Degree Of Conversion Research Articles

Selective oxidation of the 4-ethyl-3-methylcinnoline methylene group by al<sub>2</sub>o<sub>3</sub>-supported chromium oxide

The optimal conditions for the oxidation of the methylene group in 4-ethyl-3-methylcinnoline to the corresponding ketone, 3-methyl-4-acetylcinnoline, were selected. It was shown that preliminary deposition of 4-ethyl-3-methylcinnoline on some inorganic substrates has a significant effect both on the selectivity of the oxidation of only the methylene group and on a high degree of conversion to the target product.

ВЛИЯНИЕ ПРИРОДЫ Ti-СОДЕРЖАЩИХ ПРЕКУРСОРОВ И УСЛОВИЙ ПЕРЕВОДА В H-ФОРМУ НА АДСОРБЦИОННЫЕ СВОЙСТВА ОКСИДОВ Li4Ti5O12 И Li2TiO3

The solid phase synthesis was used to obtain Li4Ti5O12 and Li2TiO3 oxides. Effect of the Ti-containing precursor, pH and temperature of the regeneration solution on the conversion degree to the H-form and the sorption capacity of Li+ ions were studied, which made it possible to determine the optimal conditions of the synthesis and regeneration for obtained samples. It is shown that the obtained oxides from anatase have a high sorption capacity of 95.1 and 84.0 mg/g for Li4Ti5O12 and Li2TiO3, respectively.

Effect of polymerization activation mode and accelerated aging in the degree of conversion of self-adhesive resin cements

Indirect adhesive restorations are increasingly being part of the oral rehabilitation procedures. With the purpose to reduce and minimize the difficulties and simplify the cementing technique with conventional adhesive resin cements, it was introduced a resin cement called self-adhesive for presenting chemical adhesion to dental tissues, ceramic and metal surfaces without the need for etching and adhesive systems aplications. Some studies point out to the problems of degradation of cement during storage. The inhibitors and peroxides presented in the cement composition are organic chemical compounds and, therefore, are susceptible to degradation phenomena under storage. For all of these factors, the resin cements have limited storage period and changes in the mechanism of polymerization may occur during this period. The present study has been prepared containing some variables to research. All these variables are seeking to investigate the consequences of different activation protocols of polymerization and the accelerated aging of self-adhesive dual cured resin cements on the degree of conversion. As well as test the null hypothesis that the activation protocol of polymerization and the accelerated aging do not cause alteration in the degree of conversion of the material to be tested.

Effect of material properties on batch‐to‐glass conversion kinetics

AbstractA recently developed model of the cold cap—the reacting glass batch (melter feeds) floating on molten glass in an electric glass melter—couples heat transfer with the feed‐to‐glass conversion kinetics. The model allows for determining the distributions of temperature and various properties within the cold cap. In the present study, this model is applied to four melter feeds designed for high‐level and low‐activity nuclear wastes. Profiles of temperature, conversion degree, cold cap porosity and density, condensed matter velocity, and heating rate were determined using the material properties of the cold cap. Effects of vigorous foaming at the cold cap bottom were considered. Density, thermal conductivity, and glass production rate strongly affect the cold cap thickness and the fraction of undissolved silica entering the melt under the cold cap. The heating rate profile in the cold cap is highly nonlinear, with high heating rates observed in the foam layer.

Kinetic analysis and modeling of paper-laminated phenolic printed circuit board (PLP-PCB) pyrolysis using distributed activation energy models (DAEMs)

This work explores the pyrolysis characteristics and kinetic behavior of paper-laminated phenolic printed circuit boards (PLP-PCBs) using thermogravimetric analysis under non-isothermal linear heating programs. The initial estimation of the kinetic parameters during the pyrolysis was obtained from the analysis of the experimental data by three isoconversional kinetic models, i.e. Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) integral methods, as well as the Friedman differential method. For all three methods, the apparent activation energy exhibited a strong dependence on the degree of the reaction conversion. To allow for the complexity of the reactions involved in the PLP-PCB pyrolysis, two distributed activation energy models (DAEMs) with a first-order reaction function were derived by assuming the discrete and multi-Gaussian distributions for the activation energies. A six pseudo-component Gaussian DAEM was able to accurately describe the PLP-PCB pyrolysis. By applying the discrete DAEM algorithm, the pyrolysis of PLP-PCB could be precisely characterized by 37 dominating reactions.

