We present results of simulations with the Max Planck Institute Martian general circulation model implementing a hydrological cycle scheme. The simulations reveal a seasonal water “pump” mechanism ...responsible for the upward transport of water vapor. This mechanism occurs in high latitudes above 60° of the southern hemisphere at perihelion, when the upward branch of the meridional circulation is particularly strong. A combination of the mean vertical flux with variations induced by solar tides facilitates penetration of water across the “bottleneck” at approximately 60 km. The meridional circulation then transports water across the globe to the northern hemisphere. Since the intensity of the meridional cell is tightly controlled by airborne dust, the water abundance in the thermosphere strongly increases during dust storms.
Key Points
Global circulation modeling reveals the mechanism of water exchange between the lower and upper atmosphere
Atmospheric dust controls the circulation strength and, hence, the amount of high‐altitude water
Solar tide modulates the upwelling of water vapor by almost completely shutting it down during certain local times
1H nuclear magnetic resonance (NMR) relaxation analysis of water in progressively dried white cement paste is used to estimate the width and relative specific area of intra-C–S–H sheet pores and ...inter-C–S–H particle gel pores. The measurement is based on the ratio of solid echo to free induction decay signal amplitudes and the observation that as water is removed, so the surface fraction contributing to the solid echo increases. The intra- and inter-C–S–H pores are found to be 1.5
nm and 4.1
nm thick respectively. The total specific area and volume ratio is 2.4 and 0.88 respectively. The volume ratio of readily evaporable water within the pore types is 0.63. Hence, the sheet porosity is 47% of the total or 38% if based solely on evaporable water. The method is distinct from NMR analyses based on the relaxation time. There is good agreement between the measured widths by the two methods.
In this paper, we construct a mathematical model for estimating the mass of water flooding the coastline of a basin. The models of the relief of the bottom of the basin and the relief of the flooding ...part of the coastline are constructed by stochastic methods. The simulation is based on empirical data of measurements of depths of the basin and the study of level lines on maps of the coastal zone. The equations of the surface relief of the coastal zone are constructed by using empirical data from maps with level lines.
B. mori silkworm natural silk is a fibrous biopolymer with a block copolymer design containing both hydrophobic and hydrophilic regions. Using 1H NMR relaxation, this work studied B. mori natural ...silk fibres oriented at 0° and 90° to the static magnetic field B0 to clarify how measured NMR parameters reflect the structure and anisotropic properties of hydrated silk fibres. The FTIR method was applied to monitor the changes in the silk I and β-sheet conformations. Unloaded B. mori silk fibres at different hydration levels (HL), the silk threads before and after tensile loading in water, and fibres after a stepped increase in temperature have been explored. NMR data discovered two components in T1 and T2 relaxations for both orientations of silk fibres (0° and 90°). For the slower T2 component, the results showed an obvious anisotropic effect with higher relaxation times for the silk fibres oriented at 90° to B0. The T1 component (water protons, HL = 0.11) was sequentially decreased over a range of fibres: 0° oriented, randomly oriented, silk B. mori cocoon, 90° oriented. The degree of anisotropy in T2 relaxation was decreasing with increasing HL. The T2 in silk threads oriented at 0° and 90° also showed anisotropy in increased HL (to 0.42 g H2O/g dry matter), at tensile loading, and at an increasing temperature towards 320 K. The changes in NMR parameters and different relaxation mechanisms affecting water molecular interactions and silk properties have been discussed. The findings provide new insights relating to the water anisotropy in hydrated Bombyx mori silk fibres at tensile loading and under a changing HL and temperature.
We present the results of simulations and experimental studies of a W-band surface-wave oscillator powered by a ribbon high-current relativistic electron beam produced by SINUKI accelerator (IAP RAS, ...Nizhny Novgorod, 1 kA / 650 keV / 17 ns). Planar geometry of the interaction space facilitates efficient mode selection over wide transverse coordinate by using open waveguide at fairly large oversize factor (the width of the waveguide is ~ 8 wavelengths). Stable oscillation regime is obtained at frequency of 75 GHz with a pulse duration of about 5 ns. The output power measured by the calorimetric method reaches 25 MW.
