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61.
We present a comparative study of the application of a recently introduced heuristic algorithm to the optimization of transport on three major types of complex networks. The algorithm balances network traffic iteratively by minimizing the maximum node betweenness with as little path lengthening as possible. We show that by using this optimal routing, a network can sustain significantly higher traffic without jamming than in the case of shortest path routing. A formula is proved and tested with numerical simulation that allows quick computation of the average number of hops along the path and of the average travel times once the betweennesses of the nodes are computed. Using this formula, we show that routing optimization preserves the small-world character exhibited by networks under shortest path routing, and that it significantly reduces the average travel time on congested networks with only a negligible increase in the average travel time at low loads. Finally, we study the correlation between the weights of the links in the case of optimal routing and the betweennesses of the nodes connected by them. 相似文献
62.
Kyle M. McCall Bogdan M. Benin Michael Wörle Thomas Vonderach Detlef Günther Maksym V. Kovalenko 《Helvetica chimica acta》2021,104(1):e2000206
Inorganic, lead-free metal halides are widely sought after following the rise of the halide perovskites as outstanding optoelectronic materials, due to their enhanced stability and reduced toxicity. Herein, we report on the solvothermal synthesis of Rb7Sb3Br16, which exhibits a 0D structure comprised of [SbBr6]3− octahedra and edge-sharing bioctahedra [Sb2Br10]4− dimers that order into layers along the c-axis. This all-inorganic material is air-stable and exhibits weak orange photoluminescence (PL) at room temperature. Low-temperature PL and PL excitation (PLE) measurements reveal the presence of two distinct emission bands that originate from these structural units, with the high-energy emission quenching as temperature rises beyond 150 K. We are also able to obtain Rb7Bi3Br16 and Rb7Bi3I16 which both crystallize in orthorhombic symmetry, with Rb7Bi3Br16 presenting weak low-temperature luminescence while Rb7Bi3I16 is non-luminescent. This work expands the library of emissive inorganic metal halides and provides further evidence for the efficacy of low-dimensional Sb−X luminescent centers based on octahedral and edge-sharing [Sb2X10]4− dimers. 相似文献
63.
Our purpose is to provide an affirmative answer to Moszner’s problem [cf. Moszner (Ann Univ Paed Crac Stud Math XI:69–94, 2012), p. 93] concerning the superstability of the Cauchy equation with squaresin the class of functions mapping an Abelian semigroup into a finite-dimensional normed algebra without divisors of zero.
相似文献
$$f(x + y)^2 = (f(x) + f(y))^2$$
64.
Bogdan Tita Ionut Ledeti Geza Bandur Dumitru Tita 《Journal of Thermal Analysis and Calorimetry》2014,118(2):1293-1304
Thermal analysis is a routine method for analysis of drugs and substances of pharmaceutical interest. Thermogravimetry/derivative thermogravimetry (TG/DTG) and differential scanning calorimetry (DSC) are thermoanalytical methods which offer important information about the physical and chemical properties of drugs (purity, stability, phase transition, polymorphism, compatibility, kinetic analysis, etc.). This work exemplifies a general method of studying the drug-excipient interactions with the aim of predicting rapidly and inexpensively the long thermal stability of their mixtures. The TG/DTG and DSC were used as screening techniques for assessing the compatibility between indomethacin (IND) and its physical associations as binary mixtures with some common excipients. Based on their frequent use in preformulations eleven different excipients: corn starch, microcrystalline cellulose (PH 101; PH 102), colloidal silicon dioxide, lactose (monohydrate and anhydre), polyvinilpyrrolidone K30, magnesium stearate, talc, stearic acid, and manitol were blended with IND. The samples were prepared by mixing the analyte and excipients in a proportion of 1:1 (w:w). In order to investigate the possible interactions between the components, the thermal curves of IND and each selected excipient were compared with those of their 1:1 (w/w) physical mixtures. FT-IR spectroscopy and X-ray powder diffraction were used as complementary techniques to adequately implement and assist in interpretation of thermal results. On the basis of thermal results, confirmed by FT-IR and X-ray analyses, a possible interaction was found between IND with polyvinylpyrrolidone K30, magnesium stearate, and stearic acid. 相似文献
65.
