An inverse method for estimating thickness and volume with time of a thin CO2-filled layer at the Sleipner Field, North Sea

Migration of CO 2 through storage reservoirs can be monitored using time lapse seismic reflection surveys. At the Sleipner Field, injected CO 2 is distributed throughout nine layers within the reservoir. These layers are too thin to be seismically resolvable by direct measurement of the separation between reflections from the top and bottom of each layer. Here we develop and apply an inverse method for measuring thick ness changes of the shallowest layer. Our approach combines differences in traveltime down to a specific reflection together with amplitude measurements to determine layer thicknesses from time lapse surveys. A series of synthetic forward models were used to test the robustness of our inverse approach and to quantify uncertainties. In the absence of ambient noise, this approach can unambiguously resolve layer thickness. If a realistic ambient noise distribution is included, layer thicknesses of 1–6 m are accurately retrieved with an uncertainty of ±0.5 m. We used this approach to generate a thickness map of the shallowest layer. The fidelity of this result was tested using measurements of layer thickness determined from the 2010 broadband seismic survey. The calculated volume of CO 2 within the shallowest layer increases at a rate that is quadratic in time, despite an approximately constant injection rate into the base of the reser voir. This result is consistent with a diminished growth rate of the areal extent of underlying layers. Finally, the relationship between caprock topography and layer thickness is explored and potential migration pathways that charge this layer are identified

In the absence of memory?: Jewish fate and dramatic representation; production and critical reception of Holocaust drama on the London stage 1945-1989

Plays representing some aspect of the Holocaust produced in both the commercial and subsidised sectors of the London theatre throughout the Cold War period variously but consistently sought to evade, diminish or inappropriately qualify the cardinal fact that, in the formulation which was the Nazi's own, 'the Final Solution was that 'of the Jewish question in Europe'. Such dramatic distortions hinder perceptions of the identity and fate of the chief victims of the Holocaust. Playwrights', directors', managements', and to a marginally lesser degree, critics' failure to question or challenge these tendencies results not so much in the explicitly stated exoneration of those responsible for the Nazi genocide as the erasure or attenuation of both German guilt and Jewish suffering through dramatic speculation upon the universal human propensity to evil. In consequence the suggestion is made of Jewish agency in, and culpability for, their own fate during the Holocaust. At their most extreme these dramatic tendencies resort to the recurrent themes of anti-Semitic discourse. The ubiquitous dramatic strategies and tropes employed in the productions discussed, rather than succeed in their attempt to find and represent meaning in the respective episodes and events of the Nazi genocide dramatised, frequently re-present this elimination through the evasion, attenuation or erasure, of Jewish fate. The productions register the failure of dramatic art to find equitable metaphor and adequate representational means to provoke reflection of a kind which might transcend the meaningless facticity of mass murder and the impulse to annihilation, and are drawn into those same dynamics of annihilation, evidenced by the erasure of Jewish identity and fate. This phenomenon remains largely, but not entirely, unremarked in the immediate critical response of the British press, but almost wholly neglected in later commentary due to an 'absence of memoy: the lack of a specifically British critical discourse on dramatic representation and the Holocaust

Fixing the conformal window in QCD

A physical characterization of Landau singularities is emphasized, which should trace the lower boundary N_f^* of the conformal window in QCD and supersymmetric QCD. A natural way to disentangle ``perturbative'' from ``non-perturbative'' contributions to amplitudes below N_f^* is suggested. Assuming an infrared fixed point persists in the perturbative part of the QCD coupling even below N_f^* leads to the condition \gamma(N_f^*)=1, where \gamma is the critical exponent. Using the Banks-Zaks expansion, one gets 4<N_f^*<6. This result is incompatible with the existence of an analogue of Seiberg duality in QCD. The presence of a negative ultraviolet fixed point is required both in QCD and in supersymmetric QCD to preserve causality within the conformal window. Evidence for the existence of such a fixed point in QCD is provided.Comment: 10 pages, 1 figure, extended version of a talk given at the QCDNET2000 meeting, Paris, September 11-14 2000; main new material added is evidence for negative ultraviolet fixed point in QC

