Monitoring of water from the underground to the tree: first results with a new sap extractor on a riparian woodland

Riparian woodlands are characterized by variable hydrological conditions. Following the mapping of the complex underground water circulation of the wetlands, we studied the water uptake by trees. Although there are numerous analytical techniques available to monitor the water origin and water fluxes, no rapid technique for the extraction of xylem sap exists on the market. For this reason we designed and built a unique machine able to extract sap directly in the field from wood cores in a few minutes. A short description of the machine and its performance is given, prior to reporting the first experimental results obtained in a young riparian woodland along the Garonne River. The results compare the vertical water profile of the soil and the corresponding xylem sap at different roots horizons and in the trunk

Product formula for p-adic epsilon factors

Let X be a smooth proper curve over a finite field of characteristic p. We prove a product formula for p-adic epsilon factors of arithmetic D-modules on X. In particular we deduce the analogous formula for overconvergent F-isocrystals, which was conjectured previously. The p-adic product formula is the equivalent in rigid cohomology of the Deligne-Laumon formula for epsilon factors in l-adic \'etale cohomology (for a prime l different from p). One of the main tools in the proof of this p-adic formula is a theorem of regular stationary phase for arithmetic D-modules that we prove by microlocal techniques.Comment: Revised version: some proofs and constructions detailed, notation improved, index of notation added ; 88 page

Value-Relevance of the Outside Corporate Governance Information: a Canadian Study

This study examines whether the corporate governance rankings published by The Globe and Mail, a reputed national Canadian newspaper, are reflected in the values that investors accord to firms. A sample of 796 observations on 289 Canadian companies from 2002-2005 inclusively was analyzed using a price model (Cazavan-Jeny and JeanJean, 2006). Results suggest that the corporate governance rankings published by this market information intermediary are related not only to firm value, but also to accounting results. Thus, the relationship between corporate governance scores and market capitalization can take two forms. First, there may be a direct relationship due to investor interest in good governance practices. Second, there may be an indirect relationship due to the impact of good governance practices on the firms' accounting results. The results of this study should be useful for accounting practitioners and the various organizations involved in the regulation of corporate governance practices and the standardization of relevant data elements.Corporate governance; Financial market; Corporate governance rankings; Information intermediary; Investors; Research paper

On the center of the ring of differential operators on a smooth variety over \bZ/p^n\bZ

We compute the center of the ring of PD differential operators on a smooth variety over \bZ/p^n\bZ confirming a conjecture of Kaledin. More generally, given an associative algebra $A_0$ over \bF_p and its flat deformation $A_n$ over \bZ/p^{n+1}\bZ we prove that under a certain non-degeneracy condition the center of $A_n$ is isomorphic to the ring of length $n+1$ Witt vectors over the center of $A_0$.Comment: 16 page

The use of the stable oxygen isotope (18O) to trace the distribution and uptake of water in riparian woodlands

Streamside vegetation forming narrow "corridors" in temperate regions, is typically dominated by deciduous tree species reflecting strong influences by human activities. Riparian woodlands depend on hydrological resources and have to adapt to rapid changes in water levels and soil moisture conditions. Three main water sources are typically present in the riparian zone: river water originating in the mountains, ground water and rainfall. Stable isotopes, such as oxygen-18, are useful tools which allow for water movement to be traced within the riparian zone and which help to identify water sources utilised by the trees growing in these areas

A Fast Algorithm for Computing the p-Curvature

We design an algorithm for computing the $p$-curvature of a differential system in positive characteristic $p$. For a system of dimension $r$ with coefficients of degree at most $d$, its complexity is \softO (p d r^\omega) operations in the ground field (where $\omega$ denotes the exponent of matrix multiplication), whereas the size of the output is about $p d r^2$. Our algorithm is then quasi-optimal assuming that matrix multiplication is (\emph{i.e.} $\omega = 2$). The main theoretical input we are using is the existence of a well-suited ring of series with divided powers for which an analogue of the Cauchy--Lipschitz Theorem holds.Comment: ISSAC 2015, Jul 2015, Bath, United Kingdo

