4,368 research outputs found

    The Gould's Belt Distances Survey (GOBELINS). V. Distances and Kinematics of the Perseus molecular cloud

    Get PDF
    We derive the distance and structure of the Perseus molecular cloud by combining trigonometric parallaxes from Very Long Baseline Array (VLBA) observations, taken as part of the GOBELINS survey, and Gaia Data Release 2. Based on our VLBA astrometry, we obtain a distance of 321+/-10 pc for IC 348. This is fully consistent with the mean distance of 320+/-26 measured by Gaia. The VLBA observations toward NGC 1333 are insufficient to claim a successful distance measurement to this cluster. Gaia parallaxes, on the other hand, yield a mean distance of 293+/-22 pc. Hence, the distance along the line of sight between the eastern and western edges of the cloud is ~30 pc, which is significantly smaller than previously inferred. We use Gaia proper motions and published radial velocities to derive the spatial velocities of a selected sample of stars. The average velocity vectors with respect to the LSR are (u,v,w) = (-6.1+/-1.6, 6.8+/-1.1, -0.9+/-1.2) and (-6.4+/-1.0, 2.1+/-1.4, -2.4+/-1.0) km/s for IC 348 and NGC 1333, respectively. Finally, our analysis of the kinematics of the stars has shown that there is no clear evidence of expansion, contraction, or rotational motions within the clusters.Comment: Accepted for publication in Ap

    Application of mineralogical, petrological and geochemical tools for evaluating the palaeohdrogeological evolution of the PADAMOT study sites

    Get PDF
    The role of Work Package (WP) 2 of the PADAMOT project – ‘Palaeohydrogeological Data Measurements’ - has been to study late-stage fracture mineral and water samples from groundwater systems in Spain, Sweden, United Kingdom and the Czech Republic, with the aim of understanding the recent palaeohydrogeological evolution of these groundwater systems. In particular, the project sought to develop and evaluate methods for obtaining information about past groundwater evolution during the Quaternary (about the last 2 million years) by examining how the late-stage mineralization might record mineralogical, petrographical and geochemical evidence of how the groundwater system may have responded to past geological and climatological changes. Fracture-flow groundwater systems at six European sites were studied: • Melechov Hill, in the Bohemian Massif of the Czech Republic: a shallow (0-100 m) dilute groundwater flow system within the near-surface weathering zone in fractured granitic rocks; • Cloud Hill, in the English Midlands: a (~100 m) shallow dilute groundwater flow system in fractured and dolomitized Carboniferous limestone; • Los Ratones, in southwest Spain: an intermediate depth (0-500 m) dilute groundwater flow system in fractured granitic rocks; • Laxemar, in southeast Sweden: a deep (0-1000 m) groundwater flow system in fractured granitic rocks. This is a complex groundwater system with potential recharge and flushing by glacial, marine, lacustrine and freshwater during the Quaternary; • Sellafield, northwest England: a deep (0-2000 m) groundwater flow system in fractured Ordovician low-grade metamorphosed volcaniclastic rocks and discontinuous Carboniferous Limestone, overlain by a Permo-Triassic sedimentary sequence with fracture and matrix porosity. This is a complex coastal groundwater system with deep hypersaline sedimentary basinal brines, and deep saline groundwaters in crystalline basement rocks, overlain by a shallow freshwater aquifer system. The site was glaciated several times during the Quaternary and may have been affected by recharge from glacial meltwater; • Dounreay, northeast Scotland: a deep (0-1400 m) groundwater flow system in fractured Precambrian crystalline basement overlain by fractured Devonian sedimentary rocks. This is within the coastal discharge area of a complex groundwater system, comprising deep saline groundwater hosted in crystalline basement, overlain by a fracture-controlled freshwater sedimentary aquifer system. Like Sellafield, this area experienced glaciation and may potentially record the impact of glacial meltwater recharge. In addition, a study has been made of two Quaternary sedimentary sequences in Andalusia in southeastern Spain to provide a basis of estimating the palaeoclimatic history of the region that could be used in any reconstruction of the palaeoclimatic history at the Los Ratones site: • The Cúllar-Baza lacustrine sequence records information about precipitation and palaeotemperature regimes, derived largely from the analysis of the stable isotope (δ18O and δ13C) signatures from biogenic calcite (ostracod shells). • The Padul Peat Bog sequence provided information on past vegetation cover and palaeogroundwater inputs based on the study of fossil pollen and biomarkers as proxies for past climate change. Following on from the earlier EC 4th Framework EQUIP project, the focus of the PADAMOT studies has been on calcite mineralization. Calcite has been identified as a late stage mineral, closely associated with hydraulically-conductive fractures in the present-day groundwater systems at the Äspö-Laxemar, Sellafield, Dounreay and Cloud Hill sites. At Los Ratones and Melechov sites late-stage mineralization is either absent or extremely scarce, and both the quantity and fine crystal size of any late-stage fracture mineralization relevant to Quaternary palaeohydrogeological investigations is difficult to work with. The results from the material investigated during the PADAMOT studies indicate that the fracture fillings at these sites are related to hydrothermal activity, and so do not have direct relevance as Quaternary indicators. Neoformed calcite has not been found at these two sites at the present depth of the investigations. Furthermore, the HCO3 - concentration in all the Los Ratones groundwaters is mainly controlled by complex carbonate dissolution. The carbonate mineral saturation indices do not indicate precipitation conditions, and this is consistent with the fact that neoformed calcite, ankerite or dolomite have not been observed petrographically

