Variation In Dominant Frequency Research Articles

Abstract 14782: Expression of Ngf Shrna in the Left Atrial Appendage Alone is Sufficient to Attenuate Global Left Atrial Parasympathetic and Sympathetic Nerve Sprouting and Resulting Development of Persistent Atrial Fibrillation in a Canine Model

Introduction: The autonomic nervous system plays a major role in development of atrial fibrillation (AF), with evidence of marked autonomic remodeling in a canine rapid atrial pacing (RAP) model of AF. Nerve growth factor (NGF), a neurotrophin essential for peripheral neuron growth, was upregulated in fibrillating atria, particularly in the left atrial appendage (LAA). Hypothesis: Inhibiting NGF signaling in the entire atria or the LAA alone can prevent the development of AF. Methods: NGF shRNA was injected in both atria or in the LAA of dogs followed by electroporation to facilitate gene delivery. Animals were subjected to RAP for up to 12 weeks. Duration of AF was recorded. At terminal EP study, residual AF electrograms were recorded in the posterior left atrium, left atrial free wall and LAA for analysis of AF characteristics. Tissue of each region was used for IHC with markers for parasympathetic (acetylcholinesterase) or sympathetic nerves (dopamine beta-hydroxylase). Results: Controls (n=10) developed persistent AF (>8 hours) after a median of 14 days. In contrast, pan-atrial NGF shRNA animals (n=4) never developed this burden of AF. Residual AF was less fractionated (longer fractionation interval), more organized (higher organization index and lower Shannon's entropy) and more homogeneous (coefficient of variation of dominant frequency). RAP-induced nerve bundle hypertrophy and atrial myocardium hyperinnervation was significantly attenuated in pan-atrial NGF shRNA dogs. Importantly, these findings were reproduced when NGF shRNA injection was limited to the LAA alone (n=4), with prevention of development of persistent AF, and global attenuation of left atrial hyperinnervation. Conclusion: Targeted inhibition of atrial autonomic remodeling by NGF shRNA prevents development of persistent AF. NGF Inhibition in the LAA alone is sufficient to attenuate global atrial autonomic remodeling. This approach may lead to a novel, mechanism-guided therapy for AF.

Experimental study on the effect of swaying period and swaying amplitude on the dominant frequency of steam submerged jets pressure oscillation with vertically upward low mass flux

With the rapid development of nuclear energy under ocean conditions, the pressure oscillation of steam submerged jets will intensify under ocean conditions, causing great harm to related equipment. Therefore, an experimental study is conducted to investigate the dominant frequency of steam submerged jets pressure oscillation under swaying conditions. In the experiment, the variation in dominant frequency of pressure oscillation with swaying amplitude and period is studied. The experimental results show that compared with motionless conditions, the swaying motion not only enhances the condensation of steam bubbles in the water, but also enhances the instability of the steam bubbles, resulting in an increase in dominant frequency. The dominant frequency increases with the increase in swaying amplitude and decreases with the increase in swaying period. Considering the influence of swaying motion, this study proposes to use Res and Ref to represent the influence of steam mass flux and water velocity on the dominant frequency of pressure oscillation, respectively. The results show that St increases with the increase in Ref. In addition, the experimental correlation considering the influence of swaying motion on the dominant frequency of pressure oscillation is used to predict the dominant frequency of pressure oscillation, and the maximum deviation is less than ±15%.

Impacts of Reservoir Water Level Fluctuation on Measuring Seasonal Seismic Travel Time Changes in the Binchuan Basin, Yunnan, China

An airgun source in a water reservoir has been developed in the past decade as a green active source that had been proven effective to derive short-term subsurface structural changes. However, seasonal water level fluctuation in the reservoir affects the airgun signal, and thus whether the airgun signals can be used to derive robust seasonal variation in subsurface structure remains unclear. We use the airgun data observed in the Binchuan basin to estimate the seasonal variation of seismic travel time and compare the results with those derived from ambient noise data in the same frequency band. Our main observation is that seasonal change δt/t from airgun is negatively correlated to the variation of dominant frequency and water table fluctuation in the reservoir. One possible explanation is that water table fluctuation in the reservoir affects the dominant frequency of the airgun signal and causes significant phase shift. We also compute the travel time changes in P-wave from the empirical Green’s function after deconvolving the waveforms from a reference station that is 50 m from the airgun source. The dominant frequency after deconvolution still shows seasonal variation and correlates inversely to the travel time changes, suggesting that deconvolution cannot completely eliminate the source effect on travel time changes. We also use ambient noise cross-correlation to retrieve coda waves and then derive travel time changes in monthly stacked cross-correlations relative to a yearly average cross-correlation. We observe that seismic travel time increases to its local maximum in the end of August. The travel time changes lag behind the precipitation for about one month. We apply a poroelastic physical model to explain seismic travel time changes and find that a combined effect from precipitation and evaporation might induce the seasonal changes as shown in the ambient noise data. However, the pattern of travel time changes from the airgun differs from that from ambient noise, reflecting the strong effects of airgun source property changes. Therefore, we should be cautious to derive long-term subsurface structural variation from the airgun source and put more attention on stabilizing the dominant frequency of each excitation in the future experiments.

