Twin disc assessment of wheel/rail adhesion

Loss of adhesion between a railway wheel and the track has implications for both braking and traction. Poor adhesion in braking is a safety issue as it leads to extended stopping distances. In traction, it is a performance issue as it may lead to reduced acceleration which could cause delays. In this work, wheel/rail adhesion was assessed using a twin disc simulation. The effects of a number of contaminants, such as oil, dry and wet leaves and sand were investigated. These have been shown in the past to have significant effect on adhesion, but this has not been well quantified. The results have shown that both oil and water reduce adhesion from the dry condition. Leaves, however, gave the lowest adhesion values, even when dry. The addition of sand, commonly used as a friction enhancer, to leaves, brought adhesion levels back to the levels without leaves present. Adhesion levels recorded, particularly for the wet, dry and oil conditions are in the range seen in field measurements. Relatively severe disc surface damage and subsurface deformation was seen after the addition of sand. Leaves were also seen to cause indents in the disc surfaces. The twin disc approach has been shown to provide a good approach for comparing adhesion levels under a range of wheel/rail contact conditions, with and without contaminants

Rolling-sliding laboratory tests of friction modifiers in dry and wet wheel-rail contacts

Friction management has been carried out extensively in the majority of railway networks in the last few years. A popular practice is the application of friction modifiers to increase the adhesion level in contaminated wheel-rail contacts. Two friction modifiers have particularly been used or tested on several railway networks as adhesion enhancers to facilitate the traction and braking operation under poor adhesion conditions. However, for assessment of the performance the railway operators and infrastructure managers mostly rely on practical observations that do not elucidate completely the effectiveness and side effects of these adhesion enhancers. In this paper, the constituents of the two friction modifiers are identified and the solid components are analyzed. A twin-disk roller rig has been used to study their performance in dry and wet contacts under closely controlled laboratory conditions. The adhesion characteristics of both friction modifiers are examined for different slip ratios. Furthermore, the wheel and rail disks are examined after a series of dry tests to analyze the mass loss, the surface damage, the change in surface hardness and roughness, and the subsurface deformation caused by the friction modifiers compared to dry clean contacts. (C) 2009 Elsevier B.V. All rights reserved

Sublethal concentrations of waterborne copper induce cellular stress and cell death in zebrafish embryos and larvae

http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-97602011000100002&lng=es&nrm=isoCopper is an essential ion that forms part of the active sites of many proteins. At the same time, an excess of this metal produces free radicals that are toxic for cells and organisms. Fish have been used extensively to study the effects of metals, including copper, present in food or the environment. It has been shown that different metals induce different adaptive responses in adult fish. However, until now, scant information has been available about the responses that are induced by waterborne copper during early life stages of fish. Here, acute toxicity tests and LC50 curves have been generated for zebrafish larvae exposed to dissolved copper sulphate at different concentrations and for different treatment times. We determined that the larvae incorporate and accumulate copper present in the medium in a concentration-dependent manner, resulting in changes in gene expression. Using a transgenic fish line that expresses enhanced green fluorescent protein (EGFP) under the hsp70 promoter, we monitored tissue-specific stress responses to waterborne copper by following expression of the reporter. Furthermore, TUNEL assays revealed which tissues are more susceptible to cell death after exposure to copper. Our results establish a framework for the analysis of whole-organism management of excess external copper in developing aquatic animals

Wheel and rail contact simulation using a twin disc tester.

The contact between wheel and rail has been studied for many years in the field and using different test approaches. The wheel/rail contact in this work was simulated by a rolling-sliding twin disc contact machine. Currently this approach is widely accepted as a technique for studying different aspects of the wheel/rail contact such as; wear, rolling contact fatigue (RCF) crack propagation and issues concerning wheel/rail isolation

Optical properties of carbon nanostructures produced by laser irradiation on chemically modified multi-walledcarbon nanotubes

Apoyo a la Red Temática de Colaboración Académica: Desarrollo de Materiales Compuestos con propiedades Ópticas, Eléctricas , Magnéticas y sus aplicacionesThis research focused on the nanosecond(Nd:YAG-1064 nm) laser pulse effect on the optical and morphological properties of chemically modified multi-walled carbon nanotubes(MWCNT).Two sus- pensions of MWCNT in tetrahydrofuran (THF) were prepared,one was submitted to laser pulses for 10 min while the other (blank) was only mechanically homogenized during the same time. Following the laser irradiation, the suspension acquired a yellow-amber color,in contrast to the black translucent appearance of the blank. UV-vis spectroscopy confirmed this observation, showing the blank a higher absorption. Additionally, photoluminescence measurements exhibited a broad blue-green emission band both in the blank and irradiated suspension when excited at 369 nm, showing the blank a lower intensity. However, a modification in the excitation wave length produced a violet to green tuningin the irradiated suspension, which did not occurin the blank. Lastly, the electron microscopy analysis of the treated nanotubes showed the abundant formation of amorphous carbon, nanocages, and nanotube unzipping, exhibiting the intense surface modification produced by the laser pulse. Nanotube surface modification and the coexistence with the new carbon nanostructures were considered as the conductive conditions for optical properties modification.PROME

