Enzyme immobilization in a photosensitive conducting polymer bearing azobenzene in the main chain

A new photosensitive and thermosensitive monomer, namely bis(4-(3-thienyl ethylene)-oxycarbonyl)diazobenzene (TDAZO), was synthesized. The photochemical and thermal cis–trans isomerization of the monomer has been investigated. The rate constants of the photoisomerization of TDAZO in ACN and DCM were 0.195 and 0.308 min^?1, respectively. For spectroelectrochemical investigation and enzyme immobilization application, TDAZO copolymerized with thiophene and pyrrole. Electrochemical and spectroelectrochemical properties of P(TDAZO-co-Th) were investigated and invertase was immobilized in P(TDAZO-co-Py) copolymer. Immobilization of enzymes was carried out by the entrapment of the enzyme in conducting polymer matrices during electrochemical polymerization of pyrrole through thiophene moieties of the TDAZO. Optimum conditions for this electrode, such as pH, temperature, kinetic parameters (K _m and V _max) and operational stability were investigated. Kinetic parameters invertase-immobilized in copolymer were smaller than free enzyme. The optimum operational temperature was 10 °C higher for immobilized enzyme than that of the free enzyme. Due to strong interaction between enzyme and diazo group in the polymer main chain, thermal, pH and operational stability of enzyme has been enhanced.     

Vibration analyses of FGM plates with in-plane material inhomogeneity by Ritz method

In this study, functionally graded plates which the properties of material varying through the in-plane direction is considered. The analysis is based on a five-degree-of-freedom shear deformable plate theory with different boundary conditions. The vibration solutions are obtained using the Ritz method and assumed displacement functions are in the form of the Chebyshev polynomials. The material properties are assumed to vary as a power form of the in-plane direction. The convergence and comparison studies demonstrate the accuracy and correctness of the present method. Effects of the different material composition, the Poisson ratio and the plate geometry (side-side, side-thickness) on the free vibration frequencies and mode shapes are investigated.     

The alteration degree of the metacrystalline rocks based on UAI,Bolu (Turkey)

The geomechanical properties of the metacrystalline rock masses vary due to alteration. The Devonian aged Yedigoller formation crops out in the Asarsuyu valley (Bolu, Turkey). The aim of this study is to investigate the alteration degree of the amphibolite and metagranodiorites based on their geomechanical and petrographical properties. The P-wave velocity is 1,613–5,588 m/s and the unconfined compressive strength varies between 12.75 and 99.86 MPa. Several weathering products occurred due to carbonisation, oxidation and sericitation. These rocks, subjected to hydrothermal effects, are classified as “fresh” to “completely altered” according to the unified alteration index (UAI). In addition, the values of the loss on ignition, modified weathering potential index and chemical index of alteration were taken into account for supporting the alteration process. Since the main process is hydrothermal alteration, the rocks which were exposed to alteration are weathered on the slopes after excavation. Weathering classification and the chemical indices indicate this process. Thus, UAI is concluded to be more suitable and credible in order to evaluate the hydrothermal alteration process of such crystalline rocks numerically.     

Improvement of bitumen and bituminous mixtures performances by triethylene glycol based synthetic polyboron

This study investigates the modification of bitumen with triethylene glycol based polyboron (TEGPB). TEGPB is a new additive material which was chemically synthesized at laboratory conditions. Four different TEGPB concentrations were used to modify 50/70 penetration grade bitumen: 1%(w/w), 2%(w/w), 3%(w/w) and 5%(w/w). The effects of TEGPB modification on the bitumen and bituminous mixture properties were determined by means of softening point, Marshall stability, Nicholson stripping, rotational viscosity (RV), Dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR) tests. Amount of TEGPB to be used within the bitumen has been chosen as 2%(w/w) according to RV test results. BBR and Nicholson stripping test results have showed that creep properties and stripping resistance of the modified bitumen was not adversely affected. It was also found out that softening point and rutting resistance of the bitumen as well as Marshall stability of the bituminous mixtures were increased by TEGPB modification.     

Development of electrically conductive and anisotropic gel-coat systems using CNTs

Electrical conductivity of an unsaturated thermoset polyester based gel-coat system containing 0.05 wt.% of carbon nanotubes (CNTs) was investigated. The CNTs used were synthesized by chemical vapor deposition method by methane decomposition and Raman characterization showed that they were mostly single walled and high quality. To disperse CNTs in the gel-coat resin, 3-roll milling technique was used. It was found that as the CNTs are added to gel-coat system, resistivity value decreases significantly while neat gel-coat showed a high resistivity. By the application of an AC electrical field during curing process, it was attempted to align CNTs in the gel-coat resin and an electrically anisotropic polymer was obtained.     

4-Vinylpyridine and 2-hydroxyethylmethacrylate monomer mixture graft copolymerization onto poly(ethylene terephthalate) fibers using benzoyl peroxide

Summary Poly(ethylene terephthalate) (PET) fibers were grafted with 4-vinyl pyridine (4-VP) and 2-hydroxyethylmethacrylate (HEMA) using benzoyl peroxide (Bz₂O₂) as initiator in aqueous media. PET fibers were swelled in dichloroethane (DCE) for 2 h at 90 °C to promote the incorporation and the subsequent polymerization of 4-VP/HEMA onto PET fibers. Variations of graft yield with time, temperature, initiator concentration and monomer mixture ratio were investigated. The optimum initiator concentration was found to be 8×10^-3 mol/L. The maximum graft yield was obtained 280%. The optimum temperature and polymerization time was found to be 85 °C and 100 min. respectively. The rate of grafting was found to be proportional of the 1.5 and 0.3 powers of 4-VP/HEMA and Bz₂O₂ concentrations, respectively. The grafted PET fibers were characterized by thermo gravimetric analysis and scanning electron microscopy (SEM). Further changes in properties of grafted PET fibers such as water absorption capacity, intrinsic viscosity and diameter were determined. The dye ability of the PET fibers increased with an increase in grafting with diazo and basic dyes.