Increasing Center Frequency Research Articles

P0266 Ultrasound Spectroscopy for the detection of inflammation in inflammatory bowel disease

Abstract Background Accurate assessment of inflammation within the intestinal wall is crucial in managing patients with Inflammatory Bowel Disease (IBD), a condition with rising incidence and prevalence worldwide. Ultrasound offers an effective, non-invasive diagnostic option to diagnose and monitor the disease. However, traditional ultrasound is highly user-dependent and requires considerable experience to accurately determine the degree of inflammation. As an extension, Quantitative Ultrasound (QUS), the analysis of raw ultrasound data consisting of unprocessed acoustic signals, contains both frequency and phase information, enabling spectroscopy. We hypothesize that these signals allow a precise estimation of inflammation within the intestinal wall. Methods The study was conducted at the Sonography Departments of University Clinic Dresden and Charité- Universitätsmedizin Berlin, where patients attended bowel examinations. In addition to the Limberg-Score acquired with a Highend-Ultrasound-Systems, raw data were obtained using a handheld ultrasound device (Clarius L15). For spectroscopy analysis, time-gain compensation was first reversed from the radio frequency data, followed by frequency analysis using short-time fast Fourier transformation. Results We included 35 patients (22 male, 13 female) aged 19 to 85 years. They were either diagnosed with Crohn’s disease (24) or ulcerative colitis (11). Our results indicate a positive correlation between the Limberg score (0–4) and peak frequency in MHz, as determined through the raw ultrasound data spectroscopy. Pairwise comparisons applying analysis of variance (ANOVA) testing, followed by a t-test with Benjamini-Hochberg correction as post hoc, revealed statistically significant differences between Limberg scores 0 and 2 (p ≤ 0.05), 0 and 3 (p ≤ 0.01) and scores 0 and 4 (p ≤ 0.05). The comparison between groups 0 and 1 demonstrated a trend but did not reach statistical significance (p=0.058). Conclusion Our findings indicate that higher Limberg scores are associated with increased center frequency, with statistically significant differences evident at advanced inflammation levels. This exploratory study demonstrates, for the first time, the capability of QUS to detect changes in intestinal tissues, offering an innovative approach for objectively monitoring inflammatory bowel disease. However, potential confounders such as attenuation in varying imaging depths and mixed causality of the inflammation need to be considered. A reevaluation after including larger sample sizes is required to reinforce the study’s findings and further explore the potential of QUS in the context of IBD.

The Impact of Group Delay Dispersion on Radar Imaging With Multiresonant Antennas

Radar sensing has become very popular over the last two decades, and research has focused on high-bandwidth and high-resolution systems. Due to the steadily increasing center frequency of front-end circuits, on-chip antennas are the preferred choice over PCB antennas and horn antennas when frequencies get close to THz. However, conventional on-chip antennas are severely limited in bandwidth, leading to increased use of wideband and multiresonant on-chip antennas. Besides a more complex design process of multiresonant antennas, they have the disadvantage of a nonconstant dispersive group delay (GD). This reduces the resolution of sensing systems, such as the range resolution and angular resolution of a radar system. In this work, we show how GD affects the imaging properties of a radar system. The measured S-parameter data from a 240-GHz multiresonant antenna are used to generate synthetic intermediate frequency (IF) signals of a rectangular array. Subsequently, simulated 3-D radar images are generated using the backprojection algorithm. These images are compared with those of a nondispersive imaging system. Finally, two compensation methods using a phase correction method and an all-pass filter are explained, and their performance is compared.

