A method for screening groundwater vulnerability from subsurface hydrocarbon extraction practices.

This paper describes a new screening method for assessing groundwater vulnerability to pollution from hydrocarbon exploitation in the subsurface. The method can be used for various hydrocarbon energy sources, including conventional oil and gas, shale gas and oil, coal bed methane and underground coal gasification. Intrinsic vulnerability of potential receptors is assessed at any particular location by identifying possible geological pathways for contaminant transport. This is followed by an assessment of specific vulnerability which takes into account the nature of the subsurface hydrocarbon activity and driving heads. A confidence rating is attached to each parameter in the assessment to provide an indication of the confidence in the screening. Risk categories and associated confidence ratings are designed to aid in environmental decision making, regulation and management, highlighting where additional information is required. The method is demonstrated for conventional gas and proposed shale gas operations in northern England but can be adapted for use in any geological or hydrogeological setting and for other subsurface activities.

Combined impacts of future land-use and climate stressors on water resources and quality in groundwater and surface waterbodies of the upper Thames river basin, UK.

It is widely acknowledged that waterbodies are becoming increasingly affected by a wide range of drivers of change arising from human activity. To illustrate how this can be quantified a linked modelling approach was applied in the Thames river basin in southern UK. Changes to river flows, water temperature, river and reservoir quality were predicted under three contrasting future "storylines"; one an extension of present day rates of economic development, the others representing more extreme and less sustainable visions. Modelling revealed that lower baseflow conditions will arise under all storylines. For the less extreme storyline river water quality is likely to deteriorate but reservoir quality will improve slightly. The two more extreme futures could not be supported by current management strategies to meet water demand. To satisfy these scenarios, transfer of river water from outside the Thames river basin would be necessary. Consequently, some improvement over present day water quality in the river may be seen, and for most indicators conditions would be better than in the less extreme storyline. However, because phosphorus concentrations will rise, the invoked changes in water demand management would not be of a form suitable to prevent a marked deterioration in reservoir water quality.

A Nonlocal Model for Contact Attraction and Repulsion in Heterogeneous Cell Populations.

Instructing others to move is fundamental for many populations, whether animal or cellular. In many instances, these commands are transmitted by contact, such that an instruction is relayed directly (e.g. by touch) from signaller to receiver: for cells, this can occur via receptor-ligand mediated interactions at their membranes, potentially at a distance if a cell extends long filopodia. Given that commands ranging from attractive to repelling can be transmitted over variable distances and between cells of the same (homotypic) or different (heterotypic) type, these mechanisms can clearly have a significant impact on the organisation of a tissue. In this paper, we extend a system of nonlocal partial differential equations (integrodifferential equations) to provide a general modelling framework to explore these processes, performing linear stability and numerical analyses to reveal its capacity to trigger the self-organisation of tissues. We demonstrate the potential of the framework via two illustrative applications: the contact-mediated dispersal of neural crest populations and the self-organisation of pigmentation patterns in zebrafish.

Inducing pluripotency in vitro: recent advances and highlights in induced pluripotent stem cells generation and pluripotency reprogramming.

Induced pluripotent stem cells (iPSCs) are considered patient-specific counterparts of embryonic stem cells as they originate from somatic cells after forced expression of pluripotency reprogramming factors Oct4, Sox2, Klf4 and c-Myc. iPSCs offer unprecedented opportunity for personalized cell therapies in regenerative medicine. In recent years, iPSC technology has undergone substantial improvement to overcome slow and inefficient reprogramming protocols, and to ensure clinical-grade iPSCs and their functional derivatives. Recent developments in iPSC technology include better reprogramming methods employing novel delivery systems such as non-integrating viral and non-viral vectors, and characterization of alternative reprogramming factors. Concurrently, small chemical molecules (inhibitors of specific signalling or epigenetic regulators) have become crucial to iPSC reprogramming; they have the ability to replace putative reprogramming factors and boost reprogramming processes. Moreover, common dietary supplements, such as vitamin C and antioxidants, when introduced into reprogramming media, have been found to improve genomic and epigenomic profiles of iPSCs. In this article, we review the most recent advances in the iPSC field and potent application of iPSCs, in terms of cell therapy and tissue engineering.

The nitrate time bomb: a numerical way to investigate nitrate storage and lag time in the unsaturated zone.

