Organic farming and agri-environmental stewardship schemes in Devon

A postal survey was undertaken in North Devon looking at entry into England Rural Development Programme (ERDP) environmental schemes in relation to farming system and markets. The main survey was based in and around the North Devon Biosphere reserve. Significantly more farms replied who had Countryside Stewardship (CSS) agreements than from those who were not in the scheme. There was a greater likelihood of small farms joining CSS as were beef, sheep and cereal farms compared with dairy farms. A greater percent of organic farms had CSS agreements compared with the conventional farms. A smaller telephone survey in a CSS target area in South Devon was also undertaken which confirmed these results. Those farms with CSS agreements were more likely to have joined or be joining the new agri-environmental schemes

Spectral Properties of H-Reflex Recordings After an Acute Bout of Whole-Body Vibration

Although research supports the use of whole-body vibration (WBV) to improve neuromuscular performance, the mechanisms for these improvements remain unclear. The purpose of this study was to identify the effect ofWBV on the spectral properties of electrically evoked H-reflex recordings in the soleus (SOL) muscle. The H-reflex recordings were measured in the SOL muscle of 20 participants before and after a bout of WBV. The H-reflexes were evoked every 15 seconds for 150 seconds after WBV. A wavelet procedure was used to extract spectral data, which were then quantified with a principle components analysis. Resultant principle component scores were used for statistical analysis. The analysis extracted 1 principle component associated with the intensity of the myoelectric spectra and 1 principle component associated with the frequency. The scores of the principle component that were related to the myoelectric intensity were smaller at 30 and 60 milliseconds after WBV than before WBV. The WBV transiently decreased the intensity of myoelectric spectra during electrically evoked contractions, but it did not influence the frequency of the spectra. The decrease in intensity likely indicates a smaller electrically evoked muscle twitch response, whereas the lack of change in frequency would indicate a similar recruitment pattern of motor units before and after WBV

Paired chiral spin liquid with a Fermi surface in S=1 model on the triangular lattice

Motivated by recent experiments on Ba3NiSb2O9, we investigate possible quantum spin liquid ground states for spin S=1 Heisenberg models on the triangular lattice. We use Variational Monte Carlo techniques to calculate the energies of microscopic spin liquid wave functions where spin is represented by three flavors of fermionic spinon operators. These energies are compared with the energies of various competing three-sublattice ordered states. Our approach shows that the antiferromagnetic Heisenberg model with biquadratic term and single-ion anisotropy does not have a low-temperature spin liquid phase. However, for an SU(3)-invariant model with sufficiently strong ring-exchange terms, we find a paired chiral quantum spin liquid with a Fermi surface of deconfined spinons that is stable against all types of ordering patterns we considered. We discuss the physics of this exotic spin liquid state in relation with the recent experiment and suggest new ways to test this scenario.Comment: 18 pages, 6 figures; replaced with published versio

Three-geometry and reformulation of the Wheeler-DeWitt equation

A reformulation of the Wheeler-DeWitt equation which highlights the role of gauge-invariant three-geometry elements is presented. It is noted that the classical super-Hamiltonian of four-dimensional gravity as simplified by Ashtekar through the use of gauge potential and densitized triad variables can furthermore be succinctly expressed as a vanishing Poisson bracket involving three-geometry elements. This is discussed in the general setting of the Barbero extension of the theory with arbitrary non-vanishing value of the Immirzi parameter, and when a cosmological constant is also present. A proposed quantum constraint of density weight two which is polynomial in the basic conjugate variables is also demonstrated to correspond to a precise simple ordering of the operators, and may thus help to resolve the factor ordering ambiguity in the extrapolation from classical to quantum gravity. Alternative expression of a density weight one quantum constraint which may be more useful in the spin network context is also discussed, but this constraint is non-polynomial and is not motivated by factor ordering. The article also highlights the fact that while the volume operator has become a preeminient object in the current manifestation of loop quantum gravity, the volume element and the Chern-Simons functional can be of equal significance, and need not be mutually exclusive. Both these fundamental objects appear explicitly in the reformulation of the Wheeler-DeWitt constraint.Comment: 10 pages, LaTeX fil

Differential Geometry of Group Lattices

In a series of publications we developed "differential geometry" on discrete sets based on concepts of noncommutative geometry. In particular, it turned out that first order differential calculi (over the algebra of functions) on a discrete set are in bijective correspondence with digraph structures where the vertices are given by the elements of the set. A particular class of digraphs are Cayley graphs, also known as group lattices. They are determined by a discrete group G and a finite subset S. There is a distinguished subclass of "bicovariant" Cayley graphs with the property that ad(S)S is contained in S. We explore the properties of differential calculi which arise from Cayley graphs via the above correspondence. The first order calculi extend to higher orders and then allow to introduce further differential geometric structures. Furthermore, we explore the properties of "discrete" vector fields which describe deterministic flows on group lattices. A Lie derivative with respect to a discrete vector field and an inner product with forms is defined. The Lie-Cartan identity then holds on all forms for a certain subclass of discrete vector fields. We develop elements of gauge theory and construct an analogue of the lattice gauge theory (Yang-Mills) action on an arbitrary group lattice. Also linear connections are considered and a simple geometric interpretation of the torsion is established. By taking a quotient with respect to some subgroup of the discrete group, generalized differential calculi associated with so-called Schreier diagrams are obtained.Comment: 51 pages, 11 figure