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111.
112.
Deep electronic tunneling through molecular barriers in donor-bridge-acceptor complexes is studied using an analytically solvable model. The effective tunneling matrix element is formulated as a sum over vibronic tunneling pathways. For a symmetric system the frequency of tunneling oscillations is shown to increase with the strength of electronic-nuclear coupling at the bridge, the number of electronic-nuclear coupling sites, or the frequency of a bridge vibration. Acceleration by several orders of magnitude is demonstrated within the range of realistic molecular parameters. 相似文献
113.
Three quettamine type alkaloids, which incorporate either a benzofuran or a dihydrobenzofuran moiety within the molecular framework, have been obtained from . These are dihydrosecoquettamine (), secoquettamine (), and quettamine chloride (). Alkaloids and are racemates. Hofmann degradation of quettamine () provides secoquettamine () and the styrene which has a trans relationship between the hydrogens at C-1 and C-α, thus indicating the identical stereochemistry in quettamine. Emde reduction of quettamine leads to dihydrosecoquettamine () and the stilbene . Two other polar alkaloids in the plant are (+)-armepavine methochloride () and oblongine chloride (). An oblongine type alkaloid must be the biogenetic precursor for the quettamines. Arguments are presented favoring direct oxidative coupling in the biogenesis of the cularine alkaloids. 相似文献
114.
Versmold H Musa S Kubetzki H Urban V 《Langmuir : the ACS journal of surfaces and colloids》2005,21(10):4324-4327
In this paper, the ordering in concentrated charge stabilized colloidal dispersions is considered. Despite the impressive Bragg reflections obtained for shear ordered dispersions by light (LS), small-angle neutron (SANS), and small-angle X-ray scattering (SAXS), a number of open questions remain. Sheared dispersions are usually ordered in layers. For such systems, two questions arise: (1) What is the structure in a layer? (2) What is the stacking structure perpendicular to the layers? The second question requires a method to determine the structure perpendicular to the layers. Although originally interested only in structural aspects, we were forced to consider different methods. Two methods are treated both applicable to neutron and X-ray scattering from concentrated dispersions. One has been used by physicists and chemists for many years to determine the structure of crystals by sample rotation. In colloid science, we have used it previously in neutron and X-ray scattering. A second method is treated here which can be applied in small-angle scattering from a Couette cell. It gives the scattering intensity in a certain direction without sample rotation. Although very useful with the Couette cell, it cannot be found in any of the well-known references on colloid science. A theoretical explanation and experimental examples obtained by synchrotron X-ray scattering from a Couette cell are given in the paper. 相似文献
115.
Atıf Koca Musa Şahin Ahmet Gül Rabia Z. Uslu 《Monatshefte für Chemie / Chemical Monthly》2002,133(8):1135-1145
Summary. In this study, the electrochemical properties of metal-free and nickel-containing porphyrazines with eight tosylaminoethylthia
groups were investigated using cyclic voltammetry, double potential step chronoamperometry, double potential step chronocoulometry,
and controlled potential coulometry. Cyclic voltammetry measurements showed that both compounds exhibit two quasi-reversible and an irreversible reduction waves. The first electron transfer reaction was followed by an irreversible chemical
reaction, the second one by a reversible chemical reaction for both species. The electrode processes of metal-free and nickel-containing
porphyrazines are diffusion controlled, but the double potential step chronocoulometry measurements indicated that the nickel
porphyrazine is adsorbed at the electrode. However, a small adsorption current has no significant effect on the mass transport
mechanism of the system. Diffusion coefficients of both compounds were determined by both cyclic voltammetric and chronocoulometric
measurements. The diffusion coefficients of the reduced forms of the porphyrazines were found to be smaller than those of
the neutral forms.
Received October 29, 2001. Accepted (revised) December 17, 2001 相似文献
116.
