Este estudio fue diseñado para analizar la variación florística a lo largo de la costa del Pacífico entre Cook Inlet, Alaska (61º30'N) hasta el extremo sur de la península de Baja California, México (23º02'N), utilizando para ello los datos correspondientes a 965 inventarios fitosociológicos (que incluyen 686 plantas vasculares) obtenidos en el muestreo de 279 localidades costeras. Mediante un método de clasificación por agrupamientos (Average Linkage Clustering), y usando el índice de similitud de Sørensen como medida de la diversidad florística entre aquéllos, los datos de campo fueron relacionados con las cuatro regiones biogeográficas descritas en el área de estudio: Boreal-Norteamericana, Rocosiana, Californiana y Xerofítico-Mexicana. De acuerdo con sus respectivos patrones de distribución, los táxones registrados (géneros y especies) fueron agrupados en elementos florísticos. Los elementos florísticos, junto con la comparación entre los principales tipos de vegetación costera, sirvieron como criterios para realizar una clasificación fitogeográfica más detallada del área de estudio, en la que se han diferenciado ocho provincias florísticas. Las diferencias fitogeográficas actuales están condicionadas por ciertos acontecimientos paleoclimáticos y paleogeográficos que se discuten en este artículo. Las provincias boreales y templadas presentan porcentajes muy elevados de elementos de amplia distribución, cuyo origen hay que situar en la geoflora Boreotropical o Artoterciaria que dominó el hemisferio norte durante el Terciario. Las provincias florísticamente más diversas son las que se sitúan en la región Californiana, debido a que albergan elementos de las geofloras Artoterciaria y Madroterciaria. La flora tropical de la península de Baja California se caracteriza por un elevado núme-ro de táxones relacionados con la flora neotropical, especialmente con la de Sudamérica. This study was designed to explore floristic variation along the Pacific coast from Cook Inlet, Alaska (61º30'N), to the southern tip of Baja California, Mexico, at 23º02'N. Data corresponding to 965 phytosociological relevés (including 686 vascular plants) obtained by sampling 279 coastal sites were examined. Using an objective classification system (Average Linkage Clustering) and Sørensen's index, floristic data acquired in fieldwork were related to the biogeographical regions of the study area. According to the worldwide distribution pattern of genera and species, the registered taxa were grouped into phytogeographical elements. These elements, along with the climatic classification of the sites and comparisons among the main coastal vegetation types, gave rise to a phytogeographical classification of the study area in which four regions (North American Boreal, Rocky Mountain, Californian and Xerophytic-Mexican) and eight floristic provinces were distinguished. Each province is characterized by its climate, changes in phytogeographic elements, the presence of endemic genera or species, and by its characteristic vegetation types. Floristic ...
We have examined the phylogeographical distribution of chloroplast DNA (cpDNA) lineages of Fouquieria columnaris (Kellogg) Kellogg ex Curran (Fouquieriaceae) in the Sonoran Desert, to understand how historical climatic and/or geological changes have influenced genetic patterns in the species. Using two chloroplast intergenic DNA spacers (psbJ-petA and ndhF-rpl32), we found low levels of nucleotide diversity (π = 0.0025) but high levels of haplotype diversity (h = 0.9339). Analysis of 28 haplotypes revealed four lineages, one belonging to the continental massif and three to the peninsula of Baja California. This structure may be explained and dated by three events: (1) formation of the Gulf of California during the late Miocene (7.24 Mya), (2) activity of the Tres Vírgenes volcanic field (1.20 Mya) and (3) opening of the mid-peninsula seaway during the late Pleistocene (1.53 Mya). Furthermore, the cpDNA lineages show evidence for population contraction during the Last Glacial Maximum, with a subsequent population expansion in the Holocene.
Design features and verification results for Mitsubishi Heavy Industries’ (MHI) latest gas Dry Low NOx (DLN) combustor technology for 1500°C G-class gas turbines is presented. Key design improvements include: A) Inlet aerodynamics: CFD based design air inlet for improved flow uniformity into the pre-mixers. B) Fuel/air mixing: integrated fuel injector and swirler to decrease local flame hot-spots and reduce NOx while preventing flashback. C) Combustor aerodynamics: redesigned flame holding baffle and combustor outer wall to achieve better flame stability and NOx reduction. D) Acoustic resonator: two acoustic resonators, one in the liner to prevent high frequency combustion dynamics and the other in the bypass valve for low frequency dynamics. Tests were conducted to verify the new DLN combustor by installing it in a M501G1 gas turbine at MHI’s T-Point combined cycle power plant, with more than 1500 special measurements. Following the preliminary verification period the combustor was installed at the same plant for long-term operation. The results demonstrate the following capabilities: A) Less than 15ppm NOx operation with turn down to 60% load. B) Stable combustion dynamics at all load levels. C) High combustor ignition reliability. D) Suitable for daily start and stop (DSS) operation. E) Good reliability and durability. F) Retrofitable to existing 501G and 701G gas turbines.
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