Initial Decomposition Rate Research Articles

Reinventing primary reactive oxygen species evolved from H2O2 heterolysis on FeOCl via SiO2 encapsulation

Feδ+/3+ defects on FeOCl surface interact with H2O2 to produce diverse reactive oxygen species (ROS) including •OH, •OOH, O2•-, Fe4+=O, and 1O2, whose relative contributions to aqueous pollutant degradation have been debatable and only partially clarified. Herein, SiO2 with O2- acting as an electron donor served to encapsulate FeOCl to form FeOCl-SiO2, whose interface bore Feδ+/3+ distinct from those of FeOCl surface under H2O2-containing aqueous phases in terms of composition and electron affinity. The FeOCl-SiO2 interface bore plentiful Feδ+ and minute Fe3+, from which Fe4+=O was generated yet remained barely accessible to bulky contaminants. Conversely, the FeOCl surface afforded plentiful Fe3+ and a non-negligible amount of Feδ+, from which copious O2•- and a moderate amount of Fe4+=O were produced, respectively, with high accessibility to bulky pollutants. Albeit with the production of •OH on FeOCl and FeOCl-SiO2, plots of their initial contaminant decomposition rates versus contaminant ionization potentials subjected to the correction for contaminant adsorption or Feδ+/3+ leaching along with scavenging/recycle runs corroborated that Fe4+=O and/or 1O2 function as the major ROS in fragmenting aqueous wastes upon exposure of the FeOCl-containing catalysts to H2O2-rich conditions. This was unanticipated when considering that the lifetimes and redox potentials of Fe4+=O and 1O2 are smaller than the corresponding values of •OH and that the evolution of •OH, Fe4+=O, and 1O2 on FeOCl was energetically favorable, as demonstrated by density functional theory calculations.

Decomposition of HCN during Experimental Impacts in Dry and Wet Planetary Atmospheres.

Hydrogen cyanide (HCN), a key molecule of significant importance in contemporary perspectives on prebiotic chemistry, originates in planetary atmospheres from various processes, such as photochemistry, thermochemistry, and impact chemistry, as well as from delivery by impacts. The resilience of HCN during periods of heavy bombardment, a phenomenon caused by an influx of material on unstable trajectories after accretion, remains relatively understudied. This study extensively investigates the stability of HCN under impact conditions simulated using a laboratory Nd:YAG laser in the ELISE experimental setup. High-resolution infrared spectroscopy was employed to monitor the gas phase composition during these simulations. Impact chemistry was simulated in bulk nitrogen atmospheres with varying mixing ratios of HCN and water vapor. The probed range of compositions spans from ∼0 to 1.8% of HCN and 0 to 2.7% of H2O in a ∼1 bar nitrogen atmosphere. The primary decomposition products of HCN are CO and CO2 in the presence of water and unidentified solid phase products in dry conditions. Our experiments revealed a range of initial HCN decomposition rates between 2.43 × 1015 and 5.17 × 1017 molec J-1 of input energy depending on the initial composition. Notably, it is shown that the decomposition process induced by the laser spark simulating the impact plasma is nonlinear, with the duration of the irradiation markedly affecting the decomposition rate. These findings underscore the necessity for careful consideration and allowance for margins when applying these rates to chemical models of molecular synthesis and decomposition in planetary atmospheres.

General reversal of N-decomposition relationship during long-term decomposition in boreal and temperate forests

Decomposition of dead organic matter is fundamental to carbon (C) and nutrient cycling in terrestrial ecosystems, influencing C fluxes from the biosphere to the atmosphere. Theory predicts and evidence strongly supports that the availability of nitrogen (N) limits litter decomposition. Positive relationships between substrate N concentrations and decomposition have been embedded into ecosystem models. This decomposition paradigm, however, relies on data mostly from short-term studies analyzing controls on early-stage decomposition. We present evidence from three independent long-term decomposition investigations demonstrating that the positive N-decomposition relationship is reversed and becomes negative during later stages of decomposition. First, in a 10-y decomposition experiment across 62 woody species in a temperate forest, leaf litter with higher N concentrations exhibited faster initial decomposition rates but ended up a larger recalcitrant fraction decomposing at a near-zero rate. Second, in a 5-y N-enrichment experiment of two tree species, leaves with experimentally enriched N concentrations had faster decomposition initial rates but ultimately accumulated large slowly decomposing fractions. Measures of amino sugars on harvested litter in two experiments indicated that greater accumulation of microbial residues in N-rich substrates likely contributed to larger slowly decomposing fractions. Finally, a database of 437 measurements from 120 species in 45 boreal and temperate forest sites confirmed that higher N concentrations were associated with a larger slowly decomposing fraction. These results challenge the current treatment of interactions between N and decomposition in many ecosystems and Earth system models and suggest that even the best-supported short-term controls of biogeochemical processes might not predict long-term controls.

