-Thermoelectric energy harvesting requires a substantial temperature difference ΔΤ to be available within the device structure. This has restricted its use to particular applications such as heat engine structural monitoring, where a hot metal surface is available. An alternative approach is possible in cases where the ambient temperature undergoes regular variation. This involves using a heat storage unit, filled with a phase change material, to create an internal spatial temperature difference from the temperature variation in time. In this paper, the key design parameters and a characterisation methodology for such devices are defined. The maximum electrical energy density expected for a given temperature range is calculated. The fabrication, characterisation and analysis of a heat storage harvesting prototype device is presented for temperature variations of a few tens of degrees around 0 °C , corresponding to aircraft flight conditions. Output energy of 105 J into a 10 Ω matched resistive load, from a temperature sweep from +20 °C to -21 °C , then to +25 °C is demonstrated, using 23 g of water as the phase change material. The proposed device offers a unique powering solution for wireless sensor applications involving locations with temperature variation, such as structural monitoring in aircraft, industrial and vehicle facilities.
Infection of mice with the nematode parasite Nippostrongylus brasiliensis results in a well characterized intestinal mastocytosis with intraepithelial migration of mucosal mast cells (MMC). The molecules mediating this response are unknown. We examined expression of several putative mast cell chemoattractants in intestinal epithelium following N. brasiliensis infection. Expression of the chemokines monocyte chemoattractant protein-1 (MCP-1), macrophage inflammatory protein-1 alpha (MIP-1alpha), RANTES (regulated on activation normal T-cell expressed and secreted), fractalkine, and thymocyte expressed chemokine (TECK); and the cytokines stem cell factor (SCF) and transforming growth factor beta1 (TGFbeta1), was constitutive and no alteration was detected following infection. MCP-1 expression was also constitutive but at much lower levels and increased expression was detected on days 7 and 14 postinfection. Expression of MCP-1 in whole jejunum was at much higher levels than in epithelium. Constitutive expression of MCP-1, MIP-1alpha and TGFbeta1 was also detected in cultured bone marrow-derived homologues of MMC. In an intestinal epithelial cell line (CMT-93), there was constitutive expression of SCF, TGFalpha1, fractalkine and MCP-1. The results show that, in vivo, epithelium is a potentially important source of mast cell chemoattractants.
Nonvolatile SiO2 on Si is reduced to elemental Si and to volatile SiO, by exposing the oxidized Si to an atomic Ga beam in vacuum, at a temperature as low as 800 °C. The SiO and the Ga2O form in the process, and the excess Ga evaporates at this temperature, leaving behind a clean and damage-free surface.
This paper introduces an inductive method for harvesting energy from current-carrying structures. Numerical simulation of a structural beam shows that the skin effect can lead to significant current concentration at edges, providing a five-fold power benefit at such locations, even at frequencies below 1 kHz. The use of a rectangular ferrite core can provide a ×4 power density improvement. The adoption of funnel-like core shapes allows the reduction of core mass and coil frame size, leading to significant further power density enhancement. Magnetic field simulation and coil analysis demonstrate a power density increase of ×49 by ferrite funnels, in comparison to a coreless coil. Experimental results demonstrate rectified power over 1 mW delivered to a storage capacitor, from a 40 × 20 × 2 mm core-and-coil, in the vicinity of a spatially distributed 20 A current at 800 Hz. Rectification and impedance matching are studied experimentally using a voltage doubler circuit with input capacitor tuning to counteract the coil reactance. Experimental results from a spatially distributed 30 A current at 300 Hz and a 1:7 funnel core demonstrate power density of 36 µW/g (103 µW/cm 3 ), opening up the way to non-invasive inductive powering of systems in the vicinity of current-carrying structures.
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