Mean residence time of gas in mechanically agitated gas–liquid contactors

In the present study of gas–liquid contactors, mean residence/contact time was calculated from knowledge of superficial velocity and the gas phase hold-up, for various gas rates and impeller geometry and speeds, and compared with values obtained from RTD measurements. A new correlation, involving Flow Number, Froude Number, system geometry and the physical properties, is proposed. This uses the authors data and those available in literature.     

Grafting vinyl monomers onto silk fibers: Graft copolymerization of methyl methacrylate onto silk using acetylacetonate Mn(III) complex

The graft copolymerization of methyl methacrylate onto Mulberry silk fibers was studied in aqueous solution using Mn(acac)₃ as initiator. Perchloric acid was found to catalyze the reaction. The rate of grafting was investigated by varying the concentration of the monomer and the complex, acidity of the medium, the solvent composition of the reaction medium, the surfactants, and the inhibitors. The graft yield increases with increasing concentration of Mn(acac)₃ up to 0.01 mol/L, decreasing thereafter. Increase of MMA concentration up to 0.56 mol/L increases graft yield, and thereafter it decreases. Among the various vinyl monomers studied, MMA was found to be most suitable for grafting. Grafting increases up to 7.5 × 10^?3 mol/L of HClO₄ concentration, and thereafter it decreases. A suitable reaction scheme has been proposed and a rate equation has been derived. The energy of activation has been calculated from the Arrhenius plot. The chain transfer constants for various chain transfer solvents have been evaluated from the average molecular weight (M?) of grafted poly(methyl methacrylate).     

Grafting vinyl monomers onto wool fibers: Graft copolymerization of methyl methacrylate onto wool fibers using vanadyl acetyl acetonate complex

The graft copolymerization of methyl methacrylate (MMA) onto native and reduced Indian Chokla wool fibers was studied in aqueous solution using the acetylacetonate oxovanadium (IV) complex. The rate of grafting was investigated by varying the concentration of the monomer and the complex, acidity of the medium, and the solvent composition of the reaction medium. The graft yield increases with increasing concentration of the initiator up to 8.75 × 10^?5 mol/L, of the monomer up to 0.5634 mol/L, and thereafter it decreases. MMA was found to be the most active monomer when compared to other vinyl monomers. Grafting increases with increasing concentration of HClO₄ and with increasing temperature. Reduced and oxidized wools were found to be better substrates than untreated, esterified, crosslinked, and trinitrophenylated wools. The extent of grafting was mostly dependent upon the concentration of ? SH groups in case of reduced wool. A suitable reaction scheme has been proposed and the activation energy was calculated from Arrhenius plot.     

Moisture diffusion through (hexadecyltrimethylammonium bromide ‐ Indian bentonite)/(vinylester) nanocomposites in artificial seawater and demineralized water

This paper compares the moisture diffusion properties of organomodified (Indian Bentonite nanoclay)/vinylester containing different amounts of nanoclay on exposure to demineralized water and artificial seawater at room temperature. Moisture uptake behavior of (Indian Bentonite)/vinylester was investigated and compared with that of neat vinylester. Addition of 5 wt% nanoclay decreased the diffusivity and permeability of vinylester in artificial seawater medium, but these diffusion parameters increased in demineralized water medium. Degradation in glass transition temperature and microhardness of the nanocomposites were much greater in specimens aged in demineralized water than in those in artificial seawater medium. Moisture diffusion behavior of the specimens was analyzed by Fick's law and the Langmuir model. The aged specimens were chemically analyzed by using infrared spectroscopy after aging for 146 days. A significant amount of leached organic species was detected in the demineralized water–aged specimens but the same was absent in those aged in artificial seawater. J. VINYL ADDIT. TECHNOL., 22:441–451, 2016. © 2015 Society of Plastics Engineers     

Synthesis of SiC ceramics from processed cellulosic bio-precursor

Synthesis of SiC ceramic from processed cellulosic bio-precursor was investigated. Bamboo (Bambusa tulda Roxb.) plants abundantly available in the Jorhat district of Assam, India, were selected for extraction of fibers following Kraft pulping method and bleached bamboo pulp fibers were suitably cast in the form of rectangular boards. Coir fibers available in the Alleppy district of Kerala, India, were initially digested with dilute alkali, mixed with cellulose acetate solution, air dried and then hot-pressed at 140 ± 5 °C under 2.0–2.5 MPa pressure to make rectangular boards. Well-characterized processed bio-precursors were pyrolysed at ～800 °C under flowing N₂ atmosphere to prepare the bio-carbonaceous preforms (carbon templates) which showed nearly uniform shrinkages in all directions. Coir fiber composite board carbon showed lower pyrolytic weight loss (～66%), higher density (0.49 g cm^?3), lower porosity (～58%) and narrower pore diameter (10 μm) compared to the cast bamboo pulp fiber board carbon. The carbon samples showed perfect retention of fibrous morphological features of hierarchically grown bio-structures. Ceramization of carbon templates could be done by reactive melt silicon infiltration into porous channels at ～1600 °C under vacuum. The final ceramics were adequately dense (%theoretical density > 99%), showed negligible linear dimensional changes (indicating net-dimension formation capability), presence of crystalline Si and SiC phases and duplex microstructure with complete preservation of fibrous architecture of plant bio-structure. The Si/SiC ceramic composite synthesized from coir fiber board gave room temperature 3-point flexural strength and Young's modulus values of 121 MPa and 276 GPa, respectively. Both the ceramic composites showed adequate oxidation resistance during heating at 1300 °C for 7 h in air.     

