Analysis of potential locations of asteroidal moonlets

In this study, the potential locations of asteroidal small satellites (also called moonlets) with quasi-circular mutual orbit are analyzed. For the motion of the moonlets, only the solar gravity perturbation and the primary's 2nd degree-and-order gravity field are considered. By eliminating of short periodic terms, the dynamical behavior of the Hamiltonian for the moonlets is investigated. The observational data of some high size ratio binary asteroids show that the orbits of the moonlets lie close to the classical Laplace equilibria, which reach global minimum values of the Hamiltonian. It is found that tides or Yarkovsky effects alone cannot account for the reason why the orbits of asteroidal moonlets are not exactly at the classical Laplace equilibria. The analysis in this study is expected to provide useful information for the potential locations of asteroidal moonlets, and contribute to principles to relate predictions to observations

Application of Cellulose Nanomaterials in Thermoplastic Composites

Nanocrystalline cellulose (CNC) is a renewable and biodegradable nanomaterial obtained by acid hydrolysis of cellulose. It exhibits notable mechanical properties: a high aspect ratio and a high surface area. These properties make CNC a promising nanofiller for applications in polymer nanocomposites. But because of its surface characteristics, CNC is not compatible with hydrophobic polymers like polyethylene or polypropylene. This work focuses on the surface modification and incorporation of CNC into polyolefins (polyethylene and polypropylene). Surface modifications with organo-silanes were used to compatibilize the CNC with the polymers. The modifications increased the thermal stability of the CNC by approximately 50°C. Polyethylene nanocomposites were prepared with unmodified and modified CNCs by in situ polymerization of ethylene. The improvement in thermal stability promoted by the modification avoided the degradation of the modified CNCs during the polymer processing by extrusion and injection molding. The incorporation of the CNC into the polyethylene matrix did not have a significant influence on the mechanical properties of the polymer, with the exception being the impact strength of one of the nanocomposites that was 94% higher than the pure polyethylene. The incorporation of the modified CNC into polypropylene was done by two different methods: in situ polymerization and melt compounding. The CNC incorporation had a positive effect on some mechanical properties polypropylene, particularly the impact strength that improved by over 99%. In this work, CNC was also modified by adsorption of surfactants. Several surfactants were evaluated to change the surface characteristics of CNC from hydrophilic to hydrophobic. The hydrophobization of the CNC promoted by the modification allowed its dispersion in organic solvents. More specifically, CNC modified with a combination of two surfactants formed a clear, homogeneous and stable dispersion in toluene. At higher concentrations (7.5% in toluene), the gelation of the modified CNC was observed and a clear and homogeneous gel was formed. The ability of a CNC modified with surfactant to increase the viscosity of toluene at low concentrations was also observed

Extreme AO Observations of Two Triple Asteroid Systems with SPHERE

We present the discovery of a new satellite of asteroid (130) Elektra - S/2014 (130) 1 - in differential imaging and in integral field spectroscopy data over multiple epochs obtained with SPHERE/VLT. This new (second) moonlet of Elektra is about 2 km across, on an eccentric orbit and about 500 km away from the primary. For a comparative study, we also observed another triple asteroid system (93) Minerva. For both systems, component-resolved reflectance spectra of the satellites and primary were obtained simultaneously. No significant spectral difference was observed between the satellites and the primary for either triple system. We find that the moonlets in both systems are more likely to have been created by sub-disruptive impacts as opposed to having been captured.Comment: 8 pages, 4 figures, 1 table, accepted to be published in the Astrophysical Journal Letter

Constraining multiple systems with GAIA

GAIA will provide observations of some multiple asteroid and dwarf systems. These observations are a way to determine and improve the quantification of dynamical parameters, such as the masses and the gravity fields, in these multiple systems. Here we investigate this problem in the cases of Pluto's and Eugenia's system. We simulate observations reproducing an approximate planning of the GAIA observations for both systems, as well as the New Horizons observations of Pluto. We have developed a numerical model reproducing the specific behavior of multiple asteroid system around the Sun and fit it to the simulated observations using least-square method, giving the uncertainties on the fitted parameters. We found that GAIA will improve significantly the precision of Pluto's and Charon's mass, as well as Petit Prince's orbital elements and Eugenia's polar oblateness.Comment: 5 pages, accepted by Planetary and Space Science, Gaia GREAT-SSO-Pis

René Le Mée, Dénombrements, espaces et société

La Société de Démographie Historique a souhaité rendre hommage à René Le Mée en lui consacrant le premier de ses Cahiers. Une sélection de quinze articles, établie parmi une abondante production (la bibliographie de l’auteur est donnée en fin de volume), est ici proposée, précédée de deux avant-propos rédigés par Jean-Pierre Bardet et Hervé Le Bras. Les articles reflètent bien l’activité multiforme de René Le Mée. Documentaliste de formation, il apparaît d’abord comme un excellent connaisseur..

