Concentrations Of Oxygen Radicals Research Articles

Influence of Additive N2 on O2 Plasma Ashing Process in Inductively Coupled Plasma.

One of the cleaning processes in semiconductor fabrication is the ashing process using oxygen plasma, which has been normally used N2 gas as additive gas to increase the ashing rate, and it is known that the ashing rate is strongly related to the concentration of oxygen radicals measured OES. However, by performing a comprehensive experiment of the O2 plasma ashing process in various N2/O2 mixing ratios and RF powers, our investigation revealed that the tendency of the density measured using only OES did not exactly match the ashing rate. This problematic issue can be solved by considering the plasma parameter, such as electron density. This study can suggest a method inferring the exact maximum condition of the ashing rate based on the plasma diagnostics such as OES, Langmuir probe, and cutoff probe, which might be useful for the next-generation plasma process.

Nano-silicon alters antioxidant activities of soybean seedlings under salt toxicity.

Materials with a particle size less than 100nm are classified as nano-materials. The physical and chemical properties of nano-materials can vary considerably from those of bulk materials of the same composition. Silicon (Si) still fails to get recognized as an essential nutrient for plant growth and development, however the beneficial effects in terms of growth, biotic and abiotic stress resistance have been indicated in a variety of plant species for their growth. The aim of this study was to investigate the effects of different nano-silicon rates on the growth and antioxidant activities of soybean (Glycine max L. cv. M7) under salt stress. The results showed that salinity decreased shoot and root dry weight, potassium (K+) concentration in the root and leaf; however, increased sodium (Na+) concentration, catalase, peroxidase, ascorbate peroxidase and superoxide dismutase activities, phenolic components, ascorbic acid and α-tocopherol contents, lipid peroxidation, hydrogen peroxide, and oxygen radical's concentration. Between the treatments, 0.5 and 1mM of nanosilicon oxide (nano-SiO2) improved shoot and root growth of seedlings. In contrast, a foliar application of SiO2 at 2mM reduced the soybean growth. Overall, exogenous nano-silicon alleviated the salt stress by increase in K+ concentration, antioxidant activities, non-enzymatic compounds and decreasing of Na+ concentration, lipid peroxidation, and reactive oxygen species production.

Surface-confined activation of ultra low-k dielectrics in CO2 plasma

An approach allowing surface-confined activation of porous organosilicate based low-k dielectrics is proposed and studied. By examining the plasma damage mechanism of low-k, we came up with an initial idea that the main requirements for the surface-confined modification would be the high reactivity and high recombination rate of the plasma species. Based on this concept, CO2 plasma was selected and benchmarked with several other plasmas. It is demonstrated that a short exposure of organosilicate low-k films to CO2 plasma enables high surface hydrophilicity with limited bulk modification. CO2+ ions predominantly formed in this plasma have high oxidation potential and efficiently remove surface -CH3 groups from low-k. At the same time, the CO2+ ions get easily discharged (deactivated) during their collisions with pore walls and therefore have very limited probability of penetration into the low-k bulk. Low concentration of oxygen radicals is another factor avoiding the bulk damage. The chemical reactions describing the interactions between CO2 plasma and low-k dielectrics are proposed.

Surface Cleaning Using an Atmospheric-Pressure Plasma Jet in $\hbox{O}_{2}/\hbox{Ar}$ Mixtures

An atmospheric-pressure plasma jet generated in <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{O}_{2}/\hbox{Ar}$ </tex></formula> mixtures by specially designed equipment with two coaxial quartz tubes and double power electrodes has been investigated, and its effect on the cleaning of surface organic contaminations has been studied. The Q–V Lissajous figures are performed to evaluate the power consumed in the discharge and show no great modification in consumed power with the increase in the oxygen flow rate. From the results of the optical emission spectra, remarkably high oxygen radical concentration is obtained at a 1.5 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\%$ </tex></formula> addition of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{O}_{2}$</tex></formula> to Ar and then decreases with the further increase in the <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{O}_{2}/\hbox{Ar}$</tex> </formula> mixing ratio. The effect of the surface cleaning by <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{O}_{2}/ \hbox{Ar}$</tex></formula> -based plasma is studied with respect to the changes in the contact angle. An addition of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{O}_{2}$</tex></formula> to Ar decreases the contact angle, and the lowest contact angle is obtained at a 1.5 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\%$</tex></formula> addition of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{O}_{2}$</tex></formula> to Ar. However, further addition of oxygen does not show further improvement in the contact angle. From the results of quadrupole mass-spectrum analysis, we can identify the fragment molecules of CO and <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{H}_{2}\hbox{O}$</tex></formula> in the emitted gases, which are produced by the decomposition of the surface organic contaminations during the cleaning process.

