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1.
Erik Fooladi Bjrn Dalhus Christian Rmming Mats Tilset 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(12):m567-m569
In the title compound, [Rh(CH3)2(C2H3N)(C9H21N3)](C24H20B), the geometry around the RhIII centre is distorted octahedral, with elongated Rh—N bonds trans to the metal‐bonded methyl groups. The metal‐containing cations are located in channels formed by an anionic supramolecular mesh, in which aromatic π–π interactions between anionic [B(Ph)4]? units play a major role. 相似文献
2.
Mats Gyllenberg 《Journal of Differential Equations》2004,205(1):50-76
For time-periodic dissipative and irreducible type-K competitive Kolmogorov systems, it is proved that there is a canonically defined countable family F of unordered, disjoint invariant sets with the property that, for every persistent trajectory whose ω-limit set is not a cycle, there exists a unique trajectory in some element of F such that these two trajectories are asymptotic and the corresponding points in these two trajectories are K-related. 相似文献
3.
Richard Becker Mladen Prester Ping Hui Lin Mats Johnsson Ivica Zivkovic 《Journal of solid state chemistry》2007,180(3):1051-1059
Two new isostructural cobalt selenite halides Co5(SeO3)4Cl2 and Co5(SeO3)4Br2 have been synthesized. They crystallize in the triclinic system space group P−1 with the following lattice parameters for Co5(SeO3)4Cl2: a=6.4935(8) Å, b=7.7288(8) Å, c=7.7443(10) Å, α=66.051(11)°, β=73.610(11)°, γ=81.268(9)°, and Z=1. The crystal structures were solved from single-crystal X-ray data, R1=3.73 and 4.03 for Co5(SeO3)4Cl2 and Co5(SeO3)4Br2, respectively. The new compounds are isostructural to Ni5(SeO3)4Br2.Magnetic susceptibility measurements on oriented single-crystalline samples show anisotropic response in a broad temperature range. The anisotropic susceptibility is quantitatively interpreted within the zero-field splitting schemes for Co2+ and Ni2+ ions. Sharp low-temperature susceptibility features, at TN=18 and 20 K for Co5(SeO3)4Cl2 and Co5(SeO3)4Br2, respectively, are ascribed to antiferromagnetic ordering in a minority magnetic subsystem. In isostructural Ni5(SeO3)4Br2 magnetically ordered subsystem represents a majority fraction (TN=46 K). Nevertheless, anisotropic susceptibility of Ni5(SeO3)4Br2 is dominated at low temperatures by a minority fraction, subject to single-ion anisotropy effects and increasing population of Sz=0 (singlet) ground state of octahedrally coordinated Ni2+. 相似文献
4.
We define a smooth functional calculus for a non-commuting tuple of (unbounded) operators Aj on a Banach space with real spectra and resolvents with temperate growth, by means of an iterated Cauchy formula. The construction is also extended to tuples of more general operators allowing smooth functional calculii. We also discuss the relation to the case with commuting operators. 相似文献
5.
Mats J. Sundell Esko O. Pajunen Osmo O. E. Hormi Jan H. Nsman 《Journal of polymer science. Part A, Polymer chemistry》1993,31(9):2305-2311
The synthesis of some divinyl monomers—bis(vinylphenyl)ethane ( 2 ), bis(vinylbenzyloxy)hexane ( 3a ), and bis(vinylbenzyloxy)dodecane ( 3b ) is reported. Copolymers of the new monomers and styrene were evaluated as an alternative to divinylbenzene-crosslinked polymers for use as matrices and absorbents. The mechanical properties and the amount of residual double bonds in the copolymers were compared. It was found that the new copolymers, unlike the divinylbenzene-crosslinked polymers, retained their mechanical strength even at high crosslinking degrees. Stress at break values of 79, 68, and 18 N/mm2 were found for the polymers crosslinked with 20 mol % of 3a, 2 , and divinylbenzene; 5, 25 and 45% of the divinyl units in these polymers were left as pendant double bonds. Porous styrene– 2 copolymers were synthesized and shown to have lower surface areas than the corresponding divinylbenzene-crosslinked polymers. The pore size distribution showed that this was due to the absence of the smallest pores which are found in the divinylbenzene-crosslinked polymers in between heavily crosslinked nodules. © 1993 John Wiley & Sons, Inc. 相似文献
6.
