38 resultados para 5-39
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于1997年6月在渤海中设立5个站,用大空容量采水器进行每隔3小时一次的边续取样,对渤海的浮游动物季节性优势种-中华哲水蚤(Calanus sinicus Brodsky) 的数量分布、成体的雌雄比例和昼垂直移动节律进行调查,同时对其每日产卵量及生殖节律等进行了现场实验。结果表明,该时间中华哲水蚤在渤海各站的数量分布差异较大,雌性成体的数量超过雄性成体的数量,各站的雌雄比在1.40到1.97之间,桡足幼体与雌性和雄性成体均有昼夜垂直移动现象。中华哲水蚤的雄性成体在各站的平均产卵量为10.5卵/个体/天,处于产卵期的雌性成体日平均产卵量为18.1卵/个体/天,最大产卵量为26卵/个体/天。中华哲水蚤的产卵量有明显的昼夜节律变化,产卵主要在晚21:00到早晨9:00之间进行。根据中华哲水蚤的种群结构和产卵量推算出渤海该时间的生物量为10.882mgCm~(-3),瞬时生长率为0.918mgCm~(-3)day~(-1) ,P/B比为0.084。中华哲水蚤的种群死亡率主要集中在卵和无节幼体阶段。在97年12月和98年3月我们对采自胶州湾近岸的中华哲水蚤的日产卵量和卵孵化率进行室内实验,发现冬季的日产卵量远远低于6月在渤海的实验,培养当天的温度变化对其产卵量有显著影响,温度从7℃升至14℃使其产卵量增大,但随后两天其产卵量有所下降。温度由7℃降至0℃的当天中华哲水蚤不产卵,如果随之再将温度升至7℃,产卵量有所恢复。在开始实验的第一天,加入人工饵料与否对中华哲水蚤的产卵量影响不大。培养温度为7℃时,卵的孵化率为21.5%,升温至14℃时卵的孵化率为39.7%。在GF/F过滤海水中加入亚心型四片藻作饵料培养中华哲水蚤,其卵的孵化率为12.5%,而以新月菱形藻为饵料时,卵的孵化率为9.9%。在98年3月研究了盐度变化对中华哲水蚤的产卵量和卵孵化率的影响。结果表明,在25.5‰-39.1‰的盐度范围内,中华哲水蚤的产卵量有随盐度增大而减小的趋势,但差异不显蓍。当盐在29.4‰到35.5‰之间时,卵的孵化率基本持平,中华哲水蚤的成体存活良好。当盐度进一步或变小时,卵的孵化率降低,成体的死亡率增大。
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本研究以双壳纲、翼形亚纲、珍珠贝目、扇贝超科的栉孔扇贝(Chlamys farreri )、海湾扇贝(Argopecten irradians)和牡蛎超科巨蛎属(Crassostrea)的长牡蛎(C. gigas)、葡萄牙牡蛎(C. angulata)、熊本牡蛎(C. sikamea)、香港巨牡蛎(C. hongkongensis)和近江牡蛎(C. ariakensis)5种牡蛎及异齿亚纲、帘蛤目、帘蛤科的紫斑文蛤(Meretrix pethechialis)为研究对象,系统的研究了以上物种的线粒体基因组全序列的特点。并以线粒体12个蛋白质编码基因的序列,在氨基酸和核苷酸水平上构建了软体动物的分子系统发生树。本研究旨在为利用线粒体基因组全序列全面构建软体动物分子系统发生树,为软体动物的系统发生和进化研究提供一种新的思路和前期基础工作,本研究主要内容分为以下三个部分: 一、栉孔扇贝和海湾扇贝线粒体基因组序列分析及分子系统发生研究 采用Long-PCR技术扩增了栉孔扇贝和海湾扇贝线粒体全基因组,利用步移法结合文库构建的测序策略获得了线粒体基因组的序列。海湾扇贝线粒体全基因组长度为16,211 bp,栉孔扇贝接近全序列长度为20,789 bp。两个基因组都编码35个基因,包括12个蛋白质编码基因,2个rRNA和21个tRNA。与典型的动物线粒体基因组相比,两个基因组都缺少一个蛋白质编码基因atp8和2个trnS, 在海湾扇贝基因组中有1个trnF的重复,而在栉孔扇贝基因组中有1个trnM的重复。基因排列比较显示,尽管海湾扇贝、栉孔扇贝和巨扇贝分类学上属于同一扇贝科,但是它们的线粒体基因排列非常不同。在四种扇贝中,虾夷扇贝与栉孔扇贝的基因排列顺序非常相似;即使排除tRNA的比较,栉孔扇贝和海湾扇贝基因组仅仅共享三个小的基因块;而海湾扇贝与巨扇贝仅有一个相同的基因块。在所有的系统发生分析中,四种扇贝稳定的系统发生关系得到强有力的支持,海湾扇贝较其他三种扇贝较早的分化出来;栉孔扇贝比其他两种扇贝与虾夷扇贝亲缘关系更近。贝叶斯法和最大似然法分析都支持扇贝超科的单系发生。 二、巨蛎属牡蛎线粒体基因组全序列分析及分子系统发生研究 采用Long-PCR扩增技术和步移法结合文库构建的技术策略获得了巨蛎属C. gigas、C. angulata、C. sikamea、C. hongkongensis和C. ariakensis 5种牡蛎线粒体全基因组序列,并于GenBank已公布的美洲牡蛎C.virginica序列进行比较研究。C. gigas、C. angulata、C. sikamea、C. hongkongensis和C. ariakensis线粒体全基因组长度分别为18,225 bp、18,225 bp、18,243 bp、18,622 bp和18,414 bp,都长于C. virginica基因组17,244 bp的长度。本研究的5种牡蛎线粒体基因组都编码39个基因,包括12个蛋白质编码基因,2个rRNA和25个tRNA。