Interplay of soil characteristics and arbuscular mycorrhizal fungi diversity in alpine wetland restoration and carbon stabilization.

Alpine wetlands are critical ecosystems for global carbon (C) cycling and climate change mitigation. Ecological restoration projects for alpine grazing wetlands are urgently needed, especially due to their critical role as carbon (C) sinks. However, the fate of the C pool in alpine wetlands after restoration from grazing remains unclear. In this study, soil samples from both grazed and restored wetlands in Zoige (near Hongyuan County, Sichuan Province, China) were collected to analyze soil organic carbon (SOC) fractions, arbuscular mycorrhizal fungi (AMF), soil properties, and plant biomass. Moreover, the Tea Bag Index (TBI) was applied to assess the initial decomposition rate (k) and stabilization factor (S), providing a novel perspective on SOC dynamics. The results of this research revealed that the mineral-associated organic carbon (MAOC) was 1.40 times higher in restored sites compared to grazed sites, although no significant difference in particulate organic carbon (POC) was detected between the two site types. Furthermore, the increased MAOC after restoration exhibited a significant positive correlation with various parameters including S, C and N content, aboveground biomass, WSOC, AMF diversity, and NH4+. This indicates that restoration significantly increases plant primary production, litter turnover, soil characteristics, and AMF diversity, thereby enhancing the C stabilization capacity of alpine wetland soils.

Stem decomposition of temperate tree species is determined by stem traits and fungal community composition during early stem decay

Abstract Dead trees are vital structural elements in forests playing key roles in the carbon and nutrient cycle. Stem traits and fungal community composition are both important drivers of stem decay, and thereby affect ecosystem functioning, but their relative importance for stem decomposition over time remains unclear. To address this issue, we used a common garden decomposition experiment in a Dutch larch forest hosting fresh logs from 13 common temperate tree species. In total, 25 fresh wood and bark traits were measured as indicators of wood accessibility for decomposers, nutritional quality and chemical or physical defence mechanisms. After 1 and 4 years of decay, we assessed the richness and composition of wood‐inhabiting fungi using amplicon sequencing and determined the proportional wood density loss. Average proportional wood density loss for the first year was 18.5%, with further decomposition occurring at a rate of 4.3% year−1 for the subsequent 3 years across tree species. Proportional wood density loss varied widely across tree species in the first year (8.7–24.8% year−1) and subsequent years (0–11.3% year−1). The variation was directly driven by initial wood traits during the first decay year, then later directly driven by bark traits and fungal community composition. Moreover, bark traits affected the composition of wood‐inhabiting fungi and thereby indirectly affected decomposition rates. Specifically, traits promoting resource acquisition of the living tree, such as wide conduits that increase accessibility and high nutrient concentration, increased initial wood decomposition rates. Fungal community composition, but not fungal richness explained differences in wood decomposition after 4 years of exposure in the field, where fungal communities dominated by brown‐rot and white‐rot Basidiomycetes were linked to higher wood decomposition rate. Synthesis: Understanding what drives deadwood decomposition through time is important to understand the dynamics of carbon stocks. Here, using a tailor‐made experimental design in a temperate forest setting, we have shown that stem trait variation is key to understanding the roles of these drivers; initially, wood traits explained decomposition rates while subsequently, bark traits and fungal decomposer composition drove decomposition rates. These findings inform forest management with a view to selecting tree species to promote carbon storage.

