9,394 research outputs found
Zero-mode contribution to the light-front Hamiltonian of Yukawa type models
Light-front Hamiltonian for Yukawa type models is determined without the
framework of canonical light-front formalism. Special attention is given to the
contribution of zero modes.Comment: 14 pages, Latex, revised version with minor changes, Submitted to
J.Phys.
Angular EPR paradox
The violation of local uncertainty relations is a valuable tool for detecting
entanglement, especially in multi-dimensional systems. The orbital angular
momentum of light provides such a multi-dimensional system. We study quantum
correlations for the conjugate variables of orbital angular momentum and
angular position. We determine an experimentally testable criterion for the
demonstration of an angular version of the EPR paradox. For the interpretation
of future experimental results from our proposed setup, we include a model for
the indeterminacies inherent to the angular position measurement. For this
measurement angular apertures are used to determine the probability density of
the angle. We show that for a class of aperture functions a demonstration of an
angular EPR paradox, according to our criterion, is to be expected.Comment: 21 pages, 9 figures, to be published in J. Mod. Opt. special issue on
quantum imagin
A conserved U-rich RNA region implicated in regulation of translation in Plasmodium female gametocytes.
Translational repression (TR) plays an important role
in post-transcriptional regulation of gene expression
and embryonic development in metazoans. TR
also regulates the expression of a subset of the
cytoplasmic mRNA population during development
of fertilized female gametes of the unicellular
malaria parasite, Plasmodium spp. which results
in the formation of a polar and motile form, the
ookinete. We report the conserved and sex-specific
regulatory role of either the 3’- or 5’-UTR of a subset
of translationally repressed mRNA species as
shown by almost complete inhibition of expression
of a GFP reporter protein in the female gametocyte.
A U-rich, TR-associated element, identified previously
in the 3’-UTR of TR-associated transcripts,
played an essential role in mediating TR and a
similar region could be found in the 5’-UTR shown in
this study to be active in TR. The silencing effect of
this 5’-UTR was shown to be independent of its
position relative to its ORF, as transposition to a
location 3’ of the ORF did not affect TR. These
results demonstrate for the first time in a unicellular
organism that the 5’ or the 3’-UTR of TR-associated
transcripts play an important and conserved role in
mediating TR in female gametocytes
Polarisation structuring of broadband light
Spatial structuring of the intensity, phase and polarisation of light is useful in a wide variety of modern applications, from microscopy to optical communications. This shaping is most commonly achieved using liquid crystal spatial light modulators (LC-SLMs). However, the inherent chromatic dispersion of LC-SLMs when used as diffractive elements presents a challenge to the extension of such techniques from monochromatic to broadband light. In this work we demonstrate a method of generating broadband vector beams with dynamically tunable intensity, phase and polarisation over a bandwidth of 100 nm. We use our system to generate radially and azimuthally polarised vector vortex beams carrying orbital angular momentum, and beams whose polarisation states span the majority of the Poincaré sphere. We characterise these broadband vector beams using spatially and spectrally resolved Stokes measurements, and detail the technical and fundamental limitations of our technique, including beam generation fidelity and efficiency. The broadband vector beam shaper that we demonstrate here may find use in applications such as ultrafast beam shaping and white light microscopy
Polarisation structuring of broadband light
Spatial structuring of the intensity, phase and polarisation of light is useful in a wide variety of modern applications, from microscopy to optical communications. This shaping is most commonly achieved using liquid crystal spatial light modulators (LC-SLMs). However, the inherent chromatic dispersion of LC-SLMs when used as diffractive elements presents a challenge to the extension of such techniques from monochromatic to broadband light. In this work we demonstrate a method of generating broadband vector beams with dynamically tunable intensity, phase and polarisation over a bandwidth of 100 nm. We use our system to generate radially and azimuthally polarised vector vortex beams carrying orbital angular momentum, and beams whose polarisation states span the majority of the Poincaré sphere. We characterise these broadband vector beams using spatially and spectrally resolved Stokes measurements, and detail the technical and fundamental limitations of our technique, including beam generation fidelity and efficiency. The broadband vector beam shaper that we demonstrate here may find use in applications such as ultrafast beam shaping and white light microscopy
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