Initial Stage Of Degradation Research Articles

Research on rolling bearing fault detection in the initial stage of degradation based upon optimized NLM and TKEO

Research on rolling bearing fault detection in the initial stage of degradation based upon optimized NLM and TKEO

Plastid Genome Degradation in the Endangered, Mycoheterotrophic, North American Orchid Hexalectris warnockii.

Heterotrophic plants provide evolutionarily independent, natural experiments in the genomic consequences of radically altered nutritional regimes. Here, we have sequenced and annotated the plastid genome of the endangered mycoheterotrophic orchid Hexalectris warnockii. This orchid bears a plastid genome that is ∼80% the total length of the leafy, photosynthetic Phalaenopsis, and contains just over half the number of putatively functional genes of the latter. The plastid genome of H. warnockii bears pseudogenes and has experienced losses of genes encoding proteins directly (e.g., psa/psb, rbcL) and indirectly involved in photosynthesis (atp genes), suggesting it has progressed beyond the initial stages of plastome degradation, based on previous models of plastid genome evolution. Several dispersed and tandem repeats were detected, that are potentially useful as conservation genetic markers. In addition, a 29-kb inversion and a significant contraction of the inverted repeat boundaries are observed in this plastome. The Hexalectris warnockii plastid genome adds to a growing body of data useful in refining evolutionary models in parasites, and provides a resource for conservation studies in these endangered orchids.

Systems analysis of the glycoside hydrolase family 18 enzymes from Cellvibrio japonicus characterizes essential chitin degradation functions

Understanding the strategies used by bacteria to degrade polysaccharides constitutes an invaluable tool for biotechnological applications. Bacteria are major mediators of polysaccharide degradation in nature; however, the complex mechanisms used to detect, degrade, and consume these substrates are not well-understood, especially for recalcitrant polysaccharides such as chitin. It has been previously shown that the model bacterial saprophyte Cellvibrio japonicus is able to catabolize chitin, but little is known about the enzymatic machinery underlying this capability. Previous analyses of the C. japonicus genome and proteome indicated the presence of four glycoside hydrolase family 18 (GH18) enzymes, and studies of the proteome indicated that all are involved in chitin utilization. Using a combination of in vitro and in vivo approaches, we have studied the roles of these four chitinases in chitin bioconversion. Genetic analyses showed that only the chi18D gene product is essential for the degradation of chitin substrates. Biochemical characterization of the four enzymes showed functional differences and synergistic effects during chitin degradation, indicating non-redundant roles in the cell. Transcriptomic studies revealed complex regulation of the chitin degradation machinery of C. japonicus and confirmed the importance of CjChi18D and CjLPMO10A, a previously characterized chitin-active enzyme. With this systems biology approach, we deciphered the physiological relevance of the glycoside hydrolase family 18 enzymes for chitin degradation in C. japonicus, and the combination of in vitro and in vivo approaches provided a comprehensive understanding of the initial stages of chitin degradation by this bacterium.

Bacterial Genes of Non-Heme Iron Oxygenases, Which Have a Rieske-Type Cluster, Catalyzing Initial Stages of Degradation of Chlorophenoxyacetic Acids

Hydroxylation of the benzoic ring by non-heme iron oxygenases having a Rieske-type cluster is the key step in the aerobic degradation of chloroaromatic compounds by bacteria. Rieske oxygenases (RO) catalyze the oxidative decarboxylation reaction unique to the enzymes of this family with the formation of corresponding phenolic compounds. This review discusses the general structure, function, and classification of ROs that catalyze the oxidation of chlorophenoxyacetic acids; genes encoding the ROs with their phylogenetic classes are also reviewed.

