Evaluation of plant derivatives of Meliaceae family as a source of nitrogen for trees

Soil application of fresh organic matter is a way to increase soil organic matter and provide nutrients to trees. The effect of application of organic matter depends on the interaction among soil, root and microbial biomass. The aim of this research was to evaluate the potential release of N for hybrid GF677 (P. persica x P. dulcis) uptake, of 6 neemcakes available on the Italian market compared with fresh leaves of Melia azedarach, an ornamental tree that grows in the area of investigation. The release of N, and consequently root uptake was related to C:N ratio, the lower the ratio the higher the N concentration in plant tissues and plant growth. Using the 15N isotope technique, we found that up to 30% of the N applied with fresh Melia leaves, was accumulated in the tree, however the mineral N concentration in soil and plant and plant growth was not affected by the application of plant derivatives

Reading derived words by Italian children with and without dyslexia: The effect of root length

Children with dyslexia are extremely slow at reading long words but they are faster with stimuli composed of roots and derivational suffixes (e.g., CASSIERE, \u2018cashier\u2019) than stimuli not decomposable in morphemes (e.g., CAMMELLO, \u2018camel\u2019). The present study assessed whether root length modulates children\u2019s morphological processing. For typically developing readers, root activation was expected to be higher for longer than shorter roots because longer roots are more informative access units than shorter ones. By contrast, readers with dyslexia were not expected to be facilitated by longer roots because these roots might exceed dyslexics\u2019 processing capacities. Two groups of Italian 6th graders, with and without dyslexia, read aloud low-frequency derived words, with familiar roots and suffixes. Word reaction times (RTs) and mispronunciations were recorded. Linear mixed-effects regression analyses on RTs showed the inhibitory effect of word length and the facilitating effect of root frequency for both children with and without dyslexia. Root length predicted RTs of typically developing readers only, with faster RTs for longer roots, over and above the inhibitory effect of word length. Furthermore, typically developing children had faster RTs on words with more frequent suffixes while children with dyslexia were faster when roots had a small family size. Generalized linear regression analyses on accuracy showed facilitating effects of word frequency and suffix frequency, for both groups. The large word length effect on latencies confirmed laborious whole-word processing in children when reading low-frequency derived words. The absence of a word frequency effect along with the facilitating effect of root frequency indicated morphemic processing in all readers. The reversed root length effect in typically developing readers pointed to a stronger activation for longer roots in keeping with the idea that these represent particularly informative units for word decoding. For readers with dyslexia the facilitating effect of root frequency (not modulated by root length) confirmed a pervasive benefit of root activation while the lack of root length modulation indicated that the longest roots were for them too large units to be processed within a single fixation

Scheduling reactivo de procesos make-and-pack operando en modo campaña: enfoque CP novedoso

Se presenta un modelo matemático de Constraint Programming (CP) para resolver el problema de scheduling de corto plazo en plantas industriales de tipo batch, multiproducto, multietapa; las cuales operan con procesos make-andpack. Se trata de un enfoque novedoso, capaz de considerar, entre otros aspectos, la operación en modo campañas y tiempos de changeover dependientes de la secuencia y/o del equipo productivo involucrado. El mismo permitió resolver 20 instancias, de tamaño creciente en cuanto al número de lotes a agendar, correspondiente a un problema ampliamente abordado en la bibliografía (proceso de producción de helados). Los resultados obtenidos indican un buen desempeño (veloz y eficaz). Asimismo, se trata de una formulación cuyo tamaño no se incrementa exponencialmente con el crecimiento en el número de lotes considerados.Sociedad Argentina de Informática e Investigación Operativ

Polycyclic aromatic hydrocarbon processing in a hot gas

Context: PAHs are thought to be a ubiquitous and important dust component of the interstellar medium. However, the effects of their immersion in a hot (post-shock) gas have never before been fully investigated. Aims: We study the effects of energetic ion and electron collisions on PAHs in the hot post-shock gas behind interstellar shock waves. Methods: We calculate the ion-PAH and electron-PAH nuclear and electronic interactions, above the carbon atom loss threshold, in H II regions and in the hot post-shock gas, for temperatures ranging from 10^3 to 10^8 K. Results: PAH destruction is dominated by He collisions at low temperatures (T < 3x10^4 K), and by electron collisions at higher temperatures. Smaller PAHs are destroyed faster for T < 10^6 K, but the destruction rates are roughly the same for all PAHs at higher temperatures. The PAH lifetime in a tenuous hot gas (n_H ~ 0.01 cm^-3, T ~ 10^7 K), typical of the coronal gas in galactic outflows, is found to be about thousand years, orders of magnitude shorter than the typical lifetime of such objects. Conclusions: In a hot gas, PAHs are principally destroyed by electron collisions and not by the absorption of X-ray photons from the hot gas. The resulting erosion of PAHs occurs via C_2 loss from the periphery of the molecule, thus preserving the aromatic structure. The observation of PAH emission from a million degree, or more, gas is only possible if the emitting PAHs are ablated from dense, entrained clumps that have not yet been exposed to the full effect of the hot gas.Comment: 16 pages, 11 figures, 3 tables, typos corrected and PAH acronym in the title substituted with full name to match version published in Astronomy and Astrophysic

