Observation of Griffiths phase in antiferromagnetic La(0.32)Eu(0.68)MnO3

We report the Griffiths phase (GP) scenario for isovalent doping in antiferromagnetic La(0.32)Eu(0.68)MnO(3). Rietveld refinement of structural data displays strong crystal structural distortion. The dc and ac magnetic studies nicely demonstrate unambiguous aspects of robust GP. The presence of ferromagnetically correlated spin clusters is found above the transition temperature, T(N). The disorder-driven phase inhomogeneity is correlated to strong structural distortion, giving rise to the GP. This is an unique example in manganite where double exchange interaction does not play any role for the observed phenomenon.     

Universality of the plastic instability in strained amorphous solids

By comparing the response to external strains in metallic glasses and in Lennard-Jones glasses we find a quantitative universality of the fundamental plastic instabilities in the athermal, quasistatic limit. Microscopically these two types of glasses are as different as one can imagine, the latter being determined by binary interactions, whereas the former is determined by multiple interactions due to the effect of the electron gas that cannot be disregarded. In spite of this enormous difference the plastic instability is the same saddle-node bifurcation. As a result, the statistics of stress and energy drops in the elastoplastic steady state are universal, sharing the same system-size exponents.     

A mild and expedient one-pot synthesis of substituted benzimidazoles in water using a phase-transfer catalyst

Abstract  1-Alkyl/phenyl-2-arylbenzimidazoles have been synthesized in very good to excellent yields by a one-pot condensation of N-alkyl/phenyl-o-phenylenediamines with aryl aldehydes in water at room temperature using cetylpyridinium bromide as a cheap and eco-friendly catalyst. Graphical abstract        

A synthetic route to 1,3-dihydroisobenzofuran natural products: the synthesis of methyl ethers of pestacin

A synthetic route to 1-(2,6-dihydroxyphenyl)phthalan natural products is described. It is typified by the synthesis of permethyl and monomethyl ethers (21 and 22) of pestacin (1), a 1,3-dihydroisobenzofuran natural product. The key step is hydrodeoxygenation of the corresponding isobenzofuranone 19 in 2 steps: reduction and intramolecular etherification. A route involving hydrodesulfurization of a thionophthalide to a phthalan (e.g., 8) is also reported.     

A Perylene diimide based fluorescent probe for caffeine in aqueous medium

Caffeine is a legal stimulant drug which has received considerable attention due to its widespread use as a beverage and in pharmaceutical formulations. However, reported chemosensors for caffeine are limited. In the present study use of a perylene diimide (PDI) derivative has been explored for the first time for detection and quantification of caffeine in an aqueous medium. Spectroscopic studies (UV-Vis, Fluorescence, FTIR and 1H-NMR) suggest that aspartic acid modified perylene diimide (PASP) may bind to caffeine through π-π interaction. This interaction results in immediate quenching of fluorescence and optical color change which can be perceived through naked eyes. This probe has been successfully used for bio-imaging of caffeine in living cells.     

Recent Advancements in Ln‐Ion‐Based Upconverting Nanomaterials and Their Biological Applications

Upconversion nanoparticles (UCNPs) convert low‐energy infrared (IR) or near‐infrared (NIR) photons into high‐energy emission radiation ranging from ultraviolet to visible through a photon upconversion process. In comparison to conventional fluorophores, such as organic dyes or semiconductor quantum dots, lanthanide‐ion‐doped UCNPs exhibit high photostability, no photoblinking, no photobleaching, low cytotoxicity, sharp emission lines, and long luminescent lifetimes. Additionally, the use of IR or NIR for excitation in such UCNPs reduces the autofluorescence background and enables deeper penetration into biological samples due to reduced light scattering with negligible damage to the samples. Because of these attributes, UCNPs have found numerous potential applications in biological and medicinal fields as novel fluorescent materials. Different upconversion mechanisms commonly observed in UCNPs, various methods that are used in their synthesis, and surface modification processes are discussed. Recent applications of Ln‐UCNPs in the biological and medicinal fields, including in vivo and in vitro biological imaging, multimodal imaging, photodynamic therapy, drug delivery, and antibacterial activity, are also presented.     

A non-primitive boundary element technique for modeling flow through non-deformable porous medium using Brinkman equation

In this study, we develop a non-primitive boundary integral equation (BIE) method for steady two-dimensional flows of an incompressible Newtonian fluids through porous medium. We assume that the porous medium is isotropic and homogeneous, and use Brinkman equation to model the fluid flow. First, we present BIE method for 2D Brinkman equation in terms of the non-primitive variables namely, stream-function and vorticity variables. Subsequently, a test problem namely, the lid-driven porous cavity over a unit square domain is presented to assert the accuracy of our BEM code. Finally, we discuss an application of our proposed method to flows through porous wavy channel, which is a problem of significant interest in the micro-fluidics, biological domains and groundwater flows. We observe that the rate of convergence (\(R_{c}\)) increases with increasing Darcy number. For low Darcy number streamlines follow the curvature of the wavy-walled channel and no circulation occurs irrespective of the wave–amplitude, while for high Darcy number the flow circulation occurs near the crest of the wavy-walled channel, when the wave–amplitude is large enough.     

Uncapped silver nanoparticles synthesized by DC arc thermal plasma technique for conductor paste formulation

Uncapped silver nanoparticles were synthesized by DC arc thermal plasma technique. The synthesized nanoparticles were structurally cubic and showed wide particle size variation (between 20–150 nm). Thick film paste formulated from such uncapped silver nanoparticles was screen-printed on alumina substrates and the resultant ‘green’ films were fired at different firing temperatures. The films fired at 600 °C revealed better microstructure properties and also yielded the lowest value of sheet resistance in comparison to those corresponding to conventional peak firing temperature of 850 °C. Our findings directly support the role of silver nanoparticles in substantially depressing the operative peak firing temperature involved in traditional conductor thick films technology.