147,970 research outputs found
Marvin: A Heuristic Search Planner with Online Macro-Action Learning
This paper describes Marvin, a planner that competed in the Fourth
International Planning Competition (IPC 4). Marvin uses
action-sequence-memoisation techniques to generate macro-actions, which are
then used during search for a solution plan. We provide an overview of its
architecture and search behaviour, detailing the algorithms used. We also
empirically demonstrate the effectiveness of its features in various planning
domains; in particular, the effects on performance due to the use of
macro-actions, the novel features of its search behaviour, and the native
support of ADL and Derived Predicates
Adherence to prophylaxis in adolescents and young adults with severe haemophilia, A qualitative study with patients
© 2018 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.Abstract Introduction: Reported levels of adherence to prophylaxis among young people with haemophilia (YPH) vary widely and are predominately based on estimations made by healthcare professionals and parents. Reasons for (non)adherence among YPH in particular have not been evidenced. Aim: to examine experiences in relation to prophylaxis with YPH themselves, and barriers and facilitators to their adherence. Methods: 11 Participants were recruited in five haemophilia centres across England and Wales. All patients who met the inclusion criteria (aged 12-25, diagnosed with haemophilia, on prophylaxis) were approached during a routine check-up appointment, and all participants who agreed to take part were interviewed. Interviews were audio recorded, transcribed and analysed using Interpretative Phenomenological Analysis. Results: Self-reported adherence to prophylaxis was good. Few participants admitted to intentionally skipping injections although they reported sometimes forgetting. However, due to the increasingly personalised and flexible approach to prophylaxis, adherence is not straightforward to define. Barriers to adherence included a busy lifestyle, dislike of the intravenous injection, venous access issues, anxiety or stress and being out of one’s normal routine. Support was an important facilitator to adherence, including support from health professionals at the haemophilia centre as well as friends. Parents appear to be very involved with their sons’ haemophilia management, even after their sons leave home. Conclusion: What this study adds is that the increasingly flexible and personalized approach to managing prophylaxis in haemophilia may sometimes lead to confusion around treatment frequency and dosing. This may lead to accidental non-adherence, which is distinct from both skipping and forgetting. Advice from haemophilia teams may not always be consistent, and is likely to be interpreted differently by different individuals. Some additional training and education of patients and their families to increase their knowledge and skills around prophylaxis may reduce this confusion and therefore is likely to improve adherence further.Peer reviewedFinal Published versio
Studies of waveform requirements for intermediate mass-ratio coalescence searches with advanced detectors
The coalescence of a stellar-mass compact object into an intermediate-mass
black hole (intermediate mass-ratio coalescence; IMRAC) is an important
astrophysical source for ground-based gravitational-wave interferometers in the
so-called advanced configuration. However, the ability to carry out effective
matched-filter based searches for these systems is limited by the lack of
reliable waveforms. Here we consider binaries in which the intermediate-mass
black hole has mass in the range 24 - 200 solar masses with a stellar-mass
companion having masses in the range 1.4 - 18.5 solar masses. In addition, we
constrain the mass ratios, q, of the binaries to be in the range 1/140 < q <
1/10 and we restrict our study to the case of circular binaries with
non-spinning components. We investigate the relative contribution to the
signal-to-noise ratio (SNR) of the three different phases of the coalescence:
inspiral, merger and ringdown. We show that merger and ringdown contribute to a
substantial fraction of the total SNR over a large portion of the mass
parameter space, although in a limited portion the SNR is dominated by the
inspiral phase. We further identify three regions in the IMRAC mass-space in
which: (i) inspiral-only searches could be performed with losses in detection
rates L in the range 10% < L < 27%, (ii) searches based on inspiral-only
templates lead to a loss in detection rates in the range 27% < L < 50%$, and
(iii) templates that include merger and ringdown are essential to prevent
losses in detection rates greater than 50%. We investigate the effectiveness
with which the inspiral-only portion of the IMRAC waveform space is covered by
comparing several existing waveform families in this regime. Our results
reinforce the importance of extensive numerical relativity simulations of
IMRACs and the need for further studies of suitable approximation schemes in
this mass range.Comment: 10 pages, 3 figure
How effective is harassment on infalling late-type dwarfs?
A new harassment model is presented that models the complex, and dynamical
tidal field of a Virgo like galaxy cluster. The model is applied to small,
late-type dwarf disc galaxies (of substantially lower mass than in previous
harassment simulations) as they infall into the cluster from the outskirts.
