High Frequency Low Amplitude Research Articles

Measurement of elastic nonlinearity using remote laser ultrasonics and CHeap Optical Transducers and dual frequency surface acoustic waves

A nonlinear ultrasonic technique for evaluating material elastic nonlinearity has been developed. It measures the phase modulation of a high frequency (82 MHz) surface acoustic wave interacting with a low frequency (1 MHz) high amplitude stress inducing surface acoustic wave. A new breed of optical transducers has been developed and used for the generation and detection of the high frequency wave. The CHeap Optical Transducer (CHOT) is an ultrasonic transducer system, optically activated and read by a laser. We show that CHOTs offer advantages over alternative transducers. CHOTs and nonlinear ultrasonics have great potential for aerospace applications. Results measuring changes in ultrasonic velocity corresponding to different stress states of the sample are presented on fused silica and aluminium.

Low Amplitude High Frequency Atomic Force Microscopy

Heterodyne laser Doppler interferometry was used to implement a high frequency atomic force microscope (AFM) that can accommodate a cantilever with a natural frequency of up to 200 MHz. Since Doppler interferometry measures velocity, the signal level increases proportionally with frequency for a given amplitude of oscillation, or the noise floor in terms of displacement decreases with 1/f. A noise level of 0.5 fm/√Hz was attained around 2 MHz, giving a large signal to noise margin for high frequency cantilevers and higher vibration mode detection. We have so far confirmed the following: (i) atomic resolution of Si(111) 7×7 with an amplitude of drive as low as 0.03 nm at 1.6 MHz, (ii) true atomic resolution dynamic lateral force microscopy, (iii) lateral force gradient detection at the atomic level, (iv) manipulation of Si atoms at room temperature, (v) vibration measurement of Si nanowires, tungsten oxide whiskers and graphene cantilevers above 100 MHz, (vi) atomic resolution imaging with the 2nd and 3rd mode of deflection and (v) true atomic resolution imaging in water using deflection or torsion with a few 10 pm amplitude of drive.

High frequency (900 MHz) low amplitude (5 V m−1) electromagnetic field: a genuine environmental stimulus that affects transcription, translation, calcium and energy charge in tomato

Using an especially-designed facility, the Mode Stirred Reverberation Chamber, we exposed tomato plants (Lycopersicon esculentum Mill. VFN8) to low level (900 MHz, 5 V m(-1)) electromagnetic fields for a short period (10 min) and measured changes in abundance of three specific mRNA soon after exposure. Within minutes of electromagnetic stimulation, stress-related mRNA (calmodulin, calcium-dependent protein kinase and proteinase inhibitor) accumulated in a rapid, large and 3-phase manner typical of an environmental stress response. Accumulation of these transcripts into the polysomal RNA also took place (indicating that the encoded proteins were translated) but was delayed (indicating that newly-synthesized mRNA was not immediately recruited into polysomes). Transcript accumulation was maximal at normal Ca(2+) levels and was depressed at higher Ca(2+), especially for those encoding calcium-binding proteins. Removal of Ca(2+) (by addition of chelating agents or Ca(2+) channel blocker) led to total suppression of mRNA accumulation. Finally, 30 min after the electromagnetic treatment, ATP concentration and adenylate energy charge were transiently decreased, while transcript accumulation was totally prevented by application of the uncoupling reagent, CCCP. These responses occur very soon after exposure, strongly suggesting that they are the direct consequence of application of radio-frequency fields and their similarities to wound responses strongly suggests that this radiation is perceived by plants as an injurious stimulus.

Exercise‐induced modulation of calcineurin activity parallels the time course of myofibre transitions

