Surface and Image-Potential States on the MgB_2(0001) Surfaces

We present a self-consistent pseudopotential calculation of surface and image-potential states on $MgB_2(0001)$ for both $B$-terminated ($B-t$) and $Mg$-terminated ($Mg-t$) surfaces. We find a variety of very clear surface and subsurface states as well as resonance image-potential states n=1,2 on both surfaces. The surface layer DOS at $E_F$ is increased by 55% at $B-t$ and by 90% at the $Mg-t$ surface compared to DOS in the corresponding bulk layers.Comment: 3 pages, 6 figure

Bioresorbable carbonated hydroxyapatite Ca10-xNax (PO4)6-x(CO3)x (OH)2 powders for bioactive materials preparation

The purpose of this work was to find and investigate a correlation between the carbonate ion content in crystalline lattice and defect structure, and solubility of the materials; finally, to prepare the materials under study for in vitro tests. Various techniques, such as XRD, FTIR, TEM, FESEM/EDX, TG/DTA, AES (ICP), wet chemical analysis, Ca-ionometry, microvolumetric analysis of evolved CO2, BET adsorption, were applied to determine the efficiency of carbonate substitution, and to quantify the elemental composition, as well as to characterize the structure of the carbonated hydroxyapatite and the site(s) of carbonate substitution,. It was shown that AB-type substitution prevails over other types with the carbonate content increase. According to in vitro tests, the bioactivity of the samples is correlated with the carbonate content in carbonate-doped hydroxyapatite due to accumulation of defects in carbonated hydroxyapatite nanocrystals. © Versita Warsaw and Springer-Verlag Berlin Heidelberg 2009

Cu(II) content in the structures of the peripheral nervous system at their damage

Employing electron paramagnetic resonance with diethyldithiocarbamate as a spin trap it was shown that after the transection of the rat sciatic nerve the Cu(II) content increased in the proximal stump and did not change in the distal stump. No changes of the Cu(II) content in dorsal root ganglia L4-L5 containing sensory neurons with their peripheral processes in the damaged nerve were registered. © Springer-Verlag 2006

Dielectric functions and collective excitations in MgB_2

The frequency- and momentum-dependent dielectric function $\epsilon{(\bf q,\omega)}$ as well as the energy loss function Im[-$\epsilon^{-1}{(\bf q,\omega)}$\protect{]} are calculated for intermetallic superconductor $MgB_2$ by using two {\it ab initio} methods: the plane-wave pseudopotential method and the tight-binding version of the LMTO method. We find two plasmon modes dispersing at energies $\sim 2$-8 eV and $\sim 18$-22 eV. The high energy plasmon results from a free electron like plasmon mode while the low energy collective excitation has its origin in a peculiar character of the band structure. Both plasmon modes demonstrate clearly anisotropic behaviour of both the peak position and the peak width. In particular, the low energy collective excitation has practically zero width in the direction perpendicular to boron layers and broadens in other directions.Comment: 3 pages with 10 postscript figures. Submitted to PRB on May 14 200

Energy loss of charged particles moving parallel to a magnesium surface

We present it ab initio calculations of the electronic energy loss of charged particles moving outside a magnesium surface, from a realistic description of the one-electron band structure and a full treatment of the dynamical electronic response of valence electrons. Our results indicate that the finite width of the plasmon resonance, which is mainly due to the presence of band-structure effects, strongly modifies the asymptotic behaviour of the energy loss at large distances from the surface. This effect is relevant for the understanding of the interaction between charged particles and the internal surface of microcapillaries.Comment: 7 pages, 3 figures. To appear in Phys. Rev.

Surface plasmons in metallic structures

Since the concept of a surface collective excitation was first introduced by Ritchie, surface plasmons have played a significant role in a variety of areas of fundamental and applied research, from surface dynamics to surface-plasmon microscopy, surface-plasmon resonance technology, and a wide range of photonic applications. Here we review the basic concepts underlying the existence of surface plasmons in metallic structures, and introduce a new low-energy surface collective excitation that has been recently predicted to exist.Comment: 14 pages, 14 figures, to appear in J. Opt. A: Pure Appl. Op

Pb 3+ radiation defects in Ca 9Pb(PO 4) 6(OH) 2 hydroxyapatite nanoparticles studied by high-field (W-band) EPR and ENDOR

W-band pulsed EPR and ENDOR investigations of X-ray irradiated nanoparticles of synthetic hydroxyapatite Ca 9Pb(PO 4) 6(OH) 2 are performed. It is shown that in the investigated species lead ions probably replace the Ca(1) position in the hydroxyapatite structure. © 2012 the Owner Societies

Stationary and high-frequency pulsed electron paramagnetic resonance of a calcified atherosclerotic plaque

New possibilities of applying high-frequency electron paramagnetic resonance in medicine are demonstrated on an example of the investigation of a calcified atherosclerotic plaque. After the irradiation of the atherosclerotic plaque by x rays, a new type of paramagnetic centers-organomineral radicals-is detected. The spectral and relaxation characteristics of these radicals depend on the calcification degree of the atherosclerotic plaque and can be used for diagnostics. © 2008 Pleiades Publishing, Ltd

Mutagenesis and Functional Studies with Succinate Dehydrogenase Inhibitors in the Wheat Pathogen Mycosphaerella graminicola

A range of novel carboxamide fungicides, inhibitors of the succinate dehydrogenase enzyme (SDH, EC 1.3.5.1) is currently being introduced to the crop protection market. The aim of this study was to explore the impact of structurally distinct carboxamides on target site resistance development and to assess possible impact on fitness