111 research outputs found
Estimation of neutral-beam-induced field reversal in MFTF by an approximate scaling law
Scaling rules are derived for field-reversed plasmas whose dimensions are common multiples of the ion gyroradius in the vacuum field. These rules are then applied to the tandem MFTF configuration, and it is shown that field reversal appears to be possible for neutral beam currents of the order of 150 amperes, provided that the electron temperature is at least 500 eV
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Intense synchrotron radiation from a magnetically compressed relativistic electron layer
Using a simple model of a relativistic electron layer rotating in an axial magnetic field, energy gain by an increasing magnetic field and energy loss by synchrotron radiation were considered. For a typical example, initial conditions were approximately 8 MeV electron in approximately 14 kG magnetic field, at a layer radius of approximately 20 mm, and final conditions were approximately 4 MG magnetic field approximately 100 MeV electron layer energy at a layer radius of approximately 1.0 mm. In the final state, the intense 1-10 keV synchrotron radiation imposes an electron energy loss time constant of approximately 100 nanoseconds. In order to achieve these conditions in practice, the magnetic field must be compressed by an imploding conducting liner; preferably two flying rings in order to allow the synchrotron radiation to escape through the midplane. The synchrotron radiation loss rate imposes a lower limit to the liner implosion velocity required to achieve a given final electron energy (approximately 1 cm/sec in the above example). In addition, if the electron ring can be made sufficiently strong (field reversed), the synchrotron radiation would be a unique source of high intensity soft x-radiation. (auth
Short time scale pulse stability of the Crab pulsar in the optical band
The fine structure and the variations of the optical pulse shape and phase of
the Crab pulsar are studied on various time scales. The observations have been
carried out on 4-m William Hershel and 6-m BTA telescopes with APD photon
counter, photomultiplier based 4-channel photometer and PSD based panoramic
spectrophotopolarimeter with 1s time resolution in 1994, 1999, 2003 and
2005-2006 years. The upper limit on the pulsar precession on Dec 2, 1999 is
placed in the 10 s - 2 hours time range. The evidence of a varying from set to
set fine structure of the main pulse is found in the 1999 and 2003 years data.
No such fine structure is detected in the integral pulse shape of 1994, 1999
and 2003 years.
The drastic change of the pulse shape in the 2005-2006 years set is detected
along with the pulse shape variability and quasi-periodic phase shifts.Comment: 4 pages, 6 figures. To appear in ApSS, in the proceedings of the
conference "Isolated Neutron Stars: from the Interior to the Surface",
London, April 2006; eds. D. Page, R. Turolla and S. Zan
Exploring the sensitivity of coastal inundation modelling to DEM vertical error
© 2018 Informa UK Limited, trading as Taylor & Francis Group. As sea level is projected to rise throughout the twenty-first century due to climate change, there is a need to ensure that sea level rise (SLR) models accurately and defensibly represent future flood inundation levels to allow for effective coastal zone management. Digital elevation models (DEMs) are integral to SLR modelling, but are subject to error, including in their vertical resolution. Error in DEMs leads to uncertainty in the output of SLR inundation models, which if not considered, may result in poor coastal management decisions. However, DEM error is not usually described in detail by DEM suppliers; commonly only the RMSE is reported. This research explores the impact of stated vertical error in delineating zones of inundation in two locations along the Devon, United Kingdom, coastline (Exe and Otter Estuaries). We explore the consequences of needing to make assumptions about the distribution of error in the absence of detailed error data using a 1 m, publically available composite DEM with a maximum RMSE of 0.15 m, typical of recent LiDAR-derived DEMs. We compare uncertainty using two methods (i) the NOAA inundation uncertainty mapping method which assumes a normal distribution of error and (ii) a hydrologically correct bathtub method where the DEM is uniformly perturbed between the upper and lower bounds of a 95% linear error in 500 Monte Carlo Simulations (HBM+MCS). The NOAA method produced a broader zone of uncertainty (an increase of 134.9% on the HBM+MCS method), which