Microscopy Tests Research Articles

Preparation and performance of waterborne polyurethane coatings based on the intumescent flame retardant of boron, phosphorus, and nitrogen

AbstractPNB organic flame retardant was synthesized using 4‐formylphenylboronic acid, 4‐aminophenylthiophenol, 9,10‐dihydro‐9‐oxa‐10‐phos‐phaphenanthrene‐10‐oxide (DOPO), and then introduced into the hydroxyl‐terminated polybutadiene acrylonitrile (HTBN) molecular chain to successfully prepare a macromolecular flame retardant, which was used to prepare flame retardant waterborne polyurethane. The mechanical properties, thermal properties, and flame retardancy of waterborne polyurethane (FR‐WPU) were studied using thermogravimetic analysis (TGA), limiting oxygen index (LOI), scanning electron microscope (SEM), cone calorimeter, and universal testing machine, respectively, and the flame retardant mechanism of macromolecular flame retardants was explored. An LOI value of 29.76% and a UL‐94 V‐0 rating could be realized when the APFBH conjugation is 7.5 wt%, showing a significant improvement of melt dripping behavior and flame retardancy. It indicated that the fire resistance of FR‐WPU remarkably improved and displayed both gas and condensed phase mechanism. As the content of APBDH increased, the tensile strength and the elongation at break of FR‐WPU increased firstly and then decreased.

Effect of anionic polyacrylamide amendment on the climatic durability of solidified waste rock fine

In order to improve the climatic durability of solidified waste rock fine (WRF), anionic polyacrylamide (APAM) was innovatively introduced to amend solidified WRF in this study. The effects of APAM content, freeze-thaw (F-T), and wet-dry (W-D) cycles on the mechanical behaviors of solidified WRF were explored. After that, zeta potential, fourier transform infrared (FTIR) spectroscopy, and scanning electron microscope (SEM) tests were initiated to understand the behavioral mechanisms of APAM. The results show that APAM can significantly improve the mechanical properties and durability of solidified WRF, and there exist a threshold content of APAM (0.3%~0.8% in this study), beyond which the strength will decrease. The microscopic test shows that the bridging effect and the filming effect induced by APAM are considered to be the two decisive factors affecting the mechanical behavior of S-WRF. On the one hand, the linear APAM long chain enables the cohesion between particles to be stronger through ion bridging, on the other hand, the long chains cross-link with each other to form a network interwoven inside the structure, thus playing a microfabric reinforcement role and enhancing the crack resistance of the solidified matrix. In addition, life cycle assessment (LCA) further confirmed the advantages of using industrial by-products combined with APAM to amend solidified-WRF. These results provide a theoretical basis for using APAM as trace additives to mitigate climatic durability-related issues.

A Study on a New Method for Simultaneous Internal Curing and hydrophobic in Concrete

The high hydrophilicity and permeability of concrete caused by many pores and hydroxyl groups produced by cement hydration are the main factors leading to dry shrinkage, cracking, and poor corrosion resistance of concrete. Giving concrete internal curing and hydrophobicity is an effective measure to solve the above problems. In this paper, a new idea and preparation method for an organic combination of hydrophilic and hydrophobic materials are proposed to improve the service life of concrete structures. Furthermore, the combined effects of hydrophilic and hydrophobic amphoteric materials (HAM) on the mechanical properties, internal curing properties, and hydrophobic properties of concrete were comprehensively investigated. In addition, the physical and chemical action mechanisms were analyzed in conjunction with microscopic tests. The results indicated that HAM rapidly released water within 3-7 days before concrete curing, and then slowly released water accompanied by the release of hydrophobic materials, gradually from hydrophilic to hydrophobic properties; The addition of HAM did not reduce the mechanical properties of concrete, which solved the problem of low compressive strength of integral hydrophobic concrete; The addition of HAM reduced the drying shrinkage of concrete by 154.12%, increased the contact angle to 96°, and decreased the water absorption rate by 36%, allowing the concrete to achieve better internal curing and a hydrophobic effect. The preparation of this material can open up a new way to solve the hydrophilic and hydrophobic properties required by concrete at the same time, and fill the gap that concrete can not balance hydrophilic and hydrophobic properties.

