Heavy-Quark Form Factors and Threshold Cross Section at O(\alpha_S^2)

During the last year, analytic expressions for the two-loop QCD corrections to the form factors for the vector, axial-vector, scalar and pseudo-scalar vertices involving a pair of heavy quarks, $Q \bar{Q}$, were calculated. The results are valid for arbitrary momentum transfer and mass of the heavy quarks. These form factors have a number of applications, including anomalous couplings, the $e^{+}e^{-} \to Q \bar Q$ cross section, and the forward-backward asymmetry of heavy quarks. Here the $Q {\bar Q}$ threshold cross section is presented with some new second order axial vector contributions.Comment: 5 pages. Presented at the International Europhysics Conference on High Energy Physics (HEP2005), July 21-27 2005, Lisboa, Portuga

VOC and ozone fluxes from a pine forest in the north of Belgium

Plants release large amounts of carbon as Volatile Organic Compounds (VOCs) into the atmosphere. These VOCs play an important role in the chemistry of the troposphere as they can be involved in the mechanisms of ozone and aerosol formation. The key mechanisms underneath biogenic VOC emissions are still not well understood, leading to large uncertainties in BVOC inventories on global and regional scales. Measurements of VOCs, ozone and micro-meteorology are conducted at the ‘De inslag’, a 80-year old mixed pine–oak forest located in the Campine region near Antwerp, Belgium. The forest site is a level-II plot of the European Programme of Intensive Monitoring Forest Ecosystems and is part of the Carboeuro and Nitroeurope-flux research network. The site is equipped with a flux tower that reaches above the 23m canopy. A Proton Transfer Reaction Mass Spectrometer and a Fast Ozone analyser allow determining VOC and ozone fluxes by Eddy Covariance. An analytic footprint model is used to exclude non-forest fluxes. In this study, we will test the accuracy of this footprint model with anthropogenic tracers (benzene and toluene)

Seasonal variation of LAI in the footprint of a flux measurement tower

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Chamber-based continuous measurement of N2O fluxes in a winter wheat field: comparison of tillage treatments and identification of emission peak dynamic

Agriculture is the first anthropogenic source of N2O, notably through fertilized croplands. Though, few publications have studied through continuous measurement the N2O emissions in cultivated lands. We conducted this study to assess the effect of farming practices and climate on N2O emissions from a winter wheat crop. The experiment was held in an experimental field in the loamy region in Belgium from March 2016 till crop harvest in August 2016. The N2O fluxes are measured on two nearby parcels in a winter wheat field with restitution of the residues from previous crop. For the past 8 years, one parcel was subjected to a reduced tillage (RT, 10 cm depth) and the other one to a conventional tillage (CT, 25 cm depth). On each parcel, the N2O emissions were assessed with homemade automated closed chambers. Measurement continuity and good temporal resolution (one mean flux every 4 hours) of the system allowed a fine detection and quantification of the emission peaks which usually represent the major part of N2O fluxes. In addition to gas fluxes, soil water content at various depths and surface temperature were measured continuously. Soil samples were taken regularly to determine soil pH, soil organic carbon and nitrogen pools (total, NO3- and NH4+) and study microbial diversity and nitrification/denitrification gene expression. Measurements are still in progress. First results suggested that fluxes were about 3 times larger in the RT parcel than in the CT parcel. Several emissions peaks were observed during the measurement period. The peaks occurred after fertilization events and seemed to be triggered by an elevation of soil water content. A comparison of the emissions between RT and CT and a discussion on peak temporal dynamics, focusing on their intensity, duration and starting time will be presented.AgriGE

Compasion of CVaR and markowitz approaches to formation of investment porfolios

The aim of research is formation of efficient frontiers of CVaR and Mean-Variance optimal portfolios. As a result, CVaR and Mean-Variance efficient frontiers were formed, graphs of dependencies risk vs yield, and yield vs CVaR were plotted