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.     

Investigation of low-temperature regeneration of activated carbon

Granular activated carbon loaded with aniline,o-nitroaniline oro-nitrophenol, regenerated at relatively low temperature (450° in N₂ atmosphere), shows losses of cyclic adsorption performances (about 5 % per cycle) comparable to those occurring with standard thermal regeneration (950° in controlled atmosphere). Adsorbate build-ups and related surface modifications have been determined.

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Zusammenfassung Mit Anilin,o-Nitroanilin undo-Nitrophenol beladene, bei relativ niedriger Temperatur (450° in N₂-Atmosphäre) regenerierte granulierte Aktivkohle, zeigt zyklische Verluste der Adsorptionsleistung (etwa 5 % je Zyklus), welche mit den bei thermischer Standard-Regenerierung (950° in gesteuerter Atmosphäre) vorkommenden vergleichbar sind. Der Aufbau der Adsorbate und die damit verbundenen Oberflächenänderungen wurden bestimmt.

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Résumé Le charbon actif en granulés, chargé d'aniline, d'o-nitroaniline et d'o-nitrophénol, régénéré à une température relativement faible (450° dans une atmosphère d'azote) montre des pertes de rendement d'adsorption cyclique (environ 5 p.c. par cycle) comparables à celles qui ont lieu lors de la régénération thermique standard (950° en atmosphère contrôlée). On a déterminé la constitution des adsorbats et les modifications relatives de surface.

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, , -, - – 450° . , ( 5% ) – 950° . .

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Work supported by IRSA-CNR, contract no. 77.01823.11.

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Thanks are due to Mr. L. Pace for skilful contribution to the experimental work.     

High resolution chromatographic techniques for the evaluation of atmospheric pollutants

The use of high resolution chromatographic techniques for the determination of species of great importance in atmospheric pollution is critically reviewed. Attention has been focused on those pollutants recently recognized to be responsible for biological activity of particulate matter, acid deposition, and photochemical smog generation. The unique contribution made by capillary GC to the solution of environmental problems is demonstrated by the results obtained in the identification of several nitrofluoranthene/pyrene isomers in urban dust, industrial emissions, and automobile exhaust and by the selective determination of 2,3,7,8-tetrachlorodibenzo-ρ-dioxin in fly-ash emitted from urban incinerators. Also organic components dissolved in rain-water can be analyzed by capillary chromatography after sample enrichment on traps filled with solid sorbents. The recent availability of sampling precedures suitable for the collection of gaseous species which play an important role in acid deposition makes possible their determination by chromatographic techniques. Inorganic acids, sampled through high efficiency annular denuders to obtain discrimination between gaseous species and aerosols, can be determined by ion chromatography. Peroxyacyl nitrates, relevant to photochemical pollution, can be determined by GC combined with electron capture detection. New fields of application for high resolution chromatography are discussed.     

Determination of moxifloxacin in tablets and human urine by square-wave adsorptive voltammetry

This work presents an electroanalytical methodology developed for square-wave voltammetry based in the electrochemical reduction in hanging mercury drop electrode (HMDE), which is simple, fast, reliable and sensitive for determination of moxifloxacin (MOXI) in tablets and spiked urine human samples. The support electrolyte that provided a more defined and intense peak current for MOXI determination was the phosphate buffer 0.04 mol l^{− 1} pH 8.0. In the best-optimized conditions the drug presented an only peak of reduction at − 1.38 V vs. Ag/AgCl, using an E_acc. of − 0.30 V. An LOD of 0.44 and 3.20 ng ml^{− 1} and an LOQ of 1.46 and 10.60 ng ml^{− 1} were found for the pure standard of moxifloxacin and in the presence of matrix, respectively. A good recovery was obtained for assay spiked urine samples and a good quantification of MOXI was achieved in a commercial formulation. The methodology proposed was more sensitive than the spectrofluorimetric and spectrophotometric method with precision and accuracy equivalent.     

