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Waveforms
Kinds of Waveforms Terms modified by Waveforms Selected AbstractsChronaxie of Defibrillation: A Pathway Toward Further Optimization of Defibrillation Waveform?JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 3 2009IGOR R. EFIMOV Ph.D. No abstract is available for this article. [source] A Pilot Study of a Low-Tilt Biphasic Waveform for Transvenous Cardioversion of Atrial Fibrillation: Improved Efficacy Compared with Conventional Capacitor-Based Waveforms in PatientsPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 8 2008BENEDICT M. GLOVER M.D. Background:The optimal waveform tilt for defibrillation is not known. Most modern defibrillators used for the cardioversion of atrial fibrillation (AF) employ high-tilt, capacitor-based biphasic waveforms. Methods:We have developed a low-tilt biphasic waveform for defibrillation. This low-tilt waveform was compared with a conventional waveform of equivalent duration and voltage in patients with AF. Patients with persistent AF or AF induced during a routine electrophysiology study (EPS) were randomized to receive either the low-tilt waveform or a conventional waveform. Defibrillation electrodes were positioned in the right atrial appendage and distal coronary sinus. Phase 1 peak voltage was increased in a stepwise progression from 50 V to 300V. Shock success was defined as return of sinus rhythm for ,30 seconds. Results:The low-tilt waveform produced successful termination of persistent AF at a mean voltage of 223 V (8.2 J) versus 270 V (6.7 J) with the conventional waveform (P = 0.002 for voltage, P = ns for energy). In patients with induced AF the mean voltage for the low-tilt waveform was 91V (1.6 J) and for the conventional waveform was 158 V (2.0 J) (P = 0.005 for voltage, P = ns for energy). The waveform was much more successful at very low voltages (less than or equal to 100 V) compared with the conventional waveform (Novel: 82% vs Conventional 22%, P = 0.008). Conclusion:The low-tilt biphasic waveform was more successful for the internal cardioversion of both persistent and induced AF in patients (in terms of leading edge voltage). [source] Effects of Cyclic Stretch Waveform on Endothelial Cell Morphology Using Fractal AnalysisARTIFICIAL ORGANS, Issue 6 2010Nooshin Haghighipour Abstract Endothelial cells are remodeled when subjected to cyclic loading. Previous in vitro studies have indicated that frequency, strain amplitude, and duration are determinants of endothelial cell morphology, when cells are subjected to cyclic strain. In addition to those parameters, the current study investigated the effects of strain waveform on morphology of cultured endothelial cells quantified by fractal and topological analyses. Cultured endothelial cells were subjected to cyclic stretch by a designed device, and cellular images before and after tests were obtained. Fractal and topological parameters were calculated by development of an image-processing code. Tests were performed for different load waveforms. Results indicated cellular alignment by application of cyclic stretch. By alteration of load waveform, statistically significant differences between cell morphology of test groups were observed. Such differences are more prominent when load cycles are elevated. The endothelial cell remodeling was optimized when the applied cyclic load waveform was similar to blood pressure waveform. Effects of load waveform on cell morphology are influenced by alterations in load amplitude and frequency. It is concluded that load waveform is a determinant of endothelial morphology in addition to amplitude and frequency, and such effect is elevated by increase of load cycles. Due to high correlation between fractal and topological analyses, it is recommended that fractal analysis can be used as a proper method for evaluation of alteration in cell morphology and tissue structure caused by application of external stimuli such as mechanical loading. [source] Analysis of the Arterial Blood Pressure Waveform Using Fast Fourier Transform Technique During Left Ventricular Nonpulsatile Assistance: In Vitro StudyARTIFICIAL ORGANS, Issue 7 2000Shinji Kawahito Abstract: The arterial blood pressure waveform is variable during left ventricular assistance. The aim of this study is to examine the correlation between the left ventricular assist device (LVAD) condition and the arterial blood pressure waveform in a fixed cardiac output condition using a mock circuit. This mock circulation loop was composed of an aortic compliance chamber, a left atrial compliance chamber, a pneumatic pulsatile pump as a native heart, and a rotary blood pump representing the LVAD with left atrial drainage. The Fast Fourier Transform technique was utilized to analyze the arterial blood pressure waveform and calculate the pulsatility index (PI) and the pulse power index (PPI). The PI and PPI decreased with the increase of the LVAD rotational speed, exponentially. There was a significant negative correlation between the PI, PPI, and the LVAD rotational speed, flow rate, and assist ratio. The best correlation was observed between the PPI and the assist ratio (r = 0.986). From this viewpoint, an ideal LVAD condition may be estimated from the pulsatility change of the arterial blood pressure waveform. [source] Optimizing the Quadruple-potential Waveform for the Determination of Gentamicin Sulfate by High Performance Liquid Chromatography with Pulsed Electrochemical DetectionCHINESE JOURNAL OF CHEMISTRY, Issue 9 2005Ya-Qi Cai Abstract In this paper, a quadruple-potential waveform was investigated and optimized for the determination of gentamicin by reversed phase ion-pair chromatography. Instead of a relatively high positive potential, a negative potential was adopted as a potential for the cleaning of gold working electrode. By this way, the formation