Under mild conditions (40 atm O(2), 28 degrees C, 10-15 h), an efficient aerobic oxidation of cycloalkanes to cycloalkanols can be achieved using nanostructured amorphous metals such as Fe and Co and an amorphous alloy like Fe(20)Ni(80) as catalysts. For example, cyclohexane is oxidized to cyclohexanol with 32-41 % conversion, while 1-adamantanol is formed from adamantane with 52-57 % conversion.
In a domino‐type reaction sequence, the redox chemistry of [BnNEt3]2MoS4 is exploited in forming and cleaving disulfides (see scheme). This strategy has been utilized effectively in a one‐pot tandem sulfur transfer/reduction/Michael addition sequence.
The gasoline additive Methyl-tertiary-Butyl Ether (MtBE) is the second most common contaminant of groundwater in the USA and represents an important soil contaminant. This compound has been detected in the groundwater in at least 27 states as a result of leaking underground storage facilities (gasoline storage tanks and pipelines). Since the health effects of MtBE are unclear the potential threat to drinking water supplies is serious. Therefore, the ability to detect MtBE at low levels (ppb) and on-line at high-risk groundwater sites would be highly desirable. This paper reports the use of ‘commercial’ and metal oxide sensor arrays for the detection of MtBE in drinking and surface waters at low ppb level (μg.L−1 range). The output responses from some of the sensors were found to correlate well with MtBE concentrations under laboratory conditions.
Sensors based on composites of metal oxides were fabricated and tested
extensively under high-humidity and high-flow conditions with exposure to
vapours reported to increase in the headspace of wheat grain (Triticum aestivum
cv Hereward) colonized by fungi. The sensors that exhibited high sensitivity to
target vapours combined with high stability were selected for inclusion into a
four-sensor array prototype system. A sampling protocol aligned to parallel gas
chromatography–mass spectrometry and human olfactory assessment studies was
established for use with the sensor system. The sensor system was utilized to
assess irradiated wheat samples that had been conditioned to 25% moisture
content and inoculated with pathogens known to cause spoilage of grain in
storage. These included the fungi Penicillium aurantiogriseum, Penicillium
vulpinum, Penicillium verrucosum, Fusarium culmorum, Aspergillus niger, and
Aspergillus flavus and the actinomycete, Streptomyces griseus. The sensor system
successfully tracked the progress of the infections from a very early stage and
the results were compared with human olfactory assessment panels run
concurrently. A series of dilution studies were undertaken using previously
infected grain mixed with sound grain, to improve the sensitivity and
maximize the differentiation of the sensor system. An optimum set of
conditions including incubation temperature, incubation time, sampling time,
and flow rate were ascertained utilizing this method. The sensor system
differentiated samples of sound grain from samples of sound grain with 1% (w/w)
fungus infected grain added. Following laboratory trials, the prototype
sensor system was evaluated in a commercial wheat grain intake facility.
Thresholds calculated from laboratory tests were used to differentiate between
sound and infected samples (classified by intake laboratory technicians)
collected routinely from trucks delivering grain for use in food manufacture.
All samples identified as having an odour-related problem by the intake
laboratory gave a total system output above the set threshold and were
therefore rejected by the prototype system. A number of samples passed by
the intake laboratory were rejected by the prototype system, resulting
in what appeared to be false positive results. However, the thresholds
were selected on the basis of a limited number of samples and may need
to be adjusted to minimize false positives. The output from the sensor
system was also compared with moisture content values for the wheat
(where available) to demonstrate that the system was not simply measuring
differences in moisture. A separate study (carried out at the intake facility)
assessed 37 newly harvested wheat samples of different varieties and from
different geographic locations within the UK. These samples were analysed
by the sensor system, using the same thresholds as before. Six samples
rejected by the system were then assessed by the wheat intake laboratory,
where only one sample was rejected. This rejected sample had given the
highest output wh...
Wir danken dem Ministerium für Wissenschaft und Kunst (Israel) und dem Ministerium für Wissenschaft und Technologie (New Delhi, Indien) für einen India-Israel research grant.
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