42 research outputs found
Abundances and Physical Conditions in the Warm Neutral Medium Towards mu Columbae
We present ultraviolet interstellar absorption line measurements for the
sightline towards the O9.5 V star mu Columbae obtained with the Goddard High
Resolution Spectrograph (GHRS) on board the Hubble Space Telescope. These
archival data represent the most complete GHRS interstellar absorption line
measurements for any line of sight towards an early-type star. The 3.5 km/s
resolution of the instrument allow us to accurately derive the gas-phase column
densities of many important ionic species in the diffuse warm neutral medium
using a combination of apparent column density and component fitting
techniques, and we study in detail the contamination from ionized gas along
this sightline. The low-velocity material shows gas-phase abundance patterns
similar to the warm cloud (cloud A) towards the disk star zeta Oph, while the
component at v = +20.1 km/s shows gas-phase abundances similar to those found
in warm halo clouds. We find the velocity-integrated gas-phase abundances of
Zn, P, and S relative to H along this sightline are indistinguishable from
solar system abundances. We discuss the implications of our gas-phase abundance
measurements for the composition of interstellar dust. The relative ionic
column density ratios of the intermediate velocity components show the imprint
both of elemental incorporation into grains and (photo)ionization. The
components at v = -30 and -48 km/s along this sightline likely trace shocked
gas with very low hydrogen column densities. Appendices include a new
derivation of the GHRS instrumental line spread function, and a new very
accurate determination of the total H I column along this sightline. (Abridged)Comment: Accepted for publication in the Astrophysical Journal. 80 pages
including 19 embedded figures and 12 embedded tables. Version with higher
resolution figures can be downloaded from
http://fuse.pha.jhu.edu/~howk/Papers/papers.htm
Angular Momentum and the Formation of Stars and Black Holes
The formation of compact objects like stars and black holes is strongly
constrained by the requirement that nearly all of the initial angular momentum
of the diffuse material from which they form must be removed or redistributed
during the formation process. The mechanisms that may be involved and their
implications are discussed for (1) low-mass stars, most of which probably form
in binary or multiple systems; (2) massive stars, which typically form in
clusters; and (3) supermassive black holes that form in galactic nuclei. It is
suggested that in all cases, gravitational interactions with other stars or
mass concentrations in a forming system play an important role in
redistributing angular momentum and thereby enabling the formation of a compact
object. If this is true, the formation of stars and black holes must be a more
complex, dynamic, and chaotic process than in standard models. The
gravitational interactions that redistribute angular momentum tend to couple
the mass of a forming object to the mass of the system, and this may have
important implications for mass ratios in binaries, the upper stellar IMF in
clusters, and the masses of supermassive black holes in galaxies.Comment: Accepted by Reports on Progress in Physic
The Evolution of the Elemental Abundances in the Gas and Dust Phases of the Galaxy
We present models for the evolution of the elemental abundances in the gas
and dust phases of the interstellar medium (ISM) of our Galaxy by generalizing
standard models for its dynamical and chemical evolution. In these models, the
stellar birthrate history is determined by the infall rate of primordial gas,
and by its functional dependence on the mass surface density of the stars and
gas. We adopt a two component model for the Galaxy, consisting of a central
bulge and an exponential disk with different infall rates and stellar birthrate
histories. Condensation in stellar winds, Type Ia and Type II supernovae, and
the accretion of refractory elements onto preexisting grains in dense molecular
clouds are the dominant contributors to the abundance of elements locked up in
the dust. Grain destruction by sputtering and evaporative grain-grain
collisions in supernova remnants are the most important mechanisms that return
these elements back to the gas phase.
We calculate the dust production rate by the various dust sources, analyze
the origin of the elemental depletion pattern, and study the relation between
dust abundance and ISM metallicity, and the evolution of the the dust abundance
and composition at each Galactocentric radius as a function of time.
The derived relation of dust mass with metallicity is compared to the
observed Galactic dust abundance gradient, and to the M versus
log(O/H) relation that is observed in external Dwarf galaxies.
The dependence of dust composition on the mass of the progenitor star, and
the delayed recycling of newly synthesized dust by low mass stars back to the
ISM give rise to variations in the dust composition as a function of time.
