On the microstructure, growth pattern and original porosity of belemnite rostra: insights from calcitic Jurassic belemnites

[EN] Calcitic belemnite rostra are usually employed to perform paleoenvironmental studies based on geochemical data. However, several questions, such as their original porosity and microstructure, remain open, despite they are essential to make accurate interpretations based on geochemical analyses. This paper revisits and enlightens some of these questions. Petrographic data demonstrate that calcite crystals of the rostrum solidum of belemnites grow from spherulites that successively develop along the apical line, resulting in a “regular spherulithic prismatic” microstructure. Radially arranged calcite crystals emerge and diverge from the spherulites: towards the apex, crystals grow until a new spherulite is formed; towards the external walls of the rostrum, the crystals become progressively bigger and prismatic. Adjacent crystals slightly vary in their c-axis orientation, resulting in undulose extinction. Concentric growth layering develops at different scales and is superimposed and traversed by a radial pattern, which results in the micro-fibrous texture that is observed in the calcite crystals in the rostra. Petrographic data demonstrate that single calcite crystals in the rostra have a composite nature, which strongly suggests that the belemnite rostra were originally porous. Single crystals consistently comprise two distinct zones or sectors in optical continuity: 1) the inner zone is fluorescent, has relatively low optical relief under transmitted light (TL) microscopy, a dark-grey color under backscatter electron microscopy (BSEM), a commonly triangular shape, a “patchy” appearance and relatively high Mg and Na contents; 2) the outer sector is non-fluorescent, has relatively high optical relief under TL, a light-grey color under BSEM and low Mg and Na contents. The inner and fluorescent sectors are interpreted to have formed first as a product of biologically controlled mineralization during belemnite skeletal growth and the non-fluorescent outer sectors as overgrowths of the former, filling the intra- and inter-crystalline porosity. This question has important implications for making paleoenvironmental and/or paleoclimatic interpretations based on geochemical analyses of belemnite rostra. Finally, the petrographic features of composite calcite crystals in the rostra also suggest the non-classical crystallization of belemnite rostra, as previously suggested by other authors.[ES] Los análisis geoquímicos obtenidos en rostros de los belemnites se utilizan habitualmente para llevar a cabo estudios paleoambientales. Sin embargo, hay cuestiones esenciales, como la porosidad y la microestructura original de los belemnites, que están todavía en discusión y que hay que tener en cuenta si se quieren realizar interpretaciones geoquímicas adecuadas. Los datos petrográficos obtenidos en este trabajo demuestran que los cristales de calcita del rostrum solidum de los belemnites crecen a partir de esferulitos que sucesivamente se desarrollan a lo largo de la línea apical, dando lugar a una microestructura “esferulítica prismática regular”. Los cristales de calcita surgen y divergen radialmente desde los esferulitos: hacia el apex, hasta que se forma un nuevo esferulito y hacia los bordes externos del rostro donde los cristales se van haciendo progresivamente mayores y prismáticos. La ligera variación de la orientación del eje-c de los cristales adyacentes explica la extinción ondulante. Al patrón radial, que da lugar a la textura micro-fibrosa de southlos cristales de calcita del rostro, se le superpone un bandeado de crecimiento concéntrico. Los datos petrográficos también indican que los rostros de los belemnites eran originalmente porosos como lo demuestra la naturaleza compuesta de los cristales de calcita que están formados sistemáticamente por dos zonas distintas que están en continuidad óptica: 1) la zona interna es fluorescente, tiene relieve óptico bajo, en microscopia de luz transmitida (TL), color gris oscuro en microscopia electrónica con electrones retrodispersados (BSEM), morfología triangular y contenidos en Mg y Na relativamente altos; 2) la zona exterior no es fluorescente, tiene relieve óptico alto (TL), color gris claro (BSEM), y contenidos en Mg y Na relativamente bajos. La zona fluorescente interior se formó primero, durante el crecimiento de los belemnites y la zona no fluorescente precipitó como un cemento rellenando la porosidad intra- e intercristalina. Las características petrográficas de los cristales de calcita también sugieren que la cristalización no clásica del esqueleto de los belemnites, como han sugerido algunos autores previamente.This research was carried out with the financial support of the projects CGL2011-22709, CGL2014-52670-P and RYC- 2009-04316 (Ramón y Cajal Program, Ministerio de Ciencia e Innovación), and by the “Sedimentary Basin Analysis” and “Paleoclimatology and Global Change” research groups of the Complutense University of Madrid.Peer reviewe

