Characterization of sludge structure and activity in submerged membrane bioreactor.

Sludge characteristics of a submerged membrane bioreactor (MBR) and an activated sludge process (AS) were compared, during a first phase at the same operating conditions (low MLSS and conventional SRT) and in a second phase with a high sludge retention time (SRT) in the membrane bioreactor. During the first phase, a bimodal flocs size distribution was observed in the MBR with simultaneously a macro-flocs population (240 microm) bigger than the flocs of activated sludge due to the absence of recirculating pump, and also more microflocs (1 to 15 microm) and free suspended cells retained by the membrane. It is shown that the membrane leads to an accumulation of proteins and polysaccharides in the sludge supernatant which is probably responsible for the high fouling propensity of the sludge during the starting period of MBR. These compounds are partially degraded after 50 to 60 days of operation. In the first phase respirometric experiments didn't demonstrate a significant difference in the maximal removal rates of either MBR or AS biomass (with excess substrate), except in the dynamic period during which the membrane retention gave an advantage by increasing the biomass activity. On the other hand, the respirometry shows that the half saturation constant for nitrification was significantly higher in the MBR process, suggesting higher substrate transfer limitation. During the last phase, it is shown that an increase of SRT from 9 to 106 days leads to a diminution of average macro-flocs size in the MBR from about 240 to 70 microm. With the SRT increase, modification in the organic compounds is also observed (proteins, polysaccharides and COD) in the sludge supernatant. Increasing the SRT from 9 to 40 days seems to slightly reduce the level of organic compounds (probable biodegradation), but the concentrations increased when SRT changes from 40 days to 106 days (probable accumulation of non biodegradable compounds).     

Electrodeposition of platinum on polytyramine-modified electrodes for electrocatalytic applications

Cyclic voltammetry was used in order to deposit conducting polytyramine (PTy) on graphite substrates. In acidic media, ca. 40 deposition cycles resulted in the formation of stable polymer films with reasonably good resistivity. Electrochemical deposition of platinum on the PTy-covered graphite substrate allowed us to obtain a composite material that exhibits, for a platinum loading of 0.34 mg cm⁻², a specific electrochemically active surface area of the Pt particles of ca. 57 m² g⁻¹. Good electrocatalytic activity of this electrode material for phenol oxidation in acidic media was found, and the results suggested that, when deposited as small particles in a PTy matrix, platinum is less sensitive to deactivation by phenol oxidation polymeric products.     

Der österreichische Bergbau im internationalen Spannungsfeld

The paper deals with the development of Austrian mining activities in 2009. Special attention is payed to the Raw Materials Initiative and the Austrian Minerals Plan, both important instruments of a sustainable minerals planning policy. Finally, the concentrations of producers and producer countries regarding market conditions are discussed in detail.     

The Cambridge University Multimedia Document Retrieval Demo System

The Cambridge University Multimedia Document Retrieval (CU-MDR) Demo System is a web-based application that allows the user to query a database of radio broadcasts that are available on the Internet. The audio from several radio stations is downloaded and transcribed automatically. This gives a collection of text and audio documents that can be searched by a user. The paper describes how speech recognition and information retrieval techniques are combined in the CU-MDR Demo System and shows how the user can interact with it.     

Non-stoichiometry and electronic properties of interfaces

The paper gives an overview on the influence of point defects on electronic properties of interfaces including band alignment (barrier heights) and transport properties. As examples interfaces between metals and the II–VI semiconductors CdTe and ZnTe are presented. In addition untypical phenomena at semiconductor heterocontact formation at In₂S₃/ZnO and CuInSe₂/CdS interfaces is described. It is suggested that the barrier heights as well as the transport properties at both interfaces are strongly affected by defects, which are either present because of non-stoichiometry of the materials or introduced by contact formation due to chemical interactions.     

Heterologous fibrinogen for tissue adhesion. immunological and histological investigations (author's transl)

The immunological reactions of heterologous fibrin were investigated in a sensitive experimental system. In 10 rabbits autologous full-thickness skin grafts were glued with bovine fibrinogen cryoprecipitate. 5 of these animals had been immunized against this adhesive before transplantation. In a control group the graft was fixed with homologous fibrinogen cryoprecipitate. Examination of the sera of the animals for antibodies against fibrinogen was performed before immunization, 1 day prior to and 14 days after skin grafting. 14 days after skin adhesion all grafted areas were examined by histological methods. In the group without preoperative immunization antibodies were found against fibrinogen. The skin graft healed in this series in the same manner as in the sham group. In the series with preoperative immunization the glued skin graft was discharged early and the healing procedure of the defect was retarded.     

