982 resultados para 02270625 TM-3


Relevância:

30.00% 30.00%

Publicador:

Resumo:

带3蛋白胞质片段(cdb3)具有多种生理功能:它可以将膜和膜骨架蛋白相联,起着维持细胞形状以及沟通内外环境的作用。而且,它还通过与多个糖酵解酶的相互作用来调节红细胞内糖酵解速率。它的这些功能很大程度上归因于它的分子柔性大,可以通过各种构象与膜蛋白、糖酵解酶等竞争性结合。 在本文中,我们首先运用分子克隆技术在大肠杆菌BL21(DE3)中成功地构建pET28b-cdb3表达体系。经37℃培养至OD600达0.6时,加入1mM IPTG ,于30℃诱导表达cdb3蛋白。经离子交换和亲和层析两步纯化得到电泳纯的具有生物活性的cdb3蛋白。之后,我们首次较为系统地表征了cdb3蛋白的构象特点:在常规的生理环境下, cdb3蛋白呈现典型的α-螺旋、β折叠二级结构, cdb3的四个Trp残基很大程度地包埋于疏水环境中;随溶液GuHCl浓度增加,cdb3 的四个Trp残基逐渐暴露于极性环境中;当pH值从6.0升高到10.0时,cdb3的Tm值逐渐降低约15℃,其内源荧光强度增加两倍,并在pH 7.2和pH9.2处呈现拐点,而蛋白的二级结构却没有发生变化。金属离子Cd2+、Ca2+、Cu2+、Co2+、Mg2 、Zn2+的结合位点在cdb3蛋白的Trp残基附近,而50μM的金属离子对重组cdb3蛋白的二级结构影响微小。最后,我们合成了cdb3蛋白N端肽段1-23,发现其在水溶液中呈无规卷曲结构,TFE可诱导其形成α螺旋,当TFE浓度增至80%时α螺旋含量达最高。无规卷曲的肽段不与醛缩酶相结合,其以α螺旋形式与醛缩酶相结合。 ATP可与肽段、重组cdb3蛋白结合,并对其光谱学性质有一定影响。当ATP浓度达到3mM时,重组cdb3蛋白发生聚集。

Relevância:

30.00% 30.00%

Publicador:

Resumo:

国内首次报道了LP-MOVPE法生长高质量的高、张应变交替InGaAsP多量子阱结构的研制过程及其材料的高精度X-ray双晶摇摆衍射曲线和荧光光谱特性表征。经过双腔面镀增透射膜后,其TE模与TM模自发发射谱光强差为3dBm,呈现偏振补偿特性。

Relevância:

30.00% 30.00%

Publicador:

Resumo:

土壤有机碳是陆地生态系统的一个动态组成部分,其储量、分布及其转化在陆地碳循环中起着重要的作用,是土壤肥力的核心指标之一。土壤有机碳含量的多少及其空间分布特性受气候、母质、地形等结构性因子以及施肥、耕作等随机性因子的影响。作为陆地生态系统中的一个区域化随机变量,土壤有机碳在系统内部垂直和水平方向上发生变化的同时,参与大气圈和生物圈这两个碳库之间的循环。为了揭示土壤有机碳的空间分布特性,传统统计学、地统计学、遥感与地理信息系统等方法被相继引入且逐渐走向成熟,其中,利用遥感与地理信息系统相结合的方法来反演土壤有机碳库储量及其空间分布格局为越来越多的专家学者所重视。本文在对不同方法基本理论进行简单阐述的基础上,对利用Landsat TM影像分析表层土壤有机碳格局的可行性进行了分析,并就遥感技术在反演表层土壤有机碳的空间分布格局中的应用前景进行了展望。 以黑龙江省部分黑土地区为研究对象,在不同时空尺度下分析了表层土壤有机碳与Landsat TM影像的TM1-TM5、TM7六个波段以及由其计算出的NDVI、NDTI、NDI5、NDI7、NDSVI、SAVI、RDVI和MSAVI 8个遥感指数之间的相关性。结果表明当Landsat TM影像的成像时间为2002年9月份时:(1)小尺度下表层土壤有机碳与TM1极显著相关(r=0.32, p<0.01),与TM2、TM3和NDSVI显著相关(p<0.05),相关系数分别为r=0.27,r=-0.29,r=0.26。(2)大尺度下,表层土壤有机碳与TM1、TM2、TM5和NDI5存在极显著的正相关(p<0.01),相关系数分别为r=0.30,r=0.34,r=0.35,r=0.32;而与NDI7之间存在显著相关性(r=0.27, p=0.02)。(3)当空间尺度一定时,在不同的时间尺度下与表层土壤有机碳具有显著相关性的遥感指标不同。(4)在大尺度下利用遥感技术测定法得到的回归模型对表层土壤有机碳空间分布格局具有较好的预测效果(R2=0.7097, p<0.05);(5)在大尺度下海拔高于200 m的地区表层土壤有机碳浓度显著高于海拔低于200 m的地区(p<0.05)。 通过分别利用地统计方法和遥感技术测定法分析海伦市表层土壤有机碳的空间分布格局,以步长为6170m时球状模型对表层土壤有机碳进行了拟合并利用Kriging插值方法得到了海伦市表层土壤有机碳分布格局;将这一结果与我们利用Landsat TM影像通过遥感技术测定方法得到表层土壤有机碳空间格局进行比较发现:在精度一致的前提下,遥感技术测定法在所需样本数量约为地统计方法的一半,同时在所消耗的人力、物力以及在时间上的循环周期等方面,遥感技术测定方法与地统计方法相比也有着明显的优势。

