1,097 research outputs found
Predicting effects of environmental change on a migratory herbivore
Changes in climate, food abundance and disturbance from humans threaten the ability of species to successfully use stopover sites and migrate between non-breeding and breeding areas. To devise successful conservation strategies for migratory species we need to be able to predict how such changes will affect both individuals and populations. Such predictions should ideally be process-based, focusing on the mechanisms through which changes alter individual physiological state and behavior. In this study we use a process-based model to evaluate how Black Brant (Branta bernicla nigricans) foraging on common eelgrass (Zostera marina) at a stopover site (Humboldt Bay, USA), may be affected by changes in sea level, food abundance and disturbance. The model is individual-based, with empirically based parameters, and incorporates the immigration of birds into the site, tidal changes in availability of eelgrass, seasonal and depth-related changes in eelgrass biomass, foraging behavior and energetics of the birds, and their mass- dependent decisions to emigrate. The model is validated by comparing predictions to observations across a range of system properties including the time birds spent foraging, probability of birds emigrating, mean stopover duration, peak bird numbers, rates of mass gain and distribution of birds within the site: all 11 predictions were within 35% of the observed value, and 8 within 20%. The model predicted that the eelgrass within the site could potentially support up to five times as many birds as currently use the site. Future predictions indicated that the rate of mass gain and mean stopover duration were relatively insensitive to sea level rise over the next 100 years, primarily because eelgrass habitat could redistribute shoreward into intertidal mudflats within the site to compensate for higher sea levels. In contrast, the rate of mass gain and mean stopover duration were sensitive to changes in total eelgrass biomass and the percentage of time for which birds were disturbed. We discuss the consequences of these predictions for Black Brant conservation. A wide range of migratory species responses are expected in response to environmental change. Process-based models are potential tools to predict such responses and understand the mechanisms which underpin them
Patellofemoral contact forces and pressures during intramedullary tibial nailing
Patellofemoral joint forces and pressures
were measured in a cadaver model during
intramedullary nailing of the tibia. A significant
increase in contact pressures was found at the
lateral facet of the patellofemoral articulation
using the medial paratendinous approach (P= 0.01)
and at the medial facet when using the trans-patellar
tendon approach (P = 0.001) to the proximal
tibia. Increased contact pressures at the patellofemoral
joint may result in chondral injury, which
in turn may cause anterior knee pain, a common
complication of tibial nailing
Identifying the mechanisms underpinning recognition of structured sequences of action
© 2012 The Experimental Psychology SocietyWe present three experiments to identify the specific information sources that skilled participants use to make recognition judgements when presented with dynamic, structured stimuli. A group of less skilled
participants acted as controls. In all experiments, participants were presented with filmed stimuli containing structured action sequences. In a subsequent recognition phase, participants were presented with new and previously seen stimuli and were required to make judgements as to whether or not each sequence had been presented earlier (or were edited versions of earlier sequences). In Experiment 1,
skilled participants demonstrated superior sensitivity in recognition when viewing dynamic clips compared with static images and clips where the frames were presented in a nonsequential, randomized manner, implicating the importance of motion information when identifying familiar or unfamiliar sequences. In Experiment 2, we presented normal and mirror-reversed sequences in order to distort access to absolute motion information. Skilled participants demonstrated superior recognition sensitivity, but no significant differences were observed across viewing conditions, leading to the suggestion
that skilled participants are more likely to extract relative rather than absolute motion when making such judgements. In Experiment 3, we manipulated relative motion information by occluding several display
features for the duration of each film sequence. A significant decrement in performance was reported when centrally located features were occluded compared to those located in more peripheral positions.
Findings indicate that skilled participants are particularly sensitive to relative motion information when attempting to identify familiarity in dynamic, visual displays involving interaction between numerous features
The UK risk assessment scheme for all non-native species
1. A pest risk assessment scheme, adapted from the EPPO (European and Mediterranean Plant Protection Organisation) scheme, was developed to assess the risks posed to UK species, habitats and ecosystems by non-native taxa.
2. The scheme provides a structured framework for evaluating the potential for non-native organisms, whether intentional or unintentional introductions, to enter, establish, spread and cause significant impacts in all or part of the UK. Specialist modules permit the relative importance of entry pathways, the vulnerability of receptors and the consequences of policies to be assessed and appropriate risk management options to be selected. Spreadsheets for summarising the level of risk and uncertainty, invasive attributes and economic impact were created. In addition, new methods for quantifying economic impact and summarising risk and uncertainty were explored.
