ABSTRACT
Interferometric gravitational-wave antennas are based on Michelson interferometers whose sensitivity to small differential length changes has been enhanced by the addition of multiple coupled optical resonators. The use of optical cavities is essential for reaching the required sensitivity but sets challenges for the control system, which must maintain the cavities near resonance. The goal for the strain sensitivity of the Laser Interferometer Gravitational-Wave Observatory (LIGO) is 10(-21) rms, integrated over a 100-Hz bandwidth centered at 150 Hz. We present the major design features of the LIGO length and frequency sensing and control system, which will hold the differential length to within 5 x 10(-14) m of the operating point. We also highlight the restrictions imposed by couplings of noise into the gravitational-wave readout signal and the required immunity against them.
ABSTRACT
In an investigation of the health effects of a Christmas eve snowstorm in 1982, a review of emergency room records in the Denver area identified a cluster of 17 cases of finger amputations. Fifteen (88) percent of these amputations were associated with snowblower use. An additional 12 persons with hand or finger injuries without amputations from snowblowers were identified. A case-control study was performed comparing these patients with a control group who had used snowblowers. Patients were more likely than controls to have had their machines become clogged with snow (odds ratio [OR], 3.4, 95 percent confidence limits [CL], 0.74-15.4). Using a hand to dislodge trapped snow was the only risk factor identified for the patients (OR, 116; 95 percent CL, 16-820). No differences were found for other variables such as type of snowblower, instruction for use, or previous experience using a snowblower. The findings suggest that the most feasible measure to prevent such injuries is a change in snowblower design to preclude entry of a hand while the machine is running. This investigation illustrates the importance of surveillance in detecting and controlling injuries. Without such surveillance, the similarity among injuries reported on this paper would not have been recognized. Ongoing surveillance for injuries might identify other clusters of injuries.
Subject(s)
Accidents, Home/statistics & numerical data , Amputation, Traumatic/epidemiology , Finger Injuries/epidemiology , Snow , Weather , Adolescent , Adult , Amputation, Traumatic/etiology , Colorado , Emergency Service, Hospital , Equipment Design , Equipment Safety , Finger Injuries/etiology , Humans , Male , Middle Aged , Population Surveillance , Seasons , Space-Time ClusteringABSTRACT
This population-based case-control study was designed to investigate risk indicators for the occurrence of the birth defect craniosynostosis in Colorado. A total of 173 children who underwent craniectomy for craniosynostosis and 759 children without craniosynostosis were included in the study. Multivariable logistic regression analysis of birth certificate data showed that male sex (odds ratio (OR) = 1.6, 95% confidence interval (CI) = 1.1-2.2), maternal five-year age "increase" (OR = 1.3, 95% CI = 1.1-1.5), plural birth (OR = 3.0, 95% CI = 1.2-7.1) and black maternal race (OR = 0.0, 95 per cent CI = 0.0-0.6) were independently associated with craniosynostosis. There was a weak positive association between craniosynostosis and the altitude of the town closest to the maternal residence, but no association was found with maternal education, marital status, number of previous births, or previous pregnancy termination. The association of craniosynostosis with plural birth is consistent with the hypothesis of fetal head constraint.
