Degree Of Conversion Research Articles

In Vitro Testing of Protective Eye Wear in Blocking Blue Light from Dental Light Curing Unit

Aim: To evaluate the ef?cacy of wearing protective eyewear in preventing harmful Dental light-curing units (LCUs). Background: Dental light-curing units generate blue light, capable of inducing soft-tissue burns and ocular harm like retinal damage. The intensity of blue light emitted by dental Light Curing Units is substantially higher, thereby potentially constituting a significant "blue light hazard." Material and Methods: To study the effect of protective glasses, reverse methodology was followed as the effect of blue light on the eye is difficult to measure; Circular composite disc samples were grouped into two, one of which was polymerized directly while the other had protective glass in between, Fourier transform infrared spectroscopy (FTIR) analysis was done and the degree of conversion was calculated. Results: Data obtained were analysed using One Way ANOVA. The mean values for "Degree of Conversion" in Group I (Without Protective Glass) is 1.334 +512 and for Group II (with protective glass) is -2.623 + 1.544 .One Way ANOVA revealed statistically significant difference between Group I and Group II (p=0.000) Conclusion: Within the limitations of this in vitro study, it can be concluded that the protective glasses are successful in filtering the harmful blue light emitted by LCU and should be used in day-to-day practice to improve the amount of light they deliver to the restoration from the LCU and prevent any harm to the ocular tissues. Clinical implications: Blue light filtering glasses in a dental operatory provide optimum protection, and the operator can safely watch and improve the amount of light delivered to the restoration from the LCU.

Impact of Battery Levels of a Cordless LED Curing Unit on Resin Cement under Varied Lithium Disilicate Thicknesses and Translucencies.

This study aimed to evaluate the impact of battery levels on the emission of a multi-peak cordless LED light-curing unit (LCU) and the effect on the degree of conversion (DC) and Knoop hardness (KH) of a light-cure resin luting agent activated through varying lithium disilicate (LiS2) ceramic thicknesses and translucencies. High and low translucency LiS2 discs (IPS e.max Press HT and LT, respectively; shade A1) with thickness of 0.5, 1.0, 1.5, and 2.0 mm were fabricated. Resin luting agent specimens (Variolink Esthetic LC) were prepared and cured using a Bluephase G2 LCU at different battery levels (100%, 50%, and 10%) through the LiS2 ceramics. The transmitted irradiance was evaluated using USB4000 MARC, while FTIR and a microhardness tester assessed DC and KH, respectively. After ensuring homoscedasticity, the data wee analyzed using analysis of variance and Tukey HSD test (α=0.05). The study found strong positive correlations between battery levels and irradiance, particularly with no ceramic interposition and through HT ceramics (R2=0.9471), although this correlation diminished with thicker HT (R2=0.7907) and LT ceramics (R2<0.2980). Both battery levels and ceramic thickness significantly influenced transmitted irradiance (p<0.0001), resulting in lower values with decreased battery levels and increased ceramic thicknesses (p<0.0001). LT ceramics showed lower transmittance than HT. DC was significantly affected by both battery levels and ceramic thicknesses, with generally lower DC values except for LT ceramics at a 10% battery level (p<0.0001). No significant differences in DC were observed between HT and LT translucencies (p=0.548). KH was higher in HT than LT ceramics at 100% and 50% battery levels, with thicker ceramics showing lower KH values at 10% battery level (p<0.0001). Conclusion: Reduced battery levels in cordless LED curing units significantly affect the irradiance, degree of conversion, and hardness of light-curable resin luting agents. Maintaining battery levels above 50% is recommended for optimal performance. Thicker and more opaque ceramics significantly impacted incident irradiance. However, preserving radiant energy could potentially mitigate these limitations.

Effect of replacing Bis-GMA with a biobased trimethacrylate on the physicochemical and mechanical properties of experimental resin composites.

