3,758 research outputs found

    Inheritance of resistance to root-lesion nematode (Pratylenchus thornei) in wheat landraces and cultivars from the West Asia and North Africa (WANA) region.

    Get PDF
    The root-lesion nematode Pratylenchus thornei causes substantial loss to bread wheat production in the northern grain region of Australia and other parts of the world. West Asia and North Africa (WANA) wheat accessions with partial resistance to P. thornei were analysed for mode of inheritance in a half-diallel crossing design of F1 hybrids (10 parents) and F2 populations (7 parents). General combining ability was more important than specific combining ability as indicated by components of variance ratios of 0.93 and 0.95 in diallel ANOVA of the F1 and F2 generations, respectively. General combining ability values of the 'resistant' parents were predictive of the mean nematode numbers of their progeny in crosses with the susceptible Australian cv. Janz at the F1 (R populations showed relatively continuous distributions. Heritability was 0.68 for F2 populations in the half-diallel of resistant parents and 0.82-0.92 for 5 'resistant' parent/Janz doubled-haploid populations (narrow-sense heritability on a line mean basis). The results indicate polygenic inheritance of P. thornei resistance with a minimum of from 2 to 6 genes involved in individual F populations of 5 resistant parents crossed with Janz. Morocco 426 and Iraq 43 appear to be the best of the parents tested for breeding for resistance to P. thornei. None of the P. thornei-resistant WANA accessions was resistant to Pratylenchus neglectus

    The geometry and thickness of deformation-band fault core and its influence on sealing characteristics of deformation-band fault zones

    Get PDF
    Deformation-band faults in high-porosity reservoir sandstones commonly contain a fault core of intensely crushed rock surrounding the main slip surfaces. The fault core has a substantially reduced porosity and permeability with respect to both the host rock and individual deformation bands. Although fault core thickness is a large uncertainty in calculations of transmissibility multipliers used to represent faults in single-phase reservoir flow models, few data exist on fault core thickness in deformation-band fault zones. To provide accurate estimates of deformation-band fault petrophysical properties, we measured fault core thickness at six sites (each 4–15 m [13–49 ft] along strike) along the Big Hole fault in the Navajo Sandstone, central Utah. These data show that the thickness is highly variable and does not correlate with either the amount of slip or the number of slip surfaces. The thickness of the fault core is likely to be dependent on local growth processes, specifically the linkage of fault segments. This suggests that correlations of fault permeability with throw may not apply to deformation-band faults. Simple calculations of two-phase flowproperties based on measured porosity and permeability values suggest that deformation-band faults containing fault core are likely barriers to two-phase flow.More data on the variability of fault core thickness and its petrophysical properties need to be collected to characterize population statistics for models of deformation-band fault fluid-flow properties

    Root-lesion nematode (Pratylenchus thornei) limits response of wheat but not barley to stored soil moisture in the Hermitage long-term tillage experiment

    Get PDF
    The cumulative effects of factorial treatments of tillage (no tillage, conventional), stubble retention (burnt, retained), and nitrogen fertiliser (0, 23, 69 kg N/ha) on yield of continuous winter cereals and on soil properties have been tested in the Hermitage fallow management experiment since 1969. Despite increased soil water stored from the combination of no tillage and stubble retention, wheat responses to the extra water were disappointing in the first 11 years of the experiment. Soil samples from the experiment were shown to be heavily infested with the root-lesion nematode (Pratylenchus thornei Sher and Allen), and therefore in 1980, the main plots were split for crop (wheat cv. Timgalen, barley cv. Clipper) and nematicide treatment (nil, aldicarb). Barley (maximum yield 3.2 t/ha) tolerated the nematodes and responded in this dry year to the extra stored water accumulated with no tillage and stubble retention, but wheat (maximum yield 1.22 t/ha) did not. Nematicide increased wheat yields by 42%. The results from the changes to the Hermitage experiment in 1980 show the importance of considering root-lesion nematodes in interpreting results from long-term experiments involving wheat and in applying those results to farms. Control of root-lesion nematodes on farms by crop rotation and by growing tolerant and resistant wheat varieties is needed to obtain full yield benefits from improved tillage practices

    Twist Angle Tuning of Moir\ue9 Exciton Polaritons in van der Waals Heterostructures

