Course Of Decomposition Research Articles

Synthesis of MoS2@MoO3/(Cu+/g-C3N4) ternary composites with double S-scheme heterojunction for peroxymonosulfate activation exposing to visible light

The construction of semiconductor heterojunction is an effective way for charge separation in photocatalytic degradation of pollutants. In this study, a novel MoS2@MoO3/(Cu+/g-C3N4) ternary composites (MMCCN) was prepared via a simple calcination method. The as-prepared composites exhibited exceptional performance in activating peroxymonosulfate (PMS) for the degradation of rhodamine B (RhB). The activity testing results indicated that 99.41 % of RhB (10 mg·L−1, 10 mL) was effectively removed by the synergistic effect of composites photocatalyst (0.1 g·L−1) and PMS (0.1 g·L−1) under visible light irradiation for 40 min. Its reaction rate constant exceeded that of Cu+/g-C3N4, MoO3 and MoS2 by a factor of 3.56, 17.30 and 11.73 times, respectively. The crystal structure, band gap and density of states (DOS) of the semiconductors were calculated according to the density functional theory (DFT). Free radical trapping tests and electron spin resonance spectroscopy validated that 1O2, O2− and h+ are primary reactive species participating in the decomposition of RhB. The ternary composites demonstrated good stability and maintained excellent degradation efficiency even across four reaction cycles. Furthermore, the activation mechanism and the intermediates produced during the decomposition course of RhB by MMCCN/PMS/vis system were analyzed and elucidated. A double S-scheme heterojunctions was responsible for efficient separation of photo-induced electron-hole pairs. This work presents a novel method in the construction of double S-scheme heterojunctions for PMS activation which is expected to find wide applications in wastewater treatment and environmental remediation.

Studies on the Thermal Decomposition Course of Nitrogen-Rich Heterocyclic Esters as Potential Drug Candidates and Evaluation of Their Thermal Stability and Properties.

Drug candidates must undergo thermal evaluation as early as possible in the preclinical phase of drug development because undesirable changes in their structure and physicochemical properties may result in decreased pharmacological activity or enhanced toxicity. Hence, the detailed evaluation of nitrogen-rich heterocyclic esters as potential drug candidates, i.e., imidazolidinoannelated triazinylformic acid ethyl esters 1-3 (where R1 = 4-CH3 or 4-OCH3 or 4-Cl, and R2 = -COOC2H5) and imidazolidinoannelated triazinylacetic acid methyl esters 4-6 (where R1 = 4-CH3 or 4-OCH3 or 4-Cl, and R2 = -CH2COOCH3)-in terms of their melting points, melting enthalpy values, thermal stabilities, pyrolysis, and oxidative decomposition course-has been carried out, using the simultaneous thermal analysis methods (TG/DTG/DSC) coupled with spectroscopic techniques (FTIR and QMS). It was found that the melting process (documented as one sharp peak related to the solid-liquid phase transition) of the investigated esters proceeded without their thermal decomposition. It was confirmed that the melting points of the tested compounds increased in relation to R1 and R2 as follows: 2 (R1 = 4-OCH3; R2 = -COOC2H5) < 6 (R1 = 4-Cl; R2 = -CH2COOCH3) < 5 (R1 = 4-OCH3; R2 = -CH2COOCH3) < 3 (R1 = 4-Cl; R2 = -COOC2H5) < 1 (R1 = 4-CH3; R2 = -COOC2H5) < 4 (R1 = 4-CH3; R2 = -CH2COOCH3). All polynitrogenated heterocyclic esters proved to be thermally stable up to 250 °C in inert and oxidising conditions, although 1-3 were characterised by higher thermal stability compared to 4-6. The results confirmed that both the pyrolysis and the oxidative decomposition of heterocyclic ethyl formates/methyl acetates with para-substitutions at the phenyl moiety proceed according to the radical mechanism. In inert conditions, the pyrolysis process of the studied molecules occurred with the homolytic breaking of the C-C, C-N, and C-O bonds. This led to the emission of alcohol (ethanol in the case of 1-3 or methanol in the case of 4-6), NH3, HCN, HNCO, aldehydes, CO2, CH4, HCl, aromatics, and H2O. In turn, in the presence of air, cleavage of the C-C, C-N, and C-O bonds connected with some oxidation and combustion processes took place. This led to the emission of the corresponding alcohol depending on the analysed class of heterocyclic esters, NH3, HCN, HNCO, aldehydes, N2, NO/NO2, CO, CO2, HCl, aromatics, and H2O. Additionally, after some biological tests, it was proven that all nitrogen-rich heterocyclic esters-as potential drug candidates-are safe for erythrocytes, and some of them are able to protect red blood cells from oxidative stress-induced damage.