Abstract— Two methods to perform actinometry in an EPR-cavity are described. One method is based on the observation that photoproduced anion radicals of hematoporphyrin react with the stable free radical 2,2,6,6-tetramethyl-4-piperidone-N-oxyl to eliminate the spin. The other method is based on the dye sensitized photoproduction of nitroxyl radicals resulting from the reaction of singlet oxygen with sterically hindered amines. 相似文献
7.
Gustafsson MG 《Journal of chemical information and modeling》2005,45(5):1244-1255
This work shows that independent component analysis (ICA) can be used to obtain statistically independent and, therefore, chemically interpretable latent variables (LVs) in multivariate regression. Two novel algorithms based on ICA are introduced and compared with two classical methods on simulated data: principal component regression and partial least-squares regression. All methods compared yield accurate predictions, but only those based on ICA yield LVs that are chemically interpretable. Practical limitations of ICA-based regression with respect to the underlying assumptions, sample size, and measurement noise are discussed and illustrated by means of simulations. 相似文献
8.
Christer Albano William Dunn Ulf Edlund Erik Johansson Bo Nordén Michael Sjöström Svante Wold 《Analytica chimica acta》1978,103(4):429-443
Problems of pattern recognition in chemistry and other subjects can be divided conveniently into four different types depending on the level of scope of the problem.(1) Classification into one of a number of defined classes. As an example blood samples taken from persons known to be either controls or welders are considered. The problem is whether trace element concentrations in these samples contain information on whether or not a person is a welder.(2) Level 1 plus the possibility that an object is an outlier, i.e. does not belong to any of the defined classes. As an example, the üse of 13C-n.m.r. data to decide whether 2-substituted norbornanes have the exo or endo structure is discussed. (2A) Level 2, asymmetric. This situation occurs when one class does not have a systematic structure, but another class is homogeneous and can be described by a level 2 model. This occurs in the classification of materials or compounds as good or bad, active or inactive, and in binary classifications. As an example the use of trace element data to classify steel samples as having good or poor properties of strength is discussed.(3) Level 2 plus the ability to relate the variables measured to external properties of continuous character. As an example, the classification of a series of chemical compounds as β -receptor blockers, β -receptor stimulants, or neither, on the basis of their structural variables is discussed. In addition, relations between these structural variables and the measured biological activity are sought within each of the two classes.(4) Level 3 with the difference that several external property variables in the objects are measured. It may be desirable to use variables of the objects both for classification and for relations to several property variables: such examples are numerous in analytical chemistry. 相似文献
9.
The development of microwave-accelerated protocols for palladium(0)-catalyzed carbonylative cyclization of unsaturated aryl bromides and chlorides is described. By employing o-bromostyryl derivatives lacking substituents on the vinylic bond, molybdenum hexacarbonyl-mediated in situ carbonylation delivered a set of indan-1-one products in high yield after only 20 min of heating. Without the addition of the tri-tert-butylphosphine releasing Fu-salt ((t-Bu)(3)PHBF(4)), only incomplete conversions of sluggish o-styryl bromides and chlorides were realized. Internal and chemoselective palladium(0)-catalyzed Heck arylations of enamides afforded suitable starting materials for subsequent rapid ring-closing reactions. Microwave-heated intramolecular in situ carbonylation of these electron-rich and sterically congested olefins conveniently afforded eight functionalized 3-acylaminoindanone derivatives in a novel synthetic process. Attempted carbonylative annulation of electron-poor o-bromocinnamic acid derivatives furnished only the corresponding lactones via a competing hydroxycarbonylation-Michael addition reaction sequence. 相似文献
10.
Weigelt J Wikström M Schultz J van Dongen MJ 《Combinatorial chemistry & high throughput screening》2002,5(8):623-630
NMR based screening has become an important tool in the pharmaceutical industry. Methods that provide information on the location of small molecule binding sites on the surface of a drug target (e. g. SAR-by-NMR and related techniques) are of particular interest. In order to extend the applicability of such techniques to drug targets of higher molecular weight, selective labeling strategies may be employed. Dual-amino acid selective labeling and site directed non-native amino acid replacement (SNAAR) allow for the selective detection of NMR resonances of a specific amino acid residue. This results in significantly reduced spectral complexity, which not only enables application to higher molecular weight systems, but also eliminates the need for sequential resonance assignment in order to identify the binding site. Regio-selective (or segmental) labeling of an entire protein domain of a multi domain protein may also be achieved. Labeling only a selected part of a multi domain protein (e. g. a catalytic or ligand binding domain) is an attractive way to simplify the spectral interpretation without disturbing the system under study. 相似文献