1H NMR study of temperature-induced phase transitions in aqueous solutions of poly(N-isopropylmethacrylamide)/poly(N-vinylcaprolactam) mixtures

¹H NMR spectroscopy was used to investigate the temperature-induced phase transitions in aqueous solutions of poly(N-isopropylmethacrylamide)/poly(N-vinylcaprolactam) (PIPMAm/PVCL) mixtures to find out if the phase transition of the given component (PIPMAm or PVCL) is affected by the presence of the second component. Our results that PVCL and PIPMAm transitions are in polymer mixtures shifted by ~2 K towards higher temperatures in comparison with neat polymers and depend on polymer concentration show that such effect exists. Spin–spin relaxation times of water (HDO) indicate that in solutions with c ≥ 1 wt% a portion of water is predominantly bound in PVCL mesoglobules even at temperatures above the LCST transition of PIPMAm component. Water is with time released from these mesoglobules without any induction period so indicating that it is mostly indirectly bound water. We assume that there is a direct connection between character of the bound water and the transition temperatures.     

Fine dispersed blends for compatibilizers for laminates of immiscible polymers

Blends of high-density polyethylene (HDPE) and isotactic polypropylene (iPP) are used to increase the strength of adhesive bonds between the immiscible polymers HDPE and iPP. Melt blended as well as solution blended material is examined for its suitability to compatibilize the interface between the bonded members. Two standard test methods, the T-peel test and the tensile test, are applied to determine the strengths of adhesive joints. Laminated samples for the peel-tests as well as specimens subjected to the tensile tests were prepared at a temperature exceeding the melting temperature of both homopolymers. TEM and LVSEM examinations were performed for characterizing the morphology of the interface with the aim to determine the parameters which significantly influence the blends' adhesive properties. The bonding strengths obtained with the blended material are discussed with respect to the morphologies of the interfaces, the degree of dispersion in the blend, and the bonding mechanisms.     

Using 3D-scanners and finite element method to assess the fatigue life of welded joints based on the actual geometry of seam welds: realistic modelling of notches at the weld toe

To predict the service life of welded joints, the seam welds of samples (cross joint, K-seam, sheet thickness 15 mm and a laser-welded butt joint, sheet thickness 6 mm, both made of steel quality S 355) are recorded using a 3D scanner. The data obtained in this way is processed and transferred to a finite element method program. The meshing of the weld seams is very detailed. A finite-element-method stress calculation is then carried out. The real samples are tested in a fatigue test up to the point of cracking. The results from calculation and test are then compared. A possible crack location can be predicted very well using the finite element method results. The cracks in the real test are always in the area of very high or often the absolute highest calculated stresses. A prediction of the service life in the fatigue test is possible with a certain scatter – close to the usual scatter for welded joints. Based on the results of 19 samples, a fatigue class for local stress (based on the real geometry) of FAT 300 can be preliminary estimated for the cross-joint specimens. Definition according to the specifications of the International Institute of Welding (FAT at 2 mio. cycles, survival probability 97.7 %).     

Effect of ion-irradiation on the microstructure and microhardness of the W-2Y2O3 composite materials fabricated by sintering and hot forging

A W-2Y₂O₃ material was developed in collaboration with the Plansee Company (Austria). An ingot of the material having approximate dimension of 95 mm × 20 mm was fabricated by mixing the elemental powders followed by pressing, sintering and hot forging. The microstructure of the W-2Y₂O₃ composite was investigated using transmission electron microscopy (TEM). The microhardness was studied using nano-indentation technique. We observed that the W-grains having a mean size of about 1 μm already formed and these grains contain very low density of dislocations. The size of the yttria particles was between 300 nm and 1 μm and the Berkovich hardness was about 4.8 GPa. The specimens were irradiated/implanted with Fe and He ions at JANNuS facility located at Orsay/Saclay, France. The TEM disks kept were irradiated/implanted at 300 and 700 °C using Fe and He ions with an energy of 24 and 2 MeV, respectively. The calculated radiation dose was about 5 dpa produced by Fe ions and total He content is 75 appm at both 300 and 700 °C. From the TEM investigation of irradiated samples, few radiation loops are present on the W grains, whereas on yttria particles, the radiation induced damages appear as voids. Berkovich hardness of the irradiated sample is higher than that of the non-irradiated sample. Results on the microstructure and microhardness of the ion-irradiated W-2Y₂O₃ composites are presented in detail.