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In this work we show how to retrieve information about temporal changes of turbulence in the atmosphere based on in situ wind velocity measurements performed by aircraft. We focus on the stratocumulus-topped boundary layer high-resolution data taken by a helicopter-borne platform Airborne Cloud Turbulence Observation System (ACTOS). We calculate two nondimensional indicators, the dissipation factor and the integral-to-Taylor-scale ratio, and study their dependence on the Taylor-scale-based Reynolds number. By analyzing these results, we can identify regions where turbulence is in its stationary state and regions where turbulence decays in time or, on the contrary, becomes stronger. We can also detect nonequilibrium turbulence states, which indicate the presence of rapidly changing external conditions.

We compare turbulence properties in coupled and decoupled marine stratocumulus-topped boundary layers (STBLs) using high-resolution in situ measurements performed by the helicopter-borne Airborne Cloud Turbulence Observation System (ACTOS) platform in the region of the eastern North Atlantic. The thermodynamically well-mixed coupled STBL was characterized by a comparable latent heat flux at the surface and in the cloud-top region, and substantially smaller sensible heat flux in the entire depth. Turbulence kinetic energy (TKE) was efficiently generated by buoyancy in the cloud and at the surface, and dissipated with comparable rate across the entire depth. Structure functions and power spectra of velocity fluctuations in the inertial range were reasonably consistent with the predictions of Kolmogorov theory. The turbulence was close to isotropic. In the decoupled STBL, decoupling was most obvious in humidity profiles. Heat fluxes and buoyant TKE production at the surface were similar to the coupled case. Around the transition level, latent heat flux decreased to zero and TKE was consumed by weak stability. In the cloud-top region, heat fluxes almost vanished and buoyancy production was significantly smaller than for the coupled case. The TKE dissipation rate inside the decoupled STBL varied between its sublayers. Structure functions and power spectra in the inertial range deviated from Kolmogorov scaling. This was more pronounced in the cloud and subcloud layer in comparison to the surface mixed layer. The turbulence was more anisotropic than in the coupled STBL, with horizontal fluctuations dominating. The degree of anisotropy was largest in the cloud and subcloud layer of the decoupled STBL. Integral length scales, of the order of 100 m in both cases, indicate turbulent eddies smaller than the depth of the coupled STBL or of the sublayers of the decoupled STBL. We hypothesize that turbulence produced in the cloud or close to the surface is redistributed across the entire coupled STBL but rather only inside the sublayers where it was generated in the case of the decoupled STBL. Scattered cumulus convection, developed below the stratocumulus base, may play a role in transport between those sublayers.

Magnesium-based lightweight structural materials exhibit potential for energy savings. However, the state-of-the-art quest for novel compositions with improved properties through conventional bulk metallurgy is time, energy, and material intensive. Here, the opportunities provided by combinatorial thin film materials design for the sustainable development of magnesium alloys are evaluated. To characterise the impurity level of (Mg,Ca) solid solution thin films within grains and grain boundaries, scanning transmission electron microscopy and atom probe tomography are correlatively employed. It is demonstrated that control of the microstructure enables impurity levels similar to bulk-processed alloys. In order to substantially reduce time, energy, and material requirements for the sustainable development of magnesium alloys, we propose a three-stage materials design strategy: (1) Efficient and systematic investigation of composition-dependent phase formation by combinatorial film growth. (2) Correlation of microstructural features and mechanical properties for selected composition ranges by rapid alloy prototyping. (3) Establishment of synthesis–microstructure–property relationships by conventional bulk metallurgy.

A natural radioactivity in thermal water was investigated based on 19 selected thermal waters from Poland. The analysed results show that the radionuclides’ concentrations in the study waters vary over a wide range. The temperature of the waters varies from above 20 °C to above 80 °C. The waters are characterised by different mineralisation, chemical compositions, and belong to different hydrochemical types. There is a good correlation between the water temperature and the depths of the aquifer formations occurrence, suggesting the thermal energy originates from the thermal geogradient. The concentration of radium is well correlated with the water mineralisation. The ratio of radium activity (226Ra/228Ra) in groundwater relates not only the ratio of uranium activity to that of thorium (238U/232Th) in aquifer formation, but also depends on the physical and chemical water properties. Based on the concentration of radon and its transport model, the radiation exposures due to inhalation of 222Rn and its progeny for employees and clients of the spa were assessed. The use of the thermal waters as a drinking resource may be problematic due to the possibility of exceeding the recommended annual committed effective dose 0.1 mSv.

