Efficient and solvent-free synthesis of bis-indolylmethanes using silica gel supported aluminium chloride as a reusable catalyst

Stable and non-hygroscopic silica gel supported aluminium chloride（SiO₂-AlCl₃）,which is prepared easily from cheap and commercially available compounds was found to be an environmentally friendly heterogeneous catalyst for the condensation of indole with aldehydes and ketones to afford bis-indolylmethanes at room temperature under solvent-free conditions.The catalyst can be reused up to five times after simple washing with ether.     

Super Face Antimagic Labelings of Union of Antiprisms

In this paper we deal with the problem of labeling the vertices, edges and faces of a disjoint union of m copies of antiprism by the consecutive integers starting from 1 in such a way that the set of face-weights of all s-sided faces forms an arithmetic progression with common difference d, where by the face-weight we mean the sum of the label of that face and the labels of vertices and edges surrounding that face. Such a labeling is called super if the smallest possible labels appear on the vertices. The paper examines the existence of such labelings for union of antiprisms for several values of the difference d.     

Live cell refractometry using microfluidic devices

Using Hilbert phase microscopy for extracting quantitative phase images, we measured the average refractive index associated with live cells in culture. To decouple the contributions to the phase signal from the cell refractive index and thickness, we confined the cells in microchannels. The results are confirmed by comparison with measurements of spherical cells in suspension.     

Design of Multi-Metallic-Based Electrocatalysts for Enhanced Water Oxidation

Electrochemical water splitting by renewable energy resources is an efficient and green approach for hydrogen gas production. However, the anodic oxygen evolution reaction (OER) largely impedes the industrial application due to its sluggish four-electron-transition kinetics. Although various materials have been developed to accelerate the OER rate, still some issues should be addressed to meet the industrial demand: (i) considerable 200–300 mV overpotential as extra onset energy input, (ii) limited survival and performance in acidic electrolyte for the majority of oxide/hydroxide composite materials, (iii) unsatisfying long-term durability and (iv) the need for facile and scalable preparation methods. Here, we emphasize on multi-metallic composites with enhanced OER activity based on both precious and nonprecious elements that outperform the unary and binary composites. The regulation effect from multi-metal incorporation is also summarized systematically: (i) introducing foreign metal atoms to the host material boosts the physical properties such as conductivity, surface area, defect density, morphology, wettability, etc., (ii) metal doping can synergistically regulate the electronic features of the host material, e. g. oxygen vacancy, e_g orbit filling, coordinative number and covalence state, which can optimize the absorption/desorption energy of the M−O intermediate, (iii) chaotic impact from the added atoms twists the catalyst lattice into a more aggressive and higher energy state, which is more feasible to transform to an active intermediate with lower required energy supply. This review aims to provide a practical approach to further improve the OER performance via multi-metallic-based catalysts.     

Pistacia integerrima gall extract mediated green synthesis of gold nanoparticles and their biological activities

This paper reports a rapid, facile and one-pot synthesis of environmentally safe gold nanoparticles capped and stabilized with galls extract of Pistacia integerrima. The aqueous gold ions when exposed to P. integerrima galls extract were rapidly reduced as evident from abrupt color change to ruby red, suggesting the biosynthesis of gold nanoparticles (Au-NPs) which were further characterized by UV–Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). Their stability was evaluated against varying pH and different volumes of sodium chloride (NaCl) as well as at a range of temperature (20–80 °C). Au-NPs were tested for enzyme inhibition, antibacterial, antifungal, antinociceptive, muscle relaxant and sedative activities. The UV–Vis spectra of the gold nanoparticles gave surface plasmon resonance at 540 nm while the SEM analysis revealed the particle size in the range of 20–200 nm. FTIR spectra confirmed the involvement of amines, amide groups and alcohols in capping and reduction of gold nanoparticles. Au-NPs showed remarkable stability in different NaCl and pH solutions as well as at elevated temperature. Au-NPs have good antifungal activity and possessed antinociceptive and muscle relaxant properties as observed from their zone of inhibition and significant attenuation of acetic acid induced writhing and reduction of time spent on the rota rod respectively. These results concluded that the gall extract of P. integerrima is a very good bioreductant for the synthesis of gold nanoparticles that have potential for various biomedical and pharmaceutical applications.     

The occurrence of multistability and normal mode splitting in an optomechanical system

We provide a theoretical technique to study the occurrence of multistability and normal mode splitting in an optomechanical system driven by a single mode cavity field. For this purpose, we consider the position-dependent mass mechanical resonator (PDMR) which produces the nonlinearity in the system. This shifts the system from monostable to bistable regime and bistable to a multistable regime at different conditions of the nonlinearity. Further, we use the Fourier transform technique to find out the fluctuation in the position of the nano-mechanical resonator and their energy spectrum as well. Moreover, we used the input-output theory to analyze the transmitted field spectrum as well as x and y quadratures spectra of the output field. We explain the effect of the non-linearity on the normal mode splitting of the former and later spectra. In addition, we also explain the normal mode splitting as a function of cavity decay rate and laser power, respectively.     

Synchronization control of oscillator networks using symbolic regression

Networks of coupled dynamical systems provide a powerful way to model systems with enormously complex dynamics, such as the human brain. Control of synchronization in such networked systems has far-reaching applications in many domains, including engineering and medicine. In this paper, we formulate the synchronization control in dynamical systems as an optimization problem and present a multi-objective genetic programming-based approach to infer optimal control functions that drive the system from a synchronized to a non-synchronized state and vice versa. The genetic programming-based controller allows learning optimal control functions in an interpretable symbolic form. The effectiveness of the proposed approach is demonstrated in controlling synchronization in coupled oscillator systems linked in networks of increasing order complexity, ranging from a simple coupled oscillator system to a hierarchical network of coupled oscillators. The results show that the proposed method can learn highly effective and interpretable control functions for such systems.     

Flow visualization and wall shear stress of a flapping model hummingbird wing

The unsteady low Reynolds number aerodynamics of flapping flight was investigated experimentally through flow visualization by suspended particle imagery and wall shear stress measurement from micro-array hot-film anemometry. In conjunction, a mechanism was developed to create a flapping motion with three degrees of freedom and adjustable flapping frequency. The flapping kinematics and wing shape were selected for dynamic similarity to a hummingbird during hovering flight. Flow visualization was used to validate the anemometry observations of leading edge vortex (LEV) characteristics and to investigate the necessity of spanwise flow in LEV stability. The shear sensors determined LEV characteristics throughout the translation section of the stroke period for various wing speeds. It was observed that a minimum frequency between 2 and 3.5 Hz is required for the formation and stabilization of a LEV. The vortex strength peaked around 30% of the flapping cycle (corresponding to just past the translation midpoint), which agrees with results from previous studies conducted by others. The shear sensors also indicated a mild growth in LEV size during translation sections of the wing’s motion. This growth magnitude was nearly constant through a range of operating frequencies.     

A new two-dimensional Ag coordination polymer with Ag?C interactions: Thermal, fluorescence, structural and solution studies

A 2D polymer with Ag?C interactions, [Ag(μ₅-TS)]_n (1) [TS⁻ = toluene-4-sulfonate], has been synthesized and characterized and its structure was determined by X-ray crystallography. In addition to coordination of the O atoms of TS⁻, the Ag atoms also form weak η¹ Ag?C interactions. The thermal stability of 1 was studied by thermal gravimetric (TG) and differential thermal analyses (DTA). The ligand and compound 1 are luminescent in DMF, with emission maxima at 358 and 335, respectively. Solution studies of complex 1 were done in DMF and in CH₃CN.