2,200 research outputs found
Translational cooling and storage of protonated proteins in an ion trap at subkelvin temperatures
Gas-phase multiply charged proteins have been sympathetically cooled to
translational temperatures below 1 K by Coulomb interaction with laser-cooled
barium ions in a linear ion trap. In one case, an ensemble of 53 cytochrome c
molecules (mass ~ 12390 amu, charge +17 e) was cooled by ~ 160 laser-cooled
barium ions to less than 0.75 K. Storage times of more than 20 minutes have
been observed and could easily be extended to more than an hour. The technique
is applicable to a wide variety of complex molecules.Comment: same version as published in Phys. Rev.
Dynamic fracture of icosahedral model quasicrystals: A molecular dynamics study
Ebert et al. [Phys. Rev. Lett. 77, 3827 (1996)] have fractured icosahedral
Al-Mn-Pd single crystals in ultrahigh vacuum and have investigated the cleavage
planes in-situ by scanning tunneling microscopy (STM). Globular patterns in the
STM-images were interpreted as clusters of atoms. These are significant
structural units of quasicrystals. The experiments of Ebert et al. imply that
they are also stable physical entities, a property controversially discussed
currently. For a clarification we performed the first large scale fracture
simulations on three-dimensional complex binary systems. We studied the
propagation of mode I cracks in an icosahedral model quasicrystal by molecular
dynamics techniques at low temperature. In particular we examined how the shape
of the cleavage plane is influenced by the clusters inherent in the model and
how it depends on the plane structure. Brittle fracture with no indication of
dislocation activity is observed. The crack surfaces are rough on the scale of
the clusters, but exhibit constant average heights for orientations
perpendicular to high symmetry axes. From detailed analyses of the fractured
samples we conclude that both, the plane structure and the clusters, strongly
influence dynamic fracture in quasicrystals and that the clusters therefore
have to be regarded as physical entities.Comment: 10 pages, 12 figures, for associated avi files, see
http://www.itap.physik.uni-stuttgart.de/~frohmut/MOVIES/emitted_soundwaves.avi
and
http://www.itap.physik.uni-stuttgart.de/~frohmut/MOVIES/dynamic_fracture.av
Laser spectroscopy of hyperfine structure in highly-charged ions: a test of QED at high fields
An overview is presented of laser spectroscopy experiments with cold,
trapped, highly-charged ions, which will be performed at the HITRAP facility at
GSI in Darmstadt (Germany). These high-resolution measurements of ground state
hyperfine splittings will be three orders of magnitude more precise than
previous measurements. Moreover, from a comparison of measurements of the
hyperfine splittings in hydrogen- and lithium-like ions of the same isotope,
QED effects at high electromagnetic fields can be determined within a few
percent. Several candidate ions suited for these laser spectroscopy studies are
presented.Comment: 5 pages, 1 figure, 1 table. accepted for Canadian Journal of Physics
(2006
The polarization observables T, P, and H and their impact on multipoles
Data on the polarization observables T, P, and H for the reaction are reported. Compared to earlier data from other experiments, our
data are more precise and extend the covered range in energy and angle
substantially. The results were extracted from azimuthal asymmetries measured
using a transversely polarized target and linearly polarized photons. The data
were taken at the Bonn electron stretcher accelerator ELSA with the CBELSA/TAPS
detector. Within the Bonn-Gatchina partial wave analysis, the new polarization
data lead to a significant narrowing of the error band for the multipoles for
neutral-pion photoproduction
New and simple algorithms for stable flow problems
Stable flows generalize the well-known concept of stable matchings to markets
in which transactions may involve several agents, forwarding flow from one to
another. An instance of the problem consists of a capacitated directed network,
in which vertices express their preferences over their incident edges. A
network flow is stable if there is no group of vertices that all could benefit
from rerouting the flow along a walk.
Fleiner established that a stable flow always exists by reducing it to the
stable allocation problem. We present an augmenting-path algorithm for
computing a stable flow, the first algorithm that achieves polynomial running
time for this problem without using stable allocation as a black-box
subroutine. We further consider the problem of finding a stable flow such that
the flow value on every edge is within a given interval. For this problem, we
present an elegant graph transformation and based on this, we devise a simple
and fast algorithm, which also can be used to find a solution to the stable
marriage problem with forced and forbidden edges.
Finally, we study the stable multicommodity flow model introduced by
Kir\'{a}ly and Pap. The original model is highly involved and allows for
commodity-dependent preference lists at the vertices and commodity-specific
edge capacities. We present several graph-based reductions that show
equivalence to a significantly simpler model. We further show that it is
NP-complete to decide whether an integral solution exists
Pulmonary and extrapulmonary infection caused by Mycobacterium conceptionense: the first report from Iran
The N(1520) 3/2- helicity amplitudes from an energy-independent multipole analysis based on new polarization data on photoproduction of neutral pions
New data on the polarization observables T, P, and H for the reaction are reported. The results are extracted from azimuthal
asymmetries when a transversely polarized butanol target and a linearly
polarized photon beam are used. The data were taken at the Bonn electron
stretcher accelerator ELSA using the CBELSA/TAPS detector. These and earlier
data are used to perform a truncated energy-independent partial wave analysis
in sliced-energy bins. This energy-independent analysis is compared to the
results from energy-dependent partial wave analyses
Company âEmigrationâ and EC Freedom of Establishment: Daily Mail Revisited
Following the ECJâs recent case law on EC freedom of establishment (the Centros, Ăberseering and Inspire Art cases), regulatory competition for corporate law within the European Union takes place at an early stage of the incorporation of new companies. In contrast, as regards the âmoving outâ of companies from the country of incorporation, the ECJ once considered a tax law restriction against the transfer abroad of a companyâs administrative seat as compatible with EC freedom of establishment (the Daily Mail case). For years, this decision has been regarded as applicable to all restrictions imposed by countries of incorporation, even the forced liquidation of the âemigratingâ company. This paper addresses the question whether EC freedom of establishment really allows Member States to place any limit on the âemigrationâ of nationally registered companies. It argues that EC freedom of establishment covers the transfer of the administrative seat as well as the transfer of the registered office and, therefore, that the country of incorporation cannot liquidate âemigratingâ companies. In addition, it addresses the question whether a new Directive is needed to allow the transfer of a com- panyâs registered office and the identity-preserving company law changes. It argues that such a Directive is necessary to avoid legal uncertainty and to protect the interests of employees, creditors and minority shareholders, among others, who could be detrimentally affected by the âemigrationâ of national companies
Negotiating the EU data protection reform: reflections on the household exemption
The re-drafting of the household exemption comprises one of the main areas of dispute in the ongoing negotiations for the EU data protection reform. The aim of this paper is twofold: First, we present and critically assess the wording proposals that have been put forward mainly at EU institutional level and identify the particular areas which cause tension. Second, we concomitantly ask which is the most appropriate wording for the exemption in question and in particular, whether the household exemption should comprise a set of decisive criteria or whether it should provide a more general framework. We eventually argue for a broad wording of the Article 2(2)(d) coupled with the addition of further non-determinative criteria at Recital 15, i.e. the non-operative part of the proposed Regulation
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