We report on the Azores Stratocumulus Measurements of Radiation, Turbulence and Aerosols (ACORES) campaign, which took place around Graciosa and Pico Islands/Azores in July 2017. The main objective was to investigate the vertical distribution of aerosol particles, stratocumulus microphysical and radiative properties, and turbulence parameters in the eastern North Atlantic. The vertical exchange of mass, momentum, and energy between the free troposphere (FT) and the cloudy marine boundary layer (MBL) was explored over a range of scales from submeters to kilometers. To cover these spatial scales with appropriate measurements, helicopter-borne observations with unprecedented high resolution were realized using the Airborne Cloud Turbulence Observation System (ACTOS) and Spectral Modular Airborne Radiation Measurement System–Helicopter-Borne Observations (SMART-HELIOS) instrumental payloads. The helicopter-borne observations were combined with ground-based aerosol measurements collected at two continuously running field stations on Pico Mountain (2,225 m above sea level, in the FT), and at the Atmospheric Radiation Measurement (ARM) station on Graciosa (at sea level). First findings from the ACORES observations we are discussing in the paper are as follows: (i) we have observed a high variability of the turbulent cloud-top structure on horizontal scales below 100 m with local temperature gradients of up to 4 K over less than 1 m vertical distance, (ii) we have collected strictly collocated radiation measurements supporting the relevance of small-scale processes by revealing significant inhomogeneities in cloud-top brightness temperature to scales well below 100 m, and (iii) we have concluded that aerosol properties are completely different in the MBL and FT with often-complex stratification and frequently observed burst-like new particle formation.

Developments in the field of nanostructures open new ways for designing and manufacturing innovative materials. Here, we focused on new original ways of calculating energy changes during the substitution of foreign ions into the structure of apatites and bioapatites. Using these tools, the energetic costs of ion exchanges were calculated for the exemplary cases known from the literature. It was established that the most costly were ion exchanges of some cations inside apatites and of anions, and the least costly exchanges in tetrad channel positions. Real energy expenses for bioapatites are much smaller in comparison to mineral apatites due to the limited involvement of magnesium and carbonates in the structure of hard tissues. They are of the order of several electron volts per ion. The rigorous dependences of the energy changes and crystallographic cell volumes on the ionic radii of introduced cations were proved. The differentiation of the positioning of foreign ions in locations of Ca(I) and Ca(II) could be calculated in the case of a Ca-Pb reaction in hydroxyapatite. The energetic effects of tooth aging were indicated. The ability of energy change calculation during the ion exchange for isomorphic substances widens the advantages resulting from X-ray diffraction measurements.

The representation of subtropical stratocumulus and trade‐wind cumulus clouds by preliminary versions of Integrated Forecasting System (IFS) and ICON km‐scale global coupled climate models is explored. These models differ profoundly in their strategy to represent subgrid‐scale processes. The IFS employs complex parameterizations, including eddy‐diffusivity mass‐flux and convection schemes. ICON applies a minimal set of paramaterizations, including the Smagorinsky‐Lilly closure. Five‐year simulations are performed and evaluated for their representation of cloud albedo, its variability with environmental parameters and the vertical structure of the atmospheric boundary layer in eight regions: four corresponding to canonical Atlantic and Pacific stratocumulus and four in their downstream trades. For stratocumulus, both models capture the albedo's mean, annual cycle, and its relationship with the parameters relevant for low cloudiness, including lower tropospheric stability. They simulate an expected thermodynamic vertical structure of a stratocumulus‐topped boundary layer. ICON largely exhibits a lower cloud base and inversion height than IFS. We speculate the disagreement can be attributed to the contrasting treatment of subgrid mixing and cloud top entrainment. In the case of trade‐wind cumulus, both models well differentiate the cloud amount, the character of annual cycles and parameter correlations, and the vertical structure from the upstream stratocumulus. The annual cycles and parameter correlations reflect the dry and wet periods. Both models overestimate mean albedo and underestimate the strength of trade‐wind inversion. With an additional ICON run, we demonstrate the strong sensitivity of stratocumulus and the weaker response of trade‐wind cumulus to the treatment of subgrid mixing. Plain Language Summary Low‐level clouds over tropical oceans play an important role in regulating climate and shaping its response to changes because they reflect much of the incoming solar radiation. We explore how the two types of such clouds ‐ stratocumulus and trade‐wind cumulus ‐ are simulated by the two novel global climate models: Integrated Forecasting System (IFS) and ICON. The models cover the Earth with the grid cells of about 5 km. They differ in handling the processes occurring at the scales smaller than the grid cell. The IFS employs sophisticated routines while ICON adopts a much simpler approach with limited options for adjustments. Our analysis focused on eight regions over the Atlantic and Pacific: four corresponding to frequent stratocumulus cover and four dominated by trade‐wind cumulus. Both models simulate average stratocumulus amount and the changes of its properties throughout the year in agreement with satellite observations. Their skill is comparable despite differing modeling strategy. In the case of trade‐wind cumulus, both models overestimate the cloud amount, yet cumuli structures appear in the expected regions and follow the changes characteristic of dry and wet seasons. Additionally, we demonstrate that simulated stratocumulus amount depends sensitively on the strength of the mixing between the cloud and the warm dry air above. Key Points Early versions of IFS and ICON km‐scale global climate models satisfactorily simulate albedo and vertical structure for subtropical clouds Despite distinct approaches to sub‐grid parameterizations, the models achieve comparable skills in the stratocumulus regions Stratocumulus exhibits strong sensitivity to the treatment of cloud top mixing by sub‐grid turbulence scheme

