Minimal model for active nematics: quasi-long-range order and giant fluctuations

We propose a minimal microscopic model for active nematic particles similar in spirit to the Vicsek model for self-propelled polar particles. In two dimensions, we show that this model exhibits a Kosterlitz-Thouless-like transition to quasi-long-range orientational order and that in this non-equilibrium context, the ordered phase is characterized by giant density fluctuations, in agreement with the predictions of Ramaswamy {\it et al.} [Europhys. Lett. {\bf 62}, 196 (2003)].Comment: Submitted to Phys. Rev. Lett. 4 pages, 4 figure

Frozen spatial chaos induced by boundaries

We show that rather simple but non-trivial boundary conditions could induce the appearance of spatial chaos (that is stationary, stable, but spatially disordered configurations) in extended dynamical systems with very simple dynamics. We exemplify the phenomenon with a nonlinear reaction-diffusion equation in a two-dimensional undulated domain. Concepts from the theory of dynamical systems, and a transverse-single-mode approximation are used to describe the spatially chaotic structures.Comment: 9 pages, 6 figures, submitted for publication; for related work visit http://www.imedea.uib.es/~victo

Madagascar, politique forestière : Bilan 1990 – 2013 et propositions

Les auteurs dressent une rétrospective de la mise en oeuvre de la politique environnementale et forestière 1990-2013 qui repose sur quatre lois, à savoir la Charte de l’environnement (loi 90-033 du 21 décembre 1990), la GELOSE (loi 96-025 du 30 septembre 1996), la loi forestière (loi 97-017 du 8 août 1997) et le Code des Aires protégées (loi 2001-005 du 11 février 2003). Vingt ans après l’adoption de la Nouvelle Politique Forestière, un bilan est possible. Ces textes ont connu un début d’application avec un bilan décevant dans un contexte surtout marqué par une extension de la superficie des aires protégées. Dans le même temps, des évolutions importantes et positives sont apparues. Avec la  décentralisation, l’.é.tat de droit s’est construit quotidiennement au niveau des communes à travers les guichets fonciers, les contrats de transferts de gestion et les expériences positives de contrôle forestier décentralisé. Ont également été réalisées des expériences concluantes de valorisation économique des ressources forestières exploitées dans le cadre des transferts de gestion : bois d’oeuvre, bois énergie, raphia, huiles essentielles. Il est donc possible, en novembre 2013, d’envisager de façon réaliste une relance vigoureuse de la politique forestière en tenant compte des invariants comme les faibles effectifs de l’administration et la modicité des financements extérieurs aléatoires. Il est d’abord nécessaire de  répondre aux urgences : décrets à publier et à appliquer ; mise en oeuvre  systématique des avantages économiques prévus pour les communautés de base signataires des contrats de transfert de gestion. . . . ; sécurisation des espaces communs sous contrats de transfert de gestion. Il faut enfin et surtout faire de la valorisation conservatoire des ressources des produits forestiers ligneux et non ligneux le moteur du développement local.This paper presents a retrospective on the implementation of Malagasy environmental and forest policy between 1990 and 2013 on the basis of four laws, namely the Environmental Charter (Law 90-033 of 21 December 1990), GELOSE (Law 95-025 of 30 September 1996), the Forest Law (Law 97-017 of 8 August 1997) and the Protected Areas Code (Law 2001-005 of 11 February 2003). Twenty years after the adoption of the new forest policy, an assessment is possible. These texts have started to be applied but with disappointing results, primarily centered on the increase of protected area coverage. Nevertheless, important and positive changes have occurred. With decentralization, the reach of the law has increased day by day in communes through land offices, management transfer contracts, and positive experiences of decentralized forest control. Successful experiences of the economic valorization of forest resources (such as timber, fuelwood, raphia palm and essential oils), have also been gained within management transfers. It is therefore possible, in December 2013, to realistically envisage a strong revival of forest policy, even  accounting for permanent constraints such as the weakness of the forest administration and the uncertainty of external funding. It is first necessary to respond to urgent needs; to publish and apply un-finalized decrees, to systematically establish the economic benefits anticipated for the  community signatories of management transfer contracts, and to secure common property areas within management transfers. Most importantly, the sustainable economic valorization of woody and non - woody forest products should be used as a tool for local development

When Madagascar produced natural rubber: a brief, forgotten yet informative history.

