4,834 research outputs found
Contrast in chloride exclusion between two grapevine genotypes and its variation in their hybrid progeny
Potted grapevines of 140 Ruggeri (Vitis berlandieri Ă Vitis rupestris), a good Clâ excluder, and K 51-40 (Vitis champinii Ă Vitis riparia âGloireâ), a poor Clâ excluder, and of a family obtained by crossing the two genotypes, were used to examine the inheritance of Clâ exclusion. Rooted leaves were then used to further investigate the mechanism for Clâ exclusion in 140 Ruggeri. In both a potting mix trial (plants watered with 50 mM Clâ) and a solution culture trial (plants grown in 25 mM Clâ), the variation in Clâ accumulation was continuous, indicating multiple rather than single gene control for Clâ exclusion between hybrids within the family. Upper limits of 42% and 35% of the phenotypic variation in Clâ concentration could be attributed to heritable sources in the potting mix and solution culture trials, respectively. Chloride transport in roots of rooted leaves of both genotypes appeared to be via the symplastic pathway, since addition of 8-hydroxy-1,3,6-pyrenetrisulphonic acid (PTS), an apoplastic tracer, revealed no obvious PTS fluorescence in the laminae of either genotype, despite significant accumulation of Clâ in laminae of K 51-40 during the PTS uptake period. There was no significant difference in either unidirectional 36Clâ flux (10 min) or 36Clâ uptake (3 h) into roots of rooted leaves exposed to 5, 10, or 25 mM Clâ. However, the percentage of 36Clâ transported to the lamina (3 h) was significantly lower in 140 Ruggeri than in K 51-40, supporting reduced Clâ loading into xylem and implicating the root stele in the Clâ exclusion mechanism
The Socio-Economic Value of the Shark-Diving Industry in Fiji
Based on a survey of divers, dive operators, resort managers, estimates business revenues from shark diving and related expenditures by area; tax revenues; and economic benefit to local communities
Site percolation and random walks on d-dimensional Kagome lattices
The site percolation problem is studied on d-dimensional generalisations of
the Kagome' lattice. These lattices are isotropic and have the same
coordination number q as the hyper-cubic lattices in d dimensions, namely q=2d.
The site percolation thresholds are calculated numerically for d= 3, 4, 5, and
6. The scaling of these thresholds as a function of dimension d, or
alternatively q, is different than for hypercubic lattices: p_c ~ 2/q instead
of p_c ~ 1/(q-1). The latter is the Bethe approximation, which is usually
assumed to hold for all lattices in high dimensions. A series expansion is
calculated, in order to understand the different behaviour of the Kagome'
lattice. The return probability of a random walker on these lattices is also
shown to scale as 2/q. For bond percolation on d-dimensional diamond lattices
these results imply p_c ~ 1/(q-1).Comment: 11 pages, LaTeX, 8 figures (EPS format), submitted to J. Phys.
Variation for potassium and sodium accumulation in a family from a cross between grapevine rootstocks K 51-40 and 140 Ruggeri
The variation in potassium (K+) and sodium (Na+) accumulation was investigated between 60 hybrids within a family obtained by crossing grapevine rootstocks K 51-40 (Vitis champinii 'Dogridge' Ă V. riparia 'Gloire', seed parent) with 140 Ruggeri (V. cinerea var. helleri 'Resseguier #2' Ă V. rupestris'St. George', pollen parent), which are known to result in higher and lower concentrations of K+, respectively, but similar concentrations of Na+, in grape juice and resultant wine from scions grafted to them. The hybrids, their parents and two standard rootstocks, Ramsey (V. champinii 'Ramsey') and 1103 Paulsen (V. cinerea var. helleri 'Resseguier #2' x V. rupestris'St. George') were replicated by clonal propagation and grown under glasshouse conditions either in potting mix, drip-irrigated with a nutrient solution containing 50, 1.7 and 30 mM Cl-, K+ and Na+, respectively, or in aerated nutrient solution containing 25, 1.7 and 15 mM Cl-, K+ and Na+, respectively. In both pot and solution culture trials, there were significant (P < 0.001) differences between parents for mean K+ (but not Na+) concentrations, and between hybrids for mean K+ and Na+ concentrations in laminae. This variation between the hybrids was continuous, indicating multiple rather than single gene control for K+ and Na+ accumulation within the family. Differences among the hybrids for lamina K+ accumulation were not strongly associated with plant vigour. While the ranking of some hybrids for K+ and Na+ accumulation was consistent between the trials, others responded differently, suggesting the environment of the rootzone may affect the K+ and Na+ accumulation phenotype.
Soft Listeria: actin-based propulsion of liquid drops
We study the motion of oil drops propelled by actin polymerization in cell
extracts. Drops deform and acquire a pear-like shape under the action of the
elastic stresses exerted by the actin comet. We solve this free boundary
problem and calculate the drop shape taking into account the elasticity of the
actin gel and the variation of the polymerization velocity with normal stress.
The pressure balance on the liquid drop imposes a zero propulsive force if
gradients in surface tension or internal pressure are not taken into account.
Quantitative parameters of actin polymerization are obtained by fitting theory
to experiment.Comment: 5 pages, 4 figure
Planetary Science Goals for the Spitzer Warm Era
The overarching goal of planetary astronomy is to deduce how the present collection of objects found in our Solar System were formed from the original material present in the proto-solar nebula. As over two hundred exo-planetary systems are now known, and multitudes more are expected, the Solar System represents the closest and best system which we can study, and the only one in which we can clearly resolve individual bodies other than planets. In this White Paper we demonstrate how to use Spitzer Space Telescope InfraRed Array Camera Channels 1 and 2 (3.6 and 4.5 ”m) imaging photometry with large dedicated surveys to advance our knowledge of Solar System formation and evolution. There are a number of vital, key projects to be pursued using dedicated large programs that have not been pursued during the five years of Spitzer cold operations. We present a number of the largest and most important projects here; more will certainly be proposed once the warm era has begun, including important observations of newly discovered objects
Complex-Temperature Singularities in the Ising Model. III. Honeycomb Lattice
We study complex-temperature properties of the uniform and staggered
susceptibilities and of the Ising model on the honeycomb
lattice. From an analysis of low-temperature series expansions, we find
evidence that and both have divergent singularities at the
point (where ), with exponents
. The critical amplitudes at this
singularity are calculated. Using exact results, we extract the behaviour of
the magnetisation and specific heat at complex-temperature
singularities. We find that, in addition to its zero at the physical critical
point, diverges at with exponent , vanishes
continuously at with exponent , and vanishes
discontinuously elsewhere along the boundary of the complex-temperature
ferromagnetic phase. diverges at with exponent
and at (where ) with exponent , and
diverges logarithmically at . We find that the exponent relation
is violated at ; the right-hand side is 4
rather than 2. The connections of these results with complex-temperature
properties of the Ising model on the triangular lattice are discussed.Comment: 22 pages, latex, figures appended after the end of the text as a
compressed, uuencoded postscript fil
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