Nitrate pollution in groundwater, which is mainly from agricultural activities, remains an international problem. It threatens the environment, economics and human health. There is a rising trend in nitrate concentrations in many UK groundwater bodies. Research has shown it can take decades for leached nitrate from the soil to discharge into groundwater and surface water due to the 'store' of nitrate and its potentially long travel time in the unsaturated and saturated zones. However, this time lag is rarely considered in current water nitrate management and policy development. The aim of this study was to develop a catchment-scale integrated numerical method to investigate the nitrate lag time in the groundwater system, and the Eden Valley, UK, was selected as a case study area. The method involves three models, namely the nitrate time bomb-a process-based model to simulate the nitrate transport in the unsaturated zone (USZ), GISGroundwater--a GISGroundwater flow model, and N-FM--a model to simulate the nitrate transport in the saturated zone. This study answers the scientific questions of when the nitrate currently in the groundwater was loaded into the unsaturated zones and eventually reached the water table; is the rising groundwater nitrate concentration in the study area caused by historic nitrate load; what caused the uneven distribution of groundwater nitrate concentration in the study area; and whether the historic peak nitrate loading has reached the water table in the area. The groundwater nitrate in the area was mainly from the 1980s to 2000s, whilst the groundwater nitrate in most of the source protection zones leached into the system during 1940s-1970s; the large and spatially variable thickness of the USZ is one of the major reasons for unevenly distributed groundwater nitrate concentrations in the study area; the peak nitrate loading around 1983 has affected most of the study area. For areas around the Bowscar, Beacon Edge, Low Plains, Nord Vue, Dale Springs, Gamblesby, Bankwood Springs, and Cliburn, the peak nitrate loading will arrive at the water table in the next 34 years; statistical analysis shows that 8.7 % of the Penrith Sandstone and 7.3 % of the St Bees Sandstone have not been affected by peak nitrate. This research can improve the scientific understanding of nitrate processes in the groundwater system and support the effective management of groundwater nitrate pollution for the study area. With a limited number of parameters, the method and models developed in this study are readily transferable to other areas.

A review of the impact of climate change on future nitrate concentrations in groundwater of the UK.

This paper reviews the potential impacts of climate change on nitrate concentrations in groundwater of the UK using a Source-Pathway-Receptor framework. Changes in temperature, precipitation quantity and distribution, and atmospheric carbon dioxide concentrations will affect the agricultural nitrate source term through changes in both soil processes and agricultural productivity. Non-agricultural source terms, such as urban areas and atmospheric deposition, are also expected to be affected. The implications for the rate of nitrate leaching to groundwater as a result of these changes are not yet fully understood but predictions suggest that leaching rate may increase under future climate scenarios. Climate change will affect the hydrological cycle with changes to recharge, groundwater levels and resources and flow processes. These changes will impact on concentrations of nitrate in abstracted water and other receptors, such as surface water and groundwater-fed wetlands. The implications for nitrate leaching to groundwater as a result of climate changes are not yet well enough understood to be able to make useful predictions without more site-specific data. The few studies which address the whole cycle show likely changes in nitrate leaching ranging from limited increases to a possible doubling of aquifer concentrations by 2100. These changes may be masked by nitrate reductions from improved agricultural practices, but a range of adaption measures need to be identified. Future impact may also be driven by economic responses to climate change.

How does cellular contact affect differentiation mediated pattern formation?

In this paper, we present a two-population continuous integro-differential model of cell differentiation, using a non-local term to describe the influence of the local environment on differentiation. We investigate three different versions of the model, with differentiation being cell autonomous, regulated via a community effect, or weakly dependent on the local cellular environment. We consider the spatial patterns that such different modes of differentiation produce, and investigate the formation of both stripes and spots by the model. We show that pattern formation only occurs when differentiation is regulated by a strong community effect. In this case, permanent spatial patterns only occur under a precise relationship between the parameters characterising cell dynamics, although transient patterns can persist for biologically relevant timescales when this condition is relaxed. In all cases, the long-lived patterns consist only of stripes, not spots.

Cellular automata and integrodifferential equation models for cell renewal in mosaic tissues.

