Risk management activities for oil and gas producers and the impact on firm value

This study analyses whether hedging activities of oil and gas firms have a significant effect on the performance of the companies. The performance of companies is proxied by Tobin’s Q and panel regression models are built to estimate the coefficients for firm value and derivative use. The speculative use of derivatives is eliminated in models by the regulations under IFRS and GAAP. The results give critical information regarding asymmetric information and signalling effect. Since the coefficient of derivatives use is negative, it shows the critical meaning of disclosures on the financial healthiness. If companies are publishing high level of hedging activities, it might be a warning for investors to avoid investing at that company. This study also seeks for explanation behind firms’ hedging decisions. To our knowledge, it is among the first studies with a wide range of region and data.

     

Monitoring changes in forest and other land use forms in Istanbul

This study introduces the monitoring system to be established within this project, it aims to determine changes occurring within forested areas, settlement areas and other land use forms located at the peripheral area of Istanbul during consecutive decades. The first phase of the study was completed in 1998 and published, covering the period from 1984 to 1994. This study is the second phase of the first one and implemented to determine land use changes which have occurred on the same site from 1994 to 2000. Standard topographic maps with 1/25 000 scale, forest management maps with the same scale, results of the previous study, orthophoto maps of the year 2000 that were produced from aerial color photographs of the site with 1/5 000 scale, and 4-band IRS_LISS III multispectral satellite data for July 2000 were used as data. The changes in land use within the study area occurring during a six year period were studied.     

An investigation of waste foundry sand in asphalt concrete mixtures.

A laboratory study regarding the reuse of waste foundry sand in asphalt concrete production by replacing a certain portion of aggregate with WFS was undertaken. The results showed that replacement of 10% aggregates with waste foundry sand was found to be the most suitable for asphalt concrete mixtures. Furthermore, the chemical and physical properties of waste foundry sand were analysed in the laboratory to determine the potential effect on the environment. The results indicated that the investigated waste foundry sand did not significantly affect the environment around the deposition     

Evaluating the seasonal changes of some water quality parameters of the Buyuk Melen River Basin (Duzce, Turkey)

In this study, some heavy metal concentrations (Pb, Zn, Fe, Cr, Cu), suspended sediment, chemical oxygen demand (COD), biological oxygen demand (BOD), cyanide, phenol, fecal coliform and total coliform water parameters were determined in the streams (Kucuk Melen, Asarsuyu, Ugursuyu, Buyuk Melen and Aksu) of Buyuk Melen Watershed that provides drinking water to Istanbul in Western Black Sea Region of Turkey. Measurements of water quality parameters were done monthly in eleven separate stations (4 in Kucuk Melen Stream, 1 in Asarsuyu Stream, 1 in Ugur Stream, 1 in Aksu Stream and 4 in Buyuk Melen Stream) from August 2001 to August 2002. The seasonal changes in water quality parameters were evaluated statistically. The results, the parameters, COD, BOD, Pb, Zn, Fe, Cr, Cu, cyanide, fecal coliform, total coliform and suspended sediment showed significant differences among seasons and streams (ANOVA; P <0.05). According to Turkish Standarts (TS) 266, European Union (EU) and World Health Organization (WHO) criteria, the maximum values of each parameter in streams within the Buyuk Melen watershed are recorded and evaluated in this study.     

Treatment of the textile wastewater by combined electrocoagulation

Electrocoagulation (EC) due to some advantages over chemical coagulation is becoming a popular process to be used for wastewater treatment. The aim of this paper is to investigate the effect of initial addition of a chemical coagulant such as polyaluminum chloride (PAC) or alum on the COD removal efficiency of EC treatment of textile wastewaters. The two salts exhibited the same performance in chemical coagulation, but in the combined electrocoagulation (CEC), PAC was found to significantly enhance the COD removal rate and efficiency, depending on the amount of the total aluminum supplied, by initial addition and electrochemical generation. A comparative operating cost analysis was also given and it was found that with the same operating cost per mass of COD removed, CEC performance was 80%, in contrast to 23% with EC, in 5 min of operation.     

Recovery of phosphate from calcinated bone by dissolution in hydrochloric acid solutions

In this study, the optimum conditions of dissolution of calcinated bone in HCl solutions with different concentrations are investigated. Recovery of phosphate from calcinated bone by dissolution with hydrochloric acid solutions was investigated in a batch reactor, it was observed that a 32% hydrochloric acid solution can dissolve the calcinated bone effectively. Using the Taguchi fractional design method, it was found that the optimum process conditions, at which 67.2% P₂O₅ dissolution was reached, were as follows: Reaction temperature: 318 K, solid-to-liquid ratio: 1/5 (g ml⁻¹), acid concentrations:32 (% w/v), stirring speed:400 min⁻¹ and reaction time: 60 min.     

