bluuebunny/crossref_metadata_2025 huggingface dataset:
Time course and magnitude of blood flow changes in the human quadriceps muscles during and following rhythmic exercise.
Authors: Walløe L , Wesche J
Published: December 2014

1. Pulsed bidirectional Doppler‐ultrasound equipment was used to measure changes in blood velocities in the femoral artery on a beat to beat basis for consecutive contraction and relaxation phases during voluntary rhythmic exercise of the quadriceps muscle group in man. 2. Rapid and large fluctuations of blood velocities were found, being high during relaxation and low during contraction phases. At the onset of contraction phase, negative velocities were present, indicating retrograde flow. During the rest of the contraction phase, forward flow occurred comparable to the resting flow level even at high loads. 3. Estimated maximal flow to the whole leg during relaxation phase, calculated from these blood velocity measurements and vessel diameter (measured with echo‐ultrasound equipment with high resolution) was in two of the subjects 3.32 l min‐1 (female) and 5.97 l min‐1 (male). When using computer tomography to estimate the volume of the quadriceps muscle group, the calculated maximum flow to this muscle group was 243 (female) and 257 (male) ml min‐1 100 ml muscle‐1. The time‐averaged flow during exercise to the whole leg was 1.51 l min‐1 (female) and 2.47 l min‐1 (male). The calculated time‐averaged flow to the quadriceps muscle group was 101 (female) and 98 (male) ml min‐1 100 ml muscle‐1. 4. The duration of post‐contraction hyperaemia following such rhythmic exercise of up to 6 min duration and up to 75% maximum voluntary contraction was never in excess of 150 s.
Quantitative comparisons of hydraulic permeability and endothelial intercellular cleft dimensions in single frog capillaries.
Authors: Clough G , Michel C C
Published: December 2014

1. We have investigated the ultrastructure of the intercellular clefts of the walls of single capillaries and venules of the frog mesentery in which the hydraulic permeability (Lp) and the reflection coefficient of the vessel walls to serum albumin (sigma BSA) had been measured using the micro‐occlusion technique of Michel (1980). Our aim was to investigate whether the dimensions of the clefts were sufficient to accommodate the pathways through the vessel walls necessary to account for the measured permeability. 2. Lp was measured in seventeen individually perfused vessels. The walls of fourteen of these were relatively impermeable to macromolecules with a sigma to albumin greater than 0.66 (mean value 0.83, S.E.M. +/‐ 0.04). The Lp of these fourteen vessels ranged from 1.8 x 10(‐7) to 12.5 x 10(‐7) cm s‐1 cmH2O‐1 and had a mean value of 5.9 (S.E.M. +/‐ 0.85) x 10(‐7) cm s‐1 cmH2O‐1. 3. Cleft dimensions estimated from electron micrographs of 642 transversely sectioned endothelial cell junctions from the same seventeen vessels gave a value for the mean cleft width (W) of 0.0220 micron (S.E.M. +/‐ 0.0064 micron). The mean depth of the clefts from luminal to abluminal surface of the endothelium (delta x) was 0.395 micron (S.E.M. +/‐ 0.091 micron) with a range of 0.104‐1.70 micron. The cleft length per unit area of cell wall (L), calculated using the formulation of Bundgaard & Frøkjaer‐Jensen (1982), was 2064 (S.E.M. +/‐ 112) cm cm‐2. Measurements were also made of cleft dimensions from longitudinally sectioned junctions from five of the seventeen vessels. 4. The fraction of the surface area of capillary wall occupied by the clefts (Ap = LW) had a mean value of 0.0048 (+/‐ 0.00014) for all seventeen vessels with a range of 0.0030‐0.0074 when estimated from transverse sections. There was no correlation between the variation of Lp between different vessels and the variations of Ap. 5. Data from the fourteen vessels when sigma BSA was greater than 0.66 revealed a correlation between values of Lp and the reciprocal of delta x (r = 0.6675, P less than 0.01). No correlation was found between Lp and the mean thickness of the endothelial cells in the vicinity of the clefts. This is strong evidence for the intercellular cleft being the principal pathway for fluid movements. Variation in cleft depth appears to be a factor determining variation in permeability between different capillaries.(ABSTRACT TRUNCATED AT 400 WORDS)
Arterial pulsation and lymph formation in an isolated sheep hindlimb preparation.
Authors: McGeown J G , McHale N G , Thornbury K D
Published: December 2014

1. Lymph flow was measured by cannulating metatarsal lymphatics in the sheep hindlimb. The region was perfused with warmed, heparinized, oxygenated blood via the tibio‐cranial artery cannulated just distal to the hock. Constant and pulsatile perfusion pressures were compared. A cuff was inflated over the metatarsals to maintain venous pressure at 20 mmHg. 2. The lymph flow rates during constant perfusion at 80 mmHg were comparable to control flows in intact metatarsal preparations and oedema (monitored by measuring tissue volume) did not accumulate. Flow records were similar to those obtained from anaesthetized animals, lymph being expelled by regular lymphatic contractions. 3. Pulsatile perfusion using 120/60 mmHg (systolic cuff cycle 0.25 s inflation, 0.5 s deflation) did not increase the rate of lymph flow. Increasing the pulse pressure to 100 mmHg (150/50 mmHg) produced a 20% increase in flow but this was not statistically significant. The cuff deflation time was also increased (1 s inflation, 1 s deflation) using 120/60 mmHg but this had little effect. 4. It may be concluded that arterial pulsation is not important for lymph formation in this preparation.
Effect of prostaglandin E2 on thermoresponsive neurones in the preoptic and ventromedial hypothalamic regions of rats.
Authors: Morimoto A , Murakami N , Watanabe T
Published: December 2014

