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1.
Zboril R. Mashlan M. Machala L. Walla J. Barcova K. Martinec P. 《Hyperfine Interactions》2004,156(1-4):403-410
Hyperfine Interactions - The natural garnets from almandine (Fe3Al2Si3O12)–pyrope (Mg3Al2Si3O12) series with the iron to magnesium atomic ratio ranging from 0.2 to 1 were characterised and... 相似文献
2.
Muhammad WT Fox KF Fox A Cotham W Walla M 《Rapid communications in mass spectrometry : RCM》2002,16(24):2278-2285
Single nucleotide polymorphisms (SNPs) and mutations were genotyped for both homozygous and heterozygous PCR products of p53, a tumor suppressor gene, and K-ras, an oncogene, using electrospray ionization (ESI) quadrupole time-of-flight (Q-TOF) mass spectrometry (MS) and ESI-quadrupole MS analysis. Mass accuracy was adequate for both instruments to detect genetic changes in homozygous PCR products, including the most difficult to distinguish (adenine [A] --> thymine [T] transversion). However, for the detection of A --> T shifts (9.0 Da difference) in heterozygous PCR products, the increased resolution of ESI-Q-TOFMS proved essential. Although, greater mass differences in heterozygotes (e.g. cytosine [C] <--> T or guanine [G] <--> A) can be discriminated using ESI-quadrupole MS analysis. 相似文献
3.
Trávníček Zdeněk Walla Jan Kvítek Libor Šindelář Zdeněk Biler Martin 《Transition Metal Chemistry》1999,24(6):633-637
Nickel(II) xanthate complexes of general formula, [Ni(Rxa)2(L)] [R = i-Pr, i-Am, xa = OCS–
2, L = 4,7-diphenyl-1,10-phenanthroline(baphen), 4,4-dimethyl-2,2-bipyridyl (me2bpy), 2-9-dimethyl-1,10-phenanthroline(neo) or trans-1,2-diaminocyclohexane (dch)] and [Ni(Rxa)(cyclam)](Rxa) (= 1,4,8,11-tetraazacyclotetradecane) have been synthesized and characterized by elemental analyses, i.r. and electronic spectroscopy, magnetic and conductivity measurements. The complexes with cyclam were studied by cyclic voltammetry. Values of magnetic moments at room temperature lie within the 3.25–3.51 B.M. range and thus indicate the presence of two unpaired electrons, except for the complexes with cyclam, where the anomalous values of 1.76 and 1.74 B.M. were obtained in respect to the nickel(II) complexes. Magnetic susceptibility data for [Ni(i-Prxa)(cyclam)](i-Prxa) were measured over the 79–298 K range and indicate no exchange interaction between paramagnetic nickel(II) centres. 相似文献
4.
Axel Wehling Dr. Wiebke H. Pohl Birgit Gerke Stephan Kipp Dr. Peter J. Walla Prof. Dr. 《Chemphyschem》2008,9(2):327-331
Scanning electron microscope images show that it is easy to generate nanopores on polycarbonate membranes with well‐defined pore diameters by ion‐track perforation and subsequent magnetron sputtering with metal. The size reduction of the nanopores during sputtering with gold is a linear function of time. Images of different angles and from the bottom side of the membrane show that the channels are the smallest very close to the surface of the metal layer, have a conelike shape, and reach about half as much into the polymer membranes as the metal‐layer thickness. This topographical pore shape is ideal for use as optically coherent near‐field sources in deep‐nulling microscopy. We present the first results of significantly improved nulling stabilization in the presence (<2 nm optical pathway difference) and the absence (<0.6 nm optical pathway difference) of the nanoapertures in the focal region of a deep‐nulling microscope. 相似文献
5.
