Dendrochronology and Deer Park Farms

This chapter examines some aspects of the environmental
context for the constructional activity observed at Deer
Park Farms (DPF). This can be done at several levels by
observing what dendrochronology suggests in terms of
environment and environmental change across the period
from around AD 500 to 1000. Looking at the broad sweep
of tree growth across the period, something not previously
attempted, we can make comparisons between tree
growth in Ireland and elsewhere in Europe. We can study
abrupt events in the records and draw on information
from other sources in an attempt to paint a picture of the
period against which to view the constructional activity
on the site itself. It is worth remarking that there is no
blueprint for this work. Most of the information used has
only recently been produced and it is largely independent
of conventional history.

Coordinated Control of DFIG and FSIG-based Wind Farms under Unbalanced Grid Conditions

This paper investigates the control and operation of doubly-fed induction generator (DFIG) and fixed-speed induction generator (FSIG) based wind farms under unbalanced grid conditions. A DFIG system model suitable for analyzing unbalanced operation is developed, and used to assess the impact of an unbalanced supply on DFIG and FSIG operation. Unbalanced voltage at DFIG and FSIG terminals can cause unequal heating on the stator windings, extra mechanical stresses and output power fluctuations. These problems are particularly serious for the FSIG-based wind farm without a power electronic interface to the grid. To improve the stability of a wind energy system containing both DFIG and FSIG based wind farms during network unbalance, a control strategy of unbalanced voltage compensation by the DFIG systems is proposed. The DFIG system compensation ability and the impact of transmission network impedance are illustrated. The simulation results implemented in Matlab/Simulink show that the proposed DFIG control system improves not only its own performance, but also the stability of the FSIG system with the same grid connection point during network unbalance.

Collective excitations of trapped Bose-Einstein condensates in the energy and time domains

A time-dependent method for calculating the collective excitation frequencies and densities of a trapped, inhomogeneous Bose-Einstein condensate with circulation is presented. The results are compared with time-independent solutions of the Bogoliubov-de Gennes equations. The method is based on time-dependent linear-response theory combined with spectral analysis of moments of the excitation modes of interest. The technique is straightforward to apply, extremely efficient in our implementation with parallel fast Fourier transform methods, and produces highly accurate results. For high dimensionality or low symmetry the time-dependent approach is a more practical computational scheme and produces accurate and reliable data. The method is suitable for general trap geometries, condensate flows and condensates permeated with defects and vortex structures.

Collective decoherence of cold atoms coupled to a Bose-Einstein condensate

We examine the time evolution of cold atoms (impurities) interacting with an environment consisting of a degenerate bosonic quantum gas. The impurity atoms differ from the environment atoms, being of a different species. This allows one to superimpose two independent trapping potentials, each being effective only on one atomic kind, while transparent to the other. When the environment is homogeneous and the impurities are confined in a potential consisting of a set of double wells, the system can be described in terms of an effective spin-boson model, where the occupation of the left or right well of each site represents the two (pseudo)-spin states. The irreversible dynamics of such system is here studied exactly, i.e. not in terms of a Markovian master equation. The dynamics of one and two impurities is remarkably different in respect of the standard decoherence of the spin-boson system. In particular, we show: (i) the appearance of coherence oscillations, (ii) the presence of super and subdecoherent states that differ from the standard ones of the spin-boson model, and (iii) the persistence of coherence in the system at long times. We show that this behaviour is due to the fact that the pseudospins have an internal spatial structure. We argue that collective decoherence also prompts information about the correlation length of the environment. In a one-dimensional (1D) configuration, one can change even more strongly the qualitative behaviour of the dephasing just by tuning the interaction of the bath.

Parish farms and the poor law: a response to unemployment in rural southern England, c.1815-1835

Finding a ‘solution’ for the seemingly intractable problem of unemployment in post-Napoleonic rural England was the Holy Grail for many vestries. Yet, whilst we know much about the depth and consequences of unemployment, parish-driven schemes to set the poor to work have been subjected to remarkably little in the way of systematic study. This paper focuses on one such policy that remains entirely obscure: parish farms, the hiring of pre-existing farms or fields by the parish on which to employ those out of work. Bearing a ‘family resemblance’ to allotments and other land-based attempts to alleviate poverty, parish farms were unique in that they were managed in all regards by the parish and were an employment strategy as opposed to a scheme to supplement the incomes of the poor. Whilst the archive of parish farms is often frustratingly opaque, it is shown that before they were effectively outlawed by the passing of the New Poor Law, many southern parishes, especially in the Weald of Kent and Sussex, adopted the scheme, occasionally with great success.

Temporal distribution of porcine circovirus 2 genogroups recovered from postweaning multisystemic wasting syndrome-affected and -nonaffected farms in Ireland and Northern Ireland

Porcine circovirus type 2 (PCV2) is now recognized as the essential infectious component of porcine postweaning multisystemic wasting syndrome (PMWS). PMWS was first recognized in high-status, specific pathogen-free pigs in Canada in 1991 and is now an economically important disease that affects the swine industry around the world. Recently, reports of genomic studies on PCV2 viruses indicated that 2 distinctive genogroups of PCV2 exist.(4,10) This report involves the results of a study on the distribution of predominant PCV2 genogroups recovered from samples taken from PMWS-affected and PMWS-nonaffected farms on the island of Ireland over a 9-year period and the results of a study on PCV2 genogroup recovery from fecal samples taken from a farm in Northern Ireland from 2003 to 2005 that was first diagnosed as PMWS positive in August 2005. The results indicate that, although at least 2 distinct genogroups of PCV2 have been circulating on pig farms on the island of Ireland, there does not appear to be a direct relationship between infection with these different genogroups of PCV2 and the development of PMWS.