bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of grazing Lotus corniculatus during late summer - autumn on reproductive efficiency and wool production in ewes
Authors: Luque A. , Barry T. N. , McNabb W. C. , Kemp P. D. , McDonald M. F.
Published: September 2002

A grazing experiment was conducted at Massey University (Palmerston North, New
Zealand) over 80 days in the late summer–autumn of 1998 (9
February–29 April). Reproductive performance and wool growth of ewes
grazing on Lotus corniculatus (birdsfoot trefoil) were
compared with those of ewes grazing perennial ryegrass–white clover
pasture. A rotational grazing system with 210 mixed-age dry ewes (59.80.9
kg/ewe) was used, with 80 ewes grazing pasture [1 g of condensed
tannin (CT) per kg dry matter (DM)] and 130 ewes grazing
L. corniculatus (24 g CT/kg DM). Half of the ewes
grazing L. corniculatus were supplemented orally, twice
daily, with polyethylene glycol (PEG; MW, 3500) to inactivate the CTs.
The effect of forage species and PEG supplementation on voluntary feed intake
(VFI), reproductive performance (as measured by ovulation rate), and wool
production was measured during 4 synchronised oestrous cycles. The ewes were
restricted to maintenance feeding during the first 10 days of each oestrous
cycle and then increased to ad libitum for the 6 days
leading up to and including ovulation. In vitro organic
matter digestibility in the selected diet was higher for lotus than for
pasture (0.80 v. 0.76), with L. corniculatus containing
less nitrogen than pasture (36.5 v. 40.8 g/kg organic matter).
Ewes grazing on L. corniculatus produced 11% more
wool and had an ovulation rate up to 14% higher than ewes grazing
pasture, with neither parameter being affected by PEG supplementation. Higher
mean ovulation rates of ewes grazing L. corniculatus
were due to increases in fecundity (multiple ovulations/ovulating ewe; P
< 0.05), with no effect on ewes cycling/ewes mated. Three cycles of
grazing on L. corniculatus were required to achieve the
maximum response in multiple ovulation, but most of this was achieved after 2
cycles. As the VFI of ewes grazing on L. corniculatus
was not greater than that of ewes grazing pasture, the greater wool production
and higher ovulation rate of ewes grazing this forage was due to improved
efficiency of feed utilisation. It was concluded that feeding ewes
L. corniculatus increased the efficiency of both
reproduction and wool production without increasing VFI.
In vitro microbial digestion of straw cell wall polysaccharides in response to supplementation with different sources of carbohydrates
Authors: Urdaneta A. Barrios , Fondevila M. , Balcells J. , Dapoza C. , Castrillo C.
Published: September 2002

The effect of carbohydrate supplementation on microbial fibre digestion was
studied in vitro, by measuring the disappearance of cell
wall monosaccharides, bacterial adhesion (mmol purine bases per g residue),
and total (per g residue) and bacterial (per mmol purine bases)
polysaccharidase activity. Straw cell walls (CW, 0.5% w/v) were
cultured in medium supplemented with (0.275% w/v) or without
starch, a sugar mixture, or pectin. Supplementation with these constituents
did not cause a drop in pH below 6.1, and increased all parameters
investigated with the exception of bacterial polysaccharidase activity, which
was higher for CW cultures, suggesting a higher proportion of fibrolytic
bacteria in the adherent population. By comparison with starch and sugar,
pectin supplementation resulted in a lower proportion of residual sugars
remaining from cell walls after 60 and 72 h (P < 0.05), which resulted in
greater bacterial adhesion after 8 and 12 h (P < 0.05) and higher total
cellulase activity after 8 h (P < 0.01). This was perhaps because pectin
may cover particle surfaces, protecting the digestive area from external
factors, or may act as a substrate for cellulolytic bacteria. The lack of
differences in bacterial enzymatic activities suggests the absence of
qualitative or quantitative differences in the adherent fibrolytic population.
The incidence of barley scald in cultivar mixtures
Authors: Abbott D. C. , Burdon J. J. , Brown A. H. D. , Read B. J. , Bittisnich D.
Published: September 2002

A field trial incorporating resistant and susceptible plants in mixed plots,
where the proportion of resistant plants was 0%, 50%, or
100%, indicated that cultivar mixtures were not particularly effective
for the control of barley scald disease. Combining 2 scald resistance genes
into a single line was more effective in controlling disease than deploying
the same genes singly in different lines in a mixture. The lack of benefit
from mixtures in this experiment differed from the findings of 2 previous
studies investigating scald resistance in mixtures. Although the study
included only one growing season and one location, the findings suggest that
the use of mixtures for controlling this disease may carry some risk and that
breeding for a resistance pyramid is likely to be more widely effective.
Water stress and redlegged earth mites affect the early growth of seedlings in a subterranean clover/capeweed pasture community
Authors: Chapman R. , Ridsdill-Smith T. J. , Turner N. C.
Published: September 2002

