Upward Frequency Shift Research Articles

Upward vibrational frequency shift due to electron–phonon polar-coupling interaction in C12H17ClN4OS·HCl·H2O crystals

Electron–phonon (e–p) polar-coupling interactions in C12H17ClN4OS·HCl·H2O crystals exhibiting an upward frequency shift with increasing temperature are investigated using terahertz and far-infrared spectroscopies, and the structural condition required for effective e–p polar-coupling interactions in crystals are uncovered. X-ray crystallography and first-principles calculations reveal that the key structure for the e−p polar-coupling interaction is an open cavity near the considered vibration. Based on the temperature-dependent frequency shift proportional to the Bose−Einstein statistical factor, the interaction strength and characteristic frequency of phonons interacting with electrons are determined at 5.3 × 10–3 cm–1 K–1 and 76.6 cm–1, respectively. From the phonon dispersion curves exhibiting LO (longitudinal optical)–TO (transverse optical) splitting, we find that the highest frequency LO phonon participates in the polar-coupling interaction.

IS THERE EARNINGS DISCONTINUITY AFTER THE IMPLEMENTATION OF IFRS IN NIGERIA?

Earnings metrics are major financial indicators which capital market participants and investors focus on for informed decisions. Because reporting earnings increase may enhance firms’ stock price, many managers are motivated to avoid reporting earnings decreases, but prefer to consistently report increase earnings greater than its previous valuation. There is evidence that such practice has led to a situation of conspicuous upward shift in frequency of observations, starting from the left of identified earnings benchmark to the right. Recent studies have shown that a change in accounting regulation may have effects on the shape of the firm-year distribution of earnings. This paper examines the discontinuity evidence for Nigeria, in relation to the adoption of the international financial reporting standard. The aim is to establish whether discontinuity in earnings, represented by the asset-scaled net profits, as well the discontinuity in earnings-change, has reduced following the adoption. According to literature, the study employs three methods – empirical histogram, standardise differences tests and the permutation tests – to validate the aims. The findings suppose evidence for increase in discontinuity, indicating increased in small profits’ earnings management, after the adoption. Contrary, the evidence is not sufficient to conclude that the discontinuity has increase for the earnings-change. It can be argued that the adoption has not achieve much in ensuring firms are monitored against earnings management to avoid losses. The study has limitation, since it considers only the distributions of earnings and earnings-changes. The distribution of forecast errors is not investigated because such is influence by forecast management. Future studies may consider this for improvement.

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.

Carbamazepine induces upward frequency shifts of spontaneous otoacoustic emissions

In three subjects, we measured spontaneous otoacoustic emissions (SOAEs) when they were using carbamazepine (CBZ), and compared this to the SOAE measurement when they were not using CBZ. We observed 14 SOAEs showing a consistent upward shift of center frequency, related to CBZ intake. On average, the magnitude of the frequency shift increased with increasing frequency. The magnitude of the shift was 30–104 Hz, at frequencies ranging from 1.3 to 2.3 kHz, corresponding to a shift between 2.3 and 4.5%. Compared to other causes and manipulations known to change SOAE frequency, these shifts are relatively large. The underlying mechanism is most likely an increased stiffness of the cochlear partition. This would also explain the downward pitch shift due to CBZ, which has been reported by subjects with absolute pitch.

Investigation of the protolytic equilibrium of a highly Brønsted acidic ionic liquid and residual water using Raman spectroscopy

Protic ionic liquids (PILs) are promising candidates as non-aqueous proton-conducting electrolytes for use in polymer electrolyte membrane fuel cells with operating temperatures over 100 °C. 2-sulfoethylammonium triflate [2-Sea][TfO] is one such PIL electrolyte, in which the highly Brønsted acidic sulfoalkylammonium cations act as mobile protonic charge carriers and proton donors. In order to gain a molecular-level understanding of proton transfer in a PIL electrolyte containing a small amount of residual water from fuel cell operation, the protolytic equilibrium of the highly acidic cation was investigated by means of Raman spectroscopy. Density functional theory (DFT) calculations were conducted to identify the vibration modes sensitive to protonation and to gain information on the possible conformation of the cation. The deprotonation of the 2-sulfoethylammonium cation resulted in a characteristic upward frequency shift in the ν(SC) stretching vibration. An equilibrium constant of 0.23 ± 0.09 was calculated for the protolytic reaction, indicating [2-Sea][TfO] as a promising proton donor for the fuel cell application.

