1,266 research outputs found
Confinement, Crossing Symmetry, and Glueballs
We suggest that the quark-confining force is related by crossing symmetry to
a color-singlet glueball which is well described as a loop of one
quantum of color magnetic flux. Electron pair annihilation as high as above the mass could produce accompanied by or one of its excited states.Comment: LaTeX, 12 pages, no figures, Los Alamos preprint LA-UR-94-263
Three-Dimensional Effects on the Electronic Structure of Quasiperiodic Systems
We report on a theoreticl study of the electronic structure of quasiperiodic,
quasi-one-dimensional systems where fully three dimensional interaction
potentials are taken into account. In our approach, the actual physical
potential acting upon the electrons is replaced by a set of nonlocal separable
potentials, leading to an exactly solvable Schrodinger equation. By choosing an
appropriate trial potential, we obtain a discrete set of algebraic equations
that can be mapped onto a general tight-binding-like equation. We introduce a
Fibonacci sequence either in the strength of the on-site potentials or in the
nearest-neighbor distances, and we find numerically that these systems present
a highly fragmented, self-similar electronic spectrum, which becomes singular
continuous in the thermodynamical limit. In this way we extend the results
obtained so far in one-dimensional models to the three-dimensional case. As an
example of the application of the model we consider the chain polymer case.Comment: REVTeX 3.0, 19 pages, 6 figures (available upon request). To appear
in Physica
Calculation of the two-photon decay rates of hydrogen-like ions by using B-polynomials
A new approach is laid out to investigate the two photon atomic transitions.
It is based on application of the finite basis solutions constructed from the
Bernstein Polynomial (B-Polynomial) sets. We show that such an approach
provides a very promising route for the relativistic second- (and even
higher-order) calculations since it allows for analytical evaluation of the
involved matrices elements. In order to illustrate possible applications of the
method and to verify its accuracy, detailed calculations are performed for the
2s_{1/2}-1s_{1/2} transition in neutral hydrogen and hydrogen-like ions, and
are compared with the theoretical predictions based on the well-established
B-spline-basis-set approach
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Systematic evaluation of spliced alignment programs for RNA-seq data
High-throughput RNA sequencing is an increasingly accessible method for studying gene structure and activity on a genome-wide scale. A critical step in RNA-seq data analysis is the alignment of partial transcript reads to a reference genome sequence. To assess the performance of current mapping software, we invited developers of RNA-seq aligners to process four large human and mouse RNA-seq data sets. In total, we compared 26 mapping protocols based on 11 programs and pipelines and found major performance differences between methods on numerous benchmarks, including alignment yield, basewise accuracy, mismatch and gap placement, exon junction discovery and suitability of alignments for transcript reconstruction. We observed concordant results on real and simulated RNA-seq data, confirming the relevance of the metrics employed. Future developments in RNA-seq alignment methods would benefit from improved placement of multimapped reads, balanced utilization of existing gene annotation and a reduced false discovery rate for splice junctions
QED Calculation of E1M1 and E1E2 Transition Probabilities in One-Electron Ions with Arbitrary Nuclear Charge
The quantum electrodynamical theory of the two-photon transitions in
hydrogenlike ions is presented. The emission probability for 2s1/2 -> 2E1+1s1/2
transitions is calculated and compared to the results of the previous
calculations. The emission probabilities 2p12 -> E1E2+1s1/2 and 2p1/2 ->
E1M1+1s1/2 are also calculated for the nuclear charge Z values 1-100. This is
the first calculation of the two latter probabilities. The results are given in
two different gauges.Comment: 14 pages, 4 tables, 1 figur
Relativistic Symmetry Suppresses Quark Spin-Orbit Splitting
Experimental data indicate small spin-orbit splittings in hadrons. For
heavy-light mesons we identify a relativistic symmetry that suppresses these
splittings. We suggest an experimental test in electron-positron annihilation.
Furthermore, we argue that the dynamics necessary for this symmetry are
possible in QCD.Comment: 16 pages, LaTeX. Two postscript figures. Final version to be
published in Physical Review Letter
Relativistic J-matrix method
The relativistic version of the J-matrix method for a scattering problem on
the potential vanishing faster than the Coulomb one is formulated. As in the
non-relativistic case it leads to a finite algebraic eigenvalue problem. The
derived expression for the tangent of phase shift is simply related to the
non-relativistic case formula and gives the latter as a limit case. It is due
to the fact that the used basis set satisfies the ``kinetic balance
condition''.Comment: 21 pages, RevTeX, accepted for publication in Phys. Rev.
What Do Audiences Want from a Public Art Gallery in the Digital Age?
This paper outlines the human-centred design approach taken to create a new analytical framework to understand audiences and establish themes, patterns and behaviours at MOSTYN, a public contemporary art gallery in Llandudno, North Wales. Wrexham Glyndwr University PhD student Clare Harding collaborated with Dr Adrian Gradinar, and Dr Mark Lochrie from Media Innovation Studio, University of Central Lancashire, to test the conceptual framework with the EDGE (Experiential Display to Generate Engagement) research project that secured Innovate UK and the Arts Council of Wales funding. EDGE applied a Human Centred Design process to MOSTYN, Wales’ foremost contemporary Art Gallery MOSTYN to investigate audience expectations of a public art gallery in the digital age. EDGE was designed to help MOSTYN define their purpose as a public art gallery in the face of rapidly developing, culturally competing technologies. Phase one of the project used design thinking and iterative processes to explore new and authentic ways in which MOSTYN can co-design their visitor experience with audiences. Phase two, from April 2019, will use findings to build a digital interface within the gallery to create an interactive exhibition of digital art. This will be accompanied by a six-month engagement programme to build links with new audiences and up-skill both the general public and regional artists. The scope and limitation of the research as identified so far are discussed with a focus on how human-centred design approaches were used to create a new analytical framework. The testing of lo-fi prototypes will be discussed within the gallery setting and the insights uncovered by deployment of the framework, tools and MOSTYN’s engagement programme with a critical review of the methodological approach used and findings to date
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