Amplitude Asymmetry Research Articles

Empirical Distribution of Glottal Edges (EDGE): A Statistical Assessment of Vocal Fold Kinematics Using High-Speed Videoendoscopy.

Although laryngeal high-speed videoendoscopy (HSV) is crucial for studying vocal fold vibrations, its translation to clinical practice has been hindered by the large volume of data it produces and the difficulty in interpreting current analysis methods. Although image processing techniques have been developed to map spatial-temporal data into two-dimensional representations, they alter the geometrical construction of the glottis and do not provide standard quantitative features, thus challenging clinical interpretation. In response, we propose a new visualization and analysis framework for assessing the dynamics of vocal folds based on the empirical distribution of the glottal edge using HSV. This procedure analyzes vocal fold oscillations by preserving the shape of the glottis and quantifying the asymmetry between right and left vocal fold displacements along the anterior-posterior axis. This method was evaluated on four groups of participants: ten with normal voices, ten with vocal fold nodules, ten with muscle tension dysphonia, and two with unilateral vocal fold paralysis. The proposed method produces distinct representations for normal and pathological vocal fold vibratory behaviors and derived features based on amplitude and phase asymmetry metrics that show statistically significant differences between normal and pathological groups. Comparative analysis with state-of-the-art techniques indicates that our proposed method can complement the assessment of vocal fold vibration and enhance the clinical translation of HSV.

Investigation of the Relationship between ENSO Amplitude Asymmetry and the Nonlinear Sensitivity of Atmospheric Convection to Sea Surface Temperature in the Equatorial Pacific

Investigation of the Relationship between ENSO Amplitude Asymmetry and the Nonlinear Sensitivity of Atmospheric Convection to Sea Surface Temperature in the Equatorial Pacific

Value of high-speed videoendoscopy as an auxiliary tool in differentiation of benign and malignant unilateral vocal lesions

PurposeThe study aimed to assess the relevance of objective vibratory parameters derived from high-speed videolaryngoscopy (HSV) as a supporting tool, to assist clinicians in establishing the initial diagnosis of benign and malignant glottal organic lesions.MethodsThe HSV examinations were conducted in 175 subjects: 50 normophonic, 85 subjects with benign vocal fold lesions, and 40 with early glottic cancer; organic lesions were confirmed by histopathologic examination. The parameters, derived from HSV kymography: amplitude, symmetry, and glottal dynamic characteristics, were compared statistically between the groups with the following ROC analysis.ResultsAmong 14 calculated parameters, 10 differed significantly between the groups. Four of them, the average resultant amplitude of the involved vocal fold (AmpInvolvedAvg), average amplitude asymmetry for the whole glottis and its middle third part (AmplAsymAvg; AmplAsymAvg_2/3), and absolute average phase difference (AbsPhaseDiffAvg), showed significant differences between benign and malignant lesions. Amplitude values were decreasing, while asymmetry and phase difference values were increasing with the risk of malignancy. In ROC analysis, the highest AUC was observed for AmpAsymAvg (0.719; p < 0.0001), and next in order was AmpInvolvedAvg (0.70; p = 0.0002).ConclusionThe golden standard in the diagnosis of organic lesions of glottis remains clinical examination with videolaryngoscopy, confirmed by histopathological examination. Our results showed that measurements of amplitude, asymmetry, and phase of vibrations in malignant vocal fold masses deteriorate significantly in comparison to benign vocal lesions. High-speed videolaryngoscopy could aid their preliminary differentiation noninvasively before histopathological examination; however, further research on larger groups is needed.

The effect of general osteopathic treatment on muscle tone according to electromyography data

