Observing complete gravitational wave signals from dynamical capture binaries

We assess the detectability of the gravitational wave signals from highly eccentric compact binaries. We use a simple model for the inspiral, merger, and ringdown of these systems. The model is based on mapping the binary to an effective single black hole system described by a Kerr metric, thereby including certain relativistic effects such as zoom-whirl-type behavior. The resultant geodesics source quadrupolar radiation and, in turn, are evolved under its dissipative effects. At the light ring, we attach a merger model that was previously developed for quasicircular mergers but also performs well for eccentric mergers with little modification. We apply this model to determine the detectability of these sources for initial, Enhanced, and Advanced LIGO across the parameter space of nonspinning close capture compact binaries. We conclude that, should these systems exist in nature, the vast majority will be missed by conventional burst searches or by quasicircular waveform templates in the advanced detector era. Other methods, such as eccentric templates or, more practically, a stacked excess power search, must be developed to avoid losing these sources. These systems would also have been missed frequently in the initial LIGO data analysis. Thus, previous null coincidence results with detected gamma-ray bursts cannot exclude the possibility of coincident gravitational wave signals from eccentric binaries.Comment: 18 pages, 18 figures; revised to match accepted version, PRD in pres

In search of ‘lost’ knowledge and outsourced expertise in flood risk management

This paper examines the parallel discourses of ‘lost’ local flood expertise and the growing use of commercial consultancies to outsource aspects of flood risk work. We critically examine the various claims and counter-claims about lost, local and external expertise in flood management, focusing on the aftermath of the 2007 floods in East Yorkshire, England. Drawing on interviews with consultants, drainage engineers and others, we caution against claims that privilege ‘local’ floods knowledge as ‘good’ and expert knowledge as somehow suspect. This paper urges carefulness in interpreting claims about local knowledge, arguing that it is important always to think instead of hybrid knowledge formations. We conclude by arguing that experiments in the co-production of flood risk knowledge need to be seen as part of a spectrum of ways for producing shared knowledge

A qualitative study of men’s recollections of growing up with father absence: childhood father figures and family resilience

© 2017 Informa UK Limited, trading as Taylor & Francis Group. Background: Families come in many forms and single parent women headed households are common with nurses being well positioned to provide support for these women and their children. For children growing up in lone parent households, the nature of family relationships and the availability of a social support network are important factors in reducing developmental risks. Aim: The aim of this study was to explore adult men’s recollections of growing up in a father-absent home. Design: This study utilised a qualitative methodology. Methods: Semi-structured interviews were conducted with 21 adult men who grew up in a father-absent home due to family discord. Interview transcripts were thematically analysed using an inductive approach. Findings: Analysis of the interview transcripts revealed two themes relating to childhood father figures and family relational networks. For some men, ambivalent, violent or unavailable father figures stepped into the void created by the absent father. Others experienced positive father figures or multigenerational relationships, which provided positive relational supports and attachments. Conclusion: The findings illuminate the dynamics of family resilience and provide important insights for nurses and other family healthcare workers

“Being a father”: constructions of fatherhood by men with absent fathers

© 2018 Informa UK Limited, trading as Taylor & Francis Group Family dynamics and parenting styles are influential on children's wellbeing [Walsh, F. (2016). Strengthening family resilience (3rd ed.). New York: Guilford Press]. Additionally, childhood experiences and how an individual experienced being parented can impact on how individuals as mothers and fathers choose to parent their own children [Herland, M. D., Hauge, M.-I., & Helegland, I. M. (2015). Balancing fatherhood: Experiences of fatherhood among men with a difficult past. Qualitative Social Work, 14(2), 242–258]. However, growing up in a home with an absent parent may create challenges associated with parenting for individuals, due to not having these experiences themselves. Therefore, the article reports findings on men who grew up in a father-absent household and how their experiences influenced their understanding of fatherhood and becoming a father. Twenty-one men participated in this qualitative study. Findings revealed that although men felt unprepared for fatherhood they attempted to learn to be a father and expressed the importance of not wanting their children to experience father absence. The study findings provide important insights in the provision of support for fathers who have experienced father absence

