Impulse Duration Research Articles

3-sheet structure of Inconel 718 superalloy processed by LBW/SPF and its load response

The 3-sheet structure of Inconel 718 superalloy will be used in flying vehicles as heat resisting and shielding structure due to its lightweight, high strength and stiffness. The 3-sheet structure of Inconel 718 superalloy processed by LBW/SPF (laser beam welding/superplastic forming) technology exhibited good configuration and uniform thickness distribution. The LBW parameters for 3-sheet structure were as follows: Pulse frequency was 32 Hz, impulse duration 3 ms, peak power per pulse 4500 W, and welding speed 180 mm/min. The SPF parameters were as follows: Temperature T=965°C, forming pressure P=4.2 MPa, and forming time t=130 min. The microstructure in weld fusion zone was constituted of austenite dendritics and Laves phase precipitated in interdendritics. After the SPF process, austenite dendritics in the weld fusion became coarser and most of Laves phases were dissolved and turned into δ precipitated phase, but a few of Laves phases were still reserved. And Nb concentration in dendritics increased to 5.42% compared to 2.82% in as-weld condition. Weld metal Vickers-hardness increased from 331.63 in as-weld condition to 391.74 in post-SPF condition which was closed to the base material Vickers-hardness of post-SPF. Grain size of base material grew slightly and an amount of precipitated phase appeared in the base material undergoing SPF process. The tensile test results of base material showed that tensile strength increased obviously and the ductility decreased slightly after SPF process. Load response test results indicated that the 3-sheet structure possessed good resistance to compression and bending load. Accordingly, the LBW/SPF technology is an appropriate forming technique for the 3-sheet structure of Inconel 718 superalloy.

Targeting of cardiac autonomic plexus for modulation of intracardiac neural tone

Ventricular rate control is considered as an initial choice of therapy in many patients with atrial fibrillation (AF). We could previously show that electrostimulation of the right inferior ganglionated plexus (RIGP), which supplies the AV node, instantly decreases ventricular rate during AF. This study describes the development of a technique to reliably implant a chronic lead inside the RIGP. In nine mongrel dogs with AF, the RIGP was identified by neuromapping with probatory high-frequency stimulation (20 Hz) over steerable electrode catheters until a significant ventricular rate slowing was achieved. Then an active fixation, permanent pacemaker lead was fixed closed to the mapping catheter left in place as anatomical marker. Initially (n = 4) available guiding catheters and steerable lead stylets were employed to navigate and anchor the lead, which resulted in repetitive screw-in attempts. Therefore, a guiding catheter was developed, which allowed angiography, lead advancement through its lumen, and probatory neurostimulation over its tip. This tool allowed lead delivery within 40 min (n = 5). Neurostimulation via the permanent lead elicited negative dromotropic effects with stimulation frequency, voltage, and impulse duration as determinants of stimulation efficacy. Active fixation of a permanent pacing lead inside the RIGP is feasible without thoracotomy. Thereby, ventricular rate control during AF can be achieved with stimulus voltages applied for myocardial electrostimulation.

Autonomic mechanism for initiation of rapid firing from atria and pulmonary veins: evidence by ablation of ganglionated plexi

Previous studies showed that autonomic activation by high-frequency electrical stimulation (HFS) during myocardial refractoriness evokes rapid firing from pulmonary vein (PV) and atria, both in vitro and in vivo. This study sought to investigate the autonomic mechanism underlying the rapid firings at various sites by systematic ablation of multiple ganglionated plexi (GP). In 43 mongrel dogs, rapid firing-mediated atrial fibrillation (AF) was induced by local HFS (200 Hz, impulse duration 0.1 ms, train duration 40 ms) to the PVs and atria during myocardial refractoriness. The main GP in the atrial fat pads or the ganglia along the ligament of Marshall (LOM) were then ablated. Ablation of the anterior right GP and inferior right GP significantly increased the AF threshold by HFS at the right atrium and PVs. The AF threshold at left atrium and PVs was significantly increased by ablation of the superior left GP and inferior left GP, and was further increased by ablation of the LOM. Ablation of left- or right-sided GP on the atria had a significant effect on contralateral PVs and atrium. Administration of esmolol (1 mg/kg) or atropine (1 mg) significantly increased AF threshold at all sites. HFS applied to local atrial and PV sites initiated rapid firing via activation of the interactive autonomic network in the heart. GP in either left side or right side contributes to the rapid firings and AF originating from ipsolateral and contralateral PVs and atrium. Autonomic denervation suppresses or eliminates those rapid firings.

