Fourier-transform sum-frequency surface vibrational spectroscopy with femtosecond pulses

We present a Fourier-transform spectroscopic technique for investigation of surfaces and interfaces based on IR-visible sum-frequency generation with femtosecond light pulses. The observed spectrum has a resolution that is independent of the input pulse characteristics.     

Regenbogenstreuung an Kalium-Quecksilber

Differential cross section measurements for the scattering of K by Hg at thermal energies are reported. Rainbow angles are compared with literature data and agreement within 2% is found. The data indicate a departure of the rainbow cross section from the Airy integral approximation. The measured variation of the rainbow angle with collision energy cannot safely be explained by those intermolecular potentials for which numerical calculations are available.     

Lake eutrophication: Identification of tributary nutrient loading and sediment resuspension dynamics

In a shallow lake system two problems are of particular significance. It is important to know the distribution of (polluting) nutrient loads among various agricultural and municipal sources within the lake's catchment. It is also important to know what effects the nutrients already deposited in the lake's sediments will have on the biological and chemical features of the lake's ecological system. The paper presents results for the analysis of time-series observations of sediment resuspension characteristics in Lake Balaton, Hungary, and of nutrient loadings in the principal tributary of this lake, the River Zala. Two recursive methods of estimation, an instrumental-variable (IV) algorithm and the extended Kalman filter (EKF), are used for analysis of the time series. The paper takes the view that models are most useful in terms of their failure to replicate observed behavior, in that this is the primary stimulus to insight and progress in understanding. Brief comments on some limitations of method are given. Two potentially fruitful modifications of existing identification methods are outlined, one being broadly consistent with the conceptual analog of engineering structural analysis, while the second makes reference to the development of algorithms based on expert systems.     

On a combinatorial problem of P. Erdös and L. Lovász

Miller was the first to investigate the problem of the chromatic number of set-systems. In the present paper I give a condition concerning the number of edges, which implies that the chromatic number of the n-graph equals 2. This result is sharper than the earlier results obtained by P. Erdös, A. Hajnal and W.M. Schmidt.     

Synthesis of ethyl (±1)-(e)-5-(4- and 5-(3-hydroxy-1-octenyl)-1-methyl-2-imidazolin-2-yl)-5-thia pentanoates

The racemic title compounds 1a,b and 2a,b were prepared from L-asparagine.     

Quasi-free \pi^0 photoproduction from the bound nucleon

Differential cross-sections for quasi-free photoproduction from the proton and neutron bound in the deuteron have been measured for MeV at using the Glasgow photon tagger at MAMI, the Mainz 48 cm cm NaI(Tl) photon detector and the Göttingen SENECA recoil detector. For the proton measurements made with both liquid-deuterium and liquid-hydrogen targets allow direct comparison of free photoproduction cross-sections as extracted from the bound-proton data with experimental free cross-sections which are found to be in reasonable agreement below 320 MeV. At higher energies the free cross-sections extracted from quasi-free data are significantly smaller than the experimental free cross-sections and theoretical predictions based on multipole analysis. For the first time, free neutron cross-section have been extracted in the -region. They are also in agreement with the predictions from multipole analysis up to 320 MeV and significantly smaller at higher photon energies.Received: 28 May 2003, Published online: 27 January 2004PACS: 13.60.Le Meson production - 14.20.Dh Protons and neutrons - 25.20.Lj Photoproduction reactionsK. Kossert: Part of the Doctoral Thesis.,Present address: Physikalisch-Technische Bundesanstalt, Bundesallee 100, D-38116 Braunschweig, Germany.Present address F. Wissmann: Physikalisch-Technische Bundesanstalt, Bundesallee 100, D-38116 Braunschweig, Germany. Present address B. Seitz: II. Physikalisches Institut der Universität Gießen, Germany.