Litter consumption by macrodetritivores depends more on mechanical than on nutritional constraints

Ecosystem functions greatly depend on trophic interactions between consumers and their resources. Resource consumption depends on ingestion, digestion, and allocation processes. Mechanical constraints are expected to influence ingestion, while metabolic and nutritional constraints are expected to influence allocation. Leaf litter are resources presenting a high mechanical and nutritional heterogeneity that depends on plant identity and on physical and microbial processing over the course of decomposition. Litter consumption by detritivores is known to depend on metabolic and nutritional constraints but the importance of mechanical constraints is yet unknown. After accounting for metabolic constraints on consumption rate, we tested the relative importance of mechanical and nutritional constraints in explaining litter consumption rates by detritivores. For this, we exposed 16 leaf treatments (eight leaf species either just leached or leached and microbially conditioned) to four aquatic and five terrestrial detritivore taxa in laboratory no‐choice consumption experiments. We investigated two mechanical constraints: grabbing and fragmenting the resource, by measuring suitable couples of mechanical traits for both litter and detritivores. We also investigated four nutritional constraints related to N, P, K and Ca contents in both detritivores and litter. For each constraint, we also tested if trait matching significantly contribute to explain consumption. Our analysis revealed that both mechanical and nutritional constraints are influencing mass‐independent consumption rate but that mechanical constraints predominate over nutritional constraints. Litter fragmentation, studied through litter toughness and detritivore biting force, was especially important to explain consumption rate. Nutritional constraints were dominated by P constraints. Trait‐matching had very weak importance and was significant only for P constraints. Our findings highlight the importance of mechanical constraints for litter consumption by detritivores.

Variation in the contribution of macroinvertebrates to wood decomposition as it progresses

AbstractAlthough necromass decay rates are limited by the slowest portions to decompose, most decomposition studies examine only the earliest stage of decay. As such, these studies run the risk of yielding misleading results regarding the relative contributions of different decomposers. For example, the contributions of macroinvertebrates to wood decomposition remain mostly unknown beyond the first 50% of mass lost, despite drastic changes in substrate conditions over time. We sought to clarify how the macroinvertebrate contribution to decay changes over the course of wood decomposition in the Southeastern United States—a region with a long history of wood decomposition research. To this end, we (1) compiled data from published studies comparing wood decay with and without macroinvertebrates; and (2) conducted a field study assessing wood mass loss, with and without macroinvertebrate access, at three sites across the region over four years. With these combined data, we analyzed macroinvertebrate contribution as decay progressed, revealing a quadratic relationship, wherein macroinvertebrate contribution increased early in decomposition and then began to decline as decay progressed. Strong local site effects, particularly the abundance and activity of termites, determine the time required for wood to reach this point of mass loss.

Application of Simultaneous and Coupled Thermal Analysis Techniques in Studies on the Melting Process, Course of Pyrolysis and Oxidative Decomposition of Fused Triazinylacetohydrazides.

The effect of the structure of promising antioxidant agents with prospective medical use, i.e., unsubstituted and para-substituted annelated triazinylacetic acid hydrazides, on their melting points, thermal stabilities, pyrolysis and oxidative decomposition stages and the type of volatiles emitted under heating with the use of DSC and TG/DTG/FTIR/QMS methods was evaluated and discussed. The melting point of the investigated compounds increased with an enhanced number of electrons (directly correlated with their molecular weight). Melting enthalpy values were determined and presented for all the studied compounds. The pyrolysis and oxidative decomposition processes of the analysed molecules consisted of several poorly separated stages, which indicated a multi-step course of the decomposition reactions. It was found that the thermal stability of the tested compounds depended on the type of substituent at the para position of the phenyl moiety or its absence. In both atmospheres used (air and helium), the thermal stability increased in relation to R as follows: -CH3 ≤ -OCH3 < -H < -OC2H5. In an inert atmosphere, it was higher by approx. 8-18 °C than in an oxidative atmosphere. The pyrolysis was connected with the emission of NH3, HCN, HNCO, HCONH2, HCHO, CO2, CO and H2O in the case of all the tested compounds, regardless of the substituent attached. In the case of the derivative containing the para-CH3 group, para-toluidine was an additional emitted aromatic product. In turn, emissions of aniline and alcohol (methanol or ethanol) for compounds with the para-OCH3 and para-OC2H5 groups, respectively, were confirmed. In oxidative conditions, the release of NH3, NO, HCN, HNCO, HCONH2, CO2, H2O and cyanogen (for all the compounds) and para-toluidine (for the para-CH3 derivative), aniline (for para-OCH3, para-OC2H5 and unsubstituted derivatives) and acetaldehyde (for the para-OC2H5 derivative) were clearly observed. No alcohol emissions were recorded for either compound containing the para-OCH3- or para-OC2H5-substitututed phenyl ring. These results confirmed that the pyrolysis and oxidative decomposition of the investigated annelated triazinylacetohydrazides occurred according to the radical mechanism. Moreover, in the presence of oxygen, the reactions of volatiles and residues with oxygen (oxidation) and the combustion process additionally proceeded.