The Dynamical and Chemical Evolution of Dwarf Spheroidal Galaxies

We present a large sample of fully self-consistent hydrodynamical Nbody/Tree-SPH simulations of isolated dwarf spheroidal galaxies (dSphs). It has enabled us to identify the key physical parameters and mechanisms at the origin of the observed variety in the Local Group dSph properties. The initial total mass (gas + dark matter) of these galaxies is the main driver of their evolution. Star formation (SF) occurs in series of short bursts. In massive systems, the very short intervals between the SF peaks mimic a continuous star formation rate, while less massive systems exhibit well separated SF bursts, as identified observationally. The delay between the SF events is controlled by the gas cooling time dependence on galaxy mass. The observed global scaling relations, luminosity-mass and luminosity-metallicity, are reproduced with low scatter. We take advantage of the unprecedentedly large sample size and data homogeneity of the ESO Large Programme DART, and add to it a few independent studies, to constrain the star formation history of five Milky Way dSphs, Sextans, LeoII, Carina, Sculptor and Fornax. For the first time, [Mg/Fe] vs [Fe/H] diagrams derived from high-resolution spectroscopy of hundreds of individual stars are confronted with model predictions. We find that the diversity in dSph properties may well result from intrinsic evolution. We note, however, that the presence of gas in the final state of our simulations, of the order of what is observed in dwarf irregulars, calls for removal by external processes.Comment: 21 Pages, 19 figures ; Accepted for publication in A&A. Higher resolution version may be downloaded here : http://obswww.unige.ch/~revaz/publications/aa2009_1173

Las Secuencias Depositacionales del Plioceno-Cuaternario en la Plataforma Submarina adyacente al Litoral del Este Bonaerense

Se describen las características sismoestratigráficas, sedimentológicas y morfológicas del sector de plataforma submarina adyacente al este bonaerense. El trabajo se basa en los resultados obtenidos durante el desarrollo de sucesivos proyectos destinados al estudio de la cubierta sedimentaria del Plioceno-Cuaternario y reciente, utilizando metodologías de relevamiento sísmico de reflexión de media a alta resolución y muestreos de sedimentos. El sector de plataforma estudiado constituye una típica plataforma submarina silicoclástica de margen pasivo, de gran extensión y suave relieve. Su configuración morfológica está caracterizada por relieves aterrazados con una cobertura sedimentaria de depósitos arenosos relicto a palimpsestos que resultaron del retrabajamiento de sistemas costeros de playas, barreras y lagunas litorales durante el retroceso de la línea de costa como consecuencia del ascenso del nivel del mar durante la transgresión postglacial, con una etapa final de remodelado parcial durante el descenso del nivel del mar del Holoceno superior. Se diferencian dos ámbitos, la plataforma interior ("Terraza Rioplatense", entre la línea de costa y los 30/40 m de profundidad) con geoformas ajustadas a la hidrodinámica actual, y la plataforma exterior (entre la isobata de 70 m y el borde exterior de la plataforma en transición al talud), con sedimentos relicto de poca movilidad; en ambas se hallan relieves pre-transgresivos labrados en depósitos marinos y continentales del Plio-Pleistoceno que afloran bajo la cubierta sedimentaria reciente. Un escalón abrupto de 30/40 m de desnivel separa ambas plataformas. La secuencia estratigráfica estudiada está constituida por seis Secuencias Depositacionales (SD 1 a SD 6 de techo a base) que representan paquetes sedimentarios separados por discordancias. La SD 6 constituye la base de la secuencia, y corresponde a depósitos marinos del Mioceno correlacionables con las unidades costeras conocida como "Paranense-Entrerriense-Chapadmalense". La SD 5 son depósitos marinos en transición a continentales equivalentes a la Fm Barranca de los Lobos del litoral marplatense y a la unidad conocida como "Fm Puelches Equivalente" del Plioceno. La SD 4 está caracterizada por sedimentos marinos correspondientes al denominado "Interensenadense" en el litoral bonaerense, de edad aproximada a los 2,41 Ma (Plioceno superior), y se reconocen en ella diversas sismofacies de ambientes marinos, costeros y continentales con una secuencia litológica granodecreciente hacia arriba. La SD 3, marina, tiene la particularidad de tener una distribución saltuaria, a diferencia de las restantes que se extienden de manera uniforme en toda la región, lo que demuestra la ocurrencia, con posterioridad a su depositación, de importantes procesos erosivos probablemente asociados a tectónica y/o glacioeustatismo. La SD 2 representa a los depósitos marinos-costeros formados durante el estadío isotópico 5e (120 ka), que en las llanuras costeras vecinas se lo conoce como "Belgranense", y está constituida por diversas facies entre las que se destacan barreras-lagunas litorales, playas y estuarios. La SD 1 es la cobertura superficial formada durante la transgresión postglacial en ambientes de barreras-lagunas costeras-estuarios. La secuencia integrada por las SD 5 a 1 representa a las transgresiones glacioeustáticas del Plioceno- Cuaternario, con diferentes grados de preservación en la plataforma y el Río de la Plata en virtud de variantes tectónicas y morfológicas. Existe la posibilidad de que no todas las transgresiones marinas ocurridas en la región hayan quedado preservadas en el registro geológico

The double sub-giant branch of NGC 6656 (M22): a chemical characterization

We present an abundance analysis of 101 subgiant branch (SGB) stars in the globular cluster M22. Using low resolution FLAMES/GIRAFFE spectra we have determined abundances of the neutron-capture strontium and barium and the light element carbon. With these data we explore relationships between the observed SGB photometric split in this cluster and two stellar groups characterized by different contents of iron, slow neutron-capture process (s-process) elements, and the alpha element calcium, that we previously discovered in M22's red-giant stars. We show that the SGB stars correlate in chemical composition and color-magnitude diagram position: the stars with higher metallicity and relative s-process abundances define a fainter SGB, while stars with lower metallicity and s-process content reside on a relatively brighter SGB. This result has implications for the relative ages of the two stellar groups of M22. In particular, it is inconsistent with a large spread in ages of the two SGBs. By accounting for the chemical content of the two stellar groups, isochrone fitting of the double SGB suggests that their ages are not different by more than 300 Myr.Comment: 21 pages, 12 figures, accepted for publication in A&