Variabilités spatiales et temporelles de la qualité physico-chimique et des invertébrés pélagiques des eaux de la retenue hydroélectrique de Petit Saut (Guyane française).

Le bassin versant du fleuve Sinnamary est situé en Guyane française, au nord du continent sud américain, en zone néo-tropicale. Il s'étend entre 4 et 5°de latitude Nord et entre 52°50' et 53°30' de longitude Ouest. En 1994, la mise en eau du barrage hydroélectrique construit sur le site de Petit Saut occasionne l'ennoiement de 365 km2 de forêt primaire. Le remplissage s'effectue en 18 mois, et la demande en oxygène dissous nécessaire à la dégradation de la matière organique est telle qu'en quelques jours la masse d'eau se stratifie en un épilimnion oxygéné et un hypolimnion anoxique. Représentant quelques centimètres en 1994, l'épilimnion s'épaissit progressivement jusqu'en 1998. Depuis, cette progression s'est nettement ralentie et l'épilimnion oscille autour d'une valeur moyenne de 5 à 6 mètres. Il abrite la plus grande partie du zooplancton pélagique. L'hypolimnion est anoxique et riche en éléments réduits. Le zooplancton s'est rapidement installé avec des rotifères, des cladocères et des copépodes. Des ostracodes et des Chaoboridae y sont désormais associés. La retenue présente une zonation longitudinale, de la tête de la retenue vers la queue, aussi bien en termes de densités que de composition des peuplements. De même, il existe une zonation transversale, notamment marquée par un gradient croissant de la conductivité de l'axe vers les berges. Ces ressources endogènes ainsi que des apports complémentaires (végétaux, invertébrés terrestres, détritus…) sont utilisées par la faune ichtyque qui a su s'adapter au changement du milieu. Le temps de rétention des eaux qui fluctue saisonnièrement en fonction des pluies semble être le facteur prépondérant de variabilité pour la qualité physico-chimique des eaux et les communautés biologiques.The Sinnamary River is located in a neotropical zone, in French Guiana, in the northern part of South America. Its flood basin extends between 4° and 5° N latitude and 52°50' and 53°30' W longitude. The river is found in an equatorial climate, and is influenced by its proximity to the ocean. The temperature varies little, with an average of 25°C for the least hot month (January) and 27°C for the hottest month (October). The humidity is always high and averages more than 90%. The Sinnamary River bed is broad (> 50 m), and runs from south to north for approximately 240 km with a very weak slope (0.0003%). Petit Saut, the site of the hydroelectric dam, is located approximately 60 km from the mouth of the river, with a flood basin area of 5927 km2 and an average flow rate 260 m3 /s.The construction of the hydroelectric dam at Petit Saut in 1994 resulted in the flooding of 365 km2 of primary forest in a neotropical zone (the average depth of the reservoir is 11 m). The dam reservoir was filled over a period of 18 months and the amount of dissolved oxygen necessary for the organic matter to decompose was such that, in a matter of days, the body of water became stratified into an oxygenated epilimnion and an anoxic hypolimnion. Only centimeters thick in 1994, by 1998 the epilimnion had progressively expanded. Since that time it has varied between an average thickness of 5 to 6 m and is home to various biological communities. The hypolimnion is anoxic and rich in reduced compounds (nitrogen and phosphorus minerals, dissolved organic matter, particles, metals and gas). The products of the degradation of the flooded organic matter, which still prevail at the bottom, are gradually relayed towards surface by phenomena of dilution, hydrolysis and oxidation.The river fauna disappeared from the reservoir and was replaced after a few weeks by various pelagic fauna. The zooplanktonic communities, primarily confined to the epilimnion, were quickly settled with rotifera, cladocera and copepoda. Initially dominated by detritivores (Bosminidae) and Cyclopidae from February to May 1994, the settlements diversified with phytophagous zooplankton (Calanidae and Daphniidae) when the phytoplankton developed. This procession was quickly accompanied by Sididae, which has dominated the cladocera since mid-1996 and by ostracoda, which were particularly abundant from 1995 to 1997. Carnivores such as Chaoboridae larvae were also present in Petit Saut reservoir. In contrast to the other zooplankton species, Chaoboridae larvae occupy the entire water column. As a result of great quantities of organic matter available at the time the reservoir was filled, the biomasses were initially large and have gradually decreased with decreasing nutrient concentrations.The reservoir was not homogeneous in terms of zooplankton density, with a longitudinal zonation from the dam towards the upstream tail. In the tail, fauna were identical to those of the river. In the lake zone, phytophagous Calanidae dominated. In the intermediate zone, known as the zone of transition, the zooplankton biomass normalized to the volume of oxygenated water was less important than in the lake zone. Cyclopidae, well represented at the time of the reservoir colonization, dominated the communities in the transition zone. This distribution of zooplankton was likely connected with the dissolved oxygen concentrations, as well as with the quantities of phytoplankton and bacterio-chlorophyll. Similarly, there was a transverse zonation, marked by an increase in conductivity towards the reservoir banks. The density of the communities varied seasonally. The highest biomasses were measured along the central axis at the time of high waters and close to the banks at the time of low waters.The time of water retention, which fluctuates according to the rainy season, seemed to be the factor dominating the physicochemical water quality variability and the biological communities. The rainy season is characterized by the dilution of various elements (e.g., conductivity is reduced). Conversely, during the dry season, the elements concentrate again in the water mass. Nevertheless, the peaks of pelagic invertebrate density were observed during times of high waters, when the hydraulic conditions favour the exchanges between the hypolimnion (anoxic and rich in nutritive elements) and the epilimnion (oxygenated and very low in nutrients).These endogenous resources, as well as complementary contributions (vegetation, invertebrate, terrestrial, refuse), are used by the fish fauna, which adapted to the change in their environment. Predation contributes to the seasonal evolution of the zooplankton. Predation pressure was more important in the dry season than in the rainy season