Seasonal mouse cadaver microbial study: rupture time and postmortem interval estimation model construction.

The estimation of postmortem interval (PMI) has long been a focal point in the field of forensic science. Following the death of an organism, microorganisms exhibit a clock-like proliferation pattern during the course of cadaver decomposition, forming the foundation for utilizing microbiology in PMI estimation. The establishment of PMI estimation models based on datasets from different seasons is of great practical significance. In this experiment, we conducted microbiota sequencing and analysis on gravesoil and mouse intestinal contents collected during both the winter and summer seasons and constructed a PMI estimation model using the Random Forest algorithm. The results showed that the MAE of the gut microbiota model in summer was 0.47±0.26 d, R2 = 0.991, and the MAE of the gravesoil model in winter was 1.04 ± 0.22d, R2 = 0.998. We propose that, in practical applications, it is advantageous to selectively build PMI estimation models based on seasonal variations. Additionally, through a combination of morphological observations, gravesoil microbiota sequencing results, and soil physicochemical data, we identified the time of cadaveric rupture for mouse cadavers, occurring at around days 24-27 in winter and days 6-9 in summer. This study not only confirms previous research findings but also introduces novel insights, contributing to the foundational knowledge necessary to advance the utilization of microbiota for PMI estimation.

INTERACTION OF THIOUREA DIOXIDE WITH n-BUTYLAMINE

The influence of n-butylamine on the stability and reducing activity of thiourea dioxide (TDO, aminoiminomethanesulfinic acid, formamidinesulfinic acid) in the reaction with azo dye Orange II has been studied. The addition of an excess of n-butylamine leads to the increase in reducing activity of thiourea dioxide in the reaction with the azo dye Orange II in strongly alkaline solutions, whereas the stability of thiourea dioxide decreases under these conditions. It has been shown that with an excess of n-butylamine, N,N'-di-n-butylthiourea dioxide is formed. N-n-butylthiourea dioxide was synthesized and isolated in the solid state as a product of the reaction of thiourea dioxide with n-butylamine in an acidic medium (pH 5) at a molar ratio of reagents 1:1. This compound was characterized by IR, 1Н and 13С NMR spectroscopy. N-n-butylthiourea dioxide has a higher solubility in water than the thiourea dioxide, but lower reducing activity in the reaction with azo dye Orange II in the range of pH 6.9–11.8. The formation of active reducing agent sulfoxylate in course of TDO decomposition leads to its high reducing activity in alkaline aqueous solutions. It has been shown that the rates of decomposition of the studied compounds increase with increasing pH. It has been established that N-n-butylthiourea dioxide is more stable in alkaline media than thiourea dioxide. Based on the previous data and data obtained in this work the following sequence of reducing activity of thioureas dioxides in strongly alkaline media was proposed: N,N'-dialkylthiourea dioxides &gt; thiourea dioxide &gt; N-alkylthiourea dioxides. The stability of thiourea dioxides in strongly alkaline aqueous solutions increases in reverse order.

