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Earthquake Engineering and Engineering Vibration 2023年第3期22卷 647-666页

作者： Usama Zafar Chandra Shekhar Goit masato saitoh Riku Fukuda School of Science and Engineering Saitama University255 Shimo-OkuboSaitamaJapan

Piles in a group experience additional displacements in soil due to pile-to-pile interactions apart from those resulting from the external *** effect of these interactions determined assuming soil as an elastic and/or viscoelastic material on pile head impedance functions of the pile group is studied by relating the group stiffness to the static stiffness of a single ***,the prevailing elastic solutions may misestimate the resulting pile group response due to the lack of consideration for either soil(material)and/or soil-pile interface *** is well established that soil behaves nonlinearly under moderate-to-high loading amplitudes,and besides,the soil-pile interface nonlinearity can exist even at small loading *** study addresses the effects of these nonlinearities on the vertical impedance functions of a 3×3-pile group using numerical methods by direct analyses and superposition using pile-to-pile interaction *** numerical results are validated using scaled model tests under 1 g *** results highlight the overestimation of pile-to-pile interactions in the pile group when assuming elastic soil *** cases either by direct analyses or superposition approach involving soil and soil-pile interface nonlinearities agree well with the experimental pile group responses under close-to-elastic and nonlinear conditions.

关键词： impedance functions numerical simulations model-scale experiment superposition approach soil-pile interface nonlinearity

Improving the performance of conventional base isolation systems by an external variable negative stiffness device under near-fault and long-period ground motions

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Earthquake Engineering and Engineering Vibration 2020年第4期19卷 985-1003页

作者： Sandhya Nepal masato saitoh Graduate School of Science and Engineering Saitama University255 Shimo-OkuboSakura-kuSaitamaJapan

Recent studies have shown that base-isolated objects with long fundamental natural periods are highly influenced by long-period earthquakes. These long-period waves result in large displacements for isolators, possibly leading to exceedance of the allowable displacement limits. Conventional isolation systems, in general, fail to resist such large displacements. This has prompted the need to modify conventional base isolation systems. The current work focuses on the development of an external device, comprising a unit of negative and positive springs, for improving the performance of conventional base isolation systems. This unit accelerates the change in the stiffness of the isolation system where the stiffness of the positive spring varies linearly in terms of the displacement response of the isolated objects. The target objects of the present study are small structures such as computer servers, sensitive instruments and machinery. Numerical studies show that the increase in the damping of the system and the slope of the linear function is effective in reducing the displacement response. An optimal range of damping values and slope, satisfying the stability condition and the allowable limits of both displacement and acceleration responses when the system is subjected to near-fault and long-period ground motions simultaneously, is proposed.

关键词： base isolation near-fault earthquakes long-period earthquakes negative stiffness variable stiffness

Model tests and numerical analyses on horizontal impedance functions of inclined single piles embedded in cohesionless soil

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Earthquake Engineering and Engineering Vibration 2013年第1期12卷 143-154页

作者： Chandra Shekhar Goit masato saitoh Department of Civil and Environmental Engineering Saitama University

Horizontal impedance functions of inclined single piles are measured experimentally for model soil-pile systems with both the effects of local soil nonlinearity and resonant *** practical pile inclinations of 5掳 and 10掳 in addition to a vertical pile embedded in cohesionless soil and subjected to lateral harmonic pile head loadings for a wide range of frequencies are *** obtained with low-to-high amplitude of lateral loadings on model soil-pile systems encased in a laminar shear box show that the local nonlinearities have a profound impact on the horizontal impedance functions of *** impedance functions of inclined piles are found to be smaller than the vertical pile and the values decrease as the angle of pile inclination *** values of horizontal impedance functions are obtained for the ＇positive＇ and ＇negative＇ cycles of harmonic loadings,leading to asymmetric force-displacement relationships for the inclined *** of these experimental results is carried out through three-dimensional nonlinear finite element analyses,and the results from the numerical models are in good agreement with the experimental *** analyses conducted on the numerical models suggest that the consideration of local nonlinearity at the vicinity of the soil-pile interface influence the response of the soil-pile systems.

