bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrophysiological responses of dissociated type I cells of the rabbit carotid body to cyanide.
Authors: Biscoe T J , Duchen M R
Published: December 2014

1. The carotid body is the major peripheral sensor of arterial PO2 in the mammal and is excited by cyanide (CN‐). Type I cells, the presumed sites for transduction, were freshly dissociated from the carotid body of the adult rabbit and studied with the whole‐cell patch clamp technique. 2. Type I cells were hyperpolarized by CN‐, the action potential was shortened, and there was an increased after‐hyperpolarization. 3. Under voltage clamp control, CN‐ increased a voltage‐dependent outward current, which showed pronounced outward rectification. Tail currents increased by CN‐ reversed close to the predicted EK, the reversal potential of the CN‐‐induced current depended on extracellular [K+], and the current was blocked by intracellular TEA+ and Cs+. 4. The i‐V relation of the CN‐‐induced conductance strongly mirrored that of voltage‐gated Ca2+ entry, and the response was abolished by removal of extracellular Ca2+. We conclude that the increased gK is Ca2+ ‐dependent (gK(Ca]. 5. The Ca2+ current was attenuated by CN‐, and showed an increased rate of inactivation. Thus, the increased gK(Ca) must result from an alteration in Ca2+ homeostasis independent of the Ca2+ current, and not an increased Ca2+ entry through voltage‐activated channels. 6. Carbachol also hyperpolarized cells and increased a K+ conductance. 7. At depolarized holding potentials a steady‐state outward current was increased by CN‐. The current reversed close to EK, and was associated with increased current fluctuations. Noise analysis showed that a channel conductance of 3 pS carries the current. 8. The response to CN‐ was not impaired by the inclusion of 5 mM‐MgATP in the patch pipette. 9. If signals to the CNS are initiated by the calcium‐dependent release of transmitters from type I cells, transduction would appear to be the direct consequence of the energy dependence of Ca2+ homeostasis.
Neurogenic slow depolarizations and rapid oscillations in the membrane potential of circular muscle of mouse colon.
Authors: Bywater R A , Small R C , Taylor G S
Published: December 2014

1. Intracellular microelectrodes have been used to record the electrical activity of smooth muscle cells of the circular layer from full length strips of mouse colon in vitro. The membrane potential was unstable and showed slow depolarizations (mean amplitude, 10.9 mV; mean frequency, 0.008 Hz; mean duration, 56.4 s). 2. A variable number (mean fifty‐six) of rapid oscillations in membrane potential (mean amplitude, 10.2 mV) with a frequency of approximately 2 Hz and a duration of approximately 400 ms were superimposed on each slow depolarization. Occasionally, action potentials arose from the rapid oscillations. The action potentials, but neither the slow depolarizations nor the rapid oscillations, were abolished by 1.0 microM‐nifedipine. 3. The majority of the slow depolarizations and the associated rapid oscillations migrated aborally along the colon at a velocity of between 0.5 and 1.5 mm s‐1; in the distal colon the slow depolarization was often preceded by a small hyperpolarization. 4. During the rising and plateau phase of the slow depolarization the amplitude of electronic potentials was decreased. Hyperpolarization induced by passing current during the slow depolarization increased the amplitude of the rapid oscillations. 5. Transmural electrical stimulation (single pulses) in the presence of nifedipine evoked (1 mm anal to the stimulating electrodes) an inhibitory junction potential which was sometimes preceded by an excitatory junction potential. The amplitude, of the evoked inhibitory junction potential was decreased during the rising and plateau phase of the slow depolarization. 6. The slow depolarization and the rapid oscillations were abolished by hexamethonium (500 microM), morphine (1‐10 microM) and tetrodotoxin (3.1 microM). Atropine (3.5 microM) abolished the rapid oscillations and reduced the amplitude of the slow depolarization. 7. Atropine (3.5 microM) and morphine (10 microM) abolished the evoked excitatory junction potential whilst tetrodotoxin (3.1 microM) abolished both the excitatory and the inhibitory junction potential. 8. It is suggested that the migrating depolarization and accompanying oscillations, which are neurogenic in origin, represent the electrical correlate in the circular muscle layer of the migrating colonic motor complex which has been associated with the propulsion of faecal pellets along the colon.
Analysis of H2 clearance curves used to measure blood flow in rat sciatic nerve.
Authors: Day T J , Lagerlund T D , Low P A
Published: December 2014

