Time filter

Source Type

Hakkari, Turkey

Stigmaeus pulchellus Kuznetzov, 1978, reported for the first time from Turkey, is described and illustrated based on females. In addition to the male and nymphal stages of this species, the male of Stigmaeus kumalariensis Akyol and Koç, 2007 is also described and illustrated in this article for the first time. The males and females presented differences in chaetotaxy, notably the absence of seta h3in the male of S. pulchellus. © 2015, Les Amis d'Acarologia. All rights reserved.

Freshwater fish, Oreochromis niloticus, were individually exposed to 0, 0.1, 0.5, 1.0, and 1.5 96 h (acute) and 0.05 μg/mL concentrations of the same metals for 0, 5, 10, 20, and 30 days (chronic). Following each period, metal accumulation and ion levels (Na +, K +, Ca +2, and Mg +2) were measured in the gills, kidneys, and muscles. Except for Ag +, none of the metals killed the fish within 30 days. Silver killed all the fish within 16 days. With the exceptions of Ag + and Cr 6+, as their levels were below detection limits, metal accumulation occurred in the tissues following both acute and chronic exposures. Ion levels in the tissues were altered by metal exposure, the general tendency being a decrease in Na + and K + levels and an increase in Mg 2+ and Ca 2+ levels. Acute exposure to heavy metals seemed to be more effective in altering ion levels of the tissues than chronic exposure. Na + was the most affected ion while Mg 2+ was the least affected. Results of this study emphasize that ion levels in the tissues of O. niloticus can be altered by heavy metals, both in acute and chronic exposures. This suggests that heavy metals should be monitored carefully in ecotoxicological studies in the field due to their importance in fish physiology. © TÜBİTAK.

Atli G.,Hakkari University | Canli M.,Cukurova University
Ecotoxicology and Environmental Safety | Year: 2010

Antioxidant systems are known to be sensitive to metal exposures and are suggested to use in predicting sublethal metal toxicity. In this study, several antioxidant enzymes, such as catalase (CAT), superoxide dismutase (SOD), glutathione S-transferase (GST), glutathione peroxidase (GPX) and glutathione reductase (GR) were measured in the liver and kidney of Oreochromis niloticus exposed to sublethal concentrations of metals (Cd, Cu, Cr, Zn and Fe), using an acute (20 μM, 48. h) or subchronic (10 μM, 20. d) protocol. Beside the several increases of antioxidant enzyme activities, general inhibition was recorded after acute and chronic metal exposures. Results indicated that there were variations in responses of the enzymes to metal exposures, depending upon tissues, metals and exposure types. This study emphasized that the antioxidant enzymes are very sensitive to metals as their activities altered significantly, suggesting they could be helpful in predicting sublethal metal toxicity and useful as an early warning tool in natural monitoring studies. © 2010 Elsevier Inc.

Kurt E.,Gazi University | Gor H.,Hakkari University | Demirtas M.,Gazi University
Energy Conversion and Management | Year: 2014

A new single phase generator has been designed and preliminary experimental results have been reported. The effects of two types of alternator cores have been explored. The proposed generator has one stator and two rotors with rare-earth-element-made permanent magnets (PMs). The physical and electromagnetic features of this PM generator are presented. The electromagnetic analyses are realized by the finite element method (FEM). The proposed machine has a combined type of flux directing mechanism, namely with axial and radial directions. The flux orientations are provided by 12 cores at the double-sided stator. The design has 2 rotors with totally 24 permanent magnets, which are positioned at different radial distances. It has been found that this design reduces the cogging torque values compared to the simple axial flux machine with 2 rotors having cylindrical cores. Thus a new cogging torque reduction technique is also proposed beside the new design. The electromagnetic simulations have been realized at different rotor speeds. The analyses also include the waveforms of currents, voltages, magnetic fluxes and cogging torque calculations. The maintenance and control of the machine is easier in operation, since the output power increases smoothly and become nearly constant up to the rotor speeds 1000 rpm. Preliminary results indicate that peak-to-peak voltage Up = 34 V is generated at the rotor speed ω = 200 rpm and it increases linearly with ω. The rated speed is expected to be 1000 rpm and 95% of efficiency is measured in the preliminary tests. © 2013 Elsevier B.V. All rights reserved.

Bayrakdar H.,Hakkari University
Progress In Electromagnetics Research M | Year: 2012

We have synthesis ferrite-polymer nanocomposite structures, theoretically and experimentally investigated electromagnetic propagation, absorption properties of these nanocomposite materials at 8-20 GHz in microwave guides. The microwave properties of the samples were investigated by transmission line method, and reflection loss of -59.60 dB was found at 12 GHz for an absorber thickness of 2 mm. These nanocomposites may be attractive candidates for microwave absorption materials.

Discover hidden collaborations