Biomedical subjects

C P Flynn

Publications and source records attributed to C P Flynn.

5 recordsLinked to original sources

PubMed2006

Sublimation of atomic layers from a chromium surface.

We employ low-energy electron microscopy to study the kinetics of thermal etching, or sublimation, of Cr(001) at approximately 1100 K. Atomic layers are removed from the surface by spontaneous nucleation and growth of two-dimensional vacancy islands, by rotation of spiral steps, and by island decay. The growth rates of vacancy islands and the rotation frequencies of double spirals are measured as a function of temperature, and the results are correlated with activation barriers of surface processes. Mass transport between the surface and bulk is shown to be unimportant.

Journal Article↗

PubMed2001

Thermally activated stripe reconstruction induced by O on Nb (011).

We report scanning tunneling microscopy and low energy electron microscopy (LEEM) observations for thin films of Nb (011) of stripe-phase behavior by two variants of an O-induced reconstruction. Stripes occur for thin films but not bulk crystals. At low temperatures the less-favored variant is thermally activated as single stripes on surface heterogeneities. Near T0 = 1505 K, where the reconstruction is lifted, the stripes crowd to form a periodic array with a temperature dependent spacing. LEEM permits quantitative insight into stripe behavior and reveals novel details of stripes interacting with topographic features such as steps, facets, and dislocations.

Journal Article↗

PubMed2001

Magnetostatic effects in the nucleation of rare earth ferromagnetic phases.

It has been reported that superheating, supercooling, and explosive kinetics coupled to other degrees of freedom occur at the ferromagnetic transitions of Er and Dy, and that metastable phases occur during the transition kinetics of Er. We explain these observations in terms of magnetostatic energy, which requires highly eccentric nuclei in the homogeneous nucleation of magnetic transitions in heavy rare earths. The magnetostatics favor transitions through ferrimagnetic intermediaries. The unusual kinetics derive from effective spin lattice relaxation.

Journal Article↗

PubMed2000

Antistructure and point defect response in the recovery of ion-irradiated Cu3Au.

The response of the point defect and antistructure systems to ion beam irradiation is investigated using methods of linear response on thin single crystals of ordered Cu3Au grown by molecular beam epitaxy. We demonstrate that antisite evolution, as measured by electrical resistance, quantitatively determines both the defect populations and diffusion in the irradiation field, and we explore new linear and nonlinear response processes as the antistructure system is driven from equilibrium.

Journal Article↗

PubMed1982

Protein conformation from electron spin relaxation data.

Electron spin relaxation data from five ferric proteins are analyzed in terms of the fractal model of protein structures. Details of this model are presented. The results lead to a characterization of protein structures by a single parameter, the fractal dimension, d. This structural parameter is shown to determine the temperature dependence of the Raman electron spin relaxation rate, which varies as T3 + 2d. Computations of d are made using x-ray data for 17 proteins. The results range from d = 1.76 for lysozyme to d = 1.34 for ferredoxin. These values are compared with values of d obtained from the present electron spin relaxation data on five ferric proteins. Typical results are d = 1.34 +/- 0.06 from relaxation data and 1.34 +/- 0.05 from x-ray data for ferredoxin; d = 1.67 +/- 0.03 from relaxation data and 1.66 +/- 0.05 from x-ray data for ferricytochrome c. The data thus support the theoretical model. Applications of this spin resonance technique to the study of changes in protein conformation are discussed.

Animals↗