291 research outputs found
An evolvable space telescope for future astronomical missions
Astronomical flagship missions after JWST will require affordable space telescopes and science instruments. Innovative spacecraft-electro-opto-mechanical system architectures matched to the science requirements are needed for observations for exoplanet characterization, cosmology, dark energy, galactic evolution formation of stars and planets, and many other research areas. The needs and requirements to perform this science will continue to drive us toward larger and larger apertures. Recent technology developments in precision station keeping of spacecraft, interplanetary transfer orbits, wavefront/sensing and control, laser engineering, macroscopic application of nano-technology, lossless optical designs, deployed structures, thermal management, interferometry, detectors and signal processing enable innovative telescope/system architectures with break-through performance. Unfortunately, NASAâs budget for Astrophysics is unlikely to be able to support the funding required for the 8 m to 16 m telescopes that have been studied as a follow-on to JWST using similar development/assembly approaches without decimating the rest of the Astrophysics Divisionâs budget. Consequently, we have been examining the feasibility of developing an âEvolvable Space Telescopeâ that would begin as a 3 to 4 m telescope when placed on orbit and then periodically be augmented with additional mirror segments, structures, and newer instruments to evolve the telescope and achieve the performance of a 16 m or larger space telescope. This paper reviews the approach for such a mission and identifies and discusses candidate architectures
An evolvable space telescope for future astronomical missions 2015 update
In 2014 we presented a concept for an Evolvable Space Telescope (EST) that was assembled on orbit in 3 stages, growing from a 4x12 meter telescope in Stage 1, to a 12-meter filled aperture in Stage 2, and then to a 20-meter filled aperture in Stage 3. Stage 1 is launched as a fully functional telescope and begins gathering science data immediately after checkout on orbit. This observatory is then periodically augmented in space with additional mirror segments, structures, and newer instruments to evolve the telescope over the years to a 20-meter space telescope. In this 2015 update of EST we focus upon three items: 1) a restructured Stage 1 EST with three mirror segments forming an off-axis telescope (half a 12-meter filled aperture); 2) more details on the value and architecture of the prime focus instrument accommodation; and 3) a more in depth discussion of the essential in-space infrastructure, early ground testing and a concept for an International Space Station testbed called MoDEST. In addition to the EST discussions we introduce a different alternative telescope architecture: a Rotating Synthetic Aperture (RSA). This is a rectangular primary mirror that can be rotated to fill the UV-plane. The original concept was developed by Raytheon Space and Airborne Systems for non-astronomical applications. In collaboration with Raytheon we have begun to explore the RSA approach as an astronomical space telescope and have initiated studies of science and cost performance
Innovative telescope architectures for future large space observatories
Over the past few years, we have developed a concept for an evolvable space telescope (EST) that is assembled on orbit in three stages, growing from a 4Ă12-m telescope in Stage 1, to a 12-m filled aperture in Stage 2, and then to a 20-m filled aperture in Stage 3. Stage 1 is launched as a fully functional telescope and begins gathering science data immediately after checkout on orbit. This observatory is then periodically augmented in space with additional mirror segments, structures, and newer instruments to evolve the telescope over the years to a 20-m space telescope. We discuss the EST architecture, the motivation for this approach, and the benefits it provides over current approaches to building and maintaining large space observatories
Influenza vaccine effectiveness among outpatients in the US Influenza Vaccine Effectiveness Network by study site 2011â2016
BackgroundInfluenza vaccination is recommended for all US residents aged âĽ6 months. Vaccine effectiveness (VE) varies by age, circulating influenza strains, and the presence of highârisk medical conditions. We examined siteâspecific VE in the US Influenza VE Network, which evaluates annual influenza VE at ambulatory clinics in geographically diverse sites.MethodsAnalyses were conducted on 27 180 outpatients âĽ6 months old presenting with an acute respiratory infection (ARI) with cough of â¤7âday duration during the 2011â2016 influenza seasons. A testânegative design was used with vaccination status defined as receipt of âĽ1 dose of any influenza vaccine according to medical records, registries, and/or selfâreport. Influenza infection was determined by reverseâtranscription polymerase chain reaction. VE estimates were calculated using odds ratios from multivariable logistic regression models adjusted for age, sex, race/ethnicity, time from illness onset to enrollment, highârisk conditions, calendar time, and vaccination statusâsite interaction.ResultsFor all sites combined, VE was statistically significant every season against all influenza and against the predominant circulating strains (VE = 19%â50%) Few differences among four sites in the US Flu VE Network were evident in five seasons. However, in 2015â16, overall VE in one site was 24% (95% CI = â4%â44%), while VE in two other sites was significantly higher (61%, 95% CI = 49%â71%; P = .002, and 53%, 95% CI = 33,67; P = .034).ConclusionWith few exceptions, siteâspecific VE estimates aligned with each other and overall VE estimates. Observed VE may reflect inherent differences in community characteristics of the sites and highlights the importance of diverse settings for studying influenza vaccine effectiveness.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155981/1/irv12741_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155981/2/irv12741.pd
Vaccine effectiveness against COVID-19 among symptomatic persons aged âĽ12âyears with reported contact with COVID-19 cases, February-September 2021
BACKGROUND: Individuals in contact with persons with COVID-19 are at high risk of developing COVID-19; protection offered by COVID-19 vaccines in the context of known exposure is poorly understood.
