Optical Transmittance of AlOOH/Al2O3 Porous Gel Preforms

Monolithic boehmite gel discs (1.2 cm) of 0.12 and 0.25 mm thickness were examined by DTA, TGA, measurements of surface area, pore volume, pore radius and on-line measurements of optical transmittance from room temperature (RT) to 1200°C. The optical transmittance reflects the water liberation out of sample discs and provides information on processes associated with the phase/microstructure changes taking place such as the crystallization of the -alumina grains.     

Two Positions of Potassium in Chemically Doped C(60) Peapods: An in situ Spectroelectrochemical Study

The state of doping of fullerene peapods C60@SWCNT treated with K vapor was studied by in situ Raman spectroelectrochemistry. For all samples under study, a heavy chemical n doping was proved by the vanishing of the radial breathing mode and the downshift of tangential displacement mode. The K-treated peapods remain partly doped even if they are exposed to humid air. The Ag(2) mode of intratubular fullerene in K-doped peapods in contact with air was still redshifted as referred to its position in pristine peapods. Potassium inserted into the peapods is the reason for the air-insensitive residual doping, which can be removed only by electrochemical oxidation. This indicates the presence of two positions of potassium in doped sample.     

Radikalreaktionen an N-Heterocyclen,X. Radikalreaktionen cyclischer 1,2-Diacylhydrazine

Free Radical Reactions of N-Heterocyclic Compounds, X^[1]. – Radical Reactions of Cyclic 1,2-Diacylhydrazines Cyclic 1,2-diacylhydrazyls 3 have been detected by ESR spectroscopy during oxidation of the corresponding NH compounds 2 . The N coupling constants are determined and confirmed by simulation and by ¹⁵N labeling. The hydrazyls 3 react by dimerization to the corresponding tetrazanes of type 5 or by β scission to the diacyl azo compounds 4 and C radicals. The β scission of the radicals 3 is elucidated by UV/Vis detection of the azo compound 4b and reaction of 4b to Diels-Alder adducts. The alkyl radicals are trapped by nitrosobenzene ( 8 ) (ESR).     

Electrochemical nanostructuring of fullerene films--spectroscopic evidence for C60 polymer formation and hydrogenation

Electrochemical reduction of ordered C60 fullerene films in aqueous solution was studied by AFM, FTIR and Raman spectroscopy, mass spectrometry and elastic recoil detection analysis. During the irreversible reduction process the film morphology changed from a heteroepitaxial (111) surface to a nanostructured array with clusters of 20 to 50 nm lateral size on average. On the molecular level the initial C60 underwent electrochemical reactions to form C60 polymers and hydrogenated C60. Chemical follow-up reactions of electrochemically formed C60- with water are responsible for the different reduction behaviour of C60 films in aqueous solution compared to C60 reduction in organic solvents and to C60 doping with alkali metals. Based on the spectroscopic analysis a reaction scheme accounting for the chemical processes at the C60 / aqueous electrolyte interface is presented.     

Unexpected ring closure reaction of α,β‐unsaturated ketones with aminoguanidine. entry into 1,3,5‐trisubstituted pyrazoles

Cyclizations of α,β‐unsaturated ketones with aminoguanidine under neutral conditions were examined. In contrast to literature reports of 1,2,4‐triazines as reaction products, formation of 5‐aryl‐4,5‐dihy‐dro‐3‐methyl‐1H‐pyrazole‐1‐carboximidamides and carboxamides was observed. An explanation based on the Hard‐Soft Acid‐Base principle is presented and the probable causes of divergent reaction pathways are discussed.     

An algebraic characterization of geodetic graphs

We say that a binary operation * is associated with a (finite undirected) graph G (without loops and multiple edges) if * is defined on V(G) and uv E(G) if and only if u v, u * v = v and v * u = u for any u, v V(G). In the paper it is proved that a connected graph G is geodetic if and only if there exists a binary operation associated with G which fulfils a certain set of four axioms. (This characterization is obtained as an immediate consequence of a stronger result proved in the paper).     

Haplotype inferring via galled-tree networks using a hypergraph covering problem for special genotype matrices

Since exact determination of haplotype blocks is usually not possible, it is desirable to develop a haplotyping method which can account for recombinations. A natural candidate for such a method is haplotyping via phylogenetic networks or their simplified version: galled-tree networks. In earlier work we characterized the existence of the galled-tree networks. Building on this, we reduce the problem of haplotype inferring via galled-tree networks to a hypergraph covering problem for genotype matrices satisfying a combinatorial condition. Our experiments on actual data show that this condition is almost always satisfied when the percentage of minor alleles for each SNP reaches at least 30%.     

Closure for the property of having a hamiltonian prism

We prove that a graph G of order n has a hamiltonian prism if and only if the graph Cl_4n/3–4/3(G) has a hamiltonian prism where Cl_4n/3–4/3(G) is the graph obtained from G by sequential adding edges between non‐adjacent vertices whose degree sum is at least 4n/3–4/3. We show that this cannot be improved to less than 4n/3–5. © 2006 Wiley Periodicals, Inc. J Graph Theory 54: 209–220, 2007     

The fourth power of the Fermat quotient

Let p be an odd prime and qp(a)=(ap−1−1)/p be the Fermat quotient with base a, p?a. The main purpose of this paper is to investigate the fourth power problem of qp(2) and deduce an explicit formula represented by a linear combination of Mirimanoff polynomial values.