Main approaches of biofilm formation in composite resins: a concise systematic review

Introduction: Composite resins are widely used in clinical dental practice to restore the structure lost by caries and dental defects, achieving aesthetic and functional results. Failures in the photoactivation process can cause problems in the mechanical resistance to wear in regions of direct occlusal contact on the restorative material. This occurs due to the reduction in the degree of conversion of monomers into polymers, compromising the clinical performance of the composite resin. Polymerization shrinkage leads to microleakage of the restoration, leading to staining and the development of bacterial biofilms. Objective: It was to carry out a systematic review of the main scientific evidence of biofilm formation on composite resin veneers, identifying potential predictors, as well as proposals to mitigate this problem. Methods: The systematic review rules of the PRISMA Platform were followed. The search was carried out from December 2022 to March 2023 in the Scopus, PubMed, Science Direct, Scielo, and Google Scholar databases, using articles from 2015 to 2022. The quality of the studies was based on the GRADE instrument and the risk of bias was analyzed accordingly, according to the Cochrane instrument. Results and Conclusion: A total of 125 articles were found, 25 articles were evaluated and 20 were included and developed in this systematic review study. Considering the Cochrane tool for risk of bias, the overall assessment resulted in 10 studies with a high risk of bias and 70 studies that did not meet GRADE. It was concluded that the surface properties of resin-based composite materials, as well as surface treatments, can strongly affect bacterial adhesion and biofilm formation. In addition, scientific evidence highlights that cariogenic biofilm formation can alter the surface properties of materials, thus stimulating bacterial adhesion and biofilm formation. Photoactivation allows the curing and crosslinking of polymer chains, essential for the clinical longevity of the composite resin. Insufficient photoactivation culminates in marginal microleakage in restorations and biofilm accumulation on surfaces exposed to the oral environment.

Hydrogen absorption-desorption properties and hydrolysis performance of MgH2-Zr3V3O0.6Hx and MgH2-Zr3V3O0.6Hx-C composites

In this work, the catalytic effect of additions of η-Zr3V3O0.6 mixed suboxide and the title intermetallic composite with graphite on the properties of MgH2 in the processes of hydrogen storage and hydrogen generation has been studied. The hydride composites were obtained by high-energy reactive ball milling (RBM). The samples were characterized by X-ray diffraction and scanning electron microscopy. The cycling performance of hydrogen desorption and absorption as well as hydrogen generation in the hydrolysis reaction were studied. We found that during the reactive ball milling the studied composites are able in a few minutes to absorb ∼6.5 wt% of hydrogen. The addition of Zr3V3O0.6 and Zr3V3O0.6 + С catalysts not only increases the rates of hydrogen absorption and release, but also lowers the activation energy and the temperature of hydrogen desorption. For a composite containing 10 wt% of suboxide and 3 wt% of graphite, the activation energy of hydrogen desorption determined by the Kissinger method was very low, just 58 kJ/mol, and this value is among the lowest described in the reference publications. We also show that the intermetallic additive forms the Zr3V3O0.6H∼10 hydride, which results in a higher gravimetric capacity of the composite as H storage material. The improved kinetics of hydrogen exchange and increased hydrogenation capacity at modest operating temperatures of 150–200 °C appear to be characteristic for the composites containing suboxide and graphite additions. The reason for the advanced performance is in the different the morphology of the synthesized samples, particularly the graphite-containing composites showing a more developed dispergation of the material (the fraction with a particle size of 1–3 μm is >80 wt%). We furthermore show that the synthesized materials can be used in the hydrolysis process resulting in hydrogen generation. The amount of hydrogen released from the hydride Mg-Zr3V3O0.6-C composite in the hydrolysis reaction reaches 1364 ml/g (the conversion degree is ∼85 % for the process duration of 120 min) when using 0.04 M MgCl2 solutions.

