Rheological studies and optimization of Herschel–Bulkley parameters of an environmentally friendly drilling fluid using genetic algorithm

The Herschel–Bulkley rheological parameters of an environmentally friendly drilling fluid formulated based on an Algerian bentonite and two polymers—hydroxyethyl cellulose and polyethylene glycol—have been optimized using a genetic algorithm. The effect of hydroxyethyl cellulose, temperature, pH and sodium chloride (NaCl) on the three-parameter Herschel-Bulkley model was also studied. The genetic algorithm technique provided improved rheological parameter characterization compared to the nonlinear regression, especially in the case of drilling fluids formulated with sodium chloride making it a better choice. Furthermore, the oscillatory test offered more reliable yield stress values. The rheological parameters were found to be very sensitive to different conditions. Yield stress and consistency index increased with increasing the hydroxyethyl cellulose concentration, reaching maximum at a temperature of 65 °C and decreased with decreasing pH and also when adding sodium chloride to the drilling fluid. The flow index changed inversely to yield stress and consistency index. The physical origins of these changes in rheological parameters were discussed and correlation between variation in rheological parameters and bentonite suspension properties were concluded. Based on these results, it is recommended to use the proposed formulation of drilling fluid at high temperature and when the formation of alkaline pH is encountered due to the gelation mechanism and to select the optimum concentration of NaCl to avoid degradation of the rheological parameters.

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Erratum to: Synthesis,X-ray structure and theoretical study of benzazole thioether and its zinc complex as corrosion inhibitors for steel in acidic medium

Research on Chemical Intermediates -     

A Convenient and efficient method for the preparation of 6-Acyl-2(3H)-benzoxazolones

Benzoxazolinone derivatives have been found to exhibit various pharmacological properties and 6-acyl-2(3H)-benzoxazolones are considered as key starting materials for the preparation of these compounds. Reported here are the optimal conditions for a regioselective acylation at the 6-position of the benzoxazolinone ring. A general method leading to the expected products in excellent yields consists in using a mixture of aluminum chloride-dimethylformamide as catalyst and acid anhydrides or chlorides as acylating agents.     

Low-Temperature Synthesis of Nanosize Zn2SiO4:Mn2+ Phosphor from the Precursor Sol in Supercritical Ethanol and its Photoluminescent Properties

Acetylcellulose (AC)/silica and polyvinylpyrrolidone (PVP)/silica composites were prepared by the sol–gel method from Si(OCH₃)₄-AC-HNO₃-H₂O-tetrahydrofuran-CH₃OC₂H₄OH and Si(OCH₃)₄-PVP-(CH₃COOH or NH₃)-H₂O-CH₃OH-CH₃OC₂H₄OH solutions. AC/silica composites were composed of micrometer-sized particles rich in silica and a matrix rich in AC, while PVP/silica composites were single-phase on the SEM length scale. The AC/silica composites exhibited elastic-plastic behavior, and had excellent machinability without chipping on cutting with an electric saw while the PVP/silica composites showed less plasticity and machinability. Youngs modulus and bending strength were increased by post-drying, 1.8–2.8 GPa and 49–88 MPa, respectively, for the AC/silica composites, and 1.0–3.9 GPa and 17–79 MPa, respectively, for the PVP/silica composites.     

Senecipyrrolidine,an unusual pyrrolidine alkaloid isolated from Jacobaea gigantea (Desf.) Pelser (Asteraceae)

Alkaloids and phenolic compounds are among the most biologically active natural products from the Jacobaea/Senecio genera (Asteraceae). To isolate original natural products directly from Jacobaea gigantea crude polar extracts, centrifugal partition chromatography (CPC) was used. Previously, we reported the phytochemical study of J. gigantea (syn. Senecio giganteus) n-butanol extract using various classical chromatographical techniques combined with CPC. Herein major constituents from the J. gigantea crude ethyl acetate extract and further compounds from the n-butanol extract were purified in only one step using this technique. A new pyrrolidine alkaloid, named senecipyrrolidine was isolated along with thirteen known compounds – chiro-inositol, three phenolic acids, six flavonoids, two quinones and emiline, another pyrrolidine alkaloid – from crude n-butanol or ethyl acetate extracts. Pyrrolidine alkaloids were isolated for the first time in the Jacobaea/Senecio genera and were probably biogenetically related to the two isolated quinones derivatives jacaranone and 3a-hydroxy-3,3a,7,7a-tetrahydrobenzofuran-2,6-dione, isolated in this species.     

The new one‐dimensional coordination polymer catena‐poly[[diaquasodium(I)]‐μ‐oxalato‐[diaquairon(III)]‐μ‐oxalato]

The oxalate dianion is one of the most studied ligands and is capable of bridging two or more metal centres and creating inorganic polymers based on the assembly of metal polyhedra with a wide variety of one‐, two‐ or three‐dimensional extended structures. Yellow single crystals of a new mixed‐metal oxalate, namely catena‐poly[[diaquasodium(I)]‐μ‐oxalato‐κ⁴O¹,O²:O^1′,O^2′‐[diaquairon(III)]‐μ‐oxalato‐κ⁴O¹,O²:O^1′,O^2′], [NaFe(C₂O₄)₂(H₂O)₄]_n, have been synthesized and the crystal structure elucidated by X‐ray diffraction analysis. The compound crystallizes in the noncentrosymmetric space group I4₁ (Z = 4). The asymmetric unit contains one Na^I and one Fe^III atom lying on a fourfold symmetry axis, one μ₂‐bridging oxalate ligand and two aqua ligands. Each metal atom is surrounded by two chelating oxalate ligands and two equivalent water molecules. The structure consists of infinite one‐dimensional chains of alternating FeO₄(H₂OW1)₂ and NaO₄(H₂OW2)₂ octahedra, bridged by oxalate ligands, parallel to the [100] and [010] directions, respectively. Because of the cis configuration and the μ₂‐coordination mode of the oxalate ligands, the chains run in a zigzag manner. This arrangement facilitates the formation of hydrogen bonds between neighbouring chains involving the H₂O and oxalate ligands, leading to a two‐dimensional framework. The structure of this new one‐dimensional coordination polymer is shown to be unique among the A^IM^III(C₂O₄)₂(H₂O)_n series. In addition, the absorption bands in the IR and UV–Visible regions and their assignments are in good agreement with the local symmetry of the oxalate ligand and the irregular environment of iron(III). The final product of the thermal decomposition of this precursor is the well‐known ternary oxide NaFeO₂.     

Exterior penalty in optimal control problem with state-control constraints

We consider an abstract optimal control problem with additional equality and inequality state and control constraints, we use the exterior penalty function to transform the constrained optimal control problem into a sequence of unconstrained optimal control problems, under conditions in control lie in L ₁, the sequence of the solution to the unconstrained problem contains a subsequence converging of the solution of constrained problem, this convergence is strong when the problemis non convex, and is weak if the problemis convex in control. This generalizes the results of P.Nepomiastcthy [4] where he considered the control in the Hilbert space L ²(I,? ^m ).