A fundamental study of electrophilic gases for plasma quenching

Electron attachment properties of high molecular weight gases for plasma quenchin

Launch vehicle trajectory optimization computer program, phase 4 Final technical report

Computer program for retrieving stored data and determining variations in launch vehicle performance as function of mission and vehicle parameter

Launch vehicle trajectory optimization computer program, phase 4 Summary report

Computer program for launch vehicle trajectory optimizatio

Zonal mean and tidal dynamics from space: An empirical examination of aliasing and sampling issues

Interpretations of space-based measurements of atmospheric parameters in the mesosphere and thermosphere are complicated by large local-time variations at these altitudes. For this reason, satellite orbits are often preferred which precess through all local times one or more times per season. However, the local-time structure of the atmosphere is inherently non-stationary, which can lead to sampling and aliasing difficulties when attempting to deconvolve the measurements into zonal mean and tidal components. In the present study, hourly radar measurements of mesopause-region winds are used to form a mock data base which can be used to gain insight into implications of the aforementioned problems; the use of actual measurements introduces a realistic element of geophysical temporal variability. Assuming zonal symmetry (i.e., migrating tides superimposed on a zonal mean circulation), the radar measurements are sampled from the satellite perspective for orbital inclinations of 57° and 70°, and compared to the ground or true perspective. These comparisons provide realistic estimates of the errors to be expected when attempting to derive mean and tidal components from space-based measurements. For both diurnal and semidiurnal components, and the quoted satellite inclinations, acceptable errors (3–4m/srms) are obtained for data covering 24h local time (i.e., ascending plus descending nodes); the corresponding errors for single-node data (12h local-time coverage) are of order 8–11m/s, and therefore may not represent reliable estimates of the actual tidal components. There exist certain caveats in connection with the latter conclusion which are discussed

Kilonova Spectral Inverse Modelling with Simulation-Based Inference: An Amortized Neural Posterior Estimation Analysis

Kilonovae represent a category of astrophysical transients, identifiable as the electromagnetic observable counterparts associated with the coalescence events of binary systems comprising neutron stars and neutron star-black hole pairs. They act as probes for heavy-element nucleosynthesis in astrophysical environments. These studies rely on inference of the physical parameters (e.g., ejecta mass, velocity, composition) that describe kilonovae based on electromagnetic observations. This is a complex inverse problem typically addressed with sampling-based methods such as Markov-chain Monte Carlo (MCMC) or nested sampling algorithms. However, repeated inferences can be computationally expensive due to the sequential nature of these methods. This poses a significant challenge to ensuring the reliability and statistical validity of the posterior approximations and, thus, the inferred kilonova parameters themselves. We present a novel approach: Simulation-Based Inference (SBI) using simulations produced by KilonovaNet. Our method employs an ensemble of Amortized Neural Posterior Estimation (ANPE) with an embedding network to directly predict posterior distributions from simulated spectral energy distributions (SEDs). We take advantage of the quasi-instantaneous inference time of ANPE to demonstrate the reliability of our posterior approximations using diagnostics tools, including coverage diagnostic and posterior predictive checks. We further test our model with real observations from AT2017gfo, the only kilonova with multi-messenger data, demonstrating agreement with previous likelihood-based methods while reducing inference time down to a few seconds. The inference results produced by ANPE appear to be conservative and reliable, paving the way for testable and more efficient kilonova parameter inference

Implementation research for the prevention of antimicrobial resistance and healthcare-associated infections; 2017 Geneva infection prevention and control (IPC)-think tank (part 1)

Background Around 5–15% of all hospital patients worldwide suffer from healthcare-associated infections (HAIs), and years of excessive antimicrobial use in human and animal medicine have created emerging antimicrobial resistance (AMR). A considerable amount of evidence-based measures have been published to address these challenges, but the largest challenge seems to be their implementation. Methods In June 2017, a total of 42 experts convened at the Geneva IPC-Think Tank to discuss four domains in implementation science: 1) teaching implementation skills; 2) fostering implementation of IPC and antimicrobial stewardship (AMS) by policy making; 3) national/international actions to foster implementation skills; and 4) translational research bridging social sciences and clinical research in infection prevention and control (IPC) and AMR. Results Although neglected in the past, implementation skills have become a priority in IPC and AMS. They should now be part of any curriculum in health care, and IPC career paths should be created. Guidelines and policies should be aligned with each other and evidence-based, each document providing a section on implementing elements of IPC and AMS in patient care. International organisations should be advocates for IPC and AMS, framing them as patient safety issues and emphasizing the importance of implementation skills. Healthcare authorities at the national level should adopt a similar approach and provide legal frameworks, guidelines, and resources to allow better implementation of patient safety measures in IPC and AMS. Rather than repeating effectiveness studies in every setting, we should invest in methods to improve the implementation of evidence-based measures in different healthcare contexts. For this, we need to encourage and financially support collaborations between social sciences and clinical IPC research. Conclusions Experts of the 2017 Geneva Think Tank on IPC and AMS, CDC, and WHO agreed that sustained efforts on implementation of IPC and AMS strategies are required at international, country, and hospital management levels, to provide an adequate multimodal framework that addresses (not exclusively) leadership, resources, education and training for implementing IPC and AMS. Future strategies can build on this agreement to make strategies on IPC and AMS more effective

Swope Supernova Survey 2017a (SSS17a), the Optical Counterpart to a Gravitational Wave Source

On 2017 August 17, the Laser Interferometer Gravitational-wave Observatory (LIGO) and the Virgo interferometer detected gravitational waves emanating from a binary neutron star merger, GW170817. Nearly simultaneously, the Fermi and INTEGRAL telescopes detected a gamma-ray transient, GRB 170817A. 10.9 hours after the gravitational wave trigger, we discovered a transient and fading optical source, Swope Supernova Survey 2017a (SSS17a), coincident with GW170817. SSS17a is located in NGC 4993, an S0 galaxy at a distance of 40 megaparsecs. The precise location of GW170817 provides an opportunity to probe the nature of these cataclysmic events by combining electromagnetic and gravitational-wave observations.Comment: 25 pages, 10 figures, 2 tables, published today in Scienc

The Old Host-Galaxy Environment of SSS17a, the First Electromagnetic Counterpart to a Gravitational Wave Source

We present an analysis of the host-galaxy environment of Swope Supernova Survey 2017a (SSS17a), the discovery of an electromagnetic counterpart to a gravitational wave source, GW170817. SSS17a occurred 1.9 kpc (in projection; 10.2") from the nucleus of NGC 4993, an S0 galaxy at a distance of 40 Mpc. We present a Hubble Space Telescope (HST) pre-trigger image of NGC 4993, Magellan optical spectroscopy of the nucleus of NGC 4993 and the location of SSS17a, and broad-band UV through IR photometry of NGC 4993. The spectrum and broad-band spectral-energy distribution indicate that NGC 4993 has a stellar mass of log (M/M_solar) = 10.49^{+0.08}_{-0.20} and star formation rate of 0.003 M_solar/yr, and the progenitor system of SSS17a likely had an age of >2.8 Gyr. There is no counterpart at the position of SSS17a in the HST pre-trigger image, indicating that the progenitor system had an absolute magnitude M_V > -5.8 mag. We detect dust lanes extending out to almost the position of SSS17a and >100 likely globular clusters associated with NGC 4993. The offset of SSS17a is similar to many short gamma-ray burst offsets, and its progenitor system was likely bound to NGC 4993. The environment of SSS17a is consistent with an old progenitor system such as a binary neutron star system.Comment: ApJL in pres