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Distribution by Scientific Domains

Chemistry	40%

Selected Abstracts

Reconstruction of palaeo-burial history and pore fluid pressure in foothill areas: a sensitivity test in the Hammam Zriba (Tunisia) and Koh-i-Maran (Pakistan) ore deposits

GEOFLUIDS (ELECTRONIC), Issue 2 2003
L. Benchilla
Abstract The burial and pore fluid pressure history of fluorite ore deposits is reconstructed: (i) at Hammam Zriba,Djebel Guebli along the eastern margin of the Tunisian Atlas; and (ii) at Koh-i-Maran within the northern part of the Kirthar Range in Pakistan. Both the deposits are hosted by Late Jurassic carbonate reservoirs, unconformably overlain by Late Cretaceous seals. Microthermometric analyses on aqueous and petroleum fluid inclusions with pressure,volume,temperature,composition (PVTX) modeling of hydrocarbon fluid isochores are integrated with kinematics and thermal 2D basin modeling in order to determine the age of mineralization. The results suggest a Cenozoic age for the fluorite mineralization and a dual fluid migration model for both ore deposits. The PVTX modeling indicates that the initial stage of fluorite cementation at Hammam Zriba occurred under fluid pressures of 115 ± 5 bars and at a temperature close to 130°C. At Koh-i-Maran, the F3 geodic fluorite mineralization developed under hydrostatic pressures of 200 ± 10 bars, and at temperatures of 125,130°C. The late increase in temperature recorded in the F3 fluorites can be accounted for by rapid rise of hotter fluids (up to 190°C) along open fractures, resulting from hydraulic fracturing of overpressured sedimentary layers. [source]

Continuous Flow Radio Frequency Heating of Water and Carboxymethylcellulose Solutions

JOURNAL OF FOOD SCIENCE, Issue 1 2003
Q. Zhong
ABSTRACT Tap water and 1% CMC solutions were heated in a 40.68 MHz, 30 kW continuous flow radio frequency unit. Temperatures at different vertical and radial locations were monitored by fiber optic probes during batch heating of tap water and 1% CMC solution. Temperatures at different locations were similar during batch heating of tap water, while a significant temperature difference was observed for 1% CMC solutions, with the temperature close to the wall being higher than that at the center. Similar trends were observed during continuous heating of tap water and 1% CMC solutions, with Twall > TR/2 > Tcenter for the latter. The observations were a result of different dielectric properties of these 2 fluids, as well as the fluid flow characteristics during continuous heating. [source]

New Biodegradable Amphiphilic Block Copolymers of , -Caprolactone and , -Valerolactone Catalyzed by Novel Aluminum Metal Complexes

MACROMOLECULAR BIOSCIENCE, Issue 9 2005
Jing Yang
Abstract Summary: In our previous study [J. Yang, L. Jia, L. Yin, J. Yu, Z. Shi, Q. Fang, A. Cao, Macromol. Biosci.2004, 4, 1092.], new biodegradable copolymers of diblock methoxy poly(ethylene glycol)- block -poly(, -caprolactone) and methoxy poly(ethylene glycol)- block -poly(, -valerolactone), and triblock poly(, -caprolactone)- block -poly(ethylene glycol)- block -poly(, -caprolactone) and poly(, -valerolactone)- block -poly(ethylene glycol)- block -poly(, -valero-lactone) bearing narrow molecular weight distributions and well-defined block architectures were reported to be prepared with our original aluminum metal complex templates. This work will continue to report new investigations on their water solubility, and reversible thermal responsive micellization and solution to gel transition in distilled water. Among the new synthesized copolymers (P1,P23), seven diblock or triblock samples (P3, P6, P7, P11, P12, P19, and P21) with higher hydrophilic building block populations were revealed to be water soluble under ambient temperature. By means of UV spectrophotometer attached with a thermostat, important parameters as critical micellization mass concentrations (CMCs) and critical micellization temperatures (CMTs) were characterized for these new amphiphile dilute aqueous solution with the aid of an lipophilic organic dye probe of 1,6-diphenyl-1,3,5-hexatriene (DPH). Furthermore, the critical gelation temperatures (CGTs) were simultaneously investigated for these water-soluble block copolymers via a tube tilting method. It was found that the CMC, CMT, and CGT were strongly affected by the population and nature of the hydrophobic building blocks, and a higher hydrophobicity of the new amphiphilic block copolymer finally led to lower CMC and CMT, and higher CGT. In addition, the salts of KBr and NaCl were found to play as a salt-out effect on the solution to gel transition for the diblock P6 and triblock P11, exhibiting an interesting tunable gelation temperature close to 35,42,°C. These results will pave new possibility for the synthesized block structural amphiphiles as potential biomaterials to be applied in vivo. Thermal responsive micellization and gelation of diblock MPEG- b -PCL/PVL and triblock PVL/PCL- b -PEG- b -PCL/PVL. [source]

Phase transitions in ZnTe co-doped with Mg and oxygen

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 5 2007
V. A. Elyukhin
Abstract Self-assembling of 1O4Mg tetrahedral clusters in ZnTe isoelectronically co-doped with Mg and oxygen in the ultra dilute oxygen impurity limit is described by a phase diagram. The occurrence of 1O4Mg clusters is a result of the second-order transition. The final stage of self-assembling when all oxygen impurities are in 1O4Mg clusters has to be reached also as a result of the second-order transition at the temperature close to the temperature of the occurrence of these clusters. The conditions of these phase transitions are obtained. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Microencapsulation of n -Eicosane as Energy Storage Material

CHINESE JOURNAL OF CHEMISTRY, Issue 5 2004
Xiao-Zheng Lan
Abstract For heat energy storage application, polyurea microcapsules containing phase change material, n -eicosane, were synthesized by using interfacial polymerization method with toluene-2,4-diisocyanate (TDI) and diethylenetriamine (DETA) as monomers in an emulsion system. Poly(ethylene glycol)octyl-phenyl ether (OP), a nonionic surfactant, was the emulsifier for the system. The experimental result indicates that TDI was reacted with DETA in a mass ratio of 3 to 1. FT-IR spectra confirm the formation of wall material, polyurea, from the two monomers, TDI and DETA. Encapsulation efficiency of n -eicosane is about 75%. Microcapsule of n -eicosane melts at a temperature close to that of n -eicosane, while its stored heat energy varies with core material n -eicosane when wall material fixed. Thermo-gravimetric analysis shows that core material n -eicosane, micro- n -eicosane and wall material polyurea can withstand temperatures up to 130, 170 and 250 °C, respectively. [source]