Hasan Gürbüz

A neural network-based approach for calculating dissolved oxygen profiles in reservoirs

A Neural Network (NN) modelling approach has been shown to be successful in calculating pseudo steady state time and space dependent Dissolved Oxygen (DO) concentrations in three separate reservoirs with different characteristics using limited number of input variables. The Levenberg–Marquardt algorithm was adopted during training. Pre-processing before training and post processing after simulation steps were the treatments applied to raw data and predictions respectively. Generalisation was improved and over-fitting problems were eliminated: Early stopping method was applied for improving generalisation. The correlation coefficients between neural network estimates and field measurements were as high as 0.98 for two of the reservoirs with experiments that involve double layer neural network structure with 30 neurons within each hidden layer. A simple one layer neural network structure with 11 neurons has yielded comparable and satisfactorily high correlation coefficients for complete data set, and training, validation and test sets of the third reservoir.

Predicting dominant phytoplankton quantities in a reservoir by using neural networks

The Levenberg–Marquardt algorithm was used to train artificial neural networks to predict the abundance of Cyclotella ocellata Pant. and Cyclotella kützingiana Thwaites using time, depth, temperature, pH, dissolved oxygen, and electrical conductivity as input parameters for the oligo-mesotrophic Kuzgun Dam Reservoir, Turkey. The data were collected in monthly intervals during two ice-free seasons: between April 2000–November 2000 and April 2001–November 2001. To reduce over-fitting of the neural network based models, we employed single hidden layer networks with early stopping of training. Correlation coefficients of neural network predictions with measurements of abundance of Cyclotella ocellata Pant. and Cyclotella kützingiana Thwaites were 0.88 and 0. 86, respectively.

Turkish prospective teachers’ understanding and misunderstanding on global warming

The key objective of this study is to determine the Turkish elementary prospective teachers’ opinions on global warming. It is also aimed to establish prospective teachers’ views about the environmental education in Turkish universities. A true–false type scale was administered to 564 prospective teachers from science education, social studies education and primary school education departments of three universities in Turkey. The findings revealed that prospective teachers had some misunderstandings about global warming. It was also found that they accessed information on global warming through informal sources such as TV, radio and Internet. In addition, there were significant differences in participants’ total scores in terms of gender and department. According to the findings, prospective teachers thought that environmental education given at universities was not adequate for various reasons.

The evaluation of the genotoxic and oxidative damage potentials of Ulothrix tenuissima (Kütz.) in vitro

Several alga species are known to produce a variety of toxic metabolites that pose a threat to aquatic organisms, animals and humans. Moreover, these metabolites have been thought to cause serious diseases including certain cancers and neurodegenerative disorders. On the other hand, Ulothrix is a genus of filamentous green algae, generally found in fresh water and marine and abundantly available in some lakes and rivers of Turkey. To our best knowledge, no study has been performed to assess the genotoxic and biochemical effects of U. tenuissima on cultured human blood cells. Therefore, in order to determine clastogenic or aneugenic effects of aqueous alga extracts the micronucleus assay was carried out. Nuclear division index (NDI) in peripheral lymphocytes was also analyzed for cytotoxicity evaluations. In addition, biochemical parameters (total antioxidant capacity (TAC) and total oxidative stress (TOS)) were examined to determine oxidative effects. For this aim, we obtained heparinized blood samples from three healthy persons. The alga samples were collected from Porsuk Pond in Hasankale (Erzurum, Turkey) in summer period of the year 2010. The aqueous extracts of this species were added to cultures at different concentrations (0 to 5000 ppm) for 72 h. Our results showed that this alga did not cause any statistically important changes in the rates of studied genotoxicity endpoint. But dose-dependent alterations were observed in TAC and TOS levels and NDI rates. In conclusion, U. tenuissima was found to be non-genotoxic but caused sterility at higher concentrations due to oxidative stress.

Seasonal Changes in Phytoplankton Community Structure in a High Mountain Reservoir, Kuzgun Reservoir, Turkey

ABSTRACT Seasonal changes in phytoplankton community structure of Kuzgun reservoir, a high mountain reservoir, were studied during the ice-free period in 2000 and 2001. Bacillariophyta was the dominant group, followed by Chlorophyta and Dinophyta. The dominant species were Synedra delicatissima, Asterionella formosa, Fragilaria crotonensis, Cyclotella kützingiana, Cyclotella ocellata, Oocystis borgei, Staurastrum longiradiatum, Ankistrodesmus falcatus, Ceratium hirundinella, and Peridinium cinctum. Maximum phytoplankton density was observed in late spring.

DETERMINATION OF LOW ATOMIC NUMBER ELEMENTS IN ALGAE OF THE KARASU (FIRAT) RIVER USING AN Fe-55 RADIOISOTOPE

Planctonic algae are very important in aquatics systems because they occur in primary productivity in the nutrient system. The energy fluctuation rate in the lake or river ecosystem depends on the production rate of algae.(1) The most change in the lake or river ecosystem occurs in phytoplankton. For this reason, the phytoplankton changes provide the most information about environmental changes.(2) In recent years, in Turkey, the studies on phytoplankton were conducted by many authors.(3-21) Altuner and Gürbuz(7,11,14) have investigated seasonal changes of composition and density of the phytoplankton in the River Karasu (Firat). In this study, Bacilloriophyta was found as the dominant group among the phytoplankton. It showed that the Cyclotella, Fragilaria, Synedra, Melosira, Nitzschia, Diatoma, Cymbelle, Ceratoneis, and Chlorella genus in the phytoplankton are commonly found in each station. The Chlorophota, Cyanophyta, and Euglenophyta members are rare here. The counts of species of other algae, except the diatomes, are unimportant. The flora increases at the beginning of summer and autumn and decreases during the winter months. Physical factors, e.g., light, flow rate, and temperature have played a greater role in this change. INSTRUMENTATION SCIENCE & TECHNOLOGY, 29(5), 441–447 (2001)

Hepatoprotective potential of astaxanthin against 2,3,7,8-tetrachlorodibenzo-p-dioxin in cultured rat hepatocytes

The purpose of this study was to evaluate the effect of carotenoid astaxanthin (ASTA) on cultured primary rat hepatocytes treated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on the cell viability (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide, MTT), lactate dehydrogenase (LDH) activity, 8-oxo-2-deoxyguanosine (8-OH-dG), total antioxidant capacity (TAC), and total oxidative stress (TOS) levels, and liver micronucleus rates. ASTA (2.5, 5, and 10 µM) was added to cultures alone or simultaneously with TCDD (5 and 10 µM) for 48 h. The results of MTT and LDH assays showed that both doses of TCDD caused significant decrease in cell viability. Also, TCDD significantly increased TOS and decreased TAC level in rat hepatocytes. On the basis of increasing doses, the dioxin caused significant increase in micronucleated hepatocytes) and 8-OH-dG level as compared to control culture. The presence of ASTA with TCDD minimized its effects on primary hepatocytes cultures and DNA damages.

Determination of Medium Elements in Algae of Karasu (Fırat) River by EDXRF Using an 241Am Excitation Source

Abstract Trace element analysis of algae in the Fırat River was performed. To measure elemental concentration, an 241Am radioisotope source and a Si(Li) solid‐state detector were used. The Fe, Ni, Zn, As, Se, Sr, Y, Zr, Mo, Cd, Sn, I, and Ba elements were found in algae samples by using 59.5 keV gamma photons from 241Am.