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Tytuł:
Kinetic analysis of thermogravimetric data collected from bigger samples
Autorzy:
Nowicki, L.
Markowski, M.
Powiązania:
https://bibliotekanauki.pl/articles/185111.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
termograwimetria
kinetyka
redukcja tlenków metali
thermogravimetry
kinetics
thermal lag
cellulose pyrolysis
metal oxide reduction
Opis:
Results for microcrystalline cellulose pyrolysis are presented, which includes thermogravimetric measurements and kinetic analysis of experimental data. The effect of sample mass size and heating rate on estimated values of activation energy and pre-exponential factor is demonstrated and a simple modification of procedure is proposed that allows for the correct values of kinetic parameters regardless of the experimental conditions. The efficiency of the proposed method is confirmed for two endothermic chemical reactions. A method of nonlinear regression is used for calculation of kinetic parameters for a single or TG curve or several curves simultaneously.
Źródło:
Chemical and Process Engineering; 2012, 33, 1; 85-94
0208-6425
2300-1925
Pojawia się w:
Chemical and Process Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermogravimetric and Kinetic Analysis of Raw and Torrefied Biomass Combustion
Autorzy:
Kopczyński, M.
Plis, A.
Zuwała, J.
Powiązania:
https://bibliotekanauki.pl/articles/185721.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
torrefied biomass
torrefaction
combustion
TG-MS-FTIR investigation
kinetic model (F1F1)
biomasa poddana toryfikacji
prażenie
spalanie
TG-MS-FTIR
model kinetyczny (F1F1)
Opis:
The use of torrefied biomass as a substitute for untreated biomass may decrease some technological barriers that exist in biomass co-firing technologies e.g. low grindability, high moisture content, low energy density and hydrophilic nature of raw biomass. In this study the TG-MS-FTIR analysis and kinetic analysis of willow (Salix viminalis L.) and samples torrefied at 200, 220, 240, 260, 280 and 300 oC (TSWE 200, 220, 240, 260, 280 and 300), were performed. The TG-DTG curves show that in the case of willow and torrefied samples TSWE 200, 220, 240 and 260 there are pyrolysis and combustion stages, while in the case of TSWE 280 and 300 samples the peak associated with the pyrolysis process is negligible, in contrast to the peak associated with the combustion process. Analysis of the TG-MS results shows m/z signals of 18, 28, 29 and 44, which probably represent H2O, CO and CO2. The gaseous products were generated in two distinct ranges of temperature. H2O, CO and CO2 were produced in the 500 K to 650 K range with maximum yields at approximately 600 K. In the second range of temperature, 650 K to 800 K, only CO2 was produced with maximum yields at approximately 710 K as a main product of combustion process. Analysis of the FTIR shows that the main gaseous products of the combustion process were H2O, CO2, CO and some organics including bonds: C=O (acids, aldehydes and ketones), C=C (alkenes, aromatics), C-O-C (ethers) and C-OH. Lignin mainly contributes hydrocarbons (3000–2800 cm−1), while cellulose is the dominant origin of aldehydes (2860–2770 cm−1) and carboxylic acids (1790–1650 cm−1). Hydrocarbons, aldehydes, ketones and various acids were also generated from hemicellulose (1790–1650 cm−1). In the kinetic analysis, the two-steps first order model (F1F1) was assumed. Activation energy (Ea) values for the first stage (pyrolysis) increased with increasing torrefaction temperature from 93 to 133 kJ/mol, while for the second stage (combustion) it decreased from 146 to 109 kJ/mol for raw willow, as well as torrefied willow at the temperature range of 200-260°C. In the case of samples torrefied at 280 and 300°C, the Ea values of the first and second stage were comparable to Ea of untreated willow and torrefied at 200°C. It was also found that samples torrefied at a higher temperature, had a higher ignition point and also a shorter burning time.
Źródło:
Chemical and Process Engineering; 2015, 36, 2; 209-223
0208-6425
2300-1925
Pojawia się w:
Chemical and Process Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Application of artificial neural nerworks in oxidation kinetic analysis of nanocomposites
Autorzy:
Straszko, J.
Biedunkiewicz, A.
Strzelczak, A.
