Enhancement of the magnetoelectric effect in multiferroic CoFe2_2O4_4/PZT bilayer by induced uniaxial magnetic anisotropy

In this study we have compared magnetic, magnetostrictive and piezomagnetic properties of isotropic and anisotropic cobalt ferrite pellets. The isotropic sample was prepared by the ceramic method while the sample exhibiting uniaxial anisotropy was made by reactive sintering using Spark Plasma Sintering (SPS). This technique permits to induce a magnetic anisotropy in cobalt ferrite in the direction of the applied pressure during SPS process. Sample with uniaxial anisotropy revealed a higher longitudinal magnetostriction and piezomagnetism compared to the isotropic sample, but the transversal magnetostriction and piezomagnetism were dramatically reduced. In the case of magnetoelectric layered composite, the magnetoelectric coefficient is directly related to the sum of the longitudinal and transversal piezomagnetic coefficients. These two coefficients being opposite in sign, the use of material exhibiting high longitudinal and low transversal piezomagnetic coefficient (or vice versa) in ME devices is expected to improve the ME effect. Hence, ME bilayer devices were made using isotropic and anisotropic cobalt ferrite stuck with a PZT layer. ME measurements at low frequencies revealed that bilayer with anisotropic cobalt ferrite exhibits a ME coefficient three times higher than a bilayer with isotropic cobalt ferrite. We also investigated the behavior of such composites when excited at resonant frequency

First vs second order magnetocaloric material for thermomagnetic energy conversion

International audienceWe estimate the power and efficiency of a thermal energy harvesting thermodynamic Brayton cycle using a first and second order magnetocaloric materials as active substance. The thermodynamic cycle was computed using a simple thermal exchange model and an equation of state deduced from a phenomenological Landau model. For the first and second order materials, narrow and high frequency cycles are optimum and give similar performances. Considering technological issues hindering the increase of frequency, we introduced a more detailed approach where we take into account the time needed to switch the material between two heat reservoirs. We show that the first order material equation of state leads thermodynamic cycle shape keeping it closer to the optimum cycle. Conditions to improve the performance of second order materials are discussed. In addition, we infer key remarks for prototype design regarding the power density and efficiency reachable in different configurations

Système de récupération d'énergie thermique à base de matériaux magnétocaloriques

International audience-Les générateurs thermomagnétiques convertissent le flux de chaleur en énergie électrique. Le matériau magnétocalorique (MMC) réalise un cycle thermodynamique entre deux sources de chaleur ce qui produit une variation d'aimantation du matériau. Cette énergie (variation d'aimantation) est ensuite transformée en énergie mécanique via les forces magnétiques et enfin en énergie électrique via un transducteur électromécanique. Le dimensionnement du cantilever permettant l'auto-oscillation du MMC entre les deux sources de chaleur nous a permis de déduire la vitesse au cours des déplacements. Ainsi à partir du modèle où le transducteur est découplé de la partie mécanique, nous avons à l'aide de simulation par éléments finis estimé l'aptitude d'un transducteur piézoélectriques (PZT 5a) et de bobines à convertir l'énergie mécanique en énergie électrique. Le système à base de piézoélectriques et de bobines récupèrent seulement 0,025 % et 0,018% respectivement de l'énergie mécanique disponible (116 mJ/cm 3). Finalement quelques pistes seront soulevées pour expliquer les faibles valeurs obtenues et les stratégies possibles pour y remédier Mots-clés-Matériaux Magnétocalorique, Thermomagnétique, Récupération d'énergie thermique, Energie

Freezing and chemical preservatives alter the stable isotope values of carbon and nitrogen of the Asiatic clam (Corbicula fluminea)

We tested the impacts of most common sample preservation methods used for aquatic sample materials on the stable isotope ratios of carbon and nitrogen in clams, a typical baseline indicator organism for many aquatic food web studies utilising stable isotope analysis (SIA). In addition to common chemical preservatives ethanol and formalin, we also assessed the potential impacts of freezing on δ¹³C and δ¹⁵N values and compared the preserved samples against freshly dried and analysed samples. All preservation methods, including freezing, had significant impacts on δ¹³C and δ¹⁵N values and the effects in general were greater on the carbon isotope values (1.3-2.2% difference) than on the nitrogen isotope values (0.9-1.0% difference). However, the impacts produced by the preservation were rather consistent within each method during the whole 1 year experiment allowing these to be accounted for, if clams are intended for use in retrospective stable isotope studies

Mesurer la fièvre palestinienne. Notes sur une expérience de monitoring pendant la deuxième Intifada, 2000-2006

Depuis l’automne 2000 et le début de la deuxième Intifada dans les Territoires palestiniens occupés (tpo), l’Unité de recherche sur la Palestine (urp) de l’Institut universitaire d’études du développement (iued) est engagée dans un projet portant sur le monitoring des conditions de vie de la population civile, ainsi que sur le rôle et les effets de l’aide internationale. Initialement financé sur le budget de l’aide humanitaire suisse, le projet est ensuite entré dans celui de la coopération a..