1. By use of the H2 clearance technique, blood flow was measured in the sciatic nerve of healthy, anaesthetized Sprague‐Dawley rats at rest, during inferior vena cava occlusion and during 5‐hydroxytryptamine infusion. The purpose was to clarify the mechanisms underlying the biexponential curves which are commonly obtained using this technique. 2. An analysis of the frequency distribution of rate constants of 270 nerve and thirty‐three arterial samples indicated that H2 clearance rates cluster below 20 ml min‐1 100 g‐1 and between 70 and 100 ml min‐1 100 g‐1. This suggests that at least two compartments are present. 3. The contribution of diffusion was studied by recording H2 clearance immediately following circulatory arrest. Slow clearance rates (median = 2.4 ml min‐1 100 g‐1) were observed, indicating that diffusion is not likely to contribute significantly to nutritive flow under most situations. 4. The contribution of arteriovenous shunts to H2 clearance was assessed by determining H2 clearance during inferior vena cava occlusion and the infusion of 5‐hydroxytryptamine. Both manoeuvres caused abolition of, or a significant reduction in the weight of, the fast component which indicates that this compartment is closely related to arteriovenous shunts in nerve. 5. By use of a multi‐compartmental model, it was shown that H2 clearance should follow a multi‐exponential course, where the weights of the components reflect the relative volumes of each compartment and the exponents represent the relative flow (i.e. flow per unit volume) in each compartment. 6. By use of other mathematical models, estimates were made for the clearance rates attributable to polarographic oxidation of H2 at the tip of the microelectrode (0.2 ml min‐1 100 g‐1) and to diffusion to air (2 ml min‐1 100 g‐1). The latter estimate is very close to the measured value of 2.4 ml min‐1 100 g‐1. 7. These findings indicate that it is possible to separately assess nutritive and non‐nutritive flow by application of biexponential analysis to H2 clearance curves. The data suggest that the fast component of a H2 clearance curve is closely associated with arteriovenous shunts, while the slower component is likely to represent capillary flow. Processes such as diffusion to air or oxidation of H2 by the electrode are very slow and therefore are unlikely to distort the assessment of blood flow by using this technique.
Effects of new non‐N‐methyl‐D‐aspartate antagonists on synaptic transmission in the in vitro rat hippocampus.
Authors: Andreasen M , Lambert J D , Jensen M S
Published: December 2014

1. The effects of new, potent non‐N‐methyl‐D‐aspartate (NMDA) receptor antagonists, 6,7‐dinitroquinoxaline‐2,3‐dione (DNQX) and 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione (CNQX), have been examined using intra‐ and extracellular recordings in the hippocampal slice preparation. In terms of potency and selectivity, the action of the two blockers was similar and CNQX was used in most experiments. 2. CNQX reduced the responses to ionophoretic applications of the non‐NMDA agonists kainate (KAI) and quisqualate (QUIS) with IC50 values of 1.2 and 4.8 microM, respectively. In Mg2+‐free solutions responses to NMDA were generally not affected by concentrations of CNQX up to 25 microM. 3. The action of CNQX was only slowly and poorly reversible on washing. Responses to QUIS and KAI were also reversibly reduced by ionophoretic application of CNQX. 4. CNQX blocked the evoked EPSP in CA1 and CA3 neurones with an IC50 of around 2 microM, which is similar to the IC50 for responses to KAI. CNQX was without effect on the passive membrane properties, the afferent volley and paired pulse potentiation. 5. In the presence of CNQX (greater than 5 microM) a small EPSP remained which was largest in CA1 neurones. It was blocked by low concentrations of the NMDA receptor antagonist (+/‐)‐2‐amino‐5‐phosphonovaleric acid (APV), was markedly enhanced on removing Mg2+ ions from the bathing medium and, in voltage‐clamp experiments, showed a potential dependence which is characteristic of the NMDA ionophore. 6. The latency of the APV‐sensitive EPSP in CA1 was the same as the CNQX‐sensitive EPSP, indicating that NMDA receptors participate in monosynaptic excitation. 7. Feedback and feed‐forward inhibition in both area CA1 and CA3 were sensitive to CNQX. There seemed to be two components of the inhibition, both of which appear to be GABAergic since they could be blocked by picrotoxin (PTX), but only one of which was blocked by CNQX. The CNQX‐resistant IPSP was not affected by APV. 8. In conclusion, quinoxalinediones have been used to demonstrate that non‐NMDA receptors mediate the majority of the EPSP. Additionally, a component of the EPSP in CA1 is mediated by NMDA receptors and is manifested at resting membrane potentials and in the presence of Mg2+.
Modulation of an electrical synapse between solitary pairs of catfish horizontal cells by dopamine and second messengers.
Authors: DeVries S H , Schwartz E A
Published: December 2014

1. Retinas from channel catfish were dissociated and the cells maintained in culture. Horizontal cells that normally receive input from cone photoreceptors were identified. The conductance of the electrical junction formed between a pair of ‘cone’ horizontal cells was measured by controlling the membrane voltage of each cell with a voltage clamp maintained through either a micropipette or a patch pipette. The two techniques yielded similar results. 2. Transjunctional current was measured while transjunctional voltage was stepped to values between +/‐ 60 mV. The current (measured 5 ms after a step) was proportional to voltage over the range tested. For steps to voltages greater than +/‐ 45 mV, the current exhibited a slight time‐dependent decline. 3. Dopamine decreased junctional conductance in a dose‐dependent fashion. A 50% reduction was obtained with 10 nM‐dopamine. The D1 agonist fenoldopam (100 nM) also decreased junctional conductance. The uncoupling produced by either agent was rapid and reversible. 4. The introduction of 100 microM‐cyclic AMP into one cell of a pair decreased junctional conductance by, on average, 40%. Forskolin (1‐10 microM), an activator of adenylate cyclase, decreased junctional conductance 50‐90%. 5. The introduction of 80 microM‐cyclic GMP into one cell of a pair decreased junctional conductance by, on average, 40%. Nitroprusside (1‐10 microM), an activator of guanylate cyclase, reduced junctional conductance 40‐65%. 6. The introduction of a peptide inhibitor specific for the cyclic AMP‐dependent protein kinase reversed a decrease in junctional conductance produced by superfusion with either dopamine (1 microM), fenoldopam (100 nM) or forskolin (5‐10 microM). 7. Intracellular Ca2+ concentration was measured with the fluorescent indicator Fura‐2. The intracellular Ca2+ concentration was increased by activation of a Ca2+ current. Junctional conductance remained constant as the internal Ca2+ concentration changed from 100 to 700 nM. 8. Intracellular pH was measured with the fluorescent indicator bis‐carboxyethylcarboxyfluorescein. The application of acetate (2.5 mM) reduced intracellular pH by 0.2‐0.3 units and decreased junctional conductance by approximately 50%. A subsequent application of fenoldopam did not alter intracellular pH, but decreased junctional conductance by more than 50%. 9. The sensitivity of the junctional conductance between isolated horizontal cells to dopamine is consistent with dopamine having a direct effect on coupling in intact retina. Dopamine regulates the activity of a cyclic AMP‐dependent protein kinase which in turn modulates junctional conductance. Changes in intracellular pH and Ca2+ concentration are not involved in mediating the effect of dopamine on coupling. Cyclic GMP and intracellular pH may participate in regulatory pathways independent of that used by cyclic AMP.
Sodium‐calcium exchange in guinea‐pig cardiac cells: exchange current and changes in intracellular Ca2+.
Authors: Beuckelmann D J , Wier W G
Published: December 2014

