Course Of Decomposition Research Articles

Features of propagation of droplets of water and special water-based compositions in a sample of forest fuel material

The article presents the results of experimental studies of water droplets propagation through the sample of typical forest fuel materials: needles, leaves, and their mixture. Different conditions are considered: without any additional energy supply, with heating, in the course of intensive thermal decomposition and flaming combustion. Three methods of registration are applied: thermocouple measurements, control of the weight of the sample as a whole and of its individual layers, and high-speed video recording. Water-based compositions with special additives (bentonite, bischofite, and foaming agents) typical for forest fire extinguishing systems are used. The experiments are carried out using aerosol and single water drops, as well as a small group of the latter. It is shown that the mechanisms, conditions and characteristics of droplet propagation through the layers of needles, leaves and their mixtures differ significantly. The scientific novelty of the work is the determining of the values of all the key characteristics of these processes in the conditions of intensive pyrolysis of the material, as well as through its inert layers.

Comparative study of the thermal decomposition behaviour of different amino acids and peptides

Thirteen nitrogen-containing compounds, including 2 peptides and 11 amino acids, were analysed for their thermal decomposition behaviour using TGA/DSC coupled with MS and FTIR.Various decomposition courses have been found. Glycine, cysteine, cystine, proline, D- and L-threonine decomposed in two stages, whereas arginine, asparagine, glutamine, histidine and tryptophan decomposed in three stages. The peptides of glycine both decomposed in four decomposition steps, except for the glycylglycine under oxidative conditions, which decomposed in three stages. Proline proved to be exceptional, as it needed only one decomposition step under nitrogen to decompose (99.5% mass loss).The decomposition products of amino acids and peptides described in literature could be confirmed in this work. These were mainly carbon dioxide, water, ammonia, hydrocyanic acid and nitrogen oxides. In traces, also isocyanates and nitriles could be detected, but no clear identification of these substances could be made due to superposition of the signals. For example, in the absorption spectrum at 3000 cm−1, a superposition of the hydrocarbons and amines occurred and in the two sulphur-containing amino acids cysteine and cystine at 2100 cm−1, a superposition of the resulting sulfur compounds could be observed.It has also been shown that with increasing chain length of the peptides, in this case of glycine, the molecule becomes thermally more stable. Concerning cystine, something similar was observed for cystine, this is due to the strong sulphur bonding of the monomers. In addition, glycine and its peptides have been shown to have doubled or tripled the volume of the resulting carbon foam formed as length increased, a feature interesting for future research involving intumescent materials.

Temperature Influence on Prevailing Necrophagous Diptera and Bacterial Taxa With Forensic Implications for Postmortem Interval Estimation: A Review.

The decomposition process of human (and other mammalian) remains is influenced by numerous factors such as the environmental temperature, relative humidity, precipitation, geographical location of the remains, as well as the medical conditions of and any injuries sustained by the deceased person. The decomposition process generally follows a consistent pattern (fresh, bloat, active decomposition, advanced decomposition, and dry stage). Understanding the time-span of each stage of decomposition and the influence of the biotic and abiotic factors involved is imperative when trying to estimate the time elapsed since death (postmortem interval [PMI]). Over the course of decomposition, the tissues are gradually consumed by necrophagous insects and bacteria. The environmental temperature and its variations influence how insects colonize the remains, having a significant impact on their presence and developmental cycle. Additionally, the bacterial community colonizing decomposing tissues is also greatly affected by variations in environmental temperature. Because both the rate of decomposition of human remains and the relative abundance of certain insects and bacterial species are all temperature-dependent, insect and bacterial colonization data are useful as key points for the PMI estimation. This article reviews the current literature documenting the data collected on the occurrence and development cycles of predominant necrophagous Diptera (Calliphoridae, Muscidae, Sarcophagidae) and bacterial taxa involved in the decomposition of various carcasses at different temperatures. This review will impact the forensic community by providing an overview on the temperature, insect and bacterial records for the PMI estimation, seeking to aid forensic entomologists, microbiologists, pathologists, and the legal community.

