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  1. Home
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Browsing by Department "Facultad de Ciencias"

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    2D-QSAR and 3D-QSAR/CoMSIA Studies on a Series of (R)-2-((2-(1H-Indol-2-yl)ethyl)amino)-1-Phenylethan-1-ol with Human β3-Adrenergic Activity
    (MDPI AG, 2017-03-05)
    Gastón Apablaza
    ;
    Luisa Montoya
    ;
    Cesar Morales-Verdejo
    ;
    Marco Mellado
    ;
    Cuellar, Mauricio  
    ;
    Carlos Lagos
    ;
    Jorge Soto-Delgado
    ;
    Hery Chung
    ;
    Carlos Pessoa-Mahana
    ;
    Mella, Jaime  
    The β3 adrenergic receptor is raising as an important drug target for the treatment of pathologies such as diabetes, obesity, depression, and cardiac diseases among others. Several attempts to obtain selective and high affinity ligands have been made. Currently, Mirabegron is the only available drug on the market that targets this receptor approved for the treatment of overactive bladder. However, the FDA (Food and Drug Administration) in USA and the MHRA (Medicines and Healthcare products Regulatory Agency) in UK have made reports of potentially life-threatening side effects associated with the administration of Mirabegron, casting doubts on the continuity of this compound. Therefore, it is of utmost importance to gather information for the rational design and synthesis of new β3 adrenergic ligands. Herein, we present the first combined 2D-QSAR (two-dimensional Quantitative Structure-Activity Relationship) and 3D-QSAR/CoMSIA (three-dimensional Quantitative Structure-Activity Relationship/Comparative Molecular Similarity Index Analysis) study on a series of potent β3 adrenergic agonists of indole-alkylamine structure. We found a series of changes that can be made in the steric, hydrogen-bond donor and acceptor, lipophilicity and molar refractivity properties of the compounds to generate new promising molecules. Finally, based on our analysis, a summary and a regiospecific description of the requirements for improving β3 adrenergic activity is given.
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    3D hydrodynamic simulations for the formation of the Local Group satellite planes
    (Oxford University Press (OUP), 2022-03-16)
    Indranil Banik
    ;
    Ingo Thies
    ;
    Roy Truelove
    ;
    Candlish, Graeme  
    ;
    Benoit Famaey
    ;
    Marcel S Pawlowski
    ;
    Rodrigo Ibata
    ;
    Pavel Kroupa
    The existence of mutually correlated thin and rotating planes of satellite galaxies around both the Milky Way (MW) and Andromeda (M31) calls for an explanation. Previous work in Milgromian dynamics (MOND) indicated that a past MW–M31 encounter might have led to the formation of these satellite planes. We perform the first-ever hydrodynamical MOND simulation of the Local Group using phantom of ramses. We show that an MW–M31 encounter at z ≈ 1, with a perigalactic distance of about 80 kpc, can yield two disc galaxies at z = 0 oriented similarly to the observed galactic discs and separated similarly to the observed M31 distance. Importantly, the tidal debris are distributed in phase space similarly to the observed MW and M31 satellite planes, with the correct preferred orbital pole for both. The MW–M31 orbital geometry is consistent with the presently observed M31 proper motion despite this not being considered as a constraint when exploring the parameter space. The mass of the tidal debris around the MW and M31 at z = 0 compare well with the mass observed in their satellite systems. The remnant discs of the two galaxies have realistic radial scale lengths and velocity dispersions, and the simulation naturally produces a much hotter stellar disc in M31 than in the MW. However, reconciling this scenario with the ages of stellar populations in satellite galaxies would require that a higher fraction of stars previously formed in the outskirts of the progenitors ended up within the tidal debris, or that the MW–M31 interaction occurred at z > 1.
