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101.
A two-step sulfurization for efficient solution-phase synthesis of phosphorothioate oligonucleotides
Amar B.T. Ghisaidoobe Howard I. Duynstee Herman S. Overkleeft Gijs A. van der Marel 《Tetrahedron letters》2008,49(19):3129-3132
A solution-phase approach for the synthesis of phosphorothioate oligonucleotides that circumvents the use of chromatographic purifications of protected phosphorothioate intermediates was developed. Implementation of a two-step sulfurization protocol in the phosphoramidite method allows efficient isolation of the intermediate phosphorothioates by extractions. The viability of this approach is demonstrated by the synthesis of a hexameric phosphorothioate oligonucleotide fragment. 相似文献
102.
Taichi Ikeda Dr. Sourav Saha Dr. Ivan Aprahamian Dr. Ken C.‐F. Leung Dr. Adides Williams Wei‐Qiao Deng Dr. Amar H. Flood Dr. William A. Goddard III Prof. J. Fraser Stoddart Prof. 《化学:亚洲杂志》2007,2(1):76-93
Encouraged by the prospect of producing an electrochemical, color‐switchable red–green–blue (RGB) dye compound, we have designed, synthesized, and characterized two three‐station [2]catenanes. Both are composed of macrocyclic polyethers containing three π‐electron‐rich stations, which act as recognition sites for a π‐electron‐deficient tetracationic cyclophane. The molecular structures of the two three‐station [2]catenanes were characterized fully by mass spectrometry and 1H NMR spectroscopy. To anticipate the relative occupancies of the three stations in each [2]catenane by the cyclophane, model compounds with the same constitutions in the vicinity of the stations were synthesized. The relative ground‐state populations of the three stations occupied in both [2]catenanes were estimated from the thermodynamic parameters for 1:1 complexes between all these model compounds and the cyclophane, obtained from isothermal titration calorimetry (ITC). The electrochemical and electromechanical properties of the three‐station [2]catenanes were analyzed by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and spectroelectrochemistry (SEC). The first three‐station [2]catenane was found to behave like a bistable system, whereas the second can be described as a quasi‐tristable system. 相似文献
103.
Let be a prime power and be a positive integer. A subspace partition of , the vector space of dimension over , is a collection of subspaces of such that each nonzero vector of is contained in exactly one subspace in ; the multiset of dimensions of subspaces in is then called a Gaussian partition of . We say that contains a direct sum if there exist subspaces such that . In this paper, we study the problem of classifying the subspace partitions that contain a direct sum. In particular, given integers and with , our main theorem shows that if is a subspace partition of with subspaces of dimension for , then contains a direct sum when has a solution for some integers and belongs to the union of two natural intervals. The lower bound of captures all subspace partitions with dimensions in that are currently known to exist. Moreover, we show the existence of infinite classes of subspace partitions without a direct sum when or when the condition on the existence of a nonnegative integral solution is not satisfied. We further conjecture that this theorem can be extended to any number of distinct dimensions, where the number of subspaces in each dimension has appropriate bounds. These results offer further evidence of the natural combinatorial relationship between Gaussian and integer partitions (when ) as well as subspace and set partitions. 相似文献
104.
105.
Graft copolymerization of methyl methacrylate (MMA) onto chemically modified coir fiber was studied using a CuSO4–KIO4 combination as initiator in an aqueous medium in the temperature range of 50–70 °C. Concentrations or [IO4−] = 0.005 mol/l and [Cu2+] = 0.002 mol/l produce optimum grafting. The effects of time, temperature, amount of coir fiber, some inorganic salts and organic solvents on graft yield have also been investigated. On the basis of experimental findings, a reaction mechanism has been proposed. Evidence of grafting was studied from fourier transform infrared spectroscopy and scanning electron microscopy of chemically modified coir and MMA‐grafted coir. Tensile properties such as maximum stress at break, extension at break and Young's modulus of untreated, defatted, chemically treated and grafted coir fibers were evaluated and compared. Grafted coir fiber showed an increase in tensile properties such as maximum stress at break, extension at break and Young's modulus. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
106.
Carla T. Cioffi Dr. Amit Palkar Dr. Frederic Melin Dr. Amar Kumbhar Luis Echegoyen Prof. Dr. Manuel Melle‐Franco Francesco Zerbetto Prof. Dr. G. M. Aminur Rahman Dr. Christian Ehli Vito Sgobba Dr. Dirk M. Guldi Prof. Dr. Maurizio Prato Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(17):4419-4427
Don't cry! The attachment of ferrocene moieties on the surface of carbon nano‐onions influences the electrochemical properties of these moieties and the photophysical properties of the carbon nano‐onions (see figure). Quantum chemical calculations confirm that the spectral properties of carbon nano‐onions depend on their size and the degree of functionalisation.
107.
Afif Ben Amar 《Numerical Functional Analysis & Optimization》2013,34(11):1213-1220
We present some new variants of Leray–Schauder type fixed point theorems and eigenvalue results for decomposable single-valued nonlinear weakly compact operators in Dunford-Pettis spaces. 相似文献
108.
Pinak Pani Biswas Rishi Srivastava Subhabrata Ray Amar Nath Samanta 《Mechatronics》2009,19(4):548-561
The process investigated herein is the quadruple tank system that is stable only within a limited zone of operating parameters. The process model has been developed from fundamentals and tuned with experimental data. A controller design based on feedback linearization has been tested on this process model. Coupling feedback linearization with sliding mode algorithm provides robust control of the process and performs far superior to conventional PI control. A PC based controller interfaced to the experimental quadruple tank experimental set up has been used to implement this algorithm and test its performance. Inserting a ‘boundary layer’ around the sliding surface reduced the ‘chattering’ associated with sliding mode control. The implemented controller provides robust control and excellent set point tracking. 相似文献
109.
In this paper we study spectral properties of a 3 × 3 block operator matrix with unbounded entries and with domain consisting
of vectors which satisfy certain relations between their components. It is shown that, under certain conditions, this block
operator matrix defines a closed operator, and the essential spectra of this operator are determined. These results are applied
to a three-group transport equation. 相似文献
110.