179 research outputs found
Optimisation of phosphate loading on graphene oxide-Fe(iii) composites-possibilities for engineering slow release fertilisers
Current commercially available phosphorus (P) fertilisers, which are highly soluble salts, are susceptible to surface runoff to waterways, and leaching to groundwaters where soils are light/medium textured. Here, we report the synthesis of a graphene oxide (GO)/iron (GO–Fe) composite, a promising carrier for loading P. The GO–Fe carriers loaded with P acted as slow release fertilisers with tunable loading/release properties. The amount of P loaded onto the GO–Fe composite was 15%, similar to commercial products. Investigation of the morphology and spectroscopic and chemical analysis revealed a complex loading mechanism of Fe onto GO. Iron, as an active center for P sorption, could interact with the oxygen functional groups at the edge of GO sheets as well as the π-electron system of the aromatic part of GO. Column perfusion studies, visualisation of P diffusion in soils and chemical analysis of soils after diffusion showed the composites to have slow-release properties. Pot experiments using wheat and our composites resulted in the same yield as using highly soluble commercial fertiliser.Ivan B. Andelkovic, Shervin Kabiri, Rodrigo C. da Silva, Ehsan Tavakkoli, Jason K. Kirby, Dusan Losic and Michael J. McLaughli
Isotopic signatures reveal zinc cycling in the natural habitat of hyperaccumulator Dichapetalum gelonioides subspecies from Malaysian Borneo
Background: Some subspecies of Dichapetalum gelonioides are the only tropical woody zinc (Zn)-hyperaccumulator plants described so far and the first Zn hyperaccumulators identified to occur exclusively on non-Zn enriched 'normal' soils. The aim of this study was to investigate Zn cycling in the parent rock-soil-plant interface in the native habitats of hyperaccumulating Dichapetalum gelonioides subspecies (subsp. pilosum and subsp. sumatranum). We measured the Zn isotope ratios (δ66Zn) of Dichapetalum plant material, and associated soil and parent rock materials collected from Sabah (Malaysian Borneo). Results: We found enrichment in heavy Zn isotopes in the topsoil (δ66Zn 0.13 ‰) relative to deep soil (δ66Zn -0.15 ‰) and bedrock (δ66Zn -0.90 ‰). This finding suggests that both weathering and organic matter influenced the Zn isotope pattern in the soil-plant system, with leaf litter cycling contributing significantly to enriched heavier Zn in topsoil. Within the plant, the roots were enriched in heavy Zn isotopes (δ66Zn ~ 0.60 ‰) compared to mature leaves (δ66Zn ~ 0.30 ‰), which suggests highly expressed membrane transporters in these Dichapetalum subspecies preferentially transporting lighter Zn isotopes during root-to-shoot translocation. The shoots, mature leaves and phloem tissues were enriched in heavy Zn isotopes (δ66Zn 0.34–0.70 ‰) relative to young leaves (δ66Zn 0.25 ‰). Thisindicates that phloem sources are enriched in heavy Zn isotopes relative to phloem sinks, likely because of apoplastic retention and compartmentalization in the Dichapetalum subspecies. Conclusions: The findings of this study reveal Zn cycling in the rock-soil-plant continuum within the natural habitat of Zn hyperaccumulating subspecies of Dichapetalum gelonioides from Malaysian Borneo. This study broadens our understanding of the role of a tropical woody Zn hyperaccumulator plant in local Zn cycling, and highlights the important role of leaf litter recycling in the topsoil Zn budget. Within the plant, phloem plays key role in Zn accumulation and redistribution during growth and development. This study provides an improved understanding of the fate and behaviour of Zn in hyperaccumulator soil-plant systems, and these insights may be applied in the biofortification of crops with Zn.Antony van der Ent, Philip Nti Nkrumah, Mark G. M. Aarts, Alan J. M. Baker, Fien Degryse, Chris Wawryk, and Jason K. Kirb
Seismic Reflection Imaging of the Low-Angle Panamint Normal Fault System, Eastern California
Shallowly dipping (<30°) low-angle normal faults (LANFs) have been documented globally; however, examples of active LANFs in continental settings are limited. The western margin of the Panamint Range in eastern California is defined by a LANF that dips west beneath Panamint Valley and has evidence of Quaternary motion. In addition, high-angle dextral-oblique normal faults displace middle to late Quaternary alluvial fans near the range front. To image shallow (<1 km depth), crosscutting relationships between the low- and high-angle faults along the range front, we acquired two high-resolution P wave seismic reflection profiles. The northern, 4.6-km-long profile crosses the 2-km-wide Wildrose graben and the southern, 0.8-km-long profile extends onto the Panamint Valley playa, ~7.5 km S of Ballarat, CA. The profile across the Wildrose graben reveals a robust, low-angle reflector interpreted to represent the LANF separating Plio-Pleistocene alluvial fanglomerate and Proterozoic metasedimentary deposits. High-angle faults interpreted in the seismic profile correspond to fault scarps on Quaternary alluvial fan surfaces. Interpretation of the reflection data suggests that the high-angle faults vertically displace the LANF up to 80 m within the Wildrose graben. Similarly, the profile south of Ballarat reveals a low-angle reflector, which appears both rotated and displaced up to 260 m by high-angle faults. These results suggest that near the Panamint range front, the high-angle faults are the dominant active structures. We conclude that at least at shallow (<1 km) depths, the LANF we imaged is not active today
Effects of silver sulfide nanomaterials on mycorrhizal colonization of tomato plants and soil microbial communities in biosolid-amended soil
