모형 담즙과 담낭 답즙에서 콜레스테롤 핵형성 촉진 인자로서의 Phospholipase C 의 역할

김정룡(Chung Yong Kim),김용태(Yong Tae Kim),윤용범(Yong Bum Yoon) 대한내과학회 1995 대한내과학회지 Vol.49 No.1

Objectives: There are a number of proteins that may influence cholesterol nucleation in bile, Recently, phospholipase C has been suggested as a nucleation-promoting factor in human gallbladder(GB) bile. However, it is not known whether there is a quantitative difference in phospholipase and normal controls, and whether suppression of phospholipase C in human GB bile might alter the nucleation time. So we tried to investigate the role of phospholipase C as a cholesteol nucleation-promoting factor in model bile and in human GB bile. Methods: To determine if phospholipase C has a capacity to promote nucleation of cholesterol in model bile, nucleation times were compared among model biles which were mixed with serially diluted phospholipase C(0, 10, 100, 1,000, 10,000, 100,000 U /L). To investigate if phospholipase C is a main promoting factor of cholesterol nucleation in human GB bile, nucleation times and phospholipase C activities in GB bile were compared among patients with cholesterol gallstones(n=12), pigment gallstones(n=12), and controls(n=7). The influence of suppression of phospholipase C by EDTA(2 mM) on the nucleation time in GB biles of patients with cholesterol gallstones was also studied. Phospholipese C activity was measured by the release of phosphoryl [H3] choline from the substrate 3H-phosphatidylcholine after delipidation by gel chromatography. Results: Phospholipase C decreased the nucleation time of model bile in a dose dependent way from more than 21 days to 5 days, but the activity in human GB bile was elevated more than that of the controls in only 17% of patients with cholesterol gallstones. Suppression of phospholipase C activity by EDTA did not prolong the nucleation time of the GB bile of the patients with cholesterol gallstones. Conclns1on: Phospholipase C has a capacity to decrease the nucleation time in model bile but it does not play a significant role in cholesterol gallstone formation in human GB bile.

Non-reciprocal Heterogeneous Nucleation in Solidification of Ag–Cu Alloys

Qingyuan Qin,Zhao Zhang,Lin Yang,Jinfu Li 대한금속·재료학회 2024 METALS AND MATERIALS International Vol.30 No.5

Taking Ag-27 at% Cu hypoeutectic and Ag-67 at% Cu hypereutectic alloys as examples, a theoretical criterion was establishedbased on the classical nucleation theory to predict the non-reciprocal nucleation. For a eutectic alloy composed of αand β solid phases, non-reciprocal nucleation will not occur if the critical nucleation work of one phase on the other phaseis approximately equal to that of the latter on the former. Otherwise, one phase can act as the more effective nucleationsubstrate for the other phase and non-reciprocal nucleation takes place. For Ag–Cu alloys, the wetting angle of β-Cu onα-Ag is larger than that of α-Ag on β-Cu, but the critical nucleation work for β-Cu to heterogeneously nucleate on α-Ag inhypoeutectic alloys is obviously smaller than that for α-Ag on β-Cu in hypereutectic Ag–Cu alloys. Thus, α-Ag phase is abetter nucleant for β-Cu phase than vice versa and the Ag–Cu alloys solidify with non-reciprocal nucleation, reflected byonly a halo of α-Ag around primary β-Cu phase in the hypereutectic Ag–Cu alloy.

Bias process for heteroepitaxial diamond nucleation on Ir substrates

Wang Weihua,Yang Shilin,Liu Benjian,Hao Xiaobin,Han Jiecai,Dai Bing,Zhu Jiaqi 한국탄소학회 2023 Carbon Letters Vol.33 No.2

Heteroepitaxy is a better method of enlarging SCD wafer size than homoepitaxy. In this work, several aspects of the bias process for heteroepitaxial diamond nucleation are studied experimentally. First, with increasing bias time, the diamond-nucleation pathway is found to transform from “isolated-crystal nucleation” to “typical domain-nucleation” and back to “isolated-crystal nucleation.” An interdependent relationship between bias voltage and bias time is proposed: the higher the bias voltage, the shorter the bias time. Second, a correlation exists between the threshold bias voltage and reactor-chamber pressure: a higher reactor chamber pressure usually requires a higher threshold bias voltage to realize “typical domain nucleation.” Third, diamond bias-enhanced nucleation and growth is observed at a high CH4 content, where the dynamic equilibrium between amorphous-carbon-layer deposition and atomic-hydrogen etching is broken. Finally, epitaxial nucleation is obtained on a substrate with ∅30 mm in a home-made MPCVD setup.

