أحمد رحيم شلتاغ كرعاوي

The influence of capped gold nanospheres (GNSs) on the direct current (DC) electric conductivity (σDC) of a ferroelectric liquid crystal (FLC) confined in a cell with blocking electrodes was experimentally investigated. In framework of this work, several measurement techniques of σDC, such as dielectric and conductivity spectroscopies, were utilised. However, it was demonstrated that only the capacitive technique allowed estimating values of σDC of both pure FLC and FLC/GNSs nanodispersion confined in the cell with blocking electrodes. The experimental results confirm the assumption that the gold nanoparticles adsorb the impurities' ions in FLC which leads to the decrease in the conductivity of the FLC layer.

Liquid crystals are a perspective type of materials for application in the field of tactile pressure sensors owning to their unique physical properties. One of such properties is the anisotropic electric conductivity, the value of which can be controlled by the external electric field. In this report we will consider a capacitive method of the measurement of the direct current conductivity in the liquid crystal layer, confined in the cell with blocking electrodes. It will be demonstrated that this technique allows estimating the direct current conductivity of a liquid crystal in a broad temperature range. The retrieved results can be used

It is well established that incorporation of nanoparticles (NPs) in the structure of ferroelectric liquid crystals (FLCs) leads to a decrease in their electrooptic response time. Several approaches have been suggested to explain this effect (decrease in rotational viscosity of FLCs, ions enhanced localised electric field, dipole–dipole interaction among NPs and FLC molecules, FLC ordering). In this article, we will report the role of the voltage divider formed by the structural elements of a FLC cell based on ferroelectric liquid crystal/gold nanospheres (FLC/GNSs) dispersion in enhancement of the switching time. Using the impedance spectroscopic measurements, it was demonstrated that the dispersing of GNSs leads to the increase in the voltage drop on FLC/GNSs layer in comparison with the pristine FLC one. Consequently, the electrooptic response time of the FLC/ GNSs cell is faster than that of the pristine one. However, the rotational viscosity of the FLC does not depend on the presence of the GNSs.

Biscuits are an important type of food, widely consumed by babies in Iraq and other countries. This work uses gamma spectroscopy to measure the natural radioactivity due to long-lived gamma emitters in children’s biscuits; it also estimates radiation hazard indices, that is, the radium equivalent activity, the representative of gamma level index, the internal hazard index, and the annual effective dose in children. Ten samples were collected from the Iraqi market from different countries of origin. The average specific activities for 226Ra, 232Th, and 40K were 9.390, 3.1213, and 214.969 Bq/kg, respectively, but the average of the radium equivalent activity and the internal hazard index were 33.101 Bq/kg and 0.107, respectively. The total average annual effective dose from consumption by adults, children, and infants is estimated to be 0.655, 1.009, and 0.875 mSv, respectively. The values found for specific activity, radiation hazard indices, and annual effective dose in all samples in this study were lower than worldwide median values for all groups; therefore, these values are found to be safe.

In this work, Radon concentrations in drinking water were measured at 42 locations in Al- Najaf cities, using RAD-7 radon monitoring system of Durridge company USA. The annual effective dose for all samples of drinking water were estimated by equations depending on UNSCEAR organization. It is found that the radon concentrations in samples in studied area were varied from (2.43±0.879 Bq/m3) to (225.5±12.657 Bq/m3), while the mean annual effective dose of Ingestion and Inhalation varied from (0.017739 μS.y-1) to (1.64615 μS.y-1) and (0.088807 μS.y-1) to (0.704526 μS.y-1) respectively. When the results were compared of radon concentrations with the internationally recommended reference levels (World healthy Organization limit 500 Bq/m3) and the mean effective annual dose for radon in drink water normal limits of world (1 mSv/y), there were no indications of existence of radon problems in the water sources in this survey. therefore the drinking water in Al-Najaf city is safe as far as radon concentration is concerned.

Soil gas Radon, 222Rn , concentration was measured at 15 location in the Najaf Al-Ashraf city, using RAD7 radon monitoring system of Durridge company USA. In each location four different depths were taken for soil gas measurements, staring from the ground surface. The results suggested that the largest concentration was 9290±400 Bq/m3 for 60cm depth at in Al-Amir district, point sample P14, and the smallest concentration was 9±17 Bq/m3 for 5cm depth at Al- Shoara district, point sample P5. The results obtained from this study indicate that the region has background radioactivity levels within the natural limits.

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