11,239 research outputs found

    Assessing the ecological soundness of organic and conventional agriculture by means of life cycle assessment (LCA) - a case study of leek production

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    Purpose – Sustainable agriculture implies the ability of agro-ecosystems to remain productive in the long-term. It is not easy to point out unambiguously whether or not current production systems meet this sustainability demand. A priori thinking would suggest that organic crops are environmentally favourable, but may ignore the effect of reduced productivity, which shifts the potential impact to other parts of the food provision system. The purpose of this paper is to assess the ecological sustainability of conventional and organic leek production by means of life cycle assessment (LCA). Design/methodology/approach – A cradle-to-farm gate LCA is applied, based on real farm data from two research centres. For a consistent comparison, two functional units (FU) were defined: 1ha and 1?kg of leek production. Findings – Assessed on an area basis, organic farming shows a more favourable environmental profile. These overall benefits are strongly reduced when the lower yields are taken into account. Related to organic farming it is therefore important that solutions are found to substantially increase the yields without increasing the environmental burden. Related to conventional farming, important potential for environmental improvements are in optimising the farm nutrient flows, reducing pesticide use and increasing its self-supporting capacity. Research limitations/implications – The research is a cradle-to-farm gate LCA, future research can be expanded to comprise all phases from cradle-to-grave to get an idea of the total sustainability of our present food consumption patterns. The research is also limited to the case of leek production. Future research can apply the methodology to other crops. Originality/value – To date, there is still lack of clear evidence of the added value of organic farming compared to conventional farming on environmental basis. Few studies have compared organic and conventional food production by means of LCA. This paper addresses these issues

    Scattering Polarization of the Ca II IR Triplet for Probing the Quiet Solar Chromosphere

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    The chromosphere of the quiet Sun is an important stellar atmospheric region whose thermal and magnetic structure we need to decipher for unlocking new discoveries in solar and stellar physics. To this end, we must identify and exploit observables sensitive to weak magnetic fields (B<100 G) and to the presence of cool and hot gas in the bulk of the solar chromosphere. Here we report on an investigation of the Hanle effect in two semi-empirical models of the quiet solar atmosphere with different chromospheric thermal structures. Our study reveals that scattering polarization in the Ca II IR triplet has thermal and magnetic sensitivities potentially of great diagnostic value. The linear polarization in the 8498 A line shows a strong sensitivity to inclined magnetic fields with strengths between 0.001 and 10 G, while the emergent linear polarization in the 8542 A and 8662 A lines is mainly sensitive to magnetic fields with strengths between 0.001 and 0.1 G. The reason for this is that the scattering polarization of the 8542 A and 8662 A lines, unlike the 8498 A line, is controlled mainly by the Hanle effect in their (metastable) lower levels. Therefore, in regions with magnetic strengths sensibly larger than 1 G, their Stokes Q and U profiles are sensitive only to the orientation of the magnetic field vector. We also find that for given magnetic field configurations the sign of the Q/I and U/I profiles of the 8542 A and 8662 A lines is the same in both atmospheric models, while the sign of the linear polarization profile of the 8498 A line turns out to be very sensitive to the thermal structure of the lower chromosphere. We suggest that spectropolarimetric observations providing information on the relative scattering polarization amplitudes of the Ca II IR triplet will be very useful to improve our empirical understanding of the thermal and magnetic structure of the quiet chromosphere.Comment: 27 pages, 16 figures, to appear in Ap

    Community engagement as a new and contested ritual: an ethnographic study of five pentecostal congregations in El Salvador

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    There is growing evidence that more Pentecostal congregations and adherents are participating in new ways to address poverty and justice worldwide. Pentecostals are starting their projects as well as partnering with international and local NGOs and FBOs to implement development programmes. The increased participation in social engagement has generated new discussions among scholars on whether the shift in practice reflects a change in beliefs within some Pentecostal congregations. It has also renewed older debates on whether Pentecostal beliefs, practices and organisational cultures can contribute to or hinder development interventions. This thesis provides an ethnographic study of five traditional Pentecostal congregations in El Salvador that partner with community leaders, local associations, and public and private entities to identify and implement community-wide development initiatives. For these congregations, the practice of engaging with their communities to address individual and structural issues through collective action is a new and contested church practice. The thesis examines why pastors and leaders choose to introduce the new practice and how they use available cultural strategies to ritualize community engagement into their congregations. By studying community engagement as a rhetorical, embodied, and creative ritual practice, the thesis argues that the new practice reinforces, challenges and transforms Pentecostal adherents’ sense of identity, sociality, and way-in-the-world. The in-depth ethnographic examination of how Pentecostal congregations participate in development initiatives contributes both to understanding the importance of ritualization for Pentecostals and to discussions about the role of Pentecostal congregations in development. The thesis suggests that the role of Pentecostal congregations in community development is contingent upon pastors’ authority to introduce and ritualize new development practices as well as their ability to create and sustain relationships of trust with non-church, community members to catalyse stable linking networks needed for a community to thrive

    Non-standard Dirac adjoint spinor: The emergence of a new dual

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    In this present communication we provide a new derivation of the Dirac dual structure by employing a different approach from the originally proposed. Following a general and rigorous mathematical process to compute the dual structure, we investigate if is possible to break the existing "rigidity" in its primordial formulation. For this task, firstly, we look towards to understand the core of the Dirac spinors construction and then, we suggest to built an alternative dual structure for the Dirac spinor, which preserve an invariant norm under any SL(2,C)SL(2,\mathcal{C}) transformation. Finally, we verify if the prominent physical contents are maintained or if it is affected by such construction.Comment: 7 pages, 0 figure

    Are collisions with neutral hydrogen important for modelling the Second Solar Spectrum of Ti I and Ca II ?

