A review of ordering phenomena in iron-silicon steels

Silicon steel is an industrially-desired alloy of iron and silicon, characterised by soft magnetic properties, low eddy-current losses, and low magnetostriction. Silicon steels have narrow hysteresis cycles, making them particularly advantageous in applications using electromagnetic fields, such as transformers, generators, electric motor cores, and few other components in industry. Despite its incontestable industrial value, there is not much agreement on the atomic structure of silicon steel. Gaining better understanding of e.g. ordering processes in Fe-Si alloys could not only explain their magnetic properties, but also open opportunities to reduce their weaker characteristics, such as brittleness that adversely affects silicon steel workability and its associated high production costs. This review summarises the state-of-the-art knowledge about ordering in silicon steel and describes the most relevant experimental techniques used for studying its microstructure. In addition, the process of building the iron rich part of the Fe-Si phase diagram is explained. Lastly, the influence of order on the alloy's magnetic and mechanical properties is illustrated

Crystal-chemistry and short-range order of fluoro-edenite and fluoro-pargasite: a combined x-ray diffraction and ftir spectroscopic approach

In this study we address the crystal-chemistry of a set of five samples of F-rich amphiboles from the Franklin marble (USA), using a combination of microchemical (EMPA), SREF, and FTIR spectroscopy methods. The EMPA data show that three samples fall into the compositional field of fluoro-edenite whereas two samples are enriched in high-charged C cations, and must be classified as fluoro-pargasite. Mg is by far the dominant C cation, Ca is the dominant B cation (with BNa in the range 0.00-0.05 apfu, atoms per formula unit), and Na is the dominant A cation, with A0 (vacancy) in the range 0.07-0.21 apfu; WF is in the range 1.18-1.46 apfu. SREF data show that: TAl is completely ordered at the T(1) site; the M(1) site is occupied only by divalent cations (Mg and Fe2+); CAl is disordered between the M(2) and M(3) sites; ANa is ordered at the A(m) site, as expected in F-rich compositions. The FTIR spectra show a triplet of intense and sharp components at ~ 3690, 3675, and 3660 cm-1, which are assigned to the amphibole, and the systematic presence of two very broad absorptions at 3560 and 3430 cm-1. These latter are assigned, on the basis of polarized measurements and FPA imaging, to chlorite-type inclusions within the amphibole matrix. Up to eight components can be fitted to the spectra; band assignment based on previous literature on similar compositions shows that CAl is disordered over the M(2) and M(3) sites, thus supporting the SREF conclusions based on the bond distance analysis. The measured frequencies are typical of O-H groups pointing toward Si-O(7)-Al tetrahedral linkages, thus allowing to characterize the SRO (short-range-order) of TAl in the double chain. Accordingly, the spectra show that in the fluoroedenite/pargasite structure, the T cations, Si and Al, are ordered in such a way that Si- O(7)-Si linkages regularly alternate with Si-O(7)-Al linkages along the double chain.Comment: 38 pages, 10 figures - in press. Mineralogical Magazine, special issue for the international year of crystallography (2013) in pres

New Mineral Names

n/

Transect sampling of vegetation formations of phanerophytes and chamaephytes (I): methodological fundamentals

Se presenta un Método geobotánico cuantitativo de Inventario de formaciones vegetales homogéneas (Fanerófitos y Caméfitos) (método MIFC). La técnica utilizada es un inventario de vegetación (fanerófitos y caméfitos) en transectos lineales de 50x2 m, dando lugar a parcelas de 0,1 has, atributos y posición relativa de la vegetación a lo largo del transecto. El método considera como base analítica del estudio de la vegetación, 10 parcelas de muestreo. Los resultados proporcionan datos sobre la biodiversidad (Shannon, Simpson), factores mesológicos e índice de valor de importancia (IVI) ecológica. Finalmente el método MIFC desarrolla una representación gráfica estructural específica, consistente en el "Diagrama Ecodinámico de Riqueza-Estructura-Cobertura" (DEREC) para la vertical y en un "Diagrama de Burbujas" (DB) para la horizontal.Nous présentons ici une méthode géobotanique quantitative d'Inventaire de formations végétales homogènes (Phanérophytes et Chamaephytes) (méthode MIFC). La technique utilisée est un inventaire de la végétation (phanérophytes et chamaephytes) des transects linéaires de 50x2 m, donnant lieu à des parcelles de 0,1 ha, à des attributs et à une position relative de la végétation au long du dit transect. La méthode prende comme base d'analyse de l'étude de la végétation 10 parcelles d'échantillonnage. Les résultats fournissent des données sur la biodiversité (Shannon, Simpson), les facteurs mésologiques et l'Indice de Valeur d'Importance (IVI) écologique. Finalement, la méthode MIFC développe une représentation graphique structurelle spécifique consistant en un Diagramme Ecodynamique de Richesse-Structure-Couverture (DERSC) pour la verticale et en un Diagramme à bulles (DB) en horizontal

