11,050 research outputs found
The lattice gluon propagator in renormalizable gauges
We study the SU(3) gluon propagator in renormalizable gauges
implemented on a symmetric lattice with a total volume of (3.25 fm) for
values of the guage fixing parameter up to . As expected, the
longitudinal gluon dressing function stays constant at its tree-level value
. Similar to the Landau gauge, the transverse gauge gluon
propagator saturates at a non-vanishing value in the deep infrared for all
values of studied. We compare with very recent continuum studies and
perform a simple analysis of the found saturation with a dynamically generated
effective gluon mass.Comment: 6 pages, 4 figure
The role of outer membrane protein(S) harboring slh/oprb-domains in extracellular vesicles’ production in synechocystis sp. pcc 6803
Cyanobacteria are a group of photosynthetic prokaryotes that contribute to primary production on a global scale. These microorganisms release vesicles to the extracellular environment, spherical nanosized structures, derived essentially from the outer membrane. Even though earlier works in model Gram-negative bacteria have hypothesized that outer membrane stability is crucial in vesicle formation, the mechanisms determining vesicle biogenesis in cyanobacteria remain unknown. Here, we report on the identification of six candidate genes encoding outer membrane proteins harboring SLH/OprB-domains in the genome of the model cyanobacterium Synechocystis sp. PCC 6803. Using a genetics-based approach, one gene was found to encode an essential protein (Slr1841), while the remaining five are not essential for growth under standard conditions. Vesicle production was monitored, and it was found that a mutant in the gene encoding the second most abundant SLH/OprB protein in Synechocystis sp. PCC 6803 outer membrane (Slr1908) produces more vesicles than any of the other tested strains. Moreover, the Slr1908-protein was also found to be important for iron uptake. Altogether, our results suggest that proteins containing the SLH/OprB-domains may have dual biological role, related to micronutrient uptake and to outer membrane stability, which, together or alone, seem to be involved in cyanobacterial vesicle biogenesis.This work was financed by Fundo Europeu de Desenvolvimento Regional (FEDER) funds through the COMPETE 2020 Operacional Programme for Competitiveness and Internationalisation (POCI), Portugal, 2020, and by Portuguese funds through Fundação para a Ciência e a Tecnolo-gia/Ministério da Ciência, Tecnologia e Ensino Superior in the framework of the project POCI-01-0145-FEDER-029540 (PTDC/BIA-OUT/29540/2017). Fundação para a Ciência e a Tecnologia is also greatly acknowledged for the PhD fellowship SFRH/BD/130478/2017 (SL) and FCT Investigator grant IF/00256/2015 (PO)
The world-sheet corrections to dyons in the Heterotic theory
All the linear alpha-prime corrections, however excluding the gravitational
Chern-Simons correction, are studied in the toroidally compactified critical
Heterotic string theory. These corrections are computed to the entropy for a
BPS static spherical four dimensional dyonic black hole which represents a
wrapped fundamental string carrying arbitrary winding and momentum charges
along one cycle in the presence of KK-monopole and H-monopole charges
associated to another cycle. It is verified that after the inclusion of the
gravitational Chern-Simons corrections [hep-th/0608182], all the linear
alpha-prime corrections to the entropy for the supersymmetric dyon can be
reproduced by the inclusion of only the Gauss-Bonnet Lagrangian to the
supergravity approximation of the induced Lagrangian.Comment: JHEP style, 17 Pages; v2: a typo corrected ; v3: The coupling of the
gravitational Chern-Simons terms to the three form field strength taken into
account. The conclusion correcte
Relations between (κ, τ)-regular sets and star complements
Let G be a finite graph with an eigenvalue μ of multiplicity m. A set X of m vertices in G is called a star set for μ in G if μ is not an eigenvalue of the star complement G\X which is the subgraph of G induced by vertices not in X. A vertex subset of a graph
is (k ,t)-regular if it induces a k -regular subgraph and every vertex not in the subset has t neighbors in it. We investigate the graphs having a (k,t)-regular set which induces a star complement for some eigenvalue. A survey of known results is provided and new properties for these graphs are deduced. Several particular graphs where these properties stand out are presented as examples
Pulmonary hypertension in AIDS/HIV infection: a rare disease
A Hipertensão pulmonar (HTP) é uma patologia rara mas que condiciona elevada morbilidade e mortalidade. É conhecida
a sua associação com o Vírus da Imunodeficiência Humana (VIH), mas muitos dos mecanismos implicados na sua patogénese
bem como o impacto da terapêutica antiretroviral (TARV) no tratamento e prognóstico desta doença ainda se encontram
por definir.
Apresenta-se um caso clínico de uma doente de 62 anos com infecção VIH internada por um quadro interpretado inicial-
mente como infecção respiratória. A má evolução e os exames adicionais permitiram o diagnóstico de Hipertensão pulmonar
grave que viria a determinar o falecimento da doente em poucos dias.
Atendendo à elevada prevalência de doentes com infecção VIH, é expectável o aumento do número de casos de Hipertensão
pulmonar, pelo que se chama a atenção para a necessidade de um diagnóstico precoce antes da evolução da mesma.info:eu-repo/semantics/publishedVersio
On gravitational-wave spectroscopy of massive black holes with the space interferometer LISA
Newly formed black holes are expected to emit characteristic radiation in the
form of quasi-normal modes, called ringdown waves, with discrete frequencies.
LISA should be able to detect the ringdown waves emitted by oscillating
supermassive black holes throughout the observable Universe. We develop a
multi-mode formalism, applicable to any interferometric detectors, for
detecting ringdown signals, for estimating black hole parameters from those
signals, and for testing the no-hair theorem of general relativity. Focusing on
LISA, we use current models of its sensitivity to compute the expected
signal-to-noise ratio for ringdown events, the relative parameter estimation
accuracy, and the resolvability of different modes. We also discuss the extent
to which uncertainties on physical parameters, such as the black hole spin and
the energy emitted in each mode, will affect our ability to do black hole
spectroscopy.Comment: 44 pages, 21 figures, 10 tables. Minor changes to match version in
press in Phys. Rev.
Gravitational Larmor formula in higher dimensions
The Larmor formula for scalar and gravitational radiation from a pointlike
particle is derived in any even higher-dimensional flat spacetime. General
expressions for the field in the wave zone and the energy flux are obtained in
closed form. The explicit results in four and six dimensions are used to
illustrate the effect of extra dimensions on linear and uniform circular
motion. Prospects for detection of bulk gravitational radiation are briefly
discussed.Comment: 5 pages, no figure
Large Charge Four-Dimensional Extremal N=2 Black Holes with R^2-Terms
We consider N=2 supergravity in four dimensions with small R^2 curvature
corrections. We construct large charge extremal supersymmetric and
non-supersymmetric black hole solutions in all space, and analyze their
thermodynamic properties.Comment: 18 pages. v2,3: minor fixe
Black hole entropy functions and attractor equations
The entropy and the attractor equations for static extremal black hole
solutions follow from a variational principle based on an entropy function. In
the general case such an entropy function can be derived from the reduced
action evaluated in a near-horizon geometry. BPS black holes constitute special
solutions of this variational principle, but they can also be derived directly
from a different entropy function based on supersymmetry enhancement at the
horizon. Both functions are consistent with electric/magnetic duality and for
BPS black holes their corresponding OSV-type integrals give identical results
at the semi-classical level. We clarify the relation between the two entropy
functions and the corresponding attractor equations for N=2 supergravity
theories with higher-derivative couplings in four space-time dimensions. We
discuss how non-holomorphic corrections will modify these entropy functions.Comment: 21 pages,LaTeX,minor change
- …