ALBERT — All Library Books, journals and Electronic Records Telegrafenberg

1

Unbekannt

Identification of emission-line stars in transition phase from pre-main sequence to main sequence (2021)

Bhattacharyya, Suman ; Mathew, Blesson ; Banerjee, Gourav ; [weitere]

Oxford University Press

In: Monthly Notices of the Royal Astronomical Society. 2021; Published 2021 Aug 20. doi: 10.1093/mnras/stab2385. [early online release]

zur Merkliste hinzufügen auf der Merkliste

Details

Publikationsdatum: 2021-08-20

Beschreibung: Pre-main sequence (PMS) stars evolve into main sequence (MS) phase over a period of time. Interestingly, we found a scarcity of studies in existing literature that examines and attempts to better understand the stars in PMS to MS transition phase. The purpose of the present study is to detect such rare stars, which we named as ‘Transition Phase’ (TP) candidates – stars evolving from the PMS to the MS phase. We identified 98 TP candidates using photometric analysis of a sample of 2167 classical Be (CBe) and 225 Herbig Ae/Be (HAeBe) stars. This identification is done by analyzing the near- and mid-infrared excess and their location in the optical colour-magnitude diagram. The age and mass of 58 of these TP candidates are determined to be between 0.1–5 Myr and 2–10.5 M⊙, respectively. The TP candidates are found to possess rotational velocity and colour excess values in between CBe and HAeBe stars, which is reconfirmed by generating a set of synthetic samples using the machine learning approach.

Print ISSN: 0035-8711

Digitale ISSN: 1365-2966

Thema: Physik

Publiziert von Oxford University Press im Namen von The Royal Astronomical Society.

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

AKTUELLE ARTIKEL

S·F·X

Volltext

2

Unbekannt

Neutral CGM as damped Lyα absorbers at high redshift (2021)

Stern, Jonathan ; Sternberg, Amiel ; Faucher-Giguére, Claude-André ; [weitere]

Oxford University Press

In: Monthly Notices of the Royal Astronomical Society. 2021; Published 2021 Aug 20. doi: 10.1093/mnras/stab2240. [early online release]

zur Merkliste hinzufügen auf der Merkliste

Details

Publikationsdatum: 2021-08-20

Beschreibung: Recent searches for the hosts of z ∼ 4 damped Lyα absorbers (DLAs) have detected bright galaxies at distances of tens of kpc from the DLA. Using the FIRE-2 cosmological zoom simulations, we argue that these relatively large distances are due to a predominantly cool and neutral inner circumgalactic medium (CGM) surrounding high-redshift galaxies. The inner CGM is cool because of the short cooling time of hot gas in ≲ 1012 M⊙ haloes, which implies that accretion and feedback energy are radiated quickly, while it is neutral due to high volume densities and column densities at high redshift which shield cool gas from photoionization. Our analysis predicts large DLA covering factors ($gtrsim 50{{ m per cent}}$) out to impact parameters ∼0.3((1 + z)/5)3/2Rvir from the central galaxies at z ≳ 1, equivalent to a proper distance of $sim 21, M_{12}^{1/3} left(left(1+z ight)/5 ight)^{1/2}, { m kpc}$ (Rvir and M12 are the halo virial radius and mass in units of 1012 M⊙, respectively). This implies that DLA covering factors at z ∼ 4 may be comparable to unity out to a distance ∼10 times larger than stellar half-mass radii. A predominantly neutral inner CGM in the early universe suggests that its mass and metallicity can be directly constrained by absorption surveys, without resorting to the large ionization corrections as required for ionized CGM.

Print ISSN: 0035-8711

Digitale ISSN: 1365-2966

Thema: Physik

Publiziert von Oxford University Press im Namen von The Royal Astronomical Society.

