Soils ranging in texture from sand to clay were used to compare permittivity measurements made using a Surface Capacitance Insertion Probe (SCIP) and time domain reflectometer (TDR). Measurements were made using the same electrodes embedded in each soil, making the measurements directly comparable. The objective of the work was to test a model describing the frequency response of the SCIP to both permittivity and electrode conductance, and to compare results with TDR and network analyzer measurements. The model was tested using liquids of known permittivity and in saline, dielectric solutions. Surface Capacitance Insertion Probe and TDR determined permittivity values are similar for sandy soils but diverge for loam and clay soils. Using Topp's values as a reference, the SCIP‐determined permittivities for loams and clays lay close to the curve at water contents <0.25 m3 m−3, then often rose above the curve with increasing water content. Surface Capacitance Insertion Probe permittivity correction, using electrical conductivity (EC) measured at 1 kHz, corrected the results in sands reasonably well but not enough in loams and clays for reliable calibration. We propose three possible reasons for the higher than expected permittivity values observed using the SCIP: (i) higher than expected real permittivity created by dielectric dispersion, (ii) a large contribution of the imaginary permittivity due to relaxation processes assumed to be negligible, and (iii) poor model prediction of permittivity due to excessive damping of the oscillator circuit with high EC and dielectric losses. Results from network analyzer measurements for one of the clay soils were used to aid data interpretation. The TDR measurements were much more consistent, producing apparent relative permittivity values below those of the Topp curve for the finer textured soils.

An experimental study of water fluxes from roofs in a residential area has quantified water fluxes from different types of roof and identified the major controls on the process. Roofs with pitches of 0°, 22° and 50° and orientations of 15° (from true north) (NNE) and 103° (ESE) were selected. A novel automatic system for monitoring has been developed. Noticeable differences in rainfall, runoff and evaporation were found for different roof slopes, aspects and heights. Depending on height, flat roofs collected 90 to 99% of rainfall recorded at ground level. Roofs with a 22° slope; facing south‐south‐west (i.e. facing the prevailing wind) captured most rain, whereas east‐south‐east facing roofs with slopes of 50° received the least. Depending on the roof slope, the average rainfall captured ranged from 62 to 93% of that at ground level. For the same slope, the results indicated that from roofs orientated normal to the prevailing wind; (i) captured rainfall was higher, (ii) evaporation was higher and (iii) runoff was less than that from roofs having other aspects. Monthly variations in the runoff–rainfall ratio followed the rainfall distribution, being lowest in summer and highest in winter. The highest mean ratio (0·91) was associated with the steeper roof slope; the lowest ratio (0·61) was for roofs facing the prevailing wind direction. For the same amount of rainfall, the runoff generated from a steeper roof was significantly higher than that generated by a moderate roof slope, but the lowest runoff was from roofs facing the prevailing wind. The results have also shown that the amount of runoff collected (under UK climatic condition) was sufficient to supply an average household in the studied area with the major part of its annual water requirements. The use of this water not only represents a financial gain for house owners but also will help protect the environment by reducing demand on water resources through the reduction of groundwater abstraction, construction of new reservoirs, and a reduction of the flood risk as its in situ use is considered a preventive measure known as a source control. Copyright © 2003 John Wiley & Sons, Ltd.

This paper summarizes the results of a comparative study on seismic design of highway bridges jointly undertaken by the US. Federal Highway Administration and Japan's Public Works Research Institute. The seismic design specifications for highway bridges of the two countries are reviewed and compared with respect to their design philosophies and procedures. Some major design parameters including design seismic forces, response modification factors and minimum support lengths are addressed in detail. The differences between the two specifications are illustrated via a design example of a reinforced concrete column for simple, two-span bridges common in both countries. Three different scale models of the column are designed in accordance with the seismic design specifications of the United States and Japan, and tested on a shake table for their comparative seismic performance. The results of the shake table tests are discussed separately in a companion paper.

