3,286 research outputs found
Tuning the Clock: Uranium and Thorium Chronometers Applied to CS 31082-001
We obtain age estimates for the progenitor(s) of the extremely metal-poor
([Fe/H = -2.9) halo star CS 31082-001, based on the recently reported first
observation of a Uranium abundance in this (or any other) star. Age estimates
are derived by application of the classical r-process model with updated
nuclear physics inputs. The [U/Th] ratio yields an age of 13+-4 Gyr or 8+-4
Gyr, based on the use of the ETFSI-Q or the new HFBCS-1 nuclear mass models,
respectively. Implications for Thorium chronometers are discussed.Comment: 5 pages incl. 1 figure, a shorter 3 page version will be published in
the proceedings of the "Astrophysical Ages and Timescales" conference held in
Hilo, Hawaii, Feb 5-9, 200
A Comprehensive Audit of Professional Development for K-12 School Leaders in the Commonwealth of Virginia
The intent of this paper is to provide a mixed-methods audit of professional development provided to K-12 school leadership in Virginia\u27s diverse landscape to include identification of providers, funding, effectiveness, and expectations.
In the Commonwealth of Virginia, geographical, political, and socio-economical differences across 132 school divisions cause variability in leaders\u27 experiences with professional development. A mixed-methods approach was used, including a review of current literature, an online survey, virtual interviews, and virtual focus group discussions. This data collection results in a comprehensive audit of professional development provided to school leaders in Virginia\u27s diverse landscape. The study defines effective professional development for school leaders and considers commonalities and disparities of school leaders\u27 experience with professional development, including divisions\u27 commitment to funding, leaders’ access to providers, and leaders’ exposure to traditional and emerging content topics in order to provide recommendations to Virginia Commonwealth University\u27s School of Education as an external provider of professional development for school leaders
Identification of a Novel 0.7-kb Polyadenylated Transcript in the LAT Promoter Region of HSV-1 That Is Strain Specific and May Contribute to Virulence
AbstractHerpes Simplex virus expresses latency-associated transcripts (LATs) the function of which remains obscure despite increasing knowledge of their structure and expression. Upstream of the LAT coding region is a region of the genome that is poorly characterized although it lies in an area that is responsible for modulation of reactivation efficiency in two different animal models. Transcript mapping with strains 17, McKrae, KOS, and F has revealed strain differences in this region of the viral genome. Strain 17 and McKrae expressed a novel polyadenylated 0.7-kb transcript that is absent from KOS and F. This transcript is expressed in the LAT direction and has the kinetics of a true late gene during the lytic cycle of infection. A deletion mutant, 17ΔBsa, which does not express the 0.7-kb RNA, is less virulent than the parental strain 17. A rescuant with F sequence (17ΔBsa/RF) shows virulence similar to F, whereas a rescuant with strain 17 sequence (17ΔBsa/R17) is similar to strain 17. Virulence is altered by deletion or substitution in the region encoding the 0.7-kb transcript (BsaI-BsaI); however, reactivation in the mouse explant cocultivation assay or the adrenergically induced rabbit reactivation model remained unchanged. The importance of this region for virulence is discussed
Directly Imaged L-T Transition Exoplanets in the Mid-Infrared
Gas-giant planets emit a large fraction of their light in the mid-infrared
(3m), where photometry and spectroscopy are critical to our
understanding of the bulk properties of extrasolar planets. Of particular
importance are the L and M-band atmospheric windows (3-5m), which are the
longest wavelengths currently accessible to ground-based, high-contrast
imagers. We present binocular LBT AO images of the HR 8799 planetary system in
six narrow-band filters from 3-4m, and a Magellan AO image of the 2M1207
planetary system in a broader 3.3m band. These systems encompass the five
known exoplanets with luminosities consistent with LT transition
brown dwarfs. Our results show that the exoplanets are brighter and have
shallower spectral slopes than equivalent temperature brown dwarfs in a
wavelength range that contains the methane fundamental absorption feature
(spanned by the narrowband filters and encompassed by the broader 3.3m
filter). For 2M1207 b, we find that thick clouds and non-equilibrium chemistry
caused by vertical mixing can explain the object's appearance. For the HR 8799
planets, we present new models that suggest the atmospheres must have patchy
clouds, along with non-equilibrium chemistry. Together, the presence of a
heterogeneous surface and vertical mixing presents a picture of dynamic
planetary atmospheres in which both horizontal and vertical motions influence
the chemical and condensate profiles.Comment: Accepted to Ap
AMCIS 2006 Panel Report: The Web as a Digital Reflection of Reality
The web is increasingly relied upon as a reflection of reality, which raises a number of key issues not yet fully recognized or articulated, warranting further study. This new digital reality and the unprecedented capabilities it embodies in terms of searchability, aggregatability, temporal persistence, and so on, give rise to great challenges in the areas of Digital Identity Management, Social Impacts, Currency and Accuracy of Digital Data, Distorting Factors, Legal Issues and Implications, among others, that are only just becoming recognized and articulated. This paper reports on a panel exploring these issues and speculating creatively on how they might be addressed in IS academic research by adopting a fundamental information processing approach to design, incorporating analogs from evolutionary biology, for example
Does the Debris Disk around HD 32297 Contain Cometary Grains?
