Wear resistance of reaction sintered alumina/mullite composites

Alumina and alumina/mullite composites with mullite content of 0.96-8.72 vol.% were subjected to an abrasive wear test under loads of 0.1-2.0 N with a ball-on-disc apparatus. The wear rate and area fraction of pullout f(po) on the worn surfaces were measured. The wear resistances of the alumina/mullite composites were better by a factor of 1-2 than that of pure alumina. The main wear mechanism of alumina is fracture wear, and for alumina/mullite composites, fracture wear and plastic wear mechanisms work together. The influence of mechanical properties on wear resistance was estimated by Evans' method. It was found that the wear rate depends on f(po), and the primary reason for the better wear resistance of alumina/mullite composites is the reduction off, induced by fracture mode transition. (c) 2007 Elsevier B.V. All rights reserved.

Well-width dependence of in-plane optical anisotropy in (001) GaAs/AlGaAs quantum wells induced by in-plane uniaxial strain and interface asymmetry

The well-width dependence of in-plane optical anisotropy (IPOA) in (001) GaAs/AlxGa1-xAs quantum wells induced by in-plane uniaxial strain and interface asymmetry has been studied comprehensively. Theoretical calculations show that the IPOA induced by in-plane uniaxial strain and interface asymmetry exhibits much different well-width dependence. The strain-induced IPOA is inversely proportional to the energy spacing between heavy- and light-hole subbands, so it increases with the well width. However, the interface-related IPOA is mainly determined by the probability that the heavy- and light-holes appear at the interfaces, so it decreases with the well width. Reflectance difference spectroscopy has been carried out to measure the IPOA of (001) GaAs/AlxGa1-xAs quantum wells with different well widths. Strain- and interface-induced IPOA have been distinguished by using a stress apparatus, and good agreement with the theoretical prediction is obtained. The anisotropic interface potential parameters are also determined. In addition, the energy shift between the interface- and strain-induced 1H1E reflectance difference (RD) structures, and the deviation of the 1L1E RD signal away from the prediction of the calculation model have been discussed.

Preparation and characterization of Si sheets by renewed SSP technique

Silicon sheets from powder (SSP) ribbons have been prepared by modified SSP technique using electronic-grade (9N purity) silicon powder. The surface morphology, crystallographic quality, composition and electric properties of the SSP ribbons were investigated by surface profiler, X-ray diffraction (XRD), scanning electron microscopy (SEM), metallurgical microscope, Auger electron spectroscopy (AES) and four-point probe apparatus, respectively. The results show that the SSP ribbon made from electronic-grade silicon powder is a suitable candidate for the substrates of crystalline silicon thin film (CSiTF) solar cells, which could meet the primary requirements of CSiTF solar cell process on the substrates, including surface smoothness, crystallographic quality, purity and electric conductivity, etc. (C) 2004 Elsevier B.V. All rights reserved.

Strain-induced in-plane optical anisotropy in (001) GaAs/AlGaAs superlattice studied by reflectance difference spectroscopy

In-plane optical anisotropy (IPOA) in (001) GaAs/AlGaAs superlattice induced by uniaxial strain has been investigated by reflectance difference spectroscopy (RDS). Uniaxial strain on the order of 10(-4) was introduced by bending a strip sample with a stress apparatus. The IPOA of all interband transitions shows a linear dependence on strain. The birefringence and dichroism spectra induced by strain are obtained by RDS on the basis of a three-phase model, which is in good agreement with the reported results. (c) 2006 American Institute of Physics.

Effects of multistage coupling and disk flexibility on mistuned bladed disk dynamics

The effects ofdisk flexibility and multistage coupling on the dynamics of bladed disks with and without blade mistuning are investigated. Both free and forced responses are examined using finite element representations of example single and two-stage rotor models. The reported work demonstrates the importance of proper treatment of interstage (stage-to-stage) boundaries in order to yield adequate capture of disk-blade modal interaction in eigenfrequency veering regions. The modified disk-blade modal interactions resulting from interstage-coupling-induced changes in disk flexibility are found to have a significant impact on (a) tuned responses due to excitations passing through eigenfrequency veering regions, and (b) a design's sensitivity to blade mistuning. Hence, the findings in this paper suggest that multistage analyses may be required when excitations are expected to fall in or near eigenfrequency veering regions or when the sensitivity to blade mistuning is to be accounted for Conversely, the observed sensitivity to disk flexibility also indicates that the severity of unfavorable structural interblade coupling may be reduced significantly by redesigning the disk(s) and stage-to-stage connectivity. The relatively drastic effects of such modifications illustrated in this work indicate that the design modifications required to alleviate veering-related response problems may be less comprehensive than what might have been expected.