Lack of accurate data has led some hydrologists and city planners to assume that urban infiltration is zero and runoff is 100% of the rainfall. These assumptions lead to an over estimation of road runoff volume and an underestimation of direct recharge to groundwater, which is already rising under some UK cities. This study investigates infiltration and runoff processes and quantifies the percentage of rainfall that contributes to storm drainage, and that which infiltrates through different types of road surface. Access tubes were installed for measuring soil water content using a neutron probe in three car parks, a road and a grass site at the Centre for Ecology and Hydrology, Crowmarsh Gifford, Wallingford. Storm drainage was recorded at the exit of the Thamesmead Estate in Crowmarsh Gifford, just before the drain joins the River Thames at Wallingford. Rainfall and water table depth were also recorded. Weekly measurements of soil moisture content indicated that the top 40 cm layer is not influenced by water‐table fluctuations and, therefore, positive changes in soil moisture could be attributed to infiltration of rainfall through the surface. Depending on the nature of the surface, subsurface layers, level of traffic, etc., between 6 and 9% of rainfall was found to infiltrate through the road surfaces studied. The storm drainage generated by road runoff revealed a flow pattern similar to that of the receiving watercourse (River Thames) and increased with the increase of infiltration and soil water content below the road surface. The ratio of runoff to rainfall was 0·7, 0·9 and 0·5 for annual, winter (October–March) and summer (April–September) respectively. As the results of the infiltration indicated that 6 to 9% of annual rainfall infiltrates through the road surface, this means that evaporation represents, 21–24% of annual rainfall, with more evaporation taking place during summer than winter. Copyright © 2003 John Wiley & Sons, Ltd.

A model describing the increase in the relative permittivity of water with distance from the soil mineral surface is presented. The model assumes an exponential increase in the value of permittivity with increasing distance from the mineral surface; arguments are presented supporting this approach. The volume of bound water (within the bandwidth of time domain reflectometry, (TDR) 0.01–1GHz) is considered to be equivalent to the soil hygroscopic water content. The refractive index mixing equation is used as a geometric base into which the model is incorporated. The new equation is tested using measurements of permittivity collected from two drying undisturbed soil cores that contained ∼10% hygroscopic water. The RMSE of predicted permittivity as a function of water content was found to decrease from ∼3.5 to less than 1. The model was further tested on data previously presented in the literature and found to correspond reasonably well.

Seismic performance of reinforced concrete bridge column under repeated earthquake ground motions is investigated through shake-table experimentation on a scale model. The specimen is subjected to a series of simulated ground motions at different levels of shaking intensity. The deformation and damage evolution of the test column is addressed in terms of selected mechanical quantities including the effective stiffness, hysteretic energy dissipation, residual displacement, and dominant vibration frequency. The test column, designed according to the AASHTO seismic design specifications, survived successive ground motions by virtue of its outstanding energy-absorption and ductility capacity. Analysis of the experimental data indicates that structural degradation of the column closely correlates with its decreasing effective stiffness and increasing hysteretic energy dissipation. The residual displacement measured at the column top after each shaking event increases with the growth of damage in the column. A frequency-domain analysis of the vibration response of the column during successive ground motions indicates that increase in the structural degradation of the column results in a decrease in the dominant vibration frequency of the column.

Measurement of the apparent dielectric permittivity of soils (dielectric constant) is becoming a popular way of estimating soil volumetric water content. This paper focuses on the measurement of apparent permittivity in four sandy soils using; time domain reflectometry (TDR), a surface capacitance insertion probe (SCIP) and a Theta probe. Measurement of the apparent permittivity using the SCIP and Theta probe are compared with the apparent permittivity measured using the TDR.

