How does aromaticity rule the thermodynamic stability of hydroporphyrins?

Several measures of aromaticity including energetic, magnetic, and electron density criteria are employed to show how aromatic stabilization can explain the stability sequence of hydroporphyrins, ranging from porphin to octahydroporphin, and their preferred hydrogenation paths. The methods employed involve topological resonance energies and their circuit energy effects, bond resonance energies, multicenter delocalization indices, ring current maps, magnetic susceptibilities, and nuclear-independent chemical shifts. To compare the information obtained by the different methods, the results have been put in the same scale by using recently proposed approaches. It is found that all of them provide essentially the same information and lead to similar conclusions. Also, hydrogenation energies along different hydrogenation paths connecting porphin with octahydroporphin have been calculated with density functional theory. It is shown by using the methods mentioned above that the relative stability of different hydroporphyrin isomers and the observed inaccessibility of octahydroporphin both synthetically and in nature can be perfectly rationalized in terms of aromaticity

Arenitic deposits of Mesones Unity (Lower Cambrian) in the Eastern Iberian Chain Petrographical analysis and material provenance

[Resumen] El Cámbrico inferior de la Unidad de Mesones, de características esencialmente detríticas, reúne unas especiales condiciones para su estudio petrográfico. A través de él se puede concluir que la Fm. Bámbola tiene una composici6n promedio de grauwacas cuárclcas, depositadas en un medio poco profundo de elevada energía; los depósitos de que la Fm. Embid, con una composici6n grauwáquico feldespática, corresponden a un medio de depósito más distal; por último, los materiales de la Fm. Jal6n, con depósitos detríticos de composición grauwáquico feldespática que alternan con niveles estromatolíticos de dolomías férricas, representan el depósito en un medio más somero pero de reducida energía. La secuencia diagenética de transformación de los depósitos primarios sigue una pauta similar en las tres formaciones: una cementaci6n temprana de cuarzo sintaxial asociada a formación de películas arcillosas y ferruginosas, se prosigue con una cementaci6n posterior de carbonatos, cementos silíceos y rellenos de matriz. Los procesos diagenéticos tardíos comprenden fenómenos de recristalización y autigénesis de micas (cloritas en los tramos superiores), autigénesis de piritas (especialmente en las Formaciones Embid yJalón) y fenómenos de silicificación, generalmente asociados a fenómenos tectónicos. Muy puntualmente se aprecian autigénesis de feldespatos y turmalinas. La aplicaci6n del análisis modal de componentes primarios, según las ideas de DICKINSON (1985), permite clasificar el área fuente de estos materiales como de cratón estable, correspondiente a una plataforma pasiva con oscilaciones eustáticas[Abstract] Lower Cambrian materials of Mesones Unity, mainly of detrital characters, show suitable conditions for its petrographical analysis. This study indicates that Bambola Formation presents average composition of quartzitic graywackes, related to shallow, high-energy environment; Embid Formation materials, constituted by detrital deposits of feldespatic-graywakic composition alternating with stromatolitic ferroan-dolomitic levels, are related to shallow, low-energy environment. Diagenetic transformations of primary deposits show similar trends in the three formations. Early sintaxial quartz overgrowths, associated to pelicular argillitic- ferruginous cements, are followed by carbonatic, silicic, cementation processes and matrix infilling. Later diagenetic stages are represented by recristallization, mica (of chloritic type in the upper sections) or pyrite authigenesis (mainly in Embid and jalón Formations) and silicification phenomena (related to tectonic activity). Feldspar and tourmaline authigenesis are locally observed. Primary components modal analysis following DICKINSON (1985) concepts, allow to classify the source area of these materials as belonging to a stable craton zone constituted by a passive platform with eustatic oscillations

Extracciones quimicas secuenciales de metales pesados. Aplicacion en ciencias geologicas

