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81.
Corrosion processes in drinking water distribution systems have been investigated for years. This paper proves the existence of a layer of steady water surrounding and partly filling corrosion scale in corroded water pipes. It is expected that steady water may substantially influence the corrosion. The idea of steady water explains why longer retention times would lead to more turbid waters containing more suspended Fe oxides (hydroxides). During stagnation period stagnant water mixes partially with steady water and the compensation of ions' concentration as well as particle diffusion is observed. Steady water is rich in ions and has reductive properties causing quick disappearance of nitrates and unwanted ammonia formation. Ammonia in turn may be responsible for fast oxygen and chlorine decay in the distribution system due to nitrification. Nitrates may also undergo denitrification in steady water, i.e. they would support bacterial existence in the distribution system. Such an environment makes favourable conditions for sulphate reducing bacteria and in fact in all of the steady water samples we have detected sulphides. Moreover, our results have shown that considerable amounts of assimilable organic carbon (AOC) can be formed in the corroded distribution system. 相似文献
82.
Janicka M Kot-Wasik A Kot J Namieśnik J 《International journal of molecular sciences》2010,11(11):4631-4659
Isoprostanes (IsoPs) are key biomarkers for investigating the role of free radical generation in the pathogenesis of human disorders. To solve IsoPs-related problems with regard to isoprostanes, analytical tools are required. This paper reviews the problems and trends in this field focusing on the methodology for assaying biomarkers in exhaled breath condensate (EBC) samples. A large amount of work has been done in the qualitative and quantitative analysis of IsoPs, but a standardized method has yet to emerge. The methodologies described differ, either in the sample preparation steps or in the detection techniques, or both. Requiring a number of chromatographic steps, the relevant extraction and purification procedures are often critical and time-consuming, and they lead to a substantial loss of target compounds. Recent data show that EBC is a promising non-invasive tool for the evaluation of different diseases. Two main analytical approaches have been adopted for IsoPs measurement: immunological methods and mass spectrometry. The methodologies for the extraction, purification and analysis of IsoPs in EBC samples are presented. 相似文献
83.
Marcin Pastorczak Michael Wübbenhorst Gustavo Dominguez-Espinosa Lidia Okrasa Marek Pyda Marcin Kozanecki Slawomir Kadlubowski Piotr Ulanski Janusz M. Rosiak Jacek Ulanski 《Polymer》2012,53(1):161-168
The phase transition observed by various methods in poly(vinyl methyl ether)/water systems at around 18 °C has been assigned by some investigators to the pre-melting of water and by others to a glass transition of the polymer. In this study, broadband dielectric spectroscopy and temperature modulated differential scanning calorimetry were used to identify this transition in radiationally crosslinked poly(vinyl methyl ether) hydrogels, as well as to analyse sub-zero relaxation processes in such a three-phase (polymer/ice/liquid water) system. The process at 18 °C was related to the pre-melting of water induced by the segmental motions of the polymer; however, it was seen to be one transition due to the cooperative motions of both compounds. The atypical (two regimes) temperature dependence of the segmental motion process was observed and was related to confinement of the polymer chains between ice clusters below approximately ?24 °C; furthermore, the main dielectric process of hexagonal ice was identified and a Maxwell-Wagner effect was observed. 相似文献
84.
ABSTRACT The deformations and drying-induced stresses in a saturated porous plate insulated on one side and dried convectively on the others were analysedPlate material is assumed to be elastic and viscoelastic. A rigorous solution of the problem is presented using Laplace transformations and the method of variable separation. The results are presented in the form of a series resulting from the solution of a Sturm-Liouville problem. The shrinkage stresses in the plate are caused by non-uniform distribution of the moisture content. The thermal stresses are not included as the consideration were confined to only constant rate drying period. 相似文献
85.
86.
Sławomir Wybraniec Karolina Starzak Anna Skopińska Maciej Szaleniec Jacek Słupski Katarzyna Mitka Piotr Kowalski Tadeusz Michałowski 《Food science and biotechnology》2013,22(2):353-363
An effect of metal cations on betanin stability was investigated in aqueous and organic-aqueous solutions. The presence of organic solvents (methanol, ethanol, and acetonitrile) affects substantially the pigments decomposition in acidic media induced by metal cations whose degrading action in such media is significantly higher than in aqueous solutions. The influence of Cu2+ on the stability was studied by spectrophotometry in more detailed manner, because of its ability to form complexes with betanin. The possibility of a complex formation between betanin and Ni2+ was also stated at pH 7–8; its relatively high stability in aqueous samples was observed. A presence of numerous products of betanin decomposition was detected in the wavelength range 380–500 nm in spectra obtained for most of metal cations investigated, especially for higher concentrations of the organic solvents. 相似文献
87.