Dietary Supplementation of Gingerols- and Shogaols-Enriched Ginger Root Extracts Attenuate Pain-Associated Behaviors in Animals with Spinal Nerve Ligation

Abstract Objectives Neuropathic pain (NP), arising from damage to the nervous system, could be a consequence of the imbalance between reactive oxygen species (ROS) and endogenous antioxidants after nerve injury, leading to neuroinflammation. Therefore, this study was to evaluate the effects of two ginger root extracts rich in gingerols and shogoals, respectively, on pain sensitivity and anxiety-like behaviors in neuropathic animals. We also assessed the plasma circulating cell-free mitochondrial DNA (ccf-mtDNA) damage, a biomarker of excessive mitochondria-derived ROS linked to inflammation. Methods Sixteen male rats were randomly divided into 4 groups: sham group, spinal nerve ligation (SNL) group as the pain control group, SNL+ gingerols-enriched ginger (GEG) extract group, and SNL+ shogoals-enriched ginger (SEG) extract group. Animals in GEG and SEG groups were fed with their respective diets on the day of SNL surgery for 30 days. At 1 day before and 10, 20, and 30 days post operation, (i) paw withdrawal mechanical thresholds were measured using von Frey filaments for pain sensory assessment; and (ii) center frequency and center duration in the open field test (OFT) were measured to assess anxiety-like behavior. At Day 30, plasma was obtained for ccf-mtDNA concentration measurement. Data were analyzed by one-way ANOVA or one-way repeated measures analysis of variance follow by post-hoc analysis. Results Compared to the sham group, the SNL group had significant greater pain sensitivity to mechanical stimuli. When compared to the SNL group, both GEG and SEG groups showed significantly (50%) reduced pain sensitivity (increased thresholds) as early as at 10 days and sustained at 30 days. Relative to the SNL group, both GEG and SEG groups also had less anxiety-like behavior (as indicated by the elongated center duration and increased center frequency in OFT). The SNL group had significantly higher plasma ccf-mtDNA levels relative to the sham group. When SNL-animals were fed a diet supplemented with either gingerols or shogaols, both groups showed reduction in plasma ccf-mtDNA. Conclusions Both gingerols and shogaols supplementation decreased pain sensitivity and improved anxiety-like behavior mediated in part through the suppression of mitochondrial damage. Funding Sources Texas Tech University Health Sciences Center.

Frequency selectivity in macaque monkeys measured using a notched-noise method

The auditory system is thought to process complex sounds through overlapping bandpass filters. Frequency selectivity as estimated by auditory filters has been well quantified in humans and other mammalian species using behavioral and physiological methodologies, but little work has been done to examine frequency selectivity in nonhuman primates. In particular, knowledge of macaque frequency selectivity would help address the recent controversy over the sharpness of cochlear tuning in humans relative to other animal species. The purpose of our study was to investigate the frequency selectivity of macaque monkeys using a notched-noise paradigm. Four macaques were trained to detect tones in noises that were spectrally notched symmetrically and asymmetrically around the tone frequency. Masked tone thresholds decreased with increasing notch width. Auditory filter shapes were estimated using a rounded exponential function. Macaque auditory filters were symmetric at low noise levels and broader and more asymmetric at higher noise levels with broader low-frequency and steeper high-frequency tails. Macaque filter bandwidths (BW3dB) increased with increasing center frequency, similar to humans and other species. Estimates of equivalent rectangular bandwidth (ERB) and filter quality factor (QERB) suggest macaque filters are broader than human filters. These data shed further light on frequency selectivity across species and serve as a baseline for studies of neuronal frequency selectivity and frequency selectivity in subjects with hearing loss.

Sex differences in sensitivity to prenatal and early childhood manganese exposure on neuromotor function in adolescents

