8,554 research outputs found
Modelling predicts that heat stress and not drought will limit wheat yield in Europe
Global warming is characterised by shifts in weather patterns and increases in extreme weather events. New crop cultivars with specific physiological traits will therefore be required if climate change is not to result in losses of yield and food shortages. However, the intrinsic uncertainty of climate change predictions poses a challenge to plant breeders and crop scientists who have limited time and resources and must select the most appropriate traits for improvement. Modelling is, therefore, a powerful tool to identify future threats to crop production and hence targets for improvement. Wheat is the most important crop in temperate zones, including Europe, and is the staple food crop for many millions of humans and their livestock. However, its production is highly sensitive to environmental conditions, with increased temperature and incidence of drought associated with global warming posing potential threats to yield in Europe. We have therefore predicted the future impacts of these environmental changes on wheat yields using a wheat simulation model combined with climate scenarios based on fifteen global climate models from the IPCC AR4 multi-model ensemble. Despite the lower summer precipitation predicted for Europe, the impact of drought on wheat yields is likely to be smaller than at present, because the warmer conditions will result in earlier maturation before drought becomes severe later in the summer. By contrast, the probability of heat stress around flowering is predicted to increase significantly which is likely to result in considerable yield losses for heat sensitive wheat cultivars commonly grown in north Europe. Breeding strategies should therefore focus on the development of wheat varieties which are tolerant to high temperature around flowering, rather than on developing varieties resistant to drought which may be required for other parts of the world
Taxing the "Family" in the Individual Income Tax
In this paper we examine international practices in the ways in which the individual income tax is applied to families, focusing upon country practices in OECD countries. We find that countries differ significantly in their taxation of the family, but that the dominant practice is the choice of the individual rather than the family as the unit of taxation. We also calculate the income tax consequences for "representative" taxpayers across these countries, and find that the differences in taxes between singles and married couples can often be quite large. We conclude that choosing the individual as the tax unit is likely to represent the most equitable approach to income taxation, especially given the increasing complexity of family units in modern societies
Doubly virtual Compton scattering and the beam normal spin asymmetry
We construct an invariant basis for Compton scattering with two virtual
photons (VVCS). The basis tensors are chosen to be gauge invariant and
orthogonal to each other. The properties of the corresponding 18 invariant
amplitudes are studied in detail. We consider the special case of elastic VVCS
with the virtualities of the initial and final photons equal. The invariant
basis for VVCS in this orthogonal form does not exist in the literatur. We
furthermore use this VVCS tensor for a calculation of the beam normal spin
asymmetry in the forward kinematics. For this, we relate the invariant
amplitudes to the helicity amplitudes of the VVCS reaction. The imaginary parts
of these latter are related to the inclusive cross section by means of the
optical theorem. We use the phenomenological value of the transverse cross
section mbarn and the Callan-Gross relation which relates the
longitudinal cross section to the transverse one. The result of the
calculation agrees with an existing calculation and predicts the negative
values of the asymmetry of the order of 4-6 ppm in the energy range from
6 to 45 ppm and for very forward angles.Comment: 13 pages, 2 figures, revtex, submitted to Phys. Rev. C; new version:
two figures added, typos correcte
Rotational and rotationless states of weakly-bound molecules
By making use of the quantization rule of Raab and Friedrich [P. Raab and H.
Friedrich, Phys. Rev. A 78, 022707 (2008)], we derive simple and accurate
formulae for the number of rotational states supported by a weakly-bound
vibrational level of a diatomic molecule and the rotational constants of any
such levels up to the threshold, and provide a criterion for determining
whether a given weakly-bound vibrational level is rotationless. The results
depend solely on the long-range part of the molecular potential and are
applicable to halo molecules.Comment: slightly corrected version, 4 pages, 1 figure, 3 table
Boost the Impact of Continuous Formal Verification in Industry
Software model checking has experienced significant progress in the last two
decades, however, one of its major bottlenecks for practical applications
remains its scalability and adaptability. Here, we describe an approach to
integrate software model checking techniques into the DevOps culture by
exploiting practices such as continuous integration and regression tests. In
particular, our proposed approach looks at the modifications to the software
system since its last verification, and submits them to a continuous formal
verification process, guided by a set of regression test cases. Our vision is
to focus on the developer in order to integrate formal verification techniques
into the developer workflow by using their main software development
methodologies and tools.Comment: 7 page
Mutual Phase Locking of Very Nonidentical Spin Torque Nanooscillators via Spin Wave Interaction
In this paper the mutual phase locking theory of very nonidentical
spin-torque nanooscillators, which is based on the Slavin-Tiberkevich model,
considering the theory of nonlinear oscillations, is developed. Using
generalized Adler equation we calculate phase-locking region of the system with
spinwave coupling in the parameter plane - distance between nanocontacts and
radii difference. We describe trajectories of such a system in the phase space
and show the effect of a broadband synchronization. We introduce a
generalization of this approach to the ensembles of spin-torque nanooscillatorsComment: 6 pages, 2 figure
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