Concentration Of Free Radicals Research Articles

Bisphenol S degradation by visible light assisted peroxymonosulfate process based on BiOI/B4C photocatalysts with Z-scheme heterojunction

• The Z-scheme heterojunction BiOI/B 4 C (BOBC) photocatalyst was first fabricated successfully. • The BOBC-24-5/PMS/light system exhibits superior degradation effect on bisphenol S. • The formation of Z-scheme heterojunction assisted reduce the recombination rate of photogenerated electron-hole pairs. • Intermediates of BPS were detected and rational degradation pathways were proposed. In this study, we developed the BiOI based photocatalytic activation of peroxymonosulfate technology by synthesized Z-scheme heterojunction BiOI/B 4 C (BOBC). The BOBC could remove 90.4% of bisphenol S (BPS) in 30 min under optimal condition ([BOBC-24-5] 0 = 0.1 g/L, [PMS] 0 = 0.05 mmol/L, pH = 7) and had good reusability. Meanwhile, the results of control experiments indicated that the synergistic effects resulted in higher activity than single photocatalysis system and single peroxymonosulfate system. From the characteristic results, the Z-scheme heterojunction formed by hydrothermal method improved the separation efficiency of photogenerated electron and hole pairs, thereby increasing the content of active free radicals in the system and improving the degradation efficiency of BPS. Free radical quenching experiments and electron paramagnetic resonance (EPR) showed that O 2 •− , h + , • OH and SO 4 •− played important roles in the system. The photogenerated electrons and holes generated by the photocatalyst under visible light activated PMS and generated free radicals to degrade BPS. Based on the intermediates identified by ultra-performance liquid chromatography-quadrupole-time of flight mass spectrometer/mass spectrometer (UPLC-QTOF-MS/MS), the possible degradation pathways of BPS were proposed. This work provided a new reference for improving the oxidation efficiency of peroxymonosulfate assisted by visible light.

γ-ray irradiation reduces the formation of polycyclic aromatic hydrocarbons during the baking of sausage

As a common food preservation method, γ-ray irradiation can effectively improve the microbial safety of raw meat. However, the effects of irradiation decontamination on chemical hazard formation, such as polycyclic aromatic hydrocarbons (PAHs), in subsequent meat processing have not been studied. In this study, fresh sausage was irradiated with γ-rays at doses of 0, 1, 4, and 8 kGy, and the lipid oxidation, fatty acid composition and total free radical content were determined. The contents of four types of higher molecular weight PAHs (BaA, CHR, BbFA, BaP - called as PAH4) were determined after 20 min of baking at 220 °C. The peroxide value (POV) of sausages after 1, 4, 8 kGy of irradiation were 1.86, 2.42, 3.84 meq/kg, respectively, and the thiobarbituric acids (TBARs) values were 0.08, 0.12, 0.19 mg/kg, respectively, which were significantly increased compared with those of the unirradiated sausages (P < 0.05). The total free radical content estimated by electron spin-resonance spectroscopy (ESR) and the content of saturated fatty acids (SFAs) both increased as the dose of irradiation increased. The concentration of PAH4 in irradiated sausage was notably reduced by 16.89% (1 kGy), 36.79% (4 kGy), and 51.68% (8 kGy) compared with unirradiated sausages. There was a significant correlation between the proportion of unsaturated fatty acids (UFAs) and the PAH4 content (P < 0.01). γ-ray irradiation can effectively reduce the PAH4 content of baked sausages at 1, 4, and 8 kGy. The mechanism by which PAH4 decrease in sausage might be caused by the reduction of UFAs result from irradiation. This study illustrates that application of γ-ray irradiation is an effective mean for reducing chemical hazards formation during the baking of sausage.

Effects of Acute and Chronic Gamma Irradiation on the Cell Biology and Physiology of Rice Plants.

