Initial Stages Of Decomposition Research Articles

Effect of the Schiff base complex diaqua-(N-salicylidene-l-glutamato)copper(II) monohydrate on human tumor cells

The aim of our study was to estimate cytostatic/cytotoxic activity of the copper(II) Schiff base complex of the composition [Cu(N-salicylidene-l-glutamato)(H2O)2]·H2O, further Cu(SG-L)H2O, against human colon carcinoma cell line HT-29, as well as to determine type of cell death and to find out the molecular mechanism of apoptosis induced by this complex. Two highest concentrations (50, 100µmol/l) of the complex showed a strong cytotoxic activity against human colon carcinoma cells HT-29 after 72h of influence. Other concentrations had a cytostatic activity. Unchelated copper(II) ions and free ligands had no effect on the cell growth. Cu(SG-L)H2O preferentially reduced cancer cell viability compared to healthy cells (NIH-3T3). Cu(SG-L)H2O induced apoptosis of cells HT-29 at all concentrations used (1–100µmol/l) after 48h of influence. Apoptosis was carried out by the mitochondrial pathway with active caspases 3 and 9. By the spin-trapping technique combined with electron paramagnetic resonance we found that our complex is photochemically stable in aqueous systems and does not exhibit radical-scavenging activity when 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) cation radical was used as an oxidant. The complex exhibits a strong prooxidant property in the initial stages of thermal decomposition of K2S2O8 in water solutions leading to the massive production of ·OH radicals. Therefore, this complex could strongly participate in anticancer action via a free radical mechanism.

Plasma-Induced Decomposition of Dichlorophenols and Trichlorophenols in Water by Means of Anodic Contact Glow Discharge Electrolysis

Decomposition of aqueous dichlorophenols and trichlorophenols was investigated by means of contact glow discharge electrolysis. With the decay of chlorophenols (CPs), the amount of total organic carbon (TOC) in water also decreased smoothly, indicating that carbon atoms of benzene nucleus could be eventually converted to inorganic carbons. And, it was found that chlorine atoms in the CPs were released as chloride ions. As the by-products, oxalate and formate were formed. The chlorine derivatives of 1,4-hydroquinone and 1,4-benzoquinone were detected as the primary intermediates in the initial stage of decomposition of each of CPs. The decay of both CPs and TOC obeyed the first-order rate law, respectively. The apparent rate constants for the decay of CPs increased with the decrease in pKa values of CPs, while those for the decay of TOC were substantially unaffected.

Dynamics of dissolved organic carbon from aerobic and anaerobic decomposition of Typha domingensis Pers. and Eleocharis interstincta (Vahl) Roem. & Schult. in a tropical coastal lagoon

AIM: The aim of this study was to evaluate the initial stage of decomposition of two aquatic macrophytes (Typha domingensis and Eleocharis interstincta) under aerobic and anaerobic conditions; METHODS: The samples of aquatic macrophytes and water were collected in Cabiúnas lagoon, Rio de Janeiro, Brazil. In the experiment 1 mineralization chambers were prepared with fresh plant fragments and water from the lagoon in aerobic and anaerobic conditions. DOC and CO2 formation and O2 consumption were measured during 30 days. In the experiment 2 mineralization chambers were prepared with aquatic macrophytes leachate and glucose for each experimental condition. CO2 formation and O2 consumption were measured during 1 day; RESULTS: In experiment 1 DOC concentrations in T. domingensis decomposition were higher. Despite this, CO2 formation was more efficient in E. interstincta decomposition. The oxygen consumption increased in the beginning of decomposition and tended to stabilize towards the end. The O/C values increased in the beginning of decomposition and decreased thereafter. In experiment 2, aerobic decomposition presented higher CO2 formation. E. interstincta leachate presented higher CO2 concentration than T. domingensis; CONCLUSION: Our results showed that aerobic decomposition in the initial stages is higher only in T. domingensis mineralization. Oxygen consumption varies according to the alterations in the chemical composition of the detritus. The formation of CO2 from T. domingensis and E. interstincta decomposition in the water column is irrelevant in Cabiúnas Lagoon. The low DOC release from fresh aquatic macrophytes detritus indicates that particulate organic matter mineralization is the main route of T. domingensis and E. interstincta decomposition.

