Search results for "hydrogen peroxide"

Evaluation of the effect of different enamel surface treatments and waiting times on the staining prevention after bleaching

2017

Background Bleached dental enamel can be more susceptible to staining than the enamel that has never been bleached, especially right after tooth bleaching. The aim of this study is to evaluate the effect of surface treatments and waiting time prior to contact with dye on bleached enamel staining susceptibility. Material and Methods One hundred teeth were bleached with 35% hydrogen peroxide (Whiteness HP, FGM) and randomly assigned to G1 artificial saliva, G2 2% sodium fluoride (Flugel, Nova DFL), G3 casein phosphopeptide-amorphous calcium phosphate fluoride paste (CPP-ACPF, MI Paste Plus, GC America), G4 rinse for color maintenance after bleaching (Keep White Rinse, DMC) and G5 polishing wi…

Hydrogen peroxide as a biodegradation stimulator in remediation processes of soils heavily contaminated with petrochemicals

2015

Abstract The soil contaminated with petroleum products must be excluded from the crops and treated to reclamation processes. Natural processes of decomposition of hydrocarbon compounds go very slow, so it is necessary to use bioaugumentation or stimulation in order to accelerate the return of the soil to high culture. In this study the effect of hydrogen peroxide on the process of cleaning soil strongly contaminated with pertochemicals was investigated. For this purpose, a pot experiment lasting 60 days was carried. The dynamics of changes in the population of filamentous fungi, yeasts and bacteria were examined and also content of aliphatic hydrocarbons (n-alkanes), monoaromatic and polycy…

ELECTROCHEMICAL ABATEMENT OF AZO 7 IN WATER SOLUTION IN MACRO AND MICRO CELLS

2012

An on-line system for preconcentration and determination of lead in wine samples by FAAS

2002

A flow injection method has been developed for the direct determination of free available Pb(II) and total Pb content in wine samples. The method is based on the chemical sorption of Pb(II), from pH 7 buffered solutions, on a packed polyurethane foam column, modified by addition of 2-(2-benzothiazolylazo)-p-cresol (BTAC). After this step, lead was directly eluted with a stream of 0.1 mol l(-1) HCl into an air C(2)H(2) flame in which lead was determined by atomic absorption spectrometry. Total lead was analyzed after sample digestion with nitric acid and hydrogen peroxide, being free available lead determined by direct sample on-line preconcentration and elution. The method provides a limit …

Induction of mitochondrial xanthine oxidase activity during apoptosis in the rat mammary gland

2006

Oxidative stress is an important signal for apoptosis to start. So far the mitochondrial respiratory chain has been considered as the major, if not the only, cause of such stress. Here we report that this is not the case. Xanthine oxidase, a O2(-) and H2O2 generating enzyme which is important in causing significant oxidative stress in the cytosol, is also present in the mitochondrial fraction of rat mammary gland. After weaning, during the involution of the mammary gland, massive apoptosis occurs. Mitochondrial xanthine oxidase activity increases and high mitochondrial H2O2 production takes place. Inhibition of xanthine oxidase activity by allopurinol, a specific inhibitor of xanthine oxida…

Creatine kinase is the main target of reactive oxygen species in cardiac myofibrils.

1996

Abstract Reactive oxygen species (ROS) have been reported to alter cardiac myofibrillar function as well as myofibrillar enzymes such as myosin ATPase and creatine kinase (CK). To understand their precise mode and site of action in myofibrils, the effects of the xanthine/xanthine oxidase (X/XO) system or of hydrogen peroxide (H 2 O 2 ) have been studied in the presence and in the absence of phosphocreatine (PCr) in Triton X-100–treated cardiac fibers. We found that xanthine oxidase (XO), with or without xanthine, induced a decrease in maximal Ca 2+ -activated tension. We attributed this effect to the high contaminating proteolytic activity in commercial XO preparations, since it could be p…

Stymulacja rozkładu substancji ropopochodnych w skażonej glebie z wykorzystaniem nadtlenku wodoru i szczepionki Yarrowia lipolytica A101

2016

Skażenia substancjami ropopochodnymi stanowią ogromny problem, nie tylko w rolnictwie, ponieważ negatywnie wpływają na właściwości fizyko-chemiczne i aktywność biologiczną gleb. Związki te mogą się również akumulować w roślinach lub wraz z pyłem osiadać na ich zielonych częściach. Większość z nich to substancje karcenogenne, dlatego ich usuwanie ze środowiska wymaga zastosowania efektywnych, tanich i bezpiecznych metod. W warunkach laboratoryjnych oceniono przydatność łącznego wykorzystania techniki stymulacji nadtlenkiem wodoru i bioaugmentacji szczepionką drożdżową Yarrowia lipolytica A101 do oczyszczania gleby z substancji ropopochodnych oraz wpływ na dynamikę zmian mikrobioty gleby. Wyk…

Determination of hydrogen peroxide using glassy carbon and graphite/polyester composite electrodes modified by vanadium-doped zirconias

2002

Abstract Synthetic monoclinic and tetragonal vanadium-doped zirconias (VZrO2) with vanadium loading ranging from 0.5 to 15 mol% are used to modify glassy carbon and graphite/polyester composite electrodes able to detect oxygen and hydrogen peroxide in neutral aqueous media. Electrodes modified by monoclinic VZrO2 decrease the overpotential for the reduction of oxygen and hydrogen peroxide in neutral and alkaline media and enhance their reduction currents with respect to unmodified carbon electrodes. This is associated to seven-coordinated vanadium centers isomorphously substituting zirconium ones in the ZrO2 lattice. The catalytic effect shows site-selectivity, since it is almost entirely a…

Removal of selected antibiotics and antiretroviral drugs during post‐treatment of municipal wastewater with UV, UV/chlorine and UV/hydrogen peroxide

2020

Active pharmaceutical ingredients (APIs) are only partially removed by convectional wastewater treatment plants. This study aimed at assessing the post‐treatment degradation of selected antibiotics and antiretroviral drugs by direct UV photolysis and advanced oxidation processes (UV/H2O2 and UV/Cl2) using low‐pressure mercury lamp. The rate of degradation largely followed pseudo first‐order reaction kinetics. Amongst the six studied APIs, sulfamethoxazole, ciprofloxacin and zidovudine were readily degraded by more than 90% using direct UV photolysis. Addition of Cl2 and H2O2 to the UV process led to an increase in the rate of degradation for all the compounds. The effectiveness UV/Cl2 proce…

Production of cecropin A in transgenic rice plants has an impact on host gene expression.

2008

Summary Expression of the cecropin A gene in rice confers resistance to the rice blast fungus Magnaporthe oryzae. In this study, a polymerase chain reaction-based suppression subtractive hybridization approach was used to generate a cDNA macroarray from the elite japonica rice (Oryza sativa L.) cultivar ‘Senia’. Gene expression studies revealed that the expression of components of the protein secretory and vesicular transport machinery is co-ordinately activated at the pre-invasive stage of infection of rice by the blast fungus. Comparisons of gene expression between wild-type and cecropin A plants revealed the over-expression of genes involved in protection against oxidative stress in tran…