The impact of water stress and infestations of redlegged earth mite
[Halotydeus destructor Tucker (Acarina :
Penthaleidae)] on the early growth and botanical composition of a mixed
subterranean clover (Trifolium subterraneum L.) and
capeweed (Arctotheca calendula Levyns) pasture was
investigated in a controlled environment experiment. Water stress and
redlegged earth mite infestations both significantly reduced herbage
production from both species. The yield of the subterranean clover was
suppressed less by water stress than that of the capeweed. The differing
sensitivities of the two species to water stress were attributed to
differences in seedling size and growth rates at the onset of the drought.
Redlegged earth mites caused greater feeding damage on cotyledons of the
subterranean clover than of the capeweed. Despite this, the mites had a
greater deleterious impact on the growth of the capeweed, which was suppressed
both in the presence and absence of water stress. Redlegged earth mites in the
presence of water stress did not significantly affect the growth of the
subterranean clover. Furthermore, in the absence of water stress, the growth
of the subterranean clover was greater when mites were present than when
absent. The greater sensitivity of the capeweed to the effects of feeding by
the redlegged earth mites was attributed to the smaller size of its seedlings
at the time the redlegged earth mites were introduced. The increase in growth
of the subterranean clover following the introduction of redlegged earth mites
is more likely due to a change in the competitive relationships between the
two plant species than to any direct effect of the mites’ feeding.
Our observations indicate that the presence of water stress and redlegged
earth mites significantly affects the competitive interactions between
seedlings of subterranean clover and capeweed.
Yellow lupin (Lupinus luteus) tolerates waterlogging better than narrow-leafed lupin (L. angustifolius) IV. Root genotype is more important than shoot genotype
Authors: Davies C. L. , Turner D. W. , Munns R. , Dracup M.
Published: September 2002

To understand how yellow lupin tolerates waterlogging better than
narrow-leafed lupin, we investigated the roles of the roots and the shoots of
these species. Reciprocal- and self-grafted combinations (scion =
shoot/rootstock) of yellow and narrow-leafed lupin were made at the 2-leaf
stage and waterlogged 45 days later (8–10 leaf stage). Responses to
waterlogging were examined at the end of waterlogging and following a recovery
period of 14 days.Waterlogging of reciprocal and self-grafted plants reduced
total plant dry weight by 15–58% compared with non-waterlogged
controls. These reductions were greater when the rootstock was narrow-leafed
rather than yellow lupin, and were similar for the roots and shoots.
Waterlogging increased dry weight of hypocotyl roots in most grafting
combinations (by 2–19-fold), but grafts with narrow-leafed lupin scions
produced almost twice the hypocotyl root length of grafts with yellow lupin
scions. During the waterlogging period, leaf gas exchange decreased by
16–74% in all grafting combinations except in narrow-leafed lupin
scion/yellow lupin rootstock where it increased by 17–30%.
During waterlogging, stem water potential decreased and leaf osmotic pressure
increased. These changes compensated one another and consequently there was no
effect on bulk leaf turgor. After 14 days recovery, water relations returned
to initial values.
Tolerance of the whole plant to waterlogging was influenced more by the root
genotype than the shoot genotype. However, production of hypocotyl roots in
response to waterlogging was related to the shoot genotype rather than the
root genotype.
Genetic parameters and predicted response to selection for lean growth in an Australian commercial nucleus pig herd
Authors: Nguyen Nguyen Hong , McPhee Cam P. , Wade Claire M. , Luxford Brian G.
Published: September 2002

Genetic parameters for performance traits in a pig population were estimated
using a multi-trait derivative-free REML algorithm. The 2590 total data
included 922 restrictively fed male and 1668 ad libitum
fed female records. Estimates of heritability (standard error in parentheses)
were 0.25 (0.03), 0.15 (0.03), and 0.30 (0.05) for lifetime daily gain, test
daily gain, and P2-fat depth in males, respectively; and 0.27 (0.04) and 0.38
(0.05) for average daily gain and P2-fat depth in females, respectively. The
genetic correlation between P2-fat depth and test daily gain in males was
–0.17 (0.06) and between P2-fat and lifetime average daily gain in
females 0.44 (0.09). Genetic correlations between sexes were 0.71 (0.11) for
average daily gain and –0.30 (0.10) for P2-fat depth. Genetic response
per standard deviation of selection on an index combining all traits was
predicted at $AU120 per sow per year. Responses in daily gain and
backfat were expected to be higher when using only male selection than when
using only female selection. Selection for growth rate in males will improve
growth rate and carcass leanness simultaneously.
Protein metabolism in skin and muscle of sheep selected for or against staple strength
Authors: Adams N. R. , Liu S. M. , Briegel J. R. , Greeff J. C.
Published: September 2002