与典型的线粒体基因组相比,都缺少一个蛋白质编码基因atp8,有trnM、trnK和trnQ 3个tRNA基因的重复,更特别的是基因组中的rrnL分为两段,这在其它线粒体基因组中未见报道,有一个重复的rrnS;而C. virginica基因组编码37个基因,与其他牡蛎相比,没有trnK和trnQ重复,只有一个rrnS。基因排列比较显示,巨蛎属的5种牡蛎C. gigas、C. angulata、C. sikamea、C. hongkongensis和C. ariakensis基因排列完全一致,而与C. virginica的基因排列相比仍然有较大的差别,有多个tRNA发生易位。系统发生分析显示,C. gigas和C. angulata首先聚在一起,然后与C. sikamea聚为一支。C. hongkongensis和C. ariakensis聚成一支。C. virginica为单独的一支。系统树清楚的显示出C. gigas和C. angulata以及C. hongkongensis和C. ariakensis非常近的亲缘关系,这也是长期以来,牡蛎分类学上的经典问题,有学者认为C. gigas和C. angulata为同一物种,线粒体基因组的数据显示C. gigas和C. angulata可能达到不同物种的差异。传统分类上的“近江牡蛎”的“白蚝”和“赤蚝”,线粒体序列差别明显,完全支持两种牡蛎新种名的制定。 三、紫斑文蛤线粒体基因组全序列分析及分子系统发生研究 采用Long-PCR扩增技术和步移法结合文库构建的技术策略获得了紫斑文蛤线粒体基因组全序列。该基因组全长19,567 bp,编码36个基因,包括12个蛋白质编码基因,2个rRNA和22个tRNA。与典型的线粒体基因组相比,缺少一个蛋白质编码基因atp8和1个trnS, 有1个trnQ基因的重复。基因排列比较显示,双壳类的基因排列在低的分类阶元时相对保守。在帘蛤科中,紫斑文蛤M. petechialis和菲律宾蛤仔V. philippinarum共享四个完全一致的基因块,两个大的基因块是cox1-L1-nad1-nad2-nad4L-I 和 cox2-P-cob-rrnL-nad4-H-E-S2-atp6-nad3-nad5,另两个小基因块只包括tRNA基因。在以氨基酸序列构建的分子系统树中,帘蛤科紫斑文蛤与菲律宾蛤仔首先聚在一起,然后,它们与A. tuberculata形成一个进化枝。这一枝与H. arctica结合起来,支持异齿亚纲单系发生。
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青海地道中药材“西宁大黄”,野生资源濒临枯竭,人工种植规模不断扩大。定期采集了青海西宁及邻近地区两年生种植大黄叶,分析测试了其矿物质元素,为西宁大黄资源的可持续开发和利用提供科学依据。研究表明,种植大黄叶中矿物质营养元素的协同性以及有效蓄积对大黄的生长具有重要意义。钠元素在大黄叶中的有效蓄积以及环境中水分的及时补给对种植大黄的生长具有重要作用。
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一般地说,用APT语言编写的描述数控机床的刀具及要加工的工件的有关数据经计算机专门程序处理后,产生的适用于指定的NC控制器的命令代码要被输送到纸带上,然后以此纸带上的信息去控制机床工作。但是,在实际情况中,先不能立即进行这最后一步。应先对带上的信息进行检验,以免由于编程人员的计算和编写程序上的错误所造成的刀具损伤或零件报废的现象发生。本文将给出利用仿真程序借助绘图仪画出刀具运动轨迹以验证其正确与否的方法。
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NaA zeolite membranes were successfully synthesized on a porous alpha -Al2O3 support from clear solution. The synthesis parameters, such as surface seeding, synthesis time, synthesis stages, etc. were investigated. Surface seeding can not only accelerate the formation of NaA zeolite on the support surface, but can also inhibit the transformation of NaA zeolite into other types of zeolites. A continuous NaA zeolite membrane formed on the seeded support after 2 h of synthesis. Gas permeation results showed that a synthesis time of 3 h produced the best NaA zeolite membrane. When the synthesis time was longer than 4 h, the NaA zeolite on the support surface began to transform into other types of zeolites, and the quality of the NaA zeolite membrane