Pseudoguaiane-type sesquiterpenes and inhibitors on nitric oxide production from Dichrocephala integrifolia

Three new pseudoguaiane-type sesquiterpenes, dichrocepholides A-C, and two new pseudoguaiane-type sesquiterpene dimers, dichrocepholides D and E, were isolated from the aerial part of Dichrocephala integrifolia. Their stereostructures were determined on the basis of chemical and physicochemical evidence. In addition, the extract and its principal sesquiterpene constituent, parthenin, showed an inhibitory activity on nitric oxide (NO) production and on induction of inducible NO synthase.     

Absorption, fluorescence, and semiempirical ASED-MO studies on a typical Brooker''s merocyanine dye

Solvatochromism and Solvatofluorchromism of Brooker's merocyanine 1-methyl-4- (4′-hydroxystyryl) pyridinium betaine, M, were studied in twelve polar protic and aprotic solvents. Moderate hypsochromic fluorescence energy shifts are 4.57 kcal mole⁻¹ while strong hypsochromic absorption energy shifts are 16.63 kcal mole⁻¹. Decreasing of the dipole moment of M upon excitation is the factor, which is responsible for the difference between the two energy shifts. The change of both energies rectilinearly with solvent acidity scale shows the importance of oxygen atom of M as a strong basic center. The application of the atom superposition and electron delocalization molecular orbital (ASED-MO) theory reproduces geometrical and electronic structures for M, which agree well with the experimental observations. The calculations suggest strongly that the dye has a benzenoid valence structure in the ground state and shifts towards a quinonoid one upon excitation with an observed decreasing of the dipole moment. The changing of the dipole moment is explained clearly depending upon the calculated charge distribution over the whole skeleton of the molecule. The formation of a H-bond between the water molecule and the highly negative oxycyclic oxygen atom of M has slightly effect on its dipole moment in the ground state. This leads to suggest that this kind of interaction could be represented as attacking of water with acidic character on the basic site of M. Also, the calculations predict that the formation of monohydrated complex is an exothermic, down hill reaction, which is confirmed from the stabilization of the frontier molecular orbitals, oxygen lone-pair and the HOMO levels.     

Decentralized optimum load frequency control of interconnected power systems

A new approach for designing a linear regulator for the problem of load frequency control (LFC) of interconnected power systems is developed. The control is specified to be of proportional-plus-integral (P-I) form and is only a function of the measurable states. The LFC problem is formulated as a parameter optimization problem.This work was supported in part by the National Research Council of Canada, Grant No. A4146.     

Microwave-assisted synthesis of highly luminescent CdSeTe@ZnS-SiO2 quantum dots and their application in the detection of Cu(II)

Highly luminescent and low toxic glutathione-capped CdSeTe@ZnS-SiO(2) quantum dots were successfully synthesized via a promising microwave strategy, and then applied in the detection of Cu(2+).     

E.M.F. and kinetic studies of the ion-pairing effects on the rate of aquation of chloropentamminechromium(III) perchlorate in different dicarboxylate medium

Summary Rate coefficients, k, for aquation of [Cr(NH₃)₅Cl]²⁺ in 10% ethanol solutions of some dicarboxylates have been determined by potentiometric titration methods. The dissociation constants of ion-pairs so formed have been obtained from e.m.f.s. of a cell comprising glass and calomel electrodes. A wide range of k(ion) and k(ion-pair) values and dissociation constants has been obtained and a new correlation between k(ion-pair) and association constants among the dicarboxylate series studied has been established.     

Environmental pollution study around a large industrial area near Cairo, Egypt

Neutron activation analysis is one of the most extensively used methods for environmental studies due to its high sensitivity, precision, versatility and multielemental character. Cement factories at Helwan, south of Cairo, contribute substantially to environmental pollution. Determination of minor and trace-elements in dust particulates from the cement industrial areas has been performed to assess the air quality from an environmental and human health point of view. Soil-7 standard reference material from IAEA and SRM-1571 from NBS were used for quality assurance testing. The data obtained indicate there is an indication that the pollution could be hazardous to people living in and around the area surveyed.     

