Determination of thermal stability and activation energy of polyvinyl alcohol–cassava starch blends

2011 ◽  
Vol 83 (1) ◽  
pp. 303-305 ◽  
Author(s):  
Lee Tin Sin ◽  
W.A.W.A. Rahman ◽  
A.R. Rahmat ◽  
M. Mokhtar
Keyword(s):  
Activation Energy ◽  
Thermal Stability ◽  
Polyvinyl Alcohol ◽  
Cassava Starch ◽  
Starch Blends

Rheology and thermal transition state of polyvinyl alcohol–cassava starch blends

2010 ◽  
Vol 81 (3) ◽  
pp. 737-739 ◽  
Author(s):  
Lee Tin Sin ◽  
A.R. Rahmat ◽  
W.A.W.A. Rahman ◽  
Zhao-Yan Sun ◽  
A.A. Samad
Keyword(s):  
Polyvinyl Alcohol ◽  
Transition State ◽  
Cassava Starch ◽  
Thermal Transition ◽  
Starch Blends

scholarly journals Developing an internally consistent methodology for K-feldspar MAAD TL thermochronology

2021 ◽  
Author(s):  
Nathan Brown ◽  
Edward Rhodes
Keyword(s):  
Activation Energy ◽  
Thermal Stability ◽  
Dose Response ◽  
Accurate Determination ◽  
Rock Surface ◽  
Exhumation Rates ◽  
Parameter Values ◽  
Center Density ◽  
Best Fit

Luminescence thermochronology and thermometry can quantify recent changes in rock exhumation rates and rock surface temperatures, but these methods require accurate determination of several kinetic parameters. For K-feldspar thermoluminescence (TL) glow curves, which comprise overlapping signals of different thermal stability, it is challenging to develop measurements that capture these parameter values. Here, we present multiple-aliquot additive-dose (MAAD) TL dose response and fading measurements from bedrock-extracted K-feldspars. These measurements are compared with Monte Carlo simulations to identify best-fit values for recombination center density ($\rho$) and activation energy ($\Delta E$). This is done for each dataset separately, and then by combining dose-response and fading misfits to yield more precise $\rho$ and $\Delta E$ values consistent with both experiments. Finally, these values are used to estimate the characteristic dose ($D_0$) of samples. This approach produces kinetic parameter values consistent with comparable studies and results in expected fractional saturation differences between samples.

Detection of synergistic interactions of polyvinyl alcohol–cassava starch blends through DSC

2010 ◽  
Vol 79 (1) ◽  
pp. 224-226 ◽  
Author(s):  
Lee Tin Sin ◽  
W.A.W.A. Rahman ◽  
A.R. Rahmat ◽  
M.I. Khan
Keyword(s):  
Polyvinyl Alcohol ◽  
Cassava Starch ◽  
Synergistic Interactions ◽  
Starch Blends

A Study of Specific Heat Capacity Functions of Polyvinyl Alcohol–Cassava Starch Blends

2010 ◽  
Vol 31 (3) ◽  
pp. 525-534 ◽  
Author(s):  
Lee Tin Sin ◽  
W. A. W. A. Rahman ◽  
A. R. Rahmat ◽  
N. A. Morad ◽  
M. S. N. Salleh
Keyword(s):  
Heat Capacity ◽  
Polyvinyl Alcohol ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Cassava Starch ◽  
Starch Blends

Development of HPLC Method for the Purity Test by Design of Experiments and Determination of Activation Energy of Hydrolytic Degradation Reactions of Sofosbuvir

2020 ◽  
Vol 16 (7) ◽  
pp. 976-987
Author(s):  
Jakub Petřík ◽  
Jakub Heřt ◽  
Pavel Řezanka ◽  
Filip Vymyslický ◽  
Michal Douša
Keyword(s):  
Activation Energy ◽  
Design Of Experiments ◽  
Mobile Phase ◽  
Hydrolytic Degradation ◽  
Isoconversional Method ◽  
Hplc Method ◽  
Organic Modifier ◽  
Calculation Methods ◽  
Degradation Reactions

