No evidence for large subglacial source of mercury from the southwestern margin of the Greenland Ice Sheet.

In the current Matters Arising we present results from verifying control measurements of dissolved mercury (Hg) in glacial meltwater from the Greenland Ice Sheet (GrIS), which significantly challenges the conclusions of the recent publication by Hawkings et al. (2021). By direct measurements of meltwater in the same glacial catchment area, we demonstrate that the input Hg concentration for the regional upscaling in Hawkings et al (2021) is likely vastly over-estimated with major implications for the validity of the asserted extreme yield of Hg from the GrIS. In addition, we present a plausible explanation for the high Hg concentration values in the study, namely hitherto unidentified cross-contamination of water samples by mercury chloride (HgCl2), which was present and used for other purposes during field work. Together, the result of our control study potentially invalidates the suggested implications of geologically sourced Hg under the southwestern margin of the GrIS on the Arctic ecosystem in both current and future climate conditions.

Mechanical work accounts for most of the energetic cost in human running

The metabolic cost of human running is not well explained, in part because the amount of work performed actively by muscles is largely unknown. Series elastic tissues such as tendon can save energy by performing work passively, but there are few direct measurements of the active versus passive contributions to work in running. There are, however, indirect biomechanical measures that can help estimate the relative contributions to overall metabolic cost. We developed a simple cost estimate for muscle work in humans running (N = 8) at moderate speeds (2.2–4.6 m/s) based on measured joint mechanics and passive dissipation from soft tissue deformations. We found that even if 50% of the work observed at the lower extremity joints is performed passively, active muscle work still accounts for 76% of the net energetic cost. Up to 24% of this cost compensates for the energy lost in soft tissue deformations. The estimated cost of active work may be adjusted based on assumptions of multi-articular energy transfer, elasticity, and muscle efficiency, but even conservative assumptions yield active work costs of at least 60%. Passive elasticity can reduce the active work of running, but muscle work still explains most of the overall energetic cost.

Sustained coral reef growth in the critical wave dissipation zone of a Maldivian atoll

Sea-level rise is expected to outpace the capacity of coral reefs to grow and maintain their wave protection function, exacerbating coastal flooding and erosion of adjacent shorelines and threatening coastal communities. Here we present a new method that yields highly-resolved direct measurements of contemporary reef accretion on a Maldivian atoll reef rim, the critical zone that induces wave breaking. Results incorporate the suite of physical and ecological processes that contribute to reef accumulation and show growth rates vary from 6.6 ± 12.5 mm.y−1 on the reef crest, and up to 3.1 ± 10.2 mm.y−1, and −0.5 ± 1.8 mm.yr−1 on the outer and central reef flat respectively. If these short-term results are maintained over decades, the reef crest could keep pace with current sea-level rise. Findings highlight the need to resolve contemporary reef accretion at the critical wave dissipation zone to improve predictions of future reef growth, and re-evaluate exposure of adjacent shorelines to coastal hazards.

In silico analyses of blood flow and oxygen transport in human micro-veins and valves

BACKGROUND: Almost 95% of the venous valves are micron scale found in veins smaller than 300μm diameter. The fluid dynamics of blood flow and transport through these micro venous valves and their contribution to thrombosis is not yet well understood or characterized due to difficulty in making direct measurements in murine models. OBJECTIVE: The unique flow patterns that may arise in physiological and pathological non-actuating micro venous valves are predicted. METHODS: Computational fluid and transport simulations are used to model blood flow and oxygen gradients in a microfluidic vein. RESULTS: The model successfully recreates the typical non-Newtonian vortical flow within the valve cusps seen in preclinical experimental models and in clinic. The analysis further reveals variation in the vortex strengths due to temporal changes in blood flow. The cusp oxygen is typically low from the main lumen, and it is regulated by systemic venous flow. CONCLUSIONS: The analysis leads to a clinically-relevant hypothesis that micro venous valves may not create a hypoxic environment needed for endothelial inflammation, which is one of the main causes of thrombosis. However, incompetent micro venous valves are still locations for complex fluid dynamics of blood leading to low shear regions that may contribute to thrombosis through other pathways.

Application of ASAS method to PAMELA calorimeter

In this paper, we propose a method that makes it possible to to improve energy reconstruction for data obtained via thin heterogeneous calorimeters for direct measurements of cosmic rays with energies of TeV and higher. Despite the large number of modern experimental complexes, the primary energy of cosmic nuclei with energies above 1 TeV is determined with large errors associated with fluctuations in the development of the cascade. For heterogeneous calorimeters, transient effects give an additional negative effect. In this paper we analyze the main causes of fluctuations and discuss a method for reducing the effect of fluctuations on the results of primary energy reconstruction. The method of accumulation of signal along the spectrum (ASAS) is used to reduce fluctuations associated with transient effects. The method was tested using the heterogeneous calorimeter of the PAMELA collaboration. It is shown that the proposed approach makes it possible to correctly determine the energy of slowly developing showers, the maxima of which are not measured.

Semi-Experimental Determination of the Linear Clamped Electro-Optical Coefficients of Polar Crystals from Vibrational Spectroscopic Data

The present work highlights a new general method devoted to computations of the clamped linear electro-optical coefficients from the measured fundamental vibrational frequencies and the nonlinear dielectric susceptibility constants. The calculations are based on the formula analog to that of the Lyddane–Sachs–Teller relation, which is systematically used for the calculations of the clamped linear electro-optical coefficient of oxide ferroelectric crystals such as LiNbO3, LiTaO3, BaTiO3, PbTiO3, and KNbO3. The computed electro-optical coefficients are in good agreement with those obtained from direct measurements and the first-principles calculations or other semi-empirical models. In addition, the famous r51 or r42 coefficients of the tetragonal BaTiO3, PbTiO3, and KNbO3 crystals are finally calculated with high accuracy and discussed in connection with the soft mode behavior.

