The use of nanoshells as an exogenous absorber allows the usage of light sources that are minimally absorbed by tissue components, thereby, minimizing damage to surrounding tissue and allowing welding of thicker tissues.
Year-round observations of the physical snow and ice properties and processes that govern the ice pack evolution and its interaction with the atmosphere and the ocean were conducted during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition of the research vessel Polarstern in the Arctic Ocean from October 2019 to September 2020. This work was embedded into the interdisciplinary design of the 5 MOSAiC teams, studying the atmosphere, the sea ice, the ocean, the ecosystem, and biogeochemical processes. The overall aim of the snow and sea ice observations during MOSAiC was to characterize the physical properties of the snow and ice cover comprehensively in the central Arctic over an entire annual cycle. This objective was achieved by detailed observations of physical properties and of energy and mass balance of snow and ice. By studying snow and sea ice dynamics over nested spatial scales from centimeters to tens of kilometers, the variability across scales can be considered. On-ice observations of in situ and remote sensing properties of the different surface types over all seasons will help to improve numerical process and climate models and to establish and validate novel satellite remote sensing methods; the linkages to accompanying airborne measurements, satellite observations, and results of numerical models are discussed. We found large spatial variabilities of snow metamorphism and thermal regimes impacting sea ice growth. We conclude that the highly variable snow cover needs to be considered in more detail (in observations, remote sensing, and models) to better understand snow-related feedback processes. The ice pack revealed rapid transformations and motions along the drift in all seasons. The number of coupled ice–ocean interface processes observed in detail are expected to guide upcoming research with respect to the changing Arctic sea ice.
Sea ice thickness is a key parameter in the polar climate and ecosystem. Thermodynamic and dynamic processes alter the sea ice thickness. The Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition provided a unique opportunity to study seasonal sea ice thickness changes of the same sea ice. We analyzed 11 large-scale (∼50 km) airborne electromagnetic sea thickness and surface roughness surveys from October 2019 to September 2020. Data from ice mass balance and position buoys provided additional information. We found that thermodynamic growth and decay dominated the seasonal cycle with a total mean sea ice thickness increase of 1.4 m (October 2019 to June 2020) and decay of 1.2 m (June 2020 to September 2020). Ice dynamics and deformation-related processes, such as thin ice formation in leads and subsequent ridging, broadened the ice thickness distribution and contributed 30% to the increase in mean thickness. These processes caused a 1-month delay between maximum thermodynamic sea ice thickness and maximum mean ice thickness. The airborne EM measurements bridged the scales from local floe-scale measurements to Arctic-wide satellite observations and model grid cells. The spatial differences in mean sea ice thickness between the Central Observatory (<10 km) of MOSAiC and the Distributed Network (<50 km) were negligible in fall and only 0.2 m in late winter, but the relative abundance of thin and thick ice varied. One unexpected outcome was the large dynamic thickening in a regime where divergence prevailed on average in the western Nansen Basin in spring. We suggest that the large dynamic thickening was due to the mobile, unconsolidated sea ice pack and periodic, sub-daily motion. We demonstrate that this Lagrangian sea ice thickness data set is well suited for validating the existing redistribution theory in sea ice models. Our comprehensive description of seasonal changes of the sea ice thickness distribution is valuable for interpreting MOSAiC time series across disciplines and can be used as a reference to advance sea ice thickness modeling.
ABSTRACT. Personal samplers used to determine the inhalable fraction of workplace dust are tested while mounted on a manikin, which simulates a worker. To understand the mechanisms affecting the performance of such samplers, researchers must measure the air ow around the body where the samplers are mounted. Therefore, wind tunnel facilities to determine both air ow conditions around samplers and sampling ef ciency are needed.A wind tunnel system was developed that was large enough to accommodate the top half of a life-sized manikin and employed a laser Doppler velocimeter for velocity measurements around the manikin. For generating particles up to 70 m m, an aerosol generation system, using a two-dimensional scanning system to cover an extended area, was developed and tested. The generation system had carriages with linear bearings mounted on rod assemblies for scanning in the horizontal and vertical directions. Screw drives, powered by stepper motors under computer control, moved the carriages in a preprogrammed pattern. The generation system was characterized for its ability to generate uniform concentrations of aerosols over an extended area at wind speeds of 0.5 and 2 m/s and particle sizes of 7 and 70 m m. Uniformity of concentration over the area studied, in the absence of the manikin, was 10% relative standard deviation (RSD) or better, except for 7 m m particles at a wind speed of 0.5 m/s where some nonuniformity was observed. The uniformity under these conditions was improved by rearranging the distances between components in the wind tunnel.
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