Reactivity of mixed organozinc and organocopper reagents. 3. Atom economic electrophilic amination of methyl arylzinc reagents

Reaction of methyl arylzincs with acetone O‐(mesitylenesulfonyl)oxime in THF in the presence of CuCN at room temperature is efficient in selective electrophilic amination of aryl carbanions. This procedure allows for the preparation of arylamines in moderate to good yields and provides an efficient and atom economic alternative to existing amination methods for diarylzincs. Copyright © 2009 John Wiley & Sons, Ltd.     

Modeling Anisotropic Single Crystal Growth Kinetics in Liquid Phase Sintered α-Al2O3

Single crystals of -alumina with {0001}, {11 and {01 2} orientations were embedded in a matrix of liquid phase sintered alumina to study -alumina single crystal growth in the presence of a calcium aluminosilicate liquid. Growth on the {11 0} and {01 2} surfaces was observed to occur by a diffusion-controlled mechanism while growth on the basal surface was controlled by two-dimensional nucleation. Growth models, which incorporate the change in matrix grain size, were derived and shown to fit the growth kinetics.     

Synthesis,spectroscopic and voltammetric studies of mixed-ligand copper(II) complexes of amino acids

Two Cu^II complexes of the type [Cu(L¹)(L²)] (where L¹ = tryptophanate or phenylalaninate; L² = cysteine thiolate) have been prepared and characterised, and their spectrophotometric and voltammetric behaviour has been investigated. The results obtained by means of FT-IR, e.s.r., u.v.–vis. spectroscopy and by voltammetry revealed the existence of two different [Cu(L¹)(L²)] complexes. A significance decrease in the g _|| value and, concomitantly, an increase in the d–d transition energy was observed when a mixed-ligand complex is present. The observed anisotropic g-values indicate the presence of Cu^II in a tetragonally distorted octahedral geometry. Formation of a mixed-ligand copper complex can be considered as a type of synergism in the presence of cysteine. The redox state Cu^II or Cu^I of copper in the Cu(L²) complex depends on the analysing conditions, i.e., cysteine forms a Cu^II complex under aerobic conditions and a Cu^I complex in anaerobic media. Tryptophan or phenylalanine is bound to Cu^II ions in the Cu(L¹) complexes.     

Evolution of the ion velocity distribution after sudden turn-on of a periodic electric field: A charge exchange model

An analytical solution to the problem of the ion velocity distribution evolution after turn-on of a periodic electric field is derived. The solution is constructed for the case of resonance charge exchange at a constant collision frequency (charge exchange model). The specific features of the transient process at the early stage of evolution are revealed. The phase shift between the applied field and the ion current at the periodic stage of the process is analyzed. The distribution function exhibits abrupt steps propagating in the velocity space. A method is proposed to study the ion-atom interaction cross section using a periodic electric field. The method is based on analysis of the current toward the electrode with a retarding potential.     

Adaptive linear combination of heuristic orderings in constructing examination timetables

In this paper, we investigate adaptive linear combinations of graph coloring heuristics with a heuristic modifier to address the examination timetabling problem. We invoke a normalisation strategy for each parameter in order to generalise the specific problem data. Two graph coloring heuristics were used in this study (largest degree and saturation degree). A score for the difficulty of assigning each examination was obtained from an adaptive linear combination of these two heuristics and examinations in the list were ordered based on this value. The examinations with the score value representing the higher difficulty were chosen for scheduling based on two strategies. We tested for single and multiple heuristics with and without a heuristic modifier with different combinations of weight values for each parameter on the Toronto and ITC2007 benchmark data sets. We observed that the combination of multiple heuristics with a heuristic modifier offers an effective way to obtain good solution quality. Experimental results demonstrate that our approach delivers promising results. We conclude that this adaptive linear combination of heuristics is a highly effective method and simple to implement.     

