R-3 Repository :: Browsing by Author "Rorschach, Harold E."

Browsing by Author "Rorschach, Harold E."

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100-microsecond-resolved exafs technique for studying photolyzed hemoproteins
(1984) Teng, Tsu-Yi; Huang, Huey W.; Rorschach, Harold E.; Mutchler, Gordon S.
This thesis describes a 1-jus-resolved extended x-ray absorption fine structre (EXAFS) technique for studying protein dynamics. Both the time-resolved EXAFS spectrometer and the protein samples are described in detail. About ten years ago synchrotron radiation from electron storage rings began to be used for research in condensed matter. As a result a new technique for studying local structures in non-crystalline system was developed i.e. the extended x-ray absorption fine structure. This technique has now become an important tool for the structural studies of biological systems, particularly metalloproteins. In recent years the development of wiggler and undulator magnets has increased the radiation intensity to a level that, according to photon statistics, it should be possible to measure the EXAFS of hemoproteins in their transient states. Such measurements would provide structural insight to the very difficult but important problem of protein dynamics. However the conventional method of EXAFS measurement is inefficient for time-resolved measurement. We have developed a new spectrometer to take full advantage of the intense radiation. The time resolution of our spectrometer is about 1 us; below that the measurement time would be too long. Myoglobin was chosen as our sample for its importance in protein biophysics. The complex of myoglobin and carbon monoxide (CO) can be dissociated by light (flash photolysis). Its recombination time ranges from microseconds to infinity depending on temperature. The time resolved EXAFS measurement of photolyzed carboxymyoglobin will reveal the structural changes of protein around the CO binding site during the recombination process. We made our sample in the form of a thin film so that it can meet different requirments of x-ray absorption and optical photolysis. A special procedure of sample making was developed, and a transient optical absorption spectrometer was built for testing the samples. All optical absorption properties of our samples are in agreement with known results. An actual time-resolved EXAFS experiment was performed in February, 1983. The result showed no change in EXAFS with time. This might be due to a failure in photolysis (we lacked an on-line transient optical absorption spectrometer). However, these results demonstrated the feasibility and reliability of our spectrometer.
A polarized helium ion beam for surface electronic structure studies
(1980) Harrison, Allen Ray; Walters, G. King; Dunning, F. Barry; Rorschach, Harold E.
This thesis describes the development of a spinpolarized He+ ion beam suitable for use as a- probe of surface electronic structure of metals. The method would represent an extension of ion neutralization spectroscopy (INS), and should provide new information on surface magnetism, electron correlation effects, and the dynamics of the ion neutralization process. Production of the polarized helium ion beam involves optically pumping helium metastable atoms in an rf electric discharge with subsequent extraction of ions created by metastable-metastable collisions. The principles of this technique and details of the experimental apparatus are presented. Ion currents of up to 1~ A were attained and optical pumping absorption measurements suggest a beam polarization of 8 to 1%. For a moderately low beam energy, about 15 eV, an ion density at the target surface of roughly 2 X 1 A-cm- with an energy spread of about 3 eV was attained. A specific experiment is proposed in which the polarized He+ beam would be used to probe the surface magnetic properties of nickel.
Anisotropy of the self-diffusion coefficient of water in skeletal muscle
(1973) Cleveland, Gregor George; Rorschach, Harold E.
