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Solid-state Nuclear Magnetic Resonance (NMR)is one of the premiere biophysical methods that can be applied for addressing the structure and dynamics of biomolecules, including proteins, lipids, and nucleic acids. It illustrates the general problem of determining the average biomolecular structure, including the motional mean-square amplitudes and rates of the fluctuations. Lineshape and relaxtion studies give us a view into the molecular properties under different environments. To help the understanding of NMR theory, both lineshape and relaxation experiments are conducted with hexamethylbezene (HMB). This chemical compound with a simple structure serves as a perfect test molecule. Because of its highly symmetric structure, its motions are not very difficult to understand. The results for HMB set benchmarks for other more complicated systems like membrane proteins. After accumulating a large data set on HMB, we also proceed to develop a completely new method of data analysis, which yields the spectral densities in a body-fixed frame revealing internal motions of the system. Among the possible applications of solid-state NMR spectroscopy, we study the light activation mechanism of visual rhodopsin in lipid membranes. As a prototype of G-protein-coupled receptors, which are a large class of membrane proteins, the cofactor isomerization is triggered by photon absorption, and the local structural change is then propagated to a large-scale conformational change of the protein. Facilitation of the binding of transducin then passes along the visual signal to downstream effector proteins like transducin. To study this process, we introduce 2H labels into the rhodopsin chromophore retinal and the C-terminal peptide of transducin to probe the local structure and dynamics of these two hotspots of the rhodopsin activation process. In addition to the examination of local sites with solid-state 2H NMR spectroscopy, wide angle X-ray scattering (WAXS) provides us the chance of looking at the overall conformational changes through difference scattering profiles. Although the resolution of this method is not as high as NMR spectroscopy, which gives information on atomic scale, the early activation probing is possible because of the short duration of the optical pump and X-ray probe lasers. We can thus visualize the energy dissipation process by observing and comparing the difference scattering profiles at different times after the light activation moments.

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Selective excitation pulsed NMRON, CW-NMRON and Thermal NMR methods have been used to study the low temperature ⁵⁴Mn nuclear spin-lattice relaxation mechanisms in magnetic insulators. The selective single and double quantum excitation sequences have been used for the first time in NMRON to obtain single and double quantum rotation patterns, Free Induction Decays, Hahn spin echoes and pulsed T₁ measurements. Two insulating magnets have been studied; MnCl₂.4H₂O and Mn(COOCH₃ )₂ .4H₂O. In the ⁵⁴Mn-MnCl₂ .4H₂O system the temperature dependence of the ⁵⁴Mn spin-lattice relaxation time at zero field was measured between 35 mK and 90 mK and it was found that the dominant relaxation process between 65 mK and 90 mK is an electronic magnon Raman process and below 65 mK a direct relaxation process dominates. Single and double quantum Free Induction Decays and Hahn spin echoes have been used to determine the magnitude and nature of the spin-spin relaxation mechanism for ⁵⁴Mn oriented in MnCl₂.4H₂O at zero applied field. NMRON was observed for the first time in the paramagnetic phase of MnCl₂.4H₂O. The resonance lines are inhomogeneously broadened and 300 kHz wide. A value of <⁵⁴AS>/h=-513.6(3) MHz has been determined for the paramagnetic phase hyperfine coupling constant, and this value has been used to determine the zero point spin deviation of the antiferromagnetic phase. The field and temperature dependence of the ⁵⁴Mn T₁ was measured for values of field above the spin flop paramagnetic phase transition and a field dependent T₁ minimum was discovered at Ba=2.64 T. For the ⁵⁴Mn-Mn(COOCH₃) .4H₂O system two ⁵⁴Mn resonances have been observed and the value of the hyper fine coupling constants for the two sites were found to be <⁵⁴AS>/h=-435 (1) MHz for the ⁵⁴Mn1 site and <⁵⁴AS>/h=-478(1) MHz for the ⁵⁴Mn2 site. The high field spin-lattice relaxation behavior has also been investigated and a T₁ minimum at Ba =2.74 T analogous to that observed in MnCl₂ .4H₂O was discovered. A Hahn echo study of the low field single quantum spin-spin relaxation processes has been performed and anomalous behavior of the spin echo amplitude revealed. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

