Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta

GWTC-2.1: Deep extended catalog of compact binary coalescences observed by LIGO and Virgo during the first half of the third observing run

The second Gravitational-Wave Transient Catalog, GWTC-2, reported on 39 compact binary coalescences observed by the Advanced LIGO and Advanced Virgo detectors between 1 April 2019 15 ∶ 00 UTC and 1 October 2019 15 ∶ 00 UTC. Here, we present GWTC-2.1, which reports on a deeper list of candidate events observed over the same period. We analyze the final version of the strain data over this period with improved calibration and better subtraction of excess noise, which has been publicly released. We employ three matched-filter search pipelines for candidate identification, and estimate the probability of astrophysical origin for each candidate event. While GWTC-2 used a false alarm rate threshold of 2 per year, we include in GWTC-2.1, 1201 candidates that pass a false alarm rate threshold of 2 per day. We calculate the source properties of a subset of 44 high-significance candidates that have a probability of astrophysical origin greater than 0.5. Of these candidates, 36 have been reported in GWTC-2. We also calculate updated source properties for all binary black hole events previously reported in GWTC-1. If the eight additional high-significance candidates presented here are astrophysical, the mass range of events that are unambiguously identified as binary black holes (both objects ≥ 3 M⊙ ) is increased compared to GWTC-2, with total masses from ∼ 14 M ⊙ for GW190924_021846 to ∼ 182 M⊙ for GW190426_190642. Source properties calculated using our default prior suggest that the primary components of two new candidate events (GW190403_051519 and GW190426_190642) fall in the mass gap predicted by pair-instability supernova theory. We also expand the population of binaries with significantly asymmetric mass ratios reported in GWTC-2 by an additional two events (the mass ratio is less than 0.65 and 0.44 at 90% probability for GW190403_051519 and GW190917_114630 respectively), and find that two of the eight new events have effective inspiral spins χeff > 0 (at 90% credibility), while no binary is consistent with χeff < 0 at the same significance. We provide updated estimates for rates of binary black hole and binary neutron star coalescence in the local Universe

All-sky search for continuous gravitational waves from isolated neutron stars in the early O3 LIGO data

We report on an all-sky search for continuous gravitational waves in the frequency band 20-2000 Hz and with a frequency time derivative in the range of [-1.0,+0.1]×10-8 Hz/s. Such a signal could be produced by a nearby, spinning and slightly nonaxisymmetric isolated neutron star in our Galaxy. This search uses the LIGO data from the first six months of Advanced LIGO's and Advanced Virgo's third observational run, O3. No periodic gravitational wave signals are observed, and 95% confidence-level (C.L.) frequentist upper limits are placed on their strengths. The lowest upper limits on worst-case (linearly polarized) strain amplitude h0 are ∼1.7×10-25 near 200 Hz. For a circularly polarized source (most favorable orientation), the lowest upper limits are ∼6.3×10-26. These strict frequentist upper limits refer to all sky locations and the entire range of frequency derivative values. For a population-averaged ensemble of sky locations and stellar orientations, the lowest 95% C.L. upper limits on the strain amplitude are ∼1.4×10-25. These upper limits improve upon our previously published all-sky results, with the greatest improvement (factor of ∼2) seen at higher frequencies, in part because quantum squeezing has dramatically improved the detector noise level relative to the second observational run, O2. These limits are the most constraining to date over most of the parameter space searched

All-sky, all-frequency directional search for persistent gravitational waves from Advanced LIGO’s and Advanced Virgo’s first three observing runs

