Observing Gravitational Waves with a Single Detector

A major challenge of any search for gravitational waves is to distinguish true astrophysical signals from those of terrestrial origin. Gravitational-wave experiments therefore make use of multiple detectors, considering only those signals which appear in coincidence in two or more instruments. It is unclear, however, how to interpret loud gravitational-wave candidates observed when only one detector is operational. In this paper, we demonstrate that the observed rate of binary black hole mergers can be leveraged in order to make confident detections of gravitational-wave signals with one detector alone. We quantify detection confidences in terms of the probability $P(S)$ that a signal candidate is of astrophysical origin. We find that, at current levels of instrumental sensitivity, loud signal candidates observed with a single Advanced LIGO detector can be assigned $P(S)\gtrsim0.4$. In the future, Advanced LIGO may be able to observe single-detector events with confidences exceeding $P(S)\sim90\%$.Comment: 8 pages, 4 figures; published in CQG; minor updates to match published versio

Effect of additive concentration during copper deposition using EnFACE electrolyte

Copper deposition from solutions using high concentration of acid, metal ions and polyethylene glycol (PEG), and bis-(3-sulphopropyl) disulphide (SPS) and chloride ions (Cl-) is well known. A recent maskless micropatterning technology, which has the potential to replace the traditional photolithographic process, called EnFACE, proposed using an acid-free, low metal ion solution which is in direct contrast to those used in standard plating technology. In this work copper has been deposited using both standard electroplating solutions and those used in the EnFACE process. In the standard electrolyte 0.63 M CuSO4 and 2.04 M H2SO4 has been used, along with Gleam additives supplied by Dow Chemicals. For the Enface electrolyte, copper deposition has been carried out without any acid, and with different concentrations of additives between 17%-200% of those recommended by suppliers. 25 μm of metal has been plated on stainless steel coupons as suggested by ASTM, peeled off and subjected to ductility and resistance measurements. Scanning electron microscopy and electron back scatter diffraction have been carried out to determine the deposit morphology. It was found that copper deposits obtained from acid-free solutions containing low concentration of metal ion and additives produced copper deposits with properties which are comparable to those obtained from standard electrolytes. The optimum additive concentration for the EnFACE electrolyte was 50% of the supplier recommended value

No peaks without valleys: The stable mass transfer channel for gravitational-wave sources in light of the neutron star-black hole mass gap

Gravitational-wave (GW) detections are starting to reveal features in the mass distribution of double compact objects. The lower end of the black hole (BH) mass distribution is especially interesting as few formation channels contribute here and because it is more robust against variations in the cosmic star formation than the high mass end. In this work we explore the stable mass transfer channel for the formation of GW sources with a focus on the low-mass end of the mass distribution. We conduct an extensive exploration of the uncertain physical processes that impact this channel. We note that, for fiducial assumptions, this channel reproduces the peak at $\sim9 \mathrm{M_{\odot}}$ in the GW-observed binary BH mass distribution remarkably well, and predicts a cutoff mass that coincides with the upper edge of the purported neutron star BH mass gap. The peak and cutoff mass are a consequence of unique properties of this channel, namely (1) the requirement of stability during the mass transfer phases, and (2) the complex way in which the final compact object masses scale with the initial mass. We provide an analytical expression for the cutoff in the primary component mass and show that this adequately matches our numerical results. Our results imply that selection effects resulting from the formation channel alone can provide an explanation for the purported neutron star--BH mass gap in GW detections. This provides an alternative to the commonly adopted view that the gap emerges during BH formation.Comment: Accepted for publication in ApJ associated code is available at https://github.com/LiekeVanSon/LowMBH_and_StableChanne

Optimal Packings of Superballs

Dense hard-particle packings are intimately related to the structure of low-temperature phases of matter and are useful models of heterogeneous materials and granular media. Most studies of the densest packings in three dimensions have considered spherical shapes, and it is only more recently that nonspherical shapes (e.g., ellipsoids) have been investigated. Superballs (whose shapes are defined by |x1|^2p + |x2|^2p + |x3|^2p <= 1) provide a versatile family of convex particles (p >= 0.5) with both cubic- and octahedral-like shapes as well as concave particles (0 < p < 0.5) with octahedral-like shapes. In this paper, we provide analytical constructions for the densest known superball packings for all convex and concave cases. The candidate maximally dense packings are certain families of Bravais lattice packings. The maximal packing density as a function of p is nonanalytic at the sphere-point (p = 1) and increases dramatically as p moves away from unity. The packing characteristics determined by the broken rotational symmetry of superballs are similar to but richer than their two-dimensional "superdisk" counterparts, and are distinctly different from that of ellipsoid packings. Our candidate optimal superball packings provide a starting point to quantify the equilibrium phase behavior of superball systems, which should deepen our understanding of the statistical thermodynamics of nonspherical-particle systems.Comment: 28 pages, 16 figure

