The Cl-36 in the stratosphere

Initial measurements of the cosmogenic radionuclide, Cl-36, in the lower stratosphere were made by accelerator mass spectrometry. Samples were obtained using the large volume LASL air sampling pods on a NASA WB-57F aircraft. Untreated (for collection of particulates only) and tetrabutyl ammonium hydroxide treated (for collection of particulates and HCl) IPC-1478 filters were flown on three flights in the lower stratosphere. Chlorine (Cl) and Cl compounds are important trace constituents for stratospheric chemistry, in particular with respect to O3 destruction. Stratospheric Cl chemistry has recently received increased attention with the observation of strong O3 depletion in the Antarctic winter vortex and in the weaker and more complex Arctic winter vortices. Cosmogenic (Cl-36) is produced by spallation reactions from Ar mainly in the stratosphere, and has had several applications as a geochemical tracer. The large amounts of Cl-36 introduced by nuclear weapon testing have been removed from the stratosphere by now, and measurements in the stratosphere to obtain cosmogenic production rates and concentration distributions is now possible. The use of cosmogenic Cl-36 as a tracer for stratospheric Cl chemistry and for stratospheric/tropospheric exchange processes is investigated. A first attempt to determine stratospheric and tropospheric production rates, the partitioning of Cl-36 among particulate and gaseous Cl compounds, and the respective inventories and removal rates is being made. Results from a flight at 13.7 km, 30-33 degrees N, 97-107 degrees W, and from a second flight at 17.7 km, 43-45-36 degrees N, 92-94 degrees W, for the untreated and treated filters respectively are presented

Post-depositional impacts on ‘Findlinge' (erratic boulders) and their implications for surface-exposure dating

Understanding and interpretation of ‘numbers' produced about the depositional age of an erratic boulder by cosmogenic nuclide surface-exposure dating is important in the construction of glacial chronology. We have sampled three ‘Findlinge' (glacially transported boulders) located on the right-lateral margin of the Aare glacier at Möschberg, Grosshöchstetten, southeast of Bern, with the aim of shedding light on this topic. The boulders have the same depositional, but different post-depositional histories: simple exposure; exhumation; and human impact. This sampling is specially selected for this study, since the boulders showing exhumation and human impact would not have been sampled in a regular surface-exposure dating application. We measured cosmogenic 10Be concentrations and calculated apparent exposure ages that are 13.6±0.5, 18.1±0.8, and 7.5±0.4ka, respectively. The exposure age of the first boulder reflects exhumation. The apparent exposure age of 18.1±0.8ka (erosion-corrected exposure age 19.0±0.9ka) from the second boulder correlates well with the end of the Alpine and global last glacial maximum. The third boulder shows evidence of quarrying as it is surrounded by a rim of excavation material, which is also reflected by the 7.5±0.4ka apparent exposure age. We modeled the variation of 10Be concentrations with depth down into the sediment in which the first (exhumed) boulder was once buried in, and down into the third (quarried) boulder. According to our modeling, we determined that the exhumed ‘Findling' was buried in sediment at a depth of around 0.5m, and around 2m of rock was quarried from the third ‘Findling'. Our results reveal the importance of sampling for surface-exposure dating within a well defined field context, as post-depositional impacts can easily hinder exposure-dating of surface

Erratum to: Cosmogenic 10Be-derived denudation rates of the Eastern and Southern European Alps

Denudation rates from cosmogenic 10Be measured in quartz from recent river sediment have previously been used in the Central Alps to argue that rock uplift occurs through isostatic response to erosion in the absence of ongoing convergence. We present new basin-averaged denudation rates from large rivers in the Eastern and Southern European Alps together with a detailed topographic analysis in order to infer the forces driving erosion. Denudation rates in the Eastern and Southern Alps of 170-1,400mmky−1 are within a similar range to those in the Central Alps for similar lithologies. However, these denudation rates vary considerably with lithology, and their variability generally increases with steeper landscapes, where correlations with topographic metrics also become poorer. Tertiary igneous rocks are associated with steep hillslopes and channels and low denudation rates, whereas pre-Alpine gneisses usually exhibit steep hillslopes and higher denudation rates. Molasse, flysch, and schists display lower mean basin slopes and channel gradients, and, despite their high erodibility, low erosion rates. Exceptionally low denudation rates are also measured in Permian rhyolite, which has high mean basin slopes. We invoke geomorphic inheritance as a major factor controlling erosion, such that large erosive glaciers in the late Quaternary cold periods were more effective in priming landscapes in the Central Alps for erosion than in the interior Eastern Alps. However, the difference in tectonic evolution of the Eastern and Central Alps potentially adds to differences in their geomorphic response; their deep structures differ significantly and, unlike the Central Alps, the Eastern Alps are affected by ongoing tectonic influx due to the slow motion and rotation of Adria. The result is a complex pattern of high mountain erosion in the Eastern Alps, which has evolved from one confined to the narrow belt of the Tauern Window in late Tertiary time to one affecting the entire underthrust basement, orogenic lid, and parts of the Southern Alps toda

