Modulation of flexo-rigid balance in photoresponsive thymine grafted copolymers towards designing smart healable coating

Efficacy and durability of the photovoltaic device mandates its protection against hot, humid weather condition, high energy of UV light and unwanted scratches. Such challenges can be mitigated by smart polymeric coating with inherent properties e.g. hydrophobicity to prevent moisture, optimal viscocity for better processibility and crack-healing. The hydrophobic polymers TP1–TP4 containing pendant photo-crosslinkable thymine moieties are designed that undergo [2 + 2] photocycloaddition upon UV_B irradiation and can be dynamically reverted back upon irradiation with UV_C light. A judicious control of solvent environment, chain length, functionality% and concentration of the polymers regulate the aspects of photodimerization thereby, rendering intra or inter-chain collapse to form diverse nanostructures. Photodimerization of the thymine moieties renders coil to globule transformation in dilute condition whereas irradiation performed at high macromolecular concentration regime exhibits higher order nanostructures. The photoresponsive chain collapse leads to the formation of rigid crosslinked domains within flexible polymer chains akin to the hard–soft phases of thermoplastic elastomers. Such rigidification of the crosslinked segments endows a tool to photomodulate the glass transition temperature (T_g) that can dynamically revert back upon decrosslinking. Further, the structural modulation of the polymers is explored towards autonomic and nonautonomic self-healing behaviour at ambient conditions. Moreover, the self-healing efficacy can be tuned with the film thickness and it remains unaltered upon using solar simulator or direct sunlight. Overall, such hydrophobic low T_g polymers display photo-regulated self-healing mechanism consisting of both autonomic and non-autonomic self-healing and may find applications in designing smart protective coatings for photovoltaic devices.

Photo-crosslinking using [2 + 2] cycloaddition in thymine grafted low viscosity polymer generates flexorigid domain to result self-healing polymer with increased hydrophobicity for potential use as smart coating material.     

Chemical synthesis of Nd2Fe14B/Fe–Co nanocomposite with high magnetic energy product

Nd₂Fe₁₄B is one of the most popular permanent magnets (PMs) possessing the best energy product (BH)_max among the common PM materials. However, exchange-coupled nanocomposite magnets fabricated by embedding nanostructures of soft-phase magnetic materials into a hard-phase magnetic matrix manifest higher remanence and a higher energy product. Here we present the fabrication of exchange coupled Nd₂Fe₁₄B/Fe–Co magnetic nanocomposites using gel-combustion and diffusion–reduction processes. Pre-fabricated CoFe₂O₄ nanoparticles (NPs) of ∼5 nm diameter were incorporated into a Nd–Fe–B oxide matrix during its synthesis by gel-combustion. The obtained mixed oxide was further processed with oxidative annealing at 800 °C for 2 h and reductive annealing at 900 °C for 2 h to form a Nd₂Fe₁₄B/Fe–Co nanocomposite. Nanocomposites with different mol% of soft-phase were prepared and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and physical property measurement system (PPMS) to study their crystalline phase, morphology and magnetic behavior. Addition of 7.7 mol% of soft-phase was found to be optimum, producing a coercivity (H_c) of 5.6 kOe and remanence (M_r) of 54 emu g⁻¹ in the nanocomposite.

Nd₂Fe₁₄B is one of the most popular permanent magnets (PMs) possessing the best energy product (BH)_max among the common PM materials.     

Variations in screening and management practices for subsequent asymptomatic meningiomas in childhood,adolescent and young adult cancer survivors

Journal of Neuro-Oncology - Childhood, adolescent and young adult (CAYA) cancer survivors treated with cranial radiotherapy are at risk for developing subsequent meningiomas. There is insufficient...     

Automated Detection of Caffeinated Coffee-Induced Short-Term Effects on ECG Signals Using EMD,DWT, and WPD

The effect of coffee (caffeinated) on electro-cardiac activity is not yet sufficiently researched. In the current study, the occurrence of coffee-induced short-term changes in electrocardiogram (ECG) signals was examined. Further, a machine learning model that can efficiently detect coffee-induced alterations in cardiac activity is proposed. The ECG signals were decomposed using three different joint time–frequency decomposition methods: empirical mode decomposition, discrete wavelet transforms, and wavelet packet decomposition with varying decomposition parameters. Various statistical and entropy-based features were computed from the decomposed coefficients. The statistical significance of these features was computed using Wilcoxon’s signed-rank (WSR) test for significance testing. The results of the WSR tests infer a significant change in many of these parameters after the consumption of coffee (caffeinated). Further, the analysis of the frequency bands of the decomposed coefficients reveals that most of the significant change was localized in the lower frequency band (<22.5 Hz). Herein, the performance of nine machine learning models is compared and a gradient-boosted tree classifier is proposed as the best model. The results suggest that the gradient-boosted tree (GBT) model that was developed using a db2 mother wavelet at level 2 decomposition shows the highest mean classification accuracy of 78%. The outcome of the current study will open up new possibilities in detecting the effects of drugs, various food products, and alcohol on cardiac functionality.     

Premenstrual tension and behaviour problems

This prospective study examined the role of premenstrual tension in producing behavioural problems in menstruating women with mental handicaps in two hospital settings. Clinical evaluation and hormonal studies were undertaken for two years, helped by the Mersey Research Grant Scheme. The main findings were that 11 women out of a random sample of 40 (27.5 per cent) showed a behaviour change for the worse clinically just prior to menstruation, in addition to having physical symptomatology and hormonal abnormalities highly suggestive of premenstrual tension. The findings and implications in care and management of such behaviour problems are discussed.