Systematic Analysis of Direct-Drive Baseline Designs for Shock-Ignition with the Laser Megajoule

Direct-drive inertial confinement thermonuclear fusion consists in illuminating a shell of cryogenic Deuterium and Tritium (DT) mixture with many intense beams of laser light. Capsule is composed of DT gassurrounded by cryogenic DT as combustible fuel. Basic rules are used to define shell geometry from aspect ratio, fuel mass and layers densities. We define baseline designs using two aspect ratio (A=3 and A=5) who complete HiPER baseline design (A=7.7). Aspect ratio is defined as the ratio of ice DT shell inner radius over DT shell thickness. Low aspect ratio improves hydrodynamics stabilities of imploding shell. Laser impulsion shape and ablator thickness are initially defined by using Lindl (1995) pressure ablation and mass ablation formulae for direct-drive using CH layer as ablator. In flight adiabat parameter is close to one during implosion. Velocitie simplosions chosen are between 260 km/s and 365 km/s. More than thousand calculations are realized for each aspect ratio in order to optimize the laser pulse shape. Calculations are performed using the one-dimensional version of the Lagrangian radiation hydrodynamics FCI2. We choose implosion velocities for each initial aspect ratio, and we compute scaled-target family curves for each one to find self-ignition threshold. Then, we pick points on each curves that potentially product high thermonuclear gain and compute shock ignition in the context of Laser MegaJoule. This systematic analyze reveals many working points which complete previous studies ´allowing to highlight baseline designs, according to laser intensity and energy, combustible mass and initial aspect ratio to be relevant for Laser MegaJoule.

Visualization of Cavitated Vessels in Winter and Refilled Vessels in Spring in Diffuse-Porous Trees by Cryo-Scanning Electron Microscopy1

Xylem cavitation in winter and recovery from cavitation in the spring were visualized in two species of diffuse-porous trees, Betula platyphylla var. japonica Hara and Salix sachalinensis Fr. Schm., by cryo-scanning electron microscopy after freeze-fixation of living twigs. Water in the vessel lumina of the outer three annual rings of twigs of B. platyphylla var. japonica and of S. sachalinensis gradually disappeared during the period from January to March, an indication that cavitation occurs gradually in these species during the winter. In April, when no leaves had yet expanded, the lumina of most of the vessels of both species were filled with water. Many vessel lumina in twigs of both species were filled with water during the period from the subsequent growth season to the beginning of the next winter. These observations indicate that recovery in spring occurs before the onset of transpiration and that water transport through twigs occurs during the subsequent growing season. We found, moreover, that vessels repeat an annual cycle of winter cavitation and spring recovery from cavitation for several years until irreversible cavitation occurs.

Regulation of Oleoresinosis in Grand Fir (Abies grandis)1 : Differential Transcriptional Control of Monoterpene, Sesquiterpene, and Diterpene Synthase Genes in Response to Wounding

Grand fir (Abies grandis Lindl.) has been developed as a model system for the study of wound-induced oleoresinosis in conifers as a response to insect attack. Oleoresin is a roughly equal mixture of turpentine (85% monoterpenes [C10] and 15% sesquiterpenes [C15]) and rosin (diterpene [C20] resin acids) that acts to seal wounds and is toxic to both invading insects and their pathogenic fungal symbionts. The dynamic regulation of wound-induced oleoresin formation was studied over 29 d at the enzyme level by in vitro assay of the three classes of synthases directly responsible for the formation of monoterpenes, sesquiterpenes, and diterpenes from the corresponding C10, C15, and C20 prenyl diphosphate precursors, and at the gene level by RNA-blot hybridization using terpene synthase class-directed DNA probes. In overall appearance, the shapes of the time-course curves for all classes of synthase activities are similar, suggesting coordinate formation of all of the terpenoid types. However, closer inspection indicates that the monoterpene synthases arise earlier, as shown by an abbreviated time course over 6 to 48 h. RNA-blot analyses indicated that the genes for all three classes of enzymes are transcriptionally activated in response to wounding, with the monoterpene synthases up-regulated first (transcripts detectable 2 h after wounding), in agreement with the results of cell-free assays of monoterpene synthase activity, followed by the coordinately regulated sesquiterpene synthases and diterpene synthases (transcription beginning on d 3–4). The differential timing in the production of oleoresin components of this defense response is consistent with the immediate formation of monoterpenes to act as insect toxins and their later generation at solvent levels for the mobilization of resin acids responsible for wound sealing.

Hd6, a rice quantitative trait locus involved in photoperiod sensitivity, encodes the α subunit of protein kinase CK2

Hd6 is a quantitative trait locus involved in rice photoperiod sensitivity. It was detected in backcross progeny derived from a cross between the japonica variety Nipponbare and the indica variety Kasalath. To isolate a gene at Hd6, we used a large segregating population for the high-resolution and fine-scale mapping of Hd6 and constructed genomic clone contigs around the Hd6 region. Linkage analysis with P1-derived artificial chromosome clone-derived DNA markers delimited Hd6 to a 26.4-kb genomic region. We identified a gene encoding the α subunit of protein kinase CK2 (CK2α) in this region. The Nipponbare allele of CK2α contains a premature stop codon, and the resulting truncated product is undoubtedly nonfunctional. Genetic complementation analysis revealed that the Kasalath allele of CK2α increases days-to-heading. Map-based cloning with advanced backcross progeny enabled us to identify a gene underlying a quantitative trait locus even though it exhibited a relatively small effect on the phenotype.

Chemical communication in scarab beetles: reciprocal behavioral agonist-antagonist activities of chiral pheromones.

A novel mechanism of reciprocal behavioral agonist-antagonist activities of enantiomeric pheromones plays a pivotal role in overcoming the signal-to-noise problem derived from the use of a single-constituent pheromone system in scarab beetles. Female Anomala osakana produce (S, Z)-5-(+)-(1-decenyl)oxacyclopentan-2-one, which is highly attractive to males; the response is completely inhibited even by 5% of its antipode. These two enantiomers have reverse roles in the Popillia japonica sex pheromone system. Chiral GC-electroantennographic detector experiments suggest that A. osakana and P. japonica have both R and S receptors that are responsible for behavioral agonist and antagonist responses.

Mexican papita viroid: putative ancestor of crop viroids.

The potato spindle tuber disease was first observed early in the 20th century in the northeastern United States and shown, in 1971, to be incited by a viroid, potato spindle tuber viroid (PSTVd). No wild-plant PSTVd reservoirs have been identified; thus, the initial source of PSTVd infecting potatoes has remained a mystery. Several variants of a novel viroid, designated Mexican papita viroid (MPVd), have now been isolated from Solanum cardiophyllum Lindl. (papita güera, cimantli) plants growing wild in the Mexican state of Aguascalientes. MPVd's nucleotide sequence is most closely related to those of the tomato planta macho viroid (TPMVd) and PSTVd. From TPMVd, MPVd may be distinguished on the basis of biological properties, such as replication and symptom formation in certain differential hosts. Phylogenetic and ecological data indicate that MPVd and certain viroids now affecting crop plants, such as TPMVd, PSTVd, and possibly others, have a common ancestor. We hypothesize that commercial potatoes grown in the United States have become viroid-infected by chance transfer of MPVd or a similar viroid from endemically infected wild solanaceous plants imported from Mexico as germplasm, conceivably from plants known to have been introduced from Mexico to the United States late in the 19th century in efforts to identify genetic resistance to the potato late blight fungus, Phytophthora infestans.