Identifying the potential loss of monitoring wells using an uncertainty analysis

From the mid-1940s through the 1980s, large volumes of waste water were discharged at the Hanford Site in southeastern Washington State, causing a large-scale rise (>20 m) in the water table. When waste water discharges ceased in 1988, ground water mounds began to dissipate. This caused a large number of wells to go dry and has made it difficult to monitor contaminant plume migration. To identify monitoring wells that will need replacement, a methodology has been developed using a first-order uncertainty analysis with UCODE, a nonlinear parameter estimation code. Using a three-dimensional, finite-element ground water flow code, key parameters were identified by calibrating to historical hydraulic head data. Results from the calibration period were then used to check model predictions by comparing monitoring wells' wet/dry status with field data. This status was analyzed using a methodology that incorporated the 0.3 cumulative probability derived from the confidence and prediction intervals. For comparison, a nonphysically based trend model was also used as a predictor of wells' wet/dry status. Although the numerical model outperformed the trend model, for both models, the central value of the intervals was a better predictor of a wet well status. The prediction interval, however, was more successful at identifying dry wells. Predictions made through the year 2048 indicated that 46% of the wells in the monitoring well network are likely to go dry in areas near the river and where the ground water mound is dissipating.     

The 2dF Galaxy Redshift Survey: the power spectrum and the matter content of the Universe

The 2dF Galaxy Redshift Survey has now measured in excess of 160 000 galaxy redshifts. This paper presents the power spectrum of the galaxy distribution, calculated using a direct Fourier transform based technique. We argue that, within the k -space region     , the shape of this spectrum should be close to that of the linear density perturbations convolved with the window function of the survey. This window function and its convolving effect on the power spectrum estimate are analysed in detail. By convolving model spectra, we are able to fit the power-spectrum data and provide a measure of the matter content of the Universe. Our results show that models containing baryon oscillations are mildly preferred over featureless power spectra. Analysis of the data yields 68 per cent confidence limits on the total matter density times the Hubble parameter     , and the baryon fraction     , assuming scale-invariant primordial fluctuations.     

Colour display for Culgoora solar radio spectrograph

A real-time colour display of the Culgoora acousto-optical radio spectrograph is described and illustrated.     

The relationship of the boundary layer of the magnetosphere to IPRP events

A model is proposed in which a mixture of hot solar wind and cold atmospheric plasma flowing in the dayside equatorial boundary layer towards the dawn-dusk plane generates hydromagnetic waves near the frequency $\text{ω = ω}{}_{\mathrm{Bi}}\text{¦1 ? T}{}_{\mathrm{\parallel }}\text{¦T}{}_{\mathrm{\perp }}\text{¦}$ where ω_Bi is the ion gyrofrequency and T_∥, T_⊥ are the temperatures of the solar wind plasma, parallel and perpendicular respectively to the magnetic field B. The model accounts for the properties of IPRP events, i.e. intervals of geomagnetic pulsations of periods rising on average from about 2 s to about 7 s over an interval of about 5 min. The diagnostic potential of this phenomenon for study of the boundary layer is indicated.     

Transient thermospheric heating and movement caused by an auroral electric field

Two closed form solutions for the velocity distribution of the upper thermosphere were found using magnetohydrodynamic formalism. One corresponds to a constant altitude, is timedependent, and has non-moving boundaries. This case asympotically approaches the steady solution obtained by Cole (1971). The other solution corresponds to a time- and altitude-dependence case with free boundaries. Solutions of electrodynamic (joule) and viscous heating for both cases are given. Some numerical results corresponding to the latter case are presented. It is clearly demonstrated that joule heating is dominant within the electric field region, and that viscous heating becomes important in the neighbourhood of the electric field region. It is also shown that the induced movement extends beyond the electric field region as far as four times the original width of the electric field region.     

Modelling the Extinction Properties of Galaxies

Recently (Granato, Lacey, Silva et al., 2000, astro-ph/0001308)we have combined our spectrophotometric galaxy evolution code which includes dust reprocessing (GRASIL, Silva et al., 1998) with semi-analytical galaxy formation models (GALFORM, Cole et al. 1999). One of the most characteristic features of the former is that the dust is divided in two main phases: molecular cloud complexes, where stars are assumed to be born, and the diffuse interstellar medium. As a consequence, stellar populations of different ages have different geometrical relationships with the two phases, which is essential in understanding several observed properties of galaxies, in particular those undergoing major episodes of star formation at any redshift. Indeed, our merged GRASIL+GALFORM model reproduces fairly well the SEDs of normal spirals and starbursts from the far-UV to the sub-mm and their internal extinction properties. In particular in the model the observed starburst attenuation law (Calzetti, 1999) is accounted for as an effect of geometry of stars and dust, and has nothing to do with the optical properties of dust grains.     

Social Mix and the `Balanced Community' in British housing policy – a tale of two epochs

In Britain, concepts of `social mix' and the `balanced community' provide an example of how policy discourses have adapted to changing conceptions of the role of the state in public provision, forms of social division and inequality, and housing market transformations. The recent development of a policy agenda by the Labour government in Britain devised to promote more socially balanced neighbourhoods is not new, and its lineage may be traced back to the origins of housing and urban policy. However, the manner in which this objective has been framed and the intervention it has provoked have varied considerably over time. One is struck more by the episodic and discontinuous nature of the application of mix and balance in British policy than any sense of a coherent set of strategies pursued through changing times. This paper contrasts the place of social mix and balance in the discourses of the immediate post-war period in Britain with the renewed emphasis on such ideas in the policies of the New Labour government elected in 1997. In the first period, the claims of social mix were infused with the language of national reconstruction and the post-war settlement and the development of universal state provision. More recently, interest in social balance has arisen partly as a response to increased management difficulties and the process of `residualisation' in social housing and partly in response to new concepts of the underclass, social exclusion and social capital. The promotion of social mix and balance in contemporary policy has been shaped by notions of the underclass, social exclusion and the development of social capital in poorer communities. Policy intervention is overtly premised on the assumption that more mixed communities will promote more positive social interaction for residents, despite the lack of evidence for this claim. In practice, much of the discourse has now taken on a stronger sense of discipline and control in order to manage social housing estates. The meaning of social balance remains confused, however, and the achievement of this objective through policy intervention is likely to remain fraught with problems.