Direct transition to high-dimensional chaos through a global bifurcation

In the present work we report on a genuine route by which a high-dimensional (with d>4) chaotic attractor is created directly, i.e., without a low-dimensional chaotic attractor as an intermediate step. The high-dimensional chaotic set is created in a heteroclinic global bifurcation that yields an infinite number of unstable tori.The mechanism is illustrated using a system constructed by coupling three Lorenz oscillators. So, the route presented here can be considered a prototype for high-dimensional chaotic behavior just as the Lorenz model is for low-dimensional chaos.Comment: 7 page

Repetitive element hypomethylation in blood leukocyte DNA and cancer incidence, prevalence, and mortality in elderly individuals : the Normative Aging Study

BACKGROUND: Global genomic hypomethylation is a common epigenetic event in cancer that mostly results from hypomethylation of repetitive DNA elements. Case-control studies have associated blood leukocyte DNA hypomethylation with several cancers. Because samples in case-control studies are collected after disease development, whether DNA hypomethylation is causal or just associated with cancer development is still unclear. METHODS: In 722 elderly subjects from the Normative Aging Study cohort, we examined whether DNA methylation in repetitive elements (Alu, LINE-1) was associated with cancer incidence (30 new cases, median follow-up: 89 months), prevalence (205 baseline cases), and mortality (28 deaths, median follow-up: 85 months). DNA methylation was measured by bisulfite pyrosequencing. RESULTS: Individuals with low LINE-1 methylation (<median) had a 3.0-fold (95%CI 1.3-6.9) increased incidence of all cancers combined. LINE-1 and Alu methylation were not significantly associated with cancer prevalence at baseline (all cancers combined). However, individuals with low LINE-1 methylation (<median) had a 3.2-fold (95% CI 1.4-7.5) higher prevalence of lung cancer. Individuals with low LINE-1 or Alu methylation (<median) had increased cancer mortality (HR = 3.2, 95%CI 1.3-7.9 for LINE-1; HR = 2.5, 95%CI 1.1-5.8 for Alu). CONCLUSION: These findings suggest that individuals with lower repetitive element methylation are at high risk of developing and dying from cancer

Allergen sensitization is associated with increased dna methylation in older men

Background: Variation in epigenetic modifications, arising from either environmental exposures or internal physiological changes, can influence gene expression and may ultimately contribute to complex diseases such as asthma and allergies. We examined the association of asthma and allergic phenotypes with DNA methylation levels of retrotransposon-derived elements. Methods: We used data from 704 men (mean age 73 years) in the longitudinal Normative Aging Study to assess the relationship between asthma, allergic phenotypes and DNA methylation levels of the retrotransposon-derived elements Alu and long interspersed nuclear element (LINE)-1. Retrotransposons represent a large fraction of the genome (>30%) and are heavily methylated to prevent expression. Percent methylation of Alu and LINE-1 elements in peripheral white blood cells was quantified using PCR pyrosequencing. Data on sensitization to common allergens from skin prick testing, asthma and methacholine responsiveness were gathered approximately 8 years prior to DNA methylation analysis. Results: Prior allergen sensitization was associated with increased methylation of Alu (\u3b2 = 0.32 for sensitized vs. nonsensitized patients; p = 0.003) in models adjusted for pack-years of smoking, body mass index, current smoking, air pollutants, percentage of eosinophils, white blood cell count and age. Of the men interviewed, 5% of subjects reported a diagnosis of asthma. Neither Alu nor LINE-1 methylation was associated with asthma. Conclusions: These data suggest that increased DNA methylation of repetitive elements may be associated with allergen sensitization but does not appear to be associated with asthma. Future work is needed to identify potential underlying mechanisms for these relationships

A generalised ecohydrological landscape classification for assessing ecosystem risk in Australia due to an altering water regime

