Synthesis,structural characterization,and antiproliferative/cytotoxic effects of a novel modified poly(maleic anhydride-co-vinyl acetate)/doxorubicin conjugate

Polymer Bulletin - Drug carrier, poly(maleic anhydride-co-vinyl acetate) (MAVA or poly[MA-co-VA]) copolymer, was traditionally synthesized by free radical chain polymerization reaction, in methyl...     

Dimensional changes and creep of silica core ceramics used in investment casting of superalloys

Dimensional changes and creep deformation of a silica/zircon (74%/24%, respectively) and a high silica (93% silica and 3% zircon) ceramic were characterized and compared. All specimens were tested with a thermal profile that consisted of a 300°C/h heating rate to 1475 or 1525°C, followed by a one-hour isothermal hold (where each specimen was compressively crept under a static stress of 2.07, 4.14, or 6.21 MPa). The specimens were cooled at a rate of 900°C/h under stress. Dimensional changes were interpreted from apparent thermal expansion behavior during heating as well as before-and-after dimensional measurements. The silica/zircon ceramic generally exhibited less total contraction than the high silica ceramic for a specific test condition even though it crept faster at all stresses and temperatures during the one-hour isothermal/isostress segment. This indicates that the total contraction for both was dominated by reinitiated sintering and subsequent cristobalite formation that occurred during the heating segment. Minimum creep rate during the one-hour isothermal/isostress segment was examined as a function of stress and temperature for both ceramics using a power-law creep model. Creep-rate stress exponents (n) and activation energies (Q) were equivalent (within 95% confidence) for both ceramics showing that their different contents of zircon (3 vs. 24%) did not affect them. Lastly, n 1.3–1.4 and Q 170 kJ/mol indicate that diffusion-assisted crystallization of cristobalite, combined with power-law sintering owing to the high concentration of porosity (28–30%) was likely the rate-limiting mechanism in the creep deformation for both ceramics.     

Structure, Properties and Behavior of Kyanite： Use in Refractory Monolithics

1 Introduction Kyanite is an important naturally occurring in-dustrial mineral and is used in the manufacture of avariety of industrial ceramic products; notable exam-ples include refractories and porcelains. It is a high-pressure polymorph of the aluminosilicates of the ne-sosilicate group, which includes kyanite, sillimanite,and andalusite. These three aluminous or alumina-rich minerals are chemically identical with the compo-sition, Al_2SiO_5, but have different crystal structuresand physical properties. It is, however, their alumina     

Purification of peroxidase from Amsonia orientalis by three-phase partitioning and its biochemical characterization

The present work describes the purification and characterization of peroxidase from the medicinal plant, Amsonia orientalis, for the first time. The activity recovery for peroxidase was 162% with 12.5-fold purification. Optimal purification parameters were 20% (w/v) (NH₄)₂SO₄ saturation at pH 6.0 and 25°C with 1.0:1.0 (v/v) ratio of crude extract to t-butanol ratio for 30 min. The molecular mass of the enzyme was found to be ca. 59 kDa. Peroxidase showed K_m values of 1.88 and 2.0 mM for pyrogallol and hydrogen peroxide, respectively. FeSO₄, CuSO₄, HgCl₂, MnSO₄ and MgSO₄ did not inhibit the enzyme activity.     

Appraising the methods accounting for 3D tunnelling effects in 2D plane strain FE analysis

Numerical analysis is widely used method in geotechnical engineering when calculating and predicting soil and rock behaviour under different loading and excavation conditions. For instance, simulation of tunnelling using 2D or 3D finite element (FE) analyses can often calculate any deformations and stress redistributions due to tunnelling operations without constructing real trial tunnels. Modelling the excavation process in 2D plane strain analysis, however, requires an approach that can consider 3D tunnelling effect as a result of volume loss. In addition, modelling shotcrete or similar support measures, using either beam elements, solid continuum elements or other special elements are needed to be adopted. Therefore, convergence-confinement, stiffness reduction, disk calculation and hypothetical modulus of elasticity (HME) soft lining approaches have been employed in the numerical analysis. Moreover, compatibility of each method with beam and solid continuum element models in 2D FE analysis was investigated. Thus, eight plane strain, non-linear FE analyses of tunnel construction in London Clay were performed and the results are presented and discussed in this article.     

