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Influence of Surface Roughness of Tools on the Friction Stir Welding Process
Michael Hartmann,Stefan Böhm,Sven Schüddekopf 대한용접접합학회 2014 대한용접·접합학회지 Vol.32 No.6
Most publications on friction stir welding describe phenomena or results with given process parameters like feed rate, rotation speed, angle and depth of penetration. But without a complete documentation of tool design, the results under the same process parameters are completely different. For this purpose, the Institute of Cutting and Joining Manufacturing Processes (tff), University of Kassel investigated the influence of tool roughness on the friction stir welding process. Therefore a defined surface finish was produced by turning and die sinking. As basis of comparison the constant parameters were rotation speed, feed rate, tilt angle and a heel plunge depth. Sound butt-welds were produced in aluminium alloy 6082 (AlMgSi1) with 1.5 mm sheet thickness with a turned reference tool with a surface of Ra = 0.575 µm in position controlled mode. The surfaces are manufactured from a very fine to a very rough structure, classified by the VDI-classes with differences in the arithmetical mean roughness. It can be demonstrated with the help of temperature measures, that less heat is generated at the surfaces of the shoulder and the pin by the higher roughness due to lower active friction contact surface. This can also be seen in the resulting wormhole defects.
Molecular Imaging of CXCL12 Promoter-driven HSV1-TK Reporter Gene Expression
Lina Alon,Dara L. Kraitchman,Michael Schär,Angel Cortez,Nirbhay N. Yadav,Rebecca Krimins,Peter V. Johnston,Michael T. McMahon,Peter C. M. van Zijl,Sridhar Nimmagadda,Martin G. Pomper,Jeff W. M. Bulte 한국생물공학회 2018 Biotechnology and Bioprocess Engineering Vol.23 No.2
The C-X-C motif chemokine 12 (CXCL12, SDF1a) and its receptor, CXCR4, play a fundamental role in several biological processes, including hematopoiesis, cardiogenesis, cancer progression, and stem cell migration. Noninvasive monitoring of CXCL12 is highly desirable for optimizing strategies that combine mobilization of therapeutic cells to combat cancer or to assist in cardiac tissue repair after myocardial infarction. Here, we report on an MRI reporter gene system for directly monitoring CXCL12 expression in vivo. Glioma cells and human adipose-derived stem cells (hADSC) were transduced with the herpes simplex virus type-1-thymidine kinase (HSV1- tk) reporter gene expressed under the CXCL12 promoter. HSV1-tk expression resulted in accumulation of the PET tracer [125I]FIAU in vitro and in vivo and induced cell death after ganciclovir treatment. Furthermore, the results show that conditional expression of the reporter gene can be induced by hypoxia in transduced cells. Transduced hADSC were incubated with the CEST MRI probe 5-methyl-5, 6- dihydrothymidine (5-MDHT) and transplanted into swine heart. Transplanted cells were clearly visible on Chemical Exchange Saturation Transfer (CEST) MRI using a 3T clinical scanner. Therefore, we conclude that it is possible to image CXCL12 expression with MRI in a large animal model, opening up a possible route to clinical translation.
Jan-Markus Rödger,Jan Beier,Malte Schönemann,Christine Schulze,Sebastian Thiede,Niki Bey,Christoph Herrmann,Michael Z. Hauschil 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.8 No.3
The eco-efficiency of actual production processes is still one dominating research area in engineering. However, neglecting the environmental impacts of production equipment, technical building services and energy supply might lead to sub-optimization or burden-shifting and thus reduced effectiveness. As an established method used in sustainability management, Life Cycle Assessment aims at calculating the environmental impacts from all life cycle stages of a product or system. In order to cope with shortcomings of the static character of life cycle models and data gaps this approach combines Life Cycle Assessment with manufacturing system simulation. Therefore, the two life cycles of product and production system are merged to assess environmental sustainability on product level. Manufacturing simulation covers the production system and Life Cycle Assessment is needed to relate the results to the final product. This combined approach highlights the influences from dynamic effects in manufacturing systems on resulting life cycle impact from both product and production system. Furthermore, the importance of considering indirect peripheral equipment and its effects on the manufacturing system operation in terms of output and energy demands is underlined. The environmental flows are converted into impacts for the five recommended environmental impact categories. Thus, it can be demonstrate that Life Cycle Assessment can enhance the process simulation and help identify hot-spots along the life cycle. The combined methodology is applied for analysing a case study in fourteen scenarios for the integration of volatile energy sources into energy flexible manufacturing control.
Apostolos G. Pitoulias,Nizar Abu Bakr,Majid Kazemtash,Firouza Dahi,Michael Schütz,Konstantinos P. Donas 대한혈관외과학회 2023 Vascular Specialist International Vol.39 No.2
Von Gierke disease, also known as glycogen storage disease type I, co-existent with an abdominal aortic aneurysm (AAA), is an extremely rare combination of diseases that requires challenging therapeutic measures. We present, for the first time in literature, the case of a 62-year-old female with von Gierke disease who required open surgical repair of an AAA with challenging neck anatomy outside of instructions for use of endovascular repair. Even though the surgical risks for lifethreatening complications, such as pancreatitis, metabolic acidosis, and kidney failure, were high, the 6-month postoperative course was uneventful. Despite the invasiveness of the treatment, surgery to treat the AAA was safe and effective. Further data is needed to draw robust conclusions about the treatment of choice for those patients with diseases in co-existence with AAAs.