Simulations of dispersion and deposition of coarse particulate matter

In order to study the dispersion and deposition of coarse anthropogenic particulate matter (PMc, aerodynamic diameters> 10 mm), a FORTRAN simulator based on the numerical integrator of Bulirsch and Stoer has been developed. It calculates trajectories of particles of several shapes released into the atmosphere under very general conditions. This first version, fully three-dimensional, models the meteorology under neutral stability conditions. The simulations of such pollutants are also important because the standard software (usually originating in the United States Environmental Protection Agency-EPA-) describe only the behavior of PM10 (diameter less than 10 mm). Bulirsch and Stoer integrator of widespread use in astrophysics, is also very fast and accurate for this type of simulations. We present 2D and 3D trajectories in physical space and discuss the final deposition in function of various parameters. PMc simulations results in the range of 50-100 mm and densities of 5.5 g cm-3 emitted from chimneys, indicate that for the purpose of deposition, the emission velocities are not as important as wind speed and the shape of the particles. For densities less than 2 g cm-3, the lack of consideration of buoyancy introduces important changes in the distribution of deposited PMc.Con el objeto de estudiar dispersión y deposición de material particulado grueso antropogénico (PMc, diámetros aerodinámicos > 10 mm), se ha desarrollado un simulador FORTRAN basado en el integrador numérico de Bulirsch y Stoer, que calcula trayectorias de partículas de diversas formas liberadas al ambiente bajo condiciones muy generales. Esta primera versión, totalmente tridimensional, modela la meteorología en circunstancias de estabilidad neutral. La presentación de un simulador de dispersión de este tipo de contaminantes es, además, relevante debido a que los software de uso corriente (generalmente originados en la United States Environmental Protection Agency –USEPA-) describen sólo el comportamiento del PM10 (diámetros menores que 10 mm). El integrador Bulirsch y Stoer, de difundido uso en astrofísica, resulta también muy rápido y preciso para este tipo de simulaciones. Se presentan trayectorias 2D y 3D en el espacio físico y se analiza la deposición en función de diversos parámetros. Resultados de simulaciones de PMc en el rango de 50-100 mm y densidades de 5.5 g cm-3 emitidos por chimeneas indican que, a efectos de la deposición, las velocidades de emisión del PMc no son tan importantes frente a la velocidad del viento y la forma de las partículas. Para densidades menores que 2 g cm-3, la no consideración de la flotabilidad introduce importantes modificaciones en la distribución del PMc depositado

On the degradation mechanisms under the influence of pedological factors through the study of archeological bronze patina

This experimental thesis concerns the study of the long-term behaviour of ancient bronzes recently excavated from burial conditions. The scientific interest is to clarify the effect of soil parameters on the degradation mechanisms of ancient bronze alloy. The work took into consideration bronzes recovered from the archaeological sites in the region of Dobrudja, Romania. The first part of research work was dedicated to the characterization of bronze artefacts using non destructive (micro-FTIR, reflectance mode) and micro-destructive (based on sampling and analysis of a stratigraphical section by OM and SEM-EDX) methods. Burial soils were geologically classified and analyzed by chemical methods (pH, conductivity, anions content). Most of objects analyzed showed a coarse and inhomogeneous corroded structure, often made up of several corrosion layers. This has been explained by the silt nature of soils, which contain low amount of clay and are, therefore, quite accessible to water and air. The main cause of a high dissolution rate of bronze alloys is the alternate water saturation and instauration of the soil, for example on a seasonal scale. Moreover, due to the vicinity of the Black Sea, the detrimental effect of chlorine has been evidenced for few objects, which were affected by the bronze disease. A general classification of corrosion layers was achieved by comparing values of the ratio Cu/Sn in the alloy and in the patina. Decuprification is a general trend, and enrichment of copper within the corrosion layers, due to the formation of thick layers of cuprite (Cu2O), is pointed out as well. Uncommon corrosion products and degradation patterns were presented as well, and they are probably due to peculiar local conditions taking place during the burial time, such as anaerobic conditions or fluctuating environmental conditions. In order to acquire a better insight into the corrosion mechanisms, the second part of the thesis has regarded simulation experiments, which were conducted on commercial Cu-Sn alloys, whose composition resembles those of ancient artefacts one. Electrochemical measurements were conducted in natural electrolytes, such as solutions extracted from natural soil (sampled at the archaeological sites) and seawater. Cyclic potentiodynamic experiments allowed appreciating the mechanism of corrosion in both cases. Soil extract’s electrolyte has been evaluated being a non aggressive medium, while artificial solution prepared by increasing the concentration of anions caused the pitting corrosion of the alloy, which is demonstrated by optical observations. In particular, electrochemical impedance spectroscopy allows assessing qualitatively the nature of corroded structures formed in soil and seawater. A double-structured layer is proposed, which differ, in the two cases, for the nature of the internal passive layer, which result defectiveness and porous in case of seawater

