A branch-and-cut method for 0-1 mixed convex programming

We generalize the disjunctive approach of Balas, Ceria, and Cornuéjols [2] and devevlop a branch-and-cut method for solving 0-1 convex programming problems. We show that cuts can be generated by solving a single convex program. We show how to construct regions similar to those of Sherali and Adams [20] and Lovász and Schrijver [12] for the convex case. Finally, we give some preliminary computational results for our method. Received January 16, 1996 / Revised version received April 23, 1999?Published online June 28, 1999     

An experimental investigation on pool boiling heat transfer enhancement using Cu-Al2O3 nano-composite coating

Pool boiling heat transfer performances of Cu-Al₂O₃-coated copper surfaces have been studied experimentally for its potential use in heat transfer applications. In the present study, a two-step electrochemical deposition method is examined. This method provides an easy control on surface properties such as porosity and coating thickness. The deposition method is studied carefully and responsible surface morphology parameters are reported. After performing the pool boiling experiments on coated surfaces with DI water, the maximum critical heat flux of 1800 kW/m² and heat transfer coefficient of 193 kW/m² K, which are 68% and 260% higher than that of bare surface, respectively.     

A novel confocal optical pulse stretcher for laser pulses

We present an analytical and experimental study of a novel confocal optical pulse stretcher (COPS). The simple and passive pulse stretcher consists of two concave mirrors and a scraper beam-splitter and its optical configuration ensures a perfect spatial overlapping of laser pulses at the beam-splitter. The pulse stretcher is compact and suitable for laser pulses of large divergences. The confocal optical pulse stretcher is demonstrated on a pulsed copper vapour laser to convert a 40 ns (1/e² % points) pulse into a 55 ns with reduction of peak power by a factor of 1.375 without loss of pulse energy.     

On a weakly forced third order weakly non-linear system

The behaviour of a weakly non-linear third order system under a weak forcing function is considered. By the method of multiple time scales, it is found that the amplitude of the forced oscillation increases with the amplitude of the forcing function until a critical value is reached. Beyond this value, stable oscillations exist whose amplitude decreases with the amplitude of the forcing function but which are superimposed on a constant of increasing magnitude.     

An efficient, rapid, and regioselective bromination of anilines and phenols with 1-butyl-3-methylpyridinium tribromide as a new reagent/solvent under mild conditions

1-Butyl-3-methylpyridinium tribromide, [BMPy]Br₃ proves to be a highly efficient, regioselective reagent/solvent for nuclear bromination of various anilines and phenols. The synthesis and characterization of the room temperature ionic liquid [BMPy]Br₃ (2) is described. The bromination was carried out in the absence of organic solvents and in most cases the only extraction solvent needed was water. The spent 1-butyl-3-methylpyridinium bromide (1) was easily recycled.     

Direct synthesis of esters and amides from unprotected hydroxyaromatic and -aliphatic carboxylic acids

A facile method for the activation of hydroxy-substituted carboxylic acids using benzotriazole chemistry without prior protection of the hydroxy substituents is presented. The N-acylbenzotriazole intermediates 2a-g, 6a-d, and 9a-c have been used for high-yielding synthesis of both aliphatic (3a-l) and aromatic (7a-h, 10a-f) hydroxy carboxamides. High yields of aromatic hydroxy esters 12a-h and 13a-i were obtained using either neat alcohols in neutral microwave conditions or nucleophilic alkoxides and the intermediate N-(arylacyl)benzotriazoles. Moderate yields were obtained in the case of aliphatic hydroxy esters 11a,b and thiolesters 11e-g from the intermediates 2a-c.     

Control of structure formation in phase-separating systems

In this paper, we study the evolution of phase-separating binary mixtures which are subjected to alternate cooling and heating cycles. An initially homogeneous mixture is rapidly quenched to a temperature T(1)T(c). These cycles are repeated to create a domain morphology with multiple length scales, i.e., the structure factor is characterized by multiple peaks. For phase separation in d = 2 systems, we present numerical and analytical results for the emergence and growth of this multiple-scale morphology.     

Effect of a cocatalyst modifier in the synthesis of ultrahigh molecular weight polyethylene having reduced number of entanglements

The use of a hindered phenol to trap free trimethylaluminum (TMA) in methylaluminoxane (MAO) solutions has been reported to improve the performance of single‐site, homogeneous catalysts for olefin polymerization. In the present study, with the help of rheological analyses, we have investigated and compared the molecular weight, molecular weight distribution and entanglement density of ultrahigh molecular weight polyethylene synthesized with a single‐site catalyst activated by MAO and phenol‐modified MAO. While the number average molecular weight (M_n) of the obtained polymers remains the same for both activations, a higher yield and a higher entanglement density are found in the initial stages of polymerization on using phenol‐modified MAO as the cocatalyst. These results suggest that on using the phenol‐modified MAO as activator, a higher number of active sites are obtained. Surprisingly in the presence of untreated MAO, a tail in the higher molecular mass region is produced. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013     

Immobilized Carboxypeptidase A for Sequential Analysis

The use of carboxypeptidase for sequence determination is attractive because of its technical simplicity. In chemical methods all molecules of a peptide are made to go through a degradation cycle before a new cycle is started. In the enzymatic degradation of a protein, the order of the amino acid residues is not necessarily determined in a stepwise fashion but rather from the rate at which the amino acids appear in the digest, i.e., an amino acid appearing faster than another presumably precedes it in the sequence. Under favorable circumstances the rate of appearance of the amino acids released during digestion give sufficient evidence for the C-terminal sequence to be deduced. The present work pertains to a study on the use of immobilized carboxypeptidase A columns for sequential analyses.     

RuCl3 · xH2O: A New Efficient Catalyst for Facile Preparation of 1,1‐Diacetates from Aldehydes

An efficient, facile preparation of aldehyde 1,1‐diacetates (acylals) in excellent yields catalyzed by RuCl₃ · xH₂O is described. Ketones do not react under these conditions.