库布齐沙漠油蒿群落水量平衡研究

鄂尔多斯高原位于中国北方敏感的生态过渡带，水分往往是制约该区域内植物生存、生长和生态系统结构与功能的最主要的限制因子。境内分布大面积的沙地，沙地天然植被以油蒿（Artemisia ordosica）灌丛为主，是重要的沙地牧场。油蒿在新固定沙地上和半流动沙地上长势良好，随着沙地的固定、地表土壤结皮的形成，生长变差，呈现出衰败的迹象。这种现象被认为是由于沙地土壤水分状况改变而驱动的自发演替。沙地土壤水分状况通常与降水量直接相关，降水格局影响植物根系层土壤水分的补充，植被、土壤结构及地表结皮、微地形等其它生物和非生物因素也会引起土壤水分在时间和空间上的再分配。降水只有克服植被和土壤表层的截留与直接蒸发，并下渗到根系层土壤中，才能有效地补充为土壤水分，进而为植物利用。因此，小雨量的降雨往往对土壤水分的补充，特别是对油蒿根系层土壤水分的补充效果有限。在该地区特定自然条件下，单次降雨雨量多大才能有效地补充沙地油蒿群落的土壤水分？在特定降雨格局下，一年内补充到土壤中且能被植物生长利用的有效降雨量究竟是多少？这些都直接影响土壤水分状况和群落的稳定以及长期演替。 为了解决以上两个问题，借助涡度相关技术对鄂尔多斯高原库布齐沙漠油蒿群落的蒸散过程及土壤水分状况进行观测，配合以地面植物群落、土壤物理特性调查，综合考虑生态系统水文平衡的各个环节，对沙地土壤水分状况以及降雨格局对土壤水分的补充进行了研究。 结果表明，2006年全年降水总量为229.4 mm，年蒸散量281.4 mm，降雨、蒸散主要集中在5～10月。5～10月间，降雨29次，总降雨量223.2 mm，各次降雨量、降雨历时、降雨强度变异较大。5.0 mm以下降雨16次，累计降雨量14.0 mm，5.0 mm以上降雨对总降雨量贡献大。雨后被植被和地表截留直接蒸发的水分和的有效降雨受降雨特性及其他气象条件共同影响，通常5.0 mm以上降雨能有效补充到油蒿根系层土壤，有效降雨量累计153.9 mm，降雨效率约68.9%。

Investigation of the effect of combustor cooling geometry on acoustic energy absorption

To control combustion instabilities occurring in LPP gas turbine combustors, several active and passive systems have been developed in recent years. The combustion chamber cooling geometry has the potential to influence instability feedback loops by absorbing acoustical energy inside the combustor. The design of the cooling liner and the geometry of the cooling plenum and the cooling air flow rate have a significant influence on the absorption characteristics of the system. This paper presents the results of a cold flow study which was carried out in the course of a comprehensive study on the influence of the cooling geometry on combustor thermoacoustics. Absorption characteristics of three different cooling liner geometries and non-perforated plates were determined over a frequency range from 50 Hz to 600 Hz for different cooling flow rates and different cooling plenum volumes. The experimental results compared well with results from a low order thermoacoustic network model. The acoustic energy absorption spectrum of a cooling liner with 90°-hole configuration was found to be strongly dependent on cooling flow rate and cooling plenum volume, whereas the absorption spectrum of cooling liners with 25°-holes were found to be strongly dependent on the cooling plenum volume, but less dependent on the cooling air flow rate. All cooling liner setups with perforations were capable of increased acoustic absorption over a broad band of frequencies compared to the case of non-perforated combustor walls. © 2010 by Johannes Schmidt.

Methods of patterning magnetic fields using bulk superconductors

High Temperature superconductors are able to carry very high current densities, and thereby sustain very high magnetic fields. There are many projects which use the first property and these have concentrated on power generation, transmission and utilization, however there are relatively few which are currently exploiting the ability to sustain high magnetic fields. There are two main reasons for this: high field wound magnets can and have been made from both BSCCO and YBCO but currently their cost is much higher than the alternative provided by low Tc materials such as Nb3Sn and NbTi. An alternative form of the material is the bulk form which can be magnetized to high fields and using flux pumping this can be done in situ. This paper explores some of the applications of bulk superconductors and describes methods of producing field patterns using the highly uniform magnetic fields required for MRI and accelerator magnets as the frame of reference. The patterns are not limited to uniform fields and it is entirely possible to produce a field varying sinusoidally in space such as would be required for a motor or a generator. The scheme described in this paper describes a dipole magnet such as is found in an accelerator magnet. The tunnel is 30 × 50 × 1000 mm and we achieve a uniformity of better than 200 ppm over the 1000 mm length and better than 1 ppm over the central 500 mm region. The paper presents results for both the overall uniformity and the integrated uniformity which is 302 ppm over the 1000 mm length. © 2010 IEEE.

