Degree Of Conversion Research Articles

Ecosystem health evaluation based on land use change-case study of the riparian zone of the Yangtze River in Jiangsu Province, China.

Evaluating the ecosystem health of riparian zones is helpful for decision-makers to formulate appropriate management measures. However, there are few methods for such evaluation which account for both the human requirements and ecological aspects of riparian zones. To address this, we created a Pressure-State(Vigor-Organization-Resilience)-Response framework for evaluating the ecosystem health of the riparian zone of the Yangtze River in Jiangsu Province, a region experiencing intense land use changes. Evaluation indicators, including land use change and ecosystem services, were selected. The comprehensive index method was used to calculate the evaluation indicators of ecosystem health, namely pressure, state, and response, and the comprehensive evaluation indicator itself. Using the cold and hot spot analysis, we also analyzed the spatial heterogeneity of ecosystem health in the riparian zone, constructed an ecological management pattern, and proposed corresponding management and protection measures. The results show that (1) from 2010 to 2020, construction land in the study area increased by more than 20%, and all studied land types underwent some degree of conversion to construction land, with cultivated land and water bodies being the main focus of conversion. (2) In 2020, the average ecosystem health in the riparian zone was normal, with a spatial distribution characterized by "high dispersion and low clustering"; and (3) according to the results of the ecosystem health evaluation and cold and hot spot analysis, key areas for stronger ecological protection were identified and, based on this, a number of management recommendations were proposed.

Orthodontic adhesive loaded with different proportions of ZrO2 silver-doped nanoparticles: An in vitro μTBS, SEM, EDX, FTIR, and antimicrobial analysis.

Zirconium dioxide silver-doped nanoparticles (ZrO2AgDNPs) impacts the adhesive material in terms of its physical characteristics, antimicrobial properties, degree of conversion (DC), and micro-tensile bond strength (μTBS) of orthodontic brackets to the enamel surface. A comprehensive methodological analysis utilizing a range of analytical techniques, including scanning electron microscopy coupled with energy-dispersive x-ray spectroscopy (EDX), Fourier-transform infrared (FTIR) spectroscopy, DC analysis, and μTBS testing. A light-curable orthodontic adhesive, specifically Transbond XT, was combined with ZrO2AgDNPs at 2.5% and 5%. As a control, an adhesive with no incorporation of ZrO2AgDNPs was also prepared. The tooth samples were divided into three groups based on the weightage of NPs: group 1: 0% ZrO2AgDNPs (control), group 2: 2.5 wt% ZrO2AgDNPs, and group 3: 5 wt% ZrO2AgDNPs. EDX graph demonstrated silver (Ag), Zirconium (Zr), and Oxygen (O2), The antibacterial efficacy of adhesives with different concentrations of NPs (0%, 2.5%, and 5%) was assessed using the pour plate method. The FTIR spectra were analyzed to identify peaks at 1607 cm-1 corresponding to aromatic CC bonds and the peaks at 1638 cm-1 indicating the presence of aliphatic CC bonds. The μTBS was assessed using universal testing machine (UTM) and bond failure of orthodontic brackets was seen using adhesive remanent index (ARI) analysis. Kruskal-Wallis test assessed the disparities in survival rates of Streptococcus mutans. Analysis of variance (ANOVA) and post hoc Tukey multiple comparisons test calculated μTBS values. The lowest μTBS was observed in group 1 adhesive loaded with 0% ZrO2AgDNPs (21.25 ± 1.22 MPa). Whereas, the highest μTBS was found in group 3 (26.19 ± 1.07 MPa) adhesive loaded with 5% ZrO2AgDNPs. ZrO2AgDNPs in orthodontic adhesive improved μTBS and has acceptable antibacterial activity against S mutans. ZrO2AgDNPs at 5% by weight can be used in orthodontic adhesive alternative to the conventional method of orthodontic adhesive for bracket bonding. RESEARCH HIGHLIGHTS: The highest μTBS was found in orthodontic adhesive loaded with 5% ZrO2AgDNPs. ARI analysis indicates that the majority of the failures fell between 0 and 1 among all investigated groups. The colony-forming unit count of S. mutans was significantly less in orthodontic adhesive loaded with nanoparticles compared with control. The 0% ZrO2AgDNPs adhesive showed the highest DC.

