Monthly economic review: August 2014

Summary: The Monthly Economic Review is an overview of the New Zealand economy. It includes the latest data on New Zealand’s economic growth, unemployment, inflation, merchandise trade and balance of payments figures, along with certain financial data (such as the Reserve Bank’s official cash rate). The unemployment rate, economic growth and central bank interest rates for several of our main OECD trading partners are also included. Each publication highlights a specific topic of interest. The Monthly Economic Review is produced eleven times per year

What are the perceived benefits of an adoption support package using video interaction guidance with prospective adopters? An exploratory study

"An adoption support package using video interaction guidance (VIG) with a focus on child-led play was provided by two educational psychologists to eight prospective adopters with whom a pre-school child had been placed recently. Piloted with the encouragement of social workers, it promoted working in partnership with parents to share successes and address concerns. VIG is an attachment-based coaching method, which works collaboratively on client-chosen goals for improved relationships, building on their existing strengths and insights.

The mirror box illusion : Manipulation of visual information during bimanual coordination in children with and without spastic hemiparetic cerebral palsy

Savelsbergh, G.J.P. [Promotor]Ledebt, A. [Copromotor]Deconinck, F.J.A. [Copromotor

Representations of the subject ‘woman’ and the politics of abortion : an analysis of South African newspaper articles from 1978 to 2005

A key element in cultural and gender power relations surrounding abortion is how women who undergo an abortion are represented in public talk. We analyse how women were named and positioned, and the attendant constructions of abortion, in South African newspaper articles on abortion from 1978 to 2005, a period during which there were radical political and legislative shifts. The name ‘woman’ was the most frequently used (70% of articles) followed by ‘girl/teenager/child’ (25%), ‘mother’ (25%), ‘patient’ (11%) and ‘minor’ (6%). The subject positionings enabled by these names were dynamic and complex and were interwoven with the localised, historical politics of abortion. The ‘innocent mother’ and the bifurcated ‘patient’ (woman/foetus) positionings were invoked in earlier epochs to promote abortion under medical conditions. The ‘dangerous mother’ and woman as ‘patient’ positionings were used more frequently under liberal abortion legislation to oppose and to advocate for abortion, respectively. The positioning of the ‘girl/teenager/child’ as dependent and vulnerable was used in contradictory ways, both to oppose abortion and to argue for a liberalisation of restrictive legislation, depending on the attendant construction of abortion. The neutral naming of ‘woman’ was, at times, linked to the liberal imaginary of ‘choice’

Experimental evidence of the benefit of wild flower strips to crop pollination

Wild bees provide a free and potentially diverse ecosystem service to farmers growing pollinator dependent crops. Whilst many crops benefit from insect pollination, soft fruit crops, including strawberries are commonly dependent on this ecosystem service to produce viable fruit. However, as a result of intensive farming practices and declining pollinator populations, farmers are increasingly turning to commercially reared bees to ensure that crops are adequately pollinated throughout the season. Wildflower strips are a commonly used measure aimed at the conservation of wild pollinators. It has been suggested that commercial crops may also benefit from the presence of sown wild flowers however, the efficacy and economic benefits of sowing flower strips for crops has been little investigated. Here we test whether wildflower strips increase the number of visits to adjacent commercial strawberry crops by wild pollinators. This was quantified by experimentally sowing wildflower strips approximately 20 meters away from the crop and recording the number of pollinator visits to crops with, and without, flower strips. Between June and August 2013 we walked 292 crop transects at six farms in Scotland, recording a total of 3,102 pollinators. On average, the frequency of pollinator visits was 25% higher for crops with adjacent flower strips compared to those without, with bumblebees (Bombus spp.) accounting for 62% of all pollinators observed. This effect was independent of other (potentially important) confounding effects, such as the number of flowers on the crop, date and temperature. Whilst commercial bees may still be required early in the season, this study provides evidence that soft fruit farmers can increase the number of pollinators that visit their crops by sowing inexpensive flower seed mixes nearby. The cost of planting these strips was substantially lower than the annual cost of purchasing commercial bumblebees, with the added advantage that this management option has the potential to increase and sustain pollinator populations over time

