Ocean Seismic Network Pilot Experiment

Author Posting. © American Geophysical Union, 2003. It is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 4 (2003): 1092, doi:10.1029/2002GC000485.The primary goal of the Ocean Seismic Network Pilot Experiment (OSNPE) was to learn how to make high quality broadband seismic measurements on the ocean bottom in preparation for a permanent ocean seismic network. The experiment also had implications for the development of a capability for temporary (e.g., 1 year duration) seismic experiments on the ocean floor. Equipment for installing, operating and monitoring borehole observatories in the deep sea was also tested including a lead-in package, a logging probe, a wire line packer and a control vehicle. The control vehicle was used in three modes during the experiment: for observation of seafloor features and equipment, for equipment launch and recovery, and for power supply and telemetry between ocean bottom units and the ship. The OSNPE which was completed in June 1998 acquired almost four months of continuous data and it demonstrated clearly that a combination of shallow buried and borehole broadband sensors could provide comparable quality data to broadband seismic installations on islands and continents. Burial in soft mud appears to be adequate at frequencies below the microseism peak. Although the borehole sensor was subject to installation noise at low frequencies (0.6 to 50 mHz), analysis of the OSNPE data provides new insights into our understanding of ocean bottom ambient noise. The OSNPE results clearly demonstrate the importance of sediment borne shear modes in ocean bottom ambient noise behavior. Ambient noise drops significantly at high frequencies for a sensor placed just at the sediment basalt interface. At frequencies above the microseism peak, there are two reasons that ocean bottom stations have been generally regarded as noisier than island or land stations: ocean bottom stations are closer to the noise source (the surface gravity waves) and most ocean bottom stations to date have been installed on low rigidity sediments where they are subject to the effects of shear wave resonances. When sensors are placed in boreholes in basement the performance of ocean bottom seismic stations approaches that of continental and island stations. A broadband borehole seismic station should be included in any real-time ocean bottom observatory.This work was sponsored by the National Science Foundation (NSF Grant Numbers: OCE-9522114, OCE-9523541 and OCE-9819439) with additional support from Incorporated Research Institutions for Seismology (IRIS), Joint Oceanographic Institutions, Inc. (JOI Contract No: 12-94), Scripps Institution of Oceanography, a Mellon Grant from Woods Hole Oceanographic Institution, and the Earthquake Research Institute at the University of Tokyo (Visiting Professorship for RAS)

Risk Factors of Typhoid Infection in the Indonesian Archipelago.

BACKGROUND: Knowledge of risk factors and their relative importance in different settings is essential to develop effective health education material for the prevention of typhoid. In this study, we examine the effect of household level and individual behavioural risk factors on the risk of typhoid in three Indonesian islands (Sulawesi, Kalimantan and Papua) in the Eastern Indonesian archipelago encompassing rural, peri-urban and urban areas. METHODS: We enrolled 933 patients above 10 years of age in a health facility-based case-control study between June 2010 and June 2011. Individuals suspected of typhoid were tested using the typhoid IgM lateral flow assay for the serodiagnosis of typhoid fever followed by blood culture testing. Cases and controls were defined post-recruitment: cases were individuals with a culture or serology positive result (n = 449); controls were individuals negative to both serology and culture, with or without a diagnosis other than typhoid (n = 484). Logistic regression was used to examine the effect of household level and individual level behavioural risk factors and we calculated the population attributable fraction (PAF) of removing each risk significant independent behavioural risk factor. RESULTS: Washing hands at critical moments of the day and washing hands with soap were strong independent protective factors for typhoid (OR = 0.38 95% CI 0.25 to 0.58 for each unit increase in hand washing frequency score with values between 0 = Never and 3 = Always; OR = 3.16 95% CI = 2.09 to 4.79 comparing washing hands with soap sometimes/never vs. often). These effects were independent of levels of access to water and sanitation. Up to two thirds of cases could be prevented by compliance to these practices (hand washing PAF = 66.8 95% CI 61.4 to 71.5; use of soap PAF = 61.9 95%CI 56.7 to 66.5). Eating food out in food stalls or restaurant was an important risk factor (OR = 6.9 95%CI 4.41 to 10.8 for every unit increase in frequency score). CONCLUSIONS: Major gains could potentially be achieved in reducing the incidence of typhoid by ensuring adherence to adequate hand-washing practices alone. This confirms that there is a pivotal role for 'software' related interventions to encourage behavior change and create demand for goods and services, alongside development of water and sanitation infrastructure