Representative Environmental Conditions Research Articles

Interference of gastrointestinal barriers with antibiotic susceptibility of foodborne pathogens: an in vitro case study of ciprofloxacin and tetracycline against Salmonella enterica and Listeria monocytogenes

Minimum inhibitory concentrations (MIC) assays are often questioned for their representativeness. Especially when foodborne pathogens are tested, it is of crucial importance to also consider parameters of the human digestive system. Hence, the current study aimed to assess the inhibitory capacity of two antibiotics, ciprofloxacin and tetracycline, against Salmonella enterica and Listeria monocytogenes, under representative environmental conditions. More specifically, aspects of the harsh environment of the human gastrointestinal tract (GIT) were gradually added to the experimental conditions starting from simple aerobic lab conditions into an in vitro simulation of the GIT. In this way, the effects of parameters including the anoxic environment, physicochemical conditions of the GIT (low gastric pH, digestive enzymes, bile acids) and the gut microbiota were evaluated. The latter was simulated by including a representative consortium of selected gut bacteria species. In this study, the MIC of the two antibiotics against the relevant foodborne pathogens were established, under the previously mentioned environmental conditions. The results of S. enterica highlighted the importance of the anaerobic environment when conducting such studies, since the pathogen thrived under such conditions. Inclusion of physicochemical barriers led to exactly opposite results for S. enterica and L. monocytogenes since the former became more susceptible to ciprofloxacin while the latter showed lower susceptibility towards tetracycline. Finally, the inclusion of gut bacteria had a bactericidal effect against L. monocytogenes even in the absence of antibiotics, while gut bacteria protected S. enterica from the effect of ciprofloxacin.

Global design methodology for semi-submersible hulls of floating wind turbines

Designing the support structures for floating wind turbines (FWTs) involves a step-by-step process, typically in three phases, i.e., starting from concept selection and determining the overall dimensions for a given configuration, and finally, determining the detailed specifications. The global design of the hull is used to select the floater concept and determine the global dimensions for the subsequent detailed design. This global design process is a crucial part of the entire design cycle because it has a significant impact on the detailed design, which can be computationally expensive. However, because FWTs are still in the infancy stage of development, there is a lack of effective methods and procedures for determining the global dimensions of floaters. Additionally, the global response characteristics of different hull layouts are not yet well understood. To address these limitations, this paper deals with a global design of semi-submersible floaters to support large-scale wind turbines (using a 10-MW turbine as an example). The paper proposes and describes a methodology and procedures for the global design in detail, specifying criteria and values for a case study. Furthermore, a sensitivity study is conducted to determine the global dimensions of the floaters. Then, intact stability is studied to evaluate their safety in operation under wind loads. Subsequently, global aspects of structural design are analyzed based on wave-induced response amplitude operators (RAOs) of cross-sectional forces and moments, taking into account representative environmental conditions for an offshore site. These analyses provide a foundation for the subsequent detailed design. The results indicate that the spacing of the column centerline and the outer column radius are the most critical design variables for the global response of the semi-submersible hull. Moreover, increasing the outer column radius or freeboard can effectively enhance intact stability. In addition, the study highlights the importance of critical wave periods that cause splitting or prying force on the hull columns in the structural design. Finally, the main findings and conclusions are summarized. This study presents a simplified yet innovative methodology for the global design of mainstream semi-submersible hulls for FWTs. It addresses the lack of effective methods for determining global dimensions and provides valuable insights into the structural design considerations.

Influence of reef structure and its flow field effect on the spatial behavior of Sebastes schlegelii adults

