bluuebunny/crossref_metadata_2025 huggingface dataset:
ASSESSMENT OF METHODS FOR MEASURING EMBEDDEDNESS: APPLICATION TO SEDIMENTATION IN FLOW REGULATED STREAMS1
Authors: Sennatt Kelly M. , Salant Nira L. , Renshaw Carl E. , Magilligan Francis J.
Published: August 2007

Abstract:Five commonly used methods for measuring embeddedness the — degree to which fine particles surround coarse substrate on the surface of the streambed — are assessed and used to evaluate the sedimentation pattern resulting from impoundment on tributaries of the Connecticut River. Results show that the U.S. Environmental Protection Agency (USEPA) method best reflects the sediment regime on these rivers. On the Ompompanoosuc River, regulated by a run‐of‐the‐river/flood control dam, embeddedness increases significantly directly downstream of the dam. On the unregulated White River, no downstream trends in embeddedness are observed. The USEPA results on the Ompompanoosuc River reflect the movement of a local decrease in embeddedness, interpreted as a moving region of scour, with a calculated transport rate of approximately 5 to 25 m/day. Observed transport rates are similar to previously measured sediment transport rates and consistent with results from a multifraction sediment transport model. Application of the USEPA method to an additional regulated tributary demonstrates the effects of dam management on embeddedness. Flow regulation with high sediment trapping efficiency results in a decrease in embeddedness downstream of the dam. Results provide insight into the utility of available methods for evaluating the effects of management practice on streambed composition.
Chronic hypoxia up‐regulates α1HT‐type channels and low‐threshold catecholamine secretion in rat chromaffin cells
Authors: Carabelli V. , Marcantoni A. , Comunanza V. , De Luca A. , Díaz J. , Borges R. , Carbone E.
Published: August 2007

α1HT‐type channels recruited by β1‐adrenergic stimulation in rat chromaffin cells (RCCs) are coupled to fast exocytosis with the same Ca2+dependence of high‐threshold Ca2+channels. Here we show that RCCs exposed to chronic hypoxia (CH) for 12–18 h in 3% O2express comparable densities of functional T‐type channels that depolarize the resting cells and contribute to low‐voltage exocytosis. Following chronic hypoxia, most RCCs exhibited T‐type Ca2+channels already available at −50 mV with the same gating, pharmacological and molecular features as the α1Hisoform. Chronic hypoxia had no effects on cell size and high‐threshold Ca2+current density and was mimicked by overnight incubation with the iron‐chelating agent desferrioxamine (DFX), suggesting the involvement of hypoxia‐inducible factors (HIFs). T‐type channel recruitment occurred independently of PKA activation and the presence of extracellular Ca2+. Hypoxia‐recruited T‐type channels were partially open at rest (T‐type ‘window‐current’) and contributed to raising the resting potential to more positive values. Their block by 50 μmNi2+caused a 5–8 mV hyperpolarization. The secretory response associated with T‐type channels could be detected following mild cell depolarizations, either by capacitance increases induced by step depolarizations or by amperometric current spikes induced by increased [KCl]. In the latter case, exocytotic bursts could be evoked even with 2–4 mmKCl and spike frequency was drastically reduced by 50 μmNi2+. Chronic hypoxia did not alter the shape of spikes, suggesting that hypoxia‐recruited T‐type channels increase the number of secreted vesicles at low voltages, without altering the mechanism of catecholamine release and the quantal content of released molecules.
Human cerebrovascular and ventilatory CO2 reactivity to end‐tidal, arterial and internal jugular vein PCO2
Authors: Peebles Karen , Celi Leo , McGrattan Ken , Murrell Carissa , Thomas Kate , Ainslie Philip N.
Published: August 2007

This study examined cerebrovascular reactivity and ventilation during step changes in CO2 in humans. We hypothesized that: (1) end‐tidal P (P) would overestimate arterial P (P) during step variations in P and thus underestimate cerebrovascular CO2 reactivity; and (2) since P from the internal jugular vein (P) better represents brain tissue P, cerebrovascular CO2 reactivity would be higher when expressed against P than with P, and would be related to the degree of ventilatory change during hypercapnia. Incremental hypercapnia was achieved through 4 min administrations of 4% and 8% CO2. Incremental hypocapnia involved two 4 min steps of hyperventilation to change P, in an equal and opposite direction, to that incurred during hypercapnia. Arterial and internal jugular venous blood was sampled simultaneously at baseline and during each CO2 step. Cerebrovascular reactivity to CO2 was expressed as the percentage change in blood flow velocity in the middle cerebral artery (MCAv) per mmHg change in P and P. During hypercapnia, but not hypocapnia, P overestimated P by +2.4 ± 3.4 mmHg and underestimated MCAv‐CO2 reactivity (P < 0.05). The hypercapnic and hypocapnic MCAv‐CO2 reactivity was higher (∼97% and ∼24%, respectively) when expressed with P than P (P < 0.05). The hypercapnic MCAv–P reactivity was inversely related to the increase in ventilatory change (R2= 0.43; P < 0.05), indicating that a reduced reactivity results in less central CO2 washout and greater ventilatory stimulus. Differences in the P, P and P–MCAv relationships have implications for the true representation and physiological interpretation of cerebrovascular CO2 reactivity.
The effect of lung volume on the co‐ordinated recruitment of scalene and sternomastoid muscles in humans
Authors: Hudson Anna L. , Gandevia Simon C. , Butler Jane E.
Published: August 2007