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

AKTUELLE ARTIKEL

S·F·X

Volltext

3

Unbekannt

Improved data sets and evaluation methods for the automatic prediction of DNA-binding proteins (2021)

Zaitzeff, Alexander ; Leiby, Nicholas ; Motta, Francis C ; [weitere]

Oxford University Press

In: Bioinformatics. 2021; Published 2021 Aug 20. doi: 10.1093/bioinformatics/btab603. [early online release]

zur Merkliste hinzufügen auf der Merkliste

Details

Publikationsdatum: 2021-08-20

Beschreibung: Motivation Accurate automatic annotation of protein function relies on both innovative models and robust data sets. Due to their importance in biological processes, the identification of DNA-binding proteins directly from protein sequence has been the focus of many studies. However, the data sets used to train and evaluate these methods have suffered from substantial flaws. We describe some of the weaknesses of the data sets used in previous DNA-binding protein literature and provide several new data sets addressing these problems. We suggest new evaluative benchmark tasks that more realistically assess real-world performance for protein annotation models. We propose a simple new model for the prediction of DNA-binding proteins and compare its performance on the improved data sets to two previously published models. Additionally, we provide extensive tests showing how the best models predict across taxonomies. Results Our new gradient boosting model, which uses features derived from a published protein language model, outperforms the earlier models. Perhaps surprisingly, so does a baseline nearest neighbor model using BLAST percent identity. We evaluate the sensitivity of these models to perturbations of DNA-binding regions and control regions of protein sequences. The successful data-driven models learn to focus on DNA-binding regions. When predicting across taxonomies, the best models are highly accurate across species in the same kingdom and can provide some information when predicting across kingdoms. Code and Data Availability The data and results for this paper can be found at https://doi.org/10.5281/zenodo.5153906. The code for this paper can be found at https://doi.org/10.5281/zenodo.5153683. The code, data and results can also be found at https://github.com/AZaitzeff/tools_for_dna_binding_proteins.

Print ISSN: 1367-4803

Digitale ISSN: 1460-2059

Thema: Biologie , Informatik , Medizin

Publiziert von Oxford University Press

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

AKTUELLE ARTIKEL

S·F·X

Volltext

4

Unbekannt

A new approach of estimating the Galactic thermal dust and synchrotron polarized emission template in the microwave bands (2021)

Adak, Debabrata

Oxford University Press

In: Monthly Notices of the Royal Astronomical Society. 2021; Published 2021 Aug 20. doi: 10.1093/mnras/stab2392. [early online release]

zur Merkliste hinzufügen auf der Merkliste

Details

Publikationsdatum: 2021-08-20

Beschreibung: The Internal Linear Combination (ILC) method has been extensively used to extract the cosmic microwave background (CMB) anisotropy map from foreground contaminated multi-frequency maps. However, the performance of simple ILC is limited and can be significantly improved by heavily constraint equations, dubbed constrained ILC (cILC). The standard ILC and cILC works on spin-0 fields. Recently, a generalised version of ILC has been developed, named Polarization ILC (PILC), in which Q ± iU at multiple frequencies are combined using complex coefficients to estimate Stokes Q and U maps. A statistical moment expansion method has recently been developed for high precision modelling of the Galactic foregrounds. This paper develops a semi-blind component separation method combining the moment approach of foreground modelling with a generalised version of the PILC method for heavily constraint equations. The algorithm is developed in pixel space over a spin-2 field. We demonstrate the performance of the method on three sets of absolutely calibrated simulated maps at WMAP and Planck frequencies with varying foreground models. We apply this component separation technique in simultaneous estimation of Stokes Q and U maps of the thermal dust at 353 GHz and synchrotron at 30 GHz. We also recover both dust and synchrotron maps at 100 and 143 GHz, where separating two components is challenging.

Print ISSN: 0035-8711

Digitale ISSN: 1365-2966

Thema: Physik

Publiziert von Oxford University Press im Namen von The Royal Astronomical Society.