Searching for Optimal Measurement Parameters by Thermogravimetry for Determining the Degree of Modification of Thermally Modified Wood

When wood is thermally modified, several chemical reactions take place that change the chemical and physical properties of the wood. These changes correlate with the degree of modification, which is mostly a function of the temperature and duration of modification, and consequently with the mass loss during this process. There is a lack of standardised quality control to verify the degree of heat treatment of wood and thus its quality. One of the possible methods to check the degree of thermal modification of a particular type of wood is thermogravimetry (TG). It is based on the assumption that processes that did not take place during thermal modification continue when the TG experiment is carried out. In this method, calibration curves have to be established based on TG measurements of standard samples that have been thermally modified at different temperatures and whose mass loss during modification is known. The calibration curves show the mass loss during the TG measurement as a function of the mass loss during the previous thermal modification. The course of thermal decomposition during the TG measurements is influenced by many parameters, such as the mass of the sample, the heating rate, the atmosphere in which the measurement takes place, and the shape of the crucible in which the sample is placed. In this paper, the influence of these parameters on the calibration curves was investigated. We have focused on oak wood. The best parameters result in a calibration curve with the largest correlation coefficient R2 and the highest slope of the line k. On this basis, we can determine the mass loss during the thermal modification of unknown samples of the same wood species under the same measurement conditions.

New Mechanistic Insights into the Primary Thermolysis Reactions of 1,3,4,6-Tetranitrooctahydroimidazo-[4,5-d]imidazole (BCHMX) from Predictive Local Coupled Cluster Calculations.

Theoretical studies of the decomposition mechanism of energetic materials quite often scrutinize only the primary thermolysis reactions. However, the secondary reactions are crucial, inter alia, for proper building of the combustion models and understanding the autocatalytic processes. In the present study, we applied predictive DLPNO-CCSD(T) calculations to elucidate the kinetics and decomposition mechanism of a novel promising energetic material, 1,3,4,6-tetranitrooctahydroimidazo [4,5-d] imidazole (BCHMX). We identified eight previously unknown BCHMX conformers, both cis and trans in accordance to the spatial position of the H atoms bonded to a carbon bridge. Among them, the relative enthalpies of cis isomers lie in the narrow range ∼10 kJ mol-1 rendering them thermally accessible in the course of decomposition. The radical N-NO2 bond cleavage via one of the novel conformers is the dominant primary decomposition channel of BCHMX with the kinetic parameters Ea = 168.4 kJ mol-1 and log(A, s-1) = 18.5. We also resolved several contradictory assumptions on the mechanism and key intermediates of BCHMX thermolysis. To get a deeper understanding of the decomposition mechanism, we examined a series of unimolecular and bimolecular secondary channels of BCHMX. Among the former reactions, the C-C bond unzipping followed by another radical elimination of a nitro group is the most energetically favorable pathway with an activation barrier ∼113 kJ mol-1. However, contrary to the literature assumptions, the bimolecular H atom abstraction from a pristine BCHMX molecule by a primary nitramine radical product, not the nitro one, followed by another NO2 radical elimination, is the most important bimolecular secondary thermolysis reaction of BCHMX at lower temperatures. The isokinetic temperature of the bimolecular and unimolecular secondary reactions is ∼620 K. Unimolecular reactions might be important in dilute solutions, where bimolecular reactions are suppressed. The secondary reactions considered in the present work might be pertinent in the case of related energetic nitramines (e.g., RDX, HMX, and CL-20).

Changes in composition and structure of nitrogenous bases of resin components of heavy oil from the Nurlatskoe oilfield in the course of thermal decomposition

The relevance. The need to obtain information on heat treatment effect on composition and structure of nitrogenous bases of resin components of heavy oil from the Nurlatskoe field (Republic of Tatarstan) to solve the problems associated with their negative impact on oil refining. The aim. To characterize the composition of nitrogenous organic bases, isolated from the resins of bituminous oil of the Nurlatskoe field, and the products of their thermal cracking. Methods. Complex formation, extraction, liquid adsorption chromatography, potentiometric titration, 1H NMR spectroscopy, structural group analysis, combined gas chromatography-mass spectrometry. Results. Based on a comparative study of the composition and structure of nitrogenous bases of the initial and thermally treated resins of the bituminous oil from the Nurlatskoe field, the authors found out that they both contain high- and low-molecular nitrogenous bases with predominance of high-molecular compounds precipitated by hydrogen chloride. As a result of thermal exposure, the number of such bases increases due to an increase in the proportion of compounds with shorter alkyl substituents in their composition. The method of structural group analysis was used to show that the main directions of thermal transformations of high- and low-molecular bases of resins in Nurlatskoe oil are destruction of alkyl substituents and cyclization of shortened alkyl chains with formation of naphthenic rings. Among the lowest molecular weight bases of the initial resins and thermolysate the authors have identified alkyl-substituted quinolines, benzoquinolines, azapyrenes, thiophenoquinolines, and benzothiophenoquinolines with similar molecular weight distributions. During the thermolysis of resins, the relative content of low molecular weight homologues in the identified nitrogenous bases increases. The share of structures with reduced chromatographic mobility caused by a decrease in the degree of spatial screening of a nitrogen atom increases among similar homologues.

