Experimental estimation of the residual fatigue life of in-service wind turbine bolts

This study presents an experimental methodology aimed at estimating the residual fatigue life of in-service wind turbine bolts. The main objective is to assess the residual life of the bolts to plan their replacement and to avoid unexpected breakages of wind turbine blade connections. To develop the methodology, M16 bolts of quality 10.9 with controlled predamage were used, simulating in-service operating conditions. The fatigue tests were carried out taking care to place the nut at the point on the bolt that produces the highest damage at the same point where the predamage was performed. In addition, the influence of a possible angular positioning error on the residual fatigue life has been investigated. The residual fatigue life is estimated from the difference in fatigue life of new bolt tests and the fatigue life of predamaged bolt tests, simulating service conditions. Special care has been taken to guarantee that the most damaged zone of the bolt in service is also in the position that produces the highest damage during tests. An experimental procedure for determining the fatigue life of a new bolt from tests conducted on a bolt under the same operating conditions was developed. The developed methodology has been applied to M20 bolts belonging to real turbines in service

Multiscale Modelling and Simulation of Advanced Battery Materials

Development of efficient strategies for the rational design of materials involved in the production and storage of renewable energy is essential for accelerating the transition to a low-carbon economy. To contribute to this goal, we propose a novel workflow for the assessment and optimization of battery materials. The approach effectively combines quantum and atomistic modelling/simulations, enhanced by efficient sampling, Bayesian parameterization, and experimental information. It is implemented to study prospective materials for lithium and sodium batteries

Unveiling Interfacial Li-Ion Dynamics in Li7La3Zr2O12/PEO(LiTFSI) Composite Polymer-Ceramic Solid Electrolytes for All-Solid-State Lithium Batteries

Unlocking the full potential of solid-state electrolytes (SSEs) is key to enabling safer and more-energy dense technologies than today’s Li-ion batteries. In particular, composite materials comprising a conductive, flexible polymer matrix embedding ceramic filler particles are emerging as a good strategy to provide the combination of conductivity and mechanical and chemical stability demanded from SSEs. However, the electrochemical activity of these materials strongly depends on their polymer/ceramic interfacial Li-ion dynamics at the molecular scale, whose fundamental understanding remains elusive. While this interface has been explored for nonconductive ceramic fillers, atomistic modeling of interfaces involving a potentially more promising conductive ceramic filler is still lacking. We address this shortfall by employing molecular dynamics and enhanced Monte Carlo techniques to gain unprecedented insights into the interfacial Li-ion dynamics in a composite polymer-ceramic electrolyte, which integrates polyethylene oxide plus LiN(CF3SO2)2 lithium imide salt (LiTFSI), and Li-ion conductive cubic Li7La3Zr2O12 (LLZO) inclusions. Our simulations automatically produce the interfacial Li-ion distribution assumed in space-charge models and, for the first time, a long-range impact of the garnet surface on the Li-ion diffusivity is unveiled. Based on our calculations and experimental measurements of tensile strength and ionic conductivity, we are able to explain a previously reported drop in conductivity at a critical filler fraction well below the theoretical percolation threshold. Our results pave the way for the computational modeling of other conductive filler/polymer combinations and the rational design of composite SSEs.-Juan de la Cierva grant IJC2018-037214-I, -PID2019-106519RB-I00, as -HPC-Europa3 grant HPC17ERWTO -AI in BCAM, EXP. 2019/004

Effect of Bay Leaves Essential Oil Concentration on the Properties of Biodegradable Carboxymethyl Cellulose-Based Edible Films

Films containing bay leaves essential oils (BEOs) were prepared and evaluated for edible packaging applications. The BEOs were extracted by the Soxhlet method, using ethanol or methanol as organic solvent. Then, films were prepared by “solvent casting” technique using carboxymethyl cellulose (CMC), with different concentrations for the as-obtained BEOs (from 1% to 30% wt.). The resulting films were characterized to evaluate their physical (thickness, moisture content, water solubility and water vapor permeability), optical (transparency and UV-light barrier), mechanical (tensile strength and elongation at break), antioxidant and antimicrobiological properties Attractive films were obtained for food active packaging applications, as they presented a high antioxidant activity (up to 99%) and total phenolic content, and good barrier properties against water vapor (50% improved of CMC) in the case of CMC-film containing 15% wt. ethanolic extract. Related to optical properties, UV-light barrier effect was increased (almost 100% of protection) avoiding typical lipids oxidation in food systems. High water solubility (93%) was also found, ensuring also their biodegradability. Moreover, it was demonstrated that developed films inhibit microorganisms’ growth (Escherichia coli and Candida glabrata), this avoiding an early food oxidation

