14th International Conference on Computational Management Science

Computational Management Science -     

Telechelic Melt Polymer's Structure Variation Depending on Shear Deformation

We present the result of molecular dynamics (MD) simulations of bead and spring models of associating polymers at melt-like densities, both in static conditions and when a shear rate is applied. Specifically, we consider the response of telechelic polymers of general formula AB₁₂A to four different values of shear rate. The A terminals tend to associate with each other and in bulk conditions form clusters or micelles. A reversible network or physical gel is formed by a large fraction of bridging chains that interconnect different clusters. The micelles assume different form depending on the interaction strengths. When a shear rate is applied, the clusters are broken and the chains tend to stretch.     

Reactions of 1,2,5‐thiadiazole 1,1‐dioxide derivatives with nitrogen nucleophiles. Part IV. Addition of α‐diamines

α‐diamines, such as ethylendiamine and o‐phenylendiamine, add to 3,4‐aryl‐disubstituted 1,2,5‐thiadiazole 1,1‐dioxides to give dihydropyrazines or quinoxalines, respectively and sulfamide. The new compound acenaphtho [5,6‐b]‐2,3‐dihydropyrazine was synthesized and characterized. The addition of ethylendiamine to 3,4‐diphenyl‐ 1,2,5‐thiadiazoline 1,1‐dioxide gives 3,4‐disubstituted thiadiazolidine 1,1‐dioxide, dihydropyrazines, or pyrazines, depending on the reaction condition used. The reactions were followed by cyclic voltammetry and NMR spectroscopy which, in some cases, allowed the detection of the thiadiazolidine intermediate. Copyright © 2008 John Wiley & Sons, Ltd.     

Role of rational surfaces on fluctuations and transport in the plasma edge of the TJ-II stellarator

It has been shown that transport barriers in toroidal magnetically confined plasmas tend to be linked to regions of unique magnetic topology such as the location of a minimum in the safety factor, rational surfaces or the boundary between closed and open flux surfaces. In the absence ofE×B sheared flows, fluctuations are expected to show maximum amplitude near rational surfaces, and plasma confinement might tend to deteriorate. On the other hand, if the generation ofE×B sheared flows were linked to low order rational surfaces, these would be beneficial for confinement. Experimental evidence ofE×B sheared flows linked to rational surfaces has been obtained in the plasma edge region of the TJ-II stellarator. Presented at the Workshop on the Role of Electric Fields in Plasma Confinement and Exhaust, Budapest, 18–19 June, 2000.     

Preliminary study of HCHO spatial and temporal distribution from Coastal to Plateau areas in Antarctica

Formaldehyde concentrations were determined in over 1800 snow samples (snowpit, firn cores and superficial snow) from Antarctica by a sensitive spectrofluorimetric Flow Injection Analysis method. The method performances (detection limit: 55?ng/L; reproducibility: 2.5% at 1?µg/L level; linear range: 0.1–3000?µg/L) allowed a reliable determination of formaldehyde content in all the collected samples. The range of determined concentrations was 0–70?µg/L with a mean concentration of 7.7?µg/L and a median concentration of 5.8?µg/L. The formaldehyde background level was estimated at a few micrograms per liter in coastal and plateau areas of Northern Victoria Land. In some stations the background values are modulated by HCHO deposition events recurring over relatively large time periods.     

Dependence of the product on the P–P ligand in reactions of [RuCl3(NO)(P–P)] complexes (P–P = aromatic diphosphines) with 2-mercaptopyridine

This study presents the syntheses and characterization of 2-mercaptopyridine (pyS⁻) complexes containing ruthenium(II) with the following general formula [Ru(pyS)₂(P–P)], P–P = (c-dppen) = cis-1,2-bis(diphenylphosphino)ethylene) (1); (dppe) = 1,2-bis(diphenylphosphino)ethane (2); (dppp) = 1,3-bis(diphenylphosphino)propane (3) and (dppb) = 1,4-bis(diphenylphosphino)butane (4). The complexes were synthesized from the mer- or fac-[RuCl₃(NO)(P–P)] precursors in the presence of triethylamine in methanol solution with dependence of the product on the P–P ligand. The reaction of pyS⁻ with a ruthenium complex containing a bulky aromatic diphosphine dppb disclosed a major product with a dangling coordinated dppbO-P, the [Ru(pyS)₂(NO)(η¹-dppbO-P)]PF₆(5). In addition, this work also presents and discusses the spectroscopic and electrochemical behavior of 1–5, and report the X-ray structures for 1 and 5.     

Theoretical study in gas phase of linear and nonlinear optical properties of the ortho-, meta- and para-nitrophenol isomers

The linear (α), and nonlinear (β, γ) optical NLO properties of ortho-, meta- and para-nitrophenol (ONP, MNP and PNP) isomers have been calculated in gas phase by using ab initio (HF, MP2 and MP4) and density functional theory (DFT) (B3LYP, CAM-B3LYP) methods, with the 6-31+G(d,p) and 6-311+G(3d,3p) standard and the Sadlej specialized basis sets. These properties were evaluated both at static and at dynamic regime within the finite field FF numerical techniques and the time-dependent-Hartree–Fock approach at 1,910 nm, respectively. Additional calculations were performed for the β static hyperpolarizability of these isomers in presence of p-dioxane solvent with the Onsager Model and the SCRF-PCM approach, using B3LYP/6-31+G(d,p) and MP2/6-31+G(d,p) levels of theory. Additionally, CCSD/6-31+G(d,p) calculations were performed for the α, β and γ properties of PNP isomer. The B3LYP and MP2 α _ave results of the nitrophenol isomers are comparable to the experimental α _ave reports; while the tendency for the β _v calculated values (β _v PNP > β _v MNP > β _v ONP), that can be explained in terms of the O _x atomic charge of the –NO₂ group, does not follow exactly the experimental ones. The B3LYP γ _ave results are in correspondence to the experimental measurements, the correlation of which is r ² = 0.99. The use of FF methodology in conjunction with the B3LYP and MP2 methods and the 6-31+G(d,p) basis set show to be appropriate approaches to predict qualitative optical properties of Push–Pull like organic molecules, provided are considered the solvent effects or frequency dependence. However, to have a clear picture of the NLO properties of an isolated molecule, higher order correlation effects combined with specialized basis sets, frequency and solvent effects should be employed. We have demonstrated that MP4/Sadlej level of theory is able to reproduce NLO properties that can be considered equivalent to those from more sophisticated approaches, such as CCSD together with extended basis sets.     

The analysis of serum effects on structure, size and toxicity of DDAB-DOPE and DC-Chol-DOPE lipoplexes contributes to explain their different transfection efficiency

The effect of serum on structural properties of dimethyl-dioctadecyl-ammonium bromide (DDAB)–1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) liposomes and DDAB–DOPE/DNA lipoplexes has been investigated by energy dispersive X-ray diffraction (EDXD) technique, at different cationic lipid/DNA weight ratios (ρ). The role of serum on the size of lipoplexes has also been studied by dynamic light scattering. Lipoplex transfection efficiency (TE) as a function of ρ, and lipoplex toxicity to C6 rat glioma cells have been evaluated in Dulbecco's Modified Eagle Medium (DMEM) with and without serum. A multi-parametric analysis concerning the role of size, structure and cytotoxicity on transfection efficiency contributes to explain the experimental observation that 3β-[N-(N′,N′-dimethylaminoethane)carbamoyl]-cholesterol (DC-Chol)–DOPE/DNA transfect C6 cells better than DDAB–DOPE/DNA lipoplexes.