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Meteorological radars that are capable of making both polarisation diversity and phase measurements require an accurate method for absolute power calibration to achieve their full potential. A technique is described which uses a combination of differential reflectivity and differential phase measurements in rain to achieve this. The method is demonstrated using data obtained with the 3 GHz Chilbolton radar, which was recently upgraded to measure differential phase and Doppler velocity. The sensitivity of this technique to the assumed drop size distribution is estimated, and shown to have a minor effect on the accuracy of the calibration.

Background Iron deficiency anaemia (IDA) occurs in 2–5% of adult men and postmenopausal women in the developed world and is a common cause of referral to gastroenterologists. Gastrointestinal (GI) blood loss from colonic cancer or gastric cancer, and malabsorption in coeliac disease are the most important causes that need to be sought. Defining iron deficiency anaemia The lower limit of the normal range for the laboratory performing the test should be used to define anaemia (B). Any level of anaemia should be investigated in the presence of iron deficiency (B). The lower the haemoglobin the more likely there is to be serious underlying pathology and the more urgent is the need for investigation (B). Red cell indices provide a sensitive indication of iron deficiency in the absence of chronic disease or haemoglobinopathy (A). Haemoglobin electrophoresis is recommended when microcytosis and hypochromia are present in patients of appropriate ethnic background to prevent unnecessary GI investigation (C). Serum ferritin is the most powerful test for iron deficiency (A). Investigations Upper and lower GI investigations should be considered in all postmenopausal female and all male patients where IDA has been confirmed unless there is a history of significant overt non-GI blood loss (A). All patients should be screened for coeliac disease (B). If oesophagogastroduodenoscopy (OGD) is performed as the initial GI investigation, only the presence of advanced gastric cancer or coeliac disease should deter lower GI investigation (B). In patients aged >50 or with marked anaemia or a significant family history of colorectal carcinoma, lower GI investigation should still be considered even if coeliac disease is found (B). Colonoscopy has advantages over CT colography for investigation of the lower GI tract in IDA, but either is acceptable (B). Either is preferable to barium enema, which is useful if they are not available. Further direct visualisation of the small bowel is not necessary unless there are symptoms suggestive of small bowel disease, or if the haemoglobin cannot be restored or maintained with iron therapy (B). In patients with recurrent IDA and normal OGD and colonoscopy results, Helicobacter pylori should be eradicated if present. (C). Faecal occult blood testing is of no benefit in the investigation of IDA (B). All premenopausal women with IDA should be screened for coeliac disease, but other upper and lower GI investigation should be reserved for those aged 50 years or older, those with symptoms suggesting gastrointestinal disease, and those with a strong family history of colorectal cancer (B). Upper and lower GI investigation of IDA in post-gastrectomy patients is recommended in those over 50 years of age (B). In patients with iron deficiency without anaemia, endoscopic investigation rarely detects malignancy. Such investigation should be considered in patients aged >50 after discussing the risk and potential benefit with them (C). Only postmenopausal women and men aged >50 years should have GI investigation of iron deficiency without anaemia (C). Rectal examination is seldom contributory, and, in the absence of symptoms such as rectal bleeding and tenesmus, may be postponed until colonoscopy. Urine testing for blood is important in the examination of patients with IDA (B). Management All patients should have iron supplementation both to correct anaemia and replenish body stores (B). Parenteral iron can be used when oral preparations are not tolerated (C). Blood transfusions should be reserved for patients with or at risk of cardiovascular instability due to the degree of their anaemia (C).

A design feasibility study has been conducted for a 240 MVA high-temperature superconducting grid auto-transformer. Conclusions are relevant to superconducting power transformers in general. It is argued that economic benefits may be predicted, subject to assumptions about achievable conductor properties, costs of components and power system operating requirements. Liquid nitrogen cryogenics is relatively cheap and simple, and refrigeration power demand is reduced by a factor of the order of 20 compared to the low-temperature case. Attention is drawn to the importance of AC losses in the superconductor and the difficulty of keeping these sufficiently low. Various technical problem areas, and their likely influence on the overall design concept, are reviewed. Three particularly important influences are identified: insulating properties of liquid nitrogen coolant; required transformer performance in the through fault condition; and mechanical strength to withstand electromagnetic forces. Design proposals are detailed, and recommendations made for future development of high-temperature superconductors for power applications.

