Unveiling the self-assembly behavior of copolymers of AAc and DMAPMA in situ to form smart hydrogels displaying nanogels-within-macrogel hierarchical morphology

Stimulus responsive hydrogels are being considered as one of the most crucial biomaterials of current generation. A new technique has been established for developing hydrogels based on Acrylic acid (AAc) and N-[3-(Dimethylamino)propyl]-methacrylamide (DMAPMA), and relevant mechanism has been delineated. Aqueous redox copolymerization of different molar ratios of AAc and DMAPMA at 41 ± 1 °C, leading to the formation of interlocked nanogels of ∼300 nm diameter, which acted as the building blocks of a series of superabsorbent hydrogels having robust, honey-comb type three-dimensional architecture. Monomer composition, monomer feed ratio and water content in feed has been found to be important factors in the development of the stable poly(AAc-co-DMAPMA) hydrogel membranes (PADMAs) without any active crosslinking agent. At the cues of pH change from 7.0 to 3.5, pulsatile swelling-deswelling behavior varied, ranging from ∼5900% to ∼60% (mass) respectively, underlining smart hydrogel characteristics needed for specific biomedical applications. Elastic modulus of the gels, equilibrated at pH 7.0, is recorded to be >15 kPa under uniaxial compression. Underlying mechanism of the formation of such robust three-dimensional structures in poly(AAc-co-DMAPMA) hydrogel membranes, and the origin of hierarchical ‘nano-to-macro’ scale morphological features has been proposed.     

Wheat-Legume Composite Flour Quality

Wheat-legume composite flours were produced by blending Canada Western Extra Strong (CWES) and Canada Western Red Spring (CWRS) wheat with varying amounts of three legume proteins. Legume protein addition produced breads with lower specific loaf volume, coarser crumb and firmer texture, and cooked white-salted noodles with greater compression stress and less cutting stress than the wheat controls. The CWES wheat compensated for the negative baking effects of the legume proteins as much as the CWRS wheat. End-use quality did not change at 2% soybean protein addition. Yellow pea protein produced the greatest quality changes, followed by chickpea and soybean protein.     

Testing mediators of intervention effects in randomized controlled trials: An evaluation of three depression prevention programs.

Objective: Evaluate a new 5-step method for testing mediators hypothesized to account for the effects of depression prevention programs. Method: In this indicated prevention trial, at-risk teens with elevated depressive symptoms were randomized to a group cognitive–behavioral (CB) intervention, group supportive expressive intervention, CB bibliotherapy, or assessment-only control condition. Results: The group CB intervention reduced depressive symptoms and negative cognitions and increased pleasant activities. Change in these mediators predicted change in depression, and intervention effects became weaker controlling for change in the mediators; yet, change in depression appeared typically to occur before change in the mediators. The supportive expressive intervention reduced depressive symptoms but affected only 1 of 2 mediators (emotional expression but not loneliness). Change in emotional expression did not correlate with change in depression, and change in depression usually occurred before change in the mediators. Bibliotherapy did not significantly affect depressive symptoms or the ostensive mediators (negative cognitions and pleasant activities), and change in depression usually occurred before change in the mediators. Conclusion: Results imply that this procedure provides a sensitive test of mediation but yielded limited support for the hypothesized mediators, suggesting that nonspecific factors may play an important mediational role. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Uniform star‐polystyrene nanoparticles prepared by emulsion atom transfer radical polymerization

Pentaerythritol (PT) was converted into four‐arm initiator pentaerythritol tetrakis(2‐chloropropionyl) (PT‐Cl) via reaction with 2‐chloropropionyl chloride. Uniform (monodisperse) star‐polystyrene nanoparticles were prepared by emulsion atom transfer radical polymerization of styrene, using PT‐Cl/CuCl/bpy (bpy is 2,2′‐dipyridyl) as the initiating system. The structures of PT‐Cl and polymer were characterized by Fourier transform infrared spectroscopy and nuclear magnetic resonance. The morphology, size and size distribution of the star‐polystyrene nanoparticles were characterized by transmission electron microscopy, atomic force microscopy and photon correlation spectroscopy. It was found that the average diameters of star‐polystyrene nanoparticles were smaller than 100 nm (30–90 nm) and monodisperse; moreover, the particle size could be controlled by the monomer/initiator ratio and the surfactant concentration. The average hydrodynamic diameter (D_h) of the nanoparticles increased gradually on increasing the ratio of styrene to PT‐Cl and decreased on enhancing the surfactant concentration or increasing the catalyst concentration. Copyright © 2011 Society of Chemical Industry     

Iron-Doped,Mullite-Impregnated PVDF Composite: An Alternative Separator for a High Charge Storage Ceramic Capacitor

In this communication, the formation mechanism of the electroactive β phase, morphology and the dielectric activities of increasing doping concentration (0–1.2 M.W % of mullite) of Fe²⁺ ion-doped, mullite-impregnated polyvinylidene fluoride (PVDF) nanocomposite have been investigated. Differential thermal analysis (DTA) confirms the formation of an electroactive β phase, and Fourier transform infrared spectroscopy (FTIR) showed that the β phase increases simultaneously and attains the maximum increment of 2.6 times compared to pristine PVDF. X-ray diffraction (XRD) spectra also agreed well with the β-phase increment behaviour and also confirmed the presence of required mullite phases. Field emission scanning electron microscopy (FESEM) images indicate the strong interaction between the polymer matrix and different concentrations of Fe²⁺ ion-doped mullite particles, resulting in enhanced electroactive β phase formation and large dielectric constant of the nanocomposite films followed by significant low dielectric loss with high ac conductivity compared to pristine PVDF films at room temperature. This doped polymer composite can be used as a high dielectric separator and, using this separator, we have successfully fabricated a high-charge-storage device. This paper also demonstrates that the loading of conductive Fe²⁺ ions within the highly insulating mullite matrix has a critical concentration for the enhancement and nucleation of the electroactive β phase of the PVDF polymer. In this critical concentration, the highest formation of a β network and maximum numbers of homogeneously distributed iron-doped mullite (FeM) particles in PVDF matrix improves the effective interfacial polarization by Maxwell–Wagner–Sillar (MWS) polarization effect which is responsible for the enhancement of dielectric constant and ac conductivity followed by significant tangent loss. So, it can be concluded that the incorporation of Fe²⁺-doped mullite into PVDF matrix is an effective way to fabricate a high dielectric separator of high-charge-storage electronic devices.     

Effects of Online Comments on Smokers' Perception of Antismoking Public Service Announcements

On YouTube antismoking PSAs are widely viewed and uploaded; they also receive extensive commentary by viewers. This study examined whether such evaluative comments with or without uncivil expressions influence evaluations by subsequent viewers. Results showed PSAs with positive (i.e. antismoking) comments were perceived by smokers as more effective than PSAs with negative (prosmoking) comments. Smokers in the no‐comment condition gave the highest perceived effectiveness score to PSAs. Smokers' readiness to quit smoking moderated the effect of comments on PSA evaluation. Smokers reading negative uncivil comments reported more negative attitude toward quitting and a lower level of perceived risk of smoking than those reading negative civil comments but positive civil and positive uncivil comments did not elicit different responses.     

Well Supported Approximate Equilibria in Bimatrix Games

In view of the apparent intractability of constructing Nash Equilibria (NE in short) in polynomial time, even for bimatrix games, understanding the limitations of the approximability of the problem is an important challenge.