We investigated effects of Ag2S engineered nanomaterials (ENMs), polyvinylpyrrolidone (PVP) coated Ag ENMs (PVP-Ag), and Ag+ on arbuscular mycorrhizal fungi (AMF), their colonization of tomato (Solanum lycopersicum), and overall microbial community structure in biosolids-amended soil. Concentration-dependent uptake was measured in all treatments. Plants exposed to 100 mg kg−1 PVP-Ag ENMs and 100 mg kg−1 Ag+ exhibited reduced biomass and greatly reduced mycorrhizal colonization. Bacteria, actinomycetes and fungi were inhibited by all treatment classes, with the largest reductions measured in 100 mg kg−1 PVP-Ag ENMs and 100 mg kg−1 Ag+. Overall, Ag2S ENMs were less toxic to plants, less disruptive to plant-mycorrhizal symbiosis, and less inhibitory to the soil microbial community than PVP-Ag ENMs or Ag+. However, significant effects were observed at 1 mg kg−1 Ag2S ENMs, suggesting that the potential exists for microbial communities and the ecosystem services they provide to be disrupted by environmentally relevant concentrations of Ag2S ENMs.Jonathan D. Judy, Jason K. Kirby, Courtney Creamer, Mike J. McLaughlin, Cathy Fiebiger, Claire Wright, Timothy R. Cavagnaro, Paul M. Bertsc
Electronic and optical spectra in a diluted magnetic semiconductor multilayer
The effects of random distribution of magnetic impurities with concentration
in a semiconductor alloy multilayer at a paramagnetic temperature are
investigated by means of coherent potential approximation and tight-binding
model. The change in the electronic states and the optical absorption spectrum
with is calculated for weak and strong exchange interactions between
carrier spins and localized spin moments on magnetic ions. We find that the
density of states and optical absorption are strongly layer-dependent due to
the quantum size effects. The electronic and optical spectra are broadened due
to the spin fluctuations of magnetic ions and in the case of strong exchange
interaction, an energy gap appears in both spectra. Furthermore, the interior
layers show higher contribution in the optical absorption of the system. The
results can be helpful for magneto-optical devices at a paramagnetic
temperature.Comment: 7 pages, 5 figure
Search for Higgs bosons decaying to tautau pairs in ppbar collisions at sqrt(s) = 1.96 TeV
We present a search for the production of neutral Higgs bosons decaying into
tautau pairs in ppbar collisions at a center-of-mass energy of 1.96 TeV. The
data, corresponding to an integrated luminosity of 5.4 fb-1, were collected by
the D0 experiment at the Fermilab Tevatron Collider. We set upper limits at the
95% C.L. on the product of production cross section and branching ratio for a
scalar resonance decaying into tautau pairs, and we then interpret these limits
as limits on the production of Higgs bosons in the minimal supersymmetric
standard model (MSSM) and as constraints in the MSSM parameter space.Comment: 7 pages, 5 figures, submitted to PL
Measurement of three-jet differential cross sections d sigma-3jet / d M-3jet in p anti-p collisions at sqrt(s)=1.96 TeV
We present the first measurement of the inclusive three-jet differential
cross section as a function of the invariant mass of the three jets with the
largest transverse momenta in an event in p anti-p collisions at sqrt(s) = 1.96
TeV. The measurement is made in different rapidity regions and for different
jet transverse momentum requirements and is based on a data set corresponding
to an integrated luminosity of 0.7 fb^{-1} collected with the D0 detector at
the Fermilab Tevatron Collider. The results are used to test the three-jet
matrix elements in perturbative QCD calculations at next-to-leading order in
the strong coupling constant. The data allow discrimination between
parametrizations of the parton distribution functions of the proton.Comment: 10 pages, 4 figures, 2 tables, submitted to Phys. Lett. B, corrected
chi2 values for NNPD
Measurements of inclusive W+jets production rates as a function of jet transverse momentum in ppbar collisions at sqrt{s}=1.96 TeV
This Letter describes measurements of inclusive W (--> e nu) + n jet cross
sections (n = 1-4), presented as total inclusive cross sections and
differentially in the nth jet transverse momentum. The measurements are made
using data corresponding to an integrated luminosity of 4.2 fb-1 collected by
the D0 detector at the Fermilab Tevatron Collider, and achieve considerably
smaller uncertainties on W +jets production cross sections than previous
measurements. The measurements are compared to next-to-leading order
perturbative QCD (pQCD) calculations in the n =1-3 jet multiplicity bins and to
leading order pQCD calculations in the 4-jet bin. The measurements are
generally in agreement with pQCD predictions, although certain regions of phase
space are identified where the calculations could be improved
Measurement of spin correlation in ttbar production using dilepton final states
We measure the correlation between the spin of the top quark and the spin of
the anti-top quark in (ttbar -> W+ W- b bbar -> l+ nu b l- nubar bbar) final
states produced in ppbar collisions at a center of mass energy sqrt(s)=1.96
TeV, where l is an electron or muon. The data correspond to an integrated
luminosity of 5.4 fb-1 and were collected with the D0 detector at the Fermilab
Tevatron collider. The correlation is extracted from the angles of the two
leptons in the t and tbar rest frames, yielding a correlation strength C=
0.10^{+0.45}_{-0.45}, in agreement with the NLO QCD prediction within two
standard deviations, but also in agreement with the no correlation hypothesis.Comment: 10 pages, 3 figures, submitted to PL
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