Sequential chemical extraction methodologies are applied in Geological Sciences with the objective of determining the solid speciation for trace metals present in soil, sediment and rock samples. Such information is not available from a conventional chemica1 analysis. At the present time a wide variety of sequential protocols exists, but none of them has been imposed as an international standard method as yet. The fractions of solid material that these protocols usually allow to distinguish are the following: Exchangeable, carbonate, Fe-Mn oxide-hydroxide, organic, and residual. Different methods differ in the used reagents as well as in the experimental conditions, depending on the particular objectives. Sequential extraction methods are used in different fields of geological sciences, mainly in environmental geochemistry of aquatic systems (rivers, lakes, estuaries), edaphology and also in groundwater hydrology. In general, sequential extraction protocols involve important methodological problems which have been pointed out for severa1 authors. Among these problems are the following: Reagent selectivity, operative definition of methods, elemental redistribution (or readsorption), variable experimental conditions, scarcity of reference solid certificated materials, strong difficulty in order to validate the existing methods, and the evaluation of its precision. In spite of al1 methodological problems mentioned, at the present time sequential extraction protocols constitute the better approach in order to describe the geochemical association of trace elements with different fractions of solid materials.Las metodologías de extracción química secuencial se aplican en Geología con el objetivo de determinar la especiación de los metales traza en suelos, sedimentos o rocas, información que no se puede conseguir a partir únicamente de un análisis químico convencional sobre muestra total. En la actualidad existe una amplia variedad de protocolos de extracción secuencial diferentes, sin haberse impuesto todavía uno de ellos como un método estándar plenamente aceptado. Las fracciones de metales pesados que comúnmente se suelen diferenciar en los sólidos mediante este tipo de metodologías son: intercambiable, asociada a carbonatos, asociada a óxidos Fe y Mn, asociada a materia orgánica y fracción residual. Los distintos protocolos existentes difieren en los reactivos empleados y también en las condiciones experimentales, todo ello dependiendo de los objetivos concretos del estudio a realizar. Las extracciones secuenciales han encontrado unos campos de aplicación muy amplios en las ciencias geológicas, sobre todo en los estudios de geoquímica ambiental en medios acuáticos (ríos, lagos, estuarios), en edafología y también en hidrología subterránea. Los protocolos de extracción secuencial adolecen, en conjunto, de una serie de problemas metodológicos de cierta envergadura y que han sido abordados por distintos autores, pudiendo destacar entre ellos la selectividad de los reactivos empleados, la propia definición operativa de estos métodos, la redistribución (o readsorción) elemental, las condiciones experimentales bajo las que se pueden ejecutar los protocolos, la escasez de materiales sólidos de referencia y, derivados de este último problema, la dificultad de validación de los distintos métodos y la evaluación de su precisión. A pesar de todos estos inconvenientes metodológicos, los procedimientos de extracción secuencial constituyen en la actualidad la mejor aproximación para describir la asociación geoquímica de los elementos traza con las diferentes fracciones de los sólidos

Results from Bottom Trawl Survey on Flemish Cap of June-July 2018

A stratified random bottom trawl survey on Flemish Cap was carried out from June 26th to July 24th 2018. The area surveyed was extended up to depths of 800 fathoms (1460 meters) following the same procedures as in previous years and 181 fishing stations planned. The survey was carried out by the R/V Vizconde de Eza with the usual survey gear (Lofoten). A total of 181 valid hauls were made by the vessel R/V Vizconde de Eza, 120 up to 730 meters depth and 61 up to 1460 meters. Survey results including abundance indices of the main commercial species and age distributions for cod, redfish, American plaice, Greenland halibut, roughhead grenadier, squid and shrimp are presented. The general indexes for this year are estimated taken into account the traditional swept area (strata 1-19, up to depths of 730 m.) and the total area surveyed (strata 1-34, up to depths of 1460

Full benchmark review of the 3M cod assessment

Steps of the development and timetable for the 3M Cod benchmark to be carried out by April 2017Postprint0,000

Results from Bottom Trawl Survey on Flemish Cap of June-July 2017

A stratified random bottom trawl survey on Flemish Cap was carried out from June 16th to July 15th 2017. The area surveyed was extended up to depths of 800 fathoms (1460 meters) following the same procedures as in previous years and 181 fishing stations planned. The survey was carried out by the R/V Vizconde de Eza with the usual survey gear (Lofoten). A total of 181 valid hauls were made by the vessel R/V Vizconde de Eza, 120 up to 730 meters depth and 61 up to 1460 meters. Survey results including abundance indices of the main commercial species and age distributions for American plaice, Greenland halibut, roughhead grenadier and shrimp are presented. Cod and redfish age distributions are not available for 2017 due to administrative problems. The general indexes for this year are estimated taken into account the traditional swept area (strata 1-19, up to depths of 730 m.) and the total area surveyed (strata 1-34, up to depths of 1460 m.).Versión del editor

Depósitos silexíticos en el terciario continental de la Cuenca de Calatayud: Caracterización y génesis

