315 research outputs found
Energy cost and return for hunting in African wild dogs and Cheetahs
African wild dogs (Lycaon pictus) are reported to hunt with energetically costly long chase distances. We used high-resolution GPS and inertial technology to record 1,119 high-speed chases of all members of a pack of six adult African wild dogs in northern Botswana. Dogs performed multiple short, high-speed, mostly unsuccessful chases to capture prey, while cheetahs (Acinonyx jubatus) undertook even shorter, higher-speed hunts. We used an energy balance model to show that the energy return from group hunting and feeding substantially outweighs the cost of multiple short chases, which indicates that African wild dogs are more energetically robust than previously believed. Comparison with cheetah illustrates the trade-off between sheer athleticism and high individual kill rate characteristic of cheetahs, and the energetic robustness of frequent opportunistic group hunting and feeding by African wild dogs
Freeze casting of porous monolithic composites for hydrogen storage†
This is the author accepted manuscript. The final version is available from the Royal Society of Chemistry via the DOI in this recordHydrogen storage by adsorption offers operational benefits over energy intensive compression
techniques. Incorporating physisorption materials in compression stores could improve hydrogen
capacities, reducing the volume or pressure needed for storage vessels. However, such materials are
often presented as fine powders and development efforts to date have predominantly focused on
improving hydrogen uptake alone. Without due attention to industry-relevant attributes, such as
handling, processability, and mechanical properties it is unlikely that these materials will find commercial
application. In the paper, the desirable mechanical properties of hydrogen-adsorbent PIM-1 are
exploited to yield a series of composite monoliths doped with a high surface area activated carbon,
intended to act as pressure vessel inserts. Freeze casting techniques were successfully adapted for use
with chloroform, facilitating the production of coherent and controlled three-dimensional geometries.
This included the use of an innovative elastomeric mould made by additive manufacture to allow facile
adoption, with the ability to vary multiple forming factors in the future. The composite monolith formed
exhibited a stiffness of 0.26 GPa, a compressive strength of 6.7 MPa, and an increased BET surface area
of 847 m2 g1 compared to PIM-1 powders, signifying the first steps towards producing hydrogen
adsorbents in truly useful monolithic forms.Engineering and Physical Sciences Research Counci
Gastrointestinal stromal tumour and hypoglycemia in a Fjord pony: Case report
<p>Abstract</p> <p>Background</p> <p>Neoplasia may cause hypoglycemia in different species including the horse, but hypoglycemia has not previously been reported in the horse associated with gastrointestinal stromal tumours.</p> <p>Case presentation</p> <p>A case of a gastrointestinal stromal tumour in a Fjord pony with severe recurrent hypoglycemia is presented. The mechanism causing the hypoglycemia was not established.</p> <p>Conclusion</p> <p>This case indicates that a gastrointestinal stromal tumour may cause hypoglycemia also in the horse.</p
Discovery of the Onset of Rapid Accretion by a Dormant Massive Black Hole
Massive black holes are believed to reside at the centres of most galaxies.
They can be- come detectable by accretion of matter, either continuously from a
large gas reservoir or impulsively from the tidal disruption of a passing star,
and conversion of the gravitational energy of the infalling matter to light.