Introduction. Clinical research in osteopathy is criticized for the lack of standardization of treatment and insufficient use of instrumental methods to assess its effectiveness. Therefore, in order to increase evidence in osteopathy, it is relevant to search for instrumental methods that allow recording and measuring objective indicators and their changes after standardized osteopathic correction. The aim of the study is to research the effect of general osteopathic treatment on muscle tone using electromyography in practically healthy people. Materials and methods. A study was conducted on the basis of the Department of Osteopathy of the Mechnikov NWSMU. 30 practically healthy volunteers without any active complaints, aged 20 to 42 years (median 25 years), took part in the study. The criteria for non-inclusion were the presence of diseases and/or conditions that are an absolute contraindication to osteopathic correction, taking muscle relaxants or acetylcholinesterase inhibitors, diseases belonging to the G00-G83 group according to ICD-10, the presence of a trauma history for less than 1 year. All volunteers underwent general osteopathic treatment (GOT) as a standardized variant of osteopathic correction. Before and immediately after the GOT, muscle tone was studied using surface electromyography (sEMG), which was performed on the complex of wireless monitoring of electrophysiological signals «Kolibri» (manufacturer LLC «Neurotech», Russia). At rest, the average amplitude of the electrical activity of the muscles of the upper arms, the interscapular region, the anterior and posterior muscle groups of the thigh and lower legwere measured. The recording was made simultaneously from several muscle groups, synchronously from the right and left sides of the body. Results. After the GOT, a statistically significant decrease in the average amplitude of the thigh anterior surface muscles electrical activity from the median of 8 MV to 4 MV (p = 0,00001), the lower leg anterior surface from the median of 9 MV to 7 mv (p = 0,008) was detected, which indicates their relaxation. The tone of the other muscle groups did not change statistically significantly. The asymmetry of the average amplitude of electrical activity was observed in the studied muscles, which shows an imbalance of tone between symmetrical muscles. In most of the studied muscle groups, this indicator did not change statistically significantly after the GOT. And only in the anterior thigh muscle group, the asymmetry of the average amplitude of electrical activity decreased statistically significantly from the median of 7 MV to 2 MV (p = 0,0046). Conclusion. With the help of the sEMG, it was found that one session of GOT leads to a decrease in the tone of the anterior thigh and lower leg muscle groups, as well as a decrease in the asymmetry of the tone of the anterior thigh muscle group. These results can be explained from the standpoint of the GOT effect on skeletal muscles by means of improving the characteristics of the muscle tissue itself and the surrounding fascia, as well as by inhibitory and harmonizing effects on the nervous system, which ensures the maintenance and regulation of muscle tone. Surface EMG can be used to objectively record and measure the results of osteopathic correction to increase the evidence of clinical trials in osteopathy.

Masseter vestibular evoked myogenic potential result of possible meniere's patients

BACKGROUND: The Masseter Vestibular-Evoked Myogenic Potential (mVEMP) test evaluates the vestibulo-masseteric reflex neural pathway between the sound-stimulated saccule hair cells and the motor neurons of the trigeminal nerve. PURPOSE: This study aims to investigate the contribution of mVEMP to the conclusive diagnosis of recurrent vestibulopathy patients that were diagnosed with Possible Ménière's disease. METHODS: The study includes 20 healthy individuals aged 18-40 years and 20 patients that were diagnosed with possible Ménière's disease according to the American Academy of Otorhinolaryngology and Head and Neck Surgery (AAO-HNS, 1995) Guidelines for the Definition of Ménière's Disease. In addition to the AAO-HNS, 1995 criteria, the presence of aural signs on the affected side was questioned according to the Meniere's criteria updated in 2015. mVEMP records were obtained by using surface electrodes placed on masseter muscles. Latency and amplitude values and asymmetry ratios of mVEMP waves were used for statistical analysis. RESULTS: Asymmetry ratios were 15.9±9.7% for the control group, and 60.61±45.52 for the experimental group, this difference was statistically significant (p&lt;0.05). The absolute latency and amplitude results were not statistically different between groups (p&gt;0.05). CONCLUSION: As Murofishi (2001) stated in the literature, cervical VEMP/ocular VEMP latencies were not affected in peripheral pathologies, and in our study, no difference was observed between the groups in mVEMP latencies. The findings of our study showed that asymmetry ratio and absence of waves should be used in the clinical evaluation of Possible Meniere's disease. We conclude that mVEMP can be used to determine the lateralization of vestibular disorders and to support the presence of a vestibular pathology. mVEMP can contribute to the vestibular test battery.

Unveiling the brain's hidden symmetry: Investigating alpha amplitude asymmetry and its intriguing link with skull thickness variation

Unveiling the brain's hidden symmetry: Investigating alpha amplitude asymmetry and its intriguing link with skull thickness variation

The Validation of a Simultaneous Ocular and Cervical VEMP Recording Protocol to Unilateral AC Stimuli.