Whereas different hydrometeor types cannot be readily distinguished using radar reflectivity alone, this paper shows how the differential reflectivity available from dual-polarization radars can be used as an indicator of hydrometeor type (when supported by reflectivity factor also), and that the spatial variability of differential reflectivity is a useful addition. Various hydrometeor types, ground targets, and burnt chaff from straw fires may be identified, whereas conventional radar reflectivity measurement alone would require considerable pattern recognition to make the same distinctions.

Using conventional (single-polarization) radar data to assess attenuation due to rain on satellite-to-Earth paths requires the assumptions that the drops have a particular statistical distribution of sizes, and that the drops are of water. In the very localised regions of intense rain which influence such paths most severely, these assumptions can lead to large errors. This paper presents comparisons between direct measurements of attenuation and those computed using data from a dual-polarization radar technique. This technique can considerably reduce the errors of radar-derived estimates of attenuation. It also gives a clear distinction between ice and water.

Dual-polarization radar measurements of ZH and ZDR, where ZDR = 10 logZH/ZV and ZH, ZV are the radar reflectivity factors for horizontal and vertical polarizations, respectively, are compared with values derived from raindrop-size distributions measured by a Joss-Waldvogel disdrometer. The measurements were made simultaneously, with the radar pulse volume situated 120 m above the ground-based disdrometer. Despite the difference in size of the respective sampling volumes, agreement between the radar and disdrometer measurements was generally good. The radar estimates of ZH exceeded the disdrometer estimates by 1.6 dB on average, well within the expected experimental error. The disdrometer estimates of ZDR exceeded the radar estimates by 0.3 dB on average. This was somewhat larger than could be accounted for by experimental error, and further analysis suggested that some modification to the theoretical ratios of horizontal and vertical backscattering cross sections was required, for drops of diamet...

Dual-polarization radar measurements of rain (using horizontal and vertical polarizations with copolar transmit and receive) are compared with simultaneous measurements using a Joss-Waldvogel distrometer and a rapid response rain gauge. The radar pulse volume was situated 200 m above the ground-based instruments, at a range of 8 km. The parameters compared are absolute and differential radar reflectivity factors and rainfall rate. A correlation of 0.95 was found between the radar and distrometer measurements of absolute and differential reflectivity factor, with the radar estimate of absolute reflectivity exceeding the distrometer estimate by 1.6 dB on average, and the distrometer estimate of differential reflectivity exceeding the radar estimate (assuming Pruppacher and Pitter drop shapes) by 0.1 dB on average. The latter difference is small but significant and is possibly attributable to drop canting or oscillation. A new relationship between drop shape and drop size is proposed, reducing the mean difference in differential reflectivity to ±0.02 dB. Radar estimates of rainfall rate, assuming an exponential drop-size distribution, tend to produce significant overestimates compared with the direct measurements of the two ground-based devices. This is shown to be largely attributable to departure from a strictly exponential distribution of drop sizes, and a correction factor is derived to compensate for this.

A 10 cm (*) radar has been used on the steerable 25 m diameter aerial at Chilbolton, U.K., to produce detailed threedimensional maps of raincell distribution and intensity. The present paper examines differences in variation of radar reflectivity with height from the model at present recommended by theCcir.Wind shear can have a considerable influence on the distribution of rain as it falls, and may cause a 45° angle of inclination of a cell. This remains constant as the rain cell travels and is usually offset from the direction of travel of the cell. The information on the variation of radar reflectivity with height and the inclination of the rain cells are each important in the field of radio communications.

An experiment is described where rain at heights well above ground level was observed simultaneously by an airborne distrometer and a dual-polarization radar. The parameters of the distribution of drop sizes and the rainfall rate were computed from both sets of observations assuming the distribution to have a negative exponential form. The parameters derived from the two sources of data are compared, and differences discussed.

