129 research outputs found
Playscapes for Piano Trio
Playscapes is a piano trio of an approximate duration of 43 minutes. It is in three movements: Playscape I, II, and III. The top range of the piano(G7-C8) is prepared in such a way that these notes become essentially a percussive effect. Playscapes explores the concept of “Musical Activity” – areas of music where simple rules are established and create a context wherein anomalies can occur. Playscape I is a series of these musical activities. In Playscape II, one musical activity goes on for a long time. In Playscape III, two musical activities alternate. In addition, a general trend towards noise occurs throughout Playscapes
A Hybrid Godunov Method for Radiation Hydrodynamics
From a mathematical perspective, radiation hydrodynamics can be thought of as
a system of hyperbolic balance laws with dual multiscale behavior (multiscale
behavior associated with the hyperbolic wave speeds as well as multiscale
behavior associated with source term relaxation). With this outlook in mind,
this paper presents a hybrid Godunov method for one-dimensional radiation
hydrodynamics that is uniformly well behaved from the photon free streaming
(hyperbolic) limit through the weak equilibrium diffusion (parabolic) limit and
to the strong equilibrium diffusion (hyperbolic) limit. Moreover, one finds
that the technique preserves certain asymptotic limits. The method incorporates
a backward Euler upwinding scheme for the radiation energy density and flux as
well as a modified Godunov scheme for the material density, momentum density,
and energy density. The backward Euler upwinding scheme is first-order accurate
and uses an implicit HLLE flux function to temporally advance the radiation
components according to the material flow scale. The modified Godunov scheme is
second-order accurate and directly couples stiff source term effects to the
hyperbolic structure of the system of balance laws. This Godunov technique is
composed of a predictor step that is based on Duhamel's principle and a
corrector step that is based on Picard iteration. The Godunov scheme is
explicit on the material flow scale but is unsplit and fully couples matter and
radiation without invoking a diffusion-type approximation for radiation
hydrodynamics. This technique derives from earlier work by Miniati & Colella
2007. Numerical tests demonstrate that the method is stable, robust, and
accurate across various parameter regimes.Comment: accepted for publication in Journal of Computational Physics; 61
pages, 15 figures, 11 table
A Godunov Method for Multidimensional Radiation Magnetohydrodynamics based on a variable Eddington tensor
We describe a numerical algorithm to integrate the equations of radiation
magnetohydrodynamics in multidimensions using Godunov methods. This algorithm
solves the radiation moment equations in the mixed frame, without invoking any
diffusion-like approximations. The moment equations are closed using a variable
Eddington tensor whose components are calculated from a formal solution of the
transfer equation at a large number of angles using the method of short
characteristics. We use a comprehensive test suite to verify the algorithm,
including convergence tests of radiation-modified linear acoustic and
magnetosonic waves, the structure of radiation modified shocks, and
two-dimensional tests of photon bubble instability and the ablation of dense
clouds by an intense radiation field. These tests cover a very wide range of
regimes, including both optically thick and thin flows, and ratios of the
radiation to gas pressure of at least 10^{-4} to 10^{4}. Across most of the
parameter space, we find the method is accurate. However, the tests also reveal
there are regimes where the method needs improvement, for example when both the
radiation pressure and absorption opacity are very large. We suggest
modifications to the algorithm that will improve accuracy in this case. We
discuss the advantages of this method over those based on flux-limited
diffusion. In particular, we find the method is not only substantially more
accurate, but often no more expensive than the diffusion approximation for our
intended applications.Comment: 42 pages, 22 figures, 2 tables, accepted by ApJ
Amyloid-β accumulation in the CNS in human growth hormone recipients in the UK
Human-to-human transmission of Creutzfeldt–Jakob disease (CJD) has occurred through medical procedures resulting in iatrogenic CJD (iCJD). One of the commonest causes of iCJD was the use of human pituitary-derived growth hormone (hGH) to treat primary or secondary growth hormone deficiency. As part of a comprehensive tissue-based analysis of the largest cohort yet collected (35 cases) of UK hGH-iCJD cases, we describe the clinicopathological phenotype of hGH-iCJD in the UK. In the 33/35 hGH-iCJD cases with sufficient paraffin-embedded tissue for full pathological examination, we report the accumulation of the amyloid beta (Aβ) protein associated with Alzheimer’s disease (AD) in the brains and cerebral blood vessels in 18/33 hGH-iCJD patients and for the first time in 5/12 hGH recipients who died from causes other than CJD. Aβ accumulation was markedly less prevalent in age-matched patients who died from sporadic CJD and variant CJD. These results are consistent with the hypothesis that Aβ, which can accumulate in the pituitary gland, was present in the inoculated hGH preparations and had a seeding effect in the brains of around 50% of all hGH recipients, producing an AD-like neuropathology and cerebral amyloid angiopathy (CAA), regardless of whether CJD neuropathology had occurred. These findings indicate that Aβ seeding can occur independently and in the absence of the abnormal prion protein in the human brain. Our findings provide further evidence for the prion-like seeding properties of Aβ and give insights into the possibility of iatrogenic transmission of AD and CAA
