771 resultados para Riemenschneider, Tilman, m. 1531
Resumo:
UNLABELLED: PREMISE OF THE STUDY: The Sphagnopsida, an early-diverging lineage of mosses (phylum Bryophyta), are morphologically and ecologically unique and have profound impacts on global climate. The Sphagnopsida are currently classified in two genera, Sphagnum (peat mosses) with some 350-500 species and Ambuchanania with one species. An analysis of phylogenetic relationships among species and genera in the Sphagnopsida were conducted to resolve major lineages and relationships among species within the Sphagnopsida. • METHODS: Phylogenetic analyses of nucleotide sequences from the nuclear, plastid, and mitochondrial genomes (11 704 nucleotides total) were conducted and analyzed using maximum likelihood and Bayesian inference employing seven different substitution models of varying complexity. • KEY RESULTS: Phylogenetic analyses resolved three lineages within the Sphagnopsida: (1) Sphagnum sericeum, (2) S. inretortum plus Ambuchanania leucobryoides, and (3) all remaining species of Sphagnum. Sister group relationships among these three clades could not be resolved, but the phylogenetic results indicate that the highly divergent morphology of A. leucobryoides is derived within the Sphagnopsida rather than plesiomorphic. A new classification is proposed for class Sphagnopsida, with one order (Sphagnales), three families, and four genera. • CONCLUSIONS: The Sphagnopsida are an old lineage within the phylum Bryophyta, but the extant species of Sphagnum represent a relatively recent radiation. It is likely that additional species critical to understanding the evolution of peat mosses await discovery, especially in the southern hemisphere.
Resumo:
We show that "commodity currency" exchange rates have surprisingly robust power in predicting global commodity prices, both in-sample and out-of-sample, and against a variety of alternative benchmarks. This result is of particular interest to policy makers, given the lack of deep forward markets in many individual commodities, and broad aggregate commodity indices in particular. We also explore the reverse relationship (commodity prices forecasting exchange rates) but find it to be notably less robust. We offer a theoretical resolution, based on the fact that exchange rates are strongly forward-looking, whereas commodity price fluctuations are typically more sensitive to short-term demand imbalances. © 2010 by the President and Fellows of Harvard College and the Massachusetts Institute of Technology.
Resumo:
OBJECTIVE: A study was undertaken to determine whether better cognitive functioning at midlife among more physically fit individuals reflects neuroprotection, by which fitness protects against age-related cognitive decline, or neuroselection, by which children with higher cognitive functioning select more active lifestyles. METHODS: Children in the Dunedin Longitudinal Study (N = 1,037) completed the Wechsler Intelligence Scales and the Trail Making, Rey Delayed Recall, and Grooved Pegboard tasks as children and again at midlife (age = 38 years). Adult cardiorespiratory fitness was assessed using a submaximal exercise test to estimate maximum oxygen consumption adjusted for body weight in milliliters/minute/kilogram. We tested whether more fit individuals had better cognitive functioning than their less fit counterparts (which could be consistent with neuroprotection), and whether better childhood cognitive functioning predisposed to better adult cardiorespiratory fitness (neuroselection). Finally, we examined possible mechanisms of neuroselection. RESULTS: Participants with better cardiorespiratory fitness had higher cognitive test scores at midlife. However, fitness-associated advantages in cognitive functioning were already present in childhood. After accounting for childhood baseline performance on the same cognitive tests, there was no association between cardiorespiratory fitness and midlife cognitive functioning. Socioeconomic and health advantages in childhood and healthier lifestyles during young adulthood explained most of the association between childhood cognitive functioning and adult cardiorespiratory fitness. INTERPRETATION: We found no evidence for a neuroprotective effect of cardiorespiratory fitness as of midlife. Instead, children with better cognitive functioning are selecting healthier lives. Fitness interventions may enhance cognitive functioning. However, observational and experimental studies testing neuroprotective effects of physical fitness should consider confounding by neuroselection.
