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111.
Xiaole Weng Paul Boldrin Isaac Abrahams Suela Kellici 《Journal of solid state chemistry》2008,181(5):1123-1132
A new direct route for the “bottom up” syntheses of phases in the Lan+1NinO3n+1 series (n=1, 2, 3 and ∞) has been achieved via single-step heat treatments of nanosized co-crystallized precursors. The co-crystallized precursors were prepared using a continuous hydrothermal flow synthesis system that uses a superheated water flow at ca. 400 °C and 24.1 MPa to produce nanoparticulate slurries. Overall, a significant reduction in time and number of steps for the syntheses of La3Ni2O7 and La4Ni3O10 was achieved compared with more conventional synthesis methods, which typically require multiple homogenization and reheating steps over several days. 相似文献
112.
Isaac Pesenson 《Transactions of the American Mathematical Society》2008,360(10):5603-5627
A notion of Paley-Wiener spaces on combinatorial graphs is introduced. It is shown that functions from some of these spaces are uniquely determined by their values on some sets of vertices which are called the uniqueness sets. Such uniqueness sets are described in terms of Poincare-Wirtinger-type inequalities. A reconstruction algorithm of Paley-Wiener functions from uniqueness sets which uses the idea of frames in Hilbert spaces is developed. Special consideration is given to the -dimensional lattice, homogeneous trees, and eigenvalue and eigenfunction problems on finite graphs.
113.
Youxuan Zheng Majid Motevalli Rendy H.C. Tan Isaac Abrahams William P. Gillin Peter B. Wyatt 《Polyhedron》2008
3,4,5,6-Tetrafluoro-2-nitrophenoxide (L−) forms complexes with rare earth M3+ ions. X-ray crystal structures of substances with the stoichiometry Cs2ML5 · mEt2O (M = Er, m = 0; M = Er, m = 1; M = Y, m = 1.5; M = Yb, m = 1) have been determined. Each M3+ ion is coordinated to two bidentate and three monodentate L− ions; Et2O does not coordinate to M3+. The complexes absorb both visible and ultraviolet light. The solid Er3+ and Yb3+ complexes have unusually long lifetimes (τ = 20.2 μs and 142 μs, respectively) for the decay of their luminescence in the near-infrared region following photoexcitation; this is attributed to the lack of C–H bonds and other high frequency oscillators that could cause vibrational quenching. 相似文献
114.
Carrico IS 《Chemical Society reviews》2008,37(7):1423-1431
The use of synthetic molecules to modulate and track biological events is a central component of chemical biology. As a result, the precise, covalent modification of biomolecules is a key goal for this field. Several strategies have emerged that allow specific tailoring of polypeptides through either endogenous residues or introduced functionality. This tutorial review discusses these recent advances in the context of in vitro and in vivo applications. 相似文献
115.
116.
We discuss a new applied probability model: there is a system whose evolution is described by a Markov chain (MC) with known transition matrix on a discrete state space and at each moment of a discrete time a decision maker can apply one of three possible actions: continue, quit, and restart MC in one of a finite number of fixed “restarting” points. Such a model is a generalization of a model due to Katehakis and Veinott (Math. Oper. Res. 12:262, 1987), where a restart to a unique point was allowed without any fee and quit action was absent. Both models are related to Gittins index and to another index defined in a Whittle family of stopping retirement problems. We propose a transparent recursive finite algorithm to solve our model by performing O(n3) operations. 相似文献
117.