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

AKTUELLE ARTIKEL

S·F·X

Volltext

5

Unbekannt

Disc tearing and Bardeen–Petterson alignment in GRMHD simulations of highly tilted thin accretion discs (2021)

Liska, M ; Hesp, C ; Tchekhovskoy, A ; [weitere]

Oxford University Press

In: Monthly Notices of the Royal Astronomical Society. 2021; 507(1): 983-990. Published 2021 Aug 20. doi: 10.1093/mnras/staa099.

zur Merkliste hinzufügen auf der Merkliste

Details

Publikationsdatum: 2021-08-20

Beschreibung: Luminous active galactic nuclei and X-ray binaries often contain geometrically thin, radiatively cooled accretion discs. According to theory, these are – in many cases – initially highly misaligned with the black hole equator. In this work, we present the first general relativistic magnetohydrodynamic simulations of very thin (h/r ∼ 0.015–0.05) accretion discs around rapidly spinning (a ∼ 0.9) black holes and tilted by 45°–65°. We show that the inner regions of the discs with h/r ≲ 0.03 align with the black hole equator, though out to smaller radii than predicted by analytic work. The inner aligned and outer misaligned disc regions are separated by a sharp break in tilt angle accompanied by a sharp drop in density. We find that frame dragging by the spinning black hole overpowers the disc viscosity, which is self-consistently produced by magnetized turbulence, tearing the disc apart and forming a rapidly precessing inner sub-disc surrounded by a slowly precessing outer sub-disc. We find that the system produces a pair of relativistic jets for all initial tilt values. At small distances, the black hole launched jets precess rapidly together with the inner sub-disc, whereas at large distances they partially align with the outer sub-disc and precess more slowly. If the tearing radius can be modeled accurately in future work, emission model independent measurements of black hole spin based on precession-driven quasi-periodic oscillations may become possible.

Print ISSN: 0035-8711

Digitale ISSN: 1365-2966

Thema: Physik

Publiziert von Oxford University Press im Namen von The Royal Astronomical Society.

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

AKTUELLE ARTIKEL

S·F·X

Volltext

6

Unbekannt

Detecting quantitative trait loci and exploring chromosomal pairing in autopolyploids using polyqtlR (2021)

Bourke, Peter M ; Voorrips, Roeland E ; Hackett, Christine A ; [weitere]

Oxford University Press

In: Bioinformatics. 2021; Published 2021 Aug 06. doi: 10.1093/bioinformatics/btab574. [early online release]

zur Merkliste hinzufügen auf der Merkliste

Details

Publikationsdatum: 2021-08-06

Beschreibung: Motivation The investigation of quantitative trait loci (QTL) is an essential component in our understanding of how organisms vary phenotypically. However, many important crop species are polyploid (carrying more than two copies of each chromosome), requiring specialized tools for such analyses. Moreover, deciphering meiotic processes at higher ploidy levels is not straightforward, but is necessary to understand the reproductive dynamics of these species, or uncover potential barriers to their genetic improvement. Results Here, we present polyqtlR, a novel software tool to facilitate such analyses in (auto)polyploid crops. It performs QTL interval mapping in F1 populations of outcrossing polyploids of any ploidy level using identity-by-descent probabilities. The allelic composition of discovered QTL can be explored, enabling favourable alleles to be identified and tracked in the population. Visualization tools within the package facilitate this process, and options to include genetic co-factors and experimental factors are included. Detailed information on polyploid meiosis including prediction of multivalent pairing structures, detection of preferential chromosomal pairing and location of double reduction events can be performed. Availabilityand implementation polyqtlR is freely available from the Comprehensive R Archive Network (CRAN) at http://cran.r-project.org/package=polyqtlR. Supplementary information Supplementary data are available at Bioinformatics online.

