The Western Siberia Lowland (WSL), the world's largest permafrost peatland, is of importance for understanding the high-latitude carbon (C) cycle and its response to climate change. Warming ...temperatures increase permafrost thaw and production of greenhouse gases. Also, permafrost thaw leads to the formation of lakes which are hotspots for atmospheric C emissions. Although lakes occupy ~6% of WSL, lake C emissions from WSL remain poorly quantified. Here we show high C emissions from lakes across all permafrost zones of WSL. The C emissions were especially high in shoulder seasons and in colder permafrost-rich regions. The total C emission from permafrost-affected lakes of WSL equals ~12 ± 2.6 Tg C yr
and is 2-times greater than region's C export to the Arctic coast. The results show that C emission from WSL lakes is a significant component in the high-latitude C cycle, but also suggest that C emission may decrease with warming.
Despite relatively good knowledge of the biogeochemistry of Siberian thermokarst lakes during summer base flow, their seasonal dynamics remains almost unexplored. This work describes the chemical ...composition of ~130 thermokarst lakes ranging in size from a few m2 to several km2, located in the discontinuous permafrost zone. Lakes were sampled during spring flood, just after the ice break (early June), the end of summer (August), the beginning of ice formation (October) and during the full freezing season in winter (February). The lakes larger than 1000 m2 did not exhibit any statistically significant control of the lake size on dissolved organic carbon (DOC), the major and trace element concentrations over three major open water seasons. On the annual scale, the majority of dissolved elements including organic carbon increased their concentration from 30 to 500%, with a statistically significant (p < 0.05) trend from spring to winter. The concentrations of most trace elements (TEs) increased in the order spring > summer > autumn > winter. The ice formation in October included several stages: first, surface layer freezing followed by crack (fissure) formation with unfrozen water from the deeper layers spreading over the ice surface. This water was subsequently frozen and formed layered ice rich in organic matter. As a result, the DOC and metal (Mn, Fe, Ni, Cu, Zn, As, Ba and Pb) concentrations were highest near the surface of the ice column (0 to 20 cm) and decreased by a factor of 2 towards the bottom. The main implications of discovered freeze-driven solute concentrations in thermokarst lake waters are enhanced colloidal coagulation and removal of dissolved organic matter and associated insoluble metals from the water column to the sediments. The measured distribution coefficients of a TE between amorphous organo-ferric coagulates and lake water (<0.45 μm) were similar to those reported earlier for Fe-rich colloids and low molecular weight (<1 kDa, or <1–2 nm) fractions of thermokarst lake waters, suggesting massive co-precipitation of TE with amorphous Fe oxyhydroxide stabilized by organic matter. Although the concentration of most elements was lowest in spring, this period of maximal water coverage of land created a significant reservoir of DOC and soluble metals in the water column that can be easily mobilized to the hydrological network. The highest DOC concentration observed in the smallest (<100 m2) water bodies in spring suggests their strongly heterotrophic status and, therefore, a potentially elevated CO2 flux from the lake surface to the atmosphere.
Bose-Einstein condensation of magnons is one of few macroscopic quantum phenomena observed at room temperature. Since its discovery, it became an object of intense research, which led to the ...observation of many exciting phenomena such as quantized vortices, second sound, and Bogolyubov waves. However, it remained unclear what physical mechanisms can be responsible for the spatial stability of the magnon condensate. Indeed, since magnons are believed to exhibit attractive interaction, it is generally expected that the condensate is unstable with respect to the real-space collapse, contrarily to experimental findings. Here, we provide direct experimental evidence that magnons in a condensate exhibit repulsive interaction resulting in the condensate stabilization and propose a mechanism, which is responsible for this interaction. Our experimental conclusions are additionally supported by the theoretical model based on the Gross-Pitaevskii equation. Our findings solve a long-standing problem, providing a new insight into the physics of magnon Bose-Einstein condensates.
Methods for targeting enzymes exhibiting anticancer properties, such as methionine γ-lyase (MGL), have not yet been sufficiently developed. Here, we present the data describing the physico-chemical ...properties and cytotoxic effect of fusion protein MGL-S3 - MGL from Clostridium sporogenes translationally fused to S3 domain of the viral growth factor of smallpox. MGL-S3 has methioninase activity comparable to native MGL. In solution, MGL-S3 protein primarily forms octamers, whereas native MGL, on the contrary, usually forms tetramers. MGL-S3 binds to the surface of the neuroblastoma SH-SY5Y and epidermoid carcinoma A431 cells and, unlike native MGL, remains there and retains its cytotoxic effect after media removal. In HEK293T cells lacking EGFRs, no adhesion was recorded. Confocal fluorescence microscopy confirms the preferential adhesion of MGL-S3 to tumor cells, while it avoids getting into lysosomes. Both MGL and MGL-S3 arrest cell cycle of SH-SY5Y cells mainly in the G1 phase, while only MGL-S3 retains this ability after washing the cells.
