Does the Gaussian thermostat maximize the phase-space compression factor?

A recent hypothesis of D. J. Evans and A. Baranyai according to which the Gaussian thermostat maximizes the average phase-space compression factor in nonequilibrium steady states is analyzed for a dilute gas under uniform shear flow. Three routes have been followed: (i) an exact solution of the Bhatnagar-Gross-Krook kinetic equation for arbitrary shear rate, (ii) an exact solution of the Boltzmann equation through super-Burnett order, and (iii) a numerical solution of the Boltzmann equation for finite shear rates. The results show that the above hypothesis does not exactly hold for arbitrary shear rates, although the thermostat that maximizes is close to the Gaussian one. In addition, the influence of the thermostat considered on the nonlinear shear viscosity is also analyzed.     

Constructive approach to logics of physical systems: Application to EPR case

A constructive approach to logics of physical systems, according to which families of propositions about physical systems are not defined in an axiomatic way, but are built up in the course of experiments, is proposed. Several ways of joining Boolean algebras of propositions obtained in single experiments are studied. The proposed approach is applied to study families of propositions encountered in EPR-type experiments. Two examples of such experimental families of EPR propositions are studied and they are compared with two theoretical families of EPR propositions in the literature.     

Adsorption of Cu(II) on porous chitosan membranes functionalized with histidine

The ability of chitosan to form complexes with bivalent metal ions has been broadly explored in the literature. The present work investigates the influence of functionalization of macroporous chitosan membranes with histidine on their ability to remove copper ions from aqueous solution in the range of pH 4–6. The maximum adsorption capacity for Cu(II) ion was 2.5 mmol metal/g pristine chitosan membranes. Under this condition, no influence of membrane porosity was observed. However, for membranes with immobilized histidine, the porosity was shown to be a factor that affects the maximum adsorption capacity, with values ranging from 2.0 to 3.0 mmol metal/g chitosan. These results indicate that the immobilization of histidine on porous chitosan membranes presents synergy with porosity in the ability to complex Cu(II) ions. This synergy may be negative or positive, depending on the initial membrane porosity.     

Kinetic study of dipivaloylmethane by ozawa method

The lanthanidic complexes of general formula Ln(C₁₁H₁₉O₂)₃ were synthesized and characterized by elementary analysis, infrared absorption espectroscopy, thermogravimetry (TG) and differential scanning calorimetry (DSC). The reaction of thermal decomposition of complexes has been studied by non-isothermal and isothermal TG. The thermal decomposition reaction of complexes began in the solid phase for Tb(thd)₃, Tm(thd)₃ and Yb(thd)₃ and in the liquid phase for Er(thd)₃ and Lu(thd)₃, as it was observed by TG/DTG/DSC superimposed curves. The kinetic model that best adjusted the experimental isothermal thermogravimetric data was the R1 model. Through the Ozawa method it was possible to find coherent results in the kinetic parameters and according to the activation energy the following stability order was obtained: Tb(thd)₃>Lu(thd)₃>Yb(thd)₃>Tm(thd)₃>Er(thd)₃ This revised version was published online in August 2006 with corrections to the Cover Date.     

Comparative study of the properties of post-consumption high density polyethylene used in the injection process

The high-density polyethylene, thermoplastic widely-used in the production of industrial domestic utilities, was collected in two situations: virgin high-density polyethylene (JV 060) and post-consumption high-density polyethylene (with features of low-density polyethylene). After collecting the samples, they were submitted to natural aging with the quantification of the incident solar radiation for 180 days. The samples were characterized by melt flow index, differential scanning calorimetry, tensile strength, rupture load, elongation at break and infrared. The results showed that after 180 days of exposure the virgin high-density polyethylene presented physical properties similar to the post-consumption polyethylene. This revised version was published online in August 2006 with corrections to the Cover Date.     

Probing the mechanism of the Petasis olefination reaction by atmospheric pressure chemical ionization mass and tandem mass spectrometry

Atmospheric pressure chemical ionization mass (APCI-MS) and tandem mass spectrometry (APCI-MS/MS) is used to probe the mechanism of the Petasis olefination reaction. Oxatitanacycle intermediates 4 were transferred from solution to the gas phase, detected as 4H+ by APCI-MS with characteristic Ti-isotopic patterns, and structurally characterized by APCI-MS/MS. Detection of 4H+, which upon collision activation dissociates to both 3H+ and Cp(2)TiOH+, fully supports the Hughes mechanism as depicted above. [reaction: see text]     

Influence of ultrasonic waves on phosphate determination by the molybdenum blue method

Polymeric bonds between molybdate monomeric ions in acidic medium were broken by 40 kHz ultrasonic wave irradiation, improving the reaction kinetics with o-phosphate in the presence of ascorbic acid. It could be assumed that the ultrasonic wave irradiation of molybdate solution in acidic medium during 1.0 min was sufficient to increase the rate of the molybdenum blue formation. The approach was applied to the o-phosphate determination in natural waters. Precise results were obtained in the range from 0.05 to 0.50 μg ml⁻¹ (r=0.9994; N=6), and the detection limit was estimated as 0.027 μg ml⁻¹ PPO₄. Advantages over the classical analogous procedure are emphasised.     

Synthesis and luminescent properties of Eu-complexes with 2-acyl-1,3-indandionates (ACIND) and TPPO ligands: The first X-ray structure of Eu–ACIND complex

Europium complexes presenting general formulas [Eu(ACIND)₃(H₂O)₂] and [Eu(ACIND)₃(TPPO)₂] have been synthesized and characterized. In these formulas ACIND is stands for the ligands 2-acetyl-1,3-indandionate (AIND), 2-isovaleryl-1,3-indandionate (ISOVIND) or 2-benzyl-1,3-indandionate (BIND). The [Eu(ISOVIND)₃(H₂O)(EtOH)] complex was also prepared and its structure determined by single crystal X-ray analysis, showing that this complex crystallize in a monoclinic space group P2₁/n with the water molecules bridging through the hydrogen bond. The Eu(III) ion is eight-coordinate in a bicapped trigonal prismatic geometry defined by the oxygen donor atoms with a site of symmetry close to C_2ν. Isovaleryl groups in the ISOVIND molecules in the structure are disordered over two positions of the europium complex. Carbon atoms in ethanol molecule are disordered by the thermal vibration. Photoluminescence properties of these complexes in solid state were investigated both experimentally and theoretically, suggesting an efficient ligand-to-metal intramolecular energy transfer process.