Conduction mechanism in H‐type polysiloxane‐polypyrrole block copolymers

Conducting polymers of polysiloxane‐polypyrrole were synthesized by electropolymerization of the pyrrole monomer through pyrrole moieties in N‐pyrrole‐terminated polysiloxanes. Sodium paratoluene sulfonate was used as the electrolyte. Scanning electron microscopy (SEM) was used to determine the surface morphology of the films. The room‐temperature conductivity values of the films were found to be in the range of 1.9–4.4 × 10^?4 (Ω cm)^?1, depending on the supporting electrolyte concentration. The temperature dependence of the dc conductivities of the copolymers having different dopant concentrations was investigated within the temperature range of 100–320 K. The evaluated parameters showed that the electrical transport is dominated by variable range hopping. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 52–56, 2002     

Fatty acid composition of wild and cultivated gilthead seabream (Sparus aurata) and sea bass (Dicentrarchus labrax)

Total lipid content and fatty acid composition were determined for wild and cultivated gilthead seabream and sea bass. Fatty acid analyses were carried out by gas chromatography‐ mass spectrometry. Respective total lipid content of flesh in cultivated gilthead seabream and sea bass were 1.7‐5.0‐times those of wild samples. Palmitic acid (C16:0) and oleic acid (C18:1n‐9) were the major fatty acids respectively among the saturated fatty acids and monounsaturated fatty acids of each fish species. It is noteworthy that both linoleic acid (C18:2n‐6) and arachidonic acid (C20:4n‐6) were predominant in total n‐6 polyunsaturated fatty acids in the respective cultivated and wild types. Eicosapentaenoic acid (C20:5n‐3) and docosahexaenoic acid (C22:6n‐3) amounts were significantly higher in flesh of cultivated fish than in wild fish.     

NaOCl degradation of one-step one-bottle self-etch adhesives bonded to bovine dentine

Objective: The aim of the present study was to assess the influence of an in vitro aging regime (NaOCl storage) on dentine microtensile bond strength (μTBS) of five one-step one-bottle self-etch adhesives in comparison with bond strength of two-step self-etch adhesive.

Material and methods: Flattened dentine surfaces from 30 bovine incisors were bonded with five one-step one-bottle self-etch adhesives (iBond, Clearfil S3 Bond, AdheSE One F, G-Bond, Optibond all-in-one) and one two-step self-etching adhesive (Clearfil SE Bond). Composite buildups were done with microhybrid resin composite. Bonded samples were sectioned into resin–dentine sticks of 0.8 mm² cross section. Randomly selected 20 sticks were tested directly by microtensile bond strength testing machine, whereas another randomly selected 20 sticks were tested after being stored in solution of 10% NaOCl for 5 h. Data were analyzed by two-way analysis of variance (ANOVA) and Tukey’s honest significant difference (HSD) tests (p < 0.05).

Results: All adhesives exhibited similar dentine bond strength with exception of G-Bond. After NaOCl storage, μTBS reduced in all groups significantly. The lowest μTBS were found for G-Bond. Rest of one-step self-etch adhesives presented similar μTBS with two-step self-etch adhesive.

Conclusion: Interfaces of resin–dentine bonding are susceptible to NaOCl degradation. The amount of the destruction depends on adhesive system. NaOCl degradation of the nonresin encapsulated collagen fibers might decrease long-term stability of resin bonding with dentine.     

Combined quantitative ultrasonic and time-resolved interaction force AFM imaging

The authors describe a method where quantitative ultrasonic atomic force microscopy (UAFM) is achieved during time-resolved interaction force (TRIF) imaging in intermittent contact mode. The method uses a calibration procedure for quantitative UAFM. It improves elasticity measurements of stiff regions of surfaces while retaining the capabilities of the TRIF mode for topography, adhesion, dissipation, and elasticity measurements on soft regions of sample surfaces. This combination is especially advantageous when measuring and imaging samples with broad stiffness range in a nondestructive manner. The experiments utilize an active AFM probe with high bandwidth and the UAFM calibration is performed by measuring the magnitude of the time-resolved UAFM signal at a judiciously chosen frequency for different contact stiffness values during individual taps. Improved sensitivity to stiff surface elasticity is demonstrated on a special sample. The results show that combining UAFM with TRIF provides 2.5 GPa (5%) standard deviation on the silicon surface reduced Young's modulus, representing 5× improvement over using only TRIF mode imaging.     

Effect of heat treatment on the bending behavior of aluminum alloy tubes

Quasistatic experiments and numerical simulations were performed to investigate the three-point bending behavior of different temper AA6082 tubes in this study. The effect of heat treatment on the samples was investigated by microstructural analyses. Temper designations of T6, T4 and O were applied to the samples to study the load-carrying capacity and bendability of AA6082 tubes. The samples with T4 and O tempers show appropriate bendability of up to the punch travel distance of 60 mm under low-punch forces. However, the samples with T6 temper require three times more punch force than the other temper samples. Furthermore, the T6 temper samples cannot hold their structural integrity. Therefore, crack formation occurred at the enhanced bending angle stages. Experimental results were compared with the numerical simulation outputs, and the deformation mechanism was observed with finite element method. In addition, various element formulations in the numerical simulations were compared in terms of bending force and computational time. Based on the numerical results, element formulations exhibit different performances with respect to temper conditions.     