BIOMARKERS OF OXIDATIVE STRESS IN RED BLOOD CELLS

Exposure to high concentrations of oxygen radicals, the lack of nucleus and mitochrondria, inability to synthesise new protein and degradation of detoxifying enzymes makes red blood cells (RBCs) uniquely vulnerable to oxidative stress. This review summarizes the changes in biochemical parameters that primarily contribute to alterations in red blood cells during oxidative stress. PubMed, Science Direct and Springer online databases and updates from the Indian Council of Medical Research (ICMR). As one of the first cells to be affected by changes in the redox status of the body, alterations in red blood cells are widely used in first step-diagnoses of a number of pathological conditions. The information presented in this review provides an update on biomarkers of redox balance in red blood cells. These biomarkers may be used for assessment of oxidative stress during human health and disease.

Low-intensity pulsed ultrasound (LIPUS) therapy may enhance the negative effects of oxygen radicals in the acute phase of fracture

Though it is well accepted that low-intensity pulsed ultrasound (LIPUS) can accelerate the healing process of a fracture with very good results, we should still pay attention to its side effects and further improve its application in detail, such as the appropriate time and point for the application. In the early phase of a bone fracture, there are millions of oxygen radicals released by neutrophils in the injured area. This article focuses on whether the increased permeability of normal cell membranes by LIPUS makes the concentration of oxygen radicals increase to such a high degree that damage occurs to healthy tissue cells. It is proposed that it may be better not to use LIPUS in the acute phase of a fracture (i.e. within 1week after injury) but instead delay its application until after any inflammatory reaction has weakened to yield better results.

Study of spin centers in nanocrystalline titanium dioxide with a high degree of photocatalytic activity

Electron spin resonance spectroscopy is used to study the effects of illumination and changes in temperature on spin centers in nanocrystalline anatase powders synthesized by sol-gel methods with various complexing agents. A correlation between the concentration of oxygen radicals at the surface and the rate of photocatalytic decomposition of organic compounds in the presence of TiO2 is observed. It is shown that the concentration of centers active in the electron spin resonance spectra can be used for monitoring the photocatalytic activity of TiO2.

Curcumin Attenuates Airway Hyperreactivity Induced by Ischemia-Reperfusion of the Pancreas in Rats

ObjectivesIschemia-reperfusion (I/R) of the rat pancreas induces acute pancreatitis with a systemic inflammatory response. Activated inflammatory cells are sequestered in the lung, and the consequent respiratory burst may increase airway reactivity. In this study, we characterized the effect of the antioxidant curcumin on airway hyperreactivity induced by pancreatic I/R. MethodsIschemia of the pancreas was induced by clamping the gastroduodenal and the splenic artery for 2 hours followed by reperfusion for 6 hours. The pulmonary function data of Penh, a measurement of airway resistance, were used to show the airway responses to a methacholine challenge. The blood concentration of oxygen radicals, nitric oxide, and tumor necrosis factor-α (TNFα) were measured after pancreatic I/R. mRNA expressions of inducible nitric oxide synthase (iNOS) and TNFα in lung tissues were measured after pancreatic I/R. Pretreatment with curcumin (20 mg/kg) was administered by intraperitoneal injection 2 hours before pancreatic I/R. ResultsThe protocol resulted in significant elevations of the blood concentrations of amylase, hydroxyl radical, nitric oxide, TNFα, and white cells among the I/R group. iNOS and TNFα mRNA expressions also significantly increased in lung tissues. Pulmonary function data showed that pancreatic I/R induced significant increases in responses to methacholine challenge: Penh increased significantly in the I/R group when compared with the sham group. Pretreatment with curcumin significantly attenuated the inflammatory, oxidative, and nitrosative responses and lung tissue iNOS and TNFα expressions. Curcumin also attenuated airway reactivity to methacholine challenge. ConclusionsI/R of the pancreas induced systemic inflammatory responses with respiratory burst, nitrosative stress, and hyperresponses in the airways. Curcumin, which has antioxidant and anti-inflammatory effects, significantly attenuated the inflammatory responses and airway hyperreactivity induced by pancreatic I/R.

