2,242 research outputs found
Slow equivariant lump dynamics on the two sphere
The low-energy, rotationally equivariant dynamics of n CP^1 lumps on S^2 is
studied within the approximation of geodesic motion in the moduli space of
static solutions. The volume and curvature properties of this moduli space are
computed. By lifting the geodesic flow to the completion of an n-fold cover of
the moduli space, a good understanding of nearly singular lump dynamics within
this approximation is obtained.Comment: 12 pages, 3 figure
A mathematical model for the sequestering of chemical contaminants by magnetic particles
A mathematical model is developed and implemented to characterize the pickup of various liquid chemical contaminants by
polyethylene-coated magnetic particles. The model and its associated experimental and analytical protocols were applied to a wide range
of liquid chemicals in order to gain insights into the physical basis for the pickup phenomenon. The characteristics of the pickup isotherms
range between “ideal” and “nonideal” behaviors that are reflected in the mathematical model by a single parameter, �0, where �0=1
corresponds to ideal behavior and �0�1 corresponds to a departure from idealized behavior that is directly quantified by the magnitude
of �0. The parameter �0 is also related to the efficiency of pickup, and since most isotherms observed in the study deviate from ideality,
the high efficiency of pickup observed in these systems has been attributed in part to this deviation. The proposed model and its associated
experimental and analytical protocols demonstrate great potential for the systematic evaluation of the uptake of chemical contaminants
using magnetic particle technology
Analyzing X-ray variability by State Space Models
In recent years, autoregressive models have had a profound impact on the
description of astronomical time series as the observation of a stochastic
process. These methods have advantages compared with common Fourier techniques
concerning their inherent stationarity and physical background. If
autoregressive models are used, however, it has to be taken into account that
real data always contain observational noise often obscuring the intrinsic time
series of the object. We apply the technique of a Linear State Space Model
which explicitly models the noise of astronomical data and allows to estimate
the hidden autoregressive process. As an example, we have analysed a sample of
Active Galactic Nuclei (AGN) observed with EXOSAT and found evidence for a
relationship between the relaxation timescale and the spectral hardness.Comment: 4 pages, Latex, uses Kluwer Style file crckapb.cls To appear in Proc.
of Astronomical Time Series, Tel Aviv, 199
Glass transition and alpha-relaxation dynamics of thin films of labeled polystyrene
The glass transition temperature and relaxation dynamics of the segmental
motions of thin films of polystyrene labeled with a dye,
4-[N-ethyl-N-(hydroxyethyl)]amino-4-nitraozobenzene (Disperse Red 1, DR1) are
investigated using dielectric measurements. The dielectric relaxation strength
of the DR1-labeled polystyrene is approximately 65 times larger than that of
the unlabeled polystyrene above the glass transition, while there is almost no
difference between them below the glass transition. The glass transition
temperature of the DR1-labeled polystyrene can be determined as a crossover
temperature at which the temperature coefficient of the electric capacitance
changes from the value of the glassy state to that of the liquid state. The
glass transition temperature of the DR1-labeled polystyrene decreases with
decreasing film thickness in a reasonably similar manner to that of the
unlabeled polystyrene thin films. The dielectric relaxation spectrum of the
DR1-labeled polystyrene is also investigated. As thickness decreases, the
-relaxation time becomes smaller and the distribution of the
-relaxation times becomes broader. These results show that thin films
of DR1-labeled polystyrene are a suitable system for investigating confinement
effects of the glass transition dynamics using dielectric relaxation
spectroscopy.Comment: 10 pages, 11 figures, 2 Table
Omega-3 Fatty Acids Improve Recovery, whereas Omega-6 Fatty Acids Worsen Outcome, after Spinal Cord Injury in the Adult Rat
Spinal cord injury (SCI) is a cause of major neurological disability, and no satisfactory treatment is currently available. Evidence suggests that polyunsaturated fatty acids (PUFAs) could target some of the pathological mechanisms that underlie damage after SCI. We examined the effects of treatment with PUFAs after lateral spinal cord hemisection in the rat. The ω-3 PUFAs α-linolenic acid and docosahexaenoic acid (DHA) injected 30 min after injury induced significantly improved locomotor performance and neuroprotection, including decreased lesion size and apoptosis and increased neuronal and oligodendrocyte survival. Evidence showing a decrease in RNA/DNA oxidation suggests that the neuroprotective effect of ω-3 PUFAs involved a significant antioxidant function. In contrast, animals treated with arachidonic acid, an ω-6 PUFA, had a significantly worse outcome than controls. We confirmed the neuroprotective effect of ω-3 PUFAs by examining the effects of DHA treatment after spinal cord compression injury. Results indicated that DHA administered 30 min after spinal cord compression not only greatly increased survival of neurons but also resulted in significantly better locomotor performance for up to 6 weeks after injury.
