ahmad hassani

In this paper, the effect of the the vertical component of the earthquake acceleration on the seismic bearing capacity factors (i.e. Nq, Ncand Nγ) are investigated by employing the method of stress characteristics. By mixing the differential equations of stress equilibrium and the Moher-coulomb failure criterion, a system of plastic equilibrium equations is obtained. The generated stresses in the soil mass under the foot surface and next to it in limit state is calculated by solving plastic equilibrium equation system with the method of characteristics. Results show that, the effect of the vertical component of the earthquake acceleration in absence of horizontal component will cause reduction of the bearing capacity factors Nq, Nγ; because having no effect on Nc.The effect of the vertical component of the earthquake acceleration associated with horizontal component will cause reduction resonance on the seismic bearing capacity factors. Using the principle of superposition to obtain of the ultimate bearing pressure of the footing can be a safety.

Ribosomal DNA (rDNA) genes contain signature structures which are unique for groups of organisms. Considering their great number in cells and their protected areas, they render ideal targets for specific nucleic acid probes. The present study aimed to investigate the capability of some specific regions of 23S rDNA gene as a DNA target for differentiation and screening of Escherichia coli, Salmonella enterica, and Shigella dysenteriae. Bacterial reference strains used in this study were E. coli, S. enterica and Sh. dysenteriae that were provided by the centers for microbial culture collection (CMCC) at Pasture Institute of Iran. DNA extraction was performed by boiling method. Alignment of the 23S rDNA sequences of bacterial species was performed by using AlignX (a component of Vector NTI Advance 11.0) and areas displaying sequence divergence among species were used for designing universal primers and individual bacteria specific probe. The universal polymerase chain reaction (PCR) products of each bacterial species showed bands of approximately 880 bp to be being equivalent to the fragment size of 23S rDNA gene. Different size bands of 23S rDNA probes were produced and included 228 bp for E. coli, 444 bp for S. enterica, and 776 bp for Sh. dysenteriae. Comparative sequence analysis of variable and specific regions of 23S rDNA genes among the studied bacterial species showed that we were able to amplify specific target among universal region for the detection of many enteric pathogenic bacteria.