Males do mundo contemporâneo : efeitos de perturbações de ritmicidade circadiana e de estresse crônico sobre saúde e comportamento

Objetivo: Identificar, através de revisão sistemática, o efeito de perturbações da ritmicidade circadiana sobre a saúde humana e, através de experimento animal, o efeito sobre a vulnerabilidade a eventos estressantes. Métodos: Estudo 1: Foi conduzida uma revisão sistemática da literatura nas bases de dados eletrônicas PubMed, Scopus, Embase e LILACS utilizando os termos “social AND (jet lag OR jetlag)”. A busca foi finalizada em 22 de agosto de 2016, resultando em 26 artigos incluídos na revisão. Estudo 2: Camundongos Balb/c foram submetidos a um protocolo de estresse crônico moderado (CMS), sozinho ou precedido de 4 ciclos claro-escuro de período encurtado (10h claro, 10h escuro), e foram comparados a animais submetidos apenas ao encurtamento do ciclo claro-escuro ou a nenhuma intervenção. Em um primeiro experimento, os animais dos grupos estressados foram submetidos a 3 semanas de CMS e foram avaliados parâmetros dos ritmos de atividade-repouso e temperatura central e o ganho de peso corporal. Em um segundo experimento, o período de CMS foi reduzido para 2 semanas e foram analisados parâmetros metabólicos séricos, teste de preferência por solução de sacarose (para aferir comportamento tipo-depressivo) e teste claro-escuro (para aferir comportamento tipo-ansioso). Resultados: Estudo 1: Os desfechos de saúde e comportamento associados ao jetlag social são diversos (epilepsia, sintomas psiquiátricos menores, agressão e problemas de conduta, transtornos de humor, prejuízo cognitivo, uso de substâncias, risco cardiometabólico e perfil endócrino adverso), mas há grande variabilidade de metodologias e populações e grande risco de viés dos estudos analisados. Estudo 2: A exposição ao CMS precedida de ciclos claro-escuro encurtados resultou em aumento na amplitude do ritmo de temperatura, mantido mesmo após o término do protocolo de estresse, e redução do peso corporal no período do CMS, havendo uma clara associação entre estes desfechos. Não foram observadas alterações significativas no comportamento, possivelmente devido a problemas metodológicos, nem nos parâmetros metabólicos avaliados. Conclusões: Este trabalho contribui para o conhecimento sobre o papel da cronorruptura na vulnerabilidade ao desenvolvimento de patologias através de revisão das evidências associadas a um modelo de cronorruptura em humanos (jetlag social) e de demonstração de evidências em um modelo animal (encurtamento do ciclo claro-escuro). As evidências relacionadas ao jetlag social devem ser avaliadas com cautela devido à heterogeneidade metodológica e alto risco de viés, sendo necessários estudos longitudinais e com metodologia padronizada para estabelecer associações mais confiáveis. Em animais, a vulnerabilidade ao estresse parece ser aumentada pelo encurtamento do ciclo claro-escuro no que se refere a ritmos circadianos e metabolismo, mas resta determinar o efeito sobre comportamentos tipo-depressivo e tipo-ansioso. Apoio: FIPE/HCPA, CNPq e CAPES.Objective: Identify through a systematic review the effect of circadian disturbances on human health and, through animal experimentation, the effect on vulnerability to stress. Methods: Study 1: A systematic review of the literature was conducted on PubMed, Scopus, Embase and LILACS electronic databases using the terms "social AND (jet lag OR jetlag)". The search was finalized on August 22, 2016, resulting in 26 research articles included in the review. Study 2: Balb/c mice were exposed to a chronic mild stress (CMS) protocol alone or preceded by 4 shortened light-dark cycles (10h light, 10h dark) and compared to animals exposed only to the shortened light-dark cycles or to no intervention. In one experiment, animals of stressed groups were exposed to 3 weeks of CMS for evaluation of rest-activity and core body temperature rhythms and body weight gain. In a second experiment, CMS was shortened to 2 weeks and serum metabolic parameters, sucrose preference test (to assess depressive-like behavior) and black and white test (to assess anxiety-like behavior) were evaluated. Results: Study 1: The health and behavioral outcomes associated to social jetlag are diverse (epilepsy, minor psychiatric symptoms, aggression and conduct problems, mood disorders, cognitive impairment, substance use, cardiometabolic risk and adverse endocrine profile), but there is great variation of methodologies and populations as well as high risk of bias in analyzed studies. Study 2: Exposure to CMS preceded by shortened light-dark cycles resulted in increased amplitude of core body temperature rhythm, sustained even after the end of CMS, and reduced body weight during CMS, with a clear association between these two outcomes. No significant alterations were observed either in behavior, likely due to methodological issues, or metabolic parameters assessed. Conclusions: This work contributes to the knowledge on the role of chronodisruption on the vulnerability to development of pathologies through a review of evidences associated with a model of chronodisruption in humans (social jetlag) and demonstration of evidences from an animal model of chonodisruption (shortened light-dark cycles). The evidence regarding social jetlag must be analyzed with caution due to methodological heterogeneity and high risk of bias of articles reviewed and longitudinal studies with standardized methodology are needed to establish reliable associations. In animals, it seems that vulnerability to stress is increased by the light-dark cycle shortening in what refers to circadian rhythms and metabolism, but the effect on depressive-like and anxiety-like behaviors remains to be determined. Financial support: FIPE/HCPA, CNPq and CAPES

