Hz Frequency Interval Research Articles

Dynamic cerebral autoregulation is preserved during orthostasis and intrathoracic pressure regulation in healthy subjects: A pilot study.

Resistance breathing may restore cardiac output (CO) and cerebral blood flow (CBF) during hypovolemia. We assessed CBF and cerebral autoregulation (CA) during tilt, resistance breathing, and paced breathing in 10 healthy subjects. Blood velocities in the internal carotid artery (ICA), middle cerebral arteries (MCA, four subjects), and aorta were measured by Doppler ultrasound in 30° and 60° semi-recumbent positions. ICA blood flow and CO were calculated. Arterial blood pressure (ABP, Finometer), and end-tidal CO2 (ETCO2) were recorded. ICA blood flow response was assessed by mixed-models regression analysis. The synchronization index (SI) for the variable pairs ABP-ICA blood velocity, ABP-MCA velocities in 0.005-0.08 Hz frequency interval was calculated as a measure of CA. Passive tilting from 30° to 60° resulted in 12% decrease in CO (p = 0.001); ICA blood flow tended to fall (p = 0.04); Resistance breathing restored CO and ICA blood flow despite a 10% ETCO2 drop. ETCO2 and CO contributed to ICA blood flow variance (adjusted R2: 0.9, p < 0.0001). The median SI was low (<0.2) indicating intact CA, confirmed by surrogate date testing. The peak SI was transiently elevated during resistance breathing in the 60° position. Resistance breathing may transiently reduce CA efficiency. Paced breathing did not restore CO or ICA blood flow.

Sport-related concussion alters cerebral hemodynamic activity during controlled respiration.

Sport-related concussion (SRC) is known to disrupt neurohemodynamic activity, cardiac function, and blood pressure (BP) autoregulation. This study aims to observe changes in cerebrovascular and cardiovascular responses during controlled respiration after sustaining an SRC. University varsity athletes (n = 81) completed a preseason physiological assessment and were followed up within 5 days of sustaining an SRC. During preseason and follow-up assessments, participants' continuous beat-to-beat BP was collected by finger photoplethysmography, and right prefrontal cortex oxygenation was collected using near-infrared spectroscopy (NIRS). Participants completed 5 min of seated rest and 5 min of a 6-breaths per minute controlled breathing protocol (5 s inhale and 5 s exhale; 0.10 Hz). Wavelet transformation was applied to the NIRS and BP signals, separating them into respiratory (0.10-0.6 Hz) and cardiac (0.6-2 Hz) frequency intervals. Of the 81 participants, 74 had a usable BP signal, 43 had usable NIRS signals, and 28 had both usable BP and NIRS signals. Wavelet amplitudes were calculated and coherence between NIRS and BP on the 28 participants were assessed. There was a significant (P < 0.05) decrease in oxygenated hemoglobin amplitude from 0.062 to 0.054 Hz and hemoglobin difference amplitude from 0.059 to 0.051 Hz, both at the respiratory (0.10-0.6 Hz) frequency interval, from preseason to acute SRC, respectively. Therefore, during controlled respiration, there was a reduction in intensity at the respiratory band, suggesting a protective, reduced respiratory contribution to cerebral hemodynamic activity following acute SRC.NEW & NOTEWORTHY This study investigated cerebral hemodynamic activity following sport-related concussion. Prefrontal cortex oxygenation was assessed by near-infrared spectroscopy (NIRS) during a controlled breathing protocol. Wavelet transformation of the NIRS signals showed significant decreases in HbO2 and HbD amplitude at the respiratory frequency interval (0.10-0.6 HZ) from preseason baseline to acute concussion. These results suggest a decreased respiratory contribution to cerebral hemodynamic activity following acute concussion.

Seismic Velocity Variations Observed Prior to the La Palma Volcano Eruption on 19 September 2021, in Cumbre Vieja, Canary Islands (Spain)

Abstract In the recent years, coda-wave interferometry from seismic noise correlation functions has been increasingly used for volcanic eruption forecasting through velocity changes observed in the crust. Because La Palma Island in the Canary Archipelago is very well instrumented, we studied the possible velocity variations related to the last Cumbre Vieja eruption on 19 September 2021, aiming to obtain clear variations in the seismic velocity. For this purpose, we used the moving-window cross-spectral analysis technique for seismic noise within the 0.1–1.0 Hz frequency interval for determining two- and single-station cross-component correlations. During the 2018–2022 observation period, we first detected a seasonal seismic velocity variation possibly caused by annual rainfall and the induced pore pressure change. On 12 September 2021, a dramatic decrease in the velocity of −0.15% was detected, leading to the volcanic eruption at Cumbre Vieja seven days later. The results are compatible with those of models proposed for rapid magma migration from a shallow reservoir at 11 km to the surface.

