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- Dirri, Fabrizio, et al.
(författare)
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VISTA instrument: a PCM-based sensor for organics and volatiles characterization by using Thermogravimetric technique
- 2018
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Konferensbidrag (refereegranskat)abstract
- VISTA (Volatile In Situ Thermogravimetry Analyser) is a µ-Thermogravimeter sensor developed by Consortium of Italian Institutes. ThermoGravimetric Analysis (TGA) is a widely used technique to monitor thermal processes involving volatile compounds, e.g. deposition/sublimation and absorption/ desorption. The instrument core is composed by a Piezoelectric Crystal Microbalance (PCM), equipped with built-in heater and built-in temperature sensor, and provided of its own Proximity Electronics (PE). The PCM oscillation frequency linearly depends on the mass deposited on its sensible area (according to Sauerbrey equation) while the PCM temperature can be increased by means of integrated heaters. Thus, mass and volatile composition can be inferred by the frequency change and by desorption temperature, respectively. The instrument is divided in two sensor heads: VISTA1, able to monitor outgassing processes in space, and VISTA2, able to reach higher temperatures, studying the dehydration and organics decomposition in minerals in different environmental conditions. An Engineering Model of VISTA1 and a laboratory breadboard of VISTA2 have been developed. Pure organic compounds and contaminant have been characterized by using deposition processes and TGA cycles obtaining some physical-chemical parameters, i.e. enthalpy of sublimation/evaporation, ΔHHsub,evap , deposition rates, kk and vapor pressures, Pvap . The instrument concept, the scientific objectives and the laboratory measurements are explained in this work.
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| 2. |
- Karremans, Adam P., et al.
(författare)
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Evolution of Seed Dispersal Modes in the Orchidaceae : Has the Vanilla Mystery Been Solved?
- 2023
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Ingår i: Horticulturae. - : MDPI. - 2311-7524. ; 9:12
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Tidskriftsartikel (refereegranskat)abstract
- Orchid seeds are predominantly wind-dispersed, often developed within dry, dehiscent fruits that typically release millions of dust-like seeds into the air. Animal-mediated seed dispersal is a lesser-known phenomenon in the family and predominantly occurs in groups belonging to early-diverging lineages bearing indehiscent, fleshy fruits with hard, rounded, dark seeds. In this review, we explore the evolutionary trends of seed dispersal mechanisms in Orchidaceae, focusing on the pantropical genus Vanilla. Notably, certain Neotropical species of Vanilla produce vanillin-aromatic compounds synthesized naturally in their fruits, which plays a pivotal role in seed dispersal. Ectozoochory occurs in dry, dehiscent fruits, whose seeds are dispersed by (i) male euglossine bees collecting the fruit’s vanillin aromatic compounds and (ii) female stingless bees collecting the fruit’s mesocarp. Endozoochory occurs in (iii) highly nutritious, indehiscent fruits consumed by terrestrial mammals or (iv) fleshy, dehiscent fruits whose mesocarp is consumed by arboreal mammals. Wind dispersal appears to be a derived state in Orchidaceae and, given its predominance, a trait likely associated with enhanced speciation rates. Zoochory primarily occurs in groups derived from early-diverging lineages; occasional reversions suggest a link between dispersal mode and fruit and seed traits. Interestingly, fruit dehiscence and fleshiness in Vanilla lack phylogenetic signal despite their role in determining dispersal modes, suggesting potential environmental adaptability.
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