1,732 research outputs found
Predicting Avian Influenza Co-Infection with H5N1 and H9N2 in Northern Egypt.
Human outbreaks with avian influenza have been, so far, constrained by poor viral adaptation to non-avian hosts. This could be overcome via co-infection, whereby two strains share genetic material, allowing new hybrid strains to emerge. Identifying areas where co-infection is most likely can help target spaces for increased surveillance. Ecological niche modeling using remotely-sensed data can be used for this purpose. H5N1 and H9N2 influenza subtypes are endemic in Egyptian poultry. From 2006 to 2015, over 20,000 poultry and wild birds were tested at farms and live bird markets. Using ecological niche modeling we identified environmental, behavioral, and population characteristics of H5N1 and H9N2 niches within Egypt. Niches differed markedly by subtype. The subtype niches were combined to model co-infection potential with known occurrences used for validation. The distance to live bird markets was a strong predictor of co-infection. Using only single-subtype influenza outbreaks and publicly available ecological data, we identified areas of co-infection potential with high accuracy (area under the receiver operating characteristic (ROC) curve (AUC) 0.991)
Revisiting the g-null paradox
The parametric g-formula is an approach to estimating causal effects of
sustained treatment strategies from observational data. An often cited
limitation of the parametric g-formula is the g-null paradox: a phenomenon in
which model misspecification in the parametric g-formula is guaranteed under
the conditions that motivate its use (i.e., when identifiability conditions
hold and measured time-varying confounders are affected by past treatment).
Many users of the parametric g-formula know they must acknowledge the g-null
paradox as a limitation when reporting results but still require clarity on its
meaning and implications. Here we revisit the g-null paradox to clarify its
role in causal inference studies. In doing so, we present analytic examples and
a simulation-based illustration of the bias of parametric g-formula estimates
under the conditions associated with this paradox. Our results highlight the
importance of avoiding overly parsimonious models for the components of the
g-formula when using this method
BRST Quantization of the Proca Model based on the BFT and the BFV Formalism
The BRST quantization of the Abelian Proca model is performed using the
Batalin-Fradkin-Tyutin and the Batalin-Fradkin-Vilkovisky formalism. First, the
BFT Hamiltonian method is applied in order to systematically convert a second
class constraint system of the model into an effectively first class one by
introducing new fields. In finding the involutive Hamiltonian we adopt a new
approach which is more simpler than the usual one. We also show that in our
model the Dirac brackets of the phase space variables in the original second
class constraint system are exactly the same as the Poisson brackets of the
corresponding modified fields in the extended phase space due to the linear
character of the constraints comparing the Dirac or Faddeev-Jackiw formalisms.
Then, according to the BFV formalism we obtain that the desired resulting
Lagrangian preserving BRST symmetry in the standard local gauge fixing
procedure naturally includes the St\"uckelberg scalar related to the explicit
gauge symmetry breaking effect due to the presence of the mass term. We also
analyze the nonstandard nonlocal gauge fixing procedure.Comment: 29 pages, plain Latex, To be published in Int. J. Mod. Phys.
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Restoring the Heart: A Community Vision for the Neighborhood of Aldenville
The goal of the Master of Regional Planning Studio is to develop a studentâs techniques for collecting, analyzing, and synthesizing spatial and non-spatial data and then presenting that collective data in a manner (i.e., report, video, presentation, and charettes) that is understandable to academics, professionals, and the public. Planning Studio allows students to integrate knowledge from coursework and research, and apply such knowledge to resolving representative planning problems. At UMASS Amherst, these problems are found in neighborhood, rural, urban, and/or regional settings.
