Synthesis of an alkali‐swellable emulsion and its effect on the rate of polymer diffusion in poly(vinyl acetate‐butyl acrylate) latex films

We describe the synthesis and characterization of a weakly cross‐linked poly(methacrylic acid‐co‐ethyl acrylate) alkali‐swellable emulsion (ASE), as well as an investigation of its influence on the rate of polymer diffusion in latex films. The films examined were formed from poly(vinyl acetate‐co‐butyl acrylate) latex particles containing a small amount of acrylic acid as a comonomer. Polymer diffusion rates were monitored by the energy transfer technique. We found that the presence of the ASE component, either in the acid form or fully neutralized by ammonia or sodium hydroxide, had very little effect on the polymer diffusion rate. However, in the presence of 2 wt % NH₄‐ASE, there was a small but significant increase in the polymer diffusion rate. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5632–5642, 2005     

Measurement of mixing time and holdup of solids in gas–solid fluidized bed using radiotracer technique

Mixing times and holdup of solids were measured in a gas–solid fluidized bed using radiotracer technique. Sand and air were used as solid and gas phase, respectively in the fluidized bed. Gold-198 labeled sand particles were used as radiotracer for mixing time measurement at different operating conditions and ¹³⁷Cs sealed source was used for holdup measurement at different axial and radial positions. The experiments were conducted at different operating conditions. The measured mixing times ranged from 1.4 to 21 s at different conditions. It was observed that at a particular bed height, the mixing time initially decreases with increasing gas velocity and tend to become constant at higher gas velocities. However, mixing time increases with increasing bed height. The holdup fraction of solid was found to be more towards the wall compared to the centre of the column. The study provided inputs to improve the existing design, design of a new system and scale-up of the process.     

Non-conventional Hydrogen Bonding and Aromaticity: A Systematic Study on Model Nucleobases and Their Solvated Clusters

The conceptual development of aromaticity is essential to rationalize and understand the structure and behavior of aromatic heterocycles. This work addresses for the first time, the interconnection between aromaticity and sulfur/selenium centered hydrogen bonds (S/SeCHBs) involved in representative heterocycle models of canonical nucleobases (2-Pyridone; 2PY) and its sulfur (2-Thiopyridone; 2TPY) and selenium (2-Selenopyridone; 2SePY) analogs. The nucleus-independent chemical shift (NICS) and gauge induced magnetic current density (GIMIC) values suggested significant reduction of aromaticity upon replacement of exocyclic carbonyl oxygen with sulfur and selenium. However, we observed two-fold (57 %) and three-fold (80 %) enhancement in the aromaticity for 2TPY dimer, and 2SePY dimer, respectively which are connected through S/SeCHBs. Aromaticity enhancement was also noticed in 1 : 1 H-bonded complexes (heterodimers), micro hydrated clusters and for bulk hydration. It is expected that exocyclic S and Se incorporation into heterocycles without compromising aromatic loss would definitely reinforce to design new supramolecular building blocks via S/SeCH-bonded complexes.     

Comparison of APPI, APCI and ESI for the LC-MS/MS analysis of bezafibrate, cyclophosphamide, enalapril, methotrexate and orlistat in municipal wastewater

The applicability of three different ionization techniques: atmospheric pressure photoionization (APPI), atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) was tested for the liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis of five target pharmaceuticals (cyclophosphamide, methotrexate, bezafibrate, enalapril and orlistat) in wastewater samples. Performance was compared both by flow injection analysis (FIA) and on-column analysis in deionized water and wastewater samples. A column switching technique for the on-line extraction and analysis of water samples was used. For both FIA and on-column analysis, signal intensity and signal-to-noise (S/N) ratio of the target analytes in the three sources were studied. Limits of detection and matrix effects during the analysis of wastewater samples were also investigated. ESI generated significantly larger peak areas and higher S/N ratios than APCI and APPI in FIA and in on-column analysis. ESI was proved to be the most suitable ionization method as it enabled the detection of the five target compounds, whereas APCI and APPI ionized only four compounds.     

