scholarly journals Asteroseismic inference of subgiant evolutionary parameters with deep learning

2020 ◽  
Vol 499 (2) ◽  
pp. 2445-2461
Author(s):  
Marc Hon ◽  
Earl P Bellinger ◽  
Saskia Hekker ◽  
Dennis Stello ◽  
James S Kuszlewicz
Keyword(s):  
Deep Learning ◽  
Diffusion Processes ◽  
Physical Parameters ◽  
Fundamental Parameters ◽  
Fundamental Properties ◽  
Wide Range ◽  
Modelling Techniques ◽  
Subgiant Stars ◽  
Good Agreement

ABSTRACT With the observations of an unprecedented number of oscillating subgiant stars expected from NASA’s TESS mission, the asteroseismic characterization of subgiant stars will be a vital task for stellar population studies and for testing our theories of stellar evolution. To determine the fundamental properties of a large sample of subgiant stars efficiently, we developed a deep learning method that estimates distributions of fundamental parameters like age and mass over a wide range of input physics by learning from a grid of stellar models varied in eight physical parameters. We applied our method to four Kepler subgiant stars and compare our results with previously determined estimates. Our results show good agreement with previous estimates for three of them (KIC 11026764, KIC 10920273, KIC 11395018). With the ability to explore a vast range of stellar parameters, we determine that the remaining star, KIC 10005473, is likely to have an age 1 Gyr younger than its previously determined estimate. Our method also estimates the efficiency of overshooting, undershooting, and microscopic diffusion processes, from which we determined that the parameters governing such processes are generally poorly constrained in subgiant models. We further demonstrate our method’s utility for ensemble asteroseismology by characterizing a sample of 30 Kepler subgiant stars, where we find a majority of our age, mass, and radius estimates agree within uncertainties from more computationally expensive grid-based modelling techniques.

scholarly journals Comparison of Above-Water Seabird and TriOS Radiometers along an Atlantic Meridional Transect

2020 ◽  
Vol 12 (10) ◽  
pp. 1669
Author(s):  
Krista Alikas ◽  
Viktor Vabson ◽  
Ilmar Ansko ◽  
Gavin H. Tilstone ◽  
Giorgio Dall’Olmo ◽  
...  
Keyword(s):  
State Of The Art ◽  
Ocean Color ◽  
Percentage Difference ◽  
Wide Range ◽  
Before And After ◽  
Reference Measurements ◽  
Satellite Ocean Color ◽  
Good Agreement

The Fiducial Reference Measurements for Satellite Ocean Color (FRM4SOC) project has carried out a range of activities to evaluate and improve the state-of-the-art in ocean color radiometry. This paper described the results from a ship-based intercomparison conducted on the Atlantic Meridional Transect 27 from 23rd September to 5th November 2017. Two different radiometric systems, TriOS-Radiation Measurement Sensor with Enhanced Spectral resolution (RAMSES) and Seabird-Hyperspectral Surface Acquisition System (HyperSAS), were compared and operated side-by-side over a wide range of Atlantic provinces and environmental conditions. Both systems were calibrated for traceability to SI (Système international) units at the same optical laboratory under uniform conditions before and after the field campaign. The in situ results and their accompanying uncertainties were evaluated using the same data handling protocols. The field data revealed variability in the responsivity between TRiOS and Seabird sensors, which is dependent on the ambient environmental and illumination conditions. The straylight effects for individual sensors were mostly within ±3%. A near infra-red (NIR) similarity correction changed the water-leaving reflectance (ρw) and water-leaving radiance (Lw) spectra significantly, bringing also a convergence in outliers. For improving the estimates of in situ uncertainty, it is recommended that additional characterization of radiometers and environmental ancillary measurements are undertaken. In general, the comparison of radiometric systems showed agreement within the evaluated uncertainty limits. Consistency of in situ results with the available Sentinel-3A Ocean and Land Color Instrument (OLCI) data in the range from (400…560) nm was also satisfactory (−8% < Mean Percentage Difference (MPD) < 15%) and showed good agreement in terms of the shape of the spectra and absolute values.

