1,658 research outputs found
Silicon oxynitride based photonics
Silicon oxynitride is a very attractive material for integrated optics. Besides possessing excellent optical properties it can be deposited with refractive indices varying over a wide range by tuning the material composition. In this contribution we will summarize the key properties of this material class and discuss several application examples. Preliminary results on novel processes, which will lead to largely reduced hydrogen incorporation and enable reflow of SiON material, are being presented
White-light toxicity, resulting from systemically administered 5-aminolevulinic acid, under normal operating conditions
This study has investigated damage to the intraperitoneal organs of the rat after systemic (intraperitoneal and intravenous) administration of low doses of 5-aminolevulinic acid (ALA) and illumination with a standard white-light operating-room (o.r.) lamp. The study has been done within the framework of a larger study in which the possibility of using ALA for localization of small-volume macroscopically non-visible peritoneal metastasis of ovarian tumors is being investigated. Fluorescence diagnostics are done in addition to the standard staging and localization procedures, either through a laparoscope or during laparotomy. In these circumstances, fluorescence diagnostics involve some risk of photosensitization of critical organs since a broad-band (o.r.) light source is used during the surgical procedures for illumination of the operating area. The drug dose and the time interval between administration of ALA and illumination are varied and normal tissues are examined both macroscopically and microscopically for damage. A relationship is demonstrated between the maximum tolerable dose (MTD) of ALA (defined as the dose that does not cause any tissue damage) and the time interval between administration and illumination. The white light that is used for illumination of the operating area is sufficient to induce damage to the peritoneal organs at relatively low ALA doses. The MDTs for 2, 6 and 16 h intervals are found to be respectively 1, 10 and 100 mg kg-1. The results are similar for both intraperitoneal and intravenous administration
A calculation of the QCD phase diagram at finite temperature, and baryon and isospin chemical potentials
We study the phases of a two-flavor Nambu-Jona-Lasinio model at finite
temperature , baryon and isospin chemical potentials:
, . This study
completes a previous analysis where only small isospin chemical potentials
were consideredComment: 21 pages, 13 figures included, two more refernces adde
Stilling project: advances in the compilation and homogenization of historical wind speed data for the assessment of the stilling phenomenon
Póster presentado en: EGU General Assembly 2018 celebrada del 8 al 13 de abril en Viena, Austria.During the last decade scientists have reported a terrestrial slowdown in wind speed across the world. This weakening in wind speed has been recently termed the “stilling” phenomenon, with a worldwide average trend of -0.140 m s-1 decade-1 reported since the 1960s. The precise causes of this “stilling” remain largely uncertain and have been hypothetically attributed to several factors, mainly related to an increase in surface roughness (i.e. forest growth, land use changes, and urbanization) with little attention paid to changes in atmospheric circulation. Unlike this “stilling” over land, satellite measurements have revealed that wind speed has increased over ocean surfaces, which introduces uncertainty to the “stilling” debate. Therefore, scientists are currently debating if global warming has and will impact on changes in wind speed.The uncertainty on the causes driving the “stilling” over land is mainly due to short availability (i.e. since the 1960s) and low quality of observed wind speed records as stated by the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC) and the recent report “State of the Climate in 2015” . The main objective of the ongoing EU funded project STILLING (MSCAIF-2015 GA-703733) is to fill the key gap of short availability and low quality of wind speed datasets, and improve the limited knowledge on the causes driving the “stilling” in a climate change scenario. This has not yet been addressed by the scientific community due to (i) scientists have traditionally paid little attention on variability of wind speed; (ii) digitization of climate series at National Weather Services (NWS) systematically started in the 1960s, however, some longer but isolated past wind speed records are available for scientists to be rescued and analyzed; and (iii) efforts on advances in homogenization algorithms to improve quality of wind speed series have been scarce. The STILLING project covers a novel research niche on the “stilling” debate, and this contribution will present the advances in the compilation and homogenization of historical wind speed data (prior to the 1960s) to better assess trends/cycles and causes on multidecadal time periods and reliable datasets than previous studies.This research has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 703733 (STILLING project)
Riemann's theorem for quantum tilted rotors
The angular momentum, angular velocity, Kelvin circulation, and vortex
velocity vectors of a quantum Riemann rotor are proven to be either (1) aligned
with a principal axis or (2) lie in a principal plane of the inertia ellipsoid.
