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Thermal property of Quasi 1D S = 1 chain NiTe2O5
No full textOne-dimensional magnets are very interesting, although it is well-known that there is no long range-order[1]. Because a spin chain, which is defined as a one-dimensional line of spins pointing in particular directions, in one-dimensional magnets has the possibility of complex excitations like spinons which have spin-1/2 in chains with S=1/2. Lately, we have reported a quasi-one-dimensional S=1 chain system NiTe2O5[2]. About the crystallographic structural feature of NiTe2O5, NiO6 octahedra are connected to each other through the edge-sharing and the spin(S=1) of each Ni2+ ion at the center of the octahedra forms a quasi-one-dimensional spin chain. By decreasing temperature, spins of Ni2+ ions are ordered as antiferromagnetic long-range order at 30.5 K. The single crystal neutron diffraction reveals the unconventional critical behavior of the order parameter around the ordering temperature. 125Te nuclear magnetic resonance(NMR) experiments exhibit intriguing persistent spin fluctuation above the ordering temperature[3]. More recently, even magnetoelectric(ME) coupling was reported[4]. Thermal transport has been used to an experimental tool in solid-state physics even when dealing with magnetic systems[5]. Because heat transport via the spin system itself and thermal conductivities are influenced by scattering between phonon and magnetic excitations. By using the thermal transport experiments on NiTe2O5 single crystal, we studied thermodynamic properties associated with these unusual magnetic behaviors in NiTe2O5.
[1] Stephen Blundell, Magnetism in Condensed Matter, Oxford ; New York : Oxford University Press (2001).
[2] Jun Han Lee, Marie Kratochv??lov??, Huibo Cao, Zahra Yamani, JS Kim, Je-Geun Park, GR Stewart, Yoon Seok Oh, Unconventional critical behavior in the quasi-one-dimensional S=1 chain NiTe2O5, Physical Review B 100, 144441 (2019).
[3] Seung-Ho Baek, Jun Han Lee, Yoon Seok Oh, Kwang-Yong Choi, Bernd B??chner, Persistence of Ising-like easy-axis spin correlations in the paramagnetic state of the spin-1 chain compound NiTe2O5, Physical Review B 104, 214431 (2021).
[4] Ajay Tiwari, D. Chandrasekhar Kakarla, G. Macam, C. H. Hsu, F. C. Chuang, H. C. Wu, T. W. Kuo, Arkadeb Pal, H. Chou, D. P. Gulo, H.L. Liu, Y. C. Lai, C. A. Lee, Mitch M. C. Chou, H. D. Yang, Spin-lattice-charge coupling in quasi-one-dimensional spin-chain NiTe2O5, Physical Review Materials 6, 044409 (2022).
[5] A. V. Sologubenko, T. Lorenz, H. R. Ott, A. Freimuth, Thermal conductivity via magnetic excitations in spin-chain materials, J. Low Temp. Phys. 147, 387-403 (2007)
Model-driven experimental design workflow expands understanding of regulatory role of Nac in Escherichia coli
No full textThe establishment of experimental conditions for transcriptional regulator network (TRN) reconstruction in bacteria continues to be impeded by the limited knowledge of activating conditions for transcription factors (TFs). Here, we present a novel genome-scale model-driven workflow for designing experimental conditions, which optimally activate specific TFs. Our model-driven workflow was applied to elucidate transcriptional regulation under nitrogen limitation by Nac and NtrC, in Escherichia coli. We comprehensively predict alternative nitrogen sources, including cytosine and cytidine, which trigger differential activation of Nac using a model-driven workflow. In accordance with the prediction, genome-wide measurements with ChIP-exo and RNA-seq were performed. Integrative data analysis reveals that the Nac and NtrC regulons consist of 97 and 43 genes under alternative nitrogen conditions, respectively. Functional analysis of Nac at the transcriptional level showed that Nac directly down-regulates amino acid biosynthesis and restores expression of tricarboxylic acid (TCA) cycle genes to alleviate nitrogen-limiting stress. We also demonstrate that both TFs coherently modulate ??-ketoglutarate accumulation stress due to nitrogen limitation by co-activating amino acid and diamine degradation pathways. A systems-biology approach provided a detailed and quantitative understanding of both TF???s roles and how nitrogen and carbon metabolic networks respond complementarily to nitrogen-limiting stress
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No full textBaTiO3 ????????? ??? Dy ?????? ???????????? ?????? ?????? ??? ????????? ?????? ??????
