Stress responses investigated; application of zinc and heat to Terrestrial Model Ecosystems from heavy metal polluted grassland

This study tested the hypothesis that soils with a deprived biodiversity due to metal pollution are less stable than non-polluted soils, containing a more diverse community. For this, soils were sampled from specific grasslands in the Netherlands that contain elevated heavy metal concentrations (Cu, Pb and Zn). Soils that showed the largest differences in metal concentrations were incubated in the laboratory using Terrestrial Model Ecosystems (TMEs). This approach enabled simultaneous measurement of structural (bacteria, nematodes, enchytraeids, earthworms) and functional parameters (nitrogen leaching, feeding activity, CO₂ production, plant growth). The highest polluted soils showed a lower bacterial growth, and decreased enchytraeid and nematode biomass and diversity, hence a deprived community. More nitrate leached from high polluted soils, while all other functional endpoints did not differ. Additional stress application of zinc and heat was used to test the stability. Zinc treatment caused effects only in the higher polluted soils, observed at several moments in time for enchytraeids, CO₂ fluxes and plant growth. Heat stress caused a large reduction in enchytraeid and earthworm biomass. Ammonium leaching was decreased by heat treatments in the most polluted soils, while CO₂ was increased by heat in less polluted soils. Most effects were seen in the most polluted systems and it was concluded that they seem less stable.     

Environmental and individual exposure to secondhand aerosol of electronic cigarettes in confined spaces: Results from the TackSHS Project†

Secondhand electronic cigarette (e-cigarette) aerosol (SHA) might impair indoor air quality and expose bystanders. This study aims to investigate exposure to SHA in controlled conditions of enclosed settings simulating real-world scenario. An experiment was performed in a car and in a room, in which SHA was generated during a 30-minute ad libitum use of an e-cigarette. The experiment was replicated on five consecutive days in each setting. We measured PM_2.5, airborne nicotine concentrations, and biomarkers of exposure to SHA, such as nicotine metabolites, tobacco-specific nitrosamines, propylene glycol, and glycerol in bystanders’ saliva samples before, during, and after the exposure period. Self-reported health symptoms related to exposure to SHA were also recorded. The results showed that the highest median PM_2.5 concentration was recorded during the exposure period, being 21 µg/m³ in the room setting and 16 µg/m³ in the car setting—about twofold increase compared to the baseline. Most concentrations of the airborne nicotine and all biomarkers were below the limit of quantification in both settings. Bystanders in both settings experienced some short-term irritation symptoms, expressed as dry throat, nose, eyes, and phlegm. In conclusion, short-term use of an e-cigarette in confined spaces increased indoor PM_2.5 level and caused some irritation symptoms in bystanders.     

Correlating indoor and outdoor temperature and humidity in a sample of buildings in tropical climates

The incidence of several respiratory viral infections has been shown to be related to climate. Because humans spend most of their time indoors, measures of indoor climate, rather than outdoor climate, may be better predictors of disease incidence and transmission. Therefore, understanding the relationship between indoor and outdoor climate will help illuminate their influence on the seasonality of diseases caused by respiratory viruses. Indoor-outdoor relationships between temperature and humidity have been documented in temperate regions, but little information is available for tropical regions, where seasonal patterns of respiratory viral diseases differ. We have examined indoor-outdoor correlations of temperature, relative humidity (RH), and absolute humidity (AH) over a 1-year period in each of seven tropical cities. Across all cities, the average monthly indoor temperature was 25 ± 3°C (mean ± standard deviation) with a range of 20–30°C. The average monthly indoor RH was 66 ± 9% with a range of 50–78%, and the average monthly indoor AH was 15 ± 3 g/m³ with a range of 10–23 g/m³. Indoor AH and RH were linearly correlated with outdoor AH when the air conditioning (AC) was off, suggesting that outdoor AH may be a good proxy of indoor humidity in the absence of AC. All indoor measurements were more strongly correlated with outdoor measurements as distance from the equator increased. Such correlations were weaker during the wet season, especially when AC was in operation. These correlations will provide insight for assessing the seasonality of respiratory viral infections using outdoor climate data, which is more widely available than indoor data, even though transmission of these diseases mainly occurs indoors.     

A study of the influence of muscovite on the thermal transformations of kaolinite from room temperature up to 1,100 °C

Global thermal transformation of kaolinite–muscovite mixtures containing at most 25 mass % of muscovite was studied up to 1,100 °C. Quantitative and qualitative DTA analysis reveals a great intereaction between the two phylosilicates above 900 °C, which is characterized by an enhancement of spinodal demixion contribution during the structural reorganization of metakaolinite. The corresponding enthalpy variation are respectively −32 ± 1 kJ/mol and −15 ± 1 kJ/mol of kaolinite for pure kaolinite and for the mixture containing 15 mass % of muscovite. This interaction is mainly correlated with the diffusion of potassium ions from muscovite platelets into metakaolinite structure. The resulting consequence is an enhancement of mullite crystallization and grain growth at 1,050 °C (earlier than in the case of pure kaolinite mineral).     