Sebases schlegelii is an important economic reef fish in northern China. Its distribution in the reef area is affected by the reef structure and flow field. To evaluate the effects of differently shaped artificial reefs with distinct flow field properties on the distribution of adult S. schlegelii, four types of artificial reefs (cubic (CAR), pyramidal (PAR), star-shaped (SAR) and tubular (TAR) artificial reef) and the related flow regimes were experimentally examined. The mean gathering rate (MGR) and wavelet analysis were adopted to analyze the distribution patterns of S. schlegelii adults around reef bodies in three representative environmental conditions (static water (FE1), 40 Hz water flow environment (FE2), and 50 Hz water flow environment (FE3)). The significant gathering behaviors around the artificial reefs were depicted through the MGR of adult fish during physical observations. For FE1, the MGR of adult fish showed a decrease in the order PAR > CAR > SAR > TAR. With increasing incoming velocities, the MGR changed such that the quantity of adult fish in the CAR gradually increased more than that in the PAR, but no significant differences were observed between them (P>0.05). Wavelet analysis showed that the fluctuations in the gathering behaviors of adults decreased with increasing flow velocities. Based on the two-factor analysis of variance, the reef structural characteristics had a more significant impact than the flow velocities on the gathering behavior of adult fish. In summary, the PAR and CAR are recommended to restore the habitats of S. schlegelii in marine ranches given their dominant aggregation effects on S. schlegelii.

Revealing the coupled effects of hygrothermal environment and geometrical parameters on the failure of double-lap, single-bolt composite joints

Coupled effects of hygrothermal environment and geometrical parameters on the failure of a double-lap, single-bolt composite joint are investigated numerically. The studied geometrical parameters include the ratio of end distance to hole diameter (e/D) and that of width to hole diameter (w/D). Three representative environmental conditions, including −55 °C/dry (CTD), 23 °C/dry (RTD) and 70 °C/wet (ETW), are considered. Numerical progressive damage models (PDMs) that consider hygrothermal effects are established to predict the failure load and failure mode of the joints. Good agreement between the predicted and experimental results confirm the applicability of the established PDMs. The results indicate that the CTD condition increases the failure load of the joint, whereas the ETW condition decreases it. The extent of the hygrothermal effect changes with e/D, but is insusceptible to w/D. Further, the relationship between the failure load and e/D is affected by the hygrothermal condition. Under the CTD condition, the failure load reaches a plateau at a smaller critical value of e/D, compared with that under the ETW condition. However, the relationship between the failure load and w/D is unaffected by the hygrothermal condition. The failure mode depends on e/D and w/D, and is not affected by the hygrothermal condition.

ExoFiT trial at the Atacama Desert (Chile): Raman detection of biomarkers by representative prototypes of the ExoMars/Raman Laser Spectrometer

In this work, the analytical research performed by the Raman Laser Spectrometer (RLS) team during the ExoFiT trial is presented. During this test, an emulator of the Rosalind Franklin rover was remotely operated at the Atacama Desert in a Mars-like sequence of scientific operations that ended with the collection and the analysis of two drilled cores. The in-situ Raman characterization of the samples was performed through a portable technology demonstrator of RLS (RAD1 system). The results were later complemented in the laboratory using a bench top RLS operation simulator and a X-Ray diffractometer (XRD). By simulating the operational and analytical constraints of the ExoMars mission, the two RLS representative instruments effectively disclosed the mineralogical composition of the drilled cores (k-feldspar, plagioclase, quartz, muscovite and rutile as main components), reaching the detection of minor phases (e.g., additional phyllosilicate and calcite) whose concentration was below the detection limit of XRD. Furthermore, Raman systems detected many organic functional groups (–C≡N, –NH2 and C–(NO2)), suggesting the presence of nitrogen-fixing microorganisms in the samples. The Raman detection of organic material in the subsurface of a Martian analogue site presenting representative environmental conditions (high UV radiation, extreme aridity), supports the idea that the RLS could play a key role in the fulfilment of the ExoMars main mission objective: to search for signs of life on Mars.

A new method to assess the acute toxicity toward honeybees of the abrasion particles generated from seeds coated with insecticides

