Influence of gas atmosphere (Ar or He) on the laser powder bed fusion of a Ni-based alloy
JOURNAL OF MATERIALS PROCESSING TECHNOLOGY
Authors: Traore, S.; Schneider, M.; Koutiri, I; Coste, F.; Fabbro, R.; Charpentier, C.; Lefebvre, P.; Peyre, P.
Abstract
The gaseous atmosphere plays a major role in the quality of the manufactured parts in Laser Powder Bed Fusion (L-PBF) by protecting the metal from high temperature oxidation. If argon and nitrogen are the most commonly used gases, helium has almost never been considered as a possible candidate as a chemically inert shielding gas. To provide a better understanding of the influence of the gas atmosphere on the process stability, a comparative study of L-PBF manufacturing under argon and helium atmospheres has been carried out, considering a nickel-based alloy Inconel (R) 625 and a single bead configuration. To this end, in-situ process measurements were carried out on a dedicated experimental setup. The melt pool behaviour, the expansion of the vapour plume and the amount of spatters were evaluated with high-speed imaging for the two gases considered, together with the final L-PBF bead dimensions. Results were also compared to single fusion beads carried out in an industrial L-PBF machine for a comparable range of volume energy densities. The influence of the shielding atmosphere on L-PBF single beads was as follows: (1) dimensions of beads were shown to be constant whatever the gas; (2) fewer and smaller spatters were produced under helium atmosphere, especially for high volume energy densities. Physical mechanisms were then discussed to understand those specific effects.
Crosstalk between Androgen-ZIP9 Signaling and Notch Pathway in Rodent Sertoli Cells
INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES
Authors: Kaminska, Alicja; Marek, Sylwia; Pardyak, Laura; Brzoskwinia, Malgorzata; Bilinska, Barbara; Hejmej, Anna
Abstract
Our recent study demonstrated altered expression of Notch ligands, receptors, and effector genes in testes of pubertal rats following reduced androgen production or signaling. Herein we aimed to explore the role of nuclear androgen receptor (AR) and membrane androgen receptor (Zrt- and Irt-like protein 9; ZIP9) in the regulation of Notch pathway activation in rodent Sertoli cells. Experiments were performed using TM4 and 15P-1 Sertoli cell lines and rat primary Sertoli cells (PSC). We found that testosterone (10(-8) M-10(-6) M) increased the expression of Notch1 receptor, its active form Notch1 intracellular domain (N1ICD) (p < 0.05, p < 0.01, p < 0.001), and the effector genes Hey1 (p < 0.05, p < 0.01, p < 0.001) and Hes1 (p < 0.05, p < 0.001) in Sertoli cells. Knockdown of AR or ZIP9 as well as antiandrogen exposure experiments revealed that (i) action of androgens via both AR and ZIP9 controls Notch1/N1ICD expression and transcriptional activity of recombination signal binding protein (RBP-J), (ii) AR-dependent signaling regulates Hey1 expression, (iii) ZIP9-dependent pathway regulates Hes1 expression. Our findings indicate a crosstalk between androgen and Notch signaling in Sertoli cells and point to cooperation of classical and non-classical androgen signaling pathways in controlling Sertoli cell function.