This study examined the differential effects of an audiotaped progressive relaxation message and an audiotaped positive reinterpretation message, repeatedly presented over three sessions to socially anxious subjects. Self report measures of social anxiety, attitude towards anxiety, coping effectiveness, and acceptance of anxious self, and the frequency of action taken in target situations were examined. The subjects were 14 males and females aged 19-38 (M=26.14) who were randomly assigned to either positive reinterpretation or progressive relaxation treatment condition. Repeated measures analysis of variance indicated no clear statistically significant support for the superiority of one treatment approach over the other, or for the uniform differential effectiveness of the two treatments over time. There was a significant difference between the two groups on the measure of social anxiety but this difference was time dependent, that is, time interacted positively with one group relative to the other group at follow-up, and the reverse was true at post-test. Effect size indicated clinically meaningful differences between treatment groups on attitude towards anxiety and on acceptance of anxious self. / Education, Faculty of / Graduate

An expression for the spin-lattice relaxation time, T₁, of a dilute monatomic gas can be derived starting from the quantum-mechanical Boltzmann equation. The real difficulty in calculating the relaxation time for a particular system lies in the evaluation of the transition operator which appears in the expression for T₁ˉ¹. In this thesis, the relevant part of the transition operator, t₁, is estimated by a distorted-wave Born approximation (DWBA). The monatomic gas is approximated by a specific model. In this model the collisions described by t₁ are governed by two potentials: one, the isotropic rigid sphere potential, V₀, and the other, the anisotropic dipole-dipole nuclear spin interaction potential, V₁. The latter interaction describes the coupling between the degenerate nuclear spin states of the atoms and the translational degrees of freedom in the gas. The former (isotropic) potential governs the explicit form of the rigid sphere distorted wave. After the DWBA transition operator is substituted into the equation for the relaxation time, the expression for T₁ˉ¹ breaks up into two terms, the "diagonal" and "non-diagonal" contributions. At this stage the explicit expression for T₁ˉ is sufficiently complicated that, in order to finish the calculation, analytical approximations to the diagonal and non-diagonal terms are made. These approximations may be succinctly described by stating that they result in two separate evaluations, a linear and a quadratic one, for the overall relaxation time. The magnitude of a small parameter c² , which appears in the exponential term of T₁ˉ¹ , is used as the basis for neglecting certain contributions to the integrals which arise in estimating T₁ˉ¹. The linear and quadratic approximations yield numerical factors of 3,50 and 2.56 respectively, in the expression for the relaxation time. These values are to be compared with the factor of 2 obtained elsewhere. / Science, Faculty of / Chemistry, Department of / Graduate

Experimental proof is presented that some of the motions responsible for transverse relaxation (T₂) in deuterium magnetic resonance (²H NMR) experiments on acyl chains of a model membrane in the liquid crystalline phase are extremely slow on the ²H NMR time scale being characterized by a correlation time T₂ > ѡq⁻¹. The experiments used to investigate these slow motions involve a form of the Carr-Purcell-Meiboom-Gill pulse sequence modified so as to be suitable for ²H NMR (q-CPMG). The most plausible mechanism responsible for T₂ relaxation is the gradual change in the average molecular orientation due to lateral diffusion of the phospholipid molecules along curved membrane surfaces. Presence of such diffusion is directly established by a selective inversion recovery experiment in which magnetization transfer across the spectrum is seen. The results of the T₂ relaxation as measured in the q-CPMG experiments are fitted to an average correlation time, T₂ ≈ 62 ms, yielding an estimate of the average effective radius of curvature of 1.2 µm for a typical model membrane system, in good agreement with other methods of measurement. The implications of this main result are examined for a number of model membranes; in particular, considerable changes are seen in the character of molecular motions in systems containing small concentrations of sterols. Similarly, changes caused by the topological differences between the lamellar L∝ and hexagonal H₁₁ phases are examined in a model membrane system which undergoes a L∝ to H₁₁ phase transition. A novel way of quantifying the differences in the orientational order parameters across the phase transition is used; the observed differences are consistent with the different symmetry properties of the two phases. Perdeuteriated polycrystalline hexamethylbenzene is used to demonstrate various methods of measuring ²H NMR relaxation. In addition, some aspects of orientation dependence of the relaxation rates are examined, and found to agree with the theory. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Thirty-six subjects participated in a restricted environmental stimulation technique (REST) study investigating the psychophysiological effects of flotation. Subjects floated for one hour under differing expectations regarding duration of a float session and the physical properties of the environment that was to follow. EMG and two measures of cardiac activity (T-wave amplitude and heart rate) were recorded for the entire session; however, EMG was dropped as a variable due to an excessive noise-to-signal ratio. It was found that neither durational expectations nor beliefs about a dissimilar environment had any significant effects on the patterns of response of the two remaining variables. Subjects did show a significant within-subjects trend when considered as a whole group. Further research in the area of cardiovascular and muscle activity patterns in the flotation tank is suggested. / Arts, Faculty of / Psychology, Department of / Graduate

