Uncooled bolometer response of a low noise La2/3Sr1/3MnO3 thin film

We report measurements of the optical responses of a La2/3Sr1/3MnO3 (LSMO) sample at a wavelength of 533 nm in the 300-400 K range. The 200 nm thick film was grown by pulsed laser deposition on (100) SrTiO3 substrate and showed remarkably low noise. At 335 K the temperature coefficient of the resistance of a 100 micrometers wide 300 micrometers long LSMO line was 0.017 K-1 and the normalized Hooge parameter was 9 e-30 m3, which is among the lowest reported values. We then measured an optical sensitivity at I = 5 mA of 10.4 V.W-1 and corresponding noise equivalent power (NEP) values of 8.1 e-10 W.Hz-1/2 and 3.3 e-10 W. Hz-1/2 at 30 Hz and above 1kHz, respectively. Simple considerations on bias current conditions and thermal conductance G are finally given for further sensitivity improvements using LSMO films. The performances were indeed demonstrated on bulk substrates with G of 10-3 W.K-1. One could expect a NEP reduction by three orders of magnitude if a membrane-type geometry was used, which makes this LSMO device competitive against commercially available uncooled bolometers.Comment: 15 pages. Accepted for publication in Appl. Phys. Let

Propagation of social representations

Based on a minimal formalism of social representations as a set of associated cognems, a simple model of propagation of representations is presented. Assuming that subjects share the constitutive cognems, the model proposes that mere focused attention on the set of cognems in the field of common conscience may replicate the pattern of representation from context into subjects, or, from subject to subject, through actualization by language, where cognems are represented by verbal signs. Limits of the model are discussed, and evolutionist perspectives are presented with the support of field data

Differential roles of p39Mos–Xp42Mpk1 cascade proteins on Raf1 phosphorylation and spindle morphogenesis in Xenopus oocytes

AbstractFully-grown G2-arrested Xenopus oocytes resume meiosis upon hormonal stimulation. Resumption of meiosis is characterized by germinal vesicle breakdown, chromosome condensation, and organization of a bipolar spindle. These cytological events are accompanied by activation of MPF and the p39Mos–MEK1–Xp42Mpk1–p90Rsk pathways. The latter cascade is activated upon p39Mos accumulation. Using U0126, a MEK1 inhibitor, and p39Mos antisense morpholino and phosphorothioate oligonucleotides, we have investigated the role of the members of the p39Mos–MEK1–Xp42Mpk1–p90Rsk in spindle morphogenesis. First, we have observed at a molecular level that prevention of p39Mos accumulation always led to MEK1 phosphorylation defects, even when meiosis was stimulated through the insulin Ras-dependent pathway. Moreover, we have observed that Raf1 phosphorylation that occurs during meiosis resumption was dependent upon the activity of MEK1 or Xp42Mpk1 but not p90Rsk. Second, inhibition of either p39Mos accumulation or MEK1 inhibition led to the formation of a cytoplasmic aster-like structure that was associated with condensed chromosomes. Spindle morphogenesis rescue experiments using constitutively active Rsk and purified murine Mos protein suggested that p39Mos or p90Rsk alone failed to promote meiotic spindle organization. Our results indicate that activation of the p39Mos–MEK1–Xp42Mpk1–p90Rsk pathway is required for bipolar organization of the meiotic spindle at the cortex

Autonomy and forage grasses in goat farming of western France First results of a sociological survey

International audienceOur communication is based on the results of a multidisciplinary research (PSDR FLECHE-Fromages et Laits issus d'Élevages de Chèvres conduites avec de l'Herbe-2016-2020) which aims to study the potential of grass valorization in goat systems, with the dual objective of strengthening the economic resilience of farms and the social image of the dairy goat sector of Western France. The latter currently represent almost half of the national goat population and 58% of the milk supplied in France. The sociological aspect of the research concerns the representations, value systems, interests and constraint systems (technical, economic, etc.) that guide the practices of all the actors in the sector: farmers, upstream and downstream actors. The objective of this approach is to analyse, at all levels of the value chain, the incentives and obstacles to a possible transition to more grassy feeding systems. Based on 76 semi-directive interviews, this paper presents the first results of this survey by showing how contextual elements (socio-economic, professional, etc.) impact farmers' choices of practices. While, in principle, the whole goat sector seems to be converging towards an agro-ecological transition that ensures its sustainability, in practice, each of its actors is confronted with a system of constraints that limit actual developments. The articulation of these obstacles seems to lead to a kind of inertia, which prevents the adoption of practices that are nevertheless perceived as recommendable by most actors. Autonomie et fourrages herbagers dans les élevages caprins de l'Ouest de la France. Premiers résultats d'une enquête sociologique. Résumé. Notre communication s'inscrit dans le cadre d'une recherche pluridisciplinaire (Programme PSDR-FLECHE-Fromages et Laits issus d'Élevages de Chèvres conduites avec de l'Herbe-2016-2020) qui vise à étudier le potentiel de valorisation de l'herbe dans les systèmes caprins, dans le double objectif de renforcer la résilience économique des exploitations et l'image sociale des filières caprines laitières de l'Ouest de la France. Ces dernières représentent actuellement près de la moitié de l'effectif national de chèvres et 58% du lait livré en France. Le volet sociologique de la recherche porte sur les représentations, les systèmes de valeurs, les intérêts et les systèmes de contraintes (techniques, économiques, etc.) qui orientent les pratiques de l'ensemble des acteurs de la filière : éleveurs, acteurs de l'amont et de l'aval. L'objectif de cette démarche est d'analyser, à tous les niveaux de la filière, les incitations et les freins à une éventuelle transition vers des systèmes alimentaires plus herbagers. A partir de 76 entretiens semi-directifs, ce papier présente les premiers résultats de cette enquête en montrant, notamment, comment les éléments contextuels (socio-économiques, professionnels, etc.) impactent les choix des pratiques des exploitants agricoles. Si, en principe, l'ensemble de la filière caprine semble converger vers une transition agroécologique qui en assure la durabilité, dans la pratique, chacun de ses acteurs est confronté à un univers de contraintes qui limitent les évolutions effectives. L'articulation des freins relevant des différents maillons de la filière, semble ainsi déboucher sur une sorte d'inertie, qui empêche l'adoption de pratiques pourtant perçues comme souhaitables par la plupart des acteurs. Mots-clés. Autonomie-fourrages herbagers-caprins-sociologie

