International transferability of accident modification functions for horizontal curves

Studies of the relationship between characteristics of horizontal curves and accident rate have been reported in several countries. The characteristic most often studied is the radius of a horizontal curve. Functions describing the relationship between the radius of horizontal curves and accident rate have been developed in Australia, Canada, Denmark, Germany, Great Britain, New Zealand, Norway, Portugal, Sweden, and the United States. Other characteristics of horizontal curves that have been studied include deflection angle, curve length, the presence of transition curves, super-elevation in curves and distance to adjacent curves. This paper assesses the international transferability of mathematical functions (accident modification functions) that have been developed to relate the radius of horizontal curves to their accident rate. The main research problem is whether these functions are similar, which enhances international transferability, or dissimilar, which reduces international transferability. Accident modification functions for horizontal curve radius developed in the countries listed above are synthesised. The sensitivity of the functions to other characteristics of curves than radius is examined. Accident modification functions developed in different countries have important similarities. The functions diverge with respect to accident rate in the sharpest curves.     

Can a road safety measure be both effective and ineffective at the same time? A game-theoretic model of the effects of daytime running lights

Studies that have evaluated the effects on accidents of daytime running lights for cars have consistently found that cars using daytime running lights are involved in fewer multi-party accidents in daylight than cars not using daytime running lights. However, studies evaluating the effects of mandatory use of daytime running lights have not always found an accident reduction. Although findings are mixed, there is a tendency for the aggregate effects of daytime running lights (i.e. the effects of an increasing share of traffic using daytime running lights) to be smaller than the intrinsic effects (i.e. the difference in accident involvement between cars using and not using daytime running lights). This paper presents a game-theoretic model to explain these apparently inconsistent findings. The game-theoretic model is based on so called Schelling-diagrams, originally introduced by Nobel laureate in economics Schelling. The effects of daytime running lights are modelled by means of Schelling-diagrams. It is shown that it is by no means impossible for cars using daytime running lights to always be safer than cars not using daytime running lights, while the total number of accidents remains constant even if the percentage of cars using daytime running lights increases from, say, 10% to 90%.     

A study of metal concentrations and metallothionein binding capacity in liver, kidney and brain tissues of three Arctic seal species

Arctic seals are known to accumulate relatively high concentrations of potential toxic heavy metals in their vital organs, such as livers and kidneys, as well as in their central nervous system. We therefore decided to determine whether mercury, copper, cadmium and zinc levels in liver, kidney and brain tissues of three Arctic seal species were associated with the intracellular metal-binding protein metallothionein (MT) as a sign of toxic exposure. Samples from four ringed (Phoca hispida), five harp (P.groenlandica) and five hooded (Cystophora cristata) seals taken during field trips to Central West Greenland (Godhavn) and the Barents Sea in the spring of 1999 were used for the present study. In all three seal species concentrations of mercury, zinc and copper were highest in the liver, except for cadmium which was highest in the kidneys. Metal concentrations increased significantly in the order: ringed seal < harp seal < hooded seal for both kidney and liver tissues. MT concentrations were highest in the kidneys and the concentrations increased in the order: ringed seal < hooded seal < harp seal. MT metal-binding capacity was highest in the kidneys for all three species and increased in the same order: ringed seals (2-10%) < hooded seals (8-15%) < harp seals (27-63%). We therefore suggest that there are species-specific differences in the sub-cellular handling of heavy metals which indicate differences in sensitivity and health implications. However, a larger sample size is needed in order to test the relationship between metal concentrations and MT up-regulation in order to decide which metals are the most important and to elucidate whether the MT binding capacity is sufficient to protect tissues (i.e. kidney) from metal toxicosis. MT with its binding capacity could be a useful marker for environmental exposure to metals and their potential toxicity in the Arctic.     

