RESUMEN
Demographic histories are frequently a product of the environment, as populations expand or contract in response to major environmental changes, often driven by changes in climate. Meso- and bathy-pelagic fishes inhabit some of the most temporally and spatially stable habitats on the planet. The stability of the deep-pelagic could make deep-pelagic fishes resistant to the demographic instability commonly reported in fish species inhabiting other marine habitats, however the demographic histories of deep-pelagic fishes are unknown. We reconstructed the historical demography of 11 species of deep-pelagic fishes using mitochondrial and nuclear DNA sequence data. We uncovered widespread evidence of population expansions in our study species, a counterintuitive result based on the nature of deep-pelagic ecosystems. Frequency-based methods detected potential demographic changes in nine species of fishes, while extended Bayesian skyline plots identified population expansions in four species. These results suggest that despite the relatively stable nature of the deep-pelagic environment, the fishes that reside here have likely been impacted by past changes in climate. Further investigation is necessary to better understand how deep-pelagic fishes, by far Earth's most abundant vertebrates, will respond to future climatic changes.
RESUMEN
We demonstrate a strategy for surface-enhanced Raman spectroscopy (SERS) of supported lipid membranes with arrays of plasmonic nanoantennas. Colloidal lithography refined with plasma etching is used to synthesize arrays of triangular shaped gold nanoparticles. Reducing the separation distance between the triangle tips leads to plasmonic coupling and to a strong enhancement of the electromagnetic field in the nanotriangle gap. As a result, the Raman scattering intensity of molecules that are located at this plasmonic "hot-spot" can be increased by several orders of magnitude. The nanoantenna array is then embedded with a supported phospholipid membrane which is fluid at room temperature and spans the antenna gap. This configuration offers the advantage that molecules that are mobile within the bilayer membrane can enter the "hot-spot" region via diffusion and can therefore be measured by SERS without static entrapment or adsorption of the molecules to the antenna itself.
Asunto(s)
Membrana Dobles de Lípidos/química , Nanopartículas del Metal/química , Espectrometría Raman , Oro/química , Lípidos/química , Membranas/química , Resonancia por Plasmón de SuperficieRESUMEN
Early during ventricular fibrillation, the defibrillation threshold may be low, as ventricular fibrillation most probably arises from a localized area with only a few wavefronts and the effects of global ischemia, ventricular dilatation, and sympathetic discharge have not yet fully developed. The purpose of this study was to explore the effect of the timing of shock delivery in humans. During implantation of an ICD in 26 patients (24 men, 60 +/- 11 years, 19 coronary artery disease, NYHA 2.2 +/- 0.4, left ventricular ejection fraction 0.42 +/- 0.16), the defibrillation threshold was determined after approximately 10 and 2 seconds of ventricular fibrillation. Ventricular fibrillation was induced by T wave shocks. Mean defibrillation threshold was 9.9 +/- 3.6 J after 10.3 +/- 1.0 seconds. Within 2 seconds, 20 of 26 patients could be successfully defibrillated with < or = 8 J. In these patients, the mean defibrillation threshold was 4.0 +/- 2.1 J after 1.4 +/- 0.3 seconds compared to 9.5 +/- 3.1 J after 10.2 +/- 1.1 seconds (P < 0.001). There were no clinical differences between patients who could be successfully defibrillated within 2 seconds and those patients without successful defibrillation within 2 seconds. In the majority of patients, the defibrillation threshold was significantly lower within the first few cycles of ventricular fibrillation than after 10 seconds of ventricular fibrillation. These results should lead to exploration of earlier shock delivery in implantable devices. This could possibly reduce the incidence of syncope in patients with rapid ventricular tachyarrhythmias and ICDs.
Asunto(s)
Desfibriladores Implantables , Fibrilación Ventricular/terapia , Distribución de Chi-Cuadrado , Femenino , Humanos , Masculino , Persona de Mediana Edad , Estadísticas no Paramétricas , Factores de Tiempo , Fibrilación Ventricular/fisiopatologíaRESUMEN
La política como profesión. La ciencia como profesión
Asunto(s)
Humanos , Ciencia/educación , Política , Filosofía , Métodos , Políticas , Sociología/educaciónRESUMEN
Se terminó de imprimir en agosto de 1991
RESUMEN
Se terminó de imprimir en agosto de 1991
RESUMEN
La política como profesión. La ciencia como profesión