Tuning sodium nucleation and stripping by the mixed surface of carbon nanotube-sodium composite electrodes for improved reversibility

Kim, Yun-Jung,Lee, Jinhong,Yuk, Seongmin,Noh, Hyungjun,Chu, Hyunwon,Kwack, Hobeom,Kim, Seokwoo,Ryou, Myung-Hyun,Kim, Hee-Tak Elsevier 2019 Journal of Power Sources Vol.438 No.-

<P><B>Abstract</B></P> <P>Metallic sodium is regarded as a promising anode material for sodium rechargeable batteries. However, sodium dendrite growth and exhaustive electrolyte decomposition cause the poor reversibility of the sodium metal electrode. Here, we present that, by forming a mixed surface of carbon and sodium metal, the sodium electrodeposition mode and stripping mechanism can be tuned. In order to systematically investigate sodium plating/stripping behavior on a mixed surface of carbon and sodium, we fabricate a carbon nanotube-sodium composite electrode with a simple rolling and folding method. As the carbon nanotube content is increased, the overpotentials for sodium nucleation and pit-formation are remarkably reduced. Postmortem and chronoamperometry analysis elucidate that sodium and sodiated carbon nanotube have a different sodium nucleation mode, and sodium nucleation is preferred on the sodiated carbon nanotube surface with lower nucleation energy, inducing a more uniform sodium deposition. Furthermore, the embedded carbon nanotube appears to help sodium stripping by providing a channel for a more facile sodium ion transport. As a result, the carbon nanotube-sodium composite electrode exhibites a 5 times higher cycling stability. The tuning of the nucleation and stripping behaviors by forming a mixed surface can be a viable approach for enhancing the reversibility of metal electrode.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Carbon nanotube(CNT) is introduced to Na metal anode by a rolling and folding method. </LI> <LI> Electrically conductive CNT network induces more uniform and dense Na nucleation. </LI> <LI> Embedded CNT helps Na stripping by providing a facile channels for Na ion transport. </LI> <LI> CNT-Na composite electrode exhibits a 5-times improved cycling stability. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Factors Affecting Nucleation and Growth of Chromium Electrodeposited from Cr³⁺ Electrolytes Based on Deep Eutectic Solvents

El-Hallag, Ibrahim S.,Moharram, Youssef I.,Darweesh, Mona A.,Tartour, Ahmed R. The Korean Electrochemical Society 2020 Journal of electrochemical science and technology Vol.11 No.3

Chromium was electrodeposited from deep eutectic solvents-based Cr³⁺ electrolytes on HB-pencil graphite electrode. Factors influencing the electrochemical behavior and the processes of Cr nucleation and growth were explored using cyclic voltammetry and chronoamperometry techniques, respectively. Cr³⁺ reduction was found to occur through an irreversible diffusion-controlled step followed by another irreversible one of impure diffusional behaviour. The reduction behavior was found to be greatly affected by Cr³⁺ concentration, temperature, and type of hydrogen bond donor used in deep eutectic solvents (DESs) preparation. A more comprehensive model was suggested and successfully applied to extract a consistent data relevant to Cr nucleation kinetics from the experimental current density transients. The potential, the temperature, and the hydrogen bond donor type were estimated to be critical factors controlling Cr nucleation. The nucleation and growth processes of Cr from either choline chloride/ethylene glycol (EG-DES) or choline chloride/urea (U-DES) deep eutectic solvents were evaluated at 70℃ to be three-dimensional (3D) instantaneous and diffusion-controlled, respectively. However, the kinetics of Cr nucleation from EG-DES was found to be faster than that from U-DES. Cr nucleation was tending to be instantaneous at higher temperature, potential, and Cr³⁺ concentration. Cr nuclei electrodeposited from EG-DES were characterized at different conditions using scanning electron microscope (SEM). SEM images show that high number density of fine spherical nuclei of almost same sizes was nearly obtained at higher temperature and more negative potential. Energy dispersive spectroscopy (EDS) analysis confirms that Cr deposits were obtained.

2D–3D nucleation and growth of palladium on graphite electrode

Iman Danaee 한국공업화학회 2013 Journal of Industrial and Engineering Chemistry Vol.19 No.3

Nucleation and growth of palladium on graphite electrode was studied by electrochemical techniques. Crossovers in cyclic voltammograms demonstrate that the deposition of palladium proceed via a nucleation/growth mechanism. In the early stage of the deposition, two-dimensional (2D–3D)nucleation and growth proceeding through instantaneous and a multitude of progressive steps followed the initial double layer charging. Non-linear fitting methods were applied to obtain the kinetic parameters in the light of Bewick, Fleischmann, and Thirsk theory for 2D and Armstrong, Fleischmann,and Thirsk model for 3D nucleation and growth process.