Two experiments were carried out to determine the mechanisms underlying the
reduced effect of nutritional status on wool growth rate in Merino sheep that
have been selected for high staple strength (SS). In Expt 1, each group of 6
young sheep of SS+ and SS– genotypes were fed at 0.4 or 1.1 times
maintenance, and in Expt 2, groups of 8 sheep of each genotype were fed at 1.1
and 1.8 times maintenance. In both experiments, rates of protein synthesis in
skin, muscle, gut, rumen, and liver were determined using a flooding dose of
labelled phenylalanine. Feed intake and the digestibility of feed were not
affected by genotype. Neither dissection of the carcasses at slaughter, nor
deuterated water analysis in Expt 1, detected any differences between the
genotypes in body composition. The feeding level affected the total daily
amount of protein synthesised in all the organs examined, and the fractional
rate of protein synthesis was affected by feeding level in all organs except
the liver. The fractional synthesis rate of protein was less responsive to
feeding level in the SS+ sheep in both skin and muscle
(P < 0.05), but not in the liver, jejunum, or rumen.
Total protein synthesis in muscle, and the estimated rate of protein
degradation, were also less responsive to feeding level in the SS+ sheep
(P < 0.05). We conclude that sheep genetically
selected for high or low SS have altered local mechanisms in both skin and
muscle that control the way they respond to nutrition. These findings provide
a mechanism by which selection for wool growth rate also affects body
metabolism.
Virus incidence in Australian hop (Humulus lupulus L.) gardens and cultivar differences in susceptibility to infection
Authors: Pethybridge S. J. , Wilson C. R. , Sherriff L. J. , Leggett G. W. , Munro D.
Published: September 2002

0uo;Victoria’ (98%) was significantlyhigher than in ‘T11’ (58%), which was higher than‘Opal’ (31%). Results suggested that ‘Victoria’was more susceptible to infection by all 3 viruses than traditionally growncultivars and recently released or experimental cultivars. Planting with elitematerial and roguing of infected plants has been ineffective as a viruscontrol strategy with this cultivar.
Dietary lysine requirements of heavy and light pigs weaned at 14 days of age
Authors: Dunshea F. R. , Kerton D. K. , Cranwell P. D. , Campbell R. G. , Mullan B. P. , King R. H. , Pluske J. R.
Published: September 2002

Seventy 14-day-old male pigs that were either heavy (6.0 kg) or light (3.6 kg)
for age were weaned into individual pens and fed 1 of 7 diets containing
9.2–21.0 g lysine/kg feed in a study designed to determine the
effect of dietary lysine and weight on lysine requirements of pigs. Five pigs
from each weight group were used to determine initial body composition. When
pigs reached 10 kg they were slaughtered and empty body composition was
analysed to determine protein tissue accretion rates. Protein deposition rate
was not affected by weight at weaning but increased with dietary lysine
content before reaching a plateau. The relationship between protein deposition
(PD, g/day) and dietary lysine (L, g/kg) was described by 3 models.
The rectilinear model, which had a linear ascending phase (PD = 4.84
+ 1.948L, R2 = 0.935,
P = 0.002) and a horizontal component
representing maximum protein deposition rate of 32.3 g/day, revealed that
maximum protein deposition occurred at 14.1 g lysine/kg. The quadratic
function (PD = – 2.74 + 3.74L –
0.099L2 , R2
= 0.916, P = 0.003) provided an estimate
of the lysine requirement of 14.9 g lysine/kg occurring at a point where
PD reached 95% of the maximum protein deposition rate (32.5 g/day).
Use of an asymptotic model (PD = 32.60 – 186 0.727L,
R2 = 0.919,
P = 0.003) provided an estimate of 14.9 g
lysine/kg occurring at a point where PD reached 95% of the maximum
protein deposition rate (32.6 g/day). These data indicate that early
weaned pigs should be fed a highly digestible diet containing 14–15 g
lysine/kg to maximise protein deposition.
Water use by lucerne and effect on crops in the Victorian Wimmera
Authors: McCallum M. H. , Connor D. J. , O'Leary G. J.
Published: September 2002

The effect of the perennial legume lucerne on the soil water regime of a
farming system in the Victorian Wimmera was investigated by a combination of
direct field measurements and the use of simulation modelling. In the field,
soil profiles under lucerne-based pastures (also containing annual medic and
Wimmera ryegrass) remained consistently drier throughout the year compared
with continuous annual cropping. The amount of plant-available soil water
(0–2.0 m) after 3–4 years of lucerne pasture was on average 48 mm
less than after annual crops (wheat, field pea), most of which (81%)
was extracted at depth (1.0–2.0 m). A wheat simulation study evaluated
yield responses post-lucerne under a range of environmental conditions likely
to be experienced within the region. It was predicted that the yield penalty
for the first wheat crop after lucerne would vary from 0 to 0.87 t/ha,
depending upon seasonal conditions. Overall, the analysis predicted a median
yield penalty of 0.4 t/ha (15%) for wheat after lucerne. The risk
of a large yield penalty (>0.8 t/ha) was low (5 years in 100). In the
simulation, the risk of yield loss decreased during a cropping phase with each
year after lucerne as the soil profile progressively became recharged with
water. The time taken to recharge the soil prof ile fully after lucerne to
levels equivalent to that under continuous cropping was not resolved in the
field, but simulation studies suggested that it would be within 5 years.
Lucerne in crop rotations on the Riverine Plains. 1. The soil water balance
Authors: Ridley A. M. , Christy B. , Dunin F. X. , Haines P. J. , Wilson K. F. , Ellington A.
Published: September 2002