decreased. The quality of the NaA zeolite membrane can be improved by employing the multi-stage synthesis method. The NaA zeolite membrane with a synthesis time of 2 h after a two-stage synthesis showed the best gas permeation performance. The permeances of H-2, O-2, N-2, and n-C4H10 decreased as the molecular kinetic diameter of the gases increased. which showed the molecular sieving effect of the NaA zeolite membrane. The permselectivities of H-2/n-C4H10 and O-2/N-2 were 19.1 and 1.8, respectively. These values are higher than the Knudsen diffusion ratios of 5.39 and 0.94. However, the permeation of n-C4H10 also indicated that the NaA zeolite membrane had certain defects with diameters larger than the pore size of NaA zeolite. A synthesis model was proposed to clarify the effect of surface seeding. (C) 2001 Elsevier Science B.V. All rights reserved.
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The synthesis of NaA zeolite membrane on a porous alpha -Al2O3 support from clear solution and the evaluation of the perfection of the as-synthesized membrane by gas permeation were investigated. When an unseeded support was used, the NaA zeolite began to transform into other types of zeolites before a continuous NaA zeolite membrane formed. When the support was coated with nucleation seeds, not only the formation of NaA zeolite on the support surface was accelerated, but also the transformation of NaA zeolite into other types of zeolites was inhibited. A continuous NaA zeolite membrane can be formed. Perfection evaluation indicated that the NaA zeolite membrane with the synthesis time of 3 h showed the best perfection after a one-stage synthesis. The perfection of NaA zeolite membrane can be improved by employing the multi-stage synthesis method. The NaA zeolite membrane with a synthesis time of 2 h after a two-stage synthesis showed the best gas permeation performance, The permselectivity of H-2/n-C4H10 and O-2/N-2 were 19.1 and 1.8, respectively, higher than those of the corresponding Knudsen diffusion selectivity of 5.39 and 0.94, which showed the molecular sieving effect of NaA zeolite. However, the permeation of n-C4H10 also indicated that the NaA zeolite membrane had certain defects, the diameter of which were larger than the NaA zeolite channels. (C) 2001 Elsevier Science B.V. All rights reserved.
