Helve'tweet: exploration d'un million de tweets géolocalisés en Suisse, février-août 2017

Réseau social utilisé activement par 8% de la population suisse, Twitter permet à ses utilisateurs de géolocaliser leurs messages. Cette étude exploratoire quantitative, basée sur des messages géolocalisés en Suisse écrits entre le 18 février et le 31 août 2017, fait suite au projet GEoTweet consacré aux tweets genevois en 2014-2015. Elle se propose de répondre à trois questions de recherche pour évaluer les possibilités et les limites de l’utilisation des données fournies par l’API de Twitter lors des recherches sur la Suisse, dans les domaines de la sociologie des données et des sciences de l’information. Le focus est porté plus spécifiquement sur l’exploitation des données de géolocalisation, sur la problématique de l’identification des langues et sur les critères définissant un tweet suisse dans une perspective d’archivage. Après l’introduction et la revue de littérature, le rapport présente la méthodologie utilisée, les biais identifiés et les outils créés pour les mesurer, les éviter ou du moins les minimiser. Une concordance a ainsi été créée entre les place.id de Twitter et la liste officielle des communes suisses pour pallier au caractère non vérifié (en partie obsolètes, en partie erronées) des données géographiques fournies par Twitter. Trois séries de tests ont également été menés pour vérifier la fiabilité de l’algorithme de reconnaissance de langue de Twitter pour l’échantillon. Ils montrent une marge d’erreur de 4,25% sur les grandes langues européennes, mais qui peut monter jusqu’à 92% pour une langue « exotique » comme l’indonésien. Les analyses des tweets et des twittos ont permis de dégager des résultats importants. D’une part, elles montrent les fortes variations de leur nombre et de leur diversité linguistique à travers l’espace et le temps (p.ex. plus de comptes actifs en Suisse alémanique, mais plus de tweets en français dans l’ensemble ; plus de tweets pendant les périodes de vacances, mais baisse de la proportion des tweets et des twittos en langues nationales et en anglais). D’autre part la durée et l’étendue géographique de leur activité sont très variables (p.ex. 82% des comptes avec moins de 10 tweets, 68% actifs pendant un seul mois et 71% dans un seul canton). Des hypothèses ont été formulées et vérifiées pour expliquer ces résultats qui relèvent de la propension élevée des germanophones à twitter en anglais et de l’effet positif des loisirs sur l’envie et l’opportunité de twitter avec géolocalisation. Dans la dernière partie, l’étude propose des pistes afin d’établir des critères pour reconnaître un tweet suisse, en se basant sur les analyses menées préalablement ainsi que sur les expériences menées dans d’autres pays du monde. Le contexte international et suisse de l’archivage des tweets est abordé, sans prétention de vouloir proposer une méthode, au vu de la complexité des enjeux sociologiques, techniques et légaux

Development of an olive phenological model in relation to air temperature

The effect of air temperature on olive phenological development has not been extensively studied. Indirectly related data are available, mostly from air pollen concentration measurements rather than direct observation of phenological stages. Data on phenological stages of olive collected in Sicily, by the Sicilian Agrometeorological Service (SIAS), in 10 locations characterized by different climatic conditions were used to develop and calibrate a phenological model for the most important developmental stages in olive. Phenological stages under study were: bud break, inflorescence emission, and full bloom A base-temperature linear model was developed by choosing a temperature threshold using as optimization criteria the Mean Bias Error (MBE) and the R2 of the relationship between observed vs. predicted phenological stage dates. A model with base temperature of 12\ub0C was found to be the best predictor for all initial phenological stages. A more detailed analysis within each single phase showed a decreasing performance compared to predictions performed on the whole period (January 1st to full bloom). Highest displacements of model predictions from observed values occurred starting from bloom, whereas bud-break predictions had the best fit, with lowest residuals. This difference in the predicting ability of the model in different phenological stages could be ascribed to the stronger limitations by low temperatures that can occur early in the season, as for bud-break stage

Influence of Culture Conditions on In Vitro Asymbiotic Germination of Anacamptis longicornu and Ophrys panormitana (Orchidaceae)

This study is the first approach to in vitro asymbiotic germination of two species of Sicilian threatened terrestrial orchids, Anacamptis longicornu and Ophrys panormitana. Seeds were collected in the wild and cultured in two different media—Orchimax medium (OM) and Murashige and Skoog (MS)—and exposed to different photoperiods and temperatures to evaluate the best conditions for the specific stages of development. The germination of A. longicornu was very high on OM (95.5%) and lower on MS medium (21.4%), whereas O. panormitana germinated only on OM medium, with significantly lower percentages (12.0%), compared with A. longicornu. This difference is caused by variation in quality and quantity of nutrients used, primarily by nitrogen source. The results show that temperature and photoperiod widely affect seed germination and development. Although further investigations on asymbiotic and symbiotic germination are needed for the improvement of conservation of Mediterranean terrestrial orchids, our results contribute to the conservation of this group of plants

Valoriser, optimiser, autonomiser: information literacy dans la formation du Bachelor en Travail social de la HES-SO