Destruction of 4-phenolsulfonic acid in water by anodic contact glow discharge electrolysis

Destruction of 4-phenolsulfonic acid (4-PSA) in water was carried out using anodic contact glow discharge electrolysis. Accompanying the decay of 4-PSA, the amount of total organic carbon (TOC) in water correspondingly decreased, while the sulfonate group of 4-PSA was released as sulfate ion. Oxalate and formate were obtained as minor by-products. Additionally, phenol, 1,4-hydroquinone, hydroxyquinol and 1,4-benzoquinone were detected as primary intermediates in the initial stages of decomposition of 4-PSA. A reaction pathway involving successive attacks of hydroxyl and hydrogen radicals was assumed on the basis of the observed products and kinetics. It was revealed that the decay of both 4-PSA and TOC obeyed a first-order rate law. The effects of different Fe ions and initial concentrations of 4-PSA on the degradation rate were investigated. It was found that the presence of Fe ions could increase the degradation rate of 4-PSA, while initial concentrations lower than 80 mmol/L had no significant effect on kinetic behaviour. The disappearance rate of 4-PSA was significantly affected by pH.

Thermal stability of Al1−xInxN (0 0 0 1) throughout the compositional range as investigated during in situ thermal annealing in a scanning transmission electron microscope

The thermal stability of Al1−xInxN (0⩽x⩽1) layers was investigated by scanning transmission electron microscopy (STEM) imaging, electron diffraction, and monochromated valence electron energy loss spectroscopy during in situ annealing from 750 to 950°C. The results show two distinct decomposition paths for the layers richest in In (Al0.28In0.72N and Al0.41In0.59N) that independently lead to transformation of the layers into an In-deficient, nanocrystalline and a porous structure. The In-richest layer (Al0.28In0.72N) decomposes at 750°C, where the decomposition process is initiated by In forming at grain boundaries and is characterized by an activation energy of 0.62eV. The loss of In from the Al0.41In0.59N layer was initiated at 800°C through continuous desorption. No In clusters were observed during this decomposition process, which is characterized by an activation energy of 1.95eV. Finally, layers richest in Al (Al0.82In0.18N and Al0.71In0.29N) were found to resist thermal annealing, although the initial stages of decomposition were observed for the Al0.71In0.29N layer.

Soil–litter nitrogen transfer and changes in δ13C and δ15N values in decomposing leaf litter during laboratory incubation

Abtract Leaf litter is the main source of nutrient and energy input into the soil. Therefore, detailed knowledge on the short-term variations in the isotopic composition of plant litter is needed for correctly estimating the “isotopic baseline” in stable isotope-based studies on detrital foodwebs. In a laboratory experiment, standardized fragments of freshly fallen leaves of Quercus robur, Ulmus glabra, and Populus tremula were incubated on the surface of natural or 15N-labeled soil during 260 days. At the end of the experiment, the remaining mass represented 62, 53 and 50% of the initial mass for oak, elm and aspen litter, respectively. There was a small decrease in the mean δ13C values during the initial stages of decomposition, although it was inconsistent among the three litter species tested and did not exceed 1.0‰ during the decomposition period. Calculations based on the total N content, as well as the isotope mixing model suggested that up to 50% of the total litter N was incorporated from the underlying soil. The rates of N transfer from the soil to litter were not affected by the disruption of mycelial connections between the soil and litter. As indicated by δ15N values of filter paper placed on the soil surface, labile soil N was depleted by 6–8‰ in 15N relative to bulk soil organic matter. However, in the given experimental settings the input of 15N-depleted labile N from mineral soil was likely counterbalanced by an increase in the 15N-enriched microbial biomass and bulk litter δ15N values changed little.

Effect of aluminum chloride on formation of a polyconjugated bond system in the initial stage of polyvinyl alcohol thermal decomposition

Fine-structure bands have been located in electronic absorption spectra of polyvinyl alcohol (PVA) films decomposed thermally in air at 80–150°C. Doping of the PVA film with aluminum chloride (thermolysis catalyst) was found both to enhance the degree of thermal decomposition and to reduce the starting temperature for formation of poly-π-conjugated chains although it had no effect on the spectral positions of the polyene-unit absorption bands. Values of the band gap of heat-treated PVA films were determined to be in the range 1.65–1.78 eV based on an analysis of the electronic spectra long-wavelength edge.

