Uncertainty of pesticide residue concentration determined from ordinary and weighted linear regression curve

Determination of pesticide residues is based on calibration curves constructed for each batch of analysis. Calibration standard solutions are prepared from a known amount of reference material at different concentration levels covering the concentration range of the analyte in the analysed samples. In the scope of this study, the applicability of both ordinary linear and weighted linear regression (OLR and WLR) for pesticide residue analysis was investigated. We used 782 multipoint calibration curves obtained for 72 different analytical batches with high-pressure liquid chromatography equipped with an ultraviolet detector, and gas chromatography with electron capture, nitrogen phosphorus or mass spectrophotometer detectors. Quality criteria of the linear curves including regression coefficient, standard deviation of relative residuals and deviation of back calculated concentrations were calculated both for WLR and OLR methods. Moreover, the relative uncertainty of the predicted analyte concentration was estimated for both methods. It was concluded that calibration curve based on WLR complies with all the quality criteria set by international guidelines compared to those calculated with OLR. It means that all the data fit well with WLR for pesticide residue analysis. It was estimated that, regardless of the actual concentration range of the calibration, relative uncertainty at the lowest calibrated level ranged between 0.3% and 113.7% for OLR and between 0.2% and 22.1% for WLR. At or above 1/3 of the calibrated range, uncertainty of calibration curve ranged between 0.1% and 16.3% for OLR and 0% and 12.2% for WLR, and therefore, the two methods gave comparable results.     

Can primary failure of arteriovenous fistulas be anticipated?

Primary failure, early thrombosis, and inadequate maturation are the main complications encountered in arteriovenous fistulas. Doppler ultrasonographic assessment of flow‐mediated dilatation (FMD) is currently used for the early diagnosis of atherosclerosis. Clinical experience in the use of FMD for preoperative assessment of vasculature is rather limited; therefore, we sought to elucidate the relationship between preoperative FMD and primary failure of the fistula. Thirty‐three patients with end‐stage renal disease who were admitted to our hospital between January and July 2005 were included in our study. Medical histories were established and the internal diameter, wall thickness, peak systolic flow rate, and resistive index (RI) were measured in the cephalic vein and radial and brachial arteries. Flow‐mediated dilatation and nitrate‐mediated dilatation (NMD) of the brachial artery were assessed. Fistulas were evaluated 48 hours and 30 days postoperatively. Brachial arterial internal diameter was lower in all fistulas that developed primary failure in 48 hours (0.4 ± 0.07 cm vs. 0.35 ± 0.07 cm, P = 0.016). The radial artery RI was found to be significantly elevated in fistulas with both early (48‐hour) and late‐term (30‐day) failure (0.9 ± 0.08 vs. 0.68 ± 0.3, P = 0.01, and 0.86 ± 0.8 vs. 0.67 ± 0.3, P = 0.038, respectively). The brachial artery peak systolic flow rate was significantly reduced in patients in the radiocephalic fistula group that developed early and late‐term failure (42.9 ± 12 cm/sec vs. 68.4 ± 10 cm/sec, P = 0.01, and 44.1 ± 13 cm/sec vs. 57.7 ± 16 cm/sec, P = 0.038, respectively). Our study, constrained by a smaller, older patient group, was unable to show a statistically significant correlation between FMD, NMD, and fistula success. Any single parameter may not be sufficient to assess vascular health preoperatively. A multifactorial approach incorporating parameters evaluating arterial and venous function might be more effective in predicting fistula success. Further studies on larger patient groups may indeed demonstrate the value of these assessments.     

Failure analysis of an aircraft piston engine components

In this study, failed parts from the piston engine of TB-20 Trinidad aircraft which declared an emergency landing to Anadolu University Airport, Eski?ehir, Turkey due to the overspeed of propeller during a training flight were investigated. Fortunately, landing was successful, however, most of the engine parts were found to be damaged. Some of the failed parts such as propeller governor idler gear and cam followers were examined by using a variable pressure scanning electron microscope (SEM) attached with an energy dispersive X-ray spectrometer (EDX) to identify the cause of failure in the engine.     

