1,481 research outputs found

    Network reinforcement requirements for Scotland and the rest of the UK (RUK) - and possible solutions for this

    Get PDF
    A novel multi-objective transmission expansion planning (MOTEP) tool has been developed to analyse, on a comprehensive geographical scale, the reinforcements required to a base case electrical transmission network following application of a chosen future energy scenario, and to generate optimal network expansion plans, designed to alleviate these areas of strain, for a range of crucial network planning objectives. Here, we report the application of the MOTEP tool to a base case predicted 2014 GB transmission network (thereby including already planned reinforcements such as the Beauly to Denny line) under heavy strain from three 2020 energy scenarios developed by the two-region UK MARKAL energy system model. Reinforcement requirements for Scotland and the RUK beyond 2014, along with optimal network expansion plan options, are examined

    Modelling self-potentials as a predictor of seawater intrusion in coastal groundwater boreholes

    Get PDF
    Seawater intrusion is pervasive on every inhabited continent, although existing monitoring techniques typically fail to predict the timing of its occurrence in groundwater boreholes. Recent monitoring of a coastal groundwater observation borehole suggests that a nearby saline front can affect self-potential (SP) signals and could be used to predict saline intrusion. The borehole displays a persistent SP gradient, which is absent in boreholes further inland. This gradient reduces several days before saline breakthrough, constituting a possible precursor to intrusion, and fluctuates at the same frequency as oceanic tides. The magnitude of the oscillations reduces prior to breakthrough. A numerical model of the surrounding Chalk aquifer explains the SP gradient and precursor for the first time. The gradient requires spatial variation in the exclusion-efficiency of the aquifer, a parameter that, in the context of seawater intrusion in the Chalk, describes the extent to which anions are excluded from the pore space and which has been linked previously to rocks with narrow pore throats. The modelled precursor is a response to seawater moving through fractures with a change in exclusion-efficiency across them. The fractures driving the precursor may either intersect the borehole or lie immediately beneath it. However, the observed reduction in SP oscillations can only be replicated in the latter scenario. The model relies on relatively high values of exclusion-efficiency in marl horizons, a parameter that had not been measured previously in this lithology. The results of marl testing carried out as part of this project closely agree with the simulated values and provide greater confidence in the model. These SP phenomena were observed in a single coastal groundwater observation borehole. To understand fully the applicability of SP monitoring and modelling for predicting seawater intrusion, it should now be applied to boreholes in different aquifer types, including operating abstraction boreholes.Open Acces

    Observations in man and animals on the distribution and excretion of sodium and potassium