Initial stages of thermal decomposition of LiPF6-based lithium ion battery electrolytes by detailed Raman and NMR spectroscopy

Independent of the specific electrode chemistry, the state-of-the-art lithium ion battery electrolytes based on LiPF6 in organic solvents have a low thermal abuse tolerance and poor cycle life at elevated temperatures. We present here a detailed investigation of the initial stages of the thermal decomposition of LiPF6 in EC/DMC stored at 85 °C using Raman and NMR spectroscopy. During storage (up to 160 h), significant amounts of CO2 are evolved, as detected in the Raman spectra. Time-resolved 1H, 31P, and 19F NMR spectra show the evolution of POF3, POF(OH)2, POF2(OCH2CH2)nF, and POF2OMe as reactive decomposition products. Our unique 19F NMR approach, measuring while heating with both high energy and time resolution, allows for a first quantitative analysis of the evolved species and reveals several decomposition reactions during the first 30 min up to 72 h, where the rates of HF and POF2OMe formation are surprisingly linear. EC is found to be much less reactive compared to DMC. All information is used in the formulation of an updated decomposition pathway chart for LiPF6 based electrolytes.

Influence of short heat pulses on properties of martensite in medium carbon steels

The process of tempering a martensitic medium carbon steel was investigated with the aim to study resulting material properties. The experimental results were used to model residual stresses caused by local heating, with the finite element method. Tempering was followed for times from 0.1s up to 1h by using laser heating and conventional salt bath furnace treatments within the temperature interval 500–700°C. In addition, the thermal expansion was evaluated using dilatometry. Experiments showed that the initial stages of martensite decomposition, associated with loss of crystal tetragonality, proceed almost instantly. An initial large decrease of hardness within the first tenth of a second of the tempering process was measured, followed by only limited further softening with increased tempering time. Thus for the current material the tempering time had limited influence on hardness, governed primarily by the peak temperature during the heating process. Finite element modelling of rapid local heating and cooling showed that the tempering behaviour and associated dilatation effects yield a peak temperature dependent residual stress field with a broad tensile stress distribution for the case of un-tempered martensite. However, for tempered martensite the residual stress field depends primarily on the heating rate and peak temperature and shows large gradients with tensile stresses in the surface and compressive below. Thereby, for both cases, residual stresses were obtained but with completely different residual stress gradients.

Do canopy herbivores mechanically facilitate subsequent litter decomposition in soil? A pilot study from a Neotropical cloud forest

AbstractThere is increasing evidence that the above‐ and belowground components of ecosystems influence one another, thereby controlling key processes such as organic matter decomposition. The aim of this study was to test the hypothesis that leaf herbivory in forest canopies could facilitate subsequent leaf litter decomposition in soils, through changes in leaf quality (i.e., litter palatability) or geometric form (i.e., increased availability of leaf edges made by herbivore damages). In a 9‐month field experiment in an Ecuadorian tropical cloud forest, we compared the decomposition rates of entire leaves (EL) and 15 %‐damaged leaves (DL) of Ficuscuatrecasana showing similar initial leaf chemistry. We found that DL decomposed significantly faster than EL in early stages of decomposition (i.e., between 0 and 38 days). A parallel experiment using cellulose discs on which we simulated different degrees of damages revealed, however, that geometry per se (i.e., increased edge availability) did not influence decomposition rates. We discuss these contrasting results and propose that higher edge availability in damaged leaves may promote the access of microbes and/or macro‐detritivores to leaf tissues thereby enhancing the initial stages of leaf decomposition.

Environmental control of lignin peroxidase, manganese peroxidase, and laccase activities in forest floor layers in humid Asia

We investigated the activities of ligninolytic enzymes, lignin peroxidase (LiP), manganese peroxidase (MnP), and laccase (Lac), in forest floor layers collected from temperate and tropical regions in Japan, Thailand, and Indonesia. The effects of pH and Mn levels on the ligninolytic enzyme activities in the forest floor layers were analyzed. The activities of LiP, MnP, and Lac varied depending on the decomposition stage (i.e., depth) and pH of forest floor layers both in temperate and tropical regions. The activities of LiP, which has the lowest optimal pH, were higher in the highly acidic FH layers (pH < 5.0) than in the L layers. The activities of MnP and Lac were commonly detected in the less acidic L layers (pH > 5.0), whereas no MnP activity was detected in the highly acidic FH layers. These results indicate that MnP and LiP activities are dependent on pH and independent of the Mn concentrations in the forest floor layer. MnP and Lac play roles in the initial stage of litter decomposition, whereas acidification of forest floor layers enhances fungal activity and production of LiP in the FH layer.