This study establishes a causal link between the limitation of myofibre transitions and modulation of calcineurin activity, during different exercise paradigms. We have designed a new swimming-based training protocol in order to draw a comparison between a high frequency and amplitude exercise (swimming) and low frequency and amplitude exercise (running). We initially analysed the time course of muscle adaptations to a 6- or 12-week swimming- or running-based training exercise program, on two muscles of the mouse calf, the slow-twitch soleus and the fast-twitch plantaris. The magnitude of exercise-induced muscle plasticity proved to be dependent on both the muscle type and the exercise paradigm. In contrast to the running-based training which generated a continuous increase of the slow phenotype throughout a 12-week training program, swimming induced transitions to a slower phenotype which ended after 6 weeks of training. We then compared the time course of the exercise-induced changes in calcineurin activity during muscle adaptation to training. Both exercises induced an initial activation followed by the inhibition of calcineurin. In the muscles of animals submitted to a 12-week swimming-based training, this inhibition was concomitant with the end of myofibre transition. Calcineurin inhibition was a consequence of the inhibition of its catalytic subunit gene expression on one hand, and of the expression increase of the modulatory calcineurin interacting proteins 1 gene (MCIP1), on the other. The present study provides the first experimental cues for an interpretation of muscle phenotypic variation control.

The changes of electrocardiography and signal-averaged electrocardiography after surgical repair of Tetralogy of Fallot

Purpose : The purpose of this study was to analyze the changes of the late potential of Signal- averaged electrocardiography (SAECG) and Electrocardiography (ECG) parameters during follow up of those who had taken surgical repair of Tetralogy of Fallot (TOF). Methods : Nine patients who had taken surgical repair of TOF since 1985 checked SAECG and standard 12 leads ECG twice in 1999 and 2005 in Kyungpook national university hospital. We evaluated changes of QRS duration, QT interval and JT interval, QRS dispersion, QT dispersion and JT dispersion of standard 12 leads ECG and Filtered QRS (f-QRS), High frequency low amplitude potential (HFLA), Root mean square in terminal 40 ms (RMS) and Mean voltage in terminal 40 ms (MV) of SAECG between in 1999 and 2005. Results : There were significant decrease of JT dispersion (101.11±50.11 vs 71.11±22.61 ms, P

Automatic removal of high-amplitude artefacts from single-channel electroencephalograms

In this work, we present a method to extract high-amplitude artefacts from single channel electroencephalogram (EEG) signals. The method is called local singular spectrum analysis (local SSA). It is based on a principal component analysis (PCA) applied to clusters of the multidimensional signals obtained after embedding the signals in their time-delayed coordinates. The decomposition of the multidimensional signals in each cluster is achieved by relating the largest eigenvalues with the large amplitude artefact component of the embedded signal. Then by reverting the clustering and embedding processes, the high-amplitude artefact can be extracted. Subtracting it from the original signal a corrected EEG signal results. The algorithm is applied to segments of real EEG recordings containing paroxysmal epileptiform activity contaminated by large EOG artefacts. We will show that the method can be applied also in parallel to correct all channels that present high-amplitude artefacts like ocular movement interferences or high-amplitude low frequency baseline drifts. The extracted artefacts as well as the corrected EEG will be presented.

Long-term follow-up of the signal-averaged ECG in arrhythmogenic right ventricular cardiomyopathy: correlation with arrhythmic events and echocardiographic findings

The aims of our study were to evaluate late potential changes during long-term follow-up in patients with arrhythmogenic right ventricular cardiomyopathy (ARVC) and to correlate these results with echocardiographic findings and sustained ventricular tachycardia (VT) occurrence. We studied 31 patients (22 males and 9 females; mean age 29+/-16) during 8 years of follow-up by signal-averaged ECG (SAECG) and echocardiography. Ten subjects experienced episodes of sustained VT. During follow-up, all the SAECG parameters showed a progressive significant increase in late potentials. In contrast, echocardiographic indices did not show evidence of relevant modifications. Patients with sustained VT were characterized by significantly lower left and right ventricular ejection fractions, longer values of filtered QRS at 25/40/80-250 Hz filters, and longer high-frequency low-amplitude (HFLA) signals at 25-250 Hz at baseline. The analysis of SAECG modification during follow-up indicated that only HFLA signals at 25-250 Hz increased significantly in the sustained VT group. We detected a progressive increase in delayed ventricular conduction by SAECG not associated with significant echocardiographic changes. Therefore, the conduction disturbance seems to increase independently from anatomical alterations. The baseline SAECG and echocardiographic parameters, more than their modifications during follow-up, appear to be useful in identifying patients with sustained VT.

