Search

Abstract: In the regions surrounding the Qinghai Tibet Plateau, changes in erosion rates have been linked to the tectonics, climate and topography over different time scales. To understand the mechanisms governing the changes of erosion rates, it is important to study erosion rates by different methods and for different time scales. In inland drainage basins, deposition rates of terminal lake sediments can indicate basin-wide erosion rates at the millennial-scale. This paper presents three lake records of the Last Deglaciation and Holocene (Huahai Lake, Zhuye Lake and Yanchi Lake) from the Hexi Corridor, north of the Qilian Mountains, in arid China. Organic matter, terrestrial pollen concentrates, seeds, grasses and plant debris are used for conventional and AMS 14C dating. On the basis of 66 radiocarbon dates, lithology and grain-size, we infer relatively high basin-wide erosion rates during the Last Deglaciation and early Holocene in the three drainage basins, when the three lake sediments were seriously affected by reworking. The deposition rates were an order of magnitude or greater in these lakes during the Last Deglaciation and early Holocene than during the mid-to-late Holocene. During the transition period of the last glacial–interglacial cycle, significant climatic changes occurred in East and Central Asia, corresponding to the strengthening of the Asian summer monsoon and to increasing effective moisture in arid Central Asia, which can have strong impacts on basin-wide erosion rates north of the Qinghai Tibet Plateau. Moreover, melting glaciers in the Qilian Mountains probably also contributed to the high basin-wide erosion rates. At the same time, tectonic activity was not recognizable in the study area during that period. In the arid and semiarid regions surrounding the Qinghai Tibet Plateau, dramatic changes in erosion rates appear during the transition periods of the glacial–interglacial cycles, which illustrate the climatic controls on erosion rates at this time scale. [Copyright &y& Elsevier]

Abstract: Recently, Applied Materials has demonstrated the ability to manufacture large area a-Si/μc-Si thin film modules with total area efficiencies of 10% and above. Reducing the production costs is now the key objective for an economic success of this technology. Decreasing the absorber layer thickness or increasing the deposition rate can reduce the cost significantly because the PECVD deposition of the silicon layers is one of the main cost contributors. But this would also reduce the conversion efficiency of amorphous/microcrystalline tandem cells (a-Si/μc-Si TJ cells). Therefore, optimizing TJ cells for maximal productivity requires a careful balancing of layer thicknesses and deposition rates. In this paper we studied the impact of deposition rates and absorber layer thicknesses for top and bottom cells. The reduction of the bottom cell (BC) thickness from 2μm to less than 1μm showed only a small impact on the stabilized module efficiency while having a big impact on the productivity of a production line. The influence of the top cell (TC) deposition rate on the other hand results in a big decrease of the efficiency while having only a small impact on the line output. 10.2% stable mini-module efficiency could be achieved with 900nm BC thickness, reducing the deposition time by 50%. [Copyright &y& Elsevier]

Abstract: A number of proposed applications of carbon nanotube (CNT) arrays require that uniform deposition of well-aligned CNTs is achieved. The CNT deposition profiles inside a chemical vapor deposition (CVD) reactor are strongly dependant on the reaction temperatures, feed gas flow rates, carrier gas flow rates and reactor geometry. In addition, objects placed in the path of the flow of feed material could affect the deposition patterns. In this paper, an experimental study aimed at achieving better control of the deposition patterns of CNTs is presented. Multiwalled CNTs were grown on a long substrate by the catalytic CVD of a xylene/ferrocene solution. The deposition patterns on the substrate were examined for different furnace temperatures, xylene/ferrocene feed rates and carrier gas flow rates. Small objects representative of electronic devices were placed at different locations on the substrate and their effect on the deposition patterns was explored. The effect of changing the height and the gap distance between these objects was also studied. [Copyright &y& Elsevier]

Abstract: The role of the Setúbal–Lisbon canyon in accumulation and transport of labile organic matter from the coastal sea and ocean surface water towards the deep sea was assessed by investigating the distribution of organic matter of different quality in sedimentary aggregates and surface sediments of the canyon and adjacent slopes. Total hydrolysable amino acids (THAA) and organic carbon (Corg) were measured from aggregates, and contents of Corg, chlorophyll a (chl a), phaeopigments (phaeo), chloroplastic pigment equivalents (CPE) from sediments. As indices of organic matter (OM) quality THAA:Corg, degradation index (DI), chl a:phaeo, chl a:Corg and C:N ratio were determined. Sediment profiles of chl a and the isotope 210 of lead (210Pb) were used as tracers in a transport model to estimate deposition rates and background levels of the tracers, and sediment mixing rates (Db). Whereas bulk Corg contents of canyon and slope sediments were practically similar at all depths, higher contents of THAA, chl a and CPE, as well as higher THAA:Corg, DI and chl a:Corg, in aggregates and sediments from the upper reaches of the canyon indicate that labile organic matter accumulates in the upper canyon. This is confirmed by higher chl a and 210Pb deposition and Db calculated from the model. Hence, the Setúbal–Lisbon canyon, specially the upper region, acts as a natural trap of organic matter that is transported to the region via lateral transport and vertical settling from primary productivity. Organic matter might be further transported in downward canyon direction via rebound processes. The chl a and 210Pb profiles reveal active sediment mixing by physical processes and/or animal reworking. [Copyright &y& Elsevier]