of gold oxide resulting from the application of high positive potential during the analyte detection and electrode cleaning was greatly reduced, and therefore, the dissolution and recession of gold working electrode was also reduced. The good condition of gold working electrode achieved by this quadruple-potential waveform can help us to obtain a good reproducibility. In order to acquire signal-to-noise ratio as high as possible, several waveform parameters affecting the detection of gentamicin were carefully selected. The analytical method has been applied to the determination of two real gentamicin samples, and good results with low relative standard deviation not more than 4% were obtained. [source] Electrical penetration graphs of the nymphal stage of Bemisia argentifoliiENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2003Y.X. Jiang Abstract Electrical penetration graph (EPG, DC system) waveforms were recorded from first, second, and third instar Bemisia argentifolii nymphs. Waveforms recorded were similar among the three instars. Four waveforms were recorded and were named C, J, L, and H. Waveform J is new, whereas waveforms C, L, and H of B. argentifolii nymphs were similar to those published previously from greenhouse whitefly nymphs. As in the previous study on greenhouse whitefly nymphs, there was variation in each of waveforms C, L, and H. Waveform C was recorded at an extracellular voltage level, and represents a pathway phase where the stylets penetrate the plant tissue in an intercellular pathway. At the end of waveform C, the voltage dropped to an intracellular level, indicating penetration of a living cell, and the stylet tips then remained in that cell for the rest of the EPG recording, which was sometimes as long as 16 h. Three waveforms (J, L, and H) were recorded during this intracellular phase, beginning with J, a brief (average = 31 s), low amplitude, irregular waveform. J appeared only at the beginning of the intracellular phase, and was followed by either L (five out of eight times) or H (three out of eight times). Waveforms L and H then alternated with one another for the remainder of the intracellular phase. The most conspicuous difference between L and H was the frequency of their voltage fluctuations; L had a lower frequency and H a higher frequency. Usually the shape of waveform L was dominated by voltage peaks in a positive direction, while waveform H was characterized by strong voltage peaks in a negative direction; although some variants of both L and H had distinct voltage peaks in both directions. The electrical origin of both the positive and negative voltage peaks was electromotive force (emf) fluctuation rather than resistance fluctuation. During waveform H, copious amounts of honeydew were produced, indicating that the penetrated cell was a sieve element. We conclude, therefore, that H represents phloem sap ingestion; and because J and L are produced in the same cell as H, then phloem phase is represented by waveforms J, L, and H. The biological correlations for J and L are not yet known. [source] Spin Echo Analysis of Restricted Diffusion under Generalized Gradient Waveforms for Spherical Pores with Relaxivity and InterconnectionsISRAEL JOURNAL OF CHEMISTRY, Issue 1-2 2003Brett N. Ryland The problem of restricted diffusion in spherical pores is examined under conditions of finite gradient pulse width in pulsed gradient spin echo (PGSE)-NMR experiments. Closed form analytic expressions are derived, and the case of interconnected pores is briefly examined. An expression, based on the pore hopping approximation, is presented that predicts the echo attenuation for diffusion between pores under any gradient waveform. [source] Analysis of the Defibrillation Efficacy for 5-ms WaveformsJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 4 2004DONGXU GUAN Ph.D. Introduction: Empirical studies have shown that biphasic defibrillation waveforms are more efficacious than monophasic waveforms. However, a more systematic approach to waveform development might be more productive. This study tested 147 multiphasic waveforms uniformly sampled from all possible 5-ms waveforms. Methods and Results: One hundred ninety-eight guinea pigs (850,1,050 g) received 30 episodes of ventricular fibrillation followed by transthoracic defibrillation. The first 10 shocks were used to determine the ED50 for a biphasic control. Then, 20 waveforms including 2 controls were tested once at the ED50. Of the 147 waveforms tested here, 21 waveforms showed equivalent or greater efficacies than the biphasic control, with one being statistically more efficacious (P < 0.05). Two fundamental assumptions were addressed: (1) similarly efficacious waveforms are analytically similar, and (2) a single optimal waveform can be described. The mean percentage of similarly efficacious waveforms with similar shapes was greater than zero in the most efficacious 21 waveforms (P = 0.023), but less efficacious waveforms showed randomly distributed shapes. Cluster analysis revealed that the best waveforms share a major phase containing most of the defibrillation energy. The optimal waveform shape extrapolated from the sample waveforms was a 2.5/1-ms biphasic-type waveform (highest correlation r = 0.701, P < 0.001). Conclusion: This work supports the assumption that efficacious waveforms are similarly shaped and the notion that one single optimum exists. (J Cardiovasc Electrophysiol, Vol. 15, pp. 447-454, April 2004) [source] Defibrillation Efficacy and Pain Perception of Two Biphasic Waveforms for Internal Cardioversion of Atrial FibrillationJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 8 2003Jens Jung M.D. Introduction: We evaluated the influence of the peak voltage of waveforms used for internal cardioversion of atrial fibrillation on defibrillation efficacy and pain perception. A low peak voltage biphasic