Spectral Fine Structure Research Articles

原子基态光谱精细结构的全相对论理论

原子基态光谱精细结构的全相对论理论

原子基态光谱精细结构的全相对论理论

We focus on the full relativistic quantum mechanical calculations from boron to fluorine atoms with electronic configuration of 1s22s22pn (n = 1, 2, 3, 4, and 5), where 1s22s2 is the closed shell and 2pn is the open shell. Their active electrons in the open shell occupy all the six spinors as far as possible. Therefore, we suggest a new rule called

Spectral fine structure of the atomic ground states based on full relativistic theory

Spectral fine structure of the atomic ground states based on full relativistic theory

Temporal and Spectral Cues for Musical Timbre Perception in Electric Hearing

The purpose of this study was to investigate musical timbre perception in cochlear-implant (CI) listeners using a multidimensional scaling technique to derive a timbre space. Methods Sixteen stimuli that synthesized western musical instruments were used (McAdams, Winsberg, Donnadieu, De Soete, & Krimphoff, 1995). Eight CI listeners and 15 normal-hearing (NH) listeners participated. Each listener made judgments of dissimilarity between stimulus pairs. Acoustical analyses that characterized the temporal and spectral characteristics of each stimulus were performed to examine the psychophysical nature of each perceptual dimension. For NH listeners, the timbre space was best represented in three dimensions, one correlated with the temporal envelope (log-attack time) of the stimuli, one correlated with the spectral envelope (spectral centroid), and one correlated with the spectral fine structure (spectral irregularity) of the stimuli. The timbre space from CI listeners, however, was best represented by two dimensions, one correlated with temporal envelope features and the other weakly correlated with spectral envelope features of the stimuli. Temporal envelope was a dominant cue for timbre perception in CI listeners. Compared to NH listeners, CI listeners showed reduced reliance on both spectral envelope and spectral fine structure cues for timbre perception.

PP-07. Intrauterine growth restriction may not suppress bone formation at term, as indicated by circulating concentrations of undercarboxylated osteocalcin and Dickkopf-1

The spectral envelope conveys sound quality and the time envelope is responsible for speech intelligibility. The spectral envelope can be identified in terms of the poles and zeros according to the linear system theory. This chapter deals with the poles and zeros creating spectral envelopes by taking an example of spectral records on piano string vibration. Sinusoidal modeling of spectral peaks due to poles in the frequency domain represents spectral fine structure of a temporally changing response such as a piano tone. Time-waveform decomposition in the transient state into pulse sequences in the time domain is explored in order to find the zeros that make the spectral envelope in the frequency domain. The two approaches to sound quality or signal signatures in the time and frequency domains are formulated on the basis of the least square error (LSE) criterion. The zeros are mainly responsible for the source signatures. The exciting source, such as a piano hammer, makes the outer spectral envelopes of the vibration response, while the inner envelope is rendered by the zeros due to a single cycle of the cyclic source-wave traveling on the piano string.

Temporal fine structure for sequential segregation.

Pitch based sequential segregation is reputed to benefit from spectral cues and temporal envelope cues. However, some previous results with hearing impaired listeners raised the possibility that other cues could promote segregation. These other cues could be responsible for the high inter‐subject variability across hearing impaired listeners in streaming experiments. Temporal fine structure cues appeared then to be a valuable candidate. The current study is dedicated to assess the potential benefit from temporal fine structure cues for sequential segregation. Unresolved complex tones (A) and unresolved complex tones with the same F0 in which all components were shifted upward by the same number of Hertz (B) were presented in ABA‐ABA‐ sequences. Using these stimuli, a rhythm discrimination task was used to estimate the amount of primitive segregation. Cochlear models will be applied first to the stimuli to establish the respective amount of spectral, temporal envelope and temporal fine structure cues. The results from the discrimination task will then be discussed at the light of the outputs of the models.

