Statistics of Ground Motions in a Foam Rubber Model of a Strike-Slip Fault

The peak acceleration and velocity from 5058 ruptures of a foam rubber stick-slip model are not distributed according to a lognormal probability distribution function. PGA and PGV values are decomposed using the method of Anderson and Uchiyama (2011). The statistically significant de- viations from the lognormal distribution occur near the peak of the distribution. In some cases, high-amplitude tails differ by a much greater ratio, but the statistical significance of this effect is low. This result is true of both raw data and data adjusted for site and magnitude. Event terms are also not lognormal, but can be modeled as a sum of three or four lognormal subdistributions, which possibly represent different preferred rupture initiation points rather than a uniform distribution of initiation points. The event term subdistributions with highest median values have small standard deviations, so if shapes of this nature were used in ground motion prediction equations (GMPEs) during a probabilistic seismic hazard analysis, the effect of the long tail of the lognormal distribu- tion in controlling the hazard would be weakened considerably. Static stress drop was recorded for each event, and event terms for PGA and PGV are well correlated with static stress drop. Unlike NGAW2 GMPEs, residual variances for the foam model are dominated by variability in the source slip function, rather than the path and site effects. This difference in the variance budget results from the way in which the source and site residuals are defined in this study; the source uncertainty includes variation in the rupture size (magnitude) and location, along with deviations in distance and path. We do not know if these results apply to earthquakes but we do think tests of repeating stick-slip events in a physical system are useful to expand the set of credible hypotheses regarding possible behavior modes of earthquake faults

Screening mammography use and chemotherapy among female stage II colon cancer patients: a retrospective cohort study

<p>Abstract</p> <p>Background</p> <p>Although chemotherapy is not a routine recommendation for stage II colon cancer by the U.S. national guidelines, 20-30% of patients have received chemotherapy. This study investigated whether screening mammography use before the cancer diagnosis was associated with chemotherapy use among female elderly patients with stage II colon cancer.</p> <p>Methods</p> <p>Retrospective cohort study on 2910 female stage II colon cancer patients aged 67-79 using the Surveillance, Epidemiology and End Results (SEER)-Medicare data (1996-2002). Screening mammography use and chemotherapy use were identified using Medicare claims data. Multivariate logistic regression and Kaplan-Meier curves were used.</p> <p>Results</p> <p>About 25% of female elderly patients received chemotherapy. The chemotherapy rates increased from 22% in 1996-1998 to 26% in 2001-2002. After adjusting for socio-demographic variables, tumor characteristics and Charlson index for comorbidities, the odds of receiving chemotherapy were 28% higher among those who had a screening mammogram before the cancer diagnosis than those who did not (OR: 1.28, 95% CI: 1.07-1.54). Those with a prior mammogram also received chemotherapy earlier than those without. In addition, patients with unfavorable tumor characteristics were more likely to receive chemotherapy. Mammography use before the cancer diagnosis was associated with favorable tumor characteristics.</p> <p>Conclusions</p> <p>Despite the controversy about the chemotherapy use among stage II colon cancer, female elderly patients still received chemotherapy at a high rate. Our findings suggest that patient's health beliefs and health care seeking behavior, together with physician's recommendation, play important roles in the cancer treatment decision.</p

Design and control of a voice coil actuated robot arm for human-robot interaction

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.Includes bibliographical references (leaf 68).The growing field of human-robot interaction (HRI) demands robots that move fluidly, gracefully, compliantly and safely. This thesis describes recent work in the design and evaluation of long-travel voice coil actuators (VCAs) for use in robots intended for interacting with people. The basic advantages and shortcomings of electromagnetic actuators are discussed and evaluated in the context of human-robot interaction, and are compared to alternative actuation technologies. Voice coil actuators have been chosen for their controllability, ease of implementation, geometry, compliance, biomimetic actuation characteristics, safety, quietness, and high power density. Several VCAs were designed, constructed, and tested, and a 4 Degree of Freedom (DOF) robotic arm was built as a test platform for the actuators themselves, and the control systems used to drive them. Several control systems were developed and implemented that, when used with the actuators, enable smooth, fast, life-like motion.by John M. McBean.S.M

