@article{SchulzOrgzallDiezetal.2010,
  author    = {Schulz, Burkhard and Orgzall, Ingo and Diez, Isabel and Dietzel, Birgit and Tauer, Klaus},
  title     = {Template mediated formation of shaped polypyrrole particles},
  issn      = {0927-7757},
  doi       = {10.1016/j.colsurfa.2009.11.034},
  year      = {2010},
  abstract  = {The formation of different micro- and nanostructures during the chemical synthesis of polypyrrole is reviewed shortly based on the conceptions of hard- and soft-templating models. Contrary to other models that emphasize the role of micelles it is found here that during the oxidative polymerization of pyrole using sulfonic acid dopants a crystalline hard template is found in the first steps of the reaction before the addition of the oxidant. This template is formed by a complex consisting of 2,5-bis(pyrrole-2-yl)pyrrolidine and the sulfonic acid anion. The acid catalyzed formation of this specific tripyrrole is discussed. (C) 2009 Elsevier B.V. All rights reserved.},
  language  = {en}
}
@article{ValoriKliemToeroeketal.2010,
  author    = {Valori, Gherardo and Kliem, Bernhard and T{\"o}r{\"o}k, Tibor and Titov, Viacheslav S.},
  title     = {Testing magnetofrictional extrapolation with the Titov-Demoulin model of solar active regions},
  issn      = {0004-6361},
  doi       = {10.1051/0004-6361/201014416},
  year      = {2010},
  abstract  = {We examine the nonlinear magnetofrictional extrapolation scheme using the solar active region model by Titov and Demoulin as test field. This model consists of an arched, line-tied current channel held in force-free equilibrium by the potential field of a bipolar flux distribution in the bottom boundary. A modified version with a parabolic current density profile is employed here. We find that the equilibrium is reconstructed with very high accuracy in a representative range of parameter space, using only the vector field in the bottom boundary as input. Structural features formed in the interface between the flux rope and the surrounding arcade - "hyperbolic flux tube" and "bald patch separatrix surface" - are reliably reproduced, as are the flux rope twist and the energy and helicity of the configuration. This demonstrates that force-free fields containing these basic structural elements of solar active regions can be obtained by extrapolation. The influence of the chosen initial condition on the accuracy of reconstruction is also addressed, confirming that the initial field that best matches the external potential field of the model quite naturally leads to the best reconstruction. Extrapolating the magnetogram of a Titov-Demoulin equilibrium in the unstable range of parameter space yields a sequence of two opposing evolutionary phases, which clearly indicate the unstable nature of the configuration: a partial buildup of the flux rope with rising free energy is followed by destruction of the rope, losing most of the free energy.},
  language  = {en}
}
@article{BornLevermann2010,
  author    = {Born, Andreas and Levermann, Anders},
  title     = {The 8.2 ka event : abrupt transition of the subpolar gyre toward a modern North Atlantic circulation},
  issn      = {1525-2027},
  doi       = {10.1029/2009gc003024},
  year      = {2010},
  abstract  = {Climate model simulations of the 8.2 ka event show an abrupt strengthening of the Atlantic subpolar gyre that allows us to connect two major but apparently contradictory climate events of the early Holocene: the freshwater outburst from proglacial lakes and the onset of Labrador Sea water formation. The 8.2 ka event is the largest climatic signal of our present interglacial with a widespread cooling in the North Atlantic region about 8200 years before present. It coincides with a meltwater outburst from North American proglacial lakes that is believed to have weakened the Atlantic meridional overturning circulation and northward heat transport, followed by a recovery of the deep ocean circulation and rising temperatures after a few centuries. Marine proxy data, however, date the onset of deep water formation in Labrador Sea to the same time. The subsequent strengthening of the slope current system created a regional signal recorded as an abrupt and persistent surface temperature decrease. Although similarities in timing are compelling, a mechanism to reconcile these apparently contradictory events was missing. Our simulations show that an abrupt and persistent strengthening of the Atlantic subpolar gyre provides a plausible explanation. The intense freshwater pulse triggered a transition of the gyre circulation into a different mode of operation, stabilized by internal feedbacks and persistent after the cessation of the perturbation. As a direct consequence, deep water formation around its center intensifies. This corresponds to the modern flow regime and stabilizes the meridional overturning circulation, possibly contributing to the Holocene's climatic stability.},
  language  = {en}
}
@article{TodtPenaHamannetal.2010,
  author    = {Todt, Helge Tobias and Pena, Maria A. and Hamann, Wolf-Rainer and Gr{\"a}fener, G{\"o}tz},
  title     = {The central star of the planetary nebula PB8 : a Wolf-Rayet-type wind of an unusual WN/WC chemical composition},
  issn      = {0004-6361},
  doi       = {10.1051/0004-6361/200912183},
  year      = {2010},
