Geometric thermodynamics: black holes and the meaning of the scalar curvature

In this paper we show that the vanishing of the scalar curvature of Ruppeiner-like metrics does not characterize the ideal gas. Furthermore, we claim through an example that flatness is not a sufficient condition to establish the absence of interactions in the underlying microscopic model of a thermodynamic system, which poses a limitation on the usefulness of Ruppeiner's metric and conjecture. Finally, we address the problem of the choice of coordinates in black hole thermodynamics. We propose an alternative energy representation for Kerr-Newman black holes that mimics fully Weinhold's approach. The corresponding Ruppeiner's metrics become degenerate only at absolute zero and have non-vanishing scalar curvatures.Comment: LaTeX file, no figure

Conserved and distinct roles of kreisler in regulation of the paralogous Hoxa3 and Hoxb3 genes

11 pages, 8 figures.-- et al.During anteroposterior patterning of the developing hindbrain, the anterior expression of 3′ Hox genes maps to distinct rhombomeric boundaries and, in many cases, is upregulated in specific segments. Paralogous genes frequently have similar anterior boundaries of expression but it is not known if these are controlled by common mechanisms. The expression of the paralogous Hoxa3 and Hoxb3 genes extends from the posterior spinal cord up to the rhombomere (r) 4/5 boundary and both genes are upregulated specifically in r5. However, in this study, we have found that Hoxa3 expression is also upregulated in r6, showing that there are differences in segmental expression between paralogues. We have used transgenic analysis to investigate the mechanisms underlying the pattern of segmental expression of Hoxa3. We found that the intergenic region between Hoxa3 and Hoxa4 contains several enhancers, which summed together mediate a pattern of expression closely resembling that of the endogenous Hoxa3 gene. One enhancer specifically directs expression in r5 and r6, in a manner that reflects the upregulation of the endogenous gene in these segments. Deletion analysis localized this activity to a 600 bp fragment that was found to contain a single high-affinity binding site for the Maf bZIP protein Krml1, encoded by the kreisler gene. This site is necessary for enhancer activity and when multimerized it is sufficient to direct a kreisler-like pattern in transgenic embryos. Furthermore the r5/r6 enhancer activity is dependent upon endogenous kreisler and is activated by ectopic kreisler expression. This demonstrates that Hoxa3, along with its paralog Hoxb3, is a direct target of kreisler in the mouse hindbrain. Comparisons between the Krml1-binding sites in the Hoxa3 and Hoxb3 enhancers reveal that there are differences in both the number of binding sites and way that kreisler activity is integrated and restricted by these two control regions. Analysis of the individual sites revealed that they have different requirements for mediating r5/r6 and dorsal roof plate expression. Therefore, the restriction of Hoxb3 to r5 and Hoxa3 to r5 and r6, together with expression patterns of Hoxb3 in other vertebrate species suggests that these regulatory elements have a common origin but have later diverged during vertebrate evolution.This work was funded in part by Core MRC Programme support and a EEC Biotechnology Network grant (#BIO2 CT-930060).Peer reviewe

Effects of the second virial coefficient on the adiabatic lapse rate of dry atmospheres

We study the effect of the second virial coefficient on the adiabatic lapse rate of a dry atmosphere. To this end, we compute the corresponding adiabatic curves, the internal energy, and the heat capacity, among other thermodynamic parameters. We apply these results to Earth, Mars, Venus, Titan, and the exoplanet G1 851d, considering three physically relevant virial coefficients in each case: the hard-sphere, van der Waals, and the square-well potential. These examples illustrate under which atmospheric conditions the effect of the second virial coefficient is relevant. Taking the latter into account yields corrections towards the experimental values of the lapse rates of Venus and Titan in some instances.Comment: 12 pages, 8 figures. Comments are welcom

Pensamiento diagramático y narratividad.

Existe una larga trayectoria en la relación entre matemáticas y narrativa; en este trabajo se muestran los modos específi cos en que se vinculan pese a lo disímiles que, en apariencia, pueden llegar a ser. A partir de un modelo semántico se construye un esquema de análisis narrativo de carácter diagramático y articulación relacional, que considera y se apoya en la noción de ‘Visibilidad’ como dimensión semiótica

Hacia una interpretación semiótica de los signos matemáticos.

El análisis de las propiedades geométricas de las configuraciones finitas ha sido uno de los objetivos fundamentales del estudio de las diversas geometrías discretas y de la geometría combinatoria. Este artículo propone plantear la posibilidad de una elucidación de lo matemático desde una perspectiva derivada de las ‘matemáticas en acción’ y no desde una concepción ‘analítico gramatical’ de sus fundamentos, y establecer, al menos, un mínimo umbral de validez, que articule una interpretación semiótica de los signos matemáticos, a través del análisis de un par de ejemplos elementales de geometría configuracional, cuyas construcciones son propuestas por el autor

Teoría semántica y matemáticas.

