764 research outputs found

    Cereal Supplies in Rural Families of the Senegalese Groundnut Basin. Who is Responsible for Meeting Family Food Needs?

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    In the traditional operation of production-consumption groups in rural areas of Senegal, the group chief, or Borom njël, has a social duty to make sure family food needs are met. His ability to do this is supported by certain social rules governing these groups, and by a favourable environment. However, various changes have now adversely affected the environment. These changes prompted us to assess the Borom njël's current ability to go on playing his social rule as a food provider. From data collected in two villages of the Senegalese Groundnut Basin, using multivariate analysis, we identified three production-consumption group profiles according to how the Borom njël ensured main cereal supplies: (i°) market purchase with migrants' remittances; (ii°) home production and (iii°) market purchase with own resources. The ability of the Borom njël to ensure cereal supplies differed according to the profile. We used a multivariate logit model to study the determinants affecting the Borom njël's ability to ensure cereal supplies for the production-consumption group. We found that physical assets and wage labour employment increased this ability. We also found that agricultural income, including livestock, was positively correlated to the likelihood of the Borom njël successfully ensuring cereal supplies, particularly those depending heavily on own production. Additional income earned by the Borom njël from non-agricultural activity had the same positive effect, particularly when ensuring cereals provision through market purchase. We end with some thoughts on the increasing reliance of Borom njëls on migrants' remittances to ensure that family cereal needs are met. ...French Abstract : Dans le passé, le fonctionnement traditionnel des populations rurales du Bassin arachidier Sénégalais regroupées au sein de groupes de production-consommation, reposait sur un système de droits et obligations gouvernant l'allocation des ressources en terre, en travail et en nourriture entre les différents membres de groupes familiaux. Ainsi, le chef du groupe familial de production-consommation, encore appelé Borom njël en wolof, avait l'obligation de satisfaire les besoins alimentaires des autres membres essentiellement, grâce à sa production agricole. En contrepartie ceux-ci travaillaient sur ses parcelles alors que chaque adulte dépendant avait un droit de culture sur une parcelle d'arachide dont il gardait les revenus. Vu tous les changements qui ont affecté le contexte socio-économique de ces populations rurales, il est devenu plus difficile pour les Borom njël d'honorer leurs obligations. Et, nous nous sommes plus particulièrement intéressés à la capacité du Borom njël à assurer l'approvisionnement en céréales et satisfaire les besoins alimentaires des différents membres. A partir de données collectées dans deux villages du Bassin Arachidier, nous avons procédé à une analyse multivariée qui nous a permis d'identifier trois profils de groupes de production-consommation, suivant que les besoins alimentaires sont principalement assurés avec: i°) les achats sur le marché grâce aux transferts d'argent des migrants ; ii°) la production agricole du Borom njël permettant ainsi l'autoconsommation ; iii°) les achats sur le marché grâce aux revenus du Borom njël. Ensuite, nous avons utilisé un modèle de logit multivarié pour étudier les déterminants qui affectent la capacité du Borom njël à assurer l'approvisionnement en céréales du groupe de production-consommation. Les résultats montrent que la possession d'actifs physiques ainsi que l'emploi de salariés agricoles augmentent cette capacité à assurer l'approvisionnement en céréales. En outre, le revenu agricole -y compris celui de l'élevage- est positivement corrélé à la probabilité du Borom njël à assurer l'approvisionnement en céréales, particulièrement pour ceux qui dépendent de leurs propres productions agricoles. Quant aux revenus non agricoles obtenus grâce à la diversification locale, ils augmentent aussi cette probabilité, mais uniquement à l'intérieur des groupes où l'approvisionnement en céréales est assuré grâce aux achats sur le marché avec les revenus du Borom njël.CEREAL SUPPLIES; CONSUMPTION-PRODUCTION GROUPS; MULTINOMIAL LOGIT; GROUNDNUT BASIN; SENEGAL

    Stress buildup in the Himalaya

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    The seismic cycle on a major fault involves long periods of elastic strain and stress accumulation, driven by aseismic ductile deformation at depth, ultimately released by sudden fault slip events. Coseismic slip distributions are generally heterogeneous with most of the energy being released in the rupture of asperities. Since, on the long term, the fault's walls generally do not accumulate any significant permanent deformation, interseismic deformation might be heterogeneous, revealing zones of focused stress buildup. The pattern of current deformation along the Himalayan arc, which is known to produce recurring devastating earthquakes, and where several seismic gaps have long been recognized, might accordingly show significant lateral variations, providing a possible explanation for the uneven microseismic activity along the Himalayan arc. By contrast, the geodetic measurements show a rather uniform pattern of interseismic strain, oriented consistently with long-term geological deformation, as indicated from stretching lineation. We show that the geodetic data and seismicity distribution are reconciled from a model in which microseismicity is interpreted as driven by stress buildup increase in the interseismic period. The uneven seismicity pattern is shown to reflect the impact of the topography on the stress field, indicating low deviatoric stresses (<35 MPa) and a low friction (<0.3) on the Main Himalayan Thrust. Arc-normal thrusting along the Himalayan front and east-west extension in southern Tibet are quantitatively reconciled by the model

