Addition of hypobromous acid to 1-phenylcycloalkenes

Reaction of 1-phenylcyclooctene and 1-phenylcycloheptene with N-bromosuccinimide (NBS) in aqueous DMSO gives the corresponding 3-bromo-2-phenylcycloalkenes and 2-phenylcycloalk-2-enols in a ratio of 3 : 1. Unlike them, 1-phenylcyclohexene gives a mixture of 3-bromo-2-phenylcyclohexene and 2-bromo-l-phenylcyclohexanol. The oxidation of allylic alcohols with pyridinium chlorochromate afforded the corresponding α,β-unsaturated ketones.     

Harmonic Riemannian maps on locally conformal Kaehler manifolds

We study harmonic Riemannian maps on locally conformal Kaehler manifolds (lcK manifolds). We show that if a Riemannian holomorphic map between lcK manifolds is harmonic, then the Lee vector field of the domain belongs to the kernel of the Riemannian map under a condition. When the domain is Kaehler, we prove that a Riemannian holomorphic map is harmonic if and only if the lcK manifold is Kaehler. Then we find similar results for Riemannian maps between lcK manifolds and Sasakian manifolds. Finally, we check the constancy of some maps between almost complex (or almost contact) manifolds and almost product manifolds.     

A stochastic theory of pension dynamics

Based on a semi-Markov reward process, a stochastic theory of pension dynamics is developed to characterize the ultimate benefits (and costs) to be derived by a group of similar workers from their career membership in pension plans. This characterization is in terms of a number of basic functions representing the expected value and variability of benefits and costs. Analytical and numerical investigation of these functions provide useful insights into the effects of plan types, vesting rules, coverage, and portability.     

Moment inequalities for a class of stochastic systems

First moment inequalities are developed for the limiting behaviour of a class of stochastic systems, such as queues, storage or insurance-risk systems, subject to two types of input where the “primary” input is generated by a compound Poisson process and the “secondary” input by a cumulative renewal process.     

Entropy generation in developing laminar fluid flow through a circular pipe with variable properties

Entropy generation in a circular pipe is analyzed numerically. A two-dimensional solution for the velocity ant temperature profiles is obtained considering temperature dependent thenmophysical properties. Uniform wall heat flux case is considered as the thermal boundary condition. The distribution of the entropy generation rate is investigated throughout the volume of the fluid as it flows through the pipe. Engine oil is selected as the working fluid. In addition, ethylene glycol and air are used in a parametric study. The total entropy generation rate is calculated by integration over the various cross-sections as well as over the entire volume. The results are compared with those obtained for the constant viscosity case. A considerable discrepancy is found between the two cases since the viscosity of these fluids is highly sensitive to the temperature variation.     

An experimental study on optimization of $${\mathbf{SiO}}_{2}$$ SiO 2 /water nanofluid flows in circular minichannels

Journal of Thermal Analysis and Calorimetry - An experimental research was performed to examine the effect of hydrodynamically and thermally developing distilled water-based SiO $$_2$$ nanofluid...     

Highly Efficient Method Towards In Situ Immobilization of Invertase Using Cryogelation

A novel method was developed for the immobilization of Saccharomyces cerevisiae invertase within supermacroporous polyacrylamide cryogel and was used to produce invert sugar. First, the cross-linking of invertase with soluble polyglutaraldehyde (PGA) was carried out prior to immobilization in order to increase the bulkiness of invertase and thus preventing the leakage of the cross-linked enzyme after immobilization by entrapment. And then, in situ immobilization of PGA cross-linked invertase within cryogel synthesis was achieved by free radical polymerization in semi-frozen state. The method resulted in 100 % immobilization and 74 % activity yields. The immobilized invertase retained all the initial activity for 30 days and 30 batch reactions. Immobilization had no effect on optimum temperature and it was 60 °C for both free and immobilized enzyme. However, optimum pH was affected upon immobilization. Optimum pH values for free and immobilized enzyme were 4.5 and 5.0, respectively. The immobilized enzyme was more stable than the free enzyme at high pH and temperatures. The kinetic parameters for free and immobilized invertase were also determined. The newly developed method is simple yet effective and could be used for the immobilization of some other enzymes and microorganisms.     

Sub-doppler absorption resonances of ring-shaped laser beams in a thin vapor cell

Experimental research is carried out into the features of sub-Doppler absorption resonances caused by optical pumping and transit relaxation of Cs atoms in a thin 120-μm cell (with rarefied Cs vapor) for ring-shaped laser beams. Such resonances are analyzed both in the transmission of the single running beam and at the interaction of counterpropagating beams for different degrees of their spatial overlapping in the cell.     

On sufficient conditions for cost rate function unimodality in periodic review (s, S) inventory models

The cost rate function that arises in the stationary analysis of a class of periodic review regenerative inventory systems is known to be unimodal if the renewal density of the underlying demand sequence is decreasing. We prove that the same result holds, under zero leadtimes, if the renewal density is concave increasing.     

Synthesis of new sulfanyl-, sulfinyl-, and sulfonyl-substituted polychlorobuta-1,3-dienes

New R-sulfanyl-substituted polychlorobuta-1,3-dienes were synthesized by reactions of hexachloro-1,3-butadiene or 1,1,2,4,4-pentachlorobuta-1,3-diene with dimethylbenzenethiols, heptane-1-thiol, and 4-methyl-7-sulfanyl-2H-chromen-2-one. Some sulfides were oxidized to the corresponding sulfoxides and sulfones or brominated with bromine. Among the synthesized compounds, the coumarin derivative, 4-methyl-7-(1,2,3,4,4-pentachlorobuta-1,3-dien-1-ylsulfanyl)-2H-chromen-2-one showed fluorescence properties. 1,1′,1″-[3,4-Dichlorobuta-1,3-diene-1,1,4-triyltris(sulfanediyl)]tris(2,4-dimethylbenzene) reacted with potassium tert-butoxide in petroleum ether to afford a mixture of isomeric 1,1′,1″-[4-chlorobuta-1,2,3-triene-1,1.4-triyltris(sulfanediyl)]tris(2,4-dimethylbenzene) and 1,1′,1″-[2-chlorobut-1-en-3-yne-1,1,4-triyltris(sulfanediyl)]-tris(2,4-dimethylbenzene). The GC/MS method was found to be useful for the separation of some sulfanyl-substituted butadiene isomer mixtures. The synthesized compounds were characterized by elemental analyses, mass spectrometry, UV-Vis, IR, and NMR (¹H, ¹³C) or fluorescence spectroscopy.