Breeding for high water-use efficiency Condon, A.G; Richards, R.A; Rebetzke, G.J ...
Journal of experimental botany,
11/2004, Letnik:
55, Številka:
407
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
There is a pressing need to improve the water-use efficiency of rain-fed and irrigated crop production. Breeding crop varieties with higher water-use efficiency is seen as providing part of the ...solution. Three key processes can be exploited in breeding for high water-use efficiency: (i) moving more of the available water through the crop rather than it being wasted as evaporation from the soil surface or drainage beyond the root zone or being left behind in the root zone at harvest; (ii) acquiring more carbon (biomass) in exchange for the water transpired by the crop, i.e. improving crop transpiration efficiency; (iii) partitioning more of the achieved biomass into the harvested product. The relative importance of any one of these processes will vary depending on how water availability varies during the crop cycle. However, these three processes are not independent. Targeting specific traits to improve one process may have detrimental effects on the other two, but there may also be positive interactions. Progress in breeding for improved water-use efficiency of rain-fed wheat is reviewed to illustrate the nature of some of these interactions and to highlight opportunities that may be exploited in other crops as well as potential pitfalls. For C3 species, measuring carbon isotope discrimination provides a powerful means of improving water-use efficiency of leaf gas exchange, but experience has shown that improvements in leaf-level water-use efficiency may not always translate into higher crop water-use efficiency or yield. In fact, the reverse has frequently been observed. Reasons for this are explored in some detail. Crop simulation modelling can be used to assess the likely impact on water-use efficiency and yield of changing the expression of traits of interest. Results of such simulations indicate that greater progress may be achieved by pyramiding traits so that potential negative effects of individual traits are neutralized. DNA-based selection techniques may assist in such a strategy.
Lupus nephritis (LN) is a serious complication of systemic lupus erythematosus (SLE). All current treatment regimens include oral steroids, which are associated with severe adverse events and ...long-term damage. We have piloted a steroid-avoiding protocol (rituxilup) for the treatment of biopsy-proven active International Society of Nephrology/Renal Pathology Society (ISN/RPS) class III, IV, or class V LN.
We report the findings from the first 50 consecutive patients, treated with 2 doses of rituximab (1 g) and methyl prednisolone (500 mg) on days 1 and 15, and maintenance treatment of mycophenolate mofetil. Patients on maintenance steroids or with life-threatening SLE or requiring dialysis were excluded. Renal remission was defined as serum creatinine no greater than 15% above baseline; complete biochemical remission (CR) was defined as urine protein : creatinine ratio (PCR)<50 mg/mmol or partial remission (PR) if PCR>50 mg/mmol but non-nephrotic and >50% reduction.
A total of 45 (90%) patients achieved CR or PR by a median time of 37 weeks (range 4-200). Overall, 72% (n=36) achieved CR (median time 36 weeks (11-58)) and a further 18% (n=9) achieved persistent PR (median time 32 weeks (19-58)). By 52 weeks, CR and PR had been achieved in 52% (n=26) and 34% (n=17) respectively. In all, 12 relapses occurred in 11 patients, at a median time of 65.1 weeks (20-112) from remission. A total of 6/50 patients had systemic flares. Of the 45 responders, only 2 required >2 weeks of oral steroids. Adverse events were infrequent; 18% were admitted, 10% for an infective episode.
The rituxilup cohort demonstrates that oral steroids can be safely avoided in the treatment of LN. If findings are confirmed, it could mark a step change in the approach to the treatment of LN.
