Effective and Green Synthesis of Methyl Pyrrole-1-carboxylate with Dimethyl Carbonate Over Solid Base

The methyl pyrrole-1-carboxylate (1-MPC) was synthesized by highly selective one-pot N-methoxycarbonylation of pyrrole with dimethyl carbonate (DMC). Solid bases were found to be effective catalysts and the formation of 1-MPC was closely related to their basicity. The in-situ FTIR indicated that the role of solid base catalysts was to activate pyrrole via the formation of O–H bond and the weakening of N–H bond, which was attributed to the interaction between pyrrole and surface oxygen anion of solid base. Furthermore, the reaction temperature and the reactants molar ratio were found to be the main factors for the improvement of pyrrole conversion.     

Neurite outgrowth of PC12 cells is suppressed by wortmannin, a specific inhibitor of phosphatidylinositol 3-kinase

The effects of wortmannin (WT), an inhibitor of phosphatidylinositol (PI) 3-kinase, on differentiation of PC12 cells were analyzed. WT inhibited PI 3-kinase activity of PC12 cells at a concentration of 10(-7) M in vivo and in vitro. Transient inhibition of PI 3-kinase activity at the time of nerve growth factor stimulation had no effect on activation of the ras protein or neurite formation by the cells. However, continuous inhibition of PI 3-kinase blocked differentiation at the step just before neurite formation. When WT was applied to cells growing neurites, elongation of the neurites was stopped at that step. These results suggest that PI 3-kinase may be involved in neurite elongation.     

Analysis of thermal residual stress in a thick-walled ring of duralcan-base Al-SiC functionally graded material

A ring-cutting test and an elastic theory were applied to evaluate the macroscopic residual stress in a thick-walled ring made of Al-SiC functionally graded material (FGM). The FGM ring specimens, with outer diameter 90 mm, radial thickness approximately 8.4 to 10 mm, and width 30 mm, were fabricated by the centrifugal casting method from an ingot of Duralcan F3D.20S of Al-20 vol pct SiC master composite. Because of a difference in centrifugal forces of SiC particles and of molten aluminum alloy, the rings had a graded composition of SiC particles in the radial direction. The volume fractions of SiC particles in each ring specimen varied in the range of 0 to 43 vol pct from the inner to the outer surface of the ring, depending on the applied mold spin speed. A ring diametral compression test was performed to validate an analytical formula based on the curved beam theory that can account for the graded properties of the material. Excellent agreement between the theory and the experiment was found. The residual stress was found to be generated by a cooling of Δt=140 K, which was from half the melting point corresponding stress-free condition to the ambient temperature. The hoop residual stresses in the FGM ring varied in the range of −50 to +35 MPa and from tension at the inner surface to compression at the outer surface because of the graded composition. With an increase in wall thickness and/or composition gradation, the residual stresses were found to increase.     

New field-effect transistor with quantum wire and modulation-dopedheterostructures

A new field-effect transistor, consisting of an AlGaAs/GaAs heterostructure and an (AlAs)_0.25(GaAs)_0.75 vertical superlattice, is fabricated. It has a large transconductance of 14 mS/mm at a gate length of 250 μm, corresponding to a transconductance of 3.5 S/mm for 1 μm gate length. Hall measurement revealed a novel FET operation mode called `velocity modulation'     

The high performance liquid chromatographic determination of total malondialdehyde in vegetable oil with dansyl hydrazine

A simple high-performance liquid chromatographic (h.p.l.c.) method has been developed for determining total malondialdehyde (MDA), including free MDA and MDA released from its precursor in vegetable oils. Free MDA was reacted with dansyl hydrazine in an acidic medium, and the product, 1-dansyl-pyrazole(DP), was determined by h.p.l.c. The reaction releasing MDA from its precursor requires Fe³⁺ in 5% hydrochloric acid medium. Recoveries of free MDA and tetramethoxypropane (used as an MDA precursor) in vegetable oils were satisfactory. During autoxidation, a remarkable difference between the DP values of methyl oleate, methyl linoleate and some vegetable oils, and that of methyl linolenate was observed. Only methyl linolenate released MDA during autoxidation. For autoxidised methyl linolenate the DP value correlated with the thiobarbituric acid(TBA) value, although the DP value was only 30% of the TBA value.     

Effects of phenol on the properties of pitch produced thermally from the petroleum vacuum residue

A petroleum vacuum residue was thermally treated at 430 °C, with continuous addition of phenol to either the vapour phase or the liquid phase of the reacting system. Addition of phenol to the vapour phase increased the yield of the cracked oil and the fixed carbon of the residual pitch. When phenol was charged to the liquid phase, the yield of the oil remained unchanged, but the amount of the benzeneinsoluble matter in the pitch decreased, probably owing to the inhibition by phenol of the polymerization-condensation reactions of aromatic compounds. In both additions the cracked oil had a higher boiling point than that produced without phenol. Substitution of phenol with methyl groups increased the extent of cracking and coking properties (Roga Index) of the pitch. The effective order of phenol and its derivatives is: Phenol < m-Cresol < o-Cresol < p-Cresol < 2, 4-Dimethylphenol < 2, 6-Dimethylphenol < 2, 4, 6-Trimethylphenol Polyhydric phenol, e.g. catechol, and naphthol also enhanced the cracking reactivity of the residue.