Experimental Investigation into the Production Behavior of Methane Hydrate in Porous Sediment with Hot Brine Stimulation

The gas production behavior from methane hydrate in porous sediment by injecting the brine with the salinity of 0−24 wt % and the temperature of −1 to 130 °C was investigated in a one-dimensional experimental apparatus. The results show that the gas production process consists of three periods: the free gas production, the hydrate dissociation, and the general gas reservoir production. The hydrate dissociation accompanies the temperature decrease with the injection of the brine (NaCl solution), and the dissociation duration is shortened with the increase of the salinity. With the injection of hot brine, instantaneous hydrate dissociation rate also increases with the increase of the salinity. However, while the NaCl concentration is beyond a certain value, the rate has no longer continued increasing. Thermal efficiency and energy ratio for the hydrate production can be enhanced by injecting hot brine, and the enhanced effectiveness is quite good with the injection of high salinity at lower temperature.

Experimental investigation of production behavior of methane hydrate under ethylene glycol injection in unconsolidated sediment

This article investigates the gas production behavior from methane hydrate (MH) in porous sediment by injecting ethylene glycol (EG) solution with the different concentrations and the different injection rates in an one-dimensional experimental apparatus. The results suggest that the gas production process can be divided into the four stages: (1) the initial injection, (2) the EG diluteness, (3) the hydrate dissociation, and (4) the remained gas output. Nevertheless, the water production rate keeps nearly constant during the whole production process. The production efficiency is affected by both the EG concentration and the EG injection rate, and it reaches a maximum with the EG concentration of 60 wt %.

Aspheric surface testing with a liquid compensatory interferometer

A simple method of testing deep aspheric surfaces is presented. The apparatus consists of a Twyman-Green interferometer and a liquid compensatory container. Two lenses, one with spherical surfaces and the other with a spherical surface and an aspheric surface, were tested by using this method. The device is very simple and easy to assemble. (C) 1998 Society of Photo-Optical Instrumentation Engineers.

新型渗透变形仪的研制

针对现有渗透变形仪存在的密封止水效果差、试样固定装置影响过流面积、仪器复杂等缺陷,通过对岩土渗透变形特性及测试原理进行分析,研制出一种适用于黏性土、水泥土类的新型渗透变形仪,该仪器设计方法独特,在试样外套橡皮膜并加围压的柔性密封止水,以及在试样顶部采用圆环型透水石固定试样等方法,既能测定岩土体的渗透系数又能测定渗透变形特性,同时,既保证试样的渗流面积不受影响又允许试样产生渗透变形,而且在渗透水压力作用下试样周围的密封性良好。实际工程应用结果表明,该仪器测定的岩土体的渗透系数及抗渗比降具有很高的可靠性和精度。

