Representing molecule-surface interactions with symmetry-adapted neural networks

The accurate description of molecule-surface interactions requires a detailed knowledge of the underlying potential-energy surface (PES). Recently, neural networks (NNs) have been shown to be an efficient technique to accurately interpolate the PES information provided for a set of molecular configurations, e.g. by first-principles calculations. Here, we further develop this approach by building the NN on a new type of symmetry functions, which allows to take the symmetry of the surface exactly into account. The accuracy and efficiency of such symmetry-adapted NNs is illustrated by the application to a six-dimensional PES describing the interaction of oxygen molecules with the Al(111) surface.Comment: 13 pages including 8 figures; related publications can be found at http://www.fhi-berlin.mpg.de/th/th.htm

Techniques of Irony in Light of the Romantic Theory

Paper by Ernst Behle

Loudspeaker Crossover Design (from analog to digital)

Loudspeaker systems are quite complex devices and considered ‘musical instruments’ for many HiFi-enthusiasts. However, from the technical point of view the description of an optimal loudspeaker seems to be simple: the reproduction of any electrical input signal in such a way that the acoustical output looks the same with respect to the waveform. Unfortunately, the demands to reach this task are manifold and very often when fulfilling one requirement problems arise with other demands. A typical one is that with only one transducer it is rather impossible to reproduce the entire frequency spectrum in a satisfying manner and with sufficient output. Therefore several transducers may be used with specific capabilities in low mid or high frequency range. In consequence the frequency content of the input signal needs to be distributed in a correct way so to insure that the overall output of the loudspeaker system fulfills the above mentioned requirement. The technical solution for this is the so-called crossover network. Since several years audio goes digital and the possibilities in creating crossover networks have become more flexible with digital filter design. Digital IIR and FIR filter design is well established, but a simple treatment of analog filter concepts in Loudspeaker Crossover Design (from analog to digital) digital domain would not help to improve the reproduction of a loudspeaker. Therefore new concepts with digital filters are required. In this talk we will firstly discuss the general filter strategies (either analog or digital) for loudspeakers. Then we will introduce both methods – IIR and FIR filter - for loudspeaker crossover design in digital domain. The advantages and some disadvantages will be addressed as well. A real word example will finally show what is possible when making the optimum use of the system

Fingerprints for spin-selection rules in the interaction dynamics of O2 at Al(111)

We performed mixed quantum-classical molecular dynamics simulations based on first-principles potential-energy surfaces to demonstrate that the scattering of a beam of singlet O2 molecules at Al(111) will enable an unambiguous assessment of the role of spin-selection rules for the adsorption dynamics. At thermal energies we predict a sticking probability that is substantially less than unity, with the repelled molecules exhibiting characteristic kinetic, vibrational and rotational signatures arising from the non-adiabatic spin transition.Comment: 4 pages including 3 figures; related publications can be found at http://www.fhi-berlin.mpg.de/th/th.htm

Wie sollte das deutsche Bildungssystem reformiert werden? - PISA und die Konsequenzen

Die jüngst veröffentlichte OECD-Studie PISA bestätigte erneut, dass das deutsche Bildungssystem im internationalen Vergleich nur mittelmäßige Leistungen hervorbringt. Wie könnte es reformiert werden? --

Signatures of nonadiabatic O2 dissociation at Al(111): First-principles fewest-switches study

Recently, spin selection rules have been invoked to explain the discrepancy between measured and calculated adsorption probabilities of molecular oxygen reacting with Al(111). In this work, we inspect the impact of nonadiabatic spin transitions on the dynamics of this system from first principles. For this purpose the motion on two distinct potential-energy surfaces associated to different spin configurations and possible transitions between them are inspected by means of the Fewest Switches algorithm. Within this framework we especially focus on the influence of such spin transitions on observables accessible to molecular beam experiments. On this basis we suggest experimental setups that can validate the occurrence of such transitions and discuss their feasibility.Comment: 13 pages, 7 figure

Pride and Penalty in Hawthorne\u27s Tales

For Hawthorne pride is the root evil, for it is a voluntary separation by which man sets himself aloof from conmunication with himself, his fellow men, and God. Pride is an attitude which takes possession of him first as he allows himself to become blinded to his own faults and inadequacies, next as he ignores the virtues and claims of his fellow men, and eventually as he develops the bigoted idea that since he is superior to the rest of tho human race, he must make himself a place on the Godly level. He is now completely isolated from humanity by his own choice, from God by the incongruity of his presumptive claims, and from himself by the absence or any further self-comnunication on the basis of honest humility