Evidence of spin disorder at the surface–core interface of oxygen passivated Fe nanoparticles

Hysteresis, thermal dependence of magnetization, and coercivity of oxide coated ultrafine Fe particles prepared by inert gas condensation and oxygen passivation have been studied in the 5–300 K range. The results are found to be consistent with a spin-glasslike state of the oxide layer inducing, through exchange interaction with the ferromagnetic core, a shift of the field cooled hysteresis loops at temperatures below the freezing at approximately 50 K.Dirección General de Investigación y Desarrollo. Gobierno de España-CICYT MAT95- 1042-C02-02Dirección General de Investigación y Desarrollo. Gobierno de España-PB96-0863-C02-02.Comisión Europea-ERBFMBI-CT95-0534

Maurolicus stehmanni Parin & Kobyliansky, 1993 (Sternoptychidae): length of first maturation, and spawning seasons in the south-southeast Brazilian region

Maurolicus stehmanni (Sternoptychidae) é um pequeno peixe mesopelágico que habita a plataforma continental e o talude da região entre Cabo de São Tomé (22 S) e Chuí (34 S). No Atlântico Oeste, apresenta biomassa de cerca de 1 ton e é um importante componente da dieta de peixes pelágicos e demersais com valor comercial. A partir de capturas realizadas com rede de meia água, em 1996 e 1997, dentro do programa (REVIZEE), exemplares provenientes de 38 lances de pesca foram analisados em relação à estrutura da população em comprimento e aos estágios de maturação macroscópica das gônadas, dados que, associados a dados biométricos, permitiram estimar o tamanho médio da 1ª maturação e épocas de desova da espécie. Foram realizados, ainda, cortes histológicos de ovários e testículos com vistas a aferir a avaliação macroscópica e analisar o desenvolvimento ovocitário da espécie. Os resultados indicam que o tamanho médio da 1ª maturação é de 32 mm de comprimento padrão, as fêmeas desovam o ano todo e que a desova ocorre ao longo de toda a borda da plataforma continental sudeste-sul do Brasil. O desenvolvimento ovocitário é assincrônico, mostrando que M. stehmanni apresenta desova parcelada.Maurolicus stehmanni (Sternoptychidae) is a mesopelagic species of fish inhabiting the outer continental shelf and slope of the south-southeastern Brazilian (ZEE), where it presents a considerable biomass and is an important component of the trophic chain, as a forage species. On the basis of catches made with a mid-water-trawl net in 1996 and 1997, as part of the REVIZEE program, samples from 38 hauls were analyzed as regards the length structure of the population, the average length of the first maturation and the spawning seasons of the species. The analysis of histological cross-sections of the ovaries made it possible to describe the oocytic development and assess the macroscopic criteria used to classify the ovary maturation. Results showed that the average length of the first maturation occurs at 32 mm (standard length), females spawn all year round throughout the area studied and the oocytic development is asynchronous

Estudo das variações da relação peso total/comprimento total em função do ciclo reprodutivo e comportamento, de Sardinella brasiliensis (Steindachner, 1879) da costa do Brasil entre 23ºS e 28ºS

This paper analyses some aspects on the length/weight relation ship of Sardinella brasiliensis and its variations as a function of their reproductive cycle and displacements along the Brazilian coast between 23ºS and 28ºS. The area surveyed was divided into five sub-areas, each one covering one degree of latitude. The relationship and its variations between shoals were studied for each sub-area at different seasons and for the sub-areas at the same season. The absence of a variation pattern for the length/weight relationship has shown to be the result of seasonal changes in the physiological aspects of fish (as a function of their reproductive cycle) as well as result of behaviour of individuals in two main areas: 23ºS-25ºS and 26ºS-28ºS, which are spawning areas, spawning occuring during spring and summer at the first and only during spring at the latter. After spawning the young (from both areas) more at different times to a common trophic area where they find suitable conditions (25ºS26ºS), returning to their original sub-areas at different occasions, following their first sexual maturation. Although spawning takes place at different times and sites, with the convergence of young to a common nursery, mixing might occur. Further studies on meristics and body proportions are being developed regarding the existence of different populations

Relações comprimento-peso da ictiofauna associada à sardinha-verdadeira, Sardinella brasiliensis, na Bacia do Sudeste do Brasil (22ºS‑29ºS) entre 2008 e 2010