Powiązania:
https://bibliotekanauki.pl/articles/779035.pdf
Data publikacji:
2008
Wydawca:
Zachodniopomorski Uniwersytet Technologiczny w Szczecinie. Wydawnictwo Uczelniane ZUT w Szczecinie
Tematy:
sztuczne sieci neuronowe
nanokompozyty ceramiczne
utlenianie
kinetyka
artificial neural networks
ceramic nanocomposites
oxidation
kinetics
Opis:
This study concerns the application of artificial neural networks in oxidation kinetic analysis of ceramic nanocomposites. The oxidation of the Ti-Si-C ceramic nanocomposite in dry air was studied. The size of the nanoparticles was determined by scanning electron microscopy (SEM). The gaseous oxidation products were analysed by mass spectroscopy (MS) while the solid oxidation products by X-ray diffraction (XRD). The kinetic analysis of the oxidation was based on the Coats-Redfern equation. The kinetic models were identified for the consecutive stages and then the A and E parameters of the Arrhenius equations were evaluated. Artificial neural networks were used at each step of the kinetic calculations.
Źródło:
Polish Journal of Chemical Technology; 2008, 10, 3; 21-28
1509-8117
1899-4741
Pojawia się w:
Polish Journal of Chemical Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Translocation of polysialic acid across model membranes: Kinetic analysis and dynamic.
Autorzy:
Janas, Teresa
Krajiński, Henryk
Timoszyk, Anna
Janas, Tadeusz
Powiązania:
https://bibliotekanauki.pl/articles/1044181.pdf
Data publikacji:
2001
Wydawca:
Polskie Towarzystwo Biochemiczne
Tematy:
polysialic acid
1H-NMR
electrical equivalent circuit
polycation flux
polyanion flux
lipid bilayers
membrane transport
Opis:
Transmembrane translocation of polyion homopolymers takes place in the case of polyanionic polysialic acid (polySia), polyanionic polynucleotides and polycationic polypeptides. The purpose of this work was to determine the role of membrane electrical parameters on the kinetics of polyion translocation, the influence of polysialic acid on ion adsorption on positively charged membrane surface and the dynamics of the phospholipid hydrocarbon chains and choline group by using 1H-NMR. The analysis of polyion translocation was performed by using the electrical equivalent circuit of the membrane for the initial membrane potential equal to zero. The changes in polysialic acid flux was up to 75% after 1 ms in comparison with the zero-time flux. Both a decrease of membrane conductance and an increase of polyion chain length resulted in the diminution of this effect. An increase of praseodymium ions adsorption to positively charged liposomes and an increase of the rate of segmental movement of the -CH2 and -CH3 groups, and the choline headgrup of lipid molecules, was observed in the presence of polySia. The results show that the direction of the vectorial polyion translocation depends both on the membrane electrical properties and the degree of polymerization of the polymer, and that polysialic acid can modulate the degree of ion adsorption and the dynamics of membrane lipids.
Źródło:
Acta Biochimica Polonica; 2001, 48, 1; 163-173
0001-527X
Pojawia się w:
Acta Biochimica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Kinetic analysis of LDL apoB transport and metabolism in non-steady states
Autorzy:
Weryński, A.
Nahorski, Z.
Angelin, B.
Berglund, L.
Eriksson, M.
Powiązania:
https://bibliotekanauki.pl/articles/206021.pdf
Data publikacji:
2000
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
biocybernetyka
apheresis
kinetic modelling
low density lipoprotein (LDL)
Opis:
In this paper a novel kinetic analysis is used for evaluation of the low density lipoprotein (LDL) apoB fractional catabolic rate (FCR) after LDL apheresis which creates a nonsteady state. The formulae for calculation of FCR, and LDL rate of appearance (Ra) as functions of time have been derived. Calculations for one normal and one familial hypercholesterolemic (FH) subjects showed that FCR as well as Ra exhibited variations which can be attributed to the circadian rhythm in LDL metabolism. LDL apheresis had a little impact on both Ra and FCR in normal as well as in FH subjects. However, Ra in FH subject was found to be much higher than - that in the normal subject.
