静止和充气培养条件下短期紫外辐射对钝顶螺旋藻光化学效率的影响

为了研究短期太阳紫外辐射对钝顶螺旋藻的影响,作者将静止和充气培养的藻体,暴露在全波长太阳辐射PAB(PAR+UVA+UVB),去除UVB辐射PA(PAR+UVA)及切断所有紫外辐射的光合有效辐射P(PAR)三种光处理条件下,测定了其光化学效率的变化。结果表明,紫外辐射(UVP)及光合有效辐射(PAR)均能导致钝顶螺旋藻的光化学效率降低,表现出了明显的光抑制,但是,UVR可导致更大程度的光抑制。充气培养条件下,与早晨(07:00)初始值相比,PAR导致了11%~20%的光抑制,而UVR(PAB-P)所产生的

鳡鱼仔稚鱼耳石的标记和其日轮的确证

用茜素络合物对鳡鱼仔鱼进行了浸泡标记,耳石上能检测到橘红色荧光标记环。100mg/L茜素络合物溶液的标记效果较差;120mg/L和150mg/L溶液浸泡后微耳石的标记率很高,矢耳石和星耳石的标记率低。标记后耳石上的生长轮数与饲养天数间呈一一对应关系,相关方程为:N=0.2663+0.9276D(n=68,r~2=0.9664)。方程的斜率0.9276与1无显著差异,证明生长轮确系日轮。鱼体长与微耳石、矢耳石及星耳石的直径间呈显著的线性关系,相关方程为:BL=66.8723LD+2.7064(n=73,r~

盐泽螺旋藻(Spirulina subsalsa)藻胆体的分离和特性

采用一种简便而快速的方法分离了盐泽螺旋藻的藻胆体。藻胆体的最大吸收波长位于618 nm,室温下荧光反射峰位于677～678 nm。利用7～15％SDS—聚丙烯酸胺梯度凝胶板状电泳,可分出三条有色多肽,其中藻蓝蛋白的α亚单位与别藻蓝蛋白的α亚单位几乎重叠,不易区分;另有分子量为117,99,53,49,27,24.5和14kD的七条无色多肽。117和 99kD多肽可能联结藻胆体和类囊体,并作为末端能量受体,而14kD多肽多为“核”亚结构的组分,其余的可能为“棒”亚结构内和“核”“棒”亚结构间的联结蛋白。

Physico-chemical properties of alkaline phosphatases released by a planktonic crustacean, Daphnia magna (Cladocera)

Our studies investigated the physico-chemical properties of alkaline phosphatase excreted by D. magna. This cladoceran mainly released alkaline phosphatase, though it also released a small amount of acid phosphatase. The alkaline phosphatase showed a broad pH optimum (8.05-10.0), and had a broad optimum temperature (30-35 degrees C) with a temperature coefficient (Q(10)) of 2.45. The K-m of the enzyme is 0.15 +/- 0.02 mM when p-nitrophenyl phosphate is used as a substrate, and the V-max is 0.43 +/- 0.01 mu M pNP mg(-1) DW h(-1). Even though alkaline phosphatase had been incubated in chloroform saturated with WC medium for 13 days, its activity was 54% that of the original. The enzyme was strongly inactivated by EDTA, and appeared to be zinc dependent. The alkaline phosphatase activity remained constant when D. magna was fed different quantities of Chlorella sp. The sensitivity of D. magna phosphatase activity to phosphate was time-dependent. During the first 16 hrs, the enzyme was insensitive to phosphate addition, after 24 hrs incubation the enzyme became sensitive to phosphate addition.

Stress and its effect on optical properties of GaN epilayers grown on Si(111), 6H-SiC(0001), and c-plane sapphire

The stress states in unintentionally doped GaN epilayers grown on Si(111), 6H-SiC(0001), and c-plane sapphire, and their effects on optical properties of GaN films were investigated by means of room-temperature confocal micro-Raman scattering and photoluminescence techniques. Relatively large tensile stress exists in GaN epilayers grown on Si and 6H-SiC while a small compressive stress appears in the film grown on sapphire. The latter indicates effective strain relaxation in the GaN buffer layer inserted in the GaN/sapphire sample, while the 50-nm-thick AlN buffer adopted in the GaN/Si sample remains highly strained. The analysis shows that the thermal mismatch between the epilayers and the substrates plays a major role in determining the residual strain in the films. Finally, a linear coefficient of 21.1+/-3.2 meV/GPa characterizing the relationship between the luminescent bandgap and the biaxial stress of the GaN films is obtained. (C) 2003 American Institute of Physics.

High Q microring resonator in silicon-on-insulator rib waveguides - art. no. 68380J

A high quality (Q) factor microring resonator in silicon-on-insulator rib waveguides was fabricated by electron beam lithography, followed by inductively coupled plasma etching. The waveguide dimensions were scaled down to submicron, for a low bending loss and compactness. Experimentally, the resonator has been realized with a quality factor as high as 21,200, as well as a large extinction ratio 12.5dB at telecommunication wavelength near 1550nm. From the measured results, propagation loss in the rib waveguide is determined as low as 6.900/cm. This high Q microring resonator is expected to lead to high speed optical modulators and bio-sensing devices.

域间动态角色转换中的静态互斥角色约束违反

安全互操作是实现跨管理域的资源共享与保护的关键技术．Kapadia等人的IRBAC2000模型提供了一种灵活的通过角色关联和动态角色转换实现安全互操作的方法．廖俊国等人指出该模型可能违反静态互斥角色约束，对问题的原因进行了分析，提出了约束违反检测算法和添加角色关联的先决条件．首先指出廖俊国等人关于约束违反原因的分析是片面的，其检测算法和先决条件也不能保证系统不会违反约束；然后指出在给定角色关联的前提下，外域的用户／角色分配是造成约束违反的根本原因；进而提出动态角色转换违反静态互斥角色约束的充要条件和约束违反检测算法；给出了添加角色关联和用户／角色分配的先决条件，保证了模型状态始终满足静态互斥角色约束．

慢光在光子晶体弯折波导中的高透射传播

研究了慢光模式在SOI(silicon-on-insulator)材料光子晶体线缺陷弯折波导中的传输特性.通过优化波导弯折处的结构参数,慢光模式在光子晶体60°与120°弯折波导中的透射率提高10倍以上,归一化透射率分别达到80%和60%以上.为了进一步减慢光速,设计了新颖的高Q值耦合腔弯折波导结构,在归一化透射率达到75%的基础上,光波群速度低至c/170(c为真空光速).研究结果对于增强光子晶体的慢光效应,提高光子晶体慢光器件的微型化和集成化都有一定的积极意义.

Bandwidth Design for CMOS Monolithic Photoreceiver

A monolithic photoreceiver which consists of a double photodiode (DPD) detector and a regulated cascade(RGC) transimpedance amplifier (TIA) is designed. The small signal circuit model of DPD is given and the band width design method of a monolithic photoreceiver is presented. An important factor which limits the bandwidth of DPD detector and the photoreceiver is presented and analyzed in detail. A monolithic photoreceiver with 1.71GHz bandwidth and 49dB transimpedance gain is designed and simulated by applying a low-cost 0. 6um CMOS process and the test result is given.