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Sökning: WFRF:(Petrus L)

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1.
  • Desgrange, C., et al. (författare)
  • In-depth direct imaging and spectroscopic characterization of the young Solar System analog HD 95086
  • 2022
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 664
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. HD 95086 is a young nearby Solar System analog hosting a giant exoplanet orbiting at 57 au from the star between an inner and outer debris belt. The existence of additional planets has been suggested as the mechanism that maintains the broad cavity between the two belts.Aims. We present a dedicated monitoring of HD 95086 with the VLT/SPHERE instrument to refine the orbital and atmospheric properties of HD 95086 b, and to search for additional planets in this system.Methods. SPHERE observations, spread over ten epochs from 2015 to 2019 and including five new datasets, were used. Combined with archival observations, from VLT/NaCo (2012-2013) and Gemini/GPI (2013-2016), the extended set of astrometric measurements allowed us to refine the orbital properties of HD 95086 b. We also investigated the spectral properties and the presence of a circumplanetary disk around HD 95086 b by using the special fitting tool exploring the diversity of several atmospheric models. In addition, we improved our detection limits in order to search for a putative planet c via the K-Stacker algorithm.Results. We extracted for the first time the JH low-resolution spectrum of HD 95086 b by stacking the six best epochs, and confirm its very red spectral energy distribution. Combined with additional datasets from GPI and NaCo, our analysis indicates that this very red color can be explained by the presence of a circumplanetary disk around planet b, with a range of high-temperature solutions (1400–1600 K) and significant extinction (Av ≳ 10 mag), or by a super-solar metallicity atmosphere with lower temperatures (800–300 K), and small to medium amount of extinction (Av ≲ 10 mag). We do not find any robust candidates for planet c, but give updated constraints on its potential mass and location.
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  • Mesa, D., et al. (författare)
  • VLT/SPHERE exploration of the young multiplanetary system PDS70
  • 2019
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 632
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. PDS 70 is a young (5.4 Myr), nearby (similar to 113 pc) star hosting a known transition disk with a large gap. Recent observations with SPHERE and NACO in the near-infrared (NIR) allowed us to detect a planetary mass companion, PDS 70 b, within the disk cavity. Moreover, observations in H-alpha with MagAO and MUSE revealed emission associated to PDS 70 b and to another new companion candidate, PDS 70 c, at a larger separation from the star. PDS 70 is the only multiple planetary system at its formation stage detected so far through direct imaging.Aims. Our aim is to confirm the discovery of the second planet PDS 70 c using SPHERE at VLT, to further characterize its physical properties, and search for additional point sources in this young planetary system.Methods. We re-analyzed archival SPHERE NIR observations and obtained new data in Y, J, H and K spectral bands for a total of four different epochs. The data were reduced using the data reduction and handling pipeline and the SPHERE data center. We then applied custom routines (e.g., ANDROMEDA and PACO) to subtract the starlight.Results. We re-detect both PDS 70 b and c and confirm that PDS 70 c is gravitationally bound to the star. We estimate this second planet to be less massive than 5 M-Jup and with a T-eff around 900 K. Also, it has a low gravity with log g between 3.0 and 3.5 dex. In addition, a third object has been identified at short separation (similar to 0.12 '') from the star and gravitationally bound to the star. Its spectrum is however very blue, meaning that we are probably seeing stellar light reflected by dust and our analysis seems to demonstrate that it is a feature of the inner disk. We cannot however completely exclude the possibility that it is a planetary mass object enshrouded by a dust envelope. In this latter case, its mass should be of the order of a few tens of M-circle plus. Moreover, we propose a possible structure for the planetary system based on our data, and find that this structure cannot be stable on a long timescale.
