Authors:Tamás Fekecs, István Zapf, Andrea Ferencz, and Dénes Lőrinczy
methods to monitor in MM patients in any stages.
Differentialscanningcalorimetry (DSC) is unsurpassed for understanding the stability of biological systems. DSC directly measures the stability and unfolding of a protein, lipid, or nucleic acid
Authors:Jiawu Gao, Lin Li, Yanping Deng, Zongming Gao, Changhua Xu, and Mingxi Zhang
A new method for determining the degree of conversion of gelation (αgel) and gel time (tgel) at gel point using a single technology, DSC, is discussed in this work. Four kinds of thermoset resins are evaluated. It
is found that the mutation points of reduced reaction rate (Vr) vs. reaction conversion (α) curves, corresponding with the changes of reaction mechanism, represents the gelation of the
reaction. The α at the mutation point is defined as αgel. From isothermal DSC curves, the point at αgel is defined astgel. Traditional techniques (ASTM D3532 and DSC method) are also used to determine αgel andtgel in order to demonstrate this new method. We have found that the results obtained from this new method are very consistent
with the results obtained from traditional methods.
Authors:J. Farkas, É. Andrássy, Z. Formanek, and L. Mészáros
A bioluminescent derivative of Bacillus subtilis containing a plasmid encoding a luxAB fusion under control of a vegetative promoter and gives bioluminescence upon addition of an exogenous long-chain aldehyde has been used as test organism. Its spore populations have been produced and their heat- and radiation survival curves established. Heat-sensitization effect of pre-irradiation of spores was proven not only by colony counting but also with differential scanning calorimetry. Under a linearly programmed temperature increase, the heat destruction of spores surviving 2.5 kGy gamma irradiation resulted in at a few centigrade lower temperature than that of untreated spores. Heat denaturation endotherms in the DSC-thermogram of irradiated spores were shifted to lower temperatures as well. Comparative turbidimetric, luminometric and phase-contrast microscopic studies of untreated, heat-treated and irradiated spore populations showed that the kinetics of germination and the light emission during germination of radiation-inactivated spores were the same as those of untreated spores, revealing that the pre-formed luciferase enzyme packaged into the spores during sporulation remained intact after an irradiation dose causing 90% decrease in number of colony forming spores. Therefore, in contrast to heat-treated spores, the initial bioluminescence reading upon germination of irradiated spores does not reflect the viable count of their population.
Authors:R. Filho, P. Franco, E. Conceição, and M. Leles
A formulation of nifedipine tablets was prepared in the present research. The tablets were conditioned in amber-colored glass
containers and placed in a climatized room at 40°C and relative humidity of 75% for 180 days. Differential scanning calorimetry
(DSC) and thermogravimetry (TG) were used in order to evaluate the thermal properties of nifedipine, the excipients and two
well-known nifedipine degradation products. The results demonstrated that there is no evidence on the interaction between
nifedipine and excipients, or degradation products.
Authors:S. Lin, J. Tseng, Y. Lin, W. Huang, and C. Shu
The polymerization mechanisms of styrene and various derivatives by α-methylstyrene (AMS) and trans-β-methylstyrene (TBMS) were evaluated. Experiments were carried out for dimerization identification and thermal polymerization
estimation by differential scanning calorimetry (DSC), thermal activity monitor (TAM) and Fourier transform infrared absorption
spectrophotometer (FTIR). The results show that, under temperature ranges of 60–190 and 50–170°C, AMS and TBMS performed dimerization
by benzene ring and ethylene double bond, respectively. AMS and TBMS would form unsaturated dimers, saturated dimers and trimers,
etc., during the period of thermal polymerization. Through this study, one can estimate possible intermediates of the polymerization
process for the monomer of interest in the petrochemical industry.
Thermal runaway reactions associated with exothermic behaviors of tert-butyl hydroperoxide (TBHP) solutions and TBHP reacting with alkaline contaminants were studied. A differential scanning calorimetry
(DSC) was used to characterize these inherent behaviors of TBHP solutions with KOH, NaOH, LiOH and NH4OH. The exothermic peak in thermal curves of TBHP solutions with different alkali were detected by DSC thermal analysis. By
thermal analysis, we compared various heats of decomposition of TBHP solutions with alkaline impurities, and determined the
incompatible hazards of various TBHP solutions with alkaline contaminants. Comparing with TBHP in various diluents, the adiabatic
runaway reaction via vent sizing package 2 (VSP2) indicated that aqueous TBHP intrinsically possesses the phenomena of thermal
explosion with dramatic self-reactive rate and pressure rise under adiabatic conditions. Many commercial organic peroxides
may have different hazard behaviors. Therefore, using thermal method to classify the hazards is an important subject.
Authors:Y. Chen, Y. Chou, H. Hou, Y. I, and C. Shu
Organic peroxides (OPs) are very susceptible to thermal sources, chemical pollutants or even mechanical shock. Over the years,
they have caused many serious explosions. Cumene hydroperoxide (CHP) is widely employed to produce phenol and dicumyl peroxide
(DCPO) in the manufacturing process. Differential scanning calorimetry (DSC) and thermal activity monitor (TAM) were employed
to determine the potential thermal hazards and thermokinetic parameters (such as exothermic onset temperature (T0), maximum temperature (Tmax), and enthalpy (ΔH)) of CHP mixed with sodium hydroxide (NaOH) and sulfuric acid (H2SO4). High performance liquid chromatography (HPLC) was used to analyze the concentration vs. time of CHP.When CHP is mixed with NaOH, the T0 is induced earlier and reactions become more intricate than the pure CHP solution. CHP added to NaOH or H2SO4 is more dangerous than pure CHP alone. Depending on the operating conditions, NaOH and H2SO4 are the incompatible chemicals for CHP.
Complex mixtures of long chain organic compounds often show overlapping glass transition temperatures (Tgs) when analyzed by differential scanning calorimetry (DSC) or modulated DSC (MDSC). In such cases, subjective and inconsistent
smoothing of data acquired under different conditions can lead to the misinterpretation of results. A quantitative method
for the selection of smoothing factors for the analysis and comparison of (M)DSC results is presented. The method is most
useful for the analysis of the derivative of the heat capacity, dCp/dt or dCp/dT, plots which best highlight overlapping Tgs. Four equations are shown to relate the heating rate and the smoothing factor. The equations allow a comparison of data
acquired i) at different heating rates and plotted vs. temperature, ii) at a single heating rate and plotted vs. both time and temperature, i.e., dCp/dt vs. dCp/dT, iii) at different heating rates and plotted vs. both time and temperature, and iv) at different heating rates, and shown exclusively in the time domain. Examples of the use of the equations are provided
for the analysis of bitumen, a complex mixture of natural origin.