Chemical conversion during transient liquid-phase hot pressing of TaSi2–TaC–SiC SHS-powder

This article presents a study on the manufacturing of three-phase TaSi2–TaC–SiC ceramics through self-propagating high-temperature synthesis (SHS) and their subsequent chemical conversion to TaC–SiC carbide composites during transient liquid-phase hot pressing (HP). The effect of carbon black doping, ranging from 0% to 7%, on the degree of chemical conversion, structure, mechanical, and thermophysical properties of the ceramics was investigated. Our results showed that the proportionate increase of carbide content and decrease of TaSi2 content in hot-pressed samples was achieved through carbon black doping. The increase of TaSi2 content during hot pressing led to an increase in porosity from 4.3% to 23.8%, while the density decreased from 6.3 to 4.6 g/cm3. Superior mechanical properties were obtained when SHS-powder was doped with 1.5% carbon black (HV = 15.2 GPa, KIC = 4.8 MPa × m1/2, and σbend = 331 MPa). The structure of the ceramics was characterized by a TaSi2–SiC matrix and highly dispersed TaC grains predominantly residing inside TaSi2, with the TaC–TaSi2 and TaSi2–SiC interface being incoherent, as demonstrated through TEM studies. Complete conversion of TaSi2 to TaC and SiC was achieved through 7% carbon black doping, resulting in the hot-pressed sample consisting solely of carbide grains. Two-stage hot pressing was employed to enhance the relative density of the two-phase TaC–SiC sample, resulting in ceramics characterized by HV up to 22.3 GPa, KIC up to 6.1 MPa × m1/2, σbend up to 256 MPa, and λ up to 36 W/(m × K).

Employing NaYF4: Yb, Tm upconversion particles (UCPs) in combination with rGO and PANI nanomaterials for the fabrication of radiation-curable anticorrosion composites/coatings

Upconversion particles (UCPs) able to emit photons from the ultraviolet to near-infrared (NIR) region of the electromagnetic spectrum when excited by a NIR laser may be used as internal radiation sources for the manufacture of thick composites with uniform and deep polymerization. In this work, NaYF4: Yb, Tm-based UCPs were synthesized and employed to cure composites using a dual curing method via UV and blue light produced from the UCPs to activate the photo-initiators (PIs), and the resulting cure depth and degree of double bond conversion (DC) were measured. In addition, the influence of UCP content and laser power on cure depth and DC was investigated. The emission rate of the UCPs demonstrated a non-linear, wavelength-specific relationship with increasing laser power and exposure time. Using optimal conditions, 62 % DC with a 2.5 cm cure depth was achieved. For the first time, the ability of UCPs to cure composites in the presence of reduced graphene oxide (rGO) and polyaniline (PANI) nanoparticles was studied. Results indicated that DC was almost consistent across samples (except the sample containing 1 wt% rGO), although the addition of nanomaterials decreased DC and cure depth. The addition of 0.5–0.5 wt% rGO-PANI increased the nanocomposites' compressive strength and strain at failure by 66 and 37 %, respectively. The nanocomposite formulations were applied to steel and the anti-corrosion properties were also investigated. The findings revealed low-frequency impedance (|Z|10 mHz) numbers higher than 1010 Ω.cm2 up to 4 w immersion duration, proving this coating's exceptional barrier anti-corrosion capabilities.

