• 한국자기공명학회:학술대회논문집
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• 한국자기공명학회 1999년도 하계총회 및 제15회 자기공명 학술발표회
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• pp.36-36
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• 1999

• 한국자기공명학회논문지
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• 제21권2호
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• pp.55-62
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• 2017

It is now well established that RNAs exhibit fundamental roles in regulating cellular processes. Many of these RNAs do not exist in a single conformation. Rather, they undergo dynamic transitions among many different conformations to mediate critical interactions with other biomolecules such as proteins, RNAs, DNAs, or small molecules. Here, we briefly review NMR techniques that describe the dynamic behavior of RNA by determining structural, kinetic, and thermodynamic properties.

• Advances in nano research
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• 제12권6호
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• pp.605-616
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• 2022

We prepared two samples of ultrafine ferrihydrite (FH) nanoparticle ensembles of quite a different origin. First is the biosynthesized sample (as a product of the vital activity of bacteria Klebsiella oxytoca (hereinafter marked as FH-bact) with a natural organic coating and negligible magnetic interparticle interactions. And the second one is the chemically synthesized ferrihydrite (hereinafter FH-chem) without any coating and high level of the interparticle interactions. The interparticle magnetic interactions have been tuned by modifying the nanoparticle surface in both samples. The coating of the FH-bact sample has been partially removed by annealing at 150℃ for 24 h (hereinafter FH-annealed). The FH-chem sample, vice versa, has been coated (1.0 g) with biocompatible polysaccharide (arabinogalactan) in an ultrasonic bath for 10 min (hereinafter FH-coated). The changes in the surface properties of nanoparticles have been controlled by XPS. According to the electron microscopy data, the modification of the nanoparticle surface does not drastically change the particle shape and size. A change in the average nanoparticle size in sample FH-annealed to 3.3 nm relative to the value in the other samples (2.6 nm) has only been observed. The estimated particle coating thickness is about 0.2-0.3 nm for samples FH-bact and FH-coated and 0.1 nm for sample FH-annealed. Mössbauer and magnetization measurements are definitely shown that the drastic change in the blocking temperature is caused by the interparticle interactions. The experimental temperature dependences of the hyperfine field hf>(T) for samples FH-bact and FH-coated have not revealed the effect of interparticle interactions. Otherwise, the interparticle interaction energy E_int estimated from the hf>(T) for samples FH-chem and FH-annealed has been found to be 121k_B and 259k_B, respectively.

• 한국자기공명학회논문지
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• 제20권4호
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• pp.109-113
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• 2016

Resonance frequencies from the $^{113}Cd$ and $^{133}Cs$ nuclear magnetic resonance (NMR) spectra for the $CsCdBr_3$ single crystal were measured at varying temperatures by the static NMR method. The temperature-dependent changes of these frequencies are related to the changing structural geometry of the ${CdBr_6}^{4-}$ units, which affects the environment of $^{133}Cs$. The spin-lattice relaxation rates ($1/T_1$) for the $^{113}Cd$ and $^{133}Cs$ nuclei were measured in order to obtain detailed information about the dynamics of $CsCdBr_3$ crystals. The dominant relaxation mechanisms for $^{113}Cd$ and $^{133}Cs$ nuclei are direct single-phonon and Raman spin-phonon processes, respectively.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2003년도 하계학술연구발표회 및 한.일 공동심포지엄
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• pp.150-151
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• 2003

In the past years, a giant magnetoresistance (GMR) effect found in perovskite-like structured materials has attracted considerable attention among scientists and manufacturers, since, a practical point of view, the capacity of producing magnetic and sensing sensors. In a stream of this interest, further efforts to understand the underlying mechanism that leads to the GMR effect relative to the correlation between transport and magnetic properties, have been extensively devoted. In these cases, spin-glass-like behaviors are ascribed to the frustration of random competing exchange interactions, namely the ferromagnetic double-exchange interaction between Co$\^$3+/ (or Mn$\^$3+/) and Co$\^$4+/(or Mn$\^$4+/) and the antiferromagnetic one like spins. Noticeably, the distinction of spin-glass region from cluster-glass one, involved in the remarkable changes in transport and magnetic properties at a critical value of doping concentration, was observed. Magnetic anomalies in zero-field-cooled (ZFC) magnetization as well as ac magnetic susceptibility below Curie temperature T$\sub$c/ and the charge/orbital fluctuation were also realized. In this work, we present a study of magnetic properties of a deficient manganese perovskites system of La$\sub$0.6/Sr$\sub$x/MnTi$\sub$y/O$_3$, and particularly provide its new magnetic phase diagram.