Segmentation of diesel spray images with log-likelihood ratio test algorithm for non-Gaussian distributions

A methodology for processing images of diesel sprays under different experimental situations is presented. The new approach has been developed for cases where the background does not follow a Gaussian distribution but a positive bias appears. In such cases, the lognormal and the gamma probability density functions have been considered for the background digital level distributions. Two different algorithms have been compared with the standard log-likelihood ratio test (LRT): a threshold defined from the cumulative probability density function of the background shows a sensitive improvement, but the best results are obtained with modified versions of the LRT algorithm adapted to non-Gaussian cases.     

Tunnel junctions with multiferroic barriers

Multiferroics are singular materials that can exhibit simultaneously electric and magnetic orders. Some are ferroelectric and ferromagnetic and provide the opportunity to encode information in electric polarization and magnetization to obtain four logic states. However, such materials are rare and schemes allowing a simple electrical readout of these states have not been demonstrated in the same device. Here, we show that films of La(0.1)Bi(0.9)MnO(3) (LBMO) are ferromagnetic and ferroelectric, and retain both ferroic properties down to a thickness of 2 nm. We have integrated such ultrathin multiferroic films as barriers in spin-filter-type tunnel junctions that exploit the magnetic and ferroelectric degrees of freedom of LBMO. Whereas ferromagnetism permits read operations reminiscent of magnetic random access memories (MRAM), the electrical switching evokes a ferroelectric RAM write operation. Significantly, our device does not require the destructive ferroelectric readout, and therefore represents an advance over the original four-state memory concept based on multiferroics.     

Single-scan extraction of two-dimensional parameters of infrared focal plane arrays utilizing a Fourier-transform spectrometer

We present what is believed to be a novel experimental method to measure the technological parameters (spectral response and quantum yield) of an infrared focal plane array. This method makes original use of a Fourier transform spectrometer, which allows us to simultaneously extract the spectral performances of all pixels from one single set of measurements. The methodology used and the principle of the experimental setup are detailed. A Fourier analysis is shown to provide various optogeometrical information on the detector microstructure. A demonstrator based on the HgCdTe technology was designed, and satisfactory experimental results were obtained.     

Spark plasma sintering of ductile ceramic particles: study of LiF

Densification of cuboidal micrometer-sized lithium fluoride particles as ductile ceramic by spark plasma sintering (SPS) was investigated. Specimens were fabricated at different pressures and temperature conditions, ranging from 2 to 100 MPa at 500 °C and from 200 to 700 °C under 100 MPa of applied pressure, respectively. Dense specimens of 99 % relative density were fabricated by heating to 500 °C under constant pressure of 100 MPa. The densification showed first compaction by particle rearrangement, followed by plastic deformation via dislocation glide. Hot-pressing models were used to describe the densification by considering the temperature dependences of the yield stress, the strain hardening behavior and coefficients, and the pore size and shape dependences on the applied stress. A good agreement was found between the experimental and the theoretical densification curves. At low pressure of 2 MPa, the densification occurs by particle sliding, assisted by viscous flow at their surfaces, and local plastic deformation at the particle contacts, due to the intensified local stress. Finally, the micrometer-sized structural features and the contiguity achieved by plastic deformation at the start of spark plasma sintering (SPS) nullify any field effects in this model system at higher pressures; good agreement was obtained with expected conventional hot pressing.     

The creep of an elastoviscoplastic beam under a bending loading

Thermoplastics start to manifest a nonlinear mechanical behavior from relatively low loading levels. Under a bending solicitation, which generates a nonuniform stress field, the material behavior becomes more challenging. Indeed, a flexed specimen may have different behaviors from one point to another according to the local stress state. In the present work, a six-parameter rheological model is used to simulate the nonlinear behavior of an elastoviscoplastic beam, subjected to a three-point bending load. In the framework of Euler–Bernoulli theory, the mathematical formulation of a bent beam behavior involves the bending curvature function. This function allows the determination of the strain and stress fields along and through the beam. However, when the beam reaches the viscoplastic stage, the differential equation providing the bending curvature of the beam requires a numerical integration, which has been accomplished in this work. This theoretical modeling approach is supported by experimental creep tests carried out on polyamide specimens (PA6). The testing results are qualitatively consistent with the predictions of the proposed rheological model.