Spatial analyses of wildlife contact networks

Datasets from which wildlife contact networks of epidemiological importance can be inferred are becoming increasingly common. A largely unexplored facet of these data is finding evidence of spatial constraints on who has contact with whom, despite theoretical epidemiologists having long realized spatial constraints can play a critical role in infectious disease dynamics. A graph dissimilarity measure is proposed to quantify how close an observed contact network is to being purely spatial whereby its edges are completely determined by the spatial arrangement of its nodes. Statistical techniques are also used to fit a series of mechanistic models for contact rates between individuals to the binary edge data representing presence or absence of observed contact. These are the basis for a second measure that quantifies the extent to which contacts are being mediated by distance. We apply these methods to a set of 128 contact networks of field voles (Microtus agrestis) inferred from mark–recapture data collected over 7 years and from four sites. Large fluctuations in vole abundance allow us to demonstrate that the networks become increasingly similar to spatial proximity graphs as vole density increases. The average number of contacts, , was (i) positively correlated with vole density across the range of observed densities and (ii) for two of the four sites a saturating function of density. The implications for pathogen persistence in wildlife may be that persistence is relatively unaffected by fluctuations in host density because at low density is low but hosts move more freely, and at high density is high but transmission is hampered by local build-up of infected or recovered animals.     

Polycyclic aromatic hydrocarbons in flames, in diesel fuels, and in diesel emissions

Numerous chemical analyses of gaseous and particulate samples from laboratory flames provide a library of data on the polycyclic aromatic hydrocarbon (PAH) species found in diverse flame types burning fuels consisting of pure gaseous hydrocarbons. The diesel fuels utilized by the more complex combustion in compression ignition engines are composed of thousands of hydrocarbon species. Mass spectrometry by the laser microprobe and gas chromatography were used in a complementary manner to distinguish the PAHs originating in the fuel from those produced by engine combustion. The C_xH_y PAH products of premixed and diffusion flame processes, which also occur in the unsteady diesel combustion, range in mass from 128 u (two rings, x=10, y=8) to beyond 350 u (eight rings, x=28, y=14). Graphs of the number of hydrogen atoms y vs the number of carbon atoms x for the species found by many investigators of laboratory flames show these pyrogenic PAHs to lie on or near the staircase curve that describes the most stable, pericondensed, benzenoid PAHs. In contrast, samples of diesel fuels from the United Kingdom and the United States contain petrogenic alkyl-PAHs with high hydrogen contents. Samples of diesel particulate emissions typical of the 1990s from two different sources display the full mass range of PAHs from 128 to 350 u, including both the benzenoid PAHs and the alkyl-PAHs. Thus diesel emissions, in general, may contain petrogenic fuel components ranging up to 206 u and also the combustion-generated four- to seven-ring species in the 228 to 302 u mass range that have greater carcinogenic potency. The absence of petrogenic components larger than 206 u facilitates their detection and delineation from pyrogenic PAHs by methods of chemical analysis.     

Renewable corn-ethanol and energy security

Though corn-ethanol is promoted as renewable, models of the production process assume fossil fuel inputs. Moreover, ethanol is promoted as a means of increasing energy security, but there is little discussion of the dependability of its supply. This study investigates the sensibility of promoting corn-ethanol as an automobile fuel, assuming a fully renewable production process. We then use historical data to estimate the supply risk of ethanol relative to imported petroleum. We find that devoting 100% of US corn to ethanol would displace 3.5% of gasoline consumption and the annual supply of the ethanol would be inherently more risky than that of imported oil. Finally, because large temperature increases can simultaneously increase fuel demand and the cost of growing corn, the supply responses of ethanol producers to temperature-induced demand shocks would likely be weaker than those of gasoline producers.     

Effects of packaging SrI2(Eu) scintillator crystals

Recent renewed emphasis placed on gamma-ray detectors for national security purposes has motivated researchers to identify and develop new scintillator materials capable of high energy resolution and growable to large sizes. We have discovered that SrI₂(Eu) has many desirable properties for gamma-ray detection and spectroscopy, including high light yield of ∼90,000 photons/MeV and excellent light yield proportionality. We have measured <2.7% FWHM at 662 keV with small detectors (<1 cm³) in direct contact with a photomultiplier tube, and ∼3% resolution at 662 keV is obtained for 1 in.³ crystals. Due to the hygroscopic nature of SrI₂(Eu), similar to NaI(Tl), proper packaging is required for field use. This work describes a systematic study performed to determine the key factors in the packaging process to optimize performance. These factors include proper polishing of the surface, the geometry of the crystal, reflector materials and windows. A technique based on use of a collimated ¹³⁷Cs source was developed to examine light collection uniformity. Employing this technique, we found that when the crystal is packaged properly, the variation in the pulse height at 662 keV from events near the bottom of the crystal compared to those near the top of the crystal could be reduced to <1%. This paper describes the design and engineering of our detector package in order to improve energy resolution of 1 in.³-scale SrI₂(Eu) crystals.     

