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Sample records for amplitude modulated tones

  1. Beating frequency and amplitude modulation of the piano tone due to coupling of tones

    NASA Astrophysics Data System (ADS)

    Cartling, Bo

    2005-04-01

    The influence on a piano tone from weak coexcitation of damped adjacent tones due to coupling via the bridge is studied. The frequency and amplitude modulation of the sound resulting from coexcitation of one strong and one or two weak tones is analyzed. One weak tone causes frequency and amplitude modulation of the sound, and two weak tones produce beating frequency and amplitude modulation, where the beatings of the two modulations are of opposite phase. By digital recording of the sound of piano tones, the appearance of these phenomena is verified. The audibility of the observed frequency and amplitude modulation is discussed in terms of previously determined detection thresholds. The beating character of both frequency and amplitude modulations, however, distinguishes the phenomena from those previously studied and prompts further psychoacoustic investigations. It is shown that detuning of unison strings may significantly increase the frequency deviation of the frequency modulation in conjunction with affected amplitude modulation. The modulatory effects of coupling to adjacent tones therefore may possibly be utilized in the tuning process. A coupling of tones analogous to the situation in a piano may arise in other stringed musical instruments transferring string vibrations to a soundboard via a bridge. .

  2. Amplitude modulation reduces loudness adaptation to high-frequency tones

    PubMed Central

    Wynne, Dwight P.; George, Sahara E.; Zeng, Fan-Gang

    2015-01-01

    Long-term loudness perception of a sound has been presumed to depend on the spatial distribution of activated auditory nerve fibers as well as their temporal firing pattern. The relative contributions of those two factors were investigated by measuring loudness adaptation to sinusoidally amplitude-modulated 12-kHz tones. The tones had a total duration of 180 s and were either unmodulated or 100%-modulated at one of three frequencies (4, 20, or 100 Hz), and additionally varied in modulation depth from 0% to 100% at the 4-Hz frequency only. Every 30 s, normal-hearing subjects estimated the loudness of one of the stimuli played at 15 dB above threshold in random order. Without any amplitude modulation, the loudness of the unmodulated tone after 180 s was only 20% of the loudness at the onset of the stimulus. Amplitude modulation systematically reduced the amount of loudness adaptation, with the 100%-modulated stimuli, regardless of modulation frequency, maintaining on average 55%–80% of the loudness at onset after 180 s. Because the present low-frequency amplitude modulation produced minimal changes in long-term spectral cues affecting the spatial distribution of excitation produced by a 12-kHz pure tone, the present result indicates that neural synchronization is critical to maintaining loudness perception over time. PMID:26233027

  3. Human Neuromagnetic Steady-State Responses to Amplitude-Modulated Tones, Speech, and Music

    PubMed Central

    Parkkonen, Lauri; Hari, Riitta

    2014-01-01

    Objectives: Auditory steady-state responses that can be elicited by various periodic sounds inform about subcortical and early cortical auditory processing. Steady-state responses to amplitude-modulated pure tones have been used to scrutinize binaural interaction by frequency-tagging the two ears’ inputs at different frequencies. Unlike pure tones, speech and music are physically very complex, as they include many frequency components, pauses, and large temporal variations. To examine the utility of magnetoencephalographic (MEG) steady-state fields (SSFs) in the study of early cortical processing of complex natural sounds, the authors tested the extent to which amplitude-modulated speech and music can elicit reliable SSFs. Design: MEG responses were recorded to 90-s-long binaural tones, speech, and music, amplitude-modulated at 41.1 Hz at four different depths (25, 50, 75, and 100%). The subjects were 11 healthy, normal-hearing adults. MEG signals were averaged in phase with the modulation frequency, and the sources of the resulting SSFs were modeled by current dipoles. After the MEG recording, intelligibility of the speech, musical quality of the music stimuli, naturalness of music and speech stimuli, and the perceived deterioration caused by the modulation were evaluated on visual analog scales. Results: The perceived quality of the stimuli decreased as a function of increasing modulation depth, more strongly for music than speech; yet, all subjects considered the speech intelligible even at the 100% modulation. SSFs were the strongest to tones and the weakest to speech stimuli; the amplitudes increased with increasing modulation depth for all stimuli. SSFs to tones were reliably detectable at all modulation depths (in all subjects in the right hemisphere, in 9 subjects in the left hemisphere) and to music stimuli at 50 to 100% depths, whereas speech usually elicited clear SSFs only at 100% depth. The hemispheric balance of SSFs was toward the right hemisphere

  4. Cochlear Gain Control Estimated from Distortion Product Otoacoustic Emissions Evoked by Amplitude Modulated Tones

    NASA Astrophysics Data System (ADS)

    Chen, Shixiong; Bian, Lin

    2011-11-01

    It is known that cochlear outer hair cells (OHCs) can provide dynamic feedback to the basilar membrane vibration. Nonlinearities in OHC activities can generate distortion product otoacoustic emissions (DPOAEs) measurable in the ear canal. If evoked by amplitude modulation (AM) signals, DPOAEs could provide a means to access the dynamic gain control of the cochlea. In this study, one of the primary stimuli was replaced with an AM tone to evoke DPOAEs in human ears. The results showed that the estimated cochlear gain decreased with the increase in stimulus level and the gain functions obtained from different AM tone levels were continuous. However, there was a difference in the gain functions depending on which primary was modulated. The gain showed a stronger compression when f2 was modulated. Considering that DPOAEs are mainly generated at the f2 place, it suggests that the cochlear gain control is more nonlinear for on-frequency signals. Using AM stimulus could provide clues on how dynamic signals are processed in the cochlea.

  5. Comparison of discrete multi-tone and pulse amplitude modulation for beyond 100 Gbps short-reach application

    NASA Astrophysics Data System (ADS)

    Nishihara, Masato; Kai, Yutaka; Tanaka, Toshiki; Takahara, Tomoo; Li, Lei; Yan, Weizhen; Liu, Bo; Tao, Zhenning; Rasmussen, Jens C.

    2013-12-01

    Advanced multi-level modulation is an attractive modulation technique for beyond 100 Gbps short reach optical transmission system. Above all, discrete multi-tone (DMT) technique and pulse amplitude modulation (PAM) technique are the strong candidates. We compared the 100 Gbps transmission characteristics of DMT and PAM by simulation and experiment. The comparison was done by using same devices and only the digital signal processing was changed. We studied the transmission distance dependence for 0.5 to 40 km and the impact of the frequency responses of the optical devices. Finally we discuss the features of the both modulation techniques.

  6. Detection of modulated tones in modulated noise by non-human primates.

    PubMed

    Bohlen, Peter; Dylla, Margit; Timms, Courtney; Ramachandran, Ramnarayan

    2014-10-01

    In natural environments, many sounds are amplitude-modulated. Amplitude modulation is thought to be a signal that aids auditory object formation. A previous study of the detection of signals in noise found that when tones or noise were amplitude-modulated, the noise was a less effective masker, and detection thresholds for tones in noise were lowered. These results suggest that the detection of modulated signals in modulated noise would be enhanced. This paper describes the results of experiments investigating how detection is modified when both signal and noise were amplitude-modulated. Two monkeys (Macaca mulatta) were trained to detect amplitude-modulated tones in continuous, amplitude-modulated broadband noise. When the phase difference of otherwise similarly amplitude-modulated tones and noise were varied, detection thresholds were highest when the modulations were in phase and lowest when the modulations were anti-phase. When the depth of the modulation of tones or noise was varied, detection thresholds decreased if the modulations were anti-phase. When the modulations were in phase, increasing the depth of tone modulation caused an increase in tone detection thresholds, but increasing depth of noise modulations did not affect tone detection thresholds. Changing the modulation frequency of tone or noise caused changes in threshold that saturated at modulation frequencies higher than 20 Hz; thresholds decreased when the tone and noise modulations were in phase and decreased when they were anti-phase. The relationship between reaction times and tone level were not modified by manipulations to the nature of temporal variations in the signal or noise. The changes in behavioral threshold were consistent with a model where the brain subtracted noise from signal. These results suggest that the parameters of the modulation of signals and maskers heavily influence detection in very predictable ways. These results are consistent with some results in humans and avians

  7. The Role of Amplitude Envelope in Lexical Tone Perception: Evidence from Cantonese Lexical Tone Discrimination in Adults with Normal Hearing

    ERIC Educational Resources Information Center

    Zhou, Yining Victor

    2012-01-01

    Previously published studies on the role of amplitude envelope in lexical tone perception focused on Mandarin only. Amplitude envelope was found to co-vary with fundamental frequency in Mandarin lexical tones, and amplitude envelope alone could cue tone perception in Mandarin which uses primarily tone contour for phonemic tonal contrasts. The…

  8. Amplitude Modulator Chassis

    SciTech Connect

    Erbert, G

    2009-09-01

    The Amplitude Modulator Chassis (AMC) is the final component in the MOR system and connects directly to the PAM input through a 100-meter fiber. The 48 AMCs temporally shape the 48 outputs of the MOR using an arbitrary waveform generator coupled to an amplitude modulator. The amplitude modulation element is a two stage, Lithium Niobate waveguide device, where the intensity of the light passing through the device is a function of the electrical drive applied. The first stage of the modulator is connected to a programmable high performance Arbitrary Waveform Generator (AWG) consisting of 140 impulse generators space 250 ps apart. An arbitrary waveform is generated by independently varying the amplitude of each impulse generator and then summing the impulses together. In addition to the AWG a short pulse generator is also connected to the first stage of the modulator to provide a sub 100-ps pulse used for timing experiments. The second stage of the modulator is connect to a square pulse generator used to further attenuate any pre or post pulse light passing through the first stage of the modulator. The fast rise and fall time of the square pulse generator is also used to produce fast rise and fall times of the AWG by clipping the AWG pulse. For maximum extinction, a pulse bias voltage is applied to each stage of the modulator. A pulse voltage is applied as opposed to a DC voltage to prevent charge buildup on the modulator. Each bias voltage is adjustable to provide a minimum of 50-dB extinction. The AMC is controlled through ICCS to generate the desired temporal pulse shape. This process involves a closed-loop control algorithm, which compares the desired temporal waveform to the produced optical pulse, and iterates the programming of the AWG until the two waveforms agree within an allowable tolerance.

  9. Modulator for tone and binary signals. [phase of modulation of tone and binary signals on carrier waves in communication systems

    NASA Technical Reports Server (NTRS)

    Mcchesney, J. R.; Lerner, T.; Fitch, E. J. (Inventor)

    1975-01-01

    Tones and binary information are transmitted as phase variations on a carrier wave of constant amplitude and frequency. The carrier and tones are applied to a balanced modulator for deriving an output signal including a pair of sidebands relative to the carrier. The carrier is phase modulated by a digital signal so that it is + or - 90 deg out of phase with the predetermined phase of the carrier. The carrier is combined in an algebraic summing device with the phase modulated signal and the balanced modulator output signal. The output of the algebraic summing device is hard limited to derive a constant amplitude and frequency signal having very narrow bandwidth requirements. At a receiver, the tones and binary data are detected with a phase locked loop having a voltage controlled oscillator driving a pair of orthogonal detection channels.

  10. Speech recognition with amplitude and frequency modulations

    NASA Astrophysics Data System (ADS)

    Zeng, Fan-Gang; Nie, Kaibao; Stickney, Ginger S.; Kong, Ying-Yee; Vongphoe, Michael; Bhargave, Ashish; Wei, Chaogang; Cao, Keli

    2005-02-01

    Amplitude modulation (AM) and frequency modulation (FM) are commonly used in communication, but their relative contributions to speech recognition have not been fully explored. To bridge this gap, we derived slowly varying AM and FM from speech sounds and conducted listening tests using stimuli with different modulations in normal-hearing and cochlear-implant subjects. We found that although AM from a limited number of spectral bands may be sufficient for speech recognition in quiet, FM significantly enhances speech recognition in noise, as well as speaker and tone recognition. Additional speech reception threshold measures revealed that FM is particularly critical for speech recognition with a competing voice and is independent of spectral resolution and similarity. These results suggest that AM and FM provide independent yet complementary contributions to support robust speech recognition under realistic listening situations. Encoding FM may improve auditory scene analysis, cochlear-implant, and audiocoding performance. auditory analysis | cochlear implant | neural code | phase | scene analysis

  11. Pulse amplitude modulated chlorophyll fluorometer

    DOEpatents

    Greenbaum, Elias; Wu, Jie

    2015-12-29

    Chlorophyll fluorometry may be used for detecting toxins in a sample because of changes in micro algae. A portable lab on a chip ("LOAC") based chlorophyll fluorometer may be used for toxin detection and environmental monitoring. In particular, the system may include a microfluidic pulse amplitude modulated ("PAM") chlorophyll fluorometer. The LOAC PAM chlorophyll fluorometer may analyze microalgae and cyanobacteria that grow naturally in source drinking water.

  12. On the existence in human auditory pathways of channels selectively tuned to the modulation present in frequency-modulated tones

    PubMed Central

    Kay, R. H.; Matthews, D. R.

    1972-01-01

    1. The sensitivity of detecting modulation in a test tone sinusoidally frequency-modulated at a rate ϕtest is diminished after exposure to a conditioning tone more deeply frequency-modulated at a rate ϕcond provided that ϕcond is not very different from ϕtest, the sound amplitude being kept constant for each tone at a comfortable hearing level 40-45 dB above threshold. 2. When ϕcond = ϕtest the frequency deviation in the modulated test tone must be increased to about three times the unconditioned threshold magnitude to be detectable immediately after exposure to the conditioning tone. Detection sensitivity returns to normal in about one minute. 3. At low modulation frequencies the conditioning effects are tuned, being much diminished when ϕcond differs from ϕtest by a few cycles per second. 4. Comparing monaural with contra-aural conditioning demonstrates a considerable interaural transfer of about 60-80% of the effect, indicating that the conditioning and its selectivity are predominantly central phenomena. 5. The magnitude of the deterioration in detection sensitivity after conditioning is about 3 × at modulation frequencies between about 3/sec and 30/sec. It diminishes at lower and higher modulation frequencies and is effectively absent at 100/sec modulation. The bandwidth of the effect increases from a few cycles per second at the lower end of this range, to some tens of cycles per second at the upper end. 6. For the same modulation frequency, the conditioning is relatively insensitive to the mean `carrier' audiofrequency, f0. The band width in terms of carrier frequency is at least as wide as `critical bands'. With a test signal f0 = 250 Hz, ϕtest = 8/sec, conditioning is still appreciable for a conditioning tone of ϕcond = 8/sec but centred upon f0 = 150 Hz or = 350 Hz. Conditioning is thus not explicable in terms of coincidences between particular spectral components in the conditioning and test tones. 7. Whereas the sensitivity of detecting 8/sec

  13. Pocket-sized tone-modulated FM transmitter

    NASA Technical Reports Server (NTRS)

    Couvillon, L. A.

    1969-01-01

    Pressure of a button on a crystal-controlled transmitter causes generation of a tone. The tone modulates the FM transmitter which in turn radiates by way of the enclosed loop antenna, through the radio-frequency-transparent wall of the transmitters case to the receiver.

  14. Brainstem cholinergic modulation of muscle tone in infant rats.

    PubMed

    Gall, Andrew J; Poremba, Amy; Blumberg, Mark S

    2007-06-01

    In week-old rats, lesions of the dorsolateral pontine tegmentum (DLPT) and nucleus pontis oralis (PnO) have opposing effects on nuchal muscle tone. Specifically, pups with DLPT lesions exhibit prolonged bouts of nuchal muscle atonia (indicative of sleep) and pups with PnO lesions exhibit prolonged bouts of high nuchal muscle tone (indicative of wakefulness). Here we test the hypothesis that nuchal muscle tone is modulated, at least in part, by cholinergically mediated interactions between these two regions. First, in unanesthetized pups, we found that chemical infusion of the cholinergic agonist carbachol (22 mm, 0.1 microL) within the DLPT produced high muscle tone. Next, chemical lesions of the PnO were used to produce a chronic state of high nuchal muscle tone, at which time the cholinergic antagonist scopolamine (10 mm, 0.1 microL) was infused into the DLPT. Scopolamine effectively decreased nuchal muscle tone, thus suggesting that lesions of the PnO increase muscle tone via cholinergic activation of the DLPT. Using 2-deoxyglucose autoradiography, metabolic activation throughout the DLPT was observed after PnO lesions. Finally, consistent with the hypothesis that PnO inactivation produces high muscle tone, infusion of the sodium channel blocker lidocaine (2%) into the PnO of unanesthetized pups produced rapid increases in muscle tone. We conclude that, even early in infancy, the DLPT is critically involved in the regulation of muscle tone and behavioral state, and that its activity is modulated by a cholinergic mechanism that is directly or indirectly controlled by the PnO.

  15. Visual emotional context modulates brain potentials elicited by unattended tones.

    PubMed

    Sugimoto, Sayaka; Nittono, Hiroshi; Hori, Tadao

    2007-10-01

    To examine whether brain electrical responses to environmental stimuli were influenced by emotional contexts, event-related potentials (ERPs) elicited by nonstartle probe tones were recorded from 13 student volunteers while they were viewing emotionally positive, neutral, and negative slides of the International Affective Picture System. The auditory stimuli consisted of high-deviant (2000 Hz, p=.08), low-deviant (1050 Hz, p=.08), and standard (1000 Hz, p=.84) tones with a mean onset-to-onset interval of 600 ms. Participants were told to ignore the tones. High-deviant tones elicited a larger N1 (peaking around 100 ms) when participants were viewing negative slides than when viewing positive slides. The amplitude of the P2 elicited by standard tones (peaking around 170 ms) was smaller when participants were viewing positive slides than when viewing negative and neutral slides. The amplitude of the mismatch negativity (150-200 ms) tended to reduce during positive slide presentation, but this difference appeared to be due to reduction of the P2 elicited by standard tones. These findings suggest that visually induced emotional states have a sequential effect on auditory information processing, in that the influence of negative emotion appears at an earlier stage than that of positive emotion.

  16. Amplitude Modulations of Acoustic Communication Signals

    NASA Astrophysics Data System (ADS)

    Turesson, Hjalmar K.

    2011-12-01

    In human speech, amplitude modulations at 3 -- 8 Hz are important for discrimination and detection. Two different neurophysiological theories have been proposed to explain this effect. The first theory proposes that, as a consequence of neocortical synaptic dynamics, signals that are amplitude modulated at 3 -- 8 Hz are propagated better than un-modulated signals, or signals modulated above 8 Hz. This suggests that neural activity elicited by vocalizations modulated at 3 -- 8 Hz is optimally transmitted, and the vocalizations better discriminated and detected. The second theory proposes that 3 -- 8 Hz amplitude modulations interact with spontaneous neocortical oscillations. Specifically, vocalizations modulated at 3 -- 8 Hz entrain local populations of neurons, which in turn, modulate the amplitude of high frequency gamma oscillations. This suggests that vocalizations modulated at 3 -- 8 Hz should induce stronger cross-frequency coupling. Similar to human speech, we found that macaque monkey vocalizations also are amplitude modulated between 3 and 8 Hz. Humans and macaque monkeys share similarities in vocal production, implying that the auditory systems subserving perception of acoustic communication signals also share similarities. Based on the similarities between human speech and macaque monkey vocalizations, we addressed how amplitude modulated vocalizations are processed in the auditory cortex of macaque monkeys, and what behavioral relevance modulations may have. Recording single neuron activity, as well as, the activity of local populations of neurons allowed us to test both of the neurophysiological theories presented above. We found that single neuron responses to vocalizations amplitude modulated at 3 -- 8 Hz resulted in better stimulus discrimination than vocalizations lacking 3 -- 8 Hz modulations, and that the effect most likely was mediated by synaptic dynamics. In contrast, we failed to find support for the oscillation-based model proposing a

  17. Coding of amplitude-modulated signals in the cochlear nucleus of a grass frog

    NASA Astrophysics Data System (ADS)

    Bibikov, N. G.

    2002-07-01

    To study the mechanisms that govern the coding of temporal features of complex sound signals, responses of single neurons located in the dorsal nucleus of the medulla oblongata (the cochlear nucleus) of a curarized grass frog ( Rana temporaria) to pure tone bursts and amplitude modulated tone bursts with a modulation frequency of 20 Hz and modulation depths of 10 and 80% were recorded. The carrier frequency was equal to the characteristic frequency of a neuron, the average signal level was 20 30 dB above the threshold, and the signal duration was equal to ten full modulation periods. Of the 133 neurons studied, 129 neurons responded to 80% modulated tone bursts by discharges that were phase-locked with the envelope waveform. At this modulation depth, the best phase locking was observed for neurons with the phasic type of response to tone bursts. For tonic neurons with low characteristic frequencies, along with the reproduction of the modulation, phase locking with the carrier frequency of the signal was observed. At 10% amplitude modulation, phasic neurons usually responded to only the onset of a tone burst. Almost all tonic units showed a tendency to reproduce the envelope, although the efficiency of the reproduction was low, and for half of these neurons, it was below the reliability limit. Some neurons exhibited a more efficient reproduction of the weak modulation. For almost half of the neurons, a reliable improvement was observed in the phase locking of the response during the tone burst presentation (from the first to the tenth modulation period). The cooperative histogram of a set of neurons responding to 10% modulated tone bursts within narrow ranges of frequencies and intensities retains the information on the dynamics of the envelope variation. The data are compared with the results obtained from the study of the responses to similar signals in the acoustic midbrain center of the same object and also with the psychophysical effect of a differential

  18. Pre-attentive modulation of brain responses to tones in coloured-hearing synesthetes

    PubMed Central

    2012-01-01

    Background Coloured-hearing (CH) synesthesia is a perceptual phenomenon in which an acoustic stimulus (the inducer) initiates a concurrent colour perception (the concurrent). Individuals with CH synesthesia "see" colours when hearing tones, words, or music; this specific phenomenon suggesting a close relationship between auditory and visual representations. To date, it is still unknown whether the perception of colours is associated with a modulation of brain functions in the inducing brain area, namely in the auditory-related cortex and associated brain areas. In addition, there is an on-going debate as to whether attention to the inducer is necessarily required for eliciting a visual concurrent, or whether the latter can emerge in a pre-attentive fashion. Results By using the EEG technique in the context of a pre-attentive mismatch negativity (MMN) paradigm, we show that the binding of tones and colours in CH synesthetes is associated with increased MMN amplitudes in response to deviant tones supposed to induce novel concurrent colour perceptions. Most notably, the increased MMN amplitudes we revealed in the CH synesthetes were associated with stronger intracerebral current densities originating from the auditory cortex, parietal cortex, and ventral visual areas. Conclusions The automatic binding of tones and colours in CH synesthetes is accompanied by an early pre-attentive process recruiting the auditory cortex, inferior and superior parietal lobules, as well as ventral occipital areas. PMID:23241212

  19. Relativistic Electron Microburst Induced by Large Amplitude EMIC Rising-tone Emissions

    NASA Astrophysics Data System (ADS)

    Kubota, Y.; Omura, Y.

    2015-12-01

    We study dynamics of radiation belt electrons interacting with large amplitude EMIC rising-tone emissions by performing test particle simulations. Engebretson et al. [JGR, 2015] reported observation of large amplitude EMIC rising-tone emissions outside the plasmasphere and depletion of radiation belt electrons in response to these emissions. We make the two kinds of wave models; one is in low-density region based on the observation and the other is in the plasmasphere. To reproduce the large wave amplitude we include the convective wave growth, which are neglected through propagation of EMIC model waves in the previous studies [Omura and Zhao, JGR, 2012, 2013; Kubota et al., JGR, 2015]. Furthermore, we also include Landau damping in setting up the model waves. Comparing with a wave model ignoring the convective wave growth, it is found that the large wave amplitude contributes to rapid electron precipitation. Some of relativistic electrons change their equatorial pitch angles more than 15 degrees in a time scale of 0.1 s, precipitated into the atmosphere. We set up the EMIC model waves in a local longitude and distribute test electrons throughout all longitudinal direction initially. The electrons moving eastward encounter the localized EMIC waves and some of resonant electrons are precipitated into the atmosphere. We obtain distribution of radiation belt electrons with respect to their equatorial pitch angle and kinetic energy. We find that the frequency variation expands the resonant electron range of pitch angles and energies. For comparison with observation of precipitated electrons, we monitor fluxes of electrons lost into the atmosphere in a narrow longitudinal range. Furthermore, we find echo of electron depletion due to eastward drift around the Earth. Energy ranges of efficient precipitation are different depending on the regions of interaction inside and outside of the plasmapause. Inside the plasmapause, electrons with energy > 0.5 MeV are precipitated

  20. [Amplitude modulation in sound signals by mammals].

    PubMed

    Nikol'skiĭ, A A

    2012-01-01

    Periodic variations in amplitude of a signal, or amplitude modulation (AM), affect the structure of communicative messages spectrum. Within the spectrum of AM-signals, side frequencies are formed both above and below the carrier frequency that is subjected to modulation. In case of harmonic signal structure they are presented near fundamental frequency as well as near harmonics. Thus, AM may by viewed as a relatively simple mechanism for controlling the spectrum of messages transmitted by mammals. Examples of AM affecting the spectrum structure of functionally different sound signals are discussed as applied to representatives of four orders of mammals: rodents (Reodentia), duplicidentates (Lagomorpha), pinnipeds (Pinnipedia), and paridigitates (Artiodactia). For the first time, the classification of AM in animals' sound signals is given. Five forms of AM are picked out in sound signals by mammals: absence of AM, continuous AM, fragmented, heterogeneous, and multilevel one. AM presence/absence is related neither with belonging to any specific order nor with some particular function of a signal. Similar forms of AM can occur in different orders of mammals in parallel. On the contrary, different forms of AM can be detected in signals meant for similar functions. The assumption is made about AM-signals facilitating information encoding and jamprotection of messages transmitted by mammals. Preliminry analysis indicates that hard-driving amplitude modulation is incompatible with hard-driving frequency modulation.

  1. Detection of combined frequency and amplitude modulation.

    PubMed

    Moore, B C; Sek, A

    1992-12-01

    This article is concerned with the detection of mixed modulation (MM), i.e., simultaneously occurring amplitude modulation (AM) and frequency modulation (FM). In experiment 1, an adaptive two-alternative forced-choice task was used to determine thresholds for detecting AM alone. Then, thresholds for detecting FM were determined for stimuli which had a fixed amount of AM in the signal interval only. The amount of AM was always less than the threshold for detecting AM alone. The FM thresholds depended significantly on the magnitude of the coexisting AM. For low modulation rates (4, 16, and 64 Hz), the FM thresholds did not depend significantly on the relative phase of modulation for the FM and AM. For a high modulation rate (256 Hz) strong effects of modulator phase were observed. These phase effects are as predicted by the model proposed by Hartmann and Hnath [Acustica 50, 297-312 (1982)], which assumes that detection of modulation at modulation frequencies higher than the critical modulation frequency is based on detection of the lower sideband in the modulated signal's spectrum. In the second experiment, psychometric functions were measured for the detection of AM alone and FM alone, using modulation rates of 4 and 16 Hz. Results showed that, for each type of modulation, d' is approximately a linear function of the square of the modulation index. Application of this finding to the results of experiment 1 suggested that, at low modulation rates, FM and AM are not detected by completely independent mechanisms. In the third experiment, psychometric functions were again measured for the detection of AM alone and FM alone, using a 10-Hz modulation rate. Detectability was then measured for combined AM and FM, with modulation depths selected so that each type of modulation would be equally detectable if presented alone. Significant effects of relative modulator phase were found when detectability was relatively high. These effects were not correctly predicted by either a

  2. Photon Counting Chirped Amplitude Modulation Ladar

    DTIC Science & Technology

    2008-03-01

    22202-4302. Respondents should be aware that notwithstanding any other provision of law , no person shall be subject to any penalty for failing to...135 S. Taylor Ave., Room 103, Louisville, CO 80027-3025 14. ABSTRACT This work developed a method using Geiger -mode avalanche photodiode (GM-APD...architecture are discussed. 15. SUBJECT TERMS laser radar, ladar, avalanche photo-detectors, Geiger mode detectors, chirped amplitude modulation

  3. Modulated Source Interferometry with Combined Amplitude and Frequency Modulation

    NASA Technical Reports Server (NTRS)

    Gutierrez, Roman C. (Inventor)

    1998-01-01

    An improved interferometer is produced by modifying a conventional interferometer to include amplitude and/or frequency modulation of a coherent light source at radio or higher frequencies. The phase of the modulation signal can be detected in an interfering beam from an interferometer and can be used to determine the actual optical phase of the beam. As such, this improvement can be adapted to virtually any two-beam interferometer, including: Michelson, Mach-Zehnder, and Sagnac interferometers. The use of an amplitude modulated coherent tight source results in an interferometer that combines the wide range advantages of coherent interferometry with the precise distance measurement advantages of white light interferometry.

  4. Baseline blood oxygenation modulates response amplitude

    PubMed Central

    Lu, Hanzhang; Zhao, Chenguang; Ge, Yulin; Lewis-Amezcua, Kelly

    2008-01-01

    Although BOLD fMRI provides a useful tool for probing neuronal activities, large inter-subject variations in signal amplitude are commonly observed. Understanding the physiologic basis for these variations will have a significant impact on many fMRI studies. First, the physiologic modulator can be used as a regressor to reduce variations across subjects, thereby improving statistical power for detecting group differences. Second, if a pathologic condition or a drug treatment is shown to change fMRI responses, monitoring this modulatory parameter is useful in correctly interpreting the fMRI changes to neuronal deficits/recruitments. Here we present evidence that the task-evoked fMRI signals are modulated by baseline blood oxygenation. To measure global blood oxygenation, we used a recently developed technique, T2-Relaxation-Under-Spin-Tagging MRI, yielding baseline oxygenation of 63.7±7.2% in sagittal sinus with an estimation error of 1.3%. It was found that individuals with higher baseline oxygenation tend to have a smaller fMRI signal and vice versa. For every 10% difference in baseline oxygenation across subjects, the BOLD and cerebral blood flow signal differ by -0.4% and -30.0%, respectively, when using visual stimulation. TRUST MRI is a useful measurement for fMRI studies to control for the modulatory effects of baseline oxygenation that are unique to each subject. PMID:18666103

  5. Serotonin differentially modulates responses to tones and frequency-modulated sweeps in the inferior colliculus.

    PubMed

    Hurley, L M; Pollak, G D

    1999-09-15

    Although almost all auditory brainstem nuclei receive serotonergic innervation, little is known about its effects on auditory neurons. We address this question by evaluating the effects of serotonin on sound-evoked activity of neurons in the inferior colliculus (IC) of Mexican free-tailed bats. Two types of auditory stimuli were used: tone bursts at the neuron's best frequency and frequency-modulated (FM) sweeps with a variety of spectral and temporal structures. There were two main findings. First, serotonin changed tone-evoked responses in 66% of the IC neurons sampled. Second, the influence of serotonin often depended on the type of signal presented. Although serotonin depressed tone-evoked responses in most neurons, its effects on responses to FM sweeps were evenly mixed between depression and facilitation. Thus in most cells serotonin had a different effect on tone-evoked responses than it did on FM-evoked responses. In some neurons serotonin depressed responses evoked by tone bursts but left the responses to FM sweeps unchanged, whereas in others serotonin had little or no effect on responses to tone bursts but substantially facilitated responses to FM sweeps. In addition, serotonin could differentially affect responses to various FM sweeps that differed in temporal or spectral structure. Previous studies have revealed that the efficacy of the serotonergic innervation is partially modulated by sensory stimuli and by behavioral states. Thus our results suggest that the population activity evoked by a particular sound is not simply a consequence of the hard wiring that connects the IC to lower and higher regions but rather is highly dynamic because of the functional reconfigurations induced by serotonin and almost certainly other neuromodulators as well.

  6. Modulator-free quadrature amplitude modulation signal synthesis

    PubMed Central

    Liu, Zhixin; Kakande, Joseph; Kelly, Brian; O’Carroll, John; Phelan, Richard; Richardson, David J.; Slavík, Radan

    2014-01-01

    The ability to generate high-speed on–off-keyed telecommunication signals by directly modulating a semiconductor laser’s drive current was one of the most exciting prospective applications of the nascent field of laser technology throughout the 1960s. Three decades of progress led to the commercialization of 2.5 Gbit s−1-per-channel submarine fibre optic systems that drove the growth of the internet as a global phenomenon. However, the detrimental frequency chirp associated with direct modulation forced industry to use external electro-optic modulators to deliver the next generation of on–off-keyed 10 Gbit s−1 systems and is absolutely prohibitive for today’s (>)100 Gbit s−1 coherent systems, which use complex modulation formats (for example, quadrature amplitude modulation). Here we use optical injection locking of directly modulated semiconductor lasers to generate complex modulation format signals showing distinct advantages over current and other currently researched solutions. PMID:25523757

  7. Neurometric amplitude-modulation detection threshold in the guinea-pig ventral cochlear nucleus

    PubMed Central

    Sayles, Mark; Füllgrabe, Christian; Winter, Ian M

    2013-01-01

    Amplitude modulation (AM) is a pervasive feature of natural sounds. Neural detection and processing of modulation cues is behaviourally important across species. Although most ecologically relevant sounds are not fully modulated, physiological studies have usually concentrated on fully modulated (100% modulation depth) signals. Psychoacoustic experiments mainly operate at low modulation depths, around detection threshold (∼5% AM). We presented sinusoidal amplitude-modulated tones, systematically varying modulation depth between zero and 100%, at a range of modulation frequencies, to anaesthetised guinea-pigs while recording spikes from neurons in the ventral cochlear nucleus (VCN). The cochlear nucleus is the site of the first synapse in the central auditory system. At this locus significant signal processing occurs with respect to representation of AM signals. Spike trains were analysed in terms of the vector strength of spike synchrony to the amplitude envelope. Neurons showed either low-pass or band-pass temporal modulation transfer functions, with the proportion of band-pass responses increasing with increasing sound level. The proportion of units showing a band-pass response varies with unit type: sustained chopper (CS) > transient chopper (CT) > primary-like (PL). Spike synchrony increased with increasing modulation depth. At the lowest modulation depth (6%), significant spike synchrony was only observed near to the unit's best modulation frequency for all unit types tested. Modulation tuning therefore became sharper with decreasing modulation depth. AM detection threshold was calculated for each individual unit as a function of modulation frequency. Chopper units have significantly better AM detection thresholds than do primary-like units. AM detection threshold is significantly worse at 40 dB vs. 10 dB above pure-tone spike rate threshold. Mean modulation detection thresholds for sounds 10 dB above pure-tone spike rate threshold at best modulation

  8. Amplitude-modulated circular-harmonic filter for pattern recognition.

    PubMed

    Chen, X W; Chen, Z P

    1995-02-10

    An amplitude-modulated circular-harmonic filter is proposed for rotation-invariant pattern recognition. We investigate the filter characteristics by varying two design parameters, A(ρ) and B(ρ), and select optimum values to design an amplitude-modulated circular-harmonic filter. When compared with the phase-only circular-harmonic filter, the amplitude-modulated circular-harmonic filter is found to yield a sharper correlation peak, a better noise tolerance, and an improved correlation discrimination.

  9. Principal pitch of frequency-modulated tones with asymmetrical modulation waveform: a comparison of models.

    PubMed

    Etchemendy, Pablo E; Eguia, Manuel C; Mesz, Bruno

    2014-03-01

    In this work, the overall perceived pitch (principal pitch) of pure tones modulated in frequency with an asymmetric waveform is studied. The dependence of the principal pitch on the degree of asymmetric modulation was obtained from a psychophysical experiment. The modulation waveform consisted of a flat portion of constant frequency and two linear segments forming a peak. Consistent with previous results, significant pitch shifts with respect to the time-averaged geometric mean were observed. The direction of the shifts was always toward the flat portion of the modulation. The results from the psychophysical experiment, along with those obtained from previously reported studies, were compared with the predictions of six models of pitch perception proposed in the literature. Even though no single model was able to predict accurately the perceived pitch for all experiments, there were two models that give robust predictions that are within the range of acceptable tuning of modulated tones for almost all the cases. Both models point to the existence of an underlying "stability sensitive" mechanism for the computation of pitch that gives more weight to the portion of the stimuli where the frequency is changing more slowly.

  10. The perception of speech modulation cues in lexical tones is guided by early language-specific experience.

    PubMed

    Cabrera, Laurianne; Tsao, Feng-Ming; Liu, Huei-Mei; Li, Lu-Yang; Hu, You-Hsin; Lorenzi, Christian; Bertoncini, Josiane

    2015-01-01

    A number of studies showed that infants reorganize their perception of speech sounds according to their native language categories during their first year of life. Still, information is lacking about the contribution of basic auditory mechanisms to this process. This study aimed to evaluate when native language experience starts to noticeably affect the perceptual processing of basic acoustic cues [i.e., frequency-modulation (FM) and amplitude-modulation information] known to be crucial for speech perception in adults. The discrimination of a lexical-tone contrast (rising versus low) was assessed in 6- and 10-month-old infants learning either French or Mandarin using a visual habituation paradigm. The lexical tones were presented in two conditions designed to either keep intact or to severely degrade the FM and fine spectral cues needed to accurately perceive voice-pitch trajectory. A third condition was designed to assess the discrimination of the same voice-pitch trajectories using click trains containing only the FM cues related to the fundamental-frequency (F0) in French- and Mandarin-learning 10-month-old infants. Results showed that the younger infants of both language groups and the Mandarin-learning 10-month-olds discriminated the intact lexical-tone contrast while French-learning 10-month-olds failed. However, only the French 10-month-olds discriminated degraded lexical tones when FM, and thus voice-pitch cues were reduced. Moreover, Mandarin-learning 10-month-olds were found to discriminate the pitch trajectories as presented in click trains better than French infants. Altogether, these results reveal that the perceptual reorganization occurring during the first year of life for lexical tones is coupled with changes in the auditory ability to use speech modulation cues.

  11. Amplitude-modulation detection by gerbils in reverberant sound fields.

    PubMed

    Lingner, Andrea; Kugler, Kathrin; Grothe, Benedikt; Wiegrebe, Lutz

    2013-08-01

    Reverberation can dramatically reduce the depth of amplitude modulations which are critical for speech intelligibility. Psychophysical experiments indicate that humans' sensitivity to amplitude modulation in reverberation is better than predicted from the acoustic modulation depth at the receiver position. Electrophysiological studies on reverberation in rabbits highlight the contribution of neurons sensitive to interaural correlation. Here, we use a prepulse-inhibition paradigm to quantify the gerbils' amplitude modulation threshold in both anechoic and reverberant virtual environments. Data show that prepulse inhibition provides a reliable method for determining the gerbils' AM sensitivity. However, we find no evidence for perceptual restoration of amplitude modulation in reverberation. Instead, the deterioration of AM sensitivity in reverberant conditions can be quantitatively explained by the reduced modulation depth at the receiver position. We suggest that the lack of perceptual restoration is related to physical properties of the gerbil's ear input signals and inner-ear processing as opposed to shortcomings of their binaural neural processing.

  12. Roles for Coincidence Detection in Coding Amplitude-Modulated Sounds

    PubMed Central

    Ashida, Go; Kretzberg, Jutta; Tollin, Daniel J.

    2016-01-01

    Many sensory neurons encode temporal information by detecting coincident arrivals of synaptic inputs. In the mammalian auditory brainstem, binaural neurons of the medial superior olive (MSO) are known to act as coincidence detectors, whereas in the lateral superior olive (LSO) roles of coincidence detection have remained unclear. LSO neurons receive excitatory and inhibitory inputs driven by ipsilateral and contralateral acoustic stimuli, respectively, and vary their output spike rates according to interaural level differences. In addition, LSO neurons are also sensitive to binaural phase differences of low-frequency tones and envelopes of amplitude-modulated (AM) sounds. Previous physiological recordings in vivo found considerable variations in monaural AM-tuning across neurons. To investigate the underlying mechanisms of the observed temporal tuning properties of LSO and their sources of variability, we used a simple coincidence counting model and examined how specific parameters of coincidence detection affect monaural and binaural AM coding. Spike rates and phase-locking of evoked excitatory and spontaneous inhibitory inputs had only minor effects on LSO output to monaural AM inputs. In contrast, the coincidence threshold of the model neuron affected both the overall spike rates and the half-peak positions of the AM-tuning curve, whereas the width of the coincidence window merely influenced the output spike rates. The duration of the refractory period affected only the low-frequency portion of the monaural AM-tuning curve. Unlike monaural AM coding, temporal factors, such as the coincidence window and the effective duration of inhibition, played a major role in determining the trough positions of simulated binaural phase-response curves. In addition, empirically-observed level-dependence of binaural phase-coding was reproduced in the framework of our minimalistic coincidence counting model. These modeling results suggest that coincidence detection of excitatory

  13. Age-related Shifts in Distortion Product Otoacoustic Emissions Peak-ratios and Amplitude Modulation Spectra

    PubMed Central

    Lai, Jesyin; Bartlett, Edward L.

    2015-01-01

    Amplitude modulation (AM) is an important temporal cue for precise speech and complex sound recognition. However, functional decline of the auditory periphery as well as degradation of central auditory processing due to aging can reduce the salience and resolution of temporal cues. Age-related deficits in central temporal processing have previously been observed at more rapid AM frequencies and various AM depths. These centrally observed changes result from cochlear changes compounded with changes along the ascending auditory pathway. In fact, a decrease in ability to detect temporally modulated sounds accurately could originate from changes in cochlear filtering properties and in cochlear mechanics due to aging. Nonetheless, few studies have examined cochlear mechanisms in AM detection. To assess integrity of the mechanical properties of the auditory periphery, distortion product otoacoustic emissions (DPOAEs) are a tool commonly used in clinics and in research. In this study, we measured DPOAEs to reveal age-related changes in peak f2/f1 ratio and degradation in AM detection by basilar membrane vibration. Two tones (f1 and f2, f2>f1) at various f2/f1 ratios and simultaneous presentation of one AM and one pure tone were used as stimuli to evoke DPOAEs. In addition of observing reduced DPOAE amplitudes and steeper slopes in the input-output DPOAE functions, higher peak f2/f1 ratios and broader f2/f1 tuning were also observed in aged animals. Aged animals generally had lower distortion product (DP) and first sideband (SB 1) responses evoked by an f1 pure tone and an f2 AM tone, regardless of whether the AM frequency was 45 Hz or 128 Hz. SB 1 thresholds, which corresponds to the smallest stimulus AM depth that can induce cochlear vibrations at the DP generator locus, were higher in aged animals as well. The results suggest that age-related changes in peak f2/f1 ratio and AM detection by basilar membrane vibration are consistent with a reduction in endocochlear

  14. Preliminary analysis of amplitude and phase fluctuations in the JAPE multiple tone data to distances of 500 meters

    NASA Technical Reports Server (NTRS)

    Rogers, James; Sokolov, Radomir; Hicks, Daniel; Cartwright, Lloyd

    1993-01-01

    The JAPE short range data provide a good opportunity for studying phase and amplitude fluctuations of acoustic signals in the atmosphere over distances of several hundred meters. Several factors contribute to the usefulness of these data: extensive meteorological measurements were made, controlled sources were used, the data were recorded with a high dynamic range digital system that preserved phase information and a significant number of measurement points were obtained allowing both longitudinal and transverse studies. Further, Michigan Tech, in cooperation with the U.S. Army TARDEC, has developed phase tracking algorithms for studying vehicle acoustic signals. These techniques provide an excellent tool for analyzing the amplitude and phase fluctuations of the JAPE data. The results of studies such as those reported here have application at several levels: the mechanisms of signal amplitude and phase fluctuations in propagating acoustic signals are not well understood nor are the mathematical models highly developed, acoustic arrays depend strongly on signal coherence and signal amplitude stability in order to perform to their design specifications and active noise control implementation in regions considerably removed from the primary and secondary sources depends upon signal amplitude and phase stability. Work reported here is preliminary in nature but it does indicate the utility of the phase tracking and amplitude detection algorithms. The results obtained indicate that the phase fluctuations of the JAPE continuous multiple tone data (simultaneous transmission of 80, 200 and 500 Hz) are in general agreement with existing theories but the amplitude fluctuations are seen to be less well behaved and show less consistency.

  15. Comparison of perceptual properties of auditory streaming between spectral and amplitude modulation domains.

    PubMed

    Yamagishi, Shimpei; Otsuka, Sho; Furukawa, Shigeto; Kashino, Makio

    2017-03-18

    The two-tone sequence (ABA_), which comprises two different sounds (A and B) and a silent gap, has been used to investigate how the auditory system organizes sequential sounds depending on various stimulus conditions or brain states. Auditory streaming can be evoked by differences not only in the tone frequency ("spectral cue": ΔFTONE, TONE condition) but also in the amplitude modulation rate ("AM cue": ΔFAM, AM condition). The aim of the present study was to explore the relationship between the perceptual properties of auditory streaming for the TONE and AM conditions. A sequence with a long duration (400 repetitions of ABA_) was used to examine the property of the bistability of streaming. The ratio of feature differences that evoked an equivalent probability of the segregated percept was close to the ratio of the Q-values of the auditory and modulation filters, consistent with a "channeling theory" of auditory streaming. On the other hand, for values of ΔFAM and ΔFTONE evoking equal probabilities of the segregated percept, the number of perceptual switches was larger for the TONE condition than for the AM condition, indicating that the mechanism(s) that determine the bistability of auditory streaming are different between or sensitive to the two domains. Nevertheless, the number of switches for individual listeners was positively correlated between the spectral and AM domains. The results suggest a possibility that the neural substrates for spectral and AM processes share a common switching mechanism but differ in location and/or in the properties of neural activity or the strength of internal noise at each level.

  16. Timbral Sharpness and Modulations in Frequency and Amplitude: Implications for the Fusion of Musical Sounds.

    NASA Astrophysics Data System (ADS)

    Goad, Pamela Joy

    The fusion of musical voices is an important aspect of musical blend, or the mixing of individual sounds. Yet, little research has been done to explicitly determine the factors involved in fusion. In this study, the similarity of timbre and modulation were examined for their contribution to the fusion of sounds. It is hypothesized that similar timbres will fuse better than dissimilar timbres, and, voices with the same kind of modulation will fuse better than voices of different modulations. A perceptually-based measure, known as sharpness was investigated as a measure of timbre. The advantages of using sharpness are that it is based on hearing sensitivities and masking phenomena of inner ear processing. Five musical instrument families were digitally recorded in performances across a typical playing range at two extreme dynamic levels. Analyses reveal that sharpness is capable of uncovering subtle changes in timbre including those found in musical dynamics, instrument design, and performer-specific variations. While these analyses alone are insufficient to address fusion, preliminary calculations of timbral combinations indicate that sharpness has the potential to predict the fusion of sounds used in musical composition. Three experiments investigated the effects of modulation on the fusion of a harmonic major sixth interval. In the first experiment using frequency modulation, stimuli varied in deviation about a mean fundamental frequency and relative modulation phase between the two tones. Results showed smaller frequency deviations promoted fusion and relative phase differences had a minimal effect. In a second experiment using amplitude modulation, stimuli varied in deviation about a mean amplitude level and relative phase of modulation. Results showed smaller amplitude deviations promoted better fusion, but unlike frequency modulation, relative phase differences were also important. In a third experiment, frequency modulation, amplitude modulation and mixed

  17. Tip-surface forces, amplitude, and energy dissipation in amplitude-modulation (tapping mode) force microscopy

    NASA Astrophysics Data System (ADS)

    Paulo, Álvaro San; García, Ricardo

    2001-11-01

    Amplitude-modulation (tapping mode) atomic force microscopy is a technique for high resolution imaging of a wide variety of surfaces in air and liquid environments. Here by using the virial theorem and energy conservation principles we have derived analytical relationships between the oscillation amplitude, phase shift, and average tip-surface forces. We find that the average value of the interaction force and oscillation and the average power dissipated by the tip-surface interaction are the quantities that control the amplitude reduction. The agreement obtained between analytical and numerical results supports the analytical method.

  18. Scaling the perceived fluctuation strength of frequency-modulated tones

    NASA Astrophysics Data System (ADS)

    Wickelmaier, Florian; Ellermeier, Wolfgang

    2004-05-01

    Fluctuation strength is one of the major psychoacoustic variables considered in sound-quality evaluation. Zwicker and Fastl [Psychoacoustics (Springer, Berlin, 1999)] summarize recommendations for its computation, which have already been implemented in various software applications, even though the data basis is rather limited. In particular, the dependency of fluctuation strength on modulation frequency and modulation depth has seemingly never been tested in a factorial design. Therefore, in experiment I both of these factors were varied simultaneously in order to create 54 different frequency-modulated sinusoids. The task of the subjects was to directly estimate the perceived magnitude of fluctuation strength. The results do not conform well with the prevalent model of fluctuation strength. In experiment II this finding was further investigated by varying only one factor at a time. The results show that large individual differences, particularly in the effect of modulation frequency, persist. Thus, in experiment III the interaction of both factors was analyzed on an individual basis. By employing a 2AFC procedure, matches in fluctuation strength were obtained. The results suggest that most listeners are not able to integrate modulation frequency and modulation depth additively into a unidimensional percept. [Work supported by Centercontract on Sound Quality, Aalborg University.

  19. Cholinergic Modulation of the Hippocampus during Encoding and Retrieval of Tone/Shock-Induced Fear Conditioning

    ERIC Educational Resources Information Center

    Rogers, Jason L.; Kesner, Raymond P.

    2004-01-01

    We investigated the role of acetylcholine (ACh) during encoding and retrieval of tone/shock-induced fear conditioning with the aim of testing Hasselmo's cholinergic modulation model of encoding and retrieval using a task sensitive to hippocampal disruption. Lesions of the hippocampus impair acquisition and retention of contextual conditioning with…

  20. Discriminating Simulated Vocal Tremor Source Using Amplitude Modulation Spectra

    PubMed Central

    Carbonell, Kathy M.; Lester, Rosemary A.; Story, Brad H.; Lotto, Andrew J.

    2014-01-01

    Objectives/Hypothesis Sources of vocal tremor are difficult to categorize perceptually and acoustically. This paper describes a preliminary attempt to discriminate vocal tremor sources through the use of spectral measures of the amplitude envelope. The hypothesis is that different vocal tremor sources are associated with distinct patterns of acoustic amplitude modulations. Study Design Statistical categorization methods (discriminant function analysis) were used to discriminate signals from simulated vocal tremor with different sources using only acoustic measures derived from the amplitude envelopes. Methods Simulations of vocal tremor were created by modulating parameters of a vocal fold model corresponding to oscillations of respiratory driving pressure (respiratory tremor), degree of vocal fold adduction (adductory tremor) and fundamental frequency of vocal fold vibration (F0 tremor). The acoustic measures were based on spectral analyses of the amplitude envelope computed across the entire signal and within select frequency bands. Results The signals could be categorized (with accuracy well above chance) in terms of the simulated tremor source using only measures of the amplitude envelope spectrum even when multiple sources of tremor were included. Conclusions These results supply initial support for an amplitude-envelope based approach to identify the source of vocal tremor and provide further evidence for the rich information about talker characteristics present in the temporal structure of the amplitude envelope. PMID:25532813

  1. Amplitude-Modulated Bursting: A Novel Class of Bursting Rhythms

    NASA Astrophysics Data System (ADS)

    Vo, Theodore; Kramer, Mark A.; Kaper, Tasso J.

    2016-12-01

    We report on the discovery of a novel class of bursting rhythms, called amplitude-modulated bursting (AMB), in a model for intracellular calcium dynamics. We find that these rhythms are robust and exist on open parameter sets. We develop a new mathematical framework with broad applicability to detect, classify, and rigorously analyze AMB. Here we illustrate this framework in the context of AMB in a model of intracellular calcium dynamics. In the process, we discover a novel family of singularities, called toral folded singularities, which are the organizing centers for the amplitude modulation and exist generically in slow-fast systems with two or more slow variables.

  2. Damage detection and locating using tone burst and continuous excitation modulation method

    NASA Astrophysics Data System (ADS)

    Li, Zheng; Wang, Zhi; Xiao, Li; Qu, Wenzhong

    2014-03-01

    Among structural health monitoring techniques, nonlinear ultrasonic spectroscopy methods are found to be effective diagnostic approach to detecting nonlinear damage such as fatigue crack, due to their sensitivity to incipient structural changes. In this paper, a nonlinear ultrasonic modulation method was developed to detect and locate a fatigue crack on an aluminum plate. The method is different with nonlinear wave modulation method which recognizes the modulation of low-frequency vibration and high-frequency ultrasonic wave; it recognizes the modulation of tone burst and high-frequency ultrasonic wave. In the experiment, a Hanning window modulated sinusoidal tone burst and a continuous sinusoidal excitation were simultaneously imposed on the PZT array which was bonded on the surface of an aluminum plate. The modulations of tone burst and continuous sinusoidal excitation was observed in different actuator-sensor paths, indicating the presence and location of fatigue crack. The results of experiments show that the proposed method is capable of detecting and locating the fatigue crack successfully.

  3. Self-demodulation of amplitude-modulated signal components in amplitude-modulated bone-conducted ultrasonic hearing

    NASA Astrophysics Data System (ADS)

    Ito, Kazuhito; Nakagawa, Seiji

    2015-07-01

    A novel hearing aid system utilizing amplitude-modulated bone-conducted ultrasound (AM-BCU) is being developed for use by profoundly deaf people. However, there is a lack of research on the acoustic aspects of AM-BCU hearing. In this study, acoustic fields in the ear canal under AM-BCU stimulation were examined with respect to the self-demodulation effect of amplitude-modulated signal components generated in the ear canal. We found self-demodulated signals with an audible sound pressure level related to the amplitude-modulated signal components of bone-conducted ultrasonic stimulation. In addition, the increases in the self-demodulated signal levels at low frequencies in the ear canal after occluding the ear canal opening, i.e., the positive occlusion effect, indicate the existence of a pathway by which the self-demodulated signals pass through the aural cartilage and soft tissue, and radiate into the ear canal.

  4. The effect of amplitude modulation on subharmonic imaging with chirp excitation.

    PubMed

    Harput, Sevan; Arif, Muhammad; McLaughlan, James; Cowell, David M J; Freear, Steven

    2013-12-01

    Subharmonic generation from ultrasound contrast agents depends on the spectral and temporal properties of the excitation signal. The subharmonic response can be improved by using wideband and long-duration signals. However, for sinusoidal tone-burst excitation, the effective bandwidth of the signal is inversely proportional to the signal duration. Linear frequency-modulated (LFM) and nonlinear frequency-modulated (NLFM) chirp excitations allow independent control over the signal bandwidth and duration; therefore, in this study LFM and NLFM signals were used for the insonation of microbubble populations. The amplitude modulation of the excitation waveform was achieved by applying different window functions. A customized window was designed for the NLFM chirp excitation by focusing on reducing the spectral leakage at the subharmonic frequency and increasing the subharmonic generation from microbubbles. Subharmonic scattering from a microbubble population was measured for various excitation signals and window functions. At a peak negative pressure of 600 kPa, the generated subharmonic energy by ultrasound contrast agents was 15.4 dB more for NLFM chirp excitation with 40% fractional bandwidth when compared with tone-burst excitation. For this reason, the NLFM chirp with a customized window was used as an excitation signal to perform subharmonic imaging in an ultrasound flow phantom. Results showed that the NLFM waveform with a customized window improved the subharmonic contrast by 4.35 ± 0.42 dB on average over a Hann-windowed LFM excitation.

  5. Contextual Modulation of N400 Amplitude to Lexically Ambiguous Words

    ERIC Educational Resources Information Center

    Titone, Debra A.; Salisbury, Dean F.

    2004-01-01

    Through much is known about the N400 component, an event-related EEG potential that is sensitive to semantic manipulations, it is unclear whether modulations of N400 amplitude reflect automatic processing, controlled processing, or both. We examined this issue using a semantic judgment task that manipulated local and global contextual cues. Word…

  6. Superposed pulse amplitude modulation for visible light communication.

    PubMed

    Li, J F; Huang, Z T; Zhang, R Q; Zeng, F X; Jiang, M; Ji, Y F

    2013-12-16

    We propose and experimentally demonstrate a novel modulation scheme called superposed pulse amplitude modulation (SPAM) which is low-cost, insensitive to non-linearity of light emitting diode (LED). Multiple optical pulses transmit parallelly from different spatial position in the LED array and overlap linearly in free space to realize SPAM. With LED arrangement, the experimental results show that using the modulation we proposed the data rate of 120 Mbit/s with BER 1 × 10(-3) can be achieved with an optical blue filter and RC post-equalization.

  7. Unpredicted Pitch Modulates Beta Oscillatory Power during Rhythmic Entrainment to a Tone Sequence

    PubMed Central

    Chang, Andrew; Bosnyak, Dan J.; Trainor, Laurel J.

    2016-01-01

    Extracting temporal regularities in external stimuli in order to predict upcoming events is an essential aspect of perception. Fluctuations in induced power of beta band (15–25 Hz) oscillations in auditory cortex are involved in predictive timing during rhythmic entrainment, but whether such fluctuations are affected by prediction in the spectral (frequency/pitch) domain remains unclear. We tested whether unpredicted (i.e., unexpected) pitches in a rhythmic tone sequence modulate beta band activity by recording EEG while participants passively listened to isochronous auditory oddball sequences with occasional unpredicted deviant pitches at two different presentation rates. The results showed that the power in low-beta (15–20 Hz) was larger around 200–300 ms following deviant tones compared to standard tones, and this effect was larger when the deviant tones were less predicted. Our results suggest that the induced beta power activities in auditory cortex are consistent with a role in sensory prediction of both “when” (timing) upcoming sounds will occur as well as the prediction precision error of “what” (spectral content in this case). We suggest, further, that both timing and content predictions may co-modulate beta oscillations via attention. These findings extend earlier work on neural oscillations by investigating the functional significance of beta oscillations for sensory prediction. The findings help elucidate the functional significance of beta oscillations in perception. PMID:27014138

  8. 3D dynamic holographic display by modulating complex amplitude experimentally.

    PubMed

    Li, Xin; Liu, Juan; Jia, Jia; Pan, Yijie; Wang, Yongtian

    2013-09-09

    Complex amplitude modulation method is presented theoretically and performed experimentally for three-dimensional (3D) dynamic holographic display with reduced speckle using a single phase-only spatial light modulator. The determination of essential factors is discussed based on the basic principle and theory. The numerical simulations and optical experiments are performed, where the static and animated objects without refinement on the surfaces and without random initial phases are reconstructed successfully. The results indicate that this method can reduce the speckle in reconstructed images effectively; furthermore, it will not cause the internal structure in the reconstructed pixels. Since the complex amplitude modulation is based on the principle of phase-only hologram, it does not need the stringent alignment of pixels. This method can be used for high resolution imaging or measurement in various optical areas.

  9. Detection and rate discrimination of amplitude modulation in electrical hearing.

    PubMed

    Chatterjee, Monita; Oberzut, Cherish

    2011-09-01

    Three experiments were designed to examine temporal envelope processing by cochlear implant (CI) listeners. In experiment 1, the hypothesis that listeners' modulation sensitivity would in part determine their ability to discriminate between temporal modulation rates was examined. Temporal modulation transfer functions (TMTFs) obtained in an amplitude modulation detection (AMD) task were compared to threshold functions obtained in an amplitude modulation rate discrimination (AMRD) task. Statistically significant nonlinear correlations were observed between the two measures. In experiment 2, results of loudness-balancing showed small increases in the loudness of modulated over unmodulated stimuli beyond a modulation depth of 16%. Results of experiment 3 indicated small but statistically significant effects of level-roving on the overall gain of the TMTF, but no impact of level-roving on the average shape of the TMTF across subjects. This suggested that level-roving simply increased the task difficulty for most listeners, but did not indicate increased use of intensity cues under more challenging conditions. Data obtained with one subject, however, suggested that the most sensitive listeners may derive some benefit from intensity cues in these tasks. Overall, results indicated that intensity cues did not play an important role in temporal envelope processing by the average CI listener.

  10. Response of plasmonic terahertz detectors to amplitude modulated signals

    NASA Astrophysics Data System (ADS)

    Rupper, Greg; Rudin, Sergey; Shur, Michael

    2015-09-01

    We present theoretical study of the response of two-dimensional gated electron gas to an amplitude modulated signals with carrier frequency in the terahertz range. The model is based on complete hydrodynamic equations, and includes effects of viscosity, pressure gradients and thermal transport in the conduction channel of a high electron mobility semiconductor transistor (HEMT). The modulation response was evaluated as a function of modulation frequency fM for a wide range of mobility values. Maximum modulation frequency fMAX was evaluated as a function of channel mobility, with typical values of fMAX in the subterahertz range of frequencies. Our analysis shows that short channel field effect transistors operating in the plasmonic regime can meet all the requirements for applications as terahertz detectors and modulators in ultra high-speed wireless communication circuits.

  11. Two-tone frequency modulation spectroscopy from laser light scattered off a hard target.

    PubMed

    Powers, P E; Taatjes, C A; Kulp, T J

    1996-08-20

    One can apply two-tone frequency modulation spectroscopy techniques to the detection of gas-phase species by using laser light scattered from hard targets. High sensitivities are demonstrated, with a minimum detectable absorption of 10(-4) possible with a simple apparatus. The effects of laser speckle on the FM signal are described, and we show that the detection signal-to-noise ratio can be improved by collecting an increased number of speckle cells.

  12. Discrimination and Identification of Modulation-Frequency Using Noise, Tone, and Tonal-Complex Carriers

    DTIC Science & Technology

    1988-05-23

    choice discrimination task (2I- 2AFC ) and an identifi- cation task were used to measure listeners’ abilities to resolve modulation frequency using three...different types of carrier—noise, a 1-kHz tone, or a tonal complex. Identification performance was not simply related to 2I- 2AFC discrimination...LABORATORY ii ABSTRACT A two-interval, two-alternative, forced-choice discrimination task (2I- 2AFC ) and an identification task were used to measure

  13. Differential pulse amplitude modulation for multiple-input single-output OWVLC

    NASA Astrophysics Data System (ADS)

    Yang, S. H.; Kwon, D. H.; Kim, S. J.; Son, Y. H.; Han, S. K.

    2015-01-01

    White light-emitting diodes (LEDs) are widely used for lighting due to their energy efficiency, eco-friendly, and small size than previously light sources such as incandescent, fluorescent bulbs and so on. Optical wireless visible light communication (OWVLC) based on LED merges lighting and communications in applications such as indoor lighting, traffic signals, vehicles, and underwater communications because LED can be easily modulated. However, physical bandwidth of LED is limited about several MHz by slow time constant of the phosphor and characteristics of device. Therefore, using the simplest modulation format which is non-return-zero on-off-keying (NRZ-OOK), the data rate reaches only to dozens Mbit/s. Thus, to improve the transmission capacity, optical filtering and pre-, post-equalizer are adapted. Also, high-speed wireless connectivity is implemented using spectrally efficient modulation methods: orthogonal frequency division multiplexing (OFDM) or discrete multi-tone (DMT). However, these modulation methods need additional digital signal processing such as FFT and IFFT, thus complexity of transmitter and receiver is increasing. To reduce the complexity of transmitter and receiver, we proposed a novel modulation scheme which is named differential pulse amplitude modulation. The proposed modulation scheme transmits different NRZ-OOK signals with same amplitude and unit time delay using each LED chip, respectively. The `N' parallel signals from LEDs are overlapped and directly detected at optical receiver. Received signal is demodulated by power difference between unit time slots. The proposed scheme can overcome the bandwidth limitation of LEDs and data rate can be improved according to number of LEDs without complex digital signal processing.

  14. Residual amplitude modulation mechanisms in modulation transfer spectroscopy that use electro-optic modulators

    NASA Astrophysics Data System (ADS)

    Jaatinen, Esa; Hopper, David J.; Back, Julian

    2009-02-01

    Three independent mechanisms are described that contaminate the phase-modulated pump beam of an optical frequency reference stabilized by modulation transfer spectroscopy (MTS) with residual amplitude modulation (RAM). The electro-optic modulator, the beam geometry and the absorption of the saturated medium all separately generate undesired RAM that degrades the accuracy of the optical frequency reference. An analysis is presented that shows how frequency shifts introduced by the different mechanisms can be evaluated in typical MTS set-ups and minimized. The analysis also shows how the detector phase can be used to measure the total RAM in the system and how the phase required to remove any remaining frequency offsets can be evaluated.

  15. Multiplexing technique using amplitude-modulated chirped fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Wong, Allan C. L.; Childs, Paul A.; Peng, Gang-Ding

    2007-07-01

    We propose a new multiplexing technique using amplitude-modulated chirped fiber Bragg gratings that have an identical center Bragg wavelength. Each grating is inscribed with a unique amplitude modulation that allows them to be multiplexed with complete overlapping within a certain bandwidth. To demodulate the multiplexed signal, the discrete wavelet transform is employed. Concurrently, a wavelet denoising technique is used to reduce the noise. This proposed multiplexing technique has been verified through strain measurements. Experimental results showed that for strains applied up to 1250 μɛ the absolute error and cross-talk are within ±20 μɛ and 16 μɛ, respectively. A strain resolution of 4 μɛ is obtained.

  16. Symbol rate identification for auxiliary amplitude modulation optical signal

    NASA Astrophysics Data System (ADS)

    Wei, Junyu; Dong, Zhi; Huang, Zhiping; Zhang, Yimeng

    2016-09-01

    In this paper, we creatively propose and demonstrate a method for symbol rate identification (SRI) of auxiliary amplitude modulation (AAM) optical signal based on asynchronous delay-tap sampling (ADTS) and average magnitude difference function (AMDF). The method can accurately estimate symbol rate and has large transmission impairments tolerance. Furthermore, it can be realized in the digital signal processor (DSP) with low logical resources because of multiplication-free. In order to improve the accuracy of SRI, the peak to valley ratio (PTVR) of AMDF is introduced into our method for blind chromatic dispersion (CD) compensation. The results of the numerical simulations show that the overall maximum SRI error is smaller 0.079% for return-to-zero (RZ) on-off keying (OOK), RZ differential phase-shift keying (DPSK), RZ differential quadrature phase-shift keying (DQPSK) and RZ 16-ary quadrature amplitude modulation (QAM) with 50% duty cycles.

  17. Observer weighting of interaural cues in positive and negative envelope slopes of amplitude-modulated waveforms

    PubMed Central

    Hsieh, I-Hui; Petrosyan, Agavni; Gonçalves, Óscar F.; Hickok, Gregory; Saberi, Kourosh

    2011-01-01

    The auditory system can encode interaural delays in highpass-filtered complex sounds by phase locking to their slowly modulating envelopes. Spectrotemporal analysis of interaurally time delayed highpass waveforms reveals the presence of a concomitant interaural level cue. The current study systematically investigated the contribution of time and concomitant level cues carried by positive and negative envelope slopes of a modified sinusoidally amplitude-modulated (SAM) high-frequency carrier. The waveforms were generated from concatenation of individual modulation cycles whose envelope peaks were extended by the desired interaural delay, allowing independent control of delays in the positive and negative modulation slopes. In experiment 1, thresholds were measured using a 2-interval forced-choice adaptive task for interaural delays in either the positive or negative modulation slopes. In a control condition, thresholds were measured for a standard SAM tone. In experiment 2, decision weights were estimated using a multiple-observation correlational method in a single-interval forced-choice task for interaural delays carried simultaneously by the positive, and independently, negative slopes of the modulation envelope. In experiment 3, decision weights were measured for groups of 3 modulation cycles at the start, middle, and end of the waveform to determine the influence of onset dominance or recency effects. Results were consistent across experiments: Thresholds were equal for the positive and negative modulation slopes. Decision weights were positive and equal for the time cue in the positive and negative envelope slopes. Weights were also larger for modulations cycles near the waveform onset. Weights estimated for the concomitant interaural level cue were positive for the positive envelope slope and negative for the negative slope, consistent with exclusive use of time cues. PMID:21272630

  18. Amplitude-modulation chirp imaging for contrast detection.

    PubMed

    Li, Meng-Lin; Kuo, Yu-Chen; Yeh, Chih-Kuang

    2010-09-01

    We propose an amplitude-modulation chirp imaging method for contrast detection with high-frequency ultrasound. Our proposed method detects microbubbles by extracting and then selectively compressing the component of the backscattered chirp signal modulated by changes in the radii of microbubbles at their resonance frequency. Microbubbles are sonicated simultaneously with a narrowband, low-frequency pumping signal at their resonance frequency and a wideband, high-frequency imaging chirp signal. Changes in the radii of the resonant microbubbles result in periodic changes in their acoustic cross section that modulate the amplitude of the backscattered imaging chirp signal, forming pumping and imaging frequency sum-and-difference chirp terms. The frequency-sum or -difference chirp component is then extracted by a bandpass filter (BPF). Because a long imaging pulse duration is required to obtain a sufficient modulation depth on the chirp for contrast detection and to facilitate frequency-sum-and-difference signal extraction with the BPF, a chirp with a longer-than-usual waveform is used so pulse compression of the extracted chirp signal can then be performed to maintain the axial resolution, and even further improve the signal-to-noise ratio and contrast-to-tissue ratio. Experiments performed on flow phantoms with and without a speckle-generating background were performed to demonstrate the efficacy of the proposed technique. These results indicate that our proposed method can potentially provide high-resolution contrast detection in the microvasculature.

  19. Research of frequency modulation to amplitude modulation with multi-frequency modulation

    NASA Astrophysics Data System (ADS)

    Zhou, Yuliang; Zhan, Sui; Geng, Yuanchao; Liu, Lanqin; Xu, Lixin; Ming, Hai

    2013-12-01

    For better performance of laser coupling in inertial confinement fusion (ICF), beam shaping of the focus spot is required. Among all the beam smoothing methods, the multi frequency modulation smoothing by spectral dispersion (MultiFM-SSD) proposed by LLE has the advantages of the faster smoothing and better operability. Strong frequency modulation to amplitude modulation conversion(FM-to-AM) will take place because of the complex spectrum imposed by the multi frequency modulators applied in the Multi FM-SSD method. The FM-to-AM effect is studied with numerical simulation including the polarization mode dispersion and group velocity dispersion. The results reveal that the modulation frequencies and bandwidths of multi modulators will influence the contrast degree of the FM-to-AM effect. The compensation of the FM-to-AM with arbitrary waveform generator (AWG) is also numerically simulated. The FM-to-AM effect is effectively suppressed, i.e. the non-uniformity of the pulse decreases substantially, by applying multiple intensity and phase compensation (the compensation function is obtained via G-S algorithm).

