Understanding Water Flows and Air Venting Features of Spillway—A Case Study

For safe spillway discharge of floods, attention is paid to the water flow. The resulting air flow inside the facility, an issue of personnel security, is sometimes disregarded. The spillway in question comprises two surface gates and two bottom outlet gates lying right below. Air passages to the outlet gates include an original gallery and a recently constructed vertical shaft. To understand water-air flow behavior, 3D CFD modelling is performed in combination with the physical model tests. The simulations are made with fully opened radial gates and at the full pool water level (FPWL). The results show that the operation of only the bottom outlets leads to an air supply amounting to ~57 m3/s, with the air flow rates 35 and 22 m3/s to the left and right outlets. The air supply to the right outlet comes from both the shaft and the gallery. The averaged air velocity in the shaft and the gallery are approximately 5 and 7 m/s. If only the surface gates are fully open, the water jet impinges upon the canal bottom, which encloses the air space leading to the bottom outlets; the air flow rate fluctuates about zero. If all the four gates are open, the total air demand is limited to ~10 m3/s, which is mainly attributable to the shear action of the meeting jets downstream. The air demand differs significantly among the flow cases. It is not the simultaneous discharge of all openings that results in the largest air demand. The flood release from only the two outlets is the most critical situation for the operation of the facility. The findings should provide reference for spillways with the same or similar layout.

Make it two: A case report of dual sequential external defibrillation

ABSTRACTDual sequential external defibrillation (DSED) is the process of near simultaneous discharge of two defibrillators with differing pad placement to terminate refractory arrhythmias. Previously used in the electrophysiology suite, this technique has recently been used in the emergency department and prehospital setting for out-of-hospital cardiac arrest (OHCA). We present a case of successful DSED in the emergency department with neurologically intact survival to hospital discharge after refractory ventricular fibrillation (RVF) and review the putative mechanisms of action of this technique.

Proton- and ion-transfer reactions

We consider the transfer of an ion or proton from the solution to the surface of a metal electrode; often this is accompanied by a simultaneous discharge of the transferring particle, such as by a fast electron transfer. The particle on the surface may be an adsorbate as in the reaction: . . .Cl - (sol) ⇋ Clad + e- (metal) . . . (9.1) In this case the discharge can be partial; that is, the adsorbate can carry a partial charge, as discussed in Chapter 4. Alternatively the particle can be incorporated into the electrode as in the deposition of a metal ion on an electrode of the same composition, or in the formation of an alloy. An example of the latter is the formation of an amalgam such as: . . . Zn2++2e- ⇋ Zn(Hg) . . . (9.2) The reverse process is the transfer of a particle from the electrode surface to the solution; often the particle on the surface is uncharged or partially charged, and is ionized during the transfer. Ion- and proton-transfer reactions are almost always preceded or followed by other reaction steps. We first consider only the chargetransfer step itself. Ions and protons are much heavier than electrons. While electrons can easily tunnel through layers of solution 5 to 10 Å thick, protons can tunnel only over short distances, up to about 0.5 Å, and ions do not tunnel at all at room temperature. The transfer of an ion from the solution to a metal surface can be viewed as the breaking up of the solvation cage and subsequent deposition, the reverse process as the jumping of an ion from the surface into a preformed favorable solvent configuration. In simple cases the transfer of an ion obeys a slightly modified form of the Butler-Volmer equation. Consider the transfer of an ion from the solution to the electrode. As the ion approaches the electrode surface, it loses a part of its solvation sphere, and it displaces solvent molecules from the surface; consequently its Gibbs energy increases at first.

Rapid baroreceptor resetting is unaltered by chronic hypertension in rats

This study compares rapid baroreceptor resetting in spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). Single-fiber baroreceptor activity and aortic diameter were measured in in vitro preparations. Baroreceptor pressure threshold (Pth) and suprathreshold pressure sensitivity were measured during periods after various levels of conditioning mean arterial pressure (cMAP). The ability of a baroreceptor to reset was expressed as the resetting ratio (delta Pth/delta cMAP). Rapid resetting was successfully characterized in 30 baroreceptors (18 SHR and 12 WKY). SHR blood pressures were higher, and aortic distensibility was lower than in WKY. SHR baroreceptors showed signs of chronic resetting, i.e., elevated Pth (105.4 vs. 88.5 mmHg, SHR and WKY, respectively) and decreased suprathreshold sensitivity (0.92 vs. 1.42 spikes.s.-1.mmHg-1, SHR and WKY, respectively), but their resetting ratios were similar to WKY (0.260 and 0.237, SHR and WKY, respectively). Characterization of rapid resetting of more than one baroreceptor from single animals reveals that the resetting ratio can vary by greater than 50% within animals. During simultaneous discharge-diameter recordings, the strain threshold was better correlated to cMAP than Pth. We conclude that the ability of baroreceptors to rapidly reset is unaltered by chronic hypertension or chronic baroreceptor resetting, and we hypothesize that rapid resetting is probably a result of an intrinsic neural property rather than vessel mechanics.