  abstract  = {A considerable fraction of the central stars of planetary nebulae (CSPNe) are hydrogen-deficient. As a rule, these CSPNe exhibit a chemical composition of helium, carbon, and oxygen with the majority showing Wolf-Rayet-like emission line spectra. These stars are classified as CSPNe of a spectral type [WC]. We perform a spectral analysis of CSPN PB 8 with the Potsdam Wolf-Rayet (PoWR) models for expanding atmospheres. The source PB8 displays wind-broadened emission lines from strong mass loss. Most strikingly, we find that its surface composition is hydrogen-deficient, but not carbon-rich. With mass fractions of 55\% helium, 40\% hydrogen, 1.3\% carbon, 2\% nitrogen, and 1.3\% oxygen, it differs greatly from the 30-50\% of carbon which are typically seen in [WC]-type central stars. The atmospheric mixture in PB8 has an analogy in the WN/WC transition type among the massive Wolf-Rayet stars. Therefore we suggest to introduce a new spectral type [WN/WC] for CSPNe, with PB8 as its first member. The central star of PB8 has a relatively low temperature of T-* = 52 kK, as expected for central stars in their early evolutionary stages. Its surrounding nebula is less than 3000 years old, i.e. relatively young. Existing calculations for the post-AGB evolution can produce hydrogen-deficient stars of the [WC] type, but do not predict the composition found in PB8. We discuss various scenarios that might explain the origin of this unique object.},
  language  = {en}
}
@article{EichlerGuettaPohl2010,
  author    = {Eichler, David and Guetta, Dafne and Pohl, Martin},
  title     = {The high energy budget allocations in shocks and gamma ray bursts},
  issn      = {0004-637X},
  doi       = {10.1088/0004-637x/722/1/543},
  year      = {2010},
  abstract  = {The statistical distribution of energies among particles responsible for long gamma-ray burst (GRB) emission is analyzed in light of recent results of the Fermi Observatory. The all-sky flux, F., recorded by the Gamma-Ray Burst Monitor (GBM) is shown, despite its larger energy range, to be not significantly larger than that reported by the Burst and Transient Explorer, suggesting a relatively small flux in the 3-30MeV energy range. The present-day energy input rate in gamma-rays recorded by the GBM from long GRBs is found, assuming star formation rates in the literature, to be W(0) = 0.5F gamma H/c = 5x10(42) erg Mpc(-3) yr(-1). The Large Area Telescope fluence, when observed, is about 5\%-10\% per decade of the total, in good agreement with the predictions of saturated, nonlinear shock acceleration. The high- energy component of long GRBs, as measured by Fermi, is found to contain only similar to 10-2.5 of the energy needed to produce ultrahigh-energy cosmic rays (UHECRs) above 4 EeV, assuming the latter to be extragalactic, when various numerical factors are carefully included, if the cosmic-ray source spectrum has a spectral index of -2. The observed. - ray fraction of the required UHECR energy is even smaller if the source spectrum is softer than E-2. The AMANDA II limits rule out such a GRB origin for UHECRs if much more than 10(-2) of the cosmic-ray energy goes into neutrinos that are within, and simultaneous with, the gamma-ray beam. It is suggested that "orphan" neutrinos out of the gamma-ray beam might be identifiable via orphan afterglow or other wide angle signatures of GRBs in lieu of coincidence with prompt gamma-rays, and it is recommended that feasible single neutrino trigger criteria be established to search for such coincidences.},
  language  = {en}
}
@article{ToeroekBergerKliem2010,
  author    = {T{\"o}r{\"o}k, Tibor and Berger, Mitch A. and Kliem, Bernhard},
  title     = {The writhe of helical structures in the solar corona},
  issn      = {0004-6361},
  doi       = {10.1051/0004-6361/200913578},
  year      = {2010},
  abstract  = {Context. Helicity is a fundamental property of magnetic fields, conserved in ideal MHD. In flux rope geometry, it consists of twist and writhe helicity. Despite the common occurrence of helical structures in the solar atmosphere, little is known about how their shape relates to the writhe, which fraction of helicity is contained in writhe, and how much helicity is exchanged between twist and writhe when they erupt. Aims. Here we perform a quantitative investigation of these questions relevant for coronal flux ropes. Methods. The decomposition of the writhe of a curve into local and nonlocal components greatly facilitates its computation. We use it to study the relation between writhe and projected S shape of helical curves and to measure writhe and twist in numerical simulations of flux rope instabilities. The results are discussed with regard to filament eruptions and coronal mass ejections (CMEs). Results. (1) We demonstrate that the relation between writhe and projected S shape is not unique in principle, but that the ambiguity does not affect low- lying structures, thus supporting the established empirical rule which associates stable forward (reverse) S shaped structures low in the corona with positive (negative) helicity. (2) Kink-unstable erupting flux ropes are found to transform a far smaller fraction of their twist helicity into writhe helicity than often assumed. (3) Confined flux rope eruptions tend to show stronger writhe at low heights than ejective eruptions (CMEs). This argues against suggestions that the writhing facilitates the rise of the rope through the overlying field. (4) Erupting filaments which are S shaped already before the eruption and keep the sign of their axis writhe (which is expected if field of one chirality dominates the source volume of the eruption), must reverse their S shape in the course of the rise. Implications for the occurrence of the helical kink instability in such events are discussed. (5) The writhe of rising loops can easily be estimated from the angle of rotation about the direction of ascent, once the apex height exceeds the footpoint separation significantly. Conclusions. Writhe can straightforwardly be computed for numerical data and can often be estimated from observations. It is useful in interpreting S shaped coronal structures and in constraining models of eruptions.},