waveform generated by a 500-,F capacitor with 40% tilt was compared to a standard biphasic waveform generated by a 60-,F capacitor with 80% tilt. Methods and Results: In 19 patients with paroxysmal atrial fibrillation (79% male, age 55 ± 11 years, 21% with heart disease), the atrial defibrillation threshold (ADFT) was determined during deep sedation with midazolam for both waveforms in a randomized fashion using a step-up protocol. Internal cardioversion with a single lead (shock vector: coronary sinus to right atrium) was successful in 18 (95%) of 19 patients. ADFT energy and peak voltage were significantly lower for the low-voltage waveform (2.1 ± 2.4 J vs 3.5 ± 3.9 J, P < 0.01; 100 ± 53 V vs 290 ± 149 V, P < 0.01). Sedation then was reversed with flumazenil after ADFT testing. Two shocks at the ADFT (or a 3-J shock if ADFT >3 J) were administered to the patient using each waveform in random order. Pain perception was assessed using both a visual scale and a numerical score. ADFTs were above the pain threshold in 17 (94%) of 18 patients, even though the ADFT with the 500-,F waveform was <100 V in 63% of the patients. Pain perception was comparable for both waveforms (numerical score: 6.5 ± 2.4 vs 6.3 ± 2.6; visual scale: 5.4 ± 2.6 vs 5.2 ± 3.1; P = NS, 500-,F vs 60-,F). The second shock was perceived as more painful in 88% of the patients, independent of the waveform used. Conclusion: Despite a 66% lower peak voltage and a 40% lower energy, the 40% tilt, 500-,F capacitor biphasic waveform did not change the pain perceived by the patient during delivery of internal cardioversion shocks. Pain perception for internal cardioversion probably is not influenced by peak voltage alone and increases with the number of applied shocks. (J Cardiovasc Electrophysiol, Vol. 14, pp. 837-840, August 2003) [source] Reentry Site During Fibrillation Induction in Relation to Defibrillation Efficacy for Different Shock WaveformsJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 5 2001Ph.D., RAYMOND E. IDEKER M.D. Reentry Site and Defibrillation Waveform Efficacy.Introduction: Unsuccessful defibrillation shocks may reinitiate fibrillation by causing postshock reentry. Methods and Results: To better understand why some waveforms are more efficacious for defibrillation, reentry was induced in six dogs with 1-, 2-, 4-, 8-, and 16-msec monophasic and 1/1- (both phases 1 msec) 2/2-, 4/4-, and 8/8-msec biphasic shocks. Reentry was initiated by 141 ± 15 V shocks delivered from a defibrillator with a 150- , F capacitance during the vulnerable period of paced rhythm (183 ± 12 msec after the last pacing stimulus). The shock potential gradient field was orthogonal to the dispersion of refractoriness. Activation was mapped with 121 electrodes covering 4 × 4 cm of the right ventricular epicardium, and potential gradient and degree of recovery of excitability were estimated at the sites of reentry. Defibrillation thresholds (DFTs) were estimated by an up-down protocol for the same nine waveforms in eight dogs internally and in nine other dogs externally. DFT voltages for the different waveforms were positively correlated with the magnitude of shock potential gradient and negatively correlated with the recovery interval at the site at which reentry was induced by the waveform during paced rhythm for both internal (DFT = 1719 + 64.5 , V , 11.1RI; R2= 0.93) and external defibrillation (DFT = 3445 + 150 , V , 22RI; R2= 0.93). Conclusion: The defibrillation waveforms with the lowest DFTs were those that induced reentry at sites of low shock potential gradient, indicating efficacious stimulation of myocardium. Additionally, the site of reentry induced by waveforms with the lowest DFTs was in myocardium that was more highly recovered just before the shock, perhaps because this high degree of recovery seldom occurs during defibrillation due to the rapid activation rate during fibrillation. [source] New Approach to Biphasic Waveforms for Internal Defibrillation:JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 8 2000Fully Discharging Capacitors Internal Defibrillation with Fully Discharging Capacitors. Introduction: The use of two independent, fully discharging capacitors for each phase of a biphasic defibrillation waveform may lead to the design of a simpler, smaller, internal defibrillator. The goal of this study was to determine the optimal combination of capacitor sizes for such a waveform. Methods and Results: Eight full-discharge (95/95% tilt), biphasic waveforms produced by several combinations of phase-1 capacitors (30, 60, and 90 ,F) and phase-2 capacitors (1/3, 2/3, and 1.0 times the phase-1 capacitor) were tested and compared to a single-capacitor waveform (120 ,F, 65/65% tilt) in a pig ventricular fibrillation model (n = 12, 23 ± 2 kg). In the full-discharge waveforms, phase-2 peak voltage was equal to phase-1 peak voltage. Shocks were delivered between a right ventricular lead and a left pectoral can electrode. E50s and V50s were determined using a ten-step Bayesian process. Full-discharge waveforms with phase-2 capacitors of ,40 ,F had the same E50 (6.7 ± 1.7 J to 7.3 ± 3.9 J) as the single-capacitor truncated waveform (7.3 ± 3.7 J), whereas waveforms with phase-2 capacitors of ,60 ,F had an extremely high E50 (14.5 ± 10.8 J or greater, P < 0.05). Moreover, of the former set of energy-efficient waveforms, those with phase-1 capacitors of ,60 ,F additionally exhibited V50s that were equivalent to the V50 of the single-capacitor waveform (344 ± 65 V to 407 ± 50 V vs 339 ± 83 V). Conclusion: Defibrillation efficacy can be maintained in a full-discharge, two-capacitor waveform with the proper choice of capacitors. [source] A Pilot Study of a Low-Tilt Biphasic Waveform for Transvenous Cardioversion of Atrial Fibrillation: Improved Efficacy Compared with Conventional Capacitor-Based Waveforms in PatientsPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 8 2008BENEDICT M. GLOVER M.D. Background:The optimal waveform tilt for defibrillation is not known. Most modern defibrillators used for the cardioversion of atrial fibrillation (AF) employ high-tilt, capacitor-based biphasic waveforms. Methods:We have developed a low-tilt biphasic waveform for defibrillation. This low-tilt waveform was compared with a conventional waveform of equivalent duration and voltage in patients with AF. Patients with persistent AF or AF induced during a routine electrophysiology study (EPS) were randomized to receive either the low-tilt waveform or a conventional waveform. Defibrillation electrodes were positioned in the right atrial appendage and distal coronary sinus. Phase 1 peak voltage was increased in a stepwise progression from 50 V to 300V. Shock success was defined as return of sinus rhythm for ,30 seconds. Results:The low-tilt waveform produced successful termination of persistent AF at a mean voltage of 223 V (8.2 J) versus 270 V (6.7 J) with the conventional waveform (P = 0.002 for voltage, P = ns for energy). In patients with induced AF the mean voltage for the low-tilt waveform was 91V (1.6 J) and for the conventional waveform was 158 V (2.0 J) (P = 0.005 for voltage, P = ns for energy). The waveform was much more successful at very low voltages (less than or equal to 100 V) compared with the conventional waveform (Novel: 82% vs Conventional 22%, P = 0.008). Conclusion:The low-tilt biphasic waveform was more successful for the internal cardioversion of both persistent and induced AF in patients (in terms of leading edge voltage). [source] Analysis of the Electrocardiographic Waveforms Produced by Right Ventricular Pacing: Relation to the Nonpaced PatternsPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 5 2008HOWARD S. FRIEDMAN M.D. Background: Ventricular aberrant conduction has a confounding effect on the known relationships between the electrocardiogram (ECG) and left ventricular (LV) mass. By relating the ECG of right ventricular pacing to LV mass and to nonpaced recordings, clarification of these effects might emerge. Methods and Results: In 30 patients (age, 81 ± 7 years; 13 women) who had right ventricular paced ECGs and echocardiograms, 24 of who also had nonpaced ECGs, comparative analyses were performed. Although the nonpaced ECGs had strong correlations with various echocardiographic measurements, for paced ECGs, only QRS complex voltage and interventricular septal thickness (IVS) were significantly related. However, paced QRS complex voltage relationships correlated with those of nonpaced QRS complexes, ranging from an r = 0.54, P < 0.006, for the sum of the R in aVL and the S in V-3 to r = 0.78, P < 0.001, for the sum of the R in I and the S in III. Paced ECGs had a QRS complex with a greater spatial amplitude, a longer duration, and a more superior position, and had more deeply inverted T waves than nonpaced ECGs. The differences between the voltages of paced and nonpaced QRS complexes, moreover, diminished as LV mass and/or IVS increased. When compared with nonpaced ECGs, paced ECGs showed the most similarity to nonpaced ECGs having a left bundle branch block (LBBB) pattern. Except for the presence of more superiorly directed QRS complexes, paced impulses were not significantly different (P < 0.008) from nonpaced impulses having a LBBB pattern. Also, the nonpaced ECG pattern had no discernable effect on ECG produced by right ventricular (RV) pacing. Conclusions: Despite having weak relations with echocardiographic measurements, the QRS complex voltage of the paced ECG correlated with those of nonpaced ECGs, and the voltage differences between them were smaller as LV mass increased. [source] "Tuned" Defibrillation Waveforms Outperform 50/50% Tilt Defibrillation Waveforms: A Randomized Multi-Center StudyPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 2007SENTHIL NATARAJAN M.D. Introduction: A superior performance of a tuned waveform based on duration using an assumed cardiac membrane time constant of 3.5 ms and of a 50/50% tilt waveform over a standard 65/65% tilt waveform has been documented before. However, there has been no direct comparison of the tuned versus the 50/50% tilt waveforms. Methods: In 34 patients, defibrillation thresholds (DFTs) for tuned versus 50/50% tilt waveforms in a random order were measured by using the optimized binary search method. High voltage lead impedance was measured and used to select the pulse widths for tuned and 50/50% tilt defibrillation waveforms. Results: Delivered energy (7.3 ± 4.6 J vs 8.7 ± 5.3 J, P = 0.01), stored energy (8.2 ± 5.1 J vs 9.7 ± 5.6 J, P = 0.01), and delivered voltage (405.9 ± 121.7 V vs 445.0 ± 122.6 V, P = 0.008) were significantly lower for the tuned than for the 50/50% tilt waveform. In four patients with DFT ,15 J, the tuned waveform lowered the mean energy DFT by 2.8 J and mean voltage DFT by 45 V. For all patients, the mean peak delivered energy DFT was reduced from 29 J to 22 J (24% decrease). Multiple regression analysis showed that a left ventricular ejection fraction <20% is a significant predictor of this advantage. Conclusion: Energy and voltage DFTs are lowered with an implantable cardioverter defibrillator that uses a tuned waveform compared to a standard 50% tilt biphasic waveform. [source] The Defibrillation Efficacy of High Frequency Alternating Current Sinusoidal Waveforms in Guinea PigsPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 2p1 2003SCOTT J. ROBERTS ROBERTS, S.J., et al.: The Defibrillation Efficacy of High Frequency Alternating Current Sinusoidal Waveforms in Guinea Pigs. There have been few basic studies of alternating current (AC) defibrillation, despite growing interest in the ability of AC to terminate or alter ongoing fibrillation. Based on fibrillation threshold testing, it has been suggested that