From 1891 to 1914, Madagascar, like other western African countries, was a production zone for forest rubber destined for export to Europe when Asian plantations where not yet sufficiently developed . Numerous species endemic to the forests of the three major Malagasy ecosystems were exploited, often with a view to maximising short term productivity without any consideration for the sustainable management of the resource. This episode represents one of the first cases of industrial exploitation of Madagascar's biological resources. Although Madagascar occupies a modest position on the world rubber market at that time, the exploitation of rubber bore major consequences for the island's forestry resources and, moreover, influenced the vision and discourse of scientists and politicians concerning their management. It was one of the factors triggering awareness of the value of Madagascar's biodiversity and the threat to which it might be exposed through poorly-controlled human activity. As a result, highly repressive and forcible legislation was introduced aimed at containing the activity practiced by local populations considered to be mostly to blame. But from the early days of French colonial rule, naturalists judged the outcomes of political decisions too weak to offer any guarantee of an effective defence. They responded by adopting an intentionally alarmist and catastrophist discourse with the object of provoking a reaction from the politicians, considered too lax. This discourse, in fact, took an about-turn from 1942-45 when the war effort led to a revitalisation of the Malagasy rubber sector as Asian production was mainly out of reach. A second consequence came in 1927 with the creation of a network of protected areas managed by naturalists, making Madagascar at that time, a pioneer in Africa. There was a simultaneous flurry of activity to promote the domestication of Malagasy rubber species, combined with the introduction of new species with high potential (Hevea brasiliensis, Castilloa elastica). However, with the emergence of far more profitable Asian rubber, all attempts at cultivation in Madagascar were abandoned when exploitation ceased to be profitable, and thus the Malagasy forests were redeemed. This episode demonstrates how it was in fact economic reality, by condemning an unprofitable sector, that was the real vehicle by which the survival of Malagasy rubber species was secured, and not the naturalists' discourse, nor the creation of protected zones, nor the promulgation of repressive legislations. This case study is of more than purely historical interest, in that it still has currency where, for example, the exploitation of Prunus africana is concerned

Caspase-generated fragment of the Met receptor favors apoptosis via the intrinsic pathway independently of its tyrosine kinase activity

The receptor tyrosine kinase Met and its ligand, the hepatocyte growth factor, are essential to embryonic development, whereas the deregulation of Met signaling is associated with tumorigenesis. While ligand-activated Met promotes survival, caspase-dependent generation of the p40 Met fragment leads to apoptosis induction – hallmark of the dependence receptor. Although the survival signaling pathways induced by Met are well described, the pro-apoptotic signaling pathways are unknown. We show that, although p40 Met contains the entire kinase domain, it accelerates apoptosis independently of kinase activity. In cell cultures undergoing apoptosis, the fragment shows a mitochondrial localization, required for p40 Met-induced cell death. Fulminant hepatic failure induced in mice leads to the generation of p40 Met localized also in the mitochondria, demonstrating caspase cleavage of Met in vivo. According to its localization, the fragment induces mitochondrial permeabilization, which is inhibited by Bak silencing and Bcl-xL overexpression. Moreover, Met silencing delays mitochondrial permeabilization induced by an apoptotic treatment. Thus, the Met-dependence receptor in addition to its well-known role in survival signaling mediated by its kinase activity, also participates in the intrinsic apoptosis pathway through the generation of p40 Met – a caspase-dependent fragment of Met implicated in the mitochondrial permeabilization process

Improvement of radiology requisition

AbstractPurposeInadequate or incomplete information on radiology requisitions may have a substantial impact on the radiological process. This study aimed to evaluate the impact of standardization and computerization of radiology requisitions on the quality of provided data, satisfaction of hospital staff and access time.MethodsThe impact of requisition support was assessed at each step of the improvement process for inpatients: before (Step 1), after standardization (Step 2) and after computerization of radiology requisition (Step 3). The quality of information provided was assessed by proportion of missing data on MRI and CT requisitions. Satisfaction was assessed by an anonymous auto-questionnaire filled by ordering physicians, radiologists and radiology technicians. Access time was prospectively assessed.ResultsStandardization of radiology requisition resulted in a significant drop in proportion of missing data. Computerization of radiology requisition, based on the single standardized radiology requisition, further improved the quality of information reported on radiology requisitions. The median access time was significantly improved (from 5 to 3days) for the largest provider of CT requisitions.ConclusionsStandardization and computerization have a synergistic effect on the overall quality improvement. Moreover, the computerized provider order entry enables traceability of information, makes communication between radiologists and ordering physicians easier and improves examination planning