An investigation of agricultural use potential of wastewater sludges in Turkey--case of heavy metals.

Landfilling is one of the most common methods that are used in the final disposal of sludge world wide, as well as in Turkey. However, increasing sludge quantities and limited landfilling areas make this method difficult to apply. The use of sludge in agriculture presents a possible alternative for disposal. However, it also poses some risks to be evaluated. In this respect, it is important to identify the heavy metal content of sewage sludges because of its adverse health effects. This study aims to determine the heavy metal contents of sludges and wastewaters from three different wastewater treatment plants in Turkey. The selection of plants was carried out according to the different treatment technologies applied to wastewater and sludge in those plants. Heavy metal analysis of sludges and wastewaters was conducted using a microwave assisted digestion procedure. After sampling and analysis, the results show that all the related metal concentrations are below the values that are set in the Soil Pollution Control Regulation of Turkey. However, in two of the three plants, Zn and Ni concentration should be tracked carefully.     

Preparation and characterization of ethylenediamine and cysteamine plasma polymerized films on piezoelectric quartz crystal surfaces for a biosensor

This paper describes a method for the modification of quartz crystal surfaces to be used as a transducer in biosensors that allow recognition and quantification of certain biomolecules (antibodies, enzymes, proteins, etc). Quartz crystal sensors were modified by a plasma based electron beam generator in order to detect the level of the toxin histamine within biological liquids (blood, serum) and food (wine, cheese, fish etc.). Cysteamine and ethylenediamine were used as precursors in the plasma. After each modification step, the layers on the quartz crystal were characterized by frequency measurements. Modified surfaces were also characterized by contact angle, X-ray photoelectron spectroscopy and atomic force microscopy to determine the physical and chemical characteristics of the surfaces after each modification. Finally, the performance of the sensors were tested by the response to histamine via frequency shifts. The frequency shifts of the sensors prepared by plasma polymerization of ethylenediamine and cysteamine were approximately 3230 Hz and 5630 Hz, respectively, whereas the frequency change of the unmodified crystal surface was around 575 Hz.     

Effects of salinity on growth and nickel accumulation capacity of Lemna gibba (Lemnaceae)

The effect of salinization of water on the growth rate and nickel accumulation capacity of Lemna gibba was studied under laboratory conditions. At high salinity (375 and 500 mol m(-3) NaCl), we observed that decreasing growth rate with increasing water salt level. Especially, at a salinity of 500 mol m(-3) NaCl, the net growth rate became negative. Additionally, growth rate of roots was significantly reduced at salinity of 250 mol m(-3) NaCl and significantly reduced at 500 mol m(-3) NaCl compared to a freshwater control. Biomass production was inhibited by an increase in salinity. Furthermore, high salinity caused decreasing nickel accumulation by L. gibba. In this study, a simple model was created according to data obtained from this study. The model has suggested that salinity is an important factor in limitation of growth of L. gibba.     

Microwave Drying Kinetics of Okra

In this work, the effects of power level and sample mass on moisture content, moisture ratio, drying rate, and drying time of Turkey okra (Hibiscus esculenta L.) were investigated using microwave drying technique. Various microwave power levels ranging from to 180 to 900 W were used for drying of 100 g of okra. To investigate the effect of sample mass on drying, the samples in the range of 25 to 100 g were dried at microwave power level of 360 W. To determine the kinetic parameters, the drying data were fitted to various models based on the ratios of the differences between the initial and final moisture contents and equilibrium moisture content. Among of the models proposed, Page's model gave a better fit for all drying conditions used. The activation energy for microwave drying of okra was calculated using an exponential expression based on Arrhenius equation and was found to be 5.54 W/g.     

