• Investigative Magnetic Resonance Imaging
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• v.13 no.1
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• pp.74-80
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• 2009

Purpose : To evaluate the characteristic MR imaging findings of Langerhans cell histiocytosis (LCH) in the skull and to compare them with those of plain radiography and computed tomography. Materials and Methods : A total of 10 lesions in 9 patients (Age range; 5-42 years, Mean age; 18, all women) with Langerhans cell histiocytosis in the skull were included in our study. Nine lesions in nine patients were histologically confirmed by surgery or fine needle aspiration biopsy. All patients performed with MRI, and plain radiography and CT scan were done in 7 patients (8 lesions). Two experienced neuroradiologists reviewed the radiological examinations independently with attention to location, size, shape and nature of the lesions in the skull and compared the extent and extension of the lesions to adjacent structures. Results : The lesions were distributed in all of the skulls without predilection site. On MRI, the masses were shown as well-enhancing soft tissue masses (10/10) mainly in diploic spaces (8/10) with extension to scalp (9/10) and dura mater (7/10). Dural enhancement (7/10) and thickening (4/10) were seen. The largest diameter of the soft tissue masses ranged 1.1 cm to 6.8 cm, shaped as round (5/10) or oval (5/10). On CT scans, the lesions were presented as soft tissue masses involving diploic space (6/8) and scalp extension (7/8) were also well visualized. Although bony erosion or destruction was more clearly seen on CT rather than those of MRI, enhancement of soft tissue masses and dura were not well visualized on CT. In contrast, all of the lesions in LCH were seen as punched out (4/8), beveled-edge appearance (4/8) osteolytic masses in plain radiography, but scalp and dural extension could not be seen. Conclusion : Characteristic MR findings in patients with LCH are soft tissue mass in diploic space with extension to dura and scalp, and MRI would be better imaging modality than plain radiography or CT.

• The Journal of Korean Academy of Prosthodontics
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• v.41 no.6
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• pp.720-731
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• 2003

Statement of problem. The importance of fixture design and surface treatment. Purpose. The clinical success of dental in plants is affected by many factors such like as degree of osseointegration, the effective load dispersion for the prostheses, and a lot of attempts have been made to overcome the difficulties. In this study, efforts were made to find the possibility of clinical acceptance of the dental implants of newly designed surface and resorbable blast media surcace. Materials and methods. In this study, two groups of custom-made, screw-shaped implants were prepared. The first with the consisting of Branemark clone design and the other with the new design. These implants were divided into four groups according to the kinds of surface treatment. Four implants($AVANA^{(R)}$, Osstem, Busan, Korea)of each group were installed in twenty rabbits. Group A was consisted of Branemark done implant left as machined, Group B with Branemark clone implants with RBM(Resorbable blast media) surface, Group C with newly designed implants left as machined and Group D with newly designed implants with RBM surface. One of the twenty rabbits died from inflammation and the observation was made for six weeks. Specimens from four groups were observed using scanning electron microscopy with 40, 100, 1000 magnification power and microsurface structures were measured by white-light scanning interferometry for three dimensional surface roughness measurements(Accura $2000^{(R)}$, Intek-Plus, Korea.). Removal torque was measured in 17 rabbits using digital torque gauge(MGT 12R, Mark-10 corp., NY, U.S.A.) immediately after the sacrifice and two rabbits were used for the histologic preparation(EXAKT $310^{(R)}$, Heraeus Kulzer, wehrheim, Germany) of specimens and observed under light microscope. Resonance frequency measurement($Osstell^{(R)}$) was taken with the 19 rabbits at the beginning of the implant fixation and immediately after the sacrifice. Results. Following results were taken from the experiment. 1. The surface of the RBM implants as seen with SEM had rough and irregular pattern with reticular formation compared to that of fumed specimens showing different surface topographies. 2. The newly designed implant with RBM surface had high removal torque value among four groups with no statistical significance. The average removal torque was $49.95{\pm}6.70Ncm$ in Group A, $51.15{\pm}4.40Ncm$ in Group B, $50.78{\pm}9.37Ncm$ in Group C, $51.09{\pm}4.69Ncm$ in Group D. 3. The RFA values were $70.8{\pm}4.3Hz$ in Group A, $71.8{\pm}3.1Hz$ in Group B, $70.9{\pm}2.5Hz$, $72.7{\pm}2.5Hz$ in Group D. Higher values were noted in the groups which had surface treatment compared to the untreated groups with no statistical significance. 4. The results from the histomorphometric evaluation showed a mean percentage of bone-to-implant contact of $45{\pm}0.5%$ in Group A, $55{\pm}3%$ in Group B, $49.5{\pm}0.5%$ in Group C, and $55{\pm}3%$ in Group D. Quite amount of newly formed bone were observed at the surface RBM-treated implants in bone marrow space.

