866 research outputs found
Imprints of the nuclear symmetry energy on gravitational waves from the axial w-modes of neutron stars
The eigen-frequencies of the axial w-modes of oscillating neutron stars are
studied using the continued fraction method with an Equation of State (EOS)
partially constrained by the recent terrestrial nuclear laboratory data. It is
shown that the density dependence of the nuclear symmetry energy
affects significantly both the frequencies and the damping
times of these modes. Besides confirming the previously found universal
behavior of the mass-scaled eigen-frequencies as functions of the compactness
of neutron stars, we explored several alternative universal scaling functions.
Moreover, the -mode is found to exist only for neutron stars having a
compactness of independent of the EOS used.Comment: Version appeared in Phys. Rev. C80, 025801 (2009
Pembentukan 8-OHdG Dari Zat Toksik Pemicu Radikal Bebas
This study was conducted to observethe profile of DNA Adduct (8-OHdG) formation as DNA damage indicators, by using calf thymus DNA incubated with toxic and carcinogenic compounds. The compounds which could trigger free radicals in this research were PAH(Benzo[a]Pyrene), TiO2, and CuCl2. Calf thymus DNA was incubated with Benzo[a]Pyrene and CuCl2 compounds under pH and temperature variations. The incubation of calf thymus DNA with TiO2-UV radiation (254 nm) wasused to induce the formation of reactive oxygen species (ROS) in the process of oxidative DNA damage. From this research, all of compounds have potency to trigger the formation of DNA Adduct (8-OHdG). The ratio of absorbance to assess the purity of DNA at 260 nm and 280 nm (λ260/ λ280 ) was measured at ~1.9. The shifted peaks at λmax were indicating changes on structures of DNA as a result of calf thymus DNA incubation with B[a]P and CuCl2. The highest level of 8-OHdG results in calf thymus DNA incubation with B[a]P and CuCl2 under pH 8.5 and incubation temperature at 60°C, was about 120.856 Όg/L. Calf thymus DNA incubation with TiO2-UV radiation (254 nm) under pH 8.5 resulting 8-OHdG level at 57.025 Όg/L
Phase Equilibration and Magnetic Field Generation in U(1) Bubble Collisions
We present the results of lattice computations of collisions of two expanding
bubbles of true vacuum in the Abelian Higgs model with a first-order phase
transition. New time-dependent analytical solutions for the Abelian field
strength and the phase of the complex field are derived from initial conditions
inferred from linear superposition and are shown to be in excellent agreement
with the numerical solutions especially for the case where the initial phase
difference between the bubbles is small. With a step-function approximation for
the initial phase of the complex field, solutions for the Abelian field
strength and other gauge-invariant quantities are obtained in closed form.
Possible extensions of the solution to the case of the electroweak phase
transition and the generation of primordial magnetic fields are briefly
discussed.Comment: LaTeX, 41 pages, 6 figures, submitted to Physical Review
Carbon States in Carbon-Encapsulated Nickel Nanoparticles Studied by Means of X-Ray Absorption, Emission, and Photoelectron Spectroscopies
Electronic structure of nickel nanoparticles encapsulated in carbon was
characterized by photoelectron, X-ray absorption, and X-ray emission
spectroscopies. Experimental spectra are compared with the density of states
calculated in the frame of the density functional theory. The carbon shell of
Ni nanoparticles has been found to be multilayer graphene with significant
(about 6%) amount of Stone--Wales defects. Results of the experiments evidence
protection of the metallic nanoparticles from the environmental degradation by
providing a barrier against oxidation at least for two years. Exposure in air
for 2 years leads to oxidation only of the carbon shell of Ni@C nanoparticles
with coverage of functional groups.Comment: 16 pages, 6 figures, accepted in J. Phys. Chem.
Efficiency optimization in a correlation ratchet with asymmetric unbiased fluctuations
The efficiency of a Brownian particle moving in periodic potential in the
presence of asymmetric unbiased fluctuations is investigated. We found that
there is a regime where the efficiency can be a peaked function of temperature,
which proves that thermal fluctuations facilitate the efficiency of energy
transformation, contradicting the earlier findings (H. kamegawa et al. Phys.
