Local Frequency Research Articles

Wind turbine gearbox fault diagnosis via adaptive IMFogram

Wind turbines usually operate in mountainous, offshore and other field environments. As the wind speed is constantly changing, the gearboxes of wind turbines operate under variable operating conditions, resulting in a non-stationery and time-varying signal characteristic. For existing time–frequency analysis (TFA) methods, they undergo low time–frequency energy concentration as well as noise interference during the fault feature extraction. IMFogram, a recently proposed time–frequency representation (TFR) method, calculates local frequency and amplitude information of signals based on fast iterative filtering (FIF). Moreover, it is able to remove uncertainty on the time–frequency plane, allowing a long enough time window to reduce the local boundary effects associated with the signal decomposition methods. Therefore, it has potential advantages for TFA. However, the actual performance of IMFogram calculation largely depends on the decomposition effect provided by FIF and the selection of model parameters. With the purpose of obtaining a more distinct and focused TFR of the wind turbine vibration signal, a novel TFA method, namely Adaptive IMFogram (AIMFogram), is proposed in this paper. Firstly, a range of intrinsic mode functions (IMFs) are gained after the decomposition of vibration signals using an improved variational nonlinear chirp mode decomposition, which is treated as the input to AIMFogram to solve the unsatisfied result by traditional FIF under strong noise. Secondly, Renyi entropy-based particle swarm optimization is conducted to perform adaptive parameter optimization of the AIMFogram. Later, using the optimal parameter, the proposed AIMFogram achieves a high-resolution TFR of complex multi-component vibration signals. To verify whether the proposed AIMFogram is effective or not, the method was successfully employed to the fault diagnosis of the rolling bearing in an experimental bench and the gearbox in a 850-kW wind turbine.

Simplified colorless characterization scheme for coherent receivers in DWDM scenarios using a single interferer

Intradyne coherent receivers, capable of detecting an individual wavelength-division multiplexed channel just by tuning the local oscillator frequency, is of great interest for the development of high-capacity flexible optical networks. Nevertheless, the unavoidable amplitude imbalances inherent to any realistic coherent receiver induce an interference contribution from the self-beating of the coincident channels present at its input. The characterization of this degraded colorless reception operation is of fundamental importance, but it usually requires the use of rather complex experimental setups, especially when the effects of tens of interference channels should be evaluated. In this work we propose a novel experimental setup that only requires the use of a single intense interferer to emulate those coincident channels, thus drastically simplifying the characterization process. In addition, we develop a general expression for the signal-to-noise ratio of the system that theoretically justifies the intended setup and demonstrate by massive numerical simulations its accuracy in different scenarios. We believe that the proposed approach may contribute to facilitate the experimental characterization of high-performance colorless coherent receivers.

Modelling the spread of cystic fibrosis in Brittany using genealogical data over five centuries

BackgroundThe French region of Brittany presents one of the highest cystic fibrosis (CF)-causing allele frequency in Europe. Here, we tested two hypotheses: i) CF-causing allele carriers arrived by sea in the middle of the 1st millennium AD, and ii) a selective advantage for healthy carriers explains this high rate. MethodsFrom the census of cystic fibrosis patients, frequency maps of the most widespread alleles were established. A mathematical model was developed, based on birth date and place of the ancestors of these patients over 5 centuries, to determine the distribution of local migrations and their parameters for inter-generational intervals of 32 years. This model was applied to simulate the spread of CF-causing variant carriers, according to different scenarios that corresponded to the immigration of a given number of variant carriers at different times (year) and places, and to compare their results to current frequency maps. ResultsMigrants carrying a CFTR variant settled in several locations, around which they spread, notably in Central Brittany (F508del variant), Léon (G551D variant) and Cornouaille (1078delT variant). Until the end of the 18th century, the spreading of disease-causing allele carriers was relatively slow, and allele frequencies progressively increased. Then, the mean migration distances increased rapidly, leading to a decline in local frequencies. ConclusionsThe main CFTR variants could only have reached their current frequencies through a selective advantage for healthy carriers of the order of 4–6 % at each generation. For the most widespread variant (F508del), the model supports the hypothesis that it appeared around 190 generations ago.

