Lawson criterion for ignition exceeded in an inertial fusion experiment

For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin "burn propagation" into surrounding cold fuel, enabling the possibility of high energy gain. While "scientific breakeven" (i.e., unity target gain) has not yet been achieved (here target gain is 0.72, 1.37 MJ of fusion for 1.92 MJ of laser energy), this Letter reports the first controlled fusion experiment, using laser indirect drive, on the National Ignition Facility to produce capsule gain (here 5.8) and reach ignition by nine different formulations of the Lawson criterion

Deuterium Quadrupole Coupling Constants and Asymmetry Parameters in Bridging Metal Hydride Complexes

The deuterium quadrupole coupling constants and the asymmetry parameters for six bridging metal hydrides, [Et4N][2HCr2(CO)l0], [(Ph3P)2N][2HCr2(CO)10], [Ph4P][2HCr2(CO)10], [Et4N][2HW2(CO)10], [(Ph3P)2N][2HW2(CO)10], and [Ph4P] [2HW2(CO)10], were determined from the Levenberg-Marquardt nonlinear least-squares fit of the solid-state deuterium NMR powder patterns. The quadrupole coupling constant (absolute value) varies from 54.1 (8) to 90.4 (2) kHz; the asymmetry parameter ranges from 0.027 (3) to 0.31 (2). The relationships between the quadrupole coupling constant and M-H bond length and between the asymmetry parameter and the M-H-M bond geometry are discussed on the basis of a point charge model. In order to assess motional averaging at the deuterium site, the temperature dependence of the 2H NMR spectrum for two bridging metal hydrides was examined at 140, 200, and 300 K. In addition, the isotropic chemical shifts have been obtained from 1H CRAMPS. These NMR results are highly pertinent to NMR spectroscopy of adsorbed hydrogen on metal surfaces. The solid-state structure of [Ph4P][2HCr2(CO)10] has been determined by X-ray diffraction. © 1991, American Chemical Society. All rights reserved

Reappraisal of microsurgical decompression and neurectomy of the occipital nerve in the treatment of occipital neuralgia

The subventricular zone (SVZ) is greatly expanded in primates with gyrencephalic cortices and is thought to be absent from vertebrates with three-layered, lissencephalic cortices, such as the turtle. Recent work in rodents has shown that Tbr2-expressing neural precursor cells in the SVZ produce excitatory neurons for each cortical layer in the neocortex. Many excitatory neurons are generated through a two-step process in which Pax6-expressing radial glial cells divide in the VZ to produce Tbr2-expressing intermediate progenitor cells, which divide in the SVZ to produce cortical neurons. We investigated the evolutionary origin of SVZ neural precursor cells in the prenatal cerebral cortex by testing for the presence and distribution of Tbr2-expressing cells in the prenatal cortex of reptilian and avian species. We found that mitotic Tbr2(+) cells are present in the prenatal cortex of lizard, turtle, chicken, and dove. Furthermore, Tbr2(+) cells are organized into a distinct SVZ in the dorsal ventricular ridge (DVR) of turtle forebrain and in the cortices of chicken and dove. Our results are consistent with the concept that Tbr2(+) neural precursor cells were present in the common ancestor of mammals and reptiles. Our data also suggest that the organizing principle guiding the assembly of Tbr2(+) cells into an anatomically distinct SVZ, both developmentally and evolutionarily, may be shared across vertebrates. Finally, our results indicate that Tbr2 expression can be used to test for the presence of a distinct SVZ and to define the boundaries of the SVZ in developing cortices. J. Comp. Neurol. 524:433-447, 2016. © 2015 Wiley Periodicals, Inc