نرگس خدابخشی

A cylindrical PA cell is designed and constructed; also the Q factor, thermal and viscous loss depths and resonance frequencies are calculated for each buffer gas. The NO2 sample gas and Ar buffer are inserted to the cell and minimum concentration is detected 47.5 ppm at 700 mbar. In this experiment the cell is illuminated with a chopped CW CO2 laser beam. Then the buffer gas is replaced by N2 in the same pressure and minimum detectable concentration is obtained to be 62.2 ppm. The output of another CW Nd:YAG laser after passing through the chopper illuminates the cell in the same experimental condition giving 32.8 and 16.2 ppm minimum detectable concentration for Ar and N2 buffers, respectively. For these four experiments, the magnitude of PA signals are plotted against pressure and it is shown that the slope of the graph when using Nd:YAG laser and N2 buffer gas is approximately 2 times greater than the others.

In order to study the effect of Synorhizobium meliloti on growth and nutrients uptake of sesame, a greenhouse test was carried out. The first isolates investigated in IAA and siderophore producing and their ability in solubilizing inorganic phosphates. The results showed that all of isolates were able to produce auxin with different among. The maximum amount of IAA production was 59.5 g ml-1 that was related to SR24 isolate. All isolates could solubilize tricalcium phosphate (Ca3(PO4)2) in Sperber medium, and SR18 with 139 µg ml-1 had the highest ability to solubilize tricalcium phosphate. Also SR3 and SR32 isolates produced the highest amont of siderophore. According to the results, five isolates that were better in IAA and siderophore producing and solubilizing inorganic phosphates were selected and used in a greenhouse test. This experiment was conducted base on completely randomized design with five treatment including four isolates of Synorhizobium meliloti and one treatment without bacteria as control and four replications. The results indicated that inoculation of isolates enhanced Sesame shoot dry weight compared to control and this increasing was significant for SR18, SR16 and SR3. Application of most isolates also increased measured nutrients uptake in Sesame shoot. However only isolate SR18 significantly increased the nutrients uptake including P, Zn, Cu and Fe compared to control.