2,658 research outputs found
Catharanthus mosaic virus: A potyvirus from a gymnosperm, Welwitschia mirabilis
A virus from a symptomatic plant of the gymnosperm Welwitschia mirabilis Hook. growing as an ornamental plant in a domestic garden in Western Australia was inoculated to a plant of Nicotiana benthamiana where it established a systemic infection. The complete genome sequence of 9636 nucleotides was determined using high-throughput and Sanger sequencing technologies. The genome sequence shared greatest identity (83% nucleotides and 91% amino acids) with available partial sequences of catharanthus mosaic virus, indicating that the new isolate belonged to that taxon. Analysis of the phylogeny of the complete virus sequence placed it in a monotypic group in the genus Potyvirus. This is the first record of a virus from W. mirabilis, the first complete genome sequence of catharanthus mosaic virus determined, and the first record from Australia. This finding illustrates the risk to natural and managed systems posed by the international trade in live plants and propagules, which enables viruses to establish in new regions and infect new hosts
Strangeness Production and Ultrarelativistic Cascades
A two phase cascade, LUCIFER II, developed for the treatment of ultra high
energy ion-ion collisions is applied to the production of strangeness at SPS
energies . This simulation is able to simultaneously describe
both hard processes such as Drell-Yan and slower, soft processes such as the
production of light mesons, including strange mesons, by separating the
dynamics into two steps, a fast cascade involving only nucleons in the original
colliding relativistic ions followed, after an appropriate delay, by
multiscattering of the resulting excited baryons and mesons produced virtually
in the first step. No energy loss can take place in the short time interval
over which the first cascade takes place. The chief result is a reconciliation
of the important Drell-Yan measurements with the apparent success of standard
cascades to describe the nucleon stopping and meson production in heavy ion
experiments at the CERN SPS. A byproduct, obtained here in preliminary
calculations, is a description of strangeness production in the collision of
massive ions.Comment: 10 pages, 5 figure
Low-temperature critical current of Y1-xCaxBa2Cu3O7-delta thin films as a function of hole content and oxygen deficiency
The effects of hole content (p) and oxygen deficiency (delta) on the
zero-field critical current density, Jc0, were investigated for high-quality
c-axis oriented Y1-xCaxBa2Cu3O7-delta (x = 0, 0.05, 0.10, and 0.20) thin films.
Ca was used to introduce hole carriers in the CuO2 planes, independent of the
oxygen deficiency in the CuO1-delta chains. Low-temperature Jc0(16K) of these
films above the optimum doping were found to be high (> 10^7 Amp/cm^2) and were
primarily determined by the hole concentration, reaching a maximum at p ~
0.185+/-0.005, irrespective of oxygen deficiency. This implies that oxygen
disorder plays only a secondary role and the intrinsic Jc0 is mainly governed
by the carrier concentration and consequently by the superconducting
condensation energy which also peaks at p ~ 0.19 where the pseudogap
correlation vanishes
Deeply Christian and serving the common good? A survey of Anglican cathedral provision for schools
The Church of Englandâs vision for education is generous and seeks to allow the riches of Christian life to overflow throughout schools. The vision is captured by the strapline âDeeply Christian, serving the common goodâ. The present study assesses the contribution made to service this vision by the 43 Anglican cathedrals within England and the Isle of Man. Drawing on a careful analysis of information presented by the websites of these cathedrals, the study concluded that all 43 Anglican cathedrals dedicated considerable space on their websites to a regular programme of teaching and learning provision across the age range from early years foundation stage to sixth-form, relevant to a range of curriculum areas, and giving attention to pupilsâ personal development and well-being
Proton-proton bremsstrahlung below and above pion-threshold: the influence of the -isobar
The proton-proton bremsstrahlung is investigated within a coupled-channel
model with the degree of freedom. The model is consistent with the
scattering up to 1 GeV and the vertex determined in the
study of pion photoproduction reactions. It is found that the
excitation can significantly improve the agreements with the at MeV. Predictions at and MeV are
presented for future experimental tests.Comment: 26 pages Revtex, 12 figures are available from the authors upon
request ([email protected]
Thermal Stabilization of the HCP Phase in Titanium
We have used a tight-binding model that is fit to first-principles
electronic-structure calculations for titanium to calculate quasi-harmonic
phonons and the Gibbs free energy of the hexagonal close-packed (hcp) and omega
crystal structures. We show that the true zero-temperature ground-state is the
omega structure, although this has never been observed experimentally at normal