Rev. Lett. 80 (1998) 5251). It is also found that the mutual interplay between
asymmetry of fluctuation and asymmetry of the potential may induce optimized
efficiency at finite temperature. The ratchet is not most efficiency when it
gives maximum current.Comment: 10 pages, 7 figure
X-ray continuum variability of MCG-6-30-15
This paper presents a comprehensive examination of the X-ray continuum
variability of the bright Seyfert 1 galaxy MCG-6-30-15. The source clearly
shows the strong, linear correlation between rms variability amplitude and flux
first seen in Galactic X-ray binaries. The high frequency power spectral
density (PSD) of MCG-6-30-15 is examined in detail using a Monte Carlo fitting
procedure and is found to be well represented by a steep power-law at high
frequencies (with a power-law index alpha ~ 2.5), breaking to a flatter slope
(alpha ~ 1) below f_br ~ 0.6 - 2.0 x 10^-4 Hz, consistent with the previous
results of Uttley, McHardy & Papadakis. The slope of the power spectrum above
the break is energy dependent, with the higher energies showing a flatter PSD.
At low frequencies the variations between different energy bands are highly
coherent while at high frequencies the coherence is significantly reduced. Time
lags are detected between energy bands, with the soft variations leading the
hard. The magnitude of the lag is small (<200 s for the frequencies observed)
and is most likely frequency dependent. These properties are remarkably similar
to the temporal properties of the Galactic black hole candidate Cygnus X-1. The
characteristic timescales in these two types of source differ by ~10^5;
assuming that these timescales scale linearly with black hole mass then
suggests a black hole mass ~10^6 M_sun for MCG-6-30-15. We speculate that the
timing properties of MCG-6-30-15 may be analogous to those of Cyg X-1 in its
high/soft state and discuss a simple phenomenological model, originally
developed to explain the timing properties of Cyg X-1, that can explain many of
the observed properties of MCG-6-30-15.Comment: 19 pages, 24 figures, accepted for publication in MNRA
Erratum to: Synthesis and Magnetic Properties of Nearly Monodisperse CoFe2O4 Nanoparticles Through a Simple Hydrothermal Condition
<p>Abstract</p> <p>Nearly monodisperse cobalt ferrite (CoFe<sub>2</sub>O<sub>4</sub>) nanoparticles without any size-selection process have been prepared through an alluring method in an oleylamine/ethanol/water system. Well-defined nanospheres with an average size of 5.5 nm have been synthesized using metal chloride as the law materials and oleic amine as the capping agent, through a general liquid–solid-solution (LSS) process. Magnetic measurement indicates that the particles exhibit a very high coercivity at 10 K and perform superparamagnetism at room temperature which is further illuminated by ZFC/FC curves. These superparamagnetic cobalt ferrite nanomaterials are considered to have potential application in the fields of biomedicine. The synthesis method is possible to be a general approach for the preparation of other pure binary and ternary compounds.</p
Hydrodynamic Stability Analysis of Burning Bubbles in Electroweak Theory and in QCD
Assuming that the electroweak and QCD phase transitions are first order, upon
supercooling, bubbles of the new phase appear. These bubbles grow to
macroscopic sizes compared to the natural scales associated with the Compton
wavelengths of particle excitations. They propagate by burning the old phase
into the new phase at the surface of the bubble. We study the hydrodynamic
stability of the burning and find that for the velocities of interest for
cosmology in the electroweak phase transition, the shape of the bubble wall is
stable under hydrodynamic perturbations. Bubbles formed in the cosmological QCD
phase transition are found to be a borderline case between stability and
instability.Comment: preprint # SLAC-PUB-5943, SCIPP 92/56 38 pages, 10 figures (submitted
via `uufiles'), phyzzx format minor snafus repaire
Charmless Decays Based on the six-quark Effective Hamiltonian with Strong Phase Effects II
We provide a systematic study of charmless decays (
and denote pseudoscalar and vector mesons, respectively) based on an
approximate six-quark operator effective Hamiltonian from QCD. The calculation
of the relevant hard-scattering kernels is carried out, the resulting
transition form factors are consistent with the results of QCD sum rule
calculations. By taking into account important classes of power corrections
involving "chirally-enhanced" terms and the vertex corrections as well as weak
annihilation contributions with non-trivial strong phase, we present
predictions for the branching ratios and CP asymmetries of decays into
PP, PV and VV final states, and also for the corresponding polarization
observables in VV final states. It is found that the weak annihilation
contributions with non-trivial strong phase have remarkable effects on the
observables in the color-suppressed and penguin-dominated decay modes. In
addition, we discuss the SU(3) flavor symmetry and show that the symmetry
relations are generally respected
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