Nonlinear cross-Kerr quasiclassical dynamics

We study the quasiclassical dynamics of the cross-Kerr effect. In this approximation, the typical periodical revivals of the decorrelation between the two polarization modes disappear and they remain entangled. By mapping the dynamics onto the Poincare space, we find simple conditions for polarization squeezing. When dissipation is taken into account, the shape of the states in such a space is not considerably modified, but their size is reduced.Comment: 16 pages, 5 figure

Angular performance measure for tighter uncertainty relations

The uncertainty principle places a fundamental limit on the accuracy with which we can measure conjugate physical quantities. However, the fluctuations of these variables can be assessed in terms of different estimators. We propose a new angular performance that allows for tighter uncertainty relations for angle and angular momentum. The differences with previous bounds can be significant for particular states and indeed may be amenable to experimental measurement with the present technology.Comment: 4 pages, 1 figures. Comments welcom

Characteristics of <u>></u> 290 keV magnetosheath ions

International audienceWe performed a statistical analysis of 290-500 keV ion data obtained by IMP-8 during the years 1982-1988 within the earth's magnetosheath and analysed in detail some time periods withdistinct ion bursts. These studies reveal the following characteristics for magnetosheath 290-500 keV energetic ions: (a) the occurrence frequency and the flux of ions increase with increasing geomagnetic activity as indicated by the Kp index; the occurrence frequency was found to be as high as P > 42% for Kp > 2, (b) the occurrence frequency in the dusk magnetosheath was found to be slightly dependent on the local time and ranged between ~30% and ~46% for all Kp values; the highest occurrence frequency was detected near the dusk magnetopause (21 LT), (c) the high energy ion bursts display a dawn-dusk asymmetry in their maximum fluxes, with higher fluxes appearing in the dusk magnetosheath, and (d) the observations in the dusk magnetosheath suggest that there exist intensity gradients of energetic ions from the bow shock toward the magnetopause. The statistical results are consistent with the concept that leakage of magnetospheric ions from the dusk magnetopause is a semi-permanent physical process often providing the magnetosheath with high energy (290-500 keV) ions

Communicating graphical information to blind users using music : the role of context

We describe the design and use of AUDIOGRAPH - a tool for investigating the use of music in the communication of graphical information to blind and partially sighted users. This paper examines the use of the system to communicate complex diagrams and gives some examples of user output. Performance is not as good as expected and it is postulated that context will play an important part in the perception of diagrams communicated using music. A set of experiments are reported which indicate that context does indeed seem to play an important role in assisting meaningful understanding of the diagrams communicated. The implications for using music in auditory interface design are discussed

Orbital angular momentum from marginals of quadrature distributions

We set forth a method to analyze the orbital angular momentum of a light field. Instead of using the canonical formalism for the conjugate pair angle-angular momentum, we model this latter variable by the superposition of two independent harmonic oscillators along two orthogonal axes. By describing each oscillator by a standard Wigner function, we derive, via a consistent change of variables, a comprehensive picture of the orbital angular momentum. We compare with previous approaches and show how this method works in some relevant examples.Comment: 7 pages, 2 color figure

Extraction of consensus protein patterns in regions containing non-proline cis peptide bonds and their functional assessment

<p>Abstract</p> <p>Background</p> <p>In peptides and proteins, only a small percentile of peptide bonds adopts the <it>cis </it>configuration. Especially in the case of amide peptide bonds, the amount of <it>cis </it>conformations is quite limited thus hampering systematic studies, until recently. However, lately the emerging population of databases with more 3D structures of proteins has produced a considerable number of sequences containing non-proline <it>cis </it>formations (<it>cis</it>-nonPro).</p> <p>Results</p> <p>In our work, we extract regular expression-type patterns that are descriptive of regions surrounding the <it>cis</it>-nonPro formations. For this purpose, three types of pattern discovery are performed: i) exact pattern discovery, ii) pattern discovery using a chemical equivalency set, and iii) pattern discovery using a structural equivalency set. Afterwards, using each pattern as predicate, we search the Eukaryotic Linear Motif (ELM) resource to identify potential functional implications of regions with <it>cis</it>-nonPro peptide bonds. The patterns extracted from each type of pattern discovery are further employed, in order to formulate a pattern-based classifier, which is used to discriminate between <it>cis</it>-nonPro and <it>trans</it>-nonPro formations.</p> <p>Conclusions</p> <p>In terms of functional implications, we observe a significant association of <it>cis</it>-nonPro peptide bonds towards ligand/binding functionalities. As for the pattern-based classification scheme, the highest results were obtained using the structural equivalency set, which yielded 70% accuracy, 77% sensitivity and 63% specificity.</p