Low-frequency Shift Research Articles

Development of a flat cutoff probe covered with a dielectric layer for non-invasive plasma diagnostics

Abstract Herein, we investigated the effect of a dielectric film on the transmission spectrum of a bar-type flat cutoff probe (BCP). By conducting electromagnetic wave simulations, we found that placing a dielectric film with a thickness of 1 mm or less on the sensor did not affect the measurement of the BCP under thin sheath condition. However, a film thickness of 1 mm or more results in a low-frequency shift in the cutoff frequency. The shift in the cutoff frequency was related not only to the film thickness, but also to the dielectric constant of the film and sheath width, which could be understood through a circuit model of the BCP. The calculated results were experimentally validated using alumina plates of various thicknesses. Consequently, our findings demonstrate that measuring the electron density on a BCP is feasible even when a dielectric film is deposited, thereby improving the accuracy of the measurement.

Effect of the electronic properties of the side charges of neutral solvent molecules on the charges of the N and H atoms of the carbazole molecule: IR experiment and DFT calculations

The IR spectral parameters of the absorption band of the valence vibration of the NH bond of the carbazole molecule in several neutral solvents (n-hexane C6H14, carbon tetrachloride CCl4, chloroform CHCl3, benzene C6H6) have been measured. It has been experimentally established that the position of the maximum of the NH vibrational band of the carbazole molecule in solvents undergoes a low-frequency shift relative to the gas phase. This shift increases in the series C6H14, CCl4, CHCl3, C6H6. The change in the magnitude of the linear shift is well described by the Kirkwood-Bauer-Magat KBM ratio in C6H14, CCl4, CHCl3. The presence of a linear shift may indicate that only universal interactions take place. The deviation of this ratio of shift magnitude for carbazole in benzene is interpreted as a manifestation of intermolecular complexation. Quantum-chemical calculations of the position of the absorption band position of the valence vibration of the NH bond of the carbazole molecule in these solvents, carried out by the electron density functional method B3LYP/6-31G using the Gaussian 09W program package, also showed a low-frequency shift relative to the gas phase.It was found that for the carbazole molecule in the condensed phase relative to the gas phase the following effects of changing the magnitude of charges on atoms N13 and H14 take place: 1 – increase in the positive sign of the charge on both atoms; 2 – the change in charge magnitude is larger on the nitrogen atom than on the hydrogen atom for both solvents (whose molecules have a dipole moment ∼0: C6H14, CCl4); 3 – the chlorine containing environment has a greater effect on the charge change in the carbazole molecule than the proton containing environment (whose molecules have a dipole moment ∼0: C6H14, CCl4).The correlation between the change of charges on atoms N13 and H14 with the value of electronegativity ξ of the side solvent atoms was established.Thus, it is shown that the charges on the 13N and 14H atoms of the carbazole molecule undergo changes in the presence of universal interactions, and the magnitude of the charge change depends on the electronic properties of the side atoms of the nearest solvent molecules. A hypothesis is proposed to explain the different frequency shift of the NH vibrational frequency of the molecule for chlorine-containing and hydrogen-containing side atoms of neutral solvent molecules, which takes into account different values of ξ for nitrogen and hydrogen atoms.

Investigation on enhanced band-gap properties of 2D hierarchical phononic crystals

Phononic crystals have garnered considerable attention in recent years for their unique band-gap properties, which can effectively manipulate the propagation of acoustic and elastic waves. This research focuses on exploring richer band gaps and utilizing band gap characteristics to achieve structural vibration reduction. In this study, a novel two-dimensional (2D) hierarchical phononic crystal with rich periodicities is proposed, which possesses enhanced band-gap properties. The research method used for the proposed structure is numerical simulation using the finite element method (FEM). By applying Bloch’s theorem, FEM is a more convenient tool for calculating the band gap of structures. Based on the numerical results, it can be concluded that the band gaps of the proposed 2D hierarchical phononic crystal can be classified not just into full and directional band gaps, but also into more fascinating categories based on the vibration patterns of macro and micro unit cells, which are referred to as Type I, Type II and Type III band gaps. Furthermore, the impact of structural parameter variations on the band gap is also studied, and results indicate that appropriate adjustments to the structural parameters (such as the number of unit cell n, the angle θ and the length l1) can lead to low-frequency shift and bandwidth increase in certain band gaps. A prototype of the hierarchical phononic crystal is manufactured using the 3D printing technique. Vibration tests are conducted and the simulation and experimental results are compared to verify the vibration reduction performance of the 2D hierarchical phononic crystal. The important contribution of this study is to reveal an interesting band gap generation characteristic of 2D hierarchical phononic crystals, which is beneficial for promoting understanding of the band gap mechanism in periodic structures. The enhanced band-gap properties in hierarchical periodic structures provide more potentialities and possibilities for practical vibration and noise reduction applications.

