Carbon dioxide concentration in Mediterranean greenhouses : how much lost production?

In the absence of artificial supply of carbon dioxide in the greenhouse environment, the CO2 absorbed in the process of photosynthesis must ultimately come from the external ambient through the ventilation openings. This requires that the CO2 concentration within the house must be lower than the external concentration, as there would be no flow inwards otherwise. Since potential assimilation (that is, the assimilation level that can be attained when no other factor is limiting) is heavily dependent on carbon dioxide concentration, this implies that assimilation is reduced, whatever the light level or crop status. The ventilation of the greenhouse implies a trade-off between ensuring inflow of carbon dioxide and maintaining an adequate temperature within the house, particularly during sunny, chilly days. We apply a simple model, on which the Dutch ¿philosophy¿ of CO2 fertilisation is based, for estimating the potential production loss, through data measured in commercial greenhouses in Almeria and Sicily. Thereafter we discuss the management options for a grower to limit losses. In particular we analyse costs, potential benefits and consequences of bringing in more carbon dioxide either through increased ventilation, at the cost of lowering temperature, or through artificial supply. We find out that, whereas the reduction in production caused by depletion is comparable to the reduction resulting from the lower temperature caused by ventilation to avoid depletion, compensating the effect of depletion is much cheaper than making up the loss by heating

The combined effects of cover design parameters on tomato production of a passive greenhouse

The objective of this paper is to demonstrate the need of a multiple design parameter approach to greenhouse design. To illustrate this need, we determined the combined effects of cover design parameters on tomato production of a passive greenhouse, that is a greenhouse with only natural ventilation and seasonal whitewash for climate management. The design parameters investigated in this research were the transmission of the cover for photosynthetically active radiation (PAR) and near infrared (NIR) radiation, the emission coefficient for long wave radiation of the cover and the ventilation area. First, we developed a model to link the tomato yield to the cover design parameters, through their effects on greenhouse climate. The model was validated by comparing the simulated greenhouse climate and yield with data obtained from field studies conducted in Almería, Spain. Thereafter, the sensitivity of the yield to the cover design parameters was analysed for three greenhouse configurations. This analysis gave insight into the effects of the cover design parameters on crop yield. Results showed that the sensitivity of the yield to a single design parameter depended on the absolute values of the other ones. For example, the yield in a greenhouse with a high ventilation capacity was the most sensitive to PAR transmission (0.45 % more yield for each 1% increase of PAR transmission) while in a greenhouse with a low ventilation capacity the crop yield is most sensitive to the ventilation area (0.63 %) and NIR transmission (-0.56 %). In addition, the yield sensitivity to the design parameters also varied over time because of changing outdoor climate conditions. In conclusion, a significant improvement of greenhouse design can be attained only through a multifactorial approach that accounts for the joint effect of design parameters, local climate and desired production period upon crop yield

Direct Marketing: Theoretical delimitation and impact on consumer buying behavior

Direct marketing has become one of the most important communication tools for marketers. Direct marketing activities' budget is even higher than that for traditional advertising mass media, such as TV. However, there is not a single definition. On the contrary, several definitions have emerged in the literature. In this work, we establish a theoretical delimitation for direct marketing concept from those different perspectives analysed in marketing literature. In addition, an empirical analysis is presented in order to know if (really) direct marketing activities affect consumer buying behavior. From the results, key managerial implications are extracted in order to improve and optimise marketers' communicational budget

La gradazione dei cristalli di gesso nella Cuevade las Espadas (Naica, Messico): un classico esempio di controllo della sovrasaturazione sui processi di nucleazioneJosè Marìa Calaforra, Paolo Forti, Fernando Gazquez, Laura Sanna

