The pH dependence of adsorption reactions of cationic metals is due, in part, to the preferential adsorption of the hydrolyzed metal species, in comparison to the free metal ion (McBride, 1977; McLauren and Crawford, 1973; Davis and Leckie, 1978; Farrah and Pickering, 1976a,b; James and Healy, 1972; McBride, 1982; Cavallaro and McBride, 1980; Harter, 1983). The pH of the soil system is a very important parameter that directly influences sorption/desorption, precipitation/ dissolution, complex formation, and oxidation-reduction reactions. In general, maximum retention of cationic metals occurs at pH>7 and maximum retention of anionic metals occurs at pH<7. However, because of the complexity of the soil-waste system, with its myriad of surface types and solution composition, such a generalization may not hold true. For example, cationic metal mobility has been observed to increase with increasing pH due to the formation of metal complexes with dissolved organic matter.
In 2001 FDA (Food and Drug administration, USA) gave its permission for simultaneous oesophageal intraluminal impedance examination and pH testing in the clinical practice. In 2002 in Porto, Portugal, a committee of international experts proposed a new classification of reflux types.Material and methods. From October 2005 to June 2006, we examined 36 patients sent to the clinic with GERD symptoms using a Sleuth® recording device.Results. The group of 36 patients (19 women and 17 men); mean age of 47 years with a range of 16-74 years) was examined. The mean length of time for the examination was 22 h 47 min, the shortest one lasting 18 h 36 min; brakes were caused by battery failure. 1509 episodes of reflux were confirmed by impedance channels. Only 538 (35.65%) of these reflux episodes were acidic or weakly acidic and 971 (64.35%) were non-acidic. There was one patient without acid reflux episodes during examination and only 12 non-acidic episodes. The proximal extend, defined as 15 cm above the LES, achieved 616 reflux episodes (40.82%). None of the patients had abnormal physical clearing times; 5 had extended chemical clearing times (13.8%) in recumbent positions.Summary. This paper is not a statistical evaluation of a MII-pH study and is only a report of our first experiences with this new diagnostic method. Objective evaluation of symptom correlation to reflux in MII and the chemical character of the refluxate gives a much more precise qualification to the best type of treatment. In cases of non-acidic reflux, MII-pH testing hastens decision making about surgery.
The influence of pH, ionic strength and selected natural ligands on the measurement of mercury by the diffusive gradients in thin films technique (DGT) using recently introduced sorption gels was determined. Sorption gels containing Chelex 100, Spheron-Thiol, Duolite GT73 and modified Iontosorb AV resins were investigated, with the sorption capacity determined for all used sorption gels. The minimum DGT measurable concentrations were calculated from 3 times the standard deviation of mercury amount in unexposed sorption gels. [...]
Human neutrophil peptides (HNPs, alpha-defensins) are a group of six defensins being considered as new antimicrobial drugs because of their multifunctional efficiency against bacteria, viruses and fungi. Regardless of the unique biological properties alpha-defensins are unstable compounds and their activity depends on many physical and chemical factors as well as on the kind of the used cultivation media. This leads to research difficulties and obstructions in their therapeutic application. The purpose of this study was to determine antibacterial activity of alpha-defensin 2 dissolved in pharmacopeia buffers and in parallel to develop selective and accurate analytical tests for identification and assay of alpha-defensin 2 in the course of study. The antibacterial effect of alpha-defensin 2 was determined against the strain Escherichia coli (ATCC 25922). It was found that 10 mg/l of Human neutrophil peptide-2 (HNP-2, alpha-defensin 2) dissolved in pH 9.0 buffer caused 90% inhibition of the bacterial respiratory activity. This buffer was considered as a suitable environment for deploying the antibacterial activity of the alpha-defensin. А selective MS analysis method for identification of alpha-defensin 2 in sample mixtures was developed. Also HPLC method with alternative selectivity was elaborated for identification and assay of mixtures containing alpha-defensin 2 and aminoacids in Mueller Hinton broth. The procedure includes development of system suitability test determination.
The influence of using formic, oxalic, citric, tartaric, hydrochloric, nitric, sulphuric and phosphoric acid for dyebath pH adjustment was investigated upon the dyeing of polyester fabric with CI Disperse Yellow 60. The positions of colour in CIELab coordinates of the samples dyed with the addition of tested acids were assessed and compared to those dyed with the addition of acetic acid. It was found that the differences in dyeabilities obtained with the addition of citric, oxalic, hydrochloric, nitric and sulphuric acid are entirely acceptable according to both M&S 83A and CMC (2:1) standards in comparison to the dyeability obtained with the addition of acetic acid.
