Heat Treatment Design for IN718 by Laser Metal Deposition with High Deposition Rates: Modeling, Simulation, and Experiments.

Laser metal deposited processed Ni-based superalloy IN718 is characterized by elemental micro-segregation, anisotropy, and Laves phases due to the rapid solidification and therefore needs homogenization heat treatment to achieve comparable properties of wrought alloys. In this article, we report a simulation-based methodology to design heat treatment IN718 in a laser metal deposition (LMD) process by using Thermo-calc. Initially, the finite element modeling simulates the laser melt pool to compute the solidification rate (G) and temperature gradient (R). Then, the primary dendrite arm spacing (PDAS) is computed through Kurz-Fisher and Trivedi modeling integrated with finite element method (FEM) solver. Later, a DICTRA homogenization model based on the PDAS input values computes the homogenization heat treatment time and temperature. The simulated time scales are verified for two different experiments with contrast laser parameters and are found to be in good agreement confirmed with the results from scanning electron microscopy. Finally, a methodology for integrating the process parameter with the heat treatment design is developed, and a heat treatment map for IN718 is generated that can be integrated with an FEM solver for the first time in the LMD process.

Localization of urea transporter B in the developing bovine rumen.

Urea nitrogen secreted from blood to rumen is a crucial factor shaping the symbiotic relationship between host ruminants and their microbial populations. Passage of urea across rumen epithelia is facilitated by urea transporter B (UT-B), but the long-term regulation of these proteins remains unclear. As ruminal function develops over a period of months, the developing rumen is an excellent model with which to investigate this regulation. Using rumen epithelium samples of calves from birth to 96 d of age, this study performed immunolocalization studies to localize and semi-quantify UT-B protein development. As expected, preliminary experiments confirmed that ruminal monocarboxylate transporter 1 (MCT1) short chain fatty acid transporter protein abundance increased with age (P < 0.01, n = 4). Further investigation revealed that ruminal UT-B was present in the first few weeks of life and initially detected in the basolateral membrane of stratum basale cells. Over the next 2 months, UT-B staining spread to other epithelial layers and semi-quantification indicated that UT-B abundance significantly increased with age (P < 0.01, n = 4 or 6). These changes were in line with the development of rumen function after the advent of solid feed intake and weaning, exhibiting a similar pattern to both MCT1 transporters and papillae growth. This study therefore confirmed age-dependent changes of in situ ruminal UT-B protein, adding to our understanding of the long-term regulation of ruminal urea transporters.

The role of rumen epithelial urea transport proteins in urea nitrogen salvage: A review.

The symbiotic relationship between the host and the rumen microbiome plays a crucial role in ruminant physiology. One of the most important processes enabling this relationship is urea nitrogen salvaging (UNS). This process is important for both maintaining ruminant nitrogen balance and supporting production of their major energy supply, bacterially-derived short chain fatty acids (SCFA). The key step in UNS is the trans-epithelial movement of urea across the ruminal wall and this is a highly regulated process. At the molecular level, the key transport route is via the facilitative urea transporter-B2, localized to ruminal papillae epithelial layers. Additional urea transport through aquaporins (AQP), such as AQP3, is now also viewed as important. Long-term regulation of these ruminal urea transport proteins appears to mainly involve dietary fermentable carbohydrates; whereas, transepithelial urea transport is finely regulated by local conditions, such as CO2 levels, pH and SCFA concentration. Although the key principles of ruminal urea transport physiology are now understood, there remains much that is unknown regarding the regulatory pathways. One reason for this is the limited number of techniques currently used in many studies in the field. Therefore, future research in this area that combines a greater range of techniques could facilitate improvements to livestock efficiency, and potentially, reductions in the levels of waste nitrogen entering the environment.

Development of a novel green coating process with laser.

