The explanation of high specificity of discriminating optical isomers in enzymatic reactions by the molecular anvil model of enzyme

The molecular anvil model of enzyme is proposed and applied to explain high specificity of discriminating optical isomers in enzymatic reactions. The molecular anvil is a mechanism which can accumulate energy from two interacting molecules and produce locally a high energy spot called anvil site. Two conditions neccessary for formation of the molecular anvil are described. For a pair of enzyme and substrate molecules these two conditions are considered to be satisfied. Assuming proper shapes and sizes for molecules of optical isomers and a hole on the surface of the enzyme molecule into which the optical isomers can fit and also assuming Lenard-Jones 12-6 type potential for each pair of interacting molecular sites. The amount of energy accumulated at the anvil site is calculated. Following the assumption that the total reactivity is determined by binding process and chemical process in which the accumulated energy at the anvil site is utilized to enhance the reaction, total reactivities for L- and D-isomers are calculated and the values of specificity of discriminating L-isomer from D-isomer are derived for various values of interaction energy. It is shown that the molecular anvil plays an important role in elevating specificity as well as producing high catalytic power of enzyme.     

Cardinalities of Primitive Fixing Systems for Convex Bodies

We establish the exact upper bound of cardinalities of primitive fixing systems for any compact, convex body M , depending on dim M and md, M . In a sense, this is the last touch to the theory of fixing systems for compact, convex bodies. Received October 14, 1998, and in revised form May 5, 1999.     

Unsteady coupling of Navier-Stokes and radiative heat transfer solvers applied to an anisothermal multicomponent turbulent channel flow

Direct numerical simulations (DNS) of an anisothermal reacting turbulent channel flow with and without radiative source terms have been performed to study the influence of the radiative heat transfer on the optically non-homogeneous boundary layer structure. A methodology for the study of the emitting/absorbing turbulent boundary layer (TBL) is presented. Details on the coupling strategy and the parallelization techniques are exposed. An analysis of the first order statistics is then carried out. It is shown that, in the studied configuration, the global structure of the thermal boundary layer is not significantly modified by radiation. However, the radiative transfer mechanism is not negligible and contributes to the heat losses at the walls. The classical law-of-the-wall for temperature can thus be improved for RANS/LES simulations taking into account the radiative contribution.     

Memetic cooperative models for the tool switching problem

This work deals with memetic-computing agent-models based on the cooperative integration of search agents endowed with (possibly different) optimization strategies, in particular memetic algorithms. As a proof-of-concept of the model, we deploy it on the tool switching problem (ToSP), a hard combinatorial optimization problem that arises in the area of flexible manufacturing. The ToSP has been tackled by different algorithmic methods ranging from exact to heuristic methods (including local search meta-heuristics, population-based techniques and hybrids thereof, i.e., memetic algorithms). Here we consider an ample number of instances of this cooperative memetic model, whose agents are adapted to cope with this problem. A detailed experimental analysis shows that the meta-models promoting the cooperation among memetic algorithms provide the best overall results compared with their constituent parts (i.e., memetic algorithms and local search approaches). In addition, a parameter sensitivity analysis of the meta-models is developed in order to understand the interplay among the elements of the proposed topologies.     

Influences des entraîneurs Ga2O3 et NaF sur la volatilisation et l'excitation du vanadium dans la methode de Scribner—Mullin

A study has been made of the effect of NaF and Ga₂O₃ as entrainers, on the spectral line intensities of vanadium, and on the sensitivity and detection limits by the Scribner-Mullin method. The two entrainers have different effects on the volatilization of vanadium. By radiotracer methods with ⁴⁸V, the degree of volatilization was found to be 37% with NaF and 0·9% with Ga₂O₃. Use of NaF greatly increases the sensitivity, lowering the detection limit by a factor of about 50, without affecting the precision. The physicochemical conditions in the plasma do not seem to influence the line intensities with either entrainer.     

Efficient synthesis of thiazoloquinazolinone derivatives

An original route to the rare 8H-thiazolo[5,4-f]quinazolin-9-one 1 and the novel 7H-thiazolo[4,5-h]quinazolin-6-one 2 is described. Access to the regioisomers was realized by fusion of a thiazole and a quinazoline ring via Appel's salt chemistry. Thermal reactions were carried out using a focused microwave reactor, reducing the overall time of the multi-step synthesis.     

Synthesis of self-doped polyaniline bearing phosphonic acid moiety via Pd-catalyzed phosphonation of poly(2-bromoaniline)

Self-doped conducting polyaniline bearing phosphonic acid moiety was synthesized via the Pd-catalyzed phosphonation of poly(2-bromoaniline) as a key reaction.     

Iron(III) nitrate-induced aerobic and catalytic oxidative cleavage of olefins

Microwave-assisted catalytic oxidative cleavage of olefins using Fe(NO₃)₃·9H₂O under O₂ is reported. This reaction system is particularly effective when 9-benzylidene-9H-fluorene derivatives are used as substrates even though they are tri- and tetra-substituted olefins.