'Surely the most natural scenario in the world’: Representations of ‘Family’ in BBC Pre-school Television

Historically, the majority of work on British children’s television has adopted either an institutional or an audience focus, with the texts themselves often overlooked. This neglect has meant that questions of representation in British children’s television – including issues such as family, gender, class or ethnicity - have been infrequently analysed in the UK context. In this article, we adopt a primarily qualitative methodology and analyse the various textual manifestations of ‘family’, group, or community as represented in a selected number of BBC pre-school programmes. In doing so, we question the (limited amount of) international work that has examined representations of the family in children’s television, and argue that nuclear family structures do not predominate in this sphere

A First Search for Prompt Radio Emission from a Gravitational-Wave Event

Multimessenger observations of the binary neutron star merger GW170817 have enabled the discovery of a diverse array of electromagnetic counterparts to compact binary mergers, including an unambiguous kilonova, a short gamma-ray burst, and a late-time radio jet. Beyond these counterparts, compact binary mergers are additionally predicted to be accompanied by prompt low-frequency radio emission. The successful observation of a prompt radio counterpart would be immensely valuable, but is made difficult by the short delay between the gravitational-wave and prompt electromagnetic signals as well as the poor localization of gravitational-wave sources. Here, we present the first search for prompt radio emission accompanying a gravitational-wave event, targeting the binary black hole merger GW170104 detected by the Advanced LIGO and Virgo gravitational-wave observatories during their second (O2) observing run. Using the Owens Valley Radio Observatory Long Wavelength Array (OVRO-LWA), we search a $\sim900\,\mathrm{deg}^2$ region for transient radio emission within approximately one hour of GW170104, obtaining an upper limit of $2.5\times10^{41}\,\mathrm{erg}\,\mathrm{s}^{-1}$ on its equivalent isotropic luminosity between 27-84 MHz. We additionally discuss plans to target binary neutron star mergers in Advanced LIGO and Virgo's upcoming O3 observing run.Comment: 13 pages + appendices, 7 figures, submitted to Ap

Increased plasma thioredoxin levels in patients with sepsis: positive association with macrophage migration inhibitory factor.

PURPOSE: To establish the relationship between plasma levels of thioredoxin (Trx) and macrophage migration inhibitory factor (MIF) in systemic inflammatory stress syndrome (SIRS)/sepsis. METHODS: Enzyme-linked immunosorbent assay measurements of Trx, MIF, IL-6, -8, and -10 and enzyme-linked fluorescent assay determination of procalcitonin (PCT) in plasma from patients with SIRS/sepsis, neutropenic sepsis, healthy volunteers and pre-oesophagectomy patients. RESULTS: Thioredoxin was significantly higher in SIRS/sepsis patients [101.3 ng ml(−1), interquartile range (IQR) 68.7–155.6, n = 32] compared with that in healthy controls (49.5 ng ml(−1), IQR 31.4–71.1, P < 0.001, n = 17) or pre-oesophagectomy patients (40.5 ng ml(−1), IQR 36.9–63.2, P < 0.01, n = 7), but was not raised in neutropenics (n = 5). MIF levels were also significantly higher in SIRS/sepsis patients (12.1 ng ml(−1), IQR 9.5–15.5, n = 35), but not in the neutropenic group, when compared with healthy controls (9.3 ng ml(−1), IQR 7.3–10.7, P < 0.01, n = 20). Trx levels correlated, positively, with MIF levels and APACHE II scores. Plasma levels of IL-6, -8 and -10 and PCT increased significantly in patients with SIRS/sepsis (P < 0.001) and with neutropenic sepsis, but did not correlate with Trx or MIF levels. CONCLUSION: Plasma levels of Trx, MIF, IL-6, -8, -10 and PCT were raised in patients with SIRS/sepsis. Comparisons between mediators suggest a unique correlation of Trx with MIF. Moreover, Trx and MIF differed from cytokines and PCT in that levels were significantly lower in patients with neutropenia compared with the main SIRS/sepsis group. By contrast, IL-8 and PCT levels were significantly greater in the neutropenic patient group. The link between MIF and Trx highlighted in this study has implications for future investigations into the pathogenesis of SIRS/sepsis