Techno-economic evaluation of a grid-connected hybrid PV-wind power generation system in San Luis Potosi, Mexico

This paper presents a study of the installation of a hybrid PV-Wind power generation system for social interest houses in the city of San Luis Potosi, Mexico. To assess the benefits of the implementation of this type of systems, a technological, economic and environmental evaluation is carried out based on the available renewable energy resources and considering a typical load profile of consumers. The obtained results show the feasibility of installation of small capacity hybrid generation systems in the city, however governmental incentives must be implemented to make more attractive and affordable the proposed systems for medium/low income users

Failure Diagnosis on Photovoltaic Modules Using Thermography, Electroluminescence, Rgb and I-V Techniques

Different techniques can be used to detect and quantify PV modules anomalies, as visual inspections, electrical tests like the I-V curve test, infrared thermography (IRT) or electroluminescence (EL). PV plants operators usually apply only one or two of them within the Operation and Maintenance (O&M) activities. Additionally, researchers usually studied them separately. However, these methods provide complementary results, glimpsing interesting information about the PV site state. The main strength of the research performed is the simultaneous study of all these inspection techniques, studying the correlation between them. Results confirm that, EL and IRT under current injection on modules are closely correlated, while IRT under normal operation (sun exposure) reveals complementary information not detected in EL but existing in the visible spectrum. In conclusion, it is advisable using as many techniques as possible to characterize the actual state of the module and to explain its I-V curve.Proyecto de Investigación ENE2017-89561-C4-3-R (MCIN)Proyecto de Investigación RTC-2017-6712-3 (MCIN)Proyecto de Investigación VA283P18 (Junta de Castilla y León

Early and annual projected savings from anti-CGRP monoclonal antibodies in migraine prevention: a cost-benefit analysis in the working-age population

Anti-CGRP monoclonal antibodies; Migraine prevention; Cost-benefitAnticuerpos monoclonales anti-CGRP; Prevención de la migraña; Costo-beneficioAnticossos monoclonals anti-CGRP; Prevenció de la migranya; Cost-beneficiBackground Migraine is one of the main causes of disability worldwide. Anti-CGRP monoclonal antibodies (MAbs) have proven to be safe and efficacious as preventive migraine treatments. However, their use is restricted in many countries due to their apparently high cost. Cost-benefit studies are needed. Objective To study the cost-benefit of anti-CGRP MAbs in working-age patients with migraine. Methods This is a prospective cohort study of consecutive migraine patients treated with anti-CGRP MAbs (erenumab, fremanezumab and galcanezumab) following National reimbursement policy in a specialized headache clinic. Migraine characteristics and the work impact scale (WPAI) were compared between baseline (M0) and after 3 (M3) and 6 months (M6) of treatment. Using WPAI and the municipal average hourly wage, we calculated indirect costs (absenteeism and presenteeism) at each time point. Direct costs (emergency visits, acute medication use) were also analysed. A cost-benefit study was performed considering the different costs and savings of treating with MAbs. Based on these data an annual projection was conducted. Results From 256 treated working-age patients, 148 were employed (89.2% women; mean age 48.0 ± 8.5 years), of which 41.2% (61/148) were responders (> 50% reduction in monthly headache days (MHD)). Statistically significant reductions between M0 and M3/M6 were found in absenteeism (p < 0.001) and presenteeism (p < 0.001). Average savings in indirect costs per patient at M3 were absenteeism 105.4 euros/month and presenteeism 394.3 euros/month, similar for M6. Considering the monthly cost of anti-CGRP MAbs, the cost-benefit analysis showed savings of 159.8 euros per patient at M3, with an annual projected savings of 639.2 euros/patient. Both responders and partial responders (30–50% reduction in MHD) presented a positive cost-benefit balance. The overall savings of the cohort at M3/M6 compensated the negative cost-benefit balance for non-responders (< 30% reduction in MHD). Conclusion Anti-CGRP MAbs have a positive impact in the workforce significantly reducing absenteeism and presenteeism. In Spain, this benefit overcomes the expenses derived from their use already at 3 months and is potentially sustainable at longer term; also in patients who are only partial responders, prompting reconsideration of current reimbursement criteria and motivating the extension of similar cost-benefit studies in other countries