A model of driver steering control incorporating the driver's sensing of steering torque

Steering feel, or steering torque feedback, is widely regarded as an important aspect of the handling quality of a vehicle. Despite this, there is little theoretical understanding of its role. This paper describes an initial attempt to model the role of steering torque feedback arising from lateral tyre forces. The path-following control of a nonlinear vehicle model is implemented using a time-varying model predictive controller. A series of Kalman filters are used to represent the driver's ability to generate estimates of the system states from noisy sensory measurements, including the steering torque. It is found that under constant road friction conditions, the steering torque feedback reduces path-following errors provided the friction is sufficiently high to prevent frequent saturation of the tyres. When the driver model is extended to allow identification of, and adaptation to, a varying friction condition, it is found that the steering torque assists in the accurate identification of the friction condition. The simulation results give insight into the role of steering torque feedback arising from lateral tyre forces. The paper concludes with recommendations for further work. © 2011 Taylor & Francis.

涡鞭毛虫类的染色质碱性蛋白研究及其进化地位的重新认识

通过对涡鞭毛虫这一特殊生物类群的染色质碱性蛋白研究的综述,并结合作者近来的工作和国际上有关的最新进展,对这类生物染色质碱性蛋白的特殊性和多样性进行了阐述。在此基础上对这类生物进化地位及系统发育进行了探讨。认为其染色质碱性蛋白不应是组蛋白的祖先蛋白,相反,它们是一些由于次生的原因而替代了组蛋白的碱性蛋白,并由于替代蛋白的不同而形成了它们的次生多样性;其染色质的特性即是由此而形成的与真细菌类核体的趋同相似性;其进化地位并非以前所认为的位于原核生物向真核生物的过渡环节,这类生物应是在真核细胞的基础上由于次生原因而形成的特殊类群;其系统发育也正是这一次生物进化过程的反映。

蛇毒胶囊治疗海洛因成瘾临床疗效观察

使用华南亚种眼镜蛇纯化神经毒素胶囊治疗海洛因成瘾１６６例，并与美沙酮疗法平行对照（８ｏ例），结果表明，蛇毒胶囊对海洛因成瘾戒断症状具有明显缓解和一定控制作用，蛇毒加用适量美沙酮

滇池控藻围隔中水生植物和浮游藻类对不同形态铁浓度的影响

运用围隔试验来研究围隔生态系统内浮游藻类的组成和数量以及水生植物变化对不同形态铁浓度的影响,再反过来探讨微量元素铁在蓝藻水华暴发过程中对水生植物和浮游藻类生态生理的作用,从而为探索治理蓝藻水华的新途径提供基础证据。从2003年6月至10月,定期采样测定了控藻围隔水体中的亚铁、颗粒态铁(>0.22μm)、小胶体态铁(0.22～0.025μm)、溶解态铁(<0.025μm)的浓度和叶绿素a的浓度,同时对浮游藻类进行了组成鉴定和细胞计数。结果表明,不同形态的铁之间是可以相互转化的,胶体态铁比颗粒态铁活跃,是溶解

Characterization of the surface acoustic wave devices based on ZnO/nanocrystalline diamond structures

Nanocrystalline ZnO films with strong (0002) texture and fine grains were deposited onto ultra-nanocrystalline diamond (UNCD) layers on silicon using high target utilization sputtering technology. The unique characteristic of this sputtering technique allows room temperature growth of smooth ZnO films with a low roughness and low stress at high growth rates. Surface acoustic wave (SAW) devices were fabricated on ZnO/UNCD structure and exhibited good transmission signals with a low insertion loss and a strong side-lobe suppression for the Rayleigh mode SAW. Based on the optimization of the layered structure of the SAW device, a good performance with a coupling coefficient of 5.2% has been realized, promising for improving the microfluidic efficiency in droplet transportation comparing with that of the ZnO/Si SAW device. An optimized temperature coefficient of frequency of -23.4 ppm°C-1 was obtained for the SAW devices with the 2.72 μm-thick ZnO and 1.1 μm-thick UNCD film. Significant thermal effect due to the acoustic heating has been redcued which is related to the temperature stability of the ZnO/UNCD SAW device. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Stiffness of clays and silts: Normalizing shear modulus and shear strain