L’étude, mandatée par la filière Travail social de la Haute école de Travail social de Genève, a eu deux objectifs principaux : d’abord réfléchir sur la place de l’information literacy dans la formation de bachelor en Travail social de la Haute école spécialisée de Suisse occidentale (HES-SO) ; ensuite avancer des pistes de solutions pour la valorisation de l’IL et pour l’optimisation de son enseignement. Pour ce faire, elle a proposé une revue de la littérature, une enquête qualitative auprès des parties prenantes de la formation, ainsi que l’analyse comparative du référentiel de compétences et du concept pédagogique du PEC 2006 avec deux référentiels métiers du TS, deux référentiels de compétences informationnelles de l’enseignement supérieur et de six plans d’études BATS suisses, français et candiens. Les résultats de l’étude ont démontré l’importance de l’information literacy pour la pratique et pour la formation du Travail social. Le rôle des professionnel-le-s du Travail social en tant que facilitatrices de l’accès à l’information qui les confronte à la problématique de l’inégalité devant l’information a particulièrement été mis en lumière. Des enjeux informationnels actuels du Travail social qui nécessitent l’acquisition de nouvelles compétences ou la mobilisation des compétences « classiques » à un niveau d’expertise élevé ont également été identifiés. L’étude a confirmé l’importance de visibiliser la transversalité des compétences informationnelles à la fois dans le référentiel de compétences et dans la structure des études. Bien que les compétences informationnelles figurent en grand nombre dans le PEC 2006 et que leur formation soit en partie assurée, une optimisation de leur présentation dans une vision holistique est donc souhaitable. L’étude a abouti à la proposition d’un modèle de référentiel de compétences, d’un modèle de formations et d’un modèle de référentiel de formation. Après des analyses coûts/bénéfices et SWOT de l’élaboration d’une réforme conjointe du référentiel et de la formation jusqu’à sa formalisation officielle, elle présente un calendrier priorisé à court, à moyen et à long terme des recommandations concrètes pour le domaine Travail social de la HES-SO

Potassium deficiency and drought stress in grapevine cultivars

Potassium availability affects drought responses in plants through several metabolic roles, among which stomatal regulation, cell growth and xylem hydraulics. Vitis vinifera L. is a highly valuable crop and several genotypes have been selected during its millennial cultivation. Varieties show differences in their adaptability to stress conditions, making them more or less suitable to certain climatic and edaphic conditions. The varieties cultivated in Sicily are characterized by high variability. We investigated the response of two Sicilian cultivars (Nero d'Avola and Catarratto) to potassium deficiency and drought stress. Two-year-old grafted plants were grown in agriperlite, with or without potassium in the fertigation solution, and subjected to moderate drought stress by suspending irrigation for 6-8 days. Potassium content of xylem sap, leaf and root tissues were measured with an ion-selective electrode. Changes in stomatal conductance, plant transpiration and hydraulic conductance were compared between genotypes and treatments, in order to gain information for the development of optimal fertigation practices and the selection of the most drought tolerant varieties

Machine learning models to predict daily actual evapotranspiration of citrus orchards under regulated deficit irrigation

Precise estimations of actual evapotranspiration (ETa) are essential for various environmental issues, including those related to agricultural ecosystem sustainability and water management. Indeed, the increasing demands of agricultural production, coupled with increasingly frequent drought events in many parts of the world, necessitate a more careful evaluation of crop water requirements. Artificial Intelligence-based models represent a promising alternative to the most common measurement techniques, e.g. using expensive Eddy Covariance (EC) towers. In this context, the main challenges are choosing the best possible model and selecting the most representative features. The objective of this research is to evaluate two different machine learning algorithms, namely Multi-Layer Perceptron (MLP) and Random Forest (RF), to predict daily actual evapotranspiration (ETa) in a citrus orchard typical of the Mediterranean ecosystem using different feature combinations. With many features available coming from various infield sensors, a thorough analysis was performed to measure feature importance, scatter matrix observations, and Pearson's correlation coefficient calculation, which resulted in the selection of 12 promising feature combinations. The models were calibrated under regulated deficit irrigation (RDI) conditions to estimate ETa and save irrigation water. On average up to 38.5% water savings were obtained, compared to full irrigation. Moreover, among the different input variables adopted, the soil water content (SWC) feature appears to have a prominent role in the prediction of ETa. Indeed, the presented results show that by choosing the appropriate input features, the accuracy of the proposed machine learning models remains acceptable even when the number of features is reduced to only 4. The best performance was achieved by the Random Forest method, with seven input features, obtaining a root mean square error (RMSE) and a coefficient of determination (R2) of 0.39 mm/day and 0.84, respectively. Finally, the results show that the joint use of SWC, weather and satellite data significantly improves the performance of evapotranspiration forecasts compared to models using only meteorological variables