<i>Diospyros</i> <i>crassiflora</i> (HIERN) surface and subsoil leaf litter decomposition pattern along a time gradient in a humid rainforest

Litter decomposition is a crucial bedrock of nutrient recycling, organic matter accumulation, soil physicochemical properties, biodiversity and life support of forest and agroforestry systems. We therefore investigated <i>Diospyros</i> <i>crassiflora</i> surface and subsoil leaf litter decomposition pattern along a duration gradient in a humid rainforest. The study was conducted in the nursery of the humid forest research station of the Forestry Research Institute of Nigeria (FRIN) in Umuahia, Abia State. One gram (1g) of <i>D.</i> <i>crassiflora</i> fresh leaf litter was placed on the surface and subsoil of 4kg of topsoil contained in 32cm x 20cm polyethene bags; there were a total of 108 bags in a completely randomized experimental design layout and the treatments were the duration gradient of litter decomposition which were: 2, 4, 6, 8, 10, 12, and 14 weeks; on each of the duration, litter was collected from nine of the polyethene bags for laboratory analysis and estimate of decomposition rate. The results showed a significantly high initial decomposition rate (3.19±0.13 %day-1; 4.28±0.03 %day-1) in the 2 week duration followed by significant continuous decline until the lowest (0.04±0.00%day-1; 0.28±0.02%day-1) in the 14 week in the surface and subsoil respectively. There was a positive correlation (r=0.80) in decomposition rate between the surface and subsoil leaf litter, which yielded a model with a significant R2 (0.64), for site-specific estimates of decomposition rate <i>D.</i> <i>crassiflora</i> leaf litter. A steeper and smoother subsoil cumulative percentage decomposition curve showed that leaf litter decomposition was significantly faster in the subsoil than surface soil.

Thermal decomposition mechanism and thermal stability prediction of n-pentane/n-butane mixture

Mixtures appear to hold more promise in organic Rankine cycle (ORC) system than pure working fluids due to their better performance. The key limiting factor for the screening of mixture in the medium- and high temperature ORC system is its thermal stability. ReaxFF reactive molecular dynamic simulations and density functional theory calculations are performed in this study to investigate the thermal decomposition mechanism of n-pentane/n-butane mixture and predict its thermal stability. The results show that the presence of n-butane improves the thermal stability of n-pentane. According to the initial decomposition time, decomposition rates and apparent activation energies of mixture and pure working fluids, n-pentane/n-butane mixture has a better thermal stability than n-pentane and worse than n-butane. Based on the decomposition temperature ranges of n-pentane and n-butane, it can be determined that the n-pentane/n-butane mixture is stable at 280 °C. Therefore, the safe use temperature of the mixture can be roughly predicted based on the thermal stability data of the known working fluids and comparing the thermal decomposition of the mixture with these known working fluids. This paper provides a simple, economical and fast way for the safe use temperature prediction of mixture.

General analytical solution expressions for analyzing Langmuir-type kinetics of sonochemical degradation of nonvolatile organic contaminants in water

Detailed kinetic studies of the ultrasonic decomposition of contaminants in water are scarce. Most of the work has used a pseudo-first order kinetics law, which is unrealistic. The model based on a Langmuir-type mechanism has been shown to fit the sonolytic decomposition data well, especially by using the non-linear technique. To avoid unrealistic assumptions, general analytical solutions to a time-dependent non-linear Langmuir-type equation may be the appropriate method. In this work, the sonolytic oxidation of organic contaminants, i.e., naphthol blue black and furosemide, in water was analyzed using two general analytical solution expressions of the Langmuir-type kinetics model, which describe the pollutant concentration in water. The validity of the two general analytical solution expressions was tested under a diversity of operating conditions, such as initial substrate concentration and varying ultrasonication frequency and intensity. As the initial substrate concentration increased, the sonolytic oxidation kinetics decreased, while the initial ultrasonic decomposition rate increased and then plateaued. Consequently, a heterogeneous kinetics equation based on a Langmuir-type mechanism can be used to simulate the sono-decomposition process. The decomposition yield increased with increasing sonication intensity and decreasing frequency. The two analytical solution expressions seem to be in excellent agreement with the experimental results of the sonochemical decomposition of the nonvolatile organic contaminants tested for the different operating conditions examined. These expressions provide a valuable tool for the analysis and simulation of advanced sonochemical oxidation processes under various experimental conditions.

