W Crichton | PubMed Health

PubMed2005

Rubberlike dynamics in sulphur above the lambda-transition temperature.

The high-frequency acoustic dynamics of sulfur across the liquid-liquid, lambda transition has been studied using inelastic x-ray scattering. The combination of these high-frequency data with lower frequency, literature data indicates that liquid sulfur develops, in the high-temperature, polymeric solution phase, some characteristic features of a rubber. In particular, entanglement coupling among polymeric chains plays a relevant role in the dynamics of this liquid phase.

Journal Article↗

PubMed1991

Nicardipine sustained release in hypertension.

1. A novel formulation of nicardipine (25% standard, 75% sustained release--SR) was evaluated in mild hypertension in a double-blind, randomized, placebo-controlled comparison with standard nicardipine (STD), using clinic measurements (Hawksley) augmented by home recorded blood pressures (Copal UA 251). 2. At 2 h after dosing (peak effect) both STD nicardipine (30 mg three times daily) and SR nicardipine (60 mg twice daily) for 28 days produced a highly significant reduction in sitting and standing blood pressure. The mean sitting blood pressure was reduced by 20/16 mm Hg (STD) and by 25/18 mm Hg (SR) compared with placebo. 3. Predose (8-11 h after last dose of STD, 12-15 h after last dose of SR) the reductions in sitting blood pressure relative to placebo were 11/6 mm Hg (STD) and 14/7 mm Hg (SR). 4. Home recordings confirmed the hypotensive effect of both formulations. Both exhibited a distinct 'peak dose' effect between 1-3 h after dosing. The effect of the SR formulation was sustained throughout the 12 h dosing interval. 5. Of the 60 patients entering the study, one died of unexplained staphylococcal septicaema, two were withdrawn for non drug-related reasons and 14 (32%) were withdrawn because of adverse effects on active therapy (headaches, facial flushing, leg oedema, chest pain, dizziness). 6. In the 43 patients who completed the study adverse symptoms were reported more frequently while they were on the two active formulations of nicardipine compared with placebo. Most of these reactions were again of vasodilator origin.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1990

Bench and ambulatory field evaluation of the A & D TM-2420 automated sphygmomanometer.

Adequate evaluation of automated sphygmomanometers, in terms of safety, accuracy, mechanical reliability, patient acceptability and ability to record ambulatory blood pressure is essential before these devices are used in clinical practice and in clinical trials. We have evaluated the accuracy and performance of the A & D TM-2420 automated sphygmomanometer, an auscultatory device designed for ambulatory blood pressure recording. Four devices were tested for accuracy by simultaneous comparison against two experienced observers using standard mercury column sphygmomanometers. Two of these devices developed faults that precluded complete evaluation. One of the remaining devices met and one failed to meet the somewhat liberal criteria for accuracy recommended by the American Association for the Advancement of Medical Instrumentation, the current standard for evaluation (mean difference of less than or equal to 5 mmHg and standard deviation of differences less than or equal to 8 mmHg). The mean differences (standard deviation of differences) between observers for simultaneous triplicate observations of systolic/diastolic pressure in 50 subjects, including 35 hypertensives, were 0.8 (3.0)/-0.6 (2.4) mmHg. In comparison, the differences between each device and each observer were: device 11, observer 1, -6.4 (5.4)/-6.3 (9.9); device 11, observer 2, -5.6 (4.7)/-7.0 (10.4); device 12, observer 1, -4.9 (5.2)/-4.0 (7.5); device 12, observer 2, -4.1 (4.9)/- -4.5 (7.7) mmHg. Ambulatory trials were carried out with a further 10 devices. Of these, seven developed faults requiring their return to the supplier. Numerous additional problems were encountered with microphones, cuffs, leads and connections, the processing unit, error algorithms and data-handling software. The device was not capable of making truly ambulatory recordings. We do not confirm the previously favourable, but limited, evaluation of this device. We stress the vital importance of subjecting a number of devices to benchtesting for accuracy, and the need to undertake extensive 'field' testing before any devices can be considered suitable for ambulatory recording. Exercise testing under laboratory conditions is not an adequate substitue for true ambulatory evaluation.

Algorithms↗