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111.
The center-of-mass excitations are identified in the spectrum of electrons on a two-dimensional surface in the lowest Landau level. The correspondence between the quantum numbers labeling electron states on a sphere and on a plane is drawn. The excitation spectrum on a sphere with increasing radius is shown to converge to that on a plane. In particular, in the presence of a lateral confinement (i.e. for the case of quantum dots), identical series of magic states appear in both cases. Also, a class of interaction potentials which lead to the fractional quantum Hall effect in an extended system are identified. 相似文献
112.
Joanna Dzierzawska Arkadiusz Jarota Michal Karolak Lukasz Piotrowski Izabela Placek Katarzyna Swiderek Lukasz Szatkowski Piotr Paneth 《Journal of Physical Organic Chemistry》2007,20(12):1114-1120
Carbon and secondary deuterium kinetic isotope effect (KIE) for three types of SN2 methyl transfer reactions have been predicted theoretically at a DFT level in gas phase and in aqueous solution modelled by the PCM continuum solvent model. No correlation between these isotope effects and geometrical features of the corresponding transition states (TSs), force constants of the imaginary frequency or Gibbs free energies of the studied reactions has been found. These findings suggest that comparative analysis of the magnitudes of the studied KIEs should be constrained to interpretation of the TS localization on the reaction coordinate only in a series of very closely related reactions. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
113.
Lucyna A. Wozniak Arkadiusz Chworos W. J. Stec 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1)
Abstract DBU-assisted phosphonylating properties of diastereomerically pure 5′-O-DMT- thymidine (O-2,4,6-trimetylbenzoyl methanephosphonothiate)(1) towards alcohols [1] have been used for the synthesis of [Rp]-dithymidylyl(3′,5′)-methanephosphonothiótes (2) and metanephosphonates (3). Substrates (4) and (5) have been obtained according to the previously described methods [2]. 相似文献
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Magnetic liquids are stable colloidal suspensions of nano-sized magnetic particles in a carrier liquid medium. In the present paper the determination of the particle size distribution function using ultrasonic spectroscopy is described. The ultrasonic spectra of water-based magnetic fluid measured in the 3.5-50 MHz frequency range are analyzed using formulas for the velocity and absorption of sound in dispersion media obtained by Vinogradov. The results of the ultrasonic studies are compared with the particles size distribution function evaluated from the processing of the magnetic susceptibility data. 相似文献
117.
The article presents a proposal for a new method of automatic quality control of microlenses arrays, which is based on a semiderivative
real filter. The use of the semiderivative filter for examining pure-phase objects involves modifying the spatial frequency.
The basis of the proposed setup is a 4f correlator setup with coherent light. The phase object examined is placed in the input
plane of the correlator. Next, the light passes through a filter located in the frequency plane, which gives an intensity
signal. In the output plane a charge-coupled device (CCD) camera registers the light intensity, the range of which informs
the shape of the phase object. The proposed method is shift invariant, so it allows for examination of single elements or
a set of micro-optical elements simultaneously. Additionally, the same setup allows for measuring the phase of objects whose
thickness is either considerably smaller or much bigger than 2π. 相似文献
118.
Marek K. Wcawski Irena Deperasiska Marzena Banasiewicz David C. Young Arkadiusz Leniak Daniel T. Gryko 《化学:亚洲杂志》2019,14(10):1763-1770
The double Knoevenagel condensation of 1,4‐dibenzoyloxyanthraquinone with methyl esters of arylacetic acids affords a series of compounds based upon a previously unknown 1,8‐dioxa‐benzo[e]pyrene‐2,7‐dione heterocyclic core. The aryl groups incorporated in the 3‐ and 6‐positions can be oxidatively coupled to the π‐expanded backbone to produce a further new heterocyclic core: 1,10‐dioxa‐dibenzo[dj]coronene‐2,9‐dione. The intriguing optical properties of these π‐expanded coumarin derivatives are discussed and rationalized through quantum chemical calculations. The broad absorption bands of 1,8‐dioxa‐benzo[e]pyrene‐2,7‐dione‐based dyes are attributed to both HOMO?1→LUMO and HOMO→LUMO transitions, which have a similar energy. Weakly coupled electron‐donating aryl substituents result in a moderate bathochromic shift of both the absorption and emission by 30–60 nm in toluene. The emissive properties of these compounds are in part determined by the oscillator strength of the main transition, lifetimes of the excited state, and by the energy match of the excited state with a triplet state of a similar energy. The 1,10‐dioxa‐dibenzo[dj]coronene‐2,9‐dione displays a much smaller Stokes shift, yet a markedly increased fluorescence quantum yield of 90 % owing to the increased rigidity compared with the 1,8‐dioxa‐benzo[e]pyrene‐2,7‐dione core. 相似文献
119.
The formation of mixed seleno-sulfides by means of activation of methanephosphonoseleno(thio)ic acids with arylsulfenyl chloride is rationalized on the basis of NMR and identification of the products of their reactions with triphenylphosphine. 相似文献
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Stanisław Baran Vladimir Dyakonov Andreas Hoser Arkadiusz Zarzycki Andrzej Szytuła 《Phase Transitions》2016,89(4):319-327
We report on the X-ray and neutron diffraction and magnetic measurements of the nanosamples of DyMnO3 annealed at temperatures of 800 °C, 850 °C and 900 °C. The diffraction data indicate that all the samples crystallize in an orthorhombic crystal structure (space group Pnma). The crystal structure parameters change slightly with preparation. All the samples are antiferromagnets at low temperatures. The Mn magnetic moments order near 40 K, while those of Dy below 8.4 K. The macroscopic magnetic and neutron diffraction data indicate a small difference of properties between the DyMnO3 samples synthesized at different temperatures. The observed broadening of magnetic peaks connected with the Dy sublattice suggests a cluster-like character of magnetic ordering. 相似文献