1,182 research outputs found

    The Potential and Limitations of 2D Seismic Experiments for 3D Tomography

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    The Liguro-Provençal Basin is located in a complex tectonic area, at the junction of the Western Alps and Northern Apennines. Despite its central location within Europe, much about the basin, including the character of the crust, and the continuation of the Alpine orogen offshore, remain ambiguous. The basin began opening in the late Oligocene as a back-arc basin related to the retreat of the Apennine subduction zone. Opening continued into the early Miocene with the counter-clockwise rotation of the Corsica-Sardinia block to its current position. In the southern part of the basin where this rotation opened the widest, seismic tomography has shown evidence of oceanic crust, however, the extent of this spreading zone northward into the Ligurian Sea is poorly mapped. The nature of the crust in the basin, whether atypical oceanic crust or partially serpentinized mantle overlain by sediments or highly thinned continental crust is still a matter of debate. At a larger scale there are still open questions as to the continuation of the alpine orogen offshore, and the change in polarity between the Alp and Apennine subduction zones. As well, present day seismicity with thrust-faulting focal mechanisms have been observed in the basin, indicating that the stress field is now compressive. This could potentially reactivate rift-structures in the basin, which are difficult to map due to thick sediment cover including a layer of Messinian salt with variable thickness. These open questions, and the accessibility of the basin in the heart of Europe, have led to the collection of at least 18 active seismic profiles, and even more multi-channel seismic lines. Each of these studies have contributed to understanding the tectonics of the area through 2D tomography along the profile, but these are small snapshots of a complex setting. The amount of data that has been collected provides a unique opportunity to combine data sets and examine the possibility of gaining new information in the form of 3D tomography from existing 2D data sets. In this project we use active seismic data from the LOBSTER-AlpArray Experiment, the GROSMarin Experiment, and the SARDINIA Experiment, as well as passive seismic data from the AlpArray Experiment and the ISC Bulletin. We explore the potential and limitations of these data sets for use in 3D tomography using two new methods. We first use off-profile stations along a 2D seismic line combined with passive seismicity to provide back-shots for the stations, then in the Gulf of Lion we use two parallel seismic profiles where stations recorded shots from both profiles. This project is part of the DFG Priority Program “Mountain Building Processes in Four Dimensions (4DMB)”

    Sub-dekahertz ultraviolet spectroscopy of 199Hg+

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    Using a laser that is frequency-locked to a Fabry-Perot etalon of high finesse and stability, we probe the 5d10 6s 2S_1/2 (F=0) - 5d9 6s 2D_5/2 (F=2) Delta-m_F = 0 electric-quadrupole transition of a single laser-cooled 199Hg+ ion stored in a cryogenic radio-frequency ion trap. We observe Fourier-transform limited linewidths as narrow as 6.7 Hz at 282 nm (1.06 X 10^15 Hz), yielding a line Q = 1.6 X 10^14. We perform a preliminary measurement of the 5d9 6s2 2D_5/2 electric-quadrupole shift due to interaction with the static fields of the trap, and discuss the implications for future trapped-ion optical frequency standards.Comment: 4 pages, 4 figures, submitted for publicatio

    Coherent optical phase transfer over a 32-km fiber with 1-s instability at 101710^{-17}

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    The phase coherence of an ultrastable optical frequency reference is fully maintained over actively stabilized fiber networks of lengths exceeding 30 km. For a 7-km link installed in an urban environment, the transfer instability is 6×10186 \times 10^{-18} at 1-s. The excess phase noise of 0.15 rad, integrated from 8 mHz to 25 MHz, yields a total timing jitter of 0.085 fs. A 32-km link achieves similar performance. Using frequency combs at each end of the coherent-transfer fiber link, a heterodyne beat between two independent ultrastable lasers, separated by 3.5 km and 163 THz, achieves a 1-Hz linewidth.Comment: 4 pages, 4 figure

    Potential Use of Quantum Dots in Flow Cytometry

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    QDs may offer significant advantages in environmental and bead-based applications where the target cells need to be discriminated above background fluorescence. We have examined the possible applications of QDs for flow cytometric measurements (FCM) by studying their excitation - emission spectra and their binding to paramagnetic beads. We labelled beads with either QDs or a commonly-used fluorochrome (FITC) and studied their fluorescence intensity by FCM. Flow cytometric comparisons indicated that the minimum fluorophore concentration required for detection of QDs above autofluorescent background was 100-fold less than for FITC