BackgroundLarge amounts of insecticide-containing dusts produced from abrasion of the seed dressing can be released into the atmosphere during sowing operations. Neonicotinoid pesticides, introduced in the 1990s for several crops, are the leading products for seed-coating treatments in many countries. Neonicotinoid containing dusts can be effectively intercepted by bees in flight over the sowing field, inducing lethal acute effects, so that restrictions in the use of the main neonicotinoids have been adopted in the European Union. This led to the consequent introduction of replacement insecticides for seed-coating, i.e. methiocarb and thiacloprid, despite the lack of information on both the toxicity and the exposure scenarios for honeybees.ResultsIn this study, a laboratory apparatus was developed in order to quantify the toxicity of the dusts produced from the abrasion of the seed coating. This quantification is based on (i) an airstream transporting coating particles into an exposure chamber; (ii) exposure of bees to reproducible and measurable concentrations of insecticide, and (iii) direct measurement of the exposure dose on single bees. The method allowed us to perform in vivo experiments of honeybee exposure to provide toxicity data in more realistic exposure conditions. In fact, the formulation rather than the active principle alone can be tested, and the exposure is through dusts rather than a solution so that specific absorption behavior can be studied in representative environmental conditions. The method was used to quantify the acute toxicity (LD50) of dusts obtained from the abrasion of corn seeds coated with clothianidin, thiacloprid and methiocarb.ConclusionsOur results show that, surprisingly, the replacement insecticide methiocarb has a toxicity (LD50 = 421–693 ng/bee) in the same order of magnitude as clothianidin (LD50 = 113–451 ng/bee) through this specific exposure route, while thiacloprid (LD50 = 16.9·103 ng/bee) has a significantly lower acute toxicity. Moreover, dusts containing methiocarb and clothianidin show a significant increase in toxicity when, after exposure, bees are kept under high humidity conditions. This suggests that the method here presented can be used to obtain complementary toxicity data in the risk assessment procedure for the authorization of new seed-coating insecticides or new formulations.

Progress and Challenges in Quantifying Wildfire Smoke Emissions, Their Properties, Transport, and Atmospheric Impacts

AbstractWildfire is a natural and integral ecosystem process that is necessary to maintain species composition, structure, and ecosystem function. Extreme fires have been increasing over the last decades, which have a substantial impact on air quality, human health, the environment, and climate systems. Smoke aerosols can be transported over large distances, acting as pollutants that affect adjacent and distant downwind communities and environments. Fire emissions are a complicated mixture of trace gases and aerosols, many of which are short‐lived and chemically reactive, and this mixture affects atmospheric composition in complex ways that are not completely understood. We present a review of the current state of knowledge of smoke aerosol emissions originating from wildfires. Satellite observations, from both passive and active instruments, are critical to providing the ability to view the large‐scale influence of fire, smoke, and their impacts. Progress in the development of fire emission estimates to regional and global chemical transport models has advanced, although significant challenges remain, such as connecting ecosystems and fuels burned with dependent atmospheric chemistry. Knowledge of the impact of smoke on radiation, clouds, and precipitation has progressed and is an essential topical research area. However, current measurements and parameterizations are not adequate to describe the impacts on clouds of smoke particles (e.g., CNN, INP) from fire emissions in the range of representative environmental conditions necessary to advance science or modeling. We conclude by providing recommendations to the community that we believe will advance the science and understanding of the impact of fire smoke emissions on human and environmental health, as well as feedback with climate systems.

Parameterization-induced uncertainties and impacts of crop management harmonization in a global gridded crop model ensemble

Global gridded crop models (GGCMs) combine agronomic or plant growth models with gridded spatial input data to estimate spatially explicit crop yields and agricultural externalities at the global scale. Differences in GGCM outputs arise from the use of different biophysical models, setups, and input data. GGCM ensembles are frequently employed to bracket uncertainties in impact studies without investigating the causes of divergence in outputs. This study explores differences in maize yield estimates from five GGCMs based on the public domain field-scale model Environmental Policy Integrated Climate (EPIC) that participate in the AgMIP Global Gridded Crop Model Intercomparison initiative. Albeit using the same crop model, the GGCMs differ in model version, input data, management assumptions, parameterization, and selection of subroutines affecting crop yield estimates via cultivar distributions, soil attributes, and hydrology among others. The analyses reveal inter-annual yield variability and absolute yield levels in the EPIC-based GGCMs to be highly sensitive to soil parameterization and crop management. All GGCMs show an intermediate performance in reproducing reported yields with a higher skill if a static soil profile is assumed or sufficient plant nutrients are supplied. An in-depth comparison of setup domains for two EPIC-based GGCMs shows that GGCM performance and plant stress responses depend substantially on soil parameters and soil process parameterization, i.e. hydrology and nutrient turnover, indicating that these often neglected domains deserve more scrutiny. For agricultural impact assessments, employing a GGCM ensemble with its widely varying assumptions in setups appears the best solution for coping with uncertainties from lack of comprehensive global data on crop management, cultivar distributions and coefficients for agro-environmental processes. However, the underlying assumptions require systematic specifications to cover representative agricultural systems and environmental conditions. Furthermore, the interlinkage of parameter sensitivity from various domains such as soil parameters, nutrient turnover coefficients, and cultivar specifications highlights that global sensitivity analyses and calibration need to be performed in an integrated manner to avoid bias resulting from disregarded core model domains. Finally, relating evaluations of the EPIC-based GGCMs to a wider ensemble based on individual core models shows that structural differences outweigh in general differences in configurations of GGCMs based on the same model, and that the ensemble mean gains higher skill from the inclusion of structurally different GGCMs. Although the members of the wider ensemble herein do not consider crop-soil-management interactions, their sensitivity to nutrient supply indicates that findings for the EPIC-based sub-ensemble will likely become relevant for other GGCMs with the progressing inclusion of such processes.