Multivalent Recognition of Concanavalin A by {Mo132} Glyconanocapsules—Toward Biomimetic Hybrid Multilayers 下载免费PDF全文
Dr. Mihail Barboiu Dr. Zineb Mouline Dr. Mihaela Silion Erol Licsandru Prof. Bogdan C. Simionescu Dr. Eugene Mahon Dr. Mariana Pinteala 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(22):6678-6683
Herein, we consider Müller’s spherical, porous, anionic, molybdenum oxide based capsule, (NH4)42‐ [{(MoVI)MoVI5O21(H2O)6}12{MoV2O4(CH3COO)}30]?10 CH3COONH4? 300 H2O≡(NH4)42? 1 a ?crystal ingredients≡ 1 , {Mo132}, as an effective sugar‐decorated nanoplatform for multivalent lectin recognition. The ion‐exchange of NH4+ ions of 1 with cationic‐sugars, D ‐mannose‐ammonium chloride ( 2 ) or D ‐glucose‐ammonium chloride ( 3 ) results in the formation of glyconanocapsules (NH4)42?n 2 n? 1 a and (NH4)42?m 3 m? 1 a . The Mannose (NH4)42?n 2 n? 1 a capsules bind selectively Concanavalin A (Con A) in aqueous solution, giving an association avidity constant of ${K{{{\rm multi}\hfill \atop {\rm a}\hfill}}}$ =4.6×104 M ?1 and an enhancement factor of β=K${{{{\rm multi}\hfill \atop {\rm a}\hfill}}}$ /K${{{{\rm mono}\hfill \atop {\rm ass}\hfill}}}$ =21.9, reminiscent of the formation of “glycoside clusters” on the external surface of glyconanocapsule. The glyconanocapsules (NH4)42?n 2 n? 1 a and (NH4)42?m 3 m? 1 a self‐assemble in “hybrid multilayers” by successive layer‐by‐layer deposition of (NH4)42?n 2 n? 1 a or (NH4)42?m 3 m? 1 a and Con A. These architectures, reminiscent of versatile mimics of artificial tissues, can be easily prepared and quantified by using quartz crystal microgravimetry (QCM). The “biomimetic hybrid multilayers” described here are stable under a continual water flow and they may serve as artificial networks for a greater depth of understanding of various biological mechanisms, which can directly benefit the fields of chemical separations, sensors or storage‐delivery devices. 相似文献
66.
From Enantiopure Hydroxyaldehydes to Complex Heterocyclic Scaffolds: Development of Domino Petasis/Diels–Alder and Cross‐Metathesis/Michael Addition Reactions 下载免费PDF全文
Dr. Alexandre Cannillo Dr. Stéphanie Norsikian Dr. Marie‐Elise Tran Huu Dau Dr. Pascal Retailleau Dr. Bogdan I. Iorga Prof. Jean‐Marie Beau 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(38):12133-12143
One‐step assembly of hexahydroisoindole scaffolds by a sequence that combines the Petasis (borono‐Mannich) and Diels–Alder reactions is described. The unique selectivity observed experimentally was confirmed by quantum calculations. The current method is applicable to a broad range of substrates, including free sugars, and holds significant potential to efficiently and stereoselectively build new heterocyclic structures. This easy and fast entry to functionalized polycyclic compounds can be pursued by further transformations, for example, additional ring closure by a cross‐metathesis/Michael addition domino sequence. 相似文献
67.
Macromolecule Loading into Spherical,Elliptical, Star‐Like and Cubic Calcium Carbonate Carriers 下载免费PDF全文
Dr. Bogdan V. Parakhonskiy Dr. Alexey M. Yashchenok Dr. Senem Donatan Dr. Dmitry V. Volodkin Dr. Francesco Tessarolo Prof. Renzo Antolini Prof. Helmuth Möhwald Prof. Andre G. Skirtach 《Chemphyschem》2014,15(13):2817-2822
We fabricated calcium carbonate particles with spherical, elliptical, star‐like and cubical morphologies by varying relative salt concentrations and adding ethylene glycol as a solvent to slow down the rate of particle formation. The loading capacity of particles of different isotropic (spherical and cubical) and anisotropic (elliptical and star‐like) geometries is investigated, and the surface area of such carriers is analysed. Potential applications of such drug delivery carriers are highlighted. 相似文献
68.