Individual Variability in Recalibrating to Spectrally Shifted Speech: Implications for Cochlear Implants.

Cochlear implant (CI) recipients are at a severe disadvantage compared with normal-hearing listeners in distinguishing consonants that differ by place of articulation because the key relevant spectral differences are degraded by the implant. One component of that degradation is the upward shifting of spectral energy that occurs with a shallow insertion depth of a CI. The present study aimed to systematically measure the effects of spectral shifting on word recognition and phoneme categorization by specifically controlling the amount of shifting and using stimuli whose identification specifically depends on perceiving frequency cues. We hypothesized that listeners would be biased toward perceiving phonemes that contain higher-frequency components because of the upward frequency shift and that intelligibility would decrease as spectral shifting increased. Normal-hearing listeners (n = 15) heard sine wave-vocoded speech with simulated upward frequency shifts of 0, 2, 4, and 6 mm of cochlear space to simulate shallow CI insertion depth. Stimuli included monosyllabic words and /b/-/d/ and /∫/-/s/ continua that varied systematically by formant frequency transitions or frication noise spectral peaks, respectively. Recalibration to spectral shifting was operationally defined as shifting perceptual acoustic-phonetic mapping commensurate with the spectral shift. In other words, adjusting frequency expectations for both phonemes upward so that there is still a perceptual distinction, rather than hearing all upward-shifted phonemes as the higher-frequency member of the pair. For moderate amounts of spectral shifting, group data suggested a general "halfway" recalibration to spectral shifting, but individual data suggested a notably different conclusion: half of the listeners were able to recalibrate fully, while the other halves of the listeners were utterly unable to categorize shifted speech with any reliability. There were no participants who demonstrated a pattern intermediate to these two extremes. Intelligibility of words decreased with greater amounts of spectral shifting, also showing loose clusters of better- and poorer-performing listeners. Phonetic analysis of word errors revealed certain cues were more susceptible to being compromised due to a frequency shift (place and manner of articulation), while voicing was robust to spectral shifting. Shifting the frequency spectrum of speech has systematic effects that are in line with known properties of speech acoustics, but the ensuing difficulties cannot be predicted based on tonotopic mismatch alone. Difficulties are subject to substantial individual differences in the capacity to adjust acoustic-phonetic mapping. These results help to explain why speech recognition in CI listeners cannot be fully predicted by peripheral factors like electrode placement and spectral resolution; even among listeners with functionally equivalent auditory input, there is an additional factor of simply being able or unable to flexibly adjust acoustic-phonetic mapping. This individual variability could motivate precise treatment approaches guided by an individual's relative reliance on wideband frequency representation (even if it is mismatched) or limited frequency coverage whose tonotopy is preserved.

Efferent-induced shifts in synchronized-spontaneous-otoacoustic-emission magnitude and frequency.

