3,552 research outputs found

    How alternative food networks work in a metropolitan area? An analysis of Solidarity Purchase Groups in Northern Italy

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    Our paper focuses on Solidarity Purchase Group (SPG) participants located in a highly urbanized area, with the aim to investigate the main motivations underlining their participation in a SPG and provide a characterization of them. To this end, we carried out a survey of 795 participants involved in 125 SPGs in the metropolitan area of Milan (Italy). Taking advantage of a questionnaire with 39 questions, we run a factor analysis and a two-step cluster analysis to identify different profiles of SPG participants. Our results show that the system of values animating metropolitan SPG practitioners does not fully conform to that traditionally attributed to an alternative food network (AFN). In fact, considerations linked to food safety and healthiness prevail on altruistic motives such as environmental sustainability and solidarity toward small producers. Furthermore, metropolitan SPGs do not consider particularly desirable periurban and local food products. Observing the SPGs from this perspective, it emerges as such initiatives can flourish also in those places where the lack of connection with the surrounding territory is counterbalanced by the high motivation to buy products from trusted suppliers who are able to guarantee genuine and safe products, not necessarily located nearby

    Egg parasitoid exploitation of plant volatiles induced by single or concurrent attack of a zoophytophagous predator and an invasive phytophagous pest

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    Zoophytophagous insect predators can induce physiological responses in plants by activating defence signalling pathways, but whether plants can respond to facultative phytophagy by recruiting natural enemies remains to be investigated. In Y-tube olfactometer bioassays, using a system including a Vicia faba plant, the zoophytophagous predator Podisus maculiventris and the egg parasitoid Telenomus podisi, we first demonstrated that T. podisi females are attracted by broad bean plants damaged by feeding activity of P. maculiventris and on which host egg masses had been laid, while they are not attracted by undamaged plants or plants damaged by feeding activity alone. In a second experiment, we evaluated the impact of the invasive phytophagous pest Halyomorpha halys on this plant volatile-mediated tritrophic communication. Results showed that the invasive herbivorous adults do not induce plants to recruit the native egg parasitoid, but they can disrupt the local infochemical network. In fact, T. podisi females are not attracted by volatiles emitted by plants damaged by H. halys feeding alone or combined with oviposition activity, nor are they attracted by plants concurrently infested by P. maculiventris and H. halys, indicating the specificity in the parasitoid response and the ability of the invasive herbivore in interrupting the semiochemical communication between plants and native egg parasitoids. To the best of our knowledge, this is the first study showing that zoophytophagous predator attacks induce indirect plant defences similarly to those defence strategies adopted by plants as a consequence of single or concurrent infestations of herbivorous insects

    E-BOSS: An Extensive stellar BOw Shock Survey. II. Catalogue second release

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    Context. Stellar bow shocks have been studied not only observationally, but also theoretically since the late 1980s. Only a few catalogues of them exist. The bow shocks show emission along all the electromagnetic spectrum, but they are detected more easily in infrared wavelengths. The release of new and high-quality infrared data eases the discovery and subsequent study of new objects. Aims. We search stellar bow-shock candidates associated with nearby runaway stars, and gather them together with those found elsewhere, to enlarge the list of the E-BOSS first release. We aim to characterize the bow-shock candidates and provide a database suitable for statistical studies. We investigate the low-frequency radio emission at the position of the bow-shock features, that can contribute to further studies of high-energy emission from these objects. Methods. We considered samples from different literature sources and searched for bow-shaped structures associated with stars in the Wide-field Infrared Survey Explorer (WISE) images. We looked for each bow-shock candidate on centimeter radio surveys. Results. We reunited 45 bow-shock candidates and generated composed WISE images to show the emission in different infrared bands. Among them there are new sources, previously studied objects, and bow shocks found serendipitously. Five bow shocks show evidence of radio emission. Conclusions. Stellar bow shocks constitute an active field with open questions and enormous amounts of data to be analyzed. Future research at all wavelengths databases, and use of instruments like Gaia, will provide a more complete picture of these objects. For instance, infrared spectral energy distributions can give information about physical parameters of the bow shock matter. In addition, dedicated high-sensitivity radio observations can help to understand the radio-γ\gamma connection.Comment: 20 pages, 11 figures, and 8 tables. Accepted for publication in A&

    Surface control system for the 15 meter hoop-column antenna

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    The 15-meter hoop-column antenna fabricated by the Harris Corporation under contract to the NASA Langley Research Center is described. The antenna is a deployable and restowable structure consisting of a central telescoping column, a 15-meter-diameter folding hoop, and a mesh reflector surface. The hoop is supported and positioned by 48 quartz cords attached to the column above the hoop, and by 24 graphite cords from the base of the antenna column. The RF reflective surface is a gold plated molybdenum wire mesh supported on a graphite cord truss structure which is attached between the hoop and the column. The surface contour is controlled by 96 graphite cords from the antenna base to the rear of the truss assembly. The antenna is actually a quadaperture reflector with each quadrant of the surface mesh shaped to produce an offset parabolic reflector. Results of near-field and structural tests are given. Controls structures and electromagnetics interaction, surface control system requirements, mesh control adjustment, surface control system actuator assembly, surface control system electronics, the system interface unit, and control stations are discussed