Bose-Einstein condensation (BEC) of magnons is one of the few macroscopic quantum phenomena observable at room temperature. Due to the competition of the exchange and the magnetic dipole ...interactions, the minimum-energy magnon state is doubly degenerate and corresponds to two antiparallel non-zero wavevectors. Correspondingly, the room-temperature magnon BEC differs essentially from other condensates, since it takes place simultaneously at ± k
. The degeneracy of BEC and interaction between its two components have significant impact on condensate properties. Phase locking of the two condensates causes formation of a standing wave of the condensate density and quantized vortices. Additionally, interaction between the two components is believed to be important for stabilization of the condensate with respect to a real-space collapse. Thus, the possibility to create a non-degenerate, single-component condensate is decisive for understanding of underlying physics of magnon BEC. Here, we experimentally demonstrate an approach, which allows one to accomplish this challenging task. We show that this can be achieved by using a separation of the two components of the degenerate condensate in the real space by applying a local pulsed magnetic field, which causes their motion in the opposite directions. Thus, after a certain delay, the two clouds corresponding to different components become well separated in the real space. We find that motion of the clouds can be described well based on the peculiarities of magnon dispersion characteristics. Additionally, we show that, during the motion, the condensate cloud harvests non-condensed magnons, which results in a partial compensation of condensate depletion.
Thermokarst (thaw) lakes of the Western Siberian Lowland (WSL), the World´s largest permafrost peatland, contain important but poorly constrained stocks of organic carbon (OC) and nitrogen. These ...lakes are highly vulnerable to climate warming and permafrost thaw. The present work aims to quantify the OC and total nitrogen (TN) stocks and accumulation rates in sediments of 11 thermokarst lakes in the WSL across a permafrost gradient, from isolated to discontinuous and continuous permafrost. We found an increase in OC and TN stocks in lake sediments (0–30 cm) from the northern taiga with sporadic permafrost (285 Tg C and 10.5 Tg N) to the tundra zone with continuous permafrost (628 Tg C and 26 Tg N). The upper 30 cm thermokarst lake sediments of the permafrost-affected WSL store 1250 ± 35 Tg C and 50 ± 1.4 Tg N). The OC accumulation rates in thermokarst lake sediments ranged from 36 to 250 g C m
−2
year
−1
, which is 5 to 10 times higher than C accumulation rates in peatlands of western Siberia. The total OC accumulation in lakes of WSL is 7.8 ± 0.7 Tg C year
−1
. This is about 24–47% of the C emission from the WSL thermokarst lakes, implying that it represents an important factor in the C budget to consider in order to understand impacts of climate change and permafrost thaw on the C cycle.
A high quality inclusion-free Bi2Se3 crystal has been grown by the Bridgman method with the use of a rotating heat field. A large-area atomically flat Bi2Se3(0001) surface of excellent ...crystallographic quality has been formed by cleavage. Chemical and microstructural properties of the surface have been evaluated with reflection high-energy electron diffraction, atomic force microscopy (AFM), scanning tunneling microscopy (STM), spectroscopic ellipsometry, and X-ray photoelectron spectroscopy. There was no Bi2Se3(0001) surface oxidation detected after over a month in air under ambient conditions as shown by comparative core level spectroscopy, AFM, and STM.
Titanium dioxide (anatase, a-TiO
2
) films have been prepared by electron beam sputtering of a TiO
2
target in reactive atmosphere and their structural, microstructural, and optical properties were ...evaluated by reflection high- energy electron diffraction (RHEED) and x-ray diffraction (XRD) analyses, atomic force microscopy (AFM), and spectroscopic ellipsometry (SE). Different reflection models for determination of film optical parameters were tested and compared. The dispersive optical parameters were defined using the Tauc–Lorentz model by SE in the photon energy range of
E
= 1.12–4.96 eV. The films were transparent at
E
< 3 eV, but noticeable absorption was detected at
E
> 3 eV. The bandgap was estimated at the level of
E
g
≈ 3.44 eV.
To reveal the geographical and inter-species variability of the major and trace element (TE) compositions of freshwater mussel shells across Eurasia, we used ICP MS after acid digestion to analyze 50 ...samples of shells from five species of the genus Margaritifera spp. (Bivalvia: Margaritiferidae) collected in 20 minor rivers located in NW Russia, Sakhalin, Amur basin, Kuril Islands, Kamchatka and Laos. The variations between replicates from the same site were smaller than the variations between samples from different localities or between different mollusk species. Using normed PCA, we observed significant biological and geographical controls of the trace element composition in freshwater shells, with five main species exhibiting distinct features of TE concentration corresponding to four major geographical locations. Four PCA factors explain 81% of the TE variability, which is closely linked to specific geographical location and weakly linked to the identity of the species. The first two factors (F1×F2) are the element concentration and its biological affinity. The other two factors (F3×F4) likely are the nutrient status of the river, corresponding to its proximity to wetlands or mountains, and the degree of the influence of volcanic/hydrothermal activity. The analysis of water samples collected during the active growth period in summer baseflow was used to quantify the distribution coefficients (Kd) of trace elements between the aragonite shells and the river water. All species are significantly enriched in Mn relative to the river water, with distribution coefficients of up to 5. The other elements exhibit Kd values that were similar for the five species. This suggests that the obtained distribution coefficients may be universal constants reflecting uptake of each element by the organism from the river water and its intracellular transport and biocalcification processes. Taken together, the chemical composition data for pearl mussel shells may not only reflect the geographical locality and species identity but also provide insights into biochemical processes of element uptake in the form of biominerals.
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•Four factors control Ca-normalized TE distribution in freshwater shells.•Element concentration and biochemical affinity are the first two factors.•Landscape and the proximity to hydrothermal/volcanic sources are the two other factors.•All species are significantly enriched by Mn relative to the river water.•TE distribution coefficients between the shells and water are similar for five species.
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