Initial Stages Of Decay Research Articles

Re‐Examination of Self‐Decay Chemistry of Phthalimide‐N‐oxyl Redox‐Organocatalyst for Free‐Radical CH‐Functionalization – Puzzle Begins to Come Together

AbstractPhthalimide‐N‐oxyl radicals (PINO) are catalytically active hydrogen abstracting species generated from N‐hydroxyphthalimide (NHPI) – one of the most efficient and widely used organocatalysts for free‐radical oxidative CH‐functionalization processes. The self‐decay of PINO is one of the main limiting factors of NHPI usage, but currently there is no consensus on the mechanism of this important process. In the present work, quantitative EPR and NMR monitoring of PINO generation and degradation along with decay product analysis and control experiments allowed us to build a consistent picture of PINO decay chemistry and put together previously contradictory results. PINO yields achievable employing various oxidants were measured and compared for the first time. At least two PINO decay pathways were revealed: “trimerization” (with partial fragmentation, favored by high PINO concentrations at initial stage of decay), and medium oxidation favored by low PINO concentrations. The main PINO decomposition product, the “trimer” can easily be recycled back to NHPI.

Microbiota succession influences nematode physiology in a beetle microcosm ecosystem

Unravelling the multifaceted and bidirectional interactions between microbiota and host physiology represents a major scientific challenge. Here, we utilise the nematode model, Pristionchus pacificus, coupled to a laboratory-simulated decay process of its insect host, to mimic natural microbiota succession and investigate associated tripartite interactions. Metagenomics reveal that during initial decay stages, the population of vitamin B-producing bacteria diminishes, potentially due to a preferential selection by nematodes. As decay progresses to nutrient-depleted stages, bacteria with smaller genomes producing less nutrients become more prevalent. Lipid utilisation and dauer formation, representing key nematode survival strategies, are influenced by microbiota changes. Additionally, horizontally acquired cellulases extend the nematodes’ reproductive phase due to more efficient foraging. Lastly, the expressions of Pristionchus species-specific genes are more responsive to natural microbiota compared to conserved genes, suggesting their importance in the organisms’ adaptation to its ecological niche. In summary, we show the importance of microbial successions and their reciprocal interaction with nematodes for insect decay in semi-artificial ecosystems.

Functional Characterization of PoEP1 in Regulating the Flowering Stage of Tree Peony.

The tree peony, a traditional flower in China, has a short and concentrated flowering period, restricting the development of the tree peony industry. To explore the molecular mechanism of tree peony flowering-stage regulation, PoEP1, which regulated the flowering period, was identified and cloned based on the transcriptome and degradome data of the early-flowering mutant Paeonia ostii 'Fengdan' (MU) and Paeonia ostii 'Fengdan' (FD). Through bioinformatics analysis, expression pattern analysis, and transgene function verification, the role of PoEP1 in the regulation of tree peony flowering was explored. The open-reading frame of PoEP1 is 1161 bp, encoding 386 amino acids, containing two conserved domains. PoEP1 was homologous to the EP1 of other species. Subcellular localization results showed that the protein was localized in the cell wall and that PoEP1 expression was highest in the initial decay stage of the tree peony. The overexpression of PoEP1 in transgenic plants advanced and shortened the flowering time, indicating that PoEP1 overexpression promotes flowering and senescence and shorten the flowering time of plants. The results of this study provide a theoretical basis for exploring the role of PoEP1 in the regulation of tree peony flowering.

Characteristics of PoVIN3, a Key Gene of Vernalization Pathway, Affects Flowering Time.