Transformation of Water-Soluble Organic Substances in Litters of Podzols in the Background and Technogenic Areas of the Kola Peninsula

Mineralization of water-soluble organic substances in forest litters of different compositions under conditions of their pollution with heavy metals from aerogenic emissions is considered. Water-soluble organic substances of the pine forest litters are shown to be less stable than that under the spruce forests irrespective of their pollution; the portion of mineralized at 20°C carbon for a month reached 40%. In the spruce litters, mineralizable amounts of carbon are related to their pollution: in the technogenic areas, compared to the background ones, carbon losses from the litters are twice greater. In the course of decomposition, in the spruce and pine litters, phenol compounds accumulate among the water-soluble organic compounds, and this process is more intense in the contaminated areas. After the decomposition of all the litters, irrespectively of their composition and the distance from the pollution sources, the water-soluble organic substances are characterized by higher indices of humification (HIX), more intense fluorescence, and greater coefficients of specific extinction (E260). In the ultraviolet spectra, bands appear in the region of aromatic amines absorption. These changes indicate the transformation of water-soluble organic substances: the degrees of their condensation and aromaticity increase and nitrogen-containing aromatic compounds are formed.

Litter quality drives the differentiation of microbial communities in the litter horizon across an alpine treeline ecotone in the eastern Tibetan Plateau

Cellulose and lignin are the main polymeric components of the forest litter horizon. We monitored microbial community composition using phospholipid fatty acid (PLFA) analysis and investigated the ligninolytic and cellulolytic enzyme activities of the litter horizon across an alpine treeline ecotone in the eastern Tibetan Plateau. The activities of ligninolytic and cellulolytic enzymes and the biomass of microbial PLFAs were higher in the initial stage of litter decomposition than in the latter stage in the three vegetation types (coniferous forest, alpine shrubland and alpine meadow). Soil microbial community structure varied significantly over the course of litter decomposition in the three vegetation types. Furthermore, the BIOENV procedure revealed that the carbon to nitrogen (C:N) ratio, carbon to phosphorus (C:P) ratio and moisture content (MC) were the most important determinants of microbial community structure in the initial stage of litter decomposition, whereas pH and the lignin concentration were the major factors influencing the microbial community structure in the later stage of litter decomposition. These findings indicate that litter quality drives the differentiation of microbial communities in the litter horizon across an alpine treeline ecotone in the eastern Tibetan Plateau.

Hydroconversion of Oxidation Products of Sulfur-Containing Aromatic Compounds

Hydroconversion of benzo- and dibenzothiophene sulfone on a Ni–Mo sulfide catalyst based on mesoporous aluminosilicate Al-HMS and on unsupported catalysts prepared in situ in the course of decomposition of poorly soluble precursors (molybdenum hexacarbonyl, nickel naphthenate) was studied. Hydrogenation of sulfones was perfpormed at 250, 340, and 380°С and elevated СО pressure in the presence of water ensuring in situ generation of hydrogen via water-gas shift reaction.

Thermochemical properties of nanometer CL-20 and PETN fabricated using a mechanical milling method

2,4,6,8,10,12-Hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) and pentaerythritol tetranitrate (PETN), with mean sizes of 73.8 nm and 267.7 nm, respectively, were fabricated on a high-energy ball-mill. Scanning electron microscope (SEM) analysis was used to image the micron-scale morphology of nano-explosives, and the particle size distribution was calculated using the statistics of individual particle sizes obtained from the SEM images. Analyses, such as X-ray diffractometer (XRD), infrared spectroscopy (IR), and X-ray photoelectron spectroscopy (XPS), were also used to confirm whether the crystal phase, molecular structure, and surface elements changed after a long-term milling process. The results were as expected. Thermal analysis was performed at different heating rates. Parameters, such as the activation energy (ES), activation enthalpy (ΔH≠), activation free energy (ΔG≠), activation entropy (ΔS≠), and critical temperature of thermal explosion (Tb), were calculated to determine the decomposition courses of the explosives. Moreover, the thermal decomposition mechanisms of nano CL-20 and nano PETN were investigated using thermal-infrared spectrometry online (DSC-IR) analysis, by which their gas products were also detected. The results indicated that nano CL-20 decomposed to CO2 and N2O and that nano PETN decayed to NO2, which implied a remarkable difference between the decomposition mechanisms of the two explosives. In addition, the mechanical sensitivities of CL-20 and PETN were tested, and the results revealed that nano-explosives were more insensitive than raw ones, and the possible mechanism for this was discussed. Thermal sensitivity was also investigated with a 5 s bursting point test, from which the 5 s bursting point (T5s) and the activation of the deflagration were obtained.

