Coherent interactions of terahertz strain solitons and electronic two-level systems in photoexcited ruby

We observe coherent interactions between an ultrashort, longitudinal acoustic soliton train and the 29-cm(-1) electronic transition in photoexcited ruby. Propagation of the strain pulses over millimeter distance through an excited zone reveals striking behavior of the induced electronic population, which has been explained by impulsive excitation of the two-level systems, combined with the nonlinear properties of the solitons in the resonant medium. This opens up new possibilities for coherent manipulation of ultrashort acoustic pulses by local electronic centers.     

A mixed ladderane/n-alkyl glycerol diether membrane lipid in an anaerobic ammonium-oxidizing bacterium

A novel glycerol diether containing ladderane and tetradecyl moieties has been identified in an anaerobic ammonium-oxidizing bacterium by GC/MS and high-field NMR spectroscopy.     

ESR study of monoalkylzinc-2,2′-bipyridine complexes RZn · Bipy

Paramagnetic species are formed when LiBipy is treated with various alkylzinc halides at ?100°C and the ESR spectra are discussed. The observation that the half-life times of the radical species appear to depend only on the nature of the alkyl group bound to zinc proves that monoalkylzinc-2,2′-bipyridine complexes are formed. The nature of the bonding between zinc and 2,2′-bipyridine is discussed.     

Determination of trans-galactooligosaccharides in selected food products by ion-exchange chromatography: collaborative study

Eleven collaborating laboratories assayed 7 blind duplicate pairs of food and feed products for tans-galactooligosaccharides. The 7 laboratory sample pairs ranged from low (2%) to high levels (15%). Following the proposed method, the test samples were treated with beta-galactosidase and the released galactose was determined by ion-exchange chromatography. Repeatability standard deviation ranged from 2.9 to 11.6%; reproducibility standard deviation ranged from 4.6 to 11.6%.     

Digital simulation as an aid to sample scheduling in a routine laboratory for liquid chromatography

A computer model is described to aid decision-making in a routine laboratory for liquid chromatography. The managerial demand was to reduce the delay times of the samples in the laboratory despite an increasing sample input. Knowledge derived from records on the laboratory and from the experience of the laboratory staff is used to develop a simulation model of the laboratory. The model is applied to study the effects of several factors on the performance of the laboratory in order to trace the bottlenecks.     

PHOTOSENSITIZING PROPERTIES OF BACTERIOCHLOROPHYLLIN a and BACTERIOCHLORIN a, TWO DERIVATIVES OF BACTERIOCHLOROPHYLL a

Abstract The photosensitizing properties of two water soluble derivatives of bacteriochlorophyll a , bacteriochlorophyllin a and bacteriochlorin a (lacking the central Mg-ion) were investigated and compared to those of hematoporphyrin derivatives. At physiological pH the oxygen consumption rate of histidine, tryptophan, dithiothreitol and guanosine upon illumination was 3 to 4 times higher when bacteriochlorin a was used as photosensitizer than when hematoporphyrin derivatives were used. Especially bacteriochlorin a proved to be an effective sensitizer for the killing of L929 cells. Because bacteriochlorin a has an absorption maximum at 765 nm in phosphate buffered saline (allowing a light penetration in tissue about ten times larger than at 630 nm) and a high molar absorption coefficient (32 000 M cm⁻¹) it has promising possibilities for the application in photodynamic therapy.     

An Isogeny of K3 Surfaces

In a recent paper Ahlgren, Ono and Penniston described the L-seriesof K3 surfaces from a certain one-parameter family in termsof those of a particular family of elliptic curves. The Tateconjecture predicts the existence of a correspondence betweenthese K3 surfaces and certain Kummer surfaces related to theseelliptic curves. A geometric construction of this correspondenceis given here, using results of D. Morrison on Nikulin involutions.2000 Mathematics Subject Classification 14J27, 14G25, 14J28.