La filière des plantes aromatiques et à parfums à Haïti

Le vétiver , le bigaradier, l'amyris et le limettier sont les principales plantes à huiles essentielles cultivées en Haïti. L'absence de statistique ne permet pas une estimation des superficies exactes consacrées à ces productions. Néanmoins la filière de ces plantes est bien adaptée au pays, son importance socio-économique est réelle dans les campagnes. Les rendements en fruits des limettiers et des bigaradiers dépendent du sol, du climat, de l'âge et des soins apportés aux arbres. La qualité des produits (huiles essentielles et parfums) dépend des méthodes d'extraction et des distilleries. Le rendement est généralement faible. Le circuit de commercialisation est complexe et caractérisé par un grand nombre d'intermédiaires de niveaux sociaux et économiques divers. La France et les Etats Unis sont les plus gros importateurs; les clients sont principalement les parfumeries et les industries agro-alimentaires. La redynamisation de cette filière nécessite la mise en place d'un observatoire économique chargé notamment de surveiller les mécanismes des prix et la rénumération du travail des paysan

Quantum arrival time measurement and backflow effect

The current density for a freely evolving state without negative momentum components can temporarily be negative. The operational arrival time distribution, defined by the absorption rate of an ideal detector, is calculated for a model detector and compared with recently proposed distributions. Counterintuitive features of the backflow regime are discussed.Comment: LATEX, 9 pages, 2 postscript figure

Effect of chromophore-chromophore electrostatic interactions in the NLO response of functionalized organic-inorganic sol-gel materials

In the last years, important non-linear optical results on sol-gel and polymeric materials have been reported, with values comparable to those found in crystals. These new materials contain push-pull chromophores either incorporated as guest in a high Tg polymeric matrix (doped polymers) or grafted onto the polymeric matrix. These systems present several advantages; however they require significant improvement at the molecular level - by designing optimized chromophores with very large molecular figure of merit, specific to each application targeted. Besides, it was recently stated in polymers that the chromophore-chromophore electrostatic interactions, which are dependent of chromophore concentration, have a strong effect into their non-linear optical properties. This has not been explored at all in sol-gel systems. In this work, the sol-gel route was used to prepare hybrid organic-inorganic thin films with different NLO chromophores grafted into the skeleton matrix. Combining a molecular engineering strategy for getting a larger molecular figure of merit and by controlling the intermolecular dipole-dipole interactions through both: the tuning of the push-pull chromophore concentration and the control of TEOS (Tetraethoxysilane) concentration, we have obtained a r33 coefficient around 15 pm/V at 633 nm for the classical DR1 azo-chromophore and a r33 around 50 pm/V at 831 nm for a new optimized chromophore structure.Comment: 10 pages, 11 figures, 1 tabl

ARP2 mutation in a brown mutant of Aspergillus fumigatus leads to a loss of competitivity

Aspergillus fumigatus is the major filamentous fungus colonizing the airways of cystic fibrosis patients (CF). It is usually responsible for a chronic colonization and sometimes for chronic respiratory infections. However, it may also cause severe infections in patients undergoing lung transplantation. The prognosis for these infections still remains uncertain and there is an urgent need for the identification of new antifungal targets. Among the fungal components which have been studied, melanin of the conidial wall was confirmed as an important virulence factor, protecting the fungus against the host immune defences. Using isolates deficient in melanin synthesis because of a mutation in the ALB1 (white isolates) or in the ARP2 gene (brown isolate), we showed that melanin is required for correct assembly of the different layers of the conidial wall and, therefore, for the expression of adhesins and other virulence factors at the conidial surface. Mutations in the ALB1 gene have been shown to result in a marked reduction in virulence of the fungus in a mouse model of disseminated aspergillosis, but nothing is known about the role of the ARP2 gene. We therefore focused our attention on the brown isolate IHEM 15998, mutated in the ARP2 gene, which was recovered from respiratory secretions of a CF patient, but not detected in later samples while chronic colonization by a wild-type (WT) strain of A. fumigatus was observed. In vitro experiments were first conducted, which revealed that mutation in the ARP2 gene resulted in a fitness cost when co-cultivated with the WT strain. Likewise, flow cytometry was used to investigate the oxidative burst response of phagocytes co-incubated with the conidia. Compared to the WT strain, stimulation of neutrophils as well as macrophages was higher with the brown isolate. FITC-labeled conidia were also incubated with human cytokine-induced cultured macrophages, afterward phagocytosis was quantified by flow cytometry, which revealed an increased conidial uptake for the brown isolate. Virulence was studied in immunosuppressed (inhalation of conidia) or immunocompetent mice (intravenous inoculation). Conversely to that observed in immunosuppressed mice, mortality in immunocompetent mice was significantly lower with the brown isolate compared to a WT strain. Together, these results confirmed that the partial deficiency in melanin biosynthesis observed in the ARP2 mutant isolate could be responsible for its lack of competitivity

Testing one-body density functionals on a solvable model

There are several physically motivated density matrix functionals in the literature, built from the knowledge of the natural orbitals and the occupation numbers of the one-body reduced density matrix. With the help of the equivalent phase-space formalism, we thoroughly test some of the most popular of those functionals on a completely solvable model.Comment: Latex, 16 pages, 4 figure