Colloidal and Thermal Stability of Three-Component Hybrid Materials Containing Clay Mineral, Polysaccharide and Surfactant.

The paper presents the colloidal and thermal stability of the three-component hybrid materials containing halloysite, polysaccharides (alginic acid, cationic cellulose and hydroxyethyl cellulose) and Tritons. TX-100, TX-165 and TX-405 were used as non-ionic surfactants. Stability and other properties of the hybrid materials were tested by the following methods: UV-Vis, TGA (thermogravimetric analysis) and DSC (differential scanning calorimetry), CHN (elemental analysis), SEM-EDX (scanning electron microscopy with energy dispersive X-ray spectroscopy) and tensiometry. According to the results with the increasing polymer concentration the colloidal stability of the tested systems also increases. Moreover, the addition of the surfactants causes the increase of polysaccharide adsorption but the colloidal stability of the tested systems decreases due to large weights of formed aggregates. As follows from the thermal analysis, the comparison of the TG/DTG-DSC curves obtained for the investigated polymers confirms that their thermal decomposition courses have some common features. The obtained results have the application potential in the formation of the materials for the pollutants removal from water and sewages.

Thermal properties and the decomposition path of novel UV polymers of terpene-based monomer: citronellyl methacrylate

Thermal properties and the decomposition path of more environmentally friendly polymers in both atmospheres: inert and oxidizing have been studied with a use of simultaneous TG/FTIR/QMS and DSC methods. The polymeric materials in the UV-polymerization process of cyclohexyl methacrylate and methacrylate monomer obtained from natural terpene alcohol: citronellol, using different compositions of monomers were prepared. The glass transition temperature (Tg) and thermal stability of these high solvent and chemical resistant materials were dependent on the composition and increased with increasing cyclic monomer content in the compositions. The Tg changed from 9.8˚C to 47.5˚C and a thermal stability from 195˚C to 222˚C (inert atmosphere) and from 160˚C to 217˚C (oxidizing atmosphere). The TG/FTIR/QMS analysis proved the emission of cyclohexyl methacrylate, citronellyl methacrylate and their lower molecular mass decomposition fragments, e.g., propene, cyclohexane, citronellol, citronellal, formic acid, methacrylic acid and CO, CO2 during heating of these materials in helium and air atmospheres. It indicated the same radical mechanism of their decomposition in both atmospheres which meant that the presence of oxygen did not affect the course of decomposition but reduced the initial decomposition temperature of the copolymers.

Experimental studies on the preparation and properties of starch‐graft‐poly(hexyl acrylate) copolymers

AbstractThe preparation and the properties such as the chemical stability, solution properties, moisture absorption, ability to gelation, glass transition temperatures, thermal stabilities and the decomposition course of starch‐graft‐poly(hexyl acrylate) copolymers have been studied. In general, it can be said that as the grafting percent increases the chemical resistance in alkaline, inert, acidic and buffer environments, and the solubility in non‐polar solvents of the copolymers increases. In turn, the solubility in polar solvents decreases compared to the solubility of starch. The Tg of starch‐g‐poly(hexyl acrylate) copolymers is in the range 102–133°C and is much higher than Tg of poly(hexyl acrylate) homopolymer. The thermal stability of all tested copolymers is higher than 274°C (inert conditions) and 230°C (oxidative conditions). In inert conditions, all tested copolymers decompose in two main stages related to pyrolysis combined with the emissions of the following volatiles: CO, CO2, H2O, aldehydes, alcohols, acids, ester, furanes, aliphatic and alkene fragments. In turn, the copolymers decompose in main three stages in oxidative conditions. The emission of CO, CO2, H2O, aldehydes, alcohols, acids, aliphatic, furanes and alcohols as a result of pyrolysis, oxidation, decarboxylation, dehydration, and combustion processes was confirmed.

