Evolution of flow structure in impinging three-dimensional axial and radial jets

Direct numerical simulations of the flow field of an element of banks of impinging axial and radial slot jets for different Reynolds number are presented. Simulations have been obtained from the solution of the Navier–Stokes equations. Results show for the chosen geometry a transition from steady to periodic to chaotic flow with increasing Reynolds number. The transition Reynolds number is nearly 50% smaller for the radial jet than for the axial jet. Period doubling has been observed for both cases, but only the radial jet shows periodic windows of chaos. © 1997 John Wiley & Sons, Ltd.     

A Minimal Dynamical Scheme for “Understanding” Hadronic Widths

Using a quark model scheme of ‘least Dynamics’, an inclusive determination of the total widths of mesons and baryons is proposed via the following mechanism: There exists a short (breathing) mode for the temporary dissociation of a hadron into a pair of “qausi-free” quarks and/or diquarks which eventually hadronize with certainty, so that the requisite widths correspond to this “first stage” dissociation itself. A detailed model (described elsewhere) based on the momentum dependence of the quark's mass function m(p) suggests a significant mass reduction of these quasi-free quarks w.r.t their “constituent” values m(O). Using this logic, a phenomenological coupling scheme for the meson-(quasifree)quark-vertex function is derived from Schwinger's Partial (broken chiral). Symmetry which incorporates the conservation of isospin, baryonic charge and hypercharge with respective ‘gauge mesons’ rho, omega, phi. A very similar structure is found for baryon couplings to quark (q)-diquark (D) pairs, with the same overall coupling constant (gs) for both systems. Its tentative identification with the QCD value yields a surprisingly good pattern of agreement with data for both hadron types, using two “quasi-free” masses (m_ud and m_s) as inputs, with the corresponding diquark masses determined additively.     

Syntheses and X‐Ray Crystal Structures of New Copper(I) and Silver(I) Complexes containing Thione Ligands

The reaction of [(Ph₃P)₂CuCl]₂ with 4‐amino‐6‐methyl‐1,2,4‐triazine‐thione‐5‐one (AMTTO, 1 ) in methanol and further recrystallization from methanol/acetone solution gives [(C₄H₄N₃SON(=CMe₂)Cu(PPh₃)₂Cl] ( 2 ) as a neutral complex. [(C₄H₄N₃SON(=CMe₂)Ag(PPh₃)₂]NO₃ ( 4 ) can be obtained in excellent yield by the reaction of [(AMTTO)₂Ag]NO₃ ( 3 ) with triphenylphosphane in methanol/acetone. Both complexes were characterized by infrared spectroscopy, elemental analyses as well as by X‐ray diffraction studies. Crystal data for 2 at –80 °C: space group P1 with a = 1233.8(1), b = 1389.7(1), c = 1417.1(1) pm, α = 89.36(1)°; β = 65.10(1)°, γ = 65.95(1)°, Z = 2, R₁ = 0.0582 and for 4 at –80 °C: space group P1, with a = 1193.3(1), b = 1308.5(1), c = 1385.3(1) pm, α = 94.69(1)°, β = 109.14(1)°, γ = 93.42(1)°, Z = 2, R₁ = 0.0716.     

Crystal Structure and Properties of a New 2, 2'‐Ortho(metaxylene) E‐Bridged Stilbenophane

The synthesis and characterization of novel E and Z‐2, 2'‐ortho(metaxylene)‐bridged stilbenophane 2 by reductive McMurry condensation are described and the X‐ray structure determination of the E‐isomer is reported. The structure analysis of 2 ‐E shows weak hydrogen bonding. The complexation of Na⁺ ions in 2, 2'‐ortho(metaxylene)‐Z‐bridged stilbenophane using sodium chloride and measurements of conductivity were performed. The formation constant logK was determined to 1.45.     

