Stable Calibration of Raman Lidar Water-Vapor Measurements

A method has been devised to ensure stable, long-term calibration of Raman lidar measurements that are used to determine the altitude-dependent mixing ratio of water vapor in the upper troposphere and lower stratosphere. Because the lidar measurements yield a quantity proportional to the mixing ratio, rather than the mixing ratio itself, calibration is necessary to obtain the factor of proportionality. The present method involves the use of calibration data from two sources: (1) absolute calibration data from in situ radiosonde measurements made during occasional campaigns and (2) partial calibration data obtained by use, on a regular schedule, of a lamp that emits in a known spectrum determined in laboratory calibration measurements. In this method, data from the first radiosonde campaign are used to calculate a campaign-averaged absolute lidar calibration factor (t(sub 1)) and the corresponding campaign-averaged ration (L(sub 1)) between lamp irradiances at the water-vapor and nitrogen wavelengths. Depending on the scenario considered, this ratio can be assumed to be either constant over a long time (L=L(sub 1)) or drifting slowly with time. The absolutely calibrated water-vapor mixing ratio (q) obtained from the ith routine off-campaign lidar measurement is given by q(sub 1)=P(sub 1)/t(sub 1)=LP(sub 1)/P(sup prime)(sub 1) where P(sub 1) is water-vapor/nitrogen measurement signal ration, t(sub 1) is the unknown and unneeded overall efficiency ratio of the lidar receiver during the ith routine off-campaign measurement run, and P(sup prime)(sub 1) is the water-vapor/nitrogen signal ratio obtained during the lamp run associated with the ith routine off-campaign measurement run. If L is assumed constant, then the lidar calibration is routinely obtained without the need for new radiosonde data. In this case, one uses L=L(sub 1) = P(sup prime)(sub 1)/t(sub 1), where P(sub 1)(sup prime) is the water-vapor/nitrogen signal ratio obtained during the lamp run associated with the first radiosonde campaign. If L is assumed to drift slowly, then it is necessary to postpone calculation of a(sub 1) until after a second radiosonde campaign. In this case, one obtains a new value, L(sub 2), from the second radiosonde campaign, and for the ith routine off-campaign measurement run, one uses an intermediate value of L obtained by simple linear time interpolation between L(sub 1) and L(sub 2)

Home-Time Is a Feasible and Valid Stroke Outcome Measure in National Datasets

Background and Purpose— Home-time (HT) is a stroke outcome measure based on time spent at home after stroke. We hypothesized that HT assessment would be feasible and valid using national data. Methods— We linked the Scottish Stroke Care Audit to routine healthcare data and calculated 90-day HT for all strokes, 2005 to 2017. We described prognostic validity (Spearman rank correlation) of HT to baseline factors. Results— We were able to calculate HT for 101 969 strokes (99.3% of total Scottish strokes). Mean HT was 46 days (95% CI, 45.8–46.2; range, 0–90). HT showed consistent correlation with our prespecified prognostic factors: age: ρ, −0.35 (95% CI, −0.35 to −0.36); National Institutes of Health Stroke Scale score, −0.54 (95% CI, −0.52 to −0.55); and 6 simple variables (ordinal), −0.61 (95% CI, −0.61 to −0.62). Conclusions— HT can be derived at scale using routine clinical data and appears to be a valid proxy measure of functional recovery. Other national databases could use HT as a time and cost efficient measure of medium and longer-term outcomes

Use of modern processors in safety−critical applications

This paper investigates the implications of using modern superscalar processors in the safety-critical domain. Firstly, a description of current certification practice and devices is given as backgroun