• 소성∙가공
• /
• 제15권8호
• /
• pp.597-602
• /
• 2006

Bulk plastic forming characteristics were studied for the magnesium alloy, AZ31 in warm backward extrusion. Effects of process conditions such as extrusion ratio, forming temperature, and punching speed were investigated respectively. Variation of microstructure induced by the warm backward extrusion process was observed. Microstructure of the work piece showed evidences of recrystallization under the experiment conditions. It is estimated that in specific punch speed region fast stroke accelerates recrystllization and reduces the forming load.

• 한국식품영양과학회지
• /
• 제19권1호
• /
• pp.61-64
• /
• 1990

The influence of extraction time on the fatty acid profile and the contents of calcium and magnesium in pig's shank were examined. The 9 kinds of fatty acid were identified in water extracts from pig's shank by GLC. The profiles of fatty acids from different extraction were similer to each other,. The content of linolenic acid was increased after two-hours extraction however the amounts of MUFA, PUFA and p/s ratio were decreased by the longer extraction time. The amount of calcium was 124.7mg% in raw materials but water extracts and bone powder samples showed higher values. in case of magnesium it was 138.4mg% in raw materials, but the extracts showed lower amount and bone powder exhibited higher values.

• 한국세라믹학회지
• /
• 제34권6호
• /
• pp.659-667
• /
• 1997

The effect of calcination temperature of Mg(OH)2 on the green density and densification of MgO was investigated. It was observed that the impure magnesium hydroxide powder showed a higher crystallization rate while it had a lower tendency of agglomeration between periclae crystallites, as compared to that of the pure magnesium hydroxide powder. In the case of calcination of the powders under 85$0^{\circ}C$, the impure powder showed the higher green and sintered density. In spite of higher green density upon the calcination over 100$0^{\circ}C$, the impure powder showed the lower sintered density, caused by exaggerated growth of the periclase crystallites. The highest sintered densities in the both powders were obtained at the calcination temperature of 100$0^{\circ}C$. And the green density was inversely proportional to the sintered density at the calcination over 100$0^{\circ}C$.

• Journal of Microbiology
• /
• 제33권2호
• /
• pp.160-164
• /
• 1995

The splicing activity of T4 phage td intron RNA has been examined with various Mg$^{2+}$ ions such as MGCl$_{2}$, MgS $O_{4}$ and magnesium acetate using various splicing conditions such as different incubation time and temperature. The maximum splicing of td intron RNA occurred at the concentration of 5 mM MgCl$_{2}$. Raising the Mg$^{2+}$ concentration up to 15 mM appeared to promote P2 delection mutant to overcome the loss of some splicing activity. In both wild type and mutant, a complete hydrolysis of RNA occurred at 30 mM MgCI$_{2}$ MgS $O_{4}$ and magnesium acetate exhibited the rate and pattern of RNA splicing identical to MGCI$_{2}$. The optimal splicing conditions involve the incubation of RNA with 5 mM MgCI$_{2}$ at 58 .deg.C for 15 min. The results suggest that Mg$^{2+}$ may play a key role in the catalytic mechanism of td intron RNA.n RNA.

• Bulletin of the Korean Chemical Society
• /
• 제10권4호
• /
• pp.349-352
• /
• 1989

Two Crystal structures of fully dehydrated partially magnesium exchanged zeolite A, stoichiometries of $Mg_{2.5}Na_7-A$ (a = 12.251 (1) ${\AA}$) and $Mg_{1.5}Na_9-A\; (a\;=\;12.214(1)\;{\AA})$ per unit cell, have been determined from the 3-dimensional X-ray diffraction data gathered by counter methods. All structures were solved and refined in the cubic space group Pm3m at 21(1)$^{\circ}C$. The structures of the dehydrated $Mg_{2.5}Na_7-A$ and $Mg_{1.5}Na_9-A$ were refined to yield the final error indices $R_1$ = 0.042 and $R_2$ = 0.049 with 318 reflections, and $R_1$ = 0.034 and $R_2$ = 0.032 with 252 reflections, respectively, for which I > $3{\sigma}(I)$. Both structures indicate that $Mg^{2+}$ ions are coordinated by three framework oxygens and the angle substended at $Mg^{2+}$ ions, O(3)-Mg(1)-O(3) is ca. $120^{\circ}$, close to the idealized trigonal planar value. $Mg^{2+}$ ions preferentially occupy 6-ring sites and $Na^+$ ions occupy 8-ring sites when total number of cations per unit cell is more than 8.