关键词： inclined single piles harmonic loads horizontal impedance functions local nonlinearity finite element model

PiggyBac transposon-mediated gene delivery efficiently generates stable transfectants derived from cultured primary human deciduous tooth dental pulp cells(HDDPCs) and HDDPC-derived iPS cells

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International Journal of Oral Science 2015年第3期7卷 144-154页

作者： Emi Inada Issei saitoh Satoshi Watanabe Reiji Aoki Hiromi Miura masato Ohtsuka Tomoya Murakami Tadashi Sawami Youichi Yamasaki Masahiro Sato Department of Pediatric Dentistry Kagoshima University Graduate School of Medical and Dental Sciences Division of Pediatric Dentistry Graduate School of Medical and Dental Science Niigata University Animal Genome Research Unit Division of Animal Science National Institute of Agrobiological Sciences Functional Biomolecules Research Group National Agriculture and Food Research Organization Division of Basic Molecular Science and Molecular Medicine School of Medicine Tokai University Section of Gene Expression Regulation Frontier Science Research Center Kagoshima University

The ability of human deciduous tooth dental pulp cells（HDDPCs） to differentiate into odontoblasts that generate mineralized tissue holds immense potential for therapeutic use in the field of tooth regenerative medicine. Realization of this potential depends on efficient and optimized protocols for the genetic manipulation of HDDPCs. In this study, we demonstrate the use of a Piggy Bac（PB）-based gene transfer system as a method for introducing nonviral transposon DNA into HDDPCs and HDDPC-derived inducible pluripotent stem cells. The transfection efficiency of the PB-based system was significantly greater than previously reported for electroporation-based transfection of plasmid DNA. Using the neomycin resistance gene as a selection marker, HDDPCs were stably transfected at a rate nearly 40-fold higher than that achieved using conventional methods. Using this system, it was also possible to introduce two constructs simultaneously into a single cell. The resulting stable transfectants, expressing td Tomato and enhanced green fluorescent protein, exhibited both red and green fluorescence. The established cell line did not lose the acquired phenotype over three months of culture. Based on our results, we concluded that PB is superior to currently available methods for introducing plasmid DNA into HDDPCs. There may be significant challenges in the direct clinical application of this method for human dental tissue engineering due to safety risks and ethical concerns. However, the high level of transfection achieved with PB may have significant advantages in basic scientific research for dental tissue engineering applications, such as functional studies of genes and proteins. Furthermore, it is a useful tool for the isolation of genetically engineered HDDPC-derived stem cells for studies in tooth regenerative medicine.

关键词： drug selection electroporation genetically modified human deciduous tooth dental pulp cells Piggy Bac

A simplified protocol for the semi-large scale recovery of plasmids from <i>Escherichia coli</i>grown on agar plates

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Journal of Biomedical Science and Engineering 2012年第7期5卷 406-408页

作者： Masahiro Sato Eri Akasaka Issei saitoh masato Ohtsuka Shingo Nakamura Takayuki Sakurai Satoshi Watanabe Animal Genome Research Unit Division of Animal Science National Institute of Agrobiological Sciences Ibaraki Japan Department of Organ Regeneration Graduate School of Medicine Shinshu University Nagano Japan Department of Pediatric Dentistry Graduate School of Medical and Dental Sciences Kagoshima University Kagoshima Japan Department of Surgery II National Defense Medical College Saitama Japan Division of Basic Molecular Science and Molecular Medicine School of Medicine Tokai University Kanagawa Japan Section of Gene Expression Regulation Frontier Science Research Center Kagoshima University Kagoshima Japan

Semi-large scale liquid cultivation of transformed Escherichia coli (E. coli) in medium (100-200 ml) has been widely used for the acquisition of relatively large amounts of plasmid DNA (50-300 μg). However, this method requires an expensive high-speed centrifugation apparatus to precipitate E. coli before lysis, which is both laborious and time-consuming. Here, we demonstrate a method for agar plate-based cultivation of bacteria that does not employ a high-speed centrifugation apparatus. This procedure proves to be simple and reproducible, yielding an average of 82 μg of plasmid DNA per experiment. It may therefore be valuable for cloning/transfection experiments under limited financial backgrounds.

关键词： Agar Plate DNA Purification E. coli Gene Engineering Plasmid