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A major avenue in the study of the Galaxy is the investigation of stellar populations and Galactic chemical evolution by stellar spectroscopy. Due to the dust obscuration, stars in the centre of the Galaxy can only be observed in the near-IR wavelength region. However, existing line lists in this wavelength region are demonstratively not of good enough quality for use in stellar spectroscopy. In response to this, we have developed an empirical astrophysical line list in the K-band based on modelling against the Sun and testing against Arcturus. Of ca. 700 identified interesting lines about 570 lines have been assigned empirically determined values.
Owing to their extreme crowding and high and variable extinction, stars in the Galactic Bulge, within ±2° of the Galactic plane, and especially those in the Nuclear Star Cluster, have only rarely been targeted for an analyses of their detailed abundances. There is also some disagreement about the high end of the abundance scale for these stars. It is now possible to obtain high dispersion, high S/N spectra in the infrared K band (~2.0 − 2.4 µm) for these giants; we report our progress at Keck and VLT in using these spectra to infer the composition of this stellar population.
As new work on the proper motions (PMs) of the Large Magellanic Cloud (LMC) has come out, our view of the history of the Magellanic Clouds has evolved. We now believe they are on their first infall into the Milky Way (MW), having been tidally bound at the start of infall (though not necessarily now). Combining these observations with initial PMs of the Small Magellanic Cloud (SMC) suggests a new formation mechanism of the Magellanic Stream through the stripping of material from the SMC. However, large uncertainties remain in the exact mass of the LMC. We present a measurement of the systemic proper motions of the SMC from astrometry with the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST), covering a ~3 year baseline of 30 fields with background QSOs. We find these motions to be μW = −0.82 ± 0.06 mas/yr and μN = −1.23 ± 0.07 mas/yr. Combining these measurements with previous efforts in studying the Clouds will help constrain their interactions with each other and the MW, including the mass of the LMC and the MW, as well as provide new insight into the internal dynamics of the SMC.
We present our effort to measure the proper motions of satellites in the halo of the Milky Way with mainly ground based telescopes as a precursor on what is possible with Gaia. For our first study, we used wide field optical data from the LBT combined with a first epoch of SDSS observations, on the globular cluster Palomar 5 (Pal 5). Since Pal 5 is associated with a tidal stream it is very useful to constrain the shape of the potential of the Milky Way. The motion and other properties of the Pal 5 system constrain the inner halo of the Milky Way to be rather spherical. Further, we combined adaptive optics and HST to get an absolute proper motion of the globular cluster Pyxis. Using the proper motion and the line-of-sight velocity we find that the orbit of Pyxis is rather eccentric with its apocenter at more than 100 kpc and its pericenter at about 30 kpc. The dynamics excludes an association with the ATLAS stream, the Magellanic clouds, and all satellites of the Milky Way at least down to the mass of Leo II. However, the properties of Pyxis, like metallicity and age, point to an origin from a dwarf of at least the mass of Leo II. We therefore propose that Pyxis originated from an unknown relatively massive dwarf galaxy, which is likely today fully disrupted. Assuming that Pyxis is bound to the Milky Way we derive a 68% lower limit on the mass of the Milky Way of 9.5 × 1011 M⊙.
The association between harmful use of alcohol and HIV infection is well documented. To address this dual epidemic, the US President's Emergency Plan for AIDS Relief (PEPFAR) developed and implemented a multi-pronged approach primarily in Namibia and Botswana. We present the approach and preliminary results of the public health investigative and programmatic activities designed, initiated and supported by PEPFAR to combat the harmful use of alcohol and its association as a driver of HIV morbidity and mortality from 2008 to 2013.
PEPFAR supported comprehensive alcohol programming using a matrix model approach that combined the socio-ecological framework and the Alcohol Misuse Prevention and Intervention Continuum. This structure enabled seven component objectives: (1) to quantify harmful use of alcohol through rapid assessments; (2) to develop and evaluate alcohol-based interventions; (3) to promote screening programs and alcohol abuse resource services; (4) to support stakeholder networks; (5) to support policy interventions and (6) structural interventions; and (7) to institutionalize universal prevention messages.
