Effect of cement type on the resistance of concrete against chloride penetration

In chloride containing environment, chloride permeability of concrete is an important parameter affecting the service life of concrete structures. The primary objective of this experimental study was to study the effect of cement types on the resistance of concrete against chloride penetration for given compressive strength classes. These cements included two different types of granulated blast-furnace slag cement (CEM III/A 32.5N and CEM III/A 42.5N), a sulfate resisting cement (SRC 32.5), and a Portland cement blended with fly ash; all of which compared to an ordinary Portland cement (CEM I 42.5R). For each binder type, four concretes at different strength classes were produced and as a result 20 mixtures were obtained. Rapid chloride ion penetration tests according to ASTM C 1202 were conducted. In addition, electrical resistivity and capillary water absorption tests were carried out. In order to characterize the concrete quality, compressive strength of the specimens were also obtained. The test results clearly demonstrated that the blast-furnace slag cements have the highest resistance against chloride penetration, while the pure Portland cement and sulfate resisting cement have the lowest resistance. Concretes produced with the sulfate resisting cement had substantially higher capillary sorption compared to other mixtures. Test results confirmed the strong relationship between the chloride permeability and electrical resistivity.     

Testing for Unit Roots in Dynamic Panels with Smooth Breaks and Cross-Sectionally Dependent Errors

We develop the extended unit root testing procedure for dynamic panels characterised by slowly moving trends (SMT) and cross-section dependence (CSD). We allow SMT to follow the smooth logistic transition function and the components error terms to contain the unobserved common factors. We propose the two panel unit root test statistics, one derived by the extended common correlated effects (CCE) estimator and the other based on the Sieve bootstrap. We have conducted extensive simulation exercises and document that the failure to take into account SMT and CSD may lead to misleading inference. On the other hand, we find that both bootstrap and CCE-based tests maintain good power properties in small samples in the presence SMT and CSD. We apply our proposed tests to real interest rates for 17 OECD countries and find overwhelming evidence in favour of the Fisher hypothesis.     

Assessment of ASTER satellite images in landslide inventory mapping: Yenice-Gökçebey (Western Black Sea Region,Turkey)

In the last two decades, developments in Geographic Information Systems and Remote Sensing have allowed rapid and detailed analysis of natural hazards. The Western Black Sea region of Turkey is a major landslide prone area. Landslides in a selected area were assessed using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite imagery. Stereoscopic and two-dimensional visual image interpretations were performed at different scales and field studies were carried out such that the landslide inventories could be compared. The study indicated the best approach was stereoscopic image analysis for visual interpretations. The smallest landslide area realistically mapped using the ASTER image was 58,885 m². It is considered that ASTER satellite images provide useful information particularly in regional and/or medium scale landslide inventory studies.     

Bioengineering of a Semiautologous Arterial Vessels with Reconstructed Media and Intima,Longtime Tested In Vivo

Goal was to engineer biological, arterial grafts with antithrombotic, autologous endothelial luminal surface combined with extraluminal smooth vascular muscle layer (VSMC) and to test in vivo. (1) Different decellularisation methods described in literature were compared to identify the most suitable one with focus on the preservation of extracellular fibre matrix. (2) Endothelial precursor cells (EPC), isolated from bone marrow and VSMC from small venous segments of donor animals were cultivated. Cells were seeded sandwich‐like on homologous decellularized venous scaffolds and conditioned under pulsatile circulation in a bioreactor. (3) The semiautologous grafts were implanted in carotidal position on both sides in five Beagle dogs (n = 10; group 2) as interposition. A group of five animals, receiving only acellular grafts in both carotid positions (n = 10; group 1) served as controls. Comparison of four in literature described decellularisation methods showed different preservation of elastic and collagen fibres compared with native veins, whereas decellularity was similar in all methods. This forced us to choose a decellularization protocol with the best preservation of the extracellular matrix. The in vivo experiments showed in group 1 (control) already after one week a complete thrombotic occlusion of the decellularized implants, whereas in group 2 9/10 semiautologous grafts were patent after 98 ± 4 days in ultrasound, angiography and histology (p = 0.0001). A complete incorporation of semiautologous grafts in the surrounding tissue could be shown. The seeding with two different cell types preserved an aneurysmatic degeneration under arterial conditions with patency without anticoagulation.     

Effect of muscle stretching on meat quality of biceps femoris from beef

The objective of this study was to examine the effect of muscle stretching on meat quality and ultrastructure of biceps femoris (BF) from beef. After slaughter, the right side of the carcasses were suspended from the Achilles tendon (AS; n=10), while the left sides were re-hanged from the pelvic bone (PS; n=10). Meat quality was evaluated by water holding capacity (WHC), cooking loss (CL), color, shear force (SF) and sarcomere length (SL). As a result, PS had no impact on WHC, CL and color parameters. PS significantly decreased SF values by 7.5% only at 2 days postmortem. At pelvic suspended sides, SL was increased by 0.13 μm, 0.14 μm and 0.12 μm at 2, 7 and 10 days postmortem, respectively (P<0.001). Electron microscopy showed that the ultrastructure of BF have longer sarcomeres and smaller fiber diameter after PS. In conclusion, PS is a useful method for improving tenderness by stretching muscles.     

