Who rescues who? Understanding aquatic rescues in Australia using coronial data and a survey

Objective: To examine fatal drowning associated with aquatic rescues and prior self‐reported experience of undertaking an aquatic rescue in Australia. Methods: Previous aquatic rescue experience was sourced through the 2013 Queensland Computer Assisted Telephone Instrument Survey and compared to data on rescue‐related fatal unintentional drowning between 1 January 2006 and 31 December 2015. Results: Twenty‐three per cent (n=294/1291) of survey respondents had previously performed an aquatic rescue. Males (X2=35.2; p<0.001) were more likely to have performed a rescue; commonly at a beach/ocean/harbour location (X2=13.5; p<0.001). Females were more likely to have rescued a child (0‐4 years of age) (X2=29.2; p<0.001) from a swimming pool (X2=34.3; p<0.001). Fifty‐one people drowned while performing an aquatic rescue (Males=82.4%; 25–44 years of age=53.0%; beaches=54.9%). Conclusions: Drownings are prevented by bystanders; this is not without risk to the rescuer. Most people perform only one rescue in their life, often at a younger age, on an altruistic basis, of family members or young children. Community‐wide rescue skills, taught at a young age, with consideration for coastal, inland and swimming pool environments, may prevent drowning

Nothing Ventured — Nothing Gained? Empirical Evidence on Venture Capital Financing in Switzerland

This paper analyses the Determinants of Venture Capital Staging and Syndication in Switzerland. I find that among the different affiliations of VC investors in Switzerland especially independent investors make more extensive use of staged capital infusions. Moreover, the results suggest that staging is employed as a tool for mitigating risks in VC financing. In addition, I find that Syndication can serve as an entrance strategy for foreign VC providers. Furthermore, I find evidence that firms, which realize the benefit of staging, do also become conscious of the value added in financing Start Ups by involving partners. Consequently, VC firms that make use of staging are also more open to syndication. With respect to the value-added of Co-Investment behavior, I show that syndication positively impacts the success rate of a VC provider, whereas VC firms that are more locally embedded do exhibit lower success rates for their investment portfolio

Mathematical Model of Easter Island Society Collapse

In this paper we consider a mathematical model for the evolution and collapse of the Easter Island society, starting from the fifth century until the last period of the society collapse (fifteen century). Based on historical reports, the available primary sources consisted almost exclusively on the trees. We describe the inhabitants and the resources as an isolated system and both considered as dynamic variables. A mathematical analysis about why the structure of the Easter Island community collapse is performed. In particular, we analyze the critical values of the fundamental parameters driving the interaction humans-environment and consequently leading to the collapse. The technological parameter, quantifying the exploitation of the resources, is calculated and applied to the case of other extinguished civilization (Cop\'an Maya) confirming, with a sufficiently precise estimation, the consistency of the adopted model.Comment: 9 pages, 1 figure, final version published on EuroPhysics Letter

Surveying rip current survivors: Preliminary insights into the experiences of being caught in rip currents

This paper begins a process of addressing a significant gap in knowledge about people's responses to being caught in rip currents. While rip currents are the primary hazard facing recreational ocean swimmers in Australia, debate exists about the best advice to give swimmers caught in rip currents. Such surf rescue advice - on what to do and how to respond when caught in a rip - relies on empirical evidence. However, at present, knowledge about swimmers reactions and responses to rip currents is limited. This gap is a considerable barrier to providing effective advice to beach goers and to understanding how this advice is utilised (or not) when actually caught in the rip current. This paper reports the findings of a pilot study that focussed on garnering a better understanding of swimmers' experiences when caught in rip currents. A large scale questionnaire survey instrument generated data about rip current survivors' demographics, knowledge of beach safety and their reactions and responses when caught in a rip current. A mix of online and paper surveys produced a total of 671 completed surveys. Respondents were predominantly an informed group in terms of rip current knowledge, beach experience and had a high self-rated swimming ability. Preliminary insights from the survey show that most respondents recalled a "swim across the rip/parallel to the beach" message when caught in the rip and most escaped unassisted by acting on this message. However, while nearly a quarter of respondents recalled a message of "not to panic", short answer responses revealed that the onset of panic inhibited some respondents from recalling or enacting any other type of beach safety message when caught in the rip current. Results also showed that despite the research sample being younger, competent and frequent ocean swimmers, they were more likely to swim at unpatrolled beaches and outside of the red and yellow safety flags. Moreover, they were still caught in a rip current and they panicked. The findings of this study have significant implications for a range of demographic groups of differing beach safety knowledge and swimming ability who may be caught in rip currents behave, we know very little about how beach goers may respond to being caught in them. © 2012 Author(s)

