Polarized Parton Densities

In this talk we summarize main results of a recent determination of the polarized deeply inelastic parton distributions to NLO from the world data. In the analysis the LO and NLO parton densities and their $1\sigma$ statistical errors were derived and parameterized. The strong coupling constant $\alpha_s(M_Z^2)$ is determined $\alpha_s(M_Z^2) = 0.113 \pm 0.004 {\rm (stat.)} \pm~0.004 {\rm (fac.)} +0.008/-0.005 {\rm (ren.)}$ Comparisons of the low moments of the parton densities with recent lattice results are given. A detailed error-analysis of the gluon density is performed.Comment: 3 pages LATEX, 1 style file, 1 eps file, to appear in the Proceedings of PANIC '02, Osaka, Ocrober 200

Do Deep Inelastic Scattering Data Favor a Light Gluino

A next--to--leading order QCD analysis of deep inelastic scattering data is performed allowing for contributions due to a light gluino. We obtain the values of $\alpha_s(M_Z^2) \pm \delta \alpha_s^{stat} = 0.108 \pm 0.002, 0.124 \pm 0.001, 0.145 \pm 0.009$ for QCD, SUSY QCD with a Majorana gluino and a Dirac gluino respectively. The value of \alsm obtained in SUSY QCD with a Majorana gluino best agrees with the direct measurements of $\alpha_s(M_Z^2)$ at LEP.Comment: 8 pages with 7 pages of figures, DESY 94-00

QCD Analysis of Polarized Deep Inelastic Data and Parton Distributions

A QCD analysis of the world data on polarized deep inelastic scattering is presented in leading and next-to-leading order. New parameterizations are derived for the quark and gluon distributions for the kinematic range x \epsilon [10^{-9},1], Q^2 \epsilon [1,10^6] \GeV^2. The extrapolation far outside the domain of the current measurements is given both to allow for applications at higher values of $Q^2$ and to be able to calculate integral properties of the present distributions. The values of $\Lambda_{\rm QCD}$ and $\alpha_s(M_z)$ are determined. Emphasis is put on the derivation of the fully correlated $1\sigma$ error bands for these distributions, which are also given in terms of parameterizations and are directly applicable to determine experimental errors of other polarized observables. The impact of the variation of both the renormalization and factorization scales on the value of $\alpha_s$ is studied. Finally we perform a factorization--scheme invariant QCD analysis based on the observables $g_1(x,Q^2)$ and $d g_1(x,Q^2)/d \log(Q^2)$ in next-to-leading order, which is compared to the standard analysis. A series of low moments of parton densities, accounting for error correlation, are given to allow for comparison with results from lattice simulations.Comment: 43 pages LATEX, 1 style files, 13 eps-figures, final version, Nucl. Phys. B in prin

Investigations of minor elements in early aluminium artefacts

Study of the minor and trace element contents in the composition of early aluminium is interesting from a cultural history perspective because it can provide information on the evolution of aluminium smelting practice. A range of aluminium artefacts from the Swiss National Museum and the Lausanne Historical Museum, Switzerland, have been characterised with regard to their minor and trace element composition. This was performed using external beam Particle Induced X-ray Emission (PIXE) with 1 MeV protons and a portable X-ray fluorescence system. The concentration of Mn and Pb was significantly higher for artefacts produced by the amalgam process which confirms studies reported by others

How fast do gully headcuts retreat?

Gully erosion has important on and off site effects. Therefore, several studies have been conducted over the past decades to quantify gully headcut retreat (GHR) in different environments. Although these led to important site-specific and regional insights, the overall importance of this erosion process or the factors that control it at a global scale remain poorly understood. This study aims to bridge this gap by reviewing research on GHR and conducting a meta-analysis of measured GHR rates worldwide. Through an extensive literature review, GHR rates for 933 individual and actively retreating gullies have been compiled from more than 70 study areas worldwide (comprising a total measuring period of >19 600 years). Each GHR rate was measured through repeated field surveys and/or analyses of aerial photographs over a period of at least one year (maximum: 97 years, median: 17 years). The data show a very large variability, both in terms of gully dimensions (cross-sectional areas ranging between 0.11 and 816 m2 with a median of 4 m2) and volumetric GHR rates (ranging between 0.002 and 47 430 m3 year- 1 with a median of 2.2 m3 year- 1). Linear GHR rates vary between 0.01 and 135 m year- 1 (median: 0.89 m year- 1), while areal GHR rates vary between 0.01 and 3628 m2 year- 1 (median: 3.12 m2 year- 1). An empirical relationship allows estimating volumetric retreat rates from areal retreat rates with acceptable uncertainties. By means of statistical analyses for a subset of 724 gullies with a known contributing area, we explored the factors most relevant in explaining the observed 7 orders of magnitudes of variation in volumetric GHR rates. Results show that measured GHR rates are significantly correlated to the runoff contributing area of the gully (r2 = 0.15) and the rainy day normal (RDN; i.e. the long-term average annual rainfall depth divided by the average number of rainy days; r2 = 0.47). Other factors (e.g. land use or soil type) showed no significant correlation with the observed GHR rates. This may be attributed to the uncertainties associated with accurately quantifying these factors. In addition, available time series data demonstrate that GHR rates are subject to very large year-to-year variations. As a result, average GHR rates measured over short (100%) uncertainties. We integrated our findings into a weighted regression model that simulates the volumetric retreat rate of a gully headcut as a function of upstream drainage area and RDN. When weighing each GHR observation proportional to its measuring period, this model explains 68% of the observed variance in GHR rates at a global scale. For 76% of the monitored gullies, the simulated GHR values deviate less than one order of magnitude from their corresponding observed value. Our model clearly indicates that GHR rates are very sensitive to rainfall intensity. Since these intensities are expected to increase in most areas as a result of climate change, our results suggest that gully erosion worldwide will become more intense and widespread in the following decades. Finally, we discuss research topics that will help to address these challenges. © 2016 Elsevier B.V