2,386 research outputs found
Effective 4D propagation of a charged scalar particle in Visser brane world
In this work we extend an analysis due to Visser of the effective propagation
of a neutral scalar particle on a brane world scenario which is a particular
solution of the five dimensional Einstein-Maxwell equations with cosmological
constant having an electric field pointing in the extra spatial dimension. We
determine the dispersion relations of a charged scalar particle to first order
in a perturbative analysis around those of the neutral particle. Since
depending on whether the particle is charged or not the dispersion relations
change, we could collect bulk information, namely the presence of the electric
field, by studying the 4D dynamics of the particles.Comment: 12 pages, 5 figure
Structure of krypton isotopes within the interacting boson model derived from the Gogny energy density functional
The evolution and coexistence of the nuclear shapes as well as the
corresponding low-lying collective states and electromagnetic transition rates
are investigated along the Krypton isotopic chain within the framework of the
interacting boson model (IBM). The IBM Hamiltonian is determined through
mean-field calculations based on the several parametrizations of the Gogny
energy density functional and the relativistic mean-field Lagrangian. The
mean-field energy surfaces, as functions of the axial and triaxial
quadrupole deformations, are mapped onto the expectation value of the
interacting-boson Hamiltonian that explicitly includes the particle-hole
excitations. The resulting boson Hamiltonian is then used to compute low-energy
excitation spectra as well as E2 and E0 transition probabilities for
Kr. Our results point to a number of examples of the prolate-oblate
shape transitions and coexistence both on the neutron-deficient and
neutron-rich sides. A reasonable agreement with the available experimental data
is obtained for the considered nuclear properties.Comment: 13 pages, 9 figures, 2 table
Scalar Field Dark Matter: behavior around black holes
We present the numerical evolution of a massive test scalar fields around a
Schwarzschild space-time. We proceed by using hyperboloidal slices that
approach future null infinity, which is the boundary of scalar fields, and also
demand the slices to penetrate the event horizon of the black hole. This
approach allows the scalar field to be accreted by the black hole and to escape
toward future null infinity. We track the evolution of the energy density of
the scalar field, which determines the rate at which the scalar field is being
diluted. We find polynomial decay of the energy density of the scalar field,
and use it to estimate the rate of dilution of the field in time. Our findings
imply that the energy density of the scalar field decreases even five orders of
magnitude in time scales smaller than a year. This implies that if a
supermassive black hole is the Schwarzschild solution, then scalar field dark
matter would be diluted extremely fastComment: 15 pages, 21 eps figures. Appendix added, accepted for publication in
JCA
Casimir torque
We develop a formalism for the calculation of the flow of angular momentum
carried by the fluctuating electromagnetic field within a cavity bounded by two
flat anisotropic materials. By generalizing a procedure employed recently for
the calculation of the Casimir force between arbitrary materials, we obtain an
expression for the torque between anisotropic plates in terms of their
reflection amplitude matrices. We evaluate the torque in 1D for ideal and
realistic model materials.Comment: 8 pages, 4 figs, Submitted to Proc. of QFEXT'05, to appear in J.
Phys.
