Banaras Hindu University

About: Banaras Hindu University is a education organization based out in Varanasi, Uttar Pradesh, India. It is known for research contribution in the topics: Population & Dielectric. The organization has 11858 authors who have published 23917 publications receiving 464677 citations. The organization is also known as: Kashi Hindu Vishvavidyalay & Benares Hindu University.

Direct Imaging of a Two-Dimensional Silica Glass on Graphene

Abstract: Large-area graphene substrates provide a promising lab bench for synthesizing, manipulating, and characterizing low-dimensional materials, opening the door to high-resolution analyses of novel structures, such as two-dimensional (2D) glasses, that cannot be exfoliated and may not occur naturally. Here, we report the accidental discovery of a 2D silica glass supported on graphene. The 2D nature of this material enables the first atomic resolution transmission electron microscopy of a glass, producing images that strikingly resemble Zachariasen's original 1932 cartoon models of 2D continuous random network glasses. Atomic-resolution electron spectroscopy identifies the glass as SiO2 formed from a bilayer of (SiO4) 2− tetrahedra and without detectable covalent bonding to the graphene. From these images, we directly obtain ring statistics and pair distribution functions that span short-, medium-, and long-range order. Ab initio calculations indicate that van der Waals interactions with graphene energetically stabilizes the 2D structure with respect to bulk SiO2. These results demonstrate a new class of 2D glasses that can be applied in layered graphene devices and studied at the atomic scale.

Solar ultraviolet radiation-induced DNA damage in aquatic organisms: potential environmental impact.

Abstract: Continuing depletion of stratospheric ozone and subsequent increases in deleterious ultraviolet (UV) radiation at the Earth's surface have fueled the interest in its ecological consequences for aquatic ecosystems. The DNA is certainly one of the key targets for UV-induced damage in a variety of aquatic organisms. UV radiation induces two of the most abundant mutagenic and cytotoxic DNA lesions, cyclobutane pyrimidine dimers (CPDs) and pyrimidine pyrimidone photoproducts (6-4PPs) and their Dewar valence isomers. However, aquatic organisms have developed a number of repair and tolerance mechanisms to counteract the damaging effects of UV on DNA. Photoreactivation with the help of the enzyme photolyase is one of the most important and frequently occurring repair mechanisms in a variety of organisms. Excision repair, which can be distinguished into base excision repair (BER) and nucleotide excision repair (NER), also play an important role in DNA repair in several organisms with the help of a number of glycosylases and polymerases, respectively. In addition, mechanisms such as mutagenic repair or dimer bypass, recombinational repair, cell-cycle checkpoints, apoptosis and certain alternative repair pathways are also operative in various organisms. This review deals with the UV-induced DNA damage and repair in a number of aquatic organisms as well as methods of detecting DNA damage.