体细胞核移植影响因素的研究

尽管体细胞核移植(somatic cell nuclear transfer, SCNT)技术仍然处于 起步发展阶段，但是随着体细胞核移植技术在近些年来的飞速发展，人们已经得 到了多种哺乳动物体细胞核移植的存活后代。体细胞核移植技术在生物医药、农 业及其它领域的应用显示了这项技术的巨大发展前景。另一方面，人们发现体细 胞核移植效率低下并且体细胞克隆动物存在许多缺陷，这些主要是由于核移植技 术，供体细胞选择，体外培养系统以及卵母细胞的状态等的差异导致的。本研究 主要围绕着这些因素在体细胞核移植过程中对于克隆胚胎植入前后发育的影响 而开展，目的在于提高体细胞核移植的效率。 实验一，研究了几个因素对克隆胚胎发育和克隆效率的影响，为提高体细胞 核移植效率提供一些依据。这部分研究主要包括四倍体半克隆小鼠研究和蛋白酶 体抑制剂在克隆胚胎和孤雌激活胚胎发育中的影响。四倍体体细胞半克隆 （tetraploid semi-cloned , TSC）胚胎的体外发育结果表明，虽然TSC 胚胎可 能避免二倍体半克隆胚胎发育过程中的非整倍体现象，但是仍然不能形成胎儿。 另外，利用蛋白酶体抑制剂MG132 处理克隆胚胎的结果表明，虽然MG132 通过抑 制成熟促进因子（maturation promoting factors，MPF）活性的降低可以提高 克隆胚胎的体外发育率，但是没有改变克隆胚胎的质量。 实验二，研究了克隆技术在克隆胚胎构建和发育上的影响。首先，我们研究 了完整颗粒细胞注射到卵母细胞中所引起的变化。我们发现完整的颗粒细胞注入 到卵母细胞中之后很快引起细胞膜裂解和细胞核碎裂，从而导致激活后重构胚胎 的碎裂。这一实验表明完整供体细胞核注入的方法不适用于小鼠体细胞克隆。接 下来我们研究了不同的核移植技术――利用piezo 的直接注射法（piezoelectric microinjection，PEM）和电融合法（Electrofusion，EF）――对植入前后的克隆胚 胎以及出生后的克隆动物的影响。研究的结果发现，在PEM 法中，提高piezo 脉 冲的强度会导致供体细胞核DNA 断裂增加，使植入前克隆胚胎的细胞数目减少， 凋亡增加，从而降低克隆胚胎的质量。相反，在用EF 法产生的胚胎中细胞核DNA 的断裂很少，克隆胚胎质量相对较好。实验的结果表明，由于两种克隆技术利用 的原理不同，会对克隆胚胎的发育产生一定的影响，从而改变克隆的效率。 实验三，研究了猕猴体细胞克隆胚胎早期发育过程中细胞核内有丝分裂器蛋 白[Nuclear Mitotic Apparatus Protein，NuMA]的表达和分布。尽管在有些猕猴体 细胞核移植胚胎中没有检测到NuMA 的正确表达和分布并且有些胚胎出现了微 管组装异常，但是大多数猕猴体细胞核移植胚胎具有正常的NuMA 蛋白表达和 正常的核型。通过改进操作技术我们得到了可以发育到正常囊胚的猕猴体细胞核 移植胚胎。这些结果提示猕猴SCNT 胚胎发育失败的原因不是NuMA 等重要蛋 白的缺失。

Multifunctional darkfield microscopy using an axicon

We present a multifunctional darkfield microscopy using an axicon. It combines the functions of a darkfield microscope, fluorescence microscope, and microspectrophotometer in one platform. The advantage of the system over conventional darkfield microscopy includes the high transmittance of the illuminating flux, the high contrast of the image, and the convenient toggle between darkfield and brightfield microscopy. Examples of dark, bright, and fluorescent micrographs as well as concerned spectra of microsized specimens implemented in this apparatus are demonstrated. (C) 2008 Society of Photo-Optical Instrumentation Engineers.

窄通道内热厚材料表面火焰传播的实验研究

利用高度为14 mm的水平窄通道对微重力条件下聚甲基丙烯酸甲酯(PMMA)和聚乙烯(PE)塑料材料表面的火焰传播进行了地面实验模拟研究. 在环境气体氧气浓度为30％和50％、低速气流速度小于15 cm/s的实验条件下, 实验测量了窄通道内材料表面火焰传播速度随气流速度的变化, 它们与微重力下热厚材料火焰传播速度的理论预测结果符合得相当好. 分析认为, 窄通道能够有效地限制浮力对流, 提高燃料表面固相热辐射在火焰传播中的相对作用, 从而提供模拟微重力下热厚材料表面火焰传播特性的实验环境

