The sluggish redox reaction kinetics for aprotic Li-O2 batteries (LOBs) caused by the insulating discharge product of Li2O2 could result in the poor round-trip efficiency, low rate capability, and cyclic stability. To address these challenges, we herein fabricated NiCo2S4 supported on reduced graphene oxide (NiCo2S4@rGO), the surface of which is further modified via a unique low-pressure capacitive-coupled nitrogen plasma (CCPN-NiCo2S4@rGO). The high ionization environment of the plasma could etch the surface of NiCo2S4@rGO, introducing effective nitrogen doping. The as-prepared CCPN-NiCo2S4@rGO has been employed as an efficient catalyst for advanced LOBs. The electrochemical analysis, combined with theoretical calculations, reveals that the N-doping can effectively improve the thermodynamics and kinetics for LiO2 adsorption, giving rise to a well-knit Li2O2 formation on CCPN-NiCo2S4@rGO. The LOBs based on the CCPN-NiCo2S4@rGO oxygen electrode deliver a low overpotential of 0.75 V, a high discharge capacity of 10,490 mA h g-1, and an improved cyclic stability (more than 110 cycles). This contribution may pave a promising avenue for facile surface engineering of the electrocatalyst in LOBs and other energy storage systems.
- Klíčová slova
- Li−O2 battery, NiCo2S4@rGO, electrocatalyst, oxygen electrodes, plasma engineering,
- Publikační typ
- časopisecké články MeSH
The Trichodesmium genus comprises some of the most abundant N2-fixing organisms in oligotrophic marine ecosystems. Since nitrogenase, the key enzyme for N2 fixation, is irreversibly inhibited upon O2 exposure, these organisms have to coordinate their N2-fixing ability with simultaneous photosynthetic O2 production. Although being the principal object of many laboratory and field studies, the overall process of how Trichodesmium reconciles these two mutually exclusive processes remains unresolved. This is in part due to contradictory results that fuel the Trichodesmium enigma. In this review, we sift through methodological details that could potentially explain the discrepancy between findings related to Trichodesmium's physiology. In doing so, we exhaustively contrast studies concerning both spatial and temporal nitrogenase protective strategies, with particular attention to more recent insights. Finally, we suggest new experimental approaches for solving the complex orchestration of N2 fixation and photosynthesis in Trichodesmium.
- Klíčová slova
- O2-scavenging mechanisms, cyanobacteria, diazocyte, immunolabelling, method comparison, microscopy,
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
OBJECTIVE: The aim of the study was to evaluate the impact of different concentrations of inspirated O2 on the SpO2 values of the foetus and the mother during the 1st and 2nd stages of labor. DESIGN: Prospective study. SETTING: 1st Department of Gynecology and Obstetrics, Medical Faculty of Masaryk University, Brno. METHODS: 17 non-risk patients were enrolled in the study. The SpO2 levels of the mother and the foetus were monitored simultaneously in 10 min intervals with the room air inspiration entrainment O2 mask and the inflatable face mask during 1st and 2nd stages of labor. RESULTS: No changes in maternal SpO2 values were revealed in the three different O2 inspiration regimens neither in the 1st, nor in the 2nd stages of labor. The mean value was 98% +/- 1.6 SD. As for the foetus the SpO2 values were increased by 6% (+/- 7.9 SD) after 40% concentration of O2 and 7.7% (+/- 8.8 SD) after 98% O2 inspiration during the 1st stage of labour. These values have decreased promptly after the cessation of the O2 inspiration. The mean SpO2 values at room O2 concentration were 46.3% +/- 7.9 SD for the 1st stage of labor and 43.7% +/- 4.8 SD for the 2nd stage of labor. CONCLUSION: The O2 inspiration during the labor has no impact on the maternal SpO2 values but increases the SpO2 values of the foetus during the 1st stage of labor. We were not able to evaluate the impact of the O2 inspiration on foetal SpO2 values during the 2nd stage of labor.
