1,353 research outputs found
Diffuse Atomic and Molecular Gas in the Interstellar Medium of M82 toward SN 2014J
We present a comprehensive analysis of interstellar absorption lines seen in
moderately-high resolution, high signal-to-noise ratio optical spectra of SN
2014J in M82. Our observations were acquired over the course of six nights,
covering the period from ~6 days before to ~30 days after the supernova reached
its maximum B-band brightness. We examine complex absorption from Na I, Ca II,
K I, Ca I, CH+, CH, and CN, arising primarily from diffuse gas in the
interstellar medium (ISM) of M82. We detect Li I absorption over a range in
velocity consistent with that exhibited by the strongest Na I and K I
components associated with M82; this is the first detection of interstellar Li
in a galaxy outside of the Local Group. There are no significant temporal
variations in the absorption-line profiles over the 37 days sampled by our
observations. The relative abundances of the various interstellar species
detected reveal that the ISM of M82 probed by SN 2014J consists of a mixture of
diffuse atomic and molecular clouds characterized by a wide range of
physical/environmental conditions. Decreasing N(Na I)/N(Ca II) ratios and
increasing N(Ca I)/N(K I) ratios with increasing velocity are indicative of
reduced depletion in the higher-velocity material. Significant
component-to-component scatter in the N(Na I)/N(Ca II) and N(Ca I)/N(Ca II)
ratios may be due to variations in the local ionization conditions. An apparent
anti-correlation between the N(CH+)/N(CH) and N(Ca I)/N(Ca II) ratios can be
understood in terms of an opposite dependence on gas density and radiation
field strength, while the overall high CH+ abundance may be indicative of
enhanced turbulence in the ISM of M82. The Li abundance also seems to be
enhanced in M82, which supports the conclusions of recent gamma-ray emission
studies that the cosmic-ray acceleration processes are greatly enhanced in this
starburst galaxy.Comment: 32 pages, 6 figures, accepted to ApJ; added table giving single-epoch
equivalent widths; improved discussion regarding the lack of temporal
variations; improved analysis of the Li I regio
Mitigating uncertainty using alternative information sources and expert judgement in aquatic non-indigenous species risk assessment
Aquatic non-indigenous species (ANS) management employs risk assessment as a tool to prioritize prevention and control efforts, but timely and comprehensive risk estimates are difficult due to various sources of uncertainty, particularly knowledge gaps. Several fields use or endorse the use of precaution, as well as group Delphic processes, to mitigate this uncertainty. To test the application of these methods in ANS risk assessment, we surveyed the knowledge and attitudes held by ANS scientists and managers regarding uncertainty and involved these experts in a modified Delphic process to determine consequence for a suite of 10 ANS. We found that participants supported the application of precaution in risk assessments. We also found the Delphic process aided the risk assessment process by facilitating outcomes that are supported by experts and stakeholders involved, account for uncertainty, and are therefore useful for policy and management purposes. Finally, we provide several recommendations for mitigating uncertainty in consequence assessments. These outcomes and recommendations provide increased understanding of the presence and sources of uncertainty, and the potential use of precaution and Delphic processes to facilitate the completion of comprehensive biosecurity risk assessments, despite the challenges posed by existing knowledge gaps in ANS impact information
Knowledge About the Human Papillomavirus Vaccine Among Employees at a Tertiary Cancer Center: Room for Improvement
Introduction: The human papillomavirus (HPV) vaccine is recommended by the U.S. Centers for Disease Control and Prevention for routine vaccination of boys and girls to protect against HPV-related cancers and genital warts. To meet the Healthy People 2020 target for HPV vaccination, health care providers must understand the importance of strongly recommending the HPV vaccine to all eligible adolescents. We sought to determine HPV vaccination patterns among employees at a tertiary cancer center and their children and attitudes regarding HPV vaccination among the employees.
Methods: All employees at a tertiary cancer center were invited to participate in a cross-sectional survey administered online during July and August 2015. The survey included questions about HPV vaccination of participants and their children, including reasons why vaccine-eligible employees and children had not been vaccinated.
Results: Of those eligible, 13% of male and 33% of female employees and 44% of daughters and 24% of sons of employees had completed the vaccine series. The main reasons for not completing the series or not having one’s son completing the series were not knowing that the vaccine was needed and vaccine not recommended by a health care provider. The main reasons for not having one’s daughter complete the series were the two aforementioned reasons and daughter not yet sexually active.
Conclusion: Opportunities exist to educate health care workers about the benefits of the HPV vaccine and to increase the number of providers who recommend HPV vaccination to their patients
Spectral signature of short attosecond pulse trains
We report experimental measurements of high-order harmonic spectra generated
in Ar using a carrier-envelope-offset (CEO) stabilized 12 fs, 800nm laser field
and a fraction (less than 10%) of its second harmonic. Additional spectral
peaks are observed between the harmonic peaks, which are due to interferences
between multiple pulses in the train. The position of these peaks varies with
the CEO and their number is directly related to the number of pulses in the
train. An analytical model, as well as numerical simulations, support our
interpretation
The Inhibitory Site of a Diguanylate Cyclase Is a Necessary Element for Interaction and Signaling with an Effector Protein
Many bacteria contain large cyclic diguanylate (c-di-GMP) signaling networks made of diguanylate cyclases (DGCs) and phosphodiesterases that can direct cellular activities sensitive to c-di-GMP levels. While DGCs synthesize c-di-GMP, many DGCs also contain an autoinhibitory site (I-site) that binds c-di-GMP to halt excess production of this small molecule, thus controlling the amount of c-di-GMP available to bind to target proteins in the cell. Many DGCs studied to date have also been found to signal for a specific c-di-GMP-related process, and although recent studies have suggested that physical interaction between DGCs and target proteins may provide this signaling fidelity, the importance of the I-site has not yet been incorporated into this model. Our results from Pseudomonas fluorescens indicate that mutation of residues at the I-site of a DGC disrupts the interaction with its target receptor. By creating various substitutions to a DGC\u27s I-site, we show that signaling between a DGC (GcbC) and its target protein (LapD) is a combined function of the I-site-dependent protein-protein interaction and the level of c-di-GMP production. The dual role of the I-site in modulating DGC activity as well as participating in protein-protein interactions suggests caution in interpreting the function of the I-site as only a means to negatively regulate a cyclase. These results implicate the I-site as an important positive and negative regulatory element of DGCs that may contribute to signaling specificity
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