1. We investigated the effect of microinjection of prostaglandin E2 (PGE2) into the preoptic (POA) or the ventromedial hypothalamic (VMH) region on rectal temperature in rats. Fever was induced by microinjection of PGE2 into the POA or the VMH regions. The febrile responses induced by PGE2 injected into the VMH region were significantly greater than those induced by injection into the POA region. 2. The effect of temperature on neuronal activity in the POA and the VMH regions was investigated by using slice preparations from rats. It was revealed that there exist many thermoresponsive neurones in the VMH region as well as in the POA region, and that the proportion of thermoresponsive neurones out of the total neurones examined in the VMH region was almost identical to that in the POA region. In addition, the warm‐responsive neurones in the VMH region exhibited larger thermal coefficients than those in the POA region. 3. When PGE2 was applied in a recording chamber where the tissue slice was perfused, most of the neurones in the VMH region which responded to PGE2 showed a decrease in their firing rate, while those in the POA region showed an increase in their firing rate, regardless of their thermoresponsiveness. In the POA region, PGE2 began to affect the activities of the warm‐responsive neurones in the range of 5 x 10(‐7) to 7 x 10(‐6) M, whereas maximum responses were obtained between the concentrations of 5 x 10(‐6) and 5 x 10(‐5) M. In the VMH region, PGE2 began to change the activities of the warm‐responsive neurones in the range of 5 x 10(‐8) to 5 x 10(‐7) M, and the maximum effect of PGE2 on the VMH warm‐responsive neurones occurred between the concentrations of 8 x 10(‐7) and 4 x 10(‐5) M. 4. The present results show that neurones exhibit different responsiveness to PGE2 and different sensitivity to PGE2 between the POA and the VMH regions. Nevertheless, microinjection of PGE2 into either the POA or the VMH region produces fever. Therefore, it is suggested that fever is produced by complex neuronal networks in the central nervous system.
Effects of 2,3‐butanedione monoxime on the contractile activation properties of fast‐ and slow‐twitch rat muscle fibres.
Authors: Fryer M W , Neering I R , Stephenson D G
Published: December 2014

1. The effects of 2,3‐butanedione monoxime (BDM, 0.2‐10 mmol/l) have been examined at different temperatures on calcium transients (measured with aequorin) and isometric force in intact bundles of fibres from soleus (slow‐twitch) and extensor digitorum longus (EDL; fast‐twitch) muscles of the rat and on Ca2+‐activated isometric force of mechanically skinned soleus and EDL fibres. Ca2+ release and uptake by the sarcoplasmic reticulum has also been investigated directly on skinned EDL fibres at 1 mmol/l BDM at 23 degrees C. 2. BDM bound calcium with low affinity (KCaBDMapp = 55.9 +/‐ 4.3 M‐1 at 22 degrees C, pH 7.10, ionic strength approximately 155 mmol/l) and did not affect the kinetics and quantum yield of the Ca2+‐induced aequorin luminescence. 3. BDM reversibly reduced both force‐ and Ca2+‐dependent aequorin light during the twitch and tetanus of all intact‐muscle preparations in a dose‐related manner. Twitch responses of soleus fibres were more sensitive to BDM than were EDL fibres. Higher concentrations of BDM were needed to abolish the tetanic force response than the twitch response in both muscle types. 4. The initial rate of rise and the decay rate constants of twitches in both soleus and EDL muscles were increased in the presence of BDM. Accordingly, a higher frequency of stimulation was required to produce fusion of the tetanus. This phenomenon could be explained by the reduced magnitude of the Ca2+ transient. 5. BDM reduced maximal Ca2+‐activated force development in mechanically skinned soleus and EDL muscle fibres in a dose‐dependent fashion. This depression of force was less sensitive to BDM than were the light transients in intact fibres. Furthermore, BDM affected EDL skinned fibres to a greater extent than soleus skinned fibres, in contrast with its effects on intact fibres. 6. At concentrations of BDM greater than 2.5 mmol/l, BDM significantly decreased the sensitivity of the contractile apparatus to calcium. The relative force‐pCa (= ‐log [Ca2+]) curves for both soleus and EDL skinned fibres were shifted to the right (i.e. to higher calcium concentrations) in a dose‐related manner. 7. BDM (10 mmol/l) slowed maximal Ca2+‐activated force development of skinned preparations of both fibre types at all temperatures investigated (4‐24 degrees C). 8. BDM reduced stiffness in skinned preparations maximally activated by calcium in proportion to the reduction in the isometric force response. BDM also inhibited rigor force of all fibres but only if it was present before the onset of rigor.(ABSTRACT TRUNCATED AT 400 WORDS)
Dopamine‐induced depolarizing responses associated with negative slope conductance in LB‐cluster neurones of Aplysia.
Authors: Matsumoto M , Sasaki K , Sato M , Shozushima M , Takashima K
Published: December 2014