RR photons

Journal of High Energy Physics 2011.9 (2011): 110 reproduced by permission of Scuola Internazionale Superiore di Studi Avanzati (SISSA)Type II string compactifications to 4d generically contain massless Ramond-Ramond U(1) gauge symmetries. However there is no massless matter charged under these U(1)’s, which makes a priori difficult to measure any physical consequences of their existence. There is however a window of opportunity if these RR U(1)’s mix with the hypercharge U(1)Y (hence with the photon). In this paper we study in detail different avenues by which U(1)RR bosons may mix with D-brane U(1)’s. We concentrate on Type IIA orientifolds and their M-theory lift, and provide geometric criteria for the existence of such mixing, which may occur either via standard kinetic mixing or via the mass terms induced by Stückelberg couplings. The latter case is particularly interesting, and appears whenever D-branes wrap torsional p-cycles in the compactification manifold. We also show that in the presence of torsional cycles discrete gauge symmetries and Aharanov-Bohm strings and particles appear in the 4d effective action, and that type IIA Stückelberg couplings can be understood in terms of torsional (co)homology in M-theory. We provide examples of Type IIA Calabi-Yau orientifolds in which the required torsional cycles exist and kinetic mixing induced by mass mixing is present. We discuss some henomenological consequences of our findings. In particular, we find that mass mixing may induce corrections relevant for hypercharge gauge coupling unification in F-theory SU(5) GUT’

TRB, una metodología para el análisis cartográfico multiescalar de la distribución de formaciones vegetales

Se desarrolla un método analítico y cartográfico de distribución de biomasa y formaciones de plantas a nivel multiescalar basado en variables bioclimáticas extraídas del Balance hídrico de Thornthwaite (WB) y las Balanzas bioclimáticas (BB) de Montero de Burgos y González Rebollar. Como resultado, se obtiene un mapa de distribución que da lugar a los Tipos de Regímenes Bioclimáticos (TRB) y que conduce a la identificación de una clasificación multiescalar en diferentes niveles: zonal (macroescala) con 5 tipos, regional (mesoescala) con 27 tipos, y local (microescala) con 162 subtipos de formaciones vegetales condicionadas por suelos litológicos, la exposición al viento o insolación, y obtenida mediante la combinación de TBR y ombroclimas.An analytical and cartographic method of biomass distribution and plant formations at a multi-scalar level is developed based on bioclimatic variables extracted from the Thornthwaite Water Balance (WB) and the Bioclimatic Balances (BB) of Montero de Burgos & González Rebollar. As a result, a distribution map involving Types of Bioclimatic Regimens (TBR) is obtained leading to the identification of a multi-scale classification at different levels: zonal (macro-scale) with 5 types, regional (meso-scale) with 27 types, and local (micro-scale) with 162 plant formations subtypes, conditioned by lithology-soils, the relief exposure to wind or sunstroke respectively and obtained through the combination of TBR and ombroclimates

Electric and magnetic dipolar response of Germanium spheres: Interference effects, scattering anisotropy and optical forces

We address the scattering cross sections, and their consequences, for submicrometer Germanium spheres. It is shown that there is a wide window in the near infrared where light scattering by these particles is fully described by their induced electric and magnetic dipoles. In this way, we observe remarkable anisotropic scattering angular distributions, as well as zero forward or backward scattered intensities, which until recently was theoretically demonstrated only for hypothetically postulated magnetodielectric spheres. Also, interesting new effects of the optical forces exerted on these objects are now obtained.Comment: 13 pages, 4 figure

