Performance Improvement of the Inertial Sensors of Advanced Virgo Seismic Isolators with Digital Techniques

Gravitational waves, predicted on the basis of the General Relativity, are ripples in the curvature of space-time that propagate as a wave. The passage of a gravitational wave induces tiny oscillations in the relative separation between two test masses, that can be measured. Nevertheless these oscillations are extremely small, so that only a very sensitive detector is able to measure them. The Advanced Virgo project is a major upgrade of the 3 km-long interferometric gravitational wave detector Virgo, with the goal of increasing its sensitivity by about one order of magnitude in the whole detection band. We expect to have a maximum strain amplitude sensitivity of 4 × 10^−24 1/√Hz at ∼ 300 Hz. In other words this means that it will be able to detect a relative displacement between mirrors of about 10^−20 m, by averaging for one second. This sensitivity should allow to detect several tens of events per year. Among the various ongoing updates, an important improvement is represented by the new electronics used to control the Superattenuators, complex mechanical structures that isolate optical elements from seismic noise by a factor 10^15 at 1 Hz. Using the information of several inertial sensors, a digital control system keeps the structures as stable as possible. A new board for the Superattenuator control has been designed, that incorporates analog-to-digital and digital-to-analog converters, a Field Programmable Gate Array (FPGA) and a Digital Signal Processor (DSP) into a single unit. This board is enough to handle every single part of the Superattenuator inertial control. It performs the computation of feedback forces, and is used to synthesize sine wave to drive the coils of the inertial sensors, as well as to read their output. Furthermore it interfaces with all the other structures of Virgo. In this thesis I have studied the horizontal accelerometers, feedback-controlled sensors used in the Superattenuator inertial control to measure the seismic noise in the frequency band from DC to 100 Hz. Using the computing power of the new electronics (the new DSP has 8 cores and can compute 8.4 GFLOPS per core for double precision floating point indeed), I have designed a new control system for the accelerometers, exploiting the properties of a critically damped harmonic oscillator. This system allows to improve by about one order of magnitude the sensitivity of these sensors, with respect to the system used in Virgo, by reducing the root mean square of the force needed for the control by a factor 2. In this way, the accelerometer sensitivity can reach about 10^−9 (m/s^2)/√Hz at 1 Hz. In the last part of the thesis I have studied the Linear Variable Differential Transformer (LVDT), a kind of displacement sensor widely used in Superattenuator control. I have designed a system to read the output of LVDT using a FPGA. It consists of a Direct Digital Synthesizer (DDS) that is used both to drive the primary coil of the LVDT with a sine wave at 50 kHz, and then to demodulate the signal induced on the secondary coils, whose amplitude is modulated by a signal proportional to displacement. An algorithm, based on a Phase-Locked Loop (PLL), allows the detection of the phase shift of the signal induced on the secondary coils, and tunes the system in order to maximize the signal-to-noise ratio of the measurement of displacement

Different renal phenotypes in related adult males with Fabry disease with the same classic genotype

BACKGROUND: Fabry disease related patients with classical mutation usually exhibit similar severe phenotype especially concerning renal manifestation. METHODS: A dry blood spot screening (DBS) and the DNA analysis has been performed in a 48-year-old man (Patient 1) because of paresthesia. RESULTS: The DBS revealed absent leukocyte \u3b1-Gal A enzyme activity while DNA analysis identified the I354K mutation. Serum creatinine and e-GFR were in normal range and also albuminuria and proteinuria were absent. The brain MRI showed ischemic lesions and a diffuse focus of gliosis in the white matter, while the echocardiogram showed a left ventricular hypertrophy. The renal biopsy performed in the case index showed a massive deposition of zebra bodies. By a familiar investigation, it was recognized that his brother (Patient 2) died 2 years before from sudden death syndrome at the age of 49. He had suffered sporadic and undiagnosed pain at the extremities, a prior cataract, bilateral neurosensorial hearing loss and left ventricular hypertrophy on Echocardiogram. His previous laboratory examinations revealed a normal serum creatinine and the absence of proteinuria. Pedigree analysis of the brothers revealed a high disease burden among family members, with an affected cousin (Patient 3) who progressed early to end-stage renal disease (ESRD) that required renal transplantation. CONCLUSIONS: Here we describe the clinical history of three adult male members of the same family with the same genotype who manifested different presentation and progression of the disease, particularly concerning the renal involvement

