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活体23Na NMR及在生物医学中的应用 总被引:1,自引:0,他引:1
胞内Na+浓度和跨膜梯度的维系对于保持组织细胞的正常生理状态具有重要的作用.本文详细介绍了生物组织细胞内Na+测定的23Na NMR方法,并讨论了23Na NMR在生理病理学研究和疾病诊断等生物医学领域内的应用。 相似文献
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用23Na NMR研究竹红菌乙素光敏损伤对鼠腹水肝癌细胞Na+通透性的影响 总被引:1,自引:0,他引:1
用23Na NMR技术并借助于水溶性位移试剂Dy(PPPi)27-研究了新型光敏剂-竹红菌乙素光敏损伤对鼠腹水肝癌细胞Na+通透性的影响。实验结果表明:在乙素光敏作用下,细胞内Na+浓度随曝光时间的延长和乙素浓度增高而增加。同时观察到细胞外23Naout NMR峰的化学位移(δ值)随光照时间增加而向低场位移。分析表明:化学位移的改变与细胞膜损伤引起细胞内K+泄漏和K+、Na+竞争位移试剂有关。因此,化学位移的改变也可作为光敏损伤的指标。本文还就Na+平衡失调与细胞死亡之间的关系进行了讨论。 相似文献
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基于完全活性空间自洽场方法和多参考组态相互作用(multi-reference configuration interaction method,MRCI)方法,采用MRCI+Q/CBS(TQ5)+CV+SR(方法A)和aug-cc-pwCVnZ-DK(n=T,Q,5)(方法B)方案,分别计算了包含Davidson修正(+Q)、芯-价电子关联(core-valence correlation correction,CV)效应以及标量相对论(scalar relativistic,SR)效应的CO分子的基态X1∑+和激发态a3Π,a'3∑+和A1Π的势能曲线.在此基础上,获得了这些电子态的振-转谱.通过与实验结果比较发现:方法A适合a'3∑+和A1Π等较高激发态的振-转谱的计算,方法B更适合基态X1∑+和第一激发态a3Π的振-转谱的精细计算.该研究可以为其他小分子高精度振-转谱快速计算方案选择提供参考. 相似文献
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利用量子化学从头计算方法MRCI+Q在AVQZ级别上对BS+离子进行了研究. 通过计算得到了与BS+离解极限B+(1Sg)+S(3Pg)和B+(1Sg)+S(1D)对应的5个Λ-S态,确认了BS+离子的基态为X3∏电子态,而第一激发态1∑+的激发能Te仅仅为564.53 cm-1. 首次纳入的旋轨耦合效应(SOC)使得BS+的5个Λ-S态分裂成为9个Ω态,原有的两个离解极限分裂为B+(1S0)+S(3P2),B+(1S0)+S(3P1),B+(1S0)+(3P1)以及B+(1S0)+S(1D2). 在考虑自旋轨道耦合效应之后,Ω态的基态为X2态. 通过势能曲线(PECs)可以发现所得到的Λ-S态和Ω态均为束缚态,利用LEVEL8.0程序拟合得到了对应电子态的光谱常数,这些结果可以为实验和理论方面进一步研究BS+的光谱性质提供准确的电子结构信息.
