1,246 research outputs found

    Some applications of parabolic Dirac Operators to the instationary Navier-Stokes problem on conformally flat cylinders and tori in R^3

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    In this paper we give a survey on how to apply recent techniques of Clifford analysis over conformally flat manifolds to deal with instationary flow problems on cylinders and tori. Solutions are represented in terms of integral operators involving explicit expressions for the Cauchy kernel that are associated to the parabolic Dirac operators acting on spinor sections of these manifolds.publishe

    Pre-clearing vegetation of the coastal lowlands of the Wet Tropics Bioregion, North Queensland

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    A pre-clearing vegetation map and digital coverage at approximately 1:50 000 scale for the coastal lowlands (up to about 200 m elevation) of the Wet Tropics Bioregion, North Queensland is presented. The study area covers about 508 000 ha from Cooktown, 420 km south almost to Townsville (latitude 15° 30’–18° 20’ longitude 144° 50’–146° 40’). Data sources included historical aerial photography, early surveyors’ plans, explorers’ journals, previous vegetation maps, and maps of soils and geology. The pre-clearing mapping was built around the remnant vegetation mapping of Stanton & Stanton (2005), and the vegetation classification of this latter work was adopted. Vegetation units were further classified into regional ecosystems compatible with the standard State-wide system used by Queensland government. The digital coverage is part of the current Queensland Herbarium regional ecosystem coverage (Queensland Herbarium and Wet Tropics Management Authority 2005). Coloured maps (1:100 000 scale) of the pre-clearing vegetation of the Herbert, Tully, Innisfail and Macalister/Daintree subregions are on an accompanying CD-ROM. An evaluation of vegetation loss through clearing on the coastal lowlands of the Wet Tropics revealed several nearextinct vegetation communities and regional ecosystems, and many others that are drastically reduced in area. Even ecosystems occurring on poorly drained lands have suffered a surprisingly high level of loss due to the effectiveness of drainage operations. Grassland ecosystems were found to be widespread on the Herbert and Tully floodplains, but are now close to extinction. The lowlands vegetation of the Wet Tropics that remains today continues to be fragmented and degraded despite the introduction of State-wide broad-scale tree-clearing laws in 1999, and the cessation of broadscale tree-clearing in December 2006

    The chiral and flavour projection of Dirac-Kahler fermions in the geometric discretization

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    It is shown that an exact chiral symmetry can be described for Dirac-Kahler fermions using the two complexes of the geometric discretization. This principle is extended to describe exact flavour projection and it is shown that this necessitates the introduction of a new operator and two new structures of complex. To describe simultaneous chiral and flavour projection, eight complexes are needed in all and it is shown that projection leaves a single flavour of chiral field on each.Comment: v2: 17 pages, Latex. 5 images eps. Added references, reformatted and clarification of some point

    Solar source regions of 3HE-rich particle events

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    Hydrogen alpha X-ray, and metric and kilometric radio data to examine the solar sources of energetic 3He-rich particle events observed near earth in association with impulsive 2 to 100 keV electron events were applied. Each 3He/electron event is associated with a kilometric type 3 burst belonging to a family of such bursts characterized by similar interplanetary propagation paths from the same solar active region. The 3He/electron events correlate very well with the interplanetary low frequency radio brightnesses of these events, but progressively worse with signatures from regions closer to the Sun. When H alpha brightnings can be associated with 3He/electron events, they have onsets coinciding to within 1 min of that of the associated metric type 3 burst but are often too small to be reported. The data are consistent with the earlier idea that many type 3 bursts, the 3He/electron events, are due to particle acceleration in the corona, well above the associated H alpha and X-ray flares

