• 제목/요약/키워드: quantum phase

검색결과 185건 처리시간 0.029초

Chromite 물질의 자기상호작용에 관한 뫼스바우어 분광연구 (Mössbauer Studies of Changed Interaction on Cr Ions in Chromite)

  • 최강룡;김철성
    • 한국자기학회지
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    • 제17권1호
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    • pp.47-50
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    • 2007
  • 최근 geometrical frustration 현상 및 멀티페로익 효과가 Cr 이온의 나선 스핀 구조에 기인하는 것으로 해석되고 있다. 이에 본 연구에서는 Cr 이온 자리에 Fe을 치환하여 $CoCrFeO_4$를 제조하였고, $M\"{o}ssbauer$ 분광법에 의해 자기적 미세 구조의 상관관계를 연구하였다. 졸겔법을 이용하여 Fd3m의 cubic 스피넬 구조를 갖는 $CoCr_2O_4,\;CoCrFeO_4$ 단일상을 합성하였고, Rietveld 법에 의한 분석결과 격자상수는 $a_0=8.340$에서 $8.377{\AA}$로 증가 하였으며, Cr, Fe 이온은 모두 팔면체 구조에 위치하는 것으로 분석되었다. 자기 상전이 온도는 $T_N=97K$에서 320 K로 증가하였으며, 상호작용의 변화에 따라서 field cooled 온도에 따른 자화 곡선의 변화를 관측하였다. $M\"{o}ssbauer$ 스펙트럼 분석결과 4.2 K에서 공명흡수선에 대한 초미세자기장($H_{hf}$) 값은 각각 507, 492 kOe 정도로 나타났으며, 이성질체 이동치($\delta$)는 0.33, 0.34 mm/s 정도로 Fe 이온상태가 둘 다 +3 가의 이온상태임을 알 수 있었다.

키토산이 피복된 나노 크기의 자성체 분말 제조 (Preparation of Chitosan-coated Magnetite Nanoparticles)

  • 조준희;고상길;안양규;송기창;최은정
    • 한국자기학회지
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    • 제16권1호
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    • pp.102-106
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    • 2006
  • 이 연구의 목적은 약물의 분리나 약물전달 시스템에 이용 할 수 있도록 마그네타이트 나노 입자의 표면을 개질, 즉 생체적합성, 저독성의 특성을 갖는 키토산을 이용하여 키토산이 피복된 나노 크기의 자성체 입자를 제조하는 것이다. 본 연구에서는 음향화학법을 적용한 공침 기술을 이용, 균일한 마그네타이트 나노 입자를 합성하였다. 계면활성제인 올레인산을 가하여 입자간의 응집을 막았다. 물과 계면활성제의 농도비 R=[물]/[계면활성제]를 조절하여 평균크기가 2nm에서 9nm인 마그네타이트 입자를 선택적으로 합성하였다. 이 방법을 통하여 합성된 마그네타이트 나노 인자를 염기성 수용액에 분산시켰다. 초음파를 조사하면서 키토산 용액을 서서히 가하여 마그네타이트 나노 입자의 표면을 키토산으로 피복하였다. 이때 키토산의 농도가 증가할수록 입자가 수 나노미터 크기씩 증가하는 것을 입도 분석기와 원자 현미경 관찰을 통해서 확인 할 수 있었다. 합성된 마그네타이트 분말과 키토산이 피복된 마그네타이트 나노 입자 모두 실온에서 초상자성을 보이는 것으로 나타났다.

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.
    • 한국진공학회:학술대회논문집
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    • 한국진공학회 2009년도 제38회 동계학술대회 초록집
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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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Energy utilization, nutrient digestibility and bone quality of broiler chickens fed Tanzania-type diets in different forms with enzymes

  • Chang'a, Edwin Peter;Abdallh, Medani Eldow;Ahiwe, Emmanuel Uchenna;Al-Qahtani, Mohammed;Mbaga, Said;Iji, Paul Ade
    • Journal of Animal Science and Technology
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    • 제61권4호
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    • pp.192-203
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    • 2019
  • A study was conducted to determine the influence of feed form and microbial enzyme supplementation on energy utilization, bone quality, and amino acid and mineral digestibility of broiler chickens. Four hundred and eighty Ross 308, day-old broiler chickens were randomly assigned to eight diets formulated from commonly used ingredients in Tanzania. A 2 (pellet or mash) ${\times}$ 4 (control, Axtra XB, Quantum Blue (QB) and Axtra XB + QB enzyme) factorial array in a completely randomized design having six replicates per treatment (10 birds per replicate) was used. Birds were raised in climate-controlled rooms in a 3-phase; starter (0-10 days), grower (11-24 days) and finisher (25-35 days). Apparent metabolizable energy (AME), metabolizable energy intake, net energy of production, energy retained as protein (REp), and efficiency of metabolizable energy use for energy and protein retention were higher (p < 0.05) in birds fed pelleted diets. The AME and REp was higher (p < 0.05) with enzyme supplementation. Ash content, weight, length, width and breaking strength of tibia bones were highest (p < 0.05) in birds on pelleted diets. Tibia bone traits were improved (p < 0.05) when enzymes were included, particularly in a combination of QB and Axtra XB. However, potassium, magnesium, and zinc contents were highest (p < 0.05) when QB was supplemented. Digestibility of all amino acids was higher (p < 0.05) in birds supplied with pellets and with enzyme supplementation for most amino acids, except for serine. There was a positive interaction (p < 0.05) between feed form and enzymes on lysine and phenylalanine digestibility. Digestibility of Ca, P, K, S, Zn, and Fe was higher (p < 0.05) in birds fed pelleted diets, while those on mashed diets had higher (p < 0.05) digestibility of Cu and B. The digestibility of P, K, and Zn was highest (p < 0.001) when QB was added, while Ca, P, S, and B digestibility was highest when a combination of Axtra XB + QB was applied. Pelleted diets with or without enzymes improved energy utilization, digestibility of amino acids, and minerals, and increased bone strength in broiler chickens.