Spacecraft Worst Case Surface Charging: On the Importance of Measuring the Electron Emission Yield Under Representative Environmental Conditions

To represent the time spent by space materials on ground before launch, the measurement of secondary electron emission properties is performed after long duration exposure to ambient atmosphere and humidity. The observed change with respect to pristine samples has an impact on the estimation of worst case surface charging levels in geostationary orbit, especially for a spacecraft in eclipse. It is therefore recommended to adequately outgas the samples with respect to the expected flight conditions and aging effects.

Sensitivity of Hail Precipitation to Ensembles of Uncertainties of Representative Initial Environmental Conditions From ECMWF

AbstractThe sensitivity of hail precipitation from an idealized hailstorm to realistic environmental uncertainties was investigated through ensembles of cloud‐resolving simulations using the Weather Research and Forecasting model, with initial condition perturbations derived from the European Centre for Medium‐Range Weather Forecasting (ECMWF) operational ensemble. The analyses revealed that hail precipitation rate was very sensitive to small initial environmental perturbations, particularly in thermodynamic variables. The hail precipitation rate was significantly positively correlated with perturbations to the initial potential temperature below 750 hPa and to water vapor mixing ratio above 750 hPa. These small initial perturbations led to subsequent substantial differences in hail precipitation as well as in characteristics of the parent storm (e.g., updraft velocity, diabatic heating, and microphysical processes), all of which play a key role in hail growth. The larger sensitivity of hail precipitation to thermodynamic rather than kinematic environmental initial condition perturbations persisted even when the magnitude of the perturbations was reduced to 10% of the realistic uncertainties derived from the ECMWF ensemble. In the ensemble with reduced‐amplitude initial perturbations, there was still a moderately strong positive correlation between hail precipitation rate and the initial perturbations of the thermodynamic variables. However, these sensitivities were nonlinear, suggesting that the intrinsic predictability of hail precipitation rate may be limited, even when environmental uncertainties are reduced to 10%, 1.0 × 10−3, and 1.0 × 10−5 of the currently realistic magnitude of initial condition uncertainty.

Coupled thermal transport and mass diffusion during vapor absorption into hygroscopic liquid desiccant droplets

Phase change phenomena at a droplet scale have gained extensive attention in recent years due to the unique aspects that can be exploited in a wide range of domestic and industrial applications. Different from existing studies on droplet evaporation and/or dropwise condensation, this work focuses on the mechanisms of vapor absorption into hygroscopic liquid desiccant droplets, which are of interest to many dehumidification and absorption processes. In particular we investigate the coupled heat and mass transport during vapor absorption into single droplets using optical imaging and infrared thermography. Driven by the vapor pressure difference between the ambient and the droplet surface, desiccant droplets grow due to water uptake. The droplet growth rate and final expansion ratio depend on the ambient temperature and relative humidity. After liquid desiccant droplet deposition onto the substrate, and as a consequence of the initial fast vapor absorption, droplets experience an increase in temperature. They then gradually cool down as a result of heat dissipation into the substrate and into the ambient combined with the decrease in the vapor absorption rate, i.e., heat of absorption. The temperature rise measured by infrared thermography is confirmed by the calculation of the heat of absorption for six representative environmental conditions. Furthermore the vapor pressure at the droplet surface is estimated taking account of the changes of interfacial temperature and salt concentration within the droplet bulk. As water absorbs into the droplets, the salt concentration decreases and so does the driving force for vapor diffusion and hence the heat of absorption. As a contrast, experiments with evaporating water droplets show different evolution of droplet profile, different dynamics of the triple contact line, as well as the occurrence of evaporative cooling. We conclude on the importance of taking account of the coupling mechanisms of absorptive heating and volume growth during vapor absorption into liquid desiccant droplets. Findings presented here provide a valuable extension to existing literature of phase change at the droplet scale, and contribute to a more complete understanding of the behaviors of liquid desiccant droplets in dehumidification processes.