• Current Applied Physics
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• 제18권11호
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• pp.1422-1425
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• 2018

$NaTa_{1-x}Fe_xO_3$ ($0{\leq}x{\leq}0.40$) nanocubes were synthesized by a relatively low temperature hydrothermal method, using $Ta_2O_5$, $FeCl_3$ and NaOH as the precursors. The UV-vis diffuse reflectance spectra showed that $NaTa_{1-x}Fe_xO_3$ had significant visible-light-absorbing capability, and the absorption edge of $NaTaO_3$ shifted to longer wavelength with the increase of Fe dopants. Moreover, $NaTa_{1-x}Fe_xO_3$ exhibited room-temperature ferromagnetism when $Fe^{3+}$ occupied $Ta^{5+}$ sites in $NaTaO_3$ crystal lattice. The ferromagnetism is mainly attributed to the superexchange interactions between doped $Fe^{3+}$, rather than the contribution of oxygen vacancies caused by Fe doping. Therefore, Fe doping can simultaneously regulate the optical and magnetic properties of $NaTaO_3$ semiconductor, which will enable its potential applications in multifunctional optical-electronics and opticalspintronics devices.

• Journal of Magnetics
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• 제8권1호
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• pp.13-17
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• 2003

The longitudinal magnetooptical Kerr effect was used to analyse magnetic domains in soft magnetic ${(Fe_{97}A1_3)}_{85}N_{15}$/$Al_{2}O_{3}$ multilayers in order to get microscopic understanding of interlayer exchange coupling. The measuring system consists of a Kerr microscope, a CCIR camera (with an 8-bit framegrabber), 16 bit digital camera and computer system for real-time image processing and to control external magnetic field and cameras. The strength of ferromagnetic (EM) coupling as a function of the spacer thickness of $Al_2O_3$ was investigated. It was found that strong FM-coupling, strong uniaxial anisotropy and coherent rotation of the magnetization have been observed for the spacer thickness in the range of 0.2 nm $\leq$ t $\leq$ 1 m, however, weak FM-coupling, patch domains and $360^{\circ}$-walls occur for the spacer thickness of t = 2.5 nm. At a spacer thickness of t $\geq$ 5 nm transition takes place from weak FM-coupling to the decoupled state where complex interlayer interactions and different types of the domain walls were observed.

• Bulletin of the Korean Chemical Society
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• 제22권9호
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• pp.969-974
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• 2001

Model calculations for small molecules Li2, F2, LiF and BF have been performed at the Dirac-Fock level of theory using Dirac-Coulomb and Dirac-Coulomb-Magnetic Hamiltonians with various basis sets. In order to understand what may happen when the relativity becomes significant, the value of c, speed of light, is varied from the true value of 137.036 a.u. to 105 (nonrelativistic case) and also to 50 and 20 a.u. (exaggerated relativistic cases). Qualitative trends are discussed with special emphasis on the effect of the magnetic part of the Breit interaction term. The known relativistic effects on bonding such as the bond length contraction or expansion are demonstrated in this model study. Total energy, $\pi-orbital$ splitting, bond length, bond dissociation energy and dipole moment are calculated, and shown to be modified in a uniform direction by the effect of the magnetic term. Inclusion of the magnetic term raises the total energy, increases the bond length, reduces the $\pi-orbital$ splitting, increases the bond dissociation energy, and mitigates the changes in dipole moment caused by the Dirac term.

• Journal of Magnetics
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• 제5권1호
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• pp.19-22
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• 2000

The effects of a hard-biased Held on the magnetic and magnetoresistive properties of a crossed spin-valve head are investigated by computer simulation with particular emphasis on the asymmetry of the output signal. The spin-valve considered in this work is NiMn (25 nm)/NiFe (2.5 m)/Cu (3 nm)/NiFe (5.5 m), with a length of 1500 m and a width of 600 nm. A simple model is used where each magnetic layer consists of a single domain, and the magnetoresistance is a function of the angle between the magnetization directions of the two magnetic layers. The ideal crossed spin-valve structure is not realized with the present model and magnetic parameters, but the deviation from ideality is decreased by the hard-biased field. This results in the improvement of the linearity of the output signal with the use of the bias field. The magnetoresistance ratio and magnetoresistive sensitivity, however are reduced. The magnetic properties including the magnetoresistance are found to be strongly affected by magnetostatic interactions, particularly the inter-layer magnetostatic field.

• 한국자기공명학회논문지
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• 제1권2호
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• pp.112-125
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• 1997

It has been demonstrated that mutant Hemoglobins (Hb) which have an altered ${\alpha}$1${\beta}$2 subunit interface can be designed. A compensatory mutation for a naturally occurring abnormal human Hb, Hb Kempsey (${\beta}$99Asp\longrightarrowAsn), has been designed, and this mutation allowed the molecule to regain its allosteric response. The calculated values for the difference in the free energy of cooperativity show excellent agreement with experimentally determined thermodynamic values, suggesting that the molecular dynamics simulation results can be used to obtain information about the specific interactions which contribute to the total free energy of cooperativity. These results provide encouragement to begin a systematic investigation of the molecular basis of the subunit interactions between the ${\alpha}$1 and ${\beta}$2 chains of Hb A by designing appropriate r Hbs. These studies could lead to the design of Hbs with desired cooperativity in the oxygenation process and to the restoration of functional properties of abnormal hemoglobins associated with hemoglobinopathies. Thus, the present results also have the implications in using gene therapy to treat patients with hemoglobinpathies.