1. Membrane currents and changes in [Ca2+]i attributable to the operation of an electrogenic Na‐Ca exchange mechanism were recorded in single isolated guinea‐pig ventricular myocytes under voltage clamp and internal perfusion with the Ca2+ indicator Fura‐2. 2. Ionic currents that interfere with the measurement of Na‐Ca exchange current were blocked through the use of caesium (Cs+), verapamil and tetrodotoxin (TTX). Entry of Ca2+ through surface membrane Ca2+ channels and release of Ca2+ from sarcoplasmic reticulum were blocked with verapamil and ryanodine, respectively. 3. In the presence of the blockers listed above, depolarization to positive membrane potentials elicited slow increases in [Ca2+]i and, after an instantaneous increase, a declining outward current. Repolarization elicited a decline in [Ca2+]i and, after an instantaneous increase, a declining inward current. The changes in [Ca2+]i and a major component of the current were abolished by nickel ions (Ni2+; 5 mM). 4. The reversal potential of the current abolished by Ni2+ (Ni2+‐sensitive current) was determined at different levels of [Ca2+]i by ramp repolarizations from +80 to ‐80 mV (1‐5 mV/ms). The reversal potential of the current increased linearly with log [Ca2+]i. As a result of the foregoing and other data, the Ni2+‐sensitive current was taken to be Na‐Ca exchange current (INaCa). 5. The relation between INaCa and [Ca2+]i (less than 1 microM) at constant voltage over the range of ‐80 to +60 mV was approximately linear. No evidence of saturation could be found; small deviations from linearity at high [Ca2+]i were in the direction expected for a minor contribution from Ca2+‐activated non‐specific cation current (Ehara, Noma & Ono, 1988). 6. When measured at the same [Ca2+]i, the peak INaCa upon repolarization to ‐80 to ‐140 mV seemed to approach a limiting value at very negative potentials. 7. Over the range of +40 to +160 mV INaCa (measured soon after depolarization and thus at the same [Ca2+]i) increased exponentially with clamp‐pulse potential. These pulses (to potentials up to +160 mV) elicited a slow rise in [Ca2+]i with the peak at the end of the pulse also increasing exponentially with pulse potential. 8. Inward membrane currents with properties similar to those described above were also recorded in association with physiological [Ca2+]i transients, when Ca2+ channels and the sarcoplasmic reticulum were not blocked. 9. Some of the results are not consistent with certain predictions of a sequential step model, or with those of a simultaneous step model in which the internal binding site for Ca2+ is saturated, or with those of a model based only on thermodynamics.(ABSTRACT TRUNCATED AT 250 WORDS)
Responses of electroreceptors in the snout of the echidna.
Authors: Gregory J E , Iggo A , McIntyre A K , Proske U
Published: December 2014

1. This is a report of experiments which provide evidence in support of the existence of an electric sense in the echidna, or spiny anteater Tachyglossus aculeatus. It is the first known example of electroreception in a terrestrial animal. 2. In each of four animals anaesthetized with alpha‐chloralose, afferent responses were recorded in dissected filaments of the infraorbital branch of the trigeminal nerve which supplies skin of the upper jaw. Recordings were obtained from a total of forty‐seven units identified as electroreceptors, by their responses to weak voltage pulses using focal stimulation of the moist skin surface. 3. In the absence of a stimulus, some receptors had an irregular resting discharge; others were silent. The receptive field for each receptor consisted of a discrete spot. Receptive fields were restricted to the tip of the snout. Cathodal stimulation over the receptive spot was excitatory for the duration of an applied voltage pulse. Reversal of stimulus polarity silenced any on‐going activity and was followed by a post‐anodal rebound excitation. 4. Receptor threshold was best measured not in air but with the snout immersed in tap water. An electric field was applied between a pair of large plate electrodes on either side of the snout. Threshold for thirty receptors lay in the range 1.8‐73 mV cm‐1. Measurements of response latency and of conduction path length gave estimates of axonal conduction velocities for the afferent fibres of 10‐18 m Receptors responded to sinusoidally changing voltage gradients over the range 0.5‐200 Hz with a maximum sensitivity at 20 Hz. 5. In one experiment a receptor site was marked with fine pins. Serial sections of the piece of underlying skin revealed a large mucus‐secreting gland at the marked spot. Similar glands in skin of the platypus have previously been shown to be the sites of electroreceptors. 6. In a behavioural experiment an echidna was trained to choose between two identical tap water‐filled troughs, one of which had a weak electric field across it. The animal learned to detect field strengths down to 1.8 mV cm‐1 which corresponded to threshold for the most sensitive receptor measured in a subsequent electro‐physiological experiment. It is concluded that the echidna, like the other Australian representative of the monotremes, the platypus, has an electric sense. It remains to be determined what kinds of sources of electric fields the animal encounters in its normal habitat.
The role of inactivation in the effects of n‐alkanols on the sodium current of cultured rat sensory neurones.
Authors: Elliott A A , Elliott J R
Published: December 2014