자기공명분석기를 이용한 통증관리 (Clinical Study of Acute and Chronic Pain by the Application of Magnetic Resonance Analyser $I_{TM}$)

  • 박욱;진희철;조명현;윤석준;이진승;이정석;최석환;김성열
    • The Korean Journal of Pain
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    • 제6권2호
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    • pp.192-198
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    • 1993
  • In 1984, a magnetic resonance spectrometer(magnetic resonance analyser, MRA $I_{TM}$) was developed by Sigrid Lipsett and Ronald J. Weinstock in the USA, Biomedical applications of the spectrometer have been examined by Dr. Hoang Van Duc(pathologist, USC), and Nakamura, et al(Japan). From their theoretical views, the biophysical functions of this machine are to analyse and synthesize a healthy tissue and organ resonance pattern, and to detect and correct an abnormal tissue and organ resonance pattern. All of the above functions are based on Quantum physics. The healthy tissue and organ resonance patterns are predetermined as standard magnetic resonance patterns by digitizing values based on peak resonance emissions(response levels or high pitched echo-sounds amplified via human body). In clinical practice, a counter or neutralizing resonance pattern calculated by the spectrometer can correct a phase-shifted resonance pattern(response levels or low pitched echo-sounds) of a diseased tissue and organ. By administering the counter resonance pattern into the site of pain and trigger point, it is possible to readjust the phase-shifted resonance pattern and then to alleviate pain through regulation of the neurotransmitter function of the nervous system. For assessing clinical effectiveness of pain relief with MRA $I_{TM}$ this study was designed to estimate pain intensity by the patient's subjective verbal rating scale(VRS such as graded to no pain, mild, moderate and severe) before application of it, to evaluate an amount of pain relief as applied the spectrometer by the patients subjective pain relief scale(visual analogue scale, VAS, 0~100%), and then to observe a continuation of pain relief following its application for managing acute and chronic pain in the 102 patients during an 8 months period beginning March, 1993. An application time of the spectrometer ranged from 15 to 30 minutes daily in each patient at or near the site of pain and trigger point when the patient wanted to be treated. The subjects consisted of 54 males and 48 females, with the age distribution between 23~40 years in 29 cases, 41~60 years in 48 cases and 61~76 years in 25 cases respectively(Table 1). The kinds of diagnosis and the main site of pain, the duration of pain before the application, and the frequency of it's application were recorded on the Table 2, 3 and 4. A distinction between acute and chronic pain was defined according to both of the pain intervals lasting within and over 3 months. The results of application of the spectrometer were noted as follows; In 51 cases of acute pain before the application, the pain intensities were rated mild in 10 cases, moderate in 15 cases and severe in 26 cases. The amounts of pain relief were noted as between 30~50% in 9 cases, 51~70% in 13 cases and 71~95% in 29 cases. The continuation of pain relief appeared between 6~24 hours in two cases, 2~5 days in 10 cases, 6~14 days in 4 cases, 15 days in one case, and completely relived of pain in 34 cases(Table 5~7). In 51 cases of chronic pain before the application, the pain intensities were rated mild in 12 cases, moderate in l8 cases and severe in 21 cases. The amounts of pain relief were noted as between 0~50% in 10 cases, 51~70% in 27 cases and 71~90% in 14 cases. The continuation of pain relief appeared to have no effect in two cases. The level of effective duration was between 6~12 hours in two cases, 2~5 days in 11 cases, 6~14 days in 14 cases, 15~60 days in 9 cases and in 13 cases the patient was completely relieved of pain(Table 5~7). There were no complications in the patients except a mild reddening and tingling sensation of skin while applying the spectrometer. Total amounts of pain relief in all of the subjects were accounted as poor and fair in 19(18.6%) cases, good in 40(39.2%) cases and excellent in 43(42.2%) cases. The clinical effectiveness of MRA $I_{TM}$ showed variable distributions from no improvements to complete relief of pain by the patient's assessment. In conclusion, we suggest that MRA $I_{TM}$ may be successful in immediate and continued pain relief but still requires several treatments for continued relief and may be gradually effective in pain relief while being applied repeatedly.

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