岷江冷杉林群落几种树苗对光强的响应与适应

在青藏高原东部的亚高山针叶林区，如何尽快恢复这一生态脆弱地区的植被，改变生态环境恶化的趋势，是一个十分重要的课题。光一直被认为是植物种间相互替代，尤其是森林演替过程中植物相互替代或植被恢复中的关键环境要素之一。植物能否适应林冠下或林窗中异质的、或多变的光照条件，对其在林中的生存、分布、更新以及森林动态都是非常重要的。 本文以青藏高原东部亚高山针叶林的主要森林类型——岷江冷杉林群落的几种树苗为研究对象，采用实验生态学、生理及生物化学等方法，通过模拟针叶林不同大小林窗内光照强度的变化，在中国科学院茂县生态站内采用遮荫处理设置6个光照梯度（100、55、40、25、15与7%全光照），来研究具有不同喜光特性的植物对光强的响应与适应机制，其研究结果可为揭示亚高山针叶林的演替规律、以及人工林下幼苗的存活与定居提供科学依据，也能为苗木的生产与管理提供科学指导，尤其是对针阔树种在不同光强下的响应与适应的比较研究，能为如何将阔叶树种整合到人工针叶林中提供新的思路。 光强对植物生长的影响 光强对植物的生长具有重要作用，不同植物在各自适宜的光强梯度下才能生长良好。通过一个野外盆栽实验，来研究不同光强对植物生长的影响（第三章）。主要研究结果如下，低光强下植物株高/茎生物量增加，说明植物会将生物量更多用于高生长，以便有效地拦截光资源；在强光下，植物将生物量更多地向根部分配，使得植物在强光下能够吸收更多的水分，而避免干旱胁迫。 在第一个生长季节，以相对生长速率（RGR）表示，红桦和青榨槭在100%全光照下RGR最大，粗枝云杉在55%最大，岷江冷杉在25-40%下较好；然而，在第二个生长季节，2种阔叶树的相对生长速率（RGR）的适宜光强则变为25-55%，云杉为55-100%，而冷杉为25-100%。可见，从第一年到第二年，2种阔叶树苗更适宜在部分荫蔽的条件下生长；而2种针叶树苗对光的需求则逐渐增加，这可能是增加对根生物量相对投资的结果，因为以这种方式，强光下生长的针叶树幼苗更能保持其内部水分平衡，其生长不会因干旱胁迫而受到严重影响。另外，严重遮荫会引起冷杉幼苗死亡。 植物对光强的生理适应 植物可以通过自身形态和生理特征的调整，来发展不同的光能利用策略从而能够在林中共存。通过一个野外盆栽实验，研究了不同光强下生长的几种树苗的生理特征（第四章）对不同光强的响应与适应。结果显示：强光下，粗枝云杉和红桦的光合能力增加，而岷江冷杉和青榨槭在中度遮荫（25-55%）的条件下光合能力最大。植物叶氮和叶绿素含量增高，而光补偿点和暗呼吸速率降低，这些都是植物对低光环境的适应性反应；而强光下植物叶片和栅栏组织变厚，是对强光的一种保护性反应。 植物对光的可塑性反应 不同植物会表现出对光适应有利的生理和形态可塑性反应。本文对第三章、第四章的实验数据进行可塑性指数分析，来研究植物对光强的表型可塑性反应（第五章）。结果显示，生理特征调整是植物对不同光环境的主要适应途径。红桦和青榨槭的可塑性指数平均值要大于粗枝云杉和岷江冷杉，充分表明这2种阔叶树在生理和形态上较强的可塑性更有利于对光环境的适应，而具有比耐荫树种更强的适应能力。另外，2种针叶树相比，云杉的适应性更强。本研究结果支持树种的生理生态特性决定了其演替状况和生境选择的假说。 植物的光抑制与防御 当植物叶片吸收了过多光能，会发生光抑制现象。植物对光抑制的敏感性及防御能力对其生长具有重要意义。本文通过两个野外盆栽实验，研究了生长在强光下（第六章）和变化光强下（第八章）植物的光抑制现象及其防御策略。结果表明，在强光下或从遮荫状态转入强光下，植物都会发生光抑制，其对光抑制的敏感性与植物的耐荫性（或喜光）和演替状态有密切联系。长期生长在强光下的植物受到光抑制是可恢复的，而当处于荫蔽环境的植物突然暴露于强光下时，受到的光抑制不能完全恢复，可能是（部分）光合机构受到破坏的缘故。粗枝云杉和青榨槭防御光抑制伤害的能力较强，热耗散是其防御光抑制的主要途径。长期的强光作用能使岷江冷杉和红桦发生严重光抑制，甚至光伤害，而红桦能够通过“凋落老叶，萌发新叶”的途径来适应新的强光环境。 How to restore the vegetation of subalpine coniferous forest in eastern Qinghai-Tibet Plateau, and change the trend of ecological deterioration is a very important issue. Acclimation of tree seedlings to different and varing light environment affects to a great extent the successful regeneration and establishment of subalpine coniferous forests in southwestern China’s montane forest areas, because the ability to respond to such changing resource are commonly assumed to be critical to plant success, and have a growth advantage than others. In this paper, several species seedlings in Abies faxoniana community were chosed to study the response and adaptation to light intensity and the interspecific differences of adaptability in six shaded sheds (100, 55, 40, 25, 15 and 7% of full sunlight) in the Maoxian Ecological Station of Chinese Academy of Sciences. Our results could provide a strong theoretical evidence for understanding the forest succession laws of subalpine coniferous forests, and the survival and settlement of seedlings under plantations, and provide scientific direction for the production and management of seedlings, especially the comparative studies of the acclimation to light between the conifer and broadleaf trees could provide new ideas for how to integrate the broad-leaved trees into the artificial coniferous forest. Growth under different light intensity Light intensity plays an important role on plant growth. One field experiments was conducted to study the growth of tree seedlings of Picea asperata, Abies faxoniana, Betula albo-sinensis and Acer davidii under different light intensities. The results showed that plants under low light environment could increase the specific stem length (stem length/ stem dry mass), in order to effectively intercept light resources, while biomass greater allocation to the roots, could make plants under high light environment absorb more water, and