Groups of the photosensitive female yellow-throated sparrow were placed under various light-dark cycles, in which a fixed ultrashort photophase of 3 h was combined with dark phases of varying duration, resulting in cycles of 18-30 h. Simultaneously, two groups of birds, one in short days (8L/16D) and the other in long days (15L/9D), were kept as controls. Significant ovarian growth, observed at...

Sequences with ultrashort echo times enable new applications of MRI, including bone, tendon, ligament, and dental imaging. In this article, a sequence is presented that achieves the shortest possible encoding time for each k-space point, limited by pulse length, hardware switching times, and gradient performance of the scanner. In pointwise encoding time reduction with radial acquisition (PETRA...

We demonstrate for the first time nonresonant phase-matched frequency conversion of ultrashort pulses in gases. Broad-bandwidth ultrafast pulses, tunable around 270nm, were generated from a Ti:sapphire amplifier system using 2o~ + 2c0 ~0 parametric wave mixing in a capillary waveguide. Both the fundamental and the second-harmonic light were coupled into the lowest-order (EH11) mode. The output ...

We demonstrate a novel all-optical scheme for measuring the correlation of spectrally phase-coded ultrashort optical waveforms that uses second-harmonic generation (SHG) in long, periodically poled lithium niobate crystals. The SHG yield can be controlled over a range of ~30 dB, depending on the correlation of the applied phase codes. Such a spectral phase correlator has applications for ultras...

The possibility to use the ultrashort ion bunches produced by circularly polarized laser pulses to drive a source of fusion neutrons with sub-optical cycle duration is discussed. A two-side irradiation of a deuterated thin foil target produces two countermoving ion bunches, whose collision produces an ultrashort neutron burst. Using particle-in-cell simulations and analytical modeling, it is ev...