Self-organization of sulfopolystyrene ionomers with ionic SO<Subscript>3</Subscript>Li groups in carbon tetrachloride

Association of short-chain sulfopolystyrene ionomers containing 5.2 mol % ionic SO₃Li groups in carbon tetrachloride was studied by cold neutron scattering.     

Faceting and branching in 2D crystal growth

Using atomic scale time-dependent density functional calculations we confirm that both diffusion-controlled and diffusionless crystallization modes exist in simple 2D systems. We provide theoretical evidence that a faceted to nonfaceted transition is coupled to these crystallization modes, and faceting is governed by the local supersaturation at the fluid-crystalline interface. We also show that competing modes of crystallization have a major influence on mesopattern formation. Irregularly branched and porous structures are emerging at the crossover of the crystallization modes. The proposed branching mechanism differs essentially from dendritic fingering driven by diffusive instability.     

Partitioning 2-edge-colored graphs by monochromatic paths and cycles

We present results on partitioning the vertices of 2-edge-colored graphs into monochromatic paths and cycles. We prove asymptotically the two-color case of a conjecture of Sárközy: the vertex set of every 2-edge-colored graph can be partitioned into at most 2α(G) monochromatic cycles, where α(G) denotes the independence number of G. Another direction, emerged recently from a conjecture of Schelp, is to consider colorings of graphs with given minimum degree. We prove that apart from o(|V (G)|) vertices, the vertex set of any 2-edge-colored graph G with minimum degree at least \(\tfrac{{(1 + \varepsilon )3|V(G)|}} {4}\) can be covered by the vertices of two vertex disjoint monochromatic cycles of distinct colors. Finally, under the assumption that \(\bar G\) does not contain a fixed bipartite graph H, we show that in every 2-edge-coloring of G, |V (G)| ? c(H) vertices can be covered by two vertex disjoint paths of different colors, where c(H) is a constant depending only on H. In particular, we prove that c(C ₄)=1, which is best possible.     

Synthesis of Ristriose

ABSTRACT

A new reducing trisaccharide 0-α-D-arabinofuranosyl-(1→ 2)-0-α-D-mannopyranosyl-(1→2)-0-D-glucopyranose (11), named ristriose, has been synthesized in twenty one steps, starting from D-glucose, D-mannose and D-arabinose, with an overall yield of 3.5 %.     

Asymmetric epoxidation of substituted chalcones and chalcone analogues catalyzed by α-d-glucose- and α-d-mannose-based crown ethers

The chiral monoaza-15-crown-5 lariat ethers annellated to methyl-4,6-O-benzylidene-α-d-glucopyranoside-1 or mannopyranoside 2 have been applied as phase-transfer catalysts in the epoxidation of substituted chalcones and chalcone analogues with tert-butylhydroperoxide resulting in significant asymmetric induction. It was found that the position of the substituents in the aromatic ring of the chalcone had an influence both on the chemical yields and enantiomeric excesses. The lowest enantioselectivities (62–83% ee) were found in the case of ortho-substituted model compounds. The highest ee values (ee of 83–97%) were obtained in the case of para-substituted models. From among the chalcone analogues, the maximum ee (90–92%) was detected for the model compound having α-tert-butyl- and β-aryl groups. Using glucose-based crown ether 1, formation of the (?)-enantiomer was preferred, while applying mannose-based 2 as the catalyst, the (+)-enantiomer was in excess.     

Trace elements in bovine muscle: an ongoing project for a new certified reference material

In the framework of the activities of the Community Reference Laboratory (CRL) for residues at the Istituto Superiore di Sanità (ISS) of Rome, a number of proficiency tests were performed in order to assess and improve, wherever necessary, the quality of regulatory residue analysis within the EU. In this context, a pilot study was undertaken with the purpose of ascertaining the feasibility of a project for the certification of a new reference material for trace elements in bovine muscle. On behalf of the ISS, approximately 70 kg of bovine muscle, collected at a slaughterhouse in Geel (Belgium), were freeze-dried, homogenized, stabilized and bottled under argon atmosphere by the Institute for Reference Materials and Measurements, Joint Research Centre, European Commission (IRMM-JRC-EC). Preliminary analyses were carried out with Quadrupole (Q) and High Resolution (HR) Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to evaluate the content of As, Cd, Cu and Pb, whereas the Flow Injection Mercury System (FIMS) was used to quantify Hg. Digestion of the matrix was achieved by acid-assisted microwave irradiation. The mean values of experimentally obtained data were the following (in nanograms per gram): As, 24.2±1.2; Cd, 5.48±0.29; Cu, 4765±95; Hg, 3.37±0.73; and Pb, 184±7. Subsequently, 16 National Reference Laboratories (NRLs) for residues in the Member States plus the Norwegian one and eight Italian public laboratories were accepted to participate in the project and received one bottle of the freeze-dried bovine muscle. The laboratories were requested to perform three different analytical runs (in three different days), each consisting of three individual measurements. Preliminary results showed good agreement and fair evidence for homogeneity of the entire mass, thus setting the stage for the future certification of this candidate CRM.     

Effect of atmospheric pressure variations on the <Superscript>222</Superscript>Rn activity concentration in the air of a wine cellar

We have measured the variation of atmospheric pressure and of ²²²Rn activity concentration in the air of a wine cellar with an AlphaGAURD type ionization chamber radon monitor. We have found that the ²²²Rn activity concentration varies inversely with pressure. To explain this behavior we have done model calculations. We have compared the results of model calculations with the results of experimental measurements, and we have found that the model is capable to reproduce some part of the variation of ²²²Rn activity concentration.     

Investigation of distribution of beryllium, nickel and vanadium in subsoil of Csepel-Island

In order to investigate the long-term effect of the Százhalombatta power plant on the environment of the Csepel-Island subsoil samples were collected in 55 points within 200 km². Using a microwave-assisted extraction procedure, Be, Ni and V were extracted from the soil samples by aqua regia and the metal concentrations were determined by inductively coupled plasma mass spectrometry (ICP-MS). The analytical results were evaluated by chemometric methods and interpreted considering the main mineral constituents of the subsoil.