| 1. |
- Korablev, O., et al.
(författare)
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The Atmospheric Chemistry Suite (ACS) of Three Spectrometers for the ExoMars 2016 Trace Gas Orbiter
- 2018
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Ingår i: Space Science Reviews. - : Springer. - 0038-6308 .- 1572-9672. ; 214:1
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Tidskriftsartikel (refereegranskat)abstract
- The Atmospheric Chemistry Suite (ACS) package is an element of the Russian contribution to the ESA-Roscosmos ExoMars 2016 Trace Gas Orbiter (TGO) mission. ACS consists of three separate infrared spectrometers, sharing common mechanical, electrical, and thermal interfaces. This ensemble of spectrometers has been designed and developed in response to the Trace Gas Orbiter mission objectives that specifically address the requirement of high sensitivity instruments to enable the unambiguous detection of trace gases of potential geophysical or biological interest. For this reason, ACS embarks a set of instruments achieving simultaneously very high accuracy (ppt level), very high resolving power (>10,000) and large spectral coverage (0.7 to 17 μm—the visible to thermal infrared range). The near-infrared (NIR) channel is a versatile spectrometer covering the 0.7–1.6 μm spectral range with a resolving power of ∼20,000. NIR employs the combination of an echelle grating with an AOTF (Acousto-Optical Tunable Filter) as diffraction order selector. This channel will be mainly operated in solar occultation and nadir, and can also perform limb observations. The scientific goals of NIR are the measurements of water vapor, aerosols, and dayside or night side airglows. The mid-infrared (MIR) channel is a cross-dispersion echelle instrument dedicated to solar occultation measurements in the 2.2–4.4 μm range. MIR achieves a resolving power of >50,000. It has been designed to accomplish the most sensitive measurements ever of the trace gases present in the Martian atmosphere. The thermal-infrared channel (TIRVIM) is a 2-inch double pendulum Fourier-transform spectrometer encompassing the spectral range of 1.7–17 μm with apodized resolution varying from 0.2 to 1.3 cm−1. TIRVIM is primarily dedicated to profiling temperature from the surface up to ∼60 km and to monitor aerosol abundance in nadir. TIRVIM also has a limb and solar occultation capability. The technical concept of the instrument, its accommodation on the spacecraft, the optical designs as well as some of the calibrations, and the expected performances for its three channels are described.
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| 2. |
- Tinetti, Giovanna, et al.
(författare)
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The EChO science case
- 2015
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Ingår i: Experimental astronomy. - : Springer Science and Business Media LLC. - 0922-6435 .- 1572-9508. ; 40:2-3, s. 329-391
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Tidskriftsartikel (refereegranskat)abstract
- The discovery of almost two thousand exoplanets has revealed an unexpectedly diverse planet population. We see gas giants in few-day orbits, whole multi-planet systems within the orbit of Mercury, and new populations of planets with masses between that of the Earth and Neptune-all unknown in the Solar System. Observations to date have shown that our Solar System is certainly not representative of the general population of planets in our Milky Way. The key science questions that urgently need addressing are therefore: What are exoplanets made of? Why are planets as they are? How do planetary systems work and what causes the exceptional diversity observed as compared to the Solar System? The EChO (Exoplanet Characterisation Observatory) space mission was conceived to take up the challenge to explain this diversity in terms of formation, evolution, internal structure and planet and atmospheric composition. This requires in-depth spectroscopic knowledge of the atmospheres of a large and well-defined planet sample for which precise physical, chemical and dynamical information can be obtained. In order to fulfil this ambitious scientific program, EChO was designed as a dedicated survey mission for transit and eclipse spectroscopy capable of observing a large, diverse and well-defined planet sample within its 4-year mission lifetime. The transit and eclipse spectroscopy method, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allows us to measure atmospheric signals from the planet at levels of at least 10(-4) relative to the star. This can only be achieved in conjunction with a carefully designed stable payload and satellite platform. It is also necessary to provide broad instantaneous wavelength coverage to detect as many molecular species as possible, to probe the thermal structure of the planetary atmospheres and to correct for the contaminating effects of the stellar photosphere. This requires wavelength coverage of at least 0.55 to 11 mu m with a goal of covering from 0.4 to 16 mu m. Only modest spectral resolving power is needed, with R similar to 300 for wavelengths less than 5 mu m and R similar to 30 for wavelengths greater than this. The transit spectroscopy technique means that no spatial resolution is required. A telescope collecting area of about 1 m(2) is sufficiently large to achieve the necessary spectro-photometric precision: for the Phase A study a 1.13 m(2) telescope, diffraction limited at 3 mu m has been adopted. Placing the satellite at L2 provides a cold and stable thermal environment as well as a large field of regard to allow efficient time-critical observation of targets randomly distributed over the sky. EChO has been conceived to achieve a single goal: exoplanet spectroscopy. The spectral coverage and signal-to-noise to be achieved by EChO, thanks to its high stability and dedicated design, would be a game changer by allowing atmospheric composition to be measured with unparalleled exactness: at least a factor 10 more precise and a factor 10 to 1000 more accurate than current observations. This would enable the detection of molecular abundances three orders of magnitude lower than currently possible and a fourfold increase from the handful of molecules detected to date. Combining these data with estimates of planetary bulk compositions from accurate measurements of their radii and masses would allow degeneracies associated with planetary interior modelling to be broken, giving unique insight into the interior structure and elemental abundances of these alien worlds. EChO would allow scientists to study exoplanets both as a population and as individuals. The mission can target super-Earths, Neptune-like, and Jupiter-like planets, in the very hot to temperate zones (planet temperatures of 300-3000 K) of F to M-type host stars. The EChO core science would be delivered by a three-tier survey. The EChO Chemical Census: This is a broad survey of a few-hundred exoplanets, which allows us to explore the spectroscopic and chemical diversity of the exoplanet population as a whole. The EChO Origin: This is a deep survey of a subsample of tens of exoplanets for which significantly higher signal to noise and spectral resolution spectra can be obtained to explain the origin of the exoplanet diversity (such as formation mechanisms, chemical processes, atmospheric escape). The EChO Rosetta Stones: This is an ultra-high accuracy survey targeting a subsample of select exoplanets. These will be the bright "benchmark" cases for which a large number of measurements would be taken to explore temporal variations, and to obtain two and three dimensional spatial information on the atmospheric conditions through eclipse-mapping techniques. If EChO were launched today, the exoplanets currently observed are sufficient to provide a large and diverse sample. The Chemical Census survey would consist of > 160 exoplanets with a range of planetary sizes, temperatures, orbital parameters and stellar host properties. Additionally, over the next 10 years, several new ground- and space-based transit photometric surveys and missions will come on-line (e.g. NGTS, CHEOPS, TESS, PLATO), which will specifically focus on finding bright, nearby systems. The current rapid rate of discovery would allow the target list to be further optimised in the years prior to EChO's launch and enable the atmospheric characterisation of hundreds of planets.
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| 3. |
- Artemov, A. N., et al.
(författare)
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Large effect of thermal processes on the susceptibility of YBCO film with transport current
- 2004
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Ingår i: Physica. C, Superconductivity. - : Elsevier BV. - 0921-4534 .- 1873-2143. ; 403:3, s. 157-162
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Tidskriftsartikel (refereegranskat)abstract
- The response of YBCO film with transport current to the weak alternating magnetic field was studied. The hysteresis of the temperature dependences of the response measured under cooling and heating was revealed. The qualitative explanation of this phenomenon is proposed. It is based on the fact that under certain conditions the superconductor with transport current has two steady states. It is found that the hysteresis arises only if transport current exceeds some finite value I-0.
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| 4. |
- Pashchenko, V. P., et al.
(författare)
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Structure and properties of La0.6Sr0.4-xBaxMnO3 (0 <= x <= 0.4) magnetoresistive ceramics
- 2002
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Ingår i: Inorganic Materials (Neorganicheskie materialy). - 0020-1685 .- 1608-3172. ; 38:3, s. 302-307
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Tidskriftsartikel (refereegranskat)abstract
- The effect of Ba content on the phase composition, lattice parameter, Mn-55 NMR spectrum, resistance, and magnetoresistance of La0.6Sr0.4-xBaxMnO3 perovskites was studied. The lattice parameter of the single-phase ceramic samples was found to increase with increasing x. The tolerance factor increases and the ionic field strength decreases as x increases from 0 to 0.4. The Mn-55 NMR results obtained at 77 K indicate a high-frequency electron exchange between Mn3+ and Mn4+ in the ferromagnetic phase. The peak-magnetoresistance temperature tends to decrease with increasing x. The magnetoresistance of the ceramics is correlated with the bond covalence. It is inferred that the ceramics contain inhomogeneities differing in nature and length scale (macroscopic, mesoscopic, and microscopic), which influence their magnetoresistance.
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| 5. |
- Kuzovlev, Y. E., et al.
(författare)
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Quantum discreteness effects and flicker fluctuations in tunneling conductivity
- 2002
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Ingår i: Physics of the solid state. - : Pleiades Publishing Ltd. - 1063-7834 .- 1090-6460. ; 44:5, s. 843-851
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Tidskriftsartikel (refereegranskat)abstract
- An analysis of events in the tunneling junction shows that the interaction of one-electron processes in a many-electron system may be a source of scale-invariant low-frequency fluctuations of conductivity (the interaction consists in that the quantum probability of an electron transition depends on fast random changes in the environment in the course of the transition, including the changes caused by analogous transitions). The theory relates flicker fluctuations in the tunneling conductivity to the discrete character of the spectrum of electron states and explains the nonlinearity of the noise-current characteristic observed in nanocomposites.
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| 6. |
- Kuzovlev, Y. E., et al.
