| 1. |
- Rodriguez, Sébastien, et al.
(författare)
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Science goals and new mission concepts for future exploration of Titan's atmosphere, geology and habitability : titan POlar scout/orbitEr and in situ lake lander and DrONe explorer (POSEIDON)
- 2022
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Ingår i: Experimental astronomy. - : Springer Science and Business Media LLC. - 0922-6435 .- 1572-9508. ; 54:2-3, s. 911-973
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Tidskriftsartikel (refereegranskat)abstract
- In response to ESA’s “Voyage 2050” announcement of opportunity, we propose an ambitious L-class mission to explore one of the most exciting bodies in the Solar System, Saturn’s largest moon Titan. Titan, a “world with two oceans”, is an organic-rich body with interior-surface-atmosphere interactions that are comparable in complexity to the Earth. Titan is also one of the few places in the Solar System with habitability potential. Titan’s remarkable nature was only partly revealed by the Cassini-Huygens mission and still holds mysteries requiring a complete exploration using a variety of vehicles and instruments. The proposed mission concept POSEIDON (Titan POlar Scout/orbitEr and In situ lake lander DrONe explorer) would perform joint orbital and in situ investigations of Titan. It is designed to build on and exceed the scope and scientific/technological accomplishments of Cassini-Huygens, exploring Titan in ways that were not previously possible, in particular through full close-up and in situ coverage over long periods of time. In the proposed mission architecture, POSEIDON consists of two major elements: a spacecraft with a large set of instruments that would orbit Titan, preferably in a low-eccentricity polar orbit, and a suite of in situ investigation components, i.e. a lake lander, a “heavy” drone (possibly amphibious) and/or a fleet of mini-drones, dedicated to the exploration of the polar regions. The ideal arrival time at Titan would be slightly before the next northern Spring equinox (2039), as equinoxes are the most active periods to monitor still largely unknown atmospheric and surface seasonal changes. The exploration of Titan’s northern latitudes with an orbiter and in situ element(s) would be highly complementary in terms of timing (with possible mission timing overlap), locations, and science goals with the upcoming NASA New Frontiers Dragonfly mission that will provide in situ exploration of Titan’s equatorial regions, in the mid-2030s.
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| 2. |
- Arridge, Christopher S., et al.
(författare)
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Uranus Pathfinder : exploring the origins and evolution of Ice Giant planets
- 2012
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Ingår i: Experimental astronomy. - : Springer Science and Business Media LLC. - 0922-6435 .- 1572-9508. ; 33:2-3, s. 753-791
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Tidskriftsartikel (refereegranskat)abstract
- The "Ice Giants" Uranus and Neptune are a different class of planet compared to Jupiter and Saturn. Studying these objects is important for furthering our understanding of the formation and evolution of the planets, and unravelling the fundamental physical and chemical processes in the Solar System. The importance of filling these gaps in our knowledge of the Solar System is particularly acute when trying to apply our understanding to the numerous planetary systems that have been discovered around other stars. The Uranus Pathfinder (UP) mission thus represents the quintessential aspects of the objectives of the European planetary community as expressed in ESA's Cosmic Vision 2015-2025. UP was proposed to the European Space Agency's M3 call for medium-class missions in 2010 and proposed to be the first orbiter of an Ice Giant planet. As the most accessible Ice Giant within the M-class mission envelope Uranus was identified as the mission target. Although not selected for this call the UP mission concept provides a baseline framework for the exploration of Uranus with existing low-cost platforms and underlines the need to develop power sources suitable for the outer Solar System. The UP science case is based around exploring the origins, evolution, and processes at work in Ice Giant planetary systems. Three broad themes were identified: (1) Uranus as an Ice Giant, (2) An Ice Giant planetary system, and (3) An asymmetric magnetosphere. Due to the long interplanetary transfer from Earth to Uranus a significant cruise-phase science theme was also developed. The UP mission concept calls for the use of a Mars Express/Rosetta-type platform to launch on a Soyuz-Fregat in 2021 and entering into an eccentric polar orbit around Uranus in the 2036-2037 timeframe. The science payload has a strong heritage in Europe and beyond and requires no significant technology developments.