Ceramic bricks using pistachio shells as controlled porosity former

The present work studies the use of pistachio shells as a porosity-forming raw material in the manufacture of ceramic bricks. It focuses on the characteristics of the ceramic pieces obtained with different residual biomass contents (from 5 to 20% by volume). The specimens were shaped by uniaxial pressure of 25 MPa, and then were treated at 950°C for 3h. Based on the results obtained it is possible to conclude that the use of this residual biomass, as a pore former in the ceramic industry is feasible. The proportion of added biomass that generates the best characteristics and properties in the final product is 10%. Up to this percentage of aggregate, ceramic pieces with very good macroscopic and microscopic characteristics are obtained, with porosity and flexural strength values that meet market requirements for this type of product. Optical microscopy technique has been used to carry out a detailed analysis of the shape and size of the formed pores, which is a specific objective of this work. It has been observed that for contents of 5 and 10% biomass, the shape of pores is similar to the shape of the particles of added pistachio shells, while for higher contents (15 and 20%) it is different with elongated characteristics. In relation with the size of the pores, at lower contents is around 60% of the original particles size, and for the higher percentages of biomass, they are larger, indicating that agglomerates of particles are formed and when combusted, produce that porosity characteristics

Use of wastes from the peanut industry in the manufacture of building materials

Most of the national peanut production, estimated at 900,000 tons per year, is processed in several cities in the central area of Argentina. The third part of this amount corresponds to the shells, which are separated in the peanut selection and processing plants. In this work, the possibility of using peanut shells as raw material for the manufacture of ceramic materials for the civil construction industry is studied. There are precedents on the use of biomass residues in different building blocks, mainly with the aim of generating lightweight ceramics. With this objective, ceramic pieces were obtained from green bodies manufactured with mixtures of commercial clay and different percentages of ground and dry residue. After a drying period, the samples were heat treated following curves similar to those used in the ceramic industry. The raw material used, clay and peanut shells, were characterized with different techniques, such as XRD, SEM and DTA-TGA. The DTA-TGA analysis shows that the organic material added is burned in a wide temperature range, between 300 °C and 550 °C. Thus, the sintering process of the bricks is performed without cracking or shattering. This test also shows that after the heat treatment, the waste material eventually incorporated into bricks (ashes) is less than 3%. The obtained products have good physical and mechanical properties, with acceptable values of porosity, modulus of rupture, permanent volumetric variation and weight loss on ignition.Fil: Quaranta, Nancy Esther. Universidad Tecnológica Nacional. Facultad Regional San Nicolás; ArgentinaFil: Caligaris, Marta Graciela. Universidad Tecnológica Nacional. Facultad Regional San Nicolás; ArgentinaFil: Pelozo, Gisela Guadalupe. Universidad Tecnológica Nacional. Facultad Regional San Nicolás; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Cesari, Andrea. Universidad Tecnológica Nacional. Facultad Regional San Nicolás; ArgentinaFil: Cristobal, Adrian Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin

Sobre el cálculo de la insolación a lo largo del tiempo

El objetivo del presente trabajo es obtener expresiones aproximadas, suficientemente precisas y sencillas a fin de modelar, a partir de un valor de la constante solar, la radiación incidente en un determinado punto de la atmósfera o de la corteza terrestre, debido al cambio de orientación del Sol a lo largo del día y del año

