The production of porous glassy carbon membranes from swift heavy ion irradiated Kapton

A porous glassy carbon membrane was obtained by first producing ion tracks in a polymeric Kapton film by irradiation with high energy krypton or xenon ions. Pores are formed by selective chemical etching along the ion tracks, and then the film was converted to glassy carbon by heat treatment at 1000 °C under an inert atmosphere. The process yields a self-supported glassy carbon thin membrane. The density of the pores in the membrane depends on the ion irradiation fluence, and the length, diameter and shape of the pores could be controlled by the ion energy and etching procedure.     

Numerical modeling of rarefied gas flow through a slit into vacuum based on the kinetic equation

A rarefied gas flow through a thin slit into vacuum is calculated on the basis of the kinetic model equations applying the discrete velocity method. The calculations are carried out for the whole range of the gas rarefaction from the free-molecular regime to the hydrodynamic one. Numerical data on the flow rate and distributions of density, bulk velocity and temperature along the symmetry axis are reported. A comparison with the corresponding results obtained previously by the direct simulation Monte Carlo method is performed. A good agreement between these results shows a reliability of the model equations which require less computational effort than the Monte Carlo method.     

Poly(imide-amide)-poly(ethylene glycol) hybrid networks: nanostructure,molecular dynamics and membrane properties

Summary Nanometer-scale structure, molecular dynamics (at 100-580 K) and membrane properties were studied in two series of poly(imide-amide) (PIA)-poly(ethylene glycol) (PEG) hybrid networks with regularly varied composition and different lengths of PEG crosslinks (M_n= 1000 or 3400). Combined WAXD/SAXS/polarized microscopy/DSC/DRS/TSDC/creep rate spectroscopy (CRS) analysis of these hybrids was performed. Depending on their composition, semicrystalline or mesomorphous, or amorphous state, and nanostructural heterogeneity were observed for these networks. They could be subdivided into (a) the PIA-rich hybrids with spatially isolated PEG domains, “suppressed” dynamics in the PEG glass transition, and PIA domains with T_g=520–570 K (group 1), and (b) the other hybrids with a continuous PEG phase and low-temperature glass transition only (group 2). Heterogeneity in segmental dynamics was revealed by CRS over the temperature range from T_g^PEG to T_g^PIA. In the second group of hybrids, the permeability coefficients were higher, by two or three orders of magnitude, for organic vapors than those for air gases.     

Modeling Risk of Failure in Nitrification: Simple Model Incorporating Abundance and Diversity

A risk based approach to engineering provides a rational way to balance cost against the need to avoid failure. Such an approach has not been systematically incorporated into the design and operation of wastewater treatment plants. This is perhaps because engineers do not have the means to make risk based predictions of performance. We have adapted a classical technique for incorporating risk in engineering predictions to the oxidation of ammonia, the first step in nitrification. The approach incorporated random changes in load, aeration, and kinetic parameters. Two and three species models were used to evaluate the effect of increasing aeration on the risk of failure. Surprisingly, increased aeration did not lead to a monotonically decreasing risk of failure. Intermediate aeration rates typically increased the standard deviation of the effluent ammonia and thus the risk of failure. Reliable performance was predicted when there was a high abundance of one species or a similar abundance of both. These preliminary but encouraging results suggest risk based approaches offer new and important insights into the operation of biological treatment systems.     

Unusual Magnetic Phase Transitions in Gd<Superscript>3+</Superscript> Clusters in Multicomponent Oxide Glasses

Magnetic susceptibility, EPR and optical properties have been studied in a glass system {20La₂O₃−22Al₂O₃−23 B₂O₃−35(SiO₂+GeO₂)} with a part of La₂O₃ substituted by Gd₂O₃ in different concentrations. Positive Weiss constants have been found in more heavily doped glasses; two magnetic transitions at 55 and 12 K have been detected and ascribed, respectively, to ferromagnetic and antiferromagnetic clusters of Gd³⁺ ions. The EPR spectra confirm the clustering at higher Gd contents. At low temperatures the cluster-related resonance indicates an onset of magnetic anisotropy. The clustering, depending on the Gd concentration, correlates with a shift to lower energies of the strong optical absorption band edge.     