Measurement of Current-Voltage Curves of Superconducting Tapes by Means of Quasi Trapezoidal Current Impulses

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Nowadays the impulse measurements are taking on higher importance. This is because by means of current impulses it is possible to measure at high currents and low power loading conditions without overheating the sample or measurement equipment. In this article, we present a system enabling to measure current-voltage curves of superconducting tapes with high critical currents and in overcritical current conditions. In our measurements, the current impulses are quasi trapezoidal and include a ramp increase, a plateau and a long ramp decrease. The complete current impulse duration is of the order of ten milliseconds, though the plateau (useful part for the measurement) is of sub-millisecond range. The current derivative in the plateau is zero. Thus, this conditions are comparable with DC ones. A special ladder transmission line was used as high-current generator for shaping impulses with instantaneous currents up to 1.5 kA. A DAQ system with a sampling rate up to 100 kS/s and 24 bits resolution was used for the measurement. The signal processing was realized by software. This method using quasi trapezoidal current impulses was compared with the method of measurement by means of impulses without plateau. Measured current-voltage curves compared with curves obtained by DC measurements are presented, showing a very good agreement. </para>

Ultrasound-Triggered Controlled Drug Delivery and Biosensing Using Silica Nanotubes

Silica nanotubes (SNTs) have been demonstrated here as a versatile host for controlled drug delivery and biosensing. The sol−gel template synthesized SNTs have a slow rate of drug release. Application of an external stimulus in the form of ultrasound to or chemical functionalization of synthesized SNT results in higher yield of drug release as well as yield of drug release varying linearly with time. In case of controlled drug delivery triggered by ultrasound, drug yield as function of time is found to be heavily dependent on the ultrasound impulse protocol. Impulses of shorter duration (∼0.5 min) and shorter time intervals between successive impulses resulted in higher drug yields. Confinement of hemoglobin (Hb) inside nanometer sized channels of SNT does not have any detrimental effect on the native protein structure and function. Observance of significant enhancement in direct electron transfer of Hb makes the SNTs also promising for application in biosensors.

Analyzing the Robustness of Impulsive Synchronization Coupled by Linear Delayed Impulses

In this technical note, a class of autonomous impulsive differential systems with linear delayed impulses is considered. Sufficient conditions required for this particular class of systems with varying and constant impulse durations to be equi-attractive in the large are obtained. These conditions are then applied to impulsively synchronize two coupled chaotic systems by using delayed impulses and a robustness analysis of the model is also provided. Simulation results are given to demonstrate the analytical results.

Current Threshold for Nerve Stimulation Depends on Electrical Impedance of the Tissue: A Study of Ultrasound-Guided Electrical Nerve Stimulation of the Median Nerve

Understanding the mechanisms causing variation in current thresholds for electrical nerve stimulation may improve the safety and success rate of peripheral nerve blocks. Electrical impedance of the tissue surrounding a nerve may affect the response to nerve stimulation. In this volunteer study, we investigated the relationship between impedance and current threshold needed to obtain a neuromuscular response. Electrical nerve stimulation and impedance measurements were performed for the median nerve in the axilla and at the elbow in 29 volunteers. The needletip was positioned at a distance of 5, 2.5, and 0 mm from the nerve as judged by ultrasound. Impulse widths of 0.1 and 0.3 ms were used for nerve stimulation. A significant inverse relationship between impedance and current threshold was found at the elbow, at nerve-to-needle distances of 5 and 2.5 mm (P = 0.001 and P = 0.036). Impedance values were significantly lower in the axilla (mean 21.1, sd 9.7 kohm) than at the elbow (mean 36.6, sd 13.4 kohm) (P < 0.001). Conversely, current thresholds for nerve stimulation were significantly higher in the axilla than at the elbow (P < 0.001, P < 0.001, P = 0.024). A mean ratio of 1.82 was found for the measurements of current thresholds with 0.1 versus 0.3 ms impulse duration. Our results demonstrate an inverse relationship between impedance measurements and current thresholds and suggest that current settings used for nerve stimulation may require adjustment based on the tissue type. Further studies should be performed to investigate the clinical impact of our findings.

