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收集所有交通大學研究人員與學生個人或團體所發表之各項學術著作，涵蓋期刊論文、教師專書、學位論文等項。;;Collections of Publications of NCTU Researchers and Students Like Journal Papers and Thesis.

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Access type: Open accessSubject: search.filters.subject.Stress

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    The Impact of MOSFET Layout Dependent Stress on High Frequency Characteristics and Flicker Noise
    (2010)
    Yeh, Kuo-Liang
    ;
    Ku, Chih-You
    ;
    Guo, Jyh-Chyurn
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    電子工程學系及電子研究所
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    Department of Electronics Engineering and Institute of Electronics
    Layout dependent stress in 90 nm MOSFET and its impact on high frequency performance and flicker noise has been investigated. Donut MOSFETs were created to eliminate the transverse stress from shallow trench isolation (STI). Both NMOS and PMOS can benefit from the donut layout in terms of higher effective mobility mu(eff) and cutoff frequency f(T), as well as lower flicker noise. The measured flicker noise follows number fluctuation model for NMOS and mobility fluctuation model for PMOS, respectively. The reduction of flicker noise suggests the reduction of STI generated traps and the suppression of mobility fluctuation due to eliminated transverse stress using donut structure.
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    Item type:Item,
    A mechanistic stress model of protein evolution accounts for site-specific evolutionary rates and their relationship with packing density and flexibility
    (2014-04-09)
    Huang, Tsun-Tsao
    ;
    del Valle Marcos, Maria Laura
    ;
    Hwang, Jenn-Kang
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    Echave, Julian
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    生物資訊及系統生物研究所
    Background: Protein sites evolve at different rates due to functional and biophysical constraints. It is usually considered that the main structural determinant of a site's rate of evolution is its Relative Solvent Accessibility (RSA). However, a recent comparative study has shown that the main structural determinant is the site's Local Packing Density (LPD). LPD is related with dynamical flexibility, which has also been shown to correlate with sequence variability. Our purpose is to investigate the mechanism that connects a site's LPD with its rate of evolution. Results: We consider two models: an empirical Flexibility Model and a mechanistic Stress Model. The Flexibility Model postulates a linear increase of site-specific rate of evolution with dynamical flexibility. The Stress Model, introduced here, models mutations as random perturbations of the protein's potential energy landscape, for which we use simple Elastic Network Models (ENMs). To account for natural selection we assume a single active conformation and use basic statistical physics to derive a linear relationship between site-specific evolutionary rates and the local stress of the mutant's active conformation. We compare both models on a large and diverse dataset of enzymes. In a protein-by-protein study we found that the Stress Model outperforms the Flexibility Model for most proteins. Pooling all proteins together we show that the Stress Model is strongly supported by the total weight of evidence. Moreover, it accounts for the observed nonlinear dependence of sequence variability on flexibility. Finally, when mutational stress is controlled for, there is very little remaining correlation between sequence variability and dynamical flexibility. Conclusions: We developed a mechanistic Stress Model of evolution according to which the rate of evolution of a site is predicted to depend linearly on the local mutational stress of the active conformation. Such local stress is proportional to LPD, so that this model explains the relationship between LPD and evolutionary rate. Moreover, the model also accounts for the nonlinear dependence between evolutionary rate and dynamical flexibility.