    Frequency evaluation of the doubly forbidden 1S03P0^1S_0\to ^3P_0 transition in bosonic 174^{174}Yb

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    We report an uncertainty evaluation of an optical lattice clock based on the 1S03P0^1S_0\leftrightarrow^3P_0 transition in the bosonic isotope 174^{174}Yb by use of magnetically induced spectroscopy. The absolute frequency of the 1S03P0^1S_0\leftrightarrow^3P_0 transition has been determined through comparisons with optical and microwave standards at NIST. The weighted mean of the evaluations is ν\nu(174^{174}Yb)=518 294 025 309 217.8(0.9) Hz. The uncertainty due to systematic effects has been reduced to less than 0.8 Hz, which represents 1.5×10151.5\times10^{-15} in fractional frequency.Comment: 4 pages, 3 figure -Submitted to PRA Rapid Communication

    Prevalence of suicidal behaviour following traumatic brain injury: Longitudinal follow-up data from the NIDRR Traumatic Brain Injury Model Systems

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    Objective: This study utilized the Traumatic Brain Injury Model Systems (TBIMS) National Database to examine the prevalence of depression and suicidal behaviour in a large cohort of patients who sustained moderate-to-severe TBI. Method: Participants presented to a TBIMS acute care hospital within 72 hours of injury and received acute care and comprehensive rehabilitation in a TBIMS designated brain injury inpatient rehabilitation programme. Depression and suicidal ideation were measured with the Patient Health Questionnaire (PHQ-9). Self-reported suicide attempts during the past year were recorded at each follow-up examination, at 1, 2, 3, 10, 15 and 20 years post-injury. Results: Throughout the 20 years of follow-up, rates of depression ranged from 24.8–28.1%, suicidal ideation ranged from 7.0–10.1% and suicide attempts (past year) ranged from 0.8–1.7%. Participants who endorsed depression and/or suicidal behaviour at year 1 demonstrated consistently elevated rates of depression and suicidal behaviour 5 years after TBI. Conclusion: Compared to the general population, individuals with TBI are at greater risk for depression and suicidal behaviour many years after TBI. The significant psychiatric symptoms evidenced by individuals with TBI highlight the need for routine screening and mental health treatment in this population

    Absolute Frequency Measurements of the Hg^+ and Ca Optical Clock Transitions with a Femtosecond Laser

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    The frequency comb created by a femtosecond mode-locked laser and a microstructured fiber is used to phase coherently measure the frequencies of both the Hg^+ and Ca optical standards with respect to the SI second as realized at NIST. We find the transition frequencies to be f_Hg=1 064 721 609 899 143(10) Hz and f_Ca=455 986 240 494 158(26) Hz, respectively. In addition to the unprecedented precision demonstrated here, this work is the precursor to all-optical atomic clocks based on the Hg^+ and Ca standards. Furthermore, when combined with previous measurements, we find no time variations of these atomic frequencies within the uncertainties of |(df_Ca/dt)/f_Ca| < 8 x 10^{-14} yr^{-1}, and |(df_Hg/dt)/f_Hg|< 30 x 10^{-14} yr^{-1}.Comment: 6 pages, including 4 figures. RevTex 4. Submitted to Phys. Rev. Let

    Isothermal Recombinase Polymerase amplification (RPA) of Schistosoma haematobium DNA and oligochromatographic lateral flow detection

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    © 2015 Rosser et al. Open Access 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. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. The attached file is the published version of the article

    Factors associated with the performance and cost-effectiveness of using lymphatic filariasis transmission assessment surveys for monitoring soil-transmitted helminths: a case study in Kenya.

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    Transmission assessment surveys (TAS) for lymphatic filariasis have been proposed as a platform to assess the impact of mass drug administration (MDA) on soil-transmitted helminths (STHs). This study used computer simulation and field data from pre- and post-MDA settings across Kenya to evaluate the performance and cost-effectiveness of the TAS design for STH assessment compared with alternative survey designs. Variations in the TAS design and different sample sizes and diagnostic methods were also evaluated. The district-level TAS design correctly classified more districts compared with standard STH designs in pre-MDA settings. Aggregating districts into larger evaluation units in a TAS design decreased performance, whereas age group sampled and sample size had minimal impact. The low diagnostic sensitivity of Kato-Katz and mini-FLOTAC methods was found to increase misclassification. We recommend using a district-level TAS among children 8-10 years of age to assess STH but suggest that key consideration is given to evaluation unit size
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