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Hemissi I.,French National Institute for Agricultural Research | Hemissi I.,Institute National Dagronomie Of Tunis | Hemissi I.,Center National des science et Technology Nucleaires | Mabrouk Y.,Center National des science et Technology Nucleaires | And 6 more authors.
African Journal of Microbiology Research | Year: 2011

Rhizoctonia solani is one of the most important soil-borne fungal pathogens that attack the roots of plant and causes significant damage to different plants particularly to chickpeas (Cicer arietinum L.). The aim of this work is to study the antagonistic activity of different Rhizobium strains against R. solani in dual culture in vitro and under greenhouse conditions. The benefits of rhizobial inoculant in nitrogen fixation, phosphorous uptake and on plant growth promoting were demonstrated with 42 Rhizobium strains. Among the 42 strains tested, 24 isolates had effective control on R. solani in vitro. In order to study the biological control mechanisms, the Rhizobium strains ability to produce volatile compounds and to solubilise phosphate were investigated. The results showed that 10 strains were able to solubilise phosphorus and 13 strains produced volatile compounds. In pot trials, the percentage of chickpea plants inoculated with different rhizobia showed significant reduce of root rot symptoms compared to the control growing in uninoculated soil. Among these rhizobiums, the strain S27 proved efficient against the soil borne pathogen in vitro and in pot experiments. Our study suggested that inoculation with specific Rhizobium exerts significant disease suppress against R. solani in controlled conditions. © 2011 Academic Journals.


Hosni F.,Center National des science et Technology Nucleaires | Farah K.,Center National des science et Technology Nucleaires | Farah K.,University of Sousse | Mejri A.,Center National des science et Technology Nucleaires | And 2 more authors.
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms | Year: 2012

The present paper reports the results of the study on the effect of the fractionation dose on the response of Red-Perspex dosimeter. Several experiments were carried out by combining the two factors: number of fractionation and storage time between fractions. Dosimeters were irradiated by gamma-rays to total doses of 10 and 40 kGy. These doses were delivered as single fraction, as well as in five fractions separated by different intervals of time: 1, 24 h and stored at 10 or 40 °C between successive irradiation. Three batches of Red-Perspex dosimeters (KS, GB, and EB) were used in this study. The relative specific response of dosimeters indicates a marked dependence of the number of fractionation and storage time. It was found that response variations due to dose fractionation can reach 18% in particular at high storage time and high temperatures. The dose fractionation effect has been found to be dependent of the batches. The obtained results allowed us to determine the necessary corrections for estimating doses with high accuracy.


Marzougui K.,Center National des science et Technology Nucleaires | Soliman Y.S.,National Center for Radiation Research And Technology | Farah K.,Center National des science et Technology Nucleaires | Farah K.,University of Sousse | And 5 more authors.
Radiation Measurements | Year: 2012

In order to improve the ease of sample handling, the reproducibility of signal detection and quantification, simple methods of incorporating a homogeneous mixture containing sugar powder (30%) with wax (35%) and rubber (35%) into rods has been adopted. The dose response, the time stability of the free radicals produced in table sugar dosimeters (in both rod and powder form) by gamma radiation and the effect of the temperature during irradiation were studied by EPR (Electron Paramagnetic Resonance). The peak-to-peak height (PPH) measurement of the EPR signal is studied as a function of the absorbed gamma dose in the range 0.1-58 kGy. For the two forms, a linear dependency is found between 0.1 and 26 kGy. At higher doses the EPR signal amplitude continues to grow but non-linear up to 58 kGy. The dependence of temperature during irradiation has been investigated in the temperature range 25-40 °C and the calculated correction coefficients were found (2.7 ± 0.2)% °C -1 and (1.5 ± 0.3)% °C -1, respectively, for powder and rod forms. The time stability of the stored sugar samples was investigated for 34 days at room temperature, a rapid decrease of EPR signal was showed immediately after irradiation followed by slowly decrease. © 2012 Elsevier Ltd. All rights reserved.


Hosni F.,Center National des science et Technology Nucleaires | Farah K.,Center National des science et Technology Nucleaires | Farah K.,University of Sousse | Hamzaoui H.,Center National Of Recherche En Science Des Materiaux
Superlattices and Microstructures | Year: 2013

In this paper, photoluminescence (PL) measurements as a function of temperature (T) are carried out to study the effect of gamma irradiation on an epoxy-based polymer. A series of epoxy resin samples are irradiated by gamma-rays with doses varying from of 10-40 kGy. The PL spectra of both non-irradiated and irradiated epoxy resin are formed by a wide asymmetric band attributed to the PL of the chromophores chain. The PL intensity is found to decrease as the temperature increases. This behavior is attributed to the dynamic transfer of the photo-induced carriers in the resin with absorbed doses, via phononic interaction, and indicates a marked dependence of the absorbed doses showing the optical activation of the traps center. Finally, the PL integrated intensity as a function of 1/T is simulated by the Arrhenius model with two activation energies for non-irradiated and irradiated sample at 10 kGy, while for doses superior to 10 kGy, a simple model of one activation energy is used. These models show that the gamma irradiation decreases the activation energy. © 2012 Elsevier Ltd. All rights reserved.


