ABSTRACT
Indirect drive experiments at the National Ignition Facility are designed to achieve fusion by imploding a fuel capsule with x rays from a laser-driven hohlraum. Previous experiments have been unable to determine whether a deficit in measured ablator implosion velocity relative to simulations is due to inadequate models of the hohlraum or ablator physics. ViewFactor experiments allow for the first time a direct measure of the x-ray drive from the capsule point of view. The experiments show a 15%-25% deficit relative to simulations and thus explain nearly all of the disagreement with the velocity data. In addition, the data from this open geometry provide much greater constraints on a predictive model of laser-driven hohlraum performance than the nominal ignition target.
ABSTRACT
The first measurements of multiple, high-pressure shock waves in cryogenic deuterium-tritium (DT) ice layered capsule implosions on the National Ignition Facility have been performed. The strength and relative timing of these shocks must be adjusted to very high precision in order to keep the DT fuel entropy low and compressibility high. All previous measurements of shock timing in inertial confinement fusion implosions [T. R. Boehly et al., Phys. Rev. Lett. 106, 195005 (2011), H. F. Robey et al., Phys. Rev. Lett. 108, 215004 (2012)] have been performed in surrogate targets, where the solid DT ice shell and central DT gas regions were replaced with a continuous liquid deuterium (D2) fill. This report presents the first experimental validation of the assumptions underlying this surrogate technique.
ABSTRACT
In the albino rat, topical betamethasone 17-valerate acts as an anticorticosteroid. This steroid is inactive in a dermal atrophy assay over a dose range where betamethasone and hydrocortisone display atrophogenic activity. At appropriate concentrations betamethasone 17-valerate competitively inhibits the atrophogenic effects of both betamethasone and triamcinolone acetonide. Since betamethasone and betamethasone 17-valerate penetrate rat skin in vivo at essentially the same rate, it is concluded that the latter compound is relatively resistant to hydrolysis during penetration, and that it binds to rat corticosteroid receptor proteins in such a manner as to prevent expression of corticosteroid activity. Therefore, the rat cannot be used as a model species to predict activity in man for this compound.
Subject(s)
Adrenal Cortex Hormones/antagonists & inhibitors , Betamethasone Valerate/pharmacology , Betamethasone/analogs & derivatives , Skin/pathology , Administration, Topical , Animals , Atrophy , Betamethasone/antagonists & inhibitors , Dose-Response Relationship, Drug , Male , Rats , Skin/drug effects , Triamcinolone Acetonide/antagonists & inhibitorsABSTRACT
Corticosteroid-induced dermal atrophy has been studied in the rat using daily application of ethanolic solutions to small areas of flank skin. After 12 days of treatment, the degree of atrophy was determined by comparing the weights of skin plugs (16 mm diameter) taken from the treated areas with contralaterally paired control areas. Doses can be adjusted so that systemic effects are minimized and only local effects are observed. Hydrocortisone, hydrocortisone butyrate, dexamethasone, betamethasone, desonide and triamcinolone acetonide all produce atrophy in the rat, and the degree of thinning is dose dependent. Potencies in the dermal atrophy assay compare directly with topical anti-inflammatory potencies in the rat, and the presence of fluorine in the steroid molecule is not a determining factor in the production of atrophy.
