• Title/Summary/Keyword: Magnetic Materials

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Mossbauer Studies of the $H_2$ Reduction Effects On Magnetic Properties of Sr-Ba Substituted Hexgonal Ferrite (치환형 Sr-Ba 육방 페라이트들의 자기적 성질에 수소환원이 미치는 효과에 관한 Mossbauer 분광학적 연구)

  • 박재윤;권명회;이재광
    • Journal of the Korean Magnetics Society
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    • v.9 no.1
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    • pp.35-40
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    • 1999
  • Sr substituted materials for some barium in M-type barium ferrite powder and Co-Ti substituted Sr-Ba hexagonal ferrite powder were prepared by citrate sol-gel method and 2 MOE sol-gel method these hexaferrite particles were reduced for 1hr in the hydrogen gas. The reduction temperatures were varied in the range of 250 $^{\circ}C$ to 500 $^{\circ}C$. X-ray diffraction patterns were measured using diffractometer with Cu $K_{\Alhpa}$ radiation. Mossbauer absorption spectra were measured with a constant acceleration spectrometer. We have focused on studying the origin of increasing $M_s$ by M$\"{o}$ssbauer spectroscopy. Ferrite particles which were sintered at 105$0^{\circ}C$ were found to be typical magnetoplumbite structure and single phase. XRD patterns with varying the reduction temperatures in $Sr_{0.5}Ba_{0.5}Fe_{10}O_{19}$ indicates ferrites particles become composite hexaferrites containing $\alpha$-Fe at T_{red}=350 \;$^{\circ}C$$. On the otherhand, it was found that $Co^{2+}$ ions and $Ti^{4+}$ ions in $Sr_{0.7}Ba_{0.3}Fe_{10}CoTiO_{19}$ prevent from changing $Fe^{3+}$ ions to $\alpha$-Fe during the $H_2$ reduction. Comparing Mossbauer results with XRD results, we have determined most of $\alpha$-Fe are reduced from $4f_{vi}$ sites and 12k sites of $Fe^{3+}$ ions. These $\alpha$-Fe phase bring the induced anisotropy and increase saturation magnetization $M_s$.TEX>.

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Degradation Characteristics of Cross-linked Hyaluronic Acid Membrane (가교된 히아루론산 막의 분해 특성)

  • Cheong, Seong-Ihl;Cho, Gu-Hyun
    • Membrane Journal
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    • v.19 no.4
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    • pp.310-316
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    • 2009
  • The degradation characteristics of cross-linked lactide/hyaluronic acid (LA/HA) membranes were investigated for purpose of applying to tissue engineering. The lactide/hyaluronic acid cross-linked with 1,3-butadiene diepoxide (BD) and 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC) was degradated in deionized water in water bath at $37^{\circ}C$. As the LA/HA mole ratio or crosslinking agent concentration decreased, the degradation rate of the crosslinked membranes increased. In order to investigate the structure change of the membrane in the degradation process, the control sample and 3, 6, 9 days-degradated samples were analysed by the nuclear magnetic resonance spectroscopy. In case of the membranes crosslinked with EDC, the HA-EDC bonding structure was degradated slowly whereas the HA-LA bonding structure was degradated quickly and dissappeared completely after 6 days. In case of the membranes crosslinked with BD, all the crosslinked bonding structure degradated slowly. The HA-BD bonding structure maintained its original state about 89, 83% in case of 3, 6 days-degardated samples respectively whereas the HA-LA bonding structure maintained its original state about 83, 65%. The scanning electron microscopy of the degradated membranes showed that the pore density in the surface, and the structure in the surface and cross section, of the before and after-degradation membranes did not change greatly, so the membranes was shown to be applied to materials for tissue engineering.

