2,146 research outputs found
Cosmological Consequences of QCD Phase Transition(s) in Early Universe
We discuss the cosmological consequences of QCD phase transition(s) on the
early universe. We argue that our recent knowledge about the transport
properties of quark-gluon plasma (QGP) should throw additional lights on the
actual time evolution of our universe. Understanding the nature of QCD phase
transition(s), which can be studied in lattice gauge theory and verified in
heavy ion experiments, provides an explanation for cosmological phenomenon stem
from early universe.Comment: 8 pages, 2 eps figure
Effects of suprathermal electrons on the proton temperature anisotropy in space plasmas: Electromagnetic ion-cyclotron instability
In collision-poor plasmas from space, e.g., the solar wind and planetary
magnetospheres, the kinetic anisotropy of the plasma particles is expected to
be regulated by the kinetic instabilities. Driven by an excess of ion (proton)
temperature perpendicular to the magnetic field , the
electromagnetic ion-cyclotron (EMIC) instability is fast enough to constrain
the proton anisotropy, but the observations do not conform to the instability
thresholds predicted by the standard theory for bi-Maxwellian models of the
plasma particles. This paper presents an extended investigation of the EMIC
instability in the presence of suprathermal electrons which are ubiquitous in
these environments. The analysis is based on the kinetic (Vlasov-Maxwell)
theory assuming that both species, protons and electrons, may be anisotropic,
and the EMIC unstable solutions are derived numerically providing an accurate
description for conditions typically encountered in space plasmas. The effects
of suprathermal populations are triggered by the electron anisotropy and the
temperature contrast between electrons and protons. For certain conditions the
anisotropy thresholds exceed the limits of the proton anisotropy measured in
the solar wind considerably restraining the unstable regimes of the EMIC modes.Comment: Accepted for publication in Astrophysics and space scienc
Seven naphtho-γ-pyrones from the marine-derived fungus Alternaria alternata: structure elucidation and biological properties
Eight bioactive pyrone derivatives were identified from the culture of Alternaria alternata strain D2006, isolated from the marine soft coral Denderonephthya hemprichi, which was selected as its profound antimicrobial activities. The compounds were assigned as pyrophen (1), rubrofusarin B (2), fonsecin (3), and fonsecin B (5) beside to the four dimeric naphtho-γ-pyrones; aurasperone A (6), aurasperone B (7), aurasperone C (8), and aurasperone F (9). Structures of the isolated compounds were identified on the basis of 1D and 2D NMR spectroscopy and mass (EI, ESI, HRESI) data, and by comparison with the literature. Configuration of the four dimeric naphtho-γ-pyrones 6-9 was analyzed by CD spectra, exhibiting an identical stereochemistry
The General Solution for a linear Second Order Homogenous Differential Equations with Variable Coefficients
Abstract : The main goal in this work to find the general solution for some kind of linear second order homogenous differential equations with variable coefficients which have the general form , by using the substitution ,which transform form the above equation to Riccati equation
The Enigma of the Dark Matter
One of the great scientific enigmas still unsolved, the existence of dark
matter, is reviewed. Simple gravitational arguments imply that most of the mass
in the Universe, at least 90%, is some (unknown) non-luminous matter. Some
particle candidates for dark matter are discussed with particular emphasis on
the neutralino, a particle predicted by the supersymmetric extension of the
Standard Model of particle physics. Experiments searching for these relic
particles, carried out by many groups around the world, are also discussed.
These experiments are becoming more sensitive every year and in fact one of the
collaborations claims that the first direct evidence for dark matter has
already been observed.Comment: Invited review article for the journal Contemporary Physics. The
level is suitable for researchers which are non-specialists in the subject,
and also for students. Latex, 20 pages, 5 figure
Capacity of Reinforced Concrete Structural Elements Retrofitted with GFRP Under Cyclic Loading
Evaluation of red-light camera enforcement using traffic violations
The State of Qatar started to use red-light cameras in 2007 at key signalized intersections and the rate of installation has subsequently increased. In 2017, 19.2% of signalized intersections are equipped with red-light cameras. In many cases, the cameras are not installed on all approaches to the intersections. The purpose of this study is to compare the red-light running violations on approaches with and without red-light running enforcement cameras at the same intersections. Actual field observations were used in this study. Different variables were investigated, including the day of the week, time of day, traffic volume, the possibility of glare on an approach, and the lengths of the yellow and all-red times. A regression tree model was used to explain the characteristics associated with the violations. The results showed that the number of violations on low-volume approaches was five times higher than on high-volume approaches. The results also showed that the presence of the cameras significantly lowered red-light running violations. High-volume approaches without cameras had an approximately eight times higher rate of violations than high-volume approaches with cameras. The analysis also showed that bringing the all-red interval closer to the values recommended by the Institute of Transportation Engineers formula may bring down the rates of violations for low-volume approaches. As with any observational data mining method, the study could benefit from a larger sample size. The method used in the study was effective and is easily transferable to other locations. The results of this study can be used in developing new strategies to improve safety at signalized intersections. 2018 The AuthorsScopu
QFT results for neutrino oscillations and New Physics
The CP asymmetry in neutrino oscillations, assuming new physics at production
and/or detection processes, is analyzed. We compute this CP asymmetry using the
standard quantum field theory within a general new physics scenario that may
generate new sources of CP and flavor violation. Well known results for the CP
asymmetry are reproduced in the case of V -A operators, and additional
contributions from new physics operators are derived. We apply this formalism
to SUSY extensions of the Standard Model where the contributions from new
operators could produce a CP asymmetry observable in the next generation of
neutrino experiments.Comment: 6 pages, 3 figures, version to be published in Phys.Rev.
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