A simultaneous recording of cervical and ocular vestibular evoked myogenic potential (sVEMP) to unilateral air-conducted (AC) stimulation reduces the test time and halves the sound load. The sVEMP has been compared with the conventional sequential unilateral AC cervical and ocular VEMP in a consecutive cohort of 120 subjects attending the vestibular laboratory. The stimulus was a 500-Hz 6-ms tone burst, at 130 dB peSPL for sequential recordings but at 125 dB for the added sVEMP, for cumulative sound load containment. Amplitudes, latencies, and amplitude asymmetry ratios (ARs) were the parameters included in analysis. Relevant results were as follows: 1) significantly lower amplitudes in sVEMP versus VEMP (ocular recordings, median = 2.90 [IQR = 0-4.98] vs. 4.15 [1.73-8.98] μV, p < 0.001; cervical, 0.84 [0.30-1.69] vs. 1.36 [0.60-2.30], p < 0.001; electromyography scaled values); 2) 10% lower response rate at cervical recordings and 11% at ocular recordings in sVEMP, particularly in older subjects; 3) significant correlations between cervical amplitudes (rs = 0.88, p < 0.001), ocular amplitudes (rs = 0.71, p < 0.001), peak latencies (rs = 0.36-0.67, p < 0.001), and ARs (ocular, rs = 0.56; cervical, rs = 68, p < 0.001); and 4) good agreement in pathological AR detection (cervical recordings, Cohen's κ = 0.649, p < 0.001; ocular, κ = 0.589, p < 0.001). AC sVEMP showed good correlation/agreement with sequential AC VEMP. Test time containment and halved sound load are clinical adds in sVEMP, opening to its use as laboratory standard. However, AC sVEMP presented reduced amplitudes and response rates, secondary to the reduced AC stimulation used in this study to allow checking of the null responses and the pathological ARs at AC sVEMP with conventional AC VEMP.

Method for Assessing the Influence of Phobic Stimuli in Virtual Simulators.

In the organizing of professional training, the assessment of the trainee's reaction and state in stressful situations is of great importance. Phobic reactions are a specific type of stress reaction that, however, is rarely taken into account when developing virtual simulators, and are a risk factor in the workplace. A method for evaluating the impact of various phobic stimuli on the quality of training is considered, which takes into account the time, accuracy, and speed of performing professional tasks, as well as the characteristics of electroencephalograms (the amplitude, power, coherence, Hurst exponent, and degree of interhemispheric asymmetry). To evaluate the impact of phobias during experimental research, participants in the experimental group performed exercises in different environments: under normal conditions and under the influence of acrophobic and arachnophobic stimuli. The participants were divided into subgroups using clustering algorithms and an expert neurologist. After that, a comparison of the subgroup metrics was carried out. The research conducted makes it possible to partially confirm our hypotheses about the negative impact of phobic effects on some participants in the experimental group. The relationship between the reaction to a phobia and the characteristics of brain activity was revealed, and the characteristics of the electroencephalogram signal were considered as the metrics for detecting a phobic reaction.

Effectiveness of the sternocleidomastoid muscle contraction asymmetry and filter: cervical vestibular evoked myogenic potential.

This study aimed to determine the precautions that can be taken to increase the reliability of the vestibular evoked myogenic potentials test without being affected by the asymmetry of the sternocleidomastoid muscle and the issues that should be considered in the interpretation of vestibular evoked myogenic potential results if these precautions are not taken. Individuals with sternocleidomastoid muscle activity of less than 30 μV in cervical vestibular evoked myogenic potential testing and an asymmetry ratio of more than 0.35 were excluded. In our study, individuals were divided into different groups according to sternocleidomastoid muscle asymetry. A total of 53 individuals were included in the study. Intergroup comparisons were made to determine the effect of electromyogram scaling and filter use on amplitude asymmetry ratio according to sternocleidomastoid muscle asymmetry. Keeping the sternocleidomastoid muscle asymmetry not exceeding 10 μV maximises the reliability of cervical vestibular evoked myogenic potentials. As a result of our study, it can be concluded that in clinical applications the asymmetry should not exceed 20 μV.

Binocular head-mounted chromatic pupillometry can detect structural and functional loss in glaucoma.