Exploratory analytics on patent data sets using the SIMPLE platform

Exploratory Analytics is the process of analyzing data for the purpose of forming hypotheses. Patent data sets, because they are relatively large and diverse and because they consist of a mixture of structured and unstructured information present a formidable challenge and a great opportunity in applying exploratory analytics techniques. In this paper we describe methods we have implemented for effective exploratory analytics on patent data sets using an interactive approach and a web based software tool called SIMPLE. We use real-world case studies to demonstrate the effectiveness of our exploratory analytics approach in the discovery of useful information from the patent corpus.     

An advanced model for initiation and propagation of damage under fatigue loading – part II: Matrix cracking validation cases

A series of tests were conducted to act as validation cases for the numerical model developed in part I of this paper to predict the initiation and propagation of damage in composite materials. The onset of matrix cracking in [0₂/θ₄]_s specimens under tension–tension fatigue loading was studied using acoustic emission (AE) and dye-penetrant enhanced X-rays. The number of cracks identified by significant AE hits correlated well with the number of cracks identified by X-rays. Finite Element simulations of the [0₂/θ₄]_s specimens using the model from part I for cohesive interface elements fatigue loading showed a good correlation with the experimental results.     

Antimicrobial Activity of Natural Agents against Saccharomyces cerevisiae

The antimicrobial (AM) activity of starch‐based films coated with linalool, carvacrol or thymol against Saccharomyces cerevisiae in vitro and/or inoculated on the surface of Cheddar cheese was investigated. In solid medium using the agar diffusion method and in experiments involving the inoculation of the microorganism on the surface of Cheddar cheese, all the films containing these AM agents in coatings demonstrated an inhibitory effect against S. cerevisiae. The results suggest that the overall inhibitory effect of linalool, carvacrol or thymol increased significantly (p ≤ 0.05) with the concentration of each of the AM agents in the film coating and that the response is linear in the concentration range of 1 to 5% (w/w) of the AM agent. Thymol had the highest AM efficacy followed by carvacrol, whereas linalool had the lowest efficacy amongst the three systems. The zones of inhibition in the agar diffusion test method at 25°C for S. cerevisiae were found to be 7.6, 7.1 and 6.1 mm for thymol, carvacrol and linalool at 1% (w/w) loading and 13.2, 12.2 and 11.2 mm at 5% (w/w) loading of the AM agents, respectively. The death rates of S. cerevisiae on Cheddar cheese wrapped in films coated with thymol, carvacrol and linalool and stored for up to 28 days at 15°C were found to be 0.044, 0.043 and 0.038 per day at 1% (w/w) loading and 0.077, 0.073 and 0.063 per day at 5% (w/w) loading of the AM agents, respectively. Copyright © 2011 John Wiley & Sons, Ltd.     

GPU-based real-time small displacement estimation with ultrasound

General purpose computing on graphics processing units (GPUs) has been previously shown to speed up computationally intensive data processing and image reconstruction algorithms for computed tomography (CT), magnetic resonance (MR), and ultrasound images. Although some algorithms in ultrasound have been converted to GPU processing, many investigative ultrasound research systems still use serial processing on a single CPU. One such ultrasound modality is acoustic radiation force impulse (ARFI) imaging, which investigates the mechanical properties of soft tissue. Traditionally, the raw data are processed offline to estimate the displacement of the tissue after the application of radiation force. It is highly advantageous to process the data in real-time to assess their quality and make modifications during a study. In this paper, we present algorithms for efficient GPU parallel processing of two widely used tools in ultrasound: cubic spline interpolation and Loupas' two-dimensional autocorrelator for displacement estimation. It is shown that a commercially available graphics card can be used for these computations, achieving speed increases up to 40x compared with single CPU processing. Thus, we conclude that the GPU-based data processing approach facilitates real-time (i.e., <1 second) display of ARFI data and is a promising approach for ultrasonic research systems.     

Ultrasonic backscatter imaging by shear-wave-induced echo phase encoding of target locations

We present a novel method for ultrasound backscatter image formation wherein lateral resolution of the target is obtained by using traveling shear waves to encode the lateral position of targets in the phase of the received echo. We demonstrate that the phase modulation as a function of shear wavenumber can be expressed in terms of a Fourier transform of the lateral component of the target echogenicity. The inverse transform, obtained by measurements of the phase modulation over a range of shear wave spatial frequencies, yields the lateral scatterer distribution. Range data are recovered from time of flight as in conventional ultrasound, yielding a B-mode-like image. In contrast to conventional ultrasound imaging, where mechanical or electronic focusing is used and lateral resolution is determined by aperture size and wavelength, we demonstrate that lateral resolution using the proposed method is independent of the properties of the aperture. Lateral resolution of the target is achieved using a stationary, unfocused, single-element transducer. We present simulated images of targets of uniform and non-uniform shear modulus. Compounding for speckle reduction is demonstrated. Finally, we demonstrate image formation with an unfocused transducer in gelatin phantoms of uniform shear modulus.