Synchronized-spontaneous otoacoustic emissions (SSOAEs) present as slow-decaying emission energy that persists after the transient-evoked otoacoustic emission (TEOAE). SSOAEs possess high amplitudes and signal-to-noise ratios, making them potentially ideal candidates to assay the medial-olivocochlear reflex (MOCR). The current work quantified MOCR-induced changes to SSOAEs over a 36-dB stimulus level range and compared MOCR effects between TEOAE- and SSOAE-based assays. Otoacoustic emissions were evoked using band limited clicks from 52 to 88 dB peak sound pressure level (pSPL) with and without contralateral-acoustic stimulation (CAS) in 25 normal-hearing, female adults. The CAS was 50-dB sound pressure level (SPL) broadband noise and served to activate the MOCR. The number of SSOAEs increased with the stimulus level through approximately 70 dB pSPL. The presentation of CAS resulted in fewer SSOAEs. SSOAEs exhibited compressive growth and approached saturation for stimulus levels of 70 dB pSPL. The primary effects of CAS were a reduction in the SSOAE magnitude and an upward shift in the SSOAE frequency. These changes were not strongly affected by the stimulus level. Time-domain analysis of the SSOAE revealed an increase in the CAS-induced magnitude shift during the decay portion of the SSOAE. Compared to CAS-induced TEOAE magnitude shifts, SSOAE magnitude shifts were typically 2-3 dB larger. Findings support SSOAEs as a means to assay the MOCR.

Low Noise Multiquantum Well DAR IMPATT Diodes Based On SiXGe1-X/Si

A Multiquantum Well (MQW) SixGe1-x/Si DAR (Double Avalanche Region) IMPATT (Impact Avalanche Transit Time) diode as a high power-high efficiency-low noise source at W-band is proposed in this paper. The RF power, conversion efficiency and noise of the device are optimized with respect to number of quantum wells and Ge mole fraction. The proposed device delivers peak power of 2.7 W, conversion efficiency of 7.5% and noise measure of 25 dB when the number of wells in the MQW structure is four and mole fraction of Ge is 0.3. The admittance plots of the device exhibit distinct negative conductance bands for three different (0.1, 0.2 and 0.3) mole fractions of Ge. An upward shift of optimum frequency is observed with increasing Ge mole fraction. The noise measure of the device decreases with increasing mole fraction of Ge and decreasing current.

Design of stable and high-efficiency graphene-based polarizers for oblique angle of incidence in terahertz frequency.

Most investigations of polarizers consider a normal angle of incidence only. This paper expands our investigation to also include an oblique angle of incidence. Essential problems are encountered for an oblique angle of incidence: there is an upward shift of the center frequency, and the impedance match gets worse as the angle of incidence increases. So it is apparent that polarizers gradually deteriorate for higher angles of incidence. The new contribution given in this paper is that it considers ways to greatly improve oblique incidence performance. These ways are well confirmed by the design process of the proposed graphene-based polarizer for large-angle oblique incident stability and high efficiency.

Alfvénic gap eigenmode in a linear plasma with ending magnetic throats

To guide the experimental design of a linear plasma device for studying the interaction between energetic ions and Alfvénic gap eigenmode (AGE), this work computes AGE referring to fusion conditions in an ultra-long large plasma cylinder ended with strong magnetic throats for axial confinement of charged particles. It is shown that (i) for uniform equilibrium field between the ending throats, the dispersion relation of the computed wave field agrees well with a simple analytical model for the shear Alfvénic mode and (ii) for periodic equilibrium field with local defect, clear AGE is formed inside the spectral gap for both low and high depths of magnetic throats, although lower depth yields easier observation. The strongest AGE can be on the order of 3.1 × 10−4 to equilibrium field, making it conveniently measurable in experiment. The AGE is a standing wave localized around the defect which is introduced to break the system's periodicity, and its wavelength is twice the system's period, consistent with Bragg's law. The parameter scan reveals that the AGE remains nearly the same when the number of magnetic ripples is reduced from 18 to 8; however, there occurs an upward frequency shift when the depth of magnetic ripples drops from 0.5 to 0.1, possibly due to a flute-like effect: shrinking resonant cavity of the spectral gap.

