Synthesis of anomerically pure vinyl sulfone-modified pent-2-enofuranosides and hex-2-enopyranosides: a group of highly reactive Michael acceptors for accessing carbohydrate based synthons

Syntheses of the benzyl or the trityl protected α- and β-anomers of vinyl sulfone-modified pent-2-enofuranosides have been initiated by the ring opening of the suitably masked methyl α-lyxofuranosyl-epoxide or methyl β-ribofuranosyl-epoxide or by the nucleophilic displacement of the leaving groups in benzyl protected 3-O-tosyl xylofuranoside and 3-O-mesyl ribofuranoside by p-thiocresol. In case of the latter set of starting materials, α- and β-methyl glycosides formed in almost equal ratio only from the derivatives of d-xylose. For the synthesis of α- and β-anomers of vinyl sulfone-modified hex-2-enopyranosides, a d-glucose derivative was selected over a d-allose derivative as the starting material because the former almost exclusively produced the required methyl pyranosides whereas the latter produced a mixture. All sulfides were converted to vinyl sulfone-modified carbohydrates by the sequential application of oxidation, mesylation and base induced elimination reactions.     

Self-energy of a charge near a metal surface

A quantum mechanical expression for the self-energy of a charged particle near a metal surface has been derived. The expression incorporates the interaction of the charge with the surface and bulk plasmons including their dispersions in the hydrodynamic model. It is found that the inclusion of the plasmons dispersions gives result for the saturated value of the image potential for copper closer to experiment.     

Synthesis,microstructure, and copolymerization studies of 2-chloroethyl α-chloroacrylate

Poly(2-chloroethyl α-chloroacrylate) was synthesized by radical initiation, and its microstructure was evaluated using carbon-13 NMR. Methyl methacrylate (M₁) and 2-chloroethyl α-chloroacrylate (M₂) were copolymerized in toluene at 55°C using azobisisobutyronitrile as initiator. The reactivity ratios are 0.37 ± 0.28 and 1.21 ± 2.26, The thermal properties of these copolymers have also been reported.     

An approximation algorithm for a symmetric Generalized Multiple Depot, Multiple Travelling Salesman Problem

In this paper, we present an algorithm with an approximation factor of 2 for a Generalized, Multiple Depot, Multiple Travelling Salesman Problem (GMTSP) when the costs are symmetric and satisfy the triangle inequality. The algorithm requires finding a degree constrained minimum spanning tree which we compute using a Lagrangian relaxation.     

The migrating myoelectric complex of the small intestine

Gastric and small intestinal myoelectric and motor activity is divided into two main patterns, fed and fasted. During fasting, the predominant pattern of activity is the migrating myoelectric complex (MMC), a cyclically occurring pattern of electric and mechanical activity that is initiated in the stomach and duodenum almost simultaneously and, from there, propagates the length of the small intestine. Cyclic motor activity also occurs in the lower esophageal sphincter, the gallbladder, and the sphincter of Oddi with a duration that is related to the MMC in the small intestine. Of the possible mechanisms for initiation of the MMC in the small intestine (extrinsic neural control, intrinsic neural control, and hormonal control), intrinsic neural control via a series of coupled is the most likely. The keep this sentence in! hormone motilin also plays a role in the initiation of MMCs. After a meal, in man the MMC is disrupted and replaced by irregular contractions. The physiologic role of the MMC is to clear the stomach and small intestine of residual food, secretions, and desquamated cells and propel them to the colon. Disruption of the MMC cycle is associated with bacterial overgrowth in some patients, an observation that supports the proposed cleansing function of the MMC cycle.     

A nonlinear bilevel model for analysis of electric utility demand-side planning issues

An application of bilevel programming in the electric utility industry is presented. The model is nonlinear and is used to analyze various economic issues that affect electric utility planning. The electric utility at the upper level of the model seeks to minimize costs or maximize benefits while controlling electric rates and subsidizing energy conservation programs. Customers at the lower level attempt to maximize their net benefit by consuming electricity and investing in conservation. This model considers factors such as free riders and the rebound effect which affect the net benefits of utility resource plans but are ignored by most planning models. The model's solutions shed light on utility issues including whether there can be a practical difference between various objectives, including minimizing cost (least cost planning) and maximizing net social welfare (value based planning).     

Synthesis and properties of π-conjugated donor–acceptor macrocycles derived from phenanthrylene building blocks

Phenanthrylene-ethynylidene macrocycles combining electron donor and electron acceptor subunits in their shape-persistent fully conjugated core were synthesized. The donor subunits consisted of two 9,10-dialkoxyphenanthrenes linked either with 1,2-ethynylidene or 2,5-thienylene bridge. The acceptors were 9,10-phenanthroquinone and dibenzoquinoxaline and dibenzophenazines derived from it. Solvatochromic photoluminescence from intramolecular-charge-transfer (ICT) excited state was observed mainly in non-polar solvents. In more polar solvents, the excited states favor non-radiative relaxation. DFT calculated HOMO/LUMO energies of the macrocycles correlate well with spectroscopic and electrochemical data. In the series of substituted dibenzophenazine acceptors a good correlation with Hammett substituent constants σ_p^– was found.