1,197 research outputs found
Developing an ancient epithelial appendage: FGF signalling regulates early tail denticle formation in sharks
Background: Vertebrate epithelial appendages constitute a diverse group of organs that includes integumentary
structures such as reptilian scales, avian feathers and mammalian hair. Recent studies have provided new evidence for
the homology of integumentary organ development throughout amniotes, despite their disparate fnal morphologies.
These structures develop from conserved molecular signalling centres, known as epithelial placodes. It is not yet
certain whether this homology extends beyond the integumentary organs of amniotes, as there is a lack of knowledge
regarding their development in basal vertebrates. As the ancient sister lineage of bony vertebrates, extant chondrichthyans
are well suited to testing the phylogenetic depth of this homology. Elasmobranchs (sharks, skates and
rays) possess hard, mineralised epithelial appendages called odontodes, which include teeth and dermal denticles
(placoid scales). Odontodes constitute some of the oldest known vertebrate integumentary appendages, predating
the origin of gnathostomes. Here, we used an emerging model shark (Scyliorhinus canicula) to test the hypothesis that
denticles are homologous to other placode-derived amniote integumentary organs. To examine the conservation
of putative gene regulatory network (GRN) member function, we undertook small molecule inhibition of fbroblast
growth factor (FGF) signalling during caudal denticle formation.
Results: We show that during early caudal denticle morphogenesis, the shark expresses homologues of conserved
developmental gene families, known to comprise a core GRN for early placode morphogenesis in amniotes. This
includes conserved expression of FGFs, sonic hedgehog (shh) and bone morphogenetic protein 4 (bmp4). Additionally,
we reveal that denticle placodes possess columnar epithelial cells with a reduced rate of proliferation, a conserved
characteristic of amniote skin appendage development. Small molecule inhibition of FGF signalling revealed
placode development is FGF dependent, and inhibiting FGF activity resulted in downregulation of shh and bmp4
expression, consistent with the expectation from comparison to the amniote integumentary appendage GRN.
Conclusion: Overall, these fndings suggest the core GRN for building vertebrate integumentary epithelial appendages
has been highly conserved over 450 million years. This provides evidence for the continuous, historical homology
of epithelial appendage placodes throughout jawed vertebrates, from sharks to mammals. Epithelial placodes
constitute the shared foundation upon which diverse vertebrate integumentary organs have evolved
Infrared Behaviour of The Gluon Propagator in Non-Equilibrium Situations
The infrared behaviour of the medium modified gluon propagator in
non-equilibrium situations is studied in the covariant gauge using the
Schwinger-Keldysh closed-time path formalism. It is shown that the magnetic
screening mass is non-zero at the one loop level whenever the initial gluon
distribution function is non isotropic with the assumption that the
distribution function of the gluon is not divergent at zero transverse
momentum. For isotropic gluon distribution functions, such as those describing
local equilibrium, the magnetic mass at one loop level is zero which is
consistent with finite temperature field theory results. Assuming that a
reasonable initial gluon distribution function can be obtained from a
perturbative QCD calculation of minijets, we determine these out of equilibrium
values for the initial magnetic and Debye screening masses at energy densities
appropriate to RHIC and LHC. We also compare the magnetic masses obtained here
with those obtained using finite temperature lattice QCD methods at similar
temperatures at RHIC and LHC.Comment: 21 pages latex, 4 figures, final version to be published in Phys.
Rev.
Effect of microwave radiation on seed mortality of rubber vine (Cryptostegia grandiflora R.Br.), parthenium (Parthenium hysterophorous L.) and bellyache bush (Jatropha gossypiifolia L.)
