The Howe-Moore property for real and p-adic groups

We consider in this paper a relative version of the Howe-Moore Property, about vanishing at infinity of coefficients of unitary representations. We characterize this property in terms of ergodic measure-preserving actions. We also characterize, for linear Lie groups or p-adic Lie groups, the pairs with the relative Howe-Moore Property with respect to a closed, normal subgroup. This involves, in one direction, structural results on locally compact groups all of whose proper closed characteristic subgroups are compact, and, in the other direction, some results about the vanishing at infinity of oscillatory integrals.Comment: 25 pages, no figur

Impact du changement d'échelle sur l'étude des causes des feux de forêts du sud-est de la France

International audienceThe Modifiable Areal Unit Problem (MAUP) is a well-known issue relatedto the influence of the spatial support on statistical observations. It occurs whendifferent spatial units making different spatial partitions are used and when the resultingmeasures vary according to those partitions. In this paper, we first draw a stateof the art. Considering the particular problem of (up)scaling, we propose a methodto visualize the sensitivity of the spatial statistics to the support. We test this methodon forest fires in Southern France, handling a sample from the Promethée database.From these data, we try to find the key explanatory variables. The results show thatthe correlation coefficient varies significantly, depending on scale, and that we canselect variables and scales based on this variability. Then we propose two differentways to deal with the MAUP: (i) by using geovisualization to assess and to improvethe robustness of the correlation analysis and to choose the pertinent information thatallows to minimize the sensitivity, (ii) by considering as pertinent the spatial partitionwhich is the farthest one from a random spatial distribution of the independentvariableLe support spatial des données a potentiellement une forte influence sur le traitement statistique des observations. Cette problématique est connue en géographie sous le nom de Modifiable Areal Unit Problem (MAUP). Celle-ci survient lorsque différentes unités surfaciques peuvent être utilisées et que le résultat varie en fonction de ce choix. Dans cet article, nous présentons un état de l'art de ce problème. Considérant un des aspects du MAUP, à savoir l’influence du changement de niveau d’échelle, nous développons une méthode de visualisation de la sensibilité des statistiques à ce problème. Cette méthode est testée sur l’étude des feux de forêt du sud-est de la France, avec des données issues de la base Prométhée, à partir desquelles nous recherchons des variables explicatives. Nos résultats montrent des variations des coefficients de corrélation en fonction des niveaux d’échelle et la possibilité de sélectionner les variables et les niveaux d'échelle en fonction de cette variabilité. Nous proposons deux méthodes : (i) utiliser la visualisation de ces variations afin d’améliorer la robustesse de l’analyse de corrélation en sélectionnant les informations pertinentes selon leur sensibilité au MAUP, (ii) sélectionner un niveau d’échelle pour lequel le résultat est le plus différent possible d’une redistribution spatiale aléatoire de la variable dépendante

Arabidopsis Phyllotaxis Is Controlled by the Methyl-Esterification Status of Cell-Wall Pectins

SummaryPlant organs are produced from meristems in a characteristic pattern. This pattern, referred to as phyllotaxis, is thought to be generated by local gradients of an information molecule, auxin [1–6]. Some studies propose a key role for the mechanical properties of the cell walls in the control of organ outgrowth [7–12]. A major cell-wall component is the linear α-1-4-linked D-GalAp pectic polysaccharide homogalacturonan (HG), which plays a key role in cell-to-cell cohesion [13, 14]. HG is deposited in the cell wall in a highly (70%–80%) methyl-esterified form and is subsequently de-methyl-esterified by pectin methyl-esterases (PME, EC 3.1.1.11). PME activity is itself regulated by endogenous PME inhibitor (PMEI) proteins [15]. PME action modulates cell-wall-matrix properties and plays a role in the control of cell growth [16–18]. Here, we show that the formation of flower primordia in the Arabidopsis shoot apical meristem is accompanied by the de-methyl-esterification of pectic polysaccharides in the cell walls. In addition, experimental perturbation of the methyl-esterification status of pectins within the meristem dramatically alters the phyllotactic pattern. These results demonstrate that regulated de-methyl-esterification of pectins is a key event in the outgrowth of primordia and possibly also in phyllotactic patterning

