Increase In Temperature Research Articles

Effects of different temperatures on the embryonic development of the Lebranche mullet Mugil liza.

We herein investigated the influence of temperature on theembryonic development (from fertilisation to hatching) of Mugil liza larvae. For this purpose, oocytes (>600 μm) and sperm were obtained from breeding stock at the laboratory of marine fish culture (LAPMAR). After fertilisation, 1200 eggs were distributed in 12 cylindrical experimental units of 400 mL under four different temperatures 18, 22, 26 and 30 ºC, all in triplicate. Every 15 min until hatching, about 10 eggs were randomly sampled in each treatment. The eggs were visualized and photographed, and the classification of embryonic stages was performed. Temperature influenced the main events of the embryonic development of M. liza. More accelerated development was observed according to the increase in temperature until the gastrula phase. At temperatures of 22 and 26 °C, embryonic development occurred from fertilisation to hatching of the larvae. In the 18 °C treatment, it was verified that most of the embryos ceased development during the final phase of cleavage and the beginning of blastula formation, while in the 30 °C treatment patterns of embryo malformation were also verified, with erratic divisions of the blastomeres, resulting in irregular cells. Unlike what was observed at a temperature of 18 °C, none of the embryos incubated at 30 °C reached the blastopore closure phase, stopping in the gastrula. The larvae hatched in the treatments at 22 and 26 °C were viable and exhibited intense swimming, with a large amount of reserve material (yolk) and an evident drop of oil.

3D-printed polycaprolactone-magnetic nanoparticles composite multifunctional scaffolds for bone tissue regeneration and hyperthermia treatment

Cancer management after tumor resection is characterized by two critical needs: (i) rehabilitation of the resected tissue and (ii) preventing post-surgical tumor recurrence by destroying any residual tumors. The state of the art in literature is limited because it tackles these two major priorities individually, it achieves tissue regeneration via autologous grafting and prevents tumor recurrence through chemotherapy. In this paper, extrusion 3D printing has been employed to manufacture composite multi-functional scaffolds with polycaprolactone (PCL) as a polymeric matrix and magnetic nanoparticles (MNPs) in a 0 to 50 wt% ratio, that would aid in bone regeneration and cancer management via magnetic hyperthermia treatment. The fabricated scaffolds were evaluated for their mechanical, magnetic and thermal characteristics. The Young’s modulus of the scaffolds increased multi-fold with increasing concentration of MNPs added to PCL (26.88±9.02 MPa for pure PCL to 229.06±37.05 MPa for PCL/50 wt% MNP scaffolds). PCL/MNP scaffolds displayed a directly proportional correlation between MNP concentration and saturation magnetization. While the in vitro tests showed a statistically significant cell growth of human Mesenchymal Stem Cells (hMSCs) over 7 days for all MNP concentrations, only the 50% MNP scaffold showed an increase in temperature over 41oC when subjected to an alternating magnetic field making it suitable for the hyperthermia treatment. On application of alternating magnetic fields to PCL and PCL/50 wt% MNP scaffolds, there was an increase in hMSCs proliferation and decrease in Bone cancer cells proliferation, thus proving the potential to be used as a multi-functional scaffold for post-surgical bone cancer management.  

Crystal Structure, Microstructure, and Dielectric and Electrical Properties of Ceramic Material Prepared Using Volcanic Ash

In the present work, the electrical and dielectric properties of ceramic samples prepared from volcanic ash were investigated. For this purpose, ceramic samples were prepared using milled volcanic ash with a binder material at a sintering temperature of 950 °C for 2 h. The chemical content of the milled volcanic ash was investigated using XRF. Differential thermal analysis and thermogravimetry were performed to determine the firing conditions. The crystalline phases and microstructures of the ceramic samples were investigated using XRD and SEM, respectively. Finally, the electrical and dielectric properties of the obtained samples were evaluated at a frequency ranging from 1 × 102 to 4 × 106 Hz and temperatures ranging from room temperature to 800 °C. The XRD results revealed that the ceramic samples contained three main phases: albite, hematite, and augite. Moreover, the microstructures of the samples exhibited a large crystal size with a dense surface. The conductivities and dielectric constants of the samples remained stable up to 500 °C. The real and imaginary parts of the dielectric constant decreased with an increase in frequency and increased with an increase in temperature. The results indicated that ceramics based on volcanic ash are promising for use in technological applications such as high-voltage power insulators.

