Douglas Simpson

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Threshold estimates and superthreshold behaviors for ultrasound-induced lung hemorrhage were investigated as a function of species (adult mice and rats) and ultrasound frequency (2.8 and 5.6 MHz). A total of 151 6-to-7-week-old female ICR mice and 160 10-to-11-week-old female Sprague-Dawley rats were randomly divided into two ultrasonic frequency groups,(More)
This paper describes data which demonstrate a correlation between the magnitude of the Steady-State Visually Evoked Potential (SSVEP) and visual vigilance. The SSVEP was recorded from 64 scalp sites and elicited by a 13Hz uniform visual flicker presented continuously while subjects undertook a visual vigilance task. Fifteen right-handed males were required(More)
This paper develops methodology for regression analysis of ordinal response data subject to interval censoring. This work is motivated by the need to analyze data from multiple studies in toxicological risk assessment. Responses are scored on an ordinal severity scale, but not all responses can be scored completely. For instance, in a mortality study,(More)
The location, nature and characteristics of brain activity during detection and identification of odors are of importance if brain function techniques are to be of value to sensory systems. Steady state probe topography (SSPT) has been used in our laboratory to record steady state visual evoked potentials (SSVEP), which have demonstrated cognitive(More)
It is well documented that ultrasound-induced lung hemorrhage can occur in mice, rats, rabbits, pigs, and monkeys. The objective of this study was to assess the role of the ultrasound beamwidth (beam diameter incident on the lung surface) on lesion threshold and size. A total of 144 rats were randomly exposed to pulsed ultrasound at three exposure levels(More)
Age-dependent threshold and superthreshold behavior of ultrasound-induced lung hemorrhage were investigated with 116 2.1 +/- 0.3-kg neonate crossbred pigs (4.9 +/- 1.6 days old), 103 10 +/- 1.1-kg crossbred pigs (39 +/-5 days old), and 104 20+/-1.2-kg crossbred pigs (58 +/- 5 days old). Exposure conditions were: 3.1 MHz, 10-s exposure duration, 1-kHz pulse(More)
OBJECTIVE The purpose of this study was to enhance the findings of an earlier ultrasound-induced lung hemorrhage study (Ultrasound Med Biol 2003; 29:1625-1634) that estimated pressure thresholds as a function of pulse duration (PD: 1.3, 4.4, 8.2, and 11.6 micros; 2.8 MHz; 10-s exposure duration [ED]; 1-kHz pulse repetition frequency [PRF]). In this study,(More)
The objective of this study was to assess the threshold and superthreshold behavior of ultrasound (US)-induced lung hemorrhage in adult rabbits to gain greater understanding about species dependency. A total of 99 76 +/- 7.6-d-old 2.4 +/- 0.14-kg New Zealand White rabbits were used. Exposure conditions were 5.6-MHz, 10-s exposure duration, 1-kHz PRF and(More)
The study objective was to estimate the pressure threshold (ED(05), effective dose, or in situ peak rarefactional pressure associated with 5% probability of lesions) of ultrasound (US)-induced lung hemorrhage as a function of pulse duration (PD) in adult rats. A total of 220 10- to 11-week-old 250-g female Sprague-Dawley rats (Harlan) were randomly divided(More)