Fermi surface and quasiparticle dynamics of Na(x)CoO2 {x=0.7} investigated by Angle-Resolved Photoemission Spectroscopy

We present an angle-resolved photoemission study of Na0.7CoO2, the host cobaltate of the NaxCoO2.yH2O series. Our results show a large hexagonal-like hole-type Fermi surface, an extremely narrow strongly renormalized quasiparticle band and a small Fermi velocity. Along the Gamma to M high symmetry line, the quasiparticle band crosses the Fermi level from M toward Gamma consistent with a negative sign of effective single-particle hopping (t ): t is estimated to be about 8 meV which is on the order of exchange coupling J in this system. This suggests that t ~ J ~ 10 meV is an important energy scale in the system. Quasiparticles are well defined only in the T-linear resistivity regime. Small single particle hopping and unconventional quasiparticle dynamics may have implications for understanding the unusual behavior of this new class of compounds.Comment: Revised text, Added Figs, Submitted to PR

Clinical and epidemiological characteristics of celiac disease in children in modern conditions

30 case histories were studied and clinical and laboratory parameters were evaluated, as well as the results of studies in children 1-16 years with a diagnosis of celiac disease. The most frequent manifestations of the disease were observed on the part of the gastrointestinal tract. The leading symptoms were abdominal pain, flatulence, anorexia and chronic diarrhea. A correlation was found between these symptoms and changes in the biopsy specimen of the small intestine.Проведен анализ 30 историй болезни детей в возрасте 1 -16 лет, имеющих диагноз целиакия. Наиболее частые проявления заболевания наблюдались со стороны желудочно-кишечного тракта: боль в животе, метеоризм, наррение аппетита и хроническая диарея. Была обнаружена прямая корреляционная связь между симптомами и изменениями в биоптате слизистой тонкой кишки

Nonideality of Water-Hexafluoropropanol Mixtures as Studied by X-Ray Small Angle Scattering

Strong temperature dependent low angle X-ray scattering by trifluoroethanol- and hexafluoro-2-propanol-water mixtures was observed in conditions commonly used in NMR work on peptides. At least two types of molecular effects may contribute to the observed scattering: formation of clathrate hydrate-like aggregates of alcohol with water as have been proposed for the similar system tert-butanol-water (Iwasaki, K. and Fujiyama, T. (1976) J. Phys. Chem. 81, 1908-1912) and a further heterogeneity of the solution resulting from immiscibility of the two components

Reminiscences of Anton Chekhov,

Translation of A. P. Chekhov.Mode of access: Internet

Tribological Properties at 20 and 500°C of TiN and CrN Cathodic ARC Coatings Deposited on Ti-6Al-4V Alloy

Tribological properties of TiN and CrN coatings deposited by cathodic arc method at three different bias potentials -50, -150 and -300V on Ti-6Al-4V alloy in pair with alumina have been investigated. X-ray diffraction analysis showed that single-phase textured cubic nitrides of TiN and CrN were formed in these coatings. It is shown that the friction coefficient of the coatings is practically equal to that established for the Ti6Al4V alloy, but the wear rate is more than an order of magnitude lower than for the titanium alloy substrate. Coatings deposited at a potential of -50 V show optimal tribological properties at temperatures 20 and 500°C. Friction coefficients for TiN coatings are 0.4-0.8 at 20°C and 0,75 at 500°C; for CrN coatings they are 0.5 at 20°C and 0,7 at 500°C. Wear rates for TiN coatings are 0.86·10-5 мм3/Нм at 20°C and 3.56·10-5 мм3/Нм at 500°C; for CrN coatings they are 1.43·10-5 мм3/Нм at 20°C and 7.13·10-5 мм3/Нм at 500°C