Nonlinear radiation on Maxwell fluid in a convective heat transfer with viscous dissipation and activation energy

The present analysis addresses linear and nonlinear radiation effects in hydrodynamic viscous Maxwell fluid flow on a unidirectional stretching surface through viscous dissipation. The relaxation effect is considered in the mathematical model, which elucidates mass transport mechanisms under binary chemical reaction and activation energy. Mathematical modeling contains nonlinear partial differential equations using boundary conditions. Appropriate transformations convert the partial differential equations into ordinary differential equations. Numerical solutions for regular differential equations are brought by Runge–Kutta–Fehlberg numerical quadrature and a shooting method with a tolerance level of 10⁻⁹. The influence of physical variables, such as Deborah relaxation number, rotation parameter, Biot number, activation energy parameter, reaction rate parameter, Eckert number, and Prandtl number are investigated. Increasing the Biot number improves the temperature region in the boundary layer. With high rotation, the increasing Deborah number enhances the fluid temperature substantially throughout the boundary layer.     

Estimating regularity in epileptic seizure time-series data

The authors apply Ziv-Lempel (LZ) complexity and approximate entropy (ApEn) as measures to quantify the regularity in the various epochs of epileptic seizure time series data. They demonstrate the potential of complexity measures such as LZ and ApEn in quantifying the regularity at different epochs of epileptic seizure time-series data. It is clearly shown that these measures have high values at the beginning and the end of the seizure, and that they decrease during mid-seizure. In fact, the authors observe in the histogram plot that the frequency of the complexity measure in mid-seizure is quite prominent. This gives one an idea about the epoch where one can find more regular patterns. These measures can also be used as relative indices (comparing across state), rather than absolute indices, by using a larger number of subjects to obtain statistical validity in comparing across conditions. The analysis of time series obtained from complex systems, such as the brain, by the above measures provides an alternative easy way to quantify the regularity with finite-length segments (of the order of 1000 samples). The same can be inferred by calculating the correlation dimension and Lyapunov exponent, but the algorithms used to estimate these invariants are susceptible to error due to the finite sample size and are also highly sensitive to noise. The computational complexity of these algorithms is also high. The authors have also applied these measures across the various states of epilepsy     

In Vitro Selection of a Single-Stranded DNA Molecular Recognition Element against Atrazine

Widespread use of the chlorotriazine herbicide, atrazine, has led to serious environmental and human health consequences. Current methods of detecting atrazine contamination are neither rapid nor cost-effective. In this work, atrazine-specific single-stranded DNA (ssDNA) molecular recognition elements (MRE) were isolated. We utilized a stringent Systematic Evolution of Ligands by Exponential Enrichment (SELEX) methodology that placed the greatest emphasis on what the MRE should not bind to. After twelve rounds of SELEX, an atrazine-specific MRE with high affinity was obtained. The equilibrium dissociation constant (K_d) of the ssDNA sequence is 0.62 ± 0.21 nM. It also has significant selectivity for atrazine over atrazine metabolites and other pesticides found in environmentally similar locations and concentrations. Furthermore, we have detected environmentally relevant atrazine concentrations in river water using this MRE. The strong affinity and selectivity of the selected atrazine-specific ssDNA validated the stringent SELEX methodology and identified a MRE that will be useful for rapid atrazine detection in environmental samples.     

Synthesis of 18-octadecanolide,a major constituent of dufour’s gland secretion ofColletes bees

18-Octadecanolide, a major constituent of Dufour’s gland secretion ofColletes bees, was synthesized by polymerization followed by depolymerization of 18-hydroxyoctadecanoic acid which in turn was obtained by hydrogenation of kamlolenic acid (18-hydroxy, 9-cis, 11-trans, 13-trans-octadecatrienoic acid) isolated fromMallotus philippinensis seed oil. The structures of the intermediates as well as the final lactone were established by infrared, proton nuclear magnetic resonance and mass spectrometric methods.     

Removal of 1,4-Dioxane and Volatile Organic Compounds from Groundwater Using Ozone-Based Advanced Oxidation Process

Ozone and ozone/peroxide processes were evaluated for the removal of 1,4-dioxane from laboratory water and site groundwater. The effect of process parameters such as solution pH and dosage of peroxide was studied. Ozone alone was not very effective in removing 1,4-dioxane from water (≤ 20% removal). Enhanced oxidation of 1,4-dioxane was achieved by increasing the solution pH or by adding peroxide at neutral pH. Pseudo–first-order rate constants were calculated for the removal of 1,4-dioxane using ozone. Correlations were developed for the consumption of ozone per 1,4-dioxane removed. Acidic and neutral pH conditions resulted in higher consumption of ozone per dioxane removed. Basic solution pH and presence of hydrogen peroxide enhanced the dioxane removal, which resulted in lower consumption of ozone per dioxane removed. Following the lab study, ozonation was used for the remediation of site groundwater contaminated with 1,4-dioxane and chlorinated volatile organics. Presence of 5 mg/L of hydrogen peroxide during ozonation resulted in simultaneous removal of 1,4-dioxane and volatile organics from groundwater to target levels. For the AOP process, removal kinetics was approximately 50% slower in groundwater compared to the lab DI water.