The Chandra Dust Scattering Halo of Galactic Center transient Swift J174540.7-290015

We report the detection of a dust scattering halo around a recently discovered X-ray transient, Swift J174540.7-290015, which in early February of 2016 underwent one of the brightest outbursts (F_X ~ 5e-10 erg/cm^2/s) observed from a compact object in the Galactic Center field. We analyze four Chandra images that were taken as follow-up observations to Swift discoveries of new Galactic Center transients. After adjusting our spectral extraction for the effects of detector pileup, we construct a point spread function for each observation and compare it to the GC field before the outburst. We find residual surface brightness around Swift J174540.7-290015, which has a shape and temporal evolution consistent with the behavior expected from X-rays scattered by foreground dust. We examine the spectral properties of the source, which shows evidence that the object transitioned from a soft to hard spectral state as it faded below L_X ~ 1e36 erg/s. This behavior is consistent with the hypothesis that the object is a low mass X-ray binary in the Galactic Center.Comment: Accepted for publication in Ap

A gradient-forming MipZ protein mediating the control of cell division in the magnetotactic bacterium Magnetospirillum gryphiswaldense

Cell division needs to be tightly regulated and closely coordinated with other cellular processes to ensure the generation of fully viable offspring. Here, we investigate division site placement by the cell division regulator MipZ in the alphaproteobacterium Magnetospirillum gryphiswaldense, a species that forms linear chains of magnetosomes to navigate within the geomagnetic field. We show that M. gryphiswaldense contains two MipZ homologs, termed MipZ1 and MipZ2. MipZ2 localizes to the division site, but its absence does not cause any obvious phenotype. MipZ1, by contrast, forms a dynamic bipolar gradient, and its deletion or overproduction cause cell filamentation, suggesting an important role in cell division. The monomeric form of MipZ1 interacts with the chromosome partitioning protein ParB, whereas its ATP-dependent dimeric form shows non-specific DNA-binding activity. Notably, both the dimeric and, to a lesser extent, the monomeric form inhibit FtsZ polymerization in vitro. MipZ1 thus represents a canonical gradient-forming MipZ homolog that critically contributes to the spatiotemporal control of FtsZ ring formation. Collectively, our findings add to the view that the regulatory role of MipZ proteins in cell division is conserved among many alphaproteobacteria. However, their number and biochemical properties may have adapted to the specific needs of the host organism

Genética de poblaciones amazónicas: la historia evolutiva del jaguar, ocelote, delfín rosado, mono lanudo y piurí, reconstruida a partir de sus genes

The Amazon has more than the half of the world's biodiversity. Nevertheless, the major fraction of the Amazon species has unknown evolutionary histories. This is also certain for mammals and birds. Population genetics, employing molecular markers and theoretical mathematics models, can reconstruct these evolutionary histories and offer very powerful tools for the application of correct conservation politics. Herein, we show a comparative view of population genetics results obtained for Amazon populations of jaguar, ocelot, pink river dolphin, woolly monkey and wattled curassow and provide recommendation for their biological conservation. Each species showed its own specific evolutionary particularities, characteristics that were not shared by the other species. This finding should be taken into consideration for any effective biological conservation program. Key words: Amazon, Population genetics, Panthera, Leopardus, Inia, Lagothrix, Crax.El Amazonas contiene más de la mitad de la biodiversidad a escala mundial. Sin embargo, muchas de las especies que alberga, poseen historias evolutivas totalmente desconocidas. Esto incluye el caso de los mamíferos y de las aves. La genética de poblaciones, mediante el uso de marcadores moleculares, modelos y metodologías matemáticas, puede intentar reconstruir esa historia evolutiva y ofrecer herramientas efectivas para la aplicación de políticas correctas de conservación. Se muestra aquí un resumen de los estudios genético realizados en poblaciones amazónicas de jaguar, ocelote, delfín rosado, mono lanudo y piurí y se proponen algunas recomendaciones para su conservación biológica. En cada especie se observaron particularidades evolutivas propias no compartidas por las otras especies. Este hecho debe ser recogido por cualquier programa de conservación que pretenda ser efectivo. Palabras clave: Amazonas, Genética de poblaciones, Panthera, Leopardus, Inia, Lagothrix, Crax