Źródło:
Control and Cybernetics; 2000, 29, 1; 405-425
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Kinetic analysis of the transient phase and steady state of open multicyclic enzyme cascades
Autorzy:
Varón, Ramón
Havsteen, Bent
Valero, Edelmira
Molina-Alarcón, Milagros
García-Cánovas, Francisco
García-Moreno, Manuela
Powiązania:
https://bibliotekanauki.pl/articles/1041315.pdf
Data publikacji:
2005
Wydawca:
Polskie Towarzystwo Biochemiczne
Tematy:
steady state
fractional modification
transient phase
enzyme kinetics
multicyclic cascades
Opis:
This paper presents a kinetic analysis of the whole reaction course, i.e. of both the transient phase and the steady state, of open multicyclic enzyme cascade systems. Equations for fractional modifications are obtained which are valid for the whole reaction course. The steady state expressions for the fractional modifications were derived from the latter equations since they are not restricted to the condition of rapid equilibrium. Finally, the validity of our results is discussed and tested by numerical integration. Apart from the intrinsic value of knowing the kinetic behaviour of any of the species involved in any open multicyclic enzyme cascade, the kinetic analysis presented here can be the basis of future contributions concerning open multicyclic enzyme cascades which require the knowledge of their time course equations (e.g. evaluation of the time needed to reach the steady state, suggestion of kinetic data analysis, etc.), analogous to those already carried out for open bicyclic cascades.
Źródło:
Acta Biochimica Polonica; 2005, 52, 4; 765-780
0001-527X
Pojawia się w:
Acta Biochimica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Physicochemical, thermal and kinetic analysis of sewage sludge
Fizykochemiczna, termiczna i kinetyczna analiza osadów ściekowych
Autorzy:
Nyakuma, B. B.
Magdziarz, A.
Werle, S.
Powiązania:
https://bibliotekanauki.pl/articles/126178.pdf
Data publikacji:
2016
Wydawca:
Towarzystwo Chemii i Inżynierii Ekologicznej
Tematy:
physical properties of sewage sludge
chemical properties of sewage sludge
thermal analysis
kinetics
właściwości fizykochemiczne osadów ściekowych
analiza termiczna
kinetyka
Opis:
Sewage sludge (SS) is the residual matter generated from waste water treatment. Current treatment methods consist of mechanical dewatering and thermochemical treatment, which have become expensive, inefficient and energy consuming. Furthermore, European Union (EU) laws prohibit landfilling, agricultural and storage utilization of sewage slude (SS). Consequently, innovative and sustainable treatment, management and utilization technologies for SS are urgently required. The pyrolysis of sewage sludge can be potentially address the outlined challenges. Therefore, the main aim of this investigation was to examine the physicochemical, thermal and kinetic properties of selected sewage sludge samples (SS1 and SS2). Thermogravimetric analysis was examined to provide comprehensive description of the decomposition behaviour and kinetic characteristics of SS1 and SS2 under pyrolysis conditions at heating rates: 5, 10, 20 and 40°C/min from 30-800°C. The kinetic parameters such activation energy Ea and pre-exponential factor, A were calculated using the Kissinger model. The Ea and A values for SS1 are 205.87 kJ/mol and 9.68 · 1014 whereas SS2 are 320.40 kJ/mol and 7.44 · 1024. The general conclusion based on experimental studies is that the physicochemical and thermal kinetic properties of SS1 and SS2 are comparable with other pyrolysis feedstock and suitable for pyrolysis conversion.
Osady ściekowe są stałym produktem procesu oczyszczania ścieków. Obecne metody zagospodarowania osadów obejmujące mechaniczne odwadnianie oraz termiczne wykorzystanie stają się drogie, nieefektywne i energochłonne. Co więcej, prawo Unii Europejskiej ogranicza składowanie oraz wykorzystanie rolnicze osadów ściekowych. W efekcie znalezienie innowacyjnych oraz zrównoważonych metod zagospodarowania i utylizacji osadów ściekowych jest niezwykle istotne. Proces pirolizy wydaje się odpowiedni, by sprostać tym wymaganiom. Celem pracy jest określenie fizykochemicznych, termicznych oraz kinetycznych właściwości wybranych próbek osadów ściekowych (SS1 i SS2). Zastosowano analizę termograwimetryczną w celu przeprowadzenia analizy porównawczej opisującej proces przemian termicznych oraz ich kinetyki w warunkach pirolizy dla stałych szybkości grzania wynoszących 5, 10, 20 i 40°C/min w zakresie temperatur od 30-800°C. Parametry kinetyczne: energia aktywacji Ea oraz czynnik przedekspotencjalny A zostały wyznaczone przy użyciu modelu Kissingera. Wartość Ea oraz A dla osadu ściekowego SS1 wynosi odpowiednio 205,87 kJ/mol i 9,68×1014, podczas gdy dla osadu SS2 odpowiednio 320,40 kJ/mol i 7,44×1024. Wyniki analiz zostały porównane z innymi materiałami poddawanymi pirolizie.
Źródło:
Proceedings of ECOpole; 2016, 10, 2; 473-480
1898-617X
2084-4557
Pojawia się w:
Proceedings of ECOpole
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Kinetic Analysis of Thermal Processes in Ag-As-S-Se System Based on DSC Measurements
Autorzy:
Čajko, K.
Lukić-Petrović, S.
Štrbac, G.
Ivetić, T.
Powiązania:
https://bibliotekanauki.pl/articles/1398711.pdf
Data publikacji:
2016-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
65.60.+a
64.70.kj
64.70.P-
64.70.kg
Opis:
Thermal properties of glasses from the system $Ag_x(As_{40}S_{30}Se_{30})_{100-x}$ for x=0, 0.5, 1, 3, and 5 at.% were investigated by differential scanning calorimetry. The DSC curves were obtained under non-isothermal conditions which allowed determination of the glass transition temperature $T_{g}$ (onset temperature), crystallization temperature $T_{p}$ (corresponding to the crystallization peak maximum), melting temperature $T_{m}$, crystallization enthalpy $H_{c}$, and melting enthalpy $H_{m}$. The DSC curves obtained at the same heating rate were analyzed in order to study the variation of glass transition temperature with Ag concentration. Observed $T_{g}$ shift toward higher values, with increase in the heating rate, is in agreement with the Lasocka equation. Samples with 3 at.% and 5 at.% Ag were further thermally treated at different heating rates with the aim of analyzing kinetic processes of crystallization. The Moynihan and Kissinger models were used to calculate the activation energy of glass transition and activation energy of crystallization. For the samples that showed the crystallization processes an assessment of the thermal stability was done based on different criteria.
Źródło:
Acta Physica Polonica A; 2016, 129, 4; 509-513
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Differential Transform Method for the Kinetic Analysis of Thermal Inactivation of Enzyme as Applied in Biotechnology
Autorzy:
Adeleye, O. A.
Sobamowo, M. G.
Akinnukawe, B. I.
Powiązania:
https://bibliotekanauki.pl/articles/1031487.pdf
Data publikacji:
2020
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
Analytical solution
Differential transformation method
Enzyme
Kinetic analysis
Thermal inactivation
Opis:
In this work, approximate analytical solution is developed using differential transformation method for finding the molar concentration of the native and denatured enzyme in terms of second-order rate constant. Also, the obtained solutions are used to study the kinetics of thermal inactivation of enzyme as applied in biotechnology. The analytical solution was validated with numerical solution using fourth- order Runge-Kutta. Good agreement was established between the numerical and approximated analytical solutions.
Źródło:
World Scientific News; 2020, 142; 135-149
2392-2192
Pojawia się w:
World Scientific News
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermal and kinetic analysis of pure and contaminated ionic liquid: 1-butyl-2.3-dimethylimidazolium chloride (BDMIMCl)
Autorzy:
Muhammad, A.
Powiązania:
https://bibliotekanauki.pl/articles/949468.pdf
Data publikacji:
2016
Wydawca:
Zachodniopomorski Uniwersytet Technologiczny w Szczecinie. Wydawnictwo Uczelniane ZUT w Szczecinie
Tematy:
ionic liquid
thermal stability
kinetic analysis
activation energy
Opis:
In this research work, thermal decomposition and kinetic analysis of pure and contaminated imidazolium based ionic liquid (IL) has been investigated. As thermal decomposition and kinetics evaluation plays a pivotal role in effective process design. Therefore, thermal stability of pure 1-butyl-2,3-dimethylimidazolium chloride (BDMIMCl) was found to be higher than the sample of IL with the addition of 20% (wt.) NH4Cl as an impurity. The activation energy of thermal degradation of IL and other kinetic parameters were determined using Coats Redfern method. The activation energy for pure IL was reduced in the presence of NH4Cl as contaminant i.e., from 58.7 kJ/mol to 46.4 kJ/mol.