A survey of domestic wells and pit latrines in rural settlements of Mali: Implications of on-site sanitation on the quality of water supplies

On-site sanitation is generally advocated as a means to eradicate the health hazards associated with open defecation. While this has provided a welcome upgrade to the livelihoods of millions of people in low-income countries, improved sanitation facilities are increasingly becoming a threat to domestic groundwater-based supplies. Within this context, a survey of pit latrines, domestic wells and improved water sources was carried out in a large rural village of southern Mali. All households were surveyed for water, sanitation and hygiene habits. Domestic wells and improved water sources were georeferenced and sampled for water quality (pH, electric conductivity, temperature, turbidity, total dissolved solids, thermotolerant coliforms, chloride and nitrate) and groundwater level, while all latrines were inspected and georeferenced. A GIS database was then used to evaluate the proportion of water points within the influence area of latrines, as well as to underpin multiple regression models to establish the determinants for fecal contamination in drinking supplies. Moreover, an appraisal of domestic water treatment practices was carried out. This revealed that nearly two-thirds of the population uses bleach to purify drinking supplies, but also that domestic-scale treatment as currently implemented by the population is far from effective. It is thus concluded that existing habits could be enhanced as a means to make water supplies safer. Furthermore, population, well and latrine density were all identified as statistically significant predictors for fecal pollution at different spatial scales. These findings are policy-relevant in the context of groundwater-dependent human settlements, since many countries in the developing world currently pursue the objective of eliminating open defecation

Study of overall and local electrochemical responses of oxide films grown on CoCr alloy under biological environments

The interaction of the physiological medium and living tissues with the implant surfaces in biological environments is regulated by biopotentials that induce changes in the chemical composition, structure and thickness of the oxide film. In this work, oxide films grown on CoCr alloys at 0.5 V vs Ag/AgCl and 0.7 V vs Ag/AgCl have been characterized through overall and localized electrochemical techniques in a phosphate buffer solution and 0.3% hyaluronic acid. Nanopores of 10–50 nm diameter are homogeneously distributed along the surface in the oxide film formed at 0.7 V vs Ag/AgCl. The distribution of the Constant Phase Element studied by local electrochemical impedance spectroscopy showed a three-dimensional (3D) model on the oxide films grown at 0.5 V vs Ag/AgCl and 0.7 V vs Ag/AgCl. This behaviour is especially noticeable in oxide films grown at 0.7 V vs Ag/AgCl, probably due to surface inhomogeneities, and resistive properties generated by the potentiostatic growth of the oxide film.This work was supported by the Spanish National government [MINECO-MAT2011-29152-C02-01].Peer reviewe

Thermostability of the foot-and-mouth disease virus capsid is modulated by lethal and viability-restoring compensatory amino acid substitutions

Infection by viruses depends on a balance between capsid stability and dynamics. This study investigated biologically and biotechnologically relevant aspects of the relationship in foot-and-mouth disease virus (FMDV) between capsid structure and thermostability and between thermostability and infectivity. In the FMDV capsid, a substantial number of amino acid side chains at the interfaces between pentameric subunits are charged at neutral pH. Here a mutational analysis revealed that the essential role for virus infection of most of the 8 tested charged groups is not related to substantial changes in capsid protein expression or processing or in capsid assembly or stability against a thermally induced dissociation into pentamers. However, the positively charged side chains of R2018 and H3141, located at the interpentamer interfaces close to the capsid 2-fold symmetry axes, were found to be critical both for virus infectivity and for keeping the capsid in a state of weak thermostability. A charge-restoring substitution (N2019H) that was repeatedly fixed during amplification of viral genomes carrying deleterious mutations reverted both the lethal and capsid-stabilizing effects of the substitution H3141A, leading to a double mutant virus with close to normal infectivity and thermolability. H3141A and other thermostabilizing substitutions had no detectable effect on capsid resistance to acid-induced dissociation into pentamers. The results suggest that FMDV infectivity requires limited local stability around the 2-fold axes at the interpentamer interfaces of the capsid. The implications for the mechanism of genome uncoating in FMDV and the development of thermostabilized vaccines against foot-and-mouth disease are discussed. IMPORTANCE This study provides novel insights into the little-known structural determinants of the balance between thermal stability and instability in the capsid of foot-and-mouth disease virus and into the relationship between capsid stability and virus infectivity. The results provide new guidelines for the development of thermostabilized empty capsid-based recombinant vaccines against foot-and-mouth disease, one of the economically most important animal diseases worldwid

FOOTHILL COLOMBIAN PLAIN, HYDRODYNAMIC AND HYDROGEOCHEMICAL PATHWAY HYPOTHESIS, HYDROGEOLOGIC METHODS.