The DLV System for Knowledge Representation and Reasoning

This paper presents the DLV system, which is widely considered the state-of-the-art implementation of disjunctive logic programming, and addresses several aspects. As for problem solving, we provide a formal definition of its kernel language, function-free disjunctive logic programs (also known as disjunctive datalog), extended by weak constraints, which are a powerful tool to express optimization problems. We then illustrate the usage of DLV as a tool for knowledge representation and reasoning, describing a new declarative programming methodology which allows one to encode complex problems (up to $\Delta^P_3$-complete problems) in a declarative fashion. On the foundational side, we provide a detailed analysis of the computational complexity of the language of DLV, and by deriving new complexity results we chart a complete picture of the complexity of this language and important fragments thereof. Furthermore, we illustrate the general architecture of the DLV system which has been influenced by these results. As for applications, we overview application front-ends which have been developed on top of DLV to solve specific knowledge representation tasks, and we briefly describe the main international projects investigating the potential of the system for industrial exploitation. Finally, we report about thorough experimentation and benchmarking, which has been carried out to assess the efficiency of the system. The experimental results confirm the solidity of DLV and highlight its potential for emerging application areas like knowledge management and information integration.Comment: 56 pages, 9 figures, 6 table

Holes in my memories: A qualitative study of men affected by father absence

This qualitative study explored adult men's experiences of father absence. Interviews with 21 men between the ages of 24 and 70 explored narratives of father absence and how the men perceived this influenced their life trajectory. Thematic analysis revealed that these men experienced a range of difficulties and challenges, including episodes of sadness and depression associated with loss and grief for the paternal relationship, self-esteem issues, feelings of anger and rejection, and difficulty forming trusting relationships particularly with other men. This study contributes to understanding mental health issues that can be associated with paternal absence for men. © 2014 Informa Healthcare USA, Inc

Using machine learning to parametrize postmerger signals from binary neutron stars

There is growing interest in the detection and characterization of gravitational waves from postmerger oscillations of binary neutron stars. These signals contain information about the nature of the remnant and the high-density and out-of-equilibrium physics of the postmerger processes, which would complement any electromagnetic signal. However, the construction of binary neutron star postmerger waveforms is much more complicated than for binary black holes: (i) there are theoretical uncertainties in the neutron-star equation of state and other aspects of the high-density physics, (ii) numerical simulations are expensive and available ones only cover a small fraction of the parameter space with limited numerical accuracy, and (iii) it is unclear how to parametrize the theoretical uncertainties and interpolate across parameter space. In this work, we describe the use of a machine-learning method called a conditional variational autoencoder (CVAE) to construct postmerger models for hyper/massive neutron star remnant signals based on numerical-relativity simulations. The CVAE provides a probabilistic model, which encodes uncertainties in the training data within a set of latent parameters. We estimate that training such a model will ultimately require $\sim 10^4$ waveforms. However, using synthetic training waveforms as a proof-of-principle, we show that the CVAE can be used as an accurate generative model and that it encodes the equation of state in a useful latent representation

Heating and Acceleration of Intracluster Medium Electrons by Turbulence

In this paper we investigate the feasibility of bremsstrahlung radiation from `nonthermal' electrons as a source of hard X-rays from the intracluster medium of clusters of galaxies. With an exact treatment of the Coulomb collisions in a Fokker-Planck analysis of the electron distribution we find that the severe difficulties with lifetimes of `nonthermal' particles found earlier by Petrosian (2001) using a cold target model remain problematic. We then address possible acceleration of background electrons into a nonthermal tail. We assume a simplified but generic acceleration rate and determine the expected evolution of an initially Maxwellian distribution of electrons. We find that strong nonthermal components arise only for rapid rate of acceleration which also heats up the entire plasma. These results confirm the conclusion that if the observed `nonthermal' excesses are due to some process accelerating the background thermal electrons this process must be short lived.Comment: 28 pages, 7 figures. Astrophysical Journal, in pres