• 한국결정성장학회지
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• 제7권1호
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• pp.151-162
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• 1997

Pivalic acid를 진공 증류 및 zone refining을 이용 고순도로 정제하여 온도 표준 기준 물질로의 개발 가능성을 시험하였다. melting plateau curve를 이용하여 99.9997% 순도의 pivalic acid cell들의 삼중점을 측정한 결과 $35.956\pm 0.003^{\circ}C$를 얻을 수 있었다. 이상의 정밀도를 갖는 pivalic acid 삼중점 cell들은 고정밀도를 요구하지 않는 일반 thermistor 온도계류의 보정용으로 충분히 사용 가능한 것으로 판단된다.

• 한국주조공학회지
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• 제31권4호
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• pp.191-197
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• 2011

Transparent organic materials have been frequently used as an analog of the solidifying metallic materials, because their transparency permits an in-situ observation of the microstructural development during solidification through optical microscopy. Pivalic acid (PVA)-ethanol system showing an anisotropic property in solid-liquid interfacial energy and interface kinetics was adopted in the present experiment, and the detailed experiments performed are as follows: (1) variation of dendrite tip temperature with growth velocity, (2) correlation between primary dendrite arm spacing (${\lambda}_1$) and the growth orientation away from the heat flow direction (tilt angle: ${\theta}$), (3) variation of dendrite tip radius (R) with growth velocity (V), (4) dendrite tip stability parameter (${\sigma}^*$) and its dependence on the concentration. Concerning the correlation between the dendrite tip temperature and growth velocity the present result is well suited to Hunt-Lu equation. As the tilt angle increases, the average primary dendrite spacing tends to increase.

• 대한화학회지
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• 제19권3호
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• pp.149-155
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• 1975

플라스틱 결정체인 피발산의 temperature-dependent wide-line NMR line width, second monent 및 spin-lattice relaxation times 의 결과는 이 결정체의 특이한 운동학적 성질 및 수소결합에 기인된 것으로 해석된다. 이 분자의 운동학적 성질은 $C_3-C_3'$ reorientation 및 self-diffusion 으로 구성 되었음을 확인했다. Wide-line NMR 연구결과는 또한 Pople-Karasz 융해설과 비교검토되었고, 이 이론과의 차이점은 피발산의 수소결합에 기인되었음을 알아냈다.

• 대한금속재료학회지
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• 제49권7호
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• pp.570-576
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• 2011

The shape of a dendrite tip has long been approximated by a paraboloid of revolution, but many attempts have been made as well to more accurately match the dendrite tip profile using other mathematical functions: power function, 4th order polynomial, and hyperbolic function. In the present work, dendrite tip shapes were matched by parabolic function. The differences between the dendrite tip shapes of pivalic acid(PVA)-ethanol(Eth) and succinonitrile(SCN)-salol systems, characterized by anisotropic and isotropic solid-liquid interfacial properties, respectively, were quantitatively treated using shape parameters. The PVA-Eth system showed a slightly higher Z/R value than the SCN-salol system, their Z/R values lying in the range 2-4. (Z is the distance from the tip beyond which the parabolic fit starts to deviate from the profile, and R the tip radius.) ${\lambda}_P$ is the distance from the tip beyond which side branching starts to appear, and is larger in the PVA-Eth system than the SCNsalol system. ${\lambda}_P$ is different for both sides of the 2-dimensional dendrite profile. The difference of ${\lambda}_P$ between both sides of the dendrite is larger for PVA-Eth system than for SCN-salol, implying that the dendrite of PVA-Eth is less symmetric than that of SCN-salol.

• 한국재료학회지
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• 제26권11호
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• pp.644-648
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• 2016

In order to examine how the solid-liquid interface responds to temperature variation depending on the materials characteristics, i.e. faceted phase or nonfaceted phase, the moving solid-liquid interface of transparent organic material, as a model substance for metallic materials (pivalic acid, camphene, salol, and camphor-50wt% naphthalene) was observed in-situ. Plots of the interface movement distance against time were obtained. The solid-liquid interface of the nonfaceted phase is atomically rough; it migrates in continuous mode, giving smooth curves of the distance-time plot. This is the case for pivalic acid and camphene. It was expected that the faceted phases would show different types of curves of the distance-time plot because of the atomically smooth solid-liquid interface. However, salol (faceted phase) shows a curve of the distance-time plot as smooth as that of the nonfaceted phases. This indicates that the solid-liquid interface of salol migrates as continuously as that of the nonfaceted phases. This is in contrast with the case of naphthalene, one of the faceted phases, for which the solid-liquid interface migrates in "stop and go" mode, giving a stepwise curve of the distance-time plot.

• 대한유전성대사질환학회지
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• 제16권2호
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• pp.57-61
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• 2016

IVA는 상염색체 열성의 유전방식을 보이는 leucine 대사 장애 질환이자 대표적인 유기산 혈증이다. IVD 유전자의 돌연변이에 의한 isovaleryl-CoA dehydrogenase 효소의 결핍이 질환 발생의 원인이다. Isovaleryl-CoA dehydrogenase 효소가 결핍되면 isovaleryl-CoA의 대사물질이 비정상적으로 체내에 축적되어 대사성 산증 및 고암모니아혈증 등의 급성 대사성 위기와 발달지연, 성장지연, 및 경련성질환 등의 만성 합병증을 초래할 수 있기 때문에, 급성 대사성 위기 및 만성합병증의 발생을 예방하기 위해 조기 진단에 따른 적절한 치료의 도입이 중요하다. 현재 IVA은 국내에서 시행되는 탠덤 매스 스크리닝법을 이용한 신생아 대사질환 선별검사 항목에 포함되어 있으며, C5의 상승으로 의심할 수 있다. 그러나 SBCAD 결핍증 혹은 pivalic acid 유래물이 포함된 항생제를 투여한 경우에도 C5의 상승이 동반될 수 있기 때문에, 감별진단 및 확진을 위한 추가적인 생화학적, 유전학적 검사가 필수적이다.

• 한국분말재료학회지
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• 제25권4호
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• pp.336-339
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• 2018

A unique porous material with controlled pore characteristics can be fabricated by the freeze-drying process, which uses the slurry of organic material as the sublimable vehicle mixed with powders. The essential feature in this process is that during the solidification of the slurry, the dendrites of the organic material should repel the dispersed particles into the interdendritic region. In the present work, a model experiment is attempted using some transparent organic materials mixed with glass powders, which enable in-situ observation. The organic materials used are camphor-naphthalene mixture (hypo- and hypereutectic composition), salol, camphene, and pivalic acid. Among these materials, the constituent phases in camphor-naphthalene system, i.e. naphthalene plate, camphor dendrite, and camphor-naphthalene eutectic exclusively repel the glass powders. This result suggests that the control of organic material composition in the binary system is useful for producing a porous body with the required pore structure.