Pectin methylesterases and Arabidopsis pollen tube growth

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Evaluation of laboratory tests for cirrhosis and for alcohol use, in the context of alcoholic cirrhosis

International audienceLaboratory tests can play an important role in assessment of alcoholic patients, including for evaluation of liver damage and as markers of alcohol intake. Evidence on test performance should lead to better selection of appropriate tests and improved interpretation of results. We compared laboratory test results from 1578 patients between cases (with alcoholic cirrhosis; 753 men, 243 women) and controls (with equivalent lifetime alcohol intake but no liver disease; 439 men, 143 women). Comparisons were also made between 631 cases who had reportedly been abstinent from alcohol for over 60 days and 364 who had not. ROC curve analysis was used to estimate and compare tests' ability to distinguish patients with and without cirrhosis, and abstinent and drinking cases. The best tests for presence of cirrhosis were INR and bilirubin, with areas under the ROC curve (AUCs) of 0.91~\textpm~0.01 and 0.88~\textpm~0.01, respectively. Confining analysis to patients with no current or previous ascites gave AUCs of 0.88~\textpm~0.01 for INR and 0.85~\textpm~0.01 for bilirubin. GGT and AST showed discrimination between abstinence and recent drinking in patients with cirrhosis, including those without ascites, when appropriate (and for GGT, sex-specific) limits were used. For AST, a cut-off limit of 85~units/L gave 90% specificity and 37% sensitivity. For GGT, cut-off limits of 288~units/L in men and 138~units/L in women gave 90% specificity for both and 40% sensitivity in men, 63% sensitivity in women. INR and bilirubin show the best separation between patients with alcoholic cirrhosis (with or without ascites) and control patients with similar lifetime alcohol exposure. Although AST and GGT are substantially increased by liver disease, they can give useful information on recent alcohol intake in patients with alcoholic cirrhosis when appropriate cut-off limits are used

Early liver transplantation for severe alcohol-related hepatitis not responding to medical treatment: a prospective controlled study

peer reviewedBackground: Early liver transplantation for severe alcohol-related hepatitis is an emerging treatment option. We aimed to assess the risk of alcohol relapse 2 years after early liver transplantation for alcohol-related hepatitis compared with liver transplantation for alcohol-related cirrhosis after at least 6 months of abstinence. Methods: We conducted a multicentre, non-randomised, non-inferiority, controlled study in 19 French and Belgian hospitals. All participants were aged 18 years or older. There were three groups of patients recruited prospectively: patients with severe alcohol-related hepatitis who did not respond to medical treatment and were eligible for early liver transplantation according to a new selection scoring system based on social and addiction items that can be quantified in points (early transplantation group); patients with alcohol-related cirrhosis listed for liver transplantation after at least 6 months of abstinence (standard transplantation group); patients with severe alcohol-related hepatitis not responding to medical treatment not eligible for early liver transplantation according to the selection score (not eligible for early transplantation group), this group did not enter any further liver transplantation processes. We also defined a historical control group of patients with severe alcohol-related hepatitis unresponsive to medical therapy and non-transplanted. The primary outcome was the non-inferiority of 2-year rate of alcohol relapse after transplantation in the early transplantation group compared with the standard transplantation group using the alcohol timeline follow back (TLFB) method and a prespecified non-inferiority margin of 10%. Secondary outcomes were the pattern of alcohol relapse, 2-year survival rate post-transplant in the early transplantation group compared with the standard transplantation group, and 2-year overall survival in the early transplantation group compared with patients in the not eligible for early transplantation group and historical controls. This trial is registered with ClinicalTrials.gov, NCT01756794. Findings: Between Dec 5, 2012, and June 30, 2016, we included 149 patients with severe alcohol-related hepatitis: 102 in the early transplantation group and 47 in the not eligible for early transplantation group. 129 patients were included in the standard transplantation group. 68 patients in the early transplantation group and 93 patients in the standard transplantation group received a liver transplant. 23 (34%) patients relapsed in the early transplantation group, and 23 (25%) patients relapsed in the standard transplantation group; therefore, the non-inferiority of early transplantation versus standard transplantation was not demonstrated (absolute difference 9·1% [95% CI –∞ to 21·1]; p=0·45). The 2-year rate of high alcohol intake was greater in the early transplantation group than the standard transplantation group (absolute difference 16·7% [95% CI 5·8–27·6]) The time spent drinking alcohol was not different between the two groups (standardised difference 0·24 [95% CI −0·07 to 0·55]), but the time spent drinking a large quantity of alcohol was higher in the early transplantation group than the standard transplantation group (standardised difference 0·50 [95% CI 0·17–0·82]). 2-year post-transplant survival was similar between the early transplantation group and the standard transplantation group (hazard ratio [HR] 0·87 [95% CI 0·33–2·26]); 2-year overall survival was higher in the early transplantation group than the not eligible for early transplantation group and historical controls (HR 0·27 [95% CI 0·16–0·47] and 0·21 [0·13–0·32]). Interpretation: We cannot conclude non-inferiority in terms of rate of alcohol relapse post-transplant between early liver transplantation and standard transplantation. High alcohol intake is more frequent after early liver transplantation. This prospective controlled study confirms the important survival benefit related to early liver transplantation for severe alcohol-related hepatitis; and this study provides objective data on survival and alcohol relapse to tailor the management of patients with severe alcohol-related hepatitis. Funding: The present study has been granted by the French Ministry of Health—Programme Hospitalier de Recherche Clinique 2010