Capacitance probes are a fast, safe and relatively inexpensive means of measuring the relative permittivity of soils, which can then be used to estimate soil water content. Initial experiments with capacitance probes used empirical calibrations between the frequency response of the instrument and soil water content. This has the disadvantage that the calibrations are instrument-dependent. A twofold calibration strategy is described in this paper; the instrument frequency is turned into relative permittivity (dielectric constant) which can then be calibrated against soil water content. This approach offers the advantages of making the second calibration, from soil permittivity to soil water content, instrument-independent and allows comparison with other dielectric methods, such as time domain reflectometry.A physically based model, used to calibrate capacitance probes in terms of relative permittivity (epsilon(r)) is presented. The model, which was developed from circuit analysis, predicts, successfully, the frequency response of the instrument in liquids with different relative permittivities, using only measurements in air and water. It was used successfully to calibrate 10 prototype surface capacitance insertion probes (SCIPs) and a depth capacitance probe. The findings demonstrate that the geometric properties of the instrument electrodes were an important parameter in the model, the value of which could be fixed through measurement.The relationship between apparent soil permittivity and volumetric water content has been the subject of much research in the last 30 years. Two lines of investigation have developed, time domain reflectometry (TDR) and capacitance. Both methods claim to measure relative permittivity and should therefore be comparable. This paper demonstrates that the IH capacitance probe overestimates relative permittivity! as the ionic conductivity of the medium increases. Electrically conducting ionic solutions a ere used to test the magnitude of this effect on the determination of relative permittivity. The response was modelled so that the relative permittivity, independent of ionic conductivity, could be determined in solutions with an electrical conductivity of up to 0.25 S m(1). It was found that a solution EC of less than 0.05 S m(-1) had little impact on the permittivity. measurement.

The threat of Bovine Spongiform Encephalopathy (BSE) to humans was realized in March 1996, when the Spongiform Encephalopathy Advisory Committee (SEAC) reported to the government that the most likely explanation of the new variant Creutsfeldt-Jakob Disease (nvCJD) in humans was exposure to the BSE agent. To assess the potential risk of nvCJD, it is necessary to understand the development of the BSE epidemic within the cattle population. This paper reports on work undertaken to model the observed BSE epidemic in the UK using established Bayesian methodology. (C) 1997 John Wiley & Sons, Ltd.

This article describes measurements made at each site and for each vegetation cover as part of the soils program for the HAPEX-Sahel regional scale experiment. The measurements were based on an initial sampling scheme and included profile soil water content, surface soil water content, soil water potential, infiltration rates, additional measurements on core samples, and grain size analysis. The measurements were used to categorize the state of the surface and profile soil water regimes during the experiment and to derive functional relationships for the soil water characteristic curve, unsaturated hydraulic conductivity function, and infiltration function. Sample results for different supersites and different vegetation covers are presented showing soil water profiles and total soil water storage on days corresponding to the experimental ‘Golden Days’. Sample results are also presented for spatial and temporal distribution of surface moisture content and infiltration tests. The results demonstrate that the major experimental objective of monitoring the supersites during the most rapid vegetative growth stage with the largest change of the surface energy balance following the rainy season was very nearly achieved. Separation of the effects of probable root activity and drainage of the soil profile is possible. The potential for localized advection between the bare soil and vegetation strips of the tiger bush sites is demonstrated.

Two methods to estimate the saturated and unsaturated hydraulic conductivity of soil were compared in a catchment in south-west England. The catchment consists of three land use domains — arable, permanent grass and woodland. The methods used were in situ measurements using a Guelph permeameter and the predictive model of Rawls and Brakensiek, which uses percentage of sand, percentage of clay and porosity as input. In grassland and woodland no significant differences were found between the mean saturated and unsaturated hydraulic conductivity estimated by the two methods. It is suggested that a significant difference found for the arable land is due to the effect of farming operations on soil permeability. On a catchment scale there were no significant differences between the methods. The results obtained using the predictive model are encouraging and worth further investigation. The advantages and disadvantages of the two methods are evaluated.

