Sun Xiaoyan (孙晓燕)

Phylogenetic Positions of the Enigmatic Asiatic Fern Genera Diplaziopsis and Rhachidosorus from Analyses of Four Plastid Genes

Abstract Nucleotide sequences from four plastid genes (rbcL, atpB, atpA, rps4) were used to infer relationships of Diplaziopsis and Rhachidosorus. The phylogenetic positions of these two Asian fern genera have been debated, and neither had been included in the most recent global molecular systematic studies of ferns. Our four plastid gene sequence analyses supported a sister relationship between Diplaziopsis, Rhachidosorus and the North American Homalosorus, the monophyletic group of the newly-examined genera is an early diverging lineage of Woodsiaceae, and far away from athyrioid ferns. The inferred relationships of Diplaziopsis and Rhachidosorus are not consistent with most recent treatments, while, some synapomorphic characteristics are shared with these two genera. Further studies on more morphological characters and gametophytes of these two genera are needed to test these relationship hypotheses.

General design basis for a final optics assembly to decrease filamentary damage

The high-power laser beam in the final optics assembly of high-power laser facilities is often modulated by contamination particles, which may cause local high light intensity, thereby increasing the filamentary damage probability for optical components. To study the general design basis for a final optics assembly to decrease the risk of filamentary damage, different-sized contamination particles deposited on a component surface are simulated to modulate a 351-nm laser beam based on the optical transmission theory, and the corresponding simulation results are analyzed statistically in terms of the propagation characteristic and the light field intensity distribution of the modulated laser beam. The statistical results show that component thickness and distance between components can to some extent be optimized to reduce the appearance of local high light intensity, and the general design basis of component thickness and arrangement are given for different control levels of particle sizes. Moreover, the statistical results can also predict the laser beam quality approximately under the existing optics design and environmental cleanliness. The optimized design for final optics assembly based on environmental cleanliness level is useful to prolong the lifetime of optics and enhance the output power of high-power laser facilities.

Scaling property in one-nucleon removal reactions induced by exotic nuclei

Assuming a core plus valence nucleon structure, one-nucleon removal reaction is investigated within the framework of few-body Glauber theory. Fermi-type distribution is used for the core density, while the wavefunction of the valence nucleon is calculated by solving the single particle eigenvalue problem of the Schrodinger equation with the Woods-Saxon potential. The parallel momentum distribution (P(parallel to)) of the fragments is calculated for isotopes with 3 < Z < 18. A remarkable scaling property is observed from the dependence of the dimensionless quantity R(v)(2)/R(c)(2) on the full width at half maximum of the parallel momentum distribution (FWHM(P parallel to)). R(v)(2)/R(c)(2) is a measure of the exotic extent of the nuclear halo. Based on the obtained scaling law, FWHM(P parallel to) can be used as an experimental observable to extract R(v)(2)/R(c)(2) and measure the exotic extent for the nuclear halo.