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    A colour-excess extinction map of the southern Galactic disc from the VVV and GLIMPSE surveys
    (Oxford University Press (OUP), 2019-07-04)
    M Soto
    ;
    R Barbá
    ;
    D Minniti
    ;
    A Kunder
    ;
    D Majaess
    ;
    J L Nilo-Castellón
    ;
    J Alonso-García
    ;
    G Leone
    ;
    L Morelli
    ;
    L Haikala
    ;
    V Firpo
    ;
    P Lucas
    ;
    J P Emerson
    ;
    C Moni Bidin
    ;
    D Geisler
    ;
    R K Saito
    ;
    S Gurovich
    ;
    R Contreras Ramos
    ;
    M Rejkuba
    ;
    M Barbieri
    ;
    A Roman-Lopes
    ;
    M Hempel
    ;
    M V Alonso
    ;
    L D Baravalle
    ;
    Borissova, Jura  
    ;
    Kurtev, Radostin  
    ;
    F Milla
    An improved high-resolution and deep $A_{K_{s}}$ foreground dust extinction map is presented for the Galactic disc area within 295° ≲ l ≲ 350°, −1.0° ≲ b ≲ +1.0°. At some longitudes the map reaches up to |b| ∼ 2.25°, for a total of ∼148 deg2. The map was constructed via the Rayleigh–Jeans colour excess (RJCE) technique based on deep near-infrared (NIR) and mid-infrared (MIR) photometry. The new extinction map features a maximum bin size of 1 arcmin, and relies on NIR observations from the Two Micron All-Sky Survey (2MASS) and new data from ESO’s Vista Variables in the Vía Láctea (VVV) survey, in concert with MIR observations from the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire. The VVV photometry penetrates ∼4 mag fainter than 2MASS, and provides enhanced sampling of the underlying stellar populations in this heavily obscured region. Consequently, the new results supersede existing RJCE maps tied solely to brighter photometry, revealing a systematic underestimation of extinction in prior work that was based on shallower data. The new high-resolution and large-scale extinction map presented here is readily available to the community through a web query interface.
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    A comprehensive search for hot subdwarf stars using Gaia and TESS
    (EDP Sciences, 2024-04)
    Murat Uzundag
    ;
    Jurek Krzesinski
    ;
    Ingrid Pelisoli
    ;
    Péter Németh
    ;
    Roberto Silvotti
    ;
    Vuckovic, Maja  
    ;
    Harry Dawson
    ;
    Stephan Geier
    Hot subdwarf B (sdB) stars are evolved, subluminous, helium-burning stars that most likely form when red giant stars loose their hydrogen envelope via interactions with close companions. They play an important role in our understanding of binary evolution, stellar atmospheres, and interiors. Only a small fraction of the sdB population is known to exhibit pulsations. Pulsating sdBs have typically been discovered serendipitously in various photometric surveys because specific selection criteria for the sample are lacking. Consequently, while individual properties of these stars are well known, a comprehensive understanding of the entire population remains elusive, and many related questions remain unanswered. The Gaia mission has presented an exceptional chance to create an unbiased sample by employing precise criteria and ensuring a high degree of completeness. The progression of high-precision and high-duty cycle photometric monitoring facilitated by space missions such as Kepler/K2 and the Transiting Exoplanet Survey Satellite (TESS) has yielded an unparalleled wealth of data for pulsating sdBs. We created a dataset of confirmed pulsating sdB stars by combining information from various ground- and space-based photometric surveys. With this dataset, we present a thorough approach to search for pulsating sdB stars based on the current Gaia DR3 sample. Based on TESS photometry, we discovered 61 new pulsating sdB stars and 20 variable sdBs whose source of variability remains to be determined through future spectroscopic follow-up observations.
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    A folding reaction at the C-terminal domain drives temperature sensing in TRPM8 channels
    (Proceedings of the National Academy of Sciences, 2020-08-03)
    Ignacio Díaz-Franulic
    ;
    Natalia Raddatz
    ;
    Karen Castillo
    ;
    Fernando D. González-Nilo
    ;
    Latorre, Ramon  
    In mammals, temperature-sensitive TRP channels make membrane conductance of cells extremely temperature dependent, allowing the detection of temperature ranging from noxious cold to noxious heat. We progressively deleted the distal carboxyl terminus domain (CTD) of the cold-activated melastatin receptor channel, TRPM8. We found that the enthalpy change associated with channel gating is proportional to the length of the CTD. Deletion of the last 36 amino acids of the CTD transforms TRPM8 into a reduced temperature-sensitivity channel (Q10 ∼4). Exposing the intracellular domain to a denaturing agent increases the energy required to open the channel indicating that cold drives channel gating by stabilizing the folded state of the CTD. Experiments in the presence of an osmoticant agent suggest that channel gating involves a change in solute-inaccessible volume in the CTD of ∼1,900 Å3. This volume matches the void space inside the coiled coil according to the cryogenic electron microscopy structure of TRPM8. The results indicate that a folding–unfolding reaction of a specialized temperature-sensitive structure is coupled to TRPM8 gating.