Hydrogeological and geochemical studies of the Efteni and Derdin geothermal areas,Turkey

The Efteni and Derdin geothermal areas are located in northwestern Turkey. Relatively low-temperature springs emerge from the Duzce Fault, a normal-component-dominated fault segment of the North Anatolian Fault System. The thermal waters of the Efteni and Derdin Springs show distinct geochemical and isotopic characteristics since they originate from different geothermal reservoirs and reflect the effects of different water–rock interaction processes. Geothermometry revealed higher reservoir temperatures for the Efteni system, however a strong δ¹⁸O shift, interpreted as being the result of isotopic exchange at high temperatures, was observed in the Derdin system. Hydrogeological and geochemical techniques are applied to identify recharge mechanisms, water–rock interaction processes and to construct conceptual models of these geothermal systems.     

Synthesis,characterization and cytotoxicity of novel modified poly[(maleic anhydride)‐ co‐(vinyl acetate)]/noradrenaline conjugate

Poly[(maleic anhydride)‐co‐(vinyl acetate)] (MAVA) copolymer was synthesized by free radical polymerization reaction, in methyl ethyl ketone at 80 °C, using benzoyl peroxide as the initiator. The copolymer was then modified with a biomolecule, noradrenaline (NA). The modification reaction was performed at 70 °C in dimethylformamide containing triethylamine as the catalyst. The modified polymer was named MAVA/NA. Structural characterization of the copolymer and the modified product was carried out by Fourier transform infrared (FTIR) and ¹H NMR and ¹³C NMR spectroscopy. The FTIR, ¹H NMR and ¹³C NMR spectra confirmed that NA was successfully covalently bound to the MAVA copolymer backbone. Surface morphology was visualized by atomic force microscopy. The cumulative release of NA from MAVA/NA was determined in phosphate buffered saline solution for 7 days at 37 °C and compared with MAVA. Cytotoxicity of the MAVA/NA was evaluated by using a mouse fibroblast cell line (L929). Results obtained indicated that MAVA/NA had almost no toxicity and no negative effect on cell viability at 250 µg mL^?1 concentration. © 2012 Society of Chemical Industry     

Finite element analysis for the twin metro tunnel constructed in Ankara Clay,Turkey

The paper presents the geotechnical properties along the route of the 9,325 m twin tunnel metro route in the Greater Municipality of Ankara. Convergence measurements taken during tunnel construction are presented and discussed. In addition, the convergence of the twin metro tunnels was analysed by means of a 2D plane strain finite element (FE) analysis. The FE model estimations and the field measurements are compared.      

Modification of maleic anhydride–styrene copolymer with noradrenaline by chemical and enzymatic methods

Maleic anhydride copolymer was modified with another biologically active agent, noradrenaline (NA), using both chemical and enzymatic methods. The modification and synthesized products were named as follows: chemical modification, MASTNAc; enzymatic modification, MASTNAe; enzymatically synthesized MASTNA from individual monomers, MASTNAem. Chemical and enzymatic reactions were performed at 70°C and 38°C, respectively. In the chemical reactions azobisisobutyronitrile was used as the initiator. In the enzymatic reactions, an extracellular extract, including an enzyme with peroxidase‐like activity, was used. All the reactions were performed in an organic medium, methyl ethyl ketone. Structural characterization of the copolymer and modified copolymer were carried out by Fourier transform infrared (FTIR) and nuclear magnetic resonance (¹H NMR). FTIR and ¹H NMR spectra confirmed that NA was successfully covalently bound onto the MAST copolymer backbone by both chemical and enzymatic methods. Surface morphology of the samples was studied by scanning electron microscopy. Results obtained indicated that chemical and enzymatic addition of NA to MAST backbone yielded products having quite similar physical and chemical properties. On the other hand, MASTNA‐modified copolymer synthesized by individual monomers appeared to be different in its chemical structure. Furthermore, enzymatic modification and synthesis appeared to provide a good alternative method because it required much milder conditions such as low temperature, and better product qualities: higher solubility in water, higher yield and purity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Characterization of polypyrrole/azocalix[4]arene salts: Electrical properties and thermal stability

Polypyrrole (PPy) was doped with the azocalix[4]arene [(5,11,17,23‐tetrakis[(p‐carboxyphenyl)azo]25,26,27,28‐tetrahydroxycalix[4]arene)] host species. PPy/azocalix[4]arene salts were characterized by FTIR, TGA, SEM, X‐ray diffraction, and conductivity measurements. The properties of PPy were investigated in the presence of azocalix[4]arene host species. The conductivity of PPy increased in the presence of azocalix[4]arene. TGA results indicated that the PPy/azocalix[4]arene salts have higher thermal stability than PPy. It was observed from SEM analysis that the particle diameter of PPy decreased with increasing content of azocalix[4]arene. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010