Morphological Characteristics of Low-asphalt RAP and Influence of its Reaction Product During Combustion Heating on Regenerated Asphalt

To provide reference for regeneration of the finely separated low-asphalt reclaimed asphalt pavement (RAP), the macroscopic and microscopic laboratory testing and quantum chemical simulation were combined. The morphological characteristics of the basalt and limestone low-asphalt RAP were analyzed. The low-asphalt RAP needs to be dried before regeneration, so the reaction mechanism and product of the asphalt film on its surface during drying were clarified. The product influence on the temperature resistance and fatigue performance of the virgin asphalt was studied, so as to consider their mixing during the subsequent regeneration process. Result shows that the gradation of limestone low-asphalt RAP is coarser and particles are slenderer than basalt with the same particle size grade. The 5-10mm low-asphalt RAP particles are slenderer than those in the 10-20mm grade. In the drying cylinder, asphalt basically generate no new functional groups below 200℃, while the asphalt film on the low-asphalt RAP surface undergoes pyrolysis to produce carbon black with the particle size around 100μm in the combustion heating area. The most easily oxidation or pyrolysis site in asphalt molecule is the carbon atom connected to the benzene ring. The pyrolysis of asphalt molecules to generate free radicals in the local oxygen deficient environment is the prerequisite for the carbon black formation, and pyrolysis requires higher temperature than oxidation because of its higher energy barrier. As the carbon black content increases, the penetration and ductility of asphalt decrease, the softening point increases, the high-temperature performance is enhanced, the low-temperature performance is weakened, and the fatigue performance is not significantly affected. As the particle size of carbon black increases, the decrease range in penetration, ductility and low-temperature performance of asphalt declines, the increase or improvement range of softening point and high-temperature performance enhanced, while the fatigue performance still shows no significant and regular change.

Diffusion Mechanism of Waste Crumb Rubber Composite Modified Asphalt Based on Molecular Dynamics Simulation

Waste crumb rubber composite modified asphalt (CRCMA), composed of base asphalt, waste rubber powder, and several additives (softener, activator, and cross-linking agent), has been shown to effectively improve asphalt properties. The interactions between the components in CRCMA are complex, involving molecular diffusion that significantly impacts its performance. The diffusion behavior in asphalt molecules will affect various properties of asphalt and the reasons for the different properties of asphalt can be explained by studying its diffusion mechanism. Therefore, understanding the diffusion mechanism of CRCMA is essential. The molecular dynamics simulation was employed to analyze the factors influencing the diffusion mechanism, using the diffusion coefficient as a key indicator of molecular mobility. The findings showed that the diffusion coefficient of the asphalt system decreased over time but increased with temperature. The rubber composition type also had a significant impact on diffusion, with butadiene rubber (BR) showing the highest coefficient, followed by natural rubber (NR), crumb rubber (CR), and styrene-butadiene rubber (SBR). The diffusion coefficient was the lowest and the diffusion rate was slowest after adding softeners. The diffusion coefficient increased slightly with the addition of CR, and the diffusion rate was slightly accelerated but not significantly. The diffusion coefficient increased rapidly with adding activator and the diffusion rate increased significantly. With the addition of cross-linking agent, the diffusion coefficient began to decrease and the diffusion rate became slower. The CRCMA microscopic performance tests indicated that the swelling effect of CR limits diffusion, while activators promote degradation and desulfurization of CR due to the large molecule structure getting smaller, enhancing diffusion. The S=O bond in the asphalt system was regenerated and re-crosslinked to create a mesh after adding the cross-linking agent. The small molecule structure was transformed into large one. The molecular diffusion was restricted partly and thus the diffusion rate was slowed down.