The response to gamma irradiation varies among plant species and is affected by the total irradiation dose and dose rate. In this study, we examined the immediate and ensuing responses to acute and chronic gamma irradiation in rice (Oryza sativa L.). Rice plants at the tillering stage were exposed to gamma rays for 8 h (acute irradiation) or 10 days (chronic irradiation), with a total irradiation dose of 100, 200, or 300 Gy. Plants exposed to gamma irradiation were then analyzed for DNA damage, oxidative stress indicators including free radical content and lipid peroxidation, radical scavenging, and antioxidant activity. The results showed that all stress indices increased immediately after exposure to both acute and chronic irradiation in a dose-dependent manner, and acute irradiation had a greater effect on plants than chronic irradiation. The photosynthetic efficiency and growth of plants measured at 10, 20, and 30 days post-irradiation decreased in irradiated plants, i.e., these two parameters were more severely affected by acute irradiation than by chronic irradiation. In contrast, acutely irradiated plants produced seeds with dramatically decreased fertility rate, and chronically irradiated plants failed to produce fertile seeds, i.e., reproduction was more severely affected by chronic irradiation than by acute irradiation. Overall, our findings suggest that acute gamma irradiation causes instantaneous and greater damage to plant physiology, whereas chronic gamma irradiation causes long-term damage, leading to reproductive failure.

Causes of deactivation of an amorphous silica-alumina catalyst used for processing of thermally cracked naphtha in a bitumen partial upgrading process

Thermally cracked naphtha represents a challenging feed for many catalytic processes. Its contaminant content and reactivity cause the deactivation of catalysts. Nevertheless, the use of an amorphous silica-alumina acid catalyst to convert and reduce the alkene content in thermally cracked naphtha was possible. The purpose of this study was to determine the cause(s) of catalyst deactivation by analysis of spent catalysts after conversion of cracked naphtha at different conditions in the range 250–350 °C, 6 MPa and WHSV of 0.5–2 h−1. It was found that nitrogen bases, suspected to be important acid catalyst poisons, were not the main cause of catalyst deactivation. Nitrogen was more abundant in deposits on the catalyst at the inlet compared to the outlet of the reactor, but the accumulated nitrogen in deposits represented only a minor fraction of the total amount of basic nitrogen to which the catalyst was exposed. Carbonaceous deposits were the main cause of catalyst deactivation and the profile of the deposition on the catalyst changed with temperature. At 325 °C the amount of deposits at the reactor outlet was higher, with lower H/C ratio and higher persistent free radical content than at the reactor inlet. Although some of the precursor species that formed deposits were present in the feed, some of the precursor species that formed deposits were produced during the conversion process. Although the contribution of acid catalysis was not ruled out, many observations in the study indicated that carbonaceous deposits formed mainly due to free radical reactions.

Synthesis and primary screening of the antioxidant activity of some 4-thioxo- and 4-imino- thiazolidin-2-ones

As a result of metabolic transformations of substances in the human body in the reactions of lipid peroxidation, reactive oxygen species are formed. Normally, the regulation of the production of activated oxygen metabolites and free radicals in human tissues and organs is carried out by the antioxidant system. Despite its high efficiency, antioxidant system it is not always to protect the human body from the development of oxidative stress. Thiazolidinones are among the most intensively studied heterocyclic systems, since they possess a wide spectrum of biological activity. Based on the above, the synthesis of some 4-thioxo- and 4-iminothiazolidin-2-ones and the study of their antioxidant activity is an topical direction.&#x0D; The aim of our work was to synthesize some C5 substituted derivatives of 4-thioxothiazolidin-2-one and 4-iminothiazolidin-2-one, as well as to conduct a primary screening of their antioxidant activity.&#x0D; The objects of study were C5 substituted 4-thioxo- and 4-iminothiazolidin-2-ones. The composition and structure of the synthesized compounds were confirmed by the data of elemental analysis and 1H NMR spectroscopy. The antioxidant activity of the synthesized compounds was studied in vitro, determining the decrease in the concentration of free radicals.&#x0D; The synthesis of 12 derivatives of 4-thioxothiazolidin-2-one and 4-iminothiazolidin-2-one was carried out. These substances are obtained by structural modification to the C5 position of the base scaffolds. The antioxidant activity of the synthesized compounds was measured in vitro by the method of scavenging effect on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals. Ascorbic acid was used as a standard. As a result of screening, 2 highly active compounds with a pronounced antioxidant effect were identified.&#x0D; As a result of structural modification of the basic scafolds, 12 corresponding C5 substituted thiazolidinones were obtained. During the primary pharmacological screening of antioxidant activity, 2 substances with a pronounced antioxidant effect were isolated. Further optimization of the structure is currently in progress.

