117,635 research outputs found
Some remarks on the retrofitting of masonry structures with composite materials
No full textThis paper presents some numerical simulations, aimed to the assessment of the structural performance of masonry walls, reinforced with FRP composite materials. The problem is modeled in two dimensions, and the effects of seismic loads and of foundation settlements are studied numerically. The tool we use to perform the numerical analysis, is a new minimization software developed by the authors to analyze masonry constructions, modeled as unilateral structures. The material model we adopt, no-tension with elastic-plastic (associated) behavior in compression, is path-dependent and rate-independent. The trajectory of the system, under a given loading history, is approximated as a sequence of minimizers of a path dependent form of energy, updated at each stage of the step-by-step, time-discretized procedure. The results we obtain confirm that the application of fiber reinforced composites must be done carefully, since the increase of strength in some structural elements, due to the retrofitting, may prevent the structure from developing its natural, stress relieving, kinematics. �� 2014 Published by Elsevier Ltd
Cytoskeletal actin networks in motile cells are critically self-organized systems synchronized by mechanical interactions
Full text linkGrowing networks of actin fibers are able to organize into compact, stiff two-dimensional structures inside lamellipodia of crawling cells. We put forward the hypothesis that the growing actin network is a critically self-organized system, in which long-range mechanical stresses arising from the interaction with the plasma membrane provide the selective pressure leading to organization. We show that a simple model based only on this principle reproduces the stochastic nature of lamellipodia protrusion (growth periods alternating with fast retractions) and several of the features observed in experiments: a growth velocity initially insensitive to the external force; the capability of the network to organize its orientation; a load-history-dependent growth velocity. Our model predicts that the spectrum of the time series of the height of a growing lamellipodium decays with the inverse of the frequency. This behavior is a well-known signature of self-organized criticality and is confirmed by unique optical tweezer measurements performed in vivo on neuronal growth cones
Variability in salt tolerance in seedlings of panicum coloratum var. makarikariense l. in hydroponics
Full text linkFil: Cardamone, Luisina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Cuatrín, Alejandra. Instituto Nacional de Tecnología Agropecuaria; Argentina.Fil: Grunberg, Karina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Tomás, María Andrea. Instituto Nacional de Tecnología Agropecuaria; Argentina.Fil: Cardamone, Luisina. Instituto Nacional de Tecnología Agropecuaria; Argentina.Fil: Grunberg, Karina. Instituto Nacional de Tecnología Agropecuaria; Argentina.Soil salinity is a major constraint to plant production and an increasing phenomenon in regions with raising water tables. Improving germplasm for salinity tolerance could be a more sustainable solution than soil reclamation in subtropical areas. Panicum coloratum var. makarikariense is a warm-season perennial grass native to Africa used as forage in subtropical areas of the world. Genetic improvement to increase salinity tolerance in the species could make it a forage resource for areas with this edaphic restriction. In this study we searched for variability in salinity tolerance in a collection of P. coloratum var. makarikariense to find suitable materials to be included in a breeding program. A screening of 18 families from 4 populations (ER, DF, TS and UCB) was performed by culturing in hydroponic conditions, in a DBCA (2 replicates, ten seedlings/replicate of each family) in a greenhouse setting. Treatments were: control (Hoagland solution, 0mM NaCl) and salinity (Hoagland solution + 200 mM NaCl). Plants were cultivated for 35 days then divided into roots and aerial biomass at harvest. Tolerance was evaluated as total biomass (TB) produced under salinity and by calculating the damage as the percent reduction in growth in salt compared to the control setting. Data was analyzed by ANOVA. PCA and clustering analysis were also used to discriminate susceptible from tolerant families. Families ER3, ER6, ER9 and DF7 had the highest TB although differences were not significant. Nonetheless, clustering and PCA grouped the same families as more productive. Damage was estimated in: aerial fresh weight, root fresh weight, total fresh weight, aerial dry weight, root dry weight, total dry weight. Families ER3, ER6, ER10, TS23 and DF7 had the lowest damage in all of variables. PCA biplot and clustering based on damage distinguished; ER3, ER6, ER10, TS23 and DF7 as tolerant families while the rest were set as susceptible ones. Variability for salinity tolerance was found in the collection and promising materials were detected to enter a breeding program to increase productivity under salt conditions.https://www.agro.uba.ar/ISFB2015Fil: Cardamone, Luisina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Cuatrín, Alejandra. Instituto Nacional de Tecnología Agropecuaria; Argentina.Fil: Grunberg, Karina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Tomás, María Andrea. Instituto Nacional de Tecnología Agropecuaria; Argentina.Fil: Cardamone, Luisina. Instituto Nacional de Tecnología Agropecuaria; Argentina.Fil: Grunberg, Karina. Instituto Nacional de Tecnología Agropecuaria; Argentina.Otras Ciencias Agrícola