First-principles study of Cs/Rb co-doped FAPbI3 stability and degradation in the presence of water and oxygen

The poor stability of organometallic halide perovskite in humid environments is one of the biggest challenges for its commercialization in light harvesting and electroluminescent displays. Understanding the atomic detail of the perovskite/water (oxygen) interface is a critical way to explore the practicability of perovskite. In this work, we report a density functional study of water and oxygen adsorption on the Cs/Rb incorporated FAPbI3 (001) surface. The role played by water and oxygen molecules has been extensively studied in the initial degradation processes, where the strong interactions between adsorbates and perovskite surfaces are confirmed. Our results show that the dopant-terminated surface was relatively more stable than PbI2-termination one. The effects of doping on the optoelectronic properties were slight at low concentrations. The calculations showed that the molecule tend to adsorb on the I-top site of the Cs-terminated surface and the Pb-top site of the PbI2 (Cs)-terminated surface. The vdW contribution on the bonding between bare surface and molecule can be observed. The degradation-induced optical absorption decrease in the visible region could be found. Water and oxygen molecule destroy the perovskite surface structures and subsequently reduce its conversion efficiency. These findings contribute molecular-level insight into the initial stage of perovskite degradation, which should be helpful to inspire new interfacial modifications to improve the stability of corresponding perovskite materials under wet conditions.

Competitive reactions of hydroxyl and sulfate radicals with sulfonamides in Fe2+/S2O82− system: Reaction kinetics, degradation mechanism and acute toxicity

Four sulfonamides, viz. sulfadiazine (SD), sulfamerazine (SM), sulfadimethoxine (SDM) and sulfachloropyridazine (SCP), were selected as model compounds to be degraded in Fe2+/S2O82− system with a Fe2+:S2O82− molar ratio of 1:4. The results of degradation kinetics indicate that the rate constants follows the order of SD > SM > SDM > SCP, and the aromatic and heteroaromatic rings of the sulfonamides are relatively low in reaction activity. Both hydroxyl radicals (OH) and sulfate radicals (SO4−) are responsible for the degradation of sulfonamides, with the latter playing a more significant role. The theoretical results suggest that OH are majorly involved in the H-abstraction and addition reactions of the sulfonamides. Nonetheless there is single-electron transfer between the SO4− and sulfonamides, which results in oxidation of –NH2 group and Smiles rearrangement. Based on the experimental and theoretical results, the degradation intermediates and degradation pathways are verified. At the initial stage of degradation, there is cleavage of S-N bond, hydroxylation of parent compounds, Smiles rearrangements and oxidation of –NH2. It is found that the incomplete mineralization of sulfonamides results in increase of acute toxicity. The study sheds light on the fate and transformation of sulfonamides under the attack of reactive oxygen species in environmental water.

Influence of functionalized calcium carbonate nanofillers on the properties of melt-extruded polycarbonate composites

ABSTRACTIn an effort toward developing better tribological properties of polycarbonate (PC), a reinforcement with calcium carbonate (CaCO3) nanoparticles (3% by weight), in the size range of 30–60 nm, functionalized using stearic acid, was carried out by melt extrusion method. It was established that scratch resistance of PC/CaCO3 composites (PCC) improved by 30% in comparison with pure PC. Nevertheless, an assessment of thermal properties using thermogravimetric analysis and differential scanning calorimetry (DSC) indicated an inferior thermal stability of PCC. Thermomechanical properties as obtained from dynamic mechanical analysis revealed an improvement in storage modulus for PCC but loss tangent (tan δ) results indicated lower glass transition (Tg) values in agreement with DSC results. To comprehend the thermal behavior of PCC, degradation kinetics was studied using the model-free method, and it was observed that the presence of organically modified nanoparticles resulted in catalysis of degradation, thus, lowering apparent activation energy (Eα) for PCC at the initial stages of degradation.

The Emergence of Different Functionally Equivalent PAH Degrading Microbial Communities from a Single Soil in Liquid PAH Enrichment Cultures and Soil Microcosms Receiving PAHs with and without Bioaugmentation.