Dryland salinity, caused largely by insufficient water use of annual crops and
pastures, is increasing in southern Australia. A field experiment in
north-eastern Victoria (average annual rainfall 600 mm) assessed the potential
for lucerne grown in rotation with crops to reduce the losses of deep drainage
compared with annual crops and pasture. Soil under lucerne could store 228 mm
of water to 1.8 m depth. This compared with 84 mm under continuous crop (to
1.8 m depth), except in 1997–98 where crop dried soil by 162 mm. Between
1.8 and 3.25 m depth lucerne was able to create a soil water deficit of 78 mm.
The extra water storage capacity was due to both the increased rooting depth
and increased drying abiliy of lucerne within the root-zone of the annual
species.
Large drainage losses occurred under annuals in 1996 and small losses were
calculated in 1997 and 1999, with no loss in 1998. Averaged over
1996–1999, drainage under annual crops was 49 mm/year (maximum 143
mm) and under annual pastures 35 mm/year (maximum 108 mm). When the extra
soil water storage under lucerne was accounted for, no drainage was measured
under this treatment in any year. Following 2 years of lucerne, drainage under
subsequent crops could occur in the second crop. However, with 3 or 4 years of
lucerne, 3–4 crops were grown before drainage loss was likely. Our
calculations suggest that in this environment drainage losses are likely to
occur under annual species in 55% of years compared with 6% of
years under lucerne. In wet years water use of lucerne was higher than for
crops due to lucerne’s ability to use summer rainfall and dry soil over
the summer–autumn period. During the autumn–winter period crop
water use was generally higher than under lucerne.
The major period of increased soil water extraction under lucerne was from
late spring to midsummer, with additional drying from deeper layers until
autumn. Under both lucerne and crops, soil dried progressively from upper to
lower soil layers. Short rotations of crops and lucerne currently offer the
most practical promise for farmers in cropping areas in southern Australia to
restore the water balance to a level which reduces the risk of secondary
salinity.
First Results from the Combination of the AAO/UKST and Marseille Hα Surveys
Authors: Russeil D. , Parker Q. A.
Published: September 2002

We have combined the observational data of the AAO/UKST and Marseille Hα surveys to extract preliminary new results about ionised structures of our Galaxy. This includes the detection of a new large bubble located in
the far part of the Carina arm.
Base Band Data for Testing Interference Mitigation Algorithms
Authors: Bell Jon F. , Hall Peter J. , Wilson Warwick E. , Sault Robert J. , Smegal Rick J. , Smith Malcolm R. , van Straten Willem , Kesteven Michael J. , Ferris Richard H. , Briggs Frank H. , Carrad Graham J. , Sinclair Malcom W. , Gough Russell G. , Sarkissian John M. , Bunton John D. , Bailes Matthew
Published: September 2002

Digital signal processing is one of many valuable tools for suppressing unwanted signals or inter-ference. Building hardware processing engines seems to be the way to best implement some classes of interference suppression but is, unfortunately, expensive and time-consuming, especially if several miti-gation techniques need to be compared. Simulations can be useful, but are not a substitute for real data. CSIRO’s Australia Telescope National Facility has recently commenced a ‘software radio telescope’ project designed to fill the gap between dedicated hardware processors and pure simulation. In this approach, real telescope data are recorded coherently, then processed offline. This paper summarises the current contents of a freely available database of base band recorded data that can be used to experiment with signal processing solutions. It includes data from the following systems: single dish, multi-feed receiver; single dish with reference antenna; and an array of six 22 m antennas with and without a reference antenna. Astronomical sources such as OH masers, pulsars and continuum sources subject to interfering signals were recorded. The interfering signals include signals from the US Global Positioning System (GPS) and its Russian equivalent (GLONASS), television, microwave links, a low-Earth-orbit satellite, various other transmitters, and signals leaking from local telescope systems with fast clocks. The data are available on compact disk, allowing use in general purpose computers or as input to laboratory hardware prototypes.
Shock Geometry and Inverse Compton Emission from the Wind of a Binary Pulsar
Authors: Ball Lewis , Dodd Jennifer
Published: September 2002

PSR B1259 – 63 is a 47 ms radio pulsar with a high spin-down luminosity which is in a close, highly eccentric 3·5 yr orbit about a bright stellar companion. The binary system may be a detectable source of hard ã γ-rays produced by inverse Compton scattering of photons from the B2e star SS2883 by electrons and positrons in the pulsar wind. The star provides an enormous density of optical photons in the vicinity of the pulsar, particularly at epochs near periastron. We calculate the emission from the unshocked region of the pulsar wind, assuming that it terminates at a shock where it attains pressure balance with the companion’s wind. The spectra and light curves for the inverse Compton emission from the shock-terminated wind are compared with those for an unterminated wind. If the pulsar’s wind is weaker than that from the companion star, the termination of the wind decreases the inverse Compton flux, particularly near periastron. The termination shock geometry has the effect of decreasing the asymmetry of the γ-ray light curve around periastron, which arises because of the asymmetrical variation of the scattering angle.
Source Size Measurement from Observed Quasar Microlensing
Authors: Yonehara Atsunori
Published: September 2002

Recently, the OGLE team have reported a clear quasar microlensing signal in Q2237+0305. I have analyzed the microlens event of ‘image C’ by using their finely and densely sampled light curves. From light curve fitting, I unambiguously set the source size of ≤0.98 Einstein-Ring radius as a conservative limit. This limit corresponds to 2000 AU, if I adopt Mlens ~ 0.1M obtained by a recent statistical study of the mean mass of the lens object. This gives clear evidence for the existence of an accretion disk in the central region of the quasar.
The Active Algol Binary KZ Pavonis
Authors: Budding E. , Marsden S. C. , Slee O. B.
Published: September 2002

The Algol type eclipsing binary KZ Pav has been observed over one complete orbit (0.95 days) with theAustraliaTelescope CompactArray. Contemporaneous optical photometric data from the University of Southern Queensland’s Observatory at Mount Kent were also collected and have been included in this multi-wavelength study.