The aim of this study is to evaluate the utility of binocular chromatic pupillometry in detecting impaired pupillary light response (PLR) in patients with primary open-angle glaucoma (POAG) and to assess the feasibility of using binocular chromatic pupillometer in opportunistic POAG diagnosis in community-based or telemedicine-based services. In this prospective, cross-sectional study, 74 patients with POAG and 23 healthy controls were enrolled. All participants underwent comprehensive ophthalmologic examinations including optical coherence tomography (OCT) and standard automated perimetry (SAP). The PLR tests included sequential tests of full-field chromatic stimuli weighted by rods, intrinsically photosensitive retinal ganglion cells (ipRGCs), and cones (Experiment 1), as well as alternating chromatic light flash-induced relative afferent pupillary defect (RAPD) test (Experiment 2). In Experiment 1, the constricting amplitude, velocity, and time to maximum constriction/dilation were calculated in three cell type-weighted responses, and the post-illumination response of ipRGC-weighted response was evaluated. In Experiment 2, infrared pupillary asymmetry (IPA) amplitude and anisocoria duration induced by intermittent blue or red light flashes were calculated. In Experiment 1, the PLR of POAG patients was significantly reduced in all conditions, reflecting the defect in photoreception through rods, cones, and ipRGCs. The variable with the highest area under the receiver operating characteristic curve (AUC) was time to max dilation under ipRGC-weighted stimulus, followed by the constriction amplitude under cone-weighted stimulus and the constriction amplitude response to ipRGC-weighted stimuli. The impaired PLR features were associated with greater visual field loss, thinner retinal nerve fiber layer (RNFL) thickness, and cupping of the optic disk. In Experiment 2, IPA and anisocoria duration induced by intermittent blue or red light flashes were significantly greater in participants with POAG than in controls. IPA and anisocoria duration had good diagnostic value, correlating with the inter-eye asymmetry of visual field loss. We demonstrate that binocular chromatic pupillometry could potentially serve as an objective clinical tool for opportunistic glaucoma diagnosis in community-based or telemedicine-based services. Binocular chromatic pupillometry allows an accurate, objective, and rapid assessment of retinal structural impairment and functional loss in glaucomatous eyes of different severity levels.

Experimental Observation of Flat Bands in One-Dimensional Chiral Magnonic Crystals.

Spin waves represent the collective excitations of the magnetization field within a magnetic material, providing dispersion curves that can be manipulated by material design and external stimuli. Bulk and surface spin waves can be excited in a thin film with positive or negative group velocities and, by incorporating a symmetry-breaking mechanism, magnetochiral features arise. Here we study the band diagram of a chiral magnonic crystal consisting of a ferromagnetic film incorporating a periodic Dzyaloshinskii-Moriya coupling via interfacial contact with an array of heavy-metal nanowires. We provide experimental evidence for a strong asymmetry of the spin wave amplitude induced by the modulated interfacial Dzyaloshinskii-Moriya interaction, which generates a nonreciprocal propagation. Moreover, we observe the formation of flat spin-wave bands at low frequencies in the band diagram. Calculations reveal that depending on the perpendicular anisotropy, the spin-wave localization associated with the flat modes occurs in the zones with or without Dzyaloshinskii-Moriya interaction.

Influence of the Electrode Montage to Detect Ocular Vestibular Evoked Myogenic Potentials.

To compare ocular vestibular evoked myogenic potentials (oVEMPs) obtained with three different electrode montages (infra-orbital vs belly-tendon vs chin) in a group of healthy subjects. To assess the electrical activity recorded at the level of the reference electrode in the belly-tendon and chin montages. Prospective study. Tertiary referral center. Twenty-five healthy adult volunteers. Each ear was tested separately via air-conducted sound (500 Hz Narrow Band CE-Chirps at 100 dB nHL) for recording contralateral myogenic responses. Recording conditions were randomized. n1-p1 amplitudes values, interaural amplitude asymmetry ratios (ARs) and response rates. The belly-tendon electrode montage (BTEM) produced larger amplitudes than the chin ( p = 0.008) and the IOEM (infra-orbital electrode montage; p < 0.001). The chin montage displayed larger amplitudes than the IOEM ( p < 0.001). The interaural amplitude asymmetry ratios (ARs) were not affected by the different electrode montages ( p = 0.549). In 100% of cases, oVEMPs were detected bilaterally with the BTEM which is higher than with the chin and the IOEM ( p < 0.001; p = 0.020, respectively). We did not record any VEMP when placing the active electrode on the contralateral internal canthus or the chin and the reference electrode on the dorsum of the hand. The BTEM increased the amplitudes recorded and response rate in healthy subjects. No positive or negative reference contamination was observed with the belly-tendon or chin montages.

