Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
Results
Showing 1 to 20 of 23 for “"Longitudinal Relaxation"”.
-
THE FREQUENCY-DEPENDENCE OF THE NMR LONGITUDINAL RELAXATION RATE, T(1)(-1), OF WATER IN CYSTS OF THE BRINE SHRIMP (ARTEMIA)
The NMR spin-lattice relaxation rate, T(,1)('-1), of water is independent of the Larmor frequency, (omega)/2(pi), in the normal rf range. However, T(,1)('-1) of intracellular water in biological systems, which accounts for as much as 80% of the cell mass, is frequency-dependent. This indicates that …
-
Spin coherence and optical properties of alkali-metal atoms in solid parahydrogen
… we studied optical spectra, optical pumping,and longitudinal relaxation of spins in the ground state. We find a large variation in the magnitude of the ground state spin polarization from one alkali species to another; however, all the species exhibit similar longitudinal relaxation times on the …
-
Nuclear spin coherence times of HD trapped in solid parahydrogen matrices
… measurements of nuclear spin coherence and relaxation across controlled impurity conditions remain limited. This dissertation describes the design, construction, and operation of an apparatus that addresses the need to improve existing coherence-time measurements. In this dissertation, we …
-
The Development and Application of Nuclear Magnetic Cross Relaxation Spectroscopy to Model and Retrograding Starch Systems
… of the methods for nuclear magnetic cross relaxation spectroscopy (CRS) data collection and analysis was conducted using water and an aqueous waxy corn starch suspension to better perform and interpret the results obtained using CRS. The CRS data collection properties evaluated were the …
-
Effect of Nitroxides and Molecular Oxygen on Proton Relaxation Rates in Aqueous Systems and in Lipids
… presented. The effect of these species on proton relaxation in both aqueous systems and in lipids is studied. The basic experimental approach for this study is the measurement of proton longitudinal relaxation rates (1/T$\sb1$) over a broad range of magnetic field strengths (corresponding to …
-
Determining optimum imaging parameters for SWIFT: application to superparamagnetic iron oxides and magnetized objects.
… spins with both short and long transverse and longitudinal relaxation rates. It is desirable to have equations that accurately describe the signal of spins when excited by SWIFT; however the Bloch equations are not easily solvable for the SWIFT sequence for all relaxation rates and flip angles. …
-
Fluorinated Paramagnetic Probes for 19-F and 1-H MRS/ MRI
… defined. Notably, the 19-F magnetic resonance relaxation processes for the complexes have been assessed, allowing for the analysis of the interplay between applied field, Ln(III) ion and rotational correlation time on relaxation properties. Strategies employed to enhance signal intensity are …
-
Non-Invasive Detection of Anaerobic Metabolism in Exercising Muscle Using Proton MRI
… changes in magnetization transfer (MT) or other longitudinal relaxation mechanisms. Isolated frog gastrocnemii were treated with iodoacetate (IAA; to inhibit lactate production), NaCN (to maximize lactate production), or left untreated and then performed 60 1s/min maximal isometric contractions. …
-
Coherence characterization with a superconducting flux qubit through NMR approaches
… information by measuring the driven-evolution longitudinal relaxation. This technique shows improved accuracy over other methods, due to its insensitivity to low-frequency noise. Spectral signatures of coherent fluctuators are resolved, and further confirmed in a time-domain spin-echo …
-
Magnetic resonance imaging contrast agents for chemical sensing
… prevents clearance of the contrast material. The longitudinal relaxation time, T1, of these agents is proportional to the amount of dissolved oxygen in the material and is indicative of local oxygen tension. A microparticulate formulation of these agents was tested in a rat model and was shown to …
-
Simultaneous multislice spiral and EPI chemical shift imaging
… time is necessary for magnetization moments' longitudinal relaxation, and so a good SNR efficiency. The fact that SNR is one of the dominant challenges that MRSI faces makes it an expensive tradeoff to decrease the dead time in the 3D excitation methods. Therefore, I investigate the …
-
Measurement of wall relaxation times of polarized 3He in bulk liquid 4He for the Neutron Electric Dipole Moment experiment
… Since depolarized 3He will produce a background, relaxation of the polarized 3He, characterized by the probability of depolarization per bounce, Pd , was measured for materials that will be in contact with polarized 3He. Depolarization probabilities were determined from measurements of the …
-
FLUORINATED RESPONSIVE LANTHANIDE COMPLEXES FOR MAGNETIC RESONANCE
… 6.5 Å from the metal ion caused the fluorine longitudinal and transversal relaxation rates to be strongly enhanced. This allows faster MR signal acquisition, reducing the sample concentration and acquisition time required to obtain the desired signal intensity. The lanthanide ion also enhanced …
-
Investigation of NMR properties of gel volume change with magnetic resonance imaging
… scale δω (perturber strength) of the system the relaxation behavior is categorized into five diffusion regimes. Two empirical models are proposed, one for the spin echo and the other the gradient echo sequence, to account for the relaxation dependence of such variables as sphere radius R, δω , …
-
A contrast agent for MRI of calcifications in breast cancer
… of hydroxyapatite-adsorbed contrast was 1 pM. Longitudinal relaxation time measurements were used to estimate the apparent relaxivity of the hydroxyapatite contrast agent to be >1000 s-I/mM. The targeted agent relaxivity is enhanced more than a 100-fold compared to conventional untargeted …
-
Preserving hyperpolarised nuclear spin order to study cancer metabolism
… exponential decay of the polarisation with the longitudinal relaxation time constant T1. This work aimed to improve the combination of hyperpolarisation and metabolic NMR/ MRI by extending the observation timescale of the technique. Working with quantum mechanical properties of the detected …
-
The Development of a Novel Tumor -Specific MRI Contrast Agent Targeting the High Affinity Folate Receptor: In Vitro and in Vivo Specificity, Toxicity, and Biodistribution
… The folate-dendrimer increased the in vitro longitudinal relaxation rate of hFR-positive cells by 110% at 1.2T, and was inhibited by free folic acid. In vivo treatment of hFR-positive ovarian tumor xenografts with the folate-dendrimer chelate resulted in a 33% contrast enhancement after 24 …
-
Dynamic Contrast-Enhanced MR Microscopy: Functional Imaging in Preclinical Models of Cancer
… the uncertainty in measuring the pre-injection longitudinal relaxation time. The histogram of the time-to-peak provides useful knowledge about the spatial distribution of K^trans and microvascular density. Two regions with distinct kinetic parameters were identified when the TTP map from DCE-MRM …
-
X-Band Rapid-Scan EPR
… to CW and pulse techniques for samples with long longitudinal relaxation time T<sub>1</sub> (N<sub>s</sub><sup>0</sup> defects in diamond, N@C<sub>60</sub>, and amorphous hydrogenated silicon), heterogeneous samples (crystalline 1:1 α,γ-bisdiphenylene-β-phenylallyl (BDPA):benzene), lossy samples …
-
Nuclear Spin Relaxation and Diffusion Studies of Adsorption and Dynamics at the Catalyst-Liquid Interface
… chemicals and fuels from biomass. Nuclear spin relaxation time measurements have recently emerged as a novel tool for probing surface dynamics within such systems; herein, we detail the state-of-the-art of such measurements, and extend our current understanding of how such characteristics may be …
Page 1 of 2