Charge migration in caffeine: A real‐time time‐dependent density functional theory study

AbstractWe present a real‐time time dependent density functional theory approach to simulate charge migration of caffeine molecule after selective photoionization. According to the fact that the time evolution of the created hole can affect the molecular reaction and subsequent dynamics difference from its original structure, we studied the dominant frequency variation of caffeine charge oscillation after ionization of outer shell orbital. In this work, we determined the main orbitals participating in the total charge migration process by comparing the dipole moment peaks to the Fourier signals of the time dependent molecular orbitals (MOs) occupation. Having used the Bader charge analysis, we showed that different valence ionization of molecule resulted in a distinct charge migration between different regions, functional groups, and atoms of cations. We represented two interesting different cases: 1‐for ionization out from 46th MO of caffeine, the MOs interfere of the cation resulted in a charge migration between oxygen atoms and upper nitrogen of five‐membered ring, 2‐ for ionization out from 39th MO of caffeine, a different behavior of hole occurred according to which the hole spread throughout the whole molecule. Therefore, a specific MO ionization could result in a dramatically different migration and active site of cation.

Computer vision‐based real‐time cable tension estimation in Dubrovnik cable‐stayed bridge using moving handheld video camera

Cables are essential components of the cable-stayed bridges as they serve as the main load-bearing component. Hence, continuous monitoring of such cables becomes necessary as they are vulnerable to the fatigue damage induced by dynamic loads. Sensors are attached to the cables to examine the health of the cables; however, these contact-based sensors can malfunction in harsh weather condition, which makes impossible to estimate the cable health in such unfavorable condition. Therefore, in this paper, we propose a completely noncontact video-based stay-cable tension measurement technique where the video is recorded using a moving handheld camera at a significant distance from the structure itself. Here, the cable tension is determined from vibration-based measurement, but the vibration of the cable recorded in the video includes the true vibration of the cable along with the camera motion. Hence, we amalgamated a series of image processing techniques to nullify the camera movement. First, we detect the camera movement based on the movement of the bridge deck and pylon, which are fixed objects, using Kanade–Lucas–Tomasi (KLT) feature tracking algorithm. Then we nullify the camera movement by using the affine transformation matrix obtained by random sample consensus (RANSAC) algorithm. Subsequently from the steady video, the cable motions are estimated using the phase-based motion estimation technique. From the time history of the cable vibration, real-time frequency variations are estimated using Short-Time Fourier Transform (STFT). Finally, the real-time tension is determined from this dominant frequency variation history using the taut-string theory. This paper shows the significant potential of camera-based sensing techniques in structural health monitoring as the mean estimated tension and the design cable tension are found to be comparable.

Dominant frequency characteristics analysis of reclosing transient overvoltage in 10 kV cable-overhead hybrid line

Studying the characteristics of reclosing overvoltage is of great importance for risk assessment of reclosing in the cable-overhead hybrid networks because transient overvoltage (TOV) at different dominant frequency can have quite different negative effect to cable insulation. In a hybrid line, when a cable connects with an overhead line (OHL), the surge propagation can become very complex. To clarify the frequency characteristics of the reclosing transient overvoltage in a 10kV hybrid line, in this paper, the simulations are carried out using ATP-EMTP (Alternative Transients Program, Electro-Magnetic Transients Program). The traditional approach to estimate the dominant frequency is suitable for pure cable-based or overhead line-based networks. However, for a hybrid line, due to the difference in line parameters between the cable and OHL, the characteristics of dominant frequency is investigated based on the distributed-parameter theory with new boundary conditions at the junction. According to the variation of dominant frequency considering the source impedance and the wave propagation in the modal domain, the non-monotonous variation of TOV with cable proportion is analyzed. The frequency calculation and the TOV analysis are verified by ATP-EMTP simulation.

