9,326 research outputs found
Comment on “Effects of focused ion beam milling on the nanomechanical behavior of a molybdenum-alloy single crystal” Appl. Phys. Lett. 91, 111915 (2007)
While this article provides insight into differences in mechanics between Ga+-irradiated and “pure” surfaces of molybdenum, there are several statements that are either inaccurate or poorly stated. It is clear that when a surface is directly irradiated by orthogonal ion beam (0.07–0.21 mW), a focused ion beam (FIB) damage layer will likely form and affect the strength. However, this finding does not provide adequate foundation for raising the question of FIB-induced hardening in nanopillars, given the vast differences between these experiments and procedure used in pillar fabrication. These issues would cause considerable confusion and result in disservice to mechanical testing community if not clarified
Semiconductor cavity QED: Bandgap induced by vacuum fluctuations
We consider theoretically a semiconductor nanostructure embedded in
one-dimensional microcavity and study the modification of its electron energy
spectrum by the vacuum fluctuations of the electromagnetic field. To solve the
problem, a non-perturbative diagrammatic approach based on the Green's function
formalism is developed. It is shown that the interaction of the system with the
vacuum fluctuations of the optical cavity opens gaps within the valence band of
the semiconductor. The approach is verified for the case of large photon
occupation numbers, proving the validity of the model by comparing to previous
studies of the semiconductor system excited by a classical electromagnetic
field. The developed theory is of general character and allows for unification
of quantum and classical descriptions of the strong light-matter interaction in
semiconductor structures
Some Cosmological Implications of Hidden Sectors
We discuss some cosmological implications of extensions of the Standard Model
with hidden sector scalars coupled to the Higgs boson. We put special emphasis
on the conformal case, in which the electroweak symmetry is broken radiatively
with a Higgs mass above the experimental limit. Our refined analysis of the
electroweak phase transition in this kind of models strengthens the prediction
of a strongly first-order phase transition as required by electroweak
baryogenesis. We further study gravitational wave production and the
possibility of low-scale inflation as well as a viable dark matter candidate.Comment: 23 pages, 8 figures; some comments added, published versio
Defect chemistry and transport properties of BaxCe0.85M0.15O3-d
The site-incorporation mechanism of M3+ dopants into A2+B4+O3 perovskites controls the overall defect chemistry and thus their transport properties. For charge-balance reasons, incorporation onto the A2+-site would require the creation of negatively charged point defects (such as cation vacancies), whereas incorporation onto the B4+-site is accompanied by the generation of positively charged defects, typically oxygen vacancies. Oxygen-vacancy content, in turn, is relevant to proton-conducting oxides in which protons are introduced via the dissolution of hydroxyl ions at vacant oxygen sites. We propose here, on the basis of x-ray powder diffraction studies, electron microscopy, chemical analysis, thermal gravimetric analysis, and alternating current impedance spectroscopy, that nominally B-site doped barium cerate can exhibit dopant partitioning as a consequence of barium evaporation at elevated temperatures. Such partitioning and the presence of significant dopant concentrations on the A-site negatively impact proton conductivity. Specific materials examined are BaxCe0.85M0.15O3-d (x = 0.85 - 1.20; M = Nd, Gd, Yb). The compositional limits for the maximum A-site incorporation are experimentally determined to be: (Ba0.919Nd0.081)(Ce0.919Nd0.081)O3, (Ba0.974Gd0.026)(Ce0.872Gd0.128)O2.875, and Ba(Ce0.85Yb0.15)O2.925. As a consequence of the greater ability of larger cations to exist on the Ba site, the H2O adsorption and proton conductivities of large-cation doped barium cerates are lower than those of small-cation doped analogs
Actitudes hacia la ciencia y asignaturas pendientes : dos factores que afectan al rendimiento en ciencias
This paper analyses the influence of the attitude towarda Science with which some students attain secondary education (BUP) and the role of outstanding subjecrs in their school record
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