Multidimensional divergent selection, local adaptation, and speciation

Divergent selection applied to one or more traits drives local adaptation and may lead to ecological speciation. Divergent selection on many traits might be termed “multidimensional” divergent selection. There is a commonly held view that multidimensional divergent selection is likely to promote local adaptation and speciation to a greater extent than unidimensional divergent selection. We disentangle the core concepts underlying dimensionality as a property of the environment, phenotypes, and genome. In particular, we identify a need to separate the overall strength of selection and the number of loci affected from dimensionality per se, and to distinguish divergence dimensionality from dimensionality of stabilizing selection. We then critically scrutinize this commonly held view that multidimensional selection promotes speciation, re-examining the evidence base from theory, experiments, and nature. We conclude that the evidence base is currently weak and generally suffers from confounding of possible causal effects. Finally, we propose several mechanisms by which multidimensional divergent selection and related processes might influence divergence, both as a driver and as a barrier

Seismic data reveal eastern Black Sea Basin structure

Rifted continental margins are formed by progressive extension of the lithosphere. The development of these margins plays an integral role in the plate tectonic cycle, and an understanding of the extensional process underpins much hydrocarbon exploration. A key issue is whether the lithosphere extends uniformly, or whether extension varies\ud with depth. Crustal extension may be determined using seismic techniques. Lithospheric extension may be inferred from the waterloaded subsidence history, determined from\ud the pattern of sedimentation during and after rifting. Unfortunately, however, many rifted margins are sediment-starved, so the subsidence history is poorly known.\ud To test whether extension varies between the crust and the mantle, a major seismic experiment was conducted in February–March 2005 in the eastern Black Sea Basin (Figure 1), a deep basin where the subsidence history is recorded\ud by a thick, post-rift sedimentary sequence. The seismic data from the experiment indicate the presence of a thick, low-velocity zone, possibly representing overpressured sediments. They also indicate that the basement and\ud Moho in the center of the basin are both several kilometers shallower than previously inferred. These initial observations may have considerable impact on thermal models of the petroleum system in the basin. Understanding\ud the thermal history of potential source rocks is key to reducing hydrocarbon exploration risk. The experiment, which involved collaboration between university groups in the United Kingdom, Ireland, and Turkey, and BP and\ud Turkish Petroleum (TPAO), formed part of a larger project that also is using deep seismic reflection and other geophysical data held by the industry partners to determine the subsidence history and hence the strain evolution of\ud the basin

Genetic consequences of multiple translocations of the banded hare-qallaby in Western Australia

Many Australian mammal species now only occur on islands and fenced mainland havens free from invasive predators. The range of one species, the banded hare-wallaby (Lagostrophus fasciatus), had contracted to two offshore islands in Western Australia. To improve survival, four conservation translocations have been attempted with mixed success, and all occurred in the absence of genetic information. Here, we genotyped seven polymorphic microsatellite markers in two source (Bernier Island and Dorre Island), two historic captive, and two translocated L. fasciatus populations to determine the impact of multiple translocations on genetic diversity. Subsequently, we used population viability analysis (PVA) and gene retention modelling to determine scenarios that will maximise demographic resilience and genetic richness of two new populations that are currently being established. One translocated population (Wadderin) has undergone a genetic bottleneck and lost 8.1% of its source population’s allelic diversity, while the other (Faure Island) may be inbred. We show that founder number is a key parameter when establishing new L. fasciatus populations and 100 founders should lead to high survival probabilities. Our modelling predicts that during periodic droughts, the recovery of source populations will be slower post-harvest, while 75% more animals—about 60 individuals—are required to retain adequate allelic diversity in the translocated population. Our approach demonstrates how genetic data coupled with simulations of stochastic environmental events can address central questions in translocation programmes

Optical realization of universal quantum cloning

Beyond the no-cloning theorem, the universal symmetric quantum cloning machine was first addressed by Buzek and Hillery. Here, we realized the one-to-two qubits Buzek-Hillery cloning machine with linear optical devices. This method relies on the representation of several qubits by a single photon. We showed that, the fidelities between the two output qubits and the original qubit are both 5/6 (which proved to be the optimal fidelity of one-to-two qubits universal cloner) for arbitrary input pure states.Comment: 5 Pages, 2 Figure

[Epidemiology of oral cavity cancers in France].