Computational study on the decomposition of tetraneopentyl zirconium for the chemical vapor deposition of zirconium carbide

The overall gas phase decomposition mechanism of tetraenopentyl zirconium precursor (Zr[CH2C(CH3)3]4) for the chemical vapor deposition of zirconium carbide thin films was investigated by using computational thermochemistry. Density functional theory (DFT) and harmonic vibrational frequency calculation were used to generate thermodynamic properties at each reaction step, based on which thermodynamic or kinetic preference of a reaction pathway was evaluated. While the preference of γ-hydrogen abstraction of neopentane over α-hydrogen abstraction was confirmed in the initial stage of ZrNp4 decomposition, they turned out to be competing instead of the dominant preference of γ-hydrogen abstraction. Methane formation at three subsequent reaction steps was explained by β-methyl migration, and the following α-hydrogen abstraction of methane based on the suggestion that α- and γ-hydrogen abstractions of neopentane are competing kinetically in previous reaction steps. Computational thermochemistry showed a possibility as a general tool to anticipate the gas phase decomposition mechanism of a precursor in chemical vapor deposition.

Growth and succession patterns of major phylogenetic groups of marine bacteria during a mesocosm diatom bloom

Our objective was to track microbial processes associated with serial degradation of organic matter derived from algal blooms. To do this, we analyzed population fluctuations and growth responses of major phylogenetic groups of free-living marine bacteria. We used bromodeoxyuridine immunocytochemistry–fluorescence in situ hybridization methodology to examine marine bacterial community development during and after a diatom bloom in a mesocosm. We revealed that the Roseobacter/Rhodobacter, SAR11, Alteromonas, and Bacteroidetes groups were clearly major phylotypes responsible for most free-living bacterial biomass and production throughout the experiment. The clearest bacterial response was a proliferation of the Alteromonas group (cells with large volumes) during development of the bloom (up to 30 % of actively growing cells). Populations of these bacteria declined sharply thereafter, likely due to grazing. Alteromonas group responses suggest that these bacteria strongly influenced the flux of organic matter at an early bloom stage. The growth potential of Bacteroidetes was relatively large as the bloom peaked; this early development probably contributed to the initial stage of bloom decomposition. In contrast, the contribution of Roseobacter/Rhodobacter to total bacterial production increased at a late stage of decomposing of the bloom. The contributions of Betaproteobacteria, SAR11, and SAR86 groups to total bacterial abundance and production were relatively minor throughout the experiment. These results imply that the ability to utilize organic matter derived from diatoms varies among bacterial phylotypes, and, frequently, less abundant but ecological specialist taxa such as Alteromonas may play major roles in the flux of organic matter during diatom blooms.

Generalized Autoregressive Conditional Heteroskedastic Model for Water Quality Analyses and Time Series Investigation in Reservoir Watersheds

A vector time series is coupled with both the Generalized Autoregressive Conditional Heteroskedastic (GARCH) model and an impact response analyses of the multiple time series Vector Autoregressive Moving Average (VARMA) model in this research to investigate the time series variation of organic pollution factors. The analyses target three organic pollution factors, that is, dissolved oxygen (DO), biochemical oxygen demand (BOD), and ammonia nitrogen (NH3-N), for understanding their time series influence pattern and responses among the various water quality parameters. After model matching of the many vectors, the optimal matching model combination, VARMA(1,0,1)–GARCH(1,1), was selected for depicting the time series dependence of the selected pollutant factors. Results of impulse response analyses reveal that BOD responds immediately to changes of current DO and that the consumption of DO is not obvious during the initial stage of NH3-N decomposition. During the one time lag period, NH3-N is further oxidized into nitrite and nitrate to cause obvious increase of DO consumption. In this article, the statistical technology is used to develop the VARMA–GARCH integration model for simulating and predicting the water quality using data collected in the watershed of northern Taiwan. Therefore, the internal mechanism and the significance represented by the process of constructing the model can be expanded. The model proposed in this research will allow the user to grasp the instantaneous changes of the time series water quality in the watershed. Results will provide valuable references for the water quality authority to implement timely and effective water management measures in response to changes of water quality.

First Principles Simulations of the Initial Stages of Organic Solvent Decomposition on Spinel Li(x)Mn(2)O(4) (100) Surfaces

not Available.

