Influence of impurities in polygonization of fcc metals of low stacking fault energy

Several studies performed on metal polygonization [1-3] indicate that impurities lock the dislocations and prevent their motion during a thermal treatment of previously deformed crystals. Nevertheless, the study made on polygonization of Cu showed contradictory results. Young [4, 5] and Wei et al. [6] observed polygonization in OFHC Cu, but not in 99.999% Cu, and pointed out that polygonization in Cu is very slow and occurs upon prolonged annealing at temperatures near the melting point. Seeger and Schoeck [7, 8] suggested that, in metals of low stacking fault energy like Cu, Ag and Au, the dislocations would be extended into widely separated partials, and thus climbing would be difficult. The fact that polygonization has been observed [4, 5] in OFHC Cu, but not in 99.999% Cu, was explained by considering that impurities tend to allow the partial dislocations to recombine. More recently, French workers [9 - 13], showed that pure Cu polygonizes more easily than impure. In order to clarify the effect of impurities in climbing of the extended dislocations in fcc metals, and to find the effect of the stacking fault energy, the present study was carried out in Cu and Ag crystals.Laboratorio de Investigaciones de Metalurgia Físic

Influence of impurities in polygonization of fcc metals of low stacking fault energy

Several studies performed on metal polygonization [1-3] indicate that impurities lock the dislocations and prevent their motion during a thermal treatment of previously deformed crystals. Nevertheless, the study made on polygonization of Cu showed contradictory results. Young [4, 5] and Wei et al. [6] observed polygonization in OFHC Cu, but not in 99.999% Cu, and pointed out that polygonization in Cu is very slow and occurs upon prolonged annealing at temperatures near the melting point. Seeger and Schoeck [7, 8] suggested that, in metals of low stacking fault energy like Cu, Ag and Au, the dislocations would be extended into widely separated partials, and thus climbing would be difficult. The fact that polygonization has been observed [4, 5] in OFHC Cu, but not in 99.999% Cu, was explained by considering that impurities tend to allow the partial dislocations to recombine. More recently, French workers [9 - 13], showed that pure Cu polygonizes more easily than impure. In order to clarify the effect of impurities in climbing of the extended dislocations in fcc metals, and to find the effect of the stacking fault energy, the present study was carried out in Cu and Ag crystals.Laboratorio de Investigaciones de Metalurgia Físic

Seudomicetoma dermatofítico en un gato persa : aspectos clínicos, patológicos y evolutivos

En este trabajo presentamos los aspectos clínicos, anatomopatológicos y evolutivos de un caso de dermatitis piogranulomatosa múltiple causada por hongos del género Microsporum, también conocida como seudomicetoma dermatofítico, en un gato persa, no castrado, de un año de edad al comienzo de la enfermedad. Las lesiones se caracterizaron macroscópicamente por la formación de numerosos nódulos de diferentes tamaños, localizados en la cabeza y antebrazo derecho, extendiéndose posteriormente a zona dorso lateral del tronco. La evolución de estos nódulos, que se generalizaron en algo menos de un mes, era hacia la coalescencia y fistulización, con descarga de un material grumoso blanco-grisáceo. El estudio histopatológico reveló una dermatitis piogranulomatosa, supeficial y profunda, caracterizada por presentar en el centro de los granulomas agregados de hongos septados inmersos en una matriz acidófila. La extirpación quirúrgica de un gran número de nódulos proporcionó mejorías transitorias, aunque reaparecieron nuevas lesiones. En este trabajo se describe la evolución tras dos años de seguimiento clínico. Tras el tratamiento con griseofulvina no se detectan nuevas lesiones después de 6 meses de su aplicación y seguimiento.This paper reports the clinical and histopathological features of a case of pyogranulomatous dermatitis caused by Microsporum fungi, a condition also known as dermatophyte pseudomycetoma, in a eneyear-old Persian cat. Grossly apparent fistulized nodules of varying sizes displaying a granular discharge were localized on the head, back, elbow and tail. Microscopic analysis revealed a deep piogranulomatous dermatitis characterized by centrally-located clusters of fungi within an acidophilic matrix. In just under a month, nodules had beco me generalized. Partial surgical excision and non-specific treatment provided temporary improvement, but new lesions subsequentlyappeared

Maximum entropy niche-based modelling of seasonal changes in little bustard (Tetrax tetrax) distribution

P. 17-29The effects of habitat fragmentation on species may change seasonally mainly due to variations in resource availability and biotic interactions. In critical periods, such as winter, when the importance of intraspecific competition diminish, species may relax their environmental requirements widening their ecological niche to exploit the scarcer trophic resources more efficiently in comparison with spring. Those variations in niche width may implicate seasonal expansions/retractions in species distribution. In this sense, an integrated knowledge on the spatial arrangement of breeding and wintering suitable patches is essential to infer seasonal movements (migratory connectivity). This paper shows that little bustard environmental preferences were more predictable and complex (controlled by a larger number of environmental factors) in spring than in winter, when potential distribution and ecological niche width were slightly larger. In spring, habitat variables (i.e. percentage of dry crops and pasturelands and altitude) ruled species’ distribution; while, winter pattern was driven by mixed criteria, based on both habitat and climate (i.e. percentage of dry crops and wastelands and winter rainfall). Suitable patches were more connected across spatial scales in winter than in spring, i.e. landscape was perceived as less fragmented. The overlap between potential breeding and wintering distribution areas was high. In fact, most of the predicted wintering areas coincided or showed high connectedness with predicted breeding patches. Conversely, there were significant breeding patches that were predicted with low suitability, showing little connectedness with potential winter areas. Spring habitat was a better predictor of little bustard’s wintering range than vice versa, which has clear management implications (preserving breeding sites closer to wintering areas ensures the conservation of a larger proportion of the total distribution range). This is an example of how predictive large-scale modeling procedures can contribute to the optimization of land management aimed at species conservation.S