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    A hard X-ray view of luminous and ultra-luminous infrared galaxies in GOALS – I. AGN obscuration along the merger sequence
    (Oxford University Press (OUP), 2021-07-19)
    C Ricci
    ;
    G C Privon
    ;
    R W Pfeifle
    ;
    L Armus
    ;
    K Iwasawa
    ;
    N Torres-Albà
    ;
    S Satyapal
    ;
    F E Bauer
    ;
    E Treister
    ;
    L C Ho
    ;
    S Aalto
    ;
    Arevalo, Patricia  
    ;
    L Barcos-Muñoz
    ;
    V Charmandaris
    ;
    T Diaz-Santos
    ;
    A S Evans
    ;
    T Gao
    ;
    H Inami
    ;
    M J Koss
    ;
    G Lansbury
    ;
    S T Linden
    ;
    A Medling
    ;
    D B Sanders
    ;
    Y Song
    ;
    D Stern
    ;
    V U
    ;
    Y Ueda
    ;
    S Yamada
    The merger of two or more galaxies can enhance the inflow of material from galactic scales into the close environments of active galactic nuclei (AGNs), obscuring and feeding the supermassive black hole (SMBH). Both recent simulations and observations of AGN in mergers have confirmed that mergers are related to strong nuclear obscuration. However, it is still unclear how AGN obscuration evolves in the last phases of the merger process. We study a sample of 60 luminous and ultra-luminous IR galaxies (U/LIRGs) from the GOALS sample observed by NuSTAR. We find that the fraction of AGNs that are Compton thick (CT; NH ≥ 1024 cm−2) peaks at 74+14−19 per cent at a late merger stage, prior to coalescence, when the nuclei have projected separations (dsep) of 0.4–6 kpc. A similar peak is also observed in the median NH [(1.6 ± 0.5) × 1024 cm−2]. The vast majority (85+7−9 per cent) of the AGNs in the final merger stages (dsep 10 kpc) are heavily obscured (NH ≥ 1023 cm−2), and the median NH of the accreting SMBHs in our sample is systematically higher than that of local hard X-ray-selected AGN, regardless of the merger stage. This implies that these objects have very obscured nuclear environments, with the NH ≥ 1023 cm−2 gas almost completely covering the AGN in late mergers. CT AGNs tend to have systematically higher absorption-corrected X-ray luminosities than less obscured sources. This could either be due to an evolutionary effect, with more obscured sources accreting more rapidly because they have more gas available in their surroundings, or to a selection bias. The latter scenario would imply that we are still missing a large fraction of heavily obscured, lower luminosity (L2−10 1043 erg s−1) AGNs in U/LIRGs.
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    A hybrid model of viscous and Chaplygin gas to tackle the Universe acceleration
    (Springer Science and Business Media LLC, 2021-04)
    A. Hernández-Almada
    ;
    Miguel A. García-Aspeitia
    ;
    M. A. Rodríguez-Meza
    ;
    Motta, Veronica  
    Motivated by two seminal models proposed to explain the Universe acceleration, this paper is devoted to study a hybrid model which is constructed through a generalized Chaplygin gas with the addition of a bulk viscosity. We call the model a viscous generalized Chaplygin gas (VGCG) and its free parameters are constrained through several cosmological data like the Observational Hubble Parameter, Type Ia Supernovae, Baryon Acoustic Oscillations, Strong Lensing Systems, HII Galaxies and using Joint Bayesian analysis. In addition, we implement a Om-diagnostic to analyze the VGCC dynamics and its difference with the standard cosmological model. The hybrid model shows important differences when compared with the standard cosmological model. Finally, based on our Joint analysis we find that the VGCG could be an interesting candidate to alleviate the well-known Hubble constant tension.
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    A kpc-scale-resolved study of unobscured and obscured star formation activity in normal galaxies at z  = 1.5 and 2.2 from ALMA and HiZELS
    (Oxford University Press (OUP), 2020-10-02)
    Cheng Cheng
    ;
    Ibar, Eduardo  
    ;
    Ian Smail
    ;
    Juan Molina
    ;
    David Sobral
    ;
    Andrés Escala
    ;
    Philip Best
    ;
    Rachel Cochrane
    ;
    Steven Gillman
    ;
    Mark Swinbank
    ;
    R J Ivison
    ;
    Jia-Sheng Huang
    ;
    Thomas M Hughes
    ;
    Eric Villard
    ;
    Michele Cirasuolo
    We present Atacama Large Millimeter/Submillimeter Array (ALMA) continuum observations of a sample of nine star-forming galaxies at redshifts 1.47 and 2.23 selected from the High-z Emission Line Survey (HiZELS). Four galaxies in our sample are detected at high significance by ALMA at a resolution of 0${_{.}^{\prime\prime}}$25 at rest-frame 355 μm. Together with the previously observed H α emission, from adaptive optics-assisted integral-field-unit spectroscopy (∼0${_{.}^{\prime\prime}}$15 resolution), and F606W and F140W imaging from the Hubble Space Telescope (∼0${_{.}^{\prime\prime}}$2 resolution), we study the star formation activity, stellar and dust mass in these high-redshift galaxies at ∼kpc-scale resolution. We find that ALMA detection rates are higher for more massive galaxies (M* > 1010.5 M⊙) and higher [N ii]/H α ratios (>0.25, a proxy for gas-phase metallicity). The dust extends out to a radius of 8 kpc, with a smooth structure, even for those galaxies presenting clumpy H α morphologies. The half-light radii (Rdust) derived for the detected galaxies are of the order ∼4.5 kpc, more than twice the size of submillimetre-selected galaxies at a similar redshift. Our global star formation rate estimates – from far-infrared and extinction-corrected H α luminosities – are in good agreement. However, the different morphologies of the different phases of the interstellar medium suggest complex extinction properties of the high-redshift normal galaxies.
