~(22)Na(p,γ)~(23)Mg反应的实验研究

讨论了目前有关2 2 Na(p ,γ) 2 3Mg反应的实验研究工作 ,结合兰州放射性束流线上的放射性束流2 3Al的β+延发质子衰变实验的测量结果 ,给出了2 3Al延发衰变的质子能谱 ,并比较了近期实验给出的相关能级的自旋、宇称值 ,正是由于这种自旋、宇称和能级部分宽度的不确定性 ,导致了反应率计算的不确定性 .计算了同位旋相似态的共振强度 .对于测量到的新的延发衰变能级Ed =8.91 6MeV ,由于没有相应的能级宽度值 ,实验仅给出其相对共振强度值

Effect of Crystallographic Texture on Magnetic Characteristics of Cobalt Nanowires

Cobalt nanowires with controlled diameters have been synthesized using electrochemical deposition in etched ion-track polycarbonate membranes. Structural characterization of these nanowires with diameter 70, 90, 120 nm and length 30 mu m was performed by scanning electron microscopy, high-resolution transmission electron microscopy, and X-ray diffraction techniques. The as-prepared wires show uniform diameter along the whole length and X-ray diffraction analysis reveals that [002] texture of these wires become more pronounced as diameter is reduced. Magnetic characterization of the nanowires shows a clear difference of squareness and coercivity between parallel and perpendicular orientations of the wires with respect to the applied field direction. In case of parallel applied field, the coercivity has been found to be decreasing with increasing diameter of the wires while in perpendicular case; the coercivity observes lower values for larger diameter. The results are explained by taking into account the magnetocrystalline and shape anisotropies with respect to the applied field and domain transformation mechanism when single domain limit is surpassed.

福建柏与杉木纯林生长过程比较分析

在福建三明对临近的、土壤肥力相近的33年生福建柏与杉木人工纯林生长特性进行比较分析,结果表明:密度、平均胸径、平均高、林分蓄积量福建柏人工林分别为975株/hm2,21.6cm,21.37m,420.7m3/hm2;而杉木则分别为1117株/hm2,23.3cm,21.89m,488.7m3/hm2.33年生福建柏人工林的生产力低于杉木.福建柏在幼林阶段生长慢,但在成林阶段连年生长量超过杉木.福建柏10年生前树高、胸径、单株材积的总生长量均显著小于杉木,10年生后连年生长量逐渐增加,树高、胸径和材积连年生长量分别在15,18,19年生时超过杉木,33年生时树高、胸径和材积连年生长量分别是杉木的1.20,1.35和1.50倍.

模拟酸雨条件下树木氨基酸变化与害虫的发生关系

本文通过人工模拟酸雨试验小区置木招引的研究方法,对马尾松次期性害虫进行了招引试验,并对样木中16种氨基酸含量进行了分析。结果表明,马尾松样木在人工模拟酸雨条件下比对照都易招次期性害虫的入侵,样木中氨基酸含量也比对照高。但在强酸(pH=2)条件下其氨基酸含量比对照低,其原因还有待进一步探讨。

区域水土流失研究综述

以区域水土流失为主题 ,分析并阐述了该领域的研究现状 ,指出了当前存在的主要问题 ,并对研究的今后发展方向进行了展望。

农田生态系统微量元素循环研究进展

微量元素含量很低,但对生物却有着重要的生物学效应,因而微量元素研究的重要性也逐渐被人们所认同,许多人对土壤中微量元素的形态、有效性进行了研究。从农田生态系统中微量元素的含量、影响循环效率的因素及前人研究概况等方面对农田生态系统微量元素循环方面的研究进行了综述,同时指出了未来的研究方向。

杉木连栽土壤微生物多样性的比较研究

分析了位于湖南会同广坪镇1～4代人工杉木林根际土壤微生物数量变化情况,结果表明,随杉木连栽代数的增加,根际土壤中三大类群微生物数量发生显著变化,细菌和放线菌数量明显减少,真菌数量显著增加.利用PCR和DGGE技术分析了1～4代杉木林根际土壤细菌区系和真菌区系.结果表明,细菌生物多样性在不同连栽代数杉木根际土壤中变化不明显,各代杉木土壤之间细菌的遗传相似性为87%.而真菌随连栽代数的增加,DGGE图谱带逐渐减少,真菌生物多样性降低,各代杉木土壤之间真菌的遗传相似性也较低,仅为45%.对各代杉木土壤主要真菌类群的分析表明,随连栽代数的增加,病原真菌及产毒真菌增加显著.

土壤微生物生态过程与微生物功能基因多样性

土壤微生物在陆地生态系统中具有重要的生态功能,包括参与地球化学物质循环、污染物降解、环境剧烈变化的缓冲等.土壤微生物的生态功能与土壤功能联系密切,微生物群落结构与组成变化会直接影响土壤功能的发挥.土壤微生物通过具有生物活性的酶参与一系列的代谢活动,编码酶的功能基因成为微生物功能标记物.近10年中,以功能基因多样性为核心的分子生态学研究迅速发展,为从功能基因角度了解土壤微生物的生态功能提供了一个新的切入点.本文综述了与土壤微生物生态功能相关的功能基因多样性研究进展,并对该领域的发展前景提出展望.