Subjective visual horizontal correlates better with ocular than with cervical vestibular evoked myogenic potentials

ObjectiveTo examine the relationship between widely used otolith function tests: the Subjective Visual Horizontal (SVH) and Vestibular Evoked Myogenic Potentials (VEMP). MethodsA retrospective analysis was performed on 301 patients who underwent SVH, ocular and cervical VEMP (oVEMP and cVEMP) tests on the same day. Correlations between the mean SVH tilt and amplitude asymmetry ratios for bone-conducted (BC) oVEMP and air-conducted (AC) cVEMP were examined. Diagnoses included vestibular neuritis, stroke, vestibular migraine, Meniere’s disease, sudden sensorineural hearing loss (SSNHL) and vestibular schwannoma. ResultsSVH results were concordant with the oVEMP in 64% of cases and the cVEMP in 51%. Across all patients, SVH demonstrated a significant moderate correlation with BC oVEMP amplitude asymmetry ratios (r = 0.55, p < 0.001) and a weak correlation with AC cVEMP amplitude asymmetry ratios (r = 0.35, p < 0.001). A stronger correlation between SVH and oVEMPs was observed in patients with vestibular neuritis (r = 0.67, p < 0.001) and SSNHL (r = 0.76, p = 0.001). ConclusionsSVH correlates better with oVEMP than cVEMP symmetry. SignificanceThis finding reinforces the hypothesis of a common utricular origin for both SVH and oVEMPs which is distinct from the saccular origin of cVEMPs.

Analyses of Head-Impulse Tests in Patients With Posterior Circulation Stroke and Vestibular Neuritis.

The interpretation of video head-impulse tests (video-HITs) can often be complicated, limiting their clinical utility in acute vestibular syndrome. We aimed to determine video-HIT findings in patients with posterior circulation strokes (PCSs) and vestibular neuritis (VN). We retrospectively analyzed the results of video-HITs in 59 patients with PCS. Irrespective of the actual lesion revealed later on MRIs, ipsilateral and contralateral sides were assigned according to the direction of slow phase of spontaneous nystagmus (SN). Then, the patterns of video-HIT findings were classified according to the vestibulo-ocular reflex (VOR) gain for the horizontal canals; (1) ipsilaterally positive, (2) contralaterally positive, (3) bilaterally normal, and (4) bilaterally positive. The abnormal responses were further defined into (5) wrong-way saccades, (6) perverted, and (7) early acceleration followed by premature deceleration. We also analyzed the asymmetry of the corrective saccadic amplitude between the sides, calculated from the sum of cumulative saccadic amplitudes on both sides. The results were compared with video-HIT results from 71 patients with VN. Video-HITs were normal in 32 (54%), ipsilaterally positive in 11 (19%), bilaterally positive in 10 (17%), and contralaterally positive in 6 (10%) patients with PCS. Wrong-way saccades were more frequently observed in VN than in PCS (31/71 [44%] vs 5/59 [8%], p < 0.001). Saccadic amplitude asymmetry was greater in VN than in PCS (median 100% [interquartile range 82-144, 95% CI 109-160] vs 0% [-29 to 34, -10 to 22, p < 0.001]). When differentiating VN from PCS, the sensitivity was 81.7%, and specificity was 91.5% at the cutoff value of 71% for saccadic amplitude asymmetry with an area under the curve (AUC) of 0.91 (95% CI 0.86-0.97). The AUC for saccadic amplitude asymmetry was larger than that for the ipsilateral VOR gain (p = 0.041) and other parameters. Patients with PCS may show various head-impulse responses that deviate from the findings expected in VN, which include normal, contralaterally positive, and negative saccadic amplitude asymmetry (i.e., greater cumulative saccadic amplitude contralaterally). A thorough analysis of corrective saccades in video-HITs can improve the differentiation of PCS from VN even before MRIs.

