Operational modes for a wave injection facility aboard spacelab and a sub-satellite

Various modes of operation are described for an orbiting wave injection facility planned to measure the properties of waves propagating in space plasma. Such a facility would cover a wide frequency range including MF and HF. Phase shift and Doppler shift measurements will yield more accurate measurements of echo time delay and the angle of arrival. Because Spacelab will involve some sub-satellites, some consideration is given to propagation between two vehicles both at HF and VHF

Macroscopic limits of individual-based models for motile cell populations with volume exclusion

Partial differential equation models are ubiquitous in studies of motile cell populations, giving a phenomenological description of events which can be analyzed and simulated using a wide range of existing tools. However, these models are seldom derived from individual cell behaviors and so it is difficult to accurately include biological hypotheses on this spatial scale. Moreover, studies which do attempt to link individual- and population-level behavior generally employ lattice-based frameworks in which the artifacts of lattice choice at the population level are unclear. In this work we derive limiting population-level descriptions of a motile cell population from an off-lattice, individual-based model (IBM) and investigate the effects of volume exclusion on the population-level dynamics. While motility with excluded volume in on-lattice IBMs can be accurately described by Fickian diffusion, we demonstrate that this is not the case off lattice. We show that the balance between two key parameters in the IBM (the distance moved in one step and the radius of an individual) determines whether volume exclusion results in enhanced or slowed diffusion. The magnitude of this effect is shown to increase with the number of cells and the rate of their movement. The method we describe is extendable to higher-dimensional and more complex systems and thereby provides a framework for deriving biologically realistic, continuum descriptions of motile populations

Asymptotic Level Spacing of the Laguerre Ensemble: A Coulomb Fluid Approach

We determine the asymptotic level spacing distribution for the Laguerre Ensemble in a single scaled interval, $(0,s)$, containing no levels, E_{\bt}(0,s), via Dyson's Coulomb Fluid approach. For the $\alpha=0$ Unitary-Laguerre Ensemble, we recover the exact spacing distribution found by both Edelman and Forrester, while for $\alpha\neq 0$, the leading terms of $E_{2}(0,s)$, found by Tracy and Widom, are reproduced without the use of the Bessel kernel and the associated Painlev\'e transcendent. In the same approximation, the next leading term, due to a ``finite temperature'' perturbation (\bt\neq 2), is found.Comment: 10pp, LaTe

Dietary advice for people with diabetes: the role of carbohydrate in dietary treatment and an assessment of video education

This thesis investigated novel approaches to the delivery of lifestyle education for people with diabetes. The principles of dietary advice for diabetes recommend a high carbohydrate intake, yet carbohydrate foods raise blood glucose levels significantly. Study 1 was designed as a randomised controlled trial to evaluate the effect of a low carbohydrate (LC) and low fat (LF) diet on glycaemic control and body weight in 26 subjects. Weight loss was greater in the LC group (-6.9kg v -2.1kg, p=0.003). Glycaemic control improved in both groups with a reduction in Alc in both LC and LF groups (-0.3% v -0.2%, p=0.582). There were no significant changes in cardiovascular risk assessed by lipid levels and blood pressure. Study 2 was designed as a randomised controlled trial to assess a novel education programme delivered by video for 42 people newly diagnosed with Type 2 diabetes. At six months follow-up, there was a significant increase in knowledge in the video intervention group (p=<O.OOOI). There were reductions in A1c (-0.7% v -0.6%, p=0.843), total cholesterol (-0.5mmo1l1 v -0.2mmolll, p=0.347) and LDL cholesterol (-0.5mmo/1 v 0.2mmolll, p=O.l), and physical activity increased in the intervention group. There were no changes in the control group, but these differences failed to reach between group significance. Study 3 was an intervention study examining structured education in 51 people with Type 1 diabetes. At one year's follow-up, there was a significant improvement in Ale levels (-0.3%, p=0.03) with no increase in body weight or hypoglycaemia. Diabetes related distress improved significantly at six months follow-up and this was maintained at one year (p=O.O 19). These studies indicate that both education and modification of carbohydrate intake have a positive effect on outcomes in people with diabetes. People with Type 2 diabetes show increased knowledge after video education, and can achieve significant weight loss by adopting a low carbohydrate diet. People with long-standing Type 1 diabetes can significantly improve glycaemic control and quality of life by adopting a strategy of carbohydrate counting and insulin adjustment

Flows along cometary tails in the Helix planetary nebula NGC 7293

Previous velocity images which reveal flows of ionized gas along the most prominent cometary tail (from Knot 38) in the Helix planetary nebula are compared with that taken at optical wavelengths with the Hubble Space Telescope and with an image in the emission from molecular hydrogen. The flows from the second most prominent tail from Knot 14 are also considered. The kinematics of the tail from the more complex Knot 32, shown here for the first time, also reveals an acceleration away from the central star. All of the tails are explained as accelerating ionized flows of ablated material driven by the previous, mildly supersonic, AGB wind from the central star. The longest tail of ionized gas, even though formed by this mechanism in a very clumpy medium, as revealed by the emission from molecular hydrogen, appears to be a coherent outflowing feature.Comment: 8 pages, 4 figures, accepted for publication in MNRA