Influence of the Bracket Material on the Post-Cure Degree of Conversion of Resin-Based Orthodontic Adhesive Systems.

The aim of this study was to examine the influence of the orthodontic bracket material on the short-term and long-term post-cure development of the degree of conversion (DC) of resin-based orthodontic adhesive systems. Five commercially available materials characterized by different compositions and curing modes (light-curable or dual-curable) were tested under three different light curing conditions: without brackets (control group, CO), and in the presence of metal brackets (MB group) or ceramic brackets (CB group). Fourier-transform infrared spectroscopy was used to determine the post-cure DC development, both after "short-term" periods (2, 6, and 10 min) and "long-term" periods (1, 7, and 28 days). The short-term DC values ranged from 43.9% to 76.1%, and the long-term DC values were higher and ranged from 54.3% to 85.3%. The MB group demonstrated significantly lower short-term DC values compared to the CO and the CB groups, while the CB group had statistically similar or slightly lower DC values compared to the CO group. Long-term DC values in the MB and the CB groups were statistically lower or similar compared to the CO group, which depended on the post-cure time. The results indicated that the post-cure DC development was highly material-dependent and affected by the presence of different types of bracket material.

A Computational Evaluation of Minimum Feature Size in Projection Two-Photon Lithography for Rapid Sub-100 nm Additive Manufacturing.

Two-photon lithography (TPL) is a laser-based additive manufacturing technique that enables the printing of arbitrarily complex cm-scale polymeric 3D structures with sub-micron features. Although various approaches have been investigated to enable the printing of fine features in TPL, it is still challenging to achieve rapid sub-100 nm 3D printing. A key limitation is that the physical phenomena that govern the theoretical and practical limits of the minimum feature size are not well known. Here, we investigate these limits in the projection TPL (P-PTL) process, which is a high-throughput variant of TPL, wherein entire 2D layers are printed at once. We quantify the effects of the projected feature size, optical power, exposure time, and photoinitiator concentration on the printed feature size through finite element modeling of photopolymerization. Simulations are performed rapidly over a vast parameter set exceeding 10,000 combinations through a dynamic programming scheme, which is implemented on high-performance computing resources. We demonstrate that there is no physics-based limit to the minimum feature sizes achievable with a precise and well-calibrated P-TPL system, despite the discrete nature of illumination. However, the practically achievable minimum feature size is limited by the increased sensitivity of the degree of polymer conversion to the processing parameters in the sub-100 nm regime. The insights generated here can serve as a roadmap towards fast, precise, and predictable sub-100 nm 3D printing.

Obtaining fuel products by combined hydrogenation of coal and shale

Background: Coal and oil shale are one of the promising types of organic raw materials that can largely compensate and replace petroleum products and gas in the future. Unlike other types of solid fossil fuels oil shales contain significant amounts of hydrogen in organic matter. The possibility of obtaining liquid and gaseous hydrocarbons from a mixture of coal and oil shale similar in composition and properties to petroleum products and natural gas allows us to consider them as important strategic resources.
 Aim: This article is devoted to the study of the process of obtaining fuel products of co-hydrogenation of coal and shale.
 Materials and methods: Coal from the Taldykol deposit and slate from the Kiin deposit were taken as objects of research. The process of coal and shale liquefaction was carried out on a laboratory installation at a pressure of 5 MPa and a temperature of 425°C, a reaction time of 1 h. Gas chromatographic and elemental analyses were used.
 Results: The research results showed that the optimal amount of shale added to coal is 15.0%. The implementation of the co-hydrogenation process under these conditions has increased the yield of liquid products by 10%, namely fractions with a boiling point of up to 200°C from 14.9% to 15.3%, fractions with a boiling point of 200–370°C from 22.1% to 26.4%, fractions with a boiling point above 370°C from 34.6% to 38.8%. Solid residue with a boiling point above 370°C tested as an organic binder for road construction.
 Conclusion: The proposed process technology also makes it possible to obtain gasoline and diesel fractions, which after appropriate hydrotreating can be used as motor fuels. The addition of oil shale to coal allows the process to be carried out under optimal conditions with a high degree of conversion into liquid products without coke formation. The degree of transformation of the mixture of organic mass of shale and coal is much higher than just coal.

