Microcloning and characterization of DNA from pericentromeric heterochromatin of Drosophila melanogaster polytene chromosomes

A method of microcloning, which involves microsurgical excision of chromosome fragments, DNA amplification by means of a polymerase chain reaction (PCR), and ligation of amplified products with plasmids, was employed in studying Drosophila polytene chromosomes for the first time. Clones of the DNA library thus obtained contained inserts varying in size from 0.1 to 0.5 kb. DNA sequencing of five clones of the library showed that pericentromeric heterochromatin contained the 176 and 297 retrotransposons; the ninja retrotransposon characteristic of D. simulans; and two Drosophila repetitive elements, ag and a12, the function of which remains unknown

Ballistic Composites Reinforced with Inorganic Nanotubes of Tungsten Disulfide

This research considers a possibility of improving the impact and ballistic resistance of composite materials based on aramid fabric impregnated with poly (vinyl butyral), PVB, with the application of multi-layer inorganic nanotubes of tungsten disulfide (INT-WS2) as the reinforcement. Multi-layered nano-structures of tungsten disulfide are known by their excellent mechanical resistance, especially shock absorbing properties, which promote their use as a reinforcement in composite materials. INT-WS2 used in this research were observed using scanning electron microscope and the obtained images were analyzed in program Image Pro Plus. Before the application in the composite they were ultrasonically deagglomerated. Ballistic composites were prepared impregnating the aramid fabric with system PVB/INT-WS2 and by pressing defined number of layers under high pressure and defined temperature. Charpy impact test, ballistic shooting with two different ammunition calibers and stab resistance test with controlled knife penetration were performed on prepared composite samples, and resulted in significant improvements for samples with nano-reinforcement regarding the absorbed energy of impact, toughness and the ballistic resistance