Temporal variability of the telluric sodium layer

The temporal variability of the telluric sodium layer is investigated by analyzing 28 nights of data obtained with the Colorado State University LIDAR experiment. The mean height power spectrum of the sodium layer was found to be well fit by a power law over the observed range of frequencies, 10 microhertz to 4 millhertz. The best fitting power law was found to be 10^\beta \nu^\alpha, with \alpha = -1.79 +/- 0.02 and \beta = 1.12 +/- 0.40. Applications to wavefront sensing require knowledge of the behavior of the sodium layer at kHz frequencies. Direct measurements at these frequencies do not exist. Extrapolation from low-frequency behavior to high frequencies suggests that this variability may be a significant source of error for laser-guide-star adaptive optics on large-aperture telescopes.Comment: 3 pages, 3 figures, accepted for publication in Optics Letter

The Spectral Types of White Dwarfs in Messier 4

We present the spectra of 24 white dwarfs in the direction of the globular cluster Messier 4 obtained with the Keck/LRIS and Gemini/GMOS spectrographs. Determining the spectral types of the stars in this sample, we find 24 type DA and 0 type DB (i.e., atmospheres dominated by hydrogen and helium respectively). Assuming the ratio of DA/DB observed in the field with effective temperature between 15,000 - 25,000 K, i.e., 4.2:1, holds for the cluster environment, the chance of finding no DBs in our sample due simply to statistical fluctuations is only 6 X 10^(-3). The spectral types of the ~100 white dwarfs previously identified in open clusters indicate that DB formation is strongly suppressed in that environment. Furthermore, all the ~10 white dwarfs previously identified in other globular clusters are exclusively type DA. In the context of these two facts, this finding suggests that DB formation is suppressed in the cluster environment in general. Though no satisfactory explanation for this phenomenon exists, we discuss several possibilities.Comment: Accepted for Publication in Astrophys. J. 11 pages including 4 figures and 2 tables (journal format

The Masses of Population II White Dwarfs

Globular star clusters are among the first stellar populations to have formed in the Milky Way, and thus only a small sliver of their initial spectrum of stellar types are still burning hydrogen on the main-sequence today. Almost all of the stars born with more mass than 0.8 M_sun have evolved to form the white dwarf cooling sequence of these systems, and the distribution and properties of these remnants uniquely holds clues related to the nature of the now evolved progenitor stars. With ultra-deep HST imaging observations, rich white dwarf populations of four nearby Milky Way globular clusters have recently been uncovered, and are found to extend an impressive 5 - 8 magnitudes in the faint-blue region of the H-R diagram. In this paper, we characterize the properties of these population II remnants by presenting the first direct mass measurements of individual white dwarfs near the tip of the cooling sequence in the nearest of the Milky Way globulars, M4. Based on Gemini/GMOS and Keck/LRIS multiobject spectroscopic observations, our results indicate that 0.8 M_sun population II main-sequence stars evolving today form 0.53 +/- 0.01 M_sun white dwarfs. We discuss the implications of this result as it relates to our understanding of stellar structure and evolution of population II stars and for the age of the Galactic halo, as measured with white dwarf cooling theory.Comment: Accepted for Publication in Astrophys. J. on Aug. 05th, 2009. 19 pages including 9 figures and 2 tables (journal format

Identificación de alternativas de aprovechamiento y disposición final de residuos sólidos domiciliarios en el municipio de Tauramena Casanare.