Analysis on the Influence law and Mechanism of the Strength of Reclaimed Aggregate-Industrial Waste Slag Solidified Silt

To optimize the usage of construction waste resources, industrial waste slag and silt, this paper used Portland cement, mineral waste residue and phosphogypsum composite to make cementing material (CMPS) with construction waste reclaimed aggregate to solidify silt. The laboratory solidification test and microscopic analysis were conducted to assess the mechanical characteristics of solidified sludge. In order to clarify the mineral composition, microscopic morphology and pore characteristics of the regenerated aggregate and CMPS solidified silt (SS), XRD, SEM and nitrogen adsorption pore analyzer were employed for further explore the regenerated aggregate and CMPS solidified silt effectively, and further reveal the internal mechanism of the regenerated aggregate and CMPS solidified silt effectively. The findings indicated that the strength of Portland cementmineral waste residue phosphogypsum terpolymer system curing agent increased by 107.34% than that of single Port-land cement SS at 56 d, and the strength of CMPS solidified silt increased by 25.68% under the action of reclaimed aggregate framework. The maintenance period and water composition of the silt have high correlation with the strength. Therefore, influence law of above two influencing factors on its mechanical properties were further explored and the strength prediction were made. The microscopic test results showed that, drawing from the hydration of Portland cement and pozzolans reaction of mineral waste residue, the solidified system has pre-pared CaSiO3 hydrate gel and ettringite crystals with gelatinous properties, which help to fill the pores and form a denser structure.

Study on the hydration characteristics and mechanical properties of recycled powder-slag powder-cement system

This study systematically investigated the influence of different blending ratios of recycled powder and slag powder on hydration heat evolution and mechanical properties. Various modern microscopic testing techniques were employed to quantitatively characterize hydration products and microstructures, revealing their hydration mechanisms. The results indicate that both recycled powder and slag powder can accelerate the early hydration rate. When recycled powder and slag powder are co-blended, their early hydration rate and cumulative heat release surpass those of specimens with single additions of recycled powder. Moreover, the mechanical properties in the later stage are superior to those of specimens with single additions of recycled powder. At 60d, the PRS70-1-2 in the multi doped recycled powder and slag powder system even exceeds that of the uni doped SL system, but is much higher than that of the uni doped RP system，the compressive strength of the multi doped recycled powder and slag powder system increased by 25.5%, 37.1% and 36.9%, respectively, compared with that of the uni doped RP system. Specimens with single additions of recycled powder and slag powder have a relatively high proportion of harmful and very harmful pores. At 28d, the porosity of the multi doped recycled powder and slag powder system decreased by 19.2%, 24.2% and 14.8%, respectively, compared with that of the uni doped RP system. However, when recycled powder and slag powder are co-blended, the proportion of harmful and very harmful pores decreases, while the proportion of less harmful and harmless pores increases. This leads to an overall reduction in porosity and an improvement in mechanical properties.

Ultrasonic Welding Parameter Optimization for Electric Component Welding

Industrial requirements to establish metallic joints between dissimilar metals in the electric area. The ultrasonic welding process is an optimal process to joint thin sheets or foils. The goal of the research was to optimize the ultrasonic welding parameters to join thin nickel-coated copper sheets and aluminium sheets. It used a 0.5 mm thick high-purity copper (Cu-OF-R200) sheet coated with a 10 μm pure nickel layer and a 0.5 mm thick aluminium (1050A H24) sheet. The ultrasonic welding is made by a Branson Ultraweld L20 ultrasonic welder equipment. The mechanical properties and exacting geometrical tolerance of the joint were required. The welding parameter optimization is made empirically, with several welding tests. The optimal welding parameters were confirmed by non-destructive and destructive tests of the joints. The non-destructive tests were the visual inspection and geometrical measurements of the joint sizes. The destructive tests were tensile tests and macroscopic and microscopic tests. The completed test results confirmed the process applicability and the quality of the joint.

Synthesis of novel green nanocomposites by considering enhanced oil recovery and asphaltene adsorption effectiveness in calcite and dolomite formations

