1,128 research outputs found
Supramolecular Structure of the Mitochondrial Oxidative Phosphorylation System
The protein complexes of the mitochondrial oxidative phosphorylation system were recently reported to form supramolecular assemblies termed respiratory supercomplexes or respirasomes. These supercomplexes are considered to be of great functional importance. Here we review new insights into supercomplex structure and physiology
Linking the Quark Meson Model with QCD at High Temperature
We model the transition of a system of quarks and gluons at high energies to
a system of quarks and mesons at low energies in a consistent renormalization
group approach. Flow equations interpolate between the physics of the
high-temperature degrees of freedom and the low-temperature dynamics at a scale
of 1 GeV. We also discuss the dependence of the equation of state on baryon
density and compare our results with recent lattice gauge simulations.Comment: 11 pages, 4 figures additional discussion of the second order phase
transitio
Macroscopic Quantum Tunneling of Ferromagnetic Domain Walls
Quantum tunneling of domain walls out of an impurity potential in a
mesoscopic ferromagnetic sample is investigated. Using improved expressions for
the domain wall mass and for the pinning potential, we find that the cross-over
temperature between thermal activation and quantum tunneling is of a different
functional form than found previously. In materials like Ni or YIG, the
crossover temperatures are around 5 mK. We also find that the WKB exponent is
typically two orders of magnitude larger than current estimates. The sources
for these discrepancies are discussed, and precise estimates for the transition
from three-dimensional to one-dimensional magnetic behavior of a wire are
given. The cross-over temperatures from thermal to quantum transitions and
tunneling rates are calculated for various materials and sample sizes.Comment: 10 pages, 2 postscript figures, REVTe
Nationale Citymarketing Monitor 2010
Inleiding
Citymarketing is volop in beweging. In het begin van de jaren tachtig was het aantal gemeenten met
een citymarketingbeleid nog relatief klein; inmiddels doen veel meer gemeenten aan citymarketing1.
Anno 2010 is citymarketing Ă©Ă©n van de gemeentelijke beleidsterreinen. Citymarketing komt terug in
collegeakkoorden, er zijn wethouders met citymarketing in de portefeuille en er zijn ambtenaren
belast met het ontwikkelen, coördineren en uitvoeren van citymarketing . Ook zien we op meerdere
plaatsen externe – vaak deels door de gemeente gesubsidieerde - partijen die een belangrijke rol
vervullen in de citymarketing. Soms hebben deze externe organisaties vooral uitvoeringstaken, maar
er zijn ook externe organisaties die verantwoordelijk zijn voor het ontwikkelen en coördineren van
het citymarketingbeleid. We kunnen ook spreken van een beroepsgroep van citymarketeers. Een
goed voorbeeld hiervan is dat er veel professionals lid zijn van de Linked In groep voor citymarketing.
Ook kunnen we zeggen dat de aard en omvang van citymarketingactiviteiten in de afgelopen
decennia is veranderd. Zo was city branding nauwelijks aan de orde in de jaren tachtig en negentig.
Vanaf de millenniumwisseling is de belangstelling voor het gebruik van branding toegenomen
Fluctuations and Instabilities of Ferromagnetic Domain Wall pairs in an External Magnetic Field
Soliton excitations and their stability in anisotropic quasi-1D ferromagnets
are analyzed analytically. In the presence of an external magnetic field, the
lowest lying topological excitations are shown to be either soliton-soliton or
soliton-antisoliton pairs. In ferromagnetic samples of macro- or mesoscopic
size, these configurations correspond to twisted or untwisted pairs of Bloch
walls. It is shown that the fluctuations around these configurations are
governed by the same set of operators. The soliton-antisoliton pair has exactly
one unstable mode and thus represents a critical nucleus for thermally
activated magnetization reversal in effectively one-dimensional systems. The
soliton-soliton pair is stable for small external fields but becomes unstable
for large magnetic fields. From the detailed expression of this instability
threshold and an analysis of nonlocal demagnetizing effects it is shown that
the relative chirality of domain walls can be detected experimentally in thin
ferromagnetic films. The static properties of the present model are equivalent
to those of a nonlinear sigma-model with anisotropies. In the limit of large
hard-axis anisotropy the model reduces to a double sine-Gordon model.Comment: 15 pages RevTex 3.0 (twocolumn), 9 figures available on request, to
appear in Phys Rev B, Dec (1994
Comprehensive characterization of molecular interactions based on nanomechanics
Molecular interaction is a key concept in our understanding of the biological mechanisms of life. Two physical properties change when one molecular partner binds to another. Firstly, the masses combine and secondly, the structure of at least one binding partner is altered, mechanically transducing the binding into subsequent biological reactions. Here we present a nanomechanical micro-array technique for bio-medical research, which not only monitors the binding of effector molecules to their target but also the subsequent effect on a biological system in vitro. This label-free and real-time method directly and simultaneously tracks mass and nanomechanical changes at the sensor interface using micro-cantilever technology. To prove the concept we measured lipid vesicle (approximately 748*10(6) Da) adsorption on the sensor interface followed by subsequent binding of the bee venom peptide melittin (2840 Da) to the vesicles. The results show the high dynamic range of the instrument and that measuring the mass and structural changes simultaneously allow a comprehensive discussion of molecular interactions
Simulation of the CTF drive beam line and comparison with the experiment
The tracking of particles in accelerating structures is presented for cases where the effects of the wake-fields are high. This is particularly the case when the structures are used with high current and relatively low energy as in the drive beam of the Compact Linear Collider Test Facility (CTF 2) with its 3 GHz accelerator and its 30 GHz decelerator. High initial energy spread and transverse wake-fields may impair the beam stability and generate particle loss. The CTF modelling is made with the code PARMELA for the 3 GHz part of the beam line, which includes 3 GHz accelerating sections and a magnetic bunch compressor. For the part containing the 30 GHz power-extracting structures, simulations are done with WAKE, a new algorithm dealing with the effects of the wake-field modes 0 and 1, as well as of the group velocity. Beam transmission through the overall beam line is studied, and results are compared with measurements made on the CTF beam
- …