Design and optimization of broadband metamaterial absorber based on manganese for visible applications.

Metamaterial absorbers have been extensively researched due to their potential applications in photonics. This paper presents a highly efficient Broadband Metamaterial Absorber (BMA) based on a Manganese-Silica-Manganese three layer structure with a shaped pattern at the top layer. For maximum absorption efficiency, the geometrical parameters of the proposed absorber have been optimized based on Particle Swarm Optimization (PSO). The optimal structure with a thickness of 190 nm, can achieve more than 94% absorption spanning visible band (400-800) nm with 98.72% average absorption, and more than 90% absorption over the range from 365 to 888 nm. In the range from 447 to 717 nm, the design presented above 99% absorptivity, providing an ultra-wide bandwidth of 270 nm. The physical mechanism of absorption is illustrated through the exploration of the electric and magnetic field distributions. Additionally, the proposed structure maintains 85% absorption stability for wide incident angles up to 70° for both the TE and TM polarizations under oblique incidence. Further, the optimized absorber structure with excellent absorption capabilities makes it suitable for various applications, including optical sensors, thermal emitters, and color imaging applications.

Studying the dose level for different X-ray energy conventional radiography by TLD-100.

The purpose of this study was to investigate the x-ray energy dependence of the measured response of detectors (TLD-100) and to estimate the accurate dose delivered to patients during routine X-ray examinations. The response of thermoluminescent dosimeters TLD as a function of low energy range was determined using the X-ray tube at the Ionizing Radiation Met. Lab in the National Institute of Standards, (Secondary Standard Dosimetry Lab (SSLD) Cairo, Egypt. The X-ray dose was measured at 25, 50 and 100 kVp nominal x-ray energies. TLD-100 linearity, reproducibility and relative sensitivity were studied. Several sets of TLD-100 were to different x-ray beam energy to determine the calibration coefficient of the TLD system and the correction factors applied for the dose calculation (readings (nC)/radiation dose (mGy)) was determined in the dose range (0.69 mGy to 350 mGy). The radiation dose to the patient was estimated in diagnostic radiology for the existing working protocols (skull, pelvis, abdomen, and lumbar Spine). TLD-100 was exposed at various nominal energy used for diagnostic (40-100 kVp) and various tube current (50-120 mA) which is normally used in clinical X-ray examinations. The TLD-100 was exposed three times for each kVp value, and the exposure doses were measured in mGy. The obtained results showed a linear behavior of the TLD-100 response as a function of X-ray dose with estimated uncertainty within 10%. This indicates a good accuracy when assessing the entrance dose in diagnostic radiology procedures). The sensitivity of the TLD cards showed a standard deviation of 4.7%. Moreover, the dose-nC factor has the same value (within the standard uncertainty). Mean Entrance Skin Dose for skull, pelvis, abdomen, and lumbar spine were 0.46 ± 0.01, 1.5 ± 0.05, 7.3 ± 0.21 and 9.2 ± 0.29 mGy respectively. The obtained results reflect the agreement with the recommended values and will be useful for the formulation of national reference levels as recommended by the International Atomic Energy Agency (IAEA) SAFETY STANDARDS SERIES No. GSR Part 3 2014.

Positron annihilation lifetime studies of changes in free volume on some biorelevant nitrogen heterocyclic compounds and their S-glycosylation.

A series of N-heterocyclic compounds was investigated by positron annihilation lifetime spectroscopy as well as Doppler broadening of annihilation radiation (DBAR) at room temperature. The results showed that the formation probability and life time of ortho-positronium in this series are structure and electron-donation character dependent, and can give more information about the structure. The DBAR provides direct information about the change of core and valance electrons as well as the number of defect types present in these compounds.

Radionuclide content of local and imported cements used in Egypt.

The activity concentrations of natural and artificial gamma-ray emitting radionuclides in local and imported cement have been investigated during the period from 2000 to 2003 using a 50% HPGe gamma-spectroscopy system. The total numbers of local and imported samples were 29 and 8, respectively. The results showed a low activity concentration of (137)Cs in both the local and imported samples. The only exception was found in one imported Portland cement (2.8 +/- 0.2 Bq kg(-1)) and one local blast furnace slag cement (1.9 +/- 0.3 Bq kg(-1)). The average activity concentrations of (226)Ra, (232)Th and (40)K in local cement were 33 +/- 17, 14 +/- 2.4 and 45 +/- 26 Bq kg(-1), respectively, whereas those in imported cement were 27 +/- 7, 8 +/- 7 and 134 +/- 22 Bq kg(-1), respectively. The results showed that blast furnace slag cement contains the highest level of natural radioactivity, whereas white cement contains the lowest levels. The measured activity concentrations of the detected radionuclides were compared with other measurements carried out in Egypt and elsewhere. Radium-equivalent activities were also calculated to assess the radiation hazards arising from using such material in the construction of dwellings. Generally, the radium-equivalents of the analysed samples were smaller than the guideline limit of 370 Bq kg(-1).