Asphaltene deposition is known as the main issues in reservoirs, which causes formation damage in reservoir. This research investigated the effects of a newly introduced green nanocomposites, namely eucalyptus/CuO/Fe3O4/xanthan nanocomposites (EC-NCs), on the inhibition of asphaltene precipitation in calcite and dolomite formations. First, at two time steps of 48 and 96 h, asphaltene adsorption on EC-NCs surfaces was examined through scanning electron microscope (SEM) tests in both calcite and formation tests. Moreover, asphaltene adsorption on the surface of EC-NCs was confirmed through isotherm models including Langmuir and Freundlich and the interfacial tension between CO2 and oil. Finally, a series of static and dynamic tests were performed at the highest adsorption pressure points, including 4200, 3950, and 3700 psi, and at the highest adsorption time step, i.e., 96 h, and the effects of asphaltene adsorption were seen on permeability reduction and asphaltene precipitation. EC-NCs exhibited superior efficacy in both asphaltene adsorption and precipitation inhibition. Two separate pressure changes were observed, and the ratios of the interfacial tension slope in the 2nd to the 1st regions [1st: 200–2700 psi, 2nd:2700–4200 psi] were changed from 19.44 % to 25.00 % and 29.74 % in 48 and 96 h, respectively, and this confirms that asphaltene had indeed adhered to the surface of the EC-NCs. Moreover, at 48, and 96 h, the size reductions of particles in SEM for calcite and dolomite were (29.27 %, 56.81 %), and (59.09 %, 62.25 %), respectively, which shows asphaltene adsorption was more efficient in dolomite formation, and in 96 h.

Data set for the reporting of lung cancer: recommendations from the International Collaboration on Cancer Reporting (ICCR).

Lung cancer is the leading cause of cancer related deaths worldwide, although some patients with early-stage disease can be cured with surgical resection. Standardised reporting of all clinically relevant pathological parameters is essential for best patient care and is also important for ongoing data collection and refinement of important pathological features that impact patient prognosis, staging and clinical care. Using the established International Collaboration on Cancer Reporting (ICCR) procedure, a representative international expert panel of nine lung pathologists as well as an oncologist was convened. Essential core elements and suggested non-core elements were identified for inclusion in the resected lung cancer pathology data set based on predetermined levels of evidence as well as consensus expert opinion. A lung cancer histopathology reporting guide was developed that includes relevant clinical, macroscopic, microscopic and ancillary testing. Critical review and discussion of current evidence was incorporated into the new data set including changes from the 2021 World Health Organisation (WHO) Classification of Thoracic Tumours, fifth edition, new requirements for grading invasive non-mucinous adenocarcinomas, assessment of response to neoadjuvant therapy and requirements for molecular testing in early-stage resected lung carcinomas. This ICCR data set represents incorporation of all relevant parameters for histology reporting of lung cancer resection specimens. Routine use of this data set is recommended for all pathology reporting of resected lung cancer and it is freely available worldwide on the ICCR website (https://www.iccr-cancer.org/datasets/published-datasets/). Widespread implementation will help to ensure consistent and comprehensive pathology reporting and data collection essential for lung cancer patient care, clinical trials and other research.

Assessing pavement characteristics: An in-depth evaluation of waste engine oil and Buton rock asphalt composite modified asphalt and its mixture

To investigate the cooperative influence of waste engine oil (WEO) and Buton rock asphalt (BRA) on asphalt characteristics, the WEO/BRA composite modified asphalt and its mixture with varied dosages were prepared. The high-, moderate-, and low-temperature assessments of WEO/BRA composite modified asphalt were conducted through temperature sweep tests, multiple stress creep and recovery (MSCR), and bending beam rheometer (BBR) tests. The softening point difference was used to analyze the storage stability of composite modified asphalt. Based on the Fourier transform infrared spectroscopy (FTIR) and fluorescence microscope (FM) test, the microscopic feature and chemical constitution of WEO/BRA composite modified asphalt were analyzed. Rutting test, low-temperature bending test, immersed Marshall test, freeze-thaw splitting test, and four-point fatigue bending test were carried out to verify the pavement properties of the WEO/BRA composite modified asphalt mixture. The results indicated that WEO improved the capability in low-temperature conditions and fatigue properties of asphalt modified with BRA. BRA enhanced the high-temperature property of asphalt modified with WEO. The synergistic effect of WEO, BRA, and neat asphalt was a physical reaction, and these modifiers were uniformly distributed in the asphalt. Meanwhile, WEO/BRA composite modified asphalt had excellent storage stability for the single modified asphalt. The test results of the asphalt mixture verified the results, indicating that WEO/BRA composite modified asphalt can be considered a new green and durable asphalt pavement material.

