462 research outputs found
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
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