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    A massive open cluster hiding in full sight
    (Oxford University Press (OUP), 2021-04-24)
    I Negueruela
    ;
    A-N Chené
    ;
    H M Tabernero
    ;
    R Dorda
    ;
    Borissova, Jura  
    ;
    A Marco
    ;
    Kurtev, Radostin  
    Obscuration and confusion conspire to limit our knowledge of the inner Milky Way. Even at moderate distances, the identification of stellar systems becomes compounded by the extremely high density of background sources. Here, we provide a very revealing example of these complications by unveiling a large, massive, young cluster in the Sagittarius arm that has escaped detection until now despite containing more than 30 stars brighter than G = 13. By combining Gaia DR2 astrometry, Gaia and 2MASS photometry, and optical spectroscopy, we find that the new cluster, which we name Valparaiso 1, located at ∼ 2.3 kpc, is about 75 Ma old and includes a large complement of evolved stars, among which we highlight the 4 d classical Cepheid CM Sct and an M-type giant that probably represents the first detection of an asymptotic giant branch star in a Galactic young open cluster. Although strong differential reddening renders accurate parameter determination unfeasible with the current data set, direct comparison to clusters of similar age suggests that Valparaiso 1 was born as one of the most massive clusters in the solar neighbourhood, with an initial mass close to 104 M.
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    A method to deconvolve stellar profiles
    (EDP Sciences, 2023-08)
    P. Escárate
    ;
    Cure, Michel  
    ;
    I. Araya
    ;
    M. Coronel
    ;
    A. L. Cedeño
    ;
    L. Celedon
    ;
    J. Cavieres
    ;
    J. C. Agüero
    ;
    Arcos, Catalina  
    ;
    L. S. Cidale
    ;
    R. S. Levenhagen
    ;
    R. Pezoa
    ;
    S. Simón-Díaz
    Context. Currently, one of the standard procedures used to determine stellar and wind parameters of massive stars involves to comparing the observed spectral lines with a grid of synthetic lines. These synthetic lines are calculated using non-local thermodynamic equilibrium radiative transfer codes. In this standard procedure, after estimating the stellar-projected rotational speed (v sin i), all synthetic models need to be convolved using this value in order to perform the comparison with the observed line and estimate the stellar parameters. Aims. In this work, we propose a methodology to deconvolve the observed line profile to one from a non-rotating star. Thus, to perform a comparison, we will not need to convolve all the synthetic profiles, saving significant time and resources. Methods. The proposed deconvolution method is based on transforming this inverse problem into an optimization of a direct problem. We propose using a Gaussian sum approximation (GSA) to obtain the line profile without the broadening effect due to stellar rotation. After selecting the most adequate model to derive the fundamental GSA parameters, we convolved it with the known v sin i in order to obtain the profile considering the v sin i. Finally, we compared this approximated line profile directly with the observed spectrum. Results. The performance of the proposed method is analyzed using synthetic and observed lines. The results show that the proposed deconvolution method yields accurate non-rotating profiles. Conclusions. The proposed approach utilizing GSA is an accurate method to deconvolve spectral lines.
