3,826 research outputs found
Diffusional Relaxation in Random Sequential Deposition
The effect of diffusional relaxation on the random sequential deposition
process is studied in the limit of fast deposition. Expression for the coverage
as a function of time are analytically derived for both the short-time and
long-time regimes. These results are tested and compared with numerical
simulations.Comment: 9 pages + 2 figure
The effects of height and frequency of previous defoliation on nodulation, nitrogen fixation and regrowth of phasey bean
Inoculated seeds of phasey bean (Macroptilium lathyroides cv. Murray) were sown in a sand
culture in a naturally-lit glasshouse, and imgated daily with nitrogen-Free nutrient solution. At early
flowering, the plants were either left uncut or cut at node 5 (high) or node 1 (low), retaining the
corresponding residual leaf areas of 74, 11 and Ocm 2 plant 1respectively. Following this initial cutting,
new shoots were individually harvested at the frequency of one, two, three, four or eight times
over a penriod of 56 days in Phase 1. Total dry weight of new shoots, seed yields and nitrogen concentrations
in the herbage were assessed. A II plants were allowed to regrow during the next 21-day
recovery period in Phase 2. Then, the root systems and plant tops were harvested. Nodulation,nitrogen fixation (total N) and regression analyses on s011Je plant parameters were computed. In Phase
1, cumulative yields of new shoots harvested following high or low-level cutting declined significantly
with increasing harvesting frequency, but yield reductions due to low-level cutting were detected only
under high harvesting frequencies. In Phase 2, recovery growth was always better following high than
low-level cutting, but unexpectedly, the various harvesting frequencies had no effect on recovery
growth following high cutting. After low-level cutting, high or low harvesting frequency reduced
recovery growth compared with moderately frequent defoliation (two harvests in 56 days), which
coincided with early flowering on the new top growth. Recovery growth had a positive linear correlation
(r = 0.98 ***) with nitrogen fixation, which was also linearly correlated with nodulation. These
results are briefly discussed with reference to the current concept that regrowth of nodulated forage
legumes is largely dependent on symbiotic nitrogen fixation
Colonization of the developing rhizosphere of sugar beet seedlings by potential biocontrol agents applied as seed treatments
Aims: Poor colonization of the rhizosphere is a major constraint of seed treatment biological control. The objectives of this study were to; examine the colonization of the rhizosphere of sugar beet seedlings by selected rhizobacteria; determine the influence of the host rhizosphere and percolating water on the distribution of the bacteria; and deliver two biological control agents (BCAs) by co-inoculation. Methods and Results: Rifampicin-resistant bacterial strains (Rif(+)) applied as single treatments to seed sown in columns of field soil produced persistent populations of 5-9 log(10) cfu g(-1) in the infection court of the damping-off pathogen Aphanomyces cochlioides in a controlled environment. However, isolates varied in their ability to colonize the lower rhizosphere. Percolating water significantly increased the colonization of the upper rhizosphere. Bacterial populations in the soil profiles of "non-rhizosphere" controls declined markedly with time. There was no interaction between the two selected BCAs applied as a seed treatment mixture. Conclusions: The distribution of the bacteria resulted primarily from root colonization although percolating water may modify the colonization profiles. Co-inoculation of the sugar-beet rhizosphere is a viable proposition. Significance and Impact of Study: Potential BCAs were successfully delivered to the known infection court of A. cochloides and persisted for the infection period. This bioassay can be used as a tool for the selection of BCAs for field trials
A Wide-Field CCD Survey for Centaurs and Kuiper Belt Objects
A modified Baker-Nunn camera was used to conduct a wide-field survey of 1428
square degrees of sky near the ecliptic in search of bright Kuiper Belt objects
and Centaurs. This area is an order of magnitude larger than any previously
published CCD survey for Centaurs and Kuiper Belt Objects. No new objects
brighter than red magnitude m=18.8 and moving at a rate 1"/hr to 20"/hr were
discovered, although one previously discovered Centaur 1997 CU26 Chariklo was
serendipitously detected. The parameters of the survey were characterized using
both visual and automated techniques. From this survey the empirical projected
surface density of Centaurs was found to be SigmaCentaur(m<18.8)=7.8(+16.0
-6.6)x10^-4 per square degree and we found a projected surface density 3sigma
upper confidence limit for Kuiper Belt objects of SigmaKBO(m< 18.8)<4.1x10^-3
