Numerical evolution of Maxwell's equations for wavefronts propagating through a spherical gravitational potential

We present a scheme for numerically solving Maxwell's equations in a weakly perturbed spacetime without introducing the usual geometric optics approximation. Using this scheme, we study light propagation through a spherical perturbation of a stationary metric in the linear limit. Going beyond geometric approximation allows us to explore the wave optics effects that occur when the wavefront propagates through the gravitational potential. We find that the wavefront breaks on the gravitational potential due to the Shapiro time delay, i.e., due to the slowing down of light when propagating in an inhomogeneous spacetime. This again leads to constructive interference, resulting in a persistent frequency dependent amplification of parts of the wave amplitude. When the wave length is shorter than a certain threshold set by the induced gravitational mass, the waves are reflected on the curvature gradient.</p

New record of Sphenopid Zoanthid species Palythoa tuberculosa (Esper, 1805) from Gulf of Mannar, India

347-350Coral reefs provide a suitable habitat for many marine flora and fauna. Zoanthid is one of the most common inhabitants in coral reef habitats. A sub-massive colony of Sphenopid Zoanthid species Palythoa tuberculosa belonging to the order Zoantharia was documented for the first time from Gulf of Mannar (GoM) during an intensive coral reef monitoring survey conducted in Manoli, Manoliputti and Shingle Island. Photographic evidence of the colony along with its morphological characteristics are described in the present study

Liquid Phase Hydrogenation of Pharmaceutical Interest Nitroarenes over Gold-Supported Alumina Nanowires Catalysts

In this work, Au nanoparticles, supported in Al2O3 nanowires (ANW) modified with (3-aminopropyl)trimethoxysilane were synthetized, for their use as catalysts in the hydrogenation reaction of 4-(2-fluoro-4-nitrophenyl)-morpholine and 4-(4-nitrophenyl)morpholin-3-one. ANW was obtained by hydrothermal techniques and the metal was incorporated by the reduction of the precursor with NaBH4 posterior to superficial modification. The catalysts were prepared at different metal loadings and were characterized by different techniques. The characterization revealed structured materials in the form of nanowires and a successful superficial modification. All catalysts show that Au is in a reduced state and the shape of the nanoparticles is spherical, with high metal dispersion and size distributions from 3.7 to 4.6 nm. The different systems supported in modified-ANW were active and selective in the hydrogenation reaction of both substrates, finding for all catalytic systems a selectivity of almost 100% to the aromatic amine. Catalytic data showed pseudo first-order kinetics with respect to the substrate for all experimental conditions used in this work. The solvent plays an important role in the activity and selectivity of the catalyst, where the highest efficiency and operational stability was achieved when ethanol was used as the solventIndexación: Scopu

Nanocatalizadores metálicos soportados en estructuras 0d y 1d con aplicaciones en química fina

El desafío actual en el diseño racional de catalizadores aplicados en la producción de compuestos químicos de alto valor agregado radica en la preparación de sistemas que sean capaces de operar en ciclos catalíticos consecutivos manteniendo una alta actividad y selectividad en la producción del compuesto de interés.Centro de Investigación y Desarrollo en Ciencias Aplicada

Catalytic pyrolysis of used tires on noble-metal-based catalysts to obtain high-value chemicals: Reaction pathways

A systematic study on the use of noble metals (Pd, Pt, Au) supported on titanate nanotubes (NT-Ti) for selectively producing BTX and p-cymene from waste tire pyrolysis is provided here. All the materials were characterized for chemical, textural and structural properties using a range of analytical techniques. The M/NT-Ti (M: Pd, Pt, or Au) catalysts exhibit low nanoparticle sizes (1.8 Pt ≈ Au > support > non-catalyst. The Py-GC/MS suggest that the catalysts participate in the secondary reactions of dealkylation, dehydrogenation, isomerization, aromatization, and cyclization leading to a higher formation of BTX than the uncatalyzed reaction. Finally, a comprehensive reaction pathway describing the catalytic pyrolysis of WT over Pd/NT-Ti was proposed by studying the catalytic pyrolysis of individual polymers constituting the waste tires, and D,L-Limonene.Puede accederse a los datos primarios de este trabajo haciendo clic en "Documentos relacionados".Centro de Investigación y Desarrollo en Ciencias Aplicada

Nanocatalizadores metálicos soportados en estructuras 0d y 1d con aplicaciones en química fina

El desafío actual en el diseño racional de catalizadores aplicados en la producción de compuestos químicos de alto valor agregado radica en la preparación de sistemas que sean capaces de operar en ciclos catalíticos consecutivos manteniendo una alta actividad y selectividad en la producción del compuesto de interés.Centro de Investigación y Desarrollo en Ciencias Aplicada

Catalytic pyrolysis of used tires on noble-metal-based catalysts to obtain high-value chemicals: Reaction pathways

A systematic study on the use of noble metals (Pd, Pt, Au) supported on titanate nanotubes (NT-Ti) for selectively producing BTX and p-cymene from waste tire pyrolysis is provided here. All the materials were characterized for chemical, textural and structural properties using a range of analytical techniques. The M/NT-Ti (M: Pd, Pt, or Au) catalysts exhibit low nanoparticle sizes (1.8 Pt ≈ Au > support > non-catalyst. The Py-GC/MS suggest that the catalysts participate in the secondary reactions of dealkylation, dehydrogenation, isomerization, aromatization, and cyclization leading to a higher formation of BTX than the uncatalyzed reaction. Finally, a comprehensive reaction pathway describing the catalytic pyrolysis of WT over Pd/NT-Ti was proposed by studying the catalytic pyrolysis of individual polymers constituting the waste tires, and D,L-Limonene.Puede accederse a los datos primarios de este trabajo haciendo clic en "Documentos relacionados".Centro de Investigación y Desarrollo en Ciencias Aplicada