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    A method to deconvolve stellar rotational velocities
    (EDP Sciences, 2019-03)
    R. Orellana
    ;
    P. Escárate
    ;
    Cure, Michel  
    ;
    A. Christen
    ;
    R. Carvajal
    ;
    J. C. Agüero
    Aims. The study of accurate methods to estimate the distribution of stellar rotational velocities is important for understanding many aspects of stellar evolution. From such observations we obtain the projected rotational speed (v sin i) in order to recover the true distribution of the rotational velocity. To that end, we need to solve a difficult inverse problem that can be posed as a Fredholm integral of the first kind. Methods. In this work we have used a novel approach based on maximum likelihood (ML) estimation to obtain an approximation of the true rotational velocity probability density function (PDF) expressed as a sum of known distribution families. In our proposal, the measurements have been treated as random variables drawn from the projected rotational velocity PDF. We analyzed the case of Maxwellian sum approximation, where we estimated the parameters that define the sum of distributions. Results. The performance of the proposed method is analyzed using Monte Carlo simulations considering two theoretical cases for the PDF of the true rotational stellar velocities: (i) an unimodal Maxwellian probability density distribution and (ii) a bimodal Maxwellian probability density distribution. The results show that the proposed method yielded more accurate estimates in comparison with the Tikhonov regularization method, especially for small sample length (N = 50). Our proposal was evaluated using real data from three sets of measurements, and our findings were validated using three statistical tests. Conclusions. The ML approach with Maxwellian sum approximation is a accurate method to deconvolve the rotational velocity PDF, even when the sample length is small (N = 50).
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    A Multisubcellular Compartment Model of AMPA Receptor Trafficking for Neuromodulation of Hebbian Synaptic Plasticity
    (Frontiers Media SA, 2021-08-11)
    Stefan Mihalas
    ;
    Ardiles, Alvaro  
    ;
    Kaiwen He
    ;
    Adrian Palacios  
    ;
    Alfredo Kirkwood
    Neuromodulation can profoundly impact the gain and polarity of postsynaptic changes in Hebbian synaptic plasticity. An emerging pattern observed in multiple central synapses is a pull–push type of control in which activation of receptors coupled to the G-protein Gs promote long-term potentiation (LTP) at the expense of long-term depression (LTD), whereas receptors coupled to Gq promote LTD at the expense of LTP. Notably, coactivation of both Gs- and Gq-coupled receptors enhances the gain of both LTP and LTD. To account for these observations, we propose a simple kinetic model in which AMPA receptors (AMPARs) are trafficked between multiple subcompartments in and around the postsynaptic spine. In the model AMPARs in the postsynaptic density compartment (PSD) are the primary contributors to synaptic conductance. During LTP induction, AMPARs are trafficked to the PSD primarily from a relatively small perisynaptic (peri-PSD) compartment. Gs-coupled receptors promote LTP by replenishing peri-PSD through increased AMPAR exocytosis from a pool of endocytic AMPAR. During LTD induction AMPARs are trafficked in the reverse direction, from the PSD to the peri-PSD compartment, and Gq-coupled receptors promote LTD by clearing the peri-PSD compartment through increased AMPAR endocytosis. We claim that the model not only captures essential features of the pull–push neuromodulation of synaptic plasticity, but it is also consistent with other actions of neuromodulators observed in slice experiments and is compatible with the current understanding of AMPAR trafficking.
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    A multiwavelength-motivated X-ray model for the Circinus Galaxy
    (Oxford University Press (OUP), 2022-02-16)
    Carolina Andonie
    ;
    Claudio Ricci
    ;
    Stéphane Paltani
    ;
    Arevalo, Patricia  
    ;
    Ezequiel Treister
    ;
    Franz Bauer
    ;
    Marko Stalevski
    Reprocessed X-ray emission in active galactic nuclei can provide fundamental information about the circumnuclear environments of supermassive black holes. Recent mid-infrared studies have shown evidence of an extended dusty structure perpendicular to the torus plane. In this work, we build a self-consistent X-ray model for the Circinus Galaxy including the different physical components observed at different wavelengths and needed to reproduce both the morphological and spectral properties of this object in the mid-infrared. The model consists of four components: the accretion disc, the broad-line region (BLR), a flared disc in the equatorial plane, and a hollow cone in the polar direction. Our final model reproduces well the 3–70 keV Chandra and NuSTAR spectra of Circinus, including the complex Fe Kα zone and the spectral curvature, although several additional Gaussian lines, associated with either ionized iron or broadened Fe Kα/Kβ lines, are needed. We find that the flared disc is Compton-thick ($N_{\rm H,d}= \rm 1.01^{+0.03}_{-0.24}\times 10^{25}\, cm^{-2}$) and geometrically thick ($\mathrm{ CF}=0.55^{+0.01}_{-0.05}$), and that the hollow cone has a Compton-thin column density ($N_{\rm H,c}= \rm 2.18^{+0.47}_{-0.43}\times 10^{23}\, cm^{-2}$), which is consistent with the values inferred by mid-infrared studies. Including also the BLR, the effective line-of-sight column density is $N_{\rm H}= \rm 1.47^{+0.03}_{-0.24}\times 10^{25}\, cm^{-2}$. This approach to X-ray modelling, i.e. including all the different reprocessing structures, will be very important to fully exploit data from future X-ray missions.
