Edge atoms effects on the perpendicular anisotropy of ultrathin magnetic layers

The present work reports experimental and theoretical results for electrodeposited Co/Au(111) ultrathin layers with very specific magnetic behavior. We show that the observed two peaks in the out-of-plane magnetization versus deposition time variation could be explained by the remarkably high perpendicular anisotropy of the perimeter atoms of low-dimensional islands formed during the layer-by-layer growth, as compared to that of the surface atoms. Our results indicate that it is possible to sustain high anisotropy in very small grains without coming across the superparamagnetic limit, opening excellent opportunities for materials engineering

High Prevalence of Giardia duodenalis Assemblage B Infection and Association with Underweight in Rwandan Children

Giardia duodenalis is a protozoan parasite causing gastroenteritis. Although the parasite occurs worldwide, its regional prevalence varies considerably. Using PCR as a highly sensitive molecular diagnostic tool, we detected G. duodenalis in 60% of 583 children younger than five years in southern Rwanda. It was by far the most frequent intestinal parasite detected in this population. Importantly, two out of three infections would have been undetected if only the commonly used light microscopy had been applied. Genotyping revealed the presence of two distinct types of parasites, and only the infrequent subtype showed a weak association with gastrointestinal symptoms. However, G. duodenalis infection was associated with underweight and clinically assessed severe malnutrition. The data call for the establishment of more sensitive than light microscopy, yet simple diagnostic tools to identify infected children as well as for the consideration of abundant submicroscopic infections in evaluating the significance of G. duodenalis in high endemicity areas

Prevalence and risk factors of malaria among children in southern highland Rwanda

<p>Abstract</p> <p>Background</p> <p>Increased control has produced remarkable reductions of malaria in some parts of sub-Saharan Africa, including Rwanda. In the southern highlands, near the district capital of Butare (altitude, 1,768 m), a combined community-and facility-based survey on <it>Plasmodium </it>infection was conducted early in 2010.</p> <p>Methods</p> <p>A total of 749 children below five years of age were examined including 545 randomly selected from 24 villages, 103 attending the health centre in charge, and 101 at the referral district hospital. Clinical, parasitological, haematological, and socio-economic data were collected.</p> <p>Results</p> <p><it>Plasmodium falciparum </it>infection (mean multiplicity, 2.08) was identified by microscopy and PCR in 11.7% and 16.7%, respectively; 5.5% of the children had malaria. PCR-based <it>P. falciparum </it>prevalence ranged between 0 and 38.5% in the villages, and was 21.4% in the health centre, and 14.9% in the hospital. Independent predictors of infection included increasing age, low mid-upper arm circumference, absence of several household assets, reported recent intake of artemether-lumefantrine, and chloroquine in plasma, measured by ELISA. Self-reported bed net use (58%) reduced infection only in univariate analysis. In the communities, most infections were seemingly asymptomatic but anaemia was observed in 82% and 28% of children with and without parasitaemia, respectively, the effect increasing with parasite density, and significant also for submicroscopic infections.</p> <p>Conclusions</p> <p><it>Plasmodium falciparum </it>infection in the highlands surrounding Butare, Rwanda, is seen in one out of six children under five years of age. The abundance of seemingly asymptomatic infections in the community forms a reservoir for transmission in this epidemic-prone area. Risk factors suggestive of low socio-economic status and insufficient effectiveness of self-reported bed net use refer to areas of improvable intervention.</p

Estudo das propriedades magnéticas e estruturais de filmes ultrafinos de Fe, Co e Ni/Au(111) produzidos por eletrodeposição

Neste trabalho foram estudadas as propriedades magnéticas e estruturais de filmes ultrafinos de Fe, Co e Ni produzidos por eletrodeposição sobre substratos de Au(111). Os estágios iniciais de crescimento dos filmes foram estudados por técnicas de caracterização “in-situ”. Uma nova técnica de caracterização do estado magnético de filmes ultrafinos eletrodepositados (EC-AGFM) foi utilizada, mostrando-se uma poderosa ferramenta para o estudo das propriedades magnéticas dos filmes. Outras técnicas, como STM “in-situ”, PMOKE “in-situ”, EXAFS, XRD, RBS foram utilizadas. A análise dos dados revelaram resultados diferentes para os filmes de Fe e Co/Au(111), em comparação aos filmes de Ni/Au(111). Enquanto a anisotropia magnética perpendicular (PMA) foi observada para os filmes de Fe e Co/Au(111), não foi observada para os filmes de Ni/Au(111). Os resultados são interpretados em termos das contribuições para a anisotropia magnética dos filmes. No caso do níquel, a degradação de suas propriedades magnéticas são atribuídas à incorporação de hidrogênio durante a deposição. Os resultados das análises magnética e estrutural são correlacionados a fim de compreender o comportamento das propriedades observadas. Os resultados são comparados aos obtidos por técnicas em vácuo

