OuroborosBEM: a fast multi-GPU microscopic Monte Carlo simulation for gaseous detectors and charged particle dynamics

The design of gaseous detectors for accelerator, particle and nuclear physics requires simulations relying on multi-physics aspects. In fact, these simulations deal with the dynamics of a large number of charged particles interacting in a gaseous medium immersed in the electric field generated by a more or less complex assembly of electrodes and dielectric materials. We report here on a homemade software, called ouroborosbem, able to tackle the different features involved in such simulations. After solving the electrostatic problem for which a solver based on the boundary element method (BEM) has been implemented, particles are tracked and will microscopically interact with the gas medium. Dynamical effects have been included such as the electron-ion recombination process, the charging-up of the dielectric materials and other space charge effects that might alter the detector performances. These were made possible thanks to the nVidia CUDA language specifically optimised to run on Graphical Processor Units (GPUs) to minimize the computing times. Comparisons of the results obtained for parallel plate avalanche counters and GEM detectors to literature data on swarm parameters fully validate the performances of ouroborosbem. Moreover, we were able to precisely reproduce the measured gains of single and double GEM detectors as a function of the applied voltage.

Exploratory and machine learning analysis of the stability constants of HgII- triazene ligands complexes

Knowing stability constants for the complexes HgII with extracting ligands is very important from environmental and therapeutic standpoints. Since the selectivity of ligands can be stated by the stability constants of cation–ligand complexes, quantitative structure–property relationship (QSPR) investigations on binding constant of HgII complexes were done. Experimental data of the stability constants in ML2 complexation of HgII and synthesized triazene ligands were used to construct and develop QSPR models. Support vector machine (SVM) and multiple linear regression (MLR) have been employed to create the QSPR models. The final model showed squared correlation coefficient of 0.917 and the standard error of calibration (SEC) value of 0.141 log K units. The proposed model presented accurate prediction with the Leave-One-Out cross validation ( Q LOO 2 = 0.756) and validated using Y-randomization and external test set. Statistical results demonstrated that the proposed models had suitable goodness of fit, predictive ability, and robustness. The results revealed the importance of charge effects and topological properties of ligand in HgII - triazene complexation.

Triply Differential Positron and Electron Impact Ionization of Argon: Systematic Features and Scaling

Triply differential data are presented for the 200 eV positron and electron impact ionization of argon. Six electron emission energies between 2.6 and 19 eV, and for scattering angles of 2, 3, and 4 degrees cover a momentum transfer range of 0.16 to 0.31 a.u. The binary and recoil intensities are fitted using a double peak structure in both regions, which, for the present kinematic conditions, are unresolved. The fitted peak intensities and angular positions are shown to have systematic dependences as a function of the momentum transfer and kinematic emission angle, respectively, and illustrate projectile charge effects. A comparison with available theories is made where it is seen that the most notable differences include the fact that for the binary lobe, the observed intensity for emission angles around 100° is absent in the theories, and the theoretical predications overestimate the importance of recoil interactions.

Polystyrene Nanoplastic Behavior and Toxicity on Crustacean Daphnia magna: Media Composition, Size, and Surface Charge Effects

Concerns about the possible ecotoxicological implications of nano-sized plastic materials in the freshwater environment are growing with the increasing use of plastic materials. The present study focuses on the behavior and effects of amidine-functionalized polystyrene (NPLs) of 20, 40, 60, and 100-nm-size in freshwaters and different synthetic media. Daphnia magna was exposed to increasing concentrations from 0.5 to 30 mg/L (and from 0.5 to 100 mg/L for 100-nm-sized NPLs). The results revealed no significant aggregation in ultra-pure water, culture media, and synthetic water. In the presence of natural organic matter, NPLs of 20 and 40 nm displayed better stability in both freshwater and synthetic media, whereas a significant aggregation of 60 and 100 nm PS NPLs was found. All the studied PS NPLs with size between 20 and 100 nm exhibited acute toxicity to D. magna. The observed 48-h immobilization strongly depended on the primary size of PS NPLs, with 20 and 40-nm-size PS NPLs inducing a stronger effect in both freshwaters and synthetic media. Water quality variables such as pH, cation and anion composition, and DOC were of secondary importance. The results of the present study confirmed the toxicity of NPLs of different sizes to crustaceans in natural freshwater and synthetic media and demonstrated the importance of the primary size of NPLs in the behavior and effects of NPLs.