The Ketogenic Diet: An Answer for Autism?

Lacking substantial evidence regarding its genetic identity, autism spectrum disorder (ASD) is a remarkably misunderstood condition with limited options for effective treatment. As the prevalence of patients with ASD increases, medical professionals continue to search for a solution. Could the ketogenic diet, a high fat, low carbohydrate nutrition plan, provide the relief that ASD patients are searching for

The validity of the Youth Physical Activity Questionnaire in 12-13 year old Scottish adolescents

Background: The development of accurate methods to measure health-behaviours forms an integral component in behavioural epidemiology. Population surveillance of physical activity often relies on self/proxy reported questionnaires due to cost and relative ease of administration. The aim of this study was to examine the criterion validity and measurement agreement between the Youth Physical Activity Questionnaire (YPAQ) and accelerometry before being included in a Scotland-wide study. Methods: Forty four participants (12–13 years old; 61% girls) completed the YPAQ following 7 days wearing the Actigraph GT3X+. Mean moderate-to-vigorous physical activity (MVPA) per day was derived from YPAQ and accelerometer and validity was assessed using Spearman's correlation; Bland-Altman plots examined absolute agreement between methods. Results: Pearson's and Spearman’s correlations between YPAQ and accelerometer were r = 0.47 and rs = 0.39 (p<0.01) respectively. The YPAQ over reported mean MVPA by 25.6 ± 50.2 minutes (95% CI 10.4-40.9 minutes; p <0.001), with 95% limits of agreement of −72.69 minutes and + 123.99 minutes. Evidence of underreporting at lower levels of activity and over reporting at higher levels of activity was evident (Pearson's r=0.81), in addition to heteroscedasticity, where variances increased as MVPA increased. Conclusions: Although a moderate correlation between the two methods was apparent, the YPAQ should not be used interchangeably with accelerometry. The YPAQ does demonstrate a reasonable ability to rank MVPA, although it tends to under-report lower levels and over-report higher levels. This, and other administering factors, should be taken into consideration if being used for group or individual level analyses

Chemical reaction systems with toric steady states

Mass-action chemical reaction systems are frequently used in Computational Biology. The corresponding polynomial dynamical systems are often large (consisting of tens or even hundreds of ordinary differential equations) and poorly parametrized (due to noisy measurement data and a small number of data points and repetitions). Therefore, it is often difficult to establish the existence of (positive) steady states or to determine whether more complicated phenomena such as multistationarity exist. If, however, the steady state ideal of the system is a binomial ideal, then we show that these questions can be answered easily. The focus of this work is on systems with this property, and we say that such systems have toric steady states. Our main result gives sufficient conditions for a chemical reaction system to have toric steady states. Furthermore, we analyze the capacity of such a system to exhibit positive steady states and multistationarity. Examples of systems with toric steady states include weakly-reversible zero-deficiency chemical reaction systems. An important application of our work concerns the networks that describe the multisite phosphorylation of a protein by a kinase/phosphatase pair in a sequential and distributive mechanism

Dynamics of a salinity-prone agricultural catchment driven by markets, farmers' attitude and climate change

An agent-based simulation model has been developed with CORMAS combining simplified bio-physical processes of land cover, dry-land salinity changes, rainfall, farm profitability and farmer decisions on land uses in a dry-land agricultural catchment (no irrigation). Simulated farmers formulate individual decisions dealing with land use changes based on the combined performance of their past land cover productivity and market returns. The willingness to adapt to market drivers and the ability to maximize returns varies across farmers. In addition, farmers in the model can demonstrate various attitudes towards salinity mitigation as a consequence of experiencing and perceiving salinity on their farm, in the neighborhood or in the entire region. Consequently, farmers can adopt land cover strategies aiming at reducing salinity impact. The simulation results using historical rainfall records reproduces similar trends of crop-pasture ratios, salinity change and farm decline as observed in the last 20 years in the Katanning catchment (Western Australia). Using the model as an explorative tool for future scenarios, the simulation results highlighted the importance of rainfall changes and wide-spread willingness of farmers to combat dry-land salinity. Rainfall changes as a consequence of climate change can lead to prolonged sequences of dry and wet seasons. Adaptation to these sequences by farmers seems to be critical for farm survival in this catchment. (Résumé d'auteur

Atollscape: Simulating freshwater management in Pacific Atolls. Spatial processes and time dependence issues

Groundwater has long been ranked as a high priority research area by small island nations in the Pacific. It is the major source of freshwater on the atoll of Tarawa (Rep.of Kiribati) and its availability, quality, management and allocation are central to the atoll¿s sustainable development and poverty alleviation. From a modeling perspective, simulating freshwater lens behavior represents a challenge, as it requires sophisticated numerical models. Such models can hardly fit within an integrated management framework taking into account spatially distributed water use (e.g. wells, trees) and social interactions. Simple analytical solutions exist but they apply for steady-state conditions, verified only on an annual basis. Recent advances in the field of Distributed Artificial Intelligence have permitted the development of a Multi Agent System (MAS) approach, closely related to the problem of complexity. AtollScape uses MAS techniques to simulate water management and freshwater lens behavior on the Tarawa atoll. A distributed and nested structure is used to represent local inputs and uptakes, along with freshwater lens adjustments on a 10 day time steps. (Résumé d'auteur