Źródło:
Polish Journal of Chemical Technology; 2016, 18, 2; 122-125
1509-8117
1899-4741
Pojawia się w:
Polish Journal of Chemical Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Kinetic analysis of co formation under oxy-combustion conditions
Kinetyczna analiza powstawania co w warunkach oksy-spalania
Autorzy:
Jerzak, W.
Kuźnia, M.
Powiązania:
https://bibliotekanauki.pl/articles/388931.pdf
Data publikacji:
2014
Wydawca:
Towarzystwo Chemii i Inżynierii Ekologicznej
Tematy:
oxy-combustion
flame CO concentration
combustion kinetics
oxy-spalanie
stężenie CO w płomieniu
kinetyka reakcji
Opis:
The paper reports the results of numerical computations concerning the formation of CO in the kinetic flame during natural gas oxy-combustion. The effect of temperature, reagent residence time and the composition of an atmosphere containing CO2 with 21 and 29 vol % O2 on the variation of CO concentration in the flame was examined. The oxy-combustion process was conducted with a 25 % excess oxygen. The analysis of reactions in flames at temperatures of 1500 K and 1800 K was performed within the Chemked II program using the combustion mechanism proposed by Mendiara & Glarborg, which includes 779 reactions. The computation results have confirmed that the rate of the key reactions responsible for the production of CO in the flame depends on the flame temperature and the oxy-combustion temperature. The peak CO concentrations are higher for the oxidizing mixture containing 29 vol % O2. After attaining a maximum, the CO flame concentration drops faster for an atmosphere richer in oxygen. The longer the time of reagent residence in the flame region, the lower the CO concentration. In different atmospheres and at different combustion temperatures, an identical CO level can be achieved in wet combustion gas. Irrespective of the temperature and atmosphere of oxy-combustion, most CO is produced as a result of the reaction OH + COHCO2. The reduction of oxygen in the oxidizing atmosphere at flame temperatures of 1500 and 1800 K lowers the CO production in the dominant reactions responsible for CO formation. The contribution of individual reactions in the CO production for the identical atmospheres is different with varying temperature. In the case of the reaction HCO + O2HO2 +CO, the temperature increase reduces the CO production. A reverse dependence of CO production on temperature characterizes the reaction H2 + CO + MCH2O + M. In addition, change in temperature changes the order in which the dominant reactions occur. Within the residence time equal to 100 ms, two periods of intensified CO production and consumption can be identified. The peak concentrations of H, OH and O radicals in the flame attain a maximum within the same time; as time goes by, the highest concentration is achieved by OH radicals. The presence of considerable levels of CO2 in the combustion substrates has an inhibiting effect on the natural gas oxidation process.
W pracy zaprezentowano wyniki obliczeń numerycznych dotyczących tworzenia CO w kinetycznym płomieniu podczas oksy-spalania gazu ziemnego. Badano wpływ temperatury, czasu przebywania reagentów oraz składu atmosfery zawierającej CO2 i 21 oraz 29 % obj. O2 na zmianę stężenia CO w płomieniu. Proces oksy-spalania prowadzony był z 25 % nadmiarem tlenu. Analizę reakcji w płomieniach o temperaturach 1500 i 1800 K przeprowadzono w programie Chemked II, z zastosowaniem mechanizmu spalania zaproponowanego przez Mendiara, Glarborg zawierającego 779 reakcji. Wyniki obliczeń potwierdziły, że szybkość najistotniejszych reakcji odpowiedzialnych za tworzenie CO w płomieniu zależy od temperatury płomienia oraz atmosfery oksy-spalania. Szczytowe stężenia CO są większe dla mieszanki utleniającej zawierającej 29 % obj. O2. Po osiągnieciu maksimum, stężenie CO w płomieniu spada szybciej dla atmosfery bogatszej w tlen. Im dłuższy czas przebywania reagentów w obszarze płomienia, tym niższe stężenie CO. W różnych atmosferach oraz temperaturach spalania można uzyskać identyczny poziom CO w spalaniach mokrych. Bez względu na temperaturę oraz atmosferę oksy-spalania każdorazowo najwięcej CO utworzone zostaje w wyniku reakcji OH + CO H + CO2. Redukcja tlenu w atmosferze utleniającej przy temperaturach płomienia wynoszących 1500 i 1800K obniża produkcję CO w dominujących reakcjach odpowiedzialnych za tworzenie CO. Wkład poszczególnych reakcji w produkcję CO dla tych samych atmosfer ze zmianą temperatury płomienia jest zróżnicowany. W przypadku reakcji HCO + O2HO2 CO wzrost temperatury zmniejsza produkcję CO. Odwrotna zależność produkcji CO od temperatury charakteryzuje reakcję H2 + CO + MCH2O + M. Dodatkowo zmiana temperatury zmienia kolejność dominujących reakcji. W zakresie czasu rezydencji równego 100 ms wyróżnić można okresy wzmożonego tworzenia oraz zużywania CO. Szczytowe stężenia rodników H, OH i O w płomieniu osiągają maksimum w tym samym czasie, a w miarę jego upływu najwyższe stężenie posiadają rodniki OH. Obecność znacznych ilości CO2 w substratach spalania ma działanie hamujące proces utleniania gazu ziemnego.
