48,095 research outputs found

    Mid-infrared broadband modulation instability and 50 dB Raman assisted parametric gain in silicon photonic wires

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    Abstract: We demonstrate broadband modulation instability, > 40 dB parametric amplification with on-chip gain bandwidth > 580 nm, and narrowband Raman-assisted peak on-chip gain exceeding 50 dB, using mid-infrared dispersion-engineered silicon nanophotonic wires

    Potential secondary transmission of SARS-CoV-2 via wastewater

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    The new coronavirus, SARS-CoV-2, has spread internationally and whilst the current focus of those dealing with the COVID-19 pandemic is understandably restricting its direct transmission, the potential for secondary transmission via wastewater should not be underestimated. The virus has been identified in human fecal and wastewater samples from different countries and potential cases of transmission via wastewater have been reported. Our recommendations for hospital wastewater treatment, municipal wastewater plants, sewage sludge, water reuse and aquatic environments are designed to reduce the risk of such transmission, and contribute to limiting the resurgence of COVID-19 as current restrictions are relaxed. A particular urgent recommendation focusses on supporting low-income countries in tackling the potential for secondary transmission via wastewater

    Multi-Channel Stochastic Variational Inference for the Joint Analysis of Heterogeneous Biomedical Data in Alzheimer's Disease

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    The joint analysis of biomedical data in Alzheimer's Disease (AD) is important for better clinical diagnosis and to understand the relationship between biomarkers. However, jointly accounting for heterogeneous measures poses important challenges related to the modeling of the variability and the interpretability of the results. These issues are here addressed by proposing a novel multi-channel stochastic generative model. We assume that a latent variable generates the data observed through different channels (e.g., clinical scores, imaging, ...) and describe an efficient way to estimate jointly the distribution of both latent variable and data generative process. Experiments on synthetic data show that the multi-channel formulation allows superior data reconstruction as opposed to the single channel one. Moreover, the derived lower bound of the model evidence represents a promising model selection criterion. Experiments on AD data show that the model parameters can be used for unsupervised patient stratification and for the joint interpretation of the heterogeneous observations. Because of its general and flexible formulation, we believe that the proposed method can find important applications as a general data fusion technique.Comment: accepted for presentation at MLCN 2018 workshop, in Conjunction with MICCAI 2018, September 20, Granada, Spai

    Control of Josephson current by Aharonov-Casher Phase in a Rashba Ring

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    We study the interference effect induced by the Aharonov-Casher phase on the Josephson current through a semiconducting ring attached to superconducting leads. Using a 1D model that incorporates spin-orbit coupling in the semiconducting ring, we calculate the Andreev levels analytically and numerically, and predict oscillations of the Josephson current due to the AC phase. This result is valid from the point contact limit to the long channel length limit, as defined by the ratio of the junction length and the BCS healing length. We show in the long channel length limit that the impurity scattering has no effect on the oscillation of the Josephson current, in contrast to the case of conductivity oscillations in a spin-orbit coupled ring system attached to normal leads where impurity scattering reduces the amplitude of oscillations. Our results suggest a new scheme to measure the AC phase with, in principle, higher sensitivity. In addition, this effect allows for control of the Josephson current through the gate voltage tuned AC phase.Comment: 12pages, 8 figure

    The prediction of blood–tissue partitions, water–skin partitions and skin permeation for agrochemicals

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    YesBACKGROUND: There is considerable interest in the blood–tissue distribution of agrochemicals, and a number of researchershave developed experimental methods for in vitro distribution. These methods involve the determination of saline–blood andsaline–tissue partitions; not only are they indirect, but they do not yield the required in vivo distribution.RESULTS: The authors set out equations for gas–tissue and blood–tissue distribution, for partition from water into skin andfor permeation from water through human skin. Together with Abraham descriptors for the agrochemicals, these equationscan be used to predict values for all of these processes. The present predictions compare favourably with experimental in vivoblood–tissue distribution where available. The predictions require no more than simple arithmetic.CONCLUSIONS: The present method represents a much easier and much more economic way of estimating blood–tissuepartitions than the method that uses saline–blood and saline–tissue partitions. It has the added advantages of yielding therequired in vivo partitions and being easily extended to the prediction of partition of agrochemicals from water into skin andpermeation from water through skin

    Scalar Decay in Chaotic Mixing

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    I review the local theory of mixing, which focuses on infinitesimal blobs of scalar being advected and stretched by a random velocity field. An advantage of this theory is that it provides elegant analytical results. A disadvantage is that it is highly idealised. Nevertheless, it provides insight into the mechanism of chaotic mixing and the effect of random fluctuations on the rate of decay of the concentration field of a passive scalar.Comment: 35 pages, 15 figures. Springer-Verlag conference style svmult.cls (included). Published in "Transport in Geophysical Flows: Ten Years After," Proceedings of the Grand Combin Summer School, 14-24 June 2004, Valle d'Aosta, Italy. Fixed some typo

    Holographic Penta and Hepta Quark State in Confining Gauge Theories

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    We study a new embedding solutions of D5 brane in an asymptotic AdS5Ă—S5{}_5\times S^5 space-time, which is dual to a confining SU(Nc)SU(N_c) gauge theory. The D5 brane is wrapped on S5S^5 as in the case of the vertex of holographic baryon. However, the solution given here is different from the usual baryon vertex in the point that it couples to kk-anti-quarks and Nc+kN_c+k quarks on the opposite two points of S5S^5, the north and south poles, respectively. The total quark number of this state is preserved as NcN_c when minus one is assigned to anti-quark, then it forms a color singlet like the baryon. However, this includes anti-quarks and quarks, whose number is larger than that of the baryon. When we set as Nc=3N_c=3, we find the so called penta and hepta-quark states. We study the dynamical properties of these states by solving the vertex and string configurations for such states. The mass spectra of these states and the tension of the stretched vertex are estimated, and they are compared with that of the baryon.Comment: 24 pages, 6 figure
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