Coupling radiative properties with detailed char conversion kinetics

In pulverized solid fuel combustion, radiation is the primary heat transfer mechanism. Especially in the near-burner region with high particle loadings, particle radiation dominates gas radiation. Thus, adequate modeling of particle-radiation interactions in full-scale simulations of combustion chambers may primarily affect the overall accuracy. The radiation behavior depends strongly on the particles? optical properties, characterized by the complex index of refraction (IOR). The IOR depends on particle morphology and material composition which change during pyrolysis and char conversion. For char conversion, the focus of the present paper, the change depends on how the structural transformations take place inside the particle, characterizes by the reaction regimes, boundary layer diffusion limited, pore diffusion limited or kinetically controlled. The formation of an outer ash film layer with progressing burnout can complicate the situation even more.To quantify the effects of the structural changes during the char conversion process on the radiative properties, the output data of the char conversion kinetics (CCK) model (particle size, ash/carbon content, pore fraction) are used to build artificial particles at different conversion degrees and for the different regimes. Finally, the radiation interaction is calculated by applying an extension of the Mie theory for coated particles, and these results are compared to simplified approaches.Simplified approaches were tested to derive the IOR by applying mixing rules based on the available char and ash content with progressing char conversion. The results indicate that only a non-linear mixing rule for the IORs of ash and char lead to appropriate approximations of the radiation behavior of the particle. Furthermore, it is not necessary to model the spatial arrangement of carbon core and ash film for the radiative properties. Modeling a sphere and calculating an effective IOR depending on the carbon, ash, and pore volume fraction results in an average deviation of less than 3% to the exact solution.

Synthesis and characterisation of microcapsules for self-healing dental resin composites

AimThe purpose of this study was to i) synthesise TEGDMA-DHEPT microcapsules in a laboratory setting; ii) characterise the resultant microcapsules for quality measures.Materials & methodsMicrocapsules were prepared by in situ polymerization of PUF shells. Microcapsules characterisation include size analysis, optical and SEM microscopy to measure the diameter and analyse the morphology of PUF microcapsules. FT-IR spectrometer evaluated microcapsules and benzyl peroxide catalyst polymerization independently.ResultAverage diameter of TEGDMA-DHEPT microcapsules was 120 ± 45 μm (n: 100). SEM imaging of the capsular shell revealed a smooth outer surface with deposits of PUF nanoparticles that facilitate resin matrix retention to the microcapsules upon composite fracture. FT-IR spectra showed that microcapsules crushed with BPO catalyst had degree of conversion reached to 60.3%.ConclusionTEGDMA-DHEPT microcapsules were synthesised according to the selected parameters. The synthesised microcapsules have a self-healing potential when embedded into dental resin composite as will be demonstrated in our future work.Graphical Graphical abstract showing the microcapsule components. The shell contains poly(urea-formaldehyde), and the core consists of TEGDMA-DHEPT healing agents.

Kinetic and hydrogen production analysis in the sequential valorization of a Populus clone by cold alkaline extraction and pyrolysis

This work employed a two-step biorefining process, consisting of a hemicellulose-rich liquor production through ultrasound-assisted cold alkaline extraction (CAE), followed by thermochemical treatment of the resultant solid phase. The post-CAE solid phase’s pyrolytic potential was assessed by application of thermogravimetric analysis (TGA) and Friedman’s isoconversional method, and also from hydrogen production. The solid phases remaining after the CAE treatment were more reactive than the untreated raw material. Notably, the alkali concentration employed in the first step was the individual variable most pronounced influence on their activation energy (Ea). Thus, at a degree of conversion α = 0.50, Ea ranged from 109.7 to 254.3 kJ/mol for the solid phases, compared to 177 kJ/mol for the raw material; this value decreased with rising glucan content. At maximal degradation, the post-CAE solid phases produced up to 15.57% v/v more hydrogen than did the untreated raw material.