    Copper supply during the Final Neolithic at the Saint-Blaise/Bains des Dames site (Neuchâtel, Switzerland)

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    The Saint-Blaise/Bains des Dames stratified site in Neuchâtel, Switzerland, contains several occupations that span the Late through Final Neolithic, including the Horgen, Lüscherz, and Auvernier-Cordé periods. As part of a study on prehistoric metallurgy in western Switzerland, we compare the lead isotope ratios (multicollector inductively coupled plasma mass spectrometer) and elemental compositions (instrumental neutron activation analysis) of the site's numerous copper finds to a database of corresponding measurements for copper ores throughout Europe. The results show a considerable variation in copper compositions present at the site, suggesting complex economic relationships and multiple chaînes opératoires during the time in question. Specifically, during the Final Neolithic, we distinguished ten coherent clusters, confirmed by both the elemental compositions and lead isotope ratios. When compared to the Europe-wide database of copper ores, we observed significant changes in the provenance of the copper through time that reflect equally significant changes in social, cultural, and economic interactions

    About MoO3 as buffer layer in organic optoelectronic devices, Technology Letters

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    MoO3 is well known as efficient anode buffer layer in optoelectronic devices. Actually, MoO3 can be easily deposited under vacuum, by sublimation for instance, and also by wet process. So it is known from a long time that the films deposited by sublimation are amorphous and slightly oxygen deficient, which induces a light blue coloration due to oxygen vacancies. These oxygen vacancies imply the presence of Mo4+ and Mo5+ in the films. The presence of oxygen vacancies increases the conductivity from 10-12 to 10-6 (Ωcm)-1, while stoichiometric films are insulating and MoO2 has a metallic like behaviour with s = 2 102 (Ωcm)-1. About the efficiency of MoO3 as buffer layer, recent studies questioned the MoO3 band structure generally admitted. Under ultra high vacuum, the measured ionisation energy, IE, and electron affinity are found to be 9.7 eV and 6.7 eV respectively, while the films are strongly n-type. Its means that the very large IE energy of the MoO3 excludes any hole transport via the valence band, while the energy alignment between the band conduction minimum, CB, of MoO3 and the Highest Occupied Molecular Orbital (HOMO) of the organic material is favourable for electron transfer between the two materials. In the case of organic photovoltaic cells, the photogenerated hole recombines with an electron at the interface between MoO3 and the organic layer. Indeed, the work function, WF, of the molybdenum oxide films depends strongly of its composition, WF decreases when the oxygen deficiency increases, and on the exposition, or not, of its surface to air contamination. This makes that WF varies from 6.9 eV for a layer studied under ultra high vacuum to 5.2 eV for a layer exposed to the air a few hours. However, since the initial value of WF is very high, MoO3 remains effective if the Highest Occupied Molecular Orbital of the organic material is lower than 6 eV. The band structure of MoO3 and the large possible variations of WF make that, for specific conditions of preparation and conditioning, MoO3 can also be used as CBL

    Copper:molybdenum sub-oxide blend as transparent conductive electrode (TCE) indium free

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    Oxide/metal/oxide structures have been shown to be promising alternatives to ITO. In such structures, in order to decrease the high light reflection of the metal film it is embedded between two metal oxides dielectric. MoO3-x is often used as oxide due to its capacity to be a performing anode buffer layer in organic solar cells, while silver is the metal the most often used [1]. Some attempts to use cheaper metal such as copper have been done. However it was shown that Cu diffuses strongly into MoO3-x [2]. Here we used this property to grow simple new transparent conductive oxide (TCE), i.e., Cu: MoO3-x blend. After the deposition of a thin Cu layer, a film of MoO3-x is deposited by sublimation. An XPS study shows more than 50% of Cu is present at the surface of the structure. In order to limit the Cu diffusion an ultra-thin Al layer is deposited onto MoO3-x. Then, in order to obtain a good hole collecting contact with the electron donor of the organic solar cells, a second MoO3-x layer is deposited. After optimization of the thickness of the different layers, the optimum structure is as follow:       Cu (12 nm) : MoO3-x (20 nm)/Al (0.5 nm)/ MoO3-x (10 nm). The sheet resistance of this structure is Rsq = 5.2 Ω/sq. and its transmittance is Tmax = 65%. The factor of merit ϕM = T10/Rsq. = 2.41 × 10-3 Ω-1, which made this new TCE promising as anode in organic solar cells

    Open circuit voltage of organic photovoltaic cells using C60 as acceptor: variation with the donor

