Fast heating of ultrahigh-density plasma as a step towards laser fusion ignition

Modern high-power lasers can generate extreme states of matter that are relevant to astrophysics, equation-of-state studies and fusion energy research. Laser-driven implosions of spherical polymer shells have, for example, achieved an increase in density of 1,000 times relative to the solid state. These densities are large enough to enable controlled fusion, but to achieve energy gain a small volume of compressed fuel (known as the 'spark') must be heated to temperatures of about 108 K (corresponding to thermal energies in excess of 10 keV). In the conventional approach to controlled fusion, the spark is both produced and heated by accurately timed shock waves, but this process requires both precise implosion symmetry and a very large drive energy. In principle, these requirements can be significantly relaxed by performing the compression and fast heating separately; however, this 'fast ignitor' approach also suffers drawbacks, such as propagation losses and deflection of the ultra-intense laser pulse by the plasma surrounding the compressed fuel. Here we employ a new compression geometry that eliminates these problems; we combine production of compressed matter in a laser-driven implosion with picosecond-fast heating by a laser pulse timed to coincide with the peak compression. Our approach therefore permits efficient compression and heating to be carried out simultaneously, providing a route to efficient fusion energy production.     

Additions to knowledge of Paleocene mammals from the North Horn Formation, central Utah

The distinctive but inadequately known Paleocene faunas of central Utah are significant in that they sample a time interval not well represented by sequences in other areas. New materials from the Wagon Road (late Puercan) and Dragon (early Torrejonian) local faunas, North Horn Formation, provide additional information on the composition of the assemblages and systematics of included mammal taxa. The proteutherian ? Propalaeosinopa is recorded for the first time, from the Wagon Road fauna, indicating a significant extension for the enigmatic family Pantolestidae, otherwise first known from the Torrejonian. Associated premolars of Aphronorus simpsoni , a pentacodontid proteutherian from the Dragon fauna, indicated that the species is more distinct from its Torrejonian congener, A. fraudator , than previously suspected. New materials of Desmatoclaenus hermaeus uphold the synonymy of this species with D. paracreodus and permit more adequate definition of the genus with respect to the arctocyonid Loxolophus and the phenacodontid Tetraclaenodon ; because Desmatoclaenus appears to share derived morphology with Loxolophus , we refer it to the basal condylarth family Arctocyonidae. The periptychid condylarth Haploconus , represented in the Wagon Road fauna by the geologically oldest described species of the genus, H. elachistsus , is shown to be distinctive in the configuration of lower molars and premolars; H. elachistus appears to be more primitive than species known from the Torrejonian of New Mexico. Some features of Haploconus are suggestive of the Conacodontinae, a distinctive clade of diminutive periptychids.     

Quantum annealing with manufactured spins

Many interesting but practically intractable problems can be reduced to that of finding the ground state of a system of interacting spins; however, finding such a ground state remains computationally difficult. It is believed that the ground state of some naturally occurring spin systems can be effectively attained through a process called quantum annealing. If it could be harnessed, quantum annealing might improve on known methods for solving certain types of problem. However, physical investigation of quantum annealing has been largely confined to microscopic spins in condensed-matter systems. Here we use quantum annealing to find the ground state of an artificial Ising spin system comprising an array of eight superconducting flux quantum bits with programmable spin-spin couplings. We observe a clear signature of quantum annealing, distinguishable from classical thermal annealing through the temperature dependence of the time at which the system dynamics freezes. Our implementation can be configured in situ to realize a wide variety of different spin networks, each of which can be monitored as it moves towards a low-energy configuration. This programmable artificial spin network bridges the gap between the theoretical study of ideal isolated spin networks and the experimental investigation of bulk magnetic samples. Moreover, with an increased number of spins, such a system may provide a practical physical means to implement a quantum algorithm, possibly allowing more-effective approaches to solving certain classes of hard combinatorial optimization problems.     

Lymphopenia and lymphocyte transformation in alcoholics.

The basis of peripheral blood lymphopenia observed in patients with chronic alcoholism and liver disease was investigated by examining the effect of sera of these patients on in vitro transformation of normal human peripheral blood lymphocytes. A positive correlation was demonstrated between the serum inhibition of phytohaemagglutinin- and pokeweed mitogen-induced transformation and the degree of lymphopenia. Thus serum factors may contribute to the observed lymphopenia by inhibiting lymphocyte production in vivo.     

Mutagenicity of melanin from human red hair

Summary TheSalmonella typhimurium histidine reversion test of Ames et al. was used to demonstrate that pheomelanin, the red-brown polymeric pigment produced in human skin and hair, becomes mutagenic after exposure to long wave-length UV-light; a finding consistent with the UV-induced somatic mutation hypothesis for the origin of freckles and the high susceptibility of redheads and blonds to sunlight-induced skin cancers.Acknowledgments.S. typhimurium strains were kindly provided by Dr Bruce N. Ames. Z. Harzanyi was supported by NIEHS grant 00675-03 and an Andrew W. Mellon Teacher-Scientist Award. M. Chedekel thanks The Ohio State University Graduate School for financial assistance.