Search

Airborne radio-echo sounding (RES) surveys are widely used to measure ice-sheet bed topography. Measuring bed topography as accurately and widely as possible is of critical importance to modelling ice dynamics and hence to constraining better future ice response to climate change. Measurement accuracy of RES surveys is influenced both by the geometry of bed topography and the survey design. Here we develop a novel approach for simulating RES surveys over glaciated terrain, to quantify the sensitivity of derived bed elevation to topographic geometry. Furthermore, we investigate how measurement errors influence the quantification of glacial valley geometry. We find a negative bias across RES measurements, where off-nadir return measurement error is typically −1.8 ± 11.6 m. Topographic highlands are under-measured an order of magnitude more than lowlands. Consequently, valley depth and cross-sectional area are largely under-estimated. While overall estimates of ice thickness are likely too high, we find large glacier valley cross-sectional area to be under-estimated by −2.8 ± 18.1%. Therefore, estimates of ice flux through large outlet glaciers are likely too low when this effect is not taken into account. Additionally, bed mismeasurements potentially impact our appreciation of outlet-glacier stability.

Mass loss from glaciers and ice caps represents the largest terrestrial component of current sea level rise. However, our understanding of how the processes governing mass loss will respond to climate warming remains incomplete. This study explores the relationship between surface elevation changes (dh/dt), glacier velocity changes (du/dt), and bedrock topography at the Trinity-Wykeham Glacier system (TWG), Canadian High Arctic, using a range of satellite and airborne datasets. We use measurements of dh/dt from ICESat (2003–2009) and CryoSat-2 (2010–2016) repeat observations to show that rates of surface lowering increased from 4 m yr−1 to 6 m yr−1 across the lowermost 10 km of the TWG. We show that surface flow rates at both Trinity Glacier and Wykeham Glacier doubled over 16 years, during which time the ice front retreated 4.45 km. The combination of thinning, acceleration and retreat of the TWG suggests that a dynamic thinning mechanism is responsible for the observed changes, and we suggest that both glaciers have transitioned from fully grounded to partially floating. Furthermore, by comparing the separate glacier troughs we suggest that the dynamic changes are modulated by both lateral friction from the valley sides and the complex geometry of the bed. Further, the presence of bedrock ridges induces crevassing on the surface and provides a direct link for surface meltwater to reach the bed. We observe supraglacial lakes that drain at the end of summer and are concurrent with a reduction in glacier velocity, suggesting hydrological connections between the surface and the bed significantly impact ice flow. The bedrock topography thus has a primary influence on the nature of the changes in ice dynamics observed over the last decade.

Summary Accurate precipitation maps are essential for ecological, environmental, element cycle and hydrological models that have a spatial output component. It is well known that topography has a major influence on the spatial distribution of precipitation and that increasing topographical complexity is associated with increased spatial heterogeneity in precipitation. This means that when mapping precipitation using classical interpolation techniques (e.g. regression, kriging, spline, inverse distance weighting, etc.), a climate measuring network with higher spatial density is needed in mountainous areas in order to obtain the same level of accuracy as compared to flatter regions. In this study, we present a mean total annual precipitation mapping technique that combines topographical information (i.e. elevation and slope orientation) with average total annual rain gauge data in order to overcome this problem. A unique feature of this paper is the identification of the scale at which topography influences the precipitation pattern as well as the direction of the dominant weather circulation. This method was applied for Belgium and surroundings and shows that the identification of the appropriate scale at which topographical obstacles impact precipitation is crucial in order to obtain reliable mean total annual precipitation maps. The dominant weather circulation is determined at 260°. Hence, this approach allows accurate mapping of mean annual precipitation patterns in regions characterized by rather high topographical complexity using a climate data network with a relatively low density and/or when more advanced precipitation measurement techniques, such as radar, aren’t available, for example in the case of historical data.

Sand and dust storm events (SDEs), which result from strong surface winds in arid and semi-arid areas, exhibiting loose dry soil surfaces are detrimental to human health, agricultural land, infrastructure, and transport. The accurate detection of near-surface dust is crucial for quantifying the spatial and temporal occurrence of SDEs globally. The Arabian Peninsula is an important source region for global dust due to the presence of extensive deserts. This paper evaluates the suitability of five different MODIS-based methods for detecting airborne dust over the Arabian Peninsula: (a) Normalized Difference Dust Index (NDDI); (b) Brightness Temperature Difference (BTD) (31–32); (c) BTD (20–31); (d) Middle East Dust Index (MEDI) and (e) Reflective Solar Band (RSB). We derive detection thresholds for each index by comparing observed values for ‘dust-present’ versus ‘dust-free’ conditions, taking into account various land cover settings and analyzing associated temporal trends. Our results suggest that the BTD (31–32) method and the RSB index are the most suitable indices for detecting dust storms over different land-cover types across the Arabian Peninsula. The NDDI and BTD (20–31) methods have limitations in identifying dust over multiple land-cover types. Furthermore, the MEDI has been found to be unsuitable for detecting dust in the study area across all land-cover types.

