Formation Of Residues Research Articles

Energetic electron irradiations of amorphous and crystalline sulphur-bearing astrochemical ices.

Laboratory experiments have confirmed that the radiolytic decay rate of astrochemical ice analogues is dependent upon the solid phase of the target ice, with some crystalline molecular ices being more radio-resistant than their amorphous counterparts. The degree of radio-resistance exhibited by crystalline ice phases is dependent upon the nature, strength, and extent of the intermolecular interactions that characterise their solid structure. For example, it has been shown that crystalline CH3OH decays at a significantly slower rate when irradiated by 2 keV electrons at 20 K than does the amorphous phase due to the stabilising effect imparted by the presence of an extensive array of strong hydrogen bonds. These results have important consequences for the astrochemistry of interstellar ices and outer Solar System bodies, as they imply that the chemical products arising from the irradiation of amorphous ices (which may include prebiotic molecules relevant to biology) should be more abundant than those arising from similar irradiations of crystalline phases. In this present study, we have extended our work on this subject by performing comparative energetic electron irradiations of the amorphous and crystalline phases of the sulphur-bearing molecules H2S and SO2 at 20 K. We have found evidence for phase-dependent chemistry in both these species, with the radiation-induced exponential decay of amorphous H2S being more rapid than that of the crystalline phase, similar to the effect that has been previously observed for CH3OH. For SO2, two fluence regimes are apparent: a low-fluence regime in which the crystalline ice exhibits a rapid exponential decay while the amorphous ice possibly resists decay, and a high-fluence regime in which both phases undergo slow exponential-like decays. We have discussed our results in the contexts of interstellar and Solar System ice astrochemistry and the formation of sulphur allotropes and residues in these settings.

Analysis of Leakage in a Sustainable Water Pipeline Based on a Magnetic Flux Leakage Technique

Pipelines are typically used to transport oil, natural gas, water, etc. It is one of the most effective methods for transferring fluids over long distances. However, long-term usage of these pipes without maintenance results in the formation of residues, which will pave the way for pipeline accidents and soil contamination. To ensure the safety and protection of resources, these sustainable pipelines need to be inspected to avoid losses. This work aims to investigate various internal defect leaks in the non-uniform thickness of sustainable water pipes that are joined with a pipe expander. The magnetic flux leakage technique was implemented to evaluate these defects by means of a flexible GMR sensor array. An inspection robot containing two units was fabricated with the aid of 3D printing. The power unit provides the necessary thrust to actuate the entire robot whereas the sensing unit is responsible for analyzing the leaks. The robot’s movement is predicted by the MPU6050 and ultrasonic distance sensors that are plotted as motion plots. The sensing unit consists of permanent magnets and a giant magnetoresistance (GMR) array to interrogate the flux leakage in the defect region. The flux leakage from the defects was stored with the help of an Arduino microcontroller, which controls the overall process. In addition, the spring suspension is provided to regulate the motion of the robot. The flux leakage from the defect region was plotted as waveform graphs. Thus, the results are effectively presented and compared. The calculated signal-to-noise ratio (SNR) of the magnetic flux leakages (MFLs) for 4.5 mm-thick pipe defects was 12 to 20.8 dB, and for 6.52 mm-thick pipe defects, it was 9.5 to 19 dB. In sum, the MFL technique provides a reliable method for the sustainable development of water supply to wide areas.

New Insights into the Thermal Stability of 1-Butyl-3-methylimidazolium-Based Ionic Liquids.

One of the most promising applications of ionic liquids (ILs) with 1-butyl-3-methylimidazolium (bmim) cation is based on their unique ability to dissolve and fractionate lignocellulosic biomass, allowing for the development of green biorefining technologies. A complete dissolution of lignocellulose requires prolonged treatment at elevated temperatures, which can cause the partial degradation of ILs. In the present study, a combination of various analytical techniques (GC-MS, HPLC-HRMS, 2D-NMR, synchronous thermal analysis) was used for the comprehensive characterization of bmim acetate, chloride, and methyl sulfate degradation products formed at 150 °C during 6- and 24-h thermal treatment. A number of volatile and non-volatile products, including monomeric and dimeric alkyl substituted imidazoles, alcohols, alkyl amines, methyl and butyl acetates, and N-alkylamides, was identified. By thermal lability, ILs can be arranged in the following sequence, coinciding with the decrease in basicity of the anion: [bmim]OAc > [bmim]Cl > [bmim]MeSO4. The accumulation of thermal degradation products in ILs, in turn, affects their physico-chemical properties and thermal stability, and leads to a decrease in the decomposition temperature, a change in the shape of the thermogravimetric curves, and the formation of carbon residue during pyrolysis.

