Artículos de revistas

Permanent URI for this collection

https://repositorio.uc.cl/handle/11534/1156

Esta colección incluye artículos de revistas de profesores de la Pontificia Universidad Católica de Chile, publicados en revistas nacionales y extranjeras.

Browse

Now showing 1 - 20 of 355

A hard X-ray view of luminous and ultra-luminous infrared galaxies in GOALS - I. AGN obscuration along the merger sequence
(2021) Ricci, C.; Privon, G. C.; Pfeifle, R. W.; Armus, L.; Iwasawa, K.; Torres-Albà, N.; Satyapal, S.; Bauer, F. E.; Treister, E.; Ho, L. C.; Aalto, S.; Arévalo, P.; Barcos-Muñoz, L.; Charmandaris, V.; Diaz-Santos, T.; Evans, A. S.; Gao, T.; Inami, H.; Koss, M. J.; Lansbury, G.; Linden, S. T.; Medling, A.; Sanders, D. B.; Song, Y.; Stern, D.; U, V.; Ueda, Y.; Yamada, S.
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;N-H >= 10(24)cm(-2) ) peaks at at a late merger stage, prior to coalescence, when the nuclei have projected separations (d(sep)) of 0.4-6 kpc. A similar peak is also observed in the median N-H [[(1.6 +/- 0.5) x 10(24) cm(-2)].]. The vast majority (85(-9)(+7) per cent)) of the AGNs in the final merger stages (d(sep) less than or similar to 10 kpc) are heavily obscured (N-H = 10(23) cm(-2)), and the median N-H 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 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 less than or similar to 10(43) erg s(-1)) AGNs in U/LIRGs.
A Lyman-α protocluster at redshift 6.9
(2021) Weida Hu; Junxian Wang; Leopoldo Infante; James E. Rhoads; Zhen-Ya Zheng; Huan Yang; Sangeeta Malhotra; L. Felipe Barrientos; Chunyan Jiang; Jorge González-López; Gonzalo Prieto; Lucia A. Perez; Pascale Hibon; Gaspar Galaz; Alicia Coughlin; Santosh Harish; Xu Kong; Wenyong Kang; Ali Ahmad Khostovan; John Pharo; Francisco Valdes; Isak Wold; Alistair R. Walker; XianZhong Zheng
Protoclusters, the progenitors of the most massive structures in the Universe, have been identified at redshifts of up to 6.6 (refs. (1-6)). Besides exploring early structure formation, searching for protoclusters at even higher redshifts is particularly useful to probe the reionization. Here we report the discovery of the protocluster LAGER-z7OD1 at a redshift of 6.93, when the Universe was only 770 million years old and could be experiencing rapid evolution of the neutral hydrogen fraction in the intergalactic medium(7,8). The protocluster is identified by an overdensity of 6 times the average galaxy density, and with 21 narrowband selected Lyman-alpha galaxies, among which 16 have been spectroscopically confirmed. At redshifts similar to or above this record, smaller protogroups with fewer members have been reported(9,10). LAGER-z7OD1 shows an elongated shape and consists of two subprotoclusters, which would have merged into one massive cluster with a present-day mass of 3.7 x 10(15) solar masses. The total volume of the ionized bubbles generated by its member galaxies is found to be comparable to the volume of the protocluster itself, indicating that we are witnessing the merging of the individual bubbles and that the intergalactic medium within the protocluster is almost fully ionized. LAGER-z7OD1 thus provides a unique natural laboratory to investigate the reionization process.
A multiwavelength-motivated X-ray model for the Circinus Galaxy
(2022) Andonie, Carolina; Ricci, Claudio; Paltani, Stéphane; Arévalo, Patricia; Treister, Ezequiel; Bauer, Franz; Stalevski, Marko
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 K alpha zone and the spectral curvature, although several additional Gaussian lines, associated with either ionized iron or broadened Fe K alpha/K beta lines, are needed. We find that the flared disc is Compton-thick (N-H,N-d = 1.01(-0.24)(+0.03) x 10(25) cm(-2)) and geometrically thick (CF = 0.55(-0.05)(+0.01)), and that the hollow cone has a Compton-thin column density (N-H,N-c = 2.18(-0.43)(+0.47) x 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 NH = 1.47(-0.24)(+0.03) x 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.
A nontrivial footprint of standard cosmology in the future observations of low-frequency gravitational waves
(2020) Jorge Alfaro; Mauricio Gamonal San Martín
Recent research shows that the cosmological components of the Universe should influence on the propagation of Gravitational Waves (GWs) and even it has been proposed a new way to measure the cosmological constant using Pulsar Timing Arrays (PTAs). However, these results have considered very particular cases (e.g. a de Sitter Universe or a mixing with non-relativistic matter). In this work we propose an extension of these results, using the Hubble constant as the natural parameter that includes all the cosmological information and studying its effect on the propagation of GWs. Using linearized gravity we considered a mixture of perfect fluids permeating the spacetime and studied the propagation of GWs within the context of the Lambda CDM model. We found from numerical simulations that the timing residual of local pulsars should present a distinguishable peak depending on the local value of the Hubble constant. As a consequence, when assuming the standard Lambda CDM model, our result predicts that the region of maximum timing residual is determined by the redshift of the source. This framework represents an alternative test for the standard cosmological model, and it can be used to facilitate the measurements of gravitational waves by ongoing PTAs projects.
