Soo Park

Identification of Proteins That Interact with Podocin Using the Yeast 2-Hybrid System

Purpose As a membrane protein at the insertion site of the slit diaphragm (SD) complex in podocyte foot processes, podocin has been reported to act as a scaffolding protein required to maintain or regulate the structural integrity of the SD. In order to identify proteins that associate or interact with podocin, we screened a mouse kidney complementary DNA (cDNA) library using a yeast 2-hybrid system. Materials and Methods 1) The full-length cDNA of podocin from the mouse kidney was amplified by Polymerase Chain Reaction (PCR), 2) The PCR product was cloned into a pGBKT7 vector, pGBKT7-podocin, 3) After the pGBKT7-podocin was transformed into AH109, the AH109/pGBKT7-podocin product was obtained, 4) The mouse kidney cDNA library was transformed into the AH109/pGBKT7-podocin and screened by selection steps, 5) Next, twelve clones were cultured and isolated, 6) The yeast-purified plasmids were transformed into Escherichia coli (E. coli) by heat shock, and 7) To identify the activation domain (AD)/library inserts, we digested them with Him III, and the fragments were then sequenced. Results 12 positive clones that interacted with podocin were obtained by screening a mouse kidney cDNA library using pGBKT7-podocin. Among them, only 4 clones were found to function at the podocyte where podocin is present. Conclusion Additional studies are needed to clarify the role and interaction with podocin and candidates.

Stability Test of Artificial Joint for Hip Joint

Artificial joints are used when joints lose their function because of either the destruction or damage of the composing bones of the joints. To evaluate the primary stability of a femur-implant system, the relative displacement caused by a repeated load is measured immediately after the insertion of the artificial joint. For more accurate stability evaluation, the accurate measurement of the penetration displacement of the artificial joint to the bone and the rotation angle of the artificial joint is essential. In this study, to evaluate the primary stability of the femur-implant system, we propose a new relative displacement measurement method. By using this new method, we comparatively evaluate the primary stability for various surgical methods and the varying stiffness of the cadaver femur-implant itself.

The Compaoparison of Characteristics of Fracture Toughness of Materials for Nuclear Piping by Use of Various Types of Specimens

Since it is difficult to cut off large specimens from nuclear piping, generally the standard CT specimens of 1T are used to perform fracture toughness tests. However, when compared with the test result obtained from a real pipe, the results from CT specimens are been known to be very conservative. Therefore, the U.S. Nuclear Regulatory Commission recommends the use of specimens whose thickness is greater than or equal to the thickness of a real pipe for estimating the stability of crack resistance[1]. In this study, a series of fracture toughness tests were performed using various types of specimens: the standard CT, non-standard Compact Pipe, and Curved CT. The results of the tests were compared.

A Study on the Fatigue Life Prediction for Bending Pipe

Mechanical structures with power sources experience repeated force produced by motors. As a result, the life of the pipes reduces and ultimately, the pipes collapse. In most cases, the U-shape pipe is made from a straight pipe by complicated bending work. During this work process, plastic deformation of the pipe produces residual stress in the pipe. The residual stress significantly affects the fracture behavior of the pipe. In this paper, fatigues tests of U-shape bending pipe are performed by uniaxial testing machine and residual stresses were evaluated by FEM analysis. So we established the relation between residual stress and fatigue life. And we suggested new equation for fatigue life prediction using the residual stress of U-shape bending pipe.

A Study on the Evaluation of the Fracture Toughness for the Narrow Gap Welding Part of Nuclear Piping

초록: 원전배관의LBB 해석을위한파괴인성(J-R곡선)은일반적으로ASTM E1820에따라시험을수행하여획득한다. 그러나ASTM E1820에제시되어있는파괴인성에관한식은균질재의물성평가를위한것이며, 협개선용접부에적용할경우실제와는다른파괴인성을나타낼수있다. 따라서본연구에서는ASTM에제시되어있는균질재의파괴인성식에의한결과와협개선용접재의특성을고려하여제안된소성η계수식에의한파괴인성의차이를비교검토하기위하여협개선용접이적용된배관에서CT 시험편을채취한후파괴인성시험을수행하였다.Abstract: The fracture toughness for the LBB analysis of piping is generally determined by the J-integralaccording to ASTM E1820. However, since this evaluates a base metal, the fracture toughness for narrow gapwelding can be differently than the real value. This study evaluated the plastic  factor of the narrow gapwelding part of a nuclear piping with SA508 Cl.1a and SA312 TP316. Also, it performed the fracturetoughness test for the narrow gap welding part and applied the new plastic  factor equation by Huh, et al.and then compared the results with those according with the ASTM standard.

Evaluation of Fracture Toughness Characteristic for Nuclear Piping Using Various Types of Specimens

The leak-before-break (LBB) concept is based on the fracture resistance curve obtained by J-R tests on various types of specimens. But it has been also known that the fracture toughness data by various types of specimens are different each other. For example, the estimates for fracture toughness of standard specimens are conservative when compared to the fracture toughness of real pipes owing to the difference of the constraint effect between real pipes and standard specimens. Therefore for estimating the integrity of real pipes on the basis of elastic-plastic fracture mechanics, we have to first establish the relations among real pipes, standard CT specimens and curved CT specimens. In this study, we performed the fracture toughness tests for nuclear piping material by various types of specimen. And each J-R curve considered in the constraint effect was compared.Copyright