Lightweight sound insulation optimization of simply supported locally resonant plate

A theoretical model of the normal sound insulation of a rectangular locally resonant (LR) plate with simply supported boundary conditions is established. The accuracy of the model is verified through comparison with finite element simulation results. Considering a 1-m2 aluminum plate as the research object, a non-dominated genetic algorithm is introduced. The algorithm optimizes the lightweight sound insulation of an LR finite plate with a center frequency band of 20–800 Hz as the optimization objective of maximum average sound insulation and minimum mass. The optimization parameters are substrate thickness and local resonance parameters (including resonator target frequency (fobj), number of resonators, additional mass ratio, and resonator damping). Optimization results indicate that the average sound insulation fluctuates at approximately 2 dB due to changes in fobj. The results also provide an optimal solution to the algorithm. The optimal sound insulation value curve of LR plates corresponding to different surface densities of intermediate improved cases is fitted and compared with the sound insulation value of an equal-mass bare plate. Under lightweight optimization, the resonators are deemed capable of improving the local frequency band sound insulation. In contrast, the wideband average sound insulation can approximate but not surpass the insulation provided by the equal-mass bare plate. In practical applications, an LR plate that can improve the local frequency band sound insulation and ensure the overall lightweight sound insulation performance of the wide frequency band can be obtained. This can be achieved by analyzing the frequency spectrum of optimal points in the lightweight sound insulation optimization process. Relevant research can provide a basis for the evaluation and design of the low-frequency sound insulation of plates for transportation equipment, such as airplanes, high-speed trains, and cars.

Method for a deflection-type refractometer measuring the fringe shift by using linear Fresnelzone plates.

This study describes the design and performance of a deflection-type refractometer based on measuring the fringe shift from the Fresnel diffraction pattern to solve some major limitations of conventional differential refractometers, such as measurement range, resolution, zero balancing, and monitoring analysis. The refractometer apparatus comprises a coherent light source, linear Fresnel zone plate, measuring cell, and image capture device mounted on a movable platform. The distance measurement unit is configured to detect fringe deflection due to the difference in refractive index between the sample and the reference. To achieve this, distance measurements with an accuracy of a few nanometers by using the local frequency method and fringe shift measurement method are quite feasible. The uncertainty in this technique is determined by the smallest change in the longitudinal displacement of the image for which the CCD camera can detect a change in pixel position. The refractive index is obtained with a highly extended measurement range of at least ±0.4R I U and precision of the order of 2×10-4 R I U. A numerical comparison between computer simulation of the diffraction patterns that occur when the linear Fresnel zone plate is illuminated by a plane light traveling parallel to the z axis.

Clinical features, diagnostics and treatment of FGF23 secreting tumors: series of 40 clinical cases

Tumor-induced osteomalacia is an acquired rare disease manifested by hypophosphatemic osteomalacia due to excessive secretion of fibroblast growth factor 23 (FGF23). FGF 23 is a non-classical hormone secreted by bone tissue (osteocytes) and regulates phosphorus metabolism.The aim of this work is to present clinical experience in the diagnosis, treatment and rehabilitation of patients with tumor-induced osteomalacia. 40 patients with clinically-confirmed tumor-induced osteomalacia were included in the study, 34 of whom had the tumor localized, 27 underwent surgical treatment and 21 achieved stable remission. The median age was 48 [41; 63] years, 43% were men, the time left from the the onset of the disease was 8 [4; 10] years. Biochemical findings were hypophosphatemia 0.47 [0.4; 0.53] mmol/l, a decrease in the tubular reabsorption phosphate 62 [52; 67]%, and an increase in alkaline phosphatase of 183 [112; 294] units/l. At the time of diagnosis, 100% had multiple pathological fractures, only 10% could move independently, and 77.5% classified the pain as unbearable (8-10 points according to the 10-point pain syndrome scale ). Among the methods used to detect tumors, the most sensitive were scintigraphy with tectrotide with SPECT/CT 71.4% (20/28) and MRI 90% (18/20). In 35% of cases, the tumor was localized in soft tissues and in 65% in bone tissue; The tumor was most often detected in the lower extremities, followed by the head in frequency of localization. 18 patients currently have no remission and they receive conservative treatment (phosphorus and alfacalcidol n=15 and burosumab n=3). In case of achieving remission (n=21), regression of clinical symptoms and restoration of bone and muscle mass was observed. Extensive excision of the tumor without prior biopsy resulted in the best percentage of remission - 87%. Tumor-induced osteomalacia is characterized by severe damage to bone and muscle tissue with the development of multiple fractures, muscle weakness and severe pain syndrome. In laboratory diagnostics, attention should be paid to hypophosphatemia, a decrease in the tubular reabsorption phosphate index and increased alkaline phosphatase. The use of functional diagnostic methods with a labeled somatostatin analogue to the subtype 2 receptor and MRI with contrast enhancement are the most accurate methods of topical diagnostics. In case of localization of the tumor, a wide excision without a preliminary biopsy is recommended.