Effect of dowels and adhesive types on withdrawal strength in particleboard and MDF

Composite materials and wooden dowels are being used increasingly in the construction of furniture frames and inner decoration. However, there is little information available concerning the withdrawal strength of various fasteners and in particular, dowels in these materials. The aim of this study was to determine the withdrawal strengths of 6, 8, and 10?mm diameter dowels produced from different wood species bonded parallel or vertical to the surfaces of a medium-density fiberboard (MDF) or particleboard with poly vinylacetate or Desmodur (D-VTKA). According to TS 4539 standard, the effect of dowel species, direction of withdrawal, board type and the type of adhesive on the withdrawal strength were determined. The highest (8.35?N/mm²) withdrawal strength was obtained for oak dowels bonded with D-VTKA adhesive vertically to the surface of MDF. This value is higher than the predictive expression that allows designers to estimate the withdrawal strength of dowels.     

Optimal design of MR damper via finite element analyses of fluid dynamic and magnetic field

In the last decade many researchers have been carried out on semi-active control systems, a large number of academic publications have been presented. Semi-active control systems which are used the magnetic field controlled fluid have been shown significant improvements by the researchers. In the study, a design optimization method that has been carried out for the objectives of target damper force and maximum magnetic flux density of an MR damper has been presented. Finite element methods, electromagnetic analysis of magnetic field and CFD analysis of MR flow, have been used to obtain optimal value of design parameters. The new approach that is use of magnetic field and MR flow together and simultaneously has specified optimal design values. Two optimal design of MR damper obtained have been verified with experimental study by manufacturing and testing of the dampers.     

Removal of limonin bitterness by treatment of ion exchange and adsorbent resins

This study, the selective removal of limonin bitterness from Washington navel orange juice by batch adsorption to the Amberlite XAD-16HP and Dowex Optipore L285 was investigated and the determination of some compositional changes that occurred with orange juices debittering using adsorption resins were the primary focus. Amberlite XAD-16HP and Dowex Optipore L285 have been successfully used to reduce bitterness to acceptable levels in Washington navel orange juices. Amberlite XAD-16HP does not have any important negative effects on the quality characteristics of orange juices. However, Dowex Optipore L285 reduces the titratable acidity (TA) in the orange juices and so increases the content of soluble solids contents (SSC), pH value, and ratio accordingly.     

Mercury levels in cord blood and meconium of healthy newborns and venous blood of their mothers: clinical, prospective cohort study

OBJECTIVES: The purpose of this study is to investigate the chronic mercury intoxication in pregnant women and newborns living in Istanbul, Turkey. METHODS: The research was carried out as a prospective with 143 pregnant women and their newborns. Venous blood from the mother, cord blood from the neonate, and meconium were collected for mercury analysis. Frequency of fish and vegetable-eating and the number of teeth filled were investigated. Analyses were made in cold vapor Atomic Absorption Spectrophotometer (AAS, microg/L). RESULTS: Mercury levels were 0.38+/-0.5 microg/L (0-2.34) in venous blood of pregnant women, 0.50+/-0.64 microg/L (0-2.36) in umbilical cord blood and 9.45+/-13.8 microg/g (0-66.5) in meconium. Maternal blood mercury level was lower than the known toxic limit for humans (EPA, 5 microg/L). Mercury levels of the maternal venous blood were significantly correlated with umbilical cord blood. The primary risk factors affecting mercury levels were eating fishmeals more than twice a week and having filled teeth more than five. The fact that the mother had a regular vegetable diet everyday reduced the mercury levels. Increased levels of mercury in the mother and umbilical cord blood could lead to retarded newborns' weight and height. CONCLUSION: Pregnant women living in Istanbul may be not under the risk of chronic mercury intoxication. Fish consumption more than twice per week and tooth-filling of mother more than five may increase mercury level. On the contrary, regular diet rich in vegetable decreases the mercury level.     

An expert system approach for die and mold making operations

In the modern manufacturing of sophisticated parts with 3D sculptured surfaces, die and mold making operations are the most widely used machining processes to remove unwanted material. To manufacture a die or a mold, many different cutting tools are involved, from deep hole drills to the smallest ball nose end mills. Since the specification of each tool is very different from each other, each mold or die is specific with their complicated shapes and many machining rules exist to consider, a great deal of expertise is needed in planning the machining operations. An expert system (DieEX) developed for this purpose is described in the present work. The geometry and the material of the workpiece, tool material, tool condition and operation type are considered as input values and various recommendations about the tool type, tool specifications, work holding method, type of milling operation, direction of feed and offset values are provided.