The starting temperature of high-flow nasal cannula and perceived comfort in critically ill patients: A pragmatic randomized controlled trial.

High-flow nasal cannula (HFNC) therapy is a non-invasive respiratory treatment characterized by high tolerability, which largely derives from the patient's comfort. The primary aim of this study was to explore whether the patient's perceived comfort was the same regardless of different approaches used to reach the target humidification temperature. The secondary aim was to assess the patient's perceived nasal dryness and humidity. This single-centre, pragmatic, randomized trial was registered at clinicaltrials.gov (NCT05688189). Patients in the intensive care unit (ICU) in need of HFNC therapy were randomly assigned to one of three study arms: a two-step increase (31 to 34 to 37°C), a one-step increase in temperature (34-37°C) or no temperature increase (started and remained at 37°C). The patients were asked to rate their perceived comfort, as well as their perceived nasal dryness and humidity on a scale from 1 (lowest value) to 5 (highest value). We enrolled 21 patients, aged 34-85 years. The mean (±1 standard deviation) comfort level was 3.3 (1.3) for patients who received a one-step increase, 3.1 (1.3) for those who received no increase and 2.7 (1.7) for those who received a two-step increase (p = .714). There was also no difference in nasal dryness (p = .05) or humidity (p = .612) across the study arms. Greater comfort was fairly correlated with less nasal humidity (ρ = -0.34, 95% confidence interval -0.68 to 0.07) but not with nasal dryness (ρ = 0.01, p = .94). After 30 min of HFNC therapy at a target temperature of 37°C, overall comfort was rated similarly in the three study arms. Additional studies are needed to accumulate evidence corroborating the findings of this study. The temperature of the mixture of air and oxygen is a fundamental component of HFNC therapy. A pragmatic approach irrespective of the initial temperature setting seems to yield a similar comfort score in hospitalized patients with mild respiratory failure because of extrapulmonary causes.

Stereoregular Poly(Phenyl Glycidyl Ethers): In Situ Formation of a Polyether Stereocomplex from a Racemic Monomer Mixture

Polymer stereocomplex formation represents a promising research area as it can improve thermal and mechanical properties of co‐crystallized polymer strands of opposite chirality. Polymers that form stereocomplexes commonly feature high stereoregularity and usually require sourcing from enantiopure monomer building blocks. Herein, we report the in situ polyether stereo­complex formation from racemic epoxide monomers, i.e., substituted methyl phenyl glycidyl ethers. The bio‐renewable glycidyl ethers were explored in both enantio‐ and isoselective ring‐opening polymerizations (ROPs), resulting in isotactic poly(phenyl glycidyl ether). While the enantio­selective ROP selectively resolves a single enantiomeric, isotactic polyether stereoisomer ([mm]P ≥ 78%), the isoselective ROP leads to the concurrent formation of both isotactic (R)‐ and (S)‐poly(phenyl glycidyl ether) stereoisomers ([mm]P ≥ 92%) and thus results directly in a stereoisomer blend, which forms a stereocomplex. This is one of only a few polymer stereocomplexes generated directly during polymerization from a racemic monomer mixture. Stereo­complexes of the different poly(phenyl glycidyl ether)s show an increase in melting temperature of up to 76 °C, relative to the enantiopure parent polymers. The position of the methyl group at the phenyl ring determines both stereocomplex formation and the thermal properties of the resulting materials.

Stereoregular Poly(Phenyl Glycidyl Ethers): In Situ Formation of a Polyether Stereocomplex from a Racemic Monomer Mixture.