Nutrient retention and release in coarse woody debris of three important central European tree species and the use of NIRS to determine deadwood chemical properties

BackgroundCoarse woody debris (CWD) is very important for forest ecosystems, particularly for biodiversity and carbon storage. Its relevance as a possible reservoir and source of nutrients is less clear, especially in central Europe.MethodsBased on a chronosequence of known ages of logs, we analyzed the nutrients stored in CWD of Fagus sylvatica, Picea abies, and Pinus sylvestris at different sites in Germany. To quantify nutrient concentrations, we assessed the use of Near Infrared Reflectance Spectroscopy (NIRS) to determine the chemical properties of CWD.ResultsNIRS models were suitable to predict concentrations of C, N, P, lignin and extractives. Concentrations of most nutrients increased with mass loss, with the exception of potassium, which decreased for beech and pine and remained relatively constant for spruce. The highest nutrient concentrations (N, P, S, Ca and Mn, except Mg and K) were generally observed in highly decomposed spruce logs. The net effect of decreasing CWD mass and increasing nutrient concentrations was either a decreasing (N, P and K in beech; P, Mg, K and Mn in pine), constant (S, Ca and Mg in beech; N, S and Ca in pine) or increasing amount of nutrients (N, P, S and Ca in spruce; Mn in beech) in the logs over the course of decomposition. The C/N ratio decreased for all tree species, most markedly for spruce from ca. 1000 at the beginning of the decomposition process to 180 at 36 years. The N/P ratio converged to a value of about 30 for all three species. Lignin concentrations increased for spruce and beech and remained constant for pine.ConclusionsOur results indicate that most nutrients remain in CWD for long periods. Nutrients may be used and cycled by microorganisms within CWD, but with the exception of P (in beech), Mg (in pine) and K (in beech and pine), there appears to be little net nutrient export until two thirds of the mass is lost. Instead, N, P, S and Ca were accumulated in spruce logs, indicating that CWD became a net sink rather than a net source of some nutrients for several decades.

Thermo-oxidative decomposition behavior of starch-g-poly(citronellyl methacrylate) and starch-g-poly(citronellyl acrylate) copolymers

The paper describes the studies on the thermo-oxidative decomposition behavior of two types of starch graft copolymers: starch-g-poly(citronellyl acrylate) copolymers with the grafting percent (%G): 21.3% ± 0.5, 35.8% ± 0.6 and 59.8% ± 0.3 and starch-g-poly(citronellyl methacrylate) copolymers with %G: 21.3% ± 0.4, 37.0% ± 0.2 and 51.8% ± 0.3 prepared applying the “grafting from” method. The decomposition course of copolymers by using the TG/DTG/DSC/FTIR analysis was evaluated. As it was found, the course of TG/DTG/DSC curves was independent on the %G but it was directly dependent on the type of analyzed copolymer. It resulted in completely different decomposition course of starch-g-poly(citronellyl acrylate) copolymers under the presence of oxidative conditions as compared to starch-g-poly(citronellyl methacrylate) copolymers. Thanks to applying the FTIR analysis of the gaseous products emitted under the heating of the studied materials, the detailed decomposition course of copolymers was evaluated.