Thermospheric winds and temperatures above Mawson, Antarctica, observed with an all-sky imaging, Fabry-Perot spectrometer

A new all-sky imaging Fabry-Perot spectrometer has been installed at Mawson station (67&amp;deg;36&apos; S, 62&amp;deg;52&apos; E), Antarctica. This instrument is capable of recording independent spectra from many tens of locations across the sky simultaneously. Useful operation began in March 2007, with spectra recorded on a total of 186 nights. Initial analysis has focused on the large-scale daily and average behavior of winds and temperatures derived from observations of the 630.0 nm airglow line of atomic oxygen, originating from a broad layer centered around 240 km altitude, in the ionospheric F-region. &lt;br&gt;&lt;br&gt; The 1993 Horizontal Wind Model (HWM93), NRLMSISE-00 atmospheric model, and the Coupled Thermosphere/Ionosphere Plasmasphere (CTIP) model were used for comparison. During the geomagnetically quiet period studied, observed winds and temperatures were generally well modelled, although temperatures were consistently higher than NRLMSISE-00 predicted, by up to 100 K. CTIP temperatures better matched our data, particularly later in the night, but predicted zonal winds which were offset from those observed by 70–180 ms&lt;sup&gt;&amp;minus;1&lt;/sup&gt; westward. During periods of increased activity both winds and temperatures showed much greater variability over time-scales of less than an hour. For the active night presented here, a period of 45 min saw wind speeds decrease by around 180 ms&lt;sup&gt;&amp;minus;1&lt;/sup&gt;, and temperatures increase by approximately 100 K. Active-period winds were poorly modelled by HWM93 and CTIP, although observed median temperatures were in better agreement with NRLMSISE-00 during such periods. &lt;br&gt;&lt;br&gt; Average behavior was found to be generally consistent with previous studies of thermospheric winds above Mawson. The collected data set was representative of quiet geomagnetic and solar conditions. Geographic eastward winds in the afternoon/evening generally continued until around local midnight, when winds turned equatorward. Geographic meridional and zonal winds in the afternoon were approximately 50 ms&lt;sup&gt;&amp;minus;1&lt;/sup&gt; weaker than expected from HWM93, as was the transition to equatorward flow around midnight. There was also a negligible geographic zonal component to the post-midnight wind where HWM93 predicted strong westward flow. Average temperatures between 19:00 and 04:00 local solar time were around 60 K higher than predicted by NRLMSISE-00

Clumpy Ultracompact HII Regions I: Fully Supersonic Wind-blown Models

We propose that a significant fraction of the ultracompact HII regions found in massive star-forming clouds are the result of the interaction of the wind and ionizing radiation from a young massive star with the clumpy molecular cloud gas in its neighbourhood. Distributed mass loading in the flow allows the compact nebulae to be long-lived. In this paper, we discuss a particularly simple case, in which the flow in the HII region is everywhere supersonic. The line profiles predicted for this model are highly characteristic, for the case of uniform mass loading. We discuss briefly other observational diagnostics of these models.Comment: To appear in Monthly Notices of the Royal Astronomical Society. 5 pages LaTeX (uses mn.sty and epsf.sty macros) + 4 PS figures. Also available via http://axp2.ast.man.ac.uk:8000/Preprints.htm

Mathematical modelling of curtain coating

We present a simple mathematical model for the fluid flow in the curtain coating process, exploiting the small aspect ratio, and examine the model in the large-Reynolds-number limit of industrial interest. We show that the fluid is in free fall except for a region close to the substrate, but find that the model can not describe the turning of the curtain onto the substrate. We find that the inclusion of a viscous bending moment close to the substrate allows the curtain to “turn the corner”

High Resolution CO and H2 Molecular Line Imaging of a Cometary Globule in the Helix Nebula

We report high resolution imaging of a prominent cometary globule in the Helix nebula in the CO J=1-0 (2.6 mm) and H2 v=1-0 S(1) (2.12 micron) lines. The observations confirm that globules consist of dense condensations of molecular gas embedded in the ionized nebula. The head of the globule is seen as a peak in the CO emission with an extremely narrow line width (0.5 km/s) and is outlined by a limb-brightened surface of H2 emission facing the central star and lying within the photo-ionized halo. The emission from both molecular species extends into the tail region. The presence of this extended molecular emission provides new constraints on the structure of the tails, and on the origin and evolution of the globules.Comment: 12 pages, 3 figures. To appear in The Astrophysical Journal Letter