Time saving fluid dynamic predictions in a wetting-drying process: A hypothesis for vertisols

This paper is aimed at investigating the effect of the initial water content in a vertisol sample on the whole wetting-drying process leading the system to a change in volume. In order to do this, an experimental setup was realized and employed with very thin soil layers wetted from below (“per ascensum”). The results show that the effect of the initial water content on the swelling-shrinkage process is to shift the corresponding curve e-ϑ towards bigger-smaller values of the humidity but does not seem to affect the dynamics of the process. The text was submitted by the authors in English.     

First measurement of the ϱ spectral function in nuclear collisions

The NA60 experiment at the CERN SPS has studied low-mass muon pairs in 158 A GeV In–In collisions. A strong excess of pairs is observed above the yield expected from neutral meson decays. The unprecedented sample size close to 400000 events and the good mass resolution of about 2% made it possible to isolate the excess by subtraction of the decay sources. The shape of the resulting mass spectrum shows some non-trivial centrality dependence, but is largely consistent with a dominant contribution from π⁺π^-→ϱ→μ⁺μ^- annihilation. The associated ϱ spectral function exhibits considerable broadening, but essentially no shift in mass. The p_T-differential mass spectra show the excess to be much stronger at low p_T than at high p_T. The results are compared to theoretical model predictions; they tend to rule out models linking hadron masses directly to the chiral condensate. PACS 25.75.-q; 12.38.Mh; 13.85.Qk     

Multi-parton cross sections at hadron colliders

We present an alternative method to calculate cross sections for multi-parton scattering processes in the standard model at leading order. The helicity amplitudes are computed using recursion relations in the number of particles, based on the Dyson–Schwinger equations, whereas the summation over colour and helicity configurations is performed by Monte Carlo methods. The computational cost of our algorithm grows asymptotically as 3ⁿ, where n is the number of particles involved in the process, as opposed to the n!-growth of the Feynman diagram approach. Typical results for the total cross section, the differential distributions of the invariant masses and the transverse momenta of the partons are presented and cross checked by explicit summation over colours.     

Copolymers of acrylic acid with urea

Composition and rheological characteristics of aqueous solutions of acrylic acid/urea copolymers were studied, including the composition dependences of the equivalent conductivity and viscosity.     

The simulation of molecular and organic devices: a critical review and look at future developments

Molecular devices have lately attracted increased attention due to some appealing features such as their low production cost, flexibility in the substrate choice, possibility of large area deployment, and possibly higher integration capabilities. Starting from a series of results obtained from our groups, we critically review the state-of-the-art in the field of simulation of organic and molecular systems, by analyzing and comparing existing approaches, and looking at the open problems and possible solutions and future developments. PACS 72.80.Le     

Synthesis and characterization of model 3‐miktoarm star copolymers of poly(dimethylsiloxane) and poly(2‐vinylpyridine)

3‐Miktoarm star copolymers, 3μ‐D₂V, with two poly(dimethylsiloxane) (PDMS) and one poly(2‐vinylpyridine) (P2VP) arm, were synthesized by using anionic polymerization–high vacuum techniques and (chloromethylphenylethyl)methyl dichlorosilane, heterofunctional linking agent, with two SiCl groups and one CH₂Cl group. The synthetic strategy involves the selective reaction of the two ? SiCl groups with PDMSOLi living chains, followed by reaction of the remaining chloromethyl group with P2VPLi. Combined molecular characterization results (size exclusion chromatography, membrane osmometry, and ¹H NMR spectroscopy) revealed a high degree of structural and compositional homogeneity. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 614–619, 2006     

Synthesis and properties of thermosetting polymers from a phosphorous‐containing fatty acid derivative

A new phosphorous‐containing fatty acid diepoxide was obtained from 10‐undecenoyl chloride and 10‐(2′,5′‐dihydroxyphenyl)‐9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide and crosslinked with 4,4′‐diaminodiphenylmethane and bis(m‐aminophenyl)methylphosphine oxide. The properties of the thermosetting materials were evaluated by differential scanning calorimetry, dynamic mechanical thermal analysis, thermogravimetric analysis, and limiting oxygen index (LOI). Thermal and thermooxidative degradation was studied by gas chromatography/mass spectrometry, FTIR, ³¹P magic angle spinning NMR spectroscopy, and scanning electron microscopy. LOI values indicate good flame‐retardant properties that are related to the formation of a protective phosphorous‐rich layer that slowed down the degradation and prevented it from being total. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5630–5644, 2006     

