The determination of ammonia in flue gas from the selective catalytic reduction of nitric oxide with ammonia

The emission of NO_x from coal-fired boilers can be limited by means of the selective catalytic reduction of NO_x with ammonia. The amounts of unreacted ammonia downstream should be low to avoid processing and environmental problems. Continuous measurement of the ammonia in the flue gas is needed. The determination of ammonia and flue gas sampling techniques are discussed. Measurements of ammonia in exhausts of a laboratory reactor and of a pilot plant for the selective catalytic reduction of NO_x with ammonia are presented. Ammonia was determined by mass spectrometry and chemiluminescence in the gas phase, and by spectrophotometric (Nessler and Berthollet reactions) or potentiometry in aqueous solution, in low (<5 μl l^?1) and high (<1000 μl l^?1) concentration ranges.     

Furanosyl Oxocarbenium Ion Stability and Stereoselectivity

Lewis acid mediated substitution reactions using [D]triethylsilane as a nucleophile at the anomeric center of the four pentofuranoses, ribose, arabinose, xylose, and lyxose, all proceed with good to excellent stereoselectivity to provide the 1,2‐cis adducts. To unravel the stereoelectronic effects underlying the striking stereoselectivity in these reactions we have mapped the energy landscapes of the complete conformational space of the oxocarbenium ions of the four pentofuranoses. The potential energy surface maps provide a detailed picture of the influence of the differently oriented substituents and their mutual interactions on the stability of the oxocarbenium ions and the maps can be used to account for the observed stereoselectivities of the addition reactions.     

Quantum-electrodynamics without renormalization : IV. Comparison with renormalized quantum-electrodynamics

The generalised function method is shown to be equivalent up to a finite renormalization with standard quantum-electrodynamics (QED). The result is a theory which is complete in a physical sense. A comparison with standard renormalisation theory is given.     

Heritability of Stroop and flanker performance in 12-year old children

Background  

There is great interest in appropriate phenotypes that serve as indicator of genetically transmitted frontal (dys)function, such as ADHD. Here we investigate the ability to deal with response conflict, and we ask to what extent performance variation on response interference tasks is caused by genetic variation. We tested a large sample of 12-year old monozygotic and dizygotic twins on two well-known and closely related response interference tasks; the color Stroop task and the Eriksen flanker task. Using structural equation modelling we assessed the heritability of several performance indices derived from those tasks.     

The contribution of high frequencies to human brain activity underlying horizontal localization of natural spatial sounds

Background  

In the field of auditory neuroscience, much research has focused on the neural processes underlying human sound localization. A recent magnetoencephalography (MEG) study investigated localization-related brain activity by measuring the N1m event-related response originating in the auditory cortex. It was found that the dynamic range of the right-hemispheric N1m response, defined as the mean difference in response magnitude between contralateral and ipsilateral stimulation, reflects cortical activity related to the discrimination of horizontal sound direction. Interestingly, the results also suggested that the presence of realistic spectral information within horizontally located spatial sounds resulted in a larger right-hemispheric N1m dynamic range. Spectral cues being predominant at high frequencies, the present study further investigated the issue by removing frequencies from the spatial stimuli with low-pass filtering. This resulted in a stepwise elimination of direction-specific spectral information. Interaural time and level differences were kept constant. The original, unfiltered stimuli were broadband noise signals presented from five frontal horizontal directions and binaurally recorded for eight human subjects with miniature microphones placed in each subject's ear canals. Stimuli were presented to the subjects during MEG registration and in a behavioral listening experiment.