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The paper presents an automatic procedure for the correction of bridge weigh-in-motion (B-WIM) measurements, which are used to determine the axle loads of heavy vehicles using instrumented bridges. According to the European specifications for weigh-in-motion criteria, using this procedure the weighing results could be improved by up to one accuracy class. Whereas measurements performed on steel structures provide reliable information about the global behaviour of individual bridges, which is accounted for in the B-WIM algorithms, cracks that are present in concrete structures can, depending on their locations with respect to installed strain transducers, amplify or reduce the response. In the present work special care was taken to detect and calibrate any strain transducer which showed a disproportional response. The accuracy of the method was investigated numerically in relation to the extensive data which were available in the case of a reinforced concrete bridge (motorway underpass), located near Ljubljana, Slovenia, and then validated by a one-to-one comparison of the B-WIM weighing results and the statically weighed test vehicles. [ABSTRACT FROM AUTHOR]

Abstract: The paper discusses a possibility of using an ultrasonic wave transmission method to study the influence of superplasticizers on the formation of structure of cement pastes at early ages. When compared to mixtures without additives, lower P-wave velocity was found through superplasticized cement pastes, indicating that superplasticizers prevent formation of a solid network frame. Comparing to sulfonate naphthalene-formaldehyde superplasticizers, polycarboxylate ether (PCE) admixtures retarded the solid network frame development more intensively, resulting in a plateau on a P-wave velocity curve during the setting period. The length of the plateau is proportional to the dosage of the PCE and inversely proportional to the specific surface area of the hydration products developed, proving that the specific surface area of a solid phase affects the performance of the PCEs. Validation of ultrasonic results was determined on the basis of the temperature evolution of the material in time. [Copyright &y& Elsevier]

Abstract: A mathematical model for structural behavior of timber columns under fire has been proposed. The semi-analytical study has been carried out for evaluating the load-carrying capacity of timber columns exposed to fire. Particular emphasis has been given to critical buckling loads. For this purpose, a parametric study has been performed by which the influence of slenderness ratio, load level, and water content on critical buckling loads of timber columns have been investigated. The results of this preliminary study showed that the present semi-analytical method is conservative compared to the two simplified calculation methods offered by Eurocode 5 if the transfer of water is neglected, while, on the other hand, the results agree well for a water content of 12%. Moreover, for higher water contents, the present semi-analytical model is non-conservative compared to the Eurocode 5 methods. [Copyright &y& Elsevier]

Abstract: The HIV epidemic in Argentina is characterized by the high prevalence of infections caused by subtype B and BF variants. In this study, the Nef protein was used as a tool to study the impact of HIV-1 BF variants in the design of future vaccines. DNA and MVA vectors expressing Nef of the CRF12_BF recombinant form of HIV-1 were generated and characterized. After the administration of single DNAprime/MVAboost immunization schedules in Balb/c mice we found that NefBF delivered from these vectors generated a response of high specificity with low cross-reactivity against subtype B. But, when a more potent response was induced after 3 priming DNA doses and a booster with MVA virus, cross-reactivity against NefB was detected, although of lower magnitude than the NefBF specific. These results will be pivotal for vaccines designs in our region, indicating that antigens from these viral variants must be considered for a future vaccine. [Copyright &y& Elsevier]

Abstract: The paper presents an alternative approach to the modelling of the mechanical behaviour of steel frame material when exposed to the high temperatures expected in fires. Based on a series of stress–strain curves obtained experimentally for various temperature levels, an artificial neural network (ANN) is employed in the material modelling of steel. Geometrically and materially, a non-linear analysis of plane frame structures subjected to fire is performed by FEM. The numerical results of a simply supported beam are compared with our measurements, and show a good agreement, although the temperature–displacement curves exhibit rather irregular shapes. It can be concluded that ANN is an efficient tool for modelling the material properties of steel frames in fire engineering design studies. [Copyright &y& Elsevier]

