NDICEA as a user friendly model tool for crop rotation planning in organic farming

For organic farming systems, the challenge is to become more specific in practices to maintain high standards in sustainability. Soil processes need to be clearly understood if rotations and manure applications are to become more precise. Simulation models like the NDICEA model help in the design and maintenance of these farming systems. These models play a key-role in the design of organic precision farming. The NDICEA model has been calibrated for a number of long-term crop rotation experiments. Recently, the model was validated using research data from more than 35 organic farms all over the country. The model is used to calculate soil-specific mineralization rates in precision applications. In a new easy-to-use application, it was developed to design crop rotations and evaluate performance of crop rotations. This application is used to evaluate the sustainability of farming systems

Lucerne (Medicago sativa) or grass-clover as cut-and-carry fertilizers in organic agriculture

On-farm nitrogen fixation is a driving force in organic agriculture. The efficiency with which this nitrogen is used can be increased by using lucerne (Medicago sativa) or grass-clover directly as sources of fertilizer on arable land: cut-and-carry fertilizers. In two arable crops, the use of lucerne and grass-clover as fertilizers was compared with the use of poultry manure and slurry. The nitrogen-use efficiency at crop level was comparable or better for the cut-andcarry fertilizers as compared to the animal manures. The relative P and K content of these fertilizers came closer to the crop demand than that of the poultry manure. Crop yields were comparable or better when using lucerne or grass-clover as fertilizer. It is concluded that cutand-carry fertilizers are a serious alternative for manure as part of an overall farm soil fertility strategy

Carrier-carrier Coulomb interactions reduce power factor in organic thermoelectrics

Organic semiconductors are excellent candidates for low temperature thermoelectric generators. However, such thermoelectric applications require materials be doped and highly conductive. Here, we show how doping affects the Seebeck coefficient in organic semiconductors using kinetic Monte Carlo simulations. Employing a hopping transport approach, we demonstrate that at high dopant loading, carrier-carrier interactions can reduce the Seebeck coefficient. This results in systems with intrinsic disorder, still following Heike's formula for thermopower at high dopant density. Reducing these carrier-carrier interactions results in an increased Seebeck coefficient and power factor. Specifically, a realistic reduction in carrier-carrier interactions can increase the power factor by more than a factor 15, increasing ZT above 1 for organic thermoelectrics

Voltage Deficit in Wide Bandgap Perovskite Solar Cells:The Role of Traps, Band Energies, and Effective Density of States

Wide-bandgap ((Formula presented.) 1.7 eV) perovskite solar cells (PSCs) are plagued by relatively low open-circuit voltages. This is problematic as they are key to achieving perovskite silicon tandems, which can boost the potential of silicon solar cells. Performance in PSCs is widely considered to be limited by recombination at the interface between the perovskite and the transport layer (TL). Here, a number of design rules to increase the open-circuit voltage of wide-bandgap PSCs are introduced. A numerical device model that includes a detailed description of the interfacial recombination processes is presented. The combined effects of interface traps, ions, band alignment, and transport properties are introduced to identify the critical parameters for improving the open-circuit voltage. A large number of devices are simulated by picking random combinations of parameters and are looked for trends. It is shown that interface recombination can be suppressed by reducing the minority carrier density close to the interface with the TLs. It is demonstrated that the alignment of energy levels is only part of the story; the effective densities of states are of equal importance. The results pave the way to achieving high open-circuit voltages, despite a significant density of interface defects

In vivo insulin action and resistance. The hyperinsulinaemic, euglycaemic clamp technique in conscious rats

After almost 75 years of research and four Nobel prizes awarded for insulin-related investigations, we still do not understand how insulin works. Of course, substantial progress has been made and there are some clues. We review in vivo insulin action from the moment of insulin biosynthesis in the pancreatic β-cell to insulin action on effector systems in target tissues. The mechanism of insulin action at the whole body, tissue and cellular level is discussed. In addition, factors and conditions influencing insulin action and events leading to insulin resistance are summarized. Finally, the reader is introduced into the principles of the hyperinsulinaemic, euglycaemic clamp technique which is considered the "golden standard" for measurement of insulin action and resistance in vivo. An example is given how to clamp conscious rats in a proper way.Biomedical Reviews 1996; 5: 31-45

The existence of an insulin-stimulated glucose and non-essential but not essential amino acid substrate interaction in diabetic pigs

<p>Abstract</p> <p>Background</p> <p>The generation of energy from glucose is impaired in diabetes and can be compensated by other substrates like fatty acids (Randle cycle). Little information is available on amino acids (AA) as alternative energy-source in diabetes. To study the interaction between insulin-stimulated glucose and AA utilization in normal and diabetic subjects, intraportal hyperinsulinaemic euglycaemic euaminoacidaemic clamp studies were performed in normal (n = 8) and streptozotocin (120 mg/kg) induced diabetic (n = 7) pigs of ~40-45 kg.</p> <p>Results</p> <p>Diabetic vs normal pigs showed basal hyperglycaemia (19.0 ± 2.0 vs 4.7 ± 0.1 mmol/L, <it>P </it>< .001) and at the level of individual AA, basal concentrations of valine and histidine were increased (<it>P </it>< .05) whereas tyrosine, alanine, asparagine, glutamine, glutamate, glycine and serine were decreased (<it>P </it>< .05). During the clamp, diabetic vs normal pigs showed reduced insulin-stimulated glucose clearance (4.4 ± 1.6 vs 16.0 ± 3.0 mL/kg·min, <it>P </it>< .001) but increased AA clearance (166 ± 22 vs 110 ± 13 mL/kg· min, <it>P </it>< .05) at matched arterial euglycaemia (5-7 mmol/L) and euaminoacidaemia (2.8-3.5 mmol/L). The increase in AA clearance was mainly caused by an increase in non-essential AA clearance (93.6 ± 13.8 vs 46.6 ± 5.4 mL/kg·min, <it>P </it>< .01), in particular alanine (14.2 ± 2.4 vs 3.2 ± 0.4 mL/kg·min, <it>P </it>< .001)<b/>. Essential AA clearance was largely unchanged (72.9 ± 8.5 vs 63.3 ± 8.5 mL/kg· min), however clearances of threonine (<it>P </it>< .05) and tyrosine (<it>P </it>< .01) were increased in diabetic vs normal pigs (8.1 ± 1.3 vs 5.2 ± 0.5, and 14.3 ± 2.5 vs 6.4 ± 0.7 mL/kg· min, respectively).</p> <p>Conclusions</p> <p>The ratio of insulin-stimulated glucose versus AA clearance was decreased 5.4-fold in diabetic pigs, which was caused by a 3.6-fold decrease in glucose clearance and a 2.0-fold increase in non-essential AA clearance. In parallel with the Randle concept (glucose - fatty acid cycle), the present data suggest the existence of a glucose and non-essential AA substrate interaction in diabetic pigs whereby reduced insulin-stimulated glucose clearance seems to be partly compensated by an increase in non-essential AA clearance whereas essential AA are preferentially spared from an increase in clearance.</p