Intelligibility of interrupted and interleaved speech for normal-hearing listeners and cochlear implantees

Speech intelligibility is degraded in the presence of a competing talker for cochlear implantees, presumably because of impaired tracking and integration of speech segments glimpsed in the masker valleys. This hypothesis was tested by assessing the intelligibility of periodically-interrupted bisyllables produced by a male and female talker, for normal-hearing listeners and implantees. A 4-Hz square-wave modulator with random phase was used to interrupt bisyllables from each talker. Stimuli were either presented alone (Experiment I) or interleaved (Experiment II: the two talkers were alternated). In Experiment I, the mean identification score for each voice was 88% for normal-hearing listeners and 35% for implantees. In Experiment II, the mean score corresponding to correct identification of both voices was 50% for normal-hearing listeners and 5% for implantees. Implantees identified at least one bisyllable among the two well above chance level but showed difficulties assigning it to the correct talker. This suggests that implantees can make use of partial information, but cannot track and integrate the non-adjacent components of interleaved speech as well as normal-hearing listeners. Additional results obtained with normal-hearing listeners tested with tone-vocoded syllables suggest that impaired tracking/integration for implantees stems from limited reception of spectral and temporal fine structure cues.

When noise vocoding can improve the intelligibility of sub-critical band speech.

This study examined the redundancy of spectral and temporal information in everyday sentences, which were reduced to 16 rectangular spectral bands having center frequencies ranging from 250 to 8000 Hz, spaced at 1/3-octave intervals. High-order filtering eliminated contributions from transition bands, and the widths of the resulting effectively rectangular speech bands were varied from 4% down to 0.5% (Exp. 1) and from 40 Hz down to 5 Hz (Exp. 2). Intelligibility of these sub-critical bandwidth stimuli ranged from nearly perfect in the 4%- and 40-Hz bandwidth conditions, down to nearly zero in the 0.5%- and 5-Hz bandwidth conditions. However, a large recovery of intelligibility was obtained under adverse filtering conditions when the speech bands were used to vocode broader noise bands that approximated critical bandwidths (ERBn) at the 16 center frequencies. For example, the 0.5%- and 1%-bandwidth speech stimuli were only about 1% and 20% intelligible, respectively, whereas scores of about 26% and 60%, respectively, were obtained for the ERBn-wide modulated noise stimuli derived from the speech bands. These large intelligibility increases occurred despite elimination of spectral fine structure and the addition of stochastic fluctuations to the speech-envelope cues. Additional findings and their implications will be discussed. [Work supported by NIH.]

Reactivity of [Au25(SCH2CH2Ph)18]1−Nanoparticles with Metal Ions

We report reactivity of the gold nanoparticle [TOA+] [Au25(SC2Ph)18]1− (TOA+ = tetraoctylammonium; SC2Ph = phenylethanethiolate = L; [Au25(SC2Ph)18]1− = Au25L181−) with Ag+, Cu2+, and Pb2+ ions. Titration of solutions of Au25L181− in CH2Cl2 with one and two equivalents of Ag+ produces changes in absorbance spectra with isosbestic points, and a titration curve break at 1:1 mol ratio, indicating a stoichiometric interaction. Similar effects are seen with Cu2+ and Pb2+ additions, but the break occurs at 0.5:1 mol ratio metal/nanoparticle. Changes in Au25L181− absorbance and fluorescence spectra are qualitatively similar to those accompanying oxidation of the Au25L181− nanoparticle anion, but the spectra of the stoichiometric products differ slightly according to the metal ion. Addition of higher excess of Ag+ or Cu2+ causes loss of characteristic [Au25(SC2Ph)18]1− UV−vis spectral fine structure and apparent irreversible refining into larger nanoparticles. Voltammetric currents for nanoparticle 0/-1 and +1/0 ...