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本文研究了以PMBP-苯萃取稀土和钍、铀、钛、锆的萃取行为。测定了La、Ce、Pr、Nd、Sm、Gd、Dy、Yb、Y、U(Ⅵ)、Ti、Th和Zr的pH_(1/2)值,计算了它们的萃取平衡常数。并介绍了近十年来作者将此萃取剂应用于铀、钍、稀土、鋰、钢铁合金及岩石中痕量稀土、钍和钙的分离和测定方面的工作。实践证明,PMOP合成简便、价格低廉、萃取能力较强,是比TTA更为优越的萃取剂。
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This paper reports on the optical spectroscopic properties and thermal stability of Er3+-doped TeO2-BaO (Li2O,NaO)-La2O3 glasses for developing 1.5-mu m fiber amplifiers. Upon excitation at 977 nm laser diode, an intense 1.53-mu m infrared fluorescence has been observed with a broad full width at half maximum (FWHM) of about 60 nm for the Er3+-doped TeO2-BaO (Li2O, Na2O)-La2O3 glass with 10 mol% of BaO. The calculated fluorescence lifetime and the emission cross-sections of the 1.53-mu m transition are 2.91 ms and similar to 9.97 x 10(-21) cm(2), respectively. It is noted that the gain bandwidth, a, x FWHM, of the TeO2-BaO-La2O3Er2O3 glass is about 600, which is significantly higher than that in silicate and phosphate glasses. Meanwhile, it is interesting to note that the TeO2-BaO-La2O3-Er2O3 glass has shown a high glass thermal stability and good infrared transmittance. As a result, TeO2-BaO (Li2O, Na2O)-La2O3 glass with 10 mol% of BaO has been considered to be more useful as a host for broadband optical fiber amplifier. (c) 2005 Elsevier B.V. All rights reserved.
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AlGaN/AlN/GaN high electron mobility transistor (HEMT) structures with high mobility GaN channel layer were grown on 50 min diameter semi-insulating (SI) 6H-SiC substrates by metalorganic chemical vapor deposition and large periphery HEMT devices were fabricated and characterized. High two-dimensional electron gas mobility of 2215 cm(2)/V s at room temperature with sheet electron concentration of 1.044 x 10(13)/cm(2) was achieved. The 50 mm diameter HEMT wafer exhibited a low average sheet resistance of 251.0 Omega/square, with the resistance uniformity of 2.02%. Atomic force microscopy measurements revealed a smooth AlGaN surface with a root-mean-square roughness of 0.27 nm for a scan area of 5 mu mi x 5 pm. The 1-mm gate width devices fabricated using the materials demonstrated a very high continuous wave output power of 9.39 W at 8 GHz, with a power added efficiency of 46.2% and power gain of 7.54 dB. A maximum drain current density of 1300 mA/mm, an extrinsic transconductance of 382 mS/mm, a current gain cutoff frequency of 31 GHz and a maximum frequency of oscillation 60 GHz were also achieved in the same devices. (C) 2007 Elsevier Ltd. All rights reserved.