In this study, estimates of length-weight relationships are presented for twenty-four species caught in association with the Brazilian sardine, Sardinella brasiliensis, during four acoustics surveys carried out under the Program ECOSAR (Prospecting and evaluation of biomass of the stock of Brazilian sardine on the southeast coast by acoustic methods), which was to evaluate the biomass of species that were caught. The model parameters were estimated with the nonlinear iterative method of least squares. The value of the coefficient of determination (r2) and residual analysis were employed to verify the appropriateness of fit. The coefficient b values were tested with respect to isometry (β=3) using a tα1,0.05 test. The values of coefficient b ranged from 2.377 to 3.538. There is a tendency for positive allometry (b) in the sampled ichythyocenose.No presente estudo são apresentadas as estimativas das relações comprimento-peso para vinte e quatro espécies capturadas em associação com a sardinha-verdadeira (Sardinella brasiliensis) durante quatro cruzeiros de prospecção hidroacústica realizados no âmbito do Programa ECOSAR (Prospecção e avaliação de biomassa do estoque de sardinha-verdadeira, na costa sudeste, por métodos hidroacústicos), cujo objetivo foi permitir a avaliação das biomassas das espécies capturadas. Para estimação dos parâmetros dos modelos foi empregado o método iterativo não linear de mínimos quadrados; o valor do coeficiente de determinação (r2) e a análise de resíduos foram empregados para verificar a adequação dos ajustes. Os valores dos coeficientes b foram testados em relação à isometria (β=3) através de teste tα1,0,05. O valor do coeficiente b variou entre 2,377 e 3,538, tendo sido constatada tendência de alometria positiva para o b na ictiocenose amostrada

Growth parameters estimates of Maurolicus stehmanni Parin & Kobyliansky 1996 (Teleostei, Sternoptichydae) from south and southeastern Brazilian waters

Este estudo, baseado na análise da microestrutura dos otólitos de Maurolicus stehmanni, apresenta estimativas dos parâmetros de crescimento e longevidade para esta espécie que habita a plataforma externa e o talude da ZEE sul-sudeste do Brasil. Estes parâmetros são importantes para o conhecimento da estratégia de vida da espécie e para o manejo deste recurso, que constitui um importante elo entre os componentes iniciais e finais da teia alimentar no ecossistema de mar aberto, sendo um dos principais itens na dieta das lulas e grandes peixes pelágicos. Dentre os vários métodos aplicados, os valores dos parâmetros de crescimento mais coerentes com a estratégia da espécie e que melhor se ajustaram à equação de von Bertallanfy foram: Li= 55mm K= 0.0088/dia e to= 5.5 dias. A espécie vive cerca de 220 dias e as marcas diárias nos otólitos sagita são apropriadas para a determinação da idade.This paper on the otolith microstructure analysis of Maurolicus stehmanni presents estimates of the species growth parameters and longevity. The species inhabits the outer shelf and slope of the southern and southeastern Brazilian Exclusive Economic Zone (EEZ). Growth parameters are important for the knowledge of the species' life history and rational management. M. stehmanni constitutes an important link between the initial and final components of the alimentary chain of the open sea ecosystem, being one of the main food items for squids and large pelagic fish. Among the various applied methods those which presented the most coherent values for growth parameters and were best adapted to the von Bertallanfy's equation were: Li= 55mm K= 0.0088/day and to= 5.5 days Maurolicus stehmanni's longevity is of less than one year (around 220 days) and the sagita daily otolith rings are useful for the determination of its age

Relationship between microstructure, mechanical and magnetic properties of pure iron produced by laser powder bed fusion (L-PBF) in the as-built and stress relieved conditions

In the present work, the mechanical and magnetic properties of pure iron manufactured by laser-powder bed fusion (L-PBF) were investigated both in the as-built (AB) and stress relieved (HT) conditions, with the aim of elucidating their relationship with the microstructure and evaluating whether and to what extent it can be suitable for industrial applications. The L-PBF process was optimized to obtain high density, crack-free components. Specimens for microstructural analyses, tensile and magnetic tests were manufactured under the optimized conditions and tested both in the as-built and annealed (850 degrees C for 1 h, to relieve the residual stresses) conditions. Tensile tests showed high tensile strength in both AB and HT conditions (larger than those of conventionally produced pure iron), with higher ductility and lower strength after stress relieving. The magnetic study indicated a not optimal magnetic softness although the heat treatment enhanced the permeability and reduced the coercivity with respect to the as-built condition. The high mechanical strength and low magnetic softness came from the very fine grain size (about 5 mu m) of L-PBF pure iron. Instead, the improvement of magnetic softness and ductility after heat treatment was attributed to the possible reduction of dislocation density and consequent stress relief. The results indicated the possibility to achieve a considerably high mechanical strength, in pure iron manufactured by L-PBF, although the fine grain size limits its magnetic softness

