Markov partition in non-hyperbolic interval dynamics

We considerC ² unimodal mapsf such that all periodic points are hyperbolic, the critical point is non-degenerated and non-recurrent, and the Julia set does not contain intervals. We construct a Markov partition for a big part of the Julia set. Then we use it to estimate the limit capacity and Hausdorff dimension of the Julia set.Partially supported by CNPq, S.C.T.-Brazil     

Biosorption of Chromium(III) by Biomass of Seaweed Sargassum sp. in a Fixed-Bed Column

This work aimed at modeling chromium biosorption using the biomass of seaweed Sargassum sp. in a fixed-bed column. The mathematical model used was obtained from the mass balance of the component in the liquid phase and in the biosorbent material. The effects of both axial dispersion in the column and the resistance to mass transfer in the solid were considered for the solution of the partial differential equations of the model, using the Galerkin method on finite elements. To represent the equilibrium data of the batch system the Langmuir isotherm were used. The chromium ion adsorption capacity of the seaweed Sargassum sp., at a temperature of 30°C and pH 3.5, was 2.61 mmol/g. The model performance was evaluated from experimental data obtained at 30°C for flow rates of 2, 6 and 8 mL/min. The parameters of the model, mass transfer and axial dispersion coefficients, were adjusted from these experimental data. The model proved adequate to describe chromium biosorption dynamics in fixed-bed columns.     

Entropy and ergodic probability for differentiable dynamical systems and their bundle extensions

We answer a problem of Liao [S.T. Liao, Standard systems of differential equations and obstruction sets—from linearity to perturbations, in: System Researches, Proceedings Dedicated to the 85th Anniversary of Qian Xue-Sen, Zhejiang Education Press, Hangzhou, China, 1996, pp. 279-290 (in Chinese)]: A C¹ vector field or a C¹ diffeomorphism on an n-dimensional manifold has equal entropy with that of its bundle extensions. We also prove that each ergodic probability with simple Lyapunov spectrum has at most n²n! covering probabilities on each bundle extension.     

Synthesis of Ultra-Fine Columbite Powder MgNb2O6 by the Polymerized Complex Method

Pure MgNb₂O₆ powders with high specific surface area and high crystallinity have been successfully synthesized by the Polymerized Complex (PC) Method. A solution of water, citric acid, ethylene glycol and niobium and magnesium ions, was polymerized at 130°C by the water elimination and was calcined at 400°C for 2 h. The precursor formed was calcined at temperatures from 700°C to 1000°C in air to obtain the columbite phase. Thermal analysis, Raman spectroscopy, x-ray diffraction, adsorption/desorption hysteresis and scanning electron microscopy were used to investigate the polymer decomposition and the columbite phase evolution. No evidence for phase separation of crystalline MgCO₃ and Nb₂O₅ in Raman spectra and x-ray diffraction pattern as distinct intermediates were found, and the MgNb₂O₆ probably is formed through a single-step decomposition of oxycarbonate intermediate, as other double oxide synthesized by the PC Method, as indicated by the thermal decomposition of the precursor.     

Development of a rapid and specific assay for detection of busulfan in human plasma by high-performance liquid chromatography/electrospray ionization tandem mass spectrometry

A sensitive and specific assay for detection of busulfan in human plasma was developed. The assay is based on rapid isolation of busulfan by liquid-liquid extraction with ethyl acetate, and detection by high-performance liquid chromatography with electrospray ionization and tandem mass spectrometry. 1,6-Bis(methanesulfonyloxy)hexane, a synthesized analogue of busulfan, was used as the internal standard (IS). The acquisition was performed in the multiple reaction monitoring mode; busulfan and the IS were detected with no interferences from plasma matrix. The method was linear over the range 5-2500 ng mL(-1), with r2 > 0.99 and a run time of only 3.5 min. The intra- and inter-assay precisions were in the ranges 2.1-11.9% and 3.2-10.1%, respectively, and the intra- and inter-assay accuracies were 92.2-107.6% and 94.7-104.1%, respectively. The absolute recoveries were 82.0% (20 ng mL(-1)), 90.6% (1000 ng mL(-1)) and 80.0% (2000 ng mL(-1)) for busulfan, and 89.1% for the IS (1000 ng mL(-1)). The limits of detection and quantification were 2 and 5 ng mL(-1), respectively. The validated method was successfully applied to analyze plasma samples obtained from six adults receiving doses of 1 mg kg(-1) in a conditioning regimen prior to bone marrow transplantation. A marked intra-patient variation in busulfan concentrations during the steady state was observed, which limits the application of pharmacokinetic modeling and suggests that continuous therapeutic monitoring is necessary for adequate individualized dosing. In this regard, the present assay brings important advantages relative to other methods described in the literature, i.e., it is highly specific and simple to perform, with a rapid chromatographic run time (3.5 min), and the whole procedure can be completed in 4-5 h, which would permit dose corrections after the third dose allowing earlier and better dosing adjustments towards the target level of busulfan.     