Vicente´s poison frog (Oophaga vicentei) in the wild: calling activity, bioacoustics and diet

Calling activity, bioacoustics and the diet of males is reported for three different populations of Oophaga vicentei in central Panama. Calling activity was predicted by time of day, season and temperature with peaks between 08:00 h to 10:00 h and was more frequent during the dry season. Only at one location was calling activity positively correlated with air temperature. The temperature was also positively correlated with call repetition rates and negatively with call duration. Within the ten first calls of a call-bout, there was a cline variation in dominant frequency, call duration and silent intervals. The stomach contents of males comprised mainly insects but also a large number of oribatid mites.

Comparative Study of Tunnel Blast-Induced Vibration on Tunnel Surfaces and Inside Surrounding Rock

In tunnel blast applications, vibration monitors are typically placed on tunnel surfaces to measure the responses of rock to explosion loads for statutory compliance. Few publications in the open literature have focused on the differences between the blasting vibration on tunnel surfaces and inside the surrounding rock. During blasting excavation of the experimental tunnels in the China Jinping Underground Laboratory, velocity sensors were arranged both on the tunnel walls and inside the surrounding rock to monitor far-field vibrations. In this paper, the vibration characteristics on the tunnel surfaces and inside the surrounding rock are presented based on the recorded field data. Corresponding empirical formulae for peak particle velocity (PPV) attenuation and dominant frequency variation are derived from these data. A three-dimensional dynamic finite-element model is used to verify the site survey results. The field and numerical studies show that compared with the inside vibration, the tunnel surface vibration has a higher, more readily attenuated PPV and a lower frequency with a slower rate of decline in the dominant frequency. The mechanisms that cause the differences between the surface and inside vibration are discussed in detail. The tunnel surface vibration in the far field is dominated by surface waves, which occupy more than 75% of the total vibrational energy. For this reason, the results presented in this paper do not apply to vibration in the near field, where body waves are expected to be dominant.

The aggressive call of Dendropsophus cruzi (Pombal Bastos, 1998) (Anura; Hylidae) in Central Brazil.

Dendropsophus cruzi (Pombal Bastos, 1998) is a small hylid (male snout-to-vent length = 16.3-19.4 mm; female SVL = 21.3-25.0 mm) that is allocated in the D. microcephalus group (Faivovich et al. 2005). It is commonly found in Open and forested areas from Central Brazil to Provincia Velasco, Departamento de Santa Cruz, Bolivia (Frost 2017; Tessarolo et al. 2016). Pombal Bastos (1998) described the advertisement call of D. cruzi as a single pulsed note. Posteriorly, studies uncovered relationships between dominant frequency variation in the advertisement calls of D. cruzi and variation in the SVL and mass of males (Bastos et al. 2003), as well as the existence of a clinal geographic pattern in the variation of acoustic parameters of these calls (Tessarolo et al. 2016). However, the acoustic communication in anurans is usually mediated by more than one vocalization type (Toledo et al. 2015). Due the importance of call types in the social context of anurans (e.g., Reichert 2011; Forti et al. 2017), we expand the vocal repertoire of D. cruzi by describing its aggressive call.

Long recording sequences: how to track the intra-individual variability of acoustic signals.

Recently developed acoustic technologies - like automatic recording units - allow the recording of long sequences in natural environments. These devices are used for biodiversity survey but they could also help researchers to estimate global signal variability at various (individual, population, species) scales. While sexually-selected signals are expected to show a low intra-individual variability at relatively short time scale, this variability has never been estimated so far. Yet, measuring signal variability in controlled conditions should prove useful to understand sexual selection processes and should help design acoustic sampling schedules and to analyse long call recordings. We here use the overall call production of 36 male treefrogs (Hyla arborea) during one night to evaluate within-individual variability in call dominant frequency and to test the efficiency of different sampling methods at capturing such variability. Our results confirm that using low number of calls underestimates call dominant frequency variation of about 35% in the tree frog and suggest that the assessment of this variability is better by using 2 or 3 short and well-distributed records than by using samples made of consecutive calls. Hence, 3 well-distributed 2-minutes records (beginning, middle and end of the calling period) are sufficient to capture on average all the nightly variability, whereas a sample of 10 000 consecutive calls captures only 86% of it. From a biological point of view, the call dominant frequency variability observed in H. arborea (116Hz on average but up to 470 Hz of variability during the course of the night for one male) challenge about its reliability in mate quality assessment. Automatic acoustic recording units will provide long call sequences in the near future and it will be then possible to confirm such results on large samples recorded in more complex field conditions.

