Data gathered with the Dynamic Albedo of Neutron (DAN) instrument onboard rover Curiosity were analyzed for variations in subsurface neutron flux and tested for possible correlation with local ...geological context. A special DAN observation campaign was executed, in which 18 adjacent DAN active measurements were acquired every 0.75–1.0 m to search for the variations of subsurface hydrogen content along a 15 m traverse across geologic contacts between the Sheepbed and Gillespie Lake members of the Yellowknife Bay formation. It was found that several subunits in Sheepbed and Gillespie Lake could be characterized with different depth distributions of water‐equivalent hydrogen (WEH) and different chlorine‐equivalent abundance responsible for the distribution of neutron absorption elements. The variations of the average WEH at the top 60 cm of the subsurface are estimated at up to 2–3%. Chlorine‐equivalent neutron absorption abundances ranged within 0.8–1.5%. The largest difference in WEH and chlorine‐equivalent neutron absorption distribution is found between Sheepbed and Gillespie Lake.
Key Points
DAN special campaign in Yellowknife Bay
DAN local measurements of water and chlorine abundance
Correlation of DAN measurements and geological context
In this work, we set out to investigate the electrical conductivity of single-phase and high-density La1-xSrxScO3-δ (x = 0.05; 0.1) ceramics depending on temperature and рО2 and рН2О. The crystal ...structure of materials was characterized by XRD method. The samples show the structure of an orthorhombic perovskite with a Pnma space group. The unit cell volume increases along with the Sr concentration. The microstructure features of samples were investigated by SEM analysis. The transference numbers of protons and oxygen-ions were determined by the EMF (electromotive force) measurements in a gas concentration cell. In addition, the proton, oxygen-ion and hole conductivities were evaluated from the рО2-dependencies of electrical conductivity at different humidity. The results obtained using both methods showed a good level of agreement. It is found that the partial conductivity of each charge carrier in La1-xSrxScO3-δ increases along with an increase in the concentration of the Sr dopant from x = 0.05 to x = 0.1. The highest proton conductivity about 3 × 10−2 S cm−1 is achieved for La0·9Sr0.1ScO3-δ at 800 °C. The mobility of proton defects increases with Sr concentration and reaches 2.5 × 10−4 cm2 V−1 s−1 at 800 °C for La0·9Sr0.1ScO3-δ. Thus, La0·9Sr0.1ScO3-δ should be considered as a promising proton-conducting electrolyte for various electrochemical devices, such as protonic ceramic fuel cells.
•The transference numbers of protons, oxygen-ions and holes in La1-xSrxScO3-δ ceramics were determined by EMF and theoretical methods.•The proton conductivity and mobility of La1-xSrxScO3-δ is found to increase with temperature, humidity and Sr concentration.•La0·9Sr0.1ScO3-δ should be considered as a promising proton-conducting electrolyte for electrochemical devices.
Two-stage compression of laser pulses with a power of 250 TW is experimentally realised by broadening their spectrum during self-phase modulation in fused silica and subsequent dispersion ...compensation upon reflection from chirping mirrors. A five-fold decrease in the duration is demonstrated, from 75 to 15 fs, with a B-integral value of about 5 at each stage. It is possible to avoid small-scale self-focusing due to self-filtering of the laser beam during free propagation in vacuum. With optimal parameters of the dispersive mirror, the pulse can be compressed to a duration of less than 5 fs.
Membrane domains known as rafts are rich in cholesterol and sphingolipids, and are thought to be thicker than the surrounding membrane. If so, monolayers should elastically deform so as to avoid ...exposure of hydrophobic surfaces to water at the raft boundary. We calculated the energy of splay and tilt deformations necessary to avoid such hydrophobic exposure. The derived value of energy per unit length, the line tension γ, depends on the elastic moduli of the raft and the surrounding membrane; it increases quadratically with the initial difference in thickness between the raft and surround; and it is reduced by differences, either positive or negative, in spontaneous curvature between the two. For zero spontaneous curvature, γ is ∼1 pN for a monolayer height mismatch of ∼0.3nm, in agreement with experimental measurement. Our model reveals conditions that could prevent rafts from forming, and a mechanism that can cause rafts to remain small. Prevention of raft formation is based on our finding that the calculated line tension is negative if the difference in spontaneous curvature for a raft and the surround is sufficiently large: rafts cannot form if γ<0 unless molecular interactions (ignored in the model) are strong enough to make the total line tension positive. Control of size is based on our finding that the height profile from raft to surround does not decrease monotonically, but rather exhibits a damped, oscillatory behavior. As an important consequence, the calculated energy of interaction between rafts also oscillates as it decreases with distance of separation, creating energy barriers between closely apposed rafts. The height of the primary barrier is a complex function of the spontaneous curvatures of the raft and the surround. This barrier can kinetically stabilize the rafts against merger. Our physical theory thus quantifies conditions that allow rafts to form, and further, defines the parameters that control raft merger.
