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21.
We consider the capacity of classical information transfer for noiseless quantum channels carrying a finite average number of massive bosons and fermions. The maximum capacity is attained by transferring the Fock states generated from the grand-canonical ensemble. Interestingly, the channel capacity for a Bose gas indicates the onset of Bose-Einstein condensation, by changing its qualitative behavior at the criticality, while for a channel carrying weakly attractive fermions, it exhibits the signatures of Bardeen-Cooper-Schrieffer transition. We also show that, for noninteracting particles, fermions are better carriers of information than bosons. 相似文献
22.
This Letter describes dynamic self-assembly in a system of stainless steel spheres ( approximately 1 mm in diameter) rolling on a flat dielectric surface under the influence of an external magnetic field that rotates parallel to the plane of the surface. As the spheres move, they charge triboelectrically. Self-assembly is mediated by two types of electrostatic interactions among these charges: (i) attraction between negatively charged regions of the surface and positively charged spheres and (ii) repulsion between the like-charged spheres. The spheres organize into highly ordered rings as a result of these electrostatic interactions. 相似文献
23.
24.
Bartosz Mozgawa Dr. Filip Zasada Dr. Monika Fedyna Prof. Kinga Góra-Marek Dr. Edyta Tabor Dr. Kinga Mlekodaj Dr. Jiří Dědeček Prof. Zhen Zhao Dr. Piotr Pietrzyk Prof. Zbigniew Sojka 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(68):17159-17180
NH3 temperature-programmed desorption (NH3-TPD) is frequently used for probing the nature of the active sites in CuSSZ-13 zeolite for selective catalytic reduction (SCR) of NOx. Herein, we propose an interpretation of NH3-TPD results, which takes into account the temperature-induced dynamics of NH3 interaction with the active centers. It is based on a comprehensive DFT/GGA+D and first-principles thermodynamic (FPT) modeling of NH3 adsorption on single Cu2+, Cu+, [CuOH]+ centers, dimeric [Cu-O-Cu]2+, [Cu-O22−-Cu]2 species, segregated CuO nanocrystals and Brønsted acid sites (BAS). Theoretical TPD profiles are compared with the experimental data measured for samples of various Si/Al ratios and distribution of Al within the zeolite framework. Copper reduction, its relocation, followed by the intrazeolite olation/oxolation processes, which are concomitant with NH3 desorption, were revealed by electron paramagnetic resonance (EPR) and IR. DFT/FPT results show that the peaks in the desorption profiles cannot be assigned univocally to the particular Cu and BAS centers, since the observed low-, medium- and high-temperature desorption bands have contributions coming from several species, which dynamically change their speciation and redox states during NH3-TPD experiment. Thus, a rigorous interpretation of the NH3-TPD profiles of CuSSZ-13 in terms of the strength and concentration of the active centers of a particular type is problematic. Nonetheless, useful connections for molecular interpretation of TPD profiles can be established between the individual component peaks and the corresponding ensembles of the adsorption centers. 相似文献
25.
Federico Gallizio Angelo Iollo Bartosz Protas Luca Zannetti 《Physica D: Nonlinear Phenomena》2010,239(3-4):190-201
This investigation concerns solutions of the steady-state Euler equations in two dimensions featuring finite area regions with constant vorticity embedded in a potential flow. Using elementary methods of the functional analysis we derive precise conditions under which such solutions can be uniquely continued with respect to their parameters, valid also in the presence of the Kutta condition concerning a fixed separation point. Our approach is based on the Implicit Function Theorem and perturbation equations derived using shape-differentiation methods. These theoretical results are illustrated with careful numerical computations carried out using the Steklov–Poincaré method which show the existence of a global manifold of solutions connecting the point vortex and the Prandtl–Batchelor solution, each of which satisfies the Kutta condition. 相似文献
26.
27.
A novel and efficient method of synthesis of 3-substituted derivatives of pentane-2,4-dione is proposed, wherein cheaper and
easily accessible chloro derivatives are conversed into more reactive iodo derivatives. The method is based on the Finkelstein
reaction for which the literature suggests highly polar organic solvents as ideal reaction media. In the presented work, the
use of industrially used ketones, especially methyl isobutyl ketone, is proposed. The use of MIBK as a solvent additionally
allows an azeotropic removal of water from the reaction mixture, enabling the application of moisture sensitive alkylating
agents i.e. (3-chloropropyl)trimethoxysilane. The obtained products are isolated through distillation, which does however
not allow the separation of C-alkylation products from O-alkylation ones. The products not containing water-sensitive substituents were isolated as copper complexes. The pure product
of C-alkylation was obtained by decomposition of the copper complex with a hydrochloric acid solution and extraction of the formed
ligand to an organic phase i.e. hexane. The obtained ligand can be further purified by distillation.
Presented at the 35th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 26–30 May
2008. 相似文献
28.
Dr. Bartosz Bieszczad Prof. Dr. Declan G. Gilheany 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(15):4336-4340
A simple, general and practical method is reported for highly enantioselective construction of tertiary alcohols through the direct addition of organomagnesium reagents to ketones. Discovered by rational ligand design based on a mechanistic hypothesis, it has an unprecedented broad scope. It utilizes a new type of chiral tridentate diamine/phenol ligand that is easily removed from the reaction mixture. It is exemplified by application to a formal asymmetric synthesis (>95:5 d.r.) of vitamin E. 相似文献
29.
Schmidt B Mahmud G Soh S Kim SH Page T O'Halloran TV Grzybowski BA Hoffman BM 《Applied magnetic resonance》2011,40(4):415-425
Abstract
Rapid freeze-quench (RFQ) trapping of short-lived reaction intermediates for spectroscopic study plays an important role in the characterization of biological reactions. Recently, there has been considerable effort to achieve sub-millisecond reaction deadtimes. We present here a new, robust, high-velocity microfluidic mixer that enables such rapid freeze-quenching. It is a based on the mixing method of two impinging jets commonly used in reaction injection molding of plastics. This method achieves efficient mixing by inducing chaotic flow at relatively low Reynolds numbers (Re = 140). We present the first mathematical simulation and microscopic visualization of mixing in such RFQ micromixers, the results of which show that the impinging solutions efficiently mix within the mixing chamber. These tests, along with a practical demonstration in an RFQ setup that involves copper wheels, show that this new mixer can in practice provide reaction deadtimes as low as 100 μs. 相似文献30.
Many control problems in science and engineering can be formulated as optimal control problems (OCP) such as load changes in process control or point-to-point motion of industrial robots in a time-optimal or energy-optimal way while accounting for physical or security constraints. Hence, an efficient way to handle constrained OCPs is an important topic of research. A promising approach to address this issue is a transformation technique allowing to reformulate an inequality constrained OCP into an equality constrained counterpart. The reformulated OCP reveals to possess a particular structure that is favorable for a decomposition and the application of distributed optimization methods. Motivated by the Augmented Lagrangian approach, the structure of the reformulated OCP can be exploited to derive a decomposition method for splitting up the entire OCP into smaller subproblems. In addition, an algorithm is presented that follows the ideas of the Alternating Direction Method of Multipliers (ADMM) and solves the resulting subproblems in a distributed manner. The approach is applied to a mechatronic example system to demonstrate the performance of the presented method. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献