<Emphasis Type="Italic">f</Emphasis>(<Emphasis Type="Italic">R</Emphasis>) gravity solutions for evolving wormholes

The scalar–tensor f(R) theory of gravity is considered in the framework of a simple inhomogeneous space-time model. In this research we use the reconstruction technique to look for possible evolving wormhole solutions within viable f(R) gravity formalism. These f(R) models are then constrained so that they are consistent with existing experimental data. Energy conditions related to the matter threading the wormhole are analyzed graphically and are in general found to obey the null energy conditions (NEC) in regions around the throat, while in the limit \(f(R)=R,\) NEC can be violated at large in regions around the throat.     

Fracto-emission from neat epoxy resin

Fracto-emission is the emission of particles (e.g. electrons, photons, ions, neutral species) due to crack growth in materials. These emissions can be related to a number of fracture related phenomena including microcracking, crack speed of dynamic crack growth, locus of fracture (in filled materials), and potentially the extent of crack branching. Here, we examine the emission of electrons, positive ions, and photons during and following the fracture of a neat epoxy resin subjected to tensile and tensile impact loading in vacuum. Experiments which detect correlations of crack tip position and emission intensity show that the emissions occur during and following fracture. We also illustrate that observed variations of the fracture surface morphology under different loading conditions correlated with characteristics of the photon and charged particle emission. For example, regions of the surface exhibiting the highest degree of surface roughness resulted in more intense emission.     

Strong rotating flow in stationary droplets in low power budget using wire electrode configuration

We explore a simple strategy of generating strong rotating flow in a stationary surface‐droplet, using an intricate interplay of local electrical and thermal fields. Wire electrodes are employed to generate on‐spot heating without necessitating any elaborate micro‐fabrication, which causes strong local gradients in electrical properties to induce mobile charges into the droplet. Applying a low voltage (～10 V), strong rotational velocity of the order of mm/s can be achieved in the system, within the standard operating ranges of operating and geometrical parameters. Further, altering the diameter of the electrode, vortices can be tuned locally or globally in low power budget, without incurring any droplet oscillations. These results may turn out to be of immense consequence in enhancing micromixing in a plethora of droplet based applications ranging from thermal management to medical diagnostics to be potentially employed in resource‐limited settings.     

Reduced-order modelling of thermoacoustic instabilities in a two-heater Rijke tube

The topic of thermoacoustic instabilities in combustors is well-investigated, as it is important in the field of combustion, primarily in gas-turbine engines. In recent years, much attention has been focused on monitoring, diagnosis, prognosis, and control of high-amplitude pressure oscillations in confined combustion chambers. The Rijke tube is one of the most simple, yet very commonly used, laboratory apparatuses for emulation of thermoacoustic instabilities, which is also capable of capturing the physics of the thermally driven acoustics. A Rijke tube apparatus can be constructed with an electrical heater acting as the heat source, thus making it more flexible to operate and safer to handle than a fuel-burning Rijke tube or a fuel-fired combustor. Augmentation of the heat source of the Rijke tube with a secondary heater at a downstream location facilitates better control of thermoacoustic instabilities. Along this line, much work has been reported on the investigation of thermoacoustics by using computational fluid dynamics (CFD) modelling as well as reduced-order modelling for both single-heater and two-heater Rijke tube systems. However, since reduced-order models are often designed and built upon certain empirical relations, they may not account for the dynamic behaviour of the heater itself, which is a critical factor in the analysis and synthesis of real-time robust control systems. This issue is addressed in the current paper, where modifications have been made to existing models by incorporating heater dynamics. The model results are systematically validated with experimental data, generated from an in-house (electrically heated) Rijke tube apparatus.     

Augmented Lagrangian Digital Image Correlation

Experimental Mechanics - Digital image correlation (DIC) is a powerful experimental technique for measuring full-field displacement and strain. The basic idea of the method is to compare images of...     

Melt Processing of Chitosan‐Based Fibers and Fiber‐Mesh Scaffolds for the Engineering of Connective Tissues

We report the production of chitosan‐based fibers and chitosan fiber‐mesh structures by melt processing (solvent‐free) to be used as tissue‐engineering scaffolds. The melt‐based approach used to produce the scaffolds does not change their main characteristics, including the surface roughness and microporosity. The porosity, pore size, interconnectivity and mechanical performance of the scaffolds are all within the range required for various tissue‐engineering applications. Biological assessments are performed in direct‐contact assays. Cells are able to colonize the scaffold, including the inner porous structure. The cells show high indices of viability in all of the scaffold types.

     

Probing of ascorbic acid by CdS/dendrimer nanocomposites: a spectroscopic investigation

The gamma irradiation method has provided a route for synthesis of highly water-soluble, good-quality luminescent CdS/dendrimer nanocomposites with amino- or carboxyl-terminated PAMAM dendrimer. An attempt has been made to probe ascorbic acid with the as-synthesized CdS/dendrimer nanocomposites (DNC). Ascorbic acid (AA) is an important biological antioxidant and marker for different diseases in clinical chemistry as well as in quality control in the food industry. Micromolar concentrations of AA significantly quenched the photoluminescence (PL) of both amino (–NH₂) and carboxylic (–COOH) functionalized semiconductor nanocomposites. The quenching followed a linear Stern–Volmer equation and time-resolved photoluminescence spectroscopy confirmed its static nature. A strong size dependence of the quenching pattern was observed. The binding constants, and the corresponding thermodynamic parameters ΔG ^θ, ΔH ^θ, ΔS ^θ at different temperatures were calculated. CdS DNC showed selectivity towards ascorbic acid even in the presence of possible interfering molecules, such as uric acid, tartaric acid and citric acid. Nanocomposites-based assay techniques could override the complications involved in multitudes of assay procedures, providing a simple and fast new strategy for the quantification of Ascorbic acid in the range of 16.6 to 100 μM (R = 0.998, n = 9). The proposed method was applied to the detection of ascorbic acid in Vitamin C tablets with satisfactory results.