Identifikasi Kandungan Metabolit Sekunder dan Uji Aktivitas Antioksidan Ekstrak n-Heksana Kulit Jeruk Bali (Citrus maxima Merr.).

Degenerative diseases triggered by antioxidants in the body are unable to neutralize the increased concentration of free radicals that can cause cell damage, so to destroy free radicals it is necessary to have antioxidants from outside the body. Grapefruit peel (Citrus Maxima Merr) is one plant that is known to have a lot of secondary metabolite content however it is not fully utilized. To analyze the content of chemical compounds and the antioxidant effect of n-hexane extract of Grapefruit peel (Citrus Maxima Merr.). Identification of chemical compounds was carried out by phytochemical screening and confirmed by the analysis of the extract thin layer chromatography profile, whereas the antioxidant activity test was carried out using the radical capture method of 2,2-diphenyl-1-picrylhydrazyl (DPPH) with Trolox as a comparison. The results of the identification of Grapefruit peel (Citrus Maxima Merr) extracts is containing secondary metabolites in the form of flavonoids, saponins, alkaloids, triterpenoids/steroids, and tannins. The results of antioxidant activity test extracts of grapefruit peel(Citrus Maxima Merr) and Trolox each showed values that: IC50 111.69 ppm and 12.143 ppm. From the results of this test, the extract of grapefruit peel (Citrus Maxima Merr) has moderate antioxidant activity when compared to Trolox.

ИЗУЧЕНИЕ МЕТОДОМ ЭЛЕКТРОННОГО ПАРАМАГНИТНОГО РЕЗОНАНСА ВЛИЯНИЯ ФИЗИКО-ХИМИЧЕСКИХ И СТРУКТУРНЫХ ХАРАКТЕРИСТИК КОСТНОЙ ТКАНИ НА ПРОЦЕССЫ ОСТЕОИНТЕГРАЦИИ ДЕНТАЛЬНЫХ ИМПЛАНТАТОВ С РАЗЛИЧНОЙ МИКРОСТРУКТУРОЙ ПОВЕРХНОСТИ

Aim. Study by the method of electronic paramagnetic resonance (EPR) physical- chemical and structural features of bone tissue and their effect on the processes of osseointegration during dental implantation using implants with different macro-microstructure of the surface.&#x0D; Material and methods. The experimental study was conducted on 7 Vietnamese visobryu-pig mini-pigs. Under anesthesia, implants with different macro-microstructures of the surface (SLA, RBM, ) were installed under the methods of direct and delayed implantation. At different dates of the experiment, after the appropriate anesthesia, the gentle method was to remove implants with small fragments of periemplant bone tissue. Macro-drugs of bone tissue of the jaws after sawing on blocks and extraction of implants, as well as appropriate preparation, were investigated by the method of stationary electronic paramagnetic resonance.&#x0D; Results. As a result of the study it was revealed that the insertation of the implant into the jaw bone leads to structural changes in the surrounding bone implant. After prior exposure, the EPR spectrums, caused by different types of paramagnetic centers, were observed in the samples studied. Two types of centers, , have been identified. and F is the center. The spectrum of the second type reflects the presence in hydroxiapatites of lattice defects associated with isomorphism, and, . The findings suggest that one of the reasons for the higher content of free radicals (SR) in bone tissue derived from radiation, after dental implantation is the weakening of chemical bonds, greater mobility of fragments that make up its structure. It must be assumed that the high content of SR in the bone in the postoperative period is nothing but a result of the disruption of the mineralization process, which is accompanied by the replacement of phosphate groups with carbonate ions that are free-radicalized. It has also been revealed that the structural integrity of the bone depends to a large extent on the degree of orderliness of microcrystals of hydroxyapatite. According to EPR, the most favorable bone recovery (the process of osseointegration) occurs when using implants with a surface, .&#x0D; Conclusions. EPR research of native and carbonate radicals is a unique tool for studying the physical and chemical and structural features of bone tissue and their role in the process of osseointegration of implants. The speed of osseointegration for implants with different microstructures of the surface varies. EPR can be used as an additional method to control the integration of implants into bone tissue.

