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941.
Baishali Chakraborty Kumar S. Gupta Siddhartha Sen 《The European Physical Journal B - Condensed Matter and Complex Systems》2015,88(6):155
We analyze the screening of an external Coulomb charge in gapless graphene cone, which is taken as a prototype of a topological defect. In the subcritical regime, the induced charge is calculated using both the Green’s function and the Friedel sum rule. The dependence of the polarization charge on the Coulomb strength obtained from the Green’s function clearly shows the effect of the conical defect and indicates that the critical charge itself depends on the sample topology. Similar analysis using the Friedel sum rule indicates that the two results agree for low values of the Coulomb charge but differ for the higher strengths, especially in the presence of the conical defect. For a given subcritical charge, the transport cross-section has a higher value in the presence of the conical defect. In the supercritical regime we show that the coefficient of the power law tail of polarization charge density can be expressed as a summation of functions which vary log periodically with the distance from the Coulomb impurity. The period of variation depends on the conical defect. In the presence of the conical defect, the Fano resonances begin to appear in the transport cross-section for a lower value of the Coulomb charge. For both sub and supercritical regime we derive the dependence of LDOS on the conical defect. The effects of generalized boundary condition on the physical observables are also discussed. 相似文献
942.
Uncatalyzed Hydroamination of Electrophilic Organometallic Alkynes: Fundamental,Theoretical, and Applied Aspects 下载免费PDF全文
Dr. Yanlan Wang Camille Latouche Dr. Amalia Rapakousiou Colin Lopez Prof Isabelle Ledoux‐Rak Dr. Jaime Ruiz Prof. Jean‐Yves Saillard Prof. Didier Astruc 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(26):8076-8088
Simple reactions of the most used functional groups allowing two molecular fragments to link under mild, sustainable conditions are among the crucial tools of molecular chemistry with multiple applications in materials science, nanomedicine, and organic synthesis as already exemplified by peptide synthesis and “click” chemistry. We are concerned with redox organometallic compounds that can potentially be used as biosensors and redox catalysts and report an uncatalyzed reaction between primary and secondary amines with organometallic electrophilic alkynes that is free of side products and fully “green”. A strategy is first proposed to synthesize alkynyl organometallic precursors upon addition of electrophilic aromatic ligands of cationic complexes followed by endo hydride abstraction. Electrophilic alkynylated cyclopentadienyl or arene ligands of Fe, Ru, and Co complexes subsequently react with amines to yield trans‐enamines that are conjugated with the organometallic group. The difference in reactivities of the various complexes is rationalized from the two‐step reaction mechanism that was elucidated through DFT calculations. Applications are illustrated by the facile reaction of ethynylcobalticenium hexafluorophosphate with aminated silica nanoparticles. Spectroscopic, nonlinear‐optical and electrochemical data, as well as DFT and TDDFT calculations, indicate a strong push–pull conjugation in these cobalticenium– and Fe– and Ru–arene–enamine complexes due to planarity or near‐planarity between the organometallic and trans‐enamine groups involving fulvalene iminium and cyclohexadienylidene iminium mesomeric forms. 相似文献
943.
Gerardo Salinas Alice L. Dauphin Camille Colin Elena Villani Stphane Arbault Laurent Bouffier Alexander Kuhn 《Angewandte Chemie (International ed. in English)》2020,59(19):7508-7513
Miniaturized autonomous chemo‐electronic swimmers, based on the coupling of spontaneous oxidation and reduction reactions at the two poles of light‐emitting diodes (LEDs), are presented as chemotactic and magnetotactic devices. In homogeneous aqueous media, random motion caused by a bubble‐induced propulsion mechanism is observed. However, in an inhomogeneous environment, the self‐propelled devices exhibit positive chemotactic behavior, propelling themselves along a pH or ionic strength gradient (?pH and ?I, respectively) in order to reach a thermodynamically higher active state. In addition, the intrinsic permanent magnetic moment of the LED allows self‐orientation in the terrestrial magnetic field or following other external magnetic perturbations, which enables a directional motion control coupled with light emission. The interplay between chemotaxis and magnetotaxis allows fine‐tuning of the dynamic behavior of these swimmers. 相似文献
944.