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  • Bonavita, M., et al. (författare)
  • New binaries from the SHINE survey
  • 2022
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 663
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the multiple stellar systems observed within the SpHere INfrared survey for Exoplanet (SHINE). SHINE searched for sub-stellar companions to young stars using high contrast imaging. Although stars with known stellar companions within the SPHERE field of view (< 5.5 arcsec) were removed from the original target list, we detected additional stellar companions to 78 of the 463 SHINE targets observed so far. Twenty-seven per cent of the systems have three or more components. Given the heterogeneity of the sample in terms of observing conditions and strategy, tailored routines were used for data reduction and analysis, some of which were specifically designed for these datasets. We then combined SPHERE data with literature and archival data, TESS light curves, and Gaia parallaxes and proper motions for an accurate characterisation of the systems. Combining all data, we were able to constrain the orbits of 25 systems. We carefully assessed the completeness of our sample for separations between 50–500 mas (corresponding to periods of a few years to a few decades), taking into account the initial selection biases and recovering part of the systems excluded from the original list due to their multiplicity. This allowed us to compare the binary frequency for our sample with previous studies and highlight interesting trends in the mass ratio and period distribution. We also found that, when such an estimate was possible, the values of the masses derived from dynamical arguments were in good agreement with the model predictions. Stellar and orbital spins appear fairly well aligned for the 12 stars that have enough data, which favours a disk fragmentation origin. Our results highlight the importance of combining different techniques when tackling complex problems such as the formation of binaries and show how large samples can be useful for more than one purpose.
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  • Gratton, R., et al. (författare)
  • Investigating three Sirius-like systems with SPHERE
  • 2021
  • Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 646
  • Tidskriftsartikel (refereegranskat)abstract
    • Context. Sirius-like systems are relatively wide binaries with a separation from a few to hundreds of au; they are composed of a white dwarf (WD) and a companion of a spectral type earlier than M0. Here we consider main sequence (MS) companions, where the WD progenitor evolves in isolation, but its wind during the former asymptotic giant branch (AGB) phase pollutes the companion surface and transfers some angular momentum. They are rich laboratories to constrain stellar models and binary evolution.Aims. Within the SpHere INfrared survey for Exoplanet survey that uses the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument at the Very Large Telescope, our goal is to acquire high contrast multi-epoch observations of three Sirius-like systems, HD 2133, HD 114174, and CD-56 7708 and to combine this data with archive high resolution spectra of the primaries, TESS archive, and literature data.Methods. These WDs are easy targets for SPHERE and were used as spectrophotometric standards. We performed very accurate abundance analyses for the MS stars using methods considered for solar analogs. Whenever possible, WD parameters and orbits were obtained using Monte Carlo Markov chain methods.Results. We found brighter J and K magnitudes for HD 114174B than obtained previously and extended the photometry down to 0.95 μm. Our new data indicate a higher temperature and then shorter cooling age (5.57 ± 0.02 Gyr) and larger mass (0.75 ± 0.03 M⊙) for this WD than previously assumed. Together with the oldest age for the MS star connected to the use of the Gaia DR2 distance, this solved the discrepancy previously found with the age of the MS star. The two other WDs are less massive, indicating progenitors of ∼1.3 M⊙ and 1.5 − 1.8 M⊙ for HD 2133B and CD-56 7708B, respectively. In spite of the rather long periods, we were able to derive useful constraints on the orbit for HD 114174 and CD-56 7708. They are both seen close to edge-on, which is in agreement with the inclination of the MS stars that are obtained coupling the rotational periods, stellar radii, and the projected rotational velocity from spectroscopy. The composition of the MS stars agrees fairly well with expectations from pollution by the AGB progenitors of the WDs: HD 2133A has a small enrichment of n-capture elements, which is as expected for pollution by an AGB star with an initial mass < 1.5 M⊙; CD-56 7708A is a previously unrecognized mild Ba-star, which is also expected due to pollution by an AGB star with an initial mass in the range of 1.5 − 3.0 M⊙; and HD 114174 has a very moderate excess of n-capture elements, which is in agreement with the expectation for a massive AGB star to have an initial mass > 3.0 M⊙.Conclusions. On the other hand, none of these stars show the excesses of C that are expected to go along with those of n-capture elements. This might be related to the fact that these stars are at the edges of the mass range where we expect nucleosynthesis related to thermal pulses. More work, both theoretical and observational, is required to better understand this issue.
