Transfer Functions and Penetrations of Five Differential Mobility Analyzers for Sub-2 nm Particle Classification

The transfer functions and penetrations of five differential mobility analyzers (DMAs) for sub-2 nm particle classification were evaluated in this study. These DMAs include the TSI nanoDMA, the Caltech radial DMA (RDMA) and nanoRDMA, the Grimm nanoDMA, and the Karlsruhe-Vienna DMA. Measurements were done using tetra-alkyl ammonium ion standards with mobility diameters of 1.16, 1.47, and 1.70 nm. These monomobile ions were generated by electrospray followed by high resolution mobility classification. Measurements were focused at an aerosol-to-sheath flow ratio of 0.1. A data inversion routine was developed to obtain the true transfer function for each test DMA, and these measured transfer functions were compared with theory. DMA penetration efficiencies were also measured. An approximate model for diffusional deposition, based on the modified Gormley and Kennedy equation using an effective length, is given for each test DMA. These results quantitatively characterize the performance of the test DMAs in classifying sub-2 nm particles and can be readily used for DMA data inversion

Quality-diversity optimization: a novel branch of stochastic optimization

Traditional optimization algorithms search for a single global optimum that maximizes (or minimizes) the objective function. Multimodal optimization algorithms search for the highest peaks in the search space that can be more than one. Quality-Diversity algorithms are a recent addition to the evolutionary computation toolbox that do not only search for a single set of local optima, but instead try to illuminate the search space. In effect, they provide a holistic view of how high-performing solutions are distributed throughout a search space. The main differences with multimodal optimization algorithms are that (1) Quality-Diversity typically works in the behavioral space (or feature space), and not in the genotypic (or parameter) space, and (2) Quality-Diversity attempts to fill the whole behavior space, even if the niche is not a peak in the fitness landscape. In this chapter, we provide a gentle introduction to Quality-Diversity optimization, discuss the main representative algorithms, and the main current topics under consideration in the community. Throughout the chapter, we also discuss several successful applications of Quality-Diversity algorithms, including deep learning, robotics, and reinforcement learning

Quality-diversity optimization: a novel branch of stochastic optimization

Traditional optimization algorithms search for a single global optimum that maximizes (or minimizes) the objective function. Multimodal optimization algorithms search for the highest peaks in the search space that can be more than one. Quality-Diversity algorithms are a recent addition to the evolutionary computation toolbox that do not only search for a single set of local optima, but instead try to illuminate the search space. In effect, they provide a holistic view of how high-performing solutions are distributed throughout a search space. The main differences with multimodal optimization algorithms are that (1) Quality-Diversity typically works in the behavioral space (or feature space), and not in the genotypic (or parameter) space, and (2) Quality-Diversity attempts to fill the whole behavior space, even if the niche is not a peak in the fitness landscape. In this chapter, we provide a gentle introduction to Quality-Diversity optimization, discuss the main representative algorithms, and the main current topics under consideration in the community. Throughout the chapter, we also discuss several successful applications of Quality-Diversity algorithms, including deep learning, robotics, and reinforcement learning

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Artificial evolution of the morphology and kinematics in a flapping-wing mini-UA

