Small-scale measurements in a partially stirred reactor

This paper describes an experimental study of a partially stirred reactor (PaSR). The reactor is a cubic box in which air (either pure or mixed with a tracer) is continuously injected through 12 jets situated in two opposite planes and impinging through the center. The flow in the reactor interior is well approximated as stationary, globally homogeneous and isotropic. Global properties of turbulent flow and passive scalar mixing are studied, in terms of length scales, characteristic times, spectra, etc. Particular attention has been paid to a proper determination of the mean value of the passive scalar variance dissipation rate 〈ε _Z 〉, in the central quasi-homogeneous zone of the reactor.     

Conserved scalar mixing in a confined-opposed-jets flow

The focus of this paper is on the mixing of a conserved passive scalar for Sc = 1 (Sc is the Schmidt number) in axisymmetric turbulence for which the initial injections of turbulent kinetic energy and scalar variance are similar. Two confined-opposed-jets (COJ) are experimentally studied through simultaneous PIV (particle image velocimetry) and PLIF (planar laser induced fluorescence) measurements, for different flow regimes. One-point transport equation for the scalar variance is assessed through experimental data, along the common axis of the two opposed jets, and different physical phenomena are revealed (production, diffusion, dissipation). The production of scalar variance is equilibrated by the diffusion term (～75%) and the mean dissipation of the scalar variance (～25%). To further assess the scalar behaviour at each scale in this anisotropic, but axisymmetric, flow, a scale-by-scale scalar variance budget equation is derived for axisymmetric turbulence. This equation reduces to Yaglom's 4/3 law, under additional restrictions. The equation is assessed through experimental data, in the impingement region between the two COJ. In particular, the anisotropic energy transfer along different directions is quantified. It is shown that for scales smaller than the size of the central region, Δ, the cascade of the scalar variance is completely inhibited, independently of the particular direction. For scales larger than Δ, the apparent aspect of the energy transfer is that of an inverse cascade, with positive values of the scalar variance transfer. Nonetheless, inhomogeneity of the flow and mixing at those scales is directly responsible for these positive values.     

Theoretical study of the singlet electronically excited states of N4

Vertical excitation energies for the lowest eleven singlet states of T_d N₄ were calculated using the TD-DFT method with the B3LYP functional, and at the EOM-CCSD level of theory. The vertical excitation energies for the five lowest-lying excited states were also obtained using the state-averaged CASSCF, CASPT2, CASPT3, and MRCI + Q methods. Our results show that the five lowest-lying states are of valence character. EOM-CCSD/d-aug-cc-pVTZ calculations predict that there are two weakly allowed optical transitions of T₂ symmetry at 10.44 and 10.82 eV. The transition to the third T₂ state, which is predicted to be at 10.89 eV, has an oscillator strength about one order of magnitude higher.     

Isolation of an Annulated 1,4-Distibabenzene Diradicaloid

The first 1,4-distibabenzene-1,4-diide compound [(ADC)Sb]₂ ( 5 ) based on an anionic dicarbene (ADC) (ADC=PhC{N(Dipp)C}₂, Dipp=2,6-iPr₂C₆H₃) is reported as a bordeaux-red solid. Compound 5 , featuring a central six-membered C₄Sb₂ ring with formally Sb^I atoms may be regarded as a base-stabilized cyclic bis-stibinidene in which each of the Sb atoms bears two lone-pairs of electrons. 5 undergoes 2 e-oxidation with Ph₃C[B(C₆F₅)₄] to afford [(ADC)Sb]₂[B(C₆F₅)₄]₂ ( 6 ) as a brick-red solid. Each of the Sb atoms of 6 has an unpaired electron and a lone-pair. The broken-symmetry open-shell singlet diradical solution for ( 6 )²⁺ is calculated to be 2.13 kcal mol⁻¹ more stable than the closed-shell singlet. The diradical character of ( 6 )²⁺ according to SS-CASSCF (state-specific complete active space self-consistent field) and UHF (unrestricted Hartree-Fock) methods amounts to 36 % and 39 %, respectively. Treatments of 6 with (PhE)₂ yield [(ADC)Sb(EPh)]₂[B(C₆F₅)₄]₂ ( 7 -E) (E=S or Se). Reaction of 5 with (cod)Mo(CO)₄ affords [(ADC)Sb]₂Mo(CO)₄ ( 8 ).     

Effect of some chelating ligands on the potential response of the chalcocite copper ion-selective electrode

The effects of diethylenetriamine, triethylenetetramine, tetraethylenepentamine, aminoacetic acid, iminodiacetic acid, nitrilotriacetic acid, ethylenediaminediaminetetraacetic acid, diethylenetriaminepentaacetic acid and triethylenetetraminehexaacetic acid on the behaviour of the synthetic chalcocite (copper(I) sulphide) copper-selective electrode are described. The effects of those ligands on the electrode response at different pH values is explained on the assumption that copper(I) ions contribute to the potential indicated. Copper(I) ions originate from the membrane phase and participate in exchange and redox reactions. The effects of oxygen and temperature are reported. The electrode response can be predicted on the basis of copper(II) equilibria in solution, only if the conditions are such that there is no interference from copper(I) ions.     

Synthesis and Characterization of Eight Arylpentazoles

p‐Nitrophenyl‐, p‐methoxyphenyl‐, p‐hydroxyphenyl‐, p‐t‐butylphenyl‐, p‐HOSO₂‐phenyl‐, ¹⁵N‐p‐N,N‐dimethylaminophenyl‐, ¹⁵N₂‐p‐N,N‐dimethylaminophenyl‐, and dicyanoimidazopentazole were obtained via different synthetic routes. Cesium, barium, potassium, and sodium salts of the arylpentazoles bearing acidic hydrogens were prepared. NMR spectra (¹H, ¹³C) are reported for the arylpentazoles, their corresponding arylazides, and their salts.