MESHWR / Department of Hydrology and Water Resources / In South Africa, inland aquaculture is on the increase, especially among the rural communities. Thus aquaculture is able to provide a source of employment and improve rural incomes. This study assessed algae species and their cyanotoxins in small holder production in Vhembe district, Limpopo, South Africa. Thirteen study sites were selected to assess the algae species and their cyanotoxins. The water samples were collected in four quarters and analysed for water temperature, pH, total dissolved solids, Electrical conductivity, phosphates, nitrates, chlorophyll, cyanobacteria, cyanotoxins, metal species and quality of the water in the fish ponds. In the 1st quarter of the year there was variation in Water Temperature (23.7oC-31.4oC), pH (5.5-9.6), EC (3.82-46.8μS/cm), TDS (2.4-45 mg/L), Phosphate (0.0-1.09mgL-1), Nitrates (0.0-1.00mgL-1), Chlorophyll-a (5.8-11.5mg/m-3). In the 2nd quarter there was variation inwater temperature (22.4-25.0oC), pH (6.6-8.8.9), EC (19.23-21.47μS/cm), TDS (12.5-17.9 mg/L), Phosphate (1.64-1.84mgL-1), Nitrates (1.02-1.88mgL-1), Chlorophyll-a (4.6-15.6mg/m-3). In the 3rd quarter there was variation for water temperature (22.9-25.0oC), pH (7.5-9.1), EC (7.91-293.3μS/cm), TDS (11.7-180.9 mg/L), Phosphate (1.10-1.80mgL-1), Nitrates (1.28-1.84mgL-1),Chlorophyll-a (6.8-15.6mg/m-3). In the 4th quarter there was variation forwater temperature (23.5-30.3), pH (7.1-9.3), EC (18.24-623μS/cm), TDS (23.7-136.4 mg/L), Phosphate (1.45-1.99mgL-1), Nitrates (1.43-1.68mgL-1), Chlorophyll-a (6.6-25.9mg/m-3). The metal content of the fish pond water was variable throughout the year but with moderate levels of Al, Cd, Cr, Mn, Fe, Cu, Zn and Ba were found. The metal Fe, exceeded the DWAF guideline values during this first quarter. The presence of Cd in the fish pond water could be attributed to rainfall eroding the earthen embankments of the fish pond. The results of physico-chemical parameters promotes the growth of cyanobacteria in the fish ponds. Flow cam and SEM were used to identify the cyanobacteria species and most cyanobacteria identified are hazard to human health, fish and other aquatic organisms. Molecular technologies were used to identify cyanotoxins and there was no cyanotoxins detected which was concluded that during collection of water samples no cyanobacteria produced toxins. / NRF

Wavelength division multiplexing (WDM) is essential for further enhancement of the transmission capacities of optical telecommunication systems. Key devices in WDM networks are multiplexing/demultiplexing components, which enable the combination/separation of several carrier waves with different wavelengths for the purpose of simultaneous transmission through one optical fibre. These components can be realized using Bragg diffraction from volume holographic gratings. Especially reflection holograms provide a pronounced wavelength selectivity which makes them attractive for free-space WDM applications. Holograms can be stored permanently in photorefractive lithium niobate crystals by the method of Thermal Fixing. Heating of the crystal during or after the recording process and subsequent development by homogeneous illumination at room temperature create nonvolatile holograms. The recording and development processes of Thermal Fixing in iron- and copper-doped lithium niobate crystals were investigated. Macroscopic Gaussian-shaped intensity patterns were used to analyse the origin of the fixing mechanism. Spatially resolved absorption measurements were performed to determine the concentration profiles of electron traps (Fe II/III) and protons. Results of computer simulations were compared with experimental results, which showed that protons can be found to work as compensators during hologram recording at temperatures around 180 degree C. Nevertheless thermal fixing without protons was possible, another compensation mechanism stood in. The obtained refractive-index changes were due to the electro-optic effect, other contributions could be neglected. With this detailed knowledge about thermal fixing, a two-channel demultiplexing unit was built by superposition of two thermally fixed reflection holograms in an iron-doped lithium niobate crystal. For this purpose a special two-beam interference setup with precisely adjustable writing angles was arranged in a vacuum chamber to eliminate thermally induced phase disturbances of the holographic recording procedure. Continuous development of the holograms by incoherent light was necessary. In the dark, the enhanced dark conductivity of the crystal used gave rise to a hologram degradation within about one day. Large diffraction efficiencies were attained (intensity losses between 2.3 and 5.2 dB only) uilizing crystals with high-quality polished surfaces. The crosstalk supression of the realized demultiplexer was > 25 dB, which is comparable with the performance of other multiplexing techniques like fibre Bragg gratings or arrayed-waveguide gratings. The low polarization dependence of the demultiplexer can be improved by superposition of two holograms for each channel.

