We demonstrate a nonlinear crystal-based short pulse recirculation cavity for trapping the second harmonic of an incident high-power laser pulse. This scheme aims to increase the efficiency and flux of Compton-scattering-based light sources. We demonstrate up to 40x average power enhancement of frequency-doubled submillijoule picosecond pulses, and 17x average power enhancement of 177 mJ, 10 ps, 10 Hz pulses.

We demonstrate a compact hyperdispersion stretcher and compressor pair that permit chirped-pulse amplification in Nd:YAG. We generate 750 mJ, 0.2 nm FWHM, 10 Hz pulses recompressed to an 8 ps near-transform-limited duration. The dispersion-matched pulse compressor and stretcher impart a chirp of 7300 ps/nm, in a 3 m x 1 m footprint.

We demonstrate a nonlinear crystal-based short pulse recirculation cavity for trapping the second harmonic of an incident high-power laser pulse. This scheme aims to increase the efficiency and flux of Compton-scattering-based light sources. We demonstrate up to 40x average power enhancement of frequency-doubled submillijoule picosecond pulses, and 17x average power enhancement of 177 mJ, 10 ps, 10 Hz pulses.

A laser wakefield acceleration study has been performed in the matched, self-guided, blowout regime producing 720+/-50 MeV quasimonoenergetic electrons with a divergence Deltatheta_{FWHM} of 2.85+/-0.15 mrad using a 10 J, 60 fs 0.8 mum laser. While maintaining a nearly constant plasma density (3x10;{18} cm;{-3}), the energy gain increased from 75 to 720 MeV when the plasma length was increased from 3 to 8 mm. Absolute charge measurements indicate that self-injection of electrons occurs when the laser power P exceeds 3 times the critical power P_{cr} for relativistic self-focusing and saturates around 100 pC for P/P_{cr}>5. The results are compared with both analytical scalings and full 3D particle-in-cell simulations.

Implementing the capability to perform fast ignition experiments, as well as, radiography experiments on the National Ignition Facility (NIF) places stringent requirements on the control of each of the beam's pointing, intra-beam phasing and overall wave-front quality. In this article experimental results are presented which were taken on an interferometric adaptive optics testbed that was designed and built to test the capabilities of such a system to control phasing, pointing and higher order beam aberrations. These measurements included quantification of the reduction in Strehl ratio incurred when using the MEMS device to correct for pointing errors in the system. The interferometric adaptive optics system achieved a Strehl ratio of 0.83 when correcting for a piston, tip/tilt error between two adjacent rectangular apertures, the geometry expected for the National ignition Facility. The interferometric adaptive optics system also achieved a Strehl ratio of 0.66 when used to correct for a phase plate aberration of similar magnitude as expected from simulations of the ARC beam line. All of these corrections included measuring both the upstream and downstream aberrations in the testbed and applying the sum of these two measurements in open-loop to the MEMS deformable mirror.

We report a passively mode-locked fiber-based oscillator that has no internal dispersion-compensating gratings. This design, which we believe to be the first of its kind, produces 25 nJ pulses at 80 MHz with the pulses compressible to 150 fs. The pulses appear to be self-similar and initial data imply that their energy is further scalable.

The Dirac-Lorentz equation describes the dynamics of a classical point charge in an electromagnetic field, accounting for radiative effects in a manifestly covariant and gauge-invariant manner. The validity of this equation is assessed by direct comparison between the Dirac-Lorentz dynamics of an electron subjected to a plane wave in vacuum and the well-known recoil associated with Compton scattering. In the small recoil limit, the classical Dirac-Lorentz is shown to yield the correct momentum transfer. For larger values of the recoil, the quantum scale appears explicitly, and the classical Dirac-Lorentz equation does not properly model this situation, as shown by deriving an exact analytical solution for a monochromatic plane wave of wave number k0 to any order in k0r0, where r0 is the classical electron radius.

Enforced limb disuse strongly disrupts the cortical networks that are involved in sensorimotor activities. This disruption causes a cortical reorganization that may be functionally maladaptive. In this study, we used functional magnetic resonance imaging (fMRI) to investigate whether it is possible to prevent this reorganization by compensating for the lack of actual kinesthetic perception with illusory movements induced by "neuromimetic" proprio-tactile feedback that is artificially delivered during immobilization. Sixteen healthy volunteers were equipped for five days with full-hand ortheses that prevented them from performing finger and hand movements but allowed for kinesthetic and tactile sensations. Eight participants received a twice-daily proprio-tactile treatment consisting of the perception of kinesthetic sensations resembling those felt during actual movements generated by miniature vibrators set in the ortheses at the finger and wrist levels. Eight untreated participants received no stimulation. The effects of hand immobilization and treatment were assessed by fMRI during a calibrated voluntary hand movement task and hand tactile stimulation before cast placement and immediately after cast removal. We found that the sensorimotor network was preserved in subjects who underwent this treatment during hand immobilization, while the sensorimotor network of untreated subjects was significantly altered. These findings suggest that sensory feedback and associated movement perception may counteract disuse-induced cortical plastic changes through recruitment of a large part of the cortical network used for actual performed movement. The possibility of guiding cortical plasticity with proprioceptive augmented feedback is potentially relevant for rehabilitation efforts.

Prolactin circulates predominantly as a 23-kDa monomer, and a high-molecular-weight form largely consisting of a complex of prolactin and an anti-prolactin IgG autoantibody, called macroprolactin. This cross-reacts with conventional laboratory assays for prolactin. We here describe how quantitative adjustment for this may assist patient management.In a consecutive series of 218 patients with prolactin elevated to 400 mu/L or more in men (normal range≤180)(n=79, 36.2% of sample) and 1 000 mu/L or more in women (normal range≤500)(n=139, 63.8%) a macroprolactin screen was performed using PEG precipitation.Where present, median macroprolactin as a proportion of total prolactin was in women 13%(percentile25-percentile75: 7-25%) and in men 15%(7-30%).The distribution of macroprolactin as a proportion of total prolactin was markedly skewed to the left with 69.7% of women and 62.9% of men having macroprolactin proportion of 20% or less. There was no relation between %macroprolactin and total measured prolactin, age or gender.Of relevance to clinical management, in 24% of men and 20.5% of women, correction for estimated macroprolactin gave an adjusted monomeric prolactin level below the agreed threshold for further investigation, potentially avoiding unnecessarily referral.In our clinical series, quotation of an adjusted monomeric prolactin would have resulted in unnecessary further investigation being avoided in a number of cases.Screening for macroprolactin is a key element of laboratory assessment for hyperprolactinaemia.In cases where measured total prolactin is significantly raised, quantitative reporting of estimated monomeric prolactin instead of just ‘macroprolactin positive' can avoid unnecessary investigations.