The human scalenes are obligatory inspiratory muscles that have a greater mechanical advantage than sternomastoid, an accessory muscle. This study determined scalene and sternomastoid recruitment during voluntary inspiratory tasks, and whether this activity varied with lung volume, when feedback from the lungs and inspiratory muscles would differ. If afferent feedback has a major role in determining the recruitment of the scalenes and sternomastoid, then at each lung volume, activity would be altered. Intramuscular EMG from scalene and sternomastoid muscles, and oesophageal pressure were recorded while subjects (n= 7) performed inspiratory isovolumetric ramps to maximal inspiratory pressure (MIP) and dynamic inspirations from functional residual capacity (FRC) to total lung capacity (TLC). The static inspiratory ramps were repeated at three lung volumes: FRC, FRC + tidal volume, and TLC. To determine the profile of inspiratory activation, i.e. the initial and ongoing recruitment of the muscles, the root mean square of the EMG was measured throughout the tasks. Scalene was recruited early, and EMG increased with pressure, reaching a plateau at 80% MIP. In contrast, sternomastoid activity began later, but then increased with pressure from 20 to 100% MIP. Similar profiles of activation occurred at all three lung volumes (n.s.). The ratio of sternomastoid to scalene EMG was also the same irrespective of the initial lung volume (n.s.). In dynamic inspirations, scalene and sternomastoid activation had similar stereotypical profiles to the static tasks, but scalene EMG was 15–40% greater (P < 0.05). Sternomastoid activation was the same in both tasks (n.s.). These results suggest that in voluntary tasks, scalene and sternomastoid are recruited in the order of their mechanical advantages, and that alterations in feedback related to changes in lung volume failed to alter their activation. Thus, in humans, the mechanism responsible for the differential activation of these two inspiratory muscles has an element that is preset.
Altered potassium channel function in the superficial dorsal horn of the spastic mouse
Authors: Graham B. A. , Brichta A. M. , Schofield P. R. , Callister R. J.
Published: August 2007

The spastic mouse has a naturally occurring glycine receptor (GlyR) mutation that disrupts synaptic input in both motor and sensory pathways. Here we use the spastic mouse to examine how this altered inhibitory drive affects neuronal intrinsic membrane properties and signal processing in the superficial dorsal horn (SDH), where GlyRs contribute to pain processing mechanisms. We first used in vitro patch clamp recording in spinal cord slices (L3–L5 segments) to examine intrinsic membrane properties of SDH neurones in spastic and age‐matched wildtype controls (∼P23). Apart from a modest reduction (∼3 mV) in resting membrane potential (RMP), neurones in spastic mice have membrane and action potential (AP) properties identical to wildtype controls. There was, however, a substantial reorganization of AP discharge properties in neurones from spastic mice, with a significant increase (14%) in the proportion of delayed firing neurones. This was accompanied by a change in the voltage sensitivity of rapid A‐currents, a possible mechanism for increased delayed firing. To assess the functional consequences of these changes, we made in vivo patch‐clamp recordings from SDH neurones in urethane anaesthetized (2.2 g kg−1, i.p.) spastic and wildtype mice (∼P37), and examined responses to innocuous and noxious mechanical stimulation of the hindpaw. Overall, responses recorded in wildtype and spastic mice were similar; however, in spastic mice a small population of spontaneously active neurones (∼10%) exhibited elevated spontaneous discharge frequency and post‐pinch discharge rates. Together, these results are consistent with the altered intrinsic membrane properties of SDH neurones observed in vitro having functional consequences for pain processing mechanisms in the spastic mouse in vivo. We propose that alterations in potassium channel function in the spastic mouse compensate, in part, for reduced glycinergic inhibition and thus maintain normal signal processing in the SDH.
Blockade of phosphodiesterase Type 5 enhances rat neurohypophysial excitability and electrically evoked oxytocin release
Authors: Zhang Zhenjie , Klyachko Vitaly , Jackson Meyer B.
Published: August 2007

