New 1212-Molybdo-Cuprate phases using High pressure and high temperature synthesis

ABSTRACTNew 1212- type Molybdo-Cuprates of with composition Mo0.5Cu0.5Sr2RECu2O7.5 (RE = Rare Earth) have been prepared by High Pressure and High Temperature (HPHT) synthesis. Their crystal structures are characterized by combining the X-Ray/Neutron powder diffraction and electron diffraction techniques. All the materials show tetragonal symmetry, crystallizing in the P4/mmm space group (S.G.). The chain oxygens are randomly distributed in the two different oxygen sites, which are not completely filled and the defect induced by oxygen vacancies in fact makes the chain fragmented and disordered. The microstructure of these compounds is interpreted by a well-known diagonal cell √2ap × √2ap × 3ap, as confirmed by the Electron diffraction (ED) and transmission electron microscope (TEM). X-ray photoelectron spectroscopy (XPS) studies show the predominance of the non magnetic MoVI state over the MoV one. At the same time oxidation state of copper is found to be dominated by CuII.

Microvillar Orientation in the Retina of a Pierid Butterfly

The orientation of microvilli in the compound eye of the butterfly. Pieris protodice, has been examined using electron microscopy. The retinula cells comprising each ommatidium have been divided into four types based upon microvillar orientation, position of nucleus, and location within the om­matidium. The vertical and horizontal retinular types have microvilli in the distal one-third to half of the retina. There is alteration in the orientation of these microvilli of up to 90 . The rhabdom is dominated by the microvilli of the diagonal retinulae in the proximal retina. There is consistant orientation of the diagonal cell microvilli throughout the retina. In mid-retina, these microvilli undergo dramatic alteration in length, leading to a Crustacean-like organiza­tion. for some 50 μm. The basal, or eccentric, retinula cell is bilobed. and has only a few microvilli projecting a short distance into the rhabdom.