Postmodification of poly(9‐alkyl‐9H‐carbazole‐2,7‐diyl)s as a route to new main‐chain‐functionalized carbazole polymers

The postmodification of poly[9‐(2‐hexyldecyl)‐9H‐carbazole‐2,7‐diyl] ( P1 ) upon its reaction with N‐bromosuccinimide affords exclusive and full bromination of the 3,6‐positions of the carbazole repeat units to yield poly[3,6‐dibromo‐9‐(2‐hexyldecyl)‐9H‐carbazole‐2,7‐diyl] ( P2 ). Brominated polymer P2 can be used as a precursor for further functionalization at the 3,6‐positions with the desired functional group to afford other useful polymers. Polymer P2 has hence been reacted with copper(I) cyanide to afford poly[3,6‐dicyano‐9‐(2‐hexyldecyl)‐9H‐carbazole‐2,7‐diyl] ( P3 ). Full substitution of the bromide groups with nitrile‐functional groups has been achieved. The preparation and structural characterization of polymers P2 and P3 are presented together with studies on their electronic conjugation and photoluminescence properties. Cyclic voltammetry studies on polymer P3 indicate that the new polymer is easier to reduce (n‐dope) but more difficult to oxidize than its unsubstituted counterpart ( P1 ) as a result of the introduction of the electron‐withdrawing nitrile‐functional groups at the 3,6‐positions on the carbazole repeat units on the polymer chains. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3336–3342, 2006     

Cyclolinear polysiloxanes. II. Crosslinking and characterization

The synthesis and characterization of two groups of novel networks prepared from cyclolinear polysiloxanes are described. The first group of networks from cyclolinear polysiloxanes (N‐CLPSs) was synthesized by the hydrosilation of vinyl‐terminated cyclolinear polyorganosiloxanes [prepared from diacetoxydiethyltetramethylcyclotetrasiloxane (D₄Et₂OAc₂) or diacetoxytriethylpentamethylcyclopentasiloxane (D₅Et₃OAc₂)] with a copolymer of dimethylsiloxane and methylhydrosiloxane as the crosslinking agent. Hydrosilation was effected with a platinum carbonyl catalyst with a cyclovinylsiloxane moderator. The second group of networks (N‐eCLPSs) was prepared similarly with extended cyclolinear polysiloxanes. The mechanical properties of the novel networks were comparable to those of polydimethylsiloxane networks (N‐PDMS). The oxygen permeabilities were similar to or slightly higher than that of N‐PDMS. The glass‐transition temperatures of D₄Et₂OAc₂‐ and D₅Et₃OAc₂‐based N‐CLPSs were ?67.8 and ?90.8 °C, respectively, whereas the incorporation of polydimethylsiloxane spacers into similar N‐eCLPSs lowered their glass‐transition temperatures to ?109.7 and ?115.0 °C. Upon heating to 800 °C in air, N‐CLPSs yielded more residue than N‐eCLPSs, which in turn yielded more residue than N‐PDMS. These results may have been due to the presence of T units in the cyclic siloxane units, which may have inhibited chain degradation or the formation of volatile products. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4053–4062, 2006     

Gold ultra-microelectrode arrays: application to the steady-state voltammetry of hydroxide ion in aqueous solution.

Gold ultra-microelectrode arrays are used to explore the electrochemical oxidation of hydroxide ions and are shown to be analytical useful. Two types of ultra-microelectrode arrays are used; the first consist of 256 individual electrodes of 5 microm in radius, 170 of which are electrochemically active in a cubic arrangement which are separated from their nearest neighbour by a distance of 100 microm. The second array compromises 2597 electrodes of 2.5 microm in radius and of which 1550 of which are electrochemically active in a hexagonal arrangement separated by the nearest neighbour by 55 microm. Well defined voltammetric waves are found with peak currents proportional to the concentration of hydroxide ions in the range 50 microM to 1 mM. Detection limits of 20 microM using the 170 ultra-microelectrode and 10 microM with the 1550 ultra-microelectrode array are shown to be possible but with a higher sensitivity of 4 mA M(-1) observed using the 1550 ultra-microelectrode array compared to 1.2 mA M(-1) with the 170 ultra-microelectrode array.