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| 3. |
- Krawczyk, M., et al.
(författare)
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Liver Transplantation for Hepatic Trauma: A Study From the European Liver Transplant Registry
- 2016
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Ingår i: Transplantation. - : Ovid Technologies (Wolters Kluwer Health). - 0041-1337. ; 100:11, s. 2372-2381
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Tidskriftsartikel (refereegranskat)abstract
- Background. Liver transplantation is the most extreme form of surgical management of patients with hepatic trauma, with very limited literature data supporting its use. The aim of this study was to assess the results of liver transplantation for hepatic trauma. Methods. This retrospective analysis based on European Liver Transplant Registry comprised data of 73 recipients of liver transplantation for hepatic trauma performed in 37 centers in the period between 1987 and 2013. Mortality and graft loss rates at 90 days were set as primary and secondary outcome measures, respectively. Results. Mortality and graft loss rates at 90 days were 42.5% and 46.6%, respectively. Regarding general variables, cross-clamping without extracorporeal veno-venous bypass was the only independent risk factor for both mortality (P = 0.031) and graft loss (P = 0.034). Regarding more detailed factors, grade of liver trauma exceeding IV increased the risk ofmortality (P = 0.005) and graft loss (P = 0.018). Moreover, a tendency above the level of significance was observed for the negative impact of injury severity score (ISS) onmortality (P = 0.071). The optimal cutoff for ISS was 33, with sensitivity of 60.0%, specificity of 80.0%, positive predictive value of 75.0%, and negative predictive value of 66.7%. Conclusions. Liver transplantation seems to be justified in selected patients with otherwise fatal severe liver injuries, particularly in whom cross-clamping without extracorporeal bypass can be omitted. The ISS cutoff less than 33 may be useful in the selection process.
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| 5. |
- Gusev, A. N., et al.
(författare)
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Synthesis and photophysical properties of Zn(II) Schiff base complexes possessing strong solvent-dependent solid-state fluorescence
- 2018
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Ingår i: Polyhedron. - : Elsevier Ltd. - 0277-5387 .- 1873-3719. ; 155, s. 202-208
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Tidskriftsartikel (refereegranskat)abstract
- The present article reports on the syntheses, crystal structures and luminescence properties of three solvate forms of a zinc(II) complex containing 4-{(E)-[(2-fluorophenyl)imino]methyl}-5-methyl-2-phenyl-2,4-dihydro-3H-pyrazol-3-one (HL). The reaction of zinc(II)acetate with the HL ligand in ethanol and acetonitrile led to the formation of two solvate analogues [Zn(L)2]·Solv (Solv – ethanol (1) and acetonitrile (2)). The properties of the [Zn(L)2]·Solv complexes were investigated by UV–Vis absorption and fluorescence emission spectroscopy, and the density functional theory calculations. Bader's topological analysis was performed to investigate the electronic peculiarities of Zn(II) polyhedra and non-covalent interactions within crystal packing of studied solvates.
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| 10. |
- Andrews, David, et al.
(författare)
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Control of the topside Martian ionosphere by crustal magnetic fields
- 2015
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Ingår i: Journal of Geophysical Research - Space Physics. - 2169-9380 .- 2169-9402. ; 120:4, s. 3042-3058
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Tidskriftsartikel (refereegranskat)abstract
- We present observations from the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) instrument onboard Mars Express of the thermal electron plasma density of the Martian ionosphere and investigate the extent to which it is influenced by the presence of Mars's remnant crustal magnetic fields. We use locally measured electron densities, derived when MARSIS is operating in active ionospheric sounding (AIS) mode, covering an altitude range from approximate to 300km to approximate to 1200km. We compare these measured densities to an empirical model of the dayside ionospheric plasma density in this diffusive transport-dominated regime. We show that small spatial-scale departures from the averaged values are strongly correlated with the pattern of the crustal fields. Persistently elevated densities are seen in regions of relatively stronger crustal fields across the whole altitude range. Comparing these results with measurements of the (scalar) magnetic field also obtained by MARSIS/AIS, we characterize the dayside strength of the draped magnetic fields in the same regions. Finally, we provide a revised empirical model of the plasma density in the Martian ionosphere, including parameterizations for both the crustal field-dominated and draping-dominated regimes.
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| 11. |
- Cunha, M. S., et al.