IntroductionWhile studies have suggested that exposure to manganese (Mn) may be associated with neurodevelopment in school-age children, there is limited information on prenatal and postnatal Mn exposures and tremor or motor function in children. MethodsWe measured Mn levels in dentine of shed teeth, representing prenatal, early postnatal, and cumulative childhood exposure windows, from 195 children (predominantly right-handed, 92%) in Italy. Pursuit Aiming, Luria Nebraska Motor Battery, as well as Tremor and Sway system from Computerized Adaptive Testing System (CATSYS) were administered at 11–14 years old. We examined the relationships of tooth Mn (ln-transformed) with motor function using multivariable linear regressions and generalized additive models, adjusting for age, sex, and socioeconomic status index. Effect modification by sex was also examined. ResultsWe found that higher prenatal Mn was associated with better body stability in boys in a number of sway tests (including mean sway, transversal sway, sagittal sway, sway area, and sway intensity), while Mn was associated with poorer performance in girls on all of these metrics (all p for Mn × sex interaction < 0.05). Higher prenatal Mn was also modestly associated with better hand/finger and eye-hand coordination in boys compared to girls in sex-stratified analyses, although interaction models did not reach statistical significance. For tremor, on the other hand, higher early postnatal Mn was associated with increased right-hand center frequency in girls (p for interaction < 0.01), but increased Mn level at the later postnatal period was associated with increased center frequency in boys (p for interaction = 0.01). ConclusionsThis study, which used a direct measure of prenatal and childhood Mn exposure, suggested sex-specific critical windows of early life Mn exposure in relation to neuromotor function in adolescents. The sex-specific associations might be strongest with measures of whole body stability, for which the critical exposure window was during the prenatal period.

Design and Analysis of an Ultra-Low-Power Second-Order Asynchronous Delta–Sigma Modulator

In this paper, a second-order asynchronous delta–sigma modulator is proposed based on the active-RC integrators. The operational transconductance amplifiers used in the integrators are improved by employing a class-AB structure with bulk-driven input drivers and quasi-floating gate method in subthreshold region. These circuitry approaches provide better linearity, signal-to-noise ratio and speed for the integrators and hence an overall improvement in the performance of the modulator. Mathematical analyses of the second-order modulator confirm a higher center frequency compared to a first-order one. The increased center frequency transfers redundancy distortions to higher frequencies, which results in wider input bandwidth and better linearity. The proposed ASDM designed in TSMC 130 nm CMOS Technology with a center frequency of 1.73 kHz at supply voltage of 250 mV with a signal-to-noise-plus-distortion ratio of 67.3 dB and the power consumption of 30 nW.

On the influence of sensorineural hearing loss on the pitch strength of bandpass noise

In the perception of environmental noises and in the field of speech and music, tonality plays a crucial role. A tonal character can help the listeners to identify the sound source. However, environmental noises with a tonal character are also considered as especially annoying sounds. The psychoacoustic measure “pitch strength” describes the strength of the tonal sensation evoked by the sound on a scale from weak to strong. For normal-hearing listeners, it was shown in the literature that the pitch strength of bandpass noises decreased with increasing bandwidth when the center frequency was fixed and increased with increasing center frequency when the noise bandwidth was fixed. These results are presumably linked to the frequency selectivity of the auditory system. Since cochlear damage leads to a pathological widening of the auditory filters in the inner ear, an altered perception of pitch strength seems possible. In our study, we investigated whether and to which extent pitch strength is influenced by c...

Durations required to distinguish noise and tone: Effects of noise bandwidth and frequency

Perceptual audio coders exploit the masking properties of the human auditory system to reduce the bit rate in audio recording and transmission systems; it is intended that the quantization noise is just masked by the audio signal. The effectiveness of the audio signal as a masker depends on whether it is tone-like or noise-like. The determination of this, both physically and perceptually, depends on the duration of the stimuli. To gather information that might improve the efficiency of perceptual coders, the duration required to distinguish between a narrowband noise and a tone was measured as a function of center frequency and noise bandwidth. In experiment 1, duration thresholds were measured for isolated noise and tone bursts. In experiment 2, duration thresholds were measured for tone and noise segments embedded within longer tone pulses. In both experiments, center frequencies were 345, 754, 1456, and 2658 Hz and bandwidths were 0.25, 0.5, and 1 times the equivalent rectangular bandwidth of the auditory filter at each center frequency. The duration thresholds decreased with increasing bandwidth and with increasing center frequency up to 1456 Hz. It is argued that the duration thresholds depended mainly on the detection of amplitude fluctuations in the noise bursts.

Transmission beam characteristics of a Risso's dolphin (Grampus griseus).

