| 581. |
- Wettels, Nicholas, et al.
(författare)
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Biomimetic Tactile Sensor Array
- 2008
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Ingår i: Advanced Robotics. - Leiden : Koninklijke Brill NV. - 0169-1864 .- 1568-5535. ; :22, s. 829-849
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Tidskriftsartikel (refereegranskat)abstract
- The performance of robotic and prosthetic hands in unstructured environments is severely limited by their having little or no tactile information compared to the rich tactile feedback of the human hand. We are developing a novel, robust tactile sensor array that mimics the mechanical properties and distributed touch receptors of the human fingertip. It consists of a rigid core surrounded by a weakly conductive fluid contained within an elastomeric skin. The sensor uses the deformable properties of the finger pad as part of the transduction process. Multiple electrodes are mounted on the surface of the rigid core and connected to impedance-measuring circuitry safely embedded within the core. External forces deform the fluid path around the electrodes, resulting in a distributed pattern of impedance changes containing information about those forces and the objects that applied them. Here we describe means to optimize the dynamic range of individual electrode sensors by texturing the inner surface of the silicone skin. Forces ranging from 0.1 to 30N produced impedances ranging from 5 to 1000 kΩ. Spatial resolution (below 2mm) and frequency response (above 50Hz) appeared to be limited only by the viscoelastic properties of the silicone elastomeric skin.
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| 582. |
- Wiley, David J, et al.
(författare)
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Induction of the Yersinia type 3 secretion system as an all-or-none phenomenon
- 2007
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Ingår i: Journal of Molecular Biology. - : Elsevier BV. - 0022-2836 .- 1089-8638. ; 373:1, s. 27-37
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Tidskriftsartikel (refereegranskat)abstract
- Pathogenic Yersinia spp. possess a protein secretion system, designated as type 3, that plays a clear role in promoting their survival vis-à-vis the macrophage. Inductive expression of the Yersinia type 3 secretion system (T3SS), triggered either by host cell contact, or, in the absence of host cells, by a reduction in extracellular calcium ion levels, is accompanied by a withdrawal from the bacterial division cycle. Here, we analyzed Ca2+-dependent induction of the T3SS at the single-cell level to understand how Yersinia coordinates pro-survival and growth-related activities. We utilized a novel high-throughput quantitative microscopy approach as well as flow cytometry to determine how Ca2+ levels, T3SS expression, and cellular division are interrelated. Our analysis showed that there is a high degree of homogeneity in terms of T3SS expression levels among a population of Y. pseudotuberculosis cells following the removal of Ca2+, and that T3SS expression appears to be independent of the cellular division cycle. Unexpectedly, our analysis showed that Ca2+ levels are inversely related to the initiation of inductive T3SS expression, and not to the intensity of activation once initiated, thus providing a basis for the seemingly graded response of T3SS activation observed in bulk-level analyses. The properties of the system described here display both similarities to and differences from that of the lac operon first described 50 years ago by Novick and Weiner.
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| 583. |
- Winchester, John W, et al.
(författare)
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Trace Metals in the St. Louis Aerosol
- 1974
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Ingår i: Proceedings of the Second International Conference on Nuclear Methods in Environmental Research. ; , s. 385-394
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Konferensbidrag (refereegranskat)abstract
- The elemental composition of the St. Louis aerosol has been investigated at rooftop sites in south and central locations in the city as part of the August, 1973 field season of the Regional Air Pollution Study of the U.S. Environmental Protection Agency. Sampling by 5-stage cascade impactor with backup filter permits analysis by proton-induced x-ray emission (PIXE) of size fractions of aerodynamic diameter >4, >2m >1, >0.5, >0.25, <0.25µm for elements 16S to 35Br by K x-ray detection and 82Pb by L x-rays. The aerosol study indicates the following: 1. Particle size distributions of S, Cl, K, Ca, Ti, V, Mn, Fe, Cu, Zn, Br, and Pb can be measured in samples from 0.7 m3 of air collected over 12-hour intervals at 1 liter/min flow rate, with precision of single analyses generally 10-30%, except near the nanogram detection limit. 2. Some elements, e.g. Ca, Fe, Ti, K show a tendency for highest concentrations in air measured in largest particle size fractions, and the pattern of distribution of concentration with size is relatively invariant. Predominantly dispersion source processes may account for their entry into the atmosphere. 3. Other elements, e.g. S, Pb, Zn, have substantial proportions of their atmospheric concentrations on smallest particles and show greater variability in particle size distribution patterns, suggesting aerosol formation processes of vapor condensation at high or low temperatures. 4. During 16-22 August 1973 an atmospheric change occurred from a period of low speed and mostly southerly air flow, with evident haze and air pollution, to higher speed and westerly shifting to easterly air flow, with improved visibility and air quality. The change was associated with drops in concentrations of Ti, Fe, Ca, K, and S but not Zn or Pb at the south site and Ti but not the other elements at the central site. Transport of air pollution from industrial sources south of the city is indicated. 5. The central site showed diurnal variation during the first period where concentrations of Ti, Fe, Ca, K, and S were higher in samples taken from midnight to noon than in those from noon to midnight. Variations were greatest for intermediate sized particles.
