Global Weak Solutions for a Parabolic System Modeling a One-Dimensional Miscible Flow in Porous Media

We consider an initial boundary value problem for a nonlinear differential system of two equations. Such a system is formed by the equations of compressible miscible flow in a one-dimensional porous medium. No assumption about the mobility ratio is involved. Under some reasonable assumptions on the data, we prove the existence of a global weak solution. Our basic approach is the semi-Galerkin method. We use the technique of renormalized solutions for parabolic equations in the derivation ofa prioriestimates.     

A new method for constructing a minimal PERT network

A project is an enterprise consisting of several activities which are to be carried out in some specific order. The activities and the order in which they need to be carried out can be represented by a PERT network. The PERT technique is a traditional, well-known approach to the expert of project management. When networks are used, it often becomes necessary to draw dummy activities. Since the computation of project completion time is proportional to the number of arcs, including dummy arcs, it is desirable to draw a network with as few dummy activities as possible.In this paper, we propose a new method for constructing, for a given project scheduling problem, a PERT network having as small as possible the number of dummy arcs by using some results on line graphs. This algorithm deals with the existence of transitive arcs. The paper contains illustrative examples, proofs of some theoretical results as well as a comparative study with a similar algorithm known in the literature. Computational results showed the superiority of our algorithm.     

A Compact Solar Laser Side-Pumping Scheme Using Four Off-Axis Parabolic Mirrors

Journal of Russian Laser Research - Laser side-pumping approach is an extremely attractive configuration for many laser applications. Through this approach, the laser beam can be generated in the...     

Reaction with hydrazonoyl halides XXIII [1]: Synthesis and reactions of C‐coumarinoyl‐N‐arylformohydrazonoyl bromides

C‐Coumarinoyl‐N‐arylformohydrazonoyl bromides ( 3 ) were synthesized by reaction of N‐nitrosoarylacetamides with an appropriate sulfonium bromide in ethanol at room temperature. The reactions of potassium thiocyanate, potassium selenocyanate, thiourea, methyl phenylthiocarbomate, and methyl phenylhydrazinedithioate with hydrazonoyl bromide 3a were examined. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 355–362, 1999     

Improvement of the Pd/Al2O3 Catalyst by the Control of the Sol-Gel Preparative Parameters

In this work, the metal dispersion of the Pd/Al₂O₃ catalyst prepared by sol-gel method is improved by an adequate optimisation of the preparative variables. First, the gelation temperature and the ageing time are selected, in order to avoid the reduction of the metal precursor (palladium acetylacetonate, Pd(acac)₂) by the solvent (sec-butanol, sB). The metal sintering effect on the catalysts treated in oxygen at 500°C is then minimized when the alumina pore size is controlled by the variation of the alumium alkoxide (AsB) concentration and the acetic acid amount ([AcA]/[AsB]). The appearance of new palladium particles on the alumina surface and the matching between the particle diameters and the pore sizes were also effective for the metallic surface area improvement on the samples treated in oxygen at 800°C. Compared to the reference catalysts, the higher metal dispersion obtained on the sol-gel ones was the determinant factor for their higher catalytic activity in methane combustion.     

Synthesis and Biological Evaluation of a Novel Series of Chalcones Incorporated Pyrazole Moiety as Anticancer and Antimicrobial Agents

A newly synthesized series of chalcone derivatives containing pyrazole rings were synthesized and evaluated for their cytotoxic activities in vitro against several human cancer cell lines. Most of the prepared compounds showed potential cytotoxicity against human breast cancer cell lines MCF-7, HEPG-2, and HCT-116. Also the compounds were evaluated as antimicrobial agents. The three compounds 3, 4, and 5 were proved to be better anticancer agents than the positive standard doxorubicin with IC50 values (4.7, 4.4, and 3.9???g/ml) against the same human cancer cell lines, whereas compounds 5 and 6 showed the most active antimicrobial compounds in comparison to the other chalcones.     