Allometric Convergence, Acoustic Character Displacement, and Species Recognition in the Syntopic Cricket Frogs Acris crepitans and A. gryllus

Evidence for reproductive character displacement (RCD) has accumulated more slowly than for ecological character displacement, perhaps because sampling scales and environmental covariates can obscure the role of RCD in speciation. We examined an early example of RCD in an anuran species group, the vocalizations of the sympatric cricket frogs Acris crepitans and A. gryllus. With a relatively fine spatial scale, we compared mixed-species choruses (syntopy), nearby locations where A. gryllus is recently extirpated (historic sympatry), and surrounding areas without secondary contact (allopatry). In each of these areas, we evaluated variation in dominant frequency, click rate, and mass of males. In addition, we determined the acoustic preferences of syntopic females. Temperature influenced dominant frequency of vocalizations in A. crepitans, but not in A. gryllus. Body size varied more and had a stronger influence on dominant frequency in A. crepitans than in A. gryllus. Consequently, the decrease in mass of A. crepitans in syntopy resulted in convergence of body size and divergence of dominant frequencies of the two species. In contrast, dominant frequency of A. crepitans did not differ between historic sympatry and allopatry. Females of both species used fine temporal structure to discriminate between conspecific and heterospecific vocalizations and showed no preferences for dominant frequency. Chorus noise limited the ability of A. gryllus females to detect and discriminate vocalizations, so convergence in mass might have resulted from RCD in dominant frequency to reduce heterospecific acoustic interference. However, influences other than RCD might have caused syntopic convergence in body size.

Frequency Variation of a Reflex-Triode Virtual Cathode Oscillator

We present a study of the shot-to-shot variation in frequency of a reflex-triode virtual cathode oscillator with respect to peak diode voltage, current, impedance, and perveance. The typical electron-beam parameters were 185 kV, 7 kA, and 300 ns, with a current density of a few hundreds of amperes per square centimeter. The one-way analysis of variance was employed to examine the statistical correlation of the diode voltage, current, impedance, and perveance with the emitted microwave frequency. It was shown that the microwave dominant frequency variation is statistically correlated only with the peak diode current. However, the secondary emitted frequency is not statistically correlated with any of the electron-beam diode parameters.

Overview on the Diversity of Sounds Produced by Clownfishes (Pomacentridae): Importance of Acoustic Signals in Their Peculiar Way of Life

BackgroundClownfishes (Pomacentridae) are brightly colored coral reef fishes well known for their mutualistic symbiosis with tropical sea anemones. These fishes live in social groups in which there is a size-based dominance hierarchy. In this structure where sex is socially controlled, agonistic interactions are numerous and serve to maintain size differences between individuals adjacent in rank. Clownfishes are also prolific callers whose sounds seem to play an important role in the social hierarchy. Here, we aim to review and to synthesize the diversity of sounds produced by clownfishes in order to emphasize the importance of acoustic signals in their way of life.Methodology/Principal FindingsRecording the different acoustic behaviors indicated that sounds are divided into two main categories: aggressive sounds produced in conjunction with threat postures (charge and chase), and submissive sounds always emitted when fish exhibited head shaking movements (i.e. a submissive posture). Both types of sounds showed size-related intraspecific variation in dominant frequency and pulse duration: smaller individuals produce higher frequency and shorter duration pulses than larger ones, and inversely. Consequently, these sonic features might be useful cues for individual recognition within the group. This observation is of significant importance due to the size-based hierarchy in clownfish group. On the other hand, no acoustic signal was associated with the different reproductive activities.Conclusions/SignificanceUnlike other pomacentrids, sounds are not produced for mate attraction in clownfishes but to reach and to defend the competition for breeding status, which explains why constraints are not important enough for promoting call diversification in this group.