is particularly evident in the flatter topography of the upper estuaries. The HBM+MCS method generates a narrower band of uncertainty for these flatter areas, but very similar extents where shorelines are steeper. The differences in inundation extents produced by the methods relate to a number of underpinning assumptions, and particularly, how the stated RMSE is interpreted and used to represent error in a practical sense. Unlike the NOAA method, the HBM+MCS model is computationally intensive, depending on the areas under consideration and the number of iterations. We therefore used the HBM+ MCS method to derive a regression relationship between elevation and inundation probability for the Exe Estuary. We then apply this to the adjacent Otter Estuary and show that it can defensibly reproduce zones of inundation uncertainty, avoiding the computationally intensive step of the HBM+MCS. The equation-derived zone of uncertainty was 112.1% larger than the HBM+MCS method, compared to the NOAA method which produced an uncertain area 423.9% larger. Each approach has advantages and disadvantages and requires value judgements to be made. Their use underscores the need for transparency in assumptions and communications of outputs. We urge DEM publishers to move beyond provision of a generalised RMSE and provide more detailed estimates of spatial error and complete metadata, including locations of ground control points and associated land cover
Molecular systematics of the marine Dothideomycetes
Phylogenetic analyses of four nuclear genes, namely the large and small
subunits of the nuclear ribosomal RNA, transcription elongation factor 1-alpha
and the second largest RNA polymerase II subunit, established that the
ecological group of marine bitunicate ascomycetes has representatives in the
orders Capnodiales, Hysteriales, Jahnulales,
Mytilinidiales, Patellariales and Pleosporales.
Most of the fungi sequenced were intertidal mangrove taxa and belong to
members of 12 families in the Pleosporales: Aigialaceae,
Didymellaceae, Leptosphaeriaceae, Lenthitheciaceae,
Lophiostomataceae, Massarinaceae, Montagnulaceae,
Morosphaeriaceae, Phaeosphaeriaceae, Pleosporaceae,
Testudinaceae and Trematosphaeriaceae. Two new families are
described: Aigialaceae and Morosphaeriaceae, and three new
genera proposed: Halomassarina, Morosphaeria and
Rimora. Few marine species are reported from the
Dothideomycetidae (e.g. Mycosphaerellaceae,
Capnodiales), a group poorly studied at the molecular level. New
marine lineages include the Testudinaceae and Manglicola
guatemalensis in the Jahnulales. Significantly, most marine
Dothideomycetes are intertidal tropical species with only a few from
temperate regions on salt marsh plants (Spartina species and
Juncus roemerianus), and rarely totally submerged (e.g. Halotthia
posidoniae and Pontoporeia biturbinata on the seagrasses
Posidonia oceanica and Cymodocea nodosum). Specific
attention is given to the adaptation of the Dothideomycetes to the
marine milieu, new lineages of marine fungi and their host specificity
Response to Lawrence DJ: The global summit on the efficacy and effectiveness of spinal manipulative therapy for the prevention and treatment of non-musculoskeletal disorders: A systematic review of the literature
Thank you for the opportunity to respond to the Letter to the Editor by Dana J. Lawrence. In his letter, Lawrence states that the results of our systematic review may be due to bias. However, he does not adequately substantiate his claims..
Effects of dietary precursors to biogenic amines on the behavioural response from groups of caged worker honey bees (Apis mellifera) to the alarm pheromone component isopentyl acetate
A class-wide phylogenetic assessment of Dothideomycetes
We present a comprehensive phylogeny derived from 5 genes, nucSSU, nucLSU
rDNA, TEF1, RPB1 and RPB2, for 356 isolates and 41
families (six newly described in this volume) in Dothideomycetes. All
currently accepted orders in the class are represented for the first time in
addition to numerous previously unplaced lineages. Subclass
Pleosporomycetidae is expanded to include the aquatic order
Jahnulales. An ancestral reconstruction of basic nutritional modes
supports numerous transitions from saprobic life histories to plant associated
and lichenised modes and a transition from terrestrial to aquatic habitats are
confirmed. Finally, a genomic comparison of 6 dothideomycete genomes with
other fungi finds a high level of unique protein associated with the class,
supporting its delineation as a separate taxon
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