per square degree. We discuss the current state of the cumulative luminosity
functions of both Centaurs and Kuiper Belt objects. Through a Monte Carlo
simulation we show that the size distribution of Centaurs is consistent with a
q=4 differential power law, similar to the size distribution of the parent
Kuiper Belt Objects. The Centaur population is of order 10^7 (radius > 1 km)
assuming a geometric albedo of 0.04. About 100 Centaurs are larger than 50 km
in radius, of which only 4 are presently known. The current total mass of the
Centaurs is 10^-4 Earth Masses. No dust clouds were detected resulting from
Kuiper Belt object collisions, placing a 3sigma upper limit <600 collisionally
produced clouds of m<18.8 per year.Comment: 13 pages, 5 figures, Accepted for Publication in A
Adolescents care but don't feel responsible for farm animal welfare
Adolescents are the next generation of consumers with the potential to raise standards of farm animal welfare—to theirsatisfaction—if their preferences and concerns are translated into accurate market drivers and signals. There are no published data about adolescent views of farm animal welfare to allow meaningful design, implementation, and evaluation of educational strategies to improve consideration of—and behavior toward—farm animals. Knowledge of farm animal welfare, as well as beliefs and attitudes about farm animal welfare and behavioral intention relevant to it were determined in a sample of ukadolescents, using a survey incorporating an extended version of the theory of planned behavior and novel assessment tools. Our results indicate that adolescents have only a limited knowledge of welfare problems for farm animals and welfare-relevant product labels. Intentions to identify welfare standards for the animals from whom their food was derived were weak. Although they cared about farm animal welfare and agreed with fundamental principles—for example, the provision of space and the absence of pain and suffering—like adults they held limited belief in the power and responsibility that they possess through their choices as consumers; responsibility was often shifted to others, such as the government and farmers
Effects of Solution, Soil and Sand Cultures on Nodulation and Growth of Phasey Bean
Plants of phasey bean (Macroptilium lathyroides cv. Murray) were grown in nitrogen-free
nutrient solution, sod, or sand culture in a naturally-Nt glasshouse. Nodulation, dry matter accumulation in plant parts, and seed yields were assessed. Partitioning of symbiotic nitrogen into various
plant parts during vegetative and reproductive growth stages was also determined. In all culture
media, nodule number and size increased with plant age but the rate of increase was generally greater
in solution than in the other cultures. In sand culture, the dry weight per nodule and per plant, and
plant growth were significantly suppressed. Although tap root elongation was consistently better in
solution than soil or sand culture, leaf development and dry matter accumulation in roots and stems
were enhanced by solution culture only during flowering and fruiting stage. Seed yields were significantly
increased by solution culture, an effect apparently associated with increased symbiotic nitrogen
fixation. During vegetative growth, nitrogen accumulated largely in the leaves and stems but pods
were major sinks of nitrogen during the reproductive growth stage. The benefits and applications of
solution culture in the study of nodule development and collection of root samples for acetylene reduction
assays are discussed
Convex probability domain of generalized quantum measurements
Generalized quantum measurements with N distinct outcomes are used for
determining the density matrix, of order d, of an ensemble of quantum systems.
The resulting probabilities are represented by a point in an N-dimensional
space. It is shown that this point lies in a convex domain having at most d^2-1
dimensions.Comment: 7 pages LaTeX, one PostScript figure on separate pag
An Eccentric Hot Jupiter Orbiting the Subgiant HD 185269
We report the detection of a Jupiter-mass planet in a 6.838 day orbit around
the 1.28 solar mass subgiant HD 185269. The eccentricity of HD 185269b (e =
0.30) is unusually large compared to other planets within 0.1 AU of their
stars. Photometric observations demonstrate that the star is constant to
+/-0.0001 mag on the radial velocity period, strengthening our interpretation
of a planetary companion. This planet was detected as part of our radial
velocity survey of evolved stars located on the subgiant branch of the H-R
diagram--also known as the Hertzsprung Gap. These stars, which have masses
between 1.2 and 2.5 solar masses, play an important role in the investigation
of the frequency of extrasolar planets as a function of stellar mass.Comment: 18 pages, 4 figures, 3 tables, ApJ in press (scheduled for Dec 2006,
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