A Novel, Low-Cost Method for Teaching Breast Reduction Markings to Plastic Surgery Residents Amid the COVID-19 Pandemic
(2021) Rodrigo Tejos; Alfonso Navia; Maria Fernanda Rojas; Alvaro Cuadra; Susana Searle
A pilot study on physical training of patients in hemodialysis.
(2011) Cristian Pedreros
Background Exercise training during the dialytical procedure may have positive cardiovascular effects and prevent or revert muscle wasting in patients undergoing chronic hemodialysis. Aim To evaluate the effects of an exercise training program in patients undergoing chronic hemodialysis. Material and methods Fifteen patients on chronic hemodialysis aged 21 to 69 years (three females) were included in the study. Nine of these were included in an exercise training program. During 16 weeks, exercise sessions were carried out during each dialytical procedure that included a warm-up period, aerobic exercises done using standing cycles, and resistance exercises, performed using Thera-Band(®) elastic bands and loops. Borg scale was used to control the intensity of training. At baseline and at the end of the study, a blood sample prior and after the dialytical procedure was obtained to measure C reactive protein, tumor necrosis factor α and interleukin 6. Quadriceps muscle strength, six minutes' walk and quality of life using the SF-36 questionnaire, were also measured. Results Four experimental subjects did not complete the study period, two that withdrew before starting, one due to problems with the venous access and one that decided to withdraw after 1 month of training. Among the five patients that finished the training period, significant improvements in the six minutes' walk and quadriceps strength were observed in the experimental group. No significant changes were observed among controls. No changes were observed in either group in C reactive protein, tumor necrosis factor and interleukin 6 levels or quality of life. Conclusions Among patients undergoing chronic hemodialysis exercise training improves endurance and muscle strength.
A practice-based approach to foreign language teacher preparation: A cross-continental collaboration
(2021) Barahona, M.; Davin, K.J.
The international trend towards a practice-based approach in teacher education has permeated foreign language teacher education and English language teaching. A practice-based approach is based on the understanding that teachers learn to teach a language by engaging in "actual" teaching rather than "talking" about teaching. We report on the implementation of a practice-based approach in two different contexts: an initial English teacher education program in Chile and an initial foreign language teacher education program in the United States. We provide practical recommendations and areas of caution for future enactments. The findings demonstrate that incorporating a practice-based approach into the university classroom offers a useful affordance for examining and illuminating the complexities of foreign language teaching practice across contexts.
A Practice-Based Approach to Foreign Language Teacher Preparation: A Cross-Continental Collaboration
(2021) Malba Barahona
The international trend towards a practice-based approach in teacher education has permeated foreign language teacher education and English language teaching. A practice-based approach is based on the understanding that teachers learn to teach a language by engaging in "actual" teaching rather than "talking" about teaching. We report on the implementation of a practice-based approach in two different contexts: an initial English teacher education program in Chile and an initial foreign language teacher education program in the United States. We provide practical recommendations and areas of caution for future enactments. The findings demonstrate that incorporating a practice-based approach into the university classroom offers a useful affordance for examining and illuminating the complexities of foreign language teaching practice across contexts.
A quantitative account of the behavioral characteristics of habituation: The Sometimes Opponent Processes model of stimulus processing
(2019) Uribe-Bahamonde, Y.E.; Becerra, S.A.; Ponce, F.P.; Vogel, E.H.
A review of the alumina production from coal fly ash, with a focus in Russia
