Rapid magma ascent recorded by water diffusion profiles in mantle olivine

Mechanisms and rates of magma ascent play a critical role in eruption dynamics but remain poorly constrained phenomena. Water, dissolved in mantle minerals as hydrogen and partitioned into the magma during ascent, may provide clues to quantifying magma ascent rates prior to eruption. We determined the dehydration profiles in olivine crystals from peridotite mantle xenoliths within the Pali-Aike alkali basalt from Patagonia, Chile. The results demonstrate that the amount of water stored in the uppermost mantle has likely been underestimated due to water loss during transport. Using experimental diffusion data for hydrogen, we estimate that the xenoliths reached the surface from 60–70 km depth in several hours, a surprisingly rapid rise comparable to ascent rates for kimberlite magmas

Obsidians in archaeological sites in the province of La Pampa, Argentina : their sources

Fil: Stern, Charles R. University of Colorado Boulder. Department of Geological Sciences; Estados Unidos.Fil: Aguerre, Ana Margarita. Universidad de Buenos Aires. Facultad de Filosofía y Letras. Instituto de Arqueología; Argentina.Sixteen samples of obsidian collected from three archeological sites in the west and southwest of La Pampa province have been analyzed. Twelve samples were selected from the excavation of “Casa del Piedra 1”, Department of Puelén, on the banks of the Río Colorado, where the available radiocarbon dates indicate that obsidian was utilized, at least episodically, from the earliest occupational levels at ≥8620 ± 190 14C years BP (or ≥9720 ± 250 calibrated years BP). Four samples were selected from the surface of two sites north of the Meseta Basáltica, Department of Chicalcó. The 16 samples analyzed are derived from multiple different distant sources that include principally Laguna del Maule, located to the west of these sites in Mendoza province along the frontier with Chile, and also, after about 4000 years BP, from Cerro Huenul and Portada Covunco, located in the north and central-west of Neuquén province. Samples of obsidian from other archeological sites in La Pampa province, such as Tapera Moreira and Chenque i in Lihuel Calel, also come from these same distant sources as well as others even more distant such as Cerro Planicies/Lago Lolog in the southwest of Neuquén.Se presentan los resultados del análisis de 16 muestras de artefactos de obsidiana procedentes de tres sitios arqueológicos de La Pampa. Por un lado, se seleccionaron 12 muestras de la excavación, con fechados radiocarbónicos, del sitio “Casa de Piedra 1”, Departamento Puelén, a orillas del Río Colorado, donde la obsidiana aparece siendo utilizada, al menos episódicamente, desde el nivel más antiguo a ≥8620 ± 190 años radiocarbónicos AP (o ≥9720 ± 250 años calibrados AP). Por otro lado, se seleccionaron cuatro muestras de dos sitios de superficie, del norte de la Meseta Basáltica, departamento Chicalcó. Las 16 muestras que aquí presentamos provienen de múltiples fuentes, como Laguna del Maule, ubicada al oeste de nuestros sitios arqueológicos, en territorio mendocino casi en la frontera con Chile, y también, a partir de aproximadamente 4000 años AP, de Cerro Huenul y Portada Covunco, en el norte y centro-oeste del Neuquén respectivamente. Muestras de obsidianas procedentes de otros sitios arqueológicos en La Pampa, como Tapera Moreira y Chenque i de Lihuel Calel, al este de nuestra zona, también provienen de las mismas canteras y/o de otras más distantes, como Cerro Planicies/Lago Lolog en el sudoeste de Neuquén

Discovery of a 500 pc shell in the nucleus of Centaurus A

Spitzer Space Telescope mid-infrared images of the radio galaxy Centaurus A reveal a shell-like, bipolar, structure 500 pc to the north and south of the nucleus. This shell is seen in 5.8, 8.0 and 24 micron broad-band images. Such a remarkable shell has not been previously detected in a radio galaxy and is the first extragalactic nuclear shell detected at mid-infrared wavelengths. We estimate that the shell is a few million years old and has a mass of order million solar masses. A conservative estimate for the mechanical energy in the wind driven bubble is 10^53 erg. The shell could have created by a small few thousand solar mass nuclear burst of star formation. Alternatively, the bolometric luminosity of the active nucleus is sufficiently large that it could power the shell. Constraints on the shell's velocity are lacking. However, if the shell is moving at 1000 km/s then the required mechanical energy would be 100 times larger.Comment: submitted to ApJ Letter