Exploring the influence of the built environment on human experience through a neuroscience approach: A systematic review

The built environment provides a habitat for the most sophisticated mammal in our universe, the human being. Developments in science and technology are forcing us to reconsider the priority of human needs in current theories of architecture and the built environment. Newly developed theories and methodologies in neuroscience have allowed us to improve and deepen our knowledge of human experience in the built environment. The potential of the relationship between neuroscience and architecture for knowledge creation generates an increasing interest in theoretical and methodological approaches to explore this intersection. Thus, a common ground on which to conduct interdisciplinary studies investigating developing and emerging concepts at the intersection must be established. However, few reviews in the literature have systematically examined developing and emerging concepts at the intersection of neuroscience and architecture. The present review aims to examine the existing literature systematically to explain the influence of the built environment on human experience by using approaches from neuroscience by examining the conceptualizations in the field. The study is conducted as a systematic qualitative review that analyzes and synthesizes the developing and emerging concepts that have appeared in the ever-evolving literature. The study concludes with an overall discussion about these concepts as a means of deeply understanding the influence of the built environment on human experience, responses to the environment based on approaches from neuroscience, and their potential for providing further directions for future research.     

Micro-computerized tomography analysis of cement voids and pull-out strength of glass fiber posts luted with self-adhesive and glass-ionomer cements in the root canal

This study evaluated the pull-out strength of different glass fiber posts and measured volume of cement and voids in the cement in the root canal utilizing micro-computerized tomography (micro-CT) analysis after they were cemented with two different luting cements. Canine teeth (N = 40) were endodontically treated and randomly divided into four groups depending on the fiber post and the cement type (n = 10 per group) as follows: Group RU: (RelyX + RelyX U200), Group PU: (PINpost + RelyX U200), Group RF: (RelyX + FujiCEM 2), Group PF: (PINpost + FujiCEM 2). Each tooth was scanned using micro-CT and the percentage of cement and void volume at the coronal, middle, and apical levels was calculated. Pull-out tests were performed by applying tensile load parallel to the long axis of the posts (0.5 mm/min). Data were analyzed using, ANOVA, Kruskal–Wallis, and Mann–Whitney U tests (α = 0.05). Regardless of cement type, the percentage (%) of cement volume in the RelyX post groups (RU:31–36; RF:29–40) was significantly higher than that in the PINpost groups (PU:19–23; PF:18–22) (p < 0.05). The percentage of void volume at the PINpost groups (PU:6–11; PF:8–13) was significantly lower than that in the RelyX groups (RU:2; RF:3) (p < 0.05). No significant differences were observed in pull-out strength (N) between the four experimental groups (RU:358.8 ± 56.2; RF:299 ± 64.8; PU:311.9 ± 61.3; PF:293.1 ± 91.3) (p > 0.05). The micro-CT analysis demonstrated that the percentage of cement and void volumes vary depending on the type of fiber post and cement used. No correlation between cement, void volume, and pull-out strength was observed.     

A modified method for processing and characterization of organoclay‐based poly(ethylene terephthalate) nanocomposite fibers

In the current study, in order to prepare poly(ethylene terephthalate) (PET)/organoclay nanocomposite fibers, a slurry‐compounding method (SCM) was applied and compared to conventional melt‐compounding method (CMM) in terms of the dispersion of organoclays and the performance of the spun and or drawn fibers. The organoclays were synthesized by using three different alkyl phosphonium salts and compared with commercially available alkyl ammonium‐modified organoclays in terms of thermal stability and basal spacing. It was found that the alkyl phosphonium salts exhibited higher thermal stability and basal spacing with respect to commercial alkyl ammonium organoclays. Among them, tributylhexadecylphosphonium bromide resulted in superior properties; therefore, it was used to prepare the nanocomposite PET fibers. The organoclay content of 0.1–1 wt% was taken as the material parameter. It was demonstrated that the SCM yielded better dispersion of organoclays with respect to CMM. The drawn nanocomposite fibers prepared via SCM exhibited improved tensile strength and modulus in comparison to the neat‐PET. The maximum tensile properties for fibers were obtained at 0.5% organoclay loading in SCM. The thermal properties and the percentage of crystallinity were investigated by differential scanning calorimetry analysis. In addition, Fourier transform infrared spectroscopy was utilized to obtain the percentage of crystallinity of the fibers. POLYM. COMPOS., 34:887–896, 2013. © 2013 Society of Plastics Engineers