To analyze the incorporation of cardanol trimethacrylate monomer (CTMA), derived from the cashew nut shell liquid, as a substitute for Bis-GMA in acrylic resins formulations and its effect on experimental resin composites' physicochemical and mechanical properties. The intermediary cardanol epoxy was synthesized via cardanol epoxidation, followed by the synthesis of CTMA through methacrylic anhydride solvent-free esterification. Experimental resin composites were formulated with an organic matrix composed of Bis-GMA/TEGDMA (50/50 wt %) (control). CTMA was gradually added to replace different proportions of Bis-GMA: 10 wt % (CTMA-10), 20 wt % (CTMA-20), 40 wt % (CTMA-40), and 50 wt % (CTMA-50). The composites were characterized by degree of conversion, water sorption and solubility, viscosity, thermogravimetric analysis, dynamic mechanical analysis, flexural strength and elastic modulus. Data were analyzed with one-way ANOVA and Tukey's post-hoc test (α = 0.05), except for water sorption data, which were analyzed by Kruskall-Wallis and Dunn's method. CTMA-based and control composites did not show statistically significant differences regarding degree of conversion, flexural strength and elastic modulus. CTMA reduced the viscosity and solubility compared to the Bis-GMA-based composite. The CTMA-40 and CTMA-50 exhibited significantly lower water sorption compared to the control. Also, acceptable thermal stability and viscoelastic properties were obtained for safe use in the oral cavity. Incorporating CTMA into composites resulted in similar chemical and mechanical properties compared to Bis-GMA-based material while reducing viscosity, water sorption and solubility. CTMA could be used as a trimethacrylate monomer replacing Bis-GMA in resin composites, thereby minimizing BPA exposure.

Experimental and Chitosan-Infused Adhesive with Dentin Pretreated with Femtosecond Laser, Methylene Blue-Activated Low-Level Laser, and Phosphoric Acid.

Aim: To prepare experimental adhesive (EA) with 1% and without chitosan nanoparticles on dentin conditioned with a conventional technique phosphoric acid (PA) compared with two different contemporary techniques: photodynamic therapy (PDT) and femtosecond laser (FSL). Method: The methodology consisted of synthesis of EA and 1% chitosan-modified adhesive (CMA). Scanning electron microscopy, dentin adhesive interface assessment, energy-dispersive spectroscopy, shear bond strength (SBS), degree of conversion (DC), and bond failure were assessed. Teeth were selected, disinfected, and mounted in acrylic up to the cementoenamel junction. Occlusal enamel was removed and teeth were randomly allocated into groups and conditioned. These included Group 1: samples treated with PA; Group 2: specimens conditioned with methylene blue photosensitizer (MBP) activated by PDT; and Group 3: samples conditioned with FSL. Following different conditioning regimes, specimens were bonded using 1% CMA and EA. The composite buildup was followed by SBS testing and a bond failure assessment. DC was assessed for both EA and CMA. Analysis of variance and Tukey's post hoc test were used to compare the mean and standard deviation of SBS and DC in different experimental groups, with a significance level of p < 0.05. Results: Dentin pretreated with etch and rinse demonstrated the highest bond strength with 1% CMA. Dentin conditioned with MBP activated by PDT and bonded to EA showed the lowest bond scores. Overall SBS values of 1% CMA were better than EA irrespective of the conditioning regime of dentin. The DC was higher in EA adhesive. This was followed by DC in 1% CMA. DC in EA was found to be comparable with 1% CMA. Conclusions: PA remains the gold standard for dentin conditioning. The incorporation of 1% chitosan in adhesive improves SBS and results in no change in DC. The use of FSL in dentin conditioning can be used as an alternative approach as it results in SBS within acceptable limits. The study was approved by the ethical board of King Saud University.

Thermodynamics and kinetics of evaporation and thermal decomposition of 1-ethyl- and 1-butyl-3-methylimidazolium methanesulfonate ionic liquids: Experimental and computational study

Knudsen cell mass spectrometry was used to study the evaporation of two ionic liquids, 1-ethyl-3-methylimidazolium methanesulfonate ([EtMIm][MS], MS = CH3SO3) and 1-butyl-3-methylimidazolium methanesulfonate ([BuMIm][MS]), accompanied by thermal decomposition (thermolysis). The independent occurrence of evaporation and thermolysis reactions made it possible to determine their thermodynamic and kinetic characteristics under identical experimental conditions. The saturated vapor pressures were measured and the standard enthalpies of vaporization of [EtMIm][MS](l) and [BuMIm][MS](l) were obtained. The standard thermodynamic functions of formation in the liquid and gaseous states at 298.15 K were estimated from the available experimental data and the results of quantum chemical calculations. The gaseous decomposition products of ionic liquids were identified and the pressures of the thermolysis products of [EtMIm][MS](l) were determined. According to the experimental data and quantum chemical calculations, the thermolysis of [EtMIm][MS](l) occurs through heterogeneous reactions far from the equilibrium state. The kinetics of the reactions is described in two ways. When the degree of sample conversion is used as a variable, the constant reaction rates at the initial stage of thermolysis correspond to a pseudo-zero order reaction with a monotonic increase in the degree of conversion. In the proposed alternative approach, the reaction rates are estimated from the fluxes of thermolysis products and are expressed in terms of ionic liquid concentration.

