Occurrence of perfluoroalkyl sulfonates and carboxylates in German drinking water sources compared to other countries.

Different homologues of C4 to C8 perfluoroalkyl carboxylates (PFCAs) and perfluoroalkyl sulfonates (PFASs) were detected in German surface waters, bank filtrates, artificially recharged groundwaters, and drinking waters. If no point sources are located nearby, the typically measured levels are in the low ng/L range. In the presence of point sources, such as a fluorochemical production site, a leaching agricultural fertilizer contaminated with PFCAs and PFASs, or drained PFC containing fire-fighting foams, much higher concentrations in the microg/L range occur. This situation is similar in Germany and other countries.     

Efficient Gallium–Arsenide Disk Laser

Means that may optimize the efficiency of semiconductor disk lasers (optically pumped vertical external-cavity surface-emitting lasers) are discussed: the direct pumping of the quantum wells (QWs), the optimization of the interaction of the QWs with pump and laser field and the reduction of resonator losses by employing a dielectric/semiconductor Bragg reflector on the front face of the disk. GaAs-AlGaAs-quantum-well disk lasers designed accordingly achieved slope efficiencies of 67% and optical efficiencies of 55% (based on the absorbed pump power) with output powers well above 1 W and a pump absorption efficiency of 80%. With an additional simple pump re-imaging an output power of 1.6 W was realized with an optical efficiency of 50% related to the incident pump power.     

Parkhaus CHL Centre Hospitalier de Luxembourg: Verbunddecken mit Faserbeton

Multi‐storey car park “centre hospitalier de Luxembourg“: Composite decking with fibre reinforced concrete. A multi‐storey car park was built for the “centre hospitalier de Luxembourg” in 2006 within a construction time of only eight months. It is the first application of a composite decking Cofraplus 60 with fibre reinforced concrete. The time for installing the rebars was extremely reduced. The slabs of the 4 storey building of an area of 125 m × 43,6 m have no joints. The car park offers 643 parking spaces and a helicopter pad on the roof.     

Analog VLSI neural networks for impact signal processing

The architecture and operation of the 80170NX electrically trainable analog neural network, which recognizes objects in real time, are discussed. The 80170NX uses a discrete Fourier transform (DFT) to preprocess an accelerometer output waveform that is subsequently recognized through a multilayer perceptron neural network. It is shown that neural network hardware operating in a linear mode can perform conventional signal processing functions. The similarity of neural network computations to linear signal processing functions makes it exceedingly straightforward to integrate neural networks and conventional signal processing in the system     

Coherent coupling of vertical-cavity surface-emitting laser arrays and efficient beam combining by diffractive optical elements: concept and experimental verification

A phase-locked diode-laser system based on master-slave coupling of two-dimensional vertical-cavity surface-emitting laser (VCSEL) arrays by injection locking is presented. Frequencies and phases are adjusted by laser-trimmed microresistors. Additional beam-transformation optics consisting of two diffractive optical elements (DOEs) and a Fourier lens concentrates most of the far-field power in a nearly diffraction-limited beam. Both the VCSEL array and the microlens array are monolithically integrated and mounted in a compact module. With an array of 21 slave lasers a system coherence of 95% (for several hours) and of nearly 90% (for several months) has been demonstrated without any active phase control. The scalability of the output power has been verified by locking of an array of 77 slave lasers with a system coherence of 78%. The optical system efficiency is 20-23%; with beam-transformation optics this efficiency could be improved to 44%.     

Analysis of sulfonated naphthalene-formaldehyde condensates by ion-pair chromatography and their quantitative determination from aqueous environmental samples

An ion-pair solid-phase extraction (IPE), ion-pair chromatography (IPC) procedure with fluorescence detection for the quantitative analysis of sulfonated naphthalene-formaldehyde condensates (SNFC) was developed, which provides full resolution of SNFC up to a degree of condensation n = 5 and partial resolution up to n = 15. Liquid chromatography-electrospray ionization-mass spectrometry confirmed that SNFC elute in the order of condensation. Response factors in fluorescence detection proved to be mass-constant, thereby allowing us to determine total SNFC amounts. With this IPC method, the weight- and the number-average molecular weights of these high-volume production chemicals (kiloton per annum), used as synthetic tanning agents, concrete plasticizers, and dispersants, can be determined. Recoveries in IPE range from 73 to 85% in river Rhine water and from 79 to 93% in tap water for n = 2 to n = 7 with limits of detection of 3-8 ng/L for individual homologues from 500 mL of water. The IPE-IPC procedure was applied to samples of secondary industrial effluents, river Rhine water, a river bank filtrate, and a groundwater sample. SNFC up to n = 6 were detected in the treated effluents. Total concentrations ranged from 208 micrograms/L in a secondary treated SNFC production effluent to < 1.4 micrograms/L in groundwater. These first analyses suggest a widespread occurrence of the lower oligomers of SNFC in the aquatic environment.