LiNbO3Ni2+晶体的精细光谱和扬特勒效应焦

LiNbO₃Ni²⁺晶体的精细光谱和扬特勒效应焦

Bayesian Pitch

Event Abstract Back to Event Bayesian Pitch Phillipp Hehrmann1* and Maneesh Sahani1 1 UCL, Gatsby Computational Neuroscience Unit, United Kingdom Pitch is a fundamental perceptual attribute of many sounds. It carries melodic, prosodic and sometimes semantic information, and contributes to auditory scene analysis. However, over a century of study has failed to yield a generally-accepted definition of pitch and model of its perception. No single physical feature of the acoustic waveform correlates perfectly with the reported pitch for all tested sounds, raising the question of whether pitch perception instead relies on a combination of several different features, and in turn, mechanisms. Three implicated features are harmonic regularities in the spectrum, periodicity of the waveform envelope, and the timing of fine structure peaks within the envelope. Here, we propose a computationally unified account of pitch perception. Our hypothesis is that the pitch of a sound is a Bayesian estimate of its periodicity, as inferred from the resulting time-varying auditory nerve firing rates. Inference proceeds within a generative model in which pitched sounds are first formed by convolving a regular train of impulses with a randomly drawn impulse-response and adding Gaussian noise. These sounds are then transformed to auditory nerve activity by a cascade of bandpass filters and demodulators, corrupted by further noise. This generative process describes responses to many naturally occurring pitched sounds such as voiced speech, vocalisations and musical instrument sounds. We suggest that the aberrant or ambiguous pitch percepts reported for some laboratory constructed sounds arise because the auditory system infers periodicity assuming this same generative model, even when it does not apply. To test our hypothesis, we chose three types of stimuli to exemplify the three physical cues listed above. Evidence for the importance of spectral features comes from harmonic complex sounds with missing fundamental f0. The pitch of these sounds corresponds to f0, but its strength varies depending on the number of the lowest harmonic present in the spectrum. Evidence for temporal envelope periodicity comes from amplitude modulated noise, which is weakly pitched despite the complete lack of spectral features. Finally, the timing of fine structure peaks must be invoked to explain the ambiguous pitch of amplitude modulated pure tones, which corresponds neither exactly to the envelope modulation rate nor to the spacing of spectral components. In all three cases, our Bayesian periodicity estimate provides a good match with human pitch perception, demonstrating that the model can indeed utilise spectral, temporal envelope and temporal fine structure cues within a single computational framework. Notably, the effect of model mismatch in case of the amplitude modulated tone and noise stimuli are also consistent with human pitch perception, lending further support to our hypothesis. Viewing pitch perception as probabilistic inference relates pitch to an unobserved, yet real physical quantity and provides a normative interpretation of its role in auditory perception, rather than a purely phenomenological match. Whilst this interpretation does not address the issue of neural implementation, it suggests that different neural mechanisms, should they exist, are set up together in a way to achieve a single computational goal. Conference: Computational and Systems Neuroscience 2010, Salt Lake City, UT, United States, 25 Feb - 2 Mar, 2010. Presentation Type: Poster Presentation Topic: Poster session II Citation: Hehrmann P and Sahani M (2010). Bayesian Pitch. Front. Neurosci. Conference Abstract: Computational and Systems Neuroscience 2010. doi: 10.3389/conf.fnins.2010.03.00199 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 03 Mar 2010; Published Online: 03 Mar 2010. * Correspondence: Phillipp Hehrmann, UCL, Gatsby Computational Neuroscience Unit, London, United Kingdom, hehrmann@gatsby.ucl.ac.uk Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Phillipp Hehrmann Maneesh Sahani Google Phillipp Hehrmann Maneesh Sahani Google Scholar Phillipp Hehrmann Maneesh Sahani PubMed Phillipp Hehrmann Maneesh Sahani Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Fine Structure in the Tunneling Spectra of Electron-Doped Cuprates: No Coupling to the Magnetic Resonance Mode