Key Points We present a comprehensive, seamless bed topography across the ice‐ocean margin around GreenlandTwo to 4 times more glaciers have calving fronts grounded below 200 m compared to previous mappingsTotal ice volume of Greenland is 2.99 ± 0.02 times 106 km3, yielding a potential sea level rise of 7.42 m, 7 cm greater than previous estimates, Greenland's bed topography is a primary control on ice flow, grounding line migration, calving dynamics, and subglacial drainage. Moreover, fjord bathymetry regulates the penetration of warm Atlantic water (AW) that rapidly melts and undercuts Greenland's marine‐terminating glaciers. Here we present a new compilation of Greenland bed topography that assimilates seafloor bathymetry and ice thickness data through a mass conservation approach. A new 150 m horizontal resolution bed topography/bathymetric map of Greenland is constructed with seamless transitions at the ice/ocean interface, yielding major improvements over previous data sets, particularly in the marine‐terminating sectors of northwest and southeast Greenland. Our map reveals that the total sea level potential of the Greenland ice sheet is 7.42 ± 0.05 m, which is 7 cm greater than previous estimates. Furthermore, it explains recent calving front response of numerous outlet glaciers and reveals new pathways by which AW can access glaciers with marine‐based basins, thereby highlighting sectors of Greenland that are most vulnerable to future oceanic forcing.

KEY POINTS/HIGHLIGHTSTwo rapid ice-dammed lake drainage events gauged and ice dam geometry measured.A melt enlargement model is developed to examine the evolution of drainage mechanism(s).Lake temperature dominated conduit melt enlargement and we hypothesize a flotation trigger.Glaciological and hydraulic factors that control the timing and mechanisms of glacier lake outburst floods (GLOFs) remain poorly understood. This study used measurements of lake level at 15 min intervals and known lake bathymetry to calculate lake outflow during two GLOF events from the northern margin of Russell Glacier, west Greenland. We used measured ice surface elevation, interpolated subglacial topography and likely conduit geometry to inform a melt enlargement model of the outburst evolution. The model was tuned to best-fit the hydrograph rising limb and timing of peak discharge in both events; it achieved Mean Absolute Errors of

Monthly meteorological data from 27 observation stations provided by the Presidency of Meteorology and Environment (PME) of Saudi Arabia were used to analyze the spatial and temporal distribution of atmospheric dust in Saudi Arabia between 2000 and 2016. These data were used to analyze the effects of environmental forcing on the occurrence of dust storms across Saudi Arabia by considering the relationships between dust storm frequency and temperature, precipitation, and wind variables. We reveal a clear seasonality in the reported incidence of dust storms, with the highest frequency of events during the spring. Our results show significant positive relationships (p &lt, 0.005) between dust storm occurrence and wind speed, wind direction, and precipitation. However, we did not detect a significant relationship with temperature. Our results reveal important spatial patterns, as well as seasonal and inter-annual variations, in the occurrence of dust storms in Saudi Arabia. For instance, the eastern part of the study area experienced an increase in dust storm events over time, especially in the region near Al-Ahsa. Similarly, an increasing trend in dust storms was also observed in the west of the study area near Jeddah. However, the occurrence of dust storm events is decreasing over time in the north, in areas such as Hail and Qaisumah. Overall, the eastern part of Saudi Arabia experiences the highest number of dust storms per year (i.e., 10 to 60 events), followed by the northern region, with the south and the west having fewer dust storm events (i.e., five to 15 events per year). In addition, our results showed that the wind speeds during a dust storm are 15&ndash, 20 m/s and above, while, on a non-dust day, the wind speeds are approximately 10&ndash, 15 m/s or lower. Findings of this study provide insight into the relationship between environmental conditions and dust storm occurrence across Saudi Arabia, and a basis for future research into the drivers behind these observed spatio-temporal trends.

[1] Subglacial lakes are an established and important component of the basal hydrological system of the Antarctic ice sheets, but none have been reported from Greenland. Here we present airborne radio echo sounder (RES) measurements that provide the first clear evidence for the existence of subglacial lakes in Greenland. Two lakes, with areas ~8 and ~10 km2, are found in the northwest sector of the ice sheet, ~40 km from the ice margin, and below 757 and 809 m of ice, respectively. The setting of the Greenland lakes differs from those of Antarctic subglacial lakes, being beneath relatively thin and cold ice, pointing to a fundamental difference in their nature and genesis. Possibilities that the lakes consist of either ancient saline water in a closed system or are part of a fresh, modern open hydrological system are discussed, with the latter interpretation considered more likely.

W.C. is a recipient of the NASA Earth and Space Science Fellowship. D.M.S. is supported by a grant from the NASA Cryospheric Sciences Program. H.S. is supported by grants from the NASA Cryospheric Sciences and Sea Level Rise Programs. T.T.C and R.E.B are supported by grants from National Science Foundation (NSF) and NASA Cryospheric Sciences. S.P. is supported by the Natural Environment Research Council’s Centre for Polar Observation

We present a new method of modelling the growth of supraglacial lakes at the western margin of the Greenland ice sheet, based on routing runoff estimated by a regional climate model across a digital elevation model (DEM) of the ice sheet surface. Using data acquired during the 2003 melt season, we demonstrate that the model is 19 times more likely to correctly predict the presence (or absence) of lakes than it is to make incorrect predictions, within an elevation range of 1100 to 1700 metres above sea level (m a.s.l.), when compared with MODIS satellite imagery. Of the 66% of observed lake locations which the model correctly reproduces, the simulated lake onset day is found to be correlated with that observed with a Pearson correlation coefficient of 0.76. Our model accurately simulates maximum cumulative lake area with only a 1.5% overestimate. However, because our model does not simulate processes leading to lake stagnation or decay, such as refreezing or drainage, at present we do not simulate absolute daily lake area. We find that the maximum potential lake-covered ice sheet area is limited by topography to 6.4%. We estimate that this corresponds to a volume of 1.49 km3, 12% of the runoff produced in 2003. This can be taken as an upper bound given uncertainty in the DEM. This study has proved a good first step towards capturing the variability of supraglacial lake evolution with a numerical model. These initial results are promising and suggest that the model is a useful tool for use in analysing the behaviour of supraglacial lakes on the Greenland ice sheet in the present day and potentially beyond.