• 광물과 암석
• /
• 제34권2호
• /
• pp.121-131
• /
• 2021

마그네슘(magnesium; Mg)은 탄산염 광물이 침전된 과거의 환경 조건을 유추하기 위한 지화학 지시자로 활용되어오고 있다. Mg를 신뢰도 높은 지화학 지시자로 활용하기 위해서는 Mg의 화학종을 근거로 한 Mg의 광물 함유 기작이 반드시 규명되어야만 하며, 관련 실험 연구들은 주로 고해상도(high resolution)의 방사광가속기(synchrotron) X-선 흡수 분광(X-ray absorption spectroscopy; XAS) 기법을 통해 Mg의 화학종을 유추한다. 그러나, Mg가 미량 함유된 광물의 XAS 스펙트럼 해석의 높은 불확실성 때문에 화학종 유추가 어려운 경우가 많다. 양자역학 밀도범함수이론(density functional theory; DFT)은 결정구조에 대한 흡수 스펙트럼을 예측할 수 있기 때문에, XAS 스펙트럼 해석의 불확실성을 줄일 수 있다. 이번 논문에서는 DFT 기반의 제일원리 내각 준위 분광법(ab initio core-level spectroscopy method)을 통해 Mg 규산염 및 (수)산화광물에 대한 Mg K-edge 흡수 스펙트럼을 계산하여 Mg의 배위 결합 환경을 나타내는 구조 인자와의 상관관계를 분석하였다. 계산 결과, DFT 계산으로 얻은 Mg 규산염 및 (수)산화물의 이론 Mg K-edge 흡수 스펙트럼은 기존 XAS 실험으로 얻어진 스펙트럼의 주요 형태를 상당 부분 재현해낼 수 있었다. 계산으로 얻은 광물의 제일원리 Mg K-edge 흡수 스펙트럼의 흡수-끝(absorption edge)과 평균 Mg-O 결합거리 및 Mg 유효배위수를 비교 분석한 결과, 약한 양의 상관관계를 보여주었다. 이번 연구 결과는 DFT 계산이 다양한 광물 내 Mg의 화학종에 대한 표준 스펙트럼 세트를 제공할 수 있는 강력한 도구임을 보여주며, 추후 탄산염 광물에 함유된 정확한 Mg의 화학종을 동정하는데 DFT 계산이 큰 역할을 할 수 있음을 제시한다.

• International journal of advanced smart convergence
• /
• 제8권4호
• /
• pp.26-33
• /
• 2019

We conducted research to evaluate economically and engineering about the synthesis of Magnesium Oxide, MgO, nanoparticles using physicochemical methods. The method used was economic evaluation by calculating GPM, BEP, PBP, and CNPV. The other method used was engineering perspective. MgO nanoparticles were synthesized by reacting Mg(NO₃)₂ and NaOH with a mole ratio 1: 2. Mg(OH)₂ formed was heated and calcined to remove water content and to oxidation to form MgO. An economic evaluation by calculating GPM and CNPV for the production of MgO nanoparticles on an industrial scale shows that the payback period (PBP) occur in the third year and profits increase each year. Tax variations show that the higher of tax, the lower profits received. When there was an increase of selling prices, the profit was greater. The variable cost used is the price of raw material. When there was an increased in the variable cost price, the payback period was longer and the profits was reduced. The benefit of this research is knowing the industrial production of MgO nanoparticles is beneficial. The function of MgO nanoparticles is a material for the manufacture of ceramics and can be used as an antimicrobial in the water filtration process.

