Angular distribution and conversion of multi-keV L-shell X-ray sources produced from nanosecond laser irradiated thick-foil targets

An experimental study on the angular distribution and conversion of multi-keV X-ray sources produced from 2 ns-duration 527nm laser irradiated thick-foil targets on Shenguang II laser facility (SG-II) is reported. The angular distributions measured in front of the targets can be fitted with the function of f(theta) = alpha+ (1- alpha)cos(beta) theta (theta is the viewing angle relative to the target normal), where alpha = 0.41 +/- 0.014, beta = 0.77 +/- 0.04 for Ti K-shell X-ray Sources (similar to 4.75 keV for Ti K-shell), and alpha = 0.085 +/- 0.06, beta = 0.59 +/- 0.07 for Ag/Pd/Mo L-shell X-ray Sources (2-2.8 keV for Mo L-shell, 2.8-3.5 keV for Pd L-shell, and 3-3.8 keV for Ag L-shell). The isotropy of the angular-distribution of L-shell emission is worse than that of the K-shell emission at larger viewing angle (>70 degrees), due to its larger optical depth (stronger self-absorption) in the cold plasma side lobe Surrounding the central emission region, and in the central hot plasma region (emission region). There is no observable difference in the angular distributions of the L-shell X-ray emission among Ag, Pd, and Mo. The conversion efficiency of Ag/Pd/Mo L-shell X-ray sources is higher than that of the Ti K-shell X-ray sources, but the gain relative to the K-shell emission is not as high as that by using short pulse lasers. The conversion efficiency of the L-shell X-ray sources decrease, with increasing atomic numbers (or X-ray photon energy), similar to the behavior of the K-shell X-ray Source.

Preparation of nano-hydroxyapatite/poly(L-lactide) biocomposite microspheres

Nano-hydroxyapatite (HA)/poly(L-lactide) (PLLA) composite microspheres with relatively uniform size distribution were prepared by a solid-in-oil-in-water (s/o/w) emusion solvent evaporation method. The encapsulation of the HA nanopaticles in microshperes was significantly improved by grafting PLLA on the surface of the HA nanoparticles (p-HA) during emulsion process. This procedure gave a possibility to obtain p-HA/PLLA composite microspheres with uniform morphology and the encapsulated p-HA nanoparticle loading reached up to 40 wt% (33 wt% of pure HA) in the p-HA/PLLA composite microspheres. The microstructure of composite microspheres from core-shell to single phase changed with the variation of p-HA to PLLA ratios. p-HA/PLLA composite microspheres with the diameter range of 2-3 mu m were obtained. The entrapment efficiency of p-HA in microspheres could high up to 90 wt% and that of HA was only 13 wt%. Surface and bulk characterizations of the composite microspheres were performed by measurements such as wide angle X-ray diffraction (WAXD), thermal gravimetric analysis (TGA), environmental scanning electron microscope (ESEM) and transmission electron microscopy (TEM).

Shape-memory and biocompatibility properties of segmented polyurethanes based on poly(L-lactide)

A series of segmented poly (L-lactide)-polyurethanes (PLA-PU) were synthesized by a two-step method, with oligo-poly(L-lactide) (PLA) as the soft segments and the reaction product of 2,4-toluene diisocyanate(TDI) and ethylene glycol(EG) as the hard segments. The shape memory properties of PLA-PUs were examined. The processed PLA-PUs could recover almost 100% to their original shape within 10 degrees C from the lowest recovery temperature. In the recovery process, the PLA-PUs showed a maximum contracting stress of shape change in the range of 1.5-4 MPa depending on the PLA segmental length and the hard-segmental content and higher than that of poly (e-caprolactone polyurethane) (PCL-PU). Besides, the influence of deforming and fixing temperatures on shape memory properties of PLA-PU was studied in detail. They could affect not only the recovery temperature but also the maximum contracting stress. The experiments of cell incubation were used to evaluate the biocompatibility of PLA-PU. The results show that the biocompatibility of PLA-PU is comparable to that of the pure PLA. This kind of polyurethane can be used as implanted medical devices with a shape memory property.

Competition of lamellar orientation in thin films of a symmetric poly(styrene)-b-poly(L-lactide)diblock copolymer in melt state

We have studied the lamellar orientation in thin films of a model diblock copolymer, symmetric poly(styrene)-b-poly(L-lactide) (PS-PLLA), in the melt state on supported silicon wafer surface. In this system, while the PLLA block prefers to wet the polymer/substrate interface, the polymer/air as well as polymer/polymer interface is neutral for both blocks due to the similar surface energies of PS and PLLA in melt state. Our results demonstrate that the interplay of the interfaces during phase separation results in a series of structures before approaching the equilibrium state. Lamellar orientation of thin films with different initial film thicknesses at different annealing stages has been investigated using atomic force microscopy (AFM), transmission electronic microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). It is found that in the early stage (annealing time t < 10 min), the polymer/substrate interface dominates the structure evolution, leading to a parallel lamellar structure with holes or islands formed depending on the initial film thickness. Later on, the neutral air interface becomes important and leads to a transition of lamellar orientation from parallel to perpendicular. It is interesting to see that for films with thickness h > 2L, where L is the bulk lamellar period, the lamellar orientation transition can occur independently in different parallel lamellar domains due to the neutrality of polymer/polymer interface.

Species of rare earth(III) and calcium(II) in the presence of L-aspartic acid and L-arginine

Rare earth (III)-Asp-Arg and Ca(II)-Asp-Arg systems were studied by potentiometric titration under physiological conditon. The species of each system were determined. The distribution of Tb (III) and Ca(II) species was discussed, as well as in the quaternary system of Tb(III)-Ca(II)-Asp-Arg.

稀土与L-脯氨酸配合物的合成、表征及晶体结构

本文合成了通式为Ln(L-Pro)_3(H_2O)_2(ClO_4)_3(Ln=Pr、Nd、Er,L-Pro=L-脯氨酸)的固体配合物.元素分析、红外光谱、热分析对配合物进行了表征.培养了镨脯氨酸配合物的单晶,X射线四圓衍射确定了晶体的结构.晶体属于单斜晶系、空间群P2_1,α=0.9879(3),b=2.1883(4),c=1.3393(2)nm,β=91.23(2)°,V=2.895(1)nm~3,Z=2.晶体中每一个镨原子与来自6个L-脯氨酸羧基上的6个氧原子和2个结晶水分子键合,形成了一个八配位的稍有畸变的三角十二面体.每一个L-脯氨酸分子以羧基双齿方式与两个镨离子配位,形成了一个无限长的链状结构.