The long‐time behaviour of the thermoconvective flow in a porous medium

For the Boussinesq approximation of the equations of coupled heat and fluid flow in a porous medium we show that the corresponding system of partial differential equations possesses a global attractor. We give lower and upper bounds of the Hausdorff dimension of the attractor depending on a physical parameter of the system, namely the Rayleigh number of the flow. Numerical experiments confirm the theoretical findings and raise new questions on the structure of the solutions of the system. Copyright © 2004 John Wiley & Sons, Ltd.     

Monitoring genomic alterations with a panel of oligonucleotide probes specific for various simple repeat motifs

Germline and somatic instability of the human genome was studied, using synthetic oligonucleotides specific for simple repeat motifs. The following probes were used: (GTG)5, (GACA)4, (GATA)4, (CT)8, (TTAGGG)3, (GT)8, (GAA)6 and (GGAT)4. Each of them is unique with respect to the target regions recognized in the genome. Thus compilation of the various fingerprint data provides a complex map of the genome (and its deviations). While the fingerprints of differentiated somatic tissues never showed any alterations, in tumor tissues (namely gliomas) many changes could be detected. Most of the latter reflect secondary karyological aberrations. In nearly one third of the gliomas, drastically amplified and apparently monomorphic DNA fragments were identified. This marker should make it possible to deal with causal pathogenetic mechanisms as well as novel diagnostic strategies.     

A decomposition result for a class of polling models

Boxma and Groenendijk have shown that the workload in polling models decomposes into two independent variables. This paper demonstrates a different type of decomposition that has an explicit multi-dimensional form. This decomposition does not apply to all polling models, but does, for example, apply to models with constant switch-over times and either exhaustive or gated service disciplines. For such models, we show that the population of customers present in the system (represented by a vector indicating the number of customers at each queue) at key time points breaks into two independent subpopulations: (1) the population of customers present in the related model with zero switch-over times; (2) another population, which is particularly easy to analyze. This result has a number of theoretical and applied implications.     

Kaon production in\bar pp interactions at c.m. energies from 200 to 900 GeV

A detailed analysis ofK _s ⁰ production in \(\bar pp\) |<2.5 the average transverse momentum is found to be 0.53±0.07 GeV/c at 200 GeV and 0.62±0.08 GeV/c at 900 GeV, which is an increase with respect to data at c.m. energies below 60 GeV. TheK _s ⁰ production cross sections in inelastic collisions are 29±4 mb at 200 GeV and 63±6 mb at 900 GeV, showing an increase compared to lower energy data. The central kaon density is found to increase as a logarithmic function of energy. At 900 GeV, where statistics are sufficient to allow one to draw conclusions, the average transverse momentum is higher in events with large charged multiplicity than in events with low multiplicity.     

Züchtung und röntgenographische Untersuchung von Einkristallen der Thiosilicate (Mn,Mg)2SiS4, (Mn,Fe)2SiS4 und (Mg,Fe)2SiS4 mit Olivinstruktur

Crystal Growth and Structure of Olivine Type Compounds (Mn, Mg)₂SiS₄, (Mn,Fe)₂SiS₄ and (Mg,Fe)₂SiS₄ Single crystals of (Mn, Mg)₂SiS₄, (Mn,Fe)₂SiS₄ and (Mg,Fe)₂SiS₄ were obtained by chemical transport reactions. Characterization of the crystals was done by electron microprobe analysis and X-ray methods. The compounds have the olivine structure with space group Pnma. Cell dimensions are a = 1267.6(1), b = 743.0(2), c = 592.7(2) pm for Mn_1,4Mg_0,6SiS₄, a = 1265.1(4), 736.1(2), c = 589.9(3) pm for Mn_1,4Fe_0,6SiS₄ and a = 1258.6(7), b = 732.9(3), c = 587.0(3) pm for Mg_1,14Fe_0,86SiS₄. Crystal structure refinement yielded different distributions of the two metal cations on the octahedral sites of the olivine structure: while Mn²⁺ and Mg²⁺ are evenly distributed over the M(1) and M(2) positions in Mn_1,4Mg_0,6SiS₄, the M(1) position is enriched in Fe²⁺ relative to M(2) in Mg_1,14Fe_0,86SiS₄.     

C-c bond formation through oxidatively induced elimination of platinum complexes--a novel approach towards conjugated macrocycles

A novel and effective method for the synthesis of conjugated macrocycles is described. By the self-assembly of conveniently accessible building blocks to a metalla-macrocycle, and subsequent C-C bond formation through elimination of transition metal units, the strained cyclodimeric terthiophene-diyne 4 -as a precursor for cyclo[8]thiophene 5- was synthesized in a good overall yield.     