Structure of the indole-benzene dimer revisited

The structure of the indole-benzene dimer has been investigated using experimental techniques, namely, UV spectroscopy and infrared-ultraviolet (IR/UV) double resonance spectroscopy, combined with quantum chemical calculations such as MP2 and dispersion corrected DFT methods. The red shift of the indole N-H stretch frequency in the dimer provides direct evidence that the experimentally observed indole-benzene dimer is an N-H···π bound hydrogen bonded complex. Theoretical investigations suggest that the potential energy surface (PES) of the complex is rather flat along the coordinate describing the tilt angle between the molecular planes of indole and benzene, with several minima of similar energies, namely, parallel displaced (PD), right-angle T-shaped (T), and other intermediate structures which can be categorized as tilted T-shaped (T') and tilted parallel displaced (PD') structures. Three different computational methods, namely, RI-MP2, RI-B97-D, and PBE1-DCP, are used to arrive at a new structural assignment after assessing their performance in predicting the structure of the pyrrole dimer, for which accurate experimental data are available. By comparing the computed IR spectra of PD, T, and T'/PD' structures with the experimental IR spectrum, the tilted T-shaped (T') structure was assigned to the indole-benzene dimer. The empirically dispersion-corrected functionals (RI-B97-D and PBE1-DCP) correctly reproduce the experimental IR spectrum whereas the popular post-Hartree-Fock, MP2 method gives disappointing results. These results are also in agreement with the experimental dissociation energy (D(0)) reported in the literature. The N-H stretch frequency of the indole-benzene dimer has been found to be a more pertinent parameter for the structural assignment than the dissociation energy (D(0)).     

Axial thermal rotation of slender rods

Axial rotational diffusion of rodlike polymers is important in processes such as microtubule filament sliding and flagella beating. By imaging the motion of small kinks along the backbone of chains of DNA-linked colloids, we produce a direct and systematic measurement of axial rotational diffusivity of rods both in bulk solution and near a wall. The measured diffusivities decrease linearly with the chain length, irrespective of the distance from a wall, in agreement with slender-body hydrodynamics theory. Moreover, the presence of small kinks does not affect the chain's axial diffusivity. Our system and measurements provide insights into fundamental axial diffusion processes of slender objects, which encompass a wide range of entities including biological filaments and linear polymer chains.     

Degradation of poly(β‐amino ester) gels in alcohols through transesterification: Method to conjugate drugs to polymer matrices

Poly(β amino ester) (PβAE) polymers have received growing attention in the literature, owing to their ease of synthesis, versatile co‐monomer selection, and highly tunable degradation kinetics. As such, they have shown extensive potential in many biomedical applications as well. In this work, it is demonstrated for the first time that PβAE polymers containing primary and secondary amine groups can undergo degradation by primary alcohols via transesterification mechanism. While this work emphasizes an important aspect of solvent compatibility of these networks, it also represents an interesting, simple mechanism for post synthesis drug incorporation, with riboflavin conjugation being demonstrated as a model compound. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2019–2026     

Short aspect ratio gold nanorods prepared using gamma radiation in the presence of cetyltrimethyl ammonium bromide (CTAB) as a directing agent

The synthesis of short aspect ratio gold nanorods using gamma radiation method by incorporating cetyltrimethyl ammonium bromide (CTAB) as a directing agent is reported in this communication. The radiolysis of Au⁺, in the presence of 2.5 nm Au seeds and 0.1 mol dm^?3 isopropanol, results in the formation of Au spheres as evident from surface plasmon resonance band at 527 nm. However, by carrying out radiolysis at lower radiation dose rate, short aspect gold nanorods having surface plasmon bands at 513 and 670 nm have been prepared. The formation of rods at low radiation dose rate was observed to be governed by the kinetics of particle growth. The TEM of as-synthesized nanoparticles confirmed the formation of uniform sized nanorods having an aspect of 2.4.     

Adaptive targeting of chaotic response in periodically stimulated neural systems

We demonstrate a technique for the enhancement of chaos in a computational model of a periodically stimulated excitable neuron. "Anticontrol" of chaos is achieved through intermittent adaptive intervention, which is based on finite-time Lyapunov exponents measured from the time series. Our results suggest that an adaptive strategy for chaos anticontrol is viable for increasing the complexity in physiological systems that are typically both noisy and nonstationary.     

Anticancer therapeutic efficacy of biogenic Am-ZnO nanoparticles on 2D and 3D tumor models

The present study fabricates biogenic zinc oxide nanoparticles (ZnO NPs) with the aqueous leaf extract of Annona muricata (Am) plant collected from semi-evergreen forests of Odisha, India. The synthesized Am-ZnO NPs were physicochemically characterized. The ultraviolet/visible spectrum showed the maximum optical absorbance of Am-ZnO NPs at 355 nm. High-resolution transmission electron microscopy analysis presented the nearly spherical shape of Am-ZnO NPs with an average particle size of 80 nm. The net surface charge and hydrodynamic size of Am-ZnO NPs were measured to be ～?2.59 mV and ～417 nm, respectively. Am-ZnO NPs were found to be biocompatible and hemocompatible nature. Furthermore, Am-ZnO NPs displayed strong anticancer effects on both 2D and 3D tumor models. We observed a dose-dependent toxicity on both A549 and MOLT4 cells and observed a size reduction in the A549 tumor spheroids. Subsequently, we observed a depolarization in mitochondrial membrane potential of Am-ZnO NP–treated cancer cells leading to the apoptosis induction in cancer cells.