Investigation of physio-mechanical properties of cross-linked Bis-GMA/TEGDMA dental resins: A molecular dynamics study

In this work, molecular dynamics simulation was employed to investigate the cross-linked network structure formation and resulting physio-mechanical properties of typical Bis-GMA/TEGDMA dental resin models. An automated polymerization protocol was initially proposed to mimic the curing process and cross-linked Bis-GMA/TEGDMA models were constructed with different degrees of conversion (DCs). The network structure of the cured chains was then characterized by examining radial distribution function (RDF) and molecular weight fraction profiles. The RDF peaks at ∼1.54 Å indicated the polymerization successfully proceeds, and the molecular weight fraction of the largest cross-linked chain increases with DC, while that of the second largest molecule starts to decrease around a DC of 40 %, signifying the formation of the cross-linked network. In addition, the effects of the 3D network formation on the physio-mechanical properties, i.e., density, volume shrinkage, glass transition temperature (Tg), and elastic modulus, were also investigated. As the DC rises, both the density and volume shrinkage exhibit a significant increase due to the double bond conversion. Furthermore, Tg was evaluated and adjusted at various DCs and their relation (Tg vs. DC) agrees well with the DiBenedetto’s equation. More intriguingly, the elastic modulus was found to increase almost linearly with DC; while discrepancy still exists for models with DC < 40 % as the dental resins present a rubber-like state (T > Tg). The findings in this work are believed to provide a robust automated polymerization protocol as well as the atomic/molecular scale understanding of the cross-linked network structure and physio-mechanical properties of Bis-GMA/TEGDMA dental resins.

INCREASING OF THE CORROSION RESISTANCE OF FIBERGLASS PLASTIC REINFORCEMENT THROUGH MODIFICATION OF THE POLYMER BINDER

The issue of increasing the corrosion resistance of composite reinforcement, based on glass fiber and epoxy anhydride binder, is considered. The proposed samples of composite reinforcement were manufactured by needle extrusion technology. Glass fibers were evenly distributed in the channels and impregnated with a polymer binder based on epoxy resin. The amount of phenolic modifier in the polymer binder, according to the technological mode of obtaining composite reinforcement, was brought up to 5%. With a further increase in the content of the modifier, the degree of conversion of epoxy groups was no more than 70%, which sharply reduced the operational characteristics of the material. The overall ratio of polymer binder and glass reinforcement in the composite was ~ 60÷40. It was established that at low concentrations of the polymer modifier (up to 5 wt. parts), the processes of ordering and chemical grafting lead to compaction of the molecular grouping in the system, which in our case is characteristic of phenolic resins of the novolach and resol types. At the same time, under the conditions of the production technology, internal stresses in materials of this type increase sharply, which leads to the formation of surface defects (microcracks). At the tip of a crack or defect, sodium ions or other cations under the action of water undergo hydrolysis to form metal hydroxide, which, in turn, causes hydrolysis of siloxane bonds, thus weakening the mesh structure of silicon dioxide. The experimental activation energy was identified with the activation energy of sodium ion diffusion in the glass mass. But the plastic deformation of the glass in the region before the crack is very small, and instead of a uniform distribution of stress, the material cracks along the weakened centers The obtained data indicate that the action of the alkaline environment causes an increased loss of mass of the composite, both for the unmodified and for those modified with traditional phenolic resins. In turn, this ensures a high degree of penetration of alkalis into the volume of the material, access to reinforced fibers with their subsequent damage. To increase the corrosion resistance of composite reinforcement based on an epoxy anhydride binder, it is advisable to use a reactive sulfur-containing phenolic modifier. Its action is based on the ability to maintain the permissible monolithicity of fiberglass in the alkaline environment of concrete, the modulus of elasticity and necessary strength. Keywords: composite polymer reinforcement, fiberglass, alkaline environment, phenolic modifier.

The effect of high-irradiance rapid polymerization on degree of conversion, monomer elution, polymerization shrinkage and porosity of bulk-fill resin composites.