    Get PDF
    Twisted atomically thin semiconductors are characterized by moir\ue9 excitons. Their optical signatures and selection rules are well understood. However, their hybridization with photons in the strong coupling regime for heterostructures integrated in an optical cavity has not been the focus of research yet. Here, we combine an excitonic density matrix formalism with a Hopfield approach to provide microscopic insights into moir\ue9 exciton polaritons. In particular, we show that exciton-light coupling, polariton energy, and even the number of polariton branches can be controlled via the twist angle. We find that these new hybrid light-exciton states become delocalized relative to the constituent excitons due to the mixing with light and higher-energy excitons. The system can be interpreted as a natural quantum metamaterial with a periodicity that can be engineered via the twist angle. Our study presents a significant advance in microscopic understanding and control of moir\ue9 exciton polaritons in twisted atomically thin semiconductors

    The modelling of spatial units (parcels) in the land administration domain model (LADM)

    Get PDF
    The Land Administration Domain Model (LADM) is under development within the Technical Committee 211 (TC211) of the International Organisation for Standardization (ISO) and identified as ISO 19152. Within the LADM classical cadastral concepts as “parcel” and “boundary” have been extended to be able to include spatial representations of overlapping tenures or claims and also multidimensional objects (3D and 2D/3D, combined with temporal dimensions). Furthermore, a series of new representations are possible apart from topologically well structured parcels (here called spatial units). Text based, sketch based, point based, line-based, polygon based, or topological based representations of spatial units are possible. The topological spatial units are defined by a consistent topological structure(with no gaps, overlaps or intersections), which is in contrast with a set of polygons, where a consistent topological structure is not guaranteed. A line-based spatial unit is represented by a collection of lines which may be collected from different sources or surveys. A point-based spatial unit contains only the coordinates of the unit’s reference point. A text based spatial unit is not represented by coordinates, but has a spatial unit description in words, e.g. the metes and bounds system (a spatial unit description in terms of distance, direction, and landmarks). All these spatial units may have a 3D representation, and a provision is made for a mixture of 2D and 3D spatial units to co-exist. A level is a collection of spatial units with a geometric or thematic coherence. The concept of level is related to the notion of “legal independence” from ‘Cadastre 2014’. This allows for the flexible introduction of spatial data from different sources and accuracies, including utility networks, buildings and other 3D spatial units, such as mining claims, or construction works. The paper explores the LADM spatial component, which is further based on ISO standards, combined with new concepts as “boundary face string” and partially unbounded primitives. Spatial profiles and the different spatial representations are used to demonstrate the flexibility of spatial representations of this domain model; for formal and non formal land administrations systems alike. The first trial implementation of the Queensland (Australia)Digital Cadastral Database (DCDB) for 2D parcel encoding using the line-based spatial profile will be discussed in detail, together with the polygon based spatial profile for the spatial units of the Portuguese land administration

    Solar Stereoscopy with STEREO/EUVI A and B spacecraft from small (6 deg) to large (170 deg) spacecraft separation angles

    Full text link
    We performed for the first time stereoscopic triangulation of coronal loops in active regions over the entire range of spacecraft separation angles (αsep6,43,89,127\alpha_{sep}\approx 6^\circ, 43^\circ, 89^\circ, 127^\circ, and 170170^\circ). The accuracy of stereoscopic correlation depends mostly on the viewing angle with respect to the solar surface for each spacecraft, which affects the stereoscopic correspondence identification of loops in image pairs. From a simple theoretical model we predict an optimum range of αsep22125\alpha_{sep} \approx 22^\circ-125^\circ, which is also experimentally confirmed. The best accuracy is generally obtained when an active region passes the central meridian (viewed from Earth), which yields a symmetric view for both STEREO spacecraft and causes minimum horizontal foreshortening. For the extended angular range of αsep6127\alpha_{sep}\approx 6^\circ-127^{\circ} we find a mean 3D misalignment angle of μPF2139\mu_{PF} \approx 21^\circ-39^\circ of stereoscopically triangulated loops with magnetic potential field models, and μFFF1521\mu_{FFF} \approx 15^\circ-21^\circ for a force-free field model, which is partly caused by stereoscopic uncertainties μSE9\mu_{SE} \approx 9^\circ. We predict optimum conditions for solar stereoscopy during the time intervals of 2012--2014, 2016--2017, and 2021--2023.Comment: Solar Physics, (in press), 22 pages, 9 figure