Quantifying microcracks on fractured bone surfaces – Potential use in forensic anthropology

Bone fracture surface morphology (FSM) can provide valuable information on the cause of failure in forensic and archaeological applications and it depends primarily on three factors, the loading conditions (like strain rate), the ambient conditions (wet or dry bone material) and the quality of bone material itself. The quality of bone material evidently changes in taphonomy as a result of the decomposition process and that in turn is expected to affect FSM. Porcine bones were fractured by a standardised impact during the course of soft tissue decomposition, at 28-day intervals, over 140 days (equivalent to 638 cooling degree days). Measurements of the associated microcracks on the fractured cortical bone surfaces indicated a progressive increase in mean length during decomposition from around 180 μm–375 μm. The morphology of these microcracks also altered, from multiple intersecting microcracks emanating from a central point at 0–28 cumulative cooling degree days, to longer linear cracks appearing to track lamellae as soft tissue decomposition progressed. The implications of these findings are that taphonomic changes of bone may offer the real possibility of distinguishing perimortem and taphonomic damage and also provide a new surrogate parameter for estimation of post-mortem interval (PMI) in forensics.

Experimental Studies on the Thermal Properties and Decomposition Course of a Novel Class of Heterocyclic Anticancer Drug Candidates

The experimental studies on the thermal properties and decomposition course of a novel class of potential anticancer drugs (1-5) containing in their heterobicyclic structures the asymmetrical triazine template were performed with the use of differential scanning calorimetry (DSC) and simultaneous thermogravimetry/differential scanning calorimetry (TG/DTG/DSC) coupled online with Fourier transform infrared spectroscopy (FTIR) and quadrupole mass spectrometry (QMS) in inert and oxidizing conditions. All the compounds were thermally characterized in detail for the first time in this article. The DSC studies proved that the melting points of the tested compounds depended on the position and type of the substituent at the phenyl moiety, whereas they did not depend on the furnace atmosphere. All the tested polynitrogenated heterocycles proved to be molecules with high thermal stability in both atmospheres, and most of them (1, 3-5) were more stable in oxidizing conditions, which indicated the formation of a more thermally stable form of the compounds when interacting with oxygen. The simultaneous TG/FTIR/QMS analyses confirmed that their pyrolysis process occurred in one main stage resulting in the emission of volatiles such as NH3, HNCO, HCN, CO, CO2, H2O, NO2, aromatic amine derivatives, alkenes (for compounds 1-5), and HCl (for the compound 5). On the other hand, the oxidative decomposition process was more complicated and proceeded in two main stages leading to the emission of NH3, CO2, CO, HCN, HNCO, H2O, some aromatics (for compounds 1-5), HCl (for compounds 3-5) as well as the additional volatiles such as N2, NO2, NH2OH, and (CN)2. The type of the formed volatiles indicated that the decomposition process of the studied heterocycles under the influence of heating was initiated by the radical mechanism. Their decomposition was related to the symmetric cleavage of C-N and C-C bonds (inert conditions) and additional reaction of the volatiles and residues with oxygen (oxidizing conditions).