scholarly journals Optimal protocols for sequence-based characterization of the human vaginal microbiome

2020 ◽  
Author(s):  
Luisa W. Hugerth ◽  
Marcela Pereira ◽  
Yinghua Zha ◽  
Maike Seifert ◽  
Vilde Kaldhusdal ◽  
...  
Keyword(s):  
16S Rrna ◽  
Best Practices ◽  
Gene Sequencing ◽  
16S Rrna Gene Sequencing ◽  
Rrna Gene ◽  
Vaginal Microbiome ◽  
Wide Range ◽  
Rrna Gene Sequencing ◽  
Good Agreement

AbstractThe vaginal microbiome has been connected to a wide range of health outcomes. This has led to a thriving research environment, but also to the use of conflicting methodologies to study its microbial composition. Here we systematically assess best practices for the sequencing-based characterization of the human vaginal microbiome. As far as 16S rRNA gene sequencing is concerned, the V1-V3 region has the best theoretical properties, but limitations of current sequencing technologies mean that the V3-V4 region performs equally well. Both of these approaches present very good agreement with qPCR quantification of key taxa, provided an appropriate bioinformatic pipeline is used. Shotgun metagenomic sequencing presents an interesting alternative to 16S amplification and sequencing, but it is not without its challenges. We have assessed different tools for the removal of host reads and the taxonomic annotation of metagenomic reads, including a new, easy-to-build and – use, reference database of vaginal taxa. This strategy performed as well as the best performing previously published strategies. Despite the many advantages of shotgun sequencing none of the shotgun approaches assessed here had as good agreement with the qPCR data as 16S rRNA gene sequencing.ImportanceThe vaginal microbiome has been connected to a wide range of health outcomes, from susceptibility to sexually transmitted infections to gynecological cancers and pregnancy outcomes. This has led to a thriving research environment, but also to conflicting available methodologies, including many studies that do not report their molecular biological and bioinformatic methods in sufficient detail for them to be considered reproducible. This can lead to conflicting messages and delay progress from descriptive to intervention studies. By systematically assessing best practices for the characterization of the human vaginal microbiome, this study will enable past studies to be assessed more critically and assist future studies in the selection of appropriate methods for their specific research questions.

scholarly journals New spectro-photometric characterization of the substellar object HR 2562 B using SPHERE

2018 ◽  
Vol 612 ◽  
pp. A92 ◽  
Author(s):  
D. Mesa ◽  
J.-L. Baudino ◽  
B. Charnay ◽  
V. D’Orazi ◽  
S. Desidera ◽  
...  
Keyword(s):  
Near Infrared ◽  
Speckle Noise ◽  
Dual Band ◽  
Physical Parameters ◽  
Atmospheric Models ◽  
Fundamental Properties ◽  
Spectral Bands ◽  
Very Large Telescope ◽  
Integral Field Spectrograph

Aims. HR 2562 is an F5V star located at ~33 pc from the Sun hosting a substellar companion that was discovered using the Gemini planet imager (GPI) instrument. The main objective of the present paper is to provide an extensive characterization of the substellar companion, by deriving its fundamental properties. Methods. We observed HR 2562 with the near-infrared branch composed by the integral field spectrograph (IFS) and the infrared dual band spectrograph (IRDIS) of the spectro-polarimetric high-contrast exoplanet research (SPHERE) instrument at the very large telescope (VLT). During our observations IFS was operating in the Y J band, while IRDIS was observing with the H broadband filter. The data were reduced with the dedicated SPHERE GTO pipeline, which is custom designed for this instrument. On the reduced images, we then applied the post-processing procedures that are specifically prepared to subtract the speckle noise. Results. The companion is clearly detected in both IRDIS and IFS datasets. We obtained photometry in three different spectral bands. The comparison with template spectra allowed us to derive a spectral type of T2–T3 for the companion. Using both evolutionary and atmospheric models we inferred the main physical parameters of the companion obtaining a mass of 32 ± 14 MJup, Teff = 1100 ± 200 K, and log g = 4.75 ± 0.41.