ARGET ATRP of styrene in EtOAc/EtOH using only Na2CO3 to promote the copper catalyst regeneration

“Activator regenerated by electron transfer” “atom transfer radical polymerization” (ARGET ATRP) process catalyzed by CuCl2/tris(2-pyridylmethyl)amine (TPMA) (1/1) in ethyl acetate/ethanol (EtOAc/EtOH) for the polymerization of styrene from ethyl 2,2-dichloropropanoate (EDCP) is described. The (re)generation of the activating CuI complex is accomplished by Na2CO3 without the addition of any explicit reducing agent. Differently from the analogous process operating in the presence of ascorbic acid/carbonate as the reducing system, branching is not present and control over polymerization is improved. The activation mechanism should follow a composite route, where both EtOH and TPMA contribute to the regeneration of the catalyst. The oxidation of TPMA is suggested by the absence of the ligand in the final reaction mixture and by the reduction of CuII even in t-BuOAc/t-BuOH, notwithstanding the very poor ability of t-BuOH as a reducing agent. Oxidative degradation of TPMA causes a progressive malfunctioning of the redox catalyst. Consequently, the polymerization rate, after a prompt start, becomes slower and slower, fixing conversions at around 50% (4.5 h). This means a gradual decrease of the free radical concentration, which develops unfavorable conditions for the reductive coupling (termination) between the bifunctional growing chains, preserving a controlled growth of the polymer.

Theoretical insights into the degradation of tyrosol stimulated by hydroxyl and sulfate radicals in wastewater and ecotoxicity evaluation

The photochemical degradation of tyrosol (TY) in wastewater was investigated by theoretical method. The highly oxidative radicals (⋅OH and SO4•-) were employed to study the TY transformation behaviors and kinetic properties. The ⋅OH-addition and H-abstraction reaction mechanisms were predominant for ⋅OH and SO4•--initiated reactions, respectively. The rate constants of TY + ⋅OH and TY + SO4•- systems were determined as 9.15 × 109 M−1 s−1 and 3.14 × 1010 M−1 s−1 at 298 K. The generated SO4•- from advanced oxidation processes (AOPs) showed good performance for TY degradation in liquid phase. The direct photolysis was also considered in the excited state in order to reveal the photo-excited reaction mechanism. Due to high endothermicity and energy barrier, direct photolysis is difficult to proceed spontaneously compared to indirect photochemical processes initiated by strong oxidative radicals. Half-life values of TY with ⋅OH reactions demonstrated that the high concentration of free radicals would significantly shorten the exposure time of TY in water environment. The results of the ecotoxicity to aquatic organisms suggested TY degradation was a mainly less harmful process. However, hydroxylation product P7 (hydroquinone) was a potential developmental toxicant with greater aquatic toxicity than TY, which was an exception to deserve more concern in environment.

Developmental Hazard of Environmentally Persistent Free Radicals and Protective Effect of TEMPOL in Zebrafish Model.