Array analysis of seismic noise at the Sos Enattos mine, the Italian candidate site for the Einstein Telescope

The area surrounding the dismissed mine of Sos Enattos (Sardinia, Italy) is the Italian candidate site for hosting Einstein Telescope (ET), the third-generation gravitational wave (GW) observatory. One of the goals of ET is to extend the sensitivity down to frequencies well below those currently achieved by GW detectors, i.e. down to 2 Hz. In the bandwidth [1,10] Hz, the seismic noise of anthropogenic origin is expected to represent the major perturbation to the operation of the infrastructure, and the site that will host the future detector must fulfill stringent requirements on seismic disturbances. In this paper we describe the operation of a temporary, 15-element, seismic array deployed in close proximity to the mine. Signals of anthropogenic origin have a transient nature, and their spectra are characterized by a wide spectral lobe spanning the [3,20] Hz frequency interval. Superimposed to this wide lobe are narrow spectral peaks within the [3,8] Hz frequency range. Results from slowness analyses suggest that the origin of these peaks is related to vehicle traffic along the main road running east of the mine. Exploiting the correlation properties of seismic noise, we derive a dispersion curve for Rayleigh waves, which is then inverted for a shallow velocity structure down to depths of approx 150 m. This data, which is consistent with that derived from analysis of a quarry blast, provide a first assessment of the elastic properties of the rock materials at the site candidate to hosting ET.

Fourier Analysis of Radio Bursts Observed with Very High Time Resolution

Numerous solar radio bursts were observed in 2000 - 2001 using the Toru´ nr adio spectrograph with its unique time resolution of 80 microseconds. This high time resolution enables an in-depth analysis of the time evolution of the power spectra and Fourier spectral indices of selected short radio bursts. We analyze the power-spectrum parameters and vari- ability for two millisecond radio dm-spike events and one drifting pulsation structure (DPS) event, for which the structures of the recorded signals were analyzed with an effective time resolution of 0.0008 s in five adjacent frequency bands of their radio spectra. We found that Fourier spectral indices varied rapidly when radio fine structures were recorded. Otherwise they remained close to zero, indicating the presence of noise. For the 10 - 40 Hz frequency interval of the power spectra the mean values of the Fourier spectral indices varied up to −1.51 for the dm-spikes and up to −1.53 for the DPS event. Cross- correlation coefficients of radio fluxes in adjacent frequency bands varied between 0.12 and 0.60 for dm-spikes and between 0.77 and 0.94 for the DPS event. The shortest fine structure found in the studied events lasted 0.001 s. These results are entirely new for dm-radio spikes and confirm a single previous result found for the DPS events. On the basis of our results, we propose that dm-spikes and DPS events are physically similar and that both are signatures of cascades of interacting plas- moids of different sizes.

Frequency Dependence of Soil Parameters: Experimental Results, Predicting Formula and Influence on the Lightning Response of Grounding Electrodes

An experimental methodology was applied to determine the frequency dependence of the soil resistivity and permittivity under field conditions. A large number of soils of low-frequency resistivity ranging from 50 to 9100 .m were tested and showed strong variation of both parameters in the Hz frequency interval. Simplified expressions were proposed to predict this frequency dependence. The response of grounding electrodes subjected to lightning currents was simulated using an electromagnetic model under the assumption of variation of soil parameters given by such expressions and obtained from measurements. The results were very similar, though quite different from those obtained under the assumption of constant values for soil resistivity and permittivity.

Elimination of low-frequency fluctuations of backscattered Rayleigh radiation from optical fiber with chaotic lasers

We have experimentally demonstrated suppression of low-frequency fluctuations of backscattered Rayleigh radiation from optical fiber with chaotic single-longitudinal mode DFB and multi-longitudinal mode FP lasers subjected by incoherent optical feedback. Significant decreasing of Rayleigh power variations up to 15–20 dB for 10–1000 Hz frequency interval was recorded for both chaotic lasers. It was shown that chaotic DFB laser also efficiently suppresses stimulated Brillouin scattering in the test fiber.