    Relación entre el bienestar y el rendimiento académico en alumnos de primer año de medicina

    Get PDF
    Background: Stress may affect the sense of wellbeing and academic achievement of university students. Aim: To assess the relationship of academic engagement and burnout with academic achievement among first year medical students. Material and Methods: The Utrecht Work Engagement Scale-Student and Maslach Burnout Inventory Student Survey (MBI-SS) were applied to 277 first year medical students of four universities. Their results were correlated with the grades obtained in the different courses. Results: Moderately high engagement and low burnout levels were detected. There was a high level of satisfaction with studies and a moderate exhaustion level. Academic achievement was associated with the degree of engagement with studies but not with burnout. Conglomerate analysis detected a group of students with high levels of wellbeing, characterized by high levels of academic engagement and low burnout. Other group had moderate levels of engagement and lack of personal fulfilment. Other group, identified as extenuated, had high levels of personal exhaustion and depersonalization. Finally the disassociated group had a low academic engagement, low emotional exhaustion, high levels of depersonalization and lack of personal fulfillment. Conclusions: Academic achievement is associated with the level of engagement with studies but not with burnout

    Gaia-DR2 confirms VLBA parallaxes in Ophiuchus, Serpens and Aquila

    Get PDF
    We present Gaia-DR2 astrometry of a sample of YSO candidates in Ophiuchus, Serpens Main and Serpens South/W40 in the Aquila Rift, which had been mainly identified by their infrared excess with Spitzer. We compare the Gaia-DR2 parallaxes against published and new parallaxes obtained from our Very Long Baseline Array (VLBA) program GOBELINS. We obtain consistent results between Gaia and the VLBA for the mean parallaxes in each of the regions analyzed here. We see small offsets, when comparing mean values, of a few tens of micro-arcseconds in the parallaxes, which are either introduced by the Gaia zero-point error or due to a selection effect by Gaia toward the brightest, less obscured stars. Gaia-DR2 data alone conclusively places Serpens Main and Serpens South at the same distance, as we first inferred from VLBA data alone in a previous publication. Thus, Serpens Main, Serpens South and W40 are all part of the same complex of molecular clouds, located at a mean distance of 436+/-9 pc. In Ophiuchus, both Gaia and VLBA suggest a small parallax gradient across the cloud, and the distance changes from 144.2+/-1.3 pc to 138.4+/-2.6 pc when going from L1689 to L1688.Comment: Accepted for publication in ApJ

    Factorial structure and reliability of the academic satisfaction questionnaire on Chilean medical students

    Get PDF
    Indexación: Web of Science; Scopus.El presente estudio analiza la estructura factorial y confiabilidad del cuestionario de satisfacción académica (CSA) en una muestra de 563 estudiantes de medicina, entre 19 y 29 años (media de 20,42); provenientes de cuatro universidades chilenas. Una vez finalizada la traducción al castellano se exploró la validez de contenido de los ítems mediante un juicio de expertos. La estructura factorial del cuestionario se analizó a través de un análisis factorial exploratorio empleando el método Análisis de Ejes Principales (AEP). Los resultados preliminares de la fiabilidad y validez del instrumento han mostrado que la estructura de un factor es viable y adecuada de acuerdo a los requisitos psicométricos establecidos, aunque se recomiendan futuros estudios que evalúen su validez y confiabilidad en otros programas de pregrado.The present study examines the factorial structure and reliability of the academic satisfaction questionnaire (CSA) in a sample of 563 medical students, between 19 and 29 years (average of 20.42); from four Chilean universities. Once translated into Spanish explored the validity of the items content was evaluated through experts opinions. The factorial structure of the scale was analyzed through an exploratory factor analysis using the Principal Axis Analysis method (AEP).The preliminary results of the reliability and validity of the instrument have shown that a factor structure is viable and appropriate according to the established psychometric requirements, although future studies to evaluate its validity and reliability in other undergraduate programs are recommended.http://www.redalyc.org/articulo.oa?id=45964543200