Immediate Effect of Slow PaceBhastrika Pranayamaon Blood Pressure and Heart Rate

The objective of this study was to evaluate the immediate effect of slow pace bhastrika pranayama (respiratory rate 6/min) for 5 minutes on heart rate and blood pressure and the effect of the same breathing exercise for the same duration of time (5 minutes) following oral intake of hyoscine-N-butylbromide (Buscopan), a parasympathetic blocker drug. Heart rate and blood pressure of volunteers (n = 39, age = 25-40 years) was recorded following standard procedure. First, subjects had to sit comfortably in an easy and steady posture (sukhasana) on a fairly soft seat placed on the floor keeping head, neck, and trunk erect, eyes closed, and the other muscles reasonably loose. The subject is directed to inhale through both nostrils slowly up to the maximum for about 4 seconds and then exhale slowly up to the maximum through both nostrils for about 6 seconds. The breathing must not be abdominal. These steps complete one cycle of slow pace bhastrika pranayama (respiratory rate 6/min). During the practice the subject is asked not to think much about the inhalation and exhalation time, but rather was requested to imagine the open blue sky. The pranayama was conducted in a cool, well-ventilated room (18-20 degrees C). After 5 minutes of this breathing practice, the blood pressure and heart rate again were recorded in the aforesaid manner using the same instrument. The other group (n = 10) took part in another study where their blood pressure and heart rate were recorded following half an hour of oral intake of hyoscine-N-butylbromide 20 mg. Then they practiced the breathing exercise as stated above, and the abovementioned parameters were recorded again to study the effect of parasympathetic blockade on the same pranayama. It was noted that after slow bhastrika pranayamic breathing (respiratory rate 6/min) for 5 minutes, both the systolic and diastolic blood pressure decreased significantly with a slight fall in heart rate. No significant alteration in both blood pressure and heart rate was observed in volunteers who performed the same breathing exercise for the same duration following oral intake of hyoscine-N-butylbromide. Pranayama increases frequency and duration of inhibitory neural impulses by activating pulmonary stretch receptors during above tidal volume inhalation as in Hering Bruer reflex, which bring about withdrawal of sympathetic tone in the skeletal muscle blood vessels, leading to widespread vasodilatation, thus causing decrease in peripheral resistance and thus decreasing the diastolic blood pressure. After hyoscine-N-butylbromide, the parasympathetic blocker, it was observed that blood pressure was not decreased significantly as a result of pranayama, as it was observed when no drug was administered. Vagal cardiac and pulmonary mechanisms are linked, and improvement in one vagal limb might spill over into the other. Baroreceptor sensitivity can be enhanced significantly by slow breathing (supported by a small reduction in the heart rate observed during slow breathing and by reduction in both systolic and diastolic pressure). Slow pace bhastrika pranayama (respiratory rate 6/min) exercise thus shows a strong tendency to improving the autonomic nervous system through enhanced activation of the parasympathetic system.

Stroking Characteristics during Time to Exhaustion Tests

Race analyses during swimming reveal how exercise duration affects both clean swimming speed (v), stroke rate (SR), and stroke length (SL). The aim of this study is to provide an explanation for the change of SL and SR during paced exercise swimming the front crawl through an analysis of intracycle changes in motor organization. Trained swimmers (N = 10) swam three times to exhaustion (TTE in seconds) at predetermined velocities corresponding to 95%, 100%, and 110% of the mean speed attained in a 400-m race (V 400). During TTE tests, SR, SL, durations of the glide + catch, pull, push, and recovery phases (s) were measured. Assessment of arm coordination was made through the calculation of the index of coordination (IdC). The time allotted to propulsion per distance unit was estimated (T prop). For all tested speeds, fatigue development induced a gradual increase of SR with concomitant decrease of SL. The duration of the nonpropulsive phases decreased, whereas the duration of the propulsive phases per stroke remained constant. The IdC increased reflecting a reduction of the lag time between two consecutive propulsive actions. Consequently, T prop increased. Fatigue development induced an increase of the SR to compensate for the reduced capacity to generate a propulsive impulse per stroke. The change in arm coordination allows a better chain of the propulsive actions and leads to a greater time allotted to propulsion per distance unit. Such motor adaptation ensures that the overall propulsive impulse remained constant whereas average propulsive force per arm stroke is reduced.