Study on the mechanical properties and microscopic evolution mechanisms of weathered granite soil

Studying the effects of weathering on the mechanical properties and microscopic evolution of weathered granite soil (WGS) is essential for connecting microstructure with macroscopic behavior. This study conducts systematic monotonic and cyclic triaxial tests, along with a series of microscopic tests on WGS samples, to explore the influence of weathering on WGS mechanical properties and the mechanism of granite weathering. Results indicate that both effective internal friction angle and effective cohesion decrease progressively with increased weathering. Completely weathered granite (CWG) exhibits greater dynamic strength compared to granite residual soil (GRS). Additionally, as weathering progresses, quartz fragments are lost, while feldspar and biotite weather to form secondary minerals such as kaolinite and illite, leading to an overall enrichment in aluminum and iron in the granite. Weathering causes structural deterioration of WGS. Finally, the mechanical parameters of WGS and their chemical weathering indices show a coefficient of determination ranging from 60 to 99%. This study helps elucidate the fundamental causes of performance changes in WGS, thereby optimizing engineering design and enhancing disaster prediction accuracy, while providing new research perspectives and experimental evidence for WGS.

Using Microplates to Test Boron in Zea mays Leaf Plant and the Surrounding Soil

Background: Boron plays a crucial role in cell wall construction in plants and also facilitates the transfer of carbohydrates, which are essential for various physiological processes. The objective was to measure element concentrations in soil, water extracts and plant tissues (Zea mays) using Azomethine-H and ICP-MS within a controlled microplate assay. Methods: A microscopic plate repeat test was used to analyze the concentration of boron in soil extracts and plant tissue ash from local Zea mays leaves, considering the global trend in environmental sustainability. Tests aimed to modify the azomethine-H microscopic approach to eliminate pH and chemical interferences in soil samples and plant tissues. Due to their ability to ensure sample repeatability and quality control, micro spectrophotometers are ideal for high-throughput analysis. Result: The microplate test has enhanced boron measurement in soil and plant tissue samples. Our improvements to the microplate B assay have resulted in more accurate boron measurements in these samples. Microplate B testing is effective and suitable analysis in modern research and laboratories, using 40 times less chemical reagent per sample than traditional spectrophotometry. Additionally, microplates enable simultaneous analysis and calibration of samples. The modified plate test significantly improves boron measurement in soil and plant tissue samples, using 40 times fewer reagents than traditional spectrophotometry. This method is cost-effective, ideal research, commercial analysis and making it a valuable tool for modern laboratories.

An epitope imprinted electrochemical sensor for highly sensitive and selective determination of prostate-specific antigen.

Asimple method forhighly selective and sensitive prostate-specific antigen (PSA) detection using a molecularly imprinted electrochemical sensor ispresented. The sensor was developed through an epitope imprinted strategy combined with electrochemical measurement techniques. An epitope molecularly imprinted polymer (EMIP) film was constructed on a AuNPs-coated gold electrode surface through electropolymerization, utilizing the C-terminus epitope of PSA (KWIKDTIVANP) as the template molecular and o-phenylenediamine as the functional monomer. The characteristics of EMIP film were investigated by using a scanning electron microscope and electrochemical test methods, including electrochemical impedance spectroscopy and cyclic voltammetry. Key parameters such as electropolymerization cycles, elution and rebinding times, and the molar ratio of template molecular to functional monomer were systematically optimized. The sensor demonstrated a detection limit (LOD) of 0.31 fg/mL and exhibited an excellent linear response towards PSA concentration ranging from 1.0 fg/mL to 0.1 µg/mL. Furthermore, the EMIP sensor showed excellent selectivity against other biological macromolecules, such as bovine serum albumin, human serum albumin, alpha-fetoprotein, and carcinoembryonic antigen. With recoveriesbetween 95.89 and 106.04% for PSA detection in human serums theEMIP/AuNPs/AuE electrochemical sensor showed great potential in real sample analysis.