关键词:
势能曲线
光谱参数
多参考组态相互作用方法
Q)')" href="#">Davidson修正(+Q) 相似文献
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本文使用固体核磁共振(NMR)技术研究了SSZ-13分子筛上甲醇制烯烃反应过程中表面甲氧基物种的生成以及反应活性.通过二维13C-27Al HMQC NMR方法确证了甲醇在分子筛骨架Brønsted酸位上生成的甲氧基物种,以及在Lewis酸位上生成的另外一种表面甲氧基物种.13C NMR结合气相色谱-质谱(GC-MS)实验结果表明,这两种甲氧基物种在甲醇制烯烃反应中均具有较高的反应活性,既可以导致烃池物种的生成,也可以参与烃池反应生成碳氢化合物. 相似文献
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We calculate the branching ratios of pure annihilation type decays B 0 →Ds- (K2*)+ and Bs → a2 using the perturbative QCD approach based on k T factorization. The branching ratios are predicted to be (60.6 +17.3+4.3+3.2 16.5 10.4 2.1 )× 10-6 for B0 →Ds- (K2*)+ , (1.1 +0.4+0.1+0.1-0.4-0.2-0.1 )×10-6 for Bs → 0a20 and (2.3 +0.8+0.2+0.1-0.8-0.4-0.1 )×10-6 for Bs→D-a2+ . They are large enough to be measured in the ongoing experiment. Due to the shortage of contributions from penguin operators, there are no direct CP asymmetries for these decays in the Standard Model. We also derive simple relations among these decay channels to reduce theoretical uncertainties for the experiments, to test the accuracy of theory, and to search for a signal of new physics. 相似文献
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该文用顺磁离子对其近邻13C核的NMR吸收增宽效应,系统地研究了抗坏血酸在不同溶剂中对金属离子Mn2+、Gd3+的配合行为.在水溶液中,抗坏血酸可通过两种配合方式与Mn2+作用,但与Gd3+的作用只有一种稳定的结构.在水中抗坏血酸对金属的配位活性部位分别是1位羟基氧,3位离解的羟基氧和6位羟基氧.在DMSO中,3位羟基由于H+对该基团的静电遮蔽而变得对金属离子Mn2+表现为配位惰性,同时6位羟基配位活性较大增强.对Gd3+来说,此时没有优势配位活性部位存在.文章还讨论了抗坏血酸在H2O-DMSO混合溶剂中的13C NMR谱及在DMSO中NaOH对其13C NMR谱及其与金属络合结构的影响. 相似文献
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Cynthia J. Jameson Hyung-Mi Lim A. Keith Jameson 《Solid state nuclear magnetic resonance》1997,9(2-4):277-301
We consider the role of polarization in the adsorption of Xe in zeolites of type A by direct comparative analysis of the adsorption isotherms, distributions of occupancies, and 129Xe NMR chemical shifts of Xen in cages containing CaxNa12 −2x ions per alpha cage (x = 0, 1, 2, 3, 5). We find that the qualitative trends in the adsorption isotherms, and in the progressions of Xen chemical shifts (for n = 0–8 in cages with x = 0, 1 Ca2+ ions and for n = 0–5 in cages with x = 2, 3 Ca2+ ions) upon increasing the level of Ca2+ ion for Na+ ion substitution could only be accounted for by including polarization of the Xe atom by the zeolite framework and its ions. This system, which permits observation of individual Xen peaks and of directly comparable adsorption isotherms in several cage types, provides a good model system for the interpretation of the more general case in which only the overall average 129Xe NMR chemical shift is observed in open network zeolites, arising from free exchange of Xe among cavities of variable occupancy and variable cation distribution. 相似文献
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The adsorption of Na+ on γ-alumina surfaces at four coverages of Na2CO3 [5, 10, 15 and 20% (w/w)] was characterized by solid-state 23Na and 27Al nuclear magnetic resonance (NMR) spectroscopy. The experimental results suggest that two distinct adsorbed species are present on the alumina surface: surface species and surface salts. At the lower coverages of Na2CO3 (5 and 10%), the surface species is predominant, in which the Na+ cations are associated with the oxygen atoms of γ-alumina. Increasing the loading level to 15% results in the appearance of a second adsorbed species that is attributed to the surface salt, Na2CO3, deposited on the solid surface. Further adsorption of Na2CO3 leads to an increase in the amount of surface salt while the amount of surface species remains unchanged. 1H---27Al Cross-polarization magic angle spinning (CP-MAS) experiments give the evidence that some Na+ cations in the form of surface species are coordinated with the Brönsted acid sites of γ-alumina. This may be the main driving force that improves appreciably the catalytic efficiency of an Na2CO3---Al2O3 catalyst. 相似文献
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Effect of co-doped metal caions on the properties of Y_2O_3:Eu~(3+) phosphors synthesized by gel-combustion method 下载免费PDF全文
Y_2O_3:Eu~(3+) phosphors co-doped with different metal cations(Li~+, Na~+, K~+, Mg~(2+), Ca~(2+)) are prepared by the gelcombustion method with Y_2O_3, Eu_2O_3, and R(NO3)x(R = Li, Na, K, Mg, Ca) serving as raw materials and glycine as fuel,calcined at 1000?C for 2h. The synthesized Y_2O_3:Eu~(3+) phosphors doped with different metal cations and doping ratios are characterized by x-ray diffractometry(XRD), fluorescence and phosphorescent spectrophotometer. The co-doping metal cations are advantageous to the development of Y_2O_3:Eu~(3+) lattice. All the samples can emit red light peaked at 611 nm under 254-nm excited. The luminescence intensities of co-doping samples are increased because the cations increase the electron transition probability of Eu~(3+) from ~5D_0 level to ~7F level. The fluorescence lifetime of Eu~(3+)(~5D_0→~7F_2) is increased by doping metal cations. 相似文献
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Hydrated and dehydrated zeolites MA (where M=Li, Na and K) with LTA structure have been studied by impedance spectroscopy with scanning frequency from 1 Hz to 1 MHz at high pressure up to 4.5 GPa and high temperature up to 250 °C. Anomalous increase in electrical AC conductivity at about 1.5–2 GPa observed in hydrated zeolites is associated with changes in crystalline structure leading to the formation of high-diffusion state of cation and water stuffing of the channels.
