1,721,260 research outputs found
High temperature control in mediterranean greenhouse production: The constraints and the options
No full textWater management through indicators of water costs, price and value: an agro-hydrological modeling framework
No full textWhat limits the application of wastewater and/or closed cycle in horticulture?
No full textWe determine the ¿optimal¿ management of a closed growing system with multiple sources of water, of price decreasing with quality. The management that balances marginal costs of water and fertilizers with marginal yield loss is determined. By using a number of yield response curves, in a couple of different cases (Holland and Mediterranean basin), we show that, with realistic prices both of resources and of produce, closed systems are financially viable only in two cases: 1. in regions with good water or 2. with high-value crops that offset the costs of ensuring good water (such as rain collection or desalinisation), so that there is no advantage for a grower to maintain a closed loop whenever the quality of irrigation water is poor. This means that a price structure of water resources that shifts the economic optimum towards poorer irrigation water has the consequence that the irrigation loop cannot be closed. In other words, there is no way that low-value crops using poor irrigation water may still be profitable under stricter environmental rules. We conclude that in view of the environmental impact, it would be advisable for irrigation and local authorities in horticultural areas either to provide good water at a relatively high price or to consider subsidizing investment costs of on-site desalinization plants, rather than stimulating use of poor quality water, or attempting to prevent pollution through unrealistic regulations. This means that local authorities, seriously planning to reduce agricultural pollution, should either provide incentives for growers to switch to less sensitive or more valuable combinations of crops, or contemplate developing other economic activities than agriculture
The γ-ray emission region in the Fanaroff-Riley II radio galaxy 3C111
No full textThe broad-line radio galaxy 3C111, characterized by a Fanaroff-Riley II (FRII) radio morphology, is one of the sources of the misaligned active galactic nucleus sample, consisting of radio galaxies and steep spectrum radio quasars, recently detected by the Fermi Large Area Telescope (LAT). Our analysis of the 24 month γ-ray light curve shows that 3C111 was only occasionally detected at high energies. It was bright at the end of 2008 and faint, below the Fermi-LAT sensitivity threshold, for the rest of the time. A multifrequency campaign of 3C111, ongoing in the same period, revealed an increase of the millimeter, optical, and X-ray fluxes in 2008 September-November, interpreted by Chatterjee etal. as due to the passage of a superluminal knot through the jet core. The temporal coincidence of the millimeter-optical-X-ray outburst with the GeV activity suggests a cospatiality of the events, allowing, for the first time, the localization of the γ-ray dissipative zone in an FRII jet. We argue that the GeV photons of 3C111 are produced in a compact region confined within 0.1 pc and at a distance of about 0.3 pc from the black hole. © 2012. The American Astronomical Society. All rights reserved.
Water shortage sensing through infrared canopy temperature: timely detection is imperative
No full textThree versions of the crop water stress index (CWSI) have been tested: the theoretical approach reported by Jackson et al. (1981), its modification proposed by Clawson et al. (1989) and an original development which takes into account the actual value of the canopy resistance of a well-watered crop. All three have been considered in order to evaluate their suitability to field detection of water stress of sweet pepper plants. Water shortage detection was not fully satisfying in any case; CWSI values were strongly influenced by the rapid adaptation of plants to water shortage
Status report of the project ‘EVN observations of radio sources used for geodetic EUROPE experiments’
No full textWater use efficiency of tomatoes - in greenhouses and hydroponics
No full textMassive amounts of water are required for the production of our food, varying from several cubic metres per kilogram of beef to as low as 4 litres per kilogram for tomatoes grown in high-tech glasshouses. This article presents data on Product Water Use (PWU) of some foods and discusses how the water requirement for fresh tomatoes can be brought down from 300 to 4 litres/kg
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
- …