pressure, and that it is the entropy from the thermal population of phonon
states which stabilizes the hcp structure at room temperature. We present the
first completely theoretical prediction of the temperature- and
pressure-dependence of the hcp-omega phase transformation and show that it is
in good agreement with experiment. The quasi-harmonic approximation fails to
adequately treat the bcc phase because the zero-temperature phonons of this
structure are not all stable
Enhancing inclusivity and diversity among cathedral visitors: the Brecon Jazz Festival and psychographic segmentation
A series of previous studies concerned with the psychographic segmentation of visitors to six cathedrals across England and Wales, employing psychological type theory, reported highly similar results, suggesting that cathedrals had a well-defined, but somewhat restricted appeal. Several cathedrals are attempting to widen their appeal by engaging a variety of events or exhibitions. Taking one specific example, the Brecon Jazz Festival, the present study found that 196 visitors to Brecon Cathedral during this period differed significantly from the standard psychological type profile of cathedral visitors in two ways. There were significantly more intuitive types (41% compared with 28%) and significantly more perceiving types (27% compared with 20%). These findings demonstrate that specific events have the capacity to widen the psychographic appeal of cathedrals
Biogeochemical processes in the active layer and permafrost of a high Arctic fjord valley
Warming of ground is causing microbial decomposition of previously frozen sedimentary organic carbon in Arctic permafrost. However, the heterogeneity of the permafrost landscape and its hydrological processes result in different biogeochemical processes across relatively small scales, with implications for predicting the timing and magnitude of permafrost carbon emissions. The biogeochemical processes of iron- and sulfate-reduction produce carbon dioxide and suppress methanogenesis. Hence, in this study, the biogeochemical processes occurring in the active layer and permafrost of a high Arctic fjord valley in Svalbard are identified from the geochemical and stable isotope analysis of aqueous and particulate fractions in sediment cores collected from ice-wedge polygons with contrasting water content. In the drier polygons, only a small concentration of organic carbon (<5.40 dry weight%) has accumulated. Sediment cores from these drier polygons have aqueous and solid phase chemistries that imply sulfide oxidation coupled to carbonate and silicate dissolution, leading to high concentrations of aqueous iron and sulfate in the pore water profiles. These results are corroborated by ÎŽ34S and ÎŽ18O values of sulfate in active layer pore waters, which indicate the oxidative weathering of sedimentary pyrite utilising either oxygen or ferric iron as oxidising agents. Conversely, in the sediments of the consistently water-saturated polygons, which contain a high content of organic carbon (up to 45 dry weight%), the formation of pyrite and siderite occurred via the reduction of iron and sulfate. ÎŽ34S and ÎŽ18O values of sulfate in active layer pore waters from these water-saturated polygons display a strong positive correlation (R2 = 0.98), supporting the importance of sulfate reduction in removing sulfate from the pore water. The significant contrast in the dominant biogeochemical processes between the water-saturated and drier polygons indicates that small-scale hydrological variability between polygons induces large differences in the concentration of organic carbon and in the cycling of iron and sulfur, with ramifications for the decomposition pathway of organic carbon in permafrost environments
The (p,q) String Tension in a Warped Deformed Conifold
We find the tension spectrum of the bound states of p fundamental strings and
q D-strings at the bottom of a warped deformed conifold. We show that it can be
obtained from a D3-brane wrapping a 2-cycle that is stabilized by both electric
and magnetic fluxes. Because the F-strings are Z_M-charged with non-zero
binding energy, binding can take place even if (p,q) are not coprime.
Implications for cosmic strings are briefly discussed.Comment: 17 pages, 1 figur
Topological Features in Ion Trap Holonomic Computation
Topological features in quantum computing provide controllability and noise
error avoidance in the performance of logical gates. While such resilience is
favored in the manipulation of quantum systems, it is very hard to identify
topological features in nature. This paper proposes a scheme where holonomic
quantum gates have intrinsic topological features. An ion trap is employed
where the vibrational modes of the ions are coherently manipulated with lasers
in an adiabatic cyclic way producing geometrical holonomic gates. A crucial
ingredient of the manipulation procedures is squeezing of the vibrational
modes, which effectively suppresses exponentially any undesired fluctuations of
the laser amplitudes, thus making the gates resilient to control errors.Comment: 9 pages, 4 figures, REVTE
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