Research and simulation of electromagnetic wave absorbing performance for lightweight cement-based materials containing expanded polystyrene with different particle sizes and carbon black

The electromagnetic wave (EMW) absorbing performance of cement-based materials incorporating expanded polystyrene (EPS) with varying particle sizes is comprehensively studied through a combination of experimental and simulation methods. The addition of conductive carbon black (CB) to the cement matrix significantly increases the conductivity and dielectric constant, thereby improving the loss capacity. The frequency shift behavior of single and three-layer absorbing materials adheres to the effective medium theory and interference cancellation principle. The enhancement in overall EM parameters leads to a shift of the reflection loss (RL) peak towards lower frequencies. For three-layer materials, an increase in the thickness of absorbent layer proves beneficial for enhancing absorption performance. Simulations can effectively model cement-based materials by employing uniform material settings, with the size of EPS particles serving as the primary variable. The simulation results reveal that an increase in EPS particle size, in both single-layer and multi-layer materials, causes a shift of the RL peak towards lower frequencies. Additionally, analysis of electric field mode distribution and EM power loss density distribution indicates that scattering at the curved EPS interface alters the propagation direction of EMWs, increasing opportunities for loss inside the cement-based material. Moreover, the three-layer absorbing material, with a density ranging from 850 to 900 kg/m3 and compressive strength exceeding 4 MPa, is suitable for EMW absorption in building envelope structures. In conclusion, an increase in EPS particle size and CB content leads to a low-frequency shift of the RL absorption peak. This discovery not only provides an empirical foundation for the development of absorption materials tailored to specific frequency bands but also offers an efficient approach for repurposing waste EPS of diverse sizes. Furthermore, the grading of EPS with different particle sizes has important practical significance for increasing the content of EPS and preparing lightweight cement-based materials.

Microwave Photonics Broadband Doppler Velocity Simulator with High Spurious Suppression Ratio by Using Serrodyne Modulation

A Doppler velocity simulation method based on serrodyne modulation is proposed to achieve the frequency shift from hundred hertz to megahertz. One sub-phase modulation (PM) in a dual-parallel dual-drive Mach–Zehnder modulator loads a sawtooth signal to achieve a small frequency shift of the optical carrier. The other three sub-PMs implement carrier-suppressed double-band modulation of the RF signal. The RF signal is directly coupled from the receiving antenna to the modulator’s RF port without any electrical devices like a 90° hybrid, which ensures a broad operational bandwidth of the system. After filtering out one of the RF modulation sidebands by an optical filter, Doppler frequency shifting (DFS) is realized through frequency beating. The half-wave voltage of modulators rapidly decreases at low frequency shifts, leading to an increase in spurious signals. In order to improve the spurious suppression ratio (SSR) of DFS, a digital pre-distortion compensation based on the measured half-wave voltage is implemented in the frequency domain. Experimental results show that SSRs are larger than 35 dB when frequency shifts range from 0.1 kHz to 1 MHz. The RF operation bandwidth covers 2–40 GHz. The effectiveness of a Doppler velocity simulator is evaluated, and the simulation velocity error is less than 0.06 km/h. The proposed method has potential applications in both broadband electronic warfare and traffic metering applications.

Generalized frequency shift and attenuation in simply-supported micro/nano-beam resonators with thermoelastic dissipation

