34,389 research outputs found
A new model for procuring e-books
This paper draws on a recent ground-breaking tender for e-books for higher education libraries in the UK. The strategy for the tender was informed by standard procurement practice and by the experience of acquiring other e-resources, particularly journals under the so-called big deal. Both are examined as background to the discussion of e-books in general and the tender in particular
Nitrous oxide emissions from organic farming: the importance of well-timed ley cultivation
The period after ploughing of grass-clover within a ley-arable rotation is when nitrogen accumulated during ley cropping is most vulnerable to loss. I investigated how date of ploughing and date of cessation of grazing before ploughing influenced losses of nitrogen as nitrous oxide during establishment of the first cereal crop. Crop nitrogen uptake was also assessed. Nitrous oxide (N2O) emissions in the 1-2 month period after autumn or spring ploughing or after sowing were typically between 20 and 150 g N ha-1 day-1 and increased with temperature and rainfall. Tillage and sowing operations on previously ploughed soil stimulated N2O emissions even several months after ploughing. Cumulative N2O emissions were highest (~8 kg ha-1 over 17 months) after late cessation of grazing and late ploughing, and lowest (~5.5 kg ha-1) after early cessation of grazing and early ploughing. The optimum time of ploughing appears to be midwinter when the cold restricts nitrogen mineralisation, but sufficient nitrogen subsequently becomes available for early spring crop growth and satisfactory N offtake. Restricting tillage operations to cool conditions should help to reduce N2O emissions. However, the soil should also be dry enough to reduce the risk of damage to soil structure
Isostaticity in two dimensional pile of rigid disks
We study the static structure of piles made of polydisperse disks in the
rigid limit with and without friction using molecular dynamic simulations for
various elasticities of the disks and pile preparation procedures. The
coordination numbers are calculated to examine the isostaticity of the pile
structure. For the frictionless pile, it is demonstrated that the coordination
number converges to 4 in the rigid limit, which implies that the structure of
rigid disk pile is isostatic. On the other hand, for the frictional case with
the infinite friction constant, the coordination number depends on the
preparation procedure of the pile, but we find that the structure becomes very
close to isostatic with the coordination number close to 3 in the rigid limit
when the pile is formed through the process that tends to make a pile of random
configuration.Comment: 3 pages, 3 figures, Submitted to J. Phys. Soc. Jp
Thermodynamics of the deposition of complex waxes and asphaltenes in crude oil
Peer reviewedPublisher PD
Scale Setting for Beyond Leading Order
We present a general procedure for applying the scale-setting prescription of
Brodsky, Lepage and Mackenzie to higher orders in the strong coupling constant
\alphas. In particular, we show how to apply this prescription when the
leading coefficient or coefficients in a series in \alphas are anomalously
small. We give a general method for computing an optimum scale numerically,
within dimensional regularization, and in cases when the coefficients of a
series are known. We find significant corrections to the scales for , , , and the ratios of
the quark pole to \MSbar and lattice bare masses.Comment: Lattice 2000 (Perturbation Theory), 5 pages, 7 figures, LaTe
Transonic stability and control characteristics of a 0.015 scale model 69-0 of the space shuttle orbiter with forebody RSI modification in the NASA/LaRC 8 foot TPT (LA72)
Tests were conducted in the NASA/LaRC 8 foot transonic wind tunnel from March 26 through 31, 1976. The model was a 0.015 scale SSV Orbiter with forebody modifications to simulate slight reductions in the reusable surface insulation (RSI) thickness. Six component aerodynamic force and moment data were obtained at Mach numbers from 0.35 to 1.20 over an angle of attack range from -2 deg to 20 deg at sideslip angles of 0 deg and 5 deg
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