| 1. |
- Lanza, Nina L., et al.
(författare)
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Oxidation of manganese in an ancient aquifer, Kimberley formation, Gale crater, Mars
- 2016
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 43:14, s. 7398-7407
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Tidskriftsartikel (refereegranskat)abstract
- The Curiosity rover observed high Mn abundances (>25wt % MnO) in fracture-filling materials that crosscut sandstones in the Kimberley region of Gale crater, Mars. The correlation between Mn and trace metal abundances plus the lack of correlation between Mn and elements such as S, Cl, and C, reveals that these deposits are Mn oxides rather than evaporites or other salts. On Earth, environments that concentrate Mn and deposit Mn minerals require water and highly oxidizing conditions; hence, these findings suggest that similar processes occurred on Mars. Based on the strong association between Mn-oxide deposition and evolving atmospheric dioxygen levels on Earth, the presence of these Mn phases on Mars suggests that there was more abundant molecular oxygen within the atmosphere and some groundwaters of ancient Mars than in the present day
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| 2. |
- Chudinova, E., et al.
(författare)
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Functionalization of additive-manufactured Ti6Al4V scaffolds with poly(allylamine hydrochloride)/poly(styrene sulfonate) bilayer microcapsule system containing dexamethasone
- 2021
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Ingår i: Materials Chemistry and Physics. - : Elsevier BV. - 0254-0584 .- 1879-3312. ; 273
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Tidskriftsartikel (refereegranskat)abstract
- Porous titanium alloy Ti6Al4V scaffolds manufactured via electron beam melting (EBM®) reveal broad prospects for applications in bone tissue engineering. However, local inflammation and even implant failure may occur while placing an implant into the body. Thus, the application of drug carriers to the surface of a metallic implant can provide treatment at the inflammation site. In this study, we propose to use polyelectrolyte (PE) microcapsules formed by layer-by-layer (LbL) synthesis loaded with both porous calcium carbonate (CaCO3) microparticles and the anti-inflammatory drug dexamethasone (DEX) to functionalize implant surfaces and achieve controlled drug release. Scanning electron microscopy indicated that the CaCO3 microparticles coated with PE bilayers loaded with DEX had a spherical shape with a diameter of 2.3 ± 0.2 μm and that the entire scaffold surface was evenly coated with the microcapsules. UV spectroscopy showed that LbL synthesis allows the manufacturing of microcapsules with 40% DEX. According to high performance liquid chromatography (HPLC) analysis, 80% of the drug was released within 24 h from the capsules consisting of three bilayers of polystyrene sulfonate (PSS) and poly(allylamine)hydrochloride (PAH). The prepared scaffolds functionalized with CaCO3 microparticles loaded with DEX and coated with PE bilayers showed hydrophilic surface properties with a water contact angle below 5°. Mouse embryonic fibroblast cells were seeded on Ti6Al4V scaffolds with and without LbL surface modification. The surface modification with LbL PE microcapsules with CaCO3 core affected cell morphology in vitro. The results confirmed that DEX had no toxic effect and did not prevent cell adhesion and spreading, thus no cytotoxic effect was observed, which will be further studied in vivo.
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| 3. |
- Jansson, Tomas, et al.
(författare)
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Frequency dependence of speckle in continuous-wave ultrasound with implications for blood perfusion measurements.
- 2002
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Ingår i: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. - 0885-3010. ; 49:6, s. 715-725
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Tidskriftsartikel (refereegranskat)abstract
- Speckle in continuous wave (CW) Doppler has previously been found to cause large variations in detected Doppler power in blood perfusion measurements, where a large number of blood vessels are present in the sample volume. This artifact can be suppressed by using a number of simultaneously transmitted frequencies and averaging the detected signals. To optimize the strategy, statistical properties of speckle in CW ultrasound need to be known. This paper presents analysis of the frequency separation necessary to obtain independent values of the received power for CW ultrasound using a simplified mathematical model for insonation of a static, lossless, statistically homogeneous, weakly scattering medium. Specifically, the autocovariance function for received power is derived, which functionally is the square of the (deterministic) autocorrelation function of the effective sample volumes produced by the transducer pair for varying frequencies, at least if a delta correlated medium is assumed. A marginal broadening of the modeled autocovariance functions is expected for insonation of blood. The theory is applicable to any transducer aperture, but has been experimentally verified here with 5-MHz, 6.35-mm circular transducers using an agar phantom containing small, randomly dispersed glass particles. A similar experimental verification of a transducer used in multiple-frequency blood perfusion measurements shows that the model proposed in this paper is plausible for explaining the decorrelation between different channels in such a measurement.
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| 4. |
- Malbet, F., et al.
(författare)
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Faint objects in motion: the new frontier of high precision astrometry
- 2021
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Ingår i: Experimental Astronomy. - : Springer Science and Business Media LLC. - 0922-6435 .- 1572-9508. ; 51:3, s. 845-886
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Tidskriftsartikel (refereegranskat)abstract
- Sky survey telescopes and powerful targeted telescopes play complementary roles in astronomy. In order to investigate the nature and characteristics of the motions of very faint objects, a flexibly-pointed instrument capable of high astrometric accuracy is an ideal complement to current astrometric surveys and a unique tool for precision astrophysics. Such a space-based mission will push the frontier of precision astrometry from evidence of Earth-mass habitable worlds around the nearest stars, to distant Milky Way objects, and out to the Local Group of galaxies. As we enter the era of the James Webb Space Telescope and the new ground-based, adaptive-optics-enabled giant telescopes, by obtaining these high precision measurements on key objects that Gaia could not reach, a mission that focuses on high precision astrometry science can consolidate our theoretical understanding of the local Universe, enable extrapolation of physical processes to remote redshifts, and derive a much more consistent picture of cosmological evolution and the likely fate of our cosmos. Already several missions have been proposed to address the science case of faint objects in motion using high precision astrometry missions: NEAT proposed for the ESA M3 opportunity, micro-NEAT for the S1 opportunity, and Theia for the M4 and M5 opportunities. Additional new mission configurations adapted with technological innovations could be envisioned to pursue accurate measurements of these extremely small motions. The goal of this White Paper is to address the fundamental science questions that are at stake when we focus on the motions of faint sky objects and to briefly review instrumentation and mission profiles.
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| 5. |
- Webster, Christopher R., et al.
(författare)
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Mars methane detection and variability at Gale crater
- 2015
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 347:6220, s. 415-417
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Tidskriftsartikel (refereegranskat)abstract
- Reports of plumes or patches of methane in the Martian atmosphere that vary over monthly timescales have defied explanation to date. From in situ measurements made over a 20-month period by the Tunable Laser Spectrometer (TLS) of the Sample Analysis at Mars (SAM) instrument suite on Curiosity at Gale Crater, we report detection of background levels of atmospheric methane of mean value 0.69 ± 0.25 ppbv at the 95% confidence interval (CI). This abundance is lower than model estimates of ultraviolet (UV) degradation of accreted interplanetary dust particles (IDP’s) or carbonaceous chondrite material. Additionally, in four sequential measurements spanning a 60-sol period, we observed elevated levels of methane of 7.2 ± 2.1 (95% CI) ppbv implying that Mars is episodically producing methane from an additional unknown source.
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