The role of low-mass star clusters in massive star formation. The Orion Case

To distinguish between the different theories proposed to explain massive star formation, it is crucial to establish the distribution, the extinction, and the density of low-mass stars in massive star-forming regions. We analyze deep X-ray observations of the Orion massive star-forming region using the Chandra Orion Ultradeep Project (COUP) catalog. We studied the stellar distribution as a function of extinction, with cells of 0.03 pc x 0.03 pc, the typical size of protostellar cores. We derived stellar density maps and calculated cluster stellar densities. We found that low-mass stars cluster toward the three massive star-forming regions: the Trapezium Cluster (TC), the Orion Hot Core (OHC), and OMC1-S. We derived low-mass stellar densities of 10^{5} stars pc^{-3} in the TC and OMC1-S, and of 10^{6} stars pc^{-3} in the OHC. The close association between the low-mass star clusters with massive star cradles supports the role of these clusters in the formation of massive stars. The X-ray observations show for the first time in the TC that low-mass stars with intermediate extinction are clustered toward the position of the most massive star, which is surrounded by a ring of non-extincted low-mass stars. This 'envelope-core' structure is also supported by infrared and optical observations. Our analysis suggests that at least two basic ingredients are needed in massive star formation: the presence of dense gas and a cluster of low-mass stars. The scenario that better explains our findings assumes high fragmentation in the parental core, accretion at subcore scales that forms a low-mass stellar cluster, and subsequent competitive accretion. Finally, although coalescence does not seem a common mechanism for building up massive stars, we show that a single stellar merger may have occurred in the evolution of the OHC cluster, favored by the presence of disks, binaries, and gas accretion.Comment: 17 pages, 11 figures, 3 Tables. Accepted for publication in A&

A new intermediate mass protostar in the Cepheus A HW2 region

We present the discovery of the first molecular hot core associated with an intermediate mass protostar in the CepA HW2 region. The hot condensation was detected from single dish and interferometric observations of several high excitation rotational lines (from 100 to 880K above the ground state) of SO2 in the ground vibrational state and of HC3N in the vibrationally excited states v7=1 and v7=2. The kinetic temperature derived from both molecules is 160K. The high-angular resolution observations (1.25'' x 0.99'') of the SO2 J=28(7,21)-29(6,24) line (488K above the ground state) show that the hot gas is concentrated in a compact condensation with a size of 0.6''(430AU), located 0.4'' (300AU) east from the radio-jet HW2. The total SO2 column density in the hot condensation is 10E18cm-2, with a H2 column density ranging from 10E23 to 6 x 10E24cm-2. The H2 density and the SO2 fractional abundance must be larger than 10E7cm-3 and 2 x 10E-7 respectively. The most likely alternatives for the nature of the hot and very dense condensation are discussed. From the large column densities of hot gas, the detection of the HC3N vibrationally excited lines and the large SO2 abundance, we favor the interpretation of a hot core heated by an intermediate mass protostar of 10E3 Lo. This indicates that the CepA HW2 region contains a cluster of very young stars

Neurofeedback vs. metilfenidato para el tratamiento del trastorno por déficit de atención con hiperactividad en niños y adolescentes

Esta revisión pretende comprobar si Neurofeedback (NFB), en comparación con Metilfenidato (MFD), es un tratamiento eficaz y suficiente para el Trastorno por Déficit de Atención con Hiperactividad (TDAH) en niños y adolescentes. Con la búsqueda sistemática en las bases de datos PubMed y Science Direct se obtuvo un total de 106 artículos, de los que se seleccionaron 12 ensayos controlados aleatorios (ECA). Su gran variabilidad de resultados no respalda el uso de NFB como intervención eficaz y suficiente para el TDAH. Aunque se ha encontrado que el tratamiento combinado de NFB y MFD puede resultar una alternativa prometedora para el TDAH, siendo necesario probar su evidencia en futuras investigaciones This review aims to verify whether Neurofeedback (NFB), compared with Methylphenidate (MFD), is an effective and sufficient treatment for Attention Deficit Hyperactivity Disorder (ADHD) in children and adolescents. With the systematic search in the PubMed and Science Direct databases, a total of 106 articles were obtained, from which 12 randomized controlled trials (RCTs) were selected. The great variability of results doesn''t support the use of NFB as an effective and sufficient intervention for ADHD. Although it has been found that the combined treatment of NFB and MFD may be a promising alternative for ADHD, it is necessary to prove its evidence in future research