  20. Habituation of Auditory Steady State Responses Evoked by Amplitude-Modulated Acoustic Signals in Rats

    PubMed Central

    Prado-Gutierrez, Pavel; Castro-Fariñas, Anisleidy; Morgado-Rodriguez, Lisbet; Velarde-Reyes, Ernesto; Martínez, Agustín D.; Martínez-Montes, Eduardo

    2015-01-01

    Generation of the auditory steady state responses (ASSR) is commonly explained by the linear combination of random background noise activity and the stationary response. Based on this model, the decrease of amplitude that occurs over the sequential averaging of epochs of the raw data has been exclusively linked to the cancelation of noise. Nevertheless, this behavior might also reflect the non-stationary response of the ASSR generators. We tested this hypothesis by characterizing the ASSR time course in rats with different auditory maturational stages. ASSR were evoked by 8-kHz tones of different supra-threshold intensities, modulated in amplitude at 115 Hz. Results show that the ASSR amplitude habituated to the sustained stimulation and that dishabituation occurred when deviant stimuli were presented. ASSR habituation increased as animals became adults, suggesting that the ability to filter acoustic stimuli with no-relevant temporal information increased with age. Results are discussed in terms of the current model of the ASSR generation and analysis procedures. They might have implications for audiometric tests designed to assess hearing in subjects who cannot provide reliable results in the psychophysical trials. PMID:26557360

  1. Population transfer by an amplitude-modulated pulse

    SciTech Connect

    Vitanov, N.V.; Yatsenko, L.P.; Bergmann, K.

    2003-10-01

    We propose a technique for coherent population inversion of a two-state system, which uses an amplitude-modulated pulse. In the modulation-free adiabatic basis, the modulation introduces oscillating interaction between the adiabatic states. In a second rotating-wave approximation picture, this oscillating interaction induces a pair of level crossings between the energies of the adiabatic states if the modulation frequency is chosen appropriately. By suitably offsetting the modulation with respect to the center of the pulse, one can make the modulation act only in the vicinity of one of these crossings. In a higher-order adiabatic basis, this crossing shows up as an avoided crossing between the energies of the higher-order adiabatic states. As a result robust and efficient population transfer can be achieved between the adiabatic states, and hence, between the original bare states. We derive analytically the conditions on the interaction parameters for this technique and verify them with numerical simulations. Possible experimental implementations are discussed.

  2. Amplitude-modulated stimuli reveal auditory-visual interactions in brain activity and brain connectivity

    PubMed Central

    Laing, Mark; Rees, Adrian; Vuong, Quoc C.

    2015-01-01

    The temporal congruence between auditory and visual signals coming from the same source can be a powerful means by which the brain integrates information from different senses. To investigate how the brain uses temporal information to integrate auditory and visual information from continuous yet unfamiliar stimuli, we used amplitude-modulated tones and size-modulated shapes with which we could manipulate the temporal congruence between the sensory signals. These signals were independently modulated at a slow or a fast rate. Participants were presented with auditory-only, visual-only, or auditory-visual (AV) trials in the fMRI scanner. On AV trials, the auditory and visual signal could have the same (AV congruent) or different modulation rates (AV incongruent). Using psychophysiological interaction analyses, we found that auditory regions showed increased functional connectivity predominantly with frontal regions for AV incongruent relative to AV congruent stimuli. We further found that superior temporal regions, shown previously to integrate auditory and visual signals, showed increased connectivity with frontal and parietal regions for the same contrast. Our findings provide evidence that both activity in a network of brain regions and their connectivity are important for AV integration, and help to bridge the gap between transient and familiar AV stimuli used in previous studies. PMID:26483710

  3. Development of advanced multi-tone mask by using two different transmittance modulation materials

    NASA Astrophysics Data System (ADS)

    Kim, Sei-Min; Choi, Min-Ki; Seo, Seong-Min; Lee, Jong-Hwa; Shin, Cheol; Jeong, Woo-Gun; Jung, Sung-Mo; Nam, Kee-Soo

    2016-09-01

    Multi-tone mask (MTM) consists of more than two layers having different transmittance modulation layers. A novel method is proposed to manufacture a MTM based on two kinds of transmittance modulation materials such as chromium and molybdenum. Different modulation materials cannot be only act as etch-stopper to each other, but also they play a role as a separator between the layers consisted of MTM. Furthermore, clearly classified modulation layers contribute to define one of the targeted transmittance according to different etching process. Especially, a conventional MTM requires three mask writing processes to form three patterns whereas the proposed MTM structure makes it possible to form three patterns by using only two mask writing processes. It is found that the turnaround time of proposed MTM is remarkably decreased as value of 30% compared to that of conventional MTM. MoSi-/Cr-based tri-tone mask configuration having 37, 15, and 0% of transmittance had been demonstrated based on the optimized thin-film conditions. Optical uniformity characteristics were also carried out to evaluate the photomask performance. Consequently, the proposed MTM is not only expected to extend the variation of objective transmittance, but also it is a very promise method for achieving a high performance photo-mask by reducing its fabrication cost.

  4. Phase-shifting interferometry by wave amplitude modulation.

    PubMed

    Meneses-Fabian, Cruz; Rivera-Ortega, Uriel

    2011-07-01

    A new method for phase-shifting interferometry based on wave amplitude modulation is proposed and discussed. This proposal is based on the interference of three waves, where two waves attend as two reference waves and the other wave attends as a probe wave. Thereby, three interference terms are obtained, but because a phase difference of π/2 between the two references is kept constant, one of the three terms will be dropped, while the two remaining will be put in quadrature. Under these conditions, the resulting pattern is mathematically modeled by an interferogram of two waves, where an additional phase is given by the amplitude variations of the reference waves. In this Letter, both a theoretical model and some numerical simulations are presented.

  5. Two-tone frequency-modulation spectroscopy in off-axis cavity.

    PubMed

    Malara, P; Witinski, M F; Gagliardi, G; De Natale, P

    2013-11-15

    As opposed to a conventional optical resonator, an off-axis-aligned cavity is able to transmit without distortion radiation modulated at a frequency even far above the cavity bandpass. This allows us to implement a simple spectroscopic technique that combines the cavity path-length enhancement of integrated cavity output spectroscopy (ICOS) and the noise reduction associated with radio-frequency modulation (FM). An FM-ICOS spectrometer is demonstrated for the first time using a two-tone modulation technique. The performance is compared to the traditional ICOS by examining the acetylene absorption at 1543.77 nm. A signal-to-noise ratio improvement by a factor 3.5 is found with our proof-of-concept setup. Larger improvements are expected in a more optimized setup.

  6. Dispersion interferometer using modulation amplitudes on LHD (invited)

    SciTech Connect

    Akiyama, T. Yasuhara, R.; Kawahata, K.; Okajima, S.; Nakayama, K.

    2014-11-15

    Since a dispersion interferometer is insensitive to mechanical vibrations, a vibration compensation system is not necessary. The CO{sub 2} laser dispersion interferometer with phase modulations on the Large Helical Device utilizes the new phase extraction method which uses modulation amplitudes and can improve a disadvantage of the original dispersion interferometer: measurement errors caused by variations of detected intensities. The phase variation within ±2 × 10{sup 17} m{sup −3} is obtained without vibration compensation system. The measured line averaged electron density with the dispersion interferometer shows good agreement with that with the existing far infrared laser interferometer. Fringe jump errors in high density ranging up to 1.5 × 10{sup 20} m{sup −3} can be overcome by a sufficient sampling rate of about 100 kHz.

  7. Dispersion interferometer using modulation amplitudes on LHD (invited).

    PubMed

    Akiyama, T; Yasuhara, R; Kawahata, K; Okajima, S; Nakayama, K

    2014-11-01

    Since a dispersion interferometer is insensitive to mechanical vibrations, a vibration compensation system is not necessary. The CO2 laser dispersion interferometer with phase modulations on the Large Helical Device utilizes the new phase extraction method which uses modulation amplitudes and can improve a disadvantage of the original dispersion interferometer: measurement errors caused by variations of detected intensities. The phase variation within ±2 × 10(17) m(-3) is obtained without vibration compensation system. The measured line averaged electron density with the dispersion interferometer shows good agreement with that with the existing far infrared laser interferometer. Fringe jump errors in high density ranging up to 1.5 × 10(20) m(-3) can be overcome by a sufficient sampling rate of about 100 kHz.

  8. A role for amplitude modulation phase relationships in speech rhythm perception.

    PubMed

    Leong, Victoria; Stone, Michael A; Turner, Richard E; Goswami, Usha

    2014-07-01

    Prosodic rhythm in speech [the alternation of "Strong" (S) and "weak" (w) syllables] is cued, among others, by slow rates of amplitude modulation (AM) within the speech envelope. However, it is unclear exactly which envelope modulation rates and statistics are the most important for the rhythm percept. Here, the hypothesis that the phase relationship between "Stress" rate (∼2 Hz) and "Syllable" rate (∼4 Hz) AMs provides a perceptual cue for speech rhythm is tested. In a rhythm judgment task, adult listeners identified AM tone-vocoded nursery rhyme sentences that carried either trochaic (S-w) or iambic patterning (w-S). Manipulation of listeners' rhythm perception was attempted by parametrically phase-shifting the Stress AM and Syllable AM in the vocoder. It was expected that a 1π radian phase-shift (half a cycle) would reverse the perceived rhythm pattern (i.e., trochaic → iambic) whereas a 2π radian shift (full cycle) would retain the perceived rhythm pattern (i.e., trochaic → trochaic). The results confirmed these predictions. Listeners judgments of rhythm systematically followed Stress-Syllable AM phase-shifts, but were unaffected by phase-shifts between the Syllable AM and the Sub-beat AM (∼14 Hz) in a control condition. It is concluded that the Stress-Syllable AM phase relationship is an envelope-based modulation statistic that supports speech rhythm perception.

  9. Smart active multiwave sensing with zero background amplitude modulated probes

    SciTech Connect

    Ruggiero, A.J.; Young, R.A.; Jelsma, L.

    1994-07-01

    Recently, a new approach to multi-wavelength remote sensing has been proposed based on the generation and detection of spectral ``pickets`` synthesized from the frequency filtered bandwidth of a modelocked laser. Using linear array liquid crystal spatial light modulator (SLM) technology for spectral filtering permits real time grey scale control of individual picket amplitudes and phases, making it possible to independently modulate picket characteristics in the kHz to MHz regime. Due to the versatility of this approach, a whole suite of spectroscopies based on detection techniques that are similar to conventional sideband spectroscopies can be implemented. These techniques not only inherit the S/N advantages of their conventional counterparts, they can also be easily extended to simultaneous multi-wavelength operation using frequency multiplex techniques and configured for real time adaptive data acquisition. We report the laboratory demonstration and theoretical development of a new class of zero background AM modulated spectroscopic probes for differential absorption measurements. Preliminary detection sensitivities on the order of 10{sup {minus}6} can be inferred from our measurements. Application of this technique to realistic remote sensing scenarios, advantages over other modulation and direct detection approaches, as well as the present limitations and theoretical limits to detection sensitivity will be discussed.

  10. Amplitude modulation detection by human listeners in sound fields

    PubMed Central

    Zahorik, Pavel; Kim, Duck O.; Kuwada, Shigeyuki; Anderson, Paul W.; Brandewie, Eugene; Srinivasan, Nirmal

    2011-01-01

    The temporal modulation transfer function (TMTF) approach allows techniques from linear systems analysis to be used to predict how the auditory system will respond to arbitrary patterns of amplitude modulation (AM). Although this approach forms the basis for a standard method of predicting speech intelligibility based on estimates of the acoustical modulation transfer function (MTF) between source and receiver, human sensitivity to AM as characterized by the TMTF has not been extensively studied under realistic listening conditions, such as in reverberant sound fields. Here, TMTFs (octave bands from 2 – 512 Hz) were obtained in 3 listening conditions simulated using virtual auditory space techniques: diotic, anechoic sound field, reverberant room sound field. TMTFs were then related to acoustical MTFs estimated using two different methods in each of the listening conditions. Both diotic and anechoic data were found to be in good agreement with classic results, but AM thresholds in the reverberant room were lower than predictions based on acoustical MTFs. This result suggests that simple linear systems techniques may not be appropriate for predicting TMTFs from acoustical MTFs in reverberant sound fields, and may be suggestive of mechanisms that functionally enhance modulation during reverberant listening. PMID:22822417

  11. [The influence of amplitude modulation on the structure of call spectrum in marmots (Marmota, rodentia, sciuridae)].

    PubMed

    Nikol'skiĭ, A A

    2007-01-01

    A relationship was established between the amplitude modulation and the structure of call spectrum in animals by the example of alarm call in three marmots (Marmota sibirica, M. menzbieri, and M. caudata). In the case of amplitude modulation, side frequencies are produced higher and lower than the carrier frequencies. In the absence of amplitude modulation, no side frequencies are produced.

  12. Quadrature Amplitude Modulation Division for Multiuser MISO Broadcast Channels

    NASA Astrophysics Data System (ADS)

    Dong, Zheng; Zhang, Yan-Yu; Zhang, Jian-Kang; Gao, Xiang-Chuan

    2016-12-01

    This paper considers a discrete-time multiuser multiple-input single-output (MISO) Gaussian broadcast channel~(BC), in which channel state information (CSI) is available at both the transmitter and the receivers. The flexible and explicit design of a uniquely decomposable constellation group (UDCG) is provided based on pulse amplitude modulation (PAM) and rectangular quadrature amplitude modulation (QAM) constellations. With this, a modulation division (MD) transmission scheme is developed for the MISO BC. The proposed MD scheme enables each receiver to uniquely and efficiently detect their desired signals from the superposition of mutually interfering cochannel signals in the absence of noise. In our design, the optimal transmitter beamforming problem is solved in a closed-form for two-user MISO BC using max-min fairness as a design criterion. Then, for a general case with more than two receivers, we develop a user-grouping-based beamforming scheme, where the grouping method, beamforming vector design and power allocation problems are addressed by using weighted max-min fairness. It is shown that our proposed approach has a lower probability of error compared with the zero-forcing (ZF) method when the Hermitian angle between the two channel vectors is small in a two-user case. In addition, simulation results also reveal that for the general channel model with more than two users, our user-grouping-based scheme significantly outperforms the ZF, time division (TD), minimum mean-square error (MMSE) and signal-to-leakage-and-noise ratio (SLNR) based techniques in moderate and high SNR regimes when the number of users approaches to the number of base station (BS) antennas and it degrades into the ZF scheme when the number of users is far less than the number of BS antennas in Rayleigh fading channels.

  13. Auditory steady-state responses reveal amplitude modulation gap detection thresholds

    NASA Astrophysics Data System (ADS)

    Ross, Bernhard; Pantev, Christo

    2004-05-01

    Auditory evoked magnetic fields were recorded from the left hemisphere of healthy subjects using a 37-channel magnetometer while stimulating the right ear with 40-Hz amplitude modulated (AM) tone-bursts with 500-Hz carrier frequency in order to study the time-courses of amplitude and phase of auditory steady-state responses (ASSRs). The stimulus duration of 300 ms and the duration of the silent periods (3-300 ms) between succeeding stimuli were chosen to address the question whether the time-course of the ASSR can reflect both temporal integration and temporal resolution in the central auditory processing. Long lasting perturbations of the ASSR were found after gaps in the AM sound, even for gaps of short duration. These were interpreted as evidences for an auditory reset mechanism. Concomitant psycho-acoustical tests corroborated that gap durations perturbing the ASSR were in the same range as the threshold for AM gap detection. Magnetic source localizations estimated the ASSR sources in the primary auditory cortex, suggesting that the processing of temporal structures in the sound is performed at or below the cortical level.

  14. Inhomogeneous phase-visibility modulating interferometry by space on-off non-quadrature amplitude modulation.

    PubMed

    Rivera-Ortega, Uriel; Meneses-Fabian, Cruz; Rodriguez-Zurita, Gustavo

    2013-07-29

    A new method in interferometry based on on-off non-quadrature amplitude modulation for object phase retrieval is presented. Although the technique introduces inhomogeneous visibility and phase variations in the interferogram, it is shown that the phase retrieval of a given object is still possible. This method is implemented by using three beams and two Mach-Zehnder interferometers in series. One of the arms of the system is used as a probe beam and the other two are used as reference beams, yielding from their sum the conventional reference beam of a two-beam interferometer. We demonstrate that, if there is a phase difference within the range of (0,π) between these two beams, the effect of modulation in both amplitude and phase is generated for the case of on-off non-quadrature amplitude modulation. An analytical discussion is provided to sustain this method. Numerical and experimental results are also shown.

  15. Shuttle extravehicular activity signal processor pulse amplitude modulation decommutator

    NASA Technical Reports Server (NTRS)

    Noble, D. E.; Conrad, W. M.

    1974-01-01

    To provide data with long-term stability and accuracy, the pulse amplitude modulation (PAM) decommutator was synchronized to the PAM-return to zero wavetrain, and each channel was sampled with a common sample and hold circuit and digitized sequentially. The digital value of each channel was then scaled by the digital value of the calibration channels. The corrected digital value of each channel was stored for one complete frame and then transferred to the multiplexer-demultiplexer at a high rate in one block of serial digital data. A test model was built to demonstrate this design approach taken for the PAM decom and performance data was provided. The accuracies obtained with various signal to noise ratios are shown.

  16. Residual amplitude modulation in interferometric gravitational wave detectors.

    PubMed

    Kokeyama, Keiko; Izumi, Kiwamu; Korth, William Z; Smith-Lefebvre, Nicolas; Arai, Koji; Adhikari, Rana X

    2014-01-01

    The effects of residual amplitude modulation (RAM) in laser interferometers using heterodyne sensing can be substantial and difficult to mitigate. In this work, we analyze the effects of RAM on a complex laser interferometer used for gravitational wave detection. The RAM introduces unwanted offsets in the cavity length signals and thereby shifts the operating point of the optical cavities from the nominal point via feedback control. This shift causes variations in the sensing matrix, and leads to degradation in the performance of the precision noise subtraction scheme of the multiple-degree-of-freedom control system. In addition, such detuned optical cavities produce an optomechanical spring, which also perturbs the sensing matrix. We use our simulations to derive requirements on RAM for the Advanced LIGO (aLIGO) detectors, and show that the RAM expected in aLIGO will not limit its sensitivity.

  17. A Computational Model of Inferior Colliculus Responses to Amplitude Modulated Sounds in Young and Aged Rats

    PubMed Central

    Rabang, Cal F.; Parthasarathy, Aravindakshan; Venkataraman, Yamini; Fisher, Zachery L.; Gardner, Stephanie M.; Bartlett, Edward L.

    2012-01-01

    The inferior colliculus (IC) receives ascending excitatory and inhibitory inputs from multiple sources, but how these auditory inputs converge to generate IC spike patterns is poorly understood. Simulating patterns of in vivo spike train data from cellular and synaptic models creates a powerful framework to identify factors that contribute to changes in IC responses, such as those resulting in age-related loss of temporal processing. A conductance-based single neuron IC model was constructed, and its responses were compared to those observed during in vivo IC recordings in rats. IC spike patterns were evoked using amplitude-modulated tone or noise carriers at 20–40 dB above threshold and were classified as low-pass, band-pass, band-reject, all-pass, or complex based on their rate modulation transfer function tuning shape. Their temporal modulation transfer functions were also measured. These spike patterns provided experimental measures of rate, vector strength, and firing pattern for comparison with model outputs. Patterns of excitatory and inhibitory synaptic convergence to IC neurons were based on anatomical studies and generalized input tuning for modulation frequency. Responses of modeled ascending inputs were derived from experimental data from previous studies. Adapting and sustained IC intrinsic models were created, with adaptation created via calcium-activated potassium currents. Short-term synaptic plasticity was incorporated into the model in the form of synaptic depression, which was shown to have a substantial effect on the magnitude and time course of the IC response. The most commonly observed IC response sub-types were recreated and enabled dissociation of inherited response properties from those that were generated in IC. Furthermore, the model was used to make predictions about the consequences of reduction in inhibition for age-related loss of temporal processing due to a reduction in GABA seen anatomically with age. PMID:23129994

  18. An additional study and implementation of tone calibrated technique of modulation

    NASA Technical Reports Server (NTRS)

    Rafferty, W.; Bechtel, L. K.; Lay, N. E.

    1985-01-01

    The Tone Calibrated Technique (TCT) was shown to be theoretically free from an error floor, and is only limited, in practice, by implementation constraints. The concept of the TCT transmission scheme along with a baseband implementation of a suitable demodulator is introduced. Two techniques for the generation of the TCT signal are considered: a Manchester source encoding scheme (MTCT) and a subcarrier based technique (STCT). The results are summarized for the TCT link computer simulation. The hardware implementation of the MTCT system is addressed and the digital signal processing design considerations involved in satisfying the modulator/demodulator requirements are outlined. The program findings are discussed and future direction are suggested based on conclusions made regarding the suitability of the TCT system for the transmission channel presently under consideration.

  19. Constant RMS versus constant peak modulation for the perceptual equivalence of sinusoidal amplitude modulated signals.

    PubMed

    Regele, Oliver B; Koivuniemi, Andrew S; Otto, Kevin J

    2013-01-01

    Neuroprosthetics using intracortical microstimulation can potentially alleviate sensory deprivation due to injury or disease. However the information bandwidth of a single microstimulation channel remains largely unanswered. This paper presents three experiments that examine the importance of Peak Power/Charge and RMS Power/Charge for detection of acoustic and electrical Sinusoidal Amplitude Modulated stimuli by the auditory system. While the peripheral auditory system is sensitive to RMS power cues for the detection of acoustic stimuli, here we provide results that suggest that the auditory cortex is sensitive to peak charge cues for electrical stimuli. Varying the modulation frequency and depth do not change this effect for detection of modulated electrical stimuli.

  20. Phase-inversion-based selective harmonic elimination (PI-SHE) in multi-level switched-mode tone- and frequency-modulated excitation.

    PubMed

    Cowell, David M J; Smith, Peter R; Freear, Steven

    2013-06-01

    Switched-mode operation allows the miniaturization of excitation circuitry but suffers from high harmonic distortion. This paper presents a method of phase-inversion-based selective harmonic elimination (PI-SHE) and the use of multiple switching levels. PI-SHE is shown to enable multiples of any selected harmonic to be eliminated through controlled timing of the transition between different excitation voltage levels. Multiples of the third harmonic are shown to be eliminated in three-level tone waveforms. In addition, multiples of the fifth harmonic are shown to be eliminated using five-level tone waveforms. A method of calculating the expected amplitude of each harmonic is presented. The application of PI-SHE in linear frequency-modulated (LFM) excitation is proposed. A heuristic derivation of the spectral properties of multilevel switched LFM waveforms is presented. The performance of the proposed PI-SHE method is confirmed through experimental measurement of the harmonics present in an ultrasound wave using two, three, and five levels for both tone and LFM excitation. The proposed method of controlling harmonics through the use of multilevel switched excitation is especially suitable for applications in which portability, high channel counts, and precise harmonic control are required.

  1. Characteristics of complex light modulation through an amplitude-phase double-layer spatial light modulator.

    PubMed

    Park, Sungjae; Roh, Jinyoung; Kim, Soobin; Park, Juseong; Kang, Hoon; Hahn, Joonku; Jeon, Youngjin; Park, Shinwoong; Kim, Hwi

    2017-02-20

    The complex modulation characteristics of a light field through an amplitude-phase double-layer spatial light modulator are analyzed based on the wave-optic numerical model, and the structural conditions for the optimal double-layer complex modulation structure are investigated. The relationships of interlayer distance, pixel size, and complex light modulation performance are analyzed. The main finding of this study is that the optimal interlayer distance for the double-layer structure can be found at the Talbot effect condition. For validating the practical usefulness of our findings, a high quality reconstruction of the complex computer-generated holograms and the robustness of the angular tolerance of the complex modulation at the Talbot interlayer distance are numerically demonstrated.

  2. Modifications and lithography on iridovirus surface using amplitude modulated nanolithography

    NASA Astrophysics Data System (ADS)

    Lyuksyutov, Sergei; Paramonov, Pavel; Mayevska, Olga; Umemura, Kazuo; Vaia, Richard; Juhl, Shane; Waterhouse, Lynn

    2004-04-01

    The usage of electrostatic force on nanoscale proved to be very effective for pattering nanostructures in 20-30-nm thin polymer films using biased atomic force microscope tip (AFM) [1,2]. Similar approach can be applied to biological objects of several hundred nanometers size deposited on a smooth conductive substrate. This study demonstrates the first attempt modifying an iridovirus surface using amplitude-modulated nanolithography (AF-AFMEN) [2]. With this technique we mark an individual virus capsule by applying -10-30 V to an AFM conductive tip tapping the virus. The marks on the virus surface represent raises of 1-5 nm height. Similar to polymer molecules, the dense layer of iridovirus was subjected to AF-AFMEN technique producing distinct nanostructures (10-50 nm wide) formed of virus electrostatically attracted to the tip. Several physical reasons responsible for the virus manipulation and marking will be discussed. 1. S.F. Lyuksyutov, R.A. Vaia, P.B. Paramonov, S. Juhl, L. Waterhouse, R.M. Ralich, G. Sigalov, and E. Sancaktar, Nature Materials 2, 468 (2003) 2. S.F. Lyuksyutov, R.A. Vaia, P.B. Paramonov, and S. Juhl, Appl. Phys. Lett. 83, 4405 (2003)

  3. High-speed multilevel phase/amplitude spatial light modulator advances

    NASA Astrophysics Data System (ADS)

    Bauchert, Kipp A.; Serati, Steven A.

    1999-03-01

    Recent and near-term advancements in our multi-level (analog) phase/amplitude liquid crystal spatial light modulators will be presented. These advancements include higher resolution, smaller pixel pitch, planarized pixel pads, and higher speed modulation for phase-only, amplitude-only, and phase- amplitude-coupled modulation. These devices have applications in optical processing, optical storage, holographic display, and beam steering. Design criteria and experimental data will be presented.

  4. Auditory stream segregation using amplitude modulated bandpass noise

    PubMed Central

    Nie, Yingjiu; Nelson, Peggy B.

    2015-01-01

    The purpose of this study was to investigate the roles of spectral overlap and amplitude modulation (AM) rate for stream segregation for noise signals, as well as to test the build-up effect based on these two cues. Segregation ability was evaluated using an objective paradigm with listeners' attention focused on stream segregation. Stimulus sequences consisted of two interleaved sets of bandpass noise bursts (A and B bursts). The A and B bursts differed in spectrum, AM-rate, or both. The amount of the difference between the two sets of noise bursts was varied. Long and short sequences were studied to investigate the build-up effect for segregation based on spectral and AM-rate differences. Results showed the following: (1). Stream segregation ability increased with greater spectral separation. (2). Larger AM-rate separations were associated with stronger segregation abilities. (3). Spectral separation was found to elicit the build-up effect for the range of spectral differences assessed in the current study. (4). AM-rate separation interacted with spectral separation suggesting an additive effect of spectral separation and AM-rate separation on segregation build-up. The findings suggest that, when normal-hearing listeners direct their attention towards segregation, they are able to segregate auditory streams based on reduced spectral contrast cues that vary by the amount of spectral overlap. Further, regardless of the spectral separation they are able to use AM-rate difference as a secondary/weaker cue. Based on the spectral differences, listeners can segregate auditory streams better as the listening duration is prolonged—i.e., sparse spectral cues elicit build-up segregation; however, AM-rate differences only appear to elicit build-up when in combination with spectral difference cues. PMID:26300831

  5. ERP responses to processing prosodic phrasing of sentences in amplitude modulated noise.

    PubMed

    Carroll, Rebecca; Ruigendijk, Esther

    2016-02-01

    Intonation phrase boundaries (IPBs) were hypothesized to be especially difficult to process in the presence of an amplitude modulated noise masker because of a potential rhythmic competition. In an event-related potential study, IPBs were presented in silence, stationary, and amplitude modulated noise. We elicited centro-parietal Closure Positive Shifts (CPS) in 23 young adults with normal hearing at IPBs in all acoustic conditions, albeit with some differences. CPS peak amplitudes were highest in stationary noise, followed by modulated noise, and lowest in silence. Both noise types elicited CPS delays, slightly more so in stationary compared to amplitude modulated noise. These data suggest that amplitude modulation is not tantamount to a rhythmic competitor for prosodic phrasing but rather supports an assumed speech perception benefit due to local release from masking. The duration of CPS time windows was, however, not only longer in noise compared to silence, but also longer for amplitude modulated compared to stationary noise. This is interpreted as support for additional processing load associated with amplitude modulation for the CPS component. Taken together, processing prosodic phrasing of sentences in amplitude modulated noise seems to involve the same issues that have been observed for the perception and processing of segmental information that are related to lexical items presented in noise: a benefit from local release from masking, even for prosodic cues, and a detrimental additional processing load that is associated with either stream segregation or signal reconstruction.

  6. Unilateral Auditory Cortex Lesions Impair or Improve Discrimination Learning of Amplitude Modulated Sounds, Depending on Lesion Side

    PubMed Central

    Schulze, Holger; Deutscher, Anke; Tziridis, Konstantin; Scheich, Henning

    2014-01-01

    A fundamental principle of brain organization is bilateral symmetry of structures and functions. For spatial sensory and motor information processing, this organization is generally plausible subserving orientation and coordination of a bilaterally symmetric body. However, breaking of the symmetry principle is often seen for functions that depend on convergent information processing and lateralized output control, e.g. left hemispheric dominance for the linguistic speech system. Conversely, a subtle splitting of functions into hemispheres may occur if peripheral information from symmetric sense organs is partly redundant, e.g. auditory pattern recognition, and therefore allows central conceptualizations of complex stimuli from different feature viewpoints, as demonstrated e.g. for hemispheric analysis of frequency modulations in auditory cortex (AC) of mammals including humans. Here we demonstrate that discrimination learning of rapidly but not of slowly amplitude modulated tones is non-uniformly distributed across both hemispheres: While unilateral ablation of left AC in gerbils leads to impairment of normal discrimination learning of rapid amplitude modulations, right side ablations lead to improvement over normal learning. These results point to a rivalry interaction between both ACs in the intact brain where the right side competes with and weakens learning capability maximally attainable by the dominant left side alone. PMID:24466338

  7. Modulating Tone to Promote Motor Development Using a Neurofacilitation of Developmental Reaction (NFDR) Approach in Children with Neurodevelopmental Delay

    PubMed Central

    Batra, Vijay; Batra, Meenakshi; Pandey, Ravindra Mohan; Sharma, Vijai Prakash; Agarwal, Girdhar Gopal

    2015-01-01

    Objective To compare the efficacy of a Neurofacilitation of Developmental Reaction (NFDR) approach with that of a Conventional approach in the modulation of tone in children with neurodevelopmental delay. Methods Experimental control design. A total of 30 spastic children ranging in age from 4 to 7 years with neurodevelopmental delay were included. Baseline evaluations of muscle tone and gross motor functional performance abilities were performed. The children were allocated into two intervention groups of 15 subjects each. In groups A and B, the NFDR and conventional approaches were applied, respectively, for 3 months and were followed by subsequent re-evaluations. Results Between group analyses were performed using independent t test for tone and primitive reflex intensity and a Mann-Whitney U test for gross motor functional ability. For the within-group analyses, paired t tests were used for tone and primitive reflex intensity, and a Wilcoxon signed-rank test was used for gross motor functional ability. Conclusion The NFDR approach/technique prepares the muscle to undergo tonal modulation and thereby enhances motor development and improves the motor functional performance abilities of the children with neurodevelopmental delay. PMID:28239268

  8. Spectral broadening and inhibition of amplitude and frequency modulation in Nd: glass regenerative amplifier

    NASA Astrophysics Data System (ADS)

    Zhang, Yuqi; Pan, Xue; Wang, Jiangfeng; Li, Xuechun

    2014-11-01

    In order to broaden the spectrum of laser pulse and reduce the gain narrowing effect in Nd:glass regenerative amplifier to realize the ambition of inhibiting amplitude and frequency modulation, proper quartz birefringence crystal plate is inserted into the cavity. The influence factors of central wavelength, depth of modulation and range of modulation are obtained theoretically. The width of the spectrum is broadened by controlling all the factors. Two kinds of thickness, 5mm and 6mm, are inserted into the regenerative amplifier cavity. The results of theoretical calculation and experiment both show that the effect of spectrum widening is evident, which reduces the gain narrowing effect to some extent. The amplitude and frequency modulation resulted from gain narrowing effect is inhibited when the central wavelength deflects. The simulated results show that inhibited effect of amplitude and frequency modulation is remarkable. And the method is a potential effective technique for amplitude and frequency modulation inhibition.

  9. Calibration-free wavelength modulation spectroscopy: symmetry approach and residual amplitude modulation normalization.

    PubMed

    Behera, Amiya; Wang, Anbo

    2016-06-01

    This paper offers a simple, practical strategy to implement wavelength modulation spectroscopy (WMS) with a tunable diode laser. It eliminates the need to pre-characterize the laser intensity parameters or make any design changes to a conventional WMS system. Consequently, sensitivity and signal strength remain the same as what can be obtained from a traditional WMS setup at low modulation amplitude. Like previously proposed calibration-free approaches, this new method also yields an absolute absorption line shape function. To recover residual amplitude modulation (RAM) contributions present in the first and second harmonic signals of WMS, we exploited their even or odd symmetric nature. We then used these isolated RAM signals to estimate the absolute line shape function, thus removing the impact of optical intensity fluctuations on measurement. We have also discussed uncertainties and noises associated with the estimated absolute line shape function and the applicability of this new method to detect several gases in the near infrared region. We used measurements of the 1650.96 nm absorption line for 1% and 8% methane concentration in the 60-100 kPa pressure range to validate the efficacy of this new RAM recovery technique and demonstrated a calibration-free system. Because this approach has minimal dependency on diode laser operating conditions, it is more robust and suitable for harsh industrial environments.

  10. Optimization of phase contrast in bimodal amplitude modulation AFM

    PubMed Central

    Damircheli, Mehrnoosh; Payam, Amir F

    2015-01-01

    Summary Bimodal force microscopy has expanded the capabilities of atomic force microscopy (AFM) by providing high spatial resolution images, compositional contrast and quantitative mapping of material properties without compromising the data acquisition speed. In the first bimodal AFM configuration, an amplitude feedback loop keeps constant the amplitude of the first mode while the observables of the second mode have not feedback restrictions (bimodal AM). Here we study the conditions to enhance the compositional contrast in bimodal AM while imaging heterogeneous materials. The contrast has a maximum by decreasing the amplitude of the second mode. We demonstrate that the roles of the excited modes are asymmetric. The operational range of bimodal AM is maximized when the second mode is free to follow changes in the force. We also study the contrast in trimodal AFM by analyzing the kinetic energy ratios. The phase contrast improves by decreasing the energy of second mode relative to those of the first and third modes. PMID:26114079

  11. Trellis-coded pulse amplitude modulation for indoor visible light communication

    NASA Astrophysics Data System (ADS)

    Wang, Yu; Yang, Aiying; Wu, Yongsheng; Feng, Lihui; Sun, Yu-nan; Li, Yankun

    2013-12-01

    Trellis-coded pulse-amplitude modulation (TC-PAM) is applied in visible light communication (VLC) system using RGB-LED. Based on natural modulation, we propose a modified modulation to yield performance enhancement. Further, a decoding method of combing soft-decision Viterbi algorithm with most significant bit (MSB) decoding is developed. Finally, the results of Monte-Carlo simulation are presented to verify the best modulation and decoding method among the mentioned modulation and decoding techniques.

  12. Ultrabroadband radio-frequency arbitrary waveform generation with high-speed phase and amplitude modulation capability.

    PubMed

    Rashidinejad, Amir; Leaird, Daniel E; Weiner, Andrew M

    2015-05-04

    We introduce a novel photonic-assisted ultrabroadband radio-frequency arbitrary waveform generation setup capable of high-speed phase and amplitude modulation of the individual arbitrary waveforms. The waveform generator is based on an optical interferometer, within which a high-resolution optical pulse shaper and integrated optic phase and intensity modulators are placed, followed by frequency-to-time mapping. The phase and amplitude of each ultrabroadband waveform within the generated sequence can be continuously tuned by adjusting the driving voltages applied to the phase and intensity modulator pair, hence overcoming the slow update speed of conventional spatial light modulator-based pulse shapers. Moreover, this data modulation is completely independent from and does not interfere with RF waveform design. Programmable ultrabroadband RF sequences, spanning more than 4.7 octaves from 2 to 52 GHz, are modulated with real-time data in up to 16 level, M-ary phase-shift keying and quadrature amplitude modulation formats.

  13. High speed cross-amplitude modulation in concatenated SOA-EAM-SOA.

    PubMed

    Cleary, Ciaran S; Manning, Robert J

    2012-06-18

    We observe a near-ideal high speed amplitude impulse response in an SOA-EAM-SOA configuration under optimum conditions. Full amplitude recovery times as low as 10 ps with modulation depths of 70% were observed in pump-probe measurements. System behavior could be controlled by the choice of signal wavelength, SOA current biases and EAM reverse bias voltages. Experimental data and impulse response modelling indicated that the slow tail in the gain response of first SOA was negated by a combination of cross-absorption modulation between pump and modulated CW probe, and self-gain modulation of the modulated CW probe in both the EAM and second SOA.

  14. Postnatal development of neuronal responses to frequency-modulated tones in chinchilla auditory cortex.

    PubMed

    Brown, Trecia A; Harrison, Robert V

    2010-01-14

    Responses to cortical neurons to frequency-modulated (FM) stimuli have been described in various adult animal models. Here, we ask whether FM coding at the cortical level is innate or if it is influenced by postnatal environmental experience. We report on the FM response properties of neurons in core auditory cortex of newborn (P3), 1-month-old (P28) and adult (>1-year-old) anesthetized chinchillas (Chinchilla laniger). Upward and downward linear FM sweeps spanning frequencies from 0.1 to 20 kHz were presented monaurally at speeds of 0.05 to 0.82 kHz/ms. Results indicated that neurons in neonatal pups were responsive to FM stimulation. While we observed a developmental increase in the selectivity of units for FM sweep direction (p<0.01, one-way ANOVA), selectivity for sweep speed appeared to be established early in development. Chinchilla pup neurons also demonstrated single-peak (single dominant response during FM sweep presentation) and multi-peak (multiple distinct responses during FM sweep) temporal response patterns to FM stimuli similar to those observed in adults. A developmental increase in the proportion of multi-peak units closely paralleled a previously reported increase in the complexity of pure tone receptive fields. We suggest that units in core auditory cortex of the chinchilla are not uniquely activated by FM sounds but that FM responses are largely predictable based on how changing frequency stimuli interact with the tonal receptive fields of neurons in the auditory cortex.

  15. Quadrature amplitude modulation (QAM) using binary-driven coupling-modulated rings

    NASA Astrophysics Data System (ADS)

    Karimelahi, Samira; Sheikholeslami, Ali

    2016-05-01

    We propose and fully analyze a compact structure for DAC-free pure optical QAM modulation. The proposed structure is the first ring resonator-based DAC-free QAM modulator reported in the literature, to the best of our knowledge. The device consists of two segmented add-drop Mach Zehnder interferometer-assisted ring modulators (MZIARM) in an IQ configuration. The proposed architecture is investigated based on the parameters from SOI technology where various key design considerations are discussed. We have included the loss in the MZI arms in our analysis of phase and amplitude modulation using MZIARM for the first time and show that the imbalanced loss results in a phase error. The output level linearity is also studied for both QAM-16 and QAM-64 not only based on optimizing RF segment lengths but also by optimizing the number of segments. In QAM-16, linearity among levels is achievable with two segments while in QAM-64 an additional segment may be required.

  16. Amplitudes of solar modulation of low energy cosmic rays

    NASA Technical Reports Server (NTRS)

    Von Rosenvinge, T. T.; Paizis, C.

    1982-01-01

    There have been differences of opinion regarding the origin and behavior of the solar modulation of galactic cosmic rays. It has been shown that the return to solar maximum intensity levels beginning in early 1978 was dominated by Forbush decreases. These Forbush decreases were caused by radially moving interplanetary shocks resulting from large solar flares. The present investigation is concerned with solar modulation effects which were observed during the previous solar minimum. The effects were associated with high-speed streams in the solar wind. These streams caused the formation of corotating interaction regions with both forward and reverse shocks. The modulation effects seen near earth are intimately connected with these shocks.

  17. Envelope pulsed ultrasonic distance measurement system based upon amplitude modulation and phase modulation

    SciTech Connect

    Huang, Y. P.; Wang, J. S.; Huang, K. N.; Ho, C. T.; Huang, J. D.; Young, M. S.

    2007-06-15

    A novel microcomputer-based ultrasonic distance measurement system is presented. This study proposes an efficient algorithm which combines both the amplitude modulation (AM) and the phase modulation (PM) of the pulse-echo technique. The proposed system can reduce error caused by inertia delay and amplitude attenuation effect when using the AM and PM envelope square wave form (APESW). The APESW ultrasonic driving wave form causes a phase inversion phenomenon in the relative wave form of the receiver. The phase inversion phenomenon sufficiently identifies the ''measurement pulse'' in the received wave forms, which can be used for accurate time-of-flight (TOF) measurement. In addition, combining a countertechnique to compute the phase shifts of the last cycle for TOF, the presented system can obtain distance resolution of 0.1% of the wavelength corresponding to the 40 kHz frequency of the ultrasonic wave. The standard uncertainty of the proposed distance measurement system is found to be 0.2 mm at a range of 50-500 mm. The APESW signal generator and phase detector of this measuring system are designed on a complex programmable logic device, which is used to govern the TOF measurement and send the data to a personal computer for distance calibration and examination. The main advantages of this APESW system are high resolution, low cost, narrow bandwidth requirement, and ease of implementation.

  18. Envelope pulsed ultrasonic distance measurement system based upon amplitude modulation and phase modulation.

    PubMed

    Huang, Y P; Wang, J S; Huang, K N; Ho, C T; Huang, J D; Young, M S

    2007-06-01

    A novel microcomputer-based ultrasonic distance measurement system is presented. This study proposes an efficient algorithm which combines both the amplitude modulation (AM) and the phase modulation (PM) of the pulse-echo technique. The proposed system can reduce error caused by inertia delay and amplitude attenuation effect when using the AM and PM envelope square wave form (APESW). The APESW ultrasonic driving wave form causes a phase inversion phenomenon in the relative wave form of the receiver. The phase inversion phenomenon sufficiently identifies the "measurement pulse" in the received wave forms, which can be used for accurate time-of-flight (TOF) measurement. In addition, combining a countertechnique to compute the phase shifts of the last cycle for TOF, the presented system can obtain distance resolution of 0.1% of the wavelength corresponding to the 40 kHz frequency of the ultrasonic wave. The standard uncertainty of the proposed distance measurement system is found to be 0.2 mm at a range of 50-500 mm. The APESW signal generator and phase detector of this measuring system are designed on a complex programmable logic device, which is used to govern the TOF measurement and send the data to a personal computer for distance calibration and examination. The main advantages of this APESW system are high resolution, low cost, narrow bandwidth requirement, and ease of implementation.

  19. Amplitude modulation in δ Sct stars: statistics from an ensemble study of Kepler targets

    NASA Astrophysics Data System (ADS)

    Bowman, Dominic M.; Kurtz, Donald W.; Breger, Michel; Murphy, Simon J.; Holdsworth, Daniel L.

    2016-08-01

    We present the results of a search for amplitude modulation of pulsation modes in 983 δ Sct stars, which have effective temperatures between 6400 ≤ Teff ≤ 10 000 K in the Kepler Input Catalogue and were continuously observed by the Kepler Space Telescope for 4 yr. We demonstrate the diversity in pulsational behaviour observed, in particular non-linearity, which is predicted for δ Sct stars. We analyse and discuss examples of δ Sct stars with constant amplitudes and phases; those that exhibit amplitude modulation caused by beating of close-frequency pulsation modes; those that exhibit pure amplitude modulation (with no associated phase variation); those that exhibit phase modulation caused by binarity; and those that exhibit amplitude modulation caused by non-linearity. Using models and examples of individual stars, we demonstrate that observations of the changes in amplitude and phase of pulsation modes can be used to distinguish among the different scenarios. We find that 603 δ Sct stars (61.3 per cent) exhibit at least one pulsation mode that varies significantly in amplitude over 4 yr. Conversely, many δ Sct stars have constant pulsation amplitudes so short-length observations can be used to determine precise frequencies, amplitudes and phases for the most coherent and periodic δ Sct stars. It is shown that amplitude modulation is not restricted to a small region on the HR diagram, therefore not necessarily dependent on stellar parameters such as Teff or log g. Our catalogue of 983 δ Sct stars will be useful for comparisons to similar stars observed by K2 and TESS, because the length of the 4-yr Kepler data set will not be surpassed for some time.

  20. Uncovering signals from measurement noise by electro mechanical amplitude modulation

    NASA Astrophysics Data System (ADS)

    Droogendijk, H.; Sanders, R. G. P.; Krijnen, G. J. M.

    2013-05-01

    We present an electromechanical parametric scheme to improve the low-frequency signal-to-noise ratio of energy buffering type transducers. The method is based on periodic modulation of the stiffness in the sensory system which produces upconverted replicas of the signals of interest at frequencies where measurement is less troubled by noise or other detrimental effects. We demonstrate this principle by means of capacitive biomimetic hair flow sensors, where we modulate the rotational spring stiffness by periodic electrostatic spring softening, such that a replica of the original signal is formed around the modulation frequency. Using this replica we gain up to a 25-fold improvement of the low-frequency signal-to-noise ratio and sensing threshold. For transient measurements we demonstrate that tiny signals, which are below the noise-levels in the base-band, are revealed well when upconverted to higher frequencies.

  1. Correlation with a spatial light modulator having phase and amplitude cross coupling

    NASA Technical Reports Server (NTRS)

    Juday, Richard D.

    1989-01-01

    In correlation filtering a spatial light modulators is traditionally modeled as affecting only the phase or only the amplitude of light. Usually, however, a single operating parameter affects both phase and amplitude. An integral constraint is developed that is a necessary condition for optimizing a correlation filter having single parameter coupling between phase and amplitude. The phase-only filter is shown to be a special case.

  2. An amplitude modulated laser system for distance and displacement measurement

    NASA Technical Reports Server (NTRS)

    Rogowski, Robert S.; Heyman, Joseph S.; Holben, Milford S., Jr.

    1986-01-01

    A laser distance and displacement measurement system is being developed to monitor small displacements in large space structures for strain analysis and structural control. The reflected laser beam is focused on a detector and the detected signal is mixed with the reference. Small displacements are indicated by a change in modulation frequency which is adjusted to maintain quadrature between the received signal and the reference signal from the voltage-controlled oscillator in a phase-locked loop. Measurement of absolute distance is accomplished by sweeping the modulation frequency from a quadrature lock point to an adjacent lock point.

  3. The Chandler wobble of the poles and its amplitude modulation

    NASA Astrophysics Data System (ADS)

    Sidorenkov, N.

    2015-08-01

    It is shown that the period of the Chandler wobble of the poles (CWP) is a combined oscillation caused by three periodic processes experienced by the Earth: (a) lunisolar tides, (b) the precession of the orbit of the Earth's monthly revolution around the barycenter of the Earth-Moon system, and (c) the motion of the perigee of this orbit. The addition of the 1.20 - year Chandler wobble to sidereal, anomalistic, and synodic lunar yearly forcing gives rise slow periodic variations in the CWP amplitude with periods of 32 to 51 years.

  4. Active cancellation of residual amplitude modulation in a frequency-modulation based Fabry-Perot interferometer

    NASA Astrophysics Data System (ADS)

    Yu, Yinan; Wang, Yicheng; Pratt, Jon R.

    2016-03-01

    Residual amplitude modulation (RAM) is one of the most common noise sources known to degrade the sensitivity of frequency modulation spectroscopy. RAM can arise as a result of the temperature dependent birefringence of the modulator crystal, which causes the orientation of the crystal's optical axis to shift with respect to the polarization of the incident light with temperature. In the fiber-based optical interferometer used on the National Institute of Standards and Technology calculable capacitor, RAM degrades the measured laser frequency stability and correlates with the environmental temperature fluctuations. We have demonstrated a simple approach that cancels out excessive RAM due to polarization mismatch between the light and the optical axis of the crystal. The approach allows us to measure the frequency noise of a heterodyne beat between two lasers individually locked to different resonant modes of a cavity with an accuracy better than 0.5 ppm, which meets the requirement to further determine the longitudinal mode number of the cavity length. Also, this approach has substantially mitigated the temperature dependency of the measurements of the cavity length and consequently the capacitance.

  5. Transcutaneous cervical vagal nerve stimulation modulates cardiac vagal tone and tumor necrosis factor-alpha.

    PubMed

    Brock, C; Brock, B; Aziz, Q; Møller, H J; Pfeiffer Jensen, M; Drewes, A M; Farmer, A D

    2016-12-12

    The vagus nerve is a central component of cholinergic anti-inflammatory pathways. We sought to evaluate the effect of bilateral transcutaneous cervical vagal nerve stimulation (t-VNS) on validated parameters of autonomic tone and cytokines in 20 healthy subjects. 24 hours after t-VNS, there was an increase in cardiac vagal tone and a reduction in tumor necrosis factor-α in comparison to baseline. No change was seen in blood pressure, cardiac sympathetic index or other cytokines. These preliminary data suggest that t-VNS exerts an autonomic and a subtle antitumor necrosis factor-α effect, which warrants further evaluation in larger controlled studies.

  6. Modulation of hair cell voltage responses to tones by low-frequency biasing of the basilar membrane in the guinea pig cochlea.

    PubMed

    Russell, I J; Kössl, M

    1992-05-01

    Inner (IHC) and outer (OHC) hair cell receptor potentials were recorded during stimulation with combinations of high-frequency (HF) tones and a 100 Hz tone burst of constant level (80 dB SPL). For frequencies at and below characteristic frequency (CF), OHC AC receptor potentials were suppressed by the 100 Hz tone at levels of the HF tone below about 70 dB SPL (the initial steep part of the AC/level function) and at levels that were frequency specific for frequencies above CF. Suppression was associated with a phase lead for frequencies at and close to the CF. For frequencies above CF, the OHC AC response was either suppressed or augmented at levels of the HF tone both below and above 70 dB SPL, depending on the frequency. The action of the 100 Hz tone on the AC response/level functions was to change nonmonotonic functions into monotonic functions or vice versa. IHC DC receptor potentials were suppressed maximally at the CF and at levels and frequencies where suppression of the OHC AC response and the appearance of the IHC DC response overlapped. For levels of the HF tone above 70 dB SPL, the amplitude of the responses of both IHCs and OHCs to the 100 Hz tone are suppressed and become more symmetrical through selective attenuation of the depolarizing phase of the IHC response and the hyperpolarizing phase of the OHC response. In IHCs from insensitive preparations, the response to the 100 Hz tone is augmented in the presence of the HF tone, which may indicate a shift in the operating point of transduction. At frequencies about one-half an octave below the CF, the phase of the 100 Hz voltage response of OHCs but not IHCs is inverted for levels of the HF tone above about 90 dB SPL. It is proposed that amplitude and phase changes in the response to the HF tone due to the presence of the 100 Hz tone are the result of changes in OHC feedback processes and in the mode of movement of the interface between OHC stereocilia and tectorial membrane. The interaction between the

  7. Nonlinear Optical Systems Interacting with Amplitude-Modulated Optical Fields

    DTIC Science & Technology

    1990-07-01

    We start with the rate equations for the excited-state population of the laser transition p, d ( ltp = - (I + I + I,)P + -LI, (C.1) and the equation...spectroscopy; lasers ; parametric resonances ABSTRACT (Continue on reverse if necessary and identify by block number) Please see Abstract on Pages v-vi. I...he conducted research in the fields of modulation spectroscopy and laser instability under the guidance of Professor Carlos R. Stroud, Jr. While at

  8. Inspection of complex amplitudes of spatial light modulators using moiré techniques

    NASA Astrophysics Data System (ADS)

    Calderón-Hermosillo, C. Y.; Alcalá Ochoa, Noé; Noé Arias, E.; García-Márquez, J.

    2013-05-01

    We propose a method to get the phase and amplitude modes of an electrically driven spatial light modulator (SLM) device using the formation of moiré patterns. It is found to be a fast experimental method to visualize the complex amplitude of the SLM and it may be an excellent guide to find specific complex configurations of amplitude and phase. Experimental results and limitations of the proposal are presented using a reflective liquid crystal on silicon (LCoS SLM) modulator. With this method it has been found experimentally a phase-mostly configuration using only one polarizer, without an analyzer.

  9. Sensitivity of neurons in cat primary auditory cortex to tones and frequency-modulated stimuli. II: Organization of response properties along the 'isofrequency' dimension.

    PubMed

    Heil, P; Rajan, R; Irvine, D R

    1992-11-01

    The spatial distribution of neuronal responses to tones and frequency-modulated (FM) stimuli was mapped along the 'isofrequency' dimension of the primary auditory cortex (AI) of barbiturate-anesthetized cats. In each cat, electrode penetrations roughly orthogonal to the cortical surface were closely spaced (average separation approximately 130 microns) along the dorsoventral extent of a single 'isofrequency' strip in high frequency parts of AI (> 15 kHz). Characteristic frequency (CF), minimum threshold, sharpness of frequency tuning (Q10 and Q20), the dynamic range of the spike count-intensity function at CF, sensitivity to the rate of change of frequency (RCF) and to the direction of frequency-modulation (DS) were determined for contralaterally-presented tone and FM stimuli. Sharpness of tuning attained maximum values at central loci along the dorsoventral 'isofrequency' axis and values declined towards more dorsal and more ventral locations. Minimum threshold and dynamic range varied between high and low values in a similar and correlated periodic fashion. Their combined organization yielded an orderly spatial representation of response strength, relative to maximum, as a function of stimulus amplitude. The distributions of the most common forms of FM rate sensitivity (RCF response categories) and best RCF along 'isofrequency' strips were significantly non-random although there was a considerable degree of variability between cats. FM directional preference and sensitivity appeared to be randomly distributed. Sharpness of tuning may be related to the analysis of the spectral content of an acoustic stimulus, both minimum threshold and dynamic range are related to the encoding of stimulus intensity, and measures of FM rate and directional sensitivity assess the coding of temporal changes of stimulus spectra. The independent, or for minimum threshold and dynamic range dependent, topographic organizations of these neuronal parameters therefore suggest parallel and

  10. Propeller tone bursts

    NASA Technical Reports Server (NTRS)

    Succi, G. P.; Munro, D. H.; Ingard, K. U.

    1983-01-01

    Intense high frequency (25-38 kHz) tone bursts have been observed in acoustic tests of a scale model of a general aviation propeller. The amplitude of the tone burst is approximately equal to the amplitude of the propeller noise signature. The conditions necessary for the production of these tone bursts are described. The experiments indicate that the origin of these bursts is a periodic flow oscillation on the suction surface of the propeller blade tips which may be due to the interaction between an oscillating shock wave and a laminar boundary layer.

  11. Dissociable Neural Response Signatures for Slow Amplitude and Frequency Modulation in Human Auditory Cortex

    PubMed Central

    Henry, Molly J.; Obleser, Jonas

    2013-01-01

    Natural auditory stimuli are characterized by slow fluctuations in amplitude and frequency. However, the degree to which the neural responses to slow amplitude modulation (AM) and frequency modulation (FM) are capable of conveying independent time-varying information, particularly with respect to speech communication, is unclear. In the current electroencephalography (EEG) study, participants listened to amplitude- and frequency-modulated narrow-band noises with a 3-Hz modulation rate, and the resulting neural responses were compared. Spectral analyses revealed similar spectral amplitude peaks for AM and FM at the stimulation frequency (3 Hz), but amplitude at the second harmonic frequency (6 Hz) was much higher for FM than for AM. Moreover, the phase delay of neural responses with respect to the full-band stimulus envelope was shorter for FM than for AM. Finally, the critical analysis involved classification of single trials as being in response to either AM or FM based on either phase or amplitude information. Time-varying phase, but not amplitude, was sufficient to accurately classify AM and FM stimuli based on single-trial neural responses. Taken together, the current results support the dissociable nature of cortical signatures of slow AM and FM. These cortical signatures potentially provide an efficient means to dissect simultaneously communicated slow temporal and spectral information in acoustic communication signals. PMID:24205309

  12. Smooth Pursuit Saccade Amplitude Modulation During Exposure to Microgravity

    NASA Technical Reports Server (NTRS)

    Reschke, M. F.; Kozlovskaya, I. B.; Sayenko, D. G.; Sayenko, I.; Somers, J. T.; Paloski, W. H.

    2002-01-01

    Russian investigators have reported changes in pursuit tracking of a vertically moving point stimulus during space flight. Early in microgravity, changes were manifested by decreased eye movement amplitude (undershooting) and the appearance of correction saccades. As the flight progressed, pursuit of the moving point stimulus deteriorated while associated saccadic movements were unchanged. Immediately postflight there was an improved execution of active head movements indicating that the deficiencies in pursuit function noted in microgravity may be of central origin. In contrast, tests of two cosmonauts showed that horizontal and vertical smooth pursuit were unchanged inflight. However, results of corresponding saccadic tasks showed a tendency toward the overshooting of a horizontal target early inflight with high accuracy developing later inflight, accompanied by an increased saccade velocity and a trend toward decreased saccade latency. Based on these equivocal results, we have further investigated the effects of space flight on the smooth pursuit mechanism during and after short duration flight, and postflight on returning MIR crewmembers. Sinusoidal target movement was presented horizontally at frequencies of 0.33 and 1.0 Hz. Subjects were asked to perform two trials for each stimulus combination: (1) moving eyes-only (EO) and (2) moving eyes and head (EH) with the target motion. Peak amplitude was 30 deg for 0.33 Hz trials and 15 deg for the 1.0 Hz trials. The relationship between saccade amplitude and peak velocity were plotted as a main sequence for each phase of flight, and linear regression analysis allowed us to determine the slope of each main sequence plot. The linear slopes were then combined for each flight phase for each individual subject. The main sequence for both EO and EH trials at both the 0.33 and 1.0 Hz frequencies during flight for the short duration flyers showed a reduction in saccade velocity and amplitude when compared to the preflight

  13. Radio frequency path characterization for wide band quadrature amplitude modulation

    SciTech Connect

    Bracht, R.

    1998-12-31

    Remote, high speed, high explosive wave front monitoring requires very high bandwidth telemetry to allow transmission of diagnostic data before the explosion destroys the sensor system itself. The main motivation for this study is that no known existing implementation of this sort has been applied to realistic weapons environments. These facts have prompted the research and gathering of data that can be used to extrapolate towards finding the best modulation method for this application. In addition to research of similar existing analysis and testing operations, data was recently captured from a Joint Test Assembly (JTA) Air Launched Cruise Missile (ALCM) flight.

  14. Diffusion-induced periodic transition between oscillatory modes in amplitude-modulated patterns

    SciTech Connect

    Tang, Xiaodong; He, Yuxiu; Wang, Shaorong; Gao, Qingyu; Epstein, Irving R.; Wang, Qun

    2014-06-15

    We study amplitude-modulated waves, e.g., wave packets in one dimension, overtarget spirals and superspirals in two dimensions, under mixed-mode oscillatory conditions in a three-variable reaction-diffusion model. New transition zones, not seen in the homogeneous system, are found, in which periodic transitions occur between local 1{sup N−1} and 1{sup N} oscillations. Amplitude-modulated complex patterns result from periodic transition between (N − 1)-armed and N-armed waves. Spatial recurrence rates provide a useful guide to the stability of these modulated patterns.

  15. Pitch processing of dynamic lexical tones in the auditory cortex is influenced by sensory and extrasensory processes

    PubMed Central

    Krishnan, Ananthanarayan; Gandour, Jackson T.; Suresh, Chandan H.

    2015-01-01

    The aim is to evaluate how language experience (Chinese, English) shapes processing of pitch contours as reflected in the amplitude of cortical pitch response components. Responses were elicited from three dynamic, curvilinear, nonspeech stimuli varying in pitch direction and location of peak acceleration: Mandarin lexical Tone2 (rising) and Tone4 (falling); and a flipped variant of Tone2, Tone2′ (nonnative). At temporal sites (T7/T8), Chinese Na-Pb response amplitude to Tones 2 & 4 was greater than English in the right hemisphere only; a rightward asymmetry for Tones 2 & 4 was restricted to the Chinese group. In common to both Fz-to-linked T7/T8 and T7/T8 electrode sites, the stimulus pattern (Tones 2 & 4 > Tone2′) was found in the Chinese group only. As reflected by Pb-Nb at Fz, Chinese amplitude was larger than English in response to Tones 2 & 4; and Tones 2 & 4 were larger than Tone2′; whereas for English, Tone2 was larger than Tone2′ and Tone4. At frontal electrode sites (F3/F4), regardless of component or hemisphere, Chinese responses were larger in amplitude than English across stimuli. For either group, responses to Tones 2 & 4 were larger than Tone2′. No hemispheric asymmetry was observed at the frontal electrode sites. These findings highlight that cortical pitch response components are differentially modulated by experience-dependent, temporally distinct but functionally overlapping weighting of sensory and extrasensory effects on pitch processing of lexical tones in the right temporal lobe and, more broadly, are consistent with a distributed hierarchical predictive coding process. PMID:25943576

  16. Miniature Surface Plasmon Polariton Amplitude Modulator by Beat Frequency and Polarization Control

    PubMed Central

    Chang, Cheng-Wei; Lin, Chu-En; Yu, Chih-Jen; Yeh, Ting-Tso; Yen, Ta-Jen

    2016-01-01

    The miniaturization of modulators keeps pace for the compact devices in optical applications. Here, we present a miniature surface plasmon polariton amplitude modulator (SPPAM) by directing and interfering surface plasmon polaritons on a nanofabricated chip. Our results show that this SPPAM enables two kinds of modulations. The first kind of modulation is controlled by encoding angular-frequency difference from a Zeeman laser, with a beat frequency of 1.66 MHz; the second of modulation is validated by periodically varying the polarization states from a polarization generator, with rotation frequencies of 0.5–10 k Hz. In addition, the normalized extinction ratio of our plasmonic structure reaches 100. Such miniaturized beat-frequency and polarization-controlled amplitude modulators open an avenue for the exploration of ultrasensitive nanosensors, nanocircuits, and other integrated nanophotonic devices. PMID:27558516

  17. Dynamic nonlinear focal shift in amplitude modulated moderately focused acoustic beams.

    PubMed

    Jiménez, Noé; Camarena, Francisco; González-Salido, Nuria

    2017-03-01

    The phenomenon of the displacement of the position of the pressure, intensity and acoustic radiation force maxima along the axis of focused acoustic beams under increasing driving amplitudes (nonlinear focal shift) is studied for the case of a moderately focused beam excited with continuous and 25kHz amplitude modulated signals, both in water and tissue. We prove that in amplitude modulated beams the linear and nonlinear propagation effects coexist in a semi-period of modulation, giving place to a complex dynamic behavior, where the singular points of the beam (peak pressure, rarefaction, intensity and acoustic radiation force) locate at different points on axis as a function of time. These entire phenomena are explained in terms of harmonic generation and absorption during the propagation in a lossy nonlinear medium both for a continuous and an amplitude modulated beam. One of the possible applications of the acoustic radiation force displacement is the generation of shear waves at different locations by using a focused mono-element transducer excited by an amplitude modulated signal.

  18. Extending single molecule fluorescence observation time by amplitude-modulated excitation

    NASA Astrophysics Data System (ADS)

    Kisley, Lydia; Chang, Wei-Shun; Cooper, David; Mansur, Andrea P.; Landes, Christy F.

    2013-09-01

    We present a hardware-based method that can improve single molecule fluorophore observation time by up to 1500% and super-localization by 47% for the experimental conditions used. The excitation was modulated using an acousto-optic modulator (AOM) synchronized to the data acquisition and inherent data conversion time of the detector. The observation time and precision in super-localization of four commonly used fluorophores were compared under modulated and traditional continuous excitation, including direct total internal reflectance excitation of Alexa 555 and Cy3, non-radiative Förster resonance energy transfer (FRET) excited Cy5, and direct epi-fluorescence wide field excitation of Rhodamine 6G. The proposed amplitude-modulated excitation does not perturb the chemical makeup of the system or sacrifice signal and is compatible with multiple types of fluorophores. Amplitude-modulated excitation has practical applications for any fluorescent study utilizing an instrumental setup with time-delayed detectors.

  19. Encoding and decoding amplitude-modulated cochlear implant stimuli--a point process analysis.

    PubMed

    Goldwyn, Joshua H; Shea-Brown, Eric; Rubinstein, Jay T

    2010-06-01

    Cochlear implant speech processors stimulate the auditory nerve by delivering amplitude-modulated electrical pulse trains to intracochlear electrodes. Studying how auditory nerve cells encode modulation information is of fundamental importance, therefore, to understanding cochlear implant function and improving speech perception in cochlear implant users. In this paper, we analyze simulated responses of the auditory nerve to amplitude-modulated cochlear implant stimuli using a point process model. First, we quantify the information encoded in the spike trains by testing an ideal observer's ability to detect amplitude modulation in a two-alternative forced-choice task. We vary the amount of information available to the observer to probe how spike timing and averaged firing rate encode modulation. Second, we construct a neural decoding method that predicts several qualitative trends observed in psychophysical tests of amplitude modulation detection in cochlear implant listeners. We find that modulation information is primarily available in the sequence of spike times. The performance of an ideal observer, however, is inconsistent with observed trends in psychophysical data. Using a neural decoding method that jitters spike times to degrade its temporal resolution and then computes a common measure of phase locking from spike trains of a heterogeneous population of model nerve cells, we predict the correct qualitative dependence of modulation detection thresholds on modulation frequency and stimulus level. The decoder does not predict the observed loss of modulation sensitivity at high carrier pulse rates, but this framework can be applied to future models that better represent auditory nerve responses to high carrier pulse rate stimuli. The supplemental material of this article contains the article's data in an active, re-usable format.

  20. New asymmetric propagation invariant beams obtained by amplitude and phase modulation in frequency space.

    PubMed

    Mendoza-Hernández, J; Arroyo Carrasco, M L; Méndez Otero, M M; Chávez-Cerda, S; Iturbe Castillo, M D

    2014-12-12

    In this paper, we demonstrate, numerically and experimentally that using the mask-lens setup used by Durnin to generate Bessel beams Durnin [Phys. Rev. Lett. 58, 1499 (1987)], it is possible to generate different kinds of propagation invariant beams. A modification in the amplitude or phase of the field that illuminates the annular slit is proposed that corresponds to modulation in frequency space. In particular, we characterize the new invariant beams that were obtained by modulating the amplitude of the annular mask and when the incident field was modulated with a one-dimensional quadratic or cubic phase. Experimental results using an amplitude mask are shown in order to corroborate the numerical predictions.

  1. New asymmetric propagation invariant beams obtained by amplitude and phase modulation in frequency space

    PubMed Central

    Mendoza-Hernández, J.; Arroyo Carrasco, M.L.; Méndez Otero, M.M.; Chávez-Cerda, S.; Iturbe Castillo, M.D.

    2014-01-01

    In this paper, we demonstrate, numerically and experimentally that using the mask-lens setup used by Durnin to generate Bessel beams Durnin [Phys. Rev. Lett. 58, 1499 (1987)], it is possible to generate different kinds of propagation invariant beams. A modification in the amplitude or phase of the field that illuminates the annular slit is proposed that corresponds to modulation in frequency space. In particular, we characterize the new invariant beams that were obtained by modulating the amplitude of the annular mask and when the incident field was modulated with a one-dimensional quadratic or cubic phase. Experimental results using an amplitude mask are shown in order to corroborate the numerical predictions. PMID:25705088

  2. Amplitude modulation of sound from wind turbines under various meteorological conditions.

    PubMed

    Larsson, Conny; Öhlund, Olof

    2014-01-01

    Wind turbine (WT) sound annoys some people even though the sound levels are relatively low. This could be because of the amplitude modulated "swishing" characteristic of the turbine sound, which is not taken into account by standard procedures for measuring average sound levels. Studies of sound immission from WTs were conducted continually between 19 August 2011 and 19 August 2012 at two sites in Sweden. A method for quantifying the degree and strength of amplitude modulation (AM) is introduced here. The method reveals that AM at the immission points occur under specific meteorological conditions. For WT sound immission, the wind direction and sound speed gradient are crucial for the occurrence of AM. Interference between two or more WTs could probably enhance AM. The mechanisms by which WT sound is amplitude modulated are not fully understood.

  3. Effect of noise on modulation amplitude and phase in frequency-domain diffusive imaging

    PubMed Central

    Kupinski, Matthew A.

    2012-01-01

    Abstract. We theoretically investigate the effect of noise on frequency-domain heterodyne and/or homodyne measurements of intensity-modulated beams propagating through diffusive media, such as a photon density wave. We assumed that the attenuated amplitude and delayed phase are estimated by taking the Fourier transform of the noisy, modulated output data. We show that the estimated amplitude and phase are biased when the number of output photons is small. We also show that the use of image intensifiers for photon amplification in heterodyne or homodyne measurements increases the amount of biases. Especially, it turns out that the biased estimation is independent of AC-dependent noise in sinusoidal heterodyne or homodyne outputs. Finally, the developed theory indicates that the previously known variance model of modulation amplitude and phase is not valid in low light situations. Monte-Carlo simulations with varied numbers of input photons verify our theoretical trends of the bias. PMID:22352660

  4. VizieR Online Data Catalog: Kepler δ Sct stars amplitude modulation (Bowman+, 2016)

    NASA Astrophysics Data System (ADS)

    Bowman, D. M.; Kurtz, D. W.; Breger, M.; Murphy, S. J.; Holdsworth, D. L.

