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The interlobular duct cells of the guinea-pig pancreas secrete HC[O.sub.3.sup.-] across their luminal membrane into a HC[O.sub.3.sup.-]-rich (125 mM) luminal fluid against a sixfold concentration gradient. Since HC[O.sub.3.sup.-] transport cannot be achieved by luminal Cl-/HC[O.sub.3.sup.-] exchange under these conditions, we have investigated the possibility that it is mediated by an anion conductance. To determine whether the electrochemical potential gradient across the luminal membrane would favor HC[O.sub.3.sup.-] efflux, we have measured the intracellular potential ([V.sub.m]) in microperfused, interlobular duct segments under various physiological conditions. When the lumen was perfused with a 124 mM [Cl.sup.-]-25 mM HC[O.sub.3.sup.-] solution, a condition similar to the basal state, the resting potential was approximately -60 mV. Stimulation with dbcAMP or secretin caused a transient hyperpolarization (~5 mV) due to activation of electrogenic [Na.sup.+]- HC[O.sub.3.sup.-] cotransport at the basolateral membrane. This was followed by depolarization to a steady-state value of approximately -50 mV as a result of anion efflux across the luminal membrane. Raising the luminal HC[O.sub.3.sup.-] concentration to 125 mM caused a hyperpolarization (~10 mV) in both stimulated and unstimulated ducts. These results can be explained by a model in which the depolarizing effect of [Cl.sup.-] efflux across the luminal membrane is minimized by the depletion of intracellular [Cl.sup.-] and offset by the hyperpolarizing effects of [Na.sup.+]- HC[O.sub.3.sup.-] cotransport at the basolateral membrane. The net effect is a luminally directed electrochemical potential gradient for HC[O.sub.3.sup.-] that is sustained during maximal stimulation. Our calculations indicate that the electrodiffusive efflux of HC[O.sub.3.sup.-] to the lumen via CFTR, driven by this gradient, would be sufficient to fully account for the observed secretory flux of HC[O.sub.3.sup.-]. KEY WORDS: pancreatic ducts * membrane potentials * bicarbonate ion * cystic fibrosis transmembrane conductance regulator * sodium-bicarbonate cotransporter

Research was conducted to examine the effects of arginine vasopressin (AVP) on pancreatic ductal secretion in guinea pigs. An isolated vascularly perfused pancreas was prepared from the guinea pig to exclude the systemic effects of AVP and to examine its effect on fluid secretion and vascular resistance simultaneously. Isolated interlobular duct segments were prepared from guinea pig pancreas to investigate the effects of AVP on ductal secretion. Results suggest that AVP directly inhibits secretin-stimulated ductal fluid secretion in the guinea pig pancreas.

This paper investigates the dynamic behaviour of tap changing operations in Tap Change Under Load (TCUL) transformers. Interactions among multiple TCUL controls cause osciilatory behaviour in tap changing actions, which unnecessarily increases tap operations before they reach equilibrium. Sufficient conditions for stability are derived and features of the phenomena are examined through theoretical analysis as well as through numerical simulation. Keywords - Tap Change Under Load, TCUL, On Load Tap Changer, OLTC, Tap Changer Control, Transformer Control, Voltage Stability

The effect of the configuration of the joint between an ac superconducting cable and a normal conducting plate on the current distribution and the joule loss is investigated by using the 3-D finite element method. It is shown that the concentration of current can be reduced by changing the configuration of joint The effectiveness of the analysis is verified by measuring the current distribution on the surface of a copper plate and the quenching current.

This paper presents a solution algorithm for expansion planning in distribution systems in which fault cases are taken into consideration. The proposed method can take all the predetermined severe fault cases into consideration simultaneously, and can avoid installing excess facilities without affecting the ability for fault restoration. In the algorithm, the whole problem is decomposed into sub-problems according to pre-determined fault cases, and is efficiently solved by using the branch exchange algorithm and the decomposition-coordination technique. The validity and the effectiveness of the proposed algorithm are demonstrated by numerical examples.

The utilization of the incoherent Thomson scattering of a high-power pulsed laser for the measurement of electron temperature and density in an electron cyclotron resonance plasma is discussed. An argon discharge with a 0.3 to 2 mTorr pressure and 250 to 1000 watts of microwave powers was used for the measurements. The strong and weak dependence of electron temperature and density to pressure and to input power and discharge magnetic field respectively, were demonstrated.

Analysis of voltage stability problems by the use of perturbation theory is presented. Voltage instability problems are categorized into four types using singular perturbation. The use of perturbation theory allows intricacies to be avoided since the approximation error is kept within an estimated value and divides a power system into slow and fast subsystems. Results show that type I instability are caused by fast load changes and could lead to voltage collapse. The load flow jacobian could be an indicator of types I and II-2S instabilities. Type II-2D can be studied by eigenvalue analysis and type II-1 by nonlinear analysis.