Context. R Aqr is a symbiotic binary system consisting of a mira variable, a hot companion with a spectacular jet outflow, and an extended emission line nebula. Because of its proximity to the Sun, ...this object has been studied in much detail with many types of high resolution imaging and interferometric techniques. We have used R Aqr as test target for the visual camera subsystem ZIMPOL, which is part of the new extreme adaptive optics (AO) instrument SPHERE at the Very Large Telescope (VLT). Aims. We describe SPHERE/ZIMPOL test observations of the R Aqr system taken in Hα and other filters in order to demonstrate the exceptional performance of this high resolution instrument. We compare our observations with data from the Hubble Space Telescope (HST) and illustrate the complementarity of the two instruments. We use our data for a detailed characterization of the inner jet region of R Aqr. Methods. We analyze the high resolution ≈ 25 mas images from SPHERE/ZIMPOL and determine from the Hα emission the position, size, geometric structure, and line fluxes of the jet source and the clouds in the innermost region <2′′ (<400 AU) of R Aqr. The data are compared to simultaneous HST line filter observations. The Hα fluxes and the measured sizes of the clouds yield Hα emissivities for many clouds from which one can derive the mean density, mass, recombination time scale, and other cloud parameters. Results. Our Hα data resolve for the first time the R Aqr binary and we measure for the jet source a relative position 45 mas West (position angle −89.5°) of the mira. The central jet source is the strongest Hα component with a flux of about 2.5 × 10-12 erg cm-2 s-1. North east and south west from the central source there are many clouds with very diverse structures. Within 0.5′′ (100 AU) we see in the SW a string of bright clouds arranged in a zig-zag pattern and, further out, at 1′′−2′′, fainter and more extended bubbles. In the N and NE we see a bright, very elongated filamentary structure between 0.2′′−0.7′′ and faint perpendicular “wisps” further out. Some jet clouds are also detected in the ZIMPOL O I and He I filters, as well as in the HST-WFC3 line filters for Hα, O III, N II, and O I. We determine jet cloud parameters and find a very well defined correlation Ne ∝ r-1.3 between cloud density and distance to the central binary. Densities are very high with typical values of Ne ≈ 3 × 105 cm-3 for the “outer” clouds around 300 AU, Ne ≈ 3 × 106 cm-3 for the “inner” clouds around 50 AU, and even higher for the central jet source. The high Ne of the clouds implies short recombination or variability timescales of a year or shorter. Conclusions. Hα high resolution data provide a lot of diagnostic information for the ionized jet gas in R Aqr. Future Hα observations will provide the orientation of the orbital plane of the binary and allow detailed hydrodynamical investigations of this jet outflow and its interaction with the wind of the red giant companion.
GRAVITY K-band spectroscopy of HD 206893 B Kammerer, J; Lacour, S; Stolker, T ...
Astronomy and astrophysics (Berlin),
08/2021, Letnik:
652
Journal Article, Web Resource
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Context. Near-infrared interferometry has become a powerful tool for studying the orbital and atmospheric parameters of substellar companions. Aims. We aim to reveal the nature of the reddest known ...substellar companion HD 206893 B by studying its near-infrared colors and spectral morphology and by investigating its orbital motion. Methods. We fit atmospheric models for giant planets and brown dwarfs and perform spectral retrievals with petitRADTRANS and ATMO on the observed GRAVITY, SPHERE, and GPI spectra of HD 206893 B. To recover its unusual spectral features, first and foremost its extremely red near-infrared color, we include additional extinction by high-altitude dust clouds made of enstatite grains in the atmospheric model fits. However, forsterite, corundum, and iron grains predict similar extinction curves for the grain sizes considered here. We also infer the orbital parameters of HD 206893 B by combining the ~100 μas precision astrometry from GRAVITY with data from the literature and constrain the mass and position of HD 206893 C based on the Gaia proper motion anomaly of the system. Results. The extremely red color and the very shallow 1.4 μm water absorption feature of HD 206893 B can be fit well with the adapted atmospheric models and spectral retrievals. By comparison with AMES-Cond evolutionary tracks, we find that only some atmosphericmodels predict physically plausible objects. Altogether, our analysis suggests an age of ~ 3–300 Myr and a mass of ~ 5–30 MJup for HD 206893 B, which is consistent with previous estimates but extends the parameter space to younger and lower-mass objects. The GRAVITY astrometry points to an eccentric orbit (e = 0.29−0.11+0.06) with a mutual inclination of <34.4 deg with respectto the debris disk of the system. Conclusions. While HD 206893 B could in principle be a planetary-mass companion, this possibility hinges on the unknown influence of the inner companion on the mass estimate of 10−4+5 MJup from radial velocity and Gaia as well as a relatively small but significant Argus moving group membership probability of ~ 61%. However, we find that if the mass of HD 206893 B is <30 MJup, then the inner companion HD 206893 C should have a mass between ~ 8–15 MJup. Finally, further spectroscopic or photometric observations at higher signal-to-noise and longer wavelengths are required to learn more about the composition and dust cloud properties of HD 206893 B.