We previously studied the first stable conformations of flavone acetic acid and related compounds. In this article, a similar investigation was carried out on the second stable conformation of the same compounds. Emphasis is on the conformation dependence of the hydrogen-bonding effects, the molecular electrostatic potential (MEP), and the antitumor activity shown by these compounds. The results show that the second conformation is about 7.0 kcal mol−1 higher in energy and possibly is an inactive conformation as no correlation has been found between the antitumor activity and the MEP features. In addition, a detailed comparison with the first conformation, which is probably the active conformation, has been made of the geometry, the total energy, the Mulliken charges on some important atoms, hydrogen-bonding effects, and the MEP minima and isosurfaces. The role of the hydrogen-bonding effects, which was unclear in our previous work, is clarified in this work. The possible molecular basis of the antitumor activity is suggested. © 1996 John Wiley & Sons, Inc. 相似文献
945.
周富军 《高校应用数学学报(英文版)》2006,21(2):143-151
§1Introduction Avarietyofpartialdifferentialequationmodelsfortumorgrowthortherapyhave beendevelopedinthelastthreedecades[see2,3,16-18,21-26].Mostofthosemodelsare informoffreeboundaryproblems,andareverydiversified.Rigorousmathematical analysisofsuchfreeboundaryproblemshasdrawngreatinterest,andmanyinteresting resultshavebeenestablished[4-15].Inthispaperwedealwithamathematicalmodeldescribingtumorchemotherapy.In thismodelthetumorisviewedasdenselypacked,radially-symmetricsphereofradiusR(t)contain… 相似文献
946.
Seddique M. Ahmed 《Journal of solution chemistry》2008,37(7):919-932
The chromaticity of poly(o-anisidine) (POAN) doped with different acids (HA), HA-doped POAN, has been studied by the spectrophotometric technique and
the results were substantiated by molecular mechanics (MM+) calculations. The observed absorbance decrease (λ around 720 nm, dark green coloration) with increasing concentration of the inorganic oxidizing agent (KMnO4) can be attributed to the oxidative hydrolysis mechanism. The oxidative hydrolysis constant (K
h) is highly dependent on the strength of the acid used. The HClO4-doped POAN matrix has the ability to store about 128.878 kJ⋅g−1 chromogenic energy (CE) at the wavelength 720 nm in a condensed lightweight form. MM+ calculations suggest that the potential
energy (PE) in kJ⋅mol−1 of the optimum molecular geometric (OMG) structure of the HClO4-doped POAN matrix is at least two (2.052) times more stable than the OMG of the base form (POAN-EB) of the POAN matrix. Kinetic
parameters of the oxidative hydrolysis reaction of the HA-doped POAN matrix were deduced from absorbance variations with time.
The results of computer-oriented kinetic analysis indicate that the rate-controlling step for HA-doped POAN oxidative hydrolysis
is governed by the Ginstling-Bronshein equation that represents three-dimensional diffusion (D4). Activation parameters for
the oxidative hydrolysis of the HClO4-doped POAN matrix were computed and discussed. 相似文献
947.
948.
949.
A density functional and ab initio theory investigation on M@B9 and M@B10 molecular wheels containing planar nona- and deca-coordinate heavy group 11, 12 and 13 metals (M=Ag, Au, Cd, Hg, In, Ti)
has been performed. These unusual clusters all prove to be true minima on the potential energy surfaces of the systems and
σ+π double aromatic in nature. The first two vertical one-electron detachment energies of M@B10− (M=Ag, Au) anions and first two ionization potentials of M@B9 (M=Ag, Au) and M@B10 (M=Cd, Hg) neutrals were calculated to aid future experiments. The cluster complexes designed in this work may expend the
domain of planar hyper-coordinate elements to include heavy group 11, 12, and 13 metals and serve as interesting candidates
to be targeted in experiments.
Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.
Supported by the National Natural Science Foundation of China (Grant No. 20873117) 相似文献
950.
It was found that the interface effects in viscous capillary flow influenced the process of viscosity measurement greatly,and the abnormal viscosity behaviors of polyelectrolytes as well as neutral polymers in dilute solution region were ascribed to interface effect.According to this theory,we have reviewed the previous viscosity data of derivatives of poly-2- vinylpyridine reported by Maclay and Fuoss first.Then,the abnormal viscosity behaviors of a series of sodium polystyrene sulfonate samples with various molecular weights in dilute aqueous solutions were studied further.The solute adsorption behaviors and structural information of polymers have been discussed carefully. 相似文献