Dehydrogenation of methane on supported molybdenum oxides. Formation of benzene from methane

The dehydrogenation of methane on MoO₃ supported on various oxides has been investigated under non-oxidizing conditions in a fixed bed, continuous flow reactor. Detailed measurements were performed with MoC₃/SiO₂. The reaction of methane was observed above 923 K after a significant time lag, when a partial reduction of Mo⁶⁺ occurred, the reduced phase being characterized by X-ray photoelectron spectroscopy (XPS). The initial gaseous products are CO₂, H₂O, H₂ and CO. But this stage is followed by the dehydrogenation of methane and coupling of hydrocarbon fragments to various hydrocarbons. A possible pathway of the formation of benzene, the main product of reaction with selectivities ranging from 26 to 56%, is suggested.     

Aromatization of ethanol on Mo2C/ZSM catalysts

The reaction of ethanol was investigated on Mo₂C, Mo₂C/SiO₂ and Mo₂C/ZSM-5 catalysts at temperature ranging 573–973 K under atmospheric pressure. Mo₂C and Mo₂C/SiO₂ catalyzed only the decomposition of ethanol to H₂, ethylene, acetaldehyde and different hydrocarbons. The main reaction pathway on pure ZSM-5 is the dehydration reaction yielding ethylene, small amounts of hydrocarbons and aromatics. Deposition of Mo₂C on zeolite greatly enhanced the yield of benzene and toluene by catalyzing the aromatization of ethylene formed in dehydration process of ethanol.     

Neuroradiologic methods and findings prior to the surgical treatment of epilepsy in children

Epilepsy in childhood is often caused by morphological abnormalities and is frequently pharmacoresistant. Therefore it represents a challenge to the neuroradiologist because early and accurate diagnosis of abnormal morphology is the basis for planning surgical intervention with a high chance of controlling seizures and a low risk of complications. Both morphological (radiography, CT, MRI and angiography) and functional examinations [intracarotid amobarbital test (IAT)] are essential parts of the presurgical evaluation. In most cases MRI has proved to be most sensitive in detecting lesions except for some calcifications. Routine protocols for brain examinations are not sufficient, missing about 22% of lesions. Therefore a refined MRI and CT protocol is proposed. Even in very young children IAT can be performed at very low risk; these tests contribute highly valuable information about actual hemispheric dominance and other functions in more than 80% of procedures that is indispensable if postoperative neurological and neuropsychological deficits are to be avoided.     

General interpretation of sensitivity functions

A general interpretation of sensitivity functions of linear networks is given in order to determine any nth order sensitivity function with respect to any parameter. The calculation uses an indirect method: ‘transfer function products’ give the desired sensitivities instead of derivation. The interpretation makes it possible to construct a computer program, too, which needs only one matrix inversion for a complete sensitivity analysis (including first- and higher-order sensitivities). It is shown that the adjoint network approach is superfluous and more complicated than the given method.