avoid drought stress. During the first growing season, the relative growth rates (RGRs) of Betula albo-sinensis and Acer davidii had the greatest values under the 100% of full light, for 55% of Picea asperata, and for 25-40% of Abies faxoniana. However, in the second growing season the the relative growth rates of the two broad-leaved trees changed and were appropriate for 25-55% of full light, for 55-100% of spruce, and for 25-100% of fir. Thus, from the first year to the second year, two broad-leaved seedlings maybe more suitable to partly shading environment, and two coniferous seedlings would have an increase in light demand, which may be an increased root biomass investment. Because in this way, seedlings grown under high light could better maintain their internal water balance, and thus its growth would not be seriously affected by drought stress. In addition, serious shading would cause fir seedlings to die. Acclimation of physiology to light Plants could coexist in forest ecosystem by forming different strategies of light use. One field experiments was conducted to study the acclimation of tree seedlings to different light intensity of Picea asperata, Abies faxoniana, Betula albo-sinensis and Acer davidii. The results showed that the photosynthetic capacity of Picea asperata and Betula albo-sinensis exhibited a general tendency of increase with more light availability; but for Abies faxoniana and Acer davidii seedlings, their highest values of the same parameters were found under intermediate light regime (i.e. 25-55% of PFD relative to full sunlight). Plants under low light environment could increase the specific stem length (stem length/ stem dry mass), in order to effectively intercept light resources. Leaf nitrogen and chlorophyll content increased, while dark respiration rate and light compensation points decreased, all of which were adaptive response to the low light environment. On the contrary, plants under high light environment had the thicken leaves and palisade tissue, which was a protective response to high light. Phenotypic plasticity to light Phenotypic plasticity can be exhibited in morphological and physiological processes. Physiological characteristical adjustment is the main for plant adaptation to different light environment.The means of plasticity indexes for Betula albo-sinensis and Acer davidii seelings were greater than Picea asperata and Abies faxoniana, amplied that the two broad-leaved trees were much more adaptable to the environment. In addition, spruce had the higher adaptablity than fir. The findings supported the hypothesis that the ecological characteristics of the species determined the biological status and its biological habitat selection. Photoinhibition and photoprotection to light Compared with conifer, broad-leaved trees could better change leaf morphology and adjust biomass allocation to adapt to changing light environment. However, excess light can photoinhibit photosynthesis and may lead to photooxidative destruction of the photosynthetic appatus. Two field experiments were conducted to study the photoinhibition of photosynthesis. The results showed that when plants grown under high light environment or plants transferred from low to high irradiance, the four tree seedlings would undergo a period of photoinhibition. In four species, photoinhibited leaves could recover to initial photosynthetic rates when they were long-term planted under high light environment. However, when plants were suddenly exposed to high irradiance, this photoinhibition could not be reversible, may be the photosynthesis apparatus were (or partly) photooxidatively destructed.