Effect of Cu2+ on the Laccase-Inducted Formation of Non-Extractable Residues of Tetrabromobisphenol A in Humic Acids.

We used 14C-radiolabelling to study the non-extractable residues (NERs) formation of tetrabromobisphenol A (TBBPA) in a humic acid (HA) suspension under catalysis of laccase in the presence of copper. When entering the suspension after TBBPA adsorbing to HA supramolecular associates, Cu2+ at low concentrations (even without toxicity to laccase) significantly reduced the amount and first-order kinetic constant of the NER formation, while Cu2+ had no significant effect on the formation after it was complexed with HA. The inhibition effect of Cu2+ on the NER formation is explained to be attributed to the prevention of laccase-induced oxidation of TBBPA in the voids of HA associates by complexation of Cu2+ with periphery molecules of the associates. The results provide insights into varying effects of heavy metals on the environmental fate of organic contaminants and suggest that co-existing heavy metals could increase their environmental risk by reducing their NER formation.

Dissipation of a mix of priority PAHs in soils by using availability enhancers. Effect of aging and pollutant interactions.

A remediation strategy using three non-toxic availability enhancers (two cyclodextrins and a rhamnolipid biosurfactant) was applied to various soils artificially contaminated with a mix of Polycyclic Aromatic Hydrocarbons (PAHs) considered priority pollutants at two levels of contamination: only with 7 low molecular weight PAHs (LMW PAHs, 5 with 3-ring and 2 with 4-ring - fluoranthene and pyrene) or with 14 PAHs (from 3 to 6 rings). Natural attenuation of PAHs in all soils showed degradation capacity for the LMW PAHs, with a final content of LMW PAHs <5% of their initial concentration. Conversely, the rest of PAHs (high molecular weight PAHs, HMW) remained in the soils (61% - 83.5%), indicating abiotic dissipation of HMW PAHs due to formation of non-extractable residues in soils. The influence of the presence of HMW PAHs on the degradation of the 7 LMW PAHs was also tested, showing a general decrease in the time to obtain 50% dissipation (DT50), statistically significant for acenaphthene, acenaphthylene and fluorene. Availability enhancers showed different effects on PAHs dissipation. 2-hydroxypropyl-β-cyclodextrin (HP) decreased DT50 of some of the lighter PAHs, whereas the rhamnolipid (RL) caused a slight DT50 increase due to its initial toxicity on native soil microorganisms, but showing later high degradation rate for LMW PAHs. On the contrary, randomly methylated-β-cyclodextrin (RAMEB) slowed down PAHs degradation due to its high adsorption onto soil surface, blocking the desorption of PAHs from the soils. The high number of experimental factors not studied simultaneously before (soil type, co-contamination, availability enhancers and incubation time) allowed to conduct a statistical analysis which supported the conclusions reached. Principal Component Analysis separated the studied PAHs in 3 groups, in relation with their molecular weight and Kow. The first principal component was related with LMW PAHs, and separate the inefficient RAMEB from the other availability enhancers.

Fate of 14C-labelled ionic organic chemicals in a water-sediment system and surface water.