Corrosion causes costs of about 3-4% of each country's gross domestic product, and due to the climate change, the corrosion rates on infrastructure are likely to increase furtherly in the future1,2. For corrosion protection, hard chrome plating (HCP) is commercially used since the early 20th3. Yet the biggest drawback concerns environmental protection, since toxic and carcinogenic hexavalent chromium Cr6+ is used. As an alternative, thermal spray (TS) is increasingly used since the last 20 years. Nevertheless, the coatings are technologically constrained in regard to high porosity, low material efficiency and poor bonding to the base material. Therefore, the demand for an environmental friendly and economical process that produces high-quality coatings is increasingly coming into the research focus. With laser, dense, metallurgically bonded and therefore well-adhering coatings with high material efficiency of > 90% can be produced from a large number of metallic alloys without the need to use environmentally harmful chemicals or noise emissions. However, the typical area coating rate of < 0.4 m2/h is significantly lower than that of TS of about 10 m2/h4,5, and is too small for coating large-scale components. In this regard, a novel coating process with laser was developed in this work. By decoupling the melding of powder from the coating speed, the coating speed of < 2 m/min in conventional laser coating can be increased to > 500 m/min. Defect-free layers that metallurgically bond to the base material with a thickness of 50-250 µm and a material efficiency of > 90% can be achieved. According to the results, an area coating rate up to 20 m2/h is achievable. The pioneer work of applications in offshore and automobile sectors show, this process is already providing beneficial for the industry.

Sex-Related Differences in UT-B Urea Transporter Abundance in Fallow Deer Rumen.

Rumen studies have focused almost exclusively on livestock species under strictly regimented diets. This means that the ruminal condition of free-living and free-feeding wildlife remains practically unstudied. Urea nitrogen salvaging, a process by which urea is passed into the rumen, to both provide a valuable source of nitrogen for bacterial growth and to buffer the potentially harmful acidic effects of bacterial short chain fatty acids, has remained unexplored in wild ruminants, such as deer. UT-B2 transporters are the key proteins reported to facilitate the transepithelial ruminal urea transport. In this study, we investigate the expression, abundance and localisation of urea transporters in the rumen of a semi-wild fallow deer (Dama dama) population. Physical measurements confirmed that males had larger rumen than females, while adults had longer papillae than juveniles. Initial RT-PCR experiments confirmed the expression of UT-B2, while immunolocalisation studies revealed that strong UT-B staining was present in the stratum basale of deer rumen. Western blotting analysis demonstrated that a 50 kDa UT-B2 protein was significantly more abundant in adult females compared to adult males. This study confirms the presence of UT-B2 urea transporters in deer rumen and suggests that sex-related differences occur, bringing new insight into our understanding of rumen physiology.

Localization of aquaporin-3 proteins in the bovine rumen.

Urea nitrogen salvaging is a crucial mechanism that ruminants have evolved to conserve nitrogen. Facilitative urea transporter-B proteins are known to be involved in urea transport across the rumen epithelium and thus efficiently facilitate the urea nitrogen salvaging process. Recently, functional studies have suggested that aquaglyceroporin transporters might also play a significant role in ruminal urea transport and aquaporin-3 (AQP3) protein has previously been detected in rumen tissue. In this current study, we investigated the specific localization of AQP3 transporters in the bovine rumen. First, end-point reverse-transcription PCR experiments confirmed strong AQP3 expression in both bovine rumen and kidney. Immunoblotting analysis using 2 separate anti-AQP3 antibodies detected AQP3 protein signals at 25, 32, and 42-45 kDa. Further immunolocalization studies showed AQP3 protein located in all the layers of rumen epithelium, especially in the stratum basale, and in the basolateral membranes of kidney collecting duct cells. These data confirm that AQP3 transporters are highly abundant within the bovine rumen and appear to be located throughout the ruminal epithelial layers. The physiological significance of the multiple AQP3 proteins detected and their location is not yet clear, hence further investigation is required to determine their exact contribution to ruminal urea transport.