134 research outputs found
Black Rings in Taub-NUT and D0-D6 interactions
We analyze the dynamics of neutral black rings in Taub-NUT spaces and their
relation to systems of D0 and D6 branes in the supergravity approximation. We
employ several recent techniques, both perturbative and exact, to construct
solutions in which thermal excitations of the D0-branes can be turned on or
off, and the D6-brane can have -fluxes turned on or off in its worldvolume.
By explicit calculation of the interaction energy between the D0 and D6 branes,
we can study equilibrium configurations and their stability. We find that
although D0 and D6 branes (in the absence of fields, and at zero
temperature) repeal each other at non-zero separation, as they get together
they go over continuosly to an unstable bound state of an extremal singular
Kaluza-Klein black hole. We also find that, for -fields larger than a
critical value, or sufficiently large thermal excitation, the D0 and D6 branes
form stable bound states. The bound states with thermally excited D0 branes are
black rings in Taub-NUT, and we provide an analysis of their phase diagram.Comment: 50 pages, 8 figures; v3: minor changes and references added; v4:
improved figs. 7 and 8, matches with published versio
Input-output relations at dispersing and absorbing planar multilayers for the quantized electromagnetic field containing evanescent components
By using the Green-function concept of quantization of the electromagnetic
field in dispersing and absorbing media, the quantized field in the presence of
a dispersing and absorbing dielectric multilayer plate is studied.
Three-dimensional input-output relations are derived for both amplitude
operators in the -space and the field operators in the coordinate
space. The conditions are discussed, under which the input-output relations can
be expressed in terms of bosonic operators. The theory applies to both
(effectively) free fields and fields, created by active atomic sources inside
and/or outside the plate, including also evanescent-field components.Comment: 14 pages, 1 figur
Potential Scattering in Dirac Field Theory
We develop the potential scattering of a spinor within the context of
perturbation field theory. As an application, we reproduce, up to second order
in the potential, the diffusion results for a potential barrier of quantum
mechanics. An immediate consequence is a simple generalization to arbitrary
potential forms, a feature not possible in quantum mechanics.Comment: 7 page
Re-establishment of the genus Pseudalbizzia (Leguminosae, Caesalpinioideae, mimosoid clade): the New World species formerly placed in Albizia
Following recent mimosoid phylogenetic and phylogenomic studies demonstrating the non-monophyly of the genus Albizia, we present a new molecular phylogeny focused on the neotropical species in the genus, with much denser taxon sampling than previous studies. Our aims were to test the monophyly of the neotropical section Arthrosamanea, resolve species relationships, and gain insights into the evolution of fruit morphology. We perform a Bayesian phylogenetic analysis of sequences of nuclear internal and external transcribed spacer regions and trace the evolution of fruit dehiscence and lomentiform pods. Our results find further support for the non-monophyly of the genus Albizia, and confirm the previously proposed segregation of Hesperalbizia, Hydrochorea, Balizia and Pseudosamanea. All species that were sampled from section Arthrosamanea form a clade that is sister to a clade composed of Jupunba, Punjuba, Balizia and Hydrochorea. We find that lomentiform fruits are independently derived from indehiscent septate fruits in both Hydrochorea and section Arthrosamanea. Our results show that morphological adaptations to hydrochory, associated with shifts into seasonally flooded habitats, have occurred several times independently in different geographic areas and different lineages within the ingoid clade. This suggests that environmental conditions have likely played a key role in the evolution of fruit types in Albizia and related genera. We resurrect the name Pseudalbizzia to accommodate the species of section Arthrosamanea, except for two species that were not sampled here but have been shown in other studies to be more closely related to other ingoid genera and we restrict the name Albizia s.s. to the species from Africa, Madagascar, Asia, Australia, and the Pacific. Twenty-one new nomenclatural combinations in Pseudalbizzia are proposed, including 16 species and 5 infraspecific varietal names. In addition to the type species Pseudalbizzia berteroana, the genus has 17 species distributed across tropical regions of the Americas, including the Caribbean. Finally, a new infrageneric classification into five sections is proposed and a distribution map of the species of Pseudalbizzia is presented
Trasplante cardĂaco
A heart transplant is at present considered the
treatment of choice in cases of terminal cardiac insufficiency
refractory to medical or surgical treatment. Due
to factors such as the greater life expectancy of the
population and the more efficient management of acute
coronary syndromes, there is an increasing number of
people who suffer from heart failure. It is estimated
that the prevalence of the disease in developed countries
is around 1%; of this figure, some 10% are in an
advanced stage and are thus potential receptors of a
heart transplant. The problem is that it is still not possible
to offer this therapeutic form to all of the patients
that require it. Consequently, it is necessary to optimise
the results of the heart transplant through the
selection of patients, selection and management of
donors, perioperative management and control of the
disease due to graft rejection. Since the first transplant
carried out in 1967, numerous advances and changes
have taken place, which has made it possible to
increase survival and quality of life of those who have
received a new heart. In this article we review the most
relevant aspects of the heart transplant and the challenges
that are currently faced
Measuring CMB Polarization with BOOMERANG
BOOMERANG is a balloon-borne telescope designed for long duration (LDB)
flights around Antarctica. The second LDB Flight of BOOMERANG took place in
January 2003. The primary goal of this flight was to measure the polarization
of the CMB. The receiver uses polarization sensitive bolometers at 145 GHz.