Acromion Morphology in Coronal and Sagittal Plane; Correlation with Rotator Cuff Syndrome (관상면과 시상면에서의 견봉 형태와 회전근개 파열의 연관성)

  • Jo, Chris H.;Kim, Jung-Taek;Yoon, Kang-Sup;Lee, Ji-Ho;Kang, Seung-Baek;Lee, Jae-Hyup;Han, Hyuk-Soo;Rhee, Seung-Whan
    • Clinics in Shoulder and Elbow
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    • v.12 no.2
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    • pp.126-136
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    • 2009
  • Purpose: We evaluated the correlation of the anatomic parameters of the acromion those represent on the magnetic resonance image (MRI) of impingement syndrome. Materials and Methods: From June, 2004 to December, 2005, 71 cases were surgically proven to be impingement syndrome, and the anterior acromial hooking angle, the lateral acromial hooking angle (AAHA and LAHA) and the acromial hooking index (AHI: the sum of the AAHA and LAHA) were compared to 16 control cases. At the same period, 55 cases were surgically proven to be partial or full thickness rotator cuff tear, and age, gender and twelve anatomic parameters, including the acromial type, the acromial angle, the anterior covering, the acromial slope, the AAHA, the lateral acromial angle, the acromial torsional angle, the lateral acromial angulation, the LAHA, the lateral covering, the acromiohumeral distance and the AHI were assessed. Results: The AAHA and AHI were increased as impingement syndrome proceeded. The acromial type and acromial angle, and the AAHA, LAHA and AHI showed significant differences between the controls and the rotator cuff tear patients on univariant analysis. On multivariant analysis, gender was most strongly correlated with rotator cuff tear. Age, AAHA and the acromial angle showed similar correlation, respectively. Conclusion: The coronal acromial shape is correlated with rotator cuff tear, and it is important to correct the lateral acromial shape when performing acromioplasty.

A topological metal at the surface of an ultrathin BiSb alloy film

  • Hirahara, T.;Sakamoto, Y.;Saisyu, Y.;Miyazaki, H.;Kimura, S.;Okuda, T.;Matsuda, I.;Murakami, S.;Hasegawa, S.
    • Proceedings of the Korean Vacuum Society Conference
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    • 2010.02a
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    • pp.14-15
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    • 2010
  • Recently there has been growing interest in topological insulators or the quantum spin Hall (QSH) phase, which are insulating materials with bulk band gaps but have metallic edge states that are formed topologically and robust against any non-magnetic impurity [1]. In a three-dimensional material, the two-dimensional surface states correspond to the edge states (topological metal) and their intriguing nature in terms of electronic and spin structures have been experimentally observed in bulk Bi1-xSbx single crystals [2,3,4]. However, if we want to know the transport properties of these topological metals, high purity samples as well as very low temperature will be needed because of the contribution from bulk states or impurity effects. In a recent report, it was also shown that an intriguing coupling between the surface and bulk states will occur [5]. A simple solution to this bothersome problem is to prepare a topological metal on an ultrathin film, in which the surface-to-bulk ratio is drastically increased. Therefore in the present study, we have investigated if there is a method to make an ultrathin Bi1-xSbx film on a semiconductor substrate. From reflection high-energy electron diffraction observation, it was found that single crystal Bi1-xSbx films (0${\sim}30\;{\AA}A$ can be prepared on Si(111)-$7{\times}7$. The transport properties of such films were characterized by in situ monolithic micro four-point probes [6]. The temperature dependence of the resistivity for the x=0.1 samples was insulating when the film thickness was $240\;{\AA}A$. However, it became metallic as the thickness was reduced down to $30\;{\AA}A$, indicating surface-state dominant electrical conduction. Figure 1 shows the Fermi surface of $40\;{\AA}A$ thick Bi0.92Sb0.08 (a) and Bi0.84Sb0.16 (b) films mapped by angle-resolved photoemission spectroscopy. The basic features of the electronic structure of these surface states were shown to be the same as those found on bulk surfaces, meaning that topological metals can be prepared at the surface of an ultrathin film. The details will be given in the presentation.