The tree peony (Paeonia section Moutan DC.) is the candidate flower in China, with abundant germplasm resources and high ornamental value. However, the short and concentrated flowering period severely restricted the improvement of the economic value of tree peonies. Based on the full-length transcriptome database of tree peonies, the PoVIN3 (GenBank ID: OP341879), involved in the flowering regulation of tree peonies were identified and cloned for the first time. The PoVIN3 was also characterized by bioinformatics methods, quantitative real-time PCR (qRT-PCR), and the establishment of a transgenic system. The expression levels of PoVIN3 in seven different petals developmental stages were the highest at the initial flowering stage of the variant cultivar of Paeonia ostii 'Fengdan,' the initial decay stage of the normal flowering Paeonia ostii 'Fengdan,' and the half opening stage of the late flowering Paeonia suffruticosa 'Lianhe.' Tissue-specific expression analysis showed that the relative expression levels of PoVIN3 were the highest in sepals of both normal flowering Paeonia ostii 'Fengdan' and the late flowering Paeonia suffruticosa 'Lianhe,' and the highest expression was in stamens of early flowering mutant Paeonia ostii 'Fengdan.' In addition, the flowering time of pCAMBIA2300-PoVIN3 transgenic plants was significantly earlier than that of the wild-type, indicating that PoVIN3 could promote plant flowering. The results provide a theoretical basis for exploring the role of PoVIN3 in the regulation of flowering in tree peonies.

Influence of southern pine beetle on fungal communities of wood and bark decomposition of coarse woody debris in the New Jersey pine barrens.

Dead coarse woody debris (fungal food resources) on the forest floor is an ignition source for forest fires. The rate of decomposition of the debris is largely influenced by fungi, determining its residence time on the forest floor. We asked if southern pine bark beetle (Dendroctonus frontalis) attack of pitch pine (Pinus rigida) alters the decomposition and fungal community of dead woody resources. Wood and bark from beetle infested and non-beetle infested resources were decomposed in litter bags on the forest floor. Decomposition was measured as mass loss and the fungal community by next-generation (PCR and Illumina metabarcoding) sequencing. Bark decomposed slower than wood and resources colonized by beetles decomposed faster than resources with no beetles. The initial differences in fungal communities colonizing the resources continued throughout the 42 months of decomposition. Fungal diversity was higher in wood than bark in initial decay stages, but significantly lower in wood than bark at the end of the 42 month incubation. In contrast, there were no significant differences in fungal communities between beetle infested and uninfested resources. The rate of decomposition of woody resources on the forest floor has great implications for the longevity of fuel sources for forest fires, however, our results indicate that beetle attacked wood poses no greater fire risk than other dead coarse woody debris regarding the residence time.

Topochemical and light microscopic investigations of non-enzymatic oxidative changes at the initial decay stage of furfuryl alcohol-modified radiata pine (Pinus radiata) degraded by the brown rot fungus Rhodonia placenta

The aim of this study was to visualize non-enzymatic oxidative degradation damages in the initial decay stage of the brown rot fungus Rhodonia placenta degradation in furfuryl alcohol (FA) modified wood cell walls and untreated wood cell walls of radiata pine (Pinus radiata) sapwood. A decay test with small wood blocks (1.5 × 1.5 × 5 mm³) of untreated and furfurylated radiata pine selected from two different furfurylation processes was performed until the first mass loss occurred. The samples were exposed to the brown rot fungus R. placenta, monitored by light microscopy and analyzed topochemically by cellular UV microspectrophotometry (UMSP). The results showed that the FA modification process directly influenced: i) the fungal colonization and hyphal growth, ii) the spectral UV behavior, and iii) degradation patterns of the entire cell wall layers. For the first time, UMSP area scans and selective line scans of individual cell wall regions provide topochemical insights into oxidative degradation at the initial decay stage of furfuryl alcohol-modified P. radiata visualizing oxidative degradation in situ. Knowledge of the initial decay stage of brown rot degradation in FA-modified wood compared to untreated wood extends our understanding of the brown rot decay processes of cell wall compounds.

Substrate quality drives fungal necromass decay and decomposer community structure under contrasting vegetation types