We reanalyze high-resolution scanning tunneling spectra of the electron-doped cuprate Pr(0.88)LaCe(0.12)CuO(4) (T(c) = 24 K). We find that the spectral fine structure below 35 meV is consistent with strong coupling to a bosonic mode at about 16 meV, in quantitative agreement with early tunneling spectra of Nd(1.85)Ce(0.15)CuO(4). Since the energy of the bosonic mode is significantly higher than that (9.5-11 meV) of the magnetic resonancelike mode observed by inelastic neutron scattering, the coupling feature at about 16 meV cannot arise from strong coupling to the magnetic mode. The present work thus demonstrates that the magnetic resonancelike mode cannot be the origin of high-temperature superconductivity in electron-doped cuprates.

Melodic Contour Identification and Music Perception by Cochlear Implant Users

Research and outcomes with cochlear implants (CIs) have revealed a dichotomy in the cues necessary for speech and music recognition. CI devices typically transmit 16-22 spectral channels, each modulated slowly in time. This coarse representation provides enough information to support speech understanding in quiet and rhythmic perception in music, but not enough to support speech understanding in noise or melody recognition. Melody recognition requires some capacity for complex pitch perception, which in turn depends strongly on access to spectral fine structure cues. Thus, temporal envelope cues are adequate for speech perception under optimal listening conditions, while spectral fine structure cues are needed for music perception. In this paper, we present recent experiments that directly measure CI users' melodic pitch perception using a melodic contour identification (MCI) task. While normal-hearing (NH) listeners' performance was consistently high across experiments, MCI performance was highly variable across CI users. CI users' MCI performance was significantly affected by instrument timbre, as well as by the presence of a competing instrument. In general, CI users had great difficulty extracting melodic pitch from complex stimuli. However, musically experienced CI users often performed as well as NH listeners, and MCI training in less-experienced subjects greatly improved performance. With fixed constraints on spectral resolution, such as occurs with hearing loss or an auditory prosthesis, training and experience can provide considerable improvements in music perception and appreciation.

Fine structure and optical pumping of spins in individual semiconductor quantum dots

We review spin properties of semiconductor quantum dots and their effect on optical spectra. Photoluminescence and other types of spectroscopy are used to probe neutral and charged excitons in individual quantum dots with high spectral and spatial resolution. Spectral fine structure and polarization reveal how quantum dot spins interact with each other and with their environment. By taking advantage of the selectivity of optical selection rules and spin relaxation, optical spin pumping of the ground state electron and nuclear spins is achieved. Through such mechanisms, light can be used to process spins for use as a carrier of information.

Optical spectra of doubly charged quantum dot molecules in electric and magnetic fields

We present an experimental and theoretical study of the photoluminescence spectra of individual doubly charged quantum dot molecules. The quantum dot molecules consist of two vertically stacked InAs self-assembled quantum dots in a GaAs Schottky diode structure. We study two cases: (1) the two dots are charged with two electrons coherently coupled through electron tunneling and (2) the two dots are charged with two holes and coherently coupled through hole tunneling. The optically excited states consist of the two charges along with one or two additional electron-hole pairs, i.e., a doubly charged exciton and biexciton. We determine the spin states and the corresponding spectral fine structure and show how this fine structure depends on vertical electric and magnetic fields. We find that the results are in large part qualitatively similar for the two cases. However, when magnetic fields are applied, we find a strong $g$ factor resonance and evidence of a bonding/antibonding reversal for the hole-tunneling case only. We discuss the implications for quantum information processing using spins confined in proximate dots.

