Debris collection from implosion of microballoons

Recovery of krypton from implosion of glass microballoons has been studied in the development of a radiochemical diagnostic for determination of /sub fuel/. Collection onto metal surfaces following implosions performed on the OMEGA laser with 1-3 TW (1-2 kJ) of 0.35 ..mu..m light is consistent with an ion implantation mechanism. The dependence of the intrinsic collection efficiency on the energy fluence to the collector surface and its variation in implosions carried out under the same nominal conditions indicate ion energies extending to at least 0.1 MeV and energy distribution functions that are sensitive to the details of the implosion dynamics. Intrinsic sticking efficiencies approaching 0.5 can be obtained in the limit of low total energy fluence to the collector surface (less than or equal to 0.1 J cm/sup -2/)

The discontinuous nature of chromospheric activity evolution

Chromospheric activity has been thought to decay smoothly with time and, hence, to be a viable age indicator. Measurements in solar type stars in open clusters seem to point to a different conclusion: chromospheric activity undergoes a fast transition from Hyades level to that of the Sun after about 1 Gyr of main--sequence lifetime and any decaying trend before or after this transition must be much less significant than the short term variations.Comment: 6 pages, 1 figure, to be published in Astrophysics and Space Scienc

The Theory of Brown Dwarfs and Extrasolar Giant Planets

Straddling the traditional realms of the planets and the stars, objects below the edge of the main sequence have such unique properties, and are being discovered in such quantities, that one can rightly claim that a new field at the interface of planetary science and and astronomy is being born. In this review, we explore the essential elements of the theory of brown dwarfs and giant planets, as well as of the new spectroscopic classes L and T. To this end, we describe their evolution, spectra, atmospheric compositions, chemistry, physics, and nuclear phases and explain the basic systematics of substellar-mass objects across three orders of magnitude in both mass and age and a factor of 30 in effective temperature. Moreover, we discuss the distinctive features of those extrasolar giant planets that are irradiated by a central primary, in particular their reflection spectra, albedos, and transits. Aspects of the latest theory of Jupiter and Saturn are also presented. Throughout, we highlight the effects of condensates, clouds, molecular abundances, and molecular/atomic opacities in brown dwarf and giant planet atmospheres and summarize the resulting spectral diagnostics. Where possible, the theory is put in its current observational context.Comment: 67 pages (including 36 figures), RMP RevTeX LaTeX, accepted for publication in the Reviews of Modern Physics. 30 figures are color. Most of the figures are in GIF format to reduce the overall size. The full version with figures can also be found at: http://jupiter.as.arizona.edu/~burrows/papers/rm

Propriedades biomecânicas da fáscia lata e do ligamento cruzado cranial de cães Biomechanical properties of canine fascia lata and cranial cruciate ligament

Preparações bilaterais do ligamento cruzado cranial e da fáscia lata de 15 cães foram testadas na máquina Instron, modelo 4482. Os animais, de ambos os sexos, idade entre um e quatro anos, pesavam em média 11,80 ± 1,99kg. Os retalhos de fáscia lata foram testados retilíneos e torcidos e o ligamento cruzado cranial foi testado mantendo um ângulo de 135° entre a tíbia e o fêmur e 0°, 15° de rotação externa e 15° de rotação interna da tíbia em relação ao fêmur. A velocidade dos testes de tração foi de 8,47mm por segundo. A força máxima dos retalhos de fáscia lata foi aproximadamente de 290 Newtons, e a tensão máxima, 28 Megapascal. A torção não influenciou na resistência dos retalhos de fáscia lata. A rotação externa e interna da tíbia de 15º também não influenciou na força máxima do ligamento cruzado cranial, que foi aproximadamente de 660 Newtons, nem na tensão máxima, que foi cerca de 75 Megapascal. Os retalhos de fáscia lata apresentaram 44% da força máxima e 37% da tensão máxima do ligamento, no entanto, os retalhos torcidos mostraram maior deformação do que os retalhos retilíneos, alcançando cerca de 70% da deformação do ligamento, sendo essa forma a mais indicada na substituição do ligamento cruzado cranial.<br>Bilateral preparations of fascia lata and cranial cruciate ligament from 15 dogs were tested in Instron machine, model 4482. Dogs were from both sexes, between one and four years of age and weighing in average about 11.80 ± 1.99kg. Fascia lata strips were tested straight and twisted and the cranial cruciate ligaments were tested with an angle of 135° between the femur and tibia and 0°, 15° of external tibial rotation and 15° of internal tibial rotation in relation to femur. The traction test velocity was 8.47mm per second. The maximum force of fascia lata strips was of approximately 290 Newtons and the maximum stress, 28 Megapascal. Similar results of strength and stress properties were found for the strips of fascia lata straight and twisted, although twisted strips presented a higher deformation than straight ones. External and internal tibial rotation did not influence the maximum force and maximum stress of the cranial cruciate ligament, that were of about 660 Newtons and 75 Megapascal, respectively. Fascia lata strips reached 44% of ligaments maximum force and 37% of maximum strain, and twisted strips reached 70% of ligaments maximum deformation, deserving straight strips to be recommended for cranial cruciate ligament substitution in dogs

Polar-direct-drive experiments on OMEGA

Polar direct drive (PDD), a promising ignition path for the NIF while the beams are in the indirect-drive configuration [S. Skupsky et al., Phys. Plasmas 11, 2763 (2004)], is currently being investigated on the OMEGA laser system by using 40 beams in six rings repointed to more uniformly illuminate the target [R. S. Craxton et al., Phys. Plasmas 12, 056304 (2005).]. The OMEGA experiments are being performed with standard, “warm” targets (865-$\mu$m-diam, 20-$\mu$m-thick, CH shells filled with 15-atm D$_{2})$ with and without the use of an equatorial “Saturn-like” toroidally shaped CH ring [R. S. Craxton and D. W. Jacobs-Perkins, Phys. Rev. Lett. 94, 095002 (2005)] (nominal dimensions: 2.2-mm diam measured to ring center, 0.3-mm thick). For the Saturn case, the plasma formed around the ring refracts light toward the target equator as the ring plasma expands. The nominal laser drive is a 1-ns flat pulse, ${\sim}$400 J per beam, employing 1-THz, 2-D SSD with polarization smoothing. Target implosion symmetry is diagnosed with framed x-ray backlighting using additional OMEGA beams and by time-integrated x-ray imaging of the stagnating core. The best results have been obtained with Saturn targets by varying the beam pointing and ring diameter, achieving ${\sim}$75% of the fusion yield from symmetrically illuminated targets with the same total energy (60 beams, 15.3 kJ)