Abstract Fungal mycelium is increasingly recognized as a central component of soil biogeochemical cycling, yet our current understanding of the ecological controls on fungal necromass decomposition is limited to single sites and vegetation types. By deploying common fungal necromass substrates in a temperate oak savanna and hardwood forest in the midwestern USA, we assessed the generality of the rate at which high‐ and low‐quality fungal necromass decomposes; further, we investigated how the decomposer ‘necrobiome’ varies both across and within sites under vegetation types dominated by either arbuscular or ectomycorrhizal plants. The effects of necromass quality on decay rate were robust to site and vegetation type differences, with high‐quality fungal necromass decomposing, on average, 2.5 times faster during the initial stages of decay. Across vegetation types, bacterial and fungal communities present on decaying necromass differed from bulk soil microbial communities and were influenced by necromass quality. Moulds, yeasts and copiotrophic bacteria consistently dominated the necrobiome of high‐quality fungal substrates. Synthesis. We show that regardless of differences in decay environments, high‐quality fungal substrates decompose faster and support different types of decomposer micro‐organisms when compared with low‐quality fungal tissues. These findings help to refine our theoretical understanding of the dominant factors affecting fast cycling components of soil organic matter and the microbial communities associated with rapid decay.

Biodegradation inducers to enhance wheat straw pretreatment by Gloeophyllum trabeum to second-generation ethanol production.

The native state of lignocellulosic biomass is highly resistant to enzymatic hydrolysis and the fermentation process of biofuel production. Brown-rot fungi use an extracellular Fenton system to degrade lignocellulosic biomass in the initial stages of decay. In this work, the combined effects of Mn2+, Fe2+, and NO3- inducers were evaluated based on the activities of hydrolytic enzymes and Fe3+ reduction as well as the catechol-type compound production during wheat straw pretreatment by the brown-rot fungus Gloeophyllum trabeum. Weight loss and chemical changes were evaluated to establish the culture conditions for stimulating wheat straw degradation using a central composite design. The results showed that weight loss and the Fe3+-reducing activity were promoted at the highest concentrations of Fe2+. A positive effect on catechol compound production by the addition of Mn2+ and NO3- was observed. Cellulase activity was increased at the highest concentration of NO3-. The multiple optimizations of G. trabeum culture conditions in wheat straw resulted in 11.3% weight loss and 0.47 total crystallinity index at 0.24M NO3-, 0.95mM Fe2+, and 0.85mM Mn2+ after 40days. The wheat straw pretreatment by G. trabeum for 10days increased glucose recovery. The results indicated that the wheat straw pretreatment using G. trabeum with biodegradation inducers could be a complementary step to physicochemical pretreatment of lignocellulosic biomass for production of second-generation ethanol.

New Functional Possibilities of Fire Detectors for Residential and Industrial Rooms

The relevance of early detection of fire signs is quite obvious because due to the necessary measures for evacuating of people and material values, disconnecting the electrical equipment and extinguishing the fire at the time of the onset of fire or passive smoldering, human casualties can be completely avoided and economic losses can be minimized.A graphical representation of fire detectors' the classification in the form of a generalized scheme using all the main classification features, their advantages and disadvantages is given. The optimal areas for the use of detectors depending on the fire load are determined. The effectiveness of combined fire detectors' use, equipped in addition to traditional smoke and heat sensors with gas sensors, as an integrated approach to the organization of control over protected objects is shown.The results of development of highly sensitive two-zone sensor with sensitive elements based on iron oxide films for detecting the release of explosive and poisonous gases in the initial stage of decay before the formation of ignition conditions are presented. The use of gas sensors that respond to hazardous gases in the environment significantly reduces the risk of death due to carbon monoxide poisoning.

Dissociative Recombination of $${\text{Ne}}_{{\text{2}}}^{ + }$$ Molecular Ions with Electrons: Population of Ne(2р54р) Atoms in a Decaying Plasma

Decaying neon plasma has been investigated by kinetic spectroscopy. The experimental conditions were neon pressure of 0.2–152 Torr and electron density in the initial stage of decay [e] ≤ 5 × 1010 cm–3. The plasma was created by a pulsed barrier discharge with electrodes on the outer surface of a cylindrical glass tube. The discharge frequency was 40–160 Hz. It has been shown based on a comparative analysis of the dependences of the intensities of spectral lines on the time and electron temperature in the afterglow that the 2р54р levels are clearly divided into two groups in terms of population mechanisms. The lower levels (from 3р10 to 3р3 (Paschen notations)) are related to dissociative recombination of $${\text{Ne}}_{{\text{2}}}^{ + }$$ molecular ions with electrons, and the lines emitted by them behaved identically to the lines of the transitions 2p53s ← 2p53p and 2p53p ← 2p53d up to pressures of 0.6 Torr. The kinetics of the upper levels (3р5, 3р2, 3р4, and 3р1) had a more complicated character, and, at low pressures, the populations of all 2p54p levels were related to a collisional-radiative recombination of Ne+ ions. Significant differences in the dependences of the relative populations of 3d- and 4p levels on neon pressure are discussed.