The tertiary Calatayud Basin is a NW-SE elongated depression, extending from Calatayud (Zaragoza) to Montalbán (Teruel) and whose dimensions are approximately 130 km long and 20 km wide. This basin consists of two distinct sub-basins separated by the Daroca High (Calatayud Basin in the northern sector and Montalbán Basin in the sourthern sector). These Basins present a quite similar sedimentary evolution of the Neogene evaporitic and carbonatic lacustrine systems, that generally ocuppy central locations in both basins. Three main sedimentary units (Lower, Intermediate and Upper units) divided by two main sedimentary breaks are traditionally described in the Calatayud Basin. The lower and the Intermediate units have evaporitic sedimentation, whilst the Upper Unit is typically freshwater fluvio-lacustrine sedimentation. This work focuses on the study of carbonatic materials placed in the Cristo de Ribota hermitage area, which is localized in the Intermediate Unit of Calatayud Basin, to the Northern of Sierra de Armantes. The interest of this area lies in the presence of silexitic levels, whose thickness can be metric, exceptional in the geologic record and that it raises interesting troubles at the time of establishing a hypothesis on the possible origin of the silica that generates these sílex deposits, as well as in the establishment of a genetic model. The sílex levels in the Cristo de Ribota series appear mainly in carbonate rocks. Petrographic studies of the samples taken in this area show a replacement of silica by carbonate, as well as a silica cementation in karts cavities generated by epidiagenetic karts processes. These cavities acted as conduits for fluids saturated in silica which resulted in silex deposits. The fluids should necessarily have an episodic character and the fact that karstic cavities can be filled with silica or carbonate is an evidence of it. For the silica precipitation, not only the low temperature and a less than 9 pH are necessary, but also there must exist a lot of silica-supersatured water, as well as a high permeability. The source of silica deposits in this area is probably diagenetic, but also it would be necessary to consider a thermal origin corresponding to the contribution of silica by hydrothermal fluids

Dispersión de metales pesados en los suelos del término municipal de Zaragoza

Desde la década de los 80 existe una normativa medioambiental que asegura una buena práctica industrial, pero, las fábricas en los años anteriores vertían en su entorno los productos residuales fruto de su actividad, tal y como ocurría en la ciudad de Zaragoza.El crecimiento de Zaragoza supuso que las industrias situadas en las inmediaciones del centro de la ciudad se desplazasen hacia zonas más periféricas dejando un sustrato potencialmente contaminado en metales pesados, por ejemplo, arsénico, cadmio, cobalto, cromo, cobre, mercurio, molibdeno, plomo y zinc, cuyo riesgo para la salud y el medioambiente es ampliamente conocido.Este informe aporta información sobre aspectos relevantes como la concentración de metales pesados en los suelos de la ciudad, los factores que han podido influir en su dispersión o las causas de su origen.<br /

Brief Results of a Trawl Experimental Survey at NW Atlantic

An experimental survey was carried out in NAFO Regulatory Area (Div. 6EFGH and 4XWVs) and adjacent international Southern waters during last Quarter of year 2004, with one polyvalent Spanish trawler, using "Gloria" pelagic gear and bottom gear, with the aim to obtain data on distribution and biology on pelagic and demersal species in non-habitual grounds for the Spanish fleet. A scientific observer was on board to collect the information on fishing activity (effort, depth, etc.) and biological data (length distributions, length-weight relationships, etc.). A total of 119 hauls were carried out. Samplings were conducted in a wide geographical and bathymetrical range. During the survey, Alfonsino (Beryx splendens) was the main caught species

By-catch of cold-water corals from an Experimental Trawl Survey in three seamounts within NAFO Regulatory Area (Divs. 6EFG) during year 2004

By-catch of cold-water corals from a Trawl Experimental Survey developed during 2004 in three NAFO seamounts was examined. Three hauls were carried out over two peaks located in Divs. 6EF. In this area, catches of commercial resources were negligible and by-catch of corals was recorded (degraded pieces of dead Enallopsammia sp and Keratoisis sp and few alive corals like Solenosmilia variabilis, Metallogorgia melanotrichos, Paragorgia johnsoni, etc.), showing some interaction between fishing and vulnerable habitats and that trawl fishing in the area is unfeasible. Ninety-two hauls were carried out over one peak located in Div. 6G, with big catches of alfonsino (Beryx splendens), but only six hauls showing coral records (Enallopsamia rostrata, Solenosmilia variabilis, Madrepora oculata, Acanella eburnea and Placogorgia terceira) and in less quantities in comparison with Divs. 6EF. The low by-catch of corals in the Div. 6G peak could be related with their less rough bottom feature and with the previous alteration of sessile epifauna due to intense fishing activity developed during the last decades of XX Century. The results of the Experimental Survey indicate that the impact of trawling on seamounts could be important and that the closed area agreed in 2007 to protect the bottom habitats of the seamounts within NAFO Regulatory Area (Divs. 6EFG) should be maintained and improved