DBI equations and holographic DC conductivity

We provide a simple method for writing the Dirac-Born-Infeld (DBI) equations of a Dp-brane in an arbitrary static background whose metric depends only on the holographic radial coordinate z. Using this method we revisit the Karch-O'Bannon's procedure to calculate the DC conductivity in the presence of constant electric and magnetic fields for backgrounds where the boundary is four or three dimensional and satisfies homogeneity and isotropy. We find a frame-independent expression for the DC conductivity tensor. For particular backgrounds we recover previous results on holographic metals and strange metals.Comment: 1+21 pages; v2 : references added, minor typos correcte

Estimación de esfuerzos inducidos durante el llenado y vaciado de silos metálicos para almacenamiento de cemento

The present article show the structural analysis realized to metallic silo for storage cement through of the parametric model development in the finite element software ASNYS APDL, the fill and discharge pressures applied on the silo wall is determined with the Eurocode normative EN 1991-4.The model is development with type shell elements allowing that the structure silo fits to the cylindrical and conical geometric of the silo. It explains each of the phases having the development of the model and is made a detailed analysis of the results delivered by the software; different models are evaluated changing the sheet thickness for select the most appropriate. Also the results are analyzed when be changing the tilting the hopper and is reviewed the behavior of the silo when is analyzed with its structure. © The author; licensee Universidad Nacional de Colombia

Oxidative phosphorylation system and cell culture media

Traditional culture media do not re-semble the metabolic compositionof human blood. The concentrationof different metabolites in thesemedia influences mitochondrialbiogenesis and oxidative phos-phorylation (OXPHOS) function.This knowledge is essential for theinterpretation of results obtainedfrom cellular models used for thestudy of OXPHOS function

Fast solid-phase extraction-gas chromatography-mass spectrometry procedure for oil fingerprinting. Application to the Prestige oil spill.

A rapid and simple fractionation procedure using solid-phase extraction (SPE) cartridges was developed for an accurate determination of aliphatic and polycyclic aromatic hydrocarbons in petroleum residues and further application in chemical fingerprinting of oil spills by gas chromatography-mass spectrometry (GC-MS). Among the adsorbents evaluated, SiO2/C3-CN exhibited the best selectivity, providing, by elution with n-hexane (4 ml) and n-hexane-CH2Cl2 (1:1) (5 ml), two well-resolved aliphatic and aromatic hydrocarbon fractions, with recoveries of 97 +/- 7.2 and 99.7 +/- 13.9%, respectively. The SPE fractionation procedure was compared with the conventional silica-alumina adsorption chromatography showing similar results but practical advantages in terms of reproducibility, analysis time, solvent reduction and cost. Moreover, is particularly suitable for routine analysis with a high sample throughput. The developed methodology was tested in the characterization of fuel-oil samples collected along the Spanish north-west coast, after the Prestige oil spill accident

Virtual Compton Scattering off a Spinless Target in AdS/QCD

We study the doubly virtual Compton scattering off a spinless target $\gamma^*P\to\gamma^*P'$ within the Anti-de Sitter(AdS)/QCD formalism. We find that the general structure allowed by the Lorentz invariance and gauge invariance of the Compton amplitude is not easily reproduced with the standard recipes of the AdS/QCD correspondence. In the soft-photon regime, where the semi-classical approximation is supposed to apply best, we show that the measurements of the electric and magnetic polarizabilities of a target like the charged pion in real Compton scattering, can already serve as stringent tests.Comment: 21 pages, version to be published in JHEP

Oxidative phosphorylation inducers fight pathological angiogenesis

Pathological mutations in subunits of the oxidative phosphorylation (OXPHOS) system, or inhibitors of this biochemical pathway, increase the production of vascular endothelial growth factor (VEGF) and pathological angiogenesis. In many angiogenesis-related diseases, such as retinal, rheumatoid diseases, or cancer, OXPHOS dysfunction can be found. Thus, enhancing OXPHOS might be a promising therapeutic approach for pathologic angiogenesis

On a Holographic Model for Confinement/Deconfinement

We study the thermodynamics of the hard wall model, which consists in the introduction of an infrared cut-off in asymptotically AdS spaces. This is a toy model for confining backgrounds in the context of the gauge/gravity correspondence. We use holographic renormalization and reproduce the existence of a Hawking Page phase transition recently discussed by Herzog. We also show that the entropy jumps from $N^0$ to $N^2$, which reinforces the interpretation of this transition as the gravity dual of confinement/deconfinement. We also show that similar results hold for the phenomenologically motivated soft wall model, underlining the potential universality of our analysis.Comment: 14 pages. V2: We included a new section discussing the soft wall model and new references. V3: We clarified some points and updated the references. Results unchanged. Version published in PR