Interdiffusion in Intermetallics

Recently, Tiwari and Mehrotra asserted that the vacancy flux in interdiffusion is driven by a vacancy concentration gradient and also that interdiffusion in intermetallics cannot proceed by the six-jump cycle, triple defect, and antistructural bridge mechanisms. It is shown that those authors’ arguments are incorrect according to classical diffusion theory, by the numerous simulations that have been performed, and by analysis of these mechanisms.     

The template co-crystallization of β-cyclodextrin with polymeric inclusion complex

Summary The study of the crystal formation in aqueous solution of β-cyclodextrin in the presence of the additives of polypropylene oxide in a wide range of macrocycle:polymer molar ratios was carried out. The cyclodextrin separation from the mixture was made by 1) the isothermal crystallization; 2) the rapid crystallization via the precipitation in acetone. The influence of thermodynamic and kinetic factors on the mechanism of crystallization of unbound macrocycles was demonstrated for the first time. It was shown that the isothermal crystallization led to the formation of the mixture of two solids: the channel polymer inclusion complex and unbound β-cyclodextrin in the cage form. The precipitation method at polypropylene oxide content in the initial solutions corresponded to the range of 0,03–92% from stoichiometry of the complex resulted in the formation of the structures with the channel organization of macrocycles. Thus, the ability of β-cyclodextrin for the template co-crystallization with the polymeric inclusion complex was demonstrated. These data enable to develop the novel method of creation of the channel nanoporous structure of β-cyclodextrin. The obtained products represent lamellar structures possessing cylindrical nanopores with the diameter of ∼0,65 nm.     

Service-oriented Access to Next Generation Networks—from Service Creation to Execution

Existing telecommunication networks and classical roles of operators are subject to fundamental change. Many network operators are currently seeking for new sources to generate revenue by exposing network capabilities to 3rd party service providers. At the same time we can observe that services on the World Wide Web (WWW) are becoming mature in terms of the definition of APIs that are offered towards other services. The combinations of those services are commonly referred to as Web 2.0 mash-ups. Rapid service design and creation becomes therefore important to meet the requirements in a changing technology and competitive market environment. This report describes our approach to include Next Generation Networks (NGN)-based telecommunications application enabler into complex services by defining a service broker that mediates between 3rd party applications and NGN service enablers. It provides policy-driven orchestration mechanisms for service enablers, a service authorization functionality, and a service discovery interface for Service Creation Environments. The work has been implemented as part of the Open SOA Telco Playground testbed at Fraunhofer FOKUS.     

Acid‐Free Nickel Catalyst for Stereo‐ and Regioselective Hydrophosphorylation of Alkynes: Synthetic Procedure and Combined Experimental and Theoretical Mechanistic Study

The nickel catalyst prepared in situ from nickel bis(acetylacetonate) [Ni(acac)₂] precursor and bis(diphenylphosphino)ethane (DPPE) ligand has shown excellent performance in the hydrophosphorylation of alkynes. Markovnikov‐type regioselective addition to terminal alkynes and stereoselective addition to internal alkynes were carried out with high selectivity without an acidic co‐catalyst (in contrast to the palladium/acid catalytic system). Various H‐phosphonates and alkynes reacted smoothly in the developed catalytic system with up to 99% yield. The mechanisms of catalyst activation and C P bond formation were revealed by experimental (NMR, ESI‐MS, X‐ray) and theoretical (density functional calculations) studies. Two different pathways of the alkyne insertion in the coordination sphere of the metal are reported for the first time.     

Morphology of polypropylene/silica nano‐ and microcomposites

The aim of this study was to compare the effects of different silica grades on the structure and morphology of isotactic polypropylene (iPP)/silica composites to better understand their structure–property relationships. Isotactic polypropylene composites with 2, 4, 6, 8 vol % of added silica fillers differing in particle size (micro‐ vs. nanosilica) and surface modification (untreated vs. treated surface) were prepared by nonisothermal compression molding and characterized by different methods. The addition of all silica fillers grades to the iPP matrix significantly influenced the spherulitic morphology, while phase characteristics of the iPP matrix seemed to be unaffected. Surface modification of silica fillers exhibited stronger effects on spherulite size than size of silica particles. Nonpolar silica particles, more miscible or compatible with iPP chains than polar silica particles, enabled better spherulitic growth. The spherulite sizes tended to reach equal values at 8 vol % of added silicas showing that spherulite size became independent of filler concentration and surface modification above optimum filler concentration. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013