Warming accelerates belowground litter turnover in salt marshes – insights from a Tea Bag Index study

Abstract. Salt marshes play an important role in the global carbon cycle due to the large amount of organic carbon stored in their soils. Soil organic carbon formation in these coastal wetland ecosystems is strongly controlled by the plant primary production and initial decomposition rates of plant belowground biomass and litter. This study used a field warming experiment to investigate the response of belowground litter breakdown to rising temperature (+1.5 and +3.0 ∘C) across whole-soil profiles (0–60 cm soil depth) and the entire intertidal flooding gradient ranging from the pioneer zone via the low marsh to high marsh. We used standardized plant materials, following the Tea Bag Index approach, to assess the initial decomposition rate (k) and the stabilization factor (S) of labile organic matter inputs to the soil system. While k describes the initial pace at which labile (= hydrolyzable) organic matter decomposes, S describes the part of the labile fraction that does not decompose during deployment in the soil system and stabilizes due to biochemical transformation. We show that warming strongly increased k consistently throughout the entire soil profile and across the entire flooding gradient, suggesting that warming effects on the initial decomposition rate of labile plant materials are independent of the soil aeration (i.e., redox) status. By contrast, negative effects on litter stabilization were less consistent. Specifically, warming effects on S were restricted to the aerated topsoil in the frequently flooded pioneer zone, while the soil depth to which stabilization responded increased across the marsh elevation gradient via the low to high marsh. These findings suggest that reducing soil conditions can suppress the response of belowground litter stabilization to rising temperature. In conclusion, our study demonstrates marked differences in the response of initial decomposition rate vs. stabilization of labile plant litter to rising temperature in salt marshes. We argue that these differences are strongly mediated by the soil redox status along flooding and soil-depth gradients.

Increased storage stability of marble adhesive based on unsaturated polyester resin

In this paper, different combinations of accelerators and inhibitors were used to cure marble adhesive based on an unsaturated polyester resin. N, N- dimethyl aniline (DMA, NL-63), N, N-dimethylparatoluidine (DEP, NL-65), and ethoxylates of p-toluidine (Pergaquick A150 p.m.) were used as amine accelerators. Benzoyl peroxide (BPO) was used as a medium temperature decomposition initiator. Hydroquinone and 1,4- naphthoquinone were used as polymerization inhibitors. To study the curing behavior, gel time, pseudo-adiabatic exothermic, and storage stability measurements have been used. The low-temperature initiator decomposition rate has also influenced the exothermic peak and cure rate at various accelerators. It is shown in this study that for N, N- dimethyl aniline (DMA, NL-63), N, N-dimethylparatoluidine (DEP, NL-65) and Ethoxylates of p-toluidine (Pergaquick A-150) promoters systems, with the increasing of pergaquick A-150 concentration, namely high reactive accelerator, causes the exothermic parameters sharply change. It might be due to the more reactive nature of pergaquick A-150 in comparison with other accelerators reactivity. Due to this study, using a dual system of inhibitor, the storage stability of marble adhesive was increased. Now we can say, a judicious choice of a dual inhibitor and a dual accelerator can prevent short time exothermic reactions with high storage stability, so a dual system of the inhibitor can be much more effective than a single one.

Spectral Engineering of Hybrid Biotemplated Photonic/Photocatalytic Nanoarchitectures.

Solar radiation is a cheap and abundant energy for water remediation, hydrogen generation by water splitting, and CO2 reduction. Supported photocatalysts have to be tuned to the pollutants to be eliminated. Spectral engineering may be a handy tool to increase the efficiency or the selectivity of these. Photonic nanoarchitectures of biological origin with hierarchical organization from nanometers to centimeters are candidates for such applications. We used the blue wing surface of laboratory-reared male Polyommatus icarus butterflies in combination with atomic layer deposition (ALD) of conformal ZnO coating and octahedral Cu2O nanoparticles (NP) to explore the possibilities of engineering the optical and catalytic properties of hybrid photonic nanoarchitectures. The samples were characterized by UV-Vis spectroscopy and optical and scanning electron microscopy. Their photocatalytic performance was benchmarked by comparing the initial decomposition rates of rhodamine B. Cu2O NPs alone or on the butterfly wings, covered by a 5 nm thick layer of ZnO, showed poor performance. Butterfly wings, or ZnO coated butterfly wings with 15 nm ALD layer showed a 3 to 3.5 times enhancement as compared to bare glass. The best performance of almost 4.3 times increase was obtained for the wings conformally coated with 15 nm ZnO, deposited with Cu2O NPs, followed by conformal coating with an additional 5 nm of ZnO by ALD. This enhanced efficiency is associated with slow light effects on the red edge of the reflectance maximum of the photonic nanoarchitectures and with enhanced carrier separation through the n-type ZnO and the p-type Cu2O heterojunction. Properly chosen biologic photonic nanoarchitectures in combination with carefully selected photocatalyst(s) can significantly increase the photodegradation of pollutants in water under visible light illumination.