We present the first results from an all-sky all-frequency (ASAF) search for an anisotropic stochastic gravitational-wave background using the data from the first three observing runs of the Advanced LIGO and Advanced Virgo detectors. Upper limit maps on broadband anisotropies of a persistent stochastic background were published for all observing runs of the LIGO-Virgo detectors. However, a broadband analysis is likely to miss narrowband signals as the signal-to-noise ratio of a narrowband signal can be significantly reduced when combined with detector output from other frequencies. Data folding and the computationally efficient analysis pipeline, {\tt PyStoch}, enable us to perform the radiometer map-making at every frequency bin. We perform the search at 3072 {\tt{HEALPix}} equal area pixels uniformly tiling the sky and in every frequency bin of width $1/32$~Hz in the range $20-1726$~Hz, except for bins that are likely to contain instrumental artefacts and hence are notched. We do not find any statistically significant evidence for the existence of narrowband gravitational-wave signals in the analyzed frequency bins. Therefore, we place $95\%$ confidence upper limits on the gravitational-wave strain for each pixel-frequency pair, the limits are in the range $(0.030 - 9.6) \times10^{-24}$. In addition, we outline a method to identify candidate pixel-frequency pairs that could be followed up by a more sensitive (and potentially computationally expensive) search, e.g., a matched-filtering-based analysis, to look for fainter nearly monochromatic coherent signals. The ASAF analysis is inherently independent of models describing any spectral or spatial distribution of power. We demonstrate that the ASAF results can be appropriately combined over frequencies and sky directions to successfully recover the broadband directional and isotropic results

Search for gravitational waves associated with gamma-ray bursts detected by Fermi and Swift during the LIGO–Virgo run O3b

We search for gravitational-wave signals associated with gamma-ray bursts (GRBs) detected by the Fermi and Swift satellites during the second half of the third observing run of Advanced LIGO and Advanced Virgo (2019 November 1 15:00 UTC–2020 March 27 17:00 UTC). We conduct two independent searches: a generic gravitational-wave transients search to analyze 86 GRBs and an analysis to target binary mergers with at least one neutron star as short GRB progenitors for 17 events. We find no significant evidence for gravitational-wave signals associated with any of these GRBs. A weighted binomial test of the combined results finds no evidence for subthreshold gravitational-wave signals associated with this GRB ensemble either. We use several source types and signal morphologies during the searches, resulting in lower bounds on the estimated distance to each GRB. Finally, we constrain the population of low-luminosity short GRBs using results from the first to the third observing runs of Advanced LIGO and Advanced Virgo. The resulting population is in accordance with the local binary neutron star merger rate

Sélection d\'un champignon filamenteux pour l\'épuration des eaux usées: le phénol comme inhibiteur modèle de discrimination entre Aspergillus niger et A. oryzae

Le choix d\'un microorganisme pour épurer les eaux usées est difficile, car celui-ci doit conserver ses activités métaboliques en situation de stress. La discrimination entre Aspergillus niger et A. oryzae, a été effectuée en utilisant le test de respirométrie et le phénol comme inhibiteur modèle. Ensuite, la dégradation du phénol seul et en présence de glucose par A. niger a été conduite en milieu aérobie non renouvelé. A. niger dégrade le phénol et le catéchol sans adaptation préalable à ces substrats. Son exposition préalable au phénol augmente sa vitesse de respiration nette en présence de celui-ci et du catéchol. Par contre, son adaptation préalable au catéchol entraîne l\'inhibition de sa respiration. Relativement à A. oryzae, celui-ci ne respire, en présence du phénol et du catéchol, que lorsqu\'il est exposé préalablement à ces substrats. Cependant sa vitesse de respiration nette, en présence du phénol, reste inférieure à celle de A. niger. En présence du phénol, comme substrat unique, A. niger le dégrade au bout de 96 h, contre 118 h lorsqu\'il y a du glucose dans le milieu de culture. A. niger résiste au phénol par rapport à A. oryzae. Il peut donc être utilisé en épuration des eaux usées.Making the choice of a microorganism for wastewater treatment is difficult, since this organism must conserve it metabolic activity under stress condition. Discrimination between Aspergillus niger and A. oryzae was done using phenol as model inhibitory substrate and the respirometry test. Thereafter, aerobic stirred batch reactor was used to follow phenol degradation by A. niger, when it was used individually or in the presence of glucose. A. niger biomass not previously exposed to phenol and catechol degrades these compounds. However, it exposure to phenol increased the degradation of this compound and catechol. But, it exposure to catechol inhibits its respiration in the presence of this substrate and phenol comparing to its exposure to phenol. Concerning A. oryzae, this fungus degrades phenol and catechol only when it underwent a preliminary exposure. However, its respiration rates in the presence of phenol and catechol are inferior to A. niger biomass adapted to phenol. A. niger degraded phenol within 96 h when it was the unique substrate, and this was accomplished after 118 h in the presence of glucose. In addition, this fungus supports phenol stress in the growth medium than A. oryzae. Consequently, it cans be used to treat wastewaters. Keywords: Aspergillus, biodegradation, phenol, catechol, respirometry, wastewaterSciences & Nature Vol. 5 (2) 2008: pp. 111-11