Background: The present study was focused on the development of HPLC method for purity testing of sofosbuvir by the Design of Experiments and determination of the activation energy of hydrolytic degradation reactions of sofosbuvir using HPLC based on the kinetics of sofosbuvir degradation. Methods: Following four factors for the Design of Experiments were selected, stationary phase, an organic modifier of the mobile phase, column temperature and pH of the mobile phase. These factors were examined in two or three level experimental design using Modde 11.0 (Umetrics) software. The chromatographic parameters like resolution, USP tailing and discrimination factor were calculated and analysed by partial least squares. The chromatography was performed based on Design of Experiments results with the mobile phase containing ammonium phosphate buffer pH 2.5 and methanol as an organic modifier. Separation was achieved using gradient elution on XBridge BEH C8 at 50 °C and a flow rate of 0.8 mL/min. UV detection was performed at 220 nm. The activation energy of hydrolytic degradation reactions of sofosbuvir was evaluated using two different calculation methods. The first method is based on the slope of dependence of natural logarithm of the rate constant on inverted thermodynamic temperature and the second approach is the isoconversional method. Results and Conclusion: Calculated activation energies were 77.9 ± 1.1 kJ/mol for the first method and 79.5 ± 3.2 kJ/mol for the isoconversional method. The results can be considered to be identical, therefore both calculation methods are suitable for the determination of the activation energy of degradation reactions.

Cathodoluminescence of SiO2/Si System

2009 ◽  
Vol 156-158 ◽  
pp. 487-492 ◽  
Author(s):  
M.V. Zamoryanskaya
Keyword(s):  
Activation Energy ◽  
Electron Beam ◽  
Rise Time ◽  
Silicon Oxide ◽  
Beam Current ◽  
Electron Beam Current ◽  
Electron Traps ◽  
Definition Of ◽  
Luminescent Centers

In this paper the new method for determination of luminescent centers concentration are discussed. While the possibility of electron traps determination and definition of its activation energy are suggested. The cathodoluminescent (CL) method was used. The determination of luminescent centers concentration in silicon oxide is based on the measurements of dependences of CL intensity on electron beam current. The presence and energy of activation of electron traps were studied by measurement of rise time and decay of luminescent band during the stationary irradiation of silica by electron beam.

scholarly journals Determination of the membrane hydraulic permeability of MSCs

2016 ◽  
Vol 2 (1) ◽  
pp. 323-327
Author(s):  
Jennifer Contreras Lopez ◽  
Lothar Lauterböck ◽  
Birgit Glasmacher
Keyword(s):  
Activation Energy ◽  
Bone Marrow ◽  
Cooling Rate ◽  
Mesenchymal Stromal Cells ◽  
Stromal Cells ◽  
Hydraulic Permeability ◽  
Osmotic Behaviour ◽  
Additional Influence ◽  
Dimethyl Sulfoxid

AbstractA successful cryopreservation is based on knowledge of the optimal cooling rate. So far, this is often determined by way of complex parameter studies. Alternatively, the identification of cell specific characteristics, such as osmotic behaviour, membrane hydraulic permeability and activation energy could be used to calculate the optimal cooling rate. These parameters should be determined for supra-zero and sub-zero temperatures. In this study cryomicroscopy was used. Mesenchymal stromal cells (MSCs) from bone marrow were analysed. The determined membrane hydraulic permeability for sub-zero temperatures is significantly lower than that for supra-zero temperatures. On the contrary the activation energy is significantly higher in the presence of ice. The addition of a cryoprotective agent (CPA) such as dimethyl sulfoxid (DMSO) shows an additional influence on the characteristics of the membrane of the cell. The optimal cooling rate was determined with these parameters. For cryopreservation without DMSO the optimal cooling rate was found to be 12.82 K/min. If the MSCs were frozen with 5% (v/v) DMSO the optimal cooling rate is 16.25 K/min.

Sign in / Sign up

Export Citation Format

Share Document