Phosphodiesterase type 5 (PDE5) acts specifically on cyclic guanosine monophosphate (cGMP) and terminates cGMP‐mediated signalling. PDE5 has a well established role in vascular smooth muscle, where specific inhibitors of PDE5 such as sildenafil correct erectile dysfunction by augmenting cGMP‐mediated vascular relaxation. However, the role of PDE5 outside of the vasculature has received little attention. The present study tested PDE5 inhibitors on the cGMP‐mediated modulation of K+ channels in the neurohypophysis (posterior pituitary). Photolysis of caged‐cGMP enhanced current through Ca2+‐activated K+ channels, and this enhancement recovered in about 2 min. Sildenafil essentially eliminated this recovery, suggesting that the reversal of K+ current enhancement depends on cGMP breakdown. Activation of nitric oxide synthase during trains of activity in pituitary nerve terminals enhances excitability. When trains of stimulation were applied at regular intervals, sildenafil enhanced the excitability of neurohypophysial nerve terminals and increased the action potential firing probability. T‐1032, a compound with high specificity for PDE5 over PDE6, had a similar action. Voltage imaging in intact neurohypophysis with a voltage sensitive absorbance dye showed that T‐1032 reduced the failure of propagating action potentials during trains of activity. This indicates that PDE5 activity limits action potential propagation in neurohypophysial axons. Immunoassay of oxytocin, a neuropeptide hormone secreted by the posterior pituitary, demonstrated that sildenafil increased electrically evoked release. Thus, PDE5 plays an important role in the regulation of neurohypophysial function, and blockade of this enzyme can enhance the use‐dependent facilitation of neurohypophysial secretion.
Expression of interleukin‐15 in human skeletal muscle – effect of exercise and muscle fibre type composition
Authors: Nielsen Anders Rinnov , Mounier Remi , Plomgaard Peter , Mortensen Ole Hartvig , Penkowa Milena , Speerschneider Tobias , Pilegaard Henriette , Pedersen Bente Klarlund
Published: August 2007

The cytokine interleukin‐15 (IL‐15) has been demonstrated to have anabolic effects in cell culture systems. We tested the hypothesis that IL‐15 is predominantly expressed by type 2 skeletal muscle fibres, and that resistance exercise regulates IL‐15 expression in muscle. Triceps brachii, vastus lateralis quadriceps and soleus muscle biopsies were obtained from normally physically active, healthy, young male volunteers (n= 14), because these muscles are characterized by having different fibre‐type compositions. In addition, healthy, normally physically active male subjects (n= 8) not involved in any kind of resistance exercise underwent a heavy resistance exercise protocol that stimulated the vastus lateralis muscle and biopsies were obtained from this muscle pre‐exercise as well as 6, 24 and 48 h post‐exercise. IL‐15 mRNA levels were twofold higher in the triceps (type 2 fibre dominance) compared with the soleus muscle (type 1 fibre dominance), but Western blotting and immunohistochemistry revealed that muscle IL‐15 protein content did not differ between triceps brachii, quadriceps and soleus muscles. Following resistance exercise, IL‐15 mRNA levels were up‐regulated twofold at 24 h of recovery without any changes in muscle IL‐15 protein content or plasma IL‐15 at any of the investigated time points. In conclusion, IL‐15 mRNA level is enhanced in skeletal muscles dominated by type 2 fibres and resistance exercise induces increased muscular IL‐15 mRNA levels. IL‐15 mRNA levels in skeletal muscle were not paralleled by similar changes in muscular IL‐15 protein expression suggesting that muscle IL‐15 may exist in a translationally inactive pool.
Saccades and pursuit: two outcomes of a single sensorimotor process
Authors: Orban de Xivry Jean‐Jacques , Lefèvre Philippe
Published: August 2007

Saccades and smooth pursuit eye movements are two different modes of oculomotor control. Saccades are primarily directed toward stationary targets whereas smooth pursuit is elicited to track moving targets. In recent years, behavioural and neurophysiological data demonstrated that both types of eye movements work in synergy for visual tracking. This suggests that saccades and pursuit are two outcomes of a single sensorimotor process that aims at orienting the visual axis.
Reply in Light of Contemporary Physics to “Comment on ‘On Mach’s critique of Newton and Copernicus,”' by Herbert I. Hartman and Charles Nissim-Sabat [Am. J. Phys. 71 (11), 1163–1169 (2003)]
Authors: Hartman Herbert I. , Nissim-Sabat Charles
Published: August 2007

Mach argued for a relational rather than an absolute notion of space, insisting that centrifugal forces inside a rotating object such as a bucket can be reproduced by keeping the bucket fixed and rotating the universe. In a recent paper, Bhadra and Das elaborate on Mach’s position. We show that Mach’s relational notion of space is incomplete. Also, special and general relativity distinguish between a bucket rotating in a fixed universe and a bucket fixed in a rotating universe and between a nonrotating bucket in a nonrotating universe and a co-rotating bucket in a rotating universe, distinctions that go against Mach’s relational theory of space.
How do two moving clocks fall out of sync? A tale of trucks, threads, and twins
Authors: Styer Daniel F.
Published: August 2007

In special relativity, a pair of clocks synchronized in their own reference frame are not synchronized in another. How do two clocks, initially synchronized and at rest in the laboratory frame, fall out of sync as their speed relative to the lab gradually increases? The answer lies in general-relativistic time dilation. The path to the answer sheds light on the thread-between-spaceships paradox (also called the Bell spaceship paradox), on the twin paradox, and on the character of length contraction.
Optical response of two-electron atoms: A classical formulation
Authors: Guo Wei
Published: August 2007