• 한국주조공학회지
• /
• 제29권4호
• /
• pp.176-180
• /
• 2009

Effect of matrix microstructure on creep behaviors of squeeze cast magnesium matrix composites was investigated. Aluminum borate whisker was used as reinforcement and AZ31, AS52 and Sr added AS52 Mg alloys were used for matrix alloys. The reinforcement was distributed homogeneously and defect-free composite was manufactured. Creep tests were carried out at the temperature of $150^{\circ}C$ under the applied stress of 50 and 100 MPa for Mg alloys and Mg MMCs, respectively. The creep resistance of Mg MMCs was in this order: AS52-Sr > AS52 AZ31 MMCs. Void initiation during creep mainly occurred at $Mg/Mg_{17}Al_{12}$ interface and propagation went along grain boundaries. On the other hand, $Mg_2Si$ phase was not attributed to the creep void initiation.

• Journal of Microbiology and Biotechnology
• /
• 제24권1호
• /
• pp.36-43
• /
• 2014

Magnesium-protoporphyrin IX (Mg-PPn), which is formed through chelation of protoporphyrin IX (PPn) with Mg ion by Mg chelatase, is the first intermediate for the (bacterio)chlorophyll biosynthetic pathway. Interestingly, Mg-PPn provides peroxidase activity (approximately $4{\times}10^{-2}units/{\mu}M$) detoxifying $H_2O_2$ in the presence of electron donor(s). The peroxidase activity was not detected unless PPn was chelated with Mg ion. Mg-PPn was found freely diffusible through the membrane of Escherichia coli and Vibrio vulnificus, protecting the cells from $H_2O_2$. Furthermore, unlike photosensitizers such as tetracycline and PPn, Mg-PPn did not show any phototoxicity, but rather it protected cell from ultraviolet (UV)-A-induced stress. Thus, the exogenous Mg-PPn could be used as an antioxidant and a UV block to protect cells from $H_2O_2$ stress and UV-induced damage.

• Journal of Chest Surgery
• /
• 제31권4호
• /
• pp.339-345
• /
• 1998

부정맥은 심장수술 후 자주 발생하며 여러 인자가 요인이 되고 있다. 마그네슘의 정맥주사는 증상이 있는 심부전 환자나 급성 심근경색 환자에 있어서 심실 부정맥의 빈도를 줄여준다는 보고가 있다. 이 연구는 관상동맥 우회술 후 흔하게 발생하는 미숙 심실수축을 예방하는데 있어 마그네슘의 역할을 평가해 보고자 고안하였다. 50 명의 연속된 환자를 전향적으로 무작위로 정규 관상동맥 우회술 후 심 부정맥의 발생에 대한 술후 마그네슘 치료의 효과를 알아보고자 하였다. 모든 환자는 술전에 관상동맥 조영술, 심초음파, 심전도, 기타 임상병리 검사를 시행하였으며, 술후에는 계속적인 심전도 관찰과 마그네슘의 농도를 술직후, 술후 3시간, 6시간, 12시간, 18시간, 24시간, 36시간, 48시간, 60시간, 72시간에 각각 측정하였다. 25명의 연구군 환자들은 술후 첫 24시간 동안 4그램의 마그네슘을 계속적으로 투여받은 후 그 다음 24시간에는 2그램의 마그네슘을 72시간까지 투여받았다. 두 군 간의 임상특성은 비슷하였고(p<0.05) 술전 평균 혈청 마그네슘의 농도는 연구군에서 1.59 mg/dl, 대조군에서 1.71 mg/dl로 비슷하였다(p<0.05). 연구군에서 술후 평균 혈청 마그네슘의 농도가 술전의 농도와 비교해 보아 술후 12시간에서 36시간까지 의미있게 상승되었다(p<0.05). 대조군에서는 술후 평균 혈청 마그네슘의 농도가 술직후 감소한 상태로 72시간까지 일정한 상태를 유지하고 있었다. 대조군과 비교하여 연구군에서 평균 혈청 마그네슘의 농도가 술후 3시간에서 72시간까지 의미있게 높게 유지하고 있었다(p<0.05). 연구군에 있어서 마그네슘의 투여로 혈역학에 악영향을 끼치는 미숙 심실 수축과 같은 부정맥의 발생이 대조군에 비하여 감소하였다(p<0.01). 연구 기간동안 마그네슘 투여로 인한 부작용은 나타나지 않았다. 결론적으로 마그네슘의 예방적 투여는 관상 동맥우회술 후 부정맥의 발생과 심한 정도를 경감시킨다.