810 research outputs found
DC Conductivities from Non-Relativistic Scaling Geometries with Momentum Dissipation
We consider a gravitational theory with two Maxwell fields, a dilatonic
scalar and spatially dependent axions. Black brane solutions to this theory are
Lifshitz-like and violate hyperscaling. Working with electrically charged
solutions, we calculate analytically the holographic DC conductivities when
both gauge fields are allowed to fluctuate. We discuss some of the subtleties
associated with relating the horizon to the boundary data, focusing on the role
of Lifshitz asymptotics and the presence of multiple gauge fields. The axionic
scalars lead to momentum dissipation in the dual holographic theory. Finally,
we examine the behavior of the DC conductivities as a function of temperature,
and comment on the cases in which one can obtain a linear resistivity.Comment: 32 pages, 3 figures. Figures and references added. Discussion
modifie
Application of reflected light microscopy for non-invasive wood identification of marquetry furniture and small wood carvings
Mass And Force Relations For Einstein-Maxwell-Dilaton Black Holes
We investigate various properties of extremal dyonic static black holes in
Einstein-Maxwell-Dilaton theory. Using the fact that the long-range force
between two identical extremal black holes always vanishes, we obtain a simple
first-order ordinary differential equation for the black hole mass in terms of
its electric and magnetic charges. Although this equation appears not to be
solvable explicitly for general values of the strength a of the dilatonic
coupling to the Maxwell field, it nevertheless provides a powerful way of
characterising the black hole mass and the scalar charge. We make use of these
expressions to derive general results about the long-range force between two
non-identical extremal black holes. In particular, we argue that the force is
repulsive whenever a>1 and attractive whenever a<1 (it vanishes in the
intermediate BPS case a=1). The sign of the force is also correlated with the
sign of the binding energy between extremal black holes, as well as with the
convexity or concavity of the surface characterizing the extremal mass as a
function of the charges. Our work is motivated in part by the Repulsive Force
Conjecture and the question of whether long range forces between non-identical
states can shed new light on the Swampland.Comment: 34 pages, 3 figure
Anthocyanins inhibit tumor necrosis alpha-induced loss of Caco-2 cell barrier integrity
An increased permeability of the intestinal barrier is proposed as a major event in the pathophysiology of conditions characterized by chronic gut inflammation. This study investigated the capacity of pure anthocyanins (AC), and berry and rice extracts containing different types and amounts of AC, to inhibit tumor necrosis alpha (TNFα)-induced permeabilization of Caco-2 cell monolayers. Caco-2 cells differentiated into intestinal epithelial cell monolayers were incubated in the absence/presence of TNFα, with or without the addition of AC or AC-rich plant extracts (ACRE). AC and ACRE inhibited TNFα-induced loss of monolayer permeability as assessed by changes in transepithelial electrical resistance (TEER) and paracellular transport of FITC-dextran. In the range of concentrations tested (0.25–1 μM), O-glucosides of cyanidin, and delphinidin, but not those of malvidin, peonidin and petunidin protected the monolayer from TNFα-induced decrease of TEER and increase of FITC-dextran permeability. Cyanidin and delphinidin acted by mitigating TNFα-triggered activation of transcription factor NF-κB, and downstream phosphorylation of myosin light chain (MLC). The protective actions of the ACRE on TNFα-induced TEER increase was positively correlated with the sum of cyanidins and delphinidins (r2 = 0.83) content in the ACRE. However, no correlation was observed between TEER and ACRE total AC, malvidin, or peonidin content. Results support a particular capacity of cyanidins and delphinidins in the protection of the intestinal barrier against inflammation-induced permeabilization, in part through the inhibition of the NF-κB pathway.Fil: Cremonini, Eleonora. University of California at Davis; Estados UnidosFil: Mastaloudis, Angela. Nu Skin Enterprises; Estados UnidosFil: Hester, Shelly N.. Nu Skin Enterprises; Estados UnidosFil: Verstraeten, Sandra Viviana. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Biológica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; ArgentinaFil: Anderson, Maureen. University of California at Davis; Estados UnidosFil: Wood, Steven M.. Nu Skin Enterprises; Estados UnidosFil: Waterhouse, Andrew L.. University of California at Davis; Estados UnidosFil: Fraga, César Guillermo. University of California at Davis; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Bioquímica y Medicina Molecular. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Bioquímica y Medicina Molecular; ArgentinaFil: Oteiza, Patricia Isabel. University of California at Davis; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Anthocyanins protect the gastrointestinal tract from high fat diet-induced alterations in redox signaling, barrier integrity and dysbiosis.
