28 research outputs found
A Time Domain Waveform for Testing General Relativity
Gravitational-wave parameter estimation is only as good as the theory the
waveform generation models are based upon. It is therefore crucial to test
General Relativity (GR) once data becomes available. Many previous works, such
as studies connected with the ppE framework by Yunes and Pretorius, rely on the
stationary phase approximation (SPA) to model deviations from GR in the
frequency domain. As Fast Fourier Transform algorithms have become considerably
faster and in order to circumvent possible problems with the SPA, we test GR
with corrected time domain waveforms instead of SPA waveforms. Since a
considerable amount of work has been done already in the field using SPA
waveforms, we establish a connection between leading-order-corrected waveforms
in time and frequency domain, concentrating on phase-only corrected terms. In a
Markov Chain Monte Carlo study, whose results are preliminary and will only be
available later, we will assess the ability of the eLISA detector to measure
deviations from GR for signals coming from supermassive black hole inspirals
using these corrected waveforms.Comment: 5 pages. Proceedings of LISA Symposium X, submitted to Journal of
Physics: Conference Serie
Supermassive Black Hole Tests of General Relativity with eLISA
Motivated by the parameterized post-Einsteinian (ppE) scheme devised by Yunes
and Pretorius, which introduces corrections to the post-Newtonian coefficients
of the frequency domain gravitational waveform in order to emulate alternative
theories of gravity, we compute analytical time domain waveforms that, after a
numerical Fourier transform, aim to represent (phase corrected only) ppE
waveforms. In this formalism, alternative theories manifest themselves via
corrections to the phase and frequency, as predicted by General Relativity
(GR), at different post-Newtonian (PN) orders. In order to present a generic
test of alternative theories of gravity, we assume that the coupling constant
of each alternative theory is manifestly positive, allowing corrections to the
GR waveforms to be either positive or negative. By exploring the capabilities
of massive black hole binary GR waveforms in the detection and parameter
estimation of corrected time domain ppE signals, using the current eLISA
configuration (as presented for the ESA Cosmic Vision L3 mission), we
demonstrate that for corrections arising at higher than 1PN order in phase and
frequency, GR waveforms are sufficient for both detecting and estimating the
parameters of alternative theory signals. However, for theories introducing
corrections at the 0 and 0.5 PN order, GR waveforms are not capable of covering
the entire parameter space, requiring the use of non-GR waveforms for detection
and parameter estimation.Comment: 13 pages, 5 figure
Wireless Sensor Networks for Long-Term Monitoring of Urban Noise
Noise pollution in urban environments is becoming increasingly common and it has potential to negatively impact peopleâs health and decrease overall productivity. In order to alleviate these effects, it is important to better quantify noise patterns and levels through data collection and analysis. Wireless sensor networks offer a method for achieving this with a higher level of granularity than traditional handheld devices. In this study, a wireless sensing unit (WSU) was developed that possesses the same functionality as a handheld sound level meter. The WSU is comprised of a microcontroller unit that enables on-board computations, a wireless transceiver that uses Zigbee protocol for data transmission, and an external peripheral board that houses the microphone transducer. The WSU utilizes on-board data processing techniques to monitor noise by computing equivalent continuous sound levels, LeqT, which effectively minimizes data transmission and increases the overall longevity of the node. Strategies are also employed to ensure real-time functionality is maintained on the sensing unit, with a focus on preventing bottlenecks between data acquisition, data processing, and wireless transmission. Four units were deployed in two weeks field validation test and were shown to be capable of monitoring noise for extended periods of time
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Effect of Hydrocortisone on Mortality and Organ Support in Patients With Severe COVID-19: The REMAP-CAP COVID-19 Corticosteroid Domain Randomized Clinical Trial.
