Broadband Quantum Enhancement of the LIGO Detectors with Frequency-Dependent Squeezing

Quantum noise imposes a fundamental limitation on the sensitivity of interferometric gravitational-wave detectors like LIGO, manifesting as shot noise and quantum radiation pressure noise. Here, we present the first realization of frequency-dependent squeezing in full-scale gravitational-wave detectors, resulting in the reduction of both shot noise and quantum radiation pressure noise, with broadband detector enhancement from tens of hertz to several kilohertz. In the LIGO Hanford detector, squeezing reduced the detector noise amplitude by a factor of 1.6 (4.0 dB) near 1 kHz; in the Livingston detector, the noise reduction was a factor of 1.9 (5.8 dB). These improvements directly impact LIGO’s scientific output for high-frequency sources (e.g., binary neutron star postmerger physics). The improved low-frequency sensitivity, which boosted the detector range by 15%–18% with respect to no squeezing, corresponds to an increase in the astrophysical detection rate of up to 65%. Frequency-dependent squeezing was enabled by the addition of a 300-meter-long filter cavity to each detector as part of the LIGO A+ upgrade

New concept of solar thermal power generation combined with aluminum and supercritical CO2 gas turbine

Paper presented to the 3rd Southern African Solar Energy Conference, South Africa, 11-13 May, 2015.Existing tower type solar power plants consist of a sunbeam collecting system of a solar power tower with heliostats, a molten salt heat transfer and heat storage system, and a steam turbine power generation system. In a new system, the molten salt is replaced by aluminum. The steam turbine is replaced by a supercritical CO2 gas turbine, which can achieve 48% cycle thermal efficiency with turbine inlet temperature of 650°C. In addition, the concentrating power tower is replaced by a beam-down solar system to reduce the radiation loss at the receiver. The aluminum receiver structure and dimensions are shown based on the simplified heat transfer analyses. For the 100 MWt receiver inlet energy, the available power becomes 40.1 MWe at daytime and 8.1 MWe at night.cf201

Flow instabilities in a horizontal thermosyphon reboiler loop

Thermosyphon systems have been the subject of several studies due to instability issues negating their attractive high heat fluxes, low temperature gradients requirement, reduced weight and simple, pump-less system. There is a dearth of design data for horizontal thermosyphons hence the transient behaviour of a horizontal thermosyphon reboiler loop has been studied experimentally here. Most studies here have explored and defined geysering instability in single and parallel vertical columns with closed bottom end. This study presents geysering detected in 51 mm riser of a horizontal thermosyphon reboiler. Experiments were undertaken with water as the process fluid and steam as the heating medium, using 6 – 20 kW/m2 heat flux, 1.165 – 1.265 m static head and a range of recycle flow restrictions. Pressure, temperature and flow rate data were continuously logged at 100Hz. Flow rate was examined as a significant indicator of instability since it is the parameter with highest and varied amplitude of oscillation. Heat flux is most significant for stability: above 20 kW/m2, the system is stable; between 11 – 20 kW/m2 there are varying degrees of sustained oscillations and below 11 kW/m2 flow rate is low. Reboiler inlet flow restriction also stabilises the system by reducing the flow rate to such a level that heat transfer rate can maintain a consistent vapour product rate. Static head influences the recirculation rate and subcooling at the reboiler inlet, but has a secondary effect on stability. Churn flow pattern is detected in the riser as a characteristic aftereffect of the cyclic instability

Bcl-2 protein family: Implications in vascular apoptosis and atherosclerosis

Apoptosis has been recognized as a central component in the pathogenesis of atherosclerosis, in addition to the other human pathologies such as cancer and diabetes. The pathophysiology of atherosclerosis is complex, involving both apoptosis and proliferation at different phases of its progression. Oxidative modification of lipids and inflammation differentially regulate the apoptotic and proliferative responses of vascular cells during progression of the atherosclerotic lesion. Bcl-2 proteins act as the major regulators of extrinsic and intrinsic apoptosis signalling pathways and more recently it has become evident that they mediate the apoptotic response of vascular cells in response to oxidation and inflammation either in a provocative or an inhibitory mode of action. Here we address Bcl-2 proteins as major therapeutic targets for the treatment of atherosclerosis and underscore the need for the novel preventive and therapeutic interventions against atherosclerosis, which should be designed in the light of molecular mechanisms regulating apoptosis of vascular cells in atherosclerotic lesions

