Search Results (330)

The design of emulsions at the nanoscale is a significant application of nanotechnology. For spherical droplets and a given volume of dispersed phase, the nanometre size of droplets inversely increases the total area, $A={\displaystyle \frac{3V}{r}}$, allowing greater contact with organic and inorganic materials during application. In topical applications, not only is cell contact increased, but also permeability in the cell membrane. Nanoemulsions typically achieve kinetic stability rather than thermodynamic stability, so their commercial application requires reasonable resistance to flocculation and coalescence, which can be affected by temperature changes. Therefore, their thermoresponsive characterisation becomes relevant. In this work, we analyse this response in an O/W nanoemulsion of Palmarosa for antibacterial purposes that has already shown stability for one year at controlled room temperature. We now study hysteresis processes and the behaviour of the statistical distribution in droplet size by Dynamic Light Scattering, obtaining remarkable stability under temperature changes up to 50 °C. This includes a maintained chemical composition observed using Fourier Transform Infrared Spectroscopy and the preservation of antibacterial properties analysed through optical density tests on cultures and the Spread-Plate technique for bacteria colony counting. We obtain practically closed hysteresis curves for some tracers of droplet size distributions through controlled thermal cycles between 10 °C and 50 °C, exhibiting a non-linear behaviour in their distribution. In general, the results show notable physical, chemical, and antibacterial stability, suitable for commercial applications. Full article

TGA kinetic analysis can assess the thermal stability and degradation properties of PCMs by calculating activation energies and onset degradation temperatures, which are critical elements when developing optimal PCM composition and assessing long-term performance in thermal energy storage applications. In this study, we utilize a thermogravimetric analyzer to examine the thermal stability of both solar salt phase change material (i.e., commonly used in medium-temperature applications) (NaNO₃ + KNO₃) and a composite eutectic PCM mixture (i.e., PCM with 20% biochar). The activation energies of both the pure solar salt and composite solar salt PCM sample were evaluated using a variety of different kinetic models such as Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO), and Starink. For pure PCM, the mean activation energies calculated using the KAS, FWO, and Starink methods are 581.73 kJ/mol, 570.47 kJ/mol, and 581.31 kJ/mol, respectively. Conversely, for the composite solar salt PCM sample, the calculated experimental average activation energies are 51.67 kJ/mol, 62.124 kJ/mol, and 51.383 kJ/mol. Additionally, various machine learning models, such as linear regression, decision tree regression, gradient boosting regression, random forest regression, polynomial regression, Gaussian process regression, and KNN regression models, are developed to predict the degradation behaviour of pure and composite solar salts under different loading rates. In the machine learning models, the mass loss of the samples is the output variable and the input features are PCM type, heating rate, and temperature. The machine learning models had a great prediction performance based on experimental TGA data, with KNN regression outperforming the other models by achieving the lowest RMSE of 0.0318 and the highest R² score of 0.977. Full article

A digital twin is an effective tool for the design, testing, and validation of control strategies for electro-pneumatic actuators in industrial automation. This study presents and compares three different digital twin models of a pneumatic cylinder with varying levels of physical fidelity—from basic discrete control, through analogue control without pneumatic dynamics, to a complex model simulating pressure, friction, and airflow. The experiments were conducted using the Siemens NX Mechatronics Concept Designer, integrated with the SIMIT emulation platform and a PLC control system via the standardized OPC UA protocol. The main objective was to evaluate simulation accuracy, model flexibility for testing various control strategies, and the ability of the digital twin to reflect changes in PLC algorithms. The results showed that while simple models are suitable for verifying basic logic, only advanced models can realistically replicate the dynamic behaviour of pneumatic systems, including delay phases and pressure influence. A comparison with the experimental study by Jiménez confirmed a strong correlation between the simulated and actual actuator behaviour. In future work, the developed control algorithm will be connected to a physical cylinder to further validate the models and refine control strategies under real-world conditions. Full article

This paper presents a study on optimising self-brazing powder mixtures for powder metallurgy diamond tools, specifically focusing on wire saws used in cutting natural stone. The research aimed to understand the relationship between the chemical composition of powder mixtures and the hardness of the sintered matrix. The experimental process involved the use of various commercially available powders, including carbonyl iron, carbonyl nickel, atomised bronze, atomised copper, and ferrophosphorus. The samples made of different powder mixtures were compacted and sintered and then characterised by dimensional change, density, porosity, and hardness. The obtained results were statistically analysed using an analysis of variance (ANOVA) tool to create linear regression models that relate the material properties to their chemical composition. The investigated materials exhibited excellent sintering behaviour and very low porosity, which are beneficial for diamond retention. Very good sinterability of powder mixtures can be achieved by tin bronze addition, which provides a sufficient content of the liquid phase and promotes the shrinkage during sintering. Statistical analysis revealed that hardness was primarily affected by phosphorous content, with nickel having a lesser but still significant impact. The statistical model can predict the hardness of the matrix based on its chemical composition. This model, with a determination coefficient of approximately 80%, can be valuable for developing new metal matrices for diamond-impregnated tools, particularly for wire saw beads production. Full article

