| 1. |
- Hauber, Ernst, et al.
(författare)
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MORPHOMETRY OF ALLUVIAL FANS IN A POLAR DESERT (SVALBARD, NORWAY): IMPLICATIONS FOR INTERPRETING MARTIAN FANS.
- 2009
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Ingår i: 40th Lunar and Planetary Science Conference. ; :1648
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Konferensbidrag (refereegranskat)abstract
- Alluvial fan-like landforms have been identified on Mars. Since alluvial fans are recorders of processes that are sensitive to climatic conditions, the investigation of possible Martian fans can reveal information about the planet`s climate. In lieu of direct observations of active depositional processes on Martian fans, comparisons with terrestrial analogues can constrain models of Martian fan formation derived from remote sensing data. Since present-day Mars is cold and dry, alluvial fans formed in cold deserts should be considered as useful analogues. The probably closest climatic analogue to Mars on Earth are the Antarctic Dry Valleys , but polar deserts can also be found in the Arctic. We report on our field work in summer 2008 and a simultaneous flight campaign with an airborne version (HRSC-AX) of the High Resolution Stereo Camera (HRSC) onboard Mars Express. The results are compared with measurements of Martian fans, based on HRSC DEM.
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| 2. |
- Hauber, Ernst, et al.
(författare)
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Svalbard (Norway) as a terrestrial analogue for Martian landforms: Results on
- 2009
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Ingår i: EPSC Abstracts. European Planetary Science Congress. ; 4, EPSC2009-772
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Konferensbidrag (refereegranskat)abstract
- Small alluvial fan-like landforms have been observed on Mars in association with recent gullies. Such fans are relatively small (km-scale) when compared to large alluvial fans on Mars, which can reach dimensions of tens of kilometers. The small fans are part of an erosion-transportsedimentation system (alcove-channel-apron). Morphologically very similar systems can be studied on Svalbard (Norway), which is a cold and dry polar desert and, therefore, a potentially useful terrestrial analogue for Mars` climate and climaterelated landforms. Here we give an update on our field work in summer 2008 and a simultaneous flight campaign with an airborne version (HRSCAX) of the High Resolution Stereo Camera (HRSC) onboard Mars Express. We also present very preliminary results from the field campaign in summer 2009.
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| 3. |
- Johnsson, Andreas, 1977, et al.
(författare)
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THE ORIGIN OF STRIPE-LIKE PATTERNS ON MARTIAN GULLY SLOPES; USING SVALBARD ADVENT VALLEY AS A MARS ANALOGUE.
- 2010
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Ingår i: 41st Lunar and Planetary Science Conference. ; :1665
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Stripes are a common slope features in polar regions on Earth were active layer processes (freezing/thawing and gelifluction) occur. Their origin is most likely polygenic and closely related to frost crack plygons and sorted circles with the addition of a gravitational component. Stripes are either sorted or unsorted. Features resembling stripes have been observed on slopes on Mars with or without association with polygons. Due to the current temperature and pressure regime on Mars soil moisture and active layer processes are not likely to occur. However, in recent HiRISE images stripelike patterns can be observed in proximity to gullies . Stripe width typically ranges from ~50 cm to 1.5 m, and their orientation is consistently down slope, although it can not be excluded that it sometimes slightly deviates from the steepest topographic gradient. In our study we have examined sorted and nonsorted stripes on slopes in Svalbard in order to test the working hypothesis of an cryoturbation origin for the martian stripe-like patterns. In doing so we compare their morphological characteristics, settings, and slope to those on Mars.
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| 4. |
- Reiss, Dennis, et al.
(författare)
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MORPHOLOGIC AND MORPHOMETRIC COMPARISION OF GULLIES ON SVALBARD AND MARS.
- 2009
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Ingår i: 40th Lunar and Planetary Science Conference. ; :2362
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The morphology of gullies on Mars indi-cates that they were formed by the action of water. How-ever, it is not clear what the dominant gully forming process is. On Earth, gullies might have formed by the processes of overland flow or debris flows, or a combination of both. In this work we compare the morphologic and morphometric observations and measurements (slopes, depth-width ratios and sinuosities) of Martian gullies with terrestrial analogs from Svalbard, Norway, in order to constrain the formation process (fluvial and/or debris flow).
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| 5. |
- Reiss, Dennis, et al.
(författare)
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TERRESTRIAL GULLIES ON SVALBARD AS PLANETARY ANALOGS FOR MARS
- 2010
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Ingår i: 41st Lunar and Planetary Science Conference. ; :2492
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Martian gullies resemble terrestrial gul-lies, which are formed by a combination of processes includ-ing mass wasting, overland flow and debris flows. The gullies on Mars show several morphologic features such as braided channels, multiple terraces, point bars and cutbanks, which indicate that fluvial processes were involved in their formation. However, it remains unclear whether fluvial processes or debris flows are dominating the formation of gullies on Mars. Debris flows are viscous slurry flows with water and fines as the interstitial fluid. The flowing mix-tures of fines, clastic debris and water has a relatively low water content (≤ 30 % water by weight). Stream flows and hyperconcentrated flows have a high water content and relatively low sediment supply (≥ 30 % water by weight). The morphologies of debris flows fans show typical fea-tures such as levées, lobes, snouts and debris plugs, which are not observed from purely fluvial processes. In this work we compare the morphology of terrestrial gully analogs from Svalbard with Martian gullies in order to constrain which formation process might be dominant on Mars, i.e. fluvial and/or debris flow processes.
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| 6. |
- Gudmundsson, Magnus, et al.