We present global positioning system observations that capture the full inland extent of ice motion variations in 2009 along a transect in the west Greenland Ice sheet margin. In situ measurements of air temperature and surface ablation, and satellite monitoring of ice surface albedo and supraglacial lake drainage are used to investigate hydrological controls on ice velocity changes. We find a strong positive correlation between rates of annual ablation and changes in annual ice motion along the transect, with sites nearest the ice sheet margin experiencing greater annual variations in ice motion (15–18%) than those above 1000 m elevation (3–8%). Patterns in the timing and rate of meltwater delivery to the ice–bed interface provide key controls on the magnitude of hydrologically-forced velocity variations at each site. In the lower ablation zone, the overall contribution of variations in ice motion to annual flow rates is limited by evolution in the structure of the subglacial drainage system. At sites in the upper ablation zone, a shorter period of summer melting and delayed establishment of a hydraulic connection between the ice sheet surface and its bed limit the timeframe for velocity variations to occur. Our data suggest that land-terminating sections of the Greenland Ice Sheet will experience increased dynamic mass loss in a warmer climate, as the behaviour that we observe in the lower ablation zone propagates further inland. Findings from this study provide a conceptual framework to understand the impact of hydrologically-forced velocity variations on the future mass balance of land-terminating sections of the Greenland Ice Sheet.

We use interferometric synthetic aperture radar observations recorded in a land-terminating sector of western Greenland to characterise the ice sheet surface hydrology and to quantify spatial variations in the seasonality of ice sheet flow. Our data reveal a non-uniform pattern of late-summer ice speedup that, in places, extends over 100 km inland. We show that the degree of late-summer speedup is positively correlated with modelled runoff within the 10 glacier catchments of our survey, and that the pattern of late-summer speedup follows that of water routed at the ice sheet surface. In late-summer, ice within the largest catchment flows on average 48% faster than during winter, whereas changes in smaller catchments are less pronounced. Our observations show that the routing of seasonal runoff at the ice sheet surface plays an important role in shaping the magnitude and extent of seasonal ice sheet speedup.

Fluctuations in surface melting are known to affect the speed of glaciers and ice sheets, but their impact on the Greenland ice sheet in a warming climate remains uncertain8. Although some studies suggest that greater melting produces greater ice-sheet acceleration, others have identified a long-term decrease in Greenland's flow despite increased melting. Here we use satellite observations of ice motion recorded in a land-terminating sector of southwest Greenland to investigate the manner in which ice flow develops during years of markedly different melting. Although peak rates of ice speed-up are positively correlated with the degree of melting, mean summer flow rates are not, because glacier slowdown occurs, on average, when a critical run-off threshold of about 1.4 centimetres a day is exceeded. In contrast to the first half of summer, when flow is similar in all years, speed-up during the latter half is 62±16% per cent less in warmer years. Consequently, in warmer years, the period of fast ice flow is three times shorter and, overall, summer ice flow is slower. This behaviour is at odds with that expected from basal lubrication alone. Instead, it mirrors that of mountain glaciers, where melt-induced acceleration of flow ceases during years of high melting once subglacial drainage becomes efficient. A model of ice-sheet flow that captures switching between cavity and channel drainage modes13 is consistent with the run-off threshold, fast-flow periods, and later-summer speeds we have observed. Simulations of the Greenland ice-sheet flow under climate warming scenarios should account for the dynamic evolution of subglacial drainage; a simple model of basal lubrication alone misses key aspects of the ice sheet's response to climate warming.

This paper defines challenges currently facing the water industry globally that will affect water industry asset investment and development now and in the near future. Those challenges include energy price volatility, climate change regulation, asset capital costs and strategic resource considerations. This paper presents potential answers to these challenges in the context of the UK water industry and described a methodology developed to assess them and provide accurate cost-benefit analysis. A best practice approach which allows sustainable investment to offer water utilities operational efficiency benefits, including cost benefits, is described and the critical elements of the best practice developed by the author identified.

We have computed the velocity of Langjökull ice cap (LIC), Iceland, using InSAR data acquired by the European Remote-sensing Satellite in 1994 and an ice-surface elevation model derived from a GPS survey conducted in 1997. The velocity map covers 68% of the 925 km2of LIC. Eight principal outlet glaciers were identified, along which ice velocities increased from zero at the ice divide to a maximum of 75 m a−1. When the InSAR velocity dataset is compared with surface GPS measurements of ice flow determined in summer 2001, there is generally good agreement, suggesting interannual and seasonal stability for much of the ice cap during this period. However, non-zero ice velocities at the termini of four of the eight glaciers surveyed suggest that these glaciers were advancing in 1994. Comparison of our GPS and InSAR velocities suggests that Sudurjökull experienced elevated velocity in late February 1994, which, when other studies are considered, appears to be consistent with a glacier surge.

The contribution of the Greenland ice sheet to sea-level rise has accelerated in recent decades. Subglacial lake drainage events can induce an ice sheet dynamic response—a process that has been observed in Antarctica, but not yet in Greenland, where the presence of subglacial lakes has only recently been discovered. Here we investigate the water flow paths from a subglacial lake, which drained beneath the Greenland ice sheet in 2011. Our observations suggest that the lake was fed by surface meltwater flowing down a nearby moulin, and that the draining water reached the ice margin via a subglacial tunnel. Interferometric synthetic aperture radar-derived measurements of ice surface motion acquired in 1995 suggest that a similar event may have occurred 16 years earlier, and we propose that, as the climate warms, increasing volumes of surface meltwater routed to the bed will cause such events to become more common in the future., How the Greenland ice sheet responds to the drainage of water below the ice remains uncertain. Here, the authors combine digital elevation models and Landsat optical imagery to map subglacial drainage pathways and investigate the ice sheet surface response to a periodically draining subglacial lake.