cardiac tissue is most sensitive to long duration, low strength AC stimulation at around 50 Hz. This has not been directly tested for defibrillation. Two subcutaneous electrodes were placed 40 mm apart on opposing aspects of the guinea pig thorax. Seven seconds were allowed to elapse between fibrillation initiation and defibrillation. The tested waveforms were at 50, 100, 200, 500, and 1000 Hz with 2, 4, 8, 16, and 32-cycles. The efficacy of every waveform was measured using a single stimulus in a large population of animals. Forty-one guinea pigs were used in the fixed energy group. Thirty-three guinea pigs were used in the fixed amplitude group with additional 1-cycle waveforms tested. The 200-Hz and the 2-cycle waveforms were significantly more efficacious than those at other frequencies(P < 0.02)and other durations(P < 0.001). The 50-Hz waveforms were the least successful. Amplitude, not duration or energy, was the determinate of efficacy for 2-cycle (the most efficacious) waveforms. Unlike low strength stimulation, defibrillation strength stimuli are most effective with high frequency (200 Hz) pulses (2 cycles). (PACE 2003; 26[Pt. I]:599,604) [source] Accurate automatic visible speech synthesis of arbitrary 3D models based on concatenation of diviseme motion capture dataCOMPUTER ANIMATION AND VIRTUAL WORLDS (PREV: JNL OF VISUALISATION & COMPUTER ANIMATION), Issue 5 2004Jiyong Ma Abstract We present a technique for accurate automatic visible speech synthesis from textual input. When provided with a speech waveform and the text of a spoken sentence, the system produces accurate visible speech synchronized with the audio signal. To develop the system, we collected motion capture data from a speaker's face during production of a set of words containing all diviseme sequences in English. The motion capture points from the speaker's face are retargeted to the vertices of the polygons of a 3D face model. When synthesizing a new utterance, the system locates the required sequence of divisemes, shrinks or expands each diviseme based on the desired phoneme segment durations in the target utterance, then moves the polygons in the regions of the lips and lower face to correspond to the spatial coordinates of the motion capture data. The motion mapping is realized by a key-shape mapping function learned by a set of viseme examples in the source and target faces. A well-posed numerical algorithm estimates the shape blending coefficients. Time warping and motion vector blending at the juncture of two divisemes and the algorithm to search the optimal concatenated visible speech are also developed to provide the final concatenative motion sequence. Copyright © 2004 John Wiley & Sons, Ltd. [source] Patent ductus arteriosus and cystic periventricular leucomalacia in preterm infantsACTA PAEDIATRICA, Issue 3 2001P Pladys Aim: To test the association between early disturbances in hemodynamics induced by left-to-right shunting through the duct and cystic periventricular leucomalacia. Patients: Forty-six preterm infants (27,32 wk) admitted to the neonatal intensive care unit with risk criteria. Methods: Patent ductus arteriosus was evaluated on days 1 and 4, and was significant (sPDA) in cases of absent or reversed end diastolic flow in the subductal aorta. Resistance index was measured in the anterior cerebral artery and in the subductal aorta. Main outcome: Diagnosis of cystic periventricular leucomalacia between day 10 and day 50. Results: The 12 infants who developed cystic periventricular leucomalacia were compared with those who did not. On day 1, sPDA was more frequent (64% vs 26%; p= 0.03) in the cystic periventricular leucomalacia group, left ventricular output was higher (median = 341 vs 279mlkg -1.min -1; p= 0.005), and rescue surfactant was more frequently used (83% vs 47%; p= 0.03). This latter association was confirmed by multivariate analysis. Resistance index in the anterior cerebral artery was increased in cases of significant patent ductus arteriosus (p < 0.01) and was correlated with resistance index in the subductal aorta. Conclusion: On day 1 in this selected population, sPDA has an effect on blood flow velocity waveform in cerebral arteries and is associated with an increase in the emergence of cystic periventricular leucomalacia. This association could be casual rather than causal. [source] Abnormal fetal aortic velocity waveform and postnatal growthACTA PAEDIATRICA, Issue 11 2000D Ley Postnatal growth from birth up to 7 y of age was evaluated in 151 children with varying degrees of intrauterine growth retardation who were previously examined in their intrauterine life with Doppler velocimetry of the thoracic descending aorta. The children with abnormal fetal aortic blood flow class (BFC), of which 39/46 (85%) had a birthweight 2 SD below the mean of the population, were lean at birth and had a high rate of catch-up growth in weight and length during the first 3 and 6 mo, respectively. After the initial phases of rapid catch-up in weight and length, mean values of SD scores for weight and height remained relatively unchanged up until 2 y of age, thereafter increasing gradually up to 7 y of age, leaving 4/46 (8%) and 4/46 (8%) below ,2 SD for weight and height, respectively. The pattern of changes in length/height and weight over time did not differ between those infants with abnormal BFC and those with normal BFC. The abnormal fetal aortic waveform was not related to rate of early catch-up growth or to height or weight at 7 y of age after adjustment for deviation in growth at birth. The magnitude of deficit in weight and length at birth was more predictive of subsequent growth. [source] Nondestructive Evaluation of Elastic Properties of Concrete Using Simulation of Surface WavesCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 8 2008Jae Hong Kim In this study, to evaluate information of a