Abstract: To assess the long-term safety of a radioactive waste disposal system, mathematical models are used to describe groundwater flow, chemistry, and potential radionuclide migration through geological formations. A number of processes need to be considered, when predicting the movement of radionuclides through the geosphere. The most important input data are obtained from field measurements, which are not available for all regions of interest. For example, the hydraulic conductivity as an input parameter varies from place to place. In such cases, geostatistical science offers a variety of spatial estimation procedures. Methods for solving the solute transport equation can also be classified as Eulerian, Lagrangian and mixed. The numerical solution of partial differential equations (PDE) has usually been obtained by finite-difference methods (FDM), finite-element methods (FEM), or finite-volume methods (FVM). Kansa introduced the concept of solving partial differential equations using radial basis functions (RBF) for hyperbolic, parabolic, and elliptic PDEs. The aim of this study was to present a relatively new approach to the modeling of radionuclide migration through the geosphere using radial basis function methods in Eulerian and Lagrangian coordinates. In this study, we determine the average and standard deviation of radionuclide concentration with regard to variable hydraulic conductivity, which was modelled by a geostatistical approach. Radionuclide concentrations will also be calculated in heterogeneous and partly heterogeneous 2D porous media. [Copyright &y& Elsevier]

Abstract: A mathematical model for slip-buckling has been proposed and its analytical solution has been found for the analysis of layered and geometrically perfect composite columns with inter-layer slip between the layers. The analytical study has been carried out to evaluate exact critical forces and to compare them to those in the literature. Particular emphasis has been placed on the influence of interface compliance on decreasing the bifurcation loads. For this purpose, a preliminary parametric study has been performed by which the influence of various material and geometric parameters on buckling forces have been investigated. [Copyright &y& Elsevier]

Abstract: The purpose of this paper is to model the behaviour of timber composite beams with interlayer slip, when simultaneously exposed to static loading and fire. A transient moisture-thermal state of a timber beam is analysed by the Luikov equations, and mechanical behaviour of timber composite beam is modelled by Reissner''s kinematic equations. The model can handle layers of different materials. Material properties are functions of temperature. The thermal model is validated against the experimental data presented in the literature. Generally, the model provides excellent agreement with the experimental data. It is shown that the material properties of timber play an important role in the fire resistance analysis of timber structures when exposed to fire. [Copyright &y& Elsevier]

Abstract: The paper deals with the characteristic value determination from relatively small samples. When the distribution and its parameters of a random variable are known, the characteristic value is deterministic quantity. However, in practical problems the parameters of distribution are unknown and can only be estimated from random samples. Therefore the characteristic value is by itself a random variable. The estimates of characteristic values are strongly dependant on the distribution of random variable. In the paper we show the analytical solution for characteristic value determination from random samples of normal and lognormal random variables. The confirmation of analytical results is accomplished by the use of computer simulations. For Gumbel, and Weibull distribution the characteristic value estimates are obtained numerically by combination of simulations and bisection method. In the paper the numerical results are presented for 5% characteristic values with 75% confidence interval, which is in accord with the majority of European building standards. The proposed approach is demonstrated on the data of experimentally obtained bending strengths of finger jointed wooden beams. [Copyright &y& Elsevier]

