Density and Speed of Sound for Binary Mixtures of a Cyclic Ether with a Butanol Isomer

Densities and speeds of sound of the binary mixtures 1,3-dioxolane + 1-butanol, 1,3-dioxolane + 2-butanol, 1,4-dioxane + 1-butanol, and 1,4-dioxane + 2-butanol have been measured at 25 and 40°C. The excess molar volumes and excess isentropic compressibility coefficients were calculated from experimental data and fitted to a Redlich–Kister polynomial function. Results were analyzed in terms of molecular interactions and compared with literature data.     

Current-particle matrix elements in ACD

Using anisotropic chromo-dynamics (ACD) we compute the relevant one-particle matrix elements of the electroweak currents. Good agreement with experiments is found for light mesons, while some discrepancies for heavy mesons (?, ?′) are well understood within the limitations of our approximations.     

The role of chirality in demarcating confinement from liberation

This paper suggests that confinement implies a “bifurcation” between chiral and vector-like worlds. The analysis of the Dyson equations of abelian gauge theories shows that the confining ansatz $\text{D(q}{}^2\text{) ～}\text{1}\text{q}{}^4$ is inconsistent with a chiral interaction.     

Synthesis and characterization of two novel tin(IV) compounds containing 12‐membered metallarings

12‐Chloro‐12‐n‐butyl‐1,11‐dioxa‐4,8‐ dithia‐12‐stannacyclododecane ( 3a ) and 12‐chloro‐ 12‐n‐butyl‐1,4,8,11‐tetrathia‐12‐stannacyclododecane ( 3b ) have been prepared by reacting n‐butyltin trichloride with 1,11‐dioxa‐4,8‐dithiaundecane and 1,4,8,11‐tetrathiaundecane, respectively. Complexes 3a,b were characterized by elemental analyses, IR, electron impact mass spectrometry, and multinuclear NMR (¹H, ¹³C, and ¹¹⁹Sn). The spectroscopic data are consistent with bonding of the ligands through both sulfur and oxygen atoms in 3a and through all sulfur atoms in 3b to the Sn(IV) center. We suggest hexacoordination around the Sn atoms. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:451–453, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20040     

Analytic continuation in two-color QCD: new results on the critical line

We test the method of analytic continuation from imaginary to real chemical potential in two-color QCD, which is free from the sign problem. In particular, we consider the analytic continuation of the critical line to real values of the chemical potential.     

Aggregation Behavior of Pyridinium-Based Ionic Liquids in Aqueous Solution

Aggregation of the ionic liquids 1-butylpyridinium tetrafluoroborate, 1-butylpyridinium triflate, 1-butyl-2-methylpyridinium tetrafluoroborate, 1-butyl-3-methylpyridinium tetrafluoroborate, 1-butyl-4-methylpyridinium tetrafluoroborate, 1-butyl-3-methylpyridinium dicyanamide, and 1-octyl-3-methylpyridinium tetrafluoroborate in aqueous solution has been characterized at 298.15 K through density, ρ, speed of sound, u, and conductivity, σ, measurements. In addition, apparent molar volumes, V _φ , and isentropic compressibilities, κ _s , have been calculated from the experimental data. To characterize the formation of aggregates, the critical aggregation concentration of the ionic liquids, cac, the degree of ionization of the aggregates, β, and the standard Gibbs energy of aggregation, DG_m^°\Delta G_{\mathrm{m}}^{\circ}, have been obtained, with good agreement between results derived from the different methods. The dependence on the structural variation of these ions has been analyzed by comparing the results obtained for this series of ionic liquids.     

High order upwind scheme for modelling turbulent shallow water flow in hydraulic structures

An unstructured finite volume model for quasi-2D free surface flow with wet-dry fronts and turbulence modelling is presented. The convective flux is discretised with either a an hybrid second-order/first-order scheme, or a fully second order scheme, both of them upwind Godunov's schemes based on Roe's average. The hybrid scheme uses a second order discretisation for the two unit discharge components, whilst keeping a first order discretisation for the water depth [2]. In such a way the numerical diffusion is much reduced, without a significant reduction on the numerical stability of the scheme, obtaining in such a way accurate and stable results. It is important to keep the numerical diffusion to a minimum level without loss of numerical stability, specially when modelling turbulent flows, because the numerical diffusion may interfere with the real turbulent diffusion. In order to avoid spurious oscillations of the free surface when the bathymetry is irregular, an upwind discretisation of the bed slope source term [4] with second order corrections is used [2]. In this way a fully second order scheme which gives an exact balance between convective flux and bed slope in the hydrostatic case is obtained. The k – ε equations are solved with either an hybrid or a second order scheme. In all the numerical simulations the importance of using a second order upwind spatial discretisation has been checked [1]. A first order scheme may give rather good predictions for the water depth, but it introduces too much numerical diffusion and therefore, it excessively smooths the velocity profiles. This is specially important when comparing different turbulence models, since the numerical diffusion introduced by a first order upwind scheme may be of the same order of magnitude as the turbulent diffusion. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Speeds of sound and isentropic compressibil- ities of cyclohexane+1,3-dioxolane+2-butanol and n-hexane+1,3-dioxolane+2-butanol

Speeds of sound of the ternary mixtures cyclohexane+1,3-dioxolane+2-butanol and n-hexane+1,3-dioxolane+2-butanol have been measured at the temperatures of 298.15 and 313.15 K. Isentropic compressibilities and excess isentropic compressibilities have been calculated from experimental data. We have also compared the experimental isentropic compressibilities with calculated values from the free length theory and the collision factor theory. Experimental results show positive values of excess isentropic compressibilities in almost the whole composition range for the ternary mixture containing cyclohexane, meanwhile they are negative for the mixture containing n-hexane. Such different behaviour of these systems is related to the large free volume shown by n-hexane. This revised version was published online in July 2006 with corrections to the Cover Date.     

On the value ofR_{e^ + e^ - }

We calculate the ratioR in the framework of Anisotropic Chromo-Dynamics (ACD), a recently proposed approach to strong interactions, and we show that asymptotically the Quark Parton Model value is recovered. Scaling violations due to the quark-masses and to the structure of the \(q\bar q\) -potential are also calculated.     

Design and Synthesis of Aviram–Ratner‐Type Dyads and Rectification Studies in Langmuir–Blodgett (LB) Films

The design and synthesis of Aviram–Ratner‐type molecular rectifiers, featuring an anilino‐substituted extended tetracyanoquinodimethane (exTCNQ) acceptor, covalently linked by the σ‐spacer bicyclo[2.2.2]octane (BCO) to a tetrathiafulvalene (TTF) donor moiety, are described. The rigid BCO spacer keeps the TTF donor and exTCNQ acceptor moieties apart, as demonstrated by X‐ray analysis. The photophysical properties of the TTF‐BCO‐exTCNQ dyads were investigated by UV/Vis and EPR spectroscopy, electrochemical studies, and theoretical calculations. Langmuir–Blodgett films were prepared and used in the fabrication and electrical studies of junction devices. One dyad showed the asymmetric current–voltage (I–V) curve characteristic for rectification, unlike control compounds containing the TTF unit but not the exTCNQ moiety or comprising the exTCNQ acceptor moiety but lacking the donor TTF part, which both gave symmetric I–V curves. The direction of the observed rectification indicated that the preferred electron current flows from the exTCNQ acceptor to the TTF donor.