Bioacoustic variation of swimbladder disturbance sounds in Neotropical doradoid catfishes (Siluriformes: Doradidae, Auchenipteridae): Potential morphological correlates

Abstract Swimbladder disturbance sounds of doradoid catfishes (Doradidae and Auchenipteridae) demonstrated striking waveform and spectrographic variation. We surveyed sounds of 25 doradoid species in 20 genera comparing these to sounds of four vocal outgroup catfish families. Sounds were either continuous waveforms (lacking interpulses) or pulsed (groups of pulses repeated at fixed temporal intervals). This is the first evidence for swimbladder calls with fixed interpulse patterns in catfishes. Vocal mechanism components that were similar between doradids and auchenipterids included: swimbladder shape, swimbladder dimensions and sonic muscle-somatic index. Morphological traits that showed variation among taxa and were evaluated for potential correlates of call diversity are: 1) diverticula (marginal outpocketings of the swimbladder with no connection to inner ear) and 2) elastic spring apparatus Müllerian rami (ESA-Mr). Within the doradid subfamilies and within the Auchenipteridae most species differed significantly in dominant frequency with frequency ranges overlapping to some extent for most. Doradid swim-bladder diverticula did not explain dominant frequency variation within the doradoid superfamily. Some doradids with conical ESA-Mr had the highest dominant frequency sounds. Auchenipterids included both relatively lower and higher dominant frequency sound producers but lacked diverticula and had discoidal ESA-Mr. Comparing a phylogeny of doradoid genera with out-group taxa, we infer that complex diverticula and conical ESA-Mr are derived characters within the Doradidae. Species representing outgroup families produced either continuous lower dominant frequency sounds (aspredinids, mochokids and pseu-dopimelodids) or pulsed higher dominant frequency sounds (pimelodids).

Geographic Variation in Male Sexual Signals in Strawberry Poison Frogs (Dendrobates pumilio)

AbstractIn this paper, we compare the advertisement calls of 207 neotropical strawberry poison frogs (Dendrobates pumilio) collected in 21 localities along a transect from northern Costa Rica to western Panama. Populations varied most in call duration and call rate, while pulse rate and duty cycle were less variable. Multivariate analyses showed that call variation followed a cline with higher call rates, shorter calls, lower duty cycles and higher pulse rates in the southeast. Body size decreased towards the southeast and explained most variation in dominant frequency, as well as some residual variation in call rate. We conclude that a combination of geography and morphology is largely responsible for call variation within this species. Two inferred bio‐acoustic groups were roughly in accordance with two genetic groups, geographically separated in central Costa Rica. However, genetic distances among populations did not co‐vary with call dissimilarity after correction for geographic distances. Thus, differences in calls between genetic groups are probably mainly a result of clinal variation. These findings agree with the general observation that bio‐acoustic variation is often not (highly) associated with genetic divergence. Moreover, colour polymorphism observed among Panamanian populations was not reflected in a higher variability in call parameters relative to the monomorphic Costa Rican populations.

Singing from a constructed burrow: why vary the shape of the burrow mouth?

Male prairie mole crickets, Gryllotalpa major Saussure, studied in Oklahoma, sing sexual advertisement songs from constructed burrows in the soil. Here we report on variation in shape of the acoustic burrow mouth not previously described for this or other mole cricket species. We have identified six distinct shapes, of which only the ‘slit’ form has been previously described. Since the surface opening acts as the system ‘radiator’, we hypothesized that variation in the shape would account for at least some of the measured variation documented since 1993 in the songs produced by the population studied. We looked for patterns in the variation of dominant frequency of advertisement calls and maximum amplitude of calls that were linked to shape of burrow openings, but found none. Future work will focus on the role of previously documented weak higher harmonics in the G. major calling song, which might vary with differences in burrow mouth shape.

Geographic variation in advertisement calls of Crinia signifera (Anura:Myobatrachidae) in the Bass Strait area of south-eastern Australia

The structure of recorded advertisement calls of a total of 176 males of Crinia signifera from eight localities on the south-eastern Australian mainland and Tasmania was investigated. On the basis of number of pulses per call (samples from all localities) and call duration adjusted to 13.0°C (samples from six localities), two geographic groups are recognised: (1) south-central Victoria, and (2) the extreme south-eastern mainland and Tasmania. This pattern of variation is postulated to reflect expansion of a differentiated Tasmanian stock on to the extreme south-eastern Australian mainland along the eastern sill of the Bassian Isthmus during the lower sea levels of the Late Pleistocene. Geographic variation in pulse rate (derived from number of pulses and call duration) was also considered because of its use in previous studies. The variation in dominant frequency in samples from five localities, adjusted for snout–vent length, does not conform to that for number of pulses and call duration, and is attributed to differences in demographic structure and recruitment.

