Gold in sächsischen Kies- und Sandlagerstätten

Zur Einschätzung der Goldführung von 26 ausgewählten Sand- und Kieslagerstätten in Sachsen wurden Proben auf ihre Goldgehalte untersucht. Die Mehrzahl der untersuchten Großproben wies Goldgehalte unterhalb der durchschnittlichen Zusammensetzung der Erdkruste auf. Eine mögliche Gewinnbarkeit des Goldes in Kies- und Sandlagerstätten hängt vom Goldgehalt im Rohkies und von der Anreicherung im Laufe der Aufbereitung im Tagebaubetrieb ab. Entscheidenden Einfluss auf die Gewinnung haben auch Korngröße und Kornform der Goldflitter. Die Broschüre fasst die Ergebnisse der Untersuchung zusammen und gibt Empfehlungen für das weitere Vorgehen

Laser-sintered thin films of doped SiGe nanoparticles

We present a study of the morphology and the thermoelectric properties of short-pulse laser-sintered (LS) nanoparticle (NP) thin films, consisting of SiGe alloy NPs or composites of Si and Ge NPs. Laser-sintering of spin-coated NP films in vacuum results in a macroporous percolating network with a typical thickness of 300 nm. The Seebeck coefficient is independent of the sintering process and typical for degenerate doping. The electrical conductivity of LS films rises with increasing temperature, best described by a power-law and influenced by two-dimensional percolation effects.Comment: 4 pages, 4 figure

Cobaloxime complex salts : synthesis, patterning on carbon nanomembranes and heterogeneous hydrogen evolution studies

Cobaloximes are promising, earth-abundant catalysts for the light-driven hydrogen evolution reaction. Typically, these cobalt(III) complexes are prepared in situ or employed in their neutral form, e.g. [Co(dmgH 2 )(py)Cl], even though related complex salts have been reported previously and could in principle offer improved catalytic activity as well as more efficient immobilization on solid support. Here we report an interdisciplinary investigation into complex salts [Co(dmgH) 2 (py) 2 ] + [Co(dmgBPh 2 ) 2 Cl 2 ] - , TBA + [Co(dmgBPh 2 ) 2 Cl 2 ] - and [Co(dmgH) 2 (py) 2 ] + BArF - . We describe their strategic syntheses from commercially available complex [Co(dmgH) 2 (py)Cl] and demonstrate that these double and single complex salts are potent catalysts for the light-driven hydrogen evolution reaction. We also show that scanning electrochemical cell microscopy can be used to deposit arrays of catalysts [Co(dmgH) 2 (py) 2 ] + [Co(dmgBPh 2 ) 2 Cl 2 ] - and [Co(dmgH) 2 (py)Cl] on supported and free-standing amino-terminated ~ 1 nm thick carbon nanomembranes (CNMs). Photocatalytic H 2 evolution at such arrays was quantified with Pd microsensors using scanning electrochemical microscopy, thus providing a new approach for catalytic evaluation and opening up novel routes for the creation and analysis of “designer catalyst arrays”, nano-printed in a desired pattern on a solid support

Measurement of the cosmic ray spectrum above 4×10184{\times}10^{18} eV using inclined events detected with the Pierre Auger Observatory

A measurement of the cosmic-ray spectrum for energies exceeding $4{\times}10^{18}$ eV is presented, which is based on the analysis of showers with zenith angles greater than $60^{\circ}$ detected with the Pierre Auger Observatory between 1 January 2004 and 31 December 2013. The measured spectrum confirms a flux suppression at the highest energies. Above $5.3{\times}10^{18}$ eV, the "ankle", the flux can be described by a power law $E^{-\gamma}$ with index $\gamma=2.70 \pm 0.02 \,\text{(stat)} \pm 0.1\,\text{(sys)}$ followed by a smooth suppression region. For the energy ($E_\text{s}$) at which the spectral flux has fallen to one-half of its extrapolated value in the absence of suppression, we find $E_\text{s}=(5.12\pm0.25\,\text{(stat)}^{+1.0}_{-1.2}\,\text{(sys)}){\times}10^{19}$ eV.Comment: Replaced with published version. Added journal reference and DO

Energy Estimation of Cosmic Rays with the Engineering Radio Array of the Pierre Auger Observatory

The Auger Engineering Radio Array (AERA) is part of the Pierre Auger Observatory and is used to detect the radio emission of cosmic-ray air showers. These observations are compared to the data of the surface detector stations of the Observatory, which provide well-calibrated information on the cosmic-ray energies and arrival directions. The response of the radio stations in the 30 to 80 MHz regime has been thoroughly calibrated to enable the reconstruction of the incoming electric field. For the latter, the energy deposit per area is determined from the radio pulses at each observer position and is interpolated using a two-dimensional function that takes into account signal asymmetries due to interference between the geomagnetic and charge-excess emission components. The spatial integral over the signal distribution gives a direct measurement of the energy transferred from the primary cosmic ray into radio emission in the AERA frequency range. We measure 15.8 MeV of radiation energy for a 1 EeV air shower arriving perpendicularly to the geomagnetic field. This radiation energy -- corrected for geometrical effects -- is used as a cosmic-ray energy estimator. Performing an absolute energy calibration against the surface-detector information, we observe that this radio-energy estimator scales quadratically with the cosmic-ray energy as expected for coherent emission. We find an energy resolution of the radio reconstruction of 22% for the data set and 17% for a high-quality subset containing only events with at least five radio stations with signal.Comment: Replaced with published version. Added journal reference and DO

Measurement of the Radiation Energy in the Radio Signal of Extensive Air Showers as a Universal Estimator of Cosmic-Ray Energy

We measure the energy emitted by extensive air showers in the form of radio emission in the frequency range from 30 to 80 MHz. Exploiting the accurate energy scale of the Pierre Auger Observatory, we obtain a radiation energy of 15.8 \pm 0.7 (stat) \pm 6.7 (sys) MeV for cosmic rays with an energy of 1 EeV arriving perpendicularly to a geomagnetic field of 0.24 G, scaling quadratically with the cosmic-ray energy. A comparison with predictions from state-of-the-art first-principle calculations shows agreement with our measurement. The radiation energy provides direct access to the calorimetric energy in the electromagnetic cascade of extensive air showers. Comparison with our result thus allows the direct calibration of any cosmic-ray radio detector against the well-established energy scale of the Pierre Auger Observatory.Comment: Replaced with published version. Added journal reference and DOI. Supplemental material in the ancillary file

The effect of the geomagnetic field on cosmic ray energy estimates and large scale anisotropy searches on data from the Pierre Auger Observatory

We present a comprehensive study of the influence of the geomagnetic field on the energy estimation of extensive air showers with a zenith angle smaller than $60^\circ$, detected at the Pierre Auger Observatory. The geomagnetic field induces an azimuthal modulation of the estimated energy of cosmic rays up to the ~2% level at large zenith angles. We present a method to account for this modulation of the reconstructed energy. We analyse the effect of the modulation on large scale anisotropy searches in the arrival direction distributions of cosmic rays. At a given energy, the geomagnetic effect is shown to induce a pseudo-dipolar pattern at the percent level in the declination distribution that needs to be accounted for.Comment: 20 pages, 14 figure