The Spanish Speaking Unity Council (Unity Council) is a community development nonprofit organization that was established in 1964, during the civil rights movement, by a group of community members who wanted to ensure the political representation of the Latino community. Over its 45-year history, the Unity Council has grown into a $12 million community development organization that delivers a range of programming, including social services and employment training as well as facilitating the development and support of local businesses, low-income housing, and neighborhood improvement activities. The history of the agency presents the multiple challenges and rewards associated with development in an underserved community and an example of the important role that leadership plays in the growth of a nonprofit.

Se estudiaron algunas características anatómicas e histoquímicas de la corteza de cinco angiospermas: Cercidium plurifoliolatum Micheli, Ipomea pauciflora Martens & Galeotti, Jatropha andrieuxii Muell. Arg., Lysiloma divaricata (Jacq.) MacBride, Ziziphus amole (Sessé & Mociño) M.C. Johnston, provenientes de una selva baja de Oaxaca. Se obtuvieron porciones de corteza que incluyeran albura y se elaboraron cortes transversales, tangenciales y radiales. Para los caracteres anatómicos se usó la terminología propuesta por Trokenbrodt (1990) y se localizaron: lípidos, pectinas, pectatos de calcio, ligninas, polifenoles, hemicelulosas y celulosa. En cuanto a los radios se observan dos grupos: en uno se forman abanicos que después constituyen bandas tangenciales; en el otro los radios son interrumpidos por alguna estructura tangencial como son: bandas de parénquima axial, fibras o grupos de esclereidas. Resalta el arreglo radial del parénquima axial en Jatropha. En la localización de pectatos de calcio, resaltó una reacción intensa en la mayoría de las células de los cinco ejemplares. Los contenidos celulares muestran una diversidad en su composición resaltando los canales de Jatropha que presentan reacciones intensas a polifenoles, pectatos de calcio y lípidos. El resto de las reacciones muestran un proceso de lignificación del parénquima axial hacia el exterior. Hay presencia importante de cristales en los cinco ejemplares. Se presentan los resultados, en detalle, de las diferencias histoquímicas de la corteza de estas plantas.

No abstract

Magmas from continental arcs built on thick crust have elevated incompatible element abundances and “enriched” radiogenic isotope ratios compared to magmas erupted in island and continental arcs overlying thinner crust. The relative influence of the slab, mantle, and upper plate on this variability is heavily debated. The Andean Southern Volcanic Zone (SVZ; 33-46° S) is an ideal setting to investigate the production of enriched continental arc compositions, because both crustal thickness and magma chemistry vary coherently along strike. However, the scarcity of primitive magmas in the thick-crusted northern SVZ has hindered previous regional studies. To better address the origin of enriched continental compositions, we investigate the geochemistry (major and trace element abundances, 87Sr/86Sr and 143Nd/144Nd ratios) of new mafic samples from Don Casimiro and Maipo volcanoes in Diamante-Maipo Caldera Complex of the northern SVZ. While evolved Diamante-Maipo samples show evidence for crustal assimilation, the trace element and isotopic enrichment of the most mafic samples cannot result from crustal processing, as no known regional or global basement lithologies are enriched in all of the necessary incompatible trace elements. Subduction erosion models similarly fail to account for the enriched isotopic and trace element signature of these samples. Instead, we suggest that the enrichment of northern SVZ magmas is derived from an enriched ambient mantle component (similar to EM1-type ocean island basalts), superimposed on a northward decline in melt extent. A substantial, but nearly uniform contribution of melts from subducting sediment and altered oceanic crust are required at all latitudes. The EM1-like enrichment may arise from recycling of metasomatized subcontinental lithospheric mantle (M-SCLM), as the isotopic trajectory of primitive rear-arc monogenetic cones trend towards the compositions of SCLM melts sampled across South America. Isotopic data from spatially distributed rear-arc centres demonstrate that the arc-parallel variations in the degree of EM1-type enrichment observed in arc-front samples are also present up to 600 km behind the trench in the rear-arc. Rear-arc trace element systematics require significant but variable quantities of slab melts to be transported to the mantle wedge at these large trench distances. Overall, we show that a unified model incorporating variable mantle enrichment, slab additions, and melt extents can account for along and across-arc trends within the SVZ. The recognition that mantle enrichment plays a key role in the production of enriched continental compositions in the SVZ has important implications for our understanding of the chemical evolution of the Earth. If ambient mantle enrichment is not taken into account, petrogenetic models of evolved lavas may overestimate the role of crustal assimilation, which, in turn, may lead models of continental crust growth to overestimate the amount of continental material that has been recycled back into the mantle.

No abstract