19,333 research outputs found
Capacitive pressure transducer system
Closed loop capacitive pressure transducer with extended frequency response for very low pressure measurement
Growing Massive Black Hole Pairs in Minor Mergers of Disk Galaxies
We perform a suite of high-resolution smoothed particle hydrodynamics
simulations to investigate the orbital decay and mass evolution of massive
black hole (MBH) pairs down to scales of ~30 pc during minor mergers of disk
galaxies. Our simulation set includes star formation and accretion onto the
MBHs, as well as feedback from both processes. We consider 1:10 merger events
starting at z~3, with MBH masses in the sensitivity window of the Laser
Interferometer Space Antenna, and we follow the coupling between the merger
dynamics and the evolution of the MBH mass ratio until the satellite galaxy is
tidally disrupted. While the more massive MBH accretes in most cases as if the
galaxy were in isolation, the satellite MBH may undergo distinct episodes of
enhanced accretion, owing to strong tidal torques acting on its host galaxy and
to orbital circularization inside the disk of the primary galaxy. As a
consequence, the initial 1:10 mass ratio of the MBHs changes by the time the
satellite is disrupted. Depending on the initial fraction of cold gas in the
galactic disks and the geometry of the encounter, the mass ratios of the MBH
pairs at the time of satellite disruption can stay unchanged or become as large
as 1:2. Remarkably, the efficiency of MBH orbital decay correlates with the
final mass ratio of the pair itself: MBH pairs that increase significantly
their mass ratio are also expected to inspiral more promptly down to
nuclear-scale separations. These findings indicate that the mass ratios of MBH
pairs in galactic nuclei do not necessarily trace the mass ratios of their
merging host galaxies, but are determined by the complex interplay between gas
accretion and merger dynamics.Comment: 5 pages, 4 figures, replaced to match accepted version on Ap
Effects of Extreme Obliquity Variations on the Habitability of Exoplanets
We explore the impact of obliquity variations on planetary habitability in
hypothetical systems with high mutual inclination. We show that large
amplitude, high frequency obliquity oscillations on Earth-like exoplanets can
suppress the ice-albedo feedback, increasing the outer edge of the habitable
zone. We restrict our exploration to hypothetical systems consisting of a
solar-mass star, an Earth-mass planet at 1 AU, and 1 or 2 larger planets. We
verify that these systems are stable for years with N-body simulations,
and calculate the obliquity variations induced by the orbital evolution of the
Earth-mass planet and a torque from the host star. We run a simplified energy
balance model on the terrestrial planet to assess surface temperature and ice
coverage on the planet's surface, and we calculate differences in the outer
edge of the habitable zone for planets with rapid obliquity variations. For
each hypothetical system, we calculate the outer edge of habitability for two
conditions: 1) the full evolution of the planetary spin and orbit, and 2) the
eccentricity and obliquity fixed at their average values. We recover previous
results that higher values of fixed obliquity and eccentricity expand the
habitable zone, but also find that obliquity oscillations further expand
habitable orbits in all cases. Terrestrial planets near the outer edge of the
habitable zone may be more likely to support life in systems that induce rapid
obliquity oscillations as opposed to fixed-spin planets. Such planets may be
the easiest to directly characterize with space-borne telescopes.Comment: 46 pages, 12 Figures, 5 Table
Can variability in the effect of opioids on refractory breathlessness be explained by genetic factors?