In dehydrated zeolites, electrical conductivity is controlled by diffusion of cations (Li+, Na+ and K+), which is determined by cation sites and aluminosilicate ring windows. LiA and NaA zeolites show normal decrease of conductivity with pressure, whereas KA zeolite exhibits the anomalous dependence with considerable increase and then fast decrease of conductivity. The behaviour of KA zeolite is associated with nearly central location of cation site in 8-membered ring, different from that in LiA and NaA zeolites. 相似文献
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High silica zeolite SSZ-13 with Si/Al ratios varying from 11 to 17 was characterized by aluminum-27 and silicon-29 NMR spectroscopy. Aluminum-27 MAS and MQMAS NMR data indicated that in addition to tetrahedral aluminum sites, a fraction of aluminum sites are present in distorted tetrahedral environments. Although in samples of SSZ-13 having high Si/Al ratios all aluminum atoms are expected to be isolated, silicon-29 NMR spectra revealed that in addition to isolated aluminum atoms (Si(1Al)), non-isolated aluminum atoms (Si(2Al)) exist in the crystals. To model these contributions of the various aluminum atoms, a mixed-domain distribution was developed, using double-six membered rings (D6R) as the basic building units of SSZ-13. A combination of different ideal domains, one containing isolated and the other with non-isolated aluminum sites, has been found to describe the experimental silicon-29 NMR data. 相似文献
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Jnos Szanyi Ja Hun Kwak Sarah Burton Jose A. Rodriguez Charles H.F. Peden 《Journal of Electron Spectroscopy and Related Phenomena》2006,150(2-3):164-170
Adsorbed ionic NOx species formed upon the interaction of NO2 with dehydrated or hydrated Na- and Ba-Y, FAU zeolites were characterized using FT-IR/TPD, solid state NMR, and XANES techniques. NO2 disproportionates on both dehydrated catalyst materials forming NO+ and NO3− species. These ionic species are stabilized by their interactions with the negatively charged zeolite framework and the charge compensating cations (Na+ and Ba2+), respectively. Although the nature of the adsorbed NOx species formed on the two catalysts is similar, their thermal stabilities are strongly dependent on the charge compensating cations. In the presence of water in the channels of these zeolite materials new paths open for reactions between NO+ and H2O, and NO2 and H2O, resulting in significant changes in the adsorbed ionic species observed. These combined spectroscopic investigations afforded the understanding of the interactions between water and NO2 on these zeolite catalysts. 相似文献
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采用高温固相法制备了LiSrBO3:xEu3+ 荧光粉, 并通过XRD, 红外(FITR) 和荧光光谱(PL) 等对其表征. 结果表明, LiSrBO3: Eu3+ 荧光粉可被波长为395 nm 的紫外线和466 nm 的蓝光有效激发, 且发射主波长为612 nm (Eu3+的电偶极跃迁5D0 →7F2) 的红光. 研究了Eu3+ 掺杂浓度对LiSrBO3: Eu3+ 材料发光强度的影响, Eu3+ 掺杂浓度为6% 时样品的发射强度最大, 并且证实Eu3+ 之间的能量传递机制为电偶极子- 电偶极子相互作用. Li+, Na+, K+ 作为电荷补偿剂的引入全部导致LiSrBO3: Eu3+ 材料发射强度增强, 其中, Li+ 的引入要优于Na+ 和K+. 少量Al3+的掺杂降低了Eu3+ 所处格位的对称性, 增强了Eu3+ 的612 nm 的电偶极发射, 改善了LiSrBO3: Eu3+ 红色材料的色纯度.
关键词:
白光发光二级管
光致发光
浓度猝灭
电荷补偿剂 相似文献