Unraveling the strong covariability of tropical cyclone activity between the Bay of Bengal and the South China Sea

Herein, we report a strong in-phase covariability of tropical cyclone (TC) activity between the Bay of Bengal (BOB) and the South China Sea (SCS) during October–December of 1979–2019, and which is also the dominant mode of BOB–SCS TC activity, accounting for 35% of the total variances in TC track density. This inter-basin TC covariance is closely linked to the anomalies of tropical sea surface temperature, appearing as the intrinsic Indo-Pacific Tripole mode, which significantly affects the atmospheric circulations overlying the BOB–SCS. Interestingly, this mechanism works via modulating the local TC genesis frequency in the BOB–SCS. However, in terms of the migrated TCs among them, the Indo-Pacific Tripole mainly regulates their genesis location but not their frequency. More importantly, such inter-basin TC covariability still exists significantly even when the TC track data migrating from the SCS into the BOB are excluded. After all, only 19 TCs during the 41 years (1979–2019) are observed to migrate from the SCS to the BOB, which can only contribute slightly to increasing the covariability of BOB–SCS TC-track activity, but do not play a dominant role. Further, the numerical simulations suggest that although both the Indian and Pacific Oceans contribute to the atmospheric anomalies that affect the BOB–SCS TC activity, the Pacific-effect is twice as important.

Genomic signatures of selection, local adaptation and production type characterisation of East Adriatic sheep breeds

BackgroundThe importance of sheep breeding in the Mediterranean part of the eastern Adriatic has a long tradition since its arrival during the Neolithic migrations. Sheep production system is extensive and generally carried out in traditional systems without intensive systematic breeding programmes for high uniform trait production (carcass, wool and milk yield). Therefore, eight indigenous Croatian sheep breeds from eastern Adriatic treated here as metapopulation (EAS), are generally considered as multipurpose breeds (milk, meat and wool), not specialised for a particular type of production, but known for their robustness and resistance to certain environmental conditions. Our objective was to identify genomic regions and genes that exhibit patterns of positive selection signatures, decipher their biological and productive functionality, and provide a "genomic" characterization of EAS adaptation and determine its production type.ResultsWe identified positive selection signatures in EAS using several methods based on reduced local variation, linkage disequilibrium and site frequency spectrum (eROHi, iHS, nSL and CLR). Our analyses identified numerous genomic regions and genes (e.g., desmosomal cadherin and desmoglein gene families) associated with environmental adaptation and economically important traits. Most candidate genes were related to meat/production and health/immune response traits, while some of the candidate genes discovered were important for domestication and evolutionary processes (e.g., HOXa gene family and FSIP2). These results were also confirmed by GO and QTL enrichment analysis.ConclusionsOur results contribute to a better understanding of the unique adaptive genetic architecture of EAS and define its productive type, ultimately providing a new opportunity for future breeding programmes. At the same time, the numerous genes identified will improve our understanding of ruminant (sheep) robustness and resistance in the harsh and specific Mediterranean environment.

A semi-analytical method for vibration localization of plates integrated with low-frequency plate-type resonators

A plate-type local resonator with varying free boundaries is integrated within the plate to transform the initial low-order global vibration modes into localized vibration modes. A novel semi-analytical method is proposed to analyze the free vibration of the plate with discontinuities in thickness and displacement. The host plate and the resonator are modeled separately and coupled by the condition of displacement compatibility, based on the geometry configuration. A set of local admissible functions, consisting of global and local parts in the resonator domain, is proposed to describe the vibration localization and displacement discontinuity. The Ritz method with the proposed admissible functions is employed to investigate the effect of geometry parameters and boundary conditions on the vibration characteristics of the plates. The lack of orthogonality between the global and localized modes is determined using the analytic mode functions obtained by the proposed method and can be altered by the free boundary conditions of the resonator. The results demonstrate that by applying free boundary conditions to a resonator, the low-order localized vibration frequencies can be significantly reduced by up to 90 %, with negligible effect on low-order global frequencies. An original and exciting finding is that the global modes can be assimilated by the corresponding localized vibration modes with close frequencies.