Foamed specimens were fabricated from virgin and recycled polyethylenes (linear low-density polyethylene, LLDPE, and low-density polyethylene, LDPE) using low-cost citric acid and sodium bicarbonate foaming agents. The foaming agents chosen showed decomposition behaviour either without phase change (sodium bicarbonate, NaB) or liquefaction followed by decomposition (citric acid, CA). The manufactured polyethylene foams were then benchmarked against a polyurethane foam. Two types of mixing were used prior to foaming, viz., solid-state pulverisation or high-shear internal mixing, and the effect of mixing on properties critical for foam viability were analysed. These properties included density, pore size, shape and distribution, crystallinity, and porosity. It was found that the virgin LLDPE and recycled LDPE showed similar trends in terms of narrow pore size distribution and reduced crystallinity, while the recycled LLDPE tended towards more pore coalescence. This difference in behaviour was attributed to the more mixed phase nature of the recycled LLDPE as opposed to the majorly single-phase virgin LLDPE and recycled LDPE. Lowered densities obtained for the NaB foaming compared to CA can be speculated to be because of the ionic and simple NaB decomposition as opposed to the complex radical pathway for the CA decomposition. Full article

A binuclear Au-P complex [Au₂(2-bdppmapy)₂](PF₆)₂ (1) was synthesised by the reaction of 2-bdppmapy (N,N′-bis-(diphenylphosphanylmethyl-2-aminopyridine) with AuCN and [Cu(MeCN)₄]PF₆. The solid phase of 1 emitted bright yellow phosphorescence at λ_max = 580 nm under UV excitation (QY = 4.41%, τ = 1.88 μs), which shifted to green (λ_max = 551 nm, QY = 5.73%) after being pressurised under 5 MPa. This colour change was recoverable upon exposure to CH₂Cl₂ vapor. Similar mechanochromic photoluminescence behaviour was observed after grinding the crystals of 1. A filter paper impregnated with 1 demonstrated recyclable write/erase functionality for encrypted information transfer. Full article

An increasing lack of raw materials, resource depletion, environmental impacts and other concerns have changed the way the population faces garbage disposal and municipalities implement waste management strategies. The aggravated global rise in municipal solid waste (MSW) generation has led to a new stage in full development, with objectives and targets set by the European Union regarding reducing the production of MSW. The targets also include the increasing selective collection, reuse, recycling and recovery (organic and energetic) of the waste produced. At the same time, the European Union has also set caps for the greenhouse gas emissions and for increasing the use of alternative renewable energy sources. In this context, one of the sources of renewable energy that is beginning to be used to produce electricity in our country is biogas. Finally, AD promotes the development of a circular economy. The present study introduces the formalism for a computer application that simulates the technical–economic behaviour of the short-term management of biogas for the conversion of electricity, and the mathematical model is formulated as a mathematical programming problem with constraints. A simulation for a case study of short-term management is given using the real landfill data available. The case study proves the ability of the LandGEM, despite some authors’ support that the Tabasaran–Rettenberger model provided a more reliable estimate, especially when compared to actual landfill data. The present paper is a contribution to the optimisation of the management of electricity from the use of biogas, namely the second phase of the Strategic Plan for Urban Waste. In addition to complying with the legislation in force, the use of biogas to produce electricity is an added value for the concessionaires of waste treatment and final destination units, as this alternative energy source can provide not only self-sufficiency in electricity for these units but also the export of surplus energy to the National Electricity Grid, thus contributing to the self-sustaining management and energy flexibility that is intended for these infrastructures. Full article

In this work, we establish the existence of positive solutions for a problem driven by a multi-phase operator composed of two distinct exponent Laplacian-type operators and a generalised lower-order term, which ensures asymmetric behaviour across three subregions of the domain under consideration. The reaction term involves a mild singularity at zero and includes a possibly sign-changing perturbation function. Under additional restrictive conditions, we also obtain a uniqueness result for the problem. Our existence result is based on pseudomonotone operator theory. Moreover, a detailed analysis, combined with a Díaz–Saá-type argument, allows us to also establish a uniqueness theorem. To the best of our knowledge, this is the first work addressing such a generalisation of the multi-phase operator. These novel results can serve as a foundation for more general physical and engineering models. Full article