Adrian Pîrnău Mihaela Mic Mircea Bogdan Ioan Turcu 《Journal of inclusion phenomena and macrocyclic chemistry》2014,79(3-4):283-289
The inclusion of local anesthetic drug procaine hydrochloride by β-cyclodextrin was investigated by 1D and 2D proton NMR spectroscopy and isothermal titration calorimetry (ITC) at 298 K. The stoichiometry of the complex was determinate by the method of continuous variation, using the chemical induced shift of both host and guest protons. The association constant K, of the obtained complex was calculated and found to be 293.17 M?1. Rotating frame NOE spectroscopy, was used to ascertain the solution geometry of the host–guest complex. The result reveals that the procaine molecule penetrates into the β-cyclodextrin cavity with the aromatic ring. The energetics of complexation process is investigated by ITC technique. The analysis indicates that the complexation of procaine by β-CD is an exothermic process and show that both enthalpy and entropy contribute to the binding process. The obtained value for the association constant is in good agreement with that obtained from NMR. 相似文献
69.
Atomic-level studies of protein activity represent a significant challenge as a result of the complexity of conformational changes occurring on wide-ranging timescales, often greatly exceeding that of even the longest simulations. A prime example is the elucidation of protein allosteric mechanisms, where localized perturbations transmit throughout a large macromolecule to generate a response signal. For example, the conversion of chemical to electrical signals during synaptic neurotransmission in the brain is achieved by specialized membrane proteins called pentameric ligand-gated ion channels. Here, the binding of a neurotransmitter results in a global conformational change to open an ion-conducting pore across the nerve cell membrane. X-ray crystallography has produced static structures of the open and closed states of the proton-gated GLIC pentameric ligand-gated ion channel protein, allowing for atomistic simulations that can uncover changes related to activation. We discuss a range of enhanced sampling approaches that could be used to explore activation mechanisms. In particular, we describe recent application of an atomistic string method, based on Roux's “swarms of trajectories” approach, to elucidate the sequence and interdependence of conformational changes during activation. We illustrate how this can be combined with transition analysis and Brownian dynamics to extract thermodynamic and kinetic information, leading to understanding of what controls ion channel function. © 2019 Wiley Periodicals, Inc. 相似文献
70.
Marcel Aebli Bogdan M. Benin Kyle M. McCall Viktoriia Morad Debora Thöny Hansjörg Grützmacher Maksym V. Kovalenko 《Helvetica chimica acta》2020,103(7):e2000080
Inorganic lead halide perovskites have gained immense scientific interest for optoelectronic applications. In this work, we present a one-dimensional polymorph of cesium lead bromide (δ-CsPbBr3) synthesized through a simple anion-exchange reaction, wherein distorted edge-sharing PbBr6 octahedra form 1D chains isolated by Cs ions. δ-CsPbBr3 was characterized by Raman spectroscopy, X-ray diffraction, 207Pb and 133Cs solid-state NMR, and by optical emission and absorption spectroscopies. This non-perovskite material irreversibly transforms into the well-known three-dimensional perovskite phase (γ-CsPbBr3) upon heating to above 151 °C. The indirect bandgap was determined by absorption measurements and calculation to be 2.9 eV. δ-CsPbBr3 exhibits broadband yellow photoluminescence with a quantum yield of 3.2 %±0.2 % at room temperature and 95 %±5 % at 77 K, and this emission is attributed to the recombination of self-trapped excitons. This study emphasizes that the metastable δ-CsPbBr3 may be a persistent, concomitant phase in Cs−Pb-Br-containing materials systems, such as those used in solar cells and LEDs, and it showcases the characterization tools used for its detection. 相似文献