Synthesis and characterization of Co[3]O[4]/CeO[2] nanocomposite

Ceria based nanocoomposite oxides containing different amounts of cobalt [4, 8, 15, 21, 26, 30 wt% ad Co[3]O[4]] were prepared by impregnation method at various calcinations temperatures. The effect of both heat treatment and loading on the structural, textural and morphological properties of the as prepared nanocomposites was determined. The combined effect of cobalt oxide and ceria, at different compositions, strongly influences the properties of the nanocomposite oxide, by dispersing the Co[3]O[4] phase and promoting the efficiency of the Co[3+]-Co[2+] and Ce[4+] - Ce[3+] redox couples. The heat treatment and loading influenced the interaction between cobalt and CeO[2] evidently. The incorporation of Co ions into CeO[2] crystal lattice resulted in weaker interaction between cobalt and ceria on composite surface. Cobalt loading of sample heated at 500 [degree sign]C led to a progressive decrease in the crystallite size, lattice constant and unit cell volume of cerium and cobalt oxides. Co[3]O[4] loading at 500 [degree sign]C brought about a significant increase in the surface area of the investigated system. Opposite behavior was observed by increasing the calcinations temperature from 400 to 600 [degree sign] C. However, the sintering activation energies of cerium and cobalt oxides were evaluated to be 8 and 11 kJ/mol, respectively

Ultrastructural changes of pneumocytes of rat exposed to arabian incense [Bakhour]

Impacts of air pollution on the human health have been recognized over the last decades. Smokes, in particular, have deleterious effects on the respiratory system. According to a local tradition, incense "Bakhour" is burnt and the resultant heavy smokes are inhaled. The objective of the present study is to investigate the ultrastructural pulmonary changes which can be induced by Arabian incense, Bakhour, exposure. The study was conducted from September through to December 2003, at the Animal House, College of Science, King Saud University, Riyadh, Kingdom of Saudi Arabia. Two groups of Wister albino rats, Rattus norvegicus, were used. One group [n=16] was exposed to 420 grams of Bakhour for 14-weeks at the rate of 4 grams/day in the exposure chamber. Additional group of rats, of equal number, was used as non-exposed control. At the end of the exposure period, lung tissues were removed from all experimental animals and processed for electron microscopy. Alveolar pneumocytes of exposed animals revealed significant ultrastructural changes which involved the cell organelles and surfactant material of type II cells. Hyperplasia of alveolar cells was a feature in the affected lung tissue. Neutrophils were recognized infiltrating pulmonary alveoli and accompanied with degenerative and necrotic changes of the alveolar cells. Deposition of collagen fibrils in the alveolar walls was also observed. Basing upon the results of electron microscopy, it was concluded that exposure to Bakhour can induce ultrastructural pulmonary changes which may imply compromised respiratory efficiency