Importance: Evidence regarding corticosteroid use for severe coronavirus disease 2019 (COVID-19) is limited. Objective: To determine whether hydrocortisone improves outcome for patients with severe COVID-19. Design, Setting, and Participants: An ongoing adaptive platform trial testing multiple interventions within multiple therapeutic domains, for example, antiviral agents, corticosteroids, or immunoglobulin. Between March 9 and June 17, 2020, 614 adult patients with suspected or confirmed COVID-19 were enrolled and randomized within at least 1 domain following admission to an intensive care unit (ICU) for respiratory or cardiovascular organ support at 121 sites in 8 countries. Of these, 403 were randomized to open-label interventions within the corticosteroid domain. The domain was halted after results from another trial were released. Follow-up ended August 12, 2020. Interventions: The corticosteroid domain randomized participants to a fixed 7-day course of intravenous hydrocortisone (50 mg or 100 mg every 6 hours) (nâ=â143), a shock-dependent course (50 mg every 6 hours when shock was clinically evident) (nâ=â152), or no hydrocortisone (nâ=â108). Main Outcomes and Measures: The primary end point was organ support-free days (days alive and free of ICU-based respiratory or cardiovascular support) within 21 days, where patients who died were assigned -1 day. The primary analysis was a bayesian cumulative logistic model that included all patients enrolled with severe COVID-19, adjusting for age, sex, site, region, time, assignment to interventions within other domains, and domain and intervention eligibility. Superiority was defined as the posterior probability of an odds ratio greater than 1 (threshold for trial conclusion of superiority >99%). Results: After excluding 19 participants who withdrew consent, there were 384 patients (mean age, 60 years; 29% female) randomized to the fixed-dose (nâ=â137), shock-dependent (nâ=â146), and no (nâ=â101) hydrocortisone groups; 379 (99%) completed the study and were included in the analysis. The mean age for the 3 groups ranged between 59.5 and 60.4 years; most patients were male (range, 70.6%-71.5%); mean body mass index ranged between 29.7 and 30.9; and patients receiving mechanical ventilation ranged between 50.0% and 63.5%. For the fixed-dose, shock-dependent, and no hydrocortisone groups, respectively, the median organ support-free days were 0 (IQR, -1 to 15), 0 (IQR, -1 to 13), and 0 (-1 to 11) days (composed of 30%, 26%, and 33% mortality rates and 11.5, 9.5, and 6 median organ support-free days among survivors). The median adjusted odds ratio and bayesian probability of superiority were 1.43 (95% credible interval, 0.91-2.27) and 93% for fixed-dose hydrocortisone, respectively, and were 1.22 (95% credible interval, 0.76-1.94) and 80% for shock-dependent hydrocortisone compared with no hydrocortisone. Serious adverse events were reported in 4 (3%), 5 (3%), and 1 (1%) patients in the fixed-dose, shock-dependent, and no hydrocortisone groups, respectively. Conclusions and Relevance: Among patients with severe COVID-19, treatment with a 7-day fixed-dose course of hydrocortisone or shock-dependent dosing of hydrocortisone, compared with no hydrocortisone, resulted in 93% and 80% probabilities of superiority with regard to the odds of improvement in organ support-free days within 21 days. However, the trial was stopped early and no treatment strategy met prespecified criteria for statistical superiority, precluding definitive conclusions. Trial Registration: ClinicalTrials.gov Identifier: NCT02735707
Wireless Sensor Networks for Long-Term Monitoring of Urban Noise
Noise pollution in urban environments is becoming increasingly common and it has potential to negatively impact people’s health and decrease overall productivity. In order to alleviate these effects, it is important to better quantify noise patterns and levels through data collection and analysis. Wireless sensor networks offer a method for achieving this with a higher level of granularity than traditional handheld devices. In this study, a wireless sensing unit (WSU) was developed that possesses the same functionality as a handheld sound level meter. The WSU is comprised of a microcontroller unit that enables on-board computations, a wireless transceiver that uses Zigbee protocol for data transmission, and an external peripheral board that houses the microphone transducer. The WSU utilizes on-board data processing techniques to monitor noise by computing equivalent continuous sound levels, LeqT, which effectively minimizes data transmission and increases the overall longevity of the node. Strategies are also employed to ensure real-time functionality is maintained on the sensing unit, with a focus on preventing bottlenecks between data acquisition, data processing, and wireless transmission. Four units were deployed in two weeks field validation test and were shown to be capable of monitoring noise for extended periods of time
Hierarchically Structured Ultraporous Iridium-Based Materials: A Novel Catalyst Architecture for Proton Exchange Membrane Water Electrolyzers
International audienceIridium oxide is the goldâstandard catalyst for the oxygen evolution reaction (OER) in acidic media due to its unmatched activity and stability. Here, a new catalyst architecture comprising a nanoneedle network of iridiumâcontaining oxides assembled into macroporous micrometric particles with â75% of porosity is reported. The rationally designed porous hierarchical structure optimizes the accessibility of reactants and products to the surface of the nanoparticles and maximizes catalyst activity. The materials are easily prepared from aqueous solutions by an industrially viable sprayâdrying route through an evaporation selfâassembly mechanism. The versatility of the process enables the preparation of mixed oxides with low iridium content, particles with tunable crystallinity, and various iridium surface species with high electrochemical activity. Highly porous Ir0.7Ru0.3O2 outperforms commercial iridium oxide. These materials also represent an ideal platform to assess the reactivity of the iridium and oxygen species involved in the oxygen evolution reaction. Furthermore, it is demonstrated that these highly porous particles are optimal building blocks to be integrated into catalyst layers, without the drawbacks associated with the use of discrete nanoparticles. Freshâ and endâofâtest membraneâelectrode assemblies' characterization shows that their particular architecture is preserved upon catalyst layer preparation and after operation in a protonâexchange membrane electrolysis cell
Origins of the fern genus Hymenophyllum (Hymenophyllaceae) in New Caledonia: Multiple independent colonizations from surrounding territories and limited in situ diversification
International audienc