    2016-06-01

    We searched for amplitude modulation of pulsation modes in δ Sct stars observed by the Kepler Space Telescope. The number of pulsation modes out of a maximum of twelve that have constant amplitudes and variable amplitudes are given in the columns NoMod and AMod, respectively, along with stellar parameters from Huber et al. (2014, Cat. J/ApJS/211/2). Table 1 is the full version for all 983 δ Sct stars the abridged version of the paper. (1 data file).

  5. Effects of spanwise topographic heterogeneity on amplitude and frequency modulation of streamwise velocity fluctuations

    NASA Astrophysics Data System (ADS)

    Awasthi, Ankit; Subdberg, Matthew; Anderson, William

    2016-11-01

    We present results on the effects of topographic height, and spanwise heterogeneity, on amplitude and frequency modulation of small-scale structures in the roughness sublayer due to large-scale structures in the logarithmic region of turbulent channel flows. This work follows preceding contributions on amplitude and frequency modulation in smooth wall turbulent boundary layers. We have considered three topographic cases with different characteristics from homogeneous (sandpaper), to two spanwise heterogeneous cases where the height amplitude is increased (this topographic configuration induces turbulent secondary flows, which are known to alter the outer-layer flow characteristics). Indeed, pre-multiplied energy spectra across wavelength and elevation (so-called spectrograms) illustrate how turbulent energy is redistributed with systematic modification to the underlying topography. We have determined how the large-scale (low-pass filtered) streamwise velocity modulates the amplitude and frequency response of small-scale (high-pass filtered) signal. We find that outer-layer topographic-induced perturbations completely alter the intensity of amplitude and frequency modulation. This highlights the passive-actuator-like role of roughness heterogeneity, and underpins the need to incorporate such functional dependence in the development of wall models for LES. Air Force Office of Scientific Research, Grant # FA9550-14-1-0101.

  6. Modulation of cardiac autonomic tone in non-hypotensive hypovolemia during blood donation.

    PubMed

    Yadav, Kavita; Singh, Akanksha; Jaryal, Ashok Kumar; Coshic, Poonam; Chatterjee, Kabita; Deepak, K K

    2016-08-02

    Non-hypotensive hypovolemia, observed during mild haemorrhage or blood donation leads to reflex readjustment of the cardiac autonomic tone. In the present study, the cardiac autonomic tone was quantified using heart rate and blood pressure variability during and after non-hypotensive hypovolemia of blood donation. 86 voluntary healthy male blood donors were recruited for the study (age 35 ± 9 years; weight 78 ± 12 kg; height 174 ± 6 cms). Continuous lead II ECG and beat-to-beat blood pressure was recorded before, during and after blood donation followed by offline time and frequency domain analysis of HRV and BPV. The overall heart rate variability (SDNN and total power) did not change during or after blood donation. However, there was a decrease in indices that represent the parasympathetic component (pNN50 %, SDSD and HF) while an increase was observed in sympathetic component (LF) along with an increase in sympathovagal balance (LF:HF ratio) during blood donation. These changes were sustained for the period immediately following blood donation. No fall of blood pressure was observed during the period of study. The blood pressure variability showed an increase in the SDNN, CoV and RMSSD time domain measures in the post donation period. These results suggest that mild hypovolemia produced by blood donation is non-hypotensive but is associated with significant changes in the autonomic tone. The increased blood pressure variability and heart rate changes that are seen only in the later part of donation period could be because of the progressive hypovolemia associated parasympathetic withdrawal and sympathetic activation that manifest during the course of blood donation.

  7. Detection of frequency modulation by hearing-impaired listeners: Effects of carrier frequency, modulation rate, and added amplitude modulation

    NASA Astrophysics Data System (ADS)

    Moore, Brian C. J.; Skrodzka, Ewa

    2002-01-01

    It has been proposed that the detection of frequency modulation (FM) of sinusoidal carriers can be mediated by two mechanisms: a place mechanism based on FM-induced amplitude modulation (AM) in the excitation pattern, and a temporal mechanism based on phase-locking in the auditory nerve. The temporal mechanism appears to be ``sluggish'' and does not play a role for FM rates above about 10 Hz. It also does not play a role for high carrier frequencies (above about 5 kHz). This experiment examined FM detection in three young subjects with normal hearing and four elderly subjects with cochlear hearing loss. Carrier frequencies were 0.25, 0.5, 1, 2, 4, and 6 kHz and modulation rates were 2, 5, 10, and 20 Hz. FM detection thresholds were measured both in the absence of AM, and with AM of a fixed depth (m=0.33) added in both intervals of a forced-choice trial. The added AM was intended to disrupt cues based on FM-induced AM in the excitation pattern. Generally, the hearing-impaired subjects performed markedly more poorly than the normal-hearing subjects. For the normal-hearing subjects, the disruptive effect of the AM tended to increase with increasing modulation rate, for carrier frequencies below 6 kHz, as found previously by Moore and Sek [J. Acoust. Soc. Am. 100, 2320-2331 (1996)]. For the hearing-impaired subjects, the disruptive effective of the AM was generally larger than for the normal-hearing subjects, and the magnitude of the disruption did not consistently increase with increasing modulation rate. The results suggest that cochlear hearing impairment adversely affects both temporal and excitation pattern mechanisms of FM detection.

  8. Psychometric functions for sentence recognition in sinusoidally amplitude-modulated noises

    PubMed Central

    Shen, Yi; Manzano, Nicole K.; Richards, Virginia M.

    2015-01-01

    Listeners' speech reception is better when speech is masked by a modulated masker compared to an unmodulated masker with the same long-term root-mean-square level. It has been suggested that listeners take advantage of brief periods of quiescence in a modulated masker to extract speech information. Two experiments examined the contribution of such “dip-listening” models. The first experiment estimated psychometric functions for speech intelligibility using sentences masked by sinusoidally modulated and unmodulated speech-shaped noises and the second experiment estimated detection thresholds for a tone pip added at the central dip in the masker. Modulation rates ranging from 1 to 64 Hz were tested. In experiment 1 the slopes of the psychometric functions were shallower for lower modulation rates and the pattern of speech reception thresholds as a function of modulation rate was nonmonotonic with a minimum near 16 Hz. In contrast, the detection thresholds from experiment 2 increased monotonically with modulation rate. The results suggest that the benefits of listening to speech in temporally fluctuating maskers cannot be solely ascribed to the temporal acuity of the auditory system. PMID:26723318

  9. Micro-antennas for the phase and amplitude modulation of terahertz wave

    NASA Astrophysics Data System (ADS)

    He, Jingwen; Wang, Sen; Zhang, Yan

    2015-11-01

    Based on the localized surface plasmons (LSPs), a series of C-shaped slits antennas are designed to modulate the phase and amplitude of the cross-polarized transmitted wave in THz waveband. By adjusting the structure parameters of the antenna unit, arbitrary phase and amplitude modulation of the cross-polarized THz wave can be obtained. The C-shaped slit antenna units are designed at two operating frequencies f=0.8 THz and f=1.0 THz using a commercial software package (Lumerical Solutions), which is based on the finite-difference time-domain method. According to the simulated results, principles for modulating the phase and amplitude of THz wave are summarized as follows. Firstly, the operating wavelength depends on the effective length of the antenna and the operating wavelength increases as the effective length increases; Secondly, the phase of the cross-polarized wave can be modulated from 0 to 2π by changing the opening angle of the split; Thirdly, the amplitude transmittance of the cross-polarized wave can be changed from the extinction state to the maximum value by rotating the symmetry axis of the C-shaped slit. These principles can be used to direct the design of the field modulator in any other working frequency.

  10. Focusing through a turbid medium by amplitude modulation with genetic algorithm

    NASA Astrophysics Data System (ADS)

    Dai, Weijia; Peng, Ligen; Shao, Xiaopeng

    2014-05-01

    Multiple scattering of light in opaque materials such as white paint and human tissue forms a volume speckle field, will greatly reduce the imaging depth and degrade the imaging quality. A novel approach is proposed to focus light through a turbid medium using amplitude modulation with genetic algorithm (GA) from speckle patterns. Compared with phase modulation method, amplitude modulation approach, in which the each element of spatial light modulator (SLM) is either zero or one, is much easier to achieve. Theoretical and experimental results show that, the advantage of GA is more suitable for low the signal to noise ratio (SNR) environments in comparison to the existing amplitude control algorithms such as binary amplitude modulation. The circular Gaussian distribution model and Rayleigh Sommerfeld diffraction theory are employed in our simulations to describe the turbid medium and light propagation between optical devices, respectively. It is demonstrated that the GA technique can achieve a higher overall enhancement, and converge much faster than others, and outperform all algorithms at high noise. Focusing through a turbid medium has potential in the observation of cells and protein molecules in biological tissues and other structures in micro/nano scale.

  11. Drive-amplitude-modulation atomic force microscopy: From vacuum to liquids

    PubMed Central

    Jaafar, Miriam; Cuenca, Mariano; Melcher, John; Raman, Arvind

    2012-01-01

    Summary We introduce drive-amplitude-modulation atomic force microscopy as a dynamic mode with outstanding performance in all environments from vacuum to liquids. As with frequency modulation, the new mode follows a feedback scheme with two nested loops: The first keeps the cantilever oscillation amplitude constant by regulating the driving force, and the second uses the driving force as the feedback variable for topography. Additionally, a phase-locked loop can be used as a parallel feedback allowing separation of the conservative and nonconservative interactions. We describe the basis of this mode and present some examples of its performance in three different environments. Drive-amplutide modulation is a very stable, intuitive and easy to use mode that is free of the feedback instability associated with the noncontact-to-contact transition that occurs in the frequency-modulation mode. PMID:22563531

  12. Drive-amplitude-modulation atomic force microscopy: From vacuum to liquids.

    PubMed

    Jaafar, Miriam; Martínez-Martín, David; Cuenca, Mariano; Melcher, John; Raman, Arvind; Gómez-Herrero, Julio

    2012-01-01

    We introduce drive-amplitude-modulation atomic force microscopy as a dynamic mode with outstanding performance in all environments from vacuum to liquids. As with frequency modulation, the new mode follows a feedback scheme with two nested loops: The first keeps the cantilever oscillation amplitude constant by regulating the driving force, and the second uses the driving force as the feedback variable for topography. Additionally, a phase-locked loop can be used as a parallel feedback allowing separation of the conservative and nonconservative interactions. We describe the basis of this mode and present some examples of its performance in three different environments. Drive-amplutide modulation is a very stable, intuitive and easy to use mode that is free of the feedback instability associated with the noncontact-to-contact transition that occurs in the frequency-modulation mode.

  13. Resonant enhancement for amplitude-modulated laser filament induced magnetic field in an inhomogeneous plasma

    NASA Astrophysics Data System (ADS)

    Annou, R.; Tripathi, V. K.; Srivastava, M. P.

    1996-09-01

    The Tripathi-Liu [Phys. Plasmas 1, 990 (1994)] model of magnetic-field generation due to an amplitude-modulated laser in a plasma is revisited. At plasma resonance, where modulation frequency equals the plasma frequency, significant enhancement in the magnetic field is seen. The magnetic field is found to scale directly with laser intensity and plasma frequency, while scaling inversely with laser spot size.

  14. A high-stability non-contact dilatometer for low-amplitude temperature-modulated measurements

    NASA Astrophysics Data System (ADS)

    Luckabauer, Martin; Sprengel, Wolfgang; Würschum, Roland

    2016-07-01

    Temperature modulated thermophysical measurements can deliver valuable insights into the phase transformation behavior of many different materials. While especially for non-metallic systems at low temperatures numerous powerful methods exist, no high-temperature device suitable for modulated measurements of bulk metallic alloy samples is available for routine use. In this work a dilatometer for temperature modulated isothermal and non-isothermal measurements in the temperature range from room temperature to 1300 K is presented. The length measuring system is based on a two-beam Michelson laser interferometer with an incremental resolution of 20 pm. The non-contact measurement principle allows for resolving sinusoidal length change signals with amplitudes in the sub-500 nm range and physically decouples the length measuring system from the temperature modulation and heating control. To demonstrate the low-amplitude capabilities, results for the thermal expansion of nickel for two different modulation frequencies are presented. These results prove that the novel method can be used to routinely resolve length-change signals of metallic samples with temperature amplitudes well below 1 K. This high resolution in combination with the non-contact measurement principle significantly extends the application range of modulated dilatometry towards high-stability phase transformation measurements on complex alloys.

  15. Amplitude modulation of quantum-ion-acoustic wavepackets in electron-positron-ion plasmas: Modulational instability, envelope modes, extreme waves

    SciTech Connect

    Rahman, Ata-ur-; Kerr, Michael Mc Kourakis, Ioannis; El-Taibany, Wael F.; Qamar, A.

    2015-02-15

    A semirelativistic fluid model is employed to describe the nonlinear amplitude modulation of low-frequency (ionic scale) electrostatic waves in an unmagnetized electron-positron-ion plasma. Electrons and positrons are assumed to be degenerated and inertialess, whereas ions are warm and classical. A multiscale perturbation method is used to derive a nonlinear Schrödinger equation for the envelope amplitude, based on which the occurrence of modulational instability is investigated in detail. Various types of localized ion acoustic excitations are shown to exist, in the form of either bright type envelope solitons (envelope pulses) or dark-type envelope solitons (voids, holes). The plasma configurational parameters (namely, the relativistic degeneracy parameter, the positron concentration, and the ionic temperature) are shown to affect the conditions for modulational instability significantly, in fact modifying the associated threshold as well as the instability growth rate. In particular, the relativistic degeneracy parameter leads to an enhancement of the modulational instability mechanism. Furthermore, the effect of different relevant plasma parameters on the characteristics (amplitude, width) of these envelope solitary structures is also presented in detail. Finally, the occurrence of extreme amplitude excitation (rogue waves) is also discussed briefly. Our results aim at elucidating the formation and dynamics of nonlinear electrostatic excitations in superdense astrophysical regimes.

  16. Broadcasting Stations of the World; Part II. Amplitude Modulation Broadcasting Stations According to Frequency.

    ERIC Educational Resources Information Center

    Foreign Broadcast Information Service, Washington, DC.

    This second part of "Broadcasting Stations of the World", which lists all reported radio broadcasting and television stations with the exception of those in the United States which broadcast on domestic channels, covers amplitude modulation broadcasting stations according to frequency in ascending order. Information included covers call letters,…

  17. Broadcasting Stations of the World; Part I. Amplitude Modulation Broadcasting Stations According to Country and City.

    ERIC Educational Resources Information Center

    Foreign Broadcast Information Service, Washington, DC.

    This first part of "Broadcasting Stations of the World", which lists all reported radio broadcasting and television stations, with the exception of those in the United States which broadcast on domestic channels, covers amplitude modulation broadcasting stations. Information is indexed alphabetically by country and city. Within a city, stations…

  18. Radar transponder operation with compensation for distortion due to amplitude modulation

    DOEpatents

    Ormesher, Richard C.; Tise, Bertice L.; Axline, Jr., Robert M.

    2011-01-04

    In radar transponder operation, a variably delayed gating signal is used to gate a received radar pulse and thereby produce a corresponding gated radar pulse for transmission back to the source of the received radar pulse. This compensates for signal distortion due to amplitude modulation on the retransmitted pulse.

  19. Differential Space-Time Coding Scheme Using Star Quadrature Amplitude Modulation Method

    NASA Astrophysics Data System (ADS)

    Yu, Xiangbin; Xu, DaZhuan; Bi, Guangguo

    2006-12-01

    Differential space-time coding (DSTC) has received much interest as it obviates the requirement of the channel state information at the receiver while maintaining the desired properties of space-time coding techniques. In this paper, by introducing star quadrature amplitude modulation (star QAM) method, two kinds of multiple amplitudes DSTC schemes are proposed. One is based on differential unitary space-time coding (DUSTC) scheme, and the other is based on differential orthogonal space-time coding (DOSTC) scheme. Corresponding bit-error-rate (BER) performance and coding-gain analysis are given, respectively. The proposed schemes can avoid the performance loss of conventional DSTC schemes based on phase-shift keying (PSK) modulation in high spectrum efficiency via multiple amplitudes modulation. Compared with conventional PSK-based DSTC schemes, the developed schemes have higher spectrum efficiency via carrying information not only on phases but also on amplitudes, and have higher coding gain. Moreover, the first scheme can implement low-complexity differential modulation and different code rates and be applied to any number of transmit antennas; while the second scheme has simple decoder and high code rate in the case of 3 and 4 antennas. The simulation results show that our schemes have lower BER when compared with conventional DUSTC and DOSTC schemes.

  20. Determination of nanovibration amplitudes using frequency-modulated semiconductor laser autodyne

    SciTech Connect

    Usanov, D A; Skripal, A V; Astakhov, E I

    2014-02-28

    The method for measuring nanovibration amplitudes using the autodyne signal of a semiconductor laser at several laser radiation wavelengths is described. The theoretical description of the frequency-modulated autodyne signal under harmonic vibrations of the reflector is presented and the relations for its spectral components are derived using the expansions into the Fourier and Bessel series. The results of numerical modelling based on the proposed method for measuring the reflector nanovibration amplitudes are presented that make use of the low-frequency spectrum of the autodyne signal from the frequency-modulated laser autodyne and the solution of the appropriate inverse problem. The experimental setup is described; the results of the measurements are presented for the nanovibration amplitudes and the autodyne signal spectra under the reflector nanovibrations. (laser applications and other topics in quantum electronics)

  1. Instrument Reflections and Scene Amplitude Modulation in a Polychromatic Microwave Quadrature Interferometer

    NASA Technical Reports Server (NTRS)

    Dobson, Chris C.; Jones, Jonathan E.; Chavers, Greg

    2003-01-01

    A polychromatic microwave quadrature interferometer has been characterized using several laboratory plasmas. Reflections between the transmitter and the receiver have been observed, and the effects of including reflection terms in the data reduction equation have been examined. An error analysis which includes the reflections, modulation of the scene beam amplitude by the plasma, and simultaneous measurements at two frequencies has been applied to the empirical database, and the results are summarized. For reflection amplitudes around 1096, the reflection terms were found to reduce the calculated error bars for electron density measurements by about a factor of 2. The impact of amplitude modulation is also quantified. In the complete analysis, the mean error bar for high- density measurements is 7.596, and the mean phase shift error for low-density measurements is 1.2". .

  2. Monocular 3D see-through head-mounted display via complex amplitude modulation.

    PubMed

    Gao, Qiankun; Liu, Juan; Han, Jian; Li, Xin

    2016-07-25

    The complex amplitude modulation (CAM) technique is applied to the design of the monocular three-dimensional see-through head-mounted display (3D-STHMD) for the first time. Two amplitude holograms are obtained by analytically dividing the wavefront of the 3D object to the real and the imaginary distributions, and then double amplitude-only spatial light modulators (A-SLMs) are employed to reconstruct the 3D images in real-time. Since the CAM technique can inherently present true 3D images to the human eye, the designed CAM-STHMD system avoids the accommodation-convergence conflict of the conventional stereoscopic see-through displays. The optical experiments further demonstrated that the proposed system has continuous and wide depth cues, which enables the observer free of eye fatigue problem. The dynamic display ability is also tested in the experiments and the results showed the possibility of true 3D interactive display.

  3. Cross-Modulated Amplitudes and Frequencies Characterize Interacting Components in Complex Systems

    NASA Astrophysics Data System (ADS)

    Gans, Fabian; Schumann, Aicko Y.; Kantelhardt, Jan W.; Penzel, Thomas; Fietze, Ingo

    2009-03-01

    The dynamics of complex systems is characterized by oscillatory components on many time scales. To study the interactions between these components we analyze the cross modulation of their instantaneous amplitudes and frequencies, separating synchronous and antisynchronous modulation. We apply our novel technique to brain-wave oscillations in the human electroencephalogram and show that interactions between the α wave and the δ or β wave oscillators as well as spatial interactions can be quantified and related with physiological conditions (e.g., sleep stages). Our approach overcomes the limitation to oscillations with similar frequencies and enables us to quantify directly nonlinear effects such as positive or negative frequency modulation.

  4. Amplitude concentration in a phase-modulated spectrum due to femtosecond filamentation

    PubMed Central

    Thompson, J. V.; Zhokhov, P. A.; Springer, M. M.; Traverso, A. J.; Yakovlev, V. V.; Zheltikov, A. M.; Sokolov, A. V.; Scully, M. O.

    2017-01-01

    We present a method by which the spectral intensity of an ultrafast laser pulse can be accumulated at selected frequencies by a controllable amount. Using a 4-f pulse shaper we modulate the phase of the frequency components of a femtosecond laser. By inducing femtosecond filamentation with the modulated pulse, we can concentrate the spectral amplitude of the pulse at various frequencies. The phase mask applied by the pulse shaper determines the frequencies for which accumulation occurs, as well as the intensity of the spectral concentration. This technique provides a way to obtain pulses with adjustable amplitude using only phase modulation and the nonlinear response of a medium. This provides a means whereby information which is encoded into spectral phase jumps may be decoded into measurable spectral intensity spikes. PMID:28266540

  5. Amplitude concentration in a phase-modulated spectrum due to femtosecond filamentation

    NASA Astrophysics Data System (ADS)

    Thompson, J. V.; Zhokhov, P. A.; Springer, M. M.; Traverso, A. J.; Yakovlev, V. V.; Zheltikov, A. M.; Sokolov, A. V.; Scully, M. O.

    2017-03-01

    We present a method by which the spectral intensity of an ultrafast laser pulse can be accumulated at selected frequencies by a controllable amount. Using a 4-f pulse shaper we modulate the phase of the frequency components of a femtosecond laser. By inducing femtosecond filamentation with the modulated pulse, we can concentrate the spectral amplitude of the pulse at various frequencies. The phase mask applied by the pulse shaper determines the frequencies for which accumulation occurs, as well as the intensity of the spectral concentration. This technique provides a way to obtain pulses with adjustable amplitude using only phase modulation and the nonlinear response of a medium. This provides a means whereby information which is encoded into spectral phase jumps may be decoded into measurable spectral intensity spikes.

  6. NOTE ON TRAVEL TIME SHIFTS DUE TO AMPLITUDE MODULATION IN TIME-DISTANCE HELIOSEISMOLOGY MEASUREMENTS

    SciTech Connect

    Nigam, R.; Kosovichev, A. G. E-mail: sasha@quake.stanford.ed

    2010-01-10

    Correct interpretation of acoustic travel times measured by time-distance helioseismology is essential to get an accurate understanding of the solar properties that are inferred from them. It has long been observed that sunspots suppress p-mode amplitude, but its implications on travel times have not been fully investigated so far. It has been found in test measurements using a 'masking' procedure, in which the solar Doppler signal in a localized quiet region of the Sun is artificially suppressed by a spatial function, and using numerical simulations that the amplitude modulations in combination with the phase-speed filtering may cause systematic shifts of acoustic travel times. To understand the properties of this procedure, we derive an analytical expression for the cross-covariance of a signal that has been modulated locally by a spatial function that has azimuthal symmetry and then filtered by a phase-speed filter typically used in time-distance helioseismology. Comparing this expression to the Gabor wavelet fitting formula without this effect, we find that there is a shift in the travel times that is introduced by the amplitude modulation. The analytical model presented in this paper can be useful also for interpretation of travel time measurements for the non-uniform distribution of oscillation amplitude due to observational effects.

  7. Numerical generation of a polarization singularity array with modulated amplitude and phase.

    PubMed

    Ye, Dong; Peng, Xinyu; Zhao, Qi; Chen, Yanru

    2016-09-01

    A point having no defined polarized ellipse azimuthal angle (circularly polarized) in a space-variant vector field is called a polarization singularity, and it has three types: Lemon, Monstar, and Star. Recently, the connection of polarization singularities has been performed. Inspired by this, we conduct a numerical generation of a polarization singularity array. Our method is based on two orthogonal linearly polarized light beams with modulated amplitude and phase. With appropriate distribution functions of amplitudes and phases we can control the polarized states of polarization singularities, which offer a possibility to simulate a polarization singularity array.

  8. Dynamic enhancement of autofocusing property for symmetric Airy beam with exponential amplitude modulation

    NASA Astrophysics Data System (ADS)

    Liu, Weiwei; Lu, Yao; Gong, Lei; Chu, Xiuxiang; Xue, Guosheng; Ren, Yuxuan; Zhong, Mincheng; Wang, Ziqiang; Zhou, Jinhua; Li, Yinmei

    2016-07-01

    A symmetric Airy beam (SAB) autofocuses during free space propagation. Such autofocusing SAB is useful in optical manipulation and biomedical imaging. However, its inherently limited autofocusing property may degrade the performance of the SAB in those applications. To enhance the autofocus, a symmetric apodization mask was proposed to regulate the SAB. In combination with the even cubic phase that shapes the SAB, this even exponential function mask with an adjustable parameter regulates the contribution of different frequency spectral components to the SAB. The propagation properties of this new amplitude modulated SAB (AMSAB) were investigated both theoretically and experimentally. Simulation shows that the energy distribution and autofocusing property of an AMSAB can be adjusted by the exponential amplitude modulation. Especially, the beam energy will be more concentrated in the central lobe once the even cubic phase is modulated by the mask with a higher proportion of high-frequency spectral components. Consequently, the autofocusing property and axial gradient force of AMSABs are efficiently enhanced. The experimental generation and characterization for AMSABs were implemented by modulating the collimated beam with a phase-only spatial light modulator. The experimental results well supported the theoretical predictions. With the ability to enhance the autofocus, the proposed exponential apodization modulation will make SAB more powerful in various applications, including optical trapping, fluorescence imaging and particle acceleration.

  9. Discrimination of amplitude-modulated synthetic echo trains by an echolocating bottlenose dolphin.

    PubMed

    Dankiewicz, Lois A; Helweg, David A; Moore, Patrick W; Zafran, Justine M

    2002-10-01

    Bottlenose dolphins (Tursiops truncatus) have an acute ability to use target echoes to judge attributes such as size, shape, and material composition. Most target recognition studies have focused on features associated with individual echoes as opposed to information conveyed across echo sequences (feature envelope of the multi-echo train). One feature of aspect-dependent targets is an amplitude modulation (AM) across the return echoes in the echo train created by relative movement of the target and dolphin. The current study examined whether dolphins could discriminate targets with different AM envelopes. "Electronic echoes" triggered by a dolphin's outgoing echolocation clicks were manipulated to create sinusoidal envelopes with varying AM rate and depth. Echo trains were equated for energy, requiring the dolphin to extract and retain information from multiple echoes in order to detect and report the presence of AM. The dolphin discriminated amplitude-modulated echo trains from those that were not modulated. AM depth thresholds were approximately 0.8 dB, similar to other published amplitude limens. Decreasing the rate of modulation from approximately 16 to 2 cycles per second did not affect the dolphin's AM depth sensitivity. The results support multiple-echo processing in bottlenose dolphin echolocation. This capability provides additional theoretical justification for exploring synthetic aperture sonar concepts in models of animal echolocation that potentially support theories postulating formation of images as an ultimate means for target identification.

  10. Estimation of the level and phase of the simple distortion tone in the modulation domain

    NASA Astrophysics Data System (ADS)

    Sek, Aleksander; Moore, Brian C. J.

    2004-11-01

    These experiments were designed to test the idea that nonlinearities in the auditory system can introduce a distortion component into the internal representation of the envelope of a sound, and to estimate the phase of the hypothetical distortion component. In experiment 1, a two-alternative forced-choice (2AFC) task with feedback was used to measure psychometric functions for detecting 5-Hz probe modulation of a 4-kHz sinusoidal carrier in the presence of a masker modulator with components at 50 and 55 Hz (m=0.3 for each component). Performance was measured as a function of the relative phase, ΔΦ, of the probe relative to the ``venelope'' (envelope of the envelope) of the masker. Performance was poorest for ΔJ=135°. In experiment 2, Δφ was fixed at 135°, m was set to 0.48 for each masker component, and psychometric functions for detecting probe modulation were measured using a 2AFC task without feedback. For small probe modulation depths (m~0.03), the detectability index, d', was consistently negative, consistent with the existence of a weak distortion product which can ``cancel'' the probe modulation. The distortion component for the conditions of the experiment was estimated to have a phase of about -25° relative to the venelope. .

  11. A method of measuring the amplitude-modulated vacuum field near a conducting mirror

    NASA Technical Reports Server (NTRS)

    Youn, Sun-Hyun; Lee, Jai-Hyung; Chang, Joon-Sung

    1994-01-01

    Electromagnetic fields of the vacuum mode near a conducting mirror are modified with respect to those in free space, with their amplitudes having a sinusoidal spatial dependence from the mirror. Therefore if we combine this spatially amplitude-modulated vacuum field mode and intense coherent light with a beam splitter, we may detect this fluctuation of the vacuum mode in a homodyne detection scheme. It will give a new method to produce squeezed states of light with a single mirror placed close to an unused port of a beam splitter. We show that the amplitude fluctuation of the combined light can be reduced by a factor of 2 below that of the coherent light. We also discuss the limitations due to the finite line width of the laser and the effective absorption length of the photodiodes.

  12. Measurement of phase and amplitude modulations in Sb-based films

    NASA Astrophysics Data System (ADS)

    Avila, L. F.; Nalin, M.; Cescato, Lucila

    2009-08-01

    In this work we studied the changes of the optical constants of films in the binary system Sb2O3-Sb2S3 induced by light in the VIS-UV. The measurements were performed before and after homogeneous irradiation of the films to a Hg lamp and in real time during the holographic exposure of the samples (at 458nm). Changes of the absorption coefficient (amplitude grating) and refractive index (phase grating) were measured simultaneously using the self-diffraction using the holographic setup. Besides the films presented a strong photodarkening effect under homogeneous irradiation, the samples holographically exposed presented only refractive index modulations. None amplitude modulation was measured in real time for spatial frequencies of about 1000 l/mm.

  13. Parallel-coupled dual racetrack silicon micro-resonators for quadrature amplitude modulation.

    PubMed

    Integlia, Ryan A; Yin, Lianghong; Ding, Duo; Pan, David Z; Gill, Douglas M; Jiang, Wei

    2011-08-01

    A parallel-coupled dual racetrack silicon micro-resonator structure is proposed and analyzed for M-ary quadrature amplitude modulation. The over-coupled, critically coupled, and under-coupled scenarios are systematically studied. Simulations indicate that only the over-coupled structures can generate arbitrary M-ary quadrature signals. Analytic study shows that the large dynamic range of amplitude and phase of a modulated over-coupled structure stems from the strong cross-coupling between two resonators, which can be understood through a delicate balance between the direct sum and the "interaction" terms. Potential asymmetries in the coupling constants and quality factors of the resonators are systematically studied. Compensations for these asymmetries by phase adjustment are shown feasible.

  14. Quantitative security evaluation of optical encryption using hybrid phase- and amplitude-modulated keys.

    PubMed

    Sarkadi, Tamás; Koppa, Pál

    2012-02-20

    In the increasing number of system approaches published in the field of optical encryption, the security level of the system is evaluated by qualitative and empirical methods. To quantify the security of the optical system, we propose to use the equivalent of the key length routinely used in algorithmic encryption. We provide a calculation method of the number of independent keys and deduce the binary key length for optical data encryption. We then investigate and optimize the key length of the combined phase- and amplitude-modulated key encryption in the holographic storage environment, which is one of the promising solutions for the security enhancement of single- and double-random phase-encoding encryption and storage systems. We show that a substantial growth of the key length can be achieved by optimized phase and amplitude modulation compared to phase-only encryption. We also provide experimental confirmation of the model results.

  15. Propagation properties of apertured laser beams with amplitude modulations and phase fluctuations through atmospheric turbulence

    NASA Astrophysics Data System (ADS)

    Ji, X.; Li, X.

    2011-07-01

    The propagation properties of apertured laser beams with amplitude modulations (AMs) and phase fluctuations (PFs) through atmospheric turbulence are studied in detail both analytically and numerically. The analytical expressions for the average intensity, power in the bucket ( PIB) and Strehl ratio ( S R ) of apertured laser beams with AMs and PFs propagating through atmospheric turbulence are derived. It is found that the worse the phase fluctuation and the higher the amplitude modulation are, the less laser beams are affected by turbulence. Furthermore, apertured Gaussian beams are more sensitive to turbulence than apertured laser beams with AMs and PFs. The average intensity of apertured laser beams with AMs and PFs may be even larger than that of apertured Gaussian beams due to turbulence. In particular, the influence of turbulence on the average maximum intensity of apertured laser beams with PFs and AMs may become serious if an unsuitable truncated parameter is chosen, which should be avoided in practice.

  16. Improving the performance of bright quantum dot single photon sources using temporal filtering via amplitude modulation

    PubMed Central

    Ates, Serkan; Agha, Imad; Gulinatti, Angelo; Rech, Ivan; Badolato, Antonio; Srinivasan, Kartik

    2013-01-01

    Single epitaxially-grown semiconductor quantum dots have great potential as single photon sources for photonic quantum technologies, though in practice devices often exhibit nonideal behavior. Here, we demonstrate that amplitude modulation can improve the performance of quantum-dot-based sources. Starting with a bright source consisting of a single quantum dot in a fiber-coupled microdisk cavity, we use synchronized amplitude modulation to temporally filter the emitted light. We observe that the single photon purity, temporal overlap between successive emission events, and indistinguishability can be greatly improved with this technique. As this method can be applied to any triggered single photon source, independent of geometry and after device fabrication, it is a flexible approach to improve the performance of systems based on single solid-state quantum emitters, which often suffer from excess dephasing and multi-photon background emission. PMID:23466520

  17. Velocity-Field Measurements of an Axisymmetric Separated Flow Subjected to Amplitude-Modulated Excitation

    NASA Technical Reports Server (NTRS)

    Trosin, Barry James

    2007-01-01

    Active flow control was applied at the point of separation of an axisymmetric, backward-facing-step flow. The control was implemented by employing a Helmholtz resonator that was externally driven by an amplitude-modulated, acoustic disturbance from a speaker located upstream of the wind tunnel. The velocity field of the separating/reattaching flow region downstream of the step was characterized using hotwire velocity measurements with and without flow control. Conventional statistics of the data reveal that the separating/reattaching flow is affected by the imposed forcing. Triple decomposition along with conditional averaging was used to distinguish periodic disturbances from random turbulence in the fluctuating velocity component. A significant outcome of the present study is that it demonstrates that amplitude-modulated forcing of the separated flow alters the flow in the same manner as the more conventional method of periodic excitation.

  18. Phase and Amplitude Modulation Methods for Nonlinear Ultrasound Imaging With CMUTs.

    PubMed

    Satir, Sarp; Degertekin, F Levent

    2016-08-01

    Conventional amplitude and phase modulated pulse sequences for selective imaging of nonlinear tissue and ultrasound contrast agents are designed for piezoelectric transducers that behave linearly. Inherent nonlinearity of capacitive micromachined ultrasonic transducers (CMUTs), especially during large-signal operation, renders these methods inapplicable. In this paper, we present different pulse sequences for nonlinear imaging that are valid for small- and large-signal CMUT operations. For small-signal operation, two-pulse amplitude and phase modulation methods for microbubble and tissue harmonic imaging are presented, where CMUT nonlinearity is compensated via subharmonic excitation. In the large-signal regime, using a nonlinear model, we first show that there is a simple linear relationship between the phases of each harmonic distortion component generated and the input drive signal. Based on this observation, we demonstrate a pulse sequence using N+1 consecutive phase modulated transmit events to extract N harmonics of the nonlinear contrast agent echo content uncorrupted by CMUT nonlinearity. The proposed methods assume no apriori information about the transducer and, therefore, are applicable to any CMUT. The phase modulation method is also valid for piezoelectric transducers and systems with nonlinearities described by Taylor series where the same phase relationship between the input signal and the harmonic content is valid. The proof of principle experiments using a commercial contrast agent validates the phase modulated pulse sequences for CMUTs, operating in a highly nonlinear collapse-snapback mode and for piezoelectric transducers.

  19. Amplitude modulation of vorticity and dissipation by large-scale motions in turbulent channel flow

    NASA Astrophysics Data System (ADS)

    Yao, Yi-Chen; Deng, Bing-Qing; Huang, Wei-Xi; Xu, Chun-Xiao; Turbulence Research Team

    2015-11-01

    Amplitude modulation of both vorticity and dissipation by large-scale out-layer structures is studied using the DNS data of turbulent channel flow at Reynolds numbers up to Reτ = 1000. Carrier and modulated signals are scale decomposed in both streamwise and spanwise directions, and small-scale envelop is extracted by Hilbert transformation. Two-point amplitude modulation correlation is calculated at a range of wall-normal locations. The modulation strength on the vorticity and the dissipation rate of turbulent kinetic energy is found to be much stronger than on all the three components of velocity fluctuations. Distinct peak value of correlation is observed when large-scale signals are extracted from center log region and the corresponding modulated information from below y+ = 10. Also the strength of this peak value increases with Reynolds number, thus supporting the top-down mechanism that the near-wall layer is becoming more influenced by the large-scale structures which gradually emerge as Reynolds number increases. The work was supported by National Natural Science Foundation of China (11490551, 11132005, 11322221).

  20. One-dimensional photonic crystals with an amplitude-modulated dielectric constant in the unit cell.

    PubMed

    Carretero, Luis; Ulibarrena, Manuel; Blaya, Salvador; Fimia, Antonio

    2004-05-10

    Photonic band structures of one-dimensional photonic crystals with an amplitude-modulated dielectric constant in the unit cell were studied. With this structure two bandgaps in the visible and one in the IR region were predicted. Experimental measurements of the two photonic bandgaps in the visible spectrum were made in a photonic crystal recorded in a holographic emulsion. Good agreement between experimental and theoretical results was obtained.

  1. Modulation of Muscle Tone and Sympathovagal Balance in Cervical Dystonia Using Percutaneous Stimulation of the Auricular Vagus Nerve.

    PubMed

    Kampusch, Stefan; Kaniusas, Eugenijus; Széles, Jozsef C

    2015-10-01

    Primary cervical dystonia is characterized by abnormal, involuntary, and sustained contractions of cervical muscles. Current ways of treatment focus on alleviating symptomatic muscle activity. Besides pharmacological treatment, in severe cases patients may receive neuromodulative intervention such as deep brain stimulation. However, these (highly invasive) methods have some major drawbacks. For the first time, percutaneous auricular vagus nerve stimulation (pVNS) was applied in a single case of primary cervical dystonia. Auricular vagus nerve stimulation was already shown to modulate the (autonomous) sympathovagal balance of the body and proved to be an effective treatment in acute and chronic pain, epilepsy, as well as major depression. pVNS effects on cervical dystonia may be hypothesized to rely upon: (i) the alteration of sensory input to the brain, which affects structures involved in the genesis of motoric and nonmotoric dystonic symptoms; and (ii) the alteration of the sympathovagal balance with a sustained impact on involuntary movement control, pain, quality of sleep, and general well-being. The presented data provide experimental evidence that pVNS may be a new alternative and minimally invasive treatment in primary cervical dystonia. One female patient (age 50 years) suffering from therapy refractory cervical dystonia was treated with pVNS over 20 months. Significant improvement in muscle pain, dystonic symptoms, and autonomic regulation as well as a subjective improvement in motility, sleep, and mood were achieved. A subjective improvement in pain recorded by visual analog scale ratings (0-10) was observed from 5.42 to 3.92 (medians). Muscle tone of the mainly affected left and right trapezius muscle in supine position was favorably reduced by about 96%. Significant reduction of muscle tone was also achieved in sitting and standing positions of the patient. Habituation to stimulation leading to reduced stimulation efficiency was observed and

  2. Fuzzy control with amplitude/pulse-width modulation of nerve electrical stimulation for muscle force control.

    PubMed

    Lin, C-C K; Liu, W-C; Chan, C-C; Ju, M-S

    2012-04-01

    The main goal of this study was to study the performance of fuzzy logic controllers combined with simplified hybrid amplitude/pulse-width (AM/PW) modulation to regulate muscle force via nerve electrical stimulation. The recruitment curves with AM/PW and AM modulations were constructed for the calf muscles of rabbits. Integrated with the modulation methods, a proportional-integral-derivative (PID) and three fuzzy logic controllers were designed and applied for the electrical stimulation of tibial nerves to control the ankle torque under isometric conditions. The performance of the two modulation methods combined with the four controllers was compared when the ankle was fixed at three positions for both in vivo experiments and model simulations using a nonlinear muscle model. For the animal experiments, AM/PW modulation performed better than AM modulation alone. The fuzzy PI controller performed marginally better and was resistant to external noises, though it tended to have a larger overshoot. The performance of the controllers had a similar trend in the three different joint positions, and the simulation results with the nonlinear model matched the experimental results well. In conclusion, AM/PW modulation improved controller performance, while the contribution of fuzzy logic was only marginal.

  3. Fast terahertz optoelectronic amplitude modulator based on plasmonic metamaterial antenna arrays and graphene

    NASA Astrophysics Data System (ADS)

    Jessop, David S.; Sol, Christian W. O.; Xiao, Long; Kindness, Stephen J.; Braeuninger-Weimer, Philipp; Lin, Hungyen; Griffiths, Jonathan P.; Ren, Yuan; Kamboj, Varun S.; Hofmann, Stephan; Zeitler, J. Axel; Beere, Harvey E.; Ritchie, David A.; Degl'Innocenti, Riccardo

    2016-02-01

    The growing interest in terahertz (THz) technologies in recent years has seen a wide range of demonstrated applications, spanning from security screening, non-destructive testing, gas sensing, to biomedical imaging and communication. Communication with THz radiation offers the advantage of much higher bandwidths than currently available, in an unallocated spectrum. For this to be realized, optoelectronic components capable of manipulating THz radiation at high speeds and high signal-to-noise ratios must be developed. In this work we demonstrate a room temperature frequency dependent optoelectronic amplitude modulator working at around 2 THz, which incorporates graphene as the tuning medium. The architecture of the modulator is an array of plasmonic dipole antennas surrounded by graphene. By electrostatically doping the graphene via a back gate electrode, the reflection characteristics of the modulator are modified. The modulator is electrically characterized to determine the graphene conductivity and optically characterization, by THz time-domain spectroscopy and a single-mode 2 THz quantum cascade laser, to determine the optical modulation depth and cut-off frequency. A maximum optical modulation depth of ~ 30% is estimated and is found to be most (least) sensitive when the electrical modulation is centered at the point of maximum (minimum) differential resistivity of the graphene. A 3 dB cut-off frequency > 5 MHz, limited only by the area of graphene on the device, is reported. The results agree well with theoretical calculations and numerical simulations, and demonstrate the first steps towards ultra-fast, graphene based THz optoelectronic devices.

  4. Automatic IQ Imbalance Compensation Technique for Quadrature Modulator by Single-Tone Testing

    NASA Astrophysics Data System (ADS)

    Kim, Minseok; Konishi, Yohei; Takada, Jun-Ichi; Gao, Boxin

    This letter proposes an automatic IQ imbalance compensation technique for quadrature modulators by means of spectrum measurement of RF signal using a spectrum analyzer. The analyzer feeds back only magnitude information of the frequency spectrum of the signal. To realize IQ imbalance compensation, the conventional method of steepest descent is modified; the descent direction is empirically determined and a variable step-size is introduced for accelerating convergence. The experimental results for a four-channel transmitter operating at 11GHz are presented for verification.

  5. Collinear laser spectroscopy of francium using online rubidium vapor neutralization and amplitude modulated lasers.

    PubMed

    Sell, J F; Gulyuz, K; Sprouse, G D

    2009-12-01

    Performing collinear laser spectroscopy on low intensity radioactive beams requires sensitive detection techniques. We explain our apparatus to detect atomic resonances in neutralized (208-210)Fr ion beams at beam energies of 5 keV and intensities of 10(5) s(-1). Efficient neutralization (> or = 80%) is accomplished by passing the beam through a dense Rb vapor. Increased detection efficiency is achieved by amplitude modulating the exciting laser to decrease the scattered light background, allowing fluorescence detection only when the laser is near its minimum in the modulation cycle. Using this technique in a collinear geometry we achieve a background reduction by a factor of 180 and a signal-to-noise increase of 2.2, with the lifetime of the atomic state playing a role in the efficiency of this process. Such laser modulation will also produce sidebands on the atomic spectra which we illustrate.

  6. Collinear laser spectroscopy of francium using online rubidium vapor neutralization and amplitude modulated lasers

    NASA Astrophysics Data System (ADS)

    Sell, J. F.; Gulyuz, K.; Sprouse, G. D.

    2009-12-01

    Performing collinear laser spectroscopy on low intensity radioactive beams requires sensitive detection techniques. We explain our apparatus to detect atomic resonances in neutralized F208-210r ion beams at beam energies of 5 keV and intensities of 105 s-1. Efficient neutralization (≥80%) is accomplished by passing the beam through a dense Rb vapor. Increased detection efficiency is achieved by amplitude modulating the exciting laser to decrease the scattered light background, allowing fluorescence detection only when the laser is near its minimum in the modulation cycle. Using this technique in a collinear geometry we achieve a background reduction by a factor of 180 and a signal-to-noise increase of 2.2, with the lifetime of the atomic state playing a role in the efficiency of this process. Such laser modulation will also produce sidebands on the atomic spectra which we illustrate.

  7. Collinear laser spectroscopy of francium using online rubidium vapor neutralization and amplitude modulated lasers

    SciTech Connect

    Sell, J. F.; Gulyuz, K.; Sprouse, G. D.

    2009-12-15

    Performing collinear laser spectroscopy on low intensity radioactive beams requires sensitive detection techniques. We explain our apparatus to detect atomic resonances in neutralized {sup 208-210}Fr ion beams at beam energies of 5 keV and intensities of 10{sup 5} s{sup -1}. Efficient neutralization ({>=}80%) is accomplished by passing the beam through a dense Rb vapor. Increased detection efficiency is achieved by amplitude modulating the exciting laser to decrease the scattered light background, allowing fluorescence detection only when the laser is near its minimum in the modulation cycle. Using this technique in a collinear geometry we achieve a background reduction by a factor of 180 and a signal-to-noise increase of 2.2, with the lifetime of the atomic state playing a role in the efficiency of this process. Such laser modulation will also produce sidebands on the atomic spectra which we illustrate.

  8. Behavioral limits of auditory temporal resolution in the rat: amplitude modulation and duration discrimination.

    PubMed

    Kelly, Jack B; Cooke, James E; Gilbride, Patrick C; Mitchell, Craig; Zhang, Huiming

    2006-05-01

    Thresholds for detecting the presence of amplitude modulation in a noise carrier were determined for rats using conditioned avoidance procedures. There was a progressive increase in threshold with modulation rates between 5 Hz and 2 kHz. Further tests were conducted to determine difference thresholds for detecting an increase in modulation rate for standard rates of 10, 50, and 100 Hz. The size of the difference threshold increased progressively as the standard rate increased. In addition, thresholds for detecting an increase in the duration of a noise burst were determined for various standard durations. The difference thresholds were constant for values between 10 and 50 ms but increased progressively, with standard durations between 0.1 and 1.0 s.

  9. High Capacity Phase/Amplitude Modulated Optical Communication Systems and Nonlinear Inter-Channel Impairments

    NASA Astrophysics Data System (ADS)

    Tavassoli, Vahid

    This thesis studies and mathematically models nonlinear interactions among channels of modern high bit rate (amplitude/) phase modulated optical systems. First, phase modulated analogue systems are studied and a differential receiving method is suggested with experimental validation. The main focus of the rest of the thesis is on digital advanced modulation format systems. Cross-talk due to fiber Kerr nonlinearity in two-format hybrid systems as well as 16-QAM systems is mathematically modelled and verified by simulation for different system parameters. A comparative study of differential receivers and coherent receivers is also given for hybrid systems. The model is based on mathematically proven assumptions and provides an intuitive analytical understanding of nonlinear cross-talk in such systems.

  10. Amplitude modulation of hydromagnetic waves and associated rogue waves in magnetoplasmas.

    PubMed

    Sabry, R; Moslem, W M; Shukla, P K

    2012-09-01

    It is shown that the dynamics of amplitude-modulated compressional dispersive Alfvénic (CDA) waves in a collisional megnetoplasma is governed by a complex Ginzburg-Landau (CGL) equation. The nonlinear dispersion relation for the modulational instability of the CDA waves is derived and investigated numerically. It is found that the growth rate of the modulational instability decreases (increases) with the increase of the normalized electron-ion collision frequency α (the plasma β). The modulational instability criterion for the CGL equation is defined precisely and investigated numerically. The region of the modulational instability becomes narrower with the increase of α and β, indicating that the system dissipates the wave energy by collisions, and a stable CDA wave envelope packet in the form of a hole will be a dominant localized pulse. For a collisionless plasma, i.e., α=0, the CGL equation reduces to the standard nonlinear Schrödinger (NLS) equation. The latter is used to investigate the modulational (in)stability region for the CDA waves in a collisionless magnetoplasma. It is shown that, within unstable regions, a random set of nonlinearly interacting CDA perturbations leads to the formation of CDA rogue waves. In order to demonstrate that the characteristics of the CDA rogue waves are influenced by the plasma β, the relevant numerical analysis of the appropriate nonlinear solution of the NLS equation is presented. The application of our investigation to space and laboratory magnetoplasmas is discussed.

  11. Exposure to extinction-associated contextual tone during slow-wave sleep and wakefulness differentially modulates fear expression.

    PubMed

    Ai, Si-Zhi; Chen, Jie; Liu, Jian-Feng; He, Jia; Xue, Yan-Xue; Bao, Yan-Ping; Han, Fang; Tang, Xiang-Dong; Lu, Lin; Shi, Jie

    2015-09-01

    Recent research has used context cues (odor or auditory cues) to target memories during sleep and has demonstrated that they can enhance declarative and procedural memories. However, the effects of external cues re-presented during sleep on emotional memory are still not fully understood. In the present study, we conducted a Pavlovian fear conditioning/extinction paradigm and examined the effects of re-exposure to extinction memory associated contextual tones during slow-wave sleep (SWS) and wakefulness on fear expression. The participants underwent fear conditioning on the first day, during which colored squares served as the conditioned stimulus (CS) and a mild shock served as the unconditioned stimulus (US). The next day, they underwent extinction, during which the CSs were presented without the US but accompanied by a contextual tone (pink noise). Immediately after extinction, the participants were required to take a nap or remain awake and randomly assigned to six groups. Four of the groups were separately exposed to the associated tone (i.e. SWS-Tone group and Wake-Tone group) or an irrelevant tone (control tone, CtrT) (i.e. SWS-CtrT group and Wake-CtrT group), while the other two groups were not (i.e. SWS-No Tone group and Wake-No Tone group). Subsequently, the conditioned responses to the CSs were tested to evaluate the fear expression. All of the participants included in the final analysis showed successful levels of fear conditioning and extinction. During the recall test, the fear responses were significantly higher in the SWS-Tone group than that in the SWS-No Tone group or the SWS-CtrT group, while the Wake-Tone group exhibited more attenuated fear responses than either the Wake-No Tone group or Wake-CtrT group. Otherwise, re-exposure to auditory tones during SWS did not affect sleep profiles. These results suggest that distinct conditions during which re-exposure to an extinction memory associated contextual cue contributes to differential effects on

  12. Tip radius preservation for high resolution imaging in amplitude modulation atomic force microscopy

    SciTech Connect

    Ramos, Jorge R.

    2014-07-28

    The acquisition of high resolution images in atomic force microscopy (AFM) is correlated to the cantilever's tip shape, size, and imaging conditions. In this work, relative tip wear is quantified based on the evolution of a direct experimental observable in amplitude modulation atomic force microscopy, i.e., the critical amplitude. We further show that the scanning parameters required to guarantee a maximum compressive stress that is lower than the yield/fracture stress of the tip can be estimated via experimental observables. In both counts, the optimized parameters to acquire AFM images while preserving the tip are discussed. The results are validated experimentally by employing IgG antibodies as a model system.

  13. Subharmonic excitation in amplitude modulation atomic force microscopy in the presence of adsorbed water layers

    SciTech Connect

    Santos, Sergio; Barcons, Victor; Verdaguer, Albert; Chiesa, Matteo

    2011-12-01

    In ambient conditions, nanometric water layers form on hydrophilic surfaces covering them and significantly changing their properties and characteristics. Here we report the excitation of subharmonics in amplitude modulation atomic force microscopy induced by intermittent water contacts. Our simulations show that there are several regimes of operation depending on whether there is perturbation of water layers. Single period orbitals, where subharmonics are never induced, follow only when the tip is either in permanent contact with the water layers or in pure noncontact where the water layers are never perturbed. When the water layers are perturbed subharmonic excitation increases with decreasing oscillation amplitude. We derive an analytical expression which establishes whether water perturbations compromise harmonic motion and show that the predictions are in agreement with numerical simulations. Empirical validation of our interpretation is provided by the observation of a range of values for apparent height of water layers when subharmonic excitation is predicted.

  14. An integrated Mach-Zehnder modulator bias controller based on eye-amplitude monitoring

    NASA Astrophysics Data System (ADS)

    Kim, Min-Hyeong; Jung, Hyun-Yong; Zimmermann, Lars; Choi, Woo-Young

    2016-03-01

    A novel integrated Mach-Zehnder modulator (MZM) bias controller based on eye-amplitude monitoring is demonstrated in IHP's 0.25-μm BiCMOS technology. The bias controller monitors the MZM output light, automatically moves the MZM bias voltage to the optimal value that produces the largest eye amplitude, and maintains it there even if the MZM transfer characteristics change due to thermal drift. The controller is based on the feedback loop consisting of Si photodetector, trans-impedance amplifier, rectifier, square amplifier, track-and-hold circuit, comparator, polarity changer, and charge-pump, all of which are monolithically integrated. The area of the controller is 0.083-mm2 and it consumes 92.5-mW. Our bias controller shows successful operation for a commercially-available 850-nm LiNbO3 MZM modulated with 3-Gbps PRBS data by maintaining a very clean eye for at least 30 minutes. Without the controller, the eye for the same MZM modulation becomes completely closed due to thermal drift. The data rate is limited by the Si PD integrated in the controller not by the controller architecture. Since our controller is based on the Si BiCMOS technology which can also provide integrated Si photonics devices on the same Si, it has a great potential for realizing a Si MZM with an integrated bias controller, which should fully demonstrate the advantage of electronic-photonic integrated circuit technology.

  15. Responses of neurons in chinchilla auditory cortex to frequency-modulated tones.

    PubMed

    Brown, Trecia A; Harrison, Robert V

    2009-04-01

    Frequency-modulated (FM) stimuli have been used to explore the behavior of neurons in the auditory cortex of several animal models; however, the properties of FM-sensitive auditory cortical neurons in the chinchilla are still unknown. Single-unit responses to FM stimulation were obtained from the auditory cortex of anesthetized adult chinchillas (Chinchilla laniger). Upward and downward linear FM sweeps spanning frequencies from 0.1 to 20 kHz were presented at speeds of 0.05 to 0.82 kHz/ms. Results indicated that >90% of sampled neurons were responsive to FM sweeps. The population preference was for upward FM sweeps and for medium to fast speeds (> or =0.3 kHz/ms). Few units (3%) were selective for downward FM sweeps, whereas <22% of units preferred slow speeds (< or =0.1 kHz/ms). Velocity preference and direction sensitivity were positively correlated for upward sweeps only (r = 0.40, P = 0.0021, t-test). Three types of firing rate patterns were observed in the FM response peristimulus time histograms: a single peak at sweep onset/offset ("onset") and a single peak ("late") or multiple peaks ("burst") during the sweep. "Late" units expressed the highest mean values for direction sensitivity and speed selectivity; "onset" units were selective only for direction and "burst" units were not selective for either direction or speed. The robust responsiveness of these neurons to FM sweeps suggests a functional role for FM detection such as the identification of FM sweeps present in vocalizations of other organisms within the chinchilla's natural environment.

  16. A novel oscillation control for MEMS vibratory gyroscopes using a modified electromechanical amplitude modulation technique

    NASA Astrophysics Data System (ADS)

    Ma, Wei; Lin, Yiyu; Liu, Siqi; Zheng, Xudong; Jin, Zhonghe

    2017-02-01

    This paper reports a novel oscillation control algorithm for MEMS vibratory gyroscopes using a modified electromechanical amplitude modulation (MEAM) technique, which enhances the robustness against the frequency variation of the driving mode, compared to the conventional EAM (CEAM) scheme. In this approach, the carrier voltage exerted on the proof mass is frequency-modulated by the drive resonant frequency. Accordingly, the pick-up signal from the interface circuit involves a constant-frequency component that contains the amplitude and phase information of the vibration displacement. In other words, this informational detection signal is independent of the mechanical resonant frequency, which varies due to different batches, imprecise micro-fabrication and changing environmental temperature. In this paper, the automatic gain control loop together with the phase-locked loop are simultaneously analyzed using the averaging method and Routh-Hurwitz criterion, deriving the stability condition and the parameter optimization rules of the transient response. Then, a simulation model based on the real system is set up to evaluate the control algorithm. Further, the proposed MEAM method is tested using a field-programmable-gate-array based digital platform on a capacitive vibratory gyroscope. By optimizing the control parameters, the transient response of the drive amplitude reveals a settling time of 45.2 ms without overshoot, according well with the theoretical prediction and simulation results. The first measurement results show that the amplitude variance of the drive displacement is 12 ppm in an hour while the phase standard deviation is as low as 0.0004°. The mode-split gyroscope operating under atmospheric pressure demonstrates an outstanding performance. By virtue of the proposed MEAM method, the bias instability and angle random walk are measured to be 0.9° h-1 (improved by 2.4 times compared to the CEAM method) and 0.068° (√h)-1 (improved by 1.4 times

  17. Construction of dark spherical spot array using an amplitude-modulated radially polarized beam

    NASA Astrophysics Data System (ADS)

    Yu, Yanzhong; Li, Meng; Long, Li; Shangguan, Hongyuan

    2016-10-01

    A simple and flexible method is presented for constructing a dark spherical spot array with the prescribed spot number and interval along the optical axis. Through reversing the field radiated from a uniform magnetic current line source in combination with an electric current line source having a cosine-squared taper, the desired focal field can be realized in the 4Pi focusing system. The required incident field on the pupil plane can be obtained by solving the inverse problem and is found to be an amplitude-modulated radially polarized beam.

  18. Independent modulations of the transmission amplitudes and phases by using Huygens metasurfaces

    PubMed Central

    Wan, Xiang; Jia, Sheng Li; Cui, Tie Jun; Zhao, Yong Jiu

    2016-01-01

    We propose ultrathin Huygens metasurfaces to control transmission amplitudes and phases of electromagnetic waves independently, in which each unit cell is comprised of an electric dipole and a magnetic dipole. By altering the electric and magnetic responses of unit cells, arbitrary complex transmission coefficients with modulus values smaller than 0.85 are obtained. Two Huygens metasurfaces capable of controlling the diffraction orders are designed and fabricated by modulating the distributions of the complex transmission coefficients. More complicated functions such as holographic imaging can also be accomplished by using the proposed Huygens metasurfaces. PMID:27197759

  19. Detection of amplitude modulation with squeezed light for sensitivity beyond the shot-noise limit

    NASA Astrophysics Data System (ADS)

    Xiao, Min; Wu, Ling-An; Kimble, H. J.

    1988-06-01

    An improvement in precision beyond the limit set by the vacuum-state or zero-point fluctuations of the electromagnetic field is reported for the detection of amplitude modulation encoded on a weak signal beam. The improvement is achieved by employing the squeezed light from an optical parametric oscillator to reduce the level of fluctuations below the shot-noise limit. An increase in signal-to-noise ratio of 2.5 dB relative to the shot-noise limit is demonstrated.

  20. Quantum quadrature amplitude modulation system and its applicability to coherent-state quantum cryptography

    NASA Astrophysics Data System (ADS)

    Kato, Kentaro; Hirota, Osamu

    2005-08-01

    The quadrature amplitude modulation (QAM) signal of coherent state of light is applied to the quantum stream cipher by Y-00 protocol. We first discuss on the performance of the square-root measurement (SRM) for the QAM signals in comparison with the optimum receiver. It is shown that the quantum stream cipher with the QAM signals is designed by using the SRM, taking account of the ciphertext-only attack and the known/chosen plain attack. Furthermore, the modification of the quantum stream cipher with the QAM signals is considered.

  1. Generation of an axially super-resolved quasi-spherical focal spot using an amplitude-modulated radially polarized beam.

    PubMed

    Lin, Han; Jia, Baohua; Gu, Min

    2011-07-01

    An axially super-resolved quasi-spherical focal spot can be generated by focusing an amplitude-modulated radially polarized beam through a high numerical aperture objective. A method based on the unique depolarization properties of a circular focus is proposed to design the amplitude modulation. The generated focal spot shows a ratio of x:y:z=1:1:1.48 for the normalized FWHM in three dimensions, compared to that of x:y:z=1:0.74:1.72 under linear polarization (in the x direction) illumination. Moreover, the focusable light efficiency of the designed amplitude-modulated beam is 65%, which is more than 3 times higher than the optimized case under linear polarization and thus make the amplitude-modulated radial polarization beam more suitable for a wide range of applications.

  2. Sensitive detection of vortex-core resonance using amplitude-modulated magnetic field

    PubMed Central

    Cui, Xiaomin; Hu, Shaojie; Hidegara, Makoto; Yakata, Satoshi; Kimura, Takashi

    2015-01-01

    Understanding and manipulating the dynamic properties of the magnetic vortices stabilized in patterned ferromagnetic structures are of great interest owing to the superior resonant features with the high thermal stability and their flexible tunability. So far, numerous methods for investigating the dynamic properties of the magnetic vortex have been proposed and demonstrated. However, those techniques have some regulations such as spatial resolution, experimental facility and sensitivity. Here, we develop a simple and sensitive method for investigating the vortex-core dynamics by using the electrically separated excitation and detection circuits. We demonstrate that the resonant oscillation of the magnetic vortex induced by the amplitude- modulated alternating-sign magnetic field is efficiently picked up by the lock-in detection with the modulated frequency. By extending this method, we also investigate the size dependence and the influence of the magneto-static interaction in the resonant property of the magnetic vortex. PMID:26647840

  3. Nyquist 4-ary pulse amplitude modulation scheme based on electrical Nyquist pulse shaping and fiber Bragg grating filter

    NASA Astrophysics Data System (ADS)

    Liu, Na; Chen, Xue; Ju, Cheng; Zhang, Qi; Wang, Huitao

    2015-04-01

    Intensity modulation and direct detection signal are sensitive to power fading and nonlinear intersymbol interference (ISI) induced by modulator chirp, fiber dispersion, and square-law photo-detection. We propose and experimentally demonstrate a Nyquist 4-ary pulse amplitude modulation and direct detection scheme relying on pulse-shaping with an electrical filter and optical equalization with a vestigial-sideband (VSB) filter in the transmitter. The power fading could be eliminated by using the VSB filter. Compared with conventional 4-ary pulse amplitude modulation, the Nyquist signal has a stronger resistance to nonlinear ISI.

  4. General analytic solution for far-field phase and amplitude control, with a phase-only spatial light modulator.

    PubMed

    Liu, Lewis Z; O'Keeffe, Kevin; Lloyd, David T; Hooker, Simon M

    2014-04-01

    We present an analytical solution for the phase introduced by a phase-only spatial light modulator to generate far-field phase and amplitude distributions within a domain of interest. The solution is demonstrated experimentally and shown to enable excellent control of the far-field amplitude and phase.

  5. Generation of a widely spaced optical frequency comb using an amplitude modulator pair

    NASA Astrophysics Data System (ADS)

    Gunning, Fatima C. G.; Ellis, Andrew D.

    2005-06-01

    Multi-wavelength sources are required for wavelength division multiplexed (WDM) optical communication systems, and typically a bank of DFB lasers is used. However, large costs are involved to provide wavelength selected sources and high precision wavelength lockers. Optical comb generation is attractive solution, minimizing the component count and improving wavelength stability. In addition, comb generation offers the potential for new WDM architectures, such as coherent WDM, as it preserves the phase relation between the generated channels. Complex comb generation systems have been introduced in the past, using fibre ring lasers [1] or non-linear effects within long fibres [2]. More recently, simpler set-ups were proposed, including hybrid amplitude-phase modulation schemes [3-5]. However, the narrow line spacing of these systems, typically 17 GHz, restricts their use to bit rates up to 10 Gbit/s. In this paper, we propose and demonstrate a simple method of comb generation that is suitable for bit rates up to 42.667 Gbit/s. The comb generator was composed of two Mach-Zehnder modulators (MZM) in series, each being driven with a sinusoidal wave at 42.667 GHz with a well-defined phase relationship. As a result, 7 comb lines separated by 42.667 GHz were generated from a single source, when amplitude up to 2.2 Vp was applied to the modulators, giving flatness better than 1 dB. By passively multiplexing 8 source lasers with the comb generator and minimising inter-modulator dispersion, it was possible to achieve a multi-wavelength transmitter with 56 channels, with flatness better than 1.2 dB across 20 nm (2.4 THz).

  6. Reflection-type spatial amplitude modulation of visible light based on a sub-wavelength plasmonic absorber.

    PubMed

    Hwang, Chi-Young; Yi, Yoonsik; Choi, Choon-Gi

    2016-03-01

    We present a method for reflection-type spatial amplitude modulation using a sub-wavelength plasmonic absorber structure that can operate in the visible region. We utilize a pixelated array of absorbing elements based on a two-dimensional sub-wavelength metal grating, and the reflectance of each pixel is controlled by simple structural modification. For the purpose of validation, numerical simulations were performed on an amplitude modulation hologram fabricated using our method.

  7. Reconstructing 3-D maps of the local viscoelastic properties using a finite-amplitude modulated radiation force.

    PubMed

    Giannoula, Alexia; Cobbold, Richard; Bezerianos, Anastasios

    2014-02-01

    A modulated acoustic radiation force, produced by two confocal tone-burst ultrasound beams of slightly different frequencies (i.e. 2.0 MHz ± Δf/2, where Δf is the difference frequency), can be used to remotely generate modulated low-frequency (Δf ≤ 500 Hz) shear waves in attenuating media. By appropriately selecting the duration of the two beams, the energy of the generated shear waves can be concentrated around the difference frequency (i.e., Δf ± Δf/2). In this manner, neither their amplitude nor their phase information is distorted by frequency-dependent effects, thereby, enabling a more accurate reconstruction of the viscoelastic properties. Assuming a Voigt viscoelastic model, this paper describes the use of a finite-element-method model to simulate three-dimensional (3-D) shear-wave propagation in viscoelastic media containing a spherical inclusion. Nonlinear propagation is assumed for the two ultrasound beams, so that higher harmonics are developed in the force and shear spectrum. Finally, an inverse reconstruction algorithm is used to extract 3-D maps of the local shear modulus and viscosity from the simulated shear-displacement fields based on the fundamental and second-harmonic component. The quality of the reconstructed maps is evaluated using the contrast between the inclusion and the background and the contrast-to-noise ratio (CNR). It is shown that the shear modulus can be accurately reconstructed based on the fundamental component, such that the observed contrast deviates from the true contrast by a root-mean-square-error (RMSE) of only 0.38 and the CNR is greater than 30 dB. If the second-harmonic component is used, the RMSE becomes 1.54 and the corresponding CNR decreases by approximately 10-15 dB. The reconstructed shear viscosity maps based on the second harmonic are shown to be of higher quality than those based on the fundamental. The effects of noise are also investigated and a fusion operation between the two spectral components is

  8. Improvement of the Spatial Amplitude Isotropy of a ^4He Magnetometer Using a Modulated Pumping Beam

    NASA Astrophysics Data System (ADS)

    Chéron, B.; Gilles, H.; Hamel, J.; Moreau, O.; Noël, E.

    1997-08-01

    Optically pumped magnetometers are scalar magnetometers. Contrary to vectoriel magnetometers, they measure the total magnetic field whatever the direction of the sensor. However, for some orientations of the magnetometer with respect to the magnetic field direction, the resonant signal vanishes and the measurement is impossible. In this paper we present a simple solution to reduce the amplitude spatial anisotropy and apply it to a ^4He magnetometer developed in our Laboratory. Les magnétomètres à pompage optique sont des magnétomètres scalaires. Contrairement aux magnétomètres vectoriels, ils mesurent le module du champ magnétique quelle que soit l'orientation du capteur dans l'espace. Cependant, pour certaines orientations du magnétomètre par rapport à la direction du champ à mesurer, l'amplitude du signal de résonance s'annule et la mesure devient impossible. Dans cet article, nous présentons une solution simple pour réduire l'anisotropie spatiale d'amplitude et nous l'appliquons à un magnétomètre à hélium-4 développé dans notre Laboratoire.

  9. Propagation of shear waves generated by a modulated finite amplitude radiation force in a viscoelastic medium.

    PubMed

    Giannoula, Alexia; Cobbold, Richard S C

    2009-03-01

    An effective way to generate localized narrowband low-frequency shear waves within tissue noninvasively, is by the modulated radiation force, resulting from the interference of two confocal quasi-CW ultrasound beams of slightly different frequencies. By using approximate viscoelastic Green's functions, investigations of the properties of the propagated shear-field component at the fundamental modulation frequency were previously reported by our group. However, high-amplitude source excitations may be needed to increase the signal-to-noise-ratio for shear-wave detection in tissue. This paper reports a study of the generation and propagation of dynamic radiation force components at harmonics of the modulation frequency for conditions that generally correspond to diagnostic safety standards. We describe the propagation characteristics of the resulting harmonic shear waves and discuss how they depend on the parameters of nonlinearity, focusing gain, and absorption. For conditions of high viscosity (believed to be characteristic of soft tissue) and higher modulation frequencies, the approximate shear wave Green's function is inappropriate. A more exact viscoelastic Green's function is derived in k-space, and using this, it is shown that the lowpass and dispersive effects, associated with a Voigt model of tissue, are more accurately represented. Finally, it is shown how the viscoelastic properties of the propagating medium can be estimated, based on several spectral components of the shearwave spectrum.

