Universal scaling behavior of directed percolation around the upper critical dimension

In this work we consider the steady state scaling behavior of directed percolation around the upper critical dimension. In particular we determine numerically the order parameter, its fluctuations as well as the susceptibility as a function of the control parameter and the conjugated field. Additionally to the universal scaling functions, several universal amplitude combinations are considered. We compare our results with those of a renormalization group approach.Comment: 19 pages, 8 figures, accepted for publication in J. Stat. Phy

Radium single-ion optical clock

We explore the potential of the electric quadrupole transitions 7s\,^2S_{1/2} - 6d\,^2D_{3/2}, 6d\,^2D_{5/2} in radium isotopes as single-ion optical frequency standards. The frequency shifts of the clock transitions due to external fields and the corresponding uncertainties are calculated. Several competitive $^A$Ra$^+$ candidates with $A=$ 223 - 229 are identified. In particular, we show that the transition 7s\,^2S_{1/2}\,(F=2,m_F=0) - 6d\,^2D_{3/2}\,(F=0,m_F=0) at 828 nm in $^{223}$Ra$^+$, with no linear Zeeman and electric quadrupole shifts, stands out as a relatively simple case, which could be exploited as a compact, robust, and low-cost atomic clock operating at a fractional frequency uncertainty of $10^{-17}$. With more experimental effort, the $^{223,225,226}$Ra$^+$ clocks could be pushed to a projected performance reaching the $10^{-18}$ level.Comment: 20 pages, 1 figur

Genome-Wide Mapping of Uncapped and Cleaved Transcripts Reveals a Role for the Nuclear mRNA Cap-Binding Complex in Cotranslational RNA Decay in Arabidopsis

RNA turnover is necessary for controlling proper mRNA levels posttranscriptionally. In general, RNA degradation is via exoribonucleases that degrade RNA either from the 5′ end to the 3′ end, such as XRN4, or in the opposite direction by the multisubunit exosome complex. Here, we use genome-wide mapping of uncapped and cleaved transcripts to reveal the global landscape of cotranslational mRNA decay in the Arabidopsis thaliana transcriptome. We found that this process leaves a clear three nucleotide periodicity in open reading frames. This pattern of cotranslational degradation is especially evident near the ends of open reading frames, where we observe accumulation of cleavage events focused 16 to 17 nucleotides upstream of the stop codon because of ribosomal pausing during translation termination. Following treatment of Arabidopsis plants with the translation inhibitor cycloheximide, cleavage events accumulate 13 to 14 nucleotides upstream of the start codon where initiating ribosomes have been stalled with these sequences in their P site. Further analysis in xrn4 mutant plants indicates that cotranslational RNA decay is XRN4 dependent. Additionally, studies in plants lacking CAP BINDING PROTEIN80/ABA HYPERSENSITIVE1, the largest subunit of the nuclear mRNA cap binding complex, reveal a role for this protein in cotranslational decay. In total, our results demonstrate the global prevalence and features of cotranslational RNA decay in a plant transcriptome

Dynamic correlation functions and Boltzmann Langevin approach for driven one dimensional lattice gas

We study the dynamics of the totally asymmetric exclusion process with open boundaries by phenomenological theories complemented by extensive Monte-Carlo simulations. Upon combining domain wall theory with a kinetic approach known as Boltzmann-Langevin theory we are able to give a complete qualitative picture of the dynamics in the low and high density regime and at the corresponding phase boundary. At the coexistence line between high and low density phases we observe a time scale separation between local density fluctuations and collective domain wall motion, which are well accounted for by the Boltzmann-Langevin and domain wall theory, respectively. We present Monte-Carlo data for the correlation functions and power spectra in the full parameter range of the model.Comment: 10 pages, 9 figure

Simulationsbasierte Untersuchung der Einflussfaktoren auf die magnetischen Streufelder bei induktiven Ladesystemen von Elektrofahrzeugen