Determination of indican and tryptophan in normal and uraemic patients by high-performance liquid chromatography with a new electrochemical detector

A simple analytical procedure has been developed for the determination of indican and tryptophan in biological fluids by reversed-phase liquid chromatography using a new electrochemical detector consisting of a tubular anode obtained by moulding graphitized carbon black and polyethylene. The hydrodynamic voltammetry of these compounds has been carried out and it has been found that, by operating in isocratic conditions with phosphate buffer (pH 4.0)-methanol (93:7), the reported compounds can be determined directly. The procedure can be applied for the determination of the free compounds on ultrafiltered serum as well as of their total content on serum deproteinized with methanol. Levels of both compounds in normal and uraemic patients have been measured and the relative ratios between free and total content yield a useful marker for patients with renal disease. The limits of quantitation of indican and tryptophan in serum were 5 and 10 ng/ml, respectively. The within-day assay coefficient of variation for total indican and tryptophan ranged from 3.0 to 3.6% and from 3.8 to 4.1%, respectively. The day-to-day assay coefficient of variation for total indican and tryptophan ranged from 3.4 to 3.7% and from 4.6 to 5.0%, respectively.     

Thermogravimetric study of magnetite reduction at low temperature

Results on hydrogen reduction of pure magnetite to iron at low temperature are reported as part of research on ammonia synthesis catalyst. Experimental work was carried out by thermogravimetry and by electron microscopy.The reduction has a typical S-shaped kinetic curve, with a poorly reproducible induction period. The slope of the reduction curve at 50% conversion (k _0.5) was found to depend on sample mass (2–50 mg), particle size, temperature (220–280C) and presence of moisture in the hydrogen .The results suggest both interparticle and intraparticle (through iron ash) diffusion to be slow. Morphological examinations of the sample at various reduction degrees support this interpretation.

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Zusammenfassung Die Ergebnisse der Reduktion von reinem Magnetit zu Eisen durch Wasserstoff bei niedrigen Temperaturen werden als Teil einer Forschungsarbeit über Katalysatoren zur Ammoniak-Synthese mitgeteilt. Die Versuche wurden mittels Thermogravimetrie und Elektronenmikroskopie durchgeführt.Die Reduktion verläuft nach einer typisch S-förmigen kinetischen Kurve, mit einer schlecht reproduzierbaren Induktionsperiode. Es wurde festgestellt, daß die Steile der Kurve bei 50% Konversion (k _0.5) von der Probenmenge (2–50 mg), der Teilchengröße, der Temperatur (220 bis 280) und der Feuchtigkeit des Wasserstoffes abhängt.Diese Ergebnisse lassen darauf schliessen, daß sowohl die interpartikuläre als auch die intrapartikuläre Diffusion (durch die Eisen-Asche) langsam ist. Diese Deutung wird durch morphologische Prüfung des Musters bei verschiedenen Reduktionsstufen unterstützt.

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Résumé On communique les résultats obtenus en réduisant par l'hydrogène à basse température la magnétite pure en fer, travail faisant partie de recherches sur les catalyseurs pour la synthèse de l'ammoniac. Les expériences ont été effectuées par thermogravimétrie et par microscopic électronique.La courbe cinétique de la réduction présente la forme en S type, avec une période d'induction peu reproductible. Il est apparu que la pente de la courbe de réduction, pour un taux de conversion de 50% (k _0.5) dépendait de la prise d'essai (2–50 mg), de la dimension des particules, de la température (220 à 280) et de la présence d'humidité dans l'hydrogène .Ces résultats permettent de conclure que les processus de diffusion sont lents, qu'ils soient de type interparticule ou intraparticule. L'examen morphologique des échantillons pour divers degrés de réduction a confirmé cette interprétation.

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, , . . S- , . , 50% (_0.5) (2–50 ), , (220–280) (₂)=1,2 ). , , , , . .

     

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.