Thermogravimetric analysis of coking during dry reforming of methane

Nickel-based catalysts used for dry reforming of methane (DRM) suffer from coking and sintering, which hinders the broad application of the process in the industry. Thermogravimetric analysis was employed to investigate coking on a commercial nickel catalyst with an anti-coking additive (CaO). It was found that the catalyst sintered at temperatures between 850 and 900 °C, which resulted in permanent catalyst deactivation. For the tested Ni/CaO–Al2O3 catalyst, the coking and carbon gasification rates are equal at the temperatures of 796–860 °C, depending on the heating rate (5–20 K/min). Significant differences in the temperatures related to the maxima on TG curves for various heating rates follow from DRM kinetics. This work reveals that the coking rate is lower at higher temperatures. After 50 min, the weight gains amount to about 20% and 40% at 800 °C and 600 °C, respectively. Lower sample weight gains were observed at higher temperatures for a methane decomposition reaction over the Ni/CaO catalyst, unlike for the second tested catalyst – activated carbon. For the nickel catalyst, the reaction order for methane decomposition is 0.6 in the temperature range 640–800 °C, while the sign of the activation energy changes at 700 °C. The elaborated kinetic equation predicts the initial CH4 decomposition rate with 15% accuracy.

Litter Decomposition of Qinghai Spruce (Picea crassifolia) Is Dependent on Mn Concentration in the Qilian Mountains, Northwest China

The factors determining litter decomposition incorporated into C and nutrient cycles were examined as part of a broader study investigating the biogeochemical cycle in forest ecosystems. Litter was collected from five altitudes of Qinghai spruce (Picea crassifolia) woodland stands in the Qilian Mountains and placed in litterbags. These litterbags were installed at the crown center (CC) and crown edge (CE) at different altitudes in Qinghai spruce forests during the growing season to study the effect of litter substrate quality on litter decomposition. Results indicate that at varying altitudes in the growing season, the initial mass loss rate and initial decomposition rate of Qinghai spruce litter showed a nonlinear relationship with altitude. The Olson exponential regression equation showed that the decomposition coefficient (k) was the largest at 3050 m (k = 0.709), and the decomposition coefficient (k) was the smallest at 3250 m (k = 0.476). Meanwhile, the initial decomposition rate was highly correlated with initial litter Ca and Mn concentrations. At the CC and CE at different altitudes in the growing season, the initial mass loss rate of CE was significantly higher than that of CC (p < 0.01), and the initial decomposition rate of CE was markedly faster than that of CC (p < 0.01). The Olson exponential regression equation showed that CE’s decomposition coefficients (k) were larger than those of CC. The initial decomposition rate of CE was highly correlated with initial litter C and Mn concentrations. However, the initial decomposition rate at CC was independent of the litter substrate quality. Finally, we realize that litter decomposition in the early stages is not ultimately determined by a single common factor, but rather the result of multiple factors working together in different orders and strengths. The results lay a foundation for understanding the process and mechanism of litter decomposition in the alpine mountain forest ecosystem and further understanding the structure and function of the ecosystem.

Nascent Decomposition Pathways of CH4 Pyrolysis in Gas-Phase Metal Halides.

