124 research outputs found
MEGARA-GTC stellar spectral library: I
No full textMEGARA (Multi Espectrógrafo en GTC de Alta Resolución para Astronomía) is an optical (3650-9750 Å), fibre-fed, medium-high spectral resolution (R = 6000, 12 000 and 20 000) instrument for the Gran Telescopio CANARIAS (GTC) 10.4-m telescope, commissioned in the summer of 2017, and currently in operation. The scientific exploitation of MEGARA requires a stellar spectra library to interpret galaxy data and to estimate the contribution of the stellar populations. In this paper, we introduce the MEGARA-GTC spectral library, detailing the rationale behind the building of this catalogue. We present the spectra of 97 stars (21 individual stars and 56 members of the globular cluster M15, which are both subsamples taken during the commissioning runs, and 20 stars from our ongoing GTC Open-Time programme). The spectra have R = 20 000 in the HR-R and HR-I set-ups, centred at 6563 and 8633 Å, respectively. We describe the procedures to reduce and analyse the data. Then, we determine the best-fitting theoretical models to each spectrum through a χ2 minimization technique, to derive the stellar physical parameters, and we discuss the results. We have also measured some absorption lines and indices. Finally, we introduce our project to complete the library and the data base in order to make the spectra available to the community.© 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical SocietyThis work has been supported by MINECO-FEDER grants
AYA2016-75808-R and AYA2016-79724-C4-3-P, and has been
partially funded by FRACTAL, INAOE and CIEMAT. This work is
based on observations made with the Gran Telescopio Canarias
(GTC), installed at the Spanish Observatorio del Roque de los
Muchachos, on the island of La Palma. This work is based on
data obtained with MEGARA instrument, funded by the European
Regional Development Funds (ERDF), through Programa Operativo Canarias FEDER 2014–2020. The authors are grateful for
the support given by Dr Antonio Cabrera and Dr Daniel Reverte,
GTC Operations Group staff, during the preparation and execution
of the observations at the GTC. The authors acknowledge an
anonymous referee for comments that have substantially improved
the manuscript.Peer reviewe
MEGARA-GTC stellar spectral library: I
No full text© 2020 The Author(s). This work has been supported by MINECO-FEDER grants AYA2016-75808-R and AYA2016-79724-C4-3-P, and has been partially funded by FRACTAL, INAOE and CIEMAT. This work is based on observations made with the Gran Telescopio Canarias (GTC), installed at the Spanish Observatorio del Roque de los Muchachos, on the island of La Palma. This work is based on data obtained with MEGARA instrument, funded by the European Regional Development Funds (ERDF), through Programa Operativo Canarias FEDER 2014-2020. The authors are grateful for the support given by Dr Antonio Cabrera and Dr Daniel Reverte, GTC Operations Group staff, during the preparation and execution of the observations at the GTC. The authors acknowledge an anonymous referee for comments that have substantially improved the manuscript.MEGARA (Multi Espectrografo en GTC de Alta Resolucion para Astronomia) is an optical (3650-9750 Å), fibre-fed, medium-high spectral resolution (R = 6000, 12 000 and 20 000) instrument for the Gran Telescopio CANARIAS (GTC) 10.4-m telescope, commissioned in the summer of 2017, and currently in operation. The scientific exploitation of MEGARA requires a stellar spectra library to interpret galaxy data and to estimate the contribution of the stellar populations. In this paper, we introduce the MEGARA-GTC spectral library, detailing the rationale behind the building of this catalogue. We present the spectra of 97 stars (21 individual stars and 56 members of the globular cluster M15, which are both subsamples taken during the commissioning runs, and 20 stars from our ongoing GTC Open-Time programme). The spectra have R = 20 000 in the HR-R and HR-I set-ups, centred at 6563 and 8633 Å, respectively. We describe the procedures to reduce and analyse the data. Then, we determine the best-fitting theoretical models to each spectrum through a χ^(2) minimization technique, to derive the stellar physical parameters, and we discuss the results. We have also measured some absorption lines and indices. Finally, we introduce our project to complete the library and the data base in order to make the spectra available to the community.MINECO-FEDEREuropean Regional Development Funds (ERDF) through Programa Operativo Canarias FEDER 2014-2020Depto. de Física de la Tierra y AstrofísicaFac. de Ciencias FísicasTRUEpu