Alternative, elektrische Antriebskonzepte mit Batteriespeicher sind in Form von Hybridund reinen Elektrofahrzeugen Gegenstand von zukunftsorientierten Mobilitätskonzepten. Bisherige Markteintrittsbarrieren für Elektrofahrzeuge sind neben vergleichsweise hohen Anschaffungskosten und der Reichweitenproblematik auch zeitaufwendige und umständliche Ladeverfahren. Eine Möglichkeit, um das Laden von Elektrofahrzeugen anwenderfreundlicher zu machen sind induktive Ladeverfahren (engl. WPT – Wireless Power Transfer). Diese Systeme lassen sich einfach in bestehende Infrastrukturen integrieren und fügen sich unauffällig in das Stadtbild ein. Induktive Ladeverfahren werden seit einiger Zeit beispielsweise in der Medizintechnik oder in der Unterhaltungselektronik (Laden von Mobiltelefonen) eingesetzt [1]. Für das induktive Laden von Elektrofahrzeugen sind aktuell Leistungsklassen von 3,3 kW bis 7,7 kW und Übertragungsfrequenzen im Bereich mehrerer kHz angedacht. Der Wirkungsgrad dieser Systeme liegt im Bereich von 90% [2]. Bevor diese Systeme im öffentlichen Raum eingesetzt werden können, ist die Beeinflussung anderer Systeme und deren Einfluss auf den menschlichen Körper zu klären (Elektromagnetische Verträglichkeit [EMV] bzw. – Umweltverträglichkeit [EMVU]). Die ICNIRP 2010-Richtlinie definiert einen Referenzgrenzwert für Frequenzen ab 3 kHz von umgerechnet 24 dBμT. Dieser Wert sollte an keiner von Personen zugänglichen Stelle am Fahrzeug und in dessen Umgebung überschritten werden. Ziel dieser Studie ist es, mit Hilfe der EMV-Simulation Einflussfaktoren auf die magnetischen Streufelder eines modellierten induktiven Ladesystems für Elektrofahrzeuge zu identifizieren. Nachdem in Abschnitt 3 das Ladesystem und EMV-Maßnahmen betrachtet wurde, wird in Abschnitt 4 das Gesamtsystem aus Fahrzeugkarosserie und Ladesystem simuliert. Dabei werden unterschiedliche Karosseriematerialien betrachtet und die magnetische Flussdichte innerhalb und außerhalb des Fahrzeugs ermittelt

Phase-separation transition in one-dimensional driven models

A class of models of two-species driven diffusive systems which is shown to exhibit phase separation in d=1 dimensions is introduced. Unlike previously studied models exhibiting similar phenomena, here the relative density of the two species is fluctuating within the macroscopic domain of the phase separtated state. The nature of the phase transition from the homogeneous to the phase-separated state is discussed in view of a recently introduced criterion for phase separation in one-dimensional driven systems

Spontaneous Symmetry Breaking in a Non-Conserving Two-Species Driven Model

A two species particle model on an open chain with dynamics which is non-conserving in the bulk is introduced. The dynamical rules which define the model obey a symmetry between the two species. The model exhibits a rich behavior which includes spontaneous symmetry breaking and localized shocks. The phase diagram in several regions of parameter space is calculated within mean-field approximation, and compared with Monte-Carlo simulations. In the limit where fluctuations in the number of particles in the system are taken to zero, an exact solution is obtained. We present and analyze a physical picture which serves to explain the different phases of the model

Measurement of the branching ratio for beta-delayed alpha decay of 16N

While the 12C(a,g)16O reaction plays a central role in nuclear astrophysics, the cross section at energies relevant to hydrostatic helium burning is too small to be directly measured in the laboratory. The beta-delayed alpha spectrum of 16N can be used to constrain the extrapolation of the E1 component of the S-factor; however, with this approach the resulting S-factor becomes strongly correlated with the assumed beta-alpha branching ratio. We have remeasured the beta-alpha branching ratio by implanting 16N ions in a segmented Si detector and counting the number of beta-alpha decays relative to the number of implantations. Our result, 1.49(5)e-5, represents a 24% increase compared to the accepted value and implies an increase of 14% in the extrapolated S-factor