Radar observations of the differential reflectivity (ZDR) of developing convective clouds are presented. This parameter provides a measure of a mean hydrometeor shape, and when analysed in conjunction with the conventional reflectivity (Z), it gives an indication of whether the precipitation is ice or liquid water; for rain it enables an estimate of raindrop size and concentration to be made. the results suggest that some isolated echoes which subsequently develop into large cumulonimbus clouds initially have very small concentrations of large (diameter greater than 4 mm) supercooled raindrops, a very different size distribution from that normally observed in mature convective clouds. an alternative explanation in terms of an even lower population of much larger ice particles in wet growth is technically possible but does not seem physically realistic.

A rapidly switched dual-polarization radar technique is used for the first time to obtain two-dimensional spatial distributions of the statistical characteristics of the sizes and concentration of rain drops in rain. These have been obtained using a high-resolution 10-cm wavelength radar, and the data have been used to estimate rainfall rates within small volumes to a much greater accuracy than is available from conventional radar measurements. The technique also gives a clear distinction between ice particles and rain drops.

A parallel plate X-ray proportional counter with position sensitive anode is described. It is capable of resolving 0.2 mm in the soft X-ray region over a circular area a few centimetres across, while retaining good energy resolution.

The coefficient matrix for the set of first-order differential equations that describe a dynamic system is formed from the block diagram or equations that describe the system. The method for accomplishing this is described in terms of matrix equations. Then the derivative of this coefficient matrix with respect to one of the system parameters is found in terms of the matrices used to form it. The coefficient matrix and its derivative can be used to find the eigenvalues of the system and the sensitivities of the eigenvalues to the system's parameters.

Hail causes considerable damage to property and agriculture and a simple, unambiguous method of determining which convective storms contain hail would be of great use for short-term weather forecasting, and would also find application in the study of the mechanism of hailstone growth. Previous radar methods of hail detection1–3 have not proved reliable, but here we report results of a new technique based on the measurement of differential reflectivity using dual polarization radar and suggest an additional criterion for hail recognition. Hail is known to occur in vigorous convective storms in which the effective radar reflectivity, Z, measured by conventional radar is high. If the hail reaches the ground it is usually restricted to long narrow swathes4, often about 1 km wide but up to 50 km long, accompanied by surrounding precipitation in the form of heavy rain. The differential reflectivity technique involves comparing the radar reflectivity factor for horizontally (ZH) and vertically (ZV) polarized radiation; the comparison provides a measure of the mean shape of the precipitation particles. Close to the ground the values of Z are high for both hail and heavy rain, but because the large raindrops are oblate and fall with their horizontal diameter greater than the vertical, the value of ZH in the rain exceeds that of ZV. The smaller regions where hail is present can be clearly distinguished from the neighbouring heavy rain because, although individual hailstones may not be spherical, they tumble as they fall and so result in equal values of ZH and ZV.

Dredging of the Dalhousie Harbour and the ocean disposal of dredge spoils had been ongoing for many years prior to the implementation of the Ocean Dumping Control Act of 1975. Due to discharge from local industries and the open storage of bulk lead/zinc ore concentrates at the port, pollution levels in the Harbour were elevated and by the early 1980's open water disposal of the dredgate was no longer permitted. As a result of the elimination of Ocean Disposal and continued high rates of siltation, a siltation study has been commissioned by the Federal Government to determine ways and means to reduce or eliminate the maintenance dredging requirement through the development of engineering concepts. This paper will address the methodology developed to reduce the maintenance dredging requirement through the findings of the Siltation Study.

Summary Changes of skin electrical conductance have been monitored from induction of anaesthesia to recovery in two groups of patients. The first group receiving inhalational anaesthesia with halothane and spontaneous respiration demonstrated no changes in response to surgical stimulus. Some patients from the second group receiving muscle relaxation and ventilation with nitrous oxide and oxygen without halothane demonstrated changes in response to surgery. The changes are mediated by the sympathetic nervous system and the technique forms a simple monitor of sympathetic activity during surgery.

A comparative study of a new, simple, pneumatic, direct-recording office spirometer versus a long-accepted, water-sealed, water-filled spirometer was performed on 103 patients ranging from four to 20 years of age. Good correlation between the two spirometers was seen through a wide range of values for forced vital capacity (FVC), forced expiratory volume in one second (FEV1) and forced expiratory flow during 25% to 75% of forced vital capacity and FEV1/FVC.

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