De samenstelling van de zouten in het oppervlaktewater in het Zuidhollands glasdistrict

Aan de kwaliteit van het water dat in kassen voor de besproeiing van gewassen wordt gebruikt, dienen hoge eisen te worden gesteld. Zo is bij voorbeeld het gebruik van sproeiwater dat verontreinigd is met pathogène organismen, uit hygiënisch oogpunt niet toelaatbaar. Voorts kan verontreiniging met anorganische verbindingen nadelig zijn en wel vanwege een remmende invloed op de plantegroei of vanwege vervuiling van gewassen en kasopstanden. Bepaalde anorganische stoffen, zoals ijzer, kunnen reeds in lage concentratie - enkele milligrammen per liter - het water ongeschikt maken als sproeiwater

Zout gietwater bij kasteelten in West - Nederland

De glastuinbouwbedrijven in West-Nederland hebben van een hoog zoutgehalte van de grond herhaaldelijk veel nadeel ondervonden. Een dertig jaar geleden had hier de verzouting van de kasgronden de volgende oorzaken: zout gietwater; opstijgend grondwater; onoordeelkundig bemesten. Het zoutgehalte van het gietwater vormt ook thans nog een probleem

Osmotic pressure of the soil solution: determination and effects on some glasshouse crops.

In a factorial experiment, calcium sulphate, sodium chloride and potassium nitrate were added to a loamy sand soil in various quantities. The experiment was carried out in an unheated glasshouse. The salt status of the soil was determined with the aid of different method of aqueous extraction. The results were correlated with the osmotic pressure of the soil solution. A close correlation was obtained with the conductivity of the saturation extract. Crop yields were correlated with the conductivity of the saturation extract and with the osmotic pressure of the plant sap. The correlation with the conductivity of the saturation extract was generally highest. With tomatoes, a clear relationship was found between the conductivity and the incidence of blotch on the fruits. In lettuce, there was a clear relationship between conductivity and the occurrence of tipburn. The yield reduction of some crops was significantly greater after the application of sodium chloride than after potassium nitrate. Apparently, this was caused by specific ion effects. The desirable salt level, the salt distribution in the soil and the determination of the osmotic pressure of the soil solution for routine soil-testing purposes are discussed. The curvilinear relationship between the salt level of the soil and the incidence of tipburn may be explained by the calcium uptake of the crop. (Abstract retrieved from CAB Abstracts by CABI’s permission

Rheological Behavior of a Dispersion of Small Lipid Bilayer Vesicles

Rheological behavior of a dispersion of small nearly-unilamellar phospholipid bilayer vesicles has been investigated. We conducted steady-state shear experiments and linear viscoelastic experiments. In the dilute and semidilute regime the rheological behavior is similar to that of a hard-sphere dispersion as reported in the literature for viscoelastic measurements, but now also observed in steady shear experiments. The effect of the main acyl-chain phase transition, taking place at 23 °C, can be described with an increase of the effective volume fraction. As a result, with temperature variation one can obtain effective volume fractions larger than the maximum packing fraction for hard spheres. Near and above the maximum packing fraction a dynamic yield stress ty and a frequency independent storage modulus G' develop. In this concentration regime the rheological behavior is determined by the interplay between vesicle deformation and the intervesicle interaction, and so far, there is no indication which phenomenon is dominant. A comparison with recently reported measurements suggests that G' is proportional to a-3, where a is the vesicle radius. Furthermore, we show that ty = γcG' which is in agreement with theory. Here tγ is the dynamic yield stress and γc the critical strain which indicates the transition to nonlinear behavior in a viscoelastic experiment. There is a striking resemblance between our high concentration results and those reported in literature for vesicles in the so-called onion phase. To the best of our knowledge this is the first rheological study for concentrated nearly-unilamellar vesicle dispersions with volume fraction and temperature as variables

Talk, talk, talk: Exploring idea conversations and the micro-level foundations of knowledge sharing for innovation

In this study we explore the drivers and consequences of micro-level instances of knowledge sharing for innovation. We do so by focusing on the temporally bounded conversations that colleagues have about new ideas and we study specifically how the strength of ties between these colleagues influences the duration and breadth of knowledge sharing in the idea-related conversations they have over time. A 14-month on-site field study in a multinational company, in which we mapped 496 dyadic relationships regarding 17 new product ideas, shows that knowledge sharing can be explained by the ties between people being either strong or weak, rather than intermediate. We also discover that characteristics of the idea itself shape how tie strength influences the duration and breadth of knowledge sharing in idea conversations. Finally, we provide initial evidence to show how important conversations are for the success of an idea. Our study sheds light on micro-level instances of knowledge sharing for innovation and provides important insights into how managers can foster an environment in which weak and strong ties can be utilised optimally for sharing knowledge about ideas

Talk, talk, talk: exploring idea conversations and the micro-level foundations of knowledge sharing for innovation

In this study we explore the drivers and consequences of micro-level instances of knowledge sharing for innovation. We do so by focusing on the temporally bounded conversations that colleagues have about new ideas and we study specifically how the strength of ties between these colleagues influences the duration and breadth of knowledge sharing in the idea-related conversations they have over time. A 14-month on-site field study in a multinational company, in which we mapped 496 dyadic relationships regarding 17 new product ideas, shows that knowledge sharing can be explained by the ties between people being either strong or weak, rather than intermediate. We also discover that characteristics of the idea itself shape how tie strength influences the duration and breadth of knowledge sharing in idea conversations. Finally, we provide initial evidence to show how important conversations are for the success of an i