Financial Toxicity and Time Toxicity in Multiple Myeloma: Prevalence, Predictors, and Impact on QOL

Introduction: Patients with multiple myeloma (MM) are at ongoing risk of financial toxicity (FinTox) from medication costs and lost productivity (Richter CLML 2020, Fiala CLML 2023). Given MM's incurable nature with ongoing monitoring and supportive care, time toxicity (TimeTox) from frequent healthcare interactions may persist into the maintenance phase as well. The prevalence, predictors, and impact of FinTox and TimeTox on QOL have not been fully characterized in this population. Methods: We surveyed (by mail and online) English-speaking MM patients who had undergone auto-transplantation at our US institution. Survey questions included financial stressors (COST inventory), frequency/convenience of in-person vs telehealth visits, and physical/mental QOL [PROMIS Global Health, with minimum clinically important difference (MCID) 5]. FinTox+ was defined as COST score <23 (25th percentile). After discussions with local patients, we defined TimeTox+ as either (a) MM-related interactions (including in-person visits, telehealth / telephone calls, infusions, and labwork) ≥1x per week on average and/or (b) in-person MM-related interactions ≥1x per month in far-residing patients (defined as patients who reported that interactions with their primary MM provider usually required ≥4 hours away from home). Variables were compared descriptively using Fisher's and rank-sum test. Predictors of FinTox and TimeTox were identified using adjusted multivariable logistic regression. Results: Of 670 patients, 252 (38%) completed the survey as described in Table 1. 64% were on maintenance, 21% on observation, and 16% on active treatment for relapsed MM. Far-residing patients comprised 20% of respondents. Among n=207 (82%) who completed the COST inventory, the median COST score was 31 (IQR 23-37). Of these respondents, 22% (n=45) were FinTox+. Most (59%) reported monthly MM-related out-of-pocket costs <$100, but 15% reported MM-related expenses ≥$500 monthly. While physical QOL scores were comparable between FinTox+ and FinTox- respondents, FinTox+ respondents had significantly worsened mental QOL (median PROMIS scores 45.8 vs 50.8, p <0.01). Time toxicity was reported by 40% (n=101) overall, including 14% of 51 respondents on observation, 37% of 155 respondents on maintenance, and 82% of 38 respondents with relapse. Unsurprisingly, TimeTox was more prevalent among far-residing respondents (73% vs 31%, p<0.001). Far-residing respondents were less likely to rate in-person visits as convenient (Figure 1A, p<0.001), with 62% (far-residing) vs 89% (near-residing) agreeing that in-person visits were easy to attend. However, near-residing and far-residing respondents had similar frequencies of in-person visits (Figure 1B, p=0.37). Telehealth visits were rated similarly conveniently by both far-residing and near-residing respondents (Figure 1C, p=0.77). Telehealth visits were more common in the far-residing cohort (Figure 1D, p=0.01), with 54% vs 32% of respondents reporting ≥1 telehealth visit in the past year. Median physical QOL (44.9 vs 47.7) and mental QOL (48.3 vs 50.8) were both significantly worse in TimeTox+ respondents but within the MCID. In adjusted multivariable analyses, predictors of FinTox were younger age (OR=1.10, p<0.001) and annual income <$50K (OR=6.29, p<0.001). Predictors of TimeTox were disease status (reference: observation; relapsed OR=22.69, maintenance OR=3.21, p<0.001) and far-residing status (OR=5.72, p<0.001). Conclusion: In our study of over 250 patients with MM, 22% reported FinTox while 40% reported TimeTox. FinTox was associated with lower income as well as a clinically meaningful decrease in mental QOL, suggesting benefit for FinTox screening and early referral to financial navigation services. TimeTox was reported by over a third of patients on maintenance, and further research into reversible drivers of TimeTox is ongoing: for example, workflows to increase local lab monitoring and decrease in-person visit frequency for patients on oral maintenance. Limitations of our study include selection bias, recall bias, and lack of generalizability to transplantation-ineligible patients. Additionally, universal definitions for FinTox and TimeTox have not yet been standardized. However, this is the largest study of these toxicities in MM to date and serves as a starting point for larger more definitive prospective research.

