First-principles study of the polar O-terminated ZnO surface in thermodynamic equilibrium with oxygen and hydrogen

Using density-functional theory in combination with a thermodynamic formalism we calculate the relative stability of various structural models of the polar O-terminated (000-1)-O surface of ZnO. Model surfaces with different concentrations of oxygen vacancies and hydrogen adatoms are considered. Assuming that the surfaces are in thermodynamic equilibrium with an O2 and H2 gas phase we determine a phase diagram of the lowest-energy surface structures. For a wide range of temperatures and pressures we find that hydrogen will be adsorbed at the surface, preferentially with a coverage of 1/2 monolayer. At high temperatures and low pressures the hydrogen can be removed and a structure with 1/4 of the surface oxygen atoms missing becomes the most stable one. The clean, defect-free surface can only exist in an oxygen-rich environment with a very low hydrogen partial pressure. However, since we find that the dissociative adsorption of molecular hydrogen and water (if also the Zn-terminated surface is present) is energetically very preferable, it is very unlikely that a clean, defect-free (000-1)-O surface can be observed in experiment.Comment: 10 pages, 4 postscript figures. Uses REVTEX and epsf macro

Electron Beam-Induced Writing of Nanoscale Iron Wires on a Functional Metal Oxide

Electron beam-induced surface activation (EBISA) has been used to grow wires of iron on rutile TiO2(110)-(1 × 1) in ultrahigh vacuum. The wires have a width down to ∼20 nm and hence have potential utility as interconnects on this dielectric substrate. Wire formation was achieved using an electron beam from a scanning electron microscope to activate the surface, which was subsequently exposed to Fe(CO)5. On the basis of scanning tunneling microscopy and Auger electron spectroscopy measurements, the activation mechanism involves electron beam-induced surface reduction and restructuring

VERTEBRAL OSTEOPOROTIC COMPLICATIONS

Modern concepts of pathogenesis, current approaches of diagnosis and treatment of common complications of vertebral osteoporosis are considered on the basis of clinical cases

DISTANT DAMAGES IN PATIENTS WITH TRAUMATIC DISEASE OF SPINAL CORD

Were marked 3 groups of patients with distant damages of spine: with develope of it at early time after vertebro-spinal cord trauma, posttraumatic distant myelopathy and posttraumatic syringogydromyelia. Develope of distant damage was in 54 patients and it was by high powerfulls traumatic action, ft connected to a hard prime damage of spinal cord (79.6% had a completely disturbance of spine cord conduction). Periods of improvement conductions changed for the worse. Confirmation of defeation and level of disturbance of spine cord conduction were done by MRI and different methods of electrophysiology. Medical support and surgical operations (decompressive and bypass operations) guarantee the positive neurological results gettin almost patients