When the dielectric constant of a medium formed by many-electron atoms is studied in classical physics, the electron-electron interaction within each atom is often ignored. To examine the conditions for which this approximation is valid, we consider a simplified classical model in which each atom contains two electrons interacting with each other through the Coulomb potential. It is found that the dielectric constant becomes approximately independent of the electron-electron interaction only when the electrons have the same damping constant and binding frequency.
Using ordinary multiplication to do relativistic velocity addition
Authors: Wilson Alma Teao
Published: August 2007

Although a mainstay of undergraduate courses on relativity, relativistic velocity addition is usually a pedagogical dead-end that yields little insight. We propose instead the use of velocity factors (two-way Doppler factors). Velocities can easily be converted to velocity factors, and vice versa. Velocity factors compose by ordinary multiplication. This simplification places interesting problems within reach at the introductory level. It also provides a springboard for subsequent treatment of rapidities, Bondi’s k-calculus, null or lightlike coordinates, and even spinorial formulations of relativity.
Leptin Regulates Striatal Regions and Human Eating Behavior
Authors: Farooqi I. Sadaf , Bullmore Edward , Keogh Julia , Gillard Jonathan , O'Rahilly Stephen , Fletcher Paul C.
Published: August 2007

Studies of the fat-derived hormone leptin have provided key insights into the molecular and neural components of feeding behavior and body weight regulation. An important challenge lies in understanding how the rewarding properties of food interact with, and can override, physiological satiety signals and promote overeating. We used functional magnetic resonance imaging to measure brain responses in two human patients with congenital leptin deficiency who were shown images of food before and after 7 days of leptin replacement therapy. Leptin was found to modulate neural activation in key striatal regions, suggesting that the hormone acts on neural circuits governing food intake to diminish the perception of food reward while enhancing the response to satiety signals generated during food consumption.
Land-Use Allocation Protects the Peruvian Amazon
Authors: Oliveira Paulo J. C. , Asner Gregory P. , Knapp David E. , Almeyda Angélica , Galván-Gildemeister Ricardo , Keene Sam , Raybin Rebecca F. , Smith Richard C.
Published: August 2007

Disturbance and deforestation have profound ecological and socioeconomic effects on tropical forests, but their diffuse patterns are difficult to detect and quantify at regional scales. We expanded the Carnegie forest damage detection system to show that, between 1999 and 2005, disturbance and deforestation rates throughout the Peruvian Amazon averaged 632 square kilometers per year and 645 square kilometers per year, respectively. However, only 1 to 2% occurred within natural protected areas, indigenous territories contained only 11% of the forest disturbances and 9% of the deforestation, and recent forest concessions effectively protected against clear-cutting. Although the region shows recent increases in disturbance and deforestation rates and leakage into forests surrounding concession areas, land-use policy and remoteness are serving to protect the Peruvian Amazon.
PROTON-NUCLEUS ELASTIC SCATTERING AT ~1 GeV AND THE NN AMPLITUDE
Authors: KHAN Z. A. , SINGH MINITA
Published: August 2007

Working within the framework of Coulomb modified correlation expansion of the Glauber amplitude, we analyse the elastic scattering of ~1 GeV protons on 4 He , 12 C , 16 O and 40 Ca nuclei. Emphasis has been put on the use of different parametrizations of the basic (input) NN amplitude, which provide equivalently good accounts of the elastic NN scattering observables up to the available momentum transfer region. Using realistic form factors for target nuclei, it is found that the proton-nucleus collisions could provide a test to know which is the better choice of the NN amplitude. The analysis also considers the possibility of extracting some additional information about the matter density distributions.
NON-EXTENSIVE THERMODYNAMICS, HEAVY ION COLLISIONS AND PARTICLE PRODUCTION AT RHIC ENERGIES
Authors: DE BHASKAR , BHATTACHARYYA S. , SAU GOUTAM , BISWAS S. K.
Published: August 2007

In the light of ideas of the nonextensive thermodynamics, we have analyzed here the transverse momentum spectra of pions and protons produced at different centralities in the interactions of P+P, D+Au and Au+Au interactions, all of them at [Formula: see text] GeV at RHIC-BNL. Comparison of the results and the comments thereon have also been made with indications of suitable hints to the physical import and implications. The overall impact and the utility of the approach along with the obtained results are discussed in detail.
PARALLEL STOCHASTIC SIMULATION OF MACROSCOPIC CALCIUM CURRENTS
Authors: GONZÁLEZ–VÉLEZ VIRGINIA , GONZÁLEZ–VÉLEZ HORACIO
Published: August 2007

This work introduces MACACO, a macroscopic calcium currents simulator. It provides a parameter-sweep framework which computes macroscopic Ca 2+ currents from the individual aggregation of unitary currents, using a stochastic model for L-type Ca 2+ channels. MACACO uses a simplified 3-state Markov model to simulate the response of each Ca 2+ channel to different voltage inputs to the cell. In order to provide an accurate systematic view for the stochastic nature of the calcium channels, MACACO is composed of an experiment generator, a central simulation engine and a post-processing script component. Due to the computational complexity of the problem and the dimensions of the parameter space, the MACACO simulation engine employs a grid-enabled task farm. Having been designed as a computational biology tool, MACACO heavily borrows from the way cell physiologists conduct and report their experimental work.
PREDICTION OF TRANSCRIPTION FACTOR BINDING SITES USING GENETICAL GENOMICS METHODS
Authors: VON ROHR PETER , FRIBERG MARKUS T. , KADARMIDEEN HAJA N.
Published: August 2007

In this paper, we wanted to test whether it is possible to use genetical genomics information such as expression quantitative trait loci (eQTL) mapping results as input to a transcription factor binding site (TFBS) prediction algorithm. Furthermore, this new approach was compared to the more traditional cluster based TFBS prediction.

