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Endothermic Peaks (endothermic + peak)
Selected AbstractsDC conductivity studies in K3Na(SeO4)2 single crystalsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 7 2009G. Joseph Abstract DC electrical conductivity studies were carried out along the three crystallographic axes for Tripotassium sodium diselenate (K3Na(SeO4)2 or KNSe). Earlier studies of phase transition in this crystal show successive phase transitions at 334 K, 346 K, 730 K, and 758 K. In this paper we report the dc electrical conductivity measurements in the temperature region 303 K , 430 K along a, b and c , axes. An anomaly in conductivity was obtained around 341 K and another one around 333 K. These can be attributed as due to phase transitions in this crystal. A strong anomaly also has been observed along the c-axis and comparatively week one along a and b axes around 395 K for the first time. This can be due to newly observed phase transition in the crystal. DSC taken for the sample also shows endothermic peak supporting the occurrence of newly observed phase transition. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Comparative Structural, Emulsifying, and Biological Properties of 2 Major Canola Proteins, Cruciferin and NapinJOURNAL OF FOOD SCIENCE, Issue 3 2008J. Wu ABSTRACT:, Canola is an economically important farm-gate crop in Canada. To further explore the potential of canola protein as value-added food and nutraceutical ingredients, a better understanding of fundamental properties of 2 major canola proteins is necessary. Two major protein components, cruciferin and napin, were isolated from defatted canola meal by Sephacryl S-300 gel filtration chromatography. SDS-PAGE showed that cruciferin consists of more than 10 polypeptides, and noncovalent links are more important than disulphide bonds in stabilizing the structural conformation. Napin consists of 2 polypeptides and is stabilized primarily by disulphide bonds. Purified cruciferin showed 1 major endothermic peak at 91 °C compared with that of 110 °C for napin. Emulsion prepared by cruciferin showed significant higher specific surface area and lower particle size than that of napin. The study indicated that the presence of napin could detrimentally affect the emulsion stability of canola protein isolates. Hydrolysates from cruciferin and napin showed potent angiotensin I-converting enzyme inhibitory activity (IC50: 0.035 and 0.029 mg/mL, respectively), but weaker than that of canola protein isolate hydrolysate (IC50: 0.015 mg/mL). [source] Effects of Arabinoxylans on Thermal Behavior of Frozen Wheat Doughs as Measured by DSC, DMA, and DEAJOURNAL OF FOOD SCIENCE, Issue 1 2002T. J. Laaksonen ABSTRACT: The effects of water extractable arabinoxylans (WEA) on physical state of frozen wheat dough with added sucrose, NaCl, and their mixture were investigated using DSC, DMA, and DEA. DSC thermograms were obtained for annealed samples, and they showed only an endothermic peak of ice melting. Annealed samples were also analyzed using DMA and DEA with both dynamic heating and isothermal steps. Added sucrose and NaCl decreased the onset temperature of ice melting and it decreased with increasing WEA concentration. Isothermal measurements showed an a-relaxation peaks, taken as the Tg,. Added NaCl had a great depressing effect on the Tg, at low frequencies as measured by DEA. [source] DTG thermal analyses and viscosity measurements of three commercial agar impression materialsJOURNAL OF ORAL REHABILITATION, Issue 7 2002M. Taira Three commercial agar impression materials, two for clinical uses and one for dental laboratory, were examined for their thermal properties by differential thermogravimetric (DTG) thermal analyses and viscosity measurements. On DTG profiles, an endothermic peak along with weight loss at around 100 °C was observed on all three agar impression materials as a result of water evaporation. Two clinical agar impression materials were more susceptible to this trend than the remaining one dental laboratory agar impression material. The viscosity of three agar impression materials could be expressed in the exponential function of temperature. Viscosity at 46 °C of one dental laboratory agar impression material far exceeded those of two clinical agar impression materials. Monitoring the viscosity could facilitate the detailed analysis of setting process of agar impression