Environmentally persistent free radicals (EPFRs) can be detected in ambient PM2.5, cigarette smoke, and soils and are formed through combustion and thermal processing of organic materials. The hazards of EPFRs are largely unknown. In this study, we assess the developmental toxicity of EPFRs and the ability of TEMPOL (4-Hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl) to protect against such hazards using zebrafish embryos. Particles containing EPFRs were acquired by dosing dichlorobenzene (DCB) vapor on the Cab-o-sil/5% CuO particles at 230 °C in vacuo (referred to as DCB-230). The particles were suspended in ultrapure water to make 1 mg/mL of stock solution from which series dilution was undertaken to obtain 10, 20, 30, 40, 50, 60, 80, and 100 µg/mL final test solutions, which were then placed in individual wells with a 4 h postfertilization (hpf) zebrafish embryo. Plates were run in duplicate to obtain a sample size of 24 animals per concentration; 12 embryos were exposed per concentration per plate. Statistical analysis of the morphology endpoints was performed. We investigated overt toxicity responses to DCB-230 in a 22-endpoint battery that included developing zebrafish from 24–120 hpf. Exposure to concentrations greater than 60 µg/mL of DCB-230 induced high mortality in the developmental zebrafish model. Exposure to EPFRs induced developmental hazards that were closely related to the concentrations of free radicals and EPFRs. The potential protective effects of TEMPOL against EPFRs’ toxicity in zebrafish were investigated. Exposure to EPFRs plus TEMPOL shifted the concentration to an induced 50% adverse effect (EC50), from 23.6 to 30.8 µg/mL, which verifies TEMPOL’s protective effect against EPFRs in the early phase of zebrafish development.

Weak Magnetic Fields Enhance the Efficacy of Radiation Therapy

PurposeThe clinical efficacy of radiation therapy is mechanistically linked to ionization-induced free radicals that cause cell and tissue injury through direct and indirect mechanisms. Free radical reaction dynamics are influenced by many factors and can be manipulated by static weak magnetic fields (WMF) that perturb singlet-triplet state interconversion. Our study exploits this phenomenon to directly increase ionizing radiation (IR) dose absorption in tumors by combining WMF with radiation therapy as a new and effective method to improve treatment. Methods and MaterialsCoils were custom made to produce both homogeneous and gradient magnetic fields. The gradient coil enabled simultaneous in vitro assessment of free radical/reactive oxygen species reactivity across multiple field strengths from 6 to 66 G. First, increases in IR-induced free radical concentrations using oxidant-sensitive fluorescent dyes in a cell-free system were measured and verified. Next, human and murine cancer cell lines were evaluated in in vitro and in vivo models after exposure to clinically relevant doses of IR in combination with WMF. ResultsCellular responses to IR and WMF were field strength and cell line dependent. WMF was able to enhance IR effects on reactive oxygen species formation, DNA double-strand break formation, cell death, and tumor growth. ConclusionsWe demonstrate that the external presence of a magnetic field enhances radiation-induced cancer cell injury and death in vitro and in vivo. The effect extends beyond the timeframe when free radicals are induced in the presence of radiation into the window when endogenous free radicals are produced and therefore extends the applicability of this novel adjunct to cancer therapy in the context of radiation treatment.

Chemical and biological analysis of 4-acyloxy-3-nitrocoumarins as trypanocidal agents

Chagas disease is the most widespread contagious tropical disease in Latin America, being an important public health problem. Treatments against this disease are still very ineffective, presenting several side effects. Therefore, the search for alternative therapeutic solutions is urgent. In the present work, we evaluate the trypanocidal activity and the mechanism of action of a select series of synthetic 4-acyloxy-3-nitrocoumarins. All the coumarin derivatives showed moderate trypanocidal activity in trypomastigotes, along with low cytotoxicity. In addition, compound 1 decreased the number of infected Vero cells in an intracellular T. cruzi model. Electron spin resonance and electrochemical studies showed the formation of nitro radical anions. The Fukui index provided additional information to elucidate the proposed reduction mechanism. Furthermore, in vitro radical formation studies demonstrated the potential of these compounds to achieve higher concentrations of intracellular free radicals, proposing oxidative stress as a possible trypanocidal mechanism. Furthermore, no correlation was observed between the diffusion of these compounds, which shows that lipophilicity is not a predominant factor for activity. Elsevier Ltd. All rights reserved.