The Effect of Dual-Rate Suspension Damping on Vehicle Response to Transient Road Inputs

The acceleration response of road vehicles to shock inputs from road irregularities such as bumps and hollows is an important consideration in the design of vehicle suspensions and damping characteristics, in particular. In this paper, the influence of the damper on the shock response of a simple vehicle model is considered. An analysis is presented of a single degree-of-freedom model subjected to a transient displacement input. Simple approximate expressions are given for the peak acceleration during an impulse of both short and long durations compared to the natural period, from which the role of the damper is clearly apparent. For impulses of short duration the peak acceleration occurs during the impulse and is shown to be approximately proportional to the damping ratio. Corollary to this, the peak acceleration can be reduced by switching the damper to a lower value during the impulse. The potential benefits of doing so are illustrated through numerical simulation, and a simple formula is given for the maximum possible reduction in peak acceleration. The results are also contrasted with those of a conventional dual-rate automotive damper model. The switchable damper is found to offer sufficient benefit to warrant further investigation.

Assessment of the Outcomes of Cerebral Blood Flow Measurements After Electrical Stimulation of Upper Right Incisor Tooth in Rabbits

The cerebral vessels are innervated by sympathetic, parasympathetic, and sensory nerves. A sensory innervation of the cerebral vessels originating in the trigeminal ganglion has been described in a number of species by several investigations. It has been shown that the electrical stimulation of the trigeminal ganglion causes an increase of cerebral cortical blood flow (CCoBF). The aim of the present study was to determine the effects of dental electrical stimulation the CCoBF in rabbits. A stimulating electrode was located in the upper right incisor tooth of rabbits and trigeminal ganglion was stimulated orthodromically via the infraorbital nerve. Variations in the cortical CCoBF were evaluated by laser-Doppler flowmetry. In experiment group, CCoBF increased together with the beginning of electrical stimulation (5 V, 0.5-ms impulse duration, square-shaped, 10-Hz frequency). The right and left hemisphere CCoBF values of stimulation period at 15s, 30s, 45s, 60s, 75s, and 90s were significantly higher than those of baseline and 105 and 120s (p < 0.05). The maximum increase in right and left CCoBF was 15.6% and 15.1% respectively. In post-stimulation period, the right CCoBF decreased gradually and returned to the baseline values at 120 s. In experiment groups, the CCoBF values of right hemisphere were comparable that of left hemisphereL (p > 0.05). This study demonstrated that the electrical stimulation of the trigeminal nerve's infraorbital branch via dental pulp increases the cortical right and left CCoBF under physiological conditions.

Physiology and Treatment of Pain

Physiology and Treatment of Pain

Vagal Effects on the Occurrence of Focal Atrial Fibrillation Originating From the Pulmonary Veins

There is evidence that the autonomic nervous system may be involved in the mechanism of focal atrial fibrillation (AF), so the present study investigated the effects of the parasympathetic nervous system on the occurrence of focal AF originating from the pulmonary veins (PVs). In 10 mongrel dogs, programmed stimulation and local burst stimulation (12.5 Hz, impulse duration 0.5 ms) were performed at each of the PVs. Pacing thresholds at different sites were determined and shown as a terraced distribution. The closer to the ostium of the PV, the lower was the pacing threshold (P<0.05-0.001). The local effective refractory period (ERP), AF induction and AF threshold were measured at baseline and during bilateral vagal nerve stimulation (VNS). VNS led to local ERP shortening at each of the PV sites (P<0.05-0.001), increased the inducibility of AF at all sites in the 4 PVs (P<0.05-0.001), and decreased the AF threshold at most sites, especially in the distal portions of the 4 PVs (P<0.05-0.01). VNS changes the electrophysiological characteristics of the PVs and facilitates the induction of AF. Interaction between the autonomic nervous system and local cardiac autonomic nerve system may be a potential mechanism.