Discrimination of the spectral structures of sound signals on the background of interference

Presentation of test signals consisting of sounds with rippled spectra allowed measurements of the frequency-resolving ability (FRA) of hearing to be performed in humans without using frequency-dependent masking techniques. This allowed studies of changes in FRA in the presence of noise interference. In conditions of diotic presentation (to both ears in parallel) of the test signal and noise, FRA decreased significantly if the interference frequency was lower or equal to the test signal frequency. The relationship between this effect and the sound intensity and noise:signal ratio varied for low-frequency noise and for noise at the same frequency as the test signal, which indicates that these two types of interference have different mechanisms. However, in both cases, noise of sufficient intensity led to a complete inability to discriminate the fine spectral structure of the test signal. In dichotic presentation (test signal to one ear, noise to the other), noise had virtually no effect on FRA over a wide range of test signal and noise frequencies and noise:signal ratios. Thus, there was essentially complete dichotic release of FRA from the effects noise, which has potential to be used in constructing prosthetic hearing devices.

Reception of phonetic features in fluctuating background noise maskers

We will review recent studies investigating the reception of phonetic features (voicing, manner and place of articulation) in nonstationary background maskers. In each study, consonant identification was assessed in steady and amplitude‐modulated speech‐shaped noise at signal‐to‐noise ratios yielding about 50% correct in steady noise. The rate and depth of amplitude modulation applied to the noise masker were either fixed or systematically varied. Confusion matrices were compiled across listeners and the amount of release from masking (percent information received in nonsteady minus steady noise) was calculated for each phonetic feature and experimental condition. Speech and noise mixtures were (i) left intact (unfiltered), (ii) lowpass filtered (<1.5 kHz), or iii) processed in order to degrade spectral (place of excitation in the cochlea) and/or temporal fine structure cues. Overall, the results indicate that release from masking typically reported in normal‐hearing listeners (i.e., the substantial improvement in speech reception in fluctuating noise compared to steady noise) is not identical across phonetic features. This suggests that the ability to “glimpse” into background noise valleys involves multiple auditory processes constrained by both peripheral and central factors.

FMRI and MEG evidence of overlapping generators in auditory cortex for streaming based on spatial and spectral cues

When analyzing complex acoustic scenes, the brain continuously groups related sounds and segregates others to form coherent perceptual streams. Neural mechanisms of streaming have been proposed based on spectral differences, and more recently also relying on f0 differences with unresolved spectral fine structure. These data suggest that feature-specific forward suppression is subserving streaming based on a variety of perceptual cues, and results in explicit neural representations of auditory streams within auditory cortex. Using functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG), the present study investigated the human cortical activity during streaming based on spatial cues, and compared it to the cortical activity elicited by streaming based on f0 differences. 12 listeners were presented with 32-s sequences of a repeating ABBB pattern composed of 125-ms harmonic complex tones (lowpass filtered at 5kHz) at a normalized sound intensity level of 70 dB SPL. The fundamental frequency (f0) of the A tones was always 180Hz (i.e. the lower harmonics of the tone complex were spectrally resolved), and the tones were lateralized to the left by an inter-aural time difference (ITD) of -687.5µs. Three conditions were compared: (1) a control (no-streaming) condition, where the parameters of the B tones were identical to the A tones, (2) a spatial-streaming condition, where the B tones were lateralized to the right by an ITD of 687.5µs, yielding an ITD difference of 1375µs between A and B (no f0 difference), and (3) an f0-based-streaming condition, where the f0 of the B tones was 120.1Hz, such that the f0 difference between A and B equaled 7 semitones (no ITD difference). Psychophysical responses, recorded during the measurements, revealed reliable streaming in the spatial as well as the f0-based condition. The cortical activity measured by fMRI and MEG was stronger when the listeners perceived the tones segregated into two perceptual streams for the spatial (ITD-based), as well as the f0-based condition. In fMRI, the activation time course during both streaming conditions exhibited a similar shape and increased amplitude, this increase being slightly higher for f0-based streaming. Throughout auditory cortex, both streaming conditions involved topographically almost identical areas, with the f0-condition producing somewhat more expanded activation. In MEG, the amplitudes of the P1m, N1m, and P2m components evoked by A tones were significantly larger when listeners perceived streaming. The increase was generally similar, yet showing interactions between components. These results support the hypothesis of explicit neural representations of streaming in auditory cortex, served by feature-specific forward suppression. In particular, the data add evidence for spatial cues in streaming and show that these spatial cues involve the same sites as f0 and spectral cues for streaming. Research supported by DFG grant GU593/3–1