A Linguistic Recommender System For University Digital Libraries To Help Users In Their Research Resources Accesses

The Web is one of the most important information media and it is influencing in the development of other media, as for example, newspapers, journals, books, libraries, etc. Moreover, in recent days people want to communicate and collaborate. So, libraries must develop services for connecting people together in information environments. Then, the library staff needs automatic techniques to facilitate that a great number of users can access to a great number of resources. Recommender systems are tools whose objective is to evaluate and filter the great amount of information available on the Web. We present a model of a fuzzy linguistic recommender system to help University Digital Library users in their research resources accesses. This system recommends researchers specialized and complementary resources in order to discover collaboration possibilities to form multi-disciplinaryy groups. In this way, this system increases social collaboration possibilities in a university framework and contributes to improve the services provided by a University Digital Library

Análisis de la web semántica: estado actual y requisitos futuros

The vast and growing number of web resources show that lexical-statistical aids by themselves cannot resolve the problem of information retrieval. The "semantic web" project tries to solve these problems (and to do much more) by having the computers comprehend the content of the resources. This paper examines the current status of the required 'la-yers' put forward by Berners-Lee for the development of the Semantic web: namely, the uniform identification layer, the representation layer, the logical layer, and the security layer

Smoke and fire dynamics in atria and large enclosures: An overview

The proliferation of atria within modern large buildings is relatively recent. An atrium can be defined as a large open space connecting two or more storeys. Atria are important architectonical features since the 60's and can be found, among others, in shopping centres, office buildings and high-rise buildings, airports, stations and sports centres. However, the atrium represents an innovative, complex and non conventional architectonical element that can lead to fire environments diverging significantly from those in conventional compartments used in the development of current codes and standards. They are a source of discussion in the fire safety community because smoke can easily spread from one floor to another making the traditional methodologies for compartmentation of little or null effect. The design of smoke management in atria has been based on prescriptive codes since the 70's. It was not until the mid 80's that the phenomena started to be the objective of both experimental and numerical studies. It is because of the subsequent improved understanding on fire dynamics and smoke management together with the increased computing power available nowadays, that there is a progressive movement from prescriptive-based to performance-based codes which is also chaning the way atria are designed. The aim of the present work is to provide a broad overview of the current state-of-the-art of fires in atria. A brief introduction to the characteristics and types of atrium structures is presented first. Then, a description of the fire dynamics as well as the main safety problems that arise in case of fire are considered. A historical discussion of the research, including experimental and numerical studies, is presented, and current design methodologies and fire safety strategies are discussed. The final part of the overview addresses the international tendencies towards the introduction of performance-based fire protection codes. This overview highlights the need for further experimental studies and validations of numerical simulations for a wider range of fire conditions. © 2010 by Nova Science Publishers, Inc. All rights reserved

A review on the application of evolutionary computation to information retrieval

In this contribution, different proposals found in the specialized literature for the application of evolutionary computation to the field of information retrieval will be reviewed. To do so, different kinds of IR problems that have been solved by evolutionary algorithms are analyzed. Some of the specific existing approaches will be specifically described for some of these problems and the obtained results will be critically evaluated in order to give a clear view of the topic to the reader.CICYT under project TIC2002-03276University of Granada under project ‘‘Mejora de Metaheur ısticas mediante Hibridaci on y sus Aplicaciones