The self-diffusion of water protons in skeletal muscle has been studied using the spin-echo method of pulsed NMR. The effective spin diffusion coefficient D as well as the relaxation times T1 and T2 of water in a variety of biological samples are reduced relative to their values in pure bulk water. Two explanations for these data have been proposed. A straightforward interpretation is that the reduced values are the result of a reduction of the water mobility in some degree of freedom (not necessarily translational). The alternative interpretation is that the relaxation times are reduced as the result of an averaging effect between a major phase (9-95%) very much like pure bulk water fast exchanging with a minor phase of molecules tightly bound to the biopolymers. The reduction in the diffusion coefficient has been attributed primarily to an obstruction effect due to a non-specific interaction of the water with the large protein molecules or other barriers within the cell. In skeletal muscle the structure most likely to contribute to this obstruction effect is the actin-myosin filament network. This network is constructed very much like a regular double hexagonal array of rods. The obstruction effect would be maximum perpendicular to the filaments but should not affect diffusion parallel to the filaments. To test these models, the midportion of the tibialis anterior of mature male rats was placed in a special sample holder, which fixed the fiber orientation and could be rotated in the static magnetic field. D' was then measured as a function of the angle between the static magnetic field (the direction is which D is measured) and the fiber axis of the muscle. The average value of D’ for orientations parallel, at 45°, and perpendicular to the static field were 1.393, 1.198, and 1.5 (all x 1^-5 cm2/sec), respectively. This yields an average value for D1/D4 of .722 or an anisotropy of about 27.5%. This clearly indicates that the obstruction effect does serve to reduce the effective diffusion coefficient of intracellular water. However, the fact that the value of the diffusion coefficient parallel to the filaments is still less than the value of the diffusion coefficient D for pure water (2.283 x 1 cm /sec) by almost 4%, i.e., D4/D = .61 , indicates that this effect is not sufficient to explain all of the observed reduction. This is interpreted as support for the hypothesis that the intracellular water is motionally restricted due to some long range ordering induced by the macromolecules.
Construction of a simple dilution refrigerator
(1973) Loftin, Richard Bowen; Rorschach, Harold E.
A simple He^3-He^4 refrigerator has been designed and constructed. A brief introduction to low temperature physics in general and to dilution refrigeration in particular is given. The properties and theory of He^3-He^4 solutions as they pertain to the design of the refrigerator are discussed. A thermodynamic analysis of the dilution refrigerator is included. The construction of each part of the refrigerator is described in detail. The current status of the dilution refrigerator is presented and future experiments with it are discussed.
NMR measurement of diffusion in liquids by the pulsed field gradient technique
(1983) Egan, Thomas F.; Rorschach, Harold E.; Hannon, James P.; Estle, Thomas L.
The diffusion coefficient is an important parameter for characterizing the state of water in biological systems. A nuclear magnetic resonance method of diffusion measurement by the pulsed field gradient, technique is described. A 9-T-18 spin-echo sequence is used with one gradient pulse located on each side of the 18 rf pulse. Information on restricted diffusion is obtained by varying the measuring time, which is determined by the separation of the gradient pulse pair. Measuring times greater than 2 msec are possible with the present apparatus. Maximum magnetic field gradients of 11 gauss/cm are applied to cylindrical sample volumes of 1 cm diameter and .5 cm in height. This permits the measurement of diffusion coefficients as low as 1 cm /sec. Details of the electronic hardware and gradient coil construction and calibration are given. The measurement process is software supported and includes digital data acquisition.
QNS measurement of translational and notational water motion in polynox-water gels and hydrated artemia cysts
(1983) Heidorn, Douglas; Rorschach, Harold E.; Hannon, James P.; Roberts, Jabus B.
Quasielastic Neutron Scattering is a useful technique for obtaining information about the self-diffusion of water molecules in heterogeneous systems. Quasielastic neutron spectra have been obtained for hydrated brine shrimp (Artemia) cysts (1.2 g water/g solid) and water-polyox (1.67 g/g and 4 g/g) and deuterium-polyox (4 g/g) gels as a function of momentum transfer, Q. A triple axis spectrometer at the Oak Ridge research reactor, HFIR, was used to measure linewidths in the range .33-.1 THz at Q-values ranging from .5 to 1.9 A. A jump-diffusion model was used to describe the translational motion of the water molecules in both the brine shrimp and the polyox systems. The fitting routine employs Marquardt's algorithm which minimizes chi-squared in parameter space and determines parameters such as the Lorentzian linewidth as a function of Q . Results for the brine shrimp indicate that translational as well as rotational motion contributes to the linewidth. The measured linewidth is .329 THz at Q=.5 A, which is about twice the linewidth for pure water at the same O-value. Data for the 2% ployox in DgO mixture shows a large Lorentzian component. The magnitude of this component introduces large errors in the measurement of the motion of the water molecules in the water-polyox gels, due to the subtraction method used to determine the water spectra.