Mosaic tissues are composed of two or more genetically distinct cell types. They occur naturally, and are also a useful experimental method for exploring tissue growth and maintenance. By marking the different cell types, one can study the patterns formed by proliferation, renewal and migration. Here, we present mathematical modelling suggesting that small changes in the type of interaction that cells have with their local cellular environment can lead to very different outcomes for the composition of mosaics. In cell renewal, proliferation of each cell type may depend linearly or nonlinearly on the local proportion of cells of that type, and these two possibilities produce very different patterns. We study two variations of a cellular automaton model based on simple rules for renewal. We then propose an integrodifferential equation model, and again consider two different forms of cellular interaction. The results of the continuous and cellular automata models are qualitatively the same, and we observe that changes in local environment interaction affect the dynamics for both. Furthermore, we demonstrate that the models reproduce some of the patterns seen in actual mosaic tissues. In particular, our results suggest that the differing patterns seen in organ parenchymas may be driven purely by the process of cell replacement under different interaction scenarios.

Eyeblink conditioning leads to fewer synapses in the rabbit cerebellar cortex.

Eyeblink conditioning involves the pairing of a conditioned stimulus (tone) to an aversive unconditioned stimulus (air puff). Although the circuitry that underlies this form of learning is well defined, synaptic changes in these structures have not been fully investigated. This experiment examined synaptic structural plasticity in the cerebellar cortex, a structure that has been found to modulate the acquisition and timing of the conditioned response. Long-term depression of Purkinje cells (PCs) in the cerebellar cortex has been proposed as a mechanism for releasing inhibition of the interpositus nuclei, a structure critical for the formation of the CR. Adult albino rabbits were randomly allocated to either a paired, unpaired, or exposure-only condition. The results showed a significant decrease in the number of excitatory synapses in the outer layer of the cerebellar cortex in the conditioned rabbits compared with controls. This finding suggests that a reduction in the number of excitatory synapses may contribute to the lasting depression of PC activity that is associated with eyeblink conditioning.

Impacts of climate change on the fate and behaviour of pesticides in surface and groundwater--A UK perspective.

Over the last two decades significant effort has been dedicated to understanding the fate and transport of pesticides in surface water and groundwater and to use this understanding in the development of environmental policy and regulation. However, there have been few studies that have investigated the relationships between pesticides and climate change, and where this work has been undertaken it has principally been in relation to the impacts of climate change on agricultural production rather than in the context of environmental protection. This study addresses that gap by reviewing how climate change may impact the fate and transport of pesticides in surface and groundwaters as a pre-cursor to quantitative studies. In order to structure the review, we have adopted a source-pathway-receptor approach where climate sensitivities of pesticide source terms, environmental pathways and receptors are reviewed. The main climate drivers for changing pesticide fate and behaviour are thought to be changes in rainfall seasonality and intensity and increased temperatures, but the effect of climate change on pesticide fate and transport is likely to be very variable and difficult to predict. In the long-term, indirect impacts, such as land-use change driven by changes in climate, may have a more significant effect on pesticides in surface and groundwaters than the direct impacts of climate change on pesticide fate and transport. The review focuses on climate change scenarios and case studies from the UK; however, the general conclusions can be applied more widely.

Analysis of age, stature, body mass, BMI and quality of elite soccer players from 4 European Leagues.

AIM: The aim was to identify which league (English Premier League, Spanish La Liga Division, Italian Serie A and German Bundesliga) contained the highest quality players and whether differences in age, stature, body mass and BMI existed between the different positions in different leagues. METHODS: Data were collected concerning 2,085 professional soccer players playing in these 4 leagues during the 2001-2002 season. Player quality was determined by the leagues' number of international players and their nations' FIFA World Ranking (FWR). RESULTS: The La Liga Division contained the highest quality players (mean FWR) (11.5+/-13.8), followed by the Serie A (13.3+/-21.3), the Premier League (30.6+/-27.3) and the Bundesliga (30.7+/-27.1), respectively. Also, differences were found between the age, stature, body mass and BMI of players in different positions and in the different leagues. Age had a significant influence on position with goalkeepers (years) (27.4+/-5.3) being older than midfielders (26.2+/-4.3) and forwards (25.8+/-4.2) and defenders (26.8+/-4.3) being older than forwards. Players from the Bundesliga had the greatest stature (m) (1.83+/-0.06), body mass (kg) (77.5+/-6.4) and BMI (kg x m(-2)) (23.2+/-1.1) of the 4 leagues. In reflection, La Liga's players had the shortest stature (1.80+/-0.06) and the Serie A players had the least body mass (74.3+/-5.4) and BMI (22.8+/-1.1). CONCLUSIONS: The differences discovered suggest either differences in playing style and physical demands of the different leagues, different physical conditioning methods or, alternatively, that there are desirable characteristics of players with teams in all 4 leagues seeking such players.