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  • Abu-Ghanem, Yasmin, et al. (författare)
  • Should patients with low-risk renal cell carcinoma be followed differently after nephron-sparing surgery vs radical nephrectomy?
  • 2021
  • Ingår i: BJU International. - : John Wiley & Sons. - 1464-4096 .- 1464-410X. ; 128:3, s. 386-394
  • Tidskriftsartikel (refereegranskat)abstract
    • Objective: To investigate whether pT1 renal cell carcinoma (RCC) should be followed differently after partial (PN) or radical nephrectomy (RN) based on a retrospective analysis of a multicentre database (RECUR).Subjects: A retrospective study was conducted in 3380 patients treated for nonmetastatic RCC between January 2006 and December 2011 across 15 centres from 10 countries, as part of the RECUR database project. For patients with pT1 clear-cell RCC, patterns of recurrence were compared between RN and PN according to recurrence site. Univariate and multivariate models were used to evaluate the association between surgical approach and recurrence-free survival (RFS) and cancer-specific mortality (CSM).Results: From the database 1995 patients were identified as low-risk patients (pT1, pN0, pNx), of whom 1055 (52.9%) underwent PN. On multivariate analysis, features associated with worse RFS included tumour size (hazard ratio [HR] 1.32, 95% confidence interval [CI] 1.14–1.39; P < 0.001), nuclear grade (HR 2.31, 95% CI 1.73–3.08; P < 0.001), tumour necrosis (HR 1.5, 95% CI 1.03–2.3; P = 0.037), vascular invasion (HR 2.4, 95% CI 1.3–4.4; P = 0.005) and positive surgical margins (HR 4.4, 95% CI 2.3–8.5; P < 0.001). Kaplan–Meier analysis of CSM revealed that the survival of patients with recurrence after PN was significantly better than those with recurrence after RN (P = 0.02). While the above-mentioned risk factors were associated with prognosis, type of surgery alone was not an independent prognostic variable for RFS nor CSM. Limitations include the retrospective nature of the study.Conclusion: Our results showed that follow-up protocols should not rely solely on stage and type of primary surgery. An optimized regimen should also include validated risk factors rather than type of surgery alone to select the best imaging method and to avoid unnecessary imaging. A follow-up of more than 3 years should be considered in patients with pT1 tumours after RN. A novel follow-up strategy is proposed.
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  • Bernabé, S., et al. (författare)
  • Highly integrated VCSEL-based 10Gb/s miniature optical sub-assembly
  • 2005
  • Ingår i: Proceedings - Electronic Components and Technology Conference. - Lake Buena Vista, FL : IEEE. ; , s. 1333-1338
  • Konferensbidrag (refereegranskat)abstract
    • In order to fit with the present and future needs of the Datacom transceiver market, newly designed high rate transmitter optical subassemblies (TOSAs) have to be compact, low cost and compatible with mass production. We propose here an innovative design strategy that reaches all these targets by integrating a 10Gbps 850nmVCSEL laser diode and its laser driver with other functionalities (e.g. power monitoring and thermal monitoring) in a small form factor package. Taking advantages of the optical properties of the VCSEL and using flip-chip techniques, the transmitter exhibits excellent hyperfrequency performances and compatibility with mass production due to the use of collective manufacturing technologies and passive optical alignment. This versatile approach is also applicable to high rate receivers, parallel optics emitters, and singlemode low cost transmitter integrating long wavelength VCSELs.