The catastrophic demise of the Aral Sea in the late twentieth century has stimulated significant international efforts to understand the geological, hydrological, and climatological controls on lake ...level at timescales ranging from years to millennia. Here we extend this time range to the Late Pleistocene with sedimentological, chronological and paleontological results from a core that dates from ca. 17.6 kyr cal BP. To our knowledge, this Aral Sea core (B-05-2009) is the oldest directly-dated sediment record with multiple late Pleistocene 14C dates currently available from the region. The core shows that the modern Aral Sea formed at least as early as the end of the Last Glacial Maximum. The main source of water was most likely glacial meltwater from the Tian Shan, Pamir, and other distant mountain systems in the modern day Aral Sea watershed, carried by the Syr Darya and Amu Darya rivers. The Late Pleistocene section of the core contains ostracods and foraminifera throughout, providing evidence that the lake supported life since its inception. Our chronology suggests a relatively high average sedimentation rate at the onset of lake development, and a significant sedimentation hiatus around the time of the Pleistocene/Holocene boundary.
•The modern Aral Sea formed at least 17.6 kyr cal BP, filled by glacial meltwater at the end of the Last Glacial Maximum.•The Late Pleistocene featured relatively rapid (1 mm yr−1) terrigenous sedimentation.•The Holocene featured slower (0.5–0.6 mm yr−1) authigenic sedimentation.•Microfauna have inhabited the lake since it first formed.
Novel lyssaviruses isolated from bats in Russia Botvinkin, Alexandr D; Poleschuk, Elena M; Kuzmin, Ivan V ...
Emerging infectious diseases,
12/2003, Letnik:
9, Številka:
12
Journal Article
Recenzirano
Odprti dostop
Two new rabies-related viruses were discovered in Russia during 2002. Viruses were isolated from bats in Eastern Siberia near Baikal Lake and in the western Caucasus Mountains. After preliminary ...antigenic and genetic characterization, we found that both viruses should be considered as new putative lyssavirus genotypes.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The first radiocarbon-dated pollen record from the Mamakan section is presented. This record has become the basis for the reconstruction of the vegetation and climate of the Middle Holocene in the ...Mamakan archaeological area, where a number of well-known Siberian archaeological sites of the Late Mesolithic–Middle Bronze period are located. Reconstructions suggest that sparse spruce and larch stands dominated in the area between 6450 and 6150 cal BP. Later, from 6150 to 4700 cal BP, Scots pine began to spread in a warmer climate than before, following the general trend of its expansion in the southern part of Eastern Siberia. A cooler climate than previously with increased soil and air humidity occurred in the Mamakan region from 4700 to 3840 cal BP, causing the regional expansion of Siberian pine. The time interval from 3840 to 3600 cal BP was characterized by the significant development of pine, spruce, and larch forests. On the basis of the age model, we assume that, in the lower reaches of the Vitim River and, probably, in other mountain regions north of Lake Baikal, Scots pine spread about 600 years later than in the Cis-Baikal region and east of the lake. This transition from dark coniferous-taiga to light coniferous-taiga with a predomination of Scots pine signifies the most fundamental change in vegetation of the Baikal region in the Holocene. This is often discussed as one of the possible causes of the Middle Neolithic cultural hiatus (6660–6060 cal BP), which has been documented in the archaeological records from different parts of this vast region. Reconstruction of vegetation in the Mamakan region suggests that the territory of the Nizhnii Vitim River has been favorable for humans during most of the hiatus recorded in the Cis-Baikal area and may have been considered as a refuge for populations of hunter-gatherers in the Middle Neolithic.
