SAID SHEHATA

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.

The protein kinase ataxia telangiectasia mutated (ATM) is activated when cells are exposed to ionizing radiation (IR). It has been assumed that ATM is specifically activated by the few induced DNA double strand breaks (DSBs), although little direct evidence for this assumption has been presented. DSBs constitute only a few percent of the IR-induced DNA damage, whereas the more frequent single strand DNA breaks (SSBs) and base damage account for over 98% of the overall DNA damage. It is therefore unclear whether DSBs are the only IR-induced DNA lesions that activate ATM. To test directly whether or not DSBs are responsible for ATM activation, we exposed cells to drugs and radiation that produce different numbers of DSBs and SSBs. We determined the resulting ATM activation by measuring the amount of phosphorylated Chk2 and the numbers of SSBs and DSBs in the same cells after short incubation periods. We found a strong correlation between the number of DSBs and ATM activation but no correlation with the number of SSBs. In fact, hydrogen peroxide, which, similar to IR, induces DNA damage through hydroxyl radicals but fails to induce DSBs, did not activate ATM. In contrast, we found that calicheamicin-induced strand breaks activated ATM more efficiently than IR and that ATM activation correlated with the relative DSB induction by these agents. Our data indicate that ATM is specifically activated by IR-induced DSBs, with little or no contribution from SSBs and other types of DNA damage. These findings have implications for how ATM might recognize DSBs in cells

Ontology is the backbone of the semantic web. To apply
the semantic web concept, you should build ontology for
your domain. Building ontologies require cooperation
among domain experts to classify items in the domain,
specify properties, and determine rules for inferring new
information from the ontology. Once ontology was built,
stored in knowledge base system and published on the
web, an intelligent search engine or an inference engine
can query and make inference on this ontology. Also
ontology developers can reuse and extend this ontology. In
this paper we will show how we can build ontology for the
crop pests in the Agriculture domain, specify what the
benefits of this ontology are and how the query result is
more accurate than searching traditional web. In our
process we used the Ontology Web Language (OWL) [1]
as it is the most recent Ontology language proposed by
World Wide Web Consortium W3C (http://www.w3c.org)
and for its powerful features. Also we used protégé2000 as
Ontology Editor as it is suitable for OWL.