Doubled volatile organic compound emissions from subarctic tundra under simulated climate warming

Biogenic volatile organic compound (BVOC) emissions from arctic ecosystems are important in view of their role in global atmospheric chemistry and unknown feedbacks to global warming. These cold ecosystems are hotspots of climate warming, which will be more severe here than averaged over the globe. We assess the effects of climatic warming on non‐methane BVOC emissions from a subarctic heath. We performed ecosystem‐based chamber measurements and gas chromatography–mass spectrometry (GC‐MS) analyses of the BVOCs collected on adsorbent over two growing seasons at a wet subarctic tundra heath hosting a long‐term warming and mountain birch (Betula pubescens ssp. czerepanovii) litter addition experiment. The relatively low emissions of monoterpenes and sesquiterpenes were doubled in response to an air temperature increment of only 1.9–2.5°C, while litter addition had a minor influence. BVOC emissions were seasonal, and warming combined with litter addition triggered emissions of specific compounds. The unexpectedly high rate of release of BVOCs measured in this conservative warming scenario is far above the estimates produced by the current models, which underlines the importance of a focus on BVOC emissions during climate change. The observed changes have implications for ecological interactions and feedback effects on climate change via impacts on aerosol formation and indirect greenhouse effects

Search for leptoquarks with the ZEUS detector

Results are presented on neutral current, deep inelastic scattering measured in collisions of 26.7 GeV electrons and 820 GeV protons. The events typically populate a range in Q2 from 10 to 100 GeV2. The values of x extend down to x ∼ 10$^{−4}$ which is two orders of magnitude lower than previously measured at such Q2 values in fixed target experiments. The measured cross sections are in accord with the extrapolations of current parametrisations of parton distributions

Migration Phenomenon in Food Packaging. Food-Package Interactions, Mechanisms, Types of Migrants, Testing and Relative Legislation-A Review

The development of convenient and low-cost packages, together with the increased consumer demands for safer products, have resulted in the conduction of extensive research and the publication of numerous studies related to the phenomenon of migration. The large number of synthetic materials used for the manufacture of packages makes the evaluation of the food-package interactions quite complicated. Different parameters such as the nature of the food of interest, the type of food-package contact, the time and temperature of contact, the packaging materials used, the properties of the migrating substances, as well as the amount of potential migrants contained in the packaging materials, can drastically affect the migration rate and extent. Due to the extreme variety of foods used, several food simulants have been suggested and applied for testing the migration phenomenon under various laboratory conditions. The use of many of those simulants is defined by national and international legislation. This review article covers the main migration phenomena, which are related to the most commonly used packaging materials. It is clearly demonstrated that the complexity of the migration phenomena requires more research to establish internationally accepted risk management procedures and standardised testing methods

Dijet cross-sections in photoproduction at HERA

Dijet production by almost real photons has been studied at HERA with the ZEUS detector. Jets have been identified using the cone algorithm. A cut on xg, the fraction of the photon energy participating in the production of the two jets of highest transverse energy, is used to define cross sections sensitive to the parton distributions in the proton and in the photon. The dependence of the dijet cross sections on pseudorapidity has been measured for xg $\ge 0.75$ and xg $< 0.75$. The former is sensitive to the gluon momentum density in the proton. The latter is sensitive to the gluon in the photon. The cross sections are corrected for detector acceptance and compared to leading order QCD calculations.Comment: 21 pages, latex, 4 figures appended as uuencoded fil