Enhancement of the critical current density of YBa2Cu3Ox superconductors under hydrostatic pressure

The dependence of the critical current density Jc on hydrostatic pressure to 0.6 GPa is determined for a single 25 degrees [001]-tilt grain boundary in a bicrystalline ring of nearly optimally doped melt-textured YBa2Cu3Ox. Jc is found to increase rapidly under pressure at +20%/GPa. A new diagnostic method is introduced (pressure-induced Jc relaxation) which reveals a sizable concentration of vacant oxygen sites in the grain boundary region. Completely filling such sites with oxygen anions should lead to significant enhancements in Jc.     

Quantized electron accumulation states in indium nitride studied by angle-resolved photoemission spectroscopy

Electron accumulation states in InN have been measured using high resolution angle-resolved photoemission spectroscopy (ARPES). The electrons in the accumulation layer have been discovered to reside in quantum well states. ARPES was also used to measure the Fermi surface of these quantum well states, as well as their constant binding energy contours below the Fermi level E(F). The energy of the Fermi level and the size of the Fermi surface for these quantum well states could be controlled by varying the method of surface preparation. This is the first unambiguous observation that electrons in the InN accumulation layer are quantized and the first time the Fermi surface associated with such states has been measured.     

Surface electron accumulation and the charge neutrality level in In2O3

High-resolution x-ray photoemission spectroscopy, infrared reflectivity and Hall effect measurements, combined with surface space-charge calculations, are used to show that electron accumulation occurs at the surface of undoped single-crystalline In2O3. From a combination of measurements performed on undoped and heavily Sn-doped samples, the charge neutrality level is shown to lie approximately 0.4 eV above the conduction band minimum in In2O3, explaining the electron accumulation at the surface of undoped material, the propensity for n-type conductivity, and the ease of n-type doping in In2O3, and hence its use as a transparent conducting oxide material.     

X-ray photoemission studies of the electronic structure of single-crystalline CdO(100)

The electronic structure of single-crystalline CdO is investigated using X-ray photoemission spectroscopy. The surface is prepared by in situ Ar⁺ ion bombardment and annealing (IBA). The core level spectra before and after the IBA are presented, and reveal a dramatic reduction in the surface contamination. The semi-core Cd 4d level and valence band region following the IBA are also shown. The surface Fermi level is pinned 1.3±0.10 eV above the valence band maximum.     

Ortho-metallation of a sulphur-donor ligand: preparation structure of C6H4CH2SMeMn(CO)3(PPH3)

ortho-Metallation of PhCH₂SMe in a reaciton with MeMn(CO)₅ ahs been confirmed by a single crystal X-ray structural determination of the title complex.     

Growth and characterisation of high quality MBE grown InNx Sb1–x

The growth, structural and optical characterisation of dilute nitride alloys of InSb grown by plasma‐assisted molecular beam epitaxy is presented. The layers were characterised by high‐resolution X‐ray diffraction indicating high crystalline quality and nitrogen incorporations up to 0.68%. Fourier‐transform infrared absorption measurements reveal the position of the absorption edge to be a result of the competing effects of bandgap reduction (due to nitrogen incorporation and bandgap renormalisation) and Moss–Burstein band filling.

     

Pyrazolo[1,5-a]pyridines as p38 kinase inhibitors

[reaction: see text] A convergent synthesis of substituted pyrazolo[1,5-a]pyridines has been achieved either via a regioselective [3 + 2] cycloaddition of N-aminopyridines with alkynes or by thermal cyclization of disubstituted azirines. Subsequent palladium-catalyzed introduction of pyridines or de novo synthesis of pyrimidines affords inhibitors of p38 kinase.     

XANES study of 3d oxides: Dependence on crystal structure

XANES measurements are reported for a number of transition metal oxides. Oxide phases, in which the transition element could be widely varied (within the 3d series) while preserving the crystal structure, were systematically examined. The materials examined include monoxides, perovskites, zircons and spinels. For those samples of a given oxide phase, the near edge spectra are nearly identical but spectra for different phases are dissimilar. These observations are consistent with the simplest view of the x-ray absorption process, namely that dipole selection rules are obeyed and spectral features predominately result from transitions between the K shell and empty states with p-character.