Effect of hydrophobized active carbon on the catalytic activity and adsorptivity of supported cobalt(II)-phthalocyanine

The catalytic activity of cobalt(II)-phthalocyanine [Co(II)Pc] supported on active carbon the oxidation of sulfide ions to elemental sulfur by dioxygen in aqueous solution has been studied. Hydrophobization of the carbon surface facilitates activation of dioxygen by adsorption. The sulfide ion is activated mainly on the supported Co(II)Pc.     

A strategy for a national metrology institute to create a cost effective distributed metrology infrastructure for chemical measurements

A sound strategy for a national metrology institute (NMI) is proposed, describing how to set up an metrology infrastructure for chemical measurements. A national measurement infrastructure is defined as a collection of various measurement services (testing, calibration and reference laboratories) and the communication between these services. For clarity, in this paper the distributed metrology infrastructure covers those organisations that are involved in disseminating measurement traceability (i.e. the national metrology institute and the reference laboratories acting as national reference standard holders).The strategy aims at a proper support of sectoral field laboratories. It is based on a distributed metrology system. Such a system is composed of clearly identified national reference standard holders for particular measurement services (e.g. for a particular analyte in a particular matrix) co-ordinated via an NMI. Such national reference standard holders, appointed by the NMI, represent the best measurement capability inside the country, and their appointment is based on demonstrated measurement competence. They receive support (e.g. under contract) from the NMI to fulfil this role. They have the obligation to demonstrate their measurement capabilities on a regular basis and in a publicly open and transparent way.In particular and carefully selected cases, the NMI itself can and should act as national reference standard holder. The NMI should particularly devote a large part of its resources to cross-sectoral knowledge transfer, to advice and co-ordination. This can be achieved by participating in teaching/training, by supporting the accreditation, by being involved in advising governmental bodies in authorisation of laboratories and by assisting in the implementation of legislation.As a consequence, only when values produced at the NMI (or one of its designated national reference standard holders) are disseminated to field laboratories (e.g. for CRMs or as a calibration service) will it be necessary to have the NMI measurement capability recognised under the CIPM-MRA system.Such a distributed system requires an efficient communication tool between the three stakeholders concerned: the NMI, the national reference standard holder and the end users. The latter not only include the field laboratories, but also governmental bodies and the national accreditation body.Presented at the XVIIIth IMEKO Congress in Dubrovnik-Cavtat, June 22–27, 2003Further contributors to this paper: M. Buzoianu (National Institute of Metrology, Bucharest), W.Kozlowski (Central Office of Measures, Warsaw), P. Klenovsky, Frantisek Jelinek (CMI, Prague), C. Michael (State General Laboratory, Nicosia), Zsofia Nagyné Szilágyi, (National Office of Measures, Budapest), V. Patoprsty (Slovak Institute of Metrology, Bratislava), A. Todorova (SAMTS Sofia)     

Das Wandgleiten beim Fließen von Polymerschmelzen durch Kapillaren mit kreisförmigem Querschnitt

Zusammenfassung In Fortsetzung früherer Arbeiten wird der Einfluß von niedermolekularen Zusätzen auf die effektive Viskosität und das Wandgleiten von Polystyrol beim Fließen durch Kreiskapillaren untersucht. Die Kapillaren wurden aus unterschiedlichen Werkstoffen hergestellt: Stahl, Messing, Aluminium und Polytetrafluoräthylen (Teflon). Bei ansonsten gleichen Bedingungen wird bei der Teflonkapillare ein schnelleres Ausfließen der Polymerschmelze als bei den Metallkapillaren beobachtet. Die Geschwindigkeit des Wandgleitens kann mit Hilfe der Gleichung vonMooney bestimmt werden. Es wird festgestellt, daß diese Geschwindigkeit bei Einführung von niedermolekularen Zusätzen in den Polymeren anwächst. Bei Zugabe von Silikonöl zu Polystyrol kann sich die Durchflußmenge bis zu 400% im Vergleich zu derjenigen ohne Zusätze erhöhen. Es wurden die Anteile der Durchflußmenge berechnet, die auf die Erniedrigung der Viskosität der Polymerschmelze bzw. auf das Wandgleiten zurückzuführen sind.

