Teff and log g dependence of velocity fields in M-stars

We present an investigation of velocity fields in early to late M-type hydrodynamic stellar atmosphere models. These velocities will be expressed in classical terms of micro- and macro-turbulent velocities for usage in 1D spectral synthesis. The M-star model parameters range between log g of 3.0 - 5.0 and Teff of 2500 K - 4000 K. We characterize the Teff- and log g-dependence of the hydrodynamical velocity fields in these models with a binning method, and for the determination of micro-turbulent velocities, the Curve of Growth method is used. The macro-turbulent velocities are obtained by convolutions with Gaussian profiles. Velocity fields in M-stars strongly depend on log g and Teff. Their velocity amplitudes increase with decreasing log g and increasing Teff. The 3D hydrodynamical and 1D macro-turbulent velocities range from ~100 m/s for cool high gravity models to ~ 800 m/s - 1000 m/s for hot models or models with low log g. The micro-turbulent velocities range in the order of ~100 m/s for cool models, to ~600 m/s for hot or low log g models. Our M-star structure models are calculated with the 3D radiative-hydrodynamics (RHD) code CO5BOLD. The spectral synthesis on these models is performed with the line synthesis code LINFOR3D.Comment: 8 pages, 6 Figures, Proceeding fot the "Recent directions in astrophysical quantitative spectroscopy and radiation hydrodynamics" conferenc

Teff and logg dependence of FeH in M-dwarfs

We present synthetic FeH band spectra in the z-filter range for several M-dwarf models with logg=3.0-5.0 [cgs] and Teff=2800K -3450K. Our aim is to characterize convective velocities in M-dwarfs and to give a rough estimate of the range in which 3D-atmosphere treatment is necessary and where 1D-atmosphere models suffice for the interpretation of molecular spectral features. This is also important in order to distinguish between the velocity-broadening and the rotational- or Zeeman-broadening. The synthetic spectra were calculated using 3D CO5BOLD radiative-hydrodynamic (RHD) models and the line synthesis code LINFOR3D. We used complete 3D-models and high resolution 3D spectral synthesis for the detailed study of some well isolated FeH lines. The FeH line strength shows a dependence on surface gravity and effective temperature and could be employed to measure both quantities in M-type objects. The line width is related to the velocity-field in the model stars, which depends strongly on surface gravity. Furthermore, we investigate the velocity-field in the 3D M-dwarf models together with the related micro- and macro-turbulent velocities in the 1D case. We also search for effects on the lineshapes.Comment: Cool Stars 15 Conference Proceeding, 4 page

Teff and logg dependence of FeH in M-dwarfs

We present synthetic FeH band spectra in the z-filter range for several M-dwarf models with logg=3.0-5.0 [cgs] and Teff=2800K -3450K. Our aim is to characterize convective velocities in M-dwarfs and to give a rough estimate of the range in which 3D-atmosphere treatment is necessary and where 1D-atmosphere models suffice for the interpretation of molecular spectral features. This is also important in order to distinguish between the velocity-broadening and the rotational- or Zeeman-broadening. The synthetic spectra were calculated using 3D CO5BOLD radiative-hydrodynamic (RHD) models and the line synthesis code LINFOR3D. We used complete 3D-models and high resolution 3D spectral synthesis for the detailed study of some well isolated FeH lines. The FeH line strength shows a dependence on surface gravity and effective temperature and could be employed to measure both quantities in M-type objects. The line width is related to the velocity-field in the model stars, which depends strongly on surface gravity. Furthermore, we investigate the velocity-field in the 3D M-dwarf models together with the related micro- and macro-turbulent velocities in the 1D case. We also search for effects on the lineshapes.Comment: Cool Stars 15 Conference Proceeding, 4 page

Doping of inorganic materials in microreactors – preparation of Zn doped Fe₃O₄ nanoparticles

Microreactor systems are now used more and more for the continuous production of metal nanoparticles and metal oxide nanoparticles owing to the controllability of the particle size, an important property in many applications. Here, for the first time, we used microreactors to prepare metal oxide nanoparticles with controlled and varying metal stoichiometry. We prepared and characterised Zn-substituted Fe₃O₄ nanoparticles with linear increase of Zn content (ZnxFe₃−xO₄ with 0 ≤ x ≤ 0.48), which causes linear increases in properties such as the saturation magnetization, relative to pure Fe₃O₄. The methodology is simple and low cost and has great potential to be adapted to the targeted doping of a vast array of other inorganic materials, allowing greater control on the chemical stoichiometry for nanoparticles prepared in microreactors

Collaborative robotics: Enhance maintenance procedures on primary flight control servo-actuators

Electro-Hydraulic Servo-Actuators (EHSAs) are mainly used to command primary flight control surfaces in military and commercial aircraft. Since these devices are crucial for vehicle stability and maneuverability, a correct assessment of their health status is mandatory. Within this framework, a joint research project (HyDiag), held by Politecnico di Torino and Lufthansa Technik AG (LHT), aims to provide a more efficient and reliable procedure to determine the operating conditions of the EHSA. A smart and automatic sequence, able to extract several health features of the Unit Under Test (UUT), has been developed and integrated. The present paper discusses the implementation of a collaborative robot, equipped with a vision system and customized tools, for both health features extraction, and maintenance tasks on unserviceable servo-actuators. The main challenges related to the automation of such complex tasks in a real working environment are highlighted, togetherwith the advantages brought by the proposed approach. The paper also presents the first results of an ongoing experimental campaign. Specifically, it reports the enhancements of the maintenance procedures using collaborative robotics and possible future developments

Drifting inwards in protoplanetary discs I Sticking of chondritic dust at increasing temperatures