1. The whole‐cell patch‐clamp technique has been used to investigate the actions of n‐butanol, n‐pentanol, n‐hexanol and n‐octanol on the sodium current of cells isolated from the dorsal root ganglia (DRGs) of neonatal rats and maintained in short‐term tissue culture. 2. The influence of n‐alkanols on the level of steady‐state inactivation of the sodium current was investigated by a standard two‐pulse protocol. All alkanols increased the level of resting inactivation and this was manifested as a hyperpolarizing shift of the relationship between the steady‐state inactivation parameter (h infinity) and membrane potential. The mid‐point of the h infinity curve was moved by up to ‐30 mV. 3. The relationship between the shift in the mid‐point of the inactivation curve (delta Vh) and aqueous n‐alkanol concentration has been derived for each n‐alkanol. These are complex in shape and do not appear consistent with a hypothesis that the increase in inactivation results from 1:1 binding of an alkanol molecule to a single site on the channel protein. 4. The aqueous concentrations used ranged from 70 mM‐n‐butanol to 0.05 mM‐n‐octanol. However, equal fractional saturations of n‐alkanols produced approximately equal shifts in the h infinity curve, particularly in the range 0.01‐0.07 saturated. This implies a hydrophobic site of action, with a standard free energy per methylene group for adsorption to the site from the aqueous phase of ca ‐3.2 kJ/mol. 5. The increase in resting inactivation was not the sole means by which n‐alkanols reduced the sodium current. The current was still reduced in cells pre‐pulsed to sufficiently negative potentials to remove steady‐state inactivation even in the presence of alkanols. The concentration required to reduce the current by 50% (ED50) has been interpolated for each n‐alkanol. From these data it was estimated that the standard free energy per methylene group for adsorption to the site of action was ca ‐3.1 kJ/mol, similar to that calculated for the effect on inactivation. The concentration dependence of this residual block indicated the involvement of more than one n‐alkanol molecule. 6. The n‐alkanols increase the level of inactivation of rat DRG cell sodium channels at potentials around the resting membrane potential and this effect contributes to their local anaesthetic action.(ABSTRACT TRUNCATED AT 400 WORDS)
Voltage‐gated and agonist‐mediated rises in intracellular Ca2+ in rat clonal pituitary cells (GH3) held under voltage clamp.
Authors: Benham C D
Published: December 2014

1. Intracellular free calcium (Ca2+i) was estimated in single GH3 cells by dual wavelength emission spectrofluorimetry using the Ca2+ indicator dye Indo‐1, while cells were held under voltage clamp using patch clamp techniques. 2. Depolarization of cells evoked a transient rise in Ca2+i that increased with increasing duration of depolarization to a peak at about 10 s. 3. Calcium transients showed a bell‐shaped dependence on the amplitude of the depolarizing pulse. They were abolished in the absence of extracellular calcium and by application of 10 microM‐nifedipine. 4. Thyrotrophin‐releasing hormone (TRH) evoked a transient rise in Ca2+i that was followed by a more sustained period of elevated Ca2+i in some cells. The transient phase of the response but not the sustained phase was seen in the absence of extracellular calcium. 5. Ca2+i transients evoked by depolarization were not affected by pre‐release of internal Ca2+ stores with TRH. 6. The results demonstrate that voltage‐gated Ca2+ entry and Ca2+ store release can each elevate cytoplasmic free calcium in GH3 cells and may both be important for stimulus‐secretion coupling. Non‐voltage‐gated Ca2+ entry is not a major source of Ca2+ under these conditions.
Evidence by calorimetry for an activation of sodium‐hydrogen exchange of young rat skeletal muscle in hypertonic media.
Authors: Chinet A , Giovannini P
Published: December 2014

