How integrative modelling can break down disciplinary silos

This paper has been published in a peer-reviewed journal as: Kragt, M.E., Robson, B.J. & Macleod, C.J.A. (2013) Modellers’ roles in structuring integrative research projects. Environmental Modelling & Software, 39(1): 322-330. DOI: 10.1016/j.envsoft.2012.06.015Environmental modelling, Interdisciplinary research, Transdisciplinarity, Integration, Research Methods/ Statistical Methods, Q57, Y80, Z19,

A Field Study on the Stability of Road Cut Slopes in Nepal

The density of Nepal’s road network has more than tripled in the last three decades. This growth has been rapid, extensive and in places haphazard, occurring on both the local and strategic road networks, and has resulted in the widespread failure of road cut slopes throughout Nepal. To further understand this effect, field assessments were carried out along roads of different governing grade in Nepal, focusing on the stability of cut slopes and effectiveness of stabilisation measures adopted. This paper summarises the key findings of this study. Although there are multiple guidelines from the Government of Nepal with recommendations on the design and construction of road cut slopes and stabilisation measures, the cut slopes were commonly found to be excavated to steeper inclinations than advised in these guidelines. The cut slopes that were steeper than the advised inclination remained stable before the monsoon, but often failed during the monsoon season due to rainwater infiltration that leads to dissipation of soil suction. Field observations also revealed that the roadside drainage was either not implemented or was blocked. The retaining walls were found to be designed to the same geometry, despite differences in cutting heights and slope materials. This resulted in overturning, bulging, and cracking of the walls. Based on the findings of this study, it is clear that to build resilient road infrastructure in Nepal, the road cuttings need to be excavated according to rigorous engineering guidelines, and standards for the practice of quality assurance need to be implemented

A Computationally Efficient Method to Determine the Probability of Rainfall-Triggered Cut Slope Failure Accounting for Upslope Hydrological Conditions

We present a new computationally efficient methodology to estimate the probability of rainfall-induced slope failure based on mechanical probabilistic slope stability analyses coupled with a hydrogeological model of the upslope area. The model accounts for: (1) uncertainty of geotechnical and hydrogeological parameters; (2) rainfall precipitation recorded over a period of time; and (3) the effect of upslope topography. The methodology provides two key outputs: (1) time-varying conditional probability of slope failure; and (2) an estimate of the absolute frequency of slope failure over any time period of interest. The methodology consists of the following steps: first, characterising the uncertainty of the slope geomaterial strength parameters; second, performing limit equilibrium method stability analyses for the realisations of the geomaterial strength parameters required to calculate the slope probability of failure by a Monte Carlo Simulation. The stability analyses are performed for various phreatic surface heights. These phreatic surfaces are then matched to a phreatic surface time series obtained from the 1D Hillslope-Storage Boussinesq model run for the upslope area to generate Factor of Safety (FoS) time series. A timevarying conditional probability of failure and an absolute frequency of slope failure can then be estimated from these FoS time series. We demonstrate this methodology on a road slope cutting in Nepal where geotechnical tests are not readily conducted. We believe this methodology improves the reliability of slope safety estimates where site investigation is not possible. Also, the methodology enables practitioners to avoid making unrealistic assumptions on the hydrological input. Finally, we find that the time-varying failure probability shows marked variations over time as a result of the monsoon wet–dry weather

Colour vision of green turtle (Chelonia mydas) hatchlings: do they still prefer blue under water?

Background. Several anatomical studies have concluded that green turtles (Chelonia mydas) possess the necessary anatomy for colour vision. Behavioural experiments were conducted with newly emerged hatchlings, testing their attraction towards light sources of different colours on their journey into the ocean. It was concluded that they are attracted to shorter wavelengths compared to longer ones, suggesting a possible attraction towards blue. Methods. Forty-one green turtles at six months of age were tested for their colour discrimination capabilities during a three-choice experiment under water. Three colours were selected for experimentation: blue, yellow, and red. Four different saturations (25, 50, 75, and 100%) of each of these colours were created, in total 12 colours were tested. The colour stimuli was printed and laminated paper colour blocks with food attached to force an interaction. Turtles were individually placed into their housing tanks with three different colours in front of them, from the same level saturation. The colour of the colour plate first approached and bitten by the turtle was noted. Results. The colour of the plate significantly influenced the likelihood that one food plate was selected more than another. Overall blue was selected 66.1%, yellow 18.2% and red 15.7%. There was also a significant interaction between the colour plate selected and the colour of the housing tank. Discussion.The findings of this study are consistent with previous research, concluding that green turtles are attracted to shorter wavelength colours, blue, compared to longer wavelength colours such as yellow or red. As the colour saturation changed and the colours became darker, turtles still chose food from the blue plates compared to the other options. These results indicate an attraction towards the colour blue, and as these research animals have never been in the wild, it is suggested that this attraction be an innate behavioural characteristic for green turtles

