Miniature photonic-crystal hydrophone optimized for ocean acoustics

This work reports on an optical hydrophone that is insensitive to hydrostatic pressure, yet capable of measuring acoustic pressures as low as the background noise in the ocean in a frequency range of 1 Hz to 100 kHz. The miniature hydrophone consists of a Fabry-Perot interferometer made of a photonic-crystal reflector interrogated with a single-mode fiber, and is compatible with existing fiber-optic technologies. Three sensors with different acoustic power ranges placed within a sub-wavelength sized hydrophone head allow a high dynamic range in the excess of 160 dB with a low harmonic distortion of better than -30 dB. A method for suppressing cross coupling between sensors in the same hydrophone head is also proposed. A prototype was fabricated, assembled, and tested. The sensitivity was measured from 100 Hz to 100 kHz, demonstrating a minimum detectable pressure down to 12 {\mu}Pa (1-Hz noise bandwidth), a flatband wider than 10 kHz, and very low distortion

Life cycle cost, as a tool for decision making on concrete infrastructures

The use of Life Cycle Cost (LCC) tools in civil engineering is increasing, due to the need of infrastructure owners and operators to guarantee their assets maximum performance with an optimized budget. By considering these tools it will be possible to manage assets along their lifetime in a more sustainable and efficient way. Due to this reason, it was recently constituted a Task Group on fib to deal with existing LCC tools for concrete infrastructures. This paper gives an introduction to these tools, with a special emphasis to the added-value of LCC, and to the main contents of the fib TG 8.4 state-of-art technical report. This covers a description of existing LCC standards and guidelines, their applicability, the definition of different cost elements, the incorporation of risk in the analysis, etc.(undefined)info:eu-repo/semantics/publishedVersio

Simulating ice thickness and velocity evolution of Upernavik Isstrom 1849-2012 by forcing prescribed terminus positions in ISSM

Abstract. Tidewater glacier velocity and mass balance are known to be highly responsive to terminus position change. Yet it remains challenging for ice flow models to reproduce observed ice margin changes. Here, using the Ice Sheet System Model (Larour et al., 2012), we simulate the ice velocity and thickness changes of Upernavik Isstrøm (north-western Greenland) by prescribing a collection of 27 observed terminus positions spanning 164 years (1849–2012). The simulation shows increased ice velocity during the 1930s, the late 1970s and between 1995 and 2012 when terminus retreat was observed along with negative surface mass balance anomalies. Three distinct mass balance states are evident in the reconstruction: (1849–1932) with near zero mass balance, (1932–1992) with ice mass loss dominated by ice dynamical flow, and (1998–2012), when increased retreat and negative surface mass balance anomalies led to mass loss that was twice that of any earlier period. Over the multi-decadal simulation, mass loss was dominated by thinning and acceleration responsible for 70 % of the total mass loss induced by prescribed change in terminus position. The remaining 30 % of the total ice mass loss resulted directly from prescribed terminus retreat and decreasing surface mass balance. Although the method can not explain the cause of glacier retreat, it enables the reconstruction of ice flow and geometry during 1849–2012. Given annual or seasonal observed terminus front positions, this method could be a useful tool for evaluating simulations investigating the effect of calving laws. </jats:p

Fingerprints as a Proxy for Readership of Sales Flyers:An Empirical Assessment

  Can readership of sales flyers and free newspapers be estimated by revealing fingerprints? In this paper we report the results of an empirical analysis based on 4604 flyer-pages conducted to assess the feasibility of the method. Results are encouraging, and indicate that the method presently may serve as a conservative estimate of readership. Advertising management may thus use the fingerprints-approach as an alternative audience measure and thereby assess the convergent validity of the traditional interview method and the fingerprint approach. While the fingerprint method appears valid for sales catalogues its validity of measuring audience of small flyers is questionable. </p