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    A New Kind of Quinonic-Antibiotic Useful Against Multidrug-Resistant S. aureus and E. faecium Infections
    (MDPI AG, 2018-07-19)
    Javier Campanini-Salinas
    ;
    Juan Andrades-Lagos
    ;
    Gerardo Gonzalez Rocha
    ;
    Duane Choquesillo-Lazarte
    ;
    Soledad Bollo Dragnic
    ;
    Mario Faúndez
    ;
    Pedro Alarcón
    ;
    Francisco Silva
    ;
    Roberto Vidal
    ;
    Edison Salas-Huenuleo
    ;
    Marcelo Kogan
    ;
    Mella, Jaime  
    ;
    Gonzalo Recabarren Gajardo
    ;
    David Vásquez-Velásquez
    A rapid emergence of resistant bacteria is occurring worldwide, endangering the efficacy of antibiotics and reducing the therapeutic arsenal available for treatment of infectious diseases. In the present study, we developed a new class of compounds with antibacterial activity obtained by a simple, two step synthesis and screened the products for in vitro antibacterial activity against ATCC® strains using the broth microdilution method. The compounds exhibited minimum inhibitory concentrations (MIC) of 1–32 μg/mL against Gram-positive ATCC® strains. The structure–activity relationship indicated that the thiophenol ring is essential for antibacterial activity and the substituents on the thiophenol ring module, for antibacterial activity. The most promising compounds detected by screening were tested against methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus faecium (VREF) clinical isolates. We found remarkable activity against VREF for compounds 7 and 16, were the MIC50/90 were 2/4 µg/mL and 4/4 µg/mL, respectively, while for vancomycin the MIC50/90 was 256/512 µg/mL. Neither compound affected cell viability in any of the mammalian cell lines at any of the concentrations tested. These in vitro data show that compounds 7 and 16 have an interesting potential to be developed as new antibacterial drugs against infections caused by VREF.
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    A scenario for the origin of life: Volume regulation by bacteriorhodopsin required extremely voltage sensitive Na‐channels and very selective K‐channels
    (Wiley, 2022-08-19)
    Naranjo, David  
    AbstractThe osmotic activity produced by internal, non‐permeable, anionic nucleic acids and metabolites causes a persistent and life‐threatening cell swelling, or cellular edema, produced by the Gibbs‐Donnan effect. This evolutionary‐critical osmotic challenge must have been resolved by LUCA or its ancestors, but we lack a cell‐physiology look into the biophysical constraints to the solutions. Like mycoplasma, early cells conceivably preserved their volume with Cl−, Na+, and K+‐channels, Na+/H+‐exchangers, and a light‐dependent bacteriorhodopsin‐like H+‐pump. Here, I simulated protocells having these ionic‐permeabilities and inhabiting an oceanic pond before the Great‐Oxygenation‐Event. Protocells showed better volume control and stable resting potentials at lower external pH and higher temperatures, favoring a certain type of extremophile life. Prevention of Na+‐influx at night, with low bacteriorhodopsin activity, required deep shutdown of highly voltage‐sensitive Na+‐channels and extremely selective K+‐channels, two conserved features essential for modern neuronal encoding. The Gibbs‐Donnan effect universality implies that extraterrestrial cells, if they exist, may reveal similar volume‐controlling mechanisms.
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    A young and obscured AGN embedded in the giant radio galaxy Mrk 1498
    (Oxford University Press (OUP), 2019-08-16)
    L Hernández-García
    ;
    F Panessa
    ;
    L Bassani
    ;
    G Bruni
    ;
    F Ursini
    ;
    V Chavushyan
    ;
    O González-Martín
    ;
    S Cazzoli
    ;
    E F Jiménez-Andrade
    ;
    Arevalo, Patricia  
    ;
    Y Díaz
    ;
    A Bazzano
    ;
    P Ubertini
    Mrk 1498 is part of a sample of galaxies with extended emission line regions (extended outwards up to a distance of ∼7 kpc) suggested to be photo-ionized by an AGN that has faded away or that is still active but heavily absorbed. Interestingly, the nucleus of Mrk 1498 is at the center of two giant radio lobes with a projected linear size of 1.1 Mpc. Our multi-wavelength analysis reveals a complex nuclear structure, with a young radio source (Giga-hertz Peaked Spectrum) surrounded by a strong X-ray nuclear absorption, a mid-infrared spectrum that is dominated by the torus emission, plus a circum-nuclear extended emission in the [OIII] image (with radius of ∼ 1 kpc), most likely related to the ionization of the AGN, aligned with the small and large scale radio jet and extended also at X-rays. In addition a large-scale extended emission (up to ∼ 10 kpc) is only visible in [OIII]. These data show conclusive evidence of a heavily absorbed nucleus and has recently restarted its nuclear activity. To explain its complexity, we propose that Mrk 1498 is the result of a merging event or secular processes, such as a minor interaction, that has triggered the nuclear activity and produced tidal streams. The large-scale extended emission that gives place to the actual morphology could either be explained by star formation or outflowing material from the AGN.