Źródło:
Ecological Chemistry and Engineering. A; 2014, 21, 4; 415-424
1898-6188
2084-4530
Pojawia się w:
Ecological Chemistry and Engineering. A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Application of Daftardar-Gejiji and Jafari method to kinetic analysis of thermal inactivation of Jack bean urease
Autorzy:
Sobamowo, G.
Adeleye, O.
Powiązania:
https://bibliotekanauki.pl/articles/973622.pdf
Data publikacji:
2018
Wydawca:
Politechnika Częstochowska. Wydawnictwo Politechniki Częstochowskiej
Tematy:
kinetics
thermal activation
Jack bean urease
enzyme
biotechnology
Daftardar-Gejiji and Jafari method
Kinetyka
analiza kinetyczna
inaktywacja termiczna
enzym
ureaza
biotechnologia
metoda Daftardar-Gejiji i Jafari
Opis:
Jack bean urease has been used as a good catalyst for hydrolysis of urea in various applications such as biotechnology and biomedical engineering. The wide range of applications require proper understanding of the thermal inactivation of the enzyme. Consequently, the theoretical analysis of the enzyme kinetic of the thermal inactivation is required. In this paper, a new iterative method proposed by Daftardar-Gejiji and the Jafari method is applied to analyse the kinetic of thermal inactivation of jack bean urease (EC3.5.1.5). The kinetics of the urease consist of three-reaction steps and included the Arrhenius equation for temperature-dependent rate constants as well as the temperature change in the initial heating period. The approximate analytical solutions are verified with results of numerical method using Runge-Kutta with the shooting method, and good agreements are established between the results of the methods. From the analytical investigation, it is established that the molar concentration of the native enzyme decreases as the time increases while the molar concentration of the denatured enzyme increases as the time increases. The time taken to reach the maximum value of the molar concentration of the native enzyme is the same as the time taken to reach the minimum value of the molar concentration of the denature enzyme. It is hoped that the information given in this theoretical investigation will assist in the kinetic analysis of thermal inactivation of the experimental results over handling rate constants and molar concentrations.
Źródło:
Journal of Applied Mathematics and Computational Mechanics; 2018, 17, 2; 65-76
2299-9965
Pojawia się w:
Journal of Applied Mathematics and Computational Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Kinetic modeling of chromium(III) extraction with aliquat 336 from alkaline aqueous solutions containing chlorides
Autorzy:
Wionczyk, B.
Powiązania:
https://bibliotekanauki.pl/articles/110327.pdf
Data publikacji:
2013
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
extraction
chromium(III) chloride
Aliquat 33
kinetic analysis
Opis:
The effects of time, composition and history of preparation of the aqueous phase on the liquidliquid extraction of chromium(III) with Aliquat 336 from the aqueous alkaline solutions containing chlorides were studied. At time far from the equilibrium the yield and initial rate of the chromium(III) extraction depend on NaOH concentration, ionic strength of the aqueous phase and the way of its preparation. At the constant composition of the feed solution, rate of the Cr(III) extraction in approach to the equilibrium is higher when chromium(III) is extracted from the alkaline aqueous phase freshly prepared by direct dissolution of a weighted sample of CrCl3 than from that obtained by dilution of aged stock solution of CrCl3. Kinetic analysis by the mathematical models showed that within the whole period of time needed to reach the equilibrium, the rate of the Cr(III) extraction is limited by the second-, and third-order chemical reaction towards Cr(III), irrespective of composition and preparation history of the aqueous phase. The three-dimensional diffusion and chemical reaction at phase boundary substrateproduct (the contracting volume) models have a significant effect on the chromium(III) extraction within the initial extent of the process.