The persistence assessment of organic chemicals is based on neutral reference substances. Therefore, our study aimed at investigating the influence of a chemical charge on the degradation of organic compounds in a water-sediment system (OECD 308) and surface water (OECD 309). We used radiolabelled 4-n-dodecylbenzenesulfonic acid sodium salt (14C-DS-, anionic), 4-n-dodecylbenzyltrimethylammonium chloride (14C-DA+, cationic) and 4-n-dodecylphenol (14C-DP, non-ionic) which are structurally similar except their charges. After 120 days of incubation in a water-sediment system, 68% (14C-DS-), 6% (14C-DA+) and 63% (14C-DP) of the applied radioactivity (AR) were mineralized. The formation of non-extractable residues (NER) after 120 days was highest for 14C-DA+ (33% AR), followed by 14C-DS- (19% AR) and 14C-DP (14% AR). Dissipation half-lives (DT50) at 12°C decreased as follows: 14C-DA+ (346 days) ≫ 14C-DS- (47 days)>14C-DP (30 days). After 60 days of incubation in surface water with suspended sediment, mineralization of 14C-DS-, 14C-DA+ and 14C-DP accounted for 63%, 7% and 58% AR, respectively. Highest NER formation was observed for 14C-DP (21% AR), followed by 14C-DA+ (14% AR) and 14C-DS- (9% AR). DT50 (12°C) decreased as follows: 14C-DA+ (45 days)>14C-DP (3 days)>14C-DS- (2 days). We showed that a positive charge reduces the degradability of organic chemicals in both test systems. From a scientific point of view, simulation studies following OECD 309 should always be complimented by tests with high sorption capacity, e.g. OECD 308 and OECD 307 tests in order to assess the degradation of a compound, especially in case of cationic organic compounds.

Temperature sensitivity of dark CO2 fixation in temperate forest soils

Abstract. Globally, soil temperature to 1 m depth is predicted to be up to 4 ∘C warmer by the end of this century, with pronounced effects expected in temperate forest regions. Increased soil temperatures will potentially increase the release of carbon dioxide (CO2) from temperate forest soils, resulting in important positive feedback on climate change. Dark CO2 fixation by microbes can recycle some of the released soil CO2, and CO2 fixation rates are reported to increase under higher temperatures. However, research on the influence of temperature on dark CO2 fixation rates, particularly in comparison to the temperature sensitivity of respiration in soils of temperate forest regions, is missing. To determine the temperature sensitivity (Q10) of dark CO2 fixation and respiration rates, we investigated soil profiles to 1 m depth from beech (deciduous) and spruce (coniferous) forest plots of the Hummelshain forest, Germany. We used 13C-CO2 labelling and incubations of soils at 4 and 14 ∘C to determine CO2 fixation and net soil respiration rates and derived the Q10 values for both processes with depth. The average Q10 for dark CO2 fixation rates normalized to soil dry weight was 2.07 for beech and spruce profiles, and this was lower than the measured average Q10 of net soil respiration rates with ∼2.98. Assuming these Q10 values, we extrapolated that net soil respiration might increase 1.16 times more than CO2 fixation under a projected 4 ∘C warming. In the beech soil, a proportionally larger fraction of the label CO2 was fixed into soil organic carbon than into microbial biomass compared to the spruce soil. This suggests a primarily higher rate of microbial residue formation (i.e. turnover as necromass or release of extracellular products). Despite a similar abundance of the total bacterial community in the beech and spruce soils, the beech soil also had a lower abundance of autotrophs, implying a higher proportion of heterotrophs when compared to the spruce soil; hence this might partly explain the higher rate of microbial residue formation in the beech soil. Furthermore, higher temperatures in general lead to higher microbial residues formed in both soils. Our findings suggest that in temperate forest soils, CO2 fixation might be less responsive to future warming than net soil respiration and could likely recycle less CO2 respired from temperate forest soils in the future than it does now.

A ribosomally synthesised and post-translationally modified peptide containing a β-enamino acid and a macrocyclic motif

Ribosomally synthesized and post-translationally modified peptides (RiPPs) are structurally complex natural products with diverse bioactivities. Here we report discovery of a RiPP, kintamdin, for which the structure is determined through spectroscopy, spectrometry and genomic analysis to feature a bis-thioether macrocyclic ring and a β-enamino acid residue. Biosynthetic investigation demonstrated that its pathway relies on four dedicated proteins: phosphotransferase KinD, Lyase KinC, kinase homolog KinH and flavoprotein KinI, which share low homologues to enzymes known in other RiPP biosynthesis. During the posttranslational modifications, KinCD is responsible for the formation of the characteristic dehydroamino acid residues including the β-enamino acid residue, followed by oxidative decarboxylation on the C-terminal Cys and subsequent cyclization to provide the bis-thioether ring moiety mediated by coordinated action of KinH and KinI. Finally, conserved genomic investigation allows further identification of two kintamdin-like peptides among the kin-like BGCs, suggesting the occurrence of RiPPs from actinobacteria.

