Studies on biodegradation of crosslinked hydroxy terminated-poly(proplyene fumarate) and formation of scaffold for orthopedic applications

Biodegradation of crosslinked-hydroxy terminated-poly(proplyene fumarate) (X-HTPPF) has been studied in simulated physiological media to assess the formation of porous scaffold structure for bone growth and remodeling in load bearing orthopedic applications. Variation in crosslink density and surface hydrophilicity of X-HTPPF are observed due to non-stoichiometric mass of reacting partners. These variations influence absorption of the medium and biodegradation during aging. Though the initial absorption of medium is relatively higher with the crosslinked polymer (PNVP1) having 63.6% HT-PPF and 36.4% comonomer n-vinyl pyrrolidone (NVP) during the initial period of aging, the weight loss due to subsequent degradation with time is relatively lesser. PNVP1 undergo slow degradation with formation of fibril structure on the surface. The present crosslinked material PNVP1 is a candidate for the load bearing orthopedic applications.     

Studies on in vitro biostability and blood compatibility of polyurethane potting compound based on aromatic polymeric MDI for extracorporeal devices

Polyurethane potting compound based on aromatic isocyanurate of polymeric MDI, poly propylene glycol (PPG400) and trimethylol propane (TMP) has significant favourable properties, good pot life and setting characteristics. The cured potting compound of this formulation has appreciable thermal stability and mechanical properties. In vitro biostability of cured potting compound has been found to be excellent without any significant degradation in simulated physiological media and chemical environment. Studies on blood-material interaction and cytotoxicity reveal in vitro blood compatibility and compatibility with cells of this potting compound.     

A scaling technique for partial element equivalent circuit analysis using SPICE

A scaling technique for partial element equivalent circuit (PEEC) analysis using SPICE is introduced in this letter. The perturbation series based scaling is applied to the component values extracted by the standard PEEC method to get up to an order of magnitude improvement in relative accuracy of scattering parameters with SPICE simulation. The effectiveness of the technique is verified by using the numerical example of a stripline structure and comparing the results with that of the method of moments (IE3D).     

Modeling corrosion behavior of gas tungsten arc welded titanium alloy

The pitting corrosion characteristics of pulse TIG welded Ti-6Al-4V titanium alloy in marine environment were explained. Besides the rapid advance of titanium metallurgy, this is also due to the successful solution of problems associated with the development of titanium alloy welding. The preferred welding process of titanium alloy is frequently gas tungsten arc（GTA） welding due to its comparatively easier applicability and better economy. In the case of single pass GTA welding of thinner section of this alloy, the pulsed current has been found beneficial due to its advantages over the conventional continuous current process. The benefit of the process is utilized to obtain better quality titanium weldments. Four factors, five levels, central composite, rotatable design matrix are used to optimize the required number of experiments. The mathematical models have been developed by response surface method（RSM）. The results reveal that the titanium alloy can form a protective scale in marine environment and is resistant to pitting corrosion. Experimental results are provided to illustrate the proposed approach.     

Compatibilization of thermosetting-thermoplastic polymer blends

Polymer blends of thermosetting and thermoplastic polymers were developed by properly mixing them in the presence of compatibilizers. Two compatibilizers that are structurally and chemically similar to thermosetting and thermoplastic polymers and a compatibilizer that does not have such similarity were synthesized. Polymer blends of phenol formaldehydepoly(methyl methacrylate) and phenol formaldehyde-polystyrene were prepared by using the compatibilizers, poly(phenol formal dehyde-s-triazine-methyl methacrylate), P(PF-g-MMA), poly(phenol formaldehyde-s-triazine-styrene), P(PF-g-S), and poly (cinnamaldehyde-co-oxy propylene oxy isophthaloyl-cooxy propylene oxy fumaroyl), P(C-g-E). The effects of molecular weight and quantity of the copolymer on the compatibility of the polymer were examined. The optimum compatibility which leads to superior tensile properties of the present blends was observed with P(PF-g-MMA) and P(PF-g-S) copolymers. The superior properties were also found to occur only in the range of the optimum molecular weight and quantity of the copolymer present in the blend. The polymer blends were analyzed by differential scanning calorimetry (DSC) and Electron Microscopy. DSC scans of P(PF-g-MMA) and P(PF-g-S) copolymer blends showed a single T_g whereas the scans of P(Cg-E) copolymer blends showed an additional T_g for unblended thermoplastic fractions. The electron microscopy studies also revealed good compatibility in P(PF-g-MMA) and P(PF-g-S) copolymer blends in which the unblended thermoplastic fractions are negligibly less. The UV-vacuum and heat resistance of the P(PF-g-MMA) and P(PF-g-S) copolymer blends were found to be good.     

Changes in content of organic acids and tea polyphenols during kombucha tea fermentation

Kombucha tea is a fermented tea beverage produced by fermenting sugared black tea with tea fungus (kombucha). Tea polyphenols which includes (-)-epicatechin (EC), (-)-epicatechin gallate (ECG), (-)-epigallocatechin (EGC), (-)-epigallocatechin gallate (EGCG) and theaflavin (TF) have been reported to possess various biological activities. The present study focused on changes in content of organic acid and tea polyphenols in kombucha tea prepared from green tea (GTK), black tea (BTK) and tea manufacture waste (TWK) during fermentation. Concentration of acetic acid has reached maximum up to 9.5 g/l in GTK on 15th day and glucuronic acid concentration was reached maximum upto 2.3 g/l in BTK on 12th day of fermentation. Very less concentration of lactic acid was observed during the fermentation period and citric acid was detected only on 3rd day of fermentation in GTK and BTK but not in TWK. When compared to BTK and TWK very less degradation of EGCG (18%) and ECG (23%) was observed in GTK. TF and thearubigen (TR) were relatively stable when compared to epicatechin isomers. The biodegradation of tea catechins, TF and TR during kombucha fermentation might be due to some unknown enzymes excreted by yeasts and bacteria in kombucha culture.     

Studies on the sorption of lipids in segmented polyurethanes. II. Effect of hard-segment content

Diffusion and absorption, of a few representative components found in blood, in segmented polyurethane are studied. The absorption of the components, confined to the soft segment, is found to be Fickian. Both diffusion coefficients and equilibrium absorption was found to decrease with % hard-segment content. An empirical equation has been proposed to visualize the absorption behavior with soft/hard-segment content.