Synthese von 2,7-Dioxa-isotwistan und 2,7-Dioxatwistan. Vorläufige Mitteilung

The syntheses of 2,7-dioxa-isotwistane ( 14 ), 2,7-dioxa-twistane ( 19 ), and some of their derivatives ( 6 – 13 and 15 – 18 ) are described. The twistane-skeleton was obtained by a molecular rearrangement starting from the iodo-iso-twistane compound 8 .     

Do ion tethered functional groups affect IL solvent properties? The case of sulfoxides and sulfones

The covalent incorporation of functional groups-specifically sulfoxide and sulfone-into the cation of imidazolium ionic liquids leads to significant, quantifiable changes in solvent parameters which in turn have important effects on the bulk properties of the materials.     

Impact of Substitution Pattern and Chain Length on the Thermotropic Properties of Alkoxy-Substituted Triphenyl-Tristriazolotriazines

Tristriazolotriazines (TTTs) with a threefold alkoxyphenyl substitution were prepared and studied by DSC, polarized optical microscopy (POM) and X-ray scattering. Six pentyloxy chains are sufficient to induce liquid-crystalline behavior in these star-shaped compounds. Thermotropic properties of TTTs with varying substitution patterns and a periphery of linear chains of different lengths, branching in the chain and swallow-tails, are compared. Generally, these disks display broad and stable thermotropic mesophases, with the tangential TTT being superior to the radial isomer. The structure–property relationships of the number of alkyl chains, their position, length and structure were studied.     

Substituierte 9-Oxabicyclo[4.2.1]- und 9-Oxabicyclo[3.3.1]nonane IV. endo,endo-2,5-Dihydroxy-9-oxabicyclo[4.2.1]nonan,endo, endo-, endo,exo- und exo,exo-2,6-Dihydroxy sowie endo,exo-2,7-Dihydroxy-9-oxabicyclo[3.3.1]nonan; Darstellung und Umwandlungsprodukte

The synthesis of the following compounds and reaction products thereof are described: endo, endo-2,5-dihydroxy-9-oxabicyclo[4.2.1]nonane ( 3–5 ), epimeric 2,6-dihydroxy-9-oxabicyclo[3.3.1]nonanes (endo, endo: 6–8 , exo, exo: 29–32 , and endo, exo: 43–45 ), and endo, exo 2,7-dihydroxy-9-oxabicyclo[3.3.1]nonane ( 46–50 ).     

Minimal enclosing parallelepiped in 3D

We investigate the problem of finding a minimal volume parallelepiped enclosing a given set of n three-dimensional points. We give two mathematical properties of these parallelepipeds, from which we derive two algorithms of theoretical complexity O(n⁶). Experiments show that in practice our quickest algorithm runs in O(n²) (at least for n10⁵). We also present our application in structural biology.     

Oxygen species adsorbed on CeX zeolites identified by ESR spectroscopy

Two kinds of paramagnetidc O^?₂ ions have been identified by contacting molecular oxygen with CeX zeolite heat treated at 200°C in vacuo. The first O^?₂ species corresponds to the usual O^?₂ ions adsorbed on cerium oxide with the following parameters: g₁ = g_? ≈ 2.035 ± 0.002, g₂ = g₃ = g_⊥ = 2.0095 ± 0.0005 and a hyperfine pattern of six and eleven lines centred about g₃ and split by about 78 Oe, the other two components being not resolved. The second paramagnetic species of much higher intensity (larger by 2 or 3 orders of magnitude) presents rather ESR parameters and hyperfine structure. One has: g₁ = 2.0242, g₂ = 2.0208 and g₃ = 2.0112 ± 0.0003; c₁ = 24 ± 3, c₂ = 66 ± and c₃ = 12 ± 3 Oe. The six and eleven hyperfine line pattern which has been observed shows that the unpaired spin is qually distributed between two oxygen nuclei. The g tensor values are interpreted in terms of almost complete averaging of g₁ and g₂ components due to rotational motion at ?196°C about axis (3 (χ_ξ). The species is attributed to O^?₂ ion formed according to the equilibrium:

. The Ce ions are located in cationic sites SII within the zeolite supercages and are only weakly bonded to the oxygen leading to rotational motion and to case of desorption, the species reversibly disappearing by outgassing at room temperature.     

A new dissimilarity measure for comparing labeled graphs

We use spectral graph theory to compare graphs that share the same node set, taking into account global graph structures. We propose a general framework using eigendecomposition of graph Laplacians. We show its special cases and propose a new dissimilarity measure that avoid problems of spectral analysis. The new dissimilarity emphasizes the importance of small eigenvalues which are known to carry the main information on graphs. General properties of the dissimilarity are discussed. The dissimilarity provides an efficient and intuitive tool for graph analysis.     

The Conditional-Potts Clustering Model

This article presents a Bayesian kernel-based clustering method. The associated model arises as an embedding of the Potts density for class membership probabilities into an extended Bayesian model for joint data and class membership probabilities. The method may be seen as a principled extension of the super-paramagnetic clustering. The model depends on two parameters: the temperature and the kernel bandwidth. The clustering is obtained from the posterior marginal adjacency membership probabilities and does not depend on any particular value of the parameters. We elicit an informative prior based on random graph theory and kernel density estimation. A stochastic population Monte Carlo algorithm, based on parallel runs of the Wang–Landau algorithm, is developed to estimate the posterior adjacency membership probabilities and the parameter posterior. The convergence of the algorithm is also established. The method is applied to the whole human proteome to uncover human genes that share common evolutionary history. Our experiments and application show that good clustering results are obtained at many different values of the temperature and bandwidth parameters. Hence, instead of focusing on finding adequate values of the parameters, we advocate making clustering inference based on the study of the distribution of the posterior adjacency membership probabilities. This article has online supplementary material.     

The effect of CpG-ODN on antigen presenting cells of the foal

Background  

Cytosine-phosphate-guanosine oligodeoxynucleotide (CpG-ODN) has been used successfully to induce immune responses against viral and intracellular organisms in mammals. The main objective of this study was to test the effect of CpG-ODN on antigen presenting cells of young foals.