Alkaline hydrolysis of methyl acrylate grafted cellulose fibers

In this work, methyl acrylate grafted cellulose fibers were hydrolyzed in an aqueous NaOH solution to obtain a superabsorbent hydrogel. The effect of process variables, such as the hydrolysis reaction time, temperature, and NaOH concentration, during alkaline hydrolysis were carefully determined and optimized. The degree of hydrolysis was estimated on the basis of the determination of the carboxylate group contents. The material loss during hydrolysis followed a first‐order reaction mechanism. The differences in the behavior of the grafted fibers during hydrolysis could be explained by their structural differences. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

TecoflexTM functionalization by curdlan and its effect on protein adsorption and bacterial and tissue cell adhesion

Curdlan modified polyurethane was created by physically entrapping the former on TecoflexTM surface. ATR-FT-IR, SEM-EDAX and AFM analysis revealed the formation of stable thin curdlan layer on the film. Contact-angle measurements showed that the modified film was highly hydrophilic. Confocal laser scanning microscopy showed the existence of entrapped layer of approximately 20–25 μm in depth. Surface entrapment of curdlan minimized both protein adsorption and mouse L929 fibroblast cell adhesion relative to the control. Surface induced cellular inflammatory response was determined from the expression levels of proinflammatory cytokine TNF-α, by measuring their mRNA profiles in the cells using real time polymerase chain reaction (RT-PCR) normalized to the housekeeping gene GAPDH. The inflammatory response was suppressed on the modified substrate as expression of TNF-α mRNA was found to be up regulated on TecoflexTM, while it was significantly lower on curdlan substrate. The adhesion of S. aureus decreased by 62% on curdlan modified surface. Using such simple surface entrapment process, it will be possible to develop well-defined surface modifications that promote specific cell interactions and perhaps better performance in the long-term as implant.     

Mannosylated solid lipid nanoparticles for lung-targeted delivery of Paclitaxel

Objective: The present study discusses paclitaxel (PTX)-loaded mannosylated-DSPE (Distearoyl-phosphatidyl-ethanolamine) solid lipid nanoparticles (M-SLNs) using mannose as a lectin receptor ligand conjugate for lung cancer targeting and to increase the anticancer activity of PTX against A549 lung’s epithelial cancer cells.

Materials and methods: The PTX-SLNs were prepared by solvent injection method and mannose was conjugated to the free amine group of stearylamine. The M-SLNs obtained were characterized for their particle size, polydispersity index, zeta potential and morphology by transmission electron microscope.

Results: The M-SLNs were spherical in shape with 254?±?2.3?nm average size, positive zeta potential (3.27?mV), 79.4?±?1.6 drug entrapment efficiency and showed the lower extent of drug release 40% over 48?h in vitro. Cytotoxicity study on A549 cell lines and biodistrubtion study of drug revealed that M-SLNs deliver a higher concentration of PTX as compared to PTX-SLNs in an alveolar cell site.

Discussion and conclusion: These results suggested that mannosylated M-SLNs are safe and potential vector for lung cancer targeting.     

Mineral composition of edible seaweed Porphyra vietnamensis

Edible seaweed Porphyra vietnamensis growing along seven different localities of the Central West Coast of India was analyzed for mineral composition (Na, K, Ca, Mg, B, Pb, Cr, Co, Fe, Zn, Mn, Hg, Cu, As, Ni, Cd and Mo) by inductively coupled plasma atomic emission spectroscopy (ICP-AES). The concentration ranges found for each sample, were as follows: Na, 24.5–65.6; K, 1.76–3.19, Ca, 1.40–6.12; Mg, 4.0–5.90 (mg/g d wt); Pb, 0.01–0.15; Cr, 0.13–0.22; Co, 0.06–0.20; Fe, 33.0–298; Zn, 0.93–3.27; Mn, 4.22–10.00; Hg, 0.01–0.04; Cu, 0.54–1.05; As, 1.24–1.83; Ni, 0.02–0.25; Cd, 0.14–0.55; Mo, 0.02–0.03 and B, 0.02–0.07 expressed in mg/100 g dry weight. Mineral composition of P. vietnamensis was found relatively higher as compared to the land vegetables as well as to other edible seaweeds, and it is in concurrence with the recent macrobiotic recommendation for western countries. It could therefore be used as food supplement as a spice to improve the nutritive value in the omnivorous diet.     

Silica-silicon composites for near-infrared reflection: A comprehensive computational and experimental study

Compact layers containing embedded semiconductor particles consolidated using pulsed electric current sintering exhibit intense, broadband near-infrared reflectance. The composites consolidated from nano- or micro-silica powder have a different porous microstructure which causes scattering at the air-matrix interface and larger reflectance primarily in the visible region. The 3 mm thick composite compacts reflect up to 72% of the incident radiation in the near-infrared region with a semiconductor microinclusion volume fraction of 1% which closely matches predictions from multiscale Monte Carlo modeling and Kubelka-Munk theory. Further, the calculated spectra predict a reddish tan compact with improved reflectance can be obtained by decreasing the average particle size or broadening the standard deviation. The high reflectance is achieved with minimal dissipative losses and facile manufacturing, and the composites described herein are well-suited to control the radiative transfer of heat in devices at high temperature and under harsh conditions.     