Interaction thermodynamics of rutin (vitamin P) with basic L-amino acids at physiological pH: the effect of temperature on the affinity order

The interactions between a flavonoid, rutin (Rt), and basic L-amino acids (BAAs) were studied at physiological pH (7.40) by UV-Visible spectroscopy and voltammetric techniques. The binding stoichiometries and constants (K) at different temperatures were measured by voltammetric method. So, the thermodynamic parameters ΔH ^○, ΔG ^○, ΔS ^○ were calculated and the results indicate that the binding reaction is mainly entropy-driven and hydrophobic forces played major role in the interactions of arginine and lysine with rutin as compared to that of histidine. Whereas, the histidine binding reaction, including with the negative enthalpy and entropy changes is entalpy-driven and this interaction primarily arise from hydrogen-bonding and van der Waals interactions. Finally, it was also observed that the affinity (that is binding constant) of hydrogen-bonding and van der Waals interactions between Rt and arginine or lysine decreased, but the stability of hydrophobic interaction of Rt with histidine increased when the temperature was raised.     

Recurrence procedure for calculating kernels of the nonlinear collision integral of the Boltzmann equation

A recurrence procedure for a sequential construction of kernels \(G_{{l_1},{l_2}}^l\) (c, c₁, c₂) appearing upon the expansion of a nonlinear collision integral of the Boltzmann equation in spherical harmonics is developed. The starting kernel for this procedure is kernel G_0,0⁰ (c, c₁, c₂) of the collision integral for the distribution function isotropic with respect to the velocities. Using the recurrence procedure, a set of kernels \(G_{{l_1},{l_2}}^{ + l}\) (c, c₁, c₂) for a gas consisting of hard spheres and Maxwellian molecules is constructed. It is shown that the resultant kernels exhibit similarity and symmetry properties and satisfy the relations following from the conservation laws.     

Oligophenyls with Multiple Disulfide Bridges as Higher Homologues of Dibenzo[c,e][1,2]dithiin: Synthesis and Application in Lithium-Ion Batteries

Higher homologues of dibenzo[c,e][1,2]dithiin were synthesized from oligophenyls bearing multiple methylthio groups. Single-crystal X-ray analyses revealed their nonplanar structures and helical enantiomers of higher meta-congener 6 . Such dibenzo[1,2]dithiin homologues are demonstrated to be applicable to lithium-ion batteries as cathode, displaying a high capacity of 118 mAh g⁻¹ at a current density of 50 mA g⁻¹.     

Voltammetric study on interaction of cysteine with type I-collagen in the aqueous medium

Interaction of cysteine with type I-collagen from bovine achilles tendon in the aqueous solutions has been examined using square wave voltammetry (SWV) and cyclic voltammetry (CV) techniques. In the absence of cysteine, type I-collagen gives a reversible peak at ?0.114 V in Britton-Robinson (B-R) buffer (pH 4.0). The electrochemical parameters (I _p/f, E _p/f, E _p/pH, I _p/pH, I _p/v, I _p/v^1/2) of type I-collagen have been also studied. In addition, it has been determined that there is a linear relationship between current and concentration of type I-collagen. On the other hand, cysteine exhibits a reversible peak at ?0.383 V due to the reduction of mercurous cysteine thiolate. By using a hanging mercury drop electrode in aqueous solutions, SWV and CV voltammograms obtained for type I-collagen in the presence of cysteine indicate that there is an interaction between type I-collagen and cysteine. In the presence of cysteine, peak current of type I-collagen decreases and a new peak is observed at ?0.121 V for cysteine which is bonded to type I-collagen.     

Construction of kernels of the nonlinear collision integral in the Boltzmann equation using laplace transformation

It is shown that the relation between kernels L _l (v, v ₁) of the linear collision integral and kernels G _l,0 ^l (v, v ₁, v ₂) of the nonlinear collision integral can be reduced to the Laplace transformation. Analytic expressions for nonlinear kernels G _0,0 ⁺⁰ (v, v ₁, v ₂) and G _1,0 ⁺¹ (v, v ₁, v ₂) are determined for hard spheres and pseudo-Maxwellian molecules.