Size and profile of skyrmions in skyrmion crystals

Size is a fundamental quantity of magnetic skyrmions. A magnetic skyrmion can be a local circular object and in an isolated form. A skyrmion can also coexist with a group of its siblings in a condensed phase. Each skyrmion in a condensed phase takes a stripe shape at low skyrmion density and a circular shape at high skyrmion density. Skyrmions at high density form a skyrmion crystal (SkX). So far, skyrmion size in an SkX has not been seriously studied. Here, by using a generic chiral magnetic film, it is found that skyrmion size in an SkX has a different parameter dependence as those for isolated skyrmions and stripes. A size formula and a good spin profile for skyrmions in SkXs are proposed. These findings have important implications in searching for stable smaller skyrmions at the room temperature.

Comparison of MTF Measurement Methods in CT Images for Various Reconstruction Kernels

This study aimed to compare several methods of measuring the modulation transfer function (MTF) for different reconstruction kernels, using a point phantom, a small-circular (S-circular) Teflon object, and the automated edge of a PMMA phantom. The copper wire section of a phantom was used for the point method. The small-circular (S-circular) teflon object within the HU linearity section was used for measuring MTF using ImQuest software. The automated edge of a PMMA phantom was used to automatically measure the MTF. The three methods were implemented in images reconstructed with ten different kernels. It was found that the three methods produced comparable MTFs for all the kernels used. However, the automated edge of the PMMA phantom produced slightly smaller spatial resolutions compared with the two other methods. The differences between the automated edge of PMMA and the point method were small, i.e. 0.04 cycle/mm for both 10% MTF and 50% MTF. The differences between the automated edge of PMMA and the S-circular phantom were 0.05 cycle/mm and 0.03 cycle/mm for 10% MTF and 50% MTF. We found that the “UA” kernel produced the lowest spatial resolution values of 0.32, 0.33, and 0.31 cycle/mm of 50% MTF for point, S-circular object, and automated edge PMMA, respectively. The “YD” produced the highest spatial resolution values of 0.78, 0.76, and 0.67 cycle/mm of 10% MTF for point, S-circular object, and automated edge PMMA, respectively. We successfully compared three methods of MTF measurement. The three methods produce comparable MTFs, so that each method can be used for accurately measuring MTF depending on phantom and software available in the CT center.

DEVELOPMENT OF AN INDIGENOUS ENVIRONMENTAL FRIENDLY REFUSE PICKER

Handling and removal of harmful waste from our environment is a collective responsibility that all must embrace to make the world a safe habitat. A low cost environmental friendly waste picker was devel-oped. Biometric force evaluation of the end user obtained averaged 469.73 N. The refuse picker was calibrated to obtain the spring constant of 3030.73 N/m. The tool was tested and found to perform well in picking objects of different weights and of regular and irregular shapes ranging from 0.12 g to 2.72 kg. Serrated jaw enhanced the picking performance of the unit whilst picking a circular object without slipping off. The maximum safe horizontal and vertical loading recommended for the tool at picking was 0.5 kg. The picker was used to pick the smallest item, a pin of diameter 0.70 mm and weight of 0.12 g successfully. This tool can be very handy in the hospital where harmful waste such as needles, syringes and other unhealthy substances and waste must be removed from the environment. The tool was made from low cost materials with 40% less than the existing ones.