Genetic Influences on Cost-Efficient Organization of Human Cortical Functional Networks

The human cerebral cortex is a complex network of functionally specialized regions interconnected by axonal fibers, but the organizational principles underlying cortical connectivity remain unknown. Here, we report evidence that one such principle for functional cortical networks involves finding a balance between maximizing communication efficiency and minimizing connection cost, referred to as optimization of network cost-efficiency. We measured spontaneous fluctuations of the blood oxygenation level-dependent signal using functional magnetic resonance imaging in healthy monozygotic (16 pairs) and dizygotic (13 pairs) twins and characterized cost-efficient properties of brain network functional connectivity between 1041 distinct cortical regions. At the global network level, 60% of the interindividual variance in cost-efficiency of cortical functional networks was attributable to additive genetic effects. Regionally, significant genetic effects were observed throughout the cortex in a largely bilateral pattern, including bilateral posterior cingulate and medial prefrontal cortices, dorsolateral prefrontal and superior parietal cortices, and lateral temporal and inferomedial occipital regions. Genetic effects were stronger for cost-efficiency than for other metrics considered, and were more clearly significant in functional networks operating in the 0.09-0.18 Hz frequency interval than at higher or lower frequencies. These findings are consistent with the hypothesis that brain networks evolved to satisfy competitive selection criteria of maximizing efficiency and minimizing cost, and that optimization of network cost-efficiency represents an important principle for the brain's functional organization.

Functional Connectivity and Brain Networks in Schizophrenia

Schizophrenia has often been conceived as a disorder of connectivity between components of large-scale brain networks. We tested this hypothesis by measuring aspects of both functional connectivity and functional network topology derived from resting-state fMRI time series acquired at 72 cerebral regions over 17 min from 15 healthy volunteers (14 male, 1 female) and 12 people diagnosed with schizophrenia (10 male, 2 female). We investigated between-group differences in strength and diversity of functional connectivity in the 0.06-0.125 Hz frequency interval, and some topological properties of undirected graphs constructed from thresholded interregional correlation matrices. In people with schizophrenia, strength of functional connectivity was significantly decreased, whereas diversity of functional connections was increased. Topologically, functional brain networks had reduced clustering and small-worldness, reduced probability of high-degree hubs, and increased robustness in the schizophrenic group. Reduced degree and clustering were locally significant in medial parietal, premotor and cingulate, and right orbitofrontal cortical nodes of functional networks in schizophrenia. Functional connectivity and topological metrics were correlated with each other and with behavioral performance on a verbal fluency task. We conclude that people with schizophrenia tend to have a less strongly integrated, more diverse profile of brain functional connectivity, associated with a less hub-dominated configuration of complex brain functional networks. Alongside these behaviorally disadvantageous differences, however, brain networks in the schizophrenic group also showed a greater robustness to random attack, pointing to a possible benefit of the schizophrenia connectome, if less extremely expressed.

Anesthetic gas control with neuro-fuzzy system in anesthesia

In this study, power spectrum of the EEG data and the heartbeat data obtained from 25 patients has been applied to the designed neuro-fuzzy system. The designed system has composed of two parts; one is an artificial neural network and the other is a fuzzy system. A back-propagation artificial neural network has been developed which contains 53 nodes in the input layer, 27 nodes in the hidden and 1 node in the output layer. In the artificial neural network inputs, the power spectral density values corresponding 1–50 Hz frequency interval of the EEG slices which has 10 s of time interval, the ratio of the total of the PSD values of current EEG slice to the total PSD values of EEG slice of pre-anesthesia, the ratio of the total PSD values of the EEG data to the total PSD values of the previous EEG data, and the previous anesthetic gas ratio values have been applied and the network has been educated. At the end of the education total error has been found as 10 - 17 . In the fuzzy system block, the ratio of current heartbeat to the previous one, the ratio of the current heartbeat to the pre-operation heartbeat, the ratio of the output of the artificial neural network to the previous applied anesthetic gas have been applied as variables and in the system output gas ratio prediction has been obtained as percentage. The designed neuro-fuzzy system has been tested by using 10 data set obtained from four different patients. In the anesthetic gas prediction according to the anesthesia level, successful results have been obtained with the designed system.

Reply to comment by A. P. Nickolaenko and M. Hayakawa on “Sprite lightning heard round the world by Schumann resonance methods”

Reply to comment by A. P. Nickolaenko and M. Hayakawa on “Sprite lightning heard round the world by Schumann resonance methods”

Odiosoft-Rhino versus rhinomanometry in healthy subjects

Conclusion. Odiosoft-Rhino (OR) is a non-invasive test that is completed in an extremely short period of time. It is easy to perform and little patient cooperation is needed. OR is safe and could be used in the rhinological setting if further improved. Objective. To evaluate nasal obstruction objectively with a new technique, OR, and to compare the results with a widely accepted method, rhinomanometry, in normal subjects. Subjects and methods. OR and anterior RMM were performed in 79 subjects without any rhinologic symptoms and signs. Visual analogue scales (VAS) of nasal obstruction, nasal airway resistance and nasal expiratory and inspiratory sounds were analysed. Results. VAS of nasal obstruction was found to be correlated with OR findings of expiration at 2000–4000 Hz frequency interval on both sides (r=0.564, p<0.01 for the left side, r=0.533, p<0.01 for the right side). Correlations were found (p<0.05) between left 2000–4000 Hz in expiration OR and left expiration RMM, left 4000–6000 Hz in expiration OR and left expiration RMM, right 2000–4000 Hz in expiration OR and right expiration RMM, and right 4000–6000 Hz in expiration OR and right expiration RMM. No correlation was seen between VAS, anterior RMM and OR at inspiration in any interval.