Acoustic emission mapping of diesel engines for spatially located time series—Part II: Spatial reconstitution

In this study the characteristics of AE wave transmission around and through the cylinder head of a small four-stroke fuel injection diesel engine are investigated. Two sets of measurements have been carried out, one with simulated sources at various points on the cylinder head and one with the engine running, using a nine-sensor array. Propagation of AE waves from the simulated sources to the array sensor positions indicates attenuation factors of around 8.5. It is important to be able to estimate source–sensor distance accurately and this has been done using a threshold technique to identify the arrival time of a low frequency high amplitude wave at the sensors, then to deduce the wave speed from that information and hence calculate the source–sensor distance (transmission path length). Engine running tests were carried out and analysis focused on reconstitution of injector and exhaust valve opening events using signal mapping techniques. For injector events, the attenuation factors were similar to those measured from the simulated sources. For exhaust valve-opening events the attenuation factors varied between 5 and 7 with relatively poor correlation. This difference is thought to be due to variation in the actual source position during valve opening because the exhaust valve actuation involves a cam, push rod and rocker design. The results can be used to reconstitute the timing and amplitude of the AE emitted at the source which enables much more focussed monitoring of specific components and processes identified in the signals.

Characterization of Functional and Morphological Changes in a Rat Model of Colitis Induced by Trichinella spiralis

We intended to characterize the effect of inflammation on the spontaneous colonic motility pattern and the role of iNOS in its disruption in colitis. Colitis was induced by an intracolonic enema of T. spiralis larvae. Animals were studied 2-30 days postinfection (PI). Standard H&E and iNOS staining was performed on colonic sections. Altered stool consistency was found from day 1 to day 21 PI; leukocytosis peaked on days 6-21 PI. Edema and cell infiltration were found in mucosa and submucosa (days 2-14 PI). Contractility displayed a disorganized pattern with decreased high-amplitude, low-frequency (HALF) contractions. A progressive fading of spontaneous activity was observed and was partly restored in strips devoid of submucosa. iNOS immunoreactivity increased in epithelial and infiltrating cells (days 2-14 PI). In this model of colonic inflammation, the decrease in spontaneous contractility, which might be caused by NO generated from mucosal and submucosal iNOS, bears some traits with changes observed in ulcerative colitis and might thus be useful to study the dismotility observed in this human disease.

Spontaneous Epileptic Rats Show Changes in Sleep Architecture and Hypothalamic Pathology

The goal of the present study was to investigate the relationship between sleep, hypothalamic pathology, and seizures in spontaneous epileptic rats. Rats were implanted with radiotelemetry transmitters for measuring electrocorticogram (ECoG) and stimulation electrodes in the hippocampus. Epileptogenesis was triggered by 2 h of electical stimulation-induced self-sustained status epilepticus (SSSE). After SSSE, ECoGs were monitored over a 15-week period for the occurrence of interictal high-amplitude low-frequency (HALF) acitvity and spontaneous reoccurring seizures (SRSs). Spontaneous epileptic rats showed clinical features of temporal lobe epilepsy (TLE), such as spontaneous seizures, interictal activity and neuronal cell loss in the dorsomedial hypothalamus, a region important for normal sleep regulation. Interestingly, epileptic rats showed disturbances in sleep architecture, with a high percentage of the seizures occurring during sleep. Therefore we conclude that a close association exists between epileptiform activity and alterations in sleep architecture that may be related to hypothalamic pathology.

Well-posedness for the Benney-Roskes/Zakharov- Rubenchik system

We consider the system obtained by D. J. Benney-G. J. Roskes and V. E. Zakharov-A. M. Rubenchik to model the interaction of low amplitude high frequency waves with low frequency, acoustic type waves. We reduce it to a nonlinear Schrödinger equation with nonlinear terms involving nonlocal terms and derivatives of the unknown. Using various smoothing effects associated to the Schrödinger group and the structure of the nonlinearity we prove that the Cauchy problem is locally well-posed in $H^s(\mathbb R^n), s>n/2$ where $n=2,3$.