Polymer stereocomplex formation represents a promising research area as it can improve thermal and mechanical properties of co-crystallized polymer strands of opposite chirality. Polymers that form stereocomplexes commonly feature high stereoregularity and usually require sourcing from enantiopure monomer building blocks. Herein, we report the in situ polyether stereo-complex formation from racemic epoxide monomers, i.e., substituted methyl phenyl glycidyl ethers. The bio-renewable glycidyl ethers were explored in both enantio- and isoselective ring-opening polymerizations (ROPs), resulting in isotactic poly(phenyl glycidyl ether). While the enantio-selective ROP selectively resolves a single enantiomeric, isotactic polyether stereoisomer ([mm]P ≥ 78%), the isoselective ROP leads to the concurrent formation of both isotactic (R)- and (S)-poly(phenyl glycidyl ether) stereoisomers ([mm]P ≥ 92%) and thus results directly in a stereoisomer blend, which forms a stereocomplex. This is one of only a few polymer stereocomplexes generated directly during polymerization from a racemic monomer mixture. Stereo-complexes of the different poly(phenyl glycidyl ether)s show an increase in melting temperature of up to 76 °C, relative to the enantiopure parent polymers. The position of the methyl group at the phenyl ring determines both stereocomplex formation and the thermal properties of the resulting materials.

Paleoenvironmental Transition during the Rhuddanian–Aeronian and Its Implications for Lithofacies Evolution and Shale Gas Exploration: Insights from the Changning Area, Southern Sichuan Basin, South-West China

During the Rhuddanian–Aeronian interglacial period, global geological events such as glacial melting, synsedimentary volcanic activity, biological resurgence, and large-scale marine transgressions caused frequent fluctuations in paleoproductivity, climate changes, and sea level variations. These paleoenvironmental transitions directly influenced the development characteristics of shale lithofacies. This study investigates the Longmaxi Formation shale in the Changning area in the Southern Sichuan basin, focusing on 28 core samples from Well N1. Using scanning electron microscopy, QEMSCAN, TOC, XRD, and major and trace element analyses, we reconstructed the paleoenvironmental transitions of this period and explored their control over shale lithofacies types and mineral compositions. Four shale lithofacies were identified: carbonate rich lithofacies (CRF), biogenic quartz-rich lithofacies (BQRF), detrital clay-rich lithofacies (CRDF), and detrital quartz-rich lithofacies (DQRF). During the Rhuddanian period, rising global temperatures caused glacial melting and rapid marine transgressions. The low oxygen levels in bottom waters, combined with upwelling and abundant volcanic material, led to high paleoproductivity. This period primarily developed BQRF and CRF. Rich nutrients and abundant siliceous organisms, along with anoxic to anaerobic conditions, provided the material basis and preservation conditions for high biogenic quartz and organic matter content. High paleoproductivity and anoxic conditions also facilitated the precipitation of synsedimentary calcite and supplied Mg2⁺ and SO₄2⁻ for the formation of iron-poor dolomite via sulfate reduction. From the Late Rhuddanian to the Mid-Aeronian, the Guangxi orogeny caused sea levels to fall, increasing water oxidation and reducing upwelling and volcanic activity, which lowered paleoproductivity. Rapid sedimentation rates, stepwise global temperature increases, and the intermittent intensification of weathering affected terrigenous clastic input, resulting in the alternating deposition of CRF, CRDF, and DQRF. Two favorable shale gas reservoirs were identified from the Rhuddanian–Aeronian period: Type I (BQRF) in the L1–L3 Layers, characterized by high TOC and brittleness, and Type II (DQRF) in the L4 Layer, with significant detrital quartz content. The Type I-favorable reservoir supports ongoing gas production, and the Type II-favorable reservoir offers potential as a future exploration target.

Nanocrystallized copper phosphate endowed with photothermal conversion and photoacoustic imaging capabilities

Copper-based nanomaterials have garnered significant attention for their potential applications in photothermal (PT) conversion and photoacoustic (PA) imaging due to their unique optical properties. However, current strategies often involve complex synthesis processes and the incorporation of additional materials, which limit their practical applicability. Here, we employed a straightforward nanocrystallization method to synthesize copper phosphate nanoparticles (Cu3(PO4)2 NPs), converting free copper ions into solid-phase nano-sized particles. This approach not only simplifies the synthesis process but also enhances the optical and thermal properties of the resulting Cu3(PO4)2 NPs. The Cu3(PO4)2 NPs achieved a temperature increase of over 20∘C and a PT conversion efficiency of 10.5% under 808 nm laser irradiation. Furthermore, Cu3(PO4)2 NPs exhibited strong, concentration-dependent PA signals, which enabled effective deep tissue imaging in vivo. The enhanced properties of Cu3(PO4)2 NPs can be attributed to the nanocrystallization of the particles, which alters the local environment of copper ions and enhances d−d transitions through specific ligand field effects. These effects increase light absorption, particularly in the NIR region, by facilitating better overlap of electronic states and enabling more efficient non-radiative relaxation processes. This highlights the significance of nano-structuring in developing advanced nanomaterials with tailored functionalities for biomedical applications.