1. The rate of energy dissipation associated with Na(+)‐H+ exchange in isolated, superfused soleus muscles from young rats was measured with an isothermal microcalorimeter during quasi‐stationary states of oxidative metabolism. 2. Under normal physiological conditions, amiloride, an inhibitor of the Na(+)‐H+ exchange across plasma membranes, had no measurable effect on the specific rate of muscle heat production (E); the ouabain‐suppressible part of E was identical whether amiloride was absent or present. 3. E was increased under hyperosmotic conditions and the difference with respect to control (excess E) was proportional to the degree of hyperosmolarity of the superfusate. It was 48% of basal E during a +100 mosM stress (with no change of extracellular Na+ concentration, Na+o). Inhibition of Ca2+ release into the sarcoplasm with sodium dantrolene (10(‐5) M) or tetracaine (5 x 10(‐5) M) suppressed a substantial part (65 and 53%, respectively) of the steady‐state excess E (1.2 mW (g wet weight)‐1) induced by the +100 mosM stress. Practically 100% of excess E was suppressed in the nominal absence of extracellular sodium (Na+o = 0, Li+ substitution) or under 15 mM‐Na+o, and excess E was enhanced when Na+o was increased (hyperosomolarity by addition of Na2SO4 instead of sucrose). 4. Under hyperosmotic conditions, amiloride at the 5 x 10(‐7) M concentration had no effect on excess E whereas at 10(‐4) M it induced a significant decrease of excess E. The absolute effect of 10(‐4) M‐amiloride was ‐0.34 mW (g wet weight)‐1 (equal to 28% of the excess E due to a +100 mosM‐sucrose stress and to 14% of the excess E due to a +100 mosM‐Na2SO4 stress). It was left unaltered in the presence of dantrolene and was independent of the way the +100 mosM stress was obtained (i.e. 100 mM‐sucrose or 50 mM‐Na2SO4). It was suppressed at Na+o = 0‐15 mM and could be mimicked by guanochlor, another potent inhibitor of Na(+)‐H+ exchange. In the presence of 10(‐4) M‐amiloride, the ouabain‐suppressible E was significantly reduced. In the presence of ouabain, amiloride had no effect. 5. Muscle tissue space available to [3H]inulin was measured in parallel experiments. It was 23.3% under control conditions and 30.6% after a 2 h exposure of the muscle to a +100 mosM‐Na2SO4 stress.(ABSTRACT TRUNCATED AT 400 WORDS)
Sodium‐dependent membrane current induced by carbachol in single guinea‐pig ventricular myocytes.
Authors: Matsumoto K , Pappano A J
Published: December 2014

1. In the presence of either barium (0.2 mM) or caesium (20 mM), carbachol (3‐300 microM) depolarized isolated guinea‐pig ventricular myocytes. Carbachol induced an inward current under voltage clamp at a holding potential equal to the resting potential (‐75 mV). 2. Acetylcholine and oxotremorine also evoked an inward current but were less effective than carbachol. Atropine (0.3 microM) prevented the depolarization and inward current induced by carbachol and acetylcholine but not by oxotremorine. Moreover, oxotremorine, but not carbachol, induced an inward current in the absence of extracellular sodium. 3. Carbachol increased membrane chord conductance when it induced an inward current. These effects were recorded under experimental conditions that suppressed the voltage‐ and time‐dependent sodium current (tetrodotoxin) and calcium current (cadmium), the inwardly rectifying potassium current, iK1 (caesium, barium and tetraethylammonium) and the current generated by the sodium‐potassium pump (zero external potassium). 4. Under these same experimental conditions, the steady‐state I‐V relationship in the presence of carbachol was subtracted from that in its absence. The apparent reversal potential (Erev) was 25 mV with extracellular Na+ ([ Na+]o) at 143 mM and intracellular Na+ ([Na+]i) at 11 mM. Replacement of [Na+]o by N‐methyl‐D‐glucamine was associated with a shift of the apparent Erev to more negative voltages by approximately 61 mV per tenfold change of [Na+]o. 5. Isoprenaline induced an inward current in ventricular myocytes that depended upon sodium entry, required the accumulation of cyclic AMP and which was partially suppressed by acetylcholine (Egan, Noble, Noble, Powell, Twist & Yamaoka, 1988). In contrast to the current evoked by beta‐adrenoceptor agonist, the current induced by muscarinic agonist was smaller and sustained. Moreover, the carbachol‐induced current was not suppressed by prior addition of isoprenaline. 6. The findings are consistent with the mechanism that carbachol activates a plasma membrane ion channel that admits sodium and thereby increases intracellular sodium activity. The estimated increase of intracellular sodium activity from electrophysiological data agrees quantitatively with that obtained from measurements with sodium‐sensitive microelectrodes (Korth & Kühlkamp, 1985). 7. The ability of carbachol to increase sodium influx may be the first step in a series of reactions that eventually alters sodium‐calcium exchange and could account for catecholamine‐independent stimulation of developed force in mammalian ventricle.
Systematic Configuration Selection Methodology of Power-Split Hybrid Electric Vehicles With a Single Planetary Gear
Authors: Kang Minkuk , Kim Hyunjun , Kum Dongsuk
Published: December 2014

Nowadays, power-split hybrid electric vehicles (PS-HEV) are very popular mainly thanks to the success of Toyota Prius. Despite their superior performance, the design and control of PS-HEVs are non-trivial due to the large number of design candidates and the complex control problems. For instance, there exist twelve ways to connect the four components (two motor/generators, an engine, and a driving wheel) with a single planetary gear-set (PG), and the number increases to 1152 possible configurations when using two PGs. Moreover, if we consider the final drive (FD) and PG ratios as design variables, finding the best design becomes intractable. In this study, we introduce a simple yet powerful way to find the optimal designs of single PG PS-HEVs. The suggested method consists of two parts — full-load analysis and light-load analysis. The full-load analysis computes 0–100kph times to evaluate acceleration performance of all designs using instantaneous optimization approach. The light-load analysis evaluates the fuel economy of selected designs (designs with acceptable acceleration performance) using equivalent consumption minimization strategy (ECMS). Note that the sun-to-ring (SR) gear ratio and the FD ratio are considered design variables, and thus one can see how fuel economy and acceleration performance of each configuration vary with SR and FD ratios. Based on these analyses, the optimal design that balances full-load and light-load performances can be selected.
Asymptotically Stabilizing Potential Control for the Eye Movement Dynamics
Authors: Ghosh Bijoy K. , Oki Takafumi , Kahagalage Sanath D. , Wijayasinghe Indika
Published: December 2014