Monetary Policy Rules and Directions of Causality: a Test for the Euro Area

Using a VAR model in first differences with quarterly data for the euro zone, the study aims to ascertain whether decisions on monetary policy can be interpreted in terms of a “monetary policy rule” with specific reference to the so-called nominal GDP targeting rule (Hall and Mankiw, 1994; McCallum, 1988; Woodford, 2012). The results obtained indicate a causal relation proceeding from deviation between the growth rates of nominal gross domestic product (GDP) and target GDP to variation in the three-month market interest rate. The same analyses do not, however, appear to confirm the existence of a significant inverse causal relation from variation in the market interest rate to deviation between the nominal and target GDP growth rates. Similar results were obtained on replacing the market interest rate with the European Central Bank refinancing interest rate. This confirmation of only one of the two directions of causality does not support an interpretation of monetary policy based on the nominal GDP targeting rule and gives rise to doubt in more general terms as to the applicability of the Taylor rule and all the conventional rules of monetary policy to the case in question. The results appear instead to be more in line with other possible approaches, such as those based on post Keynesian analyses of monetary theory and policy and more specifically the so-called solvency rule (Brancaccio and Fontana, 2013, 2015). These lines of research challenge the simplistic argument that the scope of monetary policy consists in the stabilization of inflation, real GDP, or nominal income around a “natural equilibrium” level. Rather, they suggest that central banks actually follow a more complex purpose, which is the political regulation of the financial system with particular reference to the relations between creditors and debtors and the related solvency of economic units

Dark energy as a mirage

Motivated by the observed cosmic matter distribution, we present the following conjecture: due to the formation of voids and opaque structures, the average matter density on the path of the light from the well-observed objects changes from Omega_M ~ 1 in the homogeneous early universe to Omega_M ~ 0 in the clumpy late universe, so that the average expansion rate increases along our line of sight from EdS expansion Ht ~ 2/3 at high redshifts to free expansion Ht ~ 1 at low redshifts. To calculate the modified observable distance-redshift relations, we introduce a generalized Dyer-Roeder method that allows for two crucial physical properties of the universe: inhomogeneities in the expansion rate and the growth of the nonlinear structures. By treating the transition redshift to the void-dominated era as a free parameter, we find a phenomenological fit to the observations from the CMB anisotropy, the position of the baryon oscillation peak, the magnitude-redshift relations of type Ia supernovae, the local Hubble flow and the nucleosynthesis, resulting in a concordant model of the universe with 90% dark matter, 10% baryons, no dark energy, 15 Gyr as the age of the universe and a natural value for the transition redshift z_0=0.35. Unlike a large local void, the model respects the cosmological principle, further offering an explanation for the late onset of the perceived acceleration as a consequence of the forming nonlinear structures. Additional tests, such as quantitative predictions for angular deviations due to an anisotropic void distribution and a theoretical derivation of the model, can vindicate or falsify the interpretation that light propagation in voids is responsible for the perceived acceleration.Comment: 33 pages, 2 figs; v2: minor clarifications, results unchanged; v3: matches the version published in General Relativity and Gravitatio

Self-Calibration of Cluster Dark Energy Studies: Counts in Cells

Cluster number counts can constrain the properties of dark energy if and only if the evolution in the relationship between observable quantities and the cluster mass can be calibrated. Next generation surveys with ~10000 clusters will have sufficient statistics to enable some degree of self-calibration. The excess variance of counts due to the clustering of clusters provides such an opportunity and can be measured from the survey without additional observational cost. It can minimize the degradation in dark energy constraints due to an unknown power law evolution in the mass-observable relation improving constraints on the dark energy equation of state by a factor of 2 or more to sigma(w)=0.06 for a deep 4000 deg2 survey.Comment: 4 pages 2 figures submitted to PR

IL-26 Is Overexpressed in Rheumatoid Arthritis and Induces Proinflammatory Cytokine Production and Th17 Cell Generation

Interleukin-26 (IL-26), a member of the IL-10 cytokine family, induces the production of proinflammatory cytokines by epithelial cells. IL-26 has been also reported overexpressed in Crohn\u27s disease, suggesting that it may be involved in the physiopathology of chronic inflammatory disorders. Here, we have analyzed the expression and role of IL-26 in rheumatoid arthritis (RA), a chronic inflammatory disorder characterized by joint synovial inflammation. We report that the concentrations of IL-26 are higher in the serums of RA patients than of healthy subjects and dramatically elevated in RA synovial fluids compared to RA serums. Immunohistochemistry reveals that synoviolin+ fibroblast-like synoviocytes and CD68+ macrophage-like synoviocytes are the main IL-26-producing cells in RA joints. Fibroblast-like synoviocytes from RA patients constitutively produce IL-26 and this production is upregulated by IL-1-beta and IL-17A. We have therefore investigated the role of IL-26 in the inflammatory process. Results show that IL-26 induces the production of the proinflammatory cytokines IL-1-beta, IL-6, and tumor necrosis factor (TNF)-alpha by human monocytes and also upregulates the expression of numerous chemokines (mainly CCL20). Interestingly, IL-26-stimulated monocytes selectively promote the generation of RORgamma t+ Th17 cells, through IL-1-beta secretion by monocytes. More precisely, IL-26-stimulated monocytes switch non-Th17 committed (IL-23R− or CCR6− CD161−) CD4+ memory T cells into Th17 cells. Finally, synovial fluids from RA patients also induce Th17 cell generation and this effect is reduced after IL-26 depletion. These findings show that IL-26 is constitutively produced by RA synoviocytes, induces proinflammatory cytokine secretion by myeloid cells, and favors Th17 cell generation. IL-26 thereby appears as a novel proinflammatory cytokine, located upstream of the proinflammatory cascade, that may constitute a promising target to treat RA and chronic inflammatory disorders