38 research outputs found
Commentary on "Graphite and its hidden superconductivity"
No full textA Commentary on the paper by P. Esquinazi [Pap. Phys. 5, 050007 (2013)]. The author of the paper offers a Reply.Received: 10 October 2013,, Accepted: 4 November 2013; Edited by: S. A. Grigera; DOI: http://dx.doi.org/10.4279/PIP.05000
On the feasibility of exomoon detection via exoplanet phase curve spectral contrast
No full textThe author gratefully acknowledges support from the ECOGAL project, grant agreement 291227, funded by the European Research Council under ERC-2011-ADG.An exoplanet-exomoon system presents a superposition of phase curves to observers - the dominant component varies according to the planetary period, and the lesser component varies according to both the planetary and the lunar periods. If the spectra of the two bodies differ significantly, then it is likely that there are wavelength regimes where the contrast between the moon and planet is significantly larger. In principle, this effect could be used to isolate periodic oscillations in the combined phase curve. Being able to detect the exomoon component would allow a characterization of the exomoon radius, and potentially some crude atmospheric data. We run a parameter survey of combined exoplanet-exomoon phase curves, which shows that for most sets of planet-moon parameters, the lunar component of the phase curve is undetectable to current state-of-the-art transit observations. Even with future transit survey missions, measuring the exomoon signal will most likely require photometric precision of 10 parts per million or better. The only exception to this is if the moon is strongly tidally heated or in some way self-luminous. In this case, measurements of the phase curve at wavelengths greater than a few μm can be dominated by the lunar contribution. Instruments like the James Webb Space Telescope and its successors are needed to make this method feasible.Peer reviewe
Exoplanet transits as the foundation of an interstellar communications network
No full textThe author gratefully acknowledges support from the ECOGAL project, grant agreement 291227, funded by the European Research Council under ERC-2011-ADG, and the STFC grant ST/J001422/1.Two fundamental problems for extraterrestrial intelligences (ETIs) attempting to establish interstellar communication are timing and energy consumption. Humanity's study of exoplanets via their transit across the host star highlights a means of solving both problems. An ETI ‘A’ can communicate with ETI ‘B’ if B is observing transiting planets in A's star system, either by building structures to produce artificial transits observable by B, or by emitting signals at B during transit, at significantly lower energy consumption than typical electromagnetic transmission schemes. This can produce a network of interconnected civilizations, establishing contact via observing each other's transits. Assuming that civilizations reside in a Galactic Habitable Zone (GHZ), I conduct Monte Carlo Realization simulations of the establishment and growth of this network, and analyse its properties in the context of graph theory. I find that at any instant, only a few civilizations are correctly aligned to communicate via transits. However, we should expect the true network to be cumulative, where a ‘handshake’ connection at any time guarantees connection in the future via e.g. electromagnetic signals. In all our simulations, the cumulative network connects all civilizations together in a complete network. If civilizations share knowledge of their network connections, the network can be fully complete on timescales of order a hundred thousand years. Once established, this network can connect any two civilizations either directly, or via intermediate civilizations, with a path much less than the dimensions of the GHZ.Peer reviewe
Oral history interview with Pauline Hodges
No full textPauline Hodges was born in Liberal, Kansas, in 1929, one month before the stock market crashed and two years before the Dust Bowl. Since her father was a wheat farmer, both of these events had a great impact on her family. She started school at Floris in a one room schoolhouse, then moved to Turpin. When she was nine, her family moved to Forgan, where she graduated in 1947. She is co-author of the book A History of Beaver County
The Galactic Club or Galactic Cliques? Exploring the limits of interstellar hegemony and the Zoo hypothesis
No full textThe author gratefully acknowledges support from the ECOGAL project, grant agreement 291227, funded by the European Research Council under ERC-2011-ADG and the STFC grant ST/J001422/1.The Zoo solution to Fermi's Paradox proposes that extraterrestrial intelligences (ETIs) have agreed to not contact the Earth. The strength of this solution depends on the ability for ETIs to come to agreement, and establish/police treaties as part of a so-called ‘Galactic Club’. These activities are principally limited by the causal connectivity of a civilization to its neighbours at its inception, i.e. whether it comes to prominence being aware of other ETIs and any treaties or agreements in place. If even one civilization is not causally connected to the other members of a treaty, then they are free to operate beyond it and contact the Earth if wished, which makes the Zoo solution ‘soft’. We should therefore consider how likely this scenario is, as this will give us a sense of the Zoo solution's softness, or general validity. We implement a simple toy model of ETIs arising in a Galactic Habitable Zone, and calculate the properties of the groups of culturally connected civilizations established therein. We show that for most choices of civilization parameters, the number of culturally connected groups is >1, meaning that the Galaxy is composed of multiple Galactic Cliques rather than a single Galactic Club. We find in our models for a single Galactic Club to establish interstellar hegemony, the number of civilizations must be relatively large, the mean civilization lifetime must be several millions of years, and the inter-arrival time between civilizations must be a few million years or less.Peer reviewe
Is the spiral morphology of the Elias 2-27 circumstellar disc due to gravitational instability?