Danuta Krupa Jacek Baszkiewicz Jerzy Smolik Janusz W. Sobczak 《Surface & coatings technology》2010,205(6):1743-8968
This paper is concerned with the surface modification of titanium by the PEO method (plasma electrolytic oxidation) in the solutions which contain Ca, P, Si and Na. The chemical composition of the thus formed surface layers was examined by XPS and EDS. The morphology of the surface was observed by SEM. The phase composition was determined by X-ray diffraction (XRD). The adhesive strength of the oxide layers was evaluated by the scratch-test. The corrosion resistance was determined in a simulated body fluid (SBF) at a temperature of 37 °C by electrochemical methods for various exposure times.The oxide layers obtained were porous and enriched with Ca, P, Si and Na and their properties depended on the electrolyte solution and the parameters of the oxidation process. The results of the electrochemical examinations show that the surface modification by PEO does not worsen the corrosion resistance of titanium after a 13 h exposure in SBF. The electrochemical impedance spectroscopy (EIS) results indicate that the surface layers have a complex structure and that their electric properties undergo changes during long-term exposures in SBF. 相似文献
88.
Levels of 13 pesticides in 40 honey samples form Poland are reported. A rapid and sensitive method was developed for the LC-ESI-MS/MS determination of multi-class pesticide residues in honey samples. Liquid–liquid extraction (LLE) on a diatomaceous earth support (requiring the use of small amounts of organic solvent), followed by chromatographic separation on a C18 column and gradient elution were employed. The method quantifies over a dynamic linear range from respective MQLs (0.06–1.3 ng/g) to 5 ng/g. Matrix effects were evaluated by comparing the slopes of matrix-matched and solvent-based calibration curves. The mean recoveries obtained for three fortification levels (0.5, 1.0 and 4.0 ng/g) were 63–117% for most compounds, with an expanded uncertainty of <10%. The results for real honey samples collected from five regions of Poland (Pomerania, Wielkopolska, Lublin Region, Lower and Upper Silesia), showed that residue concentrations were <5 ng/g and did not pose a threat to human health. 相似文献
89.
Arun K. Sharma Jacek Krzeminski Dhimant Desai Shantu Amin 《Polycyclic Aromatic Compounds》2013,33(3):297-305
Syntheses of naphtho[8,1,2- ghi ]chrysene (naphtho[1,2- e ]pyrene, N[ e ]P) 1 , dibenzo[ c,mno ]chrysene (naphtho[1,2- a ]pyrene, N[ a ]P) 2 and their dihydrodiol metabolites are described. The hydrocarbons N[ e ]P 1 and N[ a ]P 2 and their fjord region dihydrodiols 12 and 19 were synthesized using a Suzuki cross-coupling reaction followed by the appropriate manipulation of the functional groups. The K-region cis dihydrodiols of N[ e ]P-4,5-diol 20 , N[ a ]P-4,5-diol 23 , N[ a ]P-7,8-diol 24 were obtained by OsO 4 oxidation. The cis diols thus obtained were first converted to the corresponding quinones with pyridinium chlorochromate and, finally, to the desired trans dihydrodiols 22 , 27 , and 28 by NaBH 4 reduction. The mixture of trans N[ a ]P-4,5- and 7,8-dihydrodiols was separated by high-performance liquid chromatography. 相似文献
90.
Andrzej Wrbel ukasz Zapaa Tomasz Kluz Artur Rogowski Marcin Misiek Kajetan Juszczak Jacek Sieko Daniela Gold Klaudia Stangel-Wjcikiewicz Ewa Poleszak Piotr Radziszewski 《International journal of molecular sciences》2021,22(11)
The purpose of this study was to determine if asiatic acid may act efficiently in the model of cyclophosphamide (CYP)-induced cystitis in rats. We performed experiments after administration of CYP (single dose 200 mg/kg, intraperitoneally), asiatic acid (30 mg/kg/day for 14 consecutive days, by oral gavage), or CYP plus asiatic acid, during which conscious cystometry, measurements of urothelium thickness and bladder edema, as well as selected biomarkers analyses were conducted. In rats that received asiatic acid together with CYP, a drop in bladder basal pressure, detrusor overactivity index, non-voiding contraction amplitude, non-voiding contraction frequency, and the area under the pressure curve were observed, when compared to the CYP group. Furthermore, a significant increase in threshold pressure, voided volume, intercontraction interval, bladder compliance, and volume threshold to elicit NVC were found in that group accordingly. Administration of the asiatic acid successfully restored concentrations of biomarkers both in bladder urothelium (BDNF, CGRP, OCT-3, IL-1β, IL-6, NGF, nitrotyrosine, malondialdehyde, TNF-α, SV2A, SNAP23, SNAP25, PAC-1, ORM1, occludin, IGFBP-3, HB-EGF, T–H protein, Z01, and HPX) and detrusor muscle (Rho kinase and VAChT) in CYP-treated rats. Finally, asiatic acid significantly decreased urothelium thickness and bladder oedema. Asiatic acid proved to be a potent and effective drug in the rat model of CYP-induced cystitis. 相似文献