Synthesis and characterization of novel UV-curable polyurethane–clay nanohybrid: Influence of organically modified layered silicates on the properties of polyurethane

Nanohybrids based on UV-curable polyurethane acrylate (PU) and cloisite 20B (C-20B) have been synthesized by solution blending method using different loading levels of C-20B. The structures of PU/C-20B nanohybrids were confirmed by Fourier transform infrared spectroscopy (FTIR) while X-ray diffraction and transmission electron microscopy (TEM) showed the intercalation of PU into layer silicates. The thermal properties of PU and PU/C-20B nanohybrids were investigated by thermal gravimetric analysis (TGA) and differential scanning calorimetric (DSC). TGA tests revealed that the thermal decomposition temperature (T_d10%) of the nanohybrid containing 5 wt% of C-20B increased significantly, being 61 °C higher than that of pure PU while DSC measurements indicated that the introduction of 5 wt% of clay increased the glass transition temperature from 89.7 to 101 °C. Accordingly, the mechanical and anti-water absorption properties proved also to be enhanced greatly as evidenced by nanoindentation anylsis and water absorptions data in which the nanohybrid containing 5 wt% of clay have highest elastic modulus (4.508 GPa), hardness (0.230 GPa) and lowest water absorption capacity. Thus the formations of nanohybrids manifests through the enhancement of thermal, mechanical and anti-water absorption properties as compared with neat PU due to the nanometer-sized dispersion of layered silicate in polymer matrix.     

Conformational Flexibility in the Binding Surface of the Potassium Channel Blocker ShK

ShK is a 35‐residue peptide that binds with high affinity to human voltage‐gated potassium channels through a conserved K‐Y dyad. Here we have employed NMR measurements of backbone‐amide ¹⁵N spin‐relaxation rates to investigate motions of the ShK backbone. Although ShK is rigid on the ps to ns timescale, increased linewidths observed for 11 backbone‐amide ¹⁵N resonances identify chemical or conformational exchange contributions to the spin relaxation. Relaxation dispersion profiles indicate that exchange between major and minor conformers occurs on the sub‐millisecond timescale. Affected residues are mostly clustered around the central helix‐kink‐helix structure and the critical K22–Y23 motif. We suggest that the less structured minor conformer increases the exposure of Y23, known to contribute to binding affinity and selectivity, thereby facilitating its interaction with potassium channels. These findings have potential implications for the design of new channel blockers based on ShK.     

Droplet size and stability of nano-emulsions produced by the temperature phase inversion method

We studied the formation and stability of n-decane in water nano-emulsions produced by the phase inversion temperature (PIT) emulsification method using polyoxyethylene lauryl ether as surfactant. The results obtained indicate that the droplet size and size distribution are strongly dependent on the methods of heating and cooling, and on the final temperature to which the mixture is cooled after phase inversion. Importantly, there exists an optimum storage temperature, at which the nano-emulsions are most stable, and develop ultra-small droplet sizes, ranging from 35 nm to 54 nm, with low polydispersity indices (0.2). This optimum temperature is about 20 °C below the PIT, and dependent on the surfactant concentration. Any departure in temperature from the optimum would result in increases in droplet sizes, polydispersity and instability by Ostwald ripening. Furthermore, nano-emulsions destabilized after a long period of storage at different temperatures can be rejuvenated simply by equilibration for a few minutes at the optimum temperature.     

Review of Children of alcoholics: Critical perspectives.

Reviews the book Children of alcoholics: Critical perspectives edited by Michael Windle and John S. Searles ( 1990-97263-000). This book is divided into nine separate chapters, including introductory and summary chapters and chapters on epidemiology, biochemical markers, neuropsychology and neurophysiology, behavior genetics, personality, family environment, and intervention. On balance, the contributions are up-to-date and scholarly, and they successfully illustrate the methodological issues and shortcomings across the various areas of children of alcoholics (COAs) research and provide theoretical perspectives for integrating the existing data. Throughout the book, biopsychosocial and developmental issues are stressed. The reviewer believes that this in itself is an important contribution because much of the writing in this area overemphasizes either biological or psychosocial factors to the exclusion of the other. Biologically oriented researchers often appear to support overly simplistic, reductionistic approaches, whereas psychosocial theorists (even when paying lip service to biological factors) often fail to appreciate that some of their key "environmental" constructs might be reflecting genetically determined phenomena (e.g., as in the case of gene-environment correlation). In the final chapter, Windle and Searles do an admirable job of integrating and bringing a sense of coherence to the multidisciplinary research literature. The reviewer believes their suggestions for future research are right on the mark and should be heeded by the next generation of COA researchers. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect on structure,stability, and H+ irradiation on Nd3+/Ru4+-loaded iron phosphate glass for nuclear applications

Nuclear energy generation technology is critically linked with the safe disposal of radioactive waste. In this context, iron phosphate glass (IPG) is gaining predominance as nuclear waste vitrification matrix that necessitates a thorough study on the effect of the loading of various nuclear fission waste materials in it. In this study, the effect of the loading of Nd³⁺ (which acts as a surrogate for radioactive curium (Cm)) and Ru⁴⁺ (which is a fission product of ²³⁵U) in IPG has been assessed. The optimum loading of Nd³⁺/Ru⁴⁺ leading to the formation of homogenous melt has been ascertained via powder X-ray diffraction and scanning electron microscopy techniques. The modification in the Fe³⁺/Fe²⁺ ratio in IPG and the consequent change in its average coordination number with Nd³⁺/Ru⁴⁺ loading has been deduced from the Mössbauer studies. Local structure analysis has been done using X-ray absorption spectroscopy at Nd/Ru/Fe K-edge (as applicable) for all the single and co-loaded IPG samples. All the co-loaded samples show enhanced glass stability and glass forming ability compared to unloaded IPG which has been ascertained via detailed thermal studies. The variation in IPG network structure on the addition of Nd₂O₃ and RuO₂ has been ascertained through spectroscopic techniques like Fourier transform infrared (FTIR) and Raman. The base glass and a few representative homogenous single and co-loaded IPG samples have been irradiated with 4.5 MeV proton beam to simulate the hosting of radioactive elements and the radiation effect on glass structure has been ascertained using FTIR and Raman spectroscopies. The suitability of IPG as nuclear waste vitrification matrix for Nd³⁺ and Ru⁴⁺ is established through all the above analyses.     

Functional Carbon Quantum Dots for Ocular Imaging and Therapeutic Applications

Carbon quantum dots (CDs) are a class of emerging carbonaceous nanomaterials that have received considerable attention due to their excellent fluorescent properties, extremely small size, ability to penetrate cells and tissues, ease of synthesis, surface modification, low cytotoxicity, and superior water dispersion. In light of these properties, CDs are extensively investigated as candidates for bioimaging probes, efficient drug carriers, and disease diagnostics. Functionalized CDs represent a promising therapeutic candidate for ocular diseases. Here, this work reviews the potential use of functionalized CDs in the diagnosis and treatment of eye-related diseases, including the treatment of macular and anterior segment diseases, as well as targeting Aβ amyloids in the retina.