Dieudonne crystals and Wach modules for p-divisible fgroups

Let $k$ be a perfect field of characteristic $p>2$ and $K$ an extension of $F=\mathrm{Frac} W(k)$ contained in some $F(\mu_{p^r})$. Using crystalline Dieudonn\'e theory, we provide a classification of $p$-divisible groups over $\mathscr{O}_K$ in terms of finite height $(\varphi,\Gamma)$-modules over $\mathfrak{S}:=W(k)[[u]]$. Although such a classification is a consequence of (a special case of) the theory of Kisin--Ren, our construction gives an independent proof and allows us to recover the Dieudonn\'e crystal of a $p$-divisible group from the Wach module associated to its Tate module by Berger--Breuil or by Kisin--Ren

Mirada al judaisme europeu actual : aproximació sociodemogràfica i sociològica

L'aproximació sociològica a la judaïcitat observable i autodefinida d'Europa no és gaire fàcil, ja que no representa una entitat homogènia i reductible a un model (com podia ser el cas fa unes quantes dècades a Europa o en àrees de gran població jueva com el Magrib, per exemple). Ben al contrari: és contrastada i desigual en els diferents països que componen aquesta realitat geopolítica, i a més majoritàriament cristiana; i també es tracta d'una realitat mòbil, tant des del punt de vista geogràfic com històric (el canvi ha estat constant durant tot el segle XX). En aquestes pàgines intentarem fer una ullada a la població jueva d'Europa a principis d'aquest segle XXI, començant per una incursió en la demografia i en la repartició geogràfica que ens permetrà d'apreciar la davallada numèrica de la judaïcitat europea. Seguidament, els indicadors socioculturals d'evolució i de canvi ens ajudaran a comprendre l'evolució en els hàbits de vida dels jueus. I finalment, ens acostarem al que pot representar avui en dia el component judaic de la identitat entre els jueus europeus.A sociological approach to an observable, self-defined Jewry in Europe is not simple because this Jewry is not represented by an homogenous entity, nor can it be reduced to any one model (as was the case in Europe several decades ago, or in the large Jewish populations in, for example, North Africa.) Indeed, on the contrary, the present-day Jewry is full of contrasts and is unevenly distributed in the different countries which make up this geopolitical and largely Christian part of the world that is the new Europe. From a geographical, historical and socio-religious point of view it is also mobile (this change was constant throughout the last century). In the following pages we offer an insight into the Jewish European population, at this, the beginning of the 21st century. We start referring to the demographic population and geographical distribution which will help us to understand the decline in the European Jewry. We will then look at the socio-cultural indicators of change and development to better understand the part these play in the Jewish way of life. To conclude, we will attempt to assess the survival of and future of Judaism in Europe.La aproximación sociológica a la judaicidad observable y autodefinida de Europa no es fácil, ya que no representa una entidad homogénea y reductible a un modelo (como podía ser el caso hace unas décadas en Europa o en zonas de gran población judía como el Magreb, por ejemplo). Al contrario: es contrastada y desigual en los diferentes países que componen esta realidad geopolítica y además mayoritariamente cristiana. También se trata de una realidad móvil, tanto desde el punto de vista geográfico como histórico (el cambio fue constante durante todo el siglo XX). En las siguientes páginas, intentaremos dar una ojeada a la población judía de Europa a principios de este siglo XXI, empezando por una incursión en la demografía y en el reparto geográfico que nos permitirá apreciar el descenso numérico de la judaicidad europea. En segundo lugar, los indicadores socio-culturales de evolución y de cambio ayudarán a entender la evolución en los hábitos de vida de los judíos. Y finalmente, nos asomaremos a lo que pueda representar hoy en día el componente judaico de la identidad entre los judíos europeos