3,050 research outputs found
Revisiting the phase diagram of hard ellipsoids
In this work the well-known Frenkel-Mulder phase diagram of hard ellipsoids
of revolution [Mol. Phys. 55, 1171 (1985)] is revisited by means of replica
exchange Monte Carlo simulations. The method provides good sampling of dense
systems and so, solid phases can be accessed without the need of imposing a
given structure. At high densities, we found plastic solids and fcc-like
crystals for semi-spherical ellipsoids (prolates and oblates), and SM2
structures [Phys. Rev. E 75, 020402 (2007)] for x:1-prolates and 1:x-oblates
with x>=3. The revised fluid-crystal and isotropic-nematic transitions
reasonably agree with those presented in the Frenkel-Mulder diagram. An
interesting result is that, for small system sizes (100 particles), we obtained
2:1 and 1.5:1-prolate equations of state without transitions, while some order
is developed at large densities. Furthermore, the symmetric oblate cases are
also reluctant to form ordered phases.Comment: 8 pages, 6 figure
TERA- A Tool for Aero-engine Modelling and Management
One of the distinguishing features of the civil aero-engine market is its high
competitiveness. The costs and risks associated with new projects are such that the
difference between two apparently equally attractive options could result in success from
one and a threat to the survival of the company from the other. To conceive and assess
engines with minimum global warming impact and lowest cost of ownership in a variety
of emission legislation scenarios, emissions taxation policies, fiscal and Air Traffic
Management environments, a Techno-economic and Environmental Risk Assessment
(TERA) model is needed. TERA incorporates multi-disciplinary modules for modelling
gas turbine and aircraft performance, estimation of engine weight, noise and emissions as
well as environment impact and operating economics. The TERA software is integrated
with a commercial optimiser and provides a means for cycle studies. It is to be expected
that new legislative and fiscal constraints on air travel will demand an extension to the
customary range of asset management parameters. In such a business environment there
is potential for TERA to develop into a useful tool for aircraft and engine asset
management. This paper presents a description of this tool as well as gives some results
from scenario studies
Detecting the Rise and Fall of 21 cm Fluctuations with the Murchison Widefield Array
We forecast the sensitivity with which the Murchison Widefield Array (MWA)
can measure the 21 cm power spectrum of cosmic hydrogen, using radiative
transfer simulations to model reionization and the 21 cm signal. The MWA is
sensitive to roughly a decade in scale (wavenumbers of k ~ 0.1 - 1 h Mpc^{-1}),
with foreground contamination precluding measurements on larger scales, and
thermal detector noise limiting the small scale sensitivity. This amounts
primarily to constraints on two numbers: the amplitude and slope of the 21 cm
power spectrum on the scales probed. We find, however, that the redshift
evolution in these quantities can yield important information about
reionization. Although the power spectrum differs substantially across
plausible models, a generic prediction is that the amplitude of the 21 cm power
spectrum on MWA scales peaks near the epoch when the intergalactic medium (IGM)
is ~ 50% ionized. Moreover, the slope of the 21 cm power spectrum on MWA scales
flattens as the ionization fraction increases and the sizes of the HII regions
grow. Considering detection sensitivity, we show that the optimal MWA antenna
configuration for power spectrum measurements would pack all 500 antenna tiles
as close as possible in a compact core. The MWA is sensitive enough in its
optimal configuration to measure redshift evolution in the slope and amplitude
of the 21 cm power spectrum. Detecting the characteristic redshift evolution of
our models will confirm that observed 21 cm fluctuations originate from the
IGM, and not from foregrounds, and provide an indirect constraint on the
volume-filling factor of HII regions during reionization. After two years of
observations under favorable conditions, the MWA can constrain the filling
factor at an epoch when ~ 0.5 to within roughly +/- 0.1 at 2-sigma.Comment: 14 pages, 9 figures, submitted to Ap
Assessing the Treatment Needs of Sexually Aggressive Male Students at UK Universities
Our studies are the first in the UK to assess empirically the psychological profiles of the most common perpetrators of sexual assault at UK universities: sexually aggressive male students. Study 1 assesses the characteristics and predictors of sexual aggression amongst university males at one UK university, whilst Study 2 evaluates the generalisability of findings across a national sample. Study 3 examines the heterogeneity of self-reported sexually aggressive students to see if they comprised a unique clinical population with shared treatment needs.
This poster was also presented at the SeNSS Virtual Summer Conference 2020 (16-17th July)
Empirically Assessing the Effectiveness of The Pathways Programme: An Online Self-Help Intervention for Male Sexual Aggression at UK Universities
Though contemporary evidence suggests that upwards of one-in-nine UK male university students engage in sexually violent behaviours (Hales & Gannon, 2022), few evidence-based primary prevention strategies have been developed to prevent their perpetration. To help contribute to this evidence gap, this study evaluated the short and longer-term effectiveness of a novel psychoeducation-based online self-help intervention for university male sexual aggression called The Pathways Programme. Designed around current empirical understanding of university-based sexual harm in the UK, the programme contains six modules that correspond with known risk factors for perpetration. Data were collected as part of a randomised control trial from 254 self-indentified heterosexual male students enrolled at a UK university who reported a proclivity towards sexual aggression. Results showed that participants who took part in the programme displayed moderate reductions in their self-perceived likelihood of sexual aggression (our primary treatment target) across testing points, as well as reductions in their self-reported levels of hostility towards women, rape myth acceptance, and problematic sexual fantasies (our secondary treatment targets). Control participants also displayed reductions in some domains over time, albeit to a lesser degree. Additional analyses probed the factors associated with participant drop-out, clinical and reliable change, and user feedback. Overall, our study provides preliminary evidence for the efficacy of The Pathways Programme at reducing UK university males’ risk of sexual aggression; however, we caution readers that more robust evaluation is necessary to support intervention rollout. We discuss our findings alongside the limitations of our study and provide suggestions for future research
Helical Tubes in Crowded Environments
When placed in a crowded environment, a semi-flexible tube is forced to fold
so as to make a more compact shape. One compact shape that often arises in
nature is the tight helix, especially when the tube thickness is of comparable
size to the tube length. In this paper we use an excluded volume effect to
model the effects of crowding. This gives us a measure of compactness for
configurations of the tube, which we use to look at structures of the
semi-flexible tube that minimize the excluded volume. We focus most of our
attention on the helix and which helical geometries are most compact. We found
that helices of specific pitch to radius ratio 2.512 to be optimally compact.
This is the same geometry that minimizes the global curvature of the curve
defining the tube. We further investigate the effects of adding a bending
energy or multiple tubes to begin to explore the more complete space of
possible geometries a tube could form.Comment: 10 page
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