Nighttime Midlatitude E‐F Coupling in Geomagnetic Conjugate Ionospheres: A Double Thin Shell Model and a Multi‐Source Data Investigation

AbstractGeomagnetic conjugate mid‐latitude nighttime ionospheres are frequently simultaneously populated with electrified nighttime medium‐scale traveling ionospheric disturbances (MSTIDs). Earlier observations and theoretical analysis have underscored the ionosphere E‐F coupling and the postulation of coupled conjugate hemispheres, playing a pivotal role in the formation of electrified MSTIDs. In this paper, the conjugate MSTIDs are studied to elucidate the causes and effects of E‐F coupling in the interhemispheric coupled ionosphere. The hemisphere‐coupled ionospheres over Japan and Australia are observed and analyzed using total electron content (TEC) measurements, supplemented with multi‐source observations from ionosondes, Ionospheric Connection Explorer (neutral wind), Constellation Observing System for Meteorology, Ionosphere, and Climate (electron density), and Swarm (magnetic field). A double‐thin‐shell model is introduced to analyze the ionospheric responses in E and F regions during the coupling process. For the first time, observation results provide the evidence that F‐region geomagnetic conjugate irregularities in both hemispheres are mainly driven by the Es layers in the summer hemisphere. The Es layer in the summer hemisphere subsequently triggers local E‐F coupling and inter‐hemispheric coupling. In the winter hemisphere, Es layers show amplitude reduction or even dissipation during the interhemispheric coupling process. Furthermore, thermospheric winds, non‐equipotential magnetic field lines, and background TEC are presumed candidates for the inter‐hemispheric asymmetry in MSTIDs amplitudes and growth rates.

Equatorial Submesoscale Eddies Contribute to the Asymmetry in ENSO Amplitude

AbstractEl Niño/Southern Oscillation (ENSO) exhibits evident amplitude asymmetry with stronger El Niño than La Niña events. Equatorial submesoscale eddies act as an important damper of ENSO via their induced upward heat flux () from the subsurface to the surface ocean. Yet their effect on ENSO amplitude asymmetry remains unexplored. Using a high‐resolution global climate simulation, we found that strengthening of in the Niño3.4 region during La Niña is more evident than weakening of during El Niño, resulting in stronger damping of La Niña than El Niño events. This asymmetric response of to ENSO is primarily ascribed to that of the temperature fronts associated with larger‐scale processes. Using a recharge oscillator model modified to include the effects of , we show that the asymmetric damping of ENSO by contributes importantly to the ENSO amplitude asymmetry.

QEEG characteristics associated with malnutrition-inflammation complex syndrome.

End-stage renal disease (ESRD) has been linked to cerebral complications due to the comorbidity of malnutrition and inflammation, which is referred to as malnutrition-inflammation complex syndrome (MICS). The severity of this condition is clinically assessed with the malnutrition-inflammation score (MIS), and a cutoff of five is used to optimally distinguish patients with and without MICS. However, this tool is still invasive and inconvenient, because it combines medical records, physical examination, and laboratory results. These steps require clinicians and limit MIS usage on a regular basis. Cerebral diseases in ESRD patients can be evaluated reliably and conveniently by using quantitative electroencephalogram (QEEG), which possibly reflects the severity of MICS likewise. Given the links between kidney and brain abnormalities, we hypothesized that some QEEG patterns might be associated with the severity of MICS and could be used to distinguish ESRD patients with and without MICS. Hence, we recruited 62 ESRD participants and divided them into two subgroups: ESRD with MICS (17 women (59%), age 60.31 ± 7.79 years, MIS < 5) and ESRD without MICS (20 women (61%), age 62.03 ± 9.29 years, MIS ≥ 5). These participants willingly participated in MIS and QEEG assessments. We found that MICS-related factors may alter QEEG characteristics, including the absolute power of the delta, theta, and beta 1 bands, the relative power of the theta and beta 3 subbands, the coherence of the delta and theta bands, and the amplitude asymmetry of the beta 1 band, in certain brain regions. Although most of these QEEG patterns are significantly correlated with MIS, the delta absolute power, beta 1 amplitude asymmetry, and theta coherence are the optimal inputs for the logistic regression model, which can accurately classify ESRD patients with and without MICS (90.0 ± 5.7% area under the receiver operating characteristic curve). We suggest that these QEEG features can be used not only to evaluate the severity of cerebral disorders in ESRD patients but also to noninvasively monitor MICS in clinical practice.