有机物料中有机碳和有机氮的分解进程及分解残留率

在中国科学院沈阳生态站(埋袋法)和海伦站(砂滤管法)研究了不同有机物料中有机碳和有机氮的矿化进程、分解残留率和C/N的动态变化.结果表明:有机物料中有机碳和有机氮的分解进程可分为快、慢2个阶段;各有机物料中有机氮的矿化速率均明显低于有机碳,因而其残留率高于有机碳;有机物料C/N的下降速率也可分为快、慢2个阶段.经3～5年分解后,各种有机物料残留物的C/N趋于稳定:低C/N有机物料(猪粪)残留物的C/N值接近土壤腐殖质的C/N,约为10,已完成其腐殖化过程;高C/N有机物料残留物的C/N值处于适宜微生物活动的25左右,利于增加土壤有机质、培肥土壤.

Poly(ethylene glycol-co-propylene glycol) as a Macromolecular Plasticizing Agent for Polylactide: Thermomechanical Properties and Aging

Finding a Suitable plasticizer for polylactide (PLA) is necessary to overcome its brittleness and enlarge its range of applications. In this study, commercial PLA was melt-blended with a new plasticizer, an ethylene glycol/propylene glycol random copolymer [poly(ethylene glycol-co-propylene glycol) (PEPG)] with a typical number-average molecular weight of 1.2 kDa and an ethylene glycol content of 78.7 mol %. The thermal properties, crystallization behavior, and mechanical properties of the quenched blends and the properties of the blends after storage for 2 months under the ambient conditions were investigated in detail. The advantage of using PEPG is that it does not crystallize at room temperature and has good compatibility with PLA. The quenched PLA/PEPG blends were homogeneous and amorphous systems. With an increase in the PEPG content (5-20%), the glass-transition temperature, tensile strength, and modulus of the blends decreased, whereas the elongation at break and crystallizability increased dramatically. The cold crystallization of PLA resulted in phase separation of the PLA/PEPG blends by annealing of the blends at the crystallization temperature.

A novel method to construct a third-generation biosensor: self-assembling gold nanoparticles on thiol-functionalized poly(styrene-co-acrylic acid) nanospheres

A novel method for fabrication of horseradish peroxidase (HRP) biosensor has been developed by self-assembling gold nanoparticles on thiol-functionalized poly(styrene-co-acrylic acid) (St-co-AA) nanospheres. At first, a cleaned gold electrode was immersed in thiol-functionalized poly(St-co-AA) nanosphere latex prepared by emulsifier-free emulsion polymerization of St with AA and function with dithioglycol to assemble the nanospheres, then gold nanoparticles were chemisorbed onto the thiol groups. Finally, horseradish peroxi- dase was immobilized on the surface of the gold nanoparticles. The sensor displayed an excellent electrocatalytical response to reduction of H2O2 without the aid of an electron mediator. The sensor was highly sensitive to hydrogen peroxide with a detection limit of 4.0 mumol l(-1), and the linear range was from 10.0 mumol l(-1) to 7.0 mmol l(-1). The biosensor retained more than 97.8% of its original activity after 60 days of use. Moreover, the Studied biosensor exhibited good current repeatability and good fabrication reproducibility.

Electrochemical detection of DNA immobilized on gold colloid particles modified self-assembled monolayer electrode with silver nanoparticle label

The target DNA was immobilized successfully on gold colloid particles associated with a cysteamine monolayer on gold electrode surface. Self-assembly of colloidal An onto a cysteamine modified gold electrode can enlarge the electrode surface area and enhance greatly the amount of immobilized single stranded DNA (ssDNA). The electrontransfer processes of [Fe(CN)(6)](4)-/[Fe(CN)(6)](3-) on the gold surface were blocked due to the procedures of the target DNA immobilization, which was investigated by impedance spectroscopy. Then single stranded target DNA immobilized on the gold electrode hybridized with the silver nanoparticle-oligonucleotide DNA probe, followed by the release of the silver metal atoms anchored on the hybrids by oxidative metal dissolution, and the indirect determination of the released solubilized Ag-1 ions by anodic stripping voltammetry (ASV) at a carbon fiber microelectrode. The results show that this method has good correlation for DNA detection in the range of 10-800 pmol/1 and allows the detection level as low as 5 pmol/1 of the target oligonucleotides.

Synthesis and properties of PPP-based copolymers containing phenothiazine moiety

Novel soluble alternating conjugated copolymers (PFSP and PFSR) comprised of phenothiazine unit are synthesized by palladium-catalyzed Suzuki coupling reactions. Their thermal stability, photoluminescence, electroluminescence, hole injection and transport properties are investigated. The resulting copolymers exhibit good thermal stability and excellent hole-injection ability (about -5.2eV), which are closely matched to the work function of ITO. Double-layer devices demonstrate that PFSP is a promising hole-transporting material for electroluminescent devices.

CSF纳米炭黑硫化橡胶的性能

充填聚合物用的纳米级无机填料,由于其粒径极小,比表面积很大,从而增加了与聚合物分子间的相互作用,赋予聚合物纳米复合材料以良好的力学性能、热稳定性、气体阻隔特性以及导电特性[1].