Gauge Independence and Relativistic Electron Dispersion Equation in Dense Media

We discuss the gauge parameter dependence of particle spectra in statistical quantum electrodynamics and conclude that the electron spectrum is gauge-parameter dependent. The physical spectrum being obtained in the Landau gauge, which leads to gauge invariance in a restricted class of gauge transformations.Comment: Style corrections 16 pages, three figures, RevTe

Use of superheated liquids for the extraction of non-volatile compounds from wood: HPLC studies

A study of the extraction of oak wood compounds using superheated water-ethanol mixtures ranging from 10 to 60% ethanol is reported. Identification and characterization of the extracted compounds have been made by high performance liquid chromatography. The extraction has been performed using the static mode by single or repetitive cycles. The variables affecting the extraction process have been studied and their optimum values established (extraction time: 50 min; pressure: 40 atm; extraction temperature: 180º C). The study allows to compare the non-volatile polyphenol fractions obtained in this way with those present in commercial samples with fully agreement between them. In addition, the method allows manipulation of the extract composition by changing the working pressure, temperature and water-ethanol ratio

cAMP inhibits TGFβ1-induced in vitro angiogenesis

AbstractTransforming growth factor-β (TGFβ1) is a proangiogenic factor both, in vitro and in vivo, that is mainly involved in the later phases of angiogenesis. In an attempt to identify genes that participate in this effect, we found that TGFβ1 down-regulates expression of adenylate cyclase VI. In addition, cAMP analogs (8-Bromo-cAMP) and forskolin (an adenylate cyclase activator) also reduced TGFβ1-induced in vitro angiogenesis in mouse endothelial cell lines and in primary cultures of human umbilical vein endothelial cells on collagen gels. Induction of Ets-1 and plasminogen activator inhibitor-1 (PAI-1) by TGFβ1 was blocked by these cAMP agonists and activators, in the absence of effects on endothelial cell viability. Moreover, the signal transduction pathways stimulated by TGFβ1 were unaffected. Thus, Smad2 was normally phosphorylated and translocated to the nucleus in the presence of forskolin. In contrast, transfection studies using the PAI-1-promoter indicated that these cAMP analogues inhibit transcriptional stimulation by TGFβ1. Electrophoretic mobility shift assay showed that Smad2/3 were bound normally to a TGFβ1-response region in the presence of the cAMP analogs. In all, these data suggest that the cAMP pathway inhibits the transcriptional activity of Smads, that could be responsible for the block of the TGFβ1-induced in vitro angiogenesis caused by this second messenger

Note on Scalar Fields Non-Minimally Coupled to (2+1)-Gravity

Scalar fields non--minimally coupled to (2+1)-gravity, in the presence of cosmological constant term, are considered. Non-minimal couplings are described by the term $\zeta R \Psi^2$ in the Lagrangian. Within a class of static circularly symmetric space-times, it is shown that the only existing physically relevant solutions are the anti-de Sitter space-time for $\zeta=0$, and the Martinez-Zanelli black hole for $\zeta=1/8$. We obtain also two new solutions with non-trivial scalar field, for $\zeta=1/6$ and $\zeta=1/8$ respectively, nevertheless, the corresponding space-times can be reduced, via coordinate transformations, to the standard anti-de Sitter space.Comment: 5 pages, RevTe

"Resonance" phenomena in thermal diffusion processes in two-layer structures

The dependence on chopper frequency of the effective thermal diffusivity and effective thermal conductivity in photoacoustic experiments is discussed. The theoretical model of a two-layer structure at rear-surface illumination in the high frequency limit is considered. It is shown that the effective thermal diffusivity presents ``resonance'' while the effective thermal conductivity sharply changes its magnitude and sign. Such ``resonant'' behavior strongly depends on the surface thermal conductivities associated with the interface thermal contacts.Comment: 13 pages, 3 figure

Determination of Specific Electrocatalytic Sites in the Oxidation of Small Molecules on Crystalline Metal Surfaces

The identification of active sites in electrocatalytic reactions is part of the elucidation of mechanisms of catalyzed reactions on solid surfaces. However, this is not an easy task, even for apparently simple reactions, as we sometimes think the oxidation of adsorbed CO is. For surfaces consisting of non-equivalent sites, the recognition of specific active sites must consider the influence that facets, as is the steps/defect on the surface of the catalyst, cause in its neighbors; one has to consider the electrochemical environment under which the “active sites” lie on the surface, meaning that defects/steps on the surface do not partake in chemistry by themselves. In this paper, we outline the recent efforts in understanding the close relationships between site-specific and the overall rate and/or selectivity of electrocatalytic reactions. We analyze hydrogen adsorption/desorption, and electro-oxidation of CO, methanol, and ammonia. The classical topic of asymmetric electrocatalysis on kinked surfaces is also addressed for glucose electro-oxidation. The article takes into account selected existing data combined with our original works.M.J.S.F. is grateful to PNPD/CAPES (Brazil). J.M.F. thanks the MCINN (FEDER, Spain) project-CTQ-2016-76221-P

Assessing mortgage default risk in full-recourse economies, with an application to the case of Chile

This paper is aimed at finding individual and systemic determinants of housing default in a full-recourse economy. We propose an empirical strategy that accounts for rare events and choice-based sampling bias and estimates the contribution of idiosyncratic and systemic determinants, as well as their interactions. To support our empirical approach, we adapt and extend a well-known model of mortgage default for nonrecourse economies (Geanakoplos and Zame, 2014), adding a nonpecuniary cost for defaulting to account for possible loss of utility due to the full-recourse framework. This model applies to economies such as Spain, Australia, and Chile, where defaulters can be prosecuted until their debts are completely settled. Under the proposed model, we obtain an analytical expression involving default determinants for micro and macro mortgage loans. As a case study, we estimate this relationship for the Chilean economy using information from the Chilean Survey of Household Finance (EFH). As stated by our micro–macro model, household financial conditions and their interactions with systemic determinants account for an important part of the cross-sectional probability of mortgage default

Paleopathological evidence of the cranial remains from the Sima de los Huesos Middle Pleistocene site (Sierra de Atapuerca, Spain). Description and preliminary inferences

The large Sima de los Huesos sample provides for the first time the opportunity of performing a paleopathological study of a Middle Pleistocene population. A high frequency of bilateral temporomandibular arthropathy has been observed. We found an ear hyperostosis in Cranium 4, that probably caused deafness that we consider to be of infectious origin. Three osteomata were found in the cranial collection. One severe trauma was evident on the left supraorbital torus of an immature individual. Many cranial vault erosions, mostly restricted to the external table, are found in the sample. Cranium 5 displays thirteen of these. Cranium 5 also shows an extensive maxillary osteitis associated with a dental apical abscess, as well as another dental apical abscess in its mandible. Most of the adult frontal bones show a worm-like pattern of vascular channelling in the orbital roof, also found in modern populations