<div>Increasing flexibility of light manipulation is vital for various domains including both biomedical and military applications, where a lack of photon control could become critical. The efforts conducted and projected within this proposal are focused on three major areas: semi-continuous planar thin film photomodification for infrared (IR) filtering, nanosphere core-shell structures for obscurance, and all-dielectric sub-wavelength focal lenses for advanced IR sensing.Through a collaborative effort with the Army Research Office, we advanced the tunability of planar plasmonic filters with cutoff wavelengths in the 10–16μm range with photomodification using a 10.6μm CO2laser. Surface-enhanced molecular absorption in concert with three-dimensional (3D) Au nano-structures with inherent broad absorption in the IR band was a novel approach utilized to create such planar filters.Expanding on these, efforts and the results of the 2-dimensional (2D) semicontinuous Au plasmonic planar filtering, we further advanced our research with 3D Au nano-coreshell structures to enable levitated long-wavelength pass filter obscurants. We exploited the radiative effects of Au nano-structures that mimic conventional apertures or antennas, though these structures are on the nanometer scale and demonstrated the filtering characteristics through flow cell.In parallel with our plasmonic filtering we designed, manufactured and tested low loss dielectric microlenses for IR radiation based on a dielectric metasurface layer by patterning a SI substrate and etching to sub-micron depths. For a proof-of-concept lens demonstration,we chose a fine patterned array of nano-pillars with variable diameters.Merging our plasmonic filtering and dielectric microlens efforts, we created a holographic lenslet by designing and simulating a low loss focusing metasurface lens with engineered nano-scaled features to converge off-axis IR radiation. An array of nano-pillars with varied diameter and fixed height and periodicity was chosen for ease of fabrication with single layer etching</div>

An der TU Dresden wurde eine Forschungsarbeit zur experimentell-theoretischen Analyse des Tragverhaltens von Verankerungen durchgeführt, die hauptsächlich zur oberflächenparallelen Einleitung großer Schubkräfte in einen Betongrund ausgelegt sind. Diese Verankerungen ermöglichen die Übertragung einer großen Querkraftbe¬anspruchung mit geringer Exzentrizität zur Oberfläche, die mit einer Normalbean¬spruchung in Zug- oder Druckrichtung kombiniert werden kann. Die wesentlichen Grundelemente sind zumindest ein Schubdübel, ein Zuganker und eine Grundplatte, mehrere Schubdübel oder Anker können vorhanden sein. Der quaderförmige Schub¬dübel überträgt die Kraft in den Beton. Die angreifenden Lastmomente und das Moment aus der exzentrischen Einleitung der Schublast werden in ein vor und hinter dem Dübel wirkendes Kräftepaar zerlegt. Die Zugkomponente wird dem Zuganker in Form eines Kopfbolzendübels zugewiesen. Die Grundplatte verbindet die lastseitige Befestigungskonstruktion mit den lastübertragenden Bauteilen Schubdübel und Zug¬anker. Gleichzeitig kann die Grundplatte in den Beton eingelassen sein und überträgt dann ebenfalls Schublasten. Die Lastabtragung und das Verhalten der Einbauteile im Versuch wurden analysiert. Von besonderer Bedeutung ist hierbei die Last-Verschiebungslinie, die die Lastüber¬tragung charakterisiert. Ziel war es, ein Bemessungskonzept zur Dimensionierung der Schubdübel zu erarbeiten. Um die im Versuch erkennbare maßgebende Beein¬flussung der Lastübertragungskapazität durch den sich einstellenden Verformungs¬zustand eingehender untersuchen zu können, wurde der Versuch mit finiten Elemen¬ten abgebildet. So war es möglich, in einem ersten Schritt Lastübertragungskapazitä¬ten für unverformte Systeme zu ermitteln, die praktisch im Versuch nicht oder nur extrem aufwändig realisiert werden könnten. In einem zweiten Schritt kann dann der Einfluss der Verformung berücksichtigt werden. Hierbei können die Parameter ge¬nauer und vielschichtiger