Polycyclic aromatic hydrocarbon (PAHs) are common soil contaminants of concern due to their toxicity toward plants, animals and microorganisms. The use of indigenous or added microbes (bioaugmentation) is commonly used for bioremediation of PAHs. In this work, the biodegradation rates and changes in the bacterial community structure were evaluated. The enrichment culture was useful for unambiguously identifying members of the soil bacterial community associated with PAH degradation and yielded a low diversity community. No significant difference in the rate of PAH degradation was observed between the microcosm receiving only PAHs or PAHs and bioaugmentation. Moreover, identical matches to the bioaugmentation inoculum were only observed at the initial stages of PAH degradation on day 8. After 22 days of incubation, the substantial degradation of all PAHs had occurred in both microcosms and the PAH contaminated soil had statistically significant increases in Alphaproteobacteria. There were also increases in Betaproteobacteria. In contrast, the PAH contaminated and bioaugmented soil was not enriched in PAH degrading Proteobacteria genera and, instead, an increase from 1.6% to 8% of the population occurred in the phylum Bacteroidetes class Flavobacteria, with Flavobacterium being the only identified genus. In addition, the newly discovered genus Ohtaekwangia increased from 0% to 3.2% of the total clones. These results indicate that the same soil microbial community can give rise to different PAH degrading consortia that are equally effective in PAH degradation efficiency. Moreover, these results suggest that the lack of efficacy of bioaugmentation in soils can be attributed to a lack of persistence of the introduced microbes, yet nonetheless may alter the microbial community that arises in response to PAH contamination in unexpected ways.

Multi-Scale Monitoring the First Stages of Electrochemical Behavior of AZ31B Magnesium Alloy in Simulated Body Fluid

This work applies electrochemical noise technique (EN) and scanning electrochemical microscopy (SECM) to investigate the initial stages of degradation of AZ31B magnesium alloy in simulated body fluid (SBF). The fluctuations in potential and current, caused by the alloy's spontaneous degradation, were analyzed in both time and frequency domains to determine the type of attack and the fractal nature of the degradation. Substrate-generation/tip-collection mode SECM mapped the hydrogen evolution activity at the Mg surface during the initial corrosion process. This electrochemical information was correlated with pH changes of the solution, Mg ion concentration, mass loss, SEM-EDS and XPS analysis. The Mg matrix dissolution was promoted by Al-Mn intermetallic particles, which acted as cathodic sites. The corrosion products film was mainly composed by Mg(OH)2 and Ca10(PO4)6(OH)2, and its fast formation allowed a slower degradation and H2 evolution rates. Combining EN and SECM methods allowed the description of the early degradation processes of AZ31B in SBF as a persistent stationary process, related to fractional Gaussian noise, which was characterized by the quasi-uniform corrosion of the alloy.

Fisheries productivity under progressive coral reef degradation

Abstract In response to multiple stressors, coral reef health has declined in recent decades, with reefs exhibiting reduced living coral and structural complexity, and a concomitant rise in the dominance of algal resources. Reef degradation alters food availability and reduces the diversity and density of refuges for prey. These changes affect predator–prey interactions and can have cascading impacts on food webs and fisheries productivity. We use a size‐based ecosystem model of coral reefs that incorporates the influence of structural complexity, benthic primary production and detrital recycling to explore how predator–prey interactions and fisheries productivity respond to a gradient of reef degradation. We show that fisheries productivity overall may be robust to initial stages of reef degradation because the benefits of increased resources outweigh the costs of moderate refuge decline. However, the assemblage composition and size structure of reef fish will differ on degraded reefs, with herbivores and invertivores contributing relatively more to productivity. More significant losses of refuges associated with the erosion of structural complexity correspond to fisheries productivity losses of at least 35% compared to healthy reefs. Synthesis and applications. Our model provides fisheries managers with quantitative predictions about how fisheries productivity may change in response to the ongoing degradation of coral reefs. We predict an initial increase in productivity at intermediate reef degradation, followed by a drastic decline when structural complexity is lost. We also capture subtle changes to potential catch composition and fish size, including increases in smaller herbivorous and invertivorous fish from degraded reefs, which will undoubtedly impact fisheries value. On the one hand, our results reassure for continued productivity in the short term, but on the other, we warn against complacency. Management must change to capture any potential benefits to fisheries, and long‐term sustainability still depends on the maintenance of complex coral reef habitats.