No full textDepartment of Materials Science and EngineeringMulti-layered ceramic capacitors (MLCCs) which are composed of dielectric materials are used in electronic devices and electric automobiles and have a role of stably supplying voltage required for semiconductor devices and circuits. Specially nowadays, with an automotive electrification, the demand of MLCC also increases. Therefore, it is essential to ensure high reliability for dielectrics to operate stably at wide working temperature for safety. In response to this need, dielectrics capacitors based on BaTiO3(BT) composition are actively being studied. The BaTiO3 composition shows high permittivity(????????) around 2000 at room temperature, but the low curie temperature around 120oC limits the application on capacitor leading to low reliability. So many researchers are trying to improve this disadvantage by synthesizing BT system doped with Dysprosium(Dy) which has amphoteric behavior. However, the researches about the analysis of properties according to the role of Dy are lack. Here, by introducing 2-step calcination, we doped Dy3+ ion on each site of BT (A-site, B-site, and A&B site) and systematically compared the properties according to the Dy-doped site. As a result, Dy-doped on B site in BT system showed leaky properties, leading to worse reliability and Dy-doped on A&B site exhibited improved dielectric properties and reliability. In addition, in order to confirm that Dy was well doped at the target site through 2-step calcination, dielectric and electrical properties were compared with the conventional solid solution method that was used in previous research. To conclude, there are some differences between them, meaning that it is hard to control doping site with conventional solid solution method and 2-step calcination should be introduced when the dopants has amphoteric behavior.ope
Biomechanical and Neuromuscular Investigation on the Mechanism of Neck Pain During Smartphone Use
No full textDepartment of Biomedical Engineering (Human Factors Engineering)As screen time and dependence on the smartphone have increased, the prevalence of neck discomfort and pain has also increased. Since many people adopt a smartphone posture, concerns about neck pain or injury risks related to excessive smartphone use have been increasing. Prolonged and excessive exposure to smartphone use posture can affect the active and passive tissues of the neck, and the changes in neck tissues can be connected to the development of neck pain.
The biomechanical and neuromuscular response changes in active and passive tissues were observed in extreme cases, such as exposure to the maximum flexion of the spine, and fatiguing protocols with high muscle contractions. Therefore, the relationship between exposure to that extreme posture and its effect on the changes in tissues is well established. However, there is a lack of biomechanical and neuromuscular investigation related to the smartphone use posture that requires sub-maximal flexion and low-level muscle contraction. It was unclear whether the passive tissues were deformed, or whether muscle fatigue developed during prolonged smartphone use. Objectively evaluating the effect of smartphone use on the active and passive tissues of the neck and understanding their relationship with pain development is essential to understand musculoskeletal pain related to smartphone use, and to prevent related neck injuries.
With the aim of concluding which tissues would be changed by prolonged smartphone use and related neck pain, three experiments were conducted in Study 1. The first experiment investigated the viscoelastic changes in passive tissues, but passive tissue laxity was not observed. The second experiment was conducted to investigate the occurrence of neck muscle fatigue. However, it also failed to observe local muscle fatigue. The third experiment aimed to explore the changes in passive tissues by evaluating head stability, but it also did not observe any changes in head stability. In the three experiments, neck pain developed during smartphone use. It implies that prolonged smartphone use might affect the active and passive tissues in the pain development pathway, but no objective evidence about changed tissue properties was found. It is determined that the effect of prolonged smartphone posture on the active and passive tissues should be investigated independently and sensitively with various measurements.
Three independent smartphone-use conditions that depart from each tissue's effects were newly designed to investigate the effect of each tissue on subjective pain development, excluding the other tissues' effects in Study 2. The "normal" condition was the common smartphone-use posture of flexing the head approximately 40 ??. The "posture-only" condition induced only flexed posture without muscle activation. Finally, the "muscle-only" condition activated muscles similar to the "normal" condition, without flexed posture. The biomechanical and neuromuscular changes in each tissue were also investigated in the controlled and independent conditions during 60 minutes of exposure. Pain levels, head kinematics, and electromyography (EMG) were collected over time during smartphone use. In the flexion relaxation phenomenon (FRP), tissue laxity and load-sharing timing were observed. The reflexive responses of muscles and passive tissues were evaluated in the presence of unexpected head perturbations. The local muscle fatigue was confirmed through EMG responses in isometric contraction. The seven responses were investigated three times intermittently: pre-, mid-, and post-exposure.
