We report on the simultaneous monitoring of sweat lactate concentration and sweat secretion rate. For this aim lactate oxidase-Prussian Blue enzyme-nanozyme type lactate biosensors were elaborated. ...The use of siloxane-perfluorosulfonated ionomer composite membrane for enzyme-nanozyme immobilization results in the biosensor displaying flux independence in the whole range of physiological sweat secretion rates (0.025–2 μl cm-2 min-1). On the contrary, current response of the biosensor based on solely siloxane membranes becomes saturated at physiological sweat lactate concentration, depending mostly on the flow rate. Accordingly, for simultaneous monitoring of sweat lactate concentration and its secretion rate both flow-through biosensors were integrated with high-accuracy wearable electronic devices allowing real-time remote monitoring. As found, during exhaustive physical exercise sweat secretion rate and lactate content are independent of each other, thus, confirming that this excretory liquid is suitable for non-invasive diagnostics.
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•Flow-independent enzyme-nanozyme lactate biosensors elaborated.•Wearable high-accuracy device for real-time remote metabolite monitoring designed.•The independence of sweat secretion rate and lactate content shown.
Osteogenic differentiation, the process by which bone marrow mesenchymal stem/stromal (a.k.a. skeletal stem) cells and osteoprogenitors form osteoblasts, is a critical event for bone formation during ...development, fracture repair, and tissue maintenance. Extra cellular and intracellular signaling pathways triggering osteogenic differentiation are relatively well known; however, the ensuing change in cell energy metabolism is less clearly defined. We and others have previously reported activation of mitochondria during osteogenic differentiation. To further elucidate the involved bioenergetic mechanisms and triggers, we tested the effect of osteogenic media containing ascorbate and β-glycerol phosphate, or various osteogenic hormones and growth factors on energy metabolism in long bone (ST2)- and calvarial bone (MC3T3-E1)-derived osteoprogenitors. We show that osteogenic media and differentiation factors, Wnt3a and BMP2, stimulate mitochondrial oxidative phosphorylation (OxPhos) with little effect on glycolysis. The activation of OxPhos occurs acutely, suggesting a metabolic signaling change rather than protein expression change. To this end, we found that the observed mitochondrial activation is Akt dependent. Akt is activated by osteogenic media, Wnt3a, and BMP2, leading to increased phosphorylation of various mitochondrial Akt targets, a phenomenon known to stimulate OxPhos. In sum, our data provide comprehensive analysis of cellular bioenergetics during osteoinduction in cells of two different origins (mesenchyme vs neural crest) and identify Wnt3a and BMP2 as physiological stimulators of mitochondrial respiration through Akt activation.
Despite non-invasive instant monitoring of sweat metabolites is becoming a general trend in early diagnostics and screening, the reliability and accuracy of the on-skin electrochemical biosensors in ...real-life scenarios still remain questionable. As a rule, mass transport effects in scantily excreted liquids are ignored, when considering the design of such wearable setups. Here we provide a comprehensive investigation of the disruption factors for commonly used Prussian Blue based (bio)sensors under different hydrodynamic conditions (2 × 10−5 – 5 × 100 mm s−1 electrolyte velocity). A huge effect of flow on the (bio)sensors response has been revealed and explained with transport limitations for both analyte influx and reaction product outflux. It suggests no need for improving the sensor sensitivity, while minimizing analyte consumption and enhancing product withdrawal. Some strategies concerning measurement schemes and sensor design ensuring reliable sweat analysis have been discussed and illustrated for lactate and glucose on-skin monitoring.
