Home About us Contact
|
Home About us Contact | ||
|
|
||
Commercial Grade (commercial + grade)
Selected AbstractsHistopathological effects in tissues of snail Lymnaea stagnalis (Gastropoda, Pulmonata) exposed to sublethal concentration of Thiodan® and recovery after exposureJOURNAL OF APPLIED TOXICOLOGY, Issue 6 2005Erhan Ünlü Abstract Histopathological alterations induced by Thiodan® in three tissues, namely, digestive gland, foot and mantle, of the freshwater snail Lymnaea stagnalis were investigated. Specimens of Lymnaea stagnalis were exposed to 0.36% and 0.72% Thiodan® 35 EC, a commercial grade of endosulfan, for 96 h followed by a recovery period of 30 days. Thiodan® caused significant dose dependent histopathological changes in all the tissues of the snail. Irreversible necrotic changes occurred in the digestive gland of the snail following Thiodan® exposure. Degenerative changes in the muscle fiber of the foot, protein and pigment cells of the foot and the connective tissue element of the mantle were recovered after 30 days of recovery of the snail in pesticide-free freshwater. Copyright © 2005 John Wiley & Sons, Ltd. [source] New Route for the Extraction of Crude Zirconia from ZirconJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2002Nicholas J. Welham A commercial grade of zircon (ZrSiO4) concentrate was mechanically milled with MgO for up to 100 h in a laboratory-scale mill. The resultant powders were subjected to thermal processing, chemical leaching, and X-ray diffraction (XRD). There was no direct evidence of reaction during the milling step, with no new phases evident from XRD. Leaching of the powder showed that a reaction had occurred, and increased solubility with milling time was attributed to the formation of a nanostructured Mg-Zr-Si oxide, which dissolved congruently. Heating the powders resulted in a number of thermal events, including the formation/crystallization of ZrO2 and Mg2SiO4. Thermal treatment of the milled powders allowed selective chemical leaching of the magnesium and silicon, leaving a powder containing ,90% ZrO2. [source] Comparison of Tensile and Compressive Creep Behavior in Silicon NitrideJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2000Kyung Jin Yoon The creep behavior of a commercial grade of Si3N4 was studied at 1350° and 1400°C. Stresses ranged from 10 to 200 MPa in tension and from 30 to 300 MPa in compression. In tension, the creep rate increased linearly with stress at low stresses and exponentially at high stresses. By contrast, the creep rate in compression increased linearly with stress over the entire stress range. Although compressive and tensile data exhibited an Arrhenius dependence on temperature, the activation energies for creep in tension, 715.3 ± 22.9 kJ/mol, and compression, 489.2 ± 62.0 kJ/mol, were not the same. These differences in creep behavior suggests that mechanisms of creep in tension and compression are different. Creep in tension is controlled by the formation of cavities. The cavity volume fraction increased linearly with increased tensile creep strain with a slope of unity. A cavitation model of creep, developed for materials that contain a triple-junction network of second phase, rationalizes the observed creep behavior at high and low stresses. In compression, cavitation plays a less important role in the creep process. The volume fraction of cavities in compression was ,18% of that in tension at 1.8% axial strain and approached zero at strains <1%. The linear dependence of creep rate on applied stress is consistent with a model for compressive creep involving solution,precipitation of Si3N4. Although the tensile and compressive creep rates overlapped at the lowest stresses, cavity volume fraction measurements showed that solution,precipitation creep of Si3N4 did not contribute substantially to the tensile creep rate. Instead, cavitation creep dominated at high and low stresses. [source] Scratch properties of poly(methyl methacrylate) surfaces: The time-temperature dependence of friction and hardnessLUBRICATION SCIENCE, Issue 3 2002C. Gauthier Abstract Viscoelastic-viscoplastic behaviour is usually not taken into account in models describing the scratch properties of polymeric surfaces. In the case of a standard indentation test with stationary tip, the elastic-plastic boundary and the boundary of the region being subjected to hydrostatic pressure beneath the tip are understood. Such well-known models have been used in this study to understand the geometry of the groove left on the surface of a viscoelastic-viscoplastic body by a moving diamond tip. A new apparatus was built that can control the velocity of the tip over the range 1 ,m/s to 15 mm/s, at several different temperatures from ,10 to +100°C. The material used was a commercial grade of cast poly(methyl methacrylate) (PMMA). The normal and tangential loads and groove size were used to evaluate the dynamic hardness, which behaved like a stress- and temperature-activated process. The values for the activation energy and volumes of the dynamic hardness and of the interfacial shear stress were in good agreement with the mechanical properties usually attributed to PMMA. [source] Interaction between aqueous solutions of polymer and surfactant and its effect on physicochemical propertiesASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2008Mohammad Yunus Khan Abstract Interaction between water-soluble polymers and anionic surfactants has been studied by surface tension and conductivity measurements. Sodium dodecyl sulfate (SDS) and sodium dodecylbenzene sulfonate (SDBS) were used as surfactant while polyacrylamide (PAA), commercial grade partially hydrolyzed polyacrylamide (PHPA), and xanthan gum were used as water-soluble polymers for the present study. The behavior of surfactant,polymer interaction was found to be dependent on both surfactant and polymer concentrations. After the critical aggregation concentration (CAC), interaction between the water-soluble polymer and surfactants was started and above the polymer saturation point (PSP) polymer was saturated by surfactant with no further change of surface tension and conductivity of the solution. It has also been found that alkali (NaOH) and salts (Na2CO3, NaCl) have significant influence on the polymer,surfactant interaction. Copyright © 2008 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Composition and organoleptic characteristics of oil from Arbequina olive (Olea europaea L) trees under deficit irrigationJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 15 2002J Tovar Abstract This study evaluated the effects of different regulated deficit irrigation (RDI) strategies applied to olive (Arbequina cultivar) trees on the qualitative and quantitative parameters of the resulting oil during the maximum evaporative demand period for three consecutive crop seasons. Quality indices, fatty acid composition, pigments, colour, ,-tocopherol and phenolic contents, bitter index, oxidative stability and organoleptic properties of the oil were determined. Irrigation did not affect those parameters used as criteria for classifying olive oil in its commercial grades. Only polyphenol and o -diphenol contents and, consequently, the bitter index and oxidative stability were affected by the RDI strategy, with increasing values as the water applied decreased. Regulated deficit irrigation resulted in important savings in irrigation requirements without detriment to oil quality. © 2002 Society of Chemical Industry [source] | ||||||||||