No full textThis is the author accepted manuscript. The final version is available from Oxford University Press via the DOI in this record.A recent ALMA observation of the Elias 2-27 system revealed a two-armed structure extend-
ing out to ∼300 au in radius. The protostellar disc surrounding the central star is unusually
massive, raising the possibility that the system is gravitationally unstable. Recent work has
shown that the observed morphology of the system can be explained by disc self-gravity,
so we examine the physical properties of the disc necessary to detect self-gravitating spiral
waves. Using three-dimensional Smoothed Particle Hydrodynamics, coupled with radiative
transfer and synthetic ALMA imaging, we find that observable spiral structure can only be
explained by self-gravity if the disc has a low opacity (and therefore efficient cooling), and
is minimally supported by external irradiation. This corresponds to a very narrow region of
parameter space, suggesting that, although it is possible for the spiral structure to be due to
disc self-gravity, other explanations, such as an external perturbation, may be preferred.We thank the anonymous referee for their thoughtful review, which greatly improved the clarity of this work. We would like to thank Daniel Price for his publicly available SPH plotting code SPLASH (Price 2007), which we have made use of in this paper. CH warmly thanks Farzana Meru for elucidating discussions during the process of this work. KR gratefully acknowledges support from STFC grant ST/M001229/1. DF gratefully acknowledges support from the ECOGAL project, grant agreement 291227, funded by the European Research Council under ERC-2011-ADG. The research leading to these results also received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement number 313014 (ETAEARTH). This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No 681601). This research used the
ALICE2 High Performance Computing Facility at the University of Leicester. TJH acknowledges funding from Exeter’s STFC Consolidated Grant (ST/M00127X/1
Great Southern Land
No full textThis chapter looks at Colin Clark’s 1937 sabbatical in Australia where he took up visiting appointments at the Universities of Melbourne, Sydney and Western Australia. Clark was quickly entranced by Australia, especially Queensland. By giving guest lectures and making newsworthy comments he attracted interests in his talent including the Premier William Forgan Smith of Queensland. In 1938 he co-authored The National Income of Australia (1938) with John Crawford which contained a ‘provisional’ estimate for the Australian income multiplier. With an anticipated collapse in private investment spending Clark advocated further public sector stimulus; advice which conflicted with that of one of Australia’s leading economists, Douglas Copland. Clark also argued that since Australia’s population growth rate had slowed, it would be necessary for this to increase if the country was to maintain the maximum return from the capital invested. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd
Usability of fluorescence angiography with indocyanine green in the surgical management of penetrating abdominal trauma:A case series
No full textBackground: The surgical management of penetrating abdominal trauma can be challenging, and despite improvements in diagnostics and treatment, mortality and morbidity rates remain high. Intraoperative fluorescence angiography with indocyanine green (ICG-FA) is currently implemented in many elective surgical settings. However, there are few data regarding the usability of ICG-FA in emergency surgery, and to our knowledge, ICG-FA has not been evaluated in penetrating abdominal trauma. Hence, our objective was to determine the feasibility and usability of ICG-FA in surgical management of penetrating abdominal trauma. Materials and methods: A total of 20 patients undergoing emergency laparotomy for penetrating abdominal trauma were included. The usability of ICG-FA was evaluated using the System Usability Scale (SUS®). The intraoperative macroscopic assessment was compared with that using ICG-FA, and any influence of ICG-FA on surgical management was documented. Results: The ICG-FA was completed in all cases and rendered a “good” median SUS® score of 68.8 (interquartile range, 60.6–82.5) by first-time users. The use of ICG-FA influenced surgical management in 14 cases (70%). In six of those cases, ICG-FA significantly changed surgical management. There were no postoperative complications related to surgical management. Conclusion: ICG-FA proved useable and relevant in the setting of penetrating abdominal trauma. Although this was only a small case series, the study showed that ICG-FA could substantially influence surgical management of penetrating abdominal trauma, adding considerable patient benefit.</p