The results of Study 2 revealed that increasing musculoskeletal symptoms with smartphones were highly related to sustained muscle activation, but local muscle fatigue was not related to pain development. The possible mechanisms between sustained muscle activation and pain development are capillary compression and reduced oxygenation, spine joint compression, and irritating byproducts. In addition, passively stretched passive tissue was not significantly related to pain, but its micro-damage was confirmed through biomechanical and neuromuscular investigation. Repetitive micro-damage to passive tissues without full recovery could lead to chronic neck pain or future injuries, so it should be carefully considered. These newly designed experimental conditions allowed for observing changes in each tissue that were not revealed in previous studies. The findings of this study may help understand the mechanism of neck pain resulting from prolonged smartphone use and its effect on each tissue.clos
Co-application of Colicins with Bdellovibrio bacteriovorus HD100 to Eradicate Multi-drug Resistant Escherichia coli
No full textDepartment of Biological Sciencesclos
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No full textDepartment of Biological Sciencesclos
Cooperative H-bonding on the Topology Controlled Polyether toward Advanced Adhesive Materials
No full textDepartment of ChemistryAs a crucial molecular interaction in nature, hydrogen bonding (H-bonding) is important to express their own characteristic and unique phenomena such as RNA, DNA, and protein. Inspired by this remarkable feature in H-bonding, a lot of researches have been done to design and synthesize novel functional materials and polymers including self-assembly supra-molecules, polymer blends and nanocomposites displaying interesting thermal and mechanical properties. Herein, we successfully introduced the carbonyl benzoic acid group that can induce the cooperative H-bonding in the topology controlled PGs (i.e. linear, hyper-branched, and branched cyclic types) to synthesis poly(glycidoxy carbonyl benzoic acid)s (PGCBAs)) via the simple post-polymerization process while showing high conversion in a short time. In the synthesis process, we here present a new strategy for enhancing the conversion from post-polymerization using DBU via nucleophilic catalysis mechanism. The obtained topology controlled PGCBAs contain H-bonding donor and acceptor in a single repeating unit that can induce the intramolecular and intermolecular H-bonding and they were characterized by NMR, GPC and show the interesting phenomena in the bulk and the solution state depending on the polymer topologies. The high synergistic interaction from the intermolecular and intramolecular H-bonding in the topology-controlled PGCBAs show interesting pH sensitive properties in the solution phase and stronger adhesion strength in the bulk phase compared to the conventional adhesives by the secondary interaction. We prove that it is possible to improve the adhesive performance by adjusting and controlling the interaction of H-bonding between polymer chains by simply mixing each of functional groups and topologies. Therefore, why it is important to control the topologies of a polymer, and different properties can be exhibited with the same chemical structure. Finally, as a result of the cell viability assay, we expect that PGCBAs can be used in biological fields owing to its excellent biocompatibility.clos
Crown Ether-based Hyperbranced Polymers Composed of N-Heterocyclic Linkages for Proton Conductivity
No full textSchool of Energy and Chemical Engineering (Energy Engineering)clos
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Full text linkDepartment of DesignAlthough archiving daily moods in a diary is a common behavior, reflection is difficult because of the pressure brought about by continuous self-tracking of personal moods. In this paper, I developed Lumino, a standalone device that enables users to log their daily moods with colored lights and switch mode to show the log by physically sliding a circular lighting plate. The results of three-week in-field study with six participants revealed that Lumino helped users encounter emotional archives as it separated reflective experiences from daily life activities. Moreover, Lumino helped prevent deep reflection on negative emotions and maintained privacy through abstract color expression. I also found user???s various trials to control emotion reflections in their own usage patterns. I propose considerations for augmenting daily mood recording experiences combined with existing diary practices and further implications for designing how to support positively the negative reflections in everyday spaces.ope