Improved Bounds for rr-Identifying Codes of the Hex Grid

For any positive integer $r$, an $r$-identifying code on a graph $G$ is a set $C\subset V(G)$ such that for every vertex in $V(G)$, the intersection of the radius-$r$ closed neighborhood with $C$ is nonempty and pairwise distinct. For a finite graph, the density of a code is $|C|/|V(G)|$, which naturally extends to a definition of density in certain infinite graphs which are locally finite. We find a code of density less than $5/(6r)$, which is sparser than the prior best construction which has density approximately $8/(9r)$.Comment: 12p

Selection for antibiotic resistance in complex microbial communities

Measureable concentrations of antibiotics are released into the environment from anthropogenic sources. Environmental risk assessment investigates the risks these concentrations pose to aquatic life but does not determine whether selection for resistance is occurring. Recent studies suggest environmental concentrations of tetracycline, ciprofloxacin and cefotaxime may be able to select for resistance in complex microbial communities. The aims of research presented in this thesis were to determine whether selection for resistance occurs at environmentally relevant concentrations of macrolide antibiotics; to understand how mixtures of antibiotics affect selective endpoints; to understand the effect of temperature on selective endpoints, and, finally, to compare the methods used with previously published methods. Selective endpoints of macrolide antibiotics were found to be 1,000 µg/L of azithromycin and erythromycin and 750 µg/L of clarithromycin which is significantly higher than current environmental concentrations. Mixing of antibiotics produces at least an additive, if not a synergistic, effect. The selective endpoints of sulfamethoxazole and trimethoprim decrease over 11 times and by a half, respectively, when used in combination. The selective endpoint of macrolides is reduced by a third when they are found in combination. Selective endpoints of individual genes are affected by temperature but, as only preliminary data has been produced, overall effect concentrations have not been determined across the entire experimental resistome. Alternative gene targets associated with taxa favoured at low temperatures may be under selection. Finally, the phenomenon of increased persistence has been described and the minimal increased persistence concentration has been defined for the first time. Data presented here can be used by policy makers in environmental risk assessments, in conjunction with other ecotoxicological endpoints to determine safe release levels of antibiotic residues in wastewater. This will help minimise selection for antibiotic resistance in the environment and, therefore, exposure of humans to resistant bacteria through environmental transmission.Biotechnology & Biological Sciences Research Council (BBSRC

Behavioural compensation by drivers of a simulator when using a vision enhancement system

Technological progress is suggesting dramatic changes to the tasks of the driver, with the general aim of making driving environment safer. Before any of these technologies are implemented, empirical research is required to establish if these devices do, in fact, bring about the anticipated improvements. Initially, at least, simulated driving environments offer a means of conducting this research. The study reported here concentrates on the application of a vision enhancement (VE) system within the risk homeostasis paradigm. It was anticipated, in line with risk homeostasis theory, that drivers would compensate for the reduction in risk by increasing speed. The results support the hypothesis although, after a simulated failure of the VE system, drivers did reduce their speed due to reduced confidence in the reliability of the system

Epic Human Failure on June 30, 2013

Nineteen Prescott Fire Department, Granite Mountain Hot Shot (GMHS) wildland firefighters and supervisors (WFF), perished on the June 2013 Yarnell Hill Fire (YHF) in Arizona. The firefighters left their Safety Zone during forecast, outflow winds, triggering explosive fire behavior in drought-stressed chaparral. Why would an experienced WFF Crew, leave ‘good black’ and travel downslope through a brush-filled chimney, contrary to their training and experience? An organized Serious Accident Investigation Team (SAIT) found, “… no indication of negligence, reckless actions, or violations of policy or protocol.” Despite this, many WFF professionals deemed the catastrophe, “… the final, fatal link, in a long chain of bad decisions with good outcomes.” This paper is a theoretical and realistic examination of plausible, faulty, human decisions with prior good outcomes; internal and external impacts, influencing the GMHS; and two explanations for this catastrophe: Individual Blame Logic and Organizational Function Logic, and proposed preventive mitigations

Third annual report

A large share of the Director’s time last winter was occupied in work at farmer’s institutes; stock meetings, and horticultural meetings in different parts of the state, and in preparing for the Station work of last summer. We hauled 420 loads of manure last winter from Ames to the poorest parts of the Experiment Station grounds. The sowing of the different kinds of grain and grass seeds was the first field work which was performed last spring. Some of them were sowed early and others late. On a part of the plats they were planted thick and on others thin. And the preparation of the plats for the seeds varied much, as a part of them were plowed nine inches deep; while others were plowed only four inches, and a few of them were only well scratched with cultivators and harrows at seeding time. The number of kinds of grain which we planted were as follows: Oats thirty; spring wheat nine; barley eight; rye two, and field peas two. For the purpose of finding better fodder plants than many of the common kinds if possible, we planted twenty four kinds of field and garden bush beans, and twenty one kinds of peas; but the beaus proved partial failures on account of drouth, and the peas were ruined by rust. We planted five of the best kinds of den? corn and an equal number of varieties of sweet corn; as well as dent and sweet corn which was obtained by crossing kinds which had the most desirable characteristics in 1889 We planted also for trial fifty two kinds of potatoes, and many different varieties of sorghum, sugar beets, mangolds, carrots, tomatoes, etc