Enriched mid‐ocean ridge basalts (E‐MORB) commonly erupt at mid‐ocean ridges (MOR) and seamounts, but their relationship to “depleted” MORB (D‐MORB) and the processes controlling their magmatic ...evolution at MORs are not fully understood, hence raising more general questions about magma generation in the mantle. We here explore this conundrum through an investigation of the Masirah ophiolite (southeast Oman), a near‐unique “true” MOR ophiolite. Unlike most (e.g., Tethyan) ophiolites, it was not affected by subduction and is therefore potentially able to provide valuable geological insights into the magmatic evolution of a full section of oceanic crust. Previous work has shown that the igneous crust at Masirah was thin (1.5–2.0 km) and constructed from both D‐ and E‐MORB magmas, concluding that it formed at a slow‐spreading ridge at ∼150 Ma followed by an episode of “Nb‐enriched” magmatism with trace‐element enrichments exceeding E‐MORB during intraplate rifting ∼20 Ma later. We reinvestigate the geology of Masirah and present new field observations, geochemical data and high‐precision U‐Pb ages to constrain the magmatic history of seafloor spreading and off‐axis magmatism. We found that D‐MORB and E‐MORB magmatism at Masirah was synchronous and overlapped in both composition and time with the Nb‐enriched magmatism (no older than 135 Ma). Both types of magmatism were therefore integral in the formation of the Masirah ocean crust. The relationship between D‐MORB and E‐MORB magmatism described here may be applicable to modern MORs more broadly, but is especially prominent at Masirah due to reduced magmatism and hence a weaker crustal filter.
Plain Language Summary
The oceanic crust forms approximately two‐thirds of the Earth's surface and is continuously being formed at mid‐ocean ridges. Due to the difficulties involved in accessing oceanic crust directly, especially the deeper stratigraphic levels, the magmatic processes involved in forming the oceanic crust remain poorly understood. Ophiolites, fragments of oceanic lithosphere that were emplaced onto the continent, can offer valuable insights to geologists, but since most ophiolites are thought to have originated in marginal oceanic basins or at the initiation of subduction, a direct comparison remains problematic. In this study, we circumvent this problem by investigating the Masirah Ophiolite, a rare example of a “true” mid‐ocean ridge ophiolite. By combining field observations, geochemistry and geochronology at a level of detail not possible for present‐day oceanic crust, we reconstruct the magmatic evolution of the Masirah paleoridge. We present a more accurate formation age for Masirah and find that magmatism was compositionally variable throughout crustal accretion, with later off‐axis melts becoming more enriched in incompatible trace elements. We propose that the large geochemical variations observed at Masirah may be commonplace at modern mid‐ocean ridges, but that these are often masked due to the typically higher volumes of magmatism that enhance mixing and homogenization.
Key Points
Two ophiolite nappes exposed on Masirah were formed by ocean crustal accretion at 135 and 131 Ma respectively
On‐axis magmatism shows varying degrees of trace element enrichment and depletion, and is followed by Nb‐enriched “near‐axis” magmatism
Similar processes may be common along modern mid‐ocean ridges but masked by the homogenizing effect of an enhanced “crustal filter”
The VLA Low-Frequency Sky Survey Cohen, A. S; Lane, W. M; Cotton, W. D ...
The Astronomical journal,
09/2007, Letnik:
134, Številka:
3
Journal Article
Recenzirano
Odprti dostop
The VLA Low-frequency Sky Survey (VLSS) has imaged 95% of the 3p sr of sky north of d = -30° at a frequency of 74 MHz (4 m wavelength). The resolution is 80'' (FWHM) throughout, and the typical rms ...noise level is s 0.1 Jy beam-1. The typical point-source detection limit is 0.7 Jy beam-1, and so far nearly 70,000 sources have been cataloged. This survey used the 74 MHz system added to the VLA in 1998. It required new imaging algorithms to remove the large ionospheric distortions at this very low frequency throughout the entire ~11.9° field of view. This paper describes the observation and data reduction methods used for the VLSS and presents the survey images and source catalog. All of the calibrated images and the source catalog are available from the VLSS Web site for use by the astronomical community.
Abstract
Argyle is the world’s largest source of natural diamonds, yet one of only a few economic deposits hosted in a Paleoproterozoic orogen. The geodynamic triggers responsible for its alkaline ...ultramafic volcanic host are unknown. Here we show, using U-Pb and (U-Th)/He geochronology of detrital apatite and detrital zircon, and U-Pb dating of hydrothermal titanite, that emplacement of the Argyle lamproite is bracketed between 1311 ± 9 Ma and 1257 ± 15 Ma (2σ), older than previously known. To form the Argyle lamproite diatreme complex, emplacement was likely driven by lithospheric extension related to the breakup of the supercontinent Nuna. Extension facilitated production of low-degree partial melts and their migration through transcrustal corridors in the Paleoproterozoic Halls Creek Orogen, a rheologically-weak rift zone adjacent to the Kimberley Craton. Diamondiferous diatreme emplacement during (super)continental breakup may be prevalent but hitherto under-recognized in rift zones at the edges of ancient continental blocks.