  10. Context-dependent modulation of cutaneous reflex amplitudes during forward and backward leg cycling.

    PubMed

    Zehr, E Paul; Hundza, Sandra R; Balter, Jaclyn E; Loadman, Pamela M

    2009-10-01

    We used amplitude modulation of cutaneous reflexes during leg cycling as a paradigm to investigate neural control mechanisms regulating forward (FWD) and backward (BWD) rhythmic limb movement. Our prediction was a simple reversal of reflex modulation during BWD leg cycling and context-dependent reflex modulation. Cutaneous reflexes were evoked by electrical stimulation delivered to the superficial peroneal (SP) and distal tibial (TIB) nerves at the ankle. EMG recordings were collected from muscles acting at the hip, knee, and ankle. Kinematic data were also collected at these joints. Cutaneous reflexes were analyzed according to the phase of movement in which they were evoked. When functional phases (i.e., flexion or extension) of cycling were matched between FWD and BWD, background EMG and reflex modulation patterns were generally similar. The reflex patterns when compared at similar functional phases presented as a simple reversal suggesting FWD and BWD cycling are regulated by similar neural mechanisms. The general reflex regulation of limb trajectory was maintained between cycling directions in accordance with the task requirements of the movement direction.

  11. Apoptosis induced by ultraviolet radiation is enhanced by amplitude modulated radiofrequency radiation in mutant yeast cells.

    PubMed

    Markkanen, Ari; Penttinen, Piia; Naarala, Jonne; Pelkonen, Jukka; Sihvonen, Ari-Pekka; Juutilainen, Jukka

    2004-02-01

    The aim of this study was to investigate whether radiofrequency (RF) electromagnetic field (EMF) exposure affects cell death processes of yeast cells. Saccharomyces cerevisiae yeast cells of the strains KFy417 (wild-type) and KFy437 (cdc48-mutant) were exposed to 900 or 872 MHz RF fields, with or without exposure to ultraviolet (UV) radiation, and incubated simultaneously with elevated temperature (+37 degrees C) to induce apoptosis in the cdc48-mutated strain. The RF exposure was carried out in a special waveguide exposure chamber where the temperature of the cell cultures can be precisely controlled. Apoptosis was analyzed using the annexin V-FITC method utilizing flow cytometry. Amplitude modulated (217 pulses per second) RF exposure significantly enhanced UV induced apoptosis in cdc48-mutated cells, but no effect was observed in cells exposed to unmodulated fields at identical time-average specfic absorption rates (SAR, 0.4 or 3.0 W/kg). The findings suggest that amplitude modulated RF fields, together with known damaging agents, can affect the cell death process in mutated yeast cells. Bioelectromagnetics 25:127-133, 2004.

  12. Amplitude-sensitive modulation thermography to measure moisture in building materials

    NASA Astrophysics Data System (ADS)

    Wild, Walter; Buescher, Konstantin A.; Wiggenhauser, Herbert

    1998-03-01

    There have been reports about moisture detection in building walls by reflective IR-thermography. Typically, only limited results could be obtained because of the emission coefficient variations, leaking radiation or inhomogeneous illumination of the object. In addition, the quantitative relation between remission spectra and the moisture has often been unclear. Reflectometry uses constant excitation illumination which is recorded by the IR camera. With the use of the 'lock-in-technology' a low frequency modulated signal of an IR radiation source is coupled with the thermo camera and a frequency and phase sensitive signal from the thermal images can be derived. The advantage is, that emission coefficient dependencies are eliminated and that leaking radiation does not have any influence on the measured signal. The selective water measurement is possible, because there is an interference filter mounted in front of the radiator which has its transmission maximum at the wavelength of an absorption band of water. The area investigated is therefore illuminated under well defined circumstances and quantitative moisture measurement on the surface of building materials becomes a possibility. The illumination modulation is done with a sine wave to facilitate the calculation of the temporal intensity behavior of the amplitude signal. Subsequently, the amplitude image is used to determine the distribution and the level of moisture quantitatively. Point measurements in the laboratory were carried out on several building materials with changing moisture levels. It could be shown that this method successfully eliminates disturbing contributions to the measured signal like surface effects or leaking radiation.

  13. Amplitude-Phase Modulation, Topological Horseshoe and Scaling Attractor of a Dynamical System

    NASA Astrophysics Data System (ADS)

    Li, Chun-Lai; Li, Wen; Zhang, Jing; Xie, Yuan-Xi; Zhao, Yi-Bo

    2016-09-01

    A three-dimensional autonomous chaotic system is discussed in this paper. Some basic dynamical properties of the system, including phase portrait, Poincaré map, power spectrum, Kaplan-Yorke dimension, Lyapunov exponent spectra, signal amplitude and topological horseshoe are studied theoretically and numerically. The main finding by analysis is that the signal amplitude can be modulated via controlling the coefficients of the linear term, cross-product term and squared term simultaneously or respectively, and the phase of x3 can be modulated by the product of the coefficients of the linear term and cross-product term. Furthermore, scaling chaotic attractors of this system are achieved by modified projective synchronization with an optimization-based linear coupling method, which is safer for secure communications than the existed synchronization scheme since the scaling factors can be regarded as the security encoding key. Supported by Hunan Provincial Natural Science Foundation of China under Grant No. 2016JJ4036, University Natural Science Foundation of Jiangsu Province under Grant No. 14KJB120007 and the National Natural Science Foundation of China under Grant Nos. 11504176 and 11602084

  14. Combined quadrature amplitude modulation and convolutional codes for cross-coupled multidimensional channels

    NASA Astrophysics Data System (ADS)

    Kavehrad, M.; Sundberg, C.-E.; McLane, P. J.

    The performance of cross-coupled, M-ary Quadrature Amplitude Modulation (QAM) systems is determined when bandwidth efficient trellis codes are used to combat interference. Performance with and without compensation for cross-coupled interference is presented. It is found that simple trellis codes can maintain the error probability at an acceptable level for cross-coupling parameters that render uncoded systems unusable. Up to two dimensional trellis codes are considered for four dimensional QAM signals. The average probability of the most likely error events is calculated by using the method of moments. The results are applicable to any digital communication system using multidimensional quadrature amplitude modulation, e.g., voiceband modems and cross-polarized radio systems. In the paper the analysis is restricted to nondispersive cross-coupling models. In most cases the coding gain is larger than in the absence of cross-coupling interference. Specifically, it is found that simple trellis codes have coding gains of more than 5 dB in cross-coupling interference compared to 3 dB for a Gaussian channel. This is obtained for schemes compared at equal bandwidth.

  15. Accurate Encoding and Decoding by Single Cells: Amplitude Versus Frequency Modulation

    PubMed Central

    Micali, Gabriele; Aquino, Gerardo; Richards, David M.; Endres, Robert G.

    2015-01-01

    Cells sense external concentrations and, via biochemical signaling, respond by regulating the expression of target proteins. Both in signaling networks and gene regulation there are two main mechanisms by which the concentration can be encoded internally: amplitude modulation (AM), where the absolute concentration of an internal signaling molecule encodes the stimulus, and frequency modulation (FM), where the period between successive bursts represents the stimulus. Although both mechanisms have been observed in biological systems, the question of when it is beneficial for cells to use either AM or FM is largely unanswered. Here, we first consider a simple model for a single receptor (or ion channel), which can either signal continuously whenever a ligand is bound, or produce a burst in signaling molecule upon receptor binding. We find that bursty signaling is more accurate than continuous signaling only for sufficiently fast dynamics. This suggests that modulation based on bursts may be more common in signaling networks than in gene regulation. We then extend our model to multiple receptors, where continuous and bursty signaling are equivalent to AM and FM respectively, finding that AM is always more accurate. This implies that the reason some cells use FM is related to factors other than accuracy, such as the ability to coordinate expression of multiple genes or to implement threshold crossing mechanisms. PMID:26030820

  16. Amplitude modulation schemes for enhancing acoustically-driven microcentrifugation and micromixing.

    PubMed

    Ang, Kar M; Yeo, Leslie Y; Hung, Yew M; Tan, Ming K

    2016-09-01

    The ability to drive microcentrifugation for efficient micromixing and particle concentration and separation on a microfluidic platform is critical for a wide range of lab-on-a-chip applications. In this work, we investigate the use of amplitude modulation to enhance the efficiency of the microcentrifugal recirculation flows in surface acoustic wave microfluidic systems, thus concomitantly reducing the power consumption in these devices for a given performance requirement-a crucial step in the development of miniaturized, integrated circuits for true portable functionality. In particular, we show that it is possible to obtain an increase of up to 60% in the acoustic streaming velocity in a microdroplet with kHz order modulation frequencies due to the intensification in Eckart streaming; the streaming velocity is increasing as the modulation index is increased. Additionally, we show that it is possible to exploit this streaming enhancement to effect improvements in the speed of particle concentration by up to 70% and the efficiency of micromixing by 50%, together with a modest decrease in the droplet temperature.

  17. Targeted treatment of cancer with radiofrequency electromagnetic fields amplitude-modulated at tumor-specific frequencies.

    PubMed

    Zimmerman, Jacquelyn W; Jimenez, Hugo; Pennison, Michael J; Brezovich, Ivan; Morgan, Desiree; Mudry, Albert; Costa, Frederico P; Barbault, Alexandre; Pasche, Boris

    2013-11-01

    In the past century, there have been many attempts to treat cancer with low levels of electric and magnetic fields. We have developed noninvasive biofeedback examination devices and techniques and discovered that patients with the same tumor type exhibit biofeedback responses to the same, precise frequencies. Intrabuccal administration of 27.12 MHz radiofrequency (RF) electromagnetic fields (EMF), which are amplitude-modulated at tumor-specific frequencies, results in long-term objective responses in patients with cancer and is not associated with any significant adverse effects. Intrabuccal administration allows for therapeutic delivery of very low and safe levels of EMF throughout the body as exemplified by responses observed in the femur, liver, adrenal glands, and lungs. In vitro studies have demonstrated that tumor-specific frequencies identified in patients with various forms of cancer are capable of blocking the growth of tumor cells in a tissue- and tumor-specific fashion. Current experimental evidence suggests that tumor-specific modulation frequencies regulate the expression of genes involved in migration and invasion and disrupt the mitotic spindle. This novel targeted treatment approach is emerging as an appealing therapeutic option for patients with advanced cancer given its excellent tolerability. Dissection of the molecular mechanisms accounting for the anti-cancer effects of tumor-specific modulation frequencies is likely to lead to the discovery of novel pathways in cancer.

  18. Optical-wireless-optical full link for polarization multiplexing quadrature amplitude/phase modulation signal transmission.

    PubMed

    Li, Xinying; Yu, Jianjun; Chi, Nan; Zhang, Junwen

    2013-11-15

    We propose and experimentally demonstrate an optical wireless integration system at the Q-band, in which up to 40 Gb/s polarization multiplexing multilevel quadrature amplitude/phase modulation (PM-QAM) signal can be first transmitted over 20 km single-mode fiber-28 (SMF-28), then delivered over a 2 m 2 × 2 multiple-input multiple-output wireless link, and finally transmitted over another 20 km SMF-28. The PM-QAM modulated wireless millimeter-wave (mm-wave) signal at 40 GHz is generated based on the remote heterodyning technique, and demodulated by the radio-frequency transparent photonic technique based on homodyne coherent detection and baseband digital signal processing. The classic constant modulus algorithm equalization is used at the receiver to realize polarization demultiplexing of the PM-QAM signal. For the first time, to the best of our knowledge, we realize the conversion of the PM-QAM modulated wireless mm-wave signal to the optical signal as well as 20 km fiber transmission of the converted optical signal.

  19. Targeted treatment of cancer with radiofrequency electromagnetic fields amplitude-modulated at tumor-specific frequencies

    PubMed Central

    Zimmerman, Jacquelyn W.; Jimenez, Hugo; Pennison, Michael J.; Brezovich, Ivan; Morgan, Desiree; Mudry, Albert; Costa, Frederico P.; Barbault, Alexandre; Pasche, Boris

    2013-01-01

    In the past century, there have been many attempts to treat cancer with low levels of electric and magnetic fields. We have developed noninvasive biofeedback examination devices and techniques and discovered that patients with the same tumor type exhibit biofeedback responses to the same, precise frequencies. Intrabuccal administration of 27.12 MHz radiofrequency (RF) electromagnetic fields (EMF), which are amplitude-modulated at tumor-specific frequencies, results in long-term objective responses in patients with cancer and is not associated with any significant adverse effects. Intrabuccal administration allows for therapeutic delivery of very low and safe levels of EMF throughout the body as exemplified by responses observed in the femur, liver, adrenal glands, and lungs. In vitro studies have demonstrated that tumor-specific frequencies identified in patients with various forms of cancer are capable of blocking the growth of tumor cells in a tissue- and tumor-specific fashion. Current experimental evidence suggests that tumor-specific modulation frequencies regulate the expression of genes involved in migration and invasion and disrupt the mitotic spindle. This novel targeted treatment approach is emerging as an appealing therapeutic option for patients with advanced cancer given its excellent tolerability. Dissection of the molecular mechanisms accounting for the anti-cancer effects of tumor-specific modulation frequencies is likely to lead to the discovery of novel pathways in cancer. PMID:24206915

  20. Amplitude modulation detection by human listeners in reverberant sound fields: Effects of prior listening exposure

    PubMed Central

    Zahorik, Pavel; Anderson, Paul W.

    2013-01-01

    Previous work [Zahorik et al., POMA, 15, 050002 (2012)] has reported that for both broadband and narrowband noise carrier signals in a simulated reverberant sound field, human sensitivity to amplitude modulation (AM) is higher than would be predicted based on the acoustical modulation transfer function (MTF) of the listening environment. These results may be suggestive of mechanisms that functionally enhance modulation in reverberant listening, although many details of this enhancement effect are unknown. Given recent findings that demonstrate improvements in speech understanding with prior exposure to reverberant listening environments, it is of interest to determine whether listening exposure to a reverberant room might also influence AM detection in the room, and perhaps contribute to the AM enhancement effect. Here, AM detection thresholds were estimated (using an adaptive 2-alternative forced-choice procedure) in each of two listening conditions: one in which consistent listening exposure to a particular room was provided, and a second that intentionally disrupted listening exposure by varying the room from trial-to-trial. Results suggest that consistent prior listening exposure contributes to enhanced AM sensitivity in rooms. [Work supported by the NIH/NIDCD.] PMID:24163718

  1. High-speed and reconfigurable all-optical signal processing for phase and amplitude modulated signals

    NASA Astrophysics Data System (ADS)

    Khaleghi, Salman

    Technology has empowered people in all walks of life to generate, store, and communicate enormous amounts of data. Recent technological advances in high-speed backbone data networks, together with the growing trend toward bandwidth-demanding applications such as data and video sharing, cloud computing, and data collection systems, have created a need for higher capacities in signal transmission and signal processing. Optical communication systems have long benefited from the large bandwidth of optical signals (beyond tera-hertz) to transmit information. Through the use of optical signal processing techniques, this Ph.D. dissertation explores the potential of very-high-speed optics to assist electronics in processing huge amounts of data at high speeds. Optical signal processing brings together various fields of optics and signal processing---nonlinear devices and processes, analog and digital signals, and advanced data modulation formats---to achieve high-speed signal processing functions that can potentially operate at the line rate of fiber optic communications. Information can be encoded in amplitude, phase, wavelength, polarization, and spatial features of an optical wave to achieve high-capacity transmission. Many advances in the key enabling technologies have led to recent research in optical signal processing for digital signals that are encoded in one or more of these dimensions. Optical Kerr nonlinearities have femto-second response times that have been exploited for fast processing of optical signals. Various optical nonlinearities and chromatic dispersions have enabled key sub-system applications such as wavelength conversion, multicasting, multiplexing, demultiplexing, and tunable optical delays. In this Ph.D. dissertation, we employ these recent advances in the enabling technologies for high-speed optical signal processing to demonstrate various techniques that can process phase- and amplitude-encoded optical signals at the line rate of optics. We use

  2. Suppression of phase and amplitude J(HH) modulations in HSQC experiments.

    PubMed

    Castañar, Laura; Sistaré, Eduard; Virgili, Albert; Williamson, R Thomas; Parella, Teodor

    2015-02-01

    The amplitude and the phase of cross peaks in conventional 2D HSQC experiments are modulated by both proton-proton, J(HH), and proton-carbon, (1)J(CH), coupling constants. It is shown by spectral simulation and experimentally that J(HH) interferences are suppressed in a novel perfect-HSQC pulse scheme that incorporates perfect-echo INEPT periods. The improved 2D spectra afford pure in-phase cross peaks with respect to (1)J(CH) and J(HH), irrespective of the experiment delay optimization. In addition, peak volumes are not attenuated by the influence of J(HH), rendering practical issues such as phase correction, multiplet analysis, and signal integration more appropriate.

  3. Resonance of a Metal Drop under the Effect of Amplitude-Modulated High Frequency Magnetic Field

    NASA Astrophysics Data System (ADS)

    Guo, Jiahong; Lei, Zuosheng; Zhu, Hongda; Zhang, Lijie; Magnetic Hydrodynamics(Siamm) Team; Magnetic Mechanics; Engineering(Smse) Team

    2016-11-01

    The resonance of a sessile and a levitated drop under the effect of high frequency amplitude-modulated magnetic field (AMMF) is investigated experimentally and numerically. It is a new method to excite resonance of a metal drop, which is different from the case in the presence of a low-frequency magnetic field. The transient contour of the drop is obtained in the experiment and the simulation. The numerical results agree with the experimental results fairly well. At a given frequency and magnetic flux density of the high frequency AMMF, the edge deformations of the drop with an azimuthal wave numbers were excited. A stability diagram of the shape oscillation of the drop and its resonance frequency spectrum are obtained by analysis of the experimental and the numerical data. The results show that the resonance of the drop has a typical character of parametric resonance. The National Natural Science Foundation of China (No. 51274237 and 11372174).

  4. Modulation of spin transfer torque amplitude in double barrier magnetic tunnel junctions

    SciTech Connect

    Clément, P.-Y.; Baraduc, C. Chshiev, M.; Diény, B.; Ducruet, C.; Vila, L.

    2015-09-07

    Magnetization switching induced by spin transfer torque is used to write magnetic memories (Magnetic Random Access Memory, MRAM) but can be detrimental to the reading process. It would be quite convenient therefore to modulate the efficiency of spin transfer torque. A solution is adding an extra degree of freedom by using double barrier magnetic tunnel junctions with two spin-polarizers, with controllable relative magnetic alignment. We demonstrate, for these structures, that the amplitude of in-plane spin transfer torque on the middle free layer can be efficiently tuned via the magnetic configuration of the electrodes. Using the proposed design could thus pave the way towards more reliable read/write schemes for MRAM. Moreover, our results suggest an intriguing effect associated with the out-of-plane (field-like) spin transfer torque, which has to be further investigated.

  5. Bit error probability of trellis-coded quadrature amplitude modulation over cross-coupled multidimensional channels

    NASA Astrophysics Data System (ADS)

    Kavehrad, Mohsen; Sundberg, Carl-Erik W.

    1987-04-01

    Average bit error probabilities for M-ary quadrature amplitude modulation (MQAM) systems are evaluated using a truncated union bound to calculate an approximate upper bound on the average bit error probability. Coded BPSK and QSPK are studied in a dual-polarized channel with and without an interference compensator. Trellis-coded MQAM signals are also examined. A new technique, dual-channel polarization hopping, which provides diversity gains when applied to coded cross-coupled channels is proposed. Average bit error probabilities for convolutionally coded QAM schemes in cross-coupled interference channels are derived. It is concluded that trellis-coded QAM schemes give larger coding gains in cross-coupled interference channels than in Gaussian noise and the choice of optimum code for the trellis-coded QAM scheme depends on the expected interference level.

  6. AB302. SPR-29 Sphingosine-1-phosphate in vitro and in vivo modulates corpus cavernosum smooth muscle tone

    PubMed Central

    Zhang, Xinhua; Yin, Jing; Kanika, Nirmala D.; Tong, Yuehong; Villegas, Guillermo; Melman, Arnold; DiSanto, Michael E.

    2016-01-01

    Objective The bioactive lipid sphingosine-1-phosphate (S1P) regulates smooth muscle (SM) contractility predominantly via three G protein-coupled receptors. The S1P1 receptor is associated with nitric oxide-mediated SM relaxation while S1P2 & S1P3 receptors are linked to SM contraction via activation of the Rho-kinase (ROK) pathway. The objective of this study was to determine the role of S1P in the modulation of corpus cavernosum (CC) SM (CCSM) tone. Methods Human and rat samples were used. Plasma S1P levels were detected by high-performance liquid chromatography. The expression of S1P1-3 receptors and sphingosine kinase-1 (SphK1) was determined by real-time RT-PCR and western blot. In vitro organ bath contractility and in vivo intracavernous pressure (ICP) measurements were performed. Results were expressed as mean ± SEM for n experiments. Statistical analysis was performed using either the Student’s t-test (when two sample treatments were being compared) or using ANOVA when multiple means were compared. P<0.05 was considered significant. Results Plasma S1P levels were determined to be ~200 nanomolar. Human and rat CC both express SphK1 and all S1P1-3 receptors. Exogenous S1P and the S1P receptor agonist FTY720-P contracted while antagonist JTE-013 relaxed CCSM in vitro. Meanwhile, force produced by S1P and agonists could be totally reversed by ROK inhibitor. Also, intracavernous injection of FTY720-P inhibited ICP rise induced by submaximal electrical stimulation of cavernous nerve, while JTE-013 alone induced ICP increase in vivo. Finally, SphK1 siRNA knocked down rat CC SphK1 by 80% and ICP were significantly potentiated. Conclusions In conclusion, we provide novel data that S1P, possibly coupling S1P2 and S1P3 receptors via RhoA/ROK pathway, mediates CCSM in vitro and in vivo. Antagonizing S1P or its receptors induces CCSM relaxation and proerectile effects. Thus, we provide the first clear evidences that the S1P system is another key contractile regulatory

  7. Sub-nanometer Resolution Imaging with Amplitude-modulation Atomic Force Microscopy in Liquid

    PubMed Central

    Farokh Payam, Amir; Piantanida, Luca; Cafolla, Clodomiro; Voïtchovsky, Kislon

    2016-01-01

    Atomic force microscopy (AFM) has become a well-established technique for nanoscale imaging of samples in air and in liquid. Recent studies have shown that when operated in amplitude-modulation (tapping) mode, atomic or molecular-level resolution images can be achieved over a wide range of soft and hard samples in liquid. In these situations, small oscillation amplitudes (SAM-AFM) enhance the resolution by exploiting the solvated liquid at the surface of the sample. Although the technique has been successfully applied across fields as diverse as materials science, biology and biophysics and surface chemistry, obtaining high-resolution images in liquid can still remain challenging for novice users. This is partly due to the large number of variables to control and optimize such as the choice of cantilever, the sample preparation, and the correct manipulation of the imaging parameters. Here, we present a protocol for achieving high-resolution images of hard and soft samples in fluid using SAM-AFM on a commercial instrument. Our goal is to provide a step-by-step practical guide to achieving high-resolution images, including the cleaning and preparation of the apparatus and the sample, the choice of cantilever and optimization of the imaging parameters. For each step, we explain the scientific rationale behind our choices to facilitate the adaptation of the methodology to every user's specific system. PMID:28060262

  8. A coronagraph based on two spatial light modulators for active amplitude apodizing and phase corrections

    NASA Astrophysics Data System (ADS)

    Dou, Jiangpei; Ren, Deqing; Zhang, Xi; Zhu, Yongtian; Zhao, Gang; Wu, Zhen; Chen, Rui; Liu, Chengchao; Yang, Feng; Yang, Chao

    2014-08-01

    Almost all high-contrast imaging coronagraphs proposed until now are based on passive coronagraph optical components. Recently, Ren and Zhu proposed for the first time a coronagraph that integrates a liquid crystal array (LCA) for the active pupil apodizing and a deformable mirror (DM) for the phase corrections. Here, for demonstration purpose, we present the initial test result of a coronagraphic system that is based on two liquid crystal spatial light modulators (SLM). In the system, one SLM is served as active pupil apodizing and amplitude correction to suppress the diffraction light; another SLM is used to correct the speckle noise that is caused by the wave-front distortions. In this way, both amplitude and phase error can be actively and efficiently compensated. In the test, we use the stochastic parallel gradient descent (SPGD) algorithm to control two SLMs, which is based on the point spread function (PSF) sensing and evaluation and optimized for a maximum contrast in the discovery area. Finally, it has demonstrated a contrast of 10-6 at an inner working angular distance of ~6.2 λ/D, which is a promising technique to be used for the direct imaging of young exoplanets on ground-based telescopes.

  9. An investigation of the influence of residual amplitude modulation in phase electro-optic modulator on the signal of fiber-optic gyroscope

    NASA Astrophysics Data System (ADS)

    Pogorelaya, D. A.; Smolovik, M. A.; Strigalev, V. E.; Aleynik, A. S.; Deyneka, I. G.

    2016-08-01

    The investigation is devoted to residual amplitude modulation (RAM) of phase electro-optic modulator, which guides are made in LiNbO3 crystal by Ti diffusion technology. An analysis is presented that shows influence of RAM on the signal of fiber-optic gyroscope. The RAM compensation method is offered.

  10. Shaping symmetric Airy beam through binary amplitude modulation for ultralong needle focus

    SciTech Connect

    Fang, Zhao-Xiang; Gong, Lei; Ren, Yu-Xuan; Vaveliuk, Pablo; Chen, Yue; Lu, Rong-De

    2015-11-28

    Needle-like electromagnetic field has various advantages for the applications in high-resolution imaging, Raman spectroscopy, as well as long-distance optical transportation. The realization of such field often requires high numerical aperture (NA) objective lens and the transmission masks. We demonstrate an ultralong needle-like focus in the optical range produced with an ordinary lens. This is achieved by focusing a symmetric Airy beam (SAB) generated via binary spectral modulation with a digital micromirror device. Such amplitude modulation technique is able to shape traditional Airy beams, SABs, as well as the dynamic transition modes between the one-dimensional and two-dimensional (2D) symmetric Airy modes. The created 2D SAB was characterized through measurement of the propagating fields with one of the four main lobes blocked by an opaque mask. The 2D SAB was verified to exhibit self-healing property against propagation with the obstructed major lobe reconstructed after a certain distance. We further produced an elongated focal line by concentrating the SAB via lenses with different NAs and achieved an ultralong longitudinal needle focus. The produced long needle focus will be applied in optical, chemical, and biological sciences.

  11. State-dependent representation of amplitude-modulated noise stimuli in rat auditory cortex

    PubMed Central

    Marguet, Stephan L.; Harris, Kenneth D.

    2011-01-01

    Cortical responses can vary greatly between repeated presentations of an identical stimulus. Here we report that both trial-to-trial variability and faithfulness of auditory cortical stimulus representations depend critically on brain state. A frozen amplitude-modulated white noise stimulus was repeatedly presented while recording neuronal populations and local field potentials (LFPs) in auditory cortex of urethane-anesthetized rats. An information-theoretic measure was used to predict neuronal spiking activity from either the stimulus envelope or simultaneously recorded LFP. Evoked LFPs and spiking more faithfully followed high-frequency temporal modulations when the cortex was in a “desynchronized” state. In the “synchronized” state, neural activity was poorly predictable from the stimulus envelope, but the spiking of individual neurons could still be predicted from the ongoing LFP. Our results suggest that although auditory cortical activity remains coordinated as a population in the synchronized state, the ability of continuous auditory stimuli to control this activity is greatly diminished. PMID:21525282

  12. EEG amplitude modulation analysis for semi-automated diagnosis of Alzheimer's disease

    NASA Astrophysics Data System (ADS)

    Falk, Tiago H.; Fraga, Francisco J.; Trambaiolli, Lucas; Anghinah, Renato

    2012-12-01

    Recent experimental evidence has suggested a neuromodulatory deficit in Alzheimer's disease (AD). In this paper, we present a new electroencephalogram (EEG) based metric to quantitatively characterize neuromodulatory activity. More specifically, the short-term EEG amplitude modulation rate-of-change (i.e., modulation frequency) is computed for five EEG subband signals. To test the performance of the proposed metric, a classification task was performed on a database of 32 participants partitioned into three groups of approximately equal size: healthy controls, patients diagnosed with mild AD, and those with moderate-to-severe AD. To gauge the benefits of the proposed metric, performance results were compared with those obtained using EEG spectral peak parameters which were recently shown to outperform other conventional EEG measures. Using a simple feature selection algorithm based on area-under-the-curve maximization and a support vector machine classifier, the proposed parameters resulted in accuracy gains, relative to spectral peak parameters, of 21.3% when discriminating between the three groups and by 50% when mild and moderate-to-severe groups were merged into one. The preliminary findings reported herein provide promising insights that automated tools may be developed to assist physicians in very early diagnosis of AD as well as provide researchers with a tool to automatically characterize cross-frequency interactions and their changes with disease.

  13. Sustained selective attention to competing amplitude-modulations in human auditory cortex.

    PubMed

    Riecke, Lars; Scharke, Wolfgang; Valente, Giancarlo; Gutschalk, Alexander

    2014-01-01

    Auditory selective attention plays an essential role for identifying sounds of interest in a scene, but the neural underpinnings are still incompletely understood. Recent findings demonstrate that neural activity that is time-locked to a particular amplitude-modulation (AM) is enhanced in the auditory cortex when the modulated stream of sounds is selectively attended to under sensory competition with other streams. However, the target sounds used in the previous studies differed not only in their AM, but also in other sound features, such as carrier frequency or location. Thus, it remains uncertain whether the observed enhancements reflect AM-selective attention. The present study aims at dissociating the effect of AM frequency on response enhancement in auditory cortex by using an ongoing auditory stimulus that contains two competing targets differing exclusively in their AM frequency. Electroencephalography results showed a sustained response enhancement for auditory attention compared to visual attention, but not for AM-selective attention (attended AM frequency vs. ignored AM frequency). In contrast, the response to the ignored AM frequency was enhanced, although a brief trend toward response enhancement occurred during the initial 15 s. Together with the previous findings, these observations indicate that selective enhancement of attended AMs in auditory cortex is adaptive under sustained AM-selective attention. This finding has implications for our understanding of cortical mechanisms for feature-based attentional gain control.

  14. Stimulus Phase Locking of Cortical Oscillations for Rhythmic Tone Sequences in Rats

    PubMed Central

    Noda, Takahiro; Amemiya, Tomoki; Shiramatsu, Tomoyo I.; Takahashi, Hirokazu

    2017-01-01

    Humans can rapidly detect regular patterns (i.e., within few cycles) without any special attention to the acoustic environment. This suggests that human sensory systems are equipped with a powerful mechanism for automatically predicting forthcoming stimuli to detect regularity. It has recently been hypothesized that the neural basis of sensory predictions exists for not only what happens (predictive coding) but also when a particular stimulus occurs (predictive timing). Here, we hypothesize that the phases of neural oscillations are critical in predictive timing, and these oscillations are modulated in a band-specific manner when acoustic patterns become predictable, i.e., regular. A high-density microelectrode array (10 × 10 within 4 × 4 mm2) was used to characterize spatial patterns of band-specific oscillations when a random-tone sequence was switched to a regular-tone sequence. Increasing the regularity of the tone sequence enhanced phase locking in a band-specific manner, notwithstanding the type of the regular sound pattern. Gamma-band phase locking increased immediately after the transition from random to regular sequences, while beta-band phase locking gradually evolved with time after the transition. The amplitude of the tone-evoked response, in contrast, increased with frequency separation with respect to the prior tone, suggesting that the evoked-response amplitude encodes sequence information on a local scale, i.e., the local order of tones. The phase locking modulation spread widely over the auditory cortex, while the amplitude modulation was confined around the activation foci. Thus, our data suggest that oscillatory phase plays a more important role than amplitude in the neuronal detection of tone sequence regularity, which is closely related to predictive timing. Furthermore, band-specific contributions may support recent theories that gamma oscillations encode bottom-up prediction errors, whereas beta oscillations are involved in top

  15. Heteronuclear refocusing by nonlinear phase and amplitude modulation on a single transmitter channel.

    PubMed

    Moore, Jay; Colón, Raul D; Tadanki, Sasidhar; Waddell, Kevin W

    2014-08-01

    The application of low magnetic fields to heteronuclear NMR has expanded recently alongside the emergence of methods for achieving near unity polarization of spin ensembles, independent of magnetic field strength. The parahydrogen induced hyperpolarization methods in particular, often use a hybrid arrangement where a high field spectrometer is used to detect or image polarized molecules that have been conjured on a separate, dedicated polarizer instrument operating at fields in the mT regime where yields are higher. For controlling polarizer chemistry, spare TTL channels of portable NMR spectrometers can be used to pulse program reaction timings in synchrony with heteronuclear RF transformations. The use of a spectrometer as a portable polarizer control module has the advantage of allowing detection in situ, simplifying the process of optimizing polarization yields prior to in vivo experimental trials. Suitable heteronuclear spectrometers compatible with this application are becoming more common, but are still sparsely available in comparison to a large existing infrastructure of single channel NMR consoles. With the goal of expanding the range of these systems to multinuclear applications, the feasibility of rotating a pair of heteronuclear spins ((13)C and (1)H) at 12mT was investigated in this study. Nonlinear phase and amplitude modulated waveforms designed to simultaneously refocus magnetization at 128kHz ((13)C) and 510kHz ((1)H) were generated numerically with optimal control. Although precise quantitative comparisons were not attempted due to limitations of the experimental setup, signals refocused at heteronuclear frequencies with this PANORAMIC approach (Precession And Nutation for Observing Rotation At Multiple Intervals about the Carrier) yielded amplitudes comparable to signals which were refocused using traditional block pulses on heteronuclear channels. Using this PANORAMIC approach to heteronuclear NMR at low field would reduce expense as well as

  16. Electron density in amplitude modulated microwave atmospheric plasma jet as determined from microwave interferometry and emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Faltýnek, J.; Hnilica, J.; Kudrle, V.

    2017-01-01

    Time resolved electron density in an atmospheric pressure amplitude modulated microwave plasma jet is determined using the microwave interferometry method, refined by numerical modelling of the propagation of non-planar electromagnetic waves in the vicinity of a small diameter, dense collisional plasma filament. The results are compared to those from the Stark broadening of the {{\\text{H}}β} emission line. Both techniques show, both qualitatively and quantitatively, a similar temporal evolution of electron density during one modulation period.

  17. Correlation of neural responses in the cochlear nucleus with low-frequency noise amplitude modulation of a tonal signal

    NASA Astrophysics Data System (ADS)

    Bibikov, N. G.

    2014-09-01

    The responses of single neurons of the cochlear nucleus of a grass frog to long tonal signals amplitude-modulated by repeat intervals of low-frequency noise have been studied. The carrier frequency always corresponded to the characteristic frequency of the studied cell (a range of 0.2 kHz-2 kHz); the modulated signal was noise in the ranges 0-15 Hz, 0-50 Hz, or 0-150 Hz. We obtained the correlation functions of the cyclic histogram reflecting the change in probability of a neuron pulse discharge (spike) during the modulation period with the shape of the signal envelope in the same period. The form of the obtained correlation functions usually does not change qualitatively with a change in carrier level or modulation depth; however, this could essentially depend of the frequency component of the modulating function. In the majority of cases, comparison of the cyclic histogram of the reaction with only the current amplitude value does not adequately reveal the signal's time features that determine the reaction of a neuron. The response is also determined by the other sound features, primarily by the rate of the change in amplitude. The studied neurons differed among themselves, both in preference toward a certain range of modulated frequencies and in the features of the envelope that caused the cell's response.

  18. Observations of amplitude saturation in ELF/VLF wave generation by modulated HF heating of the auroral electrojet

    NASA Astrophysics Data System (ADS)

    Moore, R. C.; Inan, U. S.; Bell, T. F.

    2006-06-01

    We present detailed observations of the onset of amplitude saturation in ELF/VLF waves generated via modulated HF heating of naturally-forming, large-scale current systems, such as the auroral electrojet. Broadband ELF/VLF measurements at a ground-based receiver located near the High-Frequency Active Auroral Research Program (HAARP) HF transmitter in Gakona, Alaska, exhibit variations in signal amplitude which are qualitatively consistent with a hard-limiting approximation of the saturation process. A method to approximate the saturation curve as a function of HF power from experimental data is presented, and the results indicate that a ~5-10% reduction in generated ELF signal amplitude is typical at the maximum radiated HF power level (771 kW) for modulation frequencies between 1225 Hz and 3365 Hz. For HF transmissions using sinusoidal amplitude modulation, the saturation dominantly affects the second harmonic of the generated ELF/VLF signal, with amplitudes on average 16% lower than expected at the maximum HF power level.

  19. Digital services using quadrature amplitude modulation (QAM) over CATV analog DWDM system

    NASA Astrophysics Data System (ADS)

    Yeh, JengRong; Selker, Mark D.; Trail, J.; Piehler, David; Levi, Israel

    2000-04-01

    Dense Wavelength Division Multiplexing (DWDM) has recently gained great popularity as it provides a cost effective way to increase the transmission capacity of the existing fiber cable plant. For a long time, Dense WDM was exclusively used for baseband digital applications, predominantly in terrestrial long haul networks and in some cases in metropolitan and enterprise networks. Recently, the performance of DWDM components and frequency-stabilized lasers has substantially improved while the costs have down significantly. This makes a variety of new optical network architectures economically viable. The first commercial 8- wavelength DWDM system designed for Hybrid Fiber Coax networks was reported in 1998. This type of DWDM system utilizes Sub-Carrier Multiplexing (SCM) of Quadrature Amplitude Modulated (QAM) signals to transport IP data digital video broadcast and Video on Demand on ITU grid lightwave carriers. The ability of DWDM to provide scalable transmission capacity in the optical layer with SCM granularity is now considered by many to be the most promising technology for future transport and distribution of broadband multimedia services.

  20. Enhanced 16 Spiral quadrature amplitude modulation scheme for coherent optical orthogonal frequency division multiplexing systems

    NASA Astrophysics Data System (ADS)

    He, Jing; Li, Chong; Chen, Lin; Chen, Ming

    2014-09-01

    We propose an enhanced 16 Spiral quadrature amplitude modulation (QAM) (16 E-Spiral QAM) scheme to overcome the laser phase noise in a coherent optical orthogonal frequency division multiplexing (CO-OFDM) system. Considering both additive white Gaussian noise and large phase noise, 16 E-Spiral QAM schemes have a better transmission performance compared to conventional 16 QAM CO-OFDM systems. The simulated results show that the required optical signal-to-noise ratio (OSNR) of the proposed 16 QAM is, respectively, 0.8 and 2.3 dB less than 16 Spiral and conventional 16 QAM at a bit error rate (BER) of 10-3 in a back-to-back case. After 800-km transmission over a single-mode fiber, the tolerance for the laser linewidth of the 16 E-Spiral QAM can improve about 30 kHz with an OSNR of 18 dB compared to that of a conventional 16 QAM.

  1. Noise tolerance in optical waveguide circuits for recognition of optical 16 quadrature amplitude modulation codes

    NASA Astrophysics Data System (ADS)

    Inoshita, Kensuke; Hama, Yoshimitsu; Kishikawa, Hiroki; Goto, Nobuo

    2016-12-01

    In photonic label routers, various optical signal processing functions are required; these include optical label extraction, recognition of the label, optical switching and buffering controlled by signals based on the label information and network routing tables, and label rewriting. Among these functions, we focus on photonic label recognition. We have proposed two kinds of optical waveguide circuits to recognize 16 quadrature amplitude modulation codes, i.e., recognition from the minimum output port and from the maximum output port. The recognition function was theoretically analyzed and numerically simulated by finite-difference beam-propagation method. We discuss noise tolerance in the circuit and show numerically simulated results to evaluate bit-error-rate (BER) characteristics against optical signal-to-noise ratio (OSNR). The OSNR required to obtain a BER less than 1.0×10-3 for the symbol rate of 2.5 GBaud was 14.5 and 27.0 dB for recognition from the minimum and maximum output, respectively.

  2. The pulse-train auditory aftereffect and the perception of rapid amplitude modulations.

    PubMed

    Gutschalk, Alexander; Micheyl, Christophe; Oxenham, Andrew J

    2008-02-01

    Prolonged listening to a pulse train with repetition rates around 100 Hz induces a striking aftereffect, whereby subsequently presented sounds are heard with an unusually "metallic" timbre [Rosenblith et al., Science 106, 333-335 (1947)]. The mechanisms responsible for this auditory aftereffect are currently unknown. Whether the aftereffect is related to an alteration of the perception of temporal envelope fluctuations was evaluated. Detection thresholds for sinusoidal amplitude modulation (AM) imposed onto noise-burst carriers were measured for different AM frequencies (50-500 Hz), following the continuous presentation of a periodic pulse train, a temporally jittered pulse train, or an unmodulated noise. AM detection thresholds for AM frequencies of 100 Hz and above were significantly elevated compared to thresholds in quiet, following the presentation of the pulse-train inducers, and both induced a subjective auditory aftereffect. Unmodulated noise, which produced no audible aftereffect, left AM detection thresholds unchanged. Additional experiments revealed that, like the Rosenblith et al. aftereffect, the effect on AM thresholds does not transfer across ears, is not eliminated by protracted training, and can last several tens of seconds. The results suggest that the Rosenblith et al. aftereffect is related to a temporary alteration in the perception of fast temporal envelope fluctuations in sounds.

  3. Envelope Interactions in Multi-Channel Amplitude Modulation Frequency Discrimination by Cochlear Implant Users

    PubMed Central

    2015-01-01

    Rationale Previous cochlear implant (CI) studies have shown that single-channel amplitude modulation frequency discrimination (AMFD) can be improved when coherent modulation is delivered to additional channels. It is unclear whether the multi-channel advantage is due to increased loudness, multiple envelope representations, or to component channels with better temporal processing. Measuring envelope interference may shed light on how modulated channels can be combined. Methods In this study, multi-channel AMFD was measured in CI subjects using a 3-alternative forced-choice, non-adaptive procedure (“which interval is different?”). For the reference stimulus, the reference AM (100 Hz) was delivered to all 3 channels. For the probe stimulus, the target AM (101, 102, 104, 108, 116, 132, 164, 228, or 256 Hz) was delivered to 1 of 3 channels, and the reference AM (100 Hz) delivered to the other 2 channels. The spacing between electrodes was varied to be wide or narrow to test different degrees of channel interaction. Results Results showed that CI subjects were highly sensitive to interactions between the reference and target envelopes. However, performance was non-monotonic as a function of target AM frequency. For the wide spacing, there was significantly less envelope interaction when the target AM was delivered to the basal channel. For the narrow spacing, there was no effect of target AM channel. The present data were also compared to a related previous study in which the target AM was delivered to a single channel or to all 3 channels. AMFD was much better with multiple than with single channels whether the target AM was delivered to 1 of 3 or to all 3 channels. For very small differences between the reference and target AM frequencies (2–4 Hz), there was often greater sensitivity when the target AM was delivered to 1 of 3 channels versus all 3 channels, especially for narrowly spaced electrodes. Conclusions Besides the increased loudness, the present results

  4. Retrieval of the pulse amplitude and phase from cross-phase modulation spectrograms using the simulated annealing method.

    PubMed

    Honzatko, Pavel; Kanka, J; Vrany, B

    2004-11-29

    The simulated annealing method is used for retrieving the amplitude and phase from cross-phase modulation spectrograms. The method allows us to take into account the birefringence of the measurement fiber and resolution of the optical spectrum analyzer. The influence of the birefringence and analyzer resolution are discussed.

  5. Aharonov-Bohm oscillations, quantum decoherence and amplitude modulation in mesoscopic InGaAs/InAlAs rings.

    PubMed

    Ren, S L; Heremans, J J; Gaspe, C K; Vijeyaragunathan, S; Mishima, T D; Santos, M B

    2013-10-30

    Low-temperature Aharonov-Bohm oscillations in the magnetoresistance of mesoscopic interferometric rings patterned on an InGaAs/InAlAs heterostructure are investigated for their dependence on excitation current and temperature. The rings have an average radius of 650 nm, and a lithographic arm width of 300 nm, yielding pronounced interference oscillations over a wide range of magnetic fields. Apart from a current and temperature dependence, the oscillation amplitude also shows a quasi-periodic modulation with applied magnetic field. The phase coherence length is extracted by analysis of the fundamental and higher Fourier components of the oscillations, and by direct analysis of the amplitude and its dependence on parameters. It is concluded that the Thouless energy forms the measure of excitation energies for quantum decoherence. The amplitude modulation finds an explanation in the effect of the magnetic flux threading the finite width of the interferometer arms.

  6. Experimental evidence of signal-optical noise interferencelike effect in underwater amplitude-modulated laser optical radar systems.

    PubMed

    Bartolini, L; De Dominicis, L; Ferri de Collibus, M; Fornetti, G; Francucci, M; Guarneri, M; Nuvoli, M; Paglia, E; Ricci, R

    2008-11-15

    We report experimental evidence that in an amplitude-modulated laser optical radar system for underwater 3D imaging the observed contrast oscillations as a function of the modulation frequency originate from an interference-like effect between target signal VT and water backscattered radiation VW. The demonstration relies on the ability to perform a direct measurement of VW in a 25 m long test tank. The proposed data processing method enables one to remove the contribution of water backscattering from the detected signal and drastically reduce signal fluctuations due to the medium. Experiments also confirm the possibility to improve the signal to optical noise ratio and contrast by increasing the modulation frequency.

  7. Spatiotemporal reconstruction of auditory steady-state responses to acoustic amplitude modulations: Potential sources beyond the auditory pathway.

    PubMed

    Farahani, Ehsan Darestani; Goossens, Tine; Wouters, Jan; van Wieringen, Astrid

    2017-03-01

    Investigating the neural generators of auditory steady-state responses (ASSRs), i.e., auditory evoked brain responses, with a wide range of screening and diagnostic applications, has been the focus of various studies for many years. Most of these studies employed a priori assumptions regarding the number and location of neural generators. The aim of this study is to reconstruct ASSR sources with minimal assumptions in order to gain in-depth insight into the number and location of brain regions that are activated in response to low- as well as high-frequency acoustically amplitude modulated signals. In order to reconstruct ASSR sources, we applied independent component analysis with subsequent equivalent dipole modeling to single-subject EEG data (young adults, 20-30 years of age). These data were based on white noise stimuli, amplitude modulated at 4, 20, 40, or 80Hz. The independent components that exhibited a significant ASSR were clustered among all participants by means of a probabilistic clustering method based on a Gaussian mixture model. Results suggest that a widely distributed network of sources, located in cortical as well as subcortical regions, is active in response to 4, 20, 40, and 80Hz amplitude modulated noises. Some of these sources are located beyond the central auditory pathway. Comparison of brain sources in response to different modulation frequencies suggested that the identified brain sources in the brainstem, the left and the right auditory cortex show a higher responsiveness to 40Hz than to the other modulation frequencies.

  8. Sensitivity evaluation of the green alga Chlamydomonas reinhardtii to uranium by pulse amplitude modulated (PAM) fluorometry.

    PubMed

    Herlory, Olivier; Bonzom, Jean-Marc; Gilbin, Rodolphe

    2013-09-15

    Although ecotoxicological studies tend to address the toxicity thresholds of uranium in freshwaters, there is a lack of information on the effects of the metal on physiological processes, particularly in aquatic plants. Knowing that uranium alters photosynthesis via impairment of the water photo-oxidation process, we determined whether pulse amplitude modulated (PAM) fluorometry was a relevant tool for assessing the impact of uranium on the green alga Chlamydomonas reinhardtii and investigated how and to what extent uranium hampered photosynthetic performance. Photosynthetic activity and quenching were assessed from fluorescence induction curves generated by PAM fluorometry, after 1 and 5h of uranium exposure in controlled conditions. The oxygen-evolving complex (OEC) of PSII was identified as the primary action site of uranium, through alteration of the water photo-oxidation process as revealed by F0/Fv. Limiting re-oxidation of the plastoquinone pool, uranium impaired the electron flux between the photosystems until almost complete inhibition of the PSII quantum efficiency ( [Formula: see text] , EC50=303 ± 64 μg UL(-1) after 5h of exposure) was observed. Non-photochemical quenching (qN) was identified as the most sensitive fluorescence parameter (EC50=142 ± 98 μg UL(-1) after 5h of exposure), indicating that light energy not used in photochemistry was dissipated in non-radiative processes. It was shown that parameters which stemmed from fluorescence induction kinetics are valuable indicators for evaluating the impact of uranium on PSII in green algae. PAM fluorometry provided a rapid and reasonably sensitive method for assessing stress response to uranium in microalgae.

  9. Influence of stimulus parameters on amplitude-modulated stimulus frequency otoacoustic emissionsa

    PubMed Central

    Johnson, Tiffany A.; Beshaler, Laura

    2013-01-01

    The present study evaluated the influence of suppressor frequency (fs) and level (Ls) on stimulus-frequency otoacoustic emissions (SFOAEs) recorded using the amplitude-modulated (AM) suppressor technique described by Neely et al. [J. Acoust. Soc. Am. 118, 2124-2127 (2005a)]. Data were collected in normal-hearing subjects, with data collection occurring in two phases. In phase 1, SFOAEs were recorded with probe frequency (fp) = 1, 2, and 4 kHz and probe levels (Lp) ranging from 0 to 60 dB sound pressure level (SPL). At each fp, Ls ranged from Ls = Lp to Ls = Lp + 30 dB. Additionally, nine relationships between fs and fp were evaluated, ranging from fs/fp = 0.80 to fs/fp = 1.16. Results indicated that for low suppressor levels, suppressors higher in frequency than fp (fs > fp) resulted in higher AM-SFOAE levels than suppressors lower in frequency than fp (fs < fp). At higher suppressor levels, suppressors both higher and lower in frequency than fp produced similar AM-SFOAE levels, and, in many cases, low-frequency suppressors produced the largest response. Recommendations for stimulus parameters that maximize AM-SFOAE level were derived from these data. In phase 2, AM-SFOAEs were recorded using these parameters for fp = 0.7-8 kHz and Lp = 20-60 dB SPL. Robust AM-SFOAE responses were recorded in this group of subjects using the parameters developed in phase 1. PMID:23927112

  10. Resolving the contribution of the uncoupled phycobilisomes to cyanobacterial pulse-amplitude modulated (PAM) fluorometry signals.

    PubMed

    Acuña, Alonso M; Snellenburg, Joris J; Gwizdala, Michal; Kirilovsky, Diana; van Grondelle, Rienk; van Stokkum, Ivo H M

    2016-01-01

    Pulse-amplitude modulated (PAM) fluorometry is extensively used to characterize photosynthetic organisms on the slow time-scale (1-1000 s). The saturation pulse method allows determination of the quantum yields of maximal (F(M)) and minimal fluorescence (F(0)), parameters related to the activity of the photosynthetic apparatus. Also, when the sample undergoes a certain light treatment during the measurement, the fluorescence quantum yields of the unquenched and the quenched states can be determined. In the case of cyanobacteria, however, the recorded fluorescence does not exclusively stem from the chlorophyll a in photosystem II (PSII). The phycobilins, the pigments of the cyanobacterial light-harvesting complexes, the phycobilisomes (PB), also contribute to the PAM signal, and therefore, F(0) and F(M) are no longer related to PSII only. We present a functional model that takes into account the presence of several fluorescent species whose concentrations can be resolved provided their fluorescence quantum yields are known. Data analysis of PAM measurements on in vivo cells of our model organism Synechocystis PCC6803 is discussed. Three different components are found necessary to fit the data: uncoupled PB (PB(free)), PB-PSII complexes, and free PSI. The free PSII contribution was negligible. The PB(free) contribution substantially increased in the mutants that lack the core terminal emitter subunits allophycocyanin D or allophycocyanin F. A positive correlation was found between the amount of PB(free) and the rate constants describing the binding of the activated orange carotenoid protein to PB, responsible for non-photochemical quenching.

  11. Phase retrieval via spatial light modulator phase modulation in 4f optical setup: numerical inverse imaging with sparse regularization for phase and amplitude.

    PubMed

    Katkovnik, Vladimir; Astola, Jaakko

    2012-01-01

    The 4f optical setup is considered with a wave field modulation by a spatial light modulator located in the focal plane of the first lens. Phase as well as amplitude of the wave field are reconstructed from noisy multiple-intensity observations. The reconstruction is optimal due to a constrained maximum likelihood formulation of the problem. The proposed algorithm is iterative with decoupling of the inverse of the forward propagation of the wave field and the filtering of phase and amplitude. The sparse modeling of phase and amplitude enables the advanced high-accuracy filtering and sharp imaging of the complex-valued wave field. Artifacts typical for the conventional algorithms (wiggles, ringing, waves, etc.) and attributed to optical diffraction can be suppressed by the proposed algorithm.

  12. Determination of refractive index and absorbance modulation amplitudes from angular selectivity of holograms in polymer material with phenanthrenequinone

    NASA Astrophysics Data System (ADS)

    Borisov, Vladimir; Veniaminov, Andrey

    2015-10-01

    Amplitude and phase contributions to mixed volume holographic gratings were extracted from measured contours of angular selectivity. Holograms for the investigation were recorded in the glassy polymer material with phenan-threnequinone (PQ) using the DPSS CW laser (532 nm) and then self-developed due to molecular diffusion of PQ, reaching diffraction efficiency about 40%. Refractive index and absorbance modulation amplitudes of those holograms were obtained as adjustable parameters from theoretical equations by fitting angular dependencies of zeros and 1st orders diffraction efficiency measured at 450, 473, 532, and 633 nm at the different stages of hologram development. Mixed gratings manifest themselves in asymmetrical transmittance selectivity contours with one minimum and one maximum shifted with respect to the Bragg angle, while symmetrical contours with a minimum or a maximum at the Bragg angle are characteristic of pure phase and amplitude gratings, respectively. In the course of a hologram development, it converts from a predominantly amplitude-mixed to almost purely phase one in the case of readout using a light within the absorption band of PQ and maintains the phase nature besides it. The value of refractive index amplitude is ranging from 5×10-6 to 10-4 and the value of absorbance amplitude is up to 140 m-1.

  13. Emphasis of spatial cues in the temporal fine structure during the rising segments of amplitude-modulated sounds

    PubMed Central

    Dietz, Mathias; Marquardt, Torsten; Salminen, Nelli H.; McAlpine, David

    2013-01-01

    The ability to locate the direction of a target sound in a background of competing sources is critical to the survival of many species and important for human communication. Nevertheless, brain mechanisms that provide for such accurate localization abilities remain poorly understood. In particular, it remains unclear how the auditory brain is able to extract reliable spatial information directly from the source when competing sounds and reflections dominate all but the earliest moments of the sound wave reaching each ear. We developed a stimulus mimicking the mutual relationship of sound amplitude and binaural cues, characteristic to reverberant speech. This stimulus, named amplitude modulated binaural beat, allows for a parametric and isolated change of modulation frequency and phase relations. Employing magnetoencephalography and psychoacoustics it is demonstrated that the auditory brain uses binaural information in the stimulus fine structure only during the rising portion of each modulation cycle, rendering spatial information recoverable in an otherwise unlocalizable sound. The data suggest that amplitude modulation provides a means of “glimpsing” low-frequency spatial cues in a manner that benefits listening in noisy or reverberant environments. PMID:23980161

  14. On the solar cycle dependence of the amplitude modulation characterizing the mid-latitude sporadic E layer diurnal periodicity

    NASA Astrophysics Data System (ADS)

    Pezzopane, M.; Pignalberi, A.; Pietrella, M.

    2016-01-01

    Spectral analyses are employed to investigate how the diurnal periodicity of the critical frequency of the sporadic E (Es) layer varies with solar activity. The study is based on ionograms recorded at the ionospheric station of Rome (41.8°N, 12.5°E), Italy, from 1976 to 2009, a period of time covering three solar cycles. It was confirmed that the diurnal periodicity is always affected by an amplitude modulation with periods of several days, which is the proof that Es layers are affected indirectly by planetary waves through their nonlinear interaction with atmospheric tides at lower altitudes. The most striking features coming out from this study is however that this amplitude modulation is greater for high-solar activity than for low-solar activity.

  15. Arbitrary shaping of on-axis amplitude of femtosecond Bessel beams with a single phase-only spatial light modulator.

    PubMed

    Ouadghiri-Idrissi, Ismail; Giust, Remo; Froehly, Luc; Jacquot, Maxime; Furfaro, Luca; Dudley, John M; Courvoisier, Francois

    2016-05-30

    Arbitrary shaping of the on-axis intensity of Bessel beams requires spatial modulation of both amplitude and phase. We develop a non-iterative direct space beam shaping method to generate Bessel beams with high energy throughput from direct space with a single phase-only spatial light modulator. For this purpose, we generalize the approach of Bolduc et al. to non-uniform input beams. We point out the physical limitations imposed on the on-axis intensity profile for unidirectional beams. Analytical, numerical and experimental results are provided.

  16. Triggerable electro-optic amplitude modulator bias stabilizer for integrated optical devices

    DOEpatents

    Conder, A.D.; Haigh, R.E.; Hugenberg, K.F.

    1995-09-26

    An improved Mach-Zehnder integrated optical electro-optic modulator is achieved by application and incorporation of a DC bias box containing a laser synchronized trigger circuit, a DC ramp and hold circuit, a modulator transfer function negative peak detector circuit, and an adjustable delay circuit. The DC bias box ramps the DC bias along the transfer function curve to any desired phase or point of operation at which point the RF modulation takes place. 7 figs.

  17. Triggerable electro-optic amplitude modulator bias stabilizer for integrated optical devices

    DOEpatents

    Conder, Alan D.; Haigh, Ronald E.; Hugenberg, Keith F.

    1995-01-01

    An improved Mach-Zehnder integrated optical electro-optic modulator is achieved by application and incorporation of a DC bias box containing a laser synchronized trigger circuit, a DC ramp and hold circuit, a modulator transfer function negative peak detector circuit, and an adjustable delay circuit. The DC bias box ramps the DC bias along the transfer function curve to any desired phase or point of operation at which point the RF modulation takes place.

  18. Cortical activities of single-trial P300 amplitudes modulated by memory load using simultaneous EEG-fMRI

    NASA Astrophysics Data System (ADS)

    Zhang, Qiushi; Zhao, Xiaojie; Zhu, Chaozhe; Yang, Xueqian; Yao, Li

    2015-03-01

    The functional magnetic resonance imaging (fMRI) researches on working memory have found that activation of cortical areas appeared dependent on memory load, and event-related potentials (ERP) studies have demonstrated that amplitudes of P300 decreased significantly when working memory load increased. However, the cortical activities related with P300 amplitudes under different memory loads remains unclear. Joint fMRI and EEG analysis which fusions the time and spatial information in simultaneous EEG-fMRI recording can reveal the regional activation at each ERP time point. In this paper, we first used wavelet transform to obtain the single-trial amplitudes of P300 caused by a digital N-back task in the simultaneous EEG-fMRI recording as the ERP feature sequences. Then the feature sequences in 1-back condition and 3-back condition were introduced into general linear model (GLM) separately as parametric modulations to compare the cortical activation under different memory loads. The results showed that the average amplitudes of P300 in 3-back significantly decreased than that in 1-back, and the activities induced by ERP feature sequences in 3-back also significantly decreased than that in the 1-back, including the insular, anterior cingulate cortex, right inferior frontal gyrus, and medial frontal gyrus, which were relevant to the storage, monitoring, and manipulation of information in working memory task. Moreover, the difference in the activation caused by ERP feature showed a positive correlation with the difference in behavioral performance. These findings demonstrated the locations of P300 amplitudes differences modulated by the memory load and its relationship with the behavioral performance.

  19. Shaping perfect optical vortex with amplitude modulated using a digital micro-mirror device

    NASA Astrophysics Data System (ADS)

    Zhang, Chonglei; Min, Changjun; Yuan, X.-C.

    2016-12-01

    We propose a technique to generate of perfect optical vortex (POV) via Fourier transformation of Bessel-Gauss (BG) beams through encoding of the amplitude of the optical field with binary amplitude digital micro-mirrors device (DMD). Furthermore, we confirm the correct phase patterns of the POV with the method of Mach-Zehnder interferometer. Our approach to generate the POV has the advantages that rapidly switch among the different modes, wide spectral regions and high energy tolerance. Since the POV possess propagation properties that not shape-invariant, we therefore suppose that our proposed approach will find potential applications in optical microscopy, optical fabrication, and optical communication.

  20. Performance improvement by orthogonal pulse amplitude modulation and discrete multitone modulation signals in hybrid fiber-visible laser light communication system

    NASA Astrophysics Data System (ADS)

    Zhang, Fangliu; He, Jing; Deng, Rui; Chen, Qinghui; Chen, Lin

    2016-10-01

    A modulation format, orthogonal pulse amplitude modulation and discrete multitone modulation (O-PAM-DMT), is experimentally demonstrated in a hybrid fiber-visible laser light communication (fiber-VLLC) system using a cost-effective directly modulated laser and blue laser diode. In addition, low overhead is achieved by utilizing only one training sequence to implement synchronization and channel estimation. Through adjusting the ratio of PAM and DMT signal, three types of O-PAM-DMT signals are investigated. After transmission over a 20-km standard single-mode fiber and 5-m free-space VLLC, the receiver sensitivity for 4.36-Gbit/s O-PAM-DMT signals can be improved by 0.4, 1.4, and 2.7 dB, respectively, at a bit error rate of 1×10-3, compared with a conventional DMT signal.

  1. [Modulating effect of dopamine on amplitude of GABA-produced chemocontrolled currents in multipolar spinal cord neurons of ammocaete].

    PubMed

    Bukinich, A A

    2010-01-01

    By using the patch-clamp method in the whole cell configuration, modulating effect of dopamine on GABA-activated currents has been studied on isolated multipolar spinal cord neurons of the ammocaete (larva of the lamprey Lampetra planeri). At application of dopamine (5 microM), there was observed in some cases a decrease of the GABA-activated current, on average, by 33.3 +/- 8.7 (n = 8, p < 0.01), in other cases--an increase of the amplitude, on average, by 37.3 +/- 11.8% (n = 5, p < 0.01). Concentration of GABA amounted to 2 mM. Study of action of agonists of D1- and D2-receptors on amplitude of che-mocontrolled currents has shown that agonist of D1-receptors (+)-SKF-38393 (5 microM) decreases the GABA-activated current amplitude, on average, by 63.1 +/- 11.7% (n = 8, p < 0.01); the agonist of D2-receptors (-)-quinpirole (5 microM) produces in various cells the dopamine-like effects: an increase of the GABA-activated current amplitude, on average, by 61.0 +/- 13.8% (n = 8, p < 0.01) and a decrease of amplitude, on average, by 55.7 +/- 2.0 % (n = 6, p < 0.01). It has been shown that antagonist of D2-receptors sulpiride (5 microM) does not block effects produced by dopamine. The dopamine effects were partially blocked by antagonist of D1-receptors (+)-SCH-23390 (5 microM): a decrease of the GABA-activated amplitude current amounted, on average, to 11.7 +/- 1.8 % (n = 7, p < 0.01), while an increase of amplitude--8.3 +/- 2.0 % (n = 5,p < 0.01). At the same time, effects of agonist of D1-receptors quinpirole (5 microM) were partially blocked by antagonist of D1-receptors (+)-SCH-23390: a decrease of the GABA-activated current amplitude amounted, on average, to 9.2 +/- 3.4 % (n = 6, p < 0.01) and an increase of amplitude--6.3 +/- 1.8 % (n = 10, p < 0.01). The obtained data indicate differences of mechanisms of the receptor-mediated effect of agonists of dopamine receptors on GABA-activated and potential-activated currents of multipolar neurons of the ammocaete spinal

  2. The onion fly modulates the adult eclosion time in response to amplitude of temperature cycle

    NASA Astrophysics Data System (ADS)

    Tanaka, Kazuhiro; Watari, Yasuhiko

    2011-08-01

    To confirm whether the amplitude of diel temperature cycles causes a phase shift of adult eclosion rhythm of the onion fly, Delia antiqua, the peak time ( Ø E) of adult eclosion was determined under various thermoperiods with a fixed temperature either in the warm or cool phase and temperature differences ranging from 1°C to 4°C between the two phases. Irrespective of the temperature level during the warm or cool phase, Ø E occurred earlier with decreasing amplitude of the temperature cycle. The results strongly support the previous conclusion of Tanaka and Watari (Naturwissenschaften 90:76-79, 2003) that D. antiqua responds to the amplitude of temperature cycle as a cue for the circadian adult eclosion timing. The phase advance was larger in thermoperiods with a fixed warm-phase temperature than in those with a fixed cool-phase temperature. This might be ascribed to the interaction between the amplitude and level of temperature in the thermoperiodic regimes.

  3. The relationship between geophysical conditions and ELF amplitude in modulated heating experiments at HAARP: Modeling and experimental results

    NASA Astrophysics Data System (ADS)

    Jin, G.; Spasojevic, M.; Cohen, M. B.; Inan, U. S.; Lehtinen, N. G.

    2011-07-01

    Experiments for generating extremely low frequency (ELF) radio waves using modulated HF heating of the auroral ionosphere have been conducted and refined at the High Frequency Active Auroral Research Program (HAARP) facility at Gakona, Alaska. Because this technique is dependent on strength of the naturally generated electrojet current system, the amplitude of the generated ELF changes with geophysical conditions. Past work has shown that electrojet current strength as measured by magnetometers often correlates with generated ELF amplitude, but there are periods of poor or negative correlation. We attempt to use additional diagnostics from a radar, riometer, ionosonde, and magnetometer chain to understand how ionospheric conditions affect ELF generation. We then present the results of a statistical model that shows that ELF amplitude is roughly proportional to magnetometer measurements for a fixed value of riometer absorption and that the proportionality constant decreases as riometer absorption increases. Theoretical simulations of modulated heating are conducted for a variety of ionospheric density profiles to verify that denser profiles result in smaller gains for ELF generation as a function of electrojet current at a given electric field.

  4. Homocysteine reduces NMDAR desensitization and differentially modulates peak amplitude of NMDAR currents, depending on GluN2 subunit composition

    PubMed Central

    Phillips, Marnie A.; Constantine-Paton, Martha

    2013-01-01

    N-methyl-d-aspartate receptors (NMDARs) have been linked to schizophrenia because agents that bind the receptor, like ketamine and phencyclidine, are capable of inducing schizophrenia-like symptoms. Here we show that the amino acid homocysteine (HCY), which is increased in the blood of schizophrenia patients, reduces desensitization of NMDARs in cultured mouse neurons, human embryonic kidney cells transfected with GluN1 + GluN2A, GluN2B, or GluN2D subunits, and hippocampal slices. HCY also alters the peak amplitude of NMDAR currents, depending on the GluN2 subunit the receptor contains; GluN1 + GluN2A-containing NMDARs show an increase in peak amplitude when exposed to HCY, while GluN1 + GluN2B-containing NMDARs show a decrease in peak amplitude. Both peak amplitude and desensitization effects of HCY can be occluded by saturating the NMDAR with glycine. Since glycine concentrations are not saturating in the brain, HCY could play an NMDAR-modulating role in the nervous system. We also show that HCY shares characteristics with glutamate and suggest that HCY affects both the agonist and co-agonist site of the NMDAR. PMID:23864370

  5. Frequency Changes in a Continuous Tone: Auditory Cortical Potentials

    PubMed Central

    Dimitrijevic, Andrew; Michalewski, Henry J.; Zeng, Fan-Gang; Pratt, Hillel; Starr, Arnold

    2009-01-01

    Objective We examined auditory cortical potentials in normal hearing subjects to spectral changes in continuous low and high frequency pure tones. Methods Cortical potentials were recorded to increments of frequency from continuous 250 Hz or 4000 Hz tones. The magnitude of change was random and varied from 0% to 50% above the base frequency. Results Potentials consisted of N100, P200 and a slow negative wave (SN). N100 amplitude, latency and dipole magnitude with frequency increments were significantly greater for low compared to high frequencies. Dipole amplitudes were greater in the right than left hemisphere for both base frequencies. The SN amplitude to frequency changes between 4 to 50% was not significantly related to the magnitude of spectral change. Conclusions Modulation of N100 amplitude and latency elicited by spectral change is more pronounced with low compared to high frequencies. Significance These data provide electrophysiological evidence that central processing of spectral changes in the cortex differs for low and high frequencies. Some of these differences may be related to both temporal- and spectral-based coding at the auditory periphery. Central representation of frequency change may be related to the different temporal windows of integration across frequencies. PMID:18635394

  6. Mosquito (Aedes aegypti) flight tones: Frequency, harmonicity, spherical spreading, and phase relationships

    PubMed Central

    Arthur, Benjamin J.; Emr, Kevin S.; Wyttenbach, Robert A.; Hoy, Ronald R.

