Synthesis of Boron Nitride by Self-Propagating Reactions at High Pressure

Peculiarities of the formation of BN in a self-propagating reaction between LiBF₄ and Li₃N have been studied under a wide range of p,T conditions within the region of thermodynamic stability of cBN. Boron nitride crystallized mainly in the form of highly ordered hBN (1700–2100 K), of mesographitic BN (2200–3000 K), or of turbostratic BN (>3000 K). Cubic boron nitride was obtained with a low yield (up to 14 vol%) as a result of precipitation from the metastable eutectic liquid in the BN-Li₃N system. These results give further evidence for an alternative metastable behavior in the BN phase formation under high pressures.     

Rauchgasreinigung mit Reststoffbehandlung und Wertstoffgewinnung in der Abfallverbrennung — Stand und Tendenzen

The design of flue gas treatment equipment in municipal waste incineration plants worldwide varies according to the requirements with respect to pollutant emissions and resource recovery. Various combinations of individual separation processes may be encountered, such as dry particle separation, gas absorption (wet or dry), adsorption, catalytic or thermal conversion. The present comparison of different basic process alternatives indicates that firstly any degree of pollutant removal can be achieved by the available process technologies with corresponding expenditure of money and energy demand, secondly, German plants generally are more complex than plants in other countries due to more stringent separation and resource recovery efficiency requirements, and thirdly, a trend can presently be seen towards more simple and cheaper processes with simultaneous separation of several pollutants in one process step.     

Bewertung von Abfallbehandlungsverfahren: Entscheidungsunterstützung durch die neue VDI‐Richtline 3925

The new VDI guideline 3925 presents assessment tools for the comparison of economic, ecological and also social aspects of different waste treatment processes. Objective of the guideline is to describe the application of suitable scientific and technical assessment methods to waste management strategies. The methods, their applicability, complexity, opportunities and limits are illustrated using practical examples.     

Silica nanotubes and hollow silica nanofibers: Gas phase mineralization,polymerization catalysis and in-situ polyethylene nanocomposites

Gas phase mineralization and mesoscopic replication of polyvinyl alcohol (PVA) nanofibers represents an attractive route to the preparation of silica nanotubes and hollow fibers with independent control of pore diameter and wall size. In the sol/gel gas phase process, PVA nanofibers, produced by electrospinning of aqueous PVA, were encapsulated in a thin silica shell by repeated sequenced feed of SiCl₄ and H₂O vapors, followed by thermal degradation of the PVA core at 550 °C. The hollow fiber wall thickness was governed by the number of SiCl₄/H₂O cycles with an average increase of the wall size of 0.7 nm per cycle. In contrast to conventional sol/gel electrospinning and wet sol/gel dip coating, shearing of such hollow silicate nanofibers afforded single silica nanotubes with an average length of a few microns. Aqueous silica sols added together with PVA gave control of the inner pore architectures. Methylalumoxane (MAO) activated silica nanotubes were used as supports for half sandwich chromium (III) (Cr) and post metallocene (Fe) catalysts for ethylene polymerization and in-situ nanocomposite formation with uniform dispersion of silica nanotubes within the polyethylene matrix. A blend of Cr and Fe was supported on silica nanotubes to produce melt processable polyethylene nanocomposites with bimodal molecular weight distributions.     

Multiphoton imaging with a novel compact diode‐pumped Ti:sapphire oscillator

Multiphoton laser scanning microscopy commonly relies on bulky and expensive femtosecond lasers. We integrated a novel minimal‐footprint Ti:sapphire oscillator, pumped by a frequency‐doubled distributed Bragg reflector tapered diode laser, into a clinical multiphoton tomograph and evaluated its imaging capability using different biological samples, i.e. cell monolayers, corneal tissue, and human skin. With the novel laser, the realization of very compact Ti:sapphire‐based systems for high‐quality multiphoton imaging at a significantly size and weight compared to current systems will become possible. Microsc. Res. Tech. 78:1154–1158, 2015. © 2015 Wiley Periodicals, Inc.     

Traceability of torque transducers under rotating and dynamic operating conditions

Torque transducers in industrial applications are usually used under dynamic and rotating operating conditions. The present article provides a survey of state-of-the-art studies which describe methods for providing traceability of torque measurements under such operating conditions.The method of investigating the effects of rotation is a comparison of measurements of torque in a rotating shaft train gained simultaneously with two different methods. The first method is using a rotating torque transducer, the second one is with a cradle-mounted absorption dynamometer. The method for investigating the effects of dynamic torque is based on experiments with periodic torque but only minimal rotational motion. Torque is generated by a rotary exciter which forces a setup with a torque transducer and some auxiliary components into a periodic rotary motion. The torque measurement provided by the torque transducer is compared to a reference torque. The reference torque is gained by accurately measuring the angular acceleration of the rotation in conjunction with a priori knowledge of the mass moment of inertia.The developments on the periodic dynamic torque have been performed by the Physikalisch-Technische Bundesanstalt (PTB), the German National Metrology Institute. The investigations on rotating torque transducers have been performed by Hottinger Baldwin Messtechnik (HBM), Germany, a manufacturer of torque transducers with a wide experience in torque calibration.     

Components for high speed atomic force microscopy

Many applications in materials science, life science and process control would benefit from atomic force microscopes (AFM) with higher scan speeds. To achieve this, the performance of many of the AFM components has to be increased. In this work, we focus on the cantilever sensor, the scanning unit and the data acquisition. We manufactured 10 microm wide cantilevers which combine high resonance frequencies with low spring constants (160-360 kHz with spring constants of 1-5 pN/nm). For the scanning unit, we developed a new scanner principle, based on stack piezos, which allows the construction of a scanner with 15 microm scan range while retaining high resonance frequencies (>10 kHz). To drive the AFM at high scan speeds and record the height and error signal, we implemented a fast Data Acquisition (DAQ) system based on a commercial DAQ card and a LabView user interface capable of recording 30 frames per second at 150 x 150 pixels.     

Abstract abstract reduction

We propose novel algebraic proof techniques for rewrite systems. Church–Rosser theorems and further fundamental statements that do not mention termination are proved in Kleene algebra. Certain reduction and transformation theorems for termination that depend on abstract commutation, cooperation or simulation properties are proved in an extension with infinite iteration. Benefits of the algebraic approach are simple concise calculational proofs by equational reasoning, connection with automata-based decision procedures and a natural formal semantics for rewriting diagrams. It is therefore especially suited for mechanization and automation.