The results of eQTL mapping are used as input to one of the top ranking TFBS prediction algorithms. Genes with observed expression profiles showing the same eQTL region are collected into eQTL groups. The promoter sequences of all the genes within the same eQTL group are used as input in the transcription factor binding site search. This approach is tested with a real data set of a recombinant inbred line population of Arabidopsis thaliana. The predicted motifs are compared to results obtained from the conventional approach of first clustering the gene expression values and then using the promoter sequences of the genes within the same cluster as input for the transcription factor binding site prediction.

Our eQTL based approach produced different motifs compared to the cluster based method. Furthermore the score of the eQTL based motifs was higher than the score of the cluster based motifs. In a comparison to already predicted motifs from the AtcisDB database, the eQTL based and the cluster based method produced about the same number of hits with binding sites from AtcisDB.

In conclusion, the results of this study clearly demonstrate the usefulness of eQTL to predict transcription factor binding sites.
AN EFFECTIVE DATA MINING TECHNIQUE FOR RECONSTRUCTING GENE REGULATORY NETWORKS FROM TIME SERIES EXPRESSION DATA
Authors: MA PATRICK C. H. , CHAN KEITH C. C.
Published: August 2007

Recent development in DNA microarray technologies has made the reconstruction of gene regulatory networks (GRNs) feasible. To infer the overall structure of a GRN, there is a need to find out how the expression of each gene can be affected by the others. Many existing approaches to reconstructing GRNs are developed to generate hypotheses about the presence or absence of interactions between genes so that laboratory experiments can be performed afterwards for verification. Since, they are not intended to be used to predict if a gene in an unseen sample has any interactions with other genes, statistical verification of the reliability of the discovered interactions can be difficult. Furthermore, since the temporal ordering of the data is not taken into consideration, the directionality of regulation cannot be established using these existing techniques. To tackle these problems, we propose a data mining technique here. This technique makes use of a probabilistic inference approach to uncover interesting dependency relationships in noisy, high-dimensional time series expression data. It is not only able to determine if a gene is dependent on another but also whether or not it is activated or inhibited. In addition, it can predict how a gene would be affected by other genes even in unseen samples. For performance evaluation, the proposed technique has been tested with real expression data. Experimental results show that it can be very effective. The discovered dependency relationships can reveal gene regulatory relationships that could be used to infer the structures of GRNs.
Landslides caused by rapid groundwater changes
Authors: Premchitt J. , Brand E.W. , Phillipson H.B.
Published: August 2007

A severe rainfall event occurs once every two years in Hong Kong, causing widespread landslides which result in human casualties and much damage. It has recently been established that these landslides are caused largely by short-period, high-intensity rainfall, with nearly all failures occurring within a few hours of peak intensity. The failures are therefore attributable mainly to rapid transient variations in groundwater conditions. These findings are in contradiction to previously accepted theories on failure mechanisms, and it is therefore necessary for these to be reconsidered.

A new theoretical model is now being examined in Hong Kong to explain the rapid landslide response following high-intensity rainfall. This is based on well-defined hillslope hydrological theories. Of particular significance in this context are thought to be subsurface erosion pipes and tunnels which have been found to exist in some of Hong Kong’s hillslopes, especially those carpeted with colluvium.
The inter-relationship between changes in groundwater conditions and engineering construction
Authors: Brassington F.C.
Published: August 2007

The presence of groundwater and its effects are often major considerations in the design of civil engineering works. The engineering geologist is expected to provide reliable information on this subject by means of appropriate site investigation techniques. In many instances possible changes in groundwater levels beyond the normal seasonal variations are not considered. Large changes can occur, for example, a reduction in groundwater pumping will cause water tables to rise, flooding basements and tunnels and possibly changes in the load bearing properties of soils. Civil engineering construction can have a similarly significant effect on local water supplies especially in the case of road cuttings, tunnels and pipelines. The British Standard Code of Practice for Site Investigations (BS 5930: 1981) does not contain any recommendation that site investigations should include an examination of local groundwater abstraction. Nor does it suggest that surveys should be carried out to locate and identify local private water supplies where there is a danger that the proposed construction will affect them. It is recommended that the Code of Practice is amended to include both these omissions.
Groundwater conditions in the coastal landslides of the Isle of Sheppey
Authors: Dixon N. , Bromhead E.N.
Published: August 2007

The paper describes an investigation into the groundwater pressure distribution in two sections through the 46 m high London Clay cliffs at Warden Point, Isle of Sheppey. Over 50 piezometers were installed, and these show a groundwater pressure regime which indicates a significant degree of response to stress relief. The paper describes the influence of these pressures on the mechanics of failure of the cliffs, and the engineering implications of their presence.
The effects and consequences of groundwater abstraction on foundations at Drax Power Station, North Yorkshire
Authors: Dobie M. , Newman R.L.
Published: August 2007

In order to provide an additional supply of water for Drax Power Station the CEGB proposed to abstract water from the Bunter Sandstone aquifer which underlies the site. A pumping test was carried out to assess the effects of abstraction, and this involved monitoring groundwater pressures and surface deformations.