Inhomogeneous Nucleation and Domain Wall Motion with Barkhausen Avalanches in Epitaxial PbZr0.4Ti0.6O3 Thin Films

양상모,Hun-Ho Kim,김태헌,Ik Joo Kim,윤종걸 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.2

We investigated the ferroelectric (FE) domain nucleation and domain wall motion in epitaxial PbZr0.4Ti0.6O3 capacitors by using modified piezoresponse force microscopy with the domaintracing method. From time-dependent FE domain evolution images, we observed that defectmediated inhomogeneous nucleation occurred with a stochastic nature. In addition, we found that the number of nuclei N(t) was linearly proportional to log t, where t is the accumulated time of the applied pulse fields. The time-dependence of N(t) suggests a distribution of energy barriers for nucleation, which may determine the stochastic nature of domain nucleation. We also observed that the domain grew with consecutive Barkhausen avalanches and that the growth direction became anisotropic when the domain radius was larger than a critical radius of about 100 nm.

Homogeneous and Heterogeneous Nucleation Simulation by Molecular Dynamics on Parallel Computers

Donguk Suh(서동욱),Woong-sup Yoon(윤웅섭),Masahiko Shibahara(시바하라 마사히코) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10

Molecular dynamics (MD) on parallel computers was used to investigate homogeneous and heterogeneous nucleation. The behavior of Lennard-Jones (LJ) molecules were studied inside a system where all dimensions of the wall were periodic and a carrier gas within the system controlled the temperature. The results with and without a seed particle were compared subject to various thermodynamic conditions. Moreover, the effects of the number of the seeds were also studied. We confirmed that even when the supersaturation ratio is inadequate for homogeneous nucleation, in some conditions, once a seed is introduced to the system, a cluster is formed. Furthermore, the addition of seeds not only enhances nucleation but renders coagulation as an important nucleation mechanism.

Acoustic Effect on Induction of Cerium Carbonate in Reaction Crystallization

He, Xin-Kuai,Kim, Rayoung,Shin, Dongmin,Kim, Woo-Sik The Society of Chemical Engineers, Japan 2012 Journal of chemical engineering of Japan Vol.45 No.4

<P>The influence of ultrasonication and agitation on the induction of nucleation in the reaction crystallization of cerium carbonate has been investigated in a semi-batch crystallizer. When the cerium chloride and sodium carbonate reactants are constantly injected, the induction time depends significantly on ultrasonication and agitation. Due to the acoustic cavitation of ultrasonication promoting micromixing of the reactants, the induction time of cerium carbonate is markedly reduced. Simultaneously, the acoustic cavitation appears to reduce the energy barrier of nucleation, inducing nucleation at a lower supersaturation level than with the turbulent fluid motion of agitation. However, the acoustic stream of ultrasonication does not promote the induction of nucleation. Meanwhile, agitation also facilitates the induction of nucleation due to turbulent mixing of the reactants. The micromixing resulting from agitation meant the supersaturation in the solution increases rapidly when increasing the agitation speed, thereby reducing the induction time. The influence of ultrasonication and agitation on the induction of nucleation has also been compared in terms of the energy dissipation. With the same energy dissipation, ultrasonication is much more effective than agitation for induction, possibly due to its unique feature of acoustic cavitation.</P>

Development of a Nucleation-Accelerated-Semisolid-Slurry-Making Method and its Application to Rheo-diecasting of ADC10 Alloy

Sim, J. G.,Choi, B. H.,Jang, Y. S.,Kim, J. M.,Hong, C. P. The Iron and Steel Institute of Japan 2010 ISIJ international Vol.50 No.8

<P>A new slurry-making method, called the nucleation-accelerated semi-solid slurry (NASS) method, was developed to fabricate high-quality semi-solid slurry with fine and uniform globular microstructures. The method's application to rheo-diecasting of ADC10 alloy was investigated. To enhance the heterogeneous nucleation of primary α particles in the initial stage of solidification, various types of funnels, including the pouring system in the slurry-making vessels, were designed and estimated by thermal analysis. It was found that the heterogeneous nucleation of primary α particles was closely related to the temperature–time history and the flow pattern. In the present study, the NASS method was set up based on the optimized funnel. It consisted of a specially designed conical-shaped funnel and the electromagnetic stirring (EMS) unit for artificial agitation. The conical-shaped funnel generated swirly flow pattern in the melt. This was further exaggerated by the EMS in the slurry-making vessel during the pouring stage, resulting in a copious heterogeneous nucleation. The qualities of the slurry were investigated using optical microscopy and rheo-diecasting. To study the effect of process parameters, the semi-solid slurry of ADC10 alloy was rheo-diecast using an 85-ton high-pressure die casting (HPDC) machine. Microstructural observation and hardness test were then carried out on the rheo-diecast specimens. The rheo-diecast products of the NASS method showed fine and uniform microstructures, with primary α-globules diameter averaging 39 μm and form-factor indicating a degree of globularity of 0.9. The optimized heat treatment condition for the rheo-diecast product of ADC10 alloy was achieved at the solution temperature of 490°C for 30–60 min, water quenching, and age hardening at 180°C for 7–8 h.</P>