1. Current‐ and voltage‐clamp methods were used to evaluate the intracellular and ionic mechanisms involved in dopamine‐induced slow depolarizations recorded from neurones of the LB cluster in the abdominal ganglion of Aplysia kurodai. 2. In voltage‐clamped cells, dopamine induced a slow inward current that, over the range studied (‐40 to ‐110 mV), decreased in amplitude with hyperpolarization of the cell, but failed to invert when the cell was hyperpolarized beyond the reversal potential for K+,(E)K. 3. Bathing the ganglion in 3‐isobutyl‐1‐methylxanthine (IBMX) caused a significant increase in the dopamine response. 4. Most of the responses to dopamine were markedly augmented in Ca2+‐free media, but were depressed in Na+‐free media. 5. An intracellular injection of cyclic adenosine 3',5'‐monophosphate (cyclic AMP) into the same cell type produced an inward current which, like the response to dopamine, diminished in amplitude with hyperpolarization of the cell. 6. Like the dopamine response, the cyclic AMP response increased in the presence of IBMX, was enhanced in Ca2+‐free media, was depressed in Na+‐free media, and was unaffected by changes in external potassium. 7. In a few cells, although the cyclic AMP‐induced responses disappeared in Na+‐free media, the dopamine‐induced slow inward current responses did not. However, these Na+‐free resistant responses disappeared completely in Na+‐ and Ca2+‐free media. 8. It was concluded that most of the dopamine‐induced inward current responses were produced by an increase in permeability, mainly to Na+, triggered by a receptor‐controlled increase in intracellular cyclic AMP.
Carbohydrate homeostasis and post‐exercise ketosis in trained and untrained rats.
Authors: Adams J H , Koeslag J H
Published: December 2014

1. Experiments were carried out to establish what relationship there is between the concentration of ketone bodies in the blood and the concentrations of glycogen in muscle and liver of thirty‐six trained and thirty‐six untrained rats exercised at the same absolute load. There were, in addition, non‐exercised control animals (of which thirty‐six were trained and thirty‐six untrained) which were studied on the same day. 2. Training occurred on a level treadmill at 0.2 m/s for 1 h/day, 5 days a week, for 6 weeks. The untrained animals ran on the treadmill every 3rd day for 5 min to maintain familiarity with treadmill running without training them. 3. At the end of the 6th week, the experimental animals ran for 1 h at 0.2 m/s on a level treadmill. Blood 3‐hydroxybutyrate and tissue glycogen concentrations were measured at the beginning and immediately after exercise, and then every 30 min for 2 h. 4. Physically trained rats had higher pre‐ and immediate post‐exercise liver glycogen concentrations than untrained rats: 413 +/‐ 15 and 300 +/‐ 8 mumol/g before exercise in trained and untrained rats respectively, and 225 +/‐ 8 and 166 +/‐ 3 mumol/g immediately after (P less than 0.05). 5. Muscle glycogen, which was also higher in trained than in untrained rats, was resynthesized at approximately the same rate in the two groups of animals (9 and 11 mumol/(g h), but the trained animals were able to achieve this without further depletion of liver glycogen beyond that which had occurred during exercise. In untrained animals liver glycogen concentrations continued to drop for 60 min beyond the end of exercise.(ABSTRACT TRUNCATED AT 250 WORDS)
Cardiovascular responses to brief static contractions in man with topical nervous blockade.
Authors: Lassen A , Mitchell J H , Reeves D R , Rogers H B , Secher N H
Published: December 2014

1. We tested the hypothesis that afferent nerves from working muscles are important in determining the heart rate and blood pressure responses to brief maximal static exercise. 2. In twenty human subjects, the heart rate and arterial blood pressure responses to a brief maximal voluntary handgrip were studied before and after axillary nerve anaesthesia or to maximal one‐leg knee extension before and after epidural anaesthesia at L3‐L4. Maximal knee extension could not be accomplished without performing a ‘Valsalva‐like’ manoeuvre, but during handgrip it was possible to avoid the use of muscles other than those directly involved in the contraction. Heart rate and blood pressure were also monitored during a Valsalva manoeuvre of similar duration to the maximal voluntary contractions (4 s). 3. During handgrip with normal breathing, axillary nerve anaesthesia reduced the heart rate response but had no effect on the blood pressure response. 4. During a Valsalva manoeuvre, blood pressure increased but heart rate remained stable as long as expiratory pressure was maintained. During one‐leg knee extension, epidural anaesthesia reduced the blood pressure response; however, the reduction in blood pressure was probably due to a reduction in the simultaneously performed ‘Valsalva‐like’ manoeuvre. 5. The results of this study suggest that afferent input from the working muscles is of importance for the heart rate responses to brief static muscle contractions. That such influence may be important for the blood pressure response remains unproven.
Influences on the cardiovascular response to graded levels of systemic hypoxia of the accompanying hypocapnia in the rat.
Authors: Marshall J M , Metcalfe J D
Published: December 2014

