Investigation of vanadium–sodium silicate glasses using XANES spectroscopy

Abstract X-ray absorption near edge structure spectroscopy has been used to investigate the electronic and atomic structure of (V2O5)x(Na2O)0.30(SiO2)0.70−x (x < 0.1) glasses obtained by melt-quench technique. The results show no sign of metallic clustering of V atoms, but mixed oxidation states (+4 and +5) of V and strong V3d–O2p hybridization in the glasses. Detailed analysis has revealed that the glass samples contain about 15% V4+ and 85% V5+ and the ligand-field splitting is about 1.6 eV. © 2006 Elsevier B.V. All rights reserved. Keywords: XANES; Vanadium–sodium silicate glasses; V L2,3 edges; O K edg

Investigation of vanadium–sodium silicate glasses using XANES spectroscopy

Abstract X-ray absorption near edge structure spectroscopy has been used to investigate the electronic and atomic structure of (V2O5)x(Na2O)0.30(SiO2)0.70−x (x < 0.1) glasses obtained by melt-quench technique. The results show no sign of metallic clustering of V atoms, but mixed oxidation states (+4 and +5) of V and strong V3d–O2p hybridization in the glasses. Detailed analysis has revealed that the glass samples contain about 15% V4+ and 85% V5+ and the ligand-field splitting is about 1.6 eV. © 2006 Elsevier B.V. All rights reserved. Keywords: XANES; Vanadium–sodium silicate glasses; V L2,3 edges; O K edg

Estimation of cortical magnification from positional error in normally sighted and amblyopic subjects

yesWe describe a method for deriving the linear cortical magnification factor from positional error across the visual field. We compared magnification obtained from this method between normally sighted individuals and amblyopic individuals, who receive atypical visual input during development. The cortical magnification factor was derived for each subject from positional error at 32 locations in the visual field, using an established model of conformal mapping between retinal and cortical coordinates. Magnification of the normally sighted group matched estimates from previous physiological and neuroimaging studies in humans, confirming the validity of the approach. The estimate of magnification for the amblyopic group was significantly lower than the normal group: by 4.4 mm deg 1 at 18 eccentricity, assuming a constant scaling factor for both groups. These estimates, if correct, suggest a role for early visual experience in establishing retinotopic mapping in cortex. We discuss the implications of altered cortical magnification for cortical size, and consider other neural changes that may account for the amblyopic results

Synthesis and characterization of atomically-thin graphite films on a silicon carbide substrate

This paper reports the synthesis and detailed characterization of graphite thin films produced by thermal decomposition of the (0001) face of a 6H-SiC wafer, demonstrating the successful growth of single crystalline films down to approximately one graphene layer. The growth and characterization were carried out in ultrahigh vacuum (UHV) conditions. The growth process and sample quality were monitored by low-energy electron diffraction, and the thickness of the sample was determined by core level x-ray photoelectron spectroscopy. High-resolution angle-resolved photoemission spectroscopy shows constant energy map patterns, which are very sharp and fully momentum-resolved, but nonetheless not resolution limited. We discuss the implications of this observation in connection with scanning electron microscopy data, as well as with previous studies

Investigation of vanadium–sodium silicate glasses using XANES spectroscopy

Abstract X-ray absorption near edge structure spectroscopy has been used to investigate the electronic and atomic structure of (V2O5)x(Na2O)0.30(SiO2)0.70−x (x < 0.1) glasses obtained by melt-quench technique. The results show no sign of metallic clustering of V atoms, but mixed oxidation states (+4 and +5) of V and strong V3d–O2p hybridization in the glasses. Detailed analysis has revealed that the glass samples contain about 15% V4+ and 85% V5+ and the ligand-field splitting is about 1.6 eV. © 2006 Elsevier B.V. All rights reserved. Keywords: XANES; Vanadium–sodium silicate glasses; V L2,3 edges; O K edg

Investigation of vanadium–sodium silicate glasses using XANES spectroscopy

Abstract X-ray absorption near edge structure spectroscopy has been used to investigate the electronic and atomic structure of (V2O5)x(Na2O)0.30(SiO2)0.70−x (x < 0.1) glasses obtained by melt-quench technique. The results show no sign of metallic clustering of V atoms, but mixed oxidation states (+4 and +5) of V and strong V3d–O2p hybridization in the glasses. Detailed analysis has revealed that the glass samples contain about 15% V4+ and 85% V5+ and the ligand-field splitting is about 1.6 eV. © 2006 Elsevier B.V. All rights reserved. Keywords: XANES; Vanadium–sodium silicate glasses; V L2,3 edges; O K edg

X-ray absorption near edge structure investigation of vanadium-doped ZnO thin films

Abstract X-ray absorption near edge structure spectroscopy has been used to investigate the electronic and atomic structure of vanadium-doped ZnO thin films obtained by reactive plasma. The results show no sign of metallic clustering of Vatoms, +4 oxidation state of V, 4-fold coordination of Zn in the films, and a secondary phase (possibly VO2) formation at 15% V doping. O K edge spectra show V 3d–O 2p and Zn 4d–O 2p hybridization, and suggest that V4+ acts as electron donor that fills the σ* band. © 2006 Elsevier B.V. All rights reserved. Keywords: ZnO; XANES; Vanadium doping; Thin films; DC-sputterin