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Evaluation of Treatment Response Using Diffusion-Weighted MAI in Metastatic Spines (척추 전이암에서 확산강조 자기공명 영상을 이용한 치료반응의 평가)

  • Lee, Jang-Jin;Shin, Sei-One
    • Journal of Yeungnam Medical Science
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    • v.18 no.1
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    • pp.30-38
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    • 2001
  • Background: The purpose of this study was to evaluate the usefulness of diffusion-weighted magnetic resonance imaging for monitoring the response to radiation therapy in metastatic bone marrow of the spines. Materials and Methods: Twenty-one patients with metastatic bone marrow of the spines were examined with MRI. Diffusion-weighted and spin-echo MRI were performed in 10 patients before and after radiation therapy with or without systemic chemotherapy, and performed in 11 patients after radiation therapy alone. Follow up spin-echo and diffusion-weighted MRI were obtained at 1 to 6 months after radiation therapy according to patients' condition. The diffusion-weighted imaging sequence was based on reversed fast imaging with steady-state precession (PSIF). Signal intensity changes of the metastatic bone marrows before and after radiation therapy on conventional spin-echo sequence MRI and diffusion-weighted MRI were evaluated. Bone marrow contrast ratios and signal-to-noise ratios before and after radiation therapy of diffusion- weighted MRI were analyzed. Results: All metastatic bone marrow of the spinal bodies were hyperintense to normal bone marrow of the spinal bodies on pretreatment diffusion-weighted MRI and positive bone marrow contrast ratios(p<0.001), and hypointense to normal spinal bodies on posttreatment diffusion-weighted MRI and negative bone marrow contrast ratios(p<0.001). The signal to noise ratios after treatment decreased comparing with those of pretreatment. Decreased signal intensity of the metastatic bone marrows on diffusion-weighted MRI began to be observed at average more than one month after the initiation of the radiation therapy. Conclusion: These results suggest that diffusion-weighted MRI would be an excellent method for monitoring the response to therapy of metastatic bone marrow of the spinal bodies, however, must be investigated in a larger series of patients with longer follow up period.

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The Trend of Uro-Oncologist About Blood Test and Imaging Studies for the Diagnosis of Biochemical Recurrence in Korea (한국에서 Biochemical Recurrence의 진단에 대한 혈액 및 영상의학적 검사에 관한 비뇨기종양을 전공하는 의사의 트렌드에 대한 고찰)

  • Seo, Sung Pil;Kim, Won Tae;Kang, Ho Won;Kim, Yong-June;Lee, Sang-Cheol;Kim, Wun-Jae;Kim, So Young;Park, Jong-Hyock;Yun, Seok Joong
    • The Korean Journal of Urological Oncology
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    • 제15권3호
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    • pp.131-136
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    • 2017
  • Purpose: The aim of this study is to investigate the criteria of biochemical recurrence (BCR) and follow-up periods and methods with and without blood and imaging test of urologic oncology before established guidelines of prostate cancer in Korea. Materials and Methods: In December 2015, we sent the questionnaire to urologic oncologist in academic hospital and received the answer from 108 urologic oncologist (50%). Also, we analyzed the data of 1,141 patients underwent radical prostatectomy in 2005 from Korean Medical Insurance. Results: In follow-up, 72 physicians (66.7%) performed blood test every 3 months, 51 physicians (47.2%) performed imaging study in case of BCR. Bone scan was the most common imaging study in the follow-up (74 physicians, 68.5%). But, bone scan was only performed in case of BCR (43 physicians, 39.8%). The criteria of BCR was PSA 0.2 ng/mL (75 physician, 69.4%), 76 physicians (70.4%) was performed different follow-up according to risk of patients. In Korean Medical Insurance data analysis, PSA were performed average 2 times every year and magnetic resonance imaging, computed tomography, Bone scan were performed average 0.1, 0.2, 0.1 times every year, respectively. Conclusions: The criteria of BCR and the follow-up of prostate cancer patients in Korea were similar Korean prostate cancer guidelines. Blood and imaging test might be increased compared to 10 years ago, it is necessary to compare the Korean Medical Insurance data between 10 years ago and present.