Nonequilibrium atmospheric pressure plasma with ultrahigh electron density and high performance for glass surface cleaning

We produced a nonequilibrium atmospheric pressure plasma by applying an alternative current between two electrodes. The gas temperature and electron density were evaluated using optical emission spectroscopy. It was found that the plasma had gas temperatures from 1800to2150K and ultrahigh electron densities in the order of 1016cm−3. A remarkably high oxygen radical concentration of 1.6×1015cm−3 was obtained at a 1% O2∕Ar gas flow rate of 15slm (standard liters per minute). Contact angles below 10° were obtained in the process of glass cleaning with a plasma exposure time of 23ms.

Free oxygen radicals in whole blood correlate strongly with high-sensitivity C-reactive protein

Increased concentrations of reactive oxygen molecules are believed to be a driving force in inflammation. Although evident in tissue culture and animal models, it has been difficult to link reactive oxygen species (ROS) and inflammatory markers in humans. In patients recruited to represent a broad spectrum of risk factors, we investigated the relationship between the plasma concentration of oxygen radicals and high-sensitivity C-reactive protein (hs-CRP), utilizing a new chemistry with an easily oxidized chromophore. ROS and hs-CRP were measured in blood from 59 fasting subjects selected to have variable risk predicted by classical risk factors. ROS were determined using the free oxygen radical monitor, which is an indirect colorimetric assay for the concentration of hydroperoxides in whole blood. Using log transformation, the correlation between ROS and hs-CRP was r = 0.505 (P < 0.0001). This relationship between ROS and hs-CRP was comparable (r = 0.527, P = 0.001) in the subgroup not currently on statin therapy (n = 39). ROS were not correlated with Framingham risk, r = -0.027 (P = 0.84). ROS directly measured in human blood correlates strongly with hs-CRP.

Long-distance oxygen plasma sterilization: Effects and mechanisms

The distribution of electrons, ions and oxygen radicals in long-distance oxygen plasma and the germicidal effect (GE) of Escherichia coli on the surface of medical poly(tetrafluoroethylene) (PTFE) film were studied. The quantity of protein leakage and the production of lipid peroxide in bacterial suspension as well as the state of DNA were measured after sterilization to analyse the inactivation mechanisms. The results showed that the concentration of electrons and ions decreased rapidly with increasing the distance from the center of induction coil, which approximated to 0 at 30 cm, whereas the concentration of oxygen radicals reduced slowly, i.e. decreased 30% within 40 cm. GE value reached 3.42 in the active discharge zone (0 cm) and exceeded 3.32 within 40 cm when plasma treatment parameters were set as follows: plasma rf power at 100 W, treatment time at 60 s and oxygen flux at 40 cm 3/min. Fast etching action on cell membrane by electrons, ions and attacking polyunsaturation fatty acid (PUFA) in cell membrane by oxygen radicals are primary reasons of oxygen plasma sterilization in the active discharge and the afterglow zone, respectively. The GE of UV radiation in long-distance oxygen plasma is feebleness.

COMPARISON OF THE EFFECTS OF VITAMIN E AND/OR QUERCETIN IN ATTENUATING CHRONIC CYCLOSPORINE A‐INDUCED NEPHROTOXICITY IN MALE RATS

1. The aim of the present study was to investigate the effects of vitamin E and/or quercetin (Q) on renal function, oxygen radical concentrations in the kidney and some anti-oxidant enzyme activities in rats treated with cyclosporine A (CsA). 2. Groups of rats (270 +/- 15 g), on standard rat chow and water, received all their treatments by gavage for either 4 or 8 weeks. Control groups received either olive oil (0.5 mL) or 25% ethanol (0.5 mL) + olive oil (0.5 mL) per day as vehicle. All experimental groups received 25 mg CsA/kg per day in 0.5 mL olive oil. The vitamin E group received 100 mg vitamin E/kg per day in olive oil in addition to CsA treatment. The quercetin group received 15 mg of Q/kg per day in 0.5 mL of 25% ethanol in addition to CsA treatment. The vitamin E + quercetin group received the two anti-oxidants at the concentrations given in addition to CsA treatment. 3. Quercetin, at a concentration less than one-quarter of vitamin E, was more efficient in lowering blood urea nitrogen, serum creatinine and kidney malondialdehyde in CsA-treated rats. However, neither of the two anti-oxidants was able to normalize these analytes to control values after either 4 or 8 weeks treatment. 4. Quercetin (50 micromol/kg per day) elevated all renal anti-oxidant enzyme activities to values observed in the negative controls. However, vitamin E (232 micromol/kg per day) only normalized glutathione peroxidase activity at the end of either 4 or 8 weeks treatment. Combination treatment with the two anti-oxidants abolished all the ill-effects of CsA. 5. Combination treatment with the two anti-oxidants of renal transplant patients receiving CsA may be beneficial in ameliorating the chronic nephrotoxic effects of the important immunosuppressive drug CsA.

