Mantle Transition Zone Receiver Functions for Bermuda:Automation, Quality Control, and Interpretation

The origin of the Bermuda rise remains ambiguous, despite, or perhaps because of, the existence of sometimes incongruous seismic wave‐speed and discontinuity models in the sub‐Bermudian mantle. Hence, whether Bermuda is the surface manifestation of a mantle plume remains in question. Using the largest data set of seismic records from Bermuda to date, we estimate radial receiver functions at the Global Seismographic Network station BBSR in multiple frequency bands, using iterative time‐domain deconvolution. Motivated by synthetic experiments using axisymmetric spectral‐element forward waveform modeling, we devise a quality metric for our receiver functions to aid in the automation and reproduction of mantle transition zone discontinuity studies. We interpret the complex signals we observe by considering the mineralogical controls on mantle transition zone discontinuity structure, and conclude that our results are likely to be indicative of a thicker than average mantle transition zone. Our result is incompatible with the canonical model of a whole mantle plume in an olivine dominated mantle; however, considerations of phase transitions in the garnet system would allow us to reconcile our observations with the possible presence of a through‐going hot thermal anomaly beneath Bermuda

Radiocarbon dating organic residues at the microgram level

Relation between submilligram sample size and {sup 14}C activity for sample blanks (wood from Pliocene sediments) and a contemporary standard (oxalic acid) for catalytically reduced graphitic carbon was examined down to 20 micrograms. Mean age of the 1 mg wood sample blanks is now about 51.3 ka (0.168 pMC) while the mean for 20 microgram sample blanks is about 42.9 ka. So far, the lowest value for a 1-mg wood sample blank is about 60.5 ka (0.056 pMC). We have determined a mean {sup 14}C age of about 9.4 ka from a suite of 7 organic extracts from hair, bone, and matting from a mummified human skeleton from Spirit Cave, Nevada. These data indicate that the Spirit Cave human is the third, oldest directly-dated, human skeleton currently known from North America

Geographic and seasonal patterns and limits on the adaptive response to temperature of European Mytilus spp. and Macoma balthica populations

Seasonal variations in seawater temperature require extensive metabolic acclimatization in cold-blooded organisms inhabiting the coastal waters of Europe. Given the energetic costs of acclimatization, differences in adaptive capacity to climatic conditions are to be expected among distinct populations of species that are distributed over a wide geographic range. We studied seasonal variations in the metabolic adjustments of two very common bivalve taxa at European scale. To this end we sampled 16 populations of Mytilus spp. and 10 Macoma balthica populations distributed from 39° to 69°N. The results from this large-scale comprehensive comparison demonstrated seasonal cycles in metabolic rates which were maximized during winter and springtime, and often reduced in the summer and autumn. Studying the sensitivity of metabolic rates to thermal variations, we found that a broad range of Q10 values occurred under relatively cold conditions. As habitat temperatures increased the range of Q10 narrowed, reaching a bottleneck in southern marginal populations during summer. For Mytilus spp., genetic-group-specific clines and limits on Q10 values were observed at temperatures corresponding to the maximum climatic conditions these geographic populations presently experience. Such specific limitations indicate differential thermal adaptation among these divergent groups. They may explain currently observed migrations in mussel distributions and invasions. Our results provide a practical framework for the thermal ecophysiology of bivalves, the assessment of environmental changes due to climate change and its impact on (and consequences for) aquaculture

Filter-Passing Anaerobic Bacteria of the Upper Respiratory Tract in Health and During Acute Respiratory Disease

The observations here reported form part of a study of the nasopharyngeal flora of persons in isolated communities during health and when they were suffering with colds. The results of studies of aerobic flora have been published (Burky and Smillie (1929); Milam and Smillie (1931)). Field studies have been made in southern Alabama, in Labrador, and in St. John, one of the Virgin Islands in the West Indies. In the course of this field work cultures were made of the filter-passing anaerobic organisms of the nasopharynx of normal persons and of those with colds. This report is a summary of the results of this work. Olitsky and Gates (1920) first isolated a minute micro6rganism from the nasopharyngeal washings of early uncomplicated cases of influenza. This organism, which they named B. pneumosintes, is a cocco-bacillus, non-motile, Gram-negative, very small, and entirely anaerobic. It was first recovered in Smith-Noguchi medium; later, it was grown on blood-agar plates. Other workers subsequently reported the isolation of B. pneumosintes; Loewe and Zeman (1921) obtained strains from 3 cases of influenza; Gordon (1922) reported its presence in fourteen of 20 cases of influenza; Detwiler and Hodge (1924) in three of 6 cases, and Lister (1922) in five out of 15 cases of the same disease. Bran