• Title, Summary, Keyword: kinetics

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Biodegradation Kinetics of 4-Chlorophenol by Pseudomonas sp. EL-091S (Pseudomonas sp. EL-091S에 의한 4-Chlorophenol의 분해 Kinetics)

  • Son, Jun-Seog;Lee, Geon;Lee, Sang-Joon
    • Journal of Environmental Science International
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    • v.2 no.2
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    • pp.95-102
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    • 1993
  • In order to find the most fitted biodegradation model, biodegradation models to the initial 4-chlorophenol concentrations were investigated and had been fitted by the linear regression. The degrading bacterium, EL-091S, was selected among phenol-degraders. The strain was identified with Pseudomows sp. from the result of taxonomical studies. The optimal condition for the biodegradation was as fellows: secondary carbon source, concentration of ammonium nitrate, temperature and pH were 200mg/l fructose, 600 mg/l, $30^{\circ}C$ and 7.0 respectively. The highest degradation rate of the 4-chlorophenol was about 58% for 24 hours incubation on the optimal condition. Biodegradation kinetics model of 5 mg/l 4-Chlorophenol, 10 mg/l 4-chlorophenol and 50 mg/l 4-chlorophenol were fitted the zero order kinetics model, respectively. Key Words : 4-chlorophenol, Pseudomonas sp., zero order kinetics model.

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Space Charge Effect on Grain Growth Kinetics of Tetragonal Zirconia Polycrystal

  • Chon, Uong
    • The Korean Journal of Ceramics
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    • v.5 no.1
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    • pp.1-11
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    • 1999
  • The effect of aliovalent dopents, $Nb_3O_5$ and MnO, on the grain growth kinetics of 12 mol% ceria stabilized tetragonal zirconia polycrystals (Ce-TZP) was studied. All specimens were sintered at $1550^{\circ}C$ for 20 minutes prior to annealing at different temperatures to study grain growth kinetics. Grain growth kinetics of Ce-TZP and 1 mol% $Nb_2O_5$ doped Ce-TZP (Ce-TZP/$Nb_3O_5$) during annealing at 1475, 1550, and $1600^{\circ}C$ adequately matched with square law $(D^2-D_\;o^2=k_at)$. However, grain growth in 1 mol% MnO suppressed grain growth in Ce-TZP by drag force exerted by $Mn^{+2}$ ions which segregated strongly to the positively-charged grain boundaries of Ce-TZP, $Nb_2O_5$ enhanced grain growth by increasing the concentration of vacancies of $Zr^{+4}$ ion and $Ce^{+4}$ ions. Surface analysis with X-ray photoelectron spectroscopy (XPS) showed the segregation of Mn+2 ions to grain boundaries. The kinetics of grain growth obtained in the base Ce-TZP and the Ce-TZPs with the aliovalent dopants were examined in the context of impurity drag effect and space charge effect.

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Folding Mechanism of WT* Ubiquitin Variant Studied by Stopped-flow Fluorescence Spectroscopy

  • Park, Soon-Ho
    • Bulletin of the Korean Chemical Society
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    • v.31 no.10
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    • pp.2877-2883
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    • 2010
  • The folding kinetics of $WT^*$ ubiquitin variant with valine to alanine mutation at sequence position 26 (HubWA) was studied by stopped-flow fluorescence spectroscopy. While unfolding kinetics showed a single exponential phase, refolding reaction showed three exponential phases. The semi-logarithmic plot of urea concentration vs. rate constant for the first phase showed v-shape pattern while the second phase showed v-shape with roll-over effect at low urea concentration. The rate constant and the amplitude of the third phase were constant throughout the urea concentrations, suggesting that this phase represents parallel process due to the configurational isomerization. Interestingly, the first and second phases appeared to be coupled since the amplitude of the second phase increased at the expense of the amplitude of the first phase in increasing urea concentrations. This observation together with the roll-over effect in the second folding phase indicates the presence of intermediate state during the folding reaction of HubWA. Quantitative analysis of Hub-WA folding kinetics indicated that this intermediate state is on the folding pathway. Folding kinetics measurement of a mutant HubWA with hydrophobic core residue mutation, Val to Ala at residue position 17, suggested that the intermediate state has significant amount of native interactions, supporting the interpretation that the intermediate is on the folding pathway. It is considered that HubWA is a useful model protein to study the contribution of residues to protein folding process using folding kinetics measurements in conjunction with protein engineering.