High-field electrostatic control of ferromagnetic resonance in NiFe/PIN-PMN-PT multiferroic heterostructures

We report electric-field control of ferromagnetic resonance in NiFe film, which was deposited on (011)-cut 0.3Pb(In1/2Nb1/2)O3-0.4Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PIN-PMN-PT) single crystals. An upward frequency shift from 11.69 to 12.53 GHz is achieved in our heterostructures for electric field from 0 to 15 kV/cm as an external magnetic field of 2090 Oe was applied along in-plane [100] direction, and a downward shift from 13.61 to 13.25 GHz is investigated for electric field from 0 to 7 kV/cm, while an external magnetic field of 2723 Oe was applied along [01$$\stackrel{-}{1}$$] direction. The large operational electric field and the high rhombohedral-tetragonal phase transition temperature TR−T (~ 127 °C) of the crystal make NiFe/PIN-PMN-PT composites great candidates for electrically tunable microwave magnetic device applications with broad electric field and temperature range.

Experimental characterisation of near field backscatter from thin resistively loaded FSS absorbers

Experimental results are employed to show that a thin metal backed resistively loaded frequency selective surface (FSS) exhibits significant radar backscatter suppression when the structure is illuminated by an antenna placed in close proximity to the periodic array. This is investigated in the range 9-11 GHz by measuring the shift in the resonant frequency of an impedance matched (| S 11 | ~15 dB at 10.22 GHz) microstrip patch which is placed in five different positions ranging from λ /30 to λ /5 distance above the surface of the FSS. Detuning of the antenna by signals reflected from the absorber surface is shown to be much less significant than the upward frequency shift in the measured | S 11 | for a metal plate and tissue phantom, therefore this technology could be used to enhance the performance of on-body wireless sensors.

Spaser quenching by off-resonant plasmon modes

We study the effect of off-resonant plasmon modes on spaser threshold in nanoparticle-based spasers. We develop an analytical semiclassical model and derive spaser threshold condition accounting for gain coupling to higher-order plasmons. We show that such a coupling originates from inhomogeneity of gain distribution near the metal surface and leads to an upward shift of spaser frequency and population inversion threshold. This effect is similar, albeit significantly weaker, to quenching of plasmon-enhanced fluorescence near metal nanostructures due to excitation of off-resonant modes with wide spectral band. We also show that spaser quenching is suppressed for high gain concentrations and establish a simple criterion for quenching onset, which we support by numerical calculations for spherical geometry.

The song of Skylarks Alauda arvensis indicates the deterioration of an acoustic environment resulting from wind farm start‐up

The rapid development of wind energy may have negative effects on bird populations, including collisions with turbines, displacement due to disturbance or habitat loss, indirect effects of reduced breeding success and barrier effects. This challenging conservation issue has attracted a great deal of interest, but the noise generated by turbines has been largely overlooked. Here, we studied acoustic behaviour of Skylarks Alauda arvensis in relation to wind farm start‐up to assess whether a change in song parameters can indicate a deterioration in the acoustic environment. We recorded territorial males displaying close to operating and non‐operating turbines and at a control site without turbines. In the following breeding season, we undertook replications at the same sites, except that the non‐operating turbines were now in operation. We found that Skylarks displaying at the wind farm were affected by wind turbine noise. Males singing close to operating wind turbines sang higher‐frequency songs than males from a control site and those that displayed near non‐operating turbines. In addition, an upward frequency shift in songs was observed when non‐operating turbines started to operate in the consecutive season. We therefore conclude that the frequency shift observed did not result from turbine presence, but from the noise they started to generate. This shows that a change in song parameters may reliably and within a relatively short time indicate a significant deterioration of the acoustic environment as a consequence of wind farm start‐up. This may help conservation biologists to identify species and populations that are particularly susceptible to wind farm noise.

