Post Polymerization of Saturated and Unsaturated Poly(3-hydroxy alkanoate)s

Summary : Chemical modification is useful to diversify poly(3-hydroxyalkanoate)s, for medical and industrial applications. In this manner, transesterification reactions of poly(3-hydroxy butyrate) were carried out under reflux condition of 1,2-dichlorobenzene in the presence of 1,4-butane diol, poly(ethylene glycol) bis(2-aminopropyl ether) with molecular weights of 1000 and 2000, poly(ethylene glycol)methacrylate or glycerol at 180 °C. Addition reactions of bromine and –SH groups of 3-mercaptopropionic acid to the double bond of poly(3-hydroxy-10-undecenoate) were also carried out. Functionalized poly(3-hydroxyalkanoate)s were characterized using ¹H NMR, FTIR, GPC and thermal analysis techniques.     

Statistical regression and artificial neural network analyses of impinging jet experiments

The purpose of this paper is to focus on the experimentally obtained results of impinging jet applications by the help of two different analysis methods. Circular round pipes (D = 7.9, 10.8, 13.8 and 23.1 mm) have been used as the impinging jets. The heat transfer is calculated with Nusselt number (Nu). The variable parameters are the dimensionless jet-to-impingement plate distance (z/D), Reynolds number (Re) and dimensionless temperature measurement points on the heated surface (x/L, y/L). Some important analysis methods such as artificial neural network (ANN), statistical regression, and uncertainty analysis are applied to the obtained data. It is shown that the ANN application is not simply a classification analysis; it is actually an application of the convergence of functions. As a result, by considering random data, 4.57% convergence level is obtained regarding the pipe diameter. The software STATISTICA 5.0 is used to estimate new empirical correlations nonlinearly. The smallest regression coefficient for the correlations is 0.87, while the highest value is 0.99. The result of the uncertainty analyses showed that the total uncertainties are in the agreeable range; 8% for Nu, and 2.89% for Re. Dr. Nevin Celik is a Post Doctoral Fellowship in University of Minnesota since August 2007.     

Thermostatistics of the g-on gas

In this study, the particles of the quantum gases, namely bosons and fermions are called g-ons by using the parameter of the fractional exclusion statistics g, where . With this point of departure, the distribution function of the g-on gas is obtained by the variational, steepest descent and statistical methods. The distribution functions which are found by means of these three methods are compared. It is shown that the thermostatistical formulations of quantum gases can be unified. By suitable choices of g, standard relations of statistical mechanics of the Bose and Fermi systems are recovered.Received: 26 March 2003, Published online: 22 September 2003PACS: 05.20.-y Classical statistical mechanics - 03.65.-w Quantum mechanics     

A direct barter model for course add/drop process

Even though course timetabling and student scheduling problems have been studied extensively, not much has been done for the optimization of student add/drop requests after the initial registration period. Add/drop registrations are usually processed with a first come first served policy. This, however, can introduce inefficiencies and dead-locks resulting in add/drop requests that are not satisfied even though they can, in fact, be satisfied. We model the course add/drop process as a direct bartering problem in which add/drop requests appear as bids. We formulate the resulting problem as an integer linear program. We show that our problem can be solved polynomially as a minimum cost flow network problem. In our model, we also introduce a two-level weighting system that enables students to express priorities among their requests. We demonstrate improvement in the satisfaction of students over the currently used model and also the fast performance of our algorithms on various test cases based on real-life registration data of our university.     

Synthesis, acidity and antioxidant properties of some novel 3,4-disubstituted-4,5-dihydro-1H-1,2,4-triazol-5-one derivatives

3-Alkyl(aryl)-4-amino-4,5-dihydro-1H-1,2,4-triazol-5-ones 2a-g reacted with 4-diethylaminobenzaldehyde to afford the corresponding 3-alkyl(aryl)-4-(4-diethyl-aminobenzylidenamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones 3a-g. The acetylation reactions of compounds 3a-e were investigated and compounds 4a-e were thus obtained. The new compounds were characterized using IR, (1)H-NMR, (13)C-NMR, UV and MS spectral data. In addition, the newly synthesized compounds 3a-g were titrated potentiometrically with tetrabutylammonium hydroxide in four non-aqueous solvents such as isopropyl alcohol, tert-butyl alcohol, acetone and N,N-dimethylformamide (DMF), and the half-neutralization potential values and the corresponding pKa values were determined for all cases. Moreover, 3 and 4 type compounds were also screened for their antioxidant activities.