Water‐dispersible nanocomposites of polyaniline and montmorillonite

The polymerization of aniline (ANI) in aqueous medium in the presence of (NH₄)₂S₂O₈ and montmorillonite (MMT) resulted in the formation of a nanocomposite (PANI–MMT). The inclusion of PANI in the composite was confirmed by FTIR studies. The extent of PANI loading in the composite increased with ANI concentration at a fixed oxidant/MMT amount and with the oxidant amount at a fixed ANI and MMT weight, but decreased with an MMT amount at a fixed ANI and oxidant level. TGA revealed a higher stability for the PANI–MMT composite relative to PANI and confirmed a PANI loading of ca. 51% in the composite. The conductivity increased in all the cases. XRD analysis revealed no expansion of the d₀₀₁ spacing at 9.8 Å, implying no intercalation of PANI within the MMT layers. Scanning electron micrography studies revealed interesting morphological features for the composites. Transmission electron micrography analysis revealed distinctive features and confirmed the formation of PANI–MMT composite particles of diameters in the 300‐ to 400‐nm range. These composites could be obtained as stable colloids in the presence of poly (N‐vinyl pyrrolidone) under selective conditions. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2948–2956, 2000     

Effect of organized anionic surfactant system on the kinetics of V(V)-organic substrate-initiated polymerization of acrylonitrile

The kinetics of polymerization of acyrlonitrile (AN) initiated by a V(V)-cyclohexanone redox system in the presence of a surfactant was studied over a temperature range of 30–50°C in acidic medium. The anionic surfactant sodium dodecyl sulfate (SDS) enhances the rate of polymerization (R_p) as well as rate of V(V) consumption (−R_v). The cationic surfactant, cetyltrimethylammonium bromide (CTAB), decreases both R_p and −R_v, while the nonionic surfactant, Triton-X-100, has no effect on the rate. The change of concentration of the surfactant, monomer, acid, and cosolvent on the rate of polymerization were examined. Both R_p and −R_v are computed in the presence of different organic substrates, i.e., cyclohexanone, cyclopentanone, glycerol, and citric acid. The viscosity-average molecular weight (M_v) of the polycrylonitrile, obtained at different [SDS], was determined using the Mark-Howink relationship. A suitable mechanistic scheme was proposed for the process. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1825–1833, 1997     

Comprehensive Identification of Deleterious TP53 Missense VUS Variants Based on Their Impact on TP53 Structural Stability

TP53 plays critical roles in maintaining genome stability. Deleterious genetic variants damage the function of TP53, causing genome instability and increased cancer risk. Of the large quantity of genetic variants identified in TP53, however, many remain functionally unclassified as variants of unknown significance (VUS) due to the lack of evidence. This is reflected by the presence of 749 (42%) VUS of the 1785 germline variants collected in the ClinVar database. In this study, we addressed the deleteriousness of TP53 missense VUS. Utilizing the protein structure-based Ramachandran Plot-Molecular Dynamics Simulation (RPMDS) method that we developed, we measured the effects of missense VUS on TP53 structural stability. Of the 340 missense VUS tested, we observed deleterious evidence for 193 VUS, as reflected by the TP53 structural changes caused by the VUS-substituted residues. We compared the results from RPMDS with those from other in silico methods and observed higher specificity of RPMDS in classification of TP53 missense VUS than these methods. Data from our current study address a long-standing challenge in classifying the missense VUS in TP53, one of the most important tumor suppressor genes.     

Modeling of the Oxygen Transfer Characteristics of a ‘See‐Saw’ Bioreactor

Animal cell line culture is difficult in the existing conventional bioreactors. A substantial amount of animal cells are destroyed by the impinging fan blades or entrapment inside the bubbles. An endeavor has been made to design and develop a new type of bioreactor suitable for animal cell culture. The bioreactor is named a ‘see‐saw’ bioreactor from its underlying principle of operation. In this paper, the oxygen transfer characteristics of the ‘see‐saw’ bioreactor are modeled and tried to be verified.     

Ceramic Filter for Small System Drinking Water Treatment: Evaluation of Membrane Pore Size and Importance of Integrity Monitoring

Ceramic filtration has recently been identified as a promising technology for drinking water treatment in households and small communities. This paper summarizes the results of a pilot-scale study conducted at the U.S. Environmental Protection Agency’s (EPA) Test & Evaluation (T&E) Facility in Cincinnati on two ceramic filtration cartridges with pore sizes of 0.05 and 0.01?μm to evaluate their ability to remove turbidity and microbiological contaminants such as bacteria [Bacillus subtilis ( ≈ 1.0?μm) and Escherichia coli ( ≈ 1.4?μm)], Cryptosporidium oocysts (4–6?μm), polystyrene latex (PSL) beads (2.85?μm) (a surrogate for Cryptosporidium), and MS2 bacteriophage ( ≈ 0.02?μm) (a surrogate for enteric viruses). The results demonstrated that the relatively tighter 0.01-μm cartridge performed better than the 0.05-μm cartridge in removing all the biological contaminants and surrogates. For turbidity removal, the 0.01-μm cartridge performed slightly better than the 0.05-μm cartridge; however, the permeate rate in the 0.01-μm cartridge reduced rapidly at higher feed water turbidity levels indicating that a tighter membrane should only be used with adequate pretreatment or at a low feed water turbidity to prolong membrane life. Microbiological monitoring was identified as a more sensitive indirect integrity monitoring method than turbidity and particle count monitoring to ensure effective treatment of water by ceramic filtration. Both PSL beads and B. subtilis showed potential as effective surrogates for Cryptosporidium, with B. subtilis showing higher degree of conservatism. Any opinions expressed in this article are those of the writer(s) and do not necessarily reflect the official positions and policies of the EPA. Any mention of products or trade names does not constitute recommendation for use by EPA. This document has been reviewed in accordance with EPA’s peer and administrative review policies and approved for publication.     