Environmental aging and degradation of multiwalled carbon nanotube reinforced polypropylene

The degradation of polypropylene (PP) and PP-multiwalled carbon nanotube (PP-MWCNT) panels during environmental weathering resulted in an increased degree of crystallinity, making them brittle, and creating surface cracks. The degradation led to a breakdown of the panels and increased the potential for nanorelease. Thermal analysis revealed that the thickness of the test panels and reinforcement with MWCNTs had a significant influence on the stability of PP-MWCNT composites. Differential scanning calorimetry indicated that the MWCNTs acted as nucleation points, increasing the crystallization temperatures of PP-MWCNT, which reduced the extent of aging. Weathering decreased both the melting and crystallization temperatures of PP by as much as 20 °C. The reduction in the temperatures was inversely proportional to the thickness of the panels. The activation energy (Ea) obtained using isoconversional kinetics of the TGA analysis showed that the effective thermo-oxidative degradations of PP changed during aging. The Ea for the initial stages of thermal degradation decreased from ∼330 kJ/mol to ∼100 kJ/mol for aged PP. During the late degradation stages, the Ea values increased to ∼300 kJ/mol. These results suggest that early degradation were altered because of the changes in the molecular structure of the aged PP and a shift in the degradation rate-limiting steps.

SAA1 participates in collagen degradation in human amnion fibroblasts

To study the expression of ADAMTs-5 and TIMP-3 in temporomandibular joint osteoarthritis (TMJOA) model rats, to explore and confer the possible effects of ADAMTs-5 and TIMP-3 involved in the degradation of the early stage of OA.32 SD rats were divided into four groups: 2-week control group (NC1), 2-week OA group (OA1), 4-week control group (NC2) and 4-week OA group (OA2). Each group had 8 rats. Injection of collagenase was used to build up the TMJOA model. HE staining was used to analyze the structural change of condyle cartilage. Western blot and RT-PCR were used to measure the expression of ADAMTs-5 and TIMP-3 in protein and mRNA levels respectively.HE analysis revealed that no significant changes were observed in NC1, NC2 and OA1 groups, while mild damages appeared in OA2 group. No significant differences were achieved in the expression of ADAMTs-5 in protein levels between NC1 and OA1, but the expression of ADAMTs-5 in 4-week group increased significantly compared to that in the NC2 group. On mRNA level, the expression of ADAMTs-5 in 2-week and 4-week OA groups increased significantly compared to that in the matched control group. Meanwhile, the expression of TIMP-3 decreased significantly, showing a completely different trend.The expression of ADAMTs-5 and TIMP-3 changed significantly in the early stage of TMJOA, which indicated that ADAMTs-5 and TIMP-3 may be play an important part in the initial stage of condylar cartilage degradation.

High-temperature pyrolysis simulation of acrylonitrile-butadiene model compound with experimental evidence

Molecular dynamic simulations (MD) were made for the first time on acrylonitrile-butadiene (NBR) model compounds to determine the thermal decomposition characteristics. The formation profile of various pyrolysis products with respect to time and temperature was examined. Acrylonitrile, 1,3-butadiene, and 2-butene were identified as major products at the initial stage of degradation of the copolymer. Other small molecular products including 4-vinylcyclohexene and cyclohex-3-enecarbonitrile were observed at high temperature. The formation mechanism of various pyrolysis products was explored with the help of the simulation method. The effect of increased monomer units on the thermal decomposition characteristics of the acrylonitrile-butadiene model compound was studied. The influence of heating rates and final heating temperatures on the formation of small major pyrolysis products was also analyzed. The initial decomposition temperature of the model compound increased with the rise in heating rate. The increase in both the heating rate and the final heating temperature reduces the initiation time for degradation. The pyrolysis products predicted from the atomistic simulation were in good agreement with the experimental results from pyrolysis gas chromatography-mass spectrometry (py-GC–MS). The ratio of the monomer units obtained during pyrolysis of the acrylonitrile-butadiene model compound in the simulation is also similar to the ratio obtained from py-GC–MS. The activation energy value for thermal decomposition of the acrylonitrile-butadiene copolymer obtained from the simulation was also consistent with the experimental findings from the thermogravimetric analysis (TGA).

Biologically Safe Poly(l-lactic acid) Blends with Tunable Degradation Rate: Microstructure, Degradation Mechanism, and Mechanical Properties.