Design of Light, Small, and High-precision Digital Servo Clock for LEO Constellation

Modern low earth orbit (LEO) satellite systems have placed increasingly stringent requirements on spaceborne time-frequency systems in the fields of constellation autonomous management, distributed synthetic aperture radar (SAR) imaging, and navigation time service. Admittedly, the original high-stability constant-temperature crystal oscillator and high-stability temperature-compensated crystal oscillator can no longer comply with the indicator requirements of clock source frequency characteristics and clock synchronization accuracy. Likewise, traditional satellites use atomic clocks (rubidium atomic clocks and cesium atomic clocks). On account of their inherent characteristics, the ground receiving system needs to observe and count the clock parameter characteristics for a long time after the satellite enters orbit and frequently modify the future working state parameters. The features of being expensive and bulky increase the operation and maintenance costs of the ground system and the complexity of engineering implementation. In this paper, a kind of light and small high-precision digital servo clock based on the deep coupling of the global navigation satellite system (GNSS) is designed for the LEO satellite constellation. The tame clock is deeply coupled with the GNSS navigation receiver, and the high precision time-frequency difference between the local clock frequency source and GNSS is obtained by using the carrier and pseudo-range measurement information of visible satellite and carrier phase measurement information of the receiver. It not only utilizes the short-term high stability of OCXO but also employs the long-term time-frequency maintenance ability of GNSS so that the tamed OCXO is locked in GNSS for a long time, which can achieve frequency calibration of local clock sources and long-term output to various space-borne systems. The system is small in size and low in power consumption, with output frequency stability better than 3E-13 (10000 s), accuracy better than ±2E-13, and timing accuracy better than ±10 ns, which is comparable to the key technical indexes of spaceborne miniaturized rubidium clocks, in line with the current demand of miniaturization, low power consumption, and low cost of LEO constellations.

Multi-Frequency 3D Shear Wave Absolute Vibro-Elastography (S-WAVE) System for the Prostate.

This article describes a novel system for quantitative and volumetric measurement of tissue elasticity in the prostate using simultaneous multi-frequency tissue excitation. Elasticity is computed by using a local frequency estimator to measure the three-dimensional local wavelengths of steady-state shear waves within the prostate gland. The shear wave is created using a mechanical voice coil shaker which transmits simultaneous multi-frequency vibrations transperineally. Radio frequency data is streamed directly from a BK Medical 8848 transrectal ultrasound transducer to an external computer where tissue displacement due to the excitation is measured using a speckle tracking algorithm. Bandpass sampling is used that eliminates the need for an ultra-fast frame rate to track the tissue motion and allows for accurate reconstruction at a sampling frequency that is below the Nyquist rate. A roll motor with computer control is used to rotate the transducer and obtain 3D data. Two commercially available phantoms were used to validate both the accuracy of the elasticity measurements as well as the functional feasibility of using the system for in vivo prostate imaging. The phantom measurements were compared with 3D Magnetic Resonance Elastography (MRE), where a high correlation of 96% was achieved. In addition, the system has been used in two separate clinical studies as a method for cancer identification. Qualitative and quantitative results of 11 patients from these clinical studies are presented here. Furthermore, an AUC of 0.87±0.12 was achieved for malignant vs. benign classification using a binary support vector machine classifier trained with data from the latest clinical study with leave one patient out cross-validation.

Local spectral attention for full-band speech enhancement.

Attention mechanism has been widely used in speech enhancement (SE) because, theoretically, it can effectively model the inherent connection of signal in time domain and spectrum domain. In this Letter, it is found that the attention over the entire frequency range hampers the inference for full-band SE and possibly leads to excessive residual noise and degradation of speech. To alleviate this problem, the local spectral attention is introduced into full-band SE model by limiting the span of attention. The ablation tests on three full-band SE models reveal that the local frequency attention can effectively improve overall performance.

Simplified assessment for chemical exchanged saturation transfer (CEST) imaging: local offset frequency and CEST effect.