Cosmogenic 10Be-derived denudation rates of the Eastern and Southern European Alps

Denudation rates from cosmogenic 10Be measured in quartz from recent river sediment have previously been used in the Central Alps to argue that rock uplift occurs through isostatic response to erosion in the absence of ongoing convergence. We present new basin-averaged denudation rates from large rivers in the Eastern and Southern European Alps together with a detailed topographic analysis in order to infer the forces driving erosion. Denudation rates in the Eastern and Southern Alps of 170-1,400mmky−1 are within a similar range to those in the Central Alps for similar lithologies. However, these denudation rates vary considerably with lithology, and their variability generally increases with steeper landscapes, where correlations with topographic metrics also become poorer. Tertiary igneous rocks are associated with steep hillslopes and channels and low denudation rates, whereas pre-Alpine gneisses usually exhibit steep hillslopes and higher denudation rates. Molasse, flysch, and schists display lower mean basin slopes and channel gradients, and, despite their high erodibility, low erosion rates. Exceptionally low denudation rates are also measured in Permian rhyolite, which has high mean basin slopes. We invoke geomorphic inheritance as a major factor controlling erosion, such that large erosive glaciers in the late Quaternary cold periods were more effective in priming landscapes in the Central Alps for erosion than in the interior Eastern Alps. However, the difference in tectonic evolution of the Eastern and Central Alps potentially adds to differences in their geomorphic response; their deep structures differ significantly and, unlike the Central Alps, the Eastern Alps are affected by ongoing tectonic influx due to the slow motion and rotation of Adria. The result is a complex pattern of high mountain erosion in the Eastern Alps, which has evolved from one confined to the narrow belt of the Tauern Window in late Tertiary time to one affecting the entire underthrust basement, orogenic lid, and parts of the Southern Alps toda

Radiochemical analysis of concrete samples from accelerator waste

For the decommissioning and disposal of shielding concrete from accelerator facilities, the Swiss Authorities require information on the radionuclide inventory. Besides the easy-to-measure γ-emitters 152Eu, 60Co, 44Sc, 133Ba, 154Eu, 134Cs, 144Ce, 22Na, also long-lived radionuclides emitting α- or β-radiation like 129I, 10Be, 36Cl, 239/240Pu and 238U have to be studied in order to obtain an overview to which extent they are produced and whether they represent a safety issue. In this study, we present the chemical separation and determination of selected radionuclides in shielding concrete from two different positions in the accelerator facilities at the Paul Scherrer Institute (PSI), the BX2 station, which was shut down in 1998, and the environment of the target M station, where the samples were taken in 1985 during reconstruction. The results of the measurements show that in no case the radionuclide content represents a safety risk. The components can be decommissioned corresponding to the Swiss safety regulation

Origin and age of submarine ferromanganese hardgrounds from the Marion Plateau, offshore northeast Australia

Be and Nd isotope compositions and metal concentrations (Mn, Fe, Co, Ni, and Cu) of surface and subsurface ferromanganese hardground crusts from Ocean Drilling Program Leg 194 Marion Plateau Sites 1194 and 1196 provide new insights into the crusts' genesis, growth rates, and ages. Metal compositions indicate that the hardgrounds, which have grown on erosional surfaces in water depths of <400 m because of strong bottom currents, are not pure hydrogenetic precipitates. Nevertheless, the ratios between cosmogenic 10Be and stable 9Be in hardgrounds from the present-day seafloor at Site 1196 between 1 x 10–7 and 1.5 x 10–7 are within the range of values expected for Pacific seawater, which shows that the hardgrounds recorded the isotope composition of ambient seawater. This is also confirmed by their Nd isotope composition (Nd between –3 and 0). The 10Be/9Be ratios in the up to 30-mm-thick and partly laminated hardgrounds do not show a decrease with depth, which suggests high growth rates on the present-day seafloor. The subsurface crust at Site 1194 (117 m below the seafloor) grew during a sedimentation hiatus, when bottom currents in the late Miocene prevented sediment accumulation on the carbonate platform during a sea level lowstand. The age of 8.65 ± 0.50 Ma for this crust obtained from 10Be-based dating agrees well with the combined seismostratigraphic and biostratigraphic evidence, which suggests an age for the hiatus between 7.7 and 11.8 Ma

Tool Wear Segmentation in Blanking Processes with Fully Convolutional Networks based Digital Image Processing