Диссоциативная рекомбинация молекулярных ионов Ne-=SUB=-2-=/SUB=--=SUP=-+-=/SUP=- с электронами. Заселение атомов конфигурации 2p-=SUP=-5-=/SUP=-4p в распадающейся плазме

The paper presents the results of the study of decaying neon plasma by the method of kinetic spectroscopy. Experimental conditions: neon pressure 0.2–152 Torr, electron density in the initial stage of decay [e] ≤ 5 × 1010 cm-3. The plasma was created by a pulsed barrier discharge with electrodes on the outer surface of a cylindrical glass tube. Discharge frequency 40–160 Hz. On the basis of a comparative analysis of the dependences of the intensities of spectral lines on the time and temperature of electrons in the afterglow, it was shown that in terms of the mechanisms of population, the levels of 2p54p are clearly divided into two groups. Lower levels: from 3p10 to 3p3 (Paschen notation) are associated with the dissociative recombination of molecular ions with electrons and, up to pressures of 0.6 Torr, the lines emitted by them behave identically to the lines of 2p53s ← 2p53p and 2p53p ← 2p53d transitions. The behavior of the upper levels (3p5, 3p2, 3p4, and 3p1) was more complex, and at low pressures, the populations of all 2p54p levels turned out to be related to the impact-radiation recombination of Ne + ions. Significant differences in the dependences of the relative populations of 3d and 4p levels on the neon pressure are discussed.

Social wasps (Vespidae: Polistinae) on carcasses of Rattus norvegicus (Mammalia: Muridae) in the Central Amazonia, Brazil: possible forensic implications

We evaluated the occurrence of social wasps in the decomposition process in tropical rainforest in central Amazonia (Ducke Reserve, Manaus, Brazil), using cadavers of rats as attractants, exposed in suspended cages. Ten species, in three genera, of social wasps were collected only in the initial stages of decay (fresh and bloated). Five species were collected, mainly in the fresh stage, feeding on flesh: Agelaia angulata, Agelaia constructor, Agelaia fulvofasciata, Agelaia pallipes and Angiopolybia pallens. Five species were collected, mainly in the bloated stage, feeding on flesh and eggs and first instar larvae of dipteran: Agelaia testacea, Angiopolybia obidensis, Apoica arborea, Apoica pallens and Apoica thoracica. Due to the aspect of the injuries caused by the wasps to the carcass, they may be mistaken as skin ulcers, burns or abrasions, which may mislead a forensic investigation.

Dynamics of nutrient concentration and microbial community composition during fine root decomposition in subtropical Mytilaria laosensis and Cunninghamia lanceolata plantations.

We conducted a 12-month fine root decomposition experiment under 19-year-old Mytilaria laosensis and Cunninghamia lanceolate plantations to explore the dynamics of nutrient concentration and microbial community composition. The aim of this study was to provide insights into nutrient cycling under plantations with different tree species. Our results showed that the initial concentrations of phosphorus (P) and potassium (K) were significantly higher in the fine root of M. laosensis than those in C. lanceolata, which significantly decreased with decomposition. Nitrogen (N) concentration in fine roots of both species increased with decay time. The variation of N concentration in fine root of C. lanceolata lagged behind that in M. laosensis. During the decomposition, magnesium (Mg) concentration in fine root of C. lanceolata showed no significant changes, but that of M. laosensis decreased at the initial decay stage and increased thereafter and was significantly lower than that of C. lanceolata at the 8th month. The ratio of fungi to bacteria (F/B) of both species decreased at the initial stage and then increased, with significantly higher F/B in fine root of M. laosensis than that of C. lanceolate after one-year decay. Redundancy analysis (RDA) showed that changes in N and K concentrations and C/N ratio explained 37.2%, 14.5% and 14.8% of the variations in microbial community composition of C. lanceolata fine root respectively. However, during the decay of M. laosensis fine root, concentrations of Mg and K were key factors, accounting for 35.9% and 17.6% of the variations in microbial community composition, respectively. We concluded that other nutrients beyond N, such as Mg, might also be an important factor affecting root decomposition in different tree species.