The echolocation system of the Risso's dolphin (Grampus griseus) remains poorly studied compared to other odontocete species. In this study, echolocation signals were recorded from a stationary Risso's dolphin with an array of 16 hydrophones and the two-dimensional beam shape was explored using frequency-dependent amplitude plots. Click source parameters were similar to those already described for this species. Centroid frequency of click signals increased with increasing sound pressure level, while the beamwidth decreased with increasing center frequency. Analysis revealed primarily single-lobed, and occasionally vertically dual-lobed, beam shapes. Overall beam directivity was found to be greater than that of the harbor porpoise, bottlenose dolphin, and a false killer whale. The relationship between frequency content, beam directivity, and head size for this Risso's dolphin deviated from the trend described for other species. These are the first reported measurements of echolocation beam shape and directivity in G. griseus.

Radar signal propagation through the ionosphere of Europa

We review the current state of knowledge of the Europan plasma environment, its effects on radio wave propagation, and its impact on the performance and design of future radar sounders for the exploration of Europa׳s ice crust. The Europan ionosphere is produced in two independently-rotating hemispheres by photo-ionization of the neutral exosphere and interaction with the Io plasma torus, respectively. This combination is responsible for temporal and longitudinal ionospheric heterogeneities not well constrained by observations. When Europa׳s ionosphere is active, the maximum cut-off frequency is 1MHz at the surface. The main impacts on radar signal propagation are dispersive phase shift and Faraday rotation, both a function of the total electron content (up to 4×1015m−2) and the Jovian magnetic field strength at Europa (~420nT). The severity of these impacts decrease with increasing center frequency and increase with altitude, latitude, and bandwidth. The 9MHz channels on the Radar for Icy Moons Exploration (RIME) and proposed Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON) will be sensitive to the Europan ionosphere. For these or similar radar sounders, the ionospheric signal distortion from dispersive phase shift can be corrected with existing techniques, which would also enable the estimation of the total electron content below the spacecraft. At 9MHz, the Faraday fading is not expected to exceed 6dB under the worst conditions. At lower frequencies, any active or passive radio probing of the ice shell exploration would be limited to frequencies above 1–8MHz (depending on survey configuration) below which Faraday rotation angle would lead to signal fading and detection ambiguity. Radar instruments could be sensitive to neutrals and electrons added in the exosphere from any plume activity if present.

Echolocation beam shape of the Risso's dolphin (Grampus griseus)

Studies have shown that echolocation signals of some odontocete species are projected in both single and sometimes vertically dual-lobed beam shapes. In this study, the echolocation beam of a Risso's dolphin (Grampus griseus) was measured from a captive individual ensonifying an underwater target. Clicks were recorded with an array of 16 hydrophones and the two dimensional beam shape was explored using frequency-dependent amplitude plots. Click source parameters were comparable to those already described for this species, while analysis revealed primarily single-lobed, and occasionally vertically dual-lobed, beam shapes. Center frequencies of click signals increased with increasing sound pressure level, while the −3 dB beam radius decreased with increasing center frequency. This study is the first to measure the beam shape of echolocation signals in G. griseus, which exhibits forms similar to those found in the bottlenose dolphin and false killer whale

Control of the stop band of an acoustic double fishnet

The acoustic transmittance of two closely spaced solid plates, each perforated with a square array of cylindrical holes, exhibits a band of near-perfect acoustic attenuation originating from hybridization between a resonance in the gap separating the plates and pipe resonances in the holes. Displacement of one plate relative to the other, such that the holes are no longer aligned, or an increase in the plate separation leads to an increased center frequency of the stop band. This ability to easily tune the frequency of the stop band may prove advantageous.

Dependency of tonality perception on frequency, bandwidth, and duration

Psychoacoustic studies show that a narrowband noise masker exhibits a stronger simultaneous masking effect than a tonal masker with the same signal power placed at the noise center frequency. Consequently, perceptual audio codecs commonly incorporate some sort of tonality estimation as part of their perceptual model. However, common tonality estimation techniques do not necessarily reflect the perception of tonality by human listeners. As long as the tone and narrowband noise signals are long enough, they are easily distinguishable for normal hearing listeners. However, if the stimulus duration decreases, both signal types approach the shape of impulses, and therefore, at some point become audibly identical. Consequently, at a given frequency and noise bandwidth, there is a duration threshold below which the signals cannot be distinguished. A series of so-called “2-AFC 3-step up-down” psychoacoustic tests are designed and carried out to investigate the frequency and bandwidth dependency of these duration thresholds. The test results, collected from 32 listeners, are statistically evaluated and confirm a decreasing threshold for increasing center frequency and bandwidth. These results can be used to improve psychoacoustic models for audio codecs by using tonality estimators with frequency and bandwidth adapted temporal resolution.