surface waveform beyond the simple wave velocity, artificial intelligence engines are employed to estimate simulation parameters, that is, the properties of elastic materials. The developed artificial neural networks are trained with a numerical database having secured its stability. In the process, the appropriate shape of the force,time function for an impact load is assumed so as to avoid Gibbs phenomenon, and the proposed principal wavelet-component analysis accomplishes a feature extraction with a wavelet transformed signal. The results of estimation are validated with experiments focused on concrete materials. [source] Numerical Model for Biaxial Earthquake Response of Reinforced ConcreteCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 4 2007Cemalettin Dönmez The model is tested using data from two types of experiments with reinforced concrete elements: (1) elements subjected to varying pseudo-static biaxial lateral loads and (2) elements that responded biaxially to simulated earthquake motions. The goal for the model was not only to help determine the absolute maxima for earthquake response but also to enable calculation of the entire waveform, including the ranges of low- and moderate-amplitude response. The comparisons of measured and calculated results and sensitivity of the proposed model to variations in the input parameters are discussed. The output was found to be insensitive to the changes in input parameters related to concrete and sensitive to input parameters related to reinforcing steel. The results of the calculations were tested using experimental data. [source] Regulation of sperm flagellar motility activation and chemotaxis caused by egg-derived substance(s) in sea cucumberCYTOSKELETON, Issue 4 2009Masaya Morita Abstract The sea cucumber Holothuria atra is a broadcast spawner. Among broadcast spawners, fertilization occurs by means of an egg-derived substance(s) that induces sperm flagellar motility activation and chemotaxis. Holothuria atra sperm were quiescent in seawater, but exhibited flagellar motility activation near eggs with chorion (intact eggs). In addition, they moved in a helical motion toward intact eggs as well as a capillary filled with the water layer of the egg extracts, suggesting that an egg-derived compound(s) causes motility activation and chemotaxis. Furthermore, demembranated sperm flagella were reactivated in high pH (>7.8) solution without cAMP, and a phosphorylation assay using (,-32P)ATP showed that axonemal protein phosphorylation and dephosphorylation also occurred in a pH-dependent manner. These results suggest that the activation of sperm motility in holothurians is controlled by pH-sensitive changes in axonemal protein phosphorylation. Ca2+ concentration affected the swimming trajectory of demembranated sperm, indicating that Ca2+ -binding proteins present at the flagella may be associated with regulation of flagellar waveform. Moreover, the phosphorylation states of several axonemal proteins were Ca2+ -sensitive, indicating that Ca2+ impacts both kinase and phosphatase activities. In addition, in vivo sperm protein phosphorylation occurred after treatment with a water-soluble egg extract. Our results suggest that one or more egg-derived compounds activate motility and subsequent chemotactic behavior via Ca2+ -sensitive flagellar protein phosphorylation. Cell Motil. Cytoskeleton 2009. © 2009 Wiley-Liss, Inc. [source] Evidence for axonemal distortion during the flagellar beat of ChlamydomonasCYTOSKELETON, Issue 8 2007Charles B. Lindemann Abstract In order to understand the working mechanism that governs the flagellar beat it is essential to know if the axoneme undergoes distortion during the course of the beat cycle. The rapid fixation method employed by Mitchell was able to preserve the waveform of Chlamydomonas flagella much as it appears during normal flagellar beating [Mitchell, Cell Motil Cytoskeleton 2003;56:120,129]. This conservation of the waveform suggests that the stress responsible for the production of bending is also trapped by the fixation procedure. Longitudinal sections of these well-preserved flagella were used to document variations in the relative axonemal diameter. Sections aligned to the plane of bending, showing both the central pair microtubules and outer doublets, were examined for this purpose. Micrographs were selected that continuously showed both the outer doublets and the central pair from a straight region to a curved region of the flagellum. Axoneme diameters measured from these select micrographs showed an increase in relative diameter that averaged 39 nm greater at the crest of the bent region. This constituted a 24% increase in the axoneme diameter in the bends. The transverse stress acting across the axoneme during bending was calculated from the Geometric Clutch computer model for a simulated Chlamydomonas -like flagellar beat. If we assume that this is representative of the transverse stress acting in a real flagellum, then the Young's modulus of the intact axoneme is ,0.02 MPa. The possibility that the distortion of the axoneme during the beat could play a significant role in regulating dynein function is discussed. Cell Motil. Cytoskeleton 2007. © 2007 Wiley-Liss, Inc. [source] Na+/Ca2+ exchanger modulates the flagellar wave pattern for the regulation of motility activation and chemotaxis in the ascidian spermatozoaCYTOSKELETON, Issue 10 2006Kogiku Shiba Abstract Ion channels and ion exchangers are known to be important participants in various aspects of sperm physiology, e.g. motility activation, chemotaxis, the maintenance of motility and the acrosome reaction in the sperm. We report here on a role of the K+ -independent Na+/Ca2+ exchanger (NCX) on ascidian sperm. Reverse-transcriptase PCR reveals that the NCX is expressed in the testis while immunoblotting and immunolocalization demonstrate that the