5,818 research outputs found
Superfluid-insulator transition of the Josephson junction array model with commensurate frustration
We have studied the rationally frustrated Josephson-junction array model in
the square lattice through Monte Carlo simulations of D XY-model. For
frustration , the model at zero temperature shows a continuous
superfluid-insulator transition. From the measurement of the correlation
function and the superfluid stiffness, we obtain the dynamical critical
exponent and the correlation length critical exponent . While the dynamical critical exponent is the same as that for cases
, 1/2, and 1/3, the correlation length critical exponent is surprisingly
quite different. When , we have the nature of a first-order transition.Comment: RevTex 4, to appear in PR
Effect of in-plane line defects on field-tuned superconductor-insulator transition behavior in homogeneous thin film
Field-tuned superconductor-insulator transition (FSIT) behavior in 2D
isotropic and homogeneous thin films is usually accompanied by a nonvanishing
critical resistance at low . It is shown that, in a 2D film including line
defects paralle to each other but with random positions perpendicular to them,
the (apparent) critical resistance in low limit vanishes, as in the 1D
quantum superconducting (SC) transition, under a current parallel to the line
defects. This 1D-like critical resistive behavior is more clearly seen in
systems with weaker point disorder and may be useful in clarifying whether the
true origin of FSIT behavior in the parent superconductor is the glass
fluctuation or the quantum SC fluctuation. As a by-product of the present
calculation, it is also pointed out that, in 2D films with line-like defects
with a long but {\it finite} correlation length parallel to the lines, a
quantum metallic behavior intervening the insulating and SC ones appears in the
resistivity curves.Comment: 16 pages, 14 figure
N_pN_n dependence of empirical formula for the lowest excitation energy of the 2^+ states in even-even nuclei
We examine the effects of the additional term of the type on the recently proposed empirical formula for the lowest excitation
energy of the states in even-even nuclei. This study is motivated by the
fact that this term carries the favorable dependence of the valence nucleon
numbers dictated by the scheme. We show explicitly that there is not
any improvement in reproducing by including the extra
term. However, our study also reveals that the excitation energies
, when calculated by the term alone (with the mass number
dependent term), are quite comparable to those calculated by the original
empirical formula.Comment: 14 pages, 5 figure
An implicit method for radiative transfer with the diffusion approximation in SPH
An implicit method for radiative transfer in SPH is described. The diffusion
approximation is used, and the hydrodynamic calculations are performed by a
fully three--dimensional SPH code. Instead of the energy equation of state for
an ideal gas, various energy states and the dissociation of hydrogen molecules
are considered in the energy calculation for a more realistic temperature and
pressure determination. In order to test the implicit code, we have performed
non--isothermal collapse simulations of a centrally condensed cloud, and have
compared our results with those of finite difference calculations performed by
MB93. The results produced by the two completely different numerical methods
agree well with each other.Comment: 25 pages, 9 figure
Hydrodynamic simulations with the Godunov SPH
We present results based on an implementation of the Godunov Smoothed
Particle Hydrodynamics (GSPH), originally developed by Inutsuka (2002), in the
GADGET-3 hydrodynamic code. We first review the derivation of the GSPH
discretization of the equations of moment and energy conservation, starting
from the convolution of these equations with the interpolating kernel. The two
most important aspects of the numerical implementation of these equations are
(a) the appearance of fluid velocity and pressure obtained from the solution of
the Riemann problem between each pair of particles, and (b the absence of an
artificial viscosity term. We carry out three different controlled
hydrodynamical three-dimensional tests, namely the Sod shock tube, the
development of Kelvin-Helmholtz instabilities in a shear flow test, and the
"blob" test describing the evolution of a cold cloud moving against a hot wind.
The results of our tests confirm and extend in a number of aspects those
recently obtained by Cha (2010): (i) GSPH provides a much improved description
of contact discontinuities, with respect to SPH, thus avoiding the appearance
of spurious pressure forces; (ii) GSPH is able to follow the development of
gas-dynamical instabilities, such as the Kevin--Helmholtz and the
Rayleigh-Taylor ones; (iii) as a result, GSPH describes the development of curl
structures in the shear-flow test and the dissolution of the cold cloud in the
"blob" test.
We also discuss in detail the effect on the performances of GSPH of changing
different aspects of its implementation. The results of our tests demonstrate
that GSPH is in fact a highly promising hydrodynamic scheme, also to be coupled
to an N-body solver, for astrophysical and cosmological applications.
[abridged]Comment: 19 pages, 13 figures, MNRAS accepted, high resolution version can be
obtained at
http://adlibitum.oats.inaf.it/borgani/html/papers/gsph_hydrosim.pd
BRST Quantization of the Proca Model based on the BFT and the BFV Formalism
The BRST quantization of the Abelian Proca model is performed using the
Batalin-Fradkin-Tyutin and the Batalin-Fradkin-Vilkovisky formalism. First, the
BFT Hamiltonian method is applied in order to systematically convert a second
class constraint system of the model into an effectively first class one by
introducing new fields. In finding the involutive Hamiltonian we adopt a new
approach which is more simpler than the usual one. We also show that in our
model the Dirac brackets of the phase space variables in the original second
class constraint system are exactly the same as the Poisson brackets of the
corresponding modified fields in the extended phase space due to the linear
character of the constraints comparing the Dirac or Faddeev-Jackiw formalisms.
