Observations of Small Scale ISM Structure in Dense Atomic Gas

We present high resolution (R~170,000) Kitt Peak National Observatory Co'ude Feed telescope observations of the interstellar KI 7698 angstrom line towards 5 multiple star systems with saturated NaI components. We compare the KI absorption line profiles in each of the two (or three) lines of sight in these systems, and find significant differences between the sight-lines in 3 out of the 5 cases. We infer that the small scale structure traced by previous NaI observations is also present in at least some of the components with saturated NaI absorption lines, and thus the small scale structures traced by the neutral species are occurring at some level in clouds of all column densities. We discuss the implications of that conclusion and a potential explanation by density inhomogeneities

Low-Metallicity Gas Clouds in a Galaxy Proto-Cluster at Redshift 2.38

We present high resolution spectroscopy of a QSO whose sight-line passes through the halo of a pair of elliptical galaxies at redshift 2.38. This pair of galaxies probably lies at the center of a galaxy proto-cluster, and is embedded in a luminous extended Ly-alpha nebula. The QSO sight-line intersects two small gas clouds within this halo. These clouds have properties similar to those of high velocity clouds (HVCs) seen in the halo of the Milky Way. The gas is in a cool (< 2 x 10^4 K) and at least 20% neutral phase, with metallicities in the range -3.0 < [Fe/H] < -1.1 and neutral hydrogen column densities of ~10^19.5 /cm^2. The origin of these clouds is unclear. The presence of low metallicity gas within this possible proto-cluster implies either that the intra-cluster medium has not been enriched with metals at this redshift, or the clouds are embedded within a hot, ionized, metal-rich gas phase.Comment: Accepted to appear in ApJ Letter

Small-Scale Interstellar Na I Structure Toward M92

We have used integral field echelle spectroscopy with the DensePak fiber-optic array on the KPNO WIYN telescope to observe the central 27" x 43" of the globular cluster M92 in the Na I D wavelength region at a spatial resolution of 4". Two interstellar Na I absorption components are evident in the spectra at LSR velocities of 0 km/s (Cloud 1) and -19 km/s (Cloud 2). Substantial strength variations in both components are apparent down to scales limited by the fiber-to-fiber separations. The derived Na I column densities differ by a factor of 4 across the Cloud 1 absorption map and by a factor of 7 across the Cloud 2 map. Using distance upper limits of 400 and 800 pc for Cloud 1 and Cloud 2, respectively, the absorption maps indicate structure in the ISM down to scales of 1600 and 3200 AU. The fiber-to-fiber Na I column density differences toward M92 are comparable to those found in a similar study of the ISM toward the globular cluster M15. Overall, the structures in the interstellar components toward M92 have significantly lower column densities than those toward M15. We interpret these low column density structures as small-scale turbulent variations in the gas and compare them to the larger-scale, higher column density variations toward M15, which may be the hallmarks of actual H I structures.Comment: 9 pages, 2 figures, accepted for publication in ApJ Letter

New Observations of the Interstellar Medium in the Lyman Break Galaxy MS 1512-cB58

We present the results of a detailed study of the interstellar medium of MS 1512-cB58, an L* Lyman break galaxy at z = 2.7276, based on new spectral observations obtained with the Echelle Spectrograph and Imager on the Keck II telescope at 58 km/s resolution. We focus in particular on the chemical abundances and kinematics of the interstellar gas and our main findings are as follows. Even at this relatively early epoch, the ISM of this galaxy is already highly enriched in elements released by Type II supernovae; the abundances of O, Mg, Si, P, and S are all about 2/5 of their solar values. In contrast, N and the Fe-peak elements Mn, Fe, and Ni are underabundant by a factor of about 3. Based on current ideas of stellar nucleosynthesis, these results can be understood if most of the metal enrichment in cB58 has taken place within the last 300 million years, the timescale for the release of N from intermediate mass stars. cB58 appears to be an example of a galaxy in the process of converting its gas into stars on a few dynamical timescales; quite possibly we are witnessing the formation of a galactic bulge or an elliptical galaxy. The energetic star formation activity has stirred the interstellar medium to high velocities of up to 1000 km/s. The net effect is a bulk outflow of the ISM at a speed of 255 km/s and at a rate which exceeds the star formation rate. It is unclear whether this gas will be lost or retained by the galaxy. We point out that the chemical and kinematic properties of cB58 are markedly different from those of most damped Lyman alpha systems at the same redshift.Comment: 38 pages, LaTeX, 9 Postscript Figures. Accepted for publication in the Astrophysical Journal. Sections 3.3 and 5.3 expanded, and two additional figures included, following referee's repor

VALID: A perceptually validated Virtual Avatar Library for Inclusion and Diversity

As consumer adoption of immersive technologies grows, virtual avatars will play a prominent role in the future of social computing. However, as people begin to interact more frequently through virtual avatars, it is important to ensure that the research community has validated tools to evaluate the effects and consequences of such technologies. We present the first iteration of a new, freely available 3D avatar library called the Virtual Avatar Library for Inclusion and Diversity (VALID), which includes 210 fully rigged avatars with a focus on advancing racial diversity and inclusion. We present a detailed process for creating, iterating, and validating avatars of diversity. Through a large online study (n=132) with participants from 33 countries, we provide statistically validated labels for each avatar's perceived race and gender. Through our validation study, we also advance knowledge pertaining to the perception of an avatar's race. In particular, we found that avatars of some races were more accurately identified by participants of the same race

Electronic tuning and uniform superconductivity in CeCoIn5

We report a globally reversible effect of electronic tuning on the magnetic phase diagram in CeCoIn_{5} driven by electron (Pt and Sn) and hole (Cd, Hg) doping. Consequently, we are able to extract the superconducting pair breaking component for hole and electron dopants with pressure and co-doping studies, respectively. We find that these nominally non-magnetic dopants have a remarkably weak pair breaking effect for a d-wave superconductor. The pair breaking is weaker for hole dopants, which induce magnetic moments, than for electron dopants. Furthermore, both Pt and Sn doping have a similar effect on superconductivity despite being on different dopant sites, arguing against the notion that superconductivity lives predominantly in the CeIn_{3} planes of these materials. In addition, we shed qualitative understanding on the doping dependence with density functional theory calculations.Comment: Accepted for publication in Phys. Rev. Lett. (October 1, 2012

Threading Through Macrocycles Enhances the Performance of Carbon Nanotubes as Polymer Fillers

In this work we study the reinforcement of polymers by mechanically interlocked derivatives of single-walled carbon nanotubes (SWNTs). We compare the mechanical properties of fibers made of polymers and of composites with pristine single-walled carbon nanotubes (SWNTs), mechanically interlocked derivatives of SWNTs (MINTs) and the corresponding supramolecular models. Improvements of both Young's modulus and tensile strength of up to 200 % were observed for the polystyrene-MINTs samples with an optimized loading of just 0.01 wt.%, while the supramolecular models with identical chemical composition and loading showed negligible or even detrimental influence. This behavior is found for three different types of SWNTs and two types of macrocycles. Molecular dynamics simulations show that the polymer adopts an elongated conformation parallel to the SWNT when interacting with MINT fillers, irrespective of the macrocycle chemical nature, whereas a more globular structure is taken upon facing with either pristine SWNTs or supramolecular models. The MINT composite architecture thus leads to a more efficient exploitation of the axial properties of the SWNTs and of the polymer chain at the interface, in agreement with experimental results. Our findings demonstrate that the mechanical bond imparts distinctive advantageous properties to SWNT derivatives as polymer fillers.Comment: 39 pages, 19 figure

Moving beyond convergence in the pheromone system of the moth

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