Experimental Dimensional Accuracy Analysis of Reformer Prototype Model Produced by FDM and SLA 3D Printing Technology

The subject of this paper is the evaluation of the dimensional accuracy of FDM and SLA 3D printing technologies in comparison with developed reformer polymer electrolyte membrane (PEM) fuel cell CAD model. 3D printing technologies allow a bottom-up approach to manufacturing, by depositing material in layers to final shape. Dimensional inaccuracy is still a problem in 3D printing technologies due to material shrinking and residual stress. Materials used in this research are PLA (Polylactic Acid) for FDM technology and the standard white resin material for SLA technology. Both materials are commonly used for 3D printing. PLA material is printed in three different height resolutions: 0.3 mm, 0.2 mm and 0.1 mm. White resin is printed in 0.1 mm height resolution. The aim of this paper is to show how layer height affects the dimensional accuracy of FDM models and to compare the dimensional accuracy of FDM and SLA printed reformer models with the same height resolution

Activation of homologous recombination in G1 preserves centromeric integrity

Centromeric integrity is key for proper chromosome segregation during cell division1. Centromeres have unique chromatin features that are essential for centromere maintenance2. Although they are intrinsically fragile and represent hotspots for chromosomal rearrangements3, little is known about how centromere integrity in response to DNA damage is preserved. DNA repair by homologous recombination requires the presence of the sister chromatid and is suppressed in the G1 phase of the cell cycle4. Here we demonstrate that DNA breaks that occur at centromeres in G1 recruit the homologous recombination machinery, despite the absence of a sister chromatid. Mechanistically, we show that the centromere-specific histone H3 variant CENP-A and its chaperone HJURP, together with dimethylation of lysine 4 in histone 3 (H3K4me2), enable a succession of events leading to the licensing of homologous recombination in G1. H3K4me2 promotes DNA-end resection by allowing DNA damage-induced centromeric transcription and increased formation of DNA–RNA hybrids. CENP-A and HJURP interact with the deubiquitinase USP11, enabling formation of the RAD51–BRCA1–BRCA2 complex5 and rendering the centromeres accessible to RAD51 recruitment and homologous recombination in G1. Finally, we show that inhibition of homologous recombination in G1 leads to centromeric instability and chromosomal translocations. Our results support a model in which licensing of homologous recombination at centromeric breaks occurs throughout the cell cycle to prevent the activation of mutagenic DNA repair pathways and preserve centromeric integrity.</p

Strain measurement of medical textile using 2d digital image correlation method

Medical textile plays an important role in the technical textiles sector as one of the most rapidly growing sectors in the technical textile market. The textile materials should have some adequate mechanical properties to be useful as medical textile. Tensile strength presents one of the basic mechanical properties used to describe textile specimens. Standardized tensile testing procedures on textile specimens were commonly used in the past. The aim of this paper was to measure in-plane strain field on the tensile medical textile specimen using 2D Digital Image Correlation method (2D-DIC). 2D-DIC is a non-contact optical method for accurate displacement and strain full-field measurement. In this study, two medical cotton textiles, with density 120 and 130 g/m2, were used to create three specimens for each material. Each specimen was placed in the tensile testing machine and measured until the break. During the tensile testing, camera was automatically recording full-field displacement in X and Y directions. Textile 1 and Textile 2 showed significant differences in point distance values, despite the small deviation in densities (less than 10%). Mean value of the elongation for Textile 1 is more than a double than the elongation for Textile 2, although the difference for mean value of Maximum force if negligible. Also, it has been showed that 2D-DIC can play significant role for measurement in textile mechanical properties measurement