Analysing discussions in social networks using group decision making methods and sentiment analysis

Social networks are one of the most preferred environments for people to carry out debates. Due to the fact that a high amount of people can participate in the process, there is a need of tools that can analyse these discussions and extract useful information from them. In this paper, a novel way of determining how the debate is going on, if there is consensus among the participants and which alternatives are preferred is presented. Sentiment analysis is used in order to measure the level of preference that social media users have about a certain set of alternatives. In order to test the presented scheme, a real application example that makes use of Twitter information is presentedThis paper has been developed with the financing of FEDER funds in the project TIN2016-75850-

Analysis of mutations in streptomycin-resistant strains reveals a simple and reliable genetic marker for identification of the Mycobacterium tuberculosis Beijing genotype

The Mycobacterium tuberculosis pandemic is a major health problem, further complicated by an increasing incidence of drug-resistant isolates and the existence of highly transmissible strains, such as those in the Beijing family. Streptomycin (STR)-resistant M. tuberculosis clinical isolates have been analyzed to look for mutations in the rpsL, rrs, and gidB genes. In addition, the Rv1258c gene, which encodes Tap, an efflux pump that transports STR, has been sequenced. Mutations affecting codons 43 and 88 of the rpsL gene were found in 44.4% of the strains, and 16.7% of the strains carried mutations in the rrs gene, both of which probably contribute to STR resistance. Many strains presented with mutations in the gidB gene, but the implication of those mutations in STR resistance remains unclear. Interestingly, a cytosine nucleotide insertion between positions 580 and 581 (denominated Tap580) in the Rv1258c gene has been found in all Beijing isolates included in this study, suggesting that it might be a novel polymorphism specific to the Beijing family of M. tuberculosis. A simple and fast restriction fragment length polymorphism (RFLP)-PCR method for detecting the Tap580 insertion has been developed and used to screen a collection of 220 DNA samples obtained from cultures of M. tuberculosis isolates and 30 respiratory specimens. In all cases, the Beijing and non-Beijing representative samples were identified correctly. Tap580 is a novel polymorphism specific to the highly transmissible Beijing family, which allows for fast detection of these strains even at the very early stages of infection

Chiral Crystal Growth under Grinding

To study the establishment of homochirality observed in the crystal growth experiment of chiral molecules from a solution under grinding, we extend the lattice gas model of crystal growth as follows. A lattice site can be occupied by a chiral molecule in R or S form, or can be empty. Molecules form homoclusters by nearest neighbor bonds. They change their chirality if they are isolated monomers in the solution. Grinding is incorporated by cutting and shafling the system randomly. It is shown that Ostwald ripening without grinding is extremely slow to select chirality, if possible. Grinding alone also cannot achieve chirality selection. For the accomplishment of homochirality, we need an enhanced chirality change on crystalline surface. With this "autocatalytic effect" and the recycling of monomers due to rinding, an exponential increase of crystal enantiomeric excess to homochiral state is realized.Comment: 10 pages, 5 figure

Análisis de la web semántica: estado actual y requisitos futuros

The vast and growing number of web resources show that lexical-statistical aids by themselves cannot resolve the problem of information retrieval. The "semantic web" project tries to solve these problems (and to do much more) by having the computers comprehend the content of the resources. This paper examines the current status of the required 'la-yers' put forward by Berners-Lee for the development of the Semantic web: namely, the uniform identification layer, the representation layer, the logical layer, and the security layer

Heavy ion beam measurement of the hydration of cementitious materials

The setting and development of strength of Portland cement concrete depends upon the reaction of water with various phases in the Portland cement. Nuclear resonance reaction analysis (NRRA) involving the 1H(15N,α,γ)12C reaction has been applied to measure the hydrogen depth profile in the few 100 nm thick surface layer that controls the early stage of the reaction. Specific topics that have been investigated include the reactivity of individual cementitious phases and the effects of accelerators and retarders