Źródło:
Physicochemical Problems of Mineral Processing; 2013, 49, 2; 587-605
1643-1049
2084-4735
Pojawia się w:
Physicochemical Problems of Mineral Processing
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermal behavior and kinetic decomposition of sweet potato starch by non-isothermal procedures
Autorzy:
Liu, Ying
Yang, Liutao
Zhang, Yingzhe
Powiązania:
https://bibliotekanauki.pl/articles/240460.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
starch
kinetic analysis
thermal degradation
activation energy
mechanism
Opis:
In this study, X-ray diffraction, thermogravimetric analysis and differential scanning calorimetry (DSC) method were used to analyze the main characteristics of sweet potato starch, and to analyze the thermal degradation process of sweet potato starch. Specifically, X-ray diffraction to study its structure, thermogravimetric analysis to study the thermal degradation kinetics, and differential scanning calorimetry to study the thermogram of sweet potato starch. The thermal decomposition kinetics of sweet potato starch was examined within different heating rates in nitrogen atmosphere. Different models of kinetic analysis were used to calculate the activation energies using thermogravimetric data of the thermal degradation process. Activation energies obtained from Kissinger, Flynn-WallOzawa, and Šatava-Šesták models were 173.85, 174.87 and 174.34 kJ/mol, respectively. The values of activation energy indicated that the thermal degradation of the sweet potato starch was a single reaction mechanism or the combination of multi-reaction mechanisms. The differential scanning calorimetry analysis show that two decomposition stages were presented: the first at a low temperature involves the decomposition of long chain; and the second at a high temperature represents the scission of glucose ring. This information was helpful to design the processing process of many natural polymers. Thermogravimetric Fourier transform-infrared (TG–FTIR) analysis showed that the main pyrolysis products included water, methane, carbon dioxide, ammonia, and others.
Źródło:
Archives of Thermodynamics; 2019, 40, 4; 67-82
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Activity and kinetic properties of phosphotransacetylase from intestinal sulfate-reducing bacteria
Autorzy:
Kushkevych, Ivan
Powiązania:
https://bibliotekanauki.pl/articles/1039142.pdf
Data publikacji:
2015
Wydawca:
Polskie Towarzystwo Biochemiczne
Tematy:
sulfate-reducing bacteria
phosphotransacetylase
kinetic analysis
inflammatory bowel diseases
Opis:
Phosphotransacetylase activity and the kinetic properties of the enzyme from intestinal sulfate-reducing bacteria Desulfovibrio piger and Desulfomicrobium sp. has never been well-characterized and has not been studied yet. In this paper, the specific activity of phosphotransacetylase and the kinetic properties of the enzyme in cell-free extracts of both D. piger Vib-7 and Desulfomicrobium sp. Rod-9 intestinal bacterial strains were presented at the first time. The microbiological, biochemical, biophysical and statistical methods in this work were used. The optimal temperature and pH for enzyme reaction was determined. Analysis of the kinetic properties of the studied enzyme was carried out. Initial (instantaneous) reaction velocity (V0), maximum amount of the product of reaction (Pmax), the reaction time (half saturation period, τ) and maximum velocity of the phosphotransacetylase reaction (Vmax) were defined. Michaelis constants (Km) of the enzyme reaction (3.36 ± 0.35 mM for D. piger Vib-7, 5.97 ± 0.62 mM for Desulfomicrobium sp. Rod-9) were calculated. The studies of the phosphotransacetylase in the process of dissimilatory sulfate reduction and kinetic properties of this enzyme in intestinal sulfate-reducing bacteria, their production of acetate in detail can be perspective for clarification of their etiological role in the development of the humans and animals bowel diseases. These studies might help in predicting the development of diseases of the gastrointestinal tract, by providing further details on the etiology of bowel diseases which are very important for the clinical diagnosis of these disease types.
Źródło:
Acta Biochimica Polonica; 2015, 62, 1; 103-108
0001-527X
Pojawia się w:
Acta Biochimica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
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