Antioxidant activity of Scots pine heartwood and knot extractives and implications for resistance to brown rot

Abstract Brown rot (BR) fungi are highly destructive wood decaying organisms that utilise free radicals in the initial stages of decay. Although many wood extractives have been shown to have antioxidant (AO) activity, their ability to protect wood from radical-based degradation has received little attention. The present paper reports on the ability of Scots pine heartwood (hW) and knotwood (knW) extractives to inhibit radical-based degradation, with a focus on the Fenton reaction. AO assays showed that extract solutions and pure pinosylvins had good radical scavenging activity and weak to moderate ferrous iron binding and ferric iron reducing activities. AO assays were repeated with wood powders and showed that extractives were also active in wood: hW and knW had significantly higher activities than their extracted counterparts or sapwood. However, when wood powders were subjected to degradation by Fenton reagent, only knW showed reduced mass loss. Based on the activity profiles of knW and hW, it appears that the radical scavenging activity of pine extractives is more important than their interaction with iron. The results suggest that the AO activity of extractives may play a role in inhibiting BR, but its importance relative to the other biological activities of extractives is unknown.

Power-law exponent in the transition period of decay in grid turbulence

Hot-wire measurements are carried out in grid-generated turbulence at moderate to low Taylor microscale Reynolds number $Re_{{\it\lambda}}$ to assess the appropriateness of the commonly used power-law decay for the mean turbulent kinetic energy (e.g. $k\sim x^{n}$, with $n\leqslant -1$). It is found that in the region outside the initial and final periods of decay, which we designate a transition region, a power law with a constant exponent $n$ cannot describe adequately the decay of turbulence from its initial to final stages. One is forced to use a family of power laws of the form $x^{n_{i}}$, where $n_{i}$ is a different constant over a portion $i$ of the decay time during the decay period. Accordingly, it is currently not possible to determine whether any grid-generated turbulence reported in the literature decays according to Saffman or Batchelor because the reported data fall in the transition period where $n$ differs from its initial and final values. It is suggested that a power law of the form $k\sim x^{n_{init}+m(x)}$, where $m(x)$ is a continuous function of $x$, could be used to describe the decay from the initial period to the final stage. The present results, which corroborate the numerical simulations of decaying homogeneous isotropic turbulence of Orlandi & Antonia (J. Turbul., vol. 5, 2004, doi:10.1088/1468-5248/5/1/009) and Meldi & Sagaut (J. Turbul., vol. 14, 2013, pp. 24–53), show that the values of $n$ reported in the literature, and which fall in the transition region, have been mistakenly assigned to the initial stage of decay.

Fungal succession in the needle litter of a montane Picea abies forest investigated through strain isolation and molecular fingerprinting

Abstract Precise knowledge of the fungal succession in the litter of coniferous forests will facilitate understanding litter decomposition, in which fungi play a major role. We investigated the development of a fungal community during 3 yr of Picea abies litter decomposition in three control forest sites and three sites where bark-beetle attacks had killed adult trees and stopped the yearly input of fresh litter, using both cultivation from needles and terminal restriction-fragment length polymorphism analysis. The two methods revealed similar dominant species during the fungal succession. Members of the Dothideales, Eurotiales and Helotiales predominated during the initial stage of decay, whereas members of Agaricales appeared only occasionally during this stage. The onset of the latter began from the seventh month, with a peak occurring after 1 yr. Bark-beetle attacks hastened litter decomposition and decreased fungal diversity only during the initial stages of decomposition.

