Electron emission from arrays of carbon nanotubes/fibres

The overall aim of this work is to produce arrays of field emitting microguns, based on carbon nanotubes, which can be utilised in the manufacture of large area field emitting displays, parallel e-beam lithography systems and electron sources for high frequency amplifiers. This paper will describe the work carried out to produce patterned arrays of aligned multiwall carbon nanotubes (MWCNTs) using a dc plasma technique and a Ni catalyst. We will discuss how the density of the carbon nanotube/fibres can be varied by reducing the deposition yield through nickel interaction with a diffusion layer or by direct lithographic patterning of the Ni catalyst to precisely define the position of each nanotube/fibre. Details of the field emission behaviour of the different arrays of MWCNTS will also be presented. © 2002 Published by Elsevier Science B.V.

Spectral measurement of diode lasers with a single-mode birefringent fibre

A new, and very simple spectrometer based on birefringent fiber is described. A resolution of 0.02 angstrom has been achieved, and the system has been used to measure diode laser chirp. A length of 10km of fiber would be sufficient to resolve single mode line widths.

烟草和衣藻中ftsZ 基因的克隆及功能分析

作为一种广泛存在于原核细胞中的原始的细胞骨架蛋白，FtsZ在植物中的发现为我们研究植物细胞中质体的分裂机制提供了可能。已有的研究证明了FtsZ与质体的分裂和形态维持有关，但高等植物中FtsZ在质体分裂和形态维持中的作用机制仍不十分清楚，同时高等植物中多个ftsZ成员的存在也使得对FtsZ功能的研究更加复杂。我们从烟草中克隆了两个ftsZ基因，序列和谱系分析表明二者均属于高等植物中的FtsZl基因家族，这也是首次在高等植物中发现多个FtsZl家族的成员。杂交分析表明ftsZ在烟草基因组中是以多拷贝形式存在，并且这两个基因具有相似的表达谱，这些结果暗示着高等植物中FtsZ在质体分裂中的作用更为复杂。GFP标记的原核定位表明二者具有与原核FtsZ类似的功能。此外，利用反义和正义表达的方法研究了二者在烟草质体分裂和形态维持中的作用。反义转化并未对烟草细胞叶绿体的数目和形态造成明显的影响，相反，二者的正义表达均导致细胞中叶绿体数目和形态上的明显变化，这一结果预示着二者在控制质体分裂和形态方面可能具有不同的功能。同时，这些结果也为高等植物中多样化的FtsZ可能具有除质体分裂之外的功能，如质体骨架．提供了证据。 　利用简并引物PCR和RACE从衣藻中扩增得到了一个ftsZ基因的部分cDNA序列，命名为CrFtsZ。序列分析表明该基因编码的蛋白具有FtsZ的典型特点，但同时还有一个与目前已知FtsZ均不同的突出c-末端：分子谱系分析认为CrFtsZ与线粒体进化祖先a -proteobacteria中的FtsZ有着共同起源，因此CrFtsZ可能是一个控制线粒体分裂的FtsZ。此外，CrFtsZ的c-端突出序列还具有目前已知真核生物线粒体分裂相关蛋白dynamin的某些特征，考虑到FtsZ在原核细胞分裂和真核细胞器分裂中的作用，我们推测CrFtsZ可能是FtsZ向dynamin过度的一种中间进化形式。这一发现为线粒体分裂机制的起源和进化提供了新的分子证据，对于认识真核线粒体分裂机制的起源与演化具有重要意义。

Applications in adaptive cluster sampling of Gulf of Alaska rockfish

Adaptive cluster sampling (ACS) has been the subject of many publications about sampling aggregated populations. Choosing the criterion value that invokes ACS remains problematic. We address this problem using data from a June 1999 ACS survey for rockfish, specifically for Pacific ocean perch (Sebastes alutus), and for shortraker (S. borealis) and rougheye (S. aleutianus) rockfish combined. Our hypotheses were that ACS would outperform simple random sampling (SRS) for S. alutus and would be more applicable for S. alutus than for S. borealis and S. aleutianus combined because populations of S. alutus are thought to be more aggregated. Three alternatives for choosing a criterion value were investigated. We chose the strategy that yielded the lowest criterion value and simulated the higher criterion values with the data after the survey. Systematic random sampling was conducted across the whole area to determine the lowest criterion value, and then a new systematic random sample was taken with adaptive sampling around each tow that exceeded the fixed criterion value. ACS yielded gains in precision (SE) over SRS. Bootstrapping showed that the distribution of an ACS estimator is approximately normal, whereas the SRS sampling distribution is skewed and bimodal. Simulation showed that a higher criterion value results in substantially less adaptive sampling with little tradeoff in precision. When time-efficiency was examined, ACS quickly added more samples, but sampling edge units caused this efficiency to be lessened, and the gain in efficiency did not measurably affect our conclusions. ACS for S. alutus should be incorporated with a fixed criterion value equal to the top quartile of previously collected survey data. The second hypothesis was confirmed because ACS did not prove to be more effective for S. borealis-S. aleutianus. Overall, our ACS results were not as optimistic as those previously published in the literature, and indicate the need for further study of this sampling method.