The use of the microbial and entomological data for the diagnostics of prescription of death coming

The objective of the present study was to demonstrate the possibility of the diagnostics of prescription of death coming (PDC) based on the results of the studies with the application of the entomological and microbiological methods. The entomological materials included larvae of two dipteran species Stearibia nigriceps (Piophilidae) and Fannia vesparia (Fanniidae) collected from bone tissue fragments and the bony bed. The detailed investigation of the succession of necrophilic insects taking place in the course of decomposition of organic matter and the development of the preimaginal stages of the dipterans made it possible to determine the duration of the period during which the corpse remained in the ambient environment. The microbiological studies made it possible to determine the composition of necrobiome of the bone remains. It included, among other things, the association of soil bacterial forms belonging to the orders Actinomycetales, Pseudomonadales, and Aeromonadales in the combination with the fungi of the order Endomycetales. The enteral microorganisms that trigger putrefaction at the early stages of corpse decomposition were totally absent in the remains that hosted soil microorganisms destroying the hard tissues. The predominance of Actinobacteria in the samples of bone remains gave evidence of active disintegration of the skeletal tissues by the bacterial species inhabiting the local soil milieu. The study demonstrated that the results of the analysis of the microbial constituent of the washouts from the surfaces of the skull and the left upper arm bone of the human corpse were consistent with the conclusion about the prescription of death coming based on the entomological data. It is agued that the development of the methods for the diagnostics of prescription of death coming, including those to be used for the examination of the skeletonized corpses, based on the results of the entomological and microbiological investigations has good prospects as an area of research in the field of forensic medicine.

Preparation and Investigation of the Thermal Stability of Phosphate-modified TiO2 Anatase Powders and Thin Films.

The temperature dependence of the anatase-to-rutile phase transition of TiO2 powders and thin films was studied. In order to shift the phase transition to higher temperature, samples were doped with a different amount of phosphate ions and their influence on the structure and thermal stability of the anatase phase was investigated. In addition, the effect of the catalyst form (powders or thin films) on the temperature of the anatase-to-rutile phase transition was observed. TiO2 thin films and powders were prepared using a simple sol-gel method with an alkoxide precursor and citric acid. The thin films were deposited on silicon and aluminum substrates using the dip-coating technique. The content of the anatase phase and the crystallite size at different annealing temperatures were monitored using X-ray diffraction. The course of the thermal decomposition was followed using thermal analyses. The morphology, particle size, shape and elemental makeup of the samples were investigated using scanning electron microscopy and energy-dispersive X-ray spectroscopy. The results showed that the phosphate ions successfully inhibited the growth of the anatase nanoparticles and delayed the phase transition to the rutile phase.

Artificial neural networks as a supporting tool for compatibility study based on thermogravimetric data

This paper focuses on applying of artificial neural networks (ANNs) for the incompatibility detection between an active pharmaceutical ingredient (API) and excipients on the basis of thermogravimetric data. In binary model mixtures, caffeine was used as API mixed with selected excipients. The interpretation of ANN results was based on the assumption that the model mixtures with relatively high content of API (70 and 90%), should undergo similar course of thermal decomposition and be placed in nearby neurons, as opposed to mixtures where excipient predominated. When different behaviour of model mixtures was observed, the incompatibility between mixture ingredients was determined. The results indicate ANNs combined with thermogravimetry to be a simple diagnostic tool that visualizes the behaviour of ingredients in binary mixtures by placing them in different neurons of the topological map so as to determine incompatibility occurrence. The findings were confirmed with complementary techniques − DSC, FTIR and XRPD.

Study of degradation products and degradation pathways of sulfonated azo dyes under ultraviolet irradiation

Monitoring the light-induced decomposition course of azo dyes is essential to understand their degradation pathways and mechanisms. In this study, two model dyes are synthesized and used for stimulating the photodegradation processes of azo and hydrazone dyes, respectively. Their intermediates formed during initial and final fading processes are characterized by high-performance liquid chromatography-electrospray ionization-mass spectrometry, gas chromatography-mass spectrometry and ion chromatography. Results reveal that no dramatic differences are observed between the two dyes, although hydrazone dye would undergo a more complicated degradation process. Hydroxyl radicals are the dominant reactive species involved in the photodegradation of both model dyes under ultraviolet irradiation. In the initial steps, the intermediates are almost hydroxylated derivatives, while low-molecular-weight dicarboxylic acids and their hydroxylated and esterified derivatives, as well as non-volatile inorganic ions, are detected and evidenced in the final steps. Furthermore, photodegradation pathways and mechanisms for the two model dyes are proposed accordingly.