Targeted PEPFAR support for alcohol activities resulted in several projects to address harmful alcohol use and HIV. Components are graphically conceptualized within the matrix model, demonstrating the intersections between primary, secondary and tertiary prevention activities and individual, interpersonal, community, and societal factors. Key initiative successes included leveraging alcohol harm prevention activities that enabled projects to be piloted in healthcare settings, schools, communities, and alcohol outlets. Primary challenges included the complexity of multi-sectorial programming, varying degrees of political will, and difficulties monitoring outcomes over the short duration of the program.
The aim of this research is to examine perceptions of those with comorbid chronic pain and obesity regarding their experience of comorbidity management in primary care settings.
Chronic pain and obesity are common comorbidities frequently managed in primary care settings. Evidence suggests individuals with this comorbidity may be at risk for suboptimal clinical interactions; however, treatment experiences and preferences of those with comorbid chronic pain and obesity have received little attention.
Semi-structured interviews conducted with 30 primary care patients with mean body mass index=36.8 and comorbid persistent pain. The constant comparative method was used to analyze data.
Participants discussed frustration with a perceived lack of information tailored to their needs and a desire for a personalized treatment experience. Participants found available medical approaches unsatisfying and sought a more holistic approach to management. Discussions also focused around the need for providers to initiate efforts at education and motivation enhancement and to show concern for and understanding of the unique difficulties associated with comorbidity. Findings suggest providers should engage in integrated communication regarding weight and pain, targeting this multimorbidity using methods aligned with priorities discussed by patients.
In 2011, we discovered a compact gas cloud (“G2”) with roughly three Earth masses that is falling on a near-radial orbit toward the massive black hole in the Galactic center. The orbit is well constrained and pericenter passage is predicted for early 2014. Our data beautifully show that G2 gets tidally sheared apart due to the massive black hole's force. During the next months, we expect that in addition to the tidal effects, hydrodynamics get important, when G2 collides with the hot ambient gas around Sgr A*. Simulations show that ultimately, the cloud's material might fall into the massive black hole. Predictions for the accretion rate and luminosity evolution, however, are very difficult due to the many unknowns. Nevertheless, this might be a unique opportunity in the next years to observe how gas feeds a massive black hole in a galactic nucleus.
Recently the gas and dust cloud “G2” was discovered on a highly eccentric orbit around the massive black hole in the Galactic center. The orbit will bring the cloud as close as 2400 Schwarzschild radii to Sgr A* beginning of 2014. With the help of hydrodynamical simulations using the PLUTO code, we investigate possible origins and the fate of the cloud in the coming years. In this proceedings article, we concentrate on a scenario where G2 is interpreted as a diffuse gas cloud and show its detailed evolution in the observable position-velocity diagrams. We further elaborate on the problem of the tail emission which might or might not be related to the G2 cloud.
The origin of the dense gas cloud “G2” discovered in the Galactic center (Gillessen et al. 2012) is still a debated puzzle. G2 might be a diffuse cloud or the result of an outflow from an invisible star embedded in it. We present here detailed simulations of the evolution of winds on G2's orbit. We find that the hydrodynamic interaction with the hot atmosphere present in the Galactic center and the extreme gravitational field of the supermassive black hole must be taken into account when modeling such a source scenario. We also find that in this scenario most of the Brγ luminosity is expected to come from the highly filamentary densest shocked wind material. G2's observational properties can be used to constrain the properties of the outflow and our best model has a mass outflow rate of Ṁw=8.8 × 10−8 M⊙ yr−1 and a wind velocity of vw = 50 km s−1. These values are compatible with those of a young TTauri star wind, as already suggested by Scoville & Burkert (2013).
