72 research outputs found
Predicting hedgehog mortality risks on British roads using habitat suitability modelling
Road vehicle collisions are likely to be an important contributory factor in the decline of the European hedgehog (Erinaceus europaeus) in Britain. Here, a collaborative roadkill dataset collected from multiple projects across Britain was used to assess when, where and why hedgehog roadkill are more likely to occur. Seasonal trends were assessed using a Generalized Additive Model. There were few casualties in winter—the hibernation season for hedgehogs—with a gradual increase from February that reached a peak in July before declining thereafter. A sequential multi-level Habitat Suitability Modelling (HSM) framework was then used to identify areas showing a high probability of hedgehog roadkill occurrence throughout the entire British road network (∼400,000 km) based on multi-scale environmental determinants. The HSM predicted that grassland and urban habitat coverage were important in predicting the probability of roadkill at a national scale. Probabilities peaked at approximately 50% urban cover at a one km scale and increased linearly with grassland cover (improved and rough grassland). Areas predicted to experience high probabilities of hedgehog roadkill occurrence were therefore in urban and suburban environments, that is, where a mix of urban and grassland habitats occur. These areas covered 9% of the total British road network. In combination with information on the frequency with which particular locations have hedgehog road casualties, the framework can help to identify priority areas for mitigation measures
Modelling the functional connectivity of landscapes for greater horseshoe bats Rhinolophus ferrumequinum at a local scale
Context: The importance of habitat connectivity for
wildlife is widely recognised. However, assessing the
movement of species tends to rely on radio-tracking or
GPS evidence, which is difficult and costly to gather.
Objectives: To examine functional connectivity of
greater horseshoe bats (GHS, Rhinolophus ferrumequinum)
at a local scale using Circuitscape software;
comparing our results against expert opinion ‘fly
ways’.
Methods: Expert opinions were used to rank and
score five environmental layers influencing GHS
movement, generating resistance scores. The slope
and resistance scores of these layers were varied, and
validated against independent ground truthed GHS
activity data, until a unimodal peak in correlation was
identified for each layer. The layers were combined
into a multivariate model and re-evaluated. Radiotracking
studies were used to further validate the
model, and the transferability was tested at other roost
locations.
Results: Functional connectivity models could be
created using bat activity data. Models had the ability
to be transferred between roost locations, although
site-specific validation is strongly recommended. For
all other bat species recorded, markedly more (125%)
bat passes occurred in the top quartile of functional
connectivity compared to any of the lower three
quartiles.
Conclusion: The model predictions identify areas of
key conservation importance to habitat connectivity
for GHS that are not recognised by expert opinion. By
highlighting landscape features that act as barriers to
movement, this approach can be used by decision-makers
as a tool to inform local management
strategies
Supermassive Binaries and Extragalactic Jets
Some quasars show Doppler shifted broad emission line peaks. I give new
statistics of the occurrence of these peaks and show that, while the most
spectacular cases are in quasars with strong radio jets inclined to the line of
sight, they are also almost as common in radio-quiet quasars. Theories of the
origin of the peaks are reviewed and it is argued that the displaced peaks are
most likely produced by the supermassive binary model. The separations of the
peaks in the 3C 390.3-type objects are consistent with orientation-dependent
"unified models" of quasar activity. If the supermassive binary model is
correct, all members of "the jet set" (astrophysical objects showing jets)
could be binaries.Comment: 31 pages, PostScript, missing figure is in ApJ 464, L105 (see
http://www.aas.org/ApJ/v464n2/5736/5736.html
Large Extra Dimensions and Decaying KK Recurrences
We suggest the possibility that in ADD type brane-world scenarios, the higher
KK excitations of the graviton may decay to lower ones owing to a breakdown of
the conservation of extra dimensional ``momenta'' and study its implications
for astrophysics and cosmology. We give an explicit realization of this idea
with a bulk scalar field , whose nonzero KK modes acquire vacuum
expectation values. This scenario helps to avoid constraints on large extra
dimensions that come from gamma ray flux bounds in the direction of nearby