Assessment of Hydraulic Oil Properties during Operation of a Mini Loader

This study employs a rigorous methodology to assess the condition of the hydraulic oil in a recently introduced mini skid-steer loader. The assessment is conducted through laboratory analysis, which adheres to a range of international standards. The objective is to provide accurate insights into the viscosity, particle count, and characterisation of the oil, along with thermographic data. The friction of oil is evaluated at specific time points: 0, 10, 100, 125, and 150 h of operation. This examination offers a comprehensive insight into the alterations in oil characteristics during a pivotal period when machine components are undergoing initial consolidation and abrasion to attain the factory-defined performance thresholds. The principal aim of this research is to provide valuable insights into the wear of oil and hydraulic system components through an in-depth analysis of a range of variables. Moreover, the investigation aims to ascertain the impact of this factor on the temperature elevation of system components and accessories to formulate enhanced technical guidelines for implementation. The main results indicate the presence of particles in the oil, resulting in a cleanliness code of 23/21/13, which exceeds the permissible threshold of 20/18/15 specified in ISO 11171. In addition, hydraulic oil shows a viscosity instability of more than 10% due to moisture absorption, leading to wear of mechanical components composed of iron, nickel, copper, zinc, and silicon. This deterioration is corroborated by thermographic evaluations, which reveal a considerable temperature increase in components such as cylinders and system accessories.

Can solar water kiosks generate sustainable revenue streams for rural water services?

Providing a sustainable supply of safe drinking water in rural Africa depends on sufficient revenue from user payments to maintain services. While handpumps have been the primary source of drinking water for rural Africans for decades, local revenue generation has been unstable, contributing to service disruptions and welfare losses. We examine the effect of upgrading manual handpumps to solar kiosks in rural Mali from 2019 to 2023. We model 452 monthly records of observed payments and metered water usage to estimate changes in volumetric use and revenue generation. Average revenues increase four-fold indicating stronger financial performance with solar kiosks. In contrast, we find no significant increase in the volume of water people use when a handpump is upgraded to a solar kiosk. We estimate that a 1 °C temperature increase is associated with a $9 increase in average monthly revenue and 366 more litres of water used every day per waterpoint. Our study suggests that rural Malians are more inclined to pay for water from professionally managed solar kiosks. However, seasonal volatility in water demand and uncertainty in the long-term revenue effect suggests caution in assuming solar kiosks are a definitive solution to the nuanced and dynamic nature of water user behaviours in rural Africa.

Combustion Process of Coal–Açai Seed Mixtures in a Circulating Fluidized Bed Boiler

This study investigates the effects of the co-combustion of coal and açai seed in circulating fluidized bed (CFB) boilers, highlighting the increase in thermal efficiency and relevance of a less-polluting source of energy. Using the computer software 1.5D CeSFaMB™® v4.3.0, simulations of the co-combustion process of coal and biomass were carried out in a CFB boiler, obtaining results such as the temperature profile, boiler efficiency and emissions. The work acquired data regarding the equipment in real operational conditions, consisting of the fundamental geometric and operational parameters used in the simulation campaign. The thermal and chemical properties of the fuels were analyzed by carrying out proximate, ultimate, heating value, particle size and specific mass analyses. The model validation was achieved by simulating the boiler in its real operating conditions and comparing the obtained results with the real data; the obtained error was below 10%. Simulations with different fractions of açai seed for energy replacement (10% and 30%) were carried out. As a result, an increase in the average temperature of the bed was observed, highlighting the region immediately above the dense bed. An increase in boiler efficiency was verified from 56% to 85% with 10% açai and to 83% with 30% açai seed. Decreases in SO2 and CO emissions with the insertion of açai were obtained, showing that co-combustion is more complete, while CO2 emissions were increased due to the higher quantity of fuel inserted into the equipment. The fossil CO2 emissions were reduced.