materials upon cooling, and might be useful for future development of agar-based dental impression materials. [source] Synthesis and characterization of new alternating, amphiphilic, comblike copolymers of poly(ethylene oxide) macromonomer and N -phenylmaleimideJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 3 2005Luminita Cianga Abstract A surface-active p -vinyl benzyloxy-,-hydroxy-poly(ethylene oxide) macromonomer containing 22 pendant structural units of ethylene oxide (St,PEO22) was synthesized with an initiation method. Because of its solubility in a large variety of solvents, the free-radical copolymerization with electron-acceptor N -phenylmaleimide (NPMI) was performed at 60 °C in benzene and tetrahydrofuran (THF) as isotropic media and in a water,THF mixture or water as a heterogeneous medium. Oil-soluble 2,2,-azobisisobutyronitrile and water-soluble 4,4,-azobis(4-cyanovaleric acid) were used as the initiators at fixed concentrations. Two different St,PEO22/NPMI comonomer ratios (1/1 and 3/7) at a fixed total comonomer concentration in the polymerization system were used. The structures, compositions, and microstructure peculiarities of the obtained alternating, amphiphilic, comblike copolymers were determined by NMR analysis. For the copolymers synthesized in hydrophilic media, differential scanning calorimetry showed, near the endothermic peak attributed to the melting of the poly(ethylene oxide) side chains, the presence of a second peak due to the partially ordered phase that could exist between the crystalline state and the isotropic melt. Also, the thermal stability of the obtained copolymers was studied with thermogravimetric analysis. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 479,492, 2005 [source] Synthesis, characterization and impedance spectroscopy of the new material [(CH3) (C6H5) 3P] 2CoBr4: a member of the A2BX4 familyCRYSTAL RESEARCH AND TECHNOLOGY, Issue 5 2008M. F. Mostafa Abstract The crystal structure of bis-(methyltriphenylphosphonium) tetrabromocobaltate (II), [(C19H18P)2 CoBr4] is determined: Mr = 933.203, monoclinic, P21, a = 9. 6977 (3) Å, b = 12.5547 (4)Å, c = 16.4503 (6)Å, , = 105.603 (2)°, V = 1929.04 (11)Å3, Z = 2, Dx = 1.607 Mg m -3, T = 298 K. Differential thermal analysis at high temperatures shows three endothermic peaks characterizing four phases, with onset temperatures at T1= 313±2 K, T2 = 320±4 K and T3= 360±1 K. The structural instability detected via the temperature dependence of permittivity at T1 is ascribed to order-disorder transition associated with cation dipole reorientation. Permittivity and ac conductivity studies as a function of temperature (295 K-375 K) and frequency (0.11 kHz < f <100 kHz) are presented. The results indicate the importance of the cation size and shape on the phase transitions in the system. Bulk conductivity behavior is thermally activated. The associated activation energies are in the range 2.9 to 1.0 eV depending on the temperature regime. Two contributions to the ac conductivity, one dominating at low temperatures and high frequencies which are characterized by superlinear frequency exponent and the second dominates at high temperatures characterized by a sublinear frequency exponent. The behavior is interpreted in terms of the jump relaxation model. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Compatibilization method applied to the chitosan-acid poly(L -lactide) solutionJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010Nugraha Edhi Suyatma Abstract We are testing the compatibilization of the chitosan/PLA blends by addition of diisocyanate and at studying the effect of several MDI concentrations (0.5 and 2.5% of the global blend mass, w/w). To evaluate the MDI efficiency as a compatibilizer of chitosan/PLA blends, we worked with the following methods: IRTF spectra with higher peak at 1558 cm,1 is due to the NH bonds that exist in urea and urethane, thermal properties shows that the temperature of the endothermic peaks of the chitosan/PLA blends with MDI is very close to the temperature of pure chitosane and SEM micrography shows that MDI addition decreases the PLA particles size in the chitosan mixture; they also comply with the compatibilization theory. After that the mechanical properties have been characterized: we can notice that the MDI compatibilized chitosan/PLA blends have a higher Young's modulus than the noncompatibilized blends. we