3,198 research outputs found
Law of large numbers for the asymmetric simple exclusion process
We consider simple exclusion processes on Z for which the underlying random
walk has a finite first moment and a non-zero mean and whose initial
distributions are product measures with different densities to the left and to
the right of the origin. We prove a strong law of large numbers for the number
of particles present at time t in an interval growing linearly with t.Comment: 16 page
Ionization of clusters in intense laser pulses through collective electron dynamics
The motion of electrons and ions in medium-sized rare gas clusters (1000
atoms) exposed to intense laser pulses is studied microscopically by means of
classical molecular dynamics using a hierarchical tree code. Pulse parameters
for optimum ionization are found to be wavelength dependent. This resonant
behavior is traced back to a collective electron oscillation inside the charged
cluster. It is shown that this dynamics can be well described by a driven and
damped harmonic oscillator allowing for a clear discrimination against other
energy absorption mechanisms.Comment: 4 pages (4 figures
Proton Decay from Excited States in Spherical Nuclei
Based on a single particle model which describes the time evolution of the
wave function during tunneling across a one dimensional potential barrier we
study the proton decay of Pb from excited states with non-vanishing
angular momentum . Several quantities of interest in this process like
the decay rate , the period of oscillation , the transient
time , the tunneling time and the average value of the proton
packet position are computed and compared with the WKB results.Comment: 12 pages, 4 figure
Die indische Rund- oder Rangoonbohne
Seitdem 1884 von Davidson und Stevenson Vergiftungen durch Samen von Phaseolus lunatus (Pois d'Achery) beschrieben wurden, sind durch den Genuß dieser Bohne (Mondbohne) zahlreiche Vergiftungsfälle beobachtet worden. 1906 untersuchte diese haricot à acide cyanhydrique eingehend Guignard, nachdem 1904 Dunstan und Henry das blausäureabspaltende Glykosid, das Phaseolunatin, näher untersucht hatten. In Deutschland gaben die von Dammann und Behrens 1906 beobachteten Massenvergiftungen von Pferden, Rindern und Schweinen Anlaß zu chemischen Untersuchungen dieser Bohnenart. Neuerdings brachten Tageszeitungen die für den Fachmann beunruhigende Nachricht, es sollten die 50000 t Bohnen der ersten Lebensmittellieferung der Entente an Deutschland aus der Rangoonbohne bestehen
Spurious oscillations from local self-interaction correction in high energy photoionization calculations for metal clusters
We find that for simple metal clusters a single-electron description of the ground state employing self-interaction correction (SIC) in the framework of local-density approximation strongly contaminates the high energy photoionization cross sections with spurious oscillations for a subshell containing node(s). This effect is shown connected to the unphysical structure that SIC generates in ensuing state-dependent radial potentials around a position where the respective orbital density attains nodal zero. Non-local Hartree-Fock that exactly eliminates the electron self-interaction is found entirely free from this effect. It is inferred that while SIC is largely unimportant in high photon-energies, any implementation of it within the local frame can induce unphysical oscillations in the high energy photospectra of metal clusters pointing to a general need for caution in choosing appropriate theoretical tools
Intermanifold similarities in partial photoionization cross sections of helium
Using the eigenchannel R-matrix method we calculate partial photoionization
cross sections from the ground state of the helium atom for incident photon
energies up to the N=9 manifold. The wide energy range covered by our
calculations permits a thorough investigation of general patterns in the cross
sections which were first discussed by Menzel and co-workers [Phys. Rev. A {\bf
54}, 2080 (1996)]. The existence of these patterns can easily be understood in
terms of propensity rules for autoionization. As the photon energy is increased
the regular patterns are locally interrupted by perturber states until they
fade out indicating the progressive break-down of the propensity rules and the
underlying approximate quantum numbers. We demonstrate that the destructive
influence of isolated perturbers can be compensated with an energy-dependent
quantum defect.Comment: 10 pages, 10 figures, replacement with some typos correcte
Natively Unstructured Loops Differ from Other Loops
Natively unstructured or disordered protein regions may increase the functional complexity of an organism; they are particularly abundant in eukaryotes and often evade structure determination. Many computational methods predict unstructured regions by training on outliers in otherwise well-ordered structures. Here, we introduce an approach that uses a neural network in a very different and novel way. We hypothesize that very long contiguous segments with nonregular secondary structure (NORS regions) differ significantly from regular, well-structured loops, and that a method detecting such features could predict natively unstructured regions. Training our new method, NORSnet, on predicted information rather than on experimental data yielded three major advantages: it removed the overlap between testing and training, it systematically covered entire proteomes, and it explicitly focused on one particular aspect of unstructured regions with a simple structural interpretation, namely that they are loops. Our hypothesis was correct: well-structured and unstructured loops differ so substantially that NORSnet succeeded in their distinction. Benchmarks on previously used and new experimental data of unstructured regions revealed that NORSnet performed very well. Although it was not the best single prediction method, NORSnet was sufficiently accurate to flag unstructured regions in proteins that were previously not annotated. In one application, NORSnet revealed previously undetected unstructured regions in putative targets for structural genomics and may thereby contribute to increasing structural coverage of large eukaryotic families. NORSnet found unstructured regions more often in domain boundaries than expected at random. In another application, we estimated that 50%–70% of all worm proteins observed to have more than seven protein–protein interaction partners have unstructured regions. The comparative analysis between NORSnet and DISOPRED2 suggested that long unstructured loops are a major part of unstructured regions in molecular networks
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