Preliminary indications are that the low levels of emission observed share similarities to those of some RS CVn binaries. The optical data show phase-linked effects which can be related to the mass transfer process of Algols. The possibility that the radio emission may be related to this process is considered.
The Effect of Nonaxisymmetric Radiative Drag on Relativistic Jets in Active Galactic Nuclei
Authors: Luo Qinghuan
Published: September 2002

The effect of nonaxisymmetric radiation drag on relativistic jets in active galactic nuclei (AGN) is discussed. The radiation force due to inverse Compton scattering of photon fields from a noncircular accretion disk is calculated. It is shown that such nonaxisymmetric drag can cause jet path distortion within the subparsec region of the black hole. This subparsec scale distortion is potentially observable with the current VLBI, VLBA techniques. Any modulation of the axially asymmetric distribution of disk emission can result in variability in electromagnetic radiation from the jet.
FLAIR II Spectroscopy of Two DENIS J Band Galaxy Samples
Authors: Mamon Gary A. , Parker Quentin A. , Proust Dominique
Published: September 2002

As a pilot survey for the forthcoming 6dF Galaxy Redshift Survey, spectroscopy of galaxies selected in the 1.2 micron J waveband with the DENIS imaging survey was performed at the UKST using the FLAIR II multi-object spectroscope. Sixty-nine galaxy redshifts were obtained in a high galactic latitude field and an additional 12 redshifts in a low galactic latitude (b = 17˚), obscured field. This spectroscopic followup of NIR selected galaxies illustrates the feasibility of obtaining redshifts with optical spectra on galaxies selected at much longer wavelengths. It validated a very preliminary algorithm for star/galaxy separation for high galactic latitude DENIS objects, with 99% reliability for J <13.9. The FLAIR II redshifts are in excellent agreement with those, previously published, of 20 common galaxies. However, the FLAIR II redshift determinations presented here required substantially longer integration times to achieve 90% completeness than expected from previous optical surveys at comparable depth. This is mainly due to a degradation in overall fibre throughput due to known problems with ageing of the prism–cement–fibre interface with exposure to UV light. In comparison to our high galactic latitude field, our low latitude (high extinction) field required 2.5 times more exposure time for less than 50% of successful redshift measurements.

Among the J ≤ 13.9 galaxies with measured redshifts, only 376% display emission lines, in comparison with 60% of emission line galaxies in optical samples of comparable depth. These galaxies are, on average, half a magnitude bluer in B-J than galaxies of the same luminosity without emission lines. We confirm a previous optically-based result that the fraction of galaxies with emission lines increases rapidly with decreasing galaxy luminosity. The J band luminosity function is estimated. Our high latitude field displays a concentration of galaxies at cz ≲ 38 000 km s−1 suggesting a possible supercluster.A radial velocity is reported for a galaxy lying near the projected centre of the Abell 1434 cluster of galaxies, for which no cluster redshift is currently available.
Shock Drift Acceleration of Electrons
Authors: Ball Lewis , Melrose D. B.
Published: September 2002

We review the theory of shock drift acceleration, developing the theory in detail for gyrophaseaveraged particles. It is shown howboth the upstream and downstream velocity spaces separate into different regions according to the interaction of the particles with the shock (reflection, transmission, head-on, overtaking). The effects of the cross-shock electric field and of the magnetic overshoot are discussed. The effectiveness of acceleration is estimated for Maxwellian and power law distributions. The condition for a beam instability to be generated by reflected particles is determined and found to be independent of the distribution function for isotropic inflowing electrons.
Nonlinear Alfvén Waves in Weakly Ionised Dusty Plasmas
Authors: Cramer N. F. , Sakai J. I. , Vladimirov S. V.
Published: September 2002

The effects of charged dust on the steepening of the fields in nonlinear Alfvén waves in astrophysical weakly ionised plasmas are investigated. It is found that the formation of current singularities in the wave due to nonlinear ambipolar diffusion is strongly modified by the effects of the dust. The basic modes for propagation along the magnetic field in a dusty plasma are highly dispersive and split by the anisotropy of the magnetic field into two modes that are oppositely circularly polarised rather than linearly polarised. The right hand circularly polarised wave experiences a cutoff due to the presence of the dust. We derive nonlinear fluid equations describing the dusty plasma, and make approximations for strong coupling of the dust to the neutrals, and for stationary dust. Numerical solution of the equations shows that a nonlinear wave with sharp current features due to ambipolar diffusion involves a rotation of the wave magnetic field about the direction of propagation, and an oscillation of the field components, due to the mode splitting effects of the dust. This is in contrast to the dust-free case, where the sharp reversal of the transverse magnetic field component occurs in a single plane.
Big Bang Nucleosynthesis, Population III, and Stellar Genetics in the Galactic Halo
Authors: Ryan Sean G.
Published: September 2002

