On equilibrium analysis of acyclic multiclass loss networks under admission control

We consider equilibrium analysis of several dynamic resource sharing policies for multiclass loss networks with acyclic topologies. The policies of interest are based on the principle of prioritizing classes via thresholding or reservation. We show that under each policy the equilibrium network state is a Markov random field and we obtain closed form expressions for the conditional probabilities therein. Such representations drastically reduce the computational complexity of blocking probability and revenue calculations. We provide revenue comparison of the considered policies and several extensions of the applied analytical technique.     

Busy period analysis of the level dependent PH/PH/1/K queue

In this paper, we study the transient behavior of a level dependent single server queuing system with a waiting room of finite size during the busy period. The focus is on the level dependent PH/PH/1/K queue. We derive in closed form the joint transform of the length of the busy period, the number of customers served during the busy period, and the number of losses during the busy period. We differentiate between two types of losses: the overflow losses that are due to a full queue and the losses due to an admission controller. For the M/PH/1/K, M/PH/1/K under a threshold policy, and PH/M/1/K queues, we determine simple expressions for their joint transforms.     

Nano-tube TiO_2 as a new catalyst for eco-friendly synthesis of imines in sunlight

Nanomaterials are considered as suitable heterogeneous catalysts for many organic reactions.Herein nano-tube TiO₂ has been reported as a heterogeneous catalyst,for synthesis of imines in sunlight at room temperature under solvent-free conditions.The condensation of less electrophilic carbonyl compounds with poorly nucleophilic amines was afforded imines in excellent yields.     

Application of hydrophobically modified water‐soluble polyacrylamide conjugated with poly(oxyethylene)‐co‐poly(oxypropylene) surfactant as emulsifier

Hydrophobically modified polyacrylamide (PAAm) was prepared by grafting PAAm with block copolymer of poly(ethylene oxide) and poly(propylene oxide), PEO‐PPO‐PEO, by melt method in the presence of benzoyl peroxide as initiator. The chemical structure of the graft copolymer was determined by FTIR and ¹HNMR analyses. The surface tension, critical micelle concentration, and surface activities were determined at different temperatures. Surface parameters such as surface excess concentration (Γ_max), the area per molecule at interface (A_min), and the effectiveness of surface tension reduction (Π_CMC) were determined at different temperatures from the adsorption isotherms of the prepared surfactants. The prepared surfactant was tested as emulsifier for water with xylene, cyclohexane, or petroleum crude oil synthetic emulsions. Copyright © 2010 John Wiley & Sons, Ltd.     

Nano sulfated titania as solid acid catalyst in direct synthesis of fatty acid amides

Nanosized sulfated titania was prepared by a sol-gel hydrothermal process. X-ray diffraction (XRD), transmission electron, and scanning electron micrographs (TEM and SEM), FT-IR specific surface area, and BET N(2) adsorption were employed to characterize the properties of the synthesized sulfated TiO(2). The results indicate that both anatase and rutile TiO(2) are obtainable. This prepared sulfated titania showed high catalytic activity in direct amidation of fatty acids as well as benzoic acids with various amines under solvent-free conditions.     

The stereoselective total synthesis of (+)-18-(6S,9R,10R)-bovidic acid

An expedient stereoselective total synthesis of 18-carbon (+)-(6S,9R,10R)-bovidic acid, isolated from the pelage and skin of a gaur B. frontalis is described using l-proline catalysed sequential α-aminoxylation and Horner-Wadsworth-Emmons olefination of aldehyde, cross metathesis and tandem Sharpless asymmetric dihydroxylation-S_N2 cyclization reaction as the key steps.     

Assisted intramolecular proton transfer in (uracil)2Ca2+ complexes

The structure and relative stability of the complexes between uracil dimers and Ca²⁺, as well as the proton transfer (PT) processes within these dimers, have been investigated by the density functional theory methods. Although in uracil dimers PT occurs as an almost synchronous double PT processes that connect the diketo dimer with a keto-enol dimer, the process within the most stable (uracil)₂Ca²⁺ complexes is much more complicated, and the product of the reaction looks like the result of an intramolecular PT from one of the NH groups of one monomer to one of the carbonyl groups of the same monomer. An analysis of the force profile along the reaction coordinate shows that the intimate mechanism implies three elementary steps, two intermolecular PTs, and an in-plane displacement of one monomer with respect to the other. The result of this so-called assisted intramolecular proton transfer is the formation of a dimer in which only one monomer is a keto-enol derivative, the other monomer being apparently unchanged, although it suffers significant structural rearrangements along the reaction coordinate. Quite importantly, this dimer is significantly stabilized upon Ca²⁺ association; therefore, while the most stable uracil dimers correspond systematically to associations involving only the diketo forms, in (uracil)₂Ca²⁺ complexes the most stable structures correspond to those in which one of the monomers is a keto-enol uracil isomer.     

Emission-photoactivity cross-processing of mesoporous interfacial charge transfer in Eu3+ doped titania

Periodic mesoporous Eu(3+) doped titania materials were obtained through the EISA (Evaporation Induced Self Assembly) process. Eu(3+) ions, entrapped within the semi-crystalline walls of the highly porous framework, appear to be advantageous during the probing of surface photochemical reactions. Its emission intensity is very sensitive to the presence of physisorbed molecules, in gas or liquid phase, that reside within the pores. In particular, strong fluctuations in intensity of the (5)D(0)→(7)F(2) transition were observed under UV light exposure on the time scale of tens of seconds. The emission modulation dynamics show a strong correlation with the crystallinity of the titania matrix. Correlation of the emission with the photocatalytic activity of the semiconductor for photodegradation of an organic molecule is observed. A model is proposed to describe the involved mechanisms.