Early-time velocity autocorrelation for charged particles diffusion and drift in static magnetic turbulence

Using test-particle simulations, we investigate the temporal dependence of the two-point velocity correlation function for charged particles scattering in a time-independent spatially fluctuating magnetic field derived from a three-dimensional isotropic turbulence power spectrum. Such a correlation function allowed us to compute the spatial coefficients of diffusion both parallel and perpendicular to the average magnetic field. Our simulations confirm the dependence of the perpendicular diffusion coefficient on turbulence energy density and particle energy predicted previously by a model for early-time charged particle transport. Using the computed diffusion coefficients, we exploit the particle velocity autocorrelation to investigate the time-scale over which the particles "decorrelate" from the solution to the unperturbed equation of motion. Decorrelation time-scales are evaluated for parallel and perpendicular motions, including the drift of the particles from the local magnetic field line. The regimes of strong and weak magnetic turbulence are compared for various values of the ratio of the particle gyroradius to the correlation length of the magnetic turbulence. Our simulation parameters can be applied to energetic particles in the interplanetary space, cosmic rays at the supernova shocks, and cosmic-rays transport in the intergalactic medium.Comment: 10 pages, 11 figures, The Astrophyical Journal in pres

Reverse electrodialysis – Multi effect distillation heat engine fed by lithium chloride solutions

Salinity Gradient Heat Engines (SG-HEs) have been proposed as a promising technology for converting low-temperature heat into electricity. The SG-HE includes two different processes: (i) a salinity gradient process where the salinity gradient between two solutions is converted into electricity and (ii) a thermal regeneration process where low-grade heat (T<100°C) is used to re-establish the original salinity gradient of the two streams. Among the proposed working solutions, aqueous solution of lithium chloride has been identified as one of the most promising thanks to its remarkable solubility and activity. In this work, a process model to study the performance of a SG-HE constituted by a Reverse ElectroDialysis (RED) unit coupled with a Multi Effect Distillation (MED) unit fed with lithium chloride solution is presented. The influence of the concentration of the inlet solution in the RED unit and the temperature difference in the evaporators of the MED unit on the performance were evaluated by considering ideal membranes. Furthermore, the impact of membrane permselectivity and resistance on the system performance was evaluated. Results showed promising system efficiencies, making this technology attractive for conversion of low-grade heat (<100°C) into electricity, but membrane properties should be enhanced

Evaluation of the economic and environmental performance of low-temperature heat to power conversion using a reverse electrodialysis - Multi-effect distillation system

In the examined heat engine, reverse electrodialysis (RED) is used to generate electricity from the salinity difference between two artificial solutions. The salinity gradient is restored through a multi-effect distillation system (MED) powered by low-temperature waste heat at 100 ◦C. The current work presents the first comprehensive economic and environmental analysis of this advanced concept, when varying the number of MED effects, the system sizing, the salt of the solutions, and other key parameters. The levelized cost of electricity (LCOE) has been calculated, showing that competitive solutions can be reached only when the system is at least medium to large scale. The lowest LCOE, at about 0.03 €/kWh, is achieved using potassium acetate salt and six MED effects while reheating the solutions. A similar analysis has been conducted when using the system in energy storage mode, where the two regenerated solutions are stored in reservoir tanks and the RED is operating for a few hours per day, supplying valuable peak power, resulting in a LCOE just below 0.10 €/kWh. A life-cycle assessment has been also carried out, showing that the case with the lowest environmental impact is the same as the one with the most attractive economic performance. Results indicate that the material manufacturing has the main impact; primarily the metallic parts of the MED. Overall, this study highlights the development efforts required in terms of both membrane performance and cost reduction, in order to make this technology cost effective in the future

Morphological variation of the newly confirmed population of the javelin sand boa, Eryx jaculus (Linnaeus, 1758) (Serpentes, erycidae) in Sicily, Italy

The presence of the Javelin sand boa in Sicily has recently been confirmed. Here the morphological characters and sexual dimorphism of the Sicilian population of Eryx jaculus are presented. Seven meristic and six metric characters in 96 specimens from Sicily were examined. The results show that tail length, snout-vent length, the distance between nostrils and the number of ventral and subcaudal scales are different between sexes. The characters found in the Sicilian population of the Javelin sand boa resemble those of the African population (ssp. jaculus) rather than the Eurasian population (ssp. turcicus), but biomolecular studies are necessary to understand its taxonomic identity

Diffusion of energetic particles in turbulent MHD plasmas

In this paper we investigate the transport of energetic particles in turbulent plasmas. A numerical approach is used to simulate the effect of the background plasma on the motion of energetic protons. The background plasma is in a dynamically turbulent state found from numerical MHD simulations, where we use parameters typical for the heliosphere. The implications for the transport parameters (i.e. pitch-angle diffusion coefficients and mean free path) are calculated and deviations from the quasi-linear theory are discussed.Comment: Accepted for publication in Ap

Contenimento naturale di Bactrocera oleae (Rossi): clima o parassitoidi? Confronto tra Western Cape (Sud Africa) e Sicilia

