Thirty Meter Telescope Site Testing I: Overview

As part of the conceptual and preliminary design processes of the Thirty Meter Telescope (TMT), the TMT site testing team has spent the last five years measuring the atmospheric properties of five candidate mountains in North and South America with an unprecedented array of instrumentation. The site testing period was preceded by several years of analyses selecting the five candidates, Cerros Tolar, Armazones and Tolonchar in northern Chile; San Pedro Martir in Baja California, Mexico and the 13 North (13N) site on Mauna Kea, Hawaii. Site testing was concluded by the selection of two remaining sites for further consideration, Armazones and Mauna Kea 13N. It showed that all five candidates are excellent sites for an extremely large astronomical observatory and that none of the sites stands out as the obvious and only logical choice based on its combined properties. This is the first article in a series discussing the TMT site testing project.Comment: Accepted for publication in PASP, April 2009 issu

Wide-Field Survey of Globular Clusters in M31. I. A Catalog of New Clusters

We present the result of a wide-field survey of globular clusters (GCs) in M31 covering a 3deg x 3deg field c. We have searched for GCs on CCD images taken with Washington CMT1 filters at the KPNO 0.9 m telescope using steps: (1) inspection of morphological parameters given by the SExtractor package such as stellarity, full maximum, and ellipticity; (2) consulting the spectral types and radial velocities obtained from spectra takena spectrograph at the WIYN 3.5 m telescope; and (3) visual inspection of the images of each object. We have and GC candidates, of which 605 are newly found GCs and GC candidates and 559 are previously known GCs. Amoects there are 113 genuine GCs, 258 probable GCs, and 234 possible GCs, according to our classification critee known objects there are 383 genuine GCs, 109 probable GCs, and 67 possible GCs. In total there are 496 genprobable GCs and 301 possible GCs. Most of these newly found GCs have T1 magnitudes of 17.5 - 19.5 mag, [17.9 < V < 19.9 mag assuming (C-T1) ~ 1.5], and (C-T1) colors in the range 1 - 2.Comment: accepted by AJ, using emulateapj.cl

TEAD and YAP regulate the enhancer network of human embryonic pancreatic progenitors.

The genomic regulatory programmes that underlie human organogenesis are poorly understood. Pancreas development, in particular, has pivotal implications for pancreatic regeneration, cancer and diabetes. We have now characterized the regulatory landscape of embryonic multipotent progenitor cells that give rise to all pancreatic epithelial lineages. Using human embryonic pancreas and embryonic-stem-cell-derived progenitors we identify stage-specific transcripts and associated enhancers, many of which are co-occupied by transcription factors that are essential for pancreas development. We further show that TEAD1, a Hippo signalling effector, is an integral component of the transcription factor combinatorial code of pancreatic progenitor enhancers. TEAD and its coactivator YAP activate key pancreatic signalling mediators and transcription factors, and regulate the expansion of pancreatic progenitors. This work therefore uncovers a central role for TEAD and YAP as signal-responsive regulators of multipotent pancreatic progenitors, and provides a resource for the study of embryonic development of the human pancreas

Multi Aperture Scintillation Sensor (MASS) used in the site selection of the Thirty Meter Telescope (TMT)

One of the main tools used in the TMT site testing campaign is the turbulence profiler MASS. We describe empirical investigations and a side by side comparison of two MASS systems which were performed in order to identify the accuracy of MASS turbulence data and its dependence on the instrument calibration. The accuracy of the total seeing delivered by the TMT MASS systems is found to be better than 0"05. The combination of MASS and DIMM allows to observe the seeing within the first few hundred meters of the atmosphere and can be used to investigate possible correlations with meteorological parameters measured close to the ground. We also compare the detection of clouds and cirrus by means of MASS data (LOSSAM method) with measurements of the thermal emission of clouds using a net radiation sensor. These methods are compared with the visual cloud detection using all sky cameras

Organic phosphorus in the terrestrial environment: a perspective on the state of the art and future priorities

Background The dynamics of phosphorus (P) in the environment is important for regulating nutrient cycles in natural and managed ecosystems and an integral part in assessing biological resilience against environmental change. Organic P (Po) compounds play key roles in biological and ecosystems function in the terrestrial environment being critical to cell function, growth and reproduction. Scope We asked a group of experts to consider the global issues associated with Po in the terrestrial environment, methodological strengths and weaknesses, benefits to be gained from understanding the Po cycle, and to set priorities for Po research. Conclusions We identified seven key opportunities for Po research including: the need for integrated, quality controlled and functionally based methodologies; assessment of stoichiometry with other elements in organic matter; understanding the dynamics of Po in natural and managed systems; the role of microorganisms in controlling Po cycles; the implications of nanoparticles in the environment and the need for better modelling and communication of the research. Each priority is discussed and a statement of intent for the Po research community is made that highlights there are key contributions to be made toward understanding biogeochemical cycles, dynamics and function of natural ecosystems and the management of agricultural systems

Influencia de las prácticas agrícolas en la dinámica de los carbonatos en los suelos