In vitro effects of erythromycin and florfenicol on primary cell lines of Unio crassus and Cyprinus carpio

Environmental Science and Pollution Research - The ubiquitous use of antibiotics leads exposure of these chemicals on non-target aquatic species, while the toxicity assays for these chemicals are...     

Pathological and toxicological investigations of chronic nitrate poisoning in cattle

In this study, three stillborn and five premature and blind calves from cows suffering from chronic nitrate poisoning were examined pathologically. The live calves were euthanized, due to a poor prognosis. Complete necropsy was performed on all the eight affected calves. Hydroperitoneum and ascites were the most predominant lesions in the stillborn calves. Edema and hemorrhage were observed in the lungs of all the calves. Hemorrhages were seen in the digestive systems of four calves. Blood samples were taken from five live calves and their mothers, and from two cows that had delivered stillborn or blind calves, for biochemical observations and measurement of methemoglobin levels. Blood values of five healthy cattle from a herd with no history of stillborn or blind calves were used as controls. Water and feed samples were taken from five different farms with a history of stillborn or blind calves and examined for nitrates. Nitrate and nitrite levels of feeds ranged from 154 to 480 and 1.5 to 20?ppm respectively; these levels can cause chronic poisoning. Levels of nitrates and nitrites in blood samples from cows and calves were found to be high. While hemoglobin values were found to be low, methemoglobin values were very high. No differences were observed between liver enzyme levels of the affected and control cattle. There were no bacteria or virus isolated from these animals, and histopathological examination revealed no indication of any other diseases.     

Three dimensional monitoring of urban development by means of ortho-rectified aerial photographs and high-resolution satellite images

Nowadays, cities are developing and changing rapidly due to the increases in the population and immigration. Rapid changing brings obligation to control the cities by planning. The satellite images and the aerial photographs enable us to track the urban development and provide the opportunity to get the current data about urban. With the help of these images, cities may have interrogated dynamic structures. This study is composed of three steps. In the first step, orthophoto images have been generated in order to track urban developments by using the aerial photographs and the satellite images. In this step, the panchromatic (PAN), the multi spectral (MS) and the pan-sharpened image of IKONOS satellite have been used as input satellite data and the accuracy of orthophoto images has been investigated in detail, in terms of digital elevation model (DEM), control points, input images and their properties. In the second step, a 3D city model with database has been generated with the help of orthophoto images and the vector layouts. And in the last step, up to date urban information obtained from 3D city model. This study shows that it is possible to detect the unlicensed buildings and the areas which are going to be nationalized and it also shows that it is easy to document the existing alterations in the cities with the help of current development plans and orthophoto images. And since accessing updated data is very essential to control development and monitor the temporal alterations in urban areas, in this study it is proven that the orthophoto images generated by using aerial photos and satellite images are very reliable to use in obtaining topographical information, in change detection and in city planning. When digital orthophoto images used with GIS, they provide quick decision control mechanisms and quick data collection. Besides, they help to find efficient solutions in a short time in the planning applications.     

Formation of Disinfection Byproducts (DBPs) in Surface Water Sources: Differential Ultraviolet (UV) Absorbance Approach

Chlorination for drinking water forms various disinfection byproducts (DBPs) of trihalomethanes (THMs) and haloacetic acids (HAAs). Chlorination has been attributed to the destruction of activated aromatic sites of the natural organic matter (NOM) predominantly at electron rich sites. Experiments with Istanbul surface waters showed that the magnitude of the decrease in the ultraviolet (UV) absorbance at 272 nm (UV₂₇₂) was an excellent indicator of destruction of these sites by chlorine. The main objective of the present study is to develop the differential UV₂₇₂ absorbance (ΔUV₂₇₂) related models for the prediction of the formation of THM, HAA, and their species in raw water samples from Terkos, Buyukcekmece, and Omerli lakes under different chlorination conditions. Significant factors affecting DBP formation in the raw waters were identified through numerical and graphical techniques. The R² values of the models varied between 0.94 and 0.97, indicating excellent predictive ability for THM₄ and HAA₉ in the raw waters. The models were validated using additional data. The results of this study concluded that addition of ΔUV₂₇₂ parameter into THM₄ and HAA₉ models make the prediction of these DBP compounds more precisely than those of DBP models developed in the past. A better understanding of these modeling systems will help the water treatment plant operators to minimize the DBP formation, providing a healthier and better drinking water quality as well as identifying strategies to improve water treatment and disinfection processes.