On Non-Ideal Simple Portal Frame Structural Model: Experimental Results under a Non-Ideal Excitation

We present measurements of the non-linear oscillations of a portal frame foundation for a non-ideal motor. We consider a three-time redundant structure with two columns, clamped in their bases and a horizontal beam. An electrical unbalanced motor is mounted at mid span of the beam. Two non-linear phenomena are studied: a) mode saturation and energy transfer between modes; b)interaction between high amplitude motions of the structure and the rotation regime of a real limited power motor. The dynamic characteristics of the structure were chosen to have one-to-two internal resonance between the anti-symmetrical mode (sway motions) and the first symmetrical mode natural frequencies. As the excitation frequency reaches near resonance conditions with the 2nd natural frequency, the amplitude of this mode grows up to a certain level and then it saturates. The surplus energy pumped into the system is transferred to the sway mode, which experiences a sudden increase in its amplitude. Energy is transformed from low amplitude high frequency motion into high amplitude low frequency motion. Such a transformation is potentially dangerous. We consider the fact that real motors, such as the one used in this study, have limited power output. In this case, this energy source is said to be non-ideal, in contrast to the ideal source whose amplitude and frequency are independent of the motion of the structure. Our experimental research detected the Sommerfeld Effect: as the motor accelerates to reach near resonant conditions, a considerable part of its output energy is consumed to generate large amplitude motions of the structure and not to increase its own angular speed. For certain parameters of the system, the motor can get stuck at resonance not having enough power to reach higher rotation regimes. If some more power is available, jump phenomena may occur from near resonance to considerably higher motor speed regimes, no stable motions being possible between these two.

Climate and seismicity in the higher Central Himalaya during 20–10 ka: evidence from the Garbayang basin, Uttaranchal, India

In the Trans-Himalaya, the Trans-Himadri fault (THF) controlled the extent of past glaciers. The rivers were impounded by glacial debris resulting in the formation of lakes that recorded regional climatic and seismic events. One such lake formed at Garbayang, where the upper 28 m lacustrine succession spanned an age range of 20–10 ka. Magnetic susceptibility and sedimentological data suggest that the region experienced high amplitude low frequency millennial scale climate changes during the period 20±3 and 13±2 ka followed by low amplitude high frequency changes from 13±2–11±1 ka. A sudden drop in magnetic susceptibility and elemental concentration of layers dated at ∼11–12 ka suggests cooling associated with the Younger Dryas. Occurrence of faulted strata/seismites during 20–17 and 14–13 ka suggests recent activation of the THF. This is noteworthy, as the THF has been considered dormant since its last reactivation at 11 Ma. Further, the luminescence dates suggest that radiocarbon ages on organic carbon are grossly overestimated due to a hard water effect caused by the dominance of limestone in the lake catchment. This implies that earlier, radiocarbon based palaeoenvironmental reconstruction in the region, will need revalidation.

Climate and seismicity in the higher Central Himalaya during 20–10 ka: evidence from the Garbayang basin, Uttaranchal, India

Abstract In the Trans-Himalaya, the Trans-Himadri fault (THF) controlled the extent of past glaciers. The rivers were impounded by glacial debris resulting in the formation of lakes that recorded regional climatic and seismic events. One such lake formed at Garbayang, where the upper 28 m lacustrine succession spanned an age range of 20–10 ka. Magnetic susceptibility and sedimentological data suggest that the region experienced high amplitude low frequency millennial scale climate changes during the period 20±3 and 13±2 ka followed by low amplitude high frequency changes from 13±2–11±1 ka. A sudden drop in magnetic susceptibility and elemental concentration of layers dated at ∼11–12 ka suggests cooling associated with the Younger Dryas. Occurrence of faulted strata/seismites during 20–17 and 14–13 ka suggests recent activation of the THF. This is noteworthy, as the THF has been considered dormant since its last reactivation at 11 Ma. Further, the luminescence dates suggest that radiocarbon ages on organic carbon are grossly overestimated due to a hard water effect caused by the dominance of limestone in the lake catchment. This implies that earlier, radiocarbon based palaeoenvironmental reconstruction in the region, will need revalidation.

Effect of dietary energy and protein density on body composition, attainment of puberty, and ovarian follicular dynamics in dairy heifers.

