SPECIFIC PHOTOALKYLATION OF POLY U AND OF POLY A WITH 2-PROPANOL AND THEIR MESSENGER PROPERTIES

Ultraviolet light induced free radical alkylation of poly U or of poly A with 2-propanol leads to the specific formation of 6-(2-hydroxy 2-propyl) 5,6-dihydro-UMP or 8-(2-hydroxy 2-propyl)-AMP residues, respectively. The biochemical significance of the alterations in the modified polynucleotides was studied by testing their messenger activities in a cell free system of E. coli. Both photoalkylated poly U and poly A have reduced functional activity, with no change in functional specificity. This was demonstrated by inhibition of polymerization of phenylalanine and lysine directed by photoalkylated poly U and poly A, respectively, and by lack of misincorporation of other amino acids. The modification of poly U also caused the disappearance of misincorporation of serine that was found with the native polynucleotide.     

Compounded genetic algorithms for the quadratic assignment problem

We introduce the compounded genetic algorithm. We propose to run a quick genetic algorithm several times as Phase 1, and compile the best solutions in each run to create a starting population for Phase 2. This new approach was tested on the quadratic assignment problem with very good results.     

Retail facility location under changing market conditions

In this paper we investigate the location of retail facilitiesunder changing market conditions when market conditions areexpected to change during the planning horizon. Three modelsare presented: (1) the minimax regret model where the objectivefunction is to minimize the maximum possible loss under differentmarket scenarios, (2) the Stackelberg equilibrium model wherebya future competitor enters the market and one wishes to maximizethe market share captured throughout the planning horizon incorporatingthe market share loss to the competitor, and (3) the thresholdmodel in which we consider a minimum threshold level such thatif the market share captured by the new facility fails to reachthat threshold, the facility will not survive. Our objectiveis to minimize the probability of failure.     

Spectroscopic and kinetic evidence for an accumulating intermediate in an SNV reaction with amine nucleophiles. Reaction of methyl beta-methylthio-alpha-nitrocinnamate with piperidine and morpholine

A spectroscopic and kinetic study of the reaction of methyl beta-methylthio-alpha-nitrocinnamate (4-SMe) with morpholine, piperidine, and hydroxide ion in 50% DMSO/50% water (v/v) at 20 degrees C is reported. The reactions of 4-SMe with piperidine in a pH range from 10.12 to 11.66 and those with morpholine at pH 12.0 are characterized by two kinetic processes when monitored at lambdamax (364 nm) of the substrate, but by only one process when monitored at lambdamax (388) nm of the product. The rate constants obtained at 388 nm were the same as those determined for the slower of the two processes at 364 nm. These rate constants refer to product formation, whereas the faster process observed at 364 nm is associated with the loss of reactant to form an intermediate. In contrast, for the reaction of 4-SMe with morpholine at pH 8.62 the rates of product formation and disappearance of the substrate were the same, i.e., there is no accumulation of an intermediate. Likewise, the reaction of 4-SMe with OH- did not yield a detectable intermediate. The factors that allow the accumulation of intermediates in certain SNV reactions but not in others are discussed in detail, and structure-reactivity comparisons are made with reactions of piperidine and morpholine with other highly activated vinylic substrates.     

A comprehensive picture of the one-electron oxidation chemistry of enols, enolates and α-carbonyl radicals: oxidation potentials and characterization of radical intermediates

Oxidation potentials of 40 enols, enolates and some selected α-carbonyl radicals are presented along with their characterization by various techniques as applicable (X-ray, EPR, ENDOR, general TRIPLE, magnetic susceptibility measurements, UV-vis, fast scan cyclic voltammetry, isotope effects). The model compounds comprise representatives of stable simple enols linked to a multitude of substituents (alkyl, alkenyl, alkynyl, aryl, heteroaryl, propargyl alcohols) and of stable simple enols of amides. The results allow to clarify the primary reaction pathway of enol radical cations as a rapid deprotonation and—if warranted by the redox potential and the strength of the oxidant—a follow-up oxidation of the resultant α-carbonyl radical to the α-carbonyl cation. Moreover, the experimental oxidation potentials were linearly correlated with AM1 computed ionization potentials after correction for solvation. The correlation allows a reliable prediction of oxidation potentials of radicals including α-carbonyl radicals. After computing redox potentials of relevant radicals, the possibility of one-electron transfer between enolates and flavin and the involvement of various radicals of ascorbic acid in oxidation processes were assessed.     

Characterizations of self-combustion reactions (SCR) for the production of nanomaterials used as advanced cathodes in Li-ion batteries

In this work, self-combustion reactions (SCR) for the preparation of important cathode materials for rechargeable Li-ion batteries were investigated by thermal analytical tools (DSC, ARC, TGA), electron microscopy, XRD, various spectroscopies (MS, Raman, FTIR) and elemental analysis by ICP. The systems studied include solutions containing metal nitrates at the right stoichiometry and sucrose as a fuel, for the preparation of LiMn_0.5Ni_0.5O₂ (layered), LiMn_1.5Ni_0.5O₄ (spinel), LiMn_0.33Ni_0.33Co_0.33O₂ (layered), and LiMn_0.4Ni_0.4Co_0.2O₂ (layered). Similar products, which do not depend on the atmosphere of the processes (air or inert) were obtained by spontaneous SCR and the gradual heating of the same solutions by DSC, ARC, and TGA. The reactions involve the partial caramelization of sucrose, complicated by red-ox reactions with the nitrates that form solid products, whose organic part is finally decomposed around 400 °C. The presence of cobalt ions has a stabilizing effect, which is expressed by the low dissolution rates of Li ions from the solid products thus formed, into aqueous solutions. The reaction mechanisms are discussed herein.     

On symmetric basic sequences in Lorentz sequence spaces

We examine the symmetric basic sequences in some classes of Banach spaces with symmetric bases. We show that the Lorentz sequence spaced(a,p) has a unique symmetric basis and every infinite dimensional subspace ofd(a,p) contains a subspace isomorphic tol ^p. The symmetric basic sequences ind(a,p) are identified and a necessary and sufficient condition for a Lorents sequence space with exactly two nonequivalent symmetric basic sequences in given. We conclude by exhibiting an example of a Lorentz sequence space having a subspace with symmetric basis which is not isomorphic either to a Lorentz sequence space or to anl ^p-space. This is part of the first author's Ph. D. thesis, prepared at the Hebrew University of Jerusalem under the supervision of Dr. L. Tzafriri.