The effect of added organic matter on the soil formation of oil-based drill cutting pyrolysis residue.

In order to explore the effects of added organic matters on the soil formation process of oil-based drill cutting pyrolysis residue, two experiment groups (pure and adding) were studied to indicate the soil microbial community and the function of nitrogen cycling. Samples were collected in the third and fourth years based on the plant growth. The 16S rRNA high-throughput sequencing technology and PICRUSt were used to study microbial communities and the function of nitrogen cycling. The results showed that MND1 (2.5-4.5%), Sphingomonas (1.4-2.4%), and other typical oil-degrading bacteria were discovered. The diversity of the microbial community decreased with the duration of the experiment. However, it was higher than that of the background soil. The relative abundance of microbial nitrogen dissimilation reduction (0.9-1.0‰) was the highest among the two experiment groups and the background soil. The second and third were denitrification and nitrogen fixation. Nitrification gene abundance was the lowest among the five main steps of nitrogen cycling. The addition of organic matters could improve soil formation of pyrolysis residues. This study provides scientific data for pyrolysis residue to restore soil functions.

Simple ultrasonic-assisted clean graphene transfer

Clean graphene transfer has received widespread research attention, where most methods are focused on cleaning the upper surface of graphene to improve the transfer technique. However, the residue formation on the bottom surface of graphene is also inevitable; therefore, cleaning the bottom surface is crucial. In this study, we proposed an improved graphene wet transfer method using an ultrasonic processing (UP) step for etching copper (Cu). Using this method, the bottom surface can be cleaned efficiently. The results of atomic force microscopy (AFM) and Raman spectroscopy mapping revealed that the graphene films transferred with UP had smoother and cleaner surfaces, less contamination, and higher quality than those transferred without UP.

Deep eutectic solvents: green solvents for the removal of degraded gelatin on cellulose nitrate cinematographic films

Cellulose nitrate (CN) has been used in the past as support for photographic negatives and cinematographic films. This material is particularly unstable and can undergoes severe degradation due to thermal, photocatalytic and hydrolytic loss of nitro groups from the lateral chain. Thus, to prevent the disappearance of the movies, their scanning and digitalization become a priority.However, CN bases degradation may prevent the scanning of the films. The decrease in pH, for instance, lowers the viscosity of gelatin, which becomes softer. This causes the formation of gelatin residues which stick on the back of the superimposed frames inside the reels creating a deposit.Traditional approaches to clean gelatin residues from the surface of CN bases include the mechanical removal with scalpels and the use of organic solvents (such as isopropyl alcohol). However, these methods are either slow and ineffective or could potentially damage the degraded CN supports.To overcome these drawbacks, we have evaluated the performance of three choline chloride and betaine-based Deep Eutectic Solvent (DES) formulations as alternative for the removal of gelatine residues from CN supports. These solvents are inexpensive (when compared to traditional solvents), easy to prepare, green (non volatile, safe towards the operators and the environment, and potentially recyclable), non flammable and have been previously proposed for the extraction of proteinaceous materials, but their use for the restoration of photographic negatives or cinematographic films has not been reported yet.Selected areas over the frames of a real deteriorated CN cinematographic film were cleaned comparing the DES performances with the ones obtained using isopropyl alcohol as an example of a traditional method.In particular, the tested DES formulations showed superior cleaning power compared to isopropyl alcohol and, at the selected application times, resulted capable to remove the gelatin residues without affecting the CN film supports.Graphical abstract

Quantum chemical hydrogenolysis strategy for elimination of heteroatoms in biomass homologous organic compounds based on oxolane and thiolane

Bio-oils obtained from biomass contain heteroatoms compounds, like oxolane and thiolane. It is quite difficult for industrialist to purify such refractory bio-oils. One of the efficient strategies for the elimination of heteroatoms is hydrogenolysis process, which results in the formation of H2O and H2S residues as by-products. In this work, quantum chemical studies have been used to analyse the reaction mechanism for the removal of hetero atoms (S and O) as H2O and H2S. We selected B3LYP functional of DFT with Pople's basis set 6-311G(d,p) for computing the hydrogenolysis steps without catalyst. LANL2DZ basis set, is used for studying hydrogenolysis steps involving AlCl3 and WS3H3+ as catalysts. All the reactions are analysed at the temperature of 600 K and pressure of 40 bars. Structural, thermodynamic, kinetic properties have been employed to study this process. The analysis of variations parameters during the hydrogenolysis process reveals that these two organic biomass compounds undergo sequential ring opening at C-X (X = O, S) bonds. Butanol and Butanethiol are obtained as a result of first hydrogenolysis process, and these compounds are converted to butane during second catalytic process while eliminating heteroatoms.

