The role of antiparasite treatment experiments in assessing the impact of parasites on wildlife

It has become increasingly clear that parasites can have significant impacts on the dynamics of wildlife populations. Recently, researchers have shifted from using observational approaches to infer the impact of parasites on the health and fitness of individuals to using antiparasite drug treatments to test directly the consequences of infection. However, it is not clear the extent to which these experiments work in wildlife systems, or whether the results of these individual-level treatment experiments can predict the population-level consequences of parasitism. Here, we assess the results of treatment experiments, laying out the benefits and limitations of this approach, and discuss how they can be used to improve our understanding of the role of parasites in wildlife populations

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

Wheel/Rail Tangential Contact Stress Evaluation by Means Of the Modified Strip Method

The article deals with the way of calculating tangential stresses over non-elliptical contact patch where Kalker's simplified method FASTSIM can be used advantageously. This method named FASTSTRIP is adapted for non-elliptical contact area calculated by means of the Strip method. This method is almost as quick as FASTSIM and the results are similar to the CONTACT results. This method may be useful for rail vehicles in track dynamics computation

Iterative Method for Railway Wheel Profile Design

The presented article deals with the methods for the railway wheel profile development on the base of the intended shape of wheelset/track contact geometric characteristics. The article deals with two methods. In short the profiles creation method through arcs radii profile variation is mentioned. The main emphasis is directed to the "Iterative method for a railway wheel profile design". This method is explained in a more detailed way in the article. The base for the creation of new profiles with the help of the first method is an interactive attitude based on the modification of the original shape which is defined by section of a railway wheel profile, with interconnected and exactly defined arcs radii. It is possible to change them according to shape needs of the final geometrical characteristics. The base of the iterative method, which is of the highest importance in this article, is to develop a new profile under given conditions - a prescribed shape of the contact points distribution and the shape of delta-r function. The newly developed wheel profile in the couple with given rail profile will have requested chosen characteristic shapes

Modified HHT Method Usage for Vehicle Vibration Analysis in Time Domain

The paper deals with the analysis of vehicle vibrations in the time domain. The main aim is to modify the HHT-method for the solution of mechanical systems with nonlinear members. The modification enables the computation with the constant system computational matrix. This causes that the triangulation is to be performed once only and the nonlinear members affect only the right side of the algebraic equations system. This can dramatically decrease the time consumption of the computation. We used the method modified in this way for the dynamic analysis of the model with the parameters of the specimen "ERRI - vehicle" that was kinematically excited

Wheelset/Rail Geometric Characteristics Assessment with Regard to Wheelset Rolling

The geometric relation between a wheelset and a rail is assessed with the help of geometric characteristics. Geometric characteristics are: equivalent conicity function, delta r function placement of contact points of a wheelset and a rail, tangent gamma function and effective conicity.It turned out that these characteristics are at present the most important not only for the judgment of ride characteristics of a vehicle on the rail but also for the wearing of wheel treads and rail heads, e. i., for the assessment of the track and vehicles in order to find out the current state and for the assessment of changes of the wheels and rails profile shapes in order to improve the current state too. The process of geometric characteristic assessment of a wheelset and rail with regard to wheelset rolling is analysed in the article

Wheel/Rail Contact Stress Evaluation by Means of The modified Strip Method

The Strip Method is often used for rail/wheel contact area and contact normal stress evaluation. The paper deals with the computational time saving procedure when the computation accuracy is guaranteed. We included the local coordinate system with a presupposed semi-circular course of the normal stress for the purpose of the integral that is necessary for deformation in the middle of individual strips evaluation. The integral is solvable analytically. The input parameters for individual parts of splines and individual strips expression are possible to insert after analytical solution

Railway Wheel and Rail Roughness Analysis

The paper deals with the railway wheel unroundness (out-of-round) analysis and with the rail head roughness analysis. Roughness of the running surfaces is the predominant source of noise of rail bound transport systems today. Reliable measurements of the roughness of rails and wheels are crucial for noise reduction purposes. In the past, the main purpose of measurements was the understanding of corrugation growth and rolling noise generation. Meanwhile, quantitative descriptions have gained considerable importance

The Usage of Arcs Radii Profile Variation for the Synthesis of Railway Wheel and Rail Head Profiles

The presented article deals with one of the ways of profile geometry design of a railway wheel and railhead. The base for the creation of new profiles is an interactive attitude based on the modification of "the original shape which is defined by section of a railway wheel profile", with to each other connected and exactly defined arcs radii. It is possible to change them according to shape needs of the final geometrical characteristics

Analysis of Vehicles Dynamic Properties from the Point of View of Passenger Comfort

The passenger ride comfort can be assessed via the indexes of comfort i.e. via the indirect method in accordance with the European standard ENV 12299: 1999 or 2006. This method is based on the values of accelerations knowledge in the analysed places of vehicle body. The signal of accelerations is filtered and weighted with functions that take into account the sensitivity of human body to the vehicle body vibrations in reference directions. The signal is statistically assessed and the ride comfort indexes for floor, sitting or standing positions are evaluated. The accelerations coming into the assessment of ride comfort indexes can be obtained from measurements or as results of a computer simulation. The paper deals with the accelerations analysis and their influence on the final comfort index