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    About the existence of warm H-rich pulsating white dwarfs
    (EDP Sciences, 2019-12-23)
    Leandro G. Althaus
    ;
    Alejandro H. Córsico
    ;
    Murat Uzundag
    ;
    Vuckovic, Maja  
    ;
    Andrzej S. Baran
    ;
    Keaton J. Bell
    ;
    María E. Camisassa
    ;
    Leila M. Calcaferro
    ;
    Francisco C. De Gerónimo
    ;
    Souza Oliveira Kepler
    ;
    Roberto Silvotti
    Context. The possible existence of warm (Teff ∼ 19 000 K) pulsating DA white dwarf (WD) stars, hotter than ZZ Ceti stars, was predicted in theoretical studies more than 30 yr ago. These studies reported the occurrence of g-mode pulsational instabilities due to the κ mechanism acting in the partial ionization zone of He below the H envelope in models of DA WDs with very thin H envelopes (MH/M⋆ ≲ 10−10). However, to date, no pulsating warm DA WD has been discovered, despite the varied theoretical and observational evidence suggesting that a fraction of WDs should be formed with a range of very low H content. Aims. We re-examine the pulsational predictions for such WDs on the basis of new full evolutionary sequences. We analyze all the warm DAs observed by the TESS satellite up to Sector 9 in order to search for the possible pulsational signal. Methods. We computed WD evolutionary sequences of masses 0.58 and 0.80 M⊙ with H content in the range −14.5 ≲ log(MH/M⋆)≲ − 10, appropriate for the study of pulsational instability of warm DA WDs. Initial models were extracted from progenitors that were evolved through very late thermal pulses on the early cooling branch. We use LPCODE stellar code into which we have incorporated a new full-implicit treatment of time-dependent element diffusion to precisely model the H–He transition zone in evolving WD models with very low H content. The nonadiabatic pulsations of our warm DA WD models were computed in the effective temperature range of 30 000 − 10 000 K, focusing on ℓ = 1 g modes with periods in the range 50 − 1500 s. Results. We find that traces of H surviving the very late thermal pulse float to the surface, eventually forming thin, growing pure H envelopes and rather extended H–He transition zones. We find that such extended transition zones inhibit the excitation of g modes due to partial ionization of He below the H envelope. Only in the cases where the H–He transition is assumed much more abrupt than predicted by diffusion do models exhibit pulsational instability. In this case, instabilities are found only in WD models with H envelopes in the range of −14.5 ≲ log(MH/M⋆)≲ − 10 and at effective temperatures higher than those typical for ZZ Ceti stars, in agreement with previous studies. None of the 36 warm DAs observed so far by TESS satellite are found to pulsate. Conclusions. Our study suggests that the nondetection of pulsating warm DAs, if WDs with very thin H envelopes do exist, could be attributed to the presence of a smooth and extended H–He transition zone. This could be considered as indirect proof that element diffusion indeed operates in the interior of WDs.
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    Active microbiome structure and its association with environmental factors and viruses at different aquatic sites of a high‐altitude wetland
    (Wiley, 2018-07-30)
    Eissler, Yoanna  
    ;
    María‐Jesús Gálvez
    ;
    Cristina Dorador
    ;
    Martha Hengst
    ;
    Verónica Molina
    AbstractSalar de Huasco is a high‐altitude wetland characterized by a highly diverse microbial life adapted to extreme climatic and environmental conditions. Our study aims to determine active microbial community structure changes within different aquatic sites and its relationship with environmental factors and viruses as potential drivers of diversification in different aquatic areas of this ecosystem. In this study, bacteria and archaea composition (16S rRNA subunit pyrolibraries) and picoplankton and viral abundance were determined at ponds, springs and lagoon sites of the wetland during wet and dry seasons (February and July 2012, respectively). In general, mixosaline waters (1,400–51,000 μS/cm) usually found in ponds and lagoon presented higher picoplanktonic abundances compared to freshwater (<800 μS/cm) spring sites, ranging from 1.07 × 105 to 1.83 × 107 cells/ml. Viral abundance and viral to picoplankton ratio (VPR) also presented greater values at ponds compared to spring sites, reaching up to 4.78 × 108 viruses‐like particles and up to 351 for VPR. In general, ponds hold a higher microbial diversity and complexity associated also with the presence of microbial mats compared with water sources or lagoon (Shannon index H′ 2.6–3.9 vs. <2.0). A greater richness of archaea was also detected in ponds characterized by functional groups such as known methanogens and ammonia oxidizers, and uncultured groups. In total, our results indicate that among the different aquatic sites of the wetland, ponds presented a great microbial community diversification associated to a higher top‐down control by viruses which may influence nutrient and greenhouse gases cycling.
