Morphological Evolution During Synthesis of New AlPO4 Center dot H2O Crystal

A new crystal of aluminophosphate, AIPO(4)(.)H(2)O, is synthesized from two-batch aqueous solution under hydrothermal conditions. Three types of the crystal habits, i.e. the tetragonal double pyramid, the tetragonal prism and the plate-type tetragonal prism, are found from batch-A solution. Two types of the crystal habits, i.e. the hexagonal pyramid and the strip-type tetragonal prism, are found from batch-B solution. The change of crystal morphology is originated from the fluctuation of the synthesis conditions, such as the supersaturation, the temperature and the impurity content. It causes change of the step energies, the defect density and the step roughness, and further, change of the growth rates. Since the crystal morphology is sensitive to the mass transport mechanism, the crystal habits could be changed under the microgravity.

Strain-energy density ratio criterion for failure of composite-materials

n the authors' previous paper, the Strain Energy Density Ratio (SEDR) criterion was proposed. As an example of applications, it was used to predict cracking direction of mixed-mode fracture in a random short fibre laminated composite.

激光二极管抽运的国产Yb:YAG陶瓷激光器

研究了国产Yb:YAG陶瓷的激光输出特性。激光器采用激光二极管(LD)纵向同轴抽运Yb:YAG陶瓷样品,样品的掺杂原子数分数为1%,一端面镀940 nm和1030 nm双增透膜,另一端面镀1030 nm增透膜,激光器在1031 nm处获得了近红外激光输出。实验中分别测试了Yb:YAG陶瓷在不同输出透射率(T=4%,8%,10%)条件下的激光输出特性。整个实验过程中,激光器维持基横模运转。当输出透射率为10%,吸收的抽运功率为9 W时,激光器获得最大的激光输出功率为1.63 W,相应的斜率效率为23.2%。

Trapping of neutral atoms with a radio-frequency field

Based on the dressed-atom approach, we discuss a two-dimensional (2D) radio-frequency trap for neutral atoms, in which the trap potential derives from the magnetic-dipole transition among the hyperfine Zeeman sublevels. By adjusting the detuning of the radiation from resonance, the trapping states will be changed predominantly from the bare states Of m(FgF) > 0 to other states of m(FgF) < 0, where m(F) and g(F) are the quantum numbers of Zeeman sublevels and the Lande factor, respectively. This character contrasts finely with that, of a static magnetic, trap that can only trap or guide the states of m(FgF) > 0. In comparison to the optical field, the radio-frequency trap eliminates the spontaneous emission heating of the atoms. Unlike other oscillating traps reported in the e literature, the configuration of the radio-frequency trap is suitable for realization of a miniature magnetic guide.

高重复频率、窄脉宽全固态光纤放大器种子源

高重复频率、窄脉宽的全固态激光器种子源级联光纤放大器是获得高功率脉冲激光输出的有效手段.短上能态寿命的Nd∶YVO4晶体在连续抽运、高重复频率Q开关工作时容易得到接近连续性能的平均输出功率.理论分析了声光(AO)调Q器件中影响输出能量和脉宽大小的主要因素,优化配置了腔型参数.利用激光二极管(LD)光纤耦合模块端面抽运Nd∶YVO4晶体,实现了声-光调Q重复频率100 kHz以上,脉宽20 ns以下,波长1064 nm的激光输出.在抽运功率5.7 W时,得到了脉宽15.3 ns,重复频率150 kHz的种子光输出,在级联单级光纤放大器后,得到了20 W的输出.

三维立体显示用稀土掺杂氧卤碲酸盐玻璃

制备了一种新的Er^3+／Tm^3+/Yb^3+共掺氧卤碲酸盐玻璃。研究了基质玻璃的热稳定性能、Raman光谱和上转换发光。发现：氧卤碲酸盐玻璃具有好的热稳定性能和低的声子能量，在980nmLD激发下，可同时观察到明显的蓝色(476nm)、绿色(530nm和545nm)和红色(656nm)上转换发光。上转换蓝光(476nm)是由于Tm^3+离子1^G4→3^3H6跃迁，上转换的绿光(530nm和545nm)是由于Er^3+离子2^H11/2→4^I15／2和4^S3/2→4^I15/2跃迁，上转换红光(6