The low frequency shift, weak frequency attenuation, and large quality factor (Q) are strongly required for micro/nano-resonators with excellent operation performance. Therefore, the accurate predictions of frequency shift, frequency attenuation, and Q based on thermoelastic dissipation (QTED ) are significant when optimally designing micro/nano-resonators. In this work, employing the modified-couple-stress (MCS) and nonlocal-single-phase-lag (NSPL) models, the generalized analytical expressions of the frequency-shift ratio, frequency-attenuation ratio, and QTED are first proposed for the simply-supported micro/nano-beam resonator with two-dimensional (2D) heat conduction. In the modeling procedure, utilizing the Galerkin approach, the function of 2D fluctuation temperature is solved from the governing equation of NSPL thermoelasticity. For simplicity, the function of one-dimensional (1D) fluctuation temperature is presented directly. Various expressions of complex natural frequency are obtained from the governing equation of MCS vibration with thermoelastic coupling, and then the models of the frequency-shift ratio, frequency-attenuation ratio, and QTED are developed based on the relevant expressions of complex natural frequency. It is confirmed that the present developed models with generality can effectively degenerate into the classical models. In the simulation cases, silicon (Si) that is a representative semiconductor material is selected. Results reveal that the MCS size-dependence effect can affect the frequency shift more markedly than the NSPL and heat-conduction-dimension (HCD) effects. Moreover, for the beam with a small thickness and operated in a high-order mode, the NSPL and HCD effects will significantly determine behaviors of the frequency shift, frequency attenuation, and QTED .

Low-Frequency Light Shift Noise in Single-Beam Atomic Magnetometer: Analysis and Suppression Based on Frequency Response

Low-Frequency Light Shift Noise in Single-Beam Atomic Magnetometer: Analysis and Suppression Based on Frequency Response

Comparison of Speech Recognition and Hearing Preservation Outcomes Between the Mid-Scala and Lateral Wall Electrode Arrays.

To assess speech recognition and hearing preservation (HP) outcomes with the Advanced Bionics Mid-Scala and SlimJ electrodes. Retrospective cohort. Tertiary referral center. A total of 237 adult patients implanted between 2013 and 2020 (Mid-Scala, n = 136; SlimJ, n = 101). Consonant-nucleus-consonant (CNC) and AzBio (Arizona Biomedical) scores at 6 and 12 months; postoperative HP, defined as low-frequency pure-tone average ≤ 80 dB HL; scalar position. Mean CNC scores did not significantly differ between Mid-Scala and SlimJ recipients at 6 (45.8% versus 46.0%, p = 0.962) and 12 (51.9% versus 48.8%, p = 0.363) months. Similarly, mean AzBio in quiet scores were equivalent for both groups at 6 (55.1% versus 59.2%, p = 0.334) and 12 (60.6% versus 62.3%, p = 0.684) months. HP rates were significantly higher with the SlimJ (48.4%) than the Mid-Scala (30.8%; p = 0.033). Scalar translocations were 34.8 and 16.1% for the Mid-Scala and SlimJ groups, respectively ( p = 0.019). Ears with postoperative HP had significantly fewer scalar translocations (16.7% versus 37.2%, p = 0.048), and postoperative HP was associated with higher AzBio in noise scores at the most recent follow-up interval (38.7% versus 25.1%, p = 0.042). CNC, AzBio in quiet and noise, low-frequency pure-tone average shifts, and PTA at 6 and 12 months were not significantly different between patients with scala tympani insertions of the SlimJ versus the Mid-Scala ( p > 0.05). Compared with the Mid-Scala, the lateral wall electrode has superior HP rates and fewer scalar translocations, whereas speech recognition scores are equivalent between both electrode arrays. These findings can help providers with electrode selection and patient counseling.

Frequency spectrum characteristics of blast-induced vibration with electronic detonators in ground blasting

With the wide application of electronic detonators in blasting engineering, further study of frequency spectrum characteristics under precise delay time is essential for blasting design and safety evaluation. In this paper, the frequency spectra induced by blasting vibration under different delay times and distances are calculated, the frequency distribution and energy characteristics of various frequency bands are then investigated, and the demonstration is conducted using numerical simulation and electronic detonator blasting experiments. The results show that the low-frequency vibration proportion increases, and the dominant frequency shifts to a lower frequency compared with the vibration frequency distribution of single-hole blasting when using a very short delay time (≤5 ms). However, when a short delay time (6–12 ms) is used, the low-frequency shift to high frequency, reducing the energy ratio of low-frequency bands. And there are certain differences in the delay time to reduce PPV at different blasting center distances. A shorter delay time (6–8 ms) in the nearer region and a longer delay time (10–20 ms) in the intermediate and farther regions better reduce blasting vibration. Finally, considering multiple influencing factors, the 7–12 ms delay time is recommended to protect structures in the blasting area factors.