Evaluation of Microbiological Susceptibility and Long-term Adhesive Properties to Dentin of Primers with Terminalia catappa Linn.

To investigate the antibacterial effects of Terminalia catappa Linn (TCL) leaf extracts at different concentrations and the effects of these extracts used as primers on the long-term adhesive properties of two universal adhesives. After extract preparation, the antimicrobial and antibacterial activities of TCL against Streptococcus mutans (UA 159) were assessed in microdilution assays to provide the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC). Additionally, to provide quantitative data on the ability of TCL extract to reduce cell viability, colony forming units (CFU) were counted. To examine adhesive properties, 288 human molars were randomly assigned to 32 experimental conditions (n = 9) according to the following variables: (1) treatment agent: negative control (untreated surface), and primers at concentrations of 1xMIC, 5xMIC, and 10xMIC; (2) adhesives: Scotchbond Universal (SBU) and Futurabond Universal (FBU); (3) adhesive strategy: etch-and-rinse (ER) or self-etch (SE); and (4) storage time: 24 h or after 2 years. Primers were applied for 60 s, upon which the teeth were incrementally restored and sectioned into adhesive-dentin bonded sticks. These were tested for microtensile bond strength (μTBS) and nanoleakage (NL) after 24-h and 2-year water storage, as well as in-situ degree of conversion (DC) at 24 h. The chemical profile of the hybrid layer was determined via micro-Raman spectroscopy. Biofilm assay data were analyzed using the Kruskal-Wallis test; the pH of culture media and the chemical profile were analyzed by one-way ANOVA. The adhesive properties (µTBS, NL, DC) were evaluated using a four-way ANOVA and Tukey's test. Significance was set at 5%. Similar values of MIC and MBC were observed (2 mg/ml), showing bactericidal potential. CFU analysis demonstrated that concentrations of 5xMIC and 10xMIC significantly inhibited biofilm formation (p < 0.001). The application of the TCL primer at all concentrations significantly increased the immediate μTBS and DC, and decreased the immediate NL values when compared to the control group (p < 0.05), regardless of the adhesive and adhesive strategies. Despite an increase in the NL values for all groups after 2 years (p > 0.05), in groups where the TCL primer was applied, the μTBS remained constant after 2 years for both adhesives, while a decrease in the μTBS was observed in the control groups (p < 0.05). Usually, 10xMIC showed better results than 1xMIC and 5xMIC (p < 0.05). The application of TCL promoted cross-linking; cross-linking rates increased proportionally to the concentration of TCL (p < 0.05). Primers containing TCL promoted bactericidal and bacteriostatic action, as well as cross-linking with dentin, while maintaining the adhesive properties of the adhesive-dentin interface after 2 years of water storage.

Kinetic and thermodynamic study of composite with jute fiber as reinforcement

In the present work, engineered by compression molding process via a hydraulic press, the A and B composite samples were carried out with 5% and 10% ratio respectively of Ricinodendron heudelotii oil-based alkyd resin in bio-based matrix made of unsaturated polyester using jute fibers as reinforcement material. The samples’ thermal decomposition was performed through thermogravimetry (TG) and derivative thermogravimetry (DTG) analyses. Both composite samples exhibit two stages of decomposition, where the main occurs at 200 - 550°C. Aiming to study and being able to model the thermal degradation of the elaborated composites, finding the kinetic triplets appears the best option to describe the kinetic process undergo by the composites in order to evaluate the performance application of the composites. Two non-isothermal techniques, Flynn-Wall-Ozawa (FWO) and Kissinger have been used to assess the activation energy Ea, and it is found that the apparent activation energy varies with the degree of conversion indicating that both composites decompose with a multiple step mechanism process. The appropriate reaction model for the second stage of decomposition was best suited with Johnson-Mel-Avrami (n&lt;1) model and has been established, allowing us to model thermal degradation behavior of our elaborated composite material and set predictions. The estimated Arrhenius factor values were respectively about A and B composites, 4.12.1015 min-1 and 10.42.1015 min-1, allowing us to set the final equation characterizing the degradation process for the second and main decomposition stage. Finally, as a result of comparison between A and B composites, A appears to be the more thermally stable due to its lower values of Arrhenius pre-exponential factor over the main stage of decomposition and higher calculated the activation energy values.

