2,804 research outputs found
Mathieu beams as versatile light moulds for 3D micro particle assemblies
We present tailoring of three dimensional light fields which act as light moulds for elaborate particle micro structures of variable shapes. Stereo microscopy is used for visualization of the 3D particle assemblies. The powerful method is demonstrated for the class of propagation invariant beams, where we introduce the use of Mathieu beams as light moulds with non-rotationally-symmetric structure. They offer multifarious field distributions and facilitate the creation of versatile particle structures. This general technique may find its application in micro fluidics, chemistry, biology, and medicine, to create highly efficient mixing tools, for hierarchical supramolecular organization or in 3D tissue engineering
Measuring orbital angular momentum superpositions of light by mode transformation
We recently reported on a method for measuring orbital angular momentum (OAM) states of light based on the transformation of helically phased beams to tilted plane waves [Phys. Rev. Lett.105, 153601 (2010)]. Here we consider the performance of such a system for superpositions of OAM states by measuring the modal content of noninteger OAM states and beams produced by a Heaviside phase plate
Mammographic image restoration using maximum entropy deconvolution
An image restoration approach based on a Bayesian maximum entropy method
(MEM) has been applied to a radiological image deconvolution problem, that of
reduction of geometric blurring in magnification mammography. The aim of the
work is to demonstrate an improvement in image spatial resolution in realistic
noisy radiological images with no associated penalty in terms of reduction in
the signal-to-noise ratio perceived by the observer. Images of the TORMAM
mammographic image quality phantom were recorded using the standard
magnification settings of 1.8 magnification/fine focus and also at 1.8
magnification/broad focus and 3.0 magnification/fine focus; the latter two
arrangements would normally give rise to unacceptable geometric blurring.
Measured point-spread functions were used in conjunction with the MEM image
processing to de-blur these images. The results are presented as comparative
images of phantom test features and as observer scores for the raw and
processed images. Visualization of high resolution features and the total image
scores for the test phantom were improved by the application of the MEM
processing. It is argued that this successful demonstration of image
de-blurring in noisy radiological images offers the possibility of weakening
the link between focal spot size and geometric blurring in radiology, thus
opening up new approaches to system optimization.Comment: 18 pages, 10 figure
Experimental high-dimensional two-photon entanglement and violations of generalised Bell inequalities
Quantum entanglement plays a vital role in many quantum information and
communication tasks. Entangled states of higher dimensional systems are of
great interest due to the extended possibilities they provide. For example,
they allow the realisation of new types of quantum information schemes that can
offer higher information-density coding and greater resilience to errors than
can be achieved with entangled two-dimensional systems. Closing the detection
loophole in Bell test experiments is also more experimentally feasible when
higher dimensional entangled systems are used. We have measured previously
untested correlations between two photons to experimentally demonstrate
high-dimensional entangled states. We obtain violations of Bell-type
inequalities generalised to d-dimensional systems with up to d = 12.
Furthermore, the violations are strong enough to indicate genuine
11-dimensional entanglement. Our experiments use photons entangled in orbital
angular momentum (OAM), generated through spontaneous parametric
down-conversion (SPDC), and manipulated using computer controlled holograms
Synthesis of perfluorinated polyethers
A series of highly fluorinated acetylenes was prepared and their cyclization reactions were studied. A series of perfluoropolytriazines with -CF2I pendent groups were prepared. These materials can be cured thermally or photochemically to an elastomeric gum. Perfluoropolytriazines with -CN pendent groups were prepared. These materials can be crosslinked by reaction with terephthalonitrile oxide
Innovation with High Social Benefits and Corporate Financial Performance
This article analyzes the effect that innovation with high social benefit has on financial performance, and to improve our understanding of this effect we extend our research by analyzing the effect of being an innovation leader has on financial performance. We intend to give insight about which innovation strategy impacts with more intensity on financial performance. To support this analysis we will make use of the resource-based view theory and the institutional theory. Our research used the panel data technique. The final sample contains 2025 observations for 418 firms. The results of this research demonstrate that there is a negative and significant effect between innovation with high social benefit and financial performance, highlighting the importance of the involvement of governmental and non-governmental institutions to create an incentive for firms to incur in innovative activities that produce social benefits
Synthesis and Analysis of Entangled Photonic Qubits in Spatial-Parity Space
We present the novel embodiment of a photonic qubit that makes use of one
continuous spatial degree of freedom of a single photon and relies on the the
parity of the photon's transverse spatial distribution. Using optical
spontaneous parametric downconversion to produce photon pairs, we demonstrate
the controlled generation of entangled-photon states in this new space.
Specifically, two Bell states, and a continuum of their superpositions, are
generated by simple manipulation of a classical parameter, the optical-pump
spatial parity, and not by manipulation of the entangled photons themselves. An
interferometric device, isomorphic in action to a polarizing beam splitter,
projects the spatial-parity states onto an even--odd basis. This new physical
realization of photonic qubits could be used as a foundation for future
experiments in quantum information processing.Comment: 6 pages, 5 figures, submitted to PR
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