Structural Shielding Design of CT Facility using Monte Carlo Simulation

Radiation application in medicine offers extraordinary benefits. But radiation is like a double-edged sword, it has both benefits and associated risks on the community in contact. To justify the safety of workers and members of the public, regulated use of radiation is assessed by the radiation protection protocols. The aim of this study is to design a Computed Tomography (CT) facility with a simplified model of CT scanner, whose shielding follows the guidelines of National Council on Radiation Protection and Measurements (NCRP) Report No. 147. To design the study model, Monte Carlo (MC) radiation transport code in MCNPX 2.6.0 was used for the simulation. Furthermore, MCNPX was used to measure the photon flux in a vicinity or the detector cell. To validate the functioning of the X-ray tube, the experimental results were compared with the X-ray Transition Energies Database of National Institute of Standards and Technology, U.S. Department of Commerce. The results obtained were within 0.60% of relative error. To confirm the functioning of shielding design, radiation protection quantity, air kerma was measured at several points outside, and inside of the CT room and they were under the radiation dose recommended by NCRP, which demonstrates that the shielding design wassuccessful in blocking the radiation. The study can be used for an easy evaluation of any CT room within the framework of the model of the study.

Newly developed method for the determination of sitagliptin phosphate using rubeanic acid as a precipitating agent via the use of ISNAG continues flow fluorimeter

A new, a simple, sensitive and fast developed method for the estimation of sitagliptin phosphate in pure and pharmaceutical drugs (tablet). This method based on the reaction between sitagliptin phosphate and rubeanic acid to form reddish-black ppt, using ISNAG-Fluorimeter analyzer via the measure of diverged light at 90° from radiation source which is used a range of high intensity ultraviolet 184.9 nm & 253.7 nm by low-pressure mercury lamp while detector cell can detect at 410-1150 nm. The resultant of diverged light by an interaction between incident photons and precipitated particles giving rise to a longer wavelength that the detector can detected. Chemical and physical parameters were studied and optimized. The calibration graph was linear in the range of (0.03-13 ) mmol.L−1 , with correlation coefficient ( r )= 0.9881 ,linearity percentage r2%= 97.64 , L.O.D = 0.7848µg/sample and RSD lower than 0.6 % for (3&7 ) mmol.L−1 ( eight replicates) concentration of sitagliptin phosphate. This method was successfully applied for the determination of sitagliptin phosphate in two different companies of pharmaceutical drugs. A comparison was made between the newly developed method analysis with the classical method (UV-spectrophotometer by measuring of absorbance ) using standard addition method via the use of t-test, it was noticed that there was no significant difference between two methods at %95 confidence level.

Break-before-Make CMOS Inverter for Power-Efficient Delay Implementation

A modified static CMOS inverter with two inputs and two outputs is proposed to reduce short-circuit current in order to increment delay and reduce power overhead where slow operation is required. The circuit is based on bidirectional delay element connected in series with the PMOS and NMOS switching transistors. It provides differences in the dynamic response so that the direct-path current in the next stage is reduced. The switching transistors are never ON at the same time. Characteristics of various delay element implementations are presented and verified by circuit simulations. Global optimization procedure is used to obtain the most power-efficient transistor sizing. The performance of the modified CMOS inverter chain is compared to standard implementation for various delays. The energy (charge) per delay is reduced up to 40%. The use of the proposed delay element is demonstrated by implementing a low-power delay line and a leading-edge detector cell.