The diverse isotopic and elemental signatures produced in different nucleosynthetic sites are passed on to successive generations of stars. By tracing these chemical signatures back through the stellar populations of the Galaxy, it is possible to unravel its nucleosynthetic history and even to study stars which are now extinct. This review considers recent applications of ‘stellar genetics’ to examine the earliest episodes of nucleosynthesis in the universe, in Population iii stars and the Big Bang.
Very High Energy γ-rays from AGN
Authors: Kifune Tadashi
Published: September 2002

Evidence of TeV γ-ray emission has been found for only a handful of active galactic nuclei, with detailed investigations limited to the blazars Mrk 421 and Mrk 501. TeV γ-ray astronomy, as the highest energy band, provides important information that is hard to obtain from longer wavelength electromagnetic radiation. The current status of TeV γ-ray studies of active galactic nuclei is summarized and our understanding of the high energy phenomena taking place in active galactic nuclei is outlined, with the prospects for future TeV γ-ray observations also considered.
Coherent Emission in AGN: A Critique
Authors: Melrose D. B.
Published: September 2002

The inverse Compton (IC) limit, TB1012 K, on synchrotron sources places a severe limit on models for intraday variables. The conventional limit is relaxed for proton synchrotron emission, or when acceleration balances IC losses. Coherent emission avoids the limit entirely but introduces other difficulties that have been inadequately discussed.
Spectral Variability of BL Lac Objects
Authors: D'Amicis R. , Nesci R. , Massaro E. , Maesano M. , Montagni F. , D'Alessio F.
Published: September 2002

We present the relation between optical luminosity and spectral slope for eight BL Lac objects (3C66A, PKS 0422+00, S5 0716+71, OJ 287, ON 231, OQ 530, S5 1803+78 and BL Lacertae), derived from B, V, R, and I observations spanning a time interval of about 5 years. Four objects show a marked correlation between spectral slope and luminosity, being bluer when brighter, while for the other four the correlation is weaker or absent. Possible explanations are briefly discussed in the framework of current models of the BL Lac phenomenon.
Microquasars: A Galactic-Extragalactic Connection?
Authors: Wu Kinwah , Stevens Jason A. , Hannikainen Diana C.
Published: September 2002

Microquasars are Galactic X-ray binaries which show radio emission from relativistic outflows. Here we argue that the origins of radio emission from microquasars and compact extragalactic radio sources are similar. In particular, both can be explained qualitatively by a model in which shocks are propagating in the relativistic jets. The microquasar GRO J1655–40 is used to illustrate that the spectral evolution of its 1994 radio outburst can be explained by the growth phase of the generalised-shock model, similar to the case of the quasar 3C 273.
Pollination of Banksia spp. by non-flying mammals in north-eastern New South Wales
Authors: Hackett Damian J. , Goldingay Ross L.
Published: September 2002

Despite the accumulating evidence that non-flying mammals are effective
pollinators, further research is required to clarify how widespread this
phenomenon is. The role of non-flying mammals as pollinators of four species
of Banksia was investigated in north-eastern New South
Wales. Nine species of non-flying mammals were captured amongst flowering
Banksia and all carried variable amounts of
Banksia pollen on their fur or in their faeces. Although
not captured, feathertail gliders (Acrobates pygmaeus)
were observed foraging at Banksia inflorescences.
Squirrel gliders (Petaurus norfolcensis) visiting
B. integrifoliaand pale field-rats
(Rattus tunneyi) visiting
B. ericifolia, carried substantial loads of pollen. Fur
pollen loads for these species were of a magnitude similar to those of
nectarivorous birds that were sampled closer to the time of foraging.
Assessment of newly opened flowers indicated that considerable amounts of
pollen were removed at night. The results of a pollinator exclusion experiment
were inconclusive but B. ericifolia inflorescences
exposed to nocturnal pollinators had consistently high fruit-set. This study
lends additional support to the notion that pollination of
Banksia by non-flying mammals is widespread.
Germination of dimorphic seeds of Suaeda moquinii under high salinity stress
Authors: Khan M. Ajmal , Gul Bilquees , Weber Darrell J.
Published: September 2002

Suaeda moquinii (Torrey) Greene (desert blite), a
succulent shrub in the family Chenopodiaceae, is widely distributed in salt
marshes of the western United States. Suaeda moquinii
produces dimorphic seeds (soft brown and hard black). Both types of seeds were
collected from a salt marsh in Faust, Utah. Experiments were conducted to
determine the seed germination responses of the black and brown seeds to
salinity and temperature. Brown seeds were found to be one of the most salt
tolerant at the germination stage when compared to other halophytes. Brown
seeds germinated (30%) at 1000 mM NaCl, but only a few black seeds
germinated (8%) at 600 mM NaCl. Seed germination occurred in most
saline treatments at the lowest thermoperiod (5–15˚C) tested. In
some salinity treatments (600, 800, 1000 mM), further increases in temperature
resulted in progressively decreased seed germination. Brown seeds germinated
better and had a higher germination rate (germination velocity) than black
seeds at all thermoperiods. The highest rate of germination of black seeds
occurred at the lowest thermoperiod (5–15˚C). Recovery of
germination for black seeds when transferred to distilled water after being in
various salinity treatments for 20 days was nearly complete
(82–100%) at the lowest thermoperiod (5–15˚C) but
decreased with increase in the temperature. Brown seeds recovered
substantially (59–97%) from salinity at all thermoperiods.
Regression analyses indicated significant differences between the germination
recovery of the black and brown seeds.
Where and why have all the flowers gone? Depletion and turnover in the New Zealand Cenozoic angiosperm flora in relation to palaeogeography and climate
Authors: Lee Daphne E. , Lee William G. , Mortimer Nick
Published: September 2002

