Experimental phase functions of mm-sized cosmic dust grains

We present experimental phase functions of three types of millimeter-sized dust grains consisting of enstatite, quartz and volcanic material from Mount Etna, respectively. The three grains present similar sizes but different absorbing properties. The measurements are performed at 527 nm covering the scattering angle range from 3 to 170 degrees. The measured phase functions show two well defined regions i) soft forward peaks and ii) a continuous increase with the scattering angle at side- and back-scattering regions. This behavior at side- and back-scattering regions are in agreement with the observed phase functions for the Fomalhaut and HR 4796A dust rings. Further computations and measurements (including polarization) for millimeter sized-grains are needed to draw some conclusions about the fluffy or compact structure of the dust grains

VLTI/AMBER spectro-interferometry of the late-type supergiants V766 Cen (=HR 5171 A), sigma Oph, BM Sco, and HD 206859

We add four warmer late-type supergiants to our previous spectro-interferometric studies of red giants and supergiants. V766 Cen (=HR 5171 A) is found to be a high-luminosity log(L/L_sun)=5.8+-0.4 source of Teff 4290+-760 K and radius 1490+-540 Rsun located close to both the Hayashi and Eddington limits; this source is consistent with a 40 Msun evolutionary track without rotation and current mass 27-36 Msun. It exhibits NaI in emission arising from a shell of radius 1.5 Rphot and a photocenter displacement of about 0.1 Rphot. V766 Cen shows strong extended molecular (CO) layers and a dusty circumstellar background component. This suggest an optically thick pseudo-photosphere at about 1.5 Rphot at the onset of the wind. V766 Cen is a red supergiant located close to the Hayashi limit instead of a yellow hypergiant already evolving back toward warmer Teff as previously discussed. The stars sigma Oph, BM Sco, and HD 206859 are found to have lower luminosities of about log(L/Lsun)=3.4-3.5 and Teff of 3900-5300 K, corresponding to 5-9 Msun tracks. They do not show extended molecular layers as observed for higher luminosity red supergiants of our sample. BM Sco shows an unusually strong contribution by an over-resolved circumstellar dust component. These stars are more likely high-mass red giants instead of red supergiants. This leaves us with an unsampled locus in the HR diagram corresponding to luminosities log(L/Lsun)~3.8-4.8 or masses 10-13 Msun, possibly corresponding to the mass region where stars explode as type II-P supernovae during the RSG stage. Our previously found relation of increasing strength of extended molecular layers with increasing luminosities is now confirmed to extend to double our previous luminosities and up to the Eddington limit. This might further point to steadily increasing radiative winds with increasing luminosity. [Abridged]Comment: 16 pages, 14 figures, accepted for publication in Astronomy and Astrophysics (A&A

Entre l’abandonament i l’ús intensiu del territori? Sistema d’assentaments i gestió del territori en espais de muntanya. El cas de l’Alt Pirineu català

La despoblació ha estat un procés present a l’Alt Pirineu fins a final del segle XX, la qual cosa ha donat lloc a profundes transformacions socioeconòmiques i territorials que encara són evidents. L’abandonament dels hàbitats i de les explotacions agràries ha provocat una important degradació ambiental, així com la desestructuració del sistema d’assentaments i de les xarxes socials que sustentaven l’estil de vida tradicional. En les darreres dècades, la crisi econòmica ha donat pas a la intensificació de les activitats de negoci i de l’ús del territori. La irrupció del turisme ha estat vista, per alguns actors de la zona, com la (millor?) via de sortida a la profunda crisi socioeconòmica, i alhora, per uns altres, com un dels factors que ha limitat l’exploració d’altres models de desenvolupament més respectuosos amb el medi. Tot aquest compendi de transformacions socioterritorials ha generat un territori completament dual(itzat), on es juxtaposen espais abandonats que han perdut la funcionalitat i espais en els quals la implantació de noves activitats que generin riquesa, sobretot dedicades al lleure, exigeix que se’n faci un ús intensiu. En aquest context, són les iniciatives des de l’escala local i des de la zona concreta les que ajudaran a pal·liar aquesta dualitat territorial i a construir un nou model de desenvolupament per a l’Alt Pirineu.Depopulation has been an important process in the Catalan Pyrenees until the end of the 20th century and can be hold responsible of profound socioeconomic and spatial changes. The abandonment of agricultural activity, supporter of traditional lifestyles, has caused important processes of environmental degradation and the destruction of territorial and social networks. During the last decades, this socioeconomic crisis has paved the way for new economic activities and the escalation of different land uses. For some people, tourist development seems the (best?) possible way to escape from this crisis, while for others tourism has become a limitation for exploring models of sustainable development. Social spatial changes have originated an important spatial duality. Thus in the Pyrenees we can find spaces which have been abandoned and spaces where new economic activities need intensive land and resource use. Under this context, local development initiatives can help to alleviate this spatial duality and build a new development model for Catalan Pyrenees.La despoblación ha sido un proceso presente en el Alt Pirineu hasta finales del siglo XX, lo cual ha dado lugar a profundas transformaciones socioeconómicas y territoriales que aún son evidentes. El abandono de los hábitats y de las explotaciones agrarias ha provocado una importante degradación ambiental y la desestructuración del sistema de asentamientos, así como las redes sociales que sustentaban el modo de vida tradicional. En las últimas décadas, la crisis socioeconómica ha dado paso a la intensificación de las actividades de negocio y del uso del territorio. La irrupción del turismo ha sido vista, por algunos actores, como la (¿mejor?) vía de salida a la profunda crisis socioeconómica, y a la vez, por otros, como uno de los factores que ha limitado la exploración de otros modelos de desarrollo más respetuo sos con el medio. Todo este compendio de transformaciones socioterritoriales ha dado lugar a un territorio completamente dual(izado), donde se yuxtaponen espacios abandonados que han perdido su funcionalidad y espacios en que la implantación de nuevas actividades que generen riqueza, sobre todo aquellas dedicadas al ocio, exigen que se haga un uso intensivo del territorio. En este contexto, son las iniciativas desde la escala local y desde la zona las que ayudarán a paliar esta dualidad territorial y a construir un nuevo modelo de desarrollo para el Alt Pirineu catalán