METHODS: Symptomatic outpatients aged âĽ12âyears reporting acute onset of COVID-19-like illness and tested for SARS-CoV-2 between February 1 and September 30, 2021 were enrolled. Participants were stratified by self-report of having known contact with a COVID-19 case in the 14âdays prior to illness onset. Vaccine effectiveness was evaluated using the test-negative study design and multivariable logistic regression.
RESULTS: Among 2229 participants, 283/451 (63%) of those reporting contact and 331/1778 (19%) without known contact tested SARS-CoV-2-positive. Adjusted vaccine effectiveness was 71% (95% confidence interval [CI], 49%-83%) among fully vaccinated participants reporting a known contact versus 80% (95% CI, 72%-86%) among those with no known contact (p-value for interactionâ=â0.2).
CONCLUSIONS: This study contributes to growing evidence of the benefits of vaccinations in preventing COVID-19 and support vaccination recommendations and the importance of efforts to increase vaccination coverage
Late Quaternary reptile extinctions : size matters, insularity dominates
Aim: A major Late Quaternary vertebrate extinction event affected mostly largeâbodied âmegafaunaâ. This is well documented in both mammals and birds, but evidence of a similar trend in reptiles is scant. We assess the relationship between body size and Late Quaternary extinction in reptiles at the global level.
Location: Global.
Methods: We compile a body size database for all 82 reptile species that are known to have gone extinct during the last 50,000 years and compare them with the sizes of 10,090 extant reptile species (97% of known extant diversity). We assess the body size distributions in the major reptile groups: crocodiles, lizards, snakes and turtles, while testing and correcting for a size bias in the fossil record. We examine geographical biases in extinction by contrasting mainland and insular reptile assemblages, and testing for biases within regions and then globally by using geographically weighted models.
Results: Extinct reptiles were larger than extant ones, but there was considerable variation in extinction size biases among groups. Extinct lizards and turtles were large, extinct crocodiles were small and there was no trend in snakes. Lizard lineages vary in the way their extinction is related to size. Extinctions were particularly prevalent on islands, with 73 of the 82 extinct species being island endemics. Four others occurred in Australia. The fossil record is biased towards largeâbodied reptiles, but extinct lizards were larger than extant ones even after we account for this.
Main conclusions: Body size played a complex role in the extinction of Late Quaternary reptiles. Larger lizard and turtle species were clearly more affected by extinction mechanisms such as over exploitation and invasive species, resulting in a prevalence of largeâbodied species among extinct taxa. Insularity was by far the strongest correlate of recent reptile extinctions, suggesting that sizeâbiased extinction mechanisms are amplified in insular environments
Smart Moves: Effects of Relative Brain Size on Establishment Success of Invasive Amphibians and Reptiles
Brain size relative to body size varies considerably among animals, but the
ecological consequences of that variation remain poorly understood. Plausibly,
larger brains confer increased behavioural flexibility, and an ability to
respond to novel challenges. In keeping with that hypothesis, successful
invasive species of birds and mammals that flourish after translocation to a new
area tend to have larger brains than do unsuccessful invaders. We found the same
pattern in ectothermic terrestrial vertebrates. Brain size relative to body size
was larger in species of amphibians and reptiles reported to be successful
invaders, compared to species that failed to thrive after translocation to new
sites. This pattern was found in six of seven global biogeographic realms; the
exception (where relatively larger brains did not facilitate invasion success)
was Australasia. Establishment success was also higher in amphibian and reptile
families with larger relative brain sizes. Future work could usefully explore
whether invasion success is differentially associated with enlargement of
specific parts of the brain (as predicted by the functional role of the
forebrain in promoting behavioural flexibility), or with a general size increase
(suggesting that invasion success is facilitated by enhanced perceptual and
motor skills, as well as cognitive ability)
Estimating population size, density and dynamics of Pre-Pottery Neolithic villages in the central and southern Levant: an analysis of Beidha, southern Jordan
The Pre-Pottery Neolithic (PPN) of the central and southern Levant played an integral role in the Neolithic Demographic Transition (NDT) from mobile hunter-gatherer to village-based, agro-pastoralist societies. An understanding of population dynamics is essential for reconstructing the trajectories of these early village societies. However, few investigations have produced absolute estimates of population parameters for these villages and those which have base estimates on a limited methodological framework. This research examines the methodological and theoretical basis for existing estimates, and explores a range of methodologies in order to derive more empirically-robust demographic data. Results reveal that commonly utilized methodologies and population density coefficients employed for estimating PPN village populations require re-evaluation. This article presents the application of methodologies to the PPNB site of Beidha in southern Jordan
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