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91.
Deoxy oligonucleotide synthesis via the triester method 总被引:20,自引:0,他引:20
92.
93.
M.S. Cramer 《Journal of sound and vibration》1983,90(1):25-28
The focusing of weak three-dimensional shock waves at an arête is examined. By aligning the co-ordinate system with the principal directions on the initial shock surface, it is shown that the focusing of an arbitrary three-dimensional shock may be regarded as locally two-dimensional. In addition, the scaling relating the two problems is given explicitly. 相似文献
94.
Pigliucci A Nikolov P Rehaman A Gagliardi L Cramer CJ Vauthey E 《The journal of physical chemistry. A》2006,110(33):9988-9994
A series of 6-styryl-2,4-diphenylpyrylium salts exhibiting dual fluorescence has been investigated by fluorescence up-conversion in conjunction with quantum chemical calculations. The short-wavelength emission is due to an excited state localized on the pyrylium fragment and the long-wavelength emission arises from a charge-transfer state delocalized over the whole molecule. The two fluorescing states do not exhibit a precursor-successor relationship. The rise time of the short-wavelength fluorescence is smaller than 200 fs, and that of the long-wavelength emission depends on the electron-donating property of the styryl group substituent. The rise is almost prompt with the weaker donors but is slower, wavelength and viscosity dependent with the strongest electron-donating group. A model involving a S(2)/S(1) conical intersection is proposed to account for these observations. 相似文献
95.
Tim Cramer 《Advances in Mathematics》2010,224(3):1097-1120
We show that the reduced Drinfeld double of the Ringel-Hall algebra of a hereditary category is invariant under derived equivalences. By associating an explicit isomorphism to a given derived equivalence, we also extend the results of Burban and Schiffmann [5] and [006], Sevenhant and Van den Bergh (1999) [25], and Xiao and Yang (2001) [31]. 相似文献
96.
Heckel BR Cramer CE Cook TS Adelberger EG Schlamminger S Schmidt U 《Physical review letters》2006,97(2):021603
We used a torsion pendulum containing approximately 9 x 10(22) polarized electrons to search for CP-violating interactions between the pendulum's electrons and unpolarized matter in the laboratory's surroundings or the Sun, and to test for preferred-frame effects that would precess the electrons about a direction fixed in inertial space. We find, /g(P)(e)g(S)(N)//(Planck's constant x c) < 1.7 x 10(-36), and /g(A)(e)g(V)(N)//(Planck's constant x c) < 4.8 x 10(-56) for lambda > 1 AU. Our preferred-frame constraints, interpreted in the Kostelecky framework, set an upper limit on the parameter /b(e)/ 相似文献
97.
98.
The effectiveness of different concrete and pictorial models on students' understanding of the part-whole construct for fractions was investigated. Using interview data from fourth and fifth grade students from three different districts that adopted the Mathematics Trailblazers series, authors identified strengths and limitations of models used. Pattern blocks had limited value in aiding students' construction of mental images for the part-whole model as well as limited value in building meaning for adding and subtracting fractions. A paper fraction chart based on a paper folding model supported students' ability to order fractions with same numerators but was less useful in helping students on estimation tasks. The dot paper model and chips did not support fifth grade students' initial understanding of the algorithm. 相似文献
99.
Substantial research activities have been carried out at HZDR during the last 15 years on the development and qualification of various methods to measure the velocity field in liquid metal flows. In this paper we report on two complementary methods for measuring the local velocity. The potential difference probe is a local sensor which is immersed into the liquid. Such sensors are very effective for investigations of the turbulent fluctuations at a local point. However, the installation of the probe in the bulk of the liquid might disturb the flow to be measured. Ultrasonic techniques are non-invasive, but need a continuous path from the ultrasonic transducer to the liquid under investigation. The ultrasound Doppler method delivers instantaneous profiles of the local velocity. Experimental applications of these measuring techniques in diverse liquid metal flows under the influence of magnetic fields will be presented here showing the capabilities and limitations of both methods. 相似文献
100.
Jai Prakash Yuan Sheng Apparao Draksharapu Johannes E. M. N. Klein Christopher J. Cramer Lawrence Que 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(7):2017-2021
The syn and anti isomers of [FeIV(O)(TMC)]2+ (TMC=tetramethylcyclam) represent the first isolated pair of synthetic non‐heme oxoiron(IV) complexes with identical ligand topology, differing only in the position of the oxo unit bound to the iron center. Both isomers have previously been characterized. Reported here is that the syn isomer [FeIV(Osyn)(TMC)(NCMe)]2+ ( 2 ) converts into its anti form [FeIV(Oanti)(TMC)(NCMe)]2+ ( 1 ) in MeCN, an isomerization facilitated by water and monitored most readily by 1H NMR and Raman spectroscopy. Indeed, when H218O is introduced to 2 , the nascent 1 becomes 18O‐labeled. These results provide compelling evidence for a mechanism involving direct binding of a water molecule trans to the oxo atom in 2 with subsequent oxo–hydroxo tautomerism for its incorporation as the oxo atom of 1 . The nonplanar nature of the TMC supporting ligand makes this isomerization an irreversible transformation, unlike for their planar heme counterparts. 相似文献