The purpose was to compare the degree of conversion (DC), monomer elution (ME), polymerization shrinkage (PS) and porosity of two addition-fragmentation chain transfer (AFCT) modified resin-based composites (RBC) light-cured with rapid- (RP), turbo- (TP) or conventional polymerization (CP) settings. Cylindrical samples (6-mm wide, 4-mm thick) were prepared from Tetric PowerFill (TPF) and Filtek One Bulk (FOB). Four groups were established according to the polymerization settings: 3s-RP, 5s-TP, 10s-CP and 20s-CP. Samples in 1mm thickness with 20s-CP settings served as controls. The DC at the top and bottom surfaces was measured with micro-Raman spectroscopy. ME was detected with high-performance liquid chromatography. PS and porosity were analyzed by micro-computed tomography. ANOVA and Tukey's post-hoc test, multivariate analysis and partial eta-squared statistics were used to analyze the data (p<0.05). FOB showed higher DC values (61.5-77.5 %) at the top compared to TPF (43.5-67.8 %). At the bottom TPF samples achieved higher DCs (39.9-58.5 %) than FOB (18.21-66.18 %). Extending the curing time increased DC (except the top of FOB) and decreased ME. BisGMA release was the highest among the detected monomers from both RBCs. The amount was three-fold more from TPF. The factor Material and Exposure significantly influenced DC and ME. PS (1.8-2.5 %) did not differ among the groups and RBCs except for the lowest value of TPF cured with the 3s_RP setting (p=0.03). FOB showed 4.5-fold lower porosity (p<0.001). Significantly higher pore volume was detected after polymerization in 3s_RP (p<0.001). High-irradiance rapid 3-s curing of AFCT modified RBCs resulted in inferior results for some important material properties. A longer exposure time is recommended in a clinical situation.

Studying the geobarier ability of furnace slag

Environmental pollution with mining waste containing dangerous metal cations necessitates the development of technologies for their disposal. This study proposes the use of blast furnace slag as a geobarrier for binding heavy metal cations. Such parameters as slag mass, temperature and time were used to determine the degree of binding of ferum and zinc cations when they are present together. A central rotatable composite experimental design was used to verify the results. According to the plan, the experiments were performed and the optimal conditions were determined with the help of statistical analysis. It was noted that a simultaneous increase in temperature and treatment time increases the degree of conversion for both ferric and zinc cations. An increase in the mass of slag leads to a decrease in the temperature and interaction time for ferum and zinc cations. However, for zinc cations, the maximum degree of conversion is 43.3% with their simultaneous presence. Experimental results showed that slag was more effective as a base for binding ferum and zinc cations with a conversion rate of 63.3% in concentrated solutions. The resulting regularities allow, by varying the process parameters, to bind metal cations in their joint presence.

Selective Oxidation of Tetrahydrofuran to Gamma-Butyrolactone over Spinel ZnFe2O4 Nanoparticle Catalyst

The selective oxidation of tetrahydrofuran (THF) to gamma-butyrolactone (GBL) on spinel ZnFe2O4 nanoparticles (ZFNPs) was investigated. The catalyst was prepared with the coprecipitation method and characterized by FTIR, XRD, TEM, SEM, EDS, TGA, XPS, and BET surface area. The characterization techniques showed that a nonuniform spherical spinal oxide with an average particle size of 26 nm was formed. The oxidation reaction was carried out using hydrogen peroxide as an oxidizing agent under solvent-free conditions. GC-MS analysis revealed that the main product was GBL. 2-hydroxytetrahydrofuran (THF-2-OH), gamma-hydroxybutyric acid (GHBA), and gamma-hydroxybutaldehyde (GHBAl) were obtained as minor products. The effects of different reaction parameters, such as temperature, H2O2/THF mole ratio, catalyst dose, reaction time, and reusability, were evaluated. A 47.3% conversion of THF with an 88.2% selectivity of GBL was achieved by conducting the reaction at 80 °C for nine hours using a 1:1 mole ratio of H2O2/THF. A slight increase in the conversion degree was attained at higher temperatures; however, an over-oxidation process was observed as the temperature exceeded 80 °C. The catalyst remained effective and stable over four reuses.

Application of infrared spectroscopy and its theoretical simulation to arsenic adsorption processes.

