Synthesis and Anticancer Activity of Novel Urea and Thiourea Bearing Thiophene-2-carboxalate Derivatives

Russian Journal of General Chemistry - A new series of urea and thiourea bearing thiophene-2-carboxalate derivatives has been designed against protein tyrosine phosphatase 1B (PTP1B) active site,...     

Velocity-Gradient Dynamics in Turbulence: Effect of Viscosity and Forcing

The restricted Euler equation is a promising but incomplete model for velocity-gradient dynamics in turbulent flows. While it captures many of the geometric features of the vorticity vector and the strain rate tensor, viscous and anisotropic pressure Hessian effects are not accounted for satisfactorily. Inadequate viscous-effect modeling causes velocity gradients to diverge in finite time, rendering the restricted Euler model unsuitable for practical applications. We perform a Lagrangian frame analysis to comprehend fully the physics of the viscous relaxation time scale and propose a variable time-scale model that can adequately account for deformation history. Most importantly, the finite-time singularity (divergence of velocity gradients) problem is fully resolved with the present model. We also model the effects of forcing that is used in numerical simulations to sustain stationary isotropic turbulence. Detailed comparison of the new model with DNS data reveals good agreement.     

Strain Engineering of Wave‐like Nanofibers for Dynamically Switchable Adhesive/Repulsive Surfaces

Engineering surfaces that enable the dynamic tuning of their wetting state is critical to many applications including integrated microfluidics systems, flexible electronics, and smart fabrics. Despite extensive progress, most of the switchable surfaces reported are based on ordered structures that suffer from poor scalability and high fabrication costs. Here, a robust and facile bottom‐up approach is demonstrated that allows for the dynamical and reversible switching between lotus leaf (repulsive) and rose petal (adhesive) states by strain engineering of wave‐like nanofiber layers. Interestingly, it is found that the controlled switching between these two distinctive states is sensitive to the shape of the nanofibers. Moreover, it is observed that the structural integrity of the nanofibers is fully preserved during multicycle dynamic switching. The application of these optimal structures is showcased as mechanical hands demonstrating the capture of water microdroplets and their subsequent release in a well‐controlled manner. It is envisioned that this low‐cost and highly scalable surface texture is a powerful platform for the design of portable microfluidics systems, and the fabrication of large‐scale devices for ambient humidity harvesting and water purification.     

Anti-skin ageing activity of napthoquinones from Arnebia nobilis Reichb.f.

The present isolation and identification of napthoquinones from roots of Arnebia nobilis Reichb.f. can lead to the discovery of new anti-skin ageing ingredient in colour cosmetics. Four compounds have been isolated and purified by rigorous column chromatography. The compounds are identified as β, β-dimethylacryl alkannin (AN-I), acetoxyisovaleryl alkannin (AAN-II), acetyl alkannin (AN-III) and alkannin (AN-IV) by interpretation of spectroscopic data. This study is the first to report the isolation of Acetoxyisovaleryl alkannin (AAN-II) from A. nobilis. The IC₅₀ values of the compounds, determined in human skin cells (human dermal fibroblasts and human keratinocytes) and mouse embryonic fibroblasts (NIH3T3) varied significantly among the four alkannins. Among the four compounds, β-acetoxyisovaleryl alkannin (AAN-II) significantly inhibited hydrogen peroxide (H₂O₂)-induced red blood corpuscle haemolysis and cellular senescence in human dermal fibroblasts. Collagen-I, elastin and involucrin syntheses in human dermal fibroblasts or keratinocytes were up regulated by AAN-II. These results support the potential utility of alkannins as novel anti-ageing ingredients.     

Effect of substituent polarity,bulk, and substitution site toward enhancing gas permeation in dibromohexafluorobisphenol‐a based polyarylates

The gas permeation properties of polyarylates were tuned by varying nature and site of substituents present on both of its monomers, viz., bisphenol and dicarboxylic acid. The phenyl rings of hexafluorobisphenol‐A were substituted in asymmetric manner by polar bromine to obtain dibromohexafluorobisphenol‐A. This bisphenol was polymerized with equimolar mixture of iso‐ and terephthalic acid (base case), bromo‐ and nitroterephthalic acid (polar group substituted acids), 4,4′‐hexafluoroisopropylidene bis(benzoic acid), and t‐butyl isophthalic acid (bulky group containing acids). Physical properties and gas permeation properties of these polyarylates were investigated to assess combined effects of asymmetric nature of bisphenol substitution, polar nature of substituent bromine, hexafluoroisopropylidene group present at the bridge position of bisphenol, and substituent present on the acid moiety. The combination of these substituent types led these polyarylates to lie near Robeson upper bound. The gas sorption analysis and estimation of diffusivity in these polyarylates shed a light on observed variations in gas permeation properties by attempted structural variations. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3156–3168, 2007     