Anti-Listeria activity of lactic acid bacteria in two traditional Sicilian cheeses
Full text linkListeria monocytogenes is a pathogen frequently found in dairy products, and its growth is difficult to control. Bacteriocinlike inhibitory substances (BLIS), produced by lactic acid bacteria (LAB), having proven in vitro anti-Listeria activity, could provide an innovative approach to control L. monocytogenes; however, this application needs to be evaluated in vivo. In this study, twenty LAB strains isolated from different Sicilian dairy environments were tested for control of growth of L. monocytogenes in three different experimental trials. First, raw and UHT milk were inoculated with LAB strains alone, and LAB strains mixed with L. monocytogenes. Second, mini-cheeses containing LAB and/or L. monocytogenes were produced. Third, two traditional Sicilian cheeses inoculated with a multi-strain LAB mixture combined with L. monocytogenes were produced. The addition of BLIS produced by LAB to milk and in mini-cheese production was unable to inhibit the growth of L. monocytogenes. However, an anti-Listeria effect was observed in the Pecorino Siciliano cheeses, where, after 15 days of ripening, the cheeses with added LAB had fewer L. monocytogenes compared to the control cheeses with no added LAB, while in the Vastedda della valle del Belìce cheeses, the multi-strain LAB mixture completely prevented the growth of L. monocytogenes
Lipid-based nanoparticles for nucleic acids delivery
No full textThis chapter highlights challenges and advancements in the production of lipid-based nanoparticles (LNPs) and their application in nucleic acid-based therapies. Recently, mRNA-based vaccines for COVID-19 immunization revealed that the use of nucleic acids is a promising strategy to develop treatments at high therapeutic efficiency and reduced side effects. In this context, LNPs emerged as favourable vehicles for nucleic acids delivery (like mRNA and DNA), due to their biocompatibility, bioavailability, and versatility. The four main components employed to produce LNPs loaded with mRNA are: cationic or ionizable lipids, helper lipids, cholesterol, and PEGylated lipids. Several conventional techniques have been proposed over the years to produce this kind of nanoparticles. However, they show many drawbacks that hinder the direct production of vesicles characterized by a nanometric size, high encapsulation efficiency of the active pharmaceutical ingredient, and prolonged stability. Processes assisted by supercritical fluids (in particular, supercritical CO2) can represent a sustainable and interesting alternative to produce LNPs without using post-processing steps for solvent removal and size reduction that are time-consuming procedures, lead to a large loss of nucleic acids, and negatively influence the general productivity of the process
Adaptation of maximum power point tracking controller for damaged wind turbines
No full textWind energy is essential for sustainable energy production, but its growth faces challenges. Wind turbines endure harsh conditions, such as rain, ice, dust, and sea spray, causing erosion and degrading aerodynamics. In this study, we address the relevant issue of leading-edge blade erosion. Initially, the power loss due to erosion will be quantified, considering three severity levels. Subsequently, a controller tuning strategy will be implemented to mitigate these losses during operation. Numerous design load cases (DLCs), each with different seeds, are necessary to achieve statistical significance. Therefore, it was decided to integrate the OpenFAST medium-fidelity software with high-fidelity CFD simulations to characterize erosion and quantify its effects. An initial evaluation of the aerodynamic coefficient maps was performed for the different levels of erosion. Subsequently, the potential gain was quantified by tuning the control strategy. Two sites were selected for the calculation of the Annual Energy Production (AEP) with medium-low wind speeds. Furthermore, a gain scheduling strategy that varies according to erosion and wind speed was considered, achieving positive results and an increase in AEP of up to 0.7% in the most severe case. This was achieved without any modifications to the turbine, but exclusively by acting on the existing controller
- …