Simulation-Guided Preparation of Copper Chalcogenide Nanoparticle-Based Transparent Photothermal Coating with Enhanced Deicing Performance.

In this investigation, transparent photothermal coatings utilizing plasmonic copper chalcogenide (Cu2-xS) nanoparticles were designed and fabricated for the deicing of glass surfaces. Cu2-xS nanoparticles, chosen for their high near-infrared (NIR) absorption and efficient photothermal conversion, were analyzed via finite difference time domain (FDTD) simulations to optimize nanoparticle morphology, thus avoiding costly trial-and-error synthesis. FDTD simulations determined that Cu2-xS nanorods (Cu-NRs) with an optimal aspect ratio of 2.2 had superior NIR absorption. Guided by FDTD simulations, the composite coating composed of Cu-NRs in clear acrylic resin paint was brush-coated to glass, achieving 62.4% visual transmittance and over 95% NIR absorbance. Photothermal conversion tests exhibited a significant temperature increase, with the coating reaching 65 °C under NIR irradiation within 6 min. The dynamic deicing process of ice beads on the coating at -20 °C completed within 220s, in contrast to the frozen state on glass coated with clear acrylic resin paint. Furthermore, heat transfer simulations in COMSOL illustrated melting initiation at the ice-coating interface and subsequent progression through the ice layer. This simulation-driven synthesis method and photothermal testing offer a design framework for the fabrication of photothermal deicing coatings with applications for automobiles, buildings, and aircraft in cold environments.

Near-Infrared Multiwavelength Raman Anti-Stokes/Stokes Thermometry of Titanium Dioxide

The use of multiple wavelengths to excite Titanium Dioxide Raman scattering in the near-infrared was investigated for optical nanothermometry. Indeed, Raman spectroscopy can be a very interesting technique for this purpose, as it offers non-disruptive contactless measurements with a high spatial resolution, down to a few µm. A method based on the ratio between the anti-Stokes and Stokes peaks of Anatase Titanium Dioxide was proposed and tested at three different wavelengths, 785, 800 and 980 nm, falling into the first biological transparency window (BTW-I). Using a temperature-controller stage, the temperature response of the sample was measured between 20 and 50 °C, allowing the thermal sensitivity for this range to be estimated. The use of sufficiently high laser power results in the generation of local heating. A proof of concept of the proposed thermometric method was performed by determining the extent of local heating induced by increasing laser power. By exciting with an 800 nm laser at low power intensities, a temperature equal to room temperature (RT) was found, while a maximum temperature increase of 15 °C was detected using the anti-Stokes/Stokes method.

Global decline in microbial-derived carbon stocks with climate warming and its future projections

Abstract Soil organic carbon (SOC) represents the largest terrestrial pool of organic carbon and is indispensable for mitigating climate change and sustaining soil fertility. As a major component of stable SOC, microbial-derived carbon (MDC) accounts for approximately half of the total SOC and has repercussions on climate feedback. However, our understanding of the spatial and temporal dynamics of MDC stocks is limited, hindering assessments of the long-term impacts of global warming on persistent SOC sequestration in the soil‒atmosphere C cycle. Here, we compiled an extensive global dataset and employed ensemble machine learning techniques to forecast the spatial-temporal dynamics of MDC stocks across 93.4% of the total global land area from 1981 to 2018. Our findings revealed that for every 1°C increase in temperature, there was a global decrease of 6.7 Pg in the soil MDC stock within the predictable areas, equivalent to 1.4% of the total MDC stock or 0.9% of the atmospheric C pool. The tropical regions experienced the most substantial declines in MDC stocks. We further projected future MDC stocks for the next century based on shared socioeconomic pathways, showing a global decline in MDC stocks with a potential 6–37 Pg reduction by 2100 depending on future pathways. We recommend integrating the response of MDC stocks to warming into socioeconomic models to enhance confidence in selecting sustainable pathways.