Resumo:
Posttraumatic stress disorder (PTSD) affects the functional recruitment and connectivity between neural regions during autobiographical memory (AM) retrieval that overlap with default and control networks. Whether such univariate changes relate to potential differences in the contributions of the large-scale neural networks supporting cognition in PTSD is unknown. In the present functional MRI study, we employed independent-component analysis to examine the influence of the engagement of neural networks during the recall of personal memories in a PTSD group (15 participants) as compared to non-trauma-exposed healthy controls (14 participants). We found that the PTSD group recruited similar neural networks when compared to the controls during AM recall, including default-network subsystems and control networks, but group differences emerged in the spatial and temporal characteristics of these networks. First, we found spatial differences in the contributions of the anterior and posterior midline across the networks, and of the amygdala in particular, for the medial temporal subsystem of the default network. Second, we found temporal differences within the medial prefrontal subsystem of the default network, with less temporal coupling of this network during AM retrieval in PTSD relative to controls. These findings suggest that the spatial and temporal characteristics of the default and control networks potentially differ in a PTSD group versus healthy controls and contribute to altered recall of personal memory.
Resumo:
Los cambios sufridos por los modelos de comunicación cientÃfica hacen que las bibliotecas universitarias se vean obligadas a dar nuevos servicios. Para adecuarse al investigador los bibliotecarios están desarrollando habilidades, colaborando con cada vez más estamentos y sustentando el acceso abierto. Apoyándose en una lista de posibles servicios, basada en la literatura especializada, este trabajo pretende cuantificar y evaluar el apoyo a la investigación desde las bibliotecas universitarias españolas. El sondeo demuestra la aparición de nuevos servicios e infraestructuras. Pero estas asistencias no suelen sistematizarse, difundirse ni evaluarse. Y, por otra parte, las consecuentes inversiones en personal y TIC han generado una brecha entre universidades
Measurement of highly transient electrical charging following high-intensity laser-solid interaction
Resumo:
The multi-million-electron-volt proton beams accelerated during high-intensity laser-solid interactions have been used as a particle probe to investigate the electric charging of microscopic targets laser-irradiated at intensity similar to10(19) W cm(2). The charge-up, detected via the proton deflection with high temporal and spatial resolution, is due to the escape of energetic electrons generated during the interaction. The analysis of the data is supported by three- dimensional tracing of the proton trajectories. (C) 2003 American Institute of Physics.
Resumo:
A new method for automated coronal loop tracking, in both spatial and temporal domains, is presented. Applying this technique to TRACE data, obtained using the 171 angstrom filter on 1998 July 14, we detect a coronal loop undergoing a 270 s kink-mode oscillation, as previously found by Aschwanden et al. However, we also detect flare-induced, and previously unnoticed, spatial periodicities on a scale of 3500 km, which occur along the coronal loop edge. Furthermore, we establish a reduction in oscillatory power for these spatial periodicities of 45% over a 222 s interval. We relate the reduction in detected oscillatory power to the physical damping of these loop-top oscillations.
Resumo:
Cell counting of bronchoalveolar lavage (BAL) fluid is performed manually in routine practice. This has both methodological and inherent errors; however, the accuracy and suitability of automated counting devices have been questioned. In this study, a Coulter(R) Counter D Industrial model was calibrated and then used to measure the total cell count in unprocessed bronchoalveolar lavage fluid, and compared to a standard manual method.
Resumo:
Peptidomics is a powerful set of tools for the identification, structural elucidation and discovery of novel regulatory peptides and for monitoring the degradation pathways of structurally and catalytically important proteins. Amphibian skin secretions, arising from specialized granular glands, often contain complex peptidomes containing many components of entirely novel structure and unique site-substituted analogues of known peptide families. Following the discovery that the granular gland transcriptome is present in such secretions in a PCR-amenable form, we designed a strategy for peptide structural characterization involving the integration of ‘shotgun’ cloning of cDNAs encoding peptide precursors, deduction of putative bioactive peptide structures, and confirmation of these structures using tandem MS/MS sequencing. Here, we illustrate this strategy by means of elucidation of the primary structures of nigrocin-2 homologues from the defensive skin secretions of four species of Chinese Odorrana frogs, O. schmackeri, O. livida, O. hejiangensis and O. versabilis. Synthetic replicates of the peptides were found to possess antimicrobial activity. Nigrocin-2 peptides occur widely in the skin secretions of Asian ranid frogs and in those of the Odorrana group, and are particularly well-represented and of diverse structure in some species. Integration of the molecular analytical technologies described provides a means for rapid structural characterization of novel peptides from complex natural libraries in the absence of systematic online database information.