The Coherent Radio Emission from the RS CVn Binary HR 1099

AbstractThe Australia Telescope was used in March–April 2005 to observe the 1.384 and 2.368-GHz emissions from the RS CVn binary HR 1099 in two sessions, each of 9-h duration and 11 days apart. Two intervals of highly polarised emission, each lasting 2–3 h, were recorded. During this coherent emission we employed a recently installed facility to sample the data at 78-ms intervals to measure the fine temporal structure and, in addition, all the data were used to search for fine spectral structure. We present the following observational results: (1) ∼100% left-hand circularly polarised emission was seen at both 1.384 and 2.368 GHz during separate epochs; (2) the intervals of highly polarised emission lasted for 2–3 h on each occasion; (3) three 22-min integrations made at 78-ms time resolution showed that the modulation index of the StokesVparameter increased monotonically as the integration time was decreased and was still increasing at our resolution limit; (4) the extremely fine temporal structure strongly indicates that the highly polarised emission is due to an electron-cyclotron maser operating in the corona of one of the binary components; (5) the first episode of what we believe is ECME (electron-cyclotron maser emission) at 1.384 GHz contained a regular frequency structure of bursts with FWHM ∼48 MHz, which drifted across the spectrum at ∼0.7 MHz min−1. Our second episode of ECME at 2.368 GHz contained wider-band frequency structure, which did not permit us to estimate an accurate bandwidth or direction of drift; (6) the two ECME events reported in this paper agree with six others reported in the literature in occurring in the binary orbital phase range 0.5–0.7; (7) in one event of 8-h duration, two independent maser sources were operating simultaneously at 1.384 and 2.368 GHz.We discuss two kinds of maser sources that may be responsible for driving the observed events that we believe are powered by ECME. One is based on the widely reported ‘loss-cone anisotropy', the second on an auroral analogue, which is driven by an unstable ‘horseshoe' distribution of fast-electron velocities with respect to the magnetic field direction. Generally, we favour the latter, because of its higher growth rate and the possibility of the escape of radiation which has been emitted at the fundamental electron cyclotron frequency. If the auroral analogue is operating, the magnetic field in the source cavity is ∼500 G at 1.384 GHz and ∼850 G at 2.368 GHz; the source brightness temperatures are of the orderTB∼ 1015K.We suggest that the ECME source may be an aurora-like phenomenon due to the transfer of plasma from the K2 subgiant to the G5 dwarf in a strong stellar wind, an idea that is based on VLBA maps showing the establishment of an 8.4 GHz source near the G5 dwarf at times of enhanced radio activity in HR 1099.

Human Cortical Activity during Streaming without Spectral Cues Suggests a General Neural Substrate for Auditory Stream Segregation

The brain continuously disentangles competing sounds, such as two people speaking, and assigns them to distinct streams. Neural mechanisms have been proposed for streaming based on gross spectral differences between sounds, but not for streaming based on other nonspectral features. Here, human listeners were presented with sequences of harmonic complex tones that had identical spectral envelopes, and unresolved spectral fine structure, but one of two fundamental frequencies (f0) and pitches. As the f0 difference between tones increased, listeners perceived the tones as being segregated into two streams (one stream for each f0) and cortical activity measured with functional magnetic resonance imaging and magnetoencephalography increased. This trend was seen in primary cortex of Heschl's gyrus and in surrounding nonprimary areas. The results strongly resemble those for pure tones. Both the present and pure tone results may reflect neuronal forward suppression that diminishes as one or more features of successive sounds become increasingly different. We hypothesize that feature-specific forward suppression subserves streaming based on diverse perceptual cues and results in explicit neural representations for auditory streams within auditory cortex.