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Volume 6, Issue 1, January 2014
Laser ablation for the preparation of isolating trenches in transparent conductive oxide films on glass has been studied comparing the use of nano- and femtosecond pulses at approximately 1 μm wavelength. By a detailed analysis of the obtained ablation craters and grooves, it can be shown that this processing, which is called P1 scribing in the field of thin film photovoltaics, can be considerably optimized with so-called “cold” ablation: Using femtosecond pulses, the P1 scribe can be done with almost rectangular cross section profiles, achieving the required electrical separation already at widths well below 10 μm, without thermal and mechanical stresses in the substrate or adjacent material. Analogous preliminary results for P2 scribes indicate that this technique allows reducing the total scribe region (optically inactive zone) to widths below 50 μm.
Perspective: Towards environmentally acceptable criteria for downstream fish passage through mini hydro and irrigation infrastructure in the Lower Mekong River Basin6(2014); http://dx.doi.org/10.1063/1.4867101View Description Hide Description
Tropical rivers have high annual discharges optimal for hydropower and irrigation development. The Mekong River is one of the largest tropical river systems, supporting a unique mega-diverse fish community. Fish are an important commodity in the Mekong, contributing a large proportion of calcium, protein, and essential nutrients to the diet of the local people and providing a critical source of income for rural households. Many of these fish migrate not only upstream and downstream within main-channel habitats but also laterally into highly productive floodplain habitat to both feed and spawn. Most work to date has focused on providing for upstream fish passage, but downstream movement is an equally important process to protect. Expansion of hydropower and irrigation weirs can disrupt downstream migrations and it is important to ensure that passage through regulators or mini hydro systems is not harmful or fatal. Many new infrastructure projects (<6 m head) are proposed for the thousands of tributary streams throughout the Lower Mekong Basin and it is important that designs incorporate the best available science to protect downstream migrants. Recent advances in technology have provided new techniques which could be applied to Mekong fish species to obtain design criteria that can facilitate safe downstream passage. Obtaining and applying this knowledge to new infrastructure projects is essential in order to produce outcomes that are more favorable to local ecosystems and fisheries.