3. Although designed for the UK, the scheme can readily be applied elsewhere
Results of the First Coincident Observations by Two Laser-Interferometric Gravitational Wave Detectors
We report an upper bound on the strain amplitude of gravitational wave bursts
in a waveband from around 800Hz to 1.25kHz. In an effective coincident
observing period of 62 hours, the prototype laser interferometric gravitational
wave detectors of the University of Glasgow and Max Planck Institute for
Quantum Optics, have set a limit of 4.9E-16, averaging over wave polarizations
and incident directions. This is roughly a factor of 2 worse than the
theoretical best limit that the detectors could have set, the excess being due
to unmodelled non-Gaussian noise. The experiment has demonstrated the viability
of the kind of observations planned for the large-scale interferometers that
should be on-line in a few years time.Comment: 11 pages, 2 postscript figure
The Functional, Metabolic, and Anabolic Responses to Exercise Training in Renal Transplant and Hemodialysis Patients
BACKGROUND.: Exercise intolerance is common in hemodialysis (HD) and renal transplant (RTx) patients and is related to muscle weakness. Its pathogenesis may vary between these groups leading to a different response to exercise. The aim of the study was to compare intrinsic muscular parameters between HD and RTx patients and controls, and to assess the response to exercise training on exercise capacity and muscular structure and function in these groups. METHODS.: Quadriceps function (isokinetic dynamometry), body composition (dual-energy x-ray absorptiometry), and vastus lateralis muscle biopsies were analyzed before and after a 12-week lasting training-program in 35 RTx patients, 16 HD patients, and 21 healthy controls. RESULTS.: At baseline, myosin heavy chain (MyHC) isoform composition and enzyme activities were not different between the groups. VO2peak and muscle strength improved significantly and comparably over the training-period in RTx, HD patients and controls (ptime<0.05). The proportion of MyHC type I isoforms decreased (ptime<0.001) and type IIa MyHC isoforms increased (ptime<0.05). The 3-hydroxyacyl-CoA-dehydrogenase activity increased (ptime=0.052). Intrinsic muscular changes were not significantly different between groups. In the HD group, changes in lean body mass were significantly related to changes in muscle insulin-like growth factor (IGF)-II and IGF binding protein-3. CONCLUSIONS.: Abnormalities in metabolic enzyme activities or muscle fiber redistribution do not appear to be involved in muscle dysfunction in RTx and HD patients. Exercise training has comparable beneficial effects on functional and intrinsic muscular parameters in RTx patients, HD patients, and controls. In HD patients, the anabolic response to exercise training is related to changes in the muscle IGF system
Managing groundwater supplies subject to drought: perspectives on current status and future priorities from England (UK)
Effective management of groundwater resources during drought is essential. How is groundwater currently managed during droughts, and in the face of environmental change, what should be the future priorities? Four themes are explored, from the perspective of groundwater management in England (UK): (1) integration of drought definitions; (2) enhanced fundamental monitoring; (3) integrated modelling of groundwater in the water cycle; and (4) better information sharing. Whilst these themes are considered in the context of England, globally, they are relevant wherever groundwater is affected by drought
Long-term evolution of orbits about a precessing oblate planet. 3. A semianalytical and a purely numerical approach
Construction of a theory of orbits about a precessing oblate planet, in terms
of osculating elements defined in a frame of the equator of date, was started
in Efroimsky and Goldreich (2004) and Efroimsky (2005, 2006). We now combine
that analytical machinery with numerics. The resulting semianalytical theory is
then applied to Deimos over long time scales. In parallel, we carry out a
purely numerical integration in an inertial Cartesian frame. The results agree
to within a small margin, for over 10 Myr, demonstrating the applicability of
our semianalytical model over long timescales. This will enable us to employ it
at the further steps of the project, enriching the model with the tides, the
pull of the Sun, and the planet's triaxiality. Another goal of our work was to
check if the equinoctial precession predicted for a rigid Mars could have been
sufficient to repel the orbits away from the equator. We show that for low
initial inclinations, the orbit inclination reckoned from the precessing
equator of date is subject only to small variations. This is an extension, to
non-uniform precession given by the Colombo model, of an old result obtained by
Goldreich (1965) for the case of uniform precession and a low initial
inclination. However, near-polar initial inclinations may exhibit considerable
variations for up to +/- 10 deg in magnitude. Nevertheless, the analysis
confirms that an oblate planet can, indeed, afford large variations of the
equinoctial precession over hundreds of millions of years, without repelling
its near-equatorial satellites away from the equator of date: the satellite
inclination oscillates but does not show a secular increase. Nor does it show
secular decrease, a fact that is relevant to the discussion of the possibility
of high-inclination capture of Phobos and Deimos
Erasmus Language students in a British University – a case study
Students’ assessment of their academic experience is actively sought by Higher Education institutions, as evidenced in the National Student Survey introduced in 2005. Erasmus students, despite their growing numbers, tend to be excluded from these satisfaction surveys, even though they, too, are primary customers of a University. This study aims to present results from bespoke questionnaires and semi-structured interviews with a sample of Erasmus students studying languages in a British University. These methods allow us insight into the experience of these students and their assessment as a primary customer, with a focus on language learning and teaching, university facilities and student support. It investigates to what extent these factors influence their levels of satisfaction and what costs of adaptation if any, they encounter. Although excellent levels of satisfaction were found, some costs affect their experience. They relate to difficulties in adapting to a learning methodology based on a low number of hours and independent learning and to a guidance and support system seen as too stifling. The results portray this cohort’s British University as a well-equipped and well-meaning but ultimately overbearing institution, which may indicate that minimising costs can eliminate some sources of dissatisfaction
Non-Invasive Mouse Models of Post-Traumatic Osteoarthritis
SummaryAnimal models of osteoarthritis (OA) are essential tools for investigating the development of the disease on a more rapid timeline than human OA. Mice are particularly useful due to the plethora of genetically modified or inbred mouse strains available. The majority of available mouse models of OA use a joint injury or other acute insult to initiate joint degeneration, representing post-traumatic osteoarthritis (PTOA). However, no consensus exists on which injury methods are most translatable to human OA. Currently, surgical injury methods are most commonly used for studies of OA in mice; however, these methods may have confounding effects due to the surgical/invasive injury procedure itself, rather than the targeted joint injury. Non-invasive injury methods avoid this complication by mechanically inducing a joint injury externally, without breaking the skin or disrupting the joint. In this regard, non-invasive injury models may be crucial for investigating early adaptive processes initiated at the time of injury, and may be more representative of human OA in which injury is induced mechanically. A small number of non-invasive mouse models of PTOA have been described within the last few years, including intra-articular fracture of tibial subchondral bone, cyclic tibial compression loading of articular cartilage, and anterior cruciate ligament (ACL) rupture via tibial compression overload. This review describes the methods used to induce joint injury in each of these non-invasive models, and presents the findings of studies utilizing these models. Altogether, these non-invasive mouse models represent a unique and important spectrum of animal models for studying different aspects of PTOA
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