762 resultados para 1480


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采用FRESNEL光学软件和MATLAB编程,详细分析了垂直腔面发射激光器的TO封装工艺操作误差对耦合效率的影响.发现在芯片横向偏移、芯片倾斜和管帽倾斜这三种操作误差中,管帽倾斜对封装组件的耦合效率影响最大。

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目的:观察一氧化氮对肿瘤细胞SMMC-7721辐射敏感性的作用效果。方法:实验于2005-06/09在兰州大学生命科学学院和中科院近代物理研究辐射医学实验室进行。处于对数生长期的肝癌细胞SMMC-7721,在用X射线照射前4h,换入含有0.1mmol/L硝普钠(一氧化氮的前体)的培养液,与对照组(不加硝普钠)一起,在200cGy/min的剂量率下,分别照射0,1,2,4,6,8Gy,换为正常培养液培养。用集落形成法计算细胞的存活率,用吖啶橙/溴乙啶双染法检测细胞的死亡情况,用流式细胞仪检测细胞周期。结果:①存活曲线细胞存活率随照射剂量增加而减少,硝普钠组细胞的克隆形成率低于对照组(2Gy时,P<0.01)。②细胞死亡百分率(坏死细胞与凋亡细胞总数/总细胞数):与照射剂量呈正相关,硝普钠组高于对照组(P<0.05)。对照组从(9.95±3.53)%(0Gy)逐渐升至(58.74±3.46)%(6Gy),而硝普钠组则从(18.53±12.02)%(0Gy)迅速升至(61.57±9.53)%(2Gy)。③细胞周期检测结果:对照组细胞经过X射线照射后,出现了G2/M期阻滞[从0Gy时(12.50±5.76)%逐渐增加到8Gy(40.36±2.74)%],而硝普钠组细胞在低剂量时主要表现为G0/G1期阻滞[0Gy:(16.06±7.19)%;2Gy:(17.93±0.92)%],而G2/M期阻滞仅在高剂量时明显[8Gy时为(50.10±3.93)%,P<0.05]。结论:经硝普钠产生的一氧化氮,通过与X射线协同作用,减少了肝癌细胞SMMC-7721的细胞存活率,促进细胞死亡,阻止细胞被阻滞至G2/M期,是一种有效的辐射增敏剂。

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IEECAS SKLLQG

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A layer-by-layer (LbL) adsorption and polymerization method was developed for the controllable preparation of polypyrrole (PPy) nanoparticles within ultrathin films. By repetitive adsorption of pyrrole and subsequent polymerization with 12-molybdophosphoric acid, the polyelectrolyte multilayer films containing PPy nanoparticles were fabricated. UV-visible absorption spectrocopy, Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM), transmission electron microscopy (TEM) and cyclic voltammograras (CVs) were used to characterize the PPy nanoparticles and their multilayer thin films. UV-visible spectra indicate that the growth of PPy nanoparticles was regular and occurred within the polyelectrolyte films. The size of prepared PPy nanoparticles was found by TEM to increase with the increasing of polymerization cycles. The electrochemistry behavior of the multilayer thin films was studied in detail on ITO. The results suggest that the LbL adsorption and polymerization method developed herein provides an effective way to prepare PPy nanoparticles in the polymer matrix.

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Isothermal crystallization behavior of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was investigated by means of differential scanning calorimetry and polarized optical microscopy (POM). The Avrami analysis can be used successfully to describe the isothermal crystallization kinetics of PHBV, which indicates that the Avrami exponent n = 3 is good for all the temperatures investigated. The spherulitic growth rate, G, was determined by POM. The result shows that the G has a maximum value at about 353 K. Using the equilibrium melting temperature (448 K) determined by the Flory equation for melting point depression together with U-* = 1500 cal mol(-1), T-infinity = 30 K and T-g = 278 K, the nucleation parameter K-g was determined, which was found to be 3.14+/-0.07 x 10(5) (K-2), lower than that for pure PHB. The surface-free energy sigma = 2.55 x 10(-2) J m(-2) and sigma(e) = 2.70+/-0.06 x 10-2 J m(-2) were estimated and the work of chain-folding (q = 12.5+/-0.2 kJ mol(-1)) was derived from sigma(e), and found to be lower than that for PHB. This implies that the chains of PHBV are more flexible than that of PHB.

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Matrix effects in now injection (FI) inductively coupled plasma mass spectrometry has been studied,and the results have been compared with those of continuous nebulization. The matrix element As and nu with higher ionization potential ( > 9eV) have enhancement effect on the analyte signal,and the heavier the analyte mass, the smaller the enhancement effects by Fl. The matrix elements Cu, In, Li, Na and Pb with lower ionization potential have suppression effect on the analyte signal. The heavier the matrix element mass, the more severe the suppression effects. The heavier the analyte mass, the smaller the suppression effects. The higher ionization potential of analyte, the more severe the suppression effects. Compared with continuous nebulization, the degree of suppression effect is smaller and the degree of the enhancement effect is larger by Fl.