Constructing solutions to the Bj\"orling problem for isothermic surfaces by structure preserving discretization

In this article, we study an analog of the Bj\"orling problem for isothermic surfaces (that are more general than minimal surfaces): given a real analytic curve $\gamma$ in ${\mathbb R}^3$, and two analytic non-vanishing orthogonal vector fields $v$ and $w$ along $\gamma$, find an isothermic surface that is tangent to $\gamma$ and that has $v$ and $w$ as principal directions of curvature. We prove that solutions to that problem can be obtained by constructing a family of discrete isothermic surfaces (in the sense of Bobenko and Pinkall) from data that is sampled along $\gamma$, and passing to the limit of vanishing mesh size. The proof relies on a rephrasing of the Gauss-Codazzi-system as analytic Cauchy problem and an in-depth-analysis of its discretization which is induced from the geometry of discrete isothermic surfaces. The discrete-to-continuous limit is carried out for the Christoffel and the Darboux transformations as well.Comment: 29 pages, some figure

Supernova 1987A: Rotation and a Binary Companion

In this paper we provide a possible link between the structure of the bipolar nebula surrounding SN1987A and the properties of its progenitor star. A Wind Blwon Bubble (WBB) scenario is emplyed, in which a fast, tenuous wind from a Blue Supergiant expands into a slow, dense wind, expelled during an earlier Red Supergiant phase. The bipolar shapre develops due to a pole-to-equator density contrast in the slow wind (ie, the slow wind forms a slow torus). We use the Wind Compressed Disk (WCD) model of Bjorkman & Cassinelli (1992) to determine the shape of the slow torus. In the WCD scenario, the shape of the torus is determined by the rotation of the progenitor star. We then use a self-similar semi-analytical method for wind blown bubble evolution to determine the shape of the resulting bipolar nebula. We find that the union of the wind-compressed-disk and bipolar-wind-blown- bubble models allows us to recover the salient properties of SN1987A's circumstellar nebula. In particular, the size, speed and density of SN1987A's inner ring are easily reproduced in our calculations. An exploration of parameter space shows the the red supergiant progenitor must be been rotating at > 0.3 of its breakup speed. We conclude that the progenitor was most likely spun up by a merger with a binary companion. Using a simple model for the binary merger we find that the companion is likely to have had a mass > 0.5 M_sun.Comment: 30 pages, 4 figure

The characteristics of drowning among different types of international visitors to Australia and how this contributes to their drowning risk

Objective: Australia is a popular destination for international visitors. This study reviews international visitor drowning deaths in Australia and analyses drowning by visitor type. Methods: A total population retrospective study exploring drowning deaths of international visitors was conducted between 2008 and 2018. Data were extracted from the Royal Life Saving National Fatal Drowning Database and categorised into four subgroups: overseas tourists, international students, working holiday makers and work-related visitors. Descriptive statistics, non-parametric tests and relative risk (RR) were calculated. Results: In total, 201 international visitors drowned in Australia, 7% of all drowning deaths; a crude drowning rate of 0.27/100,000 visitors versus 0.95/100,000 for residents (RR=0.19 [95% CI: 0.16–0.22]). Most deaths were males (79%) and people aged 18–34 years (50%). Visitors frequently drowned at beaches (33%), and when swimming (41%). Thirty-five percent recorded a pre-existing medical condition. Overseas tourists on holiday were the most likely to drown compared to other subgroups. Conclusion: International visitors represent a small but increasing proportion of people drowning in Australia. The circumstances of which visitors drown vary by travel purpose, age, country of origin, location of drowning and activity. Implications for public health: International visitors have unique safety needs, requiring tailored prevention based on the purpose of travel and country of origin