Although poly(l-lactic acid) (PLLA) is reputed to be biodegradable in the human body, its hydrophobic nature lets it persist for ca. 5.5 years. This study demonstrates that biologically safe lactide copolymers, poly(aspartic acid-co-l-lactide) (PAL) and poly(malic acid-co-l-lactide) (PML), dispersed in the PLLA function as detonators (triggers) for its hydrolytic degradation under physiological conditions. The copolymers significantly enhance hydrolysis, and consequently, the degradation rate of PLLA becomes easily tunable by controlling the amounts of PAL and PML. The present study elucidates the effects of uniaxial drawing on the structural development, mechanical properties, and hydrolytic degradation under physiological conditions of PLLA blend films. At initial degradation stages, the mass loss was not affected by uniaxial drawing; however, at late degradation stages, less developed crystals as well as amorphous chains were degradable at low draw ratio (DR), whereas not only highly developed crystals but also the oriented amorphous chains became insensitive to hydrolysis at high DR. Our work provides important molecular level results that demonstrate that biodegradable materials can have superb mechanical properties and also disappear in a required time under physiological conditions.

Initial Stages of Na2SO4-Induced Degradation of β-Ni–36Al at 700 °C: I-Intrinsic Behavior

The early-stage scaling behavior of a β-Ni–36Al alloy undergoing Na2SO4-deposit-induced degradation at 700 °C was systematically studied using SEM and TEM. After 20 h of exposure in an O2–1000 ppm SO2 ambient, the deposit-coated alloy formed a dense but thin Al2O3 scale on most areas of the surface; however, large nodules formed locally. Nodule formation occurred where the scale had lost its protective character, with rapid internal oxidation ensuing. The presence of sulfur both in the environment and in the salt played a key role in nodule formation. Removal of SO2/SO3 from the gas mixture, or of the Na2SO4 deposit from the surface, prevented nodule formation, while removing the sulfur source after nodule formation prevented further nodule growth. The degradation could be linked to the dissolution of reaction products in the Na2SO4 deposit and the formation of a low-temperature eutectic liquid. Further, when an Na2SO4–48% MgSO4 deposit was used, the nodule density increased.

潤滑油流動帯電の定量化と潤滑油劣化メカニズムの解明

Cleavage of hydrocarbon in the initial stage of oil degradation is caused by heat and mechanical shearing. However, recently it has been suggested that electrostatic discharge has a possibility of cleavage of hydrocarbon. Most of machinery has a filtering system in order to filter contaminations in oil. It is found that electrostatic discharge occurs during oil filtration and then the oil is degraded. However, this mechanism has not been elucidated. Therefore, the purpose of this study is to quantify static electricity during oil filtration and elucidate its mechanism. We used test equipment assumed filtering system of machinery, and measured electrostatic voltage of middle of filter holder while changing the parameters of pump flow rate, oil temperature and oil conductivity. As a result, it was found that static electricity during oil filtration increased with increasing of flow rate, and decreasing of oil temperature and oil conductivity. Then we discussed the relationship between static electricity and flow rate of exit.

Degradation of synthetic dye in water by solution plasma process

In this study, the solution plasma process was utilized with the aim of degrading synthetic dyes in water at atmospheric pressure. The experiments were conducted in a batch-type reactor consisting of a symmetric wire-wire electrode configuration with rhodamine B (RhB) as the target synthetic dye. The effects of the plasma treatment time and initial dye concentration on the RhB degradation were investigated by monitoring the change in absorbance of RhB solutions. The RhB solutions turned lighter in color and finally colorless with prolonged plasma treatment time, indicating the destruction of dye molecules. The RhB solutions were found to have degraded, following the first-order kinetic process. However, for high initial RhB concentrations, another kinetic process or factor seems to play a dominant role at the initial degradation stage. The fitted first-order rate constant decreased as the initial concentration increased. This result suggests that the degradation behavior and kinetic process of the RhB solution strongly depends on its initial concentration. The RhB degradation is considered to be due to a combination of factors, including the formation of chemically oxidative species, as well as the emission of intense UV radiation and high-energy electrons from the plasma. We believe that the solution plasma process may prove to be an effective and environment-friendly method for the degradation or remediation of synthetic dye in wastewater.

Complete genome sequence and transcriptomic analysis of a novel marine strain Bacillus weihaiensis reveals the mechanism of brown algae degradation.

