Masgomas-4: Physical characterization of a double-core obscured cluster with a massive and very young stellar population

The discovery of new, obscured massive star clusters has changed our understanding of the Milky Way star-forming activity from a passive to a very active star-forming machine. The search for these obscured clusters is strongly supported by the use of all-sky, near-IR surveys. The main goal of the MASGOMAS project is to search for and study unknown, young, and massive star clusters in the Milky Way, using near-IR data. Here we try to determine the main physical parameters (distance, size, total mass, and age) of Masgomas-4, a new double-core obscured cluster. Using near-IR photometry ($J$, $H$, and $K_S$) we selected a total of 21 stars as OB-type star candidates. Multi-object, near-IR follow-up spectroscopy allowed us to carry out the spectral classification of the OB-type candidates. Of the 21 spectroscopically observed stars, ten are classified as OB-type stars, eight as F- to early G-type dwarf stars, and three as late-type giant stars. Spectroscopically estimated distances indicate that the OB-type stars belong to the same cluster, located at a distance of $1.90^{+1.28}_{-0.90}$ kpc. Our spectrophotometric data confirm a very young and massive stellar population, with a clear concentration of pre-main-sequence massive candidates (Herbig Ae/Be) around one of the cluster cores. The presence of a surrounding HII cloud and the Herbig Ae/Be candidates indicate an upper age limit of 5 Myr.Comment: Accepted for publication in A&

A Novel Route to Calculate the Length Scale for the Glass Transition in Polymers

The occurrence of glass transition is believed to be associated to cooperative motion with a growing length scale with decreasing temperature. We provide a novel route to calculate the size of cooperatively rearranging regions CRR of glass-forming polymers combining the Adam-Gibbs theory of the glass transition with the self-concentration concept. To do so we explore the dynamics of glass-forming polymers in different environments. The material specific parameter $\alpha$ connecting the size of the CRR to the configurational entropy is obtained in this way. Thereby, the size of CRR can be precisely quantified in absolute values. This size results to be in the range 1 $\div$ 3 nm at the glass transition temperature depending on the glass-forming polymer

The embedded clusters DBS 77, 78, 102, and 160-161 and their link with the interstellar medium

Aims. We report a study of the global properties of some embedded clusters placed in the fourth quadrant of the Milky Way to clarify some issues related with their location into the Galaxy and their stellar formation processes. Methods. We performed BVI photometric observations in the region of DBS 77, 78, 102, 160, and 161 clusters and infrared spectroscopy in DBS 77 region. They were complemented with JHK data from VVV survey combined with 2MASS catalogue, and used mid-infrared information from GLIMPSE catalogue. We also searched for HI data from SGPS and PMN radio surveys, and previous spectroscopic stellar classification. The spectroscopic and photometric information allowed us to estimate the spectral classification of the brightest stars of each studied region. On the other hand, we used the radio data to investigate the interstellar material parameters and the continuum sources probably associated with the respective stellar components. Results. We estimated the basic physical parameters of the clusters (reddening, distance, age, and initial mass function). We searched for HII regions located near to the studied clusters and we analyzed the possible link between them. In the particular case of DBS 160-161 clusters, we identified the HI bubble B332.5-0.1-42 located around them. We found that the mechanical energy injected to the interstellar medium by the more massive stars of this couple of clusters was enough to generate the bubble.Comment: 15 pages, 14 figures, 6 tables, accepted for publication in A&

Methyl group dynamics in a confined glass

We present a neutron scattering investigation on methyl group dynamics in glassy toluene confined in mesoporous silicates of different pore sizes. The experimental results have been analysed in terms of a barrier distribution model, such a distribution following from the structural disorder in the glassy state. Confinement results in a strong decreasing of the average rotational barrier in comparison to the bulk state. We have roughly separated the distribution for the confined state in a bulk-like and a surface-like contribution, corresponding to rotors at a distance from the pore wall respectively larger and smaller than the spatial range of the interactions which contribute to the rotational potential for the methyl groups. We have estimated a distance of 7 Amstrong as a lower limit of the interaction range, beyond the typical nearest-neighbour distance between centers-of-mass (4.7 Amstrong).Comment: 5 pages, 3 figures. To be published in European Physical Journal E Direct. Proceedings of the 2nd International Workshop on Dynamics in Confinemen

Discovery of a young and massive stellar cluster: Spectrophotometric near-infrared study of Masgomas-1