In the second case, the ratios of the components of the Kelvin circulation to
the corresponding components of the angular momentum, and the ratios of the
components of the angular velocity to those of the vortex velocity are analytic
functions of the axes lengths.Comment: 8 pages, Phys. Rev.
The Energetics of Li Off-Centering in KLiTaO; First Principles Calculations
KLiTaO (KLT) solid solutions exhibit a variety of
interesting physical phenomena related to large displacements of Li-ions from
ideal perovskite A-site positions. First-principles calculations for KLT
supercells were used to investigate these phenomena. Lattice dynamics
calculations for KLT exhibit a Li off-centering instability. The energetics of
Li-displacements for isolated Li-ions and for Li-Li pairs up to 4th neighbors
were calculated. Interactions between nearest neighbor Li-ions, in a Li-Li
pair, strongly favor ferroelectric alignment along the pair axis. Such Li-Li
pairs can be considered "seeds" for polar nanoclusters in KLT.
Electrostriction, local oxygen relaxation, coupling to the KT soft-mode, and
interactions with neighboring Li-ions all enhance the polarization from Li
off-centering. Calculated hopping barriers for isolated Li-ions and for nearest
neighbor Li-Li pairs are in good agreement with Arrhenius fits to experimental
dielectric data.Comment: 14 pages including 10 figures. To Physical Review B. Replaced after
corrections due to referees' remark
Brane-skyrmions and wrapped states
In the context of a brane world and including an induced curvature term in
the brane action, we obtain the effective lagrangian for the Goldstone bosons
(branons) associated with the spontaneous breaking of the translational
invariance in the bulk. In addition to the branons, this effective action has
Skyrmion-like solitonic states which can be understood as holes in the brane.
We study their main properties such as mass and size, the Skyrmion-branon
interaction and their possible fermionic quantization. We also consider states
where the brane is wrapped around the extra dimensions and their relation with
the brane-skyrmions. Finally, we extend our results to higher-dimensional
branes, such as those appearing in M-theory, where brane-skyrmions could also
be present.Comment: 35 pages, 7 figures. Revised version. Appendix and new references
included. To appear in Phys. Rev.
The QCD Phase Diagram at Nonzero Temperature, Baryon and Isospin Chemical Potentials in Random Matrix Theory
We introduce a random matrix model with the symmetries of QCD at finite
temperature and chemical potentials for baryon number and isospin. We analyze
the phase diagram of this model in the chemical potential plane for different
temperatures and quark masses. We find a rich phase structure with five
different phases separated by both first and second order lines. The phases are
characterized by the pion condensate and the chiral condensate for each of the
flavors. In agreement with lattice simulations, we find that in the phase with
zero pion condensate the critical temperature depends in the same way on the
baryon number chemical potential and on the isospin chemical potential. At
nonzero quark mass, we remarkably find that the critical end point at nonzero
temperature and baryon chemical potential is split in two by an arbitrarily
small isospin chemical potential. As a consequence, there are two crossovers
that separate the hadronic phase from the quark-gluon plasma phase at high
temperature. Detailed analytical results are obtained at zero temperature and
in the chiral limit.Comment: 13 pages, 5 figures, REVTeX
Chaotic Inflationary Universe on Brane
The chaotic inflationary model of the early universe, proposed by Linde is
explored in the brane world considering matter described by a minimally coupled
self interacting scalar field. We obtain cosmological solutions which admit
evolution of a universe either from a singularity or without a singularity. It
is found that a very weakly coupled self-interacting scalar field is necessary
for a quartic type potential in the brane world model compared to that
necessary in general relativity. In the brane world sufficient inflation may be
obtained even with an initial scalar field having value less than the Planck
scale. It is found that if the universe is kinetic energy dominated to begin
with, it transits to an inflationary stage subsequently.Comment: 13 pages, no fig., accepted in Physical Review
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