127 research outputs found
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School of Energy and Chemical Engineering (Chemical Engineering)Nowadays, there has been demand for advanced composite materials due to their outstanding characteristics in wide ranges of academic and industrial fields. Composite materials usually possess improved properties not being observed in pure material itself. Particularly, polymer composite materials composed of constituents based on polymer matrix have been widely researched due to their highly enhanced capabilities (e.g., elasticity, flexibility, conductivity, hardness, stretchable, scalable, and so on) in various fields. Polymers, which are composed of structural repeat units with covalent bonds, have been gradually becoming essential and indispensable materials in the recent world owing to their high flexibility, elasticity, ease of processing, low cost, light weight, and other unique properties. Therefore, to utilize polymers more effectively for advanced composite materials, many fundamental studies have been researched to discover fundamental reasons (i.e., molecular origins) for their intrinsic characteristics corresponding to the polymer physics and rheology.
Recent experimental techniques offer some microscopic information. Nevertheless, it is still challenging issue to conduct a full atomic level analysis through only experimental approach. As such, depending on the rapid increase in computing power, multi-scale computer simulation methods have been developed to reveal the fundamental origin for some unique phenomena observed at the macroscopic level. Therefore, we conducted a detailed numerical analysis on rheological and mechanical properties of polymeric materials via mainly nonequilibrium molecular dynamics (NEMD) simulations and finite-element-method (FEM) simulations (Abaqus CAE and COMSOL Multiphysics).
In this dissertation, we first present comprehensive analysis on the shear rheology of polymers for various molecular architectures (linear, ring, and short-chain branched) in the bulk and confined systems using atomistic NEMD simulations. In comparison to bulk polymeric system, the interfacial chain dynamics near the boundary solid walls in the confined system are interesting. Detailed molecular-level analysis of the individual chain motions for various molecular architectures are carried out to characterize the intrinsic molecular mechanisms for interfacial chains in three characteristic flow regimes (weak, intermediate, and strong) regarding to the interfacial slip behavior (i.e., degree of slip).
Based on fundamental studies for polymers, we additionally modeled and analyzed polymer nanocomposites to fabricate versatile sensor devices using FEM simulations collaborated with experimental approach. Through a precise modeling in consideration to (particularly) mechanical properties, we found the most optimized construction of the nanostructured polymeric materials with highly improved sensing performances (ultrahigh sensitivity, linear sensing capability, and broad sensing range). Finally, we demonstrated highly sensitive triboelectric, ferroelectric, mechanochromic, and piezoresistive sensors with a proper physical (fundamental) mechanism to improve sensing ability.ope
Insect Biodiversity Informatics in Korea
Chungbuk National UniversityScedule:17-18 March 2003, Vemue: Kanazawa, Japan, Kanazawa Citymonde Hotel, Project Leader : Hayakawa, Kazuichi, Symposium Secretariat: XO kamata, Naoto, Edited by:Kamata, Naoto
A Molecular Phylogeny for the Leaf-Roller Moths (Lepidoptera: Tortricidae) and Its Implications for Classification and Life History Evolution
Tortricidae, one of the largest families of microlepidopterans, comprise about 10,000 described species worldwide, including important pests, biological control agents and experimental models. Understanding of tortricid phylogeny, the basis for a predictive classification, is currently provisional. We present the first detailed molecular estimate of relationships across the tribes and subfamilies of Tortricidae, assess its concordance with previous morphological evidence, and re-examine postulated evolutionary trends in host plant use and biogeography.We sequenced up to five nuclear genes (6,633 bp) in each of 52 tortricids spanning all three subfamilies and 19 of the 22 tribes, plus up to 14 additional genes, for a total of 14,826 bp, in 29 of those taxa plus all 14 outgroup taxa. Maximum likelihood analyses yield trees that, within Tortricidae, differ little among data sets and character treatments and are nearly always strongly supported at all levels of divergence. Support for several nodes was greatly increased by the additional 14 genes sequenced in just 29 of 52 tortricids, with no evidence of phylogenetic artifacts from deliberately incomplete gene sampling. There is strong support for the monophyly of Tortricinae and of Olethreutinae, and for grouping of these to the exclusion of Chlidanotinae. Relationships among tribes are robustly resolved in Tortricinae and mostly so in Olethreutinae. Feeding habit (internal versus external) is strongly conserved on the phylogeny. Within Tortricinae, a clade characterized by eggs being deposited in large clusters, in contrast to singly or in small batches, has markedly elevated incidence of polyphagous species. The five earliest-branching tortricid lineages are all species-poor tribes with mainly southern/tropical distributions, consistent with a hypothesized Gondwanan origin for the family.We present the first robustly supported phylogeny for Tortricidae, and a revised classification in which all of the sampled tribes are now monophyletic
Structural and Dynamical Characteristics of Short-Chain Branched Ring Polymer Melts at Interface under Shear Flow
We present a detailed analysis of the interfacial chain structure and dynamics of confined polymer melt systems under shear over a wide range of flow strengths using atomistic nonequilibrium molecular dynamics simulations, paying particular attention to the rheological influence of the closed-loop ring geometry and short-chain branching. We analyzed the interfacial slip, characteristic molecular mechanisms, and deformed chain conformations in response to the applied flow for linear, ring, short-chain branched (SCB) linear, and SCB ring polyethylene melts. The ring topology generally enlarges the interfacial chain dimension along the neutral direction, enhancing the dynamic friction of interfacial chains moving against the wall in the flow direction. This leads to a relatively smaller degree of slip (ds) for the ring-shaped polymers compared with their linear analogues. Furthermore, short-chain branching generally resulted in more compact and less deformed chain structures via the intrinsically fast random motions of the short branches. The short branches tend to be oriented more perpendicular (i.e., aligned in the neutral direction) than parallel to the backbone, which is mostly aligned in the flow direction, thereby enhancing the dynamic wall friction of the moving interfacial chains toward the flow direction. These features afford a relatively lower ds and less variation in ds in the weak-to-intermediate flow regimes. Accordingly, the interfacial SCB ring system displayed the lowest ds among the studied polymer systems throughout these regimes owing to the synergetic effects of ring geometry and short-chain branching. On the contrary, the structural disturbance exerted by the highly mobile short branches promotes the detachment of interfacial chains from the wall at strong flow fields, which results in steeper increasing behavior of the interfacial slip for the SCB polymers in the strong flow regime compared to the pure linear and ring polymers
Interactions between subjective memory complaint and objective cognitive deficit on memory performances
Background
Subjective memory complaint (SMCs) is a common trait amongst older population. The subjective cognition about their memory could depend on objective cognition. The aim of the current study was to examine the interaction between subjective memory cognition (i.e., SMC) and objective cognition on cognitive functions in participants from older generation.
Methods
A total of 219 patients, 181 normal control (NC) patients and 38 patients with mild cognitive impairment (MCI), were examined through standardized and comprehensive clinical evaluation and neuropsychological assessment. The Subjective Memory Complaints Questionnaire was used to assess SMCs along with five cognitive tasks were used to evaluate cognitive decline over following areas: verbal memory, visuospatial memory, attention, fluency, and language.
Results
The results of 2 × 2 two-way analysis of variance (ANOVA) showed that there were significant interactions between SMCs and cognitive status (NC, MCI) on memory performances. NC with SMCs showed significantly lower performance in verbal memory and visuospatial memory compared to NCs without SMCs. Conversely, no effect was observed in the MCI group.