The influence of nonlinear bottom friction on the properties of decaying cyclonic and anticyclonic vortex structures in a shallow rotated fluid

AbstractThe problem of the decay of intense vortices in a shallow rotated neutrally stratified fluid is considered using simulations with a modified model of von Kármán type and laboratory experiments. The numerical model describes a forced axisymmetric vortex, vertically confined, but infinite in the horizontal plane. It may be used for comparisons with laboratory experiments, in which a quasi-turbulent eddy flow is generated, using magnetohydrodynamic forcing. A detailed analysis of simulations of the free decay of the flow from an initial state, given either by an arbitrary Poiseuille or by a forced stationary profile of vorticity, is provided. Based on this analysis, three different regimes of decay of intense anticyclones in the parameter space of the Ekman and initial Rossby numbers are found. It is shown that anticyclones with large enough Rossby and small enough Ekman numbers may decay to a non-trivial stationary state, or at least they decay much slower than cyclones of the same intensity. The laboratory experiments show much slower decay of intense anticyclones than weak anticyclones or cyclones, and also a dominance of anticyclones over cyclones during the initial stage of decay. These observations qualitatively agree with theoretical predictions.

The impacts of treatment with biocontrol fungus (Phlebiopsis gigantea) on bacterial diversity in Norway spruce stumps

The biocontrol agent Phlebiopsis gigantea has been intensively applied to the surface of Picea abies stumps to control Heterobasidion root rot. But little is known about the possible impact of this treatment on the resident bacteria community in the stumps. High throughput DNA bar-coded pyrosequencing was used to characterize the diversity of bacteria in the stumps of P. abies at 1, 6 and 13years after treatment with P. gigantea. The sequences were classified into 12 phyla and 160 genera, of which Proteobacteria and Acidobacteria were the most abundant groups over time. Moreover, at the initial stages of decay, Proteobacteria were the most abundant whereas Acidobacteria were the most common at advanced stages of decay. Treatment with P. gigantea led to significant increase of the genus Acidobacteria-Gp1 at 1year after treatment. The analysis of observed and estimated operational taxonomic units (OTUs) as well as diversity indices revealed that P. gigantea treatment significantly decreased the initial bacterial richness in the stumps, but the bacterial community gradually recovered and the negative effects of P. gigantea was attenuated. These results provide additional insight on the risk assessment as well as environmental impact on the long-term use of P. gigantea in the control of Heterobasidion root rot in conifer forests.

Ultrafast photocarrier relaxation processes in Er-doped InAs quantum dots embedded in strain-relaxed InGaAs barriers

Time-resolved transmission change of Er-doped InAs quantum dots (QDs) embedded in strain-relaxed In0.45Ga0.55As barriers has been studied using different excitation wavelengths (1.4–1.55μm) to understand the QD-size dependence of the photocarrier relaxation. Each measured temporal profile was well reproduced by a sum of three exponential decays. Ultrafast (∼1.6ps) and fast (∼6–9ps) components are dominant in the initial stage of decay, and then the slow (∼70–130ps) component due to the radiative recombination in the QDs appears to be seen. The first two components come from photocarrier relaxation into the nonradiative centers related to Er dopants or the lattice relaxation. The difference is considered to result from whether the nonradiative centers are positioned inside or outside the QDs. The decay time for the outside case becomes shorter as the excitation wavelength is shortened, which might be due to the weaker confinement of photocarriers in the smaller-size QDs. Suppression of the QDs contributing to the radiative recombination is also more significant for the smaller-size QD excitation.

Nonequilibrum dynamics in the strongly excited inhomogeneous Dicke model

Using the exact eigenstates of the inhomogeneous Dicke model obtained by numerically solving the Bethe equations, we study the decay of bosonic excitations due to the coupling of the mode to an ensemble of two-level (spin 1/2) systems. We compare the quantum time-evolution of the bosonic mode population with the mean field description which, for a few bosons agree up to a relatively long Ehrenfest time. We demonstrate that additional excitations lead to a dramatic shortening of the period of validity of the mean field analysis. However, even in the limit where the number of bosons equal the number of spins, the initial instability remains adequately described by the mean-field approach leading to a finite, albeit short, Ehrenfest time. Through finite size analysis, we also present indications that the mean field approach could still provide an adequate description for thermodynamically large systems even at long times. However, for mesoscopic systems one cannot expect it to capture the behavior beyond the initial decay stage in the limit of an extremely large number of excitations.