• 제목/요약/키워드: Molecular Analysis

검색결과 7,915건 처리시간 0.046초

Influence of vacancy defects on vibration analysis of graphene sheets applying isogeometric method: Molecular and continuum approaches

  • Tahouneh, Vahid;Naei, Mohammad Hasan;Mashhadi, Mahmoud Mosavi
    • Steel and Composite Structures
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    • 제34권2호
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    • pp.261-277
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    • 2020
  • The main objective of this research paper is to consider vibration analysis of vacancy defected graphene sheet as a nonisotropic structure via molecular dynamic and continuum approaches. The influence of structural defects on the vibration of graphene sheets is considered by applying the mechanical properties of defected graphene sheets. Molecular dynamic simulations have been performed to estimate the mechanical properties of graphene as a nonisotropic structure with single- and double- vacancy defects using open source well-known software i.e., large-scale atomic/molecular massively parallel simulator (LAMMPS). The interactions between the carbon atoms are modelled using Adaptive Intermolecular Reactive Empirical Bond Order (AIREBO) potential. An isogeometric analysis (IGA) based upon non-uniform rational B-spline (NURBS) is employed for approximation of single-layered graphene sheets deflection field and the governing equations are derived using nonlocal elasticity theory. The dependence of small-scale effects, chirality and different defect types on vibrational characteristic of graphene sheets is investigated in this comprehensive research work. In addition, numerical results are validated and compared with those achieved using other analysis, where an excellent agreement is found. The interesting results indicate that increasing the number of missing atoms can lead to decrease the natural frequencies of graphene sheets. It is seen that the degree of the detrimental effects differ with defect type. The Young's and shear modulus of the graphene with SV defects are much smaller than graphene with DV defects. It is also observed that Single Vacancy (SV) clusters cause more reduction in the natural frequencies of SLGS than Double Vacancy (DV) clusters. The effectiveness and the accuracy of the present IGA approach have been demonstrated and it is shown that the IGA is efficient, robust and accurate in terms of nanoplate problems.

Taxonomic Position and Affinities of Isopyrum mandshuricum within Korean Isopyroideae (Ranunculaceae) Based on Molecular Data

  • Lee, Nam-Sook;Yeau, Sung-Hee;Kim, Ji-Hyun;Kim, Min-Ju
    • Animal cells and systems
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    • 제3권2호
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    • pp.133-141
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    • 1999
  • To examine the taxonomic position and affinities of Isopyrum mandshuricum (Ranunculaceae) and related taxa, genetic analysis were carried out on the basis of isozyme patterns and ITS sequences. Molecular data, both isozyme patterns and ITS sequences suggest that I. mandshuricum is closely related to Enemion raddeanum than to Semiaquilegia adoxoides. The estimation of genetic identities by isozyme analysis reveals that I. manshuricum is genetically distant from E. raddeanum. The phylogenetic tree based on molecular data is rather congruent with the phenogram based on quantitative morphological characteristics, but not consistent with one based on qualitative morphological characteristics. Incongruencies between molecular and qualitative morphological data provide clues to re-evaluate several morphological features.

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분자영상 획득을 위한 핵의학 영상기기 (Nuclear Medicine Imaging Instrumentations for Molecular Imaging)

  • 정용현;송태용;최용
    • 대한핵의학회지
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    • 제38권2호
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    • pp.131-139
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    • 2004
  • Small animal models are extensively utilized in the study of biomedical sciences. Current animal experiments and analysis are largely restricted to in vitro measurements and need to sacrifice animals to perform tissue or molecular analysis. This prevents researchers from observing in vivo the natural evolution of the process under study. Imaging techniques can provide repeatedly in vivo anatomic and molecular information noninvasively. Small animal imaging systems have been developed to assess biological process in experimental animals and increasingly employed in the field of molecular imaging studies. This review outlines the current developments in nuclear medicine imaging instrumentations including fused multi-modality imaging systems for small animal imaging.

