We show that pairs of prisms can have negative group-velocity dispersion in the absence of any negative material dispersion. A prism arrangement is described that limits losses to Brewster-surface reflections, avoids transverse displacement of the temporally dispersed rays, permits continuous adjustment of the dispersion through zero, and yields a transmitted beam collinear with the incident beam.

The Patagonian glaciations developed from the latest Miocene (c. 6 Ma) in multiple events of varied duration and intensity. Most of the present glacial landscape is the result of the glacial modelling during the Pleistocene, since the Great Patagonian Glaciation (GPG; c. 1 Ma). The Patagonian Andes were covered by a continuous mountain ice sheet, from 37°S to Cape Horn (56°S), in at least five major glaciations over more than 15 cold events over the last million years. Before GPG, the glaciers were restricted to isolated ice caps along the mountain ranges. The present drainage network was developed after the Last Glacial Maximum [LGM; c. 25 calibrated kiloyears before present (cal. ka BP)], particularly those cases with drainage reversal, when the glaciers began to melt as a result of global climatic changes. The environmental impact of glaciations extended not only all over Patagonia, but to the Pampas as well.Las glaciaciones patagónicas se desarrollaron desde el final del Mioceno (ca. 6 Ma) en múltiples eventos, de variada duración e intensidad. La mayoría del paisaje andino actual es el resultado del modelado glaciario durante el Pleistoceno, desde la Gran Glaciación Patagónica (GGP; ca. 1 Ma). Los Andes Patagónicos fueron cubiertos por un manto de hielo de montaña continuo, desde 37°S hasta el Cabo de Hornos (56°S) a lo largo de por lo menos 5 glaciaciones mayores durante más de 15 eventos fríos en el último millón de años. Antes de la GGP, los glaciares estaban restringidos a casquetes glaciarios aislados a lo largo de las cadenas montañosas. El sistema de redes de drenaje actual, en especial en lo que hace a la inversión del drenaje, se desarrolló luego del Último Máximo Glacial (UMG; ca. 25 cal. ka A.P.), cuando los glaciares comenzaron a retirarse debido a cambios climáticos globales. El impacto ambiental de las glaciaciones se extendió, no sólo a toda la Patagonia, sino también a la región pampeana.

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In this work, we characterized streptavidin-conjugated quantum dots (QDs) manufactured by Quantum Dot Corporation. We present data on: (1) two-photon excitation; (2) fluorescence lifetimes; (3) ensemble and single QD emission anisotropy; (4) QDs as donors for Forster resonance energy transfer (FRET); and (5) spectral conversion of QDs exposed to high-intensity illumination. We also demonstrate the utility of QDs for (1) imaging the binding and uptake of biotinylated transferrin on living cells, and (2) resolving by fluorescence lifetime imaging microscopy (FLIM) signals originating from QDs from those of spatially and spectrally overlapping visible fluorescent proteins (VFPs).

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A direct measurement of the amplitude and the phase of a femtosecond light pulse is performed for the first time to our knowledge. The measurement is made in the frequency domain, and the time dependence of the field can be easily obtained by a Fourier transform. The technique relies on a pulse synthesis scheme to unravel the frequency dependence of the phase. A mask filters the spectrum, which gives rise to a pulse with a measurable temporal profile related to the frequency dependence of the phase. In particular, with a rectangular slit the time delay of the synthesized pulse is the first derivative of the phase with respect to the frequency of the original pulse at the central frequency of the filter. The amplitude of the spectrum is obtained from the power spectrum.