Production of resonances in a thermal model

We discuss the π ⁺ π ^? invariant-mass correlations and the resonance production in a thermal model with single freeze-out. The predictions are confronted with the data from the STAR Collaboration.     

Modellierung der Dynamik komplexer Mehrkörpersysteme mit Hilfe von kinematischen Übertragungselementen

Übersicht Ein zentrales Problem bei der Behandlung der Dynamik komplexer Mehrkörpersysteme, d. h. Systeme mit vielen Körpern und einer komplexen Verkopplungsstruktur, bildet die Aufstellung und Behandlung der Bindungsgleichungen. Möchte man insbesondere die Bewegungsgleichungen in Minimalkoordinaten aufstellen, so besteht eine Möglichkeit darin, die im System auftretenden kinematischen Schleifen als nichtlineare Übertragungselemente aufzubereiten und die so entstehenden kinematischen Transformatoren zu einem kinematischen Netz zusammenzufügen. Der kinematische Fluß läßt sich dann in einem Blockschaltbild übersichtlich darstellen. In der vorliegenden Arbeit wird besonders auf die Systematik und die zu erzielende Effizienz bei der Aufstellung und Lösung der kinematischen Gleichungen des Mehrkörpersystems eingegangen.

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Modeling the dynamics of complex multibody systems with kinematical transmission elements

Summary A principal issue in the modeling of the dynamics of complex multibody systems, i.e. mechanical systems consisting of many bodies with a complex interconnection structure, is the statement and resolution of the constraint equations. A possible approach to tackle this problem is to treat the individual independent loops in the mechanism as nonlinear transmission elements, denominated kinematical transformers, which are assembled together by linear equations to kinematical networks representing general mechanisms. This block-diagram representation of the overall kinematics allows to find easily an appropriate solution flow and also recursive solutions. In the present paper, the details of the corresponding systematics as well as the achievable efficiency are discussed.

     

A pulsed light generator for high speed photography

A pulsed light generator for stroboscopic photography which makes use of LED's has been developed. The maximum light power which may be extracted from a single LED is approximately 1 Watt. The pulse repetition rate ranges up to 1 MHz and the length of the pulses is adjustable between 0.05 and 1 s. The light emitted from the diodes is especially suited for the observation of phase objects by interferometric methods due to its pronounced coherence. Results of the electrical and optical performance of the generator are presented.     

Automated NMR resonance assignment of large proteins for protein-ligand interaction studies

The detection and structural characterization of protein-ligand interactions by solution NMR is central to functional biology research as well as to drug discovery. Here we present a robust and highly automated procedure for obtaining the resonance assignments necessary for studies of such interactions. The procedure relies on a combination of three automated projection spectroscopy (APSY) experiments, including the new 4D APSY-HNCACB, and the use of fractionally deuterated protein samples. This labeling pattern increases the experimental sensitivity on the one hand, but it leads to peak multiplets on the other hand. The latter complications are however overcome by the geometric APSY analysis of the projection spectra. The three APSY experiments thus provide high precision chemical shift correlations of the backbone and side chain methyl groups, allowing a reliable and robust assignment of the protein by suitable algorithms. The present approach doubles the molecular size limit of APSY-based assignments to 25 kDa, thus providing the basis for efficient characterization of protein-ligand interactions at atomic resolution by NMR, such as structure-based drug design. We show the application to two human proteins with molecular weights of 15 and 22 kDa, respectively, at concentrations of 0.4 mM and discuss the general applicability to studies of protein-protein and protein-nucleic acid complexes.     

Palladium(II)-catalyzed cycloisomerization of functionalized 1,5-hexadienes

Scope and limitations of the Pd(II)-catalyzed cycloisomerization of functionalized 1,5-hexadienes have been studied. In situ NMR experiments indicate a challenging competition between various reaction pathways. A careful balance between substrate structure, nature of the precatalyst, and reaction conditions was required to gain access to a useful building block for sesquiterpene total synthesis.     

Stationary phase corrections in the process of bosonization of multi-quark interactions

The functional integration over the auxiliary bosonic variables of cubic order related with the effective action of the Nambu–Jona–Lasinio model with ’t Hooft term has recently been obtained in the form of a loop expansion. Even numbers of loops contribute to the action, while odd numbers of loops are assigned to the measure. We consider the two-loop corrections and analyse their effect on the low-lying pseudoscalar and scalar mass spectra, quark condensates and weak decay constants. The results are compared to the leading order calculations and other approaches. PACS 12.39.Fe, 11.30.Rd, 11.30.Qc     

Frequency and molecular-mass-dependent nonexponential proton NMR relaxation in polymer melts

A theoretical treatment of the nonexponential relaxation behavior of the different proton nuclear magnetic resonance (NMR) relaxation processes in polymer melts is presented. Formulas are derived for a three-component model given by two versions and a homogeneous distribution of correlation times. The theoretical results were tested with measurements of T₁, T_2e, and T₂ as functions of frequency and molecular mass in linear fractionated polyethylene samples. While the T₁ relaxation always yields exponential magnetization decays, the T_2e and T₂ measurements show biexponential relaxation behavior. From the calculations it was found that the correlation time of the local motion is independent of the molecular mass, whereas the correlation time of the slowest motional process increases with M^2.8_w for the three-component model and with M^2.2_w for the distribution of correlation times, respectively. © 1992 John Wiley & Sons, Inc.