20,766 research outputs found

    Quantum key distribution over 122 km of standard telecom fiber

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    We report the first demonstration of quantum key distribution over a standard telecom fiber exceeding 100 km in length. Through careful optimisation of the interferometer and single photon detector, we achieve a quantum bit error ratio of 8.9% for a 122km link, allowing a secure shared key to be formed after error correction and privacy amplification. Key formation rates of up to 1.9 kbit/sec are achieved depending upon fiber length. We discuss the factors limiting the maximum fiber length in quantum cryptography

    Mock-Gaussian Behaviour for Linear Statistics of Classical Compact Groups

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    We consider the scaling limit of linear statistics for eigenphases of a matrix taken from one of the classical compact groups. We compute their moments and find that the first few moments are Gaussian, whereas the limiting distribution is not. The precise number of Gaussian moments depends upon the particular statistic considered

    Track-based improvement in the jet transverse momentum resolution for ATLAS

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    We present a track-based method for improving the jet momentum resolution in ATLAS. Information is added to the reconstructed jet after the standard jet energy scale corrections have been applied. Track-based corrections are implemented, and a 10 â 15% improvement in the jet transverse momentum resolution at low pT is achieved. The method is explained, and some validation and physics results are presented. Additional variables are described and analyzed for their resolution improvement potential

    A novel metric for coronal MHD models

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    [1] In the interest of quantitatively assessing the capabilities of coronal MHD models, we have developed a metric that compares the structures of the white light corona observed with SOHO LASCO C2 to model predictions. The MAS model is compared to C2 observations from two Carrington rotations during solar cycle 23, CR1913 and CR1984, which were near the minimum and maximum of solar activity, respectively, for three radial heights, 2.5 R⊙, 3.0 R⊙, and 4.5 R⊙. In addition to simulated polarization brightness images, we create a synthetic image based on the field topology along the line of sight in the model. This open-closed brightness is also compared to LASCO C2 after renormalization. In general, the model\u27s magnetic structure is a closer match to observed coronal structures than the model\u27s density structure. This is expected from the simplified energy equations used in current global corona MHD models

    Asteroid Belts in Debris Disk Twins: VEGA and FOMALHAUT

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    Vega and Fomalhaut, are similar in terms of mass, ages, and global debris disk properties; therefore, they are often referred as "debris disk twins". We present Spitzer 10-35 um spectroscopic data centered at both stars, and identify warm, unresolved excess emission in the close vicinity of Vega for the first time. The properties of the warm excess in Vega are further characterized with ancillary photometry in the mid infrared and resolved images in the far-infrared and submillimeter wavelengths. The Vega warm excess shares many similar properties with the one found around Fomalhaut. The emission shortward of ~30 um from both warm components is well described as a blackbody emission of ~170 K. Interestingly, two other systems, eps Eri and HR 8799, also show such an unresolved warm dust using the same approach. These warm components may be analogous to the solar system's zodiacal dust cloud, but of far greater. The dust temperature and tentative detections in the submillimeter suggest the warm excess arises from dust associated with a planetesimal ring located near the water-frost line and presumably created by processes occurring at similar locations in other debris systems as well. We also review the properties of the 2 um hot excess around Vega and Fomalhaut, showing that the dust responsible for the hot excess is not spatially associated with the dust we detected in the warm belt. We suggest it may arise from hot nano grains trapped in the magnetic field of the star. Finally, the separation between the warm and cold belt is rather large with an orbital ratio >~10 in all four systems. In light of the current upper limits on the masses of planetary objects and the large gap, we discuss the possible implications for their underlying planetary architecture, and suggest that multiple, low-mass planets likely reside between the two belts in Vega and Fomalhaut.Comment: 14 pages, accepted for publication in Ap

    Scaling in Plasticity-Induced Cell-Boundary Microstructure: Fragmentation and Rotational Diffusion

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    We develop a simple computational model for cell boundary evolution in plastic deformation. We study the cell boundary size distribution and cell boundary misorientation distribution that experimentally have been found to have scaling forms that are largely material independent. The cell division acts as a source term in the misorientation distribution which significantly alters the scaling form, giving it a linear slope at small misorientation angles as observed in the experiments. We compare the results of our simulation to two closely related exactly solvable models which exhibit scaling behavior at late times: (i) fragmentation theory and (ii) a random walk in rotation space with a source term. We find that the scaling exponents in our simulation agree with those of the theories, and that the scaling collapses obey the same equations, but that the shape of the scaling functions depend upon the methods used to measure sizes and to weight averages and histograms