Geopolymer structures are a relatively new family of un-fired ceramics that are produced by alkaline slurry of mixed alumina silicate-based materials. One of the most abundant geopolymer-forming powders is the fly ash. Fly ash is a waste product of thermic coal plants, which produce electricity by coal burning. Fly ashes contain mostly Ca, Al, Si and Fe oxide mixtures and compounds formed during the burning process, followed by sedimentation. The standardization is made by SiO₂ content. Class C ash has low silica content (<50 wt.%) and class F ash has a higher silica content (>50 wt.%). The fly ash, studied in this work, was obtained from Kangal Coal Plant. The NaOH was used as the geopolymer binder and curing was performed at 80% relative humidity, at 40°C in sealed plastic molds. The obtained cylinders were aged for one week before releasing from molds. pH dependent degradation was used to determine the ionic exchange of geopolymers into the solution. Afterwards, XRD and SEM were done to detect the structural changes of geopolymers.
In the present study, we investigated how cytochrome c catalyzed the nitration of tyrosine at various pHs. The cytochrome c-catalyzed nitration of tyrosine occurred in proportion to the concentration of hydrogen peroxide, nitrite or cytochrome c. Thecytochromec-catalyzed nitration of tyrosine was inhibited by catalase, sodium azide, cystein, and uric acid. These results show that the cytochrome c-catalyzednitrotyrosine formation was due to peroxidase activity. The rate constant between cytochrome c and hydrogen peroxide within the pH range of 3 - 8 was the largest at pH 6 (37°C). The amount of nitrotyrosine formed was the greatest at pH 5. At pH 3, onlycytochromec-independent nitration of tyrosine occurred in the presence of nitrite. At this pH, the UV as well as visible spectrum of cytochrome c was changed by nitrite, even in the presence of hydrogen peroxide, probably via the formation of a heme iron - nitric oxide complex. Due to this change, the peroxidase activity of cytochrome c was lost.
This paper presents the physico-chemical characteristics of titanium dioxide/chitosan dispersion. The surface and electrostatic properties of TiO2 particles in the electrolyte solution (NaCl) and in the presence of a biopolymer were determined by static and dynamic light scattering. The stability measurements were made under different conditions, where the variable was the dispersion pH. This paper mainly includes discussion of dispersion behaviour in neutral and alkaline environments. At each pH value (6–9), the addition of chitosan caused significant improvement in stability compared to the systems of base titanium dioxide. Of the tested systems, the most stable values of diameter and zeta potential for dispersion were found at pH 7. The study allowed the conclusion that the addition of chitosan to TiO2 dispersion created the possibility of using such systems as a drug carrier for the controlled release of active substances sensitive to pH changes.
This study investigated the effect of storage on certain sachet water quality indicators over a twelve-week period. Three brands of sachet water were collected within 24 h of production and analyzed for pH, nitrate, phosphate and dissolved oxygen. These were then placed in normal storage. According to out results, pH values increased significantly in all brands after week 8. Moreover, nitrate and dissolved oxygen values decreased throughout the investigation period, while phosphate values increased in all brands tested. All tested brands showed various degree of variation over the period of study. Still, all brands analyzed were within permissible limit by World Health Organization (WHO) stipulations. However, continuous storage can significantly alter the chemical quality indicators to a level that exceeds the limit set by WHO; hence, becoming harmful to human health. Therefore, it is recommended that sachet water should not be stored for more than 12 weeks from the date of production.
Stężenie jonów wodorowych (pH) i benzodiazepiny (BDZ) są czynnikami modulującymi receptory GABAa. W szczególności, wartość pH środowiska zewnątrzkomórkowego może zmieniać się w zależności od stanu fizjologicznego lub patologicznego. W niniejszej pracy przedstawiono wyniki badań wpływu flurazepamu (benzodiazepiny) przy różnych wartościach zewnątrzkomórkowego pH (z zakresu 5.5 - 7.2) na amplitudę miniaturowych GABA-ergicznych inhibujących prądów synaptycznych (mIPSCs). Stwierdzono, że obecność flurazepamu prowadzi do zwiększenia amplitudy mIPSCs, ale efekt ten zależy od pH i je st największy przy silnie kwaśnych wartościach. Wpływ flurazepamu na amplidudę mIPSC osiąga nasycenie przy stężeniu ok. I цМ dla wszystkich badanych wartości pH. Wyniki te wskazują na to, że modulacja Prądów GABAergicznych przez benzodiazepiny jest zależna od odczynu środowiska.
The paper reports on the dependence of the absorbance and luminescent intensity from pH of novel poly(oxyethylene phosphate) tris(β-diketonate) europium (III) complexes. The photophysical data obtained allow some preliminary assumptions about the nature of this phenomenon. Increase in luminescent efficiency is a consequence of enhanced efficiency of energy transfer caused by structural changes in complexes after water deprotonation. Remarkable change has been observed in photophysical properties of the polymer complexes by studying the fluorescent emission and excitation spectra and absorption recorded at various pH both in solution and in the solid state. Some of the complexes derivative of the dibenzoylmethane (DBM) show more than hundred times increase in the luminescence after alkalization. The pH value, at which the maximum luminescent efficiency appears, depends on the type of the fourth ligand. The difference between luminescent efficiency of the complexes in alkaline and neutral environment depends on the β-diketonate ligands and on polymer type as well. [...]