Continuous accretion drives Active Galactic Nuclei (AGN), which are known to be
variable but have never been observed to turn on or off. Tidal disruption of
stars by dormant massive black holes has been inferred indirectly but the on-
set of a tidal disruption event has never been observed. Here we report the
first discovery of the onset of a relativistic accretion-powered jet in the new
extragalactic transient, Swift J164449.3+573451. The behaviour of this new
source differs from both theoretical models of tidal disruption events and
observations of the jet-dominated AGN known as blazars. These differences may
stem from transient effects associated with the onset of a powerful jet. Such
an event in the massive black hole at the centre of our Milky Way galaxy could
strongly ionize the upper atmosphere of the Earth, if beamed towards us.Comment: Submitted to Nature. 4 pages, 3 figures (main paper). 26 pages, 13
figures (supplementary information
An ultraviolet-optical flare from the tidal disruption of a helium-rich stellar core
The flare of radiation from the tidal disruption and accretion of a star can
be used as a marker for supermassive black holes that otherwise lie dormant and
undetected in the centres of distant galaxies. Previous candidate flares have
had declining light curves in good agreement with expectations, but with poor
constraints on the time of disruption and the type of star disrupted, because
the rising emission was not observed. Recently, two `relativistic' candidate
tidal disruption events were discovered, each of whose extreme X-ray luminosity
and synchrotron radio emission were interpreted as the onset of emission from a
relativistic jet. Here we report the discovery of a luminous
ultraviolet-optical flare from the nuclear region of an inactive galaxy at a
redshift of 0.1696. The observed continuum is cooler than expected for a simple
accreting debris disk, but the well-sampled rise and decline of its light curve
follows the predicted mass accretion rate, and can be modelled to determine the
time of disruption to an accuracy of two days. The black hole has a mass of
about 2 million solar masses, modulo a factor dependent on the mass and radius
of the star disrupted. On the basis of the spectroscopic signature of ionized
helium from the unbound debris, we determine that the disrupted star was a
helium-rich stellar core.Comment: To appear in Nature on May 10, 201
Strong Ultraviolet Pulse From a Newborn Type Ia Supernova
Type Ia supernovae are destructive explosions of carbon oxygen white dwarfs.
Although they are used empirically to measure cosmological distances, the
nature of their progenitors remains mysterious, One of the leading progenitor
models, called the single degenerate channel, hypothesizes that a white dwarf
accretes matter from a companion star and the resulting increase in its central
pressure and temperature ignites thermonuclear explosion. Here we report
observations of strong but declining ultraviolet emission from a Type Ia
supernova within four days of its explosion. This emission is consistent with
theoretical expectations of collision between material ejected by the supernova
and a companion star, and therefore provides evidence that some Type Ia
supernovae arise from the single degenerate channel.Comment: Accepted for publication on the 21 May 2015 issue of Natur
The implementation of the serial trial intervention for pain and challenging behaviour in advanced dementia patients (STA OP!): a clustered randomized controlled trial
<p>Abstract</p> <p>Background</p> <p>Pain (physical discomfort) and challenging behaviour are highly prevalent in nursing home residents with dementia: at any given time 45-80% of nursing home residents are in pain and up to 80% have challenging behaviour. In the USA Christine Kovach developed the serial trial intervention (STI) and established that this protocol leads to less discomfort and fewer behavioural symptoms in moderate to severe dementia patients. The present study will provide insight into the effects of implementation of the Dutch version of the STI-protocol (STA OP!) in comparison with a control intervention, not only on behavioural symptoms, but also on pain, depression, and quality of life. This article outlines the study protocol.</p> <p>Methods/Design</p> <p>The study is a cluster randomized controlled trial in 168 older people (aged >65 years) with mild or moderate dementia living in nursing homes. The clusters, Dutch nursing homes, are randomly assigned to either the intervention condition (training and implementation of the STA OP!-protocol) or the control condition (general training focusing on challenging behaviour and pain, but without the step-wise approach). Measurements take place at baseline, after 3 months (end of the STA OP! training period) and after 6 months.</p> <p>Primary outcome measures are symptoms of challenging behaviour (measured with the Cohen-Mansfield Agitation Inventory (CMAI) and the Neuropsychiatric Inventory-Nursing Home version (NPI-NH)), and pain (measure with the Dutch version of the Pain Assessment Checklist for Seniors (PACSLAC-D) and the Minimum Data Set of the Resident Assessment Instrument (MDS-RAI) pain scale). Secondary outcome measures include symptoms of depression (Cornell and MDS-RAI depression scale), Quality of Live (Qualidem), changes in prescriptions of analgesics and psychotropic drugs, and the use of non-pharmacological comfort interventions (e.g. snoezelen, reminiscence therapy).</p> <p>Discussion</p> <p>The transfer from the American design to the Dutch design involved several changes due to the different organisation of healthcare systems. Specific strengths and limitations of the study are discussed.</p> <p>Trial registration</p> <p>Netherlands Trial Register (NTR): <a href="http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=1967">NTR1967</a></p
The Evolution of Compact Binary Star Systems
We review the formation and evolution of compact binary stars consisting of
white dwarfs (WDs), neutron stars (NSs), and black holes (BHs). Binary NSs and
BHs are thought to be the primary astrophysical sources of gravitational waves
(GWs) within the frequency band of ground-based detectors, while compact
binaries of WDs are important sources of GWs at lower frequencies to be covered
by space interferometers (LISA). Major uncertainties in the current
understanding of properties of NSs and BHs most relevant to the GW studies are
discussed, including the treatment of the natal kicks which compact stellar
remnants acquire during the core collapse of massive stars and the common
envelope phase of binary evolution. We discuss the coalescence rates of binary
NSs and BHs and prospects for their detections, the formation and evolution of
binary WDs and their observational manifestations. Special attention is given
to AM CVn-stars -- compact binaries in which the Roche lobe is filled by
another WD or a low-mass partially degenerate helium-star, as these stars are
thought to be the best LISA verification binary GW sources.Comment: 105 pages, 18 figure
Burning in Banksia Woodlands: How Does the Fire-Free Period Influence Reptile Communities?
