Laser inhibited diffusion in rhodamine-ethanol solutions

The diffusion of rhodamine-6G dye in ethanol is observed to be inhibited by optical pumping by a cadmium laser. The diffusion process is observed as a function of the solution temperature. The relative difference in diffusion coefficients with and without optical pumping is calculated. The effect is interpreted as being due to a stronger solvent-dye interaction in the first excited singlet state of rhodamine-6G.     

Properties of a two-dimensional asphaltene network at the water-cyclohexane interface deduced from dynamic tensiometry

Static and dynamic tensiometries show that a newly prepared water/asphaltenated cyclohexane interface behaves as expected: the mean area occupied per asphaltene molecule is 2 nm2, and variations of interfacial tension and dilatational elastic modulus with time indicate that equilibrium is reached more slowly than that for usual surfactants. The use of the time/temperature superposition principle allows a detailed rheological study of a 2 day old interface of the same type which has reached equilibrium. It is found that the two-dimensional asphaltene network exhibits a glass transition zone, behaves as a gel near its gelation point, and is built by a universal process of aggregation.     

The multi-item capacitated lot-sizing problem with setup times and shortage costs

We address a multi-item capacitated lot-sizing problem with setup times and shortage costs that arises in real-world production planning problems. Demand cannot be backlogged, but can be totally or partially lost. The problem is NP-hard. A mixed integer mathematical formulation is presented. Our approach in this paper is to propose some classes of valid inequalities based on a generalization of Miller et al. [A.J. Miller, G.L. Nemhauser, M.W.P. Savelsbergh, On the polyhedral structure of a multi-item production planning model with setup times, Mathematical Programming 94 (2003) 375–405] and Marchand and Wolsey [H. Marchand, L.A. Wolsey, The 0–1 knapsack problem with a single continuous variable, Mathematical Programming 85 (1999) 15–33] results. We also describe fast combinatorial separation algorithms for these new inequalities. We use them in a branch-and-cut framework to solve the problem. Some experimental results showing the effectiveness of the approach are reported.     

8-Substituted Xanthines as Phosphodiesterase Inhibitors: Conformation-Dependent Lipophilicity and Structure-Activity Relationships

The 8-substituted xanthines 1 – 21 (including compound S 9795), caffeine ( 22 ), and the three isomeric dimethyl-xanthines 23 – 25 (see Table 1), were examined for their lipophilic behaviour using a reversed-phase HPLC technique. A number of flexible compounds showed a smaller-than-expected lipophilicity which based on conformational and tautomeric calculations were ascribed to the predominance of folded forms. A QSAR analysis of the phosphodiesterase-inhibitory potency of several compounds showed favourable factors to be a low lipophilicity and the absence of a substituent on the N⁷ position.     

Purification and Biochemical Characterization of an Acid-Stable Lipase from the Pyloric Caeca of Sardine (Sardinella aurita)

A lipolytic activity was located in the sardine digestive glands (pyloric caeca), from which a sardine digestive lipase (SaDL) was purified. Pure SaDL has a molecular mass of 43 kDa as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis. The enzyme was found to be more active on short-chain triacylglycerols than on long-chain ones. SaDL does not present the interfacial activation phenomenon. Control experiments were performed under the same experimental conditions, with dromedary and turkey pancreatic lipases and showed a positive interfacial activation phenomenon. Sodium deoxycholate (NaDC) has an inhibitory effect on the lipase activity. The pure enzyme lost 40% of its activity in presence of 8 mM NaDC. SaDL was found to be mostly stable at low pH values. Interestingly, no colipase was detected in the sardine pyloric caeca. Analogous results were reported for the scorpion and the crab digestive systems. This is in line with the idea that colipase might has evolved in mammal animals simultaneously with the appearance of an exocrine pancreas. No similarity was found between the NH₂-terminal amino acid residues of SaDL and those of lipases from the digestive tract of other species. Altogether, these results suggest that SaDL is a member of a new group of lipases belonging to aquatic species.     

Snail Hepatopancreatic Lipase: A New Member of Invertebrates Lipases' Group

Higher animal's lipases are well characterized; however, much less is known about lipases from mollusks. A lipolytic activity was located in the land snail (Eobania vermiculata) digestive glands (hepatopancreas), from which a snail digestive lipase (SnDL) was purified. Pure SnDL has a molecular mass of 60 kDa; it does not present the interfacial activation phenomenon. It was found to be more active on short-chain triacylglycerols than on long-chain triacylglycerols. The NH₂-terminal sequence of the SnDL shows 66% of identity with the 17 NH₂-terminal amino acids of a putative lipase from sea urchin (Strongylocentrotus purpuratus). No sequence identity was found with known lipases. Interestingly, neither colipase nor bile salts were detected in the snail hepatopancreas. This suggests that colipase evolved in vertebrates simultaneously with the appearance of an exocrine pancreas and a true liver which produces bile salts. Altogether, these results suggest that SnDL is a member of a new group of digestive lipases belonging to invertebrates.     

Coulomb dissociation of incident 16O at 4.5 GeV/c

Projectile multifragment breakup of ¹⁶O, ²C and ⁷Li at energies 3.0–4.5 A-GeV is studied by means of the Weizsäcker-Williams method. The fragmentation channels of the ¹⁶O projectile at 4.5 A-GeV are investigated and compared with that of ¹⁶O at 200 A-GeV. The events characterized by N _h=0 and the events due to both Coulomb and diffraction dissociation have been selected and analyzed as a function of impact parameter. Also, the dependence of the electromagnetic dissociation cross-section on incident energy and the charge of projectile and target is found.     

Quantitative Structure-Affinity Relationships of Dopamine D2 Receptor Antagonists: A Comparison between Orthopramides and 6-Methoxysalicylamides

A large series of orthopramides (= 2-methoxybenzamides), 6-methoxysalicylamides, and 2,6-dimethoxy-benzamides were examined for their affinity to the dopamine D₂ receptor. The binding data were correlated with physicochemical parameters and ¹³C-NMR chemical shifts using the cross-validated partial least-squares method and multiple linear regression analysis. The results quantitate the influence of electronic factors and lipophilicity to D₂ receptor binding. They also show that the N-[(1-ethylpyrroIidin-2-yl)methyl] and N-(1-benzylpiperidin-4-yl) side-chains affect the mode of binding of these compounds.