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941.
Lead magnesium niobate-lead titanate (PMN-PT) ceramic fibres with the nominal composition of 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 have been fabricated by a modified sol-gel method. Due to the difficulty of dissolving the magnesium component, the mixed oxide method was used together with the traditional sol-gel method. To obtain crack-free fibres, pyrolysis was carried out at a very slow heating rate under specific atmosphere to control the organic burnout. The thermal and microstructural properties were investigated using thermogravimetric analysis, scanning electron microscopy and X-ray diffraction. The optimum sintering temperature is 1200 °C and yields a fibre with a final diameter of around 100 μm. A single PMN-PT fibre has been poled and its electrical properties were measured. The properties of the fibre are found to be better than that of a ceramic disc.  相似文献   
942.
This paper describes the development of a new navigational aid for the frail, elderly, and visually impaired person. The users were involved both in the user requirements study and in the evaluation of different prototypes. The results show that the users were able to provide information on their current aid, the use situation, and their preference regarding different solutions, but they had difficulties to provide the detailed answers on technical solutions required by the technical development team. Further, prototype evaluations with users enabled the technical team to understand the users and their use situation.  相似文献   
943.
The impact of substrate topography on the morphological and mechanical properties of confluent MDCK-II cells cultured on porous substrates was scrutinized by means of various imaging techniques as well as atomic force microscopy comprising force volume and microrheology measurements. Regardless of the pore size, ranging from 450 to 5500 nm in diameter, cells were able to span the pores. They did not crawl into the holes or grow around the pores. Generally, we found that cells cultured on non-porous surfaces are stiffer, i.e. cortical tension rises from 0.1 to 0.3 mN m−1, and less fluid than cells grown over pores. The mechanical data are corroborated by electron microscopy imaging showing more cytoskeletal filaments on flat samples in comparison to porous ones. By contrast, cellular compliance increases with pore size and cells display a more fluid-like behaviour on larger pores. Interestingly, cells on pores larger than 3500 nm produce thick actin bundles that bridge the pores and thereby strengthen the contact zone of the cells.  相似文献   
944.
945.
Results of 4-year storage tests are reported for crude and refined soybean oils held in 50-gal drums under conditions simulating field tank operations. Once-refined oils stored in filled drums without breathers showed lower peroxide values and lower dimer contents than oil stored in full drums with breathers. Refined oils in half-filled drums exhibited higher storage temperatures and, consequently, higher peroxide values and dimer contents than any other storage condition. Nondegummed and degummed crude oils held in drum storage had lower peroxide values and lower dimer contents than refined oils stored under similar conditions. Relationships are significant not only between storage peroxide values and dimer contents, but also each of these with flavor scores. Evidently, stored crude or stored refined soybean oils with peroxide values under 60 could be deodorized to produce salad-grade oils with initial flavor quality equal to that of oils processed from stocks having considerably lower initial peroxide values. The relative rate of peroxide increase for field tank storage can be estimated from linear regression analysis on data from stor-age of soybean oil in drums. Once-refined soybean oil held under large field tank storage conditions would not be expected to reach peroxide levels of 60 until after 3-4 years, even in warm areas. ARS, USDA. No. Utiliz. Res. Dev. Div.. ARS, USDA.  相似文献   
946.
947.
948.
949.
950.
Operationally defined dissolved Titanium [Ti] (the < 0.45 μm filtered fraction) in rivers draining rural, agricultural, urban and industrial land-use types in the UK averaged 2.1 μg/l with a range in average of 0.55 to 6.48 μg/l. The lowest averages occurred for the upland areas of mid-Wales the highest just downstream of major sewage treatment works (STWs). [Ti] in rainfall and cloud water in mid-Wales averaged 0.2 and 0.7 μg/l, respectively. Average, baseflow and stormflow [Ti] were compared with two markers of sewage effluent and thus human population: soluble reactive phosphorus (SRP) and boron (B). While B reflects chemically conservative mixing, SRP declined downstream of STW inputs due to in-stream physico-chemical and biological uptake. The results are related to colloidal and sub-colloidal Ti inputs from urban/industrial conurbations coupled with diffuse background (geological) sources and within-river removal/retention under low flows as a result of processes of aggregation and sedimentation. The urban/industrial inputs increased background [Ti] by up to eleven fold, but the total anthropogenic Ti input might well have been underestimated owing to within-river retention. A baseline survey using cross-flow ultrafiltration revealed that up to 79% of the [Ti] was colloidal/nanoparticulate (> 1 kDa i.e. > c. 1-2 nm) for the rural areas, but as low as 28% for the urban/industrial rivers. This raises fundamental issues of the pollutant inputs of Ti, with the possibility of significant complexation of Ti in the sewage effluents and subsequent breakdown within the rivers, as well as the physical dispersion of fine colloids down to the macro-molecular scale. Although not directly measured, the particulate Ti can make an important contribution to the net Ti flux.  相似文献   
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