The ISOLDE facility at CERN delivers the largest range of low-energy radioactive beams, exploited by several detector systems to investigate nuclear properties from the stable isotopes to the very ...exotic systems close to the neutron or proton drip lines. These studies can largely benefit from the use of a high-resolution fragment separator. To achieve this goal, an innovative spectrometer based on a compact superconducting (SC) ring, the Isolde Superconducting Recoil Separator (ISRS), is being studied. The ring will operate as an isochronous non-scaling fixed-field alternating-gradient (FFAG) system based on Canted-Cosine-Theta (CCT) magnets. These multifunction magnets have two alternating-gradient quadrupoles nested inside an outer dipole. According to preliminary beam dynamics studies, the dipole will need to generate a maximum field of 2.2 T. A maximum quadrupole gradient of approximately 14 T/m will guarantee orbit stability for heavy ions with a maximum kinetic energy of 10 MeV/u. Fine tuning of the CCT magnets and the FFAG optics will provide very large solid angles > 100 msr and momentum acceptances Δp/p > 20%. In this paper we present, the magnet designs and their optimisation. A cost-effective active stray field superconducting coil shield design has been introduced to be able to remove approximate 4000 kg of iron yoke and the complexity of building a tightly curved yoke.
•A bimodal distribution of aerosol on Mars has been inferred from solar occultations.•The coarser mode is represented by both dust and H2O ice particles with average radius of 0.7 and 1.2μm.•The ...finer mode with a radius of 0.04–0.07μm has been detected in both hemispheres.•The lack of condensation nuclei could not fully explain the high water supersaturation.•The finer mode is unstable against coagulation and requires a continuous source of particles to be maintained.
First simultaneous analysis of the ultraviolet (UV) and infrared (IR) atmospheric extinctions from SPICAM/Mars Express solar occultations in the beginning of the Northern summer (Ls=56–97°) is presented. The two SPICAM channels allow sounding of the martian atmosphere in the spectral range from 0.118 to 1.7μm at the altitudes from 10 to 80km. Based on Mie scattering theory with adequate refraction indices for dust and H2O ice, a bimodal distribution of aerosol has been inferred from the SPICAM measurements. The coarser mode is represented by both dust and H2O particles with average radius of 0.7 and 1.2μm, respectively, with number density from 0.01 to 10 particles in cm3. Clouds belonging to the aphelion cloud belt have been observed in midlatitudes in the Southern and the Northern hemispheres at altitudes of 20–30km. The clouds are formed of large particles, and their opacity in the UV and the IR is below 0.03. The finer mode with a radius of 0.04–0.07μm and a number density from 1cm−3 at 60km to 1000cm−3 at 20km has been detected in both hemispheres. In the Southern hemisphere the finer mode extends up to 70km, whereas in the Northern hemisphere it is confined below 30–40km. The lack of condensation nuclei is consistent, but could not fully explain the high water supersaturation observed between 30 and 50km in the same Northern hemisphere dataset (Maltagliati L., Montmessin, F., Fedorova, A., Korablev, O., Forget, F., Bertaux, J.-L. 2011. Science 333, 1868–1871). The average size of the fine mode (∼50nm) and the large number density (up to 1000cm−3) most likely corresponds to Aitken particles (r<0.1μm). This mode is unstable against coagulation and requires a continuous source of particles to be maintained, at least one order of magnitude more than estimations for the meteoric flux. A possible source is the dust lifting from the surface and dust devils. A detailed microphysical modeling is required to study the probability of survival of the observed bimodal distribution.
The detection of minor species in the presence of large amounts of similar main components remains a key challenge in analytical chemistry, for instance, to obtain isotopic fingerprints. As an ...alternative to the classical NMR scheme based on coherent excitation and detection, here we introduce an approach based on spin-noise detection. Chemical shifts and transverse relaxation rates are determined using only the detection circuit. Thanks to a nonlinear effect in mixtures with small chemical shift dispersion, small signals on top of a larger one can be observed with increased sensitivity as bumps on a dip; the latter being the signature of the main magnetization. Experimental observations are underpinned by an analytical theory: the coupling between the magnetization and the coil provides an amplified detection capability of both small static magnetic field inhomogeneities and small NMR signals. This is illustrated by two-bond
C/
C isotopic measurements.
Nature Communications 8: Article number: 13914 (2017); Published 9 January 2017; Updated 19 April 2017 This Article contains typographical errors in Equation 1, where the fraction line incorrectly ...extends across the entire equation. The correct form of Equation 1 is as follows:
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