Synthesis, monomer conversion, and mechanical properties of polylysine based dental composites

ObjectiveThe aim of this study was to synthesize a new bioactive and antibacterial composite by incorporating reactive calcium phosphate and antibacterial polylysine into a resin matrix and evaluate the effect of these fillers on structural analysis, degree of monomer conversion, mechanical properties, and bioactivity of these newly developed polypropylene based dental composites. MethodologyStock monomers were prepared by mixing urethane dimethacrylate and polypropylene glycol dimethacrylate and combined with 40 wt% silica to make experimental control (E-C). The other three experimental groups contained a fixed percentage of silica (40 wt%), monocalcium phosphate monohydrate, and β-tri calcium phosphate (5 wt% each) with varying amounts of polylysine (PL). These groups include E-CCP0 (0 wt% PL), E-CCP5 (5 wt% PL) and E-CCP10 (10 wt% PL). The commercial control used was Filtek™ Z250 3M ESPE. The degree of conversion was assessed by using Fourier transform infrared spectroscopy (FTIR). Compressive strength and Vicker’s micro hardness testing were evaluated after 24 h of curing the samples. For bioactivity, prepared samples were placed in simulated body fluid for 0, 1, 7, and 28 days and were analyzed using a scanning electron microscope (SEM). SPSS 23 was used to analyze the data and one-way ANOVA and post hoc tukey’s test were done, where the significant level was set ≤0.05. ResultsGroup E-C showed better mechanical properties than other experimental and commercial control groups. Group E-C showed the highest degree of conversion (72.72 ± 1.69%) followed by E-CCP0 (72.43 ± 1.47%), Z250 (72.26 ± 1.75%), E-CCP10 (71.07 ± 0.19%), and lowest value was shown by E-CCP5 (68.85 ± 7.23%). In shear bond testing the maximum value was obtained by E-C. The order in decreasing value of bond strength is E-C (8.13 ± 3.5 MPa) > Z250 (2.15 ± 1.1 MPa) > E-CCP10 (2.08 ± 2.1 MPa) > E-CCP5 (0.94 ± 0.8 MPa) > E-CCP0 (0.66 ± 0.2 MPa). In compressive testing, the maximum strength was observed by commercial control i.e., Z250 (210.36 ± 18 MPa) and E-C (206.55 ± 23 MPa), followed by E-CCP0 (108.06 ± 19 MPa), E-CCP5 (94.16 ± 9 MPa), and E-CCP10 (80.80 ± 13 MPa). The maximum number of hardness was shown by E-C (93.04 ± 8.23) followed by E-CCP0 (38.93 ± 9.21) > E-CCP10 (35.21 ± 12.31) > E-CCP5 (34.34 ± 12.49) > Z250 (25 ± 2.61). SEM images showed that the maximum apatite layer as shown by E-CCP10 and the order followed as E-CCP10 > E-CCP5 > E-CCP0 >Z250> E-C. ConclusionThe experimental formulation showed an optimal degree of conversion with compromised mechanical properties when the polylysine percentage was increased. Apatite layer formation and polylysine at the interface may result in remineralization and ultimately lead to the prevention of secondary caries formation.