Determination of surface acidity of mixed oxide of silicon and titanium by calorimetric titration

Silica-titania mixed oxide with catalytic and adsorption properties has been of great academic and industrial interest. Metal oxides supported on silica have been used as a matrix for immobilizing electron transfer mediators, generating materials with diverse properties. The characterization of the surface acidity of these materials is essential and has been carried out using various techniques, including IR spectroscopy and calorimetry. However, no single technique completely analyses the present acidic sites. This study used calorimetric titration to investigate a mixed oxide containing titanium and silica, prepared by the sol-gel method, and its interaction with pyridine. The results showed that thermal treatment increased the enthalpy values (ΔH), indicating water removal from the matrix surface. The presence of pyridine resulted in a decrease in ΔH values, suggesting a preferential occupation of the stronger acidic sites. After thermal treatments between 473 and 573 K, the solids exhibited similar ΔH values, indicating a homogenization of the surface acidic sites. Calorimetric analysis revealed that the acidic sites were occupied in descending order of strength, with the strongest sites being filled initially. The increase in temperature did not result in new acidic sites but rather in greater occupation of the existing ones. Correlation between calorimetric and infrared data is suggested as the next investigation step. Thus, the results of this study contribute to a deeper understanding of the physicochemical properties, especially regarding their surface acidity, with the potential for more effective and controlled practical applications of this silica-titania mixed oxide in catalysis and adsorption.

A statistical physics-based physicochemical study of L-phenylalanine adsorption on activated carbon.

In this comparative study of the adsorption of L-phenylalanine (L-Phe) on two modified low-activated carbons (ACK and ACZ) at four temperatures (293-313K), steric and energetic characteristics of adsorption were investigated. An advanced statistical physics multilayer model involving single-layer and double-layer adsorption scenarios was developed to interpret the L-Phe adsorption phenomenon. Modeling results indicate that two and three L-Phe layers were arranged depending on the tested adsorption systems. The estimated number of L-Phe molecules per leading adsorption site varied from 1.71 to 2.09 and from 1.76 to 1.86 for systems L-Phe-ACK and L-Phe-ACZ, respectively. The results show that a multimolecular adsorption mechanism might connect this amino acid molecule on ACZ and ACK surfaces in a non-parallel location. These parameters changed as follows, according to the adsorbed quantity at saturation analysis: Qasat (L-Phe-ACK) ˃ Qasat (L-Phe-ACZ). This indicates that ACK material was more efficient and valuable for L-Phe adsorption than ACZ. It was also shown that the adsorption capacity decreases as the temperature increases, proving the exothermicity of the adsorption process. This analytical substantiation is confirmed by calculating the binding energies, suggesting the occurrence of physical bonds between L-Phe amino acid molecules and ACK/ACZ binding sites and among L-Phe-L-Phe molecules. Pore size distribution was interpreted and calculated by applying the Kelvin theory to data from single adsorption isotherms. All used temperatures depicted a distribution of pores below 2nm. The docking analysis involving L-Phe and the ACZ and ACK adsorbents reveal a significant resemblance in how receptors detect ligands. Consequently, the findings from the docking process confirm that the calculated binding affinities fall within the spectrum of adsorption energy. This study analyzed the adsorption capacity of the L-Phe through a model proposed by statistical physics formalism. Molecular docking was used to determine the various types of interactions between the two activated carbons. Two aspects, including orientation of L-Phe on the site, number of molecules per site n, interaction energy, density of receptor site, and adsorption capacity, were discussed to elucidate the influence of activation on the two adsorbents.

Experimental study on coal oxidation and temperature rise under different air leakage modes due to atmospheric pressure changes

ABSTRACT The spontaneous combustion of residual coal in enclosed goafs may induce coupled thermodynamic disasters with severe consequences. To study the dynamic characteristics of coal oxidation and temperature increase in an enclosed goaf under varying atmospheric pressure conditions, the air leakage model was analyzed through theoretical derivation. The resistance, temperature, and CO concentration during coal oxidation under different air leakage modes were further studied using a self-built experimental system. The results indicated three air leakage modes of coal oxidation in an enclosed goaf: constant, intermittent, and reciprocating. The resistance of the three modes increased from 5 Pa to 7 Pa with time. Compared to constant air leakage, the time of resistance change was advanced by 1428 s and 1897 s under intermittent and reciprocating air leakage, respectively. Additionally, both intermittent and reciprocating air leakage promote coal oxidation and produce higher CO levels compared to constant air leakage. However, intermittent air leakage is more likely to produce higher temperature points, while reciprocating air leakage is more likely to cause large areas of coal oxidation. The order of the promoting effect of the intermittent and reciprocating half cycle on coal oxidation is 60 s, 300 s, 600 s, and 1200 s. These results are significant for understanding coal spontaneous combustion and efficiently managing enclosed goafs.