The scaffold protein JLP plays a key role in regulating ultraviolet B-induced apoptosis in mice
No full textThe ultraviolet B (UVB) component of sunlight can cause severe damage to skin cells and even induce skin cancer. Growing evidence indicates that the UVB-induced signaling network is complex and involves diverse cellular processes. In this study, we investigated the role of c-Jun NH2-terminal kinase-associated leucine zipper protein (JLP), a scaffold protein for mitogen-activated protein kinase (MAPK) signaling cascades, in UVB-induced apoptosis. We found that UVB-induced skin epidermal apoptosis was prevented in Jlp knockout (KO) as well as in keratinocyte-specific Jlp KO mice. Analysis of the repair of UVB-induced DNA damage over time showed no evidence for the involvement of JLP in this process. In contrast, UVB-stimulated p38 MAPK activation in the skin was impaired in both Jlp KO and keratinocyte-specific Jlp KO mice. Moreover, topical treatment of UVB-irradiated mouse skin with a p38 inhibitor significantly suppressed the epidermal apoptosis in wild-type mice, but not in Jlp KO mice. Our findings suggest that JLP in skin basal keratinocytes plays an important role in UVB-induced apoptosis by modulating p38 MAPK signaling pathways. This is the first study to show a critical role for JLP in an in vivo response to environmental stimulation. © 2014 by the Molecular Biology Society of Japan and Wiley Publishing Asia Pty Ltd.journal articl
Planetary nebulae with Wolf–Rayet-type central stars – II. Dissecting the compact planetary nebula M 2-31 with GTC MEGARA
No full textA correction has been published: Monthly Notices of the Royal Astronomical Society, Volume 509, Issue 2, January 2022, Page 2896, https://doi.org/10.1093/mnras/stab3247We present a comprehensive analysis of the compact planetary nebula M 2-31 investigating its spectral properties, spatio-kinematical structure, and chemical composition using Gran Telescopio Canarias (GTC) Multi-Espectrógrafo en GTC de Alta Resolución para Astronomía (MEGARA) integral field spectroscopic observations and Nordic Optical Telescope(NOT) Alhambra Faint Object Spectrograph and Camera (ALFOSC) medium-resolution spectra and narrow-band images. The GTC MEGARA high-dispersion observations have remarkable tomographic capabilities, producing an unprecedented view of the morphology and kinematics of M 2-31 that discloses a fast spectroscopic bipolar outflow along position angles 50° and 230°, an extended shell, and a toroidal structure or waist surrounding the central star perpendicularly aligned with the fast outflows. These observations also show that the C ii emission is confined in the central region and enclosed by the [N ii] emission. This is the first time that the spatial segregation revealed by a two-dimensional map of the C ii line implies the presence of multiple plasma components. The deep NOT ALFOSC observations allowed us to detect broad Wolf-Rayet (WR) features from the central star of M 2-31, including previously undetected broad O vi lines that suggest a reclassification as a [WO4]-type star. © 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.JSRG and VMAGG acknowledge support from the Programas de Beca Posdoctorales funded by Dirección General de Asuntos del Personal Académico of the Universidad Nacional Autónoma de México (DGAPA, UNAM). JAT acknowledges funding by DGAPA, UNAM PAPIIT project IA100720 and the Marcos Moshinsky Foundation (Mexico). SC and MAG acknowledge financial support from State Agency for Research of the Spanish MCIU through the ‘Center of Excellence Severo Ochoa’ award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709). MAG acknowledges support of the Spanish Ministerio de Ciencia, Innovación y Universidades (MCIU) grant PGC2018-102184-B-100. LS acknowledges support from PAPIIT-UNAM grant IN101819. GR-L acknowledges support from CONACYT (grant 263373) and PRODEP (Mexico). The GTC Science Operations group is recognized for scheduling the GTC MEGARA observations beneath the exacting conditions requested by this program.Peer reviewe
A new insight of AGC 198691 (Leoncino) galaxy with MEGARA at the GTC