Context: Recent near-infrared data have contributed to the discovery of new (obscured) massive stellar clusters and massive stellar populations in previously known clusters in our Galaxy. These discoveries lead us to view the Milky Way as an active star-forming machine. Aims: The main purpose of this work is to determine physically the main parameters (distance, size, total mass and age) of Masgomas-1, the first massive cluster discovered by our systematic search programme. Methods: Using near-infrared (J, H, and Ks) photometry we selected 23 OB-type and five red supergiant candidates for multi-object H- and K-spectroscopy and spectral classification. Results: Of the 28 spectroscopically observed stars, 17 were classified as OB-type, four as supergiants, one as an A-type dwarf star, and six as late-type giant stars. The presence of a supergiant population implies a massive nature of Masgomas-1, supported by our estimate of the cluster initial total mass of (1.94\pm0.28)\cdot10^4 M_{sun}, obtained after integrating of the cluster mass function. The distance estimate of 3.53 kpc locates the cluster closer than the Scutum--Centaurus base but still within that Galactic arm. The presence of an O9V star and red supergiants in the same population indicates that the cluster age is in the range of 8 to 10 Myr.Comment: 11 pages, 6 figures, 2 tables, A&A accepte

Effects of varying the intensity of the primary tones on the amplitudes of Distortion Product Otoacoustic Emissions (OAEdp) in patients with normal hearing

Indexación: Web of Science; ScieloIntroducción: Las emisiones otoacústicas (EOA) son sonidos generados por las células ciliadas externas (CCE). Se ha visto que la generación y registro de las EOA evocadas depende de factores técnicos de evaluación como el nivel de intensidad de los tonos primarios, relación frecuencial entre los tonos, etc. Objetivos: Estudiar el efecto de la variación de la intensidad de los tonos primarios en la amplitud de la respuesta de las EOA producto de distorsión (pd) en individuos con audición normal. Material y método: Se evaluaron 35 individuos a los cuales se les midieron EOApd utilizando diferentes intensidades de tonos primarios: Intensidad baja (I1=50dBSPL e I2=50dBSPL), intensidad media (I1=55dBSPL e I2=65dBSPL) e intensidad alta (I1=70dBSPL e I2=70dBSPL). Resultados: Se observó que para tonos primarios a bajas intensidades (I1=50dBSPL e I2=50dBSPL) existe una disminución tanto en amplitud y presencia de las EOApd, mientras que para tonos primarios a intensidades mayores (I1=55dBSPL e I2=65dBSPL - I1=70dBSPL e I2=70dBSPL) se evidenció un aumento en amplitud y presencia de EOApd en los sujetos estudiados. Conclusión: Se evidencian diferencias estadísticamente significativas en la amplitud de las EOApd al variar la intensidad de los tonos primarios. Por lo cual se puede establecer que las intensidades medias-altas son las más adecuadas para la evaluación de EOApd en sujetos con audición normal.Introduction: Otoacoustic emissions (OAE) are sounds produced by outer hair cells. The generation and recording of evoked OAE depends on technical factors such as level of intensity of primary tones, frequency relationship between the tones, etc. Aim: To study the effect of varying the intensity of primary tones in the amplitude of the response of Distortion Product OAE (DP) in individuals with normal hearing. Material and method: 35 individuals were measured using different intensities OAEdp primary tones: Low Intensity (I1= I2 =50dBSPL 50dBSPL e), Medium Intensity (11= I2 =65dBSPL 55dBSPL e) and High Intensity (I1 =70dBSPL and I2 =70dBSPL). Results: Using Low primary tones (I1 =I2 =50dBSPL 50dBSPL) there is a decrease in amplitude and presence of DPOAE, while for primary tones at higher intensities (I1 and I2 = = 55dBSPL 65dBSPL -11 =70dBSPL and I2 =70dBSPL) an increase in amplitude and presence of OAEdp in subjects with normal hearing was observed . Conclusion: There are statistically significant differences in OAEdp amplitude by varying the intensity of the primary tones. Therefore medium-high intensities are best suited for the evaluation of OAEdp in subjects with normal hearing.http://ref.scielo.org/36dbs

