3,898 research outputs found
Polarization control of single photon quantum orbital angular momentum states
The orbital angular momentum of photons, being defined in an infinitely
dimensional discrete Hilbert space, offers a promising resource for
high-dimensional quantum information protocols in quantum optics. The biggest
obstacle to its wider use is presently represented by the limited set of tools
available for its control and manipulation. Here, we introduce and test
experimentally a series of simple optical schemes for the coherent transfer of
quantum information from the polarization to the orbital angular momentum of
single photons and vice versa. All our schemes exploit a newly developed
optical device, the so-called "q-plate", which enables the manipulation of the
photon orbital angular momentum driven by the polarization degree of freedom.
By stacking several q-plates in a suitable sequence, one can also access to
higher-order angular momentum subspaces. In particular, we demonstrate the
control of the orbital angular momentum degree of freedom within the
subspaces of and per photon. Our experiments prove
that these schemes are reliable, efficient and have a high fidelity.Comment: 9 pages, 8 figure
Non-rigid image registration to reduce beam-induced blurring of cryo-electron microscopy images
Microscopic imaging and technolog
Minimum Cost Homomorphisms to Locally Semicomplete and Quasi-Transitive Digraphs
For digraphs and , a homomorphism of to is a mapping $f:\
V(G)\dom V(H)uv\in A(G)f(u)f(v)\in A(H)u \in V(G)c_i(u), i \in V(H)f\sum_{u\in V(G)}c_{f(u)}(u)HHHGc_i(u)u\in V(G)i\in V(H)GH$ and, if one exists, to find one of minimum cost.
Minimum cost homomorphism problems encompass (or are related to) many well
studied optimization problems such as the minimum cost chromatic partition and
repair analysis problems. We focus on the minimum cost homomorphism problem for
locally semicomplete digraphs and quasi-transitive digraphs which are two
well-known generalizations of tournaments. Using graph-theoretic
characterization results for the two digraph classes, we obtain a full
dichotomy classification of the complexity of minimum cost homomorphism
problems for both classes
Sketch-a-park Study of the usability of diagrams for participatory sketching
Children’s view in participation currently gaining popularity (CABE Space and CABE Education, 2004) along with digital tools of participation based on design exploration currently known as Digital Participatory Platforms (DPPs) (Falco and Kleinhans, 2018), (Gün et al., 2020). Space Syntax Theory (SST) offers a well-proven human-centred analytic framework with applications for public engagement via digital twins (Dembski et al., 2019). Yet, as some authors argue (Baeck and Saunders, 2015), (Dembski et al., 2020), more needs to be done to improve the experiential side of these systems and empower citizens and children, in particular, to carry out their designs within these events using what is. We argue that using diagrammatic sketching as the basis of DPPs is particularly suited for SST since most SS models work out abstractions of urban morphology which can be drawn using simple diagrammatic sketches. However, this type of drawing may prove too abstract for participants and questions remain open regarding the usability of this type of drawings in a participatory environment. It is yet to be proven whether general members of the public, in particular young kids, can engage with diagrammatic sketches and what influence digital environments have on this engagement. To address these questions, we carried out two pilot studies with participants aged 10 to 11-year-old where we asked them to carry out drawings of urban proposals with different levels of information regarding diagrammatic drawings. Tests were repeated with different groups making paper drawings as well as using a bespoke digital tool at different stages of the drawing. We develop an analytic framework for drawings and carry out a comparative study of the material produced. Results from the experiment suggest that 10- to 11-year-old can easily understand the abstraction behind diagrammatic sketches and adopt this technique as a form of expression. We observe that this happens more markedly when using digital tools. This suggests diagrammatic sketches have the potential to be deployed as part of a SS driven participatory tool
Shining a light on Dar es Salaam - 1992 to 2020: utilizing nightlight intensity data as a tool for modelling rapid urban growth patterns
This paper utilizes remotely-sensed nightlight intensity (NLI) data to construct and evaluate a multi-temporal urban growth model for Dar es Salaam, Tanzania, between 1992 and 2020. This contributes towards the creation of effective, globally-available modelling and monitoring tools to support urban planners, policy-makers and communities in contexts of data-sparsity and rapid urban growth: a duality often found in the global south. Findings reveal that multi-temporal NLI models can offer new, systematic insights into patterns of urban growth at multiple intra-city scales. For instance, this NLI model identifies and tracks parts of the city which are likely to have experienced different patterns of spatial and/or socio-economic development between 1992 and 2020
DRAWSCAPES: Study of the effectiveness of online diagrammatic sketching in participatory design