Deformation behavior of titanate nanotubes subjected to high pressure

Nano-sized titania (anatase) and sodium and potassium titanate nanotubes were studied via in situ Raman spectroscopy at hydrostatic pressures up to 6 GPa. Analysis by scanning electron microscopy shows a uniform dispersion of sodium and potassium cations in the nanotubes. The effect of the pressure was observed by significant shifts in the Raman band structure of nano-sized anatase crystals and nanotube titanate. In nano-particulate anatase, the phonon frequencies (143, 395, 517, and 639 cm−1) increase linearly with pressure. In contrast, the upward frequency shifts in the sodium titanate nanotubes (NaTNT) and potassium-modified nanotubes (NaTNT+K) occur in a stepwise fashion. These stepwise changes occur in the nanotube samples between 2 and 4 GPa (ambient pressure phonon bands in NaTNT at 274, 444, 650, and 906 cm−1) and between 4.5 and 5.5 GPa, (phonons 273 cm−1 and 436 cm−1 in NaTNT+K at an ambient pressure). Post-pressure high-resolution transmission electron microscopy analysis shows evidence of nanotube distortions and a 5% contraction in the interlaminar spacing of both NaTNT and NaTNT+K.

Low frequency dove coos vary across noise gradients in an urbanized environment

Urbanization poses a challenge to bird communication due to signal masking by ambient noise and reflective surfaces that lead to signal degradation. Bird species (especially oscines) have been shown to alter their singing behaviour to increase signal efficiency in highly urbanized environments. However, few studies on the effects of noise on song structure have included birds with low frequency vocal signals which may be especially vulnerable to noise pollution due to significant frequency overlap of their signals with traffic noise. We compared the perch coos of spotted doves (Streptopelia chinensis), a species with very low frequency vocalizations, in different background noise levels across urban and peri-urban areas in Hong Kong. We documented a 10% upward shift in the minimum frequency of coos of spotted doves across the noise gradient (a relatively small but significant shift), and a reduced maximum frequency in urban habitats with a higher density of built up area. Hong Kong doves had significantly higher minimum and maximum frequencies than doves from throughout their range (from mostly rural sites). Our results indicate that urban species with extremely low sound frequencies such as doves can alter their vocalizations in response to variable urban acoustic environments.

Nonlinear acoustic propagation in bubbly liquids: Multiple scattering, softening and hardening phenomena.

The weakly nonlinear propagation of acoustic waves in monodisperse bubbly liquids is investigated numerically. A hydrodynamic model based on the averaged two-phase fluid equations is coupled with the Rayleigh-Plesset equation to model the dynamics of bubbles at the local scale. The present model is validated in the linear regime by comparing with the Foldy approximation. The analysis of the pressure signals in the linear regime highlights two resonance frequencies: the Minnaert frequency and a multiple scattering resonance that strongly depends on the bubble concentration. For weakly nonlinear regimes, the generation of higher harmonics is observed only for the Minnaert frequency. Linear combinations between the Minnaert harmonics and the multiple scattering resonance are also observed. However, the most significant effect observed is the appearance of softening-hardening effects that share some similarities with those observed for sandstones or cracked materials. These effects are related to the multiple scattering resonance. Downward or upward resonance frequency shifts can be observed depending on the characteristic of the incident wave when increasing the excitation amplitude. It is shown that the frequency shift can be explained assuming that the acoustic wave velocity depends on a law different from those usually encountered for sandstones or cracked materials.

Discomfort-related changes in pup ultrasonic calls of fat-tailed gerbils Pachyuromys duprasi

Rodent pups vocalize when placed in social isolation. We apply a method of “joint calls” for examining discomfort in rodent pup ultrasonic (>20 kHz) calls. Previously, this method has been developed for audible calls of fur farm mammals. Using a repeated measures design to exclude effects of individual identity and age on the analysed variables, we compared the ultrasonic call variables produced by 8–40-day pups of fat-tailed gerbils Pachyuromys duprasi during two subsequent experimental stages, the Isolation Stage and the Handling Stage. We considered that discomfort-related negative emotional arousal increased towards the Handling Stage compared to the Isolation Stage because of cumulative effects of handling and time of pup isolation from the nest. At the Isolation Stage, the call rate (calls/s) was higher from 10 to 18 days of age, whereas both the maximum amplitude frequency and power quartiles of joint calls were lower than at the Handling Stage from 20 to 32 days of age. At the same time, in audible (<20 kHz) vocalizations of a wide range of mammalian species, both the higher call rate and the upward shift of the maximum amplitude frequency and power quartiles indicate the discomfort-related increase of negative emotional arousal. We discuss the advantages of the method of joint calls for express-analyses of power variables for large sequences of ultrasonic vocalizations of complex acoustic structure during experimental trials.