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  • Bialesova, L, et al. (författare)
  • Epigenetic Regulation of PLIN 1 in Obese Women and its Relation to Lipolysis
  • 2017
  • Ingår i: Scientific reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 7:1, s. 10152-
  • Tidskriftsartikel (refereegranskat)abstract
    • Increased adipocyte lipolysis links obesity to insulin resistance. The lipid droplet coating-protein Perilipin participates in regulation of lipolysis and is implicated in obesity. In the present study we investigate epigenetic regulation of the PLIN1 gene by correlating PLIN1 CpG methylation to gene expression and lipolysis, and functionally evaluating PLIN1 promoter methylation. PLIN1 CpG methylation in adipocytes and gene expression in white adipose tissue (WAT) was quantified in two cohorts by array. Basal lipolysis in WAT explants and adipocytes was quantified by measuring glycerol release. CpG-methylation of the PLIN1 promoter in adipocytes from obese women was higher as compared to never-obese women. PLIN1 promoter methylation was inversely correlated with PLIN1 mRNA expression and the lipolytic activity. Human mesenchymal stem cells (hMSCs) differentiated in vitro into adipocytes and harboring methylated PLIN1 promoter displayed decreased reporter gene activity as compared to hMSCs harboring unmethylated promoter. Treatment of hMSCs differentiated in vitro into adipocytes with a DNA methyltransferase inhibitor increased levels of PLIN1 mRNA and protein. In conclusion, the PLIN1 gene is epigenetically regulated and promoter methylation is inversely correlated with basal lipolysis in women suggesting that epigenetic regulation of PLIN1 is important for increased adipocyte lipolysis in insulin resistance states.
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  • Cheng, Daphne Y. T., et al. (författare)
  • Facilitating Personal Recovery Through Mindfulness-Based Intervention Among People With Mental Illness
  • 2022
  • Ingår i: Research on social work practice. - : SAGE Publications. - 1049-7315 .- 1552-7581. ; 33:8, s. 827-848
  • Tidskriftsartikel (refereegranskat)abstract
    • Purpose: This pre-pilot randomized controlled trial (RCT) assessed a mindfulness-based intervention (MBI, “REMIND1.0”) during the COVID-19 pandemic.Methods: Twenty mental health service users were allocated to either 8 weekly mixed-mode MBI (n = 10) or treatment-as-usual (TAU) (n = 10).Results: There were significant interactions between group and time (baseline T0, post-intervention T1, and 1-month follow-up T2) across all quantitative outcomes (personal recovery, trait mindfulness, self-compassion, resilience, moods, quality of life, and general health). The main themes that emerged from qualitative interviews at T1 are previous experience with MBIs, features of current MBI, and benefits of personal recovery and at T2 are recollection of MBI content, maintaining regular practice after MBI, and retained benefits of personal recovery.Conclusions: The current MBI is acceptable, feasible, and potentially effective in facilitating personal recovery.
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  • Gilet, Ph., et al. (författare)
  • 1.3 μm VCSELs : InGaAs/GaAs, GaInNAs/GaAs multiple quantum wells and InAs/GaAs quantum dots- Three candidates as active material
  • 2007
  • Ingår i: Vertical - Cavity Surface - Emitting Lasers XI. - San Jose, CA : SPIE. ; , s. F4840-F4840
  • Konferensbidrag (refereegranskat)abstract
    • In this article, we report our results on 1.3ÎŒm VCSELs for optical interconnection applications. Room temperature continuous-wave lasing operation is demonstrated for top emitting oxide-confined devices with three different active materials, highly strained InGaAs/GaAs(A) and GalnNAs/GaAs (B) multiple quantum wells (MQW) or InAs/GaAs (C) quantum dots (QD). Conventional epitaxial structures grown respectively by Metal Organic Vapour Phase Epitaxy (MOVPE), Molecular Beam Epitaxy (MBE) and MBE, contain rully doped GaAs/AlGaAs DBRs. All three epilayers are processed in the same way. Current and optical confinement are realized by selective wet oxidation. Circular apertures from 2 ÎŒm to 16 ÎŒm diameters are defined. At room temperature and in continuous wave operation, all three systems exhibit lasing operation at wavelengths above 1 275nm and reached 1 300nm for material (A). Typical threshold currents are in the range [1-10]mA and are strongly dependent firstly on oxide diameter and secondly on temperature. Room temperature cw maximum output power corresponds respectively to 1.77mW, 0.5mW and 0.6mW. By increasing driving current, multimode operation occurs at different level depending on the oxide diameter. In case (A), non conventional modal behaviors will be presented and explained by the presence of specific oxide modes. Thermal behaviors of the different devices have been compared. In case (A) and (C) we obtain a negative T0. We will conclude on the different active materials in terms of performances with respect to 1300nm VCSEL applications.