The modern New Zealand angiosperm flora has many notable characteristics, such
as a predominance of evergreen, perennial life forms, few nitrogen-fixing
species, despecialised floral features and asymmetric genus—species
relations. The origin of these features has been attributed to antiquity of
the flora, isolation and/or environmental history. Using evidence from
palynology and macrofossils, we investigate the characteristics of the
mid–late Cenozoic angiosperm flora and the impact of environmental
changes in land area and configuration, physiography and climate on the
depletion and composition of the New Zealand flora. Climatic cooling,
increasing isolation and tectonism have each acted as important environmental
filters, contributing to regional extinctions and decreasing floral diversity,
and inducing major turnover in the floristic composition of New Zealand.
During the Miocene and Pliocene at least 15 families and a minimum of 36
genera were lost from the New Zealand flora. These included a range of life
forms and physiognomically important taxa such as
Acacia, Bombax,
Casuarina, Eucalyptus,
Ilex, many Proteaceae and several palms. The extinction
and decline in richness of subtropical families was caused by the onset of
cooling conditions in the Late Miocene—Pliocene, and exacerbated by
the absence of significant land areas to act as refugia at lower latitudes.
Many of these genera/families persist today on islands to the north (e.g.
New Caledonia), reflecting mid-Cenozoic land conduits, and in Australia. The
close floristic links with New Caledonia were probably maintained by
intermittent island stepping-stones which facilitated interchange of
subtropical taxa until the Late Miocene. The Pleistocene extinction of some
genera, tolerant of warm-temperate environments (e.g.
Acacia, Eucalyptus) may be a
reflection of the fact that persistent mesic conditions favoured widespread
dominance of dense rainforest during interglacials. The loss of these groups,
containing diverse life forms and floral structures, suggests that many of the
present characteristics of the New Zealand flora reflect strong selective
pressures, mainly driven by climate change, in the Late Miocene, Pliocene and
Pleistocene, rather than events of greater geological antiquity.
Availability of seed for recruitment of riparian vegetation: a comparison of a tropical and a temperate river ecosystem in Australia
Authors: Pettit N. E. , Froend R. H.
Published: September 2002

Processes that are important for the recruitment of plants include aspects of
the reproductive phenology, development and release of propagules, dispersal
of propagules and the storage of mature seed ready for germination when
conditions are suitable. This paper explores the relative importance of these
mechanisms by examining the contents of the seedbank in the soil, the
reproductive phenology of particular overstorey species, the importance of
dispersal by water and the survival and longevity of seed on two contrasting
rivers in Western Australia. Examination of the soil seedbank showed that
regeneration of vegetation from this source is probably important for annual
species of herbs and grasses but of only minor significance for perennial
species. This is most likely due to high levels of disturbance and the
unstable soils in the riparian zone. Reproductive phenology of the four
overstorey species monitored in this study appears to be well-adapted to the
hydrological regimes on the respective rivers. For the seed of riparian
overstorey species examined, seed longevity was poor and seed predation rates
were high. The occurrence of seed in floodwater debris indicated the
importance of secondary dispersal of seed by water, particularly for the Ord
River. For the two overstorey riparian species examined on the Ord River in
the subtropical north of Australia, there is little storage of seed and plants
are reliant on favourable conditions prevailing at the time of seed fall. The
likelihood of seed finding a safe site for successful germination is enhanced
by secondary dispersal in high river flows. For overstorey species on the
Blackwood River in the temperate zone of south-western Australia there is some
storage of seed in the canopy but dispersal of seed to safe sites is also
enhanced by river flow. For riparian vegetation on these rivers, regeneration
from seed can occur through several processes. The relative importance of
these different mechanism varies for each river, reflecting their vastly
different hydrology and climate.
The 'wilderness effect' and the decline of Callitris intratropica on the Arnhem Land Plateau, northern Australia
Authors: Bowman D. M. J. S. , Price Owen , Whitehead P. J. , Walsh Angie
Published: September 2002