Evaluating the reproducibility and paleo-hydroclimate potential of coral skeletal Ba/Ca in the Gulf of Chiriquí, Panama

Coral skeletal Ba/Ca (Ba/Cacor) has been found to be highly correlated with river discharge in some coastal settings. However, any hydrologic interpretation of Ba/Cacor time-series requires thorough evaluation of regional climate, even at sites in close proximity to one another. Here we explore how two corals can be used to provide insight into hydroclimate in the Gulf of Chiriquí, Panama (GoC) using Ba/Cacor, a region whose climate is dictated by seasonal and lower frequency shifts in the Intertropical Convergence Zone. The main purpose of this study is to provide a preliminary assessment of Ba/Cacor replication in pursuit of a regional geochemical network. The two corals analyzed in this study (Secas Island, S1 and Coiba, IC4A-2) were collected ∼74 km apart and grew in different reef settings at vastly different distances from the main river discharge points. Analytical uncertainty prevents complete confidence determining whether a small geochemical offset Ba/Cacor exists between our two records. However, temporal variability in S1 and IC4A-2 are well correlated at all examined temporal scales (rmonthly = 0.70, rannual = 0.65, rwet season = 0.67, rdry season = 0.55, rannual amplitude = 0.77). Considering a potential geochemical offset may exist between the two corals, we took a conservative approach and examined S1 and IC4A-2 separately to establish a relationship with river discharge. Both corals, barring IC4A-2 dry season averages, are statistically significantly correlated to river discharge, permitting the creation of Reduced Major Axis regressions to quantify the relationship. Ultimately, in regions where river discharge dominates, a network of Ba/Cacor records may assist in reconstructing regional variability or notable deviations in hydroclimate. With additional and temporally longer Ba/Cacor records, we will be able to apply our framework to more clearly reconstruct river discharge variability throughout the GoC.

Highly transient stimulated Raman scattering in SrMoO4 under ultrafast laser pumping with a controllable chirp.

For the first time, to the best of our knowledge, we demonstrate highly transient, multiwavelength, single-pass Raman generation with combined frequency shifts on two Raman modes of an SrMoO4 crystal with high total Raman conversion efficiency of up to 48% in conditions of competition with self-phase modulation (SPM). A 58-mm-long SrMoO4 crystal was used as the active medium under pumping by the 1030-nm, 40-µJ laser pulses with controllable dispersive stretching in a range of 0.25-6 ps at negative and positive chirping. The pump pulse chirping was optimized for both high- and low-frequency Raman shifts on the primary (888 cm-1) and secondary (327 cm-1) Raman modes of the crystal. At the optimal conditions, four Stokes components of stimulated Raman scattering (SRS) radiation with high- and low-frequency Raman shifts at the wavelengths of 1066, 1134, 1177, and 1261 nm were efficiently generated.

Modified mouse model of repeated mild traumatic brain injury through a thinned-skull window and fluid percussion.

Mild traumatic brain injury (mTBI) is a clinically highly heterogeneous neurological disorder, none of the existing animal models can replicate the entire sequelae. This study aimed to develop a modified closed head injury (CHI) model of repeated mTBI (rmTBI) for investigating Ca2+ fluctuations of the affected neural network, the alternations of electrophysiology, and behavioral dysfunctions. The transcranial Ca2+ study protocol includes AAV-GCaMP6s infection in the right motor cortex, thinned-skull preparation, and two-photon laser scanning microscopy (TPLSM) imaging. The CHI rmTBI model is fabricated using the thinned-skull site and applying 2.0 atm fluid percussion with 48-h interval. The neurological dysfunction, minor motor performance, evident mood, spatial working, and reference deficits we found in this study mimic the clinically relevant syndromes after mTBI. Besides, our study revealed that there was a trend of transition from Ca2+ singlepeak to multipeak and plateau, and the total Ca2+ activities of multipeaks and plateaus (p < .001 vs. pre-rmTBI value) were significantly increased in ipsilateral layer 2/3 motor neurons after rm TBI. In parallel, there is a low-frequency power shift from delta to theta band (p < .01 vs. control) in the ipsilateral layer 2/3 of motor cortex of the rmTBI mice, and the overall firing rates significantly increased (p < .01 vs. control). Moreover, rmTBI causes slight cortical and hippocampal neuron damage and possibly induces neurogenesis in the dentate gyrus (DG). The alternations of Ca2+ and electrophysiological characteristics in layer 2/3 neuronal network, histopathological changes, and possible neurogenesis may play concertedly and partially contribute to the functional outcome post-rmTBI.