(2022) Dmitry Valeev; Petr Bobylev; Nikita Osokin; Irina Zolotova; Ilia Rodionov; Cristian Salazar-Concha; Konstantin Verichev
A role for CXCL13 in the host response to intra-amniotic infection
(2007) Nhan-Chang, Chia-Ling; Romero, Roberto; Kusanovic, Juan Pedro; Gotsch, Francesca; Edwin, Samuel S.; Erez, Offer; Mittal, Pooja; Espinoza, Jimmy; Friel, Lara; Vaisbuch, Edi; Than, Nandor Gabor; Mazaki-Tovi, Shali; Hassan, Sonia
A role for microRNAs - Key regulators of gene expression - In chorioamnionitis and parturition
(2006) Montenegro, Daniel; Romero, Roberto; Pineles, Beth L.; Tarca, Adi L.; Kim, Yeon Mee; Draghici, Sorin; Kusanovic, Juan Pedro; Erez, Offer; Mazakitovi, Shali; Hassan, Sonia; Espinoza, Jimmy; Kim, Chong Jai
A Tribological and Ion Released Research of Ti-Materials for Medical Devices
(2021) Daniela Silva; M. Cecilia Montero; Carolina Guerra; Carola Martinez Ugalde; Xuejie Li; Armelle Ringuedé; Michel Cassir; Kevin Ogle; Danny Guzman; Claudio Aguilar; maritza paez; Mamié Sancy
The increase in longevity worldwide has intensified the use of different types of prostheses for the human body, such as those used in dental work as well as in hip and knee replacements. Currently, Ti-6Al-4V is widely used as a joint implant due to its good mechanical properties and durability. However, studies have revealed that this alloy can release metal ions or particles harmful to human health. The mechanisms are not well understood yet and may involve wear and/or corrosion. Therefore, in this work, commercial pure titanium and a Ti-6Al-4V alloy were investigated before and after being exposed to a simulated biological fluid through tribological tests, surface analysis, and ionic dissolution characterization by ICP-AES. Before exposure, X-ray diffraction and optical microscopy revealed equiaxed alpha-Ti in both materials and beta-Ti in Ti-6Al-4V. Scratch tests exhibited a lower coefficient of friction for Ti-6Al-4V alloy than commercially pure titanium. After exposure, X-ray photoelectron spectroscopy and surface-enhanced Raman spectroscopy results showed an oxide film formed by TiO2, both in commercially pure titanium and in Ti-6Al-4V, and by TiO and Al2O3 associated with the presence of the alloys. Furthermore, inductively coupled plasma atomic emission spectroscopy revealed that aluminum was the main ion released for Ti-6Al-4V, giving negligible values for the other metal ions.
El abuso de conciencia. Hacia una definición que permita su tipificación penal canónica
(2021) Cristian Hodge
Accessible LAMP-Enabled Rapid Test (ALERT) for Detecting SARS-CoV-2
(2021) Bektaş, Ali ; Covington, Michael F. ; Aidelberg, Guy ; Arce, Anibal ; Matute, Tamara ; Núñez, Isaac; Walsh, Julia ; Boutboul, David ; Delaugerre, Constance ; Lindner, Ariel B. ; Federici, Fernán ; Jayaprakash, Anitha D.
The coronavirus disease 2019 (COVID-19) pandemic has highlighted bottlenecks in large-scale, frequent testing of populations for infections. Polymerase chain reaction (PCR)-based diagnostic tests are expensive, reliant on centralized labs, can take days to deliver results, and are prone to backlogs and supply shortages. Antigen tests that bind and detect the surface proteins of a virus are rapid and scalable but suffer from high false negative rates. To address this problem, an inexpensive, simple, and robust 60-minute do-it-yourself (DIY) workflow to detect viral RNA from nasal swabs or saliva with high sensitivity (0.1 to 2 viral particles/mu L) and specificity (>97% true negative rate) utilizing reverse transcription loop-mediated isothermal amplification (RT-LAMP) was developed. ALERT (Accessible LAMP-Enabled Rapid Test) incorporates the following features: (1) increased shelf-life and ambient temperature storage, compared to liquid reaction mixes, by using wax layers to isolate enzymes from other reagents; (2) improved specificity compared to other LAMP end-point reporting methods, by using sequence-specific QUASR (quenching of unincorporated amplification signal reporters); (3) increased sensitivity, compared to methods without purification through use of a magnetic wand to enable pipette-free concentration of sample RNA and cell debris removal; (4) quality control with a nasopharyngeal-specific mRNA target; and (5) co-detection of other respiratory viruses, such as influenza B, by multiplexing QUASR-modified RT-LAMP primer sets. The flexible nature of the ALERT workflow allows easy, at-home and point-of-care testing for individuals and higher-throughput processing for labs and hospitals. With minimal effort, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific primer sets can be swapped out for other targets to repurpose ALERT to detect other viruses, microorganisms, or nucleic acid-based markers.
Adaptation of the “active communication education” programme into Spanish for older adults with hearing loss