Impact of the Scale on Several Metrics Used in Geographical Object-Based Image Analysis: Does GEOBIA Mitigate the Modifiable Areal Unit Problem (MAUP)?

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Relationship between Object-Based Image Analysis and Modifiable Areal Unit Problem

International audienceGEOBIA has to deal with several issues which can be considered as “burning research questions, research need and outlook” as expressed in the book edited by T. Blaschke, S. Lang and G. J. Hay in 2008 [2]. Related to quality in a general meaning, one of them is the reliability of the statistics used to find the correct objects boundaries, that finally reflects on objects comparability in a given spatial partition. Indeed, since the number of pixels can strongly change at a given scale, and due to the major advantage of GEOBIA to find objects with different size and shape, any statistical indice describing those objects must be used with a particular caution. Contrary to what is claimed in the chapter 1.4 of this book, “object-based approaches represent viable solutions to mitigate the modifiable areal unit problem (MAUP, Openshaw, 1984 [8]), since they focus analysis on meaningful geographical objects rather than arbitrary defined spatial units i.e., individual pixels” (p. 81), or “image-objects are less sensitive to MAUP than units that do not keep a correspondence with the structure of the phenomenon under study” (p. 83), GEOBIA is neither a solution to the MAUP, nor a way to reduce its effects

Impact of the Scale on Several Metrics Used in Geographical Object-Based Image Analysis: Does GEOBIA Mitigate the Modifiable Areal Unit Problem (MAUP)?

Using two GEOBIA (Geographical Object Based Image Analysis) algorithms on a set of segmented images compared to grid partitioning at different scales, we show that statistical metrics related to both objects and sets of pixels are (more or less) subject to the Modifiable Areal Unit Problem. Subsequently, even in a same spatial partition, there may be a bias in statistics describing the objects due to some size effect of the pixel samples. For instance, pixels homogeneity based on Grey Level Cooccurrence Matrices (GLCM), Landscape Shape Index, entropy, object compacity, perimeter/area ratio are studied according to scale. The approach consists in studying the behavior of a given statistical metrics through scales and to compare the results on several image segmentations, according to different partitioning processes, from GEOBIA (Baatz & Schäpe algorithm and Self Organizing Maps) or using reference grids. We finally discuss about the relationship between GEOBIA metrics and scale. By analysing object shape and pixels composition from different metrics points of views, we show that GEOBIA does not always mitigate the Modifiable Areal Unit Problem