Parallel flow in Hele-Shaw cells with ferrofluids

Parallel flow in a Hele-Shaw cell occurs when two immiscible liquids flow with relative velocity parallel to the interface between them. The interface is unstable due to a Kelvin-Helmholtz type of instability in which fluid flow couples with inertial effects to cause an initial small perturbation to grow. Large amplitude disturbances form stable solitons. We consider the effects of applied magnetic fields when one of the two fluids is a ferrofluid. The dispersion relation governing mode growth is modified so that the magnetic field can destabilize the interface even in the absence of inertial effects. However, the magnetic field does not affect the speed of wave propagation for a given wavenumber. We note that the magnetic field creates an effective interaction between the solitons.Comment: 12 pages, Revtex, 2 figures, revised version (minor changes

Rotating Hele-Shaw cells with ferrofluids

We investigate the flow of two immiscible, viscous fluids in a rotating Hele-Shaw cell, when one of the fluids is a ferrofluid and an external magnetic field is applied. The interplay between centrifugal and magnetic forces in determining the instability of the fluid-fluid interface is analyzed. The linear stability analysis of the problem shows that a non-uniform, azimuthal magnetic field, applied tangential to the cell, tends to stabilize the interface. We verify that maximum growth rate selection of initial patterns is influenced by the applied field, which tends to decrease the number of interface ripples. We contrast these results with the situation in which a uniform magnetic field is applied normally to the plane defined by the rotating Hele-Shaw cell.Comment: 12 pages, 3 ps figures, RevTe

Modulated optical reflectance measurements on La2/3Sr1/3MnO3 thin films

The modulated optical reflectance (MOR) measurement technique was applied to colossal magnetoresistive materials, in particular, La2/3Sr1/3MnO3 (LSMO) thin films. The contactless measurement scheme is prospective for many applications spanning from materials characterization to new devices like reading heads for magnetically recorded media. A contrasted room temperature surface scan of a 100 microns wide 400 microns long bridge patterned into LSMO film provided preliminary information about the film homogeneity. Then the temperature was varied between 240 and 400 K, i.e. through the ferromagnetic to paramagnetic transition. A clear relation between the MOR signal measured as function of the temperature and the relative derivative of the resistivity up to the Curie temperature was observed. This relationship is fundamental for the MOR technique and its mechanism was explored in the particular case of LSMO. Analysis in the framework of the Drude model showed that, within certain conditions, the measured MOR signal changes are correlated to changes in the charge carrier concentration.Comment: 29 pages, accepted for publication in J. Appl. Phy

Ridge subduction sparked reorganization of the Pacific plate-mantle system 60-50 million years ago

A reorganization centered on the Pacific plate occurred ~53–47 million years ago. A “top-down” plate tectonic mechanism, complete subduction of the Izanagi plate, as opposed to a “bottom-up” mantle flow mechanism, has been proposed as the main driver. Verification based on marine geophysical observations is impossible as most ocean crust recording this event has been subducted. Using a forward modeling approach, which assimilates surface plate velocities and shallow thermal structure of slabs into mantle flow models, we show that complete Izanagi plate subduction and margin-wide slab detachment induced a major change in sub-Pacific mantle flow, from dominantly southward before 60 Ma to north-northeastward after 50 Ma. Our results agree with onshore geology, mantle tomography, and the inferred motion of the Hawaiian hot spot and are consistent with a plate tectonic process driving the rapid plate-mantle reorganization in the Pacific hemisphere between 60 and 50 Ma. This reorganization is reflected in tectonic changes in the Pacific and surrounding ocean basins

Moored current meter, AVHRR, CTD, and drifter data from the Agulhas Current and Retroflexion region (1985-1987) Volume XLII

Stored in the Archives of the Woods Hole Oceanographic Institution is the floppy disk on which can be found the one-day average currents, the path of the Agulhas Current, CTD stations in "Live Atlas" format, SST frontal analyses (Chassignet and Olson, personal communcation) as well as programs written in QuickBASIC which allow one to access and display these observations. The programs are stored in ASCII and can be run under the Microsoft QuickBasic (Version 4.0 or higher). Instructions for running the programs can be found in a file entitled "read.me" on the disk.Data are presented from an experiment designed to explore the spatial and temporal structure of the Agulhas Current and Retroflexion by direct means. Included are the current meter results from 10 moorings in the Retroflexion region, CTD stations occupied on the deployment cruise in 1985, data from satellite tracked (ARGOS) freely during surface buoys and numerous images of the sea surface temperature.Funding was provided by the Office of Naval Research through Contract Nos. NOOO14-84C-O134, NOO014-85-C-0001, and NOOO14-87-K-0007