The gastrointestinal (GI) tract can play a critical role in the development of pathologies associated with overeating, overweight and obesity. We previously observed that supplementation with anthocyanins (AC) (particularly glycosides of cyanidin and delphinidin) mitigated high fat diet (HFD)-induced development of obesity, dyslipidemia, insulin resistance and steatosis in C57BL/6J mice. This paper investigated whether these beneficial effects could be related to AC capacity to sustain intestinal monolayer integrity, prevent endotoxemia, and HFD-associated dysbiosis. The involvement of redox-related mechanisms were further investigated in Caco-2 cell monolayers. Consumption of a HFD for 14 weeks caused intestinal permeabilization and endotoxemia, which were associated with a decreased ileum expression of tight junction (TJ) proteins (occludin, ZO-1 and claudin-1), increased expression of NADPH oxidase (NOX1 and NOX4) and NOS2 and oxidative stress, and activation of redox sensitive signals (NF-κB and ERK1/2) that regulate TJ dynamics. AC supplementation mitigated all these events and increased GLP-2 levels, the intestinal hormone that upregulates TJ protein expression. AC also prevented, in vitro, tumor necrosis factor alpha-induced Caco-2 monolayer permeabilization, NOX1/4 upregulation, oxidative stress, and NF-κB and ERK activation. HFD-induced obesity in mice caused dysbiosis and affected the levels and secretion of MUC2, a mucin that participates in intestinal cell barrier protection and immune response. AC supplementation restored microbiota composition and MUC2 levels and distribution in HFD-fed mice. Thus, AC, particularly delphinidin and cyanidin, can preserve GI physiology in HFD-induced obesity in part through redox-regulated mechanisms. This can in part explain AC capacity to mitigate pathologies, i.e. insulin resistance and steatosis, associated with HFD-associated obesity
Generating Temperature Flow for eta/s with Higher Derivatives: From Lifshitz to AdS
We consider charged dilatonic black branes in AdS_5 and examine the effects
of perturbative higher derivative corrections on the ratio of shear viscosity
to entropy density eta/s of the dual plasma. The structure of eta/s is
controlled by the relative hierarchy between the two scales in the plasma, the
temperature and the chemical potential. In this model the background
near-horizon geometry interpolates between a Lifshitz-like brane at low
temperature, and an AdS brane at high temperatures -- with AdS asymptotics in
both cases. As a result, in this construction the viscosity to entropy ratio
flows as a function of temperature, from a value in the IR which is sensitive
to the dynamical exponent z, to the simple result expected for an AdS brane in
the UV. Coupling the scalar directly to the higher derivative terms generates
additional temperature dependence, and leads to a particularly interesting
structure for eta/s in the IR.Comment: Plots and references added. Journal version of the pape
Cyanidin and delphinidin restore colon physiology in high fat diet-fed mice: Involvement of TLR-4 and redox-regulated signaling
Consumption of high fat diets (HFD) mimics a modern or “Western style” diet pattern and can impair intestinal barrier integrity, leading to endotoxemia and associated unhealthy conditions. This study investigated if supplementation with an anthocyanin (cyanidin and delphinidin glucosides)-rich extract (CDRE) could revert or mitigate HFD-induced alterations of colonic physiology in part through the regulation of Toll-Like Receptor 4 (TLR-4)- and redox-regulated signaling. C57BL/6J male mice were fed for 4 weeks with a control or an HFD. Then, mice were divided in four groups fed either control or HFD, or these diets supplemented with CDRE for the subsequent 4 weeks. After 8 weeks on the HFD we observed in the colon: i) disruption of tight junction structure and function; ii) increased TLR-4 expression; iii) increased NADPH oxidase NOX1 expression, and iv) activation