Structural,piezoelectric and dielectric properties of PSLZT–PMnN ceramics

Pb_0.94Sr_0.05La_0.01(Zr_0.54Ti_0.46)_0.9975O₃–Pb(Mn_1/3Nb_2/3)O₃ (PSLZT–PMnN) ceramics with pure perovskite structure were prepared by conventional mixed oxide method. The influence of PMnN on the structural, dielectric and piezoelectric properties was investigated. The experimental results showed that the perovskite structure changed from tetragonal to rhombohedral symmetry and the Curie temperature decreased gradually with the increase of PMnN. The composition with 3 mol% PMnN exhibited favorable properties of Q_m (400), d₃₃(660 pC/N), k_p (0.60), K^T (1940), tan δ (0.90%) and T_C (247 °C), exhibiting potential usage for piezoelectric actuator and sensor applications.     

The effect of deposition on electrochemical impedance properties of TiO<Subscript>2</Subscript>/FTO photoanodes

The integration of TiO₂ layers onto a substrate is challenging and limits the application potential of TiO₂. Even though, several studies have been reported to solve this problem by applying various deposition methods, there is still lack of information about how these methods affect the electrochemical and photo-electrochemical properties of resulting electrodes. The TiO₂ layers possessing different morphologies, deposited on the conductive FTO glass by means of various different deposition techniques (dip-coating, electrospinning and electrospraying), were used as photoanode (and working electrode) in the three-compartment electrochemical cell. The TiO₂ electrodes were calcinated at 450 °C and after that all samples revealed the crystallographic form of anatase. Using these three deposition techniques, three different morphologies were obtained. They consisted of a thin TiO₂ nanoparticle layer, TiO₂ nanoparticle/nanofiber layer and TiO₂ nanorod layer, respectively. The crystallinity and surface properties of the calcinated layers were determined by XRD, Raman spectroscopy, FTIR-ATR and SEM analyses. The electrochemical impedance (EIS) and photo-induced properties of photoanodes were studied by electrochemical measurements. The effects of surface morphology and crystal size of nanostructured layers on electrochemical impedance and photo-electrochemical properties were investigated. The electrodes prepared by dip-coating technique showed the best electrochemical impedance and photo-electrochemical results compared to other two types of electrodes. Dip-coating TiO₂ layer possesses the biggest crystal size and lowest charge transfer resistance which result the highest photocurrent density.     

Cardiac autonomic dysfunction in hemodialysis patients: The value of heart rate turbulence

Patients with end-stage renal disease (ESRD) are likely to have cardiac autonomic dysfunction, which is related with an increased risk of sudden death. The aim of this study is to detect cardiac autonomic dysfunction in patients with ESRD and to evaluate the possible acute effects of hemodialysis (HD) on cardiac autonomic functions measured by heart rate variability (HRV) and heart rate turbulence (HRT). Thirty-one (mean age 50 ± 13 years, 15 males) with ESRD on regular HD program and 31 healthy volunteers (mean age 51 ± 12 years, 15 males) were included in the study. Twenty-four-hour ambulatory electrocardiogram recordings were taken from the subjects before and after HD and from the control group. Heart rate variability and HRT parameters were calculated from these recordings. All of the HRV and HRT parameters were found to be significantly blunted in patients in comparison with healthy individuals. There were significant differences in HRV after HD, but similar differences were not observed in HRT parameters. Cardiac autonomic functions were significantly altered in patients with ESRD. Heart rate turbulence parameters seemed to be less affected from HD and may be more useful in the evaluation of cardiac autonomic functions in the ESRD population.     

Activity–Composition Relations in MnCr2O4–CoCr2O4 Solid Solutions and Stabilities of MnCr2O4 and CoCr2O4 at 1300°C

Phase equilibria in the system MnO–CoO–Cr₂O₃ were investigated at 1300°C under controlled oxygen partial pressures by using the gas equilibration technique. The CoO activities in various phase assemblages of the system were measured by determining the partial pressures of oxygen in the gas phase for coexistence with metallic cobalt. The activity data revealed that at 1300°C, MnO–CoO and MnCr₂O₄–CoCr₂O₄ solid solutions exhibit mild positive departures from ideal behavior. The activities in the stoichiometric spinel solutions were found to be in good agreement with those predicted from a model based on cation distribution equilibria. The standard free energy of formation of the compound CoCr₂O₄ from its oxide components at 1300°C was determined as −37 636 J/mol, while that for MnCr₂O₄ was found as −44 316 J/mol.     

Service Life Assessment of Existing Highway Bridges with No Planned Regular Inspections

Safety of a highway infrastructure system depends very much on the proper maintenance of bridges. The level of required maintenance is, typically, determined through a series of regular field inspections with the guidance of safety–economy trade-off. In Turkey, bridge maintenance, repair, and rehabilitation are currently performed on an as-needed basis. Time-dependent reliability analysis cannot be utilized for Turkish bridges for the time being since the majority of the bridges are either not regularly inspected or not inspected at all. The purpose of this paper is to propose a simple method to assess the remaining service life of a bridge by defining a relationship between its current condition rating and its age by evaluating a set of bridges at different ages. In a case study, 28 bridges were inspected for the first time to assess the average life expectancy. The average life of a bridge was predicted to be 80?years, and for this set of bridges, the main body components were found to deteriorate more than earth retaining and serviceability components.     

Estimation of monthly diffuse nutrient loads for a watershed in Turkey

Diffuse pollution has a complex nature depending on various land‐use activities like agriculture, livestock breeding and forestry. In this study, an alternative methodology is applied for decreasing the spatial uncertainty of diffuse nutrient load estimations. It is applied in the Melen Watershed, Turkey, which is an important watershed from where additional water will be supplied for the megacity Istanbul via interbasin water transfer. Monthly diffuse nutrient loads were estimated for each subwatershed by utilizing remote sensing (RS) and geographical information systems (GIS). Estimated nutrient loads were considerably different in various months due to the temporally irregular fertilizer application and meteorological conditions. Temporal differences were also predicted in the spatial distribution of the nutrient loads. The methodology is applicable in watershed protection studies, especially where necessary etudes should be conducted in the short term and with limited data. Such efforts in identifying and determining the diffuse loads are important for sustainable management of the watershed.