Viking GC/MS mechanisms design and performance

The Viking Lander gas chromatograph/mass spectrometer will analyze pyrolyzed samples of the Martian surface for organic content. The surface-sample loader and pyrolyzer assembly (SSPLA) is described, along with the major problems encountered during design and testing. Three mechanisms were developed to implement the required SSLPA functions: (1) a soil loader that forces soil from a filled rotating funnel into each of three ovens located on a carriage, (2) a Geneva drive for rotating and precisely indexing the ovens to receive sample, and (3) a toggle-clamp mechanism for sealing the ovens by forcing circular double knife edges into gold sealing surfaces

Fitness Norms for the Plank Exercise

PURPOSE: Adequate strength of core musculature is critical for optimal physical performance and postural control. Currently, standards for core musculature strength and stability have not been established. This study sought to determine normative fitness measurements of core musculature endurance using the plank exercise. METHODS: 168 collegiate male and female participants (18-25 years of age) were recruited. Participants were instructed in plank positioning; elbows bent at 90° directly below the shoulders, hands unclasped, feet placed hip width apart with ankles at 90° and pelvis tilted in the neutral position. After a 5-minute warm-up, participants were told to maintain the plank position as long as possible until complete fatigue was reached. The test was terminated if proper form was broken. The total time held in proper plank position was recorded. RESULTS: The mean time held in the plank position was 96.25 + 43.16 and 116.58 + 65.49 seconds for females and males, respectively. For females, quartiles showed that the 25th percentile was 63 seconds, the 50th percentile was 90 seconds, while the 75th percentile was 121 seconds. Quartiles for males were 77seconds, 106 seconds and 128.5 seconds for the 25th, 50th and 75th percentiles, respectively. CONCLUSION: This study provides normative values for the plank exercise that can be added to current fitness appraisal protocols to assess core muscular endurance. These data suggest that 1.50 minutes in females and 1.77 minutes in males (50th percentile values) could be considered average duration of the plank exercise for this age group

Does settlement plate material matter? The influence of substrate type on fouling community development

Benthic community composition and ascidian abundance can differ dramatically between adjacent man-made and natural substrates. Although multiple factors, including light exposure, surface orientation, predation exposure, and habitat type, are known to contribute to these patterns, few studies have directly tested the influence of substrate identity on community development. We compared fouling communities on settlement plates composed of commonly occurring natural (granite) and artificial (concrete, high density polyethylene, and PVC) marine materials deployed from late May to mid November 2014 from a floating dock in Newcastle, NH. We sought to determine if observed patterns resulted from differential recruitment onto substrate materials or post-settlement survival and growth. To do this, half of the plates were cleaned during bi-weekly examinations, and half were left un-cleaned. Preliminary analyses indicate that community composition differs between substrate types. These results will help us understand how substrate features contribute to non-native species establishment and habitat dominance, and may inform decisions regarding material usage in marine construction. These findings also underline the importance of settlement substrate choice in scientific studies, as plate material may influence experimental conclusions

Sanitation and Externalities: Evidence from Early Childhood Health in Rural India

This paper estimates two sources of benefits, one direct and the other external, related to sanitation infrastructure access on early childhood health: a direct benefit a household receives when moving from open to fixed-point defecation or from unimproved sanitation to improved sanitation, and an external benefit (externality) produced by the neighborhood's access to sanitation infrastructure. Using a sample of children under 48 months in rural areas of India, it finds evidence of positive and significant direct and concave positive external effects