    2014-01-01

    Mosquito flight produces a tone as a side effect of wing movement; this tone is also a communication signal that is frequency-modulated during courtship. Recordings of tones produced by tethered flying male and female Aedes aegypti were undertaken using pairs of pressure-gradient microphones above and below, ahead and behind, and to the left and right over a range of distances. Fundamental frequencies were close to those previously reported, although amplitudes were lower. The male fundamental frequency was higher than that of the female and males modulated it over a wider range. Analysis of harmonics shows that the first six partials were nearly always within 1 Hz of integer multiples of the fundamental, even when the fundamental was being modulated. Along the front-back axis, amplitude attenuated as a function of distance raised to the power 2.3. Front and back recordings were out of phase, as were above and below, while left and right were in phase. Recordings from ahead and behind showed quadratic phase coupling, while others did not. Finally, two methods are presented for separating simultaneous flight tones in a single recording and enhancing their frequency resolution. Implications for mosquito behavior are discussed. PMID:25234901

  7. Frequency and amplitude modulation of ultra-compact terahertz quantum cascade lasers using an integrated avalanche diode oscillator.

    PubMed

    Castellano, Fabrizio; Li, Lianhe; Linfield, Edmund H; Davies, A Giles; Vitiello, Miriam S

    2016-03-15

    Mode-locked comb sources operating at optical frequencies underpin applications ranging from spectroscopy and ultrafast physics, through to absolute frequency measurements and atomic clocks. Extending their operation into the terahertz frequency range would greatly benefit from the availability of compact semiconductor-based sources. However, the development of any compact mode-locked THz laser, which itself is inherently a frequency comb, has yet to be achieved without the use of an external stimulus. High-power, electrically pumped quantum cascade lasers (QCLs) have recently emerged as a promising solution, owing to their octave spanning bandwidths, the ability to achieve group-velocity dispersion compensation and the possibility of obtaining active mode-locking. Here, we propose an unprecedented compact architecture to induce both frequency and amplitude self-modulation in a THz QCL. By engineering a microwave avalanche oscillator into the laser cavity, which provides a 10 GHz self-modulation of the bias current and output power, we demonstrate multimode laser emission centered around 3 THz, with distinct multiple sidebands. The resulting microwave amplitude and frequency self-modulation of THz QCLs opens up intriguing perspectives, for engineering integrated self-mode-locked THz lasers, with impact in fields such as nano- and ultrafast photonics and optical metrology.

  8. Characterization of pulse amplitude and pulse rate modulation for a human vestibular implant during acute electrical stimulation

    NASA Astrophysics Data System (ADS)

    Nguyen, T. A. K.; DiGiovanna, J.; Cavuscens, S.; Ranieri, M.; Guinand, N.; van de Berg, R.; Carpaneto, J.; Kingma, H.; Guyot, J.-P.; Micera, S.; Perez Fornos, A.

    2016-08-01

    Objective. The vestibular system provides essential information about balance and spatial orientation via the brain to other sensory and motor systems. Bilateral vestibular loss significantly reduces quality of life, but vestibular implants (VIs) have demonstrated potential to restore lost function. However, optimal electrical stimulation strategies have not yet been identified in patients. In this study, we compared the two most common strategies, pulse amplitude modulation (PAM) and pulse rate modulation (PRM), in patients. Approach. Four subjects with a modified cochlear implant including electrodes targeting the peripheral vestibular nerve branches were tested. Charge-equivalent PAM and PRM were applied after adaptation to baseline stimulation. Vestibulo-ocular reflex eye movement responses were recorded to evaluate stimulation efficacy during acute clinical testing sessions. Main results. PAM evoked larger amplitude eye movement responses than PRM. Eye movement response axes for lateral canal stimulation were marginally better aligned with PRM than with PAM. A neural network model was developed for the tested stimulation strategies to provide insights on possible neural mechanisms. This model suggested that PAM would consistently cause a larger ensemble firing rate of neurons and thus larger responses than PRM. Significance. Due to the larger magnitude of eye movement responses, our findings strongly suggest PAM as the preferred strategy for initial VI modulation.

  9. Frequency and amplitude modulation of ultra-compact terahertz quantum cascade lasers using an integrated avalanche diode oscillator

    NASA Astrophysics Data System (ADS)

    Castellano, Fabrizio; Li, Lianhe; Linfield, Edmund H.; Davies, A. Giles; Vitiello, Miriam S.

    2016-03-01

    Mode-locked comb sources operating at optical frequencies underpin applications ranging from spectroscopy and ultrafast physics, through to absolute frequency measurements and atomic clocks. Extending their operation into the terahertz frequency range would greatly benefit from the availability of compact semiconductor-based sources. However, the development of any compact mode-locked THz laser, which itself is inherently a frequency comb, has yet to be achieved without the use of an external stimulus. High-power, electrically pumped quantum cascade lasers (QCLs) have recently emerged as a promising solution, owing to their octave spanning bandwidths, the ability to achieve group-velocity dispersion compensation and the possibility of obtaining active mode-locking. Here, we propose an unprecedented compact architecture to induce both frequency and amplitude self-modulation in a THz QCL. By engineering a microwave avalanche oscillator into the laser cavity, which provides a 10 GHz self-modulation of the bias current and output power, we demonstrate multimode laser emission centered around 3 THz, with distinct multiple sidebands. The resulting microwave amplitude and frequency self-modulation of THz QCLs opens up intriguing perspectives, for engineering integrated self-mode-locked THz lasers, with impact in fields such as nano- and ultrafast photonics and optical metrology.

  10. Frequency and amplitude modulation of ultra-compact terahertz quantum cascade lasers using an integrated avalanche diode oscillator

    PubMed Central

    Castellano, Fabrizio; Li, Lianhe; Linfield, Edmund H.; Davies, A. Giles; Vitiello, Miriam S.

    2016-01-01

    Mode-locked comb sources operating at optical frequencies underpin applications ranging from spectroscopy and ultrafast physics, through to absolute frequency measurements and atomic clocks. Extending their operation into the terahertz frequency range would greatly benefit from the availability of compact semiconductor-based sources. However, the development of any compact mode-locked THz laser, which itself is inherently a frequency comb, has yet to be achieved without the use of an external stimulus. High-power, electrically pumped quantum cascade lasers (QCLs) have recently emerged as a promising solution, owing to their octave spanning bandwidths, the ability to achieve group-velocity dispersion compensation and the possibility of obtaining active mode-locking. Here, we propose an unprecedented compact architecture to induce both frequency and amplitude self-modulation in a THz QCL. By engineering a microwave avalanche oscillator into the laser cavity, which provides a 10 GHz self-modulation of the bias current and output power, we demonstrate multimode laser emission centered around 3 THz, with distinct multiple sidebands. The resulting microwave amplitude and frequency self-modulation of THz QCLs opens up intriguing perspectives, for engineering integrated self-mode-locked THz lasers, with impact in fields such as nano- and ultrafast photonics and optical metrology. PMID:26976199

  11. Prestimulus amplitudes modulate P1 latencies and evoked traveling alpha waves

    PubMed Central

    Himmelstoss, Nicole A.; Brötzner, Christina P.; Zauner, Andrea; Kerschbaum, Hubert H.; Gruber, Walter; Lechinger, Julia; Klimesch, Wolfgang

    2015-01-01

    Traveling waves have been well documented in the ongoing, and more recently also in the evoked EEG. In the present study we investigate what kind of physiological process might be responsible for inducing an evoked traveling wave. We used a semantic judgment task which already proved useful to study evoked traveling alpha waves that coincide with the appearance of the P1 component. We found that the P1 latency of the leading electrode is significantly correlated with prestimulus amplitude size and that this event is associated with a transient change in alpha frequency. We assume that cortical background excitability, as reflected by an increase in prestimulus amplitude, is responsible for the observed change in alpha frequency and the initiation of an evoked traveling trajectory. PMID:26074804

  12. Optical Correlation Based Pose Estimation Using Bipolar Amplitude Spatial Light Modulators

    DTIC Science & Technology

    2008-12-22

    value • HMED Realizable value Re Figure 3-2 MED mapping for binary SLM For a ternary SLM device, its MED mapping is: 29 "Mkü +1, +0.5<Re(//) 0...below in Figure 3-4. Im \\ -l o H computed value • HM,,D realizable value Re Figure 3-3 MED mapping for AOSLM For coupled amplitude/phase

  13. Calcium modulates the frequency and amplitude of spontaneous otoacoustic emissions in the bobtail skink.

    PubMed

    Manley, Geoffrey A; Sienknecht, Ulrike; Köppl, Christine

    2004-11-01

    Active processes in the inner ear of lizards can be monitored using spontaneous otoacoustic emissions (SOAE) measured outside the eardrum. In the Australian bobtail lizard, SOAE are generated by an active motility process in the hair-cell bundle. This mechanism has been shown to be sensitive to the calcium-chelating agent 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid and is presumed to be related to the calcium-sensitive transduction-channel motor implicated in other nonmammalian hair cell systems. In studies of frog saccular and turtle auditory papillar hair cells in vitro, the frequency and amplitude of bundle oscillations depend on the concentration of calcium in the bathing solutions. In the present study, the calcium concentration in the endolymph was changed in vivo in the Australian bobtail lizard Tiliqua rugosa, and SOAE were monitored. Glass pipettes with large tips and containing different calcium concentrations in their fluids were introduced into scala media, and their contents were allowed to passively flow into the endolymph. Low calcium concentrations resulted in a downward shift in the frequency of SOAE spectral peaks and generally an increase in their amplitudes. Calcium concentrations > 2 mM resulted in increases in frequency of SOAE peaks and generally a loss in amplitude. These frequency shifts were consistent with in vitro data on the frequencies and amplitudes of spontaneous oscillation of hair cell bundles and thus also implicate calcium ions in the generation of active motility in nonmammalian hair cells. The data also suggest that in this lizard species, the ionic calcium concentration in the cochlear endolymph is > or = 1 mM.

  14. Blocked versus randomized presentation modes differentially modulate feedback-related negativity and P3b amplitudes

    PubMed Central

    Pfabigan, Daniela M.; Zeiler, Michael; Lamm, Claus; Sailer, Uta

    2014-01-01

    Objective Electrophysiological studies on feedback processing typically use a wide range of feedback stimuli which might not always be comparable. The current study investigated whether two indicators of feedback processing – feedback-related negativity (FRN) and P3b – differ for feedback stimuli with explicit (facial expressions) or assigned valence information (symbols). In addition, we assessed whether presenting feedback in either a trial-by-trial or a block-wise fashion affected these ERPs. Methods EEG was recorded in three experiments while participants performed a time estimation task and received two different types of performance feedback. Results Only P3b amplitudes varied consistently in response to feedback type for both presentation types. Moreover, the blocked feedback type presentation yielded more distinct FRN peaks, higher effect sizes, and a significant relation between FRN amplitudes and behavioral task performance measures. Conclusion Both stimulus type and presentation mode may provoke systematic changes in feedback-related ERPs. The current findings point at important potential confounds that need to be controlled for when designing FRN or P3b studies. Significance Studies investigating P3b amplitudes using mixed types of stimuli have to be interpreted with caution. Furthermore, we suggest implementing a blocked presentation format when presenting different feedback types within the same experiment. PMID:24144779

  15. Identification of Buried Objects in GPR Using Amplitude Modulated Signals Extracted from Multiresolution Monogenic Signal Analysis

    PubMed Central

    Qiao, Lihong; Qin, Yao; Ren, Xiaozhen; Wang, Qifu

    2015-01-01

    It is necessary to detect the target reflections in ground penetrating radar (GPR) images, so that surface metal targets can be identified successfully. In order to accurately locate buried metal objects, a novel method called the Multiresolution Monogenic Signal Analysis (MMSA) system is applied in ground penetrating radar (GPR) images. This process includes four steps. First the image is decomposed by the MMSA to extract the amplitude component of the B-scan image. The amplitude component enhances the target reflection and suppresses the direct wave and reflective wave to a large extent. Then we use the region of interest extraction method to locate the genuine target reflections from spurious reflections by calculating the normalized variance of the amplitude component. To find the apexes of the targets, a Hough transform is used in the restricted area. Finally, we estimate the horizontal and vertical position of the target. In terms of buried object detection, the proposed system exhibits promising performance, as shown in the experimental results. PMID:26690146

  16. Amplitude modulation detection by human listeners in reverberant sound fields: Carrier bandwidth effects and binaural versus monaural comparison

    PubMed Central

    Zahorik, Pavel; Kim, Duck O.; Kuwada, Shigeyuki; Anderson, Paul W.; Brandewie, Eugene; Collecchia, Regina; Srinivasan, Nirmal

    2012-01-01

    Previous work [Zahorik et al., POMA, 12, 050005 (2011)] has reported that for a broadband noise carrier signal in a simulated reverberant sound field, human sensitivity to amplitude modulation (AM) is higher than would be predicted based on the broadband acoustical modulation transfer function (MTF) of the listening environment. Interpretation of this result was complicated by the fact that acoustical MTFs of rooms are often quite different for different carrier frequency regions, and listeners may have selectively responded to advantageous carrier frequency regions where the effective acoustic modulation loss due to the room was less than indicated by a broadband acoustic MTF analysis. Here, AM sensitivity testing and acoustic MTF analyses were expanded to include narrowband noise carriers (1-octave and 1/3-octave bands centered at 4 kHz), as well as monaural and binaural listening conditions. Narrowband results were found to be consistent with broadband results: In a reverberant sound field, human AM sensitivity is higher than indicated by the acoustical MTFs. The effect was greatest for modulation frequencies above 32 Hz and was present whether the stimulation was monaural or binaural. These results are suggestive of mechanisms that functionally enhance modulation in reverberant listening. PMID:23437416

  17. A scheme for maintaining phase modulation amplitude at best value of fiber optic sensors using phase generated carrier

    NASA Astrophysics Data System (ADS)

    Zhu, Jianhui; Zhang, Min; Liao, Yanbiao; Kuang, Wu; Wang, Liwei

    2005-11-01

    This article firstly gives out when the phase modulation amplitude is at best value of homodyne demodulation using phase generated carrier, and then presents three methods that can be realized to get the best value. Some differences based on practicality are made among them, and a method which is easy to be implemented by digital circuits, is chosen to be carried out by digital circuits. Also this paper gives out simulation analysis and real experiment results. The error range is from -3.80% to 2.11% with real system. The origins of the error limiting the accuracy are discussed.

  18. Using active resonator impedance matching for shot-noise limited, cavity enhanced amplitude modulated laser absorption spectroscopy.

    PubMed

    Chow, Jong H; Littler, Ian C M; Rabeling, David S; McClelland, David E; Gray, Malcolm B

    2008-05-26

    We introduce a closed-loop feedback technique to actively control the coupling condition of an optical cavity, by employing amplitude modulation of the interrogating laser. We show that active impedance matching of the cavity facilitates optimal shot-noise sensing performance in a cavity enhanced system, while its control error signal can be used for intra-cavity absorption or loss signal extraction. We present the first demonstration of this technique with a fiber ring cavity, and achieved shot-noise limited loss sensitivity. We also briefly discuss further use of impedance matching control as a tool for other applications.

  19. Multiplexing technique using amplitude-modulated chirped fibre Bragg gratings with applications in two-parameter sensing

    NASA Astrophysics Data System (ADS)

    Wong, Allan C. L.; Childs, Paul A.; Peng, Gang-Ding

    2007-11-01

    A multiplexing technique using amplitude-modulated chirped fibre Bragg gratings (AMCFBGs) is presented. This technique realises the multiplexing of spectrally overlapped AMCFBGs with identical centre Bragg wavelength and bandwidth. Since it is fully compatible with the wavelength division multiplexing scheme, the number of gratings that can be multiplexed can be increased by several times. The discrete wavelet transform is used to demodulate such multiplexed signal. A wavelet denoising technique is applied to the multiplexed signal in conjunction with the demodulation. Strain measurements are performed to experimentally demonstrate the feasibility of this multiplexing technique. The absolute error and crosstalk are measured. An application to simultaneous two-parameter sensing is also demonstrated.

  20. The effect of microphone wind noise on the amplitude modulation of wind turbine noise and its mitigation.

    PubMed

    Kendrick, Paul; von Hünerbein, Sabine; Cox, Trevor J

    2016-07-01

    Microphone wind noise can corrupt outdoor recordings even when wind shields are used. When monitoring wind turbine noise, microphone wind noise is almost inevitable because measurements cannot be made in still conditions. The effect of microphone wind noise on two amplitude modulation (AM) metrics is quantified in a simulation, showing that even at low wind speeds of 2.5 m/s errors of over 4 dBA can result. As microphone wind noise is intermittent, a wind noise detection algorithm is used to automatically find uncorrupted sections of the recording, and so recover the true AM metrics to within ±2/±0.5 dBA.

  1. Effect on the immune system of mice exposed chronically to 50 Hz amplitude-modulated 2.45 GHz microwaves

    SciTech Connect

    Elekes, E.; Thuroczy, G.; Szabo, L.D.

    1996-12-01

    The effect of continuous (CW; 2.45 GHz carrier frequency) or amplitude-modulated (AM; 50 Hz square wave) microwave radiation on the immune response was tested. CW exposures (6 days, 3 h/day) induced elevations of the number of antibody-producing cells in the spleen of male Balb/c mice (+37%). AM microwave exposure induced elevation of the spleen index (+15%) and antibody-producing cell number (+55%) in the spleen of male mice. No changes were observed in female mice. It is concluded that both types of exposure conditions induced moderate elevation of antibody production only in male mice.

  2. Downdrift in a Tone Language with Four Tone Levels.

    ERIC Educational Resources Information Center

    Clements, G. N.

    1991-01-01

    Many tone languages exhibit some form of downdrift or automatic downstep, the lowering of high tones separated by low tones. In extreme cases, the realization of high tones at the end of a domain (such as the sentence) may be lower than the realization of low tones at the beginning. Tone languages with this property are cross-level tone languages.…

  3. Antagonists of the TMEM16A Calcium-Activated Chloride Channel Modulate Airway Smooth Muscle Tone and Intracellular Calcium

    PubMed Central

    Danielsson, Jennifer; Perez-Zoghbi, Jose; Bernstein, Kyra; Barajas, Matthew B.; Zhang, Yi; Kumar, Satish; Sharma, Pawan K.; Gallos, George; Emala, Charles W.

    2015-01-01

    Background Perioperative bronchospasm refractory to β-agonists continues to challenge anesthesiologists and intensivists. The TMEM16A calcium-activated chloride channel modulates airway smooth muscle (ASM) contraction. We hypothesized that TMEM16A antagonists would relax ASM contraction by modulating membrane potential and calcium flux. Methods Human ASM, guinea pig tracheal rings or mouse peripheral airways were contracted with acetylcholine (Ach) or leukotriene D4 (LTD4) and then treated with the TMEM16A antagonists: benzbromarone, T16Ainh-A01, MONNA or B25. In separate studies, guinea pig tracheal rings were contracted with Ach and then exposed to increasing concentrations of isoproterenol (0.01nM-10μM) ± benzbromarone. Plasma membrane potential and intracellular calcium concentrations were measured in human ASM cells. Results Benzbromarone was the most potent TMEM16A antagonist tested for relaxing an Ach-induced contraction in guinea pig tracheal rings (n=6). Further studies were done to investigate benzbromarone’s clinical utility. In human ASM, benzbromarone relaxed either an acetylcholine- or LTD4-induced contraction (n=8). Benzbromarone was also effective in relaxing peripheral airways (n=9) and potentiating relaxation by β-agonists (n=5–10). In cellular mechanistic studies, benzbromarone hyperpolarized human ASM cells (n=9–12) and attenuated intracellular calcium flux from both the plasma membrane and sarcoplasmic reticulum (n=6–12). Conclusions TMEM16A antagonists work synergistically with β-agonists and through a novel pathway of interrupting ion flux both at the plasma membrane and sarcoplasmic reticulum to acutely relax human airway smooth muscle. PMID:26181339

  4. Experience Drives Synchronization: The phase and Amplitude Dynamics of Neural Oscillations to Musical Chords Are Differentially Modulated by Musical Expertise

    PubMed Central

    Pallesen, Karen Johanne; Bailey, Christopher J.; Brattico, Elvira; Gjedde, Albert; Palva, J. Matias; Palva, Satu

    2015-01-01

    Musical expertise is associated with structural and functional changes in the brain that underlie facilitated auditory perception. We investigated whether the phase locking (PL) and amplitude modulations (AM) of neuronal oscillations in response to musical chords are correlated with musical expertise and whether they reflect the prototypicality of chords in Western tonal music. To this aim, we recorded magnetoencephalography (MEG) while musicians and non-musicians were presented with common prototypical major and minor chords, and with uncommon, non-prototypical dissonant and mistuned chords, while watching a silenced movie. We then analyzed the PL and AM of ongoing oscillations in the theta (4–8 Hz) alpha (8–14 Hz), beta- (14–30 Hz) and gamma- (30–80 Hz) bands to these chords. We found that musical expertise was associated with strengthened PL of ongoing oscillations to chords over a wide frequency range during the first 300 ms from stimulus onset, as opposed to increased alpha-band AM to chords over temporal MEG channels. In musicians, the gamma-band PL was strongest to non-prototypical compared to other chords, while in non-musicians PL was strongest to minor chords. In both musicians and non-musicians the long-latency (> 200 ms) gamma-band PL was also sensitive to chord identity, and particularly to the amplitude modulations (beats) of the dissonant chord. These findings suggest that musical expertise modulates oscillation PL to musical chords and that the strength of these modulations is dependent on chord prototypicality. PMID:26291324

  5. Predictions of psychophysical measurements for sinusoidal amplitude modulated (SAM) pulse-train stimuli from a stochastic model.

    PubMed

    Xu, Yifang; Collins, Leslie M

    2007-08-01

    Two approaches have been proposed to reduce the synchrony of the neural response to electrical stimuli in cochlear implants. One approach involves adding noise to the pulse-train stimulus, and the other is based on using a high-rate pulse-train carrier. Hypotheses regarding the efficacy of the two approaches can be tested using computational models of neural responsiveness prior to time-intensive psychophysical studies. In our previous work, we have used such models to examine the effects of noise on several psychophysical measures important to speech recognition. However, to date there has been no parallel analytic solution investigating the neural response to the high-rate pulse-train stimuli and their effect on psychophysical measures. This work investigates the properties of the neural response to high-rate pulse-train stimuli with amplitude modulated envelopes using a stochastic auditory nerve model. The statistics governing the neural response to each pulse are derived using a recursive method. The agreement between the theoretical predictions and model simulations is demonstrated for sinusoidal amplitude modulated (SAM) high rate pulse-train stimuli. With our approach, predicting the neural response in modern implant devices becomes tractable. Psychophysical measurements are also predicted using the stochastic auditory nerve model for SAM high-rate pulse-train stimuli. Changes in dynamic range (DR) and intensity discrimination are compared with that observed for noise-modulated pulse-train stimuli. Modulation frequency discrimination is also studied as a function of stimulus level and pulse rate. Results suggest that high rate carriers may positively impact such psychophysical measures.

  6. Tone-activated, remote, alert communication system

    NASA Technical Reports Server (NTRS)

    Baker, C. D.; Couvillon, L. A.; Hubbard, W. P.; Kollar, F. J.; Postal, R. B.; Tegnelia, C. R.

    1971-01-01

    Pocket sized transmitter, frequency modulated by crystal derived tones, with integral loop antenna provides police with easy operating alert signal communicator which uses patrol car radio to relay signal. Communication channels are time shared by several patrol units.

  7. The role of envelope beat cues in the detection and discrimination of second-order amplitude modulation (L)

    NASA Astrophysics Data System (ADS)

    Füllgrabe, Christian; Lorenzi, Christian

    2003-01-01

    The present study extends previous work from Lorenzi et al. [J. Acoust. Soc. Am. 110, 2470-2478 (2001)] by investigating the respective contribution of two temporal cues (fast modulation sideband and slow envelope beat cues) to the detection and discrimination of ``second-order'' sinusoidal amplitude modulation (SAM). Second-order SAM detection and rate discrimination abilities were measured at low beat rates (fm'<=128 Hz) with a ``carrier'' modulation rate fixed at a high value (fm=256 Hz). The second-order SAM data were compared with first-order SAM detection and rate discrimination thresholds measured in similar conditions at rates fm between 1 and 256 Hz. The results showed that (1) through 64 Hz, first- and second-order SAM detection thresholds increased similarly when stimulus duration decreased from 2 s to 250 ms, whereas first-order SAM detection thresholds remained unaffected by changes in duration when fm>=128 Hz, and (2) through 32 Hz, first- and second-order SAM rate discrimination thresholds were similar and substantially lower than first-order SAM rate discrimination thresholds measured at fm>=128 Hz. These data demonstrate that the perception of second-order SAM is mainly based on the slow envelope beat cues. They also suggest a substantial contribution of the slow envelope beat cues appearing at the output of modulation filters tuned to or near fm to the perception of second-order SAM.

  8. Operational modes of a ferroelectric LCoS modulator for displaying binary polarization, amplitude, and phase diffraction gratings.

    PubMed

    Martínez-García, Antonio; Moreno, Ignacio; Sánchez-López, María M; García-Martínez, Pascuala

    2009-05-20

    We analyze the performance of a ferroelectric liquid crystal on silicon display (FLCoS) as a binary polarization diffraction grating. We analyze the correspondence between the two polarization states emerging from the displayed grating and the polarization and intensity of the diffracted orders generated at the Fourier diffraction plane. This polarization-diffraction analysis leads, in a simple manner, to configurations yielding binary amplitude or binary phase modulation by incorporating an analyzer on the reflected beam. Based on this analysis, we present two useful variations of the polarization configuration. The first is a simplification using a single polarizer, which provides equivalent results for amplitude or phase modulation as the more general operational mode involving two polarizers. The second variation is proposed to compensate the reduction of the diffraction efficiency when the operating wavelength differs from the design one (for which the FLCoS liquid-crystal layer acts as a half-wave plate). In this situation we show how the ideal grating performance can be recovered in spite of the phase-shift mismatch originated by chromatic dispersion. In all cases, we provide experimental results that verify the theoretical analyses.

  9. Phase-amplitude coupling characteristics in directly modulated quantum dot lasers

    SciTech Connect

    Wang, C.; Osiński, M.; Even, J.; Grillot, F.

    2014-12-01

    We present a semi-analytical model for studying the phase-amplitude coupling (α-factor) in quantum dot (QD) semiconductor lasers, which takes into account the influence of carrier populations in the excited state and in the two-dimensional carrier reservoir on the refractive index change. Calculations of the α-factor based on the amplified spontaneous emission method and on the “FM/AM” technique are both investigated. It is shown that the α-factor of a QD laser strongly depends on the energy separation between the ground state and the off-resonant states. Through band structure engineering, the α-factor can be reduced by enlarging this energy separation.

  10. Role of Transient Receptor Potential Vanilloid 1 (TRPV1) in the Modulation of Airway Smooth Muscle Tone and Calcium Handling.

    PubMed

    Yocum, Gene T; Chen, Jun; Choi, Christine H; Townsend, Elizabeth A; Zhang, Yi; Xu, Dingbang; Fu, Xiao Wen; Sanderson, Michael J; Emala, Charles W

    2017-03-23

    Asthma is a common disorder characterized, in part, by airway smooth muscle (ASM) hyperresponsiveness. Transient receptor potential vanilloid 1 (TRPV1) is a non-selective cation channel expressed on airway nerve fibers that modulates afferent signals resulting in cough, and potentially bronchoconstriction. In the present study, the TRPV1 transcript was detected by RT-PCR in primary cultured human ASM cells, and the TRPV1 protein was detected in ASM of human trachea by immunohistochemistry. Proximity ligation assays suggest that TRPV1 is expressed in the sarcoplasmic reticulum membrane of human ASM cells in close association with sarco/endoplasmic reticulum Ca2+ ATPase 2. In guinea pig tracheal ring organ bath experiments, the TRPV1 agonist capsaicin led to ASM contraction, but this contraction was significantly attenuated by the sodium-channel inhibitor bupivicaine (N=4, p<0.05) and the NK-2 receptor antagonist GR 159897 (N=4, p<0.05), suggesting that this contraction is neurally-mediated. However, pretreatment of guinea pig and human ASM in organ bath experiments with the TRPV1 antagonist capsazepine inhibited the maintenance phase of an acetylcholine-induced contraction (N=4, p<0.01 for both species). Similarly, capsazepine inhibited methacholine-induced contraction of peripheral airways in mouse precision-cut lung slice (PCLS) experiments (N=4-5, p<0.05). Although capsazepine did not inhibit store-operated calicum entry in mouse ASM cells in PCLS (N=4-7, p=NS), it did inhibit calcium oscillations (N=3, p<0.001). These studies suggest that TRPV1 is expressed on ASM, including the SR, but that ASM TRPV1 activation does not play a significant role in initiation of ASM contraction. However, capsazepine does inhibit maintenance of contraction, likely by inhibiting calcium oscillation.

  11. Amplitude-modulated laser range-finder for 3D imaging with multi-sensor data integration capabilities

    NASA Astrophysics Data System (ADS)

    Bartolini, L.; Ferri de Collibus, M.; Fornetti, G.; Guarneri, M.; Paglia, E.; Poggi, C.; Ricci, R.

    2005-06-01

    A high performance Amplitude Modulated Laser Rangefinder (AM-LR) is presented, aimed at accurately reconstructing 3D digital models of real targets, either single objects or complex scenes. The scanning system enables to sweep the sounding beam either linearly across the object or circularly around it, by placing the object on a controlled rotating platform. Both phase shift and amplitude of the modulating wave of back-scattered light are collected and processed, resulting respectively in an accurate range image and a shade-free, high resolution, photographic-like intensity image. The best performances obtained in terms of range resolution are ~100 μm. Resolution itself can be made to depend mainly on the laser modulation frequency, provided that the power of the backscattered light reaching the detector is at least a few nW. 3D models are reconstructed from sampled points by using specifically developed software tools, optimized so as to take advantage of the system peculiarities. Special procedures have also been implemented to perform precise matching of data acquired independently with different sensors (LIF laser sensors, thermographic cameras, etc.) onto the 3D models generated using the AM-LR. The system has been used to scan different types of real surfaces (stone, wood, alloys, bones) and ca be applied in various fields, ranging from industrial machining to medical diagnostics, vision in hostile environments cultural heritage conservation and restoration. The relevance of this technology in cultural heritage applications is discussed in special detail, by providing results obtained in different campaigns with an emphasis on the system's multi-sensor data integration capabilities.

  12. Chroma key without color restrictions based on asynchronous amplitude modulation of background illumination on retroreflective screens

    NASA Astrophysics Data System (ADS)

    Vidal, Borja; Lafuente, Juan A.

    2016-03-01

    A simple technique to avoid color limitations in image capture systems based on chroma key video composition using retroreflective screens and light-emitting diodes (LED) rings is proposed and demonstrated. The combination of an asynchronous temporal modulation onto the background illumination and simple image processing removes the usual restrictions on foreground colors in the scene. The technique removes technical constraints in stage composition, allowing its design to be purely based on artistic grounds. Since it only requires adding a very simple electronic circuit to widely used chroma keying hardware based on retroreflective screens, the technique is easily applicable to TV and filming studios.

  13. Amplitude modulation of alpha-band rhythm caused by mimic collision: MEG study.

    PubMed

    Yokosawa, Koichi; Watanabe, Tatsuya; Kikuzawa, Daichi; Aoyama, Gakuto; Takahashi, Makoto; Kuriki, Shinya

    2013-01-01

    Detection of a collision risk and avoiding the collision are important for survival. We have been investigating neural responses when humans anticipate a collision or intend to take evasive action by applying collision-simulating images in a predictable manner. Collision-simulating images and control images were presented in random order to 9 healthy male volunteers. A cue signal was also given visually two seconds before each stimulus to enable each participant to anticipate the upcoming stimulus. Magnetoencephalograms (MEG) were recorded with a 76-ch helmet system. The amplitude of alpha band (8-13 Hz) rhythm when anticipating the upcoming collision-simulating image was significantly smaller than that when anticipating control images even just after the cue signal. This result demonstrates that anticipating a negative (dangerous) event induced event-related desynchronization (ERD) of alpha band activity, probably caused by attention. The results suggest the feasibility of detecting endogenous brain activities by monitoring alpha band rhythm and its possible applications to engineering systems, such as an automatic collision evasion system for automobiles.

  14. Self-amplitude and self-phase modulation of the charcoal mode-locked erbium-doped fiber lasers.

    PubMed

    Lin, Yung-Hsiang; Lo, Jui-Yung; Tseng, Wei-Hsuan; Wu, Chih-I; Lin, Gong-Ru

    2013-10-21

    With the intra-cavity nano-scale charcoal powder based saturable absorber, the 455-fs passive mode-locking of an L-band erbium-doped fiber laser (EDFL) is demonstrated. The size reduction of charcoal nano-particle is implemented with a simple imprinting-exfoliation-wiping method, which assists to increase the transmittance up to 0.91 with corresponding modulation depth of 26%. By detuning the power gain from 17 to 21 dB and cavity dispersion from -0.004 to -0.156 ps² of the EDFL, the shortening of mode-locked pulsewidth from picosecond to sub-picosecond by the transformation of the pulse forming mechanism from self-amplitude modulation (SAM) to the combining effect of self-phase modulation (SPM) and group delay dispersion (GDD) is observed. A narrower spectrum with 3-dB linewidth of 1.83-nm is in the SAM case, whereas the spectral linewidth broadens to 5.86 nm with significant Kelly sideband pair can be observed if the EDFL enters into the SPM regime. The mode-locking mechanism transferred from SAM to SPM/GDD dominates the pulse shortening procedure in the EDFL, whereas the intrinsic defects in charcoal nano-particle only affect the pulse formation at initial stage. The minor role of the saturable absorber played in the EDFL cavity with strongest SPM is observed.

  15. Neuropharmacological modulation of the P3-like event-related potential in a rat two-tone auditory discrimination task with modafinil and NS9283, a positive allosteric modulator of α4β2 nAChRs.

    PubMed

    Grupe, Morten; Grunnet, Morten; Laursen, Bettina; Bastlund, Jesper Frank

    2014-04-01

    The P300 (P3) event-related potential (ERP) is a neurophysiological signal believed to reflect cognitive processing of salient cues, and is thus used as a measure of attention and working memory. Additionally, P3 amplitude and latency is altered in neurological diseases and can be pharmacologically modulated. As P3-like ERPs can be recorded in rodents, it may serve as a potential translational biomarker of value for drug discovery. Here we investigated whether a positive allosteric modulator of α4β2 nicotinic acetylcholine receptors, NS9283, and the psychostimulant modafinil could modulate P3-like ERPs in healthy adult rats performing an auditory oddball discrimination task. ERPs were recorded with electroencephalography electrodes implanted into mediodorsal (MD) thalamus, medial prefrontal cortex, hippocampus and auditory cortex (AC). P3-like ERPs were detected in all brain regions, displaying larger amplitudes in target trials compared to non-target trials. Administration of modafinil (64 mg/kg) decreased P3-like ERP latency in MD thalamus and AC, whereas NS9283 augmented P3-like ERP amplitude in MD thalamus at 0.3 mg/kg and in AC at 3.0 mg/kg. Additionally, N1 pre-attention peak amplitude in MD thalamus was increased with 0.3 mg/kg NS9283. Neither of the compounds enhanced task performance. Rather, modafinil lowered correct rejections in non-target trials. In summary, our findings reveal pharmacological modulation of the rat P3-like ERP in cortical and subcortical regions by modafinil and NS9283. These findings encourage further exploration of the rat P3-like ERP in order to promote the understanding of its meaning within cognition, as well as its applicability as a translatable biomarker in drug development.

  16. Average symbol error rate for M-ary quadrature amplitude modulation in generalized atmospheric turbulence and misalignment errors

    NASA Astrophysics Data System (ADS)

    Sharma, Prabhat Kumar

    2016-11-01

    A framework is presented for the analysis of average symbol error rate (SER) for M-ary quadrature amplitude modulation in a free-space optical communication system. The standard probability density function (PDF)-based approach is extended to evaluate the average SER by representing the Q-function through its Meijer's G-function equivalent. Specifically, a converging power series expression for the average SER is derived considering the zero-boresight misalignment errors in the receiver side. The analysis presented here assumes a unified expression for the PDF of channel coefficient which incorporates the M-distributed atmospheric turbulence and Rayleigh-distributed radial displacement for the misalignment errors. The analytical results are compared with the results obtained using Q-function approximation. Further, the presented results are supported by the Monte Carlo simulations.

  17. Low-cost bidirectional hybrid fiber-visible laser light communication system based on carrier-less amplitude phase modulation

    NASA Astrophysics Data System (ADS)

    He, Jing; Dong, Huan; Deng, Rui; Chen, Lin

    2016-08-01

    We propose a bidirectional hybrid fiber-visible laser light communication (fiber-VLC) system. To reduce the cost of the system, the cheap and easy integration red vertical cavity surface emitting lasers, low-complexity carrier-less amplitude phase modulation format, and wavelength reuse technique are utilized. Meanwhile, the automatic gain control amplifier voltage and bias voltage for downlink and uplink are optimized. The simulation results show that, by using the proposed system, the bit error rate of 3.8×10-3 can be achieved for 16-Gbps CAP signal after 30-km standard single mode fiber and 8-m VLC bidirectional transmission. Therefore, it indicates the feasibility and potential of proposed system for indoor access network.

  18. Complex linear minimum mean-squared-error equalization of spatially quadrature-amplitude-modulated signals in holographic data storage

    NASA Astrophysics Data System (ADS)

    Sato, Takanori; Kanno, Kazutaka; Bunsen, Masatoshi

    2016-09-01

    We applied complex linear minimum mean-squared-error equalization to spatially quadrature-amplitude-modulated signals in holographic data storage (HDS). The equalization technique can improve dispersion in constellation outputs due to intersymbol interference. We confirm the effectiveness of the equalization technique in numerical simulations and basic optical experiments. Our numerical results have shown that intersymbol interference of a retrieved signal in a HDS system can be improved by using the equalization technique. In our experiments, a mean squared error (MSE), which indicates the deviation from an ideal signal, has been used for quantitatively evaluating the dispersion of equalized signals. Our equalization technique has been able to improve the MSE. However, symbols in the equalized signal have remained inseparable. To further improve the MSE and make the symbols separable, reducing errors in repeated measurements is our future task.

  19. High resolution imaging of immunoglobulin G antibodies and other biomolecules using amplitude modulation atomic force microscopy in air.

    PubMed

    Santos, Sergio; Thomson, Neil H

    2011-01-01

    The atomic force microscope (AFM) is a very versatile tool for studying biological samples at -nanometre-scale resolution. The resolution one achieves depends on many factors, including the sample properties, the imaging environment, the AFM tip and cantilever probe characteristics, and the signal detection and feedback control mechanism, to name a few. This chapter describes how to routinely achieve the highest possible spatial resolution on isolated protein molecules on mica surfaces. This is illustrated with Immunoglobulin G antibodies but the methods apply equally well to any other globular multi-subunit protein, as well as other biomolecules. Double-stranded DNA is used as a model sample to illustrate the effects of the force regime in amplitude modulation atomic force microscopy (AM AFM) on the image resolution and contrast. AM control is a widely used technique in biological AFM for reasons which are discussed.

  20. Phase-locking and amplitude modulations of EEG alpha: Two measures reflect different cognitive processes in a working memory task.

    PubMed

    Herrmann, Christoph S; Senkowski, Daniel; Röttger, Stefan

    2004-01-01

    It has been demonstrated in numerous experiments that oscillatory EEG responses in the alpha frequency band (8-12 Hz) increase with memory load during the retention interval in working memory tasks. However, the findings diverge with respect to which measurement of alpha activity is influenced by memory processes. Here, we differentiate between evoked and total alpha activity in order to separate effects of phase-locking and amplitude modulation. We present data from a delayed-matching-to-sample task (S1-S2 paradigm) for which we compared EEG alpha responses between a perception and a memory condition. Increased total alpha activity was found in the retention interval for the memory as compared to the perception condition. Evoked alpha activity, however, did not differentiate between memory and perception conditions but, instead, was increased for the more complex condition of processing non-Kanizsa figures as compared to Kanizsa figures. Thus, our results demonstrate a functional differentiation between evoked and total alpha activity. While alpha phase locking seemed to be influenced mainly by task complexity, alpha amplitude clearly reflected memory demands in our paradigm.

  1. Bi-stability of amplitude modulation AFM in air: deterministic and stochastic outcomes for imaging biomolecular systems.

    PubMed

    Santos, Sergio; Barcons, Victor; Font, Josep; Thomson, Neil H

    2010-06-04

    The dynamics of the oscillating microcantilever for amplitude modulation atomic force microscopy (AM AFM) operating in air is well understood theoretically but the experimental outcomes are still emerging. We use double-stranded DNA on mica as a model biomolecular system for investigating the connection between theory and experiment. A demonstration that the switching between the two cantilever oscillation states is stochastic in nature is achieved, and it can be induced by means of topographical anomalies on the surface. Whether one or the other attractor basin is accessed depends on the tip-sample separation history used to achieve the imaging conditions, and we show that the behaviour is reproducible when the tip is stable and well characterized. Emergence of background noise occurs in certain regions of parameter space regardless of whether two cantilever oscillation states coexist. The low state has been explored in detail and we note that at low to intermediate values of the free amplitude, noise-free imaging is achieved. The outcomes shown here are general and demonstrate that a thorough and systematic experimental approach in conjunction with standard modelling gives insight into the mechanisms behind image contrast formation in AM AFM in air.

  2. An approximate nonlinear model for time gain compensation of amplitude modulated images of ultrasound contrast agent perfusion.

    PubMed

    Mari, Jean; Hibbs, Kathryn; Stride, Eleanor; Eckersley, Robert; Tang, Meng

    2010-04-01

    Microbubble ultrasound contrast agents allow blood perfusion to be imaged at the cost of an increased attenuation that is not properly handled by existing time gain compensation methods. An automatic TGC has been developed that is able to account for different microbubble concentrations. The technique is an extension of a previously tested approach for modeling the nonlinear dependence of microbubble backscattering upon insonating pressure. The proposed method involves modeling in amplitude of the nonlinear attenuation for both forward and backward propagation, and the solution is achieved through an approximation set to overestimate the attenuation. The resulting equations are used to model and compensate amplitude modulation (AM) images; they are tested on radiofrequency data acquired using a clinical scanner from a gelatin tissue-mimicking phantom submerged in a contrast agent solution in the 0.08 MI to 0.51 MI range at 2 MHz. The nonlinear estimation equation presented here provides a significantly improved amplification profile compared with standard TGC algorithms, resulting in more accurate attenuation correction of the AM image.

  3. Effect of doping on amplitude modulation of space-charge wave in semiconductor quantum plasma

    NASA Astrophysics Data System (ADS)

    Banerjee, Sreyasi; Ghosh, Basudev

    2017-04-01

    To describe the modulational instability of space-charge waves in an n-type compensated semiconductor plasma, a nonlinear Schrödinger equation has been derived by using quantum hydrodynamical model and standard multiple scale perturbation technique. It has been shown that compensation factor (i.e. relative proportion of donor, acceptor and intrinsic carrier concentrations) and quantum diffraction parameter play important role in generating bright and dark envelope solitons within the semiconductor. Instability growth rate is also found to depend sensitively on the compensation factor and quantum diffraction parameter. From the linear dispersion relation it has been found that inclusion of quantum parameter gives rise to two new wave modes of purely quantum origin. Further the effect of compensation factor and quantum diffraction parameter on the linear dispersion characteristics has been analyzed. It has also been found that due to parabolicity of conduction band the group velocity of space-charge wave becomes dependent on compensation factor and quantum diffraction parameter.

  4. Multiple transmitter performance with appropriate amplitude modulation for free-space optical communication

    NASA Astrophysics Data System (ADS)

    Tellez, Jason A.; Schmidt, Jason D.

    2011-08-01

    The propagation of a free-space optical communications signal through atmospheric turbulence experiences random fluctuations in intensity, including signal fades, which negatively impact the performance of the communications link. The gamma--gamma probability density function is commonly used to model the scintillation of a single beam. One proposed method to reduce the occurrence of scintillation-induced fades at the receiver plane involves the use of multiple beams propagating through independent paths, resulting in a sum of independent gamma--gamma random variables. Recently an analytical model for the probability distribution of irradiance from the sum of multiple independent beams was developed. Because truly independent beams are practically impossible to create, we present here a more general but approximate model for the distribution of beams traveling through partially correlated paths. This model compares favorably with wave-optics simulations and highlights the reduced scintillation as the number of transmitted beams is increased. Additionally, a pulse-position modulation scheme is used to reduce the impact of signal fades when they occur. Analytical and simulated results showed significantly improved performance when compared to fixed threshold on/off keying.

  5. Noninvasive Focused Ultrasound Stimulation Can Modulate Phase-Amplitude Coupling between Neuronal Oscillations in the Rat Hippocampus

    PubMed Central

    Yuan, Yi; Yan, Jiaqing; Ma, Zhitao; Li, Xiaoli

    2016-01-01

    Noninvasive focused ultrasound stimulation (FUS) can be used to modulate neural activity with high spatial resolution. Phase-amplitude coupling (PAC) between neuronal oscillations is tightly associated with cognitive processes, including learning, attention, and memory. In this study, we investigated the effect of FUS on PAC between neuronal oscillations and established the relationship between the PAC index and ultrasonic intensity. The rat hippocampus was stimulated using focused ultrasound at different spatial-average pulse-average ultrasonic intensities (3.9, 9.6, and 19.2 W/cm2). The local field potentials (LFPs) in the rat hippocampus were recorded before and after FUS. Then, we analyzed PAC between neuronal oscillations using a PAC calculation algorithm. Our results showed that FUS significantly modulated PAC between the theta (4–8 Hz) and gamma (30–80 Hz) bands and between the alpha (9–13 Hz) and ripple (81–200 Hz) bands in the rat hippocampus, and PAC increased with incremental increases in ultrasonic intensity. PMID:27499733

  6. Antibody responses of mice exposed to low-power microwaves under combined, pulse-and-amplitude modulation

    SciTech Connect

    Veyret, B.; Bouthet, C.; Deschaux, P.; de Seze, R.; Geffard, M.; Joussot-Dubien, J.; le Diraison, M.; Moreau, J.M.; Caristan, A.

    1991-01-01

    Irradiation by pulsed microwaves (9.4 GHz, 1 microsecond pulses at 1,000/s), both with and without concurrent amplitude modulation (AM) by a sinusoid at discrete frequencies between 14 and 41 MHz, was assessed for effects on the immune system of Balb/C mice. The mice were immunized either by sheep red blood cells (SRBC) or by glutaric-anhydride conjugated bovine serum albumin (GA-BSA), then exposed to the microwaves at a low rms power density (30 microW/cm2; whole-body-averaged SAR approximately 0.015 W/kg). Sham exposure or microwave irradiation took place during each of five contiguous days, 10 h/day. The antibody response was evaluated by the plaque-forming cell assay (SRBC experiment) or by the titration of IgM and IgG antibodies (GA-BSA experiment). In the absence of AM, the pulsed field did not greatly alter immune responsiveness. In contrast, exposure to the field under the combined-modulation condition resulted in significant, AM-frequency-dependent augmentation or weakening of immune responses.

  7. Gas Phase Photoacoustic Sensor at 8.41 mu m Using Quartz Tuning Forks and Amplitude Modulated Quantum Cascade Lasers

    SciTech Connect

    Wojcik, Michael D.; Phillips, Mark C.; Cannon, Bret D.; Taubman, Matthew S.

    2006-10-01

    We demonstrate the performance of a novel long-wave infrared photoacoustic laser absorbance spectrometer for gas-phase species using an amplitude modulated (AM) quantum cascade (QC) laser and a quartz tuning fork microphone. Photoacoustic signal was generated by focusing the output of a Fabry-Perot QC laser operating at 8.41 ?m between the legs of a quartz tuning fork which served as a transducer for the transient acoustic pressure wave. The QC laser was modulated at the resonant frequency of the tuning fork (32.8 kHz) and delivered a modest 5.3 mW at the tuning fork. This spectrometer was calibrated using the infrared absorber Freon-134a by performing a simultaneous absorption measurement using a 35 cm absorption cell. The NEAS of this instrument was determined to be 2 x 10{sup -8} W cm-1 Hz{sup -1/2}. A corresponding theoretical analysis of the instrument sensitivity is presented and is capable of quantitatively reproducing the experimental NEAS, indicating that the fundamental sensitivity of this technique is limited by the noise floor of the tuning fork itself.

  8. Bounds and Simulation Results of 32-ary and 64-ary Quadrature Amplitude Modulation for Broadband-ISDN via Satellite

    NASA Technical Reports Server (NTRS)

    Kifle, Muli; Vanderaar, Mark

    1994-01-01

    Union bounds and Monte Carlo simulation Bit-Error-Rate (BER) performance results are presented for various 32-ary and 64-ary Quadrature Amplitude Modulation (QAM) schemes. Filtered and unfiltered modulation formats are compared for the best packing arrangement in peak power limited systems. It is verified that circular constellations which populate as many symbols as possible at the peak magnitude offer the best performance. For example: a 32-ary QAM scheme based on concentric circles offers about 1.05 dB better peak power improvement at a BER of 10(exp -6) over the scheme optimized for average power using triangular symbol packing. This peak power improvement increases to 1.25 dB for comparable 64-ary QAM schemes. This work serves as a precursor to determine the feasibility of a combined modem/codec that can accommodate Broadband Integrated Services Digital Network (B-ISDN) at a rate of 155.52 Mbps through typical transponder bandwidths of 36 MHz and 54 MHz.

  9. Auditory Distance Coding in Rabbit Midbrain Neurons and Human Perception: Monaural Amplitude Modulation Depth as a Cue

    PubMed Central

    Zahorik, Pavel; Carney, Laurel H.; Bishop, Brian B.; Kuwada, Shigeyuki

    2015-01-01

    Mechanisms underlying sound source distance localization are not well understood. Here we tested the hypothesis that a novel mechanism can create monaural distance sensitivity: a combination of auditory midbrain neurons' sensitivity to amplitude modulation (AM) depth and distance-dependent loss of AM in reverberation. We used virtual auditory space (VAS) methods for sounds at various distances in anechoic and reverberant environments. Stimulus level was constant across distance. With increasing modulation depth, some rabbit inferior colliculus neurons increased firing rates whereas others decreased. These neurons exhibited monotonic relationships between firing rates and distance for monaurally presented noise when two conditions were met: (1) the sound had AM, and (2) the environment was reverberant. The firing rates as a function of distance remained approximately constant without AM in either environment and, in an anechoic condition, even with AM. We corroborated this finding by reproducing the distance sensitivity using a neural model. We also conducted a human psychophysical study using similar methods. Normal-hearing listeners reported perceived distance in response to monaural 1 octave 4 kHz noise source sounds presented at distances of 35–200 cm. We found parallels between the rabbit neural and human responses. In both, sound distance could be discriminated only if the monaural sound in reverberation had AM. These observations support the hypothesis. When other cues are available (e.g., in binaural hearing), how much the auditory system actually uses the AM as a distance cue remains to be determined. PMID:25834060

  10. Gas Phase Photoacoustic Spectroscopy in the long-wave IR using Quartz Tuning Forks and Amplitude Modulated Quantum Cascade Lasers

    SciTech Connect

    Wojcik, Michael D.; Phillips, Mark C.; Cannon, Bret D.

    2006-12-31

    A paper to accompany a 20 minute talk about the progress of a DARPA funded project called LPAS. ABSTRACT: We demonstrate the performance of a novel long-wave infrared photoacoustic laser absorbance spectrometer for gas-phase species using an amplitude modulated (AM) quantum cascade (QC) laser and a quartz tuning fork microphone. Photoacoustic signal was generated by focusing the output of a Fabry-Perot QC laser operating at 8.41 micron between the legs of a quartz tuning fork which served as a transducer for the transient acoustic pressure wave. The QC laser was modulated at the resonant frequency of the tuning fork (32.8 kHz). This sensor was calibrated using the infrared absorber Freon-134a by performing a simultanious absorption measurement using a 35 cm absorption cell. The NEAS of this instrument was determined to be 2 x 10^-8 W cm^-1 /Hz^1/2 and the fundamental sensitivity of this technique is limited by the noise floor of the tuning fork itself.

  11. Mandarin Chinese tone identification in cochlear implants: predictions from acoustic models.

    PubMed

    Morton, Kenneth D; Torrione, Peter A; Throckmorton, Chandra S; Collins, Leslie M

    2008-10-01

    It has been established that current cochlear implants do not supply adequate spectral information for perception of tonal languages. Comprehension of a tonal language, such as Mandarin Chinese, requires recognition of lexical tones. New strategies of cochlear stimulation such as variable stimulation rate and current steering may provide the means of delivering more spectral information and thus may provide the auditory fine-structure required for tone recognition. Several cochlear implant signal processing strategies are examined in this study, the continuous interleaved sampling (CIS) algorithm, the frequency amplitude modulation encoding (FAME) algorithm, and the multiple carrier frequency algorithm (MCFA). These strategies provide different types and amounts of spectral information. Pattern recognition techniques can be applied to data from Mandarin Chinese tone recognition tasks using acoustic models as a means of testing the abilities of these algorithms to transmit the changes in fundamental frequency indicative of the four lexical tones. The ability of processed Mandarin Chinese tones to be correctly classified may predict trends in the effectiveness of different signal processing algorithms in cochlear implants. The proposed techniques can predict trends in performance of the signal processing techniques in quiet conditions but fail to do so in noise.

  12. The Duration of Motor Responses Evoked with Intracortical Microstimulation in Rats Is Primarily Modulated by Stimulus Amplitude and Train Duration

    PubMed Central

    Watson, Meghan; Sawan, Mohamad

    2016-01-01

    Microstimulation of brain tissue plays a key role in a variety of sensory prosthetics, clinical therapies and research applications, however the effects of stimulation parameters on the responses they evoke remain widely unknown. In particular, the effects of parameters when delivered in the form of a stimulus train as opposed to a single pulse are not well understood despite the prevalence of stimulus train use. We aimed to investigate the contribution of each parameter of a stimulus train to the duration of the motor responses they evoke in forelimb muscles. We used constant-current, biphasic, square wave pulse trains in acute terminal experiments under ketamine anaesthesia. Stimulation parameters were systematically tested in a pair-wise fashion in the caudal forelimb region of the motor cortex in 7 Sprague-Dawley rats while motor evoked potential (MEP) recordings from the forelimb were used to quantify the influence of each parameter in the train. Stimulus amplitude and train duration were shown to be the dominant parameters responsible for increasing the total duration of the MEP, while interphase interval had no effect. Increasing stimulus frequency from 100–200 Hz or pulse duration from 0.18–0.34 ms were also effective methods of extending response durations. Response duration was strongly correlated with peak time and amplitude. Our findings suggest that motor cortex intracortical microstimulations are often conducted at a higher frequency rate and longer train duration than necessary to evoke maximal response duration. We demonstrated that the temporal properties of the evoked response can be both predicted by certain response metrics and modulated via alterations to the stimulation signal parameters. PMID:27442588

  13. Ultra-Linear Polymer Modulator

    DTIC Science & Technology

    2006-05-01

    29 Figure 45: Coupling, ( Kappa ), between eigenmodes as a function of optical propagation (z) .... 31 Figure 46: SFDR Calculation...frequency electrode structures for radio frequency (RF) modulation of light Two-tone third-order inter-modulation distortion in integrated optic amplitude...verify lambda max of the electro-optic chromophore in thin films as well as the index of refraction and dispersion for all the polymer layers in a

  14. Despeckle Filtering for Multiscale Amplitude-Modulation Frequency-Modulation (AM-FM) Texture Analysis of Ultrasound Images of the Intima-Media Complex

    PubMed Central

    Loizou, C. P.; Murray, V.; Pattichis, M. S.; Pantziaris, M.; Nicolaides, A. N.; Pattichis, C. S.

    2014-01-01

    The intima-media thickness (IMT) of the common carotid artery (CCA) is widely used as an early indicator of cardiovascular disease (CVD). Typically, the IMT grows with age and this is used as a sign of increased risk of CVD. Beyond thickness, there is also clinical interest in identifying how the composition and texture of the intima-media complex (IMC) changed and how these textural changes grow into atherosclerotic plaques that can cause stroke. Clearly though texture analysis of ultrasound images can be greatly affected by speckle noise, our goal here is to develop effective despeckle noise methods that can recover image texture associated with increased rates of atherosclerosis disease. In this study, we perform a comparative evaluation of several despeckle filtering methods, on 100 ultrasound images of the CCA, based on the extracted multiscale Amplitude-Modulation Frequency-Modulation (AM-FM) texture features and visual image quality assessment by two clinical experts. Texture features were extracted from the automatically segmented IMC for three different age groups. The despeckle filters hybrid median and the homogeneous mask area filter showed the best performance by improving the class separation between the three age groups and also yielded significantly improved image quality. PMID:24734038

  15. Emphasis of spatial cues in the temporal fine structure during the rising segments of amplitude-modulated sounds II: single-neuron recordings

    PubMed Central

    Marquardt, Torsten; Stange, Annette; Pecka, Michael; Grothe, Benedikt; McAlpine, David

    2014-01-01

    Recently, with the use of an amplitude-modulated binaural beat (AMBB), in which sound amplitude and interaural-phase difference (IPD) were modulated with a fixed mutual relationship (Dietz et al. 2013b), we demonstrated that the human auditory system uses interaural timing differences in the temporal fine structure of modulated sounds only during the rising portion of each modulation cycle. However, the degree to which peripheral or central mechanisms contribute to the observed strong dominance of the rising slope remains to be determined. Here, by recording responses of single neurons in the medial superior olive (MSO) of anesthetized gerbils and in the inferior colliculus (IC) of anesthetized guinea pigs to AMBBs, we report a correlation between the position within the amplitude-modulation (AM) cycle generating the maximum response rate and the position at which the instantaneous IPD dominates the total neural response. The IPD during the rising segment dominates the total response in 78% of MSO neurons and 69% of IC neurons, with responses of the remaining neurons predominantly coding the IPD around the modulation maximum. The observed diversity of dominance regions within the AM cycle, especially in the IC, and its comparison with the human behavioral data suggest that only the subpopulation of neurons with rising slope dominance codes the sound-source location in complex listening conditions. A comparison of two models to account for the data suggests that emphasis on IPDs during the rising slope of the AM cycle depends on adaptation processes occurring before binaural interaction. PMID:24554782

  16. Shear wave elastography using amplitude-modulated acoustic radiation force and phase-sensitive optical coherence tomography

    PubMed Central

    Nguyen, Thu-Mai; Arnal, Bastien; Song, Shaozhen; Huang, Zhihong; Wang, Ruikang K.; O’Donnell, Matthew

    2015-01-01

    Abstract. Investigating the elasticity of ocular tissue (cornea and intraocular lens) could help the understanding and management of pathologies related to biomechanical deficiency. In previous studies, we introduced a setup based on optical coherence tomography for shear wave elastography (SWE) with high resolution and high sensitivity. SWE determines tissue stiffness from the propagation speed of shear waves launched within tissue. We proposed acoustic radiation force to remotely induce shear waves by focusing an ultrasound (US) beam in tissue, similar to several elastography techniques. Minimizing the maximum US pressure is essential in ophthalmology for safety reasons. For this purpose, we propose a pulse compression approach. It utilizes coded US emissions to generate shear waves where the energy is spread over a long emission, and then numerically compressed into a short, localized, and high-energy pulse. We used a 7.5-MHz single-element focused transducer driven by coded excitations where the amplitude is modulated by a linear frequency-swept square wave (1 to 7 kHz). An inverse filter approach was used for compression. We demonstrate the feasibility of performing shear wave elastography measurements in tissue-mimicking phantoms at low US pressures (mechanical index <0.6). PMID:25554970

  17. Handling the influence of chemical shift in amplitude-modulated heteronuclear dipolar recoupling solid-state NMR

    NASA Astrophysics Data System (ADS)

    Basse, Kristoffer; Shankar, Ravi; Bjerring, Morten; Vosegaard, Thomas; Nielsen, Niels Chr.; Nielsen, Anders B.

    2016-09-01

    We present a theoretical analysis of the influence of chemical shifts on amplitude-modulated heteronuclear dipolar recoupling experiments in solid-state NMR spectroscopy. The method is demonstrated using the Rotor Echo Short Pulse IRrAdiaTION mediated Cross-Polarization (RESPIRATIONCP) experiment as an example. By going into the pulse sequence rf interaction frame and employing a quintuple-mode operator-based Floquet approach, we describe how chemical shift offset and anisotropic chemical shift affect the efficiency of heteronuclear polarization transfer. In this description, it becomes transparent that the main attribute leading to non-ideal performance is a fictitious field along the rf field axis, which is generated from second-order cross terms arising mainly between chemical shift tensors and themselves. This insight is useful for the development of improved recoupling experiments. We discuss the validity of this approach and present quaternion calculations to determine the effective resonance conditions in a combined rf field and chemical shift offset interaction frame transformation. Based on this, we derive a broad-banded version of the RESPIRATIONCP experiment. The new sequence is experimentally verified using SNNFGAILSS amyloid fibrils where simultaneous 15N → 13CO and 15N → 13Cα coherence transfer is demonstrated on high-field NMR instrumentation, requiring great offset stability.

  18. Determination of electrostatic force and its characteristics based on phase difference by amplitude modulation atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Wang, Kesheng; Cheng, Jia; Yao, Shiji; Lu, Yijia; Ji, Linhong; Xu, Dengfeng

    2016-12-01

    Electrostatic force measurement at the micro/nano scale is of great significance in science and engineering. In this paper, a reasonable way of applying voltage is put forward by taking an electrostatic chuck in a real integrated circuit manufacturing process as a sample, applying voltage in the probe and the sample electrode, respectively, and comparing the measurement effect of the probe oscillation phase difference by amplitude modulation atomic force microscopy. Based on the phase difference obtained from the experiment, the quantitative dependence of the absolute magnitude of the electrostatic force on the tip-sample distance and applied voltage is established by means of theoretical analysis and numerical simulation. The results show that the varying characteristics of the electrostatic force with the distance and voltage at the micro/nano scale are similar to those at the macroscopic scale. Electrostatic force gradually decays with increasing distance. Electrostatic force is basically proportional to the square of applied voltage. Meanwhile, the applicable conditions of the above laws are discussed. In addition, a comparison of the results in this paper with the results of the energy dissipation method shows the two are consistent in general. The error decreases with increasing distance, and the effect of voltage on the error is small.

  19. Global characterization of a nematic liquid crystal display LCX038ARA using the retarder-rotor model in the modulation amplitude regime-coupled without applied voltage

    NASA Astrophysics Data System (ADS)

    Cuevas Cely, C. J.; Acevedo, C. H.; Torres Moreno, Y.

    2017-01-01

    This work shows experimental and theoretical results of the characterization of a nematic liquid-crystal spatial light modulator Sony model LCX038ARA for the parameters angle of molecular rotation, the birefringence and angle of the molecular axis, using the retarder-rotor model without electric field applied in the amplitude regime-coupled.

  20. Dissociation of psychophysical and EEG steady-state response measures of cross-modal temporal correspondence for amplitude modulated acoustic and vibrotactile stimulation.

    PubMed

    Timora, Justin R; Budd, Timothy W

    2013-09-01

    Research examining multisensory integration suggests that the correspondence of stimulus characteristics across modalities (cross-modal correspondence) can have a dramatic influence on both neurophysiological and perceptual responses to multimodal stimulation. The current study extends prior research by examining the cross-modal correspondence of amplitude modulation rate for simultaneous acoustic and vibrotactile stimulation using EEG and perceptual measures of sensitivity to amplitude modulation. To achieve this, psychophysical thresholds and steady-state responses (SSRs) were measured for acoustic and vibrotactile amplitude modulated (AM) stimulation for 21 and 40 Hz AM rates as a function of the cross-modal correspondence. The study design included three primary conditions to determine whether the changes in the SSR and psychophysical thresholds were due to the cross-modal temporal correspondence of amplitude modulated stimuli: NONE (AM in one modality only), SAME (the same AM rate for each modality) and DIFF (different AM rates for each modality). The results of the psychophysical analysis showed that AM detection thresholds for the simultaneous AM conditions (i.e., SAME and DIFF) were significantly higher (i.e., lower sensitivity) than AM detection thresholds for the stimulation of a single modality (i.e., NONE). SSR results showed significant effects of SAME and DIFF conditions on SSR activity. The different pattern of results for perceptual and SSR measures of cross-modal correspondence of AM rate indicates a dissociation between entrained cortical activity (i.e., SSR) and perception.

  1. Electrode Position and Current Amplitude Modulate Impulsivity after Subthalamic Stimulation in Parkinsons Disease—A Computational Study

    PubMed Central

    Mandali, Alekhya; Chakravarthy, V. Srinivasa; Rajan, Roopa; Sarma, Sankara; Kishore, Asha

    2016-01-01

    Background: Subthalamic Nucleus Deep Brain Stimulation (STN-DBS) is highly effective in alleviating motor symptoms of Parkinson's disease (PD) which are not optimally controlled by dopamine replacement therapy. Clinical studies and reports suggest that STN-DBS may result in increased impulsivity and de novo impulse control disorders (ICD). Objective/Hypothesis: We aimed to compare performance on a decision making task, the Iowa Gambling Task (IGT), in healthy conditions (HC), untreated and medically-treated PD conditions with and without STN stimulation. We hypothesized that the position of electrode and stimulation current modulate impulsivity after STN-DBS. Methods: We built a computational spiking network model of basal ganglia (BG) and compared the model's STN output with STN activity in PD. Reinforcement learning methodology was applied to simulate IGT performance under various conditions of dopaminergic and STN stimulation where IGT total and bin scores were compared among various conditions. Results: The computational model reproduced neural activity observed in normal and PD conditions. Untreated and medically-treated PD conditions had lower total IGT scores (higher impulsivity) compared to HC (P < 0.0001). The electrode position that happens to selectively stimulate the part of the STN corresponding to an advantageous panel on IGT resulted in de-selection of that panel and worsening of performance (P < 0.0001). Supratherapeutic stimulation amplitudes also worsened IGT performance (P < 0.001). Conclusion(s): In our computational model, STN stimulation led to impulsive decision making in IGT in PD condition. Electrode position and stimulation current influenced impulsivity which may explain the variable effects of STN-DBS reported in patients. PMID:27965590

  2. Amplitude modulation drive to rectangular-plate linear ultrasonic motors with vibrators dimensions 8 mm x 2.16 mm X 1 mm.

    PubMed

    Ming, Yang; Hanson, Ben; Levesley, Martin C; Walker, Peter G; Watterson, Kevin G

    2006-12-01

    In this paper, to exploit the contribution from not only the stators but also from other parts of miniature ultrasonic motors, an amplitude modulation drive is proposed to drive a miniature linear ultrasonic motor consisting of two rectangular piezoelectric ceramic plates. Using finite-element software, the first longitudinal and second lateral-bending frequencies of the vibrator are shown to be very close when its dimensions are 8 mm x 2.16 mm x 1 mm. So one single frequency power should be able to drive the motor. However, in practice the motor is found to be hard to move with a single frequency power because of its small vibration amplitudes and big frequency difference between its longitudinal and bending resonance, which is induced by the boundary condition variation. To drive the motor effectively, an amplitude modulation drive is used by superimposing two signals with nearly the same frequencies, around the resonant frequency of the vibrators of the linear motor. When the amplitude modulation frequency is close to the resonant frequency of the vibrator's surroundings, experimental results show that the linear motor can move back and forward with a maximum thrust force (over 0.016 N) and a maximum velocity (over 50 mm/s).

  3. Antimultipath communication by injecting tone into null in signal spectrum

    NASA Technical Reports Server (NTRS)

    Davarian, Faramaz (Inventor)

    1987-01-01

    A transmitter for digital radio communication creates a null by balanced encoding of data modulated on an RF carrier, and inserts a calibration tone within the null. This is accomplished by having the calibration tone coincide in phase and frequency with the transmitted radio frequency output, for coherent demodulation of data at the receiver where the tone calibration signal is extracted and used for multipath fading compensation.

  4. Using online tone generators

    NASA Astrophysics Data System (ADS)

    2017-04-01

    Online tone generators are free, user friendly, and can make for engaging and meaningful study of many topics in the areas of interference, waves, and the physics of music. By using a website such as OnlineToneGenerator.com, and through opening multiple windows simultaneously, students can immediately perform several experiments. In this article, I highlight five lesson ideas that come naturally from these types of websites.

  5. Underwater loudness for tones

    NASA Astrophysics Data System (ADS)

    Cudahy, Edward A.; Schwaller, Derek

    2002-05-01

    The loudness for pure tones was measured by loudness matching for 1-s pure tones from 100 to 50000 Hz. The standard tone was 1000 Hz. Subjects were instructed to match the loudness of the comparison tone at one of the test frequencies to the loudness of the standard tone. The standard was presented at one of five sound pressure levels (SPL) for each set of frequencies. The SPL was varied randomly across a test series. The subjects were bareheaded U.S. Navy divers tested at a depth of 3 m. All subjects had normal hearing. The tones were presented to the right side of the subject from an array of underwater sound projectors. The SPL was calibrated at the location of the subject's head with the subject absent. The loudness increased more rapidly as a function of standard SPL at mid-frequencies than at either high or low frequencies. The most compact loudness contours (the least SPL change across the range of standard SPL) were at the highest frequency. Loudness contours across frequency derived from these measurements are significantly different from in-air measurements with minimum audibility in the 1000 Hz region rather than the 2-4 kHz region observed for in-air measurements.

  6. Loudness for tone underwater

    NASA Astrophysics Data System (ADS)

    Cudahy, Edward; Schwaller, Derek

    2002-05-01

    The loudness for pure tones was measured by loudness matching for 1-s pure tones from 100 to 50000 Hz. The standard tone was 1000 Hz. Subjects were instructed to match the loudness of the comparison tone at one of the test frequencies to the loudness of the standard tone. The standard was presented at one of five sound pressure levels (SPL) for each set of frequencies. The standard SPL was varied randomly across test series. The subjects were bareheaded US Navy divers tested at a depth of 3 m. All subjects had normal hearing. The tones were presented to the right side of the subject from an array of underwater sound projectors. The SPL was calibrated at the location of the subject's head with the subject absent. The loudness increased more rapidly as a function of standard SPL at mid-frequencies than at either high or low frequencies. The most compact loudness contours (least SPL change across range of standard SPL) were at 50000 Hz. The underwater loudness contours across frequency are significantly different from in-air measurements and have a minimum in the 1000 Hz region rather than the 2-4 kHz region observed for in-air measurements. [Work supported by ONR.