• Korean Journal of Food Science and Technology
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• v.34 no.6
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• pp.1140-1144
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• 2002

Molecular relaxation behaviors of crystalline glucose anhydrous, crystalline glucose monohydrate, and amorphous glucose with different particle sizes were observed by measuring spin-spin relaxation time constant $(T_2)$ at the temperature range of $-20\;to\;110^{\circ}C$ using temperature-controlled low field nuclear magnetic resonance spectroscopy. No change in $T_2$ values of crystalline glucose anhydrous was observed throughout the temperature range, whereas $T_2$ values of crystalline glucose monohydrate and amorphous glucose increased from around $45\;and\;65^{\circ}C$, respectively. These results indicate that molecular mobility of crystalline glucose anhydrous does not change even at temperature higher than $100^{\circ}C$ and that the stability of powdered glucose could be improved by increasing the particle size of materials.

• Korean Journal of Mineralogy and Petrology
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• v.34 no.3
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• pp.157-167
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• 2021

Lead (Pb) is one of the key trace elements, exhibiting a peculiar partitioning behavior into silicate melts in contact with minerals. Partitioning behaviors of Pb between silicate mineral and melt have been known to depend on melt composition and thus, the atomic structures of corresponding silicate liquids. Despite the importance, detailed structural studies of Pb-bearing silicate melts are still lacking due to experimental difficulties. Here, we explored the effect of lead content on the atomic structures, particularly the evolution of silicate networks in Pb-bearing sodium metasilicate ([(PbO)_x(Na₂O)_1-x]·SiO₂) glasses as a model system for trace metal bearing natural silicate melts, using ²⁹Si solid-state nuclear magnetic resonance (NMR) spectroscopy. As the PbO content increases, the ²⁹Si peak widths increase, and the maximum peak positions shift from -76.2, -77.8, -80.3, -81.5, -84.6, to -87.7 ppm with increasing PbO contents of 0, 0.25, 0.5, 0.67, 0.86, and 1, respectively. The ²⁹Si MAS NMR spectra for the glasses were simulated with Gaussian functions for Qⁿ species (SiO₄ tetrahedra with n BOs) for providing quantitative resolution. The simulation results reveal the evolution of each Qⁿ species with varying PbO content. Na-endmember Na₂SiO₃ glass consists of predominant Q² species together with equal proportions of Q¹ and Q³. As Pb replaces Na, the fraction of Q² species tends to decrease, while those for Q¹ and Q³ species increase indicating an increase in disproportionation among Qⁿ species. Simulation results on the ²⁹Si NMR spectrum showed increases in structural disorder and chemical disorder as evidenced by an increase in disproportionation factor with an increase in average cation field strengths of the network modifying cations. Changes in the topological and configurational disorder of the model silicate melt by Pb imply an intrinsic origin of macroscopic properties such as element partitioning behavior.

• Investigative Magnetic Resonance Imaging
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• v.10 no.2
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• pp.98-107
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• 2006

