Millimetre wave remote sensing of the atmosphere

Recent advances in millimetre wave technology has opened up a new region of the spectrum to remote sensing from artificial satellites. The main part of this work involves a millimetre wave proving experiment for a satellite borne millimetre wave active sounder to measure surface pressure over the oceans. The Microwave Pressure Sounder is a6 channel, low power radar operating in the spectral range from 24 to 75 GHz. The strength of the return echoes from the sea surface determines the amount of oxygen in the path which can be directly related to the surface pressure to an accuracy of 1 mb, when corrected for sea surface reflectivity and atmospheric temperature and water content by this multichannel instrument. Measurements of atmospheric attenuation along a horizontal path were related to atmospheric pressure changes by a millimetre wave instrument built at Heriot-Watt University. The transmissometer measured the differential absorption between two frequencies (54 and 58 GHz) over a 650 metre path. The deduced atmospheric pressure was found to compare with the barometric pressure with a standard deviation of two millibars for the best data set. These results demonstrate that atmospheric attenuation can be measured with sufficient precision for a satellite borne instrument to determine the surface atmospheric pressure over the oceans to an accuracy of approximately one millibar. This accuracy would lead to significant improvements in the modelling of the atmosphere and weather forecasting. Various other techniques to remotely sense surface atmospheric pressure are reviewed. Recently, increased awareness of the sensitivity of the environment and evidence of the effects of man-made pollutants has given rise to an increased awareness in the health of the Earth and led to several instruments being developed to monitor our planet. One of these instruments, the Microwave Limb Sounder to be flown on the Upper Atmosphere Research Satellite (launch October 1991) is described. This instrument uses millimetre wave radiometers at 63 GHz, 183 GHz and 205 GHz to measure the amount of chlorine oxide, ozone and water vapour in the upper atmosphere. These gases are important in understanding the photochemistry of the mesosphere. Global distributions of the gases will be produced and changes in concentration will be monitored during the three year mission

The development and validation of a scoring tool to predict the operative duration of elective laparoscopic cholecystectomy

Background: The ability to accurately predict operative duration has the potential to optimise theatre efficiency and utilisation, thus reducing costs and increasing staff and patient satisfaction. With laparoscopic cholecystectomy being one of the most commonly performed procedures worldwide, a tool to predict operative duration could be extremely beneficial to healthcare organisations. Methods: Data collected from the CholeS study on patients undergoing cholecystectomy in UK and Irish hospitals between 04/2014 and 05/2014 were used to study operative duration. A multivariable binary logistic regression model was produced in order to identify significant independent predictors of long (> 90 min) operations. The resulting model was converted to a risk score, which was subsequently validated on second cohort of patients using ROC curves. Results: After exclusions, data were available for 7227 patients in the derivation (CholeS) cohort. The median operative duration was 60 min (interquartile range 45–85), with 17.7% of operations lasting longer than 90 min. Ten factors were found to be significant independent predictors of operative durations > 90 min, including ASA, age, previous surgical admissions, BMI, gallbladder wall thickness and CBD diameter. A risk score was then produced from these factors, and applied to a cohort of 2405 patients from a tertiary centre for external validation. This returned an area under the ROC curve of 0.708 (SE = 0.013, p  90 min increasing more than eightfold from 5.1 to 41.8% in the extremes of the score. Conclusion: The scoring tool produced in this study was found to be significantly predictive of long operative durations on validation in an external cohort. As such, the tool may have the potential to enable organisations to better organise theatre lists and deliver greater efficiencies in care