Discharge from marine-terminating outlet glaciers accounts for up to half the recent mass loss from the Greenland ice sheet, yet the causal factors are not fully understood. Here we assess the factors controlling the behaviour of Humboldt Glacier (HG), allowing us to evaluate the influence of basal topography on outlet glacier response to external forcing since part of HG’s terminus occupies a large overdeepening. HG’s retreat accelerated dramatically after 1999, coinciding with summer atmospheric warming of up to 0.19°C a–1 and sea-ice decline. Retreat was an order of magnitude greater in the northern section of the terminus, underlain by a major basal trough, than in the southern section, where the bedrock is comparatively shallow. Velocity change following retreat was spatially non-uniform, potentially due to a pinning point near HG’s northern lateral margin. Consistent with observations, numerical modelling demonstrates an order-of-magnitude greater sensitivity to sea-ice buttressing and crevasse depth (used as a proxy for atmospheric warming) in the northern section. The trough extends up to 72 km inland, so it is likely to facilitate sustained retreat and ice loss from HG during the 21st century.

The possibility that conditions on the Sun and in the Earth's magneto- sphere can affect human health at the Earth's surface has been debated for many decades. This work reviews the research undertaken in the field of heliobiology, focusing on the effect of variations of geomagnetic activity on human cardiovascular health. Data from previous research are analysed for their statistical significance, resulting in support for some studies and the undermining of others. Three con- clusions are that geomagnetic effects are more pronounced at higher magnetic lat- itudes, that extremely high as well as extremely low values of geomagnetic activity seem to have adverse health effects and that a subset of the population (10-15%) is predisposed to adverse health due to geomagnetic variations. The reported health effects of anthropogenic sources of electric and magnetic fields are also briefly dis- cussed, as research performed in this area could help to explain the results from studies into natural electric and magnetic field interactions with the human

Meltwater delivered to the bed of the Greenland Ice Sheet is a driver of variable ice-motion through changes in effective pressure and enhanced basal lubrication. Ice surface velocities have been shown to respond rapidly both to meltwater production at the surface and to drainage of supraglacial lakes, suggesting efficient transfer of meltwater from the supraglacial to subglacial hydrological systems. Although considerable effort is currently being directed towards improved modelling of the controlling surface and basal processes, modelling the temporal and spatial evolution of the transfer of melt to the bed has received less attention. Here we present the results of spatially distributed modelling for prediction of moulins and lake drainages on the Leverett Glacier in Southwest Greenland. The model is run for the 2009 and 2010 ablation seasons, and for future increased melt scenarios. The temporal pattern of modelled lake drainages are qualitatively comparable with those documented from analyses of repeat satellite imagery. The modelled timings and locations of delivery of meltwater to the bed also match well with observed temporal and spatial patterns of ice surface speed-ups. This is particularly true for the lower catchment (< 1000 m a.s.l.) where both the model and observations indicate that the development of moulins is the main mechanism for the transfer of surface meltwater to the bed. At higher elevations (e.g. 1250-1500 m a.s.l.) the development and drainage of supraglacial lakes becomes increasingly important. At these higher elevations, the delay between modelled melt generation and subsequent delivery of melt to the bed matches the observed delay between the peak air temperatures and subsequent velocity speed-ups, while the instantaneous transfer of melt to the bed in a control simulation does not. Although both moulins and lake drainages are predicted to increase in number for future warmer climate scenarios, the lake drainages play an increasingly important role in both expanding the area over which melt accesses the bed and in enabling a greater proportion of surface melt to reach the bed., Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe, 513

Tibia and fibula are common sites for stress fractures in runners [1, 2]. We report an unusual case of ipsilateral stress fracture of tibia in a female diabetic athlete during her rehabilitation from stress fracture of the fibula.

Seedlings of Helianthus annuus L. were grown at an initially high relative nitrate supply rate (0.27 mol N mol N–1 d–1). The supply was subsequently reduced to a low rate (0.04 mol N mol N–1 d–1). The response of leaf area development to this abrupt decrease in nitrate availability was characterized by following the expansion of the primary and secondary leaf pairs. The timing of the drop in nitrate supply was when cell division in the epidermis of the primary leaf pair was largely complete. Reducing the availability of nitrate had a strong effect on leaf area expansion. The final leaf size of the primary leaf pair was affected indicating an effect of nitrate availability on cell expansion. By the end of the experiment the secondary leaf pair was only one-third the area of that on control seedlings. The role of epidermal cell turgor pressure in this growth response was assessed by direct measurements with a miniature cell pressure probe. No reduction in cell turgor pressure following the decrease in nitrate availability was detected. It is concluded that a reduction in turgor pressure was not responsible for the reduction in leaf area expansion and it is suggested that reduced cell expansion was due to changes in cell wall properties. Concentrations of leaf and root abscisic acid increased following the reduction in nitrate availability.

