in the present work, a titanium-based ziegler-natta catalyst was employed to synthesize ultra molecular weight polyethylene in a slurry medium. the effect of different parameters such as ethylene pressure, temperature, catalyst composition, and hydrogen pressure was studied. as the results indicate, increasing either [al]/[ti] ratio or temperature causes polymerization rate to go through a maxi...

New thermal diffusion coefficients of binary mixtures are measured for n-decane-n-alkanes and 1-methylnaphthalene-n-alkanes with 25 and 75 wt % at 25 degrees C and 1 atm using the thermogravitational column technique. The alkanes range from n-pentane to n-eicosane. The new results confirm the recently observed nonmonotonic behavior of thermal diffusion coefficients with molecular weight for bin...

Deposition samples were taken at a height of 2367 m above sea level (m.a.s.l.) on the Island of Tenerife from May 1999 until July 2000 and analysed for 19 polychlorinated biphenyl (PCB) congeners, hexachlorobenzene (HCB), hexachlorocyclohexanes (HCH) and DDTs. This site is located above the inversion layer, so samples represent background concentrations of the free troposphere. The average depo...

A new method for accurately determining stock-tank oil composition to normal pentatriacontane using gas chromatography is developed and validated. The new method addresses the potential errors associated with the traditional equipment and technique employed for extended hydrocarbon gas chromatography outside a controlled laboratory environment, such as on an offshore oil platform. In particular...

Staircase electrophoresis (SCE) in polyacrilamide gels was used to analyze the stable low-molecular weight (LMW) RNA profiles of several propane and butane oxidizing bacteria belonging to different species and genera. Differences in the number and distribution of the RNA bands in these profiles allowed us to differentiate among them. Congruent results were found between the established classifi...

1. The gram molecular weight of a substance may be calculated from the osmotic pressure of its solution. 2. The radius of the hydrated molecule and, hence, the gram molecular volume of the hydrated solute may be determined from diffusion measurements. The hydration of the molecules may, therefore, be calculated from osmotic pressure and diffusion measurements. 3. Hydration may also be determine...

Mate finding and courtship involve complex interactions that require close coordination between individuals of the opposite gender. Well-organized signalling systems, sometimes involving a combination of signal modalities, are required to convey species-specific and individual information to members of the opposite gender. Previous studies of psyllids have focused on single-signal modalities an...

The fragmentation of normal alkanes during the cracking oil under geochemical conditions with high thermal stress is important for preservation crude oils in reservoirs and formation gaseous hydrocarbons. In this study, kinetics behavior, mechanisms, products n-tetradecane pyrolysis were investigated using reactive molecular dynamics (ReaxFF MD) simulations at temperatures (2000K∼3000 K). proce...

The reactions of allylic radicals have the potential to play a critical role in molecular weight growth (MWG) kinetics during hydrocarbon oxidation and/or pyrolysis. Due to their stability (when compared to alkyl radicals), they can accumulate to relatively high concentrations. Thus, even though the rate coefficients for their various reactions are small, the rates of these reactions may be sig...

Geometries, relative stabilities, electronic excited states, atomic charges, and electronic dipole polarizabilities of dimethylnaphthalene (DMN) isomers have been calculated in gas and aqueous phases by ab initio and DFT methods. At the highest levels of calculation, alpha,alpha-DMN (2,6-DMN, 2,7-DMN, and 2,3-DMN) are the lowest energy isomers, while 1,8-DMN is the less stable by 7-8 kcal mol(-...