On the geometry of null congruences in general relativity

Some theorems for the null conguences within the framework of general theory of relativity are given. These theorems are important in themselves as they illustrate the geometric meaning of the spin coefficients. The newly developed Geroch-Held-Penrose (GHP) formalism has been used throughout the investigations. The salient features of GHP formalism that are necessary for the present work are given, and these techniques are applied to a pair of null congruences C (l) and C(n).     

Highly sensitive determination of atropine using cobalt oxide nanostructures: Influence of functional groups on the signal sensitivity

This study describes sensitive determination of atropine using glassy carbon electrodes (GCE) modified with Co₃O₄ nanostructures. The as-synthesised nanostructures were grown using cysteine (CYS), glutathione (GSH) and histidine (HYS) as effective templates under hydrothermal action. The obtained morphologies revealed interesting structural features, including both cavity-based and flower-shaped structures. The as-synthesised morphologies were noted to actively participate in electro-catalysis of atropine (AT) drug where GSH-assisted structures exhibited the best signal response in terms of current density and over-potential value. The study also discusses the influence of functional groups on the signal sensitivity of atropine electro-oxidation. The functionalisation was carried with the amino acids originally used as effective templates for the growth of Co₃O₄ nanostructures. The highest increment was obtained when GSH was used as the surface functionalising agent. The GSH-functionalised Co₃O₄-modified electrode was utilised for the electro-chemical sensing of AT in a concentration range of 0.01–0.46 μM. The developed sensor exhibited excellent working linearity (R² = 0.999) and signal sensitivity up to 0.001 μM of AT. The noted high sensitivity of the sensor is associated with the synergy of superb surface architectures and favourable interaction facilitating the electron transfer kinetics for the electro-catalytic oxidation of AT. Significantly, the developed sensor demonstrated excellent working capability when used for AT detection in human urine samples with strong anti-interference potential against common co-existing species, such as glucose, fructose, cysteine, uric acid, dopamine and ascorbic acid.     

Self‐Assembled Heteroleptic Zn(II) Dithiocarbamate‐Based 2D‐Interwoven Supramolecular Giant Macrocycles and Their Redox Properties

This article presents a new heteroleptic Zn(II) dithiocarbamate ( 1 ) having molecules linked together via H···H and π···π interactions to form a giant hexanuclear macrocycle. These macrocycles are connected together through S···H interactions to offer a unique two‐dimensional cloth‐like interwoven architecture in the solid state. The redox behavior of the complex deposited on the surface of a glassy carbon electrode was investigated in different pH media. The analyte was found to oxidize and reduce in a pH‐dependent irreversible manner. On the basis of the electrochemical findings, redox mechanistic pathways were proposed.     

First-principles calculations of structural,electronic, and thermodynamic properties of ZnO_(1-x)S_x alloys

In this study the pseudo-potential method is used to investigate the structural, electronic, and thermodynamic proper- ties of ZnOl_xSx semiconductor materials. The results show that the electronic properties are found to be improved when calculated by using LDA ~ U functional as compared with local density approximation （LDA）. At various concentrations the ground-state properties are determined for bulk materials ZnO, ZnS, and their tertiary alloys in cubic zinc-blende phase. From the results, a minor difference is observed between the lattice parameters from Vegard＇s law and other calculated results, which may be due to the large mismatch between lattice parameters of binary compounds ZnO and ZnS. A small deviation in the bulk modulus from linear concentration dependence is also observed for each of these alloys. The ther- modynamic properties, including the phonon contribution to Helmholtz free energy △F, phonon contribution to internal energy △E, and specific iheat at constant-volume Cv, are calculated within quasi-harmonic approximation based on the calculated phonon dispersion relations.     

Biofabrication of silver nanoparticles from various plant extracts: blessing to nanotechnology

ABSTRACT

Nanotechnology is influencing life in many ways. Researchers are developing their interest in biofabrication of silver nanoparticles because of its excellent properties and boundless utilisation in almost every branch of science. Plant extract is used to synthesise silver nanoparticles and reduce silver ion, and act as capping and reducing agent. The phyto-chemicals and metabolites present in the extract help in biogenic reduction of silver ion, forming non-toxic nanoparticles. This review focuses on the green synthesis of nanoparticles from various plants and their parts as an easy and eco-friendly approach.     

Alumina‐Incorporated Polyesteramide from Non‐Edible Seed Oils

To improve the physico‐mechanical and chemical resistance properties, lower the curing temperature of annona squamosa and pongamia glabra seeds oils based polyesteramides [ASPEA, PGPEA], as well as to convert the non‐edible seed oils into value added products, their respective alumina‐incorporated polyesteramides resins [Al‐ASPEA, Al‐PGPEA] have been synthesized. The resins and their coatings have been tested for their chemical, physico mechanical and chemical/corrosion resistance properties. These properties were compared among the prepared resins and with that of previously reported alumina filled linseed polyesteramide [Al‐LPEA]. It was observed that Al‐PGPEA‐71, which has the highest amount of oleic acid chains, shows the best physico‐mechanical and chemical resistance properties.     

Evaluation of labelling conditions,quality control and biodistribution study of 99mTc-5-aminolevulinic acid (5-ALA): a potential liver imaging agent

Labelling of 5-aminolevulinic acid (5-ALA) with ^99mTc was achieved by using SnCl₂·2H₂O as reducing agent. Radiochemical purity and labelling efficiency was determined by instant thin layer chromatography/paper chromatography. Efficiency of labelling was dependent on many parameters such as amount of ligand, reducing agent, pH, and time of incubation. ^99mTc labelled 5-ALA remained stable for 24 h in human serum. Tissue biodistribution of ^99mTc-5-ALA was evaluated in Sprague–Dawley rats. Biodistribution study (% ID/g) in rats revealed that ^99mTc-5-ALA was accumulated significantly in liver, spleen, stomach and intestine after half hour, 4 and 24 h. Significant activity was noted in bladder and urine at 4 h. High liver uptake of ^99mTc-5-ALA makes it a promising liver imaging agent.     

Sugar-Catalyzed Synthesis of Triarylimidazoles—An Exemplary Model of Sweet Chemistry

Russian Journal of Organic Chemistry - A fine, green, and efficient method has been proposed for the synthesis of 2-aryl-4,5-diphenyl-1H-imidazoles using various sugars such as glucose, fructose,...