1. In spontaneously breathing, anaesthetized rats, a study was made of the effects upon the graded cardiovascular responses to systemic hypoxia (inspiratory fractional O2 concentration, Fi, O2: 0.15, 0.12, 0.08, 0.06) of maintaining arterial CO2 pressure (Pa,CO2) at the air‐breathing level by adding CO2 to the inspirate (eucapnic hypoxia), rather than allowing Pa,CO2 to fall (hypocapnia hypoxia). 2. At each Fi,O2, maintenance of eucapnia significantly reduced the increase in respiratory frequency, but significantly accentuated the increase in tidal and minute volume: as a result the fall in Pa,O2 at each Fi,O2 was significantly reduced. 3. Concomitantly, maintenance of eucapnia reduced the increase in heart rate (HR) and fall in arterial pressure (ABP), the effects being significant at Fi,O2 0.08 and/or 0.06. There was also a tendency for the increases in renal and femoral vascular conductances (RVC, FVC) to be reduced; at Fi,O2 0.06 mean increases from control were 2 +/‐ 10 vs. 16 +/‐ 7% (eucapnia vs. hypocapnia) for RVC, and 62 +/‐ 11 vs. 106 +/‐ 27% for FVC. 4. As maintenance of eucapnia reduced the fall in Pa,O2 at each Fi,O2, the above results were also considered as a function of Pa,O2. Then, maintenance of eucapnia had similar significant effects on the changes in respiration and HR as described above and reduced the mean increase in RVC (16 +/‐ 11 vs. 23 +/‐ 10%, at Pa,O2 31 mmHg, which was attained at Fi,O2 0.06 with eucapnia and 0.08 with hypocapnia). However, maintenance of eucapnia had no effect on the falls in ABP and accentuated the mean increase in FVC (74.9 +/‐ 13 vs. 57 +/‐ 10% at Pa,O2 31 mmHg). 5. These findings indicate that, in the rat, the hypocapnia that accompanies the hyperventilatory response to systemic hypoxia facilitates the tachycardia and may accentuate the renal vasodilation, but attenuate the hypoxia‐induced vasodilatation in skeletal muscle. Possible mechanisms are discussed.
On the effect of muscle activity on the end‐plate membrane in denervated mouse muscle.
Authors: Brenner H R , Rudin W
Published: December 2014

1. Mouse soleus muscles were denervated and some of them were chronically stimulated. Sixteen to twenty‐one days later, the number of junctional acetylcholine receptors (AChR) and their metabolic stability were examined by measuring binding of 125I‐alpha‐bungarotoxin, their gating properties by analysis of acetylcholine‐induced current fluctuations and the ultrastructure of the end‐plate membrane by electron microscopy. 2. In agreement with other studies on inactive muscles, no effect of denervation on junctional AChR number could be resolved. However, some of the fast‐gating ‘adult’ AChR channels had been replaced by slowly gating fetal AChRs, their half‐life was lowered to 38 h and the folding of the end‐plate membrane was reduced. 3. These changes were prevented in denervated but stimulated active muscles: the junctional AChR population remained homogeneously ‘adult’, the half‐life of junctional AChRs was 13 days and folding of the end‐plate membrane remained comparable to that in control muscles. 4. The significance of these results is discussed with respect to the role of muscle activity in end‐plate development.
Endothelium‐derived relaxing factor inhibits the formation of inositol trisphosphate by rabbit aorta.
Authors: Lang D , Lewis M J
Published: December 2014

1. The effects of endothelium‐derived relaxing factor (EDRF), sodium nitroprusside, 8‐bromo‐cyclic GMP and atrial natriuretic factor (ANF) on inositol trisphosphate (IP3) levels were studied in isolated rabbit aortic preparations stimulated with noradrenaline. 2. In endothelium‐containing preparations, acetylcholine, which stimulated EDRF release, inhibited noradrenaline‐stimulated IP3 formation. The EDRF inhibitor haemoglobin reversed this effect. 3. In endothelium‐denuded preparations, sodium nitroprusside, 8‐bromo‐cyclic GMP and ANF each similarly inhibited the rise in IP3 levels stimulated by noradrenaline. 4. These findings show that in rabbit aorta, agents which increase cyclic GMP inhibit the noradrenaline‐induced rise in IP3 levels and may provide an explanation for the previously reported observations that cyclic GMP inhibits the noradrenaline‐stimulated increase in calcium influx and release of intracellular calcium in vascular smooth muscle.
Latencies of membrane currents evoked in Xenopus oocytes by receptor activation, inositol trisphosphate and calcium.
Authors: Miledi R , Parker I
Published: December 2014

1. Application of serum to Xenopus oocytes elicits an oscillatory chloride membrane current, which begins after a latency of several seconds or minutes, and is mediated through a phosphoinositide‐calcium signalling pathway. We studied the characteristics and origin of this latency in voltage‐clamped oocytes. 2. Bath application of low doses of serum evoked responses beginning after latencies of 1 min or more. The latency decreased with increasing dose and reached a minimal value of several seconds that did not decrease with further increases in serum concentration. Experiments to study this minimal latency were done by applying brief ‘puffs’ of serum and other agonists at high concentrations from a local extracellular pipette. 3. The mean latency of the response evoked by local serum application was about 7 s (at 22‐24 degrees C), but individual responses showed a wide variation, from 2 s to over 20 s. Diffusion of serum from the pipette tip to the membrane did not contribute appreciably to this delay, since short (less than 100 ms) delays were obtained when KCl was applied in the same way. 4. Currents evoked by acetylcholine and serotonin, in oocytes induced to acquire muscarinic and serotonergic receptors following injection of brain messenger RNA, began following latencies similar to that of the serum response. 5. The response latency was shorter when serum was applied to the vegetal rather than the animal hemisphere of the oocyte, even though smaller currents were obtained. 6. The latency showed a slight dependence upon membrane potential, becoming shorter with depolarization. 7. Cooling to temperatures below about 22 degrees C produced a striking lengthening of the delay, corresponding to a Q10 of about 5. In contrast, above 22 degrees C the temperature dependence was slight, with a Q10 of about 1.25. 8. Intracellular injections of calcium and inositol 1,4,5‐trisphosphate (IP3) evoked chloride currents with short (a few tens of milliseconds) latency. Short (100 ms) latency responses were also evoked when intracellularly loaded caged IP3 was photolysed by strong illumination, but weak illumination gave responses with latencies of over 1 min. 9. Measurements of intracellular free calcium, made with Fura‐2 and Indo‐1, showed an increase following serum application beginning coincident with the onset of the membrane current response.(ABSTRACT TRUNCATED AT 400 WORDS)
Intramembrane charge movement in guinea‐pig and rat ventricular myocytes.
Authors: Hadley R W , Lederer W J
Published: December 2014