NCX exists on the sperm in the ascidian Ciona savignyi and C. intestinalis. A potent blocker of the NCX, KB-R7943 was found to block sperm-activating and -attracting factor (SAAF)-induced motility activation, sperm motility and sperm chemotaxis. We further analyzed the effects of this blocker on motility parameters such as the flagellar waveform, curvature, beat frequency, amplitude and wavelength of the sperm flagella. Inhibition of the NCX caused two distinct effects: a low concentration of KB-R7943 induced symmetric bending, whereas a high concentration of KB-R7943 resulted in asymmetric flagellar bending. These findings suggest that the NCX plays important roles in the regulation of SAAF-induced sperm chemotaxis, motility activation and motility maintenance in the ascidian. This study provides new information toward an understanding of Ca2+ transport systems in sperm motility and chemotaxis. Cell Motil. Cytoskeleton 2006. © 2006 Wiley-Liss, Inc. [source] On the reliability of long-period response spectral ordinates from digital accelerogramsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 5 2008Roberto Paolucci Abstract Using records from co-located broadband and digital strong motion (SM) instruments, it is first shown that the displacement waveforms obtained by double integration of the accelerogram need not be free of unrealistic baseline drift to yield reliable spectral ordinates up to at least 10,s. Secondly, to provide objective criteria for selecting reliable digital SM records for ground motion predictions at long periods, a set of synthetic accelerograms contaminated by random long-period noise has been used, and the difference between the original accelerograms and the spurious ones in terms of response spectra has been quantified, by introducing a noise index that can be easily calculated based on the velocity waveform of the record. The results of this study suggest that high-pass filtering the digital acceleration record from a cutoff period selected to suppress baseline drifts on the displacement waveform appears to be in most cases too conservative and unduly depletes reliable information on long-period spectral ordinates. Copyright © 2007 John Wiley & Sons, Ltd. [source] Clinical Value of the Tissue Doppler S Wave to Characterize Left Ventricular Hypertrophy as Defined by EchocardiographyECHOCARDIOGRAPHY, Issue 4 2010Demian Chejtman M.D. Left ventricular hypertrophy (LVH) may be a physiological finding and may also be associated with different disease entities and hence, with different outcomes. Regional myocardial function can be assessed with color Doppler tissue imaging, specifically by the waveform of the isovolumic contraction (IC) period and the regional systolic wave ("s"). Methods and Results: We studied five groups (G): healthy, sedentary young volunteers (G1, n:10); healthy sedentary adult volunteers (G2, n:8); and subjects with LVH (left ventricular mass index >125 g/m2) including: high performance athletes (G3, n:21), subjects with hypertension (G4, n:21), subjects with hypertrophic cardiomyopathy (HCM) (G5, n:18). We measured peak "s" wave velocity (cm/sec) at the basal and mid septum, the IC/s ratio, and basal to mid-septal velocity difference (BMVD) of the "s" wave. Regional "s" wave values (cm/sec) were G1 = 5.6 ± 1; G2 = 5.4 ± 0.8; G3 = 5.7 ± 0.6; G4 = 5.3 ± 1.1; G5 = 4.2 ± 1.1 (P < 0.0001). The IC/s ratio was G1 = 0.28 ± 0.18; G2 = 0.39 ± 0.21; G3 = 0.23 ± 0.10; G4 = 0.42 ± 0.15; G5 = 0.64 ± 0.15 (P < 0.0001). The BMVD (cm/sec) was G1 = 2 ± 0.51; G2 = 1.71 ± 0.29; G3 = 1.78 ± 0.44; G4 = 1.26 ± 0.96; G5 = 0.45 ± 0.4 (P < 0.0001). IC/s < 0.38 discriminated physiological from pathological forms of hypertrophy (sensitivity 90%; specificity 88%). Peak "s" wave velocity discriminated HCM from other causes of hypertrophy, with a cutoff value of 4.46 cm/sec (sensitivity 72%; specificity 90%). BMVD <0.98 cm/sec detected HCM with 89% sensitivity and 86% specificity. Conclusions: Peak "s" wave velocity and two indices: IC/s and BMDV are novel parameters that may allow to discriminate physiological from pathological forms of hypertrophy as well as different subtypes of hypertrophy. (ECHOCARDIOGRAPHY 2010;27:370-377) [source] Echo-Tracking Assessment of Carotid Artery Stiffness in Patients with Aortic Valve StenosisECHOCARDIOGRAPHY, Issue 7 2009Francesco Antonini-Canterin M.D. Background: There is little information about mechanical properties of large arteries in patients (pts) with aortic stenosis (AS). Methods: Nineteen patients with AS (aortic valve area: 0.88 ± 0.29 cm2) and 24 control subjects without AS but with a similar distribution of risk factors were recruited. , index, pressure-strain elastic modulus (Ep), arterial compliance (AC), augmentation index (AIx), and local pulse-wave velocity (PWV) were obtained at the level of right common carotid artery (CCA) by a real time echo-tracking system. Time to dominant peak of carotid diameter change waveform, corrected for heart rate (tDPc), and maximum rate of rise of carotid diameter (dD/dt) were measured. Systemic arterial compliance (SAC) was also calculated. Parameters of AS severity (mean gradient, valve area, stroke work loss [SWL]) were determined. Results: tDPc was higher in patients with AS than in controls (7.9 ± 0.6 vs. 6.6 ± 0.7, P < 0.0001) while dD/dt was lower (5.3 ± 3.6 mm/s vs. 7.8 ± 2.8 mm/s, P = 0.01). AIx was significantly higher in AS group (32.5 ± 13.6% vs. 20.6 ± 12.2%, P = 0.005) and had a linear correlation both with tDPc (r = 0.63, P < 0.0001) and with dD/dt (r =,0.38, P = 0.01). There was a significant correlation between carotid AC and SAC (r = 0.49, P = 0.03), but only carotid AC was related to SWL (r = 0.51, P = 0.02), while SAC was not (P = 0.26).Conclusions: AIx was the only parameter of arterial rigidity found to be higher in patients with AS than in controls. Carotid AC showed a