Hosni F.,Center National des science et Technology Nucleaires | Farah K.,Center National des science et Technology Nucleaires | Hamzaoui A.H.,Center National Of Recherche En Science Des Materiaux | Ouerghi A.,CNRS Optic of Semiconductor nanoStructures Group
Physica B: Condensed Matter | Year: 2014

The aim of this work is to investigate two different delta-doping (silicon and carbon) after gamma irradiation. Delta-doping GaAs/AlGaAs heterojunctions grown by molecular beam epitaxy on (1 0 0) GaAs substrates have been studied by photoluminescence (PL) spectroscopy. A theoretical study was conducted using the resolution of Schrödinger and Poisson equations written within the Hartree approximation. PL measurements as function of the power excitation at 10 K shows a red-shift due to free carriers effect on properties of GaAs/AlGaAs quantum well (QW). Its dependence on the density of the two-dimensional electron gas (2DEG) at the GaAs/AlGaAs interface has been analyzed on the basis of the quantum confined Stark, the band-gap renormalization and Burstein-Moss (BM) effects. It is noted that the gamma radiation has changed the type of the exciton recombination. © 2014 Elsevier B.V.


Mejri A.,Center National des science et Technologies Nucleaires | Mejri A.,Center National des science et Technology Nucleaires | Farah K.,Center National des science et Technology Nucleaires | Hosni F.,Center National des science et Technologies Nucleaires | And 3 more authors.
Mapan - Journal of Metrology Society of India | Year: 2015

During routine dosimetry for radiation processing applications, process interruption is widely encountered; in this case dosimeters may receive their target dose in two or more absorbed-dose increments. Some interruptions may be planned, for example double side irradiations may be used to improve dose distribution. Other interruptions may be the result of unplanned irradiator shutdowns. In this case, dosimeters may be exposed to outside factors, such as temperature, without exposure to ionizing radiation. The responses of these dosimeters are usually influenced because the conditions in irradiation facilities may differ considerably from the conditions in which the dosimeters were calibrated. These differences may lead to expected systematic errors in dose estimation. An original approach is proposed in this work in order to simulate a process interruption within limits and quantify the effects of a combination of factors on dosimeter response using complete factorial design 2n. We present an in-depth experimental study on the response of dosimeters that have been irradiated, stored for a fixed period of time at several temperatures, and then re-irradiated. This study was performed using Harwell Red Perspex dosimeter type 4035. © 2015, Metrology Society of India.


Hosni F.,Center National des science et Technology Nucleaires | Farah K.,Center National des science et Technology Nucleaires | Farah K.,University of Sousse | Kaouach H.,Institute National Of Recherche Scientifique Et Technique | And 3 more authors.
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms | Year: 2013

The present paper reports the results of the colorimetric study of gamma-irradiated epoxy-resin films. Epoxy-resin samples were irradiated by gamma-rays with doses varying from 1 to 50 kGy. Color changes of epoxy-resin were observed and studied by the measurements of the variation of the L*, a*, b* as function of dose and post-irradiation time. Where L* is a measure of the magnitude of brightness from black to white, parameter a* describe the relative amounts of red and green, and parameter b* describes the relative amounts of yellow and blue color. Color changes (ΔE) were also calculated. They indicated a marked dependence of the absorbed doses showing the optical activation of the color centers. It was found that color changes (ΔE) due to absorbed dose increase from 6 to 50. Color change showed a low variability which did not exceed 3% for the measurements carried out between 1 and 72 h. The obtained results revealed that epoxy-resin films can be used as a new routine dosimeter or irradiation indicator in dose range 1-50 kGy. © 2013 Elsevier B.V. All rights reserved.


Farah K.,Center National des science et Technology Nucleaires | Farah K.,University of Sousse | Hosni F.,Center National des science et Technology Nucleaires | Mejri A.,Center National des science et Technology Nucleaires | And 3 more authors.
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms | Year: 2014

Samples of a commercial silicate glass have been subjected to ion exchange at 320 C in a molten mixture of AgNO3 and NaNO3 with molar ratio of 1:99 and 5:95 for 60 min. The ion exchange process was followed by gamma irradiation in the dose range of 1-250 kGy and heating at the temperature of 550 C for different time periods ranging from 10 to 582 min. The spectral absorption in UV-Vis range of the Ag-Na ion exchanged glass was measured and used to determine the states of silver prevailing in the glass during the ion exchange, the gamma irradiation and the heat treatment. The gamma irradiation induced holes and electrons in the glass structure leading to the creation of a brown colour, and silver ions trapped electrons to form silver atoms. We observed the first stage of aggregation after irradiation, as well as after heating. The silver atoms diffused and then aggregated to form nanoclusters after heating at 550 C. A characteristic band at about 430 nm was induced. The surface Plasmon absorption of silver nanoclusters in the glass indicated that the nanoclusters radius grew between 0.9 and 1.43 nm with increasing of annealing time from 10 to 242 min and then saturated. We also found that the size of aggregates depends on the value of gamma radiation absorbed dose. Contrary to what was expected, we found that 20 kGy is the optimal absorbed dose corresponding to the larger size of the aggregates which decreases for absorbed doses above 20 kGy. © 2014 Elsevier B.V. All rights reserved.


Daoudi M.,Center National des science et Technology Nucleaires | Kaouach H.,University of Umm Al - Qura | Hosni F.,Center National des science et Technology Nucleaires
Optik | Year: 2016

We report on an experimental investigation of gamma radiation effects on the electronic and optical properties in carbon delta-doping GaAs/AlGaAs High Electron Mobility Transistors (HEMT) structures. Photoluminescence measurements are used to determine the electron-hole relaxation processes in the GaAs channel. For global information on the carriers dynamics in the structures examined, we studied their interactions with the crystal lattice, thermal activation states defects, the energy level activation. Gamma radiation has changed the electronic and optical properties in GaAs/AlGaAs structures, especially the carriers thermal activation. © 2016 Elsevier GmbH

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