Relevância:

30.00% 30.00%

Publicador:

Resumo:

本研究从探索新的、更有效的卫星遥感影像计算机辅助分类方法着眼,从在TM影像上识别土壤类型着手,将专家系统方法应用于到卫星遥感影像计算机辅助分类领域,并作了研究的尝试。通过RSCES在试验窗口区的初步工作结果可以看出,将专家系统方法引入到计算机辅助分类领域是可行的、实用的、有价值的,同时也代表了本领域的发展方向。在研究过程中可以得出以下几点认识。(1)目视判读经验表明,计算机对遥感影像的判读将从过去的单纯利用每个像元的光谱特征,发展到一个新的阶段,即对像元的空间关系以及多种辅助信息的综合应用;分析方法也将从精确的数学模型发展到应用判断性知识不确定性知识的专家系统分析。这代表了遥感图像计算机判读的发展方向。(2)在使用专家知识的基础上,各种辅助数据,包括地形图和原有专题力数据,寻于改善判读精度可以发挥重要的作用。(3)将专家系统应用于计算机辅助判读,目前国内外虽然做了一些工作,但还处于初期阶段,正处于发展完善之中,因此,专家系统的设计和建造没有现成的方法和严格的途径可资遵循。专家系统是一门多学科的交叉科目,在系统的建造过程中,尤其需要领域专家与系统设计人员的密切配合,相互合作。

Relevância:

30.00% 30.00%

Publicador:

Resumo:

IEECAS SKLLQG

Relevância:

30.00% 30.00%

Publicador:

Resumo:

土壤有机碳是土壤肥力的核心指标之一,理解其空间分布格局对促进精准农业的发展和科学施肥具有重要意义。本研究旨在检验TM影像结合地面采样数据分析黑龙江省黑土分布区表层土壤有机碳空间分布格局的可行性。结果表明:1)表层土壤有机碳浓度与TM5波段呈显著正相关(r=0.553,P<0.01),与TM4、TM5波段影像像素值之间满足二次多项式回归关系(R2=0.6791,P<0.05);2)回归模型对表层土壤有机碳空间分布格局具有较好的预测效果(R2=0.7097,P<0.05);3)海拔高于200m的地区表层土壤有机碳浓度显著高于海拔低于200m的地区(P<0.05)。

Relevância:

30.00% 30.00%

Publicador:

Resumo:

The large uncertainties in estimates of cropland area in China may have significant implications for major cross-cutting themes of global environmental change-food production and trade, water resources, and the carbon and nitrogen cycles. Many earlier studies have indicated significant under-reporting of cropland area in China from official agricultural census statistics datasets. Space-borne remote sensing analyses provide an alternative and independent approach for estimating cropland area in China. In this study, we report estimates of cropland area from the National Land Cover Dataset (NLCD-96) at the 1:100,000 scale, which was generated by a multi-year National Land Cover Project in China through visual interpretation and digitization of Landsat TM images acquired mostly in 1995 and 1996. We compared the NLCD-96 dataset to another land cover dataset at I-km spatial resolution (the IGBP DIScover dataset version 2.0), which was generated from monthly Advanced Very High Resolution Radiometer (AVHRR)-derived Normalized Difference Vegetation Index (NDVI) from April, 1992 to March, 1993. The data comparison highlighted the limitation and uncertainty of cropland area estimates from the DIScover dataset. (C) 2003 Elsevier Science B.V. All rights reserved.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