Molecular dynamics simulation study of the structural features and inclusion capacities of cucurbit[6]uril derivatives in aqueous solutions

Molecular dynamics (MD) simulations were performed for cucurbit[6]uril (CB6) methyl and cyclohexyl derivatives in aqueous solutions. Furthermore, MD simulations have been conducted to study the inclusion complexes between each CB6 derivative with α,ω-pentane diammonium ion (NH₃⁺(CH₂)₅NH₃⁺) to estimate the binding free energies, the complex geometries and the intermolecular forces responsible for complex formation. Results show a complete inclusion of the guest molecule in the cavity of the host for all complexes. Results also indicate that the guest dynamics inside the cavity of the substituted host is similar to that for the unsubstituted host. This demonstrates that the molecular recognition of the host is not affected by the alkyl substitution at the equator. Also, there is an insignificant conformational change of the macrocyclic structure upon inclusion of the guest. Molecular mechanics/Poisson Boltzmann surface area method was used to estimate the binding free energy of each complex. Results indicate that host–guest electrostatic interactions make the largest contribution to the complex binding free energy. Moreover, van der Waals interactions add significantly to the complex stability. The guest molecules show more or less similar binding free energies with the substituted CB6 that exhibits slightly more negative values than unsubstituted CB6 which is proved also by umbrella sampling.     

Isothermal crystallization kinetics of the chalcogenide glass Bi10Se70In20

Results of DSC under isothermal conditions on the chalcogenide glass Bi₁₀Se₇₀In₂₀ are reported and discussed. The Johnson-Mehl-Avrami equation was used to evaluate the crystallization activation energy (E _a) and the crystallization mechanism was studied. The results indicate that the crystallization mechanism involves one dimensional and surface processes for Bi₁₀Se₇₀In₂₀. The average calculated value ofE _a for Bi₁₀Se₇₀In₂₀ is 34.38±1.46 kcal/mol.

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Zusammenfassung Die Ergebnisse von isothermen DSC-Untersuchungen an dem Chalkogenglas Bi₁₀Se₇₀In₂₀ wurden beschrieben und diskutiert. Die AktivierungsenergieE _a der Kristallisierung wurde mit Hilfe der Johnson-Mehl-Avrami-Gleichung ermittelt und der Kristallisierungsmechanismus untersucht. Die Ergebnisse zeigen, da\ der Kristallisierungsmechanismus von Bi₁₀Se₇₀In₂₀ eindimensionale und OberflÄchenvorgÄnge beinhaltet. Der errechnete mittlere Wert vonE _a betrÄgt für Bi₁₀Se₇₀In₂₀ 34.38±1.46 kcal/mol.

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The authors are grateful to Dr. N. Afify for many helpful discussions. This work was partly supported by a Grant-in-Aid for Scientific Research from the Deutsche Gesellschaft für Technische Zussammenarbeit (G.T.Z.) and D.A.A.D., Germany     

New ent-kaurane diterpenoid dimer from Pulicaria inuloides

A new naturally occurring ent-kaurane diterpenoid dimer, 15β, 15′β-oxybis (ent-kaur-16-en-19-oic acid) (1) along with six known compounds, 15β-hydroxy-ent-kaur-16-en-19-oic acid (2), 15β-hydroxy-ent-kaur-16-en-19-oate-β-d-glucopyranoside (3), 6-hydroxykaempferol-3, 7-dimethyl ether (4), quercetagetin 3, 7, 3′-trimethyl ether (5), β-sitosterol (6) and β-sitosterol glucoside (daucosterol) (7) were isolated from the aerial parts of Pulicaria inuloides DC. Compounds 2–5 were isolated for the first time from genus Pulicaria. The structures of compounds 1–7 were established on the basis of extensive 1D and 2D NMR spectroscopic techniques in combination with ESI-MS. The antimicrobial activity of the isolated compounds was evaluated against Staphylococcus aureus, Escherichia coli and Candida albicans. Sulphorhodamine B cytotoxic assay against HepG2 (liver cancer) cell line and ABTS antioxidant assay were carried out.     

Application of multivariate calibration for studying competitive adsorption of two problematic colorants on acid-activated-kaolinitic clay

Research on Chemical Intermediates - The competitive adsorption of two common colorants (brilliant blue and brilliant black) by activated kaolinite was investigated after fast quantification of...