Methodological Considerations of Electron Spin Resonance Spin Trapping Techniques for Measuring Reactive Oxygen Species generated from metal oxide nanomaterials

Qualitative and quantitative analyses of reactive oxygen species (ROS) generated on the surfaces of nanomaterials are important for understanding their toxicity and toxic mechanisms, which are in turn beneficial for manufacturing more biocompatible nanomaterials in many industrial fields. Electron spin resonance (ESR) is a useful tool for detecting ROS formation. However, using this technique without first considering the physicochemical properties of nanomaterials and proper conditions of the spin trapping agent (such as incubation time) may lead to misinterpretation of the resulting data. In this report, we suggest methodological considerations for ESR as pertains to magnetism, sample preparation and proper incubation time with spin trapping agents. Based on our results, each spin trapping agent should be given the proper incubation time. For nanomaterials having magnetic properties, it is useful to remove these nanomaterials via centrifugation after reacting with spin trapping agents. Sonication for the purpose of sample dispersion and sample light exposure should be controlled during ESR in order to enhance the obtained ROS signal. This report will allow researchers to better design ESR spin trapping applications involving nanomaterials

High frequencies of Y-chromosome haplogroup O2b-SRY465 lineages in Korea: a genetic perspective on the peopling of Korea

<p>Abstract</p> <p>Background</p> <p>Koreans are generally considered a Northeast Asian group, thought to be related to Altaic-language-speaking populations. However, recent findings have indicated that the peopling of Korea might have been more complex, involving dual origins from both southern and northern parts of East Asia. To understand the male lineage history of Korea, more data from informative genetic markers from Korea and its surrounding regions are necessary. In this study, 25 Y-chromosome single nucleotide polymorphism markers and 17 Y-chromosome short tandem repeat (Y-STR) loci were genotyped in 1,108 males from several populations in East Asia.</p> <p>Results</p> <p>In general, we found East Asian populations to be characterized by male haplogroup homogeneity, showing major Y-chromosomal expansions of haplogroup O-M175 lineages. Interestingly, a high frequency (31.4%) of haplogroup O2b-SRY465 (and its sublineage) is characteristic of male Koreans, whereas the haplogroup distribution elsewhere in East Asian populations is patchy. The ages of the haplogroup O2b-SRY465 lineages (~9,900 years) and the pattern of variation within the lineages suggested an ancient origin in a nearby part of northeastern Asia, followed by an expansion in the vicinity of the Korean Peninsula. In addition, the coalescence time (~4,400 years) for the age of haplogroup O2b1-47z, and its Y-STR diversity, suggest that this lineage probably originated in Korea. Further studies with sufficiently large sample sizes to cover the vast East Asian region and using genomewide genotyping should provide further insights.</p> <p>Conclusions</p> <p>These findings are consistent with linguistic, archaeological and historical evidence, which suggest that the direct ancestors of Koreans were proto-Koreans who inhabited the northeastern region of China and the Korean Peninsula during the Neolithic (8,000-1,000 BC) and Bronze (1,500-400 BC) Ages.</p

FINAL ICONE17-75008 DEVELOPMENT OF A NEW SPACER GRID FORM TO ENHANCE THE INTEGRITY OF FUEL ROD SUPPORT AND THE CRUSH STRENGTH OF A SPACER GRID ASSEMBLY

ABSTRACT A spacer grid is one of the most important structural components in a LWR fuel assembly. The spacer grid, which supports nuclear fuel rods laterally and vertically with a friction grip, is an interconnected array of slotted grid straps welded at the intersections to form an egg-crate structure. Dimples and springs are stamped into each grid strap to support the fuel rods. The form of grid straps and spring form is known to be closely related with the crush strength of spacer grid assembly and the integrity of fuel rod support, respectively. Zircaloy is prevailing as the material of the spacer grid because of its low neutron absorption characteristic and its successful extensive in-reactor use. The primary considerations are to provide a Zircaloy spacer grid with crush strength sufficient to resist design basis loads especially due to seismic accidents, without significantly increasing pressure drop across the reactor core. Generally, the thickness and height of the Zircaloy grid strap have been the main design variables in order to meet the above considerations. Recently, it was reported that a dimple location is also a design variable that affects the crush strength of a spacer grid assembly. In this study, a new spacer grid form was developed in order to enhance the integrity of the fuel rod support and the crush strength of the spacer grid assembly by using a systematic optimization technique. Finite element analysis and crush strength tests on the developed new spacer grid form were carried out to check the performance enhancement compared to commercial spacer grids. The enhancement of fuel rod support was confirmed by comparisons of contact area, peak stresses, plastic deformation and etc. According to the results, it is estimated that the actual critical load enhancement of the spacer grid assembly is approximately up to 30 % and the actual contact area, when a fuel rod inserted into a spacer grid cell, is more than double for the developed new spacer grid form. And also, some design variables that effect the crush strength of a PWR spacer grid assembly were classified and their effects on the crush strength were investigated by a finite element analysis and a crush strength test