贡嘎山植物小枝功能性状在不同生活型和不同海拔间的比较研究

植物功能生态学研究不仅提供了植物生理生态学与生态系统生态学的连接，还为植物种群生活史对策研究提供了材料。Westoby 等 (2002) 提出了利用植物功能性状变量的主导维度来确定和量化植物生活史的生态适应策略。在他们所提出四个主导维度中，叶大小－小枝大小是研究相对较少的一维；其内部各组分的关系、对环境的响应，以及与其它重要维度的关系，目前的理解非常有限。 本研究以贡嘎山不同海拔不同功能群物种为研究对象，采用种间比较和系统发生独立性比较等研究方法，系统研究了植物的功能特征及其相关性在不同生境及不同功能群间的差异，旨在分析不同功能群物种的叶大小－小枝大小的成本和收益。其研究结果将有助于我们理解植物生活史对策的进化，进而理解物种共存和维持物种多样性的机制。主要研究结果如下： 1. 叶大小－小枝大小关系 小枝茎横截面积与单叶面积和总叶面积均呈异速生长关系，即总叶面积和单叶面积的增加比茎横截面积的增加速度快。但是，总叶面积和叶片干重的增加却基本上与小枝茎干重的增加等速。系统发生独立性比较研究的结果与此相一致。表明，在某一给定的茎投入时，至少大叶大枝物种不比小叶小枝物种在支撑叶面积和叶片干重方面具有优势。同时，在某一给定的小枝茎投入时，常绿阔叶物种比落叶阔叶物种支撑更少的叶面积。在茎干重与总叶面积的关系中，落叶复叶物种比落叶单叶物种具有更高的y轴截距，表明复叶物种比单叶物种在展叶面积方面更有效。复叶物种与单叶物种相比，通常具有较大的叶大小和小枝大小。 2. 叶大小－叶数量关系 叶大小与数量间在不同的叶片习性、不同的叶片形态以及不同的生境类型的物种间均存在稳定的负的等速生长关系，且这种关系在系统发生独立性比较时依然成立。然而，在某一给定的出叶强度 (单位小枝的叶数量) 时，常绿阔叶物种比落叶物种具有更小的叶面积。而在给定体积基础上的出叶强度时，落叶复叶物种的叶面积显著大于落叶单叶物种，且复叶物种比单叶物种具有更大的叶大小和更小的出叶强度。但是，叶大小与数量间的关系在不同的海拔间并没有显著的差异。 3. 小枝大小－总叶面积关系 在不同的生活型或不同的生境下，小枝上总叶面积与茎干重和小枝干重均呈正的异速生长关系，且斜率显著小于1.0，表明小枝上总叶面积的增加都不能赶上小枝及茎大小的增加。这种“收益递减”表明随着小枝干重的增加，光截取的收益递减。此外，叶面积比 (总叶面积与小枝干重的比值) 与单叶干重呈显著负相关关系，系统发生独立性比较的结果与此相一致。根据以上结果，可以推测，大叶的物种在质量较好的生境中出现，而群落内部小枝茎的寿命较长的物种可以拥有较大的叶片。 4. 叶片色素浓度－LMA关系 随着海拔的升高，阔叶木本植物和草本植物的叶片色素浓度减少，叶绿素a/b和类胡萝卜素/叶绿素比值以及比叶重 (LMA) 增加。然而，在草本植物中的色素浓度、色素比值和LMA的变化比阔叶木本植物的更明显。同时，LMA与叶片色素浓度呈负相关关系，但是在落叶物种中的LMA对色素浓度的影响比常绿阔叶物种更强烈。总之，草本植物的叶片特征对海拔梯度的变化似乎比木本植物更敏感，LMA对叶片色素的保护作用在落叶物种中比在常绿阔叶物种显得更重要。这些结果表明不同生活型物种可能采取不同的保护机制来降低叶绿体器官的损伤和增加他们的碳获取能力。 Studies on plant functional ecology not only bridge plant eco-physiology and ecosystem functioning, but also enrich plant population biology. As pointed out by Westoby et al (2002), plant life history strategies can be identified and quantified by four leading dimensions of variations in plant functional traits, i.e., seed size/output, leaf mass per area and leaf life span, plant height, and leaf size-twig size. Compared to the other dimensions, the cost/benefit of the leaf size-twig size spectrum has scarcely been analyzed in relation to environmental gradients and life form types, and the adaptive significance of this spectrum is not fully understood. In the present study, the relationships between functional traits of plant twigs are determined for the species with different life forms along an altitudinal gradient of Gongga Mountain with both cross-species analysis and evolutionary divergence analysis. The primary objective of this study is to examine the cost/benefit of leaf size-twig size in plants. The study results are supposed to provide insights into the understanding of the mechanism of species coexistences. The results are shown in the following. 1. The relationship between leaf size and twig size Twig cross-sectional area allometrically scaled with both individual leaf area and total leaf area supported by the twigs. However, the increase in total lamina mass/area was generally proportional to the increase in stem mass. These correlations between trait variations were significant in both interspecies analysis and phylogenetically independent comparison (PIC) analysis, which indicated that thick-twigged/large-leaved species, at least, do not have an advantage in supporting leaf/lamina area and lamina mass for the same twig stem investment than thin-twigged/ small-leaved species. Meanwhile, the evergreen broad-leaved species supported a smaller leaf area for the same twig stem investment in terms of both cross-sectional area and stem mass than the deciduous species. The deciduous compound-leaved species have a higher y-intercept in the scaling relationship of twig stem mass versus total leaf area than the deciduous simple-leaved species, indicating that compound-leaved species were more efficient in displaying leaf area. The compound-leaved species were larger in both leaf size and twig size than their counterpart in the present study. 