588 research outputs found
Time Evolution of Non-Lethal Infectious Diseases: A Semi-Continuous Approach
A model describing the dynamics related to the spreading of non-lethal
infectious diseases in a fixed-size population is proposed. The model consists
of a non-linear delay-differential equation describing the time evolution of
the increment in the number of infectious individuals and depends upon a
limited number of parameters. Predictions are in good qualitative agreement
with data on influenza.Comment: 21 page
Body mass and latitude as global predictors of vertebrate populations exposure to multiple threats
The interactive effects of multiple threats are one of the main causes of biodiversity loss, yet our understanding of what predisposes species to be impacted by multiple threats remains limited. Here we analyse a global dataset of over 7000 marine, freshwater and terrestrial vertebrate populations, alongside trait, threat and geographical data, to identify the factors influencing the number of threats a species is subjected to at the population level. Out of a suite of predictors tested, we find that body mass and latitude both are broadly available for vertebrate species and influence the number of threats a population is subjected to. Larger-bodied species and those nearer the equator are typically affected by a higher number of threats. However, whilst this pattern broadly holds across ecosystems for most taxa, amphibians and reptiles show opposing trends. We suggest that latitude and body mass should be considered as key predictors to identify which vertebrate populations are likely to be impacted by multiple threats. These general predictors can help to better understand the impacts of the Anthropocene on global vertebrate biodiversity and design effective conservation policies
Global patterns of resilience decline in vertebrate populations
Maintaining the resilience of natural populations, their ability to resist and recover from disturbance, is crucial to prevent biodiversity loss. However, the lack of appropriate data and quantitative tools has hampered our understanding of the factors determining resilience on a global scale. Here, we quantified the temporal trends of two key components of resilience—resistance and recovery—in >2000 population time-series of >1000 vertebrate species globally. We show that the number of threats to which a population is exposed is the main driver of resilience decline in vertebrate populations. Such declines are driven by a non-uniform loss of different components of resilience (i.e. resistance and recovery). Increased anthropogenic threats accelerating resilience loss through a decline in the recovery ability—but not resistance—of vertebrate populations. These findings suggest we may be underestimating the impacts of global change, highlighting the need to account for the multiple components of resilience in global biodiversity assessments
Sedative effects of intramuscular alfaxalone in pet guinea pigs (Cavia porcellus)
Objective: To evaluate the efficacy and side effects of alfaxalone administered intramuscularly (IM) as a sedative agent in guinea pigs undergoing survey radiographs
Simulations for single-dish intensity mapping experiments
HI intensity mapping is an emerging tool to probe dark energy. Observations
of the redshifted HI signal will be contaminated by instrumental noise,
atmospheric and Galactic foregrounds. The latter is expected to be four orders
of magnitude brighter than the HI emission we wish to detect. We present a
simulation of single-dish observations including an instrumental noise model
with 1/f and white noise, and sky emission with a diffuse Galactic foreground
and HI emission. We consider two foreground cleaning methods: spectral
parametric fitting and principal component analysis. For a smooth frequency
spectrum of the foreground and instrumental effects, we find that the
parametric fitting method provides residuals that are still contaminated by
foreground and 1/f noise, but the principal component analysis can remove this
contamination down to the thermal noise level. This method is robust for a
range of different models of foreground and noise, and so constitutes a
promising way to recover the HI signal from the data. However, it induces a
leakage of the cosmological signal into the subtracted foreground of around 5%.
The efficiency of the component separation methods depends heavily on the
smoothness of the frequency spectrum of the foreground and the 1/f noise. We
find that as, long as the spectral variations over the band are slow compared
to the channel width, the foreground cleaning method still works.Comment: 14 pages, 12 figures. Submitted to MNRA
Development of large radii half-wave plates for CMB satellite missions
The successful European Space Agency (ESA) Planck mission has mapped the
Cosmic Microwave Background (CMB) temperature anisotropy with unprecedented
accuracy. However, Planck was not designed to detect the polarised components
of the CMB with comparable precision. The BICEP2 collaboration has recently
reported the first detection of the B-mode polarisation. ESA is funding the
development of critical enabling technologies associated with B-mode
polarisation detection, one of these being large diameter half-wave plates. We
compare different polarisation modulators and discuss their respective
trade-offs in terms of manufacturing, RF performance and thermo-mechanical
properties. We then select the most appropriate solution for future satellite
missions, optimized for the detection of B-modes.Comment: 16 page
Persistent nonbilious vomiting in a child: Possible duodenal webbing
An association between malrotation and congenital duodenal webbing is rare. We present our experience with four patients at two centers, and a review of published reports. There are currently 94 reported cases of duodenal pathology associated with malrotation. However, only 15 of the 94 cases (15.9%) include patients with malrotation and a duodenal web. We suggest that nonbilious vomiting in a child must prompt the surgeon to consider duodenal pathology even in the presence of malrotation
Investigation of the realignment of the exchange bias in spintronic layer stacks using laser radiation
Die vorliegende Arbeit befasst sich mit der gezielten Neuorientierung des Exchange Bias in spintronischen Schichtsystemen durch selektive Aufheizung mittels fokussierter Laserstrahlung im externen Magnetfeld. Hierbei wird der Einfluss der Prozessparameter auf die resultierende Exchange Bias Feldstärke dargestellt. Neben experimentellen Untersuchungen wird die laserinduzierte Aufheizung durch Temperaturfeldsimulationen charakterisiert. Erste Untersuchungen zur Anwendung des lasergestützten Verfahrens auf Leiterbahn-strukturen werden vorgestellt
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