Nuclear magnetic resonance experiments on impurity atoms in a ferromagnetic host have shown that the measured spin-lattice relaxation time of those nuclei located in domains is strongly dependent on the degree of magnetic saturation of the host material (1, 2, 3). The relaxation time increases as the applied magnetic field is increased and reaches a constant value for a magnetically saturated specimen. Wall nuclei show a much shorter relaxation time than those in the bulk. This fact, together with the increased number of walls present in a magnetically non-saturated specimen could explain the observed field-dependent decrease of the relaxation time if an increasing fraction of wall nuclei is observed. Nuclei located in walls experience a much larger enhancement than those in domains. Therefore special techniques have to be applied to exclusively observe nuclei located in the bulk (1, 4). For this reason some uncertainty exists in the interpretation of the nuclear magnetic resonance measurements. The theory of the spin-lattice relaxation in ferromagnetic metals (5) gives an estimate for the relaxation rate observed in magnetically saturated specimens. No field dependence the relaxation time is predicted. Partly due to the uncertainty in the NMR results, this theoretical problem has received little attention so far. We therefore have employed low temperature nuclear orientation which predominantly measures bulk nuclei to investigate this problem. In most of these experiments the combined technique of nuclear orientation and nuclear magnetic resonance (NMR/ON) (6) has been applied td prepare the initial state from which the relaxation takes place. Some experiments have also been performed by an entirely non-resonant technique (7). Our experimental results on ⁶⁰Co-Fe, ⁵⁴Mn-Fe and ⁵⁴Mn-Ni clearly confirm the field dependence of the relaxation time observed in nuclear magnetic resonance experiments (8). Thus the need for a detailed theoretical study is evident. Performing an NMR/ON experiment the resonance is detected by a change in the observed y-ray intensity. Resonance lines for ⁶⁰Co-Fe, ⁵⁴Mn-Fe and ⁵⁴Mn-Ni have been recorded. We have for the first time observed that their full widths at half maximum show a strong field dependence. An explanation in terms of a local distribution in the demagnetizing field is offered. We have also measured the intensity of the resonance line as a function of the applied field. An estimate shows that this is inadequately explained in terms of the expected field dependence of the enhancement factor. The distribution of hyperfine fields has never before been studied by NMR/ON. We have employed this technique successfully to investigate an alloy of one atomic percent ⁵⁹Co-Fe which has been doped with a small amount of ⁶⁰Co. A strong, well resolved satellite line of the impurity nuclei is observed. These data are interpreted in terms of the effect of near neighbor impurity nuclei on the hyperfine field (9, 10). We have computed a theoretical curve based on parameters given in the literature (10). This provides a moderately good fit for most portions of our spectra. This pilot study demonstrates that NMR/ON is indeed a valuable tool for the investigation of hyperfine field distributions. The advantages over nuclear magnetic resonance studies are that essentially only bulk as compared to wall nuclei are studied and that the sensitivity is independent of the alloy concentration. Based partially on our own data we present a short discussion of the question whether a spin temperature is maintained by the impurity nuclei during relaxation. Finally we offer a comparison between relaxation data measured by NMR/ON and other nuclear orientation techniques (11). For ⁶⁰Co-Fe the relaxation times measured by NMR/ON are found to be almost 50% longer than those measured by techniques in which the initial condition is known. This discrepancy is generally attributed to the incomplete knowledge of the initial conditions when the NMR/ON technique is employed. We have computed theoretical relaxation curves for a number of initial conditions and find that the resulting spread in relaxation time for those curves that allow a good fit to the measured curve is larger than the difference obtained from the experiments. Thus our model indeed could explain the observed discrepancy. / Science, Faculty of / Physics and Astronomy, Department of / Graduate