Vat photopolymerization additive manufacturing process modeling: a thermal-chemical coupling approach informed by in-situ and ex-situ characterization data

Vat photopolymerization (VPP) is one of the most widely used additive manufacturing methods. The VPP process temperature and material curing reaction interplay with each other to critically determine the final product quality. Insights about the time-varying process temperature and degree of conversion (DoC) is desired for VPP process control but difficult to attain due to lacking effective operando characterization technologies. This work reports a new method to create a thermal-chemical model of the VPP process by solving an inverse heat conduction problem (IHCP) based on in-situ observable temperature measurement to estimate the chemistry reaction-induced heat source that is a function of DoC. Ex-situ photo differential scanning calorimetry (Photo-DSC) characterization is used to initialize the chemistry reaction model parameters so that DoC can be calculated. Specifically, vat substrate temperature is measured using an in-situ infrared thermal camera and used as input to solve an IHCP for estimating exothermic heat generation rate for the internal heat generation component at the curing part. Overall, the newly developed VPP modeling framework combines an IHCP that is optimized by in-situ thermal monitoring with a chemical reaction heat generation and conduction model that is educated by Photo-DSC characterization. The model predictions of temperature and DoC are experimentally validated by comparing against in-situ temperature measurement and ex-situ spectroscopy measurement of prints at different exposure times.

Synthesis and surface modification of sunflower oil‐based non‐isocyanate polyurethane: Physicochemical and antibacterial properties

AbstractIn this work, non‐isocyanate polyurethane (NIPU) films are synthesized from sunflower oil (SFO) with the object of using a renewable resource and establishing a nonpolluting process. SFO also has the advantage of having a higher level of unsaturation than other commercial oils, which provides more reactive sites to be chemically modified. This feature enables a higher degree of conversion to the two monomers, cyclocarbonate, and polyamine‐polyol. NIPU is obtained from their mixture and further crosslinking at 90°C allows the films with suitable mechanical properties to be used in biomedical applications. However, NIPU does not show antibacterial activity, so the surface must be modified. Two methods are used: layer‐by‐layer coating of alginate‐chitosan, and immersion in tea tree oil (TTO), previously activating the surface with acrylic acid (AANIPU). Surface modifications are confirmed by increased hydrophilicity, thermochemical changes, and a drop in mechanical performance. TTO on NIPU films inhibits bacterial growth against S. aureus and E. Coli. NIPU and AANIPU can be accepted as noncytotoxic, while incorporation of the two agents can produce cytotoxicity. No previous reports of such modifications have been found on NIPU films, which appear as promising alternatives for biomedical applications.

Mechanical and microbiological properties of orthodontic resin modified with nanostructured silver vanadate decorated with silver nanoparticles (βAgVO3)

ObjectiveTo investigate the impact of incorporating the antimicrobial nanomaterial β-AgVO3 into orthodontic resin, focusing on degree of conversion, surface characteristics, microhardness, adhesion properties, and antimicrobial activity. MethodsThe 3 M Transbond XT resin underwent modification, resulting in three groups (Control, 2.5% addition, 5% addition) with 20 specimens each. Fourier transform infrared spectroscopy assessed monomer conversion. Laser confocal microscopy examined surface roughness, and microhardness was evaluated using Knoop protocols. Shear strength was measured before and after artificial aging on 36 premolar teeth. Microbiological analysis against S. mutans and S. sanguinis was conducted using the agar diffusion method. ResultsDegree of conversion remained unaffected by time (P = 0.797), concentration (P = 0.438), or their interaction (P = 0.187). The 5% group exhibited the lowest surface roughness, differing significantly from the control group (P = 0.045). Microhardness showed no significant differences between concentrations (P = 0.740). Shear strength was highest in the control group (P < 0.001). No significant differences were observed in the samples with or without thermocycling (P = 0.759). Microbial analysis revealed concentration-dependent variations, with the 5% group exhibiting the largest inhibition halo (P < 0.001). ConclusionsIncorporating β-AgVO3 at 2.5% and 5% concentrations led to significant differences in surface roughness, adhesion, and antimicrobial activity. Overall, resin modification positively impacted degree of conversion, surface characteristics, microhardness, and antimicrobial activity. Further research is warranted to determine clinically optimal concentrations that maximize antimicrobial benefits while minimizing adverse effects on adhesion properties. Clinical SignificanceIncorporating β-AgVO3 into orthodontic resin could improve patient quality of life by prolonging intervention durability and reducing the impact of cariogenic microorganisms. The study's findings also hold promise for the industry, paving the way for the development of new materials with antimicrobial properties for potential applications in the health sector.