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| 584. |
- Yarime, Masaru, et al.
(författare)
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Dissipation and Recycling: What Losses, What Dissipation Impacts, and What Recycling Options?
- 2014
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Ingår i: Sustainable Phosphorus Management. - Dordrecht : Springer Netherlands. - 9789400772496 ; , s. 247-274
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This chapter describes the activities in the Dissipation and Recycling Node of Global TraPs, a multistakeholder project on the sustainable management of the global phosphorus (P) cycle. Along the P supply and demand chain, substantial amounts are lost, notably in mining, processing, agriculture via soil erosion, food waste, manure, and sewage sludge. They are not only critical with respect to wasting an essential resource, but also contribute to severe environmental impacts such as eutrophication of freshwater ecosystems or the development of dead zones in oceans. The Recycling and Dissipation Node covers the phosphorus system from those points where phosphate-containing waste or losses have occurred or been produced by human excreta, livestock, and industries. This chapter describes losses and recycling efforts, identifies knowledge implementation and dissemination gaps as well as critical questions, and outlines potential transdisciplinary case studies. Two pathways toward sustainable P management are in focus: To a major goal of sustainable P management therefore must be to (1) quantify P stocks and flows in order to (2) identify key areas for minimizing losses and realizing recycling opportunities. Several technologies already exist to recycle P from different sources, including manure, food waste, sewage, and steelmaking slag; however, due to various factors such as lacking economic incentives, insufficient regulations, technical obstacles, and missing anticipation of unintended impacts, only a minor part of potential secondary P resources has been utilized. Minimizing losses and increasing recycling rates as well as reducing unintended environmental impacts triggered by P dissipation require a better understanding of the social, technological, and economic rationale as well as the intrinsic interrelations between nutrient cycling and ecosystem stability. A useful approach will be to develop new social business models integrating innovative technologies, corporate strategies, and public policies. That requires intensive collaboration between different scientific disciplines and, most importantly, among a variety of key stakeholders, including industry, farmers, and government agencies.
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| 585. |
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| 586. |
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| 587. |
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| 588. |
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| 589. |
- Zammarano, Mauro, et al.
(författare)
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Flammability reduction of flexible polyurethane foams via carbon nanofiber network formation
- 2008
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Ingår i: Polymers for Advanced Technologies. - : Wiley. - 1042-7147 .- 1099-1581. ; 19:6, s. 588-595
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Tidskriftsartikel (refereegranskat)abstract
- Untreated polyurethane flexible foams (PUFs) are prone to rapid fire growth due to their low density and low thermal conductivity. Furthermore, the low viscosity of the decomposition products generates severe dripping that increases the fire hazard related to the combustion of PUFs. In fact, this downward flow of flaming liquid often results in a pool-fire that promotes flame propagation and boosts the rate of heat release (HRR) due to a significant increase in the burning area and to feed-back between the flame on the pool-fire and the residual foam. In this work the effect of nartoparticles, i.e., clays and carbon nanofibers (CNFs), on the HRR is investigated with special attention given to melt dripping. A modified cone calorimeter test has been developed for this purpose. It is shown that CNFs form an entangled fiber network which eliminates melt dripping and decreases the HRR.
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| 590. |
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