supernovae as well as those coming from diffuse cosmological gamma ray
background. It also relaxes the very stringent limits on reheat temperature of
the universe in ADD models.Comment: 16 pages, late
Estudo das agressões por cães, segundo tipo de interação entre cão e vÃtima, e das circunstâncias motivadoras dos acidentes, municÃpio de São Paulo, 2008 a 2009
Emulating a trial of joint dynamic strategies: An application to monitoring and treatment of HIV-positive individuals
Decisions about when to start or switch a therapy often depend on the frequency with which individuals are monitored or tested. For example, the optimal time to switch antiretroviral therapy depends on the frequency with which HIV-positive individuals have HIV RNA measured. This paper describes an approach to use observational data for the comparison of joint monitoring and treatment strategies and applies the method to a clinically relevant question in HIV research: when can monitoring frequency be decreased and when should individuals switch from a first-line treatment regimen to a new regimen?. We outline the target trial that would compare the dynamic strategies of interest and then describe how to emulate it using data from HIV-positive individuals included in the HIV-CAUSAL Collaboration and the Centers for AIDS Research Network of Integrated Clinical Systems. When, as in our example, few individuals follow the dynamic strategies of interest over long periods of follow-up, we describe how to leverage an additional assumption: no direct effect of monitoring on the outcome of interest. We compare our results with and without the “no direct effect†assumption. We found little differences on survival and AIDS-free survival between strategies where monitoring frequency was decreased at a CD4 threshold of 350 cells/μl compared with 500 cells/μl and where treatment was switched at an HIV-RNA threshold of 1000 copies/ml compared with 200 copies/ml. The “no direct effect†assumption resulted in efficiency improvements for the risk difference estimates ranging from an 7- to 53-fold increase in the effective sample size
Uncovering the heterogeneity and temporal complexity of neurodegenerative diseases with Subtype and Stage Inference
The heterogeneity of neurodegenerative diseases is a key confound to disease understanding and treatment development, as study cohorts typically include multiple phenotypes on distinct disease trajectories. Here we introduce a machine-learning technique\u2014Subtype and Stage Inference (SuStaIn)\u2014able to uncover data-driven disease phenotypes with distinct temporal progression patterns, from widely available cross-sectional patient studies. Results from imaging studies in two neurodegenerative diseases reveal subgroups and their distinct trajectories of regional neurodegeneration. In genetic frontotemporal dementia, SuStaIn identifies genotypes from imaging alone, validating its ability to identify subtypes; further the technique reveals within-genotype heterogeneity. In Alzheimer\u2019s disease, SuStaIn uncovers three subtypes, uniquely characterising their temporal complexity. SuStaIn provides fine-grained patient stratification, which substantially enhances the ability to predict conversion between diagnostic categories over standard models that ignore subtype (p = 7.18
7 10 124 ) or temporal stage (p = 3.96
7 10 125 ). SuStaIn offers new promise for enabling disease subtype discovery and precision medicine
The nutritional value of residues from farm anaerobic digesters
SIGLEAvailable from British Library Lending Division - LD:D54815/85 / BLDSC - British Library Document Supply CentreGBUnited Kingdo
On the wing density and the inflation factor of aircraft
The aviation industry is dominated by the domain of heavier-than-air, fixed-wing, subsonic
flight, and central to any design in this domain is the wing itself. One of the earliest debates in
aviation still centres around the usefulness of the wing volume. On the one hand it is held that
the wing, as an inevitable necessity, should provide the volume also for the payload. On the
other, it is argued that more efficient wings do not even have sufficient volume for the entire
wing structure. This work proposes precise definitions of the Wing Density and the Inflation
Factor, two parameters that can quantitatively reflect the economic and technological trends
in aviation. The wing volume of a hypothetical Ideal Wing is derived from the Operational
Parameters of any given Flight Objective and compared to the volume requirement of that
flight objective. We conclude that the dominant aircraft configuration of the future is likely to
remain within the same family of the current dominant configuration, in conflict with some
older prediction
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