28,012 research outputs found

    Remarks on Form Factor Bounds

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    Improved model independent upper bounds on the weak transition form factors are derived using inclusive sum rules. Comparison of the new bounds with the old ones is made for the form factors h_{A_1} and h_V in B -> D* decays.Comment: 8 pages, 2 figures, title changed and typos corrected for journal publicatio

    Predicting malting barley protein concentration

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    The preferred grain protein concentration (CP) of malting barley is 10.5-11.0%, but 9.5-11.5% is acceptable. It is a challenge for farmers to achieve this target with crops grown in heterogeneous fields and exposed to fluctuating weather conditions. There are also economic and environmental reasons to balance the supply of nutrients to plant requirements. This forms the basis for precision agriculture, where barley has received limited attention. The key factor for precision agriculture in malting barley is the ability to predict CP from early observations of the crop so as to control a second fertiliser application. This thesis investigates the possibility of predicting malting barley grain CP at an early stage of development and of using a second fertilisation application during growth for total nitrogen (N) adjustment. Three experiments were conducted. The first consisted of eleven field trials (1992-1994) and was used to compare broadcasting/harrowing and combi-drilling for applying full-rate fertiliser at sowing using two types of fertilisers; pure N and one also containing phosphorus (NP). The second experiment consisted of sixteen fertiliser field trials (2001-2003) and was used to examine the possibility of postponing the decision on total N. The third consisted of three evenly fertilised fields (2002-2004). In experiments 2 and 3, canopy reflectance was measured at developmental stages BBCH 32, 45 and 69. Soil macronutrients, organic matter and mechanical composition were analysed in all ex-periments. Malting barley yield was higher when fertiliser was combi-drilled into the soil and when NP fertiliser was used. Grain CP was predicted in the field (R2adj = 0.73) from soil electrical conductivity (SECa), the canopy reflection-based vegetation index (VI) TCARI/OSAVI estimated at BBCH 32 and the sum of daily maximum temperatures during anthesis and grain filling (STS). In the fertilisation trials, CP was predicted (R2adj = 0.83) by sowing day number and the VI TCARI evaluated together with solar angle at measurement. Grain yield was independent, and grain CP almost independent, of whether all fertiliser was applied at sowing or divided between sowing and BBCH 32

    Land use patterns and access in Mexico City

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    The problem of distribution of land uses in urban space in Latin American cities has been examined under different perspectives. Most authors tend to model patterns of population and land use as a consequence of social and economic processes alone, failing to address urban space as an intrinsic variable. Instead, the theory of cities as movement economies argues that land use patterns are influenced by movement flows, which are in turn strongly affected by the urban grid. As a result, land uses such as retail would seek highly accessible locations to take advantage of such flows while residential uses would avoid them. However, space syntax techniques traditionally used to point out this relationship do not seem to reveal it so easily in non-organic cities like Mexico. This paper addresses the relationship between patterns of accessibility and land use in the first ring of Mexico City as a spatial strategy. A new functional description of the city where plots are nodes connected to flows that represent the street network is adopted. This model enables us to measure accessibility at the level of plots. Following this, we focus on the occurrence of land use types in highly or low accessible locations using cumulative distribution functions. If the distribution of land uses was random, the proportion of land use types would be more or less uniform throughout the area. It is shown that the relationship between accessibility and land use is not linear and is guided by movement economy forces. It is suggested that the understanding of these relationship is key to plan for sustainable growth objectively

    Bosonic String and String Field Theory: a solution using Ultradistributions of Exponential Type

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    In this paper we show that Ultradistributions of Exponential Type (UET) are appropriate for the description in a consistent way string and string field theories. A new Lagrangian for the closed string is obtained and shown to be equivalent to Nambu-Goto's Lagrangian. We also show that the string field is a linear superposition of UET of compact support CUET). We evaluate the propagator for the string field, and calculate the convolution of two of them.Comment: 30 page

    Report on geophysical and geological surveys at Blackmount, Argyllshire

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    Blackmount, on the southern fringe of Rannoch Moor is largely drift covered but, where exposed, the underlying Precambrian Moine psammite contains granitic veins which probably stem from the adjacent (Devonian) Moor of Rannoch granite. These veins are generally pyritiferous and, at one locality, carry small amounts of molybdenite. Blackmount is also traversed by the Ericht-Laidon Fault, which, in theory, and by analogy with a similar fault to the south-east (the Tyndrum Fault), could be a site of significant sulphide mineralisation. Magnetic, very low frequency electro-magnetic (VLF EM), slingram EM and induced polarisation measurements carried out in the area of the veins suggest that the mineralisation has little or no lateral or depth continuation. Similar surveys were successful in locating the Ericht-Laidon Fault beneath drift, but suggest no associated mineralisation down to the\ud greatest depth investigated

    The value of forest ecosystems

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    Lie symmetries of Einstein's vacuum equations in N dimensions

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    We investigate Lie symmetries of Einstein's vacuum equations in N dimensions, with a cosmological term. For this purpose, we first write down the second prolongation of the symmetry generating vector fields, and compute its action on Einstein's equations. Instead of setting to zero the coefficients of all independent partial derivatives (which involves a very complicated substitution of Einstein's equations), we set to zero the coefficients of derivatives that do not appear in Einstein's equations. This considerably constrains the coefficients of symmetry generating vector fields. Using the Lie algebra property of generators of symmetries and the fact that general coordinate transformations are symmetries of Einstein's equations, we are then able to obtain all the Lie symmetries. The method we have used can likely be applied to other types of equations

    'Hexagon-type' photonic crystal slabs based on SOI

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    In this paper we discuss the design of a novel category of photonic crystal slabs (PCS) and as an example, we consider structures based on SOI wafers. Fabrication issues related to lithographic accuracy are addressed, too. The geometry consists in a triangular lattice of hexagons having their symmetry axes rotated with respect to the lattice.We show that the mirror-symmetric 'hexagon-type' PCS with air claddings can have an absolute (i.e. polarization independent) gap in guided modes with normalized width of approximately 10%. This gap, although reduced to about 4%, is still present in an asymmetric geometry, when the under-cladding is a silicon oxide layer with deeply etched holes
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