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    The physical interpretation of scattering line polarization offers a novel diagnostic window for exploring the thermal and magnetic structure of the quiet regions of the solar atmosphere. Here we evaluate the impact of isotropic collisions with neutral hydrogen atoms on the scattering polarization signals of the 13 lines of multiplet 42 of Ti I and on those of the K line and of the IR triplet of Ca II, with emphasis on the collisional transfer rates between nearby J-levels. To this end, we calculate the linear polarization produced by scattering processes considering realistic multilevel models and solving the statistical equilibrium equations for the multipolar components of the atomic density matrix. We confirm that the lower levels of the 13 lines of multiplet 42 of Ti I are completely depolarized by elastic collisions. We find that upper-level collisional depolarization turns out to have an unnoticeable impact on the emergent linear polarization amplitudes, except for the {\lambda 4536 line for which it is possible to notice a rather small depolarization caused by the collisional transfer rates. Concerning the Ca II lines, we show that the collisional rates play no role on the polarization of the upper level of the K line, while they have a rather small depolarizing effect on the atomic polarization of the metastable lower levels of the Ca II IR triplet.Comment: Accepted for publication in Astronomy and Astrophysic

    Densità, ricchezza, struttura demografica e spaziale della rigenerazione naturale in un rimboschimento in aree pascolate: competizione o facilitazione?

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    Nell’ultimo secolo migliaia di ettari in Europa sono stati riforestati soprattutto dopo l’abbandono delle attività agricole. Tale attività ha consentito di ridurre i fenomeni di degrado ma nonostante ciò non è raro vedere rimboschimenti che ancora mantengono la struttura e composizione iniziale. Da questo fatto emerge la necessità di capire i meccanismi che limitano la rigenerazione naturale, anche se per buona parte di questi rimboschimenti ancora mancano indicatori di base sulla demografia delle specie che caratterizzano questa rigenerazione. Questo studio ha avuto come obiettivo analizzare la ricchezza, la densità e la struttura demografica e spaziale delle piante legnose che si insediano sotto due specie arboree, il frassino (Fraxinus angustifolia) e il pino d’Aleppo (Pinus halepensis), impiantate circa 40 anni fa, in un’area di pascolo dentro la Riserva di Ficuzza (Palermo). Il campionamento è stato eseguito dentro tre macro aree, di 10 ha ciascuna. Sotto la proiezione della chioma di ciascun individuo di frassino (N = 62), sono stati verificati tre plot di 1 m² ciascuno, per un’area di saggio totale di 186 m². Sotto i pini (N = 10) sono stati verificati quattro plot per un’area totale di 40 m². Dentro questi plot, tutti gli individui di specie legnose con altezza superiore a 5 cm sono stati registrati, identificati e classificati in quattro classi di altezza (5-10; 10-50; 50-100; &gt;100 cm). Per descrivere la struttura spaziale della rigenerazione sotto i frassini, è stata realizzata un’analisi spaziale per gli indici di distanza SADIE. Dei 62 individui di frassino verificati, 44 (71%) avevano almeno una piantina di specie legnose, per un totale di 315 piantine di 13 specie, e una densità pari a 1.7 (± 0.3) piantine/m². Il prugnolo (Prunus spinosa) è stata la specie più abbondante con 36.3% degli individui, mentre le specie degli stadi più avanzati (querce) hanno rappresentato soltanto il 3.2%. Sotto i dieci pini analizzati, nove contenevano almeno una piantina, per un totale di 192 individui di dieci specie e una densità di 4.8 (± 1.2) al m². Il rovo (Rubus ulmifolius) è stata la specie più abbondante con 27.6% degli individui, mentre le querce soltanto il 3.6%. I valori di densità e ricchezza delle piantine sotto i frassini hanno presentato una distribuzione spaziale regolare lungo l’area di campionamento (SADIE p &gt; 0.05). Sotto entrambe le specie esiste una correlazione positiva fra la presenza degli individui della classe di altezza minore (5-10 cm) con quelli delle classi di altezza maggiori (Spearman p &lt; 0.05), suggerendo un potenziale meccanismo di facilitazione. Dai risultati si evince che gli individui arborei piantati stanno facilitando l’insediamento delle specie legnose spontanee. La dominanza di specie con frutti carnosi evidenzia anche il contributo della fauna nella dispersione dei semi. E’ da sottolineare tuttavia che questo risultato è stato ottenuto in una situazione favorevole di alta naturalità, spesso però assente in buona parte dei rimboschimenti, dove interventi attivi di rinaturalizzazione, cioè della diffusione di specie coerenti con la vegetazione potenziale, sono necessari, almeno nella prima fase

    Recent Advances in Chromospheric and Coronal Polarization Diagnostics

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    I review some recent advances in methods to diagnose polarized radiation with which we may hope to explore the magnetism of the solar chromosphere and corona. These methods are based on the remarkable signatures that the radiatively induced quantum coherences produce in the emergent spectral line polarization and on the joint action of the Hanle and Zeeman effects. Some applications to spicules, prominences, active region filaments, emerging flux regions and the quiet chromosphere are discussed.Comment: Review paper to appear in "Magnetic Coupling between the Interior and the Atmosphere of the Sun", eds. S. S. Hasan and R. J. Rutten, Astrophysics and Space Science Proceedings, Springer-Verlag, 200
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