Hydrogen sensors on the basis of SnO2-TiO2 systems

AbstractIn this study we compare sensor responses to H2 in air using two types of sensing materials: SnO2 bulk doped with TiO2 and mechanical mixtures of SnO2 and TiO2. The materials were analyzed in the broad range of working temperatures and H2 concentrations. Thermal stability of SnO2 bulk doped with TiO2 was studied by in-situ XRD at 700°C

Canvis en la superficie i el grau de fragmentació del bosc a la plana del Vallès entre els anys 1993 i 2000

En aquest article s'hi analitzen la variació en la superfície de bosc, el grau de fragmentació, les cobertes d'origen del bosc guanyat i la mida i la forma dels polígons de bosc perduts i guanyats a la plana del Vallès entre 1993 i 2000, combinant les dues edicions del mapa de cobertes del sòl de Catalunya (MCSC) amb el SIG MiraMon. La disminució del bosc dens no de ribera en aquesta zona ha estat gairebé del 3% en el període d'estudi. El bosc perdut ha esdevingut majoritàriament superfície forestal no arbrada (matollars i prats), urbana i agrícola. També hi ha hagut una certa recuperació de bosc, que no compensa les pèrdues i que prové principalment de cobertes forestals no arbrades i de conreus. S'observa també un increment de la fragmentació del bosc, que ha afectat a més del 10% de la superfície de les grans àrees boscoses. S'hi comenten finalment la validesa del mètode i les implicacions ecològiques i de conservació d'aquests resultats.En el presente artículo se analizan la variación en la superficie de bosque, su fragmentación, las cubiertas de origen del bosque ganado y de destino del bosque perdido y el tamaño y la forma de los polígonos de bosque perdidos y ganados en el llano del Vallès (área metropolitana de Barcelona) entre 1993 y 2000, combinando las dos ediciones del mapa de cubiertas del suelo de Cataluña (MCSC) con el SIG MiraMon. La disminución del bosque denso no de ribera en esta zona ha sido de casi el 3% en el periodo estudiado. El bosque perdido ha pasado a ser mayoritariamente superficie forestal no arbolada (matorrales y prados), urbana y agrícola. También ha habido una cierta recuperación de bosque que no compensa las pérdidas y que proviene principalmente de cubiertas forestales no arboladas y de cultivos. Se observa también un incremento de la fragmentación del bosque en la zona de estudio, que ha afectado a más del 10% de la superficie de las grandes áreas forestales. Se comentan, finalmente, la validez del método y las implicaciones ecológicas y de conservación de estos resultados.Les changements de la surface de forêt, la fragmentation, les couvertures d'origine de la forêt gagné et du destin de la forêt perdue, et la taille et forme des taches gagnées et perdues de forêt entre 1993 et 2000 ont été évalués a la plaine du Vallès (aire métropolitaine de Barcelone), en combinant les deux éditions de la carte de couverture du sol de la Catalogne (MCSC) avec le SIG MiraMon. La fôret dense non de galerie est réduite d'un 3% à l'aire d'étude. Il y a eu un petit rétablissement de forêt qui n'a pas compensé les pertes et qui viens principalement des fourrés-pelouses et des cultures. On a également observé une augmentation de fragmentation de la forêt, affectant plus de 10% de la surface des grandes aires forestières. On commente finalement l'utilité de la méthodologie et les implications écologiques de ces résultats pour la conservation.Changes in forest area, forest fragmentation, the land cover classes of origin of the gained forest and of destiny of the lost forest, and size and form of the gained and lost forest patches were evaluated in the Vallès lowlands (Barcelona Metropolitan Area) between 1993 and 2000, by combining the two editions of the land cover map of Catalonia (MCSC) using the MiraMon SIG. The area occupied by dense, non-riparian forest decreased by 3% in the studied period. The lost forest has been substituted by shrublands-grasslands, urban land, and croplands. There has been a small recovery of forest as well, mainly from shrublands- grasslands and croplands, which does not compensate the forest loss. An increase of forest fragmentation has also been observed, affecting more than 10% of the surface of the large forest areas. The validity of the methodology and the ecological implications of these results for conservation are finally addressed