The objectives were to examine the effects of dietary energy and protein density on age and body composition at puberty, and on ovarian follicular dynamics during the pre- and peripubertal periods in Holstein heifers. In Phase 1, heifers were randomly allotted (n=10 per diet) at 100 kg body weight (BW) to diets with either low (P1L), medium (P1M) or high (P1H) energy and protein formulated for an average daily gain (ADG) of 0.5, 0.8 or 1.1 kg per day, respectively. During Phase 2 (P2), all heifers were fed ad libitum a common diet formulated for an ADG of 0.8 kg per day. Half the animals within the high (n=5) and low groups (n=5) entered P2 either at 12 months of age (P2H-12; P2L-12) or at 330 kg BW (P2H-330; P2L-330). Heifers fed P1H, P1M, P1L, and P2L-12 diets attained puberty at approximately 9, 11, 16, and 14 months of age, respectively (P<0.01). Urea space estimates of body fat and protein percent, and back-fat thickness, were lower in P1L heifers compared to P1H or P1M heifers at similar chronological ages (P<0.05) but did not differ at puberty (P>0.10). Compared to P1L heifers, P1H heifers had high amplitude LH pulses at 8 months, and high frequency low amplitude LH pulses at 10 months of age (P<0.05). The mean diameter (mm) of the dominant follicle was smaller (P<0.05) in P1L heifers (10.6) compared to P1H (12.8) or P1M (12.2) heifers at 8 months. Maximum size and growth rate of the nonovulatory dominant follicle increased with age (P<0.05) but did not differ between P1H and P1M heifers at puberty. The diameter (mm) of the nonovulatory dominant follicle, and the first and second ovulatory follicles were larger in P2L-12 heifers (14.0, 14.7, and 14.9) compared to P1M heifers (13.1, 12.5, and 11.9), while the peak progesterone levels and CL growth were lower (P<0.05) in the first cycle. In conclusion, dairy heifers attained puberty at a constant body weight and body composition independent of dietary manipulation, the size of dominant follicles increased with age in association with increased LH support, and heifers realimented from a low energy diet developed larger first ovulatory follicles and smaller CL with lower peak progesterone concentrations in the first cycle.

Electrical stunning of cattle

Cattle are normally stunned electrically by three sequential cycles, first a three-second head-only cycle, to stun the animal, secondly a 15-second cardiac cycle, to induce ventricular fibrillation (cardiac arrest), and...

The short-term and long-term reproducibility of spectral turbulence and late potential variables of the signal-averaged ECG in a population sample of healthy subjects and the impact of gender, age, and noise

Previous methods for frequency domain analysis of the signal-averaged ECG (SAECG) have had low reproducibility. The reproducibility of time domain late potential analysis and spectral turbulence analysis was evaluated with 2 immediately consecutive SAECG recordings in 121 randomly selected subjects without heart disease (short-term) and also in 47 subjects after 1 month (longterm). A test was late potential positive if 2 or more of 3 variables were outside the reference limits and spectral turbulence positive if the score was 3 or 4. The short-term reproducibility was high for the filtered QRS duration (FQRSD), root mean square amplitude of the last 40 ms (RMS40) and high frequency low amplitude signals less than 40 μV (HFLAS40) of the time domain and total QRS duration (TQRSD), power spectral density of the last 40 ms and the late potential duration of time domain analogous analyses. The Spearman rank order correlation coefficients were 0.89, 0.88, and 0.84 and 0.97, 0.91 and 0.97, respectively. The reproducibility of the spectral score variables varied, and the correlation for the low slice correlation ratio was 0.71, spectral entropy 0.61, interslice correlation mean 0.58, and interslice correlation SD 0.28. A diagnostic inconsistency between 2 tests occurred in 0 (0%) subjects in late potential analysis if FQRSD was required for positivity, and in 7 (6%) otherwise, and in 9 (7%) of spectral turbulence analysis. If the spectral variable mean peaks per slice, with a correlation of 0.89, replaced interslice correlation SD in the spectral score, diagnostic inconsistency occurred in 0 (0%) subjects. The reproducibility seemed higher in women and in younger people but significantly only for interslice correlation subjects mean and HFLAS40. The long-term reproducibility did not differ significantly from shortterm for any variable. In conclusion, the reproducibility was high in all time domain and time domain analogous variables. It varied among the spectral turbulence score variables and was very low for interslice correlation SD. The reproducibility of the spectral score improved substantially if this variable was replaced by mean peaks per slice.

