Seasonal deposition processes and chronology of a varved Holocene lake sediment record from Lake Chatyr Kol (Kyrgyz Republic)

A finely laminated lake sediment record with a basal age of 11,619 ± 603 years BP was retrieved from Lake Chatyr Kol (Kyrgyz Republic). Microfacies analysis reveals the presence of seasonal laminae (varves) from the sediment basis to ~ 360 ± 40 years BP. The Chatvd19 floating varve chronology covers the time span from 360 ± 40 years BP to the base and relies on replicate varve counts on overlapping petrographic thin sections with an uncertainty of ± 5 %. The uppermost non-varved interval was chronologically constrained by 210Pb and 137Cs γ-spectrometry and interpolation based on varve thickness measurements of adjacent varved intervals with an assumed uncertainty of 10 %. Six varve types were distinguished, are described in detail and show a changing predominance of clastic-organic, clastic-calcitic or -aragonitic, calcitic-clastic, organic-clastic and clastic-diatom varves throughout the Holocene. Variations in varve thickness and the number and composition of seasonal sublayers are attributed to 1) changes in the amount of summer or winter/spring precipitation affecting local runoff and erosion and/or to 2) evaporative conditions during summer. Radiocarbon dating of bulk organic matter, daphnia remains, aquatic plant remains and Ruppia maritima seeds reveal reservoir ages with a clear decreasing trend up core from ~ 6,150 years in the early Holocene, to ~ 3,000 years in the mid-Holocene, to ~ 1,000 years and less in the late Holocene and modern times. In contrast, two radiocarbon dates from terrestrial plant remains are in good agreement with the varve-based chronology

Der Einfluß der Änderung der lokalen Gewebeleitfähigkeit auf das Elektroenzephalogramm und das Magnetoenzephalogramm

We examined the influence of local tissue conductivity changes in the vicinity of a dipolar source on the neuromagnetic field and the electric scalp potential using a high resolution finite element method model of the human head. We found that the topology of both the electric scalp potential and the neuromagnetic field (and consequently dipole localization) is influenced significantly by conductivity changes only in voxels adjacent to the source. Conductivity changes in these voxels yield a greater change in the amplitude of the magnetic field (and consequently in the dipole strength) than in the amplitude of the electric potential.Der Einfluß der Änderung der lokalen Gewebeleitfahigkeit in der Nähe einer dipolaren Quelle auf das neuromagnetische Feld und das elektrische Potential wird mit Hilfe eines hochauflösenden Finite-Elemente-Modells des menschlichen Kopfes untersucht. Für Leitfähigkeitsänderungen in den Voxeln, die an der Quelle anliegen, wurde eine signifikante Änderung der Topologie (und demzufolge der Dipollokalisation) des magnetischen Feldes und des elektrischen Potentials gefunden. In diesen Voxeln führt die Leitfähigkeitsänderung zu größeren Änderungen in der Amplitude des magnetischen Feldes (und damit der Dipolstärke) als in der Amplitude des elektrischen Potentials

k-space Imaging of the Eigenmodes of Sharp Gold Tapers for Scanning Near-Field Optical Microscopy

We investigate the radiation patterns of sharp conical gold tapers, designed as adiabatic nanofocusing probes for scanning near-field optical microscopy (SNOM). Field calculations show that only the lowest order eigenmode of such a taper can reach the very apex and thus induce the generation of strongly enhanced near-field signals. Higher order modes are coupled into the far field at finite distances from the apex. Here, we demonstrate experimentally how to distinguish and separate between the lowest and higher order eigenmodes of such a metallic taper by filtering in the spatial frequency domain. Our approach has the potential to considerably improve the signal-to-background ratio in spectroscopic experiments on the nanoscale

Der Einfluß der Änderung der Schalenleitfähigkeit bei Randelementemodellen auf die Vorwärtsrechnung und das inverse Problem in Elektroenzephalographie und Magnetoenzephalographie