Physically based hydrological models require values of saturated and unsaturated hydraulic conductivity to solve the equations used to describe subsurface flow. Variability of these parameters within and between various land uses and soil types is an important consideration if hydrological behaviour is to be described realistically.A catchment in south-west England has been chosen to validate the European Hydrological System (Systeme Hydrologique Europeen - SHE). The catchment includes three land use domains - arable (including temporary grass), permanent grassland and woodland. For the unsaturated zone component of the SHE both saturated hydraulic conductivity, K(s), and unsaturated hydraulic conductivity as a function of matric suction, K(psi), are required. The aim of this investigation was to measure the parameters for input to the model, to assess the variability of these parameters and to determine whether or not parameters should be used for each domain independently. A Guelph permeameter was used to obtain K(s) and alpha, which describes the slope of the logarithmic unsaturated hydraulic conductivity function (K(psi) = K(s) exp(alphapsi)). Measurements at four depths were carried out. Domains were chosen according to land use - arable land (including temporary grass), permanent grassland and woodland. Both K(s) and alpha were found to be log-normally distributed. The K(s) values were highest in the grassland and lowest in arable land. The difference between means was significant for K(s) but not for alpha in the three domains. High values of K(s) were attributed to preferential flow along slate faces and root-induced channels in the grassland and woodland, respectively, as indicated by dye tests. Finally, it was concluded that, as K(s) and K(psi) differ significantly between domains, different hydrological behaviour would be expected. It is therefore recommended that different parameter sets be used for modelling the individual domains.

SUMMARYCase studies are presented of the use of soil water measurements to determine the pathways, timing and quantities of natural recharge to groundwater at sites on the Chalk and Triassic Sandstone aquifers in England. Water content and potential have been monitored for several years at seven sites and unsaturated hydraulic conductivity measured in situ at three of the chalk sites. Recharge was estimated using a combination of the zero flux plane (ZFP) method and a simple water balance. Examples of the water balance are presented for three sites.It is shown that a shallow (∼1 m) depth of permeable drift and soil increased the annual drainage from the soil to the underlying formation by about 34% at a pair of sites on the Chalk aquifer. Effects upon drainage timing are equally dramatic. On thin soil directly on chalk, drainage responds quickly to rainfall and, once evaporation starts to exceed rainfall, declines rapidly. On drift‐covered sites, the drainage continues for a much longer period, as it does from the loamy soil overlying the sandstone site.

In the past, it was not uncommon to perform esophageal resection for peptic esophagitis. Today, however, thanks not only to widespread use of modern dilatation techniques but also to surgical procedures such as duodenal diversion and gastroplasty fundoplication, the indications for esophagectomy are much less frequent [1, 3, 5, 8, 13]. The rate of esophageal resection for peptic esophagitis is currently about 10% (Table 1). Esophageal resection for peptic esophagitis accounts for around 25% of all esophagectomies performed for benign lesions of the esophagus (Table 2) [3, 8]. It is important to say that in the present study patients undergoing a retrosternal by-pass without esophagectomy are not considered. This procedure should in fact not be used since it leaves in place the diseased esophagus which is still exposed to gastroesophageal reflux (G.E.R.) and inaccessible to endoscopic surveillance.

We report the use of a silicone rubber T tube for the management of complex airway problems in 47 patients during the past 15 years. The tube has been used for palliation in 11 patients with malignant obstruction of the airway, and as the sole treatment or as an adjunct to operation in 36 other patients. Based on the satisfactory results with the use of these tubes, we have utilized silicone stents in the bronchus and bifurcation prostheses at the carina. In the past, we have inserted the T tubes through a tracheostomy stoma. More recently, we have used a technique for endoscopic placement of the T tubes in which the horizontal limb is pulled out through the tracheostomy stoma. This technique facilitates introduction of the tube and maintains the airway during insertion. The use of silicone stents provides an important tool in the management of complicated airway problems, and we anticipate their increased use in the future.

Thin-needle aspiration lung biopsy has become an important diagnostic technique in chest disease. Complications, other than pneumothorax, are infrequent. We report a case of acute cardiac tamponade complicating biopsy of a lesion near the mediastinum. Caution should be exercised in selecting patients for, and in performing biopsies in, or close to the mediastinum.