The aim of this study is to develop a novel phantom for the evaluation of clinical CEST imaging settings, e.g., B0 and B1 field inhomogeneities, CEST contrast, and post-processing. We made a phantom composed of two slice sections: a grid section for local offset frequency evaluation and a sample section for CEST effect evaluation using different concentrations of an egg white albumin solution. On a 3Tesla MR scanner, a phantom study was performed using CEST imaging; the mean B1 amplitudes were set at 1.2 and 1.9µT, and CEST images with and without B0 corrections were acquired. Next, region of interest (ROI) analysis was performed for each slice. Then, CEST images with and without B0 corrections were compared at each B1 amplitude. The B0 corrected Z-spectrums at each local region in the grid section showed a shifting of the curve bottom to 0ppm. Z-spectrum at B1 = 1.9µT showed a broader curve shape than that at 1.2 µT. Moreover, MTRasym values at 3.5ppm for each albumin sample at B1 = 1.9µT were about two times higher than those at 1.2µT. Our phantom enabled us to evaluate and optimize B0 inhomogeneity and the CEST effect at the B1 amplitude.

Super-oscillatory lattices structured illumination microscopy beyond two-fold resolution enhancement

Super-oscillatory (SO) lattices are multi-lobes patterns that exhibit local spatial frequencies beyond the bandwidth limit of their Fourier spectrum. However, the method generates SO lattices by interfering multiple beams requires complicated optical systems to control the contribution of different beams. In this paper, we present a novel approach for creating SO lattices based on diffractive optics, which simplifies the system design and implementation. Using this method, we design a diffractive optical element (DOE) that produces a two-dimensional SO lattice with a local spatial frequency exceeding the cut-off frequency by 10%. To the best of our knowledge, this is the first demonstration of generating a SO lattice by diffractive optics. We then apply the SO lattice to structured illumination microscopy (SOL-SIM) and evaluate its super-resolution performance through experiments. The results demonstrate that our method provides a new perspective to break the two-fold resolution enhancement limit of linear SIM in far-field super-resolution microscopy domain.

Drifter observations of surface currents in the Cyprus Gyre

Wavelet ridge analysis was applied to the data of drifters caught in the Cyprus Gyre in the eastern Mediterranean Sea to study surface currents at low (rotating circulation) and high (near-inertial motion) frequencies. Drifter observations indicate that the orbital speed is highest at about 30 km from the gyre center (reaching ~45 cm/s) and that the Rossby number in the gyre can be as high as 0.25. Drifters also show that strong near-inertial currents with speed of 35-40 cm/s can exceed the gyre rotation speed and that the background vorticity inside the gyre generally shifts the effective inertial frequency to values smaller than the local inertial frequency. As a result, the near-inertial currents are subinertial and are trapped in the mesoscale vortex. For example, the near-inertial motions in the Cyprus Gyre in June 2017 reached 40 cm/s in its inner core with a red shift of ~0.1 cpd, while on its edge they were limited to 10-20 cm/s, under similar wind forcing. This difference is due to trapping of the near-inertial energy inside the gyre. The observed inertial currents are largely driven by the local wind, especially when the effective inertial frequency becomes diurnal and resonance with wind diurnal variability occurs. A damped slab model of the inertial currents in the mixed layer is only partially successful in simulating the observations.

Influence of neuromuscular electrical stimulation pulse waveform on corticomuscular coupling and the brain functional connectivity network

ObjectiveNeuromuscular electrical stimulation (NMES) has been shown to promote functional corticomuscular coupling (FCMC), but its effect on brain functional connectivity network (BFCN) remains uncertain. This study aims to propose a new method to analyze the influence of NMES with different stimulation waveforms on the motor system from two perspectives of FCMC and BFCN. ApproachThe bivariate empirical mode decomposition time-delay maximal information coefficient (BTDMIC) method was used to assess the local frequency band characteristics of the cortex and muscle. Main resultThe experimental results showed that the FCMC increment after NMES was prominent in the β1 (15–25 Hz), β2 (25–35 Hz), and γ1 (35–45 Hz) bands. Additionally, the coupling values of C3 after sine-NMES were highest in the β1 band, while the coupling values after square-NMES were highest in the β2 and γ1 bands. For BFCN, the cortical-cortical coupling of the C3 after square-NMES was high in the C3 → others direction. Moreover, in the α (8–14 Hz) and β1 bands, the clustering coefficient, density, and efficiency after square-NMES were significantly higher than those of the three other frequency bands. ConclusionNMES effectively promoted information exchange between the motor cortices of the brain, and the facilitating effect is particularly pronounced in the case of square-NMES. SignificanceThis study offers a novel perspective for evaluating rehabilitation therapies based on NMES.

