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giving about 417,000 per c.c. after considerable shrinkage in 5 per cent formalin during four months. This result is considered not incompatible with an ill:dependent count of 11 ,928 larvre (preserved in the slightly smaller trochosphere stage) in one drop of liquid, giving about 300,000 p er c.c. without close packing.

The critical current density, Jc  has been the most important parameter used in the design and engineering of effective devices which is one of the implementation of high temperature superconductors (HTSC). In this work, an effort has been made to further improve the critical current density of YBa2Cu3O7-x (YBCO) thin films by preventing the magnetic flux line lattice against the Lorentz force by pinning it in place with the aid of nano-dimensional defects. These defects were generated by distributing nano sized CeO2 islands after YBCO layer was created on LaAlO3 substrates perpendicular to the film using pulsed laser deposition (PLD) technique. Three samples with buffer layers of CeO2 were prepared. CeO2 with 50 pulses, 100 pulses and 150 pulses, after each 1000 pulses of YBCO were prepared five layers for each of the samples. The structural characterization of YBCO/CeO2 and YBCO pristine films were carried out using x-ray diffraction (XRD) and scanning electron microscopy (SEM). Superconducting proprieties were measured using a vibrating sample magnetometer (VSM). Jc  for the pure YBCO and the YBCO/CeO2 films were calculated from magnetization (M) versus Field (H) loops using Bean’s model. Jc  for the 50 pulses of YBCO/CeO2 films was found to be increased slightly by an order of magnitude of about 40% with respect to those of YBCO films without the nano dimensional defects.