Electrochemical transformations and antioxidant activity of some Schiff bases 1–5 containing ferrocenyl group and (thio‐)phenol, catechol fragments were investigated. Compounds under investigation ...are: 2‐(ferrocenylmethylene)amino)phenol (1), 2‐((ferrocenylmethylene)amino)‐4,6‐di‐tert‐butylphenol (2), 2‐((ferrocenylmethylene)amino)‐thiophenol (3), 3‐((ferrocenylmethylene)hydrazonomethyl)‐4,6‐di‐tert‐butylcatechol (4) and 2‐((3,5‐di‐tert‐butyl‐4‐hydroxybenzylidene)amino)thiophenol (5).
In a case of compounds 1–3 it has shown that the sequence of electrochemical transformations leads to the products of intramolecular cyclization – 2‐ferrocenylbenzoxazole (benzothiazole). o‐Quinone formation occurs during the electrochemical oxidation of catechol‐ferrocene 4 at the first anode stage. Electrochemical oxidation of the redox‐active fragments in Schiff bases 1–4 can be achieved indirectly at a lower potential corresponding to the oxidation of ferrocenyl moiety, consequently these substances can reveal more pronounced antioxidant properties. The antioxidant activities of the compounds were evaluated using 2,2′‐diphenyl‐1‐picrylhydrazyl radical (DPPH) assay, the reaction of 2,2′‐azobis(2‐amidinopropane hydrochloride) (AAPH) induced glutathione depletion (GSH), the oxidative damage of the DNA, the process of lipid peroxidation of rat (Wistar) brain homogenates in vitro. The compounds 1–4 in the antioxidant assays show effectiveness comparable with standard antioxidants (vitamin E, Trolox) and in some parameters superior to them. In the reaction of AAPH with the glutathione compounds 2–5 have a more pronounced protective activity than Trolox. Compounds 1–5 inhibit AAPH induced oxidation damage of the DNA. The more effective inhibitors of the lipid peroxidation process in vitro are molecules containing the bulky tert‐butyl groups: 2 and 4 and Schiff base 3.
Electrochemical oxidation of the redox‐active fragments can be achieved indirectly at a low potential corresponding to the oxidation of ferrocenyl moiety. The Schiff bases can be activated at lower redox potentials and show pronounced antioxidant activity in comparison with the compounds containing phenolic or catecholic groups only.
Research into the synthesis of oxide materials exhibiting high ionic conductivity values allows these materials to be used for the fabrication of such high-temperature electrochemical devices as fuel ...cells, gas sensors, electrolyzers, etc. A focused interest in the physical and chemical properties of oxide proton conductors is driven by the phenomenon of proton transfer in those solids, where hydrogen is not a structural unit. LaScO3-based materials are considered to be promising for high-temperature engineering due to their bulk conductivity at low temperatures, chemical resistance and mechanical strength as compared to widely-used proton-conducting cerate- and zirconate-based electrolytes. A series of experiments was performed to compare the properties of La1-xSrxScO3-α (х = 0.05; 0.10) solid proton-conducting electrolytes synthesized using different methods. An alternative combustion method that does not apply nitrates as precursor materials is proposed. This method allowed ceramics with a density greater than 98% of theoretical to be obtained. A detailed qualitative and quantitative evaluation was performed at different synthesis stages using the methods of X-ray diffraction, scanning electron microscopy, X-ray fluorescent and atomic emission spectroscopy. The structure parameters of La1-xSrxScO3-α were determined by full-profile Rietveld X-ray diffraction analysis. The thermal expansion and electrical conductivity of La1-xSrxScO3-α (x = 0.05, 0.10) materials having various densities were studied in oxidizing and reducing atmospheres under changes in the temperature and humidity of the gas phase. The contribution of bulk and grain boundary conductivities was assessed using the impedance method. Both conductivities are established to exhibit the same activation energy for the materials with a density of 94–98% of the theoretical value. The high porosity of the materials (30%) is shown to adversely affect the total conductivity, with the bulk conductivity remaining almost at the same level. A bridge model based on semi-coherent boundaries is proposed for explaining a low grain boundary conductivity in proton electrolytes having a low-symmetry crystal lattice.
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