Esta monografía presenta las alternativas para el aprovechamiento de los residuos sólidos domiciliarios del municipio de Tauramena, definidas a partir del análisis de los factores que intervienen dentro del proceso, para lo cual se realizó la descripción de las características del municipio y el estado actual del manejo de los residuos tanto en sus fases de separación en la fuente, recolección, transporte, tratamiento y/o disposición final, teniendo en cuenta los hallazgos presentados dentro de la actualización del Plan de Gestión Integral de Residuos Sólidos Municipales y del Plan de Gestión Ambiental de la Planta Industrial de Residuos Sólidos - PIPRST. Derivado del análisis de los documentos mencionados, se logró establecer que en el municipio de Tauramena se encuentra establecido un sistema de gestión de residuos sólidos-RS enfocado en el tratamiento post consumo a través de la PIPRST para la recuperación y el aprovechamiento de los residuos orgánicos a través del compostaje por volteo manual y la lombricultura; y la recuperación y separación de los inorgánicos a través de procesos manuales para su posterior venta. Es así como, se han logrado recuperar al año 207,8 toneladas correspondientes al 7% de un total de 2.968 toneladas generadas a nivel domiciliario. Una vez se detalló el diagnóstico se procedió a realizar la descripción, análisis y establecimiento de las alternativas y tecnologías existentes para el aprovechamiento de los residuos sólidos orgánicos e inorgánicos reciclables con base en las postulaciones descritas en la guía para la selección de tecnologías de manejo integral de residuos sólidos (Ministerio de Ambiente, 2002) y otros autores. Para el caso de los residuos orgánicos se identificaron procesos fisicoquímicos enfocados en la conversión de estos materiales en gas o abono orgánico a través de sistemas aerobios y anaerobios, dadas las características y la infraestructura presente en el municipio se realiza el análisis y la elección del sistema enfocado en la producción de abono orgánico, teniendo en cuenta características como la utilización de recursos, la densidad poblacional y el volumen de generación de los sistemas de pilas manuales, sistemas de compostaje cerrados, pilas estáticas y la lombricultura. Se llega a la conclusión de que es necesario desarrollar procesos de pilas estáticas con aireación forzada y el mejoramiento del proceso de lombricultura para la obtención de tres productos el abono orgánico, el pie de cría de la lombriz californiana y el humus líquido. En cuanto a los residuos plásticos se identificó que dentro de la PIPRST existe una maquinaria en desuso, por consiguiente se realizó un estudio de casos de implementación de procesos micro localizados para el aprovechamiento de este tipo de material, estableciendo que a través de la compra de una paletizadora, extrusora y la línea de enfriamiento se creará la línea de producción completa para la producción de productos a base de material reciclado plástico tipo PEAD y PET para el mercado regional. Por último, se establece que, para los residuos de papel, cartón, metales ferrosos y no ferrosos, y el vidrio, dada la complejidad de las tecnologías, el alto costo de implementación y el volumen de generación de cada uno de estos residuos, factores descritos en la guía para la selección de tecnologías de manejo integral de residuos sólidos (2002), se procedió a realizar la descripción de los procesos como el pulpeo y la fundición; posteriormente se realiza la recomendación de fortalecer los procesos de tratamiento, almacenamiento y compactación para comercializarlos posteriormente con terceros.This monograph presents the alternatives for the use of residues from residential services of the municipality of Tauramena, defined from the analysis of the factors that intervene in the process, for which the description of the characteristics of the municipality and the current state is made of the management of the waste in its phases of separation at the source, collection, transport, treatment and / or final disposal, taking into account the findings in the update of the Comprehensive Municipal Solid Waste Management Plan and the Environmental Management Plan of The Industrial Solid Waste Plant - PIPRST. Derived from the analysis of the aforementioned documents, it was established that in the municipality of Tauramena a solid waste management system-RS focused on post-consumption treatment through the PIPRST for the recovery and use of organic waste is established. through composting by manual turning and vermiculture; and the recovery and separation of inorganics through manual processes for their subsequent sale. In this way, 207.8 tons corresponding to 7% of a total of 2,968 tons generated at home have been recovered by the year. Once the diagnosis was detailed, the description, analysis and establishment of the alternatives and existing technologies for the use of recyclable organic and inorganic solid waste were based on the applications described in the guide for the selection of integral management technologies. of solid waste (Ministry of Environment, 2002) and other authors. In the case of organic waste, physicochemical processes focused on the conversion of these materials into organic gas or fertilizer through aerobic and anaerobic systems were identified. Given the characteristics and the infrastructure present in the municipality, the analysis and choice of the system is carried out. focused on the production of organic fertilizer, considering characteristics such as the use of resources, the population density and the volume of generation of manual piles systems, closed composting systems, static piles and vermiculture. It is concluded that it is necessary to develop static piles processes with forced aeration and the improvement of the vermiculture process to obtain three products: organic fertilizer, Californian worm breeding foot and liquid humus. Regarding the plastic waste, it was identified that within the PIPRST there is a machinery in disuse, therefore a case study was carried out of the implementation of micro localized processes for the use of this type of material, establishing that through the purchase of a palletizer, extruder and the cooling line will create the complete production line for the production of products based on PEAD and PET plastic recycled material for the regional market. Finally, it is established that, for waste paper, cardboard, ferrous and non-ferrous metals, and glass, given the complexity of the technologies, the high cost of implementation and the volume of generation of each of these residues, factors described in the guide for the selection of technologies of integral management of solid waste (2002), proceeded to make the description of processes such as pulping and smelting; Subsequently, the recommendation is made to strengthen the treatment, storage and compaction processes to commercialize them later with third parties