放牧对典型草原土壤-植物系统中碳、氮、磷库特征的影响

放牧是内蒙古典型草原最主要的利用方式。放牧已对草原生态系统的结构和功能产生了巨大的影响。本论文研究了放牧对内蒙古典型草原土壤-植物系统中碳、氮、磷库特征的影响，结果表明： （1）草地开垦已使土壤C、N贮量显著损失。放牧已使羊草草原土壤C贮量表现出下降的趋势，大针茅草原没有表现出这种变化趋势。 （2）放牧尚没有使土壤全N发生显著变化，但土壤N素一些组分的比例发生了变化。放牧后，土壤NH_3-N下降，酸不溶态N比例有所提高;放牧使Fe-P比例显著降低。 （3）蒙古草原土壤微生物量C、N与土壤有机C、全N、降雨量、温度均表现出了很好的相关性。放牧对微生物量的影响与不同草原类型和放牧率有关。 （4）放牧使土壤养分元素的空间异质性加大。退化草地恢复过程中小叶锦鸡儿灌丛诱导了植物组成、生物量和土壤化学元素含量在空间上的分异，这种生态效应有利于退化草地的恢复。 （5）不同放牧强度对土壤C、N、P库和植物系统中C、N、P含量的影响不同。放牧使植物系统地上部C含量下降，N、P含量提高。高强度的放牧使土壤N、根系中的N素向表层相对聚集，表现出明显的表聚化现象。植物C/N、C/P比在中、重度放牧强度下最低，此时植物残体分解速率最高，极度放牧最终C、N循环速率减小。不考虑放牧率，研究放牧对土壤C、N、P含量的影响可能会得出矛盾的结论。 （6）放牧草地中低等植物地衣、蓝细菌在元素化学循环中的作用提高。地衣Xanthoparmelia camtschadalis （Ach.）的生物量在经度放牧草地中最高，其体内C、N含量与放牧率的关系与维管植物相似。退化草地中蓝细菌可能是最重要的N素来源。

Frog skins keep redox homeostasis by antioxidant peptides with rapid radical scavenging ability

The question of how amphibians can protect themselves from reactive oxygen species when exposed to the sun in an oxygen-rich atmosphere is important and interesting, not only from an evolutionary viewpoint, but also as a primer for researchers interested in mammalian skin biology, in which such peptide systems for antioxidant defense are not well studied. The identification of an antioxidant peptide named antioxidin-RL from frog (Odorrana livida) skin in this report supports the idea that a peptide antioxidant system may be a widespread antioxidant strategy among amphibian skins. Its ability to eliminate most of the 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) radical tested within 2 s, which is much faster than the commercial antioxidant factor butylated hydroxytoluene, suggests that it has a potentially large impact on redox homeostasis in amphibian skins. Cys10 is proven to be responsible for its rapid radical scavenging function and tyrosines take part in the binding of antioxidin-RL to radicals according to our nuclear magnetic resonance assay. (C) 2010 Elsevier Inc. All rights reserved.

衰老及促智药影响神经细胞膜流动性机制的研究进展

细胞膜流动性通常是指膜脂质的流动性。神经细胞膜功能的正常进行要求膜脂质保持适宜的流动状 态。膜流动性改变将导致膜电位、离子通透性、跨膜物质运输、信号转导等一系列改变。老年动物及阿尔茨海 默氏病(AD) 患者脑神经细胞膜流动性显著降低, 主要与自由基增多引起的脂质过氧化反应、神经细胞钙平衡 失调有关, 此外, 还与其脑内神经元上的受体密度、β- 淀粉样蛋白沉积有关。促智药(吡咯烷酮类、人参皂 甙、银杏叶提取物EGb761) 能明显增强老年动物及AD 患者脑神经细胞膜的流动性。

High-density InAs nanowires realized in situ on (100) InP

High-density InAs nanowires embedded in an In0.52Al0.48As matrix are fabricated in situ by molecular beam epitaxy on (100) InP. The average cross section of the nanowires is 4.5 x 10 nm(2). The linear density is as high as 70 wires/mu m. The spatial alignment of the multilayer arrays exhibit strong anticorrelation in the growth direction. Large polarization anisotropic effect is observed in polarized photoluminescence measurements. (C) 1999 American Institute of Physics. [S0003-6951(99)04134-0].

优化MISTY型结构的伪随机性

该文对4轮MISTY和3轮双重MISTY两种结构进行了优化。在保持其安全性不变的情况下，把4轮MISTY结构中第1轮的伪随机置换，用一个XOR-泛置换代替，第2，第3轮采用相同的伪随机置换，3轮结构中第1轮的伪随机置换用XOR-泛置换代替，其它轮相同。伪随机置换的数量分别由原来的4个变为2个，3个变为1个，从而缩短了运行时间，节省了密钥量，大大降低了结构的实现成本。