Binuclear wirelike dimers based on ruthenium(II)-bipyridine units linked by ethynylene-oligothiophene-ethynylene bridges

The syntheses, structural characteristics, electrochemical behavior, ground-state spectra, photophysical properties, and transient absorption (TA) spectra in CH(3)CN solvent are reported for binuclear [(bpy)(2)Ru(bpy-E(T)(n)()E-bpy)Ru(bpy)(2)](4+) complexes, Ru(bpyT(n)bpy)Ru, where the Ru-based units are connected by alternating 3,4-dibutylthiophene (DBT')/thiophene (T') fragments linked via ethynyl groups (E) to bpy ligands at the 5-position (bpy is 2,2'-bipyridine). The ligand bpyT(3)bpy represents a module containing DBT'/T'/DBT' subunits, and bpyT(5)bpy accounts for a DBT'/T'/DBT'/T'/DBT' pattern. The syntheses and electrochemical and spectroscopic (emission and TA) properties in CH(2)Cl(2) solvent of the bpyT(n)()bpy ligands are likewise reported. The behavior of the Ru(bpyT(n)bpy)Ru dimers has been compared to that of the bpyT(n)bpy ligands and to that of a related mononuclear complex, [(bpy)(2)Ru(bpy-E-DBT')](2+), Ru(bpyDBT'). For the dimeric complexes, the electrochemical results show that the first reduction step takes place at the bpy ligand(s) bearing an ethynylene group, the first oxidation step is thiophene-centered, and further oxidation involves the metal centers, which are only weakly interacting. The photophysical and TA results for the Ru(bpyT(n)bpy)Ru dimers account for the presence of low-lying oligothiophene-centered (3)pi,pi levels, while higher-lying metal-ligand charge transfer ((3)MLCT) levels are thermally accessible only for the case of Ru(bpyT(3)bpy)Ru; the possible role of charge separation (CS) levels (from oxidation at the thiophene bridge and reduction at one of the coordinated bpy's) is also discussed.     

Octahedral Group 4 Metal Complexes That Contain Amine, Amido, and Aminopyridinato Ligands: Synthesis, Structure, and Application in alpha-Olefin Oligo- and Polymerization

The reaction of trimethylsilyl-substituted 2-aminopyridines with mixed chloro(dialkylamido)metal complexes (titanium and zirconium) leads via amine elimination to octahedral group 4 metal complexes that contain amine, amido, and aminopyridinato ligands. The X-ray crystal structure analyses of (4-Me-TMS-APy)(NMe(2))(HNMe(2))TiCl(2) (1) (crystallographic data: P2(1)/c (No. 14), monoclinic, a = 16.754(2) ?, b = 14.395(2) ?, c = 17.890(3) ?, beta = 110.28(1) degrees, Z = 8) and (6-Me-TMS-APy)(NEt(2))(HNEt(2))ZrCl(2) (2) (crystallographic data: P2(1)/n (No. 14) monoclinic, a = 10.125(1) ?, b = 16.331(1) ?, c = 15.276(2) ?, beta = 93.90(1), Z = 4) prove the compounds to be mononuclear with a cisoid arrangement of the two chloro ligands embedded in a reactive pocket determined by the steric demand of the three nitrogen containing ligands. Oligo- and polymerization studies with propene and 1-butene reveal the following results. First, 1 is a remarkably active precatalyst in contrast to the very low activity of 2. Second, MAO, a 1:1 mixture of i-Bu(3)Al/B(C(6)F(5))(3) (homogeneous polymerization) and ethylaluminum sesquichloride (if 1 is incorporated in a MgCl(2)-matrix) have shown to be the most active cocatalysts. Third, the polymers and oligomers are atactic.     

P840-Reaction Centers from Chlorobium tepidum–Quinone Analysis and Functional Reconstitution into Lipid Vesicles

Membranes of Chlorobium tepidum contain about 35, 45 and2–10 molecules of menaquinone-7, chlorobium quinone (1′-oxo-menaquinone-7) and of the polar menaquinone (probably 1′-OH-menaquinone-7) per reaction center, respectively. None of these quinones was retained during the isolation of P840-reaction centers beyond the detection limit of about 0.2 quinones per reaction center, neither in the core complex nor in functionally intact reaction center preparations. The latter is shown to catalyze the formation of an electrochemical proton gradient in the presence of ascorbate and phenazinium methosulfate, when it is incorporated into lipid vesicles.