In this paper, we analyze the problem of stabilizing a rotating eye movement control system satisfying the Listing’s constraint. The control system is described using a suitably defined Lagrangian and written in the corresponding Hamiltonian form. We introduce a damping control and show that this choice of control asymptotically stabilizes the equilibrium point of the dynamics, while driving the state to a point of minimum total energy. The equilibrium point can be placed by appropriately locating the minimum of a potential function. The damping controller has been shown to be optimal with respect to a suitable cost function. We choose alternate forms of this cost function, by adding a term proportional to the potential energy, and synthesize stabilizing control, using numerical solution to the the well known Hamilton Jacobi Bellman equation. Using Chebyshev collocation method, the newly synthesized controller is compared with the damping control.
Increasing Patient Engagement in Rehabilitation Through Citizen Science
Authors: Laut Jeffrey , Cappa Francesco , Nov Oded , Porfiri Maurizio
Published: December 2014

In this paper, we investigate the effects of including scientific tasks on the satisfaction of patients performing rehabilitation exercises. A low-cost system, comprised of a haptic joystick and a laptop computer, is used for patients to interact with a virtual environment. Within the virtual environment, users are presented with and classify images captured by a robot as part of a citizen science project. Results show that higher levels of satisfaction are attained when the exercise includes scientific tasks.
Model Predictive Control of Organic Rankine Cycle for Waste Heat Recovery in Heavy-Duty Diesel Powertrain
Authors: Luong David , Tsao Tsu-Chin
Published: December 2014

This paper continues the development of a previous conference paper that introduces advanced controllers for an Organic Rankine Cycle (ORC) in a heavy-duty diesel powertrain. The ORC’s heat exchangers are modeled as control-oriented, nonlinear Moving Boundary models. The pump and expander, which are coupled to the engine crankshaft, have relatively faster dynamics than the heat exchangers and are modeled as static components. The driving cycle produces transient heat source and engine conditions for the ORC whose goal is to maximize waste heat recovery under specified operating constraints. This paper describes a Model Predictive Controller (MPC) and compares it to Proportional Integral (PI) and Linear Quadratic Integral (LQI) controllers. The three controllers attempts to regulate heat exchanger pressures while satisfying specified operating constraints. Extended Kalman Filters (EKFs) are designed and implemented for state estimation feedback for MPC and LQI requiring full state feedback. The simulation results show the advantage of the advanced controllers in reducing pressure regulation error, with MPC having the lowest pressure regulation error among the three controllers and able to incorporate the operating constraints into its control law.
Development of Immunity Based Adaptive Control Laws for Aircraft Fault Tolerance
Authors: Perez Andres E. , Moncayo Hever , Moguel Israel , Perhinschi Mario G. , Al Azzawi Dia , Togayev Adil
Published: December 2014

This paper presents the development and testing of a novel fault tolerant adaptive control system based on a bio-inspired immunity-based mechanism applied to an aircraft fighter model. The proposed baseline control laws use a non-linear dynamic inversion and model reference adaptive control on the inner loops of the aircraft dynamics. In this new approach, the baseline controllers are augmented with an artificial immune system mechanism that relies on a direct compensation inspired primarily by the biological immune system response. The effectiveness of the approach is demonstrated through a full 6 degrees-of-freedom aircraft model interfaced with a Flight gear environment. The performance of the proposed control laws are investigated under a novel set of performance metrics, which quantify the level of input activity from the pilot and from the control surfaces in order to ensure the stability and performance of the aircraft under different actuator and structural failures. Optimization of the parameters of the artificial immunity system is performed using a genetic algorithm. The results show that the optimized fault tolerant adaptive control laws improve significantly the failure rejection using minimum pilot input and control surfaces activity under upset flight conditions.
Pure Time Delay Analysis for Decentralized Networked Control Systems
Authors: Taha Ahmad F. , Elmahdi Ahmed , Panchal Jitesh H. , Sun Dengfeng
Published: December 2014

The network disturbance effect can be considered as either a perturbation or as a pure time delay for the exchanged signals. The network-induced time delay is one of the main challenges when a network is inserted in the feedback loops of a control system. In this paper, our objective is to improve the behavior of a Networked Control System (NCS) by analyzing the time-delay given that the decentralized control design method is adopted. First, we review an observer-based control method for decentralized control systems. Second, we establish a map between the decentralized non-networked system, and the typical NCS state-space representation. The main idea the mapping is to put the Decentralized Networked Control System (DNCS) in a general form and then map the resulting system to the typical NCS form. Third, we derive the global dynamics of the DNCS. Fourth, an upper bound for the time-delay is derived that guarantees the stability of LTI DNCSs. Finally, we present a numerical example that illustrates the applicability of the derived bound.
Model Predictive Control of DFIG-Based Wind Turbine
Authors: Gatavi Ehsan , Shirdel Amir H.
Published: December 2014