Opacification Kinetics of PLA during Liquid Water Sorption

When in contact with water, poly(lactic acid), PLA, undergoes several physical changes. A very evident one is opacification, namely the change from the typical transparent appearance to a white opaque color. This phenomenon is particularly significant for many applications, including packaging, since opacity hinders the possibility of a clear look of the packed goods and also worsens the consumers’ perceptions. In this work, we report an analysis of the time evolution of the phenomenon in different conditions of temperature and water concentration. The results allow us to define a time-scale of the phenomenon and to put it in relationship with the temperature and water content inside the material. In particular, opacification proceeds from the outer surface of the specimens toward the center. Both craze formation due to hydrolysis and crystallization contribute to the opacification phenomenon. Opacification becomes faster as temperature increases, whereas the increase in the solution density has the opposite effect. A model for describing the evolution of opacification was proposed and found to be consistent with the experimental data.

Elucidating the Hydrolysis and Polymerization Reactions of Al3+‐Solvated Molecules by Reactive Molecular Dynamics Simulation

ABSTRACTUtilizing the reactive molecular dynamics (ReaxFF MD) simulation, we conducted a comprehensive study on the impact of basicity (OH−/Al3+ ratio), concentration, and temperature on the hydrolysis and polymerization reactions of Al3+‐solvated molecules. Through simulations, we analyzed the structural changes, energy fluctuations of the system, and the evolution patterns of reaction products under different parameters, which were subsequently validated by experimental data. The research results indicate that hydroxide ions in the solution directly influence the breakage of OH bonds in the coordinating water molecules of solvated aluminum ions. This, in turn, affects the number of H2O and OH− ions coordinated with Al3+, leading to changes in hydrolysis products. Additionally, the number of OH− ions surrounding Al3+ affects the electrostatic repulsion, making it easier for polymerization reactions to occur as the system approaches the point of zero charge. On the other hand, an increase in concentration and temperature enhances the frequency of cluster collisions, thus contributing to an increase in polymerization degree. The experimental results align closely with our simulated predictions. As the pH value increases, the particle size exhibits a trend of first increasing and then decreasing, reaching a maximum at the point of zero charge. Simultaneously, an increase in concentration also prompts an increase in particle size. The combination of these empirical results with simulations enhances the credibility and reliability of our model's predictive capabilities. This study not only expands our understanding of the relevant chemical reaction processes but also provides important theoretical support for practical applications in related fields.

Electrical impedance characterization and modelling of Ti-Β implants.

Commercially pure titanium (c.p. Ti) and Ti6Al4V alloys are the most widely used metallic biomaterials in the biomedical sector. However, their high rigidity and the controversial toxicity of their alloying elements often compromise their clinical success. The use of porous β-Titanium alloys is proposed as a solution to these issues. In this regard, it is necessary to implement economic, repetitive, and non-destructive measurement techniques that allow for the semi-quantitative evaluation of the chemical nature of the implant, its microstructural characteristics, and/or surface changes. This study proposes the use of simple measurement protocols based on electrical impedance measurements, correlating them with the porosity inherent to processing conditions (pressure and temperature), as well as the chemical composition of the implant. Results revealed a clear direct relationship between porosity and electrical impedance. The percentage and/or size of the porosity decrease with an increase in compaction pressure and temperature. Moreover, there is a notable influence of the frequency used in the measurements obtained. Additionally, the sensitivity of this measurement technique has enabled the evaluation of differences in chemical composition and the detection of intermetallics in the implants. For the first time in the literature, this research establishes relationships between stiffness and electrical impedance, using approximations and models for the observed trends. All the results obtained corroborate the appropriateness of the technique to achieve the real-time characterization of Titanium implants, in an efficient and non-invasive way.