Survival of viral pathogens in animal feed ingredients under transboundary shipping models.

The goal of this study was to evaluate survival of important viral pathogens of livestock in animal feed ingredients imported daily into the United States under simulated transboundary conditions. Eleven viruses were selected based on global significance and impact to the livestock industry, including Foot and Mouth Disease Virus (FMDV), Classical Swine Fever Virus (CSFV), African Swine Fever Virus (ASFV), Influenza A Virus of Swine (IAV-S), Pseudorabies virus (PRV), Nipah Virus (NiV), Porcine Reproductive and Respiratory Syndrome Virus (PRRSV), Swine Vesicular Disease Virus (SVDV), Vesicular Stomatitis Virus (VSV), Porcine Circovirus Type 2 (PCV2) and Vesicular Exanthema of Swine Virus (VESV). Surrogate viruses with similar genetic and physical properties were used for 6 viruses. Surrogates belonged to the same virus families as target pathogens, and included Senecavirus A (SVA) for FMDV, Bovine Viral Diarrhea Virus (BVDV) for CSFV, Bovine Herpesvirus Type 1 (BHV-1) for PRV, Canine Distemper Virus (CDV) for NiV, Porcine Sapelovirus (PSV) for SVDV and Feline Calicivirus (FCV) for VESV. For the remaining target viruses, actual pathogens were used. Virus survival was evaluated using Trans-Pacific or Trans-Atlantic transboundary models involving representative feed ingredients, transport times and environmental conditions, with samples tested by PCR, VI and/or swine bioassay. SVA (representing FMDV), FCV (representing VESV), BHV-1 (representing PRV), PRRSV, PSV (representing SVDV), ASFV and PCV2 maintained infectivity during transport, while BVDV (representing CSFV), VSV, CDV (representing NiV) and IAV-S did not. Notably, more viruses survived in conventional soybean meal, lysine hydrochloride, choline chloride, vitamin D and pork sausage casings. These results support published data on transboundary risk of PEDV in feed, demonstrate survival of certain viruses in specific feed ingredients (“high-risk combinations”) under conditions simulating transport between continents and provide further evidence that contaminated feed ingredients may represent a risk for transport of pathogens at domestic and global levels.

Intensive epidermal adsorption and specific venous deposition of carboxyl quantum dots in zebrafish early-life stages

To properly assess the environmental risk of quantum dots (QDs), it is necessary to determine their fate in living organisms, including adsorption, distribution and bioaccumulation under representative environmental or physiological conditions. We comprehensively investigated the fate of QDs with carboxyl terminal functional groups (carboxyl-QDs) in zebrafish (Danio rerio) embryo and larvae subjected to either waterborne exposure or cardiovascular system microinjection. On waterborne exposure, carboxyl-QDs exhibited an intensive adsorption and accumulation in the chorion of embryos, and their predominate target organs were the gill and intestinal tract in larvae. On microinjection, carboxyl-QDs were rapidly delivered into the cardiovascular system and specifically deposited in veins and the capillary network system of zebrafish larvae, but not in the arterial system. Taken together, we found that the exact tissue condition including epidermal structures, mucus secretion and vascular microstructures strongly affected the adsorption, uptake and distribution of carboxyl-QDs in zebrafish. This work highlights the intensive tissue epidermal adsorption and accumulation of carboxyl-QDs and their specific vein and capillary deposition in the cardiovascular system in zebrafish early-life stages.

