Triphosphane formation from the terminal zirconium phosphinidene complex [Cp2Zr=PDmp(PMe3)] (Dmp=2,6-Mes2C6H3) and crystal structure of DmpP(PPh2)2

The new terminal phosphinidene complex [Cp₂Zr=PDmp(PMe₃)] (Dmp=2,6-Mes₂C₆H₃; 1) was prepared in 81% yield by the reaction of [Li(Et₂O)][P(H)Dmp] with [Cp₂Zr(Me)Cl] in the presence of excess PMe₃. Compound 1 reacts with Ph₂PCl to produce selectively the sterically congested triphosphane DmpP(PPh₂)₂ (2) and [Cp₂ZrCl₂] in high yields. The structure of 2 obtained by X-ray diffraction analysis of a single crystal reveals phosphorus–phosphorus bond lengths of 2.251(2) and 2.234(2) Å and a PPP bond angle of 105.46(6)°.     

Predicting stable configurations of coalitions in cooperative games and exchange economies

Uniform competitive solutions are stable configurations of proposals predicting coalition formation and effective payoffs. Such “solutions” exist for almost all properly defined cooperative games and, therefore, can be proposed as substitute of the core. The new existence results obtained in the present paper concern also the case when the coalitional function of a game has empty values. All concepts and results are implemented in the competitive analysis of the exchange economies. Received: July 1997/Final version: February 2000     

Multigrid in H (div) and H (curl)

Summary. We consider the solution of systems of linear algebraic equations which arise from the finite element discretization of variational problems posed in the Hilbert spaces and in three dimensions. We show that if appropriate finite element spaces and appropriate additive or multiplicative Schwarz smoothers are used, then the multigrid V-cycle is an efficient solver and preconditioner for the discrete operator. All results are uniform with respect to the mesh size, the number of mesh levels, and weights on the two terms in the inner products. Received June 12, 1998 / Revised version received March 12, 1999 / Published online January 27, 2000     

Hydrophilicity Impact upon Physical Properties of the Environmentally Friendly Poly(3-hydroxybutyrate) Blends: Modification Via Blending

We have integrated scientific research of polymer blends on the base of poly-3-hydroxybutyrate (PHB and its copolymers) with bench testing in blend preparation by both solvent casting and melt extrusion. As a second component, we have used traditional synthetic macromolecules with various hydrophilicity degree and hence with different morphologies and physical behavior. Besides, variation of polymer hydrophilicity permits to control both the service characteristic and the rate of (bio)degradation operating in the presence of water. Therefore, a substantial part of our work is devoted to water transport in the parent PHB and its blends. Combining the morphology knowledge (SEM, WAXS, FTIR tecynique), transport characteristics (permeability cells and McBain spring microbalance), and mechanical testing, we propose that blending of the parent biodegradable polymer with synthetic macromolecules is a perspective tool to design novel materials with improved characteristics. Both the water transport coefficients and the mechanical characteristics are essentially sensitive to structure and morphology of the blends. Hydrophilicity variation in the order LDPE < SPEU < PVA at blending with PHB shows that the morphology transformation in immicsible or partly miscible blends shifted along the PHB concentration scale as LDPE (at ∼16 wt% PHB) < PVA (∼30 wt% PHB) < SPEU (∼50 wt% PHB) Our instrumental monitoring the structural hierarchy of parent polymers and their blends as well as , simultaneously, the study of transport processes, their modeling, and computer simulating open up the way to understanding the precepts of polymer operation in corrosive and bioactive media.     

Verified global optimization with GloptLab

GloptLab is a testing and development platform for solving quadratic constraint satisfaction problems, written in MATLAB. All applied methods are rigorous, hence it is guaranteed that no feasible point is lost. Some emphasis is given to finding a bounded initial box containing all feasible points, in cases where other complete solvers rely on non-rigorous heuristics. The algorithms implemented in GloptLab are used to reduce the search space: scaling, constraint propagation, linear relaxations, strictly convex enclosures, conic methods, and branch and bound. From the method repertoire custom made strategies can be built, with a user friendly graphical interface. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Albatrellus confluens (Alb. & Schwein.) Kotl. & Pouz.: Natural Fungal Compounds and Synthetic Derivatives with In Vitro Anthelmintic Activities and Antiproliferative Effects against Two Human Cancer Cell Lines

Neglected tropical diseases affect the world’s poorest populations with soil-transmitted helminthiasis and schistosomiasis being among the most prevalent ones. Mass drug administration is currently the most important control measure, but the use of the few available drugs is giving rise to increased resistance of the parasites to the drugs. Different approaches are needed to come up with new therapeutic agents against these helminths. Fungi are a source of secondary metabolites, but most fungi remain largely uninvestigated as anthelmintics. In this report, the anthelmintic activity of Albatrellus confluens against Caenorhabditis elegans was investigated using bio-assay guided isolation. Grifolin (1) and neogrifolin (2) were identified as responsible for the anthelmintic activity. Derivatives 4–6 were synthesized to investigate the effect of varying the prenyl chain length on anthelmintic activity. The isolated compounds 1 and 2 and synthetic derivatives 4–6, as well as their educts 7–10, were tested against Schistosoma mansoni (adult and newly transformed schistosomula), Strongyloides ratti, Heligmosomoides polygyrus, Necator americanus, and Ancylostoma ceylanicum. Prenyl-2-orcinol (4) and geranylgeranyl-2-orcinol (6) showed promising activity against newly transformed schistosomula. The compounds 1, 2, 4, 5, and 6 were also screened for antiproliferative or cytotoxic activity against two human cancer lines, viz. prostate adenocarcinoma cells (PC-3) and colorectal adenocarcinoma cells (HT-29). Compound 6 was determined to be the most effective against both cell lines with IC₅₀ values of 16.1 µM in PC-3 prostate cells and 33.7 µM in HT-29 colorectal cells.     

Numerical semigroups generated by primes

Semigroup Forum - Let $$p_1=2, p_2=3, p_3=5, \ldots$$ be the consecutive prime numbers, $$S_n$$ the numerical semigroup generated by the primes not less than $$p_n$$ and $$u_n$$ the largest...     

CaII,YbII and SmII Bis(Amido) Complexes Coordinated by NHC Ligands: Efficient Catalysts for Highly Regio- and Chemoselective Consecutive Hydrophosphinations with PH3

The first example of intermolecular hydrophosphination of styrene, 2-vinylpyridine and phenylacetylene with PH₃ catalyzed by bis-(amido) complexes [(Me₃Si)₂N]₂M(NHC)₂ (M=Ca, Yb, Sm) coordinated by NHC ligands is described. The reactions of styrene with PH₃ proceed under mild conditions in quantitative yields to afford only anti-Markovnikov product and allow for the chemoselective synthesis of primary, secondary and tertiary phosphines. Addition of phenylacetylene to PH₃ regardless the initial molar substrates ratio results in the exclusive formation of a tertiary tris-(Z-styryl)-phosphine. Crucial effect of the Lewis base coordinated to the metal ion in precatalyst on catalytic activity in styrene hydrophosphination with PH₃ was demonstrated. Free NHCs were also found to be able to promote addition of PH₃ to styrene, however they provide much lower reaction rates compared to the metal complexes.     

Experimental study of X-ray charge density and the selection of reference points for a source function in η6-(2-methyl-1,4-dihydro-2H-3,1-benzoxazine)tricarbonylchromium(0)

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