Photochemical trajectory modeling studies of the North Atlantic region during August 1993
No full textA Lagrangian photochemical trajectory model has been used to assess the factors affecting O-3 production during transport of polluted air masses across the North Atlantic Ocean. Sensitivity studies have been performed along idealized trajectories, and it is found that the potential impact of North American emission sources is maximized by transport of air at high altitudes, in drier conditions and in conditions where mixing of the air with background air masses is relatively limited. Measurements taken from the NCAR King Air aircraft as part of the North Atlantic Regional Experiment (NARE) August 1993 intensive have been used to initialize forward trajectories, calculated using European Centre for Medium-Range Weather Forecasting analyzed wind fields, from eastern North America to assess O-3 production over the Atlantic during this period. The effects of dilution of a polluted air parcel with air from the upper troposphere have also been studied, and the contribution of photochemical O-3 production to the air mass composition is found to be smaller than that of dilution, particularly for long trajectories and for conditions where dilution is relatively rapid or involves air from the stratosphere. Measurements taken from the Meteorological Research Flight Hercules aircraft over the eastern Atlantic as part of the Oxidizing Capacity of the Tropospheric Atmosphere campaign have been examined in the light of these studies. A backward trajectory analysis has been performed from one of the vertical profiles taken off the coast of Portugal on August 31, 1993, to assess the origin of the different air masses intercepted. While the lower levels are characteristic of air from the European boundary layer advected over the ocean, the upper levels show strong evidence for anthropogenic influence from North American sources, with elevated levels of O-3, NOy, CO, and aerosol. Although it cannot be concluded that this air mass definitely originated from over North America, the measured concentrations are shown to be consistent with those for an air mass from this source region experiencing some mixing with air masses in the upper troposphere
G11.92−0.61 MM 1: a fragmented Keplerian disk surrounding a proto-o star
No full textThis is the author accepted manuscript. The final version is available from American Astronomical Society / IOP Publishing via the DOI in this record.We present high resolution (300 au) Atacama Large Millimeter/submillimeter Array (ALMA) observations of the massive young stellar object G11.92-0.61 MM1. We resolve the immediate circumstellar environment of MM1 in 1.3mm continuum emission and CH3CN emission for the first time.
The object divides into two main sources - MM1a, which is the source of a bipolar molecular outflow, and MM1b, located 0:0057 (1920 au) to the South-East. The main component of MM1a is an elongated continuum structure, perpendicular to the bipolar outflow, with a size of 0.00141arcsec X 0.00050arcsec (480 X 170 au). The gas kinematics toward MM1a probed via CH3CN trace a variety of scales. The lower energy J = 12-11 K = 3 line traces extended, rotating gas within the outflow cavity, while the v8=1 line shows a clearly-resolved Keplerian rotation signature. Analysis of the gas kinematics and dust emission shows that the total enclosed mass in MM1a is 40 +/- 5M_solar (where between 2.2-5.8M_solar is attributed to the disk), while MM1b is < 0.6M_solar. The extreme mass ratio and orbital properties of MM1a and MM1b suggest that MM1b is one of the first observed examples of the formation of a binary star via disk fragmentation around a massive young (proto)star.Science and Technology Facilities CouncilDISCSI
