210 research outputs found
Kinetics of volatile organic compounds (VOCs) released by roasted Coffee during the first ten days after processing
No full textThe quality of coffee is linked to the aroma created by the chemical reactions that occur during the roasting process. While it is generally thought that roasted coffee is a stable product with a relatively long shelf-life, little information is available on the evolution (kinetic) of the volatile organic compounds (VOCs) in the days immediately following the process. The aim of this study is to determine the evolution of VOCs released by coffee beans, on samples of Coffea arabica (three different origins) and Coffea canephora (1 single origin), by using a Proton Transfer Reaction Time-of-Flight Mass Spectrometer (PTR-ToF-MS) 24 hours after roasting, and for the next 9 days. Results confirmed the differences already highlighted in previous studies between the VOCs spectra of the two species. There were also significant differences in the intensity of emissions for the different origins of Coffea arabica, with the highest VOCs amount over time always detected in the Honduras Arabica samples. The involved detected protonated ions were grouped into three classes: compounds (ppbv) present with decreasing quantity; weakly increasing; almost
constant trend; or always increasing. A complex dynamic emerged for the different protonated ions over time, which not only affects the mass spectra of the different species but also influences the configuration of the mass spectra of the different geographical zones of production
A new satellite experiment in the Q/V band for the verification of fade countermeasures based on the spatial non-uniformity of attenuation
No full textModelling and simulation of EV high-power recharging pools with stationary storage
No full textHigh-power recharging pools are going to be widely deployed on the highways to guarantee a fast recharge for electric vehicles. These infrastructures may ask the grid for significant levels of power, which the grid may not be always capable to provide. In this context, stationary storage can provide peak power during the charging session, limiting the maximum power request to the grid and avoiding the need for an upgrade to the grid connection. This paper carries out the modelling and simulation of a high-power recharging pool connected to the LV distribution network and coupled with a stationary storage system. A technical-economic analysis is conducted for two different storage configurations: high-capacity storage and peak-shaving storage. Results show that the peak-shaving solution, at present, is the most convenient. In addition, it is observed that a reduced size could still support the EV recharge, with a reasonable additional waiting time, while improving the return of the investment
Digital signal processing techniques for personal and broadcasting satellite communication systems
No full textElectrical Engineering, Mathematics and Computer Scienc
Reaction of Alkynes with Iodine Monochloride Revisited
No full text6-Exo-dig and/or 7-endo-dig iodocyclization reactions
of functionalized acetylenic derivatives with ICl are
disfavored in comparison with the corresponding electrophilic
addition reactions providing regioselectively (E)-1-
chloro-2-iodoethene derivatives. On the contrary, 6-endo-dig
and 5-exo-dig iodocyclizations of methyl ynoates with ICl
seem to be favored in comparison with the corresponding
electrophilic addition reactions
Metabolic Responses in Leaves of 15 Italian Olive Cultivars in Correspondence to Variable Climatic Elements
No full textThis study aims to evaluate the metabolic changes that occurred in olive leaves as responses over time to variations in climatic elements. Rainfall, temperature, and solar radiation data were collected over 4 months (August–November) to assess the impact of different climatic trends on the metabolism of the leaves of 15 Italian olive cultivars, cultivated at the experimental farm of the University of Florence. The net photosynthetic rate (AN) and stomatal conductance (gs), measured as main indicators of primary metabolism, were mainly influenced by the “cultivar” effect compared to the “climate” effect. The lowest AN value was showed by “Bianchera”, while “Ascolana” recorded the highest (8.6 and 13.6 μmol CO2 m−2s−1, respectively). On the other hand, the secondary metabolism indicators, volatile organic compound (VOC) and oleuropein (OL) content, were much more influenced by climate trends, especially rainfall. A phase of high rainfall caused a significant increase in the VOCs emission from leaves, even with different behaviors among the genotypes. The highest differences were observed between “Maiatica di Ferrandina”, with the highest average values (~85,000 npcs), and “Frantoio”, which showed the lowest (~22,700 npcs). The OL content underwent considerable fluctuations in relation to the rainfall but also appeared to be controlled by the genotype. “Coratina” always showed the highest OL concentration (reaching the maximum ~98 mg g−1), indicating the great potential of this cultivar for the industrial recovery of OL
Production of large Bose-Einstein condensates in a magnetic-shield-compatible hybrid trap
No full textWe describe the production of large Na-23 Bose-Einstein condensates in a hybrid trap characterized by a weak magnetic field quadrupole and a tightly focused infrared beam. The use of small magnetic field gradients makes the trap compatible with the state-of-the-art magnetic shields. By taking advantage of the deep cooling and high efficiency of gray molasses to improve the initial trap loading conditions, we produce condensates composed of as many as 7 million atoms in less than 30 s
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