Identita Transnazionali. Verifica di una proposta teorica dai risultati di una ricerca empirica

Nell’ambito degli studi sociali sulle migrazioni internazionali molteplici sono gli approcci che ne hanno provato a delineare le cause e le motivazioni. Negli ultimi venti anni sono emersi studi migratori che si collocano ad un livello intermedio fra teorie macro (strutturalismo) e micro (individualismo): fra questi studi si inserisce l’approccio Transnazionale, che identifica la figura del migrante come un attore sociale ricco di iniziativa e promotore di mutamenti economici, culturali e sociali. Pur avendo una ricezione contrastata, questa nuova prospettiva teorica ha assunto un forte carattere innovativo estendendo l’analisi a diversi aspetti della vita sociale ed indagando come l’appartenenza più o meno rilevante ad una comunità transnazionale incida fortemente sull’identità del migrante, sul suo capitale sociale ed in generale sulla rete migratoria formatasi tra la società ricevente e la comunità di partenza. Sono scaturiti così modelli teorici inerenti i processi di identificazione, fra cui una scala proposta dal sociologo Maurizio Ambrosini, che, partendo da un livello minimo di identificazione (assimilazione), culmina nella definizione di un transnazionalismo riflessivo, dove il migrante è pienamente consapevole della bifocalità sia nel senso di appartenenza che nelle pratiche effettive. In questo lavoro, dopo una riflessione generale relativa al fenomeno migratorio (cap. 1) ed una presentazione delle componenti dell’approccio Transnazionale allo studio delle migrazioni (cap. 2), si approfondiscono le risultanze dell’indagine condotta nel 2008 sugli studenti stranieri iscritti ai corsi dell’Università di Pisa per incrociarle con la scala teorica proposta da Ambrosini (cap. 3 e conclusioni): l’obiettivo è quello di verificare l’effettiva valenza pratica delle forme di transnazionalismo proposte. Il risultato dimostra come i risultati dell’analisi empirica sugli studenti stranieri si possano calare nella scala di misurazione dei processi di identificazione di Ambrosini che assume quindi anche un’effettiva valenza pratica negli studi sociali delle migrazioni

Il progetto RHEA: robot autonomi per la difesa mirata delle colture agrarie.

Questo volume riporta gli atti della Giornata Studio dell’Accademia dei Georgofili “Il Progetto RHEA: risultati e acquisizioni” che ha avuto luogo il 18 Luglio 2014 presso il centro “Enrico Avanzi” dell’Università di Pisa che sono stati suddivisi in tre capitoli (2, 3 e 4), cui è stata aggiunto il primo capitolo che prende in considerazione lo stato dell’arte, le tecnologie disponibili e le applicazioni inerenti l’agricoltura di precisio- ne. Questa integrazione è apparsa necessaria tenendo in considerazione la natura prettamente divulgativa di quest’opera in modo da fornire a tutti i lettori, ivi com- presi quelli completamente neofiti o non molto informati sugli argomenti inerenti l’agricoltura di precisione, la possibilità di apprenderne le nozioni di base, necessarie per poter comprendere al meglio i risultati e le acquisizioni conseguiti nel progetto di Ricerca RHEA (“Robot Fleets for Higly Effective Agriculture and Forestry Mana- gement”) finanziato dall’UE nell’ambito di una call del Settimo Programma Quadro riservata a ricerche sull’utilizzo e sulle applicazioni delle nanotecnologie in agricol- tura, che è iniziato il 1 Agosto 2010 e terminato il 31 Luglio 2014

Genetic differentiation among populations of the threatened Bellevalia webbiana (Asparagaceae) and its consequence on conservation

The narrow central Italian endemic and threatened Webb's hyacinth (Bellevalia webbiana), a perennial herb, is a clear example of a species that has disappeared from several localities due to the de..

