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81.
3,5-Bis(2-hydroxyphenyl)-1H-1,2,4-triazole (H2La) and 4-[3,5-bis(2-hydroxyphenyl)-1H-1,2,4-triazol-1-yl]benzoic acid (H3Lb) have been prepared, and crystal structure of the intermediate 2-(2-hydroxyphenyl)-4H-1,3-benzoxazin-4-one has been determined. Temperature dependent 1H NMR spectroscopic measurements of H2La indicated dynamic behavior with the equilibrium between the two asymmetric tautomers. For H3Lb, pD-dependent 1H NMR spectroscopic measurements showed small but characteristic shifts in the range of 0 ≤ pD ≤ 1, indicative of a triazole
nitrogen atom protonation; the corresponding pK
a of 0.98 ± 0.04 was determined by spectrophotometric titrations. (H2O, 26°C, 1 M KCl/HCl). Formation of [FeIII(La)]+ (pH 2.5) and [FeIII(La)2]− (pH > 6) was verified by UV-Vis spectroscopy. Complex formation of H3Lb with Al3+ and VO2+ was investigated by 1H NMR spectroscopic titration and cyclic voltammetry, respectively. Single crystals of the phenoxo bridged [VVO(HLb)(EtO)]2·2EtOH were characterized by X-ray structural analysis.
Dedicated to Professor Milan Melník on the occasion of his 70th birthday 相似文献
82.
83.
84.
Vijay R. D'Costa José Menéndez John Tolle Stefan Zollner 《Solid State Communications》2006,138(6):309-313
We present a detailed analysis of the compositional dependence of the average of the E1 and E1+Δ1 transition energies in Ge1−x−ySixSny alloys. We show that this dependence can be explained in terms of three bowing parameters—bSiGe, bGeSn, and bSiSn—which scale with the product ΔχΔR of the Phillips electronegativity and size mismatches between Si, Ge, and Sn. 相似文献
85.
Andreas Schwenke Philipp Wagener Stefan Nolte Stephan Barcikowski 《Applied Physics A: Materials Science & Processing》2011,104(1):77-82
The influence of fundamental and second harmonic wavelength on ablation efficiency and nanoparticle properties is studied
during picosecond laser ablation of silver, zinc, and magnesium in polymer-doped tetrahydrofuran. Laser ablation in stationary
liquid involves simultaneously the fabrication of nanoparticles by ablation of the target material and fragmentation of dispersed
nanoparticles by post irradiation. The ratio in which the laser pulse energy contributes to these processes depends on laser
wavelength and colloidal properties. For plasmon absorbers (silver), using the second harmonic wavelength leads to a decrease
of the nanoparticle productivity over process time along with exponential decrease in particle diameter, while using the fundamental
wavelength results in a constant ablation rate and linear decrease in particle diameter. For colloids made of materials without
plasmon absorption (zinc, magnesium), laser scattering is the colloidal property that limits nanoparticle productivity by
Mie-scattering of dispersed nanoparticle clusters. 相似文献
86.
Direct observation of tunneling and nonlinear self-trapping in a single bosonic Josephson junction 总被引:1,自引:0,他引:1
Albiez M Gati R Fölling J Hunsmann S Cristiani M Oberthaler MK 《Physical review letters》2005,95(1):010402
We report on the first realization of a single bosonic Josephson junction, implemented by two weakly linked Bose-Einstein condensates in a double-well potential. In order to fully investigate the nonlinear tunneling dynamics we measure the density distribution in situ and deduce the evolution of the relative phase between the two condensates from interference fringes. Our results verify the predicted nonlinear generalization of tunneling oscillations in superconducting and superfluid Josephson junctions. Additionally, we confirm a novel nonlinear effect known as macroscopic quantum self-trapping, which leads to the inhibition of large amplitude tunneling oscillations. 相似文献
87.
Shadow effects in spiral phase contrast microscopy 总被引:3,自引:0,他引:3
Recently it has been demonstrated that spatial filtering of images in microscopy with a spiral phase element in a Fourier plane of the optical path results in a strong edge enhancement of object structures. In principle the operation is isotropic, i.e., all phase edges of a sample object are highlighted simultaneously, independent of their local direction. However, here we demonstrate that the symmetry can be broken intentionally by controlling the phase of the central area of a spiral phase hologram, which is displayed at a computer controlled spatial light modulator. This produces an apparent shadow effect which can be rotated at video rate. The resulting relieflike impression of the sample topography with a longitudinal resolution in the subwavelength regime is demonstrated by imaging a standard low contrast test sample consisting of a human cheek cell. 相似文献
88.
We propose an experiment to observe coherent oscillations in a single quantum dot with the oscillations driven by spin-orbit interaction. This is achieved without spin-polarized leads, and relies on changing the strength of the spin-orbit coupling via an applied gate pulse. We derive an effective model of this system which is formally equivalent to the Jaynes-Cummings model of quantum optics. For parameters relevant to an InGaAs dot, we calculate a Rabi frequency of 2 GHz. 相似文献
89.
Zeitschrift für Physik A Hadrons and nuclei - In reactions between very asymmetric projectile-target systems charge is preferably transferred from the lighter to the heavier nucleus. This... 相似文献
90.
Stefan Marinov 《Foundations of Physics》1976,6(5):571-581
Proceeding from our absolute space-time conceptions, we obtain the formula for the gravitational frequency shift in an extremely simple way. Using our burst model for photons, we show that the different rates of clocks placed in spatial regions with different gravitational potentials appear as a direct result of the gravitational frequency shift and the axiomatic assumption that at any space point the time unit is to be defined by light clocks with equal arms, i.e., that at any space point the light velocity (in moving frames the there-and-back velocity) has the same numerical valuec. Considering the principle of equivalence, we come to the logical conclusion that the kinematic (Einstein-Lorentz) time dilation is an absolute phenomenon. 相似文献