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Proton-selective membranes are prepared by electrochemical reduction of graphene oxide films in aqueous electrolytes. Rapid kinetics of oxygenated groups reduction was revealed by complementary FTIR- ...and XPS-spectroscopy giving rise to a partially reduced graphene oxide with C/O ratio in the range of 2–4. The reduction is accompanied by interstitial water loss and shrinkage of d-spacing from 1.15 nm, typical for graphene oxide, to graphene-like ∼0.36 nm as revealed by X-ray diffraction analysis. The presence of remaining oxygen groups in reduced graphene oxide enables fast transport of protons with Grotthuss hopping mechanism and diffusion coefficients in the range of 3–7∙10−11 m2 s−1 at 25 °C. At the same time, the reduction of GO layers hinders dramatically the transport of H2O molecules due to suppression of capillary condensation of water in the oxygen-deficient channels of the reduced graphene oxide providing the H+/H2O selectivity of up to 1400 upon electrochemical reduction. The suggested approach opens the avenue for the performance enhancement of carbon-based membranes for proton-selective transport in fuel cells and electrolyzers.
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•Proton-selective membranes are prepared by electrochemical reduction of GO films.•Reduction affects mostly carbonyls and hydroxyls, leaving epoxides mainly intact.•Shrinkage of GO interlayer spacing to 3.6–6.0 Å is induced upon reduction.•A drop in water permeance occurs combined with H+ diffusivity of 3–7∙10−11 m2·s−1•An increase in H+/H2O selectivity up to 1400 is achieved.
Global wetlands are believed to be climate sensitive, and are the largest natural emitters of methane (CH4). Increased wetland CH4 emissions could act as a positive feedback to future warming. The ...Wetland and Wetland CH4 Inter-comparison of Models Project (WETCHIMP) investigated our present ability to simulate large-scale wetland characteristics and corresponding CH4 emissions. To ensure inter-comparability, we used a common experimental protocol driving all models with the same climate and carbon dioxide (CO2) forcing datasets. The WETCHIMP experiments were conducted for model equilibrium states as well as transient simulations covering the last century. Sensitivity experiments investigated model response to changes in selected forcing inputs (precipitation, temperature, and atmospheric CO2 concentration). Ten models participated, covering the spectrum from simple to relatively complex, including models tailored either for regional or global simulations. The models also varied in methods to calculate wetland size and location, with some models simulating wetland area prognostically, while other models relied on remotely sensed inundation datasets, or an approach intermediate between the two. Four major conclusions emerged from the project. First, the suite of models demonstrate extensive disagreement in their simulations of wetland areal extent and CH4 emissions, in both space and time. Simple metrics of wetland area, such as the latitudinal gradient, show large variability, principally between models that use inundation dataset information and those that independently determine wetland area. Agreement between the models improves for zonally summed CH4 emissions, but large variation between the models remains. For annual global CH4 emissions, the models vary by ±40% of the all-model mean (190 Tg CH4 yr−1). Second, all models show a strong positive response to increased atmospheric CO2 concentrations (857 ppm) in both CH4 emissions and wetland area. In response to increasing global temperatures (+3.4 °C globally spatially uniform), on average, the models decreased wetland area and CH4 fluxes, primarily in the tropics, but the magnitude and sign of the response varied greatly. Models were least sensitive to increased global precipitation (+3.9 % globally spatially uniform) with a consistent small positive response in CH4 fluxes and wetland area. Results from the 20th century transient simulation show that interactions between climate forcings could have strong non-linear effects. Third, we presently do not have sufficient wetland methane observation datasets adequate to evaluate model fluxes at a spatial scale comparable to model grid cells (commonly 0.5°). This limitation severely restricts our ability to model global wetland CH4 emissions with confidence. Our simulated wetland extents are also difficult to evaluate due to extensive disagreements between wetland mapping and remotely sensed inundation datasets. Fourth, the large range in predicted CH4 emission rates leads to the conclusion that there is both substantial parameter and structural uncertainty in large-scale CH4 emission models, even after uncertainties in wetland areas are accounted for.
Abstract
It is shown that various sensors are used to ensure air traffic control in civil aviation, namely: primary and secondary radars, multilateration surveillance systems, automatic dependent ...surveillance systems of broadcast and contract types, multistatic radars. Based on the analysis of the main disadvantages of the considered systems, it was concluded that the use of multilateration aircraft surveillance systems (MLAT) is promising. The need to improve the reliability of MLAT is noted. The work proposes a method of structural and informational redundancy of MLAT based on the introduction of an additional receiver into its design. It allows to measure the distance to the aircraft using the energy method. The analysis of increasing the reliability of MLAT at various redundancy rates is carried out.