For the Fall 2017 Planning Studio, Chicopee tasked the Masters of Regional Planning Studio to prepare a vision plan that focuses on improving Chicopeeâs public engagement and land-use in Aldenville. The vision plan will contain a multi-question survey that will query Chicopee residents on their opinions of Chicopee, overall, and/or the neighborhood of Aldenville. In addition, the vision plan will also include two proposed land-use studies (zoning, land-use, pedestrian access, design, street improvements) for the neighborhood of Aldenville. This project has 6 goals: § Goal 1: Develop an outreach/engagement process that includes community survey materials (in hard-copy and digital formats) for distribution to Aldenville residents and stakeholders. The Planning Studio shall develop these materials understanding the Cityâs intended re-use of materials in a City-wide comprehensive visioning process. § Goal 2: Experiment with non-traditional modes of community engagement to maximize variety and volume of community response and data collection. § Goal 3: Analyze data collected from the outreach/engagement process to best inform the neighborhood visioning process and final Aldenville Vision Plan. § Goal 4: Develop a comprehensive understanding and graphic representation of major neighborhood destinations within Aldenville from which a more connected neighborhood concept can be developed. § Goal 5: Document, analyze, and discuss neighborhood opportunities and challenges (informed by the Community Outreach/Public Engagement Process) to advance visions for improving connectivity within the neighborhood and broadening the potential for Aldenville to function as a destination for all City residents as well as visitors from outside the City. § Goal 6: Document and prioritize destinations within Aldenville and propose urban design interventions to improve these destinations while using these destinations as anchors in a larger neighborhood network
Carbon-Enhanced Metal-Poor Stars. III. Main-Sequence Turn-Off Stars from the SDSS/SEGUE Sample
The chemical compositions of seven Carbon-Enhanced Metal-Poor (CEMP) turn-off
stars are determined from high-resolution spectroscopy. Five of them are
selected from the SDSS/SEGUE sample of metal-poor stars. The effective
temperatures of these objects are all higher than 6000 K, while their
metallicities, parametrized by [Fe/H], are all below -2. Six of our program
objects exhibit high abundance ratios of barium ([Ba/H]> +1), suggesting large
contributions of the products of former AGB companions via mass transfer across
binary systems. Combining our results with previous studies provides a total of
20 CEMP main-sequence turn-off stars for which the abundances of carbon and at
least some neutron-capture elements are determined. Inspection of the [C/H]
ratios for this sample of CEMP turn-off stars show that they are generally
higher than those of CEMP giants; their dispersion in this ratio is also
smaller. We take these results to indicate that the carbon-enhanced material
provided from the companion AGB star is preserved at the surface of turn-off
stars with no significant dilution. In contrast, a large dispersion in the
observed [Ba/H] is found for the sample of CEMP turn-off stars, suggesting that
the efficiency of the s-process in very metal-poor AGB stars may differ greatly
from star to star. Four of the six stars from the SDSS/SEGUE sample exhibit
kinematics that are associated with membership in the outer-halo population, a
remarkably high fraction.Comment: 45 pages, 10 figures, 10 tables, Astrophysical Journal, in pres
Black hole determinants and quasinormal modes
We derive an expression for functional determinants in thermal spacetimes as
a product over the corresponding quasinormal modes. As simple applications we
give efficient computations of scalar determinants in thermal AdS, BTZ black
hole and de Sitter spacetimes. We emphasize the conceptual utility of our
formula for discussing `1/N' corrections to strongly coupled field theories via
the holographic correspondence.Comment: 28 pages. v2: slightly improved exposition, references adde
Online Social Networking Technologies, HIV Knowledge, and Sexual Risk and Testing Behaviors Among Homeless Youth
This study evaluates associations between online social networking and sexual health behaviors among homeless youth in Los Angeles. We analyzed survey data from 201 homeless youth accessing services at a Los Angeles agency. Multivariate (regression and logistic) models assessed whether use of (and topics discussed on) online social networking technologies affect HIV knowledge, sexual risk behaviors, and testing for sexually transmitted infections (STIs). One set of results suggests that using online social networks for partner seeking (compared to not using the networks for seeking partners) is associated with increased sexual risk behaviors. Supporting data suggest that (1) using online social networks to talk about safe sex is associated with an increased likelihood of having met a recent sex partner online, and (2) having online sex partners and talking to friends on online social networks about drugs and partying is associated with increased exchange sex. However, results also suggest that online social network usage is associated with increased knowledge and HIV/STI prevention among homeless youth: (1) using online social networks to talk about love and safe sex is associated with increased knowledge about HIV, (2) using the networks to talk about love is associated with decreased exchange sex, and (3) merely being a member of an online social network is associated with increased likelihood of having previously tested for STIs. Taken together, this study suggests that online social networking and the topics discussed on these networks can potentially increase and decrease sexual risk behaviors depending on how the networks are used. Developing sexual health services and interventions on online social networks could reduce sexual risk behaviors
Risks of cancers for carriers of monoallelic MUTYH mutation with a family history of colorectal cancer
Robust Inference of Monocot Deep Phylogeny Using an Expanded Multigene Plastid Data Set
We use multiple photosynthetic, chlororespiratory, and plastid translation apparatus loci and their associated noncoding regions (ca. 16 kb per taxon, prior to alignment) to make strongly supported inferences of the deep internal branches of monocot phylogeny. Most monocot relationships are robust (an average of ca. 91 % bootstrap support per branch examined), including those poorly supported or unresolved in other studies. Our data strongly support a sister-group relationship between Asparagales and the commelinid monocots, the inclusion of the orchids in Asparagales, and the status of Petrosaviaceae as the sister group of all monocots except Acorus and Alismatales. The latter finding supports recognition of the order Petrosaviales. Also strongly supported is a placement of Petermannia disjunct from Colchicaceae (Liliales) and a sister-group relationship between Commelinales and Zingiberales. We highlight the remaining weak areas of monocot phylogeny, including the positions of Dioscoreales, Liliales, and Pandanales. Despite substantial variation in the overall rate of molecular evolution among lineages, inferred amounts of change among codon-position data partitions are correlated with each other across the monocot tree, consistent with low incongruence between these partitions. Ceratophyllum and Chloranthaceae appear to have a destabilizing effect on the position of the monocots among other angiosperms; the issue of monocot placement in broader angiosperm phylogeny remains problematic
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