La Agricultura Social en Cataluña : una alternativa de desarrollo local sostenible frente a la crisis económica y social

A agricultura comercial procurou durante décadas maximizar a produção, o que levou a mudanças profundas nas áreas rurais de toda a Europa. Por causa da chamada "Revolução Verde", muitos têm sido marginalizados e regiões inteiras fôram despovoadas. A diversificação económica nas áreas rurais desde a década de 1980-1989 impulsionou a multifuncionalidade agrária com a incorporação, por exemplo, de actividades de turismo nas explorações agrárias e geração de produtos agrícolas com valor agregado. Este fato provocou um aumento do preço os produtos agro-alimentários e a sensibilização entre os consumidores por unha agricultura orgânica, de proximidade e de preços justos. Este facto está sendo um benefício pelo campesinato, quem nalguns casos está sendo melhor retribuido pelo seu trabalho. Desde 2008 a crise económica global agravou a situação de uma grande parte da população. Por um lado, cada vez se produzem mais alimentos de baixa qualidade e com elevados custos de energia. Além disso, a falta de trabalho tem direcionado muitos jovens a buscar oportunidades económicas no campo, através da promoção de novas formas de produção e novos produtos, em base a critérios ecológicos e comercializados em circuitos locais e de proximidade. Neste cenário, a Agricultura Social (AS) aumenta a produção e transformação de produtos agrícolas que envolvem prestações sociais direitas em termos de emprego, formação, terapia ou reabilitação de grupos em risco de exclusão social, devolvendo a sociedade o investimento público e privado em quatro áreas: a) coesão social; b) empoderamento de grupos socialmente vulneráveis; c) desenvolvimento local sustentável e inovador no mundo rural e periurbano; e d) um maior equilíbrio entre investimentos e custos para a sociedade no âmbito social. Neste artigo apresentamos o caso da Catalunha através do diagnóstico do sector e análise de uma seleção de estudos de caso

Giant Anisotropic Magneto-Resistance in ferromagnetic atomic contacts

Magneto-resistance is a physical effect of great fundamental and industrial interest since it is the basis for the magnetic field sensors used in computer read-heads and Magnetic Random Access Memories. As device dimensions are reduced, some important physical length scales for magnetism and electrical transport will soon be attained. Ultimately, there is a strong need to know if the physical phenomena responsible for magneto-resistance still hold at the atomic scale. Here, we show that the anisotropy of magneto-resistance is greatly enhanced in atomic size constrictions. We explain this physical effect by a change in the electronic density of states in the junction when the magnetization is rotated, as supported by our ab-initio calculations. This stems from the "spin-orbit coupling" mechanism linking the shape of the orbitals with the spin direction. This sensitively affects the conductance of atomic contacts which is determined by the overlap of the valence orbitals.Comment: latex AAMR.tex, 6 files, 5 figures, 4 pages (http://www-drecam.cea.fr/spec/articles/S06/011

Metoxilación anódica del acenafteno

Anodic methoxylation of acenaphthene in methanol-CHaONa is reported. The main producís obtained were: 1-methoxyacenaphthene, 4-methoxyacenaphthene and acenaphthylene. The last compound shows the participation of a carbonum ion intermedíate in the reaction

Measurements of UV aerosol optical depth in the French Southern Alps

Routine measurements of global and diffuse UV irradiances at Briançon station (1310 m a.s.l.) are used to retrieve the direct solar irradiance and the aerosol optical depth (AOD), for cloudless days. Data of three years (2003, 2004, 2005) are analyzed; the results confirm those of a preliminary analysis for 2001, 2002. <br><br> The atmosphere is very clear in winter, with AODs between 0.05 and 0.1. The turbidity increases slowly in spring, starting end of February, with AODs around 0.2–0.3 in mid summer, some values reaching 0.4. A similar behaviour is observed for all years, with somewhat higher values in late summer for the year 2003