Injection of an adenoviral (Ad) vector encoding human glial cell line-derived neurotrophic factor (GDNF) protects dopaminergic (DA) neurons in the substantia nigra (SN) of young rats. As Parkinson's ...disease occurs primarily in aged populations, we examined whether chronic biosynthesis of GDNF, achieved by adenovirus-mediated delivery of a GDNF gene (AdGDNF), can protect DA neurons and improve DA-dependent behavioral function in aged (20 months) rats with progressive 6-OHDA lesions of the nigrostriatal projection. Furthermore, the differential effects of injecting AdGDNF either near DA cell bodies in the SN or at DA terminals in the striatum were compared. AdGDNF or control vector was injected unilaterally into either the striatum or SN. One week later, rats received a unilateral intrastriatal injection of 6-OHDA on the same side as the vector injection. AdGDNF injection into either the striatum or SN significantly reduced the loss of FG labelled DA neurons 5 weeks after lesion (P </= 0.05). However, only striatal injections of AdGDNF protected against the development of behavioral deficits characteristic of unilateral DA depletion. Striatal AdGDNF injections also reduced tyrosine hydroxylase fiber loss and increased amphetamine-induced striatal Fos expression. These results demonstrate that increased levels of striatal, but not nigral, GDNF biosynthesis prevents DA neuronal loss and protects DA terminals from 6-OHDA-induced damage, thereby maintaining DA function in the aged rat.
The aim of the research was to evaluate the effects of sulfonitric and CS (CS) treatment in multilayer carbon nanotubes (MWCNT) on their electrochemical and magnetic properties. Thermogravimetric ...analysis (TG) showed an increase in thermal properties for CS functionalized MWCNT when compared in sulfonitric medium. High resolution transmission electron microscopy (HRTEM) images revealed a reduction in the average diameter of functionalized MWCNT in the presence of CS in addition to decreasing their interlayer spaces. As evidenced by X-ray Diffraction (XRD) patterns. In addition, X-ray photoelectron spectroscopy (XPS) spectra proved the functional groups inclusion of CS and sulfonitric solution on the (carbon nanotubes) CNT matrix. Unlike pristine MWCNT solutions which are unstable in aqueous media, functionalization with acidic solutions and contributed to its potential stabilization. The results obtained by Raman Spectroscopy prove the functionalization through the insertion of functional groups in the walls of the nanotubes. The electroanalysis showed higher capacitance values by mass and by area for samples functionalized with acids and that the addition of CS during functionalization increases the resistance to current flow, causing an insulating effect.
Superparamagnetic magnetite/IPEC particles Brito, E.L.; Gomes, D.N.; Plá Cid, C.C. ...
Colloids and surfaces. A, Physicochemical and engineering aspects,
01/2019, Letnik:
560
Journal Article
Recenzirano
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Hybrid magnetic composites are materials with great potential for use in biomedicine and effluent treatments, as their organic phase may be used in the adsorption/release of ...pollutants/drugs and their magnetic properties for separation/transport of particulate systems based on these materials. In this work we obtained magnetic composite particles made of magnetite nanoparticles dispersed in a polymeric matrix resultant from the formation of interpolyelectrolyte complexes based on chitosan and poly(sodium 4-styrenesulfonate). Non-stoichiometric positive and negatively charged interpolyelectrolyte complexes were obtained and characterized via thermogravimetry, Fourier transform infrared spectroscopy, X-ray diffraction analysis, transmission electron microscopy, zeta potentiometry, and vibrating sample magnetometry. The samples obtained in this work showed that nanometric magnetite was incorporated to these systems and that the resultant composites were superparamagnetic. Preliminary tests showed that the composites may be used both in the sorption of cationic and anionic drugs.
Context. With an orbital distance comparable to that of Saturn in the solar system, β Pictoris b is the closest (semi-major axis ≃9 au) exoplanet that has been imaged to orbit a star. Thus it offers ...unique opportunities for detailed studies of its orbital, physical, and atmospheric properties, and of disk-planet interactions. With the exception of the discovery observations in 2003 with NaCo at the Very Large Telescope (VLT), all following astrometric measurements relative to β Pictoris have been obtained in the southwestern part of the orbit, which severely limits the determination of the planet’s orbital parameters. Aims. We aimed at further constraining β Pictoris b orbital properties using more data, and, in particular, data taken in the northeastern part of the orbit. Methods. We used SPHERE at the VLT to precisely monitor the orbital motion of beta β Pictoris b since first light of the instrument in 2014. Results. We were able to monitor the planet until November 2016, when its angular separation became too small (125 mas, i.e., 1.6 au) and prevented further detection. We redetected β Pictoris b on the northeast side of the disk at a separation of 139 mas and a PA of 30° in September 2018. The planetary orbit is now well constrained. With a semi-major axis (sma) of a = 9.0 ± 0.5 au (1σ), it definitely excludes previously reported possible long orbital periods, and excludes β Pictoris b as the origin of photometric variations that took place in 1981. We also refine the eccentricity and inclination of the planet. From an instrumental point of view, these data demonstrate that it is possible to detect, if they exist, young massive Jupiters that orbit at less than 2 au from a star that is 20 pc away.
•Feasible route to the production of core/shell nanostructure with pure phases.•Synthesis of CoFe2O4@BiFeO3 core/shell nanoparticles by coprecipitation.•Structural, morphological and magnetic ...properties in CFO@BFO.•Wasp-waisted behavior and exchange bias effect disclosing the coupling between phases.•Spin disorder in CFO@BFO core/shell nanoparticles.
We synthesize CoFe2O4@BiFeO3 core/shell nanoparticles by coprecipitation and systematically investigate the structural, morphological, and magnetic properties in such nanostructured system. Through structural and morphological characterization, we demonstrate the obtainment of core/shell nanostructure with pure phases. By performing a broad experimental magnetic analysis, we evaluate the magnetic response for the precursor phases, as well as for the core/shell nanostructure. For this latter, we identify fingerprints of the wasp-waisted behavior and exchange bias effect, disclosing the exchange coupling between the phases taking place at the interface. Further, we reveal the exchange coupling between core and shell is strongly affected by a spin glass behavior arisen from the spin disorder in the CoFe2O4@BiFeO3 core/shell nanoparticles. After all, our findings allow us to place the used procedures taking into account the coprecipitation and calcination processes as a feasible route to the production of high-quality core/shell nanostructures.
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