(författare)
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Rapidly fluctuating fields as a source of low-frequency conductivity fluctuations and the size effects in quantum kinetics
- 2000
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Ingår i: JETP Letters. - : Pleiades Publishing Ltd. - 0021-3640 .- 1090-6487. ; 72:11, s. 574-577
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Tidskriftsartikel (refereegranskat)abstract
- Tunneling contact was taken as an example to demonstrate that the interaction of electron quantum transitions can serve as a source of low-frequency flicker fluctuations of conductivity. Estimates are made for the fluctuations of tunnel conductance. The theory explains the effect of flicker noise sensitivity to the discreteness of the electronic spectrum, as it was observed in nanocomposites.
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| 7. |
- Medvedev, Y. V., et al.
(författare)
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The diagnostics of thermal kinetic coefficients for the optimization of film bolometer properties
- 2002
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Ingår i: Technical physics. - : Pleiades Publishing Ltd. - 1063-7842 .- 1090-6525. ; 47:1, s. 114-120
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Tidskriftsartikel (refereegranskat)abstract
- A pulsed microwave technique for the fast and accurate diagnostics of a complete set of thermal kinetic coefficients in single-layer film structures is developed. The technique is tested on La-0.7(Pb0.7Sr0.3)(0.3)MnO3 films on LaAlO3 and SrTiO3 substrates-the structures featuring a temperature resistance coefficient of 5-7%, which is the highest for manganite-containing materials at room temperature. The results of numerical simulation show that the performance of the uncooled bolometers can be improved by optimizing the thermal conductivity of the substrate and matching the thermal resistances of the film-substrate and substrate-thermostat interfaces.
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| 8. |
- Nikolaenko, Y. M., et al.
(författare)
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Fast bolometric response of bulk La0.7Sr0.3MnO3 electroceramic structures
- 2000
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Ingår i: Acta Physica Polonica. A. - 0587-4246 .- 1898-794X. ; 97:6, s. 991-995
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Tidskriftsartikel (refereegranskat)abstract
- We report on the performance of a microwave electroceramic bolometer of hybrid La0.7Sr0.3MnO3/Al2O3 (0.2 x 2 x 4 mm(3)) structure. The estimated thermal resistance of the bulk ceramic manganite film-single crystal sapphire interface is about 500 K/W at room temperature. This resistance is the main thermal barrier in the heat sink system and has been found to be slightly dependent on temperature, When compared with the high-ire superconducting bolometers, the La0.7Sr0.3MnO3 microwave electroceramic bolometer works in a more wide temperature range, from 77 K to 330 K, excluding the narrow temperature interval at the metal-insulator phase transition (T = 230 K). The microwave electroceramic bolometer sensitivity and the time constant at room temperature have been found to be 0.1 V/W and 100 ms, respectively. To improve the bolometer performance the point contact has been fabricated by a break junction technique. The optimization of a microwave electroceramic bolometer design brought to a considerable improvement of basic bolometer characteristics. The microwave sensitivity was about 0.3 V/W and the time constant was less than 100 ns.
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| 9. |
- Pinches, S. D., et al.
(författare)
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Implementation of plasma simulators and plasma reconstruction workflows in ITER’s Integrated Modelling & Analysis Suite (IMAS)
- 2017
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Ingår i: 44th EPS Conference on Plasma Physics, EPS 2017. - : European Physical Society (EPS).
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Konferensbidrag (refereegranskat)abstract
- IMAS has been installed within the majority of the ITER Members and is being used to support ITPA activities including code benchmarking and validation. Sophisticated workflows, such as Plasma Simulators and those describing H&CD systems, have been adapted to IMAS and applied to ITER scenarios. The framework is considered sufficiently flexible to handle all foreseen approaches to the integrated (probabilistic) determination of measurement parameters (and their errors). The inclusion of UDA within the IMAS data Access Layer has allowed the fetching of IDSs directly from experimental databases and the demonstration of the first plasma reconstruction chain. An interactive Live Display in which signals are selected through a web interface has also been demonstrated.
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| 10. |
- Ulyanov, A.N., et al.
(författare)
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Crystal symmetry and pressure effects on the properties of mixed-valence manganites
- 2003
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Ingår i: Journal of Magnetism and Magnetic Materials vol. 258-259, Special Issue SI. - Amsterdam : Elsevier B.V.. ; , s. 312-314
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Konferensbidrag (refereegranskat)abstract
- A lattice structure effect on the magnetic and magnetotransport properties of La0.7Ca(0.3-x)SrxMnO3 lanthanum manganites have been studied. The Curie temperature pressure coefficient increased almost linearly under an applied pressure as dTc/dP=14K/GPa and as dTc/dP=7.5K/GPa in the orthorhombic and rhombohedral structures,respectively. This is caused by the different pressure effect on the Mn–O bond distances and on the Mn–O–Mn bond angles in those phases. The anomalous low value of dTc/dP(=3.5K/GPa) for La0.7Ca0.15Sr0.15MnO3 composition and a jump of the magnetoresistance maximum value at the concentrational Pbnm2R%3c phase transition were observed and discussed.
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