2. The relationship between leaf size and leaf number Significantly negative and isometric scaling relationships between leaf size and leafing intensity (leaf number per twig mass or volume) were found to be consistently conserved across species independent of leaf habit, leaf form and habitat type. The negative correlations between leaf size and leafing intensity were also observed across correlated evolutionary divergences. However, leaf area was smaller in the evergreen broad-leaved species at a given leafing intensity than in the deciduous species. The deciduous compound-leaved deciduous species were higher in leaf area than deciduous simple-laved species at a given volume-based leafing intensity. Moreover, the compound-leaved deciduous species were larger in leaf size but smaller in leafing intensity than their simple counterparts. No significant difference was found in the scaling relationships between altitudes. 3. The relationship between twig size and total leaf area Leaf area was found to scale positively and allometrically with both stem and twig mass (stem mass plus leaf mass) with slopes significantly smaller than 1.0, independent of life form and habitat type, indicating that the increase in total leaf area fails to keep pace with increasing twig size and stem size. This ‘diminishing returns’ suggests that the benefit of light intercept decreased with increasing twig mass. Moreover, the leaf area ratio (the ratio of total leaf area to stem or twig mass) correlated negatively with individual leaf mass. The results of PIC were consistent with the correlations. According to the results, it is speculated that large-leaved species may be favored when habitat is good and when stem longevity are long within community. 4. The relationship between leaf pigment concentrations and leaf mass per area With increasing altitude, the concentrations of pigments decreased, but the ratios of chlorophyll a/b and carotenoid/chlorophyll, and LMA increased, in both the broad-leaved woody species and herbaceous species groups. However, the changes in the pigment concentrations, ratios and LMA were more profound in the herbaceous species than in the woody species. In addition, pigment concentrations were negatively correlated with LMA in each life form type and in the pooled dataset. However, the LMA effect on leaf pigment concentrations was more profound in the deciduous species than in the evergreen braode-leaved species. In general, herbaceous species seemed more sensitive to the increasing altitude compared to woody species, and LMA seemed to be a more important mechanism for protecting leaf pigments in deciduous species than in evergreen broad-leaved species. These results suggested that the species with different life forms may employ different protective mechanisms to decrease the chloroplast apparatus damage and increase their carbon gain.

气体喷嘴反冲传输技术及在核科学中的应用

The gas-jet recoil transport technique is developed and improved as a new rapid and effective on-line and off beam method following "rabbit" apparatus in the study of short lives nuclei. It can transport the short half-life nuclear reaction products far from high radioactive area for collection and measurement at low background area. This technique has been widely used in the researches with accelerator and reactor. It is indispensable basic experimental technology and tool applied to nuclear reaction, spec...中文摘要：气体喷嘴反冲传输技术是继"跑兔"装置之后发展和完善起来的适合于短寿命核素研究的一种快速而有效的在线脱束方法。它能够将短寿命核反应产物传输至远离高辐射区的低本底场所进行收集和测量。该技术已在加速器和反应堆上得到了广泛的应用,是一种研究核反应、核谱学和合成与鉴别新元素、新核素的一种不可缺少的基本实验技术和工具。描述了气嘴系统的结构、基本原理、设计要求以及它的主要特性,特别是对系统的气体动力学机制以及各种参数对系统特性的影响等进行了讨论。最后,综述了它在核物理、核化学以及质谱学等领域的应用情况,并且给出了几个应用的典型例子。