The Effects of General Anesthesia on Human Skin Microcirculation Evaluated by Wavelet Transform

Time-frequency analysis of the laser Doppler flowmetry signal, using wavelet transform, shows periodic oscillations at five characteristic frequencies related to the heart (0.6-2 Hz), respiration (0.15-0.6 Hz), myogenic activity in the vessel wall (0.052-0.15 Hz), sympathetic activity (0.021-0.052 Hz), and very slow oscillations (0.0095-0.021), which can be modulated by the endothelium-dependent vasodilator acetylcholine. We hypothesized that wavelet transform of laser Doppler flowmetry signals could detect changes in the microcirculation induced by general anesthesia, such as alterations in vasomotion and sympathetic activity. Eleven patients undergoing faciomaxillary surgery were included. Skin microcirculation was measured on the lower forearm with laser Doppler flowmetry and iontophoresis with acetylcholine and sodium nitroprusside before and during general anesthesia with propofol, fentanyl, and midazolam. The laser Doppler flowmetry signals were analyzed using wavelet transform. There were significant reductions in spectral amplitudes in the 0.0095-0.021 (P < 0.01), the 0.021-0.052 (P < 0.001), and the 0.052-0.15 Hz frequency interval (P < 0.01) and a significant increase in the 0.15-0.6 Hz frequency interval. General anesthesia had no effect on the difference between acetylcholine and sodium nitroprusside on relative amplitudes in the 0.0095-0.021 Hz frequency interval (P < 0.001). General anesthesia reduces the oscillatory components of the perfusion signal related to sympathetic, myogenic activity and the component modulated by the endothelium. However, the iontophoretic data did not reveal a specific effect on the endothelium. The increase in the 0.15-0.6 Hz interval is related to the effect of mechanical ventilation.

Nasal Sound Analysis: A New Method for Evaluating Nasal Obstruction in Allergic Rhinitis

Current measurements of nasal obstruction are unreliable and may be improved with the development of new techniques. The effectiveness of odiosoft-rhino (OR) in the evaluation of nasal obstruction was investigated in a blind comparison at a referral center, institutional practice. Forty-eight patients with perennial allergic rhinitis and 52 healthy subjects were studied. Nasal endoscopic examination, acoustic rhinometry (AR), and OR were performed and symptom scores compared. Assessment of nasal blockage with OR method was the main outcome measure. Using the OR technique, significant differences were observed between the patient and control groups. OR data correlated with symptom scores and endoscopic examination. However, this was not observed with AR. A 15.5-dB cutoff point for the left side and 14.5 dB cutoff point for the right side at the 2,000 to 4,000 Hz frequency interval resulted in 93.8% sensitivity and 92.3% specificity and 72.9% sensitivity and 80.8% specificity, respectively. A 8.5-dB cutoff point for the left and right sides at the 4,000 to 6,000 Hz frequency interval resulted in 87.5% sensitivity and 80.8% specificity and 70.8% sensitivity and 78.8% specificity, respectively. OR is a simple, noninvasive test for assessing nasal obstruction. The OR technique can detect nasal obstruction with high sensitivity and specificity, and these findings correlate with symptoms and physical examination.

On the dayside region between the shocked solar wind and the ionosphere of Mars

The objective of this paper is to explore the structure and properties of the region between the shocked solar wind and the planetary plasma on the dayside of Mars. This study is based on the observations obtained by the plasma instruments carried on board the Phobos 2 spacecraft. These instruments have independently identified several plasma boundaries in the dayside magnetosphere of Mars, the boundaries are located close to each other but exhibit different plasma features. This investigation leads us to conclude that a dayside region exists on Mars with the following characteristics: (1) the bulk of the shocked solar wind protons are deflected, (2) the total magnetic field increases, (3) a plasma depletion region is formed, (4) both shocked solar wind and planetary plasma are present, (5) accelerated electrons and heavy ions are also present, (6) intensive wave activity is seen in the 5 to 150 Hz frequency interval, and (7) a current layer and associated magnetic shears can be identified. We name this region, located between the ionosphere and the shocked solar wind, the dayside boundary layer or dayside mantle. Its key features are similar to those of the Venus mantle; the variety of names given to the Martian plasma boundaries merely reflects its complicated structure. We conclude that the two boundary layers at Venus and Mars are very similar and that the physical processes (i.e., the interaction of the shocked solar wind with the planetary plasma) at work within these boundary layers are probably similar.