Accurate detection and analysis of arsenic pollutants are an important means to enhance the ability to manage arsenic pollution. Infrared (IR) spectroscopy technology has the advantages of fast analysis speed, high resolution, and high sensitivity and can be monitored by real-time in situ analysis. This paper reviews the application of IR spectroscopy in the qualitative and quantitative analysis of inorganic and organic arsenic acid adsorbed by major minerals such as ferrihydrite (FH), hematite, goethite, and titanium dioxide. The IR spectroscopy technique cannot only identify different arsenic contaminants but also obtain the content and adsorption rate of arsenic contaminants in the solid phase. The reaction equilibrium constants and the degree of reaction conversion can be determined by constructing adsorption isotherms or combining them with modeling techniques. Theoretical calculations of IR spectra of mineral adsorbed arsenic pollutant systems based on density functional theory (DFT) and analysis and comparison of the measured and theoretically calculated characteristic peaks of IR spectra can reveal the microscopic mechanism and surface chemical morphology of the arsenic adsorption process. This paper systematically summarizes the qualitative and quantitative studies and theoretical calculations of IR spectroscopy in inorganic and organic arsenic pollutant adsorption systems, which provides new insights for accurate detection and analysis of arsenic pollutants and arsenic pollution control. PRACTITIONER POINTS: This paper reviews the application of infrared spectroscopy in the qualitative and quantitative analyses of inorganic and organic arsenic acid adsorbed by major minerals such as ferrihydrite, hematite, goethite, and titanium dioxide, which can help identify and evaluate the type and concentration of arsenic pollutants in water bodies. In this paper, theoretical calculations of infrared spectra of mineral adsorbed arsenic pollutant systems based on density functional theory reveal the adsorption mechanism of arsenic pollutants in water at the solid-liquid interface and help to develop targeted arsenic pollution control technologies. This paper provides a new and reliable analytical detection technique for the study of arsenic contaminants in water bodies.

In-situ surface reconstruction of single-crystal (NiFe)3Se4 nano-pyramid arrays for efficient oxygen evolution

Transition metal-based selenides (TMSe) are considered as efficient pre-electrocatalysts towards oxygen evolution reaction (OER). However, the key factor in determining the surface reconstruction of TMSe under OER condition is not yet clear. Herein, we uncover that the crystallinity of TMSe will obviously impact the conversion degree from TMSe to transition metal oxyhydroxides (TMOOH) during OER. A novel single-crystal (NiFe)3Se4 nano-pyramid array grown on NiFe foam is fabricated by a facile one-step polyol process, which exhibits an excellent OER activity and stability, only requiring 170 mV to reach a current density of 10 mA cm−2 and can sustain for more than 300 h. In situ Raman spectrum studies reveals that the single-crystal (NiFe)3Se4 is partially oxidized on its surface during OER, generating a dense heterostructure of (NiFe)OOH/(NiFe)3Se4. Benefiting from the in situ formed heterointerface, the adsorption of OER intermediates on Ni active sites calculated by density functional theory (DFT) analysis is optimized, leading to the reduced energy barrier, which accounts for the enhanced intrinsic activity. This work not only reports a novel single-crystal (NiFe)3Se4 nano-pyramid array electrocatalyst with high-efficient OER performance, but also gains a deep insight into the role of the crystallinity of TMSe on the surface reconstruction during OER.

Co-Carbonization of Discard Coal with Waste Polyethylene Terephthalate towards the Preparation of Metallurgical Coke

