Soil organic carbon and root distribution in a temperate arable agroforestry system

Aim To determine, for arable land in a temperate area, the effect of tree establishment and intercropping treatments, on the distribution of roots and soil organic carbon to a depth of 1.5 m. Methods A poplar (Populus sp.) silvoarable agroforestry experiment including arable controls was established on arable land in lowland England in 1992. The trees were intercropped with an arable rotation or bare fallow for the first 11 years, thereafter grass was allowed to establish. Coarse and fine root distributions (to depths of up to 1.5 m and up to 5 m from the trees) were measured in 1996, 2003, and 2011. The amount and type of soil carbon to 1.5 m depth was also measured in 2011. Results The trees, initially surrounded by arable crops rather than fallow, had a deeper coarse root distribution with less lateral expansion. In 2011, the combined length of tree and understorey vegetation roots was greater in the agroforestry treatments than the control, at depths below 0.9 m. Between 0 and 1.5 m depth, the fine root carbon in the agroforestry treatment (2.56 t ha-1) was 79% greater than that in the control (1.43 t ha-1). Although the soil organic carbon in the top 0.6 m under the trees (161 t C ha-1) was greater than in the control (142 t C ha-1), a tendency for smaller soil carbon levels beneath the trees at lower depths, meant that there was no overall tree effect when a 1.5 m soil depth was considered. From a limited sample, there was no tree effect on the proportion of recalcitrant soil organic carbon. Conclusions The observed decline in soil carbon beneath the trees at soil depths greater than 60 cm, if observed elsewhere, has important implication for assessments of the role of afforestation and agroforestry in sequestering carbon

A Deformable Model for Magnetic Vortex Pinning

A two-parameter analytical model of the magnetic vortex in a thin disk of soft magnetic material is constructed. The model is capable of describing the change in evolution of net vortex state magnetization and of core position when the vortex core interacts with a magnetic pinning site. The model employs a piecewise, physically continuous, magnetization distribution obtained by the merger of two extensively used one-parameter analytical models of the vortex state in a disk. Through comparison to numerical simulations of ideal disks with and without pinning sites, the model is found to accurately predict the magnetization, vortex position, hysteretic transitions, and 2-D displacement of the vortex in the presence of pinning sites. The model will be applicable to the quantitative determination of vortex pinning energies from measurements of magnetization.Comment: 27 pages, 7 figures, including supplementary information, ancillary files:3 supplementary movie

Scaling Solutions to 6D Gauged Chiral Supergravity

We construct explicitly time-dependent exact solutions to the field equations of 6D gauged chiral supergravity, compactified to 4D in the presence of up to two 3-branes situated within the extra dimensions. The solutions we find are scaling solutions, and are plausibly attractors which represent the late-time evolution of a broad class of initial conditions. By matching their near-brane boundary conditions to physical brane properties we argue that these solutions (together with the known maximally-symmetric solutions and a new class of non-Lorentz-invariant static solutions, which we also present here) describe the bulk geometry between a pair of 3-branes with non-trivial on-brane equations of state.Comment: Contribution to the New Journal of Physics focus issue on Dark Energy; 28 page

Multi-Throat Brane Inflation

We present a scenario where brane inflation arises more generically. We start with D3 and anti-D3-branes at the infrared ends of two different throats. This setup is a natural consequence of the assumption that in the beginning we have a multi-throat string compactification with many wandering anti-D3-branes. A long period of inflation is triggered when D3-branes slowly exit the highly warped infrared region, under a potential generically arising from the moduli stabilization. In this scenario, the usual slow-roll conditions are not required, and a large warping is allowed to incorporate the Randall-Sundrum model.Comment: 11 pages; v3: minor revision, PRD versio

D-Brane Dynamics and NS5 Rings

We consider the classical motion of a probe D-brane moving in the background geometry of a ring of NS5 branes, assuming that the latter are non-dynamical. We analyse the solutions to the Dirac-Born-Infield (DBI) action governing the approximate dynamics of the system. In the near horizon (throat) approximation we find several exact solutions for the probe brane motion. These are compared to numerical solutions obtained in more general cases. One solution of particular interest is when the probe undergoes oscillatory motion through the centre of the ring (and perpendicular to it). By taking the ring radius sufficiently large, this solution should remain stable to any stringy corrections coming from open-strings stretching between the probe and the NS5-branes along the ring.Comment: 17 pages, Latex, 8 figures; References adde

Systematics of Moduli Stabilization, Inflationary Dynamics and Power Spectrum

We study the scalar sector of type IIB superstring theory compactified on Calabi-Yau orientifolds as a place to find a mechanism of inflation in the early universe. In the large volume limit, one can stabilize the moduli in stages using perturbative method. We relate the systematics of moduli stabilization with methods to reduce the number of possible inflatons, which in turn lead to a simpler inflation analysis. Calculating the order-of-magnitude of terms in the equation of motion, we show that the methods are in fact valid. We then give the examples where these methods are used in the literature. We also show that there are effects of non-inflaton scalar fields on the scalar power spectrum. For one of the two methods, these effects can be observed with the current precision in experiments, while for the other method, the effects might never be observable.Comment: 20 pages, JHEP style; v.2 and v.3: typos fixed, discussion and references adde

Integrated out-of-hours care arrangements in England: observational study of progress towards single call access via NHS Direct and impact on the wider health system

Objectives: To assess the extent of service integration achieved within general practice cooperatives and NHS Direct sites participating in the Department of Health’s national “Exemplar Programme” for single call access to out-of-hours care via NHS Direct. To assess the impact of integrated out-of-hours care arrangements upon general practice cooperatives and the wider health system (use of emergency departments, 999 ambulance services, and minor injuries units). Design: Observational before and after study of demand, activity, and trends in the use of other health services. Setting: Thirty four English general practice cooperatives with NHS Direct partners (“exemplars”) of which four acted as “case exemplars”. Also 10 control cooperatives for comparison. Main Outcome Measures: Extent of integration achieved (defined as the proportion of hours and the proportion of general practice patients covered by integrated arrangements), patterns of general practice cooperative demand and activity and trends in use of the wider health system in the first year. Results: Of 31 distinct exemplars 21 (68%) integrated all out-of-hours call management by March 2004. Nine (29%) established single call access for all patients. In the only case exemplar where direct comparison was possible, cooperative nurse telephone triage before integration completed a higher proportion of calls with telephone advice than did NHS Direct afterwards (39% v 30%; p<0.0001). The proportion of calls completed by NHS Direct telephone advice at other sites was lower. There is evidence for transfer of demand from case exemplars to 999 ambulance services. A downturn in overall demand for care seen in two case exemplars was also seen in control sites. Conclusion: The new model of out-of-hours care was implemented in a variety of settings across England by new partnerships between general practice cooperatives and NHS Direct. Single call access was not widely implemented and most patients needed to make at least two telephone calls to contact the service. In the first year, integration may have produced some reduction in total demand, but this may have been accompanied by shifts from one part of the local health system to another. NHS Direct demonstrated capability in handling calls but may not currently have sufficient capacity to support national implementation