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一 结构因子相角的代数解法晶体结构研究中的相角问题,一直是晶体学工作者努力探求的基本问题。几十年来,关于相角问题的研究已经取得了巨大的进展,直接法的成熟和普遍应用就是这个进展的显著标志。在直接法相角问题研究中,历来存在两种基本方法,即概率法和代数法。当前直接法的迅猛发展,则主要以概率法为基础,其应用的基本公式即是来自∑关系中的∑_2关系和由此发展出的TANGENT公式,并结合一系列的基本理论和辅助公式,从而使直接法的发展一直呈方兴未艾之势。与此形成鲜明对照的是,相角问题的代数法研究则有日趋下降之势,尤其近十年来则显著落后了。作者从近年来的∑关系研究中,看到要解决相角问题,代数法仍然有其潜在的应作价值,并认为在概率法可以得到应用的许多方面,在代数法那里都应找到对应的类似内容,而代数法在研究和应用中所表现出的不同于概率法的那些方面也正是在相角问题研究中最令人感兴趣的问题,这就是我们进行代数法研究的目的和出发点。(一)1.5和2.5阶代数式的提出及对±2~(II)型相角的估算。(二)一般类型相角的估算(三)结构相角通用代数式的推导。代数法不仅可用于结构半不变量O,π型相角的计算,而且可用于非结构半不变量的种种类型相角的估算,其中包括型和一般类型相角,而且其应用效果完全可以和概率法相比拟,在机时利用上前者有一定优势。通用代数式的获得将为代数法的普遍应用和计算机计算创造了方便条件。二稀土杂多酸根配合物K_8H_5[La(SiWMo_(10)O_(39))(SiW_3Mo_8O_(39))]·nH_2O的晶体结构采用低温技术,在-90 ℃的干燥氮气保护下,收集晶体衍射数据,以直接法解出结构。a = 17.485(5), b = 27.096(6), c = 21.642(5)A, β = 107.79(2)°, z = 4。最后的R值为0.097。中心离子La(III)同两个杂多酸根提供的8 个氧配合。而其中的W、Mo同氧的配位情况基本相同,者是与氧六配位,形成变形配位八面体。
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在15K测量了不同尺寸分布的In_(0.55)Al_(0.45)As/Al_(0.5)Ga_(0.5)As量子点的静压我致发光,静压范围为0--1.3GPa。常压下观察到三个发光峰,分别来源于不同尺寸的量子点(横向直径分别为26、52和62nm)的发光。它产的压力系数分别为82、94和98meV/GPa,都小于In_(0.55)Al_(0.45)As体材料带边的压力系数,特别是尺寸为26nm的小量子点比In_(0.55)Al_(0.45)As体材料带边小17%,并且压力系数随量子点尺寸的变小而减小。理论计算表明有效质量的增在和Γ-X混合是量子点压力系数变小的主要原因,并得到横向直径为26和52nm的小量子点的Γ-X混合势为15和10meV。根据实验还确定In_(0.55)Al_(0.45)As/Al_(0.5)Ga_(0.5)As量子点系统X能带具有Ⅱ类结构,并且估算出价带不连续量为0.15±0.02。
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The structure and electrochemical characteristics of melted composite Ti0.10Zr0.15V0.35Cr0.10Ni0.30 + x% LaNi4Al0.4Mn0.3Co0.3 (x = 0, 1, 5) hydrogen storage alloys have been investigated systematically. XRD shows that though the main phase of the matrix alloy remains unchanged after LaNi4Al0.4Mn0.3Co0.3 alloy is added, a new specimen is formed. The amount of the new specimen increases with increasing x. SEM-EDS analysis indicates that the V-based solid solution phase is mainly composed of V, Cr and Ni; C14 Laves phase is mainly composed of Ni, Zr and V; the new specimen containing La is mainly composed of Zr, V and Ni. The electrochemical measurements suggest that the activation performance, the low temperature discharge ability, the high rate discharge ability and the cyclic stability of composite alloy electrodes increase greatly with the growth of x.
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W1-xAlxC (x = 0.33, 0.50, 0.75, 0.86) solid solutions have been synthesized directly by ball-milling tungsten powder, aluminum powder and activated carbon. The structural development of W0.5Al0.5C phase with the milling times up to 160 h has been followed using X-ray diffraction. X-ray photoelectron spectra demonstrate that Al atom takes the place of W. High temperature annealing experiment reveals that Al is stable in hexagonal structure to 1873 K. Transmission electron microscopy image shows that the grain size of the prepared powders is about 5 nm.