Describing and classifying a landscape for environmental impact and risk assessment purposes is a non-trivial challenge because this requires region-specific landscape classifications that cater for region-specific impacts. Assessing impacts on ecosystems from the extraction of water resources across large regions requires a causal link between landscape features and their water requirements. We present the rationale and implementation of an ecohydrological classification for regions where coal mine and coal seam gas developments may impact on water. Our classification provides the essential framework for modelling the potential impact of hydrological changes from future coal resource developments at the landscape level. We develop an attribute-based system that provides representations of the ecohydrological entities and their connection to landscape features and make use of existing broad-level classification schemes into an attribute-based system. We incorporate a rule set with prioritisation, which underpins risk modelling and makes the scheme resource efficient, where spatial landscape or ecosystem classification schemes, developed for other purposes, already exist. A consistent rule set and conceptualised landscape processes and functions allow for the combination of diverse data with existing classification schemes. This makes the classification transparent, repeatable and adjustable, should new data become available. We apply the approach in three geographically different regions, with widely disparate information sources, for the classification, and provide a detailed example of its application. We propose that it is widely applicable around the world for linking ecohydrology to environmental impacts.</p

Attributing human influence on July 2017 Chinese heatwave: the influence of sea-surface temperatures

On 21st-25thJuly 2017 a record breaking heatwave occurred in Central Eastern China affecting nearly half of the national population and causing severe impacts on public health, agriculture and infrastructure. Here, we compare attribution results from two UK Met Office Hadley Centre models, HadGEM3-GA6 and weather@home (HadAM3P driving 50km HadRM3P). Within HadGEM3-GA6 July 2017-like heatwaves were unequaled in the ensemble representing the world without human influences. Such heatwaves became approximately a 1 in 50 year event and increased by a factor of 4.8 (5-95% range of 3.1 to 8.0) in weather@home as a result of human activity. Considering the risk ratio (RR) for the full range of return periods shows a discrepancy at all return times between the two model results. Within weather@home a range of different counterfactual Sea Surface Temperature (SST) patterns were used whereas HadGEM3-GA6 used a single estimate. The global mean difference in SST (between factual and counterfactual simulations) is shown to be related to the Generalised Extreme Value (GEV) location parameter and consequently the RR, especially for return periods less than 50 years. It is suggested that a suitable range of SST patterns are used for future attribution studies to ensure that this source of uncertainty is represented within the simulations and subsequent attribution results. It is shown that the risk change between factual and counterfactual simulations is not purely a simple shift in the distribution (i.e. change in GEV location parameter). For return periods greater than 50 years the GEV shape parameter is found to strongly influence the RR determined with the GEV scale parameter affecting only the most severe events

The Developing Laminar Flow and Pressure Drop in the Entrance Region of Annular Ducts

BRIEF NOTES the most frequently used assumption is that of uniform flow at inlet, which simulates the actual condition of well-rounded entrance. This assumption was adopted in the present analysis and thus, at x = 0, the axial velocity and pressure are uniform with values u 0 and p 0 , respectively. Following the procedure suggested in TT/32, 2.03 for ex = TT/16, 1.92 for a = ir/8, and 1.86 for a = 7r/4) seem to conform with the asymptotic value of 1.82 obtained in The most commonly used parameters for presenting the pressure results are the product of the friction factor and Reynolds number fRe, and the pressure defect K. In the present analysis, the friction factor was defined as: f=(D h /2)(-dp/dx)/(pu 2 b ), and hence The pressure defect is normally defined as: , which reduces to the following nondimensional form: Results based on equations Acknowledgments The authors gratefully acknowledge the support provided for this research by the Natural Sciences and Engineering Research Council of Canada. References 1 Shah, R. K., and London, A. L., Laminar Flow Forced Convection in Duels, Academic Press, 1978. 2 Wendt, R. L., and Wiginton, C. L., &quot;Incompressible Laminar Entrance Flow in a Circular Sector Duct,&quot; JOURNAL OF APPLIED MECHANICS, Vol. 98, 1976, pp.357-359. 3 Munis, A A., &quot;Analysis of Laminar Fluid Flow in the Entrance Region of Circular Sector Ducts,&quot; M.Sc. Thesis, University of-Manitoba, 1981. 4 Sparrow, E. M., Lin, S. H., and Lundgren, T. S., &quot;Flow Development in the Hydrodynamic Entrance Region of Tubes and Ducts,&quot; Physics of Fluids, Vol. 7, 1964, pp. 338-347. 5 Sparrow, E. M., and Lin, S. H., &quot;The Developing Laminar Flow and Pressure Drop in the Entrance Region of Annular Ducts,&quot; Journal of Bask Engineering, Vol. 86,1964, pp. 827-834. 6 Fleming, D. P., and Sparrow, E. M., &quot;Flow in the Hydrodynamic Entrance Region of Ducts of Arbitrary Cross-Section,&quot; ASME Journal of Heat Transfer, Vol. 91,1969, pp. 345-354. Numerical Results The resulting values of Le are listed i