The classical theory of homogeneous isotropic turbulence predicts that the ratio of transverse to longitudinal structure functions or power spectra is equal to 4/3 in the inertial subrange. For the typical turbulence cascade in the inertial subrange, it also predicts a power law scaling with an exponent of +2/3 and -5/3 for the structure functions and the power spectra, respectively. The goal of this study is to document the statistics of those ratios and exponents derived from aircraft observations, quantify their departures from theoretical predictions, and point out the differences among the aircraft. We estimate the transverse-to-longitudinal ratios and the scaling exponents from in situ high-rate turbulence measurements collected by three research aircraft during four field experiments in two regimes of the marine atmospheric boundary layer: shallow trade-wind convection and subtropical stratocumulus. The bulk values representing the inertial subrange were derived by fitting power law formulae to the structure functions and to the power spectra computed separately for the three components of the turbulent wind velocity measured in horizontal flight segments. The composite scale-by-scale transverse-to-longitudinal ratios were derived by averaging over the segments at common non-dimensional scales. The variability in the results can be attributed to how the wind velocity components are measured on each aircraft. The differences related to environmental conditions, e.g. between characteristic levels and regimes of the boundary layer, are of secondary importance. Experiment-averaged transverse-to-longitudinal ratios are 23 %–45 % smaller than predicted by the theory. The deviations of average scaling exponents with respect to the theoretical values range from −34 % to +47 % for structure functions and from −24 % to +22 % for power spectra, depending on experiment and velocity component. The composite scale-by-scale transverse-to-longitudinal ratios decrease and increasingly depart from 4/3 with decreasing scale, in contrast to previous experimental studies on local isotropy. The reason for the disagreement in transverse-to-longitudinal ratios between the observations and the theory remains uncertain.

microRNAs shape the identity and function of cells by regulating gene expression. It is known that brain-specific miR-9 is controlled transcriptionally; however, it is unknown whether post-transcriptional processes contribute to establishing its levels. Here we show that miR-9 is regulated transcriptionally and post-transcriptionally during neuronal differentiation of the embryonic carcinoma cell line P19. We demonstrate that miR-9 is more efficiently processed in differentiated than in undifferentiated cells. We reveal that Lin28a affects miR-9 by inducing the degradation of its precursor through a uridylation-independent mechanism. Furthermore, we show that constitutively expressed untagged but not GFP-tagged Lin28a decreases differentiation capacity of P19 cells, which coincides with reduced miR-9 levels. Finally, using an inducible system we demonstrate that Lin28a can also reduce miR-9 levels in differentiated P19 cells. Together, our results shed light on the role of Lin28a in neuronal differentiation and increase our understanding of the mechanisms regulating the level of brain-specific microRNAs. microRNAs regulate gene expression and control cell fate and differentiation processes. In this work, Nowak et al . reveal that brain-specific miR-9 is under post-transcriptional control and that the pre-miR-9 binding protein Lin28a decreases the levels of mature miR-9 during retinoic acid-mediated neuronal differentiation.

A commercial shadowgraph system, the Oxford Lasers VisiSize D30, originally designed to characterize industrial and agricultural sprays, was tested with respect to its application for measuring cloud microphysical properties such as droplet size distribution and number concentration. A laboratory experiment with a dense stream of polydisperse cloud-like droplets indicated a strong dependence of the depth of field, and thus also the sample volume, on particle size. This relationship was determined and a suitable correction method was developed to improve estimations of droplet number concentration and size distribution. The spatial homogeneity of the detection probability inside the sample volume and the minimum droplet diameter providing uniform detection were examined. A second experiment with monodisperse droplets produced by a Flow Focusing Monodisperse Aerosol Generator (FMAG) verified the sizing accuracy and demonstrated reasonable agreement between the instruments. Effects of collisions and the evaporation of droplets produced by the FMAG were observed. Finally, when the instrument was applied to sample atmospheric clouds at a mountain-based observatory, it performed reliably during a 3-week-long field experiment. Based on the laboratory and field tests, recommendations concerning the use of the instrument for cloud droplet measurements were formulated.