Fonctions de production représentatives de fonctions à complémentarité stricte

Dans cet article, nous analysons des fonctions de production à complémentarité stricte dans le cas d’entreprises hétérogènes. Nous restreignant pour simplifier au cas de deux facteurs, nous avons: yi= Min (a1ix1i , a2ix2i), où les coefficients techniques a1i a2i dépendent de l’entreprise i considérée. Il est alors naturel d’introduire la fonction de production moyenne (ou représentative) définie par : y = g (x1, x2 ) = Min (a1x1, a2x2 ), où la moyenne est prise sur les coefficients techniques.Nous commençons par caractériser les fonctions de production pouvant s'interpréter comme fonctions représentatives de fonctions à complémentarité stricte. Nous discutons ensuite la possibilité d'hétérogénéité π sous jacente et appliquons notamment les résultats au cas des fonctions C.E.S.Finalement nous discutons des notions de plus ou moins grande hétérogénéité regardons comment elles sont liées aux biais d'interprétation sur les coefficients de substitution et nous servons de la famille de fonctions de production obtenues pour construire des comparaisons de distributions de facteurs en terme d'efficacité technique.In this paper, we analyse production function with complementary factors for the case of heterogenous firms. As an illustration, we restrict ourselves to the two factors case and we consider the functions: yi= Min (a1ix1i , a2ix2i), where the technical coefficients vary with the form. Then it is natural to introduce the representative function : y = g (x1, x2 ) = Min (a1x1, a2x2 ), where the average is taken with respect to the technical coefficients. We first characterize the functions which may be interpreted as representative and discuss the possibility to identify the heterogeneity distribution π from the representative production function g. These results are applied to the CES functions. Finally we discuss the notion of more or less heterogenous distribution, we examine how they are linked to heterogenity biases on the substitution coefficients and we use the obtained family of production technologies to introduce an ordering on the distributions of inputs in terms of technical efficiency

Fundamental aspects of the moment problem for a particle density evolving under non-linear forces

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Fonctions de production représentatives de fonctions à complémentarité stricte

In this paper, we analyse production function with complementary factors for the case of heterogenous firms. As an illustration, we restrict ourselves to the two factors case and we consider the functions: yi= Min (a1ix1i , a2ix2i), where the technical coefficients vary with the form. Then it is natural to introduce the representative function : y = g (x1, x2 ) = Min (a1x1, a2x2 ), where the average is taken with respect to the technical coefficients. We first characterize the functions which may be interpreted as representative and discuss the possibility to identify the heterogeneity distribution π from the representative production function g. These results are applied to the CES functions. Finally we discuss the notion of more or less heterogenous distribution, we examine how they are linked to heterogenity biases on the substitution coefficients and we use the obtained family of production technologies to introduce an ordering on the distributions of inputs in terms of technical efficiency. Dans cet article, nous analysons des fonctions de production à complémentarité stricte dans le cas d’entreprises hétérogènes. Nous restreignant pour simplifier au cas de deux facteurs, nous avons: yi= Min (a1ix1i , a2ix2i), où les coefficients techniques a1i a2i dépendent de l’entreprise i considérée. Il est alors naturel d’introduire la fonction de production moyenne (ou représentative) définie par : y = g (x1, x2 ) = Min (a1x1, a2x2 ), où la moyenne est prise sur les coefficients techniques.

Hydrogen production during the irradiation of gaseous organic compounds: advantage of an extracted beam

ACE, Accélérateur, NIMBInternational audienceThis paper presents a fundamental study of the radiolysis of gaseous organic molecules induced by proton beam. For that purpose, a specific extracted beam line associated with a gas irradiation cell was set up on the 4 MV facility of the Institut de Physique Nucléaire of Lyon. The first experiments have been performed with gaseous alkanes and alkenes. The gaseous species formed during irradiation are analysed by an on-line gas chromatography instrument equipped with two detectors. In order to test our experimental faiclity, we have studied the influence of irradiation parameters (duration, beam intensity, pressure) on the production of hydrogen. In the case of propane, the radiolytic yield value of hydrogen G(H$_2$) is equal to 3.7 for total does in the range of 0.4 to 2.3 MGy at atmospheric pressure

Remanence effects in the electrical resistivity of spin glasses

We have measured the low temperature electrical resistivity of Ag : Mn mesoscopic spin glasses prepared by ion implantation with a concentration of 700 ppm. As expected, we observe a clear maximum in the resistivity (T ) at a temperature in good agreement with theoretical predictions. Moreover, we observe remanence effects at very weak magnetic fields for the resistivity below the freezing temperature Tsg: upon Field Cooling (fc), we observe clear deviations of (T ) as compared with the Zero Field Cooling (zfc); such deviations appear even for very small magnetic fields, typically in the Gauss range. This onset of remanence for very weak magnetic fields is reminiscent of the typical signature on magnetic susceptibility measurements of the spin glass transition for this generic glassy system

