Development of weeds in organic crop rotation experiments

Weeds are a major problem in organic farming. Preventive as well as curative measures must be utilised to manage the weeds and avoid proliferation. Besides direct weed control measures, many different aspects of planning and management in the cropping system affect the proliferation of weeds. However, it has rarely been investigated how the whole system affects weed populations

Økologiske sædskifter til korn - kan produktionen øges?

Hvordan kan sædskiftet indrettes så den økologiske kornproduktion øges uden at bæredygtigheden mindskes? Dette centrale spørgsmål belyses med nye resultater fra det økologiske sædskifteforsøg, der i 1996/97 blev anlagt på tre lokaliteter i Danmark og som nu har kørt to rotationer

Management of perennial weeds and nitrogen leaching in arable cropping systems

A crop rotation experiment was established in 1997 at three locations representing different soil types and climates. Three factors were tested: crop rotation, catch crop and manure. Catch crop reduced nitrate leaching, but prohibited stubble cultivation. The use of catch crops resulted in increased levels of perennial weeds (E. repens) at one location, while at another; the level of C. arvense was not affected by catch crops, when compared with the use of stubble cultivation. Management of perennial weeds should include considerations of where in a crop rotation to use stubble cultivation, and this should preferably not be after a pulse crop. Catch crops are a more profitable way to manage C. arvense than stubble cultivations

Crop rotation and crop management effects on cereal yields in arable organic farming in Denmark

One of the main challenges in organic crop production is to ensure high and stable crop yields. In this study we used data from a 12 year old crop rotation experiment in Denmark to estimate the contribution of various management factors to yields of winter and spring cereals. The experiment included three factors in two replicates: 1) Grass-clover green manure crop (with and without), 2) catch crop (with and without), and 3) animal manure (with and without). Animal manure was the most important factor for increasing grain yield of cereal crops, but also grass-clover and catch crop contributed considerably to increasing yields. The grass-clover had a larger long-term effect on grain yields on the sandy loam soils than on the sandy soil. Yields were significantly reduced by weeds, and maintaing stable yields requires good weed control and prevention measures

Metal enrichment processes

There are many processes that can transport gas from the galaxies to their environment and enrich the environment in this way with metals. These metal enrichment processes have a large influence on the evolution of both the galaxies and their environment. Various processes can contribute to the gas transfer: ram-pressure stripping, galactic winds, AGN outflows, galaxy-galaxy interactions and others. We review their observational evidence, corresponding simulations, their efficiencies, and their time scales as far as they are known to date. It seems that all processes can contribute to the enrichment. There is not a single process that always dominates the enrichment, because the efficiencies of the processes vary strongly with galaxy and environmental properties.Comment: 18 pages, 8 figures, accepted for publication in Space Science Reviews, special issue "Clusters of galaxies: beyond the thermal view", Editor J.S. Kaastra, Chapter 17; work done by an international team at the International Space Science Institute (ISSI), Bern, organised by J.S. Kaastra, A.M. Bykov, S. Schindler & J.A.M. Bleeke

The RNA chaperone Hfq is essential for the virulence of Salmonella typhimurium

The RNA chaperone, Hfq, plays a diverse role in bacterial physiology beyond its original role as a host factor required for replication of Qβ RNA bacteriophage. In this study, we show that Hfq is involved in the expression and secretion of virulence factors in the facultative intracellular pathogen, Salmonella typhimurium. A Salmonella hfq deletion strain is highly attenuated in mice after both oral and intraperitoneal infection, and shows a severe defect in invasion of epithelial cells and a growth defect in both epithelial cells and macrophages in vitro. Surprisingly, we find that these phenotypes are largely independent of the previously reported requirement of Hfq for expression of the stationary phase sigma factor, RpoS. Our results implicate Hfq as a key regulator of multiple aspects of virulence including regulation of motility and outer membrane protein (OmpD) expression in addition to invasion and intracellular growth. These pleiotropic effects are suggested to involve a network of regulatory small non-coding RNAs, placing Hfq at the centre of post-transcriptional regulation of virulence gene expression in Salmonella. In addition, the hfq mutation appears to cause a chronic activation of the RpoE-mediated envelope stress response which is likely due to a misregulation of membrane protein expression

High-throughput screening identifies a bisphenol inhibitor of SV40 large T antigen ATPase activity

The authors conducted a high-throughput screening campaign for inhibitors of SV40 large T antigen ATPase activity to identify candidate antivirals that target the replication of polyomaviruses. The primary assay was adapted to 1536-well microplates and used to screen the National Institutes of Health Molecular Libraries Probe Centers Network library of 306 015 compounds. The primary screen had an Z value of ∼0.68, signal/background = 3, and a high (5%) DMSO tolerance. Two counterscreens and two secondary assays were used to prioritize hits by EC50, cytotoxicity, target specificity, and off-target effects. Hits that inhibited ATPase activity by >44% in the primary screen were tested in dose-response efficacy and eukaryotic cytotoxicity assays. After evaluation of hit cytotoxicity, drug likeness, promiscuity, and target specificity, three compounds were chosen for chemical optimization. Chemical optimization identified a class of bisphenols as the most effective biochemical inhibitors. Bisphenol A inhibited SV40 large T antigen ATPase activity with an IC50 of 41 μM in the primary assay and 6.2 μM in a cytoprotection assay. This compound class is suitable as probes for biochemical investigation of large T antigen ATPase activity, but because of their cytotoxicity, further optimization is necessary for their use in studying polyomavirus replication in vivo

Learning from multimedia and hypermedia

Computer-based multimedia and hypermedia resources (e.g., the world wide web) have become one of the primary sources of academic information for a majority of pupils and students. In line with this expansion in the field of education, the scientific study of learning from multimedia and hypermedia has become a very active field of research. In this chapter we provide a short overview with regard to research on learning with multimedia and hypermedia. In two review sections, we describe the educational benefits of multiple representations and of learner control, as these are the two defining characteristics of hypermedia. In a third review section we describe recent scientific trends in the field of multimedia/hypermedia learning. In all three review sections we will point to relevant European work on multimedia/hypermedia carried out within the last 5 years, and often carried out within the Kaleidoscope Network of Excellence. According to the interdisciplinary nature of the field this work might come not only from psychology, but also from technology or pedagogy. Comparing the different research activities on multimedia and hypermedia that have dominated the international scientific discourse in the last decade reveals some important differences. Most important, a gap seems to exist between researchers mainly interested in a “serious” educational use of multimedia/ hypermedia and researchers mainly interested in “serious” experimental research on learning with multimedia/hypermedia. Recent discussions about the pros and cons of “design-based research” or “use-inspired basic research” can be seen as a direct consequence of an increasing awareness of the tensions within these two different cultures of research on education