Use of a remote eye-tracker for the analysis of gaze during treadmill walking and visual stimuli exposition

The knowledge of the visual strategies adopted while walking in cognitively engaging environments is extremely valuable. Analyzing gaze when a treadmill and a virtual reality environment are used as motor rehabilitation tools is therefore critical. Being completely unobtrusive, remote eye-trackers are the most appropriate way to measure the point of gaze. Still, the point of gaze measurements are affected by experimental conditions such as head range of motion and visual stimuli. This study assesses the usability limits and measurement reliability of a remote eye-tracker during treadmill walking while visual stimuli are projected. During treadmill walking, the head remained within the remote eye-tracker workspace. Generally, the quality of the point of gaze measurements declined as the distance from the remote eye-tracker increased and data loss occurred for large gaze angles. The stimulus location (a dot-target) did not influence the point of gaze accuracy, precision, and trackability during both standing and walking. Similar results were obtained when the dot-target was replaced by a static or moving 2D target and "region of interest" analysis was applied. These findings foster the feasibility of the use of a remote eye-tracker for the analysis of gaze during treadmill walking in virtual reality environments

Cross-flaming application for intra-row weed control in maize

Flame weeding is the most common thermal intra-row weed control method used in agriculture as an alternative to herbicides in heat-tolerant crops. Within the seventh framework program project “Robot fleets for Highly Effective Agriculture and Forestry Management” (RHEA), the University of Pisa was responsible for the development of an automatic machine for intra-row cross-flaming in maize (Zea mays L.). This study focused on the selection of a range of liquid petroleum gas (LPG) doses able to control weeds without affecting crop yields, for the basic calibration of the machine. Tests were conducted in 2012 and 2013 during the growing cycle of maize both in weed-free and real-field weedy conditions. Five biological LPG doses (0, 52, 65, 104, and 130 kg ha-1) were applied at different maize growth stages once (2- and 5-leaf) and twice (2-leaf the first time and 16 days after the first time). The response of maize and weeds to cross-flaming was evaluated in terms of grain yield, weed density after flame weeding, and weed dry biomass at harvest. Log-logistic models were used to describe the responses of different growth stages of maize and weeds to single and repeated applications of LPG doses. Overall response of maize yield to flame weeding was influenced by LPG dose, number of flame weedings, maize growth stage, and presence of weeds. The results of this study indicate that two cross-flaming treatments applied separately with an LPG dose ranging from 36 to 42 kg ha-1 can provide an acceptable level of weed control in maize, enough to ensure economically acceptable yields

Mechanical weed control on small-size dry bean and its response to cross-flaming

Dry bean (Phaseolus vulgaris L.) can be a profitable crop for farmers; however controlling weeds effectively without a decrease in yield remains a problem. An example where mechanical weed control is difficult to conduct is dry bean ‘Toscanello’, which is a small sized high-income niche product growing low to the ground. Concerning intra-row weed control, also flame weeding could be an opportunity but the dry bean heat tolerance needs to be studied. The aims of this research were to study the weed control efficacy of a spring-tine harrow and an inter-row cultivator in this bean variety, and to test the tolerance of dry bean cultivated under weed-free conditions to cross-flaming applied with different liquefied petroleum gas (LPG) doses. Flame weeding was applied at BBCH 13 and BBCH 14 bean growth stages by pairs of burners producing direct double flame acting into the intra-row space, with bean plants placed in the middle. The results suggest that the spring-tine harrow used two times at BBCH 13 and 14, respectively, lead to a yield similar to that of the weedy control. The inter-row cultivator could be an opportunity for small-sized dry bean crops producers, enabling them to obtain a similar yield compared to the hand-weeded control. Concerning the bean tolerance to cross-flaming the results showed that bean flamed at BBCH 13 stage had little tolerance to cross-flaming. Bean flamed at BBCH 14 stage was tolerant until an LPG dose of 39 kg/ha, giving yield responses similar to those observed in the non-flamed control

Physical weed control in urban hard surfaces and turfgrasses.