We have performed a combined quantum mechanical and microkinetic modeling study to understand the nascent decomposition pathways of methane pyrolysis, catalyzed by gas-phase ZnCl2, in a constant pressure batch reactor at 1273 K. We find that ZnCl2 catalyzes methane pyrolysis with an apparent activation energy of 227 kJ/mol. We have also performed sensitivity analysis on a reaction network comprising initiation, termination, and primary propagation reactions. The results suggest that the whole reaction network can be simplified to four reactions, which contributes to the initial rate of methane decomposition. Based on these insights, we have also explored the catalyzing effects of gas-phase AlCl3, CoCl2, CuCl2, FeCl2, and NiCl2 for methane decomposition. Our calculations suggest that gas-phase CuCl2 and NiCl2 are the most active catalysts among the metal halides studied in this work.

Climate, Soil, and Plant Controls on Early-Stage Litter Decomposition in Moso Bamboo Stands at a Regional Scale

Moso bamboo (Phyllostachys edulis) is currently distributed across a wide geographical area in East Asia. As a common bamboo species occurring along a broad environmental gradient, there is a need to understand how environmental and biotic drivers affect belowground processes at large scales. In this study, we investigated the influence of climate, soil properties, stand characteristics, and organic matter input parameters as potential drivers of the initial decomposition process in Moso bamboo stands at a regional scale. Using the Tea Bag Index method, we estimated the initial decomposition rate (k) and stabilization factor (S; potential long-term carbon storage) from standard litter incubated at 13 sites across southern Japan and Taiwan. We found that both decomposition parameters were strongly affected by the climate. The climatic conditions during the incubation period better explained the variance in k. In contrast, the long-term climate was more important for S. Notably, temperature and precipitation interactively affected the initial decomposition rates. This interaction showed that in warmer sites, precipitation increased k, whereas in cooler sites, precipitation had no effect or even decreased k. Soil parameters had no influence on k and only had minor effects on S. A structural equation model showed that the stabilization factor was indirectly affected by stand density, which suggests that higher bamboo densities could increase litter stabilization by increasing above-and below-ground organic matter input. Our study highlights the central role of climate in controlling decomposition processes in Moso bamboo stands on a broad scale. Moreover, differences in stand structure can indirectly affect potential soil carbon storage through changes in organic matter input and soil conditions.

Considering inner and outer bark as distinctive tissues helps to disentangle the effects of bark traits on decomposition

Abstract Revealing the ecological consequences of bark multifunctionality and its underlying traits has become a relatively new but essential focus in plant ecology. Although the enormous differences between the most crucial bark layers, that is, inner and outer bark, in structure and functions have been widely recognized, the overall bark has been regarded as a homogenous tissue in most bark‐related studies. This has led to poor knowledge on the functional independence, specialized contributions and possible linkages of inner and outer bark traits across tree species when further evaluating the crucial ecosystem functions that bark provides, especially in driving variation in bark decomposition. To fill this research gap, we used a ‘common garden experiment’ on deadwood of six gymnosperms in a temperate forest in the Netherlands over 4 years of decomposition. We evaluated the differences and associations between the inner and outer bark in initial functional traits, decomposition rates and afterlife effects of traits in driving in situ bark decomposition across tree species at the earlier decomposition stage. We report four main findings: (1) inner and outer bark traits varied significantly and were not coordinated across tree species; (2) correspondingly, the decomposition of the inner and outer bark were asynchronous and not coordinated across species and inner bark generally decomposed faster than outer bark; (3) the strong predictive traits driving bark decomposability were bark layer‐specific, with several inner bark traits controlling inner bark decomposition rates but outer bark decomposability being poorly predicted by outer bark traits and (4) besides being controlled by inner bark traits, inner bark decomposition was also indirectly regulated by several functional traits and the structure‐related trait spectrum of outer bark. Synthesis. This is the first study that has linked functional traits, decomposability and afterlife effects of the inner and outer bark within the bark quantitatively. We highlight the significance of separating functional traits and ecological consequences of the inner and outer bark in research in bark ecology and deadwood dynamics, rather than erroneously considering bark as a homogeneous tissue. Such research will help to better evaluate the function‐oriented contribution of bark to the turnover of forest carbon and biogeochemical cycles from local to global scale.