No full textWe describe the observations of the low metallicity nearby galaxy AGC 198691 (Leoncino Dwarf) obtained with the Integral Field Unit of the instrument MEGARA at the Gran Telescopio Canarias. The observations cover the wavelength ranges 4304–5198 Å and 6098–7306 Å with a resolving power R ≈ 6000. We present 2D maps of the ionized gas, deriving the extension of the H II region and gas kinematics from the observed emission lines. We have not found any evidence of recent gas infall or loss of metals by means of outflows. This result is supported by the closed-box model predictions, consistent with the oxygen abundance found by other authors in this galaxy and points towards Leoncino being a genuine XMD galaxy. We present for the first time spatially resolved spectroscopy allowing the detailed study of a star-forming region. We use POPSTAR + CLOUDY models to simulate the emission-line spectrum. We find that the central emission-line spectrum can be explained by a single young ionizing cluster with an age of ≈ 3.5 ± 0.5 Myr and a stellar mass of ≈ 2 ×103 M⊙. However, the radial profiles of [OIII] λ 5007Å and the Balmer lines in emission demand photoionization by clusters of different ages between 3.5 and 6.5 Myr that might respond either to the evolution of a single cluster evolving along the cooling time of the nebula (≈ 3 Myr at the metallicity of Leoncino, Z≈ 0.0004) or to mass segregation of the cluster, being both scenarios consistent with the observed equivalent widths of the Balmer lines. © 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.This work is based on observations made with the Gran Telescopio Canarias (GTC), installed in the Spanish Observatorio del Roque de los Muchachos, on the island of La Palma. The work is based on data obtained with the MEGARA instrument, funded by European Regional Development Funds (ERDF), through the Programa Operativo Canarias FEDER 2014-2020. The authors thank the support given by Dr. Antonio Cabrera and Dr. Daniel Reverté, GTC Operations Group staff, during the preparation and execution of the observations at the GTC. This work has been supported by DGICYT grant RTI2018- 096188-B-I00, which is partly funded by the European Regional Development Fund (ERDF). Jorge Iglesias acknowledges financial support from the following projects: Estallidos6 AYA2016-79724-C4 (Spanish Ministerio de Economía y Competitividad), Estallidos7 PID2019-107408GB-C44 (Spanish Ministerio de Ciencia e Innovación), grant P18-FR-2664 (Junta de Andalucía), and grantSEV-2017-0709 ‘Centro de Excelencia Severo Ochoa Program’ (Spanish Science Ministry). This research is based on observations made with the NASA/ESA Hubble Space Telescope obtained from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5–26555. These observations are associated with program 15243. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555.Peer reviewe
Unveiling gas kinematics and stellar populations in H II regions inside the low-metallicity dwarf nearby galaxy SDSSJ0859 + 3923 with MEGARA at the GTC
No full textIn this study, we present Integral Field Unit observations of the galaxy SDSSJ0859 + 3923, utilizing the MEGARA (Multi Espectrógrafo en GTC de Alta Resolución para Astronomía) instrument on the GTC (Gran Telescopio Canarias) 10.4m telescope. These observations were conducted in two distinct spectral ranges: 4332-5222 Å and 6097-7345 Å, with a high resolving power (R FWHM
∼6000
), and spatial resolution of 25 pc, considering the galaxy's distance of 8.5 Mpc. Our observations have identified five H II regions, whose precise positions were determined using data from the Wide Field Camera 3 (ultraviolet and visible) of the Hubble Space Telescope, WFC3-UVIS/HST, archive images, where we also detected the associated blue underlying continuum linked to the ionized knots. A detailed kinematic analysis of these regions revealed low-velocity dispersion values (around 10 km s −1
) in four H II regions, indicating a lack of significant turbulent events. In the fifth region, we observed a peak in velocity dispersion reaching 40 km s −1
, which we interpret as the result of hot star winds and/or a recent type-II supernova explosion. We have conducted a comprehensive spectral analysis of the H II regions, obtaining emission-line fluxes that enabled us to confirm the oxygen abundance (12 + log(O/H) = 7.41 ±
0.15) and, using POPSTAR models, to constrain the age and mass of the ionizing young clusters. © 2024 The Author(s).This research has been funded by the project PID2019-107408GB-C41, PID2022-136598NB-C32 and PID2022-136598NB-C33 and by “ERDF A way of making Europe”, granted by the Spanish Ministry of Science and Innovation/State Agency of Research MCIN/AEI/10.13039/501100011033, participated by the co-authors MGV, EC, MM, and JI. AGdP, JG, NC, ACM, and SP acknowledge financial support from the Spanish MCIU under the grants RTI2018-096188-B-I00, PID2021-123417OB-I00, and PID2022-138621NB-I00. This work has already being funded with internal R + D projects of FRACTAL S.L.N.E. and INAOE.