Quasielastic neutron scattering study of water in agarose gels
(1980) Trantham, Eugene Clark; Rorschach, Harold E.; Estle, Thomas L.; Trammell, George T.
The differential cross section for the scattering of thermal neutrons from a solid or liquid contains information about the thermal motion of the nuclei. Measurement of the line shape in liquids for small energy transfer can be interpreted in terms of the mechanism of the diffusive motion and is refered to as the Quasielastic Neutron Scattering (QNS) technique. QNS has been used in this investigation to study the effect of macromolecules on the physical properties of water. A pilot study on the aqueous agarose gel system which made use of a triple axis spectrometer at the Oak Ridge National Laboratory has been completed. Studies have been conducted on the scattering intensity vs. energy transfer as a function of gel concentration and momentum transfer. The concentration dependence was studied by preparing gels of 4%, 9%, 15%, and 2% agarose by weight in H2O. The momentum transfer was studied for values of the scattered wave vector in the range .7A^-1 to 1.9A^-1. The contribution of the agarose to the scattering was determined by measuring the quasielastic spectrum of a 2% agarose in D2O gel. This allowed the scattering contribution of the water to be separated from that of the agarose. These data were analysed using the "bound-free" model for the distribution of correlation times in water. In this model, one fraction is assumed to be identical to pure water and the remaining fraction is assumed to be tightly bound to the agarose macromolecules. This analysis gave an estimate for the "bound" fraction in the 2% HgO gel of 21% +/- 4%. This result is in good agreement with previous nuclear magnetic resonance studies of the diffusion coefficient in agarose gels.
Structure of valinomycin-K+ complex and cryptate-k+ complex in solution by extended x-ray absorption fine structure
(1981) Williams, Craig; Wang, C. C.; Rorschach, Harold E.; Hannon, James P.
A new tool used to study the structure of molecules is Extended X-ray Absorption Fine Structure (EXAFS). EXAFS is small oscillatory signals added on to the smooth x-ray absorption structure curve produced from the excitation of an inner electron out of its bound inner shell into a free electron state. The oscillations are produced from scattering of the excited electron from surrounding atoms. These oscillations, EXAFS, contain molecular structure information, such as the distances between atoms. Since EXAFS can be used for crystals, amorphous solids, solutions and gases it has a strong advantage over x-ray crystallography in many cases for determining local structural information. I used EXAFS to determine what structural changes occur between the known crystalline states and the unknown solution states of K+ complexed with the ionophores cryptate and valinomycin. Ionophores are organic molecules which have a polar oxygen and nitrogen cage in the center of the molecule and a hydrophobic organic exterior. These ionophores are capable of trapping a potassium ion within the cage. The hydrophobic exterior allows the ionophore to dissolve in organic solvents. For the K+-cryptate complex I found no differences in the structure between the crystalline and acetone solution states. For the K+-valinomycin complex I found the K+- distances increased by .3 ± .2 A in the solutions as compared to the crystalline state.
The diffusion of positive muons in palladium
(1982) Stein, Robert T.; Dodds, Stanley A.; Estle, Thomas L.; Rorschach, Harold E.
The diffusion of the isotopes of hydrogen in nonmagnetic metals has been of interest for many years. Muon spin rotation (uSR) has permitted the study of the diffusion of the positive muon as a light isotope of hydrogen. This experimental technique has been applied successfully to the diffusion of positive muons in palladium. Classical diffusion theory does not seem to explain the experimental results. A quantum mechanical calculation which explains the results has not yet been made.
The magnetic properties of chromium-vandium alloys
(1980) Dyson, Thornton Earl; Brotzen, Franz R.; Lane, Neal F.; Rorschach, Harold E.
Samples of the binary alloys of chromium and vanadium were made using both induction furnace and a standard tube furnace. These samples were used to study the magnetic properties of these alloys. The Ne'el temperature was measured for the dilute solutions of Vanadium and the magnetic susceptibility was measured for solutions ranging from % to 1% Vanadium in Chromium. Selected samples were used to measure the susceptibility as a function of temperature. The Ne'el temperatures of 228°K, 14°K, and 57°K (for 1%, 2%, 3% Va Cr) were found to be in good agreement with the temperatures found in other studies. The temperature vs. susceptibility measurements supported the use of Pauli type paramagnetism for this set of alloys.