Adaptations of a green tide forming Ulva linza (Ulvophyceae, Chlorophyta) to selected salinity and nutrients conditions mimicking representative environments in the Yellow Sea

:The massive green tide species Ulva linza undergoes an apparent rafting in a counterclockwise direction in the Yellow Sea from Jiangsu Province, China, to the west coast of Korea. During this dispersal, it undergoes development from early life history stages to senescence and experiences extensive salinity and nutrient gradients. We investigated the physiological responses of different developmental stages of U. linza to three representative environmental conditions that mimicked (1) a brackish environment at salinity 10 (S = 10) and 200 μM NO3−, (2) an inshore environment at S = 30 and 200 μM NO3−, and (3) an offshore environment at S = 30 and 4 μM NO3−. Chlorophyll a fluorescence of the early development stages (spores and germlings) of U. linza was measured using pulse amplitude modulation fluorometry to determine their photosynthetic efficiency. In addition, the photosynthesis and respiration rates of adult thalli were measured using chamber incubation. Within two hours of release, spores showed no difference in photosynthetic performance in the three conditions. Subsequently, the photosynthesis of germlings was enhanced at high-nutrient conditions regardless of salinity, suggesting that brackish and inshore waters are suitable nursery areas for early development. The adult thalli in the brackish environment showed two and three times higher growth rates than in the inshore and offshore environments, respectively. The adult thalli experienced synergistic effects of high nutrients and low salinity on photosynthesis that facilitated rapid growth in brackish environments. Overall, we suggest that brackish areas facilitate the initiation of blooms of U. linza, and the subsequent movement of floating fronds from estuaries to the inshore and then the offshore provides a continuous nutrient inoculum that maintains the population in the offshore environment.

An Intelligent Methodology for Railways Monitoring Using Ultrasonic Guided Waves

It is far from trivial to inspect railways for defections. In particular, for the foot area of the rail non destructive testing methods are known to be difficult to apply. In this paper, an ultrasonic guided wave method is considered along with classification methods for automated rail foot defect detection. In effect, given a set of gathered ultrasonic signals, multiple features are extracted from time-, frequency- and time–frequency domains. Next, a robust feature selection method is performed, to collect a small set of complementary features. The classification task is accomplished by means of a kernel-based support vector machine. To demonstrate the performance capabilities of our approach, an extensive experimental setup is designed under representative environmental and operational conditions. The sensitivity and the resolution of the proposed defect detection system are reported. A study on the influence of rail fastening on the proposed method is also reported where robust defect detection rates, greater than 93 %, are achieved assuming that a compact feature subset is considered. However, it is evident in experiments that even in the case of large defects, changes in the environmental conditions (temperature and humidity) increase the interpretation of the acquired signals, thus making the detection task more difficult.

Surface studies of environmental reactive species during exhibition or storage of ancient Ag‐based artefacts

The role played by environmental species affecting the long‐term stability of archaeological Ag‐based artefacts during museum exhibition or storage has been studied by means of the combined use of selected area X‐ray photoelectron spectroscopy, X‐ray diffraction, optical microscopy and scanning electron microscopy + energy dispersive spectrometry. The presence of fine particulate and of aggressive compounds in the museum atmospheres has been investigated by means of an innovative testing methodology based on Ag‐based reference alloys. The procedure has been applied to different areas of some museums in the Mediterranean Basin in order to consider representative environmental conditions of storage and exhibition of Ag‐based artefacts. The case studies of the National Roman Museum in Rome, Italy and of the Egyptian Museum of Cairo, Egypt will be illustrated. Furthermore, the study has been performed as a function of the alloy chemical composition and of the position of the reference specimens. The results of the superficial, micro‐chemical and morphological characterisations of the reference alloys are related to degradation parameters of ancient silver artefacts, as the presence of sulfur dioxide and chloride ions. The chosen methodology can be recommended to investigate the environmental key factors to consider for a safe storage or exhibition of archaeological silver artefacts, ensuring them a long stable life from a chemical–physical point of view. Copyright © 2014 John Wiley & Sons, Ltd.