The ligands 4,4,4-trifluoro-1-phenyl-1.3-butanedione (Hbfa) and 1,10-phenanthroline (phen) were used to prepare ternary lanthanide (Ln) complexes [Dy(bfa)(3)phen and Tm(bfa)(3)phen]. Crystal data: Dy(bfa)(3)phen C(42)H(26)FqN(2)O(6)Dy, triclinic, P (1) over bar, a= 9.9450(6) angstrom, b = 14.0944(9) angstrom, c = 14.6043(9) angstrom, alpha = 82.104(1)degrees, beta = 87.006(1)degrees, gamma = 76.490(1)degrees, V = 1971.1(2)angstrom(3), Z = 2; Tm(bfa)(3)phen C42H26F9N2O6Tm, triclinic, P (1) over bar, a = 9.898(5)angstrom, b = 13.918(5)angstrom, c = 14.753(5)angstrom, a = 83.517(5)degrees, alpha = 86.899(5)degrees, gamma = 76.818(5)degrees, V = 1965.3(14)angstrom(3), Z = 2. The coordination number of the central Ln(3+) (Ln = Dy, Tm) ion is eight, with six oxygen atoms from three Hbfa ligands and two nitrogen atoms from the phen ligand.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

LaAlO3:Tm3+ and LaAlO3:Tb3+ phosphors were prepared through a Pechini-type sol-gel process. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), photoluminescence, and cathodoluminescence (CL) spectra were utilized to characterize the synthesized phosphors. The XRD results reveal that the fully crystalline pure LaAlO3 Phase can be obtained at 800 degrees C. The FE-SEM image indicates that the phosphor samples are composed of aggregated spherical particles with sizes ranging from 40 to 80 nm. Under the excitation of ultraviolet light (230 nm) and low-voltage electron beams (1-3 kV), the LaAlO3:Tm3+ and LaAlO3:Tb3+ phosphors show the characteristic emissions of Tb3+ (D-1(2)-> H-3(6,4),F-3(4) transitions) and Tm3+ (D-5(3,4)-> F-7(6,5,4,3) transitions) respectively. The CL of the LaAlO3:Tm3+ phosphors have high color purity and comparable intensity to the Y2SiO5:Ce3+ commercial product, and the CL colors of Tb3+-doped LaAlO3 phosphors can be tuned from blue to green by changing the doping concentration of Tb3+ to some extent.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

Five new complexes based on rare-earth-radical [Ln(hfac)(3)(NIT-5-Br-3py)](2) (Ln=Pr (1), Sm (2), Eu (3), Tb (4), Tm (5); hfac = hexafluoroacetylacetonate; NIT-5-Br-3py = 2-(4,4,5,5-tetramethyl-3-oxylimidazoline-1-oxide)-5-bromo-3-pyridine) have been synthesized and characterized by X-ray crystal diffraction. The single-crystal structures show that these complexes have similar structures, in which a NIT-5-Br-3py molecule acts as a bridging ligand linking two Ln(III) ions through the oxygen atom of the N-O group and nitrogen atom from the pyridine ring to form a four-spin system. Both static and dynamic magnetic properties were measured for complex 4, which exhibits single-molecule magnetism behavior.

Relevância:

30.00% 30.00%

Publicador:

Resumo:

研究鳞石英结构碱土铝酸盐MAl2O4 Eu2+、RE3+(M=Mg,Ca,Sr,Ba;RE=Y,La,Ce,Pr,Nd,Sm,Gd,Tb,Dy,Ho,Er,Tm,Yb,Lu)的荧光及长余辉发光性质.其发光由Eu2+的4f-5d跃迁产生.Re3+作为辅助激活离子,提供合适的陷阱能级.即使用RE3+的特征波长激发,在MAl2O4 Eu2+、RE3+的发光中也观察不到RE3+的发光.基于其荧光,热释光,X-射线,红外光谱等实验结果,分析这一结构对稀土发光的影响,并总结其发光规律