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۱Theory of Square–wave Voltammetry of two Electrode Reactions Coupled by Reversible Chemical Reaction
اطلاعات انتشار: Analytical & Bioanalytical Electrochemistry، پنجم،شماره۳، June ۲۰۱۳، سال ۰
تعداد صفحات: ۱۴
An ECE mechanism in which chemical reaction is permanently in equilibrium is investigated theoretically. The calculations were performed by the method of numerical integration for fast and reversible electrode reactions as well as for the reactions that are controlled by the electron transfer kinetics. In square–wave voltammetry the response depends on the difference in standard potentials of individual electron transfers and on the dimensionless equilibrium constant of the chemical reaction. Depending on the concentration of compound X–, which is one of reactants in chemical reaction, either a single peak or the split response may appear. In the first case the peak potential depends linearly on the logarithm of X– concentration, with the slope –2.3RT\2F. The potential of the first peak of the split response is also linear function of, but the slope is –2.3RT\F. The relationship is determined between standard potentials and the critical value of the equilibrium constant above which the response splits in two peaks. Under the influence of electrode kinetics, the responses change with square–wave frequency. The first electron transfer is slow and the second one is fast if two peaks appear at the lowest frequency and merge into a single peak at the highest frequency. If the second charge transfer is slower that the first one, the difference in peak potentials increases with the increasing frequency.
۲Characterisation of Heavy Metals in Lichen Species Hypogymnia physodes and Evernia prunastri due to Biomonitoring of Air Pollution in the Vicinity of Copper Mine
اطلاعات انتشار: International Journal Of Environmental Research، ششم،شماره۳، Summer ۲۰۱۲، سال ۰
تعداد صفحات: ۱۴
Lichen species (Hypogymnia physodes and Evernia prunastri) were used for biomonitoring the possible air pollution with heavy metals in the vicinity of copper mine in the eastern part of the Republic of Macedonia. The contents of 18 elements were analysed by ICP–AES and ETAAS techniques. For data processing basic statistical methods and multivariate exploratory (factor and cluster analysis) techniques were applied. Three geogenic and one anthropogenic group of elements were singled out from factor analysis. Maps of spatial distribution of elements from the anthropogenic group showed an increased content of the anthropogenic elements only in close vicinity to the mine. A maximum value obtained for Cu content was 130 mg\kg and for Pb content was 120 mg\kg. Lichen talus of the collected species showed high retention power for accumulation of the anthropogenic group of elements compared to moss species sampled from the same study area (r=0.86 and r=0.68). Here we show that lichens can be use as biomonitors for atmospheric distribution of anthropogenicintroduced elements.
۳Trace Metal Concentrations in Size–Fractionated Urban Atmospheric Particles of Sarajevo, Bosnia and Herzegovina
نویسنده(ها): J. Sulejmanovi&ć، ، ، T. Muhi&ć، ، ، &Š، ، arac، M. Memi&ć، ، ، A. Gambaro، A. Selovi&ć،
اطلاعات انتشار: International Journal Of Environmental Research، هشتم،شماره۳، Summer ۲۰۱۴، سال ۰
تعداد صفحات: ۸
A study of the atmospheric particulate size distribution of total suspended particulate matter (TSPM) and associated heavy metals concentrations has been carried out for the urban part of Sarajevo city, Bosnia and Herzegovina. Urban particles (n=150) were collected using a high volume air sampler equipped with a 6–stage impactor. Apart from Fe which has been determined by flame atomic absorption spectrometry (FAAS), all measurements (Co, Cu, Mn) have been carried out by graphite furnace atomic absorption spectrometry (GFAAS). The average concentrations of particulate matter are 37%, 18%, 15%, 8%, 15% and 6% (averaged over all the observations) of total suspended particulate for PM 0.49, PM0.95 – 0.49, PM1.5 –0.95, PM3.0 – 1.5, PM7.2 – 3.0 and PM> 7.2, respectively. Metal concentrations in size–fractionated urban particles ranged from 0.01–3.83 ng\m3 for Co, 6.30–179.20 ng\m3 for Cu, 5.00–208.70 ng\m3 for Mn and 0.35–6.82 g\m3 for Fe. Major concentrations of investigated metals are associated with the PM 7.2–3.0 μm. Overall, the decreasing trend of average trace element concentrations (24–h) in the particulates revealed the following order: Fe>Mn>Cu>Co.
اطلاعات انتشار: Journal Of Applied Fluid Mechanics، نهم،شماره۳، ۲۰۱۶، سال ۰
تعداد صفحات: ۱۱
Stagnation flow of an electrically conducting incompressible viscous fluid towards a moving vertical plate in the presence of a constant magnetic field is investigated. By using the appropriate transformations for the velocity components and temperature, the partial differential equations governing flow and heat transfer are reduced to a set of nonlinear ordinary differential equations. These equations are solved approximately using a numerical technique for the following two problems: (i) two–dimensional stagnation–point flow on a moving vertical plate, (ii) axisymmetric stagnation–point flow on a moving vertical plate. The effects of nondimensional parameters on the velocity components, wall shear stresses, temperature and heat transfer are examined carefully.
