Research Projects
Multiquantum electron nuclear double resonance at low temperature Higher order harmonics of multiquantum (MQ) EPR saturate far less readily than low order harmonics. This makes the technique very promising in low temperature EPR work, especially for metalloproteins where normal EPR saturates very easily. In particular it is planned to perform MQ ENDOR while monitoring higher order harmonics of MQ EPR. The higher ENDOR enhancement of these harmonics promises to improve the signal to noise ratio of very weak signals. T. Christidis, H. Mouchawrab* and J.S. Hyde*. (Supported by National Institute of Health.) Stellar nucleosynthesis in massive stars This project deals with a complete description of the heavy element production in various evolutionary phases of stars of masses greater than 10 solar masses. The production of the heavy elements by the s-process is calculated during the central helium burning phase of these stars. Following the evolution through the advanced burning phases (carbon, oxygen and silicon) will lead to model stars which will serve to follow the nucleosynthesis occurring through the explosion phase (so called supernovae). M. F. El Eid, B. S. Meyer* and L. The*. (Supported in part by URB; Clemson University.) Stellar evolution of low and intermediate mass-stars The evolution of low and intermediate-mass stars is investigated from the main-sequence through their thermal pulsation phases (AGB stars). These calculations are aimed at improving the model calculations concerning the treatment of convection. The improved models will serve for the study of the formation of the heavy elements by the s-process nucleosynthesis. D. Schoenberner* and M. F. El Eid. (Supported in part by the German Science Foundation.) System identification of phycomyces light-growth response: The Box-Jenkins technique The Box-Jenkins model provides a simple representation of the input-output relation of the light-growth response of the zygomycete phycomyces blakesleeanus. The input-output relationship of the growth-response is obtained as a discrete model in the Z-transform domain. The main advantage of the resulting model lies in the fact that representation in the Z-transform domain allows easier conversion to difference equations, differential equations, state-variables models or transfer functions in the Laplace transform domain. The optimal Z-domain input-output model is found to be a transfer function containing four zeros and five poles together with a delay that reflects the lag of the output with respect to the input. Results are in agreement with earlier work using Wiener kernels as the means of the identification process. C. H. Trad. Investigation of the molecular effects of oxidation by oxidative stress inducers on erythrocyte and brain membranes This project is considered on-going research. The final stage will be completed by the end of summer 1997. C. H. Trad and D. A. Butterfield*. (Supported by National Science Foundation; National Institute of Health.) Effects of connectivity on impulse propagation in a small assembly of neurons A theoretical analysis has been made on the effect of connectivity
on signal propagation between neurons. A model, based on the somatic shunt
cable model, was constructed to describe the synaptic potentials, which
are induced by synaptic inputs, to understand how signal transmission could
be influenced by the way of interconnection of neurons in an assembly.
A neuron is represented as one or more equivalent cables connected to a
somatic impedance. A more general boundary condition is applied at the
ends of some cables, extending cable models in a very simple manner to
the case of more than one neuron. The cables are not only emanating from
the somatic surfaces but also terminating on cell bodies of other neurons.
They are combined together without any disagreement with the cable model
concept. The interaction between neurons could then be mediated by the
spread of current in the cables between interconnected neurons. The decay
constants are the same for all cables and the exponentially decaying depolarizations
are below threshold. C. H. Trad and H. Sabbagh.
Christidis, T., Mouchawrab, H.* and Hyde, J. S.*, Hyperfine selectivity using multiquantum electron-nuclear-electron triple resonance. Journal of Chemical Physics, 104, 9644-6, 1996. El Eid, M.F., Effect of convective mixing on the red-blue loops in the Hertzprung-Russel diagram. Monthly Notices of the Royal Astronomical Society, 275, 983-1002, 1995. El Eid, M.F. and Champagne, A. E., Sodium enrichment in A-F supergiants. Astrophysical Journal, 451, 298-307, 1995. El Eid, M.F. and De Loore, C., Stellar structure and evolution. Landolt-Boernstein, IV/3b, 62-120, Berlin: Springer Verlag, 1996. Kobeissi, H.* and Trad, C. H., “Nonintegral” expression for the diatomic centrifugal distortion constants. Canadian Journal of Physics, 73, 339-343, 1995. Kobeissi, H.*, Kobeissi, M.* and Trad, C. H., Vibration-rotation matrix elements for morse oscillators: a ‘local’ optimized approach. Indian Journal of Physics, 69B, (4), 1995. Meyer, B. S.*, Luo, N.*, The, L.* and El Eid, M. F., Nucleosynthesis and composition at the cosmic ray source. Lunar and Planetary Science, 27, (875), 880, 1996. Pace, D.* and Christidis, T., Proton ENDOR of dimethylnitramine free radicals. Applied Magnetic Resonance, 9, 539-52, 1995. Trad, C., James, W.*, Bhardwaj, A.* and Butterfield, D.*,
Selective labeling of membrane protein sulfhydryl groups with methanethiosulfonate
spin label. Journal of Biochemical and Biophysical Methods,
30, 287-299, 1995.
Abstracts, Presentations and Proceedings Christidis, T., Froncisz, W.* and Hyde, J. S.*, Spin lattice relaxation times of copper in liquid solution. Thirty-Eigthth Rocky Mountain Conference on Analytical Chemistry, Denver, USA, August 1996. Christidis, T., Mouchawrab, H. * and Hyde, J. S *, Multiquantum EPR: Hyperfine selective ENDOR. Thirty-Seventh Rocky Mountain Conferenceon Analytical Chemistry, Denver, USA, August 1995. El Eid, M. F., Convection in stars, “From stars to galaxies”, Porto Elounda Mare, Crete, Greece, 9-13 October 1995. Trad, C. H., System identification of phycomyces light-growth response: The Box-Jenkins technique. Fortieth Annual Meeting of The Biophysical Society, Baltimore, USA, 1996. Biophysical Journal, 70, (2), A228, 1996. Trad, C. H. and Sabbagh, H., Effects of connectivity on impulse
propagation in a small assembly of neurons in the cortex. Forty-First
Annual Meeting of the Biophysical Society, New Orleans, Louisiana,
USA, 1997. Biophysical Journal, 72, (2), A328, 1997.
Hassan, R.N., Interfacing an EPR/ENDOR spectrometer to a PC (1997). Advisor: T. Christidis. Sabbagh, H., Effects of connectivity on impulse propagation
in a small assembly of neurons in the cortex (1996). Advisor: C. H. Trad.
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