are showed that the use of 0.5% MDI is not enough sufficient to obtain a compatibilization, because a part of the MDI can be consumed by water. The addition of MDI increases the performance of the mechanical properties of the blends. Therefore, with this compatibilization, we could obtain some chitosan/PLA blends that would be water-resistant and that would also keep their mechanical properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Heating of ,-Lactoglobulin A Solution in a Closed System at High TemperaturesJOURNAL OF FOOD SCIENCE, Issue 5 2001S. Photchanachai ABSTRACT ,-Lactoglobulin A solution at pH 6.4 was heated to 180 °C at the rate of 6 °C/min. By differential scanning calorimetry two independent endothermic peaks were observed. The first peak appeared below 100 °C is corresponded to the thermal denaturation of protein. This conformational change led to the aggregation and polymerization of molecules through disulfide linkage, particularly observed above 100 °C. The second endothermic peak appeared around 150 °C, which was brought by the decomposition of molecules as judged from electrophoresis. Up to 100 °C the viscosity of ,-lactoglobulin A solution increased by heating, while the viscosity was reduced beyond 113 °C, due to change in the size of aggregate and decomposition of ,-lactoglobulin A molecules. [source] High-Temperature Crystalline Phases in Nylon 6/Clay NanocompositesMACROMOLECULAR RAPID COMMUNICATIONS, Issue 13 2005Xiaohui Liu Abstract Summary: Nylon 6/clay nanocomposites (N6CN) with different cooling histories were investigated by differential scanning calorimetry (DSC) and variable-temperature X-ray diffraction (XRD). Above the melting temperature, new endothermic peaks appeared in the DSC trace for N6CN. All the neat nylon 6 samples presented amorphous XRD patterns when heated up to the melting range. However, for N6CN samples, undefined crystalline structures remained in the substantially molten polymer matrix up to 300,°C. XRD patterns of a quenched nylon 6 sample annealed at 210,°C and N6CN samples annealed at 210, 230, and 300,°C, respectively. [source] Solid-state structure and formation of organized molecular films of methacrylate copolymers containing fluorinated and hydrogenated side-chainsPOLYMER ENGINEERING & SCIENCE, Issue 4 2007Atsuhiro Fujimori Surface morphology of monolayers related to solid-state structure for methacrylate comb copolymers having fluorocarbon and hydrocarbon side-chains was investigated by X-ray diffraction (XRD), differential scanning calorimetry, and atomic force microscopy (AFM). From the XRD profiles, two kinds of short spacing peaks were confirmed at 5.0 and 4.2 Å, which assigned the sub-cells for both side-chains. Furthermore, two kinds of endothermic peaks, which corresponded to melting peaks of the both side-chain crystals, appeared in the thermograms. From the AFM observation, it was found that there were hydrogenated domains at a few hundred nanometer diameter in their monolayers, whereas corresponding acrylate copolymer monolayers form the phase-separated structure at 10,30 nm order scales. POLYM. ENG. SCI., 47:354,364, 2007. © 2007 Society of Plastics Engineers. [source] Enthalpy relaxation of bovine serum albumin and implications for its storage in the glassy state,BIOPOLYMERS, Issue 2 2005Asgar Farahnaky Abstract Two endothermic peaks could be observed for five commercial samples of bovine serum albumin (BSA). The smaller peak observed by differential scanning calorimetry (DSC) corresponded to enthalpy relaxation. This peak was followed on storage of BSA, in its glassy state, after it had been heated above its denaturation temperature. Enthalpy and peak temperature increased with duration of storage. On storage for one week at 60°C, a sample at 8.3% moisture showed a peak at 100°C with an energy value of approximately 2 J per g protein. BSA samples were heated within the DSC sufficiently to eliminate the lower enthalpy peak but without altering the denaturation enthotherm. The amount of physical aging shown by these BSA samples was similar to that of the heat-denatured samples. It was concluded that the heating endotherms of dry BSA reflect both the storage and thermal history of the sample. Possible implications of the enthalpy relaxation of BSA on the behavior of this important protein are considered. © 2005 Wiley Periodicals, Inc. Biopolymers 78: 69,77, 2005 [source] | |||||||||||||