Phase shift cavity ring down and FT-NIR spectra of C[sbnd]H vibrational transitions and band strengths of ethyl acetate

The vibrational overtone spectra (Δυ = 5, 6) of CH transitions of ethyl acetate (CH3COO–CH2CH3) have been obtained using the phase shift cavity ring down (PS-CRD) technique at 295 K. The CH stretch fundamental and overtone transitions (Δυ = 1- 4) have been obtained using a Fourier transform infrared and near infrared spectrophotometer. Local mode frequencies ωe and anharmonicities ωexe are reported for the CH (ip) (in plane), CH (op) (out of plane) bonds of the methyl group attached to the carbonyl (CO) side and for the methyl CH3 (primary) and methylene CH2 (secondary) CH bonds of the ethyl group bonded to the O atom. The study includes computer deconvolution of the total band at each level and a density functional theory (DFT) calculation of deuterated analogues of ethyl acetate to help with the assignment of all the non-equivalent CH bonds in the molecule. From the assigned Δυ = 6 peak wavenumber, isolated frequencies and CH bond lengths are obtained for the different CH bonds. Band strengths, oscillator strengths, and transition moments were obtained experimentally for all transitions. The importance of the assigned vibrational transitions and integrated intensities for future studies of laser and atmospheric vibrational overtone photochemistry is discussed.

Experimental observation of stimulated Raman scattering enabled localized structure in a normal dispersion FP resonator

Dissipative Kerr nonlinear cavities attract intense interest due to their rich dynamics and capability to generate broadband, low-noise, mode-locked optical frequency combs for applications in optical communications, dual-comb spectroscopy, photonic lidar, etc. Different from the Kerr effect, which is an electronic response, stimulated Raman scattering (SRS) is a delayed response to molecular vibrations in materials. In microcavities, when driven in an anomalous group velocity dispersion (GVD) regime, SRS typically leads to a self-frequency shift of solitons and generation of breather solitons, which have been verified both theoretically and experimentally. However, when driven in a normal GVD regime, recent theoretical work predicts that SRS can cause the locking of switching waves (SWs) and thus support bright moving localized structure (LS), which we term as SRS enabled localized structure (SRS-LS). Limited by the design of suitable experimental parameters, experimental observation of this SRS-LS is not achieved yet. Here, we provide numerical investigation and, to our knowledge, the first experimental observation of the SRS-LS in a fiber Fabry–Perot (FP) resonator with ultra-low normal GVD. Such SRS-LS exhibits localized temporal features with strong oscillations at ∼13THz local frequency on the top of a flat-top pulse. The corresponding spectrum is a low-noise and broadband Kerr comb with a typical platicon-like spectrum in the center and two Raman Stokes and anti-Stokes peaks located near ±13THz away from the center. With such an SRS enabled broadband Kerr comb, we have achieved an SRS-LS spectrum with a repetition rate of ∼3.68GHz and a −30dB spectral width of 255 nm. The corresponding comb tooth count is >8500, covering the S + C + L telecommunication bands. Moreover, the formation process of such SRS-LS is also revealed, and it is found that the GVD plays a key role in its generation. Our work will help to advance the study of the dynamics of optical frequency combs under the influence of SRS, as well as provide a broadband coherent mode-locked optical source for wide applications.

Spatial Analysis of Attitudes Toward Timber Rattlesnakes (Crotalus Horridus) Where Encounters Occur Within an Exurban Landscape

Most human-wildlife conflict research has focused on large species, with less attention to smaller, less-charismatic species. Our objective was to evaluate landscape-level spatial relationships among human-timber rattlesnake (Crotalus horridus) encounters, attitudes toward timber rattlesnakes, and exurban residential context. Encounters and attitudes data were collected using a mail survey and encounter reports (n = 583). Residential context variables focused on land cover and parcel characteristics. Encounters and similar attitudes toward timber rattlesnakes were spatially clustered on the landscape, and residential context attributes influenced both. Some overlap existed between favorable attitudes related to coexistence with timber rattlesnakes and relatively low concern about the species, whereas encounter-similar attitude clusters were distinct with less overlap. An outreach approach with prescribed messaging strategies based on the localized frequency of encounters, relative attitudes, and land cover may facilitate ability to address resident concerns in an individualized way.