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Mesenteric Approach in Pancreatoduodenectomy
Akimasa Nakao Korean Society of Gastrointestinal Cancer 2016 Journal of digestive cancer reports Vol.4 No.2
The 26<sup>th</sup> World Congress of the International Association of Surgeons, Gastroenterologists and Oncologists (IASGO) was held in Seoul, Korea from September 8 to 10, 2016. In this congress, I gave a State-of-the-Art Lecture II entitled "Mesenteric Approach in Pancreatoduodenectomy." The ideal surgery for pancreatic head cancer is isolated pancreatoduodenectomy, which involves en bloc resection using a non-touch isolation technique. My team has been developing isolated pancreatoduodenectomy for pancreatic cancer since 1981, when we developed an antithrombogenic bypass catheter for the portal vein. In this operation, the first and most important step is the use of a mesenteric approach instead of Kocher's maneuver. The mesenteric approach allows dissection from the non-cancer infiltrating side and determination of cancer-free margins and resectability, followed by systematic lymphadenectomy around the superior mesenteric artery. This approach enables early ligation of the inferior pancreatoduodenal artery and total mesopancreas excision. It is the ideal surgery for pancreatic head cancer from both oncological and surgical viewpoints. The precise surgical techniques of the mesenteric approach are herein described.
Wear resistance of indirect composite resins used for provisional restorations supported by implants
Akimasa Tsujimoto,Carlos Jurado,Jose Villalobos-Tinoco,Wayne Barkmeier,Nicholas Fischer,Toshiki Takamizawa,Mark Latta,Masashi Miyazaki 대한치과보철학회 2019 The Journal of Advanced Prosthodontics Vol.11 No.4
PURPOSE. The aim of this study was to investigate simulated localized and generalized wear of indirect composite resins used for implant supported provisional restorations. MATERIALS AND METHODS. The study investigated ten indirect composite resins. Two kinds of wear were simulated by 400,000 cycles in a Leinfelder-Suzuki (Alabama) machine. Localized wear was simulated with a stainless-steel ball bearing antagonist and generalized with a flat-ended stainless-steel cylinder antagonist. The tests were carried out in water slurry of polymethyl methacrylate beads. Wear was measured using a Proscan 2100 noncontact profilometer in conjunction with Proscan and AnSur 3D software. RESULTS. Both localized and generalized wear were significantly different (P<.05) among the indirect composite resins. SR Nexco and Gradia Plus showed significantly less wear than the other indirect composite resins. The rank order of wear was same in both types of wear simulation. CONCLUSION. Indirect composite resins are recommended when a provisional implantsupported restoration is required to function in place over a long period. Although only some indirect composite resins showed similar wear resistance to CAD/CAM composite resins, the wear resistance of all the indirect composite resins was higher than that of bis-acryl base provisional and polymethyl methacrylate resins.
Numerical analysis of multi-parallelized swirling flow inside a circular pipe
Akimasa Takayama,Koki Kitagawa,Toru Shimada 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.3
The flow field of multi-parallelized swirling flow inside a circular pipe was investigated numerically. Two types of swirling flow configurationare considered. One type is the co-rotating type. Four co-rotating swirls are arranged at the vertex position of square in thistype. The other type is the counter-rotating type which consists of two pairs of swirls having opposite swirl rotations. Each pair is arrangeddiagonally at the vertex position of a square. By coupling the discrete vortex method and boundary element method, unsteadyflow simulation is performed. Swirl modeling with vortex elements is used in this simulation and its validity is confirmed. From thesimulation results, in the co-rotating type, the four swirls interact and their shape is deformed. Each vortex motion vanishes rapidly in thedownstream region. Finally, they are turned into a single swirling flow. In counter-rotating type, each vortex motion is maintained a littlebit longer than co-rotating type, and their shape is not so deformed. However, the flow patterns are changed completely in the downstreamregion. The swirling velocity of each swirl mostly vanishes. Finally, they are turned into an axial flow. For the investigation of themixing promoting effect due to parallelizing swirls, particle tracking simulations are performed in the co-rotating type and the counterrotatingtype. As a comparison, the simulation for single swirl flow is also performed. In these simulations, the particles are introduced inthe vicinity of pipe inner wall. In addition, the assumption that particles follow the flow motion absolutely is used. From the results, themotion of particles in these three cases is completely different. For the co-rotating and counter-rotating type, the particle entrainment intothe main axial flow is clearly observed. This indicates the mixing is improved compared to single swirl flow. The difference of particleentrainment motion between co-rotating and counter-rotating type is slight.