Print ISSN: 1367-4803

Digitale ISSN: 1460-2059

Thema: Biologie , Informatik , Medizin

Publiziert von Oxford University Press

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

AKTUELLE ARTIKEL

S·F·X

Volltext

7

Unbekannt

XMP gas-rich dwarfs in nearby voids: results of BTA spectroscopy (2021)

Pustilnik, S A ; Egorova, E S ; Kniazev, A Y ; [weitere]

Oxford University Press

In: Monthly Notices of the Royal Astronomical Society. 2021; 507(1): 944-962. Published 2021 Aug 20. doi: 10.1093/mnras/stab2084.

zur Merkliste hinzufügen auf der Merkliste

Details

Publikationsdatum: 2021-08-20

Beschreibung: We present the second part of results of the ongoing project aimed at searching for and studying eXtremely Metal-Poor (XMP) – adopted as those with Zgas ≲ Z⊙/30, or with 12+log (O/H) ≲ 7.21 dex − very gas-rich blue dwarfs in voids. They were first identified in the course of the ‘unbiased’ study of the galaxy population in the nearby Lynx–Cancer void. These very rare and unusual galaxies seem to be the best proxies of so-called Very Young Galaxies (VYGs) defined recently in model simulations by Tweed et al. To date, for 16 pre-selected void XMP candidates, using the Big Telescope Alt-azimuth (BTA), the SAO 6-m telescope, we have obtained spectra suitable for the determination of O/H. For majority of the observed galaxies, the principal line [O iii] λ4363 , used for the direct classical Te method of O/H determination, is undetected. Therefore, to estimate O/H, we use a new ‘strong-lines’ method by Izotov et al. This appears to be the most accurate empirical O/H estimator for the range of 12+log (O/H) ≲ 7.4–7.5. For objects with higher O/H, we use the semi-empirical method by Izotov & Thuan with our modification accounting for variance of the excitation parameter O32. Six of those 16 candidates are found, with confidence, to be XMP dwarfs. In addition, eight studied galaxies are less metal-poor, with 12+log (O/H) = 7.24–7.33, and these can also fall into the category of VYG candidates. Taking into account our recently published work and the previously known (nine prototype galaxies) XMP gas-rich void objects, the new findings increase the number of this type of galaxy known to date to a total of 19.

Print ISSN: 0035-8711

Digitale ISSN: 1365-2966

Thema: Physik

Publiziert von Oxford University Press im Namen von The Royal Astronomical Society.

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

AKTUELLE ARTIKEL

S·F·X

Volltext

8

Unbekannt

Comparative evaluation of shape retrieval methods on macromolecular surfaces: an application of computer vision methods in structural bioinformatics (2021)

Machat, Mohamed ; Langenfeld, Florent ; Craciun, Daniela ; [weitere]

Oxford University Press

In: Bioinformatics. 2021; Published 2021 Jul 11. doi: 10.1093/bioinformatics/btab511. [early online release]

zur Merkliste hinzufügen auf der Merkliste

Details

Publikationsdatum: 2021-07-11

Beschreibung: Motivation The investigation of the structure of biological systems at the molecular level gives insights about their functions and dynamics. Shape and surface of biomolecules are fundamental to molecular recognition events. Characterizing their geometry can lead to more adequate predictions of their interactions. In the present work, we assess the performance of reference shape retrieval methods from the computer vision community on protein shapes. Results Shape retrieval methods are efficient in identifying orthologous proteins and tracking large conformational changes. This work illustrates the interest for the protein surface shape as a higher-level representation of the protein structure that (i) abstracts the underlying protein sequence, structure or fold, (ii) allows the use of shape retrieval methods to screen large databases of protein structures to identify surficial homologs and possible interacting partners and (iii) opens an extension of the protein structure–function paradigm toward a protein structure-surface(s)-function paradigm. Availabilityand implementation All data are available online at http://datasetmachat.drugdesign.fr. Supplementary information Supplementary data are available at Bioinformatics online.