The first part of the paper details the ground and groundwater conditions, and describes the design of the pumping test and installation of the instrumentation. Theoretical aspects of analysis and response of groundwater pressures to abstraction are also discussed.

The second part of the paper outlines and analyses the results of the pumping test. The results are presented as a series of graphs of drawdown, surface deformation, and duration and rate of pumping. The true aquifer characteristics were determined from the pumping test results using the analysis of Thiem incorporating Huisman's procedures for partially penetrating wells. Using the same analyses the effects of the pumping test are extrapolated to proposed 'licenced' rates. A discussion follows on the results and some interesting observed responses.

The final part of the paper assesses the consequences of surface deformations due to groundwater abstraction on existing and proposed structures. In particular, the effects of large differential settlements between buried services and piled structures, and also induced negative skin friction on vertical and raking piles are considered. Recommendations were subsequently given on the siting of the well which minimised its effects.
Rising groundwater levels in cities
Authors: Hurst C.W. , Wilkinson W.B.
Published: August 2007

It is well documented that groundwater levels in a number of cities in this country and abroad have been rising over the past few years. Parts of central London are experiencing rises of one metre per year, while in Paris, previously dry basements are now affected by severe flooding.

The extraction of good quality water from city wells for a variety of industrial and domestic purposes led to a general lowering of groundwater levels from the early 1800s. During the period of depressed groundwater levels development within restricted city centre sites required higher buildings with deeper basements and foundations. Communication networks also moved underground to ease congestion at the surface. A large percentage of this work was carried out during a period when the groundwater was tens of metres below ground level; a situation accepted as being stable at the time. Consequently the effect of a higher water table was often not considered in the geotechnical design of structures. Within central London the water table is still very deep and may not cause problems for years to come. In Birmingham the situation is more critical and the rise in groundwater level is already causing problems.

Computer model predictions play a leading role in predicting tomorrow’s groundwater levels. Evidence suggests that groundwater levels in the near future will attain those of natural conditions. The effect that these levels will have on current structures requires assessment. Simplified calculations for the London area show that the bearing capacity of deep basement foundations and piles could be reduced by 25’30% if the rise in groundwater level continues. High levels of sulphates have been recorded during recharge experiments and these will produce adverse effects on unprotected foundations. Problems with high artesian pressure during construction are also likely if the aquifer is confined. These is an urgent need to assess the geotechnical risk to engineering structures with respect to the rising groundwater levels. This should be carried out now so that problems can be properly anticipated and solutions developed in good time.
Tidal variations of groundwater level in an estuarine aquifer
Authors: Money M.S.
Published: August 2007

Groundwater levels in coastal aquifers respond to tides with amplitudes that decrease and time lags that increase inland. Analysis of tidal variations is complicated by the fact that long-term cycles are superimposed on the main diurnal cycle so that there are small but significant differences between successive tides and in the piezometric response.

It is shown that type curves can be constructed on the basis of simple theory to predict the piezometric response by using tidal factors as in navigational calculations.

Type curves have been drawn for piezometers on a site in the Tees estuary but these do not conform with the theoretical plots and it is suggested that the discrepancies are due to groundwater flow towards the coast. Recommendations are made for data collection.
Effects of groundwater on soils, rocks and construction materials: an introduction
Authors: de Freitas M.H.
Published: August 2007

Although the effects of groundwater on soils, rocks and construction materials may appear to be slow to occur, there is increasing evidence to demonstrate that such effects progress at rates that are significant to engineering. A growing body of evidence that demonstrates the influence exerted by groundwater chemistry and flow upon the geotechnical character of the ground is also accumulating. With these thoughts in mind the papers submitted to this session of the conference are introduced and the work they describe reviewed.
The effect of groundwater flow on the strength and stability of silicate grouted soils
Authors: Shirlaw J.N.
Published: August 2007

A considerable volume of data on the strength of silicate grouted soils has been published in recent years. In particular there has been considerable discussion of the confined and unconfined strengths of grouted sands and the effect of creep on those strengths. Little has been said on the effect of groundwater seepage on the strength and residual permeability of the sand/silicate system.

Following observations on site into the effectiveness of silicate grouting, a small laboratory programme was set up to examine the effect of seepage on strength and residual permeability. The findings of the programme are summarised.
Hazardous waste containment
Authors: Mitchell J.K.
Published: August 2007

Containment systems that have been developed to isolate wastes from the soil and water that surround them in the ground include compacted clay barriers, slurry trench cutoff walls, geomembrane walls, concrete diaphragm walls, sheetpile walls, grout curtains, hydraulic barriers, compacted clay liners, and geomembrane liners. The choice in any case is dictated by whether waste from an existing facility or spill or from a new disposal site is to be contained and by the geological setting.

