Publications by authors named "Syam Kumar"

Perovskites have stood out as excellent photoactive materials with high efficiencies and stabilities, achieved via cation mixing techniques. Overcoming challenges to the stabilization of Perovskite solar cells calls for the development of design principles of large cation incorporation in halide perovskite to accelerate the discovery of optimal stable compositions. Large fluorinated organic cations incorporation is an attractive method for enhancing the intrinsic stability of halide perovskites due to their high dipole moment and moisture-resistant nature.

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A unique oxidative dehydration-oxidation of polyhydroxy-oxime (7) to the corresponding ketonitrile (8) in one pot is reported for the first time in carbohydrate literature. Key ketonitrile intermediate (8) upon palladium hydroxide mediated cascade reaction afforded 1-deoxynojirimycin (DNJ) 1b in moderate diastereoselectivity. The cascade reaction involves the conversion of nitrile to amine, heteroannulation, reduction of the imine and subsequent debenzylation to furnish the azasugars.

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The recalculation of 1 fraction from a patient treatment plan on a phantom and subsequent measurements have become the norms for measurement-based verification, which combines the quality assurance recommendations that deal with the treatment planning system and the beam delivery system. This type of evaluation has prompted attention to measurement equipment and techniques. Ionization chambers are considered the gold standard because of their precision, availability, and relative ease of use.

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Aim: To evaluate the performance of volumetric arc modulation with RapidArc against conventional IMRT for head and neck cancers.

Background: RapidArc is a novel technique that has recently been made available for clinical use. Planning study was done for volumetric arc modulation with RapidArc against conventional IMRT for head and neck cancers.

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Aim: In this study, the dosimetric properties of the electronic portal imaging device were examined and the quality assurance testing of Volumetric Modulated Arc Therapy was performed.

Background: RapidArc involves the variable dose rate, leaf speed and the gantry rotation. The imager was studied for the effects like dose, dose rate, field size, leaf speed and sag during gantry rotation.

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A five-step formal synthesis of alkaloid cryptotackiene and its 2-formyl, 11-methyl/phenyl derivatives involving conjugate addition of enolate anion from cyclohexanone (or 4-methylcyclohexanone) to bis[(methylsulfanyl)methylene]-2-oxindole followed by heterocyclization in the presence of ammonium acetate as the key step has been developed. The 11-methylsulfanyl group in the initial precursor can be either desulfurized (Raney Ni) or replaced by methyl/phenyl groups via nickel-catalyzed cross-coupling reaction with appropriate Grignard reagents.

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A simple, highly efficient, and regioselective synthesis of functionalized quinolines through Vilsmeier cyclization of a variety of alpha-oxoketene-N,S-anilinoacetals has been reported. The cyclization is found to be facile with N,S-acetals bearing strongly activating groups on aniline, whereas yields of quinolines are moderate in other cases. The reaction could also be extended for the synthesis of substituted tricyclic benzo[h]quinoline, pyrido[2,3-h]quinoline, 4,7-diphenylphenanthroline, and tetracyclic quino[8,7-h]quinoline by performing a Vilsmeier reaction on N,S-acetals derived from 1-naphthylamine, m-phenylenediamine, o-phenylenediamine, and 1,5-diaminonaphthalene, respectively.

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A new approach for the synthesis of spiropyrrolidinyloxindole alkaloids, i.e. coerulescine (4) and horsfiline (5) has been developed via iodide ion induced rearrangement of [(N-aziridinomethylthio)methylene]oxindoles 2 to the respective spiropyrroline-2-oxindole derivatives 3 and their subsequent one-pot reductive dethiomethylation-N-methylation.

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