Print ISSN: 1367-4803

Digitale ISSN: 1460-2059

Thema: Biologie , Informatik , Medizin

Publiziert von Oxford University Press

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

AKTUELLE ARTIKEL

S·F·X

Volltext

9

Unbekannt

Inference of the optical depth to reionization from low multipole temperature and polarization Planck data (2021)

de Belsunce, Roger ; Gratton, Steven ; Coulton, William ; [weitere]

Oxford University Press

In: Monthly Notices of the Royal Astronomical Society. 2021; 507(1): 1072-1091. Published 2021 Aug 11. doi: 10.1093/mnras/stab2215.

zur Merkliste hinzufügen auf der Merkliste

Details

Publikationsdatum: 2021-08-11

Beschreibung: This paper explores methods for constructing low multipole temperature and polarization likelihoods from maps of the cosmic microwave background anisotropies that have complex noise properties and partial sky coverage. We use Planck 2018 High Frequency Instrument (HFI) and updated SRoll2 temperature and polarization maps to test our methods. We present three likelihood approximations based on quadratic cross spectrum estimators: (i) a variant of the simulation-based likelihood (SimBaL) techniques used in the Planck legacy papers to produce a low multipole EE likelihood; (ii) a semi-analytical likelihood approximation (momento) based on the principle of maximum entropy; (iii) a density-estimation ‘likelihood-free’ scheme (delfi). Approaches (ii) and (iii) can be generalized to produce low multipole joint temperature-polarization (TTTEEE) likelihoods. We present extensive tests of these methods on simulations with realistic correlated noise. We then analyse the Planck data and confirm the robustness of our method and likelihoods on multiple inter- and intra-frequency detector set combinations of SRoll2 maps. The three likelihood techniques give consistent results and support a low value of the optical depth to reoinization, τ, from the HFI. Our best estimate of τ comes from combining the low multipole SRoll2momento (TTTEEE) likelihood with the CamSpec high multipole likelihood and is $au = 0.0627^{+0.0050}_{-0.0058}$. This is consistent with the SRoll2 team’s determination of τ, though slightly higher by ∼0.5σ, mainly because of our joint treatment of temperature and polarization.

Print ISSN: 0035-8711

Digitale ISSN: 1365-2966

Thema: Physik

Publiziert von Oxford University Press im Namen von The Royal Astronomical Society.

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

AKTUELLE ARTIKEL

S·F·X

Volltext

10

Unbekannt

Constraining properties of GRB central engines with X-ray flares (2021)

Yi, Shuang-Xi ; Xie, Wei ; Ma, Shuai-Bing ; [weitere]

Oxford University Press

In: Monthly Notices of the Royal Astronomical Society. 2021; 507(1): 1047-1054. Published 2021 Jul 31. doi: 10.1093/mnras/stab2186.

zur Merkliste hinzufügen auf der Merkliste

Details

Publikationsdatum: 2021-07-31

Beschreibung: X-ray flares in gamma-ray bursts (GRBs) are believed to be generated by the late activities of central engine, and thus provide an useful tool to diagnose the properties of central objects. In this paper, we work on a GRB X-ray flare sample whose bulk Lorentz factors are constrained by two different methods and the jet opening angles are determined by the jet breaks in afterglow light curves. Considering a hyperaccreting stellar-mass black hole (BH) as the central engine of GRBs and the Blandford & Znajek process (BZ) as the jet production mechanism, we constrain the parameters of central engine by using the X-ray flare data. We find that the BZ mechanism is so powerful making it possible to interpret both GRB prompt emissions and bright X-ray flares. The wind parameter (p) and accreted mass (Md) fall into reasonable ranges. Our result is also applied to GRB 170817A. The late X-ray flare in GRB 170817A, if it is true, might not be a BH origin.

Print ISSN: 0035-8711

Digitale ISSN: 1365-2966

Thema: Physik

Publiziert von Oxford University Press im Namen von The Royal Astronomical Society.

Permalink

	Standort	Signatur	Erwartet	Verfügbarkeit

Andere fanden auch interessant ...

AKTUELLE ARTIKEL

S·F·X

Volltext