An analysis is presented of a database of 67 tests on 21 clays and silts of undrained shear stress-strain data of fine-grained soils. Normalizations of secant G in terms of initial mean effective stress p9 (i.e., G=p9 versus log g) or undrained shear strength cu (i.e., G=cu versus log g) are shown to be much less successful in reducing the scatter between different clays than the approach that uses the maximum shear modulus,Gmax, a technique still not universally adopted by geotechnical researchers and constitutive modelers. Analysis of semiempirical expressions forGmax is presented and a simple expression that uses only a void-ratio function and a confining-stress function is proposed. This is shown to be superior to a Hardin-style equation, and the void ratio function is demonstrated as an alternative to an overconsolidation ratio (OCR) function. To derive correlations that offer reliable estimates of secant stiffness at any required magnitude of working strain, secant shear modulus G is normalized with respect to its small-strain value Gmax, and shear strain g is normalized with respect to a reference strain gref at which this stiffness has halved. The data are corrected to two standard strain rates to reduce the discrepancy between data obtained from static and cyclic testing. The reference strain gref is approximated as a function of the plasticity index.Aunique normalized shear modulus reduction curve in the shape of a modified hyperbola is fitted to all the available data up to shear strains of the order of 1%. As a result, good estimates can be made of the modulus reduction G/Gmax ±30% across all strain levels in approximately 90% of the cases studied. New design charts are proposed to update the commonly used design curves. © 2013 American Society of Civil Engineers.

Independent Transport and Sorting of Functionally Distinct Protein Families in Tetrahymena thermophila Dense Core Secretory Granules

Dense core granules (DCGs) in Tetrahymena thermophila contain two protein classes. Proteins in the first class, called granule lattice (Grl), coassemble to form a crystalline lattice within the granule lumen. Lattice expansion acts as a propulsive mechanism during DCG release, and Grl proteins are essential for efficient exocytosis. The second protein class, defined by a C-terminal beta/gamma-crystallin domain, is poorly understood. Here, we have analyzed the function and sorting of Grt1p (granule tip), which was previously identified as an abundant protein in this family. Cells lacking all copies of GRT1, together with the closely related GRT2, accumulate wild-type levels of docked DCGs. Unlike cells disrupted in any of the major GRL genes, Delta GRT1 Delta GRT2 cells show no defect in secretion, indicating that neither exocytic fusion nor core expansion depends on GRT1. These results suggest that Grl protein sorting to DCGs is independent of Grt proteins. Consistent with this, the granule core lattice in Delta GRT1 Delta GRT2 cells appears identical to that in wild-type cells by electron microscopy, and the only biochemical component visibly absent is Grt1p itself. Moreover, gel filtration showed that Grl and Grt proteins in cell homogenates exist in nonoverlapping complexes, and affinity-isolated Grt1p complexes do not contain Grl proteins. These data demonstrate that two major classes of proteins in Tetrahymena DCGs are likely to be independently transported during DCG biosynthesis and play distinct roles in granule function. The role of Grt1p may primarily be postexocytic; consistent with this idea, DCG contents from Delta GRT1 Delta GRT2 cells appear less adhesive than those from the wild type.

Photosynthetic physiology and growth as a function of colony size in the cyanobacterium Nostoc sphaeroides

Algal size can affect the rate of metabolism and of growth. Different sized colonies of Nostoc sphaeroides were used with the aim of determining the effects of colony size on photosynthetic physiology and growth. Small colonies showed higher maximum photosynthetic rates per unit chlorophyll, higher light saturation point, and higher photosynthetic efficiency (a) than large colonies. Furthermore, small colonies had a higher affinity for DIC and higher DIC-saturated photosynthetic rates. In addition, small colonies showed higher photosynthetic rates from 5-45degreesC than large colonies. There was a greater decrease in Fv/Fm after exposure to high irradiance and less recovery in darkness for large colonies than for small colonies. Relative growth rate decreased with increasing colony size. Small colonies had less chl a and mass per unit surface area. The results indicate that small colonies can harvest light and acquire DIC more efficiently and have higher maximum photosynthetic rates and growth rates than large colonies.

High efficiency and broad bandwidth grating coupler between nanophotonic waveguide and fibre

A high efficiency and broad bandwidth grating coupler between a silicon-on-insulator (SOI) nanophotonic waveguide and fibre is designed and fabricated. Coupling efficiencies of 46% and 25% at a wavelength of 1.55 mu m are achieved by simulation and experiment, respectively. An optical 3 dB bandwidth of 45 nm from 1530 nm to 1575 nm is also obtained in experiment. Numerical calculation shows that a tolerance to fabrication error of 10 nm in etch depth is achievable. The measurement results indicate that the alignment error of +/-2 mu m results in less than 1 dB additional coupling loss.