20% (ACR20), patients were categorized as either responders or non-responders. An untargeted metabolomics approach was used to characterize the serum metabolome of patients. High resolution one-dimensional ¹H-NMR spectra were acquired using a Bruker Avance 700 MHz spectrometer. In addition, A Thermo Scientific Q Exactive Hybrid Quadrupole-Orbitrap mass spectrometer was used for UPLC-MS/MS of serum lipids. Data processing, statistical analysis, and pathway mapping were performed in MATLAB in conjunction with several metabolomics software packages including, NMRLab, MetaboLab, Chenomx, MetaboAnalyst, MetaboSearch, VANTED, Xcalibur, and Sieve. Results: Based on the ACR20 criteria, at baseline, 14 patients were characterized as responders and 9 patients were considered non-responders. Similarly, 20 patients followed-up at six months, 13 responders and 7 non-responders. Seven polar metabolites and 15 unique lipid species achieved a p-value of less than 0.05 for a two sample t-test prior to treatment with rituximab. Following rituximab therapy, five polar metabolites and 37 lipid species were statistically significant between groups. Pathway analysis of both polar and apolar metabolites revealed metabolic differences between responder and non-responders before and after treatment with rituximab. Conclusion: A clear relationship between blood metabolic profiles and clinical response to rituximab therapy suggests that ¹H-NMR and UPLC-MS/MS are promising tools for RA therapy optimization and acceleration of treatment protocols to improve patient outcomes.