Fistula Formation Between the Disc and Dura after Percutaneous Endoscopic Lumbar Discectomy - A Case Report - (경피적 내시경 요추 추간판 절제술 후 발생한 추간판과 경막 사이의 누공 형성 - 증례 보고 -)

  • Kim, Hak Sun;Kim, Hyoung Bok;Chung, Hoon-Jae;Yang, Jea Ho
    • Journal of Korean Society of Spine Surgery
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    • v.25 no.4
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    • pp.180-184
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    • 2018
  • Study Design: Case report Objectives: To document fistula formation between the disc and dura by an unrecognized dural tear after percutaneous endoscopic lumbar discectomy (PELD). Summary of Literature Review: The risk of durotomy is relatively low with PELD, but cases of unrecognized durotomies have been reported. An effective diagnostic tool for such situations has not yet been identified. Materials and Methods: A patient twice underwent transforaminal PELD under the diagnosis of a herniated lumbar disc at L4-5. She still complained of intractable pain and motor weakness around the left lower extremity at 6 months postoperatively. Magnetic resonance imaging showed no specific findings suggestive of violation of the nerve root. However, L5 and S1 nerve root injury was noted on electromyography. An exploratory operation was planned to characterize damage to the neural structures. Results: In the exploration, a dural tear was found at the previous operative site, along with a fistula between the disc and dura was also found at the dural tear site. The durotomy site was located on the ventrolateral side of the dura and measured approximately 5 mm. The durotomy site was repaired with Nylon 5-0 and adhesive sealants. The patient's preoperative symptoms diminished considerably. Conclusions: Fistula formation between the disc and dura can be caused by an unrecognized dural tear after PELD. Discography is a reliable diagnostic tool for fistulas formed by an unrecognized durotomy.

A Thoracolumbar Pure Spinal Epidural Cavernous Hemangioma - A Case Report - (흉요추부에서 발견된 경막외 해면상 혈관종 - 증례 보고 -)

  • Choi, Byeong Sam;Kim, Ju Yeon;Lee, Sungjoon
    • Journal of Korean Society of Spine Surgery
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    • v.25 no.4
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    • pp.169-174
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    • 2018
  • Study Design: Case report. Objectives: We report a case of pure epidural cavernous hemangioma located at the thoracolumbar spine in a 53-year-old woman that mimicked a neurogenic tumor on magnetic resonance imaging (MRI). Summary of Literature Review: A pure spinal epidural cavernous hemangioma without bony involvement is a very rare lesion about which limited information is available in the literature. Materials and Methods: A 53-year-old woman visited our clinic for hypoesthesia with a tingling sensation in the left anterolateral thigh that had begun a month ago. No other neurologic symptoms or signs were present upon a neurologic examination. MRI from an outside hospital showed a $2.0{\times}0.5cm$ elongated mass at the T11-12 left neural foramen. The tumor was completely removed in piecemeal fashion. Results: The histopathologic examination revealed a cavernous hemangioma, which was the final diagnosis. The outcome was favorable in that only operation-related mild back pain remained, without any neurologic deficits, after a postoperative follow-up of 2 years and 3 months. No recurrence was observed on MRI at 2 years postoperatively. Conclusion: Pure epidural spinal cavernous hemangioma is very rare, and it is very difficult to differentiate from other epidural lesions. However, we believe that it should be included in the differential diagnosis of spinal epidural tumors due to its favorable prognosis.