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研究了流动注射小体积进样,电感耦合等离子体质谱法的基体效应,并与连续进样作了比较。流动注射小体积(100μL)进样时,电离电位较高的As和 Au基体对分析元素的信号表现为增强效应,分析元素的质量数越大,所受增强效应越小。电离电位较低的Cu、In、Li、Na和Pb基体对分析元素的信号则表现为抑制效应,基体元素的质量数越大,对分析元素的抑制效应也越大;质量数较大的分析元素,所受的抑制效应较小;对质量数相近的分析元素,电离电位较高者受的抑制较大。与连续进样相比,流动注射小体积进样时,基体元素对分析元素的抑制效应较弱,而增强效应较强。

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三倍体培育是水产动物遗传改良的重要途径之一,它在提高养殖产量、改良品质方面发挥着重要作用。对虾三倍体在性腺发育和性别比率方面与二倍体之间存在明显差异。本论文对三倍体性腺发育的分子机理进行了初步探讨,为阐明甲壳动物的性腺发育和性别控制机理提供重要依据。本论文取得的主要进展如下: 利用联会复合体的分析技术,比较分析了雄性二倍体和三倍体中精母细胞的减数分裂行为。二倍体对虾具有典型的真核生物联会复合体的形态,联会复合体在二价体联会处沿同源染色体长轴分布;未见明显的异型性别染色体;三倍体对虾精母细胞的联会行为复杂,可见二价体、单价体、非同源联会的三价体、同源转换和同源区完全配对的双联会复合体等不同形态;三倍体对虾在晚粗线期普遍表现为三价体同源区完全配对的双联会复合体形态,这种联会行为可能是导致其产生 3n 倍性精子的关键原因。 利用抑制性消减杂交技术,建立了对虾二倍体和三倍体卵巢间的2个消减文库;在正向消减文库(以三倍体卵巢作为实验组,二倍体卵巢作为驱动组)中,鉴定到54个基因;在反向消减文库(以二倍体卵巢为实验组,三倍体卵巢为驱动组)中,鉴定到16个基因;选取11个差异表达的基因,利用半定量RT-PCR的方法对其在二倍体和三倍体卵巢间的表达进行了检测,均能很好地与消减结果相吻合;这些差异基因编码多种功能的蛋白,分析表明染色体的三倍化使三倍体卵巢中的基因调控网络受到了影响;为深入揭示维持卵巢正常发育的关键分子调控事件奠定了基础。 为进一步分析特定基因对对虾性腺发育的调控机制,选取了在对虾三倍体和二倍体卵巢中差异表达显著的 3 个不同基因,PCNA (proliferating cell nuclear antigen)、CAS/CSE1 (cellular apoptosis susceptibility protein/chromosome segregation 1)和 SSRF (spermatogonial stem-cell renewal factor),进行了相关研究分析,为深入探讨特定基因对对虾性腺发育的调控机制以及三倍体中的基因表达调控机制奠定了基础; 中国明对虾PCNA基因在增殖旺盛的性腺组织及造血组织中表达量最高;在二倍体卵巢中的表达水平显著高于三倍体卵巢;在不同病原刺激下的造血组织中的表达模式不同,与对虾对抗不同病原刺激的免疫反应相关;PCNA在序列上的高度保守性,提示了其功能的保守性;利用PCNA基因可以指示细胞的增殖活性的特点,将辅助我们在对虾发育生物学和二倍体、三倍体对虾比较发育生物学的研究; 中国明对虾CAS/CSE1基因在二倍体卵巢中高表达;在卵母细胞中,其mRNA大量分布于细胞质及细胞核周围;是早期胚胎发育的母源性因子;在其氨基酸序列的N端具有importin-β 家族蛋白的保守结构,提示其可能通过参与核质运输在发育过程中发挥重要作用;利用原核表达系统成功地对其进行了体外重组表达,为进一步在蛋白水平上的功能研究提供了条件; 中国明对虾SSRF(暂时命名)基因在三倍体卵巢中高表达;在正常二倍体对虾的神经组织中表达量最高,提示该基因在神经发育中可能发挥重要作用;在氨基酸序列上与胸苷磷酸化酶(TP)具有最高的相似性;利用原核表达系统成功地对其进行了体外重组表达,为进一步在蛋白水平上的功能研究奠定了基础;对对虾SSRF活性蛋白的酶活及功能验证亟待进行。

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The coda of seismic waves consists of that part of the signal after the directly arrivials. In a finite medium, or in one that is strongly heterogeneous, the coda is dominated by waves which have repeatedly sampled the medium. Small changes in a medium which may have no detectable influence on the first arrivals are amplified by this repeated sampling and may thus be detectable in the coda. Because of this, coda wave is widely used in detecting micro variations in medium。 In this paper, we give a general view of the theory and application of coda wave, especially coda wave interferometry. We focus on discussing the application of coda wave interferometry on data source of active situ experiment。 First, we apply coda wave interferometry in a short time period situ experiment which last for three days. We also apply the method of coda wave interferometry in a situ experiment which last for one month. Daily circle variations of seismic velocity around the experiment site were obtained, and we also observed that the velocity variations in the experiment site have a significant correlation with the environment factors, including air temperature, barometric pressure, solid earth tide and the level of rainfall. We find that the velocity variation during this period is up to 10-3. The relationship between velocity variation and changes in air temperature, barometric pressure and solid earth tide was analyzed with least square linear fitting .The velocity has no dependence on the air temperature. But velocity has a change of 10-6--10-7 when the barometer or earth tide change per Pa. Generally, we conclude the work and results of previous researchers, and we also display our works and results. We hopes to contribute to the future research of coda wave interferometry.