Source localization based on magnetoencephalographic and electroencephalographic data requires knowledge of the conductivitiy values of the head. The aim of this paper is to examine the influence of compartment conductivity changes on the neuromagnetic field and the electric scalp Potential for the widely used three compartment boundary element models. Both the analysis of measurement data and the simulations with dipoles distributed in the brain produced two significant results. First, we found the electric potentials to be approximately one order of magnitude more sensitive to conductivity changes than the magnetic fields. This was valid for the field and Potential topology (and hence dipole localization), and for the amplitude (and hence dipole strength). Second, changes in brain compartment conductivity yield the lowest change in the electric potentials topology (and hence dipole localization), but a very strong change in the amplitude (and hence in the dipole strength). We conclude that for the magnetic field the influence of compartment conductivity changes is not important in terms of dipole localization and strength estimation. For the electric potentials however, both dipole localization and strength estimation are significantly influenced by the compartment conductivity.Die Gewebeleitfähigkeitswerte des Kopfes sind für Quellerdokalisationen, basierend auf magnetoenzephalographischen und elektroenzephalographischen Daten, erforderlich. Das Ziel dieser Arbeit besteht darin, den Einfluß von Leitfähigkeitsänderungen auf das neuromagnetische Feld und die elektrische Potentialverteilung auf der Kopfoberfläche für die weitverbreiteten 3-Schalen-Randelementemodelle zu untersuchen. Sowohl die Analyse von Meßdaten als auch die Simulationen mit im Gehirn verteilten Einzeldipolen führten zu zwei wesentlichen Ergebnissen. Erstens war die Empfindlichkeit gegenüber Leitfähigkeitsänderungen beim elektrischen Potential ungefähr eine Größenordnung höher als beim magnetischen Feld. Dies galt sowohl für die Topologie (und damit für die Dipollokalisation) als auch für die Amplitude (und damit für die Dipolstärke). Zweitens zeigten Leitfähigkeitsänderungen der innersten Schale (Gehirn) die geringsten Änderungen in der Topologie des elektrischen Potentials (und damit in der Dipollokalisation), aber dabei eine sehr starke Änderung in der Amplitude (und damit in der Dipolstärke). Es kann geschlußfolgert werden, daß der Einfluß der Leitfähigkeitsänderung auf die Dipollokalisation und die Bestimmung der Dipolstärke aus dem magnetischen Feld vernachlässigt werden kann. Die Berechnung von Dipolort und -stärke aus dem elektrischen Potential ist jedoch signifikant von der Leitfähigkeit der Schalen abhängig

High Velocity Dust Collisions: Forming Planetesimals in a Fragmentation Cascade with Final Accretion

In laboratory experiments we determine the mass gain and loss in central collisions between cm to dm-size SiO2 dust targets and sub-mm to cm-size SiO2 dust projectiles of varying mass, size, shape, and at different collision velocities up to ~56.5 m/s. Dust projectiles much larger than 1 mm lead to a small amount of erosion of the target but decimetre targets do not break up. Collisions produce ejecta which are smaller than the incoming projectile. Projectiles smaller than 1 mm are accreted by a target even at the highest collision velocities. This implies that net accretion of decimetre and larger bodies is possible. Independent of the original size of a projectile considered, after several collisions all fragments will be of sub-mm size which might then be (re)-accreted in the next collision with a larger body. The experimental data suggest that collisional growth through fragmentation and reaccretion is a viable mechanism to form planetesimals

Baggage handler seniority and musculoskeletal symptoms:is heavy lifting in awkward positions associated with the risk of pain?

OBJECTIVES: Heavy lifting is associated with musculoskeletal disorders but it is unclear whether it is related to acute reversible effects or to chronic effects from cumulated exposure. The aim of this study was to examine whether musculoskeletal symptoms in Danish airport baggage handlers were associated with their seniority as baggage handler, indicating chronic effects from cumulated workload. METHODS: We established a group of baggage handlers employed at Copenhagen Airport during the period 1983–2012 (n=3092) and a reference group of men in other unskilled occupations with less heavy work (n=2478). Data regarding work history, lifestyle and musculoskeletal symptoms were collected using a self-administered questionnaire (response rate 70.1% among baggage handlers and 68.8% among the reference group). RESULTS: The ORs of self-reported musculoskeletal symptoms during the last 12 months in the neck/upper back, lower back, shoulders, elbows, wrists, hips and knees were significantly higher in baggage handlers than in the reference group. These differences were explained by significant linear effects of baggage handler seniority for six anatomical regions. Adjustment for age, body mass index, smoking and leisure-time physical activity did not change these results. The findings were stable over age strata and among present and former baggage handlers. CONCLUSIONS: The risk of musculoskeletal symptoms in six anatomical regions increased with increasing seniority as a baggage handler. This is consistent with the assumption that cumulated heavy lifting may cause chronic or long-lasting musculoskeletal symptoms. However, we cannot exclude that other factors related to baggage handler seniority may explain some of the associations