- MeSH
- dospělí MeSH
- fetální krev chemie MeSH
- kyslík krev MeSH
- lidé MeSH
- monitorování plodu MeSH
- oxygenoterapie * MeSH
- porodní děj krev MeSH
- prospektivní studie MeSH
- těhotenství MeSH
- Check Tag
- dospělí MeSH
- lidé MeSH
- těhotenství MeSH
- ženské pohlaví MeSH
- Publikační typ
- anglický abstrakt MeSH
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- kyslík MeSH
Variations in external O2 supply, tissue diffusivity, and O2 consumption rates determine internal O2 gradients in roots. We tested the hypothesis that root metabolism differs between cortex and stele tissues in response to external partial pressure of O2 (pO2). Using O2 microsensors, we measured in vivo O2 dynamics in Cicer arietinum, chickpea, primary roots of contrasting diameters exposed to different external pO2 levels. Respiratory O2 consumption was assessed in the isolated cortex (plus epidermis) and stele tissues. Additionally, activity profiles for 23 key enzymes of carbohydrate and antioxidant metabolism were determined under aerobic, hypoxic, and severely hypoxic conditions. The stele of thick roots (1900 μm) became severely hypoxic/anoxic (≤ 0.3 kPa) even under external air equilibrium, whereas thinner roots (900 μm) remained oxic-to-hypoxic (c. 11.9 kPa). The stele had a 3.3-fold higher O2 consumption rate than the cortex. In 1400 μm roots, severe hypoxia occurred in the stele at 8.9 kPa external pO2 and in the cortex at 4.5 kPa. Activities of carbohydrates and antioxidant enzymes were consistently higher in the stele than in the cortex, regardless of external pO2, indicating that tissue type, in addition to external O2 availability, plays a key role in determining root metabolic activity.
- Klíčová slova
- Cicer arietinum, O2 diffusion, anaerobic metabolism, anoxic cores, bulky tissues, respiration, stele hypoxia,
- MeSH
- antioxidancia metabolismus MeSH
- Cicer * metabolismus enzymologie účinky léků MeSH
- kořeny rostlin * metabolismus enzymologie účinky léků cytologie MeSH
- kyslík * metabolismus farmakologie MeSH
- metabolismus sacharidů MeSH
- parciální tlak MeSH
- spotřeba kyslíku MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- antioxidancia MeSH
- kyslík * MeSH
Radio frequency plasma is one of the means to modify the polymer surface namely in the activation of polypropylene membranes (PPM) with O2 plasma. Activated membranes were deposited with TiO2 nanoparticles by the dip coating method and the bare sample and modified sample (PPM5-TiO2) were irradiated by UV lamps for 20-120 min. Characterization techniques such as X-ray diffraction (XRD), Attenuated total reflection technique- Fourier transform infrared spectroscopy (ATR-FTIR), Thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), Scanning electron microscope (SEM) and water contact angle (WCA) measurements were applied to study the alteration of ensuing membrane surface properties which shows the nanoparticles on the sample surface including the presence of Ti on PPM. The WCA decreased from 135° (PPM) to 90° (PPM5-TiO2) and after UV irradiation, the WCA of PPM5-TiO2 diminished from 90° to 40°.
- Klíčová slova
- O2 plasma, PP membrane, TiO2 nanoparticles, UV treatment, hydrophilicity,
- MeSH
- difrakce rentgenového záření MeSH
- fotoelektronová spektroskopie MeSH
- kyslík chemie MeSH
- membrány umělé * MeSH
- nanočástice chemie MeSH
- plazmové plyny chemie MeSH
- polypropyleny chemie MeSH
- smáčivost MeSH
- spektroskopie infračervená s Fourierovou transformací MeSH
- teplota MeSH
- termogravimetrie MeSH
- titan chemie MeSH
- voda chemie MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- kyslík MeSH
- membrány umělé * MeSH
- plazmové plyny MeSH
- polypropyleny MeSH
- titan MeSH
- titanium dioxide MeSH Prohlížeč
- voda MeSH
Interaction of molecular oxygen with semiconducting oxide surfaces plays a key role in many technologies. The topic is difficult to approach both by experiment and in theory, mainly due to multiple stable charge states, adsorption configurations, and reaction channels of adsorbed oxygen species. Here we use a combination of noncontact atomic force microscopy (AFM) and density functional theory (DFT) to resolve [Formula: see text] adsorption on the rutile [Formula: see text](110) surface, which presents a longstanding challenge in the surface chemistry of metal oxides. We show that chemically inert AFM tips terminated by an oxygen adatom provide excellent resolution of both the adsorbed species and the oxygen sublattice of the substrate. Adsorbed [Formula: see text] molecules can accept either one or two electron polarons from the surface, forming superoxo or peroxo species. The peroxo state is energetically preferred under any conditions relevant for applications. The possibility of nonintrusive imaging allows us to explain behavior related to electron/hole injection from the tip, interaction with UV light, and the effect of thermal annealing.