New xenon results of Phoenix at 28 GHz

The classical PHOENIX 28 GHz electron cyclotron resonance ion Source (ECRIS) has been developed to prospect high pulsed multi charged lead ion (MCI lead) beams for the Large Hadron Collider (LHC) [1,2]. The goal of the experiment is to reach 1 emA pulses of Pb27+ during 0.4 ms with a 10 Hz repetition rate. This high beam current is one order of magnitude higher than the ones available nowadays. The strategy to take up this challenge is based on an increase of the radio frequency (RF) to 28 GHz and an increase of the RF power density. A new high acceptance, high resolution analysing beam line has been coupled to PHOENIX in order to study efficiently the intense beams delivered by the source. Thus, 0.6 emA of Xe20+ has been measured in the afterglow (AFG) among 9 emA analysed in the Faraday Cup (FC). The lead production is under study and a preliminary beam of 0.6 emA of Pb24+ AFG has already been obtained. The cross check of a 3D beam simulation program and measured beam characteristics enables to estimate the beam emittance to be ~ 200 mm.mrad. The project of development of an upgraded version of PHOENIX is presented (a new ECRIS named APHOENIX)

Cross-Over between universality classes in a magnetically disordered metallic wire

In this article we present numerical results of conduction in a disordered quasi-1D wire in the possible presence of magnetic impurities. Our analysis leads us to the study of universal properties in different conduction regimes such as the localized and metallic ones. In particular, we analyse the cross-over between universality classes occurring when the strength of magnetic disorder is increased. For this purpose, we use a numerical Landauer approach, and derive the scattering matrix of the wire from electron's Green's function.Comment: Final version, accepted for publication in New Journ. of Physics, 27 pages, 28 figures. Replaces the earlier shorter preprint arXiv:0910.427

Alignment between PIN1 Polarity and Microtubule Orientation in the Shoot Apical Meristem Reveals a Tight Coupling between Morphogenesis and Auxin Transport

Morphogenesis during multicellular development is regulated by intercellular signaling molecules as well as by the mechanical properties of individual cells. In particular, normal patterns of organogenesis in plants require coordination between growth direction and growth magnitude. How this is achieved remains unclear. Here we show that in Arabidopsis thaliana, auxin patterning and cellular growth are linked through a correlated pattern of auxin efflux carrier localization and cortical microtubule orientation. Our experiments reveal that both PIN1 localization and microtubule array orientation are likely to respond to a shared upstream regulator that appears to be biomechanical in nature. Lastly, through mathematical modeling we show that such a biophysical coupling could mediate the feedback loop between auxin and its transport that underlies plant phyllotaxis

Noise and Robustness in Phyllotaxis

A striking feature of vascular plants is the regular arrangement of lateral organs on the stem, known as phyllotaxis. The most common phyllotactic patterns can be described using spirals, numbers from the Fibonacci sequence and the golden angle. This rich mathematical structure, along with the experimental reproduction of phyllotactic spirals in physical systems, has led to a view of phyllotaxis focusing on regularity. However all organisms are affected by natural stochastic variability, raising questions about the effect of this variability on phyllotaxis and the achievement of such regular patterns. Here we address these questions theoretically using a dynamical system of interacting sources of inhibitory field. Previous work has shown that phyllotaxis can emerge deterministically from the self-organization of such sources and that inhibition is primarily mediated by the depletion of the plant hormone auxin through polarized transport. We incorporated stochasticity in the model and found three main classes of defects in spiral phyllotaxis – the reversal of the handedness of spirals, the concomitant initiation of organs and the occurrence of distichous angles – and we investigated whether a secondary inhibitory field filters out defects. Our results are consistent with available experimental data and yield a prediction of the main source of stochasticity during organogenesis. Our model can be related to cellular parameters and thus provides a framework for the analysis of phyllotactic mutants at both cellular and tissular levels. We propose that secondary fields associated with organogenesis, such as other biochemical signals or mechanical forces, are important for the robustness of phyllotaxis. More generally, our work sheds light on how a target pattern can be achieved within a noisy background

Immunolocalization of cell wall polymers in grapevine (Vitis vinifera) internodes under nitrogen, phosphorus or sulfur deficiency

Abstract The impact on cell wall (CW) of the deficiency in nitrogen (–N), phosphorus (–P) or sulphur (–S), known to impair essential metabolic pathways, was investigated in the economically important fruit species Vitis vinifera L. Using cuttings as an experimental model a reduction in total internode number and altered xylem shape was observed. Under –N an increased internode length was also seen. CW composition, visualised after staining with calcofluor white, Toluidine blue and ruthenium red, showed decreased cellulose in all stresses and increased pectin content in recently formed internodes under –N compared to the control. Using CW-epitope specific monoclonal antibodies (mAbs), lower amounts of extensins incorporated in the wall were also observed under –N and –P conditions. Conversely, increased pectins with a low degree of methyl-esterification and richer in long linear 1,5-arabinan rhamnogalacturonan-I (RG-I) side chains were observed under –N and –P in mature internodes which, in the former condition, were able to form dimeric association through calcium ions. –N was the only condition in which 1,5-arabinan branched RG- content was not altered, as –P and –S older internodes showed, respectively, lower and higher amounts of this polymer. Higher xyloglucan content in older internodes was also observed under –N. The results suggest that impairments of specific CW components led to changes in the deposition of other polymers to promote stiffening of the CW. The unchanged extensin amount observed under –S may contribute to attenuating the effects on the CW integrity caused by this stress. Our work showed that, in organized V. vinifera tissues, modifications in a given CW component can be compensated by synthesis of different polymers and/or alternative linking between polymers. The results also pinpoint different strategies at the CW level to overcome mineral stress depending on how essential they are to cell growth and plant development