Micro-wrinkled palladium surface for hydrogen sensing and switched detection of lower flammability limit

We report the development and testing of a novel hydrogen sensor that shows a very peculiar response to hydrogen exposure, due to its micro-structured palladium surface. The fabrication of the wrinkled Pd surface is obtained using an innovative, fast and cheap technique based on the deposition of a thin Pd film on to a thermo-retractable polystyrene sheet that shrinks to 40% of its original size when heated. The buckling of the Pd surface induced by shrinking of the substrate produces nano and micro-wrinkles on the sensor surface. The micro-structured sensor surface is very stable even after repeated hydrogen sorption/desorption cycles. The hydrogen sensing mechanism is based on the transitory absorption of hydrogen atoms into the Pd layer, leading to the reversible change of its electrical resistance. Interestingly, depending on hydrogen concentration the proposed sensor shows the concurrent effect of both the usually described behaviors of increase or decrease of resistance, related to different phenomena occurring upon hydrogen exposure and formation of palladium hydride. The study reports and discusses evidences for an activation threshold of hydrogen concentration in air switching the behavior of sensor performances from, e.g., poor negative to large positive sensitivity and from slow to fast detection. Copyright © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights

Note sulla reazione biologica ai punti di sutura

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EFFECT OF COMPOST-BASED ALTERNATIVE SUBSTRATA IN POTTED ALOE VERA (L.) BURM. F.

The objective of this work was to study the use of two composts, obtained by olive mill (C3) and green waste (C5), made by the Eden ’94 firm in Manduria (Ta), as growing media components on Aloe vera (L.) plants. A one year trial was conducted in a conditioned greenhouse located in the Campus of the Faculty of Agriculture of Bari (Italy). Substrata containing 30% of inert substances in any case and increasing doses of compost (0, 30, 50, 70%) have been compared; the fulfilment at 100 of volume, if necessary, has been reached adding peat quantities to the mixture. The growing density was of 6 p m-2 for a total of 98 plants. The cultivation lasted 338 days; plants never showed any symptoms of water stress. The results were statistically analyzed. Chemical and physical properties of growing media were analyzed; plant vegetative growth, was determined 180 days after transplanting and at 338 days. The obtained results pointed out that the plants growth dramatically depends on the compost percentages. The composts used in the preparation of substrates were not phytotoxic and allowed the plants to grow disease-free and with no weeds. Due to their physical and chemical characteristics the composts prepared from urban park and garden wastes and from solid fractions of olive mill wastes may be considered as partial peat substitutes