Predicting PDF tails in systems with logarithmic non-linearity

The probability density function (PDF) of flux R is computed in systems with logarithmic non-linearity using a model non-linear dynamical equation. The PDF tails of the first moment flux are analytically predicted to be power law. These PDF tails are shown to be broader than a Gaussian distribution and are a manifestation of intermittency caused by short lived coherent structures (instantons). (c) 2010 Elsevier B.V. All rights reserved

The temporal dynamics of calibration target reflectance

A field experiment investigated the hypothesis that the nadir reflectance of calibration surface substrates (asphalt and concrete) remains stable over a range of time-scales. Measurable differences in spectral reflectance factors were found over periods as short as 30 minutes. Surface reflectance factors measured using a dual-field-of-view GER1500 spectroradiometer system showed a relationship with the relative proportion of diffuse irradiance, over periods when solar zenith changes were minimal. Reflectance measurements were collected over precise points on the calibration surfaces using a novel mobile spectroradiometer device, and uncertainty in terms of absolute reflectance was calculated as being < 0.05% within the usable range of the instrument (400-1000nm). Multi-date reflectance factors were compared using one-way ANOVA and found to differ significantly (p = 0.001). These findings illustrate the anisotropic nature of calibration surfaces, and place emphasis on the need to minimise the temporal delay in collection of field spectral measurements for vicarious calibration or empirical atmospheric correction purposes

Probability distribution function for self-organization of shear flows

The first prediction of the probability distribution function (PDF) of self-organized shear flows is presented in a nonlinear diffusion model where shear flows are generated by a stochastic forcing while diffused by a nonlinear eddy diffusivity. A novel nonperturbative method based on a coherent structure is utilized for the prediction of the strongly intermittent exponential PDF tails of the gradient of shear flows. Numerical simulations using Gaussian forcing not only confirm these predictions but also reveal the significant contribution from the PDF tails with a large population of supercritical gradients. The validity of the nonlinear diffusion model is then examined using a threshold model where eddy diffusivity is given by discontinuous values, elucidating an important role of relative time scales of relaxation and disturbance in the determination of the PDFs

Ranking games and gambling: When to quit when you're ahead

It is common for rewards to be given on the basis of a rank ordering, so that relative performance amongst a cohort is the criterion. In this paper we formulate an equilibrium model in which an agent makes successive decisions on whether or not to gamble and is rewarded on the basis of a rank ordering of final wealth. This is a model of the behaviour of mutual fund managers who are paid depending on funds under management which in turn are largely determined by annual or quarterly rank orderings. In this model fund managers can elect either to pick stocks or to use a market tracking strategy. In equilibrium the final distribution of rewards will have a negative skew. We explore how this distribution depends on the number of players, the probability of success when gambling, the structure of the rewards, and on information regarding the other player's performance

Geochemical analysis and modeling for an artificial aquifer recharge study in the shallow zone squifer near Pojoaque, New Mexico.

An artificial aquifer recharge project is currently being evaluated as a component of the Pojoaque Basin Regional Water System as part of the Aamodt Litigation Settlement Act. The purpose of the project is for aquifer storage, with later retrieval as drinking water. The total diversion of San Juan Chama Project Water (SJCPW) for this project is approximately 4,000 acre-feet per year. It should be noted that some of the SJCPW would be treated and put directly into the drinking water system. The goal of this project is to extract the SJCPW from the Rio Grande and pump it into two arroyos, the Arroyo Jocona and an unnamed arroyo. The hope is that the water will reach the shallow aquifer via infiltration. The United States Geological Survey (USGS) performed a geophysical study of the two above-mentioned arroyos near Pojoaque, New Mexico to determine the lithology if SJCPW will infiltrate through the vadose zone and into the shallow aquifer system. The USGS also drilled four borings and completed monitoring wells in two of the borings. The wells were used to collect water levels and water quality samples. After performing analysis of the groundwater, using both an inductively couple plasma (ICP) and ion chromatography (IC) instruments, and analysis of the sediments using acid digestion and a batch extraction, it was determined that several analytes exceed the United States Environmental Protection Agency Drinking Water Standards. These analytes include aluminum, beryllium, fluoride, iron, and arsenic. All of these analytes are found at concentrations would most likely be able to be treated using standard modern water treatment techniques

Postruminal Flow of Glutamate Linearly Increases Small Intestinal Starch Digestion in Cattle

Improving performance and efficiency among cattle fed corn-based diets could have large benefit to cattle production in the United States. Starch escaping ruminal fermentation is not efficiently digested in the small intestine; however, postruminal flows of casein (i.e., milk protein) or glutamate (an amino acid or building block of protein) increase small intestinal starch digestion in cattle. The objective of this study was to determine responses of small intestinal starch digestion in cattle to increasing amounts of postruminal glutamate. Increasing amounts of duodenal glutamate linearly increased small intestinal and postruminal starch digestion. These data indicate that postruminal glutamate can provide benefit to cattle fed corn-based diets

Sources of uncertainty in vicarious calibration: understanding calibration target reflectance

A field experiment investigated the hypothesis that the nadir reflectance of calibration surface substrates (asphalt and concrete) remains stable over a range of time-scales. Measurable differences in spectral reflectance factors were found over periods as short as 30 minutes. Multi-date reflectance measurements were compared using ANOVA and found to differ significantly (p = 0.001). Surface reflectance showed a relationship with the relative proportion of diffuse irradiance, over periods when solar zenith changes were minimal. These findings illustrate the anisotropic nature of calibration surfaces, and place emphasis on the need for collection of diffuse and global irradiance measurements at the time of remotely-sensed data acquisition

Dual-energy X-ray absorptiometry scans accurately predict differing body fat content in live sheep

Background There is considerable interest in implementing mobile scanning technology for on-farm body composition analysis on live animals. These experiments evaluated the use of dual energy X-ray absorptiometry (DXA) as an accurate method of total body fat measurement in live sheep. Results In Exp. 1, visceral and whole body fat analysis was undertaken in sheep with body condition scores (BCS) in the range 2 to 3.25 (scale 1: thin to 5: fat). The relationship of BCS was moderately correlated with visceral fat depot mass (r = 0.59, P  0.05, n = 9). There was a moderate correlation between DXA body fat and BCS (r = 0.70, P < 0.01, n = 17), and DXA body fat was highly correlated with chemical body fat (r = 0.81, P < 0.001, n = 9). In Exp. 3, a series of five DXA scans, at 8-week intervals, was performed on growing sheep over a 32-week period. The average BCS ranged from 2.39 ± 0.07 (S.E.M.) to 3.05 ± 0.11 and the DXA body fat (%) ranged from 16.8 ± 0.8 to 24.2 ± 1.2. There was a moderate correlation between DXA body fat and BCS over the 32 weeks (r = 0.61, P < 0.001, n = 24). Conclusions Overall, these experiments indicated that there was good agreement between BCS, DXA and chemical analysis for measuring total body fat in sheep, and that DXA scanning is a valid method for longitudinal measurement of total body fat in live sheep