Impact of sequence variation in the ul128 locus on production of human cytomegalovirus in fibroblast and epithelial cells

The human cytomegalovirus (HCMV) virion envelope contains a complex consisting of glycoproteins gH and gL plus proteins encoded by the UL128 locus (UL128L): pUL128, pUL130, and pUL131A. UL128L is necessary for efficient infection of myeloid, epithelial, and endothelial cells but limits replication in fibroblasts. Consequently, disrupting mutations in UL128L are rapidly selected when clinical isolates are cultured in fibroblasts. In contrast, bacterial artificial chromosome (BAC)-cloned strains TB40-BAC4, FIX, and TR do not contain overt disruptions in UL128L, yet no virus reconstituted from them has been reported to acquire mutations in UL128L in vitro. We performed BAC mutagenesis and reconstitution experiments to test the hypothesis that these strains contain subtle mutations in UL128L that were acquired during passage prior to BAC cloning. Compared to strain Merlin containing wild-type UL128L, all three strains produced higher yields of cell-free virus. Moreover, TB40-BAC4 and FIX spread cell to cell more rapidly than wild-type Merlin in fibroblasts but more slowly in epithelial cells. The differential growth properties of TB40-BAC4 and FIX (but not TR) were mapped to single-nucleotide substitutions in UL128L. The substitution in TB40-BAC4 reduced the splicing efficiency of UL128, and that in FIX resulted in an amino acid substitution in UL130. Introduction of these substitutions into Merlin dramatically increased yields of cell-free virus and increased cell-to-cell spread in fibroblasts but reduced the abundance of pUL128 in the virion and the efficiency of epithelial cell infection. These substitutions appear to represent mutations in UL128L that permit virus to be propagated in fibroblasts while retaining epithelial cell tropism

Macroscopic observations of diel fish movements around a shallow water artificial reef using a mid-frequency horizontal-looking sonar

Author Posting. © Acoustical Society of America, 2018. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 144 (2018): 1424-1434. doi:10.1121/1.5054013.The twilight feeding migration of fish around a shallow water artificial reef (a shipwreck) was observed by a horizontal-looking, mid-frequency sonar. The sonar operated at frequencies between 1.8 and 3.6 kHz and consisted of a co-located source and horizontal line array deployed at 4 km from the reef. The experiment was conducted in a well-mixed shallow water waveguide which is conducive to characterizing fish aggregations at these distances. Large aggregations of fish were repeatedly seen to emerge rapidly from the shipwreck at dusk, disperse into the surrounding area during the night, and quickly converge back to the shipwreck at dawn. This is a rare, macroscopic observation of an ecologically-important reef fish behavior, delivered at the level of aggregations, instead of individual fish tracks that have been documented previously. The significance of this observation on sonar performance associated with target detection in the presence of fish clutter is discussed based on analyses of echo intensity and statistics. Building on previous studies of long-range fish echoes, this study further substantiates the unique utility of such sonar systems as an ecosystem monitoring tool, and illustrates the importance of considering the impact of the presence of fish on sonar applications.We thank Jay Grove from the NOAA Southeast Fisheries Science Center for help in identifying potential fish species near the shipwreck sites. We also thank Jie Yang, B. Todd Hefner, and Kevin Williams at the Applied Physics Laboratory, University of Washington (APL-UW) for discussion on data processing and results interpretation. The study is supported by the Office of Naval Research and the Science & Engineering Enrichment & Development (SEED) Postdoctoral Fellowship from APL-UW.2019-03-1

Task analysis for error identification: Theory, method and validation

This paper presents the underlying theory of Task Analysis for Error Identification. The aim is to illustrate the development of a method that has been proposed for the evaluation of prototypical designs from the perspective of predicting human error. The paper presents the method applied to representative examples. The methodology is considered in terms of the various validation studies that have been conducted, and is discussed in the light of a specific case study

Three-dimensional modeling of acoustic backscattering from fluid-like zooplankton

Author Posting. © Acoustical Society of America, 2002. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 111 (2002): 1197-1210, doi:10.1121/1.1433813.Scattering models that correctly incorporate organism size and shape are a critical component for the remote detection and classification of many marine organisms. In this work, an acoustic scattering model has been developed for fluid-like zooplankton that is based on the distorted wave Born approximation (DWBA) and that makes use of high-resolution three-dimensional measurements of the animal's outer boundary shape. High-resolution computerized tomography (CT) was used to determine the three-dimensional digitizations of animal shape. This study focuses on developing the methodology for incorporating high-resolution CT scans into a scattering model that is generally valid for any body with fluid-like material properties. The model predictions are compared to controlled laboratory measurements of the acoustic backscattering from live individual decapod shrimp. The frequency range used was 50 kHz to 1 MHz and the angular characteristics of the backscattering were investigated with up to a 1° angular resolution. The practical conditions under which it is necessary to make use of high-resolution digitizations of shape are assessed.This work was supported in part by the Woods Hole Oceanographic Institution Education Office