The increased user-friendliness of Space Syntax (SS) packages and their improved compatibility with popular 3D modelling software has pushed the use of Space Syntax Theory (SST) into the professional realm, making it approachable, not just by dedicated researchers, but also to an increasing number of practitioners. We argue that the applicability of SST can even go further if we use sketching as a form of interaction with the software, potentially opening up its use to general members of the public as part of a wider participatory process. We present a study that tries to understand whether the diagrams required for this form of engagement are easy to produce by non-professionals and once they are produced, see whether they have an impact on the planning process. We propose an experiment using an online design tool that allows participants to make drawings of urban proposals by drafting simple diagrams, beginning with connective paths followed by urban blocks using thicker versions of the same pen tool. We develop bespoke analytic methods to extract general patterns emerging from data, identify trends across different user groups, and study user interaction, design quality and user engagement. We take the expansion of UCL East as a case study and test our tool with several participant groups from the general staff and student population as well as external design professionals. Some of these professionals carry out the exercise after reviewing the design from UCL members. We obtained 700 drawings from 400 participants and carry out comparative studies across groups. The study concludes that general members of the public can understand the type of drawing exercise requested and produce designs of an adequate standard. We can also see that planners and architects observe positively the information coming from general members of the public and are willing to incorporate it into their designs
Quantifying Spatiotemporal Chaos in Rayleigh-B\'enard Convection
Using large-scale parallel numerical simulations we explore spatiotemporal
chaos in Rayleigh-B\'enard convection in a cylindrical domain with
experimentally relevant boundary conditions. We use the variation of the
spectrum of Lyapunov exponents and the leading order Lyapunov vector with
system parameters to quantify states of high-dimensional chaos in fluid
convection. We explore the relationship between the time dynamics of the
spectrum of Lyapunov exponents and the pattern dynamics. For chaotic dynamics
we find that all of the Lyapunov exponents are positively correlated with the
leading order Lyapunov exponent and we quantify the details of their response
to the dynamics of defects. The leading order Lyapunov vector is used to
identify topological features of the fluid patterns that contribute
significantly to the chaotic dynamics. Our results show a transition from
boundary dominated dynamics to bulk dominated dynamics as the system size is
increased. The spectrum of Lyapunov exponents is used to compute the variation
of the fractal dimension with system parameters to quantify how the underlying
high-dimensional strange attractor accommodates a range of different chaotic
dynamics
LOCV calculations for polarized liquid with the spin-dependent correlation
We have used the lowest order constrained variational (LOCV) method to
calculate some ground state properties of polarized liquid at zero
temperature with the spin-dependent correlation function employing the
Lennard-Jones and Aziz pair potentials. We have seen that the total energy of
polarized liquid increases by increasing polarization. For all
polarizations, it is shown that the total energy in the spin-dependent case is
lower than the spin-independent case. We have seen that the difference between
the energies of spin-dependent and spin-independent cases decreases by
increasing polarization. We have shown that the main contribution of the
potential energy comes from the spin-triplet state.Comment: 14 pages, 5 figures. Int. J. Mod. Phys. B (2008) in pres
Photon Self-Induced Spin to Orbital Conversion in TGG crystal at high laser power
In this paper, we present experimental evidence of a newly discovered
third-order nonlinear optical process Self-Induced Spin-to-Orbital Conversion
(SISTOC) of the photon angular momentum. This effect is the physical mechanism
at the origin of the depolarization of very intense laser beams propagating in
isotropic materials. The SISTOC process, like self-focusing, is triggered by
laser heating leading to a radial temperature gradient in the medium. In this
work we tested the occurrence of SISTOC in a terbium gallium garnet (TGG) rod
for an impinging laser power of about 100~W. To study the SISTOC process we
used different techniques: polarization analysis, interferometry and tomography
of the photon orbital angular momentum. Our results confirm, in particular,
that the apparent depolarization of the beam is due to the occurrence of
maximal entanglement between the spin and orbital angular momentum of the
photons undergoing the SISTOC process. This explanation of the true nature of
the depolarization mechanism could be of some help in finding novel methods to
reduce or to compensate for this usually unwanted depolarization effect in all
cases where very high laser power and good beam quality are required.Comment: 6 pages, 10 figures, submitte
Comparison of the effect of topical application of Eugenia caryophylata extract and topical diclofenac in primary knee osteoarthritis: a clinical trial study
Background and aims: osteoarthritis is one of the most common arthritis in elderly. we evaluated to compare the effect of topical application of Eugenia caryophylata extract and topical diclofenac in primary knee osteoarthritis. Methods: This randomized double-blind clinical trial study was carried out upon 105 patients with primary knee osteoarthritis. Patients were selected randomly and divided into three groups of 35(diclofenac) and 35 (Eugenia caryophylata) and 35(placebo).The first group was given three times diclofenac 1 of one mg, the second group was given topical caryophylata 10 of one mg three times daily and third group was given placebo 1 mg three times daily. For three groups, WOMAC questionnaire (overall pain, knee pain, morning stiffness, stiffness during day, physical activity ) were completed pretreatment, one week and three and four weeks post-treatment. Findings: The findings indicated that there is a significant decrease in overall pain (p=o.oo5), stiffness during day (p=0.001), morning stiffness (p=0.001) and knee pain (p=0.017) and physical activity (p=0.001) in four weeks after the initiation of treatment in three groups of topical Eugenia caryophylata, diclofenac and placebo . In all the three groups, mean overall score of womac questionnaire was significantly decreased .no side effects related to the intake of medication in three groups was observed. Conclusion: Extract of Eugenia caryophylata is effective in decreasing knee pain, morning stiffness, and stiffness during day and improvement of physical activity in patients with knee osteoarthritis and it can be used alongside of chemical medication to reduce symptoms of knee osteoarthritis
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