O estudo das cadeias produtivas para o desenvolvimento da agricultura familiar.

Face ao contexto de globalizacao da economia, os orgaos publicos e privados de pesquisa e de desenvolvimento agricola estao recorrendo aos estudos das cadeias produtivas como subsidios e pontos de partida para responder melhor as demandas dos agentes economicos. Este trabalho apresenta alguns resultados de tres estudos de cadeias (uva de mesa, melao e leite), destacando o papel da agricultura familiar no negocio agricola, fornecendo dados qualitativos e quantitativos quanto a competitividade no quadro do processo e sua integracao nos mercados nacional e internacional. Alem de confirmar a importancia social e economica da agricultura familiar, esses estudos trazem elementos de reflexoes sobre a articulacao e a complementaridade dos estudos dos sistemas de producao com os estudos das cadeis produtivas

Cadeia produtiva de melão do Nordeste.

O estudo da cadeia produtiva do melao na regiao Nordeste se baseou na metodologia do diagnostico rapito dos circuitos de comercializacao, na metodologia "Dephi", no levantamento de dados estatisticos, em entrevistas com os principais agentes envolvidos, do produtor ate o consumidor, em vistas de campo e as feiras. No Brasil, a producao de melao se concentra na regiao Nordeste, de modo especial nos Estados do RN, BA, CE, PE e PB, os quais, conjuntamente, tem respondido, nos ultimos anos, por mais de 89% da oferta de melao, e em 1996, totalizaram uma area plantada de 9.800 hectares. Dentro da estrutura produtiva, ocorre uma diferenciacao do perfil dos produtores de melao em grandes e medias empresas, pequenas empresas e pequenos e medios produtores. Observou-se que o polo RN/CE se caracteriza pela existencia de grandes e medias empresas com modernas tecnologias, equipamentos importados para irrigacao, fertirrigacao, processamento de embalagem, classificacao de frutos, alta produtividade apresenta alta competitividade, jnto aos mercados interno e externo. As grandes e medias empresas sao responsaveis por mais de 90% da producao do polo RN/CE. Cerca de 80% das pequenas empresas tambem estao situadas neste polo com o custo de producao menor, pois nao apresentam os custos administrativos das grandes e medias empresas. Os pequenos e medios produtores representam a maioria dos envolvidos com a producao do melao no Vale do Sao Francisco. Estes frequentemente plantam em parceria com comerciantes de insumos ou com atravessadores e possuem baixo nivel tecnologico. A producao de melao do Nordeste, basicamente esta voltada, em mais de 50%, para o mercado interno, mesmo nas grandes empresas. Como atributo de mercado, e grande a preferencia por "frutos doces"(alto teor de solidos soluveis, brix). As organizacoes de comercializacao tem acumulado a maior fracao do capital circulante no agronegocio do melao (85%). Ha como excecao o caso das grandes empresas, que dispoem de infra-estrutura de comercializacao. Os principais pontos de estrangulamento no processo produtivo sao: o uso inadequado de tecnologias; a falta de cultivares com boa resistencia as pragas e as doencas e de boa qualidade comercial; a ausencia do manejo integrado de pragas; a ausencia de manejo adequado na pos-colheita; a ausencia de organizacao dos pequenos e medios produtores, principalmente para comercializacao e aquisicao de financiamentos para custeios e investimentos; a instabilidade do mercado; as pessimas condicoes do sistema rodoviario e a falta de padronizacao da producao para o mercado interno. Estes aspectos permitiram a definicao das demandas tecnologias e nao tecnologicas, a serem implementadas a outro, medio e longo prazos