A trial was undertaken to evaluate the effect of microwaves on seed mortality of three weed species. Seeds of rubber vine (Cryptostegia grandiflora R.Br.), parthenium (Parthenium hysterophorous L.) and bellyache bush (Jatropha gossypiifolia L.) were buried at six depths (0, 2.5, 5, 10, 20 and 40 cm) in coarse sand maintained at one of two moisture levels, oven dry or wet (field capacity), and then subjected to one of five microwave radiation durations of (0, 2, 4, 8 and 16 min). Significant interactions between soil moisture level, microwave radiation duration, seed burial depth and species were detected for mortality of seeds of all three species. Maximum seed mortality of rubber vine (88%), parthenium (67%) and bellyache bush (94%) occurred in wet soil irradiated for 16 min. Maximum seed mortality of rubber vine and bellyache bush seeds occurred in seeds buried at 2.5 cm depth whereas that of parthenium occurred in seeds buried at 10 cm depth. Maximum soil temperatures of 114.1 and 87.5°C in dry and wet soil respectively occurred at 2.5 cm depth following 16 min irradiation. Irrespective of the greater soil temperatures recorded in dry soil, irradiating seeds in wet soil generally increased seed mortality 2.9-fold compared with dry soil. Moisture content of wet soil averaged 5.7% compared with 0.1% for dry soil. Results suggest that microwave radiation has the potential to kill seeds located in the soil seed bank. However, many factors, including weed species susceptibility, determine the effectiveness of microwave radiation on buried seeds. Microwave radiation may be an alternative to conventional methods at rapidly depleting soil seed banks in the field, particularly in relatively wet soils that contain long lived weed seeds
Multiplicities and Transverse Energies in Central AA Collisions at RHIC and LHC from pQCD, Saturation and Hydrodynamics
We compute the particle multiplicities and transverse energies at central and
nearly central AA collisions at RHIC and LHC. The initial state is computed
from perturbative QCD supplemented by the conjecture of saturation of produced
partons. The expansion stage is described in terms of hydrodynamics assuming
longitudinal boost invariance and azimuthal symmetry. Transverse flow effects,
a realistic list of hadrons and resonance decays are included. Comparison with
the data of the multiplicities at AGeV and 130 AGeV from RHIC is
done and predictions for the full RHIC energy and LHC energy are made for the
multiplicities and transverse energies. The reduction from the initially
released minijet transverse energy to the in the final state is less than
in the one-dimensional case but still dramatic: a factor of 2.7 at RHIC, and
3.6 at the LHC.Comment: The results for LHC have been correcte
Sustaining productivity of a Vertisol at Warra, Queensland, with fertilisers, no-tillage, or legumes. 5. Wheat yields, nitrogen benefits and water-use efficiency of chickpea-wheat rotation
In this study, the benefits of chickpea–wheat rotation compared with continuous wheat cropping (wheat–wheat rotation) were evaluated for their effects on soil nitrate nitrogen, wheat grain yields and grain protein concentrations, and water-use efficiency at Warra, southern Queensland from 1988 to 1996.
Benefits in terms of wheat grain yields varied, from 17% in 1993 to 61% in 1990, with a mean increase in grain yield of 40% (825 kg/ha). Wheat grain protein concentration increased from 9.4% in a wheat–wheat rotation to 10.7% in a chickpea–wheat rotation, almost a 14% increase in grain protein. There was a mean increase in soil nitrate nitrogen of 35 kg N/ha.1.2 m after 6 months of fallow following chickpea (85 kg N/ha) compared with continuous wheat cropping (50 kg N/ha). This was reflected in additional nitrogen in the wheat grain (20 kg N/ha) and above-ground plant biomass (25 kg N/ha) following chickpea.
Water-use efficiency by wheat increased from a mean value of 9.2 kg grain/ha. mm in a wheat–wheat rotation to 11.7 kg grain/ha.mm in a chickpea–wheat rotation. The water-use efficiency values were closely correlated with presowing nitrate nitrogen, and showed no marked distinction between the 2 cropping sequences. Although presowing available water in soil in May was similar in both the chickpea–wheat rotation and the wheat–wheat rotation in all years except 1996, wheat in the former used about 20 mm additional water and enhanced water-use efficiency. Thus, by improving soil fertility through restorative practices such as incorporating chickpea in rotation, water-use efficiency can be enhanced and consequently water runoff losses reduced.
Furthermore, beneficial effects of chickpea in rotation with cereals could be enhanced by early to mid sowing (May–mid June) of chickpea, accompanied by zero tillage practice. Wheat of ‘Prime Hard’ grade protein (≥13%) could be obtained in chickpea–wheat rotation by supplementary application of fertiliser N to wheat.
In this study, incidence of crown rot of wheat caused by Fusarium graminearum was negligible, and incidence and severity of common root rot of wheat caused by Bipolaris sorokiniana were essentially similar in both cropping sequences and inversely related to the available water in soil at sowing. No other soil-borne disease was observed. Therefore, beneficial effects of chickpea on wheat yields and grain protein were primarily due to additional nitrate nitrogen following the legume crop and consequently better water-use efficiency
Effect of microwave radiation on seed mortality of rubber vine (Cryptostegia grandiflora R.Br.), parthenium (Parthenium hysterophorous L.) and bellyache bush (Jatropha gossypiifolia L.)
