Poly(N-vinylpyrrolidone)-stabilized colloidal graphene-reinforced poly(ethylene-co-methyl acrylate) to mitigate electromagnetic radiation pollution

Polymer Bulletin - Electrically conducting flexible polymeric nanocomposite has been fabricated through wet mixing method where conducting inclusion was acoustically exfoliated pristine graphene...     

Fabrication of corrosion resistant, bioactive and antibacterial silver substituted hydroxyapatite/titania composite coating on Cp Ti

The present work is aimed at developing a bioactive, corrosion resistant and anti bacterial nanostructured silver substituted hydroxyapatite/titania (AgHA/TiO₂) composite coating in a single step on commercially pure titanium (Cp Ti) by plasma electrolytic processing (PEP) technique. For this purpose 2.5 wt% silver substituted hydroxyapatite (AgHA) nanoparticles were prepared by microwave processing technique and were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy and transmission electron microscopy (TEM) methods. The as-synthesized AgHA particles with particle length ranging from 60 to 70 nm and width ranging from 15 to 20 nm were used for the subsequent development of coating on Cp Ti. The PEP treated Cp Ti showed both titania and AgHA in its coating and exhibited an improved corrosion resistance in 7.4 pH simulated body fluid (SBF) and 4.5 pH osteoclast bioresorbable conditions compared to untreated Cp Ti. The in vitro bioactivity test conducted under Kokubo SBF conditions indicated an enhanced apatite forming ability of PEP treated Cp Ti surface compared to that of the untreated Cp Ti. The Kirby-Bauer disc diffusion method or antibiotic sensitivity test conducted with the test organisms of Escherichia coli (E. coli) for 24 h showed a significant zone of inhibition for PEP treated Cp Ti compared to untreated Cp Ti.     

Gestational Exposure to Bisphenol A Affects Testicular Morphology,Germ Cell Associations,and Functions of Spermatogonial Stem Cells in Male Offspring

Exposure to bisphenol A (BPA) in the gestational period damages the reproductive health of offspring; detailed evidence regarding BPA-induced damage in testicular germ cells of offspring is still limited. In this study, pregnant mice (F0) were gavaged with three BPA doses (50 μg, 5 mg, and 50 mg/kg body weight (bw)/day; tolerable daily intake (TDI), no-observed-adverse-effect-level (NOAEL), and lowest-observed-adverse-effect level (LOAEL), respectively) on embryonic days 7 to 14, followed by investigation of the transgenerational effects of such exposure in male offspring. We observed that the NOAEL- and LOAEL-exposed F1 offspring had abnormalities in anogenital distance, nipple retention, and pubertal onset (days), together with differences in seminiferous epithelial stages and testis morphology. These effects were eradicated in the next F2 and F3 generations. Moreover, there was an alteration in the ratio of germ cell population and the apoptosis rate in germ cells increased in F1 offspring at the LOAEL dose. However, the total number of spermatogonia remained unchanged. Finally, a reduction in the stemness properties of spermatogonial stem cells in F1 offspring was observed upon LOAEL exposure. Therefore, we provide evidence of BPA-induced disruption of physiology and functions in male germ cells during the gestational period. This may lead to several reproductive health issues and infertility in offspring.     

Thermal properties of field-assisted-sintered SiCN–Y2O3 composites

Polymer-derived amorphous SiCN has excellent high-temperature stability and properties. To reduce the shrinkage during pyrolysis and to improve the high-temperature oxidation resistance, Y₂O₃ was added as a filler. In this study, polymer-derived SiCN–Y₂O₃ composites were fabricated by mixing a polymeric precursor of SiCN with Y₂O₃ submicron powders in different ratios. The mixtures were cross-linked and pyrolyzed in argon. SiCN–Y₂O₃ composites were processed using field-assisted sintering technology at 1350°C for 5 min under vacuum. Dense SiCN–Y₂O₃ composite pellets were successfully made with relative density higher than 98% and homogeneous microstructure. Due to low temperature and short time of the heat-treatment, the grain growth of Y₂O₃ was substantially inhibited. The Y₂O₃ grain size was ∼1 μm after sintering. The composites’ heat capacity, thermal diffusivity, and thermal expansion coefficients were characterized as a function of temperature. The thermal conductivity of the composites ceramics decreased as the amount of amorphous SiCN increased and the coefficient of thermal expansion (CTE) of the composites increased with Y₂O₃ content. However, the thermal conductivity and CTE did not follow the rule of mixture. This is likely due to the partial oxidation of SiCN and the resultant impurity phases such as Y₂SiO₅, Y₂Si₂O₇, and Y_4.67(SiO₄)₃O.     