An aerial survey along a transect from eastern side of the Arnhem Land Plateau
where Aboriginal people still lead a semi-traditional lifestyle, to the
unoccupied western side of the Plateau, revealed systematic differences in the
proportion of living and dead Callitris intratropica
trees. Multiple regression analysis showed that the highest proportion of dead
C. intratropica stems occurred on unoccupied, level
terrain dominated by open Eucalyptus forests, with a
minor or complete absence of Allosyncarpia ternata
closed-canopy forests. A detailed study of one population of
C. intratropica in western Arnhem Land adjacent to a
small patch of A. ternata forest, known as Round Jungle,
showed that the population had a unimodal size-class distribution, reflecting
a low density of stems less than 10 cm in diameter at breast height (dbh). A
computer simulation model was developed on the basis of estimates of annual
fecundity, mortality and growth rates derived from observations of the stand.
Sensitivity analyses suggested that a well-stocked stand could be transformed
to one similar to that observed at Round Jungle after 50 years, if annual
mortality rate of the immature stems (i.e. <12 cm dbh) was greater than
85%. Under these conditions, the stand would become extinct after 325
years. Variation in estimates of mature-stem (>12 cm dbh) mortality and
fecundity had much less effect on the predictions of the model than the rate
of mortality of the smallest size class. The model suggests that
C. intratropica populations can rapidly fluctuate in
response to changes in fire regime, while extinction is a gradual process and
is consequently unlikely if some seedlings can escape burning, for instance by
establishing in fire-protected microsites. This conclusion is consistent with
the observed greater mortality of C. intratropica on
sand sheets that have little topographic variability at the micro- or
mesoscale, compared with other habitat types in areas that are currently
unoccupied by Aboriginal people. Our study shows that predicting the fate of
individual populations will require careful consideration of local factors
such as the presence of micro-topographically safe sites for seedling
establishment, as well as the surrounding pattern of vegetation and landforms
that mediate the impact of fire on C. intratropica.
However, we suggest that rather than refining details of the adjustment of
C. intratropica in response to changed fire regimes
associated with European colonisation, subsequent research should focus on the
effect and significance of these changes for other organisms.
Buzz pollination in the Epacridaceae
Authors: Houston T. F. , Ladd P. G.
Published: September 2002

Conostephium (Epacridaceae) has flowers that conform with
a buzz-pollination syndrome but, unlike most plants with this form of
pollination, the anthers are hidden within the corolla tube. Vibrations
generated by bees grasping the apices of the corolla tubes must be transferred
via short broad filaments to the anthers. The anthers do not have pores but
each dehisces from the apex by a slit that elongates over the time the flowers
take to senesce (up to 10 days). This may limit self-fertilisation as the
stigma is receptive as soon as it appears from between the very short corolla
lobes, so little pollen is released at first but later this would increase as
the slit elongates. Visitation by pollinators has rarely been seen but several
observations of native bees (Leioproctus and
Lasioglossum) working the flowers are presented. The
bees visit the nectarless flowers of Conostephium only
for pollen and must forage at other kinds of flowers to obtain nectar. Pollen
tubes occurred in the stigmas of most older flowers of
C. pendulum, so pollen delivery does not seem to limit
seed set. Despite this, the species sets few fruit. From examination of the
taxonomic positions of likely buzz-pollinated taxa in the family, it appears
that pollination by sonication has arisen independently several times in the
Epacridaceae, with primarily two different floral configurations.
Overnight rainfall inducing rapid changes in photosynthetic behaviour in a cerrado woody species during a dry spell amidst the rainy season
Authors: de Mattos Eduardo A. , Lobo Patrícia C. , Joly Carlos A.
Published: September 2002

We examined the effects of a short rainfall during a dry spell amidst the
rainy season on CO2 and H2O gas
exchange and chlorophyll a fluorescence in leaves of
Miconia albicans (Sw.) Tr. (Melastomataceae), a common
shrub of the Brazilian cerrado. A strong midday depression of gas exchange was
observed at the end of the dry spell. Nevertheless, during the day after a
rainfall, net CO2 uptake
(JCO2), stomatal conductance to
water vapour (gs), transpiration
rates (JH2O) and the actual
photosystem II (PSII) efficiency
(ΔF/F´m) increased, whereas the fraction
of light absorbed in the PSII antennae that is dissipated directly within the
antennae (1 –
F´v/F´m) and the
degree of PSII closure (1 –
qP) decreased. Although
CO2 and H2O gas exchange were very
sensitive to the rain-free event in the wet season, the occurrence of a small
rainfall was enough to elicit rapid changes in
gs,
JH2O and
JCO2. We hypothesise that the
strong effect of the dry spell during the wet season on gas exchange may be
due to the highest leaf area available for transpiration at this time and a
lower hydraulic limit for catastrophic embolism to occur.
Aerial photography for assessing vegetation change: a review of applications and the relevance of findings for Australian vegetation history
Authors: Fensham R. J. , Fairfax R. J.
Published: September 2002

Studies attempting to calibrate vegetation attributes from aerial photography with field data are reviewed in detail. It is concluded that aerial photography has considerable advantages over satellite-based data because of its capacity to assess the vertical dimension of vegetation and the longer time period the record spans. Limitations of using the aerial photo record as digital data include standardising image contrast and rectification. Some of these problems can be circumvented by manual techniques, but problems of crown exaggeration that varies with photo scale and variation in contrast between the textures of tree crowns and the ground remain. Applications of aerial photography for assessing vegetation change are also reviewed and include deforestation, reforestation, changes in vegetation boundaries, tree density, community composition and crown dieback. These changes have been assessed at scales ranging from individual tree crowns to regional landscapes. In Australia, aerial photography has provided a clear demonstration of deforestation rates and the expansion and contraction of forest and woodland, which is generally attributed to changes in grazing and fire regimes. It is suggested that manual techniques with point-based sampling, digital processing of data for complete spatial coverages and the application of photogrammetric measurements with stereo-plotters are all techniques with great promise for utilising this underrated medium for assessment of vegetation dynamics.