Search results for "Magnesium"

Vanadium complex with tetradentate [O,N,N,O] ligand supported on magnesium type carrier for ethylene homopolymerization and copolymerization

2009

Immobilization of 1,2-cyclohexylenebis(5-chlorosalicylideneiminato)vanadium dichloride on the magnesium support obtained in the reaction of MgCl 2 .3.4EtOH with Et 2 AlCl gives a highly active precursor for ethylene homopolymerization and its copolymerization with 1-octene. This catalyst exhibits the highest activity in conjunction with MAO, but it is also highly active with AlMe 3 as a cocatalyst. On the other hand, when combined with chlorinated alkylaluminum compounds, Et 2 AlCl and EtAlCl 2 , it gives traces of polyethylene. Moreover, its catalytic activity is strongly affected by the reaction temperature: it increased with rising polymerization temperature from 20 °C to 60 °C, The kine…

Organometallic vanadium‐based heterogeneous catalysts for ethylene polymerization. Study of the deactivation process

1998

Slurry polymerizations of ethylene over vanadium catalysts (based on VCl4 and VOCl3) and their MgCl2(THF)2-supported equivalents were studied. Unsupported vanadium catalysts were found to be unstable while the vanadium active sites deposited on the MgCl2(THF)2 complex are stable. A sharply outlined correlation was found between the concentration of vanadium(III) and catalyst productivity. The high activity and stability of the vanadium catalyst when supported on the magnesium complex is attributed to the increase of resistance to reduction of active vanadium(III) to inactive vanadium(II) by an organoaluminium co-catalyst.

Neutral deoxyribonucleases of HeLa S3 cells: electrophoretic separation, characterization, substrate specificity and mode of action.

1980

Extracts of HeLa S3 cells were electrophoresed on polyacrylamide gels; gel slices were eluted and the eluates were assayed for DNase activities against native and denatured DNA substrates in the presence of MgCl2 or Na2EDTA. Aliquots of each eluate were also assayed for their ability to nick the circular supercoiled PM2 phage DNA to distinguish endonucleases from exonucleases. Peaks of endonuclease activities were characterized as forming 3′-phospho-oligonucleotides or 5′-phospho-oligonucleotides by the use of oligonucleotides produced by these enzymes as substrates for the 5′-phosphate-specific snake venom exonuclease. The total activity of DNases in gel eluates was much higher than that i…

Influence of process parameters on the product integrity in friction stir extrusion of magnesium alloys

2016

Friction Stir Extrusion is an innovative direct-recycling technology for metal machining chips. During the process a specifically designed rotating tool is plunged into a cylindrical matrix containing the scraps to be recycled. The stirring action of the tool prompts solid bonding related phenomena allowing the back extrusion of a full dense rod. This process results to be particularly relevant because allows the reuse of the scrap without any previous treatment. Experiments have been carried out in order to investigate the influence of the process parameters on the extrudes quality and a numerical model has been developed in order to simulate the evolution of the material flow.

Microwave harmonic emission in MgB2 superconductor: Comparison with YBA2CU3O7

2006

We report results of microwave second-harmonic generation in ceramic samples of MgB2, prepared by different methods. The SH signal has been investigated as a function of the temperature and the static magnetic field. The results are discussed in the framework of models reported in the literature. We show that the peculiarities of the SH signal are related to the specific properties of the sample. A comparison with the results obtained in ceramic and crystalline YBa2Cu3O7 shows that the second-harmonic emission in MgB2 is weaker than that observed in ceramic YBa2CuO7. (c) 2006 Wiley Periodicals, Inc.

Formability of friction stir welding AZ31 magnesium alloy sheets

2010

Friction Stir Welding of Magnesium Alloys under Different Process Parameters

2010

Calibrated international standards including ATHO-G, T1-G, and VG-568 (USNM 72854)

2021

Assisted phytostabilization of soil from a former military area with mineral amendments.

2019

Abstract Due to the presence of toxic pollutants, soils in former military areas need remedial actions with environmentally friendly methods. Greenhouse experiments were conducted to investigate the aided phytostabilization of multi-heavy metals (HMs), i.e. Cd, Cr, Cu, Ni, Pb, Zn, in post-military soil by Festuca rubra and three mineral amendments (diatomite, dolomite and halloysite). The amendments were applied at 0 and 3.0% to each pot filled with 5 kg of polluted soil. After seven weeks of the phytostabilization, selected soil properties, biomass yield of F. rubra and immobilization of HMs by their accumulation in plant and redistribution among individual fractions in soil were determine…

Crystal field calculations of energy levels of the Ni2+ ions in MgO

2013

Abstract The electronic energy levels of six-fold coordinated Ni 2+ ion in magnesium oxide MgO were calculated using the exchange charge model of crystal field theory. The calculated energetic positions of the Ni 2+ levels match well the experimental spectrum. Inclusion of the spin-orbit (SO) interaction is compulsory to account for the first excited 3 T 2g state fine structure; however, it does not explain why out of four levels arising from the 3 T 2g state, only two are seen in the experimental spectra. One possible explanation to this fact can be advanced by invoking the Jahn–Teller effect.