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Propylene Oxide를 이용한 졸-겔법에 의한 MO·Fe<sub>12</sub>O<sub>18</sub> (M/Ba, Sr) 나노 분말의 합성과 물리적 특성
이수진,최석범,곽형섭,백승욱,Lee, Su Jin,Choe, Seok Burm,Gwak, Hyung Sub,Paik, Seunguk 한국공업화학회 2006 공업화학 Vol.17 No.4
Propylene oxide (PPO)를 gelation agent로 한 졸-겔법으로 입자가 균일하고 자기적 특성이 우수한 $MO{\cdot}Fe_{12}O_{18}$ (M/Ba and Sr)의 구조식을 가지는 M-type hexagonal ferrite를 제조하였다. 본 방법으로 얻은 졸-겔용액은 매우 안정적인 분산상태를 보이며, $Fe^{3+}$의 겔화가 진행되고, 생성된 $Fe_2O_3$의 표면에서 $Ba^{2+}$ 또는 $Sr^{2+}$의 겔화가 진행되는 것으로 설명될 수 있어서, +3가 이하의 금속이라도 +3가 이상의 금속 존재 하에는 겔화가 가능한 것을 확인하였다. 또한, 기존 방법과 비교하여 값싼 원료를 사용하며, 반응 시간도 1 min 이내로 짧아지는 장점이 있다. 본 제조법으로 얻어진 분말은 기왕에 발표된 문헌 값과 비교하면 $150^{\circ}C$ 이상 낮은 열처리 온도에서 최고의 자기적 특성을 나타냈으며, 향상된 자기적 특성을 보였다. Sr-ferrite의 경우 최대포화자화 값 74.4 emu/g, 보자력 값 6198 Oe을, Ba-ferrite의 경우도 최대포화자화 값 68.1 emu/g, 보자력 값 5155 Oe을 보였다. 이들은 기존에 발표된 문헌 값과 비교하면 각각 10%와 5% 이상 증가된 보자력 값을 나타내어, 고밀도 자기기록재료에 적합함을 확인하였다. 제조된 분말은 1차 건조 분말의 경우 3~5 nm의 입자들이 응집된 50 nm 정도의 구형입자가 생성되고, 열처리 후에는 500 nm 정도의 고른 크기를 가진 육각판상형 입자가 생성된다. Nano sized mixed metal hexagonal ferrite powders with improved magnetic properties have been prepared by sol-gel method using propylene oxide as a gelation agent. To obtain the desired ferrite, two different metal ions were used. One of the ions has only +2 formal charge. The key step in the processes is that hydrated $Ba^{2+}$ or $Sr^{2+}$ ions are hydrolyzed and condensed at the surface of the previously formed $Fe_{2}O_{3}$ gel. In this processes, all the reaction can be finished within a few minutes. The magnetic properties of the produced powder were improved by heat treatment. The highest values of the magnetic properties were achieved at temperature $150^{\circ}C$ lower than those of the previously published values. The highest observed values of coercivity and the saturation magnetization of Sr-ferrite and Ba-ferrite powder were 6198 Oe, 5155 Oe and 74.4 emu/g, 68.1 emu/g, respectively. The ferrite powder annealed at $700^{\circ}C$ showed spherical particle shapes. The resulting spheres which were formed by the aggregation of nanoparticles with size 3~5 nm have diameter around 50 nm. The powder treated at $800^{\circ}C$ showed hexagonal-shaped grains with crystallite size above 500 nm.
Kim, Jong Woo,Kang, Won Sub,Lee, Sang Min,Kim, Su Kang,Park, Hae Jeong,Gwak, Geum-Hee,Baik, Hyung Hwan 대한독성유전단백체학회 2012 Molecular & cellular toxicology Vol.8 No.3
Extracellular matrix (ECM) abnormality is implicated in the pathogenesis of schizophrenia. Matrix metalloproteinases (MMPs) mediate the proteolysis of ECM and may play a crucial role in neuronal plasticity. We investigated whether single nucleotide polymorphisms (SNPs) of MMP1 and MMP8 are associated with the development of schizophrenia. We also assessed the relationships between MMP1, MMP8 SNPs and the core symptoms of schizophrenia such as persecutory delusion, auditory hallucinations, affective disturbances, and poor concentration according to the Operation Criteria Checklist for Psychotic Illness (OPCRIT). Three coding SNPs (rs470558, Ala216Ala in MMP1; rs3740938, Leu291Leu and rs1940475, Lys87Glu in MMP8) were selected, and 263 patients and 283 controls were evaluated. SNPStats was used to obtain the odds ratio (OR), 95% confidence intervals (CI), and P value adjusted for age and gender as covariables. Multiple logistic regression models (codominant1, codominant2, dominant, recessive, and log-additive) were employed to analyze genetic data. As a result, the three examined SNPs were not associated with the development of schizophrenia. In the analysis of clinical symptoms, the genotype frequency of rs470558 in MMP1 was associated with auditory hallucinations (P=0.04 in the codominant1 model, P=0.014 in the dominant1 model, and P=0.0066 in the log-additive model). The allele frequency of rs470558 also showed a significant difference between schizophrenia without auditory hallucinations [the auditory hallucination (-) group] and schizophrenia with auditory hallucinations [the auditory hallucination (+) group] (P=0.009, OR=1.94, 95% CI=1.19-3.28). The A allele frequency of rs470558 was higher in the auditory hallucination (+) group (19.2%) than that in the auditory hallucination (-) group (10.8%). Two MMP8 SNPs (rs3740938 and rs1940475) were not associated with the development and core symptoms of schizophrenia, respectively. These results suggest that the A allele of rs470558 (Ala216Ala) in MMP1 may contribute to the susceptibility to auditory hallucinations of schizophrenia.