Our models provide a framework for the self-consistent inclusion of dust inComment: AAS TeX manuscript - submitted to ApJ (47 pages) + 15 Figures
corrected figure file
The Mass Distribution and Rotation Curve in the Galaxy
The mass distribution in the Galaxy is determined by dynamical and
photometric methods. Rotation curves are the major tool for determining the
dynamical mass distribution in the Milky Way and spiral galaxies. The
photometric (statistical) method utilizes luminosity profiles from optical and
infrared observations, and assumes empirical values of the mass-to-luminosity
(M/L) ratio to convert the luminosity to mass. In this chapter the dynamical
method is described in detail, and rotation curves and mass distribution in the
Milky Way and nearby spiral galaxies are presented. The dynamical method is
categorized into two methods: the decomposition method and direct method. The
former fits the rotation curve by calculated curve assuming several mass
components such as a bulge, disk and halo, and adjust the dynamical parameters
of each component. Explanations are given of the mass profiles as the de
Vaucouleurs law, exponential disk, and dark halo profiles inferred from
numerical simulations. Another method is the direct method, with which the mass
distribution can be directly calculated from the data of rotation velocities
without employing any mass models. Some results from both methods are
presented, and the Galactic structure is discussed in terms of the mass.
Rotation curves and mass distributions in external galaxies are also discussed,
and the fundamental mass structures are shown to be universal.Comment: 54 pages, 25 figures, in 'Planets, Stars and Stellar Systems',
Springer, Vol. 5, ed. G. Gilmore, Chap. 19. Note: Preprint with full figures
is available from http://www.ioa.s.u-tokyo.ac.jp/~sofue/htdocs/2013psss
Systematic evaluation of immune regulation and modulation
Cancer immunotherapies are showing promising clinical results in a variety of malignancies. Monitoring the immune as well as the tumor response following these therapies has led to significant advancements in the field. Moreover, the identification and assessment of both predictive and prognostic biomarkers has become a key component to advancing these therapies. Thus, it is critical to develop systematic approaches to monitor the immune response and to interpret the data obtained from these assays. In order to address these issues and make recommendations to the field, the Society for Immunotherapy of Cancer reconvened the Immune Biomarkers Task Force. As a part of this Task Force, Working Group 3 (WG3) consisting of multidisciplinary experts from industry, academia, and government focused on the systematic assessment of immune regulation and modulation. In this review, the tumor microenvironment, microbiome, bone marrow, and adoptively transferred T cells will be used as examples to discuss the type and timing of sample collection. In addition, potential types of measurements, assays, and analyses will be discussed for each sample. Specifically, these recommendations will focus on the unique collection and assay requirements for the analysis of various samples as well as the high-throughput assays to evaluate potential biomarkers
Recommended from our members
HIV efficiently infects T cells from the endometrium and remodels them to promote systemic viral spread.
The female reproductive tract (FRT) is the most common site of infection during HIV transmission to women, but viral remodeling complicates characterization of cells targeted for infection. Here, we report extensive phenotypic analyses of HIV-infected endometrial cells by CyTOF, and use a 'nearest neighbor' bioinformatics approach to trace cells to their original pre-infection phenotypes. Like in blood, HIV preferentially targets memory CD4+ T cells in the endometrium, but these cells exhibit unique phenotypes and sustain much higher levels of infection. Genital cell remodeling by HIV includes downregulating TCR complex components and modulating chemokine receptor expression to promote dissemination of infected cells to lymphoid follicles. HIV also upregulates the anti-apoptotic protein BIRC5, which when blocked promotes death of infected endometrial cells. These results suggest that HIV remodels genital T cells to prolong viability and promote viral dissemination and that interfering with these processes might reduce the likelihood of systemic viral spread
Recommended from our members
HIV efficiently infects T cells from the endometrium and remodels them to promote systemic viral spread.
The female reproductive tract (FRT) is the most common site of infection during HIV transmission to women, but viral remodeling complicates characterization of cells targeted for infection. Here, we report extensive phenotypic analyses of HIV-infected endometrial cells by CyTOF, and use a 'nearest neighbor' bioinformatics approach to trace cells to their original pre-infection phenotypes. Like in blood, HIV preferentially targets memory CD4+ T cells in the endometrium, but these cells exhibit unique phenotypes and sustain much higher levels of infection. Genital cell remodeling by HIV includes downregulating TCR complex components and modulating chemokine receptor expression to promote dissemination of infected cells to lymphoid follicles. HIV also upregulates the anti-apoptotic protein BIRC5, which when blocked promotes death of infected endometrial cells. These results suggest that HIV remodels genital T cells to prolong viability and promote viral dissemination and that interfering with these processes might reduce the likelihood of systemic viral spread