Effect of Different Curing Time on Degree of Conversion and Depth of Curing of Supra-Nano Filled Resin Composite Compared to a Conventional One

Effect of Different Curing Time on Degree of Conversion and Depth of Curing of Supra-Nano Filled Resin Composite Compared to a Conventional One

OXIDATION OF 4-METHYLPYRIDINE ON V-Cr-O CATALYST

Isonicotinic acid derivatives are used in the development of new antibacterial agents, active ingredients in pesticides and herbicides. In addition, isonicotinic acid is a precursor for the synthesis of isoniazid, one of the most effective anti-TB drugs. Considering the importance of isoniazid in the treatment of tuberculosis, improving methods of synthesizing isonicotinic acid has a direct impact on the availability and cost of this life-saving drug. The goal of this work was to investigate the efficiency of V-Cr-O catalyst in the oxidation of 4-methylpyridine to produce isonicotinic acid, to study its composition and properties. Research methods. Methods of chemical analysis, scanning electron microscope (SEM), Raman spectroscopy were applied. Results and Discussion. In this work, the processes of isonicotinic acid synthesis by oxidation of 4-methylpyridine on the V-Cr-O catalyst were studied. Analysis of the obtained results showed that with an increase in the water feed, there is a general tendency towards a decrease in the conversion of 4-methylpyridine at all temperatures. For example, at a temperature 300oC, the degree of conversion drops from 91.72% at 1.79 g/h to 84.20% at 6.6 g/h. The yield of isonicotinic acid increases as the amount of water rises, reaching its peak at 47.46% with a temperature of 360°C and a water supply of 6.6 g/h. In contrast, the minimum yield is only 15.27% at 280°C with a water supply of 1.79 g/h. This highlights the positive correlation between water supply and yield, especially at higher temperatures.

Impact of functional monomers, bioactive particles, and HEMA, on the adhesive performance of self-etch adhesive systems applied to simulated altered dentin

ObjectivesThis study aimed to evaluate how self-etching/universal dental adhesive systems (DASs) with differing compositions interact with sound (S), post-radiotherapy (irradiated; I), and artificially eroded (E) dentin in terms of bonding properties. Methods: The DASs tested were Adper Scotchbond Multipurpose (MP; control), Clearfil SE Bond (SE), FL Bond II (FL), Adper Single Bond Universal (SU) and BeautiBond Xtreme (BX). They were analyzed for initial and 6-month microtensile bond strength (µTBS, n = 12), mode of failure (40 x), scanning electron microscopy (SEM), surface wettability (W, n = 10), and degree of conversion (DC, n = 3) via Fourier-transform infrared spectroscopy (FTIR). Normal and homogeneous distribution of the data allowed their analyses through ANOVA and Tukey tests (p < 0.05). Results: All DASs except BX exhibited higher µTBS for S decreasing for I and E. BX demonstrated the greatest stability among the altered substrates. FL showed the most hydrophobic properties, likely due to its bioactive components. Universal DASs achieved higher DC, regardless of composition. Conclusions: HEMA-free formulation combined with carboxylic and phosphoric acids in BX, achieved the most stable performance for altered substrates. Clinical SignificanceSince radiotherapy and erosion affect dentin, their characteristics compromise adhesive performance and impair the achievement of durable and satisfactory restorations. The use of universal adhesives less dependent on calcium seems less susceptible to hydrolytic degradation and may be a promising option for maintaining adhesive stability over time.

SYNTHESIS AND CHARACTERIZATIONS OF NOVEL MISWAK POWDER-BASED DENTAL COMPOSITES

This study aimed to synthesize a novel miswak based dental composite by incorporating miswak powder, chlorhexidine (CHX), and silica fillers in different proportions into a resinous mixture and assess the influence of these fillers on the physical, mechanical, and biological properties of newly developed composites. The stock monomer solution was synthesized using urethane dimethacrylate, triethylene glycol dimethacrylate, and hydroxyethyl methacrylate. Four experimental groups (A, B, C, D) were prepared using 30% stock monomer with 70% filler formulations, while two commercial composites were used as control groups (E, F). The highest value of degree of conversion was shown by Group D, whereas the lowest – by Group A. Compressive strength evaluation showed Group E had the highest value, while the lowest value was recorded for Group B. Furthermore, cytotoxicity assessment showed that all the groups of composites had a biocompatible nature, except Groups A and B, having slight cytotoxicity. Thus, the experimental groups can be used as restorative materials as they exhibited optimum properties.