MICROMETEOROLOGICAL AND SAP FLOW MEASUREMENT OF WATER VAPOUR EXCHANGES IN OLIVE: SCALING UP FROM CANOPY TO ORCHARD

A comparison of water consumption evaluated at tree and orchard level was carried out in a commercial olive orchard located in Sicily using up-scaled sap-flow evapotranspiration estimations and eddy covariance measurements. Sap flow probes were installed on olive trees placed in one of the four plots characterizing a heterogeneous orchard. Trees were chosen, from a preliminary footprint analysis, in correspondence to the peak of the “relative normalized contribution” to flux for the prevailing wind conditions measured by an eddy covariance station localized in the central part of the orchard. Tree-age and planting density as well as main tree and orchard characteristics (Leaf Area per tree, within plot distribution of Trunk Cross Sectional Area TCSA, height and canopy diameter), were used to characterize the plot-to-plot differences. Both TCSA and LAI adopted as scaling parameters showed a high performance. A good agreement between ETec (daily integral of EC-estimated evapotranspiration) and ETsf (up-scale sap flow ET estimate) was found in correspondence of limited canopy or soil evaporation conditions (absence of rain, dew, irrigation supply). Eddy covariance can be considered a reliable reference for up-scaled sap flow estimations of ET, and sap flow can be used as a replacement (proxy) of eddy covariance when atmospheric conditions invalidate the application of this technique to assess ET

Autotetraploid Emergence via Somatic Embryogenesis in Vitis vinifera Induces Marked Morphological Changes in Shoots, Mature Leaves, and Stomata

Polyploidy plays an important role in plant adaptation to biotic and abiotic stresses. Alterations of the ploidy in grapevine plants regenerated via somatic embryogenesis (SE) may provide a source of genetic variability useful for the improvement of agronomic characteristics of crops. In the grapevine, the SE induction process may cause ploidy changes without alterations in DNA profile. In the present research, tetraploid plants were observed for 9.3% of 'Frappato' grapevine somatic embryos regenerated in medium supplemented with the growth regulators β-naphthoxyacetic acid (10 µM) and N6-benzylaminopurine (4.4 µM). Autotetraploid plants regenerated via SE without detectable changes in the DNA profiles were transferred in field conditions to analyze the effect of polyploidization. Different ploidy levels induced several anatomical and morphological changes of the shoots and mature leaves. Alterations have been also observed in stomata. The length and width of stomata of tetraploid leaves were 39.9 and 18.6% higher than diploids, respectively. The chloroplast number per guard cell pair was higher (5.2%) in tetraploid leaves. On the contrary, the stomatal index was markedly decreased (12%) in tetraploid leaves. The observed morphological alterations might be useful traits for breeding of grapevine varieties in a changing environment

Eddy covariance and sap flow measurement of energy and mass exchanges of woody crops in a Mediterranean environment

Evapotranspiration estimation by micrometeorological techniques through the assessment of mass and energy exchanges in the soil-plant-atmosphere continuum (SPAC) is a very active research area, involving both well-known and novel measurement techniques. A crucial aspect in validating experimental results is the integration of independent measurements of mass and energy exchanges in the SPAC. To this aim, the development and validation of an integrated approach in major tree crop species, involving different independent techniques, are presented. Eddy covariance estimates of ET fluxes were compared to up-scaled sap flow measurements in olive, orange and grapevine, three important Mediterranean tree crop species with contrasting ecophysiological characteristics and responses to water deficits. These differences can affect directly the degree of coupling of the tree to the environment and, consequently, the degree of correspondence between instantaneous transpirational flux at tree level and the micrometeorological measurement of ET at orchard level. Data were analyzed to verify to what extent, in the three species, transpirational flow at orchard level is regulated by tree conductance, capacitance effects related to tree size or by environmental demand. Hourly observations were helpful in detecting physiological processes of the three species only when data were analyzed taking into consideration their diurnal changes

Somatic embryogenesis and flow cytometric assessment of nuclear genetic stability for Sansevieria spp.: an approach for in vitro regeneration of ornamental plants

Sansevieria Thunb. species are traditionally known as succulent ornamental plants world- wide. They are also cultivated for medicinal, fodder, soil conservation and fiber uses, and for their capacity to reduce environmental pollution. Sansevieria sexual propagation is limited by the lack of viable seeds, and reproduction is largely made via vegetative propagation by suckers or cuttings. For these reasons, genetic improvement by conventional breeding is limited. To overcome this problem and to address the increasing demand from customers for novel Sansevieria varieties, many commercial companies regularly use in vitro propagation, as is the case in the breeding process of several ornamental plants. In this paper, for the first time, we report a procedure for in vitro somatic embryogenesis and plant regeneration starting from three flower explants for seven different Sansevieria genotypes. Regeneration was attempted using stigmas/styles, anther/filament, and ovary which were cultured on a Murashige and Skoog solidified medium under three different plant growth regulator combinations. A good regeneration rate was obtained with all genotypes used under all culture conditions tested from every explant type, with percentages ranging from 0 to 73.3%. “Genetic stability” assessment of regenerated plants in respect to their mother plants was verified through flow cytometry analysis showing a high degree of uniformity, with only S. parva exhibiting a different level of DNA fluorescence among in vitro regenerated plants. This is an interesting achievement in the aim to produce true-to-type plants and new variants with desirable characteristics, both of which are desired features in ornamentals improvement