In this study, nanostructured copper oxide-based films with crystallite size below 10 nm were electrochemically synthesized on copper foil and foam electrodes and investigated for their supercapacitive behaviour. The synthesis was carried out via cyclic voltammetry (CV) for up to 1000 cycles in an alkaline electrolyte. By tuning the upper vertex potential (−0.3 V to 0.65 V vs. Ag/AgCl), both phase composition (Cu₂O, Cu(OH)₂, CuO) and morphology (grains, nanoneedles, nanoplatelets) were precisely controlled, demonstrating the versatility of this approach. The kinetics of oxide/hydroxide film formation on foil and foam electrodes were analysed based on EIS data that were interpreted in the frame of equivalent electric circuits and their changes with potential. The capacitive properties of the synthesized films were evaluated using CV in the potential range of 0 V–0.65 V, and the optimized CuO film synthesized on Cu foam exhibited a high specific capacitance of 1380 mF cm⁻². An energy density of 0.061 mWh cm⁻² and power density of 1.28 mW cm⁻² were obtained at 10 mA cm⁻² discharge current. Charge–discharge cycling at 100 mV s⁻¹ for 1000 cycles indicated an initial capacitance increase followed by stable retention, highlighting the structural integrity and electrochemical stability of the films obtained on 3D foam. These findings provide valuable insights into the controlled electrochemical synthesis of copper oxide nanostructures and their potential for high-performance capacitor applications. Full article

This study investigates the influence of nanocellulose fibre (CF) derived from wood pulp on the hydration, mechanical, shrinkage, and pore properties of ordinary Portland cement (OPC) mortar. The CF was incorporated into mortar mixes at varying dosages (0.15–1.5% by weight of mortar) to evaluate its effect on physical, mechanical, and microstructure properties. X-ray diffraction (XRD), thermogravimetric analysis (TGA/DTG), and mercury intrusion porosimetry (MIP) were employed to assess the hydration phases and microstructural changes induced by the CF addition. Experimental results indicate that CF alters the hydration kinetics of cement mortar by influencing the formation of hydration products such as calcium silicate hydrate (C-S-H), portlandite (CH), and carbonate phases. The introduction of CF enhances crack resistance and shrinkage control, particularly at an optimal dosage of 0.45%, which exhibited reduced drying shrinkage and improved phase stability. While CF incorporation had minimal impact on compressive and flexural strength at lower dosages (≤0.45%), higher CF contents (>0.99%) caused pore structure modifications, leading to an increase in total porosity and a reduction in strength. The XRD analysis revealed that CF does not introduce new hydration phases but modifies the crystallinity of existing phases. The hydration behaviour, as indicated by TGA/DTG, showed an increase in bound water content at moderate CF dosages, suggesting enhanced internal curing and prolonged hydration. Overall, the findings demonstrate that CF is a viable sustainable additive for cementitious materials, offering advantages in shrinkage control, hydration enhancement, and durability improvement. The results suggest that an optimal CF dosage of 0.45% provides a balance between workability, mechanical properties, and durability, making it an effective additive for enhancing the performance of OPC mortars in sustainable construction applications. Full article

The desert locust is documented as one of the most destructive polyphagous plant pests that require preventive or proactive management practices due to its phase polyphenism, rapid breeding, transnational migration, and heavy feeding behaviour. Desert locust situation analysis, forecasting and early warning are complex due to the systemic interaction of biological, meteorological, and geographical factors that play different roles in facilitating the survival, breeding and migration of the pest. This article seeks to elucidate the factors that affect desert locust distribution and review the application of earth observation (EO) data in explaining the pest’s infestations and impact. The review presents details concerning the application of EO data to understand factors that affect desert locust breeding and migration, elaborates on impact assessment through vegetation change detection and discusses modelling techniques that can support the effective management of the pest. The review reveals that the application of EO technology is inclined in favour of desert locust habitat suitability assessment with a limited financial quantification of losses. The review also finds a progressive advancement in the use of multi-modelling approaches to address identified gaps and reduce computational errors. Moreover, the review recognises great potential in applications of EO tools, products and services for anticipatory action against desert locusts to ensure resource use efficiency and environmental conservation. Full article

BiFeO₃/LaFeO₃ (BFO/LFO) epitaxial superlattices (SLs) with different bilayer thicknesses were grown via pulsed laser deposition on a (001)-SrTiO₃ substrate buffered with a SrRuO₃ bottom electrode. Room-temperature X-ray diffraction demonstrated strong structural changes in tuning the bilayer thickness while keeping the total thickness constant. Superlattices with thin periods were characterized by an antiferroelectric Pnma-like phase, while thick bilayers of the SLs were more likely to be described by a mixed state, including a rhombohedral ferroelectric bulk-like phase. Raman scattering analysis further confirmed the structural behaviour deduced by X-ray diffraction. Strain relaxation and symmetry changes were moreover accompanied by modifications in the dielectric properties correlated with the deduced (anti)ferroic structural phases. Full article

