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- Dahl, F, et al.
(författare)
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Imaging single DNA molecules for high precision NIPT
- 2018
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Ingår i: Scientific reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 8:1, s. 4549-
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Tidskriftsartikel (refereegranskat)abstract
- Cell-free DNA analysis is becoming adopted for first line aneuploidy screening, however for most healthcare programs, cost and workflow complexity is limiting adoption of the test. We report a novel cost effective method, the Vanadis NIPT assay, designed for high precision digitally-enabled measurement of chromosomal aneuploidies in maternal plasma. Reducing NIPT assay complexity is achieved by using novel molecular probe technology that specifically label target chromosomes combined with a new readout format using a nanofilter to enrich single molecules for imaging and counting without DNA amplification, microarrays or sequencing. The primary objective of this study was to assess the Vanadis NIPT assay with respect to analytical precision and clinical feasibility. Analysis of reference DNA samples indicate that samples which are challenging to analyze with low fetal-fraction can be readily detected with a limit of detection determined at <2% fetal-fraction. In total of 286 clinical samples were analysed and 30 out of 30 pregnancies affected by trisomy 21 were classified correctly. This method has the potential to make cost effective NIPT more widely available with more women benefiting from superior detection and false positive rates.
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- Amloy, Supaluck, et al.
(författare)
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Excitons and biexcitons in InGaN quantum dot like localization centers
- 2014
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 25:49, s. 495702-
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Tidskriftsartikel (refereegranskat)abstract
- Indium segregation in a narrow InGaN single quantum well creates quantum dot (QD) like exciton localization centers. Cross-section transmission electron microscopy reveals varying shapes and lateral sizes in the range ∼1–5 nm of the QD-like features, while scanning near field optical microscopy demonstrates a highly inhomogeneous spatial distribution of optically active individual localization centers. Microphotoluminescence spectroscopy confirms the spectrally inhomogeneous distribution of localization centers, in which the exciton and the biexciton related emissions from single centers of varying geometry could be identified by means of excitation power dependencies. Interestingly, the biexciton binding energy (Ebxx) was found to vary from center to center, between 3 to −22 meV, in correlation with the exciton emission energy. Negative binding energies are only justified by a three-dimensional quantum confinement, which confirms QD-like properties of the localization centers. The observed energy correlation is proposed to be understood as variations of the lateral extension of the confinement potential, which would yield smaller values of Ebxx for reduced lateral extension and higher exciton emission energy. The proposed relation between lateral extension and Ebxx is further supported by the exciton and the biexciton recombination lifetimes of a single QD, which suggest a lateral extension of merely ∼3 nm for a QD with strongly negative Ebxx = −15.5 meV.
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- Barragán, O., et al.
(författare)
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K2-139 b: a low-mass warm Jupiter on a 29-d orbit transiting an active K0 V star
- 2018
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 475:2, s. 1765-1776
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Tidskriftsartikel (refereegranskat)abstract
- We announce the discovery of K2-139 b (EPIC 218916923 b), a transiting warm-Jupiter (Teq = 547 ± 25 K) on a 29-d orbit around an active (log R'_HK = -4.46 ± 0.06) K0V star in K2 Campaign 7. We derive the system's parameters by combining the K2 photometry with ground-based follow-up observations. With a mass of 0.387_-0.075^+0.083 M_J and radius of 0.808_-0.033^+0.034 R_J, K2-139 b is one of the transiting warm Jupiters with the lowest mass known to date. The planetary mean density of 0.91_-0.20^+0.24 g/cm^3 can be explained with a core of ~50 M⊕. Given the brightness of the host star (V = 11.653 mag), the relatively short transit duration (~5 h), and the expected amplitude of the Rossiter-McLaughlin effect (~25m/s), K2-139 is an ideal target to measure the spin-orbit angle of a planetary system hosting a warm Jupiter.
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- Bouhafs, Chamseddine, et al.
(författare)
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Structural properties and dielectric function of graphene grown by high-temperature sublimation on 4H-SiC(000-1)
- 2015
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Ingår i: Journal of Applied Physics. - : American Institute of Physics (AIP). - 0021-8979 .- 1089-7550. ; 117:8, s. 085701-
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Tidskriftsartikel (refereegranskat)abstract
- Understanding and controlling growth of graphene on the carbon face (C-face) of SiC presents a significant challenge. In this work, we study the structural, vibrational, and dielectric function properties of graphene grown on the C-face of 4H-SiC by high-temperature sublimation in an argon atmosphere. The effect of growth temperature on the graphene number of layers and crystallite size is investigated and discussed in relation to graphene coverage and thickness homogeneity. An amorphous carbon layer at the interface between SiC and the graphene is identified, and its evolution with growth temperature is established. Atomic force microscopy, micro-Raman scattering spectroscopy, spectroscopic ellipsometry, and high-resolution cross-sectional transmission electron microscopy are combined to determine and correlate thickness, stacking order, dielectric function, and interface properties of graphene. The role of surface defects and growth temperature on the graphene growth mechanism and stacking is discussed, and a conclusion about the critical factors to achieve decoupled graphene layers is drawn. (C) 2015 AIP Publishing LLC.
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- Esposito, M., et al.
(författare)
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HD 219666 b: a hot-Neptune from TESS Sector 1
- 2019
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 623:623
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Tidskriftsartikel (refereegranskat)abstract
- We report on the confirmation and mass determination of a transiting planet orbiting the old and inactive G7 dwarf star HD219666 (M-star = 0.92 +/- 0.03 M-circle dot, R-star = 1.03 +/- 0.03 R-circle dot, tau(star) = 10 +/- 2 Gyr). With a mass of M-b = 16.6 +/- 1.3 M-circle plus, a radius of R-b = 4.71 +/- 0.17 R-circle plus, and an orbital period of P-orb similar or equal to 6 days, HD219666 b is a new member of a rare class of exoplanets: the hot-Neptunes. The Transiting Exoplanet Survey Satellite (TESS) observed HD219666 (also known as TOI-118) in its Sector 1 and the light curve shows four transit-like events, equally spaced in time. We confirmed the planetary nature of the candidate by gathering precise radial-velocity measurements with the High Accuracy Radial velocity Planet Searcher (HARPS) at ESO 3.6 m. We used the co-added HARPS spectrum to derive the host star fundamental parameters (T-eff = 5527 +/- 65 K, log g(star) = 4.40 +/- 0.11 (cgs), [Fe/H] = 0.04 +/- 0.04 dex, log R-HK' = -5.07 +/- 0.03), as well as the abundances of many volatile and refractory elements. The host star brightness (V = 9.9) makes it suitable for further characterisation by means of in-transit spectroscopy. The determination of the planet orbital obliquity, along with the atmospheric metal-to-hydrogen content and thermal structure could provide us with important clues on the formation mechanisms of this class of objects.
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