Gap formation and soft phonon mode in the Holstein model

We investigate electron-phonon coupling in many-electron systems using dynamical mean-field theory in combination with the numerical renormalization group. This non-perturbative method reveals significant precursor effects to the gap formation at intermediate coupling strengths. The emergence of a soft phonon mode and very strong lattice fluctuations can be understood in terms of Kondo-like physics due to the development of a double-well structure in the effective potential for the ions

Polarization phenomena in the reaction NN to NNpi near threshold

First calculations for spin-dependent observables of the reactions $pp \to pp\pi^0$, $pp \to pn\pi^+$ and $pp \to d\pi^+$ near threshold are presented, employing the J\"ulich model for pion production. The influence of resonant (via the excitation of the $\Delta (1232)$) and non-resonant p-wave pion production mechanisms on these observables is examined. For the reactions $pp \to pn\pi^+$ and $pp \to d\pi^+$ nice agreement of our predictions with the presently available data on spin correlation coefficents is observed whereas for $pp \to pp\pi^0$ the description of the data is less satisfying.Comment: 10 pages, 4 figure

Why Customers Value Mass-customized Products: The Importance of Process Effort and Enjoyment

We test our hypotheses on 186 participants designing their own scarves with an MC toolkit. After completing the process, they submitted binding bids for "their" products in Vickrey auctions. We therefore observe real buying behavior, not merely stated intentions. We find that the subjective value of a self-designed product (i.e., one's bid in the course of the auction) is indeed not only impacted by the preference fit the customer expects it to deliver, but also by (1) the process enjoyment the customer reports, (2) the interaction of preference fit and process enjoyment, and (3) the interaction of preference fit and perceived process effort. In addition to its main effect, we interpret preference fit as a moderator of the valuegenerating effect of process evaluation: In cases where the outcome of the process is perceived as positive (high preference fit), the customer also interprets process effort as a positive accomplishment, and this positive affect adds (further) value to the product. It appears that the perception of the self-design process as a good or bad experience is partly constructed on the basis of the outcome of the process. In the opposite case (low preference fit), effort creates a negative affect which further reduces the subjective value of the product. Likewise, process enjoyment is amplified by preference fit, although enjoyment also has a significant main effect, which means that regardless of the outcome, customers attribute higher value to a self-designed product if they enjoy the process. The importance of the self-design process found in this study bears clear relevance for companies which offer or plan to offer MC systems. It is not sufficient to design MC toolkits in such a way that they allow customers to design products according to their preferences. The affect caused by this process is also highly important. Toolkits should therefore stimulate positive affective reactions and at the same time keep negative affect to a minimum. (authors' abstract

Facilitated diffusion of proteins on chromatin

We present a theoretical model of facilitated diffusion of proteins in the cell nucleus. This model, which takes into account the successive binding/unbinding events of proteins to DNA, relies on a fractal description of the chromatin which has been recently evidenced experimentally. Facilitated diffusion is shown quantitatively to be favorable for a fast localization of a target locus by a transcription factor, and even to enable the minimization of the search time by tuning the affinity of the transcription factor with DNA. This study shows the robustness of the facilitated diffusion mechanism, invoked so far only for linear conformations of DNA.Comment: 4 pages, 4 figures, accepted versio

Heavy Meson Production in NN Collisions with Polarized Beam and Target -- A new facility for COSY

The study of near--threshold meson production in pp and pd collisions involving polarized beams and polarized targets offers the rare opportunity to gain insight into short--range features of the nucleon--nucleon interaction. The Cooler Synchrotron COSY at FZ--J\"ulich is a unique environment to perform such studies. Measurements of polarization observables require a cylindrically symmetrical detector, capable to measure the momenta and the directions of outgoing charged hadrons. The wide energy range of COSY leads to momenta of outgoing protons to be detected in a single meson production reaction between 300 and 2500 MeV/c. Scattering angles of protons to be covered extend to about $45^{\circ}$ in the laboratory system. An azimuthal angular coverage of the device around 98% seems technically achievable. The required magnetic spectrometer could consist of a superconducting toroid, providing fields around 3 T.Comment: 6 pages, 1 figure, submitted to Czechoslovak Journal of Physic

A broadband FFT spectrometer for radio and millimeter astronomy

The core architecture, tests in the lab and first results of a Fast Fourier Transform (FFT) spectrometer are described. It is based on a commercially available fast digital sampler (AC240) with an on-board Field Programmable Gate Array (FPGA). The spectrometer works continuously and has a remarkable total bandwidth of 1 GHz, resolved into 16384 channels. The data is sampled with 8 bits, yielding a dynamic range of 48 dB. An Allan time of more than 2000 s and an SFDR of 37 dB were measured. First light observations with the KOSMA telescope show a perfect spectrum without internal or external spurious signals.Comment: Astronomy and Astrophysics, in pres