Amplitude death and growth in a pair of nonidentical thermoacoustic oscillators interacting via time-delay and dissipative coupling

We numerically explore the effect of asymmetric limit-cycle amplitudes on the quenching and growth of self-excited thermoacoustic oscillations in two nonidentical Rijke tubes interacting via time-delay and dissipative coupling. When either type of coupling is applied separately, we find that increasing the asymmetry of the (uncoupled) limit-cycle amplitudes can shrink the regions of amplitude death (AD) in both oscillators, while producing a new region in which one of the oscillators becomes amplified, a state we refer to here as amplitude growth (AG). We find that the AG region resembles a 1:1 Arnold tongue when only dissipative coupling is applied, but that it splits into two discrete branches when only time-delay coupling is applied. When both types of coupling are applied simultaneously, we find that the AD and AG regions change in ways that depend sensitively on the detuning between the two oscillators. The findings of this study could be used to gain a better understanding of the can-to-can acoustic interactions in modern gas turbines, facilitating the development of both passive and active strategies to control thermoacoustic instability.

Reproducibility of Test-Retest Cortical Evoked Responses in Patients with Focal Epilepsy

This exploratory study examined the short-term reliability of cortical auditory evoked responses recorded from patients undergoing whole-head scalp elec-troencephalography (EEG) monitoring to assess their candidacy for surgical treatment of intractable focal seizures. Participants were 26 patients with either left-sided (N = 13) or right-sided focal epilepsy admitted to the hospital for continuous scalp EEG monitoring for possible epilepsy surgery planning. Cortical auditory evoked responses were recorded over multiple days from scalp EEG electrodes using tones presented binaurally in a passive oddball paradigm. Test-retest intervals were 1 - 6 days (mean 2 days). Test-retest reproducibility of the auditory N1 response was assessed by paired t-test (latency) and cross-correlation analysis (amplitude and latency). Within-patient comparisons of test-retest auditory N1 peak latencies revealed no significant differences. The cross-correlation coefficient indicated high test-retest reproducibility of the N1 waveform (rcc = 0.88). Seizure lateralization was not associated with asymmetries in N1 latencies or amplitudes. An N1 amplitude asymmetry (right > left) in patients with focal seizures originating from the left hemisphere was initially observed, but disappeared when patients with prior resections were excluded, suggesting that reduced left hemisphere tissue volume may account for the smaller N1 amplitudes. Test-retest reliability of cortical auditory evoked responses was unexpectedly high in patients with focal epilepsy regardless of seizure lateralization or localization. These findings challenge the view that neural responses are intrinsically unstable (unreliable) in patients with seizures.

High-resolution mid-mantle imaging with multiple-taper SS-precursor estimates

SUMMARY SS-precursor imaging is used to image sharp interfaces within Earth’s mantle. Current SS-precursor techniques require tightly bandpassed signals (e.g. 0.02–0.05 Hz), limiting both vertical and horizontal resolutions. Higher frequency content would allow for the detection of finer structure in and around the mantle transition zone (MTZ). Here, we present a new SS-precursor deconvolution technique based on multiple-taper correlation (MTC). We show that applying MTC to SS-precursor deconvolution can increase the frequency cut-off up to 0.5 Hz, which potentially sharpens vertical resolution to ∼10 km. Furthermore, the high-pass frequency can be lowered (≪ 0.01 Hz), allowing more long-period energy to be included in the calculation, to better constrain the signal and reduce side lobes. Our method is benchmarked on full-waveform synthetic seismograms computed via AxiSEM3D for the PREM 1-D Earth model. We apply our novel MTC-SS-precursor deconvolution to ∼7000 seismograms recorded at broad-band borehole sensors of the Global Seismographic Network with source–receiver bounce points in the North-Central Pacific Ocean. The MTZ in this region appears to be thin, which agrees with previous results. We do not observe the 520-km discontinuity in our SS-precursor estimates. Additionally, we detect a low-velocity zone above the MTZ to the north of the Hawaiian Islands that has previously been inferred from asymmetry in side lobe amplitudes. Our high-frequency analysis demonstrates this feature to be a sharp interface (≤ 10-km thickness), rather than a thick wave speed gradient.