Formation of Oxygen Radicals in 12CaO·7Al2O3: Instability of Extraframework Oxide Ions and Uptake of Oxygen Gas

The thermodynamics and kinetics of oxygen radical formation in cages of a nanoporous crystal, 12CaO·7Al2O3, were examined during isothermal annealing in a dry oxygen atmosphere. The formation of oxygen radicals, O2- and O-, involves the outward diffusion of extraframework oxide ions, their oxidation by absorbed oxygen molecules to form O- and O2- at the surface, and subsequent inward diffusion of the oxygen radicals. The instability of the extraframework oxide ions provides the driving force for this process. Evaluating the radical formation enthalpy and entropy enabled us to determine the temperature and oxygen partial pressure dependences of equilibrium oxygen radical concentration. The rate-limiting process for the radical formation is not the surface reaction, but the total ionic diffusion process, in which the smaller diffusivity of O2- likely dominates the process.

Neutrophils are primary source of O2 radicals during reperfusion after prolonged myocardial ischemia.

Although many studies document oxygen radical formation during ischemia-reperfusion, few address the sources of radicals in vivo or examine radical generation in the context of prolonged ischemia. In particular, the contribution of activated neutrophils remains unclear. To investigate this issue, we developed a methodology to detect radicals without interfering with blood-borne mechanisms of radical generation. Dogs underwent aorta and coronary sinus catheterization. No chemicals were infused; instead, blood was drawn into syringes prefilled with a spin trap and analyzed by electron paramagnetic resonance spectroscopy. After 90 min of coronary artery occlusion, transcardiac concentration of oxygen radicals rose severalfold 10 min after reflow and remained significantly elevated for at least 1 h. Radicals were mostly derived from neutrophils, as shown by marked reduction after the administration of 1) neutrophil NADPH oxidase inhibitors and 2) a monoclonal antibody (R15.7) against neutrophil CD18 adhesion molecule. Reduction of radical generation by R15.7 was also associated with a significantly smaller infarct size and no-reflow areas. Thus our data demonstrate that neutrophils are a major source of oxidants in hearts reperfused in vivo after prolonged ischemia and that antineutrophil interventions can effectively prevent the increase in oxygen radical concentration during reperfusion.

Spreading depression-induced expression of c-fos and cyclooxygenase-2 in transgenic mice that overexpress human copper/zinc-superoxide dismutase.

Spreading depression (SD) is a wave of sustained depolarization challenging the energy metabolism of cells without causing irreversible damage. SD is a major mechanism of gene induction that takes place in cortical injury, including ischemia. We studied the role of oxygen radicals in SD-induced c-fos and cyclooxygenase-2 (COX-2) induction using transgenic (Tg) mice that overexpress copper/zinc-superoxide dismutase (SOD1). The frequency, amplitude and duration of SD waves were similar in the Tg mice and wild-type littermates. c-fos and COX-2 mRNAs were strongly induced 1 and 4 h after SD. The induction of both genes was slightly but significantly less at 4 h in the Tg mice. The results indicate that even a mild, noninjurious metabolic stimulation increases the concentration of oxygen radicals to the level that contributes to gene expression.

Dry etching of copper film with hexafluoroacetylacetone via oxidation process

Dry etching of Cu film was achieved via oxidation process using oxidizing agents such as O2 plasma, O3, or O3 plasma, followed by the removal process of the copper oxides (CuOx) by reaction with hexafluoroacetylacetone [H(hfac)] to form volatile copper compound, [bis-hexafluoroacetylacetonate: Cu(hfac)2] and H2O. The etching rate was increased with the increase of etchant [H(hfac) and O3] flow rate, plasma power, and substrate temperature. Oxygen radical concentration is the highest in the plasma generated with ozone, which leads to the highest etching rate up to 1400 Å/min. The etch rate dependence on the substrate temperature showed the activation energy of about 7 kcal/mol and gas phase transport seems to be the rate controlling step.

Antioxidant vitamins C and E affect the superoxide-mediated induction of the soxRS regulon of Escherichia coli.

