In-line Flow Meters Research Articles

Efficiency of Large-Volume Plankton Pumps, and Evaluation of a Design Suitable for Deployment from Small Boats

A critical review of previously published studies, and evaluation of a newly developed pump system, showed the often stated shortcomings of large-volume pumps as instruments for sampling plankton communities (e.g. damage to organisms sampled, volumes too small to estimate plankton density accurately, and systems too cumbersome to handle) to be invalid. Previously published estimates of the comparative efficiency of large-volume pump samplers and tow nets should; however, be viewed with caution because the techniques used to estimate pumped volume are error prone. In-line flow meters are essential for accurate volume estimation. Comparative efficiency tests of a newly developed large-volume pumping system deployed simultaneously with 80- and 153-μm mesh standard plankton nets revealed that the pump, while sampling only 8% of the volume sampled by the nets, was equally effective in capturing capelin (Mallotus villosus) larvae (5-mm length), herring (Clupea harengus) larvae (9-mm length), large copepods (> 750 μm), small jellyfish, and hyperiid amphipods. The pump was superior to nets in sampling crab zoea and megalops larvae and becomes more efficient at capturing euphausiids and chaetognaths as their natural densities increase. Nets were superior in the capture of fish eggs (primarily cunner, Tautogolabrus adspersus), possibly due to the vertical distribution of eggs in the water column. The average length of capelin larvae captured by pumping was consistently 0.2 mm longer than that of larvae taken in nets, but the length–frequency distribution of larvae sampled was similar to that of larvae entering the pelagic environment. Attaching the pump intake to the cod-end of a rigid tow net is suggested as a method of surmounting potential errors when sampling organisms at densities below 1–5/m3.

Effect of thoracic venting on arterial pressure, and flow during external cardiopulmonary resuscitation in animals.

To test the hypothesis that fluctuations in global intra-thoracic pressure are the dominant cause of blood flow during external CPR, the authors studied the effects of open pneumothorax on experimental CPR in 7 domestic pigs and 12 mongrel dogs. Similar studies were conducted independently at three laboratories and are reported jointly. All studies were conducted during electrically induced ventricular fibrillation and with standard CPR technique: ventral-dorsal chest compression at 60/min, 0.5 sec compression duration, 1:5 ventilation:compression ratio. During alternate periods of CPR, intrathoracic pressure was vented through bilateral chest tubes, placed to create open pneumothorax and partial collapse of the lungs. During this maneuver, global intrathoracic pressure fluctuations were greatly attenuated, but direct cardiac compression and adequate ventilation continued. In the three laboratories, systolic/diastolic arterial pressures during CPR with thoracic venting (± se) averaged 68 ± 4.2/28 ± 3.3, 60 ± 10/18 ± 4.5, and 66 ± 6.3/23 ± 1.5 mm Hg. These values are compared to 68 ± 4.4/27 ± 3.0, 67 ± 12/17 ± 6.1, and 56 ± 6.2/22 ± 1.9 mm Hg with the thorax intact. Carotid artery mean flow, measured with an in-line flowmeter, was 13.0 ± 2.2 ml/min vented vs. 13.4 ± 2.6 intact in 7 pigs; 11.4 ± 3.8 ml/min vented vs. 11.2 ± 3.7 intact in 5 dogs. Cardiac output, determined by indicator dilution, was 25 ± 4.3 ml/min · kg vented vs. 20 ± 4.3 intact in 7 dogs. Thoracic venting did not decrease blood pressures and flows during CPR, as would be predicted from the hypothesis that generalized intrathoracic pressure fluctuations are the dominant hemodynamic mechanism. The results are consistent with the classical notion that CPR works by compression of the heart between the sternum and the spine. This mechanism should not be discounted in future attempts to improve CPR.

A New Plankton Sampler for Coral Reefs

. A new self-contained Horizontal Plankton Sampler (HOPLASA) collects near-reef plankton that is not captured by conventional net tows and emergence traps. An electrical motor-propeller assembly inside a large acrylic cylinder drives water past an in-line flowmeter and through a rigidly attached plankton net. When positioned in the coral reef environment this sampling gear filters known quantities of bottom water. Larvae and developmental stages of many invertebrates and some fishes that never migrate to upper water layers but constitute an important fraction of the food chain are captured. Larvae of sponges, corals, and gorgonians, the most important animal reef builders, are obtained live and undamaged and can be cultured in the laboratory for identification after metamorphosis.