Fatigue reliability analysis of the jacket support structure for offshore wind turbine considering the effect of corrosion and inspection

Due to the high level of fatigue loads as well as a large number of load cycles caused by wind and wave loads together, fatigue performance of welded connections is a design driving criterion for offshore wind turbine support structures. In this paper prediction of fatigue reliability of welded multi-planar tubular joints of the support structure of a fixed jacket offshore wind turbine designed for a northern North Sea site in a water depth of 70m is performed. Dynamic response of the jacket support structure due to wind and wave loads is calculated by using a decoupled procedure with good accuracy. Hot-spot stresses at failure-critical location of the relative reference brace of the selected tubular joint are derived by summation of the single stress components from axial, in-plane and out-of-plane action, the effects of planar and non-planar braces are also considered. A two-parameter Weibull function is used to fit the long-term statistical distribution of hot-spot stress ranges by combination of time domain simulation for representative environmental conditions (wind/sea states) in operational condition. The main uncertainties associated with the whole procedure of reliability analysis are identified and quantified. The load histories are normalized to ensure that fatigue design criteria based on the SN-Miner-Palmgren approach is satisfied. Hence the reliability estimates obtained refer to fatigue design of tubular joints that satisfy design criteria. The reliability analysis is based on fracture mechanics (FM) analysis of crack growth. The corrosion-induced increased crack growth rate is taken into account by considering the increased hot-spot stress range due to changes of nominal stress and stress concentration factors (SCFs) produced by the thickness thinning (wastage) effects of all braces and chord of the selected tubular joint with a general uniform corrosion model. The geometry function effect and the material degradation effect due to corrosion on the reliability analysis are also investigated. The effects of inspection and repair with and without consideration of corrosion are quantified based on the quality of inspection in terms of probability of crack detection curves. The sensitivity of the reliability index on important random variables is estimated.

Climate Change and Its Impacts on Tourism in the Alps - The Pilot Area of Auronzo Di Cadore (Belluno)

The mountain area of the Veneto Region covers a third of its entire surface. Here the importance of tourism, and especially winter tourism, has grown constantly in time, making it a primary source of alpine wealth and a driver for the regional economy. However, in the last decade, different studies have highlighted a phase of stagnation for what concerns tourist fluxes, partly due to a lower attractiveness of the mountain tourism offer. This might depend on different social and economic factors, but also on the impacts of climate change, whose occurrence makes it difficult to secure a sufficient snow cover throughout the entire winter season, particularly at lower elevations. In this context, the project ClimAlpTour (Climate change and its impacts on tourism in the Alps), funded by the European Union as part of the Alpine Space Programme 2007–2013 and led by the Veneto Region, analysed one of today’s most burning issues: the impacts of climate change on tourism in the Alpine arc with particular focus on the economic, social and environmental factors related to both summer and winter activities. The Alpine arc is characterised by both a highly heterogeneous landscape and very dissimilar climatic conditions, which shape the region’s overall richness in terms of ecosystems and habitats. Thus, climate change does not affect this territory homogeneously. The partnership of the ClimAlpTour project, in its attempt to cover this diversity, lists representatives of the entire Alpine region including institutions from Italy (Veneto, Piedmont, Aosta Valley, Lombardy, Autonomous Province of Bolzano), Austria (Vienna and Tirol), France (Rhone Alpes), Germany (Bavaria), Slovenia, and Switzerland. Such comprehensiveness and the involvement of several local institutions through whose collaboration partners were able to analyse issues and peculiarities of tourism in these areas. The project revolved around the analysis of several pilot sites, which alpine were considered by experts to possess particularly significant and representative tourist and environmental conditions. The initial surveyed data included climatic data, market data, and other economic and social parameters. One of the main objectives of ClimAlpTour was to establish and offer to the local administrations a decision support system for differentiating tourism supply while adapting to possible future changes in alpine weather conditions due to climate change. The Veneto Region selected the pilot area of Auronzo di Cadore and Misurina because it presented great opportunities – in many instances still not fully exploited – for further developments of tourist seasons. This destination, which traditionally has been alpine well positioned in terms of summer tourism, is now attempting to improve the winter season supply, taking into consideration strong neighbouring competitors and environmental sustainability. The study reported herein describes the project’s experience within the Municipality of Auronzo di Cadore. Two participatory workshops alpine were conduced with the inclusion of a representative set of local stakeholders, which led to the identification and evaluation of alternative strategies for winter tourism development within a framework of adaptation measures to climate change.