Abstract
It is shown that a significant disadvantage of the broadcast-type automatic dependent surveillance system (ADS-B) used to solve the problem of aviation surveillance is its vulnerability to ...spoofing attempts. To eliminate this disadvantage, it is currently proposed to use the monitoring of ADS-B data using multilateration aviation surveillance systems (MLAT). The work shows the necessity of MLAT modernization to ensure a reliable solution to the problem of aviation surveillance in the event of failure of one or more reception points. To do this, it is proposed to use hybrid methods for assessing the coordinates of an aircraft. It can reduce the number of minimum required receiving positions due to the structural and informational redundancy of the aviation surveillance system. Structures (scenarios) of hybrid multi-position aviation surveillance systems and algorithms for processing their measurements have been developed. The algorithms ensure an increase in the reliability of the formation of estimates of aircraft coordinates.
We propose pulse power generation (PPG) amperometry as an advanced readout realized for Prussian blue (PB)-based (bio)sensors. In contrast to the conventional power generation mode, when the current ...response is generated upon continuous short-circuiting, the suggested pulse regime is fulfilled by periodic opening and shorting of the circuit. Despite PB being electroactive, the pulse readout is advantageous over conventional steady-state power generation, providing up to a 15-fold increased signal-to-background ratio as well as dramatically improved sensitivity exceeding 10 A·M
·cm
for H
O
sensors and 3.9 A·M
·cm
for glucose biosensors. Such analytical performance characteristics are, most probably, achieved due to the enrichment of the diffusion layer by analyte mass transfer from the bulk upon opening of the circuit. Due to an improved sensitivity-to-background ratio, reduced flow-rate dependence, and enhanced operational stability, the regime allows reliable monitoring of blood glucose variations through sweat analysis with the on-skin device.
There is emerging interest in stem cell energy metabolism and its effect on differentiation. Bioenergetic changes in differentiating bone marrow mesenchymal stem cells (MSCs) are poorly understood ...and were the focus of our study. Using bioenergetic profiling and transcriptomics, we have established that MSCs activate the mitochondrial process of oxidative phosphorylation (OxPhos) during osteogenic differentiation, but they maintain levels of glycolysis similar to undifferentiated cells. Consistent with their glycolytic phenotype, undifferentiated MSCs have high levels of hypoxia-inducible factor 1 (HIF-1). Osteogenically induced MSCs downregulate HIF-1 and this downregulation is required for activation of OxPhos. In summary, our work provides important insights on MSC bioenergetics and proposes a HIF-based mechanism of regulation of mitochondrial OxPhos in MSCs.
Here we report on gas and vapor transport properties of ultra-thin graphene oxide (GO) membranes, with various C:O ratios. Graphene oxide nanosheets with an average lateral size of 800 nm and C:O ...ratio ranging from 2.11 to 1.81 have been obtained using improved Hummers’ method by variation of graphite:KMnO4 ratio. Thin-film selective layers based on the obtained graphene oxide have been spin-coated onto porous substrates. To extend the C:O range to 2.60, thermal reduction of GO membranes was applied. A decrease in C:O ratio leads to significant water vapor permeance growth to over 60 m3(STP)·m−2·bar−1·h−1 while the permeance towards permanent gases reduces slightly. According to the permeation and sorption measurements, a decisive role of H2O diffusivity has been established, while the water sorption capacity of the graphene oxide stays nearly independent of C:O ratio in GO. The result is supported by semi-empirical modeling which reveals diminution of H2O jump activation barriers with both increasing GO interlayer spacing and its oxidation degree. The height of the activation barriers was found to vary up to an order of magnitude within the entire range of relative humidity (0–100% RH), lowering significantly for strongly oxidized GO. Our results evidence the necessity of attaining maximum GO oxidation degree for improving water transport in GO, especially at low partial pressures.
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