Novel Multifunctional Magnetic Inorganic Composites: Synthesis and Characterization

We report the preparation of a series of new magnetic inorganic composites (MICs) with tuneable magnetic and mechanical properties. In the field of power inductive components and inductive heating, they could transfer energy with high robustness and excellent performances. Moreover, they may mitigate electromagnetic interference (EMI) in the LF and MF band. The MICs have been prepared using an alkaline or acidic activation process carried out in the presence of commercial magnetic micrometric particles made of anisotropic and isotropic Sr-ferrite. Three different matrices have been prepared, varying the type of activator, slag addition, water content, and aggregates

Novel Multifunctional Magnetic Inorganic Composites: Synthesis and Characterization

We report the preparation of a series of new magnetic inorganic composites (MICs) with tuneable magnetic and mechanical properties. In the field of power inductive components and inductive heating, they could transfer energy with high robustness and excellent performances. Moreover, they may mitigate electromagnetic interference (EMI) in the LF and MF band. The MICs have been prepared using an alkaline or acidic activation process carried out in the presence of commercial magnetic micrometric particles made of anisotropic and isotropic Sr-ferrite. Three different matrices have been prepared, varying the type of activator, slag addition, water content, and aggregates

Desenvolvimento ovariano de Ariomma bondi Fowler, 1930 (Teleostei: ariammatidae) na região Sudeste-Sul do Brasil

Ariomma bondi é uma espécie demerso-pelágica comum na borda da plataforma e no talude continental da região Sudeste-Sul do Brasil. Nesta região, grandes biomassas da espécie foram detectadas durante o Programa REVIZEE, sendo A. bondi considerada um recurso pesqueiro potencial. Estudos sobre a estratégia reprodutiva são essenciais para compreensão da biologia das espécies e da dinâmica de populações. A análise do desenvolvimento ovocitário é fundamental para a caracterização da maturação ovariana. Para a identificação das fases do desenvolvimento ovocitário e dos estádios de maturação ovariana, foram realizadas análises histológicas de ovários. Foram identificadas cinco fases de desenvolvimento ovocitário e folículos pós-ovulatórios, sendo descritos cinco estádios de maturação. A. bondi apresentou desenvolvimento ovariano assincrônico. A análise histológica dose ovários foi fundamental para uma correta atribuição da maturação ovariana, sendo recomendada também a aplicação de outras técnicas de estudo para o correto diagnóstico da biologia reprodutiva da espécie

Atlas of marine bony fish otoliths (sagittae) of Southeastern-Southern Brazil Part III: Clupeiformes (Clupeidae, Engraulidae, Pristigasteridae)

Esta publicação é a segunda de uma série que constituirá um Atlas de Otólitos para os Teleostei da região Sudeste-Sul brasileira. Nela são apresentados os resultados de análises morfológicas e morfométricas de 12 espécies de Clupeiformes (3 Clupeidae, 7 Engraulidae e 2 Pristigasteridae) através de feições, medidas e índices usualmente utilizados. Três otólitos de cada espécie foram desenhados e fotografados, sempre que possível. A frequência de ocorrência foi calculada para cada característica por classes de comprimento total dos peixes (CT) e as diferenças ontogenéticas foram analisadas (Teste χ² múltiplo; significância 0,05).This publication is the second in a series that will together constitute an Atlas of Teleostei Otoliths for the Southeastern-Southern Brazilian area. Here we present results of morphologic and morphometric analyses of 12 Clupeiform species (3 Clupeidae, 7 Engraulidae and 2 Pristigasteridae) by means of the most commonly used features, measurements and indices. Three otoliths of each species have been illustrated and photographed whenever possible. The frequency of occurrence has been calculated for each characteristic by total length class (TL), and the ontogenetic differences have been analyzed (multiple χ² test; significance 0.05)