IS THERE A CONTINENTAL BIAS IN TRADE?

The relationship between geography and trade is a central topic in international economics. This paper investigates the potential existence of a continental bias in world trade flows on a sample of 182 countries over the period 1990-2006. Using traditional estimation techniques and recent developments in the econometric analysis of the gravity equation, we find robust evidence of an economically significant continental bias in trade. It implies that, other things equal, countries located on the same continent trade more with each other than countries located on different continents. A continent-by-continent analysis reveals that Oceania, America, Europe and Asia are behind this result. Africa is the only region for which the results are not conclusive

Dynamical mechanism for generation of arrhythmogenic early afterdepolarizations in cardiac myocytes: insights from in silico electrophysiological models

We analyze the dynamical mechanisms underlying the formation of arrhythmogenic early afterdepolarizations (EADs) in two mathematical models of cardiac cellular electrophysiology: the Sato et al. biophysically detailed model of a rabbit ventricular myocyte of dimension 27 and a reduced version of the Luo-Rudy mammalian myocyte model of dimension 3. Based on a comparison of the two models, with detailed bifurcation analysis using spike-counting techniques and continuation methods in the simple model and numerical explorations in the complex model, we locate the point where the first EAD originates in an unstable branch of periodic orbits. These results serve as a basis to propose a conjectured scheme involving a hysteresis mechanism with the creation of alternans and EADs in the unstable branch. This theoretical scheme fits well with electrophysiological experimental data on EAD generation and hysteresis phenomena. Our findings open the door to the development of novel methods for pro-arrhythmia risk prediction related to EAD generation without actual induction of EADs

Synthesis of functionalized triblock copolyesters derived from lactic acid and macrolactones for bone tissue regeneration

Synthetic and functional grafts are a great alternative to conventional grafts. They can provide a physical support and the precise signaling for cells to heal damaged tissues. In this study, a novel RGD peptide end-functionalized poly(ethylene glycol)-b-poly(lactic acid)-b-poly(globalide)-b-poly(lactic acid)-b-poly(ethylene glycol) (RGD-PEG-PLA-PGl-PLA-PEG-RGD) is synthetized and used to prepare functional scaffolds. The PGl inner block is obtained by enzymatic ring-opening polymerization of globalide. The outer PLA blocks are obtained by ring-opening polymerization of both, l-lactide or a racemic mixture, initiated by the α-ω-telechelic polymacrolactone. The presence of PGl inner block enhances the toughness of PLA-based scaffolds, with an increase of the elongation at break up to 300% when the longer block of PGl is used. PLA-PGl-PLA copolymer is coupled with α-ω-telechelic PEG diacids by esterification reaction. PEGylation provides hydrophilic scaffolds as the contact angle is reduced from 114° to 74.8°. That difference improves the contact between the scaffolds and the culture media. Moreover, the scaffolds are functionalized with RGD peptides at the surface significantly enhancing the adhesion and proliferation of bone marrow-derived primary mesenchymal stem cells and MC3T3-E1 cell lines in vitro. These results place this multifunctional polymer as a great candidate for the preparation of temporary grafts

Utilization of Cooked Cassava and Taro as Alternative Feed in Enhancing Pig Production in Ecuadorian Backyard System

Pork production in Ecuador is of significant economic and nutritional importance. Many of these operations are family- or backyard-based and utilize alternative feed ingredients to reduce production costs. The current study aimed to determine the chemical composition of cooked cassava and taro, and to evaluate their inclusion in the feed of backyard pigs during the growth and fattening phases. A total of 42 castrated pigs from two geographic locations in Ecuador were studied over a period of 100 days, during which their weight and measurements were recorded at three-week intervals. At the end of the experiment, ileum samples were collected from the slaughtered pigs in order to calculate the apparent digestibility of the feed. The crude protein levels of cassava and taro were found to be 3.2% and 2.1%, respectively. The combination of cooked cassava and taro was found to be a suitable replacement for corn, with the best results observed in the group receiving a diet incorporating 21% each of cassava and taro. Analysis of the ileal content also revealed that this group exhibited the highest nitrogen assimilation from the diet

Large-scale gas dynamics in the adhesion model: Implications for the two-phase massive galaxy formation scenario