The mechanism of activation of Escherichia coli redox sensory protein SoxR is still unclear: a [2Fe-2S] cluster contained in a SoxR dimer is potentially redox-sensitive, but the nature of the signal is unknown. Antioxidant vitamins C (ascorbate) and E (alpha-tocopherol) were used to explore the mechanism of activation of the SoxR protein in vivo. Treating E. coli cells with ascorbate or alpha-tocopherol increased their tolerance to paraquat (PQ, a redox-cycling compound), even in the absence of the soxRS locus, suggesting a radical-quenching activity. When using a soxS'::lacZ fusion, whose expression is governed by activated SoxR, ascorbate and alpha-tocopherol also prevented the expression of beta-galactosidase after PQ treatment. A secondary activity was observed in cells carrying soxR101, a mutation resulting in the constitutive expression of the sox regulon, where the overexpression of soxS'::lacZ was also reduced by ascorbate or alpha-tocopherol treatment. Additionally, different mechanisms of action were revealed as alpha-tocopherol was capable of preventing both PQ and meanadione (MD) lethality, whilst ascorbate prevented PQ lethality but increased MD-mediated cell death. It is proposed that alpha-tocopherol, positioned in membranes, can prevent superoxide-dependent membrane damage; however, water-soluble ascorbate is unable to do so and can even increase the concentration of oxygen radicals reacting with released membrane-associated Fe(II).

Reactive Ion Etching Mechanism of RuO2 Thin Films in Oxygen Plasma with the Addition of CF4, Cl2, and N2

In this study, we thoroughly investigated the reactive ion etching mechanism of RuO2 film in oxygen plasma with the addition of CF4, Cl2, and N2. The etch rate of RuO2 was examined as functions of flow rates of input gases, substrate temperature, DC bias applied to the substrate, and pressure. The concentrations of the etching species in the plasma were determined using optical emission spectroscopy (OES) and a quadrupole mass spectrometer (QMS). The etch products were determined with a QMS and the etched surface of RuO2 film was examined with X-ray photoelectron spectroscopy (XPS). RuO4 and RuO3, which are formed by the reactions between RuO2 film and oxygen radicals, are the only etch products regardless of the kind of additive gas. The additive gases (CF4, Cl2, and N2) are not directly involved in the chemical reaction with the RuO2 film, but they increase the concentration of oxygen radicals and accordingly, appreciably increase the etch rate of the RuO2 films. The etch rate is limited by the formation rate of the etch products, which is enhanced by the bombardment of energetic ions. Therefore, the etch rate depends not only on the concentration of oxygen radicals, but also on the flux and energy of the ions bombarding the film surface. In this study, for the first time, we introduced the use of the O2/N2 plasma system in RuO2 etching.

Effects of aspirin and garlic on cyclooxygenase-induced chemiluminescence in human term placenta.

The spontaneous emission of chemiluminescence appears to reflect changes in the intracellular steady-state concentration of oxygen radicals. Stimulation of arachidonic acid metabolism in human platelets also induces chemiluminescence, which indicates the formation of highly reactive species by cyclooxygenase andlor lipooxygenase [1,2]. It was observed that arachidonic acid, linoleic acid and linolenic acid can induce luminol-induced chemiluminescence in human term placental villi. The luminol-dependent chemiluminescence activity after addition of these fatty acids was investigated after incubation of villi with aspirin and garlic extract.

The Effects of the Addition of CF4, Cl2, and N2 TO O2 ECR Plasma on the ETCH Rate, Selectivity and Etched Profile of RuO2 Film

ABSTRACTIn this study, we investigated the effects of the addition of CF4, Cl2, and N2 gases to oxygen electron cyclotron resonance (ECR) plasma on the reactive ion etching (RIE) properties of RuO2 film such as etch rate, selectivity, and etched profile. The concentration of the etching species in the plasma was analyzed with an optical emission spectroscopy (OES) and a quadrupole mass spectrometer (QMS). The etch product was also examined with QMS.The addition of a small amount of CF4, Cl2, or N2 to the O2 plasma increases the concentration of oxygen radicals and accordingly increases the etch rate of the RUO2 films appreciably. The etch rate of the RuO2 film was enhanced more with the addition of a small amount of CF4 and CI2 than with the addition of N2. On the contrary, the etched profile obtained in O2/N2 plasma was superior, without any damaged layer at the sidewall, to O2/CF4 and O2/Cl2 plasma. The selectivity of RuO2 to Si)2 mask was over 20:1 for each of the additive gas proportion at which the etch rate was maximum for each plasma system.