Near-Infrared K and L' Flux Ratios in Six Lensed Quasars

We examine the wavelength dependence of flux ratios for six gravitationally lensed quasars using K and L' images obtained at the Gemini North 8m telescope. We select lenses with source redshifts z_s < 2.8 so that K-band images probe rest-frame optical emission from accretion disks, while L'-band images probe rest-frame near-infrared flux emitted (in part) from the more extended surrounding torus. Since the observations correspond to different source sizes, the K and L' flux ratios are sensitive to structure on different scales and may be useful for studying small-structure in the lens galaxies. Four of the six lenses show differences between K and L' flux ratios. In HE 0435$-1223, SDSS 0246-0825, and HE 2149-2745 the differences may be attributable to known microlensing and/or intrinsic variability. In SDSS 0806+2006 the wavelength dependence is not easily attributed to known variations, and may indicate the presence of substructure. By contrast, in Q0142-100 and SBS 0909+523 the K and L' flux ratios are consistent within the uncertainties. We discuss the utility of the current data for studying chromatic effects related to microlensing, dust extinction, and dark matter substructure.Comment: 19 pages, 4 Figures, 4 Tables, AJ accepte

Human Immunodeficiency Virus Type 1 Infection of Cells and Tissues from the Upper and Lower Human Female Reproductive Tract

Viable tissue sections and isolated cell cultures from the human fallopian tube, uterus, cervix, and vaginal mucosa were examined for susceptibility to infection with human immunodeficiency virus type 1 (HIV-1). We examined infectivity by using the monocytotropic strain HIV-1JR-FLand several primary isolates of HIV-1 obtained from infected neonates. HIV-1 infection was measured by p24 production in short-term culture and by immunofluorescence detection of HIV-1 Nef and p24 proteins by laser scanning confocal microscopy. Three-color immunofluorescence was used to phenotype HIV-infected cells within tissue sections from each site. Our findings indicate that epithelial, stromal, and dendritic cells and cells with CD14+, CD4+, CD14-, CD4-, and CD4+, CD14- phenotypes from the female reproductive tract are infectable with HIV-1. Of importance is the finding that tissues from the upper reproductive tract are susceptible to infection with HIV-1. Moreover, tissue samples from women in all stages of the menstrual cycle, including postmenopausal women (inactive), could be infected with HIV-1. Female reproductive tract cells required a minimum of 60 min of exposure to HIV-1 in order for infection to occur, in contrast to peripheral blood lymphocytes, which became infected after being exposed to HIV-1 for only 1 min. These findings demonstrate that HIV-1 can infect cells and tissues from different sites within the female reproductive tract and suggest that multiple cell types, including epithelial cells, may be targets for the initial infection by HIV-1

An X-Ray Survey of the Open Cluster NGC 6475 (M7) with ROSAT

A ROSAT x-ray survey, with complimentary optical photometry, of the open cluster NGC 6475 has enabled the detection of approx. 50 late-F to K0 and approx. 70 K/M dwarf new candidate members, providing the first reliable detection of low-mass stars in this low. galactic latitude, 220 Myr old cluster. The x-ray observations reported here have a typical limiting sensitivity of L(sub x) approx. equal to 10(exp 29) erg/s. The detection frequency of early type cluster members is consistent with the hypothesis that the x-ray emitting early type stars are binary systems with an unseen, low-mass secondary producing the x rays. The ratio between x-ray and bolometric luminosity among NGC 6475 members saturates at a spectral-type/color which is intermediate between that in much younger and in much older clusters, consistent with rotational spindown of solar-type stars upon their arrival on the ZAMS. The upper envelope of x-ray luminosity as a function of spectral type is comparable to that of the Pleiades, with the observed spread in x-ray luminosity among low-mass members being likely due to the presence of binaries and relatively rapid rotators. However, the list of x-ray selected candidate members is likely biased against low-mass, slowly rotating single stars. While some preliminary spectroscopic information is given in an appendix, further spectroscopic observations of the new candidate members will aid in interpreting the coronal activity among solar-type NGC 6475 members and their relation to similar stars in older and younger open clusters