Fingerprints as a Proxy for Readership of Sales Flyers:An Empirical Assessment

  Can readership of sales flyers and free newspapers be estimated by revealing fingerprints? In this paper we report the results of an empirical analysis based on 4604 flyer-pages conducted to assess the feasibility of the method. Results are encouraging, and indicate that the method presently may serve as a conservative estimate of readership. Advertising management may thus use the fingerprints-approach as an alternative audience measure and thereby assess the convergent validity of the traditional interview method and the fingerprint approach. While the fingerprint method appears valid for sales catalogues its validity of measuring audience of small flyers is questionable. </p

Fingerprints as a Proxy for Readership of Sales Flyers:An Empirical Assessment

  Can readership of sales flyers and free newspapers be estimated by revealing fingerprints? In this paper we report the results of an empirical analysis based on 4604 flyer-pages conducted to assess the feasibility of the method. Results are encouraging, and indicate that the method presently may serve as a conservative estimate of readership. Advertising management may thus use the fingerprints-approach as an alternative audience measure and thereby assess the convergent validity of the traditional interview method and the fingerprint approach. While the fingerprint method appears valid for sales catalogues its validity of measuring audience of small flyers is questionable. </p

Why Are Outcomes Different for Registry Patients Enrolled Prospectively and Retrospectively? Insights from the Global Anticoagulant Registry in the FIELD-Atrial Fibrillation (GARFIELD-AF).

Background: Retrospective and prospective observational studies are designed to reflect real-world evidence on clinical practice, but can yield conflicting results. The GARFIELD-AF Registry includes both methods of enrolment and allows analysis of differences in patient characteristics and outcomes that may result. Methods and Results: Patients with atrial fibrillation (AF) and ≥1 risk factor for stroke at diagnosis of AF were recruited either retrospectively (n = 5069) or prospectively (n = 5501) from 19 countries and then followed prospectively. The retrospectively enrolled cohort comprised patients with established AF (for a least 6, and up to 24 months before enrolment), who were identified retrospectively (and baseline and partial follow-up data were collected from the emedical records) and then followed prospectively between 0-18 months (such that the total time of follow-up was 24 months; data collection Dec-2009 and Oct-2010). In the prospectively enrolled cohort, patients with newly diagnosed AF (≤6 weeks after diagnosis) were recruited between Mar-2010 and Oct-2011 and were followed for 24 months after enrolment. Differences between the cohorts were observed in clinical characteristics, including type of AF, stroke prevention strategies, and event rates. More patients in the retrospectively identified cohort received vitamin K antagonists (62.1% vs. 53.2%) and fewer received non-vitamin K oral anticoagulants (1.8% vs . 4.2%). All-cause mortality rates per 100 person-years during the prospective follow-up (starting the first study visit up to 1 year) were significantly lower in the retrospective than prospectively identified cohort (3.04 [95% CI 2.51 to 3.67] vs . 4.05 [95% CI 3.53 to 4.63]; p = 0.016). Conclusions: Interpretations of data from registries that aim to evaluate the characteristics and outcomes of patients with AF must take account of differences in registry design and the impact of recall bias and survivorship bias that is incurred with retrospective enrolment. Clinical Trial Registration: - URL: http://www.clinicaltrials.gov . Unique identifier for GARFIELD-AF (NCT01090362)

Fiber mode excitation using phase-only spatial light modulation: Guideline on free-space path design and lossless optimization

Phase-only spatial light modulators allow to reshape a Gaussian beam by imposing a given phase distribution along the beam cross section. This technique is widely used in the context of mode-division multiplexing to produce, after propagation through a free-space path, the field designed to excite a given fiber mode. In case of orbital angular momentum modes, the target field is approximated as circularly polarized and several complex algorithms have been developed to increase the purity of the obtained modes. Besides their complexity, those algorithms often exploit higher-order diffraction and spatial filtering, hence entailing power loss. In the theoretical work described here, the mode purity is increased in a simple and efficient way by improving the mode approximation adopted to obtain circularly polarized modes and by optimizing two free parameters in the setup, as demonstrated through pertinent simulations