1. Non‐linear capacitative current (charge movement) was studied in isolated guinea‐pig and rat ventricular myocytes. Linear capacitance was subtracted using standard procedures. Most of the experiments were done with guinea‐pig myocytes, while rat myocytes were used for comparison. 2. When a myocyte was held at ‐100 mV, depolarizing clamp steps produced a rapid outward current transient, which was followed by an inward current transient upon repolarization. This current was identified as the movement of charged particles in the cell membrane, rather than ionic movement across the membrane, for the following reasons: (1) the current saturated at membrane potentials positive to +20 mV; (2) the current was capacitative in nature, having no reversal potential; (3) in general, the charge moved during depolarization (Qon) approximated the charge moved during repolarization (Qoff). 3. Qoff was significantly less than Qon for a depolarization from ‐100 mV to 0 mV. However, the Qoff/Qon ratio approached unity if the cell was instead repolarized to ‐140 mV. This was interpreted as being due to the immobilization of a fraction of the charge during the depolarization, which recovered rapidly enough to be measured at ‐140 mV, but recovered too slowly at ‐100 mV. 4. Charge movement in these cells had a sigmoidal dependence on the membrane potential, which could be empirically described by the two‐state Boltzmann equation Q = Qmax/(1 + exp[‐(V‐V*)/kappa]), where Q is the charge movement at potential V, Qmax is the maximum charge, V* is the membrane potential at Q = Qmax/2, and kappa is a slope factor. Qmax was 11.7 nC/microF, V* was ‐18 mV and kappa was 16 mV in guinea‐pig myocytes held at ‐100 mV, while the values in rat myocytes were 10.9 nC/microF, ‐32 mV and 13 mV. 5. The charge movement could be partially immobilized by a prior depolarization. This effect developed over a broad voltage range, from ‐120 to +20 mV. The fraction of charge that could be immobilized by a 10 s pre‐pulse to +20 mV was 59%. 6. The time course of decay of both Qon and Qoff could basically be described as a single‐exponential process. The time constant was largest at ‐40 mV and decreased at both more positive and negative test potentials. A second, slower Qoff time constant, possibly representing remobilization of immobilized charge, could be seen under some conditions. 7. The temperature dependence of charge movement was studied between 11 and 35 degrees C.(ABSTRACT TRUNCATED AT 400 WORDS)
Roles of Organic Emissions in the Formation of Near Field Aircraft-Emitted Volatile Particulate Matter: A Kinetic Microphysical Modeling Study
Authors: Wong Hsi-Wu , Jun Mina , Peck Jay , Waitz Ian A. , Miake-Lye Richard C.
Published: December 2014

A kinetic microphysical modeling approach that describes the formation of volatile aerosols in the presence of organic emissions in near field aircraft emitted plumes at ground level is presented. Our model suggests that self nucleation of organic species, binary nucleation of water-soluble organic vapors with water, and multicomponent nucleation of water-soluble organic vapors with sulfuric acid and water all have very slow nucleation rates. The formation of new homogeneous particles in near field aircraft plumes is thus considered to be driven by binary nucleation of sulfuric acid and water. Volatile organic vapors emitted from aircraft engines primarily contribute to the nucleation process by condensing on existing homogeneous aerosols and only affect the size and the composition (not the number) of the homogeneous aerosols. Our model also shows that under low ambient relative humidity levels or high ambient temperatures, nucleation mode particles are more organic-rich than soot coatings. Organic mass fraction of nucleation mode particles is more sensitive to organic emissions levels compared to that of soot coatings. Ambient temperature and relative humidity were also predicted to affect the nucleation of sulfuric acid–water cores, where higher ambient relative humidity level and lower ambient temperature strongly favor binary sulfuric acid–water nucleation. The effect of ambient conditions on organic fractions was predicted to be relatively insignificant.
Behavior Analysis of Controllable Electrorheology Fluid Plain Journal Bearings
Authors: Lee Yong-Bok
Published: December 2014

Electrorheological (ER) lubricant is applied to a rigid rotor system supported by a hydrodynamic bearing that is subjected to a sudden imbalance and a dynamic periodic rotating load. The pressure of the ER film, which exhibits a Bingham flow, varies with the electrical field strength and depends on the yield shear stress and the thickness of the ER fluid film. The ER lubricant was found to offer a good load capacity relative to a Newtonian lubricant and its performance could be controlled to handle sudden dynamic loads. Increasing the magnitude of the electric field strength provides a greater load capacity within certain physical limitations and also reduces the magnitude of an unbalanced force due to unbalanced mass and vibration caused by vibration in the dynamically rotating load. These results could be applied to the control of a suddenly imbalanced system, such as one with rotor blades, or for reducing vibration in cyclic loading rotor systems, such as in internal combustion engines.
Manufacturability Feedback and Model Correction for Additive Manufacturing
Authors: Nelaturi Saigopal , Kim Walter , Kurtoglu Tolga
Published: December 2014