۵Effects of multiple freezing and refrigerator thawing cycles on the quality changes of sea bass (Dicentrarchus labrax)
اطلاعات انتشار: IRANIAN JOURNAL OF FISHERIES SCIENCES، دوازدهم،شماره۲، Apr ۲۰۱۲، سال ۰
تعداد صفحات: ۱۲
The freezing–thawing effect on the meat quality of whole, gutted and fillets of sea bass (Dicentrarchus labrax) were investigated. It was aimed to investigate the changes in the meat quality of whole, gutted and fillets of sea bass in multiple frozen (–18±2ºC) and thawed cycles in refrigerated conditions (4±2°C). The meat quality assessment of the sea bass groups (whole, gutted and fillets) subjected to multiple freeze and thaw cycles was performed by monitoring sensory quality, chemical analysis such as pH, total volatile basic nitrogen (TVB–N), trimethylamine nitrogen (TMA–N), thiobarbituric acid (TBA), crude protein and lipid content. The length of the thawing process caused quality changes such as dryness of the skin and undesirable odor formation. Thus the sea bass groups reached unacceptable levels after the 5th freeze\thaw process. According to the sensorial evaluation, no significant differences (P>0.05) were found in general acceptability values among the sea bass groups thawed under refrigerator conditions, but there was a significant difference in pH, TVB–N, TBA and crude protein (P0.05) results. Significant differences (P0.05) in TMA–N concentrations and crude fat were observed between the whole and gutted samples and also between the whole and fillet samples.
۶Effects of stock density on texture–colour quality and chemical composition of rainbow trout (Oncorhynchus mykiss)
اطلاعات انتشار: IRANIAN JOURNAL OF FISHERIES SCIENCES، چهاردهم،شماره۳، Jul ۲۰۱۵، سال ۰
تعداد صفحات: ۱۲
This study describes the effects of different stocking densities on texture\colour characteristics, protein content \amino acid and lipid content\fatty acid composition of rainbow trout ﬁllet. Stocking density was selected 5 (Group A), 15 (Group B), 25 (Group C) kg fish m−3. Tukey’s Multiple Comparison Test showed insigniﬁcant differences between measured size\weight measurement and condition factors. No significant differences were found between A and C groups for colour analysis (L* and a* value) and texture profile analysis (hardness, adhesiveness, cohesiveness and gumminess values) of rainbow trout fillets. The proximate composition analysis showed rainbow trout ﬁllets from the A and C groups to exhibit higher values of moisture than the B group. Fish from the A and B groups had a lower of ash and protein in comparison to C group samples. The highest fat values of rainbow trout were measured in B group samples. The content essential amino acid and non–essential amino acid was lower in A and B groups than in C groups. Fish from the C group had higher content of polyunsaturated fatty acids, especially n–3, docosahexanoic acid (DHA) and eicosapentaenoic acid (EPA) in comparison to A and C group. As a result, 25 kg fish m−3 is recommended stock density in terms of product texture\color and composition quality.
اطلاعات انتشار: Journal of Agricultural Science and Technology، شانزدهم،شماره۴، ۲۰۱۴، سال ۰
تعداد صفحات: ۱۰
Apricot (Prunus armeniaca L.) is a species particularly prone to erratic fruit set, and its flower bud drop has been repeatedly reported in different cultivars and growing conditions. A number of potential causes have been explored, but a clear main cause remains elusive. In this study, fruit set was determined for 11 apricot cultivars (‘Precoce de Tyrinthe’, ‘Feriana’, ‘Beliana’, ‘Priana’, ‘Bebeco’, ‘Early Kishinewski’, ‘Precoce de Colomer’, ‘Canino’, ‘Silistre Rona’, ‘Rouge de Sernhac’ and ‘Tokaloglu’) grown on the coast of the Mediterranean region of Turkey from 2006 to 2008. Trees budded on apricot seedlings and planted 6×6 m in 1997. On four branches of each tree randomly selected from all four directions, blossom number, percentage of initial and final fruit set, and yield per tree were determined during the experimental period. Fruit set differed significantly depending on year and cultivar. Based on three–year averages, percentage of fruit set was highest on ‘Tokaloglu’ (14%), followed by ‘Beliana’ (8.8%) and ‘Precoce de Tyrinthe’ (8.2%). The lowest fruit set (2.3%) was in ‘Early Kishinewski’ and ‘Canino’. High yields per tree were found in Tokaloglu’ (29.1 kg), ‘Precoce de Tyrinthe’ (29.0 kg), ‘Rouge de Sernhac’ (27.9 kg), and ‘Beliana’ (23.0 kg). ‘Tokaloglu’, ‘Beliana’, ‘Precoce de Tyrinthe’, and ‘Rouge de Sernhac’ cultivars showed good performance for both fruit set and yield per tree under subtropical climate conditions. However, findings of this study also suggested that fruit set and fruit drops in apricots should be assessed together with total yield amounts by years. The influence of the cultivar on fruit yield was more determinant than the seasonal effect.
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