Proteolysis-inducing factor core peptide mediates dermcidin-induced proliferation of hepatic cells through multiple signalling networks
Dermcidin is a candidate oncogene capable of increasing the number of cultured neuronal, breast cancer and prostate cancer cells and improving the survival of hepatic cells. The dermcidin gene encodes the proteolysis-inducing factor core peptide (PIF-CP) and the skin antimicrobial peptide DCD-1. The peptide responsible for inducing proliferation of cells and the mechanisms involved are unknown. In this study, we confirmed a proliferative effect of dermcidin over-expression of 20% (p<0.02) in the HuH7 human hepatic cell line. Proliferation was abrogated by prevention of PIF-CP translation or inactivation of its calcineurin-like phosphatase domain by site-directed mutagenesis. Prevention of DCD-1 translation had no effect. Treatment of cells with a 30 amino acid synthetic PIF-CP induced an analogous increase in proliferation of 14%. Microarray analysis of PIF-CP-treated cells revealed low but significant changes in 111 potential mediator genes. Pathway analysis revealed several gene networks involved in the cellular response to the peptide, one with VEGFB as a hub and two other networks converging on FOS and MYC. Quantitative PCR confirmed direct upregula-tion of VEGFB. These data reveal PIF-CP as the key mediator of dermcidin-induced proliferation and demonstrate induction of key oncogenic pathways
A Radiation Transfer Solver for Athena using Short Characteristics
We describe the implementation of a module for the Athena
magnetohydrodynamics (MHD) code which solves the time-independent,
multi-frequency radiative transfer (RT) equation on multidimensional Cartesian
simulation domains, including scattering and non-LTE effects. The module is
based on well-known and well-tested algorithms developed for modeling stellar
atmospheres, including the method of short characteristics to solve the RT
equation, accelerated Lambda iteration to handle scattering and non-LTE
effects, and parallelization via domain decomposition. The module serves
several purposes: it can be used to generate spectra and images, to compute a
variable Eddington tensor (VET) for full radiation MHD simulations, and to
calculate the heating and cooling source terms in the MHD equations in flows
where radiation pressure is small compared with gas pressure. For the latter
case, the module is combined with the standard MHD integrators using
operator-splitting and we describe this approach in detail. Implementation of
the VET method for radiation pressure dominated flows is described in a
companion paper. We present results from a suite of test problems for both the
RT solver itself, and for dynamical problems that include radiative heating and
cooling. These tests demonstrate that the radiative transfer solution is
accurate, and confirm that the operator split method is stable, convergent, and
efficient for problems of interest. We demonstrate there is no need to adopt
ad-hoc assumptions of questionable accuracy to solve RT problems in concert
with MHD: the computational cost for our general-purpose module for simple
(e.g. LTE grey) problems can be comparable to or less than a single timestep of
Athena's MHD integrators, and only few times more expensive than that for more
general problems. (Abridged)Comment: 20 pages, 13 figures, accepted for publication in ApJ Supplement
Serie
A qualitative study exploring the benefits of involving young people in mental health research
Introduction:
It is increasingly accepted that young people need to be centrally involved in research on issues that affect them. The aim of this study was to explore young people's perceptions of the benefits for them of being involved in mental health research and the processes that enabled these benefits.
Methods:
Qualitative interviews were conducted by co-researchers (young people with lived experience and/or interest in mental health) with 13 young people (aged 13–24 years) who had experience of being involved in mental health research when they were between 11 and 16 years of age. Reflective thematic analysis was used to identify important aspects of young people's experiences.
Results:
Four main themes were identified: (1) opportunity to have a meaningful impact, (2) opportunity to be part of a supportive community, (3) opportunity to learn and grow and (4) increasing opportunities for young people.
Conclusion:
This study highlights young people's experiences of being involved in mental health research and identifies ways in which researchers can ensure that involvement opportunities bring benefits to both the young people and the research.
Patient or Public Contribution:
This research was a response to issues raised by young people involved in research. The project was supported by co-researchers throughout, including design, data collection, analysis and write-up
Analysing Stratified Medicine Business Models and Value Systems:Innovation-Regulation Interactions
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