scholarly journals Fundamental parameters of “normal” B stars in the solar neighborhood

2010 ◽  
Vol 6 (S272) ◽  
pp. 566-570
Author(s):  
Maria-Fernanda Nieva ◽  
Norbert Przybilla
Keyword(s):  
Spectroscopic Analysis ◽  
Solar Neighborhood ◽  
Physical Parameters ◽  
B Stars ◽  
Fundamental Parameters ◽  
Precision Turning ◽  
Driving Mechanisms ◽  
Analysis Methodology ◽  
Quantitative Spectral Analysis ◽  
Good Agreement

AbstractUnderstanding phenomena of activity in stars, like pulsations or magnetism, benefits from systematic comparisons of some key physical parameters of active with those of “normal” stars. Here we concentrate on a careful derivation of fundamental parameters of a well selected sample of 27 “normal” B stars in nearby OB associations and in the field. A quantitative spectral analysis methodology based on hybrid non-LTE techniques is applied to high-resolution and high-S/N spectra. Results derived from the pure spectroscopic analysis are compared to other data/indicators of stellar parameters in order to prove the reliability of the method. Very good agreement is obtained among all of them. Besides the fundamental parameters, the chemical composition of the stars is also determined at high precision, turning out to be highly homogeneous. A comparative study of the present results with those of well known active massive stars will help to improve our understanding of the driving mechanisms of activity.

scholarly journals Challenges in the Physical Characterization of Lipid Nanoparticles

Pharmaceutics ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 549
Author(s):  
Supandeep Singh Hallan ◽  
Maddalena Sguizzato ◽  
Elisabetta Esposito ◽  
Rita Cortesi
Keyword(s):  
Lipid Nanoparticles ◽  
Physical Parameters ◽  
Field Flow Fractionation ◽  
Size Measurement ◽  
Potential Measurement ◽  
X Ray ◽  
Administration Routes ◽  
Wide Range ◽  
Composition Properties

Nano-sized drug transporters have become an efficient approach with considerable commercial values. Nanomedicine is not only limited to drug delivery by means of different administration routes, such as intravenous, oral, transdermal, nasal, pulmonary, and more, but also has applications in a multitude of areas, such as a vaccine, antibacterial, diagnostics and imaging, and gene delivery. This review will focus on lipid nanosystems with a wide range of applications, taking into consideration their composition, properties, and physical parameters. However, designing suitable protocol for the physical evaluation of nanoparticles is still conflicting. The main obstacle is concerning the sensitivity, reproducibility, and reliability of the adopted methodology. Some important techniques are compared and discussed in this report. Particularly, a comparison between different techniques involved in (a) the morphologic characterization, such as Cryo-TEM, SEM, and X-ray; (b) the size measurement, such as dynamic light scattering, sedimentation field flow fractionation, and optical microscopy; and (c) surface properties, namely zeta potential measurement, is described. In addition, an amperometric tool in order to investigate antioxidant activity and the response of nanomaterials towards the skin membrane has been presented.

scholarly journals Experimental and Simulation Study of n-Heptane Adsorption on Rutile

2007 ◽  
Vol 25 (7) ◽  
pp. 517-530 ◽  
Author(s):  
G.U. Rakhmatkariev ◽  
A.J. Palace Carvalho ◽  
J.P. Prates Ramalho
Keyword(s):  
Bulk Liquid ◽  
Grand Canonical Monte Carlo ◽  
Differential Heat ◽  
Wide Range ◽  
Adsorption Entropy ◽  
The Mean ◽  
Differential Heat Of Adsorption ◽  
Grand Canonical ◽  
Good Agreement