© 2015, BMJ Publishing Group. All rights reserved. Objectives: Opioids modulate the perception of breathlessness with a considerable variation in response, with poor correlation between the required opioid dose and symptom severity. The objective of this hypothesis-generating, secondary analysis was to identify candidate single nucleotide polymorphisms (SNP) from those associated with opioid receptors, signalling or pain modulation to identify any related to intensity of breathlessness while on opioids. This can help to inform prospective studies and potentially lead to better tailoring of opioid therapy for refractory breathlessness. Setting: 17 hospice/palliative care services (tertiary services) in 11 European countries. Participants: 2294 people over 18 years of age on regular opioids for pain related to cancer or its treatment. Primary outcome measures: The relationship between morphine dose, breathlessness intensity (European Organisation for Research and Treatment of Cancer Core Quality of Life Questionnaire; EORTCQLQC30 question 8) and 112 candidate SNPs from 25 genes (n=588). Secondary outcome measures: The same measures for people on oxycodone (n=402) or fentanyl (n=429). Results: SNPs not in Hardy-Weinberg equilibrium or with allele frequencies ( < 5%) were removed. Univariate associations between each SNP and breathlessness intensity were determined with Benjamini-Hochberg false discovery rate set at 20%. Multivariable ordinal logistic regression, clustering over country and adjusting for available confounders, was conducted with remaining SNPs. For univariate morphine associations, 1 variant on the 5-hydroxytryptamine type 3B (HTR3B) gene, and 4 on the β-2-arrestin gene (ARRB2) were associated with more intense breathlessness. 1 SNP remained significant in the multivariable model: people with rs7103572 SNP (HTR3B gene; present in 8.4% of the population) were three times more likely to have more intense breathlessness (OR 2.86; 95% CIs 1.46 to 5.62; p=0.002). No associations were seen with fentanyl nor with oxycodone. Conclusions: This large, exploratory study identified 1 biologically plausible SNP that warrants further study in the response of breathlessness to morphine therapy
Deriving modified rankin scores from medical records
<p><b>Background and Purpose:</b> Modified Rankin score (mRS) is traditionally graded using a face-to-face or telephone interview. Certain stroke assessment scales can be derived from a review of a patient’s case-record alone. We hypothesized that mRS could be successfully derived from the narrative within patient case-records.</p>
<p><b>Methods:</b> Sequential patients attending our cerebrovascular outpatient clinic were included. Two independent, blinded clinicians, trained in mRS, assessed case-records to derive mRS. They scored “certainty” of their grading on a 5-point Likert scale. Agreement between derived and traditional face-to-face mRS was calculated using attribute agreement analysis.</p>
<p><b>Results:</b> Fifty patients with a range of disabilities were included. Case-record appraisers were poor at deriving mRS (k=0.34 against standard). Derived mRS grades showed poor agreement between observers (k=0.33). There was no relationship between certainty of derived mRS and proportion of correct grades (P=0.727).</p>
<p><b>Conclusion:</b> Accurate mRS cannot be derived from standard hospital records. Direct mRS interview is still required for clinical trials.</p>
Orbital Decay of Supermassive Black Hole Binaries in Clumpy Multiphase Merger Remnants
We simulate an equal-mass merger of two Milky Way-size galaxy discs with
moderate gas fractions at parsec-scale resolution including a new model for
radiative cooling and heating in a multi-phase medium, as well as star
formation and feedback from supernovae. The two discs initially have a
supermassive black hole (SMBH) embedded in
their centers. As the merger completes and the two galactic cores merge, the
SMBHs form a a pair with a separation of a few hundred pc that gradually
decays. Due to the stochastic nature of the system immediately following the
merger, the orbital plane of the binary is significantly perturbed.
Furthermore, owing to the strong starburst the gas from the central region is
completely evacuated, requiring ~Myr for a nuclear disc to rebuild.
Most importantly, the clumpy nature of the interstellar medium has a major
impact on the the dynamical evolution of the SMBH pair, which undergo
gravitational encounters with massive gas clouds and stochastic torquing by
both clouds and spiral modes in the disk. These effects combine to greatly
delay the decay of the two SMBHs to separations of a few parsecs by nearly two
orders of magnitude, yr, compared to previous work. In mergers of
more gas-rich, clumpier galaxies at high redshift stochastic torques will be
even more pronounced and potentially lead to stronger modulation of the orbital
decay. This suggests that SMBH pairs at separations of several tens of parsecs
should be relatively common at any redshift.Comment: submitted to MNRAS; Comments very welcom
Playing popular science
Popular science is a critical form of science communication and dissemination. While scientific journals and detailed textbooks are well suited to dissemination of detailed theories and findings within academic communities, there is a definitive need to inform the general public of key scientific concepts and challenges. Indeed, this is increasingly seen as a central part of any research project or funding bid: in the United Kingdom, the Research Councils stipulate a need to consider public engagement and outreach in research proposals For scientists, the popular science book has long been a medium of choice, primarily because they already have a great deal of experience in writing. But in recent years scientific researchers have been increasingly engaged with other forms of popular science communication, including radio and television broadcasting. Early careers researchers are now provided with training in these areas, including guidance on how to develop programme proposals and how to write, present, direct, and edit materials for print, the airwaves, and screen. In effect, today’s scientists are expected to engage directly with popular science journalism not merely as scientific advisors, but as the writers, directors, and broadcasters.This event involved an exhibition and discussion of four popular science games, co-designed by scientific experts and designed and developed by students at Abertay University. The four games were: (1) Namaka by Crowbar Games Co-designed by Ecotoxicologist Dr Brian Quinn (2) Tides: A Shark Tale by Benthos Games Co-designed by Immunologist and sharks expert Dr Helen Dooley (3) Orbs by Quantessential Games Co-designed by Quantum Physicist Dr Erik Gauger (4) Cell Cycle by Type 3 Games Co-designed by Cell Biologist and cancer researcher Dr Adrian Sauri
- …