This work is based on data obtained with MEGARA instrument, funded by European Regional Development Funds (ERDF), through Programa Operativo Canarias FEDER 2014–2020, and based on observations made with the GTC, installed in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, in the island of La Palma.Peer reviewe
A new insight of AGC 198691 (Leoncino) galaxy with MEGARA at the GTC
No full text© 2021 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. The authors are grateful to the referee, Alec S. Hirschauer, for his constructive comments and suggestions. This work is based on observations made with the Gran Telescopio Canarias (GTC), installed in the Spanish Observatorio del Roque de los Muchachos, on the island of La Palma. The work is based on data obtained with the MEGARA instrument, funded by European Regional Development Funds (ERDF), through the Programa Operativo Canarias FEDER 2014-2020. The authors thank the support given by Dr. Antonio Cabrera and Dr. Daniel Reverte, GTC Operations Group staff, during the preparation and execution of the observations at the GTC. This work has been supported by DGICYT grant RTI2018-096188-B-I00, which is partly funded by the European Regional Development Fund (ERDF). Jorge Iglesias acknowledges financial support from the following projects: Estallidos6 AYA2016-79724-C4 (Spanish Ministerio de Economía y Competitividad), Estallidos7 PID2019-107408GB-C44 (Spanish Ministerio de Ciencia e Innovación), grant P18-FR-2664 (Junta de Andalucía), and grant SEV-2017-0709 'Centro de Excelencia Severo Ochoa Program' (Spanish Science Ministry). This research is based on observations made with the NASA/ESA Hubble Space Telescope obtained from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program 15243. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555.We describe the observations of the low metallicity nearby galaxy AGC 198691 (Leoncino Dwarf) obtained with the Integral Field Unit of the instrument MEGARA at the Gran Telescopio Canarias. The observations cover the wavelength ranges 4304-5198 Aand 6098-7306 Awith a resolving power R approximate to 6000. We present 2D maps of the ionized gas, deriving the extension of the H II region and gas kinematics from the observed emission lines. We have not found any evidence of recent gas infall or loss of metals by means of outflows. This result is supported by the closed-box model predictions, consistent with the oxygen abundance found by other authors in this galaxy and points towards Leoncino being a genuine XMD galaxy. We present for the first time spatially resolved spectroscopy allowing the detailed study of a star-forming region. We use POPSTAR + CLOUDY models to simulate the emission-line spectrum. We find that the central emission-line spectrum can be explained by a single young ionizing cluster with an age of approximate to 3.5 +/- 0.5 Myr and a stellar mass of approximate to 2 x10(3) M-circle dot. However, the radial profiles of [O III].5007Aand the Balmer lines in emission demand photoionization by clusters of different ages between 3.5 and 6.5 Myr that might respond either to the evolution of a single cluster evolving along the cooling time of the nebula (approximate to 3 Myr at the metallicity of Leoncino, Z approximate to 0.0004) or to mass segregation of the cluster, being both scenarios consistent with the observed equivalent widths of the Balmer lines.Ministerio de Ciencia e Innovación (MICINN)/FEDERMinisterio de Economía y Competitividad (MINECO)Ministerio de Ciencia e Innovación (MICINN)Centro de Excelencia Severo OchoaJunta de AndalucíaNASA National Aeronautics & Space Administration (NASA)Depto. de Física de la Tierra y AstrofísicaFac. de Ciencias FísicasTRUEpu
Clinical Outcomes and Adverse Events of Endoscopic Submucosal Dissection for Gastric Tube Cancer after Esophagectomy
No full textBackground and Aim. The clinical outcomes of endoscopic submucosal dissection (ESD) for gastric tube cancer (GTC) after esophagectomy remain unclear. The aim of this study was to evaluate the clinical outcomes and safety of ESD for GTC. Patients and Methods. Twenty GTC lesions in 18 consecutive patients who underwent ESD between February 2008 and June 2018 were included in this retrospective study. The endpoints were the treatment outcomes of ESD (i.e., en bloc resection rate, complete en bloc resection rate, and curative resection rate), the adverse events following ESD, and the long-term outcomes. Results. The en bloc resection rate was 100%, while the complete en bloc resection rate and curative resection rate were 80% each. Adverse events were observed in 16.7% (3/18) of patients: one postoperative bleeding, 1 intraoperative perforation that required emergency surgery, and 1 pyothorax that required chest drainage. The 1-, 3-, and 5-year overall survival rates were 100%, 70.9%, and 70.9%, respectively. Although local recurrence was detected in 1 case of noncurative resection, no GTC- or ESD-related deaths were observed. Conclusion. ESD for GTC was feasible and acceptable to enable en bloc resection and to prevent cancer death. However, ESD for GTC should be performed more carefully than common gastric ESD because serious adverse events specific to the gastric tube may occur