Sediment filled fractures in the Permo-Triassic sandstones of the Cheshire basin: observations and implications for pollutant transport.

Fracture mapping in a tunnel system and at nearby outcrop on the Runcorn Penninsula, UK, suggests the need for a review of the potential pathways for pollutant transport in Permo-Triassic sandstone aquifers. Sediment infilling is pervasive in the largest sub-vertical multi-layer fractures in the study area, both at the surface and to a depth of about 40 m below ground level. Sediment infill is inferred to have formed in situ. The conventional models of pollutant transport in fracture networks assume that they comprise open fractures, with pollutant mobility depending on fracture connectivity (a function of density, length, orientation and intersection) and aperture. The presence of extensive sediment fills in fractures will materially change their permeability, thereby reducing pollutant flux, and be of significance in the assessment of risks arising from chemical spillages. There has been little or no substantive evidence for such fills in Permo-Triassic sandstones in the UK, apart from observations at outcrop and anecdotes of sand being pumped from boreholes. Here, we report surface and rare, but complementary, subsurface observations of extensive fills in the Cheshire basin, and argue that they will only act as preferential pathways where they crosscut low-permeability horizons such as mudstones.

Assessing herbicide concentrations in the saturated and unsaturated zone of a Chalk aquifer in southern England.

The behavior of the herbicides isoproturon (IPU) and chlortoluron (CTU) in ground water and shallow unsaturated zone sediments were evaluated at a site situated on the Chalk in southern England. Concentrations of IPU in ground water samples varied from < 0.05 to 0.23 microgram/L over a five-year period of monitoring, and were found to correlate with application of the pesticide. Concentrations of pesticides in ground water samples collected during periods of rising water table were significantly higher than pumped samples and suggest that rapidly infiltrating recharge water contains higher herbicide concentrations than the native ground water. Significant variations in herbicide concentrations were observed over a three-month period in ground water samples collected by an automated system, with concentrations of IPU ranging from 0.1 to 0.5 microgram/L, and concentrations of a recent application of CTU ranging from 0.2 to 0.8 microgram/L. Different extraction methods were used to assess pore water concentrations of herbicides in the unsaturated zone, and samples were analyzed by standard HPLC analysis and immunoassay (ELISA) methods. These data indicated highly variable concentrations of herbicide ranging from 4 to 200 g/ha for HPLC and 0.01 to 0.04 g/ha for ELISA, but indicate a general pattern of decreasing concentrations with depth. The results of this study indicate that transport of IPU and CTU through the unsaturated zone to shallow ground water occurs and that this transport increases immediately following herbicide application. Measured concentrations of herbicides are generally lower than specified by the European Union Drinking Water Directive, but are observed to spike above this limit. These results imply that, while delivery of pesticides to ground water can occur as a result of normal agricultural practices, the impact on potable supplies is likely to be negligible due to the potential for degradation during the relatively long travel time through the unsaturated zone and high degree of dilution that occurs within the aquifer. As a result of the wide variation in concentrations detected by different techniques, it is suggested that for future site investigations more than one sampling strategy be employed to characterize the occurrence of pesticide residues and elucidate the transport mechanisms.

Environmental policy. Counting the cost of deforestation.

To halt the dramatic alteration in our climate, there must be a reduction in the emission of greenhouse gases. As Bonnie and colleagues discuss in their Perspective, conservation of forests will increase carbon sequestration and decrease greenhouse gas emissions. In this issue, a cost-benefit analysis by Kremen et al. demonstrates the benefits of forest conservation on a local and global scale.

Global biodiversity scenarios for the year 2100.