This paper presents a centralized multivariable control strategy for the control of the DFIG wind turbine. Model of one-mass wind turbine with DFIG is represented by a third-order model. Model predictive control is applied in order to compensate inaccuracies and measurement noise. The optimization problem is recast as a Quadratic Program (QP) which is highly robust and efficient. In order to bring the problematic voltages as closely as possible to the desired values, multi-step optimization is introduced. The effectiveness of the proposed algorithm is demonstrated for a variable speed wind turbine.
Iterative Feedforward Tuning Approach and Experimental Verification for Nano-Precision Motion Systems
Authors: Boeren Frank , Oomen Tom , Bruijnen Dennis
Published: December 2014

Feedforward control can significantly improve the performance of industrial motion systems through compensation of the servo error induced by the reference signal. Recently, new feedforward tuning algorithms have been proposed that exploit measured data from previous tasks and a suitable feedforward parametrization to attain high servo performance. The aim of this paper is to formulate a design procedure for motion feedforward tuning. Experimental results on an industrial motion system illustrate the improvement in servo performance obtained by means of the proposed tuning procedure.
On the Stability of Tire Torsional Oscillations Under Locked-Wheel Braking
Authors: Wang Chunjian , Adcox John , Ayalew Beshah , Dailliez Benoit , Rhyne Timothy , Cron Steve
Published: December 2014

This paper deals with the stability of self-excited tire torsional oscillations during locked-wheel braking events. Using a combination of torsionally flexible tire-wheel model and a dynamic tire-ground friction model, it is highlighted that the primary cause of unstable oscillations is the ‘Stribeck’ effect in tire-ground friction. It is also shown analytically that when suspension torsional compliances are negligible, the bifurcation parameters for the local torsional instability include forward speed, normal load and tire radius. In the presence of significant suspension torsional compliance, it is shown that the stability is also affected by suspension torsional stiffness and damping. Furthermore, the tire torsional stiffness becomes an important bifurcation parameter only in the presence of significant suspension compliance. This analysis gives useful insights for the selection of tire sidewall stiffness ranges and their proper matching with targeted vehicle suspensions at the design stage.
A Performance Comparison of EMG Classification Methods for Hand and Finger Motion
Authors: Shin Sungtae , Langari Reza , Tafreshi Reza
Published: December 2014

For recognizing human motion intent, electromyogram (EMG) based pattern recognition approaches have been studied for many years. A number of methods for classifying EMG patterns have been introduced in the literature. On the purpose of selecting the best performing method for the practical application, this paper compares EMG pattern recognition methods in terms of motion type, feature extraction, dimension reduction, and classification algorithm. Also, for more usability of this research, hand and finger EMG motion data set which had been published online was used. Time-domain, empirical mode decomposition, discrete wavelet transform, and wavelet packet transform were adopted as the feature extraction. Three cases, such as no dimension reduction, principal component analysis (PCA), and linear discriminant analysis (LDA), were compared. Six classification algorithms were also compared: naïve Bayes, k-nearest neighbor, quadratic discriminant analysis, support vector machine, multi-layer perceptron, and extreme machine learning. The performance of each case was estimated by three perspectives: classification accuracy, train time, and test (prediction) time. From the experimental results, the time-domain feature set and LDA were required for the highest classification accuracy. Fast train time and test time are dependent on the classification methods.
Control in a Safe Set: Addressing Safety in Human-Robot Interactions
Authors: Liu Changliu , Tomizuka Masayoshi
Published: December 2014

Human-robot interactions (HRI) happen in a wide range of situations. Safety is one of the biggest concerns in HRI. This paper proposes a safe set method for designing the robot controller and offers theoretical guarantees of safety. The interactions are modeled in a multi-agent system framework. To deal with humans in the loop, we design a parameter adaptation algorithm (PAA) to learn the closed loop behavior of humans online. Then a safe set (a subset of the state space) is constructed and the optimal control law is mapped to the set of control which can make the safe set invariant. This algorithm is applied with different safety constraints to both mobile robots and robot arms. The simulation results confirm the effectiveness of the algorithm.
The Inverse Problem of Continuous-Time Linear Quadratic Gaussian Control With Application to Biological Systems Analysis
Authors: Priess M. Cody , Choi Jongeun , Radcliffe Clark
Published: December 2014

In this paper, we demonstrate two methods for solving the inverse problem of continuous-time LQG control. This problem can be defined as: given a known LTI system with feedback controller K and Kalman gain L, can we find the weighting matrices Q, R (for state and input, respectively) and estimated noise intensities W, V (for process and measurement noise, respectively) such that the LQG control synthesis problem using these weights generates K and L? We formulate a regularized version of this problem as a minimization problem subject to a set of Linear Matrix Inequalities (LMIs). If feasible, a unique exact solution to the inverse LQR problem exists. If the LMIs are infeasible, we show a gradient descent algorithm that will find Q, R, W, and V to minimize the error in the recovered gain matrices K and L. We demonstrate these techniques through several numerical examples and formulate a human postural control case study to which we intend to apply our proposed techniques.
Adaptive Boundary Control and Observer of Linear Hyperbolic Systems With Application to Managed Pressure Drilling
Authors: Hasan Agus
Published: December 2014