Deep ACS Imaging in the Globular Cluster NGC6397: Dynamical Models

We present N-body models to complement deep imaging of the metal-poor core-collapsed cluster NGC6397 obtained with the Hubble Space Telescope. All simulations include stellar and binary evolution in-step with the stellar dynamics and account for the tidal field of the Galaxy. We focus on the results of a simulation that began with 100000 objects (stars and binaries), 5% primordial binaries and Population II metallicity. After 16 Gyr of evolution the model cluster has about 20% of the stars remaining and has reached core-collapse. We compare the color-magnitude diagrams of the model at this age for the central region and an outer region corresponding to the observed field of NGC6397 (about 2-3 half-light radii from the cluster centre). This demonstrates that the white dwarf population in the outer region has suffered little modification from dynamical processes - contamination of the luminosity function by binaries and white dwarfs with non-standard evolution histories is minimal and should not significantly affect measurement of the cluster age. We also show that the binary fraction of main-sequence stars observed in the NGC6397 field can be taken as representative of the primordial binary fraction of the cluster. For the mass function of the main-sequence stars we find that although this has been altered significantly by dynamics over the cluster lifetime, especially in the central and outer regions, that the position of the observed field is close to optimal for recovering the initial mass function of the cluster stars (below the current turn-off mass). More generally we look at how the mass function changes with radius in a dynamically evolved stellar cluster and suggest where the best radial position to observe the initial mass function is for clusters of any age.Comment: 34 pages, 11 figures, submitted to AJ, companion paper to 0708.403

The Space Motion of the Globular Cluster NGC 6397

As a by-product of high-precision, ultra-deep stellar photometry in the Galactic globular cluster NGC 6397 with the Hubble Space Telescope, we are able to measure a large population of background galaxies whose images are nearly point-like. These provide an extragalactic reference frame of unprecedented accuracy, relative to which we measure the most accurate absolute proper motion ever determined for a globular cluster. We find mu_alpha = 3.56 +/- 0.04 mas/yr and mu_delta = -17.34 +/- 0.04 mas/yr. We note that the formal statistical errors quoted for the proper motion of NGC 6397 do not include possible unavoidable sources of systematic errors, such as cluster rotation. These are very unlikely to exceed a few percent. We use this new proper motion to calculate NGC 6397's UVW space velocity and its orbit around the Milky Way, and find that the cluster has made frequent passages through the Galactic disk.Comment: 5 pages including 3 figures, accepted for publication in the Astrophysical Journal Letters. Very minor changes in V2. typos fixe

Deep ACS Imaging in the Globular Cluster NGC 6397: The Cluster Color Magnitude Diagram and Luminosity Function