The extend of tool wear significantly affects blanking processes and has a decisive impact on product quality and productivity. For this reason, numerous scientists have addressed their research to wear monitoring systems in order to identify or even predict critical wear at an early stage. Existing approaches are mainly based on indirect monitoring using time series, which are used to detect critical wear states via thresholds or machine learning models. Nevertheless, differentiation between types of wear phenomena affecting the tool during blanking as well as quantification of worn surfaces is still limited in practice. While time series data provides partial insights into wear occurrence and evolution, direct monitoring techniques utilizing image data offer a more comprehensive perspective and increased robustness when dealing with varying process parameters. However, acquiring and processing this data in real-time is challenging. In particular, high dynamics combined with increasing strokes rates as well as the high dimensionality of image data have so far prevented the development of direct image-based monitoring systems. For this reason, this paper demonstrates how high-resolution images of tools at 600 spm can be captured and subsequently processed using semantic segmentation deep learning algorithms, more precisely Fully Convolutional Networks (FCN). 125,000 images of the tool are taken from successive strokes, and microscope images are captured to investigate the worn surfaces. Based on findings from the microscope images, selected images are labeled pixel by pixel according to their wear condition and used to train a FCN (U-Net)

Surface exposure ages imply multiple low-amplitude Pleistocene variations in East Antarctic Ice Sheet, Ricker Hills, Victoria Land

One of the major issues in (palaeo-) climatology is the response of Antarctic ice sheets to global climate changes. Antarctic ice volume has varied in the past but the extent and timing of these fluctuations are not well known. In this study, we address the question of amplitude and timing of past Antarctic ice level changes by surface exposure dating using in situ produced cosmogenic nuclides (10Be and 21Ne). The study area lies in the Ricker Hills, a nunatak at the boundary of the East Antarctic Ice Sheet in southern Victoria Land. By determining exposure ages of erratic boulders from glacial drifts we directly date East Antarctic Ice Sheet variations. Erosion-corrected neon and beryllium exposure ages indicate that a major ice advance reaching elevations of about 500m above present ice levels occurred between 1.125 and 1.375 million years before present. Subsequent ice fluctuations were of lesser extent but timing is difficult as all erratic boulders from related deposits show complex exposure histories. Sample-specific erosion rates were on the order of 20-45cmMa-1 for a quartzite and 10-65cmMa-1 for a sandstone boulder and imply that the modern cold, arid climate has persisted since at least the early Pleistocen

The Chironico landslide (Valle Leventina, southern Swiss Alps): age and evolution

In this study, we focus on the postglacial Chironico landslide in Valle Leventina, the valley of the Ticino river immediately south of the Gotthard pass (southern Swiss Alps). At Chironico, 530 millionm3 of granite gneiss detached from the eastern wall of Valle Leventina and slid along valley-ward dipping foliation joints and fractures. The slide mass was deposited into the valley bottom and blocked the Ticino river, as well as a tributary, the Ticinetto stream, on the opposite side of the valley. Wood fragments found in lacustrine sediments in the slide-dammed upstream lake were previously dated, yielding a minimum age for the landslide of approximately 13,500calyears BP. Based on the deposit morphology, the landslide was in the past interpreted as being composed of two events. In order to directly date the landslide, ten boulders were dated using the cosmogenic nuclides 10Be and 36Cl. Mean exposure ages indicate that the landslide occurred at 13.38±1.03ka BP, during the Bølling-Allerød interstadial. This implies that the Chironico landslide, one of the few pre-Holocene slides known in Alps, is also the oldest in crystalline rock. With runout modelling using DAN3D we could reproduce the hypothesized single-event failure scenario, as well as the character and extent of motion of the landslide mass. Both the ages and the modelling suggest that the landslide was released in one event around 3,000years following deglaciation

Design Guidelines for interlocked stator cores made of CoFe sheets

CoFe lamination stacks used for high-performance electric motors can be manufactured economically in high volumes by interlocking. In order to ensure sufficient joint strength with minimized sheet thickness, a comprehensive knowledge of the influences of various process parameters, such as embossing depth, clearance and counter punch force, is essential. To analyze these parameters, which also influence the magnetic properties, experiments are carried out and resulting joint strengths are determined in top tensile tests. The negative influences of the cutting process on magnetic conductivity and thus hysteresis losses due to residual stresses and plastic deformation are well known. In the subsequent stacking step, an influence of embossing and pre-stresses on the material properties is expected. In addition, local electrical contacts between the sheets may occur due to the interlocking process, causing additional eddy currents. Loss measurements are conducted to investigate the effect of the joining process on the magnetic properties of the stack. In doing so, the influence of process parameters such as the embossing depth and clearance on eddy current power losses is analyzed