Dielectric behavior induced by vitamin E and electron beam irradiation in ultra high molecular weight polyethylene

Radiation cross‐linked ultra high molecular weight polyethylenes (UHMWPEs) have been successfully used as wear resistant bearing surfaces in total joint arthroplasty. A recent development in this field is the incorporation of the antioxidant vitamin E into radiation cross‐linked UHMWPE. This study investigates the effects of radiation cross‐linking and vitamin E incorporation on the dielectric behavior of UHMWPE. The dielectric relaxations of virgin and 0.1 wt % vitamin E‐blended UHMWPE and their irradiated counterparts (up to 300 kGy dose) were investigated. To determine the effect of vitamin E content alone, vitamin E‐loaded UHMWPEs were used. The results showed that radiation cross‐linking and vitamin E content both increased dielectric polarization in UHMWPE and under some conditions induced electrical conductivity. This result is significant because it shows that the conductive response of UHMWPE‐bearing surfaces may depend on manufacturing processes and additives. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40844.     

Ultrasonic properties of epoxy resin/marble waste powder composites

Non‐destructive techniques are suitable alternatives for characterization of composites. The aim of this study is to analyze the composites of epoxy resin (ER)/marble waste powder (MWP) by ultrasonic method. The effects of marble powder, coagulant type, and dosage on the ultrasonic properties of ER/MWP composites were investigated. The ultrasonic wave velocities of composites were measured with the pulse–echo method at room temperature by a flaw detector. The values of the acoustic impedance, Poisson's ratio, and elastic constants of the samples were calculated by the measured values of the densities and both longitudinal and shear ultrasonic wave velocities. According to the results, the ER/MWP composite using sepiolite coagulant in dosages of 4 g/500 mL has showed the highest values of elastic constants. POLYM. COMPOS. 36:584–590, 2015. © 2014 Society of Plastics Engineers     

Bubbly cavitating flow generation and investigation of its erosional nature for biomedical applications

This paper presents a study that investigates the destructive energy output resulting from hydrodynamic bubbly cavitation in microchannels and its potential use in biomedical applications. The research performed in this study includes results from bubbly cavitation experiments and findings showing the destructive effects of bubbly cavitating flow on selected solid specimens and live cells. The bubbles generated by hydrodynamic cavitation are highly destructive at the surfaces of the target medium on which they are carefully focused. The resulting destructive energy output could be effectively used for biomedical treatments, such as destroying kidney stones (renal calculi) or killing cancer cells. Motivated by this potential, the cavitation damage to cancerous cells and material removal from chalk pieces (which possess similar material properties as some kidney stones) was investigated. Our results showed that cavitation could induce damage both on chalk pieces and leukemia/lymphoma cells. We discovered that hydrodynamic cavitation exposure had early and delayed effects on cancer cell survival. Hence, the potential of hydrodynamic bubbly cavitation generated at the microscale for biomedical treatments was revealed using the microchannel configuration as a microorifice (with an inner diameter of 147 μm and a length of 1.52 cm), which acts as the source of bubbly cavitating flows.     

Crisis management in Turkish construction industry

Various economical crises have affected Turkish economy during the last decade and construction industry has always been among the hardest hit; giving the idea that a comprehensive approach to crisis management is unavoidable. However, literature showed no findings related with crisis management applications by construction companies. Thus, a questionnaire survey was undertaken by the top management of 120 construction companies to investigate the degree of crisis management applications throughout the industry, mainly focusing on the outcomes during the economical crisis in 2001. Frequency analysis, Likert scale of comparison, Thurstone's paired comparisons, Pearson's chi-square test and Fisher's exact test were used to evaluate the results.     

Hemodynamic regulation of tumor necrosis factor-alpha gene and protein expression in adult feline myocardium

During the metastatic cascade, a tumor cell passes through several connective tissue barriers which consist of various adhesive molecules, such as fibronectin, laminin, collagens, and other glucoproteins and proteoglycans. Tumor invasion is a complex process involving cell adhesion, motility (migration), and the degradation of tissue barriers caused by the different proteases secreted by tumor cells. Therefore, understanding the invasion mechanism and the control mechanisms of the invasive properties of tumor cells may help in the development of anti-metastatic and anti-invasive therapies. We here focused our attention on the functional molecules involved in the invasive process as targets to control tumor metastasis, and screened the inhibitors of tumor invasion into basement membranes.     

Ultrasonic characterization of conductive epoxy resin/polyaniline composites

This study presents the ultrasonic characterization of conductive epoxy resin (ER)/polyaniline (PANI) composites. The prepared PANI is mixed with ER matrix at weight percentages of 5%, 10%, and 15% for preparing the ER/PANI composites. The effects of PANI amount on the mechanical properties of ER/PANI composites are investigated by ultrasonic pulse‐echo‐overlap method. Also, electrical conductivity, ultrasonic wave velocity and ultrasonic micro‐hardness values of ER/PANI composites are correlated. Experimental results show that there is an excellent correlation between ultrasonic micro‐hardness and ultrasonic shear wave velocity. Also, the results of ultrasonic velocities and elastic constants values illustrate that the appropriate combination ratio is 95 : 5 for ER and PANI in ER/PANI composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42748.     

Far-field radar NDT technique for detecting GFRP debonding from concrete

A radar nondestructive testing (NDT) technique using an airborne horn antenna operating in the far-field condition is developed for detecting damages such as debonding and concrete cracking in glass fiber reinforced polymer (GFRP)-wrapped concrete columns. The far-field airborne radar (FAR) NDT technique is advantageous for distant measurement in practical applications where contact/near-contact measurement becomes an issue. In this technique the radar antenna operates in inverse synthetic aperture radar (ISAR) mode. Laboratory measurements at the frequency range 8–18 GHz are made on artificially damaged GFRP–concrete specimens for a preliminary validation of this technique. Collected frequency–angle measurements are further processed by the fast backprojection algorithm to render range–cross-range imagery for damage detection. From the reported measurements and imaging results the proposed FAR NDT technique is conceptually validated; the potential of this technique is shown in identifying defects and debonding in the GFRP–concrete interface regions of the concrete columns wrapped with these composite materials.     

Polystyrene functionalized carbazole and electrochromic device application

Polystyrene (PS) functionalized carbazole macromonomer was synthesized and polymerized by electrochemical oxidative polymerization on the ITO-glass surface. The structure of the macromonomer was elucidated by ¹H NMR, FT-IR, UV–Vis and cyclic voltammetry (CV). The spectro-electrochemical and electrochromic properties of the polymer film were investigated. Also the greenish blue colored film converted to dark blue color by the applying potential. Polystyrene-carbazole/polyethylenedioxythiophene (PS-Carb/PEDOT) electrochromic device was assembled in sandwich configuration: ITO-coated glass/anodically coloring polymer (PS-Carb)//gel electrolyte//cathodically coloring polymer (PEDOT)/ITO-coated glass. According to kinetic studies of this device, the optical contrast ΔT% at 640 nm between −1.0 and +2.0 V with a residence time of 10 s was found to be 38% and switching time was measured as 1.1 s.