Ali Alabdullah

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Effect of exposure time of an acidic beverage on the microhardness, mineral weight, and rate of calcium and phosphate ion release of human enamel

Journal of international oral health : JIOH, 2019

Aims and Objectives: The aim of this study was to investigate the effect of exposure times of Coc... more Aims and Objectives: The aim of this study was to investigate the effect of exposure times of Coca Cola on enamel’s microhardness, mineral weight, and rate of calcium and phosphate ions discharging from it. Materials and Methods: Thirty-two enamel blocks were randomly divided into four groups and exposed to 10mL of their respective solution daily for 7 days, with each group containing eight specimens: Group 1 (enamel blocks exposed to artificial saliva, control group), group 2 (enamel blocks exposed to Coca Cola for 5 minutes), group 3 (enamel blocks exposed to Coca Cola for 10 minutes), and group 4 (enamel blocks exposed to Coca Cola for 30 minutes). Microhardness data (Vickers hardness number [VHN]) and mineral weight were calculated at baseline (sound enamel) and postexposure to Coca Cola. Inductively coupled plasma–optical emission spectrometry (ICP-OES) was utilized to study calcium and phosphate ion percolation from enamel surfaces. Results: Decrease in VHN was directly proportional to exposure time for all experimental groups. Comparison of baseline and postexposure values between control and experimental groups was statistically significant (P < 0.05). Mineral weight of enamel blocks decreased as the exposure time increased for all experimental groups. ICP-OES analysis revealed linear relationship between release of calcium and phosphate ions at 5 and 10 minutes, but at 30 minutes, a decrease in concentration of both ions was observed. Conclusion: The microhardness and mineral weight of enamel decreased linearly with exposure time. The release of calcium and phosphate ions from enamel increased initially but gradually decreased as the exposure time increased.

Small-Clearance Phased Array Antenna Design with

In this paper, highly miniaturized radiation elements organized in a linear phased array form is ... more In this paper, highly miniaturized radiation elements organized in a linear phased array form is introduced for fifth generation cellular communications. The design structure is composed of eight low-profile folded-dipole in the x-y plane located at the top portion of the printed circuit board (PCB) with Rogers RT5880 substrate. The radiation elements of the design are etched on the same layer of the ground plane. The proposed array is highly compact which occupies only 0.5 mm (clearance) of the PCB plane. The critical properties of the introduced phased array are investigated. The designed antenna exhibits wide beamsteering, high efficiencies, and sufficient gain levels at 28 GHz, the main 5G band. In addition, the proposed phased array design has sufficient radiation behavior in the adjacency of user-hand phantom.

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