We present a new bed elevation dataset for Greenland derived from a combination of multiple airborne ice thickness surveys undertaken between the 1970s and 2011. Around 344 000 line kilometres of airborne data were used, with the majority of this having been collected since the year 2000, when the last comprehensive compilation was undertaken. The airborne data were combined with satellite-derived elevations for non glaciated terrain to produce a consistent bed digital elevation model (DEM) over the entire island including across the glaciated/ice free boundary. The DEM was extended to the continental margin with the aid of bathymetric data, primarily from a compilation for the Arctic. Ice shelf thickness was determined where a floating tongue exists, in particular in the north. The across-track spacing between flight lines warranted interpolation at 1 km postings near the ice sheet margin and 2.5 km in the interior. Grids of ice surface elevation, error estimates for the DEM, ice thickness and data sampling density were also produced alongside a mask of land/ocean/grounded ice/floating ice. Errors in bed elevation range from a minimum of ±6 m to about ±200 m, as a function of distance from an observation and local topographic variability. A comparison with the compilation published in 2001 highlights the improvement in resolution afforded by the new data sets, particularly along the ice sheet margin, where ice velocity is highest and changes most marked. We use the new bed and surface DEMs to calculate the hydraulic potential for subglacial flow and present the large scale pattern of water routing. We estimate that the volume of ice included in our land/ice mask would raise eustatic sea level by 7.36 m, excluding any solid earth effects that would take place during ice sheet decay.

[1] We measure hydrological parameters in meltwater draining from an outlet glacier in west Greenland to investigate seasonal changes in the structure and behaviour of the hydrological system of a large catchment in the Greenland ice sheet (GrIS). Our data reveal seasonal upglacier expansion and increase in hydraulic efficiency of the subglacial drainage system, across a catchment >600 km2, to distances >50 km from the ice-sheet margin. This expansion occurs episodically in response to the drainage of surface meltwaters into a hitherto inefficient subglacial drainage system as new input locations become active progressively further upglacier; this system is similar to Alpine glaciers. These observations provide the first synopsis of seasonal hydrological behaviour in the ablation zone of the GrIS.

The 8500 km(2) Flade Isblink ice cap (FIIC) (81 degrees 15'N, 15 degrees 0'W) is the largest ice cap in Greenland. We use repeat-pass interferometric synthetic aperture radar (InSAR) techniques to investigate the form and flow of the FIIC. European Remote Sensing satellite (ERS-1 and ERS-2) data acquired in winter 1996 were used to form a 100 m resolution digital elevation model (DEM), which we constrained using Ice Cloud and Elevation satellite (ICESat) laser altimeter elevation measurements from 2007. This InSAR DEM was used to isolate the phase due to motion from seven ERS-tandem (1 day) pairs of SAR scenes acquired between 15 August 1995 and 7 February 1996, to produce one wintertime and two summertime velocity maps. Five of the eight major outlet glaciers draining the FIIC are marine terminating, and two terminate at a lake margin. A maximum ice velocity of 581 m yr(-1) was observed in mid-August 1995. Six of the eight major outlet glaciers exhibit seasonal velocity variations between late summer and winter, and flow speeds vary by up to 20% over a 10 day period in August 1995. Our findings show that while marine terminating glaciers flow faster than land terminating glaciers, there is no simple relationship between glacier type and seasonality of ice motion.

Revision operations after fracture of the hip are costly, in both monetary and personal terms. We have assessed whether these costs applied equally to all complications after the primary procedure. We studied 3154 consecutive patients with fracture of the hip and analysed the complications and financial implications related to reoperation within one year of injury. The results showed that revision surgery is not always associated with a significant increase in morbidity, financial cost or mortality, but is directly related to the underlying complication.

We used 268 cloud-free Moderate-resolution Imaging Spectroradiometer (MODIS) images from 2003 and 2005-2007 to study the seasonal evolution of supra-glacial lakes in three different regions of the Greenland Ice Sheet. Lake area estimates were obtained by developing an automated classification method for their identification based on 250 m resolution MODIS surface reflectance observations. Widespread supra-glacial lake formation and drainage is observed across the ice sheet, with a 2-3 week delay in the evolution of total supra-glacial lake area in the northern areas compared to the south-west. The onset of lake growth varies by up to one month inter-annually, and lakes form and drain at progressively higher altitudes during the melt season. A positive correlation was found between the annual peak in total lake area and modelled annual runoff. High runoff and lake extent years are generally characterised by low accumulation and high melt season temperatures, and vice versa. Our results indicate that, in a future warmer climate Meehl, G. A., Stocker, T. F., Collins W. D., Friedlingstein, P., Gaye, A. T., Gregory, J. M., Kitoh, A., Knutti, R., Murphy, J. M., Noda, A., Raper, S. C. B., Watterson, I. G., Weaver, A. J. & Zhao, Z. C. (2007). Global Climate Projections. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K. B. Averyt, M. Tignor & H. L. Miller (eds.), Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA., Greenland supra-glacial lakes can be expected to form at higher altitudes and over a longer time period than is presently the case, expanding the area and time period over which connections between the ice sheet surface and base may be established Das, S., Joughin, M., Behn, M., Howat, I., King, M., Lizarralde, D., & Bhatia, M. (2008). Fracture propagation to the base of the Greenland Ice Sheet during supra-glacial lake drainage. Science, 5877, 778-781 with potential consequences for ice sheet discharge Zwally, H.J., Abdalati, W., Herring, T., Larson, K., Saba, J. & Steffen, K. (2002). Surface melt-induced acceleration of Greenland Ice Sheet flow. Science, 297, 218-221.. © 2009 Elsevier Inc. All rights reserved.