Despite being an important stock of carbon in soils, soil inorganic carbon (or SIC) has been largely underestimated compared to soil organic carbon (SOC). The main arguments for this are the supposed little variation in its content in soils after thousands of years. However, recent studies have recorded changes in the SIC pool over decades because of agricultural practices. The SIC forms most of the C in arid and semi-arid regions, which have a key role in the global C cycle, since the conversion to agricultural lands will generate processes of accumulation and/or dissolution of SIC. This review aims to analyse scientific investigations related to carbonates in the soil, seeking to know the influence of agricultural practices, recommended irrigation, fertilization and tillage on SIC reserves, to elucidate the dominant processes and their possible effect on the current climate change scenario. The results indicate that fertilisation and the use of pH correctors have a direct effect on the elimination of carbonates and the potential to release enormous amounts of CO2 into the atmosphere in the medium term. However, the information collected regarding irrigation and tillage is not enough to conclude which is the dominant process, nor to calculate the sequestration or release rates of C.A pesar de constituir una reserva importante de carbono en los suelos, el carbono inorgánico del suelo (o SIC por sus siglas en inglés) ha sido subvalorado en comparación al carbono orgánico del suelo (SOC por sus siglas en inglés), lo que se relaciona a una supuesta escasa variación en su contenido en los suelos tras miles de años. Sin embargo, estudios recientes han registrado alteraciones en el pool de SIC en el periodo de décadas producto de labores agrícolas. El SIC forma la mayor parte del C en regiones áridas y semiáridas, las que poseen un rol clave en el ciclo global del C, ya que la conversión a tierras agrícolas generará procesos de acumulación y/o disolución del SIC, dependiendo de los manejos del suelo. La presente recopilación analizó una serie de investigaciones científicas relacionadas a los carbonatos en el suelo, buscando conocer la influencia de las prácticas agrícolas, específicamente riego, fertilización y labranza, sobre las reservas de SIC, para dilucidar los procesos dominantes y su posible efecto en el actual escenario de cambio climático. Los resultados indican que las labores de fertilización y uso de correctores del pH tienen un efecto directo sobre la disolución de carbonatos y el potencial de liberar enormes cantidades de CO2 a la atmósfera en el mediano plazo. Sin embargo, la información recopilada respecto al riego y la labranza, no son suficientes para concluir cuál es el proceso dominante, ni para calcular las tasas de secuestro o liberación de C

Genesis y ocurrencia de carbonatos en los suelos

Soil inorganic carbon or SIC (mainly as CaCO3) is an important global C pool with an estimated maximum accumulation of 2.3 x 1015 kg C, being the dominant C species in 54% of soils worldwide. Arid and semi-arid regions, which comprise more than 35% of the earth’s surface and contain most of the carbonate in soils, play a key role in the global C cycle. In this study, we cover the dynamics of accumulation of pedogenic carbonates in soils, the morphologies associated with them and the soil&nbsp;formation factors linked to their genesis.El carbono inorgánico del suelo o SIC (principalmente como CaCO3)un importante reservorio de carbono a nivel global, con una acumulación máxima estimada de 2,3 x 1015 kg C, siendo la especie de C dominante en el 54% de los suelos en el mundo. Las regiones áridas y semiáridas, que comprenden más del 35% de la superficie terrestre, y donde se encuentra la mayor parte del carbonato en el suelo, poseen un rol clave en el ciclo global del C. En este trabajo se abordan los principales aspectos con respecto a la dinámica de acumulación de carbonatos pedogénicos en los suelos, las morfologías asociadas a éstos y los factores de formación de suelos ligados a su génesis. La actividad biológica es un factor esencial que explica la morfología que puede adquirir el carbonato en el suelo; además, participa en la dinámica del C al generar el CO2 como inicio de las reacciones de precipitación de HCO3- y CO3

Formation of SMBH seeds in Pop III star clusters through collisions : the importance of mass loss

Runaway collisions in dense clusters may lead to the formation of supermassive black hole (SMBH) seeds, and this process can be further enhanced by accretion, as recent models of SMBH seed formation in Population III star clusters have shown. This may explain the presence of supermassive black holes already at high redshift, $z>6$. However, in this context, mass loss during collisions was not considered and could play an important role for the formation of the SMBH seed. Here, we study the effect of mass loss, due to collisions of protostars, in the formation and evolution of a massive object in a dense primordial cluster. We consider both constant mass loss fractions as well as analytic models based on the stellar structure of the collision components. Our calculations indicate that mass loss can significantly affect the final mass of the possible SMBH seed. Considering a constant mass loss of 5% for every collision, we can lose between 60-80% of the total mass that is obtained if mass loss were not considered. Using instead analytical prescriptions for mass loss, the mass of the final object is reduced by 15-40%, depending on the accretion model for the cluster we study. Altogether, we obtain masses of the order of $10^4M_{\odot}$, which are still massive enough to be SMBH seeds.Comment: 12 pages, 9 figures, accepted by MNRA