Frequency difference limens at high frequencies: Evidence for a transition from a temporal to a place code

It is commonly believed that difference limens for frequency (DLFs) for pure tones depend on a temporal mechanism (phase locking) for frequencies up to 4-5 kHz and a place mechanism at higher frequencies. The DLFs predicted from a place mechanism, expressed as a proportion of center frequency (Δf/f), should be approximately invariant with frequency at medium to high frequencies. If there is a transition from a temporal to a place mechanism, Δf/f should increase with increasing center frequency until the transition occurs, and then reach a plateau. Published data do not show such an effect. In this study, DLFs were measured for center frequencies from 2 to 14 kHz, using earphones designed to produce a flat response at the eardrum. The level of every tone was varied over a range of ±4 dB, to reduce loudness cues. The value of Δf/f increased progressively from 2 to 8 kHz, but did not change significantly for frequencies from 8 to 14 kHz. The results are consistent with the idea that there is a transition from a temporal to a place mechanism at about 8 kHz, rather than at 4-5 kHz, as is commonly assumed.

Pitch perception of concurrent harmonic tones with overlapping spectra

Fundamental frequency difference limens (F0DLs) were measured for a target harmonic complex tone with nominal fundamental frequency (F0) of 200 Hz, in the presence and absence of a harmonic masker with overlapping spectrum. The F0 of the masker was 0, ± 3, or ± 6 semitones relative to 200 Hz. The stimuli were bandpass filtered into three regions: 0-1000 Hz (low, L), 1600-2400 Hz (medium, M), and 2800-3600 Hz (high, H), and a background noise was used to mask combination tones and to limit the audibility of components falling on the filter skirts. The components of the target or masker started either in cosine or random phase. Generally, the effect of F0 difference between target and masker was small. For the target alone, F0DLs were larger for random than cosine phase for region H. For the target plus masker, F0DLs were larger when the target had random phase than cosine phase for regions M and H. F0DLs increased with increasing center frequency of the bandpass filter. Modeling using excitation patterns and "summary autocorrelation" and "stabilized auditory image" models suggested that use of temporal fine structure information can account for the small F0DLs obtained when harmonics are barely, if at all, resolved.

Narrow noise band detection in a complex masker: Masking level difference due to harmonicity

Three experiments investigated listeners' ability to detect a narrow band of noise, centered on one partial of a random-phase complex tone, as a function of inharmonicity. Inharmonicity was generated by randomly mistuning the partial frequencies from a 100-Hz fundamental frequency (F0). In experiment 1, masked detection thresholds were lower when the masker was harmonic than when it was inharmonic for target bands in the range 0.5–2.5 kHz. The presence of this masking level difference due to harmonicity (HMLD) in regions of resolved partials and the reduction of the HMLD with increasing center frequency did not support the idea that HMLD was primarily caused by the envelope modulations produced by the beating of unresolved partials within an auditory filter. In experiment 2, masker mistunings ranging beyond 12% of the F0 disrupted the HMLD while smaller mistunings gave thresholds similar to a harmonic masker. In experiment 3, all partials contributed to some extent to the HMLD, but the harmonicity of partials neighboring the target had a greater influence than distant partials. The observed HMLDs can best be accounted for by a mechanism of harmonic cancellation.

