Statistical distribution of swash maxima on natural beaches

Beach response to overwash processes is a topic of significant importance. Two particular aspects of this topic were chosen for detailed analysis: the distribution of maximum wave runup elevations and the cross-beach celerity gradient of overwash bores on natural beaches. Data were collected using both traditional nearshore instrumentation and recently developed video-based techniques. Field data from three separate experiments suggest that swash elevations may be regarded as a stochastic process whose maxima have a specific probability distribution function. The exact form of the maxima distribution depends solely on the relative bandwidth of the swash power spectrum and the root-mean-square value of the swash time series. Numerical simulations indicate that the linear assumptions required by the distribution model are commonly violated. Nevertheless, the qualitative trends suggested by the model are applicable to the probability statistics for all of the data. Overwash celerity data were collected at a site on the Isles Dernieres, LA barrier island chain during Hurricane Gilbert in September 1988. A video technique was applied that allowed the quantification of overwash bore celerity vectors along several cross-shore transects. Maximum celerities were found to exceed 2 m/sec. The cross-beach velocity structure can be characterized generally as having a maximum celerity at the berm crest with a linear decrease in velocity across the washover flat. Using the celerity results, a simple model of cross-beach overwash sediment transport is discussed. Results from both investigations demonstrate that important attributes of runup and overwash processes can be sufficiently sampled using video techniques. More work is needed in terms of understanding the influence of overwash processes, specifically in the areas of runup trajectory and celerity characteristics, the interaction between fluid flow and bed permeability, and the regional scale forcing of sea level elevation

A dynamical attractor governs beach response to storms

Sandbars are ubiquitous, yet not well understood beach features that change their position and shape in response to changing wave conditions. We propose and test a simple empirical model consisting of two coupled linear differential equations that represents bar dynamics in terms of wave forcing and two other state variables: (1) the mean cross-shore bar position and (2) the alongshore variability about that mean. Model coefficients are constrained by fitting to a 2-month data set, and the modeled behavior is examined with a stability analysis. The system is found to be stable and, hence, predictable. Rates of change of the bar position and its alongshore variability are found to be significantly coupled, such that prediction of one variable requires information about the other. The system response time is slow compared to the storm wave cycle such that the bar response continually orbits time-varying equilibrium points in the state variable phase plane

Ocean wavenumber estimation from wave-resolving time series imagery

We review several approaches that have been used to estimate ocean surface gravity wavenumbers from wave-resolving remotely sensed image sequences. Two fundamentally different approaches that utilize these data exist. A power spectral density approach identifies wavenumbers where image intensity variance is maximized. Alternatively, a cross-spectral correlation approach identifies wavenumbers where intensity coherence is maximized. We develop a solution to the latter approach based on a tomographic analysis that utilizes a nonlinear inverse method. The solution is tolerant to noise and other forms of sampling deficiency and can be applied to arbitrary sampling patterns, as well as to full-frame imagery. The solution includes error predictions that can be used for data retrieval quality control and for evaluating sample designs. A quantitative analysis of the intrinsic resolution of the method indicates that the cross-spectral correlation fitting improves resolution by a factor of about ten times as compared to the power spectral density fitting approach. The resolution analysis also provides a rule of thumb for nearshore bathymetry retrievals-short-scale cross-shore patterns may be resolved if they are about ten times longer than the average water depth over the pattern. This guidance can be applied to sample design to constrain both the sensor array (image resolution) and the analysis array (tomographic resolution).KEYWORDS: wavelength measurement, adaptive signal processing, sea floor, image processing, sea surfac

Tools for characterizing biomembranes : final LDRD report.

A suite of experimental nuclear magnetic resonance (NMR) spectroscopy tools were developed to investigate lipid structure and dynamics in model membrane systems. By utilizing both multinuclear and multidimensional NMR experiments a range of different intra- and inter-molecular contacts were probed within the membranes. Examples on pure single component lipid membranes and on the canonical raft forming mixture of DOPC/SM/Chol are presented. A unique gel phase pretransition in SM was also identified and characterized using these NMR techniques. In addition molecular dynamics into the hydrogen bonding network unique to sphingomyelin containing membranes were evaluated as a function of temperature, and are discussed

Markers of Maternal and Infant Metabolism are Associated with Ventricular Dysfunction in Infants of Obese Women with Type 2 Diabetes

