Liquid water simulation using hydrogen bond corrected SCAN and neural network potentials.

Accurately reproducing the structure of liquid water with ab initio molecular dynamics (AIMD) simulation is a crucial first step on the path towards accurately predicting the properties of liquid solutions without relying on experiment. Density functional theory (DFT) is normally used to approximate the forces in these simulations. However, no DFT functional has been shown to give an entirely satisfactory description of the structure of liquid water. Here, I propose a simple correction to the strongly constrained and appropriately normalised (SCAN) DFT functional, that corrects the strength of the hydrogen bonding interaction with a simple exponential potential fitted to dimer energy calculations. The resulting SCAN-CH functional provides an excellent description of the structure of liquid water. Long time scale NPT simulations are enabled by the use of neural network potentials, which demonstrate that the simulations are well converged and that the density of water is also more accurately reproduced with this method.

Emergent gravity from stochastic fluctuations

It is possible that both the classical description of spacetime and the rules of quantum field theory emerge from a more-fundamental structure of physical law. Pregeometric frameworks transfer some of the puzzles of quantum gravity to a semiclassical arena where those puzzles pose less of a challenge. However, in order to provide a satisfactory description of quantum gravity, a semiclassical description must emerge and contain in its description a macroscopic spacetime geometry, dynamical matter, and a gravitational interaction consistent with general relativity at long distances. In this essay, we argue that a framework that includes a stochastic origin for quantum field theory can provide both the emergence of classical spacetime and a quantized gravitational interaction.

Cosmological evolution and dark energy in osculating Barthel–Randers geometry

We consider the cosmological evolution in an osculating point Barthel–Randers type geometry, in which to each point of the space-time manifold an arbitrary point vector field is associated. This Finsler type geometry is assumed to describe the physical properties of the gravitational field, as well as the cosmological dynamics. For the Barthel–Randers geometry the connection is given by the Levi-Civita connection of the associated Riemann metric. The generalized Friedmann equations in the Barthel–Randers geometry are obtained by considering that the background Riemannian metric in the Randers line element is of Friedmann–Lemaitre–Robertson–Walker type. The matter energy balance equation is derived, and it is interpreted from the point of view of the thermodynamics of irreversible processes in the presence of particle creation. The cosmological properties of the model are investigated in detail, and it is shown that the model admits a de Sitter type solution, and that an effective cosmological constant can also be generated. Several exact cosmological solutions are also obtained. A comparison of three specific models with the observational data and with the standard $$\Lambda $$ Λ CDM model is also performed by fitting the observed values of the Hubble parameter, with the models giving a satisfactory description of the observations.

Optimization of banana crop by-products solvent extraction for the production of bioactive compounds

The aim of this work is the optimization of phenolic compound extraction from three by-products of banana crops (rachis, discarded banana, and banana’s pseudostem pulp), as a way to valorize them through a green extraction process. The influence of the temperature and aqueous ethanol concentration (Et-OH) on extract properties (total phenol content (TPC) and antioxidant activity) was firstly analyzed. 78 ℃ and ethanol concentrations close to 50% yielded the best results for the three materials. The equations obtained by the response surface methodology gave a satisfactory description of the experimental data, allowing optimizing the extraction conditions. Under optimized conditions, time influence was then assessed, although this parameter seemed not influence results. Among the three by-products, rachis extract (60% Et-OH, 78 ℃, and 30 min) presented the highest TPC (796 mg gallic acid/100 g of dried material) and antioxidant activity (6.51 mg Trolox equivalents/g of dried material), followed by discarded banana, and pseudostem pulp. Under the optimal conditions, experiments were performed at a larger scale, allowing to determine the extraction yields (EY) and to characterize the extracts. The highest EY was obtained for the rachis (26%), but the extract with the highest activity was obtained for discarded banana (50% Et-OH, 78 ℃, and 60 min), which presented a TPC of 27.26 mg/g extract corresponding to 54.59 mg Trolox equivalents/g extract. This study contributes to the valorization of banana crops residues as a source of polyphenolic compounds with bioactive functions that can be extracted under economic extraction conditions. Graphical abstract

Zur vermittlung von während und seit im daf-unterricht an spanischsprechende aus konstruktionsgrammatischer sicht – ein vorschlag

Multidimensionality is a property of grammatical phenomena which describes the connection between clusters of meaning and syntactic expressions. Based on the principle that syntax builds meaning, the following article deals with the correct approach to the usage of seit and während in the DaF class, in order to discuss and propose their equivalents in Spanish. We suggest that the proper use of seit(dem) and während should become a relevant teaching topic, as a satisfactory description in grammatical manuals is still pending. With the speakers’ needs in mind, we then proceed to suggest explanatory approaches to the problem areas which will make DaF learners aware of their correct use by the means of the basic principles of construction grammar.

Resonant interaction of relativistic electrons with realistic electromagnetic ion–cyclotron wave packets

We study the influence of real structure of electromagnetic ion-cyclotron wave packets in the Earth’s radiation belts on precipitation of relativistic electrons. Automatic algorithm is used to distinguish isolated elements (wave packets) and obtain their amplitude and frequency profiles from satellite observations by Van Allen Probe B. We focus on rising-tone EMIC wave packets in the proton band, with a maximum amplitude of 1.2–1.6 nT. The resonant interaction of the considered wave packets with relativistic electrons 1.5–9 MeV is studied by numerical simulations. The precipitating fluxes are formed as a result of both linear and nonlinear interaction; for energies 2–5 MeV precipitating fluxes are close to the strong diffusion limit. The evolution of precipitating fluxes is influenced by generation of higher-frequency waves at the packet trailing edge near the equator and dissipation of lower-frequency waves in the $$\text {He}^+$$ He + cyclotron resonance region at the leading edge. The wave packet amplitude modulation leads to a significant change of precipitated particles energy spectrum during short intervals of less than 1 minute. For short time intervals about 10–15 s, the approximation of each local amplitude maximum of the wave packet by a Gaussian amplitude profile and a linear frequency drift gives a satisfactory description of the resonant interaction.