Managed Pressure Drilling (MPD) is an advanced pressure-control method that is used to precisely control the annular pressure throughout the wellbore in an oil well drilling. Because downhole measurements are unreliable due to slow sampling, transmission delay, and loss of communication for low or no-flow conditions, the challenge is to accurately estimate the flow and pressure along the annulus and the unknown in/out flux at the bottom of the well using only topside measurements. This paper describes the development of an adaptive control and observer for such problems that models the transport phenomenon as a 2×2 linear hyperbolic system. The adaptive design, which relies only on the measurements taken at the right boundary, is based on the backstepping method. The design is tested using data from a field scale flow-loop test conducted in Stavanger, Norway by the Statoil oil company. The results show that the observer converges to the actual value and that the update law accurately estimates the unknown parameter.
Modeling and Scheduling of Multiple Power Sources for a Ground Robot
Authors: Broderick John A. , Tilbury Dawn M. , Atkins Ella M.
Published: December 2014

Energy storage is a major limiting factor for small unmanned ground vehicle endurance. This paper presents a hybrid model of a robot power system and a method to optimize power production and limit power loss for extended UGV operation. The optimization is based on a hybrid automaton model of the power system and produces the optimal controls for the different power components. An abstraction of power use and averaging of dynamics within a state can model the system with sufficient accuracy for power system optimization. Simulation studies of a Packbot equipped with a fuel cell and a battery are presented. The optimized power system is shown to require less energy over the mission compared to a baseline controller.
Coordinated Control of a Dual-Stage Positioning System Using Constrained Model Predictive Control
Authors: Haghighat Sohrab , Di Cairano Stefano , Konobrytskyi Dmytro , Bortoff Scott
Published: December 2014

Dual-stage positioning systems have been widely used in factory automation, robotic manipulators, high-density data storage systems, and manufacturing systems. Trajectory generation and control of dual-stage positioning systems is of great importance and is made complicated by the presence of physical and operational constraints. In this work, we describe how to generate feasible reference trajectories for a dual-stage positioning system consisting of a fine stage and a coarse stage, and how to use them in a model predictive control algorithm for which recursive feasibility is guaranteed. The reference generation algorithm is guaranteed to generate trajectories that satisfy all the constraints for the fine and coarse stages. We also describe a constrained model predictive control algorithm used to control the coarse stage. The simulation results of applying the developed methodology to track a pre-determined pattern is presented.
Fault Diagnosis for PMSM Drive System in Electric Vehicle
Authors: Zhang Jiyu , Rizzoni Giorgio , Cordoba-Arenas Andrea
Published: December 2014

Electric and hybrid electric vehicles (EV/HEVs) have attracted considerable interest among automobile manufactures worldwide due to their advantages of better fuel economy. To guarantee safe, clean and reliable operation of electric drive systems, it is imperative to develop reliable and robust diagnostic schemes so that appropriate corrective actions can be taken in case a component or subsystem fail to operate normally. This paper proposes a diagnostic scheme for permanent magnet synchronous motor (PMSM) drives in EV/HEV applications. The proposed strategy uses two generalized observers to detect and isolate current, speed, and rotor position sensor faults in a PMSM drive. Since in real driving cases, the load torque is usually unknown due to unexpected road disturbance, the proposed diagnostic scheme uses an Unknown Input Observer (UIO) to estimate the load torque. The diagnostic algorithm is validated in Matlab/Simulink using the Ohio State University EcoCAR as testbed. The simulation results show that the proposed scheme is effective in detecting and isolating various sensor faults under road disturbance.
Model Predictive Control-Based Dynamic Control Allocation in a Hybrid Neuroprosthesis
Authors: Kirsch Nicholas A. , Alibeji Naji A. , Sharma Nitin
Published: December 2014

To date, a functional electrical stimulation (FES)-based walking technology is incapable of enabling a paraplegic user to walk more than a few hundred meters. This is primarily due to the rapid onset of muscle fatigue, which causes limited torque generation capability of the lower-limb muscles. A hybrid walking neuroprosthesis that combines FES with an electric motor can overcome this challenge, since an electric motor can be used to compensate for any reduction in force generation due to the muscle fatigue. However, the hybrid actuation structure creates an actuator redundancy control problem; i.e., a closed-loop controller must optimally distribute torque between FES and an electric motor. Further, the control inputs to FES and an electric motor must adapt as a skeletal muscle fatigues. We consider these issues as open research control problems. In this paper, we propose that a model predictive control (MPC)-based control design can be used to optimally distribute joint torque, and can adapt as the muscle fatigue sets in. Particularly, a customized quadratic programming solver (generated using CVXGEN) was used to simulate MPC-based control of the hybrid neuroprosthesis that elicits knee extension via FES and an electric actuator.
Towards Model-Based Control of Achiral Microswimmers
Authors: Cheang U Kei , Dejan Milutinović , Choi Jongeun , Kim Minjun
Published: December 2014

In this paper, we introduce the three bead achiral microswimmers controlled wirelessly using magnetic fields with the ability to swim in bulk fluid. The achirality of the microswimmer introduces unknown handedness of the microswimmer. Here, we propose to use a combination of rotating and static magnetic fields to eliminate the uncertainty in swimming direction. Our experimental results demonstrated excellent capability of direction control as well as agile movements. From the experimentally collected data, we estimated a control-oriented two-wheeled robot model. Finally, we design feedback control for microswimmers based on the estimated kinematic model. In particular, we show that the feedback control law moves the microswimmer from any initial conditions to a target set of microswimmer’s position and angle.