  La nueva información de presión de formación, fisicoquímica e isotopía ambiental, permitieron la elaboración de hipótesis preeliminares sobre el origen y movimiento del agua de formación asociada a hidrocarburos en Piedemonte y parte central de los Llanos Orientales. En Piedemonte, se sugiere la presencia de sistemas hidráulicos individuales sobrepresionados, asociados a cada estilo estructural; encontrándose un sistema levemente subpresionado al sur de Cupiagua. El origen de las aguas de formación es confuso, encontrándose aguas connatas con bajas salinidades, aguas empobrecidas isotópicamente con altas salinidades y aguas con desviaciones en las trayectorias isotópicas, sugiriendo la acción de procesos de mezcla y/o interacción roca-fluido. Se determinó flujo SW, con una anomalía de flujo W-SW (Cusiana), favorecida por canales permeables originados por la yuxtaposición de litologías permeables.   En Llanos, se sugieren sistemas hidráulicos levemente sobrepresionados (menos que en Piedemonte), con zonas de subpresión para campos paralelos y adyacentes al frente de deformación. La isotopía sugiere la acción de procesos de mezcla y/o interacción roca fluido. Anomalías de presión y fisicoquímica, sugieren mezcla de fluidos en forma ascendente, con plumas dispuestas paralelamente y adyacentemente al frente de deformación. El flujo es N-NW desde el SE, hacia zonas subpresionadas al centro de la cuenca.   Palabras Claves: Hidrodinámica, Hidrogeoquímica, Migración, Piedemonte, Llanos Orientales      New information of formation pressure, groundwater physicochemical and environmental isotopes, allowed to carry out hypothesis on the origin and movement of formation water associated to hydrocarbons in Foothill and central part of the Llanos Orientales basin. In Piedemonte, overpressured individual hydraulic systems are suggested, associated to each structural style; founding a slightly subpressured system to the south of Cupiagua. The formation water origin in not clear, founding cognate waters with low salinities, waters with isotopic impoverishment and high salinities, and waters with deviations in the isotopic trajectories, that suggest action of mixture processes and/or interaction rock-fluid. It has been established a SW flow, with a W-SW anomaly (Cusiana), which is favoured by permeable channels originated by juxtaposition of permeable lythologies.   In Llanos, slightly overpressured hydraulic systems are suggested (less than in Piedemonte), with subpressured zones for field parallel and adjacent to the deformation front. Isotopic analysis suggests the action of mixture processes and/or interaction fluid-rock. Pressure and physicochemical anomalies, suggest mixture of fluid in ascending form, with plumes parallel and adjacent to the deformation front. The flow is N-NW from SE, towards subpressured zones in the basin.   Key words: Hydrodynamic, Hidrogeochemical, Migration, Piedemonte, Llanos Orientale

Quantum interference dependence on molecular configurations for cross-conjugated systems in single-molecule junctions

We report a combined experimental and computational study of seven cross-conjugated enediyne derivatives functionalised with a pendant group (diphenyl, 9-fluorenyl, 9-thioxanthene or cyclohexyl) at the central alkene site, and with thiomethyl (SMe) or thioacetate, as protected thiol, (SAc) groups as anchors. Measurements of the conductance (G) and Seebeck coefficient (S) of gold|single-molecule|gold junctions were obtained using a modified scanning tunnelling microscope-break junction (STM-BJ) technique. It is shown that most of the molecules give multiple conductance plateaus ascribed to different molecular configurations inside the junction. The higher conductance plateaus are consistent with the aryl pendant units interacting with one of the gold electrodes, thereby circumventing transmission of electrons through the enediyne system; the lower conductance plateaus are consistent with anchoring of both of the terminal SMe or S units to the electrodes. Most of the compounds show a positive value of S in the range 3.7–12.7 μV K−1 indicating electronic transport through the HOMO, while one of them presents a negative value of S (−6.2 μV K−1) indicating a predominance of the LUMO in the electronic transport. Theoretical calculations using density functional theory show a destructive quantum interference (DQI) feature in the gap between the highest occupied and lowest unoccupied molecular orbitals (the HOMO–LUMO gap) for the lower conductance plateaus, supporting the trends observed in the experimental data