283 research outputs found
Correlation functions of scattering matrix elements in microwave cavities with strong absorption
The scattering matrix was measured for microwave cavities with two antennas.
It was analyzed in the regime of overlapping resonances. The theoretical
description in terms of a statistical scattering matrix and the rescaled
Breit-Wigner approximation has been applied to this regime. The experimental
results for the auto-correlation function show that the absorption in the
cavity walls yields an exponential decay. This behavior can only be modeled
using a large number of weakly coupled channels. In comparison to the
auto-correlation functions, the cross-correlation functions of the diagonal
S-matrix elements display a more pronounced difference between regular and
chaotic systems
A series of PDB related databases for everyday needs
The Protein Data Bank (PDB) is the world-wide repository of macromolecular structure information. We present a series of databases that run parallel to the PDB. Each database holds one entry, if possible, for each PDB entry. DSSP holds the secondary structure of the proteins. PDBREPORT holds reports on the structure quality and lists errors. HSSP holds a multiple sequence alignment for all proteins. The PDBFINDER holds easy to parse summaries of the PDB file content, augmented with essentials from the other systems. PDB_REDO holds re-refined, and often improved, copies of all structures solved by X-ray. WHY_NOT summarizes why certain files could not be produced. All these systems are updated weekly. The data sets can be used for the analysis of properties of protein structures in areas ranging from structural genomics, to cancer biology and protein design
A Critical Analysis of the Proton Form Factor with Sudakov Suppression and Intrinsic Transverse Momentum
The behavior of the proton magnetic form factor is studied within the
modified hard scattering picture, which takes into account gluonic radiative
corrections in terms of transverse separations. We parallel the analysis given
previously by Li and make apparent a number of serious objections. The
appropriate cut-off needed to render the form-factor calculation finite is both
detailed and analyzed by considering different cut-off prescriptions. The use
of the maximum interquark separation as a common infrared cut-off in the
Sudakov suppression factor is proposed, since it avoids difficulties with the
-singularities and yields a proton form factor insensitive to the
inclusion of the soft region which therefore can be confidently attributed to
perturbative QCD. Results are presented for a variety of proton wave functions
including also their intrinsic transverse momentum. It turns out that the
perturbative contribution, although theoretically self-consistent for
larger than about ~GeV to ~GeV, is too small compared to
the data.Comment: 31 pages (RevTex) + 6 figures in PS-file; preprint BUGH Wuppertal
WU-B-94-06, preprint Ruhr-Universit\"at Bochum RUB-TPII-01/9
The Importance of Equity Finance for R&D Activity – Are There Differences Between Young and Old Companies?
This paper analyzes the importance of equity finance for the R&D activity of small and medium-sized enterprises. We use information on almost 6000 German SMEs from a company survey. Using the intensity of banking competition at the district level as instrument to control for endogeneity, we find that a higher equity ratio is conducive to more R&D for young but not for old companies. Equity may be a constraining factor for young companies which have to rely on the original equity investment of their owners since they have not yet accumulated retained earnings and can relay less on outside financing. The positive influence is found for R&D intensity but not for the decision whether to perform R&D. Equity financing is therefore especially important for the most innovative, young companies
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