Scenarios of changes in biodiversity for the year 2100 can now be developed based on scenarios of changes in atmospheric carbon dioxide, climate, vegetation, and land use and the known sensitivity of biodiversity to these changes. This study identified a ranking of the importance of drivers of change, a ranking of the biomes with respect to expected changes, and the major sources of uncertainties. For terrestrial ecosystems, land-use change probably will have the largest effect, followed by climate change, nitrogen deposition, biotic exchange, and elevated carbon dioxide concentration. For freshwater ecosystems, biotic exchange is much more important. Mediterranean climate and grassland ecosystems likely will experience the greatest proportional change in biodiversity because of the substantial influence of all drivers of biodiversity change. Northern temperate ecosystems are estimated to experience the least biodiversity change because major land-use change has already occurred. Plausible changes in biodiversity in other biomes depend on interactions among the causes of biodiversity change. These interactions represent one of the largest uncertainties in projections of future biodiversity change.

Effects of fexofenadine, diphenhydramine, and alcohol on driving performance. A randomized, placebo-controlled trial in the Iowa driving simulator.

BACKGROUND: Sedating antihistamines may impair driving performance as seriously as alcohol. OBJECTIVE: To compare the effects of fexofenadine, diphenhydramine, alcohol, and placebo on driving performance. DESIGN: Randomized, double-blind, double-dummy, four-treatment, four-period crossover trial. SETTING: The Iowa Driving Simulator. PARTICIPANTS: 40 licensed drivers with seasonal allergic rhinitis who were 25 to 44 years of age. INTERVENTION: One dose of fexofenadine (60 mg), diphenhydramine (50 mg), alcohol (approximately 0.1% blood alcohol concentration), or placebo, given at weekly intervals before participants drove for 1 hour in the Iowa Driving Simulator. MEASUREMENTS: The primary end point was coherence, a continuous measure of participants' ability to match the varying speed of a vehicle that they were following. Secondary end points were drowsiness and other driving measures, including lane keeping and response to a vehicle that unexpectedly blocked the lane ahead. RESULTS: Participants had significantly better coherence after taking alcohol or fexofenadine than after taking diphenhydramine. Lane keeping (steering instability and crossing the center line) was impaired after alcohol and diphenhydramine use compared with fexofenadine use. Mean response time to the blocking vehicle was slowest after alcohol use (2.21 seconds) compared with fexofenadine use (1.95 seconds). Self-reported drowsiness did not predict lack of coherence and was weakly associated with minimum following distance, steering instability, and leftlane excursion. CONCLUSIONS: Participants had similar performance when treated with fexofenadine or placebo. After alcohol use, participants performed the primary task well but not the secondary tasks; as a result, overall driving performance was poorer. After participants took diphenhydramine, driving performance was poorest, indicating that diphenhydramine had a greater impact on driving than alcohol did. Drowsiness ratings were not a good predictor of impairment, suggesting that drivers cannot use drowsiness to indicate when they should not drive.

Driving simulation study: bilateral array multifocal versus bilateral AMO monofocal intraocular lenses.

PURPOSE: To determine whether differences exist in the driving performance of patients with bilateral Array multifocal intraocular lenses (IOLs) and those with bilateral AMO monofocal IOLs under low-contrast environmental conditions. SETTING: The Iowa Driving Simulator at the Center for Computer Aided Design, the University of Iowa, Iowa City, Iowa, USA. METHODS: This prospective study was a test-operator-masked, parallel-group comparison of the driving performance of 33 bilateral multifocal IOL patients and 33 bilateral monofocal IOL patients from the U.S. Array Multifocal study. Driving performance was evaluated under 3 poor visibility conditions (clear weather at night, clear weather at night in the presence of a glare source, and fog). Measures of performance included recognition rates and distances for signs, as well as detection rates, distances, and avoidance behaviors for hazards. Contrast acuity and sensitivity were also measured to evaluate possible correlations with driving performance. RESULTS: No statistically significant differences between the IOL groups were found in 26 of 30 comparisons (86.7%). The monofocal group performed better than the multifocal group in comparisons in which there were statistically significant differences: the percentage of correctly recognized warning signs at night in clear weather (P = .028), sign recognition distances for guide (P = .030) and warning (P = .036) signs in fog, and the detection distance for 1 of 4 hazards (suitcase; P = .026). Correlation coefficients between driving performance and low-contrast acuity and sensitivity were statistically significant; however, they were low and not likely predictive of driving performance. CONCLUSION: Differences between patients with bilateral multifocal IOLs and those with bilateral monofocal IOLs were detected; however, the results indicate no consistent difference in driving performance and safety.