Structural and optical properties of C70 fullerenes in aqueous solution

The simple method of preparation of highly stable and purified C70 fullerene aqueous solution (C70FAS) is proposed. The features of structural stabilization of C70 fullerenes in an aqueous solution by studying their structural and optical properties using Raman, photoluminescence, infrared reflection-absorption, UV–VIS absorption, and dynamic light scattering spectroscopy methods were analyzed. The experimental results showed that the most likely mechanism for C70 fullerenes stabilization in water is surface hydroxylation with covalent attachment of water hydroxyls to C70 fullerene carbons. Raman and infrared absorption spectra of C70FAS showed characteristic vibrational bands of C70 fullerenes with a slight broadening and low-frequency shift of ∼1 cm−1, indicating the attachment of water hydroxyls to the C70 fullerene carbons. The photoluminescence spectra showed excitonic emission bands of C70 molecules with intensity depending on their content. UV–VIS absorption spectra demonstrate the absorption bands typical for monomeric C70 fullerene. Finally, the dynamic light scattering data confirmed that C70FAS is a typical colloidal fluid containing both individual C70 molecules and their nano aggregates up to 100 nm. These findings provide insights into the stabilization mechanism of C70 fullerenes in water and may have implications for their potential application in nanobiotechnology.

Microfiber evanescent-field photothermal gas detection using acoustic-induced mode-dependent frequency shift

Abstract In this study, we experimentally showcase the microfiber evanescent-field photothermal gas detection by exploiting all-fiber MHz-level frequency shift scheme. Based on the acousto-optic interaction effect, the low-frequency shifts of 0.9 MHz and 1.83 MHz can be obtained through the cyclic conversion between the transverse core modes LP01 and LP11 in the few-mode fiber. Our proposed all-fiber frequency shifters show flexible MHz-level up(down) frequency shifts with superior sideband rejection ratio (over 40 dB) and low insertion loss (less than 1 dB). Furthermore, an all-fiber heterodyne interferometric detection system is implemented by leveraging the above low-frequency shifters, in which around 1-μm-diameter microfiber is investigated for photothermal gas detection. A pump-probe configuration is employed to obtain the photothermal effect induced by the gas absorption of the modulated evanescent field. By demodulating the phase of the beat signal output by the interferometer, an equivalent detection limit (1σ) of 32 ppm and a response time of 22 s are achieved for ammonia, as well as 0.24 % instability within 48 pump cycles. Given its compact all-fiber configuration and high sensitivity with fast response, the experimental results can pave the way for widespread applications like heterodyne detection, fiber optical sensors, and interplanetary coherent communications.

Severe multi-year drought coincident with Hittite collapse around 1198–1196 bc

The potential of climate change to substantially alter human history is a pressing concern, but the specific effects of different types of climate change remain unknown. This question can be addressed using palaeoclimatic and archaeological data. For instance, a 300-year, low-frequency shift to drier, cooler climate conditions around 1200 bc is frequently associated with the collapse of several ancient civilizations in the Eastern Mediterranean and Near East1–4. However, the precise details of synchronized climate and human-history-scale associations are lacking. The archaeological–historical record contains multiple instances of human societies successfully adapting to low-frequency climate change5–7. It is likely that consecutive multi-year occurrences of rare, unexpected extreme climatic events may push a population beyond adaptation and centuries-old resilience practices5,7–10. Here we examine the collapse of the Hittite Empire around 1200 bc. The Hittites were one of the great powers in the ancient world across five centuries11–14, with an empire centred in a semi-arid region in Anatolia with political and socioeconomic interconnections throughout the ancient Near East and Eastern Mediterranean, which for a long time proved resilient despite facing regular and intersecting sociopolitical, economic and environmental challenges. Examination of ring width and stable isotope records obtained from contemporary juniper trees in central Anatolia provides a high-resolution dryness record. This analysis identifies an unusually severe continuous dry period from around 1198 to 1196 (±3) bc, potentially indicating a tipping point, and signals the type of episode that can overwhelm contemporary risk-buffering practices.

Effects of Ndufs4 Deletion on Hearing after Various Acoustic Exposures.