Petrological Study on Basaltic Rocks of the Daljeon-ri Columnar Joint and the Noeseongsan Noerok Site in Pohang, Korea (포항 달전리 주상절리와 뇌성산 뇌록산지의 현무암 비교 분석)

  • Kim, Jae hwan;Yu, Yeong-wan;Jung, Seung-Ho;Kim, Tae-Hyeong;Moon, Dong Hyeok;Kong, Dal-Yong
    • The Journal of the Petrological Society of Korea
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    • v.27 no.4
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    • pp.185-194
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    • 2018
  • The basaltic rocks of Daljeon-ri columnar joint (Natural Monuments # 415) and Noeseongsan Noerok site (Natural Monuments # 547) were analysed in order to understand basalt types of two areas. The basaltic rocks of the Pohang Daljeon-ri columnar joint show a typical porphyritic texture containing phenocrysts (olivine and clinopyroxene) and groundmasses composed of clinopyroxene, plagioclase, and opaque minerals,. In contrast, basaltic rocks of Noeseongsan Noerok are characterized by fine-grained groundmass with large phenocrysts of plagioclase. Other analysis such as magnetic susceptibility, X-ray diffraction and X-ray fluorescence also support the petrological differences of two basalt rocks. The Daljeon-ri basaltic rocks are plotted on phonotephrite volcanic rocks of alkaline series in TAS(total alkali silica), and on within plate basalt in Zr-Ti diagram. The Noeseongsan basalts, on the other hand, are plotted on basaltic andesite to andesite of sub-alkaline series in TAS, and on volcanic arc basalt in Zr-Ti diagram. These results indicate that the original mantle materials between two basalt rocks were different each other, which probably originated from the change of a tectonic setting in the southeastern Korean peninsula during the Miocene.

Diffusion Tensor-Derived Properties of Benign Oligemia, True "at Risk" Penumbra, and Infarct Core during the First Three Hours of Stroke Onset: A Rat Model

  • Chiu, Fang-Ying;Kuo, Duen-Pang;Chen, Yung-Chieh;Kao, Yu-Chieh;Chung, Hsiao-Wen;Chen, Cheng-Yu
    • Korean Journal of Radiology
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    • v.19 no.6
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    • pp.1161-1171
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    • 2018
  • Objective: The aim of this study was to investigate diffusion tensor (DT) imaging-derived properties of benign oligemia, true "at risk" penumbra (TP), and the infarct core (IC) during the first 3 hours of stroke onset. Materials and Methods: The study was approved by the local animal care and use committee. DT imaging data were obtained from 14 rats after permanent middle cerebral artery occlusion (pMCAO) using a 7T magnetic resonance scanner (Bruker) in room air. Relative cerebral blood flow and apparent diffusion coefficient (ADC) maps were generated to define oligemia, TP, IC, and normal tissue (NT) every 30 minutes up to 3 hours. Relative fractional anisotropy (rFA), pure anisotropy (rq), diffusion magnitude (rL), ADC (rADC), axial diffusivity (rAD), and radial diffusivity (rRD) values were derived by comparison with the contralateral normal brain. Results: The mean volume of oligemia was $24.7{\pm}14.1mm^3$, that of TP was $81.3{\pm}62.6mm^3$, and that of IC was $123.0{\pm}85.2mm^3$ at 30 minutes after pMCAO. rFA showed an initial paradoxical 10% increase in IC and TP, and declined afterward. The rq, rL, rADC, rAD, and rRD showed an initial discrepant decrease in IC (from -24% to -36%) as compared with TP (from -7% to -13%). Significant differences (p < 0.05) in metrics, except rFA, were found between tissue subtypes in the first 2.5 hours. The rq demonstrated the best overall performance in discriminating TP from IC (accuracy = 92.6%, area under curve = 0.93) and the optimal cutoff value was -33.90%. The metric values for oligemia and NT remained similar at all time points. Conclusion: Benign oligemia is small and remains microstructurally normal under pMCAO. TP and IC show a distinct evolution of DT-derived properties within the first 3 hours of stroke onset, and are thus potentially useful in predicting the fate of ischemic brain.