Model of Vibrio cholerae toxin coregulated pilin capable of filament formation

A complete three-dimensional model (RCSB001169; PDB code 1qqz) for the Vibrio cholerae toxin coregulated pilus protein (TcpA),including residues 1–197, is presented. We have used thecrystal structure of the Neisseria gonorrhoeae pilin (PilE),available biochemical data about TcpA, variations in the primarysequences of TcpA among various Vibrio cholerae strains andsecondary structure prediction, hydrophilicity, surface probabilityand antigenicity plots for TcpA to build our model. In our TcpAmodel, the first 137 residues possess a structure similar tothe PilE, but the remainder is different. Though the ladle shapeis still preserved, TcpA possesses a larger ladle head or globulardomain compared to PilE. Using this model, it has been possibleto identify two kinds of conserved residues: (i) those formingthe core of the TcpA monomer and (ii) those involved in themonomer–monomer interactions leading to fibre formation.Residues on the fibre exterior, important in the mediation ofbacterium (pilus)–bacterium (pilus) and bacterium (pilus)–hostinteractions, show more variability in comparison to those of(i) and (ii).     

Photocatalytic,magnetic, and electrochemical properties of La doped BiFeO3 nanoparticles

We successfully prepared La_1?xBi_xFeO₃ (L_xB_1?xFO, x?=?0.01–0.1) nanoparticles using a sol-gel technique, and studied their photocatalytic, magnetic, and electrochemical properties. Structural refinement studies of the prepared nanoparticles revealed a gradual structural transition from rhombohedral to orthorhombic. The average grain size was observed to decrease with increasing the concentration of La. The photocatalytic degradation of Rhodamine B (RhB) in the presence of the prepared nanoparticles was studied under visible light irradiation. The L_0.06B_0.94FO nanoparticles showed higher degradation efficiency compared to pure BiFeO₃ (BFO) nanoparticles. Magnetic studies showed that La doping improved the magnetization of BFO due to the reduction in grain size and destruction of cycloid coupling of spins. Higher specific capacitance values were obtained for La doped BFO (LBFO) nanoparticles compared to BFO nanoparticles. A maximum specific capacitance of 219?F?g^?1 was obtained at a current density of 1?A?g^?1 for LBFO nanoparticles.     

Simultaneous abatement of diesel soot and NOX emissions by effective catalysts at low temperature: An overview

The diesel engine generally achieves the highest fuel, energy, and thermal efficiency due to its very high compression/expansion ratio (14:1 to 25:1). Diesel engines can have a thermal efficiency that exceeds 50%. The main problem is that they emit more pollution like fine black soot particulates (C₈H to C₁₀H) and nitrogen oxides (NO_X). These pollutants have been causing serious problems for human health and the global environment and also impacts on the engine. There are many types of catalysts investigated for simultaneous control of these two pollutants, i.e., platinum group metals (PGM; Pt, Pd, Rh, and Ir) based, spinel-type oxides, hydrotalcite, rare earth metal oxides, mixed transient metal oxides, etc. The high raw material cost of PGM catalysts has become a significant issue, so developing non-PGM catalysts are one of the promising challenges. There are no extra reductants required because soot catalytically oxidizes itself in the presence of NO_X at a faster rate than molecular oxygen and simultaneously NO_X is reduced to nitrogen. The order of oxidation potential of NO_X to oxidized soot in comparison to molecular oxygen is as follows: NO₂ > NO > O₂. To meet the very strict EPA US 2010 and Euro VI regulations of particulate matter (PM) and NO_X for heavy-duty and light-duty vehicular stringent emission, it is very important to apply the integrated catalytic systems to significantly remove PM and NO_X simultaneously. Many papers related to simultaneous control of soot and NO_X over different catalysts have been published but till now some of effective catalysts showing high conversion at low temperatures (possibly within the range typical of diesel exhaust: 150–450°C) have not been reviewed. Thus, this article provides a summary of published information regarding the effective catalysts, their preparation methods, properties, and application for simultaneous control of diesel soot and NO_X.     