Influence of stress and environment on the fatigue strength and failure characteristics of case carburised low alloy steels for aerospace applications

The high cycle fatigue behaviour of a number of commercially available aerospace carburising gear steels have been examined under conditions similar to those encountered in the tooth roots of helicopter gears. In particular, the related variables of tooth root stress concentration, of carburised case depth, and of applied mean stress were arranged in such a way as to provide a realistic distribution of applied stress whilst still using a simple, axially loaded, fatigue specimen. In addition, in order to ensure the specimens were tested under representative temperature and environmental conditions, experienced by helicopter gears, the specimens were enclosed in a specially designed environmental chamber.Fatigue testing showed that crack initiation occurred either within the case or the core, in which the propensity for nucleation to occur at either site was strongly dependent on applied stress. For example, by using a 2D FE model based on actual residual stress measurements, it was shown that under a tensile mean stress the highest stresses were confined to a region slightly sub-surface of the root radius, whereas in compression the most highly stressed locations were either in the root radius as before or in a region away from the notch but several millimeters from the surface, confirming the fractographic observations.Regardless of its influence on failure location, it was noted when testing was carried out at 150°C in oil, all the steels exhibited a certain degree of mean stress sensitivity in which the fatigue endurance declined generally in the form of a straight line as the load ratio became more positive. By raising the testing temperature from ambient air to elevated temperature oil (i.e. 150°C), fatigue endurance was found to decline regardless of alloy type, in which the reduction in fatigue life was considered to be primarily due to two main factors, i.e. a partial relaxation of the shot peened surface as a result of thermal stress relief and easier dislocation movement due to elevated temperature testing. A further reduction in fatigue observed during testing in elevated temperature oil was only considered to be of secondary importance.

Corrosion of Fe-9Cr Steels in Sodium Fast Reactors Environments

The sodium cooled fast reactor is selected by France as the most mature GEN IV concept to be industrially developed by the year 2040. A collaborative research program has been established together with EDF and Areva NP. In this program, different innovations are being considered in the design of the reactor leading to the use of various environments apart from liquid sodium and water vapor encountered in the “classical” sodium fast reactors. As a matter of fact, considerations on the suppression of the water-sodium reaction risk led to the proposal of the use of alternative coolants such as Pb-Bi involving an intermediate circuit between the primary sodium and the steam generator. Other concepts involve the use of supercritical CO2 instead of water vapor in the energy conversion system. In all cases, structural materials encounter severe conditions regarding corrosion concerns: high temperatures and possibly aggressive chemical environments.In this paper, status of the research performed in CEA on the corrosion behavior of the structural material and especially Fe-9Cr steels is presented in the various environments: sodium (see paper by JL Courouau), Pb-Bi, water vapor and CO2 . The materials studied are metallic materials: austenitic and ferrito-martensitic steels as well as ODS steels as an option for the cladding material.In the different environments studied, the scientific approach is identical, the objective being in all cases the understanding of the corrosion processes to establish recommendations on the chemistry control of the coolant and to predict the long term behavior of the materials by the development of corrosion models.First, the corrosion mechanisms are analyzed using dedicated experimental devices. As a matter of fact, the complex environments require also controlled, safe and precise experimental systems to perform long duration corrosion tests (several thousands of hours). Therefore, specific experiments, adapted to each corrosive medium, are carried out in the laboratory. For example:- laboratory scale loops are used for liquid metals corrosion studies (use of rotating cylinders to simulate high turbulent conditions),- thermogravimetric analyses are also used to perform gas corrosion studies in representative temperature and environmental conditions,…Then, multi-scale characterization of the materials studied is performed (FEG-SEM, EDX, XRD, GD-OES…), together with precise analyses of the environments tested (in situ measurements with specific probes, gas chromatography…). Corrosion mechanisms are then proposed and models developed, depending on the advancement and the maturity of the program.