Additive manufacturing, or 3D printing, is the process of building three-dimensional solid shapes by accumulating material laid out in sectional layers. Additive manufacturing has been recognized for enabling production of complex custom parts that are difficult to manufacture otherwise. However, the dependence on build orientation and physical limitations of printing processes invariably lead to geometric deviations between manufactured and designed shapes that are usually evaluated after manufacture. In this paper, we formalize the measurement of such deviations in terms of a printability map that simulates the printing process and partitions each printed layer into disjoint regions with distinct local measures of size. We show that manufacturing capabilities, such as printing resolution, and material specific design recommendations, such as minimal feature sizes, may be coupled in the printability map to evaluate expected deviations before manufacture. Furthermore, we demonstrate how partitions with size measures below required resolutions may be modified using properties of the medial axis transform and use the corrected printability map to construct a representation of the manufactured model. We conclude by discussing several applications of the printability map for additive manufacturing.
Evaluating the Influence of Exhaust Back Pressure on Performance and Exhaust Emissions Characteristics of a Multicylinder, Turbocharged, and Aftercooled Diesel Engine
Authors: Mittal Mayank , Donahue Ron , Winnie Peter
Published: December 2014

An experimental study was conducted to quantify the effects of exhaust back pressure (EBP) on performance and exhaust emissions characteristics of a diesel engine for generator application. The electromechanical system was composed of a commercially available six-cylinder, turbocharged, and aftercooled diesel engine, coupled with a generator rated at 500 kilowatt electrical (kWe) at full load. Experiments were conducted at different operating conditions for high and low EBPs. Exhaust emissions of nitrogen oxides (NOx), soot, particulate matter (PM), carbon monoxide (CO), and total hydrocarbons (HC) were measured. In addition, thermocouples and pressure sensors were provided at various locations to evaluate the engine performance. Results showed that the brake specific fuel consumption (BSFC) was increased at light loads for high EBP, but no significant difference was observed in BSFC at high loads. It was found that NOx emission was reduced at all operating loads, but soot and PM were increased with the increase in EBP. HC emission was relatively insensitive with increment of EBP.
Unsteady Structure and Development of a Row of Impingement Jets, Including Kelvin–Helmholtz Vortex Development
Authors: Yang Li , Ligrani Phillip , Ren Jing , Jiang Hongde
Published: December 2014

Considered is a cylinder channel with a single row of ten aligned impinging jets, with exit flow in the axial direction at one end of the channel. For the present predictions, an unsteady Reynolds-Averaged Navier–Stokes (RANS) solver is employed for predictions of flow characteristics within and nearby the ten impingement jets, where the jet Reynolds number is 15,000. Spectrum analysis of different flow quantities is also utilized to provide data on associated frequency content. Visualizations of three-dimensional, unsteady flow structural characteristics are also included, including instantaneous distributions of Y-component vorticity, three-dimensional streamlines, shear layer parameter ψ, and local static pressure. Kelvin–Helmholtz vortex development is then related to local, instantaneous variations of these quantities. Of particular importance are the cumulative influences of cross flows, which result in locally increased shear stress magnitudes, enhanced Kelvin–Helmholtz vortex generation instabilities, and increased magnitudes and frequencies of local flow unsteadiness, as subsequent jets are encountered with streamwise development.
Nonlinear Breathing Behavior Study of Transverse Crack on a Jeffcott Rotor Under Torsional Excitation
Authors: Zhao J. , DeSmidt H. A. , Yao W.
Published: December 2014

In this paper, Jeffcott rotor model is employed to explore the vibration response of breathing cracked system with unbalance mass. Based on the energy method and Lagrange principle, 6 degree-of-freedom equation of motion is derived in fixed coordinate system. The crack model is established using strain energy release theory of facture mechanics. The stiffness matrix induced by the crack is changing with the variation of crack open area. Zero stress intensity factor (SIF) method is used to determine the crack closure line by computing the SIF for opening mode. By integrating compliant coefficients over newly determined crack open area, the stiffness matrix is updated and vibration response is solved for every time step by Gear’s method. In addition, the breathing behavior of the crack is studied for multiple eccentricity phases and rotation speeds in order to provide effective guidance for damage detection. The paper explores the effect of external torsional loading on the crack breathing behavior. Finally, the coupling of lateral and torsional vibration is investigated to be used as an indicator of damage detection and health monitoring.
Evaluation of a Low-Cost Microcontroller for Real-Time Control Education and Prototyping
Authors: Krauss Ryan W.
Published: December 2014

Arduino microcontrollers are popular, low-cost, easy-to-program, and have an active user community. This paper seeks to quantitatively assess whether or not Arduinos are a good fit for real-time feedback control experiments and controls education. Bode plots and serial echo tests are used to assess the use of Arduinos in two scenarios: a prototyping mode that involves bidirectional real-time serial communication with a PC and a hybrid mode that streams data in real-time over serial. The closed-loop performance with the Arduino is comparable to that of another more complicated and more expensive microcontroller for the plant considered. Some practical tips on using an Arduino for real-time feedback control are also given.
Dynamic Formation Control of Multi-Agent Systems Using Rigid Graphs
Authors: Cai Xiaoyu , de Queiroz Marcio
Published: December 2014