Adsorption Kinetics of Cupper and Zinc Ion with Na-A Zeolite Synthesized by Coal Fly Ash (석탄 비산재로 합성한 Na-A형 제올라이트에 의한 구리와 아연 이온의 동역학적 흡착 특성)

  • Lee, Chang-Han
    • Journal of Environmental Science International
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    • v.20 no.12
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    • pp.1607-1615
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    • 2011
  • The adsorption performance of cupper and zinc ions($Cu^{2+}$ and $Zn^{2+}$) in aqueous solution was investigated by an adsorption process on reagent grade Na-A zeolite(Z-WK) and Na-A zeolite (Z-C1) prepared from coal fly ash. Z-C1 was synthesized by a fusion method with coal fly ash from a thermal power plant. Batch adsorption experiment with Z-C1 was employed to study the kinetics and equilibrium parameters such as initial metal ions concentration and adsorption time of the solution on the adsorption process. Adsorption rate of metal ions occurred rapidly and adsorption equilibrium reached at less than 120 minutes. The kinetics data of $Cu^{2+}$ and $Zn^{2+}$ ions were well fitted by a pseudo-second-order kinetics model more than a pseudo-first-order kinetics model. The equilibrium data were well fitted by a Langmuir model and this result showed $Cu^{2+}$ and $Zn^{2+}$ adsorption on Z-C1 would be occupied by a monolayer adsorption. The maximum adsorption capacity($q_{max}$) by the Langmuir model was determined as $Cu^{2+}$ 99.8 mg/g and $Zn^{2+}$ 108.3 mg/g, respectively. It appeared that the synthetic zeolite, Z-C1, has potential application as absorbents in metal ion recovery and mining wastewater.

Effects of Temperature on Flocculation Kinetics Using Fe(III) Coagulant in Water Treatment (정수처리시 Fe(III) 응집제를 사용한 응집동력학에 대한 온도의 영향)

  • 강임석
    • Journal of Environmental Science International
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    • v.4 no.2
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    • pp.181-194
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    • 1995
  • Flocculation kinetics using ferric nitrate as a coagulant to coagulate kaolin clay in water was examined as a tool to investigate the effect of low temperature under tightly controlled treatment conditions. Both the particle size distribution data obtained from Automatic Image Analysis (AIA) system and the on-line measurement of the degree of turbidity fluctuation in a flowing suspension by Photometric Dispersion Analyzer (PDA) were used to measure flocculation kinetics. Results show that cold water temperature had a pronounced detrimental effect on flocculation kinetics. For improving flocculation kinetics at low water temperature, maintaining constant pOH to adjust water chemistry for temperature changes was found to be partially effective only in the more acidic pH range studied.

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A Kinetic Studies of Pyrolysis and Combustion of Sewage Sludge (하수 슬러지의 열분해 및 연소 Kinetics 연구)

  • Roh, Seon Ah
    • Resources Recycling
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    • v.23 no.6
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    • pp.47-53
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    • 2014
  • Effective treatment and energy conversion technologies are necessary due to the ban of the dumping of organic waste including the sewage sludge. In this study, the kinetics of pyrolysis and combustion were derived in a TGA and thermobalance reactor, which is essential for thermal conversion of sewage sludge to energy. Three steps are shown for the pyrolysis in TGA and the different pre-exponential factors and activation energies are derived depending on the temperature range. Three models of gassolid reaction were applied to the reaction kinetics analysis for the combustion of sewage sludge char and shrinking core model was an appropriated model. Apparent activation energy and pre-exponential factor were evaluated and the effect of oxygen partial pressure was examined.

A Comparison of Low-Dimensional Reactor Kinetics Analysis Methods with Modified Borresen's Coarse-Mesh Method (저차원 원자로 동특성 해법과 다차원 수정형 Borresen 소격해법의 비교)

  • Kim, Chang-Hyo;Lee, Gyu-Bok
    • Nuclear Engineering and Technology
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    • v.22 no.4
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    • pp.359-370
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    • 1990
  • This study concerns with comparing low-dimensional reactor kinetics methods with a three-dimensional kinetics method to be used for safety analysis of light water reactors in order to suggest means of preparing input parameters required for low-dimensional methods. For this purpose a one-dimensional finite difference two-group diffusion theory code ODTRAN and a third-order Hermit polynomial-based point kinetics code POTRAN are developed and used to obtain low-dimensional solutions to the LRA-BWR kinetics benchmark problem. The results are compared with a three-dimensional modified Borresen's coarse-mesh solution of the kinetics problem by CMSNACK code. Through this comparison some simple but practical means of preparing input parameters of low-dimensional kinetics analysis methods are suggested.