The short-chain fatty acid acetate reduces appetite via a central homeostatic mechanism

Increased intake of dietary carbohydrate that is fermented in the colon by the microbiota has been reported to decrease body weight, although the mechanism remains unclear. Here we use in vivo11C-acetate and PET-CT scanning to show that colonic acetate crosses the blood–brain barrier and is taken up by the brain. Intraperitoneal acetate results in appetite suppression and hypothalamic neuronal activation patterning. We also show that acetate administration is associated with activation of acetyl-CoA carboxylase and changes in the expression profiles of regulatory neuropeptides that favour appetite suppression. Furthermore, we demonstrate through 13C high-resolution magic-angle-spinning that 13C acetate from fermentation of 13C-labelled carbohydrate in the colon increases hypothalamic 13C acetate above baseline levels. Hypothalamic 13C acetate regionally increases the 13C labelling of the glutamate–glutamine and GABA neuroglial cycles, with hypothalamic 13C lactate reaching higher levels than the ‘remaining brain’. These observations suggest that acetate has a direct role in central appetite regulation

Asthma severity in school-children and the quality of life of their parents

Background . The everyday management of a child with asthma can affect the parent\u27s quality of life. Past studies which examined the effects of asthma characteristics of the child on parental quality of life have not reached a consensus over findings. Few studies examine parent characteristics such as mental health and sociodemographics on the quality of life of parents of asthmatic children. Purpose . To examine the effect of asthma severity of school-children and sociodemographic characteristics onthe caregiver\u27s quality of life. It also investigates whether agreement exists between the caregiver\u27s perception of asthma severity and physician-diagnosed asthma severity. Methodology . Parents of asthmatic children (n=101) were identified in the waiting room at an outpatient pediatric pulmonology clinic in Las Vegas and were given three questionnaires: (1) the Paediatric Caregiver\u27sQuality of Life Questionnaire (PACQLQ), (2) asthma severity questionnaire, (3) sociodemographics questionnaire. Spearman\u27s correlation (rho), analysis of variance (ANOVA), linear and multivariate regression, Chi-square, independent t-tests, Kendall tau rank correlation coefficient, and descriptive analyses were performed. Results . A significant negative correlation was found between overall asthma severity, based on the 2007 NAEPP guidelines, and mean activity limitation scores (rho= .400, p \u3c .001), mean emotional function scores (rho= -.258, p \u3c .001), and mean total of PACQLQ scores (rho= -.342, p \u3c .001). A significant moderate, negative correlation was found between PACQLQ scores and asthma day symptoms, asthma night symptoms, and asthma exercise symptoms. No significant relationship was found between pulmonary function testing (PFT) scores and PACQLQ scores. Parents of children with mild intermittent asthma had higher mean PACQLQ scores, followed by those with mild persistent asthma, moderate persistent asthma, and lastly, severe persistent asthma who had the lowest PACQLQ scores. Predictors of better quality of life included increased income. Predictors of worse overall quality of life included increased hospitalization days, increased ER visits, increased school days missed, and increased work days missed. Using independent t-tests, better scores were found for those who were not of Black or African ethnicity, were able to pay for health costs, owned a home or a car, and perceived their child\u27s asthma as under control. Implications for nursing . Measuring parental quality of life allows nurse researchers to measure the burdenparents experience in caring for their child in order to develop more effective asthma programs that emphasize adherence to medical treatment. Other factors that can influence caregiver quality of life and other measurement tools for quality of life should be explored