BACKGROUND To test the hypothesis that infants born to obese women with pregestational type 2 diabetes mellitus (IBDM) have ventricular dysfunction at one month that is associated with markers of maternal lipid and glucose metabolism. METHODS In a prospective observational study of IBDM (OB+DM, n=25), echocardiography measures of septal, left (LV) and right ventricular (RV) function and structure were compared at one month of age to infants born to OB mothers without DM (OB, n=24), and non-OB without DM (Lean, n=23). Basal maternal lipid and glucose kinetics and maternal plasma and infant (cord) plasma were collected for hormone and cytokine analyses. RESULTS RV, LV, and septal strain measures were lower in the OB+DM infants vs. other groups, without evidence of septal hypertrophy. Maternal hepatic insulin sensitivity, maternal plasma free fatty acid concentration, and cord plasma insulin and leptin most strongly predicted decreased septal strain in the OB+DM infants. CONCLUSION IBDM’s have reduced septal function at one month in the absence of septal hypertrophy, which is associated with altered maternal and infant lipid and glucose metabolism. These findings suggest that maternal obesity and DM may have a prolonged impact on the cardiovascular health of their offspring, despite resolution of cardiac hypertrophy

Thermodynamic formalism for contracting Lorenz flows

We study the expansion properties of the contracting Lorenz flow introduced by Rovella via thermodynamic formalism. Specifically, we prove the existence of an equilibrium state for the natural potential $\hat\phi_t(x,y, z):=-t\log J_{(x, y, z)}^{cu}$ for the contracting Lorenz flow and for $t$ in an interval containing $[0,1]$. We also analyse the Lyapunov spectrum of the flow in terms of the pressure

Identifying component modules

A computer-based system for modelling component dependencies and identifying component modules is presented. A variation of the Dependency Structure Matrix (DSM) representation was used to model component dependencies. The system utilises a two-stage approach towards facilitating the identification of a hierarchical modular structure. The first stage calculates a value for a clustering criterion that may be used to group component dependencies together. A Genetic Algorithm is described to optimise the order of the components within the DSM with the focus of minimising the value of the clustering criterion to identify the most significant component groupings (modules) within the product structure. The second stage utilises a 'Module Strength Indicator' (MSI) function to determine a value representative of the degree of modularity of the component groupings. The application of this function to the DSM produces a 'Module Structure Matrix' (MSM) depicting the relative modularity of available component groupings within it. The approach enabled the identification of hierarchical modularity in the product structure without the requirement for any additional domain specific knowledge within the system. The system supports design by providing mechanisms to explicitly represent and utilise component and dependency knowledge to facilitate the nontrivial task of determining near-optimal component modules and representing product modularity

Extinction of cue-evoked drug-seeking relies on degrading hierarchical instrumental expectancies

There has long been need for a behavioural intervention that attenuates cue-evoked drug-seeking, but the optimal method remains obscure. To address this, we report three approaches to extinguish cue-evoked drug-seeking measured in a Pavlovian to instrumental transfer design, in non-treatment seeking adult smokers and alcohol drinkers. The results showed that the ability of a drug stimulus to transfer control over a separately trained drug-seeking response was not affected by the stimulus undergoing Pavlovian extinction training in experiment 1, but was abolished by the stimulus undergoing discriminative extinction training in experiment 2, and was abolished by explicit verbal instructions stating that the stimulus did not signal a more effective response-drug contingency in experiment 3. These data suggest that cue-evoked drug-seeking is mediated by a propositional hierarchical instrumental expectancy that the drug-seeking response is more likely to be rewarded in that stimulus. Methods which degraded this hierarchical expectancy were effective in the laboratory, and so may have therapeutic potential

Rapid tests and urine sampling techniques for the diagnosis of urinary tract infection (UTI) in children under five years: a systematic review

Background: Urinary tract infection (UTI) is one of the most common sources of infection in children under five. Prompt diagnosis and treatment is important to reduce the risk of renal scarring. Rapid, cost-effective, methods of UTI diagnosis are required as an alternative to culture. Methods: We conducted a systematic review to determine the diagnostic accuracy of rapid tests for detecting UTI in children under five years of age. Results: The evidence supports the use of dipstick positive for both leukocyte esterase and nitrite (pooled LR+ = 28.2, 95% CI: 17.3, 46.0) or microscopy positive for both pyuria and bacteriuria (pooled LR+ = 37.0, 95% CI: 11.0, 125.9) to rule in UTI. Similarly dipstick negative for both LE and nitrite (Pooled LR- = 0.20, 95% CI: 0.16, 0.26) or microscopy negative for both pyuria and bacteriuria (Pooled LR- = 0.11, 95% CI: 0.05, 0.23) can be used to rule out UTI. A test for glucose showed promise in potty-trained children. However, all studies were over 30 years old. Further evaluation of this test may be useful. Conclusion: Dipstick negative for both LE and nitrite or microscopic analysis negative for both pyuria and bacteriuria of a clean voided urine, bag, or nappy/pad specimen may reasonably be used to rule out UTI. These patients can then reasonably be excluded from further investigation, without the need for confirmatory culture. Similarly, combinations of positive tests could be used to rule in UTI, and trigger further investigation