Process Considerations for selective doping of poly-Si thin films with spin-on dopants and nickel silicide formation for planar thermoelectric devices

The formation of highly doped p-type (boron-doped) and n-type (phosphorus-doped) poly-Si thin films with spin-on dopants on the same wafer poses unique challenges. This work evaluates the pros and cons of different approaches to dopant diffusion, residue removal, and diffusion mask selection when working with spin-on dopants. The experiments have been carried out to optimize the formation of highly doped poly-Si thin films that will form the active layers of a micro-thermoelectric generator (μ-TEG). Building upon previous work on residue removal methods, we report that the residue formation is also dependent on the oxide-silicon surface with a PECVD oxide-Si interface not requiring a post-dopant diffusion nitric acid treatment to achieve a hydrophobic surface. Furthermore, comparing the direct dispense and proximity diffusion methods verifies the existing reports of enhanced diffusion in the latter case. Besides, we observe that doping first with Boron is more conducive than doping first with phosphorus to reduce sheet resistance. We also optimize the contact formation with Ti/Ni thin films and report the mean contact resistivity. Notably, contact annealing precludes the nitric acid treatment requirement even if the surface is hydrophilic after removing dopant residue. Additionally, the sequence of silicidation is observed to be dependent on the doping of the underlying areas.

Biobased coating derived from fish scale protein and phytic acid for flame-retardant cotton fabrics

The nitrogen-phosphorus flame-retardant coating was formed on the surface of cotton fabrics via strong electrostatic attraction and hydrogen bonds with layer-by-layer coating of protein extracted from fishery waste fish scales and phytic acid (PA) derived from plant seeds. The flame retardant property of the coated cotton fabrics demonstrated a significant improvement with a limiting oxygen index of 31.1%, meeting the flame retardant requirements of commercial fire-protection suit. Especially, noteworthy, due to the synergistic smoke suppression effect of fish scale protein and phytic acid, the total smoke emission was greatly reduced by 139%. Meanwhile, the charring of the cotton fabrics treated with FSP and PA was significantly enhanced. Scanning electron microscopy and Raman results of the residual char further reveal that the treatment of the combined coating facilitates the formation of dense and regular graphitized char residue during combustion or under high temperature. This waste-sourced, biomass-derived coating paves a new way towards sustainable flame-retardant fabrics and has great significance in civil, military, and industrial fields.

Removal of dye pollution by an oxidase derived from mutagenesis of the Deuteromycete Myrothecium with high potential in industrial applications

It is estimated that over 700,000 tons of synthetic dyes are produced annually, 15% of which are emitted as effluents. These highly stable dyes enter the world water ecosystems and stay in the environment, and eventually cause adverse impacts to the environment. Current wastewater treatment methods, such as filtration, coagulation, and chemical oxidation, have sideeffects, including toxic residue formation, membrane fouling, bioaccumulation, and secondary pollutant formation. Given the issues mentioned, it is necessary to study how to improve the degradation of synthetic dye with a cost-effective and ecofriendly approach. Natural oxidation provides a greener option. Recently, Deuteromycetes fungus Myrothecium verrucaria G-1 (M. verrucaria G-1) has shown great potential in producing high level of dye oxidase. This study aims to generate a dye oxidase hyperproducer, 3H6 from M. verrucaria G-1 by using atmospheric and room temperature plasma (ARTP) coupled with ultraviolet (UV) irradiation. This method increases oxidase production by nearly 106.15%. After a simple precipitation and dialysis, this mutant oxidase increases by 1.97-fold in a specific activity with dye degradation rates at 70% for Mmethylene blue (MB) and 85% for Congo red (CR). It is found that the genetic stability of 3H6 remains active for ten generations. The size of oxidase is 65 kDa, and optimum temperature for reaction is 30 °C with 4.5 pH. This study presents that the first combined mutagenesis approach by ARPT-UV on fungus species generates an impressive increment of acid dye oxidases production. As such, this method presents a cost-effective alternative to mitigate hazardous dye pollution.