Determination of the steel axial stresses in memory mode by the exponential law of magnetoelastic demagnetization

Magnetic and magnetoelastic methods of stress control are based on changes in the magnetic parameters of steel upon deformation. However, the magnetic properties of different steel grades, and even of the same grade in different heats may differ noticeably. The inhomogeneity of the magnetic and magnetoelastic properties of steel attributed to variations in the chemical composition, as well as in the modes of rolling and heating during manufacture affects the accuracy of stress control being a common disadvantage of magnetoelastic methods used for monitoring the stress-strain state of steel structures. The goal of the study is to consider the possibility of monitoring uniaxial mechanical stresses in steel structures in the «magnetoelastic memory» mode, based on H(σ) dependence of the strength of magnetic field of scattering local remanent magnetization of steel on the uniaxial stresses. The exponential function is shown to provide a satisfactory description of the experimental dependence of the strength of the magnetic field of scattering of the permanently magnetized 17G1S and 15KhSND steels on the stresses induced in steels by tension, compression, and impact. To improve the accuracy of the control, we propose to introduce the magnetoelastic sensitivity of steel (MSS) into the accepted form of the exponential dependence H(σ). A way to MSS determination not only on laboratory samples under ideal conditions, but directly on the construction under control (which reduces the errors of the control attributed to variations in the magnetic and magnetoelastic properties of steels) is considered. To implement the proposed procedure, prototypes of the devices for static and dynamic local loading of metal structure elements have been developed and manufactured. The devices have undergone a pilot test when monitoring the stress-strain state of the load-bearing beams of an automobile overpass. Using the developed devices, a local dosed loading with a hemispherical indenter was carried out through shock or static loading of a pre-magnetized region of the structure resulted in a decrease in the intensity of the magnetic field of scattering. A procedure for monitoring uniaxial stresses in steel structure elements by the method of magnetoelastic «memory» is proposed taking into account the measured magnetoelastic sensitivity of their material.

The Use of TiO2 as a Disinfectant in Water Sanitation Applications

Waterborne diseases produced by organisms of public health concern are prevalent worldwide, continuing to cause deaths annually. Conventional disinfectants (ozone, UV radiation, chlorine) have been insufficient in providing safe water as many studies revealed. TiO2 is an attractive alternative to conventional methods because of its versatility and recently explored biocidal capacity due to advanced oxidation processes. The oligodynamic effect that TiO2 seems to have on some microorganisms consists of effective lipid hyper oxidation of microorganism membranes, as well as protein interactions that lead to the alteration of the internal conditions and the inhibition of metabolic processes that eventually lead to their lysis. Nevertheless, a satisfactory description of other organisms is necessary to complete the disinfectant–organism interaction, and then the subsequent evaluation parameters of sanitation should proceed. In addition, solutions for feasibility, standardization of results for achieving consistent results and defined applications, lower costs, scalability, and security after its application need to be studied. Understanding its usage implies knowing the actual state of the art and its limitations for water disinfection purposes, as well as the potential benefits that overcoming such limitations would provide, thus allowing the possibility of establishing it as a feasible and popular technology.

Use of Gas Adsorption and Inversion Methods for Shale Pore Structure Characterization

The analysis of porosity and pore structure of shale rocks has received special attention in the last decades as unconventional reservoir hydrocarbons have become a larger parcel of the oil and gas market. A variety of techniques are available to provide a satisfactory description of these porous media. Some techniques are based on saturating the porous rock with a fluid to probe the pore structure. In this sense, gases have played an important role in porosity and pore structure characterization, particularly for the analysis of pore size and shapes and storage or intake capacity. In this review, we discuss the use of various gases, with emphasis on N2 and CO2, for characterization of shale pore architecture. We describe the state of the art on the related inversion methods for processing the corresponding isotherms and the procedure to obtain surface area and pore-size distribution. The state of the art is based on the collation of publications in the last 10 years. Limitations of the gas adsorption technique and the associated inversion methods as well as the most suitable scenario for its application are presented in this review. Finally, we discuss the future of gas adsorption for shale characterization, which we believe will rely on hybridization with other techniques to overcome some of the limitations.

Resonant Interaction Of Relativistic Electrons with Realistic Electromagnetic Ion-Cyclotron Wave Packets

We study the influence of real structure of electromagnetic ion-cyclotron wave packets in the Earth’s radiation belts on precipitation of relativistic electrons. Automatic algorithm is used to distinguish isolated elements (wave packets) and obtain their amplitude and frequency profiles from satellite observations by Van Allen Probe B. We focus on rising-tone EMIC wave packets in the proton band, with a maximum amplitude of 1.2-1.6 nT. The resonant interaction of the considered wave packets with relativistic electrons 1.5-9 MeV is studied by numerical simulations. The precipitating fluxes are formed as a result of both linear and nonlinear interaction; for energies 2-5 MeV precipitating fluxes are close to the strong diffusion limit. The evolution of precipitating fluxes is influenced by generation of higher-frequency waves at the packet trailing edge near the equator and dissipation of lower-frequency waves in the He+ cyclotron resonance region at the leading edge. The wave packet amplitude modulation leads to a significant change of precipitated particles energy spectrum during short intervals of less than 1 minute. For short time intervals about 10-15 s, the approximation of each local amplitude maximum of the wave packet by a Gaussian amplitude profile and a linear frequency drift gives a satisfactory description of the resonant interaction.