Sticking properties rule the early phases of pebble growth in protoplanetary discs in which grains regularly travel from cold, water-rich regions to the warm inner part. This drift affects composition, grain size, morphology, and water content as grains experience ever higher temperatures. In this study we tempered chondritic dust under vacuum up to 1400 K. Afterwards, we measured the splitting tensile strength of millimetre-sized dust aggregates. The deduced effective surface energy starts out as $\gamma_e = 0.07\,\rm J/m^2$. This value is dominated by abundant iron-oxides as measured by M\"ossbauer spectroscopy. Up to 1250 K, $\gamma_e$ continuously decreases by up to a factor five. Olivines dominate at higher temperature. Beyond 1300 K dust grains significantly grow in size. The $\gamma_e$ no longer decreases but the large grain size restricts the capability of growing aggregates. Beyond 1400 K aggregation is no longer possible. Overall, under the conditions probed, the stability of dust pebbles would decrease towards the star. In view of a minimum aggregate size required to trigger drag instabilities it becomes increasingly harder to seed planetesimal formation closer to a star

Two-Dimensional Impulsively Stimulated Resonant Raman Spectroscopy of Molecular Excited States

Monitoring the interactions between electronic and vibrational degrees of freedom in molecules is critical to our understanding of their structural dynamics. This is typically hampered by the lack of spectroscopic probes able to detect different energy scales with high temporal and frequency resolution. Coherent Raman spectroscopy can combine the capabilities of multidimensional spectroscopy with structural sensitivity at ultrafast timescales. Here, we develop a three-color-based 2D impulsive stimulated Raman technique that can selectively probe vibrational mode couplings between different active sites in molecules by taking advantage of resonance Raman enhancement. Three temporally delayed pulses generate nuclear wave packets whose evolution reports on the underlying potential energy surface, which we decipher using a diagrammatic approach enabling us to assign the origin of the spectroscopic signatures. We benchmark the method by revealing vibronic couplings in the ultrafast dynamics following photoexcitation of the green fluorescent protein

Two-Dimensional Impulsively Stimulated Resonant Raman Spectroscopy of Molecular Excited States

Monitoring the interactions between electronic and vibrational degrees of freedom in molecules is critical to our understanding of their structural dynamics. This is typically hampered by the lack of spectroscopic probes able to detect different energy scales with high temporal and frequency resolution. Coherent Raman spectroscopy can combine the capabilities of multidimensional spectroscopy with structural sensitivity at ultrafast timescales. Here, we develop a three-color-based 2D impulsive stimulated Raman technique that can selectively probe vibrational mode couplings between different active sites in molecules by taking advantage of resonance Raman enhancement. Three temporally delayed pulses generate nuclear wave packets whose evolution reports on the underlying potential energy surface, which we decipher using a diagrammatic approach enabling us to assign the origin of the spectroscopic signatures. We benchmark the method by revealing vibronic couplings in the ultrafast dynamics following photoexcitation of the green fluorescent protein.C. S. acknowledges financial support by the Royal Commission for the Exhibition of 1851. G. Bat. acknowledges the “Avvio Alla Ricerca 2018” grant by Sapienza Universitá di Roma. T. W. acknowledges the Marie Curie Intra-European Fellowship (PIEF-GA-2013-623651) within the 7th European Community Framework Programme. S. M. gratefully acknowledges the support of the National Science Foundation Grant No. CHE-1663822

3D simulations of M star atmosphere velocities and their influence on molecular FeH lines

We present an investigation of the velocity fields in early to late M-type star hydrodynamic models, and we simulate their influence on FeH molecular line shapes. The M star model parameters range between log g of 3.0 - 5.0 and Teff of 2500 K and 4000 K. Our aim is to characterize the Teff- and log g -dependence of the velocity fields and express them in terms of micro- and macro-turbulent velocities in the one dimensional sense. We present also a direct comparison between 3D hydrodynamical velocity fields and 1D turbulent velocities. The velocity fields strongly affect the line shapes of FeH, and it is our goal to give a rough estimate for the log g and Teff parameter range in which 3D spectral synthesis is necessary and where 1D synthesis suffices. In order to calculate M-star structure models we employ the 3D radiative-hydrodynamics (RHD) code CO5BOLD. The spectral synthesis on these models is performed with the line synthesis code LINFOR3D. We describe the 3D velocity fields in terms of a Gaussian standard deviation and project them onto the line of sight to include geometrical and limb-darkening effects. The micro- and macro-turbulent velocities are determined with the "Curve of Growth" method and convolution with a Gaussian velocity profile, respectively. To characterize the log g and Teff dependence of FeH lines, the equivalent width, line width, and line depth are regarded. The velocity fields in M-stars strongly depend on log g and Teff. They become stronger with decreasing log g and increasing Teff.Comment: 14 pages, 17 figures, 3 tables, accepted by Astronomy & Astrophysic

Direct observation of a highly spin-polarized organic spinterface at room temperature

The design of large-scale electronic circuits that are entirely spintronics-driven requires a current source that is highly spin-polarised at and beyond room temperature, cheap to build, efficient at the nanoscale and straightforward to integrate with semiconductors. Yet despite research within several subfields spanning nearly two decades, this key building block is still lacking. We experimentally and theoretically show how the interface between Co and phthalocyanine molecules constitutes a promising candidate. Spin-polarised direct and inverse photoemission experiments reveal a high degree of spin polarisation at room temperature at this interface. We measured a magnetic moment on the molecules's nitrogen pi orbitals, which substantiates an ab-initio theoretical description of highly spin-polarised charge conduction across the interface due to differing spinterface formation mechanims in each spin channel. We propose, through this example, a recipe to engineer simple organic-inorganic interfaces with remarkable spintronic properties that can endure well above room temperature