ODIN: a new model and ephemeris for the Pluto system

Reproduced with permission. Copyright ESO. The original publication is available at www.aanda.org.International audienceBecause of Pluto's distance from the Sun, the Pluto system has not yet completed a revolution since its discovery, hence an uncertain heliocentric distance. In this paper, we present the fitting of our dynamical model ODIN (Orbite, Dynamique et Intégration Numérique) to observations. The small satellites P4 and P5 are not taken into account. We fitted our model to the measured absolute coordinates (RA, DEC) of Pluto, and to the measured positions of the satellites relative to Pluto. The masses we found for the bodies of the system are consistent with those of previous studies. Yet the masses of the small satellites Nix and Hydra are artificially constrained by the number of observations of Charon. The best way to improve the determination of their masses would be to use observations of P4 and P5, but there are still not enough published observations. Concerning the heliocentric distance of the system, we compared the value we obtained using ODIN and those of other models. The difference between the models far exceeds the uncertainty needed (about 1000 km) for the mission New Horizons. A new astrometric reduction of old photographic plates may be an efficient way to constrain this distance. The ephemeris for Pluto's satellites is available on the web page of the IMCCE at http://www.imcce.fr/hosted_sites/saimirror/nssreq9hf.htm. The complete version of the ephemeris is available as a SPICE kernel at http://www.imcce.fr/~beauvalet/. Appendices A and B are available in electronic form at http://www.aanda.orgTable A.2 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/553/A1

Potencial alelopático das acículas de Pinus Taeda L. sobre espécies campestres

Pinus taeda é uma espécie arbórea exótica comum na região sul do Brasil. Dentre seus metabólitos secundários destacam-se os derivados fenólicos que são potenciais aleloquímicos pela sua alta solubilidade em água e capacidade de inibir o desenvolvimento de outras espécies vegetais. O sucesso desta espécie como planta invasora em formações vegetais campestres tem sido relacionado aos efeitos fitotóxicos das substâncias aleloquímicas. O objetivo do presente trabalho foi avaliar a fitotoxidez e assim inferir sobre o potencial alelopático de extratos aquosos de P. taeda sobre a germinação e o desenvolvimento de plântulas de espécies (uma nativa e três exóticas) ocorrentes nos Campos Sulinos. Os efeitos de diferentes concentrações dos extratos aquosos de acículas (frescas ou da serrapilheira) obtidas em plantios de quatro e 33 anos de idade foram testados sobre Paspalum notatum, Eragrostis plana, Trifolium repens e Lotus corniculatus. Também foram avaliados os métodos de processamento do material vegetal para a extração com água. Os resultados mostraram que os extratos de Pinus taeda foram fitotóxicos sobre as quatro espécies receptoras, e as respostas variaram com o estado da acícula, modo de processamento, concentração dos extratos e idade da planta fonte das acículas. As monocotiledôneas receptoras foram mais sensíveis aos extratos aquosos de acículas verdes de plantas mais velhas, enquanto que as leguminosas receptoras foram mais sensíveis aos extratos de acículas verdes oriundas de plantas de quatro anos. De maneira geral, os extratos de acículas oriundas da serapilheira exibiram baixa fitotoxidez, havendo pouca evidência de potencial alelopático para Pinus taeda, considerando essa via de liberação de aleloquímicos.Pinus taeda is an exotic tree very common in Southern Brazil. Among its secondary metabolites, phenolic derivatives are potentially allelochemicals due the water solubility and capacity to inhibit the development of other plant species. The success of P. taeda as inavsive species on grasslands has been related to phytotoxic effects from its allelochemicals substances. The aim of this research was evaluate the phytotoxicty, meanwhile interfering over its allelophatic potential of aqueous extracts from P. taeda on germination and early growth of four species (one native and three exotics) which occurs in Campos Sulinos. During laboratory essays, aqueous extracts of needles (fresh or from litters) obtained from four and 33 years old trees has been tested on Paspalum notatum, Eragrostis plana, Trifolium repens and Lotus corniculatus. It also has been evaluated the processing methods of plant before extraction. The results showed that extracts of Pinus taeda were phytotoxic on the four receptor-species and the responses vary with the state of needles (green or from litter), processing mode, extracts concentration and age of the plant source of needles. The grasses were more sensitive to aqueous extracts of green needles from younger plants, while leguminous species were more sensitive to aqueous extracts of green needles derived from 33 years old plants. In general, extracts of needles from litters showed low phytotoxity, and there is little evidence of allelopathic potential of P. taeda, considering this route of allelochemicals release