Synthesis and Crystal Structure of Diaqua bis(4‐amino‐3‐methyl‐1, 2, 4‐triazol‐5‐thione)cadmium(II) Nitrate

The reaction of 4‐amino‐5‐methyl‐1, 2, 4‐triazol‐3(2H)‐thione (HAMTT, 1 ) with cadmium(II) acetate in ethanol leads to [Cd(η²‐AMTT)₂(H₂O)₂] ( 2 ); the reaction of 2 with nitric acid in ethanol produces the single‐crystals of [Cd(η²‐HAMTT)₂(H₂O)₂](NO₃)₂ ( 3 ). 2 and 3 have been characterized by IR, Raman, ¹H NMR spectroscopy and elemental analyses; furthermore, 3 has been determined by single‐crystal X‐ray diffraction studies. 3 crystallizes in the space group Pbcn, orthorhombic with the lattice dimensions at —80 °C; a = 1604.2(1), b = 895.6(1), c = 1266.5(3) pm, Z = 4, R₁= 0.0276, wR₂= 0.0722.     

Synthesis and magneto-structural correlation of a new maleato bridged copper(II) coordination polymer

A one-dimensional (1-D) copper(II) coordination polymer [Cu(maleate)(2,2′-bipyridyl)] _n ·2H₂O has been synthesised. Single crystal X-ray diffraction study reveals that maleate ion bridges two adjacent copper(II) centres along the chain in a syn–anti fashion. A complete cryomagnetic investigation of the title complex correlates well with the distorted square pyramidal geometry of the central copper(II) ion and bridging nature of the maleate. A τ value of 0.26 indicates the distortion towards tbp coordination allowing the magnetic orbital to acquire some character leading to a weak antiferromagnetic interaction having J = −0.26 cm⁻¹. The complex has also been firmly established from several other instrumental techniques like Fourier transform infrared (FT-IR) and EPR spectroscopies.     

Photocatalytic Degradation of Orange G Dye by Using Bismuth Molybdate: Photocatalysis Optimization and Modeling via Definitive Screening Designs

In the current study, Bismuth molybdate was synthesized using simple co-precipitation procedure, and their characterization was carried out by various methods such as FT-IR, SEM, and P-XRD. Furthermore, the photocatalytic degradation of Orange G (ORG) dye using synthesized catalyst under visible light irradiation was studied. Response surface Method was used for the optimization of process variables and degradation kinetics evaluated by modeling of experimental data. Based on the experimental design outcomes, the first-order model was proven as a practical correlation between selected factors and response. Further ANOVA analysis has revealed that only two out of six factors have a significant effect on ORG degradation, however ORG concentration and irradiation time indicated the significant effects sequentially. Maximum ORG degradation of approximately 96% was achieved by keeping process parameters in range, such as 1 g L⁻¹ loading of catalyst, 50 mg L⁻¹ concentration of ORG, 1.4 mol L⁻¹ concentration of H₂O₂ at pH 7 and a temperature of 30 °C. Kinetics of ORG degradation followed the pseudo first order, and almost complete degradation was achieved within 8 h. The effectiveness of the Bi₂MoO₆/H₂O₂ photo-Fenton system in degradation reactions is due to the higher number of photo-generated e- available on the catalyst surface as a result of their ability to inhibit recombination of e- and h+ pair.     

Magnetic transition and polaron crossover in a two-site single polaron model including double exchange interaction

A two-site double exchange model with a single polaron is studied using a perturbation expansion based on the modified Lang-Firsov transformation. The antiferromagnetic to ferromagnetic transition and the crossover from small to large polaron are investigated for different values of the antiferromagnetic interaction (J) between the core spins and the hopping (t) of the itinerant electron. Effect of the external magnetic field on the small to large polaron crossover and on the polaronic kinetic energy are studied. When the magnetic transition and the small to large polaron crossover coincide for some suitable range of J/t, the magnetic field has very pronounced effect on the dynamics of polarons. Received 1 June 2000