Regulation of the Phase Structure in the Crystallizing Curing System PCL–DGEBA

Qualitative and quantitative aspects of the formation of various types of phase structures, sizes and compositions were considered. For the studied polycaprolactone–epoxy resin/4,4′-diaminediphenylsulfone system, a phase diagram characterized by amorphous separation with a lower critical solution temperature was constructed and its evolution was traced with increasing conversion degree of epoxy groups. A method is proposed for determining the temperature–concentration parameters that determine the type of phase structure of composite materials, based on the optical interferometry method. All types of phase structures and features of structure formation in the phase reversal region and at its boundaries have been studied using optical and scanning electron microscopy methods. The dimensions of the structural elements were determined and their correlation with the temperature and concentration regimes of the system’s curing was established. The composition of phases in cured compositions was studied using FTIR spectroscopy, DSC and scanning electron microscopy. It is shown that by varying the temperature–concentration parameters of curing reactive thermoplastic systems, it is possible to specifically regulate the type of phase structure, phase sizes and their composition, which determine the operational properties of the material.

Termination Kinetics of N‐Vinyl Formamide Radical Polymerization in Aqueous Solution

AbstractTermination kinetics of radical polymerization of N‐vinyl formamide (NVF) in aqueous solution has been measured via SP–PLP–NIR, i.e., single pulse (SP) initiation of pulsed laser polymerization (PLP) in conjunction with microsecond time‐resolved near‐infrared (NIR) detection of monomer concentration. Experiments are performed at initial NVF weight fractions from 0.20 up to bulk NVF, at monomer conversions up to 40%, and at temperatures from 40 to 70 °C as well as pressures from 500 to 2500 bar. Applying high pressure improves signal‐to‐noise quality. Data obtained upon pressure variation allow for extrapolation toward ambient pressure. The primary quantity from SP–PLP–NIR is kp/&lt;kt&gt;, i.e., the ratio of propagation rate coefficient, kp, to apparent chain‐length‐averaged termination rate coefficient, &lt;kt&gt;. With kp being available from literature, kp/&lt;kt&gt; yields &lt;kt&gt;. This quantity is relevant for modeling polymerization rate and polymer properties. Termination in the initial polymerization period turns out to be controlled by segmental diffusion and, at higher degrees of monomer conversion up to 40%, by translational diffusion.

Liquid-liquid equilibrium of FAEs – glycerol phase – ethanol in the ethanol regeneration and FAE separation stage

Extraction and purification of biofuel components are as important as their synthesis. Synthesis of fatty acid esters in a molar excess of ethanol above 1:30 results in the formation of a homogeneous phase including the ester and glycerol phases dissolved in ethanol. It was observed that when excess ethanol was removed, the separation of the system into ester and glycerol phases did not always occur. To improve the biodiesel purification process the experimental binodal curve for the FAE-ethanol-glycerol phase system was obtained in the synthesis of biodiesel from rapeseed oil. The data was obtained from homogeneous alkaline synthesis of FAE with molar excess of ethanol 1:50. The pseudocomponent glycerol phase contains glycerol and unreacted oil (triglycerides (TGA)). The calculated liquid-liquid equilibrium (LLE) data for FAE – ethanol – glycerol and FAE – ethanol – TGA ternary mixtures were obtained by the UNIFAC (UNIQUAC Functional-group Activity Coefficients) model and compared with experimental diagram. It was found that glycerol and unreacted triglycerides affect the behavior of the system by preventing or promoting the mixing of immiscible components. The obtained results show that, depending on the conversion, the phase behavior of the FAE-ethanol-glycerol phase system will correspond to the ternary system FAE-ethanol-glycerol or FAE-ethanol-TGA. The obtained data help to predict the separation of glycerol and ester phases at the ethanol recovery stage knowing the degree of rapeseed oil conversion at the synthesis stage. Successful separation of the glycerol and FAE phases is possible at oil conversion above 53 %.

