Photocatalytic oxidation of phenol in aqueous solutions with oxygen catalyzed by supported metallophthalocyanine catalyst

In this paper, zinc tetraaminophthalocyanine (Zn-APc) was immobilized on cellulosic fiber by covalent bond to obtain a novel cellulosic fiber supported metallophthalocyanine, named Zn-TDTAPc-F. At pH 11, upon visible light irradiation for 6 h in the presence of O2, Zn-TDTAPc-F was found to be highly effective for the degradation of phenol in aqueous solution, and the degradation rate of phenol was more than 95%. HPLC was used to confirm formic acid, fumaric acid and maleic acid as its main degradation products.     

Analysis of aerosols at the bosporus bridge of Istanbul

Air samples collected at the second Bosporus bridge of Istanbul which carries a heavy traffic load between Asia and Europe, were analyzed for 22 elements by the INAA method. Pb, Cd and Fe concentrations in the samples were determined by AAS. Iron concentrations were used as a cross check between the two methods. In order to define the enrichment factors for the elements in the bridge area, a sample collected from our university campus which can be considered as a rural site, was also analyzed. Differences were observed especially for Br, Al, Mg, Ti, Cu and Na between the two sites. Based on the results of the samples from the bridge, we got a value of 0.58(16) for the Br/Pb-ratio.     

Röntgenographische,thermoelektrische, und IR-spektroskopische Untersuchung des Spinellsystems LixMn1−xV2O4

The spinels of the system Li_xMn_1?xV₂O₄ (0 ? x ? 1) have been prepared at 700–750°C from LiV₂O₄ and MnV₂O₄. The lattice constants decrease linearly with increasing x. In the region x>0.75, the d-electrons of V should be delocalized as the VV distances are lower than the critical VV separation of 2.94 Å. Experimentally, the samples with x>0.6 show no IR absorption bands and the Seebeck coefficient is near zero. The Seebeck coefficient can be described with a model of intermediate polarons and can be expressed by the equation $\text{Θ = 198}\text{log}\text{[1 +}\text{(1 ? x)}{}^5\text{x}\text{]}$.     

Chromatographie von Carbamat- und Phenylharnstoff-Pesticiden auf Dünnschichten von basischem Zinkcarbonat

Thin layers of basic zinc carbonate can be used with good results for separation and multiple identification of carbamate and phenylurea pesticides. Five important substances could be separated by one-dimension TLC. The best results were obtained by the following developing solvents: a) benzene, b) a mixture of benzene/petroleum ether/chloroform (6∶1∶1). The substances are either recognisable in short-wave UV-light, when a fluorescence indicator (F 254 nm) is added, or in day-light, after spraying a solution of 0.1 N AgNO₃ in 3 N HNO₃, followed by an UV-exposure for about 4 min.     

Using the diphosphanyl radical as a potential spin label: effect of motion on the EPR spectrum of an R1(R2)P--PR1 radical

The EPR spectrum of the novel radical Mes*(CH3)P--PMes* (Mes*=2,4,6-(tBu)3C6H2) was measured in the temperature range 100-300 K, and was found to be drastically temperature dependent as a result of the large anisotropy of the 31P hyperfine tensors. Below 180 K, a spectrum of the liquid solution is accurately simulated by calculating the spectral modifications due to slow tumbling of the radical. To achieve this simulation, an algorithm was developed by extending the well-known nitroxide slow-motion simulation technique for the coupling of one electron spin to two nuclear spins. An additional dynamic process responsible for the observed line broadening was found to occur between 180 K and room temperature; this broadening is consistent with an exchange between two conformations. The differences between the isotropic 31P couplings associated with the two conformers are shown to be probably due to an internal rotation about the P--P bond.     

Weighted majority games and the matrix of homogeneity

If a weighted majority game (not necessarily constant sum or super additive) is described by the weights (voting strength) of the players involved and a majority level, then it is desirable to know whether the game is in addition homogeneous. The paper provides a recursive procedure defining a test for homogeneity. This procedure involves the computation of a number theoretical function, the matrix of homogeneity. If this matrix is knownall majority levels with respect to which the given set of weights represents a homogeneous simple weighted majority game are known at once.