Fire is an important management tool for both hazard reduction burning and maintenance of biodiversity. The impact of time since last fire on fauna is an important factor to understand as land managers often aim for prescribed burning regimes with specific fire-free intervals. However, our current understanding of the impact of time since last fire on fauna is largely unknown and likely dependent on vegetation type. We examined the responses of reptiles to fire age in banksia woodlands, and the interspersed melaleuca damplands among them, north of Perth, Western Australia, where the current prescribed burning regime is targeting a fire-free period of 8–12 years. The response of reptiles to fire was dependent on vegetation type. Reptiles were generally more abundant (e.g. Lerista elegans and Ctenophorus adelaidensis) and specious in banksia sites. Several species (e.g. Menetia greyii, Cryptoblepharus buchananii) preferred long unburnt melaleuca sites (>16 years since last fire, YSLF) compared to recently burnt sites (<12 YSLF). Several of the small elapids (e.g. the WA priority listed species Neelaps calonotus) were only detected in older-aged banksia sites (>16 YSLF). The terrestrial dragon C. adelaidensis and the skink Morethia obscura displayed a strong response to fire in banksia woodlands only. Highest abundances of the dragon were detected in the recently burnt (<7 YSLF) and long unburnt (>35 YSLF) banksia woodlands, while the skink was more abundant in older sites. Habitats from a range of fire ages are required to support the reptiles we detected, especially the longer unburnt (>16 YSLF) melaleuca habitat. Current burning prescriptions are reducing the availability of these older habitats
Role of N-acetylcysteine in the management of COPD
The importance of the underlying local and systemic oxidative stress and inflammation in chronic obstructive pulmonary disease (COPD) has long been established. In view of the lack of therapy that might inhibit the progress of the disease, there is an urgent need for a successful therapeutic approach that, through affecting the pathological processes, will influence the subsequent issues in COPD management such as lung function, airway clearance, dyspnoea, exacerbation, and quality of life. N-acetylcysteine (NAC) is a mucolytic and antioxidant drug that may also influence several inflammatory pathways. It provides the sulfhydryl groups and acts both as a precursor of reduced glutathione and as a direct reactive oxygen species (ROS) scavenger, hence regulating the redox status in the cells. The changed redox status may, in turn, influence the inflammation-controlling pathways. Moreover, as a mucolytic drug, it may, by means of decreasing viscosity of the sputum, clean the bronchi leading to a decrease in dyspnoea and improved lung function. Nevertheless, as successful as it is in the in vitro studies and in vivo studies with high dosage, its actions at the dosages used in COPD management are debatable. It seems to influence exacerbation rate and limit the number of hospitalization days, however, with little or no influence on the lung function parameters. Despite these considerations and in view of the present lack of effective therapies to inhibit disease progression in COPD, NAC and its derivatives with their multiple molecular modes of action remain promising medication once doses and route of administration are optimized
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