New data (U–Pb, K–Ar) on the geochronology of the alkaline-carbonatitic association of Fuerteventura, Canary Islands, Spain

Zircons from a nepheline-syenite of the Fuerteventura Basal Complex were dated by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). The age obtained from a total of 21 U–Th–Pb analyses is 25.4F0.3 Ma (2r) indicating a late Oligocene–early Miocene crystallization. This age is consistent with new K–Ar ages on nepheline-syenites and pyroxenites, and contradicts previously published 39Ar–40Ar (feldspar) ages that were interpreted to represent a late Cretaceous–early Paleocene, pyroxenitic–syenitic magmatic episode. These new geochronological data are consistent with both field observations and most of the previously published ages on alkaline silicate rocks and associated carbonatites of Fuerteventura. Therefore, they strongly support the existence of a single, late Oligocene–early Miocene event of alkaline–carbonatitic magmatism in the Basal Complex of Fuerteventura, taking place at approximately 25 Ma and comprising: alkaline-pyroxenites, melteigites-ijolites, nepheline-syenites and carbonatites, as well as their volcanic equivalents and associated dykes. These new data provide an estimate for the length of time that it took the island to grow, thus eliminating one of the major problems in explaining its development by a hot-spot model

The partially alternating ternary sum in an associative dialgebra

The alternating ternary sum in an associative algebra, $abc - acb - bac + bca + cab - cba$, gives rise to the partially alternating ternary sum in an associative dialgebra with products $\dashv$ and $\vdash$ by making the argument $a$ the center of each term: $a \dashv b \dashv c - a \dashv c \dashv b - b \vdash a \dashv c + c \vdash a \dashv b + b \vdash c \vdash a - c \vdash b \vdash a$. We use computer algebra to determine the polynomial identities in degree $\le 9$ satisfied by this new trilinear operation. In degrees 3 and 5 we obtain $[a,b,c] + [a,c,b] \equiv 0$ and $[a,[b,c,d],e] + [a,[c,b,d],e] \equiv 0$; these identities define a new variety of partially alternating ternary algebras. We show that there is a 49-dimensional space of multilinear identities in degree 7, and we find equivalent nonlinear identities. We use the representation theory of the symmetric group to show that there are no new identities in degree 9.Comment: 14 page

Sulfonated poly(ether ether sulfones) Characterization and study of dielectrical properties by impedance spectroscopy

Abstract In this work, three samples of sulfonated polysulfones of different sulfonation degree have been characterized, and the electrical properties of dense membranes based on them have been evaluated. The polymers were characterized spectroscopically, and by their inherent viscosity, and water absorption. Electrical characterization of membranes was carried out on dense membranes in contact with NaCl solutions, by impedance spectroscopy (IS) measurements using equivalent circuits as models. The results showed how the sulfonation clearly affected the membrane electrical characteristics, strongly reducing the membrane resistance, and also changing the type of circuit associated to the membrane, which could be related to the increase of electrolyte taken by the membrane when the sulfonation degree increased. Concentration dependence of the electrical parameters was also studied

Synthesis Of Ag@silica Nanoparticles By Assisted Laser Ablation.

This paper reports the synthesis of silver nanoparticles coated with porous silica (Ag@Silica NPs) using an assisted laser ablation method. This method is a chemical synthesis where one of the reagents (the reducer agent) is introduced in nanometer form by laser ablation of a solid target submerged in an aqueous solution. In a first step, a silicon wafer immersed in water solution was laser ablated for several minutes. Subsequently, an AgNO3 aliquot was added to the aqueous solution. The redox reaction between the silver ions and ablation products leads to a colloidal suspension of core-shell Ag@Silica NPs. The influence of the laser pulse energy, laser wavelength, ablation time, and Ag(+) concentration on the size and optical properties of the Ag@Silica NPs was investigated. Furthermore, the colloidal suspensions were studied by UV-VIS-NIR spectroscopy, X-Ray diffraction, and high-resolution transmission electron microscopy (HRTEM).1039

Fattening Commercial Zebu with Grazing and Low Supplementation on Small Farms.

The aim of this paper was to describe and group grazing commercial Zebu bulls, with low supplementation. Forty-four beef-producing farms from several cooperatives of credits and services were studied. Their members are private farmers from Sibanicu, Camaguey, Cuba. The farms were visited for three years,  and official records were made of each farmer for these variables: resources, animals, management, production, and economy. The main statigraph for the variables were calculated. The  average  initial weight, final weight, weight gain, and production per ha were, 202.6; 371.6; 501; and 326.2 kg, during 339.7 fattening days, respectively. The principal component  analysis (PCA) showed  a Kaiser-Meyer-Olkin coefficient higher than 0.66, and a significant Bartlett  sphericity  coefficient (P < 0.01), with self-values above 1. The two groups were made using a BIETAPIC cluster analysis