Waste plastics such as polyethylene terephthalate (w-PET) and stockpiled discard coal (d-coal) pose a global environmental threat as they are disposed of in large quantities as solid waste into landfills and are particularly hazardous due to spontaneous combustion of d-coal that produces greenhouse gases (GHG) and the non-biodegradability of w-PET plastic products. This study reports on the development of a composite material, prepared from w-PET and d-coal, with physical and chemical properties similar to that of metallurgical coke. The w-PET/d-coal composite was synthesized via a co-carbonization process at 700 °C under a constant flow of nitrogen gas. Proximate analysis results showed that a carbonized w-PET/d-coal composite could attain up to 35% improvement in fixed carbon content compared to its d-coal counterpart, such that an initial fixed carbon content of 14-75% in carbonized discard coal could be improved to 49-86% in carbonized w-PET/d-coal composites. The results clearly demonstrate the role of d-coal ash on the degree of thermo-catalytic conversion of w-PET to solid carbon, showing that the yield of carbon derived from w-PET (i.e., c-PET) was proportional to the ash content of d-coal. Furthermore, the chemical and physical characterization of the composition and structure of the c-PET/d-coal composite showed evidence of mainly graphitized carbon and a post-carbonization caking ability similar to that of metallurgical coke. The results obtained in this study show potential for the use of waste raw materials, w-PET and d-coal, towards the development of an eco-friendly reductant with comparable chemical and physical properties to metallurgical coke.

Antibacterial and fluorescent clear aligner attachment resin modified with chlorhexidine loaded mesoporous silica nanoparticles and zinc oxide quantum dots

ObjectivesTo develop an antibacterial and fluorescent clear aligner attachment resin via the incorporation of chlorhexidine loaded pore-expanded mesoporous silica nanoparticles (CHX@pMSN) and amino-silane functionalized zinc oxide quantum dots (aZnOQDs), and to evaluate its antibacterial activity, fluorescence capability, esthetic properties, mechanical performance and biocompatibility. MethodsCHX@pMSN and aZnOQDs were incorporated into the commercial resin composites (Filtek Z350 XT, 3M) at different mass fractions, control group: Filtek; fluorescent attachment resin (FAR): Filtek + 3 wt% aZnOQDs; antibacterial and fluorescent attachment resin (AFAR)-1: Filtek + 3 wt% aZnOQDs + 1 wt% CHX@pMSN; AFAR-2: Filtek + 3 wt% aZnOQDs + 3 wt% CHX@pMSN; AFAR-3: Filtek + 3 wt% aZnOQDs + 5 wt% CHX@pMSN. CHX release, antibacterial activity, fluorescence capability, color change, stain resistance, degree of conversion, depth of cure, polymerization shrinkage, water sorption and solubility, softening in solvent, flexural strength, flexural modulus, shear bond strength, and cytotoxicity were evaluated comprehensively. ResultsCHX could be continuously released from the AFAR groups for up to 30 days. CFU, MTT, lactic acid production, SEM and CLSM evaluation showed AFAR-2 and AFAR-3 could effectively inhibit S. mutans biofilms even after 1-month aging. Only AFAR-3 showed clinically perceptible color change and all the experimental groups were not more susceptible to staining. AFAR-1 and AFAR-2 could suppress polymerization shrinkage and enhance the resistance to degradation without compromising other properties, including degree of conversion, water sorption and solubility, flexural strength, flexural modulus, and shear bond strength. Depth of cure of all the four experimental groups was significantly decreased (p < 0.05) but still within the ISO standard. CCK-8 assay and live/dead cell staining denied the cytotoxicity of experimental resins. Fluorescence intensity tests showed that FAR and AFAR-2 could emit strong yellowish fluorescence under the excitation of ultraviolet for up to six months. ConclusionsAFRA-2 possessed long-term antibiofilm activity, strong fluorescence capability and satisfying biocompatibility without compromising esthetic and mechanical properties. This study proposed a new strategy for reducing bacteria accumulation around the attachment, which is also promising in helping orthodontists to remove the attachment thoroughly and precisely.