We present the CMD from deep HST imaging in the globular cluster NGC 6397. The ACS was used for 126 orbits to image a single field in two colors (F814W, F606W) 5 arcmin SE of the cluster center. The field observed overlaps that of archival WFPC2 data from 1994 and 1997 which were used to proper motion (PM) clean the data. Applying the PM corrections produces a remarkably clean CMD which reveals a number of features never seen before in a globular cluster CMD. In our field, the main sequence stars appeared to terminate close to the location in the CMD of the hydrogen-burning limit predicted by two independent sets of stellar evolution models. The faintest observed main sequence stars are about a magnitude fainter than the least luminous metal-poor field halo stars known, suggesting that the lowest luminosity halo stars still await discovery. At the bright end the data extend beyond the main sequence turnoff to well up the giant branch. A populous white dwarf cooling sequence is also seen in the cluster CMD. The most dramatic features of the cooling sequence are its turn to the blue at faint magnitudes as well as an apparent truncation near F814W = 28. The cluster luminosity and mass functions were derived, stretching from the turn off down to the hydrogen-burning limit. It was well modeled with either a very flat power-law or a lognormal function. In order to interpret these fits more fully we compared them with similar functions in the cluster core and with a full N-body model of NGC 6397 finding satisfactory agreement between the model predictions and the data. This exercise demonstrates the important role and the effect that dynamics has played in altering the cluster IMF.Comment: 43 pages including 4 tables and 12 diagrams. Figures 2 and 3 have been bitmapped. Accepted for publication in the Astronomical Journa

Outcome of African-American compared to White-American patients with early-stage breast cancer, stratified by phenotype

BACKGROUND: Breast cancer mortality rates are 39% higher in the African-American (AA) women compared to White-American (WA) women despite the advances in overall breast cancer screening and treatments. Several studies have undertaken to identify the factors leading to this disparity in United States with possible effects of lower socioeconomic status and underlying aggressive biology. METHODS: A retrospective analysis was done using a prospectively maintained database of a metropolitan health system. Patients were selected based on diagnosis of early-stage breast cancer between 10/1998 and 02/2017, and included women over age of 18 with clinically node-negative disease. Patients were then stratified by phenotype confirmed by pathology and patient-identified race. RESULTS: A total of 2,298 women were identified in the cohort with 39% AA and 61% WA women. The overall mean age at the time of diagnosis for AA women was slightly younger at 60 years compared to 62 years for WA women (p = 0.003). Follow-up time was longer for the WA women at 95 months vs. 86 months in AA women. The overall 5-year survival was analyzed for the entire cohort, with the lowest survival occurring in patients with triple-negative breast cancer (TNBC). Phenotype distribution revealed a higher incidence of TNBC in AA women compared to WA women (AA 16% vs. WA 10%; p \u3c 0.0001). AA women also had higher incidence of HER2 positive cancers (AA 16.8% vs. WA 15.3%; p \u3c 0.0001). WA women had a significantly higher distribution of Non-TNBC/HER2-negative phenotype (AA 55% vs. WA 65%; p \u3c 0.0001). Furthermore, a subgroup analysis was done for a sentinel lymph node (SLN) negative cohort that showed higher rates of grade 3 tumors in AA (AA 35% vs. WA 23%; p \u3c 0.0001); and higher rates of grade 1 and grade 2 tumors in WA (30% vs. 21% and 44% vs. 40%). Despite higher grade tumors in AA women, five-year overall survival outcomes in SLN-negative cohort did not differ between AA and WA women when stratifying based on tumor subtype. CONCLUSION: Breast cancer survival disparities in AA and WA women with SLN-negative breast cancer are diminished when evaluated at early-stage cancers defined by SLN-negative tumors. Our evaluation suggests that when diagnosed early, phenotype does not contribute to racial survival outcomes. The lower survival rate in AA women with breast cancer may be attributed to later stage biology between the two races, or underlying socioeconomic disparities