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Effect of Glucose, Its Analogs and Some Amino Acids on Pre-steady State Kinetics of ATP Hydrolysis by PM-ATPase of Pathogenic Yeast (Candida albicans)

  • Bushra, Rashid;Nikhat, Manzoor;M., Amin;Luqman A., Khan
    • Animal cells and systems
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    • v.8 no.4
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    • pp.307-312
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    • 2004
  • Fast kinetics of transient pH changes and difference spectrum formation have been investigated following mixing of ADP/ATP with partially purified plasma membrane PM-ATPase of the pathogenic yeast Candida albicans in the presence of five nutrients: glucose, glutamic acid, proline, lysine, and arginine and two analogs of glucose: 2-deoxy D-glucose and xylose. Average $H^+$- absorption to release ratio, indicative of population of ATPase undergoing complete hydrolytic cycle, was found to be 0.27 for control. This ratio varied between 0.25 (proline) to 0.36 (arginine) for all other compounds tested, except for glucose. In the presence of glucose, $H^+$- absorption to release ratio was exceptionally high (0.92). While no UV difference spectrum was observed with ADP, mixing of ATP with ATPase led to a large conformational change. Exposure to different nutrients restricted the magnitude of the conformational change; the analogs of glucose were found to be ineffective. This suppression was maximal in the case of glucose (80%); with other nutrients, the magnitude of suppression ranged from 40-50%. Rate of $H^+$- absorption, which is indicative of E~P complex dissociation, showed positive correlation with suppression of conformational change only in the case of glucose and no other nutrient/analog. Mode of interaction of glucose with plasma membrane $H^+$-ATPase thus appears to be strikingly distinct compared to that of other nutrients/analogs tested. The results obtained lead us to propose a model for explaining glucose stimulation of plasma membrane $H^+$-ATPase activity.

A Brief Review on Polarization Switching Kinetics in Fluorite-structured Ferroelectrics (플루오라이트 구조 강유전체 박막의 분극 반전 동역학 리뷰)

  • Kim, Se Hyun;Park, Keun Hyeong;Lee, Eun Been;Yu, Geun Taek;Lee, Dong Hyun;Yang, Kun;Park, Ju Yong;Park, Min Hyuk
    • Journal of the Korean institute of surface engineering
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    • v.53 no.6
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    • pp.330-342
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    • 2020
  • Since the original report on ferroelectricity in Si-doped HfO2 in 2011, fluorite-structured ferroelectrics have attracted increasing interest due to their scalability, established deposition techniques including atomic layer deposition, and compatibility with the complementary-metal-oxide-semiconductor technology. Especially, the emerging fluorite-structured ferroelectrics are considered promising for the next-generation semiconductor devices such as storage class memories, memory-logic hybrid devices, and neuromorphic computing devices. For achieving the practical semiconductor devices, understanding polarization switching kinetics in fluorite-structured ferroelectrics is an urgent task. To understand the polarization switching kinetics and domain dynamics in this emerging ferroelectric materials, various classical models such as Kolmogorov-Avrami-Ishibashi model, nucleation limited switching model, inhomogeneous field mechanism model, and Du-Chen model have been applied to the fluorite-structured ferroelectrics. However, the polarization switching kinetics of fluorite-structured ferroelectrics are reported to be strongly affected by various nonideal factors such as nanoscale polymorphism, strong effect of defects such as oxygen vacancies and residual impurities, and polycrystallinity with a weak texture. Moreover, some important parameters for polarization switching kinetics and domain dynamics including activation field, domain wall velocity, and switching time distribution have been reported quantitatively different from conventional ferroelectrics such as perovskite-structured ferroelectrics. In this focused review, therefore, the polarization switching kinetics of fluorite-structured ferroelectrics are comprehensively reviewed based on the available literature.