Diacylglycerol kinase ζ inhibits Gαq-induced atrial remodeling in transgenic mice

Our previous study showed that diacylglycerol kinase zeta (DGKzeta), which degenerates diacylglycerol (DAG), inhibits ventricular structural remodeling and rescues activated G protein (alpha)q (G(alpha)q)-induced heart failure. However, whether DGKzeta inhibits atrial remodeling is still unknown. This study aimed to elucidate the effects of DGKzeta on atrial remodeling. A transgenic mouse (G(alpha)q-TG) with cardiac expression of activated G(alpha)q and a double transgenic mouse (G(alpha)q/DGKzeta-TG) with cardiac overexpression of DGKzeta and activated G(alpha)q were created. During electrocardiogram (ECG) recording for 10 min, atrial fibrillation was observed in 5 of 11 anesthetized G(alpha)q-TG mice but not in any wild-type (WT) and G(alpha)q/DGKzeta-TG mice (P <.05). All of the ECG parameters measured were prolonged in the G(alpha)q-TG compared with WT mice. Interestingly, in G(alpha)q/DGKzeta-TG mice, although the PR and RR intervals were still prolonged, the P interval, QRS complex, and QT interval were not different from those in WT mice. In Langendorff-perfused hearts, the incidence of atrial tachyarrhythmia induced by rapid atrial pacing was greater in G(alpha)q-TG hearts than in G(alpha)q/DGKzeta-TG hearts (P <.05). Action potential duration prolongation and impulse conduction slowing were observed in G(alpha)q-TG atria compared with G(alpha)q/DGKzeta-TG atria. Dilatation of the left atrium with thrombus formation was observed in 9 G(alpha)q-TG hearts but not in any G(alpha)q/DGKzeta-TG hearts. Moreover, the degree of extensive interstitial fibrosis in the left atrium was greater in G(alpha)q-TG hearts than that in G(alpha)q/DGKzeta-TG hearts (P <.05). These results show that DGKzeta inhibits G(alpha)q-induced atrial remodeling and suggest that DGKzeta is a novel therapeutic target for atrial fibrillation.

Seismological constraints on the position of the fragmentation surfaces in the volcano conduit

The durations of the pre-explosion low-frequency impulses of the broadband seismic records of 286 Vulcanian explosions of Volcán de Colima and 15 Vulcanian explosions of Popocatépetl volcano, México were analyzed. These pre-explosion impulses are thought to be produced during the upward movement of fragmented magma in the volcano conduit before an explosion. It is shown that three different magma fragmentation surfaces acted simultaneously during the 2004 September–November episode at Volcán de Colima associated with the andesitic block lava extrusion. The optimal apparent depth for the fragmentation surface that generated the largest (with the energy ≥ 10 11 J) 2004–2005 explosions at Volcán de Colima and the 1998–2000 Popocatépetl explosions is constrained by pre-explosion low-frequency impulse durations between 3 and 7 s.

Assessment of impulse duration thresholds for electrical stimulation of muscles (chronaxy) in dogs

To determine the electrical impulse duration thresholds (chronaxy) for maximal motor contraction of various muscles without stimulation of pain fibers in dogs. 10 healthy adult Beagles. The dogs were used to assess the minimal intensity (rheobase) required to elicit motor contraction of 11 muscles (5 in the forelimb [supraspinatus, infraspinatus, deltoideus, lateral head of the triceps brachii, and extensor carpi radialis], 5 in the hind limb [gluteus medius, biceps femoris, semitendinosus, vastus lateralis, and tibialis cranialis], and the erector spinae). The rheobase was used to determine the chronaxy for each of the 11 muscles in the 10 dogs; chronaxy values were compared with those reported for the corresponding muscles in humans. Compared with values in humans, chronaxy values for stimulation of AA motor fibers in the biceps femoris and semitendinosus muscles and muscles of the more distal portions of limbs were lower in dogs. For the other muscles evaluated, chronaxy values did not differ between dogs and humans. Application of the dog-specific chronaxy values when performing electrical stimulation for strengthening muscles or providing pain relief is likely to minimize the pain perceived during treatment in dogs.