Comprehensive Evaluation of Long-Term Dentin Bond Strength, Water Sorption, Solubility, and Degree of Conversion of Self-Adhesive Resin Composites.

To evaluate the long-term microtensile bond strength (µTBS) to dentin, water sorption (WSP) and solubility (WSL), and degree of conversion (DC) of self-adhesive resin composites (SACs). The mid-coronal dentin of human molars was exposed, and teeth were randomly assigned to five groups according to the SACs (n &#61; 10): 1. FIT SA F03 (FIT); 2. Experimental (EXP); 3. Fusio Liquid Dentin (FLD); 4. Vertise Flow (VER); 5. Constic (CON). The µTBS was evaluated after 24 hours (24 h) and 6 months (6 m) storage. A scanning electron microscope examined failure modes and resin-dentin interfaces. The WSP and WSL (n &#61; 5) were evaluated following ISO 4049:2019 specifications, and DC (n &#61; 3) was measured using Raman spectroscopy. The statistical analyses were performed accepting a significance level of p &#61; 0.05. FIT, EXP, and FLD produced significantly higher µTBS median values than VER and CON after 24 h and 6 m (p 0.05). After 6m, the µTBS median of FIT and EXP significantly decreased (p 0.05), while FLD, VER, and CON showed no significant difference (p > 0.05). FLD and CON exhibited lower WSP than FIT, EXP, and VER (p 0.05). FLD presented the lowest (p 0.05), and VER revealed the highest WSL (p 0.05). FIT and EXP showed the highest (p 0.05), and VER demonstrated the lowest DC (p 0.05). Following the present study's design, SACs' bonding performance and physical properties remained restricted. Therefore, the application should be considered cautiously, and further clinical trials are necessary to evaluate their long-term performance.

Effects of minimally invasive endodontic access cavity in molar teeth on polymerization, porosity and fracture resistance

Minimally invasive access cavities have been proposed in the last decade to reduce tooth tissue loss during endodontic treatment and mitigate compromised fracture resistance of endodontically treated teeth. Fracture resistance of molars with different types of access cavity design may be affected by restorative materials and aging. Insufficient literature data exist on the effect of cavity design and type of restorative materials on restorative aspects such as material adaptation or photo-polymerization in restricted access cavities. This study analyses quality of polymerization, material adaptation and fracture resistance of molars with different types of access cavities restored with glass-ionomer, high-viscosity fiber-reinforced bulk-fill and nanofilled resin composite. Plastic molar teeth with truss (TREC) and traditional endodontic access cavity (TEC) were restored with nanofilled composite (Filtek Supreme), glass-ionomer Fuji IX and Filtek or fiber-reinforced everX Posterior and Filtek. Porosity was determined using microcomputer tomography and the degree of conversion of resin-based materals using micro-Raman spectroscopy. Human molars prepared and restored in the same way were used for fracture resistance testing at baseline and after thermocycling. The results demonstrate that high-viscosity fiber-reinforced composite was difficult to adapt in TREC cavity leading to greater porosity than Filtek or Fuji. TREC design did not affect composite polymerization and led to higher fracture resistance of restored molars compared to TEC but also more unrestorable fractures.

Effects of crosslinker concentration on curing process and performances of needled fiber preform reinforced phenolic aerogel composite using process simulation and comprehensive experiments

A kind of needled quartz/carbon fiber preform reinforced phenolic aerogel composite (NQCF/PR) was fabricated through impregnating needled fiber preform with phenolic resin precursor solution, followed by sol–gel polymerization and solvent drying. The needled fiber preform serves as lightweight quasi-three-dimensional reinforcement, while phenolic aerogel matrix provides high porosity and low thermal conductivity. During fabrication of aerogel composite part using vacuum-assisted resin infusion process, distribution of crosslinker hexamethylenetetramine (HMTA) in precursor solution can be problematic, as precipitated crosslinker particles may be filtered by fibrous preform. In this study, the impact of HMTA filtration induced heterogeneous structure on subsequent curing process was investigated using process simulation. Temperature effects of sol–gel polymerization and solvent evaporation were considered through establishment of corresponding kinetic models. Impacts of heterogenous structure on distribution of temperature, resin curing degree and solvent conversion degree in large hemispherical aerogel composite structure were investigated. This leads to variations in gel network and pore structure of aerogel, thereby affecting final material performance. Based on experimental results, as HMTA concentration increases, compressive performance of NQCF/PR obviously increases. Among these, NQCF/PR with 4.7 wt% HMTA provides a balance of lightweight nature (0.25 g/cm3), excellent thermal insulation property (0.052 W·m−1·K−1) and compressive performance (strength of 0.35 MPa).