The effect of a new drag-law parameterization on ice shelf water plume dynamics

A drag law accounting for Ekman rotation adjacent to a flat, horizontal bou ndary is proposed for use in a plume model that is written in terms of the depth-mean velocity. The drag l aw contains a variable turning angle between the mean velocity and the drag imposed by the turbulent bound ary layer. The effect of the variable turning angle in the drag law is studied for a plume of ice shelf wat er (ISW) ascending and turning beneath an Antarctic ice shelf with draft decreasing away from the groundi ng line. As the ISW plume ascends the sloping ice shelf–ocean boundary, it can melt the ice shelf, wh ich alters the buoyancy forcing driving the plume motion. Under these conditions, the typical turning ang le is of order 10° over most of the plume area for a range of drag coefficients (the minus sign arises for th e Southern Hemisphere). The rotation of the drag with respect to the mean velocity is found to be signifi cant if the drag coefficient exceeds 0.003; in this case the plume body propagates farther along and across the b ase of the ice shelf than a plume with the standard quadratic drag law with no turning angle

Continuum sea ice rheology determined from subcontinuum mechanics

[1] A method is presented to calculate the continuum-scale sea ice stress as an imposed, continuum-scale strain-rate is varied. The continuum-scale stress is calculated as the area-average of the stresses within the floes and leads in a region (the continuum element). The continuum-scale stress depends upon: the imposed strain rate; the subcontinuum scale, material rheology of sea ice; the chosen configuration of sea ice floes and leads; and a prescribed rule for determining the motion of the floes in response to the continuum-scale strain-rate. We calculated plastic yield curves and flow rules associated with subcontinuum scale, material sea ice rheologies with elliptic, linear and modified Coulombic elliptic plastic yield curves, and with square, diamond and irregular, convex polygon-shaped floes. For the case of a tiling of square floes, only for particular orientations of the leads have the principal axes of strain rate and calculated continuum-scale sea ice stress aligned, and these have been investigated analytically. The ensemble average of calculated sea ice stress for square floes with uniform orientation with respect to the principal axes of strain rate yielded alignment of average stress and strain-rate principal axes and an isotropic, continuum-scale sea ice rheology. We present a lemon-shaped yield curve with normal flow rule, derived from ensemble averages of sea ice stress, suitable for direct inclusion into the current generation of sea ice models. This continuum-scale sea ice rheology directly relates the size (strength) of the continuum-scale yield curve to the material compressive strength

Micromechanics of sea ice frictional slip from test basin scale experiments

We have conducted a series of high-resolution friction experiments on large floating saline ice floes in an environmental test basin. In these experiments, a central ice floe was pushed between two other floes, sliding along two interfacial faults. The frictional motion was predominantly stick–slip. Shear stresses, normal stresses, local strains and slip displacement were measured along the sliding faults, and acoustic emissions were monitored. High-resolution measurements during a single stick–slip cycle at several positions along the fault allowed us to identify two phases of frictional slip: a nucleation phase, where a nucleation zone begins to slip before the rest of the fault, and a propagation phase when the entire fault is slipping. This is slip-weakening behaviour. We have therefore characterized what we consider to be a key deformation mechanism in Arctic Ocean dynamics. In order to understand the micromechanics of sea ice friction, we have employed a theoretical constitutive relation (i.e. an equation for shear stress in terms of temperature, normal load, acceleration, velocity and slip displacement) derived from the physics of asperity–asperity contact and sliding (Hatton et al. 2009 Phil. Mag. 89, 2771–2799 (doi:10.1080/14786430903113769)). We find that our experimental data conform reasonably with this frictional law once slip weakening is introduced. We find that the constitutive relation follows Archard's law rather than Amontons' law, with Embedded Image (where τ is the shear stress and σn is the normal stress) and n = 26/27, with a fractal asperity distribution, where the frictional shear stress, τ = ffractal Tmlws, where ffractal is the fractal asperity height distribution, Tml is the shear strength for frictional melting and lubrication and ws is the slip weakening. We can therefore deduce that the interfacial faults failed in shear for these experimental conditions through processes of brittle failure of asperities in shear, and, at higher velocities, through frictional heating, localized surface melting and hydrodynamic lubrication