Buchbesprechungen

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Book reviews

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Notices bibliographiques

     

Buchbesprechungen

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Photochemische Reaktionen. 89. Mitteilung [1]. Zur Photochemie konjugierter Epoxy-diene I. Versuche mit (E),β-Jonyliden-epoxiden

Photolysis of conjugated epoxy-dienes UV.-irradiation (λ = 254 nm) of (E),β-ionylidene-epoxide ( 3 ) in n-pentane gives the isomeric cyclopropene-ketone 7 (90%) in a hitherto unreported type of photoreaction. The methylsubstituted (E),β-ionylidene-epoxide 6 , however, undergoes (E/Z)-photoisomerization to the (Z),β-ionylidene-epoxide 8 (91%).     

Messung von Positronstrahlern in kosmischen Staubproben

Ohne Zusammenfassung     

Robust polarization-based quantum key distribution over a collective-noise channel

We present two polarization-based protocols for quantum key distribution. The protocols encode key bits in noiseless subspaces or subsystems and so can function over a quantum channel subjected to an arbitrary degree of collective noise, as occurs, for instance, due to rotation of polarizations in an optical fiber. These protocols can be implemented using only entangled photon-pair sources, single-photon rotations, and single-photon detectors. Thus, our proposals offer practical and realistic alternatives to existing schemes for quantum key distribution over optical fibers without resorting to interferometry or two-way quantum communication, thereby circumventing, respectively, the need for high precision timing and the threat of Trojan horse attacks.     

Frequency response of a cold-wire in a flow seeded with oil particles

Experiments have been carried out to investigate the effects of aging on the frequency response of a fine cold-wire located in a flow seeded with oil particles used for laser Doppler anemometry. Transfer functions are shown to depend strongly on the running time. Photo-micrographs show that the contamination effect is due to discrete droplets, the diameter of which increases with running time. Reduction of frequency response is shown to affect at first the high-frequency range and then an intermediate range of frequencies that are larger than the inverse of the oil droplets time constant. Good agreement is found between experimental results and predictions derived from a simple model of the contaminated wire. This contamination process requires testing and cleaning the wire steadily in order to keep a significant frequency response and, if needed, to correct temperature fluctuations.     

Determination of chlormequat and mepiquat in foods by liquid chromatography/mass spectrometry or liquid chromatography/tandem mass spectrometry: interlaboratory study

Interlaboratory validation studies have been performed on 2 methods for the determination of chlormequat (CLQ) and mepiquat (MPQ). Both methods used identical extraction procedures and stable isotope internal standardization but differed in the use of liquid chromatography/mass spectrometry (LC/MS) or LC/tandem mass spectrometry (LC/MS/MS) for the determination, the amount of internal standard used, and the expected limit of detection. After addition of deuterated internal standards, CLQ and MPQ were extracted with methanol-water and determined by LC//MS or LC/MS/MS with positive electrospray ionization. Eight European laboratories participated in the LC/MS method study, analyzing mushroom, pear, wheat flour, and fruit puree with residues of CLQ in the range 0.040-1.19 mg/kg and of MPQ in the range 0.041-0.39 mg/kg. For CLQ, the Horwitz ratio (HoRat) values for individual test materials/levels were in the range 0.85-1.13 with a mean of 1.00, showing good method performance. For MPQ, the Ho values for mushroom, pear (both levels), and wheat flour were in the range 0.83-0.94, again indicating good method performance. For the determination of MPQ in infant food (fruit puree) at 0.041 mg/kg, the Ho was 1.7 when a value of 0 reported by one participant was excluded. In the LC/MS/MS study, in which 11 laboratories participated, a separate sample set was analyzed with residues of CLQ in the range 0.007-1.03 mg/kg and of MPQ in the range 0.008-0.72 mg/kg. Ho values for CLQ were in the range 0.27-1.36 and for MPQ in the range 0.51-2.10, all corresponding to acceptable method performance.