    Rules of Origin and Gains from Trade

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    This paper identifies the most restrictive limit that rules of origin can enforce and still continue to guarantee gains from trade area formation in general settings. Many commonly used rules of origin exceed this condition in practise. Second, free trade areas generally involve unharmonized tariffs requiring rules of origin that make standard analyses difficult or inapplicable. We incorporate the identified welfare-supporting rules of origin into standard existence of equilibrium proofs and prove the existence of a free trade area equilibrium involving only within-FTA transfers that is at least as satisfactory for every consumer worldwide as an arbitrary original world for allocation. The analysis explains why hub-and-spoke extensions of free areas cannot guarantee gains from trade for all participants in general.Rules of origin, free trade areas, Walrasian equilibrium, welfare analysis

    Environmental Noise and Nonlinear Relaxation in Biological Systems

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    We analyse the effects of environmental noise in three different biological systems: (i) mating behaviour of individuals of \emph{Nezara viridula} (L.) (Heteroptera Pentatomidae); (ii) polymer translocation in crowded solution; (iii) an ecosystem described by a Verhulst model with a multiplicative L\'{e}vy noise.Comment: 32 pages; In "Ecological Modeling" by Ed. Wen-Jun Zhang. ISBN: 978-1-61324-567-5. - Nova Science Publishers, New York, 201

    Sweet cherry production in South Patagonia

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    In South Patagonia, the total sweet cherry (Prunus avium L.) area has increased from 176 ha in 1997 to 507 ha in 2004, of which 232 ha are located in Los Antiguos (46°19¿ SL; 220 m elevation), 158 ha in the Lower Valley of Chubut River (LVCHR) (43°16¿ SL; 30 m elevation), 52 ha in Sarmiento (45°35¿ SL; 270 m elevation), 35 ha in Esquel (42°55¿ SL; 570 m elevation) and 30 ha in Comodoro Rivadavia (45°52¿ SL; 50 m elevation). The most common varieties are `Lapins¿, `Bing¿, `Newstar¿, `Sweetheart¿, `Stella¿, `Sunburst¿ and `Van¿ grafted on `Mahaleb¿, `Pontaleb¿, `SL 64¿, `Colt¿ or `Mazzard¿ rootstocks. Trees generally are drip-irrigated and planted at high densities, using training systems such as Tatura, central leader and modified vase (2700, 1100 and 1000 trees ha-1, respectively). Growers in Los Antiguos are more traditional, planting mainly as vase (400 to 1000 trees ha-1) or freestanding trees (280 trees ha-1) and irrigating by gravity (74% of the area). Only 4.4% of the area of Los Antiguos is frost protected, as growers rely strongly on the moderating effect of Lake Buenos Aires. Frost control systems are absent in Comodoro Rivadavia because the established orchards are located next to the sea, in an area with low risk of frost. The frost-protected area is 49% in Sarmiento, 35% in Esquel and 57% in LVCHR. Fruit are harvested from November (LVCHR) to the end of January (Los Antiguos and Esquel), and the harvest-only labour demand during the 2004/2005 season was 100,000 h. In that season, seven packinghouses exported 390 t (45% of the total production) to Europe. Most orchards have not yet reached their mature stage and new ones are being established. Therefore, fruit volumes will continue to increase and shortages of labour and packing facilities may become a constraint

    Aspectos ecológicos y ambientales de los bosques nativos y plantaciones forestales de la Argentina : una visión panorámica y conceptual

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    Fil: Frangi, Jorge Luis. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Laboratorio de Investigaciones de Sistemas Ecológicos y Ambientales; ArgentinaFil: Pérez, Carolina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Laboratorio de Investigaciones de Sistemas Ecológicos y Ambientales; ArgentinaFil: Martiarena, Rodolfo Andres. INTA EEA. Misiones; ArgentinaFil: Pinazo, Martín. INTA EEA. Misiones; ArgentinaFil: Martínez Pastur, Guillermo. Centro Austral de Investigaciones Científicas. Tierra del Fuego; ArgentinaFil: Brown, Alejandro. Fundación ProYungas; TucumánFil: Peri, Pablo L.. Universidad Nacional de la Patagonia Austral. INTA EEA. Río Gallegos; ArgentinaFil: Ceballos, Darío S.. INTA EEA. Campana; Argentin
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