    Size dependence of solar X-ray flare properties

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    Non-thermal and thermal parameters of 85 solar flares of GOES class B1 to M6 (background subtracted classes A1 to M6) have been compared to each other. The hard X-ray flux has been measured by RHESSI and a spectral fitting provided flux and spectral index of the non-thermal emission, as well as temperature and emission measure of the thermal emission. The soft X-ray flux was taken from GOES measurements. We find a linear correlation in a double logarithmic plot between the non-thermal flux and the spectral index. The higher the acceleration rate of a flare, the harder the non-thermal electron distribution. The relation is similar to the one found by a comparison of the same parameters from several sub-peaks of a single flare. Thus small flares behave like small subpeaks of large flares. Thermal flare properties such as temperature, emission measure and the soft X-ray flux also correlate with peak non-thermal flux. A large non-thermal peak flux entails an enhancement in both thermal parameters. The relation between spectral index and the non-thermal flux is an intrinsic feature of the particle acceleration process, depending on flare size. This property affects the reported frequency distribution of flare energies.Comment: Astronomy and Astrophysics, in pres

    Outpatient treatment of low-risk venous thromboembolism with monotherapy oral anticoagulation: patient quality of life outcomes and clinician acceptance

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    BACKGROUND: Oral monotherapy anticoagulation has facilitated home treatment of venous thromboembolism (VTE) in outpatients. OBJECTIVES: The aim of this study was to measure efficacy, safety, as well as patient and physician perceptions produced by a protocol that selected VTE patients as low-risk patients by the Hestia criteria, and initiated home anticoagulation with an oral factor Xa antagonist. METHODS: Patients were administered the Venous Insufficiency Epidemiological and Economic Study Quality of life/Symptoms questionnaire [VEINEs QoL/Sym] and the physical component summary [PCS] from the Rand 36-Item Short Form Health Survey [SF36]). The primary outcomes were VTE recurrence and hemorrhage at 30 days. Secondary outcomes compared psychometric test scores between patients with deep vein thrombosis (DVT) to those with pulmonary embolism (PE). Patient perceptions were abstracted from written comments and physician perceptions specific to PE outpatient treatment obtained from structured survey. RESULTS: From April 2013 to September 2015, 253 patients were treated, including 67 with PE. Within 30 days, 2/253 patients had recurrent DVT and 2/253 had major hemorrhage; all four had DVT at enrollment. The initial PCS scores did not differ between DVT and PE patients (37.2±13.9 and 38.0±12.1, respectively) and both DVT and PE patients had similar improvement over the treatment period (42.2±12.9 and 43.4±12.7, respectively), consistent with prior literature. The most common adverse event was menorrhagia, present in 15% of women. Themes from patient-written responses reflected satisfaction with increased autonomy. Physicians' (N=116) before-to-after protocol comfort level with home treatment of PE increased 48% on visual analog scale. CONCLUSION: Hestia-negative VTE patients treated with oral monotherapy at home had low rates of VTE recurrence and bleeding, as well as quality of life measurements similar to prior reports

    The Relationship of Coronal Mass Ejections to Streamers

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    We have examined images from the Large Angle Spectroscopic Coronagraph (LASCO) to study the relationship of Coronal Mass Ejections (CMEs) to coronal streamers. We wish to test the suggestion (Low 1996) that CMEs arise from flux ropes embedded in a streamer erupting, thus disrupting the streamer. The data span a period of two years near sunspot minimum through a period of increased activity as sunspot numbers increased. We have used LASCO data from the C2 coronagraph which records Thomson scattered white light from coronal electrons at heights between 1.5 and 6R_sun. Maps of the coronal streamers have been constructed from LASCO C2 observations at a height of 2.5R_sun at the east and west limbs. We have superposed the corresponding positions of CMEs observed with the C2 coronagraph onto the synoptic maps. We identified the different kinds of signatures CMEs leave on the streamer structure at this height (2.5R_sun). We find four types of CMEs with respect to their effect on streamers: 1. CMEs that disrupt the streamer 2. CMEs that have no effect on the streamer, even though they are related to it. 3. CMEs that create streamer-like structures 4. CMEs that are latitudinally displaced from the streamer. This is the most extensive observational study of the relation between CMEs and streamers to date. Previous studies using SMM data have made the general statement that CMEs are mostly associated with streamers, and that they frequently disrupt it. However, we find that approximately 35% of the observed CMEs bear no relation to the pre-existing streamer, while 46% have no effect on the observed streamer, even though they appear to be related to it. Our conclusions thus differ considerably from those of previous studies.Comment: Accepted, Journal of Geophysical Research. 8 figs, better versions at http://www.science.gmu.edu/~prasads/streamer.htm
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