Mitochondrial dysfunction can cause cochlear dysfunction and accelerate noise-induced hearing loss (NIHL). NADH dehydrogenase (ubiquinone) Fe-S protein 4 (Ndufs4) is one of the subunits of mitochondrial complex I and has a role in the assembly and stabilization of complex I. However, the involvement of Ndufs4 in the pathogenesis of NIHL has not been reported. The aim of this study was to evaluate whether Ndufs4 deletion causes vulnerability to noise exposures. The wild-type (WT) and Ndufs4 knockout (KO) mice with C57BL/6J genetic background were used. Cochlear histology and hearing thresholds were assessed after noise exposure at 100 or 86 dB sound pressure level (SPL). Immunostaining showed the widespread expression of Ndufs4 in the cochlea. After noise exposure at 100 dB SPL, auditory brainstem response (ABR) threshold shifts at 4 kHz in Ndufs4 KO mice were significantly higher than that in WT mice. After noise exposure at 86 dB SPL, ABR threshold shifts, wave 1 amplitudes, and the number of synapses in the inner hair cells were not significantly different. RNA sequencing revealed the decreased expression of energy generation-related genes inNdufs4 KO mice. Ndufs4 deficiency accelerates permanent low-frequency threshold shifts after moderate noise exposure.

Estimation of electrostatic and covalent contributions to the enthalpy of H-bond formation in H-complexes of 1,2,3-benzotriazole with proton-acceptor molecules by IR spectroscopy and DFT calculations

Using the methods of IR-spectroscopy and quantum chemical calculations, we determined the formation of an H-bond between the 1,2,3-benzotriazole molecule and the molecules of acetone, dioxane, DMF, and DMSO. Quantum chemistry methods have been used to calculate the sums of charge changes in the atoms of the 1,2,3-benzotriazole molecule and of proton acceptor molecules (acetone, dioxane, DMF, and DMSO) due to the formation of their complexes with an H-bond (H-complexes NH…O). The sum of charge changes was taken as a contribution of a covalent component to H-bond formation. It has been established that as the sum of charge changes in N, H, and O or H and O, forming the H-complex, increases, the enthalpy of H-complex formation (EF) decreases. On the contrary, the EO of H-complexes increases when the product of the initial charges on the H and O atoms increases. In the absence of H-complexes, the product of charges was considered the electrostatic component of H-bond formation. The criterion of the value of H-bond EF was the value of a low-frequency shift of the initial position of the maximum IR absorption band of the NH vibration of the 1,2,3-benzotriazole molecule relative to its position in a neutral CCl4 solvent. The results of QTAIM, NCI, and RDG analyses showed that the values of energy densities in BCPs have a positive value in the complexes formed by 1,2,3-benzotriazole with acetone, dioxane, and DMFA, and such hydrogen bonds are electrostatic in nature. In the complex formed by 1,2,3-benzotriazole and DMSO, it has a negative value and a covalent character. The data obtained have allowed for two main conclusions: (i) In the formation of the H-complexes of the 1,2,3-benzotriazole molecule with proton-acceptor molecules containing oxygen atoms, the main contribution to H-bond formation is made by the electrostatic component. (ii) The contribution of the covalent component increases with increasing enthalpy of H-bond formation.

Slim Modiolar Electrode Placement in Candidates for Electroacoustic Stimulation.

To determine rates of hearing preservation and performance in patients who met candidacy for electroacoustic stimulation (EAS) and were implanted with a slim modiolar electrode (CI532 or CI632). Adult patients meeting Food and Drug Administration criteria for electroacoustic stimulation (preoperative low-frequency pure-tone average [LFPTA] less than 60 dB at 125, 250, and 500 Hz and monosyllabic word scores between 10% and 60% in the ear to be implanted), who received a slim modiolar electrode were included. Main outcome measures included rates of hearing preservation, defined as a LFPTA ≤80 dB at 125, 250, and 500 Hz, as well as postoperative low-frequency pure-tone threshold shifts, consonant-Nucleus-Consonant (CNC) word scores and AzBio sentences in noise scores. Forty-six patients met inclusion criteria during a 4-year period. Mean (standard deviation) preoperative LFPTA was 34.5 (13.0) dB, and 71.7% had preserved hearing at initial activation. The mean LFPTA shift in patients who preserved hearing at initial activation was 19.7 (14.6) dB, compared with 62.6 (17.7) dB in patients who did not preserve hearing as per our definition. Perioperative steroid use was not different in patients with and without preserved hearing (X 2 (1, N = 46) = 0.19, p = .67, V = 0.06). One year after surgery, 57% of patients had a decline in LFPTA >80 dB and were no longer considered candidates for EAS, with 34.7% still retaining low-frequency thresholds ≤80 dB. CNC word scores at 1 year were 69.9% and 61.4% among individuals with and without preserved low-frequency hearing respectively, measured in their CI ear alone, in their regular listening condition of EAS or electric only ( t (32) = 1.13, p = 0.27, d = 0.39, 95% CI = -6.51, 22.86). Device use time did not differ between groups. Among adults with preserved residual hearing at 1 year (n = 16), 44% used EAS, although there was no significant difference in performance between EAS users and nonusers with preserved hearing. Loss of residual hearing over time did not result in a decline in speech perception performance. The present study demonstrated favorable early rates of hearing preservation with a slim modiolar array. Performance was not significantly different in individuals with and without preserved low-frequency acoustic hearing, independent of EAS use. Compared with reports of short electrode use, the loss of residual hearing in patients implanted with this array did not impact speech perception performance.

