4,580 research outputs found
Raman scattering from high frequency phonons in supported n-graphene layer films
Results of room temperature Raman scattering studies of ultrathin graphitic
films supported on Si (111)/SiO2 substrates are reported. The results are
significantly different from those known for graphite. Spectra were collected
using 514 nm radiation on films containing from n=1 to 20 graphene layers, as
determined by atomic force microscopy. Both the 1st and 2nd order Raman spectra
show unique signatures of the number of layers in the film. The nGL film analog
of the Raman G-band in graphite exhibits a Lorentzian lineshape whose center
frequency shifts linearly relative to graphite as ~1/n (for n=1 G-band
frequency ~1588 cm-1). Three weak bands, identified with disorder-induced 1st
order scattering, are observed at ~ 1350, 1450 and 1500 cm-1. The 1500 cm-1
band is weak but relatively sharp and exhibits an interesting n-dependence. In
general, the intensity of these D-bands decreases dramatically with increasing
n. Three 2nd order bands are also observed (~2450, ~2700 and 3248 cm-1). They
are analogs to those observed in graphite. However, the ~2700 cm-1 band
exhibits an interesting and dramatic change of shape with n. Interestingly, for
n<5 this 2nd order band is more intense than the G-band.Comment: 10 pages, 7 fig'
Phase composition and transformations in magnetron-sputtered (Al,V)2O3 coatings
Coatings of (Al1-xVx)2O3, with x ranging from 0 to 1, were deposited by
pulsed DC reactive sputter deposition on Si(100) at a temperature of 550
{\deg}C. XRD showed three different crystal structures depending on V-metal
fraction in the coating: {\alpha}-V2O3 rhombohedral structure for 100 at.% V, a
defect spinel structure for the intermediate region, 63 - 42 at.% V. At lower
V-content, 18 and 7 at.%, a gamma-alumina-like solid solution was observed,
shifted to larger d-spacing compared to pure {\gamma}-Al2O3. The microstructure
changes from large columnar faceted grains for {\alpha}-V2O3 to smaller
equiaxed grains when lowering the vanadium content toward pure {\gamma}-Al2O3.
Annealing in air resulted in formation of V2O5 crystals on the surface of the
coating after annealing to 500 {\deg}C for 42 at.% V and 700 {\deg}C for 18
at.% V metal fraction respectively. The highest thermal stability was shown for
pure {\gamma}-Al2O3-coating, which transformed to {\alpha}-Al2O3 after
annealing to 1100{\deg} C. Highest hardness was observed for the Al-rich
oxides, ~24 GPa. The latter decreased with increasing V-content, larger than 7
at.% V metal fraction. The measured hardness after annealing in air decreased
in conjunction with the onset of further oxidation of the coatings
Структура заболеваемости поллинозом в Витебской области
ГИПЕРСЕНСИБИЛИЗАЦИЯ НЕМЕДЛЕННОГО ТИПАПОЛЛИНОЗСЕННАЯ ЛИХОРАДК
Efficacy Beliefs are Related to Task Cohesion: Communication is a Mediator
Efficacy beliefs and communication are key constructs which have been targeted to develop task cohesion. This study’s purpose was to: (1) examine whether collective efficacy, team-focused other-efficacy, and team-focused relation-inferred self-efficacy (RISE) are predictive of task cohesion, and (2) evaluate the possibility that communication mediates efficacy-task cohesion relationships. British university team-sport athletes (n = 250) completed questionnaires assessing efficacy beliefs, communication (i.e., positive conflict, negative conflict, and acceptance communication), and task cohesion (i.e., attractions to group; ATG-T, group integration; GI-T). Data were subjected to a multi-group path analysis to test mediation hypotheses while also addressing potential differences across males and females. Across all athletes, collective efficacy and team-focused other-efficacy significantly predicted ATG-T and GI-T directly. Positive conflict and acceptance communication significantly mediated relationships between efficacy (team-focused other-efficacy, collective efficacy) and cohesion (ATG-T, GI-T). Findings suggest enhancing athletes’ collective efficacy and team-focused efficacy beliefs will encourage communication factors affecting task cohesion
Reversible Fluorination of Graphene: towards a Two-Dimensional Wide Bandgap Semiconductor
We report the synthesis and evidence of graphene fluoride, a two-dimensional
wide bandgap semiconductor derived from graphene. Graphene fluoride exhibits
hexagonal crystalline order and strongly insulating behavior with resistance
exceeding 10 G at room temperature. Electron transport in graphene
fluoride is well described by variable-range hopping in two dimensions due to
the presence of localized states in the band gap. Graphene obtained through the
reduction of graphene fluoride is highly conductive, exhibiting a resistivity
of less than 100 k at room temperature. Our approach provides a new
path to reversibly engineer the band structure and conductivity of graphene for
electronic and optical applications.Comment: 7 pages, 5 figures, revtex, to appear in PR
Renormalization Group Analysis of a Noisy Kuramoto-Sivashinsky Equation
We have analyzed the Kuramoto-Sivashinsky equation with a stochastic noise
term through a dynamic renormalization group calculation. For a system in which
the lattice spacing is smaller than the typical wavelength of the linear
instability occurring in the system, the large-distance and long-time behavior
of this equation is the same as for the Kardar-Parisi-Zhang equation in one and
two spatial dimensions. For the case the agreement is only qualitative.
On the other hand, when coarse-graining on larger scales the asymptotic flow
depends on the initial values of the parameters.Comment: 8 pages, 5 figures, revte
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