• Determination of residual mechanical properties of limestone concrete. • Influence of water to cement ratio and temperature on experimental results. • Relationships between results from destructive and nondestructive tests. • US pulse velocity and surface strength can predict the concrete residual strength. The feasibility of estimation of mechanical properties of limestone concrete after exposure to high temperatures, using nondestructive methods, was investigated. Experimental study was carried out on two concrete mixtures that differed in water to cement ratio (w/c). After standard curing time, specimens were exposed to various temperature levels, i.e. 20 °C, 200 °C, 400 °C, 600 °C or 800 °C. Basic mechanical properties of concrete specimens were determined prior heating at ambient temperature. Once the specimens were cooled down to the ambient temperature, various nondestructive tests including ultrasonic (US) method, determination of rebound number, and resonant frequency method were performed. Further on, specimens were visually inspected to assess the damage of the concrete surface. To determine the residual mechanical properties of specimens after exposure to high temperature, the compressive and flexural strengths were determined on cubic and prismatic specimens, respectively. The main goal of presented research was the estimation of the compressive and flexural strengths of limestone concrete after fire based on developed relationships between results of destructive and nondestructive measurements performed on limestone concrete mixtures 1 and 2. The best relationship for estimation of compressive strength was determined based on measured fundamental torsional frequency, whereas the best relationship for estimation of flexural strength was determined based on combination of fundamental flexural frequency and US pulse velocity, both measured on prisms. The analysis of variance (ANOVA) showed that the influence of temperature on experimental results, obtained from destructive and nondestructive tests, is highly statistically significant for both mixtures. Posteriori test revealed that the majority of the measured quantities were significantly different on the temperature interval between 400 °C and 600 °C. [ABSTRACT FROM AUTHOR]

Abstract: A new mathematical model and its finite element formulation for the non-linear analysis of mechanical behaviour of a two-layer timber planar beam is presented. A modified principle of virtual work is employed in formulating the finite element method. The basic unknowns are strains. The following assumptions are adopted in the mathematical model: materials are taken to be non-linear and can differ from layer to layer; interacting shear and normal contact tractions between layers are derived from the non-linear shear contact traction–slip and the non-linear normal contact traction–uplift characteristics of the connectors; the geometrically linear and materially non-linear Bernoulli’s beam theory is assumed for each layer. The formulation is found to be accurate, reliable and computationally effective. The suitability of the theory is validated by the comparison of the numerical solution and the experimental results of full-scale laboratory tests on a simply supported beam. An excellent agreement between measured and calculated results is observed for all load levels. The further objective of the paper is the analysis of the effect of different normal contact traction–uplift constitutive relationships on the kinematic and static quantities in a statically determined and undetermined structure. While the shear contact traction–slip constitutive relationship dictates the deformability of the composite beam and has a substantial influence on most of the static and kinematic quantities of the composite beam, a variable normal contact traction–uplift constitutive relationship is in most cases negligible. [Copyright &y& Elsevier]

During the acute phase of HIV-1 infection, a strong readaptation occurs in the viral population. Our objective was to analyze the post-transmission mutations associated with escape to the cytotoxic immune response and its relationship with the progression of the infection. In this study, a total of 17 patients were enrolled during acute/early primary HIV infection and 8 subjects that were the HIV positive partner resulting in 8 transmission pairs. Genotyping of the genetic polymorphisms of HLA class I A and B was performed using PCR-SSOP. Viral RNA extraction was from plasma. 570 single Gag-gene amplifications were obtained by limiting-dilution RT-PCR. Epitope prediction was performed with NetMHC CBS prediction server for the 19 HLA-A and B alleles. Cytotoxic response prediction was performed by using the IEDB Analysis Resource. From our results, we deduce that the transmitted CTL / gag escape frequency in the founder virus was at least double compared to the post-transmission events. Additionally, by means of an algorithm that combines these frequencies, we observed that the founder viruses better adapted to the HLA A / B alleles of the recipient could contribute to a greater progression of the infection. Our results suggest that there is a large adaptation of HIV-1 to the HLA A / B alleles prevalent in our population. However, despite this adaptive advantage, the virus needs to make "readjustments" through new escape and compensatory mutations. Interestingly, according to our results, this readaptation could have a role in the progression of the infection. • The highest proportion of HIV-1 viral escape was transmitted. • Protein p24 showed the lowest proportion of epitopes associated with escape. • The frequency of CTL escape is influenced by the frequency of the allele. • The viral readaptation to new host could influence the progression of infection. • Gag segments associated with escape presented more significant entropy variation. [ABSTRACT FROM AUTHOR]