Climatic and human influences on water resources in low atolls

Low, small islands have water supply problems amongst the most critical in the world. Fresh groundwater, the major source of water in many atolls, is vulnerable to natural and human-induced changes. Storm surges, droughts and over-extraction cause seawater intrusion. Settlements and agricultural activities can rapidly pollute shallow groundwaters. Limited land areas restrict freshwater quantities, which are especially vulnerable during frequent ENSO-related droughts. Demand for freshwater is increasing due to population growth and urbanisation. Water use for traditional crops often competes with water supplies for communities. This paper analyses the impact of frequent severe droughts on the quality and quantity of fresh groundwater in a low, atoll, Tarawa, in the Republic of Kiribati. We also examine the impacts of groundwater harvesting on traditional subsistence crops such as coconuts and of landuse on water quality. Strategies for reducing risks from climate variations and human impacts and increasing resilience are discussed. (Résumé d'auteur

SimKat: a virtual laboratory to explore the impact of rainfall variability associated with the A2 climate change scenario on the Western Australian wheat-belt [Abstract]

The wheat-belt of Western Australia is one of the most vulnerable regions to climate change in Australia (DAFWA, 2007). Over the last century, the landscape is Western Australian has changed drastically with almost 20 million hectares of native vegetation being converted into pastures and annual crops to create the so-called "Western Australian wheat-belt" (Turner and Ward, 2002) This significant landuse change has contributed to the modification of the regional water cycle. McFarlane and Williamson (2002) estimated that about 10% of cropping land in south-west Australia is affected by dry-land salinity which could increase to up to 30% in the coming decades. This loss is estimated to cost A$80 million per year in lost production, and A$500 million a year due to damaged infrastructure. Moreover, since the mid 1970's, winter rainfall has declined by more than 15% (Smith et al., 2000). Predicted changes in winter rainfall, for 2070, range from a 60% reduction up to an increase by 10% (Pittock, 2003). However, one of the more likely scenarios is a reduction in winter rainfall of about 15% by 2030 and 30% by 2070 (IOCI, 2002). In order to explore the long-term effects and consequences of rainfall uncertainty and climate change on these already threatened socio-ecological systems, we have developed SimKat, an agent-based model developed with the CORMAS platform. SimKat combines simplified biophysical processes of paddock cover with likely CO2 impact on potential yields, dry-land salinity changes, likely rainfall scenarios and farmers¿ decision making processes. Variations in temperature are not accounted for at this stage of model¿s development. Simulated agents - farmers make decisions about their future landuse pattern based on their land cover productivity and market returns. Agents are also attributed various risk-related attitudes towards market and mitigation signals. To account for rainfall variability, we use 50 rainfall series from 2005 to 2055, generated through a downscaling technique that relates changes in atmospheric predictors from a General Circulation Model. The model explores the impact of each rainfall series in association with the A2 climate change scenario on the viability of the simulated agricultural region based on the following simulated indicators: farm numbers, salinity extension, regional income, crop-pasture ratio. Yield potential and technological trends influencing farmers¿ ability to crop are also studied. Simulated scenarios discuss the impact of rainfall variability and atmospheric CO2 increase on individual and regional farm viability. The scenarios provide means to closely analyse the resilience of the simulated agricultural region to potential impacts of climate uncertainty. (Résumé d'auteur

Hydrology of conflicts over shallow groundwater use and management in low coral islands

Groundwater is the major freshwater source in coral islands. Its availability, quality, and management are central to sustainable development and poverty alleviation. Increasing populations, growing per capita demand and restricted land areas limit water availability and generate conflicts. Shallow groundwater in the Pacific is vulnerable in ENSO-related droughts and over-extraction causes seawater intrusion. Human settlements, animal production, and agro-chemicals coupled to very permeable soils, with limited water-holding capacity, result in rapid impacts on groundwater quality and human health. Coconuts, breadfruit, papaws, bananas and crops such as swamp taro, decrease groundwater supplies through direct evapotranspiration from the watertable. The trade-off between maximising and protecting groundwater resources and maximising overlying crop production presents a dilemma for island communities as does the tensions between the demands of an urbanised society and traditional cultural practices. This paper describes an UNESCO IHP project on the hydrology and hydrodynamics of shallow groundwater and the socio-cultural aspects of groundwater use in coral islands. The study was in Tarawa atoll, Kiribati in the central Pacific. A simple daily water balance model was used to suggest groundwater extraction strategies and management options. The lack of comprehensive water legislation and legal agreements between the government and landowners, combined with confusion over the responsibilities of government agencies and community vandalism to water supply infrastructure, are indicators of the tensions between the subsistence past and the urban future faced by many small island communities. The potential for using multi-agent systems to reduce conflicts is discussed. (Résumé d'auteur