Controlling the properties of InGaAs quantum dots by selective-area epitaxy

Selective growth of InGaAsquantum dots on GaAs is reported. It is demonstrated that selective-area epitaxy can be used for in-plane bandgap energy control of quantum dots.Atomic force microscopy and cathodoluminescence are used for characterization of the selectively growndots. Our results show that the composition, size, and uniformity of dots are determined by the dimensions of the mask used for patterning the substrate. Properties of dots can be selectively tuned by varying the mask dimensions. A single-step growth of a thin InGaAsquantum well and InGaAsquantum dots on the same wafer is demonstrated. By using a single-step growth,dots luminescing at different wavelengths, in the range 1150–1230nm, in different parts of the same wafer are achieved.The Australian Research Council is gratefully acknowledged for the financial support

Standing Balance and Spatiotemporal Aspects of Gait Are Impaired Upon Nocturnal Awakening in Healthy Late Middle-Aged and Older Adults

Study Objectives: Nocturnal awakenings may constitute a unique risk for falls among older adults. We describe differences in gait and balance between presleep and midsleep testing, and whether changes in the lighting environment during the midsleep testing further affect gait and balance. Methods: Twenty-one healthy, late middle-aged and older (64.7 ± 8.0 y) adults participated in this repeated-measures design consisting of four overnight laboratory stays. Each night, participants completed baseline visual acuity, gait, and balance testing. After a 2-h sleep opportunity, they were awakened for 13 min into one of four lighting conditions: very dim white light (\u3c 0.5 lux); dim white light (∼28.0 lux); dim orange light (∼28.0 lux); and white room-level light (∼200 lux). During this awakening, participants completed the same sequence of testing as at baseline. Results: Low-contrast visual acuity significantly decreased with decreasing illuminance conditions (F(3,45) = 98.26, p \u3c 0.001). Our a priori hypothesis was confirmed in that variation in stride velocity and center of pressure path length were significantly worse during the mid-sleep awakening compared to presleep baseline. Lighting conditions during the awakening, however, did not influence these parameters. In exploratory analyses, we found that over one-third of the tested gait and balance parameters were significantly worse at the midsleep awakening as compared to baseline (p \u3c 0.05), and nearly one-quarter had medium to large effect sizes (Cohen d ≥ 0.5; r ≥ 0.3). Conclusions: Balance and gait are impaired during midsleep awakenings among healthy, late middle-aged and older adults. This impairment is not ameliorated by exposure to room lighting, when compared to dim lights

Perinatal Hypoxia-Ischemia Disrupts Striatal High-Affinity [ 3 H]Glutamate Uptake into Synaptosomes

: We examined the impact of hypoxia-ischemia on high-affinity [ 3 H]glutamate uptake into a synaptosomal fraction prepared from immature rat corpus striatum. In 7-day-old pups the right carotid artery was ligated, and pups were exposed to 8% oxygen for 0, 0.5, 1, or 2.5 h, and allowed to recover for up to 24 h before they were killed. High-affinity glutamate uptakes in striatal synaptosomes derived from tissue ipsilateral and contralateral to ligation were compared. After 1 h of hypoxia plus ischemia, high-affinity glutamate uptake in the striatum was reduced by 54 ± 13% compared with values from the opposite (nonischemic) side of the brain (p < 0.01, t test versus ligates not exposed to hypoxia). There were similar declines after 2.5 h of hypoxiaischemia. Activity remained low after a 1 h recovery period in room air, but after 24 h of recovery, high-affinity glutamate uptake was equal bilaterally. Kinetic analysis revealed that loss of activity could be attributed primarily to a 40% reduction in the number of uptake sites. Hypoxia alone had no effect on high-affinity glutamate uptake although it reduced synaptosomal uptake of [ 3 H]3,4-dihydroxyphenyl-ethylamine. Addition of 1 mg/ml of bovine serum albumin to the incubation medium preferentia'ly stimulated high-affinity glutamate uptake in hypoxic-ischemic brain compared with its effects in normal tissue. These studies demonstrate that hypoxia-ischemia reversibly inhibits high-affinity glutamate uptake and this occurs earlier than the time required to produce neuronal damage in the model.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66361/1/j.1471-4159.1986.tb00803.x.pd