In this paper, we consider the problem of formation control of multi-agent systems where the desired formation is dynamic. This is motivated by applications, such as obstacle avoidance, where the formation size and/or geometric shape needs to vary in time. Using a single-integrator model and rigid graph theory, we propose a new control law that exponentially stabilizes the origin of the nonlinear, inter-agent distance error dynamics and ensures tracking of the desired formation. The extension to the formation maneuvering problem is also discussed. Simulation results for a five-agent formation demonstrate the control in action.
Numerical Analysis of the Tapping Atomic Force Microscopy on a Viscoelastic Sample
Authors: Carmichael Ben , Frey Gary , Mahmoodi S. Nima
Published: December 2014

Mechanical characterization of thin samples is now routine due to the prominence of the Atomic Force Microscope. Advances in amplitude modulation techniques have allowed for accurate measurement of a sample’s elastic properties by interpreting the changes in the vibration of a cantilevered beam in intermittent contact. However, the nonlinearities associated with contact complicate attempts to find an accurate time-history for the beam. Furthermore, the inclusion of viscous effects, common to soft samples, puts an explicit solution even farther from reach.

A numerical method is proposed that analyzes the time-history and frequency response of a microcantilever beam with a viscoelastic end-condition. The mathematics can be simplified by incorporating the viscoelastic end-condition into the equation of motion directly by modeling it as a distributed load. A forcing function can then be derived from the Standard Linear Solid model of viscoelasticity and implemented in the non-conservative work term of Hamilton’s principle. The Galerkin method can separate the resulting nonlinear equation of motion into time and space components. Performing a numerical analysis of the time factor equation provide the beam’s response over time. The results demonstrate the distinctive effects of viscoelasticity and periodic contact on the beam’s motion and provide the framework for the determination of viscous properties using dynamic techniques.
Immunity-Based Abnormal Condition Accommodation of Aircraft Sub-System Failures
Authors: Togayev Adil , Perhinschi Mario G. , Al Azzawi Dia , Moncayo Hever , Moguel Israel , Perez Andres E.
Published: December 2014

This paper describes the design, development, and flight-simulation testing of an artificial immune-system-based approach for accommodation of different aircraft sub-system failures/damages. The accommodation of abnormal flight conditions is regarded as part of a complex integrated artificial immune system scheme, which consists of four major components: detection, identification, evaluation, and accommodation. The accommodation part consists of providing compensatory commands under upset conditions for specific maneuvers.

The approach is based on building an artificial memory, which represents the self (nominal conditions) and the non-self (abnormal conditions) within the artificial immune system paradigm. Self and non-self are structured as a set of memory cells consisting of measurement strings, over pre-defined time windows. Each string is a set of features values at each sample time of the flight including pilot inputs, system states, and other variables. The accommodation algorithm is based on the cell in the memory that is the most similar to the in-coming measurement. Once the best match is found, control commands corresponding to this match will be extracted from the memory and used for control purposes.

The proposed methodology is illustrated through simulation of simple maneuvers at nominal flight conditions and under locked actuator.

The results demonstrate the possibility of extracting pilot compensatory commands from the self/non-self structure and capability of the artificial-immune-system-based scheme to accommodate an actuator malfunction, maintain control, and complete the task.
Using Dynamic Musculoskeletal Simulation to Evaluate Altered Muscle Properties in Cerebral Palsy
Authors: Steele Kat M. , Lee Sabrina
Published: December 2014

Cerebral palsy is caused by an injury to the brain, but also causes many secondary changes in the musculoskeletal system. Altered muscle properties such as contracture, an increased passive resistance to stretch, are common but vary widely between individuals and between muscles. Quantifying these changes is important to understand pathologic movement and create patient-specific treatment plans. Musculoskeletal modeling and simulation have increasingly been used to evaluate pathologic movement in CP; however, these models are based upon muscle properties of unimpaired individuals. In this study, we used a dynamic musculoskeletal simulation of a simple motion, passively moving the ankle, to determine (1) if a model based upon unimpaired muscle properties can accurately represent individuals with cerebral palsy, and (2) if an optimization can be used to adjust passive muscle properties and characterize magnitude of contracture in individual muscles. We created musculoskeletal simulations of ankle motion for nine children with cerebral palsy. Results indicate that the unimpaired musculoskeletal model cannot accurately characterize passive ankle motion for most subjects, but adjusting tendon slack lengths can reduce error and help identify the magnitude of contracture for different muscles.
Model-Based Design and Hardware-in-the-Loop Simulation of Engine Lean Operation
Authors: Agashe Pushkar , Li Yang , Chen Bo
Published: December 2014