A novel marine strain representing efficient degradation ability toward brown algae was isolated, identified, and assigned to Bacillus weihaiensis Alg07. The alga-associated marine bacteria promote the nutrient cycle and perform important functions in the marine ecosystem. The de novo sequencing of the B. weihaiensis Alg07 genome was carried out. Results of gene annotation and carbohydrate-active enzyme analysis showed that the strain harbored enzymes that can completely degrade alginate and laminarin, which are the specific polysaccharides of brown algae. We also found genes for the utilization of mannitol, the major storage monosaccharide in the cell of brown algae. To understand the process of brown algae decomposition by B. weihaiensis Alg07, RNA-seq transcriptome analysis and qRT-PCR were performed. The genes involved in alginate metabolism were all up-regulated in the initial stage of kelp degradation, suggesting that the strain Alg07 first degrades alginate to destruct the cell wall so that the laminarin and mannitol are released and subsequently decomposed. The key genes involved in alginate and laminarin degradation were expressed in Escherichia coli and characterized. Overall, the model of brown algae degradation by the marine strain Alg07 was established, and novel alginate lyases and laminarinase were discovered.

Biodegradability and biocompatibility of copoly(butylene sebacate-co-terephthalate)s

In the present study poly (butylene sebacate-co-terephthalate)s having different compositions were synthesized with a high yield and a random distribution by thermal transesterification of poly (butylene sebacate) and poly (butylene terephthalate) homopolymers. The copolymer with the highest comonomer ratio was the least crystalline sample, although the melting peaks corresponding to both, sebacate and terephthalate-rich phases were still observable in calorimetric heating runs. This copolymer was associated with interesting thermal and mechanical properties, as the maximum melting point was higher than 100 °C and the storage modulus was also high (i.e. 1.1 × 109 N/m2 and 1.7 108 N/m2 were determined just before and after the main glass transition temperature of −12 °C).As all studied samples were thermally stable up to temperatures clearly higher than the fusion temperature, they could be easily processed. Increasing the terephthalate content of the copolymers resulted in higher hydrophobicity, which had a minor influence on cell adhesion and proliferation of both fibroblast-like and epithelial-like cells. Hydrolytic and enzymatic degradability were assessed and the effect of composition and crystallinity on the degradation rate was investigated. Molecular weight measurements during exposure to a hydrolytic media indicated a first order kinetic mechanism during the initial stages of degradation before reaching a limiting molecular size, which was indicative of solubilization. The most amorphous sample appears as a highly promising biodegradable material since it showed a significant weight loss during exposure to all selected degradation media, but also exhibited good performance and properties that were comparable to those characteristic of polyethylene.

Effects of Incubation Temperature, Repeated Application, and Heavy Metal Addition on Degradation of Nitrification Inhibitor 3,4-Dimethylpyrazole Phosphate (DMPP) in Burozem with Model Experiments

3,4-Dimethylpyrazole phosphate (DMPP) is used to inhibit nitrification when NH4+ or NH4+-producing fertilizers are applied in agricultural and horticultural systems. The kinetics of DMPP decomposition were studied in pretreated and non-pretreated burozems, using model experiments. DMPP was added in same concentration (50 mg·kg-1) but incubated at various temperatures (15, 23 and 30°C). Additionally, DMPP degradation was examined after treatment with Cu2+ or Cd2+ at various doses. When DMPP was applied into the non-pretreated soil, a delay phase of about 9.5-27.4 days appeared in the initial stage of degradation. However, the delay phase disappeared when DMPP was applied into the pretreated soil. The half-life of DMPP in the non-pretreated soil was higher than that of the pretreated soil by about 58-86%. These indicated that an inducible metabolic degradation occurred, following first-order kinetics. The mineralization rate of DMPP was enhanced by increasing temperature, and the half-life decreased significantly with increasing temperature, both in pretreated and non-pretreated soil. With the addition of DMPP and heavy metal (Cu2+ or Cd2+) in the soil, the content of DMPP was different from CK after incubation, and the mineralization of DMPP was significantly decreased with the increase of heavy metal addition. The lower additional amount of Cu2+ (20 mg·kg-1) or Cd2+ (1 mg·kg-1) promoted the degradation of DMPP, while higher additional amount of Cu2+ (500 mg·kg-1) or Cd2+ (25 mg·kg-1) significantly inhibited the decomposition of DMPP.