Conclusion
There are interactions between subjective cognition (i.e., SMC) and objective cognition (i.e., cognitive status) on memory performances in older adults. The roles of SMCs on memory performances should be interpreted with older adults objective cognitive status.This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (No. NRF-2017R1D1A1A02018479). This funding source had no role in the design of this study and will not have any role during its execution,
analyses, interpretation of the data, or decision to submit result
Toward reconstructing the evolution of advanced moths and butterflies (Lepidoptera: Ditrysia): an initial molecular study
<p>Abstract</p> <p>Background</p> <p>In the mega-diverse insect order Lepidoptera (butterflies and moths; 165,000 described species), deeper relationships are little understood within the clade Ditrysia, to which 98% of the species belong. To begin addressing this problem, we tested the ability of five protein-coding nuclear genes (6.7 kb total), and character subsets therein, to resolve relationships among 123 species representing 27 (of 33) superfamilies and 55 (of 100) families of Ditrysia under maximum likelihood analysis.</p> <p>Results</p> <p>Our trees show broad concordance with previous morphological hypotheses of ditrysian phylogeny, although most relationships among superfamilies are weakly supported. There are also notable surprises, such as a consistently closer relationship of Pyraloidea than of butterflies to most Macrolepidoptera. Monophyly is significantly rejected by one or more character sets for the putative clades Macrolepidoptera as currently defined (<it>P </it>< 0.05) and Macrolepidoptera excluding Noctuoidea and Bombycoidea sensu lato (<it>P </it>≤ 0.005), and nearly so for the superfamily Drepanoidea as currently defined (<it>P </it>< 0.08). Superfamilies are typically recovered or nearly so, but usually without strong support. Relationships within superfamilies and families, however, are often robustly resolved. We provide some of the first strong molecular evidence on deeper splits within Pyraloidea, Tortricoidea, Geometroidea, Noctuoidea and others.</p> <p>Separate analyses of mostly synonymous versus non-synonymous character sets revealed notable differences (though not strong conflict), including a marked influence of compositional heterogeneity on apparent signal in the third codon position (nt3). As available model partitioning methods cannot correct for this variation, we assessed overall phylogeny resolution through separate examination of trees from each character set. Exploration of "tree space" with GARLI, using grid computing, showed that hundreds of searches are typically needed to find the best-feasible phylogeny estimate for these data.</p> <p>Conclusion</p> <p>Our results (a) corroborate the broad outlines of the current working phylogenetic hypothesis for Ditrysia, (b) demonstrate that some prominent features of that hypothesis, including the position of the butterflies, need revision, and (c) resolve the majority of family and subfamily relationships within superfamilies as thus far sampled. Much further gene and taxon sampling will be needed, however, to strongly resolve individual deeper nodes.</p
Can Deliberately Incomplete Gene Sample Augmentation Improve a Phylogeny Estimate for the Advanced Moths and Butterflies (Hexapoda: Lepidoptera)?
This paper addresses the question of whether one can economically improve the robustness of a molecular phylogeny estimate by increasing gene sampling in only a subset of taxa, without having the analysis invalidated by artifacts arising from large blocks of missing data. Our case study stems from an ongoing effort to resolve poorly understood deeper relationships in the large clade Ditrysia ( > 150,000 species) of the insect order Lepidoptera (butterflies and moths). Seeking to remedy the overall weak support for deeper divergences in an initial study based on five nuclear genes (6.6 kb) in 123 exemplars, we nearly tripled the total gene sample (to 26 genes, 18.4 kb) but only in a third (41) of the taxa. The resulting partially augmented data matrix (45% intentionally missing data) consistently increased bootstrap support for groupings previously identified in the five-gene (nearly) complete matrix, while introducing no contradictory groupings of the kind that missing data have been predicted to produce. Our results add to growing evidence that data sets differing substantially in gene and taxon sampling can often be safely and profitably combined. The strongest overall support for nodes above the family level came from including all nucleotide changes, while partitioning sites into sets undergoing mostly nonsynonymous versus mostly synonymous change. In contrast, support for the deepest node for which any persuasive molecular evidence has yet emerged (78–85% bootstrap) was weak or nonexistent unless synonymous change was entirely excluded, a result plausibly attributed to compositional heterogeneity. This node (Gelechioidea + Apoditrysia), tentatively proposed by previous authors on the basis of four morphological synapomorphies, is the first major subset of ditrysian superfamilies to receive strong statistical support in any phylogenetic study. A “more-genes-only” data set (41 taxa×26 genes) also gave strong signal for a second deep grouping (Macrolepidoptera) that was obscured, but not strongly contradicted, in more taxon-rich analyses
Two species of metallic Microlepidoptera, one new species of Adela Latreille [1796] (Adeloidea, Adelidae) and one unrecorded species of Coleophora Hübner 1822 (Gelechioidea, Coleophoridae), from Korea
Koo, Jun-Mo, Cho, Soowon (2022): Two species of metallic Microlepidoptera, one new species of Adela Latreille [1796] (Adeloidea, Adelidae) and one unrecorded species of Coleophora Hübner 1822 (Gelechioidea, Coleophoridae), from Korea. Zootaxa 5138 (4): 431-444, DOI: https://doi.org/10.11646/zootaxa.5138.4.
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