Evaluation of the effects of asphalt binder aging degree on the curing, compatibility, and mechanical behaviors of epoxy asphalt binders

The application of epoxy asphalt binder in hot mix plant recycling for reclaimed asphalt pavement (RAP) can significantly increase the utilization rate of waste material on the premise of ensuring the service quality of the asphalt pavement. However, the development of epoxy asphalt binder modified RAP is hindered by the limited understanding of the effect of aging degree and types variability of asphalt binder in RAP on the properties of epoxy asphalt binder. Therefore, short-, long- and ultra-long- term aging tests of base asphalt and SBS modified asphalt binder were conducted through rolling thin film oven (RTFO), pressure aging vessel (20 h and 40 h) tests to obtain the asphalt binders with different aging extent, and then the binders were mixed with two epoxy systems to prepare epoxy asphalt binders, respectively. Next, the effects of asphalt binders aging degree on curing, compatibility, and mechanical behaviors characteristics of epoxy asphalt binders were investigated from chemical, microscopic, mechanical, and rheological perspectives based on Brookfield viscosity, Fourier transform infrared (FTIR), laser confocal fluorescence microscopy (LSCM), Shore hardness, direct tensile, strain sweep, and frequency sweep tests. The viscosity results indicated that a higher asphalt binder aging degree brought about a faster increase in the viscosity of epoxy asphalt binders. The construction allowable time of type-A epoxy asphalt binder of at least 3.5 h was higher than that of type-B. The conversion degree model constructed with the 917 cm−1 peak area as a parameter showed that the epoxy asphalt binder prepared by the asphalt binder with a more severe aging degree presented a higher conversion degree within the same curing time since the reaction space between epoxy and curing agent reactive groups was compressed by aggregated aged asphalt binder. The LSCM and Shore hardness results suggested that the aging asphalt binders induced the phase separation between asphalt and epoxy resin. With the asphalt binders aging, the distribution of asphalt phase in the epoxy system changed from black dots (12–15 um) to island-shaped structures (50–98 um), and eventually transferred a neuron-shaped network structure to connect island-shaped synaptosomes to block the continuity of three-dimensional network structure of epoxy resin. The rheological tests showed that the linear viscoelastic (LEV) region of the epoxy asphalt binders changed with the asphalt binders aging degree, and a shear strain of 0.01% ensured that specimens was within the LEV region. The effects of asphalt binders aging degree on the complex modulus and phase angle master curves of type-A epoxy asphalt binders mainly reflected the low frequency region (10−4 to 10−1 Hz), while the effects on type-B epoxy asphalt binders were in the whole frequency range (10−4 to 103 Hz).

Конверсия пшеничных отрубей в целевые продукты биосинтеза

A more efficient bioconversion of renewable plant resources is a priority in modern biotechnology. An important aspect of the processing and pretreatment of cellulose raw materials is to obtain a high content of reducing substances in the final product. The present research objective was to determine the optimal conditions for the chemical transformation of plant polymers to obtain biologically valuable substances. The research results will reduce the final cost of biotechnological production.&#x0D; This research featured wheat bran polymers treated with sulfuric acid and relied on a set of standard research methods. The degree of polymer conversion was tested on native and mechanically activated wheat bran fractions of 600, 200, and 100 microns. The kinetics of the high-temperature chemical hydrolysis was as follows: temperature – 120–130°C, sulfuric acid concentration – 0.6–0.9%, treatment time – 30–60 min, hydromodule – 1:8;9;10. The quantitative and qualitative composition of mono- and disaccharides of hydrolysates was determined using the high performance liquid chromatography method. &#x0D; The composition of wheat bran showed a low content of lignin (7.55%) and a high content of pentosans (17.9%). The highest content of reducing substances in hydrolysates was 640 mg/g bran. The optimal technological conditions with the highest content of reducing substances were as follows: hydromodulus – 1:10, temperature – 120°C, treatment time – 45 min, and sulfuric acid concentration – 0.9%. The greatest change in the content of mono- and disaccharides of hydrolysates belonged to pentoses: 78.2 mg/g of bran (in terms of xylose). The amount of easily hydrolysable carbohydrates and wheat bran fiber decreased by 80 and 19%, respectively.&#x0D; This research revealed the optimal parameters for the chemical hydrolysis of wheat bran to obtain biologically valuable carbohydrates. This area of research can be of practical use for producers of biofuels, chemicals, and food additives.