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| 3. |
- Blazic, Marija, et al.
(författare)
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High-throughput selection of (new) enzymes : phage display-mediated isolation of alkyl halide hydrolases from a library of active-site mutated epoxide hydrolases
- 2024
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Ingår i: Faraday discussions. - : Royal Society of Chemistry. - 1359-6640 .- 1364-5498.
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Tidskriftsartikel (refereegranskat)abstract
- Epoxide hydrolase StEH1, from potato, is similar in overall structural fold and catalytic mechanism to haloalkane dehalogenase DhlA from Xanthobacter autotrophicus. StEH1 displays low (promiscuous) hydrolytic activity with (2-chloro)- and (2-bromo)ethanebenzene producing 2-phenylethanol. To investigate possibilities to amplify these very low dehalogenase activities, StEH1 was subjected to targeted randomized mutagenesis at five active-site amino acid residues and the resulting protein library was challenged for reactivity towards a bait chloride substrate. Enzymes catalyzing the first half-reaction of a hydrolytic cycle were isolated following monovalent phage display of the mutated proteins. Several StEH1 derived enzymes were identified with enhanced dehalogenase activities.
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| 4. |
- Gautier, S., et al.
(författare)
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AlGaN/AlN multiple quantum wells grown by MOVPE on AlN templates using nitrogen as a carrier gas
- 2008
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248 .- 1873-5002. ; 310:23, s. 4927-4931
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Tidskriftsartikel (refereegranskat)abstract
- AlxGa1-xN/AlN multiple quantum wells (MQWs) structures were grown by metalorganic vapour phase epitaxy (MOVPE) on pseudo AlN substrates using nitrogen as a carrier gas. Results of X-ray diffraction (XRD) and reciprocal space mapping (RSM) indicated no sign of strain relaxation in the quantum wells with respect to the AlN substrate. The MQW parameters such as thicknesses, growth rates and material compositions were extracted from XRD measurements and demonstrated an agreement with our growth conditions. No indication of parasitic reactions between ammonia and trimethyl-aluminium (TMAI) was detected in our growth process. Optical measurements revealed well-defined photoluminescence peaks at 288 and 280 nm, which are in a good agreement with the transmission experimental data. The piezoelectric field value in the Studied structures was estimated to be 900kV/cm.
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| 5. |
- Morlens, AS, et al.
(författare)
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Design and characterization of extreme-ultraviolet broadband mirrors for attosecond science
- 2006
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Ingår i: Optics Letters. - 0146-9592. ; 31:10, s. 1558-1560
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Tidskriftsartikel (refereegranskat)abstract
- A novel multilayer mirror was designed and fabricated based on a recently developed three-material technology aimed both at reaching reflectivities of about 20% and at controlling dispersion over a bandwidth covering photon energies between 35 and 50 eV. The spectral phase upon reflection was retrieved by measuring interferences in a two-color ionization process using high-order harmonics produced from a titanium: sapphire laser. We demonstrate the feasibility of designing and characterizing phase-controlled broadband optics in the extreme-ultraviolet domain, which should facilitate the manipulation of attosecond pulses for applications.
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| 6. |
- Nava, C, et al.
(författare)
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Analysis of the chromosome X exome in patients with autism spectrum disorders identified novel candidate genes, including TMLHE.