    Functional Electrical Stimulation mediated by Iterative Learning Control and 3D robotics reduces motor impairment in chronic stroke

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    Background: Novel stroke rehabilitation techniques that employ electrical stimulation (ES) and robotic technologies are effective in reducing upper limb impairments. ES is most effective when it is applied to support the patients’ voluntary effort; however, current systems fail to fully exploit this connection. This study builds on previous work using advanced ES controllers, and aims to investigate the feasibility of Stimulation Assistance through Iterative Learning (SAIL), a novel upper limb stroke rehabilitation system which utilises robotic support, ES, and voluntary effort. Methods: Five hemiparetic, chronic stroke participants with impaired upper limb function attended 18, 1 hour intervention sessions. Participants completed virtual reality tracking tasks whereby they moved their impaired arm to follow a slowly moving sphere along a specified trajectory. To do this, the participants’ arm was supported by a robot. ES, mediated by advanced iterative learning control (ILC) algorithms, was applied to the triceps and anterior deltoid muscles. Each movement was repeated 6 times and ILC adjusted the amount of stimulation applied on each trial to improve accuracy and maximise voluntary effort. Participants completed clinical assessments (Fugl-Meyer, Action Research Arm Test) at baseline and post-intervention, as well as unassisted tracking tasks at the beginning and end of each intervention session. Data were analysed using t-tests and linear regression. Results: From baseline to post-intervention, Fugl-Meyer scores improved, assisted and unassisted tracking performance improved, and the amount of ES required to assist tracking reduced. Conclusions: The concept of minimising support from ES using ILC algorithms was demonstrated. The positive results are promising with respect to reducing upper limb impairments following stroke, however, a larger study is required to confirm this

    H2 and NO2 gas sensors with ZnO nanobelt layer on 36° LiTaO3 and 64° LiNbO3 SAW transducers

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    Single crystal nanobelts of ZnO were synthesized and deposited onto 36° YX LiTaO<sub>3</sub> and 64° YX LiNbO<sub>3</sub> surface acoustic wave (SAW) devices for gas sensing applications. Sensor response, defined as the change in resonant frequency, was measured for H<sub>2</sub> and NO<sub>2</sub> between 20 and 200°C. Measured sensor responses were 3.5 kHz towards 10 ppm NO<sub>2</sub> for a 64° LiNbO<sub>3</sub> SAW transducer operating at 160°C and 3 kHz towards 1% H<sub>2</sub> for a 36° LiTaO<sub>3</sub> SAW transducer operating at 185°C temperature

    An immunotherapy survivor population: health-related quality of life and toxicity in patients with metastatic melanoma treated with immune checkpoint inhibitors

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    © The Author(s) 2019. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.Purpose The immune checkpoint inhibitors (ICIs) have resulted in subgroups of patients with metastatic melanoma achievinghigh-quality durable responses. Metastatic melanoma survivors are a new population in the era of cancer survivorship. The aimofthis study was to evaluate metastatic melanoma survivors in terms of health-related quality of life (HRQoL), immune-relatedadverse events (irAEs) and exposure to immunosuppressive agents in a large single centre in the UK.Methods We defined the survivor population as patients with a diagnosis of metastatic melanoma who achieved a durableresponse to an ICI and had been followed-up for a minimum of 12 months from initiation of ICI without disease progression.HRQoL was assessed using SF-36. Electronic health records were accessed to collect data on demographics, treatments, irAEsand survival. HRQoL data was compared with two norm-based datasets.Results Eighty-four metastatic melanoma survivors were eligible and 87% (N = 73) completed the SF-36. ICI-related toxicity ofany grade occurred in 92%of patients and 43%had experienced a grade 3 or 4 toxicity. Almost half (49%) of the patients requiredsteroids for the treatment of ICI-related toxicity, whilst 14% required treatment with an immunosuppressive agent beyondsteroids.Melanoma survivors had statistically significant lower HRQoL scores with regard to physical, social and physical rolefunctioning and general health compared with the normative population. There was a trend towards inferior scores in patientswith previous exposure to ipilimumab compared with those never exposed to ipilimumab.Conclusions Our results show that metastatic melanoma survivors have potentially experienced significant ICI-related toxicityand experience significant impairments in specific HRQoL domains. Future service planning is required to meet this population’sunique survivorship needs.Peer reviewe
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