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Point Temperature (point + temperature)

Distribution by Scientific Domains

Chemistry	71%
Polymers and Materials Science	28%

Kinds of Point Temperature

cloud point temperature

Selected Abstracts

Prediction of Flash Point Temperature of Pure Components Using a Quantitative Structure,Property Relationship Model

MOLECULAR INFORMATICS, Issue 6 2008
Farhad Gharagheizi
Abstract In this work, a general Quantitative Structure,Property Relationship (QSPR) model (, , and ) for the prediction of flash points of 1030 pure compounds is developed. Genetic Algorithm-based Multivariate Linear Regression (GA-MLR) technique is used to select four chemical structure-based molecular descriptors from a pool containing 1664 molecular descriptors. [source]

The RadA protein from a hyperthermophilic archaeon Pyrobaculum islandicum is a DNA-dependent ATPase that exhibits two disparate catalytic modes, with a transition temperature at 75 °C

FEBS JOURNAL, Issue 4 2000
Maria Spies
The radA gene is an archaeal homolog of bacterial recA and eukaryotic RAD51 genes, which are critical components in homologous recombination and recombinational DNA repair. We cloned the radA gene from a hyperthermophilic archaeon, Pyrobaculum islandicum, overproduced the radA gene product in Escherichia coli and purified it to homogeneity. The purified P. islandicum RadA protein maintained its secondary structure and activities in vitro at high temperatures, up to 87 °C. It also showed high stability of 18.3 kcal·mol,1 (76.5 kJ·mol,1) at 25 °C and neutral pH. P. islandicum RadA exhibited activities typical of the family of RecA-like proteins, such as the ability to bind ssDNA, to hydrolyze ATP in a DNA-dependent manner and to catalyze DNA strand exchange. At 75 °C, all DNAs tested stimulated ATPase activity of the RadA. The protein exhibited a break in the Arrhenius plot of ATP hydrolysis at 75 °C. The cooperativity of ATP hydrolysis and ssDNA-binding ability of the protein above 75 °C were higher than at lower temperatures, and the activation energy of ATP hydrolysis was lower above this break point temperature. These results suggest that the ssDNA-dependent ATPase activity of P. islandicum RadA displays a temperature-dependent capacity to exist in two different catalytic modes, with 75 °C being the critical threshold temperature. [source]

Spectroscopic and Thermal Properties of Ga2S3,Na2S,CsCl Glasses

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2006
Luiz C. Barbosa
The synthesis and properties of the vitreous system (0.75,x)Ga2S3,0.25Na2S,xCsCl, with x varying from 0.1 to 0.2, are presented. Thermal, optical, and structural properties such as density, viscosity, thermal expansion coefficient, glass transition temperature, softening point temperature, refractive index, and absorption coefficient were measured using several techniques: X-ray diffraction, Raman scattering, differential thermal analysis, thermal mechanical analysis, and absorption spectroscopy. This glass system presents a high third-order non-linear optical susceptibility that can be significantly increased by increasing the CsCl content without affecting the low phonon frequency. [source]

Effects of additives on surfactant phase behavior relevant to bacteriorhodopsin crystallization

PROTEIN SCIENCE, Issue 12 2006
Bryan W. Berger
Abstract The interactions leading to crystallization of the integral membrane protein bacteriorhodopsin solubilized in n-octyl-,-D-glucoside were investigated. Osmotic second virial coefficients (B22) were measured by self-interaction chromatography using a wide range of additives and precipitants, including polyethylene glycol (PEG) and heptane-1,2,3-triol (HT). In all cases, attractive protein,detergent complex (PDC) interactions were observed near the surfactant cloud point temperature, and there is a correlation between the surfactant cloud point temperatures and PDC B22 values. Light scattering, isothermal titration calorimetry, and tensiometry reveal that although the underlying reasons for the patterns of interaction may be different for various combinations of precipitants and additives, surfactant phase behavior plays an important role in promoting crystallization. In most cases, solution conditions that led to crystallization fell within a similar range of slightly negative B22 values, suggesting that weakly attractive interactions are important as they are for soluble proteins. However, the sensitivity of the cloud point temperatures and resultant coexistence curves varied significantly as a function of precipitant type, which suggests that different types of forces are involved in driving phase separation depending on the precipitant used. [source]

Cloud point extraction combined with electrothermal vaporization inductively coupled plasma mass spectrometry for the speciation of inorganic selenium in environmental water samples

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 19 2006
Beibei Chen
A new method based on cloud point extraction (CPE) separation and electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICPMS) detection has been proposed for the speciation of inorganic selenium in environmental waters. When the temperature of the system is higher than the cloud point temperature (CPT) of the selected surfactant Triton X-114, the complex of Se(IV) with ammonium pyrrolidine dithiocarbamate (APDC) seems to be extracted into the surfactant-rich phase, whereas the Se(VI) remains in aqueous solutions. Thus, an insitu separation of Se(IV) and Se(VI) could be realized. The concentrated analyte was introduced into the ETV-ICP mass spectrometer for determination of Se((IV) after dilution with 200,µL methanol. Se(VI) was reduced to Se(IV) prior to determining total selenium, and its assay was based on subtracting Se(IV) from total selenium. The main factors affecting the CPE and the vaporization behavior of the analyte were investigated in detail. Under the optimized experimental conditions, the limit of detection (LOD) for Se(IV) was 8.0,ng/L with an enhancement factor of 39 when 10,mL of sample solution was preconcentrated to 0.2,mL. The relative standard deviation (RSD) was found to be 3.9% (CSe(IV),=,1.0,µg/L, n,=,7). The proposed method was applied to the speciation of inorganic selenium in different environmental water samples with the recovery for the spiked samples in the range of 82,102%. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Thermo-Responsive Organic/Inorganic Hybrid Hydrogels based on Poly(N -vinylcaprolactam)

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 1 2003
Wouter Loos
Abstract A new type of ,intelligent' hydrogels has been developed in the form of organic/inorganic hybrid materials by making use of the sol-gel technology. Poly(N -vinylcaprolactam) (PVCL) has been incorporated in these materials for its thermo-responsive properties. The synthesis of the hybrid hydrogels was achieved by the in situ formation of an inorganic silica phase in the presence of an aqueous solution of high molecular weight PVCL. This methodology results in the preparation of micro-heterogeneous systems in which silica particles of nanometer dimensions act as physical cross-links for the PVCL molecules. Hydrogen bonds between the remaining non-condensed silanol groups and the PVCL carbonyl functions, together with physical entanglements, are responsible for the strong interactions between the organic and inorganic phases. Stress-strain tests on highly swollen materials demonstrated that the unique structure of these thermo-responsive hybrid hydrogels improves the mechanical stability to a great extent as compared to conventional hydrogels. Transmission measurements demonstrate that the presence of the inorganic phase does not influence the cloud point temperatures of PVCL significantly. On the other hand, the response of the reinforced hybrid hydrogels to temperature becomes less pronounced for increasing silica fractions. The reversibility of the swelling/deswelling process has been demonstrated by swelling experiments as a function of temperature. PVCL/SiO2 hybrid hydrogels. [source]