THE EFFECT OF LOW-LEVEL LASER IRRADIATION ON FREE RADICAL PROCESSES IN THE MITOCHONDRIAL FRACTIONS INDUCED BY THE BISPHENOL A ADMINISTRATION

Bisphenol A (BPA), the xenoestrogen and plasticizer, can induce mitochondrial dysfunction via the shift in the balance between oxidants and antioxidants. Low-level laser irradiation may influence oxidative stress parameters by changing the activity of antioxidant enzymes and the production of ROS. Our study aimed to investigate the effect of low-level laser irradiation on oxidative stress parameters in hepatic mitochondrial fractions of rats under the conditions of BPA administration. The BPA was administered per os daily for 3 days at a dose of 50 mg/kg body weight. Low-level laser irradiation was performed after each or last administration of xenobiotic. The activity of antioxidant enzymes and the content of free radicals was spectrophotometrically determined in the mitochondrial fraction of the liver. Short-term BPA exposure results in the induction of free radical processes in hepatic mitochondria by the enhanced generation of O2• – and decreased activity of antioxidant enzymes. At the same time, low-level laser irradiation reduces the prooxidant effect of this xenobiotic in mitochondria by the enhancement of the antioxidant activity, which is primarily associated with conformational changes induced by a short-term increase in the temperature of lightabsorbing biomolecules. This effect was observed only in the case of LLLI after BPA exposure.

Analysis of antioxidant activity on cocktail honey products as female pre-conception supplements

ObjectiveCocktail honey is derived from a mixture of honey (trigona sp.), bee bread, and homogeneous royal jelly. The material has a phenolic content rich in antioxidants that are beneficial for women's reproductive health, especially for pre-conception, because it can suppress the content of free radicals in the body. Antioxidants are useful to overcome oxidative damage due to free radicals in the body that prevent various diseases from increasing fertility during pre-conception. MethodThis study used the DPPH (2,2-diphenyl-1-picrylhydrazyl) test method using UV–vis spectrophotometry to express the value of free radical reduction activity as IC50 (inhibitory concentration) values. ResultsThe DPPH test on cocktail honey products obtained an average yield of 4577.7μg/mL, which was included in the product category was very weak in the antioxidant activity content. ConclusionThe content contained in the honey cocktail contains weak bioactive content by assessing the antioxidant content using DPPH. The difference in the results of antioxidant activity tests using DPPH is caused by the test method and the conditions used in processing, homogeneous ingredients, solvent volume, extraction time, temperature, and pressure in product management.

Free radical scavenging behavior of multidimensional nanomaterials in γ-irradiated epoxy resin and mechanical and thermal performance of γ-irradiated composites

In order to explore the scavenging ability of free radicals in polymers and the derivation mechanism with the different influence of the composition and various structure of nanomaterials, two-dimensional graphene oxide, one-dimensional carbon nanotubes and zero-dimensional carbon black in carbon nanomaterials, and halloysite nanotubes in silicate nanomaterials were selected to carry out a task. The results manifest that the content of free radicals produced by γ-ray irradiation in epoxy resin reduced because of the introduction nanoparticle. Among them, the epoxy resin reinforced by graphene oxide has the least free radical, followed by carbon nanotubes, halloysite nanotubes and carbon black, respectively. The analysis shows that the free radical scavenging capability was significantly different in variety types of nanomaterials. The free radical scavenging ability of carbon nanomaterials is ascribed to its well-organized honeycomb lattice, which is different from the fact that silicate nanomaterials is attributed to its electron acceptor sites. Meanwhile, the stable electron cloud was formed in the carbon nanomaterials, which is more conducive to eliminate the free radicals. The addition of nanomaterials decreases the number of free radicals in the resin, and correspondingly weakens the damage of free radicals for the resin, resulting in improving the thermal stability and mechanical properties of the epoxy resin.