Magnetization Transfer (MT) imaging generates contrast dependent on the phenomenon of magnetization exchange between free water proton and restricted proton in macromolecules. In biological materials in knee, MT or cross-relaxation is commonly modeled using two spin pools identified by their different T2 relaxation times. Two models for cross-relaxation emphasize the role of proton chemical exchange between protons of water and exchangeable protons on macromolecules, as well as through dipole-dipole interaction between the water and macromolecule protons. The most essential tool in medical image manipulation is the ability to adjust the contrast and intensity. Thus, it is desirable to adjust the contrast and intensity of an image interactively in the real time. The proton density (PD) and T2-weighted SE MR images allow the depiction of knee structures and can demonstrate defects and gross morphologic changes. The PD- and T2-weighted images also show the cartilage internal pathology due to the more intermediate signal of the knee joint in these sequences. Suppression of fat extends the dynamic range of tissue contrast, removes chemical shift artifacts, and decreases motion-related ghost artifacts. Like fat saturation, phase sensitive methods are also based on the difference in precession frequencies of water and fat. In this study, phase sensitive methods look at the phase difference that is accumulated in time as a result of Larmor frequency differences rather than using this difference directly. Although how MT work was given with clinical evidence that leads to quantitative model for MT in tissues, the mathematical formalism used to describe the MT effect applies to explaining to evaluate knee disorder, such as anterior cruciate ligament (ACL) tear and meniscal tear. Calculation of the effect of the effect of the MT saturation is given in the magnetization transfer ratio (MTR) which is a quantitative measure of the relative decrease in signal intensity due to the MT pulse.

• Progress in Medical Physics
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• v.12 no.2
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• pp.113-124
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• 2001

For veterinary imaging diagnosis, we obtained MR images of the canine brain, spine, kidney and pelvis from 3T MRI system which was equipped with the world first 3T active shield magnet. Spin echo (SE) and fast Spin Echo (FSE) images were obtained from the canine brain, spine, kidney and pelvis of normal and sick dogs using a homemade birdcage and transverse electromagnetic (TEM) resonators operating in quadrature and tuned to 128 MHz. In addition, we employed a homemade saddle shaped RF coil. Typical common acquisition parameters were as follows: matrix=512$\times$512, field of view (FOV)=20cm, slice thickness=3 w, number of excitations (NEX)=1. For T1-weighted MR images, we used TR=500 ms, TE=10 or 17.4 ms. For T2-weighted MR images, we used TR=4000 ms, TE=108 ms. Signal to noise ratio (SNR) of 3T system was measured 2.7 times greater than that of prevalent 1.57 system. The high resolution images acquired in this study represent more than a 4-fold increase in in-plane resolution relative to conventional images obtained with a 20 cm field of view and a 5 mm slice thickness. MR images obtained from 3T system revealed numerous small venous structures throughout the image plane and provided reasonable delineation between gray and white matter The present results demonstrate that the MR images from 3T system could provide better diagnostic quality of resolution and sensitivity than those of 1.5T system. The elevated SNR observed in the 3T high field magnetic resonance imaging can be utilized to acquire images with a level of resolution approaching the microscopic structural level under in vivo conditions. These images represent a significant advance in our ability to examine small anatomical features with noninvasive imaging methods. Moreover, MRI technique could begin to apply for veterinary medicine in Korea.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.251-252
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• 2012

Recently, the growing interest in organic microelectronic devices including OLEDs has led to an increasing amount of research into their many potential applications in the area of flexible electronic devices based on plastic substrates. However, these organic devices require a gas barrier coating to prevent the permeation of water and oxygen because organic materials are highly susceptible to water and oxygen. In particular, high efficiency OLEDs require an extremely low Water Vapor Transition Rate (WVTR) of $1{\times}10^{-6}g/m^2$/day. The Key factor in high quality inorganic gas barrier formation for achieving the very low WVTR required ($1{\times}10^{-6}g/m^2$/day) is the suppression of defect sites and gas diffusion pathways between grain boundaries. In this study, we developed an $Al_2O_3$ nano-crystal structure single gas barrier layer using a Neutral Beam Assisted Sputtering (NBAS) process. The NBAS system is based on the conventional RF magnetron sputtering and neutral beam source. The neutral beam source consists of an electron cyclotron Resonance (ECR) plasma source and metal reflector. The Ar+ ions in the ECR plasma are accelerated in the plasma sheath between the plasma and reflector, which are then neutralized by Auger neutralization. The neutral beam energies were possible to estimate indirectly through previous experiments and binary collision model. The accelerating potential is the sum of the plasma potential and reflector bias. In previous experiments, while adjusting the reflector bias, changes in the plasma density and the plasma potential were not observed. The neutral beam energy is controlled by the metal reflector bias. The NBAS process can continuously change crystalline structures from an amorphous phase to nano-crystal phase of various grain sizes within a single inorganic thin film. These NBAS process effects can lead to the formation of a nano-crystal structure barrier layer which effectively limits gas diffusion through the pathways between grain boundaries. Our results verify the nano-crystal structure of the NBAS processed $Al_2O_3$ single gas barrier layer through dielectric constant measurement, break down field measurement, and TEM analysis. Finally, the WVTR of $Al_2O_3$ nano-crystal structure single gas barrier layer was measured to be under $5{\times}10^{-6}g/m^2$/day therefore we can confirm that NBAS processed $Al_2O_3$ nano-crystal structure single gas barrier layer is suitable for OLED application.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.11
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• pp.5299-5304
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• 2012