Comparison of Bacteria and Archaea communities in municipal solid waste, individual refuse components, and leachate

Refuse decomposition in landfills is a microbially mediated process that occurs primarily under anaerobic conditions. Because of limited moisture conditions, hydraulic transport as a means of cellular translocation within the landfill appears limited, especially during the initial stages of decomposition. Thus, microbial communities within the incoming refuse serve as a primary source of facultative and obligate anaerobic microorganisms that initiate refuse decomposition. Fresh residential refuse was collected five times over 26 months, and microbial communities in these samples were compared with those in individual refuse components and decomposed refuse. Bacterial and archaeal community structures were determined using T-RFLP. The Bacterial microbial community richness was correlated (r(2) = 0.91) with seasonal differences in ambient air temperature. Analysis of the results shows that fresh refuse is most likely not the source of methanogens in landfills. Microbial communities in the solid and leachate phases were different, indicating that both matrices must be considered when characterizing microbial diversity within a landfill.

Effect of potassium chlorate on thermal decomposition of cyclotrimethylenetrinitramine (RDX)

The thermal decomposition process of a newly designed composite material KClO 3–RDX (KC-RDX) was investigated by combined TG–DSC–FTIR technique and DSC technique. It was shown that KC-RDX began to decompose at about 209.9 °C after melting, and the fast stage of mass loss at the temperature range of 209.9–259.8 °C is considered to be the result of the thermolysis and complex reactions of KClO 3 and RDX with energy release of 1887 J g −1, which exceeded that of pure RDX about 10%. The CO, CO 2, HCN, NO 2 and H 2O were detected as the main gaseous products of KC-RDX decomposition, and occurred in initial stage of RDX decomposition are greatly affected by KClO 3. In contrast to pure RDX, there was nearly no CH 2O detected in thermolysis products of KC-RDX. In the presence of electronegative oxygen radical produced by thermolysis of KClO 3 oxidized CH 2O through gas-phase reaction CH 2O + O 2 → HCO + HO 2, which might be one of the unique chemical reaction for KC-RDX.

English

&nbsp; Metal soaps of&nbsp;Ximenia americana&nbsp;seed oil (XSO) and&nbsp;Balanites aegyptiaca&nbsp;seed oil (BSO) were prepared by metathesis in aqueous alcohol solution. The thermal stability of the metal carboxylates (soaps) was studied thermogravimetrically in the temperature range 50 &ndash; 500&deg;C under nitrogen. The thermal stability of the carboxylates was assessed in terms of temperatures at which various extents of decomposition were attained and weight loss at the initial stage of decomposition. The weight loss for all the metal soaps was less than 10% at temperature up to 250&deg;C. The activation energies at the initial stage of decomposition of the metal carboxylates modelled using Broido&rsquo;s equation are in the range 6.93 &ndash; 14.14 kJmol-1&nbsp;for XSO while those of BSO ranged between 15.52 &ndash; 28.41 kJmol-1. Based on these results, metal soaps of BSO are thermally stable than those of the corresponding XSO soaps. The results suggest potential application of carboxylates of&nbsp;X. americana&nbsp;and&nbsp;B. aegyptiaca&nbsp;seed oils in some industrial applications. &nbsp; Key words:&nbsp;Metal soaps, thermal stability, carboxylates, thermogravimetric, decomposition.

An h.p.l.c. study of the initial stages of dextrose decomposition in neutral solution.

An h.p.l.c. study of the initial stages of dextrose decomposition in neutral solution.

Effects of elastic energy on the spinodal decomposition in InAlGaN materials

AbstractThe purpose of our study is to determine the influence of elastic energy on the spinodal decomposition ranges of InAlGaN alloys lattice‐matched to GaN. The distinction in lattice constants of the binary compounds constituting these alloys gives rise to their deformation energies. Such energies provide the tendency to disintegration that can lead to an appearance of the thermodynamically unstable states with respect to the decomposition. The initial stage of spinodal decomposition of the InAlGaN quaternary alloys is accompanied by transfers of atoms over distances of a lattice parameter. Accordingly, these transfers produce a thin two‐layer region with negligibly small differences in their compositions. Formation of these layers causes the elastic energy. The alloys are represented as quaternary regular solutions. The internal deformation energy is calculated with the interaction parameters estimated by the valence force field model. The spinodal decomposition ranges of these materials are demonstrated up to 580 °C (© 2011 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)