  language  = {en}
}
@article{BalažVidanovicBogojevićetal.2010,
  author    = {Balaž, Antun and Vidanovic, Ivana and Bogojević, Aleksandar and Pelster, Axel},
  title     = {Ultra-fast converging path-integral approach for rotating ideal Bose-Einstein condensates},
  issn      = {0375-9601},
  doi       = {10.1016/j.physleta.2010.01.034},
  year      = {2010},
  abstract  = {A recently developed efficient recursive approach for analytically calculating the short-time evolution of the one-particle propagator to extremely high orders is applied here for numerically studying the thermodynamical and dynamical properties of a rotating ideal Bose gas of Rb-87 atoms in an anharmonic trap. At first, the one-particle energy spectrum of the system is obtained by diagonalizing the discretized short-time propagator. Using this, many-boson properties such as the condensation temperature, the ground-state occupancy, density profiles, and time-of-flight absorption pictures are calculated for varying rotation frequencies. The obtained results improve previous semiclassical calculations, in particular for smaller particle numbers. Furthermore, we find that typical time scales for a free expansion are increased by an order of magnitude for the delicate regime of both critical and overcritical rotation.},
  language  = {en}
}
@article{HerzogLeitenbergerShayduketal.2010,
  author    = {Herzog, Marc and Leitenberger, Wolfram and Shayduk, Roman and van der Veen, Renske Marjan and Milne, Chris J. and Johnson, Steven Lee and Vrejoiu, Ionela and Alexe, Marin and Hesse, Dietrich and Bargheer, Matias},
  title     = {Ultrafast manipulation of hard x-rays by efficient Bragg switches},
  issn      = {0003-6951},
  doi       = {10.1063/1.3402773},
  year      = {2010},
  abstract  = {We experimentally demonstrate efficient switching of the hard x-ray Bragg reflectivity of a SrRuO3 /SrTiO3 superlattice by optical excitation of large-amplitude coherent acoustic superlattice phonons. The rocking curve changes drastically on a 1 ps timescale. The (0 0 116) reflection is almost extinguished (Delta R/R-0=-0.91), while the (0 0 118) reflection increases by more than an order of magnitude (Delta R/R-0=24.1). The change of the x-ray structure factor depends nonlinearly on the phonon amplitude, allowing manipulation of the x-ray response on a timescale considerably shorter than the phonon period. Numerical simulations for a superlattice with slightly changed geometry and realistic parameters predict a switching-contrast ratio Delta R/R-0 of 700 with high reflectivity.},
  language  = {en}
}
@article{deBeaudrap2010,
  author    = {de Beaudrap, Niel},
  title     = {Unitary-circuit semantics for measurement-based computations},
  issn      = {0219-7499},
  doi       = {10.1142/S0219749910006113},
  year      = {2010},
  abstract  = {One-way measurement based quantum computations (1WQC) may describe unitary transformations, via a composition of CPTP maps which are not all unitary themselves. This motivates the following decision problems. Is it possible to determine whether a "quantum-to-quantum" 1WQC procedure (having non-trivial input and output subsystems) performs a unitary transformation? Is it possible to describe precisely how such computations transform quantum states, by translation to a quantum circuit of comparable complexity? In this article, we present an efficient algorithm for transforming certain families of measurement-based computations into a reasonable unitary circuit model, in particular without employing the principle of deferred measurement.},
  language  = {en}
}
@article{VitaglianoRieraLatorre2010,
  author    = {Vitagliano, Giuseppe and Riera, Arnau and Latorre, Jos{\´e} Ignacio},
  title     = {Volume-law scaling for the entanglement entropy in spin-1/2 chains},
  issn      = {1367-2630},
  doi       = {10.1088/1367-2630/12/11/113049},
  year      = {2010},
  abstract  = {Entanglement entropy obeys area law scaling for typical physical quantum systems. This may naively be argued to follow from the locality of interactions. We show that this is not the case by constructing an explicit simple spin chain Hamiltonian with nearest-neighbor interactions that presents an entanglement volume scaling law. This non- translational model is contrived to have couplings that force the accumulation of singlet bonds across the half-chain. This configuration of the couplings is suggested by real-space renormalization group arguments. Computation of the entanglement entropy is performed by mapping the system to free fermions and diagonalizing numerically its correlation matrix. An analytical relationship between the entanglement entropy and the Frobenius norm of the correlation matrix is also established. Our result is complementary to the known relationship between non-translational invariant, nearest- neighbor interacting Hamiltonians and quantum Merlin-Arthur (QMA)complete problems.},
  language  = {en}
}