Then, according to the BFV formalism we obtain that the desired resulting
Lagrangian preserving BRST symmetry in the standard local gauge fixing
procedure naturally includes the St\"uckelberg scalar related to the explicit
gauge symmetry breaking effect due to the presence of the mass term. We also
analyze the nonstandard nonlocal gauge fixing procedure.Comment: 29 pages, plain Latex, To be published in Int. J. Mod. Phys.
Development of Bis-GMA-free biopolymer to avoid estrogenicity
Objective:
Although bisphenol A-glycidyl methacrylate (Bis-GMA)-based dental materials are widely used in dentistry, Estrogenicity from released bisphenol A remains a concern due to possibility of adversely affecting the growth of children and homeostasis of adults. Here, a new family of isosorbide-derived biomonomers were synthesized and experimentally utilized as a matrix of dental sealants to provide physico-mechanical and biological properties comparable to those of a conventional Bis-GMA-based material but without the the potential estrogenicity. /
Methods:
After synthesis of isosorbide-derived biomonomers (ISDB) by light polymerization, an experimental dental sealant with different silica filler concentrations (0–15 wt%) was characterized and compared to a commercially available Bis-GMA-based sealant. Cytotoxicity and estrogenicity assays were conducted with human oral keratinocytes and estrogen-sensitive MCF-7 cells, respectively. /
Results:
ISDB-based dental sealants exhibited typical initially smooth surfaces with depth of cure, Vickers hardness, compressive strength/modulus, water resorption/solubility, and flowability comparable to those of the commercial sealant and met the ISO standard for dental sealants and polymer-based restorative materials. Indirect cytotoxicity tests using an extract showed comparable viability among experimental ISDB-based materials and a commercial Bis-GMA-incorporated control. DNA synthesis in MCF-7 cells (a marker of estrogenicity) and the release of bisphenol A under enzymatic incubation were not detected in ISDB-based materials. /
Significance:
In conclusion, the comparable physico-mechanical properties of ISDB-based materials with their cytocompatibility and lack of estrogenicity suggest the potential usefulness of ISDBs as a newly developed and safe biomaterial
Phase Transitions in the Two-Dimensional XY Model with Random Phases: a Monte Carlo Study
We study the two-dimensional XY model with quenched random phases by Monte
Carlo simulation and finite-size scaling analysis. We determine the phase
diagram of the model and study its critical behavior as a function of disorder
and temperature. If the strength of the randomness is less than a critical
value, , the system has a Kosterlitz-Thouless (KT) phase transition
from the paramagnetic phase to a state with quasi-long-range order. Our data
suggest that the latter exists down to T=0 in contradiction with theories that
predict the appearance of a low-temperature reentrant phase. At the critical
disorder and for there is no
quasi-ordered phase. At zero temperature there is a phase transition between
two different glassy states at . The functional dependence of the
correlation length on suggests that this transition corresponds to the
disorder-driven unbinding of vortex pairs.Comment: LaTex file and 18 figure
Response of Invasive Longhorn Beetles (Coleoptera: Lamiinae) to Known Cerambycid Aggregation-Sex Pheromones in the Puna District of Hawaii Island
The Queensland longhorn borer (QLB; Acalolepta aesthetica [Olliff 1890]; Coleoptera: Cerambycidae: Lamiinae: Monochamini) and plumeria long- horn borer (PLB; Lagocheirus obsoletus [Thomson 1778] = Lagocheirus undatus [Voet 1778]; Coleoptera: Cerambycidae: Lamiinae: Acanthocini) are invasive longhorn beetle species that have become established on the island of Hawaii. Both QLB and PLB are polyphagous. Known hosts of QLB include cacao, citrus, kukui, and breadfruit in Hawaii, and QLB are known to attack live, healthy trees. Currently the beetle occurs in the Puna district of the island, but its range is expanding. PLB is a pest of plumeria and other ornamental plants throughout the state of Hawaii and elsewhere. As a first step towards developing a monitoring tool for these invasive beetles, we tested four known aggregation-sex pheromones of cerambycids in this subfamily—monochamol, fuscumol acetate, fuscumol, and geranylacetone—that have proven effective for attracting more than 30 lamiine species in different areas of the world. When tested in panel traps, these compounds individually and in a blend attracted 9 QLB total, which was not significantly different than the 5 QLB captured in solvent control traps. In contrast, traps baited with one of the tested compounds, fuscumol acetate, captured significantly more PLB than solvent blank control traps. We discuss future research directions for developing attractants using chemical ecology approaches to monitor QLB and PLB
Fine structure of alpha decay in odd nuclei
Using an alpha decay level scheme, an explanation for the fine structure in
odd nuclei is evidenced by taking into account the radial and rotational
couplings between the unpaired nucleon and the core of the decaying system. It
is stated that the experimental behavior of the alpha decay fine structure
phenomenon is directed by the dynamical characteristics of the system.Comment: 8 pages, 3 figures, REVTex, submitted to Physical Review
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