variiert werden als dies bei den relativ aufwändigen Versu¬chen rein quantitativ möglich war. Das in dieser Arbeit vorgestellte Berechnungsver¬fahren liefert neben der maximal aufnehmbaren Schubbeanspruchung geometrisch beliebiger Einbauteile auch die Beanspruchbarkeit einzelner Baugruppen und erlaubt es zu beurteilen, inwieweit die einzelnen Lastübertragungsmechanismen additiv oder alternativ wirksam sind. Das Verfahren gibt Auskunft über das zu erwartende lastabhängige Verhalten der Einbauteile inklusive der Vorhersage von Teilversagens¬zuständen. Das Potential der Befestigungssysteme zur Übertragung großer Schublasten ist durch die Aufsplittung der Lastkomponenten und Übertragung durch spezialisierte Bauteile begründet. Diese können in ihrer Beschaffenheit den Erfordernissen optimal angepasst werden. Einsatzgebiete für diese Befestigungen sind alle konzentrierten Lasteinleitungen oder Montagestöße zwischen Betonbauteilen oder Stahl-Holz-Kon¬struktionen auf der einen und Betonelementen auf der anderen Seite. Neben der Auflagerung von Trägern oder Fassadenelementen ist vor allem auch an die Ertüchti¬gung und Verstärkung bestehender Betonbauteile durch zusätzliche Stahlkonstrukti¬onen zu denken. / An experimental and theoretical analysis of the behaviour of complex shear loaded fastenings was carried out at Dresden University of Technology. The main focus was on applications which introduce a great amount of shear load value parallel to the surface into a concrete base using a stell shear lug. The behaviour of these special fixings is presented as the result of the finished research program. Structures, as shown in the opposite figure, are able to transmit high values of shear loads to the anchor ground. An additional loading of normal force und bending moment is suitable, but will only be supposed to cover the necessary tolerance and off centre condition of the fixture parts. The advantage of fastening with shear lugs is based on the splitting of the load transfer into different components. The shear lug/lugs caries/carry the shear load, and the tie bar itself only balances the system by tension load due to moment loading and normal loading. Thusall loads are transferred by highly specialized components. If the base plate is embedded, there will be a shear load transferred in front of the base plate, too. The load carrying behaviour of the fastenings in the experiments is analyzed. Here, the load-displacement relationship is of special importance . This thesis aims at elaborating a dimensioning concept for the design of shear lugs. The tests show a decisive influence of the movements – displacements as well as rotations – of the fastenings to the load carrying capacity. In order to to be able to examine this behaviour, the experiment is redesigned by finite elements. In a first step it is therefore possible to examine fastenings without movements based on the anchor bolt stiffness. In a second step, the influence of the deformation can be explored. Here, the parameters can be varied more exactly and in a more complex way than this is possible in terms of quantity with the comparetively extensive test setup. The calculation method being introduced here does not only supply the maximum shear load transfer capacity of the hole fastening system, a system with free geometries, but also shows the partial shear load transfer capacity of the individual parts of the unit. This method is a means of predicting the load-related behaviour of the fastenings to be expected, including the forecast of partial failure states. As a result, a suggestion for the design of the fittings is shown. This design can be applied to all fittings by splitting the different load components to especially provided anchor elements. The design resistance and behaviour of the fastenings is estimated, depending on different geometries and stiffness conditions of the lug. Different strength classes of the concrete as well as different load combinations are taken into consideration. First examples from building sites are also available.