Effect of a helium gas atmosphere on the mechanical properties of Ti-6Al-4V alloy built with laser powder bed fusion: A comparative study with argon gas

In metal additive manufacturing, the microstructures and associated mechanical properties of metal specimens can be controlled over a wide range. Although process parameters are considered important in the fabrication of functional parts, the effect of atmospheric gas has not been comprehensively documented. In laser powder bed fusion (LPBF), gas flow is used to eliminate fumes generated by laser irradiation. Simultaneously, the gas removes heat from the laser-irradiated part, which is exposed to high temperature. In this study, we investigated the capacity of helium as an alternative to argon, which is conventionally used as the LPBF atmosphere gas. He has a higher thermal conductivity and lower gas density than Ar, which may result in enhanced heat removal from the Ti-6Al-4V alloy during fabrication. Numerical simulations suggest a greater cooling rate under He flow. Further, the material built under He flow contained finer α' martensite grains and showed improved mechanical properties compared to those fabricated under Ar flow, despite the identical laser irradiation conditions. Thus, He gas is advantageous in LPBF for fabricating products with superior mechanical performance through microstructural refinement, and this is a result of its capacity for cooling and fume generation inhibition. Therefore, this study reveals the importance of the choice of atmospheric gas because of its effects on the characteristics of metallic specimens fabricated using LPBF.Amano H., Ishimoto T., Suganuma R., et al. Effect of a helium gas atmosphere on the mechanical properties of Ti-6Al-4V alloy built with laser powder bed fusion: A comparative study with argon gas. Additive Manufacturing, 48, 102444. https://doi.org/10.1016/j.addma.2021.102444

Impact of gas flow direction on the crystallographic texture evolution in laser beam powder bed fusion

This study demonstrated that the gas flow direction in the laser beam powder bed fusion (PBF-LB) significantly affects the crystallographic texture evolved in the products. The effect on texture is attributed to the difference in the melt pool depth, which depends on gas flow direction. The melt pool was shallower when the laser scanning and gas flow directions were parallel than when they were perpendicular. This phenomenon should be of particular concern when applying Scan Strategy_XY wherein the laser was scanned with a 90° rotation in each layer, which is often used in PBF-LB. The asymmetry in the melt pool depth generated by laser scanning in the x- and y-directions can lead to unintended variations in the crystallographic texture. The gas phase would interact with a part being manufactured immediately beneath the gas and affect the crystallographic feature of the product.Amano H., Ishimoto T., Hagihara K., et al. Impact of gas flow direction on the crystallographic texture evolution in laser beam powder bed fusion. Virtual and Physical Prototyping 18, e2169172 (2023); https://doi.org/10.1080/17452759.2023.2169172

Kre6 (yeast 1,6-β-transglycosylase) homolog, PhTGS, is essential for β-glucan synthesis in the haptophyte Pleurochrysis haptonemofera

Haptophytes synthesize unique β-glucans containing more β-1,6-linkages than β-1,3 linkages, as a storage polysaccharide. To understand the mechanism of the synthesis, we investigated the roles of Kre6 (yeast 1,6-β-transglycosylase) homologs, PhTGS, in the haptophyte Pleurochrysis haptonemofera. RNAi of PhTGS repressed β-glucan accumulation and simultaneously induced lipid production, suggesting that PhTGS is involved in β-glucan synthesis and that the knockdown leads to the alteration of the carbon metabolic flow. PhTGS was expressed more in light, where β-glucan was actively produced by photosynthesis, than in the dark. The crude extract of E. coli expressing PhKre6 demonstrated its activity to incorporate 14C-UDP-glucose into β-glucan of P. haptonemofera. These findings suggest that PhTGS functions in storage β-glucan synthesis specifically in light, probably by producing the β-1,6-branch

Balance between dopamine and adenosine signals regulates the PKA/Rap1 pathway in striatal medium spiny neurons

Medium spiny neurons (MSNs) expressing dopamine D1 receptor (D1R) or D2 receptor (D2R) are major components of the striatum. Stimulation of D1R activates protein kinase A (PKA) through Golf to increase neuronal activity, while D2R stimulation inhibits PKA through Gi. Adenosine A2A receptor (A2AR) coupled to Golf is highly expressed in D2R-MSNs within the striatum. However, how dopamine and adenosine co-operatively regulate PKA activity remains largely unknown. Here, we measured Rap1gap serine 563 phosphorylation to monitor PKA activity and examined dopamine and adenosine signals in MSNs. We found that a D1R agonist increased Rap1gap phosphorylation in striatal slices and in D1R-MSNs in vivo. A2AR agonist CGS21680 increased Rap1gap phosphorylation, and pretreatment with the D2R agonist quinpirole blocked this effect in striatal slices. D2R antagonist eticlopride increased Rap1gap phosphorylation in D2R-MSNs in vivo, and the effect of eticlopride was blocked by the pretreatment with the A2AR antagonist SCH58261. These results suggest that adenosine positively regulates PKA in D2R-MSNs through A2AR, while this effect is blocked by basal dopamine in vivo. Incorporating computational model analysis, we propose that the shift from D1R-MSNs to D2R-MSNs or vice versa appears to depend predominantly on a change in dopamine concentration

Administration of Kampo medicine through a tube at an advanced critical care center

In emergency and critical care medical centers, tube administration is employed for patients who have difficulty swallowing oral drugs owing to decreased consciousness or mechanical ventilation. However, tube clogging due to drug injection is a concern. We compared the crushing method with the simple suspension method for the passage of amlodipine, an antihypertensive drug, in combination with rikkunshito, which has been used to treat upper gastrointestinal disorders such as functional dyspepsia and gastroesophageal reflux in emergency and critical care medical centers, to ascertain the effect of Kampo products on the passage of other drugs during tube administration. When the crushing method was employed, poorly water-soluble solid products were formed, while a uniformly dispersed suspension was obtained using the simple suspension method. In addition, the passage rate of amlodipine through the tube was 64% and 93% in the crushing and simple suspension methods, respectively, thereby indicating that the simple suspension method provided more favorable than the crushing method. The results of this study suggested that the passage rate of amlodipine for patients who received Kampo products concurrently was higher when the simple suspension method was used, and an appropriate drug amount might well be able to administered to patients using this method

A Measure of Physical Fitness of Freshmen of Tokyo University of Fisheries in 1998

東京水産大学海洋システム工学講座東京水産大学海洋システム工学講座東京水産大学体育実技・非常勤講師東京水産大学体育実技・非常勤講師東京水産大学体育実技・非常勤講師東京水産大学体育実技・非常勤講師東京水産大学保健管理センタ