Magnesia-spinel multicomponent materials have been used as refractories for a long time. In addition to a few binary systems, the influence of spinel phases on the thermal expansion ($\alpha$) of MgO or the resulting compound has not been studied so far. As $\alpha$ is critical for refractories in application, this work investigates the thermal expansion of complex MgO-based spinel systems using X-ray diffraction (XRD) in combination with Rietveld refinement in the temperature range between 30 °C and 1200 °C. All studied periclase solid solutions, in contact with spinels of the systems Mg_1.01(Al_0.23Cr_1.64Fe_0.13)O₄, ${\mathrm{Fe}}_3{\mathrm{O}}_4$–${\mathrm{MgFe}}_2{\mathrm{O}}_4$, NiFe₂O₄–NiAl₂O₄, MgAl₂O₄–MgFe₂O₄, Fe₃O₄–FeAl₂O₄ and ${\mathrm{Fe}}_3{\mathrm{O}}_4·{\mathrm{NiFe}}_2{\mathrm{O}}_4·2{\mathrm{MgAl}}_2{\mathrm{O}}_4$ showed $\alpha$ trends below plain MgO, or even decreasing values above 1000 °C. Many spinels showed large negative thermal expansion coefficients. It was found that the structural change in spinels is constrained, leading to a common analytical expression to calculate the lattice parameter of spinels with temperature, which was used to study the nature of the investigated spinels in more detail. The work highlights that Cr-free MgO-spinel systems show similar or even better high-temperature behaviour than commonly used magnesia–chrome aggregates. Full article

Changes in cell shape have been shown to be an integral part of the mycobacterial life cycle; however, systematic investigations into its patterns of pleomorphic behaviour in connection with stages or conditions of growth are scarce. We have studied the complete growth cycle of Mycobacterium monacense cultures, a Non-Tuberculous Mycobacterium (NTM), in solid as well as in liquid media. We provide data showing changes in cell shape from rod to coccoid and occurrence of refractive cells ranging from Phase Grey to phase Bright (PGB) in appearance upon ageing. Changes in cell shape could be correlated to the bi-phasic nature of the growth curves for M. monacense (and the NTM Mycobacterium boenickei) as measured by the absorbance of liquid cultures while growth measured by colony-forming units (CFU) on solid media showed a uniform exponential growth. Based on the complete M. monacense genome we identified genes involved in cell morphology, and analyses of their mRNA levels revealed changes at different stages of growth. One gene, dnaK_3 (encoding a chaperone), showed significantly increased transcript levels in stationary phase cells relative to exponentially growing cells. Based on protein domain architecture, we identified that the DnaK_3 N-terminus domain is an MreB-like homolog. Endogenous overexpression of M. monacense dnaK_3 in M. monacense was unsuccessful (appears to be lethal) while exogenous overexpression in Mycobacterium marinum resulted in morphological changes with an impact on the frequency of appearance of PGB cells. However, the introduction of an anti-sense “gene” targeting the M. marinum dnaK_3 did not show significant effects. Using dnaK_3-lacZ reporter constructs we also provide data suggesting that the morphological differences could be due to differences in the regulation of dnaK_3 in the two species. Together these data suggest that, although its regulation may vary between mycobacterial species, the dnaK_3 might have a direct or indirect role in the processes influencing mycobacterial cell shape. Full article

Background: Despite scientific breakthroughs in vaccine development, some people remain reluctant to accept the anti-SARS-CoV-2 vaccine. This study evaluates attitudes and behaviours towards the vaccine and factors associated with refusal/hesitancy at the start of Italy’s vaccination campaign. Methods: EPICOVID19 is a two-phase observational web-based study where adult volunteers completed questionnaires in April–June 2020 and January–February 2021. Refusal/hesitancy towards the vaccine was assessed among those not yet vaccinated. We analysed factors associated with refusal/hesitancy by applying multivariate multinomial logistic regression models. Results: Among 36,820 survey participants (mean age of 51 years, 59.7% women, 63.6% highly educated), 2449 (6.7%) were against or hesitant, 4468 (12.1%) were inclined but unsure, and 29,903 (81.2%) were willing to be vaccinated. Factors positively associated with refusal/hesitancy included female sex, middle age, at-risk occupations, medium and low education, deprived status, being underweight, previous SARS-CoV-2 positivity, poor perceived health, no fear of contracting SARS-CoV-2, the fear of contaminated food and natural disasters, and low trust in science, media, government, or institutions. Low hesitancy was associated with student and retired status, overweight and obesity, moderate and high alcohol consumption, no concern about economic and working conditions, and sensitivity to climate change/environmental pollution and epidemics. Conclusions: This survey showed that, during the first month of Italy’s vaccination campaign, some individuals were reluctant to receive the anti-SARS-CoV-2 vaccine. This study highlights potential target groups for tailored communication and prevention campaigns. Full article