All’interno della Miniera di Naica (Chihuahua, Messico), la parte più interna e profonda della Cueva de las Espadas ospita una sequenza verticale di oltre 5 metri di cristalli di gesso, precipitati sulle pareti della galleria ad opera di fluidi ipogenici risalenti dalla profondità, le cui dimensioni risultano essere perfettamente gradate in modo diretto. Le analisi morfologiche, tessiturali e mineralogiche di questi cristalli, assieme ai dati relativi agli studi geochimici sulle inclusioni fluide in essi presenti, hanno permesso di dimostrare che il processo di gradazione dimensionale è stato controllato dall’oscillazione della falda freatica proprio in corrispondenza del livello di sviluppo della grotta e in un periodo di tempo compreso nell’arco degli ultimi 15.000 anni. Tale oscillazione, oltre ad aver permesso a parte della cavità di emergere a più riprese dalle acque termali, favorì l’instaurarsi di un’alternanza di fenomeni di evaporazione, che coinvolsero relativamente piccoli volumi di acqua a livello del “lago terminale”. A essi fecero seguito brevi periodi in cui le acque profonde risalenti riallagarono quasi totalmente quest’area. In questo contesto la sovrasaturazione risultò essere massima a livello dell’interfaccia acqua-aria e progressivamente registrò un calo verso le parti inferiori dove invece fu minima, limitando così la probabilità di nuova nucleazione e creando il gradiente osservato con una distribuzione continua di grossi individui nelle parti basse della parete che sfumano gradualmente verso l’alto in una densa concentrazione di cristalli più piccoli.In the Naica Mine (Chihuahua, Mexico), the deepest area of the Cueva de las Espadas hosts a 5 m high sequence of gypsum crystals. These crystals were deposited by hypogene uplifting fluids and their dimensions progressively decrease from the floor to the ceiling of the cave. The morphological, textural and mineralogical analyses of these crystals, together with the geochemical data on the fluid inclusions made possible to demonstrate that the dimensional gradation of these crystals was controlled by the swinging of the groundwater just at the level of the cavity and the development of these crystals occurred in the last 15,000 years. The swinging of the groundwater dried up the upper part of the Cueva de las Espadas several times thus inducing the evaporation of relatively small volumes of water confined in “terminal lake” just the deepest part of the cave. These periods were followed by short floods which brought the water practically to refill the whole cavity. The processes induced the supersaturation to be the highest at the air-water boundary and to lower progressively toward the bottom of the lake where it resulted the lowest thus hindering the probability of new nucleation. The result was that the biggest crystals developed on the lake’s bottom while the size of the crystals progressively lowered toward the ceiling

Guest Editorial. Service-mix: new channels and consumption patterns in services

The world’s economies are dominated by services. The average value added in the services sector as percentage of GDP was 55.43% in 2021 (TheGlobalEconomy.com, 2022). In the most advanced economies, services account for an even larger share of their GDP - 75% on average (Nayyar et al., 2021). In addition to its economic relevance, a vital services sector is also increasingly important for the competitiveness of agriculture and manufacturing, as the intertwin of the product-service bundle highly enhances value for customers. Actually, manufacturers have transformed themselves in service or solution providers (Gebauer et al., 2011). The acknowledgement that services are transversal to all business sectors (Gustafsson et al., 2016) has been furthered by the recognition that today all businesses in any sector compete on service, therefore, “it makes little sense to treat service as a special case; all businesses are essentially service businesses” (Gustafsson and Kristensson, 2020, p. 609), regardless of country and context (Gustafsson and Bowen, 2017)

18. Le fonds indochinois de la Bibliothèque nationale de France

Fonds régional particulier, le fonds indochinois est un fonds clos regroupant des documents en vietnamien romanisé (quôc ngu) édités dans l’Indochine coloniale entre 1922 et 1954 et entrés par dépôt légal. Il fait partie des nombreux fonds concernant le Vietnam colonial présent dans les différents départements. Il faut souligner l’importance de ces fonds : du fait de la colonisation, la France possède la plus importante documentation existant au monde sur le Vietnam colonial. Dans la document..