The adsorption of n-heptane on microcrystalline rutile has been studied experimentally by thermodynamic techniques (adsorption isotherms and microcalorimetry) over a wide range of coverage at 303 K and complemented by Grand Canonical Monte Carlo simulations. The differential heat of adsorption exhibited three descending segments corresponding to the adsorption of n-heptane on three types of surfaces. The mean molar adsorption entropy of n-heptane in the monolayer was less than the entropy of the bulk liquid by ca. −23 J/(mol K), thus revealing a hindered state of motion for the n-heptane molecules on the surface of rutile. Simulations of the adsorption of n-heptane were performed on the three most abundant crystallographic faces of rutile. The adsorption isotherm obtained from the combination of the isotherm for each face weighted by the respective abundance was found to be in good agreement with experimental data. A structural characterization of n-heptane near the surface was also conducted which indicated that the substrate strongly perturbed the distribution of the n-heptane conformations relative to the situation found for the gaseous phase. Adsorbed molecules are predominantly orientated with their long axes, with the zig-zag planes of their backbones parallel to the surface and preferentially aligned along the five-fold cus Ti4+ ions of the faces. Fewer gauche conformations were observed for molecules near the surface than was characteristic of the bulk phase.

scholarly journals High-throughput microfluidic characterization of erythrocyte shape and mechanical variability

2018 ◽  
Author(s):  
Felix Reichel ◽  
Johannes Mauer ◽  
Ahmad Ahsan Nawaz ◽  
Gerhard Gompper ◽  
Jochen Guck ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Red Blood Cells ◽  
High Throughput ◽  
Blood Cells ◽  
Microvascular Blood Flow ◽  
Flow Conditions ◽  
Wide Range ◽  
Single Well ◽  
Good Agreement

The motion of red blood cells (RBCs) in microchannels is important for microvascular blood flow and biomedical applications such as blood analysis in microfluidics. The current understanding of the complexity of RBC shapes and dynamics in microchannels is mainly based on several simulation studies, but there are a few systematic experimental investigations. Here, we present a combined study, which systematically characterizes RBC behavior for a wide range of flow rates and channel sizes. Even though simulations and experiments generally show good agreement, experimental observations demonstrate that there is no single well-defined RBC state for fixed flow conditions, but rather a broad distribution of states. This result can be attributed to the inherent variability in RBC mechanical properties, which is confirmed by a model that takes the variation in RBC shear elasticity into account. This represents a significant step toward a quantitative connection between RBC behavior in microfluidic devices and their mechanical properties, which is essential for a high-throughput characterization of diseased cells.Significance StatementThe ability to change shape is crucial for the proper functioning of red blood cells under harsh conditions in the microvasculature, since their shapes strongly affect the flow behavior of whole blood. Our results from simulations and systematic experiments reveal the shapes and dynamics of red blood cells for different flow conditions and channel dimensions, generally in good agreement. However, in the experiments, cells do not exhibit a single well-defined shape for fixed flow conditions. We show that this distribution of shapes can be attributed to the variability in mechanical properties of red blood cells.

Biophysical Aspects of Using Liposomes as Delivery Vehicles

2002 ◽  
Vol 22 (2) ◽  
pp. 129-150 ◽  
Author(s):  
Anne S. Ulrich
Keyword(s):  
Point Of View ◽  
Attractive Potential ◽  
Physical Parameters ◽  
Liposomal Formulations ◽  
Wide Range ◽  
Fusion Methods ◽  
Delivery Vehicles ◽  
Lipid Formulations

Liposomes are used as biocompatible carriers of drugs, peptides, proteins, plasmic DNA, antisense oligonucleotides or ribozymes, for pharmaceutical, cosmetic, and biochemical purposes. The enormous versatility in particle size and in the physical parameters of the lipids affords an attractive potential for constructing tailor-made vehicles for a wide range of applications. Some of the recent literature will be reviewed here and presented from a biophysical point of view, thus providing a background for the more specialized articles in this special issue on liposome technology. Different properties (size, colloidal behavior, phase transitions, and polymorphism) of diverse lipid formulations (liposomes, lipoplexes, cubic phases, emulsions, and solid lipid nanoparticles) for distinct applications (parenteral, transdermal, pulmonary, and oral administration) will be rationalized in terms of common structural, thermodynamic and kinetic parameters of the lipids. This general biophysical basis helps to understand pharmaceutically relevant aspects such as liposome stability during storage and towards serum, the biodistribution and specific targeting of cargo, and how to trigger drug release and membrane fusion. Methods for the preparation and characterization of liposomal formulations in vitro will be outlined, too.

