UMTS radio network evaluation and optimization beyond snapshots

A new evaluation scheme for universal mobile telecommunications system (UMTS) radio networks is introduced. The approach takes the complex coupling of coverage and capacity through interference into account. Cell load estimates, otherwise obtained through Monte-Carlo simulation, can now be approximated without time-consuming iterative simulations on user snapshots. The two cornerstones are the generalization of interference coupling matrices from user snapshots to average load and the emulation of load control by an analytical scaling scheme. Building on the new evaluation scheme, two novel radio network optimization algorithms are presented: an efficient local search procedure and a mixed integer program that aims at designing the coupling matrix. Computational experiments for optimizing antenna tilts show that our new approaches outperform traditional snapshot models     

Rotational and Translational Dynamics of Ras Proteins upon Binding to Model Membrane Systems

Plasma-membrane-associated Ras proteins typically control signal transduction processes. As nanoclustering and membrane viscosity sensing provide plausible signaling mechanisms, determination of the rotational and translational dynamics of membrane-bound Ras isoforms can help to link their dynamic mobility to their function. Herein, by using time-resolved fluorescence anisotropy and correlation spectroscopic measurements, we obtain the rotational-correlation time and the translational diffusion coefficient of lipidated boron-dipyrromethene-labeled Ras, both in bulk Ras and upon membrane binding. The results show that the second lipidation motif of N-Ras triggers dimer formation in bulk solution, whereas K-Ras4B is monomeric. Upon membrane binding, an essentially free rotation of the G-domain is observed, along with a high lateral mobility; the latter is essentially limited by the viscosity of the membrane and by lipid-mediated electrostatic interactions. This high diffusional mobility warrants rapid recognition–binding sequences in the membrane-bound state, thereby facilitating efficient interactions between the Ras proteins and scaffolding or effector proteins. The lipid-like rapid lateral diffusion observed here complies with in vivo data.     

Fluorine-bridged chain compounds as models in magnetochemistry: structures and magnetism of (imidH)2[Fe2oxF6] and [Fe2oxF4(DMSO)4]

The crystal structure of a new Fe(III) dimer obtained by fluorination of FeCl₃ with Me₃SnF in the presence of oxalic acid and crystallization from dimethyl sulfoxide (DMSO) has been determined: [Fe₂oxF₄(DMSO)₄] 1, Space group P2₁/n, Z=2, a=7.259(2), b=11.409(3), c=13.374(2) Å, β=97.26(1), R=4.47%. It shows a tetradentate bridging oxalato, equatorial cis fluorine and axial trans DMSO ligands.From an aqueous solution of FeF₃·3H₂O, oxalic acid, and imidazolium fluoride, crystals of (imidH)₂[Fe₂oxF₆] 2 could be precipitated. Space group Pban, Z=2, a=9.143(2), b=20.837(6), c=3.890(1) Å, R=2.51%. The structure shows anionic chains formed by bridging trans fluorine ligands connected, like in the dimer above, by oxalate anions to form a double chain. The magnetic properties were determined on powders by SQUID measurements. Mössbauer experiments were performed on the S=5/2 Fe³⁺ double chain of (imidH)₂[Fe₂oxF₆], where the anisotropy is of dipolar origin and is therefore very weak. The striking result is the characteristic aspect of two magnetic split spectra below T_N and additionally, the coexistence of a temperature dependent paramagnetic component (doublet) and the magnetic split spectra in the temperature range T_N=14.5 and T_H=40 K. The origin of that unusual behaviour is attributed to nonlinear excitations (magnetic solitons) in systems with small local anisotropy. Consequently, the domain wall width should be large. The subspectrum of the doublet was identified with intraband solitons. The relative intensity of the fast relaxing component increases with increasing temperature as ∝exp(−E_s/kT). From the slope of fractional intensity of the broadened doublet as a function of inverse temperature, the activation energy E_s/k=40(1) K was derived. Considering the results of magnetic susceptibility measurements of the intra-chain exchange constant J/k=−17.3(2) K, we found an anisotropy constant of D/k=0.15(2) K in agreement with our magnetic study. Additionally, parameters as the inter-chain constants J′/k=0.08(2) K and J″/k=0.60(5) K were calculated. Speculatively, from the experimental data of the magnetically split spectra the ratio (domain length/domain wall width) ≈ 2 was estimated at T_N, in agreement with the theoretical expectations. Finally, the results obtained for the double chain of (imidH)₂[Fe₂oxF₆] with weak anisotropy are compared with previously reported Mössbauer experiments on -doped powder of (ND₄)₂MnF₅, inelastic neutron scattering, and magnetic susceptibility measurements on single crystals of (ND₄)₂MnF₅ with strong anisotropy.     

Circuits through prescribed vertices in k‐connected k‐regular graphs

We show that every set of vertices in a k‐connected k‐regular graph belongs to some circuit. © 2002 John Wiley & Sons, Inc. J Graph Theory 39: 145–163, 2002     

Synthetische Versuche in der Pyranthronreihe

Ohne Zusammenfassung     

Über den Schnitt zweier quadratischer Räume im vierdimensionalen Raume

Ohne Zusammenfassung     

Über die Invarianten der Hauptgruppe

Ohne ZusammenfassungDie wichtigsten Ergebnisse dieser Arbeit bildeten den Inhalt eines Vortrages, den der Verf. gelegentlich der 85. Naturforscherversammlung in Wien (1913) gehalten hat.     

Zur Differentialgeometrie algebraischer Flächen

Ohne Zusammenfassung     

Parallelization of a multiconfigurational perturbation theory

In this work, we present a parallel approach to complete and restricted active space second‐order perturbation theory, (CASPT2/RASPT2). We also make an assessment of the performance characteristics of its particular implementation in the Molcas quantum chemistry programming package. Parallel scaling is limited by memory and I/O bandwidth instead of available cores. Significant time savings for calculations on large and complex systems can be achieved by increasing the number of processes on a single machine, as long as memory bandwidth allows, or by using multiple nodes with a fast, low‐latency interconnect. We found that parallel efficiency drops below 50% when using 8–16 cores on the shared‐memory architecture, or 16–32 nodes on the distributed‐memory architecture, depending on the calculation. This limits the scalability of the implementation to a moderate amount of processes. Nonetheless, calculations that took more than 3 days on a serial machine could be performed in less than 5 h on an InfiniBand cluster, where the individual nodes were not even capable of running the calculation because of memory and I/O requirements. This ensures the continuing study of larger molecular systems by means of CASPT2/RASPT2 through the use of the aggregated computational resources offered by distributed computing systems. © 2013 Wiley Periodicals, Inc.