(författare)
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Rotation and pulsation in Ap stars : first light results from TESS sectors 1 and 2
- 2019
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Ingår i: Monthly notices of the Royal Astronomical Society. - : OXFORD UNIV PRESS. - 0035-8711 .- 1365-2966. ; 487:3, s. 3523-3549
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Tidskriftsartikel (refereegranskat)abstract
- We present the first results from the Transiting Exoplanet Survey Satellite (TESS) on the rotational and pulsational variability of magnetic chemically peculiar A-type stars. We analyse TESS 2-min cadence data from sectors 1 and 2 on a sample of 83 stars. Five new rapidly oscillating Ap (roAp) stars are announced. One of these pulsates with periods around 4.7 min, making it the shortest period roAp star known to date. Four out of the five new roAp stars are multiperiodic. Three of these and the singly periodic one show the presence of rotational mode splitting. Individual frequencies are provided in all cases. In addition, seven previously known roAp stars are analysed. Additional modes of oscillation are found in some stars, while in others we are able to distinguish the true pulsations from possible aliases present in the ground-based data. We find that the pulsation amplitude in the TESS filter is typically a factor of 6 smaller than that in the B filter, which is usually used for ground-based observations. For four roAp stars we set constraints on the inclination angle and magnetic obliquity, through the application of the oblique pulsator model. We also confirm the absence of roAp-type pulsations down to amplitude limits of 6 and 13 mu mag, respectively, in two of the best characterized non-oscillating Ap (noAp) stars. We announce 27 new rotational variables along with their rotation periods, and provide different rotation periods for seven other stars. Finally, we discuss how these results challenge state-of-the-art pulsation models for roAp stars.
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| 12. |
- Fekete, L., et al.
(författare)
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Fast one-dimensional photonic crystal modulators for the terahertz range
- 2007
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Ingår i: Optics Express. - 1094-4087. ; 15:14, s. 8898-8912
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Tidskriftsartikel (refereegranskat)abstract
- Optically controlled one-dimensional photonic crystal structures for the THz range are studied both theoretically and experimentally. A GaAs:Cr layer constitutes a defect in the photonic crystals studied; its photoexcitation by 800 nm optical femtosecond pulses leads to the modulation of the THz beam. Since the THz field can be localized in the photoexcited layer of the photonic crystal, the interaction between photocarriers and THz light is strengthened and yields an appreciable modulation of the THz output beam even for low optical pump fluences. Optimum resonant structures are found, constructed and experimentally studied. The dynamical response of these elements is shown to be controlled by the lifetime of THz photons in the resonator and by the free carrier lifetime. The time response of the structures studied is shorter than 330 ps. (c) 2007 Optical Society of America.
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| 13. |
- Fekete, L, et al.
(författare)
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Ultrafast opto-terahertz photonic crystal modulator
- 2007
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Ingår i: Optics Letters. - 0146-9592. ; 32:6, s. 680-682
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Tidskriftsartikel (refereegranskat)abstract
- We present an agile optically controlled switch or modulator of terahertz (THz) radiation. The element is based on a one-dimensional photonic crystal with a GaAs wafer inserted in the middle as a defect layer. The THz electric field is enhanced in the photonic structure at the surfaces of the Ga-As wafer. Excitation of the front GaAs surface by ultrashort 8 10 nm laser pulses then leads to an efficient modulation of the THz beam even at low photocarrier concentrations (approximate to 10(16) cm(-3)). The response time of the element to pulsed photoexcitation is about 130 ps. (c) 2007 Optical Society of America.
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| 14. |
- Kuzel, P., et al.
(författare)
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Propagation of terahertz pulses in photoexcited media: Analytical theory for layered systems
- 2007
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 127:2
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Tidskriftsartikel (refereegranskat)abstract
- Optical pump-terahertz probe spectroscopy has become a widely used experimental tool for the investigation of the ultrafast far-infrared response of polar systems. In this paper the authors present an analytical method of calculating the propagation of ultrashort terahertz pulses in photoexcited media. The transient terahertz wave form transmitted through the sample is equal to a product of the incident terahertz field (at a mixed frequency), transient susceptibility, and a so called transfer function which depends on the properties of the sample in equilibrium. The form of the transfer function is derived for general layered systems and for specific cases including one-dimensional photonic crystals, thin films, and bulk samples. Simplified expressions directly applicable to the analysis of the experimental results related to the most common sample geometries are shown and discussed. (C) 2007 American Institute of Physics.
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| 15. |
- Němec, F., et al.
(författare)
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Characterizing Average Electron Densities in the Martian Dayside Upper Ionosphere
- 2019
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Ingår i: Journal of Geophysical Research - Planets. - 2169-9097 .- 2169-9100. ; 124:1, s. 76-93
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Tidskriftsartikel (refereegranskat)abstract
- We use more than 10years of the Martian topside ionospheric data measured by the Mars Advanced Radar for Subsurface and Ionosphere Sounding radar sounder on board the Mars Express spacecraft to derive an empirical model of electron densities from the peak altitude up to 325km. Altogether, 16,044 electron density profiles obtained at spacecraft altitudes lower than 425km and at solar zenith angles lower than 80 degrees are included in the analysis. Each of the measured electron density profiles is accurately characterized by the peak electron density, peak altitude, and three additional parameters describing the profile shape above the peak: (i) steepness at high altitudes, (ii) main layer thickness, and (iii) transition altitude. The dependence of these parameters on relevant controlling factors (solar zenith angle, solar irradiance, crustal magnetic field magnitude, and Sun-Mars distance) is evaluated, allowing for a formulation of a simple empirical model. Mars Atmosphere and Volatile EvolutioN Extreme Ultraviolet monitor data are used to show that the solar ionizing flux can be accurately approximated by the F10.7 index when taking into account the solar rotation. Electron densities predicted by the resulting empirical model are compared with electron densities locally evaluated based on the Mars Advanced Radar for Subsurface and Ionosphere Sounding measurements, with the Langmuir Probe and Waves electron density measurements on board the Mars Atmosphere and Volatile EvolutioN spacecraft, and with electron densities obtained by radio occultation measurements. Although the electron densities measured by the Langmuir Probe and Waves instrument are systematically somewhat lower than the model electron densities, consistent with former findings, the model performs reasonably well.