Structure and Functional Properties of Ti-Ni-Based Shape Memory Alloy after Electroplastic Deformation

Application of electroplastic deformation (EPD) by rolling to bulk long-sized samples of Ti-50.7 at.%Ni alloy allows increasing of the deformation strain without macrofailure by 1.5 to 3 times in comparison to cold rolling without electrical current application. Structure formation and functional properties were studied after various EPD regimes: current density (84 to 168 А/mm2) and impulse duration (80 and 160 ms). When the stage of mixed nanocrystalline and amorphous structure formation is reached as a result of EPD, a post-deformation annealing at 400 °С leads to a nanocrystalline structure formation in austenite and highest recovery stress values generation by the martensite.

A qualitative and quantitative analysis of impulse responses from balloon bursts

Anechoic recordings of balloon bursts were systematically acquired for various conditions of balloon diameters, puncture location, and inflation pressure. The recordings were analyzed to derive the average frequency spectrum over the effective duration of the acoustic impulse. Although the data show the well-known limitations for the impulse responses (in terms of repeatability and directional behavior) when viewed at high resolution, the results are quite consistent when averaged over one-third octave bands and reveal that the diameter factor (the ratio between the diameter of the inflated balloon to that of its stated maximum), rather than the overall diameter of the balloon, is a good indicator of the sound pressure level, especially above 200 Hz. The study proposes some simple empirical formulas to predict the quantitative sound pressure level and the qualitative spectral response (using the spectral centroid and skewness) from balloon bursts, based on the inflation factor as a variable. The study also offers suggestions to maximize the value of the balloon-burst methodology in building acoustics measurements by describing an effective way to measure reverberation time while simultaneously acquiring useful directional information associated with the reflected sound.

Sound insulation of artificial and natural sound signals in reeds habitats

From the point of view of acoustical communication, dense fields of reeds are strong acoustical filtre which distorts original sound signal. In this research the rate of sound signals sound insulation in massives of reeds was estimated. As a models were used artificially synthesized, modulated by frequency signals of three frequency lines: 1‐2 kHz, 2‐4 kHz, and 4‐8 kHz with duration of 0.1 and 0.25 msec. For comparison were also used elements of bird songs. The least damping was noted in signals with descending frequency modulation in 8 ‐ 4 kHz range in the upper level of reeds (6 db on 10 m). The most damping were noted in signals with descending frequency modulation in 2 ‐ 1 kHz in the middle level of juncaceous massive(18 db to 10 m). The signals with frequency modulation of 4‐2 kHz were extending better in the upper level of reeds (7‐8 db), whereas in the lower and upper levels were noted dependence of damping rate on duration of sound impulse ‐ the signals with duration of 0.25 mec were damping less than signals with duration of 0.1 msec . The elements of bird songs during their emission in the middle level of juncaceous massive were damping by 15‐20 db on 10 m.

Impulse and continuous noise reduction of tactical hearing protection systems

Tactical hearing protectors are devices designed to protect the wearer from high levels of impulse noise while providing some ambient listening and communication capability. Many of these devices also provide some attenuation of continuous noise. The efficacy of these types of devices depends on the amount of impulse noise protection and continuous noise protection, the quality of the ambient listening capability, and the intelligibility of the speech communication capability. This paper will describe the peak noise reduction of approximately 1 ms duration impulses with peak levels at 165 dB and 195 dB, for several earplugs and earmuffs. The frequency dependent reduction of impulse noise measured using an acoustic test fixture (the French German Research Institute at Saint Louis Head). Generally the data show higher levels of impulse noise reduction with earplugs than with earmuffs. Additionally, continuous noise attenuation was measured using human subjects performing the ANSI S12.6 Real Ear At Threshold (REAT) test. High speed (20k frames/sec) video will show the dynamic motion of typical tactical hearing protection earplugs and earmuffs when stimulated with a 195 dB impulse.