Weed management is a major issue not only in agriculture but also in cities and in public and sport turfs. Weed development often generates negative aesthetic effects, a sense sloppiness, mechanical damages to hard surfaces, the reduction of visibility for drivers, the reduction of the quality of the quality of the turf, and can make difficult for pedestrians to walk. Specific trials were carried out in order to develop and set up machines and techniques for weed control in urban and sub-urban areas and on turfs

Application of precision flaming to maize and garlic in the RHEA Project.

Flame weeding is actually a well known and used physical treatment according to the increase in concerns about the effects of herbicides on human health and the environment and in the light of the new European laws. Flaming historically, was used at first as a pre-emergence treatment, both prior to planting and before crop emergence. Alternatively, flaming can be used also selectively after crop emergence or planting in tolerant species. Although inter-row weeds can be effectively controlled through mechanical cultivation, weeds that grow in the row are more difficult to control as, in some cases, cultivation is both ineffective and causes unacceptable levels of crop damage. This work aims to describe the specific machine for mechanical-thermal weed control which is being realized by the University of Pisa within the RHEA project. This machine is able to perform mechanical and thermal treatments at the same time in order to remove weeds mechanically from the inter-row space and perform in-row selective and precision flaming. The project is still on-going and the machine has not been fully realized and tested yet, thus no data is available at the moment

LPG burners for weed control

This article reports on the results of a study carried out on three prototypes of open flame burners for thermal weed control. Their performance is reported in terms of flame temperature and length, in order to ascertain the best ratio between primary and secondary air, and liquefied petroleum gas (LPG) consumption. To find the best ratio between primary and secondary air, the length and temperature of the flame were recorded for each of the three burners, examined by varying the inlet sections of the primary air and secondary air. The data on temperature and the flame length of each burner were processed using multiple regression analysis. The LPG consumption was determined with one of the burners using 10 different pressures in combination with three nozzles. The data obtained were subjected to non-linear regression using two gaseous outflow models. The various combinations of primary and secondary air inlet sections affected the values of the flame length and temperature. In general, the best combinations of primary and secondary air inlet for flame temperature did not correspond to those for flame length. However, this experiment showed that the inlet of secondary air is critical for the performance of this type of burner, in terms of flame temperature. The fuel consumption trial showed that the model proposed for the gaseous outflow is suitable for describing the values of LPG consumption collected during the trial. © 2015 American Society of Agricultural and Biological Engineers

Development of machines for flaming weed control on hard surfaces

Weed control is a major issue not only in agriculture but also on hard surfaces in urban and suburban contexts. Weeds can cause serious damage to urban structures and are often considered as a sign of neglect. Moreover, citizens are becoming increasingly aware of environmental pollution and its potential risks for their health. Flaming represents a concrete alternative to herbicide applications on hard urban surfaces. Flaming can also be a good alternative to mechanical means (e.g., string trimmers) which can seriously damage surfaces because they are too intense and in any case are often not effective. The aim of this work is to describe LPG fed flaming machines designed and built at the University of Pisa, Italy. Liquefied Petroleum Gas (LPG) is a flammable mixture of hydrocarbon gases– propane and butane. Four different machines were developed and tested in four different urban and sub-urban contexts. A small backpack flamer equipped with a manual lance was tested on a stonewall, a trolley machine with a manual lance was used to clean the base of ornamental trees, a self-propelled machine was tested in a railway station, and a mounted machine was used in a suburban cycle way. Flaming was compared to the ordinary weed control systems such as using herbicides or mowing. The results showed that flaming can be both less expensive and more effective (on average less that 1 € m-2 year-1 maintaining weed cover below 5% to 6%) than the ordinary treatments in urban areas. Flaming was more effective than mowing in the suburban area but much more expensive, thus an integrated approach would be advisable in this context. Future research should be devoted to improving the efficiency of the treatment, using for example, new burners with secondary air and precision agriculture technologies