Aboul Ella Hassanien (Abo)

Effluent from the baker's yeast industry was experimented on as a culture medium for the growth and biomass production of diazotrophs. The effluent supported good growth of Azotobacter chroococcum, Enterobacter agglomerans and Klebsiella pneuomoniae, Azospirillum brasilense, Bacillus polymyxa and Pseudomonas putida and strongly proposed for biofertilizers production of associative diazotrophs. Slurry preparations containing natural polymers, e.g. Arabic gum (5%), pero-dextrin (20%), starch granules (10%) or gelatine (20%) were impregnated with cells of tested diazotrophs. With storage, entrapped cells of B. polymyxa were viable up to 160 days, while gradual decreases in Azospirillum numbers were recorded. Pero-dextrin, a by-product of the starch industry, was selected as the appropriate biocarrier accommodating diazotroph cells and maintaining prolonged survival rates and nitrogenase activity. Cell cultures of A. brasilense, A. chroococcum, B. polymyxa, E. agglomerans and P. putida were equally mixed and entrapped into pero-dextrin slurry biofertilizer formulation named as "BIOGRAMINA". Tested diazotrophs successfully survived (ca. 108 cfu ml-1) in such formulation up to 6 months at both ambient and cold temperatures. The response of wheat and barley to "BIOGRAMINA" in the presence or absence of N fertilizers was evaluated in greenhouse and field trials. Highest total biological yields were recorded for inoculated plants simultaneously supplemented with rational N fertilizer dose. © 2005 Taylor & Francis.

Industrial baker's yeast effluent (BYE) was experimented on as a culture medium for growth and biomass production of six fast-growing rhizobia strains. Diluting the effluent with distilled water was necessary to maximize bacterial biomass production. The addition of phosphate buffer, ammonium chloride or trace-elements did not improve the final biomass yield of tested micro-organisms. Rhizobial growth and biomass on the effluent were comparable to traditional yeast extract mannitol medium (YEM). The Rhizobium spp. biomass, produced using either YEM or BYE, was evaluated as inoculum for Leucaena leucocephala (Lam.) de Wit in a pot experiment. No significant differences were reported in respect of legume nodule and growth parameters. Simultaneous inoculation with rhizobia and a group of associative diazotrophs supported better nodulation and nitrogenase activity. © 2005 Taylor & Francis.

The electrical properties measurements were carried out for the complex (CH2)2Mn1-x Cd x Cl4, 0.0 ≤ x ≤ 1.0 at different temperatures as a function of frequency (100-1000 kHz). Four transition points were obtained for x = 0.5, which were assigned as thermochroism, interlayer exchange interaction, order-disorder and chain melting transition. The presence of more than one straight line in the conductivity data clarifies the presence of more than one conduction mechanism, and the calculated values of the activation energy indicate the semiconducting characteristics of the investigated complexes. The values of the relaxation time depend on Cd-content as well as the heating temperature. The expected critical concentration at x = 0.5 agrees well with the percolation theory of Mont-Carlo group. The IR spectra indicate that, the force constant of the bonds and the atomic mass vibration are affected by Cd-content. © 2005 Springer Science + Business Media, Inc.

Samples of orthoferrites La1-xCaxFeO3 (0.15≤x≤0.45) were synthesized by double sintering ceramic technique. X-ray diffraction and infrared spectroscopy experiments were carried out and discussed for the investigated samples. The data showed the formation of single-phase orthorhombic structure of space group Pbnm. The FTIR spectra were performed in the region (1200-200 cm-1). Four main absorption bands were present with some side bands and shoulders in the range (1200-400 cm -1). Another four bands were appeared in the range (400-200 cm -1). The positions, intensities and values of the absorptions bands vary depending on the Ca content in the samples. The first absorption band appeared at about 920 cm-1 was assigned to the La-O stretching vibration. © 2005 Elsevier B.V. All rights reserved.

The spinel ferrite system Ni1-xZnxLa yFe2-yO4; 0.0 ≤ x ≤ 1.0 and y = 0.0, 0.05 is prepared by standard ceramic method. X-ray diffraction is used to obtain the structural characterization of Ni, Zn, Ni-Zn and Ni-Zn-La ferrite. The influence of zinc ion substitution on the electrical properties of samples is investigated indicating, that the ac conductivity (ln σ) as well as dielectric constant (ε′) are nearly constant for small Zn ion concentration, while they increase at high Zn content (x = 0.6). The calculated values of the activation energy confirm the obtained results and indicate the semiconductor properties of the investigated samples. The dielectric constant data shows more than one peak which is discussed in view of the ionization potential of each element and hopping mechanism. © 2004 Elsevier B.V. All rights reserved.

Seven samples of the system Cu1-x Cd x Fe 2O4 were prepared by thermal decomposition of mixed metal oxalates with x = 0.0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0. The formation of the ferrispinel was studied by XRD, FT-IR, Mössbauer spectroscopy, electrical conductivity and magnetic susceptibility measurements. XRD showed single cubic spinel phase for all the samples except for CuFe2O4 sample which shows a tetragonal structure. An increase in the lattice parameter of the ferrispinel was observed with increasing the cadmium content. The temperature variation of ac conductivity showed four definite regions with three transitions which attribute to the change in the conduction mechanism with increasing temperature. Magnetic properties of the sample with x ≤ 0.5 showed a decrease in the effective magnetic moment with the increase in the cadmium content which means that the ferromagnetics are widely separated and enclosed by non-magnetic cadmium ions. A well defined hyperfine Zeeman spectrum is observed for samples with x ≥ 0.3 at room temperature and resolved into two sextets corresponding to the octahedral and tetrahedral sites. The propable ionic configuration of the system proposed is (Cd x Cu y Fe1-x-y )[Cu1-x-y Fe1+x+y ]O4. © 2005 Springer Science + Business Media, Inc.