- Klíčová slova
- O2, TiO2, nc-AFM, oxides, tip functionalization,
- Publikační typ
- časopisecké články MeSH
A barley (Hordeum vulgare) plasma membrane type aquaporin, HvPIP2;5, was identified as an H2 O2 permeable aquaporin among 21 barley and rice PIPs examined in the heterologous expression system using Saccharomyces cerevisiae. Four TIPs were also detected as H2 O2 -transporting aquaporins among 15 barley and rice TIPs. Influx of H2 O2 into yeast cells expressing HvPIP2;5 was determined with a florescent-dye-based assay. Indirect immunofluorescence indicated that the expression of HvPIP2;5 protein was ubiquitous in root tissues, and was also weakly observed in leaf epidermal cells and cells in the vascular bundle. Point mutated variants of HvPIP2;5 were generated by the site-directed mutagenesis. Growth assays of yeast cells expressing these mutated HvPIP2;5 proteins suggested that Ser-126 in HvPIP2;5 has a large impact on H2 O2 transport with a minor influence on the HvPIP2;5-mediated water transport.
- MeSH
- akvaporiny genetika metabolismus MeSH
- biologický transport MeSH
- buněčná membrána metabolismus MeSH
- epidermis rostlin genetika metabolismus MeSH
- exprese genu MeSH
- ječmen (rod) cytologie genetika metabolismus MeSH
- kořeny rostlin genetika metabolismus MeSH
- listy rostlin genetika metabolismus MeSH
- mutace MeSH
- mutageneze cílená MeSH
- orgánová specificita MeSH
- peroxid vodíku metabolismus MeSH
- regulace genové exprese u rostlin * MeSH
- rostlinné proteiny genetika metabolismus MeSH
- rýže (rod) cytologie genetika metabolismus MeSH
- Saccharomyces cerevisiae cytologie genetika metabolismus MeSH
- serin metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- akvaporiny MeSH
- peroxid vodíku MeSH
- rostlinné proteiny MeSH
- serin MeSH
- MeSH
- adenosintrifosfát terapeutické užití MeSH
- dospělí MeSH
- fetální srdce patofyziologie MeSH
- hypoxie farmakoterapie MeSH
- lidé MeSH
- monitorování fyziologických funkcí * MeSH
- nemoci plodu farmakoterapie MeSH
- novorozenec MeSH
- oxygenoterapie MeSH
- těhotenství MeSH
- Check Tag
- dospělí MeSH
- lidé MeSH
- novorozenec MeSH
- těhotenství MeSH
- ženské pohlaví MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- adenosintrifosfát MeSH
Lithium-oxygen batteries (LOBs) with ultrahigh theoretical energy density have emerged as one appealing candidate for next-generation energy storage devices. Unfortunately, some fundamental issues remain unsettled, involving large overpotential and inferior rate capability, mainly induced by the sluggish reaction kinetics and parasitic reactions at the cathode. Hence, the pursuit of suitable catalyst capable of efficiently catalyzing the oxygen redox reaction and eliminating the side-product generation, become urgent for the development of LOBs. Here, we report a universal synthesis approach to fabricate a suite of mildly oxidized MXenes (mo-Nb2CTx, mo-Ti3C2Tx, and mo-V2CTx) as cathode catalysts for LOBs. The readily prepared mo-MXenes possess expanded interlayer distance to accommodate massive Li2O2 formation, and in-situ-formed light metal oxide to enhance the electrocatalytic activity of MXenes. Taken together, the mo-V2CTx manages to deliver a high specific capacity of 22752 mAh g-1 at a current density of 100 mA g-1, and a long lifespan of 100 cycles at 500 mA g-1. More impressively, LOBs with mo-V2CTx can continuously operate for 90, 89, and 70 cycles, respectively, under a high current density of 1000, 2000, and 3000 mA g-1 with a cutoff capacity of 1000 mAh g-1. The theoretical calculations further reveal the underlying mechanism lies in the optimized surface, where the overpotentials for the formation/decomposition of Li2O2 are significantly reduced and the catalytic kinetics is accelerated. This contribution offers a feasible strategy to prepare MXenes as efficient and robust electrocatalyst toward advanced LOBs and other energy storage devices.
- Klíčová slova
- Li−O2 battery, electrocatalysts, high current density, longevous, mildly oxidized MXene,
- Publikační typ
- časopisecké články MeSH