This paper presents model-based design and hardware-in-the-loop (HIL) simulation of engine lean operation. The functionalities of the homogeneous combustion subsystem in engine Electronic Control Unit (ECU) in dSPACE Automotive Simulation Models (ASM) are first analyzed. To control the gasoline engine in lean operation without the drop of output torque, the combustion subsystem in engine ECU is modified by introducing two control loops, torque modifier and fuel multiplier. The performance of these two controllers is evaluated by HIL simulation using a dSPACE HIL simulator. The HIL simulation models, including vehicle plant model and softECUs in HIL simulator and engine lean control model in hardware engine ECU are modeled using model-based design. With HIL simulation, the designed engine control strategies can be immediately tested to evaluate the overall vehicle performance. The HIL simulation results show that the designed lean combustion control strategy can reduce fuel consumption and is able to meet the torque requirement at lean engine operating conditions.
An Integrated Physical-Learning Model of Physical Human-Robot Interactions: A Bikebot Riding Example
Authors: Chen Kuo , Zhang Yizhai , Yi Jingang
Published: December 2014

One of the main challenges for modeling human-robot interactions (pHRI) is the high dimensionality and complexity of human motion. We present an integrated physical-learning modeling framework for pHRI with applications on the bikebot riding example. The modeling framework contains a machine learning-based model of high-dimensional limb motion coupled with a physical principle-based dynamic model for the human trunk and the interacted robot. A new axial linear embedding (ALE) algorithm is introduced to obtain the lower-dimensional latent dynamics for redundant human limb motion. The integrated physical-learning model is used to estimate the human motion through an extended Kalman filter design. No sensors are required and attached on human subject’s limb segments. Extensive bikebot riding experiments are conducted to validate the integrated human motion model. Comparison results with other machine learning-based models are also presented to demonstrate the superior performance of the proposed modeling framework.
Impedance and Admittance Controller for a Multi-Axis Powered Ankle-Foot Prosthesis
Authors: Ficanha Evandro M. , Rastgaar Mohammad
Published: December 2014

This paper introduces a finite state machine to select between impedance and admittance control for a powered ankle-foot prosthesis controllable in both Dorsiflexion-Plantarflexion (DP) and Inversion-Eversion (IE). Strain gauges are installed on the prosthesis’ foot to measure the strain caused by ground reaction forces, which are correlated to the external torques in DP and IE. The external torques are used for the admittance and impedance controllers. Additionally, the finite state machine uses the strain gauges feedback to detect the heel-strike and switch to admittance control. The admittance control accepts torque feedback to generate motion, this way larger feedback torques effectively reduces the stiffness of the ankle. During push off, the finite state machine switches to impedance control, accepting motion feedback to generate the appropriated torques. The quasi-static stiffness of the prosthesis with impedance control was tested, showing a near linear relationship between the torque feedback gain and the stiffness of the ankle. The finite state machine and controllers were also evaluated using a custom-made circular treadmill and the results were compared to the results of position and passive controllers; showing that the impedance/admittance controller was capable of tracking the desired input trajectory while decreasing the required torque at the ankle joint.
Is Deterministic Real Time Control Always Necessary? A Time Scales Perspective
Authors: Poulsen Dylan , Gravagne Ian , Davis John M.
Published: December 2014

Practitioners of feedback control design often must spend a great deal of time and effort dealing with the complexities of deterministic, or “real time” computing. In this paper, we argue that if certain conditions are met, stable feedback control is possible under non-deterministic conditions. In particular, certain classes of linear systems may be uniformly exponentially stabilized by placing the closed-loop poles within an “osculating circle” if the statistics of the controller’s sampling times are known.
Model Analysis and Parameters Optimization of Magnetorheological Control Valves
Authors: Tang Jianzhong , Zhu Xiaocong , Yao Bin , Wang Qingfeng , Cao Jian
Published: December 2014

The magnetorheological (MR) control valve is a major component in MR fluid systems to achieve controllable pressure drop or damping characteristics in practice. However, the optimal design of MR control valve is fairly complex due to large extent of design parameters from both magnetic flux generation and mechanical flow characteristics, as well as different requirements or constraints in practical applications. In this paper, the analytical electro-mechanic-magnetic coupling model of the MR control valve with annular-radial flow path is firstly investigated to quantitatively predict the relationship between design parameters and achievable performances such as pressure drop and dynamic range etc.. And then comparison results based on analytical analysis and finite element method are presented to validate the effect model utilized in MR valves. Consequently, a performance-oriented optimization of MR control valves with annular-radial flow path in a non-dimensional design concept is developed through minimizing reciprocal of dynamic range and identifying several optimal internal design parameters subject to predefined constraints under fairly less quantity of combined external design parameters.Finally, the inherent sensitivity of achievable performances with respect to external design parameters is analyzed to provide practical instructions for appropriate specification of the MR control valve.
Vehicle Direct Yaw Moment Control Based on Tire Cornering Stiffness Estimation
Authors: Lei Zhang , Yu Liangyao , Ning Pan , Xiaoxue Liu , Jian Song
Published: December 2014

Direct yaw moment control (DYC) is an active safety technique developed in recent years to improve vehicle handling dynamics. Delayed or excessive intervention is a common problem in traditional logic threshold control algorithm due to the vehicle inertia. To improve the control effect, model predictive control (MPC) is applied in stability control which relies significantly on the accuracy of reference model. In this paper, a MPC stability controller with tire cornering stiffness estimation is proposed. The reference model is modified online by correcting tire cornering stiffness. In this way, yaw rate can be better predicted which improves the control effect. The effectiveness of the proposed algorithm is compared with a MPC controller with constant tire cornering stiffness and a traditional logic threshold controller through numeric simulation. The simulation result indicates that the handling performance of the proposed controller is improved from that without tire cornering stiffness estimation.