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101.
Dikarev EV Shpanchenko RV Andreini KW Block E Jin J Petrukhina MA 《Inorganic chemistry》2004,43(18):5558-5563
The crystal structure of a new hybrid product comprised of two rigid building blocks, namely dirhodium(II) tetraacetate, [Rh(2)(O(2)CCH(3))(4)] (1), and 2,6-diselenaspiro[3.3]heptane, Se(2)C(5)H(8) (2), has been solved ab initio using laboratory source X-ray powder diffraction (XRPD) data. The rigid body refinement approach has been applied to assist in finding an adequate model and to reduce the number of the refined parameters. Complex [Rh(2)(O(2)CCH(3))(4).mu(2)-Se(2)C(5)H(8)-Se,Se'] (3) conforms to the triclinic unit cell with lattice parameters of a = 8.1357(4), b = 8.7736(4), and c = 15.2183(8) A, alpha = 77.417(3), beta = 88.837(3), and gamma = 69.276(4) degrees, V = 989.66(8) A(3), and Z = 2. The centrosymmetric P space group was selected for calculations. The final values of the reduced wR(p), R(p), and chi(2) were calculated at 0.0579, 0.0433, and 5.95, respectively. The structure of 3 is a one-dimensional zigzag polymer built on axial Rh...Se interactions at 2.632(6) A. The 2,6-diselenaspiro[3.3]heptane ligand acts as a bidentate linker bridging dirhodium units via both selenium atoms. The geometrical parameters of individual groups for rigid body refinement have been obtained from X-ray powder data for dirhodium(II) tetraacetate (1) and from single-crystal X-ray diffraction for diselenium molecule 2. The crystal structures of 1 and 2 are reported here for the first time. For 1 indexing based on XRPD data has resulted in the triclinic unit cell P with lattice parameters of a = 8.3392(7), b = 5.2216(5), and c = 7.5264(6) A, alpha = 95.547(10), beta = 78.101(6), and gamma = 104.714(13) degrees, V = 309.51(5) A(3), and Z = 1. The final values were wR(p) = 0.0452, R(p) = 0.0340, and chi(2) = 1.99. The 1D polymeric motif built on axial Rh.O interactions of the centrosymmetric dirhodium units has been confirmed for the solid-state structure of 1. Compound 2,6-diselenaspiro[3.3]heptane (2) conforms to the monoclinic space group P2(1)/c with the unit cell parameters of a = 5.9123(4), b = 19.6400(13), and c = 5.8877(4) A, beta = 108.5500(10) degrees, V = 648.15(8) A(3), and Z = 4. 相似文献
102.
Knudsen KR Bachmann S Jørgensen KA 《Chemical communications (Cambridge, England)》2003,(20):2602-2603
The half-transamination reaction of alpha-keto esters with pyridoxamine or 4-picolylamine was found to be catalysed by different metal catalysts in organic solvents giving moderate yields and enantioselectivities of up to 37% ee for methyl-3-indole pyruvate. 相似文献
103.
104.
Dr. Caterina Viglianisi Kristian Vasa Dr. Damiano Tanini Prof. Antonella Capperucci Dr. Riccardo Amorati Prof. Luca Valgimigli Dr. Andrea Baschieri Prof. Stefano Menichetti 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(38):9108-9116
Symmetrical ditocopheryl disulfides ( Toc ) 2 S2 and symmetrical and unsymmetrical ditocopheryl sulfides ( Toc )2 S were simply prepared under remarkably mild conditions with complete control of the regiochemistry by using δ-, γ-, and β-tocopheryl-N-thiophthalimides ( Toc-NSPht ) as common starting materials. The roles of sulfur atom(s), H-bond and aryl ring substitution pattern on the antioxidant profile of these new compounds, which were assembled by linking together two tocopheryl units, are also discussed. 相似文献
105.
Kristian Torbensen Kristoffer Malmos Dr. Frederic Kanoufi Prof. Dr. Catherine Combellas Dr. Steen U. Pedersen Prof. Dr. Kim Daasbjerg 《Chemphyschem》2012,13(14):3303-3307
Scanning electrochemical microscopy is used to carry out local free‐radical grafting at a gold surface through mild oxidation of an aryl hydrazine. The process can be deliberately controlled by creation of a local pH gradient at the tip. Comparison of the experimental results with simulations shows that the radial expansion of the pH profile in which successful grafting can be accomplished increases with increasing generation time of OH? and with decreasing initial concentration of the grafting precursor. Furthermore, the radial expansion is faster than the nucleation of the grafting process. 相似文献
106.
107.
Ringo Grombe Günter Allmaier Jean Charoud-Got Agnieszka Dudkiewicz Håkan Emteborg Thilo Hofmann Erik Huusfeldt Larsen Angela Lehner Meritxell Llinàs Katrin Loeschner Kristian Mølhave Ruud J. Peters John Seghers Conxita Solans Frank von der Kammer Stephan Wagner Stefan Weigel Thomas P. J. Linsinger 《Accreditation and quality assurance》2015,20(1):3-16
108.
109.
Kristian Helmerson Rani Kishore William D. Phillips Howard H. Weetall 《Applied biochemistry and biotechnology》2001,96(1-3):205-213
We used optical tweezers—optical trapping with focused laser beams—to pull microspheres coated with antigens off of an antibody-coated
surface. Using this technique, we could quantify the force required to separate antigen to antibody bonds. At very low surface
density of antigen, we were able to detect the single antigen to antibody binding. The force required to break the antigen-antibody
bonds and pull the microsphere off the surface was shown to increase monotonically with increasing surface density of antigens.
Using the force determination as a transducer, we were able to detect concentrations of free antigens in solution as small
as 10−15 mol/L in a competitive binding assay. 相似文献
110.
Linear support vector machine training can be represented as a large quadratic program. We present an efficient and numerically
stable algorithm for this problem using interior point methods, which requires only O(n)\mathcal{O}(n) operations per iteration. Through exploiting the separability of the Hessian, we provide a unified approach, from an optimization
perspective, to 1-norm classification, 2-norm classification, universum classification, ordinal regression and ε-insensitive regression. Our approach has the added advantage of obtaining the hyperplane weights and bias directly from the
solver. Numerical experiments indicate that, in contrast to existing methods, the algorithm is largely unaffected by noisy
data, and they show training times for our implementation are consistent and highly competitive. We discuss the effect of
using multiple correctors, and monitoring the angle of the normal to the hyperplane to determine termination. 相似文献