Evaluation of L929 fibroblast attachment and proliferation on Arg-Gly-Asp-Ser (RGDS)-immobilized chitosan in serum-containing/serum-free cultures

In this study, chitosan membranes prepared by the solvent casting method were modified with the Arg-Gly-Asp-Ser (RGDS) sequence of fibronectin using the photochemical immobilization technique. The results obtained from attenuated total reflection-Fourier transform infrared spectra and X-ray photoelectron spectroscopy studies confirmed the successful immobilization of RGDS on chitosan membranes. The immobilized peptide concentration was determined by ninhydrin analysis on the order of 10(-7) mol/cm(2). In vitro cell culture studies were performed with L929 mouse fibroblasts to investigate the effect of biomodification on fibroblast cell behaviour in serum-free and 10% serum-containing media. The results obtained from cell culture studies pointed out the specific interactions between biosignal RGDS molecules and fibroblast cells. A triggered cell attachment and proliferation were observed on RGDS-modified chitosan membranes that were more distinguishable in serum-free medium. In addition, the photochemical immobilization technique was realized in the presence of a photomask that was used to immobilize the RGDS molecules in a defined micropattern. L929 mouse fibroblasts attached on the RGDS-micropatterned areas indicating integrin-mediated interactions.     

Deposition and Characterization of Tungsten Carbide Thin Films by DC Magnetron Sputtering for Wear-Resistant Applications

In this study, WC (tungsten carbide) thin films were deposited on high-speed steel (AISI M2) and Si (100) substrates by direct current magnetron sputtering of a tungsten carbide target having 7% cobalt as binding material. The properties of the coatings have been modified by the change in the bias voltages from grounded to 200 V. All the coatings were deposited at 250°C constant temperature. The microstructure and the thickness of the films were determined from cross-sectional field-emission gun scanning electron microscope micrographs. The chemical composition of the film was determined by electron probe micro analyzer. The x-ray diffractometer has been used for the phase analyses. Nanoindentation and wear tests were used to determine the mechanical and tribological properties of the films, respectively. It is found that the increase in the bias voltages increased drastically the hardness and elastic modulus, decreased the friction coefficient values and increased the wear resistance of tungsten carbide thin films by a phase transformation from metallic W (tungsten) to a nonstoichiometric WC_1?x (tungsten carbide) phase.     

Electrolyte type and concentration effects on poly(3-(2- aminoethyl thiophene) electro-coated on glassy carbon electrode via impedimetric study

In this study, 3-(2-Aminoethyl thiophene) (2AET) monomer was electropolymerized on glassy carbon electrode (GCE) using various electrolytes (lithium perchlorate (LiClO₄), sodium perchlorate (NaClO₄), tetrabutyl ammonium tetra fluoroborate (TBABF₄) and tetraethyl ammonium tetra fluoroborate (TEABF₄) in acetonitrile (CH₃CN) as solvent. Poly(3-(2-aminoethyl thiophene) (P(2AET))/GCE was characterized by cyclic voltammetry (CV), Fourier transform infrared reflectance spectrophotometry (FTIR-ATR), scanning electron microscopy, energy dispersive X-ray analysis (EDX), and electrochemical impedance spectroscopy (EIS) techniques. The electrochemical impedance spectroscopic results were given by Nyquist, Bode-magnitude, Bode-phase, capacitance and admittance plots. The highest low frequency capacitance (C _LF) value obtained was 0.65 mF cm^?2 in 0.1 M LiClO₄/CH₃CN for the initial monomer concentration of 1.5 mM. The highest double layer capacitance (C _dl = ~0.63 mF cm^?2) was obtained in 0.1 M LiClO₄/ACN for [2AET]₀ = 0.5, 1.0 and 1.5 mM. The maximum phase angles (θ = 76.1^o at 26.57 Hz) and conductivity (Y″ = 3.5 mS) were obtained in TEABF₄/ACN for [2AET]₀ = 0.5 and 1.0 mM, respectively. An equivalent circuit model of R(Q(R(Q(R(CR))))) was simulated for different electrolytes (LiClO₄, NaClO₄, TBABF₄ and TEABF₄)/P(2AET)/GCE system. A good fitting was obtained for the calculated experimental and theoretical EIS measurement results. The electroactivity of P(2AET)/GCE opens the possibility of using modified coated electrodes for electrochemical micro-capacitor electrodes and biosensor applications.     

A Photoluminescent Polymeric 2D Silver(I) Complex Exhibits a Fishbone-like 1D Silver Cluster and New Coordination Mode of the Pyridine-2,3-Dicarboxylate

In this study, a novel organic–inorganic hybrid compound with AgNO₃ and 2,3-pyridinedicarboxylic acid (H₂pydc), [Ag₂(μ₆-pydc)]_n (1) has been synthesized. The molecular structure of complex has been determined by the single crystal X-ray diffraction. The complex has been observed to crystallize in the monoclinic space group P2₁/c. The asymmetric unit of compound consists of two crystallographically different Ag(I) centers and one pydc ligand. The Ag1 and Ag2 adopt tetrahedral and T-shaped geometries, respectively. At the same time, the silver(I) compound consists of a fish bone similar to the 1D silver cluster. Furthermore, novel coordination mode shown by H₂pydc indicates that the crystal exhibits photoluminescence in the solid state at room temperature.