Response surface methodology for the extraction of bioactive compound from black glutinous rice

This study was aimed at the extraction of total phenolic compounds, as well as, the antioxidant activity of black glutinous rice (Oryza sativa L.). Black glutinous rice of three varieties consists of Leum Pua, Doi Saket, and Phayao were extracted using citric acid solvent. The influences of temperature, time and pH value on total phenolic content and antioxidant activity (percentage of inhibition of DPPH free radical) were investigated. A central composite design was employed to determine the optimum extraction condition to obtain the highest total phenolic content and antioxidant activity. The regression models of total phenolic content were significant (p0.05) and determination coefficients values were 0.8028, 0.8089, and 0.8603 of Leum Pua, Doi Saket, and Phayao, respectively. The regression models of DPPH inhibition were significant (p0.05) and determination coefficients values were 0.8084, 0.8928, and 0.8243 of Leum Pua, Doi Saket, and Phayao, respectively. The selected optimum conditions were 72°C, 91 mins at pH 1.44 for Leum Pua, 72.5°C, 83 mins at pH 1.39 for Doi Saket, and 66.3°C, 75 mins at pH 1.32 for Phayao. Under the optimum condition, total phenolic content and percentage of inhibition of DPPH free radical of extract from Leum Pua, Doi Saket and Phayao were 0.3814 mg GAE g-1 DW with 89.36%, 0.2607 mg GAE g-1 DW with 73.33%, and 0.2617 mg GAE g1 DW with 75.27%, respectively. The results showed that the total phenolic content of the extract indicated a highly positive correlation with antioxidant activity.

A comparative study of adrenalin and fluocinolon induced oxidative stress in male wistar rats

Hormone secretion by the hypothalamic-pituitary-adrenocortical (HPA) axis is modulated by multiple factors which include the circadian rhythm, various types of stressors and glucocorticoids. Treatment with synthetic glucocorticoids as e.g. dexamethasone or dermocorticosteroids and repeated immobilization stress, decreases the total body weight gain of animals by disturbing the HPA axis function and accelerating the catabolism of the organism. Synthetic glucocorticoids are widely used as anti-inflammatory and anti-allergic drugs. Neverteheless, their administration may cause side effects in the normal functioning of several organs. Starting from the above findings and from the important physiological roles of the glucocorticoids in the metabolism, we investigated the reactions of the adrenal and thymus, the evolution of the body and organ weight and the level of the free radicals after adrenaline- and fluocinolon stress. In this study, we used electron paramagnetic resonance spectroscopy for the direct detection of free radical content in the organs o f stressed Wistar rats. We followed the changes of the blood glucose level, body weight,structural modification and whole redox state of the rats during adrenaline and Fluocinolon-acetonid N treatment, as endogenous and exogenous sources of elevated glucocoticoid levels. We found a relationship between changes of the redox state and modified homeostasis of the organism, as an effect of elevated glucocorticoid levels. The oxidative stress induced by adrenalin treatment seemed to be an inducer rather than the result of the tissue damage.

Rapid hydrolysis of tertiary isoprene nitrate efficiently removes NOx from the atmosphere

The formation of a suite of isoprene-derived hydroxy nitrate (IHN) isomers during the OH-initiated oxidation of isoprene affects both the concentration and distribution of nitrogen oxide free radicals (NOx). Experiments performed in an atmospheric simulation chamber suggest that the lifetime of the most abundant isomer, 1,2-IHN, is shortened significantly by a water-mediated process (leading to nitric acid formation), while the lifetime of a similar isomer, 4,3-IHN, is not. Consistent with these chamber studies, NMR kinetic experiments constrain the 1,2-IHN hydrolysis lifetime to less than 10 s in deuterium oxide (D2O) at 298 K, whereas the 4,3-IHN isomer has been observed to hydrolyze much less efficiently. These laboratory findings are used to interpret observations of the IHN isomer distribution in ambient air. The IHN isomer ratio (1,2-IHN to 4,3-IHN) in a high NOx environment decreases rapidly in the afternoon, which is not explained using known gas-phase chemistry. When simulated with an observationally constrained model, we find that an additional loss process for the 1,2-IHN isomer with a time constant of about 6 h best explains our atmospheric measurements. Using estimates for 1,2-IHN Henry's law constant and atmospheric liquid water volume, we show that condensed-phase hydrolysis of 1,2-IHN can account for this loss process. Simulations from a global chemistry transport model show that the hydrolysis of 1,2-IHN accounts for a substantial fraction of NOx lost (and HNO3 produced), resulting in large impacts on oxidant formation, especially over forested regions.