We present an adaptive optics imaging detection of the HD 32297 debris disk
at L' (3.8 \microns) obtained with the LBTI/LMIRcam infrared instrument at the
LBT. The disk is detected at signal-to-noise per resolution element ~ 3-7.5
from ~ 0.3-1.1" (30-120 AU). The disk at L' is bowed, as was seen at shorter
wavelengths. This likely indicates the disk is not perfectly edge-on and
contains highly forward scattering grains. Interior to ~ 50 AU, the surface
brightness at L' rises sharply on both sides of the disk, which was also
previously seen at Ks band. This evidence together points to the disk
containing a second inner component located at 50 AU. Comparing the
color of the outer (50 /AU ) portion of the disk at L' with
archival HST/NICMOS images of the disk at 1-2 \microns allows us to test the
recently proposed cometary grains model of Donaldson et al. 2013. We find that
the model fails to match the disk's surface brightness and spectrum
simultaneously (reduced chi-square = 17.9). When we modify the density
distribution of the model disk, we obtain a better overall fit (reduced
chi-square = 2.9). The best fit to all of the data is a pure water ice model
(reduced chi-square = 1.06), but additional resolved imaging at 3.1 \microns is
necessary to constrain how much (if any) water ice exists in the disk, which
can then help refine the originally proposed cometary grains model.Comment: Accepted to ApJ January 13, 2014. 12 pages (emulateapj style), 9
figures, 1 tabl
Border patrol gone awry: Lung NKT cell activation by Francisella tularensis exacerbates tularemia-like disease
The respiratory mucosa is a major site for pathogen invasion and, hence, a site requiring constant immune surveillance. The type I, semi-invariant natural killer T (NKT) cells are enriched within the lung vasculature. Despite optimal positioning, the role of NKT cells in respiratory infectious diseases remains poorly understood. Hence, we assessed their function in a murine model of pulmonary tularemia--because tularemia is a sepsis-like proinflammatory disease and NKT cells are known to control the cellular and humoral responses underlying sepsis. Here we show for the first time that respiratory infection with Francisella tularensis live vaccine strain resulted in rapid accumulation of NKT cells within the lung interstitium. Activated NKT cells produced interferon-γ and promoted both local and systemic proinflammatory responses. Consistent with these results, NKT cell-deficient mice showed reduced inflammatory cytokine and chemokine response yet they survived the infection better than their wild type counterparts. Strikingly, NKT cell-deficient mice had increased lymphocytic infiltration in the lungs that organized into tertiary lymphoid structures resembling induced bronchus-associated lymphoid tissue (iBALT) at the peak of infection. Thus, NKT cell activation by F. tularensis infection hampers iBALT formation and promotes a systemic proinflammatory response, which exacerbates severe pulmonary tularemia-like disease in mice
Patient prioritization of comorbid chronic conditions in the Veteran population: Implications for patient-centered care
OBJECTIVE: Patients with comorbid chronic conditions may prioritize some conditions over others; however, our understanding of factors influencing those prioritizations is limited. In this study, we sought to identify and elaborate a range of factors that influence how and why patients with comorbid chronic conditions prioritize their conditions.
METHODS: We conducted semi-structured, one-on-one interviews with 33 patients with comorbidities recruited from a single Veterans Health Administration Medical Center.
FINDINGS: The diverse factors influencing condition prioritization reflected three overarching themes: (1) the perceived role of a condition in the body, (2) self-management tasks, and (3) pain. In addition to these themes, participants described the rankings that they believed their healthcare providers would assign to their conditions as an influencing factor, although few reported having shared their priorities or explicitly talking with providers about the importance of their conditions.
CONCLUSION: Studies that advance understanding of how and why patients prioritize their various conditions are essential to providing care that is patient-centered, reflecting what matters most to the individual while improving their health. This analysis informs guideline development efforts for the care of patients with comorbid chronic conditions as well as the creation of tools to promote patient-provider communication regarding the importance placed on different conditions
Synthetic High-Resolution Line Spectra of Star-Forming Galaxies Below 1200A
We have generated a set of far-ultraviolet stellar libraries using spectra of
OB and Wolf-Rayet stars in the Galaxy and the Large and Small Magellanic Cloud.
The spectra were collected with the Far Ultraviolet Spectroscopic Explorer and
cover a wavelength range from 1003.1 to 1182.7A at a resolution of 0.127A. The
libraries extend from the earliest O- to late-O and early-B stars for the
Magellanic Cloud and Galactic libraries, respectively. Attention is paid to the
complex blending of stellar and interstellar lines, which can be significant,
especially in models using Galactic stars. The most severe contamination is due
to molecular hydrogen. Using a simple model for the H line strength, we
were able to remove the molecular hydrogen lines in a subset of Magellanic
Cloud stars. Variations of the photospheric and wind features of CIII 1176, OVI
1032, 1038, PV 1118, 1128, and SIV 1063, 1073, 1074 are discussed as a function
of temperature and luminosity class. The spectral libraries were implemented
into the LavalSB and Starburst99 packages and used to compute a standard set of
synthetic spectra of star-forming galaxies. Representative spectra are
presented for various initial mass functions and star formation histories. The
valid parameter space is confined to the youngest ages of less than 10 Myr for
an instantaneous burst, prior to the age when incompleteness of spectral types
in the libraries sets in. For a continuous burst at solar metallicity, the
parameter space is not limited. The suite of models is useful for interpreting
the restframe far-ultraviolet in local and high-redshift galaxies.Comment: 33 pages including 13 figures, accepted for publication in Ap
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