The measurement of the diffusion coefficient of water in poly (ethylene oxide) water solutions using a nuclear magnetic resonance pulsed field gradient technique
(1983) Bearden, Daniel W.; Rorschach, Harold E.; Estle, Thomas L.; Huang, Huey W.
Nuclear magnetic resonance (NMR) techniques have often been used in studies of the interaction of water molecules with complex macromolecular structures such as proteins and polymers. We have measured the diffusion coefficient of protons in water/poly (ethylene oxide) solutions as a function of concentration using a pulsed field gradient NMR technique, for values of the concentration of poly-ox in H2O from to 1.2 gm poly-ox/gm. Near zero poly-ox concentration, the slope of the D vs. concentration curve is quite large. As the concentration increases, the slope decreases, and at 1.2 gm poly-ox/gm H2O the diffusion coefficient is reduced by a factor of about 6 from the value at zero concentration. This paper presents the theory of field gradient methods used to measure diffusion coefficients, describes the apparatus and technique used for our measurements, and attempts to interpret the measured diffusion coefficients by considering a two phase model which treats obstruction and hydration effects in a unified way.
The mobility of hydrogen in β-phase palladium
(1977) Hanneken, John William; Rorschach, Harold E.
Loftin's electrochemical technique for measuring the mobility of hydrogen in 3-phase palladium is analyzed in detail. In particular, four major sources of error in Loftin's work are discussed. The problems encountered in measuring pH in the CH3OH saturated with KCl solution used by Loftin are examined. To circumvent these problems an improvement employing aqueous solutions and a salt bridge was developed. Analysis of data obtained using the salt bridge offers several theories regarding the rate determining process in the electrotransport experiment. Possible hydrogen concentration gradients in the Pd wire remain a problem. The contribution of the Pd activation and charging processes to concentration gradients are discussed. Methods to measure these gradients are examined. An inductance scanning device was developed to measure the hydrogen concentration gradients and problems with this device are also discussed. Finally, suggestions for improvements in the electochemical technique are contained throughout the thesis.
The temperature dependence of the spin-spin relaxation time and magnetisation of water in skeletal muscle
(1978) Fogal, James Marlin; Rorschach, Harold E.
A Pulsed Nuclear Magnetic Resonance (NMR) method was used in this work to study water protons in skeletal muscle. The transverse relaxation times (T2) and total magnetisation of the water protons (h()) were examined as a function of temperature in the range +1.5 C to -54 C. The following results were obtained: (1) The dependence of both T2 and h() upon temperature exhibits hysteresis; (2) T2 decreases with decreasing temperature, with a characteristic activation energy of about 9.2 kcal per mole; and (3) The fraction of "non-frozen" water remaining in a sample below its nucleation temperature decreases with decreasing temperature from 19.4% at -1.2 C to 13.5% at -47 C.
Theoretical interpretation of anomalous diffusion coefficient of micellar solutions measured by light scattering
(1980) Chen, Fang-Yu; Wang, C. C.; Rorschach, Harold E.; Dodds, Stanley A.
A sodium di-2-ethyl hexylsulfosuccinate (AOTj/H2O/ decane (in the weight ratio of 3:5:95) system is believed to be a solution of micelles consisting of AOT coated water droplets dispersed in decane. A recent experiment of light scattering from such a system showed a diffusion coefficient strongly dependent on the scattering wave vector q. We examine several mechanisms which are known to cause q-dependence in diffusion coefficient. These include intermicelle interactions and mode-mode couplings. If the micelles are rigid, theories can not reproduce the data. In order to be consistent with data, the micelles should be deformate and stressless. That means the relative motion between parts of a micelle is hydrodynamic. The theory is tested by comparing the correlation length § determined from the scattering intensity with the § independently determined from the diffusion coefficient. We also found the "bare" diffusion constant to be negative.

Browsing by Author "Rorschach, Harold E."

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