A novel strategy to improve the flame retardancy and electrical conductivity of polymethyl methacrylate by controlling the configuration of phosphorus-containing polyaniline@needle coke with magnetic field

Currently, it is still a challenge to endow polymethyl methacrylate (PMMA) with excellent electroconductivity and fire safety. In this work, we have designed a novel hybrid aiming to achieve the flame resistance and electrical conductive of PMMA by fabricating an ordered structure of the FR-PANI@Fe3O4@NC. Employing a magnetic field, the FR-PANI@Fe3O4@NC hybrid shows a beneficial configuration structure to reduce the electrical resistivity of 8.9 kΩ·cm−1 for the PMMA composite by controlling the added volume at 20 wt%. Moreover, the PMMA composite exhibits conspicuous fire resistance with an LOI of 27.4% and a V-0 rating in the UL-94 tests. Simultaneously, combined with the regular configuration structure of FR-PANI@Fe3O4@NC hybrid, the thermal stability and fire behaviour of the PMMA composite has been improved by the plentiful char residue formation. The flame-retardant mechanism of FR-PANI@Fe3O4@NC hybrid in PMMA material has been deduced by TG-IR, FTIR, and SEM, and the results implied that the FR-PANI@Fe3O4@NC hybrid containing abundant P-N functional groups generates phosphorus-containing compounds to promote the dehydration reaction of the PMMA matrix in a condensed phase. This is beneficial to improve the flame retardancy of PMMA by the formation of a char layer, providing the shielding effect to prevent the heat transfer and flammable micro-molecules volatilisation process. Hence, the as-exploited FR-PANI@Fe3O4@NC hybrid herein is believed to expand the range of applications of PMMA materials in the advanced material field.

Magnolol-derived thiol-ene photo-polymerized membranes with intrinsic anti-flammability and high transparency

In this study, a phosphorus-containing bio-based monomer (MBDPP) was first synthesized from renewable magnolol, and subsequently photo-cured with tri-thiol (TPTMP) or tetra-thiol (PETMP) monomers via thiol–ene polymerization. The synthesized MBDPP/TPTMP and MBDPP/PETMP membranes exhibited high char residues at 700 °C in the TGA tests, which were 19.8 wt% and 24.2 wt% for nitrogen while 16.5 wt% and 20.2 wt% for air, respectively, indicating superior charring capacity of both membranes. DMA results indicated that both the higher stiffness and the Tg of the cured MBDPP/PETMP membrane was ascribed to its higher cross-linking density than that of the cured MBDPP/TPTMP owing to the tetra-functional groups of PETMP. In the open flame test, both MBDPP/TPTMP and MBDPP/PETMP membranes self-extinguished immediately when removing the flame source, manifesting excellent intrinsic anti-flammability. The cone calorimeter results further demonstrated that MBDPP/TPTMP and MBDPP/PETMP membranes showed lower PHRR (419 and 388 kW/m2, respectively) and THR (41.38 and 38.98 MJ/m2, respectively) values than most of the thiol-ene photo-polymerized counterparts previously reported. The excellent anti-flammability of MBDPP/TPTMP and MBDPP/PETMP membranes originated from the formation of expandable char residues that played an efficient role in hampering the transfer of flammable pyrolysis products to flame zone as well as insulating the heat irradiation during combustion. Additionally, both MBDPP/TPTMP and MBDPP/PETMP membranes showed excellent transparency (transmittance >85% in the visible region) and flexibility (breaking elongation around 40%). Taking the intrinsic anti-flammability, exceptional transparency and high flexibility into account, the MBDPP/TPTMP and MBDPP/PETMP systems are suitable as intumescent flame retardant coating materials.

