2,542 research outputs found

    Multiresolution community detection for megascale networks by information-based replica correlations

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    We use a Potts model community detection algorithm to accurately and quantitatively evaluate the hierarchical or multiresolution structure of a graph. Our multiresolution algorithm calculates correlations among multiple copies ("replicas") of the same graph over a range of resolutions. Significant multiresolution structures are identified by strongly correlated replicas. The average normalized mutual information, the variation of information, and other measures in principle give a quantitative estimate of the "best" resolutions and indicate the relative strength of the structures in the graph. Because the method is based on information comparisons, it can in principle be used with any community detection model that can examine multiple resolutions. Our approach may be extended to other optimization problems. As a local measure, our Potts model avoids the "resolution limit" that affects other popular models. With this model, our community detection algorithm has an accuracy that ranks among the best of currently available methods. Using it, we can examine graphs over 40 million nodes and more than one billion edges. We further report that the multiresolution variant of our algorithm can solve systems of at least 200000 nodes and 10 million edges on a single processor with exceptionally high accuracy. For typical cases, we find a super-linear scaling, O(L^{1.3}) for community detection and O(L^{1.3} log N) for the multiresolution algorithm where L is the number of edges and N is the number of nodes in the system.Comment: 19 pages, 14 figures, published version with minor change

    Photon number discrimination without a photon counter and its application to reconstructing non-Gaussian states

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    The non-linearity of a conditional photon-counting measurement can be used to `de-Gaussify' a Gaussian state of light. Here we present and experimentally demonstrate a technique for photon number resolution using only homodyne detection. We then apply this technique to inform a conditional measurement; unambiguously reconstructing the statistics of the non-Gaussian one and two photon subtracted squeezed vacuum states. Although our photon number measurement relies on ensemble averages and cannot be used to prepare non-Gaussian states of light, its high efficiency, photon number resolving capabilities, and compatibility with the telecommunications band make it suitable for quantum information tasks relying on the outcomes of mean values.Comment: 4 pages, 3 figures. Theory section expanded in response to referee comment

    Fabrication and Characterisation of an Adaptable Plasmonic Nanorod Array for Solar Energy Conversion

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    The surface plasmonic modes of a side-by-side aligned gold nanorod array supported on a gold substrate has been characterised by electron energy loss spectroscopy (EELS). Plasmonic coupling within the array splits the nanorods' longitudinal mode into a bright mode (symmetrically aligned dipoles) and a dark mode (anti-symmetrically aligned dipoles). We support this observation by means of finite element modelling (FEM)

    Response to comment on 'Valid molecular dynamics simulations of human hemoglobin require a surprisingly large box size'

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    We recently reported that molecular dynamics simulations for hemoglobin require a surprisingly large box size to stabilize the T(0) state relative to R(0), as observed in experiments (El Hage et al., 2018). Gapsys and de Groot have commented on this work but do not provide convincing evidence that the conclusions of El Hage et al., 2018 are incorrect. Here we respond to these concerns, argue that our original conclusions remain valid, and raise our own concerns about some of the results reported in the comment by Gapsys and de Groot that require clarification

    Valid molecular dynamics simulations of human hemoglobin require a surprisingly large box size

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    Recent molecular dynamics (MD) simulations of human hemoglobin (Hb) give results in disagreement with experiment. Although it is known that the unliganded (T 0 ) and liganded (R 4 ) tetramers are stable in solution, the published MD simulations of T 0 undergo a rapid quaternary transition to an R-like structure. We show that T 0 is stable only when the periodic solvent box contains ten times more water molecules than the standard size for such simulations. The results suggest that such a large box is required for the hydrophobic effect, which stabilizes the T 0 tetramer, to be manifested. Even in the largest box, T 0 is not stable unless His146 is protonated, providing an atomistic validation of the Perutz model. The possibility that extra large boxes are required to obtain meaningful results will have to be considered in evaluating existing and future simulations of a wide range of systems

    Knowledge and practices about family planning among women attending the Obstetrics Outpatient Department of a newly established tertiary care center

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    Background: Birth spacing and appropriate family planning is the milestone for long term good health of both the mother and the child and in turn the betterment of the whole society. Before starting the Family Planning clinic, we wanted to have a thorough understanding of the levels of awareness and acceptance of various family planning methods among the women attending the outpatient department of this tertiary care hospital. This preliminary data would be helpful in planning suitable programs which would be helpful in enhancing the family planning acceptance and modifying the existing steps of approach.Methods: A cross-sectional descriptive study was done in the department of Obstetrics and Gynecology of the tertiary care hospital. The study group included 200 women within the reproductive (18-45 years) age group.Results: 88% of the participants were aware of some or the other methods of contraception. According to the participants, the main source of information was health care workers, friends, family members (mother and sisters) and various social platforms and television. 37% of women were not using any method despite being aware of contraceptive methods. Maximum women (65) were following coitus interruptus as a natural method of contraception.16.5% of women were using barrier method of contraception. Unawareness about contraceptive methods was the major reason behind not using any method of contraception. Though knowledge about contraception was reported by 88% of the study population, only 63% of them were actually using some method of contraception.Conclusions: The study shows that there is a gap between the level of awareness about various family planning services and the actual practice of any method of contraception by the study population. So, the main aim of starting of the family planning clinic at our institute would be to bridge this gap

    Squeezed-field injection for gravitational wave interferometers

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    In a recent table-top experiment, we demonstrated the compatibility of three advanced interferometer techniques for gravitational wave detection, namely power-recycling, detuned signal recycling and squeezed-field injection. The interferometer's signal-to-noise ratio was improved by up to 2.8 dB beyond the coherent state's shot-noise. This value was mainly limited by optical losses on the squeezed field. We present a detailed analysis of the optical losses in our experiment and provide an estimation of the possible nonclassical performance of a future squeezed-field enhanced GEO 600 detector

    Experimental characterization of frequency dependent squeezed light

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    We report on the demonstration of broadband squeezed laser beams that show a frequency dependent orientation of the squeezing ellipse. Carrier frequency as well as quadrature angle were stably locked to a reference laser beam at 1064nm. This frequency dependent squeezing was characterized in terms of noise power spectra and contour plots of Wigner functions. The later were measured by quantum state tomography. Our tomograph allowed a stable lock to a local oscillator beam for arbitrary quadrature angles with one degree precision. Frequency dependent orientations of the squeezing ellipse are necessary for squeezed states of light to provide a broadband sensitivity improvement in third generation gravitational wave interferometers. We consider the application of our system to long baseline interferometers such as a future squeezed light upgraded GEO600 detector.Comment: 8 pages, 8 figure
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