Combination throttle and shutoff valve

Combination of translating sleeve throttle valve and conventional poppet valve provides capability of shutting off flow completely by poppet and sleeve control of the rate of flow. Integration of the two concepts can be accomplished without difficulty and in a manner that requires a minimum of development

Long life, low cost ball valve, with lifted seals and cartridge type construction

Ball valve design incorporates modular construction in easy-to-install, easy-to-replace cartridge housing, and a system of cams to lift upstream and downstream seals away from the ball during rotation. Tests conducted on nitrogen tetroxide prove new valve to be more efficient than previous models in preventing leakage

Shellfish Face Uncertain Future in High CO2 World: Influence of Acidification on Oyster Larvae Calcification and Growth in Estuaries

BACKGROUND: Human activities have increased atmospheric concentrations of carbon dioxide by 36% during the past 200 years. One third of all anthropogenic CO(2) has been absorbed by the oceans, reducing pH by about 0.1 of a unit and significantly altering their carbonate chemistry. There is widespread concern that these changes are altering marine habitats severely, but little or no attention has been given to the biota of estuarine and coastal settings, ecosystems that are less pH buffered because of naturally reduced alkalinity. METHODOLOGY/PRINCIPAL FINDINGS: To address CO(2)-induced changes to estuarine calcification, veliger larvae of two oyster species, the Eastern oyster (Crassostrea virginica), and the Suminoe oyster (Crassostrea ariakensis) were grown in estuarine water under four pCO(2) regimes, 280, 380, 560 and 800 microatm, to simulate atmospheric conditions in the pre-industrial era, present, and projected future concentrations in 50 and 100 years respectively. CO(2) manipulations were made using an automated negative feedback control system that allowed continuous and precise control over the pCO(2) in experimental aquaria. Larval growth was measured using image analysis, and calcification was measured by chemical analysis of calcium in their shells. C. virginica experienced a 16% decrease in shell area and a 42% reduction in calcium content when pre-industrial and end of 21(st) century pCO(2) treatments were compared. C. ariakensis showed no change to either growth or calcification. Both species demonstrated net calcification and growth, even when aragonite was undersaturated, a result that runs counter to previous expectations for invertebrate larvae that produce aragonite shells. CONCLUSIONS AND SIGNIFICANCE: Our results suggest that temperate estuarine and coastal ecosystems are vulnerable to the expected changes in water chemistry due to elevated atmospheric CO(2) and that biological responses to acidification, especially calcifying biota, will be species-specific and therefore much more variable and complex than reported previously

Influence of Alternative Shell-Drilling Behaviours on Attack Duration of the Predatory Snail, \u3cem\u3eChicoreus Dilectus\u3c/em\u3e

Edge drilling is a form of predation in which a predatory snail excavates a hole at a point along the margin of the closed valves of a bivalved animal. We tested the hypothesis that edge-drilling attacks by the predatory snail Chicoreus dilectuson its clam prey Chione elevata shorten the duration of the predation process relative to the alternative behaviour of drilling through the prey\u27s shell wall away from its edges. The time required to complete an edge-drilling attack was on average about three times less than when prey were attacked through the shell wall. This improvement in predation speed was a function of the thickness of the prey\u27s shell at the point of attack. We suggest that owing to the shorter length of time required to kill prey, the edge-drilling behaviour may be selectively advantageous in environments where enemies are abundant, especially competitors that might attempt to steal prey. Behaviours that speed up the predation process may create opportunities for more effective exploitation of available prey resources in highly competitive environments