of redox-sensitive and TLR-4-triggered pathways, i.e. NF-κB, ERK1/2, JNK1/2, PI3K/Akt. All these events were prevented or reverted by CDRE supplementation. Supporting the relevance of CDRE-mediated downregulation of TLR-4 on its colon beneficial effect; in vitro (Caco-2 cell monolayers), cyanidin, delphinidin and their metabolites protocatechuic and gallic acid, mitigated lipopolysaccharide (LPS)-induced monolayer permeabilization by restoring tight junction structure and dynamics and preventing lipid/protein oxidation. The CDRE also mitigated HFD-mediated alterations in parameters of goblet cell differentiation and function, including the downregulation of markers of goblet cell differentiation (Klf4), and intestinal mucosa healing (Tff3). Results show that a short-term supplementation with cyanidin and delphinidin, protect from HFD-induced alterations in colon physiology in part through the modulation of TLR-4- and redox-regulated signaling.Fil: Iglesias, Dario Ezequiel. University of California at Davis; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Bioquímica y Medicina Molecular. Universidad de Buenos Aires. Facultad Medicina. Instituto de Bioquímica y Medicina Molecular; ArgentinaFil: Cremonini, Eleonora. University of California at Davis; Estados UnidosFil: Hester, Shelly N.. Nuskin Inc.; Estados UnidosFil: Wood, Steven N.. Nuskin Inc.; Estados UnidosFil: Bartlett, Mark. Nuskin Inc.; Estados UnidosFil: Fraga, César Guillermo. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Analitica y Fisicoquímica. Cátedra de Fisicoquímica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Bioquímica y Medicina Molecular. Universidad de Buenos Aires. Facultad Medicina. Instituto de Bioquímica y Medicina Molecular; ArgentinaFil: Oteiza, Patricia Isabel. University of California at Davis; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Higher Derivative Corrections to R-charged Black Holes: Boundary Counterterms and the Mass-Charge Relation
We carry out the holographic renormalization of Einstein-Maxwell theory with
curvature-squared corrections. In particular, we demonstrate how to construct
the generalized Gibbons-Hawking surface term needed to ensure a perturbatively
well-defined variational principle. This treatment ensures the absence of ghost
degrees of freedom at the linearized perturbative order in the
higher-derivative corrections. We use the holographically renormalized action
to study the thermodynamics of R-charged black holes with higher derivatives
and to investigate their mass to charge ratio in the extremal limit. In five
dimensions, there seems to be a connection between the sign of the higher
derivative couplings required to satisfy the weak gravity conjecture and that
violating the shear viscosity to entropy bound. This is in turn related to
possible constraints on the central charges of the dual CFT, in particular to
the sign of c-a.Comment: 30 pages. v2: references added, some equations simplifie
Diffusion constant of supercharge density in N=4 SYM at finite chemical potential
We compute holographically the diffusion constant of supercharges in N=4 SYM
at finite chemical potential for the R-charge, by solving the equations of
motion for the transverse mode of the gravitino in the STU black hole in 5
dimensions. We consider the case of one charge and three charges, and we
present analytical solutions for small values of the charges and numerical
solutions for arbitrary values. We compare our results with other known results
in 4 dimensions.Comment: 20 pages, 4 figures; v2: typos correcte
A general condition of inflationary cosmology on trans-Planckian physics
We consider a more general initial condition satisfying the minimal
uncertainty relationship. We calculate the power spectrum of a simple model in
inflationary cosmology. The results depend on perturbations generated below a
fundamental scale, e.g. the Planck scale.Comment: 7 pages, References adde
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