A partir de la conformación de un modelo semántico fundado por la relación de presuposición se construye un entramado algebraico de carácter diagramático y articulación reticular, que considera y se apoya en la noción de orden como dimensión semiótica. Esta articulación relacional se realiza al abarcar diversos niveles de análisis, que van desde un nivel grafémico a un nivel discursivo. Se destacan de modo significativo los procesos complejos de composicionalidad semántica (asociados a modalidades de síntesis) en contraposición con procesos elementales de aditividad (asociados a sumas analíticas). Asimismo, a lo largo del análisis, quedarán establecidos los elementos configuracionales para la articulación reticular de los sucesos pertenecientes a un relato, formando unidades discursivas complejas a través de esquemas narrativos

Biomechanics of the Cornea Assessed by the CorVis ST ® Device: a Numerical Approach

To evaluate by means of finite element modeling the influence of tissue properties of the cornea on its deformation response when an air jet is applied onto its surface and, according to this, to discuss the clinical interpretation of these measurements in terms of corneal biomechanical behaviour

A survey of Mycoplasma agalactiae in dairy sheep farms in Spain

BACKGROUND: Contagious Agalactia (CA) is one of the major animal health problems in small ruminants because of its economic significance. Currently, four Mycoplasma spp. have been associated with this syndrome: M. agalactiae, M. mycoides subsp. capri, M. capricolum subsp. capricolum and M. putrefaciens. Their presence has been evaluated in several studies conducted in CA-endemic countries. However, previous Spanish studies have been focused on caprine CA, and there is a knowledge gap regarding which Mycoplasma species are present in sheep flocks from Spain, which has the second highest number of sheep amongst the 27 European Union member states. Consequently, we investigated the presence and geographic distribution of the four CA-causing mycoplasmas in Spanish dairy sheep farms. This is the first time such an investigation has been performed. RESULTS: Three hundred thirty nine out of 922 sheep flocks were positive for M. agalactiae by real time PCR (36.8%) and 85 by microbiological identification (9.2%). Interestingly, all 597 milk samples assessed for the presence of M. mycoides subsp. capri, M. capricolum subsp. capricolum and M. putrefaciens tested negative. To evaluate the intermittent excretion of the pathogen in milk, we sampled 391 additional farms from 2 to 5 times, resulting that in 26.3% of the cases a previously positive farm tested negative in a later sampling. CONCLUSIONS: M. agalactiae was the only Mycoplasma species detected in the study area showing a high frequency of presence and wide distribution. Therefore, the establishment of a permanent surveillance network is advantageous, as well as the implementation of control and prevention measures to hinder the dissemination of M. agalactiae and to prevent the entrance of other Mycoplasma species

Tu Dispensario : trabajo de emprendimiento

Tu Dispensario es una plataforma de comercio web, la cual tiene como objeto ser un market place de insumos y dispositivos médicos en la ciudad de Bogotá, ofreciendo a los vendedores un espacio en donde ofrezcan cada uno de sus productos, y a los consumidores una plataforma donde puedan comprar los insumos y dispositivos médicos. El proyecto nace de la iniciativa de una empresa familiar Colombiana, dedicada a la producción y comercialización de insumos y dispositivos médicos. Lo que buscamos es crear una plataforma donde se puedan realizar transacciones de comercio web, en la cual se unan los vendedores y lleguen los compradores o consumidores a comprar los productos pautados. Ofrecemos un nuevo canal de distribución para este sector, donde nos basamos en la premisa del mejor servicio al cliente, basados en asesoría técnica en el momento de la compra, el mejor servicio post venta por parte de los pautadores, y la entrega en menos de ocho horas hábiles para cada compra. A su vez ofrecemos buscamos que los pautadores tengan precios competitivos de sus productos, la mejor calidad y el producto disponible para los consumidores. Tu Dispensario será constituido como una sociedad de acciones simplificadas, con sede principal en la ciudad de Bogotá, e iniciara actividades en el año dos mil diecisiete. Tu Dispensario se encuentra actualmente en una etapa de validación de la propuesta de negocio, en este momento se realizan ventas mediante redes sociales y nuevos clientes referidos. Estamos buscando nuevos pautadores que amplíen el portafolio de productos ofertados, a su vez el diseño de la plataforma se está realizando para poder iniciar actividades formalmente el mes de agosto de dos mil diecisiete. El valor agregado que ofrece Tu Dispensario es la creación de un nuevo canal de comunicación entre los vendedores y profesionales del sector de las ciencias de la salud. Donde en el año dos mil veinte con consolidemos como una de las principales plataformas de ecommerce en Bogotá.Tu Dispensario is an ecommerce platform, which aims to be a market place for medical devices in the city of Bogota, offering to sellers a space where they offer each of their products, and to consumers a platform where can buy the medical devices. The project was born from the initiative of a Colombian family company, which produce and sell medical devices. What we are looking for is to create a platform, where you can carry out transactions of web commerce, in which the sellers join and the buyers or consumers arrive to buy the products. We offer a new distribution channel for this sector, where we are based on the premise of the best customer service, based on technical advice at the time of purchase, the best after sales service by the leaders, and delivery in less than eight hours for each purchase. In turn we offer that we look for that the leaders have competitive prices of their products, the best quality and the product available to the consumers. Tu Dispensario will be constituted through Sociedad por acciones simplificadas, with headquarters in the city of Bogotá, and will begin activities in the year two thousand and seventeen. Tu Dispensario is currently in a stage of validation of the business proposal, at this time sales are made through social networks and new customers referred. We are looking for new leaders that expand the portfolio of products offered; in turn the design of the platform is being done to start activities formally in the month of August two thousand and seventeen. The added value offered by Tu Dispensario is the creation of a new channel of communication between the sellers and the professionals of the health care sector. In the year two thousand and twenty we consolidate as one of the main ecommerce platforms in Bogota