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121.
122.
C. W. Whittaker F. O. Lundstrom und A. R. Merz 《Fresenius' Journal of Analytical Chemistry》1931,84(1-2):35-36
Ohne Zusammenfassung 相似文献
123.
Bobev S Merz J Lima A Fritsch V Thompson JD Sarrao JL Gillessen M Dronskowski R 《Inorganic chemistry》2006,45(10):4047-4054
Large single-crystals of two polar intermetallic phases, CaMn2Sb2 and SrMn2Sb2, have been grown using In or Sn as metal fluxes and characterized by single-crystal X-ray diffraction. The two compounds are isostructural and crystallize with the CaAl2Si2 structure (space group P3m1, No. 164) with unit cell parameters determined at 120(2) K of a = 4.5204(6) angstroms, c = 7.456(2) angstroms and a = 4.5802(17) angstroms, c = 7.730(5) angstroms for CaMn2Sb2 and SrMn2Sb2, respectively. Temperature- and field-dependent dc- and ac-magnetization measurements suggest complex magnetic ordering of the Mn moments below ca. 250 and 35 K for CaMn2Sb2 and below ca. 265 K for SrMn2Sb2. Resistivity measurements reveal metallic-like temperature dependence with rho(290) = 40 m omega cm for CaMn2Sb2 and rho290 = 100 m omega cm for SrMn2Sb2 with negligible magnetoresistance at 5 K in applied magnetic fields up to 10 kOe. Spin-polarized DFT electronic structure calculations confirm the metallic-like properties and provide further evidence for a magnetic structure where Mn atoms form two magnetic sublattices with ferromagnetic coupling within them and strong antiferromagnetic coupling between them. 相似文献
124.
Sadeghian K Bocola M Merz T Schütz M 《Journal of the American Chemical Society》2010,132(45):16285-16295
UV irradiation of DNA can lead to the formation of mutagenic (6-4) pyrimidine-pyrimidone photolesions. The (6-4) photolyases are the enzymes responsible for the photoinduced repair of such lesions. On the basis of the recently published crystal structure of the (6-4) photolyase bound to DNA [Maul et al. 2008] and employing quantum mechanics/molecular mechanics techniques, a repair mechanism is proposed, which involves two photoexcitations. The flavin chromophore, initially being in its reduced anionic form, is photoexcited and donates an electron to the (6-4) form of the photolesion. The photolesion is then protonated by the neighboring histidine residue and forms a radical intermediate. The latter undergoes a series of energy stabilizing hydrogen-bonding rearrangements before the electron back transfer to the flavin semiquinone. The resulting structure corresponds to the oxetane intermediate, long thought to be formed upon DNA-enzyme binding. A second photoexcitation of the flavin promotes another electron transfer to the oxetane. Proton donation from the same histidine residue allows for the splitting of the four-membered ring, hence opening an efficient pathway to the final repaired form. The repair of the lesion by a single photoexcitation was shown not to be feasible. 相似文献
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R. Grieser R. Klein G. Huber S. Dickopf I. Klaft P. Knobloch P. Merz F. Albrecht M. Grieser D. Habs D. Schwalm T. Kühl 《Applied physics. B, Lasers and optics》1994,59(2):127-133
Laser spectroscopy at the heavy ion storage ring TSR in Heidelberg allows for precision experiments testing the limits of the special theory of relativity. With an optical-type three-level system of7Li+ the Doppler shift has been measured by saturation spectroscopy as a test of the time dilatation factor = (1 –
2)–1/2 at an ion velocity of = 6.4% c. A precision of/ < 9 × 10–9 has been obtained, which sets a second-order limit of 1.1 × 10–6 for any deviation from the time dilatation factor. The fourth-order limit of this deviation is set below 2.7 × 10–4 by the present experiment. These limits are given at a 1 confidence level. 相似文献
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