Polarizing grids provide polarization sensitivity at 245 and 345 GHz. We
describe the BOOMERANG telescope noting changes made for 2003 LDB flight, and
discuss some of the issues involved in the measurement of polarization with
bolometers. Lastly, we report on the 2003 flight and provide an estimate of the
expected results.Comment: 12 pages, 8 figures, To be published in the proceedings of "The
Cosmic Microwave Background and its Polarization", New Astronomy Reviews,
(eds. S. Hanany and K.A. Olive). Fixed typos, and reformatted citation
Comparative interactomics analysis of different ALS-associated proteins identifies converging molecular pathways
Amyotrophic lateral sclerosis (ALS) is a devastating neurological disease with no effective treatment available. An increasing number of genetic causes of ALS are being identified, but how these genetic defects lead to motor neuron degeneration and to which extent they affect common cellular pathways remains incompletely understood. To address these questions, we performed an interactomic analysis to identify binding partners of wild-type (WT) and ALS-associated mutant versions of ATXN2, C9orf72, FUS, OPTN, TDP-43 and UBQLN2 in neuronal cells. This analysis identified several known but also many novel binding partners of these proteins. Interactomes of WT and mutant ALS proteins were very similar except for OPTN and UBQLN2, in which mutations caused loss or gain of protein interactions. Several of the identified interactomes showed a high degree of overlap: shared binding partners of ATXN2, FUS and TDP-43 had roles in RNA metabolism; OPTN- and UBQLN2-interacting proteins were related to protein degradation and protein transport, and C9orf72 interactors function in mitochondria. To conf
Numerical sedimentation particle-size analysis using the Discrete Element Method
Sedimentation tests are widely used to determine the particle size distribution of a granular sample. In this work, the Discrete Element Method interacts with the simulation of flow using the well known one-way- coupling method, a computationally affordable approach for the time-consuming numerical simulation of the hydrometer, buoyancy and pipette sedimentation tests. These tests are used in the laboratory to determine the particle-size distribution of fine-grained aggregates.
Five samples with different particle-size distributions are modeled by about six million rigid spheres pro- jected on two-dimensions, with diameters ranging from 2.5 Ă— 10−6 m to 70 Ă— 10−6 m, forming a water sus- pension in a sedimentation cylinder. DEM simulates the particle s movement considering laminar flow in- teractions of buoyant, drag and lubrication forces. The simulation provides the temporal/spatial distributions of densities and concentrations of the suspension. The numerical simulations cannot replace the laboratory tests since they need the final granulometry as initial data, but, as the results show, these simulations can identify the strong and weak points of each method and eventually recommend useful variations and draw conclusions on their validity, aspects very difficult to achieve in the laboratory.R. Bravo and J.L. Perez-Aparicio were partially supported by the project MICIIN #BIA-2012-32918. The second researcher used the grant GV BEST/2014/232 for the completion of this work. J. Jaime Gomez-Hernandez acknowledges the financial aid from project MINECO CGL2011-23295.Bravo, R.; PĂ©rez Aparicio, JL.; GĂłmez Hernández, JJ. (2015). Numerical sedimentation particle-size analysis using the Discrete Element Method. Advances in Water Resources. 86:58-72. https://doi.org/10.1016/j.advwatres.2015.09.024S58728
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