(2020) Sebastián Rivera; Anthony Marcotti; Adrian Fuente; Eduardo Fuentes-López; Louise Hickson
Objective: To adapt the Active Communication Education (ACE) programme into Spanish. In addition, this study aimed at determining the effects of the adapted ACE programme on the social/emotional impacts of hearing loss and hearing functioning in a group of older adults with hearing loss who do not wear hearing aids. Design: This was an exploratory cohort study. Study group participants received the newly adapted ACE programme and control group participants received a cognitive stimulation programme. The Shortened Hearing Handicap Inventory for the Elderly in Spanish (HHIE-S) and the Spanish version of the Amsterdam Inventory for Auditory Disability and Handicap (S-AIADH) were carried out before and after each programme. Study sample: Sixty-six older adults with hearing loss and who did not wear hearing aids were randomly assigned to either an ACE group (n = 30) or a cognitive stimulation group (n = 36). Results: Participants who received the ACE programme showed a significantly larger improvement for the S-AIADH than did the cognitive stimulation group participants. Conclusions: The ACE programme has been adapted into Spanish for use with Chilean older adults with hearing loss. The results show that older adults report better functioning in listening situations after attending the sessions of the adapted ACE programme.
Adaptive behaviours in children with Down syndrome: A cross-sectional study of developmental trajectories
(2021) Josefina Bunster; Marc J. Tassé; Marcela Tenorio; Andrés Aparicio; Paulina S. Arango
Adaptive Laboratory Evolution of Native Torulaspora delbrueckii YCPUC10 With Enhanced Ethanol Resistance and Evaluation in Co-inoculated Fermentation
(2020) Liliana Godoy Olivares
Torulaspora delbrueckii is a yeast species typically present in the early stages of the fermentation process. T. delbrueckii positively modifies the aromatic properties of wines. However, its contribution to the final quality of the wine is restricted by its low tolerance to ethanol. T. delbrueckii is capable of fermenting and tolerating an ethanol concentration ranging from 7.4% (v/v) to slightly higher than 9% (v/v). For this reason, it cannot complete fermentation, when alcohol reach levels higher than 12% (v/v), limiting their use in the industry. The objective of this work was to obtain new variants of T. delbrueckii with improved resistance to ethanol through adaptive laboratory evolution. Variants capable of tolerating ethanol levels of 11.5% (v/v) were obtained. These presented improved kinetic parameters, and additionally showed an increase in resistance to SO2 in ethanol compared to the original strain. Co-inoculated fermentations were performed with the original strain (FTd/Sc) and with the evolved strain (FTdF/Sc), in addition to a control fermentation using only Saccharomyces cerevisiae EC1118 (FSc). The results obtained show that FTdF/Sc present higher levels of 2-Ethylhexanol, compared to FTd/Sc and FSc. Furthermore, FTdF/Sc presents higher levels of total alcohols, total aldehydes, total phenolic derivatives, and total sulfur compounds with significant differences with FSc. These results provide a T. delbrueckii YCPUC10-F yeast with higher resistance to ethanol, which can be present throughout the fermentation process and be used in co-inoculated fermentations. This would positively impact the performance of T. delbrueckii by allowing it to be present not only in the early stages of fermentation but to remain until the end of fermentation.
Addressing power asymmetries in global health: Imperatives in the wake of the COVID-19 pandemic
(2021) Seye Abimbola; Sumegha Asthana; Cristian Montenegro Cortes; Renzo R. Guinto; Desmond Tanko Jumbam; Lance Louskieter; Kenneth Munge Kabubei; Shehnaz Munshi; Kui Muraya; Fredros Okumu; Senjuti Saha; Deepika Saluja; Madhukar Pai
Seye Abimbola and co-authors argue for a transformation in global health research and practice in the post-COVID-19 world.
Aesthetic Scrotoplasty: Systematic Review and a Proposed Treatment Algorithm for the Management of Bothersome Scrotum in Adults
(2020) Claudio Thomas; Alfonso Navia
Background Increased scrotal laxity is a poorly defined entity often associated with discomfort while wearing loose clothes, walking, doing sports and during intercourse. In our experience, this condition is produced by an enlarged scrotal bag hanging more than 1-2 cm below the tip of the penis and can be associated with persistent penoscrotal webbing. Our objective was to perform a systematic literature review addressing the diversity of this entity and its surgical treatment, as well as propose a diagnostic and therapeutic approach.

Browse

Browsing Artículos de revistas by browse.metadata.fuente "ORCID-mayo23"

Results Per Page

Sort Options