Malaria Parasite Stress Tolerance Is Regulated by DNMT2-Mediated tRNA Cytosine Methylation
No full textInternational audienceMalaria parasites need to cope with changing environmental conditions that require strong countermeasures to ensure pathogen survival in the human and mosquito hosts. The molecular mechanisms that protect Plasmodium falciparum homeostasis during the complex life cycle remain unknown. Here, we identify cytosine methylation of tRNAAsp (GTC) as being critical to maintain stable protein synthesis. Using conditional knockout (KO) of a member of the DNA methyltransferase family, called Pf-DNMT2, RNA bisulfite sequencing demonstrated the selective cytosine methylation of this enzyme of tRNAAsp (GTC) at position C38. Although no growth defect on parasite proliferation was observed, Pf-DNMT2KO parasites showed a selective downregulation of proteins with a GAC codon bias. This resulted in a significant shift in parasite metabolism, priming KO parasites for being more sensitive to various types of stress. Importantly, nutritional stress made tRNAAsp (GTC) sensitive to cleavage by an unknown nuclease and increased gametocyte production (>6-fold). Our study uncovers an epitranscriptomic mechanism that safeguards protein translation and homeostasis of sexual commitment in malaria parasites.IMPORTANCE P. falciparum is the most virulent malaria parasite species, accounting for the majority of the disease mortality and morbidity. Understanding how this pathogen is able to adapt to different cellular and environmental stressors during its complex life cycle is crucial in order to develop new strategies to tackle the disease. In this study, we identified the writer of a specific tRNA cytosine methylation site as a new layer of epitranscriptomic regulation in malaria parasites that regulates the translation of a subset of parasite proteins (>400) involved in different metabolic pathways. Our findings give insight into a novel molecular mechanism that regulates P. falciparum response to drug treatment and sexual commitment
Binding of Actinomycin D to Single-Stranded DNA of Sequence Motifs d(TGTCTnG) and d(TGTnGTCT)
No full textAbstractOur recent binding studies with oligomers derived from base replacements on d(CGTCGTCG) had led to the finding that actinomycin D (ACTD) binds strongly to d(TGTCATTG) of apparent single-stranded conformation without GpC sequence. A fold-back binding model was speculated in which the planar phenoxazone inserts at the GTC site with a loop-out T base whereas the G base at the 3′-terminus folds back to form a basepair with the internal C and stacks on the opposite face of the chromophore. To provide a more concrete support for such a model, ACTD equilibrium binding studies were carried out and the results are reported herein on oligomers of sequence motifs d(TGTCTnG) and d(TGTnGTC). These oligomers are not expected to form dimeric duplexes and contain no canonical GpC sequences. It was found that ACTD binds strongly to d(TGTCTTTTG), d(TGTTTTGTC), and d(TGTTTTTGTC), all exhibiting 1:1 drug/strand binding stoichiometry. The fold-back binding model with displaced T base is further supported by the finding that appending TC and TCA at the 3′-terminus of d(TGTCTTTTG) results in oligomers that exhibit enhanced ACTD affinities, consequence of the added basepairing to facilitate the hairpin formation of d(TGTCTTTTGTC) and d(TGTCTTTTGTCA) in stabilizing the GTC/GTC binding site for juxtaposing the two G bases for easy stacking on both faces of the phenoxazone chromophore. Further support comes from the observation of considerable reduction in ACTD affinity when GTC is replaced by GTTC in an oligomer, in line with the reasoning that displacing two T bases to form a bulge for ACTD binding is more difficult than displacing a single base. Based on the elucidated binding principle of phenoxazone ring requiring its opposite faces to be stacked by the 3′-sides of two G bases for tight ACTD binding, several oligonucleotide sequences have been designed and found to bind well
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