Reaction Pathways and Kinetics for Selective Catalytic Reduction (SCR) of Acidic NOx Emissions from Power Plants with NH3

Selective catalytic reduction (SCR) of NOx with NH3 by supported vanadium oxide catalysts is an important technology for reducing acidic NOx emissions from stationary sources and mobile diesel vehicles. However, rational design of improved catalysts is still hampered by a lack of consensus about reaction pathways and kinetics of this critical technology. The SCR fundamentals were resolved by applying multiple time-resolved in situ spectroscopies (ultraviolet–visible light (UV-vis), Raman and temperature-programmed surface reaction (TPSR)) and isotopically labeled molecules (18O2, H218O, 15N18O, ND3). This series of experiments directly revealed that the SCR reaction occurs at surface V5+O4 sites that are maintained in the oxidized state by O2 and the rate-determining step involves the reduction of V5+O4 sites by NO and NH3, specifically the breaking of N–H bonds during the course of formation or decomposition of the NO–NH3 intermediate.

Combustion Characteristics of HAN-based Green Propellant Assisted with Nanoporous Active Carbons

Combustion of hydroxylammonium nitrate (95 wt.% HAN) ‒ water solution in presence of high specific surface area activated carbons is investigated in a constant-pressure bomb within the pressure range of 1‒6 MPa. The linear burning rate increased for the system of HAN admixed with activated carbons compared to those of the HAN alone. Moreover, the thermal decomposition of HAN (95 wt.%) ‒ water solution spiked with activated carbons was assessed by DTA – TG method. In the presence of activated carbons, the ability to trigger the decomposition at a lower temperature (86 °C vs 185 °C) was observed. The volatile products formed in the course of thermal decomposition of HAN, spiked with activated carbons were characterized by electron ionization mass spectrometry analysis. Primary products of HAN decomposition: m/z = 33 (NH2OH) and m/z = 63 (HNO3), which are further responsible for the formation of secondary products such as N2O, NO, HNO2, NO2, O2 etc. Significant reduction of NOx emissions during thermal decomposition of HAN (95 wt.%) ‒ water solution was observed (ca. 30%) in presence of activated carbons.

Crystal Structure of DMF-Intermediate Phases Uncovers the Link Between CH3NH3PbI3 Morphology and Precursor Stoichiometry

We found for the first time a new origin of selection of perovskite crystallization pathways from DMF solutions containing MAI and PbI2 to present here a comprehensive study of a full set of essential intermediate phases determining the perovskite’s morphology. For all three discovered structurally different intermediate phases forming at a given precursor ratio, we refined their crystal structures by synchrotron X-ray radiation and investigated dynamics and phase assemblage in the course of decomposition. As a result, we revealed a clear correlation between the composition of the intermediate phases, peculiarities of their crystal structure, and the morphology of the final perovskite films. Using the DFT method we calculated formation enthalpies of these intermediate phases and explained the preferential precipitation of DMSO-adduct rather than DMF-adduct in an antisolvent approach. This finding opens up a possibility of design-on-demand of perovskite materials using simple soft chemistry approaches.

Function of bacterial community dynamics in the formation of cadaveric semiochemicals during in situ carcass decomposition.

The decomposition of dead mammalian tissue involves a complex temporal succession of epinecrotic bacteria. Microbial activity may release different cadaveric volatile organic compounds which in turn attract other key players of carcass decomposition such as scavenger insects. To elucidate the dynamics and potential functions of epinecrotic bacteria on carcasses, we monitored bacterial communities developing on still-born piglets incubated in different forest ecosystems by combining high-throughput Illumina 16S rRNA sequencing with gas chromatography-mass spectrometry of volatiles. Our results show that the community structure of epinecrotic bacteria and the types of cadaveric volatile compounds released over the time course of decomposition are driven by deterministic rather than stochastic processes. Individual cadaveric volatile organic compounds were correlated with specific taxa during the first stages of decomposition which are dominated by bacteria. Through best-fitting multiple linear regression models, the synthesis of acetic acid, indole and phenol could be linked to the activity of Enterobacteriaceae, Tissierellaceae and Xanthomonadaceae, respectively. These conclusions are also commensurate with the metabolism described for the dominant taxa identified for these families. The predictable nature of in situ synthesis of cadaveric volatile organic compounds by epinecrotic bacteria provides a new basis for future chemical ecology and forensic studies.