Determination of aerobic and anaerobic biological degradability of waste tyres

Environmental contamination of rubber from waste tyres poses a risk to the environment. Rubber particles from tyres enter the environment due to the abrasiveness of the road surface. The aim of the scientific work was to observe the biological degradability of waste tyres in aquatic environment and its ecotoxicity. Biodegradability was observed under aerobic and anaerobic conditions that simulate both aerobic and anaerobic conditions in the aquatic natural environment. Aerobic conditions in the aquatic environment take place in flowing fresh water, sea water, lakes. Leachate was prepared to simulate the behaviour of tyres in an aqueous environment. Aerobic degradability was evaluated through complete biodegradability using a 301 F manometric respirometry test. Anaerobic biodegradability was evaluated by measuring biogas production using OECD 311 Anaerobic Biodegradability of Organic Compounds in Digested Sludge. For a better simulation of the natural environment, the pH of the leachates from the tyres was adjusted to a neutral range. It should be noted that standard degradability tests were extended by 7 days due to low biodegradability. Adjusting the pH during the biodegradability test is also a modification of the original test. This modification was used to better simulate biodegradability when the pH of tyres in the natural environment is reduced by acid rain. An essential part of monitoring the behaviour of waste tyres was the assessment of ecotoxicity using standard tests. The contribution of the scientific article lies in the evaluation of the course of decomposition in aerobic and anaerobic conditions with and without pH adjustment and in the use of modified biodegradability tests. The benefit of the scientific work is in the determination of the biodegradability of waste tyres with and without pH treatment, which simulate a comparison of the degradability of tyres in an acid rain environment. Another benefit of the scientific work is the depiction of biodegradation using 3D modelling with calculations of 100% degradability at different input concentrations of waste tyres. Modelling was used for the time for the absolute decomposition of tyres without pH adjustment (outside the acid rain environment) and with pH adjustment (in the acid rain environment). By monitoring, it is possible to determine whether acid rain as an anthropogenic activity influences the degradability of waste tyres in the natural environment. Biodegradability tests confirmed the low biological degradability of waste tyres. The highest average rate of biological degradability—15% was recorded at the input concentration of waste tyres of 350 mg/L. The aerobic degradability test confirmed the improvement of tyre decomposition when adjusting the pH to the level of 6.5–7.5. On the contrary, the anaerobic degradability test confirmed the improvement of the decomposition in the alkaline region compared to the neutral pH values of the mixture. By mathematical–statistical evaluation of aerobic decomposition with preservation of degradability trends at three input concentrations, the time of absolute decomposition of waste tyre particles at a concentration of 370 mg/L was found to be approximately 336 days. By adjusting the pH to the neutral range during aerobic decomposition, the total decomposition time was reduced to 126 days. The ecotoxicity tests performed confirmed the toxic effect of tyre leachate on selected tested organisms. In the future, the authors propose to focus on a more detailed assessment of the ecotoxicity of the waste conditions and to modify the biodegradability tests by changing the conditions (wider range of input pH value, longer biodegradability time, temperature) for a better simulation of different types of environments. Adjusting the pH to a neutral environment increased aerobic degradability but had no significant effect on anaerobic degradability. Therefore, it is important to focus future research on the adjustment of various conditions to support the degradability of tyres, of which pH has clearly been confirmed as an important factor.

Synthesis of Nanocrystalline Yttrium Oxide and Evolution of Morphology and Microstructure during Thermal Decomposition of Y2(C2O4)3·10H2O

A study of the morphology and evolution of the microstructure during thermal decomposition of Y2(C2O4)3·10H2O was conducted, and the stages and factors having the greatest impact on particle size and specific surface area were identified. The effect of the yttrium oxalate hexahydrate phases on the course of decomposition was also investigated. The evolution of the morphology and microstructure of decomposition products was explained from the analysis of volume shrinkage at various stages of the reaction. The formation of oxycarbonate is accompanied by the largest shrinkage during the reaction. At this stage, there is a significant increase in the specific surface area to 60–90 m2/g. Conversely, the morphology and microstructure of the particles during the transformation of oxycarbonate into yttrium oxide change insignificantly. Yttrium oxide powders obtained from the monoclinic and triclinic hexahydrate phases have the same specific surface area, but different morphology and bulk density due to pseudomorph formation. The carbon formed during thermolysis was shown to affect the specific surface area of the decomposition product. Two methods for producing yttrium oxide with high specific surface area have been proposed, and nanocrystalline yttrium oxide with a specific surface area of 65 m2/g was obtained.

Inferring the Postmortem Interval of Rat Cadaver after Boiling Water Treatment Based on Microbial Community Succession

Abstract Background: In forensic investigations, accurate estimation of the postmortem interval (PMI) is an important task, but also an ongoing challenge. Especially in cases where the cadaver has been specially treated, for example, by boiling, the determination of PMI becomes extremely difficult. Previous studies have shown that the succession of the microbial community after decomposition of the cadaver can be used to infer PMI. However, the feasibility of determining the PMI of boiled cadavers has not yet been demonstrated. Aims and Objectives: The main objective of this study was to test whether we can infer PMI of boiled cadavers based on the succession of microbial communities. Materials and Methods: SD rats were killed by cervical dislocation. Subsequently, the rat cadavers were divided into the case (boiled cadavers) and control (unboiled cadavers) groups. Rectal samples were collected from the rats for 45 days and at nine time points. High-throughput sequencing of the 16S rRNA gene was performed to characterize the microbial community in the rectum. Results: The results showed that the composition and relative abundance of bacterial communities at the phylum level were significantly different between the case and control groups. The alpha diversity of the microbial community showed a decreasing trend with the decomposition process. Principal coordinate analysis showed that the case and control groups had obvious patterns along the succession of microbial communities. The rectal microbial communities showed a significant linear trend in the time course of decomposition. A random forest model was used to infer PMI. The goodness-of-fit (R2) of the model was 68.00% and 84.00%, and the mean absolute errors were 2.05 and 1.48 days within 45 days of decomposition for the case and control groups, respectively. Conclusions: Our results suggest that microbial community succession could be a potential method to infer PMI of boiled cadavers.

