The effects of five different variables preintensification time (without ultrasonic stirring), intensification time in ultrasonic bath (UB), temperature of UB, two acid mixtures (HNO3 H2SO4 H2O2 and HNO3 H2O2), on the recovery of Al have been investigated.
The best conditions for pseudo-digestion were as follows: a preintensification time 10 min, intensification time 20 min, volume of acid mixtures 3.0 ml and temperature of ultrasonic bath 80 °C.
In a secondary analysis using all cause mortality as the endpoint, we found a similar relation between systolic intensification threshold, time to intensification, time to follow-up, and all cause mortality (table 4).
To examine the relation between prescribing behavior and event rate without dividing systolic blood pressure intensification threshold, follow-up, and intensification time into discrete categories, we created a natural cubic spline model (fig 2).
We anticipated that treatment target, time to intensification, and time to follow-up may have a non-linear relation to risk of an event, with an optimal range of values and increased hazards outside this range.
Increased visit frequency was associated with increased risk of composite outcome after adjustment for time to intensification and time to follow-up (hazard ratio 1.00, 1.00 to 1.01, per visit; P<0.001).
We also analyzed the effect a shorter (three years) treatment strategy assessment period would have on the calculation of the optimal systolic blood pressure target (as a large fraction of patients did not have any medication intensifications during the first three years, time to intensification and time to follow-up after intensification could not be defined).
Finally, to investigate whether time to intensification and time to follow-up have an effect on outcomes independent of frequency of visits, we introduced a variable corresponding to the total number of blood pressure measurements over the 10 year treatment strategy assessment period.
Finally, in the sensitivity analysis to determine whether the effects of time to intensification and time to follow-up are independent of the frequency of visits, the inclusion of frequency of blood pressure measurement in the model did not qualitatively change the significance or direction of the previously observed risk differences between fifths for either metric (supplementary table H).
We used a Cox proportional hazards regression model to compare event-free survival for patients with various treatment strategies as defined by systolic intensification threshold, time to intensification, and time to follow-up.