Speech Recognition Performance Differences Between Precurved and Straight Electrode Arrays From a Single Manufacturer.

Precurved cochlear implant (CI) electrode arrays have demonstrated superior audiometric outcomes compared with straight electrodes in a handful of studies. However, previous comparisons have often failed to account for preoperative hearing and age. This study compares hearing outcomes for precurved and straight electrodes by a single manufacturer while controlling for these and other factors in a large cohort. Retrospective cohort study. Tertiary academic medical center. Two hundred thirty-one adult CI recipients between 2015 and 2021 with cochlear (Sydney, Australia) 522/622 (straight) or 532/632 (precurved) electrode arrays. Postactivation speech recognition and audiometric testing. Speech recognition testing (consonant-nucleus-consonant word [CNCw] and AzBio) was collected at 6 and 12 months postactivation. Hearing preservation was characterized by a low-frequency pure-tone average shift, or the change between preoperative and postoperative low-frequency pure-tone average. Two hundred thirty-one patients (253 ears) with 6-month and/or 12-month CNCw or AzBio testing were included. One hundred forty-nine (59%) and 104 (41%) ears were implanted with straight and precurved electrode arrays, respectively. Average age at implantation was 70 years (interquartile range [IQR], 58-77 y). There was no significant difference in mean age between groups. CNCw scores were significantly different ( p = 0.001) between straight (51%; IQR, 36-67%) and precurved arrays (64%; IQR, 48-72%). AzBio scores were not significantly different ( p = 0.081) between straight (72%; IQR, 51-87%) and precurved arrays (81%; IQR, 57-90%). Controlling for age, race, sex, preoperative hearing, and follow-up time, precurved electrode arrays performed significantly better on CNCw (b = 10.0; 95% confidence interval, 4.2-16.0; p < 0.001) and AzBio (b = 8.9; 95% confidence interval, 1.8-16.0;, p = 0.014) testing. Hearing preservation was not different between electrodes on adjusted models. During the study period, patients undergoing placement of precurved electrode arrays had significantly higher CNC and AzBio scores than patients receiving straight electrodes, even after controlling for age, preoperative hearing, and follow-up time. Understanding the difference in audiometric outcomes between precurved and straight electrode arrays will help to guide electrode selection. To understand differences in speech recognition scores postoperatively by electrode array type (precurved versus straight). To demonstrate a difference in hearing performance postoperatively by electrode type. III. Approved by the Institutional IRB (090155).

All-fiber low-frequency shifter based on acousto-optic interaction and its heterodyne vibration response.

We demonstrate two all-fiber low-frequency shift schemes based on the acousto-optic interaction in a few-mode fiber (FMF). Two acoustically induced fiber gratings (AIFGs) are cascaded in reverse to achieve an efficient cycle conversion between LP11 and LP01 core modes in the FMF while obtaining a frequency shift of 1.8 MHz. In addition, a long-period fiber grating (LPFG) is employed to replace the AIFG, which achieves a lower frequency shift of 0.9 MHz, and its tunable wavelength range exceeds 100 nm. Both schemes show the characteristics of an upward frequency shift. Moreover, we also present a heterodyne detection system based on the above frequency shift schemes, which is verified in response to micro-vibration signals ranging from tens to hundreds of kilohertz, as well as speech signals in a lower frequency range. The experimental results show that these all-fiber frequency shift schemes have potential applications, such as in fiber optic hydrophones, laser speech detection, and fiber optic sensors.