scholarly journals WARPFIELD-EMP: The self-consistent prediction of emission lines from evolving H ii regions in dense molecular clouds

2020 ◽  
Vol 496 (1) ◽  
pp. 339-363 ◽  
Author(s):  
E W Pellegrini ◽  
D Rahner ◽  
S Reissl ◽  
S C O Glover ◽  
R S Klessen ◽  
...  
Keyword(s):  
Line Emission ◽  
Continuum Emission ◽  
Physical Parameters ◽  
Model Parameters ◽  
Stellar Winds ◽  
H Ii Regions ◽  
Stellar Feedback ◽  
Wide Range ◽  
H Ii Region ◽  
Good Agreement

ABSTRACT We present the warpfield emission predictor, warpfield-emp, which couples the 1D stellar feedback code warpfield with the cloudy H iiregion/PDR code and the polaris radiative transfer code, in order to make detailed predictions for the time-dependent line and continuum emission arising from the H ii region and PDR surrounding an evolving star cluster. warpfield-emp accounts for a wide range of physical processes (photoionization, stellar winds, supernovae, radiation pressure, gravity, thermal conduction, radiative cooling, dust extinction etc.) and yet runs quickly enough to allow us to explore broad ranges of different model parameters. We compare the results of an extensive set of models with SITELLE observations of a large sample of H ii regions in NGC 628 and find very good agreement, particularly for the highest signal-to-noise observations. We show that our approach of modelling individual clouds from first principles (instead of in terms of dimensionless quantities such as the ionization parameter) allows us to avoid long-standing degeneracies in the interpretation of H ii region diagnostics and enables us to relate these diagnostics to important physical parameters such as cloud mass or cluster age. Finally, we explore the implications of our models regarding the reliability of simple metallicity diagnostics, the properties of long-lived embedded clusters, and the role played by winds and supernovae in regulating H ii region and PDR line emission.

scholarly journals Lagrangian Surface Wave Motion and Stokes Drift Fluctuations

2016 ◽  
Vol 46 (4) ◽  
pp. 1009-1021 ◽  
Author(s):  
T. H. C. Herbers ◽  
T. T. Janssen
Keyword(s):  
Deep Water ◽  
Diffusion Processes ◽  
Wave Theory ◽  
Finite Depth ◽  
Order Theory ◽  
Second Order ◽  
Sea Surface ◽  
Stokes Drift ◽  
Wide Range ◽  
Good Agreement

AbstractNonlinear effects in Lagrangian sea surface motions are important to understanding variability in wave-induced mass transport, wave-driven diffusion processes, and the interpretation of measurements obtained with moored or free-drifting buoys. This study evaluates the Lagrangian vertical and horizontal motions of a particle at the surface in a natural, random sea state using second-order, finite-depth wave theory. In deep water, the predicted low-frequency (infragravity) surface height fluctuations are much larger than Eulerian bound wave motions and of the opposite sign. Comparison to surface elevation bispectra observed with a moored buoy in steady, high-wind conditions shows good agreement and confirms that—in contrast to the Eulerian sea surface motion with predominant phase coupling between the spectral peak and double-frequency harmonic components—nonlinearity in Lagrangian wave observations is dominated by phase-coupled infragravity motions. Sea surface skewness estimates obtained from moored buoys in deep and shallow sites, over a wide range of wind–sea and swell conditions, are in good agreement with second-order theory predictions. Theory and field data analysis of surface drift motions in deep water reveal energetic [O(10) cm s−1] infragravity velocity fluctuations that are several orders of magnitude larger and 180° out of phase with Eulerian infragravity motions. These large fluctuations in Stokes drift may be important in upper-ocean diffusion processes.

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