A single-step fabrication of a glucose biosensor with simultaneous immobilization of both ferrocene mediator and glucose oxidase in a photocurable methacrylic film consisting of poly(methyl methacrylate-co-2-hydroxylethyl methacrylate) was reported. The entrapped ferrocene showed reversible redox behaviour in the photocured film and no significant leaching of both entrapped ferrocene and enzyme glucose oxidase was observed because of the low water absorption properties of the co-polymer films. From electrochemical studies, ferrocene entrapped in the co-polymer film demonstrated slow diffusion properties. A linear glucose response range of 2-11 mM was obtained at low applied potential of +0.25 V. The glucose biosensor fabricated by this photocuring method yielded sensor reproducibility and repeatability with relative standard deviation of <10% and long-term stability of up to 14 days. The main advantage of the use of photocurable procedure is that biosensor membrane fabrication can be performed in a single step without any lengthy chemical immobilization of enzyme. 相似文献
117.
P. Vishnu Vardhan Mustapha Balarabe Idris S. Manikandan K. S. Rajan S. Devaraj 《Journal of Solid State Electrochemistry》2018,22(6):1795-1800
Generally adopted strategies to improve capacitance of the electrode materials are tuning various properties of the electrode material or increasing the cell voltage. While tuning the properties of the electrode material is tedious, increasing the cell voltage is restricted by the stability of the electrolyte. Herein, we report a facile approach to improve the capacitance of MnCO3 by the influence of SiOx nanofluid in the electrolyte. The capacitance properties of MnCO3 are studied in 0.1 M Mg(ClO4)2 electrolyte in the presence and in the absence of SiOx nanofluid. The presence of small amount of SiOx nanofluid in the electrolyte provides higher diffusivity and more conductive percolation paths for ions and thus decreases internal resistance and increases ionic conductivity of the electrolyte. As a result, 60% enhancement in the capacitance is witnessed for MnCO3. Further, nanofluid containing electrolyte is found to be stable over a month. 相似文献
118.
Sabri Cevik Mehmet Poyraz Musa Sar Orhan Büyükgüng?r 《Journal of chemical crystallography》2007,37(7):497-502
The hydrothermal reaction of a mixture of VOSO4 · xH2O, 1,2,4,5-benzenetetracarboxylic acid (pyromellitic acid) and 0.1 M H2SO4 for 72 h at 160 °C gives blue needle like crystals of [VIV
2O2(H2O)2(C6H2(COO)4)] in 30% yield. The compound has a porous 3-D extended network structure having a rigid architecture which is held together
by the multidentate functionalities of 1,2,4,5-benzenetetracarboxylate ligand. Crystal data for the compound: monoclinic space
group C 2/c (No:15), a = 11.756(5) ?, b = 9.645(3) ?, c = 11.822(7) ?, β = 107.10(4)°, Z = 8. The compound constitutes the first example of a fully reduced oxovanadium based solid incorporating the organic ligand.
This article consists of synthesis, crystal structure and characterization of [VIV
2O2(H2O)2(C6H2(COO)4)]. 相似文献
119.
Abla S. Al‐zagameem Mustafa M. El‐Abadelah Malek A. Zihlif Randa G. Naffa Musa L. Al‐Smadi Mohammad S. Mubarak 《Journal of heterocyclic chemistry》2016,53(6):1771-1777
A new series of 9‐substituted‐4,10‐dimethylpyrano[2,3‐f]cinnolin‐2‐ones ( 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h , 5i , 5j , 5k , 5l , 5m ) were synthesized via intramolecular cyclization of the respective acyl amidrazone derivatives ( 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4h , 4i , 4j , 4k , 4l , 4m ), catalyzed by polyphosphoric acid. Compounds ( 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4h , 4i , 4j , 4k , 4l , 4m ) were synthesized through direct interaction of coumarin‐7‐yl hydrazonoyl chloride ( 3 ) with the corresponding cyclic sec‐amines in the presence of triethylamine. The structures of the new compounds were confirmed by elemental analyses, NMR, and MS spectral data. The antitumor activity of compounds 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h , 5i , 5j , 5k , 5l , 5m was evaluated in vitro on breast cancer cell line (MCF‐7) by a cell viability assay utilizing the tetrazolium dye 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide. Among the compounds tested, compounds 5d , 5f , 5k , and 5h showed potential anti‐MCF‐7 activity and were able to reduce the viability after 72 h to less than 50%. 相似文献
120.