Properly compacted clays have properties that are well-suited for waste containment, as do flexible membrane liners. Compatibility between these materials and the waste must be considered in any case. Evidence is accumulating that the hydraulic conductivity of properly compacted clay is not significantly affected by exposure to most organic solvents and inorganic chemical wastes in dilute solution. Double liner designs that incorporate both compacted clay and flexible membrane liners as well as leachate collection systems have been proposed to satisfy the requirements of recent legislation in the USA.

The higher temperatures and long times associated with nuclear waste isolation by deep burial pose special problems of barrier stability. It appears that smectite clay has adequate stability to be used for repository buffer and seal material.
Trace organic compounds in groundwater: a survey of unpolluted groundwater from three major British aquifer systems
Authors: Clark L. , Kenrick M.A.P.
Published: August 2007

In view of the increased concern about the occurrence and persistence of organic chemicals in the environment, the Water Research Centre instigated a baseline survey of trace organics in groundwater from representative cross-sections of three major British aquifer systems.

A total of 32 public and private supply boreholes in selected areas of the Permo-Triassic Sandstone, Chalk, Lincolnshire Limestone and the Great Oolite aquifers have been sampled. The areas have been chosen with the aim of characterising the organic content of ‘clean’ groundwater from the confined and unconfined zones on each cross-section. The survey was designed to encompass groundwaters of varying ages, from recent recharge in outcrop areas through to ancient waters in deep confined sections. In this way, it was expected that any compounds of anthropogenic origin would be detected only in the younger groundwaters.

The total organic carbon content of the groundwaters sampled was generally very low, between 0.2 and 1.4 mg/1; low levels of aromatic halogenated hydrocarbons, which are generally taken to be contaminants, were found in many of the samples at levels above 0.01 µg/1; low levels of aromatic hydrocarbons were often detected. Although the number of compounds detected averaged 20 per sample (range: 7 to 52), few were present at concentrations greater than 0.1 µg/1. Over 100 different compounds were detected altogether but only 75 could be identified positively. Of these, nine occurred in more than half of the samples. There were no obvious differences in either compound types or levels between the confined and unconfined zones of any of the aquifers.

Uncontaminated groundwater examined in this survey may be typified as having a TOC level below 0.8 mg/1, and no more than four compounds (none of which are chlorinated hydrocarbons) present at levels above 0.1 µg/1.
Application of isotope hydrology to groundwater problems in engineering geology
Authors: Leggo P.J. , Warren C.D. , Blakeway D.
Published: August 2007

Research on the natural variation of the isotopic species of hydrogen and oxygen has led to a firm understanding of the physical processes involved in the isotopic fractionation of these elements in water. Although much use has been made of artificially introduced chemical tracers to investigate flow patterns and characterise the groundwater, this method commonly suffers from bulk dilution and additional problems that limit its applicability to many investigations in engineering geology. Such limitations are avoided in the use of stable isotopic measurements as it is the variability in the isotope species of the water molecule itself that are used as the characterisation parameters providing a ‘fingerprint’ for each particular water sample.

In this paper background details of stable isotopic fractionation are summarised and two recent case histories presented to demonstrate its application to groundwater studies, on a small scale, commonly met in many civil engineering situations, namely investigation of possible leakage from a reservoir and identification of the source of water contained within a large landslip. By the seasonal variations in the isotopic values, trends in groundwater isotopic composition can be identified and interpreted within the often limited geological and hydrogeological constraints of the site so as to provide conclusions as to the origin of the groundwaters.
Groundwater geochemistry and mass transfer in the East Yorkshire Chalk
Authors: Pitman J.I.
Published: August 2007

The chemical composition of groundwater from the East Yorkshire Chalk exhibits a systematic change in chemistry as it moves downdip from the recharge area of the Wolds to the Holderness lowland. Three distinctive hydrogeochemical zones, coincident with the unconfined, semi-confined artesian aquifer and fully confined aquifer of Holderness exist. Chemical composition in the unconfined aquifer is dominated by carbonate equilibria at a closed system PCO
2
of −2.09 with calcite and one mole % Mg-calcite. (Ca
2+
=2.3 mmol/l; Mg
2+
=0.2 mmol/l; HCO
3
−
=4.08 mmol/l; ∑CO
2
=4.48 mmol/l; pH=7.44). In the semi-confined artesian flow aquifer, ingress of soil CO
2
and limited reduction of dissolved O
2
increase ∑Co
2
to approximately 6.4 mmol/l, whilst Ca
2+
increases to 3.69 mmol/l at a PCO
2
of −1.76, and pH of 7.17. In the fully confined aquifer, reduction of O
2
, NO
3
, SO
2
−4
occurs, with increased ∑CO
2
to 6.86 mmol/l, HCO
3
−
to 6.13 mmol/l, and PCO
2
to −1.87. Cation exchange of Ca
2+
for Na
+
also occurs. Mass transfer calculations show that the major reactions in the aquifer take place in the soil zone, and within the semi-confined zone, with low Mg-calcite undergoing solution whilst calcite is precipitated. Throughout the aquifer, groundwaters are saturated with calcite, after allowing for the effects of ion pairing and complex formation.
Pollution investigation of a Triassic sandstone aquifer: the role of mineralogy
Authors: Spears D. A.
Published: August 2007