Photopolymer-Based Composite with Substance Release Capability Manufactured Additively with DLP Method.

In this study, caffeine-loaded photoresin composites with homogeneous structures, suitable for additive manufacturing of transdermal microneedle systems, were obtained. The properties of the composites with varying caffeine concentrations (0.1-0.4% w/w) were investigated for carbon-carbon double bond conversion using Fourier Transform Infrared Spectroscopy, surface wettability and mechanical properties using a static tensile test and nanoindentation, and caffeine release in ethanol using UV-Vis. The caffeine concentration did not affect the final degree of double bond conversion, which was confirmed in tensile tests, where the strength and Young's modulus of caffeine-loaded samples had comparable values to control ones. Samples with 0.1 and 0.2% caffeine content showed an increase in nanohardness and reduced elastic modulus of 50 MPa and 1.5 MPa, respectively. The good wettability of the samples with water and the increase in surface energy is a favorable aspect for the dedicated application of the obtained composite materials. The amount of caffeine released into the ethanol solution at 1, 3 and 7 days reached a maximum value of 81%, was higher for the lower concentration of caffeine in the sample and increased over time. The conducted research may enhance the potential application of composite materials obtained through the digital light processing method in additive manufacturing.

Influence of Piperine on Collagen Color and Degree of Conversion of a Universal Adhesive System Applied to Bleached Dentin

Aims: The aim was to evaluate the influence of piperine on the collagen staining and on the degree of conversion of the universal adhesive system applied to the bleached dentin. Methods: The piperine extraction process was carried out using a water reflux system and confirmed by UV-Vis spectrophotometry. For collagen staining analysis, dentin collagen disk were analyzed with a spectrophotometer. Regarding the collagen color evaluation, there was no statistically significant difference between the groups regarding ΔL, Δa, Δb e ΔE (p&gt;0,05). Results: Regarding the degree of conversion, there was no statistically significant difference between without hydrogen peroxide, PH + 0,001% piperine, PH + 0,002% piperine and PH + 0,004% piperine (p&gt;0,05). Conclusions: It is possible to conclude that piperine, did not change the color of the dentin collagen and avoided the reduction in the degree of conversion of a universal adhesive system applied immediately after bleaching with 35% hydrogen peroxide.

Chemical Modification of Dental Dimethacrylate Copolymer with Tetramethylxylylene Diisocyanate-Based Quaternary Ammonium Urethane-Dimethacrylates-Physicochemical, Mechanical, and Antibacterial Properties.

In this study, two novel quaternary ammonium urethane-dimethacrylates (QAUDMAs) were designed for potential use as comonomers in antibacterial dental composite restorative materials. QAUDMAs were synthesized via the reaction of 1,3-bis(1-isocyanato-1-methylethyl)benzene with 2-(methacryloyloxy)ethyl-2-decylhydroxyethylmethylammonium bromide (QA10+TMXDI) and 2-(methacryloyloxy)ethyl-2-dodecylhydroxyethylmethylammonium bromide (QA12+TMXDI). Their compositions with common dental dimethacrylates comprising QAUDMA 20 wt.%, urethane-dimethacrylate monomer (UDMA) 20 wt.%, bisphenol A glycerolate dimethacrylate (Bis-GMA) 40 wt.%, and triethylene glycol dimethacrylate (TEGDMA) 20 wt.%, were photocured. The achieved copolymers were characterized for their physicochemical and mechanical properties, including their degree of conversion (DC), glass transition temperature (Tg), polymerization shrinkage (S), water contact angle (WCA), flexural modulus (E), flexural strength (FS), hardness (HB), water sorption (WS), and water leachability (WL). The antibacterial activity of the copolymers was characterized by the minimum bactericidal concentration (MBC) and minimum inhibitory concentration (MIC) against Staphylococcus aureus and Escherichia coli. The achieved results were compared to the properties of a typical dental copolymer comprising UDMA 40 wt.%, Bis-GMA 40 wt.%, and TEGDMA 20 wt.%. The introduction of QAUDMAs did not deteriorate physicochemical and mechanical properties. The WS and WL increased; however, they were still satisfactory. The copolymer comprising QA10+TMXDI showed a higher antibacterial effect than that comprising QA12+TMXDI and that of the reference copolymer.