Bijzondere Bemesting: Kansrijke strategieën voor duurzaam bodemmanagement

Om die transitie naar duurzaam bodemmanagement te ondersteunen heeft het Louis olk Instituut binnen het project Bijzondere Bemesting onderzoek uitgevoerd dat antwoord moest geven op de volgende vragen: • Wat zijn de effecten van mest en compost op bodem en gewaskwaliteit en wat zijn de mogelijkheden voor de inzet van niet dierlijke meststoffen? • Hoe kan bij een bemesting gericht op fosfaatevenwicht de beschikbaarheid van stikstof en fosfaat gewaarborgd blijven? • Waarom zijn bepaalde bedrijfsstrategieën succesvol

Investeren tot in de bodem: Evaluatie van het proefveld Mest Als Kans

Doel van het project Investeren tot in de Bodem was het verkrijgen van inzicht in het meerjarige effect van veelgebruikte organische meststoffen en bodemverbeteraars op bodemvruchtbaarheid en nutriëntenemissie. In november 2006 zijn daarom in acht van de dertien bemestingsvarianten van het sinds 1999 bestaande proefveld Mest als Kans metingen gedaan aan de fysische, chemische en biologische bodemeigenschappen en is de invloed van bemestingsstrategieën op opbrengst en productkwaliteit bepaald. De proef is opgenomen in de vruchtwisseling van een groententeeltbedrijf op lichte zavelgrond bij Lelystad. De bemesting vond plaats in mei. Op basis van een stikstofgift van 100 kg werkzame N/ha, een maximale fosfaatgift van 80 kg P2O5 per ha per jaar en voor GFT- en groencompost een wettelijk toegestane hoeveelheid droge stof van 6000 kg per hectare per jaar. Op basis van een zestal belangrijke criteria voor ondernemers en maatschappij lijken de varianten GFT+drijfmest, potstalmest en natuurcompost in de hier beschreven proefopzet de beste investering in de bodem met de minst negatieve gevolgen voor het milieu

Vrachtvaarders van Europa:Een onderzoek naar schippers afkomstig uit Makkum in Friesland van 1600 tot 1820

Friesland wordt in de historiografie vaak voorgesteld als een moderne landbouwprovincie gelegen in de periferie van het rijke gewest Holland. De provincie zelf zou nauwelijks opgenomen zijn in internationale verbanden. Dit is echter een beeld uit de negentiende eeuw dat ook vaak op de periode daarvoor is geprojecteerd. De geschiedenis van de scheepvaart in Makkum toont aan dat er in de periode voor 1800 Friesland wel degelijk over internationale connecties beschikte. Friese schippers dienden in de achttiende eeuw met hun kofschepen als de vrachtvaarders van Europa. Van Danzig, Koningsbergen en Sint Petersburg tot aan Amsterdam, Bordeaux en Lissabon. In Makkum ontstond de schippersgemeenschap uit de lokale behoefte om kalk en baksteen naar grote steden te exporteren. Doordat de schippers geweldig wisten in te spelen op de kansen die de markt van het vrachttransport hen bood wisten zij uit te groeien tot een belangrijke speler in het Europese vrachtverkeer. De familie Kingma was een prachtig voorbeeld van een succesvolle schippersfamilie. Begonnen als schippers wisten zij rijk te worden en zich op te werken tot reder en koopman. Door de scheepvaart in opdracht van kooplieden uit grote steden maakte Makkum in de achttiende eeuw een bloeiperiode door. Daar kwam een eind aan door de rampzalig verlopen Vierde Engelse Oorlog (1780 -1784) en vooral de Franse periode (1795-1815. In deze periodes werden veel schepen gekaapt en het varen voor de schippers bijna onmogelijk gemaakt. Na deze periode bleven er weinig schippers over in Makkum.The skippers community in Makkum originated from the local industry. In the seventeenth century building materials, like seashell lime and bricks were taken by local skippers to cities in Holland and Germany. From the beginning of the eighteenth century, more and more shipping was commissioned by merchants from bigger cities, like Amsterdam. The Makkum skippers found an alternative from mainly shipping to Amsterdam and places in Germany in shipping to the Baltic. Between 1750 and 1780, the Makkum freight shipping had an unpreceded good period. The downfall of the Makkum shipping was mainly caused by the obstacles of the Fourth Anglo-Dutch War (1780 - 1784) and the Frech Revolutionary and Napolenontic Wars (1795 - 1815). The ships were captured of left ashore and the shipowners investments disappeared