Transthoracic electrical impedance during external defibrillation: comparison of measured and modelled waveforms

The transthoracic electrical impedance is an important defibrillation parameter, affecting the defibrillating current amplitude and energy, and therefore the defibrillation efficiency. A close relationship between transthoracic impedance and defibrillation success rate was observed. Pre-shock measurements (using low amplitude high frequency current) of the impedance were considered a solution for selection of adequate shock voltages or for current-based defibrillation dosage. A recent approach, called `impedance-compensating defibrillation' was implemented, where the pulse duration was controlled with respect to the impedance measured during the initial phase of the shock. These considerations raised our interest in reassessment of the transthoracic impedance characteristics and the corresponding measurement methods. The purpose of this work is to study the variations of the transthoracic impedance by a continuous measurement technique during the defibrillation shock and comparing the data with results obtained by modelling. Voltage and current impulse waveforms were acquired during cardioversion of patients with atrial fibrillation or flutter. The same type of defibrillation pulse was taken from dogs after induction of fibrillation. The electrodes were located in the anterior position, for both the patients and animals.

Noninvasive vascular ultrasound: an asset in vascular medicine.

### 1.1 Introduction There are always moments in life, inviting to look back on the past. Entering the next millennium is certainly such an occasion, because it happens generally only once in a life-time. Therefore, we very much liked the idea of the Editors to publish a special issue of Cardiovascular Research on the occasion of this event and to explore the impact of the articles in the journal most frequently cited over the years on further developments in the field. We gladly accepted their invitation to evaluate in this respect the article by Levenson et al. published in Cardiovascular Research in 1981 [1]. ### 1.2 Content of the article In this article the authors described an ultrasound system to assess diameter, blood flow velocity and volume flow in the brachial artery in man. The apparatus consisted of an adjustable range-gated pulsed Doppler system, emitter frequency 8 MHz, combined with a double transducer system to accurately determine the angle between ultrasound beam and vessel axis. The latter is a prerequisite for accurate determination of both the velocity in and the diameter of the artery and, hence, for proper calculation of volume flow. The length of the sample volume could be adjusted by varying the length of the reception duration. A small sample volume was used to measure velocity locally in the artery and to determine the diameter of the vessel accurately and a large one to estimate the average velocity over the cross-sectional area of the vessel. A static high-pass filter with a lower cut-off frequency of 250 Hz was used to reduce interference of high amplitude low frequency signals reflected by the arterial walls. The validity of the system was tested in an in vitro set-up and the results showed that the diameter as assessed with the system compared favorably with the diameter of the tubing in …

Electroencephalographic responses to the formalin test in rats

The formalin test is an animal model of persistent pain. Although biphasic behavioral responses to formalin injection have been well described, the significance of the biphasic time course of the pain behaviors has not been established. To explore the significance of the behavioral responses to the formalin injection, we measured and analyzed cortical electroencephalogram (EEG) during the formalin tests in rats. Formalin was injected subcutaneously in the hindpaw of freely moving rats, and behavioral responses were visually counted and recorded. Results were compared with a control group which received saline injection. Neocortical EEG was recorded from implanted dural surface electrodes and analyzed using a Fast Fourier Transformation. Formalin produced biphasic pain behaviors with a transient pause between two phases. Cortical EEG recordings showed a biphasic change; a vigilant pattern (a low amplitude high frequency activity) followed by a non-vigilant pattern (a high amplitude low frequency activity), showing a good correlation with apparent arousal states of rats. Observed discrepancies between pain behaviors and EEG-measured vigilance stages included (1) a vigilant EEG pattern persisted during the transient pause of pain behavior, and (2) pain behaviors persisted even after non-vigilant EEG pattern became dominant. The results of the current study showed that there are temporal discrepancies between the pain behaviors and EEG-measured vigilance during the formalin test in rats. The temporal relationship between the `pain' behaviors and nociception per se may not be as solid as believed.