Syntheses and characterizations of poly[2‐(dimethylamino)ethyl methacrylate]–poly(propylene oxide)–poly[2‐(dimethylamino)ethyl methacrylate] ABA triblock copolymers

A novel, near‐monodisperse, well‐defined ABA triblock copolymer, poly[2‐(dimethylamino)ethyl methacrylate]‐b‐poly(propylene oxide)‐b‐poly[2‐(dimethylamino)ethyl methacrylate], was synthesized via oxyanion‐initiated polymerization. The initiator was a telechelic‐type potassium alcoholate prepared from poly(propylene glycol) and KH in dry tetrahydrofuran. The copolymers produced were characterized by Fourier transform infrared, ¹H NMR, and gel permeation chromatography (GPC). GPC and ¹H NMR analyses showed that the products obtained were the desired copolymers, with narrow molecular weight distributions (ca. 1.09–1.11) very close to that of the original poly(propylene glycol). ¹H NMR, surface tension measurements, and dynamic light scattering all indicated that the triblock copolymer led to interesting aqueous solution behaviors, including temperature‐induced micellization and very high surface activity. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 624–631, 2002; DOI 10.1002/pola.10144     

Facile one-pot,three-component synthesis of novel bis(heterocycles) incorporating thieno[2,3-b]thiophenes via Michael addition reaction

A synthesis of novel series of bis(2-amino-3-cyano-4H-chromene), bis(2-amino-3-cyanopyrano[3,2-c]chromene), bis(6-amino-5-cyano-1,4-dihydropyrano[2,3-c]pyrazole), and bis(2,7-diamino-3,4,6-tricyanopyrazolo[1,5-a]pyridine) derivatives linked to thieno[2,3-b]thiophene core via ether or ester linkages was reported. The formation of the target compounds presumably proceeds through a three component reaction of the appropriate bis(aldehyde) with 2 M of each of malononitrile and the corresponding active methylene compounds namely; dimedone, 4-hydroxycoumarine, 5-methyl-2,4-dihydro-3H-pyrazol-3-one, or cyanomethylpyrazole in dioxane at reflux in the presence of piperdine as a basic catalyst. The chemical structures of the new compounds were elucidated by several spectral tools.     

Utility of 2‐[4‐(3‐oxobenzo[f]‐2H‐chromen‐2‐yl)‐1,3‐thiazol‐2‐yl]ethanenitrile in heterocyclic synthesis

Pyrazolo[4,3‐d]pyrimidines, pyrazolo[4,3‐d]triazolino[4,3‐a]pyrimidines, 3‐(2‐thiazolyl)thiophenes, thiazolo[3,2‐a]pyridine and pyrazolo[1,5‐a]pyrimidines were synthesized from 2‐[4‐(3‐oxobenzo[f]‐2H‐chromen‐2‐yl)‐1,3‐thiazol‐2‐yl]ethanenitrile. The newly synthesized compounds were elucidated by elemental analysis, spectral data, chemical transformation and alternative synthesis route whenever possible.     

A new bacterial biosensor for trichloroethylene detection based on a three-dimensional carbon nanotubes bioarchitecture

Trichloroethylene (TCE), a suspected human carcinogen, is one of the most common volatile groundwater contaminants. Many different methodologies have already been developed for the determination of TCE and its degradation products in water, but most of them are costly, time-consuming and require well-trained operators. In this work, a fast, sensitive and miniaturised whole cell conductometric biosensor was developed for the determination of trichloroethylene. The biosensor assembly was prepared by immobilising Pseudomonas putida F1 bacteria (PpF1) at the surface of gold interdigitated microelectrodes through a three-dimensional alkanethiol self-assembly monolayer/carbon nanotube architecture functionalised with Pseudomonas antibodies. The biosensor response was linear from 0.07 to 100 μM of TCE (9–13,100 μg L⁻¹). No significant loss of the enzymatic activity was observed after 5 weeks of storage at 4 °C in the M457 pH 7 defined medium (two or three measurements per week). Ninety-two per cent of the initial signal still remained after 7 weeks. The biosensor response to TCE was not significantly affected by cis-1,2-dichloroethylene and vinyl chloride and, in a limited way, by phenol. Toluene was the major interference found. The bacterial biosensor was successfully applied to the determination of TCE in spiked groundwater samples and in six water samples collected in an urban industrial site contaminated with TCE. Gas chromatography–mass spectrometric analysis of these samples confirmed the biosensor measurements.