Distension-induced myoelectrical dysrhythmia and effect of intestinal pacing in dogs.

The aims of this study were to investigate the effect of duodenal distension on intestinal myoelectrical activity and to investigate whether intestinal pacing was able to reverse the effects of distension. Six female hound dogs with four pairs of electrodes on the proximal jejunum were involved in this study. The protocol consisted of 30 min of recording of jejunal myoelectrical activity as baseline and 90 min of recording during distension. Intestinal pacing was performed during the second 30 min of distension. Duodenal distension severely impaired intestinal myoelectrical activity. The percentage of normal slow waves was reduced from 90.8+/-8.4% at baseline to 73.8+/-10.2%, 57.2+/-11.4%, and 53.7+/-16.0% during the first, second and third 30 min of distension (P<0.05, ANOVA). The dominant power was similarly decreased and the minute-by-minute variation of dominant frequency was significantly increased after distension. Intestinal pacing reversed distension-induced dysrhythmia. The percentage of normal slow waves during the 30 min of distension with pacing was significantly higher than the corresponding 30 min of distension without pacing (88.5+/-6.6% vs. 57.2+/-11.4%, P<0.03). It was concluded that intestinal pacing can normalize distension-induced dysrhythmia and has a potential as a future therapeutic modality for intestinal motor disorders.

Effects of different psychophysiological stressors on the cutaneous electrogastrogram in healthy subjects.

To evaluate the effect of psychophysiological stress on the gastric electrical activity, the cutaneous electrogastrography (EGG), a non-invasive technique, was performed in ten healthy subjects. Three different stressful (cold pressor test, arithmetic task, and Stroop color-word test) tests and a non-stressful (reading a booklet) task were administered, and EGG parameters (dominant frequency, coefficient of variation of dominant frequency, and gastric power) were recorded during baseline, task and rest periods. Neutral task did not affect EGG parameters. During stressful stimulations, a slight decrease in the dominant frequency and an increase in the coefficient of variation of the dominant frequency were found. During arithmetic task, the gastric power significantly increased (baseline vs stimulus P = 0.008; stimulus vs rest P = 0.015; baseline vs rest P = 0.011), and a statistically significant difference between gastric power during arithmetic and neutral task was observed (P = 0.007). During Stroop test, the gastric power showed only a trend toward significance (baseline vs stimulus P = 0.018; stimulus vs rest P = 0.018). A wide interindividual variability was recorded during the stress period. Therefore, the individual susceptibility to psychological stress may influence the EGG response and gastric electrical activity. In conclusion, cutaneous electrogastrography may be used as a non-invasive technique to study the effects of acute stressors on the gastric electrical activity.

Dynamic response of disordered Ising alloy with competing interaction

Abstract The real χ′ and imaginary χ″ parts of the dynamic susceptibility χ(ω) of a binary Ising alloy exhibiting spin-glass like behaviour in the presence of competing exchange interactions are calculated using the cluster-variational method and the relaxational dynamics with a distribution of energy barriers to relaxation. For 2d-alloys the spin-glass transition does not appear at finite temperature. However, for both 3d- and 2d-alloys, χ′ and χ″ exhibit a peak in temperature, and the peak position shifts to a higher temperature side with an increase in frequency. The reduced response χ′/χ′ p (χ″/χ″ p ) turns out to be a unique function of T / T p ( T / T ′ p ), where χ′ p (χ ″ p ) is its value at peak temperature T p ( T ′ p ). For a given temperature, χ″ attains its maximum value at a characteristic frequency ω p , determined by the distribution of the relaxation time, and the dominant frequency variation of χ′ occurs around ω p . The Cole-Cole plot (χ″ vs. χ′) shows a maximum at χ ′ = 0.5 χ 0 and its changes from an arc of a circle at high temperatures to rectangularlike at low temperature. The qualitative character, of χ(ω) remains the same when the energy barrier distribution is changed from a rectangular to a Gaussian. The scaling behaviours of χ′ and χ″ are verified using experimental data on the χ(ω) of a disordered Fe 1.2 Mn 1.8 Si alloy, exhibiting spin glass behaviour.