468 research outputs found
Magnetic screening in proximity effect Josephson-junction arrays
The modulation with magnetic field of the sheet inductance measured on
proximity effect Josephson-junction arrays (JJAs) is progressively vanishing on
lowering the temperature, leading to a low temperature field-independent
response. This behaviour is consistent with the decrease of the two-dimensional
penetration length below the lattice parameter. Low temperature data are
quantitatively compared with theoretical predictions based on the XY model in
absence of thermal fluctuations. The results show that the description of a JJA
within the XY model is incomplete and the system is put well beyond the weak
screening limit which is usually assumed in order to invoke the well known
frustrated XY model describing classical Josephson-junction arrays.Comment: 6 pages, 5 figure
Coherent transport in Josephson-Junction rhombi chain with quenched disorder
We consider a chain of Josephson-junction rhombi (proposed originally by
Doucot and Vidal) in quantum regime. In a regular chain with no disorder in the
maximally frustrated case when magnetic flux through each rhombi \Phi_r is
equal to one half of superconductive flux quantum \Phi_0, Josephson current is
due to correlated transport of pairs of Cooper pairs, i.e. charge is quantized
in units of . Sufficiently strong deviation \delta\Phi =|\Phi_r-\Phi_0/2| >
\delta\Phi^c from the maximally frustrated point brings the system back to
usual -quantized supercurrent. For a regular chain \delta\Phi^c was
calculated by us previously. Here we present detailed analysis of the effect of
quenched disorder (random stray charges and random fluxes piercing rhombi) on
the pairing effect.Comment: 21 pages, 5 figure
Automatic generation of pseudoknotted RNAs taxonomy
Background: The ability to compare RNA secondary structures is important in understanding their biological function and for grouping similar organisms into families by looking at evolutionarily conserved sequences such as 16S rRNA. Most comparison methods and benchmarks in the literature focus on pseudoknot-free structures due to the difficulty of mapping pseudoknots in classical tree representations. Some approaches exist that permit to cluster pseudoknotted RNAs but there is not a general framework for evaluating their performance. Results: We introduce an evaluation framework based on a similarity/dissimilarity measure obtained by a comparison method and agglomerative clustering. Their combination automatically partition a set of molecules into groups. To illustrate the framework we define and make available a benchmark of pseudoknotted (16S and 23S) and pseudoknot-free (5S) rRNA secondary structures belonging to Archaea, Bacteria and Eukaryota. We also consider five different comparison methods from the literature that are able to manage pseudoknots. For each method we clusterize the molecules in the benchmark to obtain the taxa at the rank phylum according to the European Nucleotide Archive curated taxonomy. We compute appropriate metrics for each method and we compare their suitability to reconstruct the taxa
Observation of Ising-like critical fluctuations in frustrated Josephson junction arrays with modulated coupling energies
We report the results of ac sheet conductance measurements performed on fully
frustrated square arrays of Josephson junctions whose coupling energy is
periodically modulated in one of the principal lattice directions. Such systems
are predicted to exhibit two distinct transitions: a low-temperature Ising-like
transition triggered by the proliferation of domain walls and a
high-temperature transition driven by the vortex unbinding mechanism of the
Beresinskii-Kosterlitz-Thouless (BKT) theory. Both the superfluid and
dissipative components of the conductance are found to exhibit features which
unambiguously demonstrate the existence of a double transition whose properties
are consistent with the Ising-BKT scenario.Comment: To be published in Physica C (Proceedings of the 2nd European
Conference in School Format 'Vortex Matter in Superconductors'
Mapping the dynamic interactions between vortex species in highly anisotropic superconductors
Here we use highly sensitive magnetisation measurements performed using a
Hall probe sensor on single crystals of highly anisotropic high temperature
superconductors to study the dynamic interactions
between the two species of vortices that exist in such superconductors. We
observe a remarkable and clearly delineated high temperature regime that
mirrors the underlying vortex phase diagram. Our results map out the parameter
space over which these dynamic interaction processes can be used to create
vortex ratchets, pumps and other fluxonic devices.Comment: 7 pages, 3 figures, to be published in Supercond. Sci. Techno
The Qur'an Seminar Commentary
The Qur'an Seminar Commentary is an unprecedented work of collaboration in the field of Qur'anic Studies, involving the insights of 25 scholars on 50 Qur'anic passages. These scholars represent a diverse range of disciplinary backgrounds and provide readers with unique insights into the latest trends of research in the Qur'an. This Commentary is a useful and illuminating reference work for students and scholars in the field of Qur'anic Studies
- …