Investigation of reverse flow distributed combustion for gas turbine application

In this paper reverse flow modes of colorless distributed combustion (CDC) have been investigated for application to gas turbine combustors. Rapid mixing between the injected fuel and hot oxidizer has been carefully explored for spontaneous ignition of the mixture to achieve distributed combustion reactions. Distributed reactions can be achieved in premixed, partially premixed or non-premixed modes of combustor operation with sufficient entrainment of burned gases and faster turbulent mixing between the reactants. In the present investigation reverse flow modes consisting of three configurations at thermal intensity of 28 MW/m³-atm and five configurations at thermal intensity of 57 MW/m³-atm have been investigated and these high thermal loadings represent characteristic gas turbine combustion conditions. In all the configurations the air injection port is positioned at the combustor exit end, whereas the location of fuel injection ports is changed to give different configurations. The results are presented on the exhaust emissions and radical emissions using experiments, and evaluation of flowfield using numerical simulations. Ultra-low NO_x emissions were found for both the premixed and non-premixed combustion modes investigated here. Cross-flow configuration, wherein the fuel is injected at high velocity cross stream to the air jet resulted in characteristics closest to premixed combustion mode. Change in fuel injection location resulted in changing the combustion characteristics from closer to diffusion mode to distributed regime. This feature is beneficial for part load operation where higher stability limit is desirable.     

Hydrogen addition effects on methane-air colorless distributed combustion flames

In this investigation the role of hydrogen addition in a reverse flow configuration, consisting of both non-premixed and premixed combustion modes, have been examined for the CDC flames. In the non-premixed configuration the air injection port is positioned at combustor exit end while the fuel injection port is positioned on the side so that the fuel is injected in cross-flow with respect to air injection. The thermal intensity of the flames investigated is 85 MW/m³ atm to simulate high thermal intensity gas turbine combustion conditions. The results are presented on the global flame signatures, exhaust emissions, and radical emissions using experiments and flowfield using numerical simulations. Ultra low NO_x emissions are found for both the premixed and non-premixed combustion modes. Addition of hydrogen to methane fuel resulted in only a slight increase of NO emission, significant decrease of CO emission and extended the lean operational limit of the combustor.     

Investigation of forward flow distributed combustion for gas turbine application

New innovative advanced combustion design methodology for gas turbine applications is presented that is focused on the quest towards zero emissions. The new design methodology is called colorless distributed combustion (CDC) and is significantly different from the currently used methodology. In this paper forward flow modes of CDC have been investigated for application to gas turbine combustors. The CDC provides significant improvement in pattern factor, reduced NO_x emission and uniform thermal field in the entire combustion zone for it to be called as an isothermal reactor. Basic requirement for CDC is carefully tailored mixture preparation through good mixing between the combustion air and product gases prior to rapid mixing with fuel so that the reactants are at much higher temperature to result in hot and diluted oxidant stream at temperatures that are high enough to autoignite the fuel and oxidant mixture. With desirable conditions one can achieve spontaneous ignition of the fuel with distributed combustion reactions. Distributed reactions can also be achieved in premixed mode of operation with sufficient entrainment of burned gases and faster turbulent mixing between the reactants. In the present investigation forward flow modes consisting of two non-premixed combustion modes and one premixed combustion mode have been examined that provide potential for CDC. In all the configurations the air injection port is positioned at the opposite side of the combustor exit, whereas the location of fuel injection ports is changed to give different configurations. Two combustion geometries resulting in thermal intensity of 5 MW/m³-atm and 28 MW/m³-atm are investigated. Increase in thermal intensity (lower combustion volume) presents many challenges, such as, lower residence time, lower recirculation of gases and effect of confinement on jet characteristics. The results are presented on the global flame signatures, exhaust emissions, and radical emissions using experiments and flowfield using numerical simulations. Ultra-low NO_x emissions are found for both the premixed and non-premixed combustion modes at the two thermal intensities investigated here. Almost colorless flames (no visible flame signatures) have been observed for the premixed combustion mode. The reaction zone is observed to be significantly different in the two non-premixed modes. Higher thermal intensity case resulted in lower recirculation of gases within the combustion chamber and higher CO levels, possibly due to lower associated residence time. The characteristics at the two thermal intensity combustors investigated here were found to be similar.     

Effect of salinity on the IFT between aqueous surfactant solution and crude oil

The effect of salts and different surfactants on the equilibrium as well as dynamic interfacial tension (DIFT) between crude oil and water was investigated. Three different types of surfactants with identical hydrophobic chain length C₁₂: Sodium Lauryl Ether Sulphate (SLES), Dodecyl Trimethyl Ammonium Bromide (DTAB), Polyoxyethylene (23) lauryl ether (C₁₂E₂₃) were used in this study. SLES shows better synergism of salt and surfactant mixture amongst the surfactants studied. The order of synergism of salts with the surfactant observed was MgCl₂>CaCl₂> NaCl. The results obtained from partition coefficient study show that the addition of salts favours the partition of surfactants into the oil phase hence reduce IFT more effectively. DIFT results reveal that, salt accelerates the surfactant migration towards the interface, hence, reducing the t^* value.