Estudo das propriedades magnéticas e estruturais de filmes ultrafinos de Fe, Co e Ni/Au(111) produzidos por eletrodeposição

Neste trabalho foram estudadas as propriedades magnéticas e estruturais de filmes ultrafinos de Fe, Co e Ni produzidos por eletrodeposição sobre substratos de Au(111). Os estágios iniciais de crescimento dos filmes foram estudados por técnicas de caracterização “in-situ”. Uma nova técnica de caracterização do estado magnético de filmes ultrafinos eletrodepositados (EC-AGFM) foi utilizada, mostrando-se uma poderosa ferramenta para o estudo das propriedades magnéticas dos filmes. Outras técnicas, como STM “in-situ”, PMOKE “in-situ”, EXAFS, XRD, RBS foram utilizadas. A análise dos dados revelaram resultados diferentes para os filmes de Fe e Co/Au(111), em comparação aos filmes de Ni/Au(111). Enquanto a anisotropia magnética perpendicular (PMA) foi observada para os filmes de Fe e Co/Au(111), não foi observada para os filmes de Ni/Au(111). Os resultados são interpretados em termos das contribuições para a anisotropia magnética dos filmes. No caso do níquel, a degradação de suas propriedades magnéticas são atribuídas à incorporação de hidrogênio durante a deposição. Os resultados das análises magnética e estrutural são correlacionados a fim de compreender o comportamento das propriedades observadas. Os resultados são comparados aos obtidos por técnicas em vácuo

In situ magnetization measurements of Cu/Co multilayers during the process of electrodeposition

The electrocrystallization of Cu–Co multilayers has been investigated by means of in situ magnetization measurements, during the electrodeposition, using an electrochemical alternating gradient magnetometer. The hysteresis loops were also recorded in situ. This allowed us to measure a magnetization efficiency, ratio of the magnetization increase to the electrical charge used. This efficiency tends to decrease as the number of bilayers increases, probably as a result of the increase in the roughness of the surface. It exhibits the same dependency on cobalt plating time as the Faradaic efficiency, which confirms that at the beginning of cobalt deposition, hydrogen evolution is the main reaction. The multilayers exhibit a typical ferromagnetic behavior. The magnetization increases and the coercive field decreases when the number of bilayers and/or the thickness of the cobalt layer increase

In situ magnetization measurements of Cu/Co multilayers during the process of electrodeposition

The electrocrystallization of Cu–Co multilayers has been investigated by means of in situ magnetization measurements, during the electrodeposition, using an electrochemical alternating gradient magnetometer. The hysteresis loops were also recorded in situ. This allowed us to measure a magnetization efficiency, ratio of the magnetization increase to the electrical charge used. This efficiency tends to decrease as the number of bilayers increases, probably as a result of the increase in the roughness of the surface. It exhibits the same dependency on cobalt plating time as the Faradaic efficiency, which confirms that at the beginning of cobalt deposition, hydrogen evolution is the main reaction. The multilayers exhibit a typical ferromagnetic behavior. The magnetization increases and the coercive field decreases when the number of bilayers and/or the thickness of the cobalt layer increase

Magnetization process and magnetoimpedance in (110)[001]FeSi/Sub 3%

The present article investigates the relation between magnetoimpedance (MI) and the evolution of the magnetic domain structure along the magnetization curves of commercial FeSi3% sheets cut at different angles with respect to the easy magnetization axis [001]. The role of the magnetocrystalline anisotropy on MI is studied and the correlation between the basic features of the MI vs H and magnetization (M) vs H curves is established. From data obtained at appropriate frequency ranges, the frequency dependence of the effective transverse differential permeability is obtained. The frequency and field spectra of the impedance allow the identification of the rotation of the magnetization as the main contribution of the magnetization processes to the MI effects in the studied samples

Magnetization process and magnetoimpedance in (110)[001]FeSi/Sub 3%

The present article investigates the relation between magnetoimpedance (MI) and the evolution of the magnetic domain structure along the magnetization curves of commercial FeSi3% sheets cut at different angles with respect to the easy magnetization axis [001]. The role of the magnetocrystalline anisotropy on MI is studied and the correlation between the basic features of the MI vs H and magnetization (M) vs H curves is established. From data obtained at appropriate frequency ranges, the frequency dependence of the effective transverse differential permeability is obtained. The frequency and field spectra of the impedance allow the identification of the rotation of the magnetization as the main contribution of the magnetization processes to the MI effects in the studied samples