These dwarf galaxies are only mildly affected by high speed tidal encounters
with little or no observable consequences; typical stellar losses are ,
producing very low surface brightness streams ( mag arcsec),
and a factor of two drop in dynamical mass-to-light ratio. Final stellar discs
remain disc-like, and dominated by rotation although often with tidally induced
spiral structure. By means of Monte-Carlo simulations, the statistically likely
influences of harassment on infalling dwarf galaxies are determined. The
effects of harassment are found to be highly dependent on the orbit of the
galaxy within the cluster, such that newly accreted dwarf galaxies typically
suffer only mild harassment. Strong tidal encounters, that can morphologically
transform discs into spheroidals, are rare occurring in of dwarf
galaxy infalls for typical orbits of sub-structure within CDM cluster
mass halos. For orbits with small apocentric distances (250 kpc), harassment
is significantly stronger resulting in complete disruption or heavy mass loss
( dark matter and stellar), however, such orbits are expected
to be highly improbable for newly infalling galaxies due to the deep potential
well of the cluster.Comment: 15 pages, 11 figures, 4 table
Mineralogy of the Ibitira eucrite and comparison with other eucrites and lunar samples
Single crystal X-ray and energy dispersive electron-probe techniques are used to study the mineralogy and track history of Ibitira. The mineralogical features of the Ibitire eucrite are described and examined in relation to data for other eucrites and howardites and lunar samples. The processes which transformed a presumed igneous texture into a more complex one are discussed
Mathematical and computer modeling of electro-optic systems using a generic modeling approach
The conventional approach to modelling electro-optic sensor systems is to develop separate models for individual systems or classes of system, depending on the detector technology employed in the sensor and the application. However, this ignores commonality in design and in components of these systems. A generic approach is presented for modelling a variety of sensor systems operating in the infrared waveband that also allows systems to be modelled with different levels of detail and at different stages of the product lifecycle. The provision of different model types (parametric and image-flow descriptions) within the generic framework can allow valuable insights to be gained
How the minuscule can contribute to the big picture: the neutron electric dipole moment project at TRIUMF
A permanent electric dipole moment (EDM) of a fundamental particle violates
both parity (P) and time (T) reversal symmetry and combined charge and parity
(CP) reversal symmetry if the combined reversal of charge, parity \textit{and}
time (CPT) is preserved. It is a very promising place to search for physics
beyond the Standard Model. Ultracold neutrons (UCN) are the ideal tool to study
the neutron electric dipole moment since they can be observed for hundreds of
seconds. This article summarizes the current searches for the neutron EDM using
UCN and introduces the project to measure the neutron electric dipole moment at
TRIUMF using its unique accelerator driven spallation neutron and liquid helium
UCN source. The aim is to reach a sensitivity for the neutron EDM of around
cm.Comment: 12 pages, 6 figures, MENU 2016 Conference, Kyoto, Japa
Variability in wrist-tilt accelerometer based gesture interfaces
In this paper we describe a study that examines human performance in a tilt control targeting task on a PDA. A three-degree of freedom accelerometer attached to the base of the PDA allows users to navigate to the targets by tilting their wrist in different directions. Post hoc analysis of performance data has been used to classify the ease of targeting and variability of movement in the different directions. The results show that there is an increase in variability of motions upwards from the centre, compared to downwards motions. Also the variability in the x axis component of the motion was greater than that in the y axis. This information can be used to guide designers as to the ease of various relative motions, and can be used to reshape the dynamics of the interaction to make each direction equally easy to achieve
A New Basis for QED Bound State Computations
A simple method to compute QED bound state properties is presented, in which
binding energy effects are treated non-perturbatively. It is shown that to take
the effects of all ladder Coulomb photon exchanges into account, one can simply
perform the derivative of standard QED amplitudes with respect to the external
momentum. For example, the derivative of the light-by-light scattering
amplitude gives an amplitude for orthopositronium decay to three photons where
any number of Coulomb photon exchanges between the e-e+ is included.
Various applications are presented. From them, it is shown that binding
energy must be treated non-perturbatively in order to preserve the analyticity
of positronium decay amplitudes.
Interesting perspectives for quarkonium physics are briefly sketched.Comment: LaTeX, 23 pages, 16 figures. Minor corrections. Some comments adde
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