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Zusammenfassung Ein gewichtetes Majoritätsspiel (nicht notwendig superadditiv oder mit Konstantsummeneigenschaft) kann beschrieben werden durch die Gewichte (die Abstimmungsstärke) der beteiligten Spieler und durch eine Mehrheitsschranke. Wenn eine solche Darstellung gegeben ist, so ist es wünschenswert, das Spiel zusätzlich auf die Eigenschaft der Homogenität hin zu untersuchen. Die vorliegende Arbeit stellt eine rekursive Prozedur zur Verfügung, die einen Test auf Homogenität einer vorgelegten Darstellung eines Spieles impliziert. Die Prozedur ermöglicht die Berechnung einer zahlentechnischen Funktion, der Homogenitätsmatrix. Wenn diese Matrix bekannt ist, kann man bei einem vorgegebenen Gewichtssatz alle Majoritätsschranken angeben, bezüglich welcher die vorgelegten Gewichte ein homogenes einfaches gewichtetes Majoritätsspiel darstellen.

     

Preparation and Properties of Composite Polypyrrole/Pt Catalyst Systems

Three different methods for the preparation and modification of conducting polymer/noble metal catalyst systems consisting of polypyrrole (PPy) and platinum (Pt) are described for the anodic oxidation of methanol. The first method consists of the electrochemical deposition of a thin PPy film on glassy carbon substrate, which is modified with Pt either by electroreduction of hexachloroplatinate, codeposition from a nanodispersed Pt solution, or incorporation of tetrachloroplatinate as counterion followed by cathodic reduction. A second method is based on the preparation of nanoscale PPy(PSS) particles by chemical polymerization with polystyrenesulfonate PSS^– as the counterion. This material is a favorable catalyst support for nanodispersed Pt due to its mixed electronic and cationic conductivity. To study the electrochemical properties, the particulate system PPy(PSS)/Pt is fixed in a carbon fiber electrode. A third method was developed which brings the polypyrrole in close contact to a proton exchanger membrane (Nafion) using a special chemical deposition procedure. This method is useful for preparing a membrane electrode assembly (MEA) consisting of Nafion/PPy/Pt. The structural, morphological, and electrocatalytic properties for methanol oxidation were studied depending on the preparation method applied using surface analytical techniques (TEM, SEM, and EDX) and electrochemical measurements (cyclic voltammetry and transient techniques).     

The rhombidodecahedral tessellation of 3-space and a particular 15-vertex triangulation of the 3-dimensional torus

It is well known that the unique 7-vertex triangulation of the 2-dimensional torus S¹×S¹ is a consequence of the relationship between two hexagonal lattices in the euclidean plane: it is just the quotient of the triangular tessellation of the plane by a translation group. Each vertex star is a regular hexagon and the symmetry group of this triangulation is the affine group A(1,₇) in one dimension over ₇. In this paper we describe a particular 15-vertex triangulation of the 3-dimensional torus S¹×S¹×S¹ whose symmetry group is the affine group A(1,₁₅) and which is similarly related to two lattices in euclidean 3-space: it is just the quotient of a particular tessellation of 3-space by a translation group. Each vertex star happens to be a rhombidodecahedron, the dual of a (semiregular) cuboctahedron.     

Eine globalanalytische Behandlung des Douglas'schen Problems

In this paper we consider the Douglas problem of genus O. Starting point is the global analysis for minimal surfaces of the type of the disc which was developed by A.J. Tromba. The set of all k-connected minimal surfaces of genus O has a product structure, which is a consequence of the variation of the conformal type. The base space is the space of domain parameters and the fibres are the manifolds of k-connected minimal surfaces of constant conformal type (cf.[7]). It is possible to develop a global analysis also for the more general situation considered here with the following results:

-The map which assigns to every minimal surface its boundary curve (in the sense of the Douglas problem) is a Fredholm operator. The index depends on the number and the total order of the branch points.

-The analysis allows to prove isolatedness and stability results in a relatively simple way.

     

Registrierende Messung des mechanischen Verlustes von Kunststoffproben

Zusammenfassung Ein neues Verfahren, das eine unmittelbare und kontinuierliche Registrierung des mechanischen Verlustwinkels über einen weiten Temperaturbereich erm?glicht, wird beschrieben. Die Probe wird einer periodischen Biegung (f=2,5 Hz) unterworfen; die Zeit des Kraftnulldurchgangs relativ zur Bewegung ist dem Verlustwinkel proportional und wird elektronisch ermittelt. Das Me\ergebnis ist weitgehend von der Probenform und deren ?nderung w?hrend der Messung (Krümmung der Probe, thermische Ausdehnung usw). unabh?ngig. Der Deutschen Forschungsgemeinschaft sei für die Unterstützung dieser Arbeit verbindlichst gedankt.