Spatial and subannual variability of the Antarctic Slope Current in an eddying ocean-sea ice model

The Antarctic Slope Current (ASC) circumnavigates the Antarctic continent following the continental slope and separating the waters on the continental shelf from the deeper offshore Southern Ocean. Water mass exchanges across the continental slope are critical for the global climate as they impact the global overturning circulation and the mass balance of the Antarctic ice sheet via basal melting. Despite the ASC’s global importance, little is known about its spatial and subannual variability, as direct measurements of the velocity field are sparse. Here, we describe the ASC in a global eddying ocean-sea ice model and reveal its large-scale spatial variability by characterising the continental slope using three regimes: the surface-intensified ASC, the bottom-intensified ASC and the reversed ASC. Each ASC regime corresponds to a distinct classification of the density field as previously introduced in the literature, suggesting that the velocity and density fields are governed by the same leading-order dynamics around the Antarctic continental slope. Only the surface-intensified ASC regime has a strong seasonality. However, large temporal variability at a range of other timescales occurs across all regimes, including frequent reversals of the current. We anticipate our description of the ASC’s spatial and subannual variability to be helpful to guide future studies of the ASC aiming to advance our understanding of the region’s response to a changing climate.

Temperature distribution in beech wood during vacuum drying

Temperature distribution in beech wood during vacuum drying. The temperature distribution and changes in humidity in beech wood in the form of friezes during drying in a vacuum were analysed. The intensity of the occurring phenomena of desorption and the volumetric flow of moisture through the anatomical structures of the wood, depending on the absolute pressure and the temperature of the process, was determined. It was found that the fastest temperature increase took place in the subsurface layers directly adjacent to the heating plates. The introduction of conditioning between the drying phases made it possible to even out the humidity and temperature distribution in the entire element. On the basis of the analysis of changes taking place between the volumes of the three components of wood, it was found that the volume of moisture in the form of vapor removed in the initial phase of drying is over 20 times greater than the volume of voids in wood structures, and in the following phases it decreases to 0.27. The average volume of vapour removed from 1 m3 of wood at the temperature of 55℃ is 13.9 m3/h, decreasing in the following phases to 9.1 m3/h at the drying temperature of 60℃ and then 3.1 m3/h at the temperature of 65℃. The drying rates for these phases reach the value of 0.15%/h, 0.17%/h and 0.075%/h, respectively. Direct measurements of wood moisture, made during the experimental course of the drying process at an absolute pressure of 150 hPa, follow the equivalent moisture, determined on the basis of the Hailwood-Horrobin model, taking into account the appropriate calculation factors.

Electronic Visualization of Underground Tourist Routes on the Example of the Route in Sandomierz

For many years in Poland, anthropogenic objects constructed underground have been very popular with tourists. In the past they fulfilled various functions (historic mines, underground merchant warehouses, military objects, special objects, caverns and grottoes). Many of them were secured and rebuilt in such a way that a new form was created. They make interesting tourist offers and still more objects can be made available to tourists. An example of strongly modified underground anthropogenic objects of very complex geometry and extremely interesting architectural form is the Underground Tourist Route (Polish: Podziemna Trasa Turystyczna – PTT) in Sandomierz. Owing to much effort and financial means, in 1960s many interesting cellars and merchant warehouses were saved from destruction – and – with the application of mining techniques, they were joint into attractive spatial forms. So far, few publications give the full characteristic and parametric data of this object. Today’s possibilities of available measurement and information technologies allow comprehensive inventory of complicated engineering constructions, as well as the 3D visualization, regarding even tiniest elements of small architecture (doors, lattice, lamps, etc.). The article presents the results of the visualization and parameterization based on the data from integrated surveying (levelling, transects, total stations, laser scanning and other direct measurements). ELEKTRONICZNA WIZUALIZACJA PODZIEMNYCH TRAS TURYSTYCZNYCH NA PRZYKŁADZIE TRASY W SANDOMIERZU W Polsce dużą popularnością turystyczną od lat cieszą się obiekty antropogeniczne wzniesione pod powierzchnią ziemi, pełniące różnorodne funkcje użytkowe w przeszłości (zabytkowe kopalnie, podziemne składy kupieckie, obiekty militarne, obiekty specjalne, jaskinie i groty). Wiele z nich zostało w stopniu istotnym zabezpieczone i przebudowane w taki sposób, by nadać im nową formę. Udostępnione, dziś stanowią ciekawe oferty turystyczne, a ich liczba stanowi dziś zbiór otwarty. Przykładem mocno przetworzonego podziemnego obiektu antropogenicznego o bardzo zróżnicowanej geometrii i niezwykle ciekawej formie architektonicznej jest Podziemna Trasa Turystyczna w Sandomierzu. Dzięki zaangażowaniu wielu środków udało się w latach 60. XX w. ocalić od zniszczenia wiele interesujących piwnic i składów kupieckich i połączyć je z zastosowaniem technik górniczych w atrakcyjne formy przestrzenne. Dotychczas powstało niewiele opracowań, które ukazałyby w pełni ich charakterystykę oraz sparametryzowały obiekt. Możliwości dostępnych dzisiaj technik pomiarowych oraz informatycznych pozwalają na kompleksową inwentaryzację skomplikowanych budowli inżynierskich, a także wizualizację przestrzenną z uwzględnieniem nawet najdrobniejszych elementów małej architektury (drzwi, kraty, lampy itp.). W artykule zaprezentowano wyniki wizualizacji i parametryzacji na podstawie danych zintegrowanych pomiarów geodezyjnych (niwelacji, poligonizacji, tachimetrii elektronicznej, skaningu laserowego i innych pomiarów bezpośrednich).