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Surface Roughness Modification of Free Standing Single Crystal Silicon Microstructures Using KrF Excimer Laser Treatment for Mechanical Performance Improvement

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Journal of Surface Engineered Materials and Advanced Technology 2015年第1期5卷 28-41页

作者： Mohamed Elwi Mitwally Toshiyuki Tsuchiya osamu tabata Sherif Sedky Department of Micro Engineering Kyoto University Kyoto Japan Zewail City of Science and Technology Cairo Egypt

Single crystal silicon freestanding structures for tensile and fatigue testing were treated with KrF excimer laser to improve surface roughness and accordingly mechanical performance. Sample thickness was 5 μm. Localized laser treatment was successful in eliminating the scallops developed during Bosch process and in reducing surface roughness. Harsh irradiation at laser energies up to 4 J/cm2 was only possible due to localized treatment without significant vibrations occurring on the freestanding samples that led to fracture in preliminary experiments at energies as low as 0.16 J/cm2. Finite element analysis was used to investigate the temperature distribution on the irradiated structures. Atomic force microscopy (AFM) and Raman spectroscopy were also used to assess surface roughness, crystallinity changes and surface stresses developing on surfaces subjected to perpendicular laser irradiation. At a high energy (3.2 J/cm2) the top surface showed a decrease of roughness compared to fabricated samples. Raman spectroscopy showed the dominance of crystalline silicon after laser irradiation. The effects of laser energy, number of

关键词： Freestanding Mechanical Test Structures Harsh Laser Treatment Surface Roughness Improvement

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Simulation of Graphene Piezoresistivity Based on Density Functional Calculations

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Modeling and Numerical Simulation of Material Science 2013年第4期3卷 117-123页

作者： Mohammed Gamil Koichi Nakamura Ahmed M. R. Fath El-Bab osamu tabata Ahmed Abd El-Moneim Center for the Promotion of Interdisciplinary Education and Research Kyoto University Kyoto Japan Department of Micro Engineering Kyoto University Kyoto Japan Materials Science and Engineering Department Egypt-Japan University of Science and Technology Alexandria Egypt Mechatronics and Robotics Department Egypt-Japan University of Science and Technology Alexandria Egypt

The piezoresistive effect in graphene ribbon has been simulated based on the first-principles electronic-state calculation for the development of novel piezoresistive materials with special performances such as high flexibility and low fabrication cost. We modified theoretical approach for piezoresistivity simulation from our original method for semiconductor systems to improved procedure applicable to conductor systems. The variations of carrier conductivity due to strain along with the graphene ribbon models (armchair model and zigzag model) have been calculated using band carrier densities and their corresponding effective masses derived from the one-dimensional electronic band diagram. We found that the armchair-type graphene nano-ribbon models have low conductivity with heavy effective mass. This is a totally different conductivity from two-dimensional graphene sheet. The variation of band energy diagrams of the zigzag-type graphene nano-ribbon models due to strain is much more sensitive than that of the armchair models. As a result, the longitudinal and transverse gauge factors are high in our calculation, and in particular, the zigzag-type graphene ribbon has an enormous potential material with high piezoresistivity. So, it will be one of the most important candidates that can be used as a high-performance piezoresistive material for fabricating a new high sensitive strain gauge sensor.

关键词： Graphene Ribbon Piezoresitivity First-Principles Calculation Gauge Factor

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CYP1A1 , GSTM1 , GSTT1 and NQO1 polymorphisms and colorectal adenomas in Japanese men

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World Journal of Gastroenterology 2013年第25期19卷 4023-4030页

作者： Tadamichi Hamachi osamu Tajima Kousaku Uezono Shinji tabata Hiroshi Abe Keizo Ohnaka Suminori Kono Department of Preventive Medicine Graduate School of Medical Sciences Kyushu University Self Defense Forces Fukuoka Hospital Kasuga-shi Self Defense Forces Kumamoto Hospital Department of Geriatric Medicine Graduate School of Medical Sciences Kyushu University

AIM: To investigate the role of functional genetic poly-morphisms of metabolic enzymes of tobacco carcinogens in the development of colorectal adenomas. METHODS: The study subjects were 455 patients with colorectal adenomas and 1052 controls with no polyps who underwent total colonoscopy in a preretirement health examination at two Self Defense Forces hospitals. The genetic polymorphisms studied wereCYP1A1*2A (rs 4646903), CYP1A1*2C (rs 1048943), GSTM1 (null or non-null genotype), GSTT1 (null or non-null genotype) and NQO1 C609T (rs 1800566). Genotypes were determined by the polymerase chain reaction (PCR)-restriction fragment length polymorphism or PCR method using genomic DNA extracted from the buffy coat. Cigarette smoking and other life-style factors were ascertained by a self-administered questionnaire. The associations of the polymorphisms with colorectal adenomas were examined by means of OR and 95%CI, which were derived from logistic regression analysis. Statistical adjustment was made for smoking, alcohol use, body mass index and other factors. The gene-gene interaction and effect modification of smoking were evaluated by the likelihood ratio test. RESULTS: None of the five polymorphisms showed a significant association with colorectal adenomas, nor was the combination of GSTM1 and GSTT1 . A borderline significant interaction was observed for the combination of CYP1A1*2C and NQO1 (P = 0.051). The OR associated with CYP1A1*2C was significantly lower than unity among individuals with the NQO1 609CC genotype. The adjusted OR for the combination of the CYP1A1*2C allele and NQO1 609CC genotype was 0.61 (95%CI: 0.42-0.91). Although the interaction was not statistically significant (P = 0.24), the OR for individuals carrying the CYP1A1*2C allele and GSTT1 null genotype decreased significantly compared with those who had neither CYP1A1*2C allele nor GSTT1 null genotype (adjusted OR: 0.69, 95%CI: 0.49-0.97). Smoking did not modify the associations of the individual

关键词： Colorectal adenoma Smoking Polymorphism CYP1A1 GSTM1 GSTT1 NQO1

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