Transporte de fósforo en un Ultisol bajo pastura

Broadcast applications of inorganic fertilizer and organic amendments to pastures can contribute significant phosphorus (P) loads to surface waters. An experiment was conducted to quantify edge of field P concentrations in runoff and mass losses from plots in an Ultisol-Oxisol complex amended with two inorganic P levels [44 kg P/ha/yr (44PI) and 131 kg P/ha/yr (131 PI)], and an organic P source (broiler litter) [131 kg P/ha/yr (131 PC-)]. The total amount of P was split in two applications for the organic treatment and in four for the inorganic treatments. Vegetation within plots was mainly naturalized tropical pastures (80% coverage) and the soil slope was between 10 and 12%. Hydrologic discharge, suspended sediments, dissolved P and total P (TP) were quantified over a one-year period to 7 August 2003. Runoff from each field was diverted to a fractionator, where 1 or 10% was collected. Of the 174 precipitation events, 59 resulted in significant runoff, and hydrologic discharge accounted for 22% to 35% of the total rainfall (164.3 cm). Sediment losses ranged from 230 to 818 kg/ha. Cumulative TP mass losses were 3.19, 7.04, and 5.02 kg P/ha, for the 44PI, 131 PI, and 131PO treatments, respectively. These losses corresponded to 7.3, 4.9, and 3.5% of the annual P applied in the treatments 44PI, 131 PI, and 131PO, respectively. Although the magnitude of P losses was relatively low from an agricultural production standpoint, these can impact surface-water quality via nutrient enrichment. The greatest magnitude of TP mass losses occurred when application coincided with frequent intense rainfall events. RESUMEN Las aplicaciones de fertilizantes y enmiendas orgánicas a los suelos pueden contribuir cantidades significativas de fósforo (P) a las aguas superficiales. Se realizó un experimento para cuantificar las concentraciones de P en la escorrentía y las pérdidas en masa de P al borde de predio en un Ultisol enmendado con dos niveles de superfosfato triple como fuente inorgánica de P [44 kg P/ha/año (44 Pl) y 131 kg P/ha/año (131PI)] y una fuente orgánica de P [131 kg P/ha/año (131PO)] aplicado como pollinaza. La aplicación de P se fraccionó en dos para la fuente orgánica y en cuatro para la fuente inorgánica. La vegetación dentro de los predios era principalmente de pasturas tropicales naturalizadas y la pendiente varió entre 10 y 12%. La descarga hidrológica, sedimentos suspendidos, P disuelto y P total se cuantificaron durante un año. La escorrentía de cada parcela se canalizó hacia un fraccionador donde se recolectó el 1% o el 10% de la misma. De los 174 eventos de precipitación, 59 resultaron en escorrentía significativa, y la descarga hidrológica varió entre 22 y 35% de la totalidad (164.3 cm). Las pérdidas de sedimento variaron entre 230 y 818 kg/ha/año. Las pérdidas de P cumulativas fueron 3.19, 7.04, y 5.02 kg P/ha, para los tratamientos 44PI, 131 PI, y 131PO, respectivamente. Desde una perspectiva de producción agrícola, la magnitud de las pérdidas de P fueron bajas, pero estas cantidades pueden afectar las aguas superficiales vía el enriquecimiento nutricional. Las mayores pérdidas de P ocurrieron en periodos de tiempo cuando la aplicación coincidió con eventos de lluvia de relativamente alta intensidad y frecuencia. Las aplicaciones de fertilizantes y enmiendas orgánicas a los suelos pueden contribuir cantidades significativas de fósforo (P) a las aguas superficiales. Se realizó un experimento para cuantificar las concentraciones de P en la escorrentía y las pérdidas en masa de P al borde de predio en un Ultisol enmendado con dos niveles de superfosfato triple como fuente inorgánica de P [44 kg P/ha/año (44 Pl) y 131 kg P/ha/año (131PI)] y una fuente orgánica de P [131 kg P/ha/año (131PO)] aplicado como pollinaza. La aplicación de P se fraccionó en dos para la fuente orgánica y en cuatro para la fuente inorgánica. La vegetación dentro de los predios era principalmente de pasturas tropicales naturalizadas y la pendiente varió entre 10 y 12%. La descarga hidrológica, sedimentos suspendidos, P disuelto y P total se cuantificaron durante un año. La escorrentía de cada parcela se canalizó hacia un fraccionador donde se recolectó el 1% o el 10% de la misma. De los 174 eventos de precipitación, 59 resultaron en escorrentía significativa, y la descarga hidrológica varió entre 22 y 35% de la totalidad (164.3 cm). Las pérdidas de sedimento variaron entre 230 y 818 kg/ha/año. Las pérdidas de P cumulativas fueron 3.19, 7.04, y 5.02 kg P/ha, para los tratamientos 44PI, 131 PI, y 131PO, respectivamente. Desde una perspectiva de producción agrícola, la magnitud de las pérdidas de P fueron bajas, pero estas cantidades pueden afectar las aguas superficiales vía el enriquecimiento nutricional. Las mayores pérdidas de P ocurrieron en periodos de tiempo cuando la aplicación coincidió con eventos de lluvia de relativamente alta intensidad y frecuencia