Photoactivated riboflavin-doped hydroxy apatite nanospheres infiltered in orthodontic adhesives.

To assess micro-tensile bond strength (μTBS), degree of conversion (DC), microleakage (ML) antibacterial efficacy, and adhesive remnant index (ARI) of orthodontic brackets to enamel with different concentrations of photoactivated riboflavin-doped hydroxyapatite (HA) nanospheres (NS) (0%,1%,5% and 10%) and 0.5 wt% RF alone in orthodontic adhesive. Samples were included on the predefined inclusion criteria and positioned up to the cementoenamel junction (CEJ). Hydroxy apatite nanospheres (HANS) commercially bought were doped with RF. Surface characterization of HANS and RF-doped HANS were assessed along with EDX analysis. Samples were grouped based on experimental orthodontic adhesive modification. Group 1: Transbond XT no modification, Group 2: experimental Transbond XT 0.5 wt% RF, Group 3: experimental Transbond XT 0.5 wt% RF-doped 1% HANS, Group 4: experimental Transbond XT 0.5 wt % RF-doped 5% HANS and Group 5: Experimental Transbond XT 0.5 wt% RF-doped 10% HANS. Brackets were placed based on different adhesive modifications and samples underwent thermocycling. Samples were evaluated for μTBS, DC, and ML. The type of failure was assessed using ARI. Adhesive modified and un-modified in four different concentrations (0%, 1%, 5%, and 10%) and 0.5 wt% RF only were used to test efficacy against Streptococcus mutans (S.mutans). The survival rate of S.mutans and ML was determined using the Kruskal-Wallis Test. For the analysis of μTBS, ANOVA was employed, followed by a post-hoc Tukey HSD multiple comparisons test. The highest μTBS and lowest ML were observed in Group 2 experimental Transbond XT 0.5 wt% RF only. The lowest μTBS, highest ML, and lowest DC was seen in Group 5 experimental Transbond XT 0.5 wt% RF-doped 10% HANS. Samples in Group 1 in which Transbond XT was used as adhesive demonstrated significantly the highest microbial count of S.mutans and DC. Photoactivated RF-doped HANS in 1% and 0.5 wt% Riboflavin alone in orthodontic adhesive for metallic bracket bonding improved micro tensile bond strength, ML, DC, and antibacterial scores. RESEARCH HIGHLIGHTS: The highest μTBS and lowest ML were observed in Group 2 experimental Transbond XT 0.5 wt% RF only. The lowest μTBS, highest ML, and lowest DC was seen in Group 5 experimental Transbond XT 0.5 wt% RF-doped 10% HA-NS. Samples in Group 1 in which Transbond XT was used as adhesive demonstrated significantly the highest microbial count of S.mutans and DC.

Improving the mechanical, spectroscopic and laser ablation characteristics of UDMA-MMA copolymers using a titanocene photoinitiator

We have shown that the Irgacure 784 titanocene photoinitiator can be advantageously used to improve the light absorption, mechanical and nanosecond-regime laser ablation properties of urethane dimethacrylate (UDMA)-methyl methacrylate (MMA) polymer blends with photopolymerization using curing with green (520–525 nm) light. The hardness was found to be significantly higher (0.25–0.29 GPa) than that of other UDMA polymer blends photopolymerized using other initiator systems. The established 48–63 % degree of conversion is also comparable to that of similar other blends and is useful in many applications. The laser ablation and laser-induced breakdown spectroscopy (LIBS) properties of these polymers were studied at 266 and 532 nm laser wavelengths. The polymers showed consistently good laser ablation characteristics (reproducible, well-defined, shallow craters) at 266 nm wavelength, whereas at 532 nm, extensive carbonization and strong photothermal effects were observed. LIBS spectra of the blend shows lines of C, H, O, N and Ti as well as C2 and CN bands, but provide many spectral windows for interference-free analytical measurements. Our findings indicate that UDMA-MMA polymer blends can be good candidates as target matrices for laser ablation-based measurements in the UV or Vis range, in applications like analytical spectroscopy or laser-initiated fusion research.