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| 16. |
- Nemec, F., et al.
(författare)
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Empirical model of the Martian dayside ionosphere : Effects of crustal magnetic fields and solar ionizing flux at higher altitudes
- 2016
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Ingår i: Journal of Geophysical Research - Space Physics. - 2169-9380 .- 2169-9402. ; 121:2, s. 1760-1771
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Tidskriftsartikel (refereegranskat)abstract
- We use electron density profiles measured by the Mars Advanced Radar for Subsurface and Ionosphere Sounding instrument on board the Mars Express spacecraft to investigate the effects of possible controlling parameters unconsidered in the empirical model of Nemec et al. (2011, hereafter N11). Specifically, we focus on the effects of crustal magnetic fields and F-10.7 proxy of the solar ionizing flux at higher altitudes. It is shown that while peak electron densities are nearly unaffected by crustal magnetic fields, electron densities at higher altitudes are significantly increased in areas of stronger magnetic fields. The magnetic field inclination appears to have only a marginal effect. Moreover, while the N11 empirical model accounted for the variable solar ionizing flux at low altitudes, the high-altitude diffusive region was parameterized only by the solar zenith angle and the altitude. It is shown that this can lead to considerable inaccuracies. A simple correction of the N11 model, which takes into account both the crustal magnetic field magnitude and the effect of F-10.7 at higher altitudes, is suggested.
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| 17. |
- Nemec, F., et al.
(författare)
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Ionospheric Electron Densities at Mars : Comparison of Mars Express Ionospheric Sounding and MAVEN Local Measurements
- 2017
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Ingår i: Journal of Geophysical Research - Space Physics. - : AMER GEOPHYSICAL UNION. - 2169-9380 .- 2169-9402. ; 122:12, s. 12393-12405
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Tidskriftsartikel (refereegranskat)abstract
- We present the first direct comparison of Martian ionospheric electron densities measured by the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) topside radar sounder on board the Mars Express spacecraft and by the Langmuir Probe and Waves (LPW) instrument on board the Mars Atmosphere and Volatile Evolution Mission (MAVEN) spacecraft. As low electron densities are not measured by MARSIS due to the low power radiated at low sounding frequencies, MARSIS electron density profiles between the local electron density and the first data point from the ionospheric sounding (similar to 104 cm(-3)) rely on an empirical electron density profile shape. We use the LPW electron density measurements to improve this empirical description and thereby the MARSIS-derived electron density profiles. We further analyze four coincident events, where the two instruments were measuring within a 5 degrees solar zenith angle interval within 1 h. The differences between the electron densities measured by the MARSIS and LPW instruments are found to be within a factor of 2 in 90% of measurements. Taking into account the measurement precision and different locations and times of the measurements, these differences are within the estimated uncertainties.
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| 18. |
- Nemec, F., et al.
(författare)
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Oblique Reflections of Mars Express MARSIS Radar Signals From Ionospheric Density Structures : Raytracing Analysis
- 2019
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Ingår i: Journal of Geophysical Research - Planets. - : AMER GEOPHYSICAL UNION. - 2169-9097 .- 2169-9100. ; 124:5, s. 1177-1187
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Tidskriftsartikel (refereegranskat)abstract
- Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) radar sounder on board the Mars Express spacecraft revealed oblique reflections coming systematically from apparently stable density structures in the Martian ionosphere. Although these were typically interpreted by assuming a straight line propagation of the sounding signal at the speed of light, the ionospheric plasma is clearly a dispersive medium. Consequently, the ray propagation paths may be significantly bent, and, moreover, the observed time delays need to be interpreted in terms of realistic group velocities of the signal propagation. We select a single particularly well-pronounced event with oblique reflections observable over a large range of signal frequencies, and we employ raytracing calculations to perform its detailed analysis. An isolated density structure responsible for the reflection of the sounding signal back to the spacecraft is assumed, and the relevant ionospheric signal propagation is properly evaluated. We show that initially oblique sounding signals get progressively more oblique during their propagation, imposing an upper threshold on the angular propagation distance between the spacecraft and the reflecting density structure, in line with the observations. Considering realistic propagation paths further allows us to explain the frequency dependence of the observed time delays and to accurately model the entire event. The obtained results are consistent with the spacecraft passing very close to a spatially limited density structure. We also show that the results obtained using realistic raytracing calculations are significantly different from the results obtained using additional simplifying assumptions.
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