Subcomponent cues in binaural unmasking

The addition of a signal in the N0Sπ binaural configuration gives rise to fluctuations in interaural phase and amplitude. Sensitivity to these individual cues was measured by applying sinusoidal amplitude modulation (AM) or quasi-frequency modulation (QFM) to a band of noise. Discrimination between interaurally in-phase and out-of-phase modulation was measured using an adaptive task for narrow bands of noise at center frequencies from 250 to 1500 Hz, for modulation rates of 2-40 Hz, and with or without flanking bands of diotic noise. Discrimination thresholds increased steeply for QFM with increasing center frequency, but increased only modestly for AM, and mainly for modulation rates below 10 Hz. Flanking bands of noise increased thresholds for AM, but had no consistent effect for QFM. The results suggest that two underlying mechanisms may support binaural unmasking: one most sensitive to interaural amplitude modulations that is susceptible to across-frequency interference, and a second, most sensitive to interaural phase modulations that is immune to such effects.

Localization dominance and the effect of frequency in the Mongolian Gerbil, Meriones unguiculatus

Due to its good low-frequency hearing, the Mongolian Gerbil (Meriones unguiculatus) has become a well-established animal model for human hearing. In humans, sound localization in reverberant environments is facilitated by the precedence effect, i.e., the perceptual suppression of spatial information carried by echoes. The current study addresses the question whether gerbils are a valid animal model for such complex spatial processing. Specifically, we quantify localization dominance, i.e., the fact that in the context of precedence, only the directional information of the sound which reaches the ear first dominates the perceived position of a sound source whereas directional information of the delayed echoes is suppressed. As localization dominance is known to be stimulus-dependent, we quantified the extent to which the spectral content of transient sounds affects localization dominance in the gerbil. The results reveal that gerbils show stable localization dominance across echo delays, well comparable to humans. Moreover, localization dominance systematically decreased with increasing center frequency, which has not been demonstrated in an animal before. These findings are consistent with an important contribution of peripheral-auditory processing to perceptual localization dominance. The data show that the gerbil is an excellent model to study the neural basis of complex spatial-auditory processing.

Effects of center frequency and rate on the sensitivity to interaural delay in high-frequency click trains

The effects of center frequency and pulse rate on the sensitivity to ongoing envelope interaural time differences (ITDs) were investigated using bandpass-filtered pulse trains. Three center frequencies (4.6, 6.5, and 9.2 kHz) were tested with bandwidths scaled to stimulate an approximately constant range on the basilar membrane. The pulse rate was varied from 200 to 588 pps (pulses per seconds). Five normal-hearing (NH) subjects were tested. Averaged over all rates, the results show a small decrease in sensitivity with increasing center frequency. For all center frequencies, sensitivity decreases with increasing pulse rate, yielding a rate limit of approximately 500 pps. The lack of an interaction between pulse rate and center frequency indicates that auditory filtering was not the rate limiting factor in ITD perception and suggests the existence of other limiting mechanisms, such as phase locking or more central processes. It is concluded that the comparison of the rate limits in ITD perception between cochlear-implant listeners and NH subjects listening to high-frequency bandpass-filtered pulse trains is not confounded by the choice of center frequency of stimulation in NH listeners.

Relative importance of different spectral bands to consonant identification: Relevance for frequency transposition in hearing aids

Listeners with high-frequency dead regions (DRs) benefit from amplification of frequencies up to 1.7 times the edge frequency, fe, of the DR. Better consonant identification might be achieved by replacing the band from fe to 1.7fe with a higher spectral band. We aimed to identify the optimal band, using simulations with normal-hearing listeners. In experiment 1, nonsense syllables were lowpass filtered to simulate DRs with fe of 0.5, 0.75, and 1.0 kHz. Identification was measured for each of these base bands alone and with a bandpass-filtered band added (but not transposed). The added band either extended from fe to 1.7fe or its center frequency was increased, keeping bandwidth fixed in ERBN-number. Performance improved with increasing center frequency and then reached an asymptote or declined. Experiment 2 used a mid-frequency base band, and a lower-frequency added band. The results also showed a beneficial effect of frequency separation of the added and base bands. Experiment 3 resembled experiment 1, but with bandwidth fixed in Hertz. For higher-frequency added bands, the benefit was lower than for experiment 1.