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2011 RAS © 2011 The AuthorsPublished by Oxford University Press on behalf of the Royal Astronomical Society. All rights reservedWe have studied the mass assembly and star formation histories of massive galaxies identified at low redshift in different cosmological hydrodynamical simulations. To this end, we have carried out a detailed follow-up backwards in time of their constituent mass elements (sampled by particles) of different types. After that, the configurations they depict at progressively higher zs were carefully analysed. The analyses show that these histories share common generic patterns, irrespective of particular circumstances. In any case, however, the results we have found are different depending on the particle type. The most outstanding differences follow. We have found that by z∼ 3.5-6, mass elements identified as stellar particles at z= 0 exhibit a gaseous cosmic-web-like morphology with scales of ∼1 physical Mpc, where the densest mass elements have already turned into stars by z∼ 6. These settings are in fact the densest pieces of the cosmic web, where no hot particles show up, and dynamically organized as a hierarchy of flow convergence regions (FCRs), that is, attraction basins for mass flows. At high z FCRs undergo fast contractive deformations with very low angular momentum, shrinking them violently. Indeed, by z∼ 1 most of the gaseous or stellar mass they contain shows up as bound to a massive elliptical-like object at their centres, with typical half-mass radii of rmass star∼ 2-3kpc. After this, a second phase comes about where the mass assembly rate is much slower and characterized by mergers involving angular momentum. On the other hand, mass elements identified at the diffuse hot coronae surrounding massive galaxies at z= 0 do not display a clear web-like morphology at any z. Diffuse gas is heated when FCRs go through contractive deformations. Most of this gas remains hot and with low density throughout the evolution. To shed light on the physical foundations of the behaviour revealed by our analyses (i.e. a two-phase formation process with different implications for diffuse or shocked mass elements), as well as on their possible observational implications, these patterns have been confronted with some generic properties of singular flows as described by the adhesion model (i.e. potential character of the velocity field, singular versus regular points, dressing, locality when a spectrum of perturbations is implemented). We have found that the common patterns the simulations show can be interpreted as a natural consequence of flow properties that, moreover, could explain different generic observational results from massive galaxies or their samples. We briefly discuss some of themThis work was partially supported by the DGES (Spain) through the grants AYA2009-12792-C03-02 and AYA2009-12792- C03-03 from the PNAyA, as well as by the regional Madrid V PRICIT programme through the ASTROMADRID network (CAM S2009/ESP-1496

Estudio refractométrico y conoscópico de las gemas facetadas transparentes birrefringentes de la colección del Museu de Geologia de Barcelona

This work is a revision of faceted transparent birrefringent gems detailed in the catalogue of the collection of the Museu de Geologia published in 2000. The process use figures of interference as especially convincing method for a correct identification of these kind of gems. The Conoscope Figueras 93 is especially suitable for a clear and correct observation of figures of interference. The gemmological refractometer has been used for refractometric readings. Key words: Faceted gems, Figures of interference, Conoscope, Birrefringence, Refractometry, Catalogue, Museu de Geologia, Barcelona, Spain.Este trabajo recoge una revisión de las gemas facetadas birrefringentes del Museo de Geología de Barcelona, detalladas en un catálogo publicado en el año 2000. En el proceso de revisión se utilizan las figuras de interferencia como método más convincente para la correcta identificación de este tipo de gemas, estando el conoscopio Figueras 93 especialmente indicado para la mejor observación de estas figuras. Para las lecturas refractométricas se ha usado el refractómetro gemológico. Palabras clave: Gemas facetadas, Figuras de interferencia, Conoscopio, Birrefringencia, Refractometría, Catálogo, Museu de Geologia, Barcelona, España

The time traveler's guide to the quantization of zero modes

We study the relationship between the quantization of a massless scalar field on the two-dimensional Einstein cylinder and in a spacetime with a time machine. We find that the latter picks out a unique prescription for the state of the zero mode in the Einstein cylinder. We show how this choice arises from the computation of the vacuum Wightman function and the vacuum renormalized stress-energy tensor in the time-machine geometry. Finally, we relate the previously proposed regularization of the zero mode state as a squeezed state with the time-machine warp parameter, thus demonstrating that the quantization in the latter regularizes the quantization in an Einstein cylinder

Configuración Software de la directividad de arrays lineales

A line array can be defined as a column of loudspeakers that is designed so that these work together to achieve a higher directivity. This paper presents an application that enables a user to rotate the wavefront of uniform line arrays. Theoretical background and details of the implementation are provided. The validity of the application is tested with measurements of the directivity that are also compared with simulations.Este trabajo ha sido financiado Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech y el grupo de investigación Aplicación de las Tecnologías de la Información y Comunicaciones (PAI TIC-208)