Particle-resolved computational modeling of hydrogen-based direct reduction of iron ore pellets in a fixed bed. Part II: Influence of the pellet sizes and shapes

Full-fledged computational modeling of Direct Reduction reactors encompasses single-pellets models and the step-wise scaling up to industrial-scale reactors. This study delves into the particle-resolved computational modeling of hydrogen-based direct reduction of 0.5 kg iron ore fixed-beds, as a scale-bridging step and focusing on the influence of pellet sizes and shapes. To investigate the effect of particle sizes, two beds with particles sized 10.0–12.5 and 12.5–16.0 mm were characterized and numerically reconstructed using the discrete element method. While to assess the effect of particle shapes, a third numerical bed was generated directly upon a high-resolution CT-scan of a real bed. Through reactive CFD simulations, we investigated the reduction process in these three beds using hydrogen as the reducing gas. Our findings reveal that the bed structure significantly impacts the reduction efficiency and overall conversion degree. This study emphasizes the importance of accurate bed reconstruction and provides critical insights for optimizing the hydrogen-based direct reduction process in industrial applications.

NIR‐induced upconversion‐assisted photopolymerization: Key factors, challenges, and future directions

AbstractNIR‐induced upconversion‐assisted photopolymerization has gained growing attention in the past two decades because of its numerous advantages over conventional UV/visible photopolymerization and two‐photon polymerization processes. However, research in this area is still in its early stages. To extend the practical application of NIR‐induced radiation curing, it is essential to optimize the factors affecting the photopolymerization reactions. Researchers have been constantly trying to improve these factors to tune the photo‐physical characteristics (luminescence intensity and color) of upconversion particles (UCPs), enhance curing depths and degree of double bond conversion (DC), and investigate the application of UCPs in emerging fields. In this review, first, a brief discussion of the upconversion mechanisms and upconversion efficiency is provided. Then, a detailed discussion of the factors influencing the upconversion‐assisted photopolymerization comprising UCP nature and characteristics, UCP content, presence of fillers/pigments/additives, laser intensity, photoinitiator content, and maximum absorption wavelength of photoinitiator is provided, and recent progress in improving these factors is presented. Finally, the advantages and drawbacks of the UC‐initiated polymerization are discussed, and perspectives for future directions are suggested.Highlights NIR‐induced upconversion‐assisted photopolymerization garners growing interest. Influential factors in upconversion‐assisted photopolymerization are thoroughly discussed. The recent progress on improving these factors and the future directions are provided.

Conservation of mutation and recombination parameters between mammals and zebra finch.

Most of our understanding of the fundamental processes of mutation and recombination stems from a handful of disparate model organisms and pedigree studies of mammals, with little known about other vertebrates. To gain a broader comparative perspective, we focused on the zebra finch (Taeniopygia castanotis), which, like other birds, differs from mammals in its karyotype (which includes many micro-chromosomes), in the mechanism by which recombination is directed to the genome, and in aspects of ontogenesis. We collected genome sequences from three generation pedigrees that provide information about 80 meioses, inferring 202 single-point de novo mutations, 1,174 crossovers, and 275 non-crossovers. On that basis, we estimated a sex-averaged mutation rate of 5.0 × 10-9 per base pair per generation, on par with mammals that have a similar generation time. Also as in mammals, we found a paternal germline mutation bias at later stages of gametogenesis (of 1.7 to 1) but no discernible difference between sexes in early development. We also examined recombination patterns, and found that the sex-averaged crossover rate on macro-chromosomes (1.05 cM/Mb) is again similar to values observed in mammals, as is the spatial distribution of crossovers, with a pronounced enrichment near telomeres. In contrast, non-crossover rates are more uniformly distributed. On micro-chromosomes, sex-averaged crossover rates are substantially higher (4.21 cM/Mb), as expected from crossover homeostasis, and both crossover and non-crossover events are more uniformly distributed. At a finer scale, recombination events overlap CpG islands more often than expected by chance, as expected in the absence of PRDM9. Despite differences in the mechanism by which recombination events are specified and the presence of many micro-chromosomes, estimates of the degree of GC-biased gene conversion (59%), the mean non-crossover conversion tract length (~23 bp), and the non-crossover to crossover ratio (6.7:1) are all comparable to those reported in primates and mice. The conservation of mutation and recombination properties from zebra finch to mammals suggest that these processes have evolved under stabilizing selection.