Experimental and Numerical Investigation of Laminar Flame Characteristics of Isooctane/air Mixtures at High Preheating Temperatures and H2O Dilution Ratios

ABSTRACT Liquid water injection technology is an effective method to improve the fuel economy and reduce the emissions of an internal-combustion engine. In this study, the laminar burning velocity and Markstein length of isooctane/air mixtures at a fixed pressure of 101.3 kPa, H2O dilution ratios of 0–10%, and preheating temperatures of 400–500 K was investigated using a combustion bomb and high-speed schlieren photography. The different effects of water vapor and preheating temperatures on the laminar burning velocity of isooctane/air mixtures were analyzed using the CHEMKIN software. The physical (dilution and thermal) and chemical effects of water vapor on the laminar burning velocity were identified. The results demonstrate that the laminar burning velocity decreases linearly with an increasing H2O dilution ratio and increases exponentially as the preheating temperature increases. The Markstein length increases gradually with the increase of H2O dilution ratio. The laminar burning velocity decreases by 0.13 m/s-0.17 m/s with 1% H2O dilution ratio at a preheating temperature of 400 K. The addition of water vapor decreases the concentration of free radicals. The physical and chemical effects increase linearly as the H2O dilution ratio increases. The physical effects are the main reason for the decrease in the laminar burning velocity. The chemical effects reduce the mole fraction of free radicals (H and O) and increase that of OH, which increases the net reaction rate of the reaction O + H2O = 2OH.

Chemical and spectroscopic characteristics of humic acid from a clay loam soil in Ontario after 52 years of consistent fertilization and crop rotation

Long-term fertilization and crop rotation can influence both organic C sequestration as well as the C composition of soils and the more resistant organic C compounds contained in humic acid (HA). This study examined the effects of fertilization and cropping type (monoculture corn (MC) and Kentucky bluegrass sod (KBS) and corn-oat-alfalfa-alfalfa rotation (RC)) on the HA composition of soil from a 52-year field study in southern Ontario, Canada. Humic acid samples were extracted from soil, and elemental analysis, infrared spectroscopy, solid state 13 C nuclear magnetic resonance spectra, and electron paramagnetic resonance methods were used to determine the influence of the cropping type on the characteristics of HA. Both fertilization and cropping type affected the chemical characteristics of HA. Fertilization led to a 5.9% increase in C, a 7.6% decrease in O, and lower O/C and (N + O)/C ratios in HA as compared to the corresponding non-fertilized treatments. Rotation resulted in a lower proportion of C (48.1%) and a greater (N + O)/C ratio (0.7) relative to monoculture cropping. Infrared spectroscopy analysis showed that HA contained more C-O groups in fertilized soil than in non-fertilized soil under MC and KBS. Fertilization increased the O-alkyl-C, phenolic-C, and free radical contents of HA relative to non-fertilization treatments. Rotation decreased the aliphatic and carboxyl groups and increased the O-alkyl, carbohydrate, aryl, and phenolic groups and free radicals, relative to MC and KBS. Both long-term crop rotation and fertilization dramatically modified the soil HA composition. Significant relationships were observed between the molecular composition of HA and soil organic C. Hence, humic acid characterization could be used as an indicator of the long-term sustainability of crop management practices.