Исследование параметров окна частотно-временного преобразования при проведении декомпозиции сигнального радиопрофиля

Known methods of time-frequency transformation, such as the Gabor-Ville transform, wavelet transform, are complex and cumbersome in calculations, require the correct selection of basic expansion functions, may have interference points and negative values of the spectral density function. The presence of space-time uncertainty inherent in any frequency-time decomposition, as well as the lack of the possibility of correcting the found expansion coefficients, make modern methods of frequency-time transformation ineffective in the analysis of signal radio profiles (SRP). Decomposition of SRP with windowed correlation feedback eliminates the above disadvantages by multiple enumeration of parameters, however, this occurs at the expense of a significant increase in the transformation time. The transformation window here is understood as a rectangular function that moves along the time axis from the origin. In this work, the window width is understood as the number of sampling points falling into the rectangular window function, which is equivalent to the length of the function along the time axis. The window step is the number of sampling points to which the rectangular window function (transformation window) moves in the time-frequency decomposition. The purpose of this work is to increase the efficiency of the frequency-time decomposition of the SRP by analyzing the parameters of the transformation window in decomposition with windowed correlation feedback. In the study, experimental research methods are used to register the electrical component of the electromagnetic field radiated by the product - SRP. Correlation analysis methods for determining the best match between the reference and reconstructed SRP. Methods of digital signal processing with frequency-time decomposition. The paper presents the registered SRPs and their parameters, a correlation analysis of the SRP data is carried out. The dependences of the correlation functions on the width and step of the window are given for a different number of sampling points of the registered SRP. The results obtained for the first time showed the possibility of using certain parameters of the transformation window to improve the accuracy and significantly reduce the time of SRP decomposition, which makes the work novel. It has been established that with a window width equal to half the length of the SRP itself and a window step of not more than a tenth of the length of the SRP, it is possible to achieve an increase in the cross-correlation between the original and restored SRP up to 0.95. Recommendations are given on the speed of recording equipment when receiving PDS (sampling rate below 10 GS/s). The practical significance of the work lies in the reduction of iterations of the multi-parameter approximation when using correlation feedback in the course of SRP decomposition, which significantly reduces the conversion time and improves its accuracy.

TG-FTIR-QMS analysis of more environmentally friendly poly(geranyl methacrylate)-co-poly(cyclohexyl methacrylate) copolymers

The pyrolysis and thermal oxidation course of new, more environmentally friendly copolymers, not described in the literature so far, was systematically investigated by the TG/FTIR/QMS technique. New materials were obtained in the UV polymerization process of geranyl methacrylate, a monomer synthesized on the basis of natural, terpene alcohol (geraniol), and cyclohexyl methacrylate using a variable percentage of individual monomers. As confirmed, the copolymers were characterized by excellent resistance to solvents and chemical environment as well as Tg in the range 34.5–53.8 ⁰C. The TG/DTG analyses proved their high thermal stability in an inert atmosphere and satisfactory thermal resistance in an oxidizing atmosphere. The thermal resistances of the copolymers were directly dependent on the percentage of individual monomers. The simultaneous TG/DTG coupled with the FTIR and QMS analyses confirmed that the decomposition course of the tested materials was complex, in both atmospheres. The pyrolysis process included two main stages. In the first stage, depolymerization, random cleavage of the CC and CO bonds and decarboxylation were the main processes. These led to the emission of methacrylate monomers, myrcene, geraniol, citral, propene, methacrylic acid and other structure low molecular saturated and unsaturated compounds, as the main products of pyrolysis. In the second stage, the secondary reactions between intermediate volatiles and the formed residues were expected. Under oxidative conditions, the decomposition mechanism was more complicated. The depolymerization, random cleavage of the CC and CO bonds, decarboxylation and additional reactions of the intermediates with oxygen led to the emission of methacrylate monomers, myrcene, geraniol, citral, propene, methacrylic acid and other structure low molecular saturated and unsaturated compounds and more oxidized gaseous products.