Soil and sediment samples below an effluent spreading site were analysed for mineralogy, whole rock major and trace element geochemistry and porewater chemistry. In spite of the high surface loading of trace metals, sediments are contaminated to depths of only 1 m. Sediment contamination at depth in the unsaturated zone was not detected. Pore water concentrations do decrease with depth, but this is attributed to dilution rather than reaction. Trace metal porewater concentrations at depth approach the ‘natural’ background levels for Permo-Triassic sandstones. Dissolution of minerals is predictably limited, although iron oxyhydroxide and clay minerals are distributed to give large effective surface areas and probably are responsible for trace metal absorption and exchange, and the attainment of low solute concentrations.
A technique for groundwater quality monitoring using resistivity measurements made through a modified plastic well-screen
Authors: Jackson P. , Hallam J. , Allen D. , Hassett S. , Culshaw M.G.
Published: August 2007

A composite well-screen has been developed for resistivity measurements using high permeability ‘terran’ fabric wrapped around plastic well-screen containing 1.5 mm slots. Laboratory and
in situ
tests indicate that this screen presents a relatively small impedance to the flow of water and electricity while excluding fines that may be present.

Experiments with the well-screen were made
in situ
after emplacement in an unconsolidated, dense, fine coastal sand body. Results are presented of electrical resistivity measurements made through the well-screen, using a focussed resistivity tool, which indicate that changes in groundwater conductivity could be monitored as changes in formation resistivity. The groundwater inside the well-screen has been logged but suffers from the possibility of vertical mixing whereas measurements through the casing do not.

The well-screen also offers the possibility of taking water samples in unconsolidated sediments using a simple, very low pressure, double packer system. The effect of the well-screen on the resistivity measurements was found to be small after comparison with a self-bored resistivity log where the sand has been in direct contact with the formation.
Borehole sampling techniques and field analysis of groundwater in landfill pollution studies
Authors: Stuart A. , Hitchman S. P.
Published: August 2007

A borehole drilled at a landfill for site investigation and/or monitoring purposes will generally intercept a vertical interval within an aquifer which may have a wide range of permeabilities and so the entry of a pollutant into a borehole column will not be uniform. Drilling methods and the need to avoid the introduction of contaminants to groundwater mean that hydraulic testing may be restricted, particularly in unconsolidated formations. Techniques that do not add water should be used in preference to injection or tracer tests. Sampling and testing during borehole drilling are necessary to define the groundwater flow system within the borehole, to enable an effective completion to be made. In unconsolidated formations, silt and clay horizons may restrict vertical groundwater movement with the result that pollutants become stratified and move in discrete zones within the aquifer. Therefore taking a bulk or average water sample from a borehole completed to monitor full aquifer thickness will usually result in dilution and mixing of the contaminant with cleaner groundwater. Formation disturbance caused by percussion drilling can also cause vertical groundwater flow and mixing outside the borehole casing making the isolation of discrete zones difficult.

Groundwater samples obtained during site investigation drilling or from routine sampling visits will be subject to temperature and pressure change. As a sample is depressurised, variables such as pH, Eh, dissolved gas content and the speciation of certain constituents can be altered. Quantification of these changes and their minimisation means that strict procedures should be adhered to in sample handling and analysis on site.

This paper, covering landfill research work funded mainly by the Department of the Environment and carried out by the Fluid Processes Research Group of the British Geological Survey describes techniques and equipment used to overcome some of the problems cited, to obtain representative groundwater samples.
Design and application of a borehole flowmeter
Authors: Wild J.L.
Published: August 2007

A borehole flowmeter has been developed to measure low flow rates in NX (76 mm) boreholes. The instrument can be used to determine the standing water level and permeability of a test section of the borehole.

The borehole flowmeter is a short, lightweight wireline packer which is inflated pneumatically and contains a turbine flowmeter transmitter unit. The useful flow range of the standard instrument is approximately 0.7 cm
3
/s to 70 cm
3
/s. The unit was originally designed to measure small axial flow rates in an array of boreholes which was thought to intersect a series of perched aquifers.

Experimentation showed that an increased rate of flow could be induced through the unit by piping water into the top of the borehole, the flow rate being proportional to the excess head of water above the unit. Using this principle, a form of
in situ
falling head permeability test was devised. The corrected head of water at a zero flow rate was found to correspond to the standing water level in a borehole, and the linear relationship between applied head and flow rate was used to calculate the permeability of the section of borehole below the unit. The results are compared with those of packer tests carried out in the same test sections.

The method has several advantages over packer testing in many conditions. The wireline equipment is light and can be operated by one man. The permeability test results are repeatable and are completed on average within one hour, though a satisfactory relationship between flow and head is usually established within ten minutes in a moderately permeable formation.