Das Fieber Palästinas messen - Anmerkungen zu einer Monitoring-Erfahrung während der zweiten Intifada, 2000-2006

Seit dem Herbst 2000 und dem Beginn der zweiten Intifada in den besetzten palästinensischen Gebieten (OPT) beteiligt sich die Forschungsabteilung über Palästina (Unité de recherche sur la Palestine, urp) des Universitätsinstituts für Entwicklungsstudien (IUED) an einem Projekt betreffend das Monitoring der Lebensbedingungen der Zivilbevölkerung sowie die Rolle und die Auswirkungen der internationalen Hilfe. Das ursprünglich aus dem Haushalt der humanitären Hilfe finanzierte Projekt wurde in d..

Contribution of anadromous fish to the diet of European catfish in a large river system

Many anadromous fish species, when migrating from the sea to spawn in fresh waters, can potentially be a valuable prey for larger predatory fish, thereby efficiently linking these two ecosystems. Here, we assess the contribution of anadromous fish to the diet of European catfish (Silurus glanis) in a large river system (Garonne, southwestern France) using stable isotope analysis and allis shad (Alosa alosa) as an example of anadromous fish. Allis shad caught in the Garonne had a very distinct marine delta(13)C value, over 8 per thousand higher after lipid extraction compared to the mean delta(13)C value of all other potential freshwater prey fish. The delta(13)C values of European catfish varied considerably between these two extremes and some individuals were clearly specializing on freshwater prey, whereas others specialized on anadromous fish. The mean contribution of anadromous fish to the entire European catfish population was estimated to be between 53% and 65%, depending on the fractionation factor used for delta(13)C

Ancestral SARS-CoV-2, but not Omicron, replicates less efficiently in primary pediatric nasal epithelial cells

Children typically experience more mild symptoms of Coronavirus Disease 2019 (COVID-19) when compared to adults. There is a strong body of evidence that children are also less susceptible to Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection with the ancestral viral isolate. However, the emergence of SARS-CoV-2 variants of concern (VOCs) has been associated with an increased number of pediatric infections. Whether this is the result of widespread adult vaccination or fundamental changes in the biology of SARS-CoV-2 remain to be determined. Here, we use primary nasal epithelial cells (NECs) from children and adults, differentiated at an air-liquid interface to show that the ancestral SARS-CoV-2 replicates to significantly lower titers in the NECs of children compared to those of adults. This was associated with a heightened antiviral response to SARS-CoV-2 in the NECs of children. Importantly, the Delta variant also replicated to significantly lower titers in the NECs of children. This trend was markedly less pronounced in the case of Omicron. It is also striking to note that, at least in terms of viral RNA, Omicron replicated better in pediatric NECs compared to both Delta and the ancestral virus. Taken together, these data show that the nasal epithelium of children supports lower infection and replication of ancestral SARS-CoV-2, although this may be changing as the virus evolves

Final results of the tests on the resistive plate chambers for the ALICE muon arm

Abstract The trigger for the ALICE muon spectrometer will be issued by single-gap, low resistivity bakelite resistive plate chambers (RPCs). The trigger system consists of four 5.5 × 6.5 m 2 RPC planes arranged in two stations, for a total of 72 detectors. One hundred and sixteen detectors have been assembled and tested in Torino. The tests have been performed with the streamer mixture developed for heavy ion data-taking. The tests include: the detection of gas leaks and parasitic currents; the measurement of the efficiency with cosmic rays, with particular regard to the uniformity of the efficiency throughout the whole active surface, with a granularity of about 2 × 2 cm 2 ; the measurement of the dark current and of the mean and localised noise rate. All the RPCs produced have been characterised. Among them, the detectors to be finally installed in ALICE and some spare have been selected; 17% of all the produced detectors have been discarded. A short description of the test set-up is given. The results of the tests are presented, with particular regard to the performance of the selected detectors