Mass Production of Stem Cell-Derived Progeny in Bioreactors

Stem cells, including mesenchymal stem cells (MSCs) and pluripotent stem cells (PSCs), have shown great potential for various biomedical applications including drug discovery, disease modeling, and tissue engineering. Especially, the discovery of induced pluripotent stem cells (iPSCs) with similar characteristics to embryonic stem cells (ESCs) opens a new era for stem cell research and transplantations. Bioprocess engineering provides a platform to generate a controlled microenvironment that could potentially recreate a stem cell niche in view of promoting stem cell proliferation or lineage-specific differentiation

Mass Production of Stem Cell-Derived Progeny in Bioreactors

Stem cells, including mesenchymal stem cells (MSCs) and pluripotent stem cells (PSCs), have shown great potential for various biomedical applications including drug discovery, disease modeling, and tissue engineering. Especially, the discovery of induced pluripotent stem cells (iPSCs) with similar characteristics to embryonic stem cells (ESCs) opens a new era for stem cell research and transplantations. Bioprocess engineering provides a platform to generate a controlled microenvironment that could potentially recreate a stem cell niche in view of promoting stem cell proliferation or lineage-specific differentiation

Design and characterization of a scalable airlift flat panel photobioreactor for microalgae cultivation

A novel flat panel photobioreactor prototype with bulk liquid flow driven by an external airlift was designed, modeled, and experimentally characterized for the purpose of developing scalable industrial photobioreactors. Baffles were built inside the flat panel part of the reactor, directing the liquid bulk flow in a serpentine way, and the external airlift drove the liquid flow and facilitated gas mass transfer. The gas holdup, liquid flow velocity, and oxygen mass transfer of this prototype were experimentally determined and mathematically modeled, and the performance of the reactor was tested by cultivating two species of microalgae, Scenedesmus obliquus and Chlorella sorokiniana. The model-predicted trends correlated well with experimental data, indicating that the reactor might be scaled up using these models. A high cell concentration of C. sorokiniana was achieved under controlled indoor cultivation conditions although serious biofouling occurred in the case of S. obliquus cultivation. The results favor the possibility of scaling up the reactor to industrial scales, based on the models employed, and the potential advantages and disadvantages of the reactor are discussed regarding this industry-oriented photobioreactor configuration in comparison with current industrial photobioreactors. © 2014 Springer Science+Business Media Dordrecht

Design and characterization of a scalable airlift flat panel photobioreactor for microalgae cultivation

A novel flat panel photobioreactor prototype with bulk liquid flow driven by an external airlift was designed, modeled, and experimentally characterized for the purpose of developing scalable industrial photobioreactors. Baffles were built inside the flat panel part of the reactor, directing the liquid bulk flow in a serpentine way, and the external airlift drove the liquid flow and facilitated gas mass transfer. The gas holdup, liquid flow velocity, and oxygen mass transfer of this prototype were experimentally determined and mathematically modeled, and the performance of the reactor was tested by cultivating two species of microalgae, Scenedesmus obliquus and Chlorella sorokiniana. The model-predicted trends correlated well with experimental data, indicating that the reactor might be scaled up using these models. A high cell concentration of C. sorokiniana was achieved under controlled indoor cultivation conditions although serious biofouling occurred in the case of S. obliquus cultivation. The results favor the possibility of scaling up the reactor to industrial scales, based on the models employed, and the potential advantages and disadvantages of the reactor are discussed regarding this industry-oriented photobioreactor configuration in comparison with current industrial photobioreactors. © 2014 Springer Science+Business Media Dordrecht