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Summary In continuation of other recent work the effect of low molecular additives upon effective viscosity and wall slip of polystyrene through circular capillaries is studied. The capillaries are made of different materials: iron, brass, aluminium and polytetrafluorethylene. When all other conditions are unchanged it is observed that when using teflon capillaries polymer flows faster than through metal capillaries. The rate of slipping can be determined by using the equation ofMooney. It is established that this rate increases when polymer melt with low molecular additive is used. When silicon oil is used as an additive to polystyrene the melt flow is increased up to 400% in comparison with polymer without additive. Flow fractions which are due to the decrease of viscosity and due to slip, respectively, are evaluated.

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Mit 4 Abbildungen und 3 Tabellen     

Total reflection X-ray fluorescence analysis of fly ash from Bulgarian coal-fired power plants

The contents of Cl, Ca, K, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, As, Se, Rb, Sr, Ba and Pb in raw coal fly ash from five Bulgarian power plants were determined by total reflection X-ray fluorescence (TXRF), using gallium as the internal standard. The samples were analysed as in slurry form in Triton? X-114. The experimental parameters, such as grain size, concentrations of fly ash slurry and excitation time were optimised. For validation of the method, the certified reference material BCR-176R fly ash was used. The precision of the results obtained is characterised by a relative standard deviation of approximately 10%. The resulting data confirm the suitability of TXRF for the simultaneous determination of major, minor and trace elements in coal fly ash samples. Further advantages provided by TXRF are easy sample preparation (no sample dissolution) and the small sample amount required for analysis.     

A family of parametric schemes of arbitrary even order for solving nonlinear models: CMMSE2016

Many problems related to gas dynamics, heat transfer or chemical reactions are modeled by means of partial differential equations that usually are solved by using approximation techniques. When they are transformed in nonlinear systems of equations via a discretization process, this system is big-sized and high-order iterative methods are specially useful. In this paper, we construct a new family of parametric iterative methods with arbitrary even order, based on the extension of Ostrowski’ and Chun’s methods for solving nonlinear systems. Some elements of the proposed class are known methods meanwhile others are new schemes with good properties. Some numerical tests confirm the theoretical results and allow us to compare the numerical results obtained by applying new methods and known ones on academical examples. In addition, we apply one of our methods for approximating the solution of a heat conduction problem described by a parabolic partial differential equation.     

Multidimensional stability analysis of a family of biparametric iterative methods: CMMSE2016

In this paper, we present a multidimensional real dynamical study of the Ostrowsky–Chun family of iterative methods to solve systems of nonlinear equations. This family was defined initially for solving scalar equations but, in general, scalar methods can be transferred to make them suitable to solve nonlinear systems. The complex dynamical behavior of the rational operator associated to a scalar method applied to low-degree polynomials has shown to be an efficient tool for analyzing the stability and reliability of the methods. However, a good scalar dynamical behavior does not guarantee a good one in multidimensional case. We found different real intervals where both parameters can be defined assuring a completely stable performance and also other regions where it is dangerous to select any of the parameters, as undesirable behavior as attracting elements that are not solution of the problem to be solved appear. This performance is checked on a problem of chemical wave propagation, Fisher’s equation, where the difference in numerical results provided by those elements of the class with good stability properties and those showed to be unstable, is clear.     

Chaos in King’s iterative family

In this paper, the dynamics of King’s family of iterative schemes for solving nonlinear equations is studied. The parameter spaces are presented, showing the complexity of the family. The analysis of the parameter space allows us to find elements of the family that have bad convergence properties, and also other ones with stable behavior.     

Extraction systems of flame atomic absorption determination of trace impurities in high purity nickel salts

Summary Different extraction sytems including long chain quaternary alkylammonium salts and APDC were investigated in order to determine the optimal conditions for extraction separation and preconcentration of traces of Ag, Bi, Cd, Cu, Fe, Mo, Pb, Sb and Zn from high purity NiSO₄·6H₂O, NiCl₂·6H₂O, Ni(OOCCH₃)₂·4H₂O and Ni(NO)₃)₂·6 H₂O. Best results for multielement preconcentration were found with the extraction system HCl-trioctylmethylammonium chloride-0,002 mol/l APDC/MIBK. The proposed method permits the flame atomic absorption determination of 5·10^–6%, Ag, Cd, Cu and Zn, 1·10^–5% Bi, Fe, Pb and 5·10^–5% Mo and Sb with good accuracy and precision.