Aminopolyphosphonate removal during wastewater treatment

Phosphonates are used in large quantities in industry and household products as scale inhibitors and chelating agents. They are not biodegraded during wastewater treatment but are removed by adsorption processes. Field measurements from different wastewater treatment plants affirm that they are removed almost completely during wastewater treatment. Adsorption of nitrilotrismethylenephosphonic acid onto activated sludge, amorphous iron oxide and humic acids (HAs) was studied under controlled conditions. The adsorption onto HAs decreases sharply with increasing pH with negligible adsorption at pH above 6.5. Adsorption onto amorphous iron oxide follows a Langmuir behavior. The presence of 1 mM Ca doubles the maximum surface capacity at pH 7. Adsorption onto activated sludge is not very pH sensitive and is explained to a large extent by adsorption onto amorphous iron oxides, but the contribution of organic matter or other mineral phases cannot be ruled out.     

Determination of beam parameters and coherence properties of laser radiation by use of an extended Hartmann-Shack wave-front sensor

A combination of a Hartmann-Shack sensor and a standard far-field measurement on one single detector is proposed. The technique is fast and operates without movable parts, thus permitting a compact design. It is not only suited for characterization of the wave-front distribution but may also be considered for determination of the important parameters of beam width, beam divergence, and beam propagation ratio M2 of partially coherent laser beams. First results indicate that a fairly thorough beam characterization, including spatial coherence, propagation characteristics, and beam quality, can be achieved with this method.     

Collecting Statistics over Runtime Executions

By collecting statistics over runtime executions of a program we can answer complex queries, such as “what is the average number of packet retransmissions” in a communication protocol, or “how often does process P₁ enter the critical section while process P₂ waits” in a mutual exclusion algorithm. We present an extension to linear-time temporal logic that combines the temporal specification with the collection of statistical data. By translating formulas of this language to alternating automata we obtain a simple and efficient query evaluation algorithm. We illustrate our approach with examples and experimental results.     

(Ba,Ca)TiO3 PTCR Ceramics with LaNiO3 Thin-Film Electrodes: Preparation and Characterization of the Interface

Conductive LaNiO₃ thin film electrodes were deposited by chemical solution deposition (CSD) from nitrate solutions onto polycrystalline Al₂O₃ and (Ba,Ca)TiO₃ PTCR ceramic substrates. The electrical properties of the LaNiO₃ thin film on Al₂O₃ and of the interface consisting of LaNiO₃ and the semiconductive oxide ceramic were investigated. The deposited LaNiO₃ films were about 250 nm thick and consisted of nanosized particles. The resistivity of the LaNiO₃ film was about 3 × 10^-3cm at 20°C. The PTCR ceramic consisted of m sized particles and exhibited an electronic resistivity of about 10 cm at 20°C and a steep increase of the resistivity of a few orders of magnitude above the Curie point at about 120°C. The electrical properties of the LaNiO₃/PTCR interface were dominated by the properties of a barrier layer between the PTCR ceramic and the LaNiO₃ electrode. The potential dependence of the impedance indicated that the barrier layer consisted of a depletion layer within the PTCR ceramic, when the flat band potential of LaNiO₃ on the PTCR ceramic at about –250 mV was exceeded. Additionally the formation of an insulating layer at the LaNiO₃ electrode has to be taken into account.     

The risk of hydrogen embrittlement in high-strength prestressing steels under cathodic protection

High strength prestressing steels in prestressed concrete structures are protected against corrosion due to passivation resulting from the high alkalinity of the concrete. If depassivation of the prestressing steel occurs due to the ingress of chlorides the corrosion risk can be minimized by application of cathodic protection with impressed current. The risk of hydrogen embrittlement of the prestressing steel is especially pronounced if overprotection is applied due to hydrogen evolution in the cathodic reaction. The present work considers this risk by hydrogen activity measurements under practical conditions and application of different levels of cathodic protection potentials. Information on threshold potentials in prestressed concrete structures is provided, too.