Loading rate sensitivity of liquid nitrogen conditioned glass fiber reinforced polymeric composites: An emphasis on tensile and thermal responses

Glass fiber reinforced polymeric (GFRP) composites are being accepted as potential materials for ultra‐low temperature applications. The current investigation is to evaluate effect of liquid nitrogen (LN₂) conditioning (for different intervals of time) on the loading rate sensitivity of tensile response of GFRP composites. In order to assess this, tensile tests of the unconditioned and conditioned specimens were carried out at different crosshead speeds viz. 1, 10, 100, 500, and 1000 mm/min. At 1 mm/min crosshead speed, an improvement of 3.33% and 7.3% ultimate tensile strength (UTS) value was observed in case of 0.25 and 1 h conditioned GFRP composites, respectively, as compared to unconditioned GFRP composites. Similarly, the specimens tested at 1000 mm/min show an improvement of 11.39% and 12.02% UTS for 0.25 and 1 h LN₂ conditioned GFRP composites, respectively, as compared to unconditioned GFRP composites. Effect of LN₂ conditioning on crosshead speed sensitivity of modulus and strain at break are also reported. The in‐service temperature of the GFRP composite was measured using temperature modulated differential scanning calorimetry. Furthermore, dynamic mechanical thermal analyzer was used in the temperature range (40–200 °C) to correlate the mechanical and thermomechanical response of the GFRP composites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45856.     

Novel method for preparation of carboxylated nitrile rubber–natural rubber blends using bis(diisopropyl)thiophosphoryl polysulfides

Bis(diisopropyl)thiophosphoryl trisulfide (DIPTRI) and bis(diisopropyl)thiophosphoryl tetrasulfide (DIPTET) are successfully used as a novel coupling agent and accelerator, respectively, to covulcanize an elastomer blend comprising polar carboxylated nitrile rubber (XNBR) and nonpolar natural rubber (NR). These compounds are capable of forming a chemical link between these dissimilar rubbers to produce a technologically compatible blend as judged by a swelling experiment. The blend vulcanizates thus produced exhibit enhanced physical properties that can further be improved by adopting the two‐stage vulcanization technique and also by judicious selection of the NR:XNBR ratio. The blend morphology assessed by scanning electron microcroscopy micrographs accounts for significant improvement in the physical properties of the blend vulcanizates, particularly in two‐stage vulcanization. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1725–1736, 2001     

Phase Evolution,Magnetic, Optical,and Dielectric Properties of Zr‐Substituted Bi0.9Gd0.1FeO3 Multiferroics

Polycrystalline BiFeO₃ (BFO) and Bi_0.90Gd_0.10Fe_1?xZr_xO₃ (x = 0.0–0.10; BGFZ_x) ceramics were synthesized by solid‐state reaction method. Rietveld analysis of X‐ray diffraction patterns showed that BFO and BGFZ_x = 0.0 samples are stabilized in rhombohedral structure (space group R3c), whereas a small fraction of orthorhombic phase (space group Pn2₁a) is observed for BGFZ_{x = 0.03–0.10} samples. Suppression and disappearance of some Raman modes indicated a structural phase transition with addition of Zr dopant at Fe site. Magnetic measurements exhibited weak ferromagnetic behavior of BGFZ_x samples with increasing Zr⁺⁴ concentrations. The insertion of Gd⁺³ ions at Bi⁺³ sites and nonmagnetic Zr⁺⁴ ions at Fe⁺³ sites in Fe–O–Fe network suppressed the spin cycloid structure of BFO which in turn enhanced the magnetization of these ceramics. Electron spin resonance spectra revealed the breaking of spin cycloid of BFO due to the development of free spins with addition of Zr⁺⁴ dopants at Fe sites. UV–Visible diffuse reflectance spectra showed one d–d crystal field transition and two charge‐transfer (C–T) transitions along with a sharp absorption of light in visible region for all samples. Almost frequency‐independent dielectric constant and dielectric loss along with very low values of dielectric loss indicated greatly improved dielectric properties for BGFZ_{x = 0.03–0.10} samples.