Computer-aided assessment of diagnostic images for epidemiological research

<p>Abstract</p> <p>Background</p> <p>Diagnostic images are often assessed for clinical outcomes using subjective methods, which are limited by the skill of the reviewer. Computer-aided diagnosis (CAD) algorithms that assist reviewers in their decisions concerning outcomes have been developed to increase sensitivity and specificity in the clinical setting. However, these systems have not been well utilized in research settings to improve the measurement of clinical endpoints. Reductions in bias through their use could have important implications for etiologic research.</p> <p>Methods</p> <p>Using the example of cortical cataract detection, we developed an algorithm for assisting a reviewer in evaluating digital images for the presence and severity of lesions. Available image processing and statistical methods that were easily implementable were used as the basis for the CAD algorithm. The performance of the system was compared to the subjective assessment of five reviewers using 60 simulated images. Cortical cataract severity scores from 0 to 16 were assigned to the images by the reviewers and the CAD system, with each image assessed twice to obtain a measure of variability. Image characteristics that affected reviewer bias were also assessed by systematically varying the appearance of the simulated images.</p> <p>Results</p> <p>The algorithm yielded severity scores with smaller bias on images where cataract severity was mild to moderate (approximately ≤ 6/16^<it>ths</it>). On high severity images, the bias of the CAD system exceeded that of the reviewers. The variability of the CAD system was zero on repeated images but ranged from 0.48 to 1.22 for the reviewers. The direction and magnitude of the bias exhibited by the reviewers was a function of the number of cataract opacities, the shape and the contrast of the lesions in the simulated images.</p> <p>Conclusion</p> <p>CAD systems are feasible to implement with available software and can be valuable when medical images contain exposure or outcome information for etiologic research. Our results indicate that such systems have the potential to decrease bias and discriminate very small changes in disease severity. Simulated images are a tool that can be used to assess performance of a CAD system when a gold standard is not available.</p

Analysis of the shearing instability in nonlinear convection and magnetoconvection

Numerical experiments on two-dimensional convection with or without a vertical magnetic field reveal a bewildering variety of periodic and aperiodic oscillations. Steady rolls can develop a shearing instability, in which rolls turning over in one direction grow at the expense of rolls turning over in the other, resulting in a net shear across the layer. As the temperature difference across the fluid is increased, two-dimensional pulsating waves occur, in which the direction of shear alternates. We analyse the nonlinear dynamics of this behaviour by first constructing appropriate low-order sets of ordinary differential equations, which show the same behaviour, and then analysing the global bifurcations that lead to these oscillations by constructing one-dimensional return maps. We compare the behaviour of the partial differential equations, the models and the maps in systematic two-parameter studies of both the magnetic and the non-magnetic cases, emphasising how the symmetries of periodic solutions change as a result of global bifurcations. Much of the interesting behaviour is associated with a discontinuous change in the leading direction of a fixed point at a global bifurcation; this change occurs when the magnetic field is introduced