Experimental study on novel phase change composites for thermal energy storage

Journal of Thermal Analysis and Calorimetry - In this study, beeswax is studied as a phase change material (PCM) to store heat due to its high latent heat. The disadvantages of using beeswax were...     

Rapid,efficient and solvent-free synthesis of (un)symmetrical xanthenes catalyzed by recyclable sulfated polyborate

The present study describes a rapid, simple and straightforward approach to the synthesis of 1,8-dioxo-octahydroxanthenes, 14-phenyl-14H-dibenzo[a,j]xanthene and tetrahydrobenzoxanthene-11-ones under solvent-free conditions using sulfated polyborate as a highly efficient catalyst. The procedure offers several advantages including cleaner reaction profile, mild reaction condition, economic, recyclable and environmentally benign catalyst, high yields, simple experimental and workup procedures. While non-extractive work up/purification, along with reusability of catalyst make this method economically affordable for large scale.     

New trends in sustainable nanocatalysis: Emerging use of earth abundant metals

Noble metals are well-known to afford highly active, selective and durable catalysts, and have thus been at the core of the development of greener processes. In recent years, however, growing concerns about their scarcity, cost and toxicity has triggered research efforts towards the development of earth-abundant catalysts. In this Current Opinion, recent examples of the use in catalysis of pure earth-abundant metals, earth-abundant metals with minute quantities of noble metals, or earth-abundant metals activated by light are presented. This highlight article showcases the current trends in sustainable organic transformations, catalyzed by nanomaterials.     

21-cm radiation: a new probe of variation in the fine-structure constant

We investigate the effect of variation in the value of the fine-structure constant (alpha) at high redshifts (recombination > z > 30) on the absorption of the cosmic microwave background (CMB) at 21 cm hyperfine transition of the neutral atomic hydrogen. We find that the 21 cm signal is very sensitive to the variations in alpha and it is so far the only probe of the fine-structure constant in this redshift range. A change in the value of alpha by 1% changes the mean brightness temperature decrement of the CMB due to 21 cm absorption by >5% over the redshift range z < 50. There is an effect of similar magnitude on the amplitude of the fluctuations in the brightness temperature. The redshift of maximum absorption also changes by approximately 5%.     

Effect of heterocyclic ring system on formation of dimeric quinolones under catalyst-free conditions: a green approach

The intermediate-dependent green and efficient synthesis of dimeric quinolones 4a–l and 7a–l by the Knoevenagel condensation followed by Michael-type addition of 4-hydroxy-1-methylquinolin-2(1H)-one 1a, b to indole-3-aldehydes 2a–f and aromatic aldehydes 5a–l in water through the condensed compound 3a–l under catalyst-free conditions is described. This reaction was found to be environmentally friendly, has easy-workup and shorter reaction times giving good yields of the product without the need for its isolation using column chromatography.     

Nickel-catalyzed Negishi cross-coupling reactions of secondary alkylzinc halides and aryl iodides

A general Ni-catalyzed process for the cross-coupling of secondary alkylzinc halides and aryl/heteroaryl iodides has been developed. This is the first process to overcome the isomerization and β-hydride elimination problems that are associated with the use of secondary nucleophiles, and that have limited the analogous Pd-catalyzed systems. The impact of salt additives was also investigated. It was found that the presence of LiBF(4) dramatically improves both isomeric retention and yield for challenging substrates.     

A nonlinear model for footings on granular bed–stone column reinforced earth beds

In the present study, an attempt has been made to model and analyze a combined footing supporting column, which is to be constructed on very soft soil. In view of small bearing capacity and very large deflections, foundations are constructed after improving the original ground. Here, the ground has been improved by providing the stone columns in the soft soil and on top of this improved ground; a granular fill layer has been placed just below the footing. The footing has been modeled as a beam having finite flexural rigidity. Granular fill layer, soft soil and stone columns have been represented by Pasternak shear layer, Kelvin–Voigt body and the Winkler springs, respectively. Nonlinear behavior of these has been considered by means of hyperbolic constitutive relationships. Governing differential equations for response of the system have been derived and presented in non-dimensional form. These equations have been solved using appropriate boundary conditions by means of an iterative Gauss Elimination technique.     

Photocatalytic splitting of CS2 to S8 and a carbon-sulfur polymer catalyzed by a bimetallic ruthenium(II) compound with a tertiary amine binding site: toward photocatalytic splitting of CO2?

The catalytic photocleavage of CS(2) to S(8) and a (C(x)S(y))(n) polymer with visible light using a dinuclear ruthenium(II) compound with a bipyridine units for photoactivity and a vicinal tertiary amine binding site for CS(2) activation was studied. The catalyst was characterized by X-ray diffraction, (1)H NMR, and (13)C NMR, ESI-MS and elemental analysis. CS(2) photocleavage was significant (240 turnovers, 20 h) to yield isolable S(8) and a (C(x)S(y))(n) polymer. A mononuclear catalyst or one without an amine binding site showed significantly less activity. XPS of the (C(x)S(y))(n) polymer showed a carbon/sulfur ratio ～1.5-1.6 indicating that in part both C-S bonds of CS(2) had been cleaved. Catalyst was also included within the polymer. The absence of peaks in the (1)H NMR verified the (C(x)S(y))(n) nature of the polymer, while (13)C NMR and IR indicated that the polymer had multiple types of C-S and C-C bonds.