Poly (amaranth) film based sensor for resolution of dopamine in presence of uric acid: A voltammetric study

The electropolymerized film of amaranth was prepared on the surface of graphite pencil electrode (GPE) by using cyclic voltammetric technique. This poly (amaranth) film coated electrode exhibited an excellent electrocatalytic activity towards the detection of dopamine (DA) in presence of uric acid (UA) in 0.2 mol/L phosphate buffer solution at pH 7.0. The effect of interference study was carried out by using differential pulse voltammetric technique. The poly (amaranth) modified GPE was applied for the detection of DA in dopamine injection with satisfactory results.     

Spontaneous and induced chiral symmetry breaking of stereolabile pillar[5]arene derivatives upon crystallisation

Stereolabile pillar[5]arene (P[5]) derivatives, which are dynamic racemic mixtures in solution on account of their low inversion barriers, were employed as platforms to study chiral symmetry breaking during crystallisation. In the solid state, we showed that crystal enantiomeric excess of a conglomerate-forming P[5] derivative can be obtained by handpicking and Viedma ripening without the intervention of external chiral entities. On the other hand, in the presence of ethyl d/l-lactate as both optically-active solvents and chiral guests, the handedness of P[5] derivative crystals, either forming racemic compounds or conglomerates upon condensation, can be directed and subsequently inverted in a highly controllable manner.

Stereolabile pillar[5]arene derivatives, which are dynamic racemic mixtures in solution on account of their low inversion barriers, were employed as platforms to study chiral symmetry breaking during crystallisation.     

Fluorinated Covalent Organic Framework as a Positive Tribo-Material for High-Performance Triboelectric Nanogenerators

Along with the increasingly wide application of intelligent electronics, triboelectric nanogenerator (TENG), as a promising sustainable micro-power source has attracted considerable attention recently. However, most of the reported research focuses on negative triboelectric materials, while research on alternative positive tribo-layers is still limited. In this study, a new highly fluorinated covalent organic framework (COF) Tp-TFAB is successfully synthesized and utilized as positive triboelectric materials for high-performance TENGs. Unusually, compared with the non-fluorinated Tp-TAPB COF, both the pristine Tp-TFAB COF and corresponding hybrid films with polyvinyl alcohol (PVA) based TENGs demonstrate much higher triboelectric performance. Especially, a PVC-PVA/FTC TENG composed of polyvinyl chloride (PVC) and hybrid PVA/Tp-TFAB (PVA/FTC) films reveal much superior triboelectric performance with a short-circuit current density of 26.34 mA m⁻², a transferred charge density of 148.5 µC m⁻², and a maximum peak power density of 8.24 W m⁻², nearly six times higher than that of the PVC-PVA TENG. Detailed investigations revealed that the fluorinated Tp-TFAB COF has enhanced electron donating ability, which significantly boosts the triboelectric output of TENGs. This study provides an effective strategy of chemically designing and synthesizing new alternative triboelectric materials, which will pave the way to significantly enhance the triboelectric performance of TENGs.     

Multifunctional Optoelectronics via Harnessing Defects in Layered Black Phosphorus

Layered black phosphorus (BP), a promising 2D material, tends to oxidize under ambient conditions. While such defective BP is typically considered undesirable, defect engineering has in fact been exploited in contemporary materials to create new behaviors and functionalities. In this spirit, new opportunities arising from intrinsic defect states in BP, particularly through harnessing unique photoresponse characteristics, and demonstrating three distinct optoelectronic applications are demonstrated. First, the ability to distinguish between UV‐A and UV‐B radiations using a single material that has tremendous implications for skin health management is shown. Second, the same device is utilized to show an optically stimulated mimicry of synaptic behavior opening new possibilities in neuromorphic computing. Third, it is shown that serially connected devices can be used to perform digital logic operations using light. The underpinning photoresponse is further translated on flexible substrates, highlighting the viability of the technology for mechanically conformable and wearable systems. This demonstration paves the way toward utilizing the unexplored potential offered by defect engineering of 2D materials for applications spanning across a broad range of disciplines.