Preclinical Abuse Potential Assessment of Flibanserin: Effects on Intracranial Self-Stimulation in Female and Male Rats.

Flibanserin is a serotonin receptor subtype 1A agonist and 2A antagonist that has been approved by the Food and Drug Administration for treating female sexual interest and arousal disorder. Little is known about the abuse potential of flibanserin. To examine abuse-related effects of flibanserin in rats using an intracranial self-stimulation (ICSS) procedure previously used to evaluate the abuse potential of other drugs. Adult female and male Sprague-Dawley rats with electrodes implanted in the medial forebrain bundle were trained to press a lever for electrical brain stimulation under a "frequency-rate" ICSS procedure. In this procedure, increasing frequencies of brain stimulation maintain increasing rates of responding. Drugs of abuse typically increase (or "facilitate") ICSS rates and produce leftward and upward shifts in ICSS frequency-rate curves, whereas drugs that lack abuse potential typically do not alter or only decrease ICSS rates. Initial studies determined the potency and time course of effects on ICSS produced by acute flibanserin administration (1.0, 3.2 and 10.0 mg/kg). Subsequent studies determined the effects of flibanserin (3.2-18 mg/kg) before and after a regimen of repeated flibanserin administration (5.6 mg/kg/d for 5 days). Effects of the abused stimulant amphetamine (1.0 mg/kg) were examined as a positive control. Flibanserin effects on ICSS frequency-rate curves in female and male rats were examined and compared with the effects of amphetamine. Baseline ICSS frequency-rate curves were similar in female and male rats. Acute and repeated administrations of flibanserin produced only decreases in ICSS rates, and rate-decreasing effects of the highest flibanserin dose (10 mg/kg) were greater in female than in male rats. In contrast to flibanserin, amphetamine produced an abuse-related increase in ICSS rates that did not differ between female and male rats. These results suggest that flibanserin has low abuse potential. In addition, this study suggests that female rats might be more sensitive than male rats to the rate-decreasing effects of high flibanserin doses.

Effect of carbonation on the linear and nonlinear dynamic properties of cement-based materials

Carbonation causes a physicochemical alteration of cement-based materials, leading to a decrease of porosity and an increase of material hardness and strength. However, carbonation will decrease the pH of the internal pore water solution, which may depassivate the internal reinforcing steel, giving rise to structural durability concerns. Therefore, the proper selection of materials informed by parameters sensitive to the carbonation process is crucial to ensure the durability of concrete structures. The authors investigate the feasibility of using linear and nonlinear dynamic vibration response data to monitor the progression of the carbonation process in cement-based materials. Mortar samples with dimensions of 40×40×160 mm were subjected to an accelerated carbonation process through a carbonation chamber with 55% relative humidity and 95% of CO 2 atmosphere. The progress of carbonation in the material was monitored using data obtained with the test setup of the standard resonant frequency test (ASTM C215-14), from a pristine state until an almost fully carbonated state. Linear dynamic modulus, quality factor, and a material nonlinear response, evaluated through the upward resonant frequency shift during the signal ring-down, were investigated. The compressive strength and the depth of carbonation were also measured. Carbonation resulted in a modest increase in the dynamic modulus, but a substantive increase in the quality factor (inverse attenuation) and a decrease in the material nonlinearity parameter. The combined measurement of the vibration quality factor and nonlinear parameter shows potential as a sensitive measure of material changes brought about by carbonation.