Fluorescence enhancement of several hallucinogenic drugs in cyclodextrin media

The fluorescence characteristics of selected hallucinogenic drugs dissolved in solutions of α-cyclodextrin and β-cyclodextrin are reported. Fluorescence intensity enhancements in cyclodextrin media relative to aqueous solution range from 1.2 to 4.0, probably because inclusion of the drugs into cyclodextrin increases the quantum yield. Calibration graphs are linear over 2–3 orders of magnitude; limits of detection are 6–13 μg l^?1 for ibogaine and N,N-dimethyltryptamine. The mescaline derivatives show limits of detection in the 0.8–1.4 ppm range. The role of cyclodextrin in enhancing the fluorescence intensities and some of the criteria for this fluorescence enhancement are discussed.     

Diffraction of light by superposed parallel supersonic waves,one being then-th harmonic of the other. Solution of the system of difference-differential equations for the amplitudes by a series expansion method

In the problem of the diffraction of light by two parallel supersonic waves, consisting of a fundamental tone and itsn-th harmonic, the solution of the system of difference-differential equations for the amplitudes has been reduced to the integration of a partial differential equation. The expressions for the amplitudes of the diffracted light waves are obtained as the coefficients of the Laurent expansion of the solution of this partial differential equation. The latter has been integrated for two approximations:

1. Forρ = 0, the results of Murty’s elementary theory are reestablished.
2. Forρ ≤ 1, a power series inρ, the terms of which are calculated as far as the third one, leads to a new expression for the intensities of the diffracted light waves, verifying the general symmetry properties obtained by Mertens.

     

Soil delta15N patterns in old-growth forests of southern Chile as integrator for N-cycling

Old-growth forests of southern Chile represent an important reserve of temperate (rain) forests in the world. Wetter and colder forest ecosystems appear to be more efficient in conserving and recycling N such that mostly non-plant available N species are lost, which could be indicated by more depleted delta15N values of the soil and plants. Hydrological N loss from the old-growth forests in southern Chile occurs mainly via dissolved organic nitrogen and not via dissolved inorganic N. Forest disturbances (e.g. fire, clear-cutting or enhanced N deposition) cause (abrupt) changes in ecosystem N-cycling processes. In this study, we hypothesized that delta15N signatures of soil profiles under old-growth forests could be used as an integrator for ecosystem N-cycling, and changes of these delta15N profiles could be valuable to assess ecosystem resilience towards disturbances. Six old-growth forests were selected in the phytogeographical region of the Valdivian rain forest in southern Chile. One of the sites has been partly burned in February 2002. First, we observed that ecosystems with higher mean annual precipitation and lower mean annual temperature were relatively more depleted in 15N. Secondly, we found that a forest fire caused a 100-fold increase of the nitrate export and induced an enrichment of the soil delta15N signal in the upper 20 cm.     

The effect of recording and analysis bandwidth on acoustic identification of delphinid species

Because many cetacean species produce characteristic calls that propagate well under water, acoustic techniques can be used to detect and identify them. The ability to identify cetaceans to species using acoustic methods varies and may be affected by recording and analysis bandwidth. To examine the effect of bandwidth on species identification, whistles were recorded from four delphinid species (Delphinus delphis, Stenella attenuata, S. coeruleoalba, and S. longirostris) in the eastern tropical Pacific ocean. Four spectrograms, each with a different upper frequency limit (20, 24, 30, and 40 kHz), were created for each whistle (n = 484). Eight variables (beginning, ending, minimum, and maximum frequency; duration; number of inflection points; number of steps; and presence/absence of harmonics) were measured from the fundamental frequency of each whistle. The whistle repertoires of all four species contained fundamental frequencies extending above 20 kHz. Overall correct classification using discriminant function analysis ranged from 30% for the 20-kHz upper frequency limit data to 37% for the 40-kHz upper frequency limit data. For the four species included in this study, an upper bandwidth limit of at least 24 kHz is required for an accurate representation of fundamental whistle contours.     

A theoretical study of special acoustic effects caused by the staircase of the El Castillo pyramid at the Maya ruins of Chichen-Itza in Mexico

It is known that a handclap in front of the stairs of the great pyramid of Chichen Itza produces a chirp echo which sounds more or less like the sound of a Quetzal bird. The present work describes precise diffraction simulations and attempts to answer the critical question what physical effects cause the formation of the chirp echo. Comparison is made with experimental results obtained from David Lubman. Numerical simulations show that the echo shows a strong dependence on the kind of incident sound. Simulations are performed for a (delta function like) pulse and also for a real handclap. The effect of reflections on the ground in front of the pyramid is also discussed. The present work also explains why an observer seated on the lowest step of the pyramid hears the sound of raindrops falling in a water filled bucket instead of footstep sounds when people, situated higher up the pyramid, climb the stairs.     

The representation of 3D gaussian beams by means of inhomogeneous waves

There are different methods to mathematically represent a bounded beam. Perhaps the most famous method is the classical Fourier method that consists of the superposition of pure homogeneous plane waves all traveling in different directions and having an amplitude that can be found by the Fourier transform of the required profile. This method works perfectly for 2D as well as for 3D bounded beams. However, some researchers prefer the inhomogeneous wave theory to represent a bounded beam because some phenomena, e.g. the Schoch effect, are explained by this method by means of concepts that agree better with intuition. There are several papers dealing with this method for 2D gaussian beams. Until now, it has never been considered possible to represent 3D gaussian beams as well. The present paper shows a method to overcome this shortcoming and presents different sorts of 3D gaussian beams that are built up by means of inhomogeneous plane waves.     

Bombardment-induced silicide formation at rhenium-silicon interfaces studied by XPS and TEM

For further evaluation of photoemission properties of argon ion bombarded rhenium-silicon thin films pure element Re(21 nm) / Si(39 nm) / Re(21 nm) layer sandwiches were investigated on Si(111) substrates. TEM cross sectioning revealed abrupt interfaces between the polycrystalline Re layers and the amorphous Si layer in the as-deposited sample. In XPS sputter depth profiling the interfaces were severely broadened. This is not just a result of the finite electron escape depth together with atomic mixing and preferential sputtering which was demonstrated with the dynamic Monte Carlo simulation program T-DYN, but mainly caused by topographic effects and silicide formation. Factor analysis of XPS spectra results in two Re-Si principal components which can be ascribed to silicide bonding. Accordingly the valence band changes are caused by different bonding configurations. Bombardment-induced silicide formation is proved by TEM investigations of a selected cross-sectioned sandwich. Due to preferential bombardment-induced effects Re₂Si is formed at the Re/Si interfaces in contrast to the ReSi₂ growth on thermal heating. This is discussed in terms of the interface composition and the effective heat of formation (EHF) model. Received: 6 September 1998 / Revised: 17 December 1998 / Accepted: 31 January 1999     

Improved analysis of an algorithm for the coupled task problem with UET jobs

The coupled task problem is to schedule n jobs, each one consisting of two subtasks with exact delay times between them, on a single machine. We derive a new lower bound for the problem variant with unit execution times and correct a previously published analysis.     

Zur Bestimmung von Ammoniak in Chlorammonium

Ohne Zusammenfassung