Showing papers by "Andrew L. Johnson published in 2007"
TL;DR: In this paper, the authors reviewed the control on extensional growth rate and shell thickness in the Bathonian oyster Crassostrea and found that the small size in contemporaneous marine bivalves of north-west Europe was the product of reduced salinity.
Abstract: We review controls on extensional growth rate and shell thickness in the extant oyster Crassostrea Data on these shell parameters for the ecologically similar Bathonian oyster Praeexogyra hebridica, sampled at carefully selected sites, are then used to test a hypothesis that small size in contemporaneous marine bivalves of north-west Europe was the product of reduced salinity The hypothesis is refuted, at least to the extent that some additional factor must be involved The relatively low extensional growth rate and shell thickness at the highest-salinity site, together with the elongate (‘etiolated’) shape there and the low extensional growth rate at all sites in comparison with Crassostrea, suggests that this factor is reduced primary productivity Other faunal, sedimentological and diagenetic evidence is consistent with low productivity We point to other possible instances of reduced productivity during the Middle Jurassic and discuss the possible role of this factor in encouraging the widespread colonization of brackish-water environments by bivalves in the Bathonian Stage
12 citations
Patent•
07 Mar 2007TL;DR: In this article, the probe of a rotating tool (11) is inserted into the joining portion of a metal material (100, 102), and liquid CO2 is supplied to the probe and the rotating tool.
Abstract: Metal materials (100, 102) of such as Fe are abutted against each other at a joining portion (104), and the probe (12) of a rotating tool (11) is inserted into the joining portion (104). When the rotating tool (11) is moved in the longitudinal direction of the joining portion (104) while being rotated, the metal structure of the joining portion (104) is agitated to allow the metal materials (100, 102) to join with each other. When the rotating tool (11) is moved while being rotated, liquid CO2 is supplied to the joining portion (104) and the rotating tool (11). Nozzles (16, 18) discharge liquid CO2 from the rear in the moving direction of the rotating tool (11) by properly opening/closing solenoid valves (20, 22). Supplying liquid CO2 to the joining portion (104) and the rotating tool (11) can reduce abrasion of the rotating tool (11), and can improve the joint strength of the joining portion (104).
7 citations