    Assessment of psychometric properties of the academic involvement questionnaire, expectations version

    Get PDF
    Indexación: Web of Science; Scielo.Background: Academic Involvement Questionnaire, Expectations version (CIA-A), assesses the expectations of involvement in studies. It is a relevant predictor of student success. However, the evidence of its validity and reliability in Chile is low, and in the case of Medical students, there is no evidence at all. Aim: To evaluate the factorial structure and internal consistency of the CIA-A in Chilean Medical school freshmen. Material and Methods: The survey was applied to 340 Medicine freshmen, chosen by non-probability quota sampling. They answered a back-translated version of CIA-A from Portuguese to Spanish, plus a sociodemographic questionnaire. For psychometric analysis of the CIA-A, an exploratory factor analysis was carried on, the reliability of the factors was calculated, a descriptive analysis was conducted and their correlation was assessed. Results: Five factors were identified: vocational, institutional and social involvement, use of resources and student participation. Their reliabilities ranged between Cronbach’s alpha values of 0.71 to 0.87. Factors also showed statistically significant correlations between each other. Conclusions: Identified factor structure is theoretically consistent with the structure of original version. It just disagrees in one factor. In addition, the factors’ internal consistency were adequate for using them in research. This supports the construct validity and reliability of the CIA-A to assess involvement expectations in medical school freshmen.http://ref.scielo.org/r2sn6

    Estructura factorial de la escala DREEM en estudiantes de medicina chilenos

    Get PDF
    Indexación: ScieloBackground: The entry to a University requires an adaptation process that not all students solve with the same kind of success. Even though students’ social adaptation and emotional skills are essential, the educational environmental that they perceive has a significant influence in their academic life. Aim: To describe the changes in the perception about academic environment that medical students experience during the first three years of undergraduate career. Material and Methods: The Dundee Ready Education Environment Measure (DREEM) scale was applied to 525 first to third year medical students and an exploratory factorial analysis was made. Results: Four factors were identified: Academic Perception: academic quality that students attribute to the process in which they take part, as well as to the assessment that they do of their learning outcomes (coefficient α = 0.85); Academic Experience: refers to positive emotions that students experience during the career such as confidence, pleasure and energy (coefficient α = 0.76); Atmosphere Perception, comfort and calm that students experiment during their academic activities (coefficient α = 0.79); Teachers Perception: the perception that students have of teachers about their interest and disposition towards students (coefficient α = 0.50). Conclusions: The assessment of academic environment quality is inversely associated with the lapse that the students have spent in their undergraduate careers. Key words: Education, Medical; Psychometrics; Students, medical; Undergraduate

    Young women's use of a microbicide surrogate: The complex influence of relationship characteristics and perceived male partners' evaluations

    Get PDF
    This is the post-print version of the article. The official published version can be found at the link below.Currently in clinical trials, vaginal microbicides are proposed as a female-initiated method of sexually transmitted infection prevention. Much of microbicide acceptability research has been conducted outside of the United States and frequently without consideration of the social interaction between sex partners, ignoring the complex gender and power structures often inherent in young women’s (heterosexual) relationships. Accordingly, the purpose of this study was to build on existing microbicide research by exploring the role of male partners and relationship characteristics on young women’s use of a microbicide surrogate, an inert vaginal moisturizer (VM), in a large city in the United States. Individual semi-structured interviews were conducted with 40 young women (18–23 years old; 85% African American; 47.5% mothers) following use of the VM during coital events for a 4 week period. Overall, the results indicated that relationship dynamics and perceptions of male partners influenced VM evaluation. These two factors suggest that relationship context will need to be considered in the promotion of vaginal microbicides. The findings offer insights into how future acceptability and use of microbicides will be influenced by gendered power dynamics. The results also underscore the importance of incorporating men into microbicide promotion efforts while encouraging a dialogue that focuses attention on power inequities that can exist in heterosexual relationships. Detailed understanding of these issues is essential for successful microbicide acceptability, social marketing, education, and use.This study was funded by a grant from National Institutes of Health (NIHU19AI 31494) as well as research awards to the first author: Friends of the Kinsey Institute Research Grant Award, Indiana University’s School of HPER Graduate Student Grant-in-Aid of Research Award, William L. Yarber Sexual Health Fellowship, and the Indiana University Graduate and Professional Student Organization Research Grant
    corecore