  7. Neural Representation of Scale Illusion: Magnetoencephalographic Study on the Auditory Illusion Induced by Distinctive Tone Sequences in the Two Ears

    PubMed Central

    Kuriki, Shinya; Yokosawa, Koichi; Takahashi, Makoto

    2013-01-01

    The auditory illusory perception “scale illusion” occurs when a tone of ascending scale is presented in one ear, a tone of descending scale is presented simultaneously in the other ear, and vice versa. Most listeners hear illusory percepts of smooth pitch contours of the higher half of the scale in the right ear and the lower half in the left ear. Little is known about neural processes underlying the scale illusion. In this magnetoencephalographic study, we recorded steady-state responses to amplitude-modulated short tones having illusion-inducing pitch sequences, where the sound level of the modulated tones was manipulated to decrease monotonically with increase in pitch. The steady-state responses were decomposed into right- and left-sound components by means of separate modulation frequencies. It was found that the time course of the magnitude of response components of illusion-perceiving listeners was significantly correlated with smooth pitch contour of illusory percepts and that the time course of response components of stimulus-perceiving listeners was significantly correlated with discontinuous pitch contour of stimulus percepts in addition to the contour of illusory percepts. The results suggest that the percept of illusory pitch sequence was represented in the neural activity in or near the primary auditory cortex, i.e., the site of generation of auditory steady-state response, and that perception of scale illusion is maintained by automatic low-level processing. PMID:24086676

  8. Neural response to modulating the probability that actions of self or other result in auditory tones: A parametric fMRI study into causal ambiguity.

    PubMed

    de Bézenac, Christophe E; Sluming, Vanessa; Gouws, André; Corcoran, Rhiannon

    2016-09-01

    In normal circumstances we can easily distinguish between changes to the external world brought about by our own actions from those with external causes. However, in certain contexts our sense of ownership and agency over acts is not so clear. Neuroimaging studies have implicated a number of regions in the sense of agency, some of which have been shown to vary continuously with action-outcome discordance. However, little is known about dynamic, ambiguous contexts characterised by a lack of information for self-other differentiation, yet such ambiguous states are important in relation to symptoms and levels of consciousness that characterise certain mental health conditions. With a block-design fMRI paradigm, we investigated neural responses to changes in the probability that a participant's irregular finger taps over 12s would result in auditory tones as opposed to tones generated by 'another's finger taps'. The main findings were that misattribution increased in ambiguous conditions where the probability of a tone belonging to self and other was equal. Task-sensitive brain regions, previously identified in self-agency, motor cognition, and ambiguity processing, showed a quadratic response to our self-to-other manipulation, with particular sensitivity to self-control. Task performance (low error and bias) was related to attenuated response in ambiguous conditions while increased response in regions associated with the default mode network was associated with greater overall error and bias towards other. These findings suggest that causal ambiguity as it occurs over time is a prominent feature in sense of agency, one that may eventually contribute to a more comprehensive understanding of positive symptoms of psychosis.

  9. Low-amplitude rotational modulation rather than pulsations in the CoRoT B-type supergiant HD 46769

    NASA Astrophysics Data System (ADS)

    Aerts, C.; Simón-Díaz, S.; Catala, C.; Neiner, C.; Briquet, M.; Castro, N.; Schmid, V. S.; Scardia, M.; Rainer, M.; Poretti, E.; Pápics, P. I.; Degroote, P.; Bloemen, S.; Østensen, R. H.; Auvergne, M.; Baglin, A.; Baudin, F.; Michel, E.; Samadi, R.

    2013-09-01

    Aims: We aim to detect and interpret photometric and spectroscopic variability of the bright CoRoT B-type supergiant target HD 46769 (V = 5.79). We also attempt to detect a magnetic field in the target. Methods: We analyse a 23-day oversampled CoRoT light curve after detrending and spectroscopic follow-up data using standard Fourier analysis and phase dispersion minimization methods. We determine the fundamental parameters of the star, as well as its abundances from the most prominent spectral lines. We perform a Monte Carlo analysis of spectropolarimetric data to obtain an upper limit of the polar magnetic field, assuming a dipole field. Results: In the CoRoT data, we detect a dominant period of 4.84 d with an amplitude of 87 ppm and some of its (sub-)multiples. Given the shape of the phase-folded light curve and the absence of binary motion, we interpret the dominant variability in terms of rotational modulation, with a rotation period of 9.69 d. Subtraction of the rotational modulation signal does not reveal any sign of pulsations. Our results are consistent with the absence of variability in the Hipparcos light curve. The spectroscopy leads to a projected rotational velocity of 72 ± 2 km s-1 and does not reveal periodic variability or the need to invoke macroturbulent line broadening. No signature of a magnetic field is detected in our data. A field stronger than ~500 G at the poles can be excluded, unless the possible non-detected field were more complex than dipolar. Conclusions: The absence of pulsations and macroturbulence of this evolved B-type supergiant is placed into the context of instability computations and of observed variability of evolved B-type stars. Based on CoRoT space-based photometric data; the CoRoT space mission was developed and operated by the French space agency CNES, with the participation of ESA's RSSD and Science Programmes, Austria, Belgium, Brazil, Germany, and Spain. Based on observations collected at La Silla Observatory, ESO

  10. Name that percussive tune: Associative memory and amplitude envelope.

    PubMed

    Schutz, Michael; Stefanucci, Jeanine K; H Baum, Sarah; Roth, Amber

    2017-07-01

    A series of experiments demonstrated novel effects of amplitude envelope on associative memory, with tones exhibiting naturally decaying amplitude envelopes (e.g., those made by two wine glasses clinking) better associated with target objects than amplitude-invariant tones. In Experiment 1 participants learned associations between household objects and 4-note tone sequences constructed of spectrally matched pure tones with either "flat" or "percussive" amplitude envelopes. Those hearing percussive tones correctly recalled significantly more sequence-object associations. Experiment 2 demonstrated that participants hearing percussive tones learned the associations more quickly. Experiment 3 used "reverse percussive" tones (percussive tones played backwards) to test whether differences in overall energy might account for this effect, finding they did not lead to the same level of performance as percussive tones. Experiment 4 varied the envelope at encoding and retrieval to determine which stage of the task was most affected by the envelope manipulation. Participants hearing percussive tones at both encoding and retrieval performed significantly better than the other three groups (i.e., flat at encoding/percussive at retrieval, etc.). We conclude that amplitude envelope plays an important role in learning and memory, a finding with relevance to psychological research on audition and associative memory, as well as practical relevance for improving human-computer interface design.

  11. Is the effect of tinnitus on auditory steady-state response amplitude mediated by attention?

    PubMed Central

    Diesch, Eugen; Andermann, Martin; Rupp, Andre

    2012-01-01

    Objectives: Auditory steady-state response (ASSR) amplitude enhancement effects have been reported in tinnitus patients. As ASSR amplitude is also enhanced by attention, the effect of tinnitus on ASSR amplitude could be interpreted as an effect of attention mediated by tinnitus. As N1 attention effects are significantly larger than those on the ASSR, if the effect of tinnitus on ASSR amplitude were due to attention, there should be similar amplitude enhancement effects in tinnitus for the N1 component of the auditory-evoked response. Methods: MEG recordings which were previously examined for the ASSR (Diesch et al., 2010a) were analyzed with respect to the N1m component. Like the ASSR previously, the N1m was analyzed in the source domain (source space projection). Stimuli were amplitude-modulated (AM) tones with one of three carrier frequencies matching the tinnitus frequency or a surrogate frequency 1½ octave above the audiometric edge frequency in controls, the audiometric edge frequency, and a frequency below the audiometric edge. Single AM-tones were presented in a single condition and superpositions of three AM-tones differing in carrier and modulation frequency in a composite condition. Results: In the earlier ASSR study (Diesch et al., 2010a), the ASSR amplitude in tinnitus patients, but not in controls, was significantly larger in the (surrogate) tinnitus condition than in the edge condition. Patients showed less evidence than controls of reciprocal inhibition of component ASSR responses in the composite condition. In the present study, N1m amplitudes elicited by stimuli located at the audiometric edge and at the (surrogate) tinnitus frequency were smaller than N1m amplitudes elicited by sub-edge tones both in patients and controls. The relationship of the N1m response in the composite condition to the N1m response in the single condition indicated that reciprocal inhibition among component N1m responses was reduced in patients compared against controls

  12. Vagal tone as an index of mental state

    NASA Technical Reports Server (NTRS)

    Porges, Stephen W.

    1988-01-01

    The utility of monitoring oscillations in the heart rate pattern as a window to the brain is discussed as an index of general central nervous system status. Quantification of the amplitude of respiratory sinus arrhythmia provides an accurate index of cardiac vagal tone. A number of studies have demonstrated the validity of this measure; the relationship between flight performance and vagal tone has also been studied. In general, the vagal tone index appears to monitor global states of the central nervous system and may be useful in screening the general state of pilots.

  13. Tones for Profoundly Deaf Tone-Language Speakers.

    ERIC Educational Resources Information Center

    Ching, Teresa

    A study assessed the practical use of the simplified speech pattern approach to teaching lipreading in a tone language by comparing performance using an acoustic hearing-aid and a Sivo-aid in a tone labelling task. After initial assessment, subjects were given training to enhance perception of lexically contrastive tones, then post-tested. The…

  14. Brainstem sources of cardiac vagal tone and respiratory sinus arrhythmia

    PubMed Central

    Farmer, David G.S.; Dutschmann, Mathias; Paton, Julian F.R.; Pickering, Anthony E.

    2016-01-01

    Key points Cardiac vagal tone is a strong predictor of health, although its central origins are unknown.Respiratory‐linked fluctuations in cardiac vagal tone give rise to respiratory sinus arryhthmia (RSA), with maximum tone in the post‐inspiratory phase of respiration.In the present study, we investigated whether respiratory modulation of cardiac vagal tone is intrinsically linked to post‐inspiratory respiratory control using the unanaesthetized working heart‐brainstem preparation of the rat.Abolition of post‐inspiration, achieved by inhibition of the pontine Kolliker‐Fuse nucleus, removed post‐inspiratory peaks in efferent cardiac vagal activity and suppressed RSA, whereas substantial cardiac vagal tone persisted. After transection of the caudal pons, part of the remaining tone was removed by inhibition of nucleus of the solitary tract.We conclude that cardiac vagal tone depends upon at least 3 sites of the pontomedullary brainstem and that a significant proportion arises independently of RSA. Abstract Cardiac vagal tone is a strong predictor of health, although its central origins are unknown. The rat working heart‐brainstem preparation shows strong cardiac vagal tone and pronounced respiratory sinus arrhythmia. In this preparation, recordings from the cut left cardiac vagal branch showed efferent activity that peaked in post‐inspiration, ∼0.5 s before the cyclic minimum in heart rate (HR). We hypothesized that respiratory modulation of cardiac vagal tone and HR is intrinsically linked to the generation of post‐inspiration. Neurons in the pontine Kölliker‐Fuse nucleus (KF) were inhibited with bilateral microinjections of isoguvacine (50–70 nl, 10 mm) to remove the post‐inspiratory phase of respiration. This also abolished the post‐inspiratory peak of cardiac vagal discharge (and cyclical HR modulation), although a substantial level of activity remained. In separate preparations with intact cardiac vagal branches but

  15. Responses of inferior colliculus neurons to double harmonic tones.

    PubMed

    Sinex, Donal G; Li, Hongzhe

    2007-12-01

    The auditory system can segregate sounds that overlap in time and frequency, if the sounds differ in acoustic properties such as fundamental frequency (f0). However, the neural mechanisms that underlie this ability are poorly understood. Responses of neurons in the inferior colliculus (IC) of the anesthetized chinchilla were measured. The stimuli were harmonic tones, presented alone (single harmonic tones) and in the presence of a second harmonic tone with a different f0 (double harmonic tones). Responses to single harmonic tones exhibited no stimulus-related temporal pattern, or in some cases, a simple envelope modulated at f0. Responses to double harmonic tones exhibited complex slowly modulated discharge patterns. The discharge pattern varied with the difference in f0 and with characteristic frequency. The discharge pattern also varied with the relative levels of the two tones; complex temporal patterns were observed when levels were equal, but as the level difference increased, the discharge pattern reverted to that associated with single harmonic tones. The results indicated that IC neurons convey information about simultaneous sounds in their temporal discharge patterns and that the patterns are produced by interactions between adjacent components in the spectrum. The representation is "low-resolution," in that it does not convey information about single resolved components from either individual sound.

  16. Encoding of the amplitude modulation of pulsatile electrical stimulation in the feline cochlear nucleus by neurons in the inferior colliculus; effects of stimulus pulse rate

    NASA Astrophysics Data System (ADS)

    McCreery, Douglas; Han, Martin; Pikov, Victor; Yadav, Kamal; Pannu, Satinderpall

    2013-10-01

    Objectives. Persons without a functional auditory nerve cannot benefit from cochlear implants, but some hearing can be restored by an auditory brainstem implant (ABI) with stimulating electrodes implanted on the surface of the cochlear nucleus (CN). Most users benefit from their ABI, but speech recognition tends to be poorer than for users of cochlear implants. Psychophysical studies suggest that poor modulation detection may contribute to the limited performance of ABI users. In a cat model, we determined how the pulse rate of the electrical stimulus applied within or on the CN affects temporal and rate encoding of amplitude modulation (AM) by neurons in the central nucleus of the inferior colliculus (ICC). Approach. Stimulating microelectrodes were implanted chronically in and on the cats' CN, and multi-site recording microelectrodes were implanted chronically into the ICC. Encoding of AM pulse trains by neurons in the ICC was characterized as vector strength (VS), the synchrony of neural activity with the AM, and as the mean rate of neuronal action potentials (neuronal spike rate (NSR)). Main results. For intranuclear microstimulation, encoding of AM as VS was up to 3 dB greater when stimulus pulse rate was increased from 250 to 500 pps, but only for neuronal units with low best acoustic frequencies, and when the electrical stimulation was modulated at low frequencies (10-20 Hz). For stimulation on the surface of the CN, VS was similar at 250 and 500 pps, and the dynamic range of the VS was reduced for pulse rates greater than 250 pps. Modulation depth was encoded strongly as VS when the maximum stimulus amplitude was held constant across a range of modulation depth. This ‘constant maximum’ protocol allows enhancement of modulation depth while preserving overall dynamic range. However, modulation depth was not encoded as strongly as NSR. Significance. The findings have implications for improved sound processors for present and future ABIs. The performance of

  17. Simultaneous subchannel data updating for multiple channels of 16-quadrature amplitude modulation signals using a single periodically poled lithium niobate waveguide.

    PubMed

    Huang, Hao; Yang, Jeng-Yuan; Wu, Xiaoxia; Khaleghi, Salman; Ziyadi, Morteza; Tur, Moshe; Langrock, Carsten; Fejer, Martin M; Paraschis, Loukas; Willner, Alan E

    2012-11-01

    Subchannel data updating of high-order modulation format signals using cascaded sum- and difference-frequency generation in a single periodically poled lithium niobate waveguide is demonstrated. One quadrature phase-shift-keying subchannel of a 16-quadrature amplitude modulation (QAM) signal at 40 Gbit/s is successfully updated, with an optical signal-to-noise ratio (OSNR) penalty of ~2 dB for return-to-zero and ~4 dB for non-return-to-zero at a bit-error rate (BER) of 2×10(-3). Simultaneous processing of four wavelength-multiplexed 16-QAM signals with an average OSNR penalty of 4.5 dB at a BER of 2×10(-3) is also demonstrated.

  18. Efficient frequency-domain channel equalization methods for dual-polarization orthogonal frequency-division multiplexing/offset quadrature amplitude modulation-passive optical network

    NASA Astrophysics Data System (ADS)

    Lin, Bangjiang; Fang, Xi; Tang, Xuan; Lin, Chun; Li, Yiwei; Zhang, Shihao; Wu, Yi; Li, Hui

    2016-10-01

    We present dual-polarization orthogonal frequency-division multiplexing/offset quadrature amplitude modulation (OFDM/OQAM) transmission for passive optical network (PON) with intensity modulation and direct detection, which has high spectral efficiency and high robustness against chromatic dispersion (CD) and polarization mode dispersion (PMD). The frequency-domain optical fiber channel transmission model for dual-polarization OFDM/OQAM-PON with the CD- and PMD-induced intrinsic imaginary interference (IMI) effect is systemically deduced. The intrasymbol frequency-domain averaging (ISFA) and minimum mean-squared error (MMSE) with the full loaded (FL) and half loaded (HL) preamble structures are used to mitigate the IMI effect. Compared with the conventional interference approximation method, the ISFA and MMSE offer improved receiver sensitivity. For channel estimation, the FL method is more effective than the HL method in mitigating the IMI effect and optical noise.

  19. Molecular-resolution imaging of lead phthalocyanine molecules by small amplitude frequency modulation atomic force microscopy using second flexural mode

    NASA Astrophysics Data System (ADS)

    Ichii, Takashi; Hosokawa, Yoshihiro; Kobayashi, Kei; Matsushige, Kazumi; Yamada, Hirofumi

    2009-03-01

    Lead phthalocyanine molecules on MoS2(0001) substrates were imaged using an ultrahigh-vacuum AFM apparatus equipped with an optical beam deflection (OBD) sensor. The second flexural mode was employed to utilize its high effective spring constant in order to reduce the oscillation amplitude to 0.5 nm without oscillation instability. Submolecular-resolution images were obtained when a shorter cantilever, which had a very high resonance frequency and a low noise equivalent deflection in the OBD sensor, was used.

  20. Increased dynamic regulation of postural tone through Alexander Technique training

    PubMed Central

    Cacciatore, TW; Gurfinkel, VS; Horak, FB; Cordo, PJ; Ames, KE

    2010-01-01

    Gurfinkel and colleagues (2006) recently found that healthy adults dynamically modulate postural muscle tone in the body axis during anti-gravity postural maintenance and that this modulation is inversely correlated with axial stiffness. Our objective in the present study was to investigate whether dynamic modulation of axial postural tone can change through training. We examined whether teachers of the Alexander Technique (AT), who undergo “long-term” (3-year) training, have greater modulation of axial postural tone than matched control subjects. In addition, we performed a longitudinal study on the effect of “short-term” (10-week) AT training on the axial postural tone of individuals with low back pain (LBP), since short term AT training has previously been shown to reduce LBP. Axial postural tone was quantified by measuring the resistance of the neck, trunk and hips to small (±10°), slow (1°/s) torsional rotation during stance. Modulation of tone was determined by the torsional resistance to rotation (peak-to-peak, phase-advance, and variability of torque) and axial muscle activity (EMG). Peak-to-peak torque was lower (~50%), while phase-advance and cycle-to-cycle variability were enhanced for AT teachers compared to matched control subjects at all levels of the axis. In addition, LBP subjects decreased trunk and hip stiffness following short-term AT training compared to a control intervention. While changes in static levels of postural tone may have contributed to the reduced stiffness observed with the AT, our results suggest that dynamic modulation of postural tone can be enhanced through long-term training in the AT, which may constitute an important direction for therapeutic intervention. PMID:21185100

  1. Auditory stream segregation in monkey auditory cortex: effects of frequency separation, presentation rate, and tone duration.

    PubMed

    Fishman, Yonatan I; Arezzo, Joseph C; Steinschneider, Mitchell

    2004-09-01

    Auditory stream segregation refers to the organization of sequential sounds into "perceptual streams" reflecting individual environmental sound sources. In the present study, sequences of alternating high and low tones, "...ABAB...," similar to those used in psychoacoustic experiments on stream segregation, were presented to awake monkeys while neural activity was recorded in primary auditory cortex (A1). Tone frequency separation (AF), tone presentation rate (PR), and tone duration (TD) were systematically varied to examine whether neural responses correlate with effects of these variables on perceptual stream segregation. "A" tones were fixed at the best frequency of the recording site, while "B" tones were displaced in frequency from "A" tones by an amount = delta F. As PR increased, "B" tone responses decreased in amplitude to a greater extent than "A" tone responses, yielding neural response patterns dominated by "A" tone responses occurring at half the alternation rate. Increasing TD facilitated the differential attenuation of "B" tone responses. These findings parallel psychoacoustic data and suggest a physiological model of stream segregation whereby increasing delta F, PR, or TD enhances spatial differentiation of "A" tone and "B" tone responses along the tonotopic map in A1.

  2. Auditory stream segregation in monkey auditory cortex: effects of frequency separation, presentation rate, and tone duration

    NASA Astrophysics Data System (ADS)

    Fishman, Yonatan I.; Arezzo, Joseph C.; Steinschneider, Mitchell

    2004-09-01

    Auditory stream segregation refers to the organization of sequential sounds into ``perceptual streams'' reflecting individual environmental sound sources. In the present study, sequences of alternating high and low tones, ``...ABAB...,'' similar to those used in psychoacoustic experiments on stream segregation, were presented to awake monkeys while neural activity was recorded in primary auditory cortex (A1). Tone frequency separation (ΔF), tone presentation rate (PR), and tone duration (TD) were systematically varied to examine whether neural responses correlate with effects of these variables on perceptual stream segregation. ``A'' tones were fixed at the best frequency of the recording site, while ``B'' tones were displaced in frequency from ``A'' tones by an amount=ΔF. As PR increased, ``B'' tone responses decreased in amplitude to a greater extent than ``A'' tone responses, yielding neural response patterns dominated by ``A'' tone responses occurring at half the alternation rate. Increasing TD facilitated the differential attenuation of ``B'' tone responses. These findings parallel psychoacoustic data and suggest a physiological model of stream segregation whereby increasing ΔF, PR, or TD enhances spatial differentiation of ``A'' tone and ``B'' tone responses along the tonotopic map in A1.

  3. Interlinked add-drop filter with amplitude modulation routing a fiber-optic microring to a lithium niobate microwaveguide.

    PubMed

    Zhou, Suxu; Dong, Jiangli; He, Donghui; Wang, Yuan; Qiu, Wentao; Yu, Jianhui; Guan, Heyuan; Zhu, Wenguo; Zhong, Yongchun; Luo, Yunhan; Zhang, Jun; Chen, Zhe; Lu, Huihui

    2017-04-15

    We propose and experimentally demonstrate a new electro-optically controllable add-drop filter based on light coupling between a microfiber knot ring (MKR) and a lithium niobate (LN) microwaveguide. In our design, the MKR works as a resonator and routes the resonant light into the LN microwaveguide. The LN microwaveguide, as an excellent intermediary between electronics and optics, is a robust platform that not only enables stable support and manipulation of the MKR but also provides amplitude tunability taking advantage of its electro-optic property. Two add-drop filters with different diameters of the MKR, 1.12 mm, and 560 μm respectively, are studied, and a maximum amplitude tunability of ∼0.139  dB/V is obtained. The results show that this design can be a solution to interconnect a microstructured optical fiber with a microstructured on-chip device and provide an effective method to realize the active on-chip integration of the conventional fiber system.

  4. CoRoT light curves of Blazhko RR Lyrae stars. Evidence of a strong correlation between phase and amplitude modulations of CoRoT ID 0105288363

    NASA Astrophysics Data System (ADS)

    Chadid, M.; Perini, C.; Bono, G.; Auvergne, M.; Baglin, A.; Weiss, W. W.; Deboscher, J.

    2011-03-01

    Context. The CoRoT - Convection Rotation and planetary Transits - space mission provides a unique opportunity to monitor RR Lyrae stars with excellent time-sampling, unprecedented photometric precision, and a long time base of 150 days. Aims: The pulsation characteristics of RR Lyrae stars rely on robust physics, but we still lack a firm quantitative understanding of the physical mechanisms driving the Blazhko modulation and the long-term changes in their pulsation behavior. We use the high-precision space data of an unknown RR Lyrae star CoRoT ID 0105288363 observed during a second long run centered on the Galaxy - LRc02 -, to improve our understanding of the pulsation properties of RR Lyrae stars. Methods: The CoRoT data were corrected using a jump and trend filtering code. We applied different period-finding techniques including Period04, MuFrAn, PDM, and SigSpec. Amplitude and phase modulation were investigated using an analytical function method as well as traditional O-C diagrams. Results: For the first time, we detect significant cycle-to-cycle changes in the Blazhko modulation, which appear to be analogous to those predicted by Stothers - owing to the suppression of turbulent convection - to explain this phenomenon. We discuss the clear correlations between the phase and the amplitude of the bump, and the skewness and acuteness of the light curve during different Blazhko cycles. We find that these quantities are strongly anticorrelated with the fundamental pulsation period. This provides a strong support to the slow convective cycle model suggested by Stothers. We also detect a long-term modulation period in the maximum brightness spectrum. A more extended coverage of the long-term modulation is required to constrain its period. Seventh-order side peaks of the pulsation multiplet structure are also visible with the left-side peak amplitudes being higher than those of the right. This has never previously been detected. Future theoretical investigations are

  5. Stimulus frequency otoacoustic emissions evoked by swept tones.

    PubMed

    Chen, Shixiong; Deng, Jun; Bian, Lin; Li, Guanglin

    2013-12-01

    Otoacoustic emissions (OAEs) are soft sounds generated by the cochlea and the measurements of OAEs are useful in detecting cochlear damages. Stimulus frequency otoacoustic emissions (SFOAEs) are evoked by one single tone and they are the most frequency specific in probing functional status of the cochlea than other types of OAEs. However, SFOAEs are currently restricted to research only because of the difficulty and low efficiency of their measurements. To solve these problems, an efficient method of using swept tones to measure SFOAEs was proposed in this study. The swept tones had time-varying frequencies and therefore could efficiently measure SFOAEs over a wide frequency range with a resolution dependent on the sweep rate. A three-interval paradigm and a tracking filter were used to separate the swept-tone SFOAEs from background noises. The reliability of the swept-tone SFOAEs was examined by a repeated-measure design, and the accuracy was evaluated by the comparison with a standard method using pure tones as the stimuli. The pilot results of this study showed that SFOAEs could be measured successfully using swept tones in human ears with normal hearing. The amplitude and phase of the swept-tone SFOAEs were highly reproducible in the repeated measures, and were nearly equivalent to SFOAEs evoked by pure tones under various signal conditions. These findings suggest that the proposed swept-tone SFOAEs could be a useful method in estimating the cochlear functions and developing an efficient approach of OAE measurements to help with accurate hearing diagnoses in the clinic.

  6. The evaluation of eccentricity-related amplitude modulation and bundling in paleoclimate data: An inverse approach for astrochronologic testing and time scale optimization

    NASA Astrophysics Data System (ADS)

    Meyers, Stephen R.

    2015-12-01

    Cyclostratigraphic analysis has produced fundamental advancements in our understanding of climate change, paleoceanography, celestial mechanics, geochronology, and chronostratigraphy. Of central importance to this success has been the development of astrochronologic testing methods for the evaluation of astronomical-climate influence on sedimentation. Most pre-Pleistocene astrochronologic testing methods fall into one of two categories: (1) those that test for expected amplitude or frequency modulation imposed by an astronomical signal or (2) those that test for bedding hierarchies (frequency ratios or bundling) that are predicted by the dominant astronomical periods. In this study, a statistical methodology for combining these complementary approaches is developed, which identifies the time scale that simultaneously optimizes eccentricity amplitude modulation of the precession band, and the concentration of power at precession (carrier) and eccentricity (modulator) frequencies. The technique is demonstrated to have high statistical power—it is capable of identifying astronomical cycles when present—under a wide range of conditions, and its application to synthetic models illuminates a range of potential pitfalls that are encountered when more conventional nonoptimization approaches are used. The method is also independent from the interpretation of power spectrum peak significance, resolving previous concerns regarding appropriate confidence level assessment and "multiple testing." As two case studies, the algorithm is applied to Miocene strata of Ocean Drilling Program (ODP) Site 926B, and the Paleocene-Eocene Thermal Maximum-Eocene Thermal Maximum 2 interval at ODP Site 1262. The results verify published cyclostratigraphic interpretations and support the theoretical astronomical solutions. This new astrochronologic testing approach can be used to evaluate cyclostratigraphic records spanning the Phanerozoic and potentially beyond.

  7. The Effect of Phase and Amplitude Imbalance on the Performance of Offset Quadrature Phase-Shift-Keyed (OQPSK) Communication Systems

    NASA Astrophysics Data System (ADS)

    Tsou, H.

    1998-07-01

    The balanced modulator, which comprises two amplitude-modulation modules, is widely used in phase-modulated communication systems. In practice, the balance between these amplitude-modulation modules is difficult to maintain, and the amplitude and phase imbalances can cause distortion in the signal constellation and introduce undesired interfering tone signal components when such an imperfect modulator is used to modulate the data directly onto the RF carrier. The rendered imperfection inevitably degrades the receiver performance and, in a quadrature phase-shift-keyed (QPSK) system, causes cross talk between the in-phase and quadrature-phase channels. This article summarizes an analysis of the impact of these modulator imbalances on an offset QPSK (OQPSK) communication system in which an OQPSK signal is coherently demodulated by using a carrier reference extracted from a modified QPSK carrier tracking loop. Both carrier-suppression level and bit-error performance are analyzed in this article. The results show that the current Consultative Committee for Space Data Systems (CCSDS) recommendations of 2-deg maximum permissible phase imbalance and 0.2-dB amplitude imbalance are sufficient to provide a 25-dB or more carrier suppression and a system degradation of 1 dB or less at the bit-error probability of 10±4 when the OQPSK system is operated in a reasonable loop SNR region.

  8. Amplitude modulated chirp excitation to reduce grating lobes and maintain ultrasound intensity at the focus of an array.

    PubMed

    Karunakaran, Chandra P; Oelze, Michael L

    2013-09-01

    During application of high intensity focused ultrasound (HIFU) with therapy arrays, the existence of grating lobes can cause heating at unintended tissue regions. Therefore, the reduction of grating lobes in therapeutic arrays is an important goal. One way to reduce the grating lobes in therapy arrays is to excite the arrays with broadband signals (defined here as >10% fractional bandwidth). To achieve a reduction in grating lobe levels in an ultrasonic array, coded waveforms can be utilized that reduce the grating lobe levels while maintaining the spatial peak temporal average intensity. In this study, a 5-MHz, 9-element, 1.25 mm inter-elemental spacing linear array was excited by a sinusoidal waveform, a conventional linear chirp, and a modified linear chirp. Both chirps spanned the -3-dB bandwidth of the transducer. The conventional chirp was a broadband signal with a linear sweep of frequencies between 2.5 and 7.5 MHz, with all frequency components excited with equal amplitude. The modified chirp signal also swept the frequencies between 2.5 and 7.5 MHz, but the amplitude was weighted such that the edges (low and high frequencies of the band) were excited with more energy than the center of the band. In simulations, the field patterns for the sinusoidal, conventional chirp and modified chirp excitations were produced from the array using Field II and compared. For experiments, the beam pattern from a 5-MHz single-element transducer was mapped using a hydrophone for the sinusoidal, conventional chirp and modified chirp excitation. Each field from the transducer was repeated and summed to produce a field from an array of 9 elements. The difference in the time averaged intensity (in dB) in the main lobe and grating lobes were estimated for each excitation and compared. The results demonstrated that the chirp signals resulted in decreases in grating lobe levels compared to the main lobe, i.e. 10 dB down for focusing and 6 dB down for focusing and steering. A

  9. Habitat-related differences in auditory processing of complex tones and vocal signal properties in four songbirds.

    PubMed

    Lucas, Jeffrey R; Vélez, Alejandro; Henry, Kenneth S

    2015-04-01

    We examined temporal processing of harmonic tone complexes in two woodland species (tufted titmice and white-breasted nuthatches) and two open-habitat species (house sparrows and white-crowned sparrows). Envelope and fine-structure processing were quantified using the envelope following response (EFR) and frequency following response (FFR). We predicted stronger EFRs in the open-habitat species based on broader auditory filters and greater amplitude modulation of vocal signals in this group. We predicted stronger FFRs in woodland species based on narrower auditory filters. As predicted, EFR amplitude was generally greatest in the open habitat species. FFR amplitude, in contrast, was greatest in white-crowned sparrows with no clear difference between habitats. This result cannot be fully explained by species differences in audiogram shape and might instead reflect greater acoustic complexity of songs in the white-crowned sparrow. Finally, we observed stronger FFRs in woodland species when tones were broadcast with the next higher harmonic in the complex. Thus, species such as nuthatches that have songs with strong harmonics may process these sounds using enhanced spectral processing instead of enhanced amplitude-envelope processing. The results suggest coevolution between signal design and temporal processing of complex signals and underscore the need to study auditory processing with a diversity of signals.

  10. Arsenic toxicity in the water weed Wolffia arrhiza measured using Pulse Amplitude Modulation Fluorometry (PAM) measurements of photosynthesis.

    PubMed

    Ritchie, Raymond J; Mekjinda, Nutsara

    2016-10-01

    Accumulation of arsenic in plants is a serious South-east Asian environmental problem. Photosynthesis in the small aquatic angiosperm Wolffia arrhiza is very sensitive to arsenic toxicity, particularly in water below pH 7 where arsenite (As (OH)3) (AsIII) is the dominant form; at pH >7 AsO4(2-) (As(V) predominates). A blue-diode PAM (Pulse Amplitude Fluorometer) machine was used to monitor photosynthesis in Wolffia. Maximum gross photosynthesis (Pgmax) and not maximum yield (Ymax) is the most reliable indicator of arsenic toxicity. The toxicity of arsenite As(III) and arsenate (H2AsO4(2-)) As(V) vary with pH. As(V) was less toxic than As(III) at both pH 5 and pH 8 but both forms of arsenic were toxic (>90% inhibition) at below 0.1molm(-3) when incubated in arsenic for 24h. Arsenite toxicity was apparent after 1h based on Pgmax and gradually increased over 7h but there was no apparent effect on Ymax or photosynthetic efficiency (α0).

  11. The Temporal Order of Word Presentation Modulates the Amplitudes of P2 and N400 during Recognition of Causal Relations

    PubMed Central

    Liang, Xiuling; Xiao, Feng; Wu, Lijun; Chen, Qingfei; Lei, Yi; Li, Hong

    2016-01-01

    The processing of causal relations has been constantly found to be asymmetrical once the roles of cause and effect are assigned to objects in interactions. We used a relationship recognition paradigm and recorded electroencephalographic (EEG) signals to explore the neural mechanism underlying the asymmetrical representations of causal relations in semantic memory. The results revealed that the verification of causal relations is faster if two words appear in “cause-effect” order (e.g., virus-epidemic) than if they appear in “effect-cause” order (e.g., epidemic-virus), whereas no such asymmetrical representation was found for the verification of hierarchical relations with reverse orders (e.g., bird-sparrow vs. sparrow-bird) in Experiment 1. Furthermore, the P2 amplitude elicited by “superordinate-subordinate” order was larger than that when in reverse order, whereas the N400 effect elicited by “cause-effect” order was smaller (more positive) than when in reverse order. However, no such asymmetry, as well as P2 and N400 components, were observed when verifying the existence of a general associative relation in Experiment 2. We suggested that the smaller N400 in cause-effect order indicates their increased salience in semantic memory relative to the effect-cause order. These results provide evidence for dissociable neural processes, which are related to role binding, contributing to the generation of causal asymmetry. PMID:27994564

  12. Simulation study of amplitude-modulated (AM) harmonic motion imaging (HMI) for stiffness contrast quantification with experimental validation.

    PubMed

    Maleke, Caroline; Luo, Jianwen; Gamarnik, Viktor; Lu, Xin L; Konofagou, Elisa E

    2010-07-01

    The objective of this study is to show that Harmonic Motion Imaging (HMI) can be used as a reliable tumor-mapping technique based on the tumor's distinct stiffness at the early onset of disease. HMI is a radiation-force-based imaging method that generates a localized vibration deep inside the tissue to estimate the relative tissue stiffness based on the resulting displacement amplitude. In this paper, a finite-element model (FEM) study is presented, followed by an experimental validation in tissue-mimicking polyacrylamide gels and excised human breast tumors ex vivo. This study compares the resulting tissue motion in simulations and experiments at four different gel stiffnesses and three distinct spherical inclusion diameters. The elastic moduli of the gels were separately measured using mechanical testing. Identical transducer parameters were used in both the FEM and experimental studies, i.e., a 4.5-MHz single-element focused ultrasound (FUS) and a 7.5-MHz diagnostic (pulse-echo) transducer. In the simulation, an acoustic pressure field was used as the input stimulus to generate a localized vibration inside the target. Radiofrequency (rf) signals were then simulated using a 2D convolution model. A one-dimensional cross-correlation technique was performed on the simulated and experimental rf signals to estimate the axial displacement resulting from the harmonic radiation force. In order to measure the reliability of the displacement profiles in estimating the tissue stiffness distribution, the contrast-transfer efficiency (CTE) was calculated. For tumor mapping ex vivo, a harmonic radiation force was applied using a 2D raster-scan technique. The 2D HMI images of the breast tumor ex vivo could detect a malignant tumor (20 x 10 mm2) surrounded by glandular and fat tissues. The FEM and experimental results from both gels and breast tumors ex vivo demonstrated that HMI was capable of detecting and mapping the tumor or stiff inclusion with various diameters or

  13. Recognition of Frequency Modulated Whistle-Like Sounds by a Bottlenose Dolphin (Tursiops truncatus) and Humans with Transformations in Amplitude, Duration and Frequency

    PubMed Central

    Branstetter, Brian K.; DeLong, Caroline M.; Dziedzic, Brandon; Black, Amy; Bakhtiari, Kimberly

    2016-01-01

    Bottlenose dolphins (Tursiops truncatus) use the frequency contour of whistles produced by conspecifics for individual recognition. Here we tested a bottlenose dolphin’s (Tursiops truncatus) ability to recognize frequency modulated whistle-like sounds using a three alternative matching-to-sample paradigm. The dolphin was first trained to select a specific object (object A) in response to a specific sound (sound A) for a total of three object-sound associations. The sounds were then transformed by amplitude, duration, or frequency transposition while still preserving the frequency contour of each sound. For comparison purposes, 30 human participants completed an identical task with the same sounds, objects, and training procedure. The dolphin’s ability to correctly match objects to sounds was robust to changes in amplitude with only a minor decrement in performance for short durations. The dolphin failed to recognize sounds that were frequency transposed by plus or minus ½ octaves. Human participants demonstrated robust recognition with all acoustic transformations. The results indicate that this dolphin’s acoustic recognition of whistle-like sounds was constrained by absolute pitch. Unlike human speech, which varies considerably in average frequency, signature whistles are relatively stable in frequency, which may have selected for a whistle recognition system invariant to frequency transposition. PMID:26863519

  14. Color image encryption by using Yang-Gu mixture amplitude-phase retrieval algorithm in gyrator transform domain and two-dimensional Sine logistic modulation map

    NASA Astrophysics Data System (ADS)

    Sui, Liansheng; Liu, Benqing; Wang, Qiang; Li, Ye; Liang, Junli

    2015-12-01

    A color image encryption scheme is proposed based on Yang-Gu mixture amplitude-phase retrieval algorithm and two-coupled logistic map in gyrator transform domain. First, the color plaintext image is decomposed into red, green and blue components, which are scrambled individually by three random sequences generated by using the two-dimensional Sine logistic modulation map. Second, each scrambled component is encrypted into a real-valued function with stationary white noise distribution in the iterative amplitude-phase retrieval process in the gyrator transform domain, and then three obtained functions are considered as red, green and blue channels to form the color ciphertext image. Obviously, the ciphertext image is real-valued function and more convenient for storing and transmitting. In the encryption and decryption processes, the chaotic random phase mask generated based on logistic map is employed as the phase key, which means that only the initial values are used as private key and the cryptosystem has high convenience on key management. Meanwhile, the security of the cryptosystem is enhanced greatly because of high sensitivity of the private keys. Simulation results are presented to prove the security and robustness of the proposed scheme.

  15. Tone Features, Tone Perception, and Peak Alignment in Thai

    ERIC Educational Resources Information Center

    Zsiga, Elizabeth; Nitisaroj, Rattima

    2007-01-01

    This paper investigates the relationship between the phonological features of tone and tone perception in Thai. Specifically, it tests the hypothesis (proposed by Moren & Zsiga, 2006) that the principle perceptual cues to the five-way tonal contrast in Thai are high and low pitch targets aligned to moras. Results of four perception studies, one…

  16. Attention deficits revealed by passive auditory change detection for pure tones and lexical tones in ADHD children

    PubMed Central

    Yang, Ming-Tao; Hsu, Chun-Hsien; Yeh, Pei-Wen; Lee, Wang-Tso; Liang, Jao-Shwann; Fu, Wen-Mei; Lee, Chia-Ying

    2015-01-01

    Inattention (IA) has been a major problem in children with attention deficit/hyperactivity disorder (ADHD), accounting for their behavioral and cognitive dysfunctions. However, there are at least three processing steps underlying attentional control for auditory change detection, namely pre-attentive change detection, involuntary attention orienting, and attention reorienting for further evaluation. This study aimed to examine whether children with ADHD would show deficits in any of these subcomponents by using mismatch negativity (MMN), P3a, and late discriminative negativity (LDN) as event-related potential (ERP) markers, under the passive auditory oddball paradigm. Two types of stimuli—pure tones and Mandarin lexical tones—were used to examine if the deficits were general across linguistic and non-linguistic domains. Participants included 15 native Mandarin-speaking children with ADHD and 16 age-matched controls (across groups, age ranged between 6 and 15 years). Two passive auditory oddball paradigms (lexical tones and pure tones) were applied. The pure tone oddball paradigm included a standard stimulus (1000 Hz, 80%) and two deviant stimuli (1015 and 1090 Hz, 10% each). The Mandarin lexical tone oddball paradigm’s standard stimulus was /yi3/ (80%) and two deviant stimuli were /yi1/ and /yi2/ (10% each). The results showed no MMN difference, but did show attenuated P3a and enhanced LDN to the large deviants for both pure and lexical tone changes in the ADHD group. Correlation analysis showed that children with higher ADHD tendency, as indexed by parents’ and teachers’ ratings on ADHD symptoms, showed less positive P3a amplitudes when responding to large lexical tone deviants. Thus, children with ADHD showed impaired auditory change detection for both pure tones and lexical tones in both involuntary attention switching, and attention reorienting for further evaluation. These ERP markers may therefore be used for the evaluation of anti-ADHD drugs that

  17. Strategies for Analyzing Tone Languages

    ERIC Educational Resources Information Center

    Coupe, Alexander R.

    2014-01-01

    This paper outlines a method of auditory and acoustic analysis for determining the tonemes of a language starting from scratch, drawing on the author's experience of recording and analyzing tone languages of north-east India. The methodology is applied to a preliminary analysis of tone in the Thang dialect of Khiamniungan, a virtually undocumented…

  18. Four-fold increase in users of time-wavelength division multiplexing (TWDM) passive optical network (PON) by delayed optical amplitude modulation (AM) upstream

    NASA Astrophysics Data System (ADS)

    Kachhatiya, Vivek; Prince, Shanthi

    2016-12-01

    In this paper, we have proposed and simulated optical time division multiplexed passive optical network (TDM-PON) using delayed optical amplitude modulation (AM). Eight upstream wavelengths are demonstrated to show optical time wavelength division multiplexed (TWDM) by combining optical network units (ONU) users data at the remote node (RN). Each ONU generates 2.5 Gb/s user data, and it is modulated using novel return to zero (RZ) delayed AM. Optical TDM aggregates 10 Gb/s data per wavelength from four 2.5 Gb/s upstream user data, which facilitates four different ONU data on the same wavelength as 10 Gb/s per upstream wavelength and, simplify the laser requirements (2.5 Gb/s) at each optical network unit (ONU) transmitter. Upstream optical TWDM-PON is investigated for eight wavelengths with wavelength spacing of 100 GHz. Novel optical TDM for upstream increased the number of the simultaneous user to fourfold from conventional TWDM-PON using delayed AM with a high-quality-factor of received signal. Despite performance degradation due to different fiber reach and dispersion compensation technique, Optical TWDM link shows significant improvement regarding receiver sensitivity when compared with common TWDM link. Hence, it offers optimistic thinking to show optical TDM at this phase as one of the future direction, where complex digital signal processing (DSP) and coherent optical communication are frequently demonstrated to serve the access network. Downstream side conventional TWDM eight wavelengths are multiplexed at the OLT and sent downstream to serve distributed tunable ONU receivers through an optical distribution network (ODN). Each downstream wavelengths are modulated at the peak rate of 10 Gb/s using non-return to zero external modulation (NRZ-EM). The proposed architecture is cost efficient and supports high data rates as well as "pay as you grow" network for both service providers and the users perspectives. Users are classified into two categories viz home

  19. Amplitude-modulation detection by recreational-noise-exposed humans with near-normal hearing thresholds and its medium-term progression

    PubMed Central

    Stone, Michael A.; Moore, Brian C.J.

    2014-01-01

    Noise exposure can affect the functioning of cochlear inner and outer hair cells (IHC/OHC), leading to multiple perceptual changes. This work explored possible changes in detection of amplitude modulation (AM) at three Sensation Levels (SL) for carrier frequencies of 3, 4 and 6 kHz. There were two groups of participants, aged 19 to 24 (Young) and 26 to 35 (Older) years. All had near-normal audiometric thresholds. Participants self-assessed exposure to high-level noise in recreational settings. Each group was sub-grouped into low-noise (LN) or high-noise (HN) exposure. AM detection thresholds were worse for the HN than for the LN sub-group at the lowest SL, for the males only of the Young group and for both genders for the Older group, despite no significant difference in absolute threshold at 3 and 4 kHz between sub-groups. AM detection at the lowest SL, at both 3 and 4 kHz, generally improved with increasing age and increasing absolute threshold, consistent with a recruitment-like process. However, poorer AM detection was correlated with increasing exposure at 3 kHz in the Older group. It is suggested that high-level noise exposure produces both IHC- and OHC-related damage, the balance between the two varying across frequency. However, the use of AM detection offers poor sensitivity as a measure of the effects. PMID:25260433

  20. Seasonal and diel changes in photosynthetic activity of the snow alga Chlamydomonas nivalis (Chlorophyceae) from Svalbard determined by pulse amplitude modulation fluorometry.

    PubMed

    Stibal, Marek; Elster, Josef; Sabacká, Marie; Kastovská, Klára

    2007-02-01

    The seasonal and diel dynamics of the physiological state and photosynthetic activity of the snow alga Chlamydomonas nivalis were investigated in a snowfield in Svalbard. The snow surface represents an environment with very high irradiation intensities along with stable low temperatures close to freezing point. Photosynthetic activity was measured using pulse amplitude modulation fluorometry. Three types of cell (green biflagellate vegetative cells, orange spores clustered by means of mucilaginous sheaths, and purple spores with thick cell walls) were found, all of them photosynthetically active. The pH of snow ranged between 5.0 and 7.5, and the conductivity ranged between 5 and 75 microS cm(-1). The temperature of snow was stable (-0.1 to +0.1 degrees C), and the incident radiation values ranged from 11 to 1500 micromol photons m(-2) s(-1). The photosynthetic activity had seasonal and diel dynamics. The Fv/Fm values ranged between 0.4 and 0.7, and generally declined over the course of the season. A dynamic response of Fv/Fm to the irradiance was recorded. According to the saturating photon fluence values Ek, the algae may have obtained saturating light as deep as 3 cm in the snow when there were higher-light conditions, whereas they were undersaturated at prevalent low light even if on the surface.

  1. Examination of humidity effects on measured thickness and interfacial phenomena of exfoliated graphene on silicon dioxide via amplitude modulation atomic force microscopy

    SciTech Connect

    Jinkins, K.; Farina, L.; Wu, Y.; Camacho, J.

    2015-12-14

    The properties of Few-Layer Graphene (FLG) change with the number of layers and Amplitude Modulation (AM) Atomic Force Microscopy (AFM) is commonly used to determine the thickness of FLG. However, AFM measurements have been shown to be sensitive to environmental conditions such as relative humidity (RH). In the present study, AM-AFM is used to measure the thickness and loss tangent of exfoliated graphene on silicon dioxide (SiO{sub 2}) as RH is increased from 10% to 80%. We show that the measured thickness of graphene is dependent on RH. The loss tangent values of the graphene and oxide regions are both affected by humidity, with generally higher loss tangent for graphene than SiO{sub 2}. As RH increases, we observe the loss tangent of both materials approaches the same value. We hypothesize that there is a layer of water trapped between the graphene and SiO{sub 2} substrate to explain this observation. Using this interpretation, the loss tangent images also indicate movement and change in this trapped water layer as RH increases, which impacts the measured thickness of graphene using AM-AFM.

  2. Tone compatibility between HDR displays

    NASA Astrophysics Data System (ADS)

    Bist, Cambodge; Cozot, Rémi; Madec, Gérard; Ducloux, Xavier

    2016-09-01

    High Dynamic Range (HDR) is the latest trend in television technology and we expect an in ux of HDR capable consumer TVs in the market. Initial HDR consumer displays will operate on a peak brightness of about 500-1000 nits while in the coming years display peak brightness is expected to go beyond 1000 nits. However, professionally graded HDR content can range from 1000 to 4000 nits. As with Standard Dynamic Range (SDR) content, we can expect HDR content to be available in variety of lighting styles such as low key, medium key and high key video. This raises concerns over tone-compatibility between HDR displays especially when adapting to various lighting styles. It is expected that dynamic range adaptation between HDR displays uses similar techniques as found with tone mapping and tone expansion operators. In this paper, we survey simple tone mapping methods of 4000 nits color-graded HDR content for 1000 nits HDR displays. We also investigate tone expansion strategies when HDR content graded in 1000 nits is displayed on 4000 nits HDR monitors. We conclude that the best tone reproduction technique between HDR displays strongly depends on the lighting style of the content.

  3. Neurophysiological and Behavioral Responses of Mandarin Lexical Tone Processing.

    PubMed

    Yu, Yan H; Shafer, Valerie L; Sussman, Elyse S

    2017-01-01

    Language experience enhances discrimination of speech contrasts at a behavioral- perceptual level, as well as at a pre-attentive level, as indexed by event-related potential (ERP) mismatch negativity (MMN) responses. The enhanced sensitivity could be the result of changes in acoustic resolution and/or long-term memory representations of the relevant information in the auditory cortex. To examine these possibilities, we used a short (ca. 600 ms) vs. long (ca. 2,600 ms) interstimulus interval (ISI) in a passive, oddball discrimination task while obtaining ERPs. These ISI differences were used to test whether cross-linguistic differences in processing Mandarin lexical tone are a function of differences in acoustic resolution and/or differences in long-term memory representations. Bisyllabic nonword tokens that differed in lexical tone categories were presented using a passive listening multiple oddball paradigm. Behavioral discrimination and identification data were also collected. The ERP results revealed robust MMNs to both easy and difficult lexical tone differences for both groups at short ISIs. At long ISIs, there was either no change or an enhanced MMN amplitude for the Mandarin group, but reduced MMN amplitude for the English group. In addition, the Mandarin listeners showed a larger late negativity (LN) discriminative response than the English listeners for lexical tone contrasts in the long ISI condition. Mandarin speakers outperformed English speakers in the behavioral tasks, especially under the long ISI conditions with the more similar lexical tone pair. These results suggest that the acoustic correlates of lexical tone are fairly robust and easily discriminated at short ISIs, when the auditory sensory memory trace is strong. At longer ISIs beyond 2.5 s language-specific experience is necessary for robust discrimination.

  4. Neurophysiological and Behavioral Responses of Mandarin Lexical Tone Processing

    PubMed Central

    Yu, Yan H.; Shafer, Valerie L.; Sussman, Elyse S.

    2017-01-01

    Language experience enhances discrimination of speech contrasts at a behavioral- perceptual level, as well as at a pre-attentive level, as indexed by event-related potential (ERP) mismatch negativity (MMN) responses. The enhanced sensitivity could be the result of changes in acoustic resolution and/or long-term memory representations of the relevant information in the auditory cortex. To examine these possibilities, we used a short (ca. 600 ms) vs. long (ca. 2,600 ms) interstimulus interval (ISI) in a passive, oddball discrimination task while obtaining ERPs. These ISI differences were used to test whether cross-linguistic differences in processing Mandarin lexical tone are a function of differences in acoustic resolution and/or differences in long-term memory representations. Bisyllabic nonword tokens that differed in lexical tone categories were presented using a passive listening multiple oddball paradigm. Behavioral discrimination and identification data were also collected. The ERP results revealed robust MMNs to both easy and difficult lexical tone differences for both groups at short ISIs. At long ISIs, there was either no change or an enhanced MMN amplitude for the Mandarin group, but reduced MMN amplitude for the English group. In addition, the Mandarin listeners showed a larger late negativity (LN) discriminative response than the English listeners for lexical tone contrasts in the long ISI condition. Mandarin speakers outperformed English speakers in the behavioral tasks, especially under the long ISI conditions with the more similar lexical tone pair. These results suggest that the acoustic correlates of lexical tone are fairly robust and easily discriminated at short ISIs, when the auditory sensory memory trace is strong. At longer ISIs beyond 2.5 s language-specific experience is necessary for robust discrimination. PMID:28321179

  5. Spatial hearing in Cope's gray treefrog: II. Frequency-dependent directionality in the amplitude and phase of tympanum vibrations.

    PubMed

    Caldwell, Michael S; Lee, Norman; Schrode, Katrina M; Johns, Anastasia R; Christensen-Dalsgaard, Jakob; Bee, Mark A

    2014-04-01

    Anuran ears function as pressure difference receivers, and the amplitude and phase of tympanum vibrations are inherently directional, varying with sound incident angle. We quantified the nature of this directionality for Cope's gray treefrog, Hyla chrysoscelis. We presented subjects with pure tones, advertisement calls, and frequency-modulated sweeps to examine the influence of frequency, signal level, lung inflation, and sex on ear directionality. Interaural differences in the amplitude of tympanum vibrations were 1-4 dB greater than sound pressure differences adjacent to the two tympana, while interaural differences in the phase of tympanum vibration were similar to or smaller than those in sound phase. Directionality in the amplitude and phase of tympanum vibration were highly dependent on sound frequency, and directionality in amplitude varied slightly with signal level. Directionality in the amplitude and phase of tone- and call-evoked responses did not differ between sexes. Lung inflation strongly affected tympanum directionality over a narrow frequency range that, in females, included call frequencies. This study provides a foundation for further work on the biomechanics and neural mechanisms of spatial hearing in H. chrysoscelis, and lends valuable perspective to behavioral studies on the use of spatial information by this species and other frogs.

  6. Prosodic Transfer: From Chinese Lexical Tone to English Pitch Accent

    ERIC Educational Resources Information Center

    Ploquin, Marie

    2013-01-01

    Chinese tones are associated with a syllable to convey meaning, English pitch accents are prominence markers associated with stressed syllables. As both are created by pitch modulation, their pitch contours can be quite similar. The experiment reported here examines whether native speakers of Chinese produce, when speaking English, the Chinese…

  7. On the origin of falling-tone chorus elements in Earth's inner magnetosphere

    NASA Astrophysics Data System (ADS)

    Breuillard, H.; Agapitov, O.; Artemyev, A.; Krasnoselskikh, V.; Le Contel, O.; Cully, C. M.; Angelopoulos, V.; Zaliznyak, Y.; Rolland, G.

    2014-12-01

    Generation of extremely/very low frequency (ELF/VLF) chorus waves in Earth's inner magnetosphere has received increased attention recently because of their significance for radiation belt dynamics. Though past theoretical and numerical models have demonstrated how rising-tone chorus elements are produced, falling-tone chorus element generation has yet to be explained. Our new model proposes that weak-amplitude falling-tone chorus elements can be generated by magnetospheric reflection of rising-tone elements. Using ray tracing in a realistic plasma model of the inner magnetosphere, we demonstrate that rising-tone elements originating at the magnetic equator propagate to higher latitudes. Upon reflection there, they propagate to lower L-shells and turn into oblique falling tones of reduced power, frequency, and bandwidth relative to their progenitor rising tones. Our results are in good agreement with comprehensive statistical studies of such waves, notably using magnetic field measurements from THEMIS (Time History of Events and Macroscale Interactions during Substorms) spacecraft. Thus, we conclude that the proposed mechanism can be responsible for the generation of weak-amplitude falling-tone chorus emissions.

  8. A statistical study of EMIC rising and falling tone emissions observed by THEMIS

    NASA Astrophysics Data System (ADS)

    Nakamura, Satoko; Omura, Yoshiharu; Angelopoulos, Vassilis

    2016-09-01

    Electromagnetic ion cyclotron (EMIC) waves with rising or falling frequency variations have been studied intensively because of their effects on energetic particles in the Earth's magnetosphere. We develop an automated classification method of EMIC events based on the characteristics of frequency variations. We report some basic statistical properties of frequency variations in EMIC waves observed over 5-10 RE by three Time History of Events and Macroscale Interactions during Substorms probes from January 2012 to December 2014. We clarify whether rising tones or falling tones are observed in each chosen 20 min time segment. In the present analysis, we find that the occurrence rate of EMIC rising or falling tone events is more than 30% of the total EMIC wave events. The dayside magnetosphere is a preferential region for the EMIC frequency variations. The occurrence rate of rising tone events is slightly greater than that of falling tone events. We examine the relation between the frequency characteristics and the magnetospheric conditions. The solar wind pressure strongly controls the occurrence rates of frequency variations. We also calculate ranges of frequency variations. Large-amplitude EMIC waves tend to have wider frequency variations, and the range of frequency variation is largest around the prenoon region. In addition, rapid variations in wave amplitudes called "subpacket structures" are found in 70% of the EMIC rising or falling tone events in the dayside region. Subpacket structures appear mainly in large-amplitude EMIC rising or falling tones. These features are consistent with nonlinear wave growth theory.

  9. Negative response of photosynthesis to natural and projected high seawater temperatures estimated by pulse amplitude modulation fluorometry in a temperate coral

    PubMed Central

    Caroselli, Erik; Falini, Giuseppe; Goffredo, Stefano; Dubinsky, Zvy; Levy, Oren

    2015-01-01

    Balanophyllia europaea is a shallow water solitary zooxanthellate coral, endemic to the Mediterranean Sea. Extensive field studies across a latitudinal temperature gradient highlight detrimental effects of rising temperatures on its growth, demography, and skeletal characteristics, suggesting that depression of photosynthesis at high temperatures might cause these negative effects. Here we test this hypothesis by analyzing, by means of pulse amplitude modulation fluorometry, the photosynthetic efficiency of B. europaea specimens exposed in aquaria to the annual range of temperatures experienced in the field (13, 18, and 28°C), and two extreme temperatures expected for 2100 as a consequence of global warming (29 and 32°C). The indicators of photosynthetic performance analyzed (maximum and effective quantum yield) showed that maximum efficiency was reached at 20.0–21.6°C, slightly higher than the annual mean temperature in the field (18°C). Photosynthetic efficiency decreased from 20.0 to 13°C and even more strongly from 21.6 to 32°C. An unusual form of bleaching was observed, with a maximum zooxanthellae density at 18°C that strongly decreased from 18 to 32°C. Chlorophyll a concentration per zooxanthellae cell showed an opposite trend as it was minimal at 18°C and increased from 18 to 32°C. Since the areal chlorophyll concentration is the product of the zooxanthellae density and its cellular content, these trends resulted in a homogeneous chlorophyll concentration per coral surface across temperature treatments. This confirms that B. europaea photosynthesis is progressively depressed at temperatures >21.6°C, supporting previous hypotheses raised by the studies on growth and demography of this species. This study also confirms the threats posed to this species by the ongoing seawater warming. PMID:26582993

  10. Super-oscillatory focusing of circularly polarized light by ultra-long focal length planar lens based on binary amplitude-phase modulation.

    PubMed

    Chen, Gang; Li, Yuyan; Yu, Anping; Wen, Zhongquan; Dai, Luru; Chen, Li; Zhang, Zhihai; Jiang, Senlin; Zhang, Kun; Wang, Xianyou; Lin, Feng

    2016-06-29

    In traditional optics, the focal spot size of a conventional lens is restricted to the diffraction limit 0.5λ/NA, where λ is the wavelength in vacuum and NA is the numerical aperture of the lens. Recently, various sub-diffraction focusing optical devices have been demonstrated, but they usually have short focal length and high numerical aperture. Moreover, they always suffer the problem of huge sidelobes near the focal spot and small field of view, especially when the focal spot size is less than the super-oscillation criteria 0.38λ/NA. To address the problem, here, we reported a far-field sub-diffraction point-focusing lens based on binary phase and amplitude modulation with ultra-long focal length 252.8 μm (399.5λ) and small numerical aperture 0.78, and experimentally demonstrated a super-oscillatory focusing of circularly polarized light with spot size 287 nm (0.454λ), smaller than the diffraction limit 0.64λ and the super-oscillation criterion 0.487λ. What's more, on the focal plane, in the measured area within the radius of 142λ, the largest sidelobe intensity is less than 26% of the central lobe intensity. Such ultra-long distance super-oscillatory focusing with small sidelobes and large field of view has great potential applications in far-field super-resolution microscopy, ultra-high-density optical storage and nano-fabrication.

  11. Super-oscillatory focusing of circularly polarized light by ultra-long focal length planar lens based on binary amplitude-phase modulation

    NASA Astrophysics Data System (ADS)

    Chen, Gang; Li, Yuyan; Yu, Anping; Wen, Zhongquan; Dai, Luru; Chen, Li; Zhang, Zhihai; Jiang, Senlin; Zhang, Kun; Wang, Xianyou; Lin, Feng

    2016-06-01

    In traditional optics, the focal spot size of a conventional lens is restricted to the diffraction limit 0.5λ/NA, where λ is the wavelength in vacuum and NA is the numerical aperture of the lens. Recently, various sub-diffraction focusing optical devices have been demonstrated, but they usually have short focal length and high numerical aperture. Moreover, they always suffer the problem of huge sidelobes near the focal spot and small field of view, especially when the focal spot size is less than the super-oscillation criteria 0.38λ/NA. To address the problem, here, we reported a far-field sub-diffraction point-focusing lens based on binary phase and amplitude modulation with ultra-long focal length 252.8 μm (399.5λ) and small numerical aperture 0.78, and experimentally demonstrated a super-oscillatory focusing of circularly polarized light with spot size 287 nm (0.454λ), smaller than the diffraction limit 0.64λ and the super-oscillation criterion 0.487λ. What’s more, on the focal plane, in the measured area within the radius of 142λ, the largest sidelobe intensity is less than 26% of the central lobe intensity. Such ultra-long distance super-oscillatory focusing with small sidelobes and large field of view has great potential applications in far-field super-resolution microscopy, ultra-high-density optical storage and nano-fabrication.

  12. Responses of midbrain auditory neurons in rats to FM and AM tones presented simultaneously.

    PubMed

    Lee, M F; So, Edmund C; Poon, Paul W F

    2010-12-31

    Speech and other communication signals contain components of frequency and amplitude modulations (FM, AM) that often occur together. Auditory midbrain (or inferior colliculus, IC) is an important center for coding time-varying features of sounds. It remains unclear how IC neurons respond when FM and AM stimuli are both presented. Here we studied IC neurons in the urethane-anesthetized rats when animals were simultaneously stimulated with FM and AM tones. Of 122 units that were sensitive to the dual stimuli, the responses could be grossly divided into two types: one that resembled the respective responses to FM or AM stimuli presented separately ("simple" sensitivity, 45% of units), and another that appeared markedly different from their respective responses to FM or AM tones ("complex" sensitivity, 55%). These types of combinational sensitivities were further correlated with individual cell's frequency tuning pattern (response area) and with their common response pattern to FM and AM sounds. Results suggested that such combinational sensitivity could reflect local synaptic interactions on IC neurons and that the neural mechanisms could underlie more developed sensitivities to acoustic combinations found at the auditory cortex.

  13. High-frequency tone-pip-evoked otoacoustic emissions in chinchillas

    NASA Astrophysics Data System (ADS)

    Siegel, Jonathan H.; Charaziak, Karolina K.

    2015-12-01

    We measured otoacoustic emissions in anesthetized chinchillas evoked by short (1 ms) high-frequency (4 kHz) tone-pips (TEOAE) using either a compression or suppression method to separate the stimulus from the emission. Both methods revealed consistent features of the TEOAEs. The main spectral band of the emission generally corresponded to the spectrum of the stimulus, exhibiting a group delay similar to that of SFOAEs [9]. However, a second spectral band below 1.5 kHz, clearly separated from the low-frequency cut-off frequency of the stimulus spectrum, corresponded to an amplitude modulation of the waveform of the TEOAE. The group delay of this low-frequency band was similar to that of the main band near the probe frequency. The average level and group delay of the main band declined monotonically when revealed as the suppressor frequency was raised above the probe. The low-frequency band was more sensitive than the main band to shifts in compound action potential thresholds near the probe frequency induced by acute exposure to intense tones. Taken together, the experiments indicate that both the main and low-frequency bands of the TEOAE are generated primarily near the cochlear region maximally stimulated by the probe, but that significant contributions arise over a large region even more basal.

  14. 3D resolution gray-tone lithography

    NASA Astrophysics Data System (ADS)

    Dumbravescu, Niculae

    2000-04-01

    With the conventional micro machining technologies: isotropic and anisotropic, dry and wet etching, a few shapes can be done. To overcome this limitation, both binary multi- tasking technique or direct EB writing were used, but an inexpensive one-step UV-lithographic method, using a so- called 'gray-tone reticle', seems to be the best choice to produce local intensity modulation during exposure process. Although, by using this method and common technologies in standard IC fabrication it is easy to obtain an arbitrarily 3D shaping of positive thick resists, there are some limitations, too. The maximum number of gray-levels, on projection reticle, achieved by e-beam writing, are only 200. Also, for very thick resists, the limited focus depth of the projection objective gives a poor lateral resolution. These are the reasons why the author prose da new approach to enhance the 3D resolution of gray-tone lithography applied for thick resist. By a high resolution, both for vertical direction, as well as for horizontal direction. Particular emphasis was put on the design, manufacturing and use of halftone transmission masks, required for UV- lithographic step in the fabrication process of mechanical, optical or electronics components. The original design and fabrication method for the gray-tone test reticle were supported by experiments showing the main advantage of this new technology: the 3D structuring of thick resist in a single exposure step and also a very promising aspect ratio obtained of over 9:1. Preliminary experimental results are presented for positive thick resists in SEM micrographs. A future optimization of the lithographic process opens interesting perspectives for application of this high 3D resolution structuring method in the fabrication process of different products, with imposed complex smooth profiles, such as: x-ray LiGA-masks, refractive optics and surface- relief DOEs.

  15. Error performance of binary NCFSK in the presence of multiple tone interference and system noise

    NASA Astrophysics Data System (ADS)

    Bird, J. S.

    1985-03-01

    This paper presents a general solution to the problem of calculating the error performance of binary NCFSK systems in the presence of multiple tone interference and system noise. The development uses the concepts of circularly symmetric signals and expresses the results in terms of a Bessel integral. This integral is then evaluated using a rapidly converging Fourier-Bessel series. The error in this approximation to the integral is controlled by two parameters which may be adjusted so that the desired accuracy is attained. It is determined that, in the useful probability-of-error range and when the total tone power is constrained, the error rate increases for an increase in the number of interfering tones. In addition, for equal amplitude tones, the performance is independent of the distribution of the tones within the channel. The technique used is also applicable to other detection problems where the threshold is a random variable.

  16. Syzygies probing scattering amplitudes

    NASA Astrophysics Data System (ADS)

    Chen, Gang; Liu, Junyu; Xie, Ruofei; Zhang, Hao; Zhou, Yehao

    2016-09-01

    We propose a new efficient algorithm to obtain the locally minimal generating set of the syzygies for an ideal, i.e. a generating set whose proper subsets cannot be generating sets. Syzygy is a concept widely used in the current study of scattering amplitudes. This new algorithm can deal with more syzygies effectively because a new generation of syzygies is obtained in each step and the irreducibility of this generation is also verified in the process. This efficient algorithm can also be applied in getting the syzygies for the modules. We also show a typical example to illustrate the potential application of this method in scattering amplitudes, especially the Integral-By-Part(IBP) relations of the characteristic two-loop diagrams in the Yang-Mills theory.

  17. Exposures from headset interference tones

    NASA Astrophysics Data System (ADS)

    May, Noal D.

    1992-01-01

    This study evaluated the acoustic characteristics of interference tones as experienced by FAA Air Traffic Control Specialists (ATCS's) and pilots who wear headsets with insert type ear pieces. The sound pressure levels (SPL's) of generated tones were measured through the headset at five randomly selected ATCS positions in each of seven Air Route Traffic Control Centers (ARTCC's). The SPL's were compared within and between four frequencies (.5, 1, 2, and 3 KHz) over ten discrete signal power levels. The comparisons demonstrated that SPL's of tones could not be predicted for ARTCC's or for positions within an ARTCC, and that the durations of exposure were brief, i.e., limited to the time needed to remove the headset earpiece from the ear canal. Potential amounts of temporary threshold shifts (TTS's) also were evaluated in a laboratory by checking hearing levels following exposures to tones played with ATCS/pilot communication through the same headset. Audiometric checks of 20 volunteer subjects indicated TTS could be detected following 1 KHz/114 dB/60 and 145 seconds, 2 KHz/108 dB/60 and 145 seconds, and 3 KHz/99 dB/145 seconds exposures, when hearing checks were made within the first 15 minutes. Such extended durations are highly unlikely for pilots and ATCS's and no TTS was detectable following exposures to shorter durations or to other frequencies with equivalent durations.

  18. A Tone-Aided/Dual Vestigial Sideband (TA/DVSB) system for mobile satellite channels

    NASA Technical Reports Server (NTRS)

    Saulnier, Gary J.; Millar, Gilbert M.; Depaolo, Anthony D.

