Role of vortical structures for enstrophy and scalar transport in flows with and without stable stratification

We investigate the enstrophy dynamics in relation to objective Eulerian coherent structures (OECSs) and their impact on the enstrophy and scalar transport near the turbulent/non-turbulent interface (TNTI) in flows with and without stable stratification. We confirm that vortex-stretching produces enstrophy inside the boundaries of the OECSs, while viscous diffusion transfers the enstrophy across the boundaries of the structures. Although often overlooked in the literature, viscous dissipation of enstrophy within the boundaries of vortical structures is significant. Conversely, for the weakly stratified flows also investigated here, the effect of the baroclinic torque is negligible. We provide evidence that the OECSs advect the passive/active scalar and redistribute it via molecular diffusion. Finally, we use conditional analysis to show that the typical profiles of the enstrophy and scalar transport equation terms across the TNTI are compatible with the presence of OECSs positioned at the edge between the turbulent sublayer and the turbulent core region. We show that when these profiles are further conditioned to the presence of OECSs, their magnitude is considerably higher

Complex Risks from Old Urban Waste Landfills: Sustainability Perspective from Iasi, Romania

Landfills continue to represent the most frequent managerial practice for municipal solid wastes and an increasing and complex problem globally. In certain countries, a transition to an open society and free market is superimposed on the transition to sustainability, resulting in even higher complexity of management. This paper proposes an approach for problem-structuring of landfills in complex transitions: sustainability or unsustainability of a management approach is determined by a set of sustainability filters that are defined by sets of indicators and prioritized according the systemic concept of sustainability, which says that economy is embedded in society, which is embedded in nature. The writers exercise this approach with an old landfill in Iasi, Romania, and conclude for unsustainability, because the ecological sustainability filter is not successfully passed. Social and economic sustainability filters are also discussed in relation with the ecological sustainability indicators. The described approach allows a coherent, transdisciplinary synthesis of knowledge scattered across various disciplines, a pervasive problem in landfill management. The case study helps distinguish between generally true and context-dependent aspects.Peer reviewe

SARS-CoV-2 Breakthrough Infections: Incidence and Risk Factors in a Large European Multicentric Cohort of Health Workers.

Background: The research aimed to investigate the incidence of SARS-CoV-2 breakthrough infections and their determinants in a large European cohort of more than 60,000 health workers. Methods: A multicentric retrospective cohort study, involving 12 European centers, was carried out within the ORCHESTRA project, collecting data up to 18 November 2021 on fully vaccinated health workers. The cumulative incidence of SARS-CoV-2 breakthrough infections was investigated with its association with occupational and social-demographic characteristics (age, sex, job title, previous SARS-CoV-2 infection, antibody titer levels, and time from the vaccination course completion). Results: Among 64,172 health workers from 12 European health centers, 797 breakthrough infections were observed (cumulative incidence of 1.2%). The primary analysis using individual data on 8 out of 12 centers showed that age and previous infection significantly modified breakthrough infection rates. In the meta-analysis of aggregated data from all centers, previous SARS-CoV-2 infection and the standardized antibody titer were inversely related to the risk of breakthrough infection (p = 0.008 and p = 0.007, respectively). Conclusion: The inverse correlation of antibody titer with the risk of breakthrough infection supports the evidence that vaccination plays a primary role in infection prevention, especially in health workers. Cellular immunity, previous clinical conditions, and vaccination timing should be further investigated

Determination of Alkali and Halide Monovalent Ion Parameters for Use in Explicitly Solvated Biomolecular Simulations