Gómez L Garcia-Bosch I Company A Sala X Fontrodona X Ribas X Costas M 《Dalton transactions (Cambridge, England : 2003)》2007,(47):5539-5545
A novel family of chiral manganese complexes Lambda-1(CF(3)SO(3)) and Delta-2(CF(3)SO(3)), have been stereoselectively prepared, characterized and studied as epoxidation catalysts. The complexes are structurally related to [Mn(II)(CF(3)SO(3))(2)(alpha-MCP)] (MCP=N,N'-dimethyl-N,N'-bis(2-pyridylmethyl)cyclohexane-trans-1,2-diamine), recently reported as a very efficient epoxidation catalyst in combination with peracetic acid. Pinene rings have been fused to the 4 and 5 positions of the two pyridine groups of the ligand, giving rise to complexes where the two labile binding sites of the manganese ion are confined in a better-defined chiral pocket than in the parent [Mn(II)(CF(3)SO(3))(2)(alpha-MCP)]. Chirality in these complexes arises from the stereochemistry of the trans-diaminocyclohexane ring, from the pinene ring and also from the topological chirality adopted by the ligand upon binding to the manganese ion. While previous studies have demonstrated that small modifications in the structure of the MCP ligand result in a dramatic loss of efficiency, Lambda-1(CF(3)SO(3)) and Delta-2(CF(3)SO(3)) exhibit comparable catalytic activity to [Mn(II)(CF(3)SO(3))(2)(alpha-MCP)]. In addition, the complexes exhibit a remarkable stereoselectivity (up to 46% ee) in the epoxidation of selected substrates. The results reported in this work point towards modification of the 4 and 5 positions of the pyridine groups as a new strategy towards the design of stereoselective versions of this family of highly active and environmentally benign epoxidation catalysts. 相似文献
118.
We examine the morphological structures of asymmetric poly(ethylene oxide)-b-poly(1,1'-dihydroperflurooctyl methacrylate) (PEO-b-PFOMA) thin films upon annealing in a compressible fluid, supercritical CO2 (Sc-CO2). The strong affinity between PFOMA and CO2 is found to induce phase segregation when annealing PEO-b-PFOMA films at the same temperature as compared with vacuum. In vacuum, PEO-b-PFOMA films remain disordered from 80 to 180 degrees C, whereas, in Sc-CO2 at 13.9 MPa, an upper order-disorder transition (UODT) between 116 and 145 degrees C is found. In Sc-CO2, the observed ordered structure is layers of PEO spheres embedded in the matrix of PFOMA, followed by a brush layer, in which PEO wets the substrate. The swelling isotherms of PFOMA and PEO in CO2 are correlated with the Sanchez-Lacombe equation of state (SLEOS) to estimate the interaction parameters, XPFOMA-CO2 and XPEO-CO2. The phase segregation (order) induced by CO2 relative to vacuum at a given temperature is explained in terms of two factors: (1) copolymer volume fraction upon dilution with CO2, phi, and (2) the relative interaction parameter, DeltaX= XPEO-CO2 - XPFOMA-CO2. The latter factor favors order and is dominant at low temperatures over the phi factor, which always favors disorder. At high temperatures (above the T(ODT)), the preferential swelling of PFOMA by CO2 is less pronounced ( DeltaX decreases), and the copolymer is disordered. 相似文献
119.
Isaac Abrahams Michael Lazell Majid Motevalli Charlotte K. Simon Alice C. Sullivan 《Chemistry of Heterocyclic Compounds》1999,35(8):954-964
Three structurally different metallasiloxanes were formed from reactions between in situ generated suspensions of Ph2Si(OH)2/BuLi (1∶2) in tetrahydrofuran (THF) with, metal dichlorides MgCl2·2THF, CrCl2, or CoCl2 followed by toluene/Py (Py=pyridine) work-up. The X-ray structures are reported for: [Mg{O(Ph2SiO)2}2]-μ-(LiPy)-μ-{(LiPy)3(OH)(Cl)] (1) incorporating two six-membered magnesiasiloxane rings and an MgLi3O3Cl cubane fragment, [{O(Ph2SiO)2}Co{O(Ph2SiO)3}-μ-(LiPy2)2] (2) with both six-and eight-membered cobaltasiloxane rings and [Cr{O(Ph2SiO)2}2-μ-(LiPy2)2] (3) with two six-membered chromiasiloxane rings. Structure assembly in these cases is apparently dictated by the metal dichloride. The compound [{O(Ph2SiO)2}Mg{O(Ph2SiO)3}-μ-(CoClPy)2]·Py (4) is formed from [{O(Ph2SiO)2}Mg{O(Ph2SiO)3}-μ-(LiPy2)2] and CoCl2 (1∶2). 相似文献
120.
Isaac Sonin 《Mathematical Methods of Operations Research》1999,49(1):111-123
We present a new algorithm for solving the optimal stopping problem. The algorithm is based on the idea of elimination of states where stopping is nonoptimal and the corresponding correction of transition probabilities. The formal justification of this method is given by one of two presented theorems. The other theorem describes the situation when an aggregation of states is possible in the optimal stopping problem. 相似文献