Performance evaluation of bio-oil and high rubber content modified asphalt: More effective waste utilization

In this study, the bio-oil was used to reduce the viscosity and preparation temperature of high content of rubber-modified asphalt. The high rubber content modified bio-asphalt (RMBA) was prepared, the rubber and bio-oil contents were 20 %-30 % and 5 %-15 % (mass ratio of neat asphalt), respectively. The viscosity, temperature sweep (TS), frequency sweep (FS), multi-stress creep recovery (MSCR), and bending beam rheometer (BBR) tests were performed to assess the properties of RMBA. The Fourier Transform infrared spectroscopy (FTIR), Fluorescence microscopy (FM), and Scanning electron microscope (SEM) tests were conducted to explore the microscopic morphology of RMBA. Besides, the economic analysis and life cycle assessment (LCA) were assessed. Bio-oil contributed to the viscosity-reduction of the RMBA. When the rubber content was 30 %, the viscosity decreased by 48.16 % with a bio-oil content of 15 %. The temperature and frequency sensitivity of RMBA were lower than neat asphalt. Rubber improved the creep recovery and anti-rutting deformation behavior for bio-asphalt. The absorption peaks appeared at 1010 and 1038 cm−1, which represented the SO function group. The rubber did not absorb enough bio-oil for solubilization. This resulted in the functional group of SO appeared in 30 %+B-10 % and R-30 %+B-15 %. FM and SEM test results indicated that the rubber in RMBA exists in different states: undissolved rubber and dissolved rubber. The high content rubber could be partially dissolved in bio-asphalt and retained its elastic properties. The dissolved rubber particles exhibited a large crosslinked network structure. The raw material cost of RMBA decreased significantly with the rise of rubber and bio-oil contents. The reasonable application of waste rubber is beneficial to the alleviation of black pollution. The efficient application of rubber and bio-oil could contribute to the development of waste utilization and green transportation.

Optimizing epoxy asphalt tack coat formulations for improved adhesion and working performance of ultrathin wearing course

Insufficient adhesion between ultrathin wearing courses (UTWCs) and substrate layers can result in pavement distress. Epoxy asphalt exhibits potential as a tack coat due to its high bonding strength and thermal stability. However, its rapid curing may pose challenges to construction schedules. This study aimed to optimize the formulations of epoxy asphalt tack coats (EATCs) to enhance the interfacial adhesion and working performance of UTWCs. The adhesion of EATCs was evaluated through rotational viscosity and tensile tests. Design parameters were optimized using analysis of variance and microscopic tests. Road performance was assessed via interlayer shear and tensile testing on three pavement structures. The results indicated that the curing agent strongly influenced the properties and curing kinetics of EATCs. Formulations containing complex polysebacic polyanhydride (CPSPA-EA) exhibited superior bonding while meeting construction schedules. Microscopic analysis of CPSPA-EA revealed a stable crosslinked network formed at 30% binder dosage. The amount of spraying significantly impacted the adhesion in UTWC structures. The optimal spraying amounts were 0.60 kg/m2 for asphalt concrete (AC-13), 0.55 kg/m2 for stone matrix asphalt (SMA-13), and 0.40 kg/m2 for cement concrete substrate layers. These findings presented an optimization framework for designing EATCs to enhance UTWCs working and long-term performance through balanced tack formulations and application parameters.

Selection of highly ethanol productive yeast

Seventy five isolates of Saccharomyces cerevisiae were identified, they were isolated from different local sources which included decayed fruits and vegetables, vinegar, fermented pasta, baker yeast and an alcohol factory. Identification of isolates was carried out by cultural microscopical and biochemical tests. Ethanol sensitivity of the isolates showed that the minimal inhibitory concentration of the isolate (Sy18) was 16% and Lethal concentration was 17%. The isolate (Sy18) was most efficient as ethanol producer 9.36% (v/w). The ideal conditions to produce ethanol from Date syrup by yeast isolate, were evaluated, various temperatures, pH, Brix, incubation period and different levels of (NH4)2HP04. Maximum ethanol produced was 10.32% (v/v). Experimental production of ethanol using continuous methodology with immobilized cells of Saccharomyces cerevisiae showed that this method is superior by producing 5.83 g/L/h in comparison with 1.95 g/l/h produced by batch culture method

Investigation of the aggregation behavior of rubber asphalt components induced by short-term Aging: A perspective from molecular dynamic simulations and microscopic tests