Individual differences in excitation and inhibition in visual cortex

The formation of a visual percept in the human brain involves multiple processes, the extent of which may be related to each other within individuals but may show variability between participants. The aim of this thesis was to investigate the relationships between individual variability in various measures of visual processing. The non-invasive neuroimaging methods of magnetic resonance imaging (MRI), magnetic resonance spectroscopy (MRS), magnetoencephalography (MEG) and functional MRI (fMRI) were employed to measure brain structure, neurotransmitter concentration, neuronal oscillations and haemodynamic activity, respectively. Reductions in haemodynamic activity in non-stimulated areas of visual cortex (negative blood oxygen level-dependent responses) were shown to hold useful information about the stimulus, in addition to the responses in stimulated cortex. In general, there were no strong relationships between increased or decreased functional responses in visual cortex and measures of brain structure or of neurotransmitter concentration. Age was the major determinant of individual variability in the frequency of neuronal oscillations. These findings do not replicate results from previous studies that have shown links between individual differences in these measures. This discrepancy was not due to poor repeatability of MRS measures, since methods for optimisation of MRS were identified in this thesis. Simulations were also conducted to determine the sample sizes required in correlational studies involving neuroimaging measures with associated measurement noise. The lack of replication of relationships between neuroimaging measures of individual differences in visual processing is likely to be influenced by low statistical power, due to the small sample sizes and weak relationships tested. Such studies should therefore be conducted and interpreted cautiously, bearing in mind issues of power, demographic mediators of relationships and the likely strength of relationships inferred from the physiological mechanisms linking the variables tested

Evolution of nesting habitats and metapleural glands in ants

The metapleural gland is a unique and complex structure located on the propodeum of ants. Given its function in immune defence against microbes, it has undoubtedly played an important role in the ecological success of ants by enforcing colony hygiene and preventing diseases. Although this gland has an important antimicrobial function, it has been lost several times. It has been proposed that these losses are due to a shift in nesting habit, i.e. ants living in trees can afford to loose the metapleural gland because this environment harbours fewer microbes. Here we test this idea, the 'Arboreality Hypothesis', by constructing a phylogeny for 48 formicine ant species using eight markers (nuclear and mitochondrial) and Bayesian tree building methods. Character mapping for the presence/absence of the gland and nesting habitat was carried out with SIMMAP including 1000 trees from the posterior distribution of the MCMC run. Our results show several independent losses and regains of the metapleural gland across the subfamily. We also find a significant correlation between the two traits, suggesting that the 'Arboreality Hypothesis' can indeed explain the pattern of presence/absence of the metapleural gland in this group of ants

A policy-based framework for the determination of management options to protect vulnerable marine ecosystems under the EU deep-sea access regulations

Vulnerable marine ecosystems (VMEs) are particularly susceptible to bottom-fishing activity as they are easily disturbed and slow to recover. A data-driven approach was developed to provide management options for the protection of VMEs under the European Union “deep-sea access regulations.” A total of two options within two scenarios were developed. The first scenario defined VME closure areas without consideration of fishing activity. Option 1 proposed closures for the protection of VME habitats and likely habitat, while Option 2 also included areas where four types of VME geophysical elements were present. The second scenario additionally considered fishing. This scenario used VME biomass—fishing intensity relationships to identify a threshold where effort of mobile bottom-contact gears was low and unlikely to have caused significant adverse impacts. Achieving a high level of VME protection requires the creation of many closures (> 100), made up of many small (∼50 km2) and fewer larger closures (> 1000 km2). The greatest protection of VMEs will affect approximately 9% of the mobile fleet fishing effort, while closure scenarios that avoid highly fished areas reduce this to around 4–6%. The framework allows managers to choose the level of risk-aversion they wish to apply in protecting VMEs by comparing alternative strategies.En prensa2,27