Scattering from Singular Potentials in Quantum Mechanics

In non-relativistic quantum mechanics, singular potentials in problems with spherical symmetry lead to a Schrodinger equation for stationary states with non-Fuchsian singularities both as r tends to zero and as r tends to infinity. In the sixties, an analytic approach was developed for the investigation of scattering from such potentials, with emphasis on the polydromy of the wave function in the r variable. The present paper extends those early results to an arbitrary number of spatial dimensions. The Hill-type equation which leads, in principle, to the evaluation of the polydromy parameter, is obtained from the Hill equation for a two-dimensional problem by means of a simple change of variables. The asymptotic forms of the wave function as r tends to zero and as r tends to infinity are also derived. The Darboux technique of intertwining operators is then applied to obtain an algorithm that makes it possible to solve the Schrodinger equation with a singular potential containing many negative powers of r, if the exact solution with even just one term is already known.Comment: 19 pages, plain Tex. In this revised version, the analysis of Eq. (5.29) has been amended, and an appendix has been added for completenes

Home invasive mechanical ventilation in Finland in 2015-2019

Introduction: The prevalence of long-term invasive mechanical ventilation via tracheostomy in chronic respiratory insufficiency is largely unknown. We aimed to clarify prevalence and aetiology of the use of home invasive mechanical ventilation (HIMV) in Finland in 2015-2019.Methods: Information on HIMV patients was collected yearly from all Finnish Hospital District patient registries between 1 January 2015 and 1 January 2019. Data included underlying diagnosis, time from diagnosis to HIMV initiation, treatment length, mortality and basic sociodemographic data.Results: In 2015, we had 107 HIMV patients. During the follow-up we received 34 new patients (24.1%) and 46 patients (32.6%) died. In 2019, we had 95 HIMV patients and the prevalence in Finland was 2.0 in 100 000. The most common diagnoses were motor neurone disease (29.1%) and spinal cord injuries (19.9%). Mean duration of HIMV among all patients on 1 January 2019 was 12.3 years and among deceased patients, 11.2 years. Treatment durations ranged from 7.7 years for motor neurone disease patients to 47.3 years for post-polio syndrome patients. Most patients (81.6%) used HIMV 24 h.day(-1).Conclusions: HIMV is a rare, long-lasting treatment, most often used in chronic hypoventilation caused by chronic neurological disease. Based on our 4 year follow-up the prevalence of HIMV seems to be diminishing in Finland. Treatment duration and survival vary greatly depending on the underlying diagnosis. Most of the patients were totally dependent on HIMV, requiring 24-h care

Multi-objective routing optimisation for battery-powered wireless sensor mesh networks

Copyright © 2014 ACM2014 Conference on Genetic and Evolutionary Computation (GECCO ’14), Vancouver, BC, Canada, 12-16 July 2014This paper won the Best Paper award in the Real World Applications category at the GECCO ’14 conferenceMesh network topologies are becoming increasingly popular in battery powered wireless sensor networks, primarily due to the extension of network range and resilience against routing failures. However, multi-hop mesh networks suffer from higher energy costs, and the routing strategy directly affects the lifetime of nodes with limited energy sources. Hence while planning routes there are trade-offs to be considered between individual and system-wide battery lifetimes. We present a novel multi-objective routing optimisation approach using evolutionary algorithms to approximate the optimal trade-off between minimum lifetime and the average lifetime of nodes in the network. In order to accomplish this combinatorial optimisation rapidly and thus permit dynamic optimisation for self-healing networks, our approach uses novel k-shortest paths based search space pruning in conjunction with a new edge metric, which associates the energy cost at a pair of nodes with the link between them. We demonstrate our solution on a real network, deployed in the Victoria & Albert Museum, London. We show that this approach provides better trade-off solutions in comparison to the minimum energy option, and how a combination of solutions over the lifetime of the network can enhance the overall minimum lifetime