Isolation and characterization of Dehalobacter sp. strain TeCB1 including identification of TcbA: A novel tetra- and trichlorobenzene reductive Dehalogenase
© 2017 Alfán-Guzmán, Ertan, Manefield and Lee. Dehalobacter sp. strain TeCB1 was isolated from groundwater near Sydney, Australia, that is polluted with a range of organochlorines. The isolated strain is able to grow by reductive dechlorination of 1,2,4,5-tetrachlorobenzene to 1,3- and 1,4-dichlorobenzene with 1,2,4-trichlorobenzene being the intermediate daughter product. Transient production of 1,2-dichlorobenzene was detected with subsequent conversion to monochlorobenzene. The dehalogenation capability of strain TeCB1 to respire 23 alternative organochlorines was examined and shown to be limited to the use of 1,2,4,5-tetrachlorobenzene and 1,2,4-trichlorobenzene. Growth on 1,2,4-trichlorobenzene resulted in the production of predominantly 1,3- and 1,4-dichlorobenzene. The inability of strain TeCB1 to grow on 1,2-dichlorobenzene indicated that the production of monochlorobenzene during growth on 1,2,4,5-tetarchlorobezene was cometabolic. The annotated genome of strain TeCB1 contained only one detectable 16S rRNA gene copy and genes for 23 full-length and one truncated Reductive Dehalogenase (RDase) homologs, five unique to strain TeCB1. Identification and functional characterization of the 1,2,4,5-tetrachlorobenzene and 1,2,4-trichlorobenzene RDase (TcbA) was achieved using native-PAGE coupled with liquid chromatography tandem mass spectrometry. Interestingly, TcbA showed higher amino acid identity with tetrachloroethene reductases PceA (95% identity) from Dehalobacter restrictus PER-K23 and Desulfitobacterium hafniense Y51 than with the only other chlorinated benzene reductase [i.e., CbrA (30% identity)] functionally characterized to date
Time-dependent Mechanics and Lagrangian submanifolds of Dirac manifolds
A description of time-dependent Mechanics in terms of Lagrangian submanifolds
of Dirac manifolds (in particular, presymplectic and Poisson manifolds) is
presented. Two new Tulczyjew triples are discussed. The first one is adapted to
the restricted Hamiltonian formalism and the second one is adapted to the
extended Hamiltonian formalism
Uprolides N, O and P from the Panamanian Octocoral Eunicea succinea.
Three new diterpenes, uprolide N (1), uprolide O (2), uprolide P (3) and a known one, dolabellane (4), were isolated from the CH₂Cl₂-MeOH extract of the gorgonian octocoral Eunicea succinea, collected from Bocas del Toro, on the Caribbean coast of Panama. Their structures were determined using spectroscopic analyses, including 1D and 2D NMR and high-resolution mass spectrometry (HRMS) together with molecular modeling studies. Compounds 1-3 displayed anti-inflammatory properties by inhibiting production of Tumor Necrosis Factor (TNF) and Interleukin (IL)-6 induced by lipopolysaccharide (LPS) in murine macrophages
Measuring the Non-Separability of Optical Fields
Across various areas in the optical world, there has been a growing interest in exploiting the properties of non-separable optical fields. A class of non-separable fields, known as vector modes, exhibit a coupling between the spatial and polarisation degrees of freedom that is akin of entanglement in quantum mechanics. These vector modes, however, are typically characterized using qualitative measurements which are inadequate in determining to what extent an optical field is non-separable. Here, we present tools to characterize the degree of non-separability of an arbitrary optical field, exploiting the similarities between vector modes and quantum entangled states. As an example, we use vector modes carrying orbital angular momentum to demonstrate the effectiveness of our scheme, and note that the approach can be generalized to vector modes as a whole
Synthesis and Ring-Opening Metathesis Polymerization of Second-Generation Dendronized Poly(ether) Monomers Initiated by Ruthenium Carbenes
The Ring-Opening Metathesis Polymerization (ROMP) of second-generation dendronized monomers is described. Using the highly active and fast-initiating third-generation ruthenium complex [(H_2IMes)(pyr)_2Cl_2RuCHPh], moderate to high molecular weight polymers (430-2230 kDa) are efficiently synthesized with low dispersities (Ð = 1.01-1.17). This study highlights the power of the metathesis approach toward polymer synthesis in a context where monomer structure can significantly impede polymerization
Spherical Scalar Field Halo in Galaxies
We study a spherically symmetric fluctuation of scalar dark matter in the
cosmos and show that it could be the dark matter in galaxies, provided that the
scalar field has an exponential potential whose overall sign is negative and
whose exponent is constrained observationally by the rotation velocities of
galaxies. The local space-time of the fluctuation contains a three dimensional
space-like hypersurface with surplus of angle.Comment: 5 REVTeX pages, no figures. Contains important suggestions provided
by the referee. Final version, to appear in Phys. Rev.
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