High quality litters with faster initial decomposition produce more stable residue remaining in a subtropical forest ecosystem

The regulation of factors like litter quality and soil mesofauna on litter decomposition in the early stage has been studied extensively in forest ecosystems. However, how litter decomposition was influenced by its quality and soil mesofauna in the late stage is largely unclear, especially in subtropical forest ecosystem. In the present study, litters from 16 species with contrasting chemical traits were incubated in a subtropical broadleaved forest for 2 years, and then the initial decomposition rate in early stage and stable residue remaining in late stage were calculated by using an asymptotic decomposition model. Litter bags with different mesh sizes (0.1 or 2 mm) were used to evaluate the role of soil mesofauna in regulating litter decomposition. Our results showed that litters with higher quality decomposed faster in early stage, and also had a larger fraction of stable residue remaining in the late stage. In addition, soil mesofauna exclusion had no influence on the decomposition rate at early stage, but significantly increased the stable residue remaining from 8.71% to 17.96%. We highlighted that the quality of plant litters play an important role in regulating the decomposition process in both early and late stage of decomposition, and thus the nutrient cycling and soil carbon (C) sink, in subtropical forest ecosystem.

Decomposition mechanisms of insensitive 2D energetic polymer TAGP using ReaxFF molecular dynamics simulation combined with Pyro-GC/MS experiments

The two-dimensional energetic polymer triaminoguanidine–glyoxal (TAGP) has been used in modification of EMs to formation of various hybrid materials for higher density and better stability due to its excellent capability to desensitize high energetic crystals without any energy loss. In this paper, theoretical calculations based on ReaxFF-MD were performed to demonstrate the thermal decomposition mechanisms of TAGP, which has been further proved by experimental results from Pyro-GC/MS analysis. The results show that there are three dominant pathways for the initial decomposition of TAGP, i.e., the breakage of C-N bond with production of C2H3ON2 (most likely to happen), the scission of N-N bond with release of C2H2ON, and the rupture of N-N bond accompanied with the proton transfer to release C2H3ON. Therefore, the C2H3ON2, C2H2ON and C2H3ON are the dominant initial decomposition products of TAGP, which may gradually transform to the final gaseous products. The experimental results confirmed the presences of these substances. The major final gaseous products of TAGP include N2, H2, H2O, NH3, NH4, NH2, N2H, N2H2, HCN and CO2, among which the concentration of N2 is the highest, relatively higher than H2, H2O and NH3. Besides, the initial decomposition rate of TAGP largely depends on its MW. The activation energies for formation of C2H3ON2 and N2 under isothermal conditions has been obtained to further illustrate the effect of MW on the decomposition rate.

Theoretical and Experimental Considerations for a Rapid and High Throughput Measurement of Catalase In Vitro.

A rapid and high throughput protocol to measure the catalase activity in vitro has been designed. Catalase is an enzyme with unusual kinetic properties because it does not follow the standard Michaelis–Menten model and is inactivated by H2O2. This makes the analysis of the two rate equations of the second-ordered reactions of the kinetic model rather complex. A two-degree polynomial fitting of the experimental data is proposed after transforming the exponential form of the integrated rate equation of the [H2O2] into a polynomial using the Taylor series. The fitting is validated by establishing an experimental linear relationship between the initial rate of the H2O2 decomposition and the protein concentration, regardless of the suicide inactivation that catalase might undergo beyond t > 0. In addition, experimental considerations are taken into account to avoid statistical bias in the analysis of the catalase activity. ANOVA analyses show that the proposed protocol can be utilized to measure the initial rate of the H2O2 decomposition by catalase in 32 samples in triplicates if kept below 8 mM min−1 in the microplate wells. These kinetic and statistical analyses can pave the way for other antioxidant enzyme activity assays in microplate readers at small scale and low cost.

Impact of reactor materials on methane decomposition for hydrogen production

In this study, the catalytic effect of the internal surface of reactors constructed from stainless steel (SS310) for hydrogen production via methane decomposition has experimentally been proved and compared with a quartz-lined reactor. The effects of the methane decomposition temperature and volume-hourly-space velocity (VHSV) on hydrogen production, conversion of methane, and initial decomposition rates were investigated in an SS310 lab-scale reactor. Within the duration of the experiments, no change was recorded for hydrogen and methane concentration in all the experiments. The catalytic activity of the SS310 reactor's internal surface increased with increasing methane decomposition temperature (850−950°C) and decreasing VHSV (37−52h−1). The as-produced carbon was characterized using surface texture analysis, X-ray, and SEM-EDX.