PAALF People\u27s Plan: East Portland Pilot

Recognizing the traumatic experience of being forced to move and losing community, this plan reflects the hopes of community members who seek to rebuild their lives in a new place. The East Portland Pilot Plan applies the urban planning practice of placemaking as a transformative intervention for addressing challenges and stabilizing the Black community in East Portland. This plan also emerges at a critical time, as existing city plans for East Portland indicate significant future public investment and development. This plan has been written with a wide audience in mind. The material is relevant to homeowners, community activists, urban planners, nonprofit advocates and policymakers among others. The East Portland Pilot Plan is on the one hand a portrait of the Black community in East Portland; a portrait that has been narrated largely by the people themselves, and recorded in this document. On the other hand, the EPPP is a guide to action, a toolkit to address some of the most persistent issues facing Africans and African Americans and a roadmap to a thriving and vibrant Black community in East Portland. This project was conducted under the supervision of Sy Adler, Susan Hartnett and Marisa Zapata

Evaluación biomecánica de la carga final de la tenodesis de bíceps

El interés en las diferentes técnicas de tenodesis artroscópica se ha incrementado en los últimos 10 años. Sin embargo, hay muy poca información publicada sobre sus propiedades biomecánicas y clínicas. El objetivo del presente estudio es analizar una de las propiedades biomecánicas de dos tipos diferentes de tenodesis artroscópicas de bíceps: PITT vs Sutura con Arpones. Material y métodos: 15 especímenes cadavéricos frescos congelados se aleatorizaron para ambas técnicas. Una vez realizada la cirugía, los húmeros con el tendón fijado al Ligamento Transverso, se montaron en una máquina de prueba de materiales en paralelo para llevar a cabo el protocolo de carga hasta el fallo a una velocidad de 1.25 mm/sec. Se obtuvo la carga final (N) y se consideró la variable principal. Se compararon ambas técnicas mediante el test paramétrico de la t de Student. Resultados: Ambos tipos de reparaciones mostraron cargas finales adecuadas: 175,46±40,4 N la sutura con arpones y 142,79±30,9 N la técnica PITT (p>0.05). Conclusión: La Sutura con Doble Arpón y PITT demostraron una resistencia satisfactoria inicial sin diferencias significativas entre ambos grupos. Ambas técnicas son útiles a la hora de abordar la patología del bíceps, aunque la técnica PITT es más rápida, económica y accesible

The Chandra High Resolution X-ray Spectrum of Quiescent Emission from Sgr A*

In quiescence, Sgr A* is surprisingly dim, shining 100,000 times less than expected for its environment. This problem has motivated a host of theoretical models to explain radiatively inefficient accretion flows (RIAFs). The Chandra Galactic Center (GC) X-ray Visionary Program obtained approximately 3 Ms (one month) of Chandra HETG data, offering the only opportunity to examine the quiescent X-ray emission of Sgr A* with high resolution spectroscopy. Utilizing custom background regions and filters for removing overlapping point sources, this work provides the first ever look at stacked HETG spectra of Sgr A*. We model the background datasets with a cubic spline and fit the unbinned Sgr A* spectra with a simple parametric model of a power law plus Gaussian lines under the effects of interstellar extinction. We detect a strong 6.7 keV iron emission line in the HEG spectra and a 3.1 keV emission line in the MEG spectra. In all cases, the line centroids and equivalent widths are consistent with those measured from low-resolution CCD spectra. An examination of the unbinned, stacked HEG+/-1 spectrum reveals fine structure in the iron line complex. In addition to resolving the resonant and forbidden lines from He-like iron, there are apparent emission features arising with higher statistical significance at lower energy, potentially associated with FeXX-XXIV ions in a ~1 keV plasma arising near the Bondi radius of Sgr A*. With this work, we release the cleaned and stacked Sgr A* and background HETG spectra to the public as a special legacy dataset.Comment: Accepted by Ap

Acetonitrile cluster solvation in a cryogenic ethane-methane-propane liquid: Implications for Titan lake chemistry

The atmosphere of Titan, Saturn’s largest moon, exhibits interesting UV- and radiation-driven chemistry between nitrogen and methane, resulting in dipolar, nitrile-containing molecules. The assembly and subsequent solvation of such molecules in the alkane lakes and seas found on the moon’s surface are of particular interest for investigating the possibility of prebiotic chemistry in Titan’s hydrophobic seas. Here we characterize the solvation of acetonitrile, a product of Titan’s atmospheric radiation chemistry tentatively detected on Titan’s surface [H. B. Niemann et al., Nature 438, 779–784 (2005)], in an alkane mixture estimated to match a postulated composition of the smaller lakes during cycles of active drying and rewetting. Molecular dynamics simulations are employed to determine the potential of mean force of acetonitrile (CH_3CN) clusters moving from the alkane vapor into the bulk liquid. We find that the clusters prefer the alkane liquid to the vapor and do not dissociate in the bulk liquid. This opens up the possibility that acetonitrile-based microscopic polar chemistry may be possible in the otherwise nonpolar Titan lakes