Here we present the fundamental properties of the nuclear cluster of the Milky Way. First, we derive its structural properties by constructing a density map of the central 1000″ using extinction-corrected star counts. We can describe the data with a two-component model built from Sersic profiles. The inner nearly spherical component is the nuclear cluster. The outer, strongly flattened component can be identified with the stellar component of the circumnuclear zone. Second, we enlarge the radius inside which detailed dynamics are available from 1 pc to 4 pc. We use more than 10000 individual proper motions and more than 2700 radial velocities. We determine the cluster mass by means of isotropic spherical Jeans modeling. We get a nuclear cluster mass within 100″ of M100″=(6.11 ± 0.52|fix R0±0.97|R0) × 106 M⊙, which corresponds to a total cluster mass of MNC=(13.08 ± 2.51|fix R0± 2.08|R0) × 106 M⊙. By combination of our mass with the flux we calculate M/L=0.50 ± 0.12 M⊙/L⊙,Ks for the central 100″. That is broadly consistent with a Chabrier IMF. With its mass and a luminosity of MKs=−15.30±0.26 the nuclear cluster is a bright and massive specimen with a typical size.
Using large-scale, all-atom molecular dynamics simulations, we show that microscopic mechanisms found for molecules on the material surface of siloxane polymers can explain an important surface-hydrophobicity restoration process. In particular, a net orientation and polarization on the surface can be found which is the result of an augmented motion of certain molecules. Based on this result, surface hydrophobicity, its loss through oxidation, and its restoration through a unique interaction between cyclomethicone molecules, oxidized methyl groups, and counterions can be understood.
This article presents the use of flexible metal foam substrates for the growth of III-nitride nanowire light emitters to tackle the inherent limitations of thin-film light emitting diodes as well as fabrication and application issues of traditional substrates. A dense packing of gallium nitride nanowires were grown on a nickel foam substrate. The nanowires grew predominantly along the a-plane direction, normal to the local surface of the nickel foam. Strong luminescence was observed from undoped GaN and InGaN quantum well light emitting diode nanowires.
Today, all sailplanes in any particular class look and perform more or less the same. This gives credence to the view that the necessary compromises in design and sailplane technology have reached a limit. Sailplane development is on a sort of plateau. Further, apart from perhaps boundary-layer control (BLC), there appears to be nothing in the foreseeable future that promises any significant improvement in performance. It is the purpose of this paper to, once again, encourage interest in Variable Geometry (VG) and address the controversies which prevailed in abundance during the 1970s and which apparently still survive today.
The origin of the far-infrared emission from the nearby radio galaxy M87 remains a matter of debate. Some studies find evidence of a far-infrared excess due to thermal dust emission, whereas others propose that the far-infrared emission can be explained by synchrotron emission without the need for an additional dust emission component. We observed M87 with PACS and SPIRE as part of the Herschel Virgo Cluster Survey (HeViCS). We compare the new Herschel data with a synchrotron model based on infrared, submm and radio data to investigate the origin of the far-infrared emission. We find that both the integrated SED and the Herschel surface brightness maps are adequately explained by synchrotron emission. At odds with previous claims, we find no evidence of a diffuse dust component in M87.
Proton conductivity of yttrium-doped barium zirconate grown on MgO(100) using pulsed laser deposition (PLD) has been explored as a function of film thickness (60∼670nm) related to crystal and grain structure in the nano scale. Highly textured thin film (60nm) without significant grain separation showed high ionic conductivity close to the bulk BYZ value while thick polycrystalline samples showed lower values with clear grain and grain boundary formation.
Here we present optical beam induced current, electroluminescence, time resolved photoluminescence and current-voltage measurements on several 4H-SiC PiN diodes containing in-grown stacking faults (IGSFs). These defects were observed to act as either current shorts, creating a direct electrical contact between the p+ and n+ layers, or as a current barrier. Carrier lifetime measurements verify that the change in behavior is indeed associated with changes in the conductivity of the material in the vicinity of the defect and not due to local changes in the carrier lifetime. The IGSFs discussed here appear to differ from those previously discussed in the literature and may constitute a new, multi-layered IGSF.