Alkali (Li+, Na+, K+, Rb+, and Cs+) and halide (F−, Cl−, Br−, and I−) ions play an important role in many biological phenomena, roles that range from stabilization of biomolecular structure, to influence on biomolecular dynamics, to key physiological influence on homeostasis and signaling. To properly model ionic interaction and stability in atomistic simulations of biomolecular structure, dynamics, folding, catalysis, and function, an accurate model or representation of the monovalent ions is critically necessary. A good model needs to simultaneously reproduce many properties of ions, including their structure, dynamics, solvation, and moreover both the interactions of these ions with each other in the crystal and in solution and the interactions of ions with other molecules. At present, the best force fields for biomolecules employ a simple additive, nonpolarizable, and pairwise potential for atomic interaction. In this work, we describe our efforts to build better models of the monovalent ions within the pairwise Coulombic and 6-12 Lennard-Jones framework, where the models are tuned to balance crystal and solution properties in Ewald simulations with specific choices of well-known water models. Although it has been clearly demonstrated that truly accurate treatments of ions will require inclusion of nonadditivity and polarizability (particularly with the anions) and ultimately even a quantum mechanical treatment, our goal was to simply push the limits of the additive treatments to see if a balanced model could be created. The applied methodology is general and can be extended to other ions and to polarizable force-field models. Our starting point centered on observations from long simulations of biomolecules in salt solution with the AMBER force fields where salt crystals formed well below their solubility limit. The likely cause of the artifact in the AMBER parameters relates to the naive mixing of the Smith and Dang chloride parameters with AMBER-adapted Åqvist cation parameters. To provide a more appropriate balance, we reoptimized the parameters of the Lennard-Jones potential for the ions and specific choices of water models. To validate and optimize the parameters, we calculated hydration free energies of the solvated ions and also lattice energies (LE) and lattice constants (LC) of alkali halide salt crystals. This is the first effort that systematically scans across the Lennard-Jones space (well depth and radius) while balancing ion properties like LE and LC across all pair combinations of the alkali ions and halide ions. The optimization across the entire monovalent series avoids systematic deviations. The ion parameters developed, optimized, and characterized were targeted for use with some of the most commonly used rigid and nonpolarizable water models, specifically TIP3P, TIP4PEW, and SPC/E. In addition to well reproducing the solution and crystal properties, the new ion parameters well reproduce binding energies of the ions to water and the radii of the first hydration shells

Influence of Small Addition of Ti4+ Ions on the Properties of High Permeability Ferrite

Mn-Zn ferrites substituted with Ti4+ ions are now becoming commercially important. The substitution with titanium ions in Mn-Zn ferrite is recommended for ferrites with low losses and low temperature factor of initial permeability, Tk/µi because of the shift of the secondary maximum of permeability, SMP, towards lower temperatures [1] and the increase of the d.c. resistivity [3,4,5]. The present paper reports the results obtained by substitution of a small amount of titamium ions to high permeability ferrite Mn0.51Zn0.43Fe2+0.06Fe2O4, by adequate reduction of Zn2+ content. The magnetic and electric properties improve : d.c. electrical resistivity increases while the loss factor tanδ/µi and disaccommodation decrease. By addition of 0.35% by weight TiO2, the initial permeability, at 20°C, improves. We remark the flattening of µi(T) curves with the increase of content of Ti4+ ions and the diminution of the peak at the Curie point, facts that can be associated with two points of anisotropy compensation instead of one, the second minimum of K1 being in the neighborhood of Tc. Structural and magnetic properties of high permeability ferrite with substitution of titanium ions confirm that Ti4+ ions make pairs with Fe2+ ions. [4,6]

Synthesis and properties of Ni-Zn ferrite thin films

We have investigated the magnetic and structural properties of polycrystalline Ni-Zn ferrite thin films with thicknesses of about 1000Å. The films were prepared by R F sputtering deposition in 1.5x10-3 mbar argon atmosphere, using targets with nominal composition Ni0.7Zn0.3Fe2O4. The effects of substrate temperature and post deposition heat treatment of thin films were examined. The X-ray spectra of Fe-Ni-Zn oxides deposits reveal the formation of spinel phase of Ni-Zn ferrite, that is characteristic for these materials, only for temperatures higher than 500°C. TEM and ED indicate that the initially amorphous thin films, deposited at 100°C, become polycrystalline by heat treatment. The grain size of the crystallites is 800Å to 1000Å for Ni-Zn ferrite thin films annealed at 900°C. V.S.M. measurements show coercive fields of 12 kA/m for thin films annealed at 900°C, which are larger than those found for Ni-Zn ferrite targets. This value of coercive field is related to the shape anisotropy originated by the film microstructure and with the increase in the number of low angle grain boundaries, which act as pinning sites for domain walls. Saturation magnetization values of 220-250mT for Ni-Zn ferrite thin films are higher than half of bulk values