Strategic Estimation of Kinetic Parameters in VGO Cracking

Fluid catalytic cracking (FCC) unit plays most important role in the economy of a modern refinery that it is use for value addition to the refinery products. Because of the importance of FCC unit in refining, considerable effort has been done by scientists till now on the modelling of this unit for better understanding and improved productivity. To model a FCC unit we have to know the unknown kinetic parameters of the governing equations.
The basic aim of this paper is to prove that MATLAB^TM can be used as a tool to find unknown kinetic parameters of governing equations for VGO cracking. We have developed a strategic method to find the unknown kinetic parameters using MATLAB and compare the simulation results with the results obtained from methods available in literature and it was found to be the best agreement.     

Weibull modulus of nano-hardness and elastic modulus of hydroxyapatite coating

Here we report the microstructural dependence of nano-hardness (H) and elastic modulus (E) of microplasma sprayed (MIPS) 230 μm thick highly porous, heterogeneous hydroxyapatite (HAP) coating on SS316L. The nano-hardness and Young’s modulus data were measured on polished plan section (PS) of the coating by the nanoindentation technique with a Berkovich indenter. The characteristic values of nano-hardness and Young’s modulus were calculated through the application of Weibull statistics. Both nano-hardness and the Young’s modulus data showed an apparent indentation size effect. In addition, there was an increasing trend of Weibull moduli values for both the nano-hardness and the Young’s modulus data of the MIPS-HAP coating as the indentation load was enhanced from 10 to 1,000 mN. An attempt was made in the present work, to provide a qualitative model that can explain such behavior.     

Magnetic properties of (Fe)1−x–(Al2O3)x and (Fe50Ni50)1−x–(Al2O3)x nanocomposite magnetic media synthesized using gel like Al2O3 matrix

Composites with ferromagnetic nanoparticles, Fe and Fe₅₀Ni₅₀, dispersed in Al₂O₃ have been synthesized by a solution phase technique. The structure and magnetic properties of these composites with varying fractions of Al₂O₃ have been investigated. Both Fe and Fe₅₀Ni₅₀ nanoparticles are amorphous in the as-prepared state and become crystalline on heat treating with near equilibrium lattice parameters of 0.287 nm and 0.358 nm respectively. The interparticle distance increases with increasing Al₂O₃ from 0 wt.% to 20 wt.%. The size of Fe nanoparticles is 40 nm while the Fe₅₀Ni₅₀ nanoparticles are 20 nm in size. The Fe and Fe₅₀Ni₅₀ nanoparticles dispersed composites are found to be ferromagnetic at room temperature both in the as-prepared and heat treated conditions with clear coercive fields of 5.5–35 × 10³ A m⁻¹. The saturation magnetization increases by orders of magnitude on heat treatment, for e.g. from <1.0 emu g⁻¹ to 143.4 emu g⁻¹ for Fe–15 wt.% Al₂O₃ and 95.6 emu g⁻¹ for Fe₅₀Ni₅₀–15 wt.% Al₂O₃. The Fe-composites exhibit a Curie transition at 1000 K while the Fe₅₀Ni₅₀ composites exhibit a transition at 880 K, both temperatures close to bulk values.     

Interaction of 2,4,6-trichlorophenol with high carbon iron filings: Reaction and sorption mechanisms

Reductive dehalogenation of 2,4,6-trichlorophenol (2,4,6-TCP) by two types of high carbon iron filings (HCIF), HCIF-1 and HCIF-2 was studied in batch reactors. While the iron, copper, manganese and carbon content of the two types of HCIF was similar, the specific surface area of HCIF-1 and HCIF-2 were 1.944 and 3.418m(2)g(-1), respectively. During interaction with HCIF-1, 2,4,6-TCP adsorbed on HCIF-1 surface resulting in rapid reduction of aqueous phase 2,4,6-TCP concentration. However, reductive dehalogenation of 2,4,6-TCP was negligible. During interaction between 2,4,6-TCP and HCIF-2, both 2,4,6-TCP adsorption on HCIF-2, and 2,4,6,-TCP dechlorination was observed. 2,4,6-TCP partitioning between solid and aqueous phase could be described by a Freundlich isotherm, while 2,4,6-TCP dechlorination could be described by an appropriate rate expression. A mathematical model was developed for describing the overall interaction of 2,4,6-TCP with HCIF-2, incorporating simultaneous adsorption/desorption and dechlorination reactions of 2,4,6-TCP with the HCIF surface. 2,4-Dichlorophenol (2,4-DCP), 2-chlorophenol (2-CP) and minor amounts of 4-chlorophenol (4-CP) evolved as 2,4,6-TCP dechlorination by-products. The evolved 2,4-DCP partitioned strongly to the HCIF surface. 4-CP and 2-CP accumulated in the aqueous phase. No transformation of 2-CP or 4-CP to phenol was observed.