The partial hydrogenation of benzene to cyclohexene by nanoscale ruthenium catalysts in imidazolium ionic liquids

The controlled decomposition of an Ru(0) organometallic precursor dispersed in 1-n-butyl-3-methylimidazolium hexafluorophosphate (BMI.PF(6)), tetrafluoroborate (BMI.BF(4)) or trifluoromethane sulfonate (BMI.CF(3)SO(3)) ionic liquids with H(2) represents a simple and efficient method for the generation of Ru(0) nanoparticles. TEM analysis of these nanoparticles shows the formation of superstructures with diameters of approximately 57 nm that contain dispersed Ru(0) nanoparticles with diameters of 2.6+/-0.4 nm. These nanoparticles dispersed in the ionic liquids are efficient multiphase catalysts for the hydrogenation of alkenes and benzene under mild reaction conditions (4 atm, 75 degrees C). The ternary diagram (benzene/cyclohexene/BMI.PF(6)) indicated a maximum of 1 % cyclohexene concentration in BMI.PF(6), which is attained with 4 % benzene in the ionic phase. This solubility difference in the ionic liquid can be used for the extraction of cyclohexene during benzene hydrogenation by Ru catalysts suspended in BMI.PF(6). Selectivities of up to 39 % in cyclohexene can be attained at very low benzene conversion. Although the maximum yield of 2 % in cyclohexene is too low for technical applications, it represents a rare example of partial hydrogenation of benzene by soluble transition-metal nanoparticles.     

Extraction of Pb(II), Cd(II), and Hg(II) from aqueous solution by nitrogen and thiol functionality grafted to silica gel measured by calorimetry

The reaction of ethylene sulfide with 3-aminopropyltrimethoxysilane gave a new silylating agent, which was anchored onto a silica surface via the sol–gel procedure. This surface displayed a chelating moiety containing nitrogen and two sulfur basic centers potentially capable of extracting cations from aqueous solutions. The process of metal extraction was followed by a batch method, and fitted to a modified Langmuir equation. The maximum adsorption capacities found were: 2.06 ± 0.01, 3.72 ± 0.02, and 5.14 ± 0.02 mmol g⁻¹ for Pb(II), Cd(II), and Hg(II), respectively. The enthalpies of bending are: −1.16 ± 0.04, −3.60 ± 0.10, and −8.94 ± 0.03 kJ mol⁻¹ for Cd(II), Pb(II), and Hg(II), respectively. The Gibbs free energies of binding agree with the spontaneity of the proposed reactions between cations and basic centers.     

Complete 1H and 13C NMR assignments for two new monodesmoside saponins from Pentaclethra macroloba (Willd.) Kuntze

A detailed NMR study and full assignments of the 1H and 13C spectral data for two novel triterpenoid saponins isolated from the stem bark of Pentaclethra macroloba (Willd.) Kuntze are described. Their structures were established using a combination of 1D and 2D NMR techniques including 1H,1H-COSY, TOCSY, NOESY, gs-HMQC and gs-HMBC, and also electrospray ionization mass spectrometry and chemical methods. The structures were established as 3beta-O-([O-beta-D-glucopyranosyl-(1-->2)-O-beta-D-glucopyranosyl-(1-->4)-O-beta-D-glucopyranosyl-(1-->3)-O-alpha-L-rhamnopyranosyl-(1-->2)]-[O-beta-D-glucopyranosyl-(1-->3)-O-beta-D-glucopyranosyl-(1-->4)])-alpha-L-arabinopyranosylhederagenin (1) and 3beta-O-)[O-beta-D-glucopyranosyl-(1-->2)-O-beta-D-glucopyranosyl-(1-->4)-O-beta-D-glucopyranosyl-(1-->3)-O-alpha-L-rhamnopyranosyl-(1-->2)]-[O-beta-D-glucopyranosyl-(1-->3)-O-beta-D-glucopyranosyl-(1-->4)])-alpha-L-arabinopyranosyloleanolic acid (2).     

Complete 1H and 13C NMR assignments of aurasperone A and fonsecinone A, two bis-naphthopyrones produced by Aspergillus aculeatus

Complete assignments of 1H and 13C NMR chemical shifts of the polyketides aurasperone A and fonsecinone A were made by means of nuclear Overhauser enhancement and heteronuclear NMR correlation experiments. These compounds were isolated for the first time from Aspergillus aculeatus, an endophytic fungus obtained from leaves of Melia azedarach(Meliaceae).