Molecular Mechanism of Parkinson's Disease

  • Chung, Jong-Kyeong
    • 한국응용약물학회:학술대회논문집
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    • 한국응용약물학회 2008년도 Proceedings of the Convention
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    • pp.49-52
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    • 2008
  • Parkinson's disease is characterized by motor disturbances and dopaminergic neurodegeneration. parkin and PINK1, two most critical Parkinson's disease-associated genes, have been intensively studied to address the underlying molecular pathogenesis of the disease, but our understanding still remains unclear. Through generation and characterization of Drosophila mutants for PINK1, we show that PINK1 is required for mitochondrial integrity and function in both indirect flight muscles and dopaminergic neurons. Surprisingly, we find that PINK1 mutants share striking phenotypic similarities with parkin mutants. Indeed, transgenic expression of parkin dramatically ameliorates all PINK1 loss-of-function phenotypes, but not vice versa, implicating that Parkin acts downstream of PINK1 in maintaining mitochondrial integrity and function in both muscles and dopaminergic neurons. With the establishment of the PINK1-Parkin pathway, we are trying to further investigate the detailed molecular relationship between PINK1 and Parkin using both mammalian dopaminergic neuronal cells for biochemical analysis and Drosophila model animal for genetic analysis. We believe that elucidating the molecular function of Parkinson's disease-associated genes will be of big help for the ultimate understanding of the pathogenic mechanism of this disease and also for the development of effective drugs for Parkinson's disease.

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Quantitative Structure-Activity Relationships and Molecular Docking Studies of P56 LCK Inhibitors

  • Bharatham, Nagakumar;Bharatham, Kavitha;Lee, Keun-Woo
    • Bulletin of the Korean Chemical Society
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    • 제27권2호
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    • pp.266-272
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    • 2006
  • Three-dimensional quantitative structure-activity relationship (3D-QSAR) models were developed for 67 molecules of 2-amino-benzothiazole-6-anilide derivatives against lymphocyte-specific protein tyrosine kinase (P56 LCK). The molecular field analysis (MFA) and receptor surface analysis (RSA) were employed for QSAR studies and the predictive ability of the model was validated by 15 test set molecules. Structure-based investigations using molecular docking simulation were performed with the crystal structure of P56 LCK. Good correlation between predicted fitness scores versus observed activities was demonstrated. The results suggested that the nature of substitutions at the 2-amino and 6-anilide positions were crucial in enhancing the activity, thereby providing new guidelines for the design of novel P56 LCK inhibitors.

Analysis of nonionic surfactants and silicone polymers in cosmetic products using Matrix - assisted Laser Desorption/Ionization Time-of- flight Mass Spectrometry

  • Lee, Myoung-Hee;Lee, Gae-Ho;Yoo, Jong-Shin
    • 대한화장품학회:학술대회논문집
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    • 대한화장품학회 2003년도 IFSCC Conference Proceeding Book II
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    • pp.480-507
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    • 2003
  • A rapid and efficient method for analyzing the nonionic surfactants and silicone polymers, which control the shape and characteristics of cosmetic products and give influence on product quality, has been developed using Matrix-Assisted Laser Desorption Ionization Time of Flight Mass Spectrometry (MALDI- TOF IMS). The MALDI-TOF/MS could easily and effectively determine the molecular weight distribution and monomer units of nonionic surfactants. As a result, creating a library of mass spectrum data of surfactants used in cosmetic products using MALDI-TOF/MS and analyzing surfactants extracted from the products may become a useful method for detailed structural characterization of the surfactants. Furthermore, the MALDI-TOF/MS analysis was effective in obtaining the spectrum of silicone polymers from which the molecular weight distribution could be determined. The repetition units and structural data could also be obtained through molecular mass peaks. Additionally, the monomer ratio and terminal groups as properties of silicone copolymers could be determined

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