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Useful Benchmark (useful + benchmark)
Selected AbstractsPrecise/ Small Sample Size Determinations of Lithium Isotopic Compositions of Geological Reference Materials and Modern Seawater by MC-ICP-MSGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 1 2004Alistair B. Jeffcoate composition isotopique de Li; matériaux de référence silicates; eau de mer; MC-ICP-MS; Li standard The Li isotope ratios of four international rock reference materials, USGS BHVO-2, GSJ JB-2, JG-2, JA-1 and modern seawater (Mediterranean, Pacific and North Atlantic) were determined using multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS). These reference materials of natural samples were chosen to span a considerable range in Li isotope ratios and cover several different matrices in order to provide a useful benchmark for future studies. Our new analytical technique achieves significantly higher precision and reproducibility (< ± O.3%o 2s) than previous methods, with the additional advantage of requiring very low sample masses of ca. 2 ng of Li. Les rapports isotopiques du Li de 4 matériaux de référence, de provenance Internationale, BHVO-2, JB-2, JG-2, JA-1 et d'eau de mer (Méditerranée, Pacifique et Atlantique Nord) ont été déterminés par MC-ICP-MS (spectrométrie de masse avec source à plasma induit à multicollection). Ces matériaux de référence naturels ont été choisis car ils balaient un large champ des rapports isotopiques du Lithium et couvrent différentes matrices afin de fournir un point de repère utile pour les études futures. Notre nouvelle technique analytique permet d'atteindre une précision et une reproductibilité (< ± 0.3%. 2s) nettement supérieures à celles des méthodes précédemment utilisées et présente I'avantage de pouvoir travailler avec des échantillons de petite masse, , 2 ng de Li. [source] On the origin of rim textures surrounding anhydrous silicate grains in CM carbonaceous chondritesMETEORITICS & PLANETARY SCIENCE, Issue 5 2000Lauren BROWNING Bulk chemical analyses and observations of these rims indicate the presence of phyllosilicates and disseminated opaques. Because phyllosilicates could not have survived the chondrule formation process, chondrule silicate rims must have formed entirely by late-state aqueous reactions. As such, these textures provide a useful benchmark for isolating alteration features from more complex CM matrix materials. Both chondrule silicate and matrix silicate rims exhibit morphological features commonly associated with advancing stages of replacement reactions in terrestrial serpentinites. Contacts between many matrix silicate rims and the adjacent matrix materials suggest that these rims formed entirely by aqueous reactions in a parent-body setting. This contrasts with previous assertions that rim textures can only form by the accretion of nebular dust but does not imply an origin for the rims surrounding other types of CM core components, such as chondrules. [source] Long-distance dispersal and local retention of larvae as mechanisms of recruitment in an island population of a coral reef fishAUSTRAL ECOLOGY, Issue 2 2007HEATHER M. PATTERSON Abstract Although recruitment of pelagic larvae is a fundamental and well-documented process in the dynamics of benthic marine populations, identifying the sources of recruitment, or the degree to which populations are connected via dispersal of larvae, has remained elusive for most marine taxa. In this study we used natural environmental markers (trace elements) recorded in fish otoliths (ear stones) as tags of natal origin. Specifically, we used the otolith core and edge chemistries of a locally endemic wrasse (Coris bulbifrons) from Lord Howe Island (LHI), Australia, and a widely distributed species (Coris picta) from three potential mainland source regions, to determine the likely sources of recruitment to C. picta populations on LHI. The use of a local endemic species, which is by definition self-recruiting, is a novel approach for ground-truthing the dispersal history of non-endemic coral reef fish. Discriminant function analyses were able to separate LHI from mainland fish, using both edge and core signatures, with a high degree of accuracy, suggesting at least some of the C. picta collected on LHI were of local origin. This result was corroborated when half of the C. bulbifrons and LHI C. picta were introduced as unknowns into a discriminant function analysis using the remaining C. bulbifrons, LHI C. picta, and the mainland C. picta as a training data set. Overall, our findings suggest that both long distance dispersal and local retention are important sources of recruitment to populations of C. picta on LHI and that otolith chemistry of endemic species could be a useful benchmark for determining the prevalence of self-recruitment in insular populations of other widespread species. [source] Control of the Morphology and Structural Development of Solution-Processed Functionalized Acenes for High-Performance Organic TransistorsADVANCED FUNCTIONAL MATERIALS, Issue 10 2009Jung Ah Lim Abstract Solution-processable functionalized acenes have received special attention as promising organic semiconductors in recent years because of their superior intermolecular interactions and solution-processability, and provide useful benchmarks for organic field-effect transistors (OFETs). Charge-carrier transport in organic semiconductor thin films is governed by their morphologies and molecular orientation, so self-assembly of these functionalized acenes during solution processing is an important challenge. This article discusses the charge-carrier transport characteristics of solution-processed functionalized acene transistors and, in particular, focuses on the fine control of the films' morphologies and structural evolution during film-deposition processes such as inkjet printing and post-deposition annealing. We discuss strategies for controlling morphologies and crystalline microstructure of soluble acenes with a view to fabricating high-performance OFETs. [source] Plant Community Structure in Tropical Rain Forest Fragments of the Western Ghats, India,BIOTROPICA, Issue 2 2006S. Muthuramkumar ABSTRACT Changes in tree, liana, and understory plant diversity and community composition in five tropical rain forest fragments varying in area (18,2600 ha) and disturbance levels were studied on the Valparai plateau, Western Ghats. Systematic sampling using small quadrats (totaling 4 ha for trees and lianas, 0.16 ha for understory plants) enumerated 312 species in 103 families: 1968 trees (144 species), 2250 lianas (60 species), and 6123 understory plants (108 species). Tree species density, stem density, and basal area were higher in the three larger (> 100 ha) rain forest fragments but were negatively correlated with disturbance scores rather than area per se. Liana species density, stem density, and basal area were higher in moderately disturbed and lower in heavily disturbed fragments than in the three larger fragments. Understory species density was highest in the highly disturbed 18-ha fragment, due to weedy invasive species occurring with rain forest plants. Nonmetric multidimensional scaling and Mantel tests revealed significant and similar patterns of floristic variation suggesting similar effects of disturbance on community compositional change for the three life-forms. The five fragments encompassed substantial plant diversity in the regional landscape, harbored at least 70 endemic species (3.21% of the endemic flora of the Western Ghats,Sri Lanka biodiversity hotspot), and supported many endemic and threatened animals. The study indicates the significant conservation value of rain forest fragments in the Western Ghats, signals the need to protect them from further disturbances, and provides useful benchmarks for restoration and monitoring efforts. [source] | ||||||||||