    1990-01-01

    Tone-aided modulation is one way of combatting the effects of multipath fading and Doppler frequency shifts. A new tone-aided modulation format for M-ary phase-shift keyed signals (MPSK) is discussed. A spectral null for the placement of the tone is created in the center of the MPSK signal by translating the upper sideband upwards in frequency by the same amount. The key element of the system is the algorithm for recombining the data sidebands in the receiver, a function that is performed by a specialized phase-locked loop (PLL). The system structure is discussed and simulation results showing the PLL acquisition performance are presented.

  19. Tone signal generator for producing multioperator tone signals using an operator circuit including a waveform generator, a selector and an enveloper

    DOEpatents

    Dong, Qiujie; Jenkins, Michael V.; Bernadas, Salvador R.

    1997-01-01

    A frequency modulation (FM) tone signal generator for generating a FM tone signal is disclosed. The tone signal generator includes a waveform generator having a plurality of wave tables, a selector and an enveloper. The waveform generator furnishes a waveform signal in response to a phase angle address signal. Each wave table stores a different waveform. The selector selects one of the wave tables in response to a plurality of selection signals such that the selected wave table largely provides the waveform signal upon being addressed largely by the phase angle address signal. Selection of the selected wave table varies with each selection signal. The enveloper impresses an envelope signal on the waveform signal. The envelope signal is used as a carrier or modulator for generating the FM tone signal.

  20. Tone signal generator for producing multioperator tone signals using an operator circuit including a waveform generator, a selector and an enveloper

    DOEpatents

    Dong, Q.; Jenkins, M.V.; Bernadas, S.R.

    1997-09-09

    A frequency modulation (FM) tone signal generator for generating a FM tone signal is disclosed. The tone signal generator includes a waveform generator having a plurality of wave tables, a selector and an enveloper. The waveform generator furnishes a waveform signal in response to a phase angle address signal. Each wave table stores a different waveform. The selector selects one of the wave tables in response to a plurality of selection signals such that the selected wave table largely provides the waveform signal upon being addressed largely by the phase angle address signal. Selection of the selected wave table varies with each selection signal. The enveloper impresses an envelope signal on the waveform signal. The envelope signal is used as a carrier or modulator for generating the FM tone signal. 17 figs.

  1. Melodic Pitch Perception and Lexical Tone Perception in Mandarin-Speaking Cochlear Implant Users

    PubMed Central

    Tao, Duoduo; Deng, Rui; Jiang, Ye; Galvin, John J.; Fu, Qian-Jie; Chen, Bing

    2014-01-01

    Objectives To examine the relationship between lexical tone perception and melodic pitch perception in Mandarin-speaking cochlear implant (CI) users, and to investigate the influence of previous acoustic hearing on CI users’ speech and music perception. Design Lexical tone perception and melodic contour identification (MCI) were measured in 21 prelingual and 11 postlingual young (age: 6–26 years old) Mandarin-speaking CI users. Lexical tone recognition was measured for four tonal patterns: Tone 1 (flat F0), Tone 2 (rising F0), Tone 3 (falling-rising F0), and Tone 4 (falling F0). MCI was measured using 9 five-note melodic patterns that contained changes in pitch contour, as well as different semitone spacing between notes. Results Lexical tone recognition was generally good (overall mean = 81% correct), and there was no significant difference between subject groups. MCI performance was generally poor (mean = 23% correct). MCI performance was significantly better for postlingual (mean = 32% correct) than for prelingual CI participants (18% correct). After correcting for outliers, there was no significant correlation between lexical tone recognition and MCI performance for prelingual or post-lingual CI participants. Age at deafness was significantly correlated with MCI performance only for postlingual participants. CI experience was significantly correlated with MCI performance for both prelingual and postlingual participants. Duration of deafness was significantly correlated with tone recognition only for prelingual participants. Conclusions Despite the prevalence of pitch cues in Mandarin, the present CI participants had great difficulty perceiving melodic pitch. The availability of amplitude and duration cues in lexical tones most likely compensated for the poor pitch perception observed with these CI listeners. Previous acoustic hearing experience seemed to benefit postlingual CI users’ melodic pitch perception. Longer CI experience was associated with

  2. Dialectal Variation in the Lexical Tone System.

    ERIC Educational Resources Information Center

    Remijsen, Bert

    2001-01-01

    Discusses dialectal variation in the lexical tone system of Ma'ya, an Austronesian language featuring three lexically contrastive tonemes. Representative acoustic data were collected from the Missol, Slawati, and Laganyan dialects, and on the basis of these data, an account is given of their tone systems and of how these tone systems compare to…

  3. Amplitudes of Spiral Perturbations

    NASA Astrophysics Data System (ADS)

    Grosbol, P.; Patsis, P. A.

    2014-03-01

    It has proven very difficult to estimate the amplitudes of spiral perturbations in disk galaxies from observations due to the variation of mass-to-light ratio and extinction across spiral arms. Deep, near-infrared images of grand-design spiral galaxies obtained with HAWK-I/VLT were used to analyze the azimuthal amplitude and shape of arms, which, even in the K-band may, be significantly biased by the presence of young stellar populations. Several techniques were applied to evaluate the relative importance of young stars across the arms, such as surface brightness of the disk with light from clusters subtracted, number density of clusters detected, and texture of the disk. The modulation of the texture measurement, which correlates with the number density of faint clusters, yields amplitudes of the spiral perturbation in the range 0.1-0.2. This estimate gives a better estimate of the mass perturbation in the spiral arms, since it is dominated by old clusters.

  4. Root Tone: A Holistic Approach to Tone Pedagogy of Western Classical Flute

    ERIC Educational Resources Information Center

    BastaniNezhad, Arya

    2012-01-01

    This article examines how key components of holistic tone production can help flutists form a resonant tone. This is framed in an exploration of tone pedagogy and includes a model of tone evaluation and education. This research is also applicable to other instrumentalists, especially wind players. In this case study information was collected by…

  5. Binaural modulation detection interference.

    PubMed

    Sheft, S; Yost, W A

    1997-09-01

    The ability to detect amplitude modulation (AM) of a tonal probe can be disrupted by the presence of modulated masking tones. Two experiments examined whether a disparity in the interaural parameters of the probe and masker can reduce the amount of interference. In the first experiment, the effects of interaural time and intensity differences were studied in separate sets of conditions. With low-frequency carriers, the detection of 10-Hz probe modulation in the presence of 10-Hz masker modulation was not significantly affected by interaural time differences. With higher-frequency carriers, dichotic stimuli were generated through combinations of diotic, dichotic, or monotic probe and masker presentations in which the probe and masker did not share a common interaural intensity difference. In these conditions, the amount of interference was affected by the interaural configuration. However, monotic level differences between the probe and masker may have contributed to the effect of interaural configuration. In the second experiment, the probe and masker were presented through separate speakers in an enclosed listening environment. Spatial separation between the sources for the probe and masker led to a small reduction in the amount of interference. When the masker modulation rate was varied with the probe AM rate fixed at 10 Hz, the extent of tuning in the modulation domain in the sound-field conditions was similar to that obtained with diotic stimulus presentation over headphones.

  6. The molecular basis of the genesis of basal tone in internal anal sphincter.

    PubMed

    Zhang, Cheng-Hai; Wang, Pei; Liu, Dong-Hai; Chen, Cai-Ping; Zhao, Wei; Chen, Xin; Chen, Chen; He, Wei-Qi; Qiao, Yan-Ning; Tao, Tao; Sun, Jie; Peng, Ya-Jing; Lu, Ping; Zheng, Kaizhi; Craige, Siobhan M; Lifshitz, Lawrence M; Keaney, John F; Fogarty, Kevin E; ZhuGe, Ronghua; Zhu, Min-Sheng

    2016-04-22

    Smooth muscle sphincters exhibit basal tone and control passage of contents through organs such as the gastrointestinal tract; loss of this tone leads to disorders such as faecal incontinence. However, the molecular mechanisms underlying this tone remain unknown. Here, we show that deletion of myosin light-chain kinases (MLCK) in the smooth muscle cells from internal anal sphincter (IAS-SMCs) abolishes basal tone, impairing defecation. Pharmacological regulation of ryanodine receptors (RyRs), L-type voltage-dependent Ca(2+) channels (VDCCs) or TMEM16A Ca(2+)-activated Cl(-) channels significantly changes global cytosolic Ca(2+) concentration ([Ca(2+)]i) and the tone. TMEM16A deletion in IAS-SMCs abolishes the effects of modulators for TMEM16A or VDCCs on a RyR-mediated rise in global [Ca(2+)]i and impairs the tone and defecation. Hence, MLCK activation in IAS-SMCs caused by a global rise in [Ca(2+)]i via a RyR-TMEM16A-VDCC signalling module sets the basal tone. Targeting this module may lead to new treatments for diseases like faecal incontinence.

  7. The molecular basis of the genesis of basal tone in internal anal sphincter

    PubMed Central

    Zhang, Cheng-Hai; Wang, Pei; Liu, Dong-Hai; Chen, Cai-Ping; Zhao, Wei; Chen, Xin; Chen, Chen; He, Wei-Qi; Qiao, Yan-Ning; Tao, Tao; Sun, Jie; Peng, Ya-Jing; Lu, Ping; Zheng, Kaizhi; Craige, Siobhan M.; Lifshitz, Lawrence M.; Keaney Jr, John F.; Fogarty, Kevin E.; ZhuGe, Ronghua; Zhu, Min-Sheng

    2016-01-01

    Smooth muscle sphincters exhibit basal tone and control passage of contents through organs such as the gastrointestinal tract; loss of this tone leads to disorders such as faecal incontinence. However, the molecular mechanisms underlying this tone remain unknown. Here, we show that deletion of myosin light-chain kinases (MLCK) in the smooth muscle cells from internal anal sphincter (IAS-SMCs) abolishes basal tone, impairing defecation. Pharmacological regulation of ryanodine receptors (RyRs), L-type voltage-dependent Ca2+ channels (VDCCs) or TMEM16A Ca2+-activated Cl− channels significantly changes global cytosolic Ca2+ concentration ([Ca2+]i) and the tone. TMEM16A deletion in IAS-SMCs abolishes the effects of modulators for TMEM16A or VDCCs on a RyR-mediated rise in global [Ca2+]i and impairs the tone and defecation. Hence, MLCK activation in IAS-SMCs caused by a global rise in [Ca2+]i via a RyR-TMEM16A-VDCC signalling module sets the basal tone. Targeting this module may lead to new treatments for diseases like faecal incontinence. PMID:27101932

  8. Spatial hearing in Cope’s gray treefrog: II. Frequency-dependent directionality in the amplitude and phase of tympanum vibrations

    PubMed Central

    Lee, Norman; Schrode, Katrina M.; Johns, Anastasia R.; Christensen-Dalsgaard, Jakob; Bee, Mark A.

    2014-01-01

    Anuran ears function as pressure difference receivers, and the amplitude and phase of tympanum vibrations are inherently directional, varying with sound incident angle. We quantified the nature of this directionality for Cope’s gray treefrog, Hyla chrysoscelis. We presented subjects with pure tones, advertisement calls, and frequency-modulated sweeps to examine the influence of frequency, signal level, lung inflation, and sex on ear directionality. Interaural differences in the amplitude of tympanum vibrations were 1–4 dB greater than sound pressure differences adjacent to the two tympana, while interaural differences in the phase of tympanum vibration were similar to or smaller than those in sound phase. Directionality in the amplitude and phase of tympanum vibration were highly dependent on sound frequency, and directionality in amplitude varied slightly with signal level. Directionality in the amplitude and phase of tone- and call-evoked responses did not differ between sexes. Lung inflation strongly affected tympanum directionality over a narrow frequency range that, in females, included call frequencies. This study provides a foundation for further work on the biomechanics and neural mechanisms of spatial hearing in H. chrysoscelis, and lends valuable perspective to behavioral studies on the use of spatial information by this species and other frogs. PMID:24504183

  9. Impact of Altered Cholinergic Tones on the Neurovascular Coupling Response to Whisker Stimulation.

    PubMed

    Lecrux, Clotilde; Sandoe, Claire H; Neupane, Sujaya; Kropf, Pascal; Toussay, Xavier; Tong, Xin-Kang; Lacalle-Aurioles, María; Shmuel, Amir; Hamel, Edith

    2017-02-08

    Brain imaging techniques that use vascular signals to map changes in neuronal activity rely on the coupling between electrophysiology and hemodynamics, a phenomenon referred to as "neurovascular coupling" (NVC). It is unknown whether this relationship remains reliable under altered brain states associated with acetylcholine (ACh) levels, such as attention and arousal and in pathological conditions such as Alzheimer's disease. We therefore assessed the effects of varying ACh tone on whisker-evoked NVC responses in rat barrel cortex, measured by cerebral blood flow (CBF) and neurophysiological recordings (local field potentials, LFPs). We found that acutely enhanced ACh tone significantly potentiated whisker-evoked CBF responses through muscarinic ACh receptors and concurrently facilitated neuronal responses, as illustrated by increases in the amplitude and power in high frequencies of the evoked LFPs. However, the cellular identity of the activated neuronal network within the responsive barrel was unchanged, as characterized by c-Fos upregulation in pyramidal cells and GABA interneurons coexpressing vasoactive intestinal polypeptide. In contrast, chronic ACh deprivation hindered whisker-evoked CBF responses and the amplitude and power in most frequency bands of the evoked LFPs and reduced the rostrocaudal extent and area of the activated barrel without altering its identity. Correlations between LFP power and CBF, used to estimate NVC, were enhanced under high ACh tone and disturbed significantly by ACh depletion. We conclude that ACh is not only a facilitator but also a prerequisite for the full expression of sensory-evoked NVC responses, indicating that ACh may alter the fidelity of hemodynamic signals in assessing changes in evoked neuronal activity.SIGNIFICANCE STATEMENT Neurovascular coupling, defined as the tight relationship between activated neurons and hemodynamic responses, is a fundamental brain function that underlies hemodynamic-based functional brain

  10. Modulation of VLF signal amplitudes from 5 different transmitters during a C9.3-class solar flare as observed from a single receiving station in India: modeling with an ion chemistry model and LWPC

    NASA Astrophysics Data System (ADS)

    Palit, Sourav; Chakrabarti, Sandip Kumar; Pal, Sujay; Das, Bakul; Ray, Suman

    2016-07-01

    Very Low Frequency (VLF) signal at any location on Earth's surface is strongly dependent on the interference of various modes. The modulation effects on VLF signal due to any terrestrial or extra-terrestrial events vary widely from one propagation path to another depending on the interference patterns along these paths. The task of predicting or reproducing the modulation in the values of signal amplitudes or phase between any two transmitting and receiving stations is challenging. In this work we present results of modeling of the VLF signal amplitudes from five different transmitters as observed at a single receiving station in India during a C9.3 class solar flare. In this model we simulate the ionization rates at lower ionospheric heights from actual flare spectra with the GEANT4 Monte Carlo simulation code and find the equilibrium ion densities with a D-region ion-chemistry model. We find the signal amplitude variation along different propagation paths with the LWPC code. Such efforts are essential for an appropriate understanding of the VLF propagation in Earth's ionosphere waveguide and to achieve desired accuracy while using Earth's ionosphere as an efficient detector of such extra-terrestrial ionization events.

  11. Phase-amplitude cross-frequency coupling in EEG-derived cortical time series upon an auditory perception task.

    PubMed

    Papadaniil, Chrysa D; Kosmidou, Vasiliki E; Tsolaki, Anthoula; Tsolaki, Magda; Kompatsiaris, Ioannis Yiannis; Hadjileontiadis, Leontios J

    2015-01-01

    Recent evidence suggests that cross-frequency coupling (CFC) plays an essential role in multi-scale communication across the brain. The amplitude of the high frequency oscillations, responsible for local activity, is modulated by the phase of the lower frequency activity, in a task and region-relevant way. In this paper, we examine this phase-amplitude coupling in a two-tone oddball paradigm for the low frequency bands (delta, theta, alpha, and beta) and determine the most prominent CFCs. Data consisted of cortical time series, extracted by applying three-dimensional vector field tomography (3D-VFT) to high density (256 channels) electroencephalography (HD-EEG), and CFC analysis was based on the phase-amplitude coupling metric, namely PAC. Our findings suggest CFC spanning across all brain regions and low frequencies. Stronger coupling was observed in the delta band, that is closely linked to sensory processing. However, theta coupling was reinforced in the target tone response, revealing a task-dependent CFC and its role in brain networks communication.

  12. Multiple pure tone noise prediction

    NASA Astrophysics Data System (ADS)

    Han, Fei; Sharma, Anupam; Paliath, Umesh; Shieh, Chingwei

    2014-12-01

    This paper presents a fully numerical method for predicting multiple pure tones, also known as “Buzzsaw” noise. It consists of three steps that account for noise source generation, nonlinear acoustic propagation with hard as well as lined walls inside the nacelle, and linear acoustic propagation outside the engine. Noise generation is modeled by steady, part-annulus computational fluid dynamics (CFD) simulations. A linear superposition algorithm is used to construct full-annulus shock/pressure pattern just upstream of the fan from part-annulus CFD results. Nonlinear wave propagation is carried out inside the duct using a pseudo-two-dimensional solution of Burgers' equation. Scattering from nacelle lip as well as radiation to farfield is performed using the commercial solver ACTRAN/TM. The proposed prediction process is verified by comparing against full-annulus CFD simulations as well as against static engine test data for a typical high bypass ratio aircraft engine with hardwall as well as lined inlets. Comparisons are drawn against nacelle unsteady pressure transducer measurements at two axial locations as well as against near- and far-field microphone array measurements outside the duct. This is the first fully numerical approach (no experimental or empirical input is required) to predict multiple pure tone noise generation, in-duct propagation and far-field radiation. It uses measured blade coordinates to calculate MPT noise.

  13. Schematic-based 4/16/64 order quadrature amplitude modulation mapper-demapper implementation for 256 subchannel orthogonal frequency division multiplexing model on FPGA Xilinx SPARTAN 3E

    NASA Astrophysics Data System (ADS)

    Imaduddin, .; Setiyanto, Budi; Litasari, .

    2010-05-01

    Orthogonal Frequency Division Multiplexing (OFDM) is a modulation technique which provides higher bit rate and efficient bandwidth. This paper presents an implementation of a 4/16/64 Order Quadrature Amplitude Modulation (QAM) Mapper-Demapper for 256 Sub channel OFDM Model on Xilinx SPARTAN 3E Field-Programmable Gate Array (FPGA) series, using schematic approach. This QAMOFDM model is reconfigurable in term of its QAM order. The result shows that under the clock frequency around 262 MHz, the implementation works well, high precision is achieved at its serial output. A precision process conducted at 20 ns internal clock input period, with the 25 Mbps input bit rate requires 81.94 μs QAM processing-time. The implementation consumes about 80 % of the total FPGA slices (3736 slices).

  14. Dead regions and noisiness of pure tones.

    PubMed

    Huss, Martina; Moore, Brian C J

    2005-10-01

    Some hearing-impaired subjects report pure tones as sounding highly distorted and noise-like. We assessed whether such reports indicate that the tone frequency falls inside a dead region (DR). Nine hearing-impaired and four normally hearing subjects rated pure tones on a scale from 1 to 7, where 1 indicates clear tone and 7 indicates noise. A white noise was presented as a reference for a sound that should be rated as 7. Stimuli covered the whole audible range of frequencies and levels. The noisiness ratings were, on average, higher for hearing-impaired subjects than for normally hearing subjects. For the former, the ratings were not markedly different for tones with frequencies just outside or inside a DR. However, ratings always exceeded 3 for tones falling more than 1.5 octaves inside a DR. The results indicate that judgement of a tone as sounding noise-like does not reliably indicate that the tone frequency falls in a DR. Both normally hearing and hearing-impaired subjects rated 0.125 kHz and 12 kHz tones as somewhat noise-like, independently of the existence of a DR.

  15. Reflex Augmentation of a Tap-Elicited Eyeblink: The Effects of Tone Frequency and Tap Intensity.

    ERIC Educational Resources Information Center

    Cohen, Michelle E.; And Others

    1986-01-01

    Describes two experiments that examined whether the amplitude of the human eyeblink by a mild tap between the eyebrows can be increased if a brief tone is presented simultaneously with the tap and how these effects change from newborn infants to adults. (HOD)

  16. Tone Noise and Nearfield Pressure Produced by Jet-Cavity Interaction

    NASA Technical Reports Server (NTRS)

    Raman, Ganesh; Envia, Edmane; Bencic, Timothy J.

    1998-01-01

    Cavity flow resonance can cause numerous problems in aerospace applications. While our long-term goal is to understand cavity flows well enough to devise effective cavity resonance suppression techniques, this paper describes a fundamental study of resonant tones produced by jet-cavity interaction at subsonic and supersonic speeds. Our specific jet-cavity configuration can also be used as a test bed for evaluating active and passive flow resonance control concepts. Two significant findings emerge from this study. 1) Originally, we expected that tones produced by jet-cavity interaction would resemble cavity tones or jet tones or would involve some simple combinations of each. The experimental data do not support these expectations: instead, the jet cavity interaction produce a unique set of tones. We propose simple yet and physically insightful correlations for these tones. Although the pressure patterns on the cavity floor display very complex variations with the Mach number for a length/depth = 8 cavity, the tones correspond to the acoustic modes of the cavity-independent of flow. For a length/ depth = 3 cavity, however, a surprise emerges: the pressure patterns on the cavity floor are not so complex but the tones depend significantly on the flow. Additionally, we examine the role of external feedback unique to jet-cavity interaction. 2) Previous research led us to expect that traditional classifications (open, transitional, or closed) for cavities in an infinite flight stream would be insensitive to small changes in Mach number and would depend primarily on cavity length/depth ratios. Use of the novel high resolution photoluminescent pressure sensitive paint shows that the classifications are actually quite sensitive to jet Mach number for a length/depth = 8 cavity. However, these classifications provide no guidance whatsoever for tone amplitude or frequency. Detailed experimental data and insights presented here will assist researchers who are performing

  17. Airway smooth muscle cell tone amplifies contractile function in the presence of chronic cyclic strain.

    PubMed

    Fairbank, Nigel J; Connolly, Sarah C; Mackinnon, James D; Wehry, Kathrin; Deng, Linhong; Maksym, Geoffrey N

    2008-09-01

    Chronic contractile activation, or tone, in asthma coupled with continuous stretching due to breathing may be involved in altering the contractile function of airway smooth muscle (ASM). Previously, we (11) showed that cytoskeletal remodeling and stiffening responses to acute (2 h) localized stresses were modulated by the level of contractile activation of ASM. Here, we investigated if altered contractility in response to chronic mechanical strain was dependent on repeated modulation of contractile tone. Cultured human ASM cells received 5% cyclic (0.3 Hz), predominantly uniaxial strain for 5 days, with once-daily dosing of either sham, forskolin, carbachol, or histamine to alter tone. Stiffness, contractility (KCl), and "relaxability" (forskolin) were then measured as was cell alignment, myosin light-chain phosphorylation (pMLC), and myosin light-chain kinase (MLCK) content. Cells became aligned and baseline stiffness increased with strain, but repeated lowering of tone inhibited both effects (P < 0.05). Strain also reversed a negative tone-modulation dependence of MLCK, observed in static conditions in agreement with previous reports, with strain and tone together increasing both MLCK and pMLC. Furthermore, contractility increased 176% (SE 59) with repeated tone elevation. These findings indicate that with strain, and not without, repeated tone elevation promoted contractile function through changes in cytoskeletal organization and increased contractile protein. The ability of repeated contractile activation to increase contractility, but only with mechanical stretching, suggests a novel mechanism for increased ASM contractility in asthma and for the role of continuous bronchodilator and corticosteroid therapy in reversing airway hyperresponsiveness.

  18. Clause Structure and Tone in Sandawe.

    ERIC Educational Resources Information Center

    Elderkin, Edward D.

    1991-01-01

    In a tone language, tonal distinctions between words in sequence can often be analyzed using the same devices that are applied within the word (e.g., downdrift or downstep). However, it is proposed here that Sandawe is a tone language in which the tonal relationships between constituents in clause structure, and between constituents in phrase…

  19. Recovering Asynchronous Watermark Tones from Speech

    DTIC Science & Technology

    2009-04-01

    Audio steganography for covert data transmission by impercep- tible tone insertion,” Proceedings Communications Sys- tems and Applications, IEEE, vol. 4, pp. 1647–1653, 2004. 1408 ...by a comfortable margin. Index Terms— Speech Watermarking, Hidden Tones, Speech Steganography , Speech Data Hiding 1. BACKGROUND Imperceptibly

  20. The Phonology and Phonetics of Tone Perception

    ERIC Educational Resources Information Center

    Ramadoss, Deepti

    2012-01-01

    This dissertation studies the perception of tones in Thai, and aims to contribute to a formal characterization of speech perception more generally. Earlier work had argued that perception of tones involves retrieval of some abstract "autosegmental" representation provided by the phonology, while another line of work had argued for the…

  1. Effects of Lexical Tone Contour on Mandarin Sentence Intelligibility

    ERIC Educational Resources Information Center

    Chen, Fei; Wong, Lena L. N.; Hu, Yi

    2014-01-01

    Purpose: This study examined the effects of lexical tone contour on the intelligibility of Mandarin sentences in quiet and in noise. Method: A text-to-speech synthesis engine was used to synthesize Mandarin sentences with each word carrying the original lexical tone, flat tone, or a tone randomly selected from the 4 Mandarin lexical tones. The…

  2. Optimizing swept-tone protocols for recording distortion-product otoacoustic emissions in adults and newborns.

    PubMed

    Abdala, Carolina; Luo, Ping; Shera, Christopher A

    2015-12-01

    Distortion-product otoacoustic emissions (DPOAEs), which are routinely used in the audiology clinic and research laboratory, are conventionally recorded with discrete tones presented sequentially across frequency. However, a more efficient technique sweeps tones smoothly across frequency and applies a least-squares-fitting (LSF) procedure to compute estimates of otoacoustic emission phase and amplitude. In this study, the optimal parameters (i.e., sweep rate and duration of the LSF analysis window) required to record and analyze swept-tone DPOAEs were tested and defined in 15 adults and 10 newborns. Results indicate that optimal recording of swept-tone DPOAEs requires use of an appropriate analysis bandwidth, defined as the range of frequencies included in each least squares fit model. To achieve this, the rate at which the tones are swept and the length of the LSF analysis window must be carefully considered and changed in concert. Additionally, the optimal analysis bandwidth must be adjusted to accommodate frequency-dependent latency shifts in the reflection-component of the DPOAE. Parametric guidelines established here are equally applicable to adults and newborns. However, elevated noise during newborn swept-tone DPOAE recordings warrants protocol adaptations to improve signal-to-noise ratio and response quality.

  3. Optimizing swept-tone protocols for recording distortion-product otoacoustic emissions in adults and newborns

    PubMed Central

    Abdala, Carolina; Luo, Ping; Shera, Christopher A.

    2015-01-01

    Distortion-product otoacoustic emissions (DPOAEs), which are routinely used in the audiology clinic and research laboratory, are conventionally recorded with discrete tones presented sequentially across frequency. However, a more efficient technique sweeps tones smoothly across frequency and applies a least-squares-fitting (LSF) procedure to compute estimates of otoacoustic emission phase and amplitude. In this study, the optimal parameters (i.e., sweep rate and duration of the LSF analysis window) required to record and analyze swept-tone DPOAEs were tested and defined in 15 adults and 10 newborns. Results indicate that optimal recording of swept-tone DPOAEs requires use of an appropriate analysis bandwidth, defined as the range of frequencies included in each least squares fit model. To achieve this, the rate at which the tones are swept and the length of the LSF analysis window must be carefully considered and changed in concert. Additionally, the optimal analysis bandwidth must be adjusted to accommodate frequency-dependent latency shifts in the reflection-component of the DPOAE. Parametric guidelines established here are equally applicable to adults and newborns. However, elevated noise during newborn swept-tone DPOAE recordings warrants protocol adaptations to improve signal-to-noise ratio and response quality. PMID:26723333

  4. Musical duplex perception: perception of figurally good chords with subliminal distinguishing tones.

    PubMed

    Hall, M D; Pastore, R E

    1992-08-01

    In a variant of duplex perception with speech, phoneme perception is maintained when distinguishing components are presented below intensities required for separate detection, forming the basis for the claim that a phonetic module takes precedence over nonspeech processing. This finding is replicated with music chords (C major and minor) created by mixing a piano fifth with a sinusoidal distinguishing tone (E or E flat). Individual threshold intensities for detecting E or E flat in the context of the fixed piano tones are established. Chord discrimination thresholds defined by distinguishing tone intensity were determined. Experiment 2 verified masked detection thresholds and subliminal chord identification for experienced musicians. Accurate chord perception was maintained at distinguishing tone intensities nearly 20 dB below the threshold for separate detection. Speech and music findings are argued to demonstrate general perceptual principles.

  5. On the benefit of DMT modulation in nonlinear VLC systems.

    PubMed

    Qian, Hua; Cai, Sunzeng; Yao, Saijie; Zhou, Ting; Yang, Yang; Wang, Xudong

    2015-02-09

    In a visible light communication (VLC) system, the nonlinear characteristic of the light emitting diode (LED) in transmitter is a limiting factor of system performance. Modern modulation signals with large peak-to-power-ratio (PAPR) suffers uneven distortion. The nonlinear response directly impacts the intensity modulation and direct detection VLC system with pulse-amplitude modulation (PAM). The amplitude of the PAM signal is distorted unevenly and large signal is vulnerable to noise. Orthogonal linear transformations, such as discrete multi-tone (DMT) modulation, can spread the nonlinear effects evenly to each data symbol, thus perform better than PAM signals. In this paper, we provide theoretical analysis on the benefit of DMT modulation in nonlinear VLC system. We show that the DMT modulation is a better choice than the PAM modulation for the VLC system as the DMT modulation is more robust against nonlinearity. We also show that the post-distortion nonlinear elimination method, which is applied at the receiver, can be a reliable solution to the nonlinear VLC system. Simulation results show that the post-distortion greatly improves the system performance for the DMT modulation.

  6. Modulation of Auditory Responses to Speech vs. Nonspeech Stimuli during Speech Movement Planning

    PubMed Central

    Daliri, Ayoub; Max, Ludo

    2016-01-01

    Previously, we showed that the N100 amplitude in long latency auditory evoked potentials (LLAEPs) elicited by pure tone probe stimuli is modulated when the stimuli are delivered during speech movement planning as compared with no-speaking control conditions. Given that we probed the auditory system only with pure tones, it remained unknown whether the nature and magnitude of this pre-speech auditory modulation depends on the type of auditory stimulus. Thus, here, we asked whether the effect of speech movement planning on auditory processing varies depending on the type of auditory stimulus. In an experiment with nine adult subjects, we recorded LLAEPs that were elicited by either pure tones or speech syllables when these stimuli were presented prior to speech onset in a delayed-response speaking condition vs. a silent reading control condition. Results showed no statistically significant difference in pre-speech modulation of the N100 amplitude (early stages of auditory processing) for the speech stimuli as compared with the nonspeech stimuli. However, the amplitude of the P200 component (later stages of auditory processing) showed a statistically significant pre-speech modulation that was specific to the speech stimuli only. Hence, the overall results from this study indicate that, immediately prior to speech onset, modulation of the auditory system has a general effect on early processing stages but a speech-specific effect on later processing stages. This finding is consistent with the hypothesis that pre-speech auditory modulation may play a role in priming the auditory system for its role in monitoring auditory feedback during speech production. PMID:27242494

  7. Children's Acquisition of Tone 3 Sandhi in Mandarin

    ERIC Educational Resources Information Center

    Wang, Chiung-Yao

    2011-01-01

    The purpose of the dissertation is to examine Mandarin-speaking children's acquisition of a syntax-dependent phonological rule Tone 3 Sandhi (T3S). A Tone 3 (low dipping tone) is changed to a Tone 2 (mid rising tone) when it is followed by another Tone 3. Application of T3S in fact involves a complex process. In setting up the prosodic domains…

  8. Measuring non-radiative relaxation time of fluorophores by intensity-modulated laser induced photoacoustic effect

    NASA Astrophysics Data System (ADS)

    Soroushian, Behrouz; Yang, Xinmai

    2013-03-01

    Most biological chromophores and molecules relax primarily through non-radiative processes; therefore, mapping of relaxation time related to non-rediative process can be a potential indicator of tissue status. In order to map relative nonradiative relaxation time, modulated tone-burst light is used to generate photoacoustic signals. Then nonradiative relaxation time is indicated by the amplitude decay rate as modulation frequency increases. The results show that although blood is an optically weak absorber at 808 nm, by using this method a significant enhancement of contrast-tonoise ratio of a blood target compared to pulsed photoacoustic imaging at this wavelength is achieved.

  9. Positive tone oxide nanoparticle EUV (ONE) photoresists

    NASA Astrophysics Data System (ADS)

    Yu, Mufei; Giannelis, Emmanuel P.; Ober, Christopher K.

    2016-03-01

    Nanoparticles with a variety of organic/inorganic combinations have been investigated and the negative tone patterning was demonstrated using EUV radiation. Zirconium methacrylate (ZrMAA) nanoparticles had sensitivity with EUV exposure as high as 4.2 mJ/cm2 with a resolution up to 22 nm, and an LER of 5.6 nm. Meanwhile, the dual-tone behavior of ZrMAA photoresists using e-beam and deep UV exposures is another attractive feature of the nanoparticle photoresists, which may be further applied with EUV lithography. The current study investigates the positive tone patterning of ZrMAA and the process-dependent image reversal. Our proposed patterning mechanism is further illustrated and optimized based in a positive tone behavior study.

  10. Underwater loudness for pure tones: Duration effects

    NASA Astrophysics Data System (ADS)

    Cudahy, Edward A.; Schwaller, Derek; Fothergill, David; Wolgemuth, Keith

    2003-04-01

    The loudness of underwater pure tones was measured by loudness matching for pure tones from 100 to 16,000 Hz. The standard was a one second tone at 1000 Hz. The signal duration was varied from 20 milliseconds to 5 seconds. Subjects were instructed to match the loudness of the comparison tone at one of the test frequencies to the loudness of the standard tone. Loudness was measured at the threshold, the most comfortable loudness, and the maximum tolerable loudness. The intensity of the standard was varied randomly across the test series. The subjects were bareheaded U.S. Navy divers tested at a depth of 3 meters. All subjects had normal in-air hearing. Tones were presented to the right side of the subject from an array of underwater sound projectors. The sound pressure level was calibrated at the location of the subject's head with the subject absent. Loudness increased and threshold decreased as duration increased. The effect was greatest at the lowest and highest frequencies. The shape of the loudness contours across frequency and duration derived from these measurements are different from in-air measurements. [Research supported by ONR.

  11. Numerical simulation of the edge tone phenomenon

    NASA Technical Reports Server (NTRS)

    Dougherty, N. S.; Liu, B. L.; Ofarrell, J. M.

    1994-01-01

    Time accurate Navier-Stokes computations were performed to study a class 2 (acoustic) whistle, the edge tone, and to gain knowledge of the vortex-acoustic coupling mechanisms driving production of these tones. Results were obtained by solving the full Navier-Stokes equations for laminar compressible air flow of a two dimensional jet issuing from a slit interacting with a wedge. Cases considered were determined by varying the distance from the slit to the wedge. Flow speed was kept constant at 1,750 cm/s as was the slit thickness of 0.1 cm, corresponding to conditions in the experiments of Brown. The analytical computations revealed edge tones to be present in four harmonic stages of jet flow instability over the wedge as the jet length was varied from 0.3 to 1.6 cm. Excellent agreement was obtained in all four edge tone stage cases between the present computational results and the experimentally obtained frequencies and flow visualization results of Brown. Specific edge tone generation phenomena and further confirmation of certain theories and empirical formulas concerning these phenomena were brought to light in this analytical simulation of edge tones.

  12. Tone recognition in continuous Cantonese speech using supratone models.

    PubMed

    Qian, Yao; Lee, Tan; Soong, Frank K

    2007-05-01

    This paper studies automatic tone recognition in continuous Cantonese speech. Cantonese is a major Chinese dialect that is known for being rich in tones. Tone information serves as a useful knowledge source for automatic speech recognition of Cantonese. Cantonese tone recognition is difficult because the tones have similar shapes of pitch contours. The tones are differentiated mainly by their relative pitch heights. In natural speech, the pitch level of a tone may shift up and down and the F0 ranges of different tones overlap with each other, making them acoustically indistinguishable within the domain of a syllable. Our study shows that the relative pitch heights are largely preserved between neighboring tones. A novel method of supratone modeling is proposed for Cantonese tone recognition. Each supratone model characterizes the F0 contour of two or three tones in succession. The tone sequence of a continuous utterance is formed as an overlapped concatenation of supratone units. The most likely tone sequence is determined under phonological constraints on syllable-tone combinations. The proposed method attains an accuracy of 74.68% in speaker-independent tone recognition experiments. In particular, the confusion among the tones with similar contour shapes is greatly resolved.

  13. Computational Support for Early Elicitation and Classification of Tone

    ERIC Educational Resources Information Center

    Bird, Steven; Lee, Haejoong

    2014-01-01

    Investigating a tone language involves careful transcription of tone on words and phrases. This is challenging when the phonological categories--the tones or melodies--have not been identified. Effects such as coarticulation, sandhi, and phrase-level prosody appear as obstacles to early elicitation and classification of tone. This article presents…

  14. Lexical Encoding of L2 Tones: The Role of L1 Stress, Pitch Accent and Intonation

    ERIC Educational Resources Information Center

    Braun, Bettina; Galts, Tobias; Kabak, Baris

    2014-01-01

    Native language prosodic structure is known to modulate the processing of non-native suprasegmental information. It has been shown that native speakers of French, a language without lexical stress, have difficulties storing non-native stress contrasts. We investigated whether the ability to store lexical tone (as in Mandarin Chinese) also depends…

  15. Brain Plasticity in Speech Training in Native English Speakers Learning Mandarin Tones

    NASA Astrophysics Data System (ADS)

    Heinzen, Christina Carolyn

    The current study employed behavioral and event-related potential (ERP) measures to investigate brain plasticity associated with second-language (L2) phonetic learning based on an adaptive computer training program. The program utilized the acoustic characteristics of Infant-Directed Speech (IDS) to train monolingual American English-speaking listeners to perceive Mandarin lexical tones. Behavioral identification and discrimination tasks were conducted using naturally recorded speech, carefully controlled synthetic speech, and non-speech control stimuli. The ERP experiments were conducted with selected synthetic speech stimuli in a passive listening oddball paradigm. Identical pre- and post- tests were administered on nine adult listeners, who completed two-to-three hours of perceptual training. The perceptual training sessions used pair-wise lexical tone identification, and progressed through seven levels of difficulty for each tone pair. The levels of difficulty included progression in speaker variability from one to four speakers and progression through four levels of acoustic exaggeration of duration, pitch range, and pitch contour. Behavioral results for the natural speech stimuli revealed significant training-induced improvement in identification of Tones 1, 3, and 4. Improvements in identification of Tone 4 generalized to novel stimuli as well. Additionally, comparison between discrimination of across-category and within-category stimulus pairs taken from a synthetic continuum revealed a training-induced shift toward more native-like categorical perception of the Mandarin lexical tones. Analysis of the Mismatch Negativity (MMN) responses in the ERP data revealed increased amplitude and decreased latency for pre-attentive processing of across-category discrimination as a result of training. There were also laterality changes in the MMN responses to the non-speech control stimuli, which could reflect reallocation of brain resources in processing pitch patterns

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

    PubMed

    Taghipour, Armin; Moore, Brian C J; Edler, Bernd

    2016-05-01

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

  17. Tone calibration technique: A digital signaling scheme for mobile applications

    NASA Technical Reports Server (NTRS)

    Davarian, F.

    1986-01-01

    Residual carrier modulation is conventionally used in a communication link to assist the receiver with signal demodulation and detection. Although suppressed carrier modulation has a slight power advantage over the residual carrier approach in systems enjoying a high level of stability, it lacks sufficient robustness to be used in channels severely contaminated by noise, interference and propagation effects. In mobile links, in particular, the vehicle motion and multipath waveform propagation affect the received carrier in an adverse fashion. A residual carrier scheme that uses a pilot carrier to calibrate a mobile channel against multipath fading anomalies is described. The benefits of this scheme, known as tone calibration technique, are described. A brief study of the system performance in the presence of implementation anomalies is also given.

  18. Origin of suppression of otoacoustic emissions evoked by two-tone bursts.

    PubMed

    Jedrzejczak, W Wiktor; Smurzynski, Jacek; Blinowska, Katarzyna J

    2008-01-01

    Otoacoustic emission (OAE) data recorded for tone bursts presented separately and as a two-tone burst complex, that had been reported previously [Yoshikawa, H., Smurzynski, J., Probst R., 2000. Suppression of tone burst evoked otoacoustic emissions in relation to frequency separation. Hear. Res. 148, 95-106], were re-processed using the method of adaptive approximations by matching pursuit (MP). Two types of stimuli were applied to record tone burst OAEs (TBOAEs): (a) cosine-windowed tone bursts of 5-ms duration with center frequencies of 1, 1.5, 2 and 3kHz, (b) complex stimuli consisting of a digital addition of the 1-kHz tone burst together with either the 1.5-, 2- or 3-kHz tone burst. The MP method allowed decomposition of signals into waveforms of defined frequency, latency, time span, and amplitude. This approach provided a high time-frequency (t-f) resolution and identified patterns of resonance modes that were characteristic for TBOAEs recorded in each individual ear. Individual responses to single-tone bursts were processed off-line to form 'sum of singles' responses. The results confirmed linear superposition behavior for a frequency separation of two-tone bursts of 2kHz (the 1-kHz and 3-kHz condition). For the 1, 1.5-kHz condition, the MP results revealed the existence of closely positioned resonance modes associated with responses recorded individually with the stimuli differing in frequency by 500Hz. Then, the differences between t-f distributions calculated for dual (two-tone bursts) and sum-of-singles conditions exhibited mutual suppression of resonance modes common to both stimuli. The degree of attenuation depended on the individual pattern of characteristic resonance modes, i.e., suppression occurred when two resonant modes excited by both stimuli overlapped. It was postulated that the suppression observed in case of dual stimuli with closely-spaced components is due to mutual attenuation of the overlapping resonance modes.

  19. Studying Emergent Tone-Systems in Nepal: Pitch, Phonation and Word-Tone in Tamang

    ERIC Educational Resources Information Center

    Mazaudon, Martine

    2014-01-01

    This paper focuses on the particular kinds of difficulties which arise in the study of an emergent tone-system, exemplified by Tamang in Nepal, where pitch, phonation and other laryngeal features combine in the definition of a tone. As a consequence, conducting a well-ordered analysis in stages first of phonetic transcription, then variation in…

  20. Direct Numerical Simulation of Automobile Cavity Tones

    NASA Technical Reports Server (NTRS)

    Kurbatskii, Konstantin; Tam, Christopher K. W.

    2000-01-01

    The Navier Stokes equation is solved computationally by the Dispersion-Relation-Preserving (DRP) scheme for the flow and acoustic fields associated with a laminar boundary layer flow over an automobile door cavity. In this work, the flow Reynolds number is restricted to R(sub delta*) < 3400; the range of Reynolds number for which laminar flow may be maintained. This investigation focuses on two aspects of the problem, namely, the effect of boundary layer thickness on the cavity tone frequency and intensity and the effect of the size of the computation domain on the accuracy of the numerical simulation. It is found that the tone frequency decreases with an increase in boundary layer thickness. When the boundary layer is thicker than a certain critical value, depending on the flow speed, no tone is emitted by the cavity. Computationally, solutions of aeroacoustics problems are known to be sensitive to the size of the computation domain. Numerical experiments indicate that the use of a small domain could result in normal mode type acoustic oscillations in the entire computation domain leading to an increase in tone frequency and intensity. When the computation domain is expanded so that the boundaries are at least one wavelength away from the noise source, the computed tone frequency and intensity are found to be computation domain size independent.

  1. Enhanced visual perception through tone mapping

    NASA Astrophysics Data System (ADS)

    Harrison, Andre; Mullins, Linda L.; Raglin, Adrienne; Etienne-Cummings, Ralph

    2016-05-01

    Tone mapping operators compress high dynamic range images to improve the picture quality on a digital display when the dynamic range of the display is lower than that of the image. However, tone mapping operators have been largely designed and evaluated based on the aesthetic quality of the resulting displayed image or how perceptually similar the compressed image appears relative to the original scene. They also often require per image tuning of parameters depending on the content of the image. In military operations, however, the amount of information that can be perceived is more important than the aesthetic quality of the image and any parameter adjustment needs to be as automated as possible regardless of the content of the image. We have conducted two studies to evaluate the perceivable detail of a set of tone mapping algorithms, and we apply our findings to develop and test an automated tone mapping algorithm that demonstrates a consistent improvement in the amount of perceived detail. An automated, and thereby predictable, tone mapping method enables a consistent presentation of perceivable features, can reduce the bandwidth required to transmit the imagery, and can improve the accessibility of the data by reducing the needed expertise of the analyst(s) viewing the imagery.

  2. Phase and amplitude errors in FM radars

    NASA Astrophysics Data System (ADS)

    Griffiths, Hugh D.

    The constraints on phase and amplitude errors are determined for various types of FM radar by calculating the range sidelobe levels on the point target response due to the phase and amplitude modulation of the target echo. It is shown that under certain circumstances the constraints on phase linearity appropriate for conventional pulse compression radars are unnecessarily stringent, and quite large phase errors can be tolerated provided the relative delay of the local oscillator with respect to the target echo is small compared with the periodicity of the phase error characteristic. The constraints on amplitude flatness, however, are severe under almost all circumstances.

  3. Using a 1.2 GHz bandwidth reflective semiconductor optical amplifier with seeding light by 64-quadrature amplitude modulation orthogonal frequency division multiplexing modulation to achieve a 10-gbits/s upstream rate in long-reach passive optical network access

    NASA Astrophysics Data System (ADS)

    Yeh, Chien-Hung; Chen, Hsing-Yu; Chow, Chi-Wai; Wu, Yu-Fu

    2012-01-01

    We use a commercially available 1.2 GHz bandwidth reflective semiconductor optical amplifier (RSOA)--based optical network unit (ONU) to achieve 10-gbits/s upstream traffic for an optical orthogonal frequency division multiplexing (OFDM) long-reach passive optical network (LR-PON). This is the first time the 64--quadrature amplitude modulation (QAM) OFDM format has been applied to RSOA-ONU to achieve a 75 km fiber transmission length. In the proposed LR-PON, the upstream power penalty of 5.2 dB at the bit error rate of 3.8×10-3 is measured by using a 64-QAM OFDM modulation after the 75 km fiber transmission without dispersion compensation.

  4. Microprocessor Controlled Pulse Amplitude Modulation Decommutator.

    DTIC Science & Technology

    1980-10-28

    821760DAT 5 - LINE I NALOG PARALLEL PARALLEL AAO BCD DATA CONVERTERSTIME PORT Cn ND I CAT R SSEIGAL / - FPU FONETE tKIMIATO ,,,PNE C0 SINA .MCOPO E R FVAEO...Analog to Digital Converter Interface 10 5. BCD Time Code Generator Interface 12 6. Thumbwheel Switch Interface 13 7. Analog Output Latch/DAC 15 8...also appear on analog output No. 1. See Figure 5 for interface wiring. A low on the PB1 line selects the MSD switch and a positive true BCD code

  5. Production of extended plasma channels in atmospheric air by amplitude-modulated UV radiation of GARPUN-MTW Ti : sapphire—KrF laser. Part 2. Accumulation of plasma electrons and electric discharge control

    NASA Astrophysics Data System (ADS)

    Zvorykin, V. D.; Ionin, Andrei A.; Levchenko, A. O.; Mesyats, Gennadii A.; Seleznev, L. V.; Sinitsyn, D. V.; Smetanin, Igor V.; Sunchugasheva, E. S.; Ustinovskii, N. N.; Shutov, A. V.

    2013-04-01

    The problem of the production of extended (~1 m) plasma channels is studied in atmospheric air by amplitude-modulated laser pulses of UV radiation, which are a superposition of a subpicosecond USP train amplified in a regenerative KrF amplifier with an unstable confocal resonator and a quasi-stationary lasing pulse. The USPs possess a high (0.2-0.3 TW) peak power and efficiently ionise oxygen molecules due to multiphoton ionisation, and the quasi-stationary lasing pulse, which has a relatively long duration (~100 ns), maintains the electron density at a level ne = (3-5) × 1014 cm—3 by suppressing electron attachment to oxygen. Experiments in laser triggering of high-voltage electric discharges suggest that the use of combined pulses results in a significant lowering of the breakdown threshold and enables controlling the discharge trajectory with a higher efficiency in comparison with smooth pulses. It was shown that controlled breakdowns may develop with a delay of tens of microseconds relative to the laser pulse, which is many orders of magnitude greater than the lifetime of free electrons in the laser-induced plasma. We propose a mechanism for this breakdown, which involves speeding-up of the avalanche ionisation of the air by negative molecular oxygen ions with a low electron binding energy (~0.5 eV) and a long lifetime (~1 ms), which are produced upon cessation of the laser pulse.

  6. PC-PLC/sphingomyelin synthase activity plays a central role in the development of myogenic tone in murine resistance arteries.

    PubMed

    Mauban, Joseph R H; Zacharia, Joseph; Fairfax, Seth; Wier, Withrow Gil

    2015-06-15

    Myogenic tone is an intrinsic property of the vasculature that contributes to blood pressure control and tissue perfusion. Earlier investigations assigned a key role in myogenic tone to phospholipase C (PLC) and its products, inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG). Here, we used the PLC inhibitor, U-73122, and two other, specific inhibitors of PLC subtypes (PI-PLC and PC-PLC) to delineate the role of PLC in myogenic tone of pressurized murine mesenteric arteries. U-73122 inhibited depolarization-induced contractions (high external K(+) concentration), thus confirming reports of nonspecific actions of U-73122 and its limited utility for studies of myogenic tone. Edelfosine, a specific inhibitor of PI-PLC, did not affect depolarization-induced contractions but modulated myogenic tone. Because PI-PLC produces IP3, we investigated the effect of blocking IP3 receptor-mediated Ca(2+) release on myogenic tone. Incubation of arteries with xestospongin C did not affect tone, consistent with the virtual absence of Ca(2+) waves in arteries with myogenic tone. D-609, an inhibitor of PC-PLC and sphingomyelin synthase, strongly inhibited myogenic tone and had no effect on depolarization-induced contraction. D-609 appeared to act by lowering cytoplasmic Ca(2+) concentration to levels below those that activate contraction. Importantly, incubation of pressurized arteries with a membrane-permeable analog of DAG induced vasoconstriction. The results therefore mandate a reexamination of the signaling pathways activated by the Bayliss mechanism. Our results suggest that PI-PLC and IP3 are not required in maintaining myogenic tone, but DAG, produced by PC-PLC and/or SM synthase, is likely through multiple mechanisms to increase Ca(2+) entry and promote vasoconstriction.

  7. Monitoring a high-amplitude δ Scuti star for 152 days: discovery of 12 additional modes and modulation effects in the light curve of CoRoT 101155310

    NASA Astrophysics Data System (ADS)

    Poretti, E.; Rainer, M.; Weiss, W. W.; Bognár, Zs.; Moya, A.; Niemczura, E.; Suárez, J. C.; Auvergne, M.; Baglin, A.; Baudin, F.; Benkő, J. M.; Debosscher, J.; Garrido, R.; Mantegazza, L.; Paparó, M.

    2011-04-01

    Aims: The detection of small-amplitude nonradial modes in high-amplitude δ Sct (HADS) variables has been very elusive until at least five of them were detected in the light curve of V974 Oph obtained from ground-based observations. The combination of radial and nonradial modes has a high asteroseismic potential, thanks to the strong constraints we can put in the modelling. The continuous monitoring of ASAS 192647-0030.0 ≡ CoRoT 101155310 (P = 0.1258 d, V = 13.4) ensured from space by the CoRoT (COnvection, ROtation and planetary Transits) mission constitutes a unique opportunity to exploit such potential. Methods: The 22270 CoRoT measurements were performed in the chromatic mode. They span 152 d and cover 1208 consecutive cycles. After the correction for one jump and the long-term drift, the level of the noise turned out to be 29 μmag. The phase shifts and amplitude ratios of the coloured CoRoT data, the HARPS spectra, and the period-luminosity relation were used to determine a self-consistent physical model. In turn, it allowed us to model the oscillation spectrum, also giving feedback on the internal structure of the star. Results: In addition to the fundamental radial mode f1 = 7.949 d-1 with harmonics up to 10f1, we detected 12 independent terms. Linear combinations were also found and the light curve was solved by means of 61 frequencies (smallest amplitude 0.10 mmag). The newest result is the detection of a periodic modulation of the f1 mode (triplets at ± 0.193 d-1 centred on f1 and 2f1), discussed as a rotational effect or as an extension of the Blazhko effect to HADS stars. The physical model suggests that CoRoT 101155310 is an evolved star, with a slight subsolar metallic abundance, close to the terminal age main sequence. All the 12 additional terms are identified with mixed modes in the predicted overstable region. The CoRoT space mission was developed and is operated by the French space agency CNES, with the participation of ESA's RSSD and Science

  8. PULSE AMPLITUDE ANALYZER

    DOEpatents

    Greenblatt, M.H.

    1958-03-25

    This patent pertains to pulse amplitude analyzers for sorting and counting a serles of pulses, and specifically discloses an analyzer which ls simple in construction and presents the puise height distribution visually on an oscilloscope screen. According to the invention, the pulses are applied to the vertical deflection plates of an oscilloscope and trigger the horizontal sweep. Each pulse starts at the same point on the screen and has a maximum amplitude substantially along the same vertical line. A mask is placed over the screen except for a slot running along the line where the maximum amplitudes of the pulses appear. After the slot has been scanned by a photocell in combination with a slotted rotating disk, the photocell signal is displayed on an auxiliary oscilloscope as vertical deflection along a horizontal time base to portray the pulse amplitude distribution.

  9. Real topological string amplitudes

    NASA Astrophysics Data System (ADS)

    Narain, K. S.; Piazzalunga, N.; Tanzini, A.

    2017-03-01

    We discuss the physical superstring correlation functions in type I theory (or equivalently type II with orientifold) that compute real topological string amplitudes. We consider the correlator corresponding to holomorphic derivative of the real topological amplitude G_{χ } , at fixed worldsheet Euler characteristic χ. This corresponds in the low-energy effective action to N=2 Weyl multiplet, appropriately reduced to the orientifold invariant part, and raised to the power g' = -χ + 1. We show that the physical string correlator gives precisely the holomorphic derivative of topological amplitude. Finally, we apply this method to the standard closed oriented case as well, and prove a similar statement for the topological amplitude F_g.

  10. ERP correlates of pitch error detection in complex tone and voice auditory feedback with missing fundamental.

    PubMed

    Behroozmand, Roozbeh; Korzyukov, Oleg; Larson, Charles R

    2012-04-11

    Previous studies have shown that the pitch of a sound is perceived in the absence of its fundamental frequency (F0), suggesting that a distinct mechanism may resolve pitch based on a pattern that exists between harmonic frequencies. The present study investigated whether such a mechanism is active during voice pitch control. ERPs were recorded in response to +200 cents pitch shifts in the auditory feedback of self-vocalizations and complex tones with and without the F0. The absence of the fundamental induced no difference in ERP latencies. However, a right-hemisphere difference was found in the N1 amplitudes with larger responses to complex tones that included the fundamental compared to when it was missing. The P1 and N1 latencies were shorter in the left hemisphere, and the N1 and P2 amplitudes were larger bilaterally for pitch shifts in voice and complex tones compared with pure tones. These findings suggest hemispheric differences in neural encoding of pitch in sounds with missing fundamental. Data from the present study suggest that the right cortical auditory areas, thought to be specialized for spectral processing, may utilize different mechanisms to resolve pitch in sounds with missing fundamental. The left hemisphere seems to perform faster processing to resolve pitch based on the rate of temporal variations in complex sounds compared with pure tones. These effects indicate that the differential neural processing of pitch in the left and right hemispheres may enable the audio-vocal system to detect temporal and spectral variations in the auditory feedback for vocal pitch control.

  11. Test-Retest of Long Latency Auditory Evoked Potentials (P300) with Pure Tone and Speech Stimuli.

    PubMed

    Perez, Ana Paula; Ziliotto, Karin; Pereira, Liliane Desgualdo

    2017-04-01

    Introduction Long latency auditory evoked potentials, especially P300, have been used for clinical evaluation of mental processing. Many factors can interfere with Auditory Evoked Potential - P300 results, suggesting large intra and inter-subject variations. Objective The objective of the study was to identify the reliability of P3 components (latency and amplitude) over 4-6 weeks and the most stable auditory stimulus with the best test-retest agreement. Methods Ten normal-hearing women participated in the study. Only subjects without auditory processing problems were included. To determine the P3 components, we elicited long latency auditory evoked potential (P300) by pure tone and speech stimuli, and retested after 4-6 weeks using the same parameters. We identified P300 latency and amplitude by waveform subtraction. Results We found lower coefficient of variation values in latency than in amplitude, with less variability analysis when speech stimulus was used. There was no significant correlation in latency measures between pure tone and speech stimuli, and sessions. There was a significant intrasubject correlation between measures of latency and amplitude. Conclusion These findings show that amplitude responses are more robust for the speech stimulus when compared with its pure tone counterpart. The P300 indicated stability for latency and amplitude measures when the test-retest was applied. Reliability was higher for amplitude than for latency, with better agreement when the pure tone stimulus was used. However, further research with speech stimulus is needed to clarify how these stimuli are processed by the nervous system.

  12. Test-Retest of Long Latency Auditory Evoked Potentials (P300) with Pure Tone and Speech Stimuli

    PubMed Central

    Perez, Ana Paula; Ziliotto, Karin; Pereira, Liliane Desgualdo

    2016-01-01

    Introduction Long latency auditory evoked potentials, especially P300, have been used for clinical evaluation of mental processing. Many factors can interfere with Auditory Evoked Potential - P300 results, suggesting large intra and inter-subject variations. Objective The objective of the study was to identify the reliability of P3 components (latency and amplitude) over 4–6 weeks and the most stable auditory stimulus with the best test-retest agreement. Methods Ten normal-hearing women participated in the study. Only subjects without auditory processing problems were included. To determine the P3 components, we elicited long latency auditory evoked potential (P300) by pure tone and speech stimuli, and retested after 4–6 weeks using the same parameters. We identified P300 latency and amplitude by waveform subtraction. Results We found lower coefficient of variation values in latency than in amplitude, with less variability analysis when speech stimulus was used. There was no significant correlation in latency measures between pure tone and speech stimuli, and sessions. There was a significant intrasubject correlation between measures of latency and amplitude. Conclusion These findings show that amplitude responses are more robust for the speech stimulus when compared with its pure tone counterpart. The P300 indicated stability for latency and amplitude measures when the test-retest was applied. Reliability was higher for amplitude than for latency, with better agreement when the pure tone stimulus was used. However, further research with speech stimulus is needed to clarify how these stimuli are processed by the nervous system. PMID:28382119

  13. The Segments and Tones of Soyaltepec Mazatec

    ERIC Educational Resources Information Center

    Beal, Heather D.

    2011-01-01

    This dissertation describes the segments and tones of Soyaltepec Mazatec, an Oto-Manguean language of southern Mexico virtually undescribed in the literature with the exception of Pike (1956). The preliminary work done by Pike and subsequent analyses by Goldsmith (1990) and Pizer (1994) are reviewed giving evidence that the system is complex and…

  14. The value of visualizing tone of voice.

    PubMed

    Pullin, Graham; Cook, Andrew

    2013-10-01

    Whilst most of us have an innate feeling for tone of voice, it is an elusive quality that even phoneticians struggle to describe with sufficient subtlety. For people who cannot speak themselves this can have particularly profound repercussions. Augmentative communication often involves text-to-speech, a technology that only supports a basic choice of prosody based on punctuation. Given how inherently difficult it is to talk about more nuanced tone of voice, there is a risk that its absence from current devices goes unremarked and unchallenged. Looking ahead optimistically to more expressive communication aids, their design will need to involve more subtle interactions with tone of voice-interactions that the people using them can understand and engage with. Interaction design can play a role in making tone of voice visible, tangible, and accessible. Two projects that have already catalysed interdisciplinary debate in this area, Six Speaking Chairs and Speech Hedge, are introduced together with responses. A broader role for design is advocated, as a means to opening up speech technology research to a wider range of disciplinary perspectives, and also to the contributions and influence of people who use it in their everyday lives.

  15. Local adaptive tone mapping for video enhancement

    NASA Astrophysics Data System (ADS)

    Lachine, Vladimir; Dai, Min (.

    2015-03-01

    As new technologies like High Dynamic Range cameras, AMOLED and high resolution displays emerge on consumer electronics market, it becomes very important to deliver the best picture quality for mobile devices. Tone Mapping (TM) is a popular technique to enhance visual quality. However, the traditional implementation of Tone Mapping procedure is limited by pixel's value to value mapping, and the performance is restricted in terms of local sharpness and colorfulness. To overcome the drawbacks of traditional TM, we propose a spatial-frequency based framework in this paper. In the proposed solution, intensity component of an input video/image signal is split on low pass filtered (LPF) and high pass filtered (HPF) bands. Tone Mapping (TM) function is applied to LPF band to improve the global contrast/brightness, and HPF band is added back afterwards to keep the local contrast. The HPF band may be adjusted by a coring function to avoid noise boosting and signal overshooting. Colorfulness of an original image may be preserved or enhanced by chroma components correction by means of saturation function. Localized content adaptation is further improved by dividing an image to a set of non-overlapped regions and modifying each region individually. The suggested framework allows users to implement a wide range of tone mapping applications with perceptional local sharpness and colorfulness preserved or enhanced. Corresponding hardware circuit may be integrated in camera, video or display pipeline with minimal hardware budget

  16. Problems in the Acquisition of Grammatical Tone.

    ERIC Educational Resources Information Center

    Demuth, Katherine

    An autosegmental account of the child's acquisition of grammatical tone in Sesotho, a southern Bantu language, is presented. The following theoretical questions are addressed: (1) When and how does the child figure out that Sesotho is a tonal rather than intonational, stress, or accentual language?; (2) How does the child acquire tonal rules?; and…

  17. Collaborative Documentation and Revitalization of Cherokee Tone

    ERIC Educational Resources Information Center

    Herrick, Dylan; Berardo, Marcellino; Feeling, Durbin; Hirata-Edds, Tracy; Peter, Lizette

    2015-01-01

    Cherokee, the sole member of the southern branch of Iroquoian languages, is a severely endangered language. Unlike other members of the Iroquoian family, Cherokee has lexical tone. Community members are concerned about the potential loss of their language, and both speakers and teachers comment on the difficulty that language learners have with…

  18. Tone-excited jet: Theory and experiments

    NASA Technical Reports Server (NTRS)

    Ahuja, K. K.; Lepicovsky, J.; Tam, C. K. W.; Morris, P. J.; Burrin, R. H.

    1982-01-01

    A detailed study to understand the phenomenon of broadband jet-noise amplification produced by upstream discrete-tone sound excitation has been carried out. This has been achieved by simultaneous acquisition of the acoustic, mean velocity, turbulence intensities, and instability-wave pressure data. A 5.08 cm diameter jet has been tested for this purpose under static and also flight-simulation conditions. An open-jet wind tunnel has been used to simulate the flight effects. Limited data on heated jets have also been obtained. To improve the physical understanding of the flow modifications brought about by the upstream discrete-tone excitation, ensemble-averaged schlieren photographs of the jets have also been taken. Parallel to the experimental study, a mathematical model of the processes that lead to broadband-noise amplification by upstream tones has been developed. Excitation of large-scale turbulence by upstream tones is first calculated. A model to predict the changes in small-scale turbulence is then developed. By numerically integrating the resultant set of equations, the enhanced small-scale turbulence distribution in a jet under various excitation conditions is obtained. The resulting changes in small-scale turbulence have been attributed to broadband amplification of jet noise. Excellent agreement has been found between the theory and the experiments. It has also shown that the relative velocity effects are the same for the excited and the unexcited jets.

  19. Oesophageal tone in patients with achalasia

    PubMed Central

    Gonzalez, M; Mearin, F; Vasconez, C; Armengol, J; Malagelada, J

    1997-01-01

    Background—The diagnosis and classification of oesophageal motility disorders is currently based on assessment of the phasic contractile activity of the oesophagus. Tonic muscular contraction of the oesophageal body (oesophageal tone) has not been well characterised. 
Aim—To quantify oesophageal tonic activity in healthy subjects and in patients with achalasia. 
Patients—Oesophageal tone was measured in 14 patients with untreated achalasia and in 14 healthy subjects. In eight patients with achalasia, oesophageal tone was again measured one month after either endoscopic or surgical treatment. 
Methods—Tonic wall activity was quantified by means of a flaccid intraoesophageal bag, 5 cm long and of 120 ml maximal capacity, which was placed and maintained 5 cm above the lower oesophageal sphincter and connected to an external electronic barostat. The experimental design included measurement of oesophageal basal tone and compliance as well as the oesophageal tone response to a nitric oxide donor (0.5 ml amyl nitrite inhalation). 
Results—Oesophageal basal tone, expressed as the intrabag (intraoesophageal) volume at a minimal distending pressure (2 mm Hg), did not differ significantly between patients with achalasia and healthy controls (6.6 (2.5) ml versus 4.1 (0.8) ml, respectively). Oesophageal compliance (volume/pressure relation during intraoesophageal distension) was significantly increased in achalasia (oesophageal extension ratio: 3.2 (0.4) ml/mm Hg versus 1.9 (0.2) ml/mm Hg; p< 0.01). Amyl nitrite inhalation induced oesophageal relaxation both in patients and in controls, but the magnitude of relaxation was greater in the latter (intrabag volume increase: 15.3 (2.4) ml versus 36.2 (7.1) ml; p<0.01). 
Conclusion—In patients with achalasia, oesophageal tonic activity, and not only phasic activity, is impaired. Although oesophageal compliance is increased, residual oesophageal tone is maintained so that a significant relaxant response may occur

  20. The effects of non-elastic taping on muscle tone in stroke patients: a pilot study

    PubMed Central

    Kim, Ji Young; Chung, Jun Sub; Jang, Gwon Uk; Park, Seol; Park, Ji Won

    2015-01-01

    [Purpose] Hemiplegia occurs when posturing with a dominant flexor tone is present in the upper limbs, thus preventing increased abnormal tone. We attempted to improve the side effects of this condition using elbow re-positioning with non-elastic tape; this method is used to modulate abnormal muscle tone in chronic hemiplegic stroke patients. [Subjects and Methods] Fourteen post-stroke patients were included in this study. Non-elastic tape was applied to the elbow joint in a spiral manner. Before and after the tape was applied, the degree of spasticity (hypertonia) was measured in the elbow flexor muscles using the Modified Ashworth Scale (MAS). Global synkinesis (GS) intensity using electromyography (EMG) was measured in the biceps brachii and triceps brachii during voluntary isometric elbow contractions of the contralateral upper limbs. [Results] Application of non-elastic tape at the elbow joint significantly changed the GS intensity, but no significant changes were found when compared with the MAS. [Conclusion] This study demonstrates that non-elastic tape can be used to decrease abnormal elbow flexor tone. The findings may be used to influence the choice of intervention regarding muscle tone and spastic elbow flexion. PMID:26834377

  1. Problems in Nonlinear Acoustics: Parametric Receiving Arrays, Focused Finite Amplitude Sound, & Noncollinear Tone-Noise Interactions

    DTIC Science & Technology

    1987-07-01

    plane waves that propagate in different directions. This approach was followed by TenCate and Hamilton [33,34], who investigated both theoretically...75, 1383-1391 (1984). • i I ■ [33] J. A. TenCate and M. F. Hamilton, "Dispersive NonUnear Wave Interactions in a Rect- angular Duct," in...and J. A. TenCate , "Sum and Difference Frequency Generation due to Noncollinear Wave Interaction in a Rectangular Duct," J. Acoust. Soc. Am. 81

  2. Periodic amplitude variations in Jovian continuum radiation

    NASA Technical Reports Server (NTRS)

    Kurth, W. S.; Gurnett, D. A.; Scarf, F. L.

    1986-01-01

    An analysis of periodic variations in the amplitude of continuum radiation near 3 kHz trapped in the Jovian magnetosphere shows structure with periods near both five and ten hours. Contrary to a plausible initial idea, the continuum amplitudes are not organized by position of the observer relative to the dense plasma sheet. Instead, there seem to be preferred orientations of system III longitude with respect to the direction to the sun which account for the peaks. This implies a clock-like modulation of the continuum radiation intensity as opposed to a searchlight effect. The importance of the dipole longitude-solar wind alignment to the amplitude of the continuum radiation implies the source region of the radiation is near the magnetopause and may indirectly tie the generation of the radio waves to the clocklike modulation of energetic electron fluxes from Jupiter.

  3. Protostring scattering amplitudes

    NASA Astrophysics Data System (ADS)

    Thorn, Charles B.