Preparation and thermal properties of a novel DOPO‐based Schiff base derivative as a flame retardant for polystyrene

AbstractWe synthesized an acrylic acid 4‐[(10‐oxo‐10H‐9‐oxa‐10λ5‐phospaphenanthren‐10‐yl)‐phenylamino‐methyl]‐phenyl ester (DOPO‐AC), a novel Schiff base derivative based on 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide, and evaluated its utility as a flame retardant for polystyrene (PS). The synthesized DOPO‐AC was characterized by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance spectroscopy, and high‐resolution mass spectrometry. The reactive vinyl groups of DOPO‐AC further copolymerized with styrene to produce PS/DOPO‐AC. Thermogravimetric analysis showed that DOPO‐AC could clearly improve the char residue formation. By comparing the data of T5% and T10%, it was found that the thermal stability of the PS/DOPO‐AC copolymer was reduced. We investigated the influence of DOPO‐AC on the flame retardancy of PS by determining limiting oxygen indexes, conducting vertical burning tests (UL‐94), and carrying out thermogravimetry combined with differential thermal analysis. These results revealed that PS containing 5 wt% DOPO‐AC had a UL‐94V‐0 rating and a limiting oxygen index of 29.6%. Residues of PS/DOPO‐AC copolymer after the UL‐94V tests were analyzed by scanning electron microscopy, X‐ray photoelectron spectroscopy, and FTIR spectroscopy; and the results allowed us to propose a flame retardant mechanism for PS/DOPO‐AC copolymer. Taken together, our results prove that DOPO‐AC is an effective flame retardant for PS.

Mitochondrial rRNA Methylation by Mettl15 Contributes to the Exercise and Learning Capability in Mice.

Mitochondrial translation is a unique relic of the symbiotic origin of the organelle. Alterations of its components cause a number of severe human diseases. Hereby we report a study of mice devoid of Mettl15 mitochondrial 12S rRNA methyltransferase, responsible for the formation of m4C839 residue (human numbering). Homozygous Mettl15−/− mice appeared to be viable in contrast to other mitochondrial rRNA methyltransferase knockouts reported earlier. The phenotype of Mettl15−/− mice is much milder than that of other mutants of mitochondrial translation apparatus. In agreement with the results obtained earlier for cell cultures with an inactivated Mettl15 gene, we observed accumulation of the RbfA factor, normally associated with the precursor of the 28S subunit, in the 55S mitochondrial ribosome fraction of knockout mice. A lack of Mettl15 leads to a lower blood glucose level after physical exercise relative to that of the wild-type mice. Mettl15−/− mice demonstrated suboptimal muscle performance and lower levels of Cox3 protein synthesized by mitoribosomes in the oxidative soleus muscles. Additionally, we detected decreased learning capabilities in the Mettl15−/− knockout mice in the tests with both positive and negative reinforcement. Such properties make Mettl15−/− knockout mice a suitable model for mild mitochondriopathies.

Molecular Docking and Interaction Analysis of Propolis Compounds Against SARS-CoV-2 Receptor

Background: For many people, especially in developing countries, herbal medicine is the most traditional drug choice to treat all diseases including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2 infection). Propolis is one of the popular herbal medicine which has various health benefits, particularly antiviral activity. In this molecular docking study, this investigation examined twenty-five kinds of propolis to bind SARS-CoV-2 protein with the main targets of ACE-2 and M-Pro receptors. Method: Propolis ligands were downloaded from PubChem, meanwhile ACE-2 and M-Pro receptors were downloaded from Protein Data Bank. Both ligands and targets were optimized by Pymol. The pharmacokinetic analysis was conducted using SwissADME. Molecular docking was done using PyRx 0.9 and its binding interaction was visualized by Discovery Studio. To predict the potential inhibition, this study compared the ligand-protein complex of propolis to ligands from the previous study. Result: Through the Lipinski rule, only five of twenty-five types of propolis were not qualified for the criterion. The ability to bind protein targets were various between ligands, the highest affinity to ACE-2 receptors were abietic acid, galangin, chrysin, kaempferol and acacetin, respectively. The binding affinity between ligand and M-Pro were seen weaker than ACE-2 receptor, while the strongest were kaempferol, abietic acid, acacetin, galangin and chrysin, respectively. Conclusion: Â Kaempferol is the most potent form of propolis to bind to ACE-2 and M-Pro receptors by assessing the binding affinity and the amount of amino acid residue formation when compared to control ligands. Keywords: ACE-2 receptor, COVID-19, Main protease, Molecular docking, Propolis, SARS-CoV-2