Predicting the Mechanical Properties of Binary Blends of Immiscible Polymers

We couple a morphological study of an immiscible binary AB mixture with a micromechanical simulation to determine how the spatial distribution of the A and B domains and the interfacial region (interphase) affects the mechanical behavior of the blend. The morphological studies are conducted through a three-dimensional Cahn-Hilliard (CH) simulation. Through the CH calculations, we obtain the size and structure of the domains for different blend compositions. The output of the CH model serves as the input to the Lattice Spring Model (LSM), which consists of a three-dimensional network of springs. In particular, the location of the different phases is mapped onto the LSM lattice and the appropriate force constants are assigned to the LSM sites. A stress is applied to the LSM lattice and we calculate the elastic response of the material. We find that the local stress and strain fields are highly dependent on the morphology of the system. By integrating the morphological and mechanical models, we can isolate how modifications in the composition of the mixture affect the macroscopic behavior. Thus, we can establish how choices made in the components affect the ultimate performance of the material.     

Determination of mercury in sludge and materials used for HG-eliminations from industrial waste waters by zeeman atomic absorption spectrometry after matrix modification with potassium bromide and bromine

Summary Mercury was determined by Zeeman Atomic Absorption Spectrometry after matrix modification of urine and waste water by addition of 0.1M HNO₃, 0.05M KBr, and 5l Br₂/ml, and after its extraction from sludge, iron sludge and ion exchanger by a mixture containing the same additives. The same samples were also analysed by the cold vapour method after wet oxidation of the samples in closed teflon bombs. The ratio of the corresponding concentrations was 1.21±0.39 (SD) and the concentration range covered 0.1–50000 mg Hg/kg. The analytical powers of both procedures are compared.

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Bestimmung von Quecksilber in Schlamm und in für die Reinigung industrieller Abwässer verwendeten Materialien mit der Zeeman-Atomab-sorptions-Spektrometrie nach Matrixmodifizierung durch Kaliumbromid und Brom

Zusammenfassung Quecksilber wurde mit der Zeeman-Atomabsorptions-Spektroskopie in Urin und Abwässern nach einer Matrixmodifizierung durch Zugabe von 0,1M HNO₃, 0,05M KBr und 5 l Br₂/ml sowie nach seiner Extraktion aus Schlamm, Eisenschlamm und Ionenaustauschern mit einer Mischung der gleichen Zusatzstoffe bestimmt. Die gleichen Proben wurden auch nach der Kalt-Dampf-Methode nach dem Naßaufschluß in geschlossenen Teflonbomben analysiert. Das Verhältnis der betreffenden Konzentrationen betrug 1,21±0,39 (Standardabweichung), wobei der Konzentrationsbereich 0,1–50000 mg Hg/kg umfaßte. Die analytischen Leistungsfähigkeiten der beiden Verfahren wurden verglichen.

     

Synthesis of Novel <Emphasis Type="Italic">D</Emphasis>-<Emphasis Type="Italic">Seco</Emphasis>-Pregnenes

Summary. A new synthetic route was developed for the preparation of trans-3-hydroxy-16,17-seco-pregna-5,17(20)-dien-16-al, using Grob fragmentation as the key step. This seco-steroid contains a formyl group and an unsaturated side-chain in a sterically favourable position, and is therefore a promising starting material for the synthesis of novel condensed steroid heterocycles.Received March 22, 2003; accepted April 22, 2003 Published online September 25, 2003     

A new route to 2-styrylbenzimidazoles

An attempt was made to prepare 2-benzylquinoxalin-3-one by hydrolyzing the azlactone, 2-phenyl-4-benzylidene-5-oxazolone to β-phenylpyruvic acid and then treating this in situ with o-phenylenediamine (OPDA). The initial hydrolysis apparantly proceeded only as far as opening the azlactone ring forming 2-benzamidocinnamic acid which condensed with OPDA to form a substituted styrylbenzimidazole.     

Effect of hydrodynamic interactions on the evolution of chemically reactive ternary mixtures

We investigate the structural evolution of an A/B/C ternary mixture in which the A and B components can undergo a reversible chemical reaction to form C. We developed a lattice Boltzmann model for this ternary mixture that allows us to capture both the reaction kinetics and the hydrodynamic interactions within the system. We use this model to study a specific reactive mixture in which C acts as a surfactant, i.e., the formation of C at the A/B interface decreases the interfacial tension between the A and B domains. We found that the dynamics of the system is different for fluids in the diffusive and viscous regimes. In the diffusive regime, the formation of a layer of C at the interface leads to a freezing of the structural evolution in the fluid; the values of the reaction rate constants determine the characteristic domain size in the system. In the viscous regime, where hydrodynamic interactions are important, interfacial reactions cause a slowing down of the domain growth, but do not arrest the evolution of the mixture. The results provide guidelines for controlling the morphology of this complex ternary fluid.     

Determination of drug-cyclodextrin binding constants by capillary zone electrophoresis

Binding constants of the optical isomers of Deprenyl® (selegiline) and its potential metabolites with (2,6-di-O-methyl)--cyclodextrin were determined using electrophoretic mobility data gained from separations performed by capillary electrophoresis, and absorbancies obtained from spectrophotometric experiments. To calculate equilibrium constants l: l complex formation have been assumed. The comparison of the equilibrium constants calculated from different methods shows similar values in their order of magnitude. Their difference may probably be explained by the different media of the measurements. The effect of the structure of compounds on chiral discrimination were also elucidated.     

Why not ICP as atom reservoir for AAS?

The sensitivity S_A of determination by inductively coupled plasma atomic absorption spectrometry (ICP—AAS) is discussed. All important factors influencing S_A are comprised in one single sensitivity formula, which allows an estimate to be made of the correct order of magnitude of S_A for both flame—AAS and ICP—AAS measurements. The most important analytical factors are the degree of dissociation and ionization (0≤f_C, and f_I≤1), the dilution factor f_D, which takes into account the dilution of the analysis element A by its transition from the solution to the ICP, and the absorption path length b. Like flame—AAS, an analytical approach using ICP—AAS has high selectivity and makes it possible to carry out determinations without chemical and ionization interferences. This important advantage of ICP—AAS in comparison to flame—AAS is based on the fact that the ideal condition f_C→1 and Δf→0 for the analysis and standard solutions can be much more easily realized in the ICP than in flames. Serious disadvantages of an ICP as an atomic reservoir for AAS are the reduced sensitivity and lower detection power compared to flame—AAS. The reduction of S_A is caused mainly by the reduction of b/f_D by a factor of about 0.1 and to a smaller degree by stronger broadening of the absorption line and the depopulation of the lower energy state of the atom A that absorbs the resonance radiation. The estimated S_A value for A = Ag, Al, Ca, Cd, Co, Cr, Cu, Pd and Pt agree with the corresponding experimental values to within a factor of about 3. No experimental values could be obtained for B and Si. An application field of ICP—AAS is the analysis of complex compounds that are difficult to dissociate into atoms using flames. In these determinations, a high sensitivity is generally not needed but a good selectivity is important. Some applications are shown.