The effect of wax coating, aluminum and ammonium perchlorate on impact sensitivity of HMX

Abstract Interaction of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX)/ammonium perchlorate (AP) and its effect on mechanical sensitivity may result in some restrictions for the application of AP/HMX system in high energetic weapon system. In this work, impact sensitivity test is used to study the effects of wax coating of HMX, AP and aluminum (Al) powder on sensitivity properties of HMX/AP/Al mixtures. Thermogravimetry-differential scanning calorimetry (TG-DSC) analysis has been developed to investigate the mechanism of interaction between HMX and AP during the course of thermal decomposition of HMX/AP/Al mixtures. The results show that severe interaction effect exists between AP and HMX, which causes the impact sensitivity ( H 50 ) to become smaller. The impact energy ( E 50 ) of mixture can be improved under the circumstances of effective separating HMX from AP by surface coating with Wax. AP may firstly engender low-temperature decomposition under the circumstance of external heat or mechanical impact, which causes the exothermic peak of HMX forward shift about 28 °C. The gaseous product releasing from thermal decomposition of HMX accelerates further decomposition of AP. For HMX/AP composite system, the interactive catalysis effect between AP and HMX can be eliminated mostly by adding a great deal of Al powder (i.e. above 30%).

Thermal decomposition of binder based on etherified starch to use in foundry industry

In this work, the main purpose was the determination of the thermal stability of the modified starch: sodium carboxymethyl starch (CMS-Na) used in foundry technology as organic binder for molding sand. The analysis of the course of decomposition of the starch material under controlled heating in the range of 20–500 °C was based on the results of thermal analysis methods (TG, DTG, DSC) in combination with the results of spectroscopic technology (DRIFT). The use of various methods of thermal analysis and spectroscopic methods was possible to determine more entirely the mechanism of the binder decomposition process comprising reactions at the molecular level with regard to the conditions prevailing in the mold. The onset temperature of degradation of the binder and at the same time the temperature at which it begins to lose binding properties were determined. It was found that the mechanism of the binder is multistage process. The decomposition of the starch binder CMS-Na involves the gradual evaporation of the water bound at a temperature of 20–120 °C and water constitutional starch in the range of 120–200 °C, degradation of the binder in the temperature range 200–342 °C by breaking the glycosidic bonds in the polymer chains with the formation of volatile compounds and finally detaching the side groups and partial combustion of the starch material within a temperature range 342–500 °C.

The persistence of human DNA in soil following surface decomposition

Though recent decades have seen a marked increase in research concerning the impact of human decomposition on the grave soil environment, the fate of human DNA in grave soil has been relatively understudied. With the purpose of supplementing the growing body of literature in forensic soil taphonomy, this study assessed the relative persistence of human DNA in soil over the course of decomposition. Endpoint PCR was used to assess the presence or absence of human nuclear and mitochondrial DNA, while qPCR was used to evaluate the quantity of human DNA recovered from the soil beneath four cadavers at the University of Tennessee's Anthropology Research Facility (ARF). Human nuclear DNA from the soil was largely unrecoverable, while human mitochondrial DNA was detectable in the soil throughout all decomposition stages. Mitochondrial DNA copy abundances were not significantly different between decomposition stages and were not significantly correlated to soil edaphic parameters tested. There was, however, a significant positive correlation between mitochondrial DNA copy abundances and the human associated bacteria, Bacteroides, as estimated by 16S rRNA gene abundances. These results show that human mitochondrial DNA can persist in grave soil and be consistently detected throughout decomposition.