New Methods and Results in the Study of Polyacids

The present status of research on condensed vanadic, molybdic, and tungstic acids is reviewed. Information about the structure and formation of polyanions can be obtained by X-ray analysis and from nuclear magnetic resonance, infrared, and Raman spectra, as well as from complex formation in aqueous solution. Salts of the polyacids can be prepared in organic solvents by hydrolysis of esters of the metal oxoacids.     

Design and implementation of a MEMS microphone array system for real-time speech acquisition

Despite many attractive features and the potential for capturing sound in challenging acoustic environments, arrays with a large number of microphones have for a long time been discarded as a practical solution for speech acquisition. This is, among other reasons, due to the high production and computational costs. Only a few realizations of large microphone array systems have been documented, mainly for research and instrumentation use. The advent of MEMS microphones and computationally powerful off-the-shelf hardware has created new possibilities for microphone array development. We investigate a real life application, specifically the case of live sports broadcast, and the requirements that a such application imposes on a microphone array system. We present a system architecture of the first large (300 element circular array with a diameter of 2 m) MEMS microphone array system. In the proposed system, the latest technological advances are utilized to create a user-friendly array control interface. The array’s performance is examined in an anechoic chamber and on a crowded basketball field, and finally compared with existing solutions. The results illustrate the potential of a large MEMS microphone array as part of the technological development in sound acquisition for entertainment and security applications.     

Determination of alkyl, chloro and mononitrophenols in water by sample-acetylation and automatic on-line solid phase extraction-gas chromatography-mass spectrometry

Summary On-line solid phase extraction-gas chromatographymass spectrometry has been used for trace analysis of phenols in water samples at the low ng L⁻¹ level. Phenols have been derivatized by in-sample acetylation prior to an automatic SPE-GC-MS procedure. The method was validated with 26 alkyl, chloro and mononitrophenols including 4-nonylphenol and 17-ethinylestradiol. Target analysis was performed by time-scheduled, selected ion monitoring. The on-line SPE-GC approach resulted in low sample volume (typically 10 mL), good reproducibility, sensitivity and considerable saving of reagents, material and manual work.     

Eine neue chemische Methode der Wasserbestimmung in organischen L?sungsmitteln

Zusammenfassung Es wird ein Verfahren der Wasserbestimmung in organischen Lösungsmitteln beschrieben, das auf der Hydrolyse von OrthovanadinsÄure-tert.-butylester in Gegenwart einer Anhydrobase (Ammoniak bzw. Acridin) beruht. Ester und Anhydrobase werden im überschu\ angewendet. Die Hydrolyse führt in stöchiometrisch verlaufender Reaktion zur AusfÄllung eines unlöslichen Vanadats, das filtriert, mit absolutem Äther gewaschen, in SchwefelsÄure gelöst und mit Eisen(II)-ammoniumsulfatlösung titriert wird.Die Durchführung der Untersuchungen ist durch die GewÄhrung von ERP-Mitteln wesentlich gefördert worden. Die Verfasser danken dafür sehr herzlich.     

Controlled haptotropic rearrangements--towards a stereospecific molecular switch based on chiral arene chromium complexes

A stereospecific molecular switch has been designed based on a reversible thermo- or photo-induced haptotropic shift of a Cr(CO)3 fragment along a naphthohydroquinone skeleton.     

Elastische und unelastische Streuung von Deuteronen an Aluminium bei 11,8 MeV

Using the 11.8 MeV deuteron beam of a cyclotron, a study has been made of the angular dependence of the deuteron spectrum from interactions on Al²⁷. Separation of the deuterons from other products of the deuteron reactions was accomplished by recordingdE/dx, measured by a three fold proportional counter, andE, measured by a CsI-counter, on an oscilloscope screen. The experimental inelastic angular distributions have the shape of a direct interaction process. The elastic angular distribution shows pronounced diffraction maxima.