This investigation compared the sweet and bitter taste characteristics of aspartame, acesulfame K, and alitame at equisweetness levels with 10% sucrose/water solutions at 22°C using the time-intensity (T-I) sensory technique. Alitame was comparable to sucrose in all taste characteristics. Aspartame had similar taste characteristics to sucrose with the exception of having greater sweet intensities with longer duration (P

To determine if novel methods establishing patterns in EEG-EMG coupling can infer subcortical influences on the motor cortex, and the relationship between these subcortical rhythms and bradykinesia.Previous work has suggested that bradykinesia may be a result of inappropriate oscillatory drive to the muscles. Typically, the signal processing method of coherence is used to infer coupling between a single channel of EEG and a single channel of rectified EMG, which demonstrates 2 peaks during sustained contraction: one, approximately 10 Hz, which is pathologically increased in PD, and a approximately 30 Hz peak which is decreased in PD, and influenced by pharmacological manipulation of GABAA receptors in normal subjects.We employed a novel multiperiodic squeezing paradigm which also required simultaneous movements. Seven PD subjects (on and off L-Dopa) and five normal subjects were recruited. Extent of bradykinesia was inferred by reduced relative performance of the higher frequencies of the squeezing paradigm and UPDRS scores. We employed Independent Component Analysis (ICA) and Empirical Mode Decomposition (EMD) to determine EEG/EMG coupling.Corticomuscular coupling was detected during the continually changing force levels. Different components included those over the primary motor cortex (ipsilaterally and contralaterally) and over the midline. Subjects with greater bradykinesia had a tendency towards increased approximately 10 Hz coupling and reduced approximately 30 Hz coupling that was erratically reversed with L-dopa.These results suggest that lower approximately 10 Hz peak may represent pathological oscillations within the basal ganglia which may be a contributing factor to bradykinesia in PD.

Statins are central to the government's National Service Framework (NSF) for coronary heart disease (CHD). NHS spending on statins is currently about pounds sterling 500 million per annum and rising at an annual rate of 30%. Although generally considered to be a cost-effective treatment for hyperlipidaemia and cardiovascular disease, given the high and rising expenditure on statins in the UK, there is a pressing need to ensure that the choice between available statins reflects cost-effectiveness considerations. A decision model was developed to establish the cost-effectiveness of treating new hypercholesterolaemic patients to UK and European target levels of blood total cholesterol (TC) and low density lipoprotein-cholesterol (LDL-C), using rosuvastatin, atorvastatin, simvastatin, pravastatin or fluvastatin. The model was used to estimate the proportion of patients reaching target and the associated costs over a one-year period from the perspective of the NHS. The effectiveness of the alternative statins were modelled using data from the Statin Therapies for Elevated Lipid Levels compared Across doses to Rosuvastatin (STELLAR) trial. Monte Carlo simulation was used to reflect uncertainty in the parameter estimates applied in the model. Rosuvastatin is demonstrated to dominate (i.e. lower costs and a higher number of patients treated to target) atorvastatin, simvastatin and pravastatin. Compared with fluvastatin, the incremental cost per additional patient to target (PTT) for rosuvastatin was pounds sterling 24 using LDL-C and pounds sterling 83 using TC. The probability that rosuvastatin is cost-effective exceeds 95%, provided the NHS is prepared to pay at least pounds sterling 35 per PTT to achieve target LDL-C cholesterol levels (pounds sterling 160 for TC). The analysis demonstrates rosuvastatin is more cost-effective than the other statins in achieving UK and European cholesterol targets.

When delivered locally to the arterial wall by passive fluid transfer systems such as perforated balloons, water-soluble compounds in aqueous solution are not readily taken up by tissue, show low levels of cellular localization, and are quickly lost by wash-out. One approach to improve delivery is addition of an "active" component to the catheter system to change the nature of the drug-to-tissue interaction. Using an iontophoretic balloon catheter to deliver antisense oligonucleotide (ODN) to pig coronary arteries after balloon angioplasty, we determined the quantity and localization of ODN in the tissue. By radiolabeling, 7.3 +/- 2.4 micrograms ODN was present at 30 min, 1.5 +/- 0.6 at 2 h, 0.52 +/- 0.35 at 24 h, and 0.26 +/- 0.11 at 7 d. By fluorescent labeling, circumferential medial uptake and adventitial delivery at the site of medial injury was observed, with primarily cellular localization. The iontophoretic catheter thus appears to be a useful device for ODN delivery to arterial tissue.

Localized delivery of antisense oligonucleotides directed against cell cycle regulatory proteins has been proposed as a means to prevent restenosis after angioplasty. To test whether single endoluminal delivery of a combination of proliferating cell nuclear antigen (PCNA) and cell-division cycle 2 kinase (cdc2) antisense might affect restenosis, we delivered 2 ml of lipid-complexed PCNA/cdc2 antisense oligomers (1.35 mg) to the coronary arteries of pigs after balloon overstretch angioplasty (AS group) and performed planimetric histomorphometry on arterial sections of the tissue, harvested at 4 wk. Compared with controls receiving 3'-5' reversed sequence oligomers (REV group), there were no differences in absolute intimal area (AS 1.36 +/- 0.08 mm2, REV 1.23 +/- 0.10 mm2, P = NS), intimal area normalized to extent of injury (AS 0.67 +/- 0.03, REV 0.77 +/- 0.10, P = NS), or vessel perimeter (AS 7.72 +/- 0.19 mm, REV 7.36 +/- 0.22 mm, P = NS). We conclude that single endoluminal delivery of antisense against key cell cycle regulatory proteins does not affect neointima formation or vessel size in this model of restenosis.

There have been encouraging reports of the use of recombinant tissue plasminogen activator (tPA) in established veno-occlusive disease (VOD). Haemodialysis has been considered a contraindication to this therapy in view of the potential haemostatic complications. We report a case of a woman who developed moderately severe VOD complicated by anuria following an allogeneic bone marrow transplant for relapsed acute myeloid leukaemia. Following initiation of peritoneal dialysis she received tPA at a dose of 10 mg/day for 5 days. There was rapid improvement in her urine output and liver function with no bleeding complications. This case suggests that the requirement of dialysis may not preclude the use of tPA in established VOD and therefore warrants further study.