Eficacia del Neurofeedback en el Trastorno de Estrés Postraumático en población adulta. Una revisión sistemática

Esta revisión pretende comprobar si el entrenamiento de Neurofeedback (NFB) es eficaz para la mejora sintomática del Trastorno de Estrés Postraumático (TEPT) en población adulta. Se realiza una búsqueda de estudios en las bases de datos PubMed y Science Direct. Los cinco estudios encontrados se centran en la regulación de la amplitud alfa con el entrenamiento de Neurofeedback a través del electroencefalograma (EEG) e imagen por resonancia magnética funcional (fMRI). En ellos se obtiene un aumento de amplitud alfa (“rebote”) tras el entrenamiento, asociado con la mejora sintomática, una mayor relajación y una conexión significativa entre amígdala y prefrontal. En base a la literatura, los resultados no reportan la eficacia y evidencia suficiente, pero se considera que la neuromodulación obtenida con NFB y asociada a la mejora sintomática, puede potenciar un progreso para el tratamiento tanto del TEPT como de otras patologías. The given review tryes to verify if the trainning on Neurofeedback (NFB) provides a symptomatic improvement on the Posttraumatic Stress Disorder (PTSD) in an adult population. A search of studies is made in PubMed and Science Direct databases. The five studies found focus on the regulation of alpha amplitude with the training of Neurofeedback through electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI). An increase in alpha amplitude ("rebound") is obtained after training, associated with symptomatic improvement, greater relaxation, and a significant connection between amygdala and prefrontal cortex. According to the literature, there''s not enough efficiency or evidence on the results, but it''s considered that the neuromodulation obtained through NFB and its associated symptomatic improvement, can enhance a progress for PTSD and other pathologies treatments

3D culture of fibroblasts and neuronal cells on microfabricated free-floating carriers

3D cell culture is a relatively recent trend in biomedical research for artificially mimicking in vivo environment and providing three dimensions for the cells to grow in vitro, particularly with regard to surface-adherent mammalian cells. Different cells and research objectives require different culture conditions which has led to an increase in the diversity of 3D cell culture models. In this study, we show two independent on-carrier 3D cell culture models aimed at two different potential applications. Firstly, micron-scale porous spherical structures fabricated from poly (lactic-co-glycolic acid) or PLGA are used as 3D cell carriers so that the cells do not lose their physiologically relevant spherical shape. Secondly, millimetre-scale silk fibroin structures fabricated by 3D inkjet bioprinting are used as 3D cell carriers to demonstrate cell growth patterning in 3D for use in applications which require directed cell growth. The L929 fibroblasts demonstrated excellent adherence, cell-division and proliferation on the PLGA carriers, while the PC12 neuronal cells showed excellent adherence, proliferation and spread on the fibroin carriers without any evidence of cytotoxicity from the carriers. The present study thus proposes two models for 3D cell culture and demonstrates, firstly, that easily fabricable porous PLGA structures can act as excellent cell carriers for aiding cells easily retain their physiologically relevant 3D spherical shape in vitro, and secondly, that 3D inkjet printed silk fibroin structures can act as geometrically-shaped carriers for 3D cell patterning or directed cell growth in vitro. While the ‘fibroblasts on PLGA carriers’ model will help achieve more accurate results than the conventional 2D culture in cell research, such as drug discovery, and cell proliferation for adoptive cell transfer, such as stem cell therapy, the ‘neuronal cells on silk fibroin carriers’ model will help in research requiring patterned cell growth, such as treatment of neuropathies