Current status of space gravitational wave antenna DECIGO and B-DECIGO

Deci-hertz Interferometer Gravitational Wave Observatory (DECIGO) is the future Japanese space mission with a frequency band of 0.1 Hz to 10 Hz. DECIGO aims at the detection of primordial gravitational waves, which could be produced during the inflationary period right after the birth of the universe. There are many other scientific objectives of DECIGO, including the direct measurement of the acceleration of the expansion of the universe, and reliable and accurate predictions of the timing and locations of neutron star/black hole binary coalescences. DECIGO consists of four clusters of observatories placed in the heliocentric orbit. Each cluster consists of three spacecraft, which form three Fabry-Perot Michelson interferometers with an arm length of 1,000 km. Three clusters of DECIGO will be placed far from each other, and the fourth cluster will be placed in the same position as one of the three clusters to obtain the correlation signals for the detection of the primordial gravitational waves. We plan to launch B-DECIGO, which is a scientific pathfinder of DECIGO, before DECIGO in the 2030s to demonstrate the technologies required for DECIGO, as well as to obtain fruitful scientific results to further expand the multi-messenger astronomy

GWTC-3: Compact Binary Coalescences Observed by LIGO and Virgo during the Second Part of the Third Observing Run

The third Gravitational-Wave Transient Catalog (GWTC-3) describes signals detected with Advanced LIGO and Advanced Virgo up to the end of their third observing run. Updating the previous GWTC-2.1, we present candidate gravitational waves from compact binary coalescences during the second half of the third observing run (O3b) between 1 November 2019, 15∶00 Coordinated Universal Time (UTC) and 27 March 2020, 17∶00 UTC. There are 35 compact binary coalescence candidates identified by at least one of our search algorithms with a probability of astrophysical origin pastro>0.5. Of these, 18 were previously reported as low-latency public alerts, and 17 are reported here for the first time. Based upon estimates for the component masses, our O3b candidates with pastro>0.5 are consistent with gravitational-wave signals from binary black holes or neutron-star-black-hole binaries, and we identify none from binary neutron stars. However, from the gravitational-wave data alone, we are not able to measure matter effects that distinguish whether the binary components are neutron stars or black holes. The range of inferred component masses is similar to that found with previous catalogs, but the O3b candidates include the first confident observations of neutron-star-black-hole binaries. Including the 35 candidates from O3b in addition to those from GWTC-2.1, GWTC-3 contains 90 candidates found by our analysis with pastro>0.5 across the first three observing runs. These observations of compact binary coalescences present an unprecedented view of the properties of black holes and neutron stars

Constraints on the Cosmic Expansion History from GWTC-3

We use 47 gravitational wave sources from the Third LIGO-Virgo-Kamioka Gravitational Wave Detector Gravitational Wave Transient Catalog (GWTC-3) to estimate the Hubble parameter H(z), including its current value, the Hubble constant H0. Each gravitational wave (GW) signal provides the luminosity distance to the source, and we estimate the corresponding redshift using two methods: the redshifted masses and a galaxy catalog. Using the binary black hole (BBH) redshifted masses, we simultaneously infer the source mass distribution and H(z). The source mass distribution displays a peak around 34Me, followed by a drop-off. Assuming this mass scale does not evolve with the redshift results in a H(z) measurement, yielding H0 = 68+12-8 km s-1 Mpc-1 (68% credible interval) when combined with the H0 measurement from GW170817 and its electromagnetic counterpart. This represents an improvement of 17% with respect to the H0 estimate from GWTC-1. The second method associates each GW event with its probable host galaxy in the catalog GLADE+, statistically marginalizing over the redshifts of each event's potential hosts. Assuming a fixed BBH population, we estimate a value of H0 = 68+8-6 km s-1 Mpc-1 with the galaxy catalog method, an improvement of 42% with respect to our GWTC-1 result and 20% with respect to recent H0 studies using GWTC-2 events. However, we show that this result is strongly impacted by assumptions about the BBH source mass distribution; the only event which is not strongly impacted by such assumptions (and is thus informative about H0) is the well-localized event GW190814

Search for Gravitational Waves Associated with Fast Radio Bursts Detected by CHIME/FRB during the LIGO-Virgo Observing Run O3a

We search for gravitational-wave (GW) transients associated with fast radio bursts (FRBs) detected by the Canadian Hydrogen Intensity Mapping Experiment Fast Radio Burst Project, during the first part of the third observing run of Advanced LIGO and Advanced Virgo (2019 April 1 15:00 UTC-2019 October 1 15:00 UTC). Triggers from 22 FRBs were analyzed with a search that targets both binary neutron star (BNS) and neutron star-black hole (NSBH) mergers. A targeted search for generic GW transients was conducted on 40 FRBs. We find no significant evidence for a GW association in either search. Given the large uncertainties in the distances of our FRB sample, we are unable to exclude the possibility of a GW association. Assessing the volumetric event rates of both FRB and binary mergers, an association is limited to 15% of the FRB population for BNS mergers or 1% for NSBH mergers. We report 90% confidence lower bounds on the distance to each FRB for a range of GW progenitor models and set upper limits on the energy emitted through GWs for a range of emission scenarios. We find values of order 1051-1057 erg for models with central GW frequencies in the range 70-3560 Hz. At the sensitivity of this search, we find these limits to be above the predicted GW emissions for the models considered. We also find no significant coincident detection of GWs with the repeater, FRB 20200120E, which is the closest known extragalactic FRB