    2016-11-01

    We calculate some tree-level scattering amplitudes for a generalization of the protostring, which is a novel string model implied by the simplest string bit models. These bit models produce a light-cone world sheet which supports s integer moded Grassmann fields. In the generalization we supplement this Grassmann world-sheet system with d =24 -s transverse coordinate world-sheet fields. The protostring corresponds to s =24 and the bosonic string to s =0 . The interaction vertex is a simple overlap with no operator insertions at the break/join point. Assuming that s is even we calculate the multistring scattering amplitudes by bosonizing the Grassmann fields, each pair equivalent to one compactified bosonic field, and applying Mandelstam's interacting string formalism to a system of s /2 compactified and d uncompactified bosonic world-sheet fields. We obtain all amplitudes for open strings with no oscillator excitations and for closed strings with no oscillator excitations and zero winding number. We then study in detail some simple special cases. Multistring processes with maximal helicity violation have much simpler amplitudes. We also specialize to general four-string amplitudes and discuss their high energy behavior. Most of these models are not covariant under the full Lorentz group O (d +1 ,1 ). The exceptions are the bosonic string whose Lorentz group is O (25 ,1 ) and the protostring whose Lorentz group is O (1 ,1 ). The models in between only enjoy an O (1 ,1 )×O (d ) spacetime symmetry.

  4. Production of extended plasma channels in atmospheric air by amplitude-modulated UV radiation of GARPUN-MTW Ti : sapphire-KrF laser. Part 2. Accumulation of plasma electrons and electric discharge control

    SciTech Connect

    Zvorykin, V D; Ionin, Andrei A; Levchenko, A O; Mesyats, Gennadii A; Seleznev, L V; Sinitsyn, D V; Smetanin, Igor V; Sunchugasheva, E S; Ustinovskii, N N; Shutov, A V

    2013-04-30

    The problem of the production of extended ({approx}1 m) plasma channels is studied in atmospheric air by amplitude-modulated laser pulses of UV radiation, which are a superposition of a subpicosecond USP train amplified in a regenerative KrF amplifier with an unstable confocal resonator and a quasi-stationary lasing pulse. The USPs possess a high (0.2-0.3 TW) peak power and efficiently ionise oxygen molecules due to multiphoton ionisation, and the quasi-stationary lasing pulse, which has a relatively long duration ({approx}100 ns), maintains the electron density at a level n{sub e} = (3-5) Multiplication-Sign 10{sup 14} cm{sup -3} by suppressing electron attachment to oxygen. Experiments in laser triggering of high-voltage electric discharges suggest that the use of combined pulses results in a significant lowering of the breakdown threshold and enables controlling the discharge trajectory with a higher efficiency in comparison with smooth pulses. It was shown that controlled breakdowns may develop with a delay of tens of microseconds relative to the laser pulse, which is many orders of magnitude greater than the lifetime of free electrons in the laser-induced plasma. We propose a mechanism for this breakdown, which involves speeding-up of the avalanche ionisation of the air by negative molecular oxygen ions with a low electron binding energy ({approx}0.5 eV) and a long lifetime ({approx}1 ms), which are produced upon cessation of the laser pulse. (extreme light fields and their applications)

  5. Neurobiology of hedonic tone: the relationship between treatment-resistant depression, attention-deficit hyperactivity disorder, and substance abuse

    PubMed Central

    Sternat, Tia; Katzman, Martin A

    2016-01-01

    Anhedonia, defined as the state of reduced ability to experience feelings of pleasure, is one of the hallmarks of depression. Hedonic tone is the trait underlying one’s characteristic ability to feel pleasure. Low hedonic tone represents a reduced capacity to experience pleasure, thus increasing the likelihood of experiencing anhedonia. Low hedonic tone has been associated with several psychopathologies, including major depressive disorder (MDD), substance use, and attention-deficit hyperactivity disorder (ADHD). The main neural pathway that modulates emotional affect comprises the limbic–cortical–striatal–pallidal–thalamic circuits. The activity of various components of the limbic–cortical–striatal–pallidal–thalamic pathway is correlated with hedonic tone in healthy individuals and is altered in MDD. Dysfunction of these circuits has also been implicated in the relative ineffectiveness of selective serotonin reuptake inhibitors used to treat anxiety and depression in patients with low hedonic tone. Mood disorders such as MDD, ADHD, and substance abuse share low hedonic tone as well as altered activation of brain regions involved in reward processing and monoamine signaling as their features. Given the common features of these disorders, it is not surprising that they have high levels of comorbidities. The purpose of this article is to review the neurobiology of hedonic tone as it pertains to depression, ADHD, and the potential for substance abuse. We propose that, since low hedonic tone is a shared feature of MDD, ADHD, and substance abuse, evaluation of hedonic tone may become a diagnostic feature used to predict subtypes of MDD, such as treatment-resistant depression, as well as comorbidities of these disorders. PMID:27601909

  6. English and Thai Speakers' Perception of Mandarin Tones

    ERIC Educational Resources Information Center

    Li, Ying

    2016-01-01

    Language learners' language experience is predicted to display a significant effect on their accurate perception of foreign language sounds (Flege, 1995). At the superasegmental level, there is still a debate regarding whether tone language speakers are better able to perceive foreign lexical tones than non-tone language speakers (i.e Lee et al.,…

  7. Perception and Acoustic Correlates of the Taiwanese Tone Sandhi Group

    ERIC Educational Resources Information Center

    Kuo, Chen-Hsiu

    2013-01-01

    This dissertation investigates how the Taiwanese Tone Sandhi Groups are perceived, and the acoustic/phonetics correlates of listeners' judgments. A series of perception experiments have been conducted to scrutinize the following topics--Taiwanese tone neutralization, Tone Sandhi Group (TSG) as a prosodic domain, perceived boundary strength in…

  8. Organising Western Spelling into Chinese Tone-Class Patterns.

    ERIC Educational Resources Information Center

    Jou, Bienming

    The author discusses his concept of "tonal spelling" for Chinese. This system spells out the patterns for the tone classes without marking their tone values; the same spelling formation spells out the same tone class and makes tonal orthography a "regular, striking, neat and clean-shaven script." Following a discussion of the…

  9. Analysis of the cochlear microphonic to a low-frequency tone embedded in filtered noise

    PubMed Central

    Chertoff, Mark E.; Earl, Brian R.; Diaz, Francisco J.; Sorensen, Janna L.

    2012-01-01

    The cochlear microphonic was recorded in response to a 733 Hz tone embedded in noise that was high-pass filtered at 25 different frequencies. The amplitude of the cochlear microphonic increased as the high-pass cutoff frequency of the noise increased. The amplitude growth for a 60 dB SPL tone was steeper and saturated sooner than that of an 80 dB SPL tone. The growth for both signal levels, however, was not entirely cumulative with plateaus occurring at about 4 and 7 mm from the apex. A phenomenological model of the electrical potential in the cochlea that included a hair cell probability function and spiral geometry of the cochlea could account for both the slope of the growth functions and the plateau regions. This suggests that with high-pass-filtered noise, the cochlear microphonic recorded at the round window comes from the electric field generated at the source directed towards the electrode and not down the longitudinal axis of the cochlea. PMID:23145616

  10. Amplitudes of Field Theories

    SciTech Connect

    Feng Bo

    2007-11-20

    In this talk, we will present recent progresses in perturbative calculations of scattering amplitudes at tree and one-loop levels. At tree level, we will discuss MHV-diagram method and on-shell recursion relation. At one-loop level, we will establish the framework of Unitarity cut method.

  11. Reinforcing Saccadic Amplitude Variability

    ERIC Educational Resources Information Center

    Paeye, Celine; Madelain, Laurent

    2011-01-01

    Saccadic endpoint variability is often viewed as the outcome of neural noise occurring during sensorimotor processing. However, part of this variability might result from operant learning. We tested this hypothesis by reinforcing dispersions of saccadic amplitude distributions, while maintaining constant their medians. In a first experiment we…

  12. Planar amplitude ammonia sensor

    NASA Astrophysics Data System (ADS)

    Karasinski, Pawel; Rogozinski, Roman

    2004-09-01

    The paper presents the results of investigation involving the influence of the change of launching conditions on the characteristics of amplitude ammonia sensors produced with the application of strip waveguides of different refractive profiles. Strip waveguides were produced using ion exchange technique, and the absorption sensitive films were produced using sol-gel technology.

  13. Active control of turbomachine discrete tones

    NASA Astrophysics Data System (ADS)

    Fleeter, Sanford

    This paper was directed at active control of discrete frequency noise generated by subsonic blade rows through cancellation of the blade row interaction generated propagating acoustic waves. First discrete frequency noise generated by a rotor and stator in a duct was analyzed to determine the propagating acoustic pressure waves. Then a mathematical model was developed to analyze and predict the active control of discrete frequency noise generated by subsonic blade rows through cancellation of the propagating acoustic waves, accomplished by utilizing oscillating airfoil surfaces to generate additional control propagating pressure waves. These control waves interact with the propagating acoustic waves, thereby, in principle, canceling the acoustic waves and thus, the far field discrete frequency tones. This model was then applied to a fan exit guide vane to investigate active airfoil surface techniques for control of the propagating acoustic waves, and thus the far field discrete frequency tones, generated by blade row interactions.

  14. Modulatory compartments in cortex and local regulation of cholinergic tone.

    PubMed

    Coppola, Jennifer J; Ward, Nicholas J; Jadi, Monika P; Disney, Anita A

    2016-09-01

    Neuromodulatory signaling is generally considered broad in its impact across cortex. However, variations in the characteristics of cortical circuits may introduce regionally-specific responses to diffuse modulatory signals. Features such as patterns of axonal innervation, tissue tortuosity and molecular diffusion, effectiveness of degradation pathways, subcellular receptor localization, and patterns of receptor expression can lead to local modification of modulatory inputs. We propose that modulatory compartments exist in cortex and can be defined by variation in structural features of local circuits. Further, we argue that these compartments are responsible for local regulation of neuromodulatory tone. For the cholinergic system, these modulatory compartments are regions of cortical tissue within which signaling conditions for acetylcholine are relatively uniform, but between which signaling can vary profoundly. In the visual system, evidence for the existence of compartments indicates that cholinergic modulation likely differs across the visual pathway. We argue that the existence of these compartments calls for thinking about cholinergic modulation in terms of finer-grained control of local cortical circuits than is implied by the traditional view of this system as a diffuse modulator. Further, an understanding of modulatory compartments provides an opportunity to better understand and perhaps correct signal modifications that lead to pathological states.

  15. Evaluation of a prototype 6 tone modem

    NASA Astrophysics Data System (ADS)

    Bagwell, R. C.

    1989-08-01

    A prototype 6 tone Multi-Frequency Shift Keying (MFSK) modem intended for tactical data transmissions in the HF band is evaluated. The main testing consisted of extensive trials using the Cobbett Hill HF Channel Simulator. Some limited live ratio trials between Bodo, northern Norway, and Cobbett Hill, southern England, are included. The modem performed satisfactorily during the evaluation period and returned good availability figures, both on the simulator, and during the radio trials.

  16. Drawing sounds: representing tones and chords spatially.

    PubMed

    Salgado-Montejo, Alejandro; Marmolejo-Ramos, Fernando; Alvarado, Jorge A; Arboleda, Juan Camilo; Suarez, Daniel R; Spence, Charles

    2016-12-01

    Research on the crossmodal correspondences has revealed that seemingly unrelated perceptual information can be matched across the senses in a manner that is consistent across individuals. An interesting extension of this line of research is to study how sensory information biases action. In the present study, we investigated whether different sounds (i.e. tones and piano chords) would bias participants' hand movements in a free movement task. Right-handed participants were instructed to move a computer mouse in order to represent three tones and two chords. They also had to rate each sound in terms of three visual analogue scales (slow-fast, unpleasant-pleasant, and weak-strong). The results demonstrate that tones and chords influence hand movements, with higher-(lower-)pitched sounds giving rise to a significant bias towards upper (lower) locations in space. These results are discussed in terms of the literature on forward models, embodied cognition, crossmodal correspondences, and mental imagery. Potential applications sports and rehabilitation are discussed briefly.

  17. Astrocyte regulation of cerebral vascular tone

    PubMed Central

    Iddings, Jennifer A.

    2013-01-01

    Cerebral blood flow is controlled by two crucial processes, cerebral autoregulation (CA) and neurovascular coupling (NVC) or functional hyperemia. Whereas CA ensures constant blood flow over a wide range of systemic pressures, NVC ensures rapid spatial and temporal increases in cerebral blood flow in response to neuronal activation. The focus of this review is to discuss the cellular mechanisms by which astrocytes contribute to the regulation of vascular tone in terms of their participation in NVC and, to a lesser extent, CA. We discuss evidence for the various signaling modalities by which astrocytic activation leads to vasodilation and vasoconstriction of parenchymal arterioles. Moreover, we provide a rationale for the contribution of astrocytes to pressure-induced increases in vascular tone via the vasoconstrictor 20-HETE (a downstream metabolite of arachidonic acid). Along these lines, we highlight the importance of the transient receptor potential channel of the vanilloid family (TRPV4) as a key molecular determinant in the regulation of vascular tone in cerebral arterioles. Finally, we discuss current advances in the technical tools available to study NVC mechanisms in the brain as it relates to the participation of astrocytes. PMID:23792684

  18. Sequential Grouping of Pure-Tone Percepts Evoked by the Segregation of Components from a Complex Tone

    ERIC Educational Resources Information Center

    Haywood, Nicholas R.; Roberts, Brian

    2011-01-01

    A sudden change applied to a single component can cause its segregation from an ongoing complex tone as a pure-tone-like percept. Three experiments examined whether such pure-tone-like percepts are organized into streams by extending the research of Bregman and Rudnicky (1975). Those authors found that listeners struggled to identify the…

  19. New Tone Reservation Technique for Peak to Average Power Ratio Reduction

    NASA Astrophysics Data System (ADS)

    Wilharm, Joachim; Rohling, Hermann

    2014-09-01

    In Orthogonal Frequency Division Multiplexing (OFDM) the transmit signals have a highly fluctuating, non-constant envelope which is a technical challenge for the High Power Amplifier (HPA). Without any signal processing procedures the amplitude peaks of the transmit signal will be clipped by the HPA resulting in out-ofband radiation and in bit error rate (BER) performance degradation. The classical Tone Reservation (TR) technique calculates a correction signal in an iterative way to reduce the amplitude peaks. However this step leads to a high computational complexity. Therefore, in this paper an alternative TR technique is proposed. In this case a predefined signal pattern is shifted to any peak position inside the transmit signal and reduces thereby all amplitude peaks. This new procedure is able to outperform the classical TR technique and has a much lower computational complexity.

  20. Congenital amusia in speakers of a tone language: association with lexical tone agnosia.

    PubMed

    Nan, Yun; Sun, Yanan; Peretz, Isabelle

    2010-09-01

    Congenital amusia is a neurogenetic disorder that affects the processing of musical pitch in speakers of non-tonal languages like English and French. We assessed whether this musical disorder exists among speakers of Mandarin Chinese who use pitch to alter the meaning of words. Using the Montreal Battery of Evaluation of Amusia, we tested 117 healthy young Mandarin speakers with no self-declared musical problems and 22 individuals who reported musical difficulties and scored two standard deviations below the mean obtained by the Mandarin speakers without amusia. These 22 amusic individuals showed a similar pattern of musical impairment as did amusic speakers of non-tonal languages, by exhibiting a more pronounced deficit in melody than in rhythm processing. Furthermore, nearly half the tested amusics had impairments in the discrimination and identification of Mandarin lexical tones. Six showed marked impairments, displaying what could be called lexical tone agnosia, but had normal tone production. Our results show that speakers of tone languages such as Mandarin may experience musical pitch disorder despite early exposure to speech-relevant pitch contrasts. The observed association between the musical disorder and lexical tone difficulty indicates that the pitch disorder as defining congenital amusia is not specific to music or culture but is rather general in nature.

  1. Distortion Product Otoacoustic Emissions Evoked by Tone Complexes

    PubMed Central

    Meenderink, Sebastiaan W. F.

    2010-01-01

    Distortion product otoacoustic emissions (DPOAEs) are traditionally evoked by two-tone stimuli. In this study, emission data from Mongolian gerbils are reported that were obtained with stimuli consisting of six to 10 tones. The stimuli were constructed by replacing one of the tones of a tone pair by a narrowband multitone complex. This produced rich spectra of the ear canal sound pressure in which many of the third-order DPOAEs originated from the interaction of triplets of stimulus components. A careful choice of the stimulus frequencies ensured that none of these DPOAE components coincided. Three groups of DPOAEs are reported, two of which are closely related to DPOAEs evoked by tone pairs. The third group has no two-tone equivalent and only arises when using a multitone stimulus. We analyzed the relation between multitone-evoked DPOAEs and DPOAEs evoked by tone pairs, and explored the new degrees of freedom offered by the multitone paradigm. PMID:20838846

  2. Phase and Pupil Amplitude Recovery for JWST Space-Optics Control

    NASA Technical Reports Server (NTRS)

    Dean, B. H.; Zielinski, T. P.; Smith, J. S.; Bolcar, M. R.; Aronstein, D. L.; Fienup, J. R.

    2010-01-01

    This slide presentation reviews the phase and pupil amplitude recovery for the James Webb Space Telescope (JWST) Near Infrared Camera (NIRCam). It includes views of the Integrated Science Instrument Module (ISIM), the NIRCam, examples of Phase Retrieval Data, Ghost Irradiance, Pupil Amplitude Estimation, Amplitude Retrieval, Initial Plate Scale Estimation using the Modulation Transfer Function (MTF), Pupil Amplitude Estimation vs lambda, Pupil Amplitude Estimation vs. number of Images, Pupil Amplitude Estimation vs Rotation (clocking), and Typical Phase Retrieval Results Also included is information about the phase retrieval approach, Non-Linear Optimization (NLO) Optimized Diversity Functions, and Least Square Error vs. Starting Pupil Amplitude.

  3. Weak boson production amplitude zeros; equalities of the helicity amplitudes

    NASA Astrophysics Data System (ADS)

    Mamedov, Fizuli

    2002-08-01

    We investigate the radiation amplitude zeros exhibited by many standard model amplitudes for triple weak gauge boson production processes. We show that WZγ production amplitudes have an especially rich structure in terms of zeros; these amplitudes have zeros originating from several different sources. It is also shown that the type-I current null zone is the special case of the equality of the specific helicity amplitudes.

  4. Optical measures of changes in cerebral vascular tone during voluntary breath holding and a Sternberg memory task.

    PubMed

    Tan, Chin Hong; Low, Kathy A; Schneider-Garces, Nils; Zimmerman, Benjamin; Fletcher, Mark A; Maclin, Edward L; Chiarelli, Antonio M; Gratton, Gabriele; Fabiani, Monica

    2016-07-01

    The human cerebral vasculature responds to changes in blood pressure and demands for oxygenation via cerebral autoregulation. Changes in cerebrovascular tone (vasoconstriction and vasodilation) also mediate the changes in blood flow measured by the BOLD fMRI signal. This cerebrovascular reactivity is known to vary with age. In two experiments, we demonstrate that cerebral pulse parameters measured using optical imaging can quantify changes in cerebral vascular tone, both globally and locally. In experiment 1, 51 older adults (age range=55-87) performed a voluntary breath-holding task while cerebral pulse amplitude measures were taken. We found significant pulse amplitude variations across breath-holding periods, indicating vasodilation during, and vasoconstriction after breath holding. The breath-holding index (BHI), a measure of cerebrovascular reactivity (CVR) was derived and found to correlate with age. BHI was also correlated with performance in the Modified Mini-Mental Status Examination, even after controlling for age and education. In experiment 2, the same participants performed a Sternberg task, and changes in regional pulse amplitude between high (set-size 6) and low (set-size 2) task loads were compared. Only task-related areas in the fronto-parietal network (FPN) showed significant reduction in pulse amplitude, indicating vasodilation. Non-task-related areas such as the somatosensory and auditory cortices did not show such reductions. Taken together, these experiments suggest that optical pulse parameters can index changes in brain vascular tone both globally and locally, using both physiological and cognitive load manipulations.

  5. PULSE AMPLITUDE ANALYZER

    DOEpatents

    Gray, G.W.; Jensen, A.S.

    1957-10-22

    A pulse-height analyzer system of improved design for sorting and counting a series of pulses, such as provided by a scintillation detector in nuclear radiation measurements, is described. The analyzer comprises a main transmission line, a cathode-ray tube for each section of the line with its deflection plates acting as the line capacitance; means to bias the respective cathode ray tubes so that the beam strikes a target only when a prearranged pulse amplitude is applied, with each tube progressively biased to respond to smaller amplitudes; pulse generating and counting means associated with each tube to respond when the beam is deflected; a control transmission line having the same time constant as the first line per section with pulse generating means for each tube for initiating a pulse on the second transmission line when a pulse triggers the tube of corresponding amplitude response, the former pulse acting to prevent successive tubes from responding to the pulse under test. This arrangement permits greater deflection sensitivity in the cathode ray tube and overcomes many of the disadvantages of prior art pulse-height analyzer circuits.

  6. Investigation of the Acoustics of Plucked String Tones Based on the Analysis of Their Time-Varying Spectra.

    NASA Astrophysics Data System (ADS)

    Chen, Kwok-Ping John

    This research investigates two aspects of the time-varying vibration patterns of plucked string tones of classical guitar, Chinese pipa and Chinese ch'in. First, the assumption that horizontal and vertical frequencies and decay rates may be different is used as a basis for classifying the partial amplitude envelopes into four types. It is found that the partial envelopes of the tones produced by the three instruments, using the finger tip excitation method, on a single undamped string, can be described in terms of these four types. The results show that ch'in tones contain Type III, and IV, guitar tones contain Type I, II and III, and pipa tones contain all four types with a higher percentage of Type III and IV. Second, the theories of "missing modes" (Young, 1800), (Benade, 1976) and delayed generation of these modes (Fletcher, 1984), (Hall, 1987) are re-examined experimentally. The edge of a conventional guitar pick is used to excite a single undamped string on a classical guitar at nodal position N which is L/N from the bridge. As a result, it is a consistent feature that any mode whose index n is a multiple of N is attenuated during the attack phase but subsequently rises with a more gradual attack to reach a significant peak amplitude, except for the first multiple of locations L/3 to L/7. This amplitude envelope pattern, Type V, which is only applicable when the pick-edge excitation method is used, is distinct from the other four types mentioned above.

  7. A single auditory tone alters the perception of multiple visual events.

    PubMed

    Kawachi, Yousuke; Grove, Philip M; Sakurai, Kenzo

    2014-07-22

    We aimed to show that a single auditory tone crossmodally affects multiple visual events using a multiple stream/bounce display (SBD), consisting of two disk pairs moving toward each other at equal speeds, coinciding, and then moving apart in a two-dimensional (2-D) display. The temporal offsets were manipulated between the coincidences of the disk pairs (0 to ±240 ms) by staggering motion onset between the pairs. A tone was presented at the coincidence timing of one of the disk pairs on half of the trials. Participants judged whether the disks in each of two pairs appeared to stream through or bounce off each other. Results show that a tone presented at either of the disk pairs' coincidence points promoted bouncing percepts in both disk pairs compared to no-tone trials. Perceived bouncing persisted in the disk-pair whose coincidence was offset 60 ms before and up to more than 120 ms after the audiovisual coincidence timing of the other disk-pair. The temporal window of bounce promotion was comparable to that obtained with a conventional SBD. The interaction of a single auditory event and multiple visual events was also modulated by the kind of experimental task (the stream/bounce or simultaneity judgments). These findings suggest that, using a single auditory cue, the perceptual system resolves the ambiguity of the motion of multiple disk pairs presented within the conventional temporal window of crossmodal interaction.

  8. Flow Tones in a Pipeline-Cavity System: Effect of Pipe Asymmetry

    SciTech Connect

    D. Erdem; D. rockwell; P. Oshkai; M. Pollack

    2002-05-29

    Flow tones in a pipeline-cavity system are characterized in terms of unsteady pressure within the cavity and along the pipe. The reference case corresponds to equal lengths of pipe connected to the inlet and outlet ends of the cavity. Varying degrees of asymmetry of this pipe arrangement are investigated. The asymmetry is achieved by an extension of variable length, which is added to the pipe at the cavity outlet. An extension length as small as a few percent of the acoustic wavelength of the resonant mode can yield a substantial reduction in the pressure amplitude of the flow tone. This amplitude decrease occurs in a similar fashion within both the cavity and the pipe resonator, which indicates that it is a global phenomenon. Furthermore, the decrease of pressure amplitude is closely correlated with a decrease of the Q (quality)-factor of the predominant spectral component of pressure. At a sufficiently large value of extension length, however, the overall form of the pressure spectrum recovers to the form that exists at zero length of the extension. Further insight is provided by variation of the inflow velocity at selected values of extension length. Irrespective of its value, both the magnitude and frequency of the peak pressure exhibit a sequence of resonant-like states. Moreover, the maximum attainable magnitude of the peak pressure decreases with increasing extension length.

  9. Flow Tones in a Pipeline-Cavity System: Effect of Pipe Asymmetry

    SciTech Connect

    D. Erdem; D. Rockwell; P.L. Oshkai; M. Pollack

    2001-02-28

    Flow tones in a pipeline-cavity system are characterized in terms of unsteady pressure within the cavity and along the pipe. The reference case corresponds to equal lengths of pipe connected to the inlet and outlet ends of the cavity. Varying degrees of asymmetry of this pipe arrangement are investigated. The asymmetry is achieved by an extension of variable length, which is added to the pipe at the cavity outlet. An extension length as small as a few percent of the acoustic wavelength of the resonant mode can yield a substantial reduction in the pressure amplitude of the flow tone. This amplitude decrease occurs in a similar fashion within both the cavity and the pipe resonator, which indicates that it is a global phenomenon. Furthermore, the decrease of pressure amplitude is closely correlated with a decrease of the Q (quality)-factor of the predominant spectral component of pressure. At a sufficiently large value of extension length, however, the overall form of the pressure spectrum recovers to the form that exists at zero length of the extension. Further insight is provided by variation of the inflow velocity at selected values of extension length. Irrespective of its value, both the magnitude and frequency of the peak pressure exhibit a sequence of resonant-like states. moreover, the maximum attainable magnitude of the peak pressure decreases with increasing extension length.

  10. Affective evaluation of simultaneous tone combinations in congenital amusia.

    PubMed

    Marin, Manuela M; Thompson, William Forde; Gingras, Bruno; Stewart, Lauren

    2015-11-01

    Congenital amusia is a neurodevelopmental disorder characterized by impaired pitch processing. Although pitch simultaneities are among the fundamental building blocks of Western tonal music, affective responses to simultaneities such as isolated dyads varying in consonance/dissonance or chords varying in major/minor quality have rarely been studied in amusic individuals. Thirteen amusics and thirteen matched controls enculturated to Western tonal music provided pleasantness ratings of sine-tone dyads and complex-tone dyads in piano timbre as well as perceived happiness/sadness ratings of sine-tone triads and complex-tone triads in piano timbre. Acoustical analyses of roughness and harmonicity were conducted to determine whether similar acoustic information contributed to these evaluations in amusics and controls. Amusic individuals' pleasantness ratings indicated sensitivity to consonance and dissonance for complex-tone (piano timbre) dyads and, to a lesser degree, sine-tone dyads, whereas controls showed sensitivity when listening to both tone types. Furthermore, amusic individuals showed some sensitivity to the happiness-major association in the complex-tone condition, but not in the sine-tone condition. Controls rated major chords as happier than minor chords in both tone types. Linear regression analyses revealed that affective ratings of dyads and triads by amusic individuals were predicted by roughness but not harmonicity, whereas affective ratings by controls were predicted by both roughness and harmonicity. We discuss affective sensitivity in congenital amusia in view of theories of affective responses to isolated chords in Western listeners.

  11. A fundamental residue pitch perception bias for tone language speakers

    NASA Astrophysics Data System (ADS)

    Petitti, Elizabeth

    A complex tone composed of only higher-order harmonics typically elicits a pitch percept equivalent to the tone's missing fundamental frequency (f0). When judging the direction of residue pitch change between two such tones, however, listeners may have completely opposite perceptual experiences depending on whether they are biased to perceive changes based on the overall spectrum or the missing f0 (harmonic spacing). Individual differences in residue pitch change judgments are reliable and have been associated with musical experience and functional neuroanatomy. Tone languages put greater pitch processing demands on their speakers than non-tone languages, and we investigated whether these lifelong differences in linguistic pitch processing affect listeners' bias for residue pitch. We asked native tone language speakers and native English speakers to perform a pitch judgment task for two tones with missing fundamental frequencies. Given tone pairs with ambiguous pitch changes, listeners were asked to judge the direction of pitch change, where the direction of their response indicated whether they attended to the overall spectrum (exhibiting a spectral bias) or the missing f0 (exhibiting a fundamental bias). We found that tone language speakers are significantly more likely to perceive pitch changes based on the missing f0 than English speakers. These results suggest that tone-language speakers' privileged experience with linguistic pitch fundamentally tunes their basic auditory processing.

  12. Sympathetic Tone Induced by High Acoustic Tempo Requires Fast Respiration.

    PubMed

    Watanabe, Ken; Ooishi, Yuuki; Kashino, Makio

    2015-01-01

    Many studies have revealed the influences of music, and particularly its tempo, on the autonomic nervous system (ANS) and respiration patterns. Since there is the interaction between the ANS and the respiratory system, namely sympatho-respiratory coupling, it is possible that the effect of musical tempo on the ANS is modulated by the respiratory system. Therefore, we investigated the effects of the relationship between musical tempo and respiratory rate on the ANS. Fifty-two healthy people aged 18-35 years participated in this study. Their respiratory rates were controlled by using a silent electronic metronome and they listened to simple drum sounds with a constant tempo. We varied the respiratory rate-acoustic tempo combination. The respiratory rate was controlled at 15 or 20 cycles per minute (CPM) and the acoustic tempo was 60 or 80 beats per minute (BPM) or the environment was silent. Electrocardiograms and an elastic chest band were used to measure the heart rate and respiratory rate, respectively. The mean heart rate and heart rate variability (HRV) were regarded as indices of ANS activity. We observed a significant increase in the mean heart rate and the low (0.04-0.15 Hz) to high (0.15-0.40 Hz) frequency ratio of HRV, only when the respiratory rate was controlled at 20 CPM and the acoustic tempo was 80 BPM. We suggest that the effect of acoustic tempo on the sympathetic tone is modulated by the respiratory system.

  13. Process enhancements for negative tone development (NTD)

    NASA Astrophysics Data System (ADS)

    Noya, Go; Yamamoto, Kazuma; Matsumoto, Naoki; Takemura, Yukie; Ishii, Maki; Miyamoto, Yoshihiro; Ishii, Masahiro; Nagahara, Tatsuro; Pawlowski, Georg

    2013-03-01

    The negative tone development (NTD) process has proven benefits for superior imaging performance in 193nm lithography. Shrink materials, such as AZ® RELACS® have found widespread use as a resolution enhancement technology in conventional 248nm (DUV), 193 nm dry (ArF) and 193 nm immersion (ArFi) lithography. Surfactant rinses, such as AZ® FIRM® are employed as yield enhancement materials to improve the lithographic performance by avoiding pattern collapse, eliminating defects, and improving CDU. This paper describes the development and recent achievements obtained with new shrink and rinse materials for application in NTD patterning processes.

  14. Near Field Trailing Edge Tone Noise Computation

    NASA Technical Reports Server (NTRS)

    Loh, Ching Y.

    2002-01-01

    Blunt trailing edges in a flow often generate tone noise due to wall-jet shear layer and vortex shedding. In this paper, the space-time conservation element (CE/SE) method is employed to numerically study the near-field noise of blunt trailing edges. Two typical cases, namely, flow past a circular cylinder (aeolian noise problem) and flow past a flat plate of finite thickness are considered. The computed frequencies compare well with experimental data. For the aeolian noise problem, comparisons with the results of other numerical approaches are also presented.

  15. Cochlear Fine Structure—Implications for Modulation Processing at the Level of the Cochlea

    NASA Astrophysics Data System (ADS)

    Epp, Bastian; Mauermann, Manfred; Verhey, Jesko L.

    2011-11-01

    It was proposed that fine structure effects in OAEs or threshold in quiet are a consequence of the active and nonlinear processing at the level of the cochlea. For human listeners it was shown that fine structure affects the detection of sinusoidally amplitude modulated tones (SAM) with low carrier levels [Heise et al. 2009 J Acoust Soc Am 126:2490-2500]. The present study uses a one dimensional nonlinear and active transmission line model of the cochlea to simulate modulation perception and to study the explanations for the psychoacoustical effects given in the literature. The model was already successfully applied to simulate the fine structure of the threshold in quiet including SOAE in fine structure minima. It is investigated to which extent the representation of the modulated stimulus at the level of the cochlea can be used to identify the mechanism underlying differences found in data and to which extent it can be used to account for psychophysical data near threshold.

  16. Modulation of auditory processing during speech movement planning is limited in adults who stutter

    PubMed Central

    Daliri, Ayoub; Max, Ludo

    2015-01-01

    Stuttering is associated with atypical structural and functional connectivity in sensorimotor brain areas, in particular premotor, motor, and auditory regions. It remains unknown, however, which specific mechanisms of speech planning and execution are affected by these neurological abnormalities. To investigate pre-movement sensory modulation, we recorded 12 stuttering and 12 nonstuttering adults’ auditory evoked potentials in response to probe tones presented prior to speech onset in a delayed-response speaking condition vs. no-speaking control conditions (silent reading; seeing nonlinguistic symbols). Findings indicate that, during speech movement planning, the nonstuttering group showed a statistically significant modulation of auditory processing (reduced N1 amplitude) that was not observed in the stuttering group. Thus, the obtained results provide electrophysiological evidence in support of the hypothesis that stuttering is associated with deficiencies in modulating the cortical auditory system during speech movement planning. This specific sensorimotor integration deficiency may contribute to inefficient feedback monitoring and, consequently, speech dysfluencies. PMID:25796060

  17. The acoustic analysis of tone differentiation as a means for assessing tone production in speakers of Cantonese

    NASA Astrophysics Data System (ADS)

    Barry, Johanna G.; Blamey, Peter J.

    2004-09-01

    This paper reports on a methodology for acoustically analyzing tone production in Cantonese. F0 offset versus F0 onset are plotted for a series of tokens for each of the six tones in the language. These are grouped according to tone type into a set of six ellipses. Qualitative visual observations regarding the degree of differentiation of the ellipses within the tonal space are summarized numerically using two indices, referred to here as Index 1 and Index 2. Index 1 is a ratio of the area of the speaker's tonal space and the average of the areas of the ellipses of the three target tones making up the tonal space. Index 2 is a ratio of the average distance between all six tonal ellipses and the average of the sum of the two axes for all six tone ellipses. Using this methodology, tonal differentiation is compared for three groups of speakers; normally hearing adults; normally hearing children aged from 4-6 years; and, prelinguistically deafened cochlear implant users aged from 4-11 years. A potential conundrum regarding how tone production abilities can outstrip tone perception abilities is explained using the data from the acoustic analyses. It is suggested that young children of the age range tested are still learning to normalize for pitch level differences in tone production. Acoustic analysis of the data thus supports results from tone perception studies and suggests that the methodology is suitable for use in studies investigating tone production in both clinical and research contexts.

  18. Correlation dimension of woodwind multiphonic tones.

    PubMed

    Keefe, D H; Laden, B

    1991-10-01

    A multiphonic is a regime of oscillation of woodwind musical instruments that is perceived as two or more simultaneously sounding pitches. The frequencies fl,m of the line spectral components of a measured woodwind multiphonic tone fit a biperiodic spectrum at low- to mid-playing levels. For the saxophone and clarinet multiphonics investigated, the two basis frequencies of the biperiodic spectrum are phase locked, that is, their ratio is equal to a ratio of small integers. A broadband spectrum is present in multiphonic spectra that exceeds instrumentation noise and window leakage associated with signal processing. The correlation dimension D of P. Grassberger and I. Procaccia [Physica D 9, 189-208 (1983)] is measured by embedding a single measured time series in higher-dimensional space, so as to reconstruct the phase space of the dynamical system. The time delay used in the dimensional reconstruction is chosen using information theory. For the particular multiphonics analyzed, the correlation dimension ranges from 2.5 to 2.9 for the saxophone and from 1.3 to 2.2 for the clarinet. One clarinet multiphonic shows possible additional dynamical complexity at small length scales in the embedding space, with a correlation dimension of 3.3. These results give quantitative evidence that some, but not all, multiphonic tones possess a strange attractor.

  19. Coronagraphic Amplitude and Phase Correction for Detecting Planets

    NASA Technical Reports Server (NTRS)

    Woodgate, Bruce E.; Bowers, Charles W.

    2003-01-01

    Detection of earth-like planets around other stars using coronagraphy requires the optical beam into the coronagraph to be extremely uniform in both phase and amplitude. Errors in phase can be corrected using a deformable mirror, and error in amplitude can be corrected using a spatial light modulator, both in the pupil plan,a. These corrections can be combined using a Michelson interferometer. If amplitude corrections of only a few percent range are needed, the required accuracy of 10 (circumflex) -4 can be obtained with spatial light modulators with the modest dynamic range of 8 bits.

  20. Tone based command system for reception of very weak signals

    NASA Technical Reports Server (NTRS)

    Bokulic, Robert Steven (Inventor); Jensen, James Robert (Inventor)

    2006-01-01

    This disclosure presents a communication receiver system for spacecraft that includes an open loop receiver adapted to receive a communication signal. An ultrastable oscillator (USO) and a tone detector are connected to the open loop receiver. The open loop receiver translates the communication signal to an intermediate frequency signal using a highly stable reference frequency from the USO. The tone detector extracts commands from the communication signal by evaluating the difference between tones of the communication signal.

  1. Broadband metasurface holograms: toward complete phase and amplitude engineering

    NASA Astrophysics Data System (ADS)

    Wang, Qiu; Zhang, Xueqian; Xu, Yuehong; Gu, Jianqiang; Li, Yanfeng; Tian, Zhen; Singh, Ranjan; Zhang, Shuang; Han, Jiaguang; Zhang, Weili

    2016-09-01

    As a revolutionary three-dimensional imaging technique, holography has attracted wide attention for its ability to photographically record a light field. However, traditional phase-only or amplitude-only modulation holograms have limited image quality and resolution to reappear both amplitude and phase information required of the objects. Recent advances in metasurfaces have shown tremendous opportunities for using a planar design of artificial meta-atoms to shape the wave front of light by optimal control of both its phase and amplitude. Inspired by the concept of designer metasurfaces, we demonstrate a novel amplitude-phase modulation hologram with simultaneous five-level amplitude modulation and eight-level phase modulation. Such a design approach seeks to turn the perceived disadvantages of the traditional phase or amplitude holograms, and thus enable enhanced performance in resolution, homogeneity of amplitude distribution, precision, and signal-to-noise ratio. In particular, the unique holographic approach exhibits broadband characteristics. The method introduced here delivers more degrees of freedom, and allows for encoding highly complex information into designer metasurfaces, thus having the potential to drive next-generation technological breakthroughs in holography.

  2. Broadband metasurface holograms: toward complete phase and amplitude engineering

    PubMed Central

    Wang, Qiu; Zhang, Xueqian; Xu, Yuehong; Gu, Jianqiang; Li, Yanfeng; Tian, Zhen; Singh, Ranjan; Zhang, Shuang; Han, Jiaguang; Zhang, Weili

    2016-01-01

    As a revolutionary three-dimensional imaging technique, holography has attracted wide attention for its ability to photographically record a light field. However, traditional phase-only or amplitude-only modulation holograms have limited image quality and resolution to reappear both amplitude and phase information required of the objects. Recent advances in metasurfaces have shown tremendous opportunities for using a planar design of artificial meta-atoms to shape the wave front of light by optimal control of both its phase and amplitude. Inspired by the concept of designer metasurfaces, we demonstrate a novel amplitude-phase modulation hologram with simultaneous five-level amplitude modulation and eight-level phase modulation. Such a design approach seeks to turn the perceived disadvantages of the traditional phase or amplitude holograms, and thus enable enhanced performance in resolution, homogeneity of amplitude distribution, precision, and signal-to-noise ratio. In particular, the unique holographic approach exhibits broadband characteristics. The method introduced here delivers more degrees of freedom, and allows for encoding highly complex information into designer metasurfaces, thus having the potential to drive next-generation technological breakthroughs in holography. PMID:27615519

  3. Musicians' working memory for tones, words, and pseudowords.

    PubMed

    Benassi-Werke, Mariana E; Queiroz, Marcelo; Araújo, Rúben S; Bueno, Orlando F A; Oliveira, Maria Gabriela M

    2012-01-01

    Studies investigating factors that influence tone recognition generally use recognition tests, whereas the majority of the studies on verbal material use self-generated responses in the form of serial recall tests. In the present study we intended to investigate whether tonal and verbal materials share the same cognitive mechanisms, by presenting an experimental instrument that evaluates short-term and working memories for tones, using self-generated sung responses that may be compared to verbal tests. This paradigm was designed according to the same structure of the forward and backward digit span tests, but using digits, pseudowords, and tones as stimuli. The profile of amateur singers and professional singers in these tests was compared in forward and backward digit, pseudoword, tone, and contour spans. In addition, an absolute pitch experimental group was included, in order to observe the possible use of verbal labels in tone memorization tasks. In general, we observed that musical schooling has a slight positive influence on the recall of tones, as opposed to verbal material, which is not influenced by musical schooling. Furthermore, the ability to reproduce melodic contours (up and down patterns) is generally higher than the ability to reproduce exact tone sequences. However, backward spans were lower than forward spans for all stimuli (digits, pseudowords, tones, contour). Curiously, backward spans were disproportionately lower for tones than for verbal material-that is, the requirement to recall sequences in backward rather than forward order seems to differentially affect tonal stimuli. This difference does not vary according to musical expertise.

  4. Contra-Rotating Open Rotor Tone Noise Prediction

    NASA Technical Reports Server (NTRS)

    Envia, Edmane

    2014-01-01

    Reliable prediction of contra-rotating open rotor (CROR) noise is an essential element of any strategy for the development of low-noise open rotor propulsion systems that can meet both the community noise regulations and cabin noise limits. Since CROR noise spectra exhibit a preponderance of tones, significant efforts have been directed towards predicting their tone content. To that end, there has been an ongoing effort at NASA to assess various in-house open rotor tone noise prediction tools using a benchmark CROR blade set for which significant aerodynamic and acoustic data have been acquired in wind tunnel tests. In the work presented here, the focus is on the nearfield noise of the benchmark open rotor blade set at the cruise condition. Using an analytical CROR tone noise model with input from high-fidelity aerodynamic simulations, tone noise spectra have been predicted and compared with the experimental data. Comparisons indicate that the theoretical predictions are in good agreement with the data, especially for the dominant tones and for the overall sound pressure level of tones. The results also indicate that, whereas the individual rotor tones are well predicted by the combination of the thickness and loading sources, for the interaction tones it is essential that the quadrupole source is also included in the analysis.

  5. Method of differential-phase/absolute-amplitude QAM

    DOEpatents

    Dimsdle, Jeffrey William

    2008-10-21

    A method of quadrature amplitude modulation involving encoding phase differentially and amplitude absolutely, allowing for a high data rate and spectral efficiency in data transmission and other communication applications, and allowing for amplitude scaling to facilitate data recovery; amplitude scale tracking to track-out rapid and severe scale variations and facilitate successful demodulation and data retrieval; 2.sup.N power carrier recovery; incoherent demodulation where coherent carrier recovery is not possible or practical due to signal degradation; coherent demodulation; multipath equalization to equalize frequency dependent multipath; and demodulation filtering.

  6. Method of differential-phase/absolute-amplitude QAM

    DOEpatents

    Dimsdle, Jeffrey William

    2007-07-03

    A method of quadrature amplitude modulation involving encoding phase differentially and amplitude absolutely, allowing for a high data rate and spectral efficiency in data transmission and other communication applications, and allowing for amplitude scaling to facilitate data recovery; amplitude scale tracking to track-out rapid and severe scale variations and facilitate successful demodulation and data retrieval; 2.sup.N power carrier recovery; incoherent demodulation where coherent carrier recovery is not possible or practical due to signal degradation; coherent demodulation; multipath equalization to equalize frequency dependent multipath; and demodulation filtering.

  7. Method of differential-phase/absolute-amplitude QAM

    DOEpatents

    Dimsdle, Jeffrey William

    2007-10-02

    A method of quadrature amplitude modulation involving encoding phase differentially and amplitude absolutely, allowing for a high data rate and spectral efficiency in data transmission and other communication applications, and allowing for amplitude scaling to facilitate data recovery; amplitude scale tracking to track-out rapid and severe scale variations and facilitate successful demodulation and data retrieval; 2.sup.N power carrier recovery; incoherent demodulation where coherent carrier recovery is not possible or practical due to signal degradation; coherent demodulation; multipath equalization to equalize frequency dependent multipath; and demodulation filtering.

  8. Method of differential-phase/absolute-amplitude QAM

    SciTech Connect

    Dimsdle, Jeffrey William

    2009-09-01

    A method of quadrature amplitude modulation involving encoding phase differentially and amplitude absolutely, allowing for a high data rate and spectral efficiency in data transmission and other communication applications, and allowing for amplitude scaling to facilitate data recovery; amplitude scale tracking to track-out rapid and severe scale variations and facilitate successful demodulation and data retrieval; 2.sup.N power carrier recovery; incoherent demodulation where coherent carrier recovery is not possible or practical due to signal degradation; coherent demodulation; multipath equalization to equalize frequency dependent multipath; and demodulation filtering.

  9. Method of differential-phase/absolute-amplitude QAM

    DOEpatents

    Dimsdle, Jeffrey William

    2007-07-17

    A method of quadrature amplitude modulation involving encoding phase differentially and amplitude absolutely, allowing for a high data rate and spectral efficiency in data transmission and other communication applications, and allowing for amplitude scaling to facilitate data recovery; amplitude scale tracking to track-out rapid and severe scale variations and facilitate successful demodulation and data retrieval; 2.sup.N power carrier recovery; incoherent demodulation where coherent carrier recovery is not possible or practical due to signal degradation; coherent demodulation; multipath equalization to equalize frequency dependent multipath; and demodulation filtering.

  10. Involuntary switching of attention mediates differences in event-related responses to complex tones between early and late Spanish-English bilinguals.

    PubMed

    Ortiz-Mantilla, Silvia; Choudhury, Naseem; Alvarez, Barbara; Benasich, April A

    2010-11-29

    Most research with bilinguals has used speech stimuli to demonstrate differences in auditory processing abilities. Two main factors have been identified as modulators of such differences: proficiency and age of acquisition of the second language (L2). However, whether the bilingual brain differs from the monolingual in the efficient processing of non-verbal auditory events (known to be critical to the acoustic analysis of the speech stream) remains unclear. In this EEG/ERP study, using the mismatch negativity (MMN), P3a, and late negativity (LN), we examined differences in discrimination, involuntary switching of attention and reorienting of attention between monolinguals and bilinguals as they processed complex tones. Further, we examined the role that age of acquisition plays in modulating such responses. A group of English monolinguals and a group of proficient Spanish-English bilinguals were presented with a multiple-deviant oddball paradigm with four deviant conditions (duration, frequency, silent gap, and frequency modulation). Late bilinguals, who learned English after age 10, exhibited larger MMN and P3a responses than early bilinguals, across all deviant conditions. Significant associations were found between amplitude of the responses and both age of L2 acquisition and years of L2 experience. Individuals who acquired English at later ages and had fewer years of L2 experience had larger MMN, P3a, and LN responses than those who learned it earlier. These findings demonstrate that age of L2 acquisition is an important modulator of auditory responses in bilinguals even when processing non-speech signals. Involuntary attention switching is suggested as the main factor driving these differences.

  11. Silicon photonic Mach Zehnder modulators for next-generation short-reach optical communication networks

    NASA Astrophysics Data System (ADS)

    Lacava, C.; Liu, Z.; Thomson, D.; Ke, Li; Fedeli, J. M.; Richardson, D. J.; Reed, G. T.; Petropoulos, P.

    2016-02-01

    Communication traffic grows relentlessly in today's networks, and with ever more machines connected to the network, this trend is set to continue for the foreseeable future. It is widely accepted that increasingly faster communications are required at the point of the end users, and consequently optical transmission plays a progressively greater role even in short- and medium-reach networks. Silicon photonic technologies are becoming increasingly attractive for such networks, due to their potential for low cost, energetically efficient, high-speed optical components. A representative example is the silicon-based optical modulator, which has been actively studied. Researchers have demonstrated silicon modulators in different types of structures, such as ring resonators or slow light based devices. These approaches have shown remarkably good performance in terms of modulation efficiency, however their operation could be severely affected by temperature drifts or fabrication errors. Mach-Zehnder modulators (MZM), on the other hand, show good performance and resilience to different environmental conditions. In this paper we present a CMOS-compatible compact silicon MZM. We study the application of the modulator to short-reach interconnects by realizing data modulation using some relevant advanced modulation formats, such as 4-level Pulse Amplitude Modulation (PAM-4) and Discrete Multi-Tone (DMT) modulation and compare the performance of the different systems in transmission.

  12. Tune in to the Tone: Lexical Tone Identification is Associated with Vocabulary and Word Recognition Abilities in Young Chinese Children.

    PubMed

    Tong, Xiuli; Tong, Xiuhong; McBride-Chang, Catherine

    2015-12-01

    Lexical tone is one of the most prominent features in the phonological representation of words in Chinese. However, little, if any, research to date has directly evaluated how young Chinese children's lexical tone identification skills contribute to vocabulary acquisition and character recognition. The present study distinguished lexical tones from segmental phonological awareness and morphological awareness in order to estimate the unique contribution of lexical tone in early vocabulary acquisition and character recognition. A sample of 199 Cantonese children aged 5-6 years was assessed on measures of lexical tone identification, segmental phonological awareness, morphological awareness, nonverbal ability, vocabulary knowledge, and Chinese character recognition. It was found that lexical tone awareness and morphological awareness were both associated with vocabulary knowledge and character recognition. However, there was a significant relationship between lexical tone awareness and both vocabulary knowledge and character recognition, even after controlling for the effects of age, nonverbal ability, segmental phonological awareness and morphological awareness. These findings suggest that lexical tone is a key factor accounting for individual variance in young children's lexical acquisition in Chinese, and that lexical tone should be considered in understanding how children learn new Chinese vocabulary words, in either oral or written forms.

  13. Meaningful FM transmitter modulation linearity measurements

    NASA Astrophysics Data System (ADS)

    Jeske, H. O.

    The IM products in the demodulator output in this case are due only to the demodulator's transfer characteristics. IM product levels of the test system greater than 60 dB below the simultaneous modulation level of +300 kHz each by 400 and 450 kHz tones are obtained at Sandia Laboratories. The use of two-tone IM tests for the evaluation and specification of FM transmitter modulation linearity is strongly recommended.

  14. Responses of neurons in the marmoset primary auditory cortex to interaural level differences: comparison of pure tones and vocalizations.

    PubMed

    Lui, Leo L; Mokri, Yasamin; Reser, David H; Rosa, Marcello G P; Rajan, Ramesh

    2015-01-01

    Interaural level differences (ILDs) are the dominant cue for localizing the sources of high frequency sounds that differ in azimuth. Neurons in the primary auditory cortex (A1) respond differentially to ILDs of simple stimuli such as tones and noise bands, but the extent to which this applies to complex natural sounds, such as vocalizations, is not known. In sufentanil/N2O anesthetized marmosets, we compared the responses of 76 A1 neurons to three vocalizations (Ock, Tsik, and Twitter) and pure tones at cells' characteristic frequency. Each stimulus was presented with ILDs ranging from 20 dB favoring the contralateral ear to 20 dB favoring the ipsilateral ear to cover most of the frontal azimuthal space. The response to each stimulus was tested at three average binaural levels (ABLs). Most neurons were sensitive to ILDs of vocalizations and pure tones. For all stimuli, the majority of cells had monotonic ILD sensitivity functions favoring the contralateral ear, but we also observed ILD sensitivity functions that peaked near the midline and functions favoring the ipsilateral ear. Representation of ILD in A1 was better for pure tones and the Ock vocalization in comparison to the Tsik and Twitter calls; this was reflected by higher discrimination indices and greater modulation ranges. ILD sensitivity was heavily dependent on ABL: changes in ABL by ±20 dB SPL from the optimal level for ILD sensitivity led to significant decreases in ILD sensitivity for all stimuli, although ILD sensitivity to pure tones and Ock calls was most robust to such ABL changes. Our results demonstrate differences in ILD coding for pure tones and vocalizations, showing that ILD sensitivity in A1 to complex sounds cannot be simply extrapolated from that to pure tones. They also show A1 neurons do not show level-invariant representation of ILD, suggesting that such a representation of auditory space is likely to require population coding, and further processing at subsequent hierarchical stages.

  15. Responses of neurons in the marmoset primary auditory cortex to interaural level differences: comparison of pure tones and vocalizations

    PubMed Central

    Lui, Leo L.; Mokri, Yasamin; Reser, David H.; Rosa, Marcello G. P.; Rajan, Ramesh

    2015-01-01

    Interaural level differences (ILDs) are the dominant cue for localizing the sources of high frequency sounds that differ in azimuth. Neurons in the primary auditory cortex (A1) respond differentially to ILDs of simple stimuli such as tones and noise bands, but the extent to which this applies to complex natural sounds, such as vocalizations, is not known. In sufentanil/N2O anesthetized marmosets, we compared the responses of 76 A1 neurons to three vocalizations (Ock, Tsik, and Twitter) and pure tones at cells' characteristic frequency. Each stimulus was presented with ILDs ranging from 20 dB favoring the contralateral ear to 20 dB favoring the ipsilateral ear to cover most of the frontal azimuthal space. The response to each stimulus was tested at three average binaural levels (ABLs). Most neurons were sensitive to ILDs of vocalizations and pure tones. For all stimuli, the majority of cells had monotonic ILD sensitivity functions favoring the contralateral ear, but we also observed ILD sensitivity functions that peaked near the midline and functions favoring the ipsilateral ear. Representation of ILD in A1 was better for pure tones and the Ock vocalization in comparison to the Tsik and Twitter calls; this was reflected by higher discrimination indices and greater modulation ranges. ILD sensitivity was heavily dependent on ABL: changes in ABL by ±20 dB SPL from the optimal level for ILD sensitivity led to significant decreases in ILD sensitivity for all stimuli, although ILD sensitivity to pure tones and Ock calls was most robust to such ABL changes. Our results demonstrate differences in ILD coding for pure tones and vocalizations, showing that ILD sensitivity in A1 to complex sounds cannot be simply extrapolated from that to pure tones. They also show A1 neurons do not show level-invariant representation of ILD, suggesting that such a representation of auditory space is likely to require population coding, and further processing at subsequent hierarchical stages

  16. BARC surface property matching for negative-tone development of a conventional positive-tone photoresist

    NASA Astrophysics Data System (ADS)

    Guerrero, Douglas J.; Krishnamurthy, Vandana; Sullivan, Daniel M.

    2011-04-01

    The main properties controlling a successful negative-tone development (NTD) process include surface energy of the BARC or silicon hardmask, reflectivity control, and type of spin-on carbon (SOC) layer utilized. In this paper, we studied the BARC and silicon-containing hardmask properties needed to achieve successful NTD of a conventional positive-tone photoresist. The surface energy mismatch between BARC and silicon-containing hardmask poses challenges for patterning dense structures. Interaction of the SOC layer and the photoresist was observed, even with the silicon hardmask film present in between these two layers. Strict reflectivity elimination does not guarantee a successful outcome, rather precise control of reflectivity is required to enhance the overall lithographic process.

  17. PULSE AMPLITUDE DISTRIBUTION RECORDER

    DOEpatents

    Cowper, G.

    1958-08-12

    A device is described for automatica1ly recording pulse annplitude distribution received from a counter. The novelty of the device consists of the over-all arrangement of conventional circuit elements to provide an easy to read permanent record of the pulse amplitude distribution during a certain time period. In the device a pulse analyzer separates the pulses according to annplitude into several channels. A scaler in each channel counts the pulses and operates a pen marker positioned over a drivable recorder sheet. Since the scalers in each channel have the sanne capacity, the control circuitry permits counting of the incoming pulses until one scaler reaches capacity, whereupon the input is removed and an internal oscillator supplies the necessary pulses to fill up the other scalers. Movement of the chart sheet is initiated wben the first scaler reaches capacity to thereby give a series of marks at spacings proportional to the time required to fill the remaining scalers, and accessory equipment marks calibration points on the recorder sheet to facilitate direct reading of the number of external pulses supplied to each scaler.

  18. Shallow Cavity Flow Tone Experiments: Onset of Locked-On States

    SciTech Connect

    D. Rockwell; J.C. Lin; P. Oshkai; M. Reiss; M. Pollack

    2000-09-05

    Fully turbulent inflow past a shallow cavity is investigated for the configuration of an axisymmetric cavity mounted in a pipe. Emphasis is on conditions giving rise to coherent oscillations, which can lead to locked-on states of flow tones in the pipe-cavity system. Unsteady surface pressure measurements are interpreted using three-dimensional representations of amplitude-frequency-inflow velocity; these representations are constructed for a range of cavity depth. Assessment of these data involves a variety of approaches. Evaluation of pressure gradients on plan views of the three-dimensional representations allows extraction of the frequencies of the instability (Strouhal) modes of the cavity oscillation. These frequency components are correlated with traditional models originally formulated for cavities in a free-stream. In addition, they are normalized using two length scales; inflow boundary-layer thickness and pipe diameter. These scales are consistent with those employed for the hydrodynamic instability of the separated shear layer, and are linked to the large-scale mode of the shear layer oscillation, which occurs at relatively long cavity length. In fact, a simple scaling based on pipe diameter can correlate the frequencies of the dominant peaks over a range of cavity depth. The foregoing considerations provide evidence that pronounced flow tones can be generated from a fully-turbulent inflow at very low Mach number, including the limiting case of fully-developed turbulent flow in a pipe. These tones can arise even for the extreme case of a cavity having a length over an order of magnitude longer than its depth. Suppression of tones is generally achieved if the cavity is sufficiently shallow.

  19. Improving Tone Recognition with Nucleus Modeling and Sequential Learning

    ERIC Educational Resources Information Center

    Wang, Siwei

    2010-01-01

    Mandarin Chinese and many other tonal languages use tones that are defined as specific pitch patterns to distinguish syllables otherwise ambiguous. It had been shown that tones carry at least as much information as vowels in Mandarin Chinese [Surendran et al., 2005]. Surprisingly, though, many speech recognition systems for Mandarin Chinese have…

  20. A Study of Neutral-Tone Syllables in Taiwan Mandarin

    ERIC Educational Resources Information Center

    Huang, Karen

    2012-01-01

    This dissertation studies the realization of the rhythm of Taiwan Mandarin and focuses on the quality of its unstressed (neutral-tone) syllables. Taiwan Mandarin (TM) is often described as more syllable-timed than Standard Mandarin (SM). In TM, the unstressed syllables occur less frequently. The quality of the unstressed (neutral-tone) syllables…

  1. The Intragroup Stigmatization of Skin Tone Among Black Americans

    ERIC Educational Resources Information Center

    Harvey, Richard D.; LaBeach, Nicole; Pridgen, Ellie; Gocial, Tammy M.

    2005-01-01

    The purpose of this study was to examine the extent to which racial contexts moderate the importance and function of intragroup skin-tone stigma among Black Americans. One hundred and thirty-two Black students were recruited from both a predominantly Black university and a predominantly White university and completed measures on skin tone,…

  2. The Study of Tone in Languages with a Quantity Contrast

    ERIC Educational Resources Information Center

    Remijsen, Bert

    2014-01-01

    This paper deals with the study of tone in languages that additionally have a phonological contrastive of quantity, such as vowel length or stress. In such complex word-prosodic systems, tone and the quantity contrast(s) can be fully independent of one another, or they may interact. Both of these configurations are illustrated in this paper, and…

  3. Influences of Tone on Vowel Articulation in Mandarin Chinese

    ERIC Educational Resources Information Center

    Shaw, Jason A.; Chen, Wei-rong; Proctor, Michael I.; Derrick, Donald

    2016-01-01

    Purpose: Models of speech production often abstract away from shared physiology in pitch control and lingual articulation, positing independent control of tone and vowel units. We assess the validity of this assumption in Mandarin Chinese by evaluating the stability of lingual articulation for vowels across variation in tone. Method:…

  4. Tonal Instability: Tone as Part of the Feature Geometry.

    ERIC Educational Resources Information Center

    Walker, Stephen P.

    An autosegmental analysis of Kagate tone is presented. The focus is on tonal instability, which occurs as the result of a compensatory lengthening process. To account for facts of tonal stability, previously hypothesized, and tonal instability, it is proposed that the location of tone within the overall geometry is subject to parametric variation,…

  5. Studies in the Phonology of Asian Languages, VIII, Vietnamese Tones.

    ERIC Educational Resources Information Center

    Han, Mieko S.

    An acoustic-phonetic study of six Vietnamese tones was carried out on approximately 3000 sound spectrograms of four native speakers of the Hanoi dialect. Three temporal segments, four pitch levels, and glottalization were identified as important cues for tone recognition. (Author/FWB)

  6. Moderate Baseline Vagal Tone Predicts Greater Prosociality in Children

    ERIC Educational Resources Information Center

    Miller, Jonas G.; Kahle, Sarah; Hastings, Paul D.

    2017-01-01

    Vagal tone is widely believed to be an important physiological aspect of emotion regulation and associated positive behaviors. However, there is inconsistent evidence for relations between children's baseline vagal tone and their helpful or prosocial responses to others (Hastings & Miller, 2014). Recent work in adults suggests a quadratic…

  7. Dissimilation in the Second Language Acquisition of Mandarin Chinese Tones

    ERIC Educational Resources Information Center

    Zhang, Hang

    2016-01-01

    This article extends Optimality Theoretic studies to the research on second language tone phonology. Specifically, this work analyses the acquisition of identical tone sequences in Mandarin Chinese by adult speakers of three non-tonal languages: English, Japanese and Korean. This study finds that the learners prefer not to use identical lexical…

  8. 47 CFR 64.1514 - Generation of signalling tones.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 3 2011-10-01 2011-10-01 false Generation of signalling tones. 64.1514 Section 64.1514 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES... Services § 64.1514 Generation of signalling tones. No common carrier shall assign a telephone number...

  9. 47 CFR 64.1514 - Generation of signalling tones.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 3 2013-10-01 2013-10-01 false Generation of signalling tones. 64.1514 Section 64.1514 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES... Services § 64.1514 Generation of signalling tones. No common carrier shall assign a telephone number...

  10. 47 CFR 64.1514 - Generation of signalling tones.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 3 2014-10-01 2014-10-01 false Generation of signalling tones. 64.1514 Section 64.1514 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES... Services § 64.1514 Generation of signalling tones. No common carrier shall assign a telephone number...

  11. 47 CFR 64.1514 - Generation of signalling tones.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 3 2012-10-01 2012-10-01 false Generation of signalling tones. 64.1514 Section 64.1514 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES... Services § 64.1514 Generation of signalling tones. No common carrier shall assign a telephone number...

  12. Musical experience and Mandarin tone discrimination and imitation

    NASA Astrophysics Data System (ADS)

    Gottfried, Terry L.; Staby, Ann M.; Ziemer, Christine J.

    2004-05-01

    Previous work [T. L. Gottfried and D. Riester, J. Acoust. Soc. Am. 108, 2604 (2000)] showed that native speakers of American English with musical training performed better than nonmusicians when identifying the four distinctive tones of Mandarin Chinese (high-level, mid-rising, low-dipping, high-falling). Accuracy for both groups was relatively low since listeners were not trained on the phonemic contrasts. Current research compares musicians and nonmusicians on discrimination and imitation of unfamiliar tones. Listeners were presented with two different Mandarin words that had either the same or different tones; listeners indicated whether the tones were same or different. Thus, they were required to determine a categorical match (same or different tone), rather than an auditory match. All listeners had significantly more difficulty discriminating between mid-rising and low-dipping tones than with other contrasts. Listeners with more musical training showed significantly greater accuracy in their discrimination. Likewise, musicians' spoken imitations of Mandarin tones (model tokens presented by a native speaker) were rated as significantly more native-like than those of nonmusicians. These findings suggest that musicians may have abilities or training that facilitate their perception and production of Mandarin tones. However, further research is needed to determine whether this advantage transfers to language learning situations.

  13. Discrimination of Lexical Tones in the First Year of Life

    ERIC Educational Resources Information Center

    Chen, Ao; Kager, René

    2016-01-01

    In the current study, we examined the developmental course of the perception of non-native tonal contrast. We tested 4, 6 and 12-month-old Dutch infants on their discrimination of Chinese low-rising tone and low-dipping tone using the visual fixation paradigm. The infants were tested in two conditions that differed in terms of degree of…

  14. 47 CFR 64.1514 - Generation of signalling tones.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 3 2010-10-01 2010-10-01 false Generation of signalling tones. 64.1514 Section 64.1514 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES... Services § 64.1514 Generation of signalling tones. No common carrier shall assign a telephone number...

  15. Tone Gestures and Constraint Interaction in Sierra Juarez Zapotec

    ERIC Educational Resources Information Center

    Tejada, Laura

    2012-01-01

    This dissertation examines floating tones and tone gesture deactivation in Sierra Juarez Zapotec (SJZ), and provides an Optimality Theoretic account of tonal spreading and placement using insights from Articulatory Phonology. While the data portion of the dissertation is drawn from SJZ, the approach has broader implications for theories of tonal…

  16. Contra-Rotating Open Rotor Tone Noise Prediction

    NASA Technical Reports Server (NTRS)

    Envia, Edmane

    2014-01-01

    Reliable prediction of contra-rotating open rotor (CROR) noise is an essential element of any strategy for the development of low-noise open rotor propulsion systems that can meet both the community noise regulations and the cabin noise limits. Since CROR noise spectra typically exhibits a preponderance of tones, significant efforts have been directed towards predicting their tone spectra. To that end, there has been an ongoing effort at NASA to assess various in-house open rotor tone noise prediction tools using a benchmark CROR blade set for which significant aerodynamic and acoustic data had been acquired in wind tunnel tests. In the work presented here, the focus is on the near-field noise of the benchmark open rotor blade set at the cruise condition. Using an analytical CROR tone noise model with input from high-fidelity aerodynamic simulations, detailed tone noise spectral predictions have been generated and compared with the experimental data. Comparisons indicate that the theoretical predictions are in good agreement with the data, especially for the dominant CROR tones and their overall sound pressure level. The results also indicate that, whereas individual rotor tones are well predicted by the linear sources (i.e., thickness and loading), for the interaction tones it is essential that the quadrupole sources be included in the analysis.

  17. Tone-deaf ears in moths may limit the acoustic detection of two-tone bats.

    PubMed

    Mora, Emanuel C; Fernández, Yohami; Hechavarría, Julio; Pérez, Martha

    2014-01-01

    Frequency alternation in the echolocation of insectivorous bats has been interpreted in relation to ranging and duty cycle, i.e. advantages for echolocation. The shifts in frequency of the calls of these so-called two-tone bats, however, may also play its role in the success of their hunting behavior for a preferred prey, the tympanate moth. How the auditory receptors (e.g. the A1 and A2 cells) in the moth's ear detect such frequency shifts is currently unknown. Here, we measured the auditory responses of the A1 cell in the noctuid Spodoptera frugiperda to the echolocation hunting sequence of Molossus molossus, a two-tone bat. We also manipulated the bat calls to control for the frequency shifts by lowering the frequency band of the search and approach calls. The firing response of the A1 receptor cell significantly decreases with the shift to higher frequencies during the search and approach phases of the hunting sequence of M. molossus; this could be explained by the receptor's threshold curve. The frequency dependence of the decrease in the receptor's response is supported by the results attained with the manipulated sequence: search and approach calls with the same minimum frequency are detected by the moth at the same threshold intensity. The two-tone bat M. molossus shows a call frequency alternation behavior that may enable it to overcome moth audition even in the mid-frequency range (i.e. 20-50 kHz) where moths hear best.

  18. Factors Influencing Sensitivity to Lexical Tone in an Artificial Language: Implications for Second Language Learning

    ERIC Educational Resources Information Center

    Caldwell-Harris, Catherine L.; Lancaster, Alia; Ladd, D. Robert; Dediu, Dan; Christiansen, Morten H.

    2015-01-01

    This study examined whether musical training, ethnicity, and experience with a natural tone language influenced sensitivity to tone while listening to an artificial tone language. The language was designed with three tones, modeled after level-tone African languages. Participants listened to a 15-min random concatenation of six 3-syllable words.…

  19. Experimental Feedback Control of Flow Induced Cavity Tones

    NASA Technical Reports Server (NTRS)

    Cabell, Randolph H.; Kegerise, Michael A.; Cox, David E.; Gibbs, Gary P.

    2002-01-01

    An experimental study of the application of discrete-time, linear quadratic control design methods to the cavity tone problem is described. State space models of the dynamics from a synthetic jet actuator at the leading edge of the cavity to two pressure sensors in the cavity were computed from experimental data. Variations in model order, control order, control bandwidth, and properties of a Kalman state estimator were studied. Feedback control reduced the levels of multiple cavity tones at Mach 0.275, 0.35, and 0.45. Closed loop performance was often limited by excitation of sidebands of cavity tones, and creation of new tones in the spectrum. State space models were useful for explaining some of these limitations, but were not able to account for non-linear dynamics, such as interactions between tones at different frequencies.

  20. All-optical tunable multilevel amplitude regeneration based on coherent wave mixing using a polarizer.

    PubMed

    Bakhtiari, Zahra; Sawchuk, Alexander A

    2015-04-20

    We describe and demonstrate an all-optical tunable phase- preserving scheme for multilevel amplitude regeneration based on coherent optical wave mixing using a polarizer for optical star 8-quadrature-amplitude modulation (star-8QAM) and star-16QAM signals with a power ratio of 1:5. Amplitude noise can be efficiently suppressed on both amplitude levels. A regeneration factor of nearly 5 for the higher-amplitude level of star-8QAM and 3 for lower-amplitude level are achieved. The system robustness against nonlinear phase noise originating from the Gordon-Mollenauer effect in a 150 km transmission line is investigated using the proposed amplitude regenerator.