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Developmental changes in the germinability, desiccation tolerance, hardseededness, and longevity of individual seeds of Trifolium ambiguum
Background and Aims: Using two parental clones of outcrossing Trifolium ambiguum as a potential model system, we examined how during seed development the maternal parent, number of seeds per pod, seed position within the pod, and pod position within the inflorescence influenced individual seed fresh weight, dry weight, water content, germinability, desiccation tolerance, hardseededness, and subsequent longevity of individual seeds.
Methods: Near simultaneous, manual reciprocal crosses were carried out between clonal lines for two experiments. Infructescences were harvested at intervals during seed development. Each individual seed was weighed and then used to determine dry weight or one of the physiological behaviour traits.
Key Results: Whilst population mass maturity was reached at 33â36 days after pollination (DAP), seed-to-seed variation in maximum seed dry weight, when it was achieved, and when maturation drying commenced, was considerable. Individual seeds acquired germinability between 14 and 44 DAP, desiccation tolerance between 30 and 40 DAP, and the capability to become hardseeded between 30 and 47 DAP. The time for viability to fall to 50 % (p50) at 60 % relative humidity and 45 °C increased between 36 and 56 DAP, when the seed coats of most individuals had become dark orange, but declined thereafter. Individual seed f. wt at harvest did not correlate with air-dry storage survival period. Analysing survival data for cohorts of seeds reduced the standard deviation of the normal distribution of seed deaths in time, but no sub-population showed complete uniformity of survival period.
Conclusions: Variation in individual seed behaviours within a developing population is inherent and inevitable. In this outbreeder, there is significant variation in seed longevity which appears dependent on embryo genotype with little effect of maternal genotype or architectural factors
Robust ecological pattern formation induced by demographic noise
We demonstrate that demographic noise can induce persistent spatial pattern
formation and temporal oscillations in the Levin-Segel predator-prey model for
plankton-herbivore population dynamics. Although the model exhibits a Turing
instability in mean field theory, demographic noise greatly enlarges the region
of parameter space where pattern formation occurs. To distinguish between
patterns generated by fluctuations and those present at the mean field level in
real ecosystems, we calculate the power spectrum in the noise-driven case and
predict the presence of fat tails not present in the mean field case. These
results may account for the prevalence of large-scale ecological patterns,
beyond that expected from traditional non-stochastic approaches.Comment: Revised version. Supporting simulation at:
http://guava.physics.uiuc.edu/~tom/Netlogo
Spitzer and near-infrared observations of a new bi-polar protostellar outflow in the Rosette Molecular Cloud
We present and discuss \emph{Spitzer} and near-infrared H observations
of a new bi-polar protostellar outflow in the Rosette Molecular Cloud. The
outflow is seen in all four IRAC bands and partially as diffuse emission in the
MIPS 24 m band. An embedded MIPS 24 m source bisects the outflow and
appears to be the driving source. This source is coincident with a dark patch
seen in absorption in the 8 m IRAC image. \emph{Spitzer} IRAC color
analysis of the shocked emission was performed from which thermal and column
density maps of the outflow were constructed. Narrow-band near-infrared (NIR)
images of the flow reveal H emission features coincident with the high
temperature regions of the outflow. This outflow has now been given the
designation MHO 1321 due to the detection of NIR H features. We use these
data and maps to probe the physical conditions and structure of the flow.Comment: Accepted for publication in The Astrophysical Journa
Weave : Woven Fibre Images
Weave : Woven Fibre Images
Catalogue of exhibition held at the Fine Arts Gallery, University of Tasmania 12 March - 4 April , 1985
Works by Michael Butler, Bruce Carnie, Lise Cruickshank, Paul Harvey, Gabriel Rosati, Sue Rosentha
âEngage the Worldâ: examining conflicts of engagement in public museums
Public engagement has become a central theme in the mission statements of many cultural institutions, and in scholarly research into museums and heritage. Engagement has emerged as the go-to-it-word for generating, improving or repairing relations between museums and society at large. But engagement is frequently an unexamined term that might embed assumptions and ignore power relationships. This article describes and examines the implications of conflicting and misleading uses of âengagementâ in relation to institutional dealings with contested questions about culture and heritage. It considers the development of an exhibition on the Dead Sea Scrolls by the Royal Ontario Museum, Toronto in 2009 within the new institutional goal to âEngage the Worldâ. The chapter analyses the motivations, processes and decisions deployed by management and staff to âEngage the Worldâ, and the degree to which the museum was able to re-think its strategies of public engagement, especially in relation to subjects,issues and publics that were more controversial in nature
Gamma-Ray Burst 980329 and its X-Ray Afterglow
GRB 980329 is the brightest gamma-ray burst detected so far with the Wide
Field Cameras aboard BeppoSAX, both in gamma-rays and X-rays. With respect to
its fluence (2.6 X 10**-5 erg/s/cm**2 in 50 to 300 keV) it would be in the top
4% of gamma-ray bursts in the 4B catalog (Meegan et al. 1998). The
time-averaged burst spectrum from 2 to 20 and 70 to 650 keV can be well
described by the empirical model of Band et al. (1993). The resulting photon
index above the break energy is exceptionally hard at -1.32 +/- 0.03. An X-ray
afterglow was detected with the narrow-field instruments aboard BeppoSAX 7 h
after the event within the error box as determined with the Wide Field Cameras.
Its peak flux is (1.4 +/- 0.2) X 10**-12 erg/s/cm**2 (2 to 10 keV). The
afterglow decayed according to a power law function with an index of -1.35 +/-
0.03. GRB 980329 is characterized by being bright and hard, and lacking strong
spectral evolution.Comment: 13 pages with 3 figures. Accepted for publication in ApJ Let
Ab-initio calculation of Kerr spectra for semi-infinite systems including multiple reflections and optical interferences
Based on Luttinger's formulation the complex optical conductivity tensor is
calculated within the framework of the spin-polarized relativistic screened
Korringa-Kohn-Rostoker method for layered systems by means of a contour
integration technique. For polar geometry and normal incidence ab-initio Kerr
spectra of multilayer systems are then obtained by including via a 2x2 matrix
technique all multiple reflections between layers and optical interferences in
the layers. Applications to Co|Pt5 and Pt3|Co|Pt5 on the top of a semi-infinite
fcc-Pt(111) bulk substrate show good qualitative agreement with the
experimental spectra, but differ from those obtained by applying the commonly
used two-media approach.Comment: 32 pages (LaTeX), 5 figures (Encapsulated PostScript), submitted to
Phys. Rev.
Randomized Treatment of Patients with Typhoid Fever by Using Ceftriaxone or Chloramphenicol
Sixty-three patients with Salmonella typhi infections were randomly assigned to receive either ceftriaxone iv in single daily doses of 75 mg/kg for children and 3-4 g for adults for seven days or to receive 60 mg of chloramphenicol/kg a day orally or iv in four divided doses until defervescence and then 40 mg/kg a day to complete 14 d. In the ceftriaxone group, one death occurred, and two of seven patients still febrile 11 d after starting treatment were given chloramphenicol. In the chloramphenicol group, one death and one gastrointestinal perforation occurred. The probability of remaining febrile was similar for both groups during the first seven days but was significantly greater for patients receiving ceftriaxone during the 14-dperiod. Patients in the chloramphenicol group weremore likely to be bacteremic on day 3. These results suggest that a seven-day course of once-daily ceftriaxone shows promise as an alternative to 14 d of chloramphenicol for treating typhoid feve
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