Phenolic Molecules in Virgin Olive Oils: a Survey of Their Sensory Properties, Health Effects, Antioxidant Activity and Analytical Methods. An Overview of the Last Decade Alessandra

Among vegetable oils, virgin olive oil (VOO) has nutritional and sensory characteristics that to make it unique and a basic component of the Mediterranean diet. The importance of VOO is mainly attributed both to its high content of oleic acid a balanced contribution quantity of polyunsaturated fatty acids and its richness in phenolic compounds, which act as natural antioxidants and may contribute to the prevention of several human diseases. The polar phenolic compounds of VOO belong to different classes: phenolic acids, phenyl ethyl alcohols, hydroxy-isochromans, flavonoids, lignans and secoiridoids. This latter family of compounds is characteristic of Oleaceae plants and secoiridoids are the main compounds of the phenolic fraction. Many agronomical and technological factors can affect the presence of phenols in VOO. Its shelf life is higher than other vegetable oils, mainly due to the presence of phenolic molecules having a catechol group, such as hydroxytyrosol and its secoiridoid derivatives. Several assays have been used to establish the antioxidant activity of these isolated phenolic compounds. Typical sensory gustative properties of VOO, such as bitterness and pungency, have been attributed to secoiridoid molecules. Considering the importance of the phenolic fraction of VOO, high performance analytical methods have been developed to characterize its complex phenolic pattern. The aim of this review is to realize a survey on phenolic compounds of virgin olive oils bearing in mind their chemical-analytical, healthy and sensory aspects. In particular, starting from the basic studies, the results of researches developed in the last ten years will be focused

First narrow-band search for continuous gravitational waves from known pulsars in advanced detector data

Spinning neutron stars asymmetric with respect to their rotation axis are potential sources of continuous gravitational waves for ground-based interferometric detectors. In the case of known pulsars a fully coherent search, based on matched filtering, which uses the position and rotational parameters obtained from electromagnetic observations, can be carried out. Matched filtering maximizes the signalto- noise (SNR) ratio, but a large sensitivity loss is expected in case of even a very small mismatch between the assumed and the true signal parameters. For this reason, narrow-band analysis methods have been developed, allowing a fully coherent search for gravitational waves from known pulsars over a fraction of a hertz and several spin-down values. In this paper we describe a narrow-band search of 11 pulsars using data from Advanced LIGO’s first observing run. Although we have found several initial outliers, further studies show no significant evidence for the presence of a gravitational wave signal. Finally, we have placed upper limits on the signal strain amplitude lower than the spin-down limit for 5 of the 11 targets over the bands searched; in the case of J1813-1749 the spin-down limit has been beaten for the first time. For an additional 3 targets, the median upper limit across the search bands is below the spin-down limit. This is the most sensitive narrow-band search for continuous gravitational waves carried out so far

A Standard Siren Measurement of the Hubble Constant from GW170817 without the Electromagnetic Counterpart

We perform a statistical standard siren analysis of GW170817. Our analysis does not utilize knowledge of NGC 4993 as the unique host galaxy of the optical counterpart to GW170817. Instead, we consider each galaxy within the GW170817 localization region as a potential host; combining the redshifts from all of the galaxies with the distance estimate from GW170817 provides an estimate of the Hubble constant, H 0. Considering all galaxies brighter than $0.626{L}_{B}^{\star }$ as equally likely to host a binary neutron star merger, we find ${H}_{0}={77}_{-18}^{+37}$ km s−1 Mpc−1 (maximum a posteriori and 68.3% highest density posterior interval; assuming a flat H 0 prior in the range $\left[10,220\right]$ km s−1 Mpc−1). We explore the dependence of our results on the thresholds by which galaxies are included in our sample, and we show that weighting the host galaxies by stellar mass or star formation rate provides entirely consistent results with potentially tighter constraints. By applying the method to simulated gravitational-wave events and a realistic galaxy catalog we show that, because of the small localization volume, this statistical standard siren analysis of GW170817 provides an unusually informative (top 10%) constraint. Under optimistic assumptions for galaxy completeness and redshift uncertainty, we find that dark binary neutron star measurements of H 0 will converge as $40 \% /\sqrt{(N)}$, where N is the number of sources. While these statistical estimates are inferior to the value from the counterpart standard siren measurement utilizing NGC 4993 as the unique host, ${H}_{0}={76}_{-13}^{+19}$ km s−1 Mpc−1 (determined from the same publicly available data), our analysis is a proof-of-principle demonstration of the statistical approach first proposed by Bernard Schutz over 30 yr ago

