Versatile coordination chemistry towards multifunctional carbon nanotube nanohybrids

Dispersible single-walled carbon nanotubes grafted with poly(4-vinylpyridine), SWNT-PVP, were tested in coordination assays with zinc tetraphenylporphyrin (ZnP). Kinetic and spectroscopic evidence corroborates the successful formation of a SWNT-PVPZnP nanohybrid. Within this SWNT-PVPZnP nanohybrid, static electron-transfer quenching (2.0+/-0.1) x 10(9) s(-1) converts the photoexcited-ZnP chromophore into a radical-ion-pair state with a microsecond lifetime, namely one-electron oxidized-ZnP and reduced-SWNT.     

Stereoselective Michael addition of carbon-, nitrogen-, oxygen-, and sulfur-centered nucleophiles on enantiopure hydroxylated 6,7-dehydro-5-oxoindolizidine. Synthesis of carbon- or hetero-7-substituted swainsonine analogues

Enantiopure alpha,beta-unsaturated delta-lactams 1 and 2 react stereoselectively with carbon-, nitrogen-, sulfur-, and oxygen-centered nucleophiles. The synthetic potential of these conjugate additions is demonstrated through the synthesis of two new substituted indolizidines: (7R)-7-amino-8-deoxyswainsonine 3 and (7R)-7-acetylaminoswainsonine 4.     

Optimal egress time calculation and path generation for large evacuation networks

Finding the optimal clearance time and deciding the path and schedule of evacuation for large networks have traditionally been computationally intensive. In this paper, we propose a new method for finding the solution for this dynamic network flow problem with considerably lower computation time. Using a three phase solution method, we provide solutions for required clearance time for complete evacuation, minimum number of evacuation paths required for evacuation in least possible time and the starting schedules on those paths. First, a lower bound on the clearance time is calculated using minimum cost dynamic network flow model on a modified network graph representing the transportation network. Next, a solution pool of feasible paths between all O-D pairs is generated. Using the input from the first two models, a flow assignment model is developed to select the best paths from the pool and assign flow and decide schedule for evacuation with lowest clearance time possible. All the proposed models are mixed integer linear programing models and formulation is done for System Optimum (SO) scenario where the emphasis is on complete network evacuation in minimum possible clearance time without any preset priority. We demonstrate that the model can handle large size networks with low computation time. A numerical example illustrates the applicability and effectiveness of the proposed approach for evacuation.     

A versatile strategy for tuning the color of electrochemiluminescence using silica nanoparticles

Colour emission of core-shell silica-PEG nanoparticles in water is tuned with an electrochemically induced energy transfer approach. The lack of solubility problems, side electrochemical reactions involving donors and acceptors within the nanoparticle, and the possibility of using many classes of dyes in ECL applications confirm the validity of this strategy.     

Facile separation of chiral 1,3-dihydrobenzo[c]furan derivatives using a -xylose moiety as a protecting group

1,2-O-Isopropylidene-α- -xylofuranose has been used to protect one aldehyde group of o-phthalaldehyde. This chiral protecting group acts as a resolving agent and this leads to separable diastereoisomers when a new stereogenic centre is created by the conversion of the second aldehyde group to a benzyloxyhydroxyethyl chain. These separated diastereoisomers were cyclised to 1,3-dihydrobenzo[c]furans with retention of chiral integrity at the C3 site thus allowing further elaboration to enantiomerically pure nucleoside analogues.     

Cathodically deposited polypyridine films: A novel electroactive polyconjugated polymer

Poly-2,5- and poly-2,6-pyridine coatings have been produced on glassy-carbon electrodes by nickelcatalysed reduction of the corresponding dibromopyridine in acetonitrile. Poly-2,5-pyridine films display two reversible cathodic cycles, one of which is due to nickel ions coordinated to pyridine moieties and the other to the polymeric backbone. Both reductions lead to the polymer changing from the insulating to the conductive state. Conversely, Poly-2,6-pyridine films are not reversibly electroactive and the differences are discussed in terms of conjugation along the polymeric chain.     

First countable extensions of regular spaces

We investigate feebly compact extensions of first countable regular locally feebly compact spaces. Solutions of problems posed by R. M. Stephenson, Jr. and G. M. Reed are given.

     

Dye-doped nanomaterials: Strategic design and role in electrochemiluminescence

1. Download : Download high-res image (66KB)
2. Download : Download full-size image

     

Evaluation of chlorinated by-products in drinking waters of Central Friuli (Italy)

Drinkable water supplied by aqueducts undergoes preliminar potabilization which, in Italy, is mainly accomplished by chlorine addition. The bactericidal action involved in this process is always accompanied by chlorination and oxidation of organic species (mainly humic and fulvic acids) naturally present in treated waters, so that many disinfection by-products (DBPs) are formed, such as trihalomethanes (THMs) and halo-acetic acids (HAA), which can represent a chemical risk for public health. The aim of this study was the monitoring of DBPs in drinking water disinfected by chlorination, supplied by four different aqueducts of Central Friuli (Italy). DBP evaluations were performed in water samples consisting of both input and output of disinfection plants. The results of analytical determinations were worked out to provide the THM and HAA parameters for disinfected waters, while in feeding waters the following different conventional parameters were adopted: (i) trihalomethanes formation potential (THMFP), (ii) halo-acetic acids formation potential (HAAFP) and (iii) UV absorbance at 254 nm (UV254). The quite moderate content of chlorinated products found in all samples considered highlighted the excellent quality of potabilized waters available in Central Friuli. Moreover, our results confirmed that the majority of DBPs formed when chlorine is used for water disinfection consists of THMs, while chlorites and chlorates prevailed when potabilization is accomplished by using chlorine dioxide. Finally, simple UV254 monitoring turned out to be a profitable approach for the determination of chlorinated by-products only when THMs prevail among DBPs.