INTRODUCTION: We had for objective to describe the updated epidemiology of oral cancers in France. MATERIAL AND METHODS: Estimates made from data collected from various French cancer institutions. The distribution by topography, histology, regions, mean age, and specific incidence rates were calculated from the collected data. The survival data was taken from the Francim network studies. RESULTS: Approximately 7000 oral cavity cancers were diagnosed in France in 2005. In 2007, 1746 people died of that cancer. Standardized (world population) incidence rates are respectively, in men and women, 12.3 and 3.0 cases per 100,000 person-years. These cancers have significantly decreased in men: the standardized incidence rate decreased by 43.2% between 1980 and 2005. Among women, the trend is reversed with an increased incidence of 51.7% over the same period. CONCLUSION: In France, the incidence of oral cavity cancers has been strongly decreasing in men and strongly increasing in women. This trend should be compared to the frequency of the main risk factors: alcohol and tobacco

Modelling the response of phytoplankton in a shallow lake (Loch Leven, UK) to changes in lake retention time and water temperature.

The phytoplankton community of Loch Leven in 2005 was modelled and subjected to a combination of different flushing rates and water temperatures in order to assess the lake’s sensitivity to these two climatic drivers. Whilst the simulated annual mean total chlorophyll a proved relatively insensitive to these changes, at the species level marked changes were recorded. Some species responded positively to increased temperature (e.g. Aulacoseira), some negatively (e.g. Asterionella), whilst others were negatively affected by increased flow (e.g. Aphanocapsa) and others enhanced (e.g. Stephanodiscus). However, this relationship with flow was season dependent with, for example, a simulated increase in summer inflows actually benefiting some species through increased nutrient supply, whereas an equivalent increase in flow in wetter seasons would have negatively affected those species (i.e. through flushing loss). Overall, the simulations showed that the range of species types simulated in the community was sufficient for one species to always benefit from the changing niches created by the multiple climatic drivers applied in this study. The level of exploitation by such a species was only constrained by the nutrient carrying capacity of the system, which led to the overall dampened response in the total chlorophyll a measure, both at the annual and season scale. Thus, whilst overall biomass showed relatively little reaction to the two climatic drivers tested, the phytoplankton community composition responded markedly

Benchmarking of vertically-integrated CO 2 flow simulations at the Sleipner Field, North Sea

Numerical modeling plays an essential role in both identifying and assessing sub-surface reservoirs that might be suitable for future carbon capture and storage projects. Accuracy of flow simulations is tested by benchmarking against historic observations from on-going CO2 injection sites. At the Sleipner project located in the North Sea, a suite of time-lapse seismic reflection surveys enables the three-dimensional distribution of CO2 at the top of the reservoir to be determined as a function of time. Previous attempts have used Darcy flow simulators to model CO2 migration throughout this layer, given the volume of injection with time and the location of the injection point. Due primarily to computational limitations preventing adequate exploration of model parameter space, these simulations usually fail to match the observed distribution of CO2 as a function of space and time. To circumvent these limitations, we develop a vertically-integrated fluid flow simulator that is based upon the theory of topographically controlled, porous gravity currents. This computationally efficient scheme can be used to invert for the spatial distribution of reservoir permeability required to minimize differences between the observed and calculated CO2 distributions. When a uniform reservoir permeability is assumed, inverse modeling is unable to adequately match the migration of CO2 at the top of the reservoir. If, however, the width and permeability of a mapped channel deposit are allowed to independently vary, a satisfactory match between the observed and calculated CO2 distributions is obtained. Finally, the ability of this algorithm to forecast the flow of CO2 at the top of the reservoir is assessed. By dividing the complete set of seismic reflection surveys into training and validation subsets, we find that the spatial pattern of permeability required to match the training subset can successfully predict CO2 migration for the validation subset. This ability suggests that it might be feasible to forecast migration patterns into the future with a degree of confidence. Nevertheless, our analysis highlights the difficulty in estimating reservoir parameters away from the region swept by CO2 without additional observational constraints