The combination of donor leucocytes, with or without interferon, has produced encouraging responses in patients with haematological relapse following allogeneic BMT for chronic myeloid leukaemia (CML). A 25-year-old male received low-dose interferon-alpha alone for haematological relapse occurring 10 months following an allogeneic BMT for Ph-positive CML. Interferon therapy was complicated by severe GVHD requiring immunosuppressive therapy. The patient was subsequently found to be in complete haematological and cytogenetic remission, raising the possibility of an immune-mediated antileukaemic action.

Plants which experience perturbation of their immediate climatic and edaphic environment often contain increased amounts of the plant hormone, abscisic acid (ABA). In this regard, the most studied environmental stress is the effect of soil drying, which can result in increases in ABA concentration of several orders of magnitude. In addition, flooding of the soil, temperature stress and nitrogen stress also induce ABA accumulation. ABA can be a potent regulator of stomatal behaviour and may also regulate the growth of roots and leaves. In this chapter we describe how ABA concentration in the xylem stream of plants growing in drying soil may reflect the water status of the soil surrounding their roots. This may mean that the physiology, growth and development of stressed plants can be regulated by ABA acting as a measure of the degree of stress. We consider the nature of the ABA signal under different circumstances and show that along with variation in the supply of ABA, there may be variation in the sensitivity of the response to the signal. The concept of sensitivity is discussed. The importance of variation in the flux of the hormone and in the rate of ABA metabolism in the leaf are considered.

The prevalence of antibody to hepatitis C virus (HCV) was estimated in 3 tropical populations using 2 screening ELISAs to detect antibody to the c100-3 antigen and 2 supplementary assays designed to test the specificity of these tests. Two hundred and eighty-six of 385 (74.2%) sera from Kiribati, 17 of 138 (12.3%) sera from Vanuatu, and 39 of 173 (22.5%) sera from Zaire were reactive in the initial screening assay. The proportion of reactive sera which were also reactive in the second screening ELISA varied between populations (55.1% in Kiribati, 85.1% in Vanuatu, and 39.2% from Zaire). Reactive sera were selected at random for confirmatory testing. Only 3 of 49 (6.12%) of sera from Kiribati and 1 of 14 (4.76%) of sera from Vanuatu positive in the initial ELISA were reactive in the confirmatory assays. The proportion of confirmed positive sera from Zaire was higher 8 of 28 (28.5%). Based on the results of these supplementary assays the estimated prevalence of anti-HCV in these populations is 4.8% in Kiribati, less than 1% in Vanuatu, and 6.4% in Zaire. Reliance on a single screening ELISA to estimate the prevalence of anti-HCV in stored sera from tropical communities may lead to a gross over-estimate of the true prevalence in these populations.

The microbial degradation of numerous compounds has been studied and the biochemical pathways and mechanisms of enzyme action have been elucidated particularly with respect to pure cultures of bacteria. This research has been extremely valuable but to date industrial application of the knowledge has been somewhat limited. However, public awareness of the environment and governmental pressure in the form of the recent “Green Bill” has stimulated industry into taking measures to reduce the discharge of compounds likely to cause environmental problems. Biodegradation can play a significant role as, when it is achievable, it is by far the most economic method of treatment for removal of pollutants from a waste effluent.

Electron microscopy and x-ray spectroscopy were used to determine location and type of cadmium biosorption on and in bacteria, some of which produced extracellular polymers. Examined Arthrobacter and Pseudomonas species appear to have detoxification systems that precipitate cadmium internally irrespective of whether of not they excrete polymers. Capsular Klebsiella aerogenes strains showed minimal intracellular uptake but over a 5–100 mg dm−3 Cd range produced the highest net metal removal levels due to significant extracellular adsorption.

The present study was initiated to determine whether pretreatment of gerbils with calcium channel blockers, flunarizine and verapamil would prevent injury to cerebral ATPases following secondary ischemia consisting of 60-min bilateral clamping of the carotids followed by 40 min of reperfusion. The sequence of ischemia produced a deficit in Na+,K+-ATPase activity without influencing Ca++,Mg++- or Mn++-sensitive ATPases. Pretreatment with flunarizine significantly prevented the damage to Na+,K+-ATPase while the effect of verapamil was marginal. Verapamil, along with dimethylsulfoxide (DMSO), reduced the mortality rate of gerbils subjected to the paradigm of ischemia. When added directly to the cerebral fractions in vitro the two calcium channel blockers inhibited Na+,K+-ATPase alone. Flunarizine was more potent in vitro than verapamil.

A therapeutic role for naloxone during stroke has been suggested, but a neurochemical site of action remains to be determined. Previous work with the geerbil cerebral cortex has shown that either bilateral secondary ischemia (60-min occlusion of the carotid arteries followed by 40-min reflow) or unilateral primary ischemia (permanent ligation of one carotid artery for 6 hr in symptomatic animals) produced deficits in both Na+, K+-ATPase (EC 3.6.1.3) activity and various parameters of activation of adenylate cyclase (EC 4.6.1.1). Pretreatment of gerbils with either naloxone or morphine failed to ameliorate or exacerbate, respectively, the neurological signs of ischemia; however, morphine did reduce mortality. Infusion of naloxone prior to ischemia afforded varying degrees of protection to forskolin, GTP analogs, and NE (norepinephrine) activation of adenylate cyclase, as well as to Na+, K+-ATPase (bilateral ischemia only). Similarly, morphine inhibited damage to basal activity of adenylate cyclase and to stimulation by NE, forskolin, and Gpp (NH)p (5′-guanylyl imidodiphosphate). Under in vitro conditions morphine increased the basal activity of adenylate cyclase but reduced responses to NE and forskolin. Furthermore, morphine injected into control gerbils elevated basal- and forskolin-elicited activities but reduced the activation of adenylate cyclase by NE.