This report shows a striking difference in efficacy between the effects of treatment with ω-3 and ω-6 PUFAs on the outcome of SCI, with ω-3 PUFAs being neuroprotective and ω-6 PUFAs having a damaging effect. Given the proven clinical safety of ω-3 PUFAs, our observations show that these PUFAs have significant therapeutic potential in SCI. In contrast, the use of preparations enriched in ω-6 PUFAs after injury could worsen outcome after SCI
School-based curriculum development in Scotland: Curriculum policy and enactment
Recent worldwide trends in curriculum policy have re-emphasised the role of teachers in school-based curriculum development. Scotland’s Curriculum for Excellence is typical of these trends, stressing that teachers are agents of change. This paper draws upon empirical data to explore school-based curriculum development in response to Curriculum for Excellence. We focus on two case studies – secondary schools within a single Scottish local education authority. In the paper we argue that the nature and extent of innovation in schools is dependent upon teachers being able to make sense of often complex and confusing curriculum policy, including the articulation of a clear vision about what such policy means for education within each school
Using a prisoner advisory group to develop diversity research in a maximum-security prison
This paper addresses groupwork processes with a group of prisoners advising a research project in a maximum-security prison in England. The research project (Appreciative Inquiry into the Diversity Strategy of HMP Wakefield. RES-000-22-3441) was funded by the Economic and Social Research Council (ESRC) and lasted 9 months. The research explored the experiences of prisoners in diverse minority groupings and the strategies of the prison to accommodate the complex needs of these groups. The Prisoner Advisory Group (PAG) was made up of representatives from Black and Minority Ethnic (BME) prisoners; older prisoners (over 60s); Disabled prisoners (with physical disabilities, learning difficulties; and mental health problems); Gay, Bi-sexual and Transgender prisoners; and prisoners affiliated to Faith groups. It met regularly during the research. The paper considers the forming norming and performing aspects of establishing an effective participant voice in a prison-based project. It considers the contribution of the PAG to developing a research strategy that engaged prisoners in the research. It reflects on the nature of ‘participative research’ in general and whether such research is possible within a high-security prison environment
Constraining early-time dust formation in core-collapse supernovae
There is currently a severe discrepancy between theoretical models of dust
formation in core-collapse supernovae (CCSNe), which predict
M of ejecta dust forming within days, and observations at
these epochs, which infer much lower masses. We demonstrate that, in the
optically thin case, these low dust masses are robust despite significant
observational and model uncertainties. For a sample of 11 well-observed CCSNe,
no plausible model reaches carbon dust masses above M, or
silicate masses above M. Optically thick models can
accommodate larger dust masses, but the dust must be clumped and have a low
() covering fraction to avoid conflict with data at optical wavelengths.
These values are insufficient to reproduce the observed infrared fluxes, and
the required covering fraction varies not only between SNe but between epochs
for the same object. The difficulty in reconciling large dust masses with
early-time observations of CCSNe, combined with well-established detections of
comparably large dust masses in supernova remnants, suggests that a mechanism
for late-time dust formation is necessary.Comment: 14 pages, 13 figures. MNRAS accepted 10/07/2
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An optical fiber photoplethysmographic system for central nervous system tissue
A new system for measuring the oxygen saturation of blood within tissue has been developed, for a number of potential patient monitoring applications. This proof of concept project aims to address the unmet need of real-time measurement of oxygen saturation in the central nervous system (CNS) for patients recovering from neurosurgery or trauma, by developing a fiber optic signal acquisition system for internal placement through small apertures. The development and testing of a two-wavelength optical fiber reflectance photoplethysmography (PPG) system is described. It was found that good quality red and near-infrared PPG signals could be consistently obtained from the human fingertip (n=6) and rat spinal cord (n=6) using the fiber optic probe. These findings justify further development and clinical evaluation of this fiber optic system
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