The distribution characteristics of different rubber asphalt components remain a subject of debate, particularly under the influence of asphalt short-term aging. This paper leverages the visualization advantages of molecular dynamics (MD) simulation and integrates them with microscopic testing methods to observe morphological variations and property changes in the aggregation of different components induced by short-term aging. Short-term aging of rubber asphalt is simulated using a thin-film oven test (TFOT). By conducting Fluorescence microscope (FM) and scanning electron microscope (SEM) tests, the aggregation behavior of components under changes in fluorescence phase and microstructure before and after short-term aging is revealed. MD simulation is employed to analyze the degree of aggregation between different components before and after short-term aging. SEM test results indicate that the structure becomes looser and forms distinct pits as the rubber asphalt ages. FM test results reveal that the particle size of rubber powder particles in aged rubber asphalt decreases and aggregates gradually. Concurrently, the asphalt phase in rubber asphalt becomes more uniform after aging. MD simulation results demonstrate significant aggregation between asphaltene-asphaltene molecules and asphaltene-rubber powder molecules in aged rubber asphalt. A higher degree of asphaltene aggregation leads to reduce asphalt penetration and increase softening point and viscosity. Furthermore, rubber powder molecular chains can inhibit “π-π stacking,” and “offset π-π stacking” of the asphaltene molecules. Therefore, the accumulation effect in aged rubber asphalt is mitigated compared with aged base asphalt. The research outcomes provided a foundation for further studies on the aging and rejuvenation of rubber asphalt.

Novel cytotoxicity of nano-coated orthodontic micro-implants: An in vitro study

Objectives: Many attempts have been made to modify the surface of orthodontic micro-implants and prevent the development of microbes by coating them with antimicrobial nanoparticles (NPs). The purpose of the present study was to evaluate the cytotoxicity of different NPs, namely, TiO2 and zinc oxide (ZnO) NPs, that are used to coat titanium orthodontic micro-implants. Material and Methods: Thirty orthodontic micro-implants were included in this study. Those were divided into three groups: control group without coating, TiO2-coated orthodontic micro-implants, and TiO2- and ZnO-coated orthodontic micro-implants. Scanning electron microscope, energy-dispersive spectroscopy (EDS), and cytotoxicity tests were applied for all groups. Results: The results of scanning electron microscopy and EDS showed effective deposition of the titanium oxide layer onto the micro-implants. The ZnO layer applied on the micro-implants exhibited superior physicochemical characteristics in comparison to the uncoated samples with no significant cytotoxicity. Conclusion: Both NPs showed biocompatibility with the oral tissues.

Predicting the Release Mechanism of Amorphous Solid Dispersions: A Combination of Thermodynamic Modeling and In Silico Molecular Simulation

Background: During the dissolution of amorphous solid dispersion (ASD) formulations, the drug load (DL) often impacts the release mechanism and the occurrence of loss of release (LoR). The ASD/water interfacial gel layer and its specific phase behavior in connection with DL strongly dictate the release mechanism and LoR of ASDs, as reported in the literature. Thermodynamically driven liquid-liquid phase separation (LLPS) and/or drug crystallization at the interface are the key phase transformations that drive LoR. Methods: In this study, a combination of Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) thermodynamic modeling and in silico molecular simulation was applied to investigate the release mechanism and the occurrence LoR of an ASD formulation consisting of ritonavir as the active pharmaceutical ingredient (API) and the polymer, polyvinylpyrrolidone-co-vinyl acetate (PVPVA64). A thermodynamically modeled ternary phase diagram of ritonavir (PVPVA64) and water was applied to predict DL-dependent LLPS in the ASD/water interfacial gel layer. Microscopic Erosion Time Testing (METT) was used to experimentally validate the phase diagram predictions. Additionally, in silico molecular simulation was applied to provide further insights into the phase separation, the release mechanism, and aggregation behavior on a molecular level. Results: Thermodynamic modeling, molecular simulation, and experimental results were consistent and complementary, providing evidence that ASD/water interactions and phase separation are essential factors driving the dissolution behavior and LoR at 40 wt% DL of the investigated ritonavir/PVPVA64 ASD system, consistent with previous studies. Conclusions: This study provides insights into the potential of blending thermodynamic modeling, molecular simulation, and experimental research to comprehensively understand ASD formulations. Such a combined approach can be leveraged as a computational framework to gain insights into the ASD dissolution mechanism, thereby facilitating in silico screening, designing, and optimization of formulations with the benefit of significantly reducing the number of experimental tests.