A method of simulating a flat belt drive under power-transmission conditions is given. Stress-strain data are obtained using a photoelastic coating technique. Tension-strain equations are evaluated using a computer program based on Forsythe's method of orthogonal polynomials. An indication of how the data may be used to arrive at the operating tensions of an actual belt drive is given.

A study of splenic function in 28 patients with adult coeliac disease showed no significant correlation between the half life of heat-damaged red cells and either the duration of pre-treatment exposure to gluten or the length of time on a gluten free diet. A significant correlation was found between splenic size and duration of treatment; those patients who had been taking a gluten free diet for the longest time had the smallest spleens. Blood films from 11 of these 28 patients taken before treatment with a gluten free diet were compared with those taken between two and 15 years after the start of treatment. There was no tendency for the hyposplenic changes to regress. In the majority, the changes became more prominent despite strict adherence to the gluten free diet. These findings suggest that splenic atrophy in adult coeliac disease is not reversed by treatment with a gluten free diet and is unlikely to be related to the state of the jejunal mucosa or the duration of initial exposure to gluten.

The present study was an extension of earlier work regarding the role of cyclic nucleotides and related enzymes during cerebral ischemia in the gerbil. Following unilateral carotid occlusion, levels of cyclic AMP and cyclic GMP were measured in four rapidly inactivated brain regions at 3, 6, and 24 hr after permanent occlusion and at 2 hr of occlusion plus 1 hr of reflow. An analysis of variance indicated significant minor fluctuations in the steady-state levels of the two cyclic nucleotides within the frontal cortex, the hippocampus, the striatum, and especially the olfactory tubercle with respect to occlusion time (3 and 24 hr) but not when comparing control vs ischemic hemispheres (except at 3 hr). Changes occurred only in animals developing neurological symptoms of ischemia. At 24 hr postocclusion the specific activity of the low-Km form of cyclic AMP phosphodiesterase was elevated especially on the ischemic side when determined in homogenates of the four brain regions. Alternatively, the high-Km form of the enzyme in the presence or absence of Ca2+-calmodulin was unchanged. Guanylate cyclase activity in tissue homogenates was not influenced by the conditions of ischemia until 24 hr had elapsed, an event likewise unique to symptomatic gerbils. The sensitivity of the enzyme to hematin-catalase was decreased in the ischemic hemispheres of the hippocampus, striatum, and olfactory tubercle. In addition, further activation of the hematin-catalase response by NaN3 was depressed in the ischemic side of the hippocampus and striatum. Taken together these and previous studies indicate that fluctuations in the steady-state levels of cyclic nucleotides that occur rather prominently during acute and to a lesser degree during prolonged ischemia are not correlated with associated changes in enzymes responsible for their synthesis and/or degradation.

Strain data for a simple two pulley belt drive was obtained using a photoelastic coating technique. The operating strains present were not constant along the driving and load sides but varied in an irregular manner. The average strain gradually increased on the driving side and decreased on the load side as the power transmitted was increased.

Bacterial exopolysaccharides can significantly enhance bio-sorption of cadmium. Exopolysaccharide fromArthrobacterviscosus has a 2.3 times greater accumulation capacity than the equivalent weight of intact cells and is 13.7 times more effective than the cells ofArthrobacterglobiformis, an organism that does not produce exopolysaccharide.

Excretion of a polysaccharide capsular coating byP.putida provided enhanced cadmium uptake when compared to the noncapsularP.cruciviae. As this advantage is most significant for cadmium concentrations below 2.5 mg/l, levels which are commonly found in waste discharges, it does suggest a potential role for extracellular polysaccharide producers as biosorbents. These encouraging results have led to further work to determine the desorption characteristics, by pH adjustment, ofP.putida along with long term viability after successive cycles of adsorption and desorption.

Incubated tissue slices from mouse cerebral cortex and cerebellum readily accumulate cyclic GMP in response to a challenge by ouabain, NaN 3 , NH 2 OH, or KCl. Under similar conditions, l -glutamate, l -aspartate, glycine, γ-aminobutyric acid, kainic acid, and the calcium ionophore, A-23187, were ineffective. Inhibition of the ouabain-induced accumulation of cyclic GMP was evident with valproate, carbamazepine, clonazepam, phenytoin, and phenobarbital. Only phenytoin blocked the action of KCl and cyclic GMP responses to NaN 3 were inhibited by high concentrations of valproate, carbamazepine, phenytoin, or phenobarbital. The effects of NH 2 OH were attenuated by high concentrations of carbamazepine, phenobarbital, and clonazepam (cortex only). Guanylate cyclase activity in homogenates of cortex and cerebellum was enhanced in the presence of NaN 3 , NH 2 OH, or Ca 2+ (in low concentrations of Mn 2+ ). The enzyme activation induced by Ca + was blocked only by large (1 m m ) amounts of carbamazepine. In like manner, large concentrations of carbamazepine, phenytoin (cortex), or clonazepam (cortex) were effective in reducing guanylate cyclase stimulation by NaN 3 . No agent affected the NH 2 OH responses. The results suggest that anticonvulsant drug actions with regard to central cyclic GMP systems are related to the Na + -induced depolarization of nerve tissue and not to any direct actions on the guanylate cyclase enzyme.