Biodisponibilidad mineral de menús escolares

La biodisponibilidad mineral se define como el porcentaje de mineral inicialmente presente en un alimento, comida ó dieta que es absorbido y utilizado para una función fisiológica correcta y está condicionada por diversos factores de tipo fisiológico y dietético. Teniendo en cuenta la enorme importancia del calcio, hierro, zinc y cobre en la nutrición infantil, así como el creciente consumo por parte de la población escolar española de comidas fuera del hogar, y en concreto en el comedor escolar, se han seleccionado diferentes platos habitualmente incluidos en el menú mensual de un comedor para la determinación de su biodisponibilidad mineral mediante diferentes técnicas in vitro. Los métodos in vitro utilizados consisten en someter la muestra a un proceso de digestión gastrointestinal en dos etapas en el que se reproducen las condiciones que tienen lugar en el aparato digestivo humano y posterior medida de la fracción de elemento soluble (solubilidad) ó que dializa a través de una membrana semipermeable con un determinado tamaño de poro (diálisis). La evaluación de la biodisponibilidad mineral en los platos analizados se completa con la incorporación de la línea celular Caco-2. Estas células procedentes de adenocarcinoma de colon humano tienen unas características morfológicas y funcionales similares a las de los enterocitos, siendo un módelo válido para estudios de permeabilidad intestinal. Junto a lo anterior se realiza también un estudio de especiación de las diferentes formas de hierro (hierro hemo, ferroso y férrico) en el sitio de absorción intestinal a fin de relacionar los resultados obtenidos con los de biodisponibilidad. Las tres técnicas in vitro (solubilidad, diálisis y Caco-2) son ampliamente utilizadas por su buena correlación con estudios in vivo y nos sirven para evaluar la calidad nutricional de los menús estudiado

Chromium-rich vanadio-oxy-dravite from the Tzarevskoye uranium–vanadium deposit, Karelia, Russia. A second world-occurrence of Al–Cr–V–oxy-tourmaline

A green tourmaline sample from the Tzarevskoye uranium–vanadium deposit, close to the Srednyaya Padma deposit, Lake Onega, Karelia Republic, Russia, has been found to be the second world-occurrence of Cr-rich vanadio-oxy-dravite in addition to the Pereval marble quarry, Sludyanka crystalline complex, Lake Baikal, Russia, type-locality. From the crystal-structure refinement and chemical analysis, the following empirical formula is proposed: X(Na0.96K0.02□0.02)Σ1.00 Y(V1.34Al0.68Mg0.93Cu2+0.02Zn0.01Ti0.01)Σ3.00 Z(Al3.19Cr1.36V0.03Mg1.42)Σ6.00(TSi6O18)(BBO3)3V(OH)3W[O0.60(OH)0.23F0.17]Σ1.00. Together with the data from the literature, a compositional overview of Al–V–Cr–Fe3+-tourmalines is provided by using [6]Al–V–Cr–Fe3+ diagrams for tourmaline classification. These diagrams further simplify the tourmaline nomenclature as they merge the chemical information over the octahedrally-coordinated sites (Y and Z) by removing the issues of uncertainty associated with cation order–disorder across Y and Z. Results show the direct identification of tourmalines by using the chemical data alone

Carbonatos Bio-Sedimentarios en el traverino y acueducto de Santa Lucía: litoral atlántico de Cádiz (Vejer, España)

Les carbonates d'origine biosédimentaire (tufs et travertins) joinent un rôle important dans l'évolution des paysages quaternainers. Dans ce travail, sont détaillés les caractères généraux et particuliers des algues cyanophycées dans les structures stromatolitiques du travertin Santa Lucía, situé au pied de la plateforme de calcarénite de Vejer, à proximité du littoral aignages paléoenvironnmentaux (fossiles, isotopes, facies) et des références géochronologiques. Ce dernier caractère, joint à la capacité de sceller diverses types de morphologies, y compris des ouvrages publics. Fontaines et aqueducs comme celui de Santa Lucía (Vejer de la Frontera) confére à ces dépôts une importante valeur comme indicateur environnemental