    Get PDF
    The work described in the papers submitted was begun in 1950 when radioactive isotopes of sodium and potassium first became available for biological research. The initial investigations were made with ²⁴Na and methods were developed leading to the measurement of the amount of sodium in the human body that was free to exchange with the isotope. This afforded a means of ascertaining the amount of metabolically active sodium in the body and is commonly referred to as "exchangeable sodium" or Naₑ. During the course of this work it was found that there was a large amount of sodium in bone but that about 75 per cent was not available for exchange. This was confirmed by the use of the long half-life isotope ²²Na. The significance of the large amount of sodium in bone could not be investigated in man but studies in rats under various experimental conditions showed that in states of acute depletion sodium was withdrawn from the bones especially in young animals . This work demonstrated that ²²Na is not safe for use in man as a small amount may be retained in bone for a long period.The amount of exchangeable potassium in the body can likewise be measured with the isotope ⁴²K. Practically all the potassium in animals was available for exchange. When exchangeable sodium and potassium are measured simultaneously, as is often required, special techniques must be developed because the half lives of the isotopes ²⁴Na and ⁴²K (15.0 and 12.3 hours) are close. The introduction of tetraphenyl boron proved extremely satisfactory for the separation of potassium from sodium in biological fluids. Rubidium was thought to have a similar distribution to potassium in the body but investigations with the isotope ⁸⁶Rb showed that it was not a reliable alternative to ⁴²K.Previous to the use of sodium and potassium radioisotopes the only way to study the metabolism of these electrolytes in the human body was by cumulative metabolic balance methods. In long term investigations this is extremely laborious. However, measurements of Naₑ, and Kₑ at intervals can demonstrate cumulative changes, are simpler and less time consuming, and gave results in good agreement with the balance method. Furthermore, the isotope techniques yielded a measure of the amounts of sodium and potassium in the body . The potassium content of the body was related to the lean tissue mass; in comparison with healthy males the amount of potassium was reduced in females and in those with wasting diseases. In chronic disease there was an increase in the proportion of sodium in the body and this was seen to the greatest extent in oederenatous states.Characteristic changes in sodium and potassium metabolism take place after the infliction of an injury or a surgical operation (12, 13). These consisted in a retention of sodium and an enhanced excretion of potassium lasting over a few days. These changes are probably related to the levels of adrenocortical hormones in the blood as trauma increases adrenal secretion, but this response was detected in patients undergoing bilateral adrenalectomy and in patients with Addison's disease (adrenal insufficiency) given a constant exogenous supply of adrenal steroids during an operation. It is now known that the blood levels are elevated by surgical operation even in these circumstances as the metabolism and excretion of the steroids are delayed.Electrolyte metabolism may be deranged in thyroid disorders and accordingly measurements were made of exchangeable sodium and potassium in hypothyroidism and hyperthyroidism before and after treatment. Treatment of hypothyroidism with thyroxine led to a decrease in both Naₑ and Kₑ due probably to a loss of myxoedematous tissue. Successful therapy of hyperthyroidism was associated with an increase in Kₑ due to restoration of lost muscular tissue. Changes in Naₑ were variable and not readily interpreted. In some patients there was little change but in many there was a moderate decrease in Naₑ on return to health. Decalcification of the skeleton may occasionally occur in hyperthyroidism and it was considered possible that some of the difficulties in interpretation of Naₑ changes might be due to alteration in bone sodium content. However, experimental studies in rats given large doses of thyroxine did not demonstrate any effects on bone sodium metabolism. A mild degree of cardiac failure occurs in many thyrotoxic patients and the decrease in Naₑ is probably related to a loss of a small amount of latent oedema. This has been confirmed in subsequent unpublished observations.A similar pattern of changes in body electrolyte composition, namely an excess of sodium and a loss of potassium, has already been noted in cardiac patients . It was particularly evident in patients with severe mitral stenosis and after successful surgical treatment serial measurements showed a gradual restoration of the body composition towards normal. A delay in the excretion of ingested sodium is a recognised early feature of congestive cardiac failure and it was thought that this might be related to the increased sodium content of the body. This was investigated in dogs with experimental valvular lesions of the heart. Considerable changes in the ability to excrete sodium developed without any gross alterations in the amount of exchangeable sodium in the body. The reduction in sodium excretion rate could not be attributed to the dilution of infused sodium in an expanded body sodium pool. The abnormality was apparently due to a direct effect of the cardiac lesions on renal function.The introduction of chlorothiazide, an effective oral diuretic, constituted a considerable advance in aiding the excretion of the excess of sodium present in cardiac failure. However, chlorothiazide often caused a considerable excretion of potassium as well as sodium which is particularly disadvantageous in the depleted cardiac patient. This potassium loss was attributed to the carbonic anhydrase inhibitor activity of chlorothiazide. However, a later derivative, hydroflumethiazide, which was a negligible carbonic anhydrase inhibitor, nevertheless under certain circumstances caused a marked loss of potassium. The liability to lose potassium was thought not to be related so much to the choice of the thiazide diuretic as to the circumstances under which it was given. This hypothesis was tested experimentally in normal men and it was demonstrated that the extent of potassium loss following the administration of a thiazide diuretic was related to adrenal mineralocorticoid activity. Excessive potassium loss may be prevented by giving an aldosterone antagonist. Triamterene, a recently introduced oral diuretic enhances sodium excretion but depresses potassium excretion; this was probably due to a direct action on the distal renal tubule. It may be used in conjunction with a thiazide and together they may promote a large sodium diuresis without excessive potassium loss. This recent work on the action of diuretics in relation to the excretion of sodium and potassium has been reviewed in the Bradshaw lecture

    3R - A Program to Save Our Nation\u27s Highways

    Get PDF
    • …
    corecore