Experimental calibration of Mn incorporation in foraminiferal calcite

International audienc

Tidal sands as biogeochemical reactors

Sandy sediments of continental shelves and most beaches are often thought of as geochemical deserts because they are usually poor in organic matter and other reactive substances. The present study focuses on analyses of dissolved biogenic compounds of surface seawater and pore waters of Aquitanian coastal beach sediments. To quantitatively assess the biogeochemical reactions, we collected pore waters at low tide on tidal cross-shore transects unaffected by freshwater inputs. We recorded temperature, salinity, oxygen saturation state, and nutrient concentrations. These parameters were compared to the values recorded in the seawater entering the interstitial environment during floods. Cross-shore topography and position of piezometric level at low tide were obtained from kinematics GPS records. Residence time of pore waters was estimated by a tracer approach, using dissolved silica concentration and kinetics estimate of quartz dissolution with seawater. Kinetics parameters were based on dissolved silica concentration monitoring during 20-day incubations of sediment with seawater. We found that seawater that entered the sediment during flood tides remained up to seven tidal cycles within the interstitial environment. Oxygen saturation of seawater was close to 100%, whereas it was as low as 80% in pore waters. Concentrations of dissolved nutrients were higher in pore waters than in seawater. These results suggest that aerobic respiration occurred in the sands. We propose that mineralised organic matter originated from planktonic material that infiltrated the sediment with water during flood tides. Therefore, the sandy tidal sediment of the Aquitanian coast is a biogeochemical reactor that promotes or accelerates remineralisation of coastal pelagic primary production. Mass balance calculations suggest that this single process supplies about 37 kmol of nitrate and 1.9 kmol of dissolved inorganic phosphorus (DIP) to the 250-km long Aquitanian coast during each semi-diurnal tidal cycle. It represents about 1.5% of nitrate and 5% of DIP supplied by the nearest estuary

UVA-induced cyclobutane pyrimidine dimers in DNA: a direct photochemical mechanism?

International audienceThe carcinogenic action of UVA radiation is commonly attributed to DNA oxidation mediated by endogenous photosensitisers. Yet, it was recently shown that cyclobutane pyrimidine dimers (CPD), well known for their involvement in UVB genotoxicity, are produced in larger yield than oxidative lesions in UVA-irradiated cells and skin. In the present work, we gathered mechanistic information on this photoreaction by comparing formation of all possible bipyrimidine photoproducts upon UVA irradiation of cells, purified genomic DNA and dA20:dT20 oligonucleotide duplex. We observed that the distribution of photoproducts, characterized by the sole formation of CPD and the absence of (6-4) photoproducts was similar in the three types of samples. The CPD involving two thymines represented 90% of the amount of photoproducts. Moreover, the yields of formation of the DNA lesions were similar in cells and isolated DNA. In addition, the effect of the wavelength of the incident photons was found to be the same in isolated DNA and cells. This set of data shows that UVA-induced cyclobutane pyrimidine dimers are formed via a direct photochemical mechanism, without mediation of a cellular photosensitiser. This is possible because the double-stranded structure increases the capacity of DNA bases to absorb UVA photons, as evidenced in the case of the oligomer dA20:dT20. These results emphasize the need to consider UVA in the carcinogenic effects of sunlight. An efficient photoprotection is needed that can only be complete by completely blocking incident photons, rather than by systemic approaches such as antioxidant supplementation

Terrestrial groundwater and nutrient discharge along the 240-km-long Aquitanian coast

We collected samples from sea water, runnel water, beach pore waters, water from the unconfined surficial aquifer discharging at the beach face, groundwater, and rainwater from the Aquitanian coast in order to determine the flux of dissolved inorganic nitrogen (DIN), phosphorus and silica from terrestrial submarine groundwater discharge (SGD). The flux of fresh groundwater was obtained from a water balance calculation based on precipitation and evapotranspiration and assessment of the coastal watershed from hydrograph separation. Waters with intermediate salinities between sea water and freshwaters are found all along the 240-km-long coast, indicating that SGD is ubiquitous. The estimated fresh water flux is 2.25 m3 d− 1 m− 1 longshore. Terrestrial SGD provides a DIN flux of 9·106 mol each year to the adjacent coastal zone. This flux is about four times lower than the release of DIN due to tidally driven saline SGD. The freshwater DIN flux is low because the upland land use consists almost exclusively of pine forest. Dissolved organic nitrogen represents more than 60% of the total dissolved nitrogen flux. Dissolved iron, phosphorus and silica have much higher concentrations in the anoxic forest aquifer than in the fresh-water end-member of the subterranean estuary sampled in the upper beach aquifer. This suggests that the salinity gradient of the estuary does not correspond to a redox gradient. The redox front between anoxic groundwater and fresh oxic waters occurs below the soil-depleted foredune/yellow dune. Anoxic P- and Si-rich waters seep directly on the beach face only in the north Gironde, where the foredunes are eroded. This study reveals the role of the sandy foredune aquifer in biogeochemical fluxes from SGD, which is to dilute and oxidize waters from the unconfined surficial upland aquifer