Use of performic acid oxidation to expand the mass distribution of tryptic peptides

Significant identification of proteins by mass fingerprinting and partial sequencing of tryptic peptides is central to proteomics. However, peptide masses cluster with distances of approximately 1 Da. Expanding these clusters will give more peptides of unique masses, thereby identifying proteins with a higher significance. The mass clusters can be expanded downward by including more oxygen atoms in the peptides. Classic performic acid oxidation modifies three residues, Cys to CysO(3), Met to MetO(2), and Trp to TrpO(2). In this study, we compare the mass distributions of tryptic peptides computed from the predicted proteomes of Bacillus subtilis, Drosophila melanogaster, Arabidopsis thaliana, and Homo sapiens modified by oxidation, reduction, and reduction followed by carboxymethylation, carboxamidomethylation, or pyridylethylation. Forty to 46% of the eukaryotic tryptic peptides contain Cys, Met, or Trp. Additionally, the importance of mass accuracy of differentially modified tryptic peptides for significant protein identification by database searches was analyzed. The results show that performic acid oxidation gives markedly extended mass distributions at mass accuracies from +/-0.002 to +/-0.25 Da for the eukaryotes. The effect of the expanded mass distribution on significant protein identification was illustrated by searching simulated mass peak lists against the databases containing oxidized and reduced tryptic peptides. The specificity of formic acid oxidation was tested experimentally, and no general adverse effects were detected. Tryptic peptides provided a 100% sequence coverage of oxidized barley grain peroxidase by LC-MS, and the sequence coverages of oxidized and carboxymethylated bovine serum albumin were similar by MALDI-TOF MS analyses.     

Multisecular corrosion behaviour of low carbon steel in anoxic soils: Characterisation of corrosion system on archaeological artefacts

In the context of the prediction of materials behaviour used in the nuclear waste storage, the understanding of iron corrosion mechanisms in anoxic environment is of great importance. Information can be obtained using complementary analytical tools. Interactions between burial soil and archaeological artefacts are studied by performing on site soil measurements. Moreover, archaeological artefacts are studied on transverse sections using a combination of microbeam techniques. The specific interest of this project lies in the study of ferrous thick corrosion layers formed in anoxic environments.     

Can a safety-in-numbers effect and a hazard-in-numbers effect co-exist in the same data?

Safety-in-numbers denotes a non-linear relationship between exposure (traffic volume) and the number of accidents, characterised by declining risk as traffic volume increases. There is safety-in-numbers when the number of accidents increases less than proportional to traffic volume, e.g. a doubling of traffic volume is associated with less than a doubling of the number of accidents. Hazard-in-numbers, a less-used concept, refers to the opposite effect: the number of accidents increases more than in proportion to traffic volume, e.g. is more than doubled when traffic volume is doubled. This paper discusses whether a safety-in-numbers effect and a hazard-in-numbers effect can co-exist in the same data. It is concluded that both effects can exist in a given data set. The paper proposes to make a distinction between partial safety-in-numbers and complete safety-in-numbers. Another issue that has been raised in discussions about the safety-in-numbers effect is whether the effect found in some studies is an artefact created by the way exposure was measured. The paper discusses whether measuring exposure as a rate or a share, e.g. kilometres travelled per inhabitant per year, will generate a safety-in-numbers effect as a statistical artefact. It is concluded that this is the case. The preferred measure of exposure is a count of the number of road users. The count should not be converted to a rate or to the share any group of road user contribute to total traffic volume.     

Solving a real-life, large-scale energy management problem

This paper introduces a three-phase hybrid heuristic for a large-scale energy management and maintenance scheduling problem. The problem is to schedule maintenance periods and refueling amounts for nuclear power plants with a time horizon of up to five years, and handling a number of scenarios for future demand and prices. The goal is to minimize the expected total production cost. The first phase of the heuristic solves a constraint programming model of a simplified version of the problem, the second performs a local search, and the third handles overproduction in a greedy fashion. This work was initiated in the context of the ROADEF/EURO Challenge 2010. In the concluding phase of the competition, our team ranked second in the junior category and sixth overall. After correcting a small implementation bug in the program that was submitted for final evaluation, our solver ranks first in the overall results from the competition.