Phenolics, depsides and triterpenes from the chilean lichen pseudocyphellaria nudata (zahlbr.) D.J. Galloway

Indexación: ScieloThe lichen Pseudocyphellaria nudata is a species endemic to southern South América. From the lichen tallus, methyl orsellinate, 2-methoxy-3,6-dimethyl-4-hydroxybenzaldehyde, methyl-evernate, tenuiorin, hopan-6ß,22-diol and hopan-6α,76,22-triol were isolated and identified as the main lichen constituents. This is the first report of the occurrence of 2-methoxy-3,6-dimethyl-4-hydroxybenzaldehyde in lichens.http://www.scielo.cl/scielo.php?script=sci_arttext&pid=s0717-97072008000300017&nrm=is

The Organization of Agricultural Production in the Emergence of Chiefdoms in the Quijos Region, Eastern Andes of Ecuador

This dissertation examines the emergence of the ethnohistorically documented Quijos chiefdoms, in the eastern Ecuadorian Andes. It evaluates different alternatives that link the rise of centralized leadership with the organization of agricultural production. To this end I reconstructed the demographic history of a 137 km² region through a full coverage systematic survey, and the patterns of food production and consumption through the analysis of pollen, phytoliths and macroremains from the excavation of 31 tests at locations representing different environmental setting and settlement types. Based on a ceramic chronology established for this project (through the analysis of ceramic materials from 15 test pits and associated carbon dates) I propose a sequence starting at about 600 B.C., with the first manifestations of a regional system of centralized authority appearing after about 500 A.D. The most distinctive expression of this is what appear to be central places in each one of the three subregions encompassed by the survey. The analysis of botanical remains at these locations, and at others representing smaller and peripheral settlements did not show, however, signs of economic differentiation in terms of production or consumption patterns. Thus neither the varying local environmental conditions nor social status, alone or combined, produced distinctive agrarian practices or foodways. Along the same lines, the central places do not seem to have emerged as a strategic move towards controlling agricultural resources, and evidence of staple mobilization or trade networks involving the circulation of local or foreign durable prestige goods is null. Additionally, an analysis of a sample of obsidian artifacts collected through survey and excavations suggests that closeness to source, rather than status, determined the abundance of obsidian materials, while manufacture technology seems to have been standard across settlement types. I propose that frameworks that emphasize the control of economic resources or the importance of specialization of production in the development of complex societies are not useful for characterizing the social and political dynamics of the emerging Quijos chiefdoms, and that current understandings of this region as a hub of exchange activity can be readdressed in light of these findings

Aplicación de la teoría de grafos a la contabilidad

La teoría de grafos es una teoría perteneciente al álgebra moderna según a cual se estudian conjuntos de segmentos de línea y de puntos de un plano. Su diferencia con al geometría euclidiana radica en que la teoría de grafos carece de métrica, pues la conceptualización de "distancia" se obvia para hacer generalizaciones sobre las figuras o grafos