Resistant starch reduces large intestinal pH and promotes fecal lactobacilli and bifidobacteria in pigs

Research Areas: Agriculture. Veterinary SciencesABSTRACT - Dietary resistant starch (RS) may have prebiotic properties but its effects on fermentation and the microbial population are inconsistent. This meta-analysis aimed to quantify the relationship between RS type 2 (RS2) and intestinal short-chain fatty acids (SCFA) and pH as well as certain key bacterial taxa for intestinal health in pigs. From the 24 included articles with sufficient information about the animal, and dietary and physiological measurements published between 2000 and 2017, individual sub-data sets for fermentation metabolites, pH, bacterial abundances and apparent total tract digestibility were built and used to parameterize prediction models on the effect of RS2, accounting for inter- and intra-study variability. In addition, the effect of pig's BW at the start of the experiment and duration of the experimental period on response variables were also evaluated using backward elimination analysis. Dietary RS levels ranged from 0% to 78.0% RS, with median and mean RS levels of 28.8% and 210%, respectively. Negative relationships could be established between dietary RS and pH in the large intestine (P < 0.05), with a stronger effect in the mid and distal colon, and feces (R = 0.64 to 0.81; P < 0.001). A dietary level of 15% RS would lower the pH in the proximal, mid-, distal colon and feces by 0.2, 0.6, 0.4 and 0.6 units, respectively. Increasing RS levels, however, did not affect SCFA concentrations in the hindgut, but enhanced the molar proportion of propionate in mid-colon and reduced those of acetate in mid-colon and of butyrate in mid- and distal colon (R-2 = 0.46 to 0.52; P < 0.05). Backward elimination indicated an age-related decrease in mid-colonic propionate proportion and increase in mid- and distal colonic butyrate proportion (P < 0.05), thereby modulating RS2 effects. In feces, increasing RS levels promoted fecal lactobacilli (R-2 = 0.46; P < 0.01) and bifidobacteria (R-2 = 0.57; P < 0.01), whereby the slope showed the need for a minimal RS level of 10% for a 0.5 log unit-increase in their abundance. Best-fit equations further supported that a longer experimental period increased fecal lactobacilli but decreased fecal bifidobacteria (P < 0.05). In conclusion, dietary RS2 seems to effectively decrease digesta pH throughout the large intestine and increase lactic acid-producing bacteria in feces of pigs which may limit the growth of opportunistic pathogens in the hindgut. To achieve these physiologically relevant changes, dietary RS should surpass 10% to 15%.info:eu-repo/semantics/publishedVersio

The Complex Ginzburg-Landau Equation in the Presence of Walls and Corners

We investigate the influence of walls and corners (with Dirichlet and Neumann boundary conditions) in the evolution of twodimensional autooscillating fields described by the complex Ginzburg-Landau equation. Analytical solutions are found, and arguments provided, to show that Dirichlet walls introduce strong selection mechanisms for the wave pattern. Corners between walls provide additional synchronization mechanisms and associated selection criteria. The numerical results fit well with the theoretical predictions in the parameter range studied.Comment: 10 pages, 9 figures; for related work visit http://www.nbi.dk/~martine

Wound-up phase turbulence in the Complex Ginzburg-Landau equation

We consider phase turbulent regimes with nonzero winding number in the one-dimensional Complex Ginzburg-Landau equation. We find that phase turbulent states with winding number larger than a critical one are only transients and decay to states within a range of allowed winding numbers. The analogy with the Eckhaus instability for non-turbulent waves is stressed. The transition from phase to defect turbulence is interpreted as an ergodicity breaking transition which occurs when the range of allowed winding numbers vanishes. We explain the states reached at long times in terms of three basic states, namely quasiperiodic states, frozen turbulence states, and riding turbulence states. Justification and some insight into them is obtained from an analysis of a phase equation for nonzero winding number: rigidly moving solutions of this equation, which correspond to quasiperiodic and frozen turbulence states, are understood in terms of periodic and chaotic solutions of an associated system of ordinary differential equations. A short report of some of our results has been published in [Montagne et al., Phys. Rev. Lett. 77, 267 (1996)].Comment: 22 pages, 15 figures included. Uses subfigure.sty (included) and epsf.tex (not included). Related research in http://www.imedea.uib.es/Nonlinea