A trial was undertaken to evaluate the effect of microwaves on seed mortality of three weed species. Seeds of rubber vine (Cryptostegia grandiflora R.Br.), parthenium (Parthenium hysterophorous L.) and bellyache bush (Jatropha gossypiifolia L.) were buried at six depths (0, 2.5, 5, 10, 20 and 40 cm) in coarse sand maintained at one of two moisture levels, oven dry or wet (field capacity), and then subjected to one of five microwave radiation durations of (0, 2, 4, 8 and 16 min). Significant interactions between soil moisture level, microwave radiation duration, seed burial depth and species were detected for mortality of seeds of all three species. Maximum seed mortality of rubber vine (88%), parthenium (67%) and bellyache bush (94%) occurred in wet soil irradiated for 16 min. Maximum seed mortality of rubber vine and bellyache bush seeds occurred in seeds buried at 2.5 cm depth whereas that of parthenium occurred in seeds buried at 10 cm depth. Maximum soil temperatures of 114.1 and 87.5°C in dry and wet soil respectively occurred at 2.5 cm depth following 16 min irradiation. Irrespective of the greater soil temperatures recorded in dry soil, irradiating seeds in wet soil generally increased seed mortality 2.9-fold compared with dry soil. Moisture content of wet soil averaged 5.7% compared with 0.1% for dry soil. Results suggest that microwave radiation has the potential to kill seeds located in the soil seed bank. However, many factors, including weed species susceptibility, determine the effectiveness of microwave radiation on buried seeds. Microwave radiation may be an alternative to conventional methods at rapidly depleting soil seed banks in the field, particularly in relatively wet soils that contain long lived weed seeds
Schwinger Mechanism for Gluon Pair Production in the Presence of Arbitrary Time Dependent Chromo-Electric Field
We study Schwinger mechanism for gluon pair production in the presence of
arbitrary time-dependent chromo-electric background field with
arbitrary color index =1,2,...8 in SU(3) by directly evaluating the path
integral. We obtain an exact expression for the probability of non-perturbative
gluon pair production per unit time per unit volume and per unit transverse
momentum from arbitrary . We show that the
tadpole (or single gluon) effective action does not contribute to the
non-perturbative gluon pair production rate . We find
that the exact result for non-perturbative gluon pair production is independent
of all the time derivatives where
and has the same functional dependence on two casimir invariants
and as the constant
chromo-electric field result with the replacement: . This
result may be relevant to study the production of a non-perturbative
quark-gluon plasma at RHIC and LHC.Comment: 13 pages latex, Published in European Physical Journal
A gamma- and X-ray detector for cryogenic, high magnetic field applications
As part of an experiment to measure the spectrum of photons emitted in
beta-decay of the free neutron, we developed and operated a detector consisting
of 12 bismuth germanate (BGO) crystals coupled to avalanche photodiodes (APDs).
The detector was operated near liquid nitrogen temperature in the bore of a
superconducting magnet and registered photons with energies from 5 keV to 1000
keV. To enlarge the detection range, we also directly detected soft X-rays with
energies between 0.2 keV and 20 keV with three large area APDs. The
construction and operation of the detector is presented, as well as information
on operation of APDs at cryogenic temperatures
Dependence of hadron spectra on decoupling temperature and resonance contributions
Using equilibrium hydrodynamics with initial conditions for the energy and
net baryon number densities from the perturbative QCD + saturation model, a
good simultaneous description of the measured pion, kaon and (anti)proton
spectra in central Au+Au collisions at GeV is found with a
single decoupling temperature \Tdec=150...160 MeV. The interplay between the
resonance content of the EoS and the development of the transverse flow leads
to inverse slopes and of hadrons which increase with decreasing
\Tdec. The origin of this result is discussed.Comment: 4 pages, 2 eps-figures. Section 3 rewritten, table 1 and figure 1
redrawn, 2 references adde
Percutaneous vertebroplasty is not a risk factor for new osteoporotic compression fractures: results from VERTOS II
Background and purpose: Pv is increasingly used as treatment for osteoporotic vcfs. However, controversy exists as to whether pv increases the risk for new vcfs during follow-up. The purpose of our research was to assess the incidence of new vcfs in patients with acute vcfs randomized to pv and conservative therapy. Materials and methods: Vertos ii is a prospective multicenter randomized controlled trial comparing pv with conservative therapy in 202 patients. Incidence, distribution, and timing of new vcfs during follow-up were assessed from spine radiographs. In addition, further height loss during follow-up of treated vcfs was measured. Results: After a mean follow-up of 11.4 Months (Median, 12.0; Range, 1-24 months), 18 New vcfs occurred in 15 of 91 patients after pv and 30 new vcfs in 21 of 85 patients after conservative therapy. This difference was not significant (P = .44). There was no higher fracture risk for adjacent-versus-distant vertebrae. Mean time to new vcf was 16.2 Months after pv and 17.8 Months after conservative treatment (Logrank, p = .45). The baseline number of vcfs was the only risk factor for occurrence (Or, 1.43; 95% Ci, 1.05-1.95) And number (P = .01) Of new vcfs. After conservative therapy, further height loss of treated vertebrae occurred more frequently (35 Of 85 versus 11 of 91 patients, p < .001) And was more severe (P < .001) Than after pv. Conclusions: Incidence of new vcfs was not different after pv compared with conservative therapy after a mean of 11.4 Months' follow-up. The only risk factor for new vcfs was the number of vcfs at baseline. Pv contributed to preservation of stature by decreasing both the incidence and severity of further height loss in treated vertebrae
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