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    Acute Consumption of Blueberries and Short-Term Blueberry Supplementation Improve Glucose Management and Insulin Levels in Sedentary Subjects
    (MDPI AG, 2021-04-25)
    Palma, Ximena  
    ;
    Samanta Thomas-Valdés
    ;
    Cruz, Gonzalo  
    Background: Blueberries are polyphenol-rich fruits with antioxidant and anti-inflammatory properties. Polyphenols from berries act by blocking digestive enzymes, reshaping gastrointestinal microbiota, and affecting the release of gastrointestinal hormones to regulate insulin dynamics and glucose management. However, most studies use fruit extracts instead of fresh fruit. We aimed to evaluate postprandial glucose management and antioxidant capacity of fresh blueberries consumed acutely or as a six-day supplementation in 10 sedentary subjects. Methods: To evaluate the effect of acute blueberry intake, 150 g of blueberries were consumed together with 150 g of white bread by the subject and blood samples were collected at 0, 30, 60, 90 and 120 min to measure glucose, insulin, and plasma antioxidant capacity. To evaluate supplementation, 150 g of blueberries were provided daily for six days and sample collection was performed at day 7. Results: Acute consumption of blueberries decreased postprandial glucose area under the curve (AUC) and increased insulin levels at 15 min timepoint. Supplementation did not affect glucose levels but decreased insulin levels at 120 min. No changes in antioxidant capacity were observed. Conclusions: Consumption of fresh blueberries improves postprandial glucose management presumably due to actions on the gastrointestinal tract, while supplementation improves insulin sensitivity, probably due antioxidant and anti-inflammatory effects.
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    Alert Classification for the ALeRCE Broker System: The Light Curve Classifier
    (American Astronomical Society, 2021-02-23)
    P. Sánchez-Sáez
    ;
    I. Reyes
    ;
    C. Valenzuela
    ;
    F. Förster
    ;
    S. Eyheramendy
    ;
    F. Elorrieta
    ;
    F. E. Bauer
    ;
    G. Cabrera-Vives
    ;
    P. A. Estévez
    ;
    M. Catelan
    ;
    G. Pignata
    ;
    P. Huijse
    ;
    D. De Cicco
    ;
    Arevalo, Patricia  
    ;
    R. Carrasco-Davis
    ;
    J. Abril
    ;
    Kurtev, Radostin  
    ;
    J. Borissova
    ;
    J. Arredondo
    ;
    E. Castillo-Navarrete
    ;
    D. Rodriguez
    ;
    D. Ruz-Mieres
    ;
    A. Moya
    ;
    L. Sabatini-Gacitúa
    ;
    C. Sepúlveda-Cobo
    ;
    E. Camacho-Iñiguez
    We present the first version of the Automatic Learning for the Rapid Classification of Events (ALeRCE) broker light curve classifier. ALeRCE is currently processing the Zwicky Transient Facility (ZTF) alert stream, in preparation for the Vera C. Rubin Observatory. The ALeRCE light curve classifier uses variability features computed from the ZTF alert stream and colors obtained from AllWISE and ZTF photometry. We apply a balanced random forest algorithm with a two-level scheme where the top level classifies each source as periodic, stochastic, or transient, and the bottom level further resolves each of these hierarchical classes among 15 total classes. This classifier corresponds to the first attempt to classify multiple classes of stochastic variables (including core- and host-dominated active galactic nuclei, blazars, young stellar objects, and cataclysmic variables) in addition to different classes of periodic and transient sources, using real data. We created a labeled set using various public catalogs (such as the Catalina Surveys and Gaia DR2 variable stars catalogs, and the Million Quasars catalog), and we classify all objects with ≥6 g-band or ≥6 r-band detections in ZTF (868,371 sources as of 2020 June 9), providing updated classifications for sources with new alerts every day. For the top level we obtain macro-averaged precision and recall scores of 0.96 and 0.99, respectively, and for the bottom level we obtain macro-averaged precision and recall scores of 0.57 and 0.76, respectively. Updated classifications from the light curve classifier can be found at the ALeRCE Explorer website (http://alerce.online).
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