We report the discovery by the Wide-field Infrared Survey Explorer (WISE) of the z = 2.452 source WISE J181417.29+341224.9, the first hyperluminous source found in the WISE survey. WISE 1814+3412 is ...also the prototype for an all-sky sample of ~1000 extremely luminous "W1W2-dropouts" (sources faint or undetected by WISE at 3.4 and 4.6 mu m and well detected at 12 or 22 mu m). The WISE data and a 350 mu m detection give a minimum bolometric luminosity of 3.7 x 10 super(13) L sub(middot in circle), with ~10 super(14) L sub(middot in circle) plausible. Follow-up images reveal four nearby sources: a QSO and two Lyman break galaxies (LBGs) at z = 2.45, and an M dwarf star. The brighter LBG dominates the bolometric emission. Gravitational lensing is unlikely given the source locations and their different spectra and colors. The dominant LBG spectrum indicates a star formation rate ~300 M sub(middot in circle) yr super(-1), accounting for <, ~10% of the bolometric luminosity. Strong 22 mu m emission relative to 350 mu m implies that warm dust contributes significantly to the luminosity, while cooler dust normally associated with starbursts is constrained by an upper limit at 1.1 mm. Radio emission is ~10 times above the far-infrared/radio correlation, indicating an active galactic nucleus (AGN) is present. An obscured AGN combined with starburst and evolved stellar components can account for the observations. If the black hole mass follows the local M sub(BH)-bulge mass relation, the implied Eddington ratio is >, ~4. WISE 1814+3412 may be a heavily obscured object where the peak AGN activity occurred prior to the peak era of star formation.
This is the second of two papers describing the observations and source catalogues derived from sensitive 3-GHz images of the Lockman Hole North using the Karl G. Jansky Very Large Array (VLA). We ...describe the reduction and cataloguing process, which yielded an image with 8 arcsec resolution and instrumental noise of σn = 1.01 μJy beam−1 rms (before primary-beam corrections) and a catalogue of 558 sources detected above 5σn. We include details of how we estimate source spectral indices across the 2-GHz VLA bandwidth, finding a median index of −0.76 ± 0.04. Stacking of source spectra reveals a flattening of spectral index with decreasing flux density. We present a source count derived from the catalogue. We show a traditional count estimate compared with a completely independent estimate made via a P(D) confusion analysis, and find very good agreement. Cross-matches of the catalogue with X-ray, optical, infrared, radio, and redshift catalogues are also presented. The X-ray, optical and infrared data, as well as active galactic nuclei (AGN) selection criteria allow us to classify 10 per cent as radio-loud AGN, 28 per cent as radio-quiet AGN, and 58 per cent as star-forming galaxies, with only 4 per cent unclassified.
We present 33 GHz photometry of 103 galaxy nuclei and extranuclear star-forming complexes taken with the Green Bank Telescope as part of the Star Formation in Radio Survey. Among the sources without ...evidence for an active galactic nucleus, and also having lower frequency radio data, we find a median thermal fraction at 33 GHz of approximately 76% with a dispersion of approximately 24%. For all sources resolved on scales lap0.5 kpc, the thermal fraction is even larger, being gap90%. This suggests that the rest-frame 33 GHz emission provides a sensitive measure of the ionizing photon rate from young star-forming regions, thus making it a robust star formation rate (SFR) indicator. Comparing the 33 GHz to total IR flux ratios as a function of the radio spectral index, measured between 1.7 and 33 GHz, we find that the ratio increases as the radio spectral index flattens which does not appear to be a distance effect.
The Sterile Insect Technique (SIT) used to control insect pests relies on the release of large numbers of radiation-sterilized insects. Irradiation can have a negative impact on the subsequent ...performance of the released insects and therefore on the cost and effectiveness of a control program. This and other problems associated with current SIT programs could be overcome by the use of recombinant DNA methods and molecular genetics. Here we describe the construction of strains of the Mediterranean fruit fly (medfly) harboring a tetracycline-repressible transactivator (tTA) that causes lethality in early developmental stages of the heterozygous progeny but has little effect on the survival of the parental transgenic tTA insects. We show that these properties should prove advantageous for the implementation of insect pest control programs.
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