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排序方式: 共有361条查询结果,搜索用时 62 毫秒
31.
W. G. Gurewitsch und W. P. Wendt 《Fresenius' Journal of Analytical Chemistry》1937,108(3-4):134-136
Ohne Zusammenfassung 相似文献
32.
G. Ulm S. K. Bhattacherjee P. Dabkiewicz G. Huber H. -J. Kluge T. Kühl H. Lochmann E. -W. Otten K. Wendt S. A. Ahmad W. Klempt R. Neugart ISOLDE Collaboration 《Zeitschrift für Physik A Hadrons and Nuclei》1986,325(3):247-259
The technique of collinear fast-beam laser spectroscopy has been used to measure the isotope shifts of the even-even isotopes of Hg (Z=80) in the mass range 182≤A≤198 at the on-line mass separator ISOLDE at CERN. The atomic transition studied (6s 6p 3 P 2- 6s7s 3 S 1,λ=546.1 nm) starts from a metastable state, which is populated in a quasi resonant charge transfer process. The resulting changes in nuclear mean square charge radii show clearly that182Hg follows the trend of the heavier, even, weakly oblate isotopes. Correspondingly the huge odd-even shape staggering in the light Hg isotopes continues and the nuclear shape staggering and shape coexistence persists down to the last isotope investigated,181Hg. An update of isotope shift and hyperfine structure data for181–206Hg is given, with a revised evaluation of the differences in nuclear mean square charge radii and of spectroscopic quadrupole moments. 相似文献
33.
34.
A Novel Approach for Introducing Bio-Materials Into Cells 总被引:1,自引:0,他引:1
A novel approach was developed to introduce biological materials into cells for gene transfection and gene therapy applications. The method is based on the technique of electrospraying bio-materials into cells. A prototype apparatus was constructed for a feasibility study. The features of the gene transfector include: (1) A dual-capillary assembly to spray suspensions of biological materials. The outer capillary provided sheathing liquid that controlled the charge level on individual particles without altering the properties of suspensions. (2) An air–CO2 gas mixture was used for suppressing possible corona discharge and kept the same gas composition as those in incubators. (3) The designed chamber enabled the spray to operate at reduced pressure for increasing sprayed particle velocity. In the feasibility study, both suspensions of plasmid and plasmid-coated gold particles were used. The plasmid used was the commercially available Enhanced Green Fluorescent Protein gene. COS-1 cells were used as the target and the liquid media was evacuated immediately prior to the spraying process. Electrospraying was conducted at ambient pressure and the duration was no more than 2 min. After the spray transfection, the media was immediately replaced and the cell samples were returned to the incubator for 36 h. Transgene expression was detected by cellular fluorescence. This technology promises to have great potential for gene transfection and therapy studies. 相似文献
35.
Carl‐Johan Wallentin Torbjörn Wixe Ola F. Wendt Dr. Karl‐Erik Bergquist Dr. Kenneth Wärnmark Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(13):3994-4002
A pair of molecular tweezers (syn‐ 4 ) that consists of quinoline and pyrazine units fused to a bicyclic framework is presented. The tweezers were synthesised both as a racemic mixture (rac‐ 4 ) and an enantiomerically pure form ((R,R,R,R)‐ 4 ) starting from either racemic or enantiomerically pure bicyclo[3.3.1]nonane‐2,6‐dione ( 3 ). Homochiral dimers were observed in the solid state for rac‐ 4 . The self‐association of both rac‐ 4 and (R,R,R,R)‐ 4 was studied in solution. A weak self‐association constant in CDCl3 was estimated by 1H NMR spectroscopic dilution titration experiments in both cases, following several proton resonances. For this purpose, a general normalisation model for the accurate determination of association constants from multiple datasets was developed. In contrast to the solid state, no diastereomeric discrimination was observed for rac‐ 4 in solution. 相似文献
36.
37.
Planar near-rings are generalized rings which can serve as coordinate domains for geometric structures in which each pair of nonparallel lines has a unique point of intersection. It is known that all planar nearrings can be constructed from regular groups of automorphisms of groups which can be viewed as the “action groups” of the planar nearring. In this article, we study planar nearrings whose additive group is \({(\mathbb{R}^n,+)}\) , in particular, n = 1 and 2. It is natural to study topological planar nearrings in this context, following ideas of the late Kenneth D. Magill, Jr. In the case of n = 1, we characterize all topological planar nearrings by their action groups \({(\mathbb{R}^*, \cdot)}\) or \({(\mathbb{R}^+, \cdot)}\) . For n = 2, these action groups and the circle group \({(\mathbb{U}, \cdot)}\) seem to be the most interesting cases, but the last case can be excluded completely. As a consequence, we obtain characterizations of the semi-homogeneous continuous mappings from \({\mathbb{R}^n}\) to \({\mathbb{R}}\) for n = 1 and 2. Such a mapping f enjoys the property that f(f(u)v) = f(u)f(v) for all \({u,v \in \mathbb{R}^n}\) . When \({f(\mathbb{R}^n) = \mathbb{R}^+}\) , f is a positive homogeneous mapping of degree 1. 相似文献
38.
A dammarane derivative dihydrojujubogenin-2-en-1-one, which possesses a skeleton and pharmacophore partially similar to those of Territrem B, a potent AChE inhibitor, was synthesized via three different paths. The anti-AChE activity of this compound and related analogue was measured. 相似文献
39.
Richard E. Wendt III Wolfgang Nitz Joel D. Morrisett Thomas D. Hedrick 《Magnetic resonance imaging》1990,8(6):723-728
A two-dimensional, flow-enhanced gradient echo pulse sequence for nuclear magnetic resonance angiography is described. It employs interleaved, presaturated slices to acquire data efficiently on imagers which favor interleaved acquisition over sequential acquisition for multislice imaging. It is useful on any imager when the effective TR is extended to enhance the sensitivity to slow flow. The technique was applied to the region from aortic bifurcation to the iliac bifurcations of three normal volunteers. The right and left common iliac arteries and veins, the separation of the external and internal iliac arteries, and secondary branches were clearly depicted. 相似文献
40.
R. Neugart E. W. Otten K. Wendt S. Ahmad N. Panigrahy R. W. Dougherty K. C. Mishra T. P. Das J. Andriessen 《Hyperfine Interactions》1990,59(1-4):145-148
Using the relativistic linked cluster many-body perturbation procedure we have obtained the hyperfine field at the nucleus
of the Ra+ ion in the2S1/2 ground state. There is good agreement between the calculated magnetic moment of213Ra and the results of a recent Zeeman measurement by the collinear laser beam technique. Detailed comparison is carried out
between our result and earlier ones. 相似文献