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  • Hinkley, Sasha, et al. (författare)
  • The JWST Early Release Science Program for the Direct Imaging and Spectroscopy of Exoplanetary Systems
  • 2022
  • Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 134:1039
  • Tidskriftsartikel (refereegranskat)abstract
    • The direct characterization of exoplanetary systems with high-contrast imaging is among the highest priorities for the broader exoplanet community. As large space missions will be necessary for detecting and characterizing exo-Earth twins, developing the techniques and technology for direct imaging of exoplanets is a driving focus for the community. For the first time, JWST will directly observe extrasolar planets at mid-infrared wavelengths beyond 5 μm, deliver detailed spectroscopy revealing much more precise chemical abundances and atmospheric conditions, and provide sensitivity to analogs of our solar system ice-giant planets at wide orbital separations, an entirely new class of exoplanet. However, in order to maximize the scientific output over the lifetime of the mission, an exquisite understanding of the instrumental performance of JWST is needed as early in the mission as possible. In this paper, we describe our 55 hr Early Release Science Program that will utilize all four JWST instruments to extend the characterization of planetary-mass companions to ∼15 μm as well as image a circumstellar disk in the mid-infrared with unprecedented sensitivity. Our program will also assess the performance of the observatory in the key modes expected to be commonly used for exoplanet direct imaging and spectroscopy, optimize data calibration and processing, and generate representative data sets that will enable a broad user base to effectively plan for general observing programs in future Cycles.
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  • Nahálková, Jarmila, et al. (författare)
  • Affinity analysis of lectin interaction with immobilized C- and O-gylcosides studied by surface plasmon resonance assay
  • 2002
  • Ingår i: Journal of Biochemical and Biophysical Methods. - 0165-022X .- 1872-857X. ; 52:1, s. 11-18
  • Tidskriftsartikel (refereegranskat)abstract
    • A biosensor based on the surface plasmon resonance (SPR) principle was used for kinetic analysis of lectin interactions with different immobilized saccharide structures. A novel affinity ligands beta-D-glycopyranosylmethylamines derived from common D-aldohexoses linked to the carboxymethyl dextran layer of the SPR sensor surface served for interactions with a wide range of lectins. The method of preparation and use of the beta-D-mannopyranosyl glycosylated sensor surface was described. The results of affinity analysis of lectin-ligand interactions were evaluated and compared with data obtained from measurements using commercially available p-aminophenyl alpha-D-glycopyranosides. Possible applications and advantages of C- and O-glycosylated SPR biosensors are discussed.
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  • Petrus, L, et al. (författare)
  • Research of carbohydrates as the diversity factor of the living matter
  • 2000
  • Ingår i: Chemické listy (Print). - 0009-2770 .- 1213-7103. ; 94:9, s. 764-766
  • Tidskriftsartikel (refereegranskat)abstract
    • An overview of the biological roles of carbohydrate chains in glycoconjugates is given with respect to their immediate impact on the diversity of the living matter. Some space is devoted also to new applications of glycosylmethylamines in the lectin research.
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  • Pougeoise, E., et al. (författare)
  • Experimental study of the lasing modes of 1.3-ÎŒm highly strained InGaAs-GaAs quantum-well oxide-confined VCSELs
  • 2009
  • Ingår i: IEEE Photonics Technology Letters. - 1041-1135 .- 1941-0174. ; 21:6, s. 377-379
  • Tidskriftsartikel (refereegranskat)abstract
    • We present an experimental study of the main modes involved in the emission properties of InGaAs-GaAs quantum-well oxide-confined long wavelength vertical-cavity surface-emitting lasers. Lasing properties are dominated by the so-called "oxide modes" and by aperture modes, respectively, for small and large driving currents. We present complementary investigations of the laser emission including far-field angular distribution and spectroscopic near-field optical microscopy to a better understanding of the nature of the "oxide modes."
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