Stefan Bode Claudia C. Quentmeier Pen-Nan Liao Tiago Barros Peter J. Walla 《Chemical physics letters》2008,450(4-6):379-385
The Car S1 → Chl energy transfer efficiency, ΦTransfer, in xanthophyll-cycle mutants of living plants and LHC II was investigated by selective Car S1 two-photon excitation. Before high-light illumination ΦTransfer, of the violaxanthin deficient mutant npq2 is 30% smaller than the corresponding value for wild type plants. For the zeaxanthin deficient mutant, npq1, ΦTransfer is 30% larger. Wild type Arabidopsis thaliana is the only variant which is capable of a light-dependent decrease of up to 40% and complete recovery to the original ΦTransfer values. In contrast, ΦTransfer remains constant during dark adaptation in both mutants. Surprisingly, changes in ΦTransfer of LHC II preparations were less than 5% only, when substituting violaxanthin by zeaxanthin. 相似文献
6.
7.
Yi Chen Céline Le Droumaguet Kai Li William E. Cotham Norman Lee Mike Walla Qian Wang 《Journal of the American Society for Mass Spectrometry》2010,21(3):403-410
Cu(I) catalyzed alkyne-azide cycloaddition reaction was employed to synthesize a series of anthracene-based human thymidylate
synthase (hTS) inhibitor analogues. The triazolo-anthracene derivatives were characterized by ESI-MS/MS and a novel rearrangement
reaction in ESI-MS/MS was observed. The mechanism is proposed whereby the protonated triazolo-anthracene derivative forms
a carbocation, and then the carbocation electrophilically attacks an anthracene moiety resulting in formation of a rearrangement
ion. Moreover, the carbocation prefers to attack the γ position rather than the α or β position of the anthracene moiety by
an electrophilic substitution mechanism. 相似文献
8.
Time-resolved two-photon spectroscopy of photosystem I determines hidden carotenoid dark-state dynamics 总被引:2,自引:0,他引:2
We present time-resolved fs two-photon pump-probe data measured with photosystem I (PS I) of Thermosynechococcus elongatus. Two-photon excitation (lambda(exc)/2 = 575 nm) in the spectral region of the optically forbidden first excited singlet state of the carotenoids, Car S1, gives rise to a 800 fs and a 9 ps decay component of the Car S1 --> S(n) excited-state absorption with an amplitude of about 47 +/- 16% and 53 +/- 10%, respectively. By measuring a solution of pure beta-carotene under exactly the same conditions, only a 9 ps decay component can be observed. Exciting PS I at exactly the same spectral region via one-photon excitation (lambda(exc) = 575 nm) also does not show any sub-ps component. We ascribe the observed constant of 800 fs to a portion of about 47 +/- 16% beta-carotene states that can potentially transfer their energy efficiently to chlorophyll pigments via the optically dark Car S1 state. We compared these data with conventional one-photon pump-probe data, exciting the optically allowed second excited state, Car S2. This comparison demonstrates that the fast dynamics of the optically forbidden state can hardly be unravelled via conventional one-photon excitation only because the corresponding Car S1 populations are too small after Car S2 --> Car S1 internal conversion. A direct comparison of the amplitudes of the Car S1 --> S(n) excited-state absorption of PS I and beta-carotene observed after Car S2 excitation allows determination of a quantum yield for the Car S1 formation in PS I of 44 +/- 5%. In conclusion, an overall Car S2 --> Chl energy-transfer efficiency of approximately 69 +/- 5% is observed at room temperature with 56 +/- 5% being transferred via Car S2 and probably very hot Car S1 states and 13 +/- 5% being transferred via hot and "cold" Car S1 states. 相似文献
9.
Rapid Pd or Ni-catalyzed microwave-accelerated Negishi and Kumada cross-coupling reactions of aryl chlorides in solution and on solid phase are reported. 相似文献
10.
Krascsenicsová K Walla P Kasák P Uray G Kappe CO Putala M 《Chemical communications (Cambridge, England)》2004,(22):2606-2607
Negishi arylation and alkynylation of easily synthesized chiral 2,2'-diodo-1,1'-binaphthyl rapidly proceeds in refluxing THF utilizing controlled microwave irradiation, affording enantiopure 2,2'-diarylated 1,1'-binaphthyls in good to excellent yields. 相似文献