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    The open circuit voltage (Voc) of organic photovoltaic cells (OPVs) is an important parameter in terms of OPV performance. In the present work, we check that its value depends on the energy difference between the Lowest Unoccupied Molecular Orbital of the electron acceptor (LUMOA) and the Highest Occupied Molecular Orbital of the donor (HOMOD). The electron acceptor is the fullerene, while the electron acceptors are used as parameter. The results show that Voc increases with the value of Δ(LUMOA–HOMOD). However, for some molecules, this increase is not linear, which shows that other parameters are also determinant

    FPGA Mezzanine Cards for CERN’s Accelerator Control System

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    Field Programmable Gate Arrays (FPGAs) have become a key player in modern real time control systems. They offer determinism, simple design, high performance and versatility. A typical hardware architecture consists of an FPGA interfaced with a control bus and a variable number of digital IOs, ADCs and DACs depending on the application. Until recently the low-cost hardware paradigm has been using mezzanines containing a front end interface plus custom logic (typically an FPGA) and a local bus that interfaces the mezzanine to a carrier. As FPGAs grow in size and shrink in price, hardware reuse, testability and bus access speed could be improved if the user logic is moved to the carrier. The new FPGA Mezzanine Card (FMC) Vita 57 standard is a good example of this new paradigm. In this paper we present a standard kit of FPGA carriers and IO mezzanines for accelerator control. Carriers form factors will be VME, PCI and PCIe. The carriers will feature White Rabbit support for accurate synchronization of distributed systems. Initial plans include IO mezzanines for 100Ms/s ADCs and DACs, digital drivers and inputs, high accuracy time tag units and fine delay generators

    Control of the MKQA tuning and aperture kickers of the LHC

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    The large hadron collider (LHC) at CERN has been equipped with four fast pulsed kicker magnets in RA43 situated at point 4 which are part of the measurement system for the tune and the dynamic aperture of the LHC beam (Beam 1 and Beam 2). For the tune measurement 'Q', the magnets will excite oscillations in part of the beam. This is achieved by means of a generator producing a 5 µs base half-sine pulse of 1.2 kA [1] amplitude, superimposed with a 3rd harmonic to produce a 2 µs flat top. A kick repetition rate of 2 Hz will be possible. To measure the dynamic aperture 'A' of the LHC at different beam energies, the same magnets will also be driven by a more powerful generator which produces a 43 µs base half-sine current pulse of 3.8 kA. For the 'A' mode a thyristor is used as switching element inside the generator. A final third mode named 'AC dipole' will rely on the beam being excited coherently at a frequency close but outside its Eigen-frequencies by an oscillating dipole field. The beam is expected to oscillate at the exciter frequency of 3 kHz with a phase shift of π/2. The 'AC dipole' will use two 18 kW audio amplifiers capable of driving the magnets at 1 kHz(rms) around 3 kHz or between 2.7 kHz and 4 kHz. The complete system uses supervisory control implemented with Siemens PLC technology with added Siemens PROFIsafe safety feature to treat the various interlocks that have been introduced in the circuits and to assu re a safe functioning and provide 'LOCAL' and 'REMOTE' control (via CCC) of the complete installation

    Point Cloud Diffusion Models for Automatic Implant Generation

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    Advances in 3D printing of biocompatible materials make patient-specific implants increasingly popular. The design of these implants is, however, still a tedious and largely manual process. Existing approaches to automate implant generation are mainly based on 3D U-Net architectures on downsampled or patch-wise data, which can result in a loss of detail or contextual information. Following the recent success of Diffusion Probabilistic Models, we propose a novel approach for implant generation based on a combination of 3D point cloud diffusion models and voxelization networks. Due to the stochastic sampling process in our diffusion model, we can propose an ensemble of different implants per defect, from which the physicians can choose the most suitable one. We evaluate our method on the SkullBreak and SkullFix datasets, generating high-quality implants and achieving competitive evaluation scores

    Study of CuI thin films properties for application as anode buffer layer in organic solar cells

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    After chemico-physical characterization of CuI thin films, the structures indium tin oxide (ITO) /CuI are systematically studied. We show that the morphology of the 3 nm thick CuI film depends on its deposition rate. To obtain smooth homogeneous CuI film, it is necessary to depose it at 0.005 nm/s. After optimization of the deposition conditions of CuI, it is shown that it behaves like a template for the organic layer. For instance, when the organic film is copper-phthalocyanine, the molecules which are usually perpendicular to the plane of the substrate lie parallel to it when deposited onto CuI. In a same way, when the electron donor is a prophyrin derivative, CuI allows to double the power conversion efficiency of the cells based on the heterojunction porphyrin/C-60. When CuI is used as anode buffer layer, it increases systematically the short circuit current, the open circuit voltage, thus the efficiency of the organic solar cell. These effects are related, not only to the improvement of the band matching between the ITO and the electron donor, but also to the templating effect of the CuI. Moreover, we show that the beneficial effect of CuI. is effective, not only with ITO, but also with fluorine doped tin oxide
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