Obsidian circulation in Chubut, central Patagonia, Argentina: use of extra regional raw materials as a sign of mobility and interaction between hunter gatherers groups

Os conjuntos de artefatos líticos recuperados em distintos tipos de sítios arqueológicos do Chubut mostram uma proeminência de matériasprimas locais, especialmente sílex, xilopalas e vulcanitas, nessa ordem. Esses materiais são acessíveis nas redondezas dos mesmos. As obsidianas, porém, aparecem em reduzida frequência e não se acham nas jazidas locais. O fato de haver fontes de obsidiana caracterizadas geo-quimicamente e localizadas pontualmente no espaço patagônico, possibilitou a identificação da origem dos achados nos resultados das análises geo-químicas de obsidianas de vários sítios no interior de Chubut e são discutidos em relação aos circuitos de mobilidade dos grupos humanos no espaço, estruturado pelas estradas. As conclusões apontam não apenas a existência de corredores de comunicação, mas também de encruzilhadas, ao mesmo tempo em que se propõe o uso da obsidiana associado a aspectos sociais ou simbólicos, e não somente tecnológicos.The lithic assemblages recovered from various types of archaeological sites in Chubut, central Patagonia, show a predominance of local raw materials such as silica, xilopals and vulcanite. These materials are available in the vicinities of these sites. Obsidians, however, scarcely appear in archaeological sets and are not found in local quarries. The availability of geochemically characterized obsidian sources, precisely located in the Patagonian area, allowed the identification of the source location of those found in archaeological contexts. This paper presents the results of the geochemical analysis of obsidian artifacts from several sites inside Chubut and they are discussed in relation to the mobility circuits of human groups along structured routes. The conclusions suggest not only the existence of communication corridors but also of crossroads. Finally, the use of obsidians associated with social or symbolic aspects, opposed to a merely technological application, is argued.Circulación de obsidiana en Chubut, Patagonia Central, Argentina: uso de las materias primas extra-regionales como indicadores de movilidad e interacción entre grupos cazadores recolectore

Spatially Resolving a Starburst Galaxy at Hard X-ray Energies: NuSTAR, Chandra, AND VLBA Observations of NGC 253

Prior to the launch of NuSTAR, it was not feasible to spatially resolve the hard (E > 10 keV) emission from galaxies beyond the Local Group. The combined NuSTAR dataset, comprised of three ~165 ks observations, allows spatial characterization of the hard X-ray emission in the galaxy NGC 253 for the first time. As a follow up to our initial study of its nuclear region, we present the first results concerning the full galaxy from simultaneous NuSTAR, Chandra, and VLBA monitoring of the local starburst galaxy NGC 253. Above ~10 keV, nearly all the emission is concentrated within 100" of the galactic center, produced almost exclusively by three nuclear sources, an off-nuclear ultraluminous X-ray source (ULX), and a pulsar candidate that we identify for the first time in these observations. We detect 21 distinct sources in energy bands up to 25 keV, mostly consisting of intermediate state black hole X-ray binaries. The global X-ray emission of the galaxy - dominated by the off-nuclear ULX and nuclear sources, which are also likely ULXs - falls steeply (photon index >~ 3) above 10 keV, consistent with other NuSTAR-observed ULXs, and no significant excess above the background is detected at E > 40 keV. We report upper limits on diffuse inverse Compton emission for a range of spatial models. For the most extended morphologies considered, these hard X-ray constraints disfavor a dominant inverse Compton component to explain the {\gamma}-ray emission detected with Fermi and H.E.S.S. If NGC 253 is typical of starburst galaxies at higher redshift, their contribution to the E > 10 keV cosmic X-ray background is < 1%.Comment: 20 pages, 14 figures, accepted for publication in Ap