1,721,056 research outputs found
I paesaggi agricoli periurbani nelle politiche alimentari locali: proposta per una strategia sistemica
No full textIl lavoro si compone in tre sezioni: Teorie, Prassi e Azioni. Esse, oltre ad organizzare il lavoro secondo un percorso logico e metodologico, riflettono una fisiologica tripartizione del percorso di dottorato dovuta alla durata dello stesso, cioè il triennio. A partire da un’analisi teorica del problema individuato, il lavoro presenta una sezione mirata ad osservarne la fenomenologia, per terminare con una proposta strategica elaborata sulla scorta delle prime due sezioni. Tale suddivisione, che risente comunque di interferenze incrociate e necessari rimandi tra le tre sezioni, è rappresentativa e si fa metafora del percorso di dottorato stesso. Se durante il primo anno gli sforzi sono concentrati ad identificare il campo di ricerca e individuare il problema al quale si vuole rispondere, il secondo si appoggia su tali acquisizioni per analizzare e studiare le pratiche esistenti, per poi avere gli strumenti per formulare un proprio pensiero indipendente ma saldamente costruito su un percorso di studio e di ricerca. Teorie: La sezione specifica il problema di ricerca, l’ambito di lavoro e i principali approcci teorici già esistenti sul tema della sostenibilità dei sistemi alimentari e degli impatti degli stessi su paesaggio e ambiente, partendo dalla constatazione dell’importanza che i sistemi alimentari – nella loro natura di combinazioni complesse di flussi, spazi, valori, attività e rappresentazioni – hanno nel produrre paesaggio, sia in termini materiali che simbolici. Un’attenzione particolare viene dedicata all’agricoltura periurbana e al suo ruolo all’interno delle connessioni urbano-rurali e delle politiche locali del cibo. Prassi: La sezione analizza il caso francese, che si caratterizza per uno spiccato approccio territoriale alla soluzione dei problemi legati ai sistemi alimentari localizzati. In particolare, viene presentata la metodologia attraverso la quale è stato diffuso un questionario a circa 300 esperti francesi, riguardante le politiche alimentari urbane di 8 città. Nella sezione vengono presentati e discussi i risultati del questionario, al fine di delineare punti di forza e criticità di un approccio territoriale al cibo. Azioni: La terza sezione è di carattere propositivo-sperimentale. Si appoggia ai risultati e alle evidenze scaturite dalle prime due sezioni – impianto teorico per la sezione “Teorie” e analisi del fenomeno per la sezione “Prassi” – al fine di presentare una proposta per una politica del cibo e del paesaggio per la città di Roma Metropolitana. La proposta è il frutto di un lavoro di ricerca portato avanti anche grazie al supporto di un nutrito gruppo di stakeholder attualmente ingaggiati nel definire le priorità legate alla sostenibilità del sistema alimentare della Capitale
Formation and seasonal occurrence of xylem embolism in Alnus cordata.
Full text linkWe investigated the vulnerability of xylem to embolism and the seasonal occurrence of xylem embolism in Italian alder (Alnus cordata Loisel.) by acoustic and hydraulic methods. Wood anatomy was also studied. More than eighty percent of the vessels were less than 50 mm long and no vessels were longer than 120 mm. Mean vessel diameter was 48 μm. Ultrasound acoustic emissions from root and branch segments dehydrating in air followed a similar pattern: in both tissues, emission peaks were recorded when the relative water content of the xylem was around 0.2. In branches dehydrating in air, xylem embolism increased linearly as water potential decreased. In trees in the field, more than 80 percent of hydraulic conductivity was lost in the tree crowns during winter. Recovery from winter embolism occurred mostly before bud burst. In summer, xylem embolism was low (< 30%) and acoustic emissions from roots, stem and branches of trees in the field were also low
Response to light of shade-grown beech seedlings subjected to different watering regimes.
No full textThe morphological and physiological responses (net photosynthesis, stomatal conductance, leaf chlorophyll concentration and leaf orientation) of shade-grown beech seedlings after transfer to a high-light regime were studied in well-watered plants and in plants subjected to water stress. Immediately after exposure to high irradiance, shade-grown seedlings displayed a lower photosynthetic rate, a higher leaf chlorophyll concentration and a more horizontal leaf orientation than light-acclimated plants (control plants). The chlorophyll concentration of shade-grown plants gradually declined throughout the period of exposure to high irradiance reaching the amount observed in control plants. Rates of photosynthesis of shade-grown plants began to recover after 8 days of exposure to high irradiance and recovery was nearly complete after 30 days. Leaf orientation of shade-grown plants also changed rapidly during the first 8 days of exposure to high irradiance and by the end of the experiment, there were no significant differences between shade-grown and control plants. Water stress caused significant declines in net photosynthesis and leaf conductance in both shade-grown and control plants. Net photosynthesis did not recover completely in the shade-grown water-stressed plants during the 30-day exposure to high irradiance. Reversible leaf paraheliotropism and chlorophyll bleaching were observed in response to soil drying followed by rewatering
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Responses of the Populus x euramericana clone I-214 to excess zinc: Carbon assimilation, structural modifications, metal distribution and cellular localization
No full textPoplar (Populus), the model system in tree research, is a fast-growing and high biomass plant which is promising for energy, paper and pulp production, and for growth in soils contaminated with metals.
Contamination of soils and water with heavy metals has become a widespread problem; environmental pollution by excess zinc (Zn), one of the more important contaminants, occurs frequently and yet the responses of Populus to high Zn concentrations are still not clearly understood.
We investigated the effects of Zn on the functional and structural parameters in the Populus×euramericana clone I-214 by Zn localization in frozen-hydrated leaves and roots by cryo-scanning
electron microscopy (cryo-SEM)/energy-dispersive X-ray microanalysis (EDXMA). The experiment was conducted on cuttings grown in nutrient solutions with an increasing Zn concentration gradient (0.001–10 mM).
Biomass partitioning and Zn uptakewere affected by the metal treatments, showing organ- and tissuedependent responses. In particular, Zn accumulated in old leaves and moved from shoot to root as the Zn concentration in the growth medium increased. At the highest treatment concentration (10 mM), Zn was preferentially localized in photosynthetic tissues of shoots, and in epidermis and cortex tissues of roots. Gas exchange and chlorophyll measurements showed impairments in leaf biochemistry rather than in stomatal function. Modifications in foliage area, stomatal density and leaf layer thickness were
investigated to reduce and/or compensate the negative effects of excess Zn on CO2 assimilation.
To counteract Zn toxicity, clone I-214 adopted different defense/tolerance mechanisms involving complex structural, physiological and biochemical processes, attributed to both Zn excluders and accumulators.
This study demonstrates the advantages of combining cryo-SEM/EDXMA, gas exchange and chemical analyses for studying metal localization and structural as well as physiological responses in plants
- …