Particulate matter dynamics

A substantial fraction of the particulate matter released into the atmosphere by industrial or natural processes corresponds to particles whose aerodynamic diameters are greater than 50 mm. It has been shown that, for these particles, the classical description of Gaussian plume diffusion processes, is inadequate to describe the transport and deposition. In this paper we present new results concerning the dispersion of coarse particulate matter. The simulations are done with our own code that uses the Bulirsch Stoer numerical integrator to calculate threedimensional trajectories of particles released into the environment under very general conditions. Turbulent processes are simulated by the Langevin equation and weather conditions are modeled after stable (Monin-Obukhov length L> 0) and unstable conditions (L <0). We present several case studies based on Monte Carlo simulations and discusses the effect of weather on the final deposition of these particles.Comment: In spanish. 11 pages, 4 figs. Conference paper: Proyecto Integrador para la Mitigaci\'on de la Contaminaci\'on Atmosf\'erica Proyecto Integrador para la Determinaci\'on de la Calidad del Agua Tercera Reuni\'on Anual PROIMCA Primera Reuni\'on Anual PRODECA, Agosto, 201

What’s in the bee nest holes? A single aggregation of Megachile parietina reveals and helps to fill up Eltonian shortfalls

Megachile (Chalicodoma) parietina (Geoffroy, 1785) is a Palearctic solitary bee included in the Red List of some central European Countries. Females build durable nests, reused year after year, by mixing soil with a salivary secretion. Like for most solitary bees, the resources contained within M. parietina nests attract several other insects which exploit pollen supplies or feed on the immature brood. These associated insects have mainly been studied for mantained bees and considered for their effect on the host reproductive success.A very large nesting aggregation of M. parietina in Central Tuscany has been studied for three consecutive years. We have identified 32 associated insect species, which certainly are an underestimate of the species present. Among the identified species, only eight had been previously reported for M. parietina. All the species were classified both according to the specificity for the host taxon (Chalicodoma, Megachilidae, Anthophila, Hymenoptera, Others) and to the ecological relationship (cleptoparasites, parasitoids, predators of larvae, food commensal, scavengers, and occasional nest users).This highlighted both the richness of the ecological network within the nesting aggregation and the value of studying these nesting sites to fill Eltonian shortfalls, i.e. the deficiency in ecology knowledge, of bees and their associated fauna.Implications for insect conservation.We suggest that, besides their role in pollination, large and stable bee nesting sites increase the local insect biodiversity, and that attention should be paid to their conservation within actions aimed to support populations of wild pollinators

Genetic and structural analyses reveal the low potential of the SARS‐CoV‐2 EG.5 variant

The severe acute respiratory syndrome coronavirus 2 EG.5 lineage is the latest variant under monitoring, and it is generating significant concern due to its recent upward trend in prevalence. Our aim was to gain insights into this emerging lineage and offer insights into its actual level of threat. Both genetic and structural data indicate that this novel variant presently lacks substantial evidence of having a high capacity for widespread transmission. Their viral population sizes expanded following a very mild curve and peaked several months after the earliest detected sample. Currently, neither the viral population size of EG.5 nor that of its first descendant is increasing. The genetic variability appear to be flattened, as evidenced by its relatively modest evolutionary rate (9.05 × 10−4 subs/site/year). As has been observed with numerous prior variants, attributes that might theoretically provide advantages seem to stem from genetic drift, enabling the virus to continually adjust to its host, albeit without a clear association with enhanced dangerousness. These findings further underscore the necessity for ongoing genome-based monitoring, ensuring preparedness and a well-documented understanding of the unfolding situation

SARS-CoV-2 recombinants: genomic comparison between XBF and its parental lineages

Recombination events are very common and represent one of the primary drivers of RNA virus evolution. The XBF SARS-CoV-2 lineage is one of the most recently generated recombinants during the COVID-19 pandemic. It is a recombinant of BA.5.2.3 and BA.2.75.3, both descendants of lineages that caused many concerns (BA.5 and BA.2.75, respectively). Here, we performed a genomic survey focused on comparing the recombinant XBF with its parental lineages to provide a comprehensive assessment of the evolutionary potential, epidemiological trajectory, and potential risks. Genetic analyses indicated that although XBF initially showed the typical expansion depicted by a steep curve, causing several concerns, currently there is no indication of significant expansion potential or a contagion rate surpassing that of other currently active or previously prevalent lineages. BSP indicated that the peak has been reached around 19 October 2022 and then the genetic variability suffered slight oscillations until early 5 March 2023 when the population size reduced for the last time starting its last plateau that is still lasting. Structural analyses confirmed its reduced potential, also indicating that properties of NTDs and RBDs of XBF and its parental lineages present no significant difference. Of course, cautionary measures must still be taken and genome-based monitoring remains the best tool for detecting any important changes in viral genome composition