(författare)
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Angular scattering in fast ion-atom electron transfer collisions : projectile wave diffraction and Thomas mechanisms
- 2010
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Ingår i: Journal of Physics B. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 43:18, s. 185209-
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Tidskriftsartikel (refereegranskat)abstract
- We report experimental angular differential cross sections for double-electron capture in He2+ + He collisions and single-electron capture in H+ + He collisions for the 1.3-12.5 MeV kinetic energy range. In all cases, the total cross sections are dominated by forward scattering peaks in d sigma/d Omega. The shapes and widths (but not the magnitudes) of these peaks are very similar for all energies and for capture of one or two electrons corresponding also to our measured linear increases in the transverse momentum transfers with increasing projectile velocities. These observations may be ascribed to diffraction limitations which are connected to electron transfer probabilities P(b) which are significant in limited regions of b only. For the H+ + He single-electron capture we observe two additional maxima in the angular differential cross sections. We conclude that while the secondary maxima at similar to 0.5 mrad probably have large contributions from the Thomas proton-electron-nucleus scattering mechanism, the third maxima at similar to 0.75 mrad are most likely mainly due to projectile de Broglie wave diffraction.
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| 7. |
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| 8. |
- Parma, L., et al.
(författare)
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Bis(maltolato)oxovanadium(IV) Induces Angiogenesis via Phosphorylation of VEGFR2
- 2020
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Ingår i: International Journal of Molecular Sciences. - : MDPI AG. - 1422-0067. ; 21:13
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Tidskriftsartikel (refereegranskat)abstract
- VEGFR2 and VEGF-A play a pivotal role in the process of angiogenesis. VEGFR2 activation is regulated by protein tyrosine phosphatases (PTPs), enzymes that dephosphorylate the receptor and reduce angiogenesis. We aim to study the effect of PTPs blockade using bis(maltolato)oxovanadium(IV) (BMOV) on in vivo wound healing and in vitro angiogenesis. BMOV significantly improves in vivo wound closure by 45% in C57BL/6JRj mice. We found that upon VEGFR2 phosphorylation induced by endogenously produced VEGF-A, the addition of BMOV results in increased cell migration (45%), proliferation (40%) and tube formation (27%) in HUVECs compared to control. In a mouse ex vivo, aortic ring assay BMOV increased the number of sprouts by 3 folds when compared to control. However, BMOV coadministered with exogenous VEGF-A increased ECs migration, proliferation and tube formation by only 41%, 18% and 12% respectively and aortic ring sprouting by only 1-fold. We also found that BMOV enhances VEGFR2 Y951 and p38MAPK phosphorylation, but not ERK1/2. The level of phosphorylation of these residues was the same in the groups treated with BMOV supplemented with exogenous VEGF-A and exogenous VEGF-A only. Our study demonstrates that BMOV is able to enhance wound closure in vivo. Moreover, in the presence of endogenous VEGF-A, BMOV is able to stimulate in vitro angiogenesis by increasing the phosphorylation of VEGFR2 and its downstream proangiogenic enzymes. Importantly, BMOV had a stronger proangiogenic effect compared to its effect in coadministration with exogenous VEGF-A.
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| 9. |
- Thomas, Richard D., et al.
(författare)
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The double electrostatic ion ring experiment : A unique cryogenic electrostatic storage ring for merged ion-beams studies
- 2011
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 82:6, s. 065112-
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Tidskriftsartikel (refereegranskat)abstract
- We describe the design of a novel type of storage device currently under construction at Stockholm University, Sweden, using purely electrostatic focussing and deflection elements, in which ion beams of opposite charges are confined under extreme high vacuum cryogenic conditions in separate rings and merged over a common straight section. The construction of this double electrostatic ion ring experiment uniquely allows for studies of interactions between cations and anions at low and well-defined internal temperatures and centre-of-mass collision energies down to about 10 K and 10 meV, respectively. Position sensitive multi-hit detector systems have been extensively tested and proven to work in cryogenic environments and these will be used to measure correlations between reaction products in, for example, electron-transfer processes. The technical advantages of using purely electrostatic ion storage devices over magnetic ones are many, but the most relevant are: electrostatic elements which are more compact and easier to construct; remanent fields, hysteresis, and eddy-currents, which are of concern in magnetic devices, are no longer relevant; and electrical fields required to control the orbit of the ions are not only much easier to create and control than the corresponding magnetic fields, they also set no upper mass limit on the ions that can be stored. These technical differences are a boon to new areas of fundamental experimental research, not only in atomic and molecular physics but also in the boundaries of these fields with chemistry and biology. For examples, studies of interactions with internally cold molecular ions will be particular useful for applications in astrophysics, while studies of solvated ionic clusters will be of relevance to aeronomy and biology.
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| 10. |
- Zettergren, Henning, et al.
(författare)
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Magic and hot giant fullerenes formed inside ion irradiated weakly bound C-60 clusters
- 2010
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 133:10, s. 104301-
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Tidskriftsartikel (refereegranskat)abstract
- We find that the most stable fullerene isomers, C-70-C-94, form efficiently in close-to central collisions between keV atomic ions and weakly bound clusters of more than 15 C-60-molecules. We observe extraordinarily high yields of C-70 and marked preferences for C-78 and C-84. Larger even-size carbon molecules, C-96-C-180, follow a smooth log-normal (statistical) intensity distribution. Measurements of kinetic energies indicate that C-70-C-94 mainly are formed by coalescence reactions between small carbon molecules and Coo, while C-n with n >= 96 are due to self-assembly (of small molecules) and shrinking hot giant fullerenes.
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