significant correlation with SAC and it seemed to be more closely related to AS severity than to SAC. [source] A simple method for output voltage control of a three-phase multilevel inverter considering DC voltage fluctuationELECTRICAL ENGINEERING IN JAPAN, Issue 3 2010Kenji Amei Abstract Multilevel inverter circuit generates the stair-like voltage without using transformer and interphase reactor, and it is the circuit which realizes reduction in the harmonics and enlargement of the capacity. In addition, the application of PWM control improves the waveform, and reduces the switching component to the conventional half, and the filter capacity is reduced. In this paper, improvement on the voltage utilization factor and feedback control of output voltage are applied to multilevel inverter circuit. For the DC power supply with the intense fluctuation, it is necessary to construct inverter circuit which can supply stabilized AC voltage. One-chip microcomputer with various functions is used for the control equipment of this circuit, and miniaturization and cost reduction of the control equipment are realized. Here, the control principle and experimental results of this equipment are mainly reported. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(3): 40,47, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20906 [source] A Model of Ischemically Induced Ventricular Fibrillation for Comparison of Fixed-dose and Escalating-dose Defibrillation StrategiesACADEMIC EMERGENCY MEDICINE, Issue 6 2004James T. Niemann MD Abstract Objectives: Fixed- and escalating-dose defibrillation protocols are both in clinical use. Clinical observations suggest that the probability of successful defibrillation is not constant across a population of patients with ventricular fibrillation (VF). Common animal models of electrically induced VF do not represent a clinical VF etiology or reproduce clinical heterogeneity in defibrillation probability. The authors hypothesized that a model of ischemically induced VF would exhibit heterogeneous defibrillation shock strength requirements and that an escalating-dose strategy would more effectively achieve prompt defibrillation. Methods:Forty-six swine were randomized to fixed, lower-energy (150 J) transthoracic shocks (group 1) or escalating, higher-energy (200 J,300 J,360 J) shocks (group 2). VF was induced by balloon occlusion of a coronary artery. After 1 or 5 minutes of VF, countershocks with a biphasic waveform were administered. The primary endpoint was successful defibrillation (termination of VF for 5 seconds) with ,3 shocks. Results: VF was induced with occlusion or after reperfusion in 35 animals. Only five of 17 group 1 animals (29%, 95% CI = 10 to 56) could be defibrillated with ,3 shocks; 15 of 18 group 2 animals (83%, 95% CI = 59 to 96) were defibrillated with ,3 shocks (p < 0.002 vs. group 1). Nine of the group 1 animals (75%) that could not be defibrillated with 150-J shocks were rescued with ,3 shocks ranging from 200 to 360 J. Conclusions: In this ischemic VF animal model, defibrillation shock strength requirements varied among individuals, and when defibrillation was difficult, an escalating-dose strategy was more effective for prompt defibrillation than fixed, lower-energy shocks. [source] A Versatile System for Arbitrary Function Large-Amplitude Fourier Transformed VoltammetryELECTROANALYSIS, Issue 13 2007Lishi Wang Abstract A novel low-cost instrument for arbitrary function large-amplitude Fourier transformed voltammetry was developed. Description of both hardware and software was given in detail in this paper. A micro-control-unit (MCU) in combination with a field programmable gate array (FPGA) was designed to act as the controller of the instrument. Profiting from the built-in USB2.0 standard interface of the MCU, vast amount of data to/from the high resolution digital-to-analog converter (DAC)/analog-to-digital converter (ADC) then could be exchanged with computer in real-time, instead of being temporarily stored at the capacity limited memory of the instrument which always restricted the length of sampling time and the size of the collected data set. In the [Fe(CN)6]4+/3+ system, by superimposing a sinusoidal waveform with an amplitude of 120,mV onto a triangular potential and then applying to a macro electrode through the instrument, voltammograms up to the eighth harmonic could be well resolved by FT-IFT method. Excellent agreement was attained with Bond's similar experiment [Anal. Chem. 76 (2004) 3619] in respect of the shape and relative peak height of each harmonic. With the simply structured instrument, stable performance, flexible and versatile function was achieved. Arbitrary forms of AC perturbation which may not necessarily be sinusoidal or square-wave or other regular formed periodic signal could be synthesized and superimposed onto a DC potential as the excitation signal with this instrument. Some more useful electrode process information was expected to unveil by utilizing the FT-IFT algorithm to dissect the response signal. [source] Coupling Capillary Electrophoresis and Pulsed Electrochemical DetectionELECTROANALYSIS, Issue 13 2005Carlos Abstract Pulsed electrochemical detection (PED) is an excellent method for detection of analytes that normally foul electrodes. In PED, the detection electrode is first cleaned at a high positive potential, then reactivated at a negative potential dissolving the surface oxide, and finally used to oxidize the analyte at a moderate positive potential. Due to the advantages and versatility of PED, many different variations of the detection waveform can be found in literature. This review focuses on application of PED to CE and in particular, the most commonly used modes: pulsed amperometric detection (PAD) and integrated pulsed amperometric detection (iPAD). [source] | ||||||||||||||||||||||||||||||||||||||||||||||