MRI signals are significantly reduced by the magnetic field inhomogenity result from human body itself being consisted of various materials like air, fat, muscle, bone and blood vessels. In this study we used silicon which is tissue equivalent to compensate wound body shapes. Objects were eight adults who do not have any special symptoms. Feet were scanned because of their complicated structures and consequently signal reduction occurs a lot. Thirty images were acquired from the middle of arcus pedis longitudinalis including five distal phalanges parallel to the line connecting metatarsal bone and phalanges. SNR data from bones and soft tissues were compared before and after sticking silion between toes and paired t test was performed. It was came out that SNR data from bone and soft tissue were both significantly higher after applying silicon on both T1 and T2 weighted images and it was statistically meaningful having positive corelation. As a result, this study dramatically increases SNR without affecting object by increasing the object volume inside the surface coil.

• Bulletin of the Korean Chemical Society
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• v.24 no.4
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• pp.446-452
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• 2003

Some new nanohybrid materials have been synthesized by intercalating the oxotitanium(IV) meso-tetrakis(4- sulfonatophenyl) porphyrin$(O=Ti^{(IV)} TSPP)$ into the Zn/Al layered double hydroxides (LDHs), and their structures and photophysical properties have been investigated by various laser spectroscopic techniques. According to the XRD pattern of the synthesized nanohybrid materials, the macrocycle plane of $O=Ti^{(IV)}$ TSPP are grafted perpendicular to the LDH layers. The $O=Ti^{(IV)}$ TSPP-intercalated LDH exhibits band broadening of the absorption spectrum and a blue shift of Q-band as compared to that observed in solution. Resonance Raman spectral measurements demonstrate that the positively charged LDHs give rise to a slight decrease of the electronic density of the porphyrin ring accompanying a small change of the electronic distribution of the $O=Ti^{(IV)}$ TSPP. Consequently the LDH environment affects the energies of the two highest occupied molecular orbitals (HOMOs) of the $O=Ti^{(IV)}$) TSPP, $a_{1u}$ and $a_{2u}$, producing a mixed orbital character. Being consistent with these electronic structural changes of $O=Ti^{(IV)}$ TSPP in LDH, both the fluorescence spectral change and the fsdiffuse reflectance transient measurements imply that the photoexcitation of the $O=Ti^{(IV)}$ TSPP intercalated into LDH undergoes fast relaxation to the O=Ti(IV) $TSPP^+-LDH^- $charge transfer (CT) state within a few picoseconds, followed by a photoinduced electron transfer between the O=Ti(IV) TSPP and LDHs with a rate constant greater than %1×10^{10}S^{-1}$. No evidence is found for back electron transfer. In conclusion, the $O=Ti^{(IV)}$ TSPP intercalated LDH seems to be a possible candidate for an artificial reaction center for an efficient solar energy conversion system.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.2
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• pp.139-144
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• 2015

Recently, to realize sound-absorbing structures, we have to insert sound-absorbing materials into wall. These shapes are taken limitations because sound-absorbing materials should be fixed. Therefore, the sound absorption is changed by environment that used the sound-absorbing materials. On the other hand, we will take same effect without sound-absorbing material, if we change the shape of wall to sound absorbing structure. If we use this sound absorbing structure, we can get benefits by removing limitation of materials. Therefore we suggest perforated plate for effective sound-absorbing structure. We confirmed the function of sound-absorption of this structure using equivalent property. Then, we found the similarity between perforated plate and resonator. Also, we verify these theories through computer simulation by FEM(Finite Element Method). Finally, we validated that perforated plate has function of sound absorption without sound-absorbing material. This perforated plate is used for sound-absorbing material of buildings and transportations such as vehicle, train etc. Also, these results could be further used basic tool for design of sound-absorption structure.