Enhancing pyrolysis process monitoring and prediction for biomass: A machine learning approach

Biomass pyrolysis presents a viable solution to address the increasing global energy demand, and substantial efforts have been devoted worldwide to monitoring the conversion process through thermogravimetric experiments. In this study, the machine learning (ML) algorithm was employed to simulate and predict the temperature corresponding to specific conversion degrees (Tα) by utilizing the compositional properties of the feedstock and heating rate as input variables. A dataset consisting of 1750 entries was collected from literature and deployed to construct neural network (NN) and random forest (RF) algorithms. After hyperparameter optimization, the RF model, equipped with 13 estimators and a maximum tree depth of 4, exhibited impressive accuracy in predicting Tα, yielding an R2 value of 0.9462 and an RMES of 14.63 K. The subsequent feature importance analysis revealed that the conversion degree was the predominant influencing factor for Tα, while the compositional properties of biomass accounted for 32.3 % of the overall influence. Validation experiments conducted using unexploited biomass further confirmed the robustness of the developed model. This research successfully demonstrated the feasibility of an ML approach in predicting reaction temperature based on preliminary feedstock analysis and desired pyrolysis progress, effectively eliminating the necessity for repetitive experiments. Furthermore, it provided valuable references for future ML research and applications in related fields.

Improving the Sustainability of Catalytic Glycolysis of Complex PET Waste through Bio-Solvolysis.

This work addresses a novel bio-solvolysis process for the treatment of complex poly(ethylene terephthalate) (PET) waste using a biobased monoethylene glycol (BioMEG) as a depolymerization agent in order to achieve a more sustainable chemical recycling process. Five difficult-to-recycle PET waste streams, including multilayer trays, coloured bottles and postconsumer textiles, were selected for the study. After characterization and conditioning of the samples, an evaluation of the proposed bio-solvolysis process was carried out by monitoring the reaction over time to determine the degree of PET conversion (91.3-97.1%) and bis(2-hydroxyethyl) terephthalate (BHET) monomer yield (71.5-76.3%). A monomer purification process, using activated carbon (AC), was also developed to remove the colour and to reduce the metal content of the solid. By applying this purification strategy, the whiteness (L*) of the BHET greatly increased from around 60 to over 95 (L* = 100 for pure white) and the Zn content was significantly reduced from around 200 to 2 mg/kg. The chemical structure of the purified monomers was analyzed via infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC), and the composition of the samples was measured by proton nuclear magnetic resonance (1H-NMR), proving a high purity of the monomers with a BHET content up to 99.5% in mol.

Experimental Bracket Design Performance on Bonding and Polymerization of Orthodontic Composite.

To evaluate the enamel bonding ability and orthodontic adhesive resin degree of conversion using the experimental bracket design. Material and Methods. Thirteen bovine teeth were used in the study. The experimental bracket was modified with a translucent region in the center of its body. After enamel etching, Orthocem orthodontic adhesive (FGM, Joinville, Brazil) was applied on the bracket base for bonding. The groups were divided as follows (n = 10 per group): (1) control (CB) with standard brackets and (2) spot bracket (SB) with experimental brackets featuring a 0.8 mm translucent region at the center using carbide bur. Shear bond strength (SBS) was evaluated after 24 hours in a universal testing machine and adhesive remnant index (ARI). The degree of conversion (DC) was analyzed using Raman spectroscopy (n = 3 per group). Data were then analyzed using Student's t-test and Mann-Whitney statistical methods. The SB group exhibited a higher mean SBS (10.33 MPa) compared to the CB Group (8.77 MPa). However, there was no statistical difference between the groups (p = 0.376). Both SB and CB groups had a mean ARI score of 1. Raman analysis revealed a higher degree of conversion in the SB group (49.3%) compared to the CB group (25.9%). The experimental support showed a higher degree of adhesive conversion, although there was no significant increase in bond strength.