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61.
Dmitri O. Charkin Stanislav I. Bezzubov Oleg I. Siidra Artem S. Borisov Stepan N. Kalmykov 《无机化学与普通化学杂志》2020,646(11-12):540-543
Crystals of a new uranyl sulfate (C2N4H8S2)[UO2(SO4)2] · 0.3H2O ( 1 ) templated by a relatively rare bis-isothiouronium cation, were formed upon evaporation of aqueous solutions containing uranyl acetate, thiourea, and excess sulfuric acid. The new compound is orthorhombic, P212121, a = 6.928(2) Å, b = 13.398(3) Å, c = 15.225(3) Å, Z = 2. Its crystal structure is comprised of [UO2(SO4)2] moieties linked by hydrogen bonds formed between the template cations and terminal oxygen atoms of the sulfate tetrahedra. The C2N4H8S22+ template is most likely formed in situ during a redox reaction between uranyl cation and thiourea in a strongly acidic medium, with UO22+ partially reduced to U4+. 相似文献
62.
Fei Lu Ding Yi Shoujie Liu Fei Zhan Bo Zhou Lin Gu Dmitri Golberg Xi Wang Jiannian Yao 《Angewandte Chemie (International ed. in English)》2020,59(40):17712-17718
A dual‐site catalyst allows for a synergetic reaction in the close proximity to enhance catalysis. It is highly desirable to create dual‐site interfaces in single‐atom system to maximize the effect. Herein, we report a cation‐deficient electrostatic anchorage route to fabricate an atomically dispersed platinum–titania catalyst (Pt1O1/Ti1?xO2), which shows greatly enhanced hydrogen evolution activity, surpassing that of the commercial Pt/C catalyst in mass by a factor of 53.2. Operando techniques and density functional calculations reveal that Pt1O1/Ti1?xO2 experiences a Pt?O dual‐site catalytic pathway, where the inherent charge transfer within the dual sites encourages the jointly coupling protons and plays the key role during the Volmer–Tafel process. There is almost no decay in the activity of Pt1O1/Ti1?xO2 over 300 000 cycles, meaning 30 times of enhancement in stability compared to the commercial Pt/C catalysts (10 000 cycles). 相似文献
63.
Abil E. Aliev Alex J. Sinclair Shen Zhou John D. Wilden Stephen Caddick Dimitri M. Kullmann Dmitri A. Rusakov 《Journal of Physical Organic Chemistry》2009,22(6):607-612
While developing a synthesis towards tagged dizocilpine (MK‐801) analogues, we observed highly restricted inversion of a nitrogen centre in a number hydroxylamines obtained as key intermediates. These compounds are shown to possess some of the structural elements which are expected to significantly hinder the nitrogen inversion, potentially leading to hydroxylamines with a chiral nitrogen centre. Free energy barriers (ΔG≠) of the nitrogen inversion were estimated to be ca. 22 kcal mol?1 at temperatures near 420 K using variable temperature NMR measurements in DMSO‐d6. Further density functional studies of a number model systems were undertaken in order to better rationalize the measured inversion barriers and follow the role of various structural factors in raising the barrier height of the nitrogen inversion process. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
64.
S. M. Bezruchko S. M. Kuzmin O. V. Sergeev N. V. Spinko 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2011,5(1):34-42
The applicability of synchrotron radiation to implementation of medical ideas associated with introduction of nonbiological
objects into a human body—implants, drug nanocapsules, and X-ray therapeutic means (metal nanoparticles and nanocrystalline
phosphors and scintillators)—is considered. Synchrotron radiation presents new possibilities of analyzing the surface with
a resolution comparable to the sizes of biological nanostructures involved in interactions such as chemical and biochemical
modification of implant surfaces in vitro; activation of implant surface integration with biological tissue in a tissue culture
(in vitro) and in vivo; biochemical modification of therapeutic nanoparticle surface in vitro; immunocamouflage by host proteins;
attachment of “molecular targets”, i.e., antibodies, to target tissue to provide targeted delivery vehicles; and local activation
of X-ray therapeutic drugs and drug nanocapsules in biological tissues. A functional block diagram of a medical technological
station is given. 相似文献
65.
We show that a Riemannian manifold of dimension at least 3 can be recovered from the space of boundaries of rectifiable integral
2-currents (the “lcycles”) equipped with the filling area distance, and discuss possible approaches to “spaces with area structures”. 相似文献
66.
Classical molecular dynamics simulations have been performed for crystalline germanium with the aim to estimate the thermal
effects within the first three coordination shells and their influence on the single-scattering and multiple-scattering contributions
to the Ge K-edge extended x-ray absorption fine structure (EXAFS). 相似文献
67.
A new optimal control problem that incorporates the residual of the Eikonal equation into its objective is presented. The formulation of the state equation is based on the level set transport equation but extended by an additional source term, correcting the solution so as to minimize the objective functional. The method enforces the constraint so that the interface cannot be displaced at least in the continuous setting. The system of first‐order optimality conditions is derived, linearized, and solved numerically. The control also prevents numerical instabilities, so that no additional stabilization techniques are required. This approach offers the flexibility to include other desired design criteria into the objective functional. The methodology is evaluated numerically in three different examples and compared with other PDE‐based reinitialization techniques. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
68.
Dmitri Vassiliev 《General Relativity and Gravitation》2002,34(8):1239-1265
In abstract Yang–Mills theory the standard instanton construction relies on the Hodge star having real eigenvalues which makes it inapplicable in the Lorentzian case. We show that for the affine connection an instanton-type construction can be carried out in the Lorentzian setting. The Lorentzian analogue of an instanton is a spacetime whose connection is metric compatible and Riemann curvature irreducible (pseudoinstanton). We suggest a metric-affine action which is a natural generalization of the Yang–Mills action and for which pseudoinstantons are stationary points. We show that a spacetime with a Ricci flat Levi-Civita connection is a pseudoinstanton, so the vacuum Einstein equation is a special case of our theory. We also find another pseudoinstanton which is a wave of torsion in Minkowski space. Analysis of the latter solution indicates the possibility of using it as a model for the neutrino. 相似文献
69.
We argue that the amplitude does not vanish in the limit of zero quark masses. This represents a new kind of violation of the classical equation of motion for the axial current and should be interpreted as the axial anomaly for bound states. The anomaly emerges in spite of the fact that the one loop integrals are ultraviolet finite as guaranteed by the finite size of bound-state wave functions. As a result, the amplitude behaves like approximately 1/p(2) in the limit of a large momentum p of the current. The observed effect requires the modification of the classical equation of motion of the axial-vector current by nonlocal operators. 相似文献
70.
M. Klíma P. Slavíček L. Zajíčková J. Janča S. Kuzmin P. Sulovský 《Czechoslovak Journal of Physics》1999,49(3):321-328
Plasma-liquid technologies at atmospheric pressure provide a wide range of possibilities for applications. One of them, the treatment of archaeological artifacts, is presented in this paper. The effects of discharges between a metal electrode and a solution surface and/or an interaction of hollow cathode plasma jet, plasma pencil, with liquid on the corroded surface of bronze and glass artifacts were studied. It was compared with standard low pressure plasma techniques and with the effects of electrolysis. Original and treated objects were characterized by means of scanning electron microscope (SEM) with energy dispersive analyser used for the spot elemental analyses. 相似文献