- 2012
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Ingår i: Translational psychiatry. - : Springer Science and Business Media LLC. - 2158-3188. ; 2
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Tidskriftsartikel (refereegranskat)abstract
- The striking excess of affected males in autism spectrum disorders (ASD) suggests that genes located on chromosome X contribute to the etiology of these disorders. To identify new X-linked genes associated with ASD, we analyzed the entire chromosome X exome by next-generation sequencing in 12 unrelated families with two affected males. Thirty-six possibly deleterious variants in 33 candidate genes were found, including PHF8 and HUWE1, previously implicated in intellectual disability (ID). A nonsense mutation in TMLHE, which encodes the ɛ-N-trimethyllysine hydroxylase catalyzing the first step of carnitine biosynthesis, was identified in two brothers with autism and ID. By screening the TMLHE coding sequence in 501 male patients with ASD, we identified two additional missense substitutions not found in controls and not reported in databases. Functional analyses confirmed that the mutations were associated with a loss-of-function and led to an increase in trimethyllysine, the precursor of carnitine biosynthesis, in the plasma of patients. This study supports the hypothesis that rare variants on the X chromosome are involved in the etiology of ASD and contribute to the sex-ratio disequilibrium.
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| 7. |
- Ougazzaden, A., et al.
(författare)
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GaN thin films on z- and x-cut LiNbO3 substrates by MOVPE
- 2008
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Ingår i: PHYSICA STATUS SOLIDI C - CURRENT TOPICS IN SOLID STATE PHYSICS. - : Wiley. ; , s. 1565-1567
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Konferensbidrag (refereegranskat)abstract
- We report epitaxial growth of GaN layers on z- and x-cut LiNbO3 substrates using MOVPE. GaN layers with the thickness of 450 nm were characterized using X-ray diffraction. For both, z- and x-cut orientations of LiNbO3 substrates, the GaN layers have c-axis orientation normal to the substrate plane and the in-plane lattice orientation of GaN layers coincides with the primary axes of LiNbO3 substrates. Although GaN layers exhibit almost complete strain relaxation, the residual compressive strain determined with respect to a freestanding GaN is of the order of +0.37% and +0.2% for z- and x-cut substrates, respectively.
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| 8. |
- Ougazzaden, A., et al.
(författare)
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Growth of GaN by metal organic vapor phase epitaxy on ZnO-buffered c-sapphire substrates
- 2008
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248 .- 1873-5002. ; 310:5, s. 944-947
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Tidskriftsartikel (refereegranskat)abstract
- The materials quality and availability of large-area bulk GaN substrates is currently considered a key problem for the continuing development of improved GaN-based devices. Since industrial fabrication of bulk GaN substrates with suitable materials quality has proven very difficult, the opto-GaN industry is currently based on heteroepitaxy using either c-sapphire or 6H SiC substrates. ZnO is promising as a substrate material for GaN because it has the same wurtzite structure and a relatively small lattice mismatch (similar to 1.8%). In this study, we have successfully grown GaN by MOVPE on ZnO-buffered c-sapphire. The growth conditions required to both prevent ZnO degradation and grow monocrystal thin film of GaN have been obtained. SEM, HRXRD and micro-Raman characterizations underlined the presence of the two layers GaN and ZnO with high structural quality.
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| 9. |
- Ougazzaden, A., et al.
(författare)
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Progress on new wide bandgap materials BGaN, BGaAlN and their potential applications
- 2007
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Ingår i: Quantum Sensing and Nanophotonic Devices IV. - : SPIE. - 9780819465924 ; , s. G4791-G4791
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Konferensbidrag (refereegranskat)abstract
- The development of wide band gap semiconductors extends their applications in optoelectronics devices to the UV domain. Compact lasers and high sensitivity APD detectors in UV range are currently needed for different applications such as, purification, covert communication and real time detection of airborne pathogens. Until now, the full exploitation of these potential materials has been limited by the lack of suitable GaN substrates. Recently, a novel class of materials has been reported based on BGaN and BAlN, potentially reducing the crystal defect densities by orders of magnitude compared to existing wide band gap heterostructures. Characteristics of these new alloys are similar to those of AlGaN materials with the advantage that these can be lattice matched to AlN and SiC substrates. In addition, these materials offer the possibility of using quaternary BAlGaN alloys at Ultra Violet (UV) wavelengths and hence lead to more degrees of freedom in designing sophisticated device structures. In this paper we describe the MOVPE growth conditions used to incorporate boron in GaN and AlGaN. Detailed characterization and analysis in terms of structural and electrical properties are discussed.
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