First measurement of the Hubble Constant from a Dark Standard Siren using the Dark Energy Survey Galaxies and the LIGO/Virgo Binary–Black-hole Merger GW170814

International audienceWe present a multi-messenger measurement of the Hubble constant H 0 using the binary–black-hole merger GW170814 as a standard siren, combined with a photometric redshift catalog from the Dark Energy Survey (DES). The luminosity distance is obtained from the gravitational wave signal detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO)/Virgo Collaboration (LVC) on 2017 August 14, and the redshift information is provided by the DES Year 3 data. Black hole mergers such as GW170814 are expected to lack bright electromagnetic emission to uniquely identify their host galaxies and build an object-by-object Hubble diagram. However, they are suitable for a statistical measurement, provided that a galaxy catalog of adequate depth and redshift completion is available. Here we present the first Hubble parameter measurement using a black hole merger. Our analysis results in , which is consistent with both SN Ia and cosmic microwave background measurements of the Hubble constant. The quoted 68% credible region comprises 60% of the uniform prior range [20, 140] km s−1 Mpc−1, and it depends on the assumed prior range. If we take a broader prior of [10, 220] km s−1 Mpc−1, we find (57% of the prior range). Although a weak constraint on the Hubble constant from a single event is expected using the dark siren method, a multifold increase in the LVC event rate is anticipated in the coming years and combinations of many sirens will lead to improved constraints on H 0

A gravitational-wave standard siren measurement of the Hubble constant

On 17 August 2017, the Advanced LIGO 1 and Virgo 2 detectors observed the gravitational-wave event GW170817-a strong signal from the merger of a binary neutron-star system 3 . Less than two seconds after the merger, a γ-ray burst (GRB 170817A) was detected within a region of the sky consistent with the LIGO-Virgo-derived location of the gravitational-wave source 4-6 . This sky region was subsequently observed by optical astronomy facilities 7 , resulting in the identification 8-13 of an optical transient signal within about ten arcseconds of the galaxy NGC 4993. This detection of GW170817 in both gravitational waves and electromagnetic waves represents the first 'multi-messenger' astronomical observation. Such observations enable GW170817 to be used as a 'standard siren' 14-18 (meaning that the absolute distance to the source can be determined directly from the gravitational-wave measurements) to measure the Hubble constant. This quantity represents the local expansion rate of the Universe, sets the overall scale of the Universe and is of fundamental importance to cosmology. Here we report a measurement of the Hubble constant that combines the distance to the source inferred purely from the gravitational-wave signal with the recession velocity inferred from measurements of the redshift using the electromagnetic data. In contrast to previous measurements, ours does not require the use of a cosmic 'distance ladder' 19 : the gravitational-wave analysis can be used to estimate the luminosity distance out to cosmological scales directly, without the use of intermediate astronomical distance measurements. We determine the Hubble constant to be about 70 kilometres per second per megaparsec. This value is consistent with existing measurements 20,21 , while being completely independent of them. Additional standard siren measurements from future gravitationalwave sources will enable the Hubble constant to be constrained to high precision

Supplement: "Localization and broadband follow-up of the gravitational-wave transient GW150914" (2016, ApJL, 826, L13)

This Supplement provides supporting material for Abbott et al. (2016a). We briefly summarize past electromagnetic (EM) follow-up efforts as well as the organization and policy of the current EM follow-up program. We compare the four probability sky maps produced for the gravitational-wave transient GW150914, and provide additional details of the EM follow-up observations that were performed in the different bands

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