Bactrocera oleae (Rossi), mosca delle olive, e\u300 presente anche in Sud Africa, ma finora non si sono avute notizie di infestazioni economicamente rilevanti negli oliveti. L\u2019accertata presenza di un maggior numero di braconidi parassitoidi della mosca delle olive rispetto alle aree mediterranee e\u300 stata ed e\u300 considerata da molti autori la principale causa di queste minori infestazioni, senza che pero\u300 siano stati eseguiti in Sud Africa adeguati studi sulle infestazioni da B. oleae e sui fattori cli- matici delle aree interessate. Analizzando recenti dati sui livelli d\u2019infestazione di B. oleae registrati su olivo coltivato e selvatico nel Western Cape e in Sicilia, appaiono simili in una normale annata fino a meta\u300 estate, ma sono nettamente differenti a fine estate-inizio autunno, quando in Sicilia il clima diviene piu\u300 umido. Da una puntuale analisi dei corrispondenti dati climatici registrati nelle due aree e\u300 infatti emersa una sostanziale differenza nel decorso piu\u300 caldo e secco degli ultimi tre mesi precedenti la raccolta nel Western Cape; questo periodo invece in Sicilia e\u300 caratterizzato da temperature piu\u300 fresche e un aumento dell\u2019umidita\u300 relativa che favorisce l\u2019impennata delle infestazioni di B. oleae. Nei quattro mesi presi in considerazione si rileva anche una significativa differenza nell\u2019escursione termica, maggiore nel Western Cape, dovuta a minime notturne piu\u300 basse. Da un confronto dei livelli di parassitizzazione di B. oleae del Western Cape (Sud Africa) e dell\u2019area costiera della Provincia di Trapani, recentemente registrati su olivo colti- vato e selvatico (Olea europaea subsp. cuspidata in Sud Africa, Olea europaea subsp. europaea var. sylvestris in Sicilia) non sono emerse sostanziali differenze quantitative, pur confer- mando che in Sud Africa i principali parassitoidi sono tre bra- conidi (Utetes africanus (Sze\u301pligeti), Psyttalia lounsburyi (Silvestri) e Bracon celer (Sze\u301pligeti)), con il primo preva- lente sull\u2019olivo selvatico e l\u2019ultimo sul coltivato, mentre in Sicilia il braconide parassitoide Psyttalia concolor (Sze\u301pligeti) prevale sia sull\u2019olivo selvatico che sul coltivato. Comunque in entrambe le aree la parassitizzazione su B. oleae non rag- giunge elevati ed efficaci livelli. Il clima, e non la parassitizzazione dovuta ai braconidi, appare il piu\u300 importante fattore di contenimento di B. oleae anche in Sud Africa. L\u2019introduzione di parassitoidi specifici della mosca delle olive e\u300 necessaria nelle aree colonizzate di recente dove essi mancano, ma i tentativi di fornir loro una maggiore dis- ponibilita\u300 di larve dell\u2019ospite mediante l\u2019impianto di cultivar d\u2019olivo a maturazione e permanenza dei frutti piu\u300 differen- ziata, potrebbe produrre risultati certamente piu\u300 negativi che positivi nei confronti della presenza e dei livelli d\u2019infesta- zione di B. oleae sull\u2019olivo coltivato, come avviene nelle aree pandacie dove cresce spontaneo l\u2019olivastro.Natural environmental control of Bactrocera oleae (Rossi): climate or parasitoids? A comparison between the Western Cape of South Africa and Sicily. Bactrocera oleae (Rossi), the olive fruit fly is considered not a continuosly serious pest of olive trees in the Western Cape of South Africa, in spite of the climate similar to Mediterranean areas. South African braconid parasitoids of B. oleae are more numerous than in Mediterranean areas, and until now their action has been considered the factor lowering the level of infestation due to the olive fruit fly, but no deep studies on its infestation levels and climatic factors influencing them were carried out in the past. Analyzing recent data on infestation levels collected in the Western Cape and Sicily, they appear similar in a regular mid- summer, differing at the end of summer-beginning of autumn, when in Sicily the climate becomes more humid than in the Western Cape. A comparison of climatic data regarding four years underlines that Somerset West and Franshhoek, in comparison with Trapani, have significantly lower minimum daily temperatures, a higher daily thermal excursion and a lower relative humidity in the last three months preceding harvesting. Parasitization rates on B. oleae of Western Cape and Sicily, recorded on both cultivated and wild olives (Olea europaea subsp. cuspidata in South Africa, Olea europaea subsp. europaea var. sylvestris in Sicily) are not substantially different, confirming that in South Africa three braconids, Utetes africanus (Sze\u301pligeti), Psyttalia lounsburyi (Silvestri) and Bracon celer (Sze\u301pligeti), are the main parasitoids, with the first one as leader in wild olives and the last one as leader in cultivated ones, while in Sicily the braconid Psyttalia concolor (Sze\u301pligeti) is the main parasitoid in both wild and cultivated olives. Nevertheless parasitism on B. oleae doesn\u2019t reach effective levels of control in bats ragions. The climate, instead of parasitization due to braconids, is the main environmental factor limiting the olive fruit fly infestations in the Western Cape of South Africa. The introduction of parasitoids specific to the olive fruit fly is necessary in new invaded areas where they lack, but the attempt of providing them a more available amount of host fruits along the year, planting olive trees bearing fruits up to spring, could bring serious problems as those typical of Mediterranean areas where the European wild olive naturally grows