Nut production in Bertholletia excelsa across a logged forest mosaic: implications for multiple forest use

Although many examples of multiple-use forest management may be found in tropical smallholder systems, few studies provide empirical support for the integration of selective timber harvesting with non-timber forest product (NTFP) extraction. Brazil nut (Bertholletia excelsa, Lecythidaceae) is one of the world’s most economically-important NTFP species extracted almost entirely from natural forests across the Amazon Basin. An obligate out-crosser, Brazil nut flowers are pollinated by large-bodied bees, a process resulting in a hard round fruit that takes up to 14 months to mature. As many smallholders turn to the financial security provided by timber, Brazil nut fruits are increasingly being harvested in logged forests. We tested the influence of tree and stand-level covariates (distance to nearest cut stump and local logging intensity) on total nut production at the individual tree level in five recently logged Brazil nut concessions covering about 4000 ha of forest in Madre de Dios, Peru. Our field team accompanied Brazil nut harvesters during the traditional harvest period (January-April 2012 and January-April 2013) in order to collect data on fruit production. Three hundred and ninety-nine (approximately 80%) of the 499 trees included in this study were at least 100 m from the nearest cut stump, suggesting that concessionaires avoid logging near adult Brazil nut trees. Yet even for those trees on the edge of logging gaps, distance to nearest cut stump and local logging intensity did not have a statistically significant influence on Brazil nut production at the applied logging intensities (typically 1–2 timber trees removed per ha). In one concession where at least 4 trees ha-1 were removed, however, the logging intensity covariate resulted in a marginally significant (0.09) P value, highlighting a potential risk for a drop in nut production at higher intensities. While we do not suggest that logging activities should be completely avoided in Brazil nut rich forests, when a buffer zone cannot be observed, low logging intensities should be implemented. The sustainability of this integrated management system will ultimately depend on a complex series of socioeconomic and ecological interactions. Yet we submit that our study provides an important initial step in understanding the compatibility of timber harvesting with a high value NTFP, potentially allowing for diversification of forest use strategies in Amazonian Perù

Managing the co-creation of accessible and inclusive family recreation retail encounters: A critical incident analysis

Entertainment and recreation are pull factors for retail shopping malls and supercentres. For families in particular, recreation is a relevant part of their retail visits. However, families with children with disabilities (FCwD) continue to face access challenges in retail service environments. In this paper, we empirically explore how a value co-creation process undertaken with FCwD can enhance their perception of an accessible and inclusive family recreation retail visit. Our findings are based on a collaborative research project conducted in 2019 with a major shopping mall in the city of Barcelona, Spain. The methodology consisted of focus groups with stakeholders, ethnographic techniques and interviews with 20 FCwD using a constant comparative technique. The research design included two studies: Study 1, on the design of accessible and inclusive recreation retail encounters for FCwD, and Study 2, on the design of accessible and inclusive recreation retail encounters with FCwD. Using critical incident techniques (CIT), we found that the families perceived the recreation retail encounters in Study 2 to be more inclusive and accessible. From this research, we provide retail managers with recommendations for the successful design of inclusive family recreation retail opportunities in shopping malls

Rationalizing the Amplified Spontaneous Emission Mechanism in CsPbBr3 Perovskite Nanocrystals Films by means of Optical Gain Measurements

With their exceptional optoelectronic properties, CsPbBr3 perovskite nanocrystals (NCs) are promising materials for light-emitting devices. Elucidating their stimulated emission mechanisms is fundamental to grasp the limitations hindering their use as electrically pumped lasers. In particular, two questions remain open: why the Amplified Spontaneous Emission (ASE) band is significantly shifted from the fluorescence one, and why the former seems to suddenly emerge from, and coexist with, the latter. Here, these questions are addressed through experimental ASE measurements, combined with numerical simulations and a comprehensive assessment of the performance of different analytical expressions used in the literature to retrieve the optical gain from these experiments. This multi-facet study shows that the ASE behavior in CsPbBr3 NCs thin films stems from four distinctive processes: reabsorption due to a large overlap between the absorption and fluorescence spectra, a strong contribution of excited state absorption within the fluorescence window, the excitation of differently polarized waveguide modes, and the coexistence of short- and long-lived localized excitons. The results in this work delineate the best practices to analyze the optical gain in perovskite samples, help to understand their ASE mechanisms, and provide insights to boost their lasing efficiency