    Culture change in a professional sports team: Shaping environmental contexts and regulating power

    Get PDF
    Although high performing cultures are crucial for the enduring success of professional sport performance teams, theoretical and practical understanding of how they are established and sustained is lacking. To develop knowledge in this area, a case study was undertaken to examine the key mechanisms and processes of a successful culture change programme at English Rugby Union’s Leeds Carnegie. Exploring the change process from a 360 degree perspective, semi-structured interviews were conducted with team management, one specialist coach, six players, and the CEO. Analysed and explained through decentred theory, results revealed that culture change was effectively facilitated by team management: a) subtly and covertly shaping the physical, structural, and psychosocial context in which support staff and players made performance-impacting choices, and b) regulating the ‘to and fro’ of power which characterises professional sport performance teams. Decentred theory is also supported as an effective framework for culture change study

    Approaches to Styrenyl Building Blocks for the Synthesis of Polyene Xanthomonadin and its Analogues

    Get PDF
    A number of aryl building blocks for the synthesis of two xanthomonadin natural product pigments, as well as a related analogue, were accessed using a divergent hydroboration/bromoboration approach from a key alkynyl intermediate. A new approach towards substitution patterns around the ring was adopted following the isolation of an unexpected regioisomer from the bromination reaction. Potential coupling reactions onto these building blocks were explored, with a successful Sonogashira coupling performed on the key alkynyl intermediate, and with the key debrominated styrenyl boronate ester intermediate functionalised both by preliminary Suzuki–Miyaura coupling and by iododeboronation/Heck–Mizoroki coupling. Coupling reactions with brominated styrenyl intermediates proved much more challenging due to the instability of the intermediates to cross‐coupling, but some studies have shown promise

    Long range effects on the optical model of 6He around the Coulomb barrier

    Full text link
    We present an optical model (OM) analysis of the elastic scattering data of the reactions 6He+27Al and 6He+208Pb at incident energies around the Coulomb barrier. The bare part of the optical potential is constructed microscopically by means of a double folding procedure, using the Sao Paulo prescription without any renormalization. This bare interaction is supplemented with a Coulomb dipole polarization (CDP) potential, which takes into account the effect of the dipole Coulomb interaction. For this CDP potential, we use an analytical formula derived from the semiclassical theory of Coulomb excitation. The rest of the optical potential is parametrized in terms of Woods-Saxon shapes. In the 6He+208Pb case, the analysis confirms the presence of long range components, in agreement with previous works. Four-body Continuum-Discretized Coupled-Channels calculations have been performed in order to better understand the features of the optical potentials found in the OM analysis. This study searches to elucidate some aspects of the optical potential of weakly bound systems, such as the dispersion relation and the long range (attractive and absorptive) mechanisms.Comment: Accepted in Nucl. Phys. A; 26 pages, 8 figures, 6 tables

    Variations of the spectral index of dust emissivity from Hi-GAL observations of the Galactic plane

    Get PDF
    Original article can be found at: http://www.aanda.org/ Copyright The European Southern ObservatoryContext. Variations in the dust emissivity are critical for gas mass determinations derived from far-infrared observations, but also for separating dust foreground emission from the Cosmic Microwave Background (CMB). Hi-GAL observations allow us for the first time to study the dust emissivity variations in the inner regions of the Galactic plane at resolution below 1°. Aims. We present maps of the emissivity spectral index derived from the combined Herschel PACS 160 μm, SPIRE 250 μm, 350 μm, and 500 μm data, and the IRIS 100 μm data, and we analyze the spatial variations of the spectral index as a function of dust temperature and wavelength in the two science demonstration phase Hi-GAL fields, centered at l = 30° and l = 59°. Methods. Applying two different methods, we determine both dust temperature and emissivity spectral index between 100 and 500 μm, at an angular resolution (θ) of 4'. Results. Combining both fields, the results show variations of the emissivity spectral index in the range 1.8–2.6 for temperatures between 14 and 23 K. The median values of the spectral index are similar in both fields, i.e. 2.3 in the range 100–500 μm, while the median dust temperatures are equal to 19.1 K and 16.0 K in the l = 30° and l = 59° field, respectively. Statistically, we do not see any significant deviations in the spectra from a power law emissivity between 100 and 500 μm. We confirm the existence of an inverse correlation between the emissivity spectral index and dust temperature, found in previous analyses.Peer reviewe
    corecore