2,501 research outputs found
Association between genotypic diversity and biofilm production in group B Streptococcus
Background:
Group B Streptococcus (GBS) is a leading cause of sepsis and meningitis and an important factor in premature and stillbirths. Biofilm production has been suggested to be important for GBS pathogenesis alongside many other elements, including phylogenetic lineage and virulence factors, such as pili and capsule type. A complete understanding of the confluence of these components, however, is lacking. To identify associations between biofilm phenotype, pilus profile and lineage, 293 strains from asymptomatic carriers, invasive disease cases, and bovine mastitis cases, were assessed for biofilm production using an in vitro assay.
Results:
Multilocus sequence type (ST) profile, pilus island profile, and isolate source were associated with biofilm production. Strains from invasive disease cases and/or belonging to the ST-17 and ST-19 lineages were significantly more likely to form weak biofilms, whereas strains producing strong biofilms were recovered more frequently from individuals with asymptomatic colonization.
Conclusions:
These data suggest that biofilm production is a lineage-specific trait in GBS and may promote colonization of strains representing lineages other than STs 17 and 19. The findings herein also demonstrate that biofilms must be considered in the treatment of pregnant women, particularly for women with heavy GBS colonization
The Asymmetric Thick Disk: A Star Count and Kinematic Analysis. II The Kinematics
We report a kinematic signature associated with the observed asymmetry in the
distribution of thick disk/inner halo stars interior to the Solar circle
described in Paper I. In that paper we found a statistically significant excess
(20% to 25 %) of stars in quadrant I (l ~ 20 deg to 55 deg) both above and
below the plane (b ~ +/- 25 deg to +/- 45 deg) compared to the complementary
region in quadrant IV. We have measured Doppler velocities for 741 stars,
selected according to the same magnitude and color criteria, in the direction
of the asymmetry and in the corresponding fields in quadrant IV. We have also
determined spectral types and metallicities measured from the same spectra. We
not only find an asymmetric distribution in the V_LSR velocities for the stars
in the two regions, but the angular rate of rotation, w, for the stars in
quadrant I reveals a slower effective rotation rate compared to the
corresponding quadrant IV stars. We use our [Fe/H] measurements to separate the
stars into the three primary population groups, halo, thick disk, and disk, and
conclude that it is primarily the thick disk stars that show the slower
rotation in quadrant I. A solution for the radial, tangential and vertical
components of the V_LSR velocities, reveals a significant lag of ~ 80 to 90
km/s in the direction of Galactic rotation for the thick disk stars in quadrant
I, while in quadrant IV, the same population has only a ~ 20 km/s lag. The
results reported here support a rotational lag among the thick disk stars due
to a gravitational interaction with the bar as the most likely explanation for
the asymmetry in both the star counts and the kinematics. The affected thick
disk stars, however, may be associated with the recently discovered Canis Major
debris stream or a similar merger event (abridged).Comment: Accepted for publication in the Astronomical Journa
Feminization of Male Brown Treesnake Methyl Ketone Expression via Steroid Hormone Manipulation
Pheromones are useful tools for the management of invasive invertebrates, but have proven less successful in field applications for invasive vertebrates. The brown treesnake, Boiga irregularis, is an invasive predator that has fundamentally altered the ecology of Guam. The development of control tools to manage Boiga remains ongoing. Skin-based, lipophilic pheromone components facilitate mating in brown treesnakes, with females producing the same long-chain, saturated and monounsaturated (ketomonoene) methyl ketones known to function as pheromones in garter snakes, Thamnophis sirtalis. Boiga also express novel, diunsaturated methyl ketones (ketodienes) with a purported function as a sex pheromone. In our study, we implanted 17 β- estradiol in adult male brown treesnakes in order to manipulate methyl ketone expression as sex attractants, an effect that would mirror findings with garter snakes. Specifically, estrogen promoted production of two ketomonoenes, pentatriaconten-2-one and hexatriaconten-2-one, and suppressed production of one ketodiene, heptatriacontadien-2-one. In bioassays, estrogen-implanted males elicited tongue-flicking and chin rubbing behavior from unmanipulated males, though the responses were weaker than those elicited by females. On Guam, wild males exhibited greatest responses to whole female skin lipid extracts and only weak responses to the methyl ketone fractions from females and implanted males. Our results suggest that sex identity in brown treesnakes may be conferred by the ratio of ketomonoenes (female) to ketodienes (male) from skin lipids and may be augmented by a sex-specific endocrine signal (estradiol). However, a blend of long-chain methyl ketones alone is not sufficient to elicit maximal reproductive behaviors in male Boiga
Use and Protection of GPS Sidelobe Signals for Enhanced Navigation Performance in High Earth Orbit
The application of the Global Positioning System (GPS) for navigation of spacecraft in High and Geosynchronous Earth Orbit (HEO/GEO) has crossed a threshold and is now being employed in operational missions. Utilizing advanced GPS receivers optimized for these missions, space users have made extensive use of the sidelobe transmissions from the GPS satellites to realize navigation performance that far exceeds that predicted by pre-launch simulations. Unfortunately, the official specification for the GPS Space Service Volume (SSV), developed in 2006, assumes that only signals emanating from the main beam of the GPS transmit antenna are useful for navigation, which greatly under-estimates the number of signals available for navigation purposes. As a result, future high-altitude space users may be vulnerable to any GPS design changes that suppress the sidelobe transmissions, beginning with Block III space vehicles (SVs) 11-32. This paper presents proposed changes to the GPS system SSV requirements, as informed by data from recent experiments in the SSV and new mission applications that are enabled by GPS navigation in HEO/GEO regimes. The NASA/NOAA GOES-R series satellites are highlighted as an example of a mission that relies on this currently-unspecified GPS system performance to meet mission requirements
Characterization of On-Orbit GPS Transmit Antenna Patterns for Space Users
The GPS Antenna Characterization Experiment (GPS ACE) has made extensive observations of GPS L1 signals received at geosynchronous (GEO) altitude, with the objective of developing comprehensive models of the signal levels and signal performance in the GPS transmit antenna side lobes. The experiment was originally motivated by the fact that data on the characteristics and performance of the GPS signals available in GEO and other high Earth orbits was limited. The lack of knowledge of the power and accuracy of the side lobe signals on-orbit added risk to missions seeking to employ the side lobes to meet navigation requirements or improve performance. The GPS ACE Project lled that knowledge gap through a collaboration between The Aerospace Corporation and NASA Goddard Space Fight Center to collect and analyze observations from GPS side lobe transmissions to a satellite at GEO using a highly-sensitive GPS receiver installed at the ground station. The GPS ACE architecture has been in place collecting observations of the GPS constellation with extreme sensitivity for several years. This sensitivity combined with around-the-clock, all-in-view processing enabled full azimuthal coverage of the GPS transmit gain patterns over time to angles beyond 90 degrees off-boresight. Results discussed in this paper include the reconstructed transmit gain patterns, with comparisons to available pre-fight gain measurements from the GPS vehicle contractors. For GPS blocks with extensive ground measurements, the GPS ACE results show remarkable agreement with ground based measurements. For blocks without extensive ground measurements, the GPS ACE results provide the only existing assessments of the full transmit gain patterns. The paper also includes results of pseudorange deviation analysis to assess systematic errors associated with GPS side lobe signals
Comparison of Quarterly and Yearly Calibration Data for Propensity Score Adjusted Web Survey Estimates
While web surveys have become increasingly popular as a method of data collection, there is
concern that estimates obtained from web surveys may not reflect the target population of interest.
Web survey estimates can be calibrated to existing national surveys using a propensity score
adjustment, although requirements for the size and collection timeline of the reference data set
have not been investigated. We evaluate health outcomes estimates from the National Center for
Health Statistics’ Research and Development web survey. In our study, the 2016 National Health
Interview Survey as well as its quarterly subsets are considered as reference datasets for the web
data. It is demonstrated that the calibrated health estimates overall vary little when using the
quarterly or yearly data, suggesting that there is flexibility in selecting the reference dataset. This
finding has many practical implications for constructing reference data, including the reduced cost
and burden of a smaller sample size and a more flexible timeline
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Leaving Congress: House of Representatives and Senate Departures Data Since 198
Members of Congress leave the House or Senate for a variety of reasons; these may include resignation, death, or chamber action during a Congress, and retirement, electoral defeat, or pursuit of another office at the end of a Congress. This report discusses the number of Senators and Members of the House of Representatives who have left before the conclusion of a Congress since 1989
Factors associated with parents’ experiences using a knowledge translation tool for vaccination pain management: a qualitative study
Background: Vaccination is a common painful procedure for children. Parents’ concern regarding vaccination pain is a significant driver of vaccine hesitancy. Despite the wealth of evidence-based practices available for managing vaccination pain, parents lack knowledge of, and access to, these strategies. Knowledge translation (KT) tools can communicate evidence-based information to parents, however little is known about what factors influence parents’ use of these tools. A two-page, electronic KT tool on psychological, physical, and pharmacological vaccination pain management strategies for children, was shared with parents as part of a larger mixed methods study, using explanatory sequential design, exploring factors related to uptake of this KT tool. The aim of this qualitative study was to understand what influenced parents’ perceptions of the relevance of the KT tool, as well as their decision as to whether to use the tool. Methods: A qualitative descriptive design was used. A total of 20 parents of children aged 0–17 years (n = 19 mothers) reviewed the KT tool ahead of their child’s upcoming vaccination and participated in a semi-structured interview at follow-up. Interviews were recorded, transcribed verbatim, and analyzed with reflexive thematic analysis using an inductive approach. Results: The analysis generated three interrelated themes which described factors related to parents’ use of the KT tool: (1) Relevance to parents’ needs and circumstances surrounding their child’s vaccination; (2) Alignment with parents’ personal values around, and experiences with, vaccination pain management (e.g., the importance of managing pain); and (3) Support from the clinical environment for implementing evidence-based strategies (e.g., physical clinical environment and quality of interactions with the health care provider). Conclusions: Several factors were identified as central to parents’ use of the KT tool, including the information itself and the clinical environment. When the tool was perceived as relevant, aligned with parents’ values, and was supported by health care providers, parents were more inclined to use the KT tool to manage their children’s vaccination pain. Future research could explore other factors related to promoting engagement and uptake when creating parent-directed KT tools for a range of health-related contexts
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