ALBERT

Notes: Abstract The diversity of resolvase (tnpR) genes carried by a number of mercury resistant soil bacteria has been investigated by DNA sequencing. The resulting DNA sequence information was compared to previously published tnpR. DNA sequences and to previously published restriction fragment length polymorphism (RFLP) data, permitting the relationships between DNA sequencing and RFLP approaches to be studied by the use of phylogenetic trees. DNA maximum likelihood and DNA parsimony were used to construct a variety of phylogenetic trees. DNA sequencing confirmed the validity of RFLP analysis and highlighted the importance of restriction endonuclease choice upon the resulting RFLP patterns and dendrogram topology. The tnpR genes of two previously uncharacterised mercury resistant bacteria, T2–7 and T2–12 were also studied. DNA sequence data placed T2–7 in a previously described gene class, tnpR-D and T2–12 in a new gene class, tnpR-F. The significance of this data with respect to the recombination and evolution events occurring within bacterial populations are discussed.

Notes: Field surveys of Thames Water's distribution mains found the occurrence of ‘red water’ to be highly variable and localized. To model the many inter-related factors identified in the field, a controlled pipeline-testing facility was required to simulate conditions in a ‘live’ network, but on a pilot-scale. This was achieved by incorporating a specialized red-water testing facility into an existing experimental pipeline.This paper describes the hydraulic and material design features, including the addition of a ‘dead-end’ section operated on a stagnation and flow regime, quantified using computational fluid dynamics. Following commissioning, the facility has provided detailed, time-sequenced observations on corrosion-deposit development and red-water generation under different hydraulic regimes.

Notes: : A methodology has been developed to predict the responses of a range of water supply sources in Wales to global warming scenarios. Hydrologically effective rainfall is predicted from temperature and precipitation for each season based on site specific formulae developed using the Meteorological Office Rainfall and Evaporation Calculation System (MORECS) and UK Surface Water Archive databases. Comparisons are then made between the effects predicted for the scenarios established from equilibrium simulations and the new Hadley Centre High Resolution Model (UKHI) transient mode results. Though very different, both suggest increased stress on water resources late in the hydrological year.

Notes: The enumeration of heterotrophic bacteria is an important measure of water quality in mains’distribution systems. Conventional methods of enumerating bacteria by plate counts do not distinguish between single bacteria and clumps of cells; however, various methods have been reported which use epifluorescence microscopy to give a direct count of bacteria. There appears to be no standard method for the preparation of samples, with the choice of fluorochrome and staining technique varying considerably – even between workers using similar environmental samples. A number of the reported methods were tested, and a technique was developed which enabled a consistent total count of bacterial cells (occurring both singularly and in clumps) to be obtained.

Notes: Fourier transform infrared spectroscopy (FTIR) in conjunction with canonical variate analysis was found to be effective in discriminating among spectra of 9 representative strains of Bacillus spp., including B. cereus, B. mycoides and B. thuringiensis. The method was also able to discriminate according to species among spectra of 14 other non-type strains of B. cereus, 12 of B. mycoides and 12 of B. thuringiensis with a success rate of 〉95%, even without using a prior classification of the groups by species. FTIR spectroscopy can be used for the rapid and accurate differentiation of species in the genus Bacillus that are of importance to the food and dairy industry.

Notes: The ability to discriminate successfully among cultures of all species of the Listeria genus by infrared spectroscopy in combination with canonical variate analysis was confirmed. The robustness of the method was demonstrated by showing that the separation of L. monocytogenes and L. grayi was hardly affected by variations in broth medium, incubation temperature, incubation time and cell washing procedure. Discrimination among 24 strains of L. monocytogenes according to serotype allowed two groups to be recognised, one comprising serotypes 4 and 4b and the other containing serotypes 1, 1/2b and 1/2c. When strain variation was included in the species discrimination model, the classification of all the L. monocytogenes strains was virtually 100% correct.

Notes: In this paper we attempt to apply techniques that have recently been developed to describe distributed deformation on the continents to distributed deformation in subducting lithosphere slabs. We chose a part of the Tonga slab for this study because it has a simple, approximately planar, shape and high seismicity. We then used the spatial distribution of seismic strain rates, based on earthquake centroid-moment-tensor solutions in the interval 1977-1994, to recover a velocity field that describes the seismic deformation in the plane of the slab below a depth of 100 km. Between 100 and ˜450 km depth the seismic deformation is dominated by down-dip shortening and slab thickening. Below ˜450 km the down-dip shortening seen in the earthquakes is still important, but it is absorbed roughly equally by along-strike extension and by thickening. There is little evidence of along-strike shear at depth. We have more confidence in the pattern of strain rates and velocities that we obtain than in their absolute values. Nevertheless, the rates of down-dip shortening accounted for by seismicity are probably less than half those needed if the whole down-dip component of Pacific-Australia plate convergence is absorbed by shortening in the upper mantle. The style of deformation at the base of the slab is complex and, unlike many regions of distributed continental tectonics, is not easily represented by simple patterns of faulting.

Notes: We use the spatial distribution of moment tensors of earthquakes in this century to estimate the velocity field in Asia within a Eurasian reference frame. In a least-squares inversion, strain rates on the surface of the Earth are matched with continuous spline functions in order to recover the velocity gradient tensor associated with the seismic moment release in Asia. Earthquakes account for 40–60 per cent of the expected motion of India relative to Eurasia, with the missing component of strain rate equivalent to about 20 mm yr−1 of N-S shortening between Siberia and India. In this solution, South China rotates counterclockwise and moves eastwards relative to Siberia.Using rigid plate constraints, we next investigate the characteristics of the complete horizontal strain field in Asia that accommodates plate motions. Our strain-rate solutions are analogous to the response of a Newtonian thin viscous sheet in which the rate of work done by the straining medium in accommodating the velocity boundary conditions is a minimum. In these solutions the Euler pole for India relative to Eurasia is constrained (NUVEL-1A; DeMets et al. 1994), but in the process of fitting the VLBI velocity at Shanghai, China (Ward 1994; Heki et al. 1995), the Euler pole for South China is determined in the inversion. A solution that both fits the velocity at Shanghai, China and yields a strain-rate field consistent with the earthquake mechanisms is one where the South China block has a motion relative to Siberia described by the pole at (51°N, 131°E, 0.3 deg Myr−1).Comparison of the complete strain field that accommodates plate motion with the seismic strains indicates that earthquake moment release rates in this century within Mongolia are about a factor of 4 larger than the long-term rate. Within Gansu-Ningxia, the earthquake moment rates have been about a factor of 2 higher than the long-term rate. The strike-slip faulting within Mongolia, Gansu-Ningxia, western Sichuan and Yunnan is possibly a direct result of velocity boundary conditions imposed on the South China block by forces unrelated to continental collision of India and Eurasia, such as forces associated with subduction along the margins of South-eastern Asia. Verification of this requires a better understanding of the role of pre-existing zones of weakness within the Asian continental lithosphere.

Notes: A method is reported for the production of synthetic porous sandstones containing cracks of known dimensions and geometry with respect to the matrix. A synthetic sandstone was manufactured from Sand cemented with an epoxy glue. The cracks of known geometry were introduced into the material in the manufacturing stage, by emplacing thin metallic discs in the Sand-epoxy matrix. These discs were chemically leached out of the consolidated porous sandstone. Acoustic